From Surface ZrO2 Coating to Bulk Zr Doping by High Temperature Annealing of Nickel‐Rich Lithiated Oxides and Their Enhanced Electrochemical Performance in Lithium Ion Batteries

Abstract One of the major hurdles of Ni‐rich cathode materials Li 1+ x (Ni x Co z Mn z ) w O 2 , y > 0.5 for lithium‐ion batteries is their low cycling stability especially for compositions with Ni ≥ 60%, which suffer from severe capacity fading and impedance increase during cycling at elevated temperatures (e.g., 45 °C). Two promising surface and structural modifications of these materials to alleviate the above drawback are (1) coatings by electrochemically inert inorganic compounds (e.g., ZrO 2 ) or (2) lattice doping by cations like Zr 4+ , Al 3+ , Mg 2+ , etc. This paper demonstrates the enhanced electrochemical behavior of Ni‐rich material LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) coated with a thin ZrO 2 layer. The coating is produced by an easy and scalable wet chemical approach followed by annealing the material at ≥700 °C under oxygen that results in Zr doping. It is established that some ZrO 2 remains even after annealing at ≥800 °C as a surface layer on NCM811. The main finding of this work is the enhanced cycling stability and lower impedance of the coated/doped NCM811 that can be attributed to a synergetic effect of the ZrO 2 coating in combination with a zirconium doping.