The Role of Mechanical Compliance in Polymer Solid Electrolytes for Solid-State Batteries

Solid-state batteries are widely regarded as a promising technology for next-generation energy storage, particularly for electric vehicles requiring improved safety and higher energy density. However, their practical performance is often limited by interfacial instability and restricted ionic transport within solid-state systems. Recent studies suggest that these limitations are closely related to mechanical effects occurring at electrode-electrolyte interfaces. This paper analyses how mechanical compliance will influence the electrochemical performance of polymer solid electrolytes. It firstly discusses the interfacial and transport challenges in solid-state batteries and then evaluates the mechanical-electrochemical coupling mechanism. It mainly focuses on the stress generated at the solid interface, stress-induced electrolyte failure, and the influence of mechanical deformation on ionic transport. Meanwhile, this article discusses the potential of polymer and quasi-solid-state electrolyte systems as a solution to improve the interface’s contact. These findings ultimately demonstrate that refining the mechanical compliance of electrolytes is the key requirement to push the practical application of solid-state batteries.