Heat‐Resistant, Robust, and Hydrophilic Separators Based on Regenerated Cellulose for Advanced Supercapacitors

Abstract Separators in supercapacitors (SCs) typically suffer from defects of low mechanical property, limited ion transport, and electrolyte wettability, and poor thermal stability, impeding the development of SCs. Herein, high‐performance regenerated cellulose (RC) based separators are designed that are fabricated by effective hydrolytic etching of inorganic CaCO 3 nanoparticles from a filled RC membrane. The as‐prepared RC separator displays excellent comprehensive performances such as higher tensile strength (75.83 MPa) and thermal stability (200 °C), which is superior to commercial polypropylene‐based separator (Celgard 2500) and sufficient to maintain their structural integrity even at temperatures in excess of 200 °C. Benefiting from its hydrophilicity, high porosity, and outstanding electrolyte uptake rate (208.5%), the RC separator exhibits rapid transport and permeability of ions, which is 2.5× higher than that of the commercial nonwoven polypropylene separator (NKK ‐MPF30AC‐100) validated by electrochemical tests in the 1.0 m Na 2 SO 4 electrolyte. Results show that porous RC separator with unique advantages of superior electrolyte wettability, mechanical robustness, and high thermal stability, is a promising separator for SCs with high‐performance and safety.