Electroactivity of 3D conducting polymers in water-in-salt electrolyte and their electrochemical capacitor performance

Abstract Electrochemical capacitors show high power density but suffer from low energy density. The use of pseudocapacitive material can increase the cell capacitance and therefore increase the device energy density. In this work, we show that using microtubular conducting polymers, as polypyrrole (PPy) and poly(3,4-ethylenedioxythiophene) (PEDOT), alongside activated carbon (AC) in asymmetrical devices, and highly concentrated aqueous electrolyte (or water-in-salt electrolyte, WiSE), is possible to maintain the polymers electroactivity at the negative polarization and take advantage of the electrolyte electrochemical stability. The polymers electrochemical behaviours were compared in WiSE and aqueous acidic solution, which hinted that the polymers charge compensation are different in the different electrolytes. PPy-AC and PEDOT-AC cells can reach 2.6 and 2.8 V, respectively, and electrodes mass balance greatly depends on the polymers open circuit potential before and after cycling