Investigation of Electrolyte Additives with LiNi0.5Mn1.5O4/Graphite Cells at High Temperature

Abstract

The spinel-structured LiNi0.5Mn1.5O4 (LNMO) has drawn much attention as a Li-ion battery cathode material with potential electric vehicle applications due to its high operating voltage (~4.7 V vs. Li/Li+) and relatively high energy density (~680 Wh kg-1). LNMO-based cells, however, tend to suffer from capacity fading due to transition metal dissolution that is exacerbated by increased temperatures. In this study, the electrolyte additives LiDFOB, HFiP, FEC and combinations of the three were investigated to determine which additives are able to properly passivate the LNMO surface to hinder Ni and Mn dissolution and thus enable high temperature cycling with a reduced fade rate. A combination of FEC and HFiP additives yielded the best high temperature performance with a Coulombic efficiency >97% and a decreased electrolyte decomposition above 4.8 V.