Improving the Performance at Elevated Temperature of High Voltage Graphite/LiNi0.5Mn1.5O4 Cells with Added Lithium Catechol Dimethyl Borate

Performance of LiNi0.5Mn1.5O4/graphite cells cycled to 4.8 V at 55. C with the 1.2 M LiPF6 in EC/EMC (3/7, STD electrolyte) with and without added lithium catechol dimethyl borate (LiCDMB) has been investigated. The incorporation of 0.5 wt% LiCDMB to the STD electrolyte results in an improved capacity retention and coulombic efficiency upon cycling at 55 degrees C. Ex-situ analysis of the electrode surfaces via a combination of SEM, TEM, and XPS reveals that oxidation of LiCDMB at high potential results in the deposition of a passivation layer on the electrode surface, preventing transition metal ion dissolution from the cathode and subsequent deposition on the anode. NMR investigations of the bulk electrolyte stored at 85. C reveals that added LiCDMB prevents the thermal decomposition of LiPF6. (C) The Author(s) 2016. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License All rights reserved.