LICs) are being investigated as LICs possess favorable performance features of the two former technologies. [1] Significant progress has been made for room temperature LICs during the last several years, however, operation at elevated temperatures (40-150 °C) remains a major challenge and a continuing interest.The most common LICs systems contain well-studied electrode materials such as Li foil, lithiated metal oxides, or carbonaceous materials (graphite, activated carbon, and graphene) and organic solvent electrolytes such as ethylene carbonate (EC) or diethyl carbonate (DEC). Considering the diversity of the active components and electrolyte compositions used in both LIB and ECs systems, a variety of material combinations are available for fabrication of a LIC. Of particular interest to us, are the LICs composed of nonlithiated electrode materials with one of the above mentioned organic solvents containing a Li-salt, as a source of Li-ions, to enhance the electrolyte transport properties. [1f,2] Such LICs exhibit enhanced electrochemical performance.With respect to electrical energy storage device performance and stability at elevated temperatures, the low flash and boiling points of the electrolytes are key limitations of current devices. In the best-case scenario, the device stops working, and in the worst-case scenario, thermal runaway reactions afford a catastrophic failure with a resultant explosion. To address this unmet need, nonflammable and nonvolatile electrolytes based on room temperature ionic liquids (RTILs), [2h,3] ionic liquidcarbonate solvent electrolytes, [4] a composite of Bentonite clay and RTIL, [5] and solid polymer electrolytes [6] are being explored to improve the thermal stability of the devices. However, sacrificed electrochemical performance exists such as a decrease in specific capacitance, rate capability, and/or stability. As an alternative to the above electrolyte formulations for high temperature use, while being cognizant of the design requirement to use greener or more environmentally friendly (biodegradation, renewable, or recyclability) material, we are investigating glycerol carbonate-based electrolytes. Given that carbonate-based electrolytes such as ethylene carbonate dissolve high molar concentrations of Li-salts and perform especially well at RT in LIBs, we reasoned that a small molecule carbonate electrolyte based 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 ...