Effects of Li2TiO3 coating on the structure and the electrochemical properties of LiNi0.5Mn0.5O2 cathode materials at high voltages

To improve the cycle performance, z Li 2 TiO 3 @LiNi 0.5 Mn 0.5 O 2 ( z  = 0, 1, 3 and 5 mol%) (“@” means “was coated on the surface of”) cathode materials have been successfully prepared via a syn-lithiation strategy. The high-resolution transmission electron microscope (HRTEM) structural analysis results show that Li 2 TiO 3 is evenly coated on the surface of LiNi 0.5 Mn 0.5 O 2 , with the thickness of the coating layer of approximately 10 nm. The electrochemical characterizations of the synthesized z Li 2 TiO 3 @LiNi 0.5 Mn 0.5 O 2 suggest that 1 mol% Li 2 TiO 3 @LiNi 0.5 Mn 0.5 O 2 electrode shows the best electrochemical performance, including the highest capacity and best cycle stability and rate performance. The capacity retention at 25 °C is improved by approximately 23% by the 1 mol% Li 2 TiO 3 coating. The improved cycling performance of LiNi 0.5 Mn 0.5 O 2 arises from the presence of the Li 2 TiO 3 surface layer, which suppresses the direct contact between the active materials and the electrolytes, enhances the lithium ion diffusion through the electrode/electrolyte interface, expands the BET area, stabilizes the structure and prevents the pulverization of the active materials during repeated charging/discharging. The XPS results showed that Li 2 TiO 3 coating layer could inhibit electrolyte decomposition, and the decomposition of electrolyte on the surface of coating electrode is different from that of LiNi 0.5 Mn 0.5 O 2 electrode.