Wide-potential, low-temperature supercapacitors enabled by dimethyl sulfoxide-based hybrid deep eutectic solvents

Abstract

Background

Deep eutectic solvents (DES) are rapidly gaining attraction as

electrolytes in electrochemical energy storage devices due to their low melting points, enhanced safety, cost-effectiveness, broad electrochemical stability window, high thermal stability, and biodegradability.

Methods

A novel hybrid deep eutectic solvent (DES) electrolyte was formulated by combining dimethyl sulfoxide (DMSO) with LiClO₄. It exhibits versatile tunability through the addition of water and acetonitrile as co-solvents.

Significant findings

This innovative hybrid DES demonstrates superior ionic conductivity, reduced viscosity, and enhanced flame retardancy, enabling the development of a symmetric activated carbon (AC) based supercapacitor (SC) with a stable potential window of 2.2 V. The device achieves an impressive specific capacitance of 46.6 F g⁻¹ at a current density of 1 A g⁻¹, with an energy density of 28.6 Wh kg⁻¹ at a power density of 1020 W kg⁻¹. Additionally, it shows outstanding cyclic stability, retaining 92 % of its capacitance after 20,000 cycles at 5 A g⁻¹, and 86 % retention after a 120-hour floating test. Notably, due to the good anti-freezing capability of the hybrid DES electrolyte, the device maintains high performance even at temperatures as low as -20 °C.