Effect of Ni²⁺ content on lithium/nickel disorder for Ni-rich cathode materials

Li excess LiNi_0.8Co_0.1Mn_0.1O₂ was produced by sintering the Ni_0.8Co_0.1Mn_0.1(OH)₂ precursor with different amounts of a lithium source. X-ray photoelectron spectroscopy confirmed that a greater excess of Li⁺ leads to an increase in the number of Ni²⁺ ions. Interestingly, the level of Li⁺/Ni²⁺ disordering decreases with an increase in Ni²⁺ content determined by the I₀₀₃/I₁₀₄ ratio in the X-ray diffraction patterns. The electrochemical measurement shows that the cycling stability and rate capability improve with an increase in Ni²⁺ content. After cycling, electrochemical impedance spectroscopy shows decreased charge transfer resistance, and the XRD patterns exhibit an increased I₀₀₃/I₁₀₄ ratio with an increase in Ni²⁺ content, reflecting the decrease in the level of Li⁺/Ni²⁺ disorder during cycling.