Study of the Consumption of Vinylene Carbonate in Li[Ni0.33Mn0.33Co0.33]O2/Graphite Pouch Cells

The fate of the electrolyte additive, vinylene carbonate (VC), in 220 and 240 mAh Li[Ni0.33Mn0.33Co0.33]O2/graphite pouch cells filled with 1M LiPF6 EC:EMC (3:7) base electrolyte during formation, brief cycling and storage was studied using gas chromatography coupled with mass spectrometry (GC-MS). During formation, almost all VC was consumed for cells initially loaded with 1% or 2% VC while cells initially containing 4% VC or 6% VC had about 2% VC consumed. The addition of some additive combinations greatly reduced the amount of VC consumed during formation while other additives hardly affected the amount of VC consumed. Potential hold experiments at 40°C and 50°C suggested that no measurable amount of VC was consumed at the positive electrode and that VC was primarily consumed at the negative electrode. In general, the impedance of cells increased with the amount of VC consumed but cell history also affected the impedance.