Abstract

Ionic liquid analogues (ILAs) are promising electrolytes for supercapacitors due to their low cost and considerable voltage (>2.0 V). However, the voltage is <1.1 V for water-adsorbed ILAs. Herein for the first time, an amphoteric imidazole (IMZ) additive is reported to address this concern by reconfiguring the solvent shell of ILAs. Addition of only 2 wt % IMZ increases the voltage from 1.1 to 2.2 V, with an increase in capacitance from 178 to 211 F g-1 and an increase in energy density from 6.8 to 32.6 Wh kg-1. In situ Raman reveals that the strong H-bonds formed by IMZ with completive ligands 1,3-propanediol and water induce a reversal of the polarity of the solvent shells, suppressing absorbed water electrochemical activity and thus increasing the voltage. This study solves the problem of low voltage for water-adsorbed ILAs and reduces the equipment cost of ILA-based supercapacitor assembly (e.g., assembly in air without a glovebox).

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