Preferentially selective extraction of lithium from spent LiCoO_(2)cathodes by medium-temperature carbon reduction roasting

Lithium recovery from spent lithium-ion batteries(LIBs)have attracted extensive attention due to the skyrocketing price of lithium.The medium-temperature carbon reduction roasting was proposed to preferential selective extraction of lithium from spent Li-CoO_(2)(LCO)cathodes to overcome the incomplete recovery and loss of lithium during the recycling process.The LCO layered structure was destroyed and lithium was completely converted into water-soluble Li2CO_(3)under a suitable temperature to control the reduced state of the cobalt oxide.The Co metal agglomerates generated during medium-temperature carbon reduction roasting were broken by wet grinding and ultrasonic crushing to release the entrained lithium.The results showed that 99.10%of the whole lithium could be recovered as Li2CO_(3)with a purity of 99.55%.This work provided a new perspective on the preferentially selective extraction of lithium from spent lithium batteries.

Stabilizing High-Nickel Cathodes via Interfacial Hydrogen Bonding Effects Using a Hydrofluoric Acid-Scavenging Separator

Nickel-rich layered Li transition metal oxides are the most promising cathode materials for high-energydensity Li-ion batteries.However,they exhibit rapid capacity degradation induced by transition metal dissolution and structural reconstruction,which are associated with hydrofluoric acid(HF)generation from lithium hexafluorophosphate decomposition.The potential for thermal runaway during the working process poses another challenge.Separators are promising components to alleviate the aforementioned obstacles.Herein,an ultrathin double-layered separator with a 10 lm polyimide(PI)basement and a 2 lm polyvinylidene difluoride(PVDF)coating layer is designed and fabricated by combining a nonsolvent induced phase inversion process and coating method.The PI skeleton provides good stability against potential thermal shrinkage,and the strong PI-PVDF bonding endows the composite separator with robust structural integrity;these characteristics jointly contribute to the extraordinary mechanical tolerance of the separator at elevated temperatures.Additionally,unique HF-scavenging effects are achieved with the formation of-CO…H-F hydrogen bonds for the abundant HF coordination sites provided by the imide ring;hence,the layered Ni-rich cathodes are protected from HF attack,which ultimately reduces transition metal dissolution and facilitates long-term cyclability of the Ni-rich cathodes.Li||NCM811 batteries(where“NCM”indicates LiNi_(x)Co_(y)Mn_(1-x-y)O_(2))with the proposed composite separator exhibit a 90.6%capacity retention after 400 cycles at room temperature and remain sustainable at 60℃with a 91.4%capacity retention after 200 cycles.By adopting a new perspective on separators,this study presents a feasible and promising strategy for suppressing capacity degradation and enabling the safe operation of Ni-rich cathode materials.

Understanding the failure mechanism towards developing high-voltage single-crystal Ni-rich Co-free cathodes

Benefited from its high process feasibility and controllable costs,binary-metal layered structured LiNi_(0.8)Mn_(0.2)O_(2)(NM)can effectively alleviate the cobalt supply crisis under the surge of global electric vehicles(EVs)sales,which is considered as the most promising nextgeneration cathode material for lithium-ion batteries(LIBs).However,the lack of deep understanding on the failure mechanism of NM has seriously hindered its application,especially under the harsh condition of high-voltage without sacrifices of reversible capacity.Herein,singlecrystal LiNi_(0.8)Mn_(0.2)O_(2) is selected and compared with traditional LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(NCM),mainly focusing on the failure mechanism of Cofree cathode and illuminating the significant effect of Co element on the Li/Ni antisite defect and dynamic characteristic.Specifically,the presence of high Li/Ni antisite defect in NM cathode easily results in the extremely dramatic H2/H3 phase transition,which exacerbates the distortion of the lattice,mechanical strain changes and exhibits poor electrochemical performance,especially under the high cutoff voltage.Furthermore,the reaction kinetic of NM is impaired due to the absence of Co element,especially at the single-crystal architecture.Whereas,the negative influence of Li/Ni antisite defect is controllable at low current densities,owing to the attenuated polarization.Notably,Co-free NM can exhibit better safety performance than that of NCM cathode.These findings are beneficial for understanding the fundamental reaction mechanism of single-crystal Ni-rich Co-free cathode materials,providing new insights and great encouragements to design and develop the next generation of LIBs with low-cost and high-safety performances.

Unlocking fast Li-ion transport in micrometer-sized Mn-based cation-disordered rocksalt cathodes

The development of cation-disordered rocksalt(DRX)cathodes has garnered worldwide attention due to their high capacity,broad chemical space and excellent structural flexibility.However,their low intrinsic Li-ion conductivity necessitates extensive particle pulverization,typically achieved through ball-milling process,which impedes large-scale production.In this work,we present a proton-exchange assisted strategy to activate the Li-ion transport in Mn-based DRX cathodes.Short-range spinel-like ordering is observed to form within the DRX matrix after the post treatment,which significantly enhances the intrinsic Li ion mobility.Notably,more than 280 mAh g^(-1)discharge capacity can be delivered at a slow rate from micrometer-sized particles with an overall disordered cation arrangement,which retains more than150 m Ah g^(-1)when cycled at a very high rate of 2000 mA g^(-1).Furthermore,we also demonstrate that the electrochemical performance of the post-treated cathodes can be further optimized by fine-tuning the reaction parameters.

Insight into the capacity degradation and structural evolution of single-crystal Ni-rich cathodes

Single-crystal Ni-rich cathodes are a promising candidate for high-energy lithium-ion batteries due to their higher structural and cycling stability than polycrystalline materials.However,the phase evolution and capacity degradation of these single-crystal cathodes during continuous lithation/delithation cycling remains unclear.Understanding the mapping relationship between the macroscopic electrochemical properties and the material physicochemical properties is crucial.Here,we investigate the correlation between the physical-chemical characteristics,phase transition,and capacity decay using capacity differential curve feature identification and in-situ X-ray spectroscopic imaging.We systematically clarify the dominant mechanism of phase evolution in aging cycling.Appropriately high cut-off voltages can mitigate the slow kinetic and electrochemical properties of single-crystal cathodes.We also find that second-order differential capacity discharge characteristic curves can be used to identify the crystal structure disorder of Ni-rich cathodes.These findings constitute a step forward in elucidating the correlation between the electrochemical extrinsic properties and the physicochemical intrinsic properties and provide new perspectives for failure analysis of layered electrode materials.

Cationic ordering transition in oxygen-redox layered oxide cathodes

Understanding the structural origin of the competition between oxygen 2p and transition-metal 3d orbitals in oxygen-redox(OR)layered oxides is eminently desirable for exploring reversible and high-energy-density Li/Na-ion cathodes.Here,we reveal the correlation between cationic ordering transition and OR degradation in ribbon-ordered P3-Na_(0.6)Li_(0.2)Mn_(0.8)O_(2) via in situ structural analysis.Comparing two different voltage windows,the OR capacity can be improved approximately twofold when suppressing the in-plane cationic ordering transition.We find that the intralayer cationic migration is promoted by electrochemical reduction from Mn^(4+)to Jahn–Teller Mn^(3+)and the concomitant NaO_(6) stacking transformation from triangular prisms to octahedra,resulting in the loss of ribbon ordering and electrochemical decay.First-principles calculations reveal that Mn^(4+)/Mn^(3+)charge ordering and alignment of the degenerate eg orbital induce lattice-level collective Jahn–Teller distortion,which favors intralayer Mn-ion migration and thereby accelerates OR degradation.These findings unravel the relationship between in-plane cationic ordering and OR reversibility and highlight the importance of superstructure protection for the rational design of reversible OR-active layered oxide cathodes.

Lowering Sodium-Storage Lattice Strains of Layered Oxide Cathodes by Pushing Charge Transfer on Anions

Due to a high energy density,layered transition-metal oxides have gained much attention as the promising sodium-ion batteries cathodes.However,they readily suffer from multiple phase transitions during the Na extraction process,resulting in large lattice strains which are the origin of cycledstructure degradations.Here,we demonstrate that the Na-storage lattice strains of layered oxides can be reduced by pushing charge transfer on anions(O^(2-)).Specifically,the designed O3-type Ru-based model compound,which shows an increased charge transfer on anions,displays retarded O3-P3-O1 multiple phase transitions and obviously reduced lattice strains upon cycling as directly revealed by a combination of ex situ X-ray absorption spectroscopy,in situ X-ray diffraction and geometric phase analysis.Meanwhile,the stable Na-storage lattice structure leads to a superior cycling stability with an excellent capacity retention of 84%and ultralow voltage decay of 0.2 mV/cycle after 300 cycles.More broadly,our work highlights an intrinsically structure-regulation strategy to enable a stable cycling structure of layered oxides meanwhile increasing the materials’redox activity and Nadiffusion kinetics.

New insights into the pre-lithiation kinetics of single-crystalline Ni-rich cathodes for long-life Li-ion batteries

Developing single-crystalline Ni-rich cathodes is an effective strategy to improve the safety and cycle life of Li-ion batteries(LIBs).However,the easy-to-loss of Li and O in high-temperature lithiation results in unsatisfactory ordered layered structure and stoichiometry.Herein,we demonstrate the synthesis of highly-ordered and fully-stoichiometric single-crystalline LiNi_(0.83)Co_(0.12)Mn_(0.05)O_(2)(SC-NCM83)cathodes by the regulation of pre-lithiation kinetics.The well-balanced pre-lithiation kinetics have been proved to greatly improve the proportion of layered phase in the intermediate by inhibiting the formation of metastable spinel phase,which promoted the rapid transformation of the intermediate into highly-ordered layered SC-NCM83 in the subsequent lithiation process.After coating a layer of Li_(2)O–B_(2)O_(3),the resultant cathodes deliver superior cycling stability with 90.9%capacity retention at 1C after 300 cycles in pouch-type full batteries.The enhancement mechanism has also been clarified.These findings exhibit fundamental insights into the pre-lithiation kinetics process for guiding the synthesis of high-quality singlecrystalline Ni-rich cathodes.

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 mecha-nism 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 technol-ogy 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.

Phase engineering of Ni-Mn binary layered oxide cathodes for sodiumion batteries

Nickel-manganese binary layered oxides with high working potential and low cost are potential candidates for sodium-ion batteries,but their electrochemical properties are highly related to compositional diversity.Diverse composite materials with various phase structures of P3,P2/P3,P2,P2/O3,and P2/P3/O3 were synthesized by manipulating the sodium content and calcination conditions,leading to the construction of a synthetic phase diagram for Na_(x)Ni_(0.25)Mn_(0.75)O_(2)(0.45≤x≤1.1).Then,we compared the electrochemical characteristics and structural evolution during the desodiation/sodiation process of P2,P2/P3,P2/03,and P2/P3/O3-Na_(x)Ni_(0.25)Mn_(0.75)O_(2).Among them,P2/P3-Na0.75Ni0.25Mn0.75O2exhibits the best rate capability of 90.9 mA h g^(-1)at 5 C,with an initial discharge capacity of 142.62 mA h g^(-1)at 0.1 C and a capacity retention rate of 78.25%after 100 cycles at 1 C in the voltage range of 2-4.3 V.The observed superior sodium storage performance of P2/P3 hybrids compared to other composite phases can be attributed to the enhanced Na^(+)transfer dynamic,reduction of the Jahn-teller effect,and improved reaction reversibility induced by the synergistic effect of P2 and P3 phases.The systematic research and exploration of phases in Na_(x)Ni_(0.25)Mn_(0.75)O_(2)provide new sights into high-performance nickel-manganese binary layered oxide for sodium-ion batteries.

Low-Volatile Binder Enables Thermal Shock-Resistant Thin-Film Cathodes for Thermal Batteries

Manufacturing thin-film components is crucial for achieving high-efficiency and high-power thermal batteries(TBs).However,developing binders with low-gas production at the operating temperature range of TBs(400-550°C)has proven to be a significant challenge.Here,we report the use of acrylic acid derivative terpolymer(LA136D)as a low-volatile binder for thin-film cathode fabrication and studied the chain scission and chemical bondbreaking mechanisms in pyrolysis.It is shown LA136D defers to randomchain scission and cross-linking chain scission mechanisms,which gifts it with a low proportion of volatile products(ψ,ψ=39.2 wt%)at even up to 550°C,well below those of the conventional PVDF(77.6 wt%)and SBR(99.2 wt%)binders.Surprisingly,LA136D contributes to constructing a thermal shock-resistant cathode due to the step-by-step bond-breaking process.This is beneficial for the overall performance of TBs.In discharging test,the thin-film cathodes exhibited a remarkable 440%reduction in polarization and 300%enhancement in the utilization efficiency of cathode materials,while with just a slight increase of 0.05 MPa in gas pressure compared with traditional“thick-film”cathode.Our work highlights the potential of LA136D as a low-volatile binder for thin-film cathodes and shows the feasibility of manufacturing high-efficiency and high-power TBs through polymer molecule engineering.

Two-Dimensional Graphitic Carbon-Nitride(g-C_(3)N_(4))-Coated LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2) Cathodes for High-Energy-Density and Long-Life Lithium Batteries

High-capacity nickel-rich layered oxides are promising cathode materials for high-energy-density lithium batteries.However,the poor structural stability and severe side reactions at the electrode/electrolyte interface result in unsatisfactory cycle performance.Herein,the thin layer of two-dimensional(2D)graphitic carbon-nitride(g-C_(3)N_(4))is uniformly coated on the LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(denoted as NCM811@CN)using a facile chemical vaporization-assisted synthesis method.As an ideal protective layer,the g-C_(3)N_(4)layer effectively avoids direct contact between the NCM811 cathode and the electrolyte,preventing harmful side reactions and inhibiting secondary crystal cracking.Moreover,the unique nanopore structure and abundant nitrogen vacancy edges in g-C_(3)N_(4)facilitate the adsorption and diffusion of lithium ions,which enhances the lithium deintercalation/intercalation kinetics of the NCM811 cathode.As a result,the NCM811@CN-3wt%cathode exhibits 161.3 mAh g^(−1)and capacity retention of 84.6%at 0.5 C and 55°C after 400 cycles and 95.7 mAh g^(−1)at 10 C,which is greatly superior to the uncoated NCM811(i.e.129.3 mAh g^(−1)and capacity retention of 67.4%at 0.5 C and 55°C after 220 cycles and 28.8 mAh g^(−1)at 10 C).The improved cycle performance of the NCM811@CN-3wt%cathode is also applicable to solid–liquid-hybrid cells composed of PVDF:LLZTO electrolyte membranes,which show 163.8 mAh g^(−1)and the capacity retention of 88.1%at 0.1 C and 30°C after 200 cycles and 95.3 mAh g^(−1)at 1 C.

Penetrative and migratory behavior of alkali metal in different binder based TiB_2-C composite cathodes

In electrolyte melts containing K at low temperature, the penetrative and migratory path of alkali metals （K and Na） in pitch, furan, phenolic aldehyde and epoxy based TiB2-C composite cathodes during the electrolysis process were studied by EDS and self-made modified Rapoport apparatus. The electrolysis expansion rates, the diffusion coefficients of the alkali metals and the corrosion rates of the composite cathode were also calculated and discussed. The results show that no matter what kind of binder is used, alkali metals have the same penetrative path in composite cathodes：firstly in pore, then in binder and finally in carbonaceous aggregates. K and Na penetrate into both binder and carbonaceous aggregates, which leads to the expansion of composite cathodes, and K has stronger penetration ability than Na. Electrolysis expansion rate of resin based composite cathode is smaller than that of pitch based composite cathodes, and so do the diffusion coefficient and corrosion rate. Resin based composite cathode has better resistance ability to the penetration of alkali metals than pith based composite cathode, and phenolic aldehyde based composite cathode exhibits the strongest resistance ability. The penetration rate, the diffusion coefficient of alkali metals in phenolic aldehyde based TiB2-C composite cathode and the corresponding corrosion rate are 4.72 mm/h, 2.24×10^-5 cm^2/s and 2.31 mm/a, respectively.

Critical Review on cathode-electrolyte Interphase Toward High-Voltage Cathodes for Li-Ion Batteries

The thermal stability window of current commercial carbonate-based electrolytes is no longer sufficient to meet the ever-increasing cathode working voltage requirements of high energy density lithium-ion batteries.It is crucial to construct a robust cathode-electrolyte interphase(CEI)for high-voltage cathode electrodes to separate the electrolytes from the active cathode materials and thereby suppress the side reactions.Herein,this review presents a brief historic evolution of the mechanism of CEI formation and compositions,the state-of-art characterizations and modeling associated with CEI,and how to construct robust CEI from a practical electrolyte design perspective.The focus on electrolyte design is categorized into three parts:CEI-forming additives,anti-oxidation solvents,and lithium salts.Moreover,practical considerations for electrolyte design applications are proposed.This review will shed light on the future electrolyte design which enables aggressive high-voltage cathodes.

A review on liquid metals as cathodes for molten salt/oxide electrolysis

Compared with solid metals,liquid metals are considered more promising cathodes for molten slat/oxide electrolysis due to their fascinating advantages,which include strong depolarization effect,strong alloying effect,excellent selective separation,and low operating temperature.In this review,we briefly introduce the properties of the liquid metal cathodes and their selection rules,and then summarize development in liquid metal cathodes for molten salt electrolysis,specifically the extraction of Ti and separation of actinides and rare-earth metals in halide melts.We also review recent attractive progress in the preparation of liquid Ti alloys via molten oxide electrolysis by using liquid metal cathodes.Problems related to high-quality alloy production and large-scale applications are cited,and several research directions to further improve the quality of alloys are also discussed to realize the industrial applications of liquid metal cathodes.

Oxide cathodes for sodium-ion batteries:Designs,challenges,and perspectives

Sodium-ion batteries(SIBs),which are an alternative to lithium-ion batteries(LIBs),have attracted increasing attention due to their low cost of Na resources and similar Na storage mechanism to LIBs.Compared with anode materials and electrolytes,the development of cathode materials lags behind.Therefore,the key to improving the specific energy and promoting the application of SIBs is to develop high-performance sodium intercalation cathode materials.Transition-metal oxides are one of the most promising cathode materials for SIBs owing to their excellent energy density,high specific discharge capacity,and environmentally friendly nature.In the present work,the latest progress in the research of transition-metal oxides is summarized.Moreover,the existing challenges are discussed,and a series of strategies are proposed to overcome these drawbacks.This review aims at providing guidance for the development of metal oxides in the next stage.

Promise and challenge of vanadium-based cathodes for aqueous zinc-ion batteries

Aqueous zinc-ion batteries(ZIBs)have got wide attention with the increasing demands for energy resource recently.It has a number of merits compared with lithium-ion batteries,such as enhanced safety,low cost and environmental friendliness.Vanadium-based materials have been developed to serve as the cathodes of ZIBs for many years.But there are also some challenges to construct high performance ZIBs in the future.Herein,we reviewed the research progress of vanadium-based cathodes and discussed the energy storage mechanisms in ZIBs.In addition,we summarized the major challenges faced by vanadium-based cathodes and the corresponding ways to improve electrochemical performance of ZIBs.Finally,some excellent vanadium-based cathodes are summarized to pave the way for future research in ZIBs.

High entropy fluorides as conversion cathodes with tailorable electrochemical performance

With the recent development of high entropy materials, an alternative approach to develop advanced functional materials with distinctive properties that show improved values compared to conventional materials has been provided. The high entropy concept was later successfully transferred to metal fluorides and high entropy fluorides(HEFs) were successfully synthesized. Owing to their high theoretical specific capacities in energy storage applications, HEFs were utilized as cathode materials for lithiumion batteries(LIBs) and their underlying storage mechanisms were investigated. Instead of a step-bystep reduction of each individual metal cation, the HEFs seem to exhibit a single-step reduction process,indicating a solid solution compound instead of merely a mixture of different metal fluorides. It was also observed that the electrochemical behavior of the HEFs depends on each individual incorporated element. Therefore, by altering the elemental composition, new materials that exhibit improved electrochemical properties can be designed. Remarkably, HEFs with seven incorporated metal elements exhibited a better cycling stability as well as a lower hysteresis compared to binary metal fluorides.These findings offer new guidelines for material design and tailoring towards high performance LIBs.

Interface engineering for composite cathodes in sulfide-based all-solid-state lithium batteries

All-solid-state lithium battery(ASLB)based on sulfide-based electrolyte is considered to be a candidate for the next-generation high-energy storage system.Despite the high ionic conductivity of sulfide solid electrolyte,the poor interfacial stability(mechanically and chemically)between active materials and sulfide solid electrolytes in composite cathodes leads to inferior electrochemical performances,which impedes the practical application of sulfide electrolytes.In the past years,various of strategies have been carried out to achieve an interface with low impedance in the composite cathodes.Herein,a review of recent progress of composite cathodes for all-solid-state sulfide-based lithium batteries is summarized,including the interfacial issues,design strategies,fabrication methods,and characterization techniques.Finally,the main challenges and perspectives of composite cathodes for high-performance all-solidstate batteries are highlighted for future development.

A Comparative Investigation of Single Crystal and Polycrystalline Ni-Rich NCMs as Cathodes for Lithium-Ion Batteries

Nickel-rich LiNi_(1-x-y)Co_(x)Mn_(y)O_(2)(NCM,1-x-y≥0.6)is known as a promising cathode material for lithium-ion batteries since its superiority of high voltage and large capacity.However,polycrystalline Ni-rich NCMs suffer from poor cycle stability,limiting its further application.Herein,single crystal and polycrystalline LiNi_(0.84)Co_(0.07)Mn_(0.09)O_(2)cathode materials are compared to figure out the relation of the morphology and the electrochemical storage performance.According to the Li^(+)diffusion coefficient,the lower capacity of single crystal samples is mainly ascribed to the limited Li+diffusion in the large bulk.In situ XRD illustrates that the polycrystalline and single crystal NCMs show a virtually identical manner and magnitude in lattice contraction and expansion during cycling.Also,the electrochemically active surface area(ECSA)measurement is employed in lithium-ion battery study for the first time,and these two cathodes show huge discrepancy in the ECSA after the initial cycle.These results suggest that the single crystal sample exhibits reduced cracking,surface side reaction,and Ni/Li mixing but suffers the lower Li^(+)diffusion kinetics.This work offers a view of how the morphology of Ni-rich NCM effects the electrochemical performance,which is instructive for developing a promising strategy to achieve good rate performance and excellent cycling stability.