Abstract
In order to identify the failure mechanism of LiMn1.5Ni0.5O4 (LMN) spinel at elevated temperature (60{degree sign}C), the effect of carbon black, Mn3+ content and charge/discharge state storage conditions were studied. It was identified that the main degradation mechanism at elevated temperature was the systematic impedance rise rather than intrinsic capacity loss. At this early stage we attribute most of this to the anodic decomposition of the electrolyte on the surface of the spinel. We introduce a surface conversion process to improve the elevated temperature performance of the spinel. The surface converted materials exhibited much lower impedance rise with improved capacity retention and rate capability at elevated temperature.