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.