Ni‐rich LiNi x Co y Mn 1- x - y O 2 (NCM) provides high specific capacity, but its structural and thermal stability remains significantly limited. This work provides a systematic evaluation of Mg doping in LiNi 0.9 Co 0.05 Mn 0.05 1- x Mg x O 2 ( x = 0.0005, 0.02) and clarifies how Mg content and synthesis route jointly determine structural and electrochemical behavior. Mg is introduced through coprecipitation and solid‐state methods to elucidate how dopant incorporation pathways influence material behavior. While Mg doping leads to a slight decrease in initial capacity, it significantly enhances structural stability and cycling performance. Notably, the coprecipitation route enables more effective stabilization, whereas nonuniform Mg distribution in the samples synthesized via solid‐state methods results in inferior rate capability. The higher sintering temperature improves dopant uniformity and enhances the effectiveness of Mg doping, even though such excessive temperatures can adversely affect the structural stability of NCM955. Overall, this study shows that appropriately introduced Mg doping can significantly reinforce the stability and electrochemical durability of Ni‐rich NCM, particularly when incorporated through the coprecipitation route, offering guidance for designing advanced high‐energy cathode active materials.
Koo et al. (Thu,) studied this question.