Researches On Synthesis And Electrochemical Performance Of Solid Electrolytes Li₃OCl And Li₂OHCl

With the development of modern society,the problem of energy shortage and environmental pollution has become more and more serious.So,people are urgent to develop and use new energy.Among many energy storage systems,lithium ion batteries have been widely used due to their small size,light weight,high energy density,long cycle life,and so on.However,the conventional Li-ion batteries(LIBs)still suffer from issues,like leakage,flammability,or explosion,which do not satisfy the stringent or increasing demands of portable electronic devices,electric vehicles and grid-energy storage systems.The novel all-solid-state LIBs has been considered as a promising candidate for the next-generation energy storage as it can effectively avoid those shortcomings and work with a metallic lithium anode,therefore allowing much higher energy densities.As the key component in all-solid-state LIBs,the solid electrolytes have widely attention and rapid development because of the higher security,such as non-toxic,non-flammable,environmentally friendly,and safe.Recently,lithium-rich anti-perovskite(LiRAP),Li3OA(A = Cl,Br,etc.),has been developed as a promising solid electrolyte.In this paper,we prepared Li3OCl and Li2OHCl by solid-state reactions,investigated their structure characterization and electrochemical performance.The main research work is as follows:(1)In this paper,Li3OCl synthesis involved heating a LiCl·H2O and Li2O mixture at 240 ? for 24 h.The XRD,TG-DSC,photo characterization and AC impedance,cyclic voltammetry tests,galvanostatic charge and discharge tests were applied to characterize materials.After XRD,TG-DSC and photo analysis,in the sample of Li3OCl,there is evidence of a small amount of Li5(OH)2Cl3.After glass transition at 130?,the Li5(OH)2Cl3 peak weakens and even disappears but the presence of crystalline Li3OCl is still clear,although an amorphous phase becomes visible.Through the AC impedance test,we can see that Li3OCl has a high ionic conductivity,which can reach at 5.71 × 10-S cm-1 and 1.22×10-5 S cm-1 at 230? and 25?.In addition,the activation energy Ea is about 0.5 eV.Cyclic voltammetry(CV)and galvanostatic charge and discharge tests show that Li3OCl material has good electrochemical stability and cycle stability.In the cyclic voltammetry test,Li3OCl material had a wide electrochemical window up to 8 V;in the galvanostatic charge and discharge test,when the current density is 0.1 mA,the material has good cycle stability.So,it shows that Li3OCl is a good choice for all-solid-state lithium-ion battery electrolyte materials.(2)The Li2OHCl material was synthesized by the traditional method of high-temperature calcination of molten salt.The Li2OHCl material was prepared by calcining molten salt at 400 with LiCl and LiOH as raw materials.The XRD characterization,AC impedance,cyclic voltammetry tests and galvanostatic charge and discharge tests were applied to characterize materials.The AC impedance test shows that Li2OHCl has a high ionic conductivity,which can reach at 2.38×10-3 S cm-1 and 1.48×10-5 S cm-1 at 200? and 25?,and has a low activation energy(Ea =0.44 eV).Through cyclic voltammetry(CV)and galvanostatic charge and discharge test,it can be seen that Li2OHCl material has good electrochemical stability and the wide electrochemical window,emphasizing the stability of the electrolytes up to 8 V.So,Li2OHCl is suitable for solid-state electrolytes of all-solid-state lithium-ion batteries.