Sustainability serves as a predominant obstacle for advanced energy storage. Herein, we proposed biomass-based separator materials, with favorable flame retardancy, cost-effectiveness, potential sustainability, and excellent electrochemical performance. Specifically, the engineered hydroxyapatite (HAP) molecule incorporates solvent-friendly groups to establish enhanced ion transport channels. The resulting CF@HAP separator induces an orderly decomposition of the electrolyte, which could optimize the electrode/electrolyte interface layer and prevent dendrite growth, making the durable cycling process, let alone its great mechanical properties and potential versatility. The in-depth study clarifies its complicated interfacial chemistry, flame retardancy, and thermal control mechanisms, thus achieving a thermally closed pore behavior during the temperature regulation process. Furthermore, the CF@HAP separator achieves complete degradation in the soil naturally within 30 days. As-designed biomass-based separators could comprehensively improve electrochemical performance toward higher levels of reactivity, stability, and postlife self-degradability, further underscoring the promising prospects for sustainable energy storage systems.