The Research Of Ge-based Anode Materials For Lithium-ion Batteries

Lithium-ion batteries are considered to be the best energy storage devices to replace the traditional energy sources due to its high specific capacity, no pollution, long cycle life, wide operating temperature range, and no memory effect. In fact, the lithium-ion battery has been widely used in portable devices such as mobile phones, computers and digital electronic products. However, to achieve the applications of LIBs in hybrid electric vehicle (HEV) and pure electric vehicles (PEV), the demand for its power density will reach the current power density of2-5times. Graphite is currently used as commercial anode material. However, every six carbon atoms in graphite are allowed to insert one lithium atom, which corresponds to the theoretical reversible capacity is only372mAh/g. Therefore, it is an urgent to find the new anode materials with high specific capacity and high power density to replace the graphite anode.The first chapter is an overview. It describes the brief history and working principle of LIBs, and current research status about anode materials. We introduce the lithium storage mechanism of many anode materials are carbon-based materials, titanium-based materials, alloy/de-alloy materials and conversion materials.The second chapter is about the experimental analysis methods, such as X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, thermal gravimetric analysis and specific surface area measurements. It introduces the principle, the instrument composition and the applicable conditions of each test method.In the third chapter, Porous Ge@C composite was synthesized by magnesiothermic reduction reaction of GeCO2, Mg powers and glucose followed by an etching process with HCl solution. As a comparison, porous material Ge and porous composite materials Ge@C are synthesized under the same conditions. The three-dimensional porous Ge@C composite shows improved cycling performance and rate performance, which results from the synergistic effect of3D interconnected porous structure and carbon shells. The local pore could buffer the volume change and the conductive carbon shell could prevent the aggregation of Ge as well as enhance the electronic conductivity of the whole electrode.The fourth chapter summarizes the novelty and shortcomings of this thesis including the outlook for future work.