Effects of Li2TiO3 coating on the structure and the electrochemical properties of LiNi0.5Mn0.5O2 cathode materials at high voltages
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To improve the cycle performance, zLi2TiO3@LiNi0.5Mn0.5O2 (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 Li2TiO3 is evenly coated on the surface of LiNi0.5Mn0.5O2, with the thickness of the coating layer of approximately 10 nm. The electrochemical characterizations of the synthesized zLi2TiO3@LiNi0.5Mn0.5O2 suggest that 1 mol% Li2TiO3@LiNi0.5Mn0.5O2 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% Li2TiO3 coating. The improved cycling performance of LiNi0.5Mn0.5O2 arises from the presence of the Li2TiO3 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 Li2TiO3 coating layer could inhibit electrolyte decomposition, and the decomposition of electrolyte on the surface of coating electrode is different from that of LiNi0.5Mn0.5O2 electrode.
KeywordsLithium–ion batteries LiNi0.5Mn0.5O2 cathode material Li2TiO3 coating BET surface areas High voltage
This work was supported by the Natural Science Foundation of China (U1507106 and U1507114), the Natural Science Foundation of Qinghai Province (2016-GX-101), the Hunan Provincial Science and Technology Plan Project (Nos. 2016TP1007 and 2017TP1001), and the Science and Technology project of Xining Science and Technology Bureau (2017-G-05).
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Conflict of interest
The authors declare that they have no conflict of interest.
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