Tuning Thin‐Film Electrolyte for Lithium Battery by Grafting Cyclic Carbonate and Combed Poly(ethylene oxide) on Polysiloxane

A tunable polysiloxane thin‐film electrolyte for all‐solid‐state lithium‐ion batteries was developed. The polysiloxane was synthesized by hydrosilylation of polymethylhydrosiloxane with cyclic [(allyloxy)methyl]ethylene ester carbonic acid and vinyl tris(2‐methoxyethoxy)silane. 1 H NMR spectroscopy and gel‐permeation chromatography demonstrated that the bifunctional groups of the cyclic propylene carbonate (PC) and combed poly(ethylene oxide) (PEO) were well grafted on the polysiloxane. At PC/PEO=6:4, the polysiloxane‐based electrolyte had an ionic conductivity of 1.55×10 −4 and 1.50×10 −3  S cm −1 at 25 and 100 °C, respectively. The LiFePO 4 /Li batteries fabricated with the thin‐film electrolyte presented excellent cycling performance in the temperature range from 25 to 100 °C with an initial discharge capacity at a rate of 1 C of 88.2 and 140 mA h g −1 at 25 and 100 °C, respectively.