Adiponitrile-based Electrolytes for High Voltage, Graphite-based Li-ion Battery

Adiponitrile-based, ethylene carbonate-free electrolytes were investigated for a use in room temperature, 4.5V Li-ion batteries including graphite electrodes. The use of DMC as co-solvent in a 1/1, (wt/wt) ratio and the incorporation of lithium bis(fluorosulfonyl)imide (LiFSI) and lithium difluorooxalatoborate (LiDFOB) salts allows reaching conductivities of 5.8 ms cm^-1 and 3.4 mS cm^-1 at 20°C, respectively. Electrochemical stability windows of more than 5.0V were obtained with both salts. The cycling of graphite electrodes of c.a. 7.5 mg cm^-2 is demonstrated with LiDFOB, even without the use of SEI additives, given the SEI-forming properties of the salt. The addition of fluoroethylene carbonate allows improving further the electrolyte performance and reach 99.9% efficiency. As for cathode operation, cycling of 15 mg cm^-2 LiNi_0.33Mn_0.33Co_0.33O₂ was achieved in the 3V - 4.5V potential range (Vs Li⁺/Li) with only a 0.2% capacity decay per cycle.