The surface Al₂O₃ coating and bulk Zr doping drastically improve the voltage fade and cycling stability of Li(Ni_0.8Mn_0.1Co_0.1)O₂ cathode materials

One of the major hurdles of the high Ni content layered oxides (NLOs) in making lithium-ion batteries is their low cycling stability, especially for the NLOs with Ni content ≥ 60%; such NLOs have clear drawbacks including severely fading capacities and impedance increase during cycling. Two promising surface and bulk modifications of such NLOs to alleviate the drawbacks are: (1) the surface coatings by electrochemically inert inorganic compounds and/or (2) the lattice doping by cations. In this work, isopropanol alcoholysis has been used to achieve uniform surface Al₂O₃ coating on one of NLOs: LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811). The bulk Zr⁴⁺ doping and surface Al₂O₃ coating have been realized after annealing at ≥ 800 °C, which enhance the specific capacity of discharge and cycling life of the NCM@Al₂O₃ +Zr active material, and effectively suppress the voltage attenuation during cycling process. The main finding of this work is the enhanced cycling stability and the diminished impedance of the coated/doped NCM811, being provided by a synergetic effect of the Al₂O₃ coating and the Zr⁴⁺ doping.