Research On Lithium-sulfur Batteries Inorganic Solid Electrolytes

All-solid-state lithium-sulfur batteries have attracted wide attention because they can avoid the dissolution of polysulfides,and have high safety performance.However,the ionic conductivity of solid electrolytes is lower than that of liquid electrolytes.Exploring a solid electrolyte material with high ionic conductivity is the main goal at present.The ionic conductivity of Li₂S-P₂S₅ glass-ceramics in inorganic solid electrolytes is higher at room temperature.In this paper,the Li₂S-P₂S₅ system was doped to improve its room temperature ionic conductivity.Inthispaper,75Li₂S·25P₂S₅,99（0.75Li₂S·0.25P₂S₅）·1LiPF₆,98（0.75Li₂S·0.25P₂S₅）·2LiPF₆,97（0.75Li₂S·0.25P₂S₅）·3LiPF₆glassceramicsolids Electrolyte material were prepared by mechanical milling followed by low temperature heat treatment.The relationship between LiPF₆ doping content and the milling time and the effect of different LiPF₆ doping content on crystallization temperature of glassy materials were investigated by XRD and DSC analysis.According to XRD and Raman spectrogramanalysis,75Li₂S·25P₂S₅,99（0.75Li₂S·0.25P₂S₅）·1LiPF₆,98（0.75Li₂S·0.25P₂S₅）·2LiPF₆,97（0.75Li₂S·0.25P₂S₅）·3LiPF₆ glass ceramic samples containhighly ionically conductive phase thio-LISICON III similar phase,and98（0.75Li₂S·0.25P₂S₅）·2LiPF₆,97（0.75Li₂S·0.25P₂S₅）·3LiPF₆ glass ceramic samples also precipitate parts of the low-ionic conductive crystal phase Li₃PS₄,Li₄P₂S₆,and a few impurity phases.According to SEM,the doping of LiPF₆ makes the crystal grains connect tightly.The room temperature ionic conductivity of 99（0.75Li₂S·0.25P₂S₅）·1LiPF₆ is 1.45×10^-6S/cm,and the activation energy is 0.205eV.S/C/99（0.75Li₂S·0.25P₂S₅）·1LiPF₆ compositecathodematerialpreparedby mechanical milling method improved sulfur utilization due to doping of LiPF₆.At a current density of 0.38 mA/cm²,the initial discharge specific capacity is 475 mAh/g,and after 50 cycles,the discharge capacity is 310 mAh/g,and the capacity retention rate is 65%.