전고체전지용 (100-x)Li3SI-xLi6PS5Cl (x=0, 10, 20, 및 30) 복합고체전해질의 전기화학적 성능 연구

Abstract

Li3OX (X=Cl, Br, and I) called lithium rich anti-perovskite materials recently reported as super ionic conductors with 3-dimensional Li migrating channels. Li3OX with anti-perovskite structure as solid electrolytes exhibits the ionic conductivity up to ~ 10-3 S/cm and also showing good electrochemical stability due to low interfacial resistance. Li3OX with anti-perovskite structure as solid electrolytes exhibits thermodynamic stability and shows compatible with lithium metal anode and has a large band gap to hinder electric conductor. These materials have low melting point and high electrochemical stability. But Li3OX phase tends to decompose into more stable LiX and Li2O phases at service temperature of interest for LIBs. As the Li2O phase is a rather poor ionic conductor, it would be useful in examining the feasibility in substitution of O by other chalcogen elements such as S. It is recognized that Li2S is better ionic conductor than Li2O. To prevent the decomposition of the substance, Li3SX(X=Cl, Br, and I) anti-perovskite was synthesized by replacing S with O. The Li6PS5Cl argyrodite solid electrolyte is known as solid electrolyte with high ionic conductivity of 10-2~10-4 S/cm-1 at room temperature. Moreover, the high ionic conductivity could be achieved by optimizing the mechanical milling and the annealing processes. However, there is a disadvantage in that electrochemical stability is so lower than Li3SI. Based on above studies, we have synthesize (100-x)Li3SI-xLi6PS5Cl(x=0, 10, 20 and 30) to increase the lithium ionic conductivity and electrochemical stability of them. Li3SI-Li6PS5Cl was mixed by milling process. We analyzed the crystal structures of them by XRD. The morphologies, contents, and distribution of the elements in the materials were analyzed by SEM and EDS. As the electrochemical analysis, electrochemical impedance spectroscopy with various temperatures was conducted to evaluate Li+ conductivity of the materials. Further, the electrochemical performance such as cyclic voltammetry, DC-cycling, and charge and discharge tests were conducted to make synergic effects.