Nanoporous and lyophilic battery separator from regenerated eggshell membrane with effective suppression of dendritic lithium growth

Lithium metal-based batteries are attractive energy storage systems owing to the high theoretical capacity of lithium metal anode and the known lowest potential among existing anodes. However, lithium anodes usually suffer from severe growth of lithium dendrites, a main reason of safety concern. Engineering the structure of separators could be an effective solution for resolving this issue. Herein, we demonstrate that eggshell membrane (ESM) extracted from waste eggshell is a promising candidate as high-performance separator. Furthermore, we have developed a biomimetic and economic strategy to produce large-area and flat regenerated ESM (RESM) to overcome the size and shape limits of raw ESM. The ESM and RESM are highly lyophilic to electrolytes; their well-distributed pores and high electrolyte uptake allow fast ion-diffusion; and their high mechanical and thermal stability ensure the safety and cyclability of batteries. Most impressively, the nanoporous structure and the negatively-charged surface of ESM and RESM separators can effectively suppress the formation of lithium dendrites, even after long-term cycling under high rate. Lithium-ion batteries, lithium-sulfur batteries, and sodium-ion batteries using RESM separators all show boosted rate capability and cycling retention, outperforming commercial separators on almost all fronts. Even at a high temperature (120 °C), lithium-ion batteries with RESM separators can still operate normally. Our findings indicate the nanoporous RESM film can meet most if not all requirements of an ideal separator for metal ion batteries.