Magnetism and spin entropy in Ru doped Na0.5CoO2

Quasi-dynamic study of electrochemical properties of O3-high-Ni ternary single-crystal cathode materials with mirror symmetry: a first-principles study

A total of 16 O3-type high-Ni ternary crystal structures with mirror symmetry were constructed based on the relative locations of Ni, Co, and Mn in order to design high operating voltage and high-capacity cathode materials for lithium-ion batteries. Transition states, powder X-ray diffraction (XRD) patterns, intercalation potentials, and (spin) electronic structures are computed and simulated based on first-principles calculations. The results show that the Li ion diffusion energy barrier, in the structure of the lowest energy counterpart a'aa', is only 0.9 eV. When charged to 75% state of charge (SOC), the Li layer spacing reaches a maximum under electrostatic attraction and Coulomb repulsion forces. The operating voltage and theoretical capacity are up to 4.79 V and 275 mA h g-1, respectively. High-spin Ni2+ participates in the reduction reaction as the main substance and is eventually oxidized to low-spin Ni4+. Intermediate-spin Co3+ also participates in the reduction reaction and is oxidized to low-spin Co4+, with charge compensation provided by O atoms. Mn does not participate in the redox reaction. This study is expected to enrich the library of high-nickel ternary cathode materials and provides a certain reference for the design of (ultra)high-nickel ternary cathode materials with excellent electrochemical properties.