Mitigating Interfacial Instability in Polymer Electrolyte-Based Solid-State Lithium Metal Batteries with 4 V Cathodes

Solid polymer electrolytes (SPEs) are attractive for next-generation energy storage, because they are more thermally stable compared to conventional liquid electrolytes and simpler for scalable manufacturing than ceramic electrolytes. However, there is a growing body of research suggesting that the interfacial instabilities between SPEs and other battery components (e.g., electrodes and electrolyte fillers) hinder their practical applications. This Perspective highlights the degradation mechanisms at these interfaces revealed by recent works, especially in lithium/4 V cathode systems with high energy density. We also review recent progresses on mitigating such instabilities and provide perspectives on how to further understand and address these issues, such as advanced characterizations and simulations, which deliver a valuable guide for future studies to accelerate the development of SPEs-based solid-state batteries.