Peculiar role of the electrolyte viscosity in the electrochemical capacitor performance

Abstract

This paper reports on the electrochemical performance of symmetric carbon/carbon electrochemical capacitors operating in an aqueous electrolyte (1 mol L⁻¹ Li₂SO₄ solution) whose viscosity is modified by various amounts of carboxymethyl cellulose additive. The literature states that increased electrolyte viscosity usually decreases the overall capacitor performance. However, it has been found that the influence of this parameter is complex and depends significantly on the carbon electrode texture/structure properties. Fortunately, the application of viscous electrolytes is found to be beneficial in terms of reduced leakage current and internal gas evolution (by approximately 50%). Furthermore, the examination of differently structured carbons showed that in materials with well-designed micro-/mesoporous interconnectivity, it is possible to retain high power and energy performance even for devices with 104-fold increased viscosity.