Highly conducting, extremely durable, phosphorylated cellulose-based ionogels for renewable flexible supercapacitors

A renewable cellulose-based dual network ionogel electrolyte is synthesized by phosphorylating and dissolving a microcrystalline cellulose network in a tailor-made 1,3-dimethylimidazolium methyl phosphite [DMIM][MeO(H)PO₃] ionic liquid mixture, with subsequent polymerization of the 2-hydroxyethyl methacrylate monomer in the presence of a cellulose network. The as-synthesized ionogel electrolytes exhibit high ionic conductivity (2.6–22.4 mS cm⁻¹) over a wide temperature range (30–120 °C), with a maximum toughness of 1.46 MJ m⁻³ at 30 °C. A renewable flexible supercapacitor is fabricated by sandwiching the cellulose-based ionogel electrolyte between two activated carbon electrodes, delivering high specific capacitance and rate capability of 174 F g⁻¹ and 88% at 120 °C at a cell voltage of 2.5 V. These remarkable capacitive features at elevated temperature are associated with fast dynamics, facilitated by thermally activated ion transport, as demonstrated by the Vogel-Tammann-Fulcher and Nyquist plots.