Literature Review, Recycling of Lithium-Ion Batteries from Electric Vehicles, Part II: Environmental and Economic Perspective

Abstract

Lithium-ion batteries (LIBs) are crucial for consumer electronics, complex energy storage systems, space applications, and the automotive industry. The increasing requirements for decarbonization and CO₂ emissions reduction affect the composition of new production. Thus, the entire automotive sector experiences its turning point; the production capacities of new internal combustion engine vehicles are limited, and the demand for electric vehicles (EVs) has continuously increased over the past years. The growing number of new EVs leads to an increasing amount of automotive waste, namely spent LIBs. Recycling appears to be the most suitable solution for lowering EV prices and reducing environmental impacts; however, it is still not a well-established process. This work is the second part of the review collection based on the performed literature survey, where more than 250 publications about “Recycling of Lithium-ion Batteries from Electric Vehicles” were divided into five sections: Recycling Processes, Battery Composition, Environmental Impact, Economic Evaluation, and Recycling and Rest. This paper reviews and summarizes 162 publications dedicated to recycling procedures and their environmental or economic perspective. Both reviews cover the techno-environmental economic impacts of recycling spent LIBs from EVs published until 2021.

1. Introduction

Lithium-ion batteries (LIBs) represent the dominant energy source not just for portable electronics and electromobility vehicles, but they have also found growing popularity in military and aerospace applications or grid energy storage systems [1]. The ever-increasing demand for LIBs leads to the still-growing amount of battery waste, from the small formats of the battery cells to complex automotive or storage battery systems.

The entire automotive industry is undergoing a crucial turning point. The increasing requirements for decarbonization and CO₂ emissions reduction limit the production of new combustion vehicles [2], and transit to the production of electric vehicles (EVs) is the most suitable solution. Therefore, pressure to reduce EVs’ price and a detailed evaluation of their environmental impacts are necessary. Thus, these systems’ environmental and economic (E&E) assessments are inherent.

LIBs from EVs are commonly based on valuable metals, such as nickel (Ni), cobalt (Co), manganese (Mn), and lithium (Li), which are significantly high in cost. Packaging and coverings are created from an efficiently recyclable material such as aluminum (Al) or copper (Cu). Thus, one of the most suitable waste management solutions for spent LIBs seems to be recycling processing. Introducing recycling techniques will lead to the recovery of selected materials as high-quality outputs; thus, raw materials extraction, including high energy consumption and CO₂ emission production, could be reduced [3,4]. The price of a new battery based on reused materials should be lowered, as well as the price of the new EV. These days, the research is mainly dedicated to optimizing the currently operated recycling techniques, reducing their complexity, and increasing output efficiency and purity. Nevertheless, the environmental and economic demands of selected recycling routes are being examined and compared to each other; LIBs technology is evaluated within the entire life cycle or recycling framework’s financial burdens.

This paper presents the second part of the literature review study of peer-reviewed publications devoted to “Recycling of Lithium-ion Batteries from Electric Vehicles”, focusing on the E&E perspectives. In total, 162 papers have been referred to in this work and summarized into individual thematically connected units (categories), including, for example, Life Cycle Assessment (LCA) study, recycling and recovery of materials, or economic evaluation. In addition, conclusions for individual reviewed categories are provided, and recommendations for further research and development are proposed.

Both published reviews cover the entire techno-environmental economic impact of recycling EV-retired LIBs published until 2021. More than 90% of used publications from both reviews have been published in the last decade. Thus, the current overview that captures individual steps of the recycling techniques, their impacts on the environment, and the economic demands are presented. These works provide a comprehensive techno-environmental economic analysis of the selected field, and it is prepared for further use in academic and industrial spheres.

The content of this work is structured as follows: firstly, in Section 2, the methodology of the performed literature review is shortly discussed; then, in Section 3, the current state of performed recycling techniques, their recovery efficiencies primarily in terms of valuable metals considering their environmental impacts considering LCA study and economic assessments inclusive of financial analysis and evaluation are reported. Finally, in Section 4, the main conclusions of this part of the review collection are pointed out, and both parts are discussed comprehensively to capture the recycling of LIBs from EVs as a technological environmental economic unit.

2. Review Methodology

This paper is based on the literature review that has already been introduced in the first part of the review collection devoted to recycling technology of LIBs from EVs [5]. The performed search was completed during September and October 2021 and was performed on two databases, Web of Science (WoS) and Scopus, focusing on the variation of terms “recycling”, “Lithium-ion”, and “electric vehicles”. A more detailed description of this search methodology and enumerations of individual publications is presented in the first part of the literature review study devoted to recycling technology [5].

This second part of the review summarized the remaining 250 publications, including articles, reviews, proceedings papers, early accesses, editorial materials, and corrections dedicated to the environmental and economic (E&E) approach. As the results of the first part of this review collection show, there is an overlap in many scopes of selected publications. This overlay is presented in the updated

Table 1. Distribution of publications; the methodology of performed literature review.

Section	No. of Articles in Section	Category/Keyword	No. of Articles in Category	No. of Overlapped Articles
Recycling Processes	61	Pretreatment	3	0
		Metallurgy/Mechanical	6	1
		Pyrometallurgy	4	0
		Hydrometallurgy	19	11
		Direct Recycling	6	3
		Special Method	23	9
Battery Composition	54	Cathode	43	43
		Anode	9	9
		Electrolyte	2	2
Environmental Impact	75	Envi/Ecological Impact	13	5
		Life Cycle Assessment (LCA)	5	3
		Recovery of Materials	35	1
		Recycling of Materials	22	0
Economical Assessment	14	Economical Evaluation	14	3
Recycling and Rest (R&R)	47	Recycling EV LIBs	11	6
		Recycling LIBs	36	19

. Moreover, it illustrates the distribution of chosen publications into five sections (Recycling Processes, Battery Composition, Environmental Impact, Economic Evaluation, and Recycling and Rest), which are being represented by a specific category/keyword according to the content.

In total, 162 publications were one-by-one reviewed in this paper from the environmental economic field to which this work is dedicated. Thus, this paper primarily focuses on the Battery Composition, Environmental Impacts, Economical Assessment, and Recycling and Rest (R&R) sections and their relevant categories. Moreover, Appendix A provides a brief overview, including the type, publication year, and summary content of all reviewed publications.

3. Results

Within this part of the review collection, the categories of Battery Composition, Environmental Impact, Economical Assessment, and R&R were discussed. As in the previous work, the representation of individual types of publications in these distinctive sections was evaluated. A total of 124 Articles, 17 Reviews, 18 Proceedings Papers, 2 Editorial Materials, and 1 Correction were used to characterize individual recycling procedures and E&E aspects. The representation of the publications’ distribution in categories is shown in Figure 1.

The recycling process itself stands as a very complex topic. Thus, the distribution of the publication into individual categories is not fully restrictive and unambiguous. The reviewed publications were sorted and organized for the most straightforward interpretation of recycling LIBs from EVs under the environmental and economic perspectives. The methodology of the work is presented in Figure 2.

3.1. Environmental Perspective

The introduction and application of technology are not assessed only in terms of its effectiveness, efficiency, or economic feasibility of implementation. A significant role stands the impact on the environment, monitored within the individual phases and primarily during the entire life cycle.

LIBs have been developed since the last decade of the 20th century. The quality of the technology used and its application level are growing year by year, whether in terms of small portable devices (mobile phones, laptops, etc.) or electromobility (e-bicycles, e-scooters, EVs). Due to the ever-tightening rules of the EU Directive 2019/631, which proposes a reduction of CO₂ emissions of passenger vehicles and vans [2], a more significant increase in demand for EVs could occur. It could lead to a 45% growth of EVs in the total market by 2030 [6].

As EV production increases, the number of retired LIBs from these cars increases too. Thus, addressing environmental impact issues is progressively essential. Primarily, it is advisable to focus on the new battery production (used technologies and materials), effective use during an active life, and evaluate the efficiency and burden of the disposal or recycling process.

According to this work, the publications evaluating the environmental point of view were divided into four categories.

• Battery Cell Composition, which deals with the structure of the cells.
• Ecological point of view that addresses a purely ecological point of view.
• Recycling Processes and Recovery Efficiencies, which provides a detailed summary of applied recycling techniques, their efficiencies, and findings.
• LCA (Life Cycle Assessment) study that evaluates the life cycle of the battery.

An overview of frequently used abbreviations of main indicators in the framework of environmental studies or impacts monitoring, which are used later in the text, is provided in

Table 2. Overview of the main indicators for monitoring the environmental impact.

Abbreviations	Indicator
ADP	Abiotic resource depletion potential
CED	Cumulative energy demand
GHG	Greenhouse gas
GWP	Global warming potential
TETP	Terrestrial ecotoxicity potential

.

3.1.1. Battery Cell Composition

As is generally well known, there are four main components of a battery cell: two terminals (electrodes) based on different chemicals (typically metals), the anode and the cathode, the electrolyte, and a separator. The electrolyte is a chemical medium that ensures the flow of electrical charge between the electrodes. Furthermore, the battery cell contains current collectors, typically formed by metals such as Cu or Al.

LIBs contain roughly 5–20 wt.% cobalt (Co), 5–10 wt.% nickel (Ni), 5–7 wt.% lithium (Li), 5–10 wt.% other metals (manganese (Mn), copper (Cu), aluminum (Al), iron (Fe), graphite (C), etc.), 15 wt.% organic compounds, and 7 wt.% plastics. The proportion varies according to exact cell composition and the manufacturer [7,8]. The general main material composition of the individual components of LIBs—anode, cathode, and electrolyte, which is typically dissolved in propylene carbonate, ethylene carbonate, or dimethyl sulfoxide—is shown in

Table 3. The general material composition of the individual components of LIBs [8,9,10].

Anode	Cathode (Short Name)	Electrolyte
Metallic lithium	Lithium manganese oxide (LMO)	LiPF6
Graphitic carbon	Lithium cobalt oxide (LCO)	LiClO4
Hard carbon	Lithium nickel cobalt manganese oxide (NMC)	LiAsF6
Synthetic graphite	Lithium iron phosphate (LFP)	LiCF3SO3
Lithium titanate	Lithium nickel cobalt aluminum oxide (NCA)	LiBF4
Tin-based alloys	FeS2	LiSFO2
Silicon-based materials	V2O5
	Electronic conducting polymers

. Binders, flame retardants, gel precursors, and electrolyte solvents complement these components [8,9,10].

According to the performed search, the topic of “Battery Cell Composition” has not been intensively focused on by researchers since it was only addressed in six publications, including three Proceedings Papers, two Articles, and one Review, directly dedicated to the individual components of the retired LIBs from EVs.

A detailed and very well-structured review, dedicated to the recycling with emphasis on the anode (graphite) and electrolytes, was prepared by Arshad et al. [11]. This work presents essential elements of Life Cycle Assessment (LCA), focusing on End-of-Life (EOL) LIBs recycling, process limitations, and future efforts to improve the current efficiency of metal extraction and separation.

In compliance with this work, the anode and electrolyte are typically decomposed by heating (pyrometallurgy) or filtration/distillation (hydrometallurgy). Calcination or pyrolysis is habitually used for the high recovery rate of anode materials, as well as for electrolytes [11]. The mechanisms of these techniques were presented in the first part of this literature review collection [5], or it is described in more detail in the full version of the referred paper [11]. In addition, the work provides a summary of potential applications of recycled materials. The recovered carbon-based anode materials can be used as absorbents, nanocomposite thin film (in conjunction with polymers), or as part of a new anode in LIBs. Recycling and reusing electrolytes are not efficient under current conditions due to their fast capacity fade during repeated use [11].

The procedures, recovery rates, or a future application potential of recycled cathode materials have not been described in the summary publication yet. Selected publications deal with specialized implemented recycling procedures. Wen et al. [12] and Zhou et al. [13] discussed basic recycling procedures (pyrometallurgy, hydrometallurgy) supplemented by biological recycling; Meng et al. [14] provided a recycling strategy for spent graphite/LiFePO₄ batteries and complemented a cathode composition based on recovered LFP/graphite with cation/anion-co-storage capability, which design leads to the new-type dual-ion battery. Sloop et al. [15] presented the advantages of direct recycling of electrode materials and compared the process for bare and coated NMC 622 cells. Wu et al. [16] devoted their study to the physical separation process, implemented via thermal and mechanical treatments that recover active cathode materials (LiFePO₄) from current collectors (including Al fragments); the process is based on cohesive zone models verified by physical separation experiments.

3.1.2. Ecological Point of View

According to the chemical composition of batteries, they are dominantly based on precious metals such as Co, Ni, Li, Mn, and other frequently used metals, e.g., Cu and Al. The secondary use and recovery of these metals as high-quality recycling products bring many advantages, where the natural resource savings resonate the most.

Current and future environmental impacts of recycling in close-loop battery life are being addressed in many cases. It leads to the introduction and ever-tightening conditions of legislation, for example, the currently valid EU legislation (increasing recycling efficiency from 50% to 65% by 2025 and 70% by 2030 by average weight [17]) or growing efficiency for the constitution of current recycling methods. They are discussed in detail in 13 publications, i.e., in 10 Articles, 2 Proceedings papers, and 1 Review, which majorly deal with the ecological principles.

These sorts of questions are discussed in the critical analysis of natural resource savings published by Dewulf et al. [18]. This paper compares a detailed analysis of a LIB recycling scenario, including Co and Ni recovery and re-introduction into the battery production chain, with a virgin production scenario. The (a) input exergy that is necessary and allocated for the production chain of 1 kg LIB cathode material, where Scenario A describes the production of a battery based on waste with Ni and Co recovery, and Scenario B shows production from virgin resources; and (b) the contribution to the total natural resource consumption as a function of the involved processes, that includes their supply chains, are shown in Figure 3. The exergy and cumulative exergy extracted from natural sources are used for savings quantification. According to the results, the recycling scenario leads to a 51.3% natural resource savings, caused primarily by decreasing mineral ore dependency and reducing fossil resources (45.3% reduction) and nuclear energy demand (57.2%). Moreover, the paper discusses the economic benefit of recycling.

Rahman et al. further investigated the impact of reusing recovery materials during a new LIBs production [19]. This research was devoted to recovering active materials of a spent 48.8 Wh LIB (LiCoO₂) by applying the laboratory-scale hydrometallurgical procedure. The result shows that the recovery of active metals is 41% of the cathode and 8.5% of the anode materials. Due to this process, the generated emissions can be reduced by 47.61% in the case of metal production for batteries and 60.7% for disposal transportation of the spent battery. The emission can be reduced by 52.85% by recycling the active materials in this type of LIB.

The analysis presented by Dunn et al. [20] answers three critical questions about automotive LIBs energy and environmental impacts:

• Is it materials production or battery assembly that causes more of these impacts?
• What motivates battery recycling if it is the assembly step that is the primary energy consumer?
• How do the energy and environmental performance of EVs and internal combustion engine vehicles (ICVs) compare?

The study provides several additional questions and answers that confirm the obtained results, including, for example, local impacts of the recovery of metals in cathode materials’ supply chains, including high SO_x emissions. Due to the complexity of the topic, the details and the obtained results can be found in the full version of this paper [20].

When comparing the effects of recycling, it is necessary to consider the mutual comparison of currently used recycling methods; this is where the publication by Costa et al. [21] is focused. The advantages and disadvantages of the different current-state techniques are discussed in their work; these are shown in

Table 4. Comparison of used recycling techniques. Reprinted from Energy Storage Materials, Vol. 37, Costa et al. [21], Recycling and environmental issues of lithium-ion batteries: Advances, challenges and opportunities, pp. 433–465, Copyright (2022), with permission from Elsevier.

Method	Advantages	Disadvantages
Direct recycling	Environmentally friendly; High specificity; Non-destructive method.	Non-specific; Not possible processing of different cathode materials.
Pyrometallurgical method	High recycling rates; Solvent free.	High-temperature process; Other processes for the effective recovery of materials are necessary.
Hydrometallurgical method	High recycling rates; Large variety in the recovery of metals.	Complexity of the process; Application of toxic reagents; High in costs.

. Moreover, the environmental issues associated with EV LIBs’ production, use, and EOL procedures are considered and described.

The environmental impacts are well overviewed in work by Martins et al. [22] and in a comprehensive review by Meshram et al. [23]. While the paper [22] is devoted to describing the current scenario and future perspectives, which are essential for strategies of new battery design, recycling routes, and reverse logistics, the second publication [23] reviews the developments of recycling active cathode materials by using various leaching techniques. The different organic acids used to extract metals from spent LIBs have been discussed in terms of their mechanism, efficacies, and other factors (selectivity, cost, etc.) that have to be considered during battery recycling. According to the conclusions of this work, the GHG emissions of Co extraction based on the organic acids stand at 1/8 of the total emission produced using an inorganic acid leaching process.

A further ecological approach devoted to recycling LIBs cathode active materials (especially Co and Li) by using organic acid leaching was investigated by Nayaka et al. [24]. Spent LIBs were generally physically separated; they were subjected to degradable organic acids such as nitrilotriacetic acid (NTA), adipic acid (AA), and ascorbic acid in a time window lasting approximately 6 h. The main benefit of this procedure is that organic compounds are based on different acid concentrations in distilled water; thus, this process produces fewer emissions and hazardous gasses and influences the environment less. Under the optimal process conditions by atomic absorption spectrophotometry (AAS) determination, 75% of Co and 96% of Li ions were leached with NA; 85% of Co and 92% of Li ions were leached with AA via a reductive–complexation mechanism. Moreover, the work analyzes cathode materials’ structure and morphology before and after leaching by X-ray diffraction (XRD) and scanning electronic microscopy (SEM).

Eugene et al. [25] introduce a three-stage diafiltration process designed to recycle LIBs for cobalt and lithium higher material recovery. Diafiltration is a continuous green method typically used in operating mode for membrane cascades to achieve recovery of high-purity and high-value products. This paper presents a novel modeling technique and future optimization framework.

Further, Dunn et al. [26] described the environmental burdens, capturing energy consumption, and GHG emissions of the material production, assembly, and recycling of automotive LIBs based on LiMn₂O₄ cathode material. In this work, three recycling procedures (hydrometallurgical, intermediate physical, and direct physical recycling) are examined, and the effects of closed-loop recycling on the environmental impacts of battery production are calculated. According to the results of this process-level approach for fully electric vehicles, cradle-to-gate energy corresponds to 75 MJ/kg per battery and GHG emissions of 5.1 kg CO₂e/kg per battery; the direct physical recycling technique can reduce the energy consumption during material production in a closed-loop scenario by up to 48%.

The work by Boyden et al. [27] summarizes the environmental impact of recycling processes from different points of view. Firstly, the introduction devoted to recycling techniques according to their location and efficiency of material recovery is presented. Secondly, the comparative Life Cycle Assessment (LCA) for hydrometallurgy and pyrometallurgy recycling process was established. Due to the environmental impacts in conditions of global warming potential (GWP) 100 (considered over a 100-year period), TETP, and HTP, for these recycling techniques and landfilling of spent LIBs were presented.

The recycling process of spent LIBs is presently constantly evolving and being optimized. The current situation is well summarized in detail in the review work by Bai et al. [28], which, moreover, describes the concept of Battery Identity Global Passport (BIGP). The recyclability of LIBs could be increased by addressing the separation of components using markings, including labels, QR codes, or RFID tags.

Two “ecological” section studies were devoted to the environmental impacts in conditions of China: the work presented by Tang et al. [29] is focused on the social-economic-environmental effects of recycling of spent LIBs from EVs under reward–penalty mechanisms in terms of a Stackelberg game-theoretical model; it considers three different scenarios (no policy intervention, subsidy mechanism, and reward–penalty mechanism). According to the results, even a relatively low minimum recycling rate leads to environmental benefit, consumer surplus, and EV manufacturers’ profits. The second work, which Qiao et al. [30] introduced, analyzes the influence of recovered lithium quality on its future availability in China. Moreover, it evaluates the potential impact of LIB recycling. The results show, notwithstanding the cell chemistry used, that the recovered lithium would meet roughly 60% in the case of the pessimistic scenario, 53% in the neutral scenario, and 49% for the optimistic scenario of the lithium demand during LIBs production with a recovery rate of 80% by 2050.

3.1.3. Recycling Processes and Recovery Efficiencies

The recycling process covers many important topics. Many publications describe the implemented technique and its effectiveness with a focus on the yield of valuable metals or environmental or economic benefits. Therefore, the initial division of 118 publications into categories: Recovery of Materials, Recycling of Materials, Recycling EV LIBs, and Recycling LIBs were used only in the brief description of the individual publications in Appendix A. Here, the articles were once more divided, and discussed according to the structure shown in Figure 4.

First, the state-of-the-art currently implemented recycling methods and procedures leading to recovery were recorded using published reviews and other overviews. Subsequently, a detailed Table 5 was created. It summarized all selected recycling techniques leading to obtaining Co, Li/LiCoO₂/Co, valuable metals (Co, Ni, Mn, and Li), graphite, or electrolyte, describing the procedure, efficiency, or other details. Finally, publications with a different focus were categorized by: Active anode materials, Manganese recovery, LFP batteries, Organic binders, Al foils, Valuable metals, and Others.

Several reviews provide an overall description summarizing the state-of-art devoted to recycling processes and recovery efficiencies of valuable metals. Mansur et al. [31] presented an up-to-date review describing the methods and technologies to recover Co from EOL LIBs. The summary includes thermal, mechanical, and manual preprocessing; the overview of pyrometallurgy and hydrometallurgical methods considers their efficiency levels and future possibilities for improvement. Or et al. [32] devoted their work to covering recycling strategies for valuable metals in mixed-metal LIB cathodes and scrap containing different chemistries. They focused on comparing the environmental footprint and energy consumption between hydro- and pyro-metallurgy. Further, Kim et al. [33] introduced a complex study on recent advances in the anode and cathode materials for the next-generation LIBs including a discussion of the requirements for the high power and energy demands of future energy storage applications, nanostructure synthesis, performance, and reaction mechanisms, and recently used recycling techniques. In another study, Ordoñez et al. [8] presented state-of-the-art recycling technologies for LIBs. Further, Wang et al. [34] discussed the perspective of commonly used recycling processes.

The work of Garg et al. [35] was focused from a different point of; they described solutions for the screening and regrouping of retired LIBs in terms of secondary application and future recycling. The presented method describes three stages: fast screening technology of voltage and internal resistance, status of health (SOH) detection, and clustering method based on a self-organizing maps (SOM) neural network. Introducing this screening technique would facilitate the identification of the state of the batteries and their subsequent secondary or waste treatment and increase the utility aspect of LIBs. Xie et al. [36] discussed the safety of the recycling process and the consequences of incorrectly chosen disassembly or processing. Emphasis is placed on the current and future work of qualified professional battery recycling enterprises. Further, Yu et al. [37] provided a short overview of the framework of EV LIBs’ recycling, considering the access requirement of EV LIBs, transportation of waste batteries, their classification according to the size of a storage system, necessary disassembly requirements, techniques of material recycling, and current EV pollution control.

Piątek et al. [38] critically assessed published research articles and patents on the sustainability of LIBs recycling technologies. The work is devoted to characterizing individual processes, including their potential toxicity or energy consumption, causing CO₂ emissions, and debating the variances in respect of linear and circular economy principles. Moreover, this well-written review presents currently used solutions and future development of the LIBs’ recycling field from dismantling over separation to used bioderived materials. A brief clarification for valuable materials recovery from spent LIBs based on pyrometallurgy, hydrometallurgy, and biometallurgy recycling is described by Garole et al. [39]. This review can help select suitable methods for metal recovery and future repurposing. In work by Werner et al. [40], currently used recycling techniques for spent LIBs are described and categorized according to state-of-the-art schemes of waste treatment technology; therefore, the individual units of the process stages are characterized in detail. Huang et al. [41] reviewed contemporary advancements in recycling technologies of spent LIBs, considering the developments in recycling processing, the quality and quantity of obtained products, and the process’s effects from the environmental perspective. Azhari et al. [42] discussed the recycling aspects for ASSBs and compared the processes to LIBs’ treatment. The work describes in detail solid-state electrolyte chemistries and offers a strategy for ASSB recycling, using hydrometallurgy and direct recycling methods.

Because the previous study focused on Co recovery due to its economic benefit, Liu et al. [43] highlighted the recovery field for Li. They emphasized and evaluated the possibility of industrial realization of each method. Moreover, they discussed these procedures concerning Li’s recovery. According to the review: the hydrometallurgy process reclaims Li in the last step; thus, its recovery rate is poor; the pyrometallurgy method lost all the Li in the slag phase (thermal treatment). The optimal method for recovering the most Li is the mild recycling (cleaner production) method, which decreases the temperature of thermal treatment and acid/alkaline step. Li et al. [44] also addressed this issue when they briefly discussed the adsorptive behavior, synthetic methodology, and prospects of sorbents, including spinel LMO, LTO, lithium aluminum layered double hydroxide chloride (LiCl·2Al(OH)₃). Meng et al. [45] introduced a comprehensive review of Li recovery devoted to industrial practice in perspective to explore technologies for sustainable recovery of Li from minerals, brines, and LIBs.

Other very detailed summaries are provided by Zheng et al. [7], who describe recycling processes for metal extraction such as pyrometallurgy, hydrometallurgy, biometallurgy, and so forth; Zhao et al. [46], who discussed leading technologies and issues in the disposal of spent LIBs from EVs; Gaines et al. [47] brought insight into profitable recycling of LIBs containing a low contribution of Co, while considering new process developments. In other works, Natarajan et al. [48] described current recycling strategies for spent LIB cathodes, Mayyas et al. [49] overviewed challenges in the material supply for automotive LIBs, and Kurz et al. [50] introduced the global warming potential of a new waterjet-based recycling process for cathode materials of LIBs.

There are also more specialized publications that could be included in other categories of this review, such as a paper by Golroudbary et al. [51] that presented an environmental analysis of the recycling of critical minerals from spent LIBs (more oriented to the overall yield of materials recovery). Further, the work from Tan et al. [52] described the importance of recovering critical materials and improving battery designs from the cell to module level to facilitate recyclability, including the economic and environmental implications. Thyabat et al. [53] showed that applying minerals processing operations decreases the volume of LIBs and NiMH scraps; thus, the leachate purification in the hydrometallurgical process is reduced.

Table 5. Overview of the currently used recycling processes and recovery efficiencies.

Section	Recovered Material	Process	Description	Ref.
Cobalt (Co)	Co	Synthesis of Co3S4	Extraction of Co and Ni from the pregnant leach solution (PLS) by a xanthate complex; ammonia solution wash; heat treatment (250 °C, 1 h).	[54]
	Co(II)	Co(II) extraction from chloride using toluene diluted Cyphos IL 102	Co(II) transferred into the organic phase; stripped by 0.05 mol L−1 HCl with 99.9% efficiency in a single stage at O/A 1/1.	[55]
	Co, Cu	Electrodeposition	The instantaneous nucleation mechanism occurs at pH 2.7 and progresses at pH 5.4 for Co electrodeposited multilayer on platinum, vitreous carbon, and Al; the same for Cu electrodeposited on Co.	[56]
	Co, Ni	Solvent extraction	Efficient H2SO4 + H2O2 leaching assisted by diluent heptane and ammonium thiocyanate; reaching factor 372.	[57]
	Co	Carbothermal reduction, magnetic separation	Separation to 53 µm fraction; carbothermal reduction (5–45 min, 500–900 °C); distilled water leaching; magnetic separation of 90% Co.	[58]
	Co	Electrochemical reduction	Molten salt fluidized cathode technique; characterization: voltammograms, chronoamperometry; efficiency 70–80% for the commercial LiCoO2 and upwards of 80% for the spent Li-ion battery.	[59]
	Co, Ni	Leaching	Acid leaching using H2SO4, HNO3, HCl, 1–4 mol L−1, 3–18 h, 25–90 °C, with a solid to liquid ratio fixed at 5% (w/v); the recovery yields of Co and Ni are 100% and 99.99%.	[60]
	Co	Precipitation	The Co(II) hydroxide precipitation; optimal at pH = 9; Co recovery is close to 100% and the filtration flow rate is high.	[61]
	β-Co(OH)2, Co3O4	Precipitation, calcination	Chemical (CP) and electrochemical precipitation (EP); Co3O4 formation by heat-treating β-Co(OH)2 at 450 °C for 3 h.	[62]
	Co(OH)2, Co3O4	Leaching	The Co(OH)2 is electrodeposited onto conductive glass using−0.85 V, 20 C cm−2, with an efficiency of 66.67%; Co3O4 is obtained by heat treatment at 450 °C after 3 h, with an efficiency of 64.29%.	[63]
	Co	Leaching	Acidic dissolution of LiCoO2; next electrodeposition on steel to Co3O4.	[64]
	Co	Synthesis	Recovery using 3D sea-urchin-like cobalt nitride composite material (CoN-Gr-2) used as a bi-functional catalyst for water splitting; potentials of 128.9 mV and 280 mV for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively.	[65]
Lithium (Li)/Lithium Cobalt Oxide (LiCoO2)/ Cobalt (Co)	Li	Separation from solution	The maximum uptake range 20–25 mg Lig−1 reached for Amberlite IR 120 resin and molecular sieve 13X.	[66]
	Li2CO3, Li3PO4	Precipitation	Two-stage precipitation process using Na2CO3 and Na3PO4, with recovery rates of 74.72% and 92.21%, respectively.	[67]
	LiCoO2	Metal-based leaching	Leaching by Co2+ or Mn2+; 95% Li recovery rate and no metal-ions in the leachate.	[68]
	LiCoO2	Eco-friendly leaching	Resynthesis of cathode materials using oxalic acid; 90.13% purity of Li.	[69]
	LiCoO2	Leaching	Using H2SO4 and HCl as leaching agents; optimal 2 M HCl, 60–80 °C, for 90 min.	[70]
	Li2CO3	Low Li high-salt solution	Li precipitation by P; Li3PO4 anolyte dissolution, electrodialysis with cation-exchange membranes used for Li, and P separation with P/Li mass ratio 0.23; Li2CO3 precipitation rate reached 88.3%.	[71]
	LiCoO2	Structure restoration	LiCoO2 powder and Li salts sintering to layered structure; Li2CO3 addition; calcination at a temperature of 800 °C; coating with nanosized Al2O3 particles for performance improvement.	[72]
	Li, Co	Ultrasonic-assisted leaching	Recovery of 96% Co and nearly 100% Li by using 0.5 M citric acid with 0.55 M H2O2, a solid-to-liquid ratio of 25 g L−1, a temperature of 60 °C, 5 h, and ultrasonic power of 90 W.	[73]
	Li, Co	Leaching	Leaching using oxalic acid (H2C2O4) at 0.46 M at 100 °C; addition of hydrogen peroxide (H2O2) resulted in a 33% of activation energy, and 50% of energy consumption reduction.	[74]
	Li, Co	Leaching	Leaching using biodegradable organic methane sulfonic acid (MSA); recovery efficiencies ~100% for Li, Co.	[75]
	Li, Co	Hydrometallurgical-electro dialytic method	Batch extraction of 30% (Co), 69% (Li) using 0.1 M HCl by LiCoO2 dissolution; extraction by compartment electro dialytic cells, and cation-exchange membranes; it yielded a recovery of 62% (Li) and 33% (Co), whereas 80% of Co was electrodeposited at the cathode.	[76]
	Li, Co	Leaching	Cathode leaching using a mixture of citric acid (CA), tartaric acid (TA) and ascorbic acid (AA), to recover the metals; almost complete dissolution of Li, nearly 90% dissolution of Co (80 °C, 6 h).	[77]
	Li, Co	Combination of crushing, ultrasonic washing, acid leaching, and precipitation	Crushing with a 12 mm aperture screen; undersize products ultrasonic washing; filtration through a 2 mm aperture; 4.0 M HCl for 2.0 h, at 80 °C leaching; 97% of Li and 99% of Co recovery.	[78]
	Co, Li2CO3, graphite	Thermodynamical	Thermogravimetry analysis, oxygen-free roasting, and wet magnetic separation used to transfer LiCoO2 and graphite powders to Co, Li2CO3, and graphite.	[79]
	LiCoO2	Leaching, calcination	Separation of Al foil using dimethyl acetamide (DMAC), next the PVDF and carbon elimination by calcining; well-crystallized single phase LiCoO2 without Co3O4 synthesized at 850 °C,12 h.	[80]
	LiCoO2	Suspension analysis	System based on NH4HCO3, (NH4)2SO3, and NaF, where NH4+ represents a complexing agent of NH3.	[81]
	Li, Co	Ammonia leaching	Leaching rate of 91.16% (Co) and 97.57% (Li), using NH3·H2O 120 g/L, NH4HCO3 75 g/L, n (Na2SO3), 80 °C, 240 min.	[82]
Valuable metals (Co, Ni, Mn, Li)	Co, Ni, Mn, Li	Smelting reduction	Li was concentrated and recovered in the flue dust as Li2CO3 and LiF. The absence of a slag allows a nearly 100% recovery of Co, Ni, and Mn (alloy) and a nearly 100% recovery of Li (in flue dust).	[83]
	Co, Ni, Mn, Li	Smelting reduction	Smelting reduction in a pilot-scale Electric Arc Furnace in two trials; Co, Ni, Mn and Li’s yields are 98.2%, 98.4%, 91.5%, and 68.3%, respectively, in Trial I, and 97.9%, 97.7%, 85.3%, and 60,9%, respectively, in Trial II; carbonated water leaching reaches up the purity of Li2CO3 to 95.8%.	[84]
	Co, Ni, Mn, Li	Thermal treatment-ammoniacal leaching	Based on the TG-DSC analysis, cathode material calcined at 300 °C and 550 °C in air atmosphere; Ni, Co, Mn, and Li leached out with efficiencies of 98%, 81%, 92% and 98%, respectively.	[85]
	Co, Ni, Mn, Li, Cu, Al	Wet crushing, screening, and a ternary leaching system	Selective leaching under conditions: leaching time (0–300 min), temperature (40–90 °C), solid-to-liquid ratio (10–50 g/L), and agitation speed (300–700 rpm); almost completely leaching Ni and Cu, hard recovery of Al, leaching for Li (60.53%) and Co (80.99%).	[86]
	Co, Ni, Mn, Li	Leaching and sol-gel method resynthesis	Leaching using 0.4 mol/L DL-malic acid and 0.1 mol/L ascorbic acid; under conditions (70 °C, 30 min, slurry density: 20 g/L), yields: 99.06% (Li), 97.11% (Ni), 96.46% (Co), and 97.22% (Mn).	[87]
	Co, Ni, Mn, Li	Dissolution−chelation mechanism	Leaching by solution (malonic acid, hydrogen peroxide); procedure efficiency reaches 95% (Li), over 98% (Ni, Co, Mn).	[88]
	Co, Ni, Mn, Li	Leaching	Leaching by sulfuric acid leaching liquor (ammonium oxalate, sodium carbonate solution); precipitation using dimethylglyoxime reagent; solvent extraction using D2EHPA; recovery efficiencies as follows: 98.7% (Ni), 97.1% (Mn), 98.2% (Co), and 81.0% (Li).	[60]
	Co, Ni, Mn, Li	Leaching	Recovery from spent LiNi1/3Mn1/3Co1/3O2; the efficiencies for Li, Ni, Co, and Mn reached 99.7% under the optimized conditions of 1 M H2SO4, 1 vol% H2O2, 400 rpm stirring speed, 40 g/L pulp density, and 60 min leaching at 40 °C.	[89]
	Co, Ni, Mn, Li	Leaching	Replacing the oxalates/carbonates of the precipitation process with sulfides; reducing the solubility of Li2CO3 in the Li precipitation step with ethanol; reaching the recycling ratio of 94.9% (Li), 94.5% (Co), 94.4% (Ni), and 95.5% (Mn).	[90]
	Co, Ni, Mn, Li	Leaching	Selective leaching system of NH3–(NH4)2CO3-Na2SO3; for multistage leaching, high recovery of 98.4% (Li), 99.4% (Co), 97.3% (Ni), and a high-purity (>99%) MnCO3 products.	[91]
	Co, Ni, Mn, Li	Hydrothermal	Using (NH4)2SO3 as a reductant in a one-step leaching process; recovery of 100% (Co), 98.3% (Ni), and 90.3% (Li).	[92]
	Li, Fe, P, Al	Physical separation	Discharging of spent LFP batteries in 5 wt% sodium chloride solution for approx. 3 h; extended heat treatment time within the temperature range of 240–300 °C; corona electrostatic separation for metallic particles from the nonmetallic particles.	[93]
	Co, Ni, Mn, Li	Hydrometallurgical	Recycling LiNi0.5Co0.2Mn0.3O2 materials using 0.2 M phosphoric acid and 0.4 M citric acid with a solid to liquid (S/L) ratio of 20 g/L at 90 °C, 30 min; leaching efficiency of ~100% (Li), 93.38% (Ni), 91.63% (Co), and 92.00% (Mn).	[94]
	Co, Ni, Mn, Li	High-temperature calcination, and coprecipitation	Regeneration of a ternary cathode material (LiNi0.6Co0.2Mn0.2O2) using leaching, high-temperature calcination, and coprecipitation procedure; above 97.9% transition-metal elements and 81.2% Li element in the LIBs reused.	[95]
	Co, Ni, Mn, Li	Leaching	Recycling LiNi0.33Mn0.33Co0.33O2 (NMC) using water under strong agitation, and pH-adjusted solutions.	[96]
	Co, Ni, Mn, Li	Extraction and co-precipitation	Extraction by D2EHPA in kerosene—100% (Mn), 99% (Co), and 85% (Ni); Li recovery (purity of 99.2%) from the raffinate as Li2CO3 by precipitation; organic load phase stripped with 0.5 M H2SO4; cathode material directly regenerated from stripping liquor.	[97]
	Co, Ni, Mn, Li	Leaching	Leaching with 1.0 M H2SO4 mixed with 0.62 wt% H2O2 at a liquid-to-solid ratio of 25.8 mL g−1, 51 °C, 60 min results in ∼100% recovery of Li, Ni, Co, and Mn; after leaching precipitation into Ni0.15Mn0.15Co0.70(OH)2, and Li2CO3.	[98]
	Co, Ni, Mn, Li	Leaching	Using of D, L-malic acid for leaching, and as a chelating agent; synthesis of LiNi1/3Co1/3Mn1/3O2 through a sol-gel process (no other chelating reagents).	[99]
	Co, Ni, Mn, Li	Leaching, oxalate co-precipitation, and solid-phase reaction	Preparation of precursor: 50 °C, pH of 1.98, the aging time of 24 h; for calcination 850 °C, 12 h.	[100]
	Co, Ni, Mn, Li	Froth flotation	For multiple stages above 95% of NMC111 in the froth product and 95% of LMO in the tailing product separated.	[101]
	LiNi1/3Co1/3Mn1/3O2	Hydrometallurgy	Dismantling, crushing, leaching and impurity removing; LiNi1/3Co1/3Mn1/3O2 prepared from the leaching solution via co-precipitation followed by solid-state synthesis.	[102]
	Co, Ni, Mn, Li	Leaching	Two-step leaching of the LiNixCoyMnzO2; in the first step, Li and Co selectively leached into oxalic acid at the optimal condition of C2H2O4, 0.25 M, pulp density, 10%, H2O2 dosage, 0.5%, 80 °C, 90 min.; next H2SO4, 3.0 M, pulp density, 6%, H2O2 dosage, 2%, 60 ◦C, 120 min. performed; approximately 99% of all remaining metals leached.	[103]
	Co, Ni, Mn, Li	Leaching	Leaching NMC 811 by using hydrochloric acid (37% w., Sigma Aldrich).	[104]
	Co, Ni, Mn, Li	Leaching, thermal treatment	Solvent method for detaching the current collectors; thermal treatment for removing the polymer binders (PVDF using dissolution with N-methyl pyrrolidone); the polymer solution for carbon separation.	[105]
	Co, Ni, Mn, Li	Leaching	Two-step leaching of the exhausted LiNixCoyMnzO2 with 99% recovery rate; C2H2O4, 0.25 M, pulp density, 10%, H2O2 dosage, 0.5%, 80 °C, 90 min for Li, Co; H2SO4, 3.0 M, pulp density, 6%, H2O2 dosage, 2%, 60 °C, 120 min for other.	[106]
	Co, Ni, Mn, Li Co, Ni, Mn, Li	Leaching	The current collector of Al preforms used as the in-situ reductant of thermite reduction transforming valuable metals of Li, Ni, Co, and Mn were effectively leached into H2SO4 solution with efficiencies of 99.78%, 98.62%, 99.29%, and 99.91%, respectively.	[107]
	Li, Fe, P	Sintering	A direct regeneration from spent LiFePO4 batteries using a solid phase sintering; after dismantling, the cathode plate is soaked in DMAC (30 min, 30 °C, and solid-liquid ratio of 1:20 g mL−1); next regeneration at 600–700 °C.	[108]
	Co, Ni, Mn, Li	Calcination, Dissolution	Scraps regeneration suing solvent dissolution and heating at 800 °C.	[109]
	Co, Ni, Mn, Li	Leaching	Method including sol−gel method for resynthesis, and lactic acid (leaching and chelating agent); under 1.5 mol L−1, solid/liquid ratio of 20 g L−1, 70 °C, H2O2 content of 0.5 vol%, reaction for 20 min, the results: 97.7% (Li), 98.2% (Ni), 98.9% (Co), and 98.4% (Mn).	[110]
	Co, Ni, Mn, Li	Leaching	The recovery process is based on ammonia, ammonium carbonate, and ammonium sulfite. Co and Cu are completely leached out (~100%), whereas Mn and Al are hardly leached (<10%), and Ni with moderate leaching efficiency (30–50%).	[111]
	Co, Ni, Mn, Li	Hydrometallurgy	Process for recovery LiNixMnyCozO2 by applying closed loop recycling; recovery of active cathode material states for over 70% of the battery value.	[112]
	Co, Ni, Mn, Li	Hydrometallurgy	Selectively precipitation using dimethylglyoxime reagent, D2EHPA, ammonium oxalate solution, and saturated sodium carbonate solution. Recovery efficiencies as follows: 98.7% for Ni, 97.1% for Mn, 98.2% for Co, and 81.0% for Li under optimized conditions.	[113]
	Co, Ni, Mn, Li	Mechanical treatment, Chemical leaching	Mechanical treatment for recovering fractions: ferrous metals, non-ferrous metals, and electronic powders; leaching using Cyanex 272 for Ni and Co, D2EHPA for Mn.	[114]
	Co, Ni, Mn, Li	Leaching	The sulfuric acid was combined with H2O2 as a reducing agent; above 99% of valuable metals at 2 M H2SO4, 10 vol.% H2O2, 75 °C, 300 rpm agitation speed, 250 g/5 L solid/liquid ratio, and after 75 min, was recovered. More than 99% of Li and less than 1% of Co were dissolved at 3 M oxalic acid, at 80 °C, 300 rpm agitation speed, 50 g/L initial solid/liquid ratio, and in 90 min.	[115]
	Co, Ni, Mn, Li	Calcination, solvent extraction, fusion	The 5 h long calcination at 500 °C, solvent extraction aimed at 90 wt% recovery yield for Li salts; the H2SO4 and H2O2 evaporation resulted in the high purity Co and Mn sulfates; fusion with KHSO4 at 500 °C for 5 h.	[116]
Graphite (C)	C	Leaching and calcination	Sulfuric acid curing-acid leaching; sequential calcination at 1500 °C, where the XRD, Raman spectroscopy, and SAEM analysis were used; final purity of regenerated graphite around 99.6%.	[117]
Electrolyte	PF6, PO2F2, P, F	Transcritical extraction	Combination of extraction and separation; products of hexafluorophosphate (PF6−), fluoride (F−), and difluorophosphate (PO2F2−) were detected by 19F and 31P.	[118]

Table 5. Overview of the currently used recycling processes and recovery efficiencies.

Section	Recovered Material	Process	Description	Ref.
Cobalt (Co)	Co	Synthesis of Co3S4	Extraction of Co and Ni from the pregnant leach solution (PLS) by a xanthate complex; ammonia solution wash; heat treatment (250 °C, 1 h).	[54]
	Co(II)	Co(II) extraction from chloride using toluene diluted Cyphos IL 102	Co(II) transferred into the organic phase; stripped by 0.05 mol L−1 HCl with 99.9% efficiency in a single stage at O/A 1/1.	[55]
	Co, Cu	Electrodeposition	The instantaneous nucleation mechanism occurs at pH 2.7 and progresses at pH 5.4 for Co electrodeposited multilayer on platinum, vitreous carbon, and Al; the same for Cu electrodeposited on Co.	[56]
	Co, Ni	Solvent extraction	Efficient H2SO4 + H2O2 leaching assisted by diluent heptane and ammonium thiocyanate; reaching factor 372.	[57]
	Co	Carbothermal reduction, magnetic separation	Separation to 53 µm fraction; carbothermal reduction (5–45 min, 500–900 °C); distilled water leaching; magnetic separation of 90% Co.	[58]
	Co	Electrochemical reduction	Molten salt fluidized cathode technique; characterization: voltammograms, chronoamperometry; efficiency 70–80% for the commercial LiCoO2 and upwards of 80% for the spent Li-ion battery.	[59]
	Co, Ni	Leaching	Acid leaching using H2SO4, HNO3, HCl, 1–4 mol L−1, 3–18 h, 25–90 °C, with a solid to liquid ratio fixed at 5% (w/v); the recovery yields of Co and Ni are 100% and 99.99%.	[60]
	Co	Precipitation	The Co(II) hydroxide precipitation; optimal at pH = 9; Co recovery is close to 100% and the filtration flow rate is high.	[61]
	β-Co(OH)2, Co3O4	Precipitation, calcination	Chemical (CP) and electrochemical precipitation (EP); Co3O4 formation by heat-treating β-Co(OH)2 at 450 °C for 3 h.	[62]
	Co(OH)2, Co3O4	Leaching	The Co(OH)2 is electrodeposited onto conductive glass using−0.85 V, 20 C cm−2, with an efficiency of 66.67%; Co3O4 is obtained by heat treatment at 450 °C after 3 h, with an efficiency of 64.29%.	[63]
	Co	Leaching	Acidic dissolution of LiCoO2; next electrodeposition on steel to Co3O4.	[64]
	Co	Synthesis	Recovery using 3D sea-urchin-like cobalt nitride composite material (CoN-Gr-2) used as a bi-functional catalyst for water splitting; potentials of 128.9 mV and 280 mV for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively.	[65]
Lithium (Li)/Lithium Cobalt Oxide (LiCoO2)/ Cobalt (Co)	Li	Separation from solution	The maximum uptake range 20–25 mg Lig−1 reached for Amberlite IR 120 resin and molecular sieve 13X.	[66]
	Li2CO3, Li3PO4	Precipitation	Two-stage precipitation process using Na2CO3 and Na3PO4, with recovery rates of 74.72% and 92.21%, respectively.	[67]
	LiCoO2	Metal-based leaching	Leaching by Co2+ or Mn2+; 95% Li recovery rate and no metal-ions in the leachate.	[68]
	LiCoO2	Eco-friendly leaching	Resynthesis of cathode materials using oxalic acid; 90.13% purity of Li.	[69]
	LiCoO2	Leaching	Using H2SO4 and HCl as leaching agents; optimal 2 M HCl, 60–80 °C, for 90 min.	[70]
	Li2CO3	Low Li high-salt solution	Li precipitation by P; Li3PO4 anolyte dissolution, electrodialysis with cation-exchange membranes used for Li, and P separation with P/Li mass ratio 0.23; Li2CO3 precipitation rate reached 88.3%.	[71]
	LiCoO2	Structure restoration	LiCoO2 powder and Li salts sintering to layered structure; Li2CO3 addition; calcination at a temperature of 800 °C; coating with nanosized Al2O3 particles for performance improvement.	[72]
	Li, Co	Ultrasonic-assisted leaching	Recovery of 96% Co and nearly 100% Li by using 0.5 M citric acid with 0.55 M H2O2, a solid-to-liquid ratio of 25 g L−1, a temperature of 60 °C, 5 h, and ultrasonic power of 90 W.	[73]
	Li, Co	Leaching	Leaching using oxalic acid (H2C2O4) at 0.46 M at 100 °C; addition of hydrogen peroxide (H2O2) resulted in a 33% of activation energy, and 50% of energy consumption reduction.	[74]
	Li, Co	Leaching	Leaching using biodegradable organic methane sulfonic acid (MSA); recovery efficiencies ~100% for Li, Co.	[75]
	Li, Co	Hydrometallurgical-electro dialytic method	Batch extraction of 30% (Co), 69% (Li) using 0.1 M HCl by LiCoO2 dissolution; extraction by compartment electro dialytic cells, and cation-exchange membranes; it yielded a recovery of 62% (Li) and 33% (Co), whereas 80% of Co was electrodeposited at the cathode.	[76]
	Li, Co	Leaching	Cathode leaching using a mixture of citric acid (CA), tartaric acid (TA) and ascorbic acid (AA), to recover the metals; almost complete dissolution of Li, nearly 90% dissolution of Co (80 °C, 6 h).	[77]
	Li, Co	Combination of crushing, ultrasonic washing, acid leaching, and precipitation	Crushing with a 12 mm aperture screen; undersize products ultrasonic washing; filtration through a 2 mm aperture; 4.0 M HCl for 2.0 h, at 80 °C leaching; 97% of Li and 99% of Co recovery.	[78]
	Co, Li2CO3, graphite	Thermodynamical	Thermogravimetry analysis, oxygen-free roasting, and wet magnetic separation used to transfer LiCoO2 and graphite powders to Co, Li2CO3, and graphite.	[79]
	LiCoO2	Leaching, calcination	Separation of Al foil using dimethyl acetamide (DMAC), next the PVDF and carbon elimination by calcining; well-crystallized single phase LiCoO2 without Co3O4 synthesized at 850 °C,12 h.	[80]
	LiCoO2	Suspension analysis	System based on NH4HCO3, (NH4)2SO3, and NaF, where NH4+ represents a complexing agent of NH3.	[81]
	Li, Co	Ammonia leaching	Leaching rate of 91.16% (Co) and 97.57% (Li), using NH3·H2O 120 g/L, NH4HCO3 75 g/L, n (Na2SO3), 80 °C, 240 min.	[82]
Valuable metals (Co, Ni, Mn, Li)	Co, Ni, Mn, Li	Smelting reduction	Li was concentrated and recovered in the flue dust as Li2CO3 and LiF. The absence of a slag allows a nearly 100% recovery of Co, Ni, and Mn (alloy) and a nearly 100% recovery of Li (in flue dust).	[83]
	Co, Ni, Mn, Li	Smelting reduction	Smelting reduction in a pilot-scale Electric Arc Furnace in two trials; Co, Ni, Mn and Li’s yields are 98.2%, 98.4%, 91.5%, and 68.3%, respectively, in Trial I, and 97.9%, 97.7%, 85.3%, and 60,9%, respectively, in Trial II; carbonated water leaching reaches up the purity of Li2CO3 to 95.8%.	[84]
	Co, Ni, Mn, Li	Thermal treatment-ammoniacal leaching	Based on the TG-DSC analysis, cathode material calcined at 300 °C and 550 °C in air atmosphere; Ni, Co, Mn, and Li leached out with efficiencies of 98%, 81%, 92% and 98%, respectively.	[85]
	Co, Ni, Mn, Li, Cu, Al	Wet crushing, screening, and a ternary leaching system	Selective leaching under conditions: leaching time (0–300 min), temperature (40–90 °C), solid-to-liquid ratio (10–50 g/L), and agitation speed (300–700 rpm); almost completely leaching Ni and Cu, hard recovery of Al, leaching for Li (60.53%) and Co (80.99%).	[86]
	Co, Ni, Mn, Li	Leaching and sol-gel method resynthesis	Leaching using 0.4 mol/L DL-malic acid and 0.1 mol/L ascorbic acid; under conditions (70 °C, 30 min, slurry density: 20 g/L), yields: 99.06% (Li), 97.11% (Ni), 96.46% (Co), and 97.22% (Mn).	[87]
	Co, Ni, Mn, Li	Dissolution−chelation mechanism	Leaching by solution (malonic acid, hydrogen peroxide); procedure efficiency reaches 95% (Li), over 98% (Ni, Co, Mn).	[88]
	Co, Ni, Mn, Li	Leaching	Leaching by sulfuric acid leaching liquor (ammonium oxalate, sodium carbonate solution); precipitation using dimethylglyoxime reagent; solvent extraction using D2EHPA; recovery efficiencies as follows: 98.7% (Ni), 97.1% (Mn), 98.2% (Co), and 81.0% (Li).	[60]
	Co, Ni, Mn, Li	Leaching	Recovery from spent LiNi1/3Mn1/3Co1/3O2; the efficiencies for Li, Ni, Co, and Mn reached 99.7% under the optimized conditions of 1 M H2SO4, 1 vol% H2O2, 400 rpm stirring speed, 40 g/L pulp density, and 60 min leaching at 40 °C.	[89]
	Co, Ni, Mn, Li	Leaching	Replacing the oxalates/carbonates of the precipitation process with sulfides; reducing the solubility of Li2CO3 in the Li precipitation step with ethanol; reaching the recycling ratio of 94.9% (Li), 94.5% (Co), 94.4% (Ni), and 95.5% (Mn).	[90]
	Co, Ni, Mn, Li	Leaching	Selective leaching system of NH3–(NH4)2CO3-Na2SO3; for multistage leaching, high recovery of 98.4% (Li), 99.4% (Co), 97.3% (Ni), and a high-purity (>99%) MnCO3 products.	[91]
	Co, Ni, Mn, Li	Hydrothermal	Using (NH4)2SO3 as a reductant in a one-step leaching process; recovery of 100% (Co), 98.3% (Ni), and 90.3% (Li).	[92]
	Li, Fe, P, Al	Physical separation	Discharging of spent LFP batteries in 5 wt% sodium chloride solution for approx. 3 h; extended heat treatment time within the temperature range of 240–300 °C; corona electrostatic separation for metallic particles from the nonmetallic particles.	[93]
	Co, Ni, Mn, Li	Hydrometallurgical	Recycling LiNi0.5Co0.2Mn0.3O2 materials using 0.2 M phosphoric acid and 0.4 M citric acid with a solid to liquid (S/L) ratio of 20 g/L at 90 °C, 30 min; leaching efficiency of ~100% (Li), 93.38% (Ni), 91.63% (Co), and 92.00% (Mn).	[94]
	Co, Ni, Mn, Li	High-temperature calcination, and coprecipitation	Regeneration of a ternary cathode material (LiNi0.6Co0.2Mn0.2O2) using leaching, high-temperature calcination, and coprecipitation procedure; above 97.9% transition-metal elements and 81.2% Li element in the LIBs reused.	[95]
	Co, Ni, Mn, Li	Leaching	Recycling LiNi0.33Mn0.33Co0.33O2 (NMC) using water under strong agitation, and pH-adjusted solutions.	[96]
	Co, Ni, Mn, Li	Extraction and co-precipitation	Extraction by D2EHPA in kerosene—100% (Mn), 99% (Co), and 85% (Ni); Li recovery (purity of 99.2%) from the raffinate as Li2CO3 by precipitation; organic load phase stripped with 0.5 M H2SO4; cathode material directly regenerated from stripping liquor.	[97]
	Co, Ni, Mn, Li	Leaching	Leaching with 1.0 M H2SO4 mixed with 0.62 wt% H2O2 at a liquid-to-solid ratio of 25.8 mL g−1, 51 °C, 60 min results in ∼100% recovery of Li, Ni, Co, and Mn; after leaching precipitation into Ni0.15Mn0.15Co0.70(OH)2, and Li2CO3.	[98]
	Co, Ni, Mn, Li	Leaching	Using of D, L-malic acid for leaching, and as a chelating agent; synthesis of LiNi1/3Co1/3Mn1/3O2 through a sol-gel process (no other chelating reagents).	[99]
	Co, Ni, Mn, Li	Leaching, oxalate co-precipitation, and solid-phase reaction	Preparation of precursor: 50 °C, pH of 1.98, the aging time of 24 h; for calcination 850 °C, 12 h.	[100]
	Co, Ni, Mn, Li	Froth flotation	For multiple stages above 95% of NMC111 in the froth product and 95% of LMO in the tailing product separated.	[101]
	LiNi1/3Co1/3Mn1/3O2	Hydrometallurgy	Dismantling, crushing, leaching and impurity removing; LiNi1/3Co1/3Mn1/3O2 prepared from the leaching solution via co-precipitation followed by solid-state synthesis.	[102]
	Co, Ni, Mn, Li	Leaching	Two-step leaching of the LiNixCoyMnzO2; in the first step, Li and Co selectively leached into oxalic acid at the optimal condition of C2H2O4, 0.25 M, pulp density, 10%, H2O2 dosage, 0.5%, 80 °C, 90 min.; next H2SO4, 3.0 M, pulp density, 6%, H2O2 dosage, 2%, 60 ◦C, 120 min. performed; approximately 99% of all remaining metals leached.	[103]
	Co, Ni, Mn, Li	Leaching	Leaching NMC 811 by using hydrochloric acid (37% w., Sigma Aldrich).	[104]
	Co, Ni, Mn, Li	Leaching, thermal treatment	Solvent method for detaching the current collectors; thermal treatment for removing the polymer binders (PVDF using dissolution with N-methyl pyrrolidone); the polymer solution for carbon separation.	[105]
	Co, Ni, Mn, Li	Leaching	Two-step leaching of the exhausted LiNixCoyMnzO2 with 99% recovery rate; C2H2O4, 0.25 M, pulp density, 10%, H2O2 dosage, 0.5%, 80 °C, 90 min for Li, Co; H2SO4, 3.0 M, pulp density, 6%, H2O2 dosage, 2%, 60 °C, 120 min for other.	[106]
	Co, Ni, Mn, Li Co, Ni, Mn, Li	Leaching	The current collector of Al preforms used as the in-situ reductant of thermite reduction transforming valuable metals of Li, Ni, Co, and Mn were effectively leached into H2SO4 solution with efficiencies of 99.78%, 98.62%, 99.29%, and 99.91%, respectively.	[107]
	Li, Fe, P	Sintering	A direct regeneration from spent LiFePO4 batteries using a solid phase sintering; after dismantling, the cathode plate is soaked in DMAC (30 min, 30 °C, and solid-liquid ratio of 1:20 g mL−1); next regeneration at 600–700 °C.	[108]
	Co, Ni, Mn, Li	Calcination, Dissolution	Scraps regeneration suing solvent dissolution and heating at 800 °C.	[109]
	Co, Ni, Mn, Li	Leaching	Method including sol−gel method for resynthesis, and lactic acid (leaching and chelating agent); under 1.5 mol L−1, solid/liquid ratio of 20 g L−1, 70 °C, H2O2 content of 0.5 vol%, reaction for 20 min, the results: 97.7% (Li), 98.2% (Ni), 98.9% (Co), and 98.4% (Mn).	[110]
	Co, Ni, Mn, Li	Leaching	The recovery process is based on ammonia, ammonium carbonate, and ammonium sulfite. Co and Cu are completely leached out (~100%), whereas Mn and Al are hardly leached (<10%), and Ni with moderate leaching efficiency (30–50%).	[111]
	Co, Ni, Mn, Li	Hydrometallurgy	Process for recovery LiNixMnyCozO2 by applying closed loop recycling; recovery of active cathode material states for over 70% of the battery value.	[112]
	Co, Ni, Mn, Li	Hydrometallurgy	Selectively precipitation using dimethylglyoxime reagent, D2EHPA, ammonium oxalate solution, and saturated sodium carbonate solution. Recovery efficiencies as follows: 98.7% for Ni, 97.1% for Mn, 98.2% for Co, and 81.0% for Li under optimized conditions.	[113]
	Co, Ni, Mn, Li	Mechanical treatment, Chemical leaching	Mechanical treatment for recovering fractions: ferrous metals, non-ferrous metals, and electronic powders; leaching using Cyanex 272 for Ni and Co, D2EHPA for Mn.	[114]
	Co, Ni, Mn, Li	Leaching	The sulfuric acid was combined with H2O2 as a reducing agent; above 99% of valuable metals at 2 M H2SO4, 10 vol.% H2O2, 75 °C, 300 rpm agitation speed, 250 g/5 L solid/liquid ratio, and after 75 min, was recovered. More than 99% of Li and less than 1% of Co were dissolved at 3 M oxalic acid, at 80 °C, 300 rpm agitation speed, 50 g/L initial solid/liquid ratio, and in 90 min.	[115]
	Co, Ni, Mn, Li	Calcination, solvent extraction, fusion	The 5 h long calcination at 500 °C, solvent extraction aimed at 90 wt% recovery yield for Li salts; the H2SO4 and H2O2 evaporation resulted in the high purity Co and Mn sulfates; fusion with KHSO4 at 500 °C for 5 h.	[116]
Graphite (C)	C	Leaching and calcination	Sulfuric acid curing-acid leaching; sequential calcination at 1500 °C, where the XRD, Raman spectroscopy, and SAEM analysis were used; final purity of regenerated graphite around 99.6%.	[117]
Electrolyte	PF6, PO2F2, P, F	Transcritical extraction	Combination of extraction and separation; products of hexafluorophosphate (PF6−), fluoride (F−), and difluorophosphate (PO2F2−) were detected by 19F and 31P.	[118]

The rest of the publications were devoted to specialized methods describing the possibilities of application of reused outputs, recovery of various materials, or characterizing the selected state. They are described individually in the following sections.

Active Anode Materials

Part of the publications deals with the issue of active anode materials. Yang et al. [119] presented a study of roasting treatment for removing impurities of a spent carbon cathode (SCC) and its application as the anode material used in terms of LIBs. The obtained anode shows a reversible capacity of 365.5 mAh g⁻¹ at 0.1 C after 100 cycles with a decay rate per cycle of 0.028%. In a work published by Wei et al. [120], a preposition strategy for silicon/carbon nanofibers/carbon (Si/CNF/C) composite for LIBs, based on micron-sized Si and waste high-density polyethylene (HDPE) as raw materials, was introduced. According to the results, the composite provides an initial coulombic efficiency of 82.2% and a reversible capacity of 937 mAh g⁻¹ (1685 mAh g⁻¹ based on Si) after 100 cycles at a current density of 100 mA g⁻¹. In the following study, Shen et al. [121] prepared a carbon paper coated with recycled Si and pitch powder (CP-RSP). For the stabilization, 250 °C in air and carbonization at 1000 °C in an N₂ atmosphere were used. The obtained CP-RSP represents the role of the current collector and the active anode material of LIBs. Electrodes with 2.5, 5, and 10 wt.% Si exhibited capacity increases of 94, 129, and 41%, respectively (compared to the silicon-free electrode). Huang et al. [121] investigated the possibility of reusing spent graphite as anode material for LIBs and SIBs. The recovered graphite delivers a capacity of 427.9 mAh g⁻¹ after 200 cycles at 0.5 C and displays an outstanding rate capability (a capacity of 114.9 mAh g⁻¹ is achieved at 3 C). Further, according to Ruan et al. [122], the recovery graphite from spent LIBs was used as a carbon carrier and doped with N and Fe via simple pyrolysis with polyaniline and iron salt. This graphite was used to prepare the ORR electrocatalyst applied in fuel cells. In another work, Bai et al. [123] separated the electrode materials from their current collectors using ethylene glycol; the recovered collectors were intact without corrosion. In another case, Corneal et al. [124] developed used acid baths to separate the active anode materials from the Co foils. Complete separation was reported within 35 s by using 0.5 mol/L of sulfuric acid (H₂SO₄) and a temperature of 40 °C.

Manganese Recovery

In other cases, studies have focused on the recovery of Mn and its compounds. Keller et al. [125] performed solvent extraction of Mn in a lab-scale DN50 pulsed disc and doughnut column. For optimal conditions, 100 g/L D2EHPA (di-(2-ethylhexyl) phosphoric acid) was used as a liquid ion exchanger. In performance tests with 0.01 mol/L MnSO₄ solution, a maximum extraction yield of 94% Mn was achieved. Using LiAlO₂ seems suitable for recovering Li from LIBs slags [126]. Thus, Wittkowski et al. [127] focused on the characterization of slags of the system Li₂O-CaO-SiO₂-Al₂O₃-MgO-MnO_x, including up to 17 moL% MnO₂ content. According to their research based on plasma optical emission spectrometry (ICP-OES), X-ray diffraction (XRD), electron probe microanalysis (EPMA), etc., the Mn-rich grains are presented as idiomorphic and relatively large (>50 µm) crystals. Wang et al. [128] examined the direct recycling process for a cathode scrap; their procedure is based on sulfate radical-based advanced oxidation processes (SR-AOPs) and provides a complex synthesis. The results show that the cathode scrap includes high efficiency for peroxymonosulfate (PMS) activation, whereas the ortho-phenyl phenol (OPP) degradation still reached 94.8% after ten cycles. In conformity with heterogeneous catalyst thermal regeneration strategies, Poyraz. et al. [129] provided a sustainable manganese-based material, where binder-free self-supporting (BFSS) electrodes use a fibrous, high aspect ratio MnO₂ active material. After 200 discharge–charge cycles, the reuse-based BFSS electrodes showed crystallinity and oxidation state of the manganese centers on a similar level as new BFSS cathodes.

Lithium Iron Phosphate (LFP) Batteries

A wide range of current research on lithium-ion battery technology focuses only on the LFP type. The same was the case with Shin et al. [130], who presented a green process to recycle LiFePO₄/C electrode materials by using a precursor of a crystalline FePO₄·2H₂O phase (metastrengite I). According to their calcination heat treatment, cathode materials are synthesized at 700 °C and deliver a maximum discharge capacity of 168.51 mAh g⁻¹ at 0.1 C with a capacity retention of 99.36% after the 25th cycle at 1 C. The rest of their study compares their results to the commercially available LiFePO₄ powders. An approach for reusing the spent LFP electrodes was introduced by Gangaja et al. [131]. Regenerated LiFePO₄ as LIB half-cells reveal a capacity of 145 mAh/g at 1 C and 107 mAh/g at 10 C and 96% capacity retention at 5 C for 300 cycles. Other experiments performed by Li et al. [132] were devoted to direct recycling; through this procedure, high purity of cathode material, including LiFePO₄ and acetylene black, anode material based on graphite and acetylene black, and other process by-products such as shell, Al foil, Cu foil, and electrolyte solvents were obtained. The regenerated cathode material mixture regenerated at 650 °C, meeting the reuse requirement for middle-end LIBs. In the procedure presented by Liang et al. [133], spent LFP cathode material was regenerated through Li/Fe/P elements compensation, and its structure was reshaped via the heat treatment method in the temperature range of 450–650 °C. Given their results, the material is restored to the initial conditions; its surface and particle sizes are smooth and sufficiently small.

Organic Binders

Organic binders play a crucial role in LIBs’ composition; they are responsible for the active material particles’ strong connection between the electrodes and the metal contacts. Regardless, their use causes significant difficulty in extracting pure electrode materials. High-temperature treatment such as pyrolysis or incineration is being executed for their removal and separation; this approach leads to fluorinated exhaust gas emissions. Fu et al. [134] devoted themselves to extraction based on supercritical carbon dioxide (SC CO₂) combined with a cosolvent dimethyl sulfoxide in the case of liberation of the cathode materials from Al foil. The results show that 98.5 wt% polyvinylidene fluoride (PVDF) dissolves in the SC CO₂ dimethyl sulfoxide system under the optimum conditions: 70 °C, 80 bar pressure after 13 min. In another approach introduced by Hanisch et al. [135], the PVDF binder thermal decomposition was performed to weaken the adhesion between coating and foil. Moreover, they provided a laboratory-scale ANVIIL separation process (Adhesion Neutralization via Incineration and Impact Liberation). According to their results, 97.1% w/w of the electrode materials were regained with Al impurities 0.1% w/w.

Aluminum (Al) Foils

Other studies focused on the processing of Al foil. Chu et al. [136] separated positive active materials from Al foil, while the foil can be kept intact. This procedure targets prior high Li recovery. The examination of the ultrasonic-assisted acid scrubbing method for coating materials and Al foils separation was published by Chen et al. [137]. About 99%, 100%, and 46% coating materials can be detached in sulfuric acidic, oxalic acidic, and pure water medium, respectively, whereas the Al foils had a corresponding purity of 98%, 99%, and 15%.

Valuable Metals

Recovered valuable metals (Co, Li, Mn, and Ni) are reused in producing the active materials for the new LIBs. Yang et al. [138] dealt with preparing the next-generation high-performance phosphate cathode materials and examined a high voltage/energy and long-life LiFe_0.6Mn_0.4PO₄/C (LFMP/C) composite. It offers a capacity of 141.3 mAh/g at 0.1 C and 104.9 mAh/g at a high rate of 10 C, and shows a long cycle life, e.g., 86.4% capacity over 400 cycles at 1 C. Further, Sloop et al. [139] introduced an approach to producing low-cost, recycled, battery-grade electrode material. This soft-chemical treatment leads to NCM 523 and NCM 622 LIBs with a performance equivalent to the originally manufactured ones. Zheng et al. [140] exhibited four representative recycling streams to generate consistent quality cathode material of NMC111. The precursors and the cathodes show similar morphology, particle size, and tap density; the capability of recovered NMC111s was better than for a commercial NMC111.

Others (Not Specified)

The following publications were devoted to specialized, unclassified research: Liu at el. [141] proposed the reuse of Si and lignin waste from photovoltaics (PV) and the traditional paper industry to fabricate high-capacity silicon/carbon (Si/C) anode materials for LIBs using electrostatic attracting force and thermal process. The obtained Si/C composite displayed an initial charge capacity of 1016.8 mAh/g, a high-capacity retention of 74.5% at 0.2 A/g after 100 cycles. Hou et al. [142] recycled waste Cu scraps in the form of CuCl powders via the facile hydrothermal route considering its high economic value added (EVA) characteristic. After a series of characterization procedures, including scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD), the reversible discharge capacity of CuCl powders as the active anode material was determined. It was about 171.8 mAh/g at 2.0 C even after 50 cycles. Zhang et al. [143] studied the adsorption of spent LFP and LMO cathodes as adsorbents toward heavy metals in water in terms of adsorption time, initial adsorbate concentrations, and co-existing ions on adsorption kinetics. According to the results, LFP adsorption capacities were 44.28, 39.54, 25.63, and 27.34 mg g⁻¹ for Cu²⁺, Pb²⁺, Cd²⁺, and Zn²⁺, respectively; in the case of LMO, similar adsorption capacities were achieved (32.51, 31.83, 26.24, and 25.25 mg/g, respectively).

In a work by Siebenhofer et al. [144], the liquid membrane permeation with supported flat sheet membranes was examined. The stability and accuracy of supported liquid membranes (SLM) for LIBs materials were evaluated; it was performed in accordance with the HDEHPA test system. The optimum concentration for the transport of Co through the SLM with LIX 84 (hydroxy-5-nonylacetophenonxime) was found to be 10 wt.%. The other work of Zhang et al. [145] was devoted to the pyrolysis kinetics of cathode material using various methods, including Flynn–Wall–Ozawa (FWO), Friedman, Kissinger–Akahira–Sunose, Starink, Tang, and Boswell. The Coats–Redfern inspected the thermal degradation mechanism. In compliance with the thermogravimetric analysis, three stages of mass losses of cathode material decomposition (1.51%, 0.787%, and 0.449%) were established. Kim et al. [146] investigated using collected silicon oxides (SiO_x) condensed particles from Si vapors from the ingot-growing furnace as another method for green production of active anode material for LIBs. Different characterization analyses, such as FE-SEM, TEM, EDS, XRD, and XPS, were completed. A cycle with 40.6% efficiency of the produced material was determined under charge and discharge tests in 100 cycles, 0.2 C for the first three cycles and 1.0 C for the remaining 97. Further, Chen et al. [147] converted the recycled LCO from spent LIBs into an efficient electrocatalyst for oxygen evolution reaction (OER). After 500 cycles, a current density for the electrocatalyst of 9.68 mA cm⁻² at 1.65 V was determined. Beheshti et al. [148] introduced secondary Al production as an acceptable process for recycling spent LIBs. The study focused on recovering Al, Co, and Li from mixed waste streams and Al scrap.

In another work, Hoshino et al. [149] developed a procedure for Li recovery from seawater by electrodialysis using a Li separation membrane with the ionic liquid PP13-TFSI. This method suits seawater desalination and Li dissolution regarding recycling spent LIBs. Bae et al. [150] devoted their research to the waste-to-lithium system based on an electrochemical reaction with water and Li precursors, such as LiOH and Li₂CO₃, executed at room temperature. The obtained Li metals have a high purity (over 99%), and the produced Li₂CO₃ is phase-pure without any remarkable secondary phase. Sobianowska-Turek et al. [151] discussed the situation in the market of portable LIBs in the European Union (EU), focusing on Polish waste treatment management systems and disposal solutions. The work critically described current problems and deficiencies in the approaches to the end-of-life procedures for waste batteries and accumulators in the conditions of Poland and introduced possible future solutions. Peng et al. [152] studied metals’ purification, recovery, and reuse from spent LIBs with high efficiency and low costs. During their experiments, they removed target impurities from a solution individually: Fe and Al were removed by changing the pH value; Co was purified using selective electrodeposition technology and solvent extraction. Next, they co-precipitated obtained products and synthesized them for the final comparison of the LNCM-R and LNCM-N. Renault et al. [153] introduced the environmentally friendly process of recycling Li from organic electrode materials for secondary used LIBs. Over 99% of the recovered material’s capacity can be reached by this process when comparing the second applied battery with the original one. The results were achieved by a dimethyl carbonate/lithium bis(trifluoromethanesulfonyl)imide electrolyte. Asari et al. [154] provided a chemical analysis questionnaire survey and flow analysis results regarding Co recovery under LIBs recycling conditions in Japan. Jo et al. [155] initiated an efficient direct physical and combined metallurgical recycling procedure to lower LIBs’ environmental burden. The electrochemical performance of the active electrode material based on the recovered materials is similar to commercially available ones. Rouhi et al. [156] performed a systematic work devoted to the behavior of LIBs during discharge in salt solutions. The result shows that the voltage recovery effect is not stable and adequate and can cause risks during further processing. Moreover, the methodology to lower open circuit voltage in an aqueous salt solution to 2.0 V, which is acceptable for mechanical processing, is provided.

3.1.4. Life Cycle Analysis (LCA) Study

Life Cycle Assessment, also known as Life Cycle Analysis (LCA) study, represents a methodology designed for assessing environmental impacts during all the stages of the life cycle of commercial products, processes, or services. It describes environmental aspects and potential consequences that are assessed during the raw material extraction and processing (cradle), through manufacturing, distribution, and use, to the End-of-Life (EOL) activities such as recycling and final disposal of the material compositing (grave). The LCA stages diagram is illustrated in Figure 5. The main aim of the LCA study is to document and provide the lifelong overall environmental profile of the selected product [157,158].

Many attempts were conducted to standardize LCAs to deliver an objective and comparable result in study cases. Nowadays, widely recognized procedures for assessing LCA are included in the 14,000 series of environmental management standards of the International Organization for Standardization (ISO) in:

• ISO 14,040—that provides the ‘principles and framework’ of the Standard, and in simple terms, is written for a managerial audience,
• ISO 14,044—that offers concepts of the ‘requirements and guidelines’ typically used by practitioners [159].

On the contrary, limiting and introducing one unique LCA method would reduce the quality of the obtained results, and the complete assessment would be affected and not comprehensive. Therefore, the standards describe two main types of approaches:

• Attributional LCA—attempts to answer ‘how and which impacts are flowing within the chosen temporal window?’,
• Consequential LCA—tries to answer ‘how will they flow beyond the immediate system change in response to our decisions?’ [160].

As it is clear from the definition and characteristics of LCA, the studies are not performed at the same level; therefore, they cannot be mutually compared. The executed methodology, the boundaries case set, and the primary work intent are considered for each LCA individually. A total of five publications dealing with life cycle issues of LIBs from EVs were evaluated using the performed literature search (three Articles and two Proceedings Papers.

A comprehensive and complex work devoted to the life cycle assessment of different types of LIBs during their recycling processes was presented by Mohr et al. [161]. They focused on four different cell chemistries—NCA, NMC, LFP, and the emerging sodium-ion battery (SIB) technology. In their work, three different recycling techniques of spent LIBs were set in contrast:

• Two basic kinds of recycling treatments, the pyrometallurgical and hydrometallurgical one, based on secondary inventory data from the current state-of-the-art LCA models,
• One advanced hydrometallurgical technique modeled on the first-hand data obtained from industry.

Considered process flows are shown in Figure 6 and are described in more detail in the complete form of this work [161]. Details of individual technologies of the mentioned recycling processes are summarized in the first part of this literature review devoted to recycling technologies of spent LIBs from EVs [5].

Obtained results are presented in three branches: production, recycling, and net impact. Because, by interpreting the results, associated uncertainties need to be considered, detailed sensitivity analysis mapping future progression is included [161].

According to that, NMC production causes the lowest GWP per 1 kWh capacity (75.50 kg CO₂-Eq), followed by NCA, LFP LIBs, and SIB. Battery cell manufacturing represents the most significant part of the production GWPs for each chemistry type. The cathode material is a serious producer of the total GWP as abiotic resource depletion potential (ADP) for LIBs (especially NMC and NCA). The highest recycling benefits are obtained for processing components that have a high impact during primary production, such as copper, nickel, cobalt, and, considering the GWP aspects, aluminum. This, and considering ADP aspects, is shown in Figure 7. The advanced hydrometallurgical method presented in this work has the highest benefit in all cases due to the additionally recovered graphite and electrolyte [161].

Following this assessment, the highest recycling benefits and lowest net impacts for NCM and NCA LIBs were indicated. Benefits for LFP LIBs and SIB reach comparable low levels considering the similar impact criteria. Further, the GWP and ADP production is significantly affected by the procedure of the used recycling method. Moreover, this work includes a short review of existing LCAs on LIBs recycling used as a state-of-the-art base for model parametrization [161].

Unterreiner et al. [162] provided standard-based LCA devoted to the environmental impacts of recycling and material reuse of three types of batteries: lead-acid, LIBs, and vanadium redox flow. In this study, the reusing of materials is considered in a closed-loop production (cradle-to-cradle), where the EOL disposal step for products is replaced by recycling. This method is used to minimize the impacts of the products by employing principles of sustainable production, operation, and practices; it means that the materials that can be reused are counted as a benefit during the LCA study implementation [162].

The presented evaluation is based on Life Cycle Inventory (LCI) Analysis, which includes material production, energy consumption, energy losses, and transport requirements. For the interpretation, the Life Cycle Impact Assessment (LCIA), based on the categories from the ReCiPe2008 method, was used. Study categories were converted to ecological points, including waste management such as recycling, incineration, or landfilling in the recycling phase [162].

The results show that the LIBs have the lowest ecological impact compared to the other examined technologies. Nevertheless, this impact could still decrease by more than 20%. Moreover, around 62% of LIB materials are currently reusable. However, Li is not counted and reused due to economic reasons. According to the study, the recycling and reuse of Li would have a small ecological impact [162].

In the study by Gaines et al. [163], the life cycle energy performance analysis of LIBs from plug-in hybrid electric vehicle PHEV-20 was discussed. Due to the results, the environmental impacts of the cradle-to-gate cycle (it means the part of the product life cycle from material extraction to the factory gate but before the transport to the final consumer) is small, corresponding to a few percent. Further, recycling battery materials can potentially reduce the production energy by about 50%. Results are presented in the form of energy data comparable to GHG or can be used further for GHG calculation [163].

Dunn et al. inducted a series of publications [26,164,165] devoted to the environmental perspective of automotive LIBs. These issues are entirely examined in the detailed LCA [164], and potential hot spots within the life cycle for five cathode materials and a lithium anode are identified. Notwithstanding, the NMC cathode material production is over three times more energy intensive than LFP, and its energy density is, on average, 1.5 times higher. The results specify that less cathode material is needed in the battery with the more energy-dense cathode; thus, the overall battery mass is lower. It yields a lower cradle-to-gate GHG and energy intensity. Moreover, this work presents a GHG emission comparison of electric and well-to-wheels conventional vehicles (CV) [164].

The LCA of a new promising type of LIBs for EVs based on lithium cobalt phosphate (LCP) chemistry was executed by Raugei et al. [166]; the study focused on CED and GHG. As with other chemistry types, the cathode is the main contributor to high CED (higher than 60%) and GHG (at least ~70%; this percentage represents the cradle-to-gate scenario). According to the results, the inclusion of the EOL treatment steps leads to a mild marginal reduction of the total CED (2%) and a larger relative reduction of GHG emission (8%) [166].

3.2. Economic Perspective

Few publications deal with the economic questions of LIBs technology; four Reviews, four Proceedings Papers, and six Articles were described as part of this review. A comprehensive view of LIBs within their circular economy (CE) is often evaluated, or techniques’ financial costs and returns are assessed and compared. For more detailed analyses leading to the determination of the exact financial burden or benefits of recycling LIBs, e.g., in a selected location or for a designated technology, it will be necessary to carry out many other research steps.

Reusing and recycling of spent LIBs was reviewed in the work by Pagliaro et al. [167], which brings insight into the concept of circular economy (CE). The work simply describes the mechanisms of the recycling process and provides an overview devoted to renewable electricity storage on the world-wide scale. In more detail, the CE is discussed by Mossali et al. [168]; they provided a literature review of current-state opportunities of recycling treatments and, moreover, an overview of valid patents related to industrial recycling processes. Velázquez-Martínez et al. [10] offered an analysis of recycling technologies from a CE perspective focused to the industrial field. The work describes the industrial recycling mechanisms of nine companies and laboratory processing suggested by Aalto University in detail. Moreover, the work provides graphic representations of all processes and discusses the efficiency and quality of the recovery outputs. The companies and their forms of output materials based on Co, Li, and other metals are listed in

Table 6. Recovery materials of nine recycling companies with their specified form of output. Reprinted and edited from Batteries, Vol. 5, Velázquez-Martínez et al. [10], A critical review of lithium-ion battery recycling processes from a circular economy perspective, no 4., Copyright (2022), distributed under Creative Commons Attribution License.

Process Company	Forms of Output Materials
	Co	Li	Fe	Al, Cu Foils	Loses
Umicore ValéasTM	CoCl2	x	Recovered in alloy	Recovered in alloy	Al, polymer
Sumitomo-Sony	CoO	x	Recovered in alloy	Recovered in alloy	Al, polymer
Retriev Technologies	MeO + cake	Li2CO3	Recovered in shaking table	Not specified	Not specified
Recupyl Valibat	LCO/Co(OH)2/Co	Li2CO3/ Li3 PO4	Recovered with magnetic separator	Al, Cu recovered with density separation	Not specified
Akkuser	Co + graphite	x	Recovered with magnetic separator	Al, Cu recovered from fin powder	Al fraction
Accurec	Co alloy	Li2CO3	Recovered via air filtration	Al, Cu recovered via air separator, Al via leaching	Polymer
Battery Resources	NMC(OH)2	Li2CO3	Recovered with magnetic separator	Cu recovered via dense media separation and precipitation	Not specified
LithoRec	MeO	Li2CO3/ LiOH	Recovered via air filtration	Al, Cu recovered via sieves and zig-zag sifter	Not specified
OnTo	Cathode powder (refurbished)	Li2CO3/ cathode	Recovered, not specified	Recovered, not specified	Not specified

. Martins et al. [22] discussed the environmental and economic issues of recycling and future approaches considering their sustainability. The work is devoted to a detailed overview of CE in EVs. Moreover, the correlation between the number of used vehicles and GDP is described. Dalini et al. [169] reviewed the environmental and economic aspects of recycling by a hydrometallurgical technique, including the pretreatment, leaching, precipitation, extraction, and electrochemical methods leading to the regeneration and recovery of valuable metals. Further, Zhao et al. [170] reviewed the state-of-the-art of recycling processes of spent LIBs based on the LiCoO₂ system; they discussed the possible problems and prospects according to the recently published works.

Other publications provided a more specific economic point of view. Natkunarajah et al. [171] presented former scenario analyses devoted to the return rates of LIBs and return rates based on the market shares of EVs. They analyzed return rates considering the lifespan of different battery systems in their first life application (EV) and a possible second life application (battery energy storage). The prediction data for batteries of BEV, PHEV, and HEV are based on the current EVs on the German market.

Steward et al. [172] presented different directions for future developments based on the results of techno-economic analyses made for spent LIBs. Their overview discusses savings from recycling cathode materials from the EOL LIBs relative to the production use of virgin materials. Ma et al. [173] estimated the economic profits of recycling spent LiFePO₄ (LFP) and Li(NiCoMn)O₂ (NCM 523) batteries in the conditions of China. In their work, they calculated recycling revenues (R), determined recycling costs (C), and established profits of the recycling (B) for each battery type. The considered costs and profits have been converted from CNY to USD, according to the current exchange rate of July 2022, and are shown in

Table 7. The recycling profits of the spent power batteries. Reprinted and edited from IOP Conference Series: Earth and Environmental Science (EES), Vol. 159, Ma et al. [173], The Recycling of Spent Power Battery: Economic Benefits and Policy Suggestions, no. 1, Copyright (2022), distributed under Creative Commons Attribution License.

Battery Type	Profits (B) (USD/Ton)	Revenues (R) (USD/Ton)	Costs (C) (USD/Ton)
LFP NMC 523	505 2613	1.57 5.47	1.07 2.85

. Garg et al. [174] presented an artificial intelligence (AI) approach to thermo-mechanical-electrochemical-based evaluation for the residual energy of the LIBs embedded in battery packs used in EVs. The study’s findings are built on a robust model using genetic programming; it can optimize the recycling strategy for spent LIBs and leads to the reduction of the cost of the whole process.

Lander et al. [4] introduced a techno-economic model for comparing recycling locations and techniques; they presented it as a key tool for recycling cost optimization in an international battery recycling economy. According to this study, recycling of LIBs can be economically viable, with cost/profit ranging from (−21.43–+21.91) USD·kWh⁻¹. However, the final cost/profit sum depends on the form and distance of transport, design of the battery pack, and the recycling method. The study provides six different scenarios according to their location (China, South Korea, US, Belgium, and the UK) performed for five types of LIBs (NCA, NMC 622, NMC 811, LFP, and LMO). The net recycling profit in USD·kWh⁻¹ for the recycling of various commercial battery packs is shown in Figure 8.

Wang et al. [175] established a model for the profitability analysis of recycling three different types of LIBs (LCO, LFP, LMO) based on the commodity market prices for recovered materials. The profitability is highly dependent on the mix of cathode material chemistries in the waste and the resulting variableness in material mass. Considering the results, the potential values of the waste streams range from USD 860/ton for LiMn₂O₄ cathode batteries to USD 8900/ton for LiCoO₂. In another work, Li et al. [176] developed an economical green recycling method for recycling spent LiNi_1/3Co_1/3Mn_1/3O₂ cathodes; more than 98% of Li, Co, Ni, and Mn was leached out by acetic and maleic acid. The economic analysis was performed considering the costs of leachates (organic acids and reducing agents) and the energy consumption of processing. According to that, the cheapest recycling would be achieved using H₃PO₄ as a leaching acid, costing USD 16.53/kg of cathode material. The cost of used acids is USD 49.82/kg for acetic and USD 94.97/kg for maleic acid, considering the mass of the cathode material. Wang et al. [177] developed an environmental economic model considering CO₂ emission to simulate recycling spent LIBs. It provides three handling strategies: battery recycling, remanufacturing, and disposal. Moreover, a real case study from a Chinese EV manufacturer is introduced. According to the study results, a 5.7% decrease in the total cost and a 21.8% emission reduction can be achieved.

4. Discussion and Conclusions

Lithium-ion batteries are a key technology—from small portable consumer devices, through electromobility, to large-capacity energy storage. The ever-increasing number of EVs on the market, supported by still-stricter requirements for reducing decarbonization and CO₂ emission reduction, brings several requests, including lowering the prices of new EVs or searching for strategies in waste management solutions and processing of spent batteries.

Battery recycling appears to be the most suitable solution. Reusing rare metals (Ni, Co, Mn, or Li) or packaging materials (Al, Cu) limits the extraction of new raw ones and lower energy consumption and emissions. Moreover, implementing the proper process leads to a price reduction of a new battery and the whole vehicle.

This work represents the second part of the literature review based on peer-reviewed publications devoted to “Recycling of Lithium-ion Batteries from Electric Vehicles” and summarized 162 papers focusing on the environmental and economic (E&E) perspective. The reviewed works were classified into five sections: Recycling Processes, Battery Composition, Environmental Impact, Economic Evaluation, and Recycling and Rest, where this part deals in detail with the last four mentioned. The outline of discussed branches is illustrated in Figure 9.

The following can be concluded based on the review:

• Only a few publications are devoted to the recycling of the electrolyte issue. Although the organic electrolyte is the least profitable item of the whole battery (compared to the recovery of high-in-cost metals), it is required to complete studies characterizing its safe waste treatment, toxicity analysis, and environmental impacts, including wastewater treatment procedures or proper disposal.
• Several studies have been conducted addressing the effect of reclaimed materials on a new production of raw materials, either on a small scale or based on laboratory techniques. Nevertheless, it would be beneficial to study this issue further, especially on the data of implemented lines, which could represent a real scenario and outline future possibilities.
• According to Table 5, considering the available recycling processes, more than 99% of all valuable metals (Ni, Co, Mn, and Li), Al coverings, or organic binders can be recovered. Currently, these processes are being optimized to reduce necessary costs or environmental impacts.
• Several comprehensive LCA studies have been conducted, characterizing the issue of LIBs from EVs during their active and waste life. Although most works deal with GHG topics, there are extensions evaluating the effects of TETP (terrestrial ecotoxicity potential) or CED (cumulative energy demand). Including other environmental indicators would be beneficial, such as global warming potential (GWP) or abiotic resource depletion potential (ADP).
• So far, few publications have addressed the economic aspect of recycling LIBs from EVs. Although some complex works can be found, it is necessary to devote further research in this direction to achieve a high-quality evaluation of financial impacts with full use of EVs LIBs.

The first part of this review collection dealt with the technology and commonly used principles of recycling processes on the laboratory (small) and industrial (large) scale. This part brings additional E&E insight into publications considering recycling of spent LIBs from EVs published until 2021. Thus, these works provide a comprehensive techno-environmental economic overview of recycling EVs LIBs, which can be further used in academic and industrial spheres as a starting point for knowledge of this topic.