Fast-charging lithium-ion batteries are highly required,especially in reducing the mileage anxiety of the widespread electric vehicles.One of the biggest bottlenecks lies in the sluggish kinetics of the Li^(+)intercal...Fast-charging lithium-ion batteries are highly required,especially in reducing the mileage anxiety of the widespread electric vehicles.One of the biggest bottlenecks lies in the sluggish kinetics of the Li^(+)intercalation into the graphite anode;slow intercalation will lead to lithium metal plating,severe side reactions,and safety concerns.The premise to solve these problems is to fully understand the reaction pathways and rate-determining steps of graphite during fast Li^(+)intercalation.Herein,we compare the Li^(+)diffusion through the graphite particle,interface,and electrode,uncover the structure of the lithiated graphite at high current densities,and correlate them with the reaction kinetics and electrochemical performances.It is found that the rate-determining steps are highly dependent on the particle size,interphase property,and electrode configuration.Insufficient Li^(+)diffusion leads to high polarization,incomplete intercalation,and the coexistence of several staging structures.Interfacial Li^(+)diffusion and electrode transportation are the main rate-determining steps if the particle size is less than 10μm.The former is highly dependent on the electrolyte chemistry and can be enhanced by constructing a fluorinated interphase.Our findings enrich the understanding of the graphite structural evolution during rapid Li^(+)intercalation,decipher the bottleneck for the sluggish reaction kinetics,and provide strategic guidelines to boost the fast-charging performance of graphite anode.展开更多
Intercalation provides to the host materials a means for controlled variation of many physical/chemical properties and dominates the reactions in metal‐ion batteries.Of particular interest is the graphite intercalati...Intercalation provides to the host materials a means for controlled variation of many physical/chemical properties and dominates the reactions in metal‐ion batteries.Of particular interest is the graphite intercalation compounds with intriguing staging structures,which however are still unclear,especially in their nanostructure and dynamic transition mechanism.Herein,the nature of the staging structure and evolution of the lithium(Li)‐intercalated graphite was revealed by cryogenic‐transmission electron microscopy and other methods at the nanoscale.The intercalated Li‐ions distribute unevenly,generating local stress and dislocations in the graphitic structure.Each staging compound is found macroscopically ordered but microscopically inhomogeneous,exhibiting a localized‐domains structural model.Our findings uncover the correlation between the long‐range ordered structure and short‐range domains,refresh the insights on the staging structure and transition of Li‐intercalated/deintercalated graphite,and provide effective ways to enhance the reaction kinetic in rechargeable batteries by defect engineering.展开更多
With the increasing demand for high energy-density batteries for portable electronics and large-scale energy storage systems,the lithium metal anode(LMA)has received tremendous attention because of its high theoretica...With the increasing demand for high energy-density batteries for portable electronics and large-scale energy storage systems,the lithium metal anode(LMA)has received tremendous attention because of its high theoretical capacity and low redox potential.However,the commercial application of LMAs is impeded by the uncontrolled growth of lithium dendrites.Such dendrite growth may result in internal short circuits,detrimental side reactions,and the formation of dead lithium.Therefore,the growth of lithium metal must be controlled.This article summarizes our recent efforts in inhibiting such dendrite growth,decreasing the detrimental side reactions,and elongating the LMA lifespan by optimizing the electrolyte structure and by designing appropriate current collectors.After identifying that the unstable solid electrolyte inter-face(SEI)film is responsible for the potential dropping in carbonate electrolytes,we developed LiPF_(6)-LiNO_(3) dual-salt electrolyte and lithium bis(fluorosulfonyl)imide(LiFSI)-carbonate electrolyte to stabilize the SEI film of LMAs.In addition,we achieved controlled lithium depos-ition by designing the structure and material of the current collectors,including selective lithium deposition in porous current collectors,lithio-philic metal guided lithium deposition,and iron carbide induced underpotential lithium deposition in nano-cavities.The limitations of the cur-rent strategies and prospects for future research are also presented.展开更多
基金supported by the National Natural Science Foundation of China(NSFC No.52172257 and 22005334)the Natural Science Foundation of Beijing(Grant No.Z200013)the National Key Research and Development Program of China(Grant No.2022YFB2502200).
文摘Fast-charging lithium-ion batteries are highly required,especially in reducing the mileage anxiety of the widespread electric vehicles.One of the biggest bottlenecks lies in the sluggish kinetics of the Li^(+)intercalation into the graphite anode;slow intercalation will lead to lithium metal plating,severe side reactions,and safety concerns.The premise to solve these problems is to fully understand the reaction pathways and rate-determining steps of graphite during fast Li^(+)intercalation.Herein,we compare the Li^(+)diffusion through the graphite particle,interface,and electrode,uncover the structure of the lithiated graphite at high current densities,and correlate them with the reaction kinetics and electrochemical performances.It is found that the rate-determining steps are highly dependent on the particle size,interphase property,and electrode configuration.Insufficient Li^(+)diffusion leads to high polarization,incomplete intercalation,and the coexistence of several staging structures.Interfacial Li^(+)diffusion and electrode transportation are the main rate-determining steps if the particle size is less than 10μm.The former is highly dependent on the electrolyte chemistry and can be enhanced by constructing a fluorinated interphase.Our findings enrich the understanding of the graphite structural evolution during rapid Li^(+)intercalation,decipher the bottleneck for the sluggish reaction kinetics,and provide strategic guidelines to boost the fast-charging performance of graphite anode.
基金support from the National Natural Science Foundation of China(NSFC nos.52172257,22005334,21773301 and 52022106)the Natural Science Foundation of Beijing(grant no.Z200013).
文摘Intercalation provides to the host materials a means for controlled variation of many physical/chemical properties and dominates the reactions in metal‐ion batteries.Of particular interest is the graphite intercalation compounds with intriguing staging structures,which however are still unclear,especially in their nanostructure and dynamic transition mechanism.Herein,the nature of the staging structure and evolution of the lithium(Li)‐intercalated graphite was revealed by cryogenic‐transmission electron microscopy and other methods at the nanoscale.The intercalated Li‐ions distribute unevenly,generating local stress and dislocations in the graphitic structure.Each staging compound is found macroscopically ordered but microscopically inhomogeneous,exhibiting a localized‐domains structural model.Our findings uncover the correlation between the long‐range ordered structure and short‐range domains,refresh the insights on the staging structure and transition of Li‐intercalated/deintercalated graphite,and provide effective ways to enhance the reaction kinetic in rechargeable batteries by defect engineering.
基金financially supported by the National Natural Science Foundation of China(No.21773301)。
文摘With the increasing demand for high energy-density batteries for portable electronics and large-scale energy storage systems,the lithium metal anode(LMA)has received tremendous attention because of its high theoretical capacity and low redox potential.However,the commercial application of LMAs is impeded by the uncontrolled growth of lithium dendrites.Such dendrite growth may result in internal short circuits,detrimental side reactions,and the formation of dead lithium.Therefore,the growth of lithium metal must be controlled.This article summarizes our recent efforts in inhibiting such dendrite growth,decreasing the detrimental side reactions,and elongating the LMA lifespan by optimizing the electrolyte structure and by designing appropriate current collectors.After identifying that the unstable solid electrolyte inter-face(SEI)film is responsible for the potential dropping in carbonate electrolytes,we developed LiPF_(6)-LiNO_(3) dual-salt electrolyte and lithium bis(fluorosulfonyl)imide(LiFSI)-carbonate electrolyte to stabilize the SEI film of LMAs.In addition,we achieved controlled lithium depos-ition by designing the structure and material of the current collectors,including selective lithium deposition in porous current collectors,lithio-philic metal guided lithium deposition,and iron carbide induced underpotential lithium deposition in nano-cavities.The limitations of the cur-rent strategies and prospects for future research are also presented.
