Facile synthesis and characterization of a SnO2-modified LiNi0.5Mn1.5O4 high-voltage cathode material with superior electrochemical performance for lithium ion batteries

Abstract

A thin-layer-SnO₂ modified LiNi_0.5Mn_1.5O₄@SnO₂ material is synthesized via a facile synthetic approach. It is physically and electrochemically characterized as a high-voltage lithium ion battery cathode and compared to the pristine LiNi_0.5Mn_1.5O₄ material prepared under similar conditions. The two materials are proved to be crystals of a well-defined disordered spinel phase with the morphology of aggregates of micron/submicron polyhedral particles. The Mn³⁺ ions and the inactive Ni_xLi_yO phase in the LiNi_0.5Mn_1.5O₄@SnO₂ is less than those in the LiNi_0.5Mn_1.5O₄ due to incorporation of a very small amount of Sn²⁺ into the spinel structure upon high-temperature calcination of the precursor. Besides, the mean particle size of the LiNi_0.5Mn_1.5O₄@SnO₂ is obviously smaller than that of the LiNi_0.5Mn_1.5O₄. The LiNi_0.5Mn_1.5O₄@SnO₂ demonstrates much superior electrochemical performance over the LiNi_0.5Mn_1.5O₄ in terms of specific capacity, rate capability and cyclability. For example, the discharge capacities at current rates of 0.2C, 2C and 20C are 145.4, 139.9 and 112.2 mA h g⁻¹, respectively. A capacity retention rate of ca. 75% is obtained after 500 cycles at 2C rate. The improved electrochemical performance is attributed to the positive effect of the surface protective SnO₂ coating layer as well as the structural and morphological modifications of the spinel.