Cellulose Separators for Rechargeable Batteries with High Safety: Advantages, Strategies, and Perspectives

Abstract Most of the separators used in commercial rechargeable batteries are polypropylene and polyethylene, which have the characteristics of high mechanical strength and good chemical stability. Due to lower melting point, however, these separators may melt when the internal temperature of the cell rises. The direct contact of the positive and negative electrodes after the melting of separator will cause serious safety issues. Cellulose‐based separators have received increasing attention in rechargeable batteries because of advantages including high‐temperature resistance, high electrolyte affinity, renewability, and the ability to suppress the shuttle effect. Herein, the application of cellulose separators in rechargeable batteries is summarized in this review. An overview of the cellulose structure, elucidating both its advantages and the challenges as separators in rechargeable batteries is presented. The application of different types of cellulose as separators is also discussed. Furthermore, the failure mechanism of cellulose separators are explored in depth, which can provide guidance for designing safer and more reliable separators for rechargeable batteries. The modification strategies of cellulose separators are summarized in terms of the improved mechanical strength, heat resistance, good wettability, and other properties. Finally, promising perspectives are proposed for the future development of cellulose separators aimed at large‐scale applications.