Insight into the Role of Co and Mn Elements in Ni-Rich LiNi0.9CoxMn0.08–xAl0.02O2 Cathode Materials

Ni-rich quaternary layered oxide LiNixCoyMnzAl1–x–y–zO2 (NCMA, 1 – x – y – z ≥ 0.9) is one of the most promising cathode materials for lithium-ion batteries due to its high energy density and low cost. However, the roles of Co and Mn contents in NCMAs remain to be investigated. Herein, LiNi0.9CoxMn0.08–xAl0.02O2 (x = 0.07, 0.05, 0.03) are synthesized by a hydroxide coprecipitation method and high-temperature solid-phase method. The results show that Co can increase the value of the c-axis, decrease the content of Ni2+ on the surface, and inhibit lattice expansion along the c-axis in the voltage range of 2.7–4.3 V. However, Mn has a superiority in reducing the primary particle size and preventing the sharp collapse of the lattice along the c-axis in the deep delithiated state, corresponding to a voltage range of 4.3–4.5 V. These new insights are intended to guide further research on NCMAs.