Study On Doping Modification And Performance Of Li₃InCl₆ Solid Electrolyte

Lithium ion batteries play an important role in consumer electronics,electric vehicles and large-scale energy storage.Compared with the traditional lithium ion battery,the non-flammable solid electrolyte is used instead of flammable liquid electrolyte as the carrier of lithium ion transmission,which can greatly improve the safety of the battery.At present,solid-state batteries still have some serious problems,such as high preparation cost,short cycle life,fast performance decline,etc.,which is largely due to the poor stability of the electrode and electrolyte interface.Halide solid electrolytes have more negative anionic compounds than oxides and sulfides,in addition,they can achieve a wider thermo-electrochemical stability window.The halide solid electrolyte is still far from its practical application in terms of lithium ion conductivity,air stability and electrochemical stability.Therefore,it is of great significance to explore the design and preparation of halide electrolytes with higher lithium ion conductivity and better air stability.The Li₃InCl₆ electrolyte has good stability to the oxide cathode,has high ionic conductivity,and can be synthesized in water.However,its air/humidity tolerance limits further application.In this paper,Li₃InCl₆ electrolyte is selected as the research object to solve the problems of poor air stability,electrode/electrolyte interface stability,and improve ionic conductivity.The main findings of this paper are as follows:1.A new type of Li₃InCl_5.8F_0.2 electrolyte was prepared by the method of F doping,ball milling and solid sintering,which showed ionic conductivity of 1.17 m S cm^-1 at room temperature and good air stability.By testing the quality of absorbing water,contact angle,and water-absorbing in the air,it is found that doping F can improve the stability of electrolyte in the air.Temperature-dependent AC impedance experiments showed that the incorporation of F made Li₃InCl_5.8F_0.2 had lower activation energy,which was conducive to the transmission of Li⁺.F doping improves the conductivity of lithium ions,reduces the conductivity of electrons,reduces the cracks on the material surface,and improves the stability between solid electrolyte and positive electrode.The charge-discharge tests of all-solid-state batterie（ASSB）using Li₃InCl_5.8F_0.2 as the electrolyte,Li Co O₂ as cathode,Li-In alloy as anode,Li₆PS₅Cl electrolyte as protective layer,showed that F substitution could have higher specific capacity and better cycling performance than Li₃InCl₆ electrolyte.2.In order to explore the influence of cationic doping on Li₃InCl₆ electrolyte properties,Cu⁺of the same valence state as Li⁺was used to dope Li site of Li₃InCl₆electrolyte,and the electrochemical performance of Li_3-xCu_xInCl₆（0≤x≤0.4）samples were discussed.Through XRD tests,water absorption quality in the air,contact angle,ion conductivity test before and after water absorption,it was found that Cu was successfully incorporated,and improved air stability.when the doping amount of Cu is 0.1,the ionic conductivity of solid electrolyte Li_2.9Cu_0.1InCl₆ can reach 1.04 m S cm^-1,which is nearly two times higher than Li₃InCl₆ electrolyte.By fitting the activation energy obtained from ionic conductivity tests at different temperatures,it is speculated that the main reason for the increase of ionic conductivity is the decrease of activation energy and electron conductance.In addition,the assembly LiCoO₂/Li_2.9Cu_0.1InCl₆/Li₆PS₅Cl/Li-In solid-state batteries have higher specific capacity and better cycle performance.