A Si-doped flexible self-supporting comb-like polyethylene glycol copolymer (Si-PEG) film as a polymer electrolyte for an all solid-state lithium-ion battery

Herein, a self-supporting comb-like Si-PEG copolymer with flexible Si-O-C bonds in the main chain and pending short PEG chains as the side chain was synthesized to improve the low temperature performance and overcome the quandary between good mechanical and electrochemical properties of the polymer electrolyte in lithium-ion batteries. The tensile strength of Si-PEG polymer electrolytes (SPH15) is 0.8 MPa at 30 °C, which is high enough to inhibit the growth of lithium dendrites. The ion conductivities of Si-PEG (SPH15) are 1.2 × 10^-4 S cm^-1 at 30 °C and 3.2 × 10^-5 S cm^-1 at 10 °C, which are one order of magnitude higher than those for PEG-based copolymer electrolytes without Si doping. The assembled LiFePO₄/SPH15/Li half batteries can deliver the specific capacities of 84 mA h g^-1 at 10 °C and present 75% capacity retention after 500 charge-discharge cycles at 0.5C.