Adiponitrile-LiTFSI solution as alkylcarbonate free electrolyte for LTO/NMC Li-ion batteries

Recently, dinitriles (NC(CH2)nCN) and especially adiponitrile (ADN, n=4) have attracted the attention as secure electrolyte solvents due to their chemical stability, high boiling points, high flash points and low vapor pressure. The good solvating properties of ADN toward lithium salts and its high electrochemical stability (~ 6V vs. Li/Li+) make it suitable for safer Li-ions cells without performances loss. In this study, ADN is used as a single electrolyte solvent with lithium bis(trimethylsulfonyl)imide (LiTFSI). This electrolyte allows the use of aluminum collectors as almost no corrosion occurs at voltages up to 4.2 V. Physico-chemical properties of ADN-LiTFSI electrolyte such as salt dissolution, conductivity and viscosity were determined. The cycling performances of batteries using Li4Ti5O12 (LTO) as anode and LiNi1/3Co1/3Mn1/3O2 (NMC) as cathode were determined. The results indicate that LTO/NMC batteries exhibit excellent rate capabilities with a columbic efficiency close to 100%. As an example, cells were able to reach a capacity of 165 mAh.g-1 at 0.1C and a capacity retention of more than 98% after 200 cycles at 0.5C. In addition, electrodes analyses by SEM, XPS and electrochemical impedance spectroscopy after cycling confirming minimal surface changes of the electrodes in the studied battery system