Silicon-based anode materials are regarded as one of the alternative products of the existing commercial carbon anode materials. However, they cannot be commercialized due to the large volume effect in the charge and discharge process. For this reason, researchers have carried out a large number of modification studies. .

　　Silicon-based anode materials are regarded as one of the alternative products of the existing commercial carbon anode materials. However, they cannot be commercialized due to the large volume effect in the charge and discharge process. For this reason, researchers have carried out a large number of modification studies. . Based on two aspects of theoretical research and experimental research, summarize the research progress of silicon-based anode materials, hoping to promote the research of new alloy anode materials.　　 The rapid development of the field of new energy power generation in recent years has put forward new requirements for the matching energy storage system. In the replacement of energy storage batteries, lithium-ion batteries have become a key research area due to their various advantages, and have been practically applied in a large number of energy storage projects, and have achieved certain results. The capacity of a lithium ion battery is determined by the active lithium ion of the positive electrode material and the ability of the negative electrode material to insert and release lithium. The stability of the positive and negative electrodes in various environments determines the performance of the battery, and even seriously affects the safety of the battery. , The performance of the electrode determines the overall performance of the lithium-ion battery to a certain extent.　　 However, the current commercial lithium-ion battery anode materials are mainly graphite-based carbon anode materials with a theoretical specific capacity of only 372mAh/g (LiC6), which severely limits the further development of lithium-ion batteries. Silicon-based materials are the research system with the highest theoretical specific capacity in the research of anode materials. The alloy formed is LixSi (x=0～4.4), and the theoretical specific capacity is as high as 4200mAh/g, due to its low lithium insertion potential and low atomic mass , High energy density and high Li mole fraction in Li-Si alloys are considered as alternative products for carbon anode materials. However, the silicon negative electrode has serious volume expansion and contraction during the lithium insertion and desorption cycle, which causes the destruction of the material structure and mechanical pulverization, resulting in the electrode showing poor cycle performance.　　In recent years, researchers have carried out a large number of modification studies on silicon-based anode materials and have made certain progress. Based on theoretical research and experimental research, this paper summarizes the current research methods and research methods of silicon-based anode materials at home and abroad, hoping to promote the research of new alloy anode materials.　　1 Theoretical research　　 When currently researchers choose a research system, they mainly choose some systems to try based on existing relevant experience, which takes a long time, wastes resources, and is inefficient. Due to the large number of candidate systems and the uncertainty of the synthesis process, the development of new alloy anode materials based on experimental research has been slow. In recent years, through theoretical simulation methods, the structure and performance of materials have been predicted, so as to optimize the research objects and develop new materials in a targeted manner. This kind of research method that combines theoretical research and experimental research has been obtained more and more. The attention of researchers. The current theoretical research on silicon-based anode materials is mainly based on the simulation research of density functional theory. The software used is mainly MaterialsStudio developed by the American Accelrys company, which contains a large number of program modules, which are used for simulation of alloy materials. CASTEP module, CASTEP module is an advanced program module based on solid-state physics and quantum physics developed on MaterialsStudio. Its theoretical basis is charge density functional theory (DFT), and local charge density approximation (LDA) or generalized gradient can be selected. Approximate (GGA).

　　According to ICSD2009 (ICSD#29287), the crystal lattice structure of silicon belongs to the cubic crystal system, the space group type is Fd-3ms, and the space group number is 227. The schematic diagram of the lattice structure is shown in Figure 1, where the lattice constant a=b= c=0.543071nm, the edge angle a=b=g=90°. During the charging process, lithium ions from the positive electrode material are inserted into the gap positions of the host material under the action of the electrolyte.　　Hou et al. studied the lithium insertion and release mechanism of Li-Si alloy as a negative electrode material for lithium-ion batteries based on the first-principles plane wave pseudopotential method. Studies have shown that the first irreversible capacity loss of Si comes from the formation of the SEI film and the lithium-poor phase Li12Si7, which is difficult to dealloy.　　 Chou et al. conducted a first-principles study on the silicon interface after lithium intercalation and the behavior of lithium intercalation. The results show that when the concentration of lithium ions is low, the slightly lithium-rich Li-Si alloy interface is in a relatively stable state. As the concentration of lithium ions increases, in addition to the outermost Si-Si bond, the structure near the surface and The composition becomes similar to that of the host material; the influence of the interface on the material is mainly the first two atomic layers. The transport of lithium ions is related to the alloy composition, and the diffusion coefficient of lithium ions increases geometrically in the advanced lithium insertion stage.　　Rahaman et al. conducted a first-principle study on the influence of the ratio of oxygen in silicon oxide on the structure and electronic properties. The results showed that the oxygen atoms reacted violently with the intercalated lithium ions, leading to the decomposition of the host material. The high concentration of oxygen atoms can suppress the volume expansion of silicon during charging and discharging, and help to suppress the material pulverization failure caused by the volume effect. The increase in oxygen content can increase the lithium insertion capacity of the silicon oxide negative electrode, but it can lead to the formation of lithium silicate, which is difficult to dealloy, thereby introducing irreversible capacity loss. 2 Experimental research 2.1 Modification of silicon Modification of elemental silicon is mainly done by adding the second component to form Si-M alloys, reducing the volume expansion coefficient of silicon alloys, or making silicon porous and nano-sized through various engineering techniques , Reserve space for the volume expansion of silicon and reduce the influence of silicon volume effect on the cycle stability of the material.　　2.1.1 Alloying of silicon 　　The biggest obstacle affecting the commercialization of silicon anode materials is the material pulverization failure caused by the large volume effect of silicon in the charge and discharge process. Experiments have shown that the introduction of the second component to form the "Si-M" active-active or active-inactive system can effectively reduce the volume expansion coefficient of silicon, and take advantage of some of the characteristics of the active element or the inactive element itself, such as metal ductility and chemical properties. Bond characteristics, etc., alleviate the volume effect of silicon in the process of lithium insertion and removal.　　Lee et al. put silicon powder on the surface of a copper substrate and heated it to 2000°C under vacuum to form a Si-Cu alloy thin-film anode material with Cu as the substrate and gradually transitioning from the copper-rich state to the Si-rich state from bottom to top. The half-cell test shows that after 100 cycles of cycles, the mass specific capacity of the film sample is 1250 mAh/g, and the area specific capacity is 1956 mAh/cm3. However, excessive Cu leads to the presence of partially crystalline silicon, which makes the cycle stability of the sample relatively poor.webcam factory

　　 Yang Juan et al. used a combination of mechanical ball milling and annealing to prepare Si-Fe composite anode materials, and used the good electrical conductivity and ductility of Si-Fe alloys to improve the cycle performance of Si. The results show that the experimentally processed materials are partially alloyed, and different forms of Si-Fe alloy phases are formed, but the degree of alloying is not complete. The formation of Si-Fe alloy improves the cycle performance of Si as a negative electrode material for lithium-ion batteries, and the higher the degree of alloying, the better the electrochemical performance of the alloy material. Zhang et al. used a combination of chemical corrosion, electrochemical reduction and magnetron sputtering to prepare a three-dimensional nanostructured multilayer Si/Al thin film anode material. The sample showed good electrochemical performance, and the discharge rate was 4.2A/g. Under current density, the reversible specific capacity is 1015mAh/g after 120 cycles of cycles. Even if the discharge current is increased to 10A/g, the reversible specific capacity still reaches 919mAh/g. The improvement of electrochemical performance is mainly attributed to the effective distribution of three-dimensional nanostructures. 2.1.2 Porosity of silicon The porosity of silicon can increase the specific surface area of the main silicon material in contact with the electrolyte, improve the transport efficiency of lithium ions into the material, and enhance the conductivity of the material. On the other hand, it can be used for silicon. The volume expansion that may exist during the charging and discharging process reserves space to reduce the influence of the silicon volume effect on the pole piece. Porosity of silicon has been widely regarded as an effective means to solve the volume effect of silicon. Figure 2 shows the SEM topography of porous silicon.