Highly Active Rare Earth Sulfur Oxides Used for Membrane Modification of Lithium Sulfur Batteries

Abstract

How to solve the shuttle effect of soluble lithium polysulfide (LiPS) and the reversible conversion of solid LixS is an important challenge to realize the practical application of lithium sulfide battery (LSB), and the selection, preparation and design of adsorption-conversion materials have always been an important topic in the research of LSB. In this work, based on the adsorption sites of LiPS and the transport path of lithium ion, we propose that metal sulfur oxides containing both metal-O and metal-S bonds in their molecular structure may be ideal adsorption-conversion materials. Therefore, La2O2S as an air stable metal sulfur oxides is selected as the target material. With La-BTC nanorod as the precursor, by adjusting the heat treatment temperature and the use of sulfur source, we achieved the preparation of La2O2S-C composite under relative low heat treatment conditions. Through DFT theoretical calculation, XPS and electrochemical test of button simulation batteries, we find that compared with La2O3  and La2S3 , La2O2S has moderate adsorption energy and the largest Gibbs free energy, which is more suitable for the adsorption-conversion material of lithium sulfur battery. The button cell with La2O2S-C/PP retained a capacity of 664 mAh g -1  after 300 cycles at the discharge current of 1C.

Keywords: rare-earth oxysulfide, Adsorption energy, free energy, lithium polysulfide, Li-S batteries