Design of sulfur-containing additive composite electrolyte for enhancing the thermal stability and electrochemical performance of LiFePO4/Graphite lithium-ion batteries

To enhance the interfacial stability and electrochemical performance of LiFePO₄/graphite lithium-ion batteries, this study aims to design a sulfur-containing composite electrolyte by selecting four functional additives: vinylene carbonate (VC), 1,3-propane sultone (PS), methyl methane disulfonate (MMDS), and ethylene sulfate (DTD). The film-forming characteristics of these additives are evaluated using DFT density functional theory calculations. Additionally, the SEI film formed on the graphite anode surface is characterized using SEM and FTIR techniques. The results indicate that MMDS and DTD effectively reduce the thermal decomposition temperature of the electrolyte, shifting the endothermic peak to lower temperatures, thereby enhancing the rate performance of the battery and improving its performance in high-temperature environments. SEM and FTIR analyses further confirm that additives such as VC, MMDS, DTD, and PS facilitate the reduction reaction on the graphite anode surface, leading to the formation of a stable SEI film that effectively inhibits further reactions between the electrolyte and the anode material. Through the synergistic effect of these multiple additives in the composite electrolyte, not only is the performance of lithium-ion batteries improved, but their intrinsic safety is also enhanced, providing an effective solution to prevent thermal runaway.