Novel approach to preparation of LiMn ₂ O ₄ core/LiNi _x Mn _2-x O ₄ shell composite

Combining two methods, coating and doping, to modify spinel LiMn ₂ O ₄ , is a novel approach we used to synthesize active material. First we coated the LiMn ₂ O ₄ particles with the nickel oxide particles by means of homogenous precipitation, and then the nickel oxide-coated LiMn ₂ O ₄ was calcined at 750 °C to form a LiNi _x Mn _2-x O ₄ shell on the surface of spinel LiMn ₂ O ₄ particles. Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), cyclic voltammetry (CV) and charge-discharge test were performed to characterize the spinel LiMn ₂ O ₄ before and after modification. The experimental results indicated that a spinel LiMn ₂ O ₄ core is surrounded by a LiNi _x Mn _2-x O ₄ shell. The resulting composite showed excellent electrochemical cycling performance with an average fading rate of 0.014% per cycle. This improved cycle stability is greatly attributed to the suppression of Jahn-Teller distortion on the surface of spinel LiMn ₂ O ₄ particles during cycling.