Composite Polymer Solid Electrolytes for All‐Solid‐State Sodium Batteries

Abstract Sodium‐ion batteries (SIBs) are emerging as a promising alternative to lithium‐ion batteries, primarily due to their plentiful raw materials and cost‐effectiveness. However, the use of traditional organic liquid electrolytes in sodium battery applications presents significant safety risks, prompting the investigation of solid electrolytes as a more viable solution. Despite their advantages, single solid electrolytes encounter challenges, including low conductivity of sodium ions at room temperature and incompatibility with electrode materials. To overcome these limitations, the researchers develop composite polymer solid electrolytes (CPSEs), which merge the strengths of high ionic conductivity of inorganic solid electrolytes and the flexibility of polymer solid electrolytes. CPSEs are usually composed of inorganic materials dispersed in the polymer matrix. The final performance of CPSEs can be further improved by optimizing the particle size, relative content, and form of inorganic fillers. CPSEs show great advantages in improving ionic conductivity and interface compatibility, making them an important direction for future solid‐state sodium battery research. Therefore, this paper summarizes recent advancements in composite solid electrolytes, discusses the impact of their preparation processes on performance, and outlines potential future developments in sodium‐ion solid‐state batteries.