Preparation And Electrochemical Investigation Of Si-based Composite Anode Materials For Lithium-ion Batteries

Lithium ion batteries(LIBs) are important power sources in a variety of applications, including portable electronic devices and home electronics, and their use is now being expanded to electric vehicles. It is well known that the properties of the batteries strongly depend on anode and cathode materials. Thus high capacity attracted the interest of more and more researchers. Recently, silicon has attracted considerable interest as anode material, because of its highest theoretical specific capacity of 4200 m Ah/g at room temperature, low Li-uptake voltage(0.4-0.5 V vs. Li/Li+), low cost and abundant resource. However, the huge volume change(around 300%) with lithium causes pulverization and loss of electrical contact between Si particles and conductive additives, as well as an unstable solid electrolyte interphase(SEI) layer, resulting in severe capacity fading. To overcome these problems, many pioneering works have been developed. Encapsulating the silicon in conductive coating layers is one of the most effective strategies to tackle these volume changes caused interfacial and structural instability problems of Si and to design the silicon structures. Si-based composites have attracted special attention as high-capacity anode materials in LIBs.This article uses the Si/ /Mo O2/ graphite carbon composite material as the main research object and the test of this composite electrochemical performance as anode of lithium ion battery, contents of the article are as follows:1. Experiments in proportion of Si: graphite :Mo O2=7:3:1 prepared composite, by sol-gel method in 70 ℃ water bath for synthesis, carbon content is always 10% of Mo O2. The synthesized composite was annealed at 500 ℃ for 3 hours, the composite product of Si/ graphite /Mo O2/C(SGMC). By comparing before and after coating, the effects of Mo O2/C on Si/graphite joint function.2. Experiments in proportion of Si: graphite :Mo O2=7:3:2 prepared composite material, by the same method, composite product of Si / graphite /Mo O2/C(SGMC-1). In order to explore the influence of two kinds of different ratio of the sample, X-ray diffraction(XRD), scanning electron microscope(SEM), high rate transmission electron microscope(HRTEM), cyclic voltammetry(CV) and electrochemical impedance spectroscopy(EIS) are utilized to characterize the structure, component, chemical environment and morphology of the composite.3. Results analysis. Microscaled Si/graphite/Mo O2/carbon is prepared by mechanical ball-milling Si, graphite and Mo O2 powder weight ratio of 7:3:1 from SEM and electrochemical tese.The Si/graphite surface was uniformly covered by Mo O2/carbon nanoparticles with about 100 nm in size from TEM. Electrochemical tests show that the first charge and discharge capacities are 2494 and 3460.4 m Ah/g with an initial Coulombic efficiency of 72 % at 100 m A/g.