Excellent electrochemical properties of Ni-rich LiNi0.88Co0.09Al0.03O2 cathode materials co-modified with Mg-doping and LiBO2-coating for lithium ion batteries

Abstract

Although LiNi_0.88Co_0.09Al_0.03O₂ with high Ni content has received extensive attention as an inexpensive cathode material possessing high energy density, it also encounters poor cycling issues because of the micro-cracks caused by phase transition and serious side reactions between the electrodes and the electrolyte. In this study, dual-modification of the material is achieved by LiBO₂-coating and Mg-doping, aiming to stabilize its crystal structure and reduce its surface activity. Furthermore, a systematic exploration was made into the influence of Mg-doping and LiBO₂-coating layers on the particle morphology, crystal structure and electrochemical traits. According to the XRD (X-ray diffraction) outcomes, Mg-doping and LiBO₂-coating both expand the interplanar space and lower the Ni²⁺/Li⁺ cation mixing. According to the TEM (transmission electron microscopy) and XPS (X-ray photoelectron spectroscopy) findings, the LiBO₂-coating layer is within 25 nm and the Mg-doping heightens the Ni²⁺ content. In the meanwhile, the electrochemical measurement indicates that dual-modification with LiBO₂-coating and Mg-doping was effective in strengthening the discharge ability, rate capability and cycling behavior of LiNi_0.88Co_0.09Al_0.03O₂ due to the elevated rate of Li⁺ diffusion, the constrained electrode side reaction with the electrolyte, and the improved reversibility of the H2 to H3 phase. Besides, the cylindrical 18650 battery with the co-modification cathode show excellent prolonged cycling stability both at room and high temperature.