Molecular Engineering of Polymer Electrolytes for Lithium and Sodium Metal Batteries

Alkali metal batteries exhibit excellent energy storage potential due to the ultra-high specific capacity and low redox potential of lithium and sodium metal anodes. However, in the process of electroplating and stripping of lithium and sodium metals, the coupling evolution of ion transport, solvation structure, reaction kinetics, and mechanical stress leads to interface instability, which hinders the practical application of alkali metal batteries. Polymer electrolyte provides a unique opportunity to solve these challenges by regulating solvation thermodynamics, ion migration path, interfacial reaction behavior and viscoelastic relaxation through programmable molecular structure. This paper elucidates the fundamental origins of metal anode instability and establishes a molecular engineering framework based on backbone flexibility and polarity, side-chain coordination chemistry, and network topology. This framework provides a unified perspective for understanding and regulating the evolution of metal anodes and ultimately constructing stable solid-state lithium and sodium metal batteries.