Effect of Vinylene Carbonate Additive in Li-Ion Batteries: Comparison of LiCoO2/C, LiFePO4/C, and LiCoO2/Li4Ti5O12 Systems

Vinylene carbonate (VC) is a commonly used electrolyte additive in Li-ion batteries because of its beneficial role on the formation of the solid electrolyte interphase. It was shown to contribute to surface film formation on both electrodes of LiCoO2/C cells via its radical polymerization mechanism. In this paper, we carried out a comparative study of the role of VC on electrode/electrolyte interfaces in LiCoO2/C, LiFePO4/C, and LiCoO2/Li4Ti5O12 systems, in which the potential and the chemical nature of each electrode are changed. Coin-cells were charged at different potentials using a LiPF6/ethylene carbonate: diethyl carbonate: dimethyl carbonate liquid electrolyte with or without VC, and the electrodes were analyzed by X-ray photoelectron spectroscopy. We showed there is no interaction between the negative and positive electrodes in the VC polymerization mechanisms, for example, by exchange of chemical species from one electrode to the other, during the first charge. Separate mechanisms occur, although the same VC polymer is deposited at the surface of both electrodes.