The Synthesis And Battery Performances Of NASICON-type Solid Electrolyte Material LATP

In recent years,lithium ion batteries?LIBs?have been commonly used in consumer electronics,transportation and other fields.However,conventional LIBs with organic liquid electrolytes suffer from the problem of leakage and flamability.To replace the liquid electrolytes with solid state electrolytes is an effective method to solve the above problems,so more and more researchers pay attention to the research of solid state lithium ion batteries.This article focuses on the NASICON-type solid electrolyte material Li_1+xAl_xTi_2-x?PO₄?₃?LATP?,the cheapest solid-state electrolyte,improving its preparation method and battery performance.First of all,in view of the problems of high preparation temperature and complicated process for preparation of LATP materials,urea?CH₄N₂O?is introduced as a melt to promote the mixing of raw materials,and the factors such as the amount of urea,the calcination temperature of powders,the ball milling,and the calcination temperature of pellets are examined.Under the optimum preparation conditions?D=1/2,the calcination temperature for LATP powder was 700 ^oC,the sintering temperature for LATP pellet was 800 ^oC?,the sample possesses the highest total conductivity of 7.02×10^-4 S cm^-1 at room temperature.According to the Arrhenius equation,the activation energy of the LATP pellet with the highest conductivity was calculated to be 0.29 ev,which is lower than most existing literature reports.At the same time,in view of the simple operation of this method,the preliminary scale-up experiment was carried out in this article,laying the foundation for further application of the material.In addition,the reason for the decreased cycling performance of the LiFePO₄/LATP/Li half-cell assembled with the LATP pellet prepared under the optimal conditions was systematically studied.It was found that a layer of black material appeared on the contact portion of LATP and metallic lithium,which blongs to the product of the redox reaction between Ti element and metallic lithium.Since the poor ion migration ability of the black material,it leads to a decrease of cycle performance of the LiFePO₄/LATP/Li battery.However,under the effect of liquid electrolyte,lithium ions can pass through this layer of black material to ensure the normal cycle of the battery.In addition,one layer of Li₃PO₄ artificial SEI film was introduced,coupled with the auxiliary role of liquid electrolyte,the stability between LATP and lithium metal was significantly enhanced.The assembled LiFePO₄/LATP/PPA-Li-1335C battery showed excellent rate performance and cycling stability.After 50 charge-discharge cycles?0.1C?,the capacity retention reaches95.2%.We think this study will promote the development of solid state LIBs with LATP as an electrolyte.