Ethyl Methyl Sulfone-Based Electrolytes for Lithium Ion Battery Applications

Sulfone-based electrolytes, known for their higher oxidative stability compared to the typically used organic carbonate-based electrolytes, are considered promising electrolytes for high voltage cathode materials towards the objective of obtaining increased energy density in lithium ion batteries. Nevertheless, sulfones suffer from high viscosity as well as incompatibility with highly graphitic anode materials, which limit their application. In this paper, the effect of fluoroethylene carbonate (FEC) as an electrolyte additive for the application of ethyl methyl sulfone (EMS) electrolytes containing LiPF6 as conducting salt, is studied in graphite-based cells by means of selected electrochemical and spectroscopic methods. In addition, influence of ethylene acetate (EA) as co-solvent on the electrolyte viscosity and conductivity of the EMS-based electrolytes is discussed, revealing improved overall nickel cobalt manganese oxide (NMC)/graphite cell performance. X-ray photoelectron spectroscopy (XPS) measurements provide information about the surface chemistry of the graphite electrodes after galvanostatic cycling. The concept of EA as co-solvent is found to be applicable for other sulfones such as isopropyl methyl sulfone (MeiPrSO(2)) and ethyl isopropyl sulfone (EtiPrSO(2)).