Tailor-made dimethyl sulfoxide-based ternary deep eutectic solvents for high-performance supercapacitors

Deep eutectic solvents (DESs) are being recognized as possible alternatives to ionic liquids, providing similar advantageous properties at a reduced cost and less toxic. In this study, a novel ternary DES (TDES) system was created by combining lithium perchlorate, dimethyl sulfoxide, and ethylene glycol (LiClO₄/DMSO/EG). Upon successful synthesis of a TDES system, it was employed in the production of two distinct types of electrolytes. The first electrolyte was formulated by introducing acetonitrile, resulting in a high-performance liquid-type TDES (LiClO₄/DMSO/EG/ACN) electrolyte. The second electrolyte was created by integrating polyvinyl alcohol, generating a self-healing gel-type TDES (LiClO₄/DMSO/EG/PVA) electrolyte. The interactions of ternary DES components, flammability, anti-freezing ability, and ESW are properly investigated using various techniques. The symmetric SCs employed with the optimal ACN-containing TDES liquid electrolyte exhibited a specific capacitance of 36.4 F g⁻¹ with an energy density of 24.5 Wh kg⁻¹. The cyclic stability of 90.4 % was achieved by this device even at a higher current density of 5 A g⁻¹ over 20,000 cycles. This device is truly remarkable in its ability to operate at a temperature of −20°C and with an operating voltage of 2.2 V, surpassing the limitations of traditional aqueous electrolytes. The symmetric supercapacitors were crafted using a self-healing gel-type TDES electrolyte, and their performance was thoroughly assessed. The device achieved a specific capacitance of 33.7 F g⁻¹ and maintained an outstanding retention rate of 96.5% over 20,000 cycles, effectively demonstrating its remarkable self-healing capability. Therefore, it is highly recommended to use liquid and gel-type electrolytes based on the TDES for energy storage applications due to their multitude of significant benefits.