Copper Impurity Effects on LiNi(1/3)Mn(1/3)Co(1/3)O2 Cathode Material

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.

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 Many factors limit the promotion of the battery recycling rate: outdated recycling technology is the most critical one.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.

Manganese and Cobalt-Free Ultrahigh-Ni-Rich Single-Crystal Cathode for High-Performance Lithium Batteries

Current commercial nickel (Ni)-rich Mn, Co, and Al-containing cathodes are employed in high-energy-density lithium (Li) batteries all around the globe. The presence of Mn/Co in them brings out several problems, such as high toxicity, high cost, severe transition-metal dissolution, and quick surface degradation. Herein, a Mn/Co-free ultrahigh-Ni-rich single-crystal LiNi_0.94Fe_0.05Cu_0.01O₂ (SCNFCu) cathode with acceptable electrochemical performance is benchmarked against a Mn/Co-containing cathode. Despite having a slightly lower discharge capacity, the SCNFCu cathode retaining 77% of its capacity across 600 deep cycles in full-cell outperforms comparable to a high-Ni single-crystal LiNi_0.9Mn_0.05Co_0.05O₂ (SCNMC; 66%) cathode. It is shown that the stabilizing ions Fe/Cu in the SCNFCu cathode reduce structural disintegration, undesirable side reactions with the electrolyte, transition-metal dissolution, and active Li loss. This discovery provides a new extent for cathode material development for next-generation high-energy, Mn/Co-free Li batteries due to the compositional tuning flexibility and quick scalability of SCNFCu, which is comparable to the SCNMC cathode.

A phenomenological and quantitative view on the degradation of positive electrodes from spent lithium-ion batteries in humid atmosphere

The present study deals with the phenomenological observation of the corrosion of the positive electrode foil of lithium-ion batteries containing LiNi_0.6Co_0.2Mn_0.2O₂ (NMC) as cathode material. Due to the presence of moisture, localized water accumulation is formed on the NMC surface. The water absorbed by the electrolyte reacts with the NMC under Li⁺/H⁺ exchange and the resulting pH increase leads to dissolution of the carrier foil and characteristic salt-like blooms on the NMC surface. With the increase in the relative area occupied by the holes in the aluminum foil per time, a sufficiently suitable parameter was found with which to quantitatively determine the extent of corrosion. The degree of degradation depends on time and ambient humidity. It was shown that functional recycling with the water jet method is no longer applicable for degraded foils, since the mechanical stability of the foils decreases as corrosion progresses. Lithium, aluminum, sulfur and oxygen were detected in the blooms using SEM-EDX and Laser-Induced-Breakdown-Spectroscopy (LIBS). The underlying NMC layer was found to contain mainly aluminum and significantly lower lithium content than the non-degraded material. SEM and Raman microscopy analyses also showed that the active material is also locally degraded and therefore no longer suitable for functional recycling.

Reclaimed and Up-Cycled Cathodes for Lithium-Ion Batteries

As electric vehicles become more widely used, there is a higher demand for lithium-ion batteries (LIBs) and hence a greater incentive to find better ways to recycle these at their end-of-life (EOL). This work focuses on the process of reclamation and re-use of cathode material from LIBs. Black mass containing mixed LiMn₂O₄ and Ni_0.8Co_0.15Al_0.05O₂ from a Nissan Leaf pouch cell are recovered via two different recycling routes, shredding or disassembly. The waste material stream purity is compared for both processes, less aluminium and copper impurities are present in the disassembled waste stream. The reclaimed black mass is further treated to reclaim the transition metals in a salt solution, Ni, Mn, Co ratios are adjusted in order to synthesize an upcycled cathode, LiNi_0.6Mn_0.2Co_0.2O₂ via a co-precipitation method. The two reclamation processes (disassembly and shredding) are evaluated based on the purity of the reclaimed material, the performance of the remanufactured cell, and the energy required for the complete process. The electrochemical performance of recycled material is comparable to that of as-manufactured cathode material, indicating no detrimental effect of purified recycled transition metal content. This research represents an important step toward scalable approaches to the recycling of EOL cathode material in LIBs.

The Effects of Phosphate Impurity on Recovered LiNi0.6Co0.2Mn0.2O2 Cathode Material via a Hydrometallurgy Method

From portable electronics to electric vehicles, lithium-ion batteries have been deeply integrated into our daily life and industrial fields for a few decades. The booming field of battery manufacturing could lead to shortages in resources and massive accumulation of battery waste, hindering sustainable development. Therefore, hydrometallurgy-based approaches have been widely used in industrial recycling to recover cathode materials due to their high efficiency and throughput. Impurities have always been a great challenge for hydrometallurgical recycling, introducing challenges to maintain the consistency of product quality because of potential unintended effects caused by impurities. Herein, after comprehensive investigation, we first report the impacts of phosphate impurity on a recycled LiNi_0.6Co_0.2Mn_0.2O₂ ("NCM622") cathode via a hydrometallurgy method. We demonstrate that a passivation layer of Li₃PO₄ is formed at grain boundaries during sintering, which significantly raises the activation barrier and hinders lithium diffusion. In addition, the distinct degradation of cathode electrochemical properties is observed from poor particle morphology and high cation mixing as a result of phosphate impurity. Cathode powders with 1 at. % phosphate impurity retain a capacity of 146 mAh/g after 100 cycles at 0.33C, 6% less than that of a virgin cathode. Furthermore, cathodes with higher phosphate concentrations perform even worse in electrochemical tests. Therefore, phosphate impurities are detrimental to the hydrometallurgical recycling of NCM cathode materials and need to be excluded from the recycling process.

Preferential Extraction of Lithium from Spent Cathodes and the Regeneration of Layered Oxides for Li/Na-Ion Batteries

The preferentially selective extraction of Li⁺ from spent layered transition metal oxide (LiMO₂, M = Ni, Co, Mn, etc.) cathodes has attracted extensive interest based on economic and recycling efficiency requirements. Presently, the efficient recycling of spent LiMO₂ is still challenging due to the element loss in multistep processes. Here, we developed a facile strategy to selectively extract Li⁺ from LiMO₂ scraps with stoichiometric H₂SO₄. The proton exchange reaction could be driven using temperature, accompanied by the generation of soluble Li₂SO₄ and MOOH precipitates. The extraction mechanism includes a two-stage evolution, including dissolution and ion exchange. As a result, the extraction rate of Li⁺ is over 98.5% and that of M ions is less than 0.1% for S-NCM. For S-LCO, the selective extraction result is even better. Finally, Li₂CO₃ products with a purity of 99.68% can be prepared from the Li⁺-rich leachate, demonstrating lithium recovery efficiencies as high as 95 and 96.3% from NCM scraps and S-LCO scraps, respectively. In the available cases, this work also represents the highest recycling efficiency of lithium, which can be attributed to the high leaching rate and selectivity of Li⁺, and even demonstrates the lowest reagent cost. The regenerated LiNi_0.5Co_0.24Mn_0.26O₂ and Na_1.01Li_0.001Ni_0.38Co_0.18Mn_0.44O₂ cathodes also deliver a decent electrochemical performance for Li-ion batteries (LIBs) and Na-ion batteries (NIBs), respectively. Our current work offers a facile, closed-loop, and scalable strategy for recycling spent LIB cathodes based on the preferentially selective extraction of Li⁺, which is superior to the other leaching technology in terms of its cost and recycling yield.

Assessment of recycling methods and processes for lithium-ion batteries

This review discusses physical, chemical, and direct lithium-ion battery recycling methods to have an outlook on future recovery routes. Physical and chemical processes are employed to treat cathode active materials which are the greatest cost contributor in the production of lithium batteries. Direct recycling processes maintain the original chemical structure and process value of battery materials by recovering and reusing them directly. Mechanical separation is essential to liberate cathode materials that are concentrated in the finer size region. However, currently, the cathode active materials are being concentrated at a cut point that is considerably greater than the actual size found in spent batteries. Effective physical methods reduce the cost of subsequent chemical treatment and thereafter re-lithiation successfully reintroduces lithium into spent cathodes. Some of the current challenges are the difficulty in controlling impurities in recovered products and ensuring that the entire recycling process is more sustainable.

A Review on Regenerating Materials from Spent Lithium-Ion Batteries

Recycling spent lithium-ion batteries (LIBs) have attracted increasing attention for their great significance in environmental protection and cyclic resources utilization. Numerous studies focus on developing technologies for the treatment of spent LIBs. Among them, the regeneration of functional materials from spent LIBs has received great attention due to its short process route and high value-added product. This paper briefly summarizes the current status of spent LIBs recycling and details the existing processes and technologies for preparing various materials from spent LIBs. In addition, the benefits of material preparation from spent LIBs, compared with metals recovery only, are analyzed from both environmental and economic aspects. Lastly, the existing challenges and suggestions for the regeneration process are proposed.

Positive Role of Fluorine Impurity in Recovered LiNi0.6Co0.2Mn0.2O2 Cathode Materials

Lithium-ion battery (LIB) recycling is considered as an important component to enable industry sustainability. A massive number of LIBs in portable electronics, electric vehicles, and grid storage will eventually end up as wastes, leading to serious economic and environmental problems. Hence, tremendous efforts have been made to improve the hydrometallurgical recycling process because it is the most promising option for handling end-of-life LIBs owing to its wide applicability, low cost, and high productivity. Despite these advantages, some extra elements (Al, Fe, C, F, and so forth) remain as impurities in the removal process and are retained in the solution, which is a great challenge to obtain high-quality cathode materials. In this work, the impacts caused by fluorine impurity on the LiNi_0.6Co_0.2Mn_0.2O₂ (NCM622) cathode are intensively investigated via hydrometallurgical coprecipitation for the first time. Our results show that up to 1 at. % fluorine impurity brings a positive influence on the recovered material due to a higher Ni²⁺ ratio on the surface of cathode particles. In addition, the presence of fluoride ions during coprecipitation could lead to the formation of holes in cathode particles, which improves the rate capability and cyclability dramatically. Compared to the virgin material, the capacity of the NCM622 material with 0.2 at. % fluorine impurity is boosted by ∼8% (167.7 mA h/g) with a remarkable capacity retention of 98.0% after 100 cycles at 0.33 C. Besides, the cathode with 0.2 at. % fluorine impurity shows a far better rate performance, especially at high rates (∼7% increased at 5 C) than that of virgin. These results convince that a low concentration of fluorine impurity is desirable in the hydrometallurgical recycling process. More importantly, this study offers implications in the design of high-performance NCM622 cathode materials via coprecipitation production with ion doping in the near future.

Machine-Learning Approach for Predicting the Discharging Capacities of Doped Lithium Nickel-Cobalt-Manganese Cathode Materials in Li-Ion Batteries

Understanding the governing dopant feature for cyclic discharge capacity is vital for the design and discovery of new doped lithium nickel-cobalt-manganese (NCM) oxide cathodes for lithium-ion battery applications. We herein apply six machine-learning regression algorithms to study the correlations of the structural, elemental features of 168 distinct doped NCM systems with their respective initial discharge capacity (IC) and 50th cycle discharge capacity (EC). First, a Pearson correlation coefficient study suggests that the lithium content ratio is highly correlated to both discharge capacity variables. Among all six regression algorithms, gradient boosting models have demonstrated the best prediction power for both IC and EC, with the root-mean-square errors calculated to be 16.66 mAhg-1 and 18.59 mAhg-1, respectively, against a hold-out test set. Furthermore, a game-theory-based variable-importance analysis reveals that doped NCM materials with higher lithium content, smaller dopant content, and lower-electronegativity atoms as the dopant are more likely to possess higher IC and EC. This study has demonstrated the exciting potentials of applying cutting-edge machine-learning techniques to accurately capture the complex structure-property relationship of doped NCM systems, and the models can be used as fast screening tools for new doped NCM structures with more superior electrochemical discharging properties.

Challenges to Future Development of Spent Lithium Ion Batteries Recovery from Environmental and Technological Perspectives

Spent lithium ion battery (LIB) recovery is becoming quite urgent for environmental protection and social needs due to the rapid progress in LIB industries. However, recycling technologies cannot keep up with the exaltation of the LIB market. Technological improvement of processing spent batteries is necessary for industrial application. In this paper, spent LIB recovery processes are classified into three steps for discussion: gathering electrode materials, separating metal elements, and recycling separated metals. Detailed discussion and analysis are conducted in every step to provide beneficial advice for environmental protection and technology improvement of spent LIB recovery. Besides, the practical industrial recycling processes are introduced according to their advantages and disadvantages. And some recommendations are provided for existing problems. Based on current recycling technologies, the challenges for spent LIB recovery are summarized and discussed from technological and environmental perspectives. Furthermore, great effort should be made to promote the development of spent LIB recovery in future research as follows: (1) gathering high-purity electrode materials by mechanical pretreatment; (2) green metals leaching from electrode materials; (3) targeted extraction of metals from electrode materials.

Simultaneous Recovery of Metal Ions and Electricity Harvesting via K-Carrageenan@ZIF-8 Membrane

The spent lithium-ion batteries contain significant amounts of valuable metals such as lithium and cobalt. However, how to effectively recover these valuable metals and minimize environmental pollution simultaneously is still a challenge. In this work, a natural biopolymer K-Carrageenan is introduced into a stable metal-organic framework ZIF-8 to form a composite (KCZ) membrane for selectively separating Li⁺ from Co²⁺ and simultaneously harvesting the concentration gradient energy efficiently. The prepared KCZ membrane shows an Li⁺ ionic conductivity of up to 1.70 × 10^-5 S cm^-1, 5 orders of magnitude higher than 1.1 × 10^-10 S cm^-1 for pristine ZIF-8, with an Li⁺ flux of 0.342 mol m^-2 h^-1 and a selectivity of about 8.29 for Li⁺ over Co²⁺. Moreover, this asymmetric KCZ/anodic alumina oxide membrane exhibits a good output power of up to 3.54 μW when employed as a concentration-gradient energy-harvesting device during the separation process. Hence, the KCZ membrane shows great potential in application for advanced separation and simultaneous concentration gradient energy harvesting.

Toward sustainable and systematic recycling of spent rechargeable batteries

A comprehensive and novel view on battery recycling is provided in terms of the science and technology, engineering, and policy.

Influence of Na and Nb co-substitution on electrochemical performance of ternary cathode materials for Li-ion batteries

In the present study, Li_1−xNa_x(Ni_0.6Co_0.2Mn_0.2−yNb_y)O₂, a novel layered cathodic compound, is synthesized using an economically feasible polymer pyrolysis method.

Preparation and Rate Capability of Carbon Coated LiNi1/3Co1/3Mn1/3O2 as Cathode Material in Lithium Ion Batteries

LiNi_1/3Co_1/3Mn_1/3O₂ (NCM) is regarded as a promising material for next-generation lithium ion batteries due to the high capacity, but its practical applications are limited by the poor electronic conductivity. Here, a one-step method is used to prepare carbon coated LiNi_1/3Co_1/3Mn_1/3O₂ (NCM/C) by applying active carbon as reaction matrix. TEM shows LiNi_1/3Co_1/3Mn_1/3O₂ particles are homogeneously coated by carbon with a thickness about 10 nm. NCM/C delivers the discharge capacity of 191.2 mAh g^-1 at 0.5 C (85 mA g^-1) with a columbic efficiency of 91.1%. At 40 C (6800 mA g^-1), the discharge capacity of NCM/C is 54.6 mAh g^-1, whereas NCM prepared through sol-gel route only delivers 13.2 mAh g^-1. After 100 charge and discharge cycles at 1 C (170 mA g^-1) the capacity retention is 90.3% for NCM/C, whereas it is only 72.4% for NCM. The superior charge/discharge performance of NCM/C owes much to the carbon coating layer, which is not only helpful to increase the electronic conductivity but also contributive to inhibit the side reactions between LiNi_1/3Co_1/3Mn_1/3O₂ and the liquid electrolyte.

Thermodynamic and kinetic studies of LiNi0.5Co0.2Mn0.3O2 as a positive electrode material for Li-ion batteries using first principles

The cation ordering, thermodynamics and diffusion kinetics of LiNi_0.5Co_0.2Mn_0.3O₂ (NCM-523) are studied using multi-scale funnel approach with vdW corrections.