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

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 SiO 2 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 SiO 2 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 LiFePO 4 /Li cell assembled with this electrolyte exhibits excellent cycling performance and high capacity at room and low temperatures.