Research On Lithium Storage Property Of Metallic Silicon-graphite Composites For Lithium-ion Batteries

In this paper, lithium-ion battery anode electrode on the basis of the charge and discharge performance of pure silicon and different impurities of metallic silicon., put forward with the metallic silicon as the substrate material of anode material. First the different impurities content of metallic silicon mixed with different components of graphite, and then will be of the same material by mechanical alloying(MA) method for composite. Using X-ray diffraction analyzer, scanning electron microscopy(sem) analysis the crystal structure and surface morphology of the material and tested the charge-discharge cycle property by battery testing system tested dynamic analysis lithium storage used electrochemical workstation.Through the experimental data show that metallic silicon loop performance is better than the pure silicon but impurity content is not the more the better, too much impurity will hinder the lithium storage properties of metallic silicon. For the different impurities content of metallic silicon, the excellent ratio of graphite is different. The lithiation/delithiation does not fully reflect of metallic silicon. The simple mix of graphite can’t solve the problem.Further research shows that ball mill can make material grain refinement, the good refine material with serious phenomenon of reunion. After ball mill of metallic silicon-graphite composite materials, silicon phase will abate or disappear and produce the phase of silicon-carbon compound. The higher of the impurities content, the more species peak of silicon-carbon compounds. And the less of impurities, compounds shows the greater peak intensity of silicon-carbon. After the ball mill capacity and cycle performance of materials have greatly improved. And in the same metallic silicon, the increase of graphite makes the capacity and keep ability of the materials are improved; different content impurities of metallic silicon, the cycle performance of high purity material is preferred.Dynamic analysis for the composite material after the ball mill finds the higher impurities content of metallic silicon, the smaller the internal resistance of lithiation but the resilience of volume effect is weaker. And the internal resistance is reduce of lithiation/delithiation with the graphite content increases. With the increase of the cycle, the separation of silicon-carbon composite and silicon has become the main reaction.