Efficient Preparation And Performarce Research Of Metal Nano Germanium

Germanium materials is an important semiconductor material in modern technology and industry.It is widely used in transistors,optical fibers and infrared optical devices.Related nano materials of germanium have many excellent properties and have promising application prospects in the fields of photoelectronic devices,catalysis,biomedical materials and so on.With the development of technology and society,lithium-ion batteries have been widely used in human society,and there is a huge demand for the performance and the product supply of lithium-ion batteries However,in current commercial lithium-ion batteries,carbonaceous materials are mainly used as the anode materials.The low theoretical specific capacity of carbon,which is only 372 mAh·g-1,greatly limits the capacity of lithium-ion batteries.In the research of new high-capacity lithium-ion battery anode materials,germanium materials have received widespread attentions.Germanium has a theoretical specific capacity only next to silicon,which is about 1600 mAh·g-1.At the same time,germanium has higher conductivity and lithium-ion diffusion coefficient,which is very suitable as an anode material for high-rate power batteries.In the research of germanium anode materials,nano-germanium materials,represented by germanium nano-particles(0-Dimcnsion),germanium nano-wires(1-Dimension),germanium nano-films(2-Dimension)and nano-porous geranium(3-Dimension),show excellent capacity and cyclic stability.However,in the existing methods for preparing nano-germanium materials,the large-scale preparation of nano-germanium materials is still a serious subject.The published methods for preparing nano-germanium materials can be roughly divided into two kinds of methods:physical methods that use elemental germanium and chemical methods that use germanium compounds.The physical methods are not conducive to the large-scale preparation of nano-germanium materials as they require large equipment and complicated processes.Many reported chemical methods,although more practical than physical methods,often require complex conditions such as high-temperature heating,strong reducing agents and harmful organic reagents,that are still far from large-scale preparation.Exploring the economical,efficient,and safe preparation method of nano-germanium materials is still a long and arduous task.In this thesis,the simple preparation of nano-germanium materials was innovatively achieved by decomposing the ternary intermetallic compound precursor LiZnGe at room temperature.The preparation process has the characteristics of high efficiency,low cost,safety and environment friendly,and is especially suitable for large-scale batch preparation of nano-germanium materials.In this thesis,the mechanism of preparing nano-germanium materials from LiZnGe is studied in depth.It can be described as:using the crystalline structure of ternary intermetallic compound LiZnGe to achieve the homogeneous distribution of Ge and Zn elements that are originally immiscible to each other;under the action of external oxygen and water vapour,LiZnGe is reacted with the strongest metallic element Li to form a compound,which is separated from the crystalline structure of LiZnGe,leading to the collapse of the LiZnGe crystalline structure;during the collapse of the crystalline structure,the immiscible Ge atoms and Zn atoms undergo atomic diffusion to form Ge crystals and Zn crystals;since that atomic diffusion occurs at room temperature,the resulting Ge crystals and Zn crystals have extremely small crystalline sizes.In this thesis,using that mechanism,porous nano-germanium materials with mesopore size were prepared by dry or wet mechanical ball milling and buffer solution.In this thesis,the prepared nano-germanium materials are used to make half-cells,and their electrochemical performance and lithium-ion battery performance are tested.In the constant current charge-discharge cycle texting,the prepared nano-germanium materials in this thesis show extremely high charge-discharge specific capacity,and their high specific capacities keep stable during the long charge-discharge cycles.The rate tests on the prepared nano-germanium materials show that these materials have excellent rate performance.