The Effect of Elemental Doping on Nickel-Rich NCM Cathode Materials of Lithium Ion Batteries

Nickel-rich cathode materials have the advantages of high specific energy, high discharging voltage, and low cost. However, harmful phase transitions, Li+/Ni2+ cation mixing, and lattice oxygen precipitation limit the battery performance. In the present work, to address these issues, Mg- and Al-doped LiNi0.6Co0.2Mn0.2O2 (NCM) materials were synthesized by a hydrothermal method, which were used as cathodes of lithium ion batteries. Compared with NCM without doping, the Al-doped NCM (NCM-Al) exhibited improved electrochemical behavior, and the Mg-doped NCM (NCM-Mg) showed declined performance. The difference in battery behavior is further investigated. It was found that Al doping expanded the layer spacing of NCM and thus improved the ion diffusion mobility, while Mg doping reduced the layer spacing and was accompanied by drastic structural change during the charging/discharging process, leading to poor cycling stability. The present work provides an experimental reference for boosting performance of lithium ion batteries by elemental doping.