Implication of Lithium Excess Induced Structure and Electrochemical Behavior Changes of LiNi0.5Mn1.5O4 Spinel

Abstract

Cubic spinel LiNi0.5Mn1.5O4 is one of the most promising cathode materials for high energy density lithium ion batteries because of its higher voltage plateau at around 4.7 V vs Li+/Li. In this paper, LiNi0.5Mn1.5O4 spinels are synthesized with different lithium excess, and their composition, structure, morphology and electrochemical behavior are measured and compared. The results show that all samples have an ordered cubic spinel structure with Ni/Mn ordering in the octahedral sites, and the change of lithium excess can induce variations in phase composition and purity, Mn3+ amount, cation mixing and electrochemical behavior of the prepared LiNi0.5Mn1.5O4. Even with the least amount of Mn3+ and a higher amount of impurity, the sample with the least occupation of transition metal ions in the tetrahedral Li sites gives the best rate performance, justifying that the occupation of transition metal ions in the tetrahedral Li sites play a critical role in affecting the kinetics of lithium ion extraction/insertion for LiNi0.5Mn1.5O4 spinel.