Role of Mn Content on the Electrochemical Properties of Nickel-Rich Layered LiNi0.8–xCo0.1Mn0.1+xO2 (0.0 ≤ x ≤ 0.08) Cathodes for Lithium-Ion Batteries

Ni-rich layered oxides (Ni content >60%) are promising cathode candidates for Li-ion batteries because of their high discharge capacity, high energy density, and low cost. However, fast capacity fading, poor thermal stability, and sensitivity to the ambient moisture still plague their mass application. In this work, we systematically investigate the effects of Mn content on the structure, morphology, electrochemical performance, and thermal stability of the Ni-rich cathode materials LiNi0.8–xCo0.1Mn0.1+xO2 (0.0 ≤ x ≤ 0.08). It is demonstrated that with the increase in Mn content and decrease in Ni content, the cycling stability of LiNi0.8–xCo0.1Mn0.1+xO2 to a cutoff charge voltage of 4.5 V is significantly improved. The high-Mn-content electrode LiNi0.72Co0.10Mn0.18O2 shows a capacity retention of 85.7% after 100 cycles at a 0.2 C rate at room temperature, much higher than those of the lower Mn-content samples LiNi0.80Co0.10Mn0.10O2 (64.0%) and LiNi0.76Co0.10Mn0.14O2 (72.9%). The improved capacity retention of the high-Mn-content electrode LiNi0.72Co0.10Mn0.18O2 is due to the stabilization of the electrode/electrolyte interface, as evidenced by the lower solid-electrolyte interphase (SEI) resistance and charge-transfer resistance. Furthermore, with the increase in Mn content and decrease in Ni content, the thermal stability of the Ni-rich cathode is also remarkably enhanced.