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

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. Graphical Lyotropic liquid crystals (LLCs) formed through the assembly of a triblock copolymer Pluronic L64 in ion liquid [Bmim]BF 4 are employed as an electrolyte additive for supercapacitors. The addition of LLCs leads to suppressed self-discharge rate in an extended temperature range from 25 to 50 °C.