Surface modification of LiMn2O4 cathode with LaCoO3 by a molten salt method for lithium ion batteries

Abstract

Spinel LiMn2O4 is a promising cathode due to its advantages of low-cost, nontoxicity and thermal stability. However, the dissolution of manganese and the phase transformation induce the rapid capacity fade. Surface coating is an effective method to improve its electrochemical performance. In this work, spinel LiMn2O4 modified with perovskite LaCoO3 was prepared using a novel molten salt method. The resulted samples were characterized by X-ray diffraction (XRD), transmission/scanning electron microscopy (TEM/SEM), Fourier transformation infrared (FT-IR), Raman, and X-ray photoelectronic spectroscopy. The content of Mn3+ increased with the LaCoO3 coating accompanied by the increased concentration of oxygen vacancy. LiMn2O4 modified with 2% LaCoO3 shows a higher capacity and cycling stability than others at 0.2 C, while the cathode with 4% LaCoO3 shows the best rate performance at a larger current at 2 and 5 C. This enhanced performance can be attributed to improved interfacial conductivity between the cathode and electrolyte and the protective effects of coating.