Synthesis of an Environmentally Friendly Alkyl Carbonate Electrolyte Based on Glycerol for Lithium‐Ion Supercapacitor Operation at 100 °C

The increased number of electrical energy storage (EES) systems utilized in everyday products along with the demand for more reliable and safer products that provide high energy densities with faster response times over an extended range of temperatures are catalyzing advances across all areas of EES technology. Here, the preparation and performance evaluation at 100 °C of a high voltage lithium‐ion supercapacitor (LIC), comprised of activated carbon electrodes and a novel, environmentally friendly alkyl carbonate electrolyte based on glycerol containing 1 m LiTFSI, are reproted. Use of this ethoxy propylene carbonate electrolyte affords a high capacitance level with notable electrochemical performance including a specific capacitance of 162 F g⁻¹ at 1 mV s⁻¹, energy density of 14.2 Wh kg⁻¹ at 2 A g⁻¹, and power density of 7.5 kW kg⁻¹ at 10 A g⁻¹ at 100 °C. The performance of this LIC at 100 °C is compared to a conventional ethylene carbonate‐dimethyl carbonate LIC operating only at 25 °C as conventional organic and aqueous electrolytes do not allow safe operation at such an elevated temperature. Finally, insight into the increased Li⁺‐carbon intercalation mechanism is provided, observed with the system, leading to the enhanced electrochemical performance.