Layered cathode materials have been successfully commercialized and applied to electric vehicles.To further improve improve the energy density of these marterials is still the main efforts in the market.Therefore,deve...Layered cathode materials have been successfully commercialized and applied to electric vehicles.To further improve improve the energy density of these marterials is still the main efforts in the market.Therefore,developing high-voltage LiNi_(x)Co_(y)Mn_(z)O_(2)(x+y+z=1,NCM)to achieve high energy density is particularly important.However,under high voltage cycling,NCM often exhibits rapid capacity degradation,which can be attributed to oxygen release,structural phase transition and particle cracking.In this work,the representative single-crystal LiNi_(0.5)Co_(0.2)Mn_(0.3)O_(2)(NCM523)was studied under various high charge cut-off voltages.Analysis by x-ray diffraction(XRD),transmission electron microscope(TEM)and electron back scatter diffraction(EBSD)measurements indicated that the rock-salt phase is formed on the surface of the particles after high voltage cycling,which is responsible for the increase of impedance and the rapid decay of capacity.Therefore,inhibiting the formation of rock-salt phase is believed an effective strategy to address the failure of NCM under high voltages.These findings provide effective guidance for the development of high-voltage NCM.展开更多
In the context of the gradual popularity of electric vehicles(EVs),the development of lithium battery systems with high energy density and power density is regarded as the foremost way to improve the range of EVs.LiNi...In the context of the gradual popularity of electric vehicles(EVs),the development of lithium battery systems with high energy density and power density is regarded as the foremost way to improve the range of EVs.LiNi_(1-x-y)Co_(x)Mn_(y)O_(2)(NCM)cathodes have been the focus of researchers due to their high energy density,excellent power performance,and low-temperature resistance.However,the elaboration of the decay mechanism of NCM cathode based on lithium metal batteries(LMBs)is still being restricted to the primary level.In the past decades,the development and application of advanced in-situ characterization tools have facilitated researchers'understanding of the internal operation mechanism of batteries during charging and discharging.In this minireview,the latest progress of in-situ observation of the NCM cathode by X-ray diffraction(XRD),fourier transform infrared(FT-IR)spectroscopy,Raman spectroscopy,atomic force microscopy(AFM),transmission electron microscope(TEM),optical microscope,and other characterization tools is summarized.The mechanisms of structural degradation,cathode-electrolyte interfaces(CEIs)composition,and dynamic changes of NCM,electrolyte breakdown,and gas production are elaborated.Finally,based on the existing research progress,the opportunities and challenges for future in-situ characterization technology in the study of the mechanism of LMBs are discussed in depth.Therefore,the purpose of this minireview is to summarize recent work that focuses on the outstanding application of in-situ characterization techniques in the mechanistic study of LMBs,and pointing the way to the future development of high energy density and power density LMBs systems.展开更多
Polycrystalline Ni-rich layered oxide (Li Ni_(x)Co_(y)Mn_zO_(2)(NCM),x>0.8) cathode material with high specific capacity and low cost is considered as one of the most promising candidate materials for lithium-ion b...Polycrystalline Ni-rich layered oxide (Li Ni_(x)Co_(y)Mn_zO_(2)(NCM),x>0.8) cathode material with high specific capacity and low cost is considered as one of the most promising candidate materials for lithium-ion batteries (LIBs).However,it suffers from severe structural and capacity degradation during practical cycling,especially under harsh operation condition(ultrahigh cutoff voltage and elevated temperature,etc.).One promising approach to mitigate these issues is to develop a single-crystal Ni-rich NCM cathode,which could enhance structural integrity and improve capacity retention,due to its robust and stable micro-sized primary particles.However,the improved cyclic stability comes at the expense of reversible capacity and rate capability,owing to the relatively low Li^(+) diffusion efficiency for its micron-sized primary particles.Moreover,the structural degradation and exacerbation of interfacial reactions for the Ni-rich NCM cathode under highvoltage (≥4.5 V) would quickly trigger the poor electrochemical performance,limiting its practical applications.Herein,Li Ni_(0.827)Co_(0.11)Zr_(0.003)Mn_(0.06)O_(2)(Zr@SC-N_(83)) cathode material was successfully synthesized via the in situ doping strategy.It could not only effectively maintain the reversibility of phase transition between H2 and H3 after long-term cycling at high voltage (4.6 V),but also enhance lithium-ion diffusion,thus improving the cycling performance and good rate performance for the Zr@SC-N_(83)cathode.As a result,0.3 wt%Zrdoping cathode delivers an initial discharging capacity of 200.1 m Ah·g^(-1)at 1.0C and at the high cutoff voltage of 4.6 V,exhibiting the satisfactory capacity retention of 85.5%after 100cycles.It provides an effective route toward low-cost and higher energy density for lithium-ion batteries with Ni-rich cathode.展开更多
Nickel rich LiNi_(x)Co_(y)Mn_(1−x−y)O_(2)cathode materials have been studied extensively to increase the energy density of lithium-ion batteries(LIBs)due to their advantages of high capacity and low cost.However,the a...Nickel rich LiNi_(x)Co_(y)Mn_(1−x−y)O_(2)cathode materials have been studied extensively to increase the energy density of lithium-ion batteries(LIBs)due to their advantages of high capacity and low cost.However,the anisotropic crystal expansion and contraction inside the secondary particles would cause detrimental micro-cracks and severe parasitic reactions at the electrode/electrolyte interface during cycling,which severely decreases the stability of crystalline structure and cathodeelectrolyte interphase and ultimately affects the calendar life of batteries.Herein,a thermodynamically stabilized interface is constructed on the surface of single-crystalline Ni-rich cathode materials(SC811@RS)via a facile molten-salt route to suppress the generation of microcracks and interfacial parasitic side reactions simultaneously.Density functional theory calculations show that the formation energy of interface layer(−1.958 eV)is more negative than that of bulk layered structure(−1.421 eV).Such a thermodynamically stable protective layer can not only prevent the direct contact between highly reactive LiNi_(x)Co_(y)Mn_(1−x−y)O_(2)and electrolyte,but also mitigate deformation of structure caused by stress thus strengthening the mechanical properties.Raman spectra further confirm the excellent structural reversibility and reaction homogeneity of SC811@RS at particle,electrode,time scales.Consequently,SC811@RS cathode material delivers significantly improved cycling stability(high capacity retention of 92%after 200 cycles at 0.5 C)compared with polycrystalline LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(82%).展开更多
文摘Layered cathode materials have been successfully commercialized and applied to electric vehicles.To further improve improve the energy density of these marterials is still the main efforts in the market.Therefore,developing high-voltage LiNi_(x)Co_(y)Mn_(z)O_(2)(x+y+z=1,NCM)to achieve high energy density is particularly important.However,under high voltage cycling,NCM often exhibits rapid capacity degradation,which can be attributed to oxygen release,structural phase transition and particle cracking.In this work,the representative single-crystal LiNi_(0.5)Co_(0.2)Mn_(0.3)O_(2)(NCM523)was studied under various high charge cut-off voltages.Analysis by x-ray diffraction(XRD),transmission electron microscope(TEM)and electron back scatter diffraction(EBSD)measurements indicated that the rock-salt phase is formed on the surface of the particles after high voltage cycling,which is responsible for the increase of impedance and the rapid decay of capacity.Therefore,inhibiting the formation of rock-salt phase is believed an effective strategy to address the failure of NCM under high voltages.These findings provide effective guidance for the development of high-voltage NCM.
基金supports by the National Natural Science Foundation of China(Nos.U20A2072,52072352,and 21875226)the Foundation for the Youth S&T Innovation Team of Sichuan Province(No.2020JDTD0035)Tianfu Rencai Plan.
文摘In the context of the gradual popularity of electric vehicles(EVs),the development of lithium battery systems with high energy density and power density is regarded as the foremost way to improve the range of EVs.LiNi_(1-x-y)Co_(x)Mn_(y)O_(2)(NCM)cathodes have been the focus of researchers due to their high energy density,excellent power performance,and low-temperature resistance.However,the elaboration of the decay mechanism of NCM cathode based on lithium metal batteries(LMBs)is still being restricted to the primary level.In the past decades,the development and application of advanced in-situ characterization tools have facilitated researchers'understanding of the internal operation mechanism of batteries during charging and discharging.In this minireview,the latest progress of in-situ observation of the NCM cathode by X-ray diffraction(XRD),fourier transform infrared(FT-IR)spectroscopy,Raman spectroscopy,atomic force microscopy(AFM),transmission electron microscope(TEM),optical microscope,and other characterization tools is summarized.The mechanisms of structural degradation,cathode-electrolyte interfaces(CEIs)composition,and dynamic changes of NCM,electrolyte breakdown,and gas production are elaborated.Finally,based on the existing research progress,the opportunities and challenges for future in-situ characterization technology in the study of the mechanism of LMBs are discussed in depth.Therefore,the purpose of this minireview is to summarize recent work that focuses on the outstanding application of in-situ characterization techniques in the mechanistic study of LMBs,and pointing the way to the future development of high energy density and power density LMBs systems.
基金financially supported by the National Natural Science Foundation of China (NSFC, No. 52204328)the Natural Science Foundation of Hunan Province (No. 2022JJ40595)+2 种基金the Scientific Research Fund of Hunan Provincial Education Department (No. 22C0383)China Postdoctoral Science Foundation (No. 2022M713547)the Science and Technology Innovation Program of Hunan Province (No. 2020SK2007)。
文摘Polycrystalline Ni-rich layered oxide (Li Ni_(x)Co_(y)Mn_zO_(2)(NCM),x>0.8) cathode material with high specific capacity and low cost is considered as one of the most promising candidate materials for lithium-ion batteries (LIBs).However,it suffers from severe structural and capacity degradation during practical cycling,especially under harsh operation condition(ultrahigh cutoff voltage and elevated temperature,etc.).One promising approach to mitigate these issues is to develop a single-crystal Ni-rich NCM cathode,which could enhance structural integrity and improve capacity retention,due to its robust and stable micro-sized primary particles.However,the improved cyclic stability comes at the expense of reversible capacity and rate capability,owing to the relatively low Li^(+) diffusion efficiency for its micron-sized primary particles.Moreover,the structural degradation and exacerbation of interfacial reactions for the Ni-rich NCM cathode under highvoltage (≥4.5 V) would quickly trigger the poor electrochemical performance,limiting its practical applications.Herein,Li Ni_(0.827)Co_(0.11)Zr_(0.003)Mn_(0.06)O_(2)(Zr@SC-N_(83)) cathode material was successfully synthesized via the in situ doping strategy.It could not only effectively maintain the reversibility of phase transition between H2 and H3 after long-term cycling at high voltage (4.6 V),but also enhance lithium-ion diffusion,thus improving the cycling performance and good rate performance for the Zr@SC-N_(83)cathode.As a result,0.3 wt%Zrdoping cathode delivers an initial discharging capacity of 200.1 m Ah·g^(-1)at 1.0C and at the high cutoff voltage of 4.6 V,exhibiting the satisfactory capacity retention of 85.5%after 100cycles.It provides an effective route toward low-cost and higher energy density for lithium-ion batteries with Ni-rich cathode.
基金the financial support of the Key Project of Science and Technology of Xiamen(No.3502Z20201013)the National Natural Science Foundation of China(Nos.21875198,21875195,and 22021001)。
文摘Nickel rich LiNi_(x)Co_(y)Mn_(1−x−y)O_(2)cathode materials have been studied extensively to increase the energy density of lithium-ion batteries(LIBs)due to their advantages of high capacity and low cost.However,the anisotropic crystal expansion and contraction inside the secondary particles would cause detrimental micro-cracks and severe parasitic reactions at the electrode/electrolyte interface during cycling,which severely decreases the stability of crystalline structure and cathodeelectrolyte interphase and ultimately affects the calendar life of batteries.Herein,a thermodynamically stabilized interface is constructed on the surface of single-crystalline Ni-rich cathode materials(SC811@RS)via a facile molten-salt route to suppress the generation of microcracks and interfacial parasitic side reactions simultaneously.Density functional theory calculations show that the formation energy of interface layer(−1.958 eV)is more negative than that of bulk layered structure(−1.421 eV).Such a thermodynamically stable protective layer can not only prevent the direct contact between highly reactive LiNi_(x)Co_(y)Mn_(1−x−y)O_(2)and electrolyte,but also mitigate deformation of structure caused by stress thus strengthening the mechanical properties.Raman spectra further confirm the excellent structural reversibility and reaction homogeneity of SC811@RS at particle,electrode,time scales.Consequently,SC811@RS cathode material delivers significantly improved cycling stability(high capacity retention of 92%after 200 cycles at 0.5 C)compared with polycrystalline LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(82%).
