Low-salt organohydrogel electrolytes for wide-potential-window flexible all-solid-state supercapacitors

Flexible supercapacitors have received increasing attention due to their high power density, long cycle life and excellent safety, however, their limited energy density restrains their practical applications. Here, a designed organohydrogel electrolyte strategy boosted the electrochemical potential window (ESW) for flexible all-solid supercapacitor was demonstrated, by which a record-high ESW of 5 V is achieved, accompanied by improved cyclic stability and wider temperature adaptability. Hydrogen-bond of water to DMSO was found to be competitive with cationic hydration, and a wide ESW was achieved at lower salt and DMSO concentrations. DMSO-H2O/alginate/PAAm hydrogel electrolytes were prepared by simple solvent exchange, and it was found that the synergistic interactions between DMSO, water and hydrogel significantly reduced water activity in the hydrogel and realized the high ESW. Moreover, Dimethyl sulfoxide forms abundant hydrogen bonds with water and the hydrogel skeleton, which significantly improves the mechanical properties, freezing resistance, and temperature adaptability of the hydrogel electrolyte. The flexible all-solid-state supercapacitor assembled based on DMSO-H2O/alginate/PAAm hydrogel electrolyte and interdigital electrodes exhibits 2.4 V ESW, stability under different folding angles, adaptability to different temperatures ranging from −20 to 70 °C, and integration performance. The device demonstrates excellent cycling stability and retains 98.66% of capacitance after 10,000 cycles, suggesting that it has the potential to meet the requirements of flexible electronics.