A review on the recycling of spent lithium-ion batteries (LIBs) by the bioleaching approach

Humic acid-mediated mechanism for efficient biodissolution of used lithium batteries

Resource recovery of valuable metals from spent lithium batteries is an inevitable trend for sustainable development. In this study, external regulation was used to enhance the tolerance and stability of strains in the leaching of spent lithium batteries to radically improve the bioleaching efficiency. The leaching of Li, Ni, Co and Mn increased to 100 %, 85.06 %, 74.25 % and 69.44 % respectively after targeted cultivation with HA as compared to the undomesticated strain. In the process of microbial leaching of spent lithium batteries, the metabolites in the Ⅰ, Ⅳ, and Ⅴ regions of the metabolism of the undomesticated bacterial colony had a positive correlation to the dissolution of spent lithium batteries. The metabolites of Ⅰ, Ⅱ, and Ⅴ regions were directly affected by the HA domesticated flora on the dissolution of spent lithium batteries. The excess metabolism of protein substances can significantly promote the reduction of Ni, Co, Mn leaching, and at the same time in the role of a large number of humic substances complexed the toxic metal ions in the system, to ensure the activity of the bacterial colony. It can be seen that the bacteria were domesticated by humic acid, which promoted the bacteria's own metabolism, and the super-metabolised EPS promoted the solubilisation of spent lithium batteries.

Co-doped NiFe carbonate hydroxide hydrate nanosheets with edge effect constructed from spent lithium-ion battery ternary cathodes for oxygen evolution reaction

The recycling of spent lithium-ion batteries (LIBs) has received increasing attention for environment and resource reclamation. Converting LIBs wastes into high-efficiency catalysts is a win-win strategy for realizing resource reclamation and addressing sustainable energy challenges. Herein, we developed a simple method to upcycle spent-LIBs cathode powder into Co-doped NiFe carbonate hydroxide hydrate (Co/NFCH-FF) as a low-cost and efficient oxygen evolution reaction (OER) electrocatalyst. The optimized Co/NFCH-FF electrode appears very competitive OER performances with low overpotentials of 201 and 249 mV at 10 and 100 mA cm-2, respectively, a small Tafel slope of 48.4 mV dec-1, and a high long-term stability. Moreover, we reveal that the existence of Co atoms leads to the formation of a crystalline/amorphous (c/a) interface at the Co/NFCH nanosheet edge, inducing the nanosheets possess a unique edge effect to enhance electric fields and accumulate hydroxide ions (OH-) at the edge during the OER process. Benefiting from edge effect, Co/NFCH-FF shows outstanding intrinsic activity. Furthermore, Co atoms as dopants stabilize the electronic structure of Co/NFCH-FF, enabling Co/NFCH-FF to exhibit excellent catalytic stability. This work provides an effective strategy for converting the end-life LIBs to high-performance multicomponent OER electrocatalysts and proposes new insights into the mechanism of enhanced catalytic activity of Co/NFCH.

Multi-scale analysis of acidophilic microbial consortium biofilm's tolerance of lithium and cobalt ions in bioleaching

Metal ions stress will inhibit the oxidation capacity of iron and sulfur of an acidophilic microbial consortium (AMC), which leads to reduced bioleaching efficiency. This work explored the impacts of Li+ and Co2+ on the composition and function of AMC biofilms with a multi-scale approach. At the reactor scale, the results indicated that the oxidative activity, the adsorption capacity, and the biofilm formation ability of AMC on pyrite surfaces decreased under 500 mM Li+ and 500 mM Co2+. At the biofilm scale, the electrochemical measurements showed that Li+ and Co2+ inhibited the charge transfer between the pyrite working electrode and the biofilm, and decreased the corrosion current density of the pyrite working electrode. At the cell scale, the content of proteins in extracellular polymers substrate (EPS) increased as the concentrations of metal ions increased. Moreover, the adsorption capacity of EPS for Li+ and Co2+ increased. At the microbial consortium scale, a BugBase phenotype analysis showed that under 500 mM Li+ and 500 mM Co2+, the antioxidant stress capacity and the content of mobile gene elements in AMC increased. The results in this work can provide useful data and theoretical support for the regulation strategy of the bioleaching of spent lithium-ion batteries to recover valuable metals.

Direct Regeneration of Degraded LiFePO4 Cathode via Reductive Solution Relithiation Regeneration Process

The rapid growth of electronic devices, electric vehicles, and mobile energy storage has produced large quantities of spent batteries, leading to significant environmental issues and a shortage of lithium resources. Recycling spent batteries has become urgent to protect the environment. The key to treating spent lithium-ion batteries is to implement green and efficient regeneration. This study proposes a recycling method for the direct regeneration of spent lithium iron phosphate (LFP) batteries using hydrothermal reduction. Ascorbic acid (AA) was used as a low-cost and environmentally friendly reductant to reduce Fe3+ in spent LiFePO4. We also investigated the role of AA in the hydrothermal process and its effects on the electrochemical properties of the regenerated LiFePO4 cathode material (AA-SR-LFP). The results showed that the hydrothermal reduction direct regeneration method successfully produced AA-SR-LFP with good crystallinity and electrochemical properties. AA-SR-LFP exhibited excellent electrochemical properties, with an initial discharge specific capacity of 144.4 mAh g-1 at 1 C and a capacity retention rate of 98.6% after 100 cycles. In summary, the hydrothermal reduction direct regeneration method effectively repairs the defects in the chemical composition and crystal structure of spent LiFePO4. It can be regarded as a green and effective regeneration approach for spent LiFePO4 cathode materials.

Recycling and Reuse of Spent LIBs: Technological Advances and Future Directions

Recovering valuable metals from spent lithium-ion batteries (LIBs), a kind of solid waste with high pollution and high-value potential, is very important. In recent years, the extraction of valuable metals from the cathodes of spent LIBs and cathode regeneration technology are still rapidly developing (such as flash Joule heating technology to regenerate cathodes). This review summarized the studies published in the recent ten years to catch the rapid pace of development in this field. The development, structure, and working principle of LIBs were firstly introduced. Subsequently, the recent developments in mechanisms and processes of pyrometallurgy and hydrometallurgy for extracting valuable metals and cathode regeneration were summarized. The commonly used processes, products, and efficiencies for the recycling of nickel-cobalt-manganese cathodes (NCM/LCO/LMO/NCA) and lithium iron phosphate (LFP) cathodes were analyzed and compared. Compared with pyrometallurgy and hydrometallurgy, the regeneration method was a method with a higher resource utilization rate, which has more industrial application prospects. Finally, this paper pointed out the shortcomings of the current research and put forward some suggestions for the recovery and reuse of spent lithium-ion battery cathodes in the future.

Recycling of spent lithium-ion batteries for a sustainable future: recent advancements

Lithium-ion batteries (LIBs) are widely used as power storage systems in electronic devices and electric vehicles (EVs). Recycling of spent LIBs is of utmost importance from various perspectives including recovery of valuable metals (mostly Co and Li) and mitigation of environmental pollution. Recycling methods such as direct recycling, pyrometallurgy, hydrometallurgy, bio-hydrometallurgy (bioleaching) and electrometallurgy are generally used to resynthesise LIBs. These methods have their own benefits and drawbacks. This manuscript provides a critical review of recent advances in the recycling of spent LIBs, including the development of recycling processes, identification of the products obtained from recycling, and the effects of recycling methods on environmental burdens. Insights into chemical reactions, thermodynamics, kinetics, and the influence of operating parameters of each recycling technology are provided. The sustainability of recycling technologies (e.g., life cycle assessment and life cycle cost analysis) is critically evaluated. Finally, the existing challenges and future prospects are presented for further development of sustainable, highly efficient, and environmentally benign recycling of spent LIBs to contribute to the circular economy.

Urgent needs for second life using and recycling design of wasted electric vehicles (EVs) lithium-ion battery: a scientometric analysis

Currently, lithium-ion batteries are increasingly widely used and generate waste due to the rapid development of the EV industry. Meanwhile, how to reuse "second life" and recycle "extracting of valuable metals" of these wasted EVBs has been a hot research topic. The 4810 relevant articles from SCI and SSCI Scopus databases were obtained. Scientometric analysis about second life using and recycling methodologies of wasted EVBs was conducted by VOSviewer, Pajek, and Netdraw. According to analytical results, the research of second life using and recycling mythologies has been growing and the expected achievement will continue to increase. China, Germany, the USA, Italy, and the UK are the most active countries in this field. Tsinghua University in China, "Fraunhofer ISI, Karlsruhe" in Germany, and "Polytechnic di Torino" in Italy are the most productive single and collaborative institutions. The journals SAE technical papers and World Electric Vehicle Journal have the highest publication and citations than other journals. Chinese author "Li Y" has the highest number of 36 publications, and his papers were cited 589 times by other authors. By analyzing the co-occurrence and keywords, energy analysis, second life (stationary using, small industry), and treatment methods, (hydrometallurgy and pyrometallurgical, electrochemical, bio-metallurgical) were the hot research topics. The S-curve from the article indicates hydrometallurgical and bio-metallurgical methods are attached with great potential in the near future. Further, different treatment methodologies are observed especially advanced techniques in hydrometallurgical, and spent medium bioleaching techniques in bio-metallurgical are good, economically cheap, has low CO2 emission, environmentally friendly, and has high recovery rate. Finally, this research provides information on second life use and top recycling methodology opportunities for future research direction for researchers and decision-makers who are interested in this research.

Green Synergy Conversion of Waste Graphite in Spent Lithium-Ion Batteries to GO and High-Performance EG Anode Material

The increasing demand for graphite and the higher lithium content than environment abundance make the recycling of anode in spent lithium-ion batteries (LIBs) also become an inevitable trend. This work proposes a simple pathway to convert the retired graphite to high-performance expanded graphite (EG) under mild conditions. After the oxidation and intercalation by FeCl3 for the retired graphite, H2O2 molecules are more likely to penetrate into the extended layers. And the gas phase diffusion caused by the produced O2 from the redox reaction between FeCl3 and H2O2 further promotes lattice expansion of interlayers (0.535 nm), which is beneficial to the stripping of graphene oxide (GO) with fewer layers. The EG exhibits excellent electrochemical performances in both LIBs and sodium-ion batteries (SIBs). It delivers 331.5 mAh g-1 at 3C (1C = 372 mA g-1) in LIBs, while it achieves 176.8 mAh g-1 at 3C (1C = 120 mA g-1) in SIBs. Then the capacity retains 753.6 (LIBs) and 201.6 (SIBs) mAh g-1 after a long-term cycling of 500 times at 1C, respectively. The full cells with the EG electrodes after prelithium/presodiation also show excellent cycle stability. Thus, this work offers another referable strategy for the recycling of waste graphite in spent LIBs.

Techno-economic assessment of bioleaching for metallurgical by-products

This study focused on the economic feasibility of two potential industrial-scale bioleaching technologies for metal recovery from specific metallurgical by-products, mainly basic oxygen steelmaking dust (BOS-D) and goethite. The investigation compared two bioleaching scaling technology configurations, including an aerated bioreactor and an aerated and stirred bioreactor across different scenarios. Results indicated that bioleaching using Acidithiobacillus ferrooxidans proved financially viable for copper extraction from goethite, particularly when 5% and 10% pulp densities were used in the aerated bioreactor, and when 10% pulp density was used in the aerated and stirred bioreactor. Notably, a net present value (NPV) of $1,275,499k and an internal rate of return (IRR) of 65% for Cu recovery from goethite were achieved over 20-years after project started using the aerated and stirred bioreactor plant with a capital expenditure (CAPEX) of $119,816,550 and an operational expenditure (OPEX) of $5,896,580/year. It is expected that plant will start to make profit after one year of operation. Aerated and stirred bioreactor plant appeared more reliable alternative compared to the aerated bioreactor plant as the plant consists of 12 reactors which can allow better management and operation in small volume with multiple reactors. Despite the limitations, this techno-economic assessment emphasized the significance of selective metal recovery and plant design, and underscored the major expenses associated with the process.

Recycling the Spent LiNi1- x - yMnxCoyO2 Cathodes for High-Performance Electrocatalysts toward Both the Oxygen Catalytic and Methanol Oxidation Reactions

The traditional recycling methods of the spent lithium ion batteries (LIBs) involve the intricate and cumbersome steps. This work proposes a facile method of acid leaching followed by the sulfurization treatment to achieve the high Li leaching efficiency, and obtain high-performance multi-function electrocatalysts for oxygen reduction (ORR), oxygen evolution (OER), and methanol oxidation reactions (MOR) from the spent LIB ternary cathodes. By this method, the Li leaching efficiency from the spent LIB ternary cathode can reach 98.3%, and the transition metal sulfide heterostructures (LNMCO-H-450S) consisting MnS, NiS2, and NiCo2S4 phases can be obtained. LNMCO-H-450S shows the superior bifunctional oxygen catalytic activities with ORR half-wave potential of 0.763 V and OER potential at 10 mA cm-2 of 1.561 V, surpassing most of the state-of-the-art electrocatalysts. LNMCO-H-450S also demonstrates the superior MOR catalytic activity with the potential at 100 mA cm-2 being 1.37 V. Using LNMCO-H-450S as the oxygen catalyst, this work can construct the aqueous and solid-state zinc-air batteries with high power density of 309 and 257 mW cm-2, respectively. This work provides a promising strategy for the efficient recovery of Li, and reutilization of Ni, Co, and Mn from the spent LIB ternary cathodes.

Driving sustainable circular economy in electronics: A comprehensive review on environmental life cycle assessment of e-waste recycling

E-waste, encompassing discarded materials from outdated electronic equipment, often ends up intermixed with municipal solid waste, leading to improper disposal through burial and incineration. This improper handling releases hazardous substances into water, soil, and air, posing significant risks to ecosystems and human health, ultimately entering the food chain and water supply. Formal e-waste recycling, guided by circular economy models and zero-discharge principles, offers potential solutions to this critical challenge. However, implementing a circular economy for e-waste management due to chemical and energy consumption may cause environmental impacts. Consequently, advanced sustainability assessment tools, such as Life Cycle Assessment (LCA), have been applied to investigate e-waste management strategies. While LCA is a standardized methodology, researchers have employed various routes for environmental assessment of different e-waste management methods. However, to the authors' knowledge, there lacks a comprehensive study focusing on LCA studies to discern the opportunities and limitations of this method in formal e-waste management strategies. Hence, this review aims to survey the existing literature on the LCA of e-waste management under a circular economy, shedding light on the current state of research, identifying research gaps, and proposing future research directions. It first explains various methods of managing e-waste in the circular economy. This review then evaluates and scrutinizes the LCA approach in implementing the circular bioeconomy for e-waste management. Finally, it proposes frameworks and procedures to enhance the applicability of the LCA method to future e-waste management research. The literature on the LCA of e-waste management reveals a wide variation in implementing LCA in formal e-waste management, resulting in diverse results and findings in this field. This paper underscores that LCA can pinpoint the environmental hotspots for various pathways of formal e-waste recycling, particularly focusing on metals. It can help address these concerns and achieve greater sustainability in e-waste recycling, especially in pyrometallurgical and hydrometallurgical pathways. The recovery of high-value metals is more environmentally justified compared to other metals. However, biometallurgical pathways remain limited in terms of environmental studies. Despite the potential for recycling e-waste into plastic or glass, there is a dearth of robust background in LCA studies within this sector. This review concludes that LCA can offer valuable insights for decision-making and policy processes on e-waste management, promoting environmentally sound e-waste recycling practices. However, the accuracy of LCA results in e-waste recycling, owing to data requirements, subjectivity, impact category weighting, and other factors, remains debatable, emphasizing the need for more uncertainty analysis in this field.

A highly efficient process to enhance the bioleaching of spent lithium-ion batteries by bifunctional pyrite combined with elemental sulfur

Bioleaching technologies have been shown to be an environmentally friendly and economically beneficial tool for extracting metals from spent lithium-ion batteries (LIBs). However, conventional bioleaching methods have exhibited low efficiency in recovering metals from spent LIBs. Therefore, relied on the sustainability principle of using waste to treat waste, this study employed pyrite (FeS2) as an energy substance with reducing properties and investigated its effects in combination with elemental sulfur (S0) or FeSO4 on metals bioleaching from spent LIBs. Results demonstrated that the bioleaching efficiency was significantly higher in the leaching system constructed with FeS2 + S0, than in the FeS2 + FeSO4 or FeS2 system. When the pulp densities of FeS2, S0 and spent LIBs were 10 g L-1, 5 g L-1 and 10 g L-1, respectively, the leaching efficiency of Li, Ni, Co and Mn all reached 100%. Mechanistic analysis reveals that in the FeS2 + S0 system, the activity and acid-producing capabilities of iron-sulfur oxidizing bacteria were enhanced, promoting the generation of Fe (Ⅱ) and reducible sulfur compounds. Simultaneously, bio-acids were shown to disrupt the structure of the LIBs, thereby increasing the contact area between Fe (Ⅱ) and sulfur compounds containing high-valence metals. This effectively promoted the reduction of high-valence metals, thereby enhancing their leaching efficiency. Overall, the FeS2 + S0 bioleaching process constructed in this study, improved the leaching efficiency of LIBs while also effectively utilizing waste, providing technical support for the comprehensive and sustainable management of solid waste.

A review on the recycling of spent lithium iron phosphate batteries

Lithium iron phosphate (LFP) batteries have gained widespread recognition for their exceptional thermal stability, remarkable cycling performance, non-toxic attributes, and cost-effectiveness. However, the increased adoption of LFP batteries has led to a surge in spent LFP battery disposal. Improper handling of waste LFP batteries could result in adverse consequences, including environmental degradation and the mismanagement of valuable secondary resources. This paper presents a comprehensive examination of waste LFP battery treatment methods, encompassing a holistic analysis of their recycling impact across five dimensions: resources, energy, environment, economy, and society. The recycling of waste LFP batteries is not only crucial for reducing the environmental pollution caused by hazardous components but also enables the valuable components to be efficiently recycled, promoting resource utilization. This, in turn, benefits the sustainable development of the energy industry, contributes to economic gains, stimulates social development, and enhances employment rates. Therefore, the recycling of discarded LFP batteries is both essential and inevitable. In addition, the roles and responsibilities of various stakeholders, including governments, corporations, and communities, in the realm of waste LFP battery recycling are also scrutinized, underscoring their pivotal engagement and collaboration. Notably, this paper concentrates on surveying the current research status and technological advancements within the waste LFP battery lifecycle, and juxtaposes their respective merits and drawbacks, thus furnishing a comprehensive evaluation and foresight for future progress.

Metal recovery from spent lithium-ion batteries via two-step bioleaching using adapted chemolithotrophs from an acidic mine pit lake

The demand for lithium-ion batteries (LIBs) has dramatically increased in recent years due to their application in various electronic devices and electric vehicles (EVs). Great amount of LIB waste is generated, most of which ends up in landfills. LIB wastes contain substantial amounts of critical metals (such as Li, Co, Ni, Mn, and Cu) and can therefore serve as valuable secondary sources of these metals. Metal recovery from the black mass (shredded spent LIBs) can be achieved via bioleaching, a microbiology-based technology that is considered to be environmentally friendly, due to its lower costs and energy consumption compared to conventional pyrometallurgy or hydrometallurgy. However, the growth and metabolism of bioleaching microorganisms can be inhibited by dissolved metals. In this study, the indigenous acidophilic chemolithotrophs in a sediment from a highly acidic and metal-contaminated mine pit lake were enriched in a selective medium containing iron, sulfur, or both electron donors. The enriched culture with the highest growth and oxidation rate and the lowest microbial diversity (dominated by Acidithiobacillus and Alicyclobacillus spp. utilizing both electron donors) was then gradually adapted to increasing concentrations of Li+, Co2+, Ni2+, Mn2+, and Cu2+. Finally, up to 100% recovery rates of Li, Co, Ni, Mn, and Al were achieved via two-step bioleaching using the adapted culture, resulting in more effective metal extraction compared to bioleaching with a non-adapted culture and abiotic control.

Research progress on bioleaching recovery technology of spent lithium-ion batteries

Bioleaching of lithium-ion batteries is a microbially catalyzed process. Under the action of redox, acid leaching and complexation in the presence of microorganisms, the valuable metals in the cathode material enter the liquid phase as ions and are subsequently recovered from the succeeding process. This technique has the advantages of being inexpensive, environmentally friendly and having simple needs. However, it is still in development and has not yet commercialized. In this paper, the technology is fully discussed based on numerous excellent studies. The contents include commonly utilized microorganisms, bioleaching mechanism, microbial stress response and metabolic activation, enhancement strategies, leaching characteristics and interfacial phenomena, process evaluation, and a critical discussion of recent research breakthroughs. They give readers with comprehensive and in-depth understanding on the bioleaching of lithium-ion batteries and help to improve the technology's industrialization. Researchers can make new explorations from the potential research directions and methods presented in this work to make biotechnology better serve resource recovery and social development.

Recovery of LiCoO2 and graphite from spent lithium-ion batteries by molten-salt electrolysis

The recovery of spent lithium-ion batteries has not only economic value but also ecological benefits. In this paper, molten-salt electrolysis was employed to recover spent LiCoO2 batteries, in which NaCl-Na2CO3 melts were used as the electrolyte, the graphite rod and the mixtures of the spent LiCoO2 cathode and anode were used as the anode and cathode, respectively. During the electrolysis, the LiCoO2 was electrochemically reduced to Co, and Li+ and O2- entered into the molten salt. The O2- was discharged at the anode to generate CO2 and formed Li2CO3. After electrolysis, the cathodic products were separated by magnetic separation to obtain Co and graphite, and Li2CO3 was recovered by water leaching. The recovery efficiencies of Li, Co, and graphite reached 99.3%, 98.1%, and 83.6%, respectively. Overall, this paper provides a simple and efficient electrochemical method for the simultaneous recovery of the cathode and the anode of spent LiCoO2 batteries.

Material flow analysis on the critical resources from spent power lithium-ion batteries under the framework of China's recycling policies

With the rapid growth of electric vehicles in China, the number of spent power lithium-ion batteries is dramatically increased. Considering the environmental risk, security risk, and potential resource value, China has issued a series of laws and regulations to manage the spent power lithium-ion batteries. This work employs the material flow analysis method to evaluate the material flows of Li, Ni, Co, and Mn during the life cycle of power lithium-ion batteries under the framework of China's recycling policy system. The results show that the demand for primary Li, Ni, Co, and Mn can achieve 26.9, 68.1, 20.4, and 21.9 kt in 2021, and a lot of primary critical resources will inburst the in-use stage. Moreover, the number of secondary Li, Ni, Co, and Mn can achieve 6.1, 15.4, 4.6, and 5 kt in 2021, accounting for 22.7%, 22.6%, 22.5%, and 22.8% of their corresponding demand. Based on the economic evaluation under the framework of China's recycling policy system, it is found that the potential recycling values of Li, Ni, Co, and Mn are approximately 966, 523, 414, and 43 million RMB yuan, which are 66.4%, 71%, 59.6%, and 66.4% higher than those in the absence of China's recycling policy system. It is implied that China's recycling policy system could markedly improve the collection rate by reducing losses and indirectly enhancing the recycling and reuse of spent power lithium-ion batteries. This work is expected to provide guidance for policymakers to improve the management of spent power lithium-ion batteries in China.

Environment-friendly, efficient process for mechanical recovery of waste lithium iron phosphate batteries

Technology for recycling retired lithium batteries has become increasingly environment-friendly and efficient. In traditional recovery methods, pyrometallurgy or hydrometallurgy is often used as an auxiliary treatment method, which results in secondary pollution and increases the cost of harmless treatment. In this article, a new method for combined mechanical recycling of waste lithium iron phosphate (LFP) batteries is proposed to realize the classification and recycling of materials. Appearance inspections and performance tests were conducted on 1000 retired LFP batteries. After discharging and disassembling the defective batteries, the physical structure of the cathode binder was destroyed under ball-milling cycle stress, and the electrode material and metal foil were separated using ultrasonic cleaning technology. After treating the anode sheet with 100 W of ultrasonic power for 2 minutes, the anode material was completely stripped from the copper foil, and no cross-contamination between the copper foil and graphite was observed. After the cathode plate was ball-milled for 60 seconds with an abrasive particle size of 20 mm and then ultrasonically treated for 20 minutes with a power of 300 W, the stripping rate of the cathode material reached 99.0%, and the purities of the aluminium foil and LFP reached 100% and 98.1%, respectively.

Effects of incineration and pyrolysis on removal of organics and liberation of cathode active materials derived from spent ternary lithium-ion batteries

Removing organics via thermal treatment to liberate active materials from spent cathode sheets is essential for recovering lithium-ion batteries. In this study, the effects of incineration, N2 pyrolysis, and CO2 pyrolysis on the removal of organics and liberation of ternary cathode active materials (CAMs) were compared. The results indicated that the organics in the spent ternary cathode sheets comprised a residual electrolyte and polyvinylidene fluoride (PVDF) binder. Moreover, the organics could be removed to promote the liberation of CAMs via incineration, N2 pyrolysis, and CO2 pyrolysis. When the temperature was <200 °C, the chemical properties of the volatilized ester electrolyte remained unchanged during both N2 and CO2 pyrolysis, indicating that the electrolyte can be collected by controlling the pyrolysis temperature and condensation. Furthermore, PVDF binder decomposition occurred at 200-600 °C. The optimal temperatures of incineration, N2 pyrolysis, and CO2 pyrolysis were 550, 500, and 450 °C, respectively, and these treatments increased the liberation efficiency of CAMs from 81.49 % to 98.75 %, 99.26 %, and 97.98 %, respectively. In addition, heat-treated CAMs required less time to achieve adequate liberation. Following three thermal treatment processes, the sizes of the CAM particles were mainly concentrated in the ranges of 0.075-0.1 mm and <0.075 mm. Furthermore, for all types of CAMs examined, the Al concentration decreased from 1.09 % to <0.35 %, which increased the separation efficiency and improved the chemical metallurgical performance.

Comparative life cycle analysis of critical materials recovery from spent Li-ion batteries

The development of new generations of electric vehicles is expected to drive the growth of lithium-ion batteries in the global market. Life Cycle Assessment (LCA) method was utilized in this study to evaluate the environmental impacts of various hydrometallurgical processes in critical materials recovery from lithium-ion battery (LIB) cathode powder. The main objective of this work was to fill the knowledge gap regarding the environmental sustainability of various processes in LIB recycling and to generate a comprehensive comparison of the environmental burdens caused by numerous hydrometallurgical methods. According to this investigation, leaching with acetic acid, formic acid, maleic acid, and DL-malic acid demonstrates lower environmental impacts compared to lactic acid, ascorbic acid, succinic acid, citric acid, trichloroacetic acid, and tartaric acid. Among inorganic acids, nitric acid and hydrochloric acid show higher environmental impacts compared to sulfuric acid. Furthermore, the results of this study indicate that leaching with some organic acids such as citric, succinic, ascorbic, trichloroacetic, and tartaric acids leads to higher negative environmental impacts in most environmental categories compared to inorganic acids like sulfuric and hydrochloric acid. Therefore, not all organic acids utilized in the leaching of critical and strategic materials from cathode powder can enhance environmental sustainability in the recycling process. The results of the solvent extraction study as a downstream process of leaching show that sodium hydroxide, organic reagents, and kerosene have the highest environmental impact among all inputs in this process. Generally, solvent extraction has a greater environmental impact compared to the leaching process.

Recovery of valuable metals from spent lithium-ion batteries using microbial agents for bioleaching: a review

Spent lithium-ion batteries (LIBs) are increasingly generated due to their widespread use for various energy-related applications. Spent LIBs contain several valuable metals including cobalt (Co) and lithium (Li) whose supply cannot be sustained in the long-term in view of their increased demand. To avoid environmental pollution and recover valuable metals, recycling of spent LIBs is widely explored using different methods. Bioleaching (biohydrometallurgy), an environmentally benign process, is receiving increased attention in recent years since it utilizes suitable microorganisms for selective leaching of Co and Li from spent LIBs and is cost-effective. A comprehensive and critical analysis of recent studies on the performance of various microbial agents for the extraction of Co and Li from the solid matrix of spent LIBs would help for development of novel and practical strategies for effective extraction of precious metals from spent LIBs. Specifically, this review focuses on the current advancements in the application of microbial agents namely bacteria (e.g., Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans) and fungi (e.g., Aspergillus niger) for the recovery of Co and Li from spent LIBs. Both bacterial and fungal leaching are effective for metal dissolution from spent LIBs. Among the two valuable metals, the dissolution rate of Li is higher than Co. The key metabolites which drive the bacterial leaching include sulfuric acid, while citric acid, gluconic acid and oxalic acid are the dominant metabolites in fungal leaching. The bioleaching performance depends on both biotic (microbial agents) and abiotic factors (pH, pulp density, dissolved oxygen level and temperature). The major biochemical mechanisms which contribute to metal dissolution include acidolysis, redoxolysis and complexolysis. In most cases, the shrinking core model is suitable to describe the bioleaching kinetics. Biological-based methods (e.g., bioprecipitation) can be applied for metal recovery from the bioleaching solution. There are several potential operational challenges and knowledge gaps which should be addressed in future studies to scale-up the bioleaching process. Overall, this review is of importance from the perspective of development of highly efficient and sustainable bioleaching processes for optimum resource recovery of Co and Li from spent LIBs, and conservation of natural resources to achieve circular economy.

Comprehensive insights into the gallic acid assisted bioleaching process for spent LIBs: Relationships among bacterial functional genes, Co(III) reduction and metal dissolution behavior

Despite the growing demand for resource recovery from spent lithium-ion batteries (LIBs) by bioleaching, low Co leaching efficiency has hindered the development and application of this technology. Therefore, a novel process was designed, combining gallic acid (GA) and mixed culture bioleaching (MCB), to enhance the removal of metals from spent LIBs. Results indicated that the GA + MCB process achieved 98.03% Co and 98.02% Li leaching from spent LIBs, simultaneously reducing the biotoxicity, phytotoxicity and leaching toxicity of spent LIBs under optimal conditions. The results of mechanism analysis demonstrated that functional microorganisms adapted to the leaching system through various strategies, including oxidative stress reduction, DNA damage repair, heavy metal resistance and biofilm formation, maintaining normal physiological activities and the continuous production of biological acid. The biological acid erodes the surface of waste LIBs, causing some Co and a large amount of Li to be released, while also increasing the contact area between GA and Co(III). Therefore, GA is beneficial for reducing insoluble Co(III), forming soluble Co(II). Finally, biological acid can effectively promote Co(II) leaching. Collectively, the results of this study provide valuable insight into the simultaneous enhancement of metal extraction and the mitigation of environmental pollution from spent LIBs.

Spent lithium ion battery (LIB) recycle from electric vehicles: A mini-review

Electrifying transportation through the large-scale implementation of electric vehicles (EVs) is an effective route for mitigating urban atmospheric pollution and greenhouse gas emissions and alleviating petroleum-derived fossil fuel reliance. However, huge dumps of spent lithium-ion batteries (LIBs) have emerged worldwide as a consequence of their extensive use in EVs. With the increasing shortage in LIB raw materials, the recycling of spent LIBs has become a fundamental part of a sustainable approach for energy storage applications, considering the potential economic and environmental benefits. In this mini-review, we will provide a state-of-the-art overview of LIB recycling processes (e.g., echelon utilization, pretreatment, valuable metal leaching and separation). We then discuss the sustainability of current LIB recycling processes from the perspectives of life cycle assessment (LCA) and economic feasibility. Finally, we highlight the existing challenges and possibilities of LIB recycling processes and provide future directions that can bridge the gap between proof-of-concept bench demonstrations and facility-scale field deployments through mutual efforts from academia, industry, and government. It is expected that this review could provide a guideline for enhancing spent LIB recycling and facilitating the sustainable development of the field.

Advances in bioleaching of waste lithium batteries under metal ion stress

In modern societies, the accumulation of vast amounts of waste Li-ion batteries (WLIBs) is a grave concern. Bioleaching has great potential for the economic recovery of valuable metals from various electronic wastes. It has been successfully applied in mining on commercial scales. Bioleaching of WLIBs can not only recover valuable metals but also prevent environmental pollution. Many acidophilic microorganisms (APM) have been used in bioleaching of natural ores and urban mines. However, the activities of the growth and metabolism of APM are seriously inhibited by the high concentrations of heavy metal ions released by the bio-solubilization process, which slows down bioleaching over time. Only when the response mechanism of APM to harsh conditions is well understood, effective strategies to address this critical operational hurdle can be obtained. In this review, a multi-scale approach is used to summarize studies on the characteristics of bioleaching processes under metal ion stress. The response mechanisms of bacteria, including the mRNA expression levels of intracellular genes related to heavy metal ion resistance, are also reviewed. Alleviation of metal ion stress via addition of chemicals, such as spermine and glutathione is discussed. Monitoring using electrochemical characteristics of APM biofilms under metal ion stress is explored. In conclusion, effective engineering strategies can be proposed based on a deep understanding of the response mechanisms of APM to metal ion stress, which have been used to improve bioleaching efficiency effectively in lab tests. It is very important to engineer new bioleaching strains with high resistance to metal ions using gene editing and synthetic biotechnology in the near future.

Two-step leaching of spent lithium-ion batteries and effective regeneration of critical metals and graphitic carbon employing hexuronic acid

Recovering precious metal ions like Co, Li, Mn, and Ni from discarded lithium-ion batteries (LIBs) has significant environmental and economic benefits. Also, graphite will be in high demand in the coming years due to the development of LIBs for use in electric vehicles (EVs) and the need for it for electrodes in a variety of energy storage devices. However, it has been overlooked during the recycling of used LIBs, which resulted in resource waste and environmental pollution. In this work, a comprehensive and environmentally friendly approach for recycling critical metals as well as graphitic carbon from discarded LIBs was proposed. To optimize the leaching process, various leaching parameters were investigated by employing hexuronic acid or ascorbic acid. The feed sample was analyzed using XRD, SEM-EDS, and a Laser Scattering Particle Size Distribution Analyzer to determine the phases, morphology, and particle size. 100% of Li and 99.5% of Co were leached at the optimum conditions of 0.8 mol L^-1 ascorbic acid, a particle size of -25 μm, 70 °C, 60 min of leaching time, and 50 g L^-1 of S/L ratio. A detailed study of the leaching kinetics was carried out. The leaching process was found to be well-fitted with the surface chemical reaction model based on the findings of temperature, acid concentration, and particle size variations. To obtain pure graphitic carbon after the initial leaching, the leached residue was subjected to further leaching with various acids (HCl, H₂SO₄, and HNO₃). The Raman spectra, XRD, TGA, and SEM-EDS analysis of the leached residues following the two-step leaching process were examined to exemplify the quality of the graphitic carbon.

Environmentally sustainable and cost-effective recycling of Mn-rich Li-ion cells waste: Effect of carbon sources on the leaching efficiency of metals using fungal metabolites

Metals recovery from spent lithium coin cells (SCCs) is enjoying great attention due to environmental problems and metal-rich contents such as Mn and Li. Fungi can generate many organic acids, and metals can be dissolved, but sucrose is not an economical medium. The main objective of this study is to find a suitable carbon substrate in place of sucrose for fungal bioleaching. We have developed an environmentally friendly, cost-effective, and green method for recycling and detoxifying Mn and Li from SCCs using the spent culture medium fromPenicillium citrinumcultivation. Sugar cane molasses and sucrose were selected as carbon sources. Based on the extracted fungal metabolites, the effects of pulp density, temperature, and leaching time were assessed on metal dissolution. The most suitable conditions were 30 g/L of pulp density, a temperature of 40 °C, and 4 days of leaching time in spent molasses medium, which led to a high extraction of 87% Mn and 100% Li. Based on EDX-mapping analyses, it was found that the initial concentration of ∑ (Mn + C) in the SCCs powder was almost 100% while reaching nearly 6.4% after bioleaching. After bioleaching, an analysis of residual powder confirmed that metal dissolution from SCCs was effective owing to fungal metabolites. The economic study showed that the bioleaching method is more valuable for the dissolution of metals than the chemical method; In addition to improving bioleaching efficiency, molasses carbon sources can be used for industrial purposes.

Recycling Valuable Metals from Spent Lithium-Ion Batteries Using Carbothermal Shock Method

Pyrometallurgy technique is usually applied as a pretreatment to enhance the leaching efficiencies in the hydrometallurgy process for recovering valuable metals from spent lithium-ion batteries. However, traditional pyrometallurgy processes are energy and time consuming. Here, we report a carbothermal shock (CTS) method for reducing LiNi_0.3 Co_0.2 Mn_0.5 O₂ (NCM325) cathode materials with uniform temperature distribution, high heating and cooling rates, high temperatures, and ultrafast reaction times. Li can be selectively leached through water leaching after CTS process with an efficiency of >90 %. Ni, Co, and Mn are recovered by dilute acid leaching with efficiencies >98 %. The CTS reduction strategy is feasible for various spent cathode materials, including NCM111, NCM523, NCM622, NCM811, LiCoO₂ , and LiMn₂ O₄ . The CTS process, with its low energy consumption and potential scale application, provides an efficient and environmentally friendly way for recovering spent lithium-ion batteries.

A review on the bioleaching of toxic metal(loid)s from contaminated soil: Insight into the mechanism of action and the role of influencing factors

The anthropogenic activities in agriculture, industrialization, mining, and metallurgy combined with the natural weathering of rocks, have led to severe contamination of soils by toxic metal(loid)s. In an attempt to remediate these polluted sites, a plethora of conventional approaches such as Solidification/Stabilization (S/S), soil washing, electrokinetic remediation, and chemical oxidation/reduction have been used for the immobilization and removal of toxic metal(loid)s in the soil. However, these conventional methods are associated with certain limitations. These limitations include high operational costs, high energy demands, post-waste disposal difficulties, and secondary pollution. Bioleaching has proven to be a promising alternative to these conventional approaches in removing toxic metal(loid)s from contaminated soil as it is cost-effective, environmentally friendly, and esthetically pleasing. The bioleaching process is influenced by factors including pH, temperature, oxygen, and carbon dioxide supply, as well as nutrients in the medium. It is crucial to monitor these parameters before and throughout the reaction since a change in any, for instance, pH during the reaction, can alter the microbial activity and, therefore, the rate of metal leaching. However, research on these influencing factors and recent innovations has brought significant progress in bioleaching over the years. This critical review, therefore, presents the current approaches to bioleaching and the mechanisms involved in removing toxic metal(loid)s from contaminated soil. We further examined and discussed the fundamental principles of various influencing factors that necessitate optimization in the bioleaching process. Additionally, the future perspectives on adding omics for bioleaching as an emerging technology are discussed.

Advances and challenges in anode graphite recycling from spent lithium-ion batteries

Spent lithium-ion batteries (LIBs) have been one of the fast-growing and largest quantities of solid waste in the world. Spent graphite anode, accounting for 12-21 wt% of batteries, contains metals, binders, toxic, and flammable electrolytes. The efficient recovery of spent graphite is urgently needed for environmental protection and resource sustainability. Recently, more and more studies have been focused on spent graphite recycling, while the advance and challenges are rarely summarized. Hence, this study made a comprehensive review of graphite recycling including separation, regeneration, and synthesis of functional materials. Firstly, the pretreatment of graphite separation was overviewed. Then, the spent graphite regeneration methods such as leaching, pyrometallurgy, their integration processes, etc. were systematically introduced. Furthermore, the modification strategies to enhance the electrochemical performance were discussed. Subsequently, we reviewed in detail the synthesis of functional materials using spent graphite for energy and environmental applications including graphene, adsorbents, catalysts, capacitors, and graphite/polymer composites. Meanwhile, we briefly compared the economic and environmental benefits of graphite regeneration and other functional materials production. Finally, the technical bottlenecks and challenges for spent graphite recycling were summarized and some future research directions were proposed. This review contributes to spent LIBs recycling more efficiently and profitably in the future.

Lithium-Ion Battery Solid Electrolytes Based on Poly(vinylidene Fluoride)-Metal Thiocyanate Ionic Liquid Blends

Solid polymer electrolytes (SPEs) are required to improve battery safety through the elimination of the liquid electrolyte solution in current batteries. This work is focused on the development of a hybrid SPE based on poly(vinylidene fluoride), PVDF, and 1-butyl-3-methylimidazolium cobalt(II) isothiocyanate, [BMIM]₂[(SCN)₄Co] magnetic ionic liquid (MIL), and its battery cycling behavior at room temperature. The addition of MIL in filler contents up to 40 wt % to the PVDF matrix does not influence the compact morphology of the samples obtained by solvent casting. The polar β-phase of PVDF increases with increasing MIL content, whereas the degree of crystallinity, thermal degradation temperature, and mechanical properties of the MIL/PVDF blends decrease with increasing MIL content. The ionic conductivity of the MIL/PVDF blends increases both with temperature and MIL content, showing the highest ionic conductivity of 7 × 10^-4 mS cm^-1 at room temperature for the MIL/PVDF blend with 40 wt % of MIL. The cathodic half-cells prepared with this blend as SPE show good reversibility and excellent cycling behavior at different C-rates, with a discharge capacity of 80 mAh g^-1 at a C/10-rate with a Coulombic efficiency of 99%. The developed magnetic SPE, with excellent performance at room temperature, shows potential for the implementation of sustainable lithium-ion batteries, which can be further tuned by the application of an external magnetic field.

Complete bioleaching of Co and Ni from spent batteries by a novel silver ion catalyzed process

In the present work, bioleaching of two valuable metals of cobalt (Co) and nickel (Ni) from spent lithium-ion batteries (LIBs) of laptop by Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans through a novel adaptation procedure was investigated. Different bioleaching methods including A. ferrooxidans and A. thiooxidans spent medium, A. ferrooxidans one-step and two-step bioleaching were carried out. The effect of silver ion on the bioleaching of Co and Ni in these methods was evaluated. Moreover, a novel strain adaptation approach to the toxic solid content of the battery powder was chosen, which resulted in a very short adaptation time and bioleaching (2 days). Even though silver ion did not have a significant effect on the spent medium method, it had an increasing effect of 26% and 7%, for Co and Ni recovery, respectively, on two-step bioleaching with silver ion-adapted A. ferrooxidans, in gradual addition of the battery powder. The highest extraction results in the spent medium method were 45.2% and 71.5% for Co and Ni, respectively, and a very high extraction yield of 99.95% for these metals was achieved in a short time of only 3 days by two-step bioleaching with gradual addition of the solid content and in the presence of Ag⁺. KEY POINTS: • Mixed spent medium of acidophilic bacteria resulted in higher Ni and Co extraction. • Adaptation to Ag⁺ has enhanced the strain capability for Co and Ni extraction. • With Ag⁺ presence, Co and Ni extraction reached 99.95% in two-step bioleaching.

Feasibility of reduced iron species for promoting Li and Co recovery from spent LiCoO2 batteries using a mixed-culture bioleaching process

The recovery of metals from spent LiCoO₂ batteries (SLBs) is essential to avoid resource wastage and the production of hazardous waste. However, the major challenge in regard to recovering metals from SLBs using traditional bioleaching is the low Co yield. To overcome this issue, a mixed culture of Acidithiobacillus caldus and Sulfobacillus thermosulfidooxidans was designed for use in SLBs leaching in this study. With the assistance of Fe²⁺ as a reductant, 99% of Co and 100% of Li were leached using the above mixed-culture bioleaching (MCB) process, thus solving the problem of low metal leaching efficiency from SLBs. Analysis of the underlying mechanism revealed that the effective extraction of metals from SLBs by the Fe²⁺-MCB process relied on Fe²⁺-releasing electrons to reduce refractory Co(III) to Co(II) that can be easily bioleached. Finally, the hazardous SLBs was transformed into a non-toxic material after treatment utilizing the Fe²⁺-MCB process. However, effective SLBs leaching was not achieved by the addition of Fe⁰ to the MCB system. Only 25% Co and 31% Li yields were obtained, as the addition of Fe⁰ caused acid consumption and bacterial apoptosis. Overall, this study revealed that reductants that cause acid consumption and harm bacteria should be ruled out for use in reductant-assisted bioleaching processes for extracting metals from SLBs.

Strategies for anti-oxidative stress and anti-acid stress in bioleaching of LiCoO2 using an acidophilic microbial consortium

High metal ion concentrations and low pH cause severely inhibit the activity of an acidophilic microbial consortium (AMC) in bioleaching. This work investigated the effects of exogenous spermine on biofilm formation and the bioleaching efficiency of LiCoO₂ by AMC in 9K medium. After the addition of 1 mM spermine, the activities of glutathione peroxidase and catalase increased, while the amount of H₂O₂, intracellular reactive oxygen species (ROS) and malondialdehyde in AMC decreased. These results indicated that the ability of AMC biofilm to resist oxidative stress introduced by 3.5 g/L Li⁺ and 30.1 g/L Co²⁺ was improved by spermine. The activity of glutamate decarboxylase was promoted to restore the intracellular pH buffering ability of AMC. Electrochemical measurements showed that the oxidation rate of pyrite was increased by exogenous spermine. As a result, high bioleaching efficiencies of 97.1% for Li⁺ and 96.1% for Co²⁺ from a 5.0% (w v^-1) lithium cobalt oxide powder slurry were achieved. This work demonstrated that Tafel polarization can be used to monitor the AMC biofilm's ability of uptaking electrons from pyrite during bioleaching. The corrosion current density increased with 1 mM spermine, indicating enhanced electron uptake by the biofilm from pyrite.

Green Recycling Methods to Treat Lithium-Ion Batteries E-Waste: A Circular Approach to Sustainability

E-waste generated from end-of-life spent lithium-ion batteries (LIBs) is increasing at a rapid rate owing to the increasing consumption of these batteries in portable electronics, electric vehicles, and renewable energy storage worldwide. On the one hand, landfilling and incinerating LIBs e-waste poses environmental and safety concerns owing to their constituent materials. On the other hand, scarcity of metal resources used in manufacturing LIBs and potential value creation through the recovery of these metal resources from spent LIBs has triggered increased interest in recycling spent LIBs from e-waste. State of the art recycling of spent LIBs involving pyrometallurgy and hydrometallurgy processes generates considerable unwanted environmental concerns. Hence, alternative innovative approaches toward the green recycling process of spent LIBs are essential to tackle large volumes of spent LIBs in an environmentally friendly way. Such evolving techniques for spent LIBs recycling based on green approaches, including bioleaching, waste for waste approach, and electrodeposition, are discussed here. Furthermore, the ways to regenerate strategic metals post leaching, efficiently reprocess extracted high-value materials, and reuse them in applications including electrode materials for new LIBs. The concept of "circular economy" is highlighted through closed-loop recycling of spent LIBs achieved through green-sustainable approaches.

Recycling spent LiNi1-x-yMnxCoyO2 cathodes to bifunctional NiMnCo catalysts for zinc-air batteries

SignificanceIn recent years, lithium-ion batteries (LIBs) have been widely applied in electric vehicles as energy storage devices. However, it is a great challenge to deal with the large number of spent LIBs. In this work, we employ a rapid thermal radiation method to convert the spent LIBs into highly efficient bifunctional NiMnCo-activated carbon (NiMnCo-AC) catalysts for zinc-air batteries (ZABs). The obtained NiMnCo-AC catalyst shows excellent electrochemical performance in ZABs due to the unique core-shell structure, with face-centered cubic Ni in the core and spinel NiMnCoO₄ in the shell. This work provides an economical and environment-friendly approach to recycling the spent LIBs and converting them into novel energy storage devices.

Recycling of cathode material from spent lithium-ion batteries: Challenges and future perspectives

The intrinsic advancement of lithium-ion batteries (LIBs) for application in electric vehicles (EVs), portable electronic devices, and energy-storage devices has led to an increase in the number of spent LIBs. Spent LIBs contain hazardous metals (such as Li, Co, Ni, and Mn), toxic and corrosive electrolytes, metal casting, and polymer binders that pose a serious threat to the environment and human health. Additionally, spent LIBs may serve as an economic source for transition metals, which could be applied to redesigning under a closed-circuit recycling process. Thus, the development of environmentally benign, low cost, and efficient processes for recycling of LIBs for a sustainable future has attracted worldwide attention. Therefore, herein, we introduce the concept of LIBs and review state-of-art technologies for metal recycling processes. Moreover, we emphasize on LIB pretreatment approaches, metal extraction, and pyrometallurgical, hydrometallurgical, and biometallurgical approaches. Direct recycling technologies combined with the profitable and sustainable cathode healing technology have significant potential for the recycling of LIBs without decomposition into substituent elements or precipitation; hence, these technologies can be industrially adopted for EV batteries. Finally, commercial technological developments, existing challenges, and suggestions are presented for the development of effective, environmentally friendly recycling technology for the future.

Environmental Sustainability and Supply Resilience of Cobalt

Cobalt (Co) is an essential metal for the development of energy-transition technologies, decarbonising transportation, achieving several sustainable development goals, and facilitating a future net zero transition. However, the supply of Co is prone to severe fluctuation, disruption, and price instabilities. This review aims to identify the future evolution of Co supply through technologically resilient and environmentally sustainable pathways. The work shows that advances in both primary and secondary sources, Co mining methods and recycling systems are yet to be fully optimised. Moreover, responsible sourcing from both large mines and small artisanal mines will be necessary for a resilient Co supply. Regulatory approaches may increase transparency, support local mining communities, and improve secondary Co recovery. Novel Co supply options, such as deep-sea mining and bio-mining of tailings, are associated with major techno-economic and environmental issues. However, a circular economy, keeping Co in the economic loop for as long as possible, is yet to be optimised at both regional and global scales. To achieve environmental sustainability of Co, economic incentives, regulatory push, and improved public perception are required to drive product innovation and design for circularity. Although the complexity of Co recycling, due to lack of standardisation of design and chemistry in batteries, is an impediment, a sustainable net zero transition using Co will only be possible if a reliable primary supply and a circular secondary supply are established.

Mathematical modeling of metal recovery from E-waste using a dark-fermentation-leaching process

In this work, an original mathematical model for metals leaching from electronic waste in a dark fermentation process is proposed. The kinetic model consists of a system of non-linear ordinary differential equations, accounting for the main biological, chemical, and physical processes occurring in the fermentation of soluble biodegradable substrates and in the dissolution process of metals. Ad-hoc experimental activities were carried out for model calibration purposes, and all experimental data were derived from specific lab-scale tests. The calibration was achieved by varying kinetic and stoichiometric parameters to match the simulation results to experimental data. Cumulative hydrogen production, glucose, organic acids, and leached metal concentrations were obtained from analytical procedures and used for the calibration. The results confirmed the high accuracy of the model in describing biohydrogen production, organic acids accumulation, and metals leaching during the biological degradation process. Thus, the mathematical model represents a useful and reliable tool for the design of strategies for valuable metals recovery from waste or mineral materials. Moreover, further numerical simulations were carried out to analyze the interactions between the fermentation and the leaching processes and to maximize the efficiency of metals recovery due to the fermentation by-products.

An overview of global power lithium-ion batteries and associated critical metal recycling

The rapid development of lithium-ion batteries (LIBs) in emerging markets is pouring huge reserves into, and triggering broad interest in the battery sector, as the popularity of electric vehicles (EVs)is driving the explosive growth of EV LIBs. These mounting demands are posing severe challenges to the supply of raw materials for LIBs and producing an enormous quantity of spent LIBs, bringing difficulties in the areas of resource allocation and environmental protection. This review article presents an overview of the global situation of power LIBs, aiming at different methods to treat spent power LIBs and their associated metals. We provide a critical review of power LIB supply chain, industrial development, waste treatment strategies and recycling, etc. Power LIBs will form the largest proportion of the battery industry in the next decade. The analysis of the sustainable supply of critical metal materials is emphasized, as recycling metal materials can alleviate the tight supply chain of power LIBs. The existing significant recycling practices that have been recognized as economically beneficial can promote metal closed-loop recycling. Scientific thinking needs to innovate sustainable and cost-effective recycling technologies to protect the environment because of the chemicals contained in power LIBs.

Resource Availability and Implications for the Development of Plug-In Electric Vehicles

Plug-in electric vehicles (PEVs) have immense potential for reducing greenhouse gas emissions and dependence on fossil fuels, and for smart grid applications. Although a great deal of research is focused on technological limitations that affect PEV battery performance targets, a major and arguably equal concern is the constraint imposed by the finite availability of elements or resources used in the manufacture of PEV batteries. Availability of resources, such as lithium, for batteries is critical to the future of PEVs and is, therefore, a topic that needs attention. This study addresses the issues related to lithium availability and sustainability, particularly supply and demand related to PEVs and the impact on future PEV growth. In this paper, a detailed review of the research on lithium availability for PEV batteries is presented, key challenges are pinpointed and future impacts on PEV technology are outlined.

A review on recent advancements in recovery of valuable and toxic metals from e-waste using bioleaching approach

This review is intent on the environmental pollution generated from printed circuit boards and the methods employed to retrieve valuable and hazardous metals present in the e-wastes. Printed circuit boards are the key components in the electronic devices and considered as huge e-pollutants in polluting our surroundings and the environment as a whole. Composing of toxic heavy metals, it causes serious health effects to the plants, animals and humans in the environment. A number of chemical, biological and physical approaches were carried out to recover the precious metals and to remove the hazardous metals from the environment. Chemical leaching is one of the conventional PCBs recycling methods which was carried out by using different organic solvents and chemicals. Need of high cost for execution, generation of secondary wastes in the conventional methods, forces to discover the advanced recycling methods such as hydrometallurgical, bio-metallurgical and bioleaching processes to retrieve the valuable metals generate through e-wastes. Among them, bioleaching process gain extra priority due to its higher efficiency of metal recovery from printed circuit boards. There are different classes of microorganisms have been utilized for precious metal recovery from the PCBs through bioleaching process such as chemolithoautotrophy, heterotrophy and different fungal species including Aspergillus sp. and Penicillium sp. The current status and scope for further studies in printed circuit boards recycling are discussed in this review.

Biotechnological recycling of hazardous waste PCBs using Sulfobacillus thermosulfidooxidans through pretreatment of toxicant metals: Process optimization and kinetic studies

The present study dealt with the restricted microbial tolerance for lead and tin during bioleaching of waste printed circuit boards (WPCBs) and lower extraction yields of valuable metals. Pretreatment of WPCBs in 4.0 mol/L HNO₃ at 90 °C for 180 min duration prominently dissolved the toxicant metals before the microbial mobilization of valuable metals. Acid pretreatment followed the first-order kinetics that exhibiting an intermediate-controlled mechanism with the apparent activation energy determined to be E_a(Pb), 25.1 kJ/mol and E_a(Sn), 21.9 kJ/mol. Thereafter, the parametric optimization of aeration rate, O₂-enrichment, external CO₂ supply, temperature, and time for bioleaching of ground WPCBs was examined using Sulfobacillus thermosulfidooxidans (strain RDB). A favourable condition for Cu-bioleaching under higher oxidative environment in comparison to Ni and Zn exhibited the auto-catalytic behaviour of Cu²⁺ in the biological system. More than 92% of valuable metals were extracted under the optimal condition of aeration rate, 0.5 L/min; O₂-enrichement dosage, 30%; external CO₂ supply, 0.1%; temperature, 55 °C; and time, 18 days. The bioleaching kinetics followed shrinking core model that exhibiting the shifting of mass transfer from chemically-controlled to the diffusion-controlled mechanism. This process offers two-fold advantages that restoring the valuable metals with low-emission biotechnological route for waste valorization.

Acid leaching of LiCoO2 enhanced by reducing agent. Model formulation and validation

In this work, a model has been formulated to describe the complex process of LiCoO₂ leaching through the participation of competing reactions in acid media including the effect of H₂O₂ as reducing agent. The model presented here describes the extraction of Li and Co in the presence and absence of H₂O₂, and it takes into account the different phenomena affecting the controlling mechanisms. In this context, the model predicts the swift from kinetic control to diffusion control. The model has been implemented and solved to simulate the leaching process. To validate the model and to estimate the model parameters, a set of 12 (in triplicate) extraction experiments were carried out varying the concentration of hydrochloric acid (within the range of 0.5-2.5 M) and hydrogen peroxide (range 0-0.6%v/v). The simulation results match fairly well with the experimental data for a wide range of conditions. Furthermore, the model can be used to predict results with different solid-liquid ratios as well as different acid and oxygen peroxide concentrations. This model could be used to design or optimize a LiCoO₂ extraction process facilitating the corresponding economical balance of the treatment.

Cobalt Recovery from Li-Ion Battery Recycling: A Critical Review

The increasing demand for Li-ion batteries for electric vehicles sheds light upon the Co supply chain. The metal is crucial to the cathode of these batteries, and the leading global producer is the D.R. Congo (70%). For this reason, it is considered critical/strategic due to the risk of interruption of supply in the short and medium term. Due to the increasing consumption for the transportation market, the batteries might be considered a secondary source of Co. The outstanding amount of spent batteries makes them to a core of urban mining warranting special attention. Greener technologies for Co recovery are necessary to achieve sustainable development. As a result of these sourcing challenges, this study is devoted to reviewing the techniques for Co recovery, such as acid leaching (inorganic and organic), separation (solvent extraction, ion exchange resins, and precipitation), and emerging technologies—ionic liquids, deep eutectic solvent, supercritical fluids, nanotechnology, and biohydrometallurgy. A dearth of research in emerging technologies for Co recovery from Li-ion batteries is discussed throughout the manuscript within a broader overview. The study is strictly connected to the Sustainability Development Goals (SDG) number 7, 8, 9, and 12.