Synthesis And Electrochemical Characterization Of Composite Lithium-Ion Cathode Material

The lithium-ion battery is a new type storage battery which is based on the research of the lithium battery. Comparing with the traditional battery, lithium battery has good characteristic such as the high voltage and the steady discharge. So the investigation of the lithium-ion battery has very important practical significance. There are a lot of cathode materials in process of researching at present including LiCoO₂ LiNiO₂ LiMn₂O₄ and so on. But all these unitary cathode materials have advantage and disadvantage respectively. The research in recent years discovers some new-style composite cathode material which is samdwich and comprising nickel cobalt and manganese. Their outstanding performance is of high electrochemical capacity and good cycle performance. So they have great potential to develop. For these reasons, some research about these aspects is still underdone.In this work, the precursors of lithium-ion battery cathode materials were synthesized successfully by the coprecipitation method. The optimal synthetic conditions and its effects of synthetic condition on the structure and property of the samples were discussed. The experimental results indicated that the process conditions including the raw material precipitator pH value and temperature are important for the preparation of the precursor. And the optimum conditions for synthesizing Ni_1/3CO_1/3Mn_1/3C₂O₄ as follows: (NH₄)₂C₂O₄ as precipitator pH 7.0 the temperature at 55℃-60℃and the mixing time over half-hour. The results showed that the content of the nickel cobalt and manganese was equal in the oxalate precursor and the power possesses uniform particle size. The precipitator was NaHCO₃ and the pH value was 8.0 in the Ni_1/3CO_1/3Mn_1/3CO₃ synthesizing process. Other conditions were similar with the oxalate synthesis.The lithium-ion battery cathode material LiCo_1/3Ni_1/3Mn_1/3O₂ was made by sintering the precursor. The effects of conditions such as the different sintering temperatures and time on the structure and property of the compound production were assessed. The structure and electrochemical properties of the samples were characterized by ICP-AES XRD SEM and electrochemical experiments. The material states of Ni Co and Mn in the cathode materials were confirmed as+2+3 and +4 respectively. Electrochemical performance results indicated that the LiNi_1/3CO_1/3Mn_1/3O₂ made by the Ni_1/3Co_1/3Mn_1/3C₂O₄ and Ni_1/3Co_1/3Mn_1/3CO₃ both had the good electrochemical capability and cycling property. The first discharge capacities were 146.0mAh·g^-1 and 159.2mAh·g^-1.They only reduced 2.4% and 9.6% after 20 cycles respectively. Finally the system analysis for the synthesizing techniques of the lithium-ion battery cathode material was given. This could provide some theoretical instructions for optimizing the material capability and industrial production.