CN112978730A

CN112978730A - Preparation method of silicon-carbon alkene material and preparation method of electrode active material of silicon-carbon alkene material

Info

Publication number: CN112978730A
Application number: CN202110219245.3A
Authority: CN
Inventors: 范例; 张洪涛; 范霄杰; 范毂豪; 张泽森
Original assignee: Wuhan Chuneng Electronic Co ltd
Current assignee: Wuhan Chuneng Electronic Co ltd
Priority date: 2021-02-26
Filing date: 2021-02-26
Publication date: 2021-06-18
Anticipated expiration: 2041-02-26
Also published as: CN112978730B

Abstract

In order to improve the yield of the silicon carbide, when a carbon atom ring grows, a silicon monoatomic layer grows in a combined mode or a carbon monoatomic layer grows on the silicon ring layer, and a silicon carbide crystal is formed. The technology utilizes an improved plasma reaction cavity and a magnetron sputtering method to directly carry out heat treatment at 800-1300 ℃ in the reaction process, and when graphene crystal nucleus is formed in heating time, the graphene crystal nucleus and silicon crystal nucleus are subjected to self-assembly growth to form a three-layer structure with a silicon atomic layer and a carbon atomic layer, and a large silicon carbide unit layer, also called silicon carbene, is grown. The high-purity silicon-carbon alkene grown in a large scale has high specific energy and stable cycle characteristics when being used as an electrode active material of a lithium-sodium alloy rechargeable battery. The invention also provides a preparation method of the silicon-carbon alkene electrode active material. The silicon-carbon alkene electrode active material has high specific energy and stable cycle characteristics, and can improve the energy density and the power density of a lithium-sodium rechargeable battery.

Description

Preparation method of silicon-carbon alkene material and preparation method of electrode active material of silicon-carbon alkene material

Technical Field

The invention belongs to the technical field of rechargeable batteries, and particularly relates to a preparation method of a high-specific-energy long-life stable electrode active material, namely a silicon-carbon-olefin material, of a rechargeable battery and a preparation method of the silicon-carbon-olefin material applied to the electrode active material of the rechargeable battery.

Background

At present, lithium ion batteries are mainly iron phosphate lithium batteries and ternary positive electrode material batteries. The former needs phosphorus element, if the phosphorus amount for the battery is large according to the rapid increase trend of the electric automobile, the phosphorus element is in competition with the agricultural chemical fertilizer for phosphorus. Phosphorus is a non-renewable resource and is indispensable for animals and plants. Once phosphorus is used according to the current trend, the earth is under a phosphorus deficiency condition after 80 years. It will be disastrous to human beings and animals and plants. And the ternary positive electrode material battery can cause heavy metal pollution. The ternary positive material battery has an autoignition phenomenon of unknown reason and is exposed by frequency. Therefore, development of an environmentally friendly and pollution-free battery is required.

The lithium ion battery has high energy, but lithium resources are relatively short, sodium is abundant and cheap, the theoretical specific capacity of the sodium is 1166mAh/g, the electrode potential is Na/Na +, -2.71V; sodium metal batteries are gaining importance as a viable rechargeable battery. The sodium metal battery is a rechargeable battery in which sodium metal is used as a negative electrode, a counter electrode made of other materials, and a lithium/sodium ion-containing electrolyte conducting medium. Sodium metal does not resist oxidation, while lithium/sodium alloys have better resistance to oxidation, and lithium/sodium alloys are eutectic alloys. Sodium metal can ignite and explode when it encounters water, whereas lithium/sodium (or lithium-sodium) alloys do not. The use of a lithium/sodium alloy greatly reduces the amount of lithium used without causing a reduction in capacity. As the three-dimensional crystal lattice of the silicon carbide is very hard, the silicon carbide is not easy to prop open an ion channel, and lithium ions cannot be stored in a large scale. Conventional wisdom holds that nano-sized silicon carbide is also not effective in storing sodium ions due to their large diameter. However, no exact experimental support has been given to what limit is reached when sodium ions cannot be stored. Sodium ions and carbon atoms form carbon-sodium alloys, and few studies have been made on the formation of sodium-silicon complexes by sodium ions and silicon atoms. Experiments have shown that silicon can efficiently form sodium-silicon compounds. For the silicon atom which is effectively bonded or stores the sodium ions, the direct silicon atom dangling bond is given, so that the sodium ions can effectively form metal compounds, the sodium ions can be directly stored in a large scale, and the silicon carbide unit layer can form a wide sodium ion storage space due to one bond suspension in the polar covalent bonds of the chemical bonds.

The silicon carbene is a two-dimensional crystal formed by orderly arranging unit layers of silicon carbide (cubic lattice or hexagonal lattice or other polytype lattices) stacked by silicon atoms and carbon atoms along a one-dimensional direction, and the silicon atoms and the carbon atoms are connected by polar covalent bonds. Three stacking modes are arranged between silicon atoms and carbon atoms, and the structure is similar to a polytype of silicon carbide, wherein the structure is more in a cubic polytype crystal lattice (beta-SiC) and a hexagonal polytype (alpha-SiC, including polytypes of 4H,6H, 15R and the like), and the physical property is stable.

Silicon carbenes can be used for lithium ion battery active materials, however, high temperatures are required for synthesizing silicon carbene, and therefore, it is necessary to develop a battery active material having properties similar to silicon carbide in a relatively low temperature process for use in a lithium ion battery electrode, silicon carbene being such a material.

Silicon carbenes are distinguished from silicon carbide in that, in general, silicon carbide crystals are formed by periodically stacking unit layers of silicon atomic layers and carbon atomic layers bonded together in and between layers with polar covalent bonds — sp3 hybridized bonds in three dimensions with each other to form crystals, each hybridized sp3 bond of each unit layer at the surface terminating in a dangling bond; the silicon-carbon alkene is formed by combining a silicon atomic layer and a carbon atomic layer in the layers and between the layers by polar covalent bonds-sp 3 hybrid bonds, only three crystal structures of three layers of silicon atoms and carbon atomic layers are formed, and the surface is terminated by a dangling bond of one sp3 hybrid bond. Can be classified into three forms of Si-C-Si, Si-C and C-Si-C.

Although silicon-carbon-ene can be viewed as a single layer of silicon carbide, it differs greatly in properties from silicon carbide crystals. One is that the band gap is narrowed, and the dangling bond in the covalent bond tends to weaken the covalent bond due to the deformation of the sp3 hybridized orbitals of the silicon atom and the carbon atom; secondly, the crystal growing along the layer has stronger toughness and can generate larger expansion space; the silicon carbene has smaller pore diameter inside and stronger optical characteristics.

The prior art has the problems that a silicon atomic layer is directly grown on graphene by adopting enhanced plasma combined with femtosecond strong laser, a static magnetic field and a bias technology or silicon graphene is directly grown by using graphene and silicon graphene, so that the formation of sp3 hybrid bonds is difficult and the yield is very low.

Disclosure of Invention

Aiming at the problems in the prior art, the invention aims to provide a preparation method of a silicon-carbon alkene material. In order to improve the yield of the silicon carbide, when a carbon atom ring grows, a silicon monoatomic layer grows in a combined mode or the carbon monoatomic layer grows on a silicon ring layer, and a silicon carbide crystal is formed. The technology utilizes an improved plasma reaction cavity and a magnetron sputtering method to directly carry out heat treatment at 800-1300 ℃ in the reaction process, and when graphene crystal nuclei are formed in heating time, the graphene crystal nuclei and the silicon crystal nuclei are self-assembled to grow a three-layer structure with a silicon atomic layer and a carbon atomic layer, and a large silicon carbide unit layer, also called silicon carbene, is grown. The high-purity silicon-carbon alkene grown in a large scale has high specific energy and stable cycle characteristics as an electrode active material of a lithium rechargeable battery. The invention also provides a preparation method for preparing the electrode active material by adopting the silicon-carbon alkene material.

In order to achieve the technical purpose, the technical scheme adopted by the invention is as follows:

a preparation method of a silicon-carbon alkene material is characterized by comprising the following steps: the preparation method comprises the following steps:

(1) weighing pure graphite, doping gallium metal powder, pouring into an acetone solution in a vacuum stirrer, uniformly stirring, and sealing and stirring for 24 hours; after stirring, extracting acetone to volatilize part of the acetone, pressing the wet powder into a graphite boat which is used as a target material, putting the sample boat into a stainless steel shell reaction chamber, wherein the reaction chamber is provided with a reactant nozzle for generating high-hydrogen diluted silane gas and is positioned in the center right above the reaction chamber, and the nozzle is 20cm away from the center of the bottom of the reaction chamber; a radio frequency magnetron sputtering gas nozzle with an included angle theta of 89-60 with the horizontal plane is arranged at the position 10cm away from the center of the top of the reaction chamber and is parallel to the directions of cathode and anode electric fields of the reaction chamber, a strong electric field is formed between the sample base and the inert gas nozzle, and a voltage of 2000-20000V is applied between the sample base and the inert gas nozzle;

(2) vacuumizing to 10 deg.C^-4mTorr；

(3) Heating the sample boat to 1200-1500 ℃;

(4) starting inert gas high-purity argon gas injection, aligning to a target material in a sample boat, keeping the sputtering power at 90-200W and the working pressure at 0.5-2mTorr, simultaneously, opening a plasma generation switch, and starting high-hydrogen diluted silane, wherein the volume of silane is as follows: injecting hydrogen with the volume of 1:20 into a reaction chamber, converging sputtered graphene quantum dot gas in an emergent space with the surface of a target material being 10-200 nm, starting a femtosecond laser, aiming at a product generated by argon sputtering graphite in a sample boat, namely a graphene crystal nucleus or a mixture of quantum dots and silane plasma diluted by high hydrogen to bombard the mixture of the graphene quantum well crystal nucleus or the quantum dots and silane plasma diluted by high hydrogen;

(5) starting a high-frequency bias voltage in the reaction chamber to 2000 Hz-100 MHz, and superposing the high-frequency bias voltage to a 1-15 Tesla superconducting static magnetic field;

(6) the graphene quantum dots and the high-hydrogen diluted silane plasma form violent collision between crystal nuclei, and are radiated and energized by a laser gun, wherein gallium is used as a catalyst, so that three layers of silicon carbene with a large silicon carbide unit layer, two silicon atom layers and a carbon atom layer, or two silicon atom layers and a silicon atom layer are generated, and the reaction lasts for 20-50 minutes;

(7) sequentially turning off a laser power supply, a high-purity argon switch power supply, a plasma power supply and a high-hydrogen diluted silane switch, and continuously heating the sample for 20 minutes;

(8) turning off the heating power supply; naturally cooling the sample chamber to the equal room temperature, opening the reaction chamber, taking out the sample boat, and collecting the product at the bottom of the reaction chamber; obtaining the nano-scale silicon carbide powder. The silicon carbide partial typical diffraction peak is obtained through the analysis of an x-ray diffraction spectrum. Proving to be a silicon carbide structure. The high-resolution transmission electron microscope morphology image observation shows that the silicon carbide film is a laminated structure, the thickness of the silicon carbide film is different from 0.38nm to 5nm, and the silicon carbide film is a silicon carbide unit layer. X-ray diffraction analysis of five other solid phase peaks indicated that the product was a pure layer of silicon carbide units or was referred to as silicon carbene, also referred to as silicon carbide.

The invention also discloses a silicon-carbon alkene prepared by the method, which is characterized in that the silicon-carbon alkene has three basic structures, one silicon atom layer and one carbon atom layer are connected by a silicon carbide bond, and after the hybridization of a Si-C bond sp3, two sides of the silicon atom and the carbon atom layer respectively form dangling bonds; the second structure is that a silicon atom layer is sandwiched by two carbon atom layers, wherein Si-C atoms form sp3 hybridization, and a dangling bond is one bond of carbon atoms; the third is that a layer of carbon atoms is sandwiched by two layers of silicon atoms, and sp3 hybridization is formed between Si-C atoms of the carbon atoms, and the three can be regarded as a unit layer of silicon carbide; the crystal chemical formula of silicon carbide is represented as SiC; the first structure of the above-mentioned silicon-carbon alkene should have a chemical formula of SiC, and the second structure should be Si_1-xC_x，0.5<x<1; the third chemical structural formula is Si_xC_1-x，0.5<x<1。

Also provided is a preparation method of the second silicon-carbon alkene material, which is characterized by comprising the following steps:

(1) weighing pure silicon alkene, mixing with gallium metal powder, pressing into a cake shape, putting the cake into a graphite boat, putting the sample boat into a stainless steel shell reaction chamber, wherein the reaction chamber is provided with a reactant nozzle for generating high-hydrogen diluted methane gas and is positioned in the center right above the reaction chamber, and the chamber generates enhanced plasma, and the distance between the nozzle and the center of the bottom of the reaction chamber is 20 cm; a magnetron sputtering inert gas spray gun opening is arranged at the position 5-10 cm away from the center of the top, and the silylene target material aligned to the center of the sample boat can be adjusted;

(2) vacuumizing to 10 deg.C^-3mTorr；

(3) Heating the sample boat to 1000-1200 ℃;

(4) opening an inert gas high-purity argon spray gun to inject argon, aligning to a target material in a sample boat, keeping the sputtering power at 90-200W and the working pressure at 0.1-1mTorr, generating a silylene crystal nucleus or silylene quantum dot, opening a plasma generation switch, and opening high-hydrogen diluted methane to inject into a reaction chamber, wherein the volume of methane is as follows: starting a femtosecond laser, wherein the femtosecond laser is aligned to the generated silylene crystal nucleus product in the sample boat and bombards the silylene crystal nucleus or the quantum dot product;

(5) starting a high-frequency bias voltage in the reaction chamber to 1000-2000 Hz and 1000-15000V, and superposing the high-frequency bias voltage to a 6Ho static magnetic field;

(6) the reactants in the reaction chamber are subjected to carbon atom nucleation and aggregation and form bonds with carbon atoms of the silylene crystal nucleus to generate sheet silylene, and the reaction is carried out for 30-60 minutes;

(7) sequentially turning off a laser power supply, a magnetron sputtering power supply, a plasma power supply and a high-hydrogen diluted methane switch, and continuously heating the sample for 20 minutes;

(8) turning off the heating power supply; naturally cooling the sample chamber to the equal room temperature, opening the reaction chamber, taking out the sample boat, and collecting the product at the bottom of the reaction chamber; obtaining the nano-scale layered silicon carbide powder.

The invention also provides a method for manufacturing an electrode by using the silicon-carbon alkene material, which is characterized by comprising the following steps of:

(1) weighing a silicon-carbon alkene sample, PVDF and a graphene conductive agent, wherein the weight percentages of the PVDF and the graphene conductive agent are (80-90): (10-5): (10-5) placing the mixture into a stainless steel stirrer;

(2) adding nmp with certain amount into the sample of the stirrer, and stirring uniformly in a vacuum stirrer for 72 hours;

(3) taking out, and coating on the foamed nickel;

(4) putting the foamed nickel into a central control drying oven, drying for 72 hours at 120 ℃, and cooling to room temperature;

(5) taking out the foamed nickel coated with the silicon carbene sample, and pressing the foamed nickel into a sheet shape on a roll press to prepare a plurality of CR2025 electrode plates; assembling the plurality of electrode plates into a button cell, wherein the counter electrode is a lithium plate, a diaphragm is additionally arranged, and lithium ion electrolyte, ethyl carbonate containing LiPF6, is filled in the lithium plate; and sealing the opening to manufacture a plurality of CR2025 button cells.

The invention also provides a preparation method of the silicon-carbon alkene electrode active material, which is characterized by comprising the following steps:

(1) according to the molar ratio of the compounds (1-1.5): (1-2): (4-6): (7-9) matching polysiloxane, sodium acetylene, starch and absolute ethyl alcohol, and weighing corresponding compounds and organic matters;

(2) putting the weighed material components into a beaker; stirring for 12 hours by a mechanical stirrer, and forming a transparent sol after the mixture is uniform;

(3) drying the sample at 160-200 ℃ for 10 hours to obtain white powder;

(4) the compound is prepared from the following components in a molar ratio of (7-10): (7-10): (1-2): (1-3): (0.5-1), respectively weighing micron-sized sorghum micropowder, sodium ethoxide, ferrocene, 1, 2-dimethyl-1, 2-diphenyldisilene, urushiol lanthanum formal polymer and dialkyl sodium sulfonate, putting the materials into a second beaker, adding deionized water, and stirring and mixing the materials into a colloid by using a mechanical stirrer; putting the colloid into a vacuum drying oven, and heating the colloid into a gel state at 120-200 ℃ to obtain yellow powder;

(5) mixing the two gel powders in the two beakers, and stirring for 12 hours by using a mechanical pump to obtain mixed uniform pale yellow powder;

(6) putting the obtained gel into a crucible, putting the crucible into a vacuum atmosphere reaction furnace, and vacuumizing to ensure that the vacuum degree of the atmosphere reaction furnace reaches 1-3 Pa;

(7) filling argon into the atmosphere reaction furnace to enable the pressure in the furnace to reach 3-2.1 MPa;

(8) the atmosphere sintering furnace is heated at a temperature rise speed of 20-30 ℃/min until the temperature reaches 800-1300 ℃. Sintering for 1-3 hours at the temperature;

(9) and cooling to room temperature to obtain the silicon carbene electrode material.

Further, the silicon-carbon alkene is layered and curls into a spiral cylinder shape, and the thickness is between 0.6nm and 5.7 nm; the chemical composition of the generator is that the atomic weight percentage of the silicon element is 43-59%, the atomic weight percentage of the carbon element is 40.2-56%, and the atomic weight percentage of the metal element is 0.8-1%; the product is solid phase component, and the weight percentage value of the product is 90-100% of silicon-carbon alkene and 0-10% of silicon alkene phase.

The invention also provides a method for preparing a battery by adopting the silicon-carbon alkene electrode material, which is characterized in that the prepared silicon-carbon alkene electrode active material is added with a conductive agent and a binder PVDF, and the ratio of silicon-carbon alkene: conductive agent carbon black: 60 weight percent of PVDF: 20: 20, adding NMP to dissolve the mixture into a colloid, uniformly stirring, coating the colloid on a current collector copper foil, putting the current collector copper foil into a vacuum drying oven, drying the current collector copper foil for 18 hours at 170 ℃, taking out the current collector copper foil, and pressing the current collector copper foil into a sheet under the pressure of 1 MPa. The cathode sheet is cut into R2025 round sheets, and the round sheets, the counter electrode lithium sheet and the diaphragm are combined together, and electrolyte is added to assemble the button cell.

Compared with the prior art, the scheme provided by the invention has the following beneficial effects:

1. according to the preparation method of the silicon-carbon alkene material, the improved plasma reaction cavity and the magnetron sputtering method are utilized to directly carry out heat treatment at 800-1300 ℃ in the reaction process, and when graphene crystal nuclei are formed in the heating time, the graphene crystal nuclei and the silicon crystal nuclei are subjected to self-assembly growth to form a three-layer structure with a silicon atomic layer and a carbon atomic layer sandwiched therebetween, and a large silicon carbide unit layer, also called silicon carbene, is grown. Has the advantages of simple method and high yield;

2. compared with the prior art that the silicon carbide crystal growth needs 2200 ℃ of high temperature, the process is not easy to control and the doping is not easy, the preparation method of the silicon carbide material of the invention does not need the high temperature process of silicon carbide crystal synthesis and can be synthesized at relatively low temperature, thus having the advantages of low preparation temperature, easy doping and controllable process;

3. the silicon-carbon alkene prepared by the method has a compact structure similar to a diamond structure, and the C atom presents sp3 hybridization and is hard in texture. The lithium ion battery has the advantages that the space for accommodating lithium ions has large freedom degree of configuration, large lithium ion storage can be generated, and the specific capacity can reach 2500mAh/g through calculation;

4. when the silicon-carbon alkene material prepared by the method is applied to a lithium ion rechargeable battery material, the cycle characteristic is very strong, and the cycle period is more than 20000. The energy density is more than 400-1500 Wh/kg;

5. the electrode active material prepared by the silicon carbene material has high specific energy and stable cycle characteristics as the electrode active material of the lithium rechargeable battery due to the adoption of the high-purity silicon carbene grown on a large scale, so that the charge and discharge performance of the lithium rechargeable battery is improved, and the energy density and the power density of the lithium rechargeable battery are improved.

Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

Drawings

The invention can be further illustrated by the non-limiting examples given in the accompanying drawings:

FIG. 1 is a high resolution TEM image of the silylene, showing the layer formation.

FIG. 2 is an x-ray diffraction pattern of the silicon carbene. The diffraction peak profile is clear and sharp, indicating that the crystal is good. The peaks show that this is a cubic polytype crystal structure of silicon carbide.

FIG. 3 is a Raman spectrum of the silicon carbene with a distinct scattering peak profile, also indicating good crystallization.

Figure 4 voltage-capacity cycling curves for the silicon carbene active materials of a lithium/silicon carbene cell.

Figure 5 lithium/silicon carbene battery silicon carbene electrode active material cycle period-capacity curve.

Figure 6 capacity-cycling curves for the silylene active material in sodium metal/silylene cells.

FIG. 7 the x-ray diffraction pattern of the silylene in example 2, with a distinct and broadened diffraction peak profile, indicates that the phase is pure silylene, the absence of the peak position indicates the diffraction characteristics of the silylene, and the crystalline state is well crystallized.

Fig. 8 x-ray diffraction pattern of graphene and silicon carbene of example 2, with peak positions at 10.5 ° and 24 ° angles 2theta being characteristic diffraction peaks of graphene. 1567cm each appear in the Raman scattering diagram^-1And 2650cm^-1This is further illustrated by graphene.

FIG. 9 high resolution electron microscope of the silylene contained in the sample of example 2, showing the coiled cylindrical silylene and the flakes of silylene.

Fig. 10 shows the X-ray diffraction patterns of the lithium sodium alloys showing mutual immiscibility at different sodium/lithium molar ratios, showing the atomic weight percent Na: x-ray diffraction peak patterns at Li-20, 8 and 0.5, visible in sodium: when lithium is 20, the diffraction peak position of metal sodium is high, and the diffraction peak position of metal lithium is low, but a peak which marks the alloy of the two appears, and the ratio of sodium: when the proportion of lithium is 8, the diffraction peak of sodium metal reduces the intensity, and the diffraction peak position of metal lithium appears, and when most of lithium is occupied, the intensity of the sodium metal peak position further reduces, the diffraction peak position of metal lithium is prominent, and the intensity is obviously increased.

FIG. 11 SEM pictures of a lithium/sodium alloy in a Scanning Electron Microscope (SEM) of Li (d, e), Li-Na alloy (f, g) with a Na/Li molar ratio of 6, and Na (h, i) in a 0.5M NaCF3SO3/TEGDME or NaCF3SO3/DOL/TEGDME electrolyte after 5 charge-discharge cycles. The visible metallic sodium crystals and metallic lithium crystals and their boundaries are very clear.

Detailed Description

For a better understanding of the invention, its content will be elucidated in detail below with reference to an embodiment, an example of which is shown in the drawing. The embodiments described by referring to the drawings are exemplary only for the purpose of illustrating the invention and are not to be construed as limiting the invention.

The noun explains:

silicon carbene: a unit layer constructed by polar covalent bonds formed by direct hybridization of silicon atoms and carbon atoms with the silicon atoms or the carbon atoms sp3 is used as a two-dimensional crystal, or one silicon atom layer is sandwiched by two carbon atom layers, or vice versa, the silicon atoms and the carbon atoms are connected by the sp3 polar covalent bonds, and thus the two-dimensional crystal or the layer is called silicon carbene. Depending on the unit layer, its crystal chemical formula is different. Can be understood as a unit layer of the polytype of silicon carbide. If the carbon atom layer is sandwiched by the silicon atom layer, a silicon carbene with a crystal chemical formula of Si is formed_xC_1-x，0.5<x<1. If the silicon carbide is formed by two layers of carbon atoms and one layer of silicon atoms, the crystal chemical formula is Si_1-xC_x，0.5<x<1. If the silicon atom and the carbon atom form a silicon-carbon alkene unit layer through a covalent bond with sp3 polarity, the crystal chemical formula is SiC. It contains various polytypes, including cubic polytype lattice structures, and 2R, 4H, and 6H polytype lattice structures. Which may also be referred to as silicon carbide.

It is qualitatively different from bulk silicon carbide crystals that are composed of long-range and short-range ordered repetitive arrangements of silicon and carbon atomic layers in space. And the stacking of the silicon atoms and the carbon atom layers in the silicon carbene does not have the repeated stacking period, and the polar covalent bond has short-range order. The corresponding characteristic peak profile on the x-ray spectrogram is clear and the peak value is sharp.

Sodium intercalation: the process of sodium ion migration into the active material lattice in the electrode during the electrochemical process of the cell;

sodium removal: the process of sodium ion dissociation from the active material lattice in the electrode during the electrochemical process of the cell.

Lithium intercalation: a process in which lithium ions migrate into the active material lattice in the electrode during the electrochemical process of the cell;

lithium removal: the process of lithium ion dissociation from the active material lattice in the electrode during the electrochemical process of the cell.

An electrochemically active material is a material that reacts with lithium and sodium during charging and discharging in a lithium sodium alloy rechargeable battery.

Electrochemically inactive phase refers to a material that does not react with lithium and sodium in a lithium sodium rechargeable battery.

In order to improve the yield of the silicon carbene and adjust the reaction speed, the invention develops a preparation method of the silicon carbene.

Example 1

(1) Weighing 15g of pure graphite, doping gallium metal powder, pouring into an acetone solution in a vacuum stirrer, uniformly stirring, and sealing and stirring for 24 hours; after stirring, extracting acetone to volatilize part of the acetone, pressing the wet powder into a graphite boat which is used as a target material, putting the sample boat into a stainless steel shell reaction chamber, wherein the reaction chamber is provided with a reactant nozzle for generating high-hydrogen diluted silane gas and is positioned in the center right above the reaction chamber, and the nozzle is 20cm away from the center of the bottom of the reaction chamber; a radio frequency magnetron sputtering gas nozzle with an included angle theta of 89-60 with the horizontal plane is arranged at the position 10cm away from the center of the top of the reaction chamber and is parallel to the directions of cathode and anode electric fields of the reaction chamber, a strong electric field is formed between the sample base and the inert gas nozzle, and a voltage of 2000-20000V is applied between the sample base and the inert gas nozzle;

(2) vacuumizing to 10 deg.C^-4mTorr；

(3) Heating the sample boat to 1200-1500 ℃;

(4) starting inert gas high-purity argon gas injection, aligning to a target in a sample boat, keeping the sputtering power at 90-200W and the working pressure at 0.5-2mTorr, simultaneously, starting a plasma generation switch, starting high-hydrogen diluted silane (the volume of silane is 1:20), injecting the high-hydrogen diluted silane into a reaction chamber, converging sputtered graphene quantum dot gas in an emergent space of 10-200 nm on the surface of the target, then starting a femtosecond laser, aligning femtosecond laser to a product, namely a graphene crystal nucleus or a mixture of a quantum dot and high-hydrogen diluted silane plasma, generated by argon sputtering graphite in the sample boat, and bombarding a graphene quantum well crystal nucleus or a mixture of the quantum dot and the high-hydrogen diluted silane plasma;

(5) starting a high-frequency bias voltage (2000 Hz-100 MHz) in the reaction chamber, and superposing the high-frequency bias voltage to a superconducting static magnetic field (1-15 Tesla);

(6) the graphene quantum dots and the high-hydrogen diluted silane plasma mutually form violent collision between crystal nuclei and are irradiated and energized by a laser gun, wherein a gallium element is used as a catalyst to form self-organized growth of the graphene quantum dots and silicon atoms on the graphene quantum dots and the silicon atoms, the growth of a silicon atom hexagonal ring network is triggered by taking the quantum dot graphene as a template to form a structure of a silicon atom layer sandwiched by carbon atom layers or a structure of two carbon atom layers sandwiched by one silicon atom layer, the energizing effect of the laser is to provide energy for forming sp3 polar bonds by silicon carbide, namely, reactants in a reaction chamber are subjected to nucleation and aggregation of silicon atom nuclei and form silicon carbide polar covalent bonds or sp3 hybrid bonds with the carbon atoms of the graphene crystal nuclei or the quantum dots, and the process can generate large silicon carbide unit layers or two silicon atom layers sandwiched by carbon atom layers or three silicon atoms sandwiched by two carbon atom layers under the catalytic action of gallium atoms, reacting for 20-50 minutes;

(8) turning off the heating power supply; and naturally cooling the sample chamber to the equal room temperature. Opening the reaction chamber, taking out the sample boat, and collecting the product at the bottom of the reaction chamber; is nano silicon carbon alkene powder.

Two cubic lattice silicon carbide solid phase diffraction peaks appear through x-ray diffraction analysis and Raman spectrum analysis, and the diffraction peaks are widened, so that the silicon carbide solid phase diffraction peaks have dangling bonds. Observing a sample by a high-resolution electron microscope to see a folded silicon-carbon alkene layered substance; when atomic force microscope observation is carried out on the surface of the silicon-carbon alkene, three layers of atoms can be seen, wherein the atom diameter of the middle layer is small, the atom diameter of the interlayer is large, and the fact that the surface of the interlayer is a silicon atom layer is inferred. The thinnest layer of the silylene was 0.4nm, and the product was also verified to be a cubic lattice silylene. Layers of larger diameter silicon atoms in the middle atomic layer sandwiched by smaller diameter carbon atom layers were also seen, and the resultant sample weighed 35g in total.

The silicon carbene is a novel two-dimensional material and belongs to a unit layer of silicon carbide. The silicon carbene mainly has three basic structures, wherein a silicon atom layer and a carbon atom layer are connected by a silicon carbide bond, and dangling bonds are respectively formed on two sides of the silicon atom layer and the carbon atom layer after the Si-C bond sp3 is hybridized. The second structure is that one silicon atom layer is sandwiched by two carbon atom layers, wherein Si-C atoms form sp3 hybridization, and a dangling bond is one bond of carbon atoms; the third is that a layer of carbon atoms is sandwiched by two layers of silicon atoms, with the Si-C atoms forming sp3 hybridization, all of which can be considered as a single layer of silicon carbide. Due to the three crystal chemical structures, the advantages of the silicon carbide are kept, and the silicon carbene has very good mechanical properties. And belongs to a two-dimensional nano material, has good characteristics of a semiconductor, and can be developed in an attempt.

Because the silicon carbide crystal growth needs 2200 ℃ high temperature, the process is not easy to control and the silicon carbene can be synthesized at relatively low temperature without the high temperature process of silicon carbide crystal synthesis, thus the doping and process control can be easily carried out.

The crystal chemical formula of silicon carbide may be represented as SiC. The first structure of the silicon carbene has a chemical formula of SiC, and the second structure has a chemical formula of Si_1-xC_x，0.5<x<1; the third chemical structural formula is Si_xC_1-x，0.5<x<1。

The silicon carbene has both a cubic stacking structure and a hexagonal stacking structure. The former is present in all three configurations.

Silicon carbenes are two-dimensional crystals built up from unit layers of silicon carbide and are inherently different compared to bulk materials of silicon carbide. The outer layer of the crystal is provided with a large number of dangling bonds, the surface of the crystal is provided with layers of atoms of different types, the layers can be further divided into silicon-carbon alkene on the surface of a silicon atom or on the surface of a carbon atom, and the energy gap of a semiconductor is 0.2-2.98 eV less than that of silicon carbide of a corresponding crystal lattice.

The cubic stacking structure can only be the first and third silicon carbenes, i.e., a double layer of silicon atoms sandwiching a layer of carbon atoms or a double layer of carbon atoms sandwiching a layer of silicon atoms. The silicon-carbon alkene has a compact structure, is similar to a diamond structure, has sp3 hybridized C atom, and is hard in texture. The lithium ion battery has the advantages that the space configuration freedom for accommodating lithium ions is high, large lithium ion storage can be generated, and the specific capacity can reach 2500mAh/g through calculation.

The cycle characteristic is very strong, and the cycle period is more than 20000. The energy density is more than 400-1500 Wh/kg.

The electrode was fabricated from this silicon-carbon alkene sample. Weighing a silicon-carbon alkene sample, PVDF and a graphene conductive agent, wherein the weight percentages of the PVDF and the graphene conductive agent are (80-90): (10-5): (10-5) placing the mixture into a stainless steel stirrer; (2) adding 5ml of nmp into the sample in the stirrer, and uniformly stirring in a vacuum stirrer for 72 hours; (3) taking out, and coating on the foamed nickel; (4) putting the foamed nickel into a central control drying oven, drying for 72 hours at 120 ℃, and cooling to room temperature; (5) the nickel foam coated with the silylene sample was removed and pressed into a sheet on a roll press to prepare 200 CR2025 electrode sheets. Assembling the 200 electrode plates into a button cell, wherein the counter electrode is a lithium-sodium alloy metal (lithium: sodium mass percent is 100-10: 0-90) plate, a diaphragm is additionally arranged, and lithium ion and sodium ion electrolyte (Zhang Kong) containing ethyl carbonate of LiPF6 is filled; and sealing the opening to manufacture 200 CR2025 button cells. After aging for 20 hours. And (5) carrying out a battery cycle characteristic test.

The first discharge specific capacity is 1125mAh/g, the discharge capacity is put at 0V, the mixture is kept stand for 10 minutes, the first specific charge capacity is 2000mAhg, the second cycle discharge specific capacity is 2040mAh/g, and the coulombic efficiency is 98.03 percent. The 8 th charging capacity reaches 2890mAh/g, the discharging capacity reaches 2910mAh/g, and the coulombic efficiency is 99.31%. This specific capacity was maintained 6000 times thereafter, and the coulombic efficiency fluctuated around 99.9%.

And 15 of 200 battery samples are taken for battery cycle characteristic test, and the relationship between the change of the silicon carbene component and the cycle characteristic curve is made, so that the silicon carbene is the active material of the lithium ion and sodium ion batteries. The lithium ion battery constructed by the lithium ion battery is a battery with high energy density and long service life, and is safe. Such a cell is referred to as a lithium/silicon-carbon-ene cell.

The electrode was fabricated from this silicon-carbon alkene sample. Weighing a silicon-carbon alkene sample, PVDF and a graphene conductive agent, wherein the weight percentages of the PVDF and the graphene conductive agent are (80-90): (10-5): (10-5) placing the mixture into a stainless steel stirrer; (2) 5ml of nmp was added to the sample in the stirrer and stirred in a vacuum stirrer for 72 hours; (3) taking out, and coating on the foamed nickel; (4) putting the foamed nickel into a central control drying oven, drying for 72 hours at 120 ℃, and cooling to room temperature; (5) the nickel foam coated with the silylene sample was removed and pressed into a sheet on a roll press to prepare 200 CR2025 electrode sheets. Assembling the 200 electrode plates by using a button cell, wherein the counter electrode is a lithium plate, a diaphragm is additionally arranged, and lithium ion electrolyte (Zhang Jia harbor) containing ethyl carbonate of LiPF6 is filled; and sealing the opening to manufacture 200 CR2025 button cells. After aging for 20 hours. And (5) carrying out a battery cycle characteristic test.

And 15 of 200 battery samples are taken for battery cycle characteristic test, and the relationship between the change of the silicon carbene component and the cycle characteristic curve is made, so that the silicon carbene is the active material of the lithium ion and sodium ion batteries. The lithium ion and sodium ion batteries constructed by the lithium ion and sodium ion batteries are high-energy-density and long-life batteries and are safe. Such cells are referred to as lithium sodium alloy/silicon carbide cells or as lithium sodium alloy/silicon carbide cells.

Example 2

(1) Weighing 5g of pure silicon alkene, mixing the pure silicon alkene with gallium metal powder, pressing the mixture into a cake shape, putting the cake into a graphite boat, putting the sample boat into a stainless steel shell reaction chamber, wherein the reaction chamber is provided with a reactant nozzle for generating high-hydrogen diluted methane gas and is positioned in the center right above the reaction chamber, and an enhanced plasma is generated in the reaction chamber, and the nozzle is 20cm away from the center of the bottom of the reaction chamber; a magnetron sputtering inert gas spray gun opening is arranged at the position 5-10 cm away from the center of the top, and the silicon alkene target material aligned to the center of the sample boat can be adjusted;

(2) vacuumizing to 10 deg.C^-3mTorr；

(3) Heating the sample boat to 1000-1200 ℃;

(4) starting an inert gas high-purity argon spray gun to inject argon, aligning to a target material in a sample boat, keeping the sputtering power at 90-200W and the working pressure at 0.1-1mTorr to generate a silylene crystal nucleus or a silylene quantum dot, starting a plasma generation switch, starting high-hydrogen diluted methane (the volume of methane is 1 (5-30) in the volume of hydrogen), injecting into a reaction chamber, then starting a femtosecond laser, aligning the femtosecond laser to a silylene crystal nucleus product generated in the sample boat, and bombarding the silylene crystal nucleus or the quantum dot product;

(8) turning off the heating power supply; and naturally cooling the sample chamber to the equal room temperature. Opening the reaction chamber, taking out the sample boat, and collecting the product at the bottom of the reaction chamber; is nano-level layered silicon-carbon alkene powder.

Two cubic lattice silicon carbide solid phase diffraction peaks appear through x-ray diffraction analysis and Raman spectrum analysis, and the diffraction peaks are widened, so that the silicon carbide solid phase diffraction peaks have dangling bonds. Observing a sample by a high-resolution electron microscope to see a folded silicon-carbon alkene layered substance; atomic force microscope observation of the surface of the silicon-carbon alkene can see three layers of atoms, wherein the atomic diameter of the middle layer is twice of the atomic diameter of the sandwiched layer, and the middle layer is inferred to be a silicon atomic layer, and the sandwiched layer is a carbon atomic layer. The thinnest layer of the silicon carbene is 0.38nm, generally in the range of 0.38-5 nm, and the product is verified to be the silicon carbene with cubic lattice. The whole of the resultant sample weighed 33.6 g.

Lithium doping of the silicon carbene:

growing silicon carbene, adding a lithium-containing compound, and at 700-900 ℃, fully diffusing and transferring lithium ions in the synthesized silicon carbene crystal to each part including the surface of a reactant crystal, uniformly distributing the lithium ions and limiting the lithium ions in the grown crystal, wherein the lithium ions are used as interstitial impurities or substitutional impurities and retained in the crystal, so that the content of the lithium ions in the silicon carbene is improved. The capacity can be improved as an electrode material. This is because the lithium ion is doped with lithium silicon carbene, which means that the silicon carbene material is effectively doped with lithium during the preparation process (the weight percentage of lithium atom is between 0.01 and 0.1 percent). When the silicon carbide alkene grows, metal elements such as iron, nickel, manganese, tin and the like are effectively doped, so that the silicon carbide alkene crystal can generate lattice defects and lattice deformation, and the defects and the lattice deformation can cause lithium ion migration channels to form a silicon carbide lithium storage structure, so that the capacity of storing lithium ions by the silicon carbide alkene is increased. The doping amount of the metal elements can reach 0.01-0.5% of the weight percentage of the silicon-carbon alkene atoms.

The invention aims to grow a silicon carbene active material for an electrode of a lithium and sodium rechargeable battery, the material enables silicon carbene to generate large reversible lithium and sodium storage capacity, aims to solve the problems that the capacity of a negative electrode carbon material of the lithium and sodium rechargeable battery is low, the cycle life of other alloy-based negative electrode materials is short, and the migration of silicon carbide serving as a bulk material to lithium ions is closed, and provides the silicon carbene active material for the lithium rechargeable battery and the preparation method thereof, wherein the silicon carbene active material has high specific capacity and stable cycle performance. Aiming at the problems of the weak point of lithium ion migration passivation of the silicon carbide material and low capacity of the common nanometer silicon carbide, the technology is used for preparing the active material of the silicon carbene electrode with effective doping, uniform doping and high specific energy. This improves the charge and discharge performance of the lithium rechargeable battery, thereby increasing the energy density and power density of the lithium rechargeable battery.

The invention provides a novel lithium ion and sodium ion battery electrode material, which is a silicon-carbon alkene, and the crystal state of the material can change the percentage value of the solid phase content in a certain range along with the change of preparation conditions. In the general case of the above-mentioned,the relation between the contents of three solid phases of the product is typically that the content of silicon-carbon alkene is 50-100%, the content of silicon alkene is 0-50%, and the molecular structural formula (Si, Me) is_1-x(C,Me)_xWherein x represents a variable silicon and carbon composition, represents an atomic percent value, and is 0<x<Me represents a metal element contained in the nano-silicon carbene crystal, wherein Li, Fe, Co, Ni, V, Y and the like represent that silicon atoms and carbon atoms on lattice points in a substitutional silicon carbene crystal lattice or interstitial atoms exist in lattice gaps, and the metal elements do not generate new phases or simple substance phases. The method is characterized by comprising the following steps:

(1) the active material with high lithium and sodium storage capacity has one and/or two of silicon carbene with cubic crystal structure and silicon alkene with two crystal structures, and the chemical bond is a Si-C polar covalent bond containing 10% of ionic bond instead of a compound of Si and C. The silicon carbide alkene in the active material with high lithium storage capacity has cubic polytype, hexagonal polytype (4H and 6H) and rhombohedral polytype crystal structures.

(2) The prepared silicon carbide alkene with high lithium and sodium storage capacity and stable reversible lithium and sodium intercalation and deintercalation performance can be crystalline. The silicon carbene electrode active material can lead the chemical components in the silicon carbene to deviate from the chemical proportion due to different preparation conditions, namely the silicon carbene electrode active material is prepared by the molecular structural formula (Si, Me)_1-x(C,Me)_xWhere x represents the silicon and carbon composition variable, is in atomic weight percent, and is 0<x<0.5, Me represents a metal element contained in the crystal, here Li, Fe, Co, Ni, V, Y, etc., and is present in the nanocrystal as a dopant element without forming another phase. The reactant phase is limited to one phase or two phases of the silicon carbene, and the crystallography component refers to a silicon carbene single phase, and the metal elements exist in interstitial impurities and substitutional impurities or are in the same phase in a similar manner, so that solid solution or new phases except the silicon carbene phase are not generated. The molecular structural formula referred to herein considers the case where the carbon atom is substituted, but for convenience of representation, the present invention uniformly represents the substitution in the structural formula as an alternative to the silicon atom. Chemical composition expressed as the coefficient of atomic percent of silicon atoms and substitutional atoms, i.e. unified tableShown as (Si, Me)_1-xC_x. This is a representation of the crystal formula of the non-integral compound. This means that the positions of the silicon atoms on the lattice points in the lattice and the positions of the carbon atoms on the lattice points are replaced by the metal elements. The reason is that the composition of the compound deviates from the integer ratio due to the occurrence of vacancies, substitutional atoms or interstitial atoms in the crystal when the conditions of the preparation process are changed, which is a common phenomenon of chemical compositions of nano-scale crystals, quasi-crystalline crystals and amorphous crystals, and the compound is called a non-integer ratio compound, which means a compound whose relative number of each type of atoms in the composition cannot be expressed by a few small integer ratios.

(3) The synthesized silicon-carbon alkene material can also have different crystalline states along with the difference of temperature and components, and has crystalline silicon carbene, namely the atomic arrangement is in an ordered state from a short distance, the corresponding characteristic peak on an x-ray spectrogram is a peak with sharp and wide outline, and the peak shows that the position of the corresponding characteristic peak is wide and the outline is clear on the Raman spectrogram, but an electron diffraction pattern is in the shape of a dispersed point ring with diffraction spots. The silicon carbene has only short-range order and has a diffraction peak in an x-ray diffraction pattern.

(4) The high-resolution transmission electron microscope morphology image can observe that the silicon-carbon alkene is in a coiled lamellar shape, the dimension is in a micron level, and the thickness is 0.38 nm-5 nm.

In example 1, the composition contains solid phase components mainly consisting of silylene, silylene and graphene. Generally, the content of silicon-carbon alkene is 80-100% (weight percentage), the content of silicon alkene is about 10-15%, and the rest is graphene. Separating out the silicon carbene by a specific gravity method.

(5) The silylene is a new phase in the synthesis process, and is generated in the reactants when the reactant raw materials contain lithium, a combination of copper and iron, lithium, nickel and tin or a combination of rare earth, and the graphene is the reactant residue.

Example 3

The electrode was fabricated from this silicon-carbon alkene sample. Weighing a silicon-carbon alkene sample, PVDF and a graphene conductive agent, wherein the weight percentages of the PVDF and the graphene conductive agent are (80-90): (10-5): (10-5) placing the mixture into a stainless steel stirrer; (2) adding 5ml of nmp into the sample in the stirrer, and uniformly stirring in a vacuum stirrer for 72 hours; (3) taking out, and coating on the foamed nickel; (4) putting the foamed nickel into a central control drying oven, drying for 72 hours at 120 ℃, and cooling to room temperature; (5) the nickel foam coated with the silylene sample was removed and pressed into a sheet on a roll press to prepare 200 CR2025 electrode sheets. Assembling the 200 electrode plates into a button cell, wherein the counter electrode is a lithium-sodium alloy metal plate, a diaphragm is additionally arranged, and lithium ion and sodium ion electrolyte, namely ethyl carbonate containing NaPF6, is filled; and sealing and manufacturing 200 CR2025 button lithium-sodium alloy/silicon carbene (or silicon carbide alkene) batteries. After aging for 20 hours. And (5) carrying out a battery cycle characteristic test.

The first discharge specific capacity is 1125mAh/g, the sample is placed at 0V and stands for 10 minutes, the first specific charge capacity is 1200mAhg, the second cycle discharge specific capacity is 1204mAh/g, and the coulombic efficiency is 98.03 percent. The 8 th time charging capacity reaches 1289mAh/g, the discharging capacity reaches 1290mAh/g, and the coulombic efficiency is 99.31 percent. After that, the specific capacity is maintained for 9000 times, and the coulombic efficiency fluctuates around 99.9%.

And 15 of 200 battery samples are taken for battery cycle characteristic test, and the relationship between the change of the silicon carbene component and the cycle characteristic curve is made, so that the silicon carbene is the active material of the lithium ion battery. The lithium ion battery constructed by the lithium ion battery is a battery with high energy density and long service life, and is safe. Such cells are referred to as lithium/silicon-carbon-ene cells.

The electrode was fabricated from this silicon-carbon alkene sample. Weighing a silicon-carbon alkene sample, PVDF and a graphene conductive agent, wherein the weight percentages of the PVDF and the graphene conductive agent are (80-90): (10-5): (10-5) placing the mixture into a stainless steel stirrer; (2) adding 5ml of nmp into the sample in the stirrer, and uniformly stirring in a vacuum stirrer for 72 hours; (3) taking out, and coating on the foamed nickel; (4) putting the foamed nickel into a central control drying oven, drying for 72 hours at 120 ℃, and cooling to room temperature; (5) the nickel foam coated with the silylene sample was removed and pressed into a sheet on a roll press to prepare 200 CR2025 electrode sheets. Assembling the 200 electrode plates into a button cell, wherein the counter electrode is a lithium-sodium alloy metal plate, a diaphragm is additionally arranged, and lithium ion and sodium ion electrolyte, namely ethyl carbonate containing NaPF6, is filled; and sealing the opening to manufacture 200 CR2025 button cells. After aging for 20 hours. A battery cycling characteristic test was performed.

The first discharge specific capacity is 1125mAh/g, the sample is placed at 0V and stands for 10 minutes, the first specific charge capacity is 1200mAhg, the second cycle discharge specific capacity is 1204mAh/g, and the coulombic efficiency is 98.03 percent. The charge capacity reaches 1290mAh/g, the discharge capacity reaches 1291mAh/g and the coulombic efficiency is 99.31 percent at the 8 th time. This specific capacity was maintained 8000 times thereafter, and the coulombic efficiency fluctuated around 99.9%.

And 15 of 200 battery samples are taken for battery cycle characteristic test, and the relationship between the change of the silicon carbene component and the cycle characteristic curve is made, so that the silicon carbene is the active material of the lithium ion and sodium ion batteries. The lithium ion and sodium ion batteries constructed by the lithium ion and sodium ion batteries are high-energy-density and long-life batteries and are safe. Such cells are referred to as lithium sodium alloy/silicon carbon ethylene cells.

Example 4

A preparation method of a lithium/sodium (lithium sodium) alloy and battery cycle characteristic analysis of the lithium/sodium (lithium sodium) alloy are provided. The two metals form a eutectic alloy, i.e., the two metals retain their respective crystal structures in the alloy. Preparing an electrode by using silicon carbene as an electrode material (a process of using a bonding agent, a conductive agent and PVDF (polyvinylidene fluoride) and nmp), wherein the counter electrode is a lithium-sodium alloy, and the ratio of sodium to lithium is (30-10): 1.

the preparation method of the alloy is mixing and dissolving at high temperature.

In the mixed electrolyte of 0.5M NaCF3SO3/TEGDME or NaCF3SO3/DOL/TEGDME and LiPF 5/polycarbonate, NaCF3SO 3/TEGDME: the ratio of LiPF 5/polycarbonate is 3-1. SEM images of Li-Na alloy and Na having a molar ratio of Li to Na of 13 after 50 cycles of charge and discharge are shown in FIG. 11.

The first specific capacity loss is large, and the current density is 0.5A/cm at a voltage window of 3.6-0V²The cycle period can reach 50, and the specific capacity can reach 1700 mAh/g.

A method for the manufacture of a lithium/sodium nanocrystalline alloy and its use in rechargeable batteries. Lithium metal and sodiumThe metal may form a lithium/sodium alloy. This alloy is an alloy that maintains the respective crystal structures, and is a eutectic alloy, not a solid solution. The analysis of the x-ray diffraction pattern shows that the diffraction peaks respectively show the diffraction peaks of lithium and sodium metals. The conventional lithium/sodium alloys show that lithium metal crystals are often embedded in sodium metal in irregular shapes. Because these two metals are active elemental metals, it is not feasible to pulverize lithium and sodium metals at room temperature by a preprocessing process. The invention adopts a thermal spraying method to prepare the nanocrystalline lithium/sodium alloy. The method comprises the following specific steps of 1) arranging a vacuum reaction chamber. The reaction boat is made of silicon carbide. Placed on a heatable susceptor. The sample boat may be rotated during the heating process. Outside the reaction chamber, an EdgeWave picosecond laser (beam quality: M) with two wavebands²<1.5, pulse energy up to 1000 muj, pulse width 10ps, peak power up to 100MW, pulse repetition frequency up to 50MHz, average power up to 400W, wavelength 355nm) are aligned to the samples in the sample boat. 15g of sodium metal and 1 g of lithium metal are weighed and arranged in a sample boat of a reaction chamber, and a base is positioned at the center of the bottom of the cylindrical cavity reaction chamber. The diameter of the cylindrical cavity is 100cm, and the height of the column is 200 cm. The center of the bottom of the cylinder of the reaction chamber is provided with a rotary heating system. On the sample holder, a boat, which was weighed with samples of lithium metal and sodium metal, was placed. Vacuum pumping is carried out to 10^-3And (3) turning on a sample base heater, adjusting the heating rate to be 25 ℃ per minute, heating to 700 ℃, melting the two metals, turning on femtosecond laser, radiating molten metal by two laser pulses, gasifying the two metal materials, fixing a disc at a position with the height of about 195cm near the top of the cylinder, sticking an aluminum film on the disc, and reacting in a reaction chamber for 20 minutes until the two molten metals are completely gasified by the laser. And turning off the power supply, stopping heating by the heater, and turning off the laser by the laser. Naturally cooling for 72 hours. The nanometer structure alloy film material with the thickness of 30 microns and embedded with the uniform nanometer lithium metal crystal and the nanometer sodium metal crystal is obtained. The analysis of the X-ray diffraction pattern shows that the diffraction peaks of the single metals of lithium and sodium exist. As shown in fig. 10. Observed with a scanning electron microscope, it can be seen that the treatedIn the nanometer lithium/sodium alloy, the sodium metal crystal is a nanometer crystal, and the lithium metal nanometer belt is used for separation. Smaller lithium metal is surrounded by sodium metal in the nanoscale sodium metal crystals. And assembling the electrode with the current collector of aluminum foil and the silicon-carbon alkene electrode, namely a counter electrode, filling mixed electrolyte into a diaphragm by adopting Celguard, and packaging to form the button cell CR 2025. The number of samples was 150. The battery cycle characteristic experiment proves that the first discharge specific capacity is 960aAhg, the first charge specific capacity is 978mAhg and the coulombic efficiency is 100.9 percent; the first chargeable and dischargeable specific capacity reaches 1150mAhg, the chargeable and dischargeable capacity is 1200mAhg, and the coulombic efficiency is 100.8%; the third discharge capacity reaches 1580mAhg, the charge capacity is 1620mAhg, and the coulombic efficiency is 100.7%. The fourth discharge capacity is up to 1780mAhg, the charge capacity is 1780mAhg, and the coulombic efficiency is 100%. The discharge capacity of 200 th cycle was 1780mAhg, the charge capacity was 1780mAhg, and the coulombic efficiency was 100%.

The invention aims to provide a method for preparing a silicon carbene electrode active material. The conventional sol-gel process generates sewage and pollutants, and the raw material compounds generated by a special process also pollute the environment. The invention mainly utilizes green cheap raw materials of starch, sorghum micropowder and relatively small amount of organic matter to prepare the gel-growth silicon carbene. This method is difficult and the growth mechanism of the silicon carbene is complicated. In general, special measures are needed in the process for synthesizing the silicon carbene, for example, a catalyst and a special carbon triple-bond substance, preferably an ethynyl organic substance and/or polymer, such as sodium phenylacetylene and the like, and a silicon double-bond substance, preferably a silicon alkenyl substance, are added in the process for growing the silicon carbene by using starch. The purpose is to combine oxygen atoms in starch with one bond state in a carbon-carbon triple bond state in the oxidation process, the oxygen atoms are exhausted after the bond is broken, and the rest double-bond state substance is combined with double bonds in the silicon alkene substance to form layered or tubular silicon carbene. However, such material combinations cannot be put together at the same time, but are made into gel powder respectively, because relatively independent gel powder firstly undergoes a local chemical reaction in the heating process, and crystals preferably grow in a one-dimensional direction; under the action of catalyst metal elements of iron, copper, nickel or rare earth metal elements, metal atoms are embedded into lattice points and serve as unbalanced charges to create vacancies, the growth in the three-dimensional direction is degraded into the growth in the one-dimensional direction, hydrogen atoms, carbon atoms and oxygen atoms consumed by a bond which is triggered to break by a triple bond in the oxidation process of a polymer in the three-dimensional growth direction are firstly triggered to break in the three-dimensional growth direction, the limited domain is the growth in a nanometer scale or smaller scale, the silicon atom double bond and carbon double bond break to trigger the silicon atoms and carbon atoms to combine to grow into silicon carbene crystal nuclei, and the crystal nuclei further grow into micron-scale layers or tubes. Acetylene organic matters and substances doped with metal elements are put together to prepare sol and gel; the silylene substance is combined with starch and the doping substance to prepare the gel. During sintering, the two gel powders are mixed, and in the process of temperature rise, because the compound is doped with metal elements such as iron, lithium and the like, the elements play a catalytic role in the growth of the silicon carbene on one hand, and replace silicon atoms or carbon atoms on lattice points in the generated silicon carbene to form substitutional impurities on the other hand. This causes local deformation of the lattice structure, which makes vacancies, layers or even tubular crystals of the lattice structure, which allows sufficient coordination space for the silicon and carbon atoms to the lithium metal, thereby creating a space for lithium storage and becoming the active material. In addition, the silicon carbene has strong toughness and structural stability, the structure of the silicon carbene is not collapsed enough in the charge-discharge process, and the cycle period of the silicon carbene electrode material can be greatly prolonged. If single bond silicon organics and polymers are used, as well as single bond carbon organics, the above process does not produce silicon carbenes.

The silicon carbene electrode active material is prepared by the following steps:

the method comprises the following steps of (I) according to the molar ratio of compounds (1-1.5): (1-2): (4-6): (7-9) matching polysiloxane, sodium acetylene, starch and absolute ethyl alcohol, and weighing corresponding compounds and organic matters;

secondly, putting the weighed components into a 1000ml beaker; stirring for 12 hours by a mechanical stirrer, and forming a transparent sol after the mixture is uniform;

thirdly, drying the sample for 10 hours at the temperature of 160-200 ℃ to obtain white powder;

(IV) according to a compound molar ratio (7-10): (7-10): (1-2): (1-3): (0.5-1) respectively weighing micron-sized sorghum micropowder (calculated by 82% of starch contained in the sorghum micropowder, the same below), sodium ethoxide, ferrocene, 1, 2-dimethyl-1, 2-diphenyldisilene, urushiol lanthanum formal polymer and sodium dialkyl sulfonate, placing the materials into a second 1000ml beaker, adding deionized water, and stirring and mixing the materials into a colloidal body by using a mechanical stirrer; putting the colloid into a vacuum drying oven, and heating the colloid into a gel state at 120-200 ℃ to obtain yellow powder;

mixing the two gel powders in the two beakers, and stirring for 12 hours by using a mechanical pump to obtain mixed uniform pale yellow powder;

putting the obtained gel into a crucible, putting the crucible into a vacuum atmosphere reaction furnace, and vacuumizing to ensure that the vacuum degree of the atmosphere reaction furnace reaches 1-3 Pa;

filling argon into the atmosphere reaction furnace to enable the pressure in the furnace to reach 3-2.1 MPa;

(VIII) heating the atmosphere sintering furnace at a temperature rise rate of 20-30 ℃/min until the temperature rises to 800-1300 ℃. Sintering for 1-3 hours at the temperature;

and (ninthly), cooling to room temperature to obtain the silicon carbene electrode material.

Wherein the silicon carbene is layered and curly into a spiral cylinder shape, and the thickness is between 0.6nm and 5.7 nm. The biochemical composition comprises 43-59% of silicon element, 40.2-56% of carbon element and 0.8-1% of metal element. The product is solid phase component, and the weight percentage of the product is 90-100% of silicon-carbon alkene and 0-10% of silicon alkene phase.

The reason for generating the silicon carbene is very likely to be that the directional catalysis generated by the combination of the doped sodium, lithium, iron, copper and lanthanum elements generates Si-C polar covalent bonds, the silicon carbene (or called silicon carbide) layer grows along the plane, particularly rare earth lanthanum has a special electronic structure which is beneficial to reducing a silicon atomic layer when the silicon carbene is formed so as to form free silicon atoms, and the silicon atoms are stripped to form a plurality of layers of silicon atoms, and the silicon carbene grows in a self-organizing way with the carbon atoms to form a silicon carbene coiled cylindrical layer.

The electrode active material of the silicon carbide alkene prepared by the process is added with a conductive agent and a binder PVDF, and the electrode active material is prepared by mixing silicon carbide alkene: conductive agent carbon black: 60 weight percent of PVDF: 20: 20, adding NMP to dissolve the mixture into a colloid, uniformly stirring, coating the colloid on a current collector copper foil, putting the current collector copper foil into a vacuum drying oven, drying the current collector copper foil for 18 hours at 170 ℃, taking out the current collector copper foil, and pressing the current collector copper foil into a sheet under the pressure of 1 MPa. The cathode sheet is cut into R2025 round sheets, and the round sheets, the counter electrode lithium sheet and the diaphragm are combined together, and electrolyte is added to assemble the button cell. Putting the mixture into a forming box, forming the mixture for 60 hours at the temperature of 40-90 ℃, and taking out the mixture. And (5) carrying out a battery cycle test. The battery cycling test apparatus used was model CT2001A from wuhan kino. At a window voltage of 0-2V, 0.25A/cm²At a constant current of (2) and for all additional cycles between 0.4A/cm and 0.0V²Cycling the cell at a constant current.

The following describes the electrodes for lithium ion and sodium ion batteries, with a sheet of lithium sodium alloy metal as the counter electrode. The electrode is characterized by an electrochemically active phase and an electrochemically inactive phase, the electrochemically active phase comprising silicon carbene in combination with a binder, and a conductive agent. Examples of suitable binders include polyimide, polyvinylidene fluoride, and polyvinylidene fluoride. Examples of suitable conductive agents include graphene. To prepare the cell, the electrode is combined with an electrolyte, which may be in the form of a liquid, solid or gel, and a cathode (counter electrode). Examples of solid electrolytes include polymeric electrolytes such as ethylene oxide, polytetrafluoroethylene, fluorine-containing copolymers, and combinations thereof. Examples of liquid electrolytes include carbon ester ethylene, carbonic acid diacetic acid, carbonic acid propylene, and combinations thereof. The electrolyte is provided with a lithium electrolyte salt. Examples of suitable salts include LiPF₆、LiBF₄、LiClO₄. Examples of suitable cathode compositions include LiCoO₂、LiCo_0.2Ni_0.8O₂、LiMn₂O₄. The following examples are given to illustrate the preparation of the electrode active material of silicon-carbon-ene of the present inventionThe method is explained.

Example 1

weighing 20g of polysiloxane, and mixing the components in a molar ratio of (1-1.5): (1-2): (4-6): (7-9) matching polysiloxane, phenylethynyl lithium, starch and absolute ethyl alcohol, and weighing corresponding compounds and organic matters;

weighing 5g of sodium dialkyl sulfonate, wherein the molar ratio of the compounds is (7-10): (7-10): (1-2): (1-3): (0.5-1) weighing micron-sized sorghum micropowder, ferrocene, sodium ethoxide, 1, 2-dimethyl-1, 2-diphenyldisilene, neodymium methacrylate and sodium dialkyl sulfonate respectively, weighing corresponding compounds and organic matters, putting the compounds and the organic matters into a second 1000ml beaker, adding 500ml of deionized water, and stirring and mixing the materials into a colloid by using a mechanical stirrer;

putting the colloid into a vacuum drying oven, and heating the colloid into a gel state at the temperature of 120-200 ℃ to obtain yellow powder;

mixing the two gel powders in the step (three) and the step (five) according to the preparation sequence, wherein the weight percentage of the two gel powders in the two beakers is 1: 1-7, and stirring the mixture for 12 hours in a sealed manner by using a mechanical pump to obtain mixed uniform pale yellow powder;

(eighthly), filling argon into the atmosphere reaction furnace to enable the pressure in the furnace to reach 2-3.1 MPa;

(nine) heating the atmosphere sintering furnace at a temperature rise speed of 20-30 ℃/min until the temperature rises to 800-1300 ℃. Sintering for 1-3 hours at the temperature;

and (ten) cooling to room temperature to obtain the silicon carbene electrode active material.

FIG. 1 shows a high resolution transmission electron microscope image of the resultant phase, a silicon-carbon alkene electrode active material. The figure shows that the silicon carbene prepared by the invention has two shapes of a layer shape and a spiral tube shape, the volume percentage of the two shapes in the reaction phase is more than 99.9 percent, and the thickness of the layer shape and the spiral tube shape silicon carbene is more than 0.6 nanometer.

FIG. 2 is an x-ray diffraction pattern of a silicon-carbon alkene material, from which the diffraction peaks show that the crystal structure of this phase is a cubic polytype (β -SiC). The lattice constant of the silicon carbide crystal is obviously different from that of an ideal silicon carbide crystal, which shows that the local lattice structure of iron, copper and neodymium elements can be changed due to relatively large atomic radius, and the deformation of the lattice structure can be reflected by a slight shift of the peak position of an x-ray diffraction pattern. The electron diffraction pattern shows that the electron diffraction spots showing the structure of the silicon carbide substance are dispersed in a sharp diffraction ring, and are the structure of the silylene (not shown). The lithium ion has small radius, does not influence the lattice structure too much, exists in the lattice in the form of interstitial impurities, and has little influence on the structure; it can be seen from table 1 that the silylene is a cubic polytype structure, from which it can be seen that the diffraction peak positions of the silylene are all shifted to different degrees, the crystal lattice is deformed, possibly caused by doping of iron, copper and neodymium elements, and only one phase of the silylene is present. The diffraction peak of graphene is shown in an x-ray diffraction pattern, which shows that the graphene content in the composite active material prepared by the method is very low. The chemical composition of the product is that the atomic weight percentage of silicon element is 54-69%, the atomic weight percentage of carbon element is 31-46%, and the atomic weight percentage of metal element is 0.8-1%. The weight percentage of the product as solid phase component can be expressed as 98-100% of silicon carbene and 0-2% of graphene phase.

TABLE 1 SILICON CARBENE AND BODY MATERIAL SILICON CARBIDE X-RAY DEGRACTION SPECTRUM AND NUMBER DATA

Fig. 3 is a raman spectrum of a silicon-carbon alkene electrode active material, in which the scattering peak profile is sharp, but the background is high and shifted near the scattering peak of short wavenumbers, which may be caused by phonon peak shift caused by iron, copper and neodymium ions. There are no other solid phase peaks in the X-ray diffraction and raman spectra, indicating that the product is a pure mixture of silylene and helical nanotubes.

The phase analysis results of representative X-ray diffraction and the chemical component calculation structural formula of the semi-quantitative analysis product of atomic absorption spectrum in 10-20 sample of the invention are shown in Table 2.

TABLE 2 x-ray diffraction phase analysis and atomic absorption Spectroscopy analysis of silicon carbide samples

As shown in Table 2, when the coefficient of Si in the chemical structural formula reached 0.49 and the coefficient of Fe was 0.03, the nanocrystalline SiC underwent a structural polytype transformation from cubic polytype to hexagonal polytype 4H-SiC. However, when the iron element coefficient is decreased and the copper element coefficient is increased, the structure remains cubic polytype although the silicon element coefficient is further increased.

Each of the samples listed in Table 2 for examples 3-6 was formed into an electrode for characterization in an electrochemical cell having a lithium metal counter electrode.

To prepare the electrodes for electrochemical cell cycling, 30g of each powder was suspended in 20g of N-methyl-2-pyrrolidone (NMP). Then, according to the following approximate value of 1: a 10% solids suspension of 4.5g of carbon black in 1 weight of NMP and polyvinylidene fluoride was added to the suspension of powder. The resulting suspension was mixed on a mechanical stirrer at high speed, with a shear time of 2 minutes, and then coated onto a copper foil having a thickness of 230um to provide a coating of the active materials silylene 80%, polyvinylidene fluoride 8% and carbon black 12%. 180 ℃ in vacuoThe coating was dried for 12 hours to form an electrode. A metal lithium plate with a thickness of 400um was bonded as a counter electrode for constructing 5400 coin CR2032 button cells, a double layer of CELLGUARD 2400 as a separator, 1 of ethylene carbonate and diethyl carbonate: 2 1M LiPF of the mixture₆As an electrolyte. The preparation method of coin CR2032 type coin cell batteries is described in CN200680047773.9 and its references.

For the first cycle, the voltage is 0.2A/cm between 2V and 0.0V in the charging and discharging window²The cell samples were tested using the wuhan blue cell test system CT2001A cycle at constant current, and 0.4A/cm between 2V and 0.0V for all additional cycles²The cell was cycled at a constant current.

Figure 4 shows a representative up to 60 cycle curve of the 50 samples tested in example 1. Wherein for the first circulation, the capacity reaches 900mAh/g under 0.15mA discharging current; and under the current of 0.2mA, the charging capacity reaches 870mAh/g, and the coulombic efficiency is 96.7%. The first charging circulation is to discharge under the current of 0.2mA, the capacity reaches 1400mAh/g, the capacity reaches 1360mAh/g when the battery is charged under the same current, and the coulombic efficiency is 97.1%. Discharging under the current of 0.2mA at the cycle of 60 times, wherein the capacity reaches 2550 mAh/g; the capacity reaches 2540mAh/g and the coulombic efficiency reaches 99.6 percent when the battery is charged under the same current. Table 3 shows the cycling results for 60 cycles for electrodes prepared with the silylene active material versus half cells with the sodium/lithium alloy as the electrode. The data in the table show that the concentration of iron element in the silicon-carbon alkene crystal is not more than 5%, and the capacity is large when the cycle period reaches 60 times. The iron-containing silicon-carbon alkene crystal only has one solid phase, and the robustness of the iron-containing silicon-carbon alkene crystal is not damaged by the deformation of the crystal structure, so that the electrochemical performance of the active material is enhanced.

Fig. 5 shows a cycle period-capacity curve for a lithium sodium alloy/silicon carbene rechargeable battery electrode silicon carbene active material.

Table 3 example electrochemical cell of lithium sodium alloy/silicon carbon alkene cell

There appears a new phenomenon what is what causes the silicon carbene to have lithium storage properties? The explanation for this problem may be that iron, copper and neodymium ions, when forming the silylene, cause efficient formation of silicon carbide bonds due to double bonded silicon and triple bonded carbon, and promote one-dimensional directional growth of the silylene, the silicon carbene phase is generated at the same time of forming crystalline crystal lattices, the space for storing sodium and lithium is increased, and the metal ions exist in the crystal lattices of the silicon carbene to deform the crystal lattices, thereby generating corresponding vacant sites, increasing the coordination space of the lithium ions and further forming the migration channels of the lithium ions, under the action of the restoring force stability of elastic and plastic deformation of crystal lattice, the successive lithium haxate has its crystal lattice deformed, however, the deformation is in the range of elastic restoring force, so that the crystal lattice of silicon carbide alkene is kept stable after elastic plastic deformation, and the crystal lattice has stable sodium and lithium storage and sodium removing capability. Theoretically, the cycle of sodium intercalation and haxate is infinite in length. In practice, the circulation can reach more than 6000 times.

Example 2

The other steps were the same as in example 1. The experiment further increases the content of carbon, and the content of silicon-carbon alkene in the product solid phase reaches 91 percent and the content of graphene is reduced to 9 percent according to the mass percentage. The silicon carbene atomic composition ratio is carbon: silicon 37: 63. the electrode is prepared by the method of comparative example 1 by using the silicon-carbon alkene material prepared by the example, and the lithium-sodium alloy (lithium: sodium mass percent is (100-10): 0-90)) is used for the counter electrode, and the battery assembling method and the test conditions are the same as those of comparative example 1. Charging and discharging at 2.0V to 0.02V with current density of 0.1 mA/cm². The first lithium intercalation capacity is 1881mAh/g, the first lithium deintercalation capacity is 1865mAh/g, and the coulomb efficiency is 100.8%. It is shown that increasing the carbon content in the reactants reduces the first lithium intercalation sodium capacity of the composite material, but the coulombic efficiency thereof is improved because the silylene has a layered structure and the first charge-discharge coulombic efficiency is high. The subsequent 12 cycles, the lithium intercalation sodium capacity is slowly reduced, the lithium deintercalation sodium capacity is gradually increased again in 10 cycles, and is gradually reduced after 10 cycles, which shows that the increase of the content of the silicon carbene alkene causes the composite material to be increasedThe lithium and sodium intercalation and deintercalation performance of the material is reduced. The lithium intercalation capacity of the 12 th time is 1855mAh/g, the lithium deintercalation capacity is 1863mAh/g, the coulombic efficiency is 99.51%, and the lithium intercalation capacity is attenuated by 1.41% after 12 cycles (relative to the lithium intercalation capacity of the first time), while the lithium deintercalation capacity is reduced by 0.10% (relative to the lithium deintercalation capacity of the first time). The lithium intercalation sodium capacity of the electrode taking the silicon-carbon-olefin/graphene-carbon composite material as an active substance is higher, and the attenuation is reduced during the additional cycle. The increase of the content of silicon-carbon alkene in the silicon-carbon alkene material can be seen, and the cycling stability is improved. The first discharge capacity is reduced due to the increase of the carbon content, the capacity is reduced less in the subsequent 12 times of circulation, and the fact that the increase of the silicon carbene content to 90 percent has great influence on the electrical property optimization of the lithium intercalation and deintercalation sodium is shown.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

Claims

1. A preparation method of a silicon-carbon alkene material is characterized by comprising the following steps: the preparation method comprises the following steps:

(2) vacuumizing to 10 deg.C^-4mTorr；

(3) Heating the sample boat to 1200-1500 ℃;

(4) starting inert gas high-purity argon gas injection, aligning to a target material in a sample boat, keeping the sputtering power at 90-200W and the working pressure at 0.5-2mTorr, simultaneously, opening a plasma generation switch, and starting high-hydrogen diluted silane, wherein the volume of silane is as follows: injecting hydrogen with the volume of 1:20 into a reaction chamber, converging sputtered graphene quantum dot gas in an emergent space with the surface of the target material being 10-200 nm, starting a femtosecond laser, aligning the femtosecond laser to a product generated by argon sputtering graphite in a sample boat, namely a graphene crystal nucleus or a mixture of quantum dots and silane plasma diluted by high hydrogen, and bombarding the graphene quantum well crystal nucleus or the mixture of the quantum dots and the silane plasma diluted by high hydrogen;

(6) the graphene quantum dots and the high-hydrogen diluted silane plasma form violent collision between crystal nuclei, and are irradiated and energized by a laser gun, wherein gallium is used as a catalyst, so that three layers of silicon carbide of a large silicon carbide unit layer, or a silicon carbide layer sandwiched by two silicon atom layers, or a silicon atom layer sandwiched by two silicon atom layers are generated, and the reaction lasts for 20-50 minutes;

(8) turning off the heating power supply; naturally cooling the sample chamber to the equal room temperature, opening the reaction chamber, taking out the sample boat, and collecting the product at the bottom of the reaction chamber; obtaining the nano-scale silicon carbide powder.

2. A silicon carbene prepared by the method of claim 1, wherein the silicon carbene has three basic structures, one silicon atom layer and one carbon atom layer are connected by a silicon carbide bond, and after sp3 hybridization of Si-C bonds, dangling bonds are formed on two sides of the silicon atom layer and the carbon atom layer respectively; the second structure is that one silicon atom layer is sandwiched by two carbon atom layers, and Si-C atoms form sp3 hybridization between the two layersThe bond is a bond of a carbon atom; the third is that a layer of carbon atoms is sandwiched by two layers of silicon atoms, and sp3 hybridization is formed between Si-C atoms of the carbon atoms, and the three can be regarded as a unit layer of silicon carbide; the crystal chemical formula of silicon carbide is represented as SiC; the first structure of the silicon carbene has a chemical formula of SiC, and the second structure has a chemical formula of Si_1-xC_x，0.5<x<1; the third chemical structural formula is Si_xC_1-x，0.5<x<1。

3. The preparation method of the silicon-carbon alkene material is characterized by comprising the following steps:

(1) weighing pure silicon alkene, mixing with gallium metal powder, pressing into a cake shape, putting the cake into a graphite boat, putting the sample boat into a stainless steel shell reaction chamber, wherein the reaction chamber is provided with a reactant nozzle for generating high-hydrogen diluted methane gas, the reactant nozzle is positioned in the center right above the reaction chamber, the enhanced plasma is generated in the reaction chamber, and the distance between the nozzle and the center of the bottom of the reaction chamber is 20 cm; a magnetron sputtering inert gas spray gun opening is arranged at the position 5-10 cm away from the center of the top, and the silicon alkene target material at the center of the sample boat can be adjusted and aligned;

(2) vacuumizing to 10 deg.C^-3mTorr；

(3) Heating the sample boat to 1000-1200 ℃;

(4) opening an inert gas high-purity argon spray gun to inject argon, aligning to a target material in a sample boat, keeping sputtering power at 90-200W, keeping working pressure at 0.1-1mTorr, generating a silylene crystal nucleus or silylene quantum dot, opening a plasma generation switch, and opening high-hydrogen diluted methane to inject into a reaction chamber, wherein the volume of methane is as follows: starting a femtosecond laser, wherein the femtosecond laser is aligned to a generated silylene crystal nucleus product in the sample boat and bombards the silylene crystal nucleus or quantum dot product;

4. A method of making an electrode from a silicon carbide material, the method comprising the steps of:

(3) taking out, and coating on the foamed nickel;

(5) taking out the foamed nickel coated with the silicon carbene sample, and pressing the foamed nickel into a sheet shape on a roll press to prepare a plurality of CR2025 electrode plates; assembling the plurality of electrode plates into a button cell, wherein the counter electrode is a lithium plate, a diaphragm is additionally arranged, and lithium ion electrolyte, namely ethyl carbonate containing LiPF6, is filled; and sealing the opening to manufacture a plurality of CR2025 button cells.

5. An electrode made by the method of making an electrode using the silacene material of claim 4.

6. A method for preparing a silicon-carbon alkene electrode active material is characterized by comprising the following steps:

(3) drying the sample at 160-200 ℃ for 10 hours to obtain white powder;

(4) the compound is prepared from the following components in a molar ratio of (7-10): (7-10): (1-2): (1-3): (0.5-1) weighing micron-sized sorghum micropowder, sodium ethoxide, ferrocene, 1, 2-dimethyl-1, 2-diphenyldisilene, urushiol formal lanthanum polymer and dialkyl sodium sulfonate respectively, putting the materials into a second beaker, adding deionized water, and stirring and mixing the materials into a colloidal body by using a mechanical stirrer; putting the colloid into a vacuum drying oven, and heating the colloid into a gel state at 120-200 ℃ to obtain yellow powder;

7. The method of claim 6, wherein the silylene is layered and rolled into a spiral cylinder with a thickness of 0.6nm to 5.7 nm; the chemical composition of the generator is that the atomic weight percentage of the silicon element is 43-59%, the atomic weight percentage of the carbon element is 40.2-56%, and the atomic weight percentage of the metal element is 0.8-1%; the product is solid phase component, and the weight percentage value of the product is 90-100% of silicon-carbon alkene and 0-10% of silicon alkene phase.

8. A silylene electrode active material prepared by the method of claim 6.

9. A method for preparing a battery by using the silicon carbide electrode material as claimed in claim 6, characterized in that the silicon carbide electrode active material prepared by the method as claimed in claim 6 is added with a conductive agent and a binder PVDF, and the ratio of silicon carbide: conductive agent carbon black: 60 weight percent of PVDF: 20: 20, adding NMP to dissolve the mixture into a colloid, uniformly stirring, coating the colloid on a current collector copper foil, putting the current collector copper foil into a vacuum drying oven, drying the current collector copper foil for 18 hours at 170 ℃, taking out the current collector copper foil, and pressing the current collector copper foil into a sheet under the pressure of 1 MPa. The cathode sheet is cut into R2025 round sheets, and the round sheets, the counter electrode lithium sheet and the diaphragm are combined together, and electrolyte is added to assemble the button cell.

10. A lithium sodium alloy/silicon carbide unit layer rechargeable battery prepared from the silicon-carbon alkene active electrode material of claim 9, wherein the lithium: the sodium content is (100-20) and (0-80).