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

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.