Preparation of LiNi_0.5Mn_1.5O₄ as 5 V cathode materials for lithium ion battery and diffusion performance of Li⁺ in the materials

5 V cathode material LiNi_0.5M_1.5O₄ was synthesized via an oxalate co-precipitation method, and the relationship between the structure, morphology and the electrochemical performance of the material was investigated. The results show that the sample synthesized at 900°C has the best electrochemical performance. Its initial discharge capacity reaches 133.0 mA·h/g, and after cycled for 30 times, still maintains at 132.2 mA·h/g(capacity retention 99.4%). The chemical diffusion coefficient of Li⁺ ion in LiNi_0.5M_1.5O₄ cathode material was measured by potentiostatic intermittent titration technique(PITT) and electrochemical impedance spectroscopy(EIS). The chemical diffusion coefficient of Li⁺ ion ranges in 10^-10-10^-11 cm²/s.