Advances in Graphite Recycling from Spent Lithium-Ion Batteries: Towards Sustainable Resource Utilization

Abstract

Graphite has been recognized as a critical material by the United States (US), the European Union (EU), and Australia. Owing to its unique structure and properties, it is utilized in many industries and has played a key role in the clean energy sector, particularly in the lithium-ion battery (LIB) industries. With the projected increase in global graphite demand, driven by the shift to clean energy and the use of EVs, as well as the geographically concentrated production and reserves of natural graphite, interest in graphite recycling has increased, with a specific focus on using spent LIBs and other waste carbon material. Although most established and developing LIB recycling technologies are focused on cathode materials, some have started recycling graphite, with promising results. Based on the different secondary sources and recycling paths reported, hydrometallurgy-based treatment is usually employed, especially for the purification of graphite; greener alternatives are being explored, replacing HF both in lab-scale research and in industry. This offers a viable solution to resource dependency and mitigates the environmental impact associated with graphite production. These developments signal a trend toward sustainable and circular pathways for graphite recycling.

1. Introduction

Graphite is a naturally occurring crystalline allotrope of carbon (C) with significant industrial and strategic importance due to its distinct properties, which arise from its hexagonal layered structure. Its unique properties make it a key component in many applications, including refractories, lubricants, and batteries, particularly lithium-ion batteries (LIBs), in which graphite is a dominant anode material due to its reversible lithium (Li) intercalation capacity and electrochemical stability [1,2,3].

The usage of and demand for LIBs have surged in the past decade with the global adoption of clean energy technologies and the shift towards electric vehicles (EVs), which need efficient rechargeable energy storage. The forecasted global demand for graphite, which is projected to rise about 25 times between 2020 and 2040 [4], its geographically concentrated global production, and issues related to reserves [5,6] are contributing to the increasing interest in and concern about graphite supply. Moreover, as the use of LIBs rises, so does the amount of waste associated with their end-of-life (EOL) stage, including other carbon-based materials. The United States (US), the European Union (EU), and Australia have identified graphite as a critical material [5,6,7,8], highlighting its importance in future technologies and international supply chains.

As the continued reliance on mining alone may not be a viable long-term strategy, particularly for countries lacking domestic graphite production and reserves, significant efforts are now directed towards local resource exploration and the recycling of EOL products to recover graphite, to meet the current demand as well as ensuring long-term supply security [5,6,9]. In the US and Australia, the governments provide loans and financial support to accelerate the development, evaluation, and deployment of technologies for the domestic processing of graphite and other critical minerals [5,6]. Meanwhile, the EU has already implemented a formal system for monitoring resource efficiency and the end-of-life recycling input rate (EoL-RIR), which tracks the share of overall material demand through secondary raw materials [9].

Concurrently, there has been increasing research interest in sustainable LIB recycling, with various methods developed for the effective recovery of materials from spent LIBs [10,11,12,13,14], including direct recycling [15], pyrometallurgy [16,17], hydrometallurgy [18], or a combination of these methods. However, most of these recycling efforts focus on recovering precious metals, with lithium (Li) being the most widely studied for recycling, followed by nickel (Ni), cobalt (Co), manganese (Mn) and iron (Fe), with only a few studies focusing on graphite recovery from spent LIBs, as well as other waste carbon materials. Given the growing recognition of graphite as a critical raw material, there is a need to advance research and innovation in sustainable recycling technologies, not only to mitigate the environmental impact associated with graphite production but also to manage the environmental concerns associated with the increasing volume of waste, particularly from spent LIBs. Integrating recycled graphite into the manufacturing of new batteries supports a circular economy in which materials are continuously reused, minimizing the reliance on natural resources and ensuring long-term resource security.

This article examines the many approaches employed in the industry, focusing on emerging technologies and recent studies, emphasizing graphite recycling for LIB anodes. This study is structured as follows: Section 2 presents the properties and applications of graphite, Section 3 discusses the primary sources, global market, and processes of producing natural and synthetic graphite, and Section 4 reviews the secondary sources related to graphite, current processing, and emerging technologies.

2. Graphite: Properties and Applications

2.1. Properties

Graphite is one of the most stable allotropes of C under standard conditions. Its stability and properties are attributed to its layered structure, composed of graphene sheets; it is a 2D carbon allotrope with a hexagonal lattice, where each sp² hybridized carbon forms strong σ-bonds with three neighboring sp² hybridized carbon atoms, creating a planar network with unhybridized 2p_z orbitals overlapping side-by-side with adjacent 2p_z orbitals, resulting in a delocalized π-electron cloud within the layer [2,3,19,20,21,22]. These graphene sheets are stacked and held together by weak van der Waals forces, forming the layered structure of graphite [2,3,19,20,21,22,23].

The arrangement of graphite governs its anisotropic, i.e., direction-dependent properties. For instance, the delocalized π-electrons enable high in-plane electrical conductivity, while the weak van der Waals interactions between the layers make graphite a poor electrical conductor perpendicular to the planes [3,19].

Table 1. Key properties of graphite [2,3,20,23].

Property	General	Anisotropic *		Refs.
		ab	c
Appearance	Black, greyish black; shiny	–	–	[3,23]
Transparency	Opaque	–	–	[3,20,23]
Density (300 K, 1 atm, g/cm3)	2.25–2.31	–	–	[2,3,20,23]
Thermal Stress Resistance (Factor R, W/m)	50 000	–	–	[2]
Sublimation Point (1 atm, K)	~4000	–	–	[3]
Mohs Hardness	–	0.5	9–10	[2]
Elastic Modulus (GPa)	–	1060	36–36.5	[2,3]
Electrical Resistivity (Ω·m)	–	2.5–5.0 × 10−6	3000 × 10−6	[3]
Electrical Conductivity (S/m)	–	2–3 × 105	3.3 × 102	[2]
Thermal Conductivity (25 °C, W/m·K)	–	398	2.2	[3]
Stability	Resistant to acids and alkalis under most conditions; oxidation above 350–400 °C in air	–	–	[3]

* Direction-dependent: ab—within the plane; c—perpendicular to the planes.

presents some of the key properties of graphite, while

Table 2. Atomic interactions in graphite with their roles and associated properties [3,19].

Interaction	Description	Roles	Associated Properties
σ-bond	Covalent bonds formed by direct overlap of sp2 hybridized orbitals within the layers	Supports the planar hexagonal lattice with rigid framework	High in-plane mechanical strength and thermal conductivity
π-bond	Covalent bonds formed by sideways overlap of unhybridized p-orbitals within the layers	Creates delocalized π-electron cloud, allowing in-plane electron delocalization	High in-plane electrical conductivity
van der Waals forces	Weak intermolecular attractions between the layers	Maintains interlayer stacking	Anisotropic behavior; lubricity, softness, easy cleavage, low conductivity

summarizes the types of atomic interaction in graphite with their respective roles and associated properties.

2.2. Applications

The unique structure of graphite, resulting in its stability and distinctive properties, underpins its remarkable performance in a wide range of applications. Some of these include refractories, foundries, lubricants, and batteries [2,5,6,24]. For example, graphite, as one of the most refractory materials known [3], is utilized in foundries as graphite crucibles for melting steel, as well as precious and nonferrous metals [2]. Its thermal properties and corrosion resistance make it suitable for high-temperature metallurgical processes.

Another key property of graphite is the intercalation capabilities that result from the combination of atomic interactions within its structure, providing it with the ability to maintain structural integrity during the reversible intercalation–extraction process, which is suitable for battery applications [1].

Table 3. Applications and global market share of graphite materials [2,5,6,7,8,23,24].

Application	Source Type *	Purity	Size	General Use	Share *	Refs.
		%			%
Batteries	NG (F, A); SG	>99.95	–	Anode material for LIBs—used in portable devices, energy storage systems (ESS) and EVs	25 increasing	[2,4,5,6,7,8]
Refractories	NG	–	–	Linings	35	[2,5,6,8]
Foundry	NG (F)	>85	–	Graphite crucibles and molds	7	[2]
Lubricants	NG	–	<1 mm	Graphite-based lubricants—used in hot metal formation, self-lubricating bearings	10	[2,6,8]
Fuel Cells	NG (F)	–	–	Proton exchange fuel cells (PEMFCs) and phosphoric acid fuel cell (PAFC)– use graphite as bipolar plates, and gas diffusion layers for PEMFCs	–	[2,6]
Carbon Nanomaterials	NG (F)	–	1–100 nm	Used as additives or catalyst supports for high-temp PEMFC (140–160 °C operating temp)	–	[2,23]
Expanded Graphite (EG)	NG (F)	–	–	Graphite foils—used for typical sealing applications; used in manufacturing flexible graphite plates for fuel cells	3	[2]
Graphite Intercalation Compounds (GICs)	NG (F)	–	–	Used as precursors for the preparation of expanded graphite (EG)	–	[2]
Traditional	NG	–	–	Used as graphite pencils	5	[2,8]

Note: where data are not available in a particular reference, it is left blank with “–”. * NG—natural graphite, SG—synthetic graphite; A—amorphous, F—flake; Share—global market share.

lists some of the applications of graphite materials with their corresponding details, including the global market share.

3. Graphite for LIBs: Primary Sources, Global Market and Production Processes

3.1. Primary Sources

Commercial graphite materials used in LIBs are primarily sourced either as natural graphite (NG) or synthetic graphite (SG) [2,25,26,27]. NG is mined from ores, while SG is produced via the high-temperature treatment of carbon-rich materials [2,3,25,26,27]. NG ores occur in three main forms: flake, vein/lump, and amorphous/microcrystalline, each having a distinct set of properties and range of purity levels, as summarized in

Table 4. Composition and properties of the main forms of NG [2,3,25,26,27,28,29,30,31].

Property	Flake	Vein	Amorphous	Refs.
Origin	Syngenetic—from sapropelitic, silica-bearing sediments via catazonal and mesozonal metamorphism	Epinenetic—possibly from carbonaceous hydrothermal or pneumatolytic fluids	Syngenetic—from coals via epizonal metamorphism	[2,3,26,27,28,29,30,31]
% Composition
Carbon (C)	<60–95	90–99 Up to 100% (Sri Lanka)	30–90	[2,3,25,30,31]
Sulfur (S)	0.1	0.7	0.1	[3]
Density (g/cm3)	2.29	2.26	2.31	[3]
DoG * (%)	99.9	100	28	[3]
d-spacing (002) (nm)	0.3355	0.3354	0.3361	[3]
ACD (mm)	<0.1	<0.01	<0.001	[2]
Morphology	Plate	Plate Needle	Granular	[3]

* DoG—degree of graphitization; ACD—average crystallite diameter.

.

Natural flake graphite (NFG) is commonly found in high-grade metamorphic rocks [2,31]. It is the most common and commercially significant type of graphite used in the manufacture of LIB anodes [5,6]. Amorphous graphite lacks the crystalline structure of flake graphite and generally has lower carbon purity; it is mainly used in greases and lubricants [28]. Vein graphite is the highest-quality form of graphite, with carbon contents reaching around 99% [25,31].

In contrast to the naturally occurring graphite, SG is produced from carbon-rich industrial by-products, e.g., petroleum coke and coal tar pitch, through high-temperature graphitization [2,3,25,26,27]. This process yields materials with a high purity range of 97%–99.9% [27], nearly approaching the minimum purity requirement of 99.95% in LIB anode applications [2,30]. Although SG offers better purity compared to most forms of NG, it generally exhibits lower crystallinity than natural flake and vein graphite, and its production is significantly more energy intensive and costly [26]. As a result, NG, particularly NFG, dominates the global graphite market, especially for LIB anode applications [2,26,27].

3.2. Global Market: Supply and Demand

Between 2006 and 2011, the market for graphite used in LIB anodes, both NG and SG, was low and steady, accounting for only a 1.9% market share in 2011, lower than conventional carbon products [2]. A notable expansion in the LIB anode market occurred between 2011 and 2015, with the market demand increasing five times, from about 15,000 t of anode materials used in 2006 to over 75,000 t in 2015 [2]. At the time, the market was expected to double or triple by 2025 [2], but this estimate has since proven conservative, considering that, in the US alone, about 52,000 t of NG was consumed in 2024. Moreover, a total of 1.6 Mt of NG was produced globally in the same year [6], highlighting the accelerated growth of the LIB anode market in the past decade. This upward market trend is expected to continue, driven by the diverse and expanding applications of graphite, especially in LIBs. Under the Sustainable Development Scenario (SDS), the global graphite demand is estimated to increase by about 25 times, from 0.14 Mt in 2020 to over 3.5 Mt in 2040 [4]. Thus, it is important to continuously monitor global market developments, production capacity, emerging trends, and technological advancements in graphite utilization.

According to the most recent U.S. Geological Survey [6], in 2024, China continues to dominate the global graphite market, accounting for approximately 79% of global NG production (~1.27 Mt) and holding the largest reserves, estimated at 28% of global reserves (~81 Mt) [6].

Table 5. Global mine production and reserves of selected countries [6,32].

	Mine Production				Reserves
	2021	2022	2023	2024	2024
Brazil	82,000	87,000	66,300	68,000	74,000,000
China	820,000	850,000	1,210,000	1270,000	81,000,000
Madagascar	70,000	110,000	63,000	89,000	27,000,000
Mozambique	72,000	170,000	98,000	75,000	25,000,000
Sri Lanka	3000	3000	3000	3300	1,500,000
World Total *	1,130,000	1,300,000	1,530,000	1,600,000	290,000,000

* All values are in metric tons (t) and written as reported in the U.S. GS Mineral Commodity Summary in 2023 and 2025.

presents a consolidated overview of the global mine production from 2021 to 2024, along with the most recent reserves estimates from key graphite-producing countries.

As shown in Table 5, China has been the dominant global producer of NG, followed by Madagascar, Mozambique, and Brazil in 2024. While China holds the largest known reserves, Madagascar’s Molo deposit has been described as a world-class flake graphite resource with its high purity and large flake sizes [30]. Despite contributing only 0.2% of global production, Sri Lanka holds strategic significance as the world’s primary source of vein-type graphite, which is a rare, naturally graphitized material noted for its high purity and exceptional crystallinity [2,3,29], valued at around USD 2900 per metric ton [6]. Amorphous or microcrystalline graphite mostly comes from China [2], with about 15% of its NG production being amorphous and 85% being flake graphite [6]. These countries collectively represent the core global NG supply, having consistently led NG mine production over the past four years.

Some countries, such as the U.S., E.U. members and Australia, currently have limited domestic production of NG but host significant undeveloped graphite deposits [6,24,25,33]. In response to increasing demand and supply chain risks, these countries are now actively exploring domestic supply strategies, including both primary and secondary sources through recycling, to reduce reliance on imports, considering that graphite is officially classified as a critical mineral by all three regions [6,24,25,33].

In Australia, substantial graphite flake deposits include those in the Eyre Peninsula, South Australia [25,34] and the Munglinup graphite deposit, located near Ravensthorpe in Western Australia [25]. In a recent announcement (May 2025), the Kookaburra Graphite Project (KGP) in the Eyre Peninsula reported having achieved a total graphitic carbon (TGC) purity of 99.97%, which is suitable for battery anodes [35].

Unlike NG, which is tracked and reported in detail by the U.S. GS, SG global production lacks centralized public reporting, making it less traceable than NG supply chains. Instead, market trends and estimates are sourced from specialized commercial platforms, e.g., Benchmark Mineral Intelligence, and company disclosures by the leading synthetic graphite producers.

3.3. Production Processes

The production of graphite materials follows different processing routes depending on the nature of the raw materials. NG is produced through direct mining and beneficiation of ores, while SG is manufactured through the high-temperature graphitization of carbonaceous materials. In order to meet the required purity of >99.95% carbon for LIBs, both NG and SG must undergo purification treatments, which are essential not only for achieving high purity but also for enhancing the overall performance of the material.

There are two major types of purification processes employed in the industry: hydrometallurgy and pyrometallurgy purification techniques. Hydrometallurgical purification takes advantage of the chemical inertness of graphite to selectively separate it from impurities. This method is widely used due to its low energy consumption, low production cost, and modest capital cost while producing high-purity graphite [26]. In contrast, pyrometallurgical purification produces ultra-high-purity graphite through extremely high-temperature treatments under an inert atmosphere. This process removes residual impurities, but it is generally more energy-intensive and costly than hydrometallurgical approaches [2,26,29].

3.3.1. Natural Graphite Production

NG production involves a multistage processing chain consisting of mining, crushing/grinding, flotation, classification, spheroidization and purification. Figure 1 shows a generalized NFG process with different processing routes, i.e., hydrometallurgy and pyrometallurgy.

Over 95% of NG is extracted from the surface, i.e., open-pit mines, with underground mining used in limited cases [2]. The extracted ore passes the comminution circuit to achieve particle sizes suitable for flotation, which typically yields graphite concentrates of about 95%–98% carbon [2,29]. The resulting concentrate is then sieved and classified, ensuring the desired particle size distribution for spheroidization, which is a process that transforms graphite flakes into spherical shape particles, often described as potato-shaped, to address the anisotropicity issues inherent to flake graphite [2]. To achieve battery-grade purity, either chemical or thermal purification methods are applied. Chemical purification typically involves acid leaching using reagents such as hydrofluoric acid (HF), hydrochloric acid (HCl), sulfuric acid (H₂SO₄) and nitric acid (HNO₃), or alkaline treatment with sodium hydroxide (NaOH) at 500 °C [2,26,29]. These agents dissolve impurities, which are then easily separated from the graphite via washing [26].

Alternatively, thermal purification may be applied, involving treatment at temperatures above 1500 °C, reaching up to 3000 °C, in the presence of halogen gases; this volatilizes residual impurities, achieving >99.995% purity or even impurity levels below 5 ppm [2,26]. An inert atmosphere or N₂ atmosphere is essential to preventing the oxidation of graphite, which can occur in the air above 450 °C [36]. Chlorine gas can also be used during heating, i.e., chlorination roasting, to convert impurities to a chlorinated form with lower boiling points, allowing the use of lower temperatures to vaporize the impurities [26,37]. After purification, the material achieves >99.95%, making it suitable for use as an anode material for LIBs. To further enhance electrochemical performance, the purified graphite is commonly coated with synthetic graphite [30] or amorphous carbon, forming a uniform conductive shell [2].

3.3.2. Synthetic Graphite Production

In contrast to the extensive beneficiation and purification of NG, the production of SG involves a combination of mechanical and thermal treatments. There are two processing routes for SG: (1) block graphitization, which consists of milling, mixing, molding, baking, graphitization, and classification, and (2) powder graphitization, which only involves milling, graphitization, and classification [2]. Figure 2 presents generalized SG processing with different graphitization routes.

SG production begins with the selection of suitable carbon-rich precursors, usually petroleum coke or coal tar pitch, which are milled, mixed with binders and molded into compact shapes. These molded materials are then baked and graphitized at temperatures exceeding 2800 °C, usually in an Acheson furnace, to achieve a high degree of graphitization [2]. The resulting material is subsequently milled and classified to obtain the desired particle size. Due to these extreme thermal treatments, SG achieves purity levels greater than 99.95%, and, similarly to NG, it is often coated with amorphous carbon to enhance its performance [2]. There are different approaches for carbon coating, such as dry or wet methods using pitch followed by heat treatment, and gas-phase methods including chemical vapor deposition (CVD) [2], which is an efficient method of coating graphite [38]. According to the studies conducted by Ding et al. [38] and Xiao et al. [39], carbon-coated graphite produced via the CVD method demonstrated better electrochemical performance than uncoated graphite or pristine graphite anode.

4. Graphite Recycling: Secondary Sources, Current Processing and Emerging Technologies

The projected growth in graphite demand reflects its critical role in clean energy technologies, particularly in LIBs, where it serves as the dominant anode material [1,2,3]. With the classification of graphite as a critical material by the US, EU, and Australia [5,6,7,8], efforts to ensure a secure and sustainable supply chain accelerated. A key driver for this is the dominance of China in terms of global production and reserves of ~79% and ~28%, respectively [6]. Such dependence raises concerns over potential supply disruptions, trade restrictions, and price volatility. With this, increasing attention is being directed towards alternative graphite sources, categorized as secondary sources, focusing more on spent LIBs, which contain a significant amount of graphite (~12%–22%) from the anode material [27,40,41,42]. Leveraging these secondary sources not only promotes a circular economy but also provides economic opportunities while supporting supply chain independence.

4.1. Spent LIBs

The generation of spent LIBs and other graphite-rich waste materials increases with the surge in demand for EVs and portable devices. Although the lifecycle of LIBs is uncertain and affected by many factors, on average, they can last up to 1–4 years for consumer electronics [27,42,43] or 8–12 years for EV applications [42,44,45,46]. As a result, increasing usage translates directly to higher volumes of spent LIBs, with more than 11 Mt expected from 2017 to 2030 [47,48] and 4 Mt of EOL EV batteries by 2030 [49]. This may lead to major LIB waste management concerns, as, worldwide, most spent LIBs (~95%) are landfilled or incorrectly disposed of [27,42,44,50]. Therefore, the global transition to clean energy technologies demands effective LIB waste management, including spent LIB recycling, which not only reduces environmental and human health risks but also supports critical mineral supply for current and future technologies.

Spent LIBs are recognized as viable secondary sources of critical metals, often containing concentrations higher than those found in natural ores [46]. The same concept also applies to spent anodes in LIB, which consist primarily of graphite, the second-largest LIB component [27,40,41,42]. With each EV requiring about 50–70 kg of graphite [4,25,51], its recovery presents a significant opportunity and has strategic value.

While many recycling methods have emerged, including direct recycling [15], pyrometallurgy [16,17], hydrometallurgy [18], or a combination of these methods, most of them focus on the cathode, recovering critical materials such as Li, Ni, and Co [27,50,52,53], with limited studies and information on the graphite anode [27,52,54]. Given the inherent chemical inertness of graphite, it can be recovered from spent LIBs and reused as technical-grade graphite for battery manufacturing [50,52]. The following subsections discuss some of the metallurgical-based LIB recycling (Section Metallurgical-Based Recycling Process), graphite recycling studies and emerging technologies (Section 4.2), as well as other secondary sources (Section 4.3)

Metallurgical-Based Recycling Process

General LIB recycling involves four main treatments: (1) pre-processing, (2) mechanical, (3) hydrometallurgy, and (4) pyrometallurgy. Each treatment includes a series of processes, depending on the target product, that are unique for each company or institute. While some process specifics are not disclosed, those found in the literature are collected and summarized in

Table 6. Spent LIB recycling technologies worldwide [27,42,54,55,56,57] *.

No.	Company	Country	Status	Capacity	Process **	Graphite	Losses	Refs.
				ton/y
1	Retriev Technologies Inc. (Toxco)	USA Canada	Operational	~18,000	Pre, M, H	Recovered as metal oxide—carbon cake	Plastic	*, [58]
2	Umicore ValÉas™	USA Bruxelles, Belgium	Operational	7000	Pre, H, P	Used as reductant for metals	Graphite electrolyte, plastics	*
3	AkkuSer Oy	Finland	Operational	4000	Pre, M	Part of black mass	Plastic	*
4	TES France S.A.S. (Recupyl Valibat)	France	Operational	~5000	M, H	Separated in leaching stage	Graphite, Cu	*, [59]
5	BatRec Industrie AG	Switzerland	Operational	200	Pre, H, P	–	–	*
6	Inmetco	USA	Operational	6000	P	–	–	*
7	Glencore (Xstrata)	Switzerland Canada/Norway	Operational	3000 7000	H, P	–	–	*
8	Brunp Recycling Technology Co., Ltd.	China	Operational	10,000	H, P	–	–	*
9	JX Nippon Mining	Japan	Operational	5000	H, P	–	–	*
10	Quzhou Huayo	China	Operational	40,000	P	–	–	*
11	DOWA Eco-System	Japan	Operational	6500	P	–	–	*
12	Redux Recycling	Germany Austria	Operational	50,000	H	–	–	*
13	Green Eco-Manufacture, GEM Co., Ltd.	China	Operational	200,000	H	–	–	*, [60]
14	Li-Cycle	USA Canada	Operational	5000 5000	H	–	–	*
15	Taisen	China	Operational	6000	H	–	–	*
16	Envirostream	Australia	Operational	3000	Pre	–	–	*
17	Guanghua Sci-Tech	China	Operational	12,000	Pre	–	–	*
18	Accurec GmbH®	Krefeld, Germany	Operational	4000–6000	Pre, M, H, P	Partially burnt, used as a reductant, and slagged	Graphite, electrolyte, polymers	*
19	American Battery Technology Company (ABTC)	USA	Operational	20,000	–	–	–	*, [61]
20	Fortum	Finland	Operational	~3000–5000	–	–	–	*, [62]
21	Hydrovolt (Northvolt—Hydro)	Norway	Operational	12,000	–	–	–	*, [63]
22	Gotion High-Tech	China	Operational	50,000	–	–	–	*, [64]
23	Green Li-ion	USA	Operational	730	–	–	–	*, [65]
24	Tesla	USA	Operational	~5000	–	–	–	*, [66]
25	Aalto University	Finland	Emerging	–	M, H, P	Lost in the furnace	Graphite, binder plastic, Cu, water	*
26	Steven Loop: OnTo	USA	Emerging	–	Pre, M, H, P	Separated using DMS, recovered	Graphite, binder	*
27	LithoRec	Germany	Emerging	2000	Pre, M, H, P	Separated in leaching stage	Electrolyte	*
28	Sumitomo Metal Mining, SMM Co., Ltd. (Sumitomo—Sony)	Japan	Planned	10,000 (150)	(Pre, H, P)	Calcined but not recovered	Graphite, electrolyte, plastics, Li, Ni	[67] (*)
29	Ascend Elements (Battery Resourcers)	USA	Planned	30,000	(Pre, M, H, P)	–	(Electrolyte)	[68] (*)
30	Glencore & Li-cyle	Switzerland & USA	Planned	~50,000–70,000	–	–	–	*, [69]
31	Posco Hy Clean Metal	South Korea	Planned	12,000	–	–	–	*, [70]
32	Bangpu Recycling Technology Co., Ltd.	China	Planned	500,000	H	–	–	*, [71]

** Pre—pre-processing, M—mechanical, H—hydrometallurgical, P—pyrometallurgical.

, with a generalized process flow diagram (PFD) arranged in Figure 3.

There are several technologies that are used in LIB recycling, some already in commercial operation, while others remain in the development or planning stages. These processes primarily focus on metal recovery and cathode material production, often resulting in the loss of graphite. Among them, the OnTo recycling process is notable for incorporating the separation of cathode and anode materials via dense media separation (DMS), followed by leaching-based purification of both streams to remove impurities and produce battery-grade materials [42].

Though the processes differ in terms of techniques, conditions, sequencing, and combinations, each treatment has its general purpose. First, spent LIBs go through the pre-processing stage to be discharged to reduce explosion risks; they are then sorted by type or size and disassembled to remove peripherals such as casing, wiring and plastics. Then, in the mechanical stage, their sizes are reduced to liberate the materials, separate them, and prepare for either hydrometallurgical or thermal (pyrometallurgical) treatments. In the hydrometallurgical stage, metals are selectively leached into solutions. Then, these metals are precipitated in the form of metal oxides and technical- or high-grade materials, ready for different applications, such as battery production. Pyrometallurgical techniques are employed in many ways. This is either carried out after the mechanical stage to remove impurities including binders, electrolytes, and organics, or after hydrometallurgical treatments to synthesize cathode materials.

4.2. Graphite Recycling

4.2.1. Graphite Recycling Program and Emerging Technologies

Recent advances in graphite recycling demonstrate the growing industrial and academic interest in recovering graphite from waste streams. Semco Carbon, a US-based graphite manufacturer, has developed a recycling program that processes about ~1800 tons of graphite annually [72]. Its recovery process combines mechanical, thermal, and electrochemical treatments [73], allowing recycled graphite to be used in diverse applications such as lubricants and steelmaking [72]. In the EU, Tozero is developing a hydrometallurgical process for graphite recycling aimed at achieving net-zero emissions, with about 2000 tons of annual recycled graphite production by 2027, which could supply about 50,000 EVs [74].

Meanwhile, a recent study in the Helmholtz Institute, Germany, using EcoGraf HFfree™ technology, confirmed its effectiveness in graphite purification, achieving comparable electrochemical performance with recycled graphite with commercial anodes [75,76]. As EcoGraf aims to produce high-purity graphite products for LIBs, more than USD 30 million has been invested in strategic assets, including the Epanko graphite mine in Tanzania, the mechanical shaping facility in Tanzania, and the EcoGraf HFfree^® Purification technology, as well as its facilities [77]. Furthermore, it is preparing to open the world’s first HFfree anode material product qualification facility (PQF) in Western Australia (WA) [75].

Table 7. Graphite recycling technologies.

No.	Company	Country	Status	Capacity	Process **	Progress	Refs.
				ton/y
1	Semco Carbon	USA	Operational	~1800	M, H, P	Recycles graphite from external companies and within operations, offering alternatives to pristine graphite	[72,73]
2	Tozero	Germany	Emerging	2000	H	~ EUR 17 million for graphite recycling “Net zero” emissions with renewable energy	[74]
3	EcoGraf	Australia	Emerging	–	Pre, H, P	Helmholtz Institute research work confirmed effectivity of EcoGraf HFfree™ purification technology	[75,76]

** Pre—pre-processing, M—mechanical, H—hydrometallurgical, P—pyrometallurgical.

summarizes the available details of the selected graphite recycling processes, while Figure 4 presents a PFD of the collaborative work between Helmholtz Institute and EcoGraf.

4.2.2. Graphite Recycling Studies

In the hydrometallurgical treatment of spent LIBs, leaching is mainly employed to extract critical metals from spent cathodes and remove residual impurities from anodes. While there is limited information on the reagents used, some studies mention the use of hydrochloric acid (HCl), nitric acid (HNO₃), sulfuric acid (H₂SO₄), and hydrofluoric acid (HF) [26,41]. These are strong acids that are effective leaching agents but are challenging to handle, posing significant environmental and safety concerns due to their potential to generate toxic emissions, such as sulfur trioxide (SO₃), chlorine (Cl₂), and nitrogen oxides (NO_x), as well as contaminating water and soil [41]. These need proper treatment, which can be costly and energy consuming.

For instance, HF is generally used in China to produce high-purity graphite [78,79]. However, HF is highly hazardous to human health, e.g., acute exposure can cause irritation and burning of the eye, nose, throat, respiratory tract and skin, pulmonary edema and exposure to large amounts of HF can result in fatal hypocalcemia [80]. Environmentally, HF is reactive and forms toxic metal fluorides, and direct HF exposure further harms ecosystems [80]. Due to these significant health and safety risks, as well as environmental concerns, HF leaching has not been adopted by other countries [79].

With this, the use of organic acids, i.e., green acids, has been explored in recent studies as an alternative to conventional leaching agents [41,81,82]. Since they are not considered harmful to the environment at the concentration levels at which they are usually employed, they are suitable for designing sustainable and eco-friendly recycling processes or green recycling [41]. Most literature on spent LIB recycling, using green acids, focuses on metal recovery from the cathode materials [38], and only a few studies address the anode material [81,82]. Some of the research focused on graphite recycling from spent LIBs for battery applications is summarized in

Table 8. Different studies involving graphite recycling from spent LIBs for battery applications.

No.	Author	Year	Remarks	Application
1	Zeng et al. [83]	2025	Graphite from spent LIBs was purified and regenerated using low-temperature spent polyvinyl chloride (PVC) roasting-assisted leaching. Purity level reached 99.9%, then regenerated at 1000 °C. Achieved a specific capacity of 111.5 mAh/g, 75% retention rate after 500 cycles at 1 C, and 99% coulombic efficiency (CE).	LIB anodes
2	Kosenko et al. [82]	2024	Spent graphite regenerated with organic acid leaching of 1.5 M malic acid and 3% H2O2, then annealed in Ar atmosphere. Regenerated graphite (RG) has achieved a specific discharge capacity of 340.4 mAh/g at 0.1 C, and 99.9% CE.	LIB anodes
3	Badenhorst et al. [84]	2023	Graphite from spent LIBs was recovered using a combination of mechanical and chemical treatment. Citric acid leaching was employed and graphite-rich products achieved purity range 74%–88%.	LIB anodes (potential)
4	Chen et al. [85]	2023	Anode waste from spent LIBs was treated with flash joule heating within seconds followed by 0.1 M HCl leaching achieved a specific capacity of 351 mAh/g at 0.2 C, 77.3% capacity retention after 400 cycles at 0.5 C using LiFePO4 as cathode.	LIB anodes
5	Gong et al. [86]	2023	Anode has been manually separated from spent LIBs and treated by water leaching, then recovered and prepared for atmospheric plasma jet printing, which achieved a specific capacity of 402 mAh/g, and 500 mAh/g after 1000 cycles.	LIB anodes
6	Lai et al. [87]	2023	Waste graphite from spent LIBs was recovered and regenerated using deep eutectic solvent (DES) leaching. Achieved a high specific capacity of 449.4 mAh/g at 0.1 C, 285.4 mAh/g after 500 cycles at 1 C, 96% retention rate, and 100% CE.	LIB anodes
7	Zhu et al. [88]	2022	Waste carbon residue (WCR) was purified to 99.5% using constant-pressure acid leaching at 60 °C, 12% HF concentration, 180 min, and 25:1 liquid-to-solid ratio. Achieved a 91.86% DoG, 19.205 μm D50, and high thermal stability.	LIB anodes
8	Cao et al. [89]	2021	Graphite was separated from Cu foil by electrolysis, with purity of about 95%, reused to prepare for LIB anodes. Achieved a discharge and charge specific capacity of 427.81 mAh/g and 350.47 mAh/g at 0.1 C, with about 98% CE after 2nd cycle.	LIB anodes
9	Li et al. [90]	2021	Spent anode material has been manually separated from spent LIBs, and exfoliated from Cu foil using deionized water bath with rotator.	LIB anodes (potential)
10	Yang et al. [81]	2021	Anode graphite regenerated with organic acid leaching of 0.2 M citric acid, at 90 °C, 1:50 g/mL S/L ratio, and 50 min reaction time. Achieved a high discharge capacity of 330 mAh/g at 0.5 C after 80 cycles, and about 99% CE.	LIB anodes

. These recent studies support green and hybrid methods, combining leaching with thermal or electrochemical treatments to restore battery-grade performance

Recent reviews from Golmohammadzadeh et al. [41] and Chaudhary et al. [56] have outlined the potential of organic acids, including acetic, lactic, ascorbic, oxalic, and tartaric acids. Although tested for cathode materials, these green acids may be applied to spent anode purification as supported by the initial results of Yang et al. [81] and Kosenko et al. [82].

4.2.3. Direct Recycling of Spent LIBs

Direct recycling is an emerging strategy aimed at regenerating electrode materials from spent LIBs without breaking them down into elemental components [15]. Unlike pyrometallurgical and hydrometallurgical recycling, which are energy-intensive and chemically aggressive processes, direct recycling preserves the structure of cathodes and anode, minimizing cost, energy consumption, and waste. The generalized process in Figure 5 integrates mechanical, thermal, and chemical treatments designed for selective material recovery.

Direct recycling offers a promising route for LIB recycling. However, several challenges remain, including the complexity of cell designs, polyvinylidene fluoride (PVDF), and the variability in cathode chemistries [15].

4.3. Other Secondary Sources

The growing global demand for graphite has led to an increasing interest in finding alternative sources, and, as a response, recent research has focused on the conversion of these secondary carbon sources into graphitic carbon. These efforts aimed not only to support the global supply but also to mitigate environmental challenges such as carbon waste accumulation. Alternative raw materials with lower costs and reduced environmental impact, notably biomass, EOL tires and crucible wastes, have emerged as promising feedstocks for graphitic carbon synthesis [91,92,93,94,95,96,97,98,99,100,101]. Biomass, which comprises organic material derived from living organisms, has gained increasing interest as a feedstock for the production of high-quality graphite owing to its high carbon content and renewable nature [91,94,98,99]. The production of graphite from biomass offers a viable approach to meeting the rising need for carbon products that are sustainable [96]. Several methods for the conversion of secondary sources and amorphous carbon to graphite have been employed, such as pyrolysis [92,96,97], microwave heating [101], and catalytic graphitization [96,98,99].

Table 9. Different studies involving the conversion of secondary sources and amorphous carbon to graphite materials.

No.	Author	Year	Remarks	Application
1	Kim et al. [93]	2024	Investigated graphitization of wood at varying temperatures with and without catalyst. Graphitization without a catalyst occurred at higher temperature.	General industrial applications (including batteries)
2	Hegde et al. [94]	2024	Teak sawdust was used for porous graphitic carbon synthesis using FeCl3-assisted carbonization and KOH activation.	Supercapacitor electrodes
3	Makowska et al. [92]	2024	Chlorella sp. biochar pyrolyzed at 400–900 °C in CO2 atmosphere. Amorphous nature of biochar develops at higher temperature.	–
4	You et al. [91]	2024	Hardwood biochar was used for graphite synthesis through pre-heating carbonization, Fe-catalyzed graphitization (slow cooling) and acid wash using H2SO4.	Alternative to natural and synthetic graphite
5	Shi et al. [96]	2023	Green graphite from biomass using pyrolysis and catalytic graphitization. Optimized green graphite achieved a reversible capacity of 264 mAh/g, 97% capacity retention over 100 cycles in a half-cell, and 99.3% CE.	LIB anodes, printing, refractories
6	Zhang et al. [95]	2023	Used alkali-acid method with NaOH and HCl to purify waste graphite from crucibles. Achieved 98.45% fixed carbon from 93.09%.	LIB anodes (potential)
7	Veldevi et al. [97]	2022	Waste tire was used for graphite synthesis through aqua regia treatment and pyrolysis using N2/CO2 atmosphere. Achieved a reversible specific discharge capacity of 350 mAh/g, 81% capacity retention after 500 cycles at 300 mA/g, and 99% CE.	LIB anodes
8	Destyorini et al. [99]	2021	Coconut coir was used for graphite synthesis through low-temperature catalytic graphitization at 1300 °C using Ni-based catalyst. Achieved 84.88% DoG, and 25.75 S/cm conductivity from 14.97 S/cm.	Fuel cells
9	Jabarullah et al. [98]	2021	Palm kernel shell (PKS) was used for graphite synthesis through catalytic graphitization at 800–1300 °C using Fe/Ni-based catalyst. Achieved a highly ordered graphitic structure at 2θ = 26.5°, surface area of 202.932 m2/g, and 0.208 cm3/g.	–
10	Xing et al. [100]	2018	Bituminous coal was used for graphite synthesis through high-temperature graphitization at 2000–2800 °C. The synthetic graphite achieved reversible capacity of 310.3 mAh/g at 0.1 C current rate, 95.3% capacity retention after 100 cycles.	LIB anodes
11	Kim et al. [101]	2016	Amorphous carbon (activated carbon powder) was graphitized using catalytic microwave heating. Graphitization achieved in 5 min using microwave heating at a 1400 W. Similar results achieved using thermal graphitization after 1 h at 1000 °C.	–

summarizes some of the studies on the conversion of secondary sources and amorphous carbon to graphite materials, which may be used for different applications, mostly LIBs.

Materials such as wood, coconut shells, and waste tires have been successfully converted into carbon products with structural and electrochemical properties suitable for potential applications in LIBs and other electrochemical devices. The proposed approach promotes sustainability in terms of supply security by utilizing waste streams across different industries.

5. Conclusions

Graphite has been recognized as a critical material by the US, EU, and Australia due to its essential role in a wide range of industries, particularly in LIB anode production. Its unique structure and remarkable properties make it irreplaceable in many energy technologies. However, with the projected global demand, driven by the clean energy transition and the growth of EVs, as well as the geographically concentrated production and reserves of natural graphite, concerns over supply security are rising.

In response, interest in graphite recycling is increasing, particularly with spent LIBs and other waste carbon materials such as biomass, waste tires, and crucibles. Recycling graphite from these secondary sources offers a viable solution to resource dependency and mitigates the environmental impact associated with graphite production. Although most of the established and developing LIB recycling technologies have focused on cathode materials, recent developments in graphite recycling have produced promising results. Among these, hydrometallurgical methods have been explored for graphite purification, offering greener alternatives to HF-based processes, including organic acids, and proprietary industrial systems such as EcoGraf’s HFfree™ technology.

These advancements signal a trend toward more sustainable and circular strategies for graphite recycling. As the LIB industry scales, recycled graphite recovered through environmentally responsible pathways plays a key role in supporting long-term resource security and reducing environmental impact. Recent advancements in recycling methods have demonstrated the potential of graphite reuse in LIBs and other applications. Continued research and collaboration are necessary for the industrial application of graphite recycling.