Increased cycling stability of Li4Ti5O12-coated LiMn1.5Ni0.5O4 as cathode material for lithium-ion batteries

Li4Ti5O12 (LTO)-coated 5 V spinel LiMn1.5Ni0.5O4 as cathode was prepared by the sol–gel method followed by high-temperature calcinations. The structural and electrochemical properties of these cathodes were investigated using differential thermal analysis (DTA) and thermogravimetery (TG), X-ray diffraction (XRD), scanning electron microscopy (SEM), cyclic voltammetry (CV), and charge–discharge studies. TG–DTA shows that LiMn1.5Ni0.5O4 spinel forms at about 400 °C. XRD reveals that a substitutional compound LiMn2−x−yNixTiyO4 can be formed when the coated content of LTO exceeds 3 wt%. SEM exhibits that the coated LiMn1.5Ni0.5O4 is covered with small particles that consist mainly of LTO. CV and dQ/dV versus voltage curves demonstrate that the modified material exhibits remarkably enhanced electrochemical reversibility and stability. The charge–discharge test indicates that 3 wt% LTO-coated LiMn1.5Ni0.5O4 has excellent fast charge–discharge performances. These results reveal that LTO-coated layer protects the surface of the active materials from HF in the electrolyte during electrochemical cycling. As a result, the surface-modification of LiMn1.5Ni0.5O4 with LTO should be an effective way to improve the fast charge–discharge properties.