Challenges, strategies and prospects in interfaces between Li metal anode and polyether-based solid-state electrolytes

The high fluidity and flammability of conventional organic liquid electrolyte pose critical safety risk and lead to premature cell failure in commercial lithium-ion batteries. Solid polymer electrolytes, particularly polyether-based systems such as polyethylene oxide, are promising alternatives to liquid electrolytes, enabling safer, high-energy-density lithium metal batteries. However, polyether-based all-solid-state batteries (ASSBs), like liquid systems, face significant interfacial challenges - including chemical instability, poor contact, and slow ionic transport - that reduce overall performance. This review systematically surveys the evolution and categories of polyether-based electrolytes and provides a comprehensive analysis of interfacial phenomenon that undermines their application potential in ASSBs. We highlight recent advances in interfacial engineering strategies, including the optimization of polyether electrolyte, the design of in situ/ex situ solid state electrolyte interphases layers, and the development of composite Li metal anode. Finally, we outline promising directions and opportunities for addressing the interfacial bottlenecks to accelerate the practical realization of high-performance polyether-based solid state Li metal batteries.