The Syntheses, Structure And Properties Of Co-compound-based/C Composite Anode Materials For Lithium-ion Batteries

On the basis of a brief summary of the investigation and application of lithium-ion batteries and a review of the investigation and development of anode materials, the thesis aimed to introduce carbonaceous material in the cobalt-based anode materials system for preparing CoOOH/C and Co3O4/C composites anode materials. Cobalt Sulphate, Potassium hydroxide and Hydrogen peroxide were used as raw materials to fabricate nanostructured CoOOH composites by a solution method. Influence of calcination temperature and carbon content were deeply studied of the synthesized materials as anode1for lithium-ion batteries.The effect and the correlation of the fabrication technique and its parameters on the structure and electrochemical properties were investigated by XRD, SEM, TEM, Raman spectrum, TG and eletrochemical testing of galvanostatic charge-discharge, CV. The key factors that influenced the cycle stability of composites and its charge-discharge mechanism were also discussed.The results of the present investigations showed that CoOOH synthesized at calcination temperature ranging from80to140℃were ultrafine and fibrous. The electrochemical performance of CoOOH was relatively good. A discharge capacity of1200mAh/g was achieved in the first cycle of pristine CoOOH. The cycle performance of the CoOOH/C promotes as the content of acetylene black increases, whereas the specific capacity decreases. The results indicates that composite with60wt.%acetylene black showed the best electrochemical performance.The CoOOH precursor was synthesized at80℃in a solution method, and after calcination at150and200℃, the main production was CoOOH. The impurity in CoOOH was gone, and the morphology kept the same as original CoOOH. The first charge-discharge capacity increases as calcination temperature rises, yet coulombic efficiency barely changes. The material calcined at150℃has better cycle performance and rate capability. The CoOOH precursor was synthesized at80℃in a solution method, and after calcination at250,300,400℃, the Co3O4materials were obtained. The obtained particles are still nanoscale. As the calcination temperature rises, first discharge cycle capacity and cycle performance first increases and then decreases. The material calcined at300℃has a high specific capacity and a good cycle performance with a cycle capacity of711mAh/g after80cycles, and the retention rate of capacity is58%.The capacity of CoOOH and CO3O4without acetylene black decreases quickly. Increasing the the content of acetylene black proves the improvement of cycle stability of the composites, but capacities reduces. The result indicates the best option is to add40wt.%acetylene black in CoOOH/C and Co3O4/C.