1,3-Dioxolane-Based Electrolytes for Environmentally Friendly High-Voltage Supercapacitors

Supercapacitor (SC) is an important energy storage device with high power density and long cycle life. The current commonly used acetonitrile-based electrolytes often have some problems such as serious corrosion and strong toxicity. Herein, 1,3-dioxolane (DOL) is used as solvent and lithium bis((trifluoromethyl)sulfonyl)azanide (LiTFSI) as lithium salt to form a nontoxic, corrosion-free electrolyte with high ionic conductivity for SCs. The ionic conductivity of the prepared DOL-LiTFSI electrolyte reaches 3.26 × 10⁻³ S cm⁻¹. Further, the performance of the electrolyte is improved by adding 1,2-dimethoxyethane (DME). The addition of DME decreases the viscosity of the electrolyte and improves the ionic conductivity to 1.73 × 10⁻² S cm⁻¹. The DOL/DME composite electrolyte endows the activated carbon (AC) SC with higher cycle performance with a capacity retention rate of 82% after 15 000 cycles at a current density of 2 A g⁻¹. In addition, by equipping a wound cylindrical SC, the capacity retention rate is 81.4% after 11 000 cycles at a current density of 10 A g⁻¹. Notably, the electrolyte enables SCs to operate down to −30 °C and still provides a high specific capacitance and a long charge/discharge cycling. This environmentally friendly DOL-based electrolyte is expected to promote the green development of high-voltage SCs.