Wide Electrochemical Stability Window of NaClO4 Water-in-Salt Electrolyte Elevates the Supercapacitive Performance of Poly(3,4-ethylenedioxythiophene)

Water-in-salt electrolytes (WiSEs) have emerged as the primary preference in the domain of aqueous-based supercapacitors, thanks to their wide electrochemical stability window (ESW > 1.23 V). Here, we have chemically synthesized a unique lettuce coral-like structure of tosylate doped-poly(3,4-ethylenedioxythiophene) (PEDOT-tos) and tested it for supercapacitor application in a 17 molal (m) NaClO ₄ WiSE, achieving an ESW of 1.9 V. The energy and power densities (E _d and P _d) of our PEDOT-tos supercapacitor are as high as 14 Wh kg ^-1 and 7210 W kg ^-1, respectively, with over 80 % capacitance retention after 10,000 continuous Galvanostatic charge-discharge cycles. The NaClO ₄ WiSE increases the E _d and P _d of PEDOT by several folds compared to traditional H ₂SO ₄ electrolyte. This work encourages the exploration of a suitable combination of a PEDOT-based composite material and WiSE for high-performance supercapacitors.