Investigation of the Effect of Added Methylene Ethylene Carbonate (MEC) and Vinylene Carbonate (VC) on LiNi0.5Mn1.5O4/Graphite Cell Performance

Cycling performance of graphite/LiNi0.5Mn1.5O4 cells cycled up to 4.8 V (vs LiC6/C-6) with added methylene ethylene carbonate (MEC, 0.5% wt) and vinylene carbonate (VC, 0.5% wt) in 1.2MLiPF(6) in EC/EMC (3/7, v/v, STD electrolyte) has been investigated at 25 degrees C and 45 degrees C. Addition of VC to the STD electrolyte results in a decrease the cell cycling performance, especially at 45 degrees C, while addition of MEC to the standard electrolyte does not decrease performance. After 50 cycles at 45 degrees C, the cells with added MEC retain 79% of the original capacity, while the cells with added VC retain only 68% of the initial cell capacity. While improved performance can be obtained with MEC compared with VC, neither additive provides significant improvement over the STD electrolyte. Ex-situ surface analysis of the electrodes conducted by XPS and FT-IR supports the presence of a uniform passivation layer on the cathode surface with added MEC. The modification of the cathode solid electrolyte interphase (CEI) is consistent with the improved performance for cells with added MEC at 45 degrees C, compared to cells with added VC. (C) 2016 The Electrochemical Society. All rights reserved.