Research On The New High Safety Electrolyte And Its Application In Lithium Metal Battery

Secondary batteries are the most successful energy storage devices to date,bringing a huge change to our daily lives.As society advances and develops,rechargeable batteries with higher energy densities are required to shift energy storage requirements from portable electronic devices to electric vehicles.Lithium-metal batteries have attracted extensive research attention because of their extremely high theoretical capacity(3860 mAh/g)and lowest negative chemical potential(-3.040V compared to standard hydrogen electrode).However,the high activity of lithium metal is accompanied by many safety risks that need to be solved:Uncontrollable lithium dendrite growth,irreversible side reaction between lithium metal electrode and electrolyte to form unstable solid electrolyte interface(SEI),accidental leakage and volatilization of conventional electrolyte,thermal runaway and thermal escape during operation at high temperature,etc.Therefore,it is of great significance to find appropriate strategies to realize the safe and stable operation of lithium metal batteries for promoting the practical application of high energy density and high performance rechargeable lithium metal batteries.In this paper,we design two new high safety electrolytes and successfully apply them to lithium metal batteries:(1)A new leakage fast response and self-healing electrolyte system(LRE)was proposed,which has many advantages such as leakage prevention,high ionic conductivity,good wettability of electrode and high safety.A battery assembled using the electrolyte can respond quickly to air in the event of a leak,quickly assemble to repair the damage and prevent evaporation and oxidation of the liquid electrolyte.In addition,the electrolyte also helps to form a high strength of polymer SEI,lithium dendrite formation effectively,so as to improve the stability of cell cycle,the assembly of Li‖Li asymmetric battery can keep stable operation of 500 h without dendritic lithium embedded in/out,and does not improve the interfacial resistance and polarization voltage.Designed to solve the problem of leakage in lithium-metal batteries,the new electrolyte opens up the possibility of safe and economical lithium-metal batteries.(2)A novel quasi-solid electrolyte(QSE)was prepared for lithium metal batteries with thermal response and self-protection function.The electrolyte is composed of conductive lithium polymer and non-conductive lithium solution.The assembled battery is separated out from the solvent at unsafe high temperature as the polymer molecule of lithium ion transmission bridge.The ionic conductivity drops sharply and the battery stops working,avoiding the danger of thermal runaway,which is of great significance for the safe operation of the battery.In addition,the electrolyte also has high ionic conductivity and good interfacial infiltration at room temperature,which leads to excellent electrochemical performance.Constructed of solid Li‖LiFePO4 battery capacity under the condition of current density of 0.1 C to 155 mAh g-1,the excellent ratio of performance can run under 5 C current density,and more than 800 h polarized super long cycle life.Therefore,this thermally responsive quasi-solid electrolyte has an inherent intelligent thermal management function to ensure battery safety within a specified temperature range,which has a wide application prospect.