Beyond the conductivity-stability trade-off: A comprehensive review of polymer solid-state electrolytes

The commercialization of polymer solid-state electrolytes (PSEs) is hindered by the persistent trade-off between ionic conductivity and mechanical stability, both of which are essential for high-performance energy storage systems. This review examines this challenge by analyzing the underlying mechanisms governing ion transport and mechanical degradation, while discussing targeted strategies to mitigate these limitations. Recent advances are summarized, spanning molecular-level modifications, such as dynamic crosslinking and heteroatom doping, as well as multiscale design approaches, including inorganic-organic composite architectures and engineered ion-conduction pathways. Collectively, these innovations have demonstrated the potential to achieve room-temperature ionic conductivities exceeding 1 mS·cm^-1 while maintaining sufficient mechanical robustness to suppress lithium dendrite growth. Key strategies for enhancing ionic conductivity include molecular structure regulation to promote polymer segmental motion, optimization of ion transport pathways, and the design of composite electrolytes incorporating ionophilic fillers to establish continuous conduction networks. In parallel, engineering stable electrode-electrolyte interfaces is highlighted as a critical approach to improving overall electrochemical performance and long-term stability. Furthermore, emerging opportunities such as machine-learning-assisted material discovery and scalable manufacturing technologies are discussed as promising routes toward the practical implementation of PSEs. By integrating these advances, PSEs are expected to play a pivotal role in next-generation safe, flexible, and high-energy-density batteries. This review provides a comprehensive roadmap for addressing the conductivity-stability trade-off and accelerating the commercialization of advanced PSEs.