Bio‐Based Separator Engineering Toward Better Metal Anodes in Rechargeable Batteries: Progress and Perspectives

Abstract The rapidly growing global demand for intermittent renewable energy sources, such as solar and wind power, has driven an urgent requirement for next‐generation high‐energy‐density metal‐based rechargeable batteries. Nevertheless, the practical application of these advanced battery systems has been hindered by the metal anode instability, manifesting as uncontrolled dendrite growth and deleterious side reactions. Bio‐based separators derived from biopolymer materials provide tunable porosity, mechanical strength, and surface functionality, rendering them promising candidates for addressing metal anode issues. In this paper, bio‐based separators are systematically categorized, analyze their structure characteristics and material properties, and elucidate their unique advantages as sustainable separator materials for advanced metal‐based batteries. On this basis, the separator fabrication methods are summarized, and examine their applications in various battery systems. Subsequently, the mechanistic roles of bio‐based separators in overcoming anode stabilization challenges are critically analyzed. Finally, the key research challenges and future development directions for bio‐based separators are proposed, aiming to provide valuable insights for both scholars and newcomers in the field of separator research.