| In recent years,the exploitation and burning of a large number of fossil energy has led to serious environmental pollution,and the global greenhouse effect has become more and more obvious.Therefore,seeking the transformation of energy structure is the general trend of the world,wind energy,water energy,solar energy and other clean energy received extensive researches and attentions.However,most of these energy sources are constrained by relatively strict geographical conditions.This greatly hinders the large-scale development and utilization of these green renewable energy sources.The development of energy storage devices with high energy density and outstanding security can solve the problem of geographical limitations of the current development of new energy systems.Rechargeable lithium-ion batteries are considered to be an excellent energy storage system and have been successfully industrialized in portable electronic devices and electric vehicles.Nevertheless,since the theoretical specific capacity of the graphite anode which is used in the current commercial lithium ion battery is only 372 mAh g-1,the requirements for the current high energy density system are not enough.Lithium metal anode has received a lot of attentions due to its extremely high theoretical specific capacity(3860 mAh g-1)and the lowest electrochemical potential(-3.04 V compared to standard hydrogen electrode).Therefore,lithium metal anode is considered as an ideal anode material for the next generation of rechargeable batteries.However,the interface stability of lithium anode in the continuous charging and discharging process will be gradually deteriorated and lithium dendrites can be generated,which may lead to various safety accidents and reduce the cycle life of lithium metal battery.Therefore,in order to improve the interface stability of lithium metal anode,we modified the lithium anode with artificial modification layer.In this paper,the construction of artificial modification layer of lithium anode is respectively in situ generation of double conductive protective layer of lithium anode and coats the diaphragm with two-dimensional(2D)silicon oxide to improve the stability of lithium anode interface.The specific research contents are as follows:(1)A dual-conductive protecting layer is formed in situ on a lithium metal surface as an artificial solid electrolyte interface,which is composed of electronic-conductive lithiophilic lithium-gallium alloy and lithium-ion-conductive lithium nitride.The protective layer can not only ensure uniform lithium-ion diffusion but also act as a nuclear agent to lower the deposition overpotential.With this artificial solid-electrolyte interface,the dendrite growth of lithium is significantly suppressed.Symmetric half cells and full cells with a modified lithium metal anode exhibit significantly improved electrochemical performance compared with the bare lithium metal anode.(2)Dendrite-free lithium deposition was achieved by coating the polyethylene(PE)separator combined polyvinylidene fluoride with highly-lithiophilic and amorphous 2D silicon oxide particles(2D SiOx@PVDF).A flexible and robust lithiated-2D silicon oxide and PVDF(lithiated-2D SiOx-PVDF)protective layer was formed by in-situ reaction on lithium metal anodes,providing excellent interfacial stability over long cycles.By inhibiting the formation of dead lithium and random lithium deposition,reducing side reactions and buffering the volume change during lithium deposition and dissolution,the protective layer achieves dendrite free morphology of lithium anode.In addition,physicochemical 2D SiOx@PVDF ensure adequate ionic conductivity,uniform lithium ion flux and interface adaptability.The results show that the cyclic stability and coulomb efficiency of lithium metal anode are improved significantly in Li || Cu cell.When the composite separator is applied to the full cell with LiNi0.5Mn1.5O4 cathode at 2 C current density,its lifetime is improved. |
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