Research Progress on Composite Solid Polymer Electrolytes for All-Solid-State Batteries

Abstract

The growing demand for high-energy-density, long-life and safe energy-storage systems has accelerated the development of all-solid-state batteries (ASSBs), particularly for electric vehicles and grid-scale storage. Conventional liquid electrolytes suffer from flammability, leakage and thermal runaway risks and are increasingly unable to meet the requirements of next-generation batteries. Composite solid polymer electrolytes (CSPEs), which combine polymer matrices with inorganic fillers, offer a promising alternative. Compared with inorganic solid electrolytes (ISEs) and pure solid polymer electrolytes (SPEs), CSPEs provide a more balanced combination of flexibility, processability, ionic conductivity, mechanical robustness and interfacial compatibility. This review systematically summarizes the fundamental components including polymer matrices, inorganic fillers and lithium salts and ion-conduction mechanisms. Although recent studies have elucidated various ion-conduction mechanisms within CSPEs, these mechanisms remain to be further explored and understood at a deeper level. Various design and modification strategies are discussed in detail, with particular attention given to the interfacial issues between CSPEs and electrodes as well as the corresponding optimization strategies. Finally, the remaining challenges are also discussed, providing insights for future development of high-performance CSPEs for practical ASSB applications.