SnO₂ And Carbon-based Composite Materials Application In Li-Ion Battery

Recent years, with the rapid development of communications and electronics industry, the attention on chemical energy storage is increasing day by day. Lithium ion batteries(LIBs) are used widely in many portable electronic devices due to its superior specific energy, excellent rate capability, low cost and environment friendly. Graphite materials are commercially used in LIBs in current with theoretical specific capacity of 372 m Ah·g-1, which limits the application of LIBs. Sn O2-based anode materials have been intensively explored by researchers owing to their high theoretical capacity(782 m Ah·g-1). However, some obstacles exist in Sn O2-based anode materials, for example, the large volume change of the Sn O2 materials often causes pulverization problem during Li-ion insertion and extraction, which leads to the rapid deterioration of the capacity.In this Paper, unique morphology( quantum dot、hollow sphere) and carbon-coated(by amorphous carbon or graphene) methods were used in order to enhance the chemical performance. The main contents are summarized as follows:(1)Graphene oxide was prepared by modified Hummer’s method, sphere tin was prepared by redox process. Then the Sn O2/graphene aerogels(Sn O2/GAs) were synthesized by controlling the density of GO and the addition of HCl using graphene oxide(GO) and Sn as the precursors. The sample was characterized by Scanning electron microscope(SEM), Nitrogen isotherm adsorption-desorption, the results indicated that interconnected 3D porous Sn O2/GAs framework were formed, Sn O2 quantum dots(~5nm)loaded on the graphene uniformly with high specific surface area of 364.04 m2·g-1(2)Then the sample was modified by electron beam irradiation with different irradiation dosages, the X-ray diffraction(XRD), Transmission Electron Microscop(TEM), Infrared(FTIR) spectroscopy tests indicated that crystallinity of irradiated Sn O2/GAs were enhanced compared to unirradiated one, meanwhile, the cycling performance of irradiated ones were better than the unirradiated one to some extents, especially for the sample irradiated at 280 k Gy.(3)We had developed a simple hydrothermal method with the help of ultrasonic wave to synthesize carbon-coated Sn O2 sphere structure successfully by using glucose as carbon source and sphere tin as template, then calcined in vacuum and air respectively. The SEM and TEM images can clearly show that amorphous carbon-coated hollow hedgehog-like micro-sphere and carbon/ Sn O2/ carbon structure. Nitrogen isotherm Adsorption-desorption revealed that the structure had high specific surface area, which might provide more active sites during Li-ion insertion and extraction. Sn was used as reactant and template at the same time, which avoided removing the template and also environment-friendly. The electrochemical testing indicated that carbon-coated Sn O2 structure can improve the performance of Sn O2 efficiently.