High-performance, mechanically compliant silica-based ionogels for electrical energy storage applications

Abstract

The development of an ionic liquid-rich (∼94% by mass), mechanically compliant, silica-supported ionogel (ionic liquid-based gel electrolyte) is described. This new form of ionogel was created using a straightforward sol–gel process with a novel formulation of reactants, resulting in a versatile, stable, and high-performance solid electrolyte. The mechanically compliant ionogels described herein show both capacitance and ionic conductivity values at room temperature nearly equivalent to those of the neat ionic liquid (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, EMI TFSI), in addition to exhibiting a wide window of electrochemical stability. Compliant ionogels (elastic modulus of ∼5 kPa) show markedly different mechanical character than previously reported silica ionogels, which are mechanically brittle and exhibit lower ionic conductivity and double-layer capacitance. The silica microstructure is shown to be tunable by simple alterations of the reagent formulation. Compliant ionogels may be suitable for in situ fabrication of flexible, thin-film energy storage devices such as supercapacitors.