Screening electrolytes designed for high voltage electrochemical capacitors. (1st April 2021)

• Record Type: Journal Article
• Authors: Krause, Frederick C.; Jones, John-Paul; Smart, Marshall C.; Chin, Keith B.; Brandon, Erik J.
• Is Part Of: Electrochimica acta. Volume 374(2021)
• Publication Date: 2021-04-01
• Subjects: Supercapacitor -- EDLC -- High voltage -- Fluorinated solvents -- Electrolyte additives; Electrochemistry -- Periodicals; Electrochemistry, Industrial -- Periodicals; 541.37
• DOI: 10.1016/j.electacta.2021.137898
• Languages: English
• ISSNs: 0013-4686

Abstract

Abstract: Standard acetonitrile/tetraalkylammonium-tetrafluoroborate-based electrochemical capacitor electrolytes were modified with both fluorinated additives (including fluorinated analogs of ethylmethyl carbonate and diethyl carbonate, lithium difluoro(oxalato)borate, and tris(2, 2, 2-trifluoroethyl) phosphite) and spiro(1, 1′)-bipyrrolidinium tetrafluoroborate salt, to improve stability at higher voltages (>2.7 V). Compounds investigated included (2, 2, 2-trifluoroethyl) methyl carbonate (TFEMC), ethyl(2, 2, 2-trifluoroethyl) carbonate (ETFEC), bis(2, 2, 2-trifluoroethyl) carbonate (bTFEC), lithium difluoro(oxalato)borate (LiDFOB), and tris(2, 2, 2-trifluoroethyl) phosphite (TTFEPi). Screening of modified electrolytes in prototype coin cells using constant current cycling and voltage hold test protocols revealed good retention of capacitance and a reduced cell internal resistance growth when operating at maximum voltages between 3.5 and 4.0 V. These results suggest new strategies for increasing the operating limits of electric double-layer type supercapacitors, to increase stored energy and improve their compatibility with lithium-ion battery cells for use in hybrid configurations.