Supercapacitive properties of activated carbon electrode in electrolyte solution with a lithium-modified silica nanosalt

•Lithium-modified silica nanosalt (Li202) is used as a gel-forming additive in 1.5 M TEABF4/acetonitrile for a supercapacitor.•The electrochemical stability of the electrolyte is improved over 4.0 V.•The Li202 can be considered as a promising electrolyte additive for supercapacitors.

In this work, lithium-modified silica nanosalt (Li202) is solution-synthesized and used as a gel-forming additive in 1.5 M tetraethylammonium tetrafluoroborate (TEABF4)/acetonitrile (ACN) electrolyte solution for the supercapacitor with activated carbon electrode. The electrochemical properties of the supercapacitor adopting the Li202 (5 wt.%) are investigated using linear sweep voltammetry, cyclic voltammetry, and complex impedance spectroscopy. By the addition of the Li202, the electrochemical stability of the electrolyte is improved over 4.0 V (corresponding to the current density below 0.6 mA cm−2) and higher specific capacitances at the scan rates of 10–500 mV s−1 are obtained. Thus, the Li202 can be considered as a promising electrolyte additive to enhance the supercapacitive properties of activated carbon electrode.