Cotton Fiber/PVA-Based Neutral Hydrogel with Al3+ as an Electrolyte Additive for High-Performance Supercapacitors

Electrolyte additives have been widely studied in the improvement of stability of aqueous electrolytes. Here, we report a crosslinking cotton fiber-/PVA-based membrane (CPM) with an excellent porosity of 73.82% and an ultrahigh liquid electrolyte uptake of 900 wt %, prepared by the solution casting method. Li2SO4 as an electrolyte salt and various concentrations of Al3+ as additives were used for fabricating the gel polymer electrolyte (GPE). On adding Al3+ into the Li2SO4 electrolyte, dissociative water and bound water in Li+ solvation interact with Al3+; this affects water molecule activity and reduces Li+ solvation. While the presence of Al3+ electrolyte exhibits better electrochemical stability under a high operating voltage of 1.6 V, the highest specific capacitance of a supercapacitor (SC) is 136 F g–1 at 1.0 A g–1, and it has 91% initial capacitance retention after 20 000 charge–discharge cycles, which is higher than that of the Li2SO4 electrolyte. This work provides a path for designing a high-output-voltage aqueous supercapacitor via electrolytes and the membrane strategy.