Lyotropic Liquid Crystal as an Electrolyte Additive for Suppressing Self‐Discharge of Supercapacitors

Abstract

Abstract Self‐discharge severely constrains the application of supercapacitors for long‐term energy storage because it causes decay of cell voltage and loss of energy. So far, three pathways have been proposed for the self‐discharge of supercapacitors: i) ohmic leakage, ii) diffusion‐controlled self‐discharge, iii) faradaic reactions. However, solutions for mitigating the self‐discharge of supercapacitors are limited. Here, we choose lyotropic liquid crystal (LLC) as an electrolyte additive to suppress the self‐discharge of supercapacitors through the electrorheological effect of the LLC. The LLC formed by the assembly of a triblock copolymer Pluronic L64 in ion liquid [Bmim]BF 4 exhibits dielectric anisotropy and can reorient in an electric field, causing increased viscosity and slower ion diffusion of the electrolyte. It is found that, by adding 5 % (vol%) LLC into TEMABF 4 /acetonitrile electrolyte, the self‐discharge rate at room temperature can be decreased by 32 % compared to supercapacitors without LLC. Furthermore, the LLC could reduce the self‐discharge rate of supercapacitors even at 50 °C due to its stability in a relatively wide temperature range.