Inferior cycling stability, poor safety, and gas generation are long lasting problems of Ni-rich Li Ni0.80 Co0.10 Mn0.10 O2(NCM811) cathode material. Although much effort has been made, mechanisms for the above proble...Inferior cycling stability, poor safety, and gas generation are long lasting problems of Ni-rich Li Ni0.80 Co0.10 Mn0.10 O2(NCM811) cathode material. Although much effort has been made, mechanisms for the above problems are poorly understood. Studying the cycling and float-charging characteristics of Li/NCM811 cells in high voltage conditions(4.5 V and 4.7 V, respectively), in this work we find that nearly all known problems with NCM811 material can be attributed to the oxidation of lattice oxygen occurring in the capacity region corresponding to H2 → H3 phase transition. While contributing to overall capacity,the oxidation of lattice oxygen results in a loss of oxygen through oxygen evolution and relative reactions between active oxygen evolution intermediates and electrolyte solvents. It is the loss of oxygen that results in irreversible layered-spinel-rocksalt phase transition, secondary particle cracking, and performance degradation. The conclusions of this work suggest that the priority for further research on NCM811 material should give to the suppression of oxygen evolution, followed by the use of the anti-oxygen electrolyte being chemically stable against the active oxygen evolution intermediates.展开更多
Ni-rich cathode materials show great potential of applying in high-energy lithium ion batteries,but their inferior cycling stability hinders this process.Study on the electrode/electrolyte interfacial reaction is indi...Ni-rich cathode materials show great potential of applying in high-energy lithium ion batteries,but their inferior cycling stability hinders this process.Study on the electrode/electrolyte interfacial reaction is indispensable to understand the capacity failure mechanism of Ni-rich cathode materials and further address this issue.This work demonstrates the domain size effects on interfacial side reactions firstly,and further analyzes the inherent mechanism of side reaction induced capacity decay through comparing the interfacial behaviors before and after MgO coating.It has been determined that LiF deposition caused thicker SEI films may not increase the surface film resistance,while HF erosion induced surface phase transition will increase the charge transfer resistance,and the later plays the dominant factor to declined capacity of Ni-rich cathode materials.This work suggests strategies to suppress the capacity decay of layered cathode materials and provides a guidance for the domain size control to match the various applications under different current rates.展开更多
Single crystal LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2)is currently widely used due to the outstanding cycle stability and safety.However,its sensitivity to the environment and the high residual alkali makes the electrochemica...Single crystal LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2)is currently widely used due to the outstanding cycle stability and safety.However,its sensitivity to the environment and the high residual alkali makes the electrochemical performance and processing property severely degraded after long-term storage,especially for the Ni-rich single crystal material.Therefore,it is highly urgent to develop a cost-effective strategy for the revival of degraded Ni-rich cathode materials.Here,a low-carbon strategy is proposed to revive the degraded single crystal LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2)(SCNCM622)through water washing.The solid-liquid reaction mechanism of SCNCM622 and water was revealed and the strong dependence of the recovery effect on the washing time was clarified.Under optimized conditions,the sample with a washing time of 24 h shows 31.2%reduction in viscosity,18.4%improvement in discharge capacity,15.3%enhancement in cycle life,and excellent rate performance compared to the blank sample.Therefore,this strategy can achieve higher utilization of single crystal Ni-based cathode materials with a lower cost.展开更多
LiNiCoAlO（NCA） with Zr（OH）coating is demonstrated as high performance cathode material for lithium ion batteries（LIBs）. The coated materials are synthesized via a simple dry coating method of NCA with Zr（OH）po...LiNiCoAlO（NCA） with Zr（OH）coating is demonstrated as high performance cathode material for lithium ion batteries（LIBs）. The coated materials are synthesized via a simple dry coating method of NCA with Zr（OH）powders, and then characterized with scanning electron microscopy（SEM）, transmission electron microscopy（TEM） and X-ray photoelectron spectroscopy（XPS）. Experimental results show that amorphous Zr（OH）powders have been successfully coated on the surface of spherical NCA particles, exhibiting improved electrochemical performance. 0.50 wt% Zr（OH）coated NCA delivers a capacity of 197.6 mAh/g at the first cycle and 154.3 mAh/g after 100 cycles with a capacity retention of 78.1% at 1 C rate. In comparison, the pure NCA shows a capacity of 194.6 mAh/g at the first cycle and 142.5 mAh/g after 100 cycles with a capacity retention of 73.2% at 1 C rate. Electrochemical impedance spectroscopy（EIS） results show that the coated material exhibits a lower resistance, indicating that the coating layer can efficiently suppress transition metals dissolution and decrease the side reactions at the surface between the electrode and electrolyte. Therefore, surface coating with amorphous Zr（OH）is a simple and useful method to enhance the electrochemical performance of NCA-based materials for the cathode of LIBs.展开更多
The intergranular microcracking in polycrystalline Ni-rich cathode particle is led by anisotropic volume change and stress corrosion along grain boundary,accelerating battery performance decay.Herein,we have suggested...The intergranular microcracking in polycrystalline Ni-rich cathode particle is led by anisotropic volume change and stress corrosion along grain boundary,accelerating battery performance decay.Herein,we have suggested a simple but advanced solid-state method that ensures both uniform transition metal distribution and single-crystalline morphology for Ni-rich cathode synthesis without sophisticated coprecipitation.Pelletization-assisted mechanical densification(PAMD)process on solid-state precursor mixture enables the dynamic mass transfer through the increased solid-solid contact area which facilitates the grain growth during sintering process,readily forming micro-sized single-crystalline particle.Furthermore,the improved chemical reactivity by a combination of capillary effect and vacancyassisted diffusion provides homogeneous element distribution within each primary particle.As a result,single-crystalline Ni-rich cathode with PAMD process has eliminated a potential evolution of intergranular cracking,thus achieving superior energy retention capability of 85%over 150 cycles compared to polycrystalline Ni-rich particle even after high-pressure calendering process(corresponding to electrode density of~3.6 g cm^(-3))and high cut-off voltage cycling.This work provides a concrete perspective on developing facile synthetic route of micron-sized single-crystalline Ni-rich cathode materials for high energy density lithium-ion batteries(LIBs).展开更多
Layered oxide cathodes with high Ni content promise high energy density and competitive cost for Li-ion batteries(LIBs).However,Ni-rich cathodes suffer from irreversible interface reconstruction and undesirable cracki...Layered oxide cathodes with high Ni content promise high energy density and competitive cost for Li-ion batteries(LIBs).However,Ni-rich cathodes suffer from irreversible interface reconstruction and undesirable cracking with severe performance degradation upon long-term operation,especially at elevated temperatures.Herein,we demonstrate in situ surface engineering of Ni-rich cathodes to construct a dual ion/electron-conductive NiTiO 3 coating layer and Ti gradient doping(NC90–Ti@NTO)in parallel.The dual-modification synergy helps to build a thin,robust cathode–electrolyte interface with rapid Li-ion transport and enhanced reaction kinetics,and effec-tively prevents unfavorable crystalline phase transformation during long-term cycling under harsh environments.The optimized NC90–Ti@NTO delivers a high reversible capacity of 221.0 mAh g^(-1) at 0.1C and 158.9 mAh g^(-1) at 10C.Impressively,it exhibits a capacity retention of 88.4%at 25?C after 500 cycles and 90.7%at 55?C after 300 cycles in a pouch-type full battery.This finding provides viable clues for stabilizing the lattice and interfacial chemistry of Ni-rich cathodes to achieve durable LIBs with high energy density.展开更多
Nickel(Ni)-rich cathode materials have become promising candidates for the next-generation electrical vehicles due to their high specific capacity.However,the poor thermodynamic stability(including cyclic performance ...Nickel(Ni)-rich cathode materials have become promising candidates for the next-generation electrical vehicles due to their high specific capacity.However,the poor thermodynamic stability(including cyclic performance and safety performance or thermal stability)will restrain their wide commercial application.Herein,a single-crystal Ni-rich Li Ni_(0.83)Co_(0.12)Mn_(0.05)O_(2) cathode material is synthesized and modified by a dual-substitution strategy in which the high-valence doping element improves the structural stability by forming strong metal–oxygen binding forces,while the low-valence doping element eliminates high Li^(+)/Ni^(2+)mixing.As a result,this synergistic dual substitution can effectively suppress H2-H3 phase transition and generation of microcracks,thereby ultimately improving the thermodynamic stability of Ni-rich cathode material.Notably,the dual-doped Ni-rich cathode delivers an extremely high capacity retention of 81%after 250 cycles(vs.Li/Li+)in coin-type half cells and 87%after 1000 cycles(vs.graphite/Li^(+))in pouch-type full cells at a high temperature of 55℃.More impressively,the dual-doped sample exhibits excellent thermal stability,which demonstrates a higher thermal runaway temperature and a lower calorific value.The synergetic effects of this dual-substitution strategy pave a new pathway for addressing the critical challenges of Ni-rich cathode at high temperatures,which will significantly advance the high-energy-density and high-safety cathodes to the subsequent commercialization.展开更多
Water washing has been regarded as one of the most effective strategies to remove surface residual lithium of nickel-rich layered oxides for lithium-ion batteries(LIBs).However,the loss of lattice lithium during the w...Water washing has been regarded as one of the most effective strategies to remove surface residual lithium of nickel-rich layered oxides for lithium-ion batteries(LIBs).However,the loss of lattice lithium during the water washing process deteriorates the electrochemical performances and air stability.Herein,washing the LiNi_(0.90)Co_(0.05)Al_(0.02)O_(2)(NCA) with ammonium dihydrogen phosphate(NH_(4)H_(2)PO_(4)) solution has been proposed to simultaneously enhance electrochemical performances and air stability,in which in-situ generated Li_(3)PO_(4) coating layer on surface of NCA can suppress the loss of lattice lithium.Besides,as a fast ionic conductor,Li_(3)PO_(4) coating layer on NCA can prevent the direct contact with electrolyte/air.As a result,the NH_(4)H_(2)PO_(4) solution washed NCA cathode can deliver a high capacity of131.9 mAh·g^(-1) at 10.0C rate as well as impressive cycle stability with a capacity retention of 83.1% after 100 cycles at 1.0C,much higher than those of water washed NCA(WS-NCA) electrode.After exposed in air for 7 days,the NH_(4)H_(2)PO_(4) solution washed NCA electrode can more effectively maintain the structural integrity as well as the electrochemical performances than water-washed NCA.This work provides a simple and effective approach to enhance the cycle stability and air stability of Nickel-rich cathode materials.展开更多
LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(NCM811)is the most promising cathode for high-energy Li-ion batteries,despite its poor cycling stability that originates from the reactions that occur with the electrolyte.Herein,to sol...LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(NCM811)is the most promising cathode for high-energy Li-ion batteries,despite its poor cycling stability that originates from the reactions that occur with the electrolyte.Herein,to solve this interfacial issue,a facile electrolytic electrochemical polymerization process was introduced in this paper,and a uniform conductive electrolyte interface(polyaniline)was successfully constructed on the surface of the NCM811 porous electrode(PANI-NCM),which facilitated the charge transfer during charge/discharge.The side reactions at the interface between the cathode and the electrolyte are suppressed,and thereby,the cycling performance and rate capability are considerably improved.PANI-NCM delivers an initial capacity of 157.2 mAh·g^(-1)as well as excellent cyclability(capacity retention of 88%after 500 cycles at 2C),whereas the capacity of the bare NCM811 has dropped to 31.3 mAh·g^(-1).In addition,polypyrrole and polythiophene also can be formed through electrolytic electrochemical polymerization process,which provides a practicable tactic to modify the interfacial stability of cathodes for high-energy Li-ion batteries.展开更多
Generally,layered Ni-rich cathode materials exhibit the morphology of polycrystalline secondary sphere composed of numerous primary particles.While the arrangement of primary particles plays a very important role in t...Generally,layered Ni-rich cathode materials exhibit the morphology of polycrystalline secondary sphere composed of numerous primary particles.While the arrangement of primary particles plays a very important role in the properties of Ni-rich cathodes.The disordered particle arrangement is harmful to the cyclic performance and structural stability,yet the fundamental understanding of disordered structure on the structural degradation behavior is unclarified.Herein,we have designed three kinds of LiNi_(0.83)Co_(0.06)Mn_(0.11)O_(2) cathode materials with different primary particle orientations by regulating the precursor coprecipitation process.Combining finite element simulation and in-situ characterization,the Li^(+)transport and structure evolution behaviors of different materials are unraveled.Specifically,the smooth Li^(+)diffusion minimizes the reaction heterogeneity,homogenizes the phase transition within grains,and mitigates the anisotropic microstructural change,thereby modulating the crack evolution behavior.Meanwhile,the optimized structure evolution ensures radial tight junctions of the primary particles,enabling enhanced Li^(+)diffusion during dynamic processes.Closed-loop bidirectional enhancement mechanism becomes critical for grain orientation regulation to stabilize the cyclic performance.This precursor engineering with particle orientation regulation provides the useful guidance for the structural design and feature enhancement of Ni-rich layered cathodes.展开更多
LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(NCM811)layered oxides have been regarded as promising alternative cathodes for the next generation of high-energy lithium ion batteries(LIBs)due to high discharge capacities and energy ...LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(NCM811)layered oxides have been regarded as promising alternative cathodes for the next generation of high-energy lithium ion batteries(LIBs)due to high discharge capacities and energy densities at high operation voltage.However,the capacity fading under high operation voltage still restricts the practical application.Herein,the capacity degradation mechanism of NCM811 at atomic-scale is studied in detail under various cut-off voltages using aberration-corrected scanning transmission electron microscopy(STEM).It is observed that the crystal structure of NCM811 evolution from a layered structure to a rock-salt phase is directly accompanied by serious intergranular cracks under 4.9 V,which is distinguished from the generally accepted structure evolution of layered,disordered layered,defect rock salt and rock salt phases,also observed under 4.3 and 4.7 V.The electron energy loss spectroscopy analysis also confirms the reduction of Ni and Co from the surface to the bulk,not the previously reported only Li/Ni interlayer mixing.The degradation mechanism of NCM811 at a high cut-off voltage of4.9 V is attributed to the formation of intergranular cracks induced by defects,the direct formation of the rock salt phase,and the accompanied reduction of Ni^(2+)and Co^(2+)phases from the surface to the bulk.展开更多
The research and development of advanced nanocoatings for high-capacity cathode materials is currently a hot topic in the field of solid-state batteries(SSBs).Protective surface coatings prevent direct contact between...The research and development of advanced nanocoatings for high-capacity cathode materials is currently a hot topic in the field of solid-state batteries(SSBs).Protective surface coatings prevent direct contact between the cathode material and solid electrolyte,thereby inhibiting detrimental interfacial decomposition reactions.This is particularly important when using lithium thiophosphate superionic solid electrolytes,as these materials exhibit a narrow electrochemical stability window,and therefore,are prone to degradation during battery operation.Herein we show that the cycling performance of LiNbO_(3)-coated Ni-rich LiNi_(x)Co_(y)Mn_(z)O_(2)cathode materials is strongly dependent on the sample history and(coating)synthesis conditions.We demonstrate that post-treatment in a pure oxygen atmosphere at 350℃results in the formation of a surface layer with a unique microstructure,consisting of LiNbO_(3)nanoparticles distributed in a carbonate matrix.If tested at 45℃and C/5 rate in pellet-stack SSB full cells with Li_(4)Ti_(5)O_(12)and Li_(6)PS_(5)Cl as anode material and solid electrolyte,respectively,around 80%of the initial specific discharge capacity is retained after 200 cycles(~160 mAh·g^(−1),~1.7 mAh·cm^(−2)).Our results highlight the importance of tailoring the coating chemistry to the electrode material(s)for practical SSB applications.展开更多
This study explored the complex effect of graphite tortuosity on the electrochemical performance of Ni-rich NCA90 Li-ion batteries(LIBs).Different levels of graphite anode tortuosity were analyzed,revealing that low-t...This study explored the complex effect of graphite tortuosity on the electrochemical performance of Ni-rich NCA90 Li-ion batteries(LIBs).Different levels of graphite anode tortuosity were analyzed,revealing that low-tortuosity electrodes had better graphite utilization.The in-plane tortuosities of the graphite anode electrodes examined were 1.70,1.94,2.05,and 2.18,while their corresponding through-plane tortuosities were 4.74,6.94,8.19,and 9.80.In-operando X-ray diffraction and differential electrochemical mass spectrometry were employed to investigate the charge storage mechanism and gas evolution.The study revealed that while graphite electrode tortuosity impacted the amount of Li present in the lithiated graphite phase due to diffusion constraints,it did not affect gas generation.The Li-ion utilization in low-tortuosity electrodes was higher than that in high-tortuosity electrodes because of solid-diffusion limitations.Additionally,the galvanostatic intermittent titration technique(GITT) was employed to investigate a lithium-ion diffusion coefficient.Our results indicate that the lithium-ion diffusion coefficient exhibits a significant difference only during LiC_(6) phase transition.We also observed that the use of a lower tortuosity electrode leads to improved lithium-ion insertion.Consequently,graphite utilization is influenced by the porous electrode design.Safety tests adhering to UN38.3 guidelines verified battery safety.The study demonstrated the practical application of optimized NCA90 LIB cells with diverse graphite electrode tortuosities in a high-performance Lamborghini GoKart,paving the way for further advancements in Ni-rich LIB technology.展开更多
Ni-rich cathode materials have become one of the most promising cathode materials for advanced high-energy Li-ion batteries(LIBs)owing to their high specific capacity.However,Ni-rich cathode materials are sensitive to...Ni-rich cathode materials have become one of the most promising cathode materials for advanced high-energy Li-ion batteries(LIBs)owing to their high specific capacity.However,Ni-rich cathode materials are sensitive to the trace H2O and CO2 in the air,and tend to react with them to generate LiOH and Li2COg at the particle surface region(named residual lithium compounds,labeled as RLCs).The RLCs will deteriorate the comprehensive performances of Ni-rich cathode materials and make trouble in the subsequent manufacturing process of electrode,including causing low initial coulombic efficiency and poor storage property,bringing about potential safety hazards,and gelatinizing the electrode slurry.Therefore,it is of considerable significance to remove the RLCs.Researchers have done a lot of work on the corresponding field,such as exploring the formation mechanism and elimination methods.This paper investigates the origin of the surface residual lithium compounds on Ni-rich cathode materials,analyzes their adverse effects on the per-formance and the subsequent electrode production process,and summarizes various kinds of feasible methods for removing the RLCS.Finally,we propose a new research direction of eliminating the lithium residuals after comparing and summing up the above.We hope this work can provide a reference for alleviating the adverse effects of residual lithium compounds for Ni-rich cathode materials'industrial production.展开更多
文摘Inferior cycling stability, poor safety, and gas generation are long lasting problems of Ni-rich Li Ni0.80 Co0.10 Mn0.10 O2(NCM811) cathode material. Although much effort has been made, mechanisms for the above problems are poorly understood. Studying the cycling and float-charging characteristics of Li/NCM811 cells in high voltage conditions(4.5 V and 4.7 V, respectively), in this work we find that nearly all known problems with NCM811 material can be attributed to the oxidation of lattice oxygen occurring in the capacity region corresponding to H2 → H3 phase transition. While contributing to overall capacity,the oxidation of lattice oxygen results in a loss of oxygen through oxygen evolution and relative reactions between active oxygen evolution intermediates and electrolyte solvents. It is the loss of oxygen that results in irreversible layered-spinel-rocksalt phase transition, secondary particle cracking, and performance degradation. The conclusions of this work suggest that the priority for further research on NCM811 material should give to the suppression of oxygen evolution, followed by the use of the anti-oxygen electrolyte being chemically stable against the active oxygen evolution intermediates.
基金supported by the National Key R&D Program of China(2016YFB0100301)the National Natural Science Foundation of China(21875022,51802020,U1664255)+2 种基金the Science and Technology Innovation Foundation of Beijing Institute of Technology Chongqing Innovation Center(2020CX5100006)the Young Elite Scientists Sponsorship Program by CAST(2018QNRC001)the support from the Beijing Institute of Technology Research Fund Program for Young Scholars。
文摘Ni-rich cathode materials show great potential of applying in high-energy lithium ion batteries,but their inferior cycling stability hinders this process.Study on the electrode/electrolyte interfacial reaction is indispensable to understand the capacity failure mechanism of Ni-rich cathode materials and further address this issue.This work demonstrates the domain size effects on interfacial side reactions firstly,and further analyzes the inherent mechanism of side reaction induced capacity decay through comparing the interfacial behaviors before and after MgO coating.It has been determined that LiF deposition caused thicker SEI films may not increase the surface film resistance,while HF erosion induced surface phase transition will increase the charge transfer resistance,and the later plays the dominant factor to declined capacity of Ni-rich cathode materials.This work suggests strategies to suppress the capacity decay of layered cathode materials and provides a guidance for the domain size control to match the various applications under different current rates.
基金financially supported by the Science,Technology,and Innovation Commission of Shenzhen Municipality(No.JCYJ20180508151856806)the National Natural Science Foundation of China(No.51974256)+3 种基金the Outstanding Young Scholars of Shaanxi(No.2019JC-12)the Key R&D Program of Shanxi(No.2019ZDLGY04-05)the National Natural Science Foundation of Shaanxi(Nos.2019JLZ-01,2019JLM-29)the Fundamental Research Funds for the Central Universities(Nos.19GH020302,3102019JC005)。
文摘Single crystal LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2)is currently widely used due to the outstanding cycle stability and safety.However,its sensitivity to the environment and the high residual alkali makes the electrochemical performance and processing property severely degraded after long-term storage,especially for the Ni-rich single crystal material.Therefore,it is highly urgent to develop a cost-effective strategy for the revival of degraded Ni-rich cathode materials.Here,a low-carbon strategy is proposed to revive the degraded single crystal LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2)(SCNCM622)through water washing.The solid-liquid reaction mechanism of SCNCM622 and water was revealed and the strong dependence of the recovery effect on the washing time was clarified.Under optimized conditions,the sample with a washing time of 24 h shows 31.2%reduction in viscosity,18.4%improvement in discharge capacity,15.3%enhancement in cycle life,and excellent rate performance compared to the blank sample.Therefore,this strategy can achieve higher utilization of single crystal Ni-based cathode materials with a lower cost.
基金supported by the National Projects of NSFC(21322101 and 21231005)MOE(B12015 and IRT13R30)
文摘LiNiCoAlO（NCA） with Zr（OH）coating is demonstrated as high performance cathode material for lithium ion batteries（LIBs）. The coated materials are synthesized via a simple dry coating method of NCA with Zr（OH）powders, and then characterized with scanning electron microscopy（SEM）, transmission electron microscopy（TEM） and X-ray photoelectron spectroscopy（XPS）. Experimental results show that amorphous Zr（OH）powders have been successfully coated on the surface of spherical NCA particles, exhibiting improved electrochemical performance. 0.50 wt% Zr（OH）coated NCA delivers a capacity of 197.6 mAh/g at the first cycle and 154.3 mAh/g after 100 cycles with a capacity retention of 78.1% at 1 C rate. In comparison, the pure NCA shows a capacity of 194.6 mAh/g at the first cycle and 142.5 mAh/g after 100 cycles with a capacity retention of 73.2% at 1 C rate. Electrochemical impedance spectroscopy（EIS） results show that the coated material exhibits a lower resistance, indicating that the coating layer can efficiently suppress transition metals dissolution and decrease the side reactions at the surface between the electrode and electrolyte. Therefore, surface coating with amorphous Zr（OH）is a simple and useful method to enhance the electrochemical performance of NCA-based materials for the cathode of LIBs.
基金supported by the National Research Foundation of Korea(NRF)grant funded by the Korea government(MEST)(2021R1A2C1095408)supported by Basic Science Research Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Education(2022R1A6A1A03051158)。
文摘The intergranular microcracking in polycrystalline Ni-rich cathode particle is led by anisotropic volume change and stress corrosion along grain boundary,accelerating battery performance decay.Herein,we have suggested a simple but advanced solid-state method that ensures both uniform transition metal distribution and single-crystalline morphology for Ni-rich cathode synthesis without sophisticated coprecipitation.Pelletization-assisted mechanical densification(PAMD)process on solid-state precursor mixture enables the dynamic mass transfer through the increased solid-solid contact area which facilitates the grain growth during sintering process,readily forming micro-sized single-crystalline particle.Furthermore,the improved chemical reactivity by a combination of capillary effect and vacancyassisted diffusion provides homogeneous element distribution within each primary particle.As a result,single-crystalline Ni-rich cathode with PAMD process has eliminated a potential evolution of intergranular cracking,thus achieving superior energy retention capability of 85%over 150 cycles compared to polycrystalline Ni-rich particle even after high-pressure calendering process(corresponding to electrode density of~3.6 g cm^(-3))and high cut-off voltage cycling.This work provides a concrete perspective on developing facile synthetic route of micron-sized single-crystalline Ni-rich cathode materials for high energy density lithium-ion batteries(LIBs).
基金This work was supported by the National Natural Science Foundation of China(21975074,91834301)the Innovation Program of Shanghai Municipal Education Commission,and the Fundamental Research Funds for the Central Universities.
文摘Layered oxide cathodes with high Ni content promise high energy density and competitive cost for Li-ion batteries(LIBs).However,Ni-rich cathodes suffer from irreversible interface reconstruction and undesirable cracking with severe performance degradation upon long-term operation,especially at elevated temperatures.Herein,we demonstrate in situ surface engineering of Ni-rich cathodes to construct a dual ion/electron-conductive NiTiO 3 coating layer and Ti gradient doping(NC90–Ti@NTO)in parallel.The dual-modification synergy helps to build a thin,robust cathode–electrolyte interface with rapid Li-ion transport and enhanced reaction kinetics,and effec-tively prevents unfavorable crystalline phase transformation during long-term cycling under harsh environments.The optimized NC90–Ti@NTO delivers a high reversible capacity of 221.0 mAh g^(-1) at 0.1C and 158.9 mAh g^(-1) at 10C.Impressively,it exhibits a capacity retention of 88.4%at 25?C after 500 cycles and 90.7%at 55?C after 300 cycles in a pouch-type full battery.This finding provides viable clues for stabilizing the lattice and interfacial chemistry of Ni-rich cathodes to achieve durable LIBs with high energy density.
基金financially supported by the Natural Science Foundation of Jiangsu Province,China (BK20210887)the Jiangsu Provincial Double Innovation Program,China (JSSCB20210984)+1 种基金the Natural Science Fund for Colleges and Universities of Jiangsu Province,China (21KJB450003)the Jiangsu University of Science and Technology Doctoral Research Start-up Fund,China (120200012)。
文摘Nickel(Ni)-rich cathode materials have become promising candidates for the next-generation electrical vehicles due to their high specific capacity.However,the poor thermodynamic stability(including cyclic performance and safety performance or thermal stability)will restrain their wide commercial application.Herein,a single-crystal Ni-rich Li Ni_(0.83)Co_(0.12)Mn_(0.05)O_(2) cathode material is synthesized and modified by a dual-substitution strategy in which the high-valence doping element improves the structural stability by forming strong metal–oxygen binding forces,while the low-valence doping element eliminates high Li^(+)/Ni^(2+)mixing.As a result,this synergistic dual substitution can effectively suppress H2-H3 phase transition and generation of microcracks,thereby ultimately improving the thermodynamic stability of Ni-rich cathode material.Notably,the dual-doped Ni-rich cathode delivers an extremely high capacity retention of 81%after 250 cycles(vs.Li/Li+)in coin-type half cells and 87%after 1000 cycles(vs.graphite/Li^(+))in pouch-type full cells at a high temperature of 55℃.More impressively,the dual-doped sample exhibits excellent thermal stability,which demonstrates a higher thermal runaway temperature and a lower calorific value.The synergetic effects of this dual-substitution strategy pave a new pathway for addressing the critical challenges of Ni-rich cathode at high temperatures,which will significantly advance the high-energy-density and high-safety cathodes to the subsequent commercialization.
基金financially supported by the National Natural Science Foundation of China (No.51874142)the Tip-top Scientific and Technical Innovative Youth Talents of Guangdong Special Support Program (No.2019TQ05L903)the Young Elite Scientists Sponsorship Program by CAST (No.2019QNRC001)。
文摘Water washing has been regarded as one of the most effective strategies to remove surface residual lithium of nickel-rich layered oxides for lithium-ion batteries(LIBs).However,the loss of lattice lithium during the water washing process deteriorates the electrochemical performances and air stability.Herein,washing the LiNi_(0.90)Co_(0.05)Al_(0.02)O_(2)(NCA) with ammonium dihydrogen phosphate(NH_(4)H_(2)PO_(4)) solution has been proposed to simultaneously enhance electrochemical performances and air stability,in which in-situ generated Li_(3)PO_(4) coating layer on surface of NCA can suppress the loss of lattice lithium.Besides,as a fast ionic conductor,Li_(3)PO_(4) coating layer on NCA can prevent the direct contact with electrolyte/air.As a result,the NH_(4)H_(2)PO_(4) solution washed NCA cathode can deliver a high capacity of131.9 mAh·g^(-1) at 10.0C rate as well as impressive cycle stability with a capacity retention of 83.1% after 100 cycles at 1.0C,much higher than those of water washed NCA(WS-NCA) electrode.After exposed in air for 7 days,the NH_(4)H_(2)PO_(4) solution washed NCA electrode can more effectively maintain the structural integrity as well as the electrochemical performances than water-washed NCA.This work provides a simple and effective approach to enhance the cycle stability and air stability of Nickel-rich cathode materials.
基金financially supported by the National Natural Science Foundation of China(Nos.52172227 and Z190010)。
文摘LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(NCM811)is the most promising cathode for high-energy Li-ion batteries,despite its poor cycling stability that originates from the reactions that occur with the electrolyte.Herein,to solve this interfacial issue,a facile electrolytic electrochemical polymerization process was introduced in this paper,and a uniform conductive electrolyte interface(polyaniline)was successfully constructed on the surface of the NCM811 porous electrode(PANI-NCM),which facilitated the charge transfer during charge/discharge.The side reactions at the interface between the cathode and the electrolyte are suppressed,and thereby,the cycling performance and rate capability are considerably improved.PANI-NCM delivers an initial capacity of 157.2 mAh·g^(-1)as well as excellent cyclability(capacity retention of 88%after 500 cycles at 2C),whereas the capacity of the bare NCM811 has dropped to 31.3 mAh·g^(-1).In addition,polypyrrole and polythiophene also can be formed through electrolytic electrochemical polymerization process,which provides a practicable tactic to modify the interfacial stability of cathodes for high-energy Li-ion batteries.
基金supported by National Natural Science Foundation of China (52070194,52073309)Natural Science Foundation of Hunan Province (2022JJ20069)。
文摘Generally,layered Ni-rich cathode materials exhibit the morphology of polycrystalline secondary sphere composed of numerous primary particles.While the arrangement of primary particles plays a very important role in the properties of Ni-rich cathodes.The disordered particle arrangement is harmful to the cyclic performance and structural stability,yet the fundamental understanding of disordered structure on the structural degradation behavior is unclarified.Herein,we have designed three kinds of LiNi_(0.83)Co_(0.06)Mn_(0.11)O_(2) cathode materials with different primary particle orientations by regulating the precursor coprecipitation process.Combining finite element simulation and in-situ characterization,the Li^(+)transport and structure evolution behaviors of different materials are unraveled.Specifically,the smooth Li^(+)diffusion minimizes the reaction heterogeneity,homogenizes the phase transition within grains,and mitigates the anisotropic microstructural change,thereby modulating the crack evolution behavior.Meanwhile,the optimized structure evolution ensures radial tight junctions of the primary particles,enabling enhanced Li^(+)diffusion during dynamic processes.Closed-loop bidirectional enhancement mechanism becomes critical for grain orientation regulation to stabilize the cyclic performance.This precursor engineering with particle orientation regulation provides the useful guidance for the structural design and feature enhancement of Ni-rich layered cathodes.
基金supported by the National Natural Science Foundation of China(U2032131)the Key R&D Program of Shaanxi Province(2021GY-118)the Shanxi-Zheda Institute of Advanced Materials and Chemical Engineering(2022SX-TD012 and 2021SXTD012)。
文摘LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(NCM811)layered oxides have been regarded as promising alternative cathodes for the next generation of high-energy lithium ion batteries(LIBs)due to high discharge capacities and energy densities at high operation voltage.However,the capacity fading under high operation voltage still restricts the practical application.Herein,the capacity degradation mechanism of NCM811 at atomic-scale is studied in detail under various cut-off voltages using aberration-corrected scanning transmission electron microscopy(STEM).It is observed that the crystal structure of NCM811 evolution from a layered structure to a rock-salt phase is directly accompanied by serious intergranular cracks under 4.9 V,which is distinguished from the generally accepted structure evolution of layered,disordered layered,defect rock salt and rock salt phases,also observed under 4.3 and 4.7 V.The electron energy loss spectroscopy analysis also confirms the reduction of Ni and Co from the surface to the bulk,not the previously reported only Li/Ni interlayer mixing.The degradation mechanism of NCM811 at a high cut-off voltage of4.9 V is attributed to the formation of intergranular cracks induced by defects,the direct formation of the rock salt phase,and the accompanied reduction of Ni^(2+)and Co^(2+)phases from the surface to the bulk.
文摘The research and development of advanced nanocoatings for high-capacity cathode materials is currently a hot topic in the field of solid-state batteries(SSBs).Protective surface coatings prevent direct contact between the cathode material and solid electrolyte,thereby inhibiting detrimental interfacial decomposition reactions.This is particularly important when using lithium thiophosphate superionic solid electrolytes,as these materials exhibit a narrow electrochemical stability window,and therefore,are prone to degradation during battery operation.Herein we show that the cycling performance of LiNbO_(3)-coated Ni-rich LiNi_(x)Co_(y)Mn_(z)O_(2)cathode materials is strongly dependent on the sample history and(coating)synthesis conditions.We demonstrate that post-treatment in a pure oxygen atmosphere at 350℃results in the formation of a surface layer with a unique microstructure,consisting of LiNbO_(3)nanoparticles distributed in a carbonate matrix.If tested at 45℃and C/5 rate in pellet-stack SSB full cells with Li_(4)Ti_(5)O_(12)and Li_(6)PS_(5)Cl as anode material and solid electrolyte,respectively,around 80%of the initial specific discharge capacity is retained after 200 cycles(~160 mAh·g^(−1),~1.7 mAh·cm^(−2)).Our results highlight the importance of tailoring the coating chemistry to the electrode material(s)for practical SSB applications.
基金financially supported under the Program Management Unit for National Competitiveness Enhancement (PMUC) by the Office of the National Higher Education Science Research and Innovation Policy Council (NXPO) PTT Public Company LimitedIRPC Public Company Limited, Thailand Science Research and Innovation (TSRI) under the Fundamental Fund by TSRI (FRB660004/0457)+2 种基金Vidyasirimedhi Institute of Science and Technology (VISTEC)Energy Policy and Planning Office (EPPO), Ministry of Energy, Thailandthe Frontier Research Centre (FRC) supported this work, VISTEC。
文摘This study explored the complex effect of graphite tortuosity on the electrochemical performance of Ni-rich NCA90 Li-ion batteries(LIBs).Different levels of graphite anode tortuosity were analyzed,revealing that low-tortuosity electrodes had better graphite utilization.The in-plane tortuosities of the graphite anode electrodes examined were 1.70,1.94,2.05,and 2.18,while their corresponding through-plane tortuosities were 4.74,6.94,8.19,and 9.80.In-operando X-ray diffraction and differential electrochemical mass spectrometry were employed to investigate the charge storage mechanism and gas evolution.The study revealed that while graphite electrode tortuosity impacted the amount of Li present in the lithiated graphite phase due to diffusion constraints,it did not affect gas generation.The Li-ion utilization in low-tortuosity electrodes was higher than that in high-tortuosity electrodes because of solid-diffusion limitations.Additionally,the galvanostatic intermittent titration technique(GITT) was employed to investigate a lithium-ion diffusion coefficient.Our results indicate that the lithium-ion diffusion coefficient exhibits a significant difference only during LiC_(6) phase transition.We also observed that the use of a lower tortuosity electrode leads to improved lithium-ion insertion.Consequently,graphite utilization is influenced by the porous electrode design.Safety tests adhering to UN38.3 guidelines verified battery safety.The study demonstrated the practical application of optimized NCA90 LIB cells with diverse graphite electrode tortuosities in a high-performance Lamborghini GoKart,paving the way for further advancements in Ni-rich LIB technology.
基金This work was supported by the National Key R&D Program of China(No.2016YFB0100301)the National Natural Science Foun dation of China(Nos.21875022,51802020,U1664255)+2 种基金the Science and Technology Innovation Foundation of Beijing Institute of Technology Chongqing Innovation Center(No.2020CX5100006)the Young Elite Scientists Sponsorship Program by CAST(No.2018QNRC001)L.Chen and N.Li acknowledge the support from the Bejing Institute of Technology Research Fund Program for Young Scholars.
文摘Ni-rich cathode materials have become one of the most promising cathode materials for advanced high-energy Li-ion batteries(LIBs)owing to their high specific capacity.However,Ni-rich cathode materials are sensitive to the trace H2O and CO2 in the air,and tend to react with them to generate LiOH and Li2COg at the particle surface region(named residual lithium compounds,labeled as RLCs).The RLCs will deteriorate the comprehensive performances of Ni-rich cathode materials and make trouble in the subsequent manufacturing process of electrode,including causing low initial coulombic efficiency and poor storage property,bringing about potential safety hazards,and gelatinizing the electrode slurry.Therefore,it is of considerable significance to remove the RLCs.Researchers have done a lot of work on the corresponding field,such as exploring the formation mechanism and elimination methods.This paper investigates the origin of the surface residual lithium compounds on Ni-rich cathode materials,analyzes their adverse effects on the per-formance and the subsequent electrode production process,and summarizes various kinds of feasible methods for removing the RLCS.Finally,we propose a new research direction of eliminating the lithium residuals after comparing and summing up the above.We hope this work can provide a reference for alleviating the adverse effects of residual lithium compounds for Ni-rich cathode materials'industrial production.
