Synthesis And Electrochemical Performance Of LiVO₃Cathode Materials For Lithium Ion Batteries

Among vanadium derivatives, LiVO3compound is a promising candidate as a lithium ion battery cathode material, it worth researching for its high specific capacity, easy synthesis and low cost. In this research work, we have synthesized this compound by solid-state reaction method and oxalic-assisted combustion method. We have compared the characteristics and electrochemical performances of the materials synthesized under different condition. The main research contents are shown as follows:(1) We synthesized LiVO3compounds by solid-state reaction method. For the samples synthesized by calcination after ball-milling, we compared the performance of the materials synthesized under different temperatures. As a result, the pure compound can be synthesized at a relatively low temperature of350℃, it delivered the highest initial discharge capacity and had good cycling performance and rate performance. It also had the lowest resistance in the AC impedance test, which means it had low polarization. The chemical diffusion coefficient of lithium ions in the electrode was calculated by galvanostatic intermittent titration technique (GITT), the result was in the range of10-9.5-10-8cm2s-1, which indicate a good dynamic characteristic and was in accordance with the good electrochemical performances. As for the samples synthesized by calcination after oxalic acid assisted grinding, the pure compound should be synthesized under a higher temperature of450℃, and its performance was inferior to the best ball-milling samples. But if under the same calcination temperature, its performance was better, and this mixing method is simple, so in the follow experiment we will still use this mixing method.(2) Then we synthesized LiVO3compound by oxalic acid assisted combustion method. Oxalic acid not only played a role of fuel, but also can promote the mixture of the reactants. Comparing the samples synthesized under different calcination time, we could conclude that CS-2h which calcined for2h had the best performances, delivering a high discharge capacity of298.4mAh g-1and262.5mAh g-1between1.0and3.5V at a current density of50mA g-1and mA g-1，respectively, and exhibiting good cyclic stability. It also had low resistance which indicates low polarization. The chemical diffusion coefficient of lithium ions in the LiVO3electrode was calculated by electrochemical impedance spectroscopy (EIS) and galvanostatic intermittent titration technique (GITT). We also pay attention to the influence of the dosage of reactants on the material. The experiment data indicate that when the molar ration of fuel with the metal ions was2:2, the compound had batter morphology and electrochemical performances.