In order to improve the overall performance of the Li-ion secondary battery and analyze the effect of Co-dopping on the electrochemical performance of Li_xNiO₂ cathode, the average potential and density of states of Li_xNiO₂ and Li_xNi_0.5Co_0.5O₂ cathode materials for lithium battery were calculated under the framework of density functional theory. Meanwhile, the LiNiO₂ and LiNi_0.5Co_0.5O₂ materials were synthesized with coprecipitation method. The microstructure and electrochemical performance of the materials were characterized by XRD and galvanotatic cycling. The results of both of the tests and calculation showed that the potential was descended gradually and the density of states of the materials moved to the direction of low energy when Li ions intercalated the cathode materials (discharge). The average potential of Li_xNi_0.5Co_0.5O₂ was higher than that of Li_xNiO₂ (when 0.25≤x≤0.5), and when the Li ion intercalated/deintercalated the cathode, the change of the structure of LiNi_0.5Co_0.5O₂ was smaller than that of Li_xNiO₂. The distortion of the NiO₆ octahedral in Li_xNiO₂ was descended and the stability of microstructure of Li_xNiO₂ was heightened when Co was doped into Li_xNiO₂. CoO₆ and NiO₆ were mutually stabilized in Li_xNi_0.5Co_0.5O₂ material.

Key words: Li_xNi_0.5Co_0.5O₂, cathode, density functional theory, density of state