Effects of Ion Fraction in an Inorganic Ionic Liquid Electrolyte on Performance of Intermediate-Temperature Operating Sodium-Sulfur Batteries

Abstract

Sodium-sulfur (Na-S) batteries are promising energy storage systems for renewable energy sources which redeem an intermittent energy source. This study reports the effects of the Na[SO₃CF₃] fraction in an inorganic Na[SO₃CF₃]-Cs[N(SO₂CF₃)₂] ionic liquid electrolyte (x(Na[SO₃CF₃]) = 0.2, 0.3, and 0.4) on the performance of Na-S batteries. Measurements of physicochemical and electrochemical properties demonstrated that decrease in the Na[SO₃CF₃] fraction decreases viscosity and increases ionic conductivity and the solubility of polysulfides into the ionic liquid, which contributes to the enhanced capacity in the low potential region during discharging.