Li1.17Mn0.50Ni0.16Co0.17O2 assembled microspheres as a high-rate and long-life cathode of Li-ion batteries

Abstract

Assembled microspherical cathodes have attracted great attention thanks to their high tap density, good rate capability and cycling stability. However, for layered Li-rich transition-metal oxides (LROs), the preparation of uniformly assembled microspheres still faces many challenges due to harsh synthetic conditions and the nature of multiple metal elements. In this work, Li_1.17Mn_0.50Ni_0.16Co_0.17O₂ assembled microspheres have been prepared by a new route tactfully combining a solvothermal process and a molten-salt method. The use of a solvothermal process is helpful for the preparation of precursors with assembled microspherical morphology, and the addition of complex salts (NaCl and KCl), can increase the uniformity of cation distribution. The product obtained at 800 °C delivers the best electrochemical performances among all samples. At a current density of 300 mA g⁻¹, its initial discharge capacity is larger than 228 mA h g⁻¹, corresponding to a capacity retention ratio of 86.8% after 200 cycles. Even if the current density increases to 2000 mA g⁻¹, its discharge capacity is still as large as 156 mA h g⁻¹. What's more, we discover the moving rate of Li-ions during the sintering process will affect the uniformity of Li₂MnO₃-like and LiMO₂ components in LRO assembled microspheres. This discovery is helpful for the preparation of LRO assembled microspheres with excellent electrochemical performances.