Direct recycling of spent Li-ion batteries: Challenges and opportunities toward practical applications

Summary

With the exponential expansion of electric vehicles (EVs), the disposal of Li-ion batteries (LIBs) is poised to increase significantly in the coming years. Effective recycling of these batteries is essential to address environmental concerns and tap into their economic value. Direct recycling has recently emerged as a promising solution at the laboratory level, offering significant environmental benefits and economic viability compared to pyrometallurgical and hydrometallurgical recycling methods. However, its commercialization has not been realized in the terms of financial feasibility. This perspective provides a comprehensive analysis of the obstacles that impede the practical implementation of direct recycling, ranging from disassembling, sorting, and separation to technological limitations. Furthermore, potential solutions are suggested to tackle these challenges in the short term. The need for long-term, collaborative endeavors among manufacturers, battery producers, and recycling companies is outlined to advance fully automated recycling of spent LIBs. Lastly, a smart direct recycling framework is proposed to achieve the full life cycle sustainability of LIBs.

Graphical abstract

Chemical engineering; Electrochemistry; Electrochemical energy storage; Engineering

Introduction

The reduction of carbon footprints has become as a global objective in recent years, leading to a growing interest in electric vehicles (EVs) as a sustainable alternative to traditional internal combustion engine vehicles.^1,2,3,4 It is projected that approximately 140 million EVs will be in service worldwide by 2030. However, it is crucial to consider the proper management of end-of-life (EOL) Li-ion batteries (LIBs) used in EVs. Due to the high concentration of valuable metals present in spent LIBs, recycling is the most sustainable method, offering the potential to address environmental concerns and alleviate resource scarcity within the LIBs industry.^5,6

Pyrometallurgical (pyro) and hydrometallurgical (hydro) technologies are commonly employed for the recycling of spent LIBs.^7,8 Pyro recycling involves high-temperature smelting, which is a straightforward process but consumes a significant amount of energy.^9,10 Hydro recycling relies on leaching with acids or bases to dissolve cathodes to metal ions, requiring substantial quantities of chemicals and generating considerable wastewater.^11,12 Although metallurgy-based recycling is economically viable due to the high market value of metals such as Li, Co, Ni, etc., it can be influenced by metal price fluctuations and changes in cathode compositions.¹³ Moreover, it is not applicable for recycling of cathodes without valuable metals, such as LiFePO₄ (LFP) and LiMn₂O₄ (LMO). Therefore, there is an urgent need to develop cost-effective, energy-efficient, environmentally friendly, and more sustainable recycling methods.¹⁴

Direct recycling, based on chemical relithiation, presents a promising approach that can address compositional and structural defects in degraded cathodes without sacrificing the embedded energy in materials.^15,16 This method enables the production of cathodes that can be directly used in battery assembly, eliminating the need to resynthesize cathodes from precursors. Compared to pyro- and hydro-recycling routes, direct recycling offers significant advantages in terms of energy consumption, safety, cost, flexibility, and economic returns, attracting considerable attention from academia and industry. Recently, some researchers reviewed the state-of-the-art direct recycling technologies of spent LIBs, placing significant emphasis on the various relithiation routes and the importance of sustainable recycling in comparison to conventional metallurgical methods.^6,17,18 However, the critical obstacles that hinder the practical implementation of direct recycling have been overlooked.

In this context, our focus has been on analyzing the technical limitations that hinder the industrialization of direct recycling at various stages, spanning from the retirement to the regeneration of LIBs. Additionally, we proposed potential solutions to address these challenges, taking into account both short-term and long-term perspectives (Figure 1). In the short term, addressing the challenges related to disassembly, sorting, and technological limitations is crucial to achieve the initial industrialization of this process. Looking ahead, stakeholders in the LIBs chain can collaborate to establish industry-wide standards for LIBs at the pack, module, and cell levels. Alongside advancements in automated facilities, a smart recycling model for spent batteries is expected to be achieved. Ultimately, by addressing the remaining challenges, promoting collaboration, establishing industry standards, and leveraging automated facilities, the industrialization of direct recycling can advance, which will contribute to the full life cycle sustainability of LIBs.

Figure 1.

Challenges and potential solutions for the initial industrialization of direct recycling in short term (Target I), as well as the future battery design (Target II), toward a smart recycling of spent LIBs in long term (Final target)

Evaluation of direct recycling market

Due to the widespread adoption of EVs, there is a surge in demand for LIBs in these years. In 2022, it is estimated that approximately 700 GW-hours (GWh) of batteries will be required, and this figure is expected to rise to 4.7 TW-hours (TWh) by 2030 (Figure 2A).¹⁹ As the service life of LIBs typically ranges from 8 to 10 years, there will be a growing number of retired LIBs from EVs. If we consider 2015 as the onset of rapid marketization for EVs,²⁰ a significant quantity of LIBs is expected to reach the end of their service life and retire around 2025. It is estimated that by this time, there will be 900 kilotons (kt) of spent battery materials, encompassing both production scrap and EOL batteries. (Figure 2B).²⁰ These retired LIBs are predominantly composed of LFP, LiNi_1/3Co_1/3Mn_1/3O₂ (NCM111), and LiNi_0.5Co_0.2Mn_0.3O₂ (NCM523) (Figure 2C).^21,22 Cathodes with higher Ni content, such as LiNi_0.6Co_0.2Mn_0.2O₂ (NCM622), LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811), and LiNi_1-x-yCo_xAl_yO₂ (NCA), make up only 13% of the retired cathode materials due to the relative immaturity of the technology at the early stage. Additionally, the LiCoO₂ (LCO) primarily sourced from portable electronics accounts for ∼23%.

Figure 2.

The enviornmental and economic impacts of recyling market

(A) Global LIBs demand from 2022 to 2030; (B) Available battery materials for recycling from 2020 to 2040; (C) The battery chemistries of the retired LIBs by 2025; (D) Comparison of the energy consumption, GHG emissions, revenue and cost of pyro, hydro, and direct recycling methods.

Assuming all these retired cathode materials can be recycled, we primarily conducted the life-of-cycle analysis (LCA) of pyro, hydro, and direct recycling with the EverBatt Model developed by Argonne National Lab (Figure 2D).²³ It was found that a total of ∼2.48 × 10¹⁰ MJ of energy would be consumed for pyro recycling, leading to the generation of ∼3.39 × 10¹³ kg of greenhouse gas emissions (GHGs). The hydro recycling was estimated to consume ∼4.14 × 10¹⁰ MJ of energy and produce ∼4.12 × 10¹⁴ kg of GHGs, which are slightly higher compared to pyro recycling. In contrast, direct recycling was found to be a more energy-efficient and environmentally friendly option, which would consume ∼0.72 × 10¹⁰ MJ of energy and generate ∼5.55 × 10¹² kg of GHGs, corresponding to only 16% and 1.34% of the energy consumption and GHG emissions of hydro recycling, respectively. Importantly, due to the low recycling cost and high value of cathode production, the direct recycling could create a profit of 1.71 billion dollars, nearly double that of metallurgy-based recycling. These findings highlight the necessity of industrial application of direct recycling, considering its favorable environmental impact, energy efficiency, and economic benefits. However, several challenges need to be addressed for the industrialization of direct recycling, which will be discussed in detail in the following content.

Challenges of direct recycling

Manual disassembly

The initial step in the recycling process is the separation of the battery pack from the vehicle, followed by meticulous dismantling to access the individual cells. This ensures safe transportation and enables subsequent recycling operations. However, this process is still highly dependent on manual labor.²⁴ Although researchers and industry stakeholders are actively exploring automated disassembly technologies to improve the efficiency and scalability of the recycling process, the variability in battery designs, sizes, electrical connections, and packaging formats presents ongoing challenges in the development and implementation of automated disassembly solutions.²⁵ Unlike highly structured environments where robots can perform repetitive tasks on known objects in fixed positions, the LIBs present a range of uncertainties and variables at different stages of disassembly.

During the initial stage of disassembling, when the vehicle case is removed, the battery packs exhibit varying shapes due to the diverse range of EVs models available in the market (Figure 3A).²⁶ Additionally, battery packs contain complex battery manage systems, cooling systems, and insulation packages.²⁷ The arrangement of these components varies among different manufacturers. Furthermore, modules and cells within the battery pack are arranged and interconnected in specific ways to achieve the desired voltage and capacity. Series and parallel connections are commonly used, but the exact configurations may differ between EV models and manufacturers.^28,29 Figure 3B illustrates some of the methods used for assembly the battery cells, including connectors, laser welding, templating, and glue irrigation.^30,31,32 After removing all the connections in the battery pack, the cells present three types: prismatic, pouch, and cylindrical cells (Figure 3C).^26,33 The specific cell type used is determined by the battery chemistry and the design choices made by the manufacturer.

Figure 3.

Battery disassembling challenges

(A) Different frameworks of battery packs; (B) Connection methods in battery modules; (C) Different types of battery cells; (D) Potential solutions to resolve issues related to manual disassembling.

Overall, the complex and diverse nature of LIBs has hindered the adoption of automated disassembly solutions. As a result, manual labor remains the primary approach for LIB disassembly in the short term. It should be noted that prioritization of the protection and training of workers to prevent the safety issues associated with the disassembling process is critically important (Figure 3D).^34,35 The LIBs disassembly involves potential hazards such as chemical leaks, thermal runaway, and exposure to toxic materials.^10,29 To ensure worker safety, strict safety protocols must be implemented, and workers should be provided with appropriate personal protective equipment (PPE). Additionally, specialized and insulated tools should be used during the disassembly process. Moreover, workers should receive comprehensive training on the proper handling techniques, potential risks associated with LIBs, emergency response procedures, as well as the importance of adhering to environmental regulations. To resolve the time-communing issue, a practical approach could involve the implementation of a hybrid human-robot workstation. In this setup, robots would handle routine and repetitive tasks, while humans would focus on more complex and demanding activities.

Accurate sorting

Accurate sorting is an essential part for spent LIBs recycling, particularly in the context of direct regeneration, where only a single cathode type can be processed to recover high-quality materials.³⁶ The market demand for LIBs varies across different application scenarios, leading to the popularity of various cathode materials such as LFP, LMO, LCO, and NCM.^37,38 During the electrochemical cycling process, different cathode materials undergo specific chemical and structural changes that result in unique failure mechanisms (Figure 4A).^39,40 While the performance decay is primarily caused by the loss of Li⁺ ions, the resulting side reactions differ depending on the material. For instance, the loss of Li⁺ in LFP leads to the formation of Fe-Li anti-site defects.⁴¹ For LMO, the decline in performance decline is also attributed to the dissolution of Mn besides Li⁺ loss. In layered cathodes such as LCO and NCM, the appearance of Li vacancies promotes the migration of transition metals to Li position, resulting in phase transitions. If the Ni content is higher than 50%, microcracks within cathode particles can even be formed in the process.

Figure 4.

Battery sorting challenegs

(A) Comparison of degradation mechanisms and stability of different cathode materials; (B) A schematic illustration of the developed micro-CL setup for in situ visualizations of a Li-ion pouch cell; (C and D) Representative slices of the NMC cathode and graphite anode; (E) Potential solution for effective sorting of spent LIBs in short term.

In addition to the various degradation mechanisms between cathode materials, considering the structural integrity of cathode materials during regeneration is crucial as well. Different cathode materials exhibit varying levels of stability in different environments, and the regeneration process needs to be adjusted accordingly. For example, a reductive atmosphere is needed for solid-state regeneration of LFP, and an oxidative atmosphere is necessary for sintering layered cathode. Aqueous solution is not suitable for regenerating cathodes with Ni content higher than 60% due to the high sensitivity to protons.^42,43 By accurately identifying and segregating batteries with different cathode chemistries, it becomes possible to tailor the recycling processes and treatment conditions to the specific materials being recovered, allowing for better control in maintaining the desired properties of the cathode materials, such as their crystalline structure, particle morphology, and electrochemical activity.⁴⁴

However, accurate sorting without damaging batteries is still challenging primarily due to the lack of easily accessible chemistry information labeled outside the batteries. Disassembling a large quantity of spent LIBs for chemical characterization is costly and inefficient, especially in an industrial context. Advancements in battery characterization techniques are being explored to develop non-destructive methods for identifying cathode materials. Zan et al. proposed a laboratory-based high-resolution and high-throughput X-ray microcomputer tomography method, which is capable of in situ visualization of industry-related pouch batteries with excellent detection fidelity, resolution, and reliability (Figure 4B).⁴⁵ The virtual imaging of the cathode and anode electrodes (Figures 4C and 4D) can primarily indicate the battery chemistry information based on the morphological features of different cathodes. However, it can be challenging to distinguish materials with similar morphological characteristics, such as polycrystalline NCM111, NCM523, or NCM622.

In order to achieve more efficient and accurate classification of cathode materials, scientists have proposed building artificial intelligence (AI) models that leverage input parameters such as shape, size, current, voltage, and internal resistance to identify different cathode materials.⁴⁶ By training these models on a large dataset containing known cathode materials, they can learn to classify and differentiate between various compositions. The integration of AI techniques with other characterization methods, such as spectroscopic techniques or elemental analysis, may further improve the accuracy and reliability of cathode material classification. Ongoing research and advancements in AI algorithms, data collection, and model development are expected to contribute to the future development of more efficient and accurate classification methods for distinguishing specific cathode materials.

Another practical option for effective sorting of spent LIBs, especially in the absence of clear labeling, can be implemented through differentiated collection strategies (Figure 4E). End users, such as EV owners or device users, often possess important information regarding the batteries they are disposing of, including the battery manufacturer, purchase time, driving years, and accumulated mileages. This information can be relayed to the collectors responsible for gathering the spent LIBs, who can then differentiate and segregate the batteries based on the information received from the end users. Finally, collectors can transport the classified batteries to qualified recycling facilities. To make this approach successful, it is important to ensure proper education and training of awareness among end users to encourage their active participation in providing accurate information about the retired batteries.

Materials separation

LIBs are typically composed of cathodes, anodes, electrolytes, separators, and casings. Achieving effective separation of battery components is desirable to maximize the recovery of valuable materials and promote the closed-loop development of LIBs. However, it is still challenging at present. While manual disassembling by labor can achieve precise separation of materials, it comes with inherent risks and challenges. For instance, the electrolyte used in LIBs often contains toxic solvents, which poses health risks during the disassembly process.⁴⁷ Additionally, the decomposition of LiPF₆ electrolyte in humid air can lead to the generation of toxic gases like hydrogen fluoride (HF).⁴⁸ Moreover, there is a risk of combustion or explosion when the anode is exposed to air due to the high activity of LiC_x.⁴⁹

To reduce the reliance on manual labor and minimize associated risks, researchers have made efforts to develop automatic facilities to open cell and separate materials, but these facilities often require customization based on battery type and size, which results in high costs and lower throughput, limiting the scalability of this technology.⁵⁰ As an alternative approach, it has been suggested to integrate the pretreatment steps used in the hydro-recycling method, such as mechanical crushing, separation, and sieving, into the direct recycling of spent LIBs in the short term. However, it’s important to note that the implementation and feasibility of this approach would require further research and advancement. Factors such as the structural stability and morphological integrity of cathode particles, as well as the residual impurity content in cathode powder after pretreatment, need to be thoroughly investigated and optimized as they have great impacts on the downstream direct regeneration.

Mechanical crushing (M), thermomechanical (TM), and electrohydraulic fragmentation (EHF) are the primary methods developed for breaking down the robust battery cell casing, in which active materials can be liberated from current collectors (Figures 5A–5C).⁵¹ In the M process, intact LIBs are fed into the system and crushed into small particle fragments under mechanical sheer force.⁵² The high tensile strength of the metal current collector allows for effective delamination of the active particles during the deformation of the metal foils. The TM process involves vacuum pyrolysis at 500–650°C before mechanical crushing to pre-remove polymetric binder. In the following mechanical crushing, individual active materials particles without virtually aggregation can be obtained. The EHF process uses thousands of high-voltage pulsations (40 kV) in water bath to destroy batteries. The presence of water-soluble anode binder, such as carboxymethylcellulose (CMC), styrene-butadiene rubber (SBR), or polyacrylic acid (PAA), aids in the delamination of graphite particles from Cu foils, while most of cathode particles remain attached to Al foils.⁵³

Figure 5.

Materials seperation challenges

(A–C) Schematical illustration of the state-of-the-art crushing methods (M, TM, and EHF); (D) Mass distribution and losses of LIB materials after three different crushing routes; (E) Composition of the BM (<1000 μm) after the three processes; (F) Composition of the BM with fine fraction (<63 μm) after the three processes; (G) Schematic illustration of froth flotation; (H) Grade and recovery of the graphite particles in the overflow product (O/F) and cathode particles in the underflow product (U/F); (I) Morphological characterization of the graphite anode and cathode, respectively. Copyright 2018, Elsevier.

The differences of the above liberation processes result in variations in the quantity of obtained black mass (BM), as well as other characteristics such as materials yield, size distribution, and impurity composition and content, which determines the selection and optimization of the following recycling process. The M process effectively liberates active particles with minimal material loss, accounting for only 5.8% of the total mass (Figure 5D).⁵¹ Moreover, the presence of metal impurities is low, comprising only 17.53% of the total mass (Figure 5E).⁵¹ However, the residual polyvinylidene fluoride (PVDF) binder in the M process leads to serious particle aggregation, resulting in particle sizes distributed above 1,000 μm. The TM process exhibits relatively high materials loss (∼24%) attributed to the decomposition and consumption of organic materials during vacuum pyrolysis. Moreover, the thermal process increases the brittleness of Al, resulting in a small amount of Al metal residues detected in the BM after mechanical crushing. In the EHF process, most of the active particles can well be liberated from the foils and concentrated in the fraction below 1,000 μm.⁵³

Upon a full liberation, the BM will be processed through milling and screening to separate it into coarse and fine fractions. The coarse fraction contains Cu and Al metals, as well as separators, which are intended for further recycling. The fine fraction will undergo a froth flotation process to separate the graphite anode and cathode. The composition of the fine fraction obtained from the three liberation processes is depicted in Figure 5F. The presence of metal impurities is a critical consideration for direct recycling as leaving metals in the regenerated cathode can pose significant safety concerns. Consequently, the M process is regarded as the optimal pretreatment option for direct regeneration due to its lower metal content. However, this method yields only 5.1% of BM smaller than 63 μm due to the presence of residual PVDF binder.⁵¹ To increase the yield, additional milling and thermal treatment can be integrated into the M process.⁵¹ Maintaining the structural integrity during this process is crucial to prevent any adverse effects on the regeneration process.

The fine BM containing cathode and anode particles will be further separated by froth flotation, where graphite particles can be selectively adsorbed on the bubbles due to the hydrophobic properties while cathode particles will present in the underflow product (Figure 5G).^54,55,56,57 The presence of PVDF residues in the BM obtained from M process affects the hydrophilic property of cathode, leading to a low recovery of graphite (63.2%) and cathode (66.6%) (Figure 5H). These recovery rates improve to 94.4% and 89.4% for the TM process as the PVDF binder is pre-removed.⁵¹ Thus, it is reasonable to assume that a thermal treatment step following the M process can also enhance the recovery efficiency of froth flotation separation. Additionally, Pan et al. demonstrated that excessive grinding before froth flotation and increasing the oily kerosene collector dosage can improve the graphite recovery to ∼100%, while maintaining the morphology of the collected graphite anode and LCO cathode intact (Figure 5I).⁵⁷ However, due to the challenges in completely removing the binders in cathodes, around 10% of cathode materials are floated and mixed in the froth graphite products, resulting in noticeable loss of cathode materials.

To extract the maximum value from spent LIBs, acid leaching can be employed to treat the recovered powders. This process helps dissolve the entrapped cathodes and residual lithium compounds in the graphite anode, allowing for the recycling of valuable metals and the purification of graphite. Through further annealing processing, the graphite can be regenerated and reused for battery assembling alongside the regenerated cathode.⁵⁸ This approach effectively reduces the dependence on raw materials of LIBs manufacturing. Additionally, it is important to highlight that the challenges related to materials separation mainly stem from the use of the robust PVDF binder. Hence, it is crucial to develop a water-soluble binder that can replace PVDF. Such an alternative would greatly enhance the recycling efficiency of LIBs and promote a more sustainable approach to battery manufacturing.

Technology limitations

After a series of pretreatment processing, the cathode powder obtained from spent LIBs can be regenerated through various relithiation methods, typically followed by a short annealing step. There are several state-of-the-art relithiation methods available, including solid-state sintering (SS),⁵⁹ electrochemical relithiation (ECR),⁶⁰ organic relithiation (OR), ionothermal relithiation (IR),⁶¹ aqueous relithiation (AR),⁶² and molten salt relithiation (MR),⁶³ as illustrated in Figure 6A. Among these methods, SS is the simplest regeneration approach, where the spent cathode materials are directly annealed with additional Li sources. It is important to control the amount of the Li salt precisely in this process. ECR allows Li⁺ intercalation from electrolyte to repair Li deficiencies in cathodes under a specific potential. This method is environmentally friendly but may increase operational complexity when collecting regenerated cathode powder. OR utilizes organic Li salts to replenish the lost Li⁺ in cathode. Zhou et al. used 3,4-dihydroxybenzonitrile delithium to restore spent LFP cathode, where the cyano groups create a reductive atmosphere, improving relithiation kinetics.⁶⁴ Dai et al. developed an IR regeneration method using ionic liquids as the relithiation medium.⁶⁵ However, the high cost of ionic liquids may not be suitable for large-scale processing. The MR process employs a mixture of Li salts that can melt at low temperatures of 200°C–300°C to relithiate spent cathodes, but removing excess Li salts after the reaction can be challenging. AR, which utilizes an aqueous solution typically composed of LiOH, has been successfully used to relithiate spent cathodes and has demonstrated effectiveness in regenerating various cathode materials, including LFP, LMO, LCO, NCM111, NCM523, and NCM622.^{66,67,68,69,70} A notable advantage of AR is that it can be conducted at temperatures below 100°C, highlighting its simplicity and scalability (Figure 6B). While these methods have demonstrated promise in restoring the functionality of spent cathodes, there are still technological obstacles to overcome for industrial-scale direct recycling.

Figure 6.

Technology limitaions of dierct regeneration

(A) Schematical illustration of the developed relithiation methods; (B) Comparison of different relithiation methods in terms of energy consumption, chemical waste, simplicity, and scalability; (C–E) Current limitations of direct regeneration of spent LIBs cathodes.

A particular challenge is the presence of impurities in the collected cathode powder after pretreatment, including PVDF binder, conductive carbon, metal scraps, and graphite particles (Figure 6C), which complicates the direct regeneration process. Nevertheless, recent findings by Chen group indicate that the PVDF binder can be effectively removed during the hydrothermal relithiation process without compromising the quantity and performance of the regenerated cathode materials. During the hydrothermal relithiation process, they used spent cathode powder containing PVDF instead of using pure cathode powder. Surprisingly, they discovered that the PVDF binder undergoes a defluorination reaction in an alkaline environment, leading to the formation of a fragile film. This film loses mechanical integrity and disintegrates into powder during the washing process.⁶² As a result, they avoided the use of toxic organic solvents such as N-methyl-2-pyrrolidone (NMP),⁷¹ dimethylformamide (DMF),⁷² and dimethylacetamide (DMAC),⁷³ to pre-remove PVDF and conductive carbon prior to relithiation, making the entire recycling process more efficient and environmentally friendly.⁶² Moreover, they achieved a successful operational demonstration of 100 g per batch.⁶² In this demonstration, the electrochemical performance of the positive electrode active material was restored to 100% of its original capacity, with a yield rate of 91%.⁶² These promising results indicate the potential for further scale-up of the recycling process.

This discovery significantly simplifies the hydrothermal direct recycling method, offering a potential solution for addressing the presence of PVDF binder. Further investigations are needed to understand the effects of other impurities on the direct recycling process, and it is essential to develop more efficient separation processes to enhance the purity of the spent cathode materials.

In addition to impurities, another significant challenge in the direct recycling of LIBs is the limited scalability of the process (Figure 6D). Scaling up from laboratory scale to pilot scale is hindered by the availability of materials. Obtaining a large quantity of high-purity spent cathode powders is not easy in the current market. While individual cells can be manually disassembled, delaminating and purifying a substantial amount of cathode powder are time consuming and labor intensive. Currently, the largest scale achieved in direct recycling is a batch size of 100 g, as reported by the Chen group, but this scale is still far from meeting the requirements for pilot demonstrations.⁶² To advance the direct recycling technology, it is essential to address the challenges associated with materials accessibility. This may involve developing efficient methods for collecting and processing spent LIBs on a larger scale, as well as establishing supply chains and infrastructure to support the availability of high-purity cathode powders.

The complexities of materials in the market and the continuous advancement of battery materials present significant challenges for direct recycling technologies (Figure 6E). The quest for high energy density and long life cycle has led to the modification of cathode materials, such as coating and doping,⁷⁴ which further complicates the direct recycling process. During the relithiation process, there is a risk of doped elements leaching out or coating layers being destroyed, affecting the quality of the regenerated cathode materials. Additionally, cathodes with high Ni content exhibit complex degradation mechanisms and are highly sensitive to the surrounding environment,⁷⁵ requiring precise control and careful design to ensure successful direct recycling of such materials. Furthermore, some manufacturers mix different cathode materials, such as LFP and NCM, to achieve specific performance characteristics,⁷⁶ posing challenges for both metallurgy-based recycling and direct regeneration processes. Therefore, the current direct recycling technologies need to be further optimized and improved to keep pace with the rapid evolution of cathode materials.

Future direct recycling

As previously discussed, the direct recycling of LIBs has great potential for reducing environmental impacts and facilitating circular economy within the LIBs industry. However, the industrial-scale implementation of this method has not yet been realized, primarily due to the fact that modern LIBs were not originally designed with post-use recycling in mind. The lack of consideration for life cycle management and recycling-friendly designs means that current LIBs cannot be recycled in an economically and environmentally sustainable manner. To enable automatic battery recycling in the future, it is crucial to undertake a systematic reassessment of cell-manufacturing protocols and engineering management to redesign LIBs.

Standardizing the dimensions, shape, and construction of battery packs and cells is a critical step toward advancing the automation of the dismantling process (Figures 7A and 7B). When each EV model has its own unique chassis design, it can be challenging to establish standardized formats for battery packing. Nevertheless, reducing the diversity of EV models and promoting commonality in battery pack designs can facilitate the standardization process. In addition to physical standardization, it is essential to incorporate smart labeling on each cell with embedded information such as electrochemistry materials, assembly procedure, and other pertinent details. By obtaining authorization from manufacturers to access this labeling, recyclers can acquire valuable insights into the specific characteristics of the cells they are recycling, which can enable them to customize recycling processes and improve recycling efficiency.

Figure 7.

Future efforts directions of EV manufacturer (A), battery manufacturer (B), Support organization (C), and recycler (D); (E) Proposed working flow of smart direct recycling in future

In order to promote sustainable development of LIBs, EV and battery manufacturers need to prioritize recycling feasibility alongside performance and profit considerations. While it may be challenging to achieve complete standardization due to the varying requirements and preferences of different vehicle manufacturers, ongoing collaboration among vehicle manufacturers, industry associations, and regulatory bodies can foster progress in this area. The development of international standards and guidelines can provide a framework for harmonizing battery pack specifications across different EV models, ultimately contributing to the standardization of LIBs industry and achievement of automated dismantling processes.

Establishing a comprehensive battery management system (BMS) is also important for the recycling of spent LIBs (Figure 7C). The current low recycling rate of less than 5% for spent LIBs is largely due to the lack of traceability. A full-life-cycle BMS can help systematic management of batteries during their active use, refurbishment after use, and regeneration at the EOL stage. The BMS of LIBs should go beyond simply monitoring the batteries' condition; it should also have the capability to collect and upload valuable information to a cloud database for centralized storage and analysis. By leveraging the BMS with high traceability and an online database, stakeholders involved in the LIBs value chain, including manufacturers, users, refurbishes, and recyclers, can access accurate and up-to-date information about batteries to make informed decisions at various stages of the battery’s life cycle.

It should be noted that protecting proprietary information while disclosing battery information is a crucial aspect to consider. Manufacturers and downstream facilities can establish agreements or protocols to confidentiality. Measures such as confidentiality agreements or non-disclosure agreements (NDAs) can be put in place to safeguard trade secrets and maintain legal compliance. Encryption techniques and secure communication protocols can also be employed to ensure that the embedded information remains secure and inaccessible to unauthorized individuals; thus, the valuable information can be selectively disclosed to designated participants at different stages. By prioritizing recyclability, promoting standardization, and establishing appropriate protocols for information sharing, the battery industry can contribute to more sustainable and efficient recycling practices.

For recyclers, the focus should be directed toward designing and achieving an automatic recycling system that encompasses identification, sorting, disassembling, and separation based on the standardized batteries (Figure 7D). The future of efficient spent LIB recycling will rely on an intelligent workflow (Figure 7E). In this envisioned process, the collected spent LIBs first undergo an identification step utilizing advanced technologies like machine vision, barcode scanning, or radio frequency identification (RFID) to determine their battery composition.^77,78 Once identified, batteries are automatically sorted based on their chemistry. Batteries with different chemistries are then directed to specific disassembling line, where robots precisely separate the casing, cathode, anode, and separator into different bins. Each component then undergoes tailored regeneration procedures. For instance, the cathode may undergo a regeneration process involving Li⁺ supplementation, while the graphite anode may require Li⁺ removal. The separator might be subjected to a washing process to eliminate impurities. By implementing this intelligent recycling approach, the recycling of spent LIBs can be fully automated and sustainable.

Conclusions

In summary, this perspective highlights the urgency to transition from laboratory-scale direct regeneration of spent LIBs to practical applications. The challenges hindering the commercialization of direct recycling have been extensively discussed, and potential solutions have been proposed from both short-term and long-term perspectives. In the short term, efforts should be focused on establishing human-machine hybrid workstations and developing effective separation approaches to enhance pretreatment efficiency and overcome impurity-related challenges. Furthermore, it is crucial to optimize direct recycling technologies and conduct pilot demonstrations to pave the way for practical implementation in the near future. Looking toward the long term, it is important to establish industrial standards for LIBs and raise awareness about designs that facilitate recycling during EV and battery manufacturing. Lastly, collaborative efforts among EV manufacturers, battery producers, and recycling companies are deemed essential for achieving a smart recycling mode that minimizes environmental impacts and maximizes economic benefits throughout the recycling process of spent LIBs.