Impedance Reducing Additives and Their Effect on Cell Performance: I. LiN(CF3SO2)2

• Published in: Journal of the Electrochemical Society Vol. 159; no. 7; pp. A1095 - A1104
• Main Authors: Burns, J. C., Sinha, N. N., Jain, Gaurav, Ye, Hui, VanElzen, Collette M., Lamanna, W. M., Xiao, A., Scott, Erik, Choi, J., Dahn, J. R.
• Format: Journal Article
• Language: English
• Published: The Electrochemical Society 2012
• ISSN: 0013-4651; 1945-7111
• DOI: 10.1149/2.077207jes

Wound LiCoO2/graphite and Li[Ni0.42Mn0.42Co0.16]O2/graphite cells with 1 M LiPF6 in EC:EMC (3:7 by wt) electrolyte containing 2 wt% vinylene carbonate (VC) and/or lithium bis (trifluoromethanesulphonyl) imide (LiTFSI or 3M Fluorad Lithium HQ-115) were studied using the High Precision Charger at Dalhousie University, automated cycling/storage, AC impedance and long-term cycling at elevated temperature. The additive, VC, improves lifetime performance by increasing coulombic efficiency and decreasing charge and discharge end point capacity slippage, while the impact of HQ-115 alone on lifetime is minimal. However, HQ-115 reduces cell impedance when added to either control or VC-containing electrolyte. Therefore it serves as a useful additive for improving the rate capability of cells and capacity retention during high rate cycling at elevated temperature. It is our opinion that Li-ion cells incorporating VC can benefit from a simultaneous addition of HQ-115 due to a synergistic effect observed between HQ-115 and VC additives. This report is the first of two companion reports studying impedance reducing additives and their impact on cell lifetime.