Sn-Doping and Li₂SnO₃ Nano-Coating Layer Co-Modified LiNi_0.5Co_0.2Mn_0.3O₂ with Improved Cycle Stability at 4.6 V...

Nickel-rich layered LiNi_1-CoMnO₂ (LiMO₂) is widely investigated as a promising cathode material for advanced lithium-ion batteries used in electric vehicles, and a much higher energy density in higher cut-off voltage is emergent for long driving range. However, during extensive cycling when charged to higher voltage, the battery exhibits severe capacity fading and obvious structural collapse, which leads to poor cycle stability. Herein, Sn-doping and in situ formed Li₂SnO₃ nano-coating layer co-modified spherical-like LiNi_0.5Co_0.2Mn_0.3O₂ samples were successfully prepared using a facile molten salt method and demonstrated excellent cyclic properties and high-rate capabilities. The transition metal site was expected to be substituted by Sn in this study. The original crystal structures of the layered materials were influenced by Sn-doping. Sn not only entered into the crystal lattice of LiNi_0.5Co_0.2Mn_0.3O₂, but also formed Li⁺-conductive Li₂SnO₃ on the surface. Sn-doping and Li₂SnO₃ coating layer co-modification are helpful to optimize the ratio of Ni²⁺ and Ni³⁺, and to improve the conductivity of the cathode. The reversible capacity and rate capability of the cathode are improved by Sn-modification. The 3 mol% Sn-modified LiNi_0.5Co_0.2Mn_0.3O₂ sample maintained the reversible capacity of 146.8 mAh g^-1 at 5C, corresponding to 75.8% of its low-rate capacity (0.1C, 193.7mAh g^-1) and kept the reversible capacity of 157.3 mAh g^-1 with 88.4% capacity retention after 100 charge and discharge cycles at 1C rate between 2.7 and 4.6 V, showing the improved electrochemical property.