Low-temperature performance of electrochemical capacitors using acetonitrile/methyl formate electrolytes and activated carbon fabric electrodes. Issue 2 (28th January 2020)

• Record Type: Journal Article
• Authors: Brandon, Erik J.; Smart, Marshall C.; West, William C.
• Is Part Of: Journal of materials research. Volume 35:Issue 2(2020)
• Page Start: 113
• Page End: 121
• Publication Date: 2020-01-28
• Subjects: energy storage, -- calorimetry, -- carbon; Materials -- Research -- Periodicals; 620.1105
• DOI: 10.1557/jmr.2019.396
• Languages: English
• ISSNs: 0884-2914

Abstract

Abstract: Abstract : Electrochemical capacitors featuring a modified acetonitrile (AN) electrolyte and a binder-free, activated carbon fabric electrode material were assembled and tested at <−40 °C. The melting point of the electrolyte was depressed relative to the standard pure AN solvent through the use of a methyl formate cosolvent, to enable operation at temperatures lower than the rated limit of typical commercial cells (−40 °C). Based on earlier electrolyte formulation studies, a 1:1 ratio of methyl formate to AN (by volume) was selected, to maximize freezing point depression while maintaining a sufficient salt solubility. The salt spiro-(1, 1′)-bipyrrolidinium tetrafluoroborate was used, based on its improved conductivity at low temperatures, relative to linear alkyl ammonium salts. The carbon fabric electrode supported a relatively high rate capability at temperatures as low as −65 °C with a modest increase in cell resistance at this reduced temperature. The capacitance was only weakly dependent on temperature, with a specific capacitance of ∼110 F/g.