Long-Life Regenerated LiFePO4 from Spent Cathode by Elevating the d-Band Center of Fe

Biometabolically Derived Selenium Nanoparticles Armed with Protein Protective Suit toward High-Performance Li-Se Batteries

Selenium (Se) serves as a burgeoning high-energy-density cathode material in lithium-ion batteries. However, the development of Se cathode is strictly limited by low Se utilization and inferior cycling stability arising from intrinsic volume expansion and notorious shuttle effect. Herein, a microbial metabolism strategy is developed to prepare "functional vesicle-like" Se globules via Bacillus subtilis subsp. from selenite in sewage, in which Se nanoparticles are armed with a natural biological protein membrane with rich nitrogen and phosphorus, achieving the eco-efficient conversion of trash into treasure (selenite, SeO3 2- → Selenium, Se). The appealing-design "functional vesicle-like" Se globules are beneficial to accommodate volume changes of Se in electrochemical reactions, confining polyselenides via chemisorption, and enhancing mechanical strength of electrode by associated bacteria debris, realizing comprehensive utilization of microorganism. By conceptualizing "functional vesicle-like" Se globules, rather than artificial Se-host composites, as cathode for lithium-selenium batteries, it exhibits outstanding cycling stability and improved rate performance. This strategy opens the door to design smart electrode materials with unattainable structure that cannot be achieved by traditional approaches, achieving eco-efficient conversion of pollutants into energy-storage nanomaterials, which will be a promising research field for interdisciplinary of energy, biology, and environment.

A Large-Scale Fabrication of Flexible, Ultrathin, and Robust Solid Electrolyte for Solid-State Lithium-Sulfur Batteries

All-solid-state lithium metal batteries (ASSLMBs) are considered as the most promising candidates for the next-generation high-safety batteries. To achieve high energy density in ASSLMBs, it is essential that the solid-state electrolytes (SSEs) are lightweight, thin, and possess superior electrochemical stability. In this study, a feasible and scalable fabrication approach to construct 3D supporting skeleton using an electro-blown spinning technique is proposed. This skeleton not only enhances the mechanical strength but also hinders the migration of Li-salt anions, improving the lithium-ion transference number of the SSE. This provides a homogeneous distribution of Li-ion flux and local current density, promoting uniform Li deposition. As a result, based on the mechanically robust and thin SSEs, the Li symmetric cells show outstanding Li plating/stripping reversibility. Besides, a stable interface contact between SSE and Li anode has been established with the formation of an F-enriched solid electrolyte interface layer. The solid-state Li|sulfurized polyacrylonitrile (Li|SPAN) cell achieves a capacity retention ratio of 94.0% after 350 cycles at 0.5 C. Also, the high-voltage Li|LCO cell shows a capacity retention of 92.4% at 0.5 C after 500 cycles. This fabrication approach for SSEs is applicable for commercially large-scale production and application in high-energy-density and high-safety ASSLMBs.

Ferrioxalate photolysis-assisted green recovery of valuable resources from spent lithium iron phosphate batteries

Recovering valuable resources from spent cathodes while minimizing secondary waste generation is emerging as an important objective for the future recycling of spent lithium-ion batteries, including lithium iron phosphate (LFP) batteries. This study proposes the use of oxalic acid leaching followed by ferrioxalate photolysis to separate and recover cathode active material elements from spent LFP batteries. The cathode active material can be rapidly dissolved at room temperature using appropriate quantities of oxalic acid and hydrogen peroxide, as determined through thermodynamic calculations. The dissolved ferrioxalate complex ion (Fe(C2O4)33-) is selectively precipitated through subsequent photolysis at room temperature. Depending on the initial concentration, the decomposition ratio can exceed 95 % within 1-4 h. Molecular mechanism analysis reveals that the decomposition of the Fe(C2O4)33- complex ion into water-insoluble FeC2O4·2H2O results in the precipitation of iron and the separation of metal elements. Lithium can be recovered as dihydrogen phosphates through filtration and water evaporation. No additional precipitant is needed and no other side products are generated during the process. Oxalic acid leaching followed by photolysis offers an environmentally friendly and efficient method for metal recovery from spent LFP cathodes. The photochemical process is a promising approach for reducing secondary waste generation in battery recycling.

Unlocking Spin Gates of Transition Metal Oxides via Strain Stimuli to Augment Potassium Ion Storage

Transition metal oxides (TMOs) are key in electrochemical energy storage, offering cost-effectiveness and a broad potential window. However, their full potential is limited by poor understanding of their slow reaction kinetics and stability issues. This study diverges from conventional complex nano-structuring, concentrating instead on spin-related charge transfer and orbital interactions to enhance the reaction dynamics and stability of TMOs during energy storage processes. We successfully reconfigured the orbital degeneracy and spin-dependent electronic occupancy by disrupting the symmetry of magnetic cobalt (Co) sites through straightforward strain stimuli. The key to this approach lies in the unfilled Co 3d shell, which serves as a spin-dependent regulator for carrier transfer and orbital interactions within the reaction. We observed that the opening of these 'spin gates' occurs during a transition from a symmetric low-spin state to an asymmetric high-spin state, resulting in enhanced reaction kinetics and maintained structural stability. Specifically, the spin-rearranged Al-Co3O4 exhibited a specific capacitance of 1371 F g-1, which is 38 % higher than that of unaltered Co3O4. These results not only shed light on the spin effects in magnetic TMOs but also establish a new paradigm for designing electrochemical energy storage materials with improved efficiency.

Potential-Regulated Design for Direct Recycling of Degraded LiFePO4 Cathode

The rapid proliferation of power sources equipped with lithium-ion batteries poses significant challenges in terms of post-scrap recycling and environmental impacts, necessitating urgent attention to the development of sustainable solutions. The cathode direct regeneration technologies present an optimal solution for the disposal of degraded cathodes, aiming to non-destructively re-lithiate and straightforwardly reuse degraded cathode materials with reasonable profits and excellent efficiency. Herein, a potential-regulated strategy is proposed for the direct recycling of degraded LiFePO4 cathodes, utilizing low-cost Na2SO3 as a reductant with lower redox potential in the alkaline systems. The aqueous re-lithiation approach, as a viable alternative, not only enables the re-lithiation of degraded cathode while ignoring variation in Li loss among different feedstocks but also utilizes the rapid sintering process to restore the cathode microstructure with desirable stoichiometry and crystallinity. The regenerated LiFePO4 exhibits enhanced electrochemical performance with a capacity of 144 mA h g-1 at 1 C and a high retention of 98% after 500 cycles at 5 C. Furthermore, this present work offers considerable prospects for the industrial implementation of directly recycled materials from lithium-ion batteries, resulting in improved economic benefits compared to conventional leaching methods.

Direct Regeneration of Spent Lithium-Ion Battery Cathodes: From Theoretical Study to Production Practice

Direct regeneration method has been widely concerned by researchers in the field of battery recycling because of its advantages of in situ regeneration, short process and less pollutant emission. In this review, we firstly analyze the primary causes for the failure of three representative battery cathodes (lithium iron phosphate, layered lithium transition metal oxide and lithium cobalt oxide), targeting at illustrating their underlying regeneration mechanism and applicability. Efficient stripping of material from the collector to obtain pure cathode material has become a first challenge in recycling, for which we report several pretreatment methods currently available for subsequent regeneration processes. We review and discuss emphatically the research progress of five direct regeneration methods, including solid-state sintering, hydrothermal, eutectic molten salt, electrochemical and chemical lithiation methods. Finally, the application of direct regeneration technology in production practice is introduced, the problems exposed at the early stage of the industrialization of direct regeneration technology are revealed, and the prospect of future large-scale commercial production is proposed. It is hoped that this review will give readers a comprehensive and basic understanding of direct regeneration methods for used lithium-ion batteries and promote the industrial application of direct regeneration technology.

Enhancing Orbital Interaction in Spinel LiNi0.5Mn1.5O4 Cathode for High-Voltage and High-Rate Li-Ion Batteries

High voltage cobalt-free spinel LiNi0.5Mn1.5O4 (LNMO) is well organized as a high-power cathode material for lithium (Li)-ion batteries, however, the weak interaction between the 3d orbital of the transition metal (TM) ions and the 2p orbital of oxygen (O) leads to the instability of crystal structural, hindering the long-term stable cycling of LNMO cathode especially at high temperatures. Here, a design strategy of orbital interaction is initiated to strengthen TM 3d-O 2p framework in P-doped LNMO (P-LNMO) by choosing phytic acid as P dopant, which can realize more uniform doping compared to regular phosphate. The results show that the enhancement of TM 3d-O 2p orbital interaction in P-LNMO can suppress the Jahn-Teller effect and subsequent dissolution of Mn, as well as lowers the energy barrier for Li ion insertion/extraction kinetics. As a result, superior electrochemical performances including high discharge capacity, stable cycling behavior and enhanced rate capability of P-LNMO are obtained. Significantly, the P-LNMO pouch cell shows great cycling stability with 97.4% capacity retention after 100 cycles.

Toward Circular Energy: Exploring Direct Regeneration for Lithium-Ion Battery Sustainability

Lithium-ion batteries (LIBs) are rapidly developing into attractive energy storage technologies. As LIBs gradually enter retirement, their sustainability is starting to come into focus. The utilization of recycled spent LIBs as raw materials for battery manufacturing is imperative for resource and environmental sustainability. The sustainability of spent LIBs depends on the recycling process, whereby the cycling of battery materials must be maximized while minimizing waste emissions and energy consumption. Although LIB recycling technologies (hydrometallurgy and pyrometallurgy) have been commercialized on a large scale, they have unavoidable limitations. They are incompatible with circular economy principles because they require toxic chemicals, emit hazardous substances, and consume large amounts of energy. The direct regeneration of degraded electrode materials from spent LIBs is a viable alternative to traditional recycling technologies and is a nondestructive repair technology. Furthermore, direct regeneration offers advantages such as maximization of the value of recycled electrode materials, use of sustainable, nontoxic reagents, high potential profitability, and significant application potential. Therefore, this review aims to investigate the state-of-the-art direct LIB regeneration technologies that can be extended to large-scale applications.

Cyanogel-Induced Facile Synthesis of Palladium Hydride for Electrocatalytic Oxygen Reduction

Palladium hydride (PdHx) is one of the well-known electrocatalytic materials, yet its synthesis is still a challenge through an energy-efficient and straightforward method. Herein, we propose a new and facile cyanogel-assisted synthesis strategy for the preparation of PdH0.649 at a mild environment with NaBH4 as the hydrogen source. Unlike traditional inorganic Pd precursors, the unique Pd-CN-Pd bridge in Pdx[Pd(CN)4]y ⋅ aH2O cyanogel offers more favourable spatial sites for insertion of H atoms. The characteristic three-dimensional backbone of cyanogel also acts as a support scaffold resulting in the interconnected network structure of PdH0.649. Due to the incorporation of H atoms and interconnected network structure, the PdH0.649 achieves a high half-wave potential of 0.932 V, a high onset potential of 1.062 V, and a low activation energy, as well as a long-term lifetime for oxygen reduction reaction. Theoretical calculation demonstrates a downshift of the d-band centre of Pd in PdH0.649 owing to the dominant Pd-H incorporation that weakens the binding energies of the *OH intermediate species. Zn-air batteries (ZAB) based on PdH0.649 exhibits high power density, competitive open circuit voltage, and good stability, exceeding that of commercial Pt black. This work not only opens up a new avenue for the development of high-efficiency Pt-free catalysts but also provides an original approach and insight into the synthesis of PdHx.

Dynamic Li+ Capture through Ligand-Chain Interaction for the Regeneration of Depleted LiFePO4 Cathode

After application in electric vehicles, spent LiFePO4 (LFP) batteries are typically decommissioned. Traditional recycling methods face economic and environmental constraints. Therefore, direct regeneration has emerged as a promising alternative. However, irreversible phase changes can significantly hinder the efficiency of the regeneration process owing to structural degradation. Moreover, improper storage and treatment practices can lead to metamorphism, further complicating the regeneration process. In this study, a sustainable recovery method is proposed for the electrochemical repair of LFP batteries. A ligand-chain Zn-complex (ZnDEA) is utilized as a structural regulator, with its ─NH─ group alternatingly facilitating the binding of preferential transition metal ions (Fe3+ during charging and Zn2+ during discharging). This dynamic coordination ability helps to modulate volume changes within the recovered LFP framework. Consequently, the recovered LFP framework can store more Li-ions, enhance phase transition reversibility between LFP and FePO4 (FP), modify the initial Coulombic efficiency, and reduce polarization voltage differences. The recovered LFP cells exhibit excellent capacity retention of 96.30% after 1500 cycles at 2 C. The ligand chain repair mechanism promotes structural evolution to facilitate ion migration, providing valuable insights into the targeted ion compensation for environmentally friendly recycling in practical applications.

Degradation Mechanisms of Electrodes Promotes Direct Regeneration of Spent Li-Ion Batteries: A Review

The rapid growth of electric vehicle use is expected to cause a significant environmental problem in the next few years due to the large number of spent lithium-ion batteries (LIBs). Recycling spent LIBs will not only alleviate the environmental problems but also address the challenge of limited natural resources shortages. While several hydro- and pyrometallurgical processes are developed for recycling different components of spent batteries, direct regeneration presents clear environmental, and economic advantages. The principle of the direct regeneration approach is restoring the electrochemical performance by healing the defective structure of the spent materials. Thus, the development of direct regeneration technology largely depends on the formation mechanism of defects in spent LIBs. This review systematically details the degradation mechanisms and types of defects found in diverse cathode materials, graphite anodes, and current collectors during the battery's lifecycle. Building on this understanding, principles and methodologies for directly rejuvenating materials within spent LIBs are outlined. Also the main challenges and solutions for the large-scale direct regeneration of spent LIBs are proposed. Furthermore, this review aims to pave the way for the direct regeneration of materials in discarded lithium-ion batteries by offering a theoretical foundation and practical guidance.

Toward Direct Regeneration of Spent Lithium-Ion Batteries: A Next-Generation Recycling Method

The popularity of portable electronic devices and electric vehicles has led to the drastically increasing consumption of lithium-ion batteries recently, raising concerns about the disposal and recycling of spent lithium-ion batteries. However, the recycling rate of lithium-ion batteries worldwide at present is extremely low. Many factors limit the promotion of the battery recycling rate: outdated recycling technology is the most critical one. Existing metallurgy-based recycling methods rely on continuous decomposition and extraction steps with high-temperature roasting/acid leaching processes and many chemical reagents. These methods are tedious with worse economic feasibility, and the recycling products are mostly alloys or salts, which can only be used as precursors. To simplify the process and improve the economic benefits, novel recycling methods are in urgent demand, and direct recycling/regeneration is therefore proposed as a next-generation method. Herein, a comprehensive review of the origin, current status, and prospect of direct recycling methods is provided. We have systematically analyzed current recycling methods and summarized their limitations, pointing out the necessity of developing direct recycling methods. A detailed analysis for discussions of the advantages, limitations, and obstacles is conducted. Guidance for future direct recycling methods toward large-scale industrialization as well as green and efficient recycling systems is also provided.

Designing functional Li2CuO2-coated separators from Cu foil towards spent LiFePO4 cathode regeneration

A chemical-physical investigation proved that the loss of active Li represents the main mechanism of capacity-fading in spent LiFePO4. Given this, functional Li2CuO2-coated separators were fabricated from spent Cu foil and found to contribute to the regeneration of spent LiFePO4 in a full-cell system. This study presents a novel method for cathode/Cu foil recovery.

Low-Frequency Evolution Mechanism of Customized HEAs-Based Electromagnetic Response Modes Manipulated by Carbothermal Shock

An emerging carbothermal shock method is an ultra-convenient strategy for synthesizing high-entropy alloys (HEAs), in which the intelligent combination of carbon support and HEAs can be serve as a decisive factor for interpreting the trade-off relationship between conductive gene and dielectric gene. However, the feedback mechanism of HEAs ordering degree on electromagnetic (EM) response in 2-18 GHz has not been comprehensively demystified. Herein, while lignin-based carbon fiber paper (L-CFP) as carbon support, L-CFP/FeCoNiCuZn-X with is prepared by carbothermal shock method. The reflection loss of -82.6 dB with thickness of 1.31 mm is achieved by means of pointing electron enrichment within L-CFP/FeCoNiCuZn HEAs heterointerfaces verified by theoretical calculations. Simultaneously, low-frequency evolution with high-intensity and broadband EM response relies on a "sacrificing" strategy achieved by construction of polymorphic L-CFP/semi-disordered-HEAs heterointerfaces. The practicality of L-CFP/FeCoNiCuZn-X in complex environments is given prominence to thermal conductivity, hydrophobicity, and electrocatalytic property. This work is of great significance for insightful mechanism analysis of HEAs in the application of electromagnetic wave absorption.

Comprehensive Technology for Recycling and Regenerating Materials from Spent Lithium Iron Phosphate Battery

The lithium iron phosphate (LFP) battery has been widely used in electric vehicles and energy storage for its good cyclicity, high level of safety, and low cost. The massive application of LFP battery generates a large number of spent batteries. Recycling and regenerating materials from spent LFP batteries has been of great concern because it can significantly recover valuable metals and protect the environment. This paper aims to critically assess the latest technical information available on the echelon utilization and recycling of spent LFP batteries. First, it focuses on the progress of disassembly, evaluation and detection, regrouping, and application in echelon utilization. Then, the recycling technologies, including pretreatment, direct repair, and material regeneration, of spent LFPs are summarized. Finally, the paper proposes some challenges in the echelon utilization and recycling of spent LFP batteries, and concludes with recommendations for an intelligent, refined, and clean LFP battery circulation system that are required to ensure the sustainable development of spent LFP battery recycling.

One-step regeneration and upgrading of spent LiFePO4 cathodes with phytic acid

The regeneration and upgrading of spent LiFePO4 cathodes (S-LFP) were achieved via a one-step hydrothermal treatment. The reducing effect of phytic acid could restore the degraded structure associated with an aqueous Li source. Meanwhile, Li ions are easily chelated by phytic acid groups, and a Li3PO4 coating layer could be formed to reconstruct the surface of the LFP. The regenerated LFP exhibits faster reaction kinetics, larger high-rate charge/discharge capacity, and better cycling performance than commercial LFPs, suggesting that our proposed strategy is a promising technology for the recovery of spent cathode materials.

A Multifunctional Amino Acid Enables Direct Recycling of Spent LiFePO4 Cathode Material

Lithium iron phosphate (LiFePO4 , LFP) batteries are extensively used in electric vehicles and energy storage due to their good cycling stability and safety. However, the finite service life of lithium-ion batteries leads to significant amounts of retired LFP batteries, urgently required to be recycled by environmentally friendly and effective methods. Here, a direct regeneration strategy using natural and low-cost L-threonine as a multifunctional reductant is proposed. The hydroxyl groups and amino groups in L-threonine act as electron donors and nitrogen sources, respectively. The reductive environment created by L-threonine not only aids in converting the degraded FePO4 phase back to a single LFP phase but also facilitates the elimination of detrimental Li-Fe anti-site defects; thus, reconstructing fast Li+ diffusion channels. Meanwhile, N atoms derived from amino groups are able to dope into carbon layers, generating more active sites and enhancing the conductive properties of LFP particles. The regenerated LFP shows great electrochemical performance with a discharge capacity of 147.9 mAh g-1 at 1 C and a capacity retention of 86% after 500 cycles at 5 C. Further, this approach is also feasible for LFP black mass sourced from practical industrial dismantling lines, providing considerable prospects for the large-scale recycling of LFP batteries.

Why do Single-Atom Alloys Catalysts Outperform both Single-Atom Catalysts and Nanocatalysts on MXene?

Single-atom alloys (SAAs), combining the advantages of single-atom and nanoparticles (NPs), play an extremely significant role in the field of heterogeneous catalysis. Nevertheless, understanding the catalytic mechanism of SAAs in catalysis reactions remains a challenge compared with single atoms and NPs. Herein, ruthenium-nickel SAAs (RuNiSAAs ) synthesized by embedding atomically dispersed Ru in Ni NPs are anchored on two-dimensional Ti3 C2 Tx MXene. The RuNiSAA-3 -Ti3 C2 Tx catalysts exhibit unprecedented activity for hydrogen evolution from ammonia borane (AB, NH3 BH3 ) hydrolysis with a mass-specific activity (rmass ) value of 333 L min-1  gRu -1 . Theoretical calculations reveal that the anchoring of SAAs on Ti3 C2 Tx optimizes the dissociation of AB and H2 O as well as the binding ability of H* intermediates during AB hydrolysis due to the d-band structural modulation caused by the alloying effect and metal-supports interactions (MSI) compared with single atoms and NPs. This work provides useful design principles for developing and optimizing efficient hydrogen-related catalysts and demonstrates the advantages of SAAs over NPs and single atoms in energy catalysis.

Unraveling the Coupling Effect between Cathode and Anode toward Practical Lithium-Sulfur Batteries

The localized reaction heterogeneity of the sulfur cathode and the uneven Li deposition on the Li anode are intractable issues for lithium-sulfur (Li-S) batteries under practical operation. Despite impressive progress in separately optimizing the sulfur cathode or Li anode, a comprehensive understanding of the highly coupled relationship between the cathode and anode is still lacking. In this work, inspired by the Butler-Volmer equation, a binary descriptor (IBD ) assisting the rational structural design of sulfur cathode by simultaneously considering the mass-transport index (Imass ) and the charge-transfer index (Icharge ) is identified, and subsequently the relationship between IBD and the morphological evolution of Li anode is established. Guided by the IBD , a scalable electrode providing interpenetrated flow channels for efficient mass/charge transfer, full utilization of active sulfur, and mechanically elastic support for aggressive electrochemical reactions under practical conditions is reported. These characteristics induce a homogenous distribution of local current densities and reduced reaction heterogeneity on both sides of the cathode and anode. Impressive energy density of 318 Wh kg-1 and 473 Wh L-1 in an Ah-level pouch cell can be achieved by the design concept. This work offers a promising paradigm for unlocking the interaction between cathode and anode and designing high-energy practical Li-S batteries.

Direct Regenerating Cathode Materials from Spent Lithium-Ion Batteries

Recycling cathode materials from spent lithium-ion batteries (LIBs) is critical to a sustainable society as it will relief valuable but scarce recourse crises and reduce environment burdens simultaneously. Different from conventional hydrometallurgical and pyrometallurgical recycling methods, direct regeneration relies on non-destructive cathode-to-cathode mode, and therefore, more time and energy-saving along with an increased economic return and reduced CO2 footprint. This review retrospects the history of direct regeneration and discusses state-of-the-art development. The reported methods, including high-temperature solid-state, hydrothermal/ionothermal, molten salt thermochemistry, and electrochemical method, are comparatively introduced, targeting at illustrating their underlying regeneration mechanism and applicability. Further, representative repairing and upcycling studies on wide-applied cathodes, including LiCoO2 (LCO), ternary oxides, LiFePO4 (LFP), and LiMn2 O4 (LMO), are presented, with an emphasis on milestone cases. Despite these achievements, there remain several critical issues that shall be addressed before the commercialization of the mentioned direct regeneration methods.

Boosting the interfacial dynamics and thermodynamics in polyanion cathode by carbon dots for ultrafast-charging sodium ion batteries

Ultrafast-charging is the focus of next-generation rechargeable batteries for widespread economic success by reducing the time cost. However, the poor ion diffusion rate, intrinsic electronic conductivity and structural stability of cathode materials seriously hinder the development of ultrafast-charging technology. To overcome these challenges, an interfacial dynamics and thermodynamics synergistic strategy is proposed to synchronously enhance the fast-charging capability and structural stability of polyanion cathode materials. As a case study, a Na3V2(PO4)3 composite (NVP/NSC) is successfully obtained by introducing an interface layer derived from N/S co-doped carbon dots. Density functional theory calculations validate that the interfacial bonding effect of V-N/S-C significantly reduces the Na+ transport energy barrier. D-band center theory analysis confirms the downward shift of the V d-band center enhances the strength of the V-O bond and considerably inhibits irreversible phase transformation. Benefitting from this interfacial synergistic strategy, NVP/NSC achieves a high capability and excellent cycling stability with a surprisingly low carbon content (2.23%) at an extremely high rate of 100C for 10 000 cycles (87.2 mA h g-1, 0.0028% capacity decay per cycle). Furthermore, a superior performance at 5C (115.3 mA h g-1, 92.1% capacity retention after 800 cycles) is exhibited by the NVP/NSC‖HC full cell. These findings provide timely new insights for the systematic design of ultrafast-charging cathode materials.

Homogeneous Repair of Highly Degraded Ni-Rich Cathode Material with Spent Lithium Anode

Direct regeneration of spent lithium-ion batteries has received wide attention owing to its potential for resource reuse and environmental benefits. The repair effect of direct regeneration methods undergoing heterogeneous repair process is usually inferior, while homogenous repair process plays a vital role to achieve satisfactory repair results. However, the practical applications of current homogeneous repair methods are challenged by the complex operations and relatively high costs owing to the requirement of additional heating or pressurization. Herein, this work proposes a simple strategy to achieve homogeneous repair of spent cathode materials under relatively mild conditions by uniformly precoating lithium source at room temperature and atmospheric pressure. Followed by annealing, highly degraded LiNi0.83 Co0.12 Mn0.05 O2 with severe Li deficiency and irreversible phase transition is repaired to have an initial capacity of 181.6 mAh g-1 and capacity retention of 80.7% after 150 cycles at 0.5 C. The lithium source used in this strategy is from the spent lithium anode. Moreover, this strategy is suitable for the direct regeneration of various layer oxide cathode materials with different failure degrees. This work provides both theoretical guidance and practical examples for the straightforward, effective, and universally applicable direct regeneration methods.

Toward Sustainable All Solid-State Li-Metal Batteries: Perspectives on Battery Technology and Recycling Processes

Lithium (Li)-based batteries are gradually evolving from the liquid to the solid state in terms of safety and energy density, where all solid-state Li-metal batteries (ASSLMBs) are considered the most promising candidates. This is demonstrated by the Bluecar electric vehicle produced by the Bolloré Group, which is utilized in car-sharing services in several cities worldwide. Despite impressive progress in the development of ASSLMBs, their avenues for recycling them remain underexplored, and combined with the current explosion of spent Li-ion batteries, they should attract widespread interest from academia and industry. Here, the potential challenges of recycling ASSLMBs as compared to Li-ion batteries are analyzed and the current progress and prospects for recycling ASSLMBs are summarized and analyzed. Drawing on the lessons learned from Li-ion battery recycling, it is important to design sustainable recycling technologies before ASSLMBs gain widespread market adoption. A battery-recycling-oriented design is also highlighted for ASSLMBs to promote the recycling rate and maximize profitability. Finally, future research directions, challenges, and prospects are outlined to provide strategies for achieving sustainable development of ASSLMBs.

Fundamentals, status and challenges of direct recycling technologies for lithium ion batteries

Advancement in energy storage technologies is closely related to social development. However, a significant conflict has arisen between the explosive growth in battery demand and resource availability. Facing the upcoming large-scale disposal problem of spent lithium-ion batteries (LIBs), their recycling technology development has become key. Emerging direct recycling has attracted widespread attention in recent years because it aims to 'repair' the battery materials, rather than break them down and extract valuable products from their components. To achieve this goal, a profound understanding of the failure mechanisms of spent LIB electrode materials is essential. This review summarizes the failure mechanisms of LIB cathode and anode materials and the direct recycling strategies developed. We systematically explore the correlation between the failure mechanism and the required repair process to achieve efficient and even upcycling of spent LIB electrode materials. Furthermore, we systematically introduce advanced in situ characterization techniques that can be utilized for investigating direct recycling processes. We then compare different direct recycling strategies, focussing on their respective advantages and disadvantages and their applicability to different materials. It is our belief that this review will offer valuable guidelines for the design and selection of LIB direct recycling methods in future endeavors. Finally, the opportunities and challenges for the future of battery direct recycling technology are discussed, paving the way for its further development.

Engineering Functionalized 2D Metal-Organic Frameworks Nanosheets with Fast Li+ Conduction for Advanced Solid Li Batteries

Solid-state batteries can ensure high energy density and safety in lithium metal batteries, while polymer electrolytes are plagued by slow ion kinetics and low selective transport of Li+ . Metal-organic frameworks (MOFs) are proposed as emerging fillers for solid-state poly(ethylene oxide)(PEO) electrolytes, however, developing functionalized MOFs and understanding their roles on ion transfer has proven challenging. Herein, combining computational and experimental results, the functional group regulation in MOFs can effectively change surficial charge distribution and limit anion movement is revealed, providing a potential solution to these issues. Specifically, functionalized 2D MOF sheets are designed through molecular engineering to construct high-performance composite electrolytes, where the electron-donating effect of substituents in 2D-MOFs effectively limits the movement of ClO4 - and promotes mechanical properties and ion migration numbers (0.36 up to 0.64) of PEO. As a result, Li/Li cells with composite electrolyte exhibit superior cyclability for 1000 h at a current density of 0.2 mA cm-2 . Meanwhile, the solid LiFePO4 /Li battery delivers highly reversible capacities of 148.8 mAh g-1 after 200 cycles. These findings highlight a new approach for anion confinement through the use of functional group electronic effects, leading to enhanced ionic conductivity, and a feasible direction for high-performance solid-state batteries.

Probing Hybrid LiFePO4/FePO4 Phases in a Single Olive LiFePO4 Particle and Their Recovering from Degraded Electric Vehicle Batteries

The recycling of LiFePO4 from degraded lithium-ion batteries (LIBs) from electric vehicles (EVs) has gained significant attention due to resource, environment, and cost considerations. Through neutron diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy, we revealed continuous lithium loss during battery cycling, resulting in a Li-deficient state (Li1-xFePO4) and phase separation within individual particles, where olive-shaped FePO4 nanodomains (5-10 nm) were embedded in the LiFePO4 matrix. The preservation of the olive-shaped skeleton during Li loss and phase change enabled materials recovery. By chemical compensation for the lithium loss, we successfully restored the hybrid LiFePO4/FePO4 structure to pure LiFePO4, eliminating nanograin boundaries. The regenerated LiFePO4 (R-LiFePO4) exhibited a high crystallinity similar to the fresh counterpart. This study highlights the importance of topotactic chemical reactions in structural repair and offers insights into the potential of targeted Li compensation for energy-efficient recycling of battery electrode materials with polyanion-type skeletons.

A Critical Review on the Recycling Strategy of Lithium Iron Phosphate from Electric Vehicles

Electric vehicles (EVs) are one of the most promising decarbonization solutions to develop a carbon-negative economy. The increasing global storage of EVs brings out a large number of power batteries requiring recycling. Lithium iron phosphate (LFP) is one of the first commercialized cathodes used in early EVs, and now gravimetric energy density improvement makes LFP with low cost and robustness popular again in the market. Developments in LFP recycling techniques are in demand to manage a large portion of the EV batteries retired both today and around ten years later. In this review, first the operation and degradation mechanisms of LFP are revisited aiming to identify entry points for LFP recycling. Then, the current LFP recycling methods, from the pretreatment of the retired batteries to the regeneration and recovery of the LFP cathode are summarized. The emerging direct recovery technology is highlighted, through which both raw material and the production cost of LFP can be recovered. In addition, the current issues limiting the development of the LIBs recycling industry are presented and some ideas for future research are proposed. This review provides the theoretical basis and insightful perspectives on developing new recycling strategies by outlining the whole-life process of LFP.

Topotactic Transformation of Surface Structure Enabling Direct Regeneration of Spent Lithium-Ion Battery Cathodes

Recycling spent lithium-ion batteries (LIBs) has become an urgent task to address the issues of resource shortage and potential environmental pollution. However, direct recycling of the spent LiNi_0.5Co_0.2Mn_0.3O₂ (NCM523) cathode is challenging because the strong electrostatic repulsion from a transition metal octahedron in the lithium layer provided by the rock salt/spinel phase that is formed on the surface of the cycled cathode severely disrupts Li⁺ transport, which restrains lithium replenishment during regeneration, resulting in the regenerated cathode with inferior capacity and cycling performance. Here, we propose the topotactic transformation of the stable rock salt/spinel phase into Ni_0.5Co_0.2Mn_0.3(OH)₂ and then back to the NCM523 cathode. As a result, a topotactic relithiation reaction with low migration barriers occurs with facile Li⁺ transport in a channel (from one octahedral site to another, passing through a tetrahedral intermediate) with weakened electrostatic repulsion, which greatly improves lithium replenishment during regeneration. In addition, the proposed method can be extended to repair spent NCM523 black mass, spent LiNi_0.6Co_0.2Mn_0.2O₂, and spent LiCoO₂ cathodes, whose electrochemical performance after regeneration is comparable to that of the commercial pristine cathodes. This work demonstrates a fast topotactic relithiation process during regeneration by modifying Li⁺ transport channels, providing a unique perspective on the regeneration of spent LIB cathodes.

Direct regeneration of degraded lithium-ion battery cathodes with a multifunctional organic lithium salt

The recycling of spent lithium-ion batteries is an effective approach to alleviating environmental concerns and promoting resource conservation. LiFePO₄ batteries have been widely used in electric vehicles and energy storage stations. Currently, lithium loss, resulting in formation of Fe(III) phase, is mainly responsible for the capacity fade of LiFePO₄ cathode. Another factor is poor electrical conductivity that limits its rate capability. Here, we report the use of a multifunctional organic lithium salt (3,4-dihydroxybenzonitrile dilithium) to restore spent LiFePO₄ cathode by direct regeneration. The degraded LiFePO₄ particles are well coupled with the functional groups of the organic lithium salt, so that lithium fills vacancies and cyano groups create a reductive atmosphere to inhibit Fe(III) phase. At the same time, pyrolysis of the salt produces an amorphous conductive carbon layer that coats the LiFePO₄ particles, which improves Li-ion and electron transfer kinetics. The restored LiFePO₄ cathode shows good cycling stability and rate performance (a high capacity retention of 88% after 400 cycles at 5 C). This lithium salt can also be used to recover degraded transition metal oxide-based cathodes. A techno-economic analysis suggests that this strategy has higher environmental and economic benefits, compared with the traditional recycling methods.