Ultraviolet-cured polyethylene oxide-based composite electrolyte enabling stable cycling of lithium battery at low temperature

Abstract The room and low-temperature performances of solid-state lithium batteries are crucial to expand their practical application. Polyethylene oxide (PEO) has received great attention as the most representative polymer electrolyte matrix. However, most PEO-based solid-state batteries need to operate at high temperature due to low room temperature ionic conductivity. Improving the ionic conductivity by adding plasticizers or reducing the crystallinity of PEO often compromises its mechanical strength. Here, an amorphous PEO-based composite solid-state electrolyte is obtained by ultraviolet (UV) polymerizing PEO and methacryloyloxypropyltrimethoxy silane (KH570)-modified SiO2 which demonstrates both satisfactory mechanical performance and high ionic conductivity at room (3.37 × 10−4 S cm−1) and low temperatures (1.73 × 10−4 S cm−1 at 0 °C). In this electrolyte, the crystallinity of PEO is reduced through cross-linking, and therefore provides a fast Li+ ions transfer area. Moreover, the KH570-modified SiO2 inorganic particles promote the dissociation of lithium salts by Lewis acid centers to increase the ionic conductivity. Importantly, this kind of cross-linking networks endows the final electrolyte much higher mechanical strength than the pure PEO polymer electrolyte or PEO-inorganic filler blended systems. The solid-state LiFePO4/Li cell assembled with this electrolyte exhibits excellent cycling performance and high capacity at room and low temperatures.