Exceptionally Stable, Non-Aqueous, Sodium-Based Electrolytes for High Energy Electrochemical Capacitors

Current-generation, acetonitrile-based electrolytes for supercapacitors have a practical voltage window around only 2.7 V. Extending the electrochemical window can significantly increase energy density, since the energy stored in a capacitor increases quadratically with voltage. We report on electrolytes consisting of sodium salts in linear polyether (glyme) solvents which clearly show a 4 V electrochemical window. Electrolyte conductivities range between 1-10 mS/cm, which are comparable to ionic liquids or propylene carbonate-based electrolytes.  Importantly, all salts and solvents are commercially available. This family of electrolytes has the potential to double the energy density of supercapacitors, while remaining as cost-effective and scalable as today’s commercial electrolytes.

Acknowledgement

This work is supported by Laboratory Directed Research and Development (LDRD) program of Oak Ridge National Laboratory under the seed project S12-056.