Synthesis And Electrochemical Investigation Of Cathode Material LiNi_xMn_yCo_1-x-yO₂ For Lithium-ion Battery

Layered LiNixCo1-x-yMnyO2 compounds are considered to be one of the most promising cathode materials of lithium ion battery since they had a series of advantages like high capacity, low cost, good high-temperature stability, low pollution compared to the commonly used LiCoO2. Because of the co-effect of multi-element transition metals can put a great impact on performances of the compounds, it makes the researchers focus on effect of mixture ratio of transition metal elements. In this work, we set LiNi_xMn_yCo_1-x-yO₂ as aim materials, and works had been done to investigate the effect of synthesis conditions on structure and electrochemical performances of aim materials.Layered LiNi_xMn_yCo_1-x-yO₂ and the doped materials were prepared through solid-state reaction method. The optimum processing parameters were decided after analyzing the effect of different preparing conditions. XRD technology was used to analyzing the structure of the products. Charge-discharge test under constant current density, cyclic voltammograms and EIS were applied to investigate the electrochemical performance and reaction mechanism of samples. We had also used FTIR technology to study on the interfacial reactions between electrode and electrolyte.The results we obtained are as follow: LiNi_xMn_yCo_1-x-yO₂ prepared at 1050℃with Co content of 0.66 and Li/Me ratio of 1.1 exhibited best electrochemical properties and well-formed layer structure. The initial charge specific capacity of it is 211 mAh·g-1,the initial discharge specific capacity 189 mAh·g-1 with the coloumbic efficiency of 89.6%. After 20 cycles, it can remain 89.4% of the starting capacity. Proper F doping can stabilize the structure and improve the cycling capability of the electrode materials. The main component of the SEI layer is lithium carbonate.