Synthesis And Modification Of LiNi <0.57 O ₂

Lithium-ion batteries are widely used in portable electronic equipment, because of its benefits of high energy density, small volume, long cycle life and environment friendly. More and more automotive factories begin to use the lithium-ion batteries as power battery. Thus, it is crucial to develop cheaper cathode material with higher energy density. However, LiNi_0.5Mn_0.5O₂ material has a layered structure similar as LiCoC2, and doesn’t contain Co element, which is harmful to the environment. And, it has advantages of high discharge voltage and theory capacity, and long cycle life. It is a possible alternative to LiCoO₂ for advanced lithium-ion batteries.Ni_0.5Mn_0.5（HO）₂ was synthesized by co-precipitation method. And the effects of ammonia, reaction time, aging time and feed rate to the morphology of precursor were studied. From the SEM test, the results indicate that ammonia has play an important role in morphology of the precursor compared to other factors.LiNi_0.5Mn_0.5O₂ powders were synthesized by mixing LiOH·H₂O and the co-precipitated hydroxide under different calcination conditions. The results imply that the temperature to synthesis layered LiNi_0.5Mn_0.5O₂ phase is no lower than 750 ℃, and samples prepared at 850 ℃ is the better than other samples. Moreover, it is found that the samples prepared at higher temperature have larger particle size with better crystallinity, and unvaried Li/Ni disorder. There will be a balance between the particle size and crystallinity to get a well behaved sample. In addition, the lithium-ion coefficient of diffusion was calculated, and the results suggest that it increase with the increase content of lithium-ion contained in the material.LiNi_0.5Mn_0.5-xCo_xO₂ were prepared at 850 ℃ by co-precipitation method. The structure, morphology and electrochemical performance of Co doped samples were investigated. The results show that the samples become more stable and better to form layered structure with Co3+in the transition metal layer, furthermore, Co doped samples seems have a better electrochemical performance than LiNi_0.5Mn_0.5O₂.