Effect of Ionic Liquids as Additives on Lithium Electrolytes: Conductivity, Electrochemical Stability, and Aluminum Corrosion

We investigated the influence that eight ionic liquids (ILs) as additives have on the conductivity and electrochemical stability of lithium salt-based electrolytes. The investigated salts were the well-known lithium hexafluorophosphate (LiPF6), which is the preferred salt for lithium ion batteries (LIBs), and the new salt lithium difluoro(oxalato)borate (LiDFOB). Conductivity studies performed over the temperature range (238.15 to 333.15) K showed a temperature-dependent increase in conductivity caused by several IL additives. The electrochemical stabilities of the solutions were determined at platinum and aluminum electrodes. At the Pt electrode, LiPF6 is the more stable salt, whereas at the aluminum electrode, LiDFOB exhibits a 0.5 V higher potential window in comparison with LiPF6-based solutions. An investigation of the influence of added ILs on the corrosion of aluminum, the current collector material for cathodes of LIBs, did not reveal any adverse effects.