Silica-polymer ionogel for energy storage applications

Ionic Liquids (ILs) are composed of ions, usually an organic cation with an organic or inorganic anion, with melting point below 100ºC. These compounds exhibit important and characteristic properties such as high ionic conductivity, good thermal and electrochemical stability and low toxicity and flammability. Subsequently, ILs have generated interest during the last decades to be used in different applications as electrochemical and thermal energy storage, catalysis, green solvents and drug delivery among others applications.

ILs have been studied as promising substitutes for conventional electrolytes for electrochemical applications, both as bulk liquids or confined in a polymer matrix, commonly known as ionogels, which have the advantage of no leaking, enhancing safety and manipulation during device assembly.

For this work, ionogel of the IL 1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C₂C₁Im][TFSI]) has been synthesised by polymerization of Tetramethyl orthosilicate (TMOS) and Dimethyldimethoxysilane (DMDMS). Thermal and electrochemical responses of this ionogel were characterised and compared with bulk IL by using differential scanning calorimetry (DSC), thermogravimetry (TGA) and broad band dielectric spectroscopy (BBDS), respectively.

The confinement of this IL reduces the crystallinity with regard to bulk IL, widening the temperature range of operation as well as lowering the ionic conductivity although this property shows good enough values for the required application.