Novel insight into neutral medium as electrolyte for high-voltage supercapacitors

TLDR

Neutral aqueous sulfate electrolytes (Li, Na, K) at 0.1–2.5 M are inexpensive, non‑corrosive, environmentally friendly, and enable easier, cheaper capacitor assembly with diverse current collectors. The study examines how ion physicochemical properties—solvation, diffusion, and mobility—affect supercapacitor electrochemical behavior. Electrochemical tests of 1 M Li₂SO₄ show stable operation up to 2.2 V with no significant capacitance fade over 15 000 cycles.

Abstract

This paper is focused on neutral aqueous medium, i.e.lithium, sodium and potassium sulfate solutions in a wide range of concentrations (0.1–2.5 mol L−1) as promising electrolytes for electrochemical capacitors because they are cheap, non-corrosive and allow applying diverse current collectors. These properties make the capacitor assembling process much easier and cheaper. Additionally, such electrolytes are electrochemically stable and environmentally friendly. Electrochemical investigations carried out especially for 1 mol L−1Li2SO4 aqueous solution confirmed the possibility of efficient capacitor work in a wider voltage range, i.e. even at 2.2 V without any significant capacitance fade during 15 000 cycles. The physicochemical properties of ions (i.e. solvation, diffusion or mobility) and their influence on the capacitor electrochemical behaviour are considered.