Improving the Performance of Graphite/LiNi0.5Mn1.5O4 Cells with Added N,N-dimethylformamide Sulfur Trioxide Complex

N, N-dimethylformamide sulfur trioxide complex (DMF-SO3) has been investigated as an electrolyte additive for LiNi0.5Mn1.5O4/graphite cells cycled to 4.8 V. Addition of 0.1% DMF-SO3 to 1.2 M LiPF6 in EC/EMC (3/7, v/v) standard electrolyte (STD) results in a significant improvement in the capacity retention and coulombic efficiency of LiNi0.5Mn1.5O4/graphite cells after 50 cycles at 45 degrees C. Ex-situ surface analysis of the electrodes after cycling has been conducted via scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and infrared spectroscopy with attenuated total reflectance (IR-ATR). The surface analysis suggests that a uniform interfacial film is formed on the LiNi0.5Mn1.5O4 surface composed of the decomposition products of DMF-SO3. The novel cathode surface films passivates the surface at high potential leading to the improved electrochemical performance. (C) The Author(s) 2017. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives 4.0 License (CC BY-NC-ND, http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial reuse, distribution, and reproduction in any medium, provided the original work is not changed in any way and is properly cited. For permission for commercial reuse, please email: oa@electrochem.org. All rights reserved.