Robust and High-Wettability Cellulose Separators with Molecule-Reassembled Nano-Cracked Structures for High-Performance Supercapacitors.

Separators in supercapacitors (SCs) frequently suffer from high resistance and the risk of short circuits due to inadequate electrolyte wettability, depressed mechanical properties, and insufficient thermal stability. Here, we develop a high-performance regenerated cellulose separator with nano-cracked structures for SCs via a binary solvent of superbase-derived ionic liquid and dimethylsulfoxide (DMSO). The unique nano-cracks with an average width of 7.45 nm arise from the acceleration of cellulose molecular reassembly by DMSO-regulated hydrogen bonding, which endows the separator with high porosity (70.2%) and excellent electrolyte retention (329%). The outstanding thermal stability (273 °C) and mechanical strength (70 MPa) enable the separator to maintain its structural integrity under high temperatures and external forces. With these benefits, the SC utilizing the cellulose separator enables a high specific capacitance of 93.6 F g at 1.0 A g and a remarkable capacitance retention of 99.5% after 10,000 cycles compared with the commercial NKK-MPF30AC and NKK-TF4030. The robust and high-wettability cellulose separator holds promise as a superior alternative to commercial separators for advanced SCs with enhanced performance and improved safety.