Electrochemical reaction mechanism of two components in xLi2MnO3–(1–x)LiNi0.5Mn0.5O2 and effect of x on the electrochemical performance in lithium ion battery

Abstract To distinguish the charge/discharge reaction of two components such as Li2MnO3-like and LiNi0.5Mn0.5O2-like in 0.5Li2MnO3–0.5LiNi0.5Mn0.5O2, the electrochemical characteristics, structural change, and oxidation state change of each element for 0.5Li2MnO3–0.5LiNi0.5Mn0.5O2 during charging and discharging were compared with those of LiNi0.5Mn0.5O2 and Li2MnO3. The electrochemical measurement results indicate that the charge/discharge reaction potentials of two components can be clearly distinguished in the first charging; however, the reaction potentials of two components partially overlapped after the first charging. Although the two components cannot be distinguished in XRD patterns obtained before charging/discharging, the existence of two components can be confirmed in XRD patterns obtained during charging/discharging. The XAFS results indicate that Li2MnO3-like and LiNi0.5Mn0.5O2-like components mainly contributed to the discharge reaction of 0.5Li2MnO3–0.5LiNi0.5Mn0.5O2 in the low and high potential ranges, respectively. To evaluate the effect of x (ratio of Li2MnO3-like and LiNi0.5Mn0.5O2-like components) in xLi2MnO3–(1-x)LiNi0.5Mn0.5O2 on the material's electrochemical performance, xLi2MnO3–(1-x)LiNi0.5Mn0.5O2 (x = 0.4, 0.5, and 0.6) were prepared, and their electrochemical performance was investigated. The results indicate that the increase in the ratio of LiNi0.5Mn0.5O2-like component in xLi2MnO3–(1–x)LiNi0.5Mn0.5O2 (x = 0.4, 0.5, and 0.6) affects suppression of initial irreversible capacity and improvement of rate and cycling performance.