Controllable preparation of chamfered LiNi_0.5Mn_1.5O₄ monocrystal cathode materials by trace Ti atoms replacing Mn and electrochemical properties

LiNi_0.5Mn_1.5O₄ cathode materials have the advantages of high potential, high specific energy, and low cost, but poor structural stability and severe surface side reactions hinder their industrial applications. In this study, a series of LiNi_0.5Mn_1.5-xTi_xO₄ (x = 0, 0.01, 0.03, and 0.05) materials with monocrystal morphology are controllably synthesized using a solid-state method by replacing Mn with trace Ti atoms. XRD, SEM, TEM, Raman, XPS, and electrochemical tests show that the phase component, structure, planes of the octahedral monocrystal, and Mn³⁺ ionic behavior can be effectively regulated to improve their cycle life and elevated-temperature stability. The optimized LiNi_0.5Mn_1.47Ti_0.03O₄ monocrystal cathode material possesses a disordered Fd-3m space group structure, a distinctive chamfered octahedral morphology with the {100} planes, a stable solid-electrolyte interphase film, and a fast Li⁺ ion/electron transport property. As a result, the material can release an initial discharge specific capacity of about 134.88 mAh g⁻¹ at 0.2 C with a coulombic efficiency of 89.4%, capacity retention of 79.5% after 1000 cycles at 25 ℃, and 80.0% after 200 cycles at 55 °C and 1 C and also good rate performance.