Designing mechanically reinforced filler network for thin and robust composite polymer electrolyte

Developing novel solid electrolytes with high performance is of great significance for the practical application of lithium metal batteries. Among all the developed solid electrolytes, composite polymer electrolytes (CPEs) have been deemed one of the most viable candidates because of their comprehensive performance. Nevertheless, the random distribution of inorganic filler nanoparticles may cause discontinuities in ion transport and low mechanical strength. Therefore, the introduction of a filler network with fast ion conduction is an effective strategy to provide continuous ion transport and mechanical support. The mechanically reinforced filler network enhances the mechanical strength of the CPE, providing opportunities to reduce the thickness of CPE. In this review, the progress of mechanically reinforced filler structures in CPE is summarized, along with the introduction of mechanically reinforced filler networks with random and ordered structures and electrode‐integrated CPE with mechanically reinforced filler networks. Finally, challenges and possible future research directions for mechanically reinforced filler network CPE are presented.