Insight Into the Effect of Doping on the Calcination of Nickel‐Rich Layered Oxide Positive Electrode Materials

Ni‐rich layered oxides such as LiNi 0.8 Mn 0.1 Co 0.1 O 2 (i.e., NMC811) are popular cathode materials providing high practical specific capacities and energy densities, suffering from variety side reactions which can be overcome by changing the synthesis conditions and implementation of additional elements into the NMC811 crustal structure. In this work, the influence of Mg incorporation pathway and calcination conditions on the structural and electrochemical performance of NMC811 is systematically investigated. Two doping strategies are compared: Mg introduction during lithiation step and a combined dual doping approach, when Mg introduced during both coprecipitation and lithiation steps. Three NMC811(OH) 2 precursors with varying Mg contents were synthesized to evaluate the role of Mg during precursor formation. In situ high‐temperature X‐ray diffraction revealed a lithiation window of 700–900 °C, with complete lithiation achieved at 800 °C, while higher temperatures (at 900 °C) led to rapid primary particle growth and degradation of secondary particles. Electrochemical measurements demonstrated higher capacities at 850 °C and comparable capacity retention (∼84% after 100 cycles) especially for the dual Mg‐doped NMC811. These results highlight dual Mg doping as an effective strategy to enhance NMC811 performance.