Recent Progress of Polymer Electrolytes for Solid-State Lithium Batteries

The critical challenges for lithium-ion batteries today are how to improve the energy densities and solve the safety issues, which can be addressed through the construction of solid-state lithium metal batteries with solid polymer electrolytes (SPEs). Significant efforts have been devoted to the design and synthesis of SPEs, in which their electrochemical windows and corresponding compatibilities with both electrodes are crucial, particularly when taking high-voltage transition metal oxides as cathodes. In this review, the SPEs with different electrochemical windows are summarized and categorized, including (i) anode stable SPEs with good lithium metal compatibilities, (ii) cathode stable SPEs with good oxidation resistances, (iii) multilayer SPEs simultaneously withstanding reduction of a lithium anode and oxidation at high voltage. The impacts of polymer molecular structures and compositions on the SPE properties and performance are discussed. The development of high-performance SPEs that can stabilize or form stable interfacial passivation layers with both cathodes and anodes simultaneously is the desired candidate of future applications.