Ricerc@Sapienza

Due to their desirable properties such as high ionic conductivity, negligible flammability and tunability, ionic liquids (ILs) have been recognized as promising electrolyte materials in lithium-ion batteries with improved safety. In ILES project non-commercial ILs, formed by ether-functionalized N-ethoxyethyl-N-methyl piperidinium (P1,2O2) cations and bis(fluorosulfonyl)imide (FSI) or difluoro(oxalato)borate (DFOB) anions, will be synthesized and investigated. These ILs, combined with a suitable lithium salt, were recently proposed as electrolyte components in Li cells, due to their low crystallization attitude and improved ionic conductivity. Anyhow, important features, related to their stability and effectiveness for long-term safe applications under an extended temperature range, were not fully assessed. Here, temperature-activated physical and chemical processes, such as degradation and phase transitions, will be explored in both pure ILs and their mixtures with a lithium salt. The effect of different Li+ sources and of their concentration in the ILs will be considered ranging from widely used salts (i.e., LiPF6) to tailored LiFSI and LiDFOB. Moreover, the addition of molecular aprotic solvents, such as dimethyl carbonate and ethylene carbonate, adopted in commercial battery electrolytes, will be investigated with the aim of enhancing ions dissociation and mobility in the IL-based mixtures. The resulting novel electrolyte compositions will be characterized in terms of physico-chemical properties related to their thermal stability (vaporization, decomposition, melting, glass transition, flash point) and of electrochemical performances (ionic conductivity, electrochemical stability window, interfacial resistivity and charge-discharge capacity in conventional battery configurations). Overall, ILES proposes an original, very appealing approach to correlate fundamental thermodynamic properties of IL materials to their applicability in energy storage batteries.