The ternary layered material Li(NixMnyCoz)O2(NMC)(x+y+z=1) has high theoretical capacity, easy synthesis, and relatively low price, and is currently the most widely used positive electrode for lithium ion batteries. Materials (such as the positive electrode materials used in most mobile phones and Tesla electric vehicles) are also the key positive materials for the major innovation projects of the national electric vehicle power battery that the Shenzhen University Graduate School of Materials and Materials Collaboration with Shenzhen Enterprises is carrying out. However, its safety performance is poor. When overcharging or heating, it is easy to cause structural damage or phase change. The oxygen is released from the crystal lattice, and it is easy to ignite after contact with the organic electrolyte, which may cause an explosion. This has also become a major challenge for its application in electric vehicle power batteries.

Professor Pan Feng from the School of New Materials, Peking University Shenzhen Graduate School conducted a systematic study on the ternary layered NMC material of lithium battery, and systematically studied the diffusion mechanism of lithium and the performance of high and low temperature (J. Am. Chem. Soc , 2015, 137(26), pp 8364), and found that NMC622 has the best high and low temperature performance (Advanced Energy Materials 2015, DOI: 10.1002/aenm.201501309). Recently, they have verified by first-principles calculations and experiments that the stability of the ternary layered cathode material is related to the most unstable oxygen in the lattice structure, and the stability of oxygen is determined by its basic coordination unit. (Ni, Mn, Co) 3-O-Li3-x': each oxygen and three transition metal ions in the transition metal layer are coordinated while coordinating with 0 to 3 lithium ions in the lithium layer). Through this model, they systematically revealed the regulation of oxygen stability in the layered materials such as lithium content, transition metal element content and valence state, and Ni/Li reverse defect. This will provide important clues and theoretical guidance for the optimization of the stability of ternary layered lithium-ion batteries in the future.