Enhancing high-rate electrochemical properties of LiMn2O4 in a LiMn2O4/LiNi0.5Mn1.5O4 core/shell composite

Being widely considered a powerful tool for improving the capacity retention and rate capability of cathode materials for lithium-ion batteries, surface modification has never been applied for obtaining truly high-rate spinels. The stoichiometric LiMn2O4 and a material containing the LiMn2O4 core and LiNi0.5Mn1.5O4 shell with the shell/core mass ratio of 0.1:1 have been synthesized by means of a citric acid aided route. The samples studied have been characterized using thermal analysis, X-ray diffraction and scanning electron microscopy. The specific discharge capacities of LiMn2O4/LiNi0.5Mn1.5O4 and LiMn2O4 at I = 0.5C equal to 107 and 110 mAh g−1, respectively. The surface coated LiMn2O4/LiNi0.5Mn1.5O4 shows up an exceptional high-rate ability being able to retain ca. 25 mAh g−1 at the current load of 9620 mA g−1 (65C), which is 1.625 times higher than for the unmodified LiMn2O4. Such exceptional high-rate properties and better cycling ability of the core-shell LiMn2O4/LiNi0.5Mn1.5O4 compared to parent compounds prove good prospects of surface modification techniques in improving rate capabilities of spinel materials.