The Impact of Varying the Concentration of Vinylene Carbonate Electrolyte Additive in Wound Li-Ion Cells

Wound LiCoO2/graphite and Li[Ni0.42Mn0.42Co0.16]O-2/graphite cells with 1M LiPF6 EC:EMC electrolyte containing either 0, 1 or 2 wt.% vinylene carbonate were studied using the High Precision Charger at Dalhousie University, automated cell storage and AC impedance. Vinylene carbonate (VC) was found to improve the coulombic efficiency of the cells, decrease charge endpoint capacity slippage and decrease self discharge, in all cases primarily by slowing electrolyte oxidation at the positive electrode. The beneficial impacts of VC are greater in LiCoO2 cells than in Li[Ni0.42Mn0.42Co0.16]O-2 cells. One percent VC is enough to derive the benefits without causing an impedance rise in the cells. (C) 2011 The Electrochemical Society. [DOI: 10.1149/2.028202jes] All rights reserved.