Uniform and High Li⁺ Transporting Polymer Electrolytes for Stable and Long-Cycle-Life Lithium Metal Batteries:...

Solid polymer electrolytes (SPEs)-based lithium metal batteries (LMBs) are at the forefront of next-generation energy storage, offering remarkable energy density and safety. Despite their high potential, the practical use and commercialization of LMBs encounter two significant challenges: inadequate interfacial stability and low critical current density (CCD). One promising approach to tackle the problems is by designing an advanced SPE that simultaneously ensures uniform and high lithium-ion transport. Achieving uniform ion transport is key to minimizing concentration gradients that lead to dendrite formation, while selective lithium-ion conduction prevents anion accumulation, thereby improving interfacial stability. This review comprehensively examines recent progress in the development of uniform lithium-ion transporting polymer electrolytes (ULPEs) and high lithium-ion conducting polymer electrolytes (HLPEs). By combining the structural uniformity of ULPEs with the enhanced conductivity of HLPEs, uniform-high lithium-ion transporting polymer electrolytes (UHLPEs) have emerged as a promising class of materials capable of simultaneously ensuring high interfacial stability and supporting elevated CCD in practical LMBs. Key molecular design strategies, along with insights into ionic conductivity, electrochemical performance, and interfacial behavior, are systematically reviewed to provide a comprehensive understanding of the way to achieve high CCD, enhanced safety, and extend cycle life.