Environmentally Sustainable Anode Material for Lithium-Ion Batteries Derived from Cattle Bone Waste: A Full-Cell Analysis with a LiFePO₄ Cathode

Abstract

Modern society relies heavily on energy, driving global research into sustainable energy storage and conversion technologies. Concurrently, the increasing volume of waste generated by industrial and commercial activities emphasizes the need for effective waste management strategies. Carbonization emerges as a promising solution, converting waste into energy and valuable end products such as biochar. This study explores an approach for valorizing bone-based food waste, presenting innovative pathways for managing the escalating issue of food waste. We investigate carbon derived from cattle bone waste, carbonized at 800 °C (CBW8), to design sustainable full-cell lithium-ion batteries (FLIBs). FLIBs featuring CBW8 as the anode material and LiFePO₄ as the cathode exhibit exceptional cycling life, even at high current rates. The cell demonstrates a high specific capacity of 165 mAh g⁻¹ at 0.5 C, maintaining stable performance over 1800 cycles at various C-rates. This work not only advances the field of sustainable energy and waste management, but also opens new avenues for eco-friendly technological applications.

1. Introduction

In 2050, the worldwide demand for energy is projected to surge by approximately 50%, driven by factors such as population growth, urbanization, and the effects of climate change. According to the International Renewable Energy Agency (IRENA) report, achieving the 1.5 °C (e.g., limit of global temperature rise) scenario of global net zero CO₂ emissions by 2050 requires a significant expansion of renewables across all sectors [1]. This entails a twelve-fold increase in renewable electricity capacity compared to 2020, necessitating an additional 1066 GW annual capacity production from 2023 onward. In this scenario, bioenergy—renewable energy derived from organic materials like biomass and capable of being converted into liquid fuels, heat, and electricity [2]—is projected to play a significantly larger role in the global energy mix, contributing an estimated 16% of total final energy consumption by 2050 [1]. Bioenergy’s share in the total energy mix is projected to rise significantly, with the demand expected to reach 56 exajoules (EJs) by 2050. This increase is crucial for decarbonizing sectors such as industry and transport, where the infrastructure of electrification is challenging. The bioenergy demand will be split between energy production (including power and heat generation) and as a feedstock for producing bio-based chemicals and materials [3,4,5].

The high potential of various types of biowastes for application in advanced energy storage systems has been well-documented [6,7,8]. For instance, carbon derived from sustainable resources has shown promise as a replacement for standard graphite in lithium-ion batteries (LIBs) [9,10]. Additionally, in supercapacitors, plant-based biowaste materials such as industrial hemp and honeydew peel can act as sustainable carbon precursors, inherently introducing heteroatom doping for enhanced electrochemical performance [11,12]. The unique properties of biochar, including its non-graphitic structure, porosity, and abundant presence of heteroatoms, make it an ideal candidate for electrodes in secondary batteries, particularly LIBs [13,14]. Life cycle assessment studies highlight that using waste materials for biochar production yields significant environmental benefits and aligns with circular economy principles, promoting resource efficiency and sustainability [15].

Animal bone is one of the most abundant biowaste by-products, with the global meat industry generating 130 billion kg of animal bones annually, of which the European Union contributes more than 10% [16]. Bones are composed of hydroxyapatite (HA) and collagen [17], which can be converted through carbonization into porous carbon materials with high numbers of defects [13]. These materials have potential applications in various fields, such as for inducing oxygen reduction reactions [18], supercapacitors [19,20], batteries [21,22], and water treatment [23,24].

In the specific sector of batteries, among the different chemistries nowadays commercially available, batteries based on lithium iron phosphate (LiFePO₄: LFP) cathodes present the advantage of being more eco-friendly than other kinds of commercial batteries, as they eliminate the need for critical raw materials such as manganese, cobalt, and nickel. LFP-based batteries are widely favored by Chinese automakers due to their safety, technological independence, and abundant local raw materials [25]. These batteries not only offer a longer cycle life, lower costs, and reduced environmental impact but also excel in rapid charge and discharge capabilities. Additionally, LFP batteries provide high power density, high voltage, high energy density, low self-discharge rate, and minimal heating. These attributes make LFP-based batteries suitable for a wide range of applications [26], to the extent that the global market for batteries utilizing LFP cathodes was valued at USD 15.28 billion in 2023, with a growth projection reaching the remarkable amount of USD 124.42 billion by 2032 [27].

In the current study, cattle bone waste carbonized at 800 °C was used instead of graphite as the anode material and coupled with an LFP cathode to design full-cell lithium-ion batteries (FLIBs). The designed FLIBs exhibited promising electrochemical performance, with specific capacities of 155, 140, 95, and 65 mAh/g_LFP during long cycling at 1, 2, 5, and 10 C, respectively. Unlike previous studies [22,28] that predominantly focused on half-cell utilization of (cattle bone) biomass, this research demonstrates the true potential of waste materials in real-world applications.

2. Materials and Methods

2.1. Materials

Cattle bone waste was taken from a meat market in Genoa, Italy. The mineral oil (μ: 41–17 cSt), castor oil (μ: 13.5 cSt), silicone oil (μ: 500 cSt) and polyvinylidene fluoride (PVDF)were purchased from Sigma Aldrich. Carboxymethyl cellulose (CMC) and carbon black (Super P) were purchased from GELON Lib Group Co., Ltd. Lithium iron phosphate (LFP: LiFePO₄) were purchased from NEI corporation USA. Soybean oil (SALVADORI, μ: 43 cSt) was purchased from a local market. Milli-Q water was used for all the experiments.

2.2. Cattle Bone Waste (CBW) Biochar Preparation

To remove any trace amounts of meat and other organic impurities, the bone was immersed in boiling water for a short amount of time. After being cleaned, the bone was placed in a sealed plastic container and kept frozen at −18 °C for eventual use. The bone was divided into smaller pieces and placed in a tube furnace (three-zone split furnace: PSC 12/600H, Lenton, UK) for carbonization in an N₂ atmosphere at the temperature of 800 °C with a heating rate of 5 °C/min and held for 1 h. After this treatment, the produced carbonized bone waste was cooled naturally down to room temperature. The powder yield of carbon is a.u. 74%. Finally, the carbonized bone waste was grounded and sieved to less than 100 micrometers and then washed with 1 M HCl and deionized water to remove possible contaminants, with a final drying overnight step run at 110 °C. In this work, we shall refer to the final cattle bone waste obtained by following the aforementioned procedure as CBW8. Figure 1 illustrates the complete process for producing biochar (CBW8) from cattle bone waste.

2.3. CBW8 Anode and LFP Cathode Electrode Preparation

The CBW8 electrode was fabricated using an environmentally friendly process involving CMC and deionized water. These materials were chosen as replacements for the toxic N-methyl-2-pyrrolidone (NMP) and biologically hazardous PVDF binder. To prepare the anode electrode, CBW8 powder (70 wt%) was mixed with 20 wt% conductive carbon black and 10 wt% CMC. After grinding, the mixture was dispersed in deionized water to form a homogeneous slurry. This slurry was then casted onto a copper current collector (10 µm thickness) using a doctor blade and dried on a hot plate for 3 h at 60 °C. The electrodes were subsequently cut into 12 mm diameter disks and further dried using a Buchi apparatus for 4 h at 80 °C. The achieved active mass loading of the electrodes was approximately 1–1.5 mg/cm².

The cathode electrode was fabricated by mixing commercial LFP, carbon black (Super P), and PVDF with a weight ratio of 80:10:10 in NMP. Then, the cathode slurry was coated on the aluminum current collector. The active mass loading of the LFP electrode was about 1.8–2 mg cm⁻² after drying.

For the full-cell fabrication, the CBW8 anode was prelithiated in the presence of a LP30 (1 M LiPF6 in EC: DMC) carbonate electrolyte using the lithium direct contact electrochemical method [8]. The procedure for anode prelithiation and capacity balancing of cathode and anode is reported in our previous work [29]. Finally, the CBW8 anode and the LFP cathode were both combined with a Celgard 2400 separator and LP30 electrolyte into a 2032-coin cell. The half-cell and full-cell analyses were conducted using the same electrolyte and separator for consistency.

2.4. Material Characterizations

A scanning electron microscope (SEM, JEOL JSM-6490LA) was used to investigate the morphology of CBW8. Firstly, the sample was coated with a gold 10 nm thick gold layer by a Cressington 208HR sputter coater (Cressington Scientific Instrument Ltd., UK). Furthermore, to study the thermal profiles of CBW8, thermogravimetric analyses (TGAs) using a Q500 analyzer (TA instrument, USA) were employed with a heating rate of 10 °C/min in a range of 30–800 °C and N₂ atmosphere. A Fourier Transform Infrared (FTIR) spectrometer (Vertex 70v FT-IR, Bruker) with a single-reflection attenuated total reflection accessory (MIRacle ATR, PIKE Technologies) was then used to determine the functional groups in the CBW8. The spectra presented were taken in the average of 128 repetitive scans with a resolution of 4 cm⁻¹ in the range of 4000–600 cm⁻¹. A Renishaw micro-Raman spectrometer with an excitation wavelength of 514 nm, line of an Ar⁺ laser, a ×50 objective (numerical aperture: 0.75), and an incident power lower than 1 mW was instead employed for Raman analysis. A PANalytical Empyrean X-ray diffractometer with a 1.8 kW CuKα ceramic X-ray tube and a PIXcel3D 2 × 2 area detector with operating conditions of 45 kV and 40 mA was used to acquire the X-ray diffraction (XRD) response from CBW8. Furthermore, the specific surface area and pore size distribution of the CBW8 in the micro- and mesoporous range were conducted using Brunauer–Emmett–Teller (BET) and Barrette Joynere Halenda (BJH) analyses. For this purpose, under vacuum for 180 min, the sample was initially degassed at 150 °C to remove any water molecules potentially absorbed by the CBW8 material. Then, a gas sorption analysis based on nitrogen physisorption measurements was realized through an Autosorb-iQ (Quantachrome Instruments) analyser at the temperature of 77 K. By taking 20 uniformly spaced points in the relative pressure (P/P0) range from 0.05 to 0.3, the multipoint BET model was used to measure the specific surface areas of the CBW8. With the support of the BJH model, pore size distribution by considering 13 points was determined from the desorption isotherms (range 0.35 < P/P0 < 1). X-ray photoelectron spectroscopy (XPS) was then performed to analyze the chemical bonds in the CBW8 surface. The employed system was composed of a monochromatic X-ray source (set at 1486 eV), a hemispherical energy analyzer (Phoibos, HSA3500, also from Specs), and an electron spectrometer (Lab2, Specs, Berlin, Germany). The applied voltage, applied current, and pressure were chosen as 13 kV, 8 mA, and ≈1 × 10⁻⁹ millibar, respectively. For both wide and narrow scans, the large area lens mode was adopted. Furthermore, for the wide scan, an energy pass of 90 eV and an energy step of 1 eV were employed, while an energy pass of 30 eV and an energy step of 0.1 eV were instead set for the narrow high-resolution scan. Finally, the surface charge, having an energy of 7 eV and a filament current of 2.2 A, was neutralized using a flood gun.

2.5. Electrochemical Measurements

Room temperature cyclic voltammetry (CV) and galvanostatic charge and discharge analyses of the Li/CBW8 half-cell and CBW8/LFP full-cells were performed in the voltage ranges of 0.01–3 V and 0.8–3.9 V, respectively. Electrochemical impedance spectroscopy (EIS) was also performed in the frequency range from 10 kHz to 100 mHz at an open circuit potential with a 10 mV amplitude. BCS-805 BioLogic was employed for conducting all the electrochemical tests.

3. Results

3.1. Structural Characterization

SEM images of CBW8 were taken to assess the complete bone structure that resulted from the carbonization process (Figure 2a and Figure S1). Pure bone exhibits only a limited number of intrinsic pores prior to carbonization (Supporting Information, Figure S2). These pores are densely packed due to the presence of organic substances, such as collagen, proteins, lipids, and water, which occupy the pore spaces within the bone structure [19]. However, as a result of the release of the stored water and organic chemicals during the carbonization process, highly interconnected microchannels are created (Figure 2a). In this respect, the inner morphology of CBW8 is characterized also by the presence of pores in the micrometric range, as seen by the cross-section SEM images of Figure 2a. The elongated microchannels that run along the axis of most of the bone structure and associated pores are also observed. Additionally, the surface morphology of the microchannel walls also changes; it becomes rough and apparent that fiber-like structures are adorning the pore walls, which might be connected to the HA (hydroxyapatite) crystallite presence. SEM imaging of the CBW8 as a whole shows a structure with an intense network of interconnecting microchannels and micrometric pores. Figure S3 presents the SEM images of powder CBW8. For a better understanding of the pore size and distribution, BET analysis through the N₂ adsorption/desorption method was adopted. The results, shown in Figure 2b, illustrate pores with different size distributions in a specific pore diameter range in CBW8. Therefore, it exhibits a specific surface area of 136.4 m²g⁻¹, a mean pore volume of 0.319 cm³g⁻¹, and a mean pore diameter of 3.839 nm in CBW8. Figure 2c depicts N₂ adsorption/desorption isotherms at relative pressure (P/P0). The isotherm is categorized as Type IV, which is a feature of materials with mesopores (2–50 nm) [30]. Furthermore, according to the IUPAC, the narrow hysteresis loop shown in the isotherm is of the H₃ type, which is linked to mixed-shaped pores (cylindrical, wedge, and slit-shaped) and is typical of N₂ condensation in the mesopore area [31,32].

Thermogravimetric analysis (TGA) and first derivative TGA (DTGA) were used to examine the weight loss and thermal stability of the CBW8 during the heat treatment, as shown in Figure 3a and Figure S4. The analysis reveals an overall weight loss of 6.1%, confirming that CBW8 is thermally stable, with no significant organic residues remaining. This reduced weight loss reflects the material’s high purity. The primary weight loss of 2.7% up to 100 °C is attributed to the release of adsorbed moisture. Beyond this, up to 800 °C, the remaining weight loss is associated with the thermolysis of carbonates and partial dehydroxylation of HA [23].

A further important analysis that has been considered is about the verification of the chemical elements and organics located at the CBW8 surface. This study was run through X-ray photoelectron spectroscopy (XPS), with the results shown in Figure 3b–d and Figure S5. The spectra show the presence of oxygen (O), carbon (C), phosphorus (P), and calcium (Ca), with atomic percentages equal to 39.17%, 37.82%, 9.72%, and 13.28%, respectively (Figure S5 and Table S1). Furthermore, the peak area percentages of the four C1s subcomponents (C-C, C-O, C=O, and CaCO₃) are 76.31%, 12.93%, 6.21%, and 4.55%, respectively (Table S2). The subcomponents of O1s include carbonates, organic oxygen, and P-O, with percentages of 84.33%, 6.82%, and 8.84%, respectively (Table S3). It should be noted that the high content of oxygen in the CBW8 material contributes to an increase in hydrophilicity in air [33]. These XPS results prove that at 800 °C, all the organic components are removed.

The next step was to gain insights about the presence of functional groups in the CBW8 material. For this reason, Fourier Transform Infrared Spectroscopy (FTIR) was performed, with the results shown in Figure 4a. The two broad peaks at 3281 cm⁻¹ and 1642 cm⁻¹ correspond to the stretching vibration of O-H, and they are related to the adsorbed moisture [34,35]. On the other hand, the dominating band at 1007 cm⁻¹ and the band at 961 cm⁻¹ are associated with the stretching vibration of the phosphate group, while the bands at 1456, 1414, and 872 cm⁻¹ are related to the stretching vibrations of the carbonate group (CO₃²⁻) [36], the two components of HA (Ca_x(PO₄, CO₃)_y(OH)). The peaks ascribed to the phosphate and carbonate groups (1456, 1414, 1007, 961, and 872 cm⁻¹), provide evidence of HA existence. Another X-ray-based technique was employed to verify the degree of crystallinity of CBW8. Specifically, the X-ray diffraction (XRD) spectrum of CBW8 is shown in Figure 4b. According to the reference card (ICDD-01-074-9761), all detected peaks are ascribed to the characteristic peaks of standard HA [34]. The samples’ crystallinity, which results in the removal of collagen and other organic components without altering the HA structure and reveals an inorganic structure, is shown by the clear and strong peaks of the CBW8 spectra [37].

Finally, the level of graphitization of CBW8 was investigated through Raman spectroscopy, as shown in Figure 4c. Two sharp peaks at 1356 cm⁻¹ (I_D) and 1590 cm⁻¹ (I_G), respectively attributable to amorphous carbon (I_D) (i.e., characteristic peak of sp³ defects) and graphite structure (IG) (sp² bonded graphitic carbon), show the strong vibrations of the C-C of the carbonaceous material [38]. In particular, an I_G/I_D ratio of 1.18 is obtained, denoting a moderate level of graphitization [23,39] This influences both lithium-ion storage capacity and cycling stability. Moderate graphitization enhances conductivity and provides structural stability, facilitating reversible lithium-ion intercalation while maintaining long-term cycling performance [40]. This balance is crucial for maintaining both high capacity and stable cycling behavior over extended cycles.

3.2. Electrochemical Performance of CBW8 in Half-Cell and Full-Cell Configurations

The electrochemical activity of CBW8 was initially investigated in a lithium half-cell configuration (Figure 5). Afterwards, the potential application of CBW8 as anode in full-cell lithium-ion batteries (FLIBs) paired with an LFP cathode was explored. The half-cell results show that CBW8 could provide a robust capacity retention across various current densities, yielding capacities of 900, 720, 470, and 410 mAh g⁻¹ at the current densities of 0.1, 0.2, 0.5, and 0.8 A g⁻¹, respectively (see Figure 5a,b). In Figure 5b, a marginal capacity decrease is observed when the current density returns to 0.1 A g⁻¹, indicating a good reversibility of the engineered electrode. Furthermore, the charge–discharge cycling also demonstrated an initial discharge capacity as high as 2300 mAh g⁻¹, with an initial coulombic efficiency (ICE) of 37% at the current rate of 0.1 A g⁻¹ (Figure 5b). This low ICE value is synonymous with the presence of a solid electrolyte interphase (SEI), an insulating film which is formed during the first reduction process, a typical characteristic of turbostratic porous carbon materials [41,42]. The half-cell was also tested for over 600 cycle at 0.5 A g⁻¹, in order to evaluate its long cycling stability. The results demonstrate a remarkable average specific capacity of 417 mAh g⁻¹ with 84% capacity retention throughout cycling (see Figure 5c). It is noted that the presence of oxygen groups in the electrode promotes rapid redox processes [43]. Moreover, the observed capacity and electrochemical stability of Li/CBW8 batteries can be attributed to the high surface area, porous architecture, and the presence of heteroatoms in the CBW8 electrode. On the other hand, the capacity fade of CBW8 in Li-metal half-cells is mainly due to irreversible lithium consumption, excessive SEI formation, and structural degradation induced by oxygen-rich functional groups. Furthermore, electrolyte decomposition and gas evolution exacerbate performance degradation.

To contextualize CBW8 performance, it is essential to compare it with conventional anodes such as graphite- and silicon-based materials. Graphite, the most widely used anode in LIBs, has a theoretical capacity of 372 mAh g⁻¹ but is limited by sluggish kinetics and moderate rate capability [44]. Silicon-based anodes, while offering an exceptionally high theoretical capacity (~3590 mAh g⁻¹), suffer from severe volumetric expansion and rapid capacity degradation [45]. In contrast, CBW8 not only delivers a comparable or slightly higher capacity than graphite but also exhibits remarkable cycling stability, making it a promising alternative. Additionally, its biomass-derived origin and straightforward synthesis process provide key advantages in terms of sustainability and cost-effectiveness, reinforcing its potential for practical energy storage applications.

Figure 5d describes the cyclic-voltammetry (CV) behavior of the half-cell at various scan rates. The well pronounced broad peaks are a characteristic of disordered carbon, a typical situation for lithium batteries [46]. During the lithiation process, a cathodic peak associated with the lithiation process is observed at about 0.1 V, while an anodic peak related to the delithiation process is observed at 0.2 V [47]. Furthermore, the figure also shows an increase in electrode current while the scan rate rises. This behavior is commonly attributed to the dynamic electrochemical processes occurring at the electrode–electrolyte interface. At higher scan rates, the charge/discharge processes are more limited by the available surface area, and the current response becomes more dependent on the electrochemical surface area (ECSA). The increase in current with higher scan rates is likely indicative of an increase in the effective electroactive surface area. This is often seen with materials exhibiting high porosity and complex microstructures, such as biomass-derived electrodes. As the scan rate increases, the rate of ion diffusion to the surface becomes faster, and the electrode’s surface reactivity plays a more significant role in determining the overall current response. For biomass anodes, this phenomenon may also be due to the complex porous structure of the material, which offers more accessible sites for ion interaction as the scan rate increases, thereby leading to a higher apparent surface area. However, this increase in surface area is not necessarily indicative of a true physical increase in the material’s surface but rather reflects the enhanced electrochemical response due to the increased interaction between the electrode surface and the electrolyte ions at higher scan rates.

One of the foremost challenges encountered by FLIBs is their capacity degradation occurring during storage and charge–discharge cycles. This degradation may manifest in various forms, including diminished coulombic efficiency (CE), reduced cell usable capacity, and increased cell impedance. Throughout the charge and discharge processes, the diffusion of lithium atoms in and out of the host electrode may determine diffusion-induced stresses and volume fluctuations within the electrode, which may result in SEI fractures [48]. In this work, prior to cell assembly, the CBW8 electrode underwent the lithiation process following the procedure outlined in the experimental section. This lithiation step facilitates the formation of an SEI layer on the anode surface, mitigating lithium-ion loss during the initial discharge of the full-cell. Another action that was taken to ensure a better cell performance was to establish a proper balance between the anode and cathode. Varying their ratio significantly impacts the cell voltage and delivered capacity. Precise balancing is imperative to avoid battery overcharge and anode plating, which can compromise safety and diminish the cycle life. In this research, optimal results, characterized by a high ICE of 80% and stable capacity, were achieved with an anode loading of 1.3 mg (active mass loading) coupled with an LFP cathode of 2 mg.

Figure 6a illustrates the CV profile for the first three cycles of the prelithiated CBW8/LFP full-cell at the scan rate of 0.1 mV s⁻¹ within the potential range 0.8–3.9 V. During the positive voltage sweep (at ~3.6 V), lithium ions enter into the biochar electrode, while lithium-ion extraction occurs within the LFP cathode. Conversely, during the negative sweep (at ~3.3 V), lithium ions intercalate into the LFP cathode and de-intercalate from the CBW8 anode. Similarly, during the second and third cycles, the peaks at ~2.8/2.9 V during charging and ~2.5 V during discharging may stem from the two-step process of lithium-ion insertion/extraction into/from the electrodes [49]. The voltage differential of 0.3 V between the positive and negative peaks is indicative of electronic polarization. Figure 6b illustrates the extensive cycling tests of the full-cell, with varied C-rates ranging from 1 C to 10 C, then reverting to 1 C to assess the cell stability. The observed decrease in capacity at higher applied currents is attributed to increased polarization. The cell exhibits an initial discharge capacity (based on cathode active mass) of approximately 160 mAh g⁻¹ at 1 C, closely approaching the theoretical capacity of LFP versus Li/Li+ (~170 mAh g⁻¹). Upon increasing the C-rate to 2 C, a minimal capacity drop is observed. Furthermore, transitioning from 2 C to 5 C results in a capacity reduction of 25%, with a similarly marginal capacity change noted when shifting from 5 C to 10 C. Notably, the FLIBs demonstrate a good reversible capacity by reaching 140 mAh g⁻¹ when returning at 1 C after 1750 cycles. Additionally, the cell exhibits an average CE of 99.62%.

The galvanostatic charge and discharge profiles (Figure 6c) encapsulate a composite representation of the anode and cathode profiles in full-cell configuration versus Li/Li⁺. The specific capacity decreases with increasing C-rate, reflecting the expected capacity fade at higher charge/discharge rates. At lower C-rates, the cell achieves capacities close to the theoretical value of LFP. The voltage plateau around 3.4 V during charging and 3.3 V during discharging corresponds to the Fe²⁺/Fe³⁺ redox reaction in the LFP cathode. Furthermore, Figure 6d, along with Figure S6, reports the cycling performance of the FLIBs in terms of gravimetric energy density and specific capacity of the CBW8/LFP cell at 0.5 C, respectively. Considering the active mass of the cathode only, the resultant gravimetric energy density of the cell stands at 480 Wh kg⁻¹. Conversely, the cell gravimetric energy density is 295 Wh kg⁻¹ when considering the weight of both electrodes (active mass). The electrochemical impedance spectroscopy (EIS) analysis of the CBW8/LFP full-cell has also been explored and documented in the Supporting Information (Figure S7). Notably, a negligible increase in internal resistance is observed after cycling, suggesting a properly balanced and performing cell. This is closely aligned with the results reported by Xu et al. [50]. They posited that the minimal capacity loss observed in cells with a higher capacity anode may be elucidated by two potential stress-related mechanisms: (i) with increased anode loading, the current density on the anode surface diminishes, potentially mitigating electrode particle cracking throughout cycling; and (ii) elevated anode loading diminishes anode utilization, thereby limiting electrode particle expansion and contraction during lithiation and delithiation, thereby alleviating mechanical degradation [50].

Importantly, the attained energy and reversibility of the CBW8/LFP full-cell under high current rates surpass what is reported for similar cells in the existing literature. In this respect, a comparison of the results obtained in this work with the main electrochemical properties of LFP-based LIBs recently reported in the literature is shown in

Table 1. Comparison of the main electrochemical properties of LFP-based LIBs.

Anode	Mass Ratio (Anode/Cathode)	ICE%	Working Voltage (V)	Initial Discharge Capacity (mAh g−1)	Specific Capacity (mAh g−1)	Ref.
Sn-C	1:2	-	2.8	150	120 at 3 C	[51]
Graphene	1:4	89	3	165	160 at 1 C	[52]
TiO2 hollow nanofibers	1:1.3	68	1.4	140	110 at 0.1 A g−1, 80 at 0.2 A g−1, 50 at 0.5 A g−1, and 30 at 1 A g−1	[53]
Binary Li4 Ti5O12-Li2 Ti3O7	-	-	1.8	125	75 at 0.08 A g−1	[54]
ZnFe2O4-C	1:1.5	-	2.1	120	80 at 9.6 C	[55]
Si-Graphene	-	83.2	3	157	130 at 1 C	[56]
Ge	-	93	2.8	105	90 at 0.5 C	[57]
CBW8	1:1.5	80	3	167	165 at 0.5 C, 155 at 1 C, 142 at 2 C, 95 at 5 C, 65 at 10 C	This work

.

4. Conclusions

In this study, we convincingly demonstrate the high potential of food waste as an economical, abundantly available, and scalable bio-based material for applications in the energy sector. The synergistic behavior of biowaste, derived from a simple carbonization process, exhibits inherent heteroatoms, high surface area, interlinked microchannels, and a hierarchical porous structure. These properties contribute to high storage capacity in lithium-ion batteries (LIBs). Our investigation reveals that full-cell LIBs using cattle bone waste (CBW) as the anode, coupled with LiFePO₄ (LFP) as the cathode, maintain very stable capacity over prolonged cycling. This underscores the high potential of biowaste in Li intercalation/de-intercalation processes.

This work focuses on the practical application of this unique porous mechanism in real-world LIBs. This approach aligns with the United Nation’s Sustainable Development Goals (SDGs), advancing efforts toward sustainable development.