Study On Midification Of Graphite/Cu Composite Material For Lithium Ion Battery Cathode

Since the development of lithium ion batteries, it has attracted significant attention due to its good performances and wide applications. Its great achievement in the field of small-sized electric equipments powerfully promote the develop of lithium ion batteries by scientific researchers over the world. The birth of LiFePO4 cathode material let lithium ion batteries make an important step toward power batteries, and effectively relieve the energy supply limitation and environmental pollution. Currently, the research focusing on development and application of cathode materials is systemic and updates rapidly. Graphite is the ideal selection of anode material since its development attribute to its low built-in lithium potential, stable voltage platform and rich material sources. However, the poor charge-discharge performance in large current and cyclic performance of graphite materials made it difficult in meeting with the need of lithium ion power batteries. Therefore, it’s urgent to promote the improvement of graphite materials.In this paper, we use natural graphite materials as raw materials, coating a layer of nano-sized copper particles on the surface of graphite powder by electroless copper plating. SEM test was used to observe the morphology and particle size of surface copper particles, and the effect of copper particles on charge-discharge performance was investigated. Furthermore, based on the principles of kinetics and thermodynamics of chemical deposition, every single influence factor is optimized in the electroless copper plating process by single factor optimization method. We analyzed the relationship between parameter variation and the morphology, copper content of the composites, and discussed the impact of various parameters on electrochemical properties of the composites in detail. Meanwhile, in the case of incident self-decomposition of electroless copper plating solution, we discussed the influences of different complexing agents and additives on the quality of copper layer. The optimized electroless copper plating formulation is obtained through a series of experiments: the concentration of formaldehyde is 18 mL/L, CuSO4?5H2O is 13 g/L, EDTA?2Na is 23 g/L, potassium sodium tartrate is 12 g/L, and the pH is 12.5, the temperature is 40oC. Finally, the internal structure of the composites were analyzed. It was concluded that the surface copper particles does not cause any damage to the structure of graphite, and the composites still keep low potential and steady voltage platforms. The surface copper particles can improve the electronic conductivity, lithium ion migration rate and strengthen the structure of graphite, thus improving the charge-discharge performance and cyclic performance of composite materials.