Silicon-based negative electrode material, manufacturing method and application of silicon-based negative electrode material

Abstract

To provide a silicon-based negative electrode material and a manufacturing method for a silicon-based negative electrode material.SOLUTION: A silicon-based negative electrode material includes a silicon-based core and a coating layer. The silicon-based core includes nano silicon and a silicon oxygen-lithium-containing compound. The coating layer includes at least a polymer layer with -Si-O-Si- bonds. The manufacturing method for a silicon-based negative electrode material includes a step (I) for manufacturing the silicon-based core and a step (II) for coating the polymer layer. The silicon-based negative electrode material of the present invention has higher initial coulombic efficiency and lithium insertion capacity. The coating layer includes a polymer layer having -Si-O-Si- bonds that are not soluble in water. This makes it possible to avoid problems in which a paste settles and the coating performance is not good. Thereby, good processing performance is provided to the silicon-based negative electrode material.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to the technical field of material manufacturing, and in particular to silicon-based negative electrode materials, manufacturing methods and applications of silicon-based negative electrode materials. [Background technology]

[0002] With the development of the economy and the progress of society, power tools play an important role in people's lives, and rechargeable batteries have become an indispensable core of power tools. As people pursue larger capacity and lighter weight, existing rechargeable battery technologies have already been unable to meet the rapidly increasing needs, such as the pursuit of longer driving range for electric vehicles and lighter weight for smart wearable devices. The core of all these problems is the practical problem of the low energy density of existing rechargeable batteries.

[0003] Currently, the most widely used negative electrode material for secondary batteries commercially available is graphite, which has a theoretical gram capacity of only 372 mAh / g. Conventional technologies already approach this theoretical gram capacity, spurring the development of a negative electrode material with a higher gram capacity. Silicon anode materials have been studied by many scholars due to their extremely high gram capacity (theoretical gram capacity of 4200 mAh / g). Silicon anode materials also have the advantages of lower lithium intercalation / intercalation potentials and abundant raw material sources, making them a recognized next-generation negative electrode material. However, their disadvantages include large volume expansion (>300%), which leads to particle rupture and efflorescence due to repeated contraction and expansion during charging and discharging. The SEI layer on the surface of the material constantly ruptures and regenerates, consuming large amounts of electrolyte and reversible capacity, and rapidly deteriorating the battery's cycling performance.

[0004] To address the problem of large expansion, silicon-oxygen-containing anode materials have begun to attract attention. They offer higher gram capacities (1500-1800 mAh / g) and lower cycle expansion (<160%). However, their initial coulombic efficiency typically does not exceed 75%, due to the large amount of lithium ions consumed by compounds such as lithium silicate formed during the lithium insertion process, which is the major limiting factor for their application. Prelithiation of silicon-oxygen-containing anodes can increase their initial coulombic efficiency to over 85%, but prelithiation can have adverse effects on the material's processing. For example, during the aqueous homogenization process, surface compounds such as lithium silicate are easily dissolved in water, and the internal nanosilicon reacts with water to produce gas and increase the pH of the paste system, disrupting the paste system's equilibrium, causing paste settling, and potentially resulting in pinholes and uneven coating during the application process.

[0005] Therefore, improving the gas generation behavior of prelithiated silicon-oxygen-containing negative electrode materials and enhancing the processing performance of the materials has become a pressing problem in the industry. Summary of the Invention [Problem to be solved by the invention]

[0006] In view of the above problems, the present invention provides a silicon-based negative electrode material and a method for manufacturing the silicon-based negative electrode material. The silicon-based negative electrode material according to the present invention has the advantages of higher reversible capacity and initial coulombic efficiency, a stable aqueous paste, and excellent processability. In particular, it can suppress gas generation at high temperatures and maintain sufficient stability during the homogenization process. [Means for solving the problem]

[0007] To achieve the above object, a first aspect of the present invention provides a silicon-based negative electrode material, comprising a silicon-based core and a coating layer, wherein the silicon-based core comprises nanosilicon and a silicon-oxygen-lithium-containing compound, and the coating layer comprises at least a polymer layer having an -Si-O-Si- bond.

[0008] The core of the silicon-based negative electrode material of the present invention comprises nanosilicon and a silicon-oxygen-lithium-containing compound, and the coating layer comprises a polymer layer having a water-insoluble -Si-O-Si- bond, which prevents the nanosilicon in the silicon-based core from reacting with water to produce gas, and also prevents problems such as paste settling and poor application performance, thereby providing the silicon-based negative electrode material with good processing performance.

[0009] In some embodiments, the median diameter of the silicon-based negative electrode material is 2 to 15 μm.

[0010] In some embodiments, the nanosilicon has a grain size of 20 nm or less.

[0011] In some embodiments, the silicon-oxygen-lithium-containing compound comprises Li2SiO3 or a mixture of Li2SiO3 and Li2Si2O5.

[0012] In some embodiments, the coating layer is a polymer layer having -Si-O-Si- bonds.

[0013] In some embodiments, the coating layer comprises a carbon coating layer and a polymer layer having -Si-O-Si- bonds, and both the polymer layer and the carbon coating layer are coated on the surface of the silicon-based core.

[0014] In some embodiments, the coating layer comprises a carbon coating layer and a polymer layer having -Si-O-Si- bonds, and the polymer layer is interposed between the carbon coating layer and the silicon-based core.

[0015] In some embodiments, the coating layer comprises a carbon coating layer and a polymer layer having -Si-O-Si- bonds, and the carbon coating layer is interposed between the polymer layer and the silicon-based core.

[0016] In some embodiments, the carbon coating layer has a thickness of 5 to 300 nm.

[0017] In some embodiments, the carbon coating layer accounts for 0.5 to 20% of the combined mass of the silicon-based core and the coating layer.

[0018] In some embodiments, the polymer layer has a thickness of 2 to 50 nm.

[0019] In some embodiments, the polymer layer comprises 0.1 to 10% of the combined mass of the silicon-based core and the coating layer.

[0020] In a second aspect of the present invention, there is provided a method for producing a silicon-based negative electrode material, which includes steps (I) and (II).

[0021] Step (I) is the preparation of a silicon-based core, in which a silicon-based material and a lithium source are mixed together and subjected to a heat treatment reaction, and the silicon-based material is converted into SiO x or carbon-coated SiO x and 0.5≦x≦1.6.

[0022] Step (II) is coating with a polymer layer. An aqueous dispersion of a hydrogen-releasing agent is prepared and added to the silicon-based core with stirring to obtain a mixed solution. The pH value of the mixed solution is maintained at 10-11. A film-forming accelerator containing a silicic acid group is added and stirred continuously. Further, solid-liquid separation is performed to remove the solid phase material, which is then heat-treated and dispersed.

[0023] In the method for producing a silicon-based negative electrode material of the present invention, in step (I), a silicon-based material and a lithium source are subjected to a heat treatment reaction to prelithiate the silicon oxide in the silicon-based material to form a silicon-oxy-lithium-containing compound, thereby obtaining a silicon-based negative electrode material with high reversible capacity and further improving the initial Coulombic efficiency. In step (II), a silicon-based core is added to the aqueous dispersion of a hydrogen-sustaining agent, and the silicon-oxy-lithium-containing compound dissolves in the aqueous solution to form silicate ions. The film-forming accelerator can maintain a sufficient amount of silicate ions in solution. At a pH of 10-11, multiple silicic acids and multiple silicate ions undergo dehydration polycondensation to form a large amount of -Si-O-Si- polymer, which is further condensed by heat treatment to form a three-dimensional network-structured polymer layer. The produced silicon-based negative electrode material effectively avoids gas generation behavior and has good processability.

[0024] In some embodiments, the lithium source comprises at least one of alkyl lithium, metallic lithium, lithium aluminum hydride, lithium amide, lithium carbide, lithium silicide, and lithium borohydride.

[0025] In some embodiments, the lithium source comprises 2-25% by mass of the silicon-based material.

[0026] In some embodiments, the temperature of the heat treatment during the production of the silicon-based core in step (I) is 300 to 1000°C.

[0027] In some embodiments, the duration of the heat treatment during the preparation of the silicon-based core in step (I) is 1 to 10 hours.

[0028] In some embodiments, the heat treatment during the fabrication of the silicon-based core in step (I) is carried out in a vacuum or a non-oxidizing atmosphere, where the non-oxidizing atmosphere is at least one of a hydrogen gas atmosphere, a nitrogen gas atmosphere, a helium gas atmosphere, a neon gas atmosphere, an argon gas atmosphere, a krypton gas atmosphere, and a xenon gas atmosphere.

[0029] In some embodiments, during the preparation of the silicon-based core in step (I), the heat treatment reaction is followed by washing with water.

[0030] In some embodiments, the means used for solid-liquid separation is centrifugation, suction filtration, or pressure filtration.

[0031] In some embodiments, the temperature of the heat treatment during coating of the polymer layer in step (II) is 40 to 800°C.

[0032] In some embodiments, the duration of the heat treatment during coating of the polymer layer in step (II) is 5 to 60 hours.

[0033] In some embodiments, the heat treatment during the deposition of the polymer layer in step (II) is carried out in a vacuum or a non-oxidizing atmosphere, where the non-oxidizing atmosphere is at least one of a hydrogen gas atmosphere, a nitrogen gas atmosphere, a helium gas atmosphere, a neon gas atmosphere, an argon gas atmosphere, a krypton gas atmosphere, and a xenon gas atmosphere.

[0034] In some embodiments, the temperature increase rate of the heat treatment during coating of the polymer layer in step (II) is 0.5 to 5° C. / min.

[0035] In some embodiments, producing the hydrogen sustained-release agent aqueous dispersion comprises dispersing a hydrogen sustained-release agent in a solvent, wherein the hydrogen sustained-release agent comprises at least one of silicon phosphate, silicon tripolyphosphate, magnesium phosphate, calcium phosphate, and magnesium carbonate.

[0036] In some embodiments, the preparation of the aqueous dispersion of the hydrogen-releasing agent comprises dispersing the hydrogen-releasing agent in a solvent, and the solvent adjusts the pH value of the mixture to 10-11.

[0037] In some embodiments, the film-forming accelerator comprises at least one of silica sol, potassium silicate, sodium silicate, ammonium silicate, sodium metasilicate, and potassium metasilicate.

[0038] In some embodiments, the deposition enhancer comprises 0.1-1% of the mass of the silicon-based core.

[0039] In some embodiments, the mass ratio of the solid phase material to the liquid phase material in the mixture is 1:1 to 1:5.

[0040] In some embodiments, the stirring device is a magnetic stirrer, a propeller stirrer, a turbine stirrer, or a ribbon stirrer.

[0041] In some embodiments, the stirring duration is 0.5 to 12 hours.

[0042] In some embodiments, the dispersing comprises grinding and sieving.

[0043] The present invention further provides an application of silicon-based negative electrode materials in negative electrode materials, which can meet the needs of high energy density applications in power tools by using the silicon-based negative electrode materials as negative electrode active materials. [Brief explanation of the drawings]

[0044] [Figure 1] FIG. 1 is an XRD graph of the silicon-based negative electrode material in Example 1. [Figure 2] FIG. 2 is a diagram showing the gas generation state when the paste in Example 1 is left at room temperature for 268 hours. [Figure 3] FIG. 3 is a diagram showing the gas generation state when the paste in Comparative Example 1 is left at room temperature for 2 hours. DETAILED DESCRIPTION OF THE INVENTION

[0045] The silicon-based negative electrode material of the present invention can be applied to secondary batteries as a negative electrode active material, and can be used independently as a negative electrode active material or mixed with other negative electrode active materials (e.g., natural graphite, artificial graphite, soft carbon, and / or hard carbon, etc.).

[0046] The silicon-based negative electrode material of the present invention includes a silicon-based core and a coating layer. The silicon-based negative electrode material has a median diameter of 2 to 15 μm. For example, the median diameter of the silicon-based negative electrode material may be, but is not limited to, 2 μm, 2.5 μm, 3 μm, 4.5 μm, 4.9 μm, 5.2 μm, 6.3 μm, 6.7 μm, 8.2 μm, 10 μm, 12 μm, or 15 μm. In some embodiments, the median diameter may be 4 to 9 μm.

[0047] The silicon-based core comprises nanosilicon and a silicon-oxygen-lithium-containing compound. The nanosilicon has a grain size of 20 nm or less, specifically, but not limited to, 20 nm, 18 nm, 16 nm, 14 nm, 12 nm, 10 nm, 8 nm, 6 nm, or 5 nm. In some embodiments, the nanosilicon has a grain size of 10 nm or less. In some embodiments, nanosilicon with a smaller grain size can prevent the material from expanding too much and causing efflorescence, effectively ensuring its cycle stability. The silicon-oxygen-lithium-containing compound comprises Li2SiO3 or a mixture of Li2SiO3 and Li2SiO5. Due to the tendency of Li2SiO3 to convert to Li2SiO3, the Li2SiO3 formed after lithiation is generally large. During actual operation, the content and specific components of the silicon-oxygen-lithium-containing compound in the silicon-based core are affected by the degree of prelithiation. In some embodiments, the silicon-oxygen-lithium-containing compound is Li2SiO3 or a mixture of Li2SiO3 and Li2SiO5.

[0048] The coating layer of the silicon-based negative electrode material of the present invention can be in several forms.

[0049] In a first embodiment, the coating layer is a polymer layer having -Si-O-Si- bonds, i.e., silicic acid and silicate ions undergo dehydration polycondensation on the surface of the silicon-based core to form a polymer layer with a three-dimensional network structure having -Si-O-Si- bonds.

[0050] In some embodiments, a carbon coating layer is applied to the surface of the silicon-based core before the polymer coating is performed, and the coating layer of the resulting silicon-based negative electrode material includes the carbon coating layer and a polymer layer having -Si-O-Si- bonds. The surface of the silicon-based core may be entirely coated with carbon, or there may be partial or small areas that are not coated with carbon (e.g., areas of ≦50%, ≦40%, ≦30%, ≦20%, ≦10%, ≦5%, ≦3%, ≦1%).

[0051] In a second embodiment, the coating layer comprises a carbon coating layer and a polymer layer having an -Si-O-Si- bond, and both the polymer layer and the carbon coating layer are coated on the surface of the silicon-based core. This is mainly because the carbon coating layer does not entirely cover the silicon-based core, and the polymer layer is coated on the surface area of ​​the silicon-based core that is not covered by the carbon coating layer. Alternatively, the carbon coating layer covers at least 10%, at least 20%, at least 30%, at least 40%, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 93%, at least 95%, at least 97%, or at least 99% of the surface of the silicon-based core, thereby suppressing the expansion of the silicon-based core.

[0052] In a third embodiment, when preparing a silicon-based anode material, a silicon-based core is added to an aqueous dispersion of a hydrogen sustained-release agent, and the solution infiltrates the carbon coating layer and slowly passes through the carbon coating layer to contact the silicon-oxygen-lithium-containing compound in the silicon-based core. The silicon-oxygen-lithium-containing compound then dissolves, penetrates the carbon coating layer, diffuses into the solution, and polymerizes with silicic acid, polycondensing on the surface of the carbon coating layer, thereby forming a three-layer structure of silicon-based core-carbon coating layer-polymer layer. At this time, the coating layer includes a carbon coating layer and a polymer layer having an -Si-O-Si- bond, and the carbon coating layer is interposed between the polymer layer and the silicon-based core.

[0053] In a fourth embodiment, when a silicon-based core is added to an aqueous dispersion of a hydrogen sustained-release agent and immersed for a certain period of time, the amount of silicon-oxygen-lithium-containing compound dissolved is sufficiently large, and the carbon coating layer and the silicon-based core are separated, leaving a gap between them. At this time, the carbon coating layer does not adhere to the silicon-based core, but the dissolved silicon-oxygen-lithium-containing compound begins to polymerize in the gap between the silicon-based core and the carbon coating layer, forming a three-layer structure of silicon-based core-polymer layer-carbon coating layer. That is, the coating layer includes a carbon coating layer and a polymer layer having an -Si-O-Si- bond, and the polymer layer is interposed between the carbon coating layer and the silicon-based core. Alternatively, a four-layer structure of silicon-based core-polymer layer-carbon coating layer-polymer layer may be formed.

[0054] Of course, in actual processes, the coating layer of a silicon-based negative electrode material is not limited to the above-mentioned forms and may be a combination of several forms. For example, if the carbon coating layer does not completely cover the silicon-based core, the polymer layer may be present on the surface of the silicon-based core that is not covered with carbon and on the outer surface of the carbon coating layer. Alternatively, the polymer layer may be present on the surface of the silicon-based core that is not covered with carbon, and on the outer and inner surfaces of the carbon coating layer. Alternatively, the polymer layer may be present on the surface of the silicon-based core that is not covered with carbon and on the inner surface of the carbon coating layer. Alternatively, if the carbon coating layer completely covers the silicon-based core, the polymer layer may be present simultaneously on the outer and inner surfaces of the carbon coating layer. The form of the coating layer of a silicon-based negative electrode material is affected by several factors, such as the coating state, bonding strength, porosity, and immersion time of the silicon-based core in the solution of the carbon coating layer. Regardless of the form of the coating layer, the coating layer at least includes a polymer layer having an -Si-O-Si- bond, and both can suppress gas generation and maintain the silicon-based negative electrode material sufficiently stable during the homogenization process.

[0055] In one embodiment, the carbon coating layer of the present invention has a thickness of 5 to 300 nm. The thickness of the carbon coating layer may be, but is not limited to, 5 nm, 10 nm, 20 nm, 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, or 300 nm. In some embodiments, the thickness of the carbon coating layer is 20 to 100 nm.

[0056] In one embodiment, the carbon coating layer of the present invention accounts for 0.5 to 20% of the combined mass of the silicon-based core and the coating layer. The mass of the carbon coating layer may be, but is not limited to, 0.5%, 1%, 2%, 2.5%, 5%, 6%, 7%, 8%, 9%, 10%, 12%, 15%, or 20%. In some embodiments, the mass of the carbon coating layer is 1 to 10%.

[0057] In one embodiment, the polymer layer of the present invention has a thickness of 2 to 50 nm. Specific examples of the thickness of the polymer layer include, but are not limited to, 2 nm, 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, and 50 nm. In some embodiments, the thickness of the polymer layer is 2 to 10 nm.

[0058] In one embodiment, the polymer layer of the present invention comprises 0.1-10% of the combined mass of the silicone-based core and coating layer. The polymer layer may comprise, but is not limited to, 0.1%, 0.2%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10% of the combined mass. In some embodiments, the polymer layer comprises 1-3% of the combined mass.

[0059] The method for producing a silicon-based negative electrode material of the present invention comprises: The silicon-based core is manufactured by mixing a silicon-based material with a lithium source and carrying out a heat treatment reaction to convert the silicon-based material into SiO x or carbon-coated SiO x and 0.5≦x≦1.6; and step (I) Coating with a polymer layer includes the steps of: preparing an aqueous dispersion of a hydrogen-releasing agent, adding it to a silicon-based core and stirring to obtain a mixed solution; maintaining the pH value of the mixed solution at 10-11; adding a film-forming accelerator containing a silicic acid group and continuing to stir; further performing solid-liquid separation; taking out the solid phase material, heat-treating it, and then dispersing it; (II)

[0060] Generally, SiO x is considered to be nanosilicon dispersed in silicon oxide, where x may be, but is not limited to, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, and in some embodiments, 0.7≦x≦1.2.

[0061] Carbon-coated SiO xis prelithiated as a silicon-based material and contributes to the progress of prelithiation. During the prelithiation process, the liquid prelithiated agent flows along the carbon coating layer and penetrates the carbon coating layer. In addition, it is preferable to release heat during the dissolution process of the prelithiated agent and perform carbon coating to prevent rapid growth of nanosilicon crystal grains in the region. Carbon-coated SiO x can be coated in the usual manner.

[0062] In one embodiment, the lithium source comprises at least one of alkyl lithium, metallic lithium, lithium aluminum hydride, lithium amide, lithium carbide, lithium silicide, and lithium borohydride. The lithium source accounts for 2-25% by mass of the silicon-based material, and the amount of the lithium source may be, but is not limited to, 2%, 5%, 7%, 9%, 10%, 12%, 15%, 17%, 19%, 21%, or 25% by mass. In some embodiments, the amount of the lithium source accounts for 3-15% by mass of the silicon-based material.

[0063] In one embodiment, the heat treatment temperature is 300 to 1000°C. The heat treatment temperature may be, but is not limited to, 300°C, 450°C, 550°C, 600°C, 700°C, 800°C, 900°C, or 1000°C. In some embodiments, the heat treatment temperature is 500 to 800°C. The heat treatment time is 1 to 10 hours. The heat treatment time may be, but is not limited to, 1 hour, 2 hours, 2.5 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, or 10 hours. In some embodiments, the heat treatment temperature is 3 to 7 hours. The heat treatment is performed in a vacuum or a non-oxidizing atmosphere, and the non-oxidizing atmosphere is at least one of a hydrogen gas atmosphere, a nitrogen gas atmosphere, a helium gas atmosphere, a neon gas atmosphere, an argon gas atmosphere, a krypton gas atmosphere, and a xenon gas atmosphere.

[0064] In one embodiment, after the heat treatment reaction, the material is washed with water and dried to remove excess material from the surface. The drying temperature is 40 to 150°C, and the drying temperature may be, but is not limited to, 40°C, 60°C, 80°C, 100°C, 120°C, 140°C, or 150°C. In some embodiments, the drying temperature is 40 to 100°C. The drying time is 6 to 48 hours, and the drying time may be, but is not limited to, 6 hours, 12 hours, 18 hours, 24 hours, 30 hours, 36 hours, 42 hours, 46 hours, or 48 hours. In some embodiments, the heat treatment temperature is 6 to 24 hours.

[0065] In the step (II) of coating the polymer layer, the preparation of the aqueous dispersion of the hydrogen-releasing agent includes dispersing the hydrogen-releasing agent in a solvent.

[0066] In one embodiment, the hydrogen-release agent comprises at least one of silicon phosphate, silicon tripolyphosphate, magnesium phosphate, calcium phosphate, and magnesium carbonate. For example, the hydrogen-release agent is silicon phosphate or silicon tripolyphosphate. The hydrogen-release agent accounts for 0.1-10% of the mass of the silicon-based core. The mass of the hydrogen-release agent may be, but is not limited to, 0.1%, 0.2%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%. In some embodiments, the mass of the hydrogen-release agent is 1-3%, which is lighter in mass and does not undergo side reactions with the silicon-based core, thereby maintaining the original high capacity and high initial efficiency characteristics of the silicon-based core. By selecting the above-mentioned substance as the hydrogen-release agent, it is possible to slowly hydrolyze the hydrogen-release agent to release H. + The single silicate group in the system can be released by the released H + The silicic acid reacts with the silicic acid group to form a dimer, which is then converted back to H +and react with a single silicic acid group to form a trimer, which continuously generates silicic acid polymers, thereby forming a three-dimensional network structure with -Si-O-Si- bonds in subsequent heat treatment.The hydrogen-releasing agent is in particulate form, and its particle size can be reduced to the nano-level, for example, 100nm, 200nm, 300nm, 400nm, 500nm, by sanding, polishing, etc., and for example, the particle size of the hydrogen-releasing agent is D50<200nm.

[0067] In one embodiment, the solvent is a weakly acidic buffer solution, a weakly alkaline buffer solution, or a mixed solution further containing water or alcohol. The pH value of the mixed solution is adjusted with the solvent to 10-11, for example, 10.0, 10.1, 10.2, 10.3, 10.4, 10.5, 10.6, 10.7, 10.8, 10.9, or 11.0. By adjusting the pH value of the mixed solution with the solvent to 10-11, the silicic acid group can exist in the system in the form of a polymer rather than a dimer, and further, a three-dimensional network structure with -Si-O-Si- bonds can be formed during subsequent heat treatment.

[0068] In one embodiment, the film-forming accelerator includes at least one of silica sol, potassium silicate, sodium silicate, ammonium silicate, sodium metasilicate, and potassium metasilicate. The present invention selects these materials as film-forming accelerators, as they are water-soluble and can provide silicate groups to the solution system. For example, the film-forming accelerator is silica sol. The film-forming accelerator accounts for 0.1-1% of the mass of the silicon-based core, including, but not limited to, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, and 1%.

[0069] In one embodiment, the stirring device is a magnetic stirrer, a propeller stirrer, a turbine stirrer, or a ribbon stirrer. In one embodiment, the stirring duration is 0.5 to 12 hours, specifically, but not limited to, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12 hours. In aqueous conditions, the activity of the silicon-based core is high, and the dissolution rate of the silicon-oxygen-lithium-containing compound on the surface is faster. Therefore, if stirring is continued for a long time, a large amount of the silicon-oxygen-lithium-containing compound will dissolve, and the nanosilicon will react with water to generate gas.

[0070] In one embodiment, the mass ratio of the solid phase material to the liquid phase material in the mixed solution is 1:1 to 1:5, specifically, but not limited to, 1:1, 1:2, 1:3, 1:4, or 1:5. For example, the mass ratio of the solid phase material to the liquid phase material in the mixed solution is 1:1 to 1:2. Using a smaller amount of liquid phase material (i.e., solvent) contributes to increasing the concentration of silicic acid and silicic acid groups in the system, contributing to the polycondensation reaction occurring therein. The solid-liquid separation can be performed by centrifugation, suction filtration, or pressure filtration.

[0071] The purpose of heat-treating the solid-phase material obtained by solid-liquid separation in the polymer layer coating step (II) is to dry the solid-phase material and remove moisture, while at the same time allowing the formed silicic acid polymer to undergo further dehydration condensation under the influence of a certain temperature and atmosphere to form a polymer film with a three-dimensional structure. In one embodiment, the heat-treatment temperature is 40 to 800°C, specifically, but not limited to, 40°C, 60°C, 80°C, 100°C, 200°C, 300°C, 400°C, 500°C, 600°C, 700°C, or 800°C. In some embodiments, the heat-treatment temperature is 60 to 500°C. The heat-treatment time is 5 to 60 hours, specifically, but not limited to, 5 hours, 6 hours, 8 hours, 10 hours, 12 hours, 20 hours, 24 hours, 30 hours, 36 hours, 40 hours, 48 ​​hours, 53 hours, or 60 hours. In some embodiments, the heat-treatment time is 6 to 24 hours. The temperature rise rate of the heat treatment is 0.5 to 5°C / min, and specifically may be, but is not limited to, 0.5°C / min, 1.0°C / min, 2°C / min, 3°C / min, 4°C / min, or 5°C / min. In some embodiments, the temperature rise rate of the heat treatment is 1.0 to 1.5°C / min. The heat treatment is performed in a vacuum or a non-oxidizing atmosphere, and the non-oxidizing atmosphere is at least one of a hydrogen gas atmosphere, a nitrogen gas atmosphere, a helium gas atmosphere, a neon gas atmosphere, an argon gas atmosphere, a krypton gas atmosphere, and a xenon gas atmosphere.

[0072] In one embodiment, the dispersion includes grinding and sieving. The linear speed of the grinding device is 5 to 10 m / s, thereby ensuring that the formed polymer film is not destroyed. The sieving may be performed using a 400 mesh sieve.

[0073] In order to better explain the objectives, technical solutions and beneficial effects of the present invention, the present invention will be further described below by way of specific examples. Note that the methods in the following examples are intended to further explain and illustrate the present invention, but are not intended to limit the present invention.

[0074] Example 1 This example is a method for producing a silicon-based negative electrode material, (I) for preparing a silicon-based core, comprising mixing carbon-coated SiO (the carbon coating layer is a total coating, its thickness is 50 nm, and the carbon coating layer accounts for 3.0% of the mass of the carbon-coated SiO) and metallic Li (metallic Li accounts for 10.5% of the mass of the carbon-coated SiO), placing the mixture in a box furnace under nitrogen gas protection atmosphere and heat-treating at 650°C for 4 hours at a heating rate of 2°C / min, and after the reaction is completed, washing the mixture with water, the mass ratio of the mixture to water is 1:3, and removing the water by centrifugation, and placing the wet mixture in a blast dryer at 60°C to oven-dry to obtain a silicon-based core; Coating of the polymer layer involves weighing out 2.0 kg of alkaline buffer solution of sodium carbonate-sodium hydroxide (0.025 mol / L), adding 10 g of silicon tripolyphosphate, and stirring at a rotation speed of 500 rpm / min for 10 minutes to produce an aqueous dispersion of a hydrogen sustained-release agent. 1.0 kg of silicon core is then added and stirred at a rotation speed of 500 rpm / min for 60 minutes to form a mixture, and the pH value of the mixture is maintained at 10.5 and further increased to 16. Step (II) includes adding 7 g of 30 wt% silica sol to make the mass ratio of solid phase material to liquid phase material in the mixture 1:3, stirring for 30 minutes, then filtering under pressure, taking out the solid phase material, heat-treating it in a vacuum atmosphere at 60°C for 24 hours in a blower dryer, with a heating rate of 1.5°C / min, and then naturally cooling it. Then, the solid phase material is pulverized in a pulverizer at a linear velocity of 7 m / s and sieved through a 400 mesh sieve to obtain a silicon-based negative electrode material, and the stirring device is a propeller-type agitator.

[0075] The silicon-based anode material produced had a median diameter of 6 μm. Combining FTIR with electron microscope observation and the XRD graph in Figure 1, the silicon-based anode material was found to contain a silicon-based core and a coating layer. The silicon-based core was composed of nanosilicon, Li2SiO3, and Li2Si2O5, and the coating layer contained a carbon coating layer and a polymer layer with -Si-O-Si- bonds.

[0076] Example 2 This example is a method for producing a silicon-based negative electrode material, Manufacture of silicon-based cores, including carbon-coated SiO x (x is 0.8, the carbon coating layer is a full coating with a thickness of 40 nm, and the carbon coating layer is SiO x 2.5% of the mass of the Li-ion battery) and metallic Li (metallic Li coated with carbon, SiO x (10.5% of the mass of the silicon-based core) is mixed, and placed in a box furnace under nitrogen gas protection atmosphere to heat-treat at 650°C for 4 hours with a heating rate of 2°C / min. After the reaction is completed, the mixed material is washed with water, and the mass ratio of the mixed material to water is 1:3. The water is removed by centrifugation, and the wet mixed material is placed in a blast oven at 60°C to oven-dry to obtain a silicon-based core (I); Coating of the polymer layer: 1.0 kg of alkaline buffer solution of sodium carbonate-sodium hydroxide (0.025 mol / L) was weighed, 10 g of silicon triphosphate was added, and the mixture was stirred at a rotation speed of 500 rpm / min for 10 minutes to prepare an aqueous dispersion of hydrogen sustained-release agent; 1.0 kg of silicon-based core was added, and the mixture was stirred at a rotation speed of 500 rpm / min for 60 minutes to form a mixture; the pH value of the mixture was maintained at 10.7; and the pH value was further increased to 16. and (II) adding 0.7g of 30wt% silica sol, making the mass ratio of solid phase material to liquid phase material in the mixture 1:3, stirring for 30 minutes, then filtering under pressure, taking out the solid phase material, heat-treating it in a vacuum atmosphere at 60°C for 12 hours in a blower dryer, with a heating rate of 1.5°C / min, and after natural cooling, grinding it in a grinding device at a linear velocity of 7m / s and passing it through a 400 mesh sieve to obtain a silicon-based negative electrode material, in which the stirring device used is a propeller-type stirrer.

[0077] The silicon-based anode material produced had a median diameter of 5 μm. FTIR combined with electron microscope observation revealed that the silicon-based anode material contained a silicon-based core and a coating layer. The silicon-based core was composed of nanosilicon, Li2SiO3, and Li2Si2O5, and the coating layer contained a carbon coating layer and a polymer layer with -Si-O-Si- bonds.

[0078] Example 3 This example is a method for producing a silicon-based negative electrode material, Manufacture of silicon-based cores, including carbon-coated SiO x (x is 1.2, the carbon coating layer is a full coating, and its thickness is 60 nm, and the carbon coating layer is SiO x 3.5% of the mass of the Li-ion battery) and metallic Li (metallic Li coated with carbon, SiO x (10.5% of the mass of the silicon-based core) is mixed and placed in a box furnace under nitrogen gas protection atmosphere to be heat-treated at 650°C for 4 hours with a heating rate of 2°C / min. After the reaction is completed, the mixed material is washed with water, the mass ratio of the mixed material to water is 1:3, and the water is removed by centrifugation. The wet mixed material is placed in a blast oven at 60°C to be oven-dried to obtain a silicon-based core (I); Coating of the polymer layer: 1.0 kg of alkaline buffer solution of sodium carbonate-sodium hydroxide (0.025 mol / L) was weighed, 10 g of silicon tripolyphosphate was added, and the mixture was stirred at a rotation speed of 500 rpm / min for 10 minutes to prepare an aqueous dispersion of hydrogen sustained-release agent; 1.0 kg of silicon-based core was added, and the mixture was stirred at a rotation speed of 500 rpm / min for 60 minutes to form a mixture, and the pH value of the mixture was maintained at 10.6, and further increased to 16. and (II) adding 0.7g of 30wt% silica sol, making the mass ratio of solid phase material to liquid phase material in the mixture 1:3, stirring for 30 minutes, then filtering under pressure, taking out the solid phase material, heat-treating it in a vacuum atmosphere at 60°C for 24 hours in a blower dryer, with a heating rate of 1.5°C / min, and after natural cooling, grinding it in a grinding device at a linear velocity of 7m / s and passing it through a 400 mesh sieve to obtain a silicon-based negative electrode material, in which the stirring device used is a propeller-type stirrer.

[0079] The silicon-based anode material produced had a median diameter of 6 μm. FTIR combined with electron microscope observation revealed that the silicon-based anode material contained a silicon-based core and a coating layer. The silicon-based core was composed of nanosilicon, Li2SiO3, and Li2Si2O5, and the coating layer contained a carbon coating layer and a polymer layer with -Si-O-Si- bonds.

[0080] Example 4 This example is a method for producing a silicon-based negative electrode material, Manufacture of silicon-based cores, including carbon-coated SiO x (x is 0.9, the carbon coating layer is a full coating with a thickness of 50 nm, and the carbon coating layer is SiO x 3.0% of the mass of the Li-ion battery) and metallic Li (metallic Li coated with carbon, SiO x (10.5% of the mass of the silicon-based core) is mixed and placed in a box furnace under nitrogen gas protection atmosphere to be heat-treated at 650°C for 4 hours with a heating rate of 2°C / min. After the reaction is completed, the mixed material is washed with water, the mass ratio of the mixed material to water is 1:3, and the water is removed by centrifugation. The wet mixed material is placed in a blast oven at 60°C to be oven-dried to obtain a silicon-based core (I); Coating of the polymer layer: 1.0 kg of alkaline buffer solution of sodium carbonate-sodium hydroxide (0.025 mol / L) was weighed, 10 g of silicon triphosphate was added, and the mixture was stirred at a rotation speed of 500 rpm / min for 10 minutes to prepare an aqueous dispersion of hydrogen sustained-release agent; 1.0 kg of silicon-based core was added, and the mixture was stirred at a rotation speed of 500 rpm / min for 60 minutes to form a mixture; the pH value of the mixture was maintained at 10.5, and further increased to 16. and (II) adding 0.7g of 30wt% silica sol, making the mass ratio of solid phase material to liquid phase material in the mixture 1:3, stirring for 30 minutes, then filtering under pressure, taking out the solid phase material, heat-treating it in a vacuum atmosphere at 400°C for 4 hours in a blower dryer, setting the heating rate at 1.5°C / min, and after natural cooling, grinding it in a grinding device at a linear velocity of 7m / s and passing it through a 400 mesh sieve to obtain a silicon-based negative electrode material, in which the stirring device used is a propeller-type stirrer.

[0081] The silicon-based anode material produced had a median diameter of 7 μm. FTIR combined with electron microscope observation revealed that the silicon-based anode material contained a silicon-based core and a coating layer. The silicon-based core was composed of nanosilicon, Li2SiO3, and Li2Si2O5, and the coating layer contained a carbon coating layer and a polymer layer with -Si-O-Si- bonds.

[0082] Example 5 This example is a method for producing a silicon-based negative electrode material, (I) for preparing a silicon-based core, comprising mixing carbon-coated SiO (the carbon coating layer is a total coating, its thickness is 50 nm, and the carbon coating layer accounts for 3.0% of the mass of the carbon-coated SiO) and metallic Li (metallic Li accounts for 10.5% of the mass of the carbon-coated SiO), placing the mixture in a box furnace under nitrogen gas protection atmosphere and heat-treating at 650°C for 4 hours at a heating rate of 2°C / min, and after the reaction is completed, washing the mixture with water, the mass ratio of the mixture to water is 1:3, and removing the water by centrifugation, and placing the wet mixture in a blast dryer at 60°C to oven-dry to obtain a silicon-based core; Coating of the polymer layer: 2.0 kg of alkaline buffer solution of sodium carbonate-sodium hydroxide (0.025 mol / L) was weighed, 10 g of silicon phosphate was added, and the mixture was stirred at a rotation speed of 500 rpm / min for 10 minutes to prepare an aqueous dispersion of hydrogen sustained-release agent; 1.0 kg of silicon-based core was added, and the mixture was stirred at a rotation speed of 500 rpm / min for 60 minutes to form a mixture, and the pH value of the mixture was maintained at 10.5, and further increased to 16.7. and (II) adding 30 wt% silica sol of 1 g, so that the mass ratio of solid phase material to liquid phase material in the mixture is 1:3, and stirring is continued for 30 minutes, followed by pressure filtration, and the solid phase material is taken out and heat-treated in a vacuum atmosphere at 60°C in a blower dryer for 24 hours at a heating rate of 1.5°C / min, and then naturally cooled. After that, the solid phase material is pulverized in a pulverizer at a linear velocity of 7 m / s and sieved through a 400 mesh sieve to obtain a silicon-based negative electrode material, and the stirring device is a propeller-type agitator.

[0083] The silicon-based anode material produced had a median diameter of 10 μm. FTIR combined with electron microscope observation revealed that the silicon-based anode material contained a silicon-based core and a coating layer. The silicon-based core was composed of nanosilicon, Li2SiO3, and Li2Si2O5, and the coating layer contained a carbon coating layer and a polymer layer with -Si-O-Si- bonds.

[0084] Example 6 This example is a method for producing a silicon-based negative electrode material, (I) for preparing a silicon-based core, comprising mixing carbon-coated SiO (the carbon coating layer is a total coating, its thickness is 80 nm, and the carbon coating layer accounts for 5.0% of the mass of the carbon-coated SiO) and metallic Li (metallic Li accounts for 10.5% of the mass of the carbon-coated SiO), placing the mixture in a box furnace under a nitrogen gas protective atmosphere and heat-treating at 650°C for 4 hours at a heating rate of 2°C / min, and after the reaction is completed, washing the mixture with water, making the mass ratio of the mixture to water 1:3, removing the water by centrifugation, and placing the wet mixture in a 60°C blower dryer to oven-dry to obtain a silicon-based core; Coating of the polymer layer: 2.0 kg of alkaline buffer solution of sodium carbonate-sodium hydroxide (0.025 mol / L) was weighed out, 10 g of magnesium phosphate was added, and the mixture was stirred at a rotation speed of 500 rpm / min for 10 minutes to produce an aqueous dispersion of hydrogen sustained-release agent. 1.0 kg of silicon-based core was then added, and the mixture was stirred at a rotation speed of 500 rpm / min for 60 minutes to form a mixture, and the pH value of the mixture was maintained at 10.5, and further increased to 16. and (II) adding 7 g of 30 wt% silica sol, making the mass ratio of solid phase material to liquid phase material in the mixture 1:3, stirring for 30 minutes, and then filtering under pressure. The solid phase material is taken out and heat-treated in a vacuum atmosphere at 60°C for 24 hours in a blower dryer, with a heating rate of 1.5°C / min, and then naturally cooled. After that, the solid phase material is pulverized in a pulverizer at a linear velocity of 7 m / s and sieved through a 400 mesh sieve to obtain a silicon-based negative electrode material, and the stirring device is a propeller-type agitator.

[0085] The silicon-based anode material produced had a median diameter of 6 μm. FTIR combined with electron microscope observation revealed that the silicon-based anode material contained a silicon-based core and a coating layer. The silicon-based core was composed of nanosilicon, Li2SiO3, and Li2Si2O5, and the coating layer contained a carbon coating layer and a polymer layer with -Si-O-Si- bonds.

[0086] Example 7 This example is a method for producing a silicon-based negative electrode material, (I) for preparing a silicon-based core, comprising mixing carbon-coated SiO (the carbon coating layer is a total coating, its thickness is 50 nm, and the carbon coating layer accounts for 3.0% of the mass of the carbon-coated SiO) and metallic Li (metallic Li accounts for 10.5% of the mass of the carbon-coated SiO), placing the mixture in a box furnace under nitrogen gas protection atmosphere and heat-treating at 650°C for 4 hours at a heating rate of 2°C / min, and after the reaction is completed, washing the mixture with water, the mass ratio of the mixture to water is 1:3, and removing the water by centrifugation, and placing the wet mixture in a blast dryer at 60°C to oven-dry to obtain a silicon-based core; Coating of the polymer layer: 2.0 kg of alkaline buffer solution of sodium carbonate-sodium hydroxide (0.025 mol / L) was weighed out, 10 g of magnesium carbonate was added, and the mixture was stirred at a rotation speed of 500 rpm / min for 10 minutes to produce an aqueous dispersion of hydrogen sustained-release agent. 1.0 kg of silicon-based core was then added and the mixture was stirred at a rotation speed of 500 rpm / min for 60 minutes to form a mixture, and the pH value of the mixture was maintained at 10.5 and further increased to 16. and (II) adding 7 g of 30 wt% silica sol, making the mass ratio of solid phase material to liquid phase material in the mixture 1:3, stirring for 30 minutes, and then filtering under pressure. The solid phase material is taken out and heat-treated in a vacuum atmosphere at 60°C for 24 hours in a blower dryer, with a heating rate of 1.5°C / min, and then naturally cooled. After that, the solid phase material is pulverized in a pulverizer at a linear velocity of 7 m / s and sieved through a 400 mesh sieve to obtain a silicon-based negative electrode material, and the stirring device is a propeller-type agitator.

[0087] The silicon-based anode material produced had a median diameter of 6 μm. FTIR combined with electron microscope observation revealed that the silicon-based anode material contained a silicon-based core and a coating layer. The silicon-based core was composed of nanosilicon, Li2SiO3, and Li2Si2O5, and the coating layer contained a carbon coating layer and a polymer layer with -Si-O-Si- bonds.

[0088] Example 8 This example is a method for producing a silicon-based negative electrode material, The silicon-based core is prepared by mixing carbon-coated SiO (the carbon coating layer is a total coating, its thickness is 50 nm, and the carbon coating layer accounts for 3.0% of the mass of the carbon-coated SiO) and metallic Li (metallic Li accounts for 10.5% of the mass of the carbon-coated silicon-oxygen-containing material SiO), and then heat-treating the mixture in a box furnace under a nitrogen gas protective atmosphere at 650°C for 4 hours with a heating rate of 2°C / min. After the reaction is completed, the mixture is washed with water, and the mass ratio of the mixture to water is 1:3. The water is removed by centrifugation, and the wet mixture is placed in a blast oven at 60°C to oven-dry, thereby obtaining a silicon-based core. (I) Coating of the polymer layer: 2.0 kg of alkaline buffer solution of sodium carbonate-sodium hydroxide (0.025 mol / L) was weighed, 10 g of calcium phosphate was added, and the mixture was stirred at a rotation speed of 500 rpm / min for 10 minutes to produce an aqueous dispersion of hydrogen sustained-release agent. 1.0 kg of silicon-based core was then added and the mixture was stirred at a rotation speed of 500 rpm / min for 60 minutes to form a mixture, and the pH value of the mixture was maintained at 10.5 and further increased to 16. and (II) adding 7 g of 30 wt% silica sol, making the mass ratio of solid phase material to liquid phase material in the mixture 1:3, stirring for 30 minutes, and then filtering under pressure. The solid phase material is taken out and heat-treated in a vacuum atmosphere at 60°C for 24 hours in a blower dryer, with a heating rate of 1.5°C / min, and then naturally cooled. After that, the solid phase material is pulverized in a pulverizer at a linear velocity of 7 m / s and sieved through a 400 mesh sieve to obtain a silicon-based negative electrode material, and the stirring device is a propeller-type agitator.

[0089] The silicon-based anode material produced had a median diameter of 6 μm. FTIR combined with electron microscope observation revealed that the silicon-based anode material contained a silicon-based core and a coating layer. The silicon-based core was composed of nanosilicon, Li2SiO3, and Li2Si2O5, and the coating layer contained a carbon coating layer and a polymer layer with -Si-O-Si- bonds.

[0090] Example 9 This example is a method for producing a silicon-based negative electrode material, (I) for preparing a silicon-based core, comprising mixing carbon-coated SiO (the carbon coating layer is a total coating, its thickness is 50 nm, and the carbon coating layer accounts for 3.0% of the mass of the carbon-coated SiO) and metallic Li (metallic Li accounts for 10.5% of the mass of the carbon-coated SiO), placing the mixture in a box furnace under nitrogen gas protection atmosphere and heat-treating at 650°C for 4 hours at a heating rate of 2°C / min, and after the reaction is completed, washing the mixture with water, the mass ratio of the mixture to water is 1:3, and removing the water by centrifugation, and placing the wet mixture in a blast dryer at 60°C to oven-dry to obtain a silicon-based core; Coating the polymer layer, 2.0 kg of alkaline buffer solution of sodium carbonate-sodium hydroxide (0.025 mol / L) was weighed, 10 g of silicon triphosphate was added, and the mixture was stirred at a rotation speed of 500 rpm / min for 10 minutes to prepare an aqueous dispersion of hydrogen sustained-release agent, and 1.0 kg of silicon-based core was added, and the mixture was stirred at a rotation speed of 500 rpm / min for 60 minutes to form a mixture, and the pH value of the mixture was maintained at 10.5, and and (II) adding 5g of potassium silicate to the mixture, making the mass ratio of solid phase material to liquid phase material in the mixture 1:3, stirring for 30 minutes, and then filtering under pressure. The solid phase material is taken out and heat-treated in a vacuum atmosphere at 60°C for 24 hours in a blower dryer, with a heating rate of 1.5°C / min, and then naturally cooled. After that, the solid phase material is pulverized in a pulverizer at a linear velocity of 7m / s and sieved through a 400 mesh sieve to obtain a silicon-based negative electrode material, and the stirring device is a propeller-type agitator.

[0091] The silicon-based anode material produced had a median diameter of 6 μm. FTIR combined with electron microscope observation revealed that the silicon-based anode material contained a silicon-based core and a coating layer. The silicon-based core was composed of nanosilicon Li2SiO3 and Li2Si2O5, and the coating layer contained a carbon coating layer and a polymer layer with -Si-O-Si- bonds.

[0092] Example 10 This example is a method for producing a silicon-based negative electrode material, (I) for preparing a silicon-based core, comprising mixing carbon-coated SiO (the carbon coating layer is a total coating, its thickness is 50 nm, and the carbon coating layer accounts for 3.0% of the mass of the carbon-coated SiO) and metallic Li (metallic Li accounts for 10.5% of the mass of the carbon-coated SiO), placing the mixture in a box furnace under nitrogen gas protection atmosphere and heat-treating at 650°C for 4 hours at a heating rate of 2°C / min, and after the reaction is completed, washing the mixture with water, the mass ratio of the mixture to water is 1:3, and removing the water by centrifugation, and placing the wet mixture in a blast dryer at 60°C to oven-dry to obtain a silicon-based core; Coating the polymer layer, 2.0 kg of alkaline buffer solution of sodium carbonate-sodium hydroxide (0.025 mol / L) was weighed, 10 g of silicon triphosphate was added, and the mixture was stirred at a rotation speed of 500 rpm / min for 10 minutes to prepare an aqueous dispersion of hydrogen sustained-release agent, and 1.0 kg of silicon-based core was added, and the mixture was stirred at a rotation speed of 500 rpm / min for 60 minutes to form a mixture, and the pH value of the mixture was maintained at 10.5; Step (II) includes adding 5 g of sodium metasilicate to make the mass ratio of solid phase material to liquid phase material in the mixture 1:3, stirring for 30 minutes, filtering under pressure, taking out the solid phase material, heat-treating it in a vacuum atmosphere at 60°C for 24 hours in a blower dryer, increasing the temperature at a rate of 1.5°C / min, allowing it to cool naturally, and then pulverizing it in a pulverizer at a linear velocity of 7 m / s and passing it through a 400 mesh sieve to obtain a silicon-based negative electrode material, wherein the stirring device is a propeller-type agitator.

[0093] The silicon-based anode material produced had a median diameter of 6 μm. FTIR combined with electron microscope observation revealed that the silicon-based anode material contained a silicon-based core and a coating layer. The silicon-based core was composed of nanosilicon, Li2SiO3, and Li2Si2O5, and the coating layer contained a carbon coating layer and a polymer layer with -Si-O-Si- bonds.

[0094] Example 11 This example is a method for producing a silicon-based negative electrode material, The silicon-based core is prepared by mixing carbon-coated SiO (the carbon coating layer is a total coating, its thickness is 100 nm, and the carbon coating layer accounts for 4.0% of the mass of the carbon-coated SiO) with lithium borohydride (lithium borohydride accounts for 25% of the mass of the carbon-coated SiO), and then heat-treating the mixture in a box furnace under nitrogen gas protection atmosphere at 650°C for 4 hours with a heating rate of 2°C / min. After the reaction is completed, the mixture is washed with water, and the mass ratio of the mixture to water is 1:3. The water is removed by centrifugation, and the wet mixture is placed in a blast oven at 60°C to oven-dry, thereby obtaining a silicon-based core. (I) Coating of the polymer layer: 1.5 kg of alkaline buffer solution of sodium carbonate-sodium hydroxide (0.025 mol / L) was weighed, 5 g of silicon triphosphate was added, and the mixture was stirred at a rotation speed of 500 rpm / min for 10 minutes to prepare an aqueous dispersion of hydrogen sustained-release agent; 0.8 kg of silicon-based core was added, and the mixture was stirred at a rotation speed of 500 rpm / min for 60 minutes to form a mixture; the pH value of the mixture was maintained at 10.6; and the mixture was further stirred for 20 minutes. and (II) adding 30 wt% silica sol of 1 g, so that the mass ratio of solid phase material to liquid phase material in the mixture is 1:3, and stirring is continued for 30 minutes, followed by pressure filtration, and the solid phase material is taken out and heat-treated in a vacuum atmosphere at 60°C in a blower dryer for 24 hours at a heating rate of 1.5°C / min, and then naturally cooled. After that, the solid phase material is pulverized in a pulverizer at a linear velocity of 7 m / s and sieved through a 400 mesh sieve to obtain a silicon-based negative electrode material, and the stirring device is a propeller-type agitator.

[0095] The silicon-based anode material produced had a median diameter of 6 μm. FTIR combined with electron microscope observation revealed that the silicon-based anode material contained a silicon-based core and a coating layer. The silicon-based core was composed of nanosilicon, Li2SiO3, and Li2Si2O5, and the coating layer contained a carbon coating layer and a polymer layer with -Si-O-Si- bonds.

[0096] Example 12 This example is a method for producing a silicon-based negative electrode material, (I) for producing a silicon-based core, comprising mixing carbon-coated SiO (the carbon coating layer is a total coating, its thickness is 50 nm, and the carbon coating layer accounts for 3.0% of the mass of the carbon-coated SiO) and metallic Li (metallic Li accounts for 10.5% of the mass of the carbon-coated SiO), placing the mixture in a box furnace in a helium gas atmosphere and heat-treating it at 860°C for 2 hours at a heating rate of 3°C / min, and after the reaction is completed, washing the mixture with water, making the mass ratio of the mixture to water 1:2, removing the water by centrifugation, and placing the wet mixture in a blower dryer at 80°C to oven-dry to obtain a silicon-based core; Coating of the polymer layer involves weighing out 2.0 kg of alkaline buffer solution of sodium carbonate-sodium hydroxide (0.05 mol / L), adding 10 g of silicon tripolyphosphate, and stirring at a rotation speed of 700 rpm / min for 15 minutes to produce an aqueous dispersion of hydrogen sustained-release agent. 0.9 kg of silicon-based core is then added and stirred at a rotation speed of 700 rpm / min for 60 minutes to form a mixture, and the pH value of the mixture is maintained at 10.5 and further increased to 16. and (II) adding 7 g of 20 wt% silica sol to make the mass ratio of solid phase material to liquid phase material in the mixture 1:1, stirring for 30 minutes, then filtering under pressure, taking out the solid phase material, heat-treating it in a vacuum atmosphere at 60°C for 24 hours in a blower dryer, with a heating rate of 2.5°C / min, and then naturally cooling, and then pulverizing it in a pulverizer at a linear velocity of 5 m / s and passing it through a 400 mesh sieve to obtain a silicon-based negative electrode material, wherein the stirring device is a propeller-type agitator.

[0097] The silicon-based anode material produced had a median diameter of 6 μm. FTIR combined with electron microscopy revealed that the silicon-based anode material contained a silicon-based core and a coating layer. The silicon-based core contained nanosilicon, Li2SiO3, and Li2Si2O5, and the coating layer contained a carbon coating layer and a polymer layer with -Si-O-Si- bonds.

[0098] The silicon-based negative electrode materials prepared in Examples 1 to 12 were subjected to infrared absorption spectrum tests. The powder samples were prepared by mixing a certain amount of powder sample and a certain amount of KBr in a certain ratio using a KBr tableting method, and then grinding the mixture under an infrared lamp. The resulting mixture was subjected to an infrared absorption spectrum test at 600 Kgf / cm. 2 The pressure was maintained for about 1 minute. The silicon-based negative electrode material was -1 There is a strong antisymmetric stretching vibration absorption peak of the -Si-O-Si- bond at 800 cm -1 There is a symmetric stretching vibration absorption peak of the -Si-O-Si- bond at about 1000 nm.

[0099] Comparative Example 1 This example is a method for producing a silicon-based negative electrode material, (I) for preparing a silicon-based core, comprising mixing carbon-coated SiO (the carbon coating layer is a total coating, its thickness is 50 nm, and the carbon coating layer accounts for 3.0% of the mass of the carbon-coated SiO) and metallic Li (metallic Li accounts for 10.5% of the mass of the carbon-coated SiO), placing the mixture in a box furnace under nitrogen gas protection atmosphere and heat-treating at 650°C for 4 hours at a heating rate of 2°C / min, and after the reaction is completed, washing the mixture with water, the mass ratio of the mixture to water is 1:3, and removing the water by centrifugation, and placing the wet mixture in a blast dryer at 60°C to oven-dry to obtain a silicon-based core; and (II) coating the polymer layer by weighing 2.0 kg of an alkaline buffer solution of sodium carbonate-sodium hydroxide (0.025 mol / L), adding 1.0 kg of silicon-based cores, and stirring at a rotation speed of 500 rpm / min for 60 minutes to form a mixture, maintaining the pH value of the mixture at 10.5. 16.7 g of 30 wt% silica sol is further added, so that the mass ratio of solid phase material to liquid phase material in the mixture is 1:3. Stirring is continued for 30 minutes, followed by pressure filtration. The solid phase material is collected and heat-treated in a vacuum atmosphere at 60°C in a blower dryer for 24 hours at a heating rate of 1.5°C / min. After natural cooling, the solid phase material is pulverized in a pulverizer at a linear velocity of 7 m / s and sieved through a 400 mesh sieve to obtain a silicon-based negative electrode material, wherein the stirring device is a propeller-type agitator.

[0100] Combining FTIR with electron microscope observation, it was found that the silicon-based negative electrode material produced in Comparative Example 1 had neither a polymer layer nor -Si-O-Si- bonds.

[0101] Comparative Example 2 This example is a method for producing a silicon-based negative electrode material, (I) for preparing a silicon-based core, comprising mixing carbon-coated SiO (the carbon coating layer is a total coating, its thickness is 50 nm, and the carbon coating layer accounts for 3.0% of the mass of the carbon-coated SiO) and metallic Li (metallic Li accounts for 10.5% of the mass of the carbon-coated SiO), placing the mixture in a box furnace under nitrogen gas protection atmosphere and heat-treating at 650°C for 4 hours at a heating rate of 2°C / min, and after the reaction is completed, washing the mixture with water, the mass ratio of the mixture to water is 1:3, and removing the water by centrifugation, and placing the wet mixture in a blast dryer at 60°C to oven-dry to obtain a silicon-based core; Coating of polymer layer includes step (II), in which 2.0 kg of deionized water is weighed, 10 g of silicon tripolyphosphate is added, and the mixture is stirred at a rotation speed of 500 rpm / min for 10 minutes to prepare a hydrogen sustained-release agent aqueous dispersion; 1.0 kg of silicon-based core is added, and the mixture is stirred at a rotation speed of 500 rpm / min for 60 minutes to form a mixture; the pH value of the mixture is measured to be 12; 16.7 g of 30 wt% silica sol is further added, and the mass ratio of solid phase material to liquid phase material in the mixture is 1:3; the mixture is stirred for 30 minutes, and then filtered under pressure; the solid phase material is taken out and heat-treated in a vacuum atmosphere at 60°C for 24 hours in a blower dryer, and the heating rate is 1.5°C / min; after natural cooling, the solid phase material is pulverized in a pulverizer at a linear velocity of 7 m / s and sieved through a 400 mesh sieve to obtain a silicon-based negative electrode material; the stirring device is a propeller-type agitator.

[0102] In Comparative Example 2, no polymerization occurred, and the FTIR combined with the observation by electron microscope revealed that the produced silicon-based negative electrode material had neither a polymer layer nor -Si-O-Si- bonds.

[0103] Comparative Example 3 This example is a method for producing a silicon-based negative electrode material, (I) for preparing a silicon-based core, comprising mixing carbon-coated SiO (the carbon coating layer is a total coating, its thickness is 50 nm, and the carbon coating layer accounts for 3.0% of the mass of the carbon-coated SiO) and metallic Li (metallic Li accounts for 10.5% of the mass of the carbon-coated SiO), placing the mixture in a box furnace under nitrogen gas protection atmosphere and heat-treating at 650°C for 4 hours at a heating rate of 2°C / min, and after the reaction is completed, washing the mixture with water, the mass ratio of the mixture to water is 1:3, and removing the water by centrifugation, and placing the wet mixture in a blast dryer at 60°C to oven-dry to obtain a silicon-based core; Coating of polymer layer includes step (II), in which 2.0 kg of alkaline buffer solution of sodium carbonate-sodium hydroxide (0.025 mol / L) is weighed, 10 g of silicon tripolyphosphate is added, and the mixture is stirred at a rotation speed of 500 rpm / min and stirred for 10 minutes, thereby preparing an aqueous dispersion of hydrogen sustained-release agent; and 1.0 kg of silicon-based core is added, and the mixture is stirred at a rotation speed of 500 rpm / min for 60 minutes to form a mixture, the pH value of the mixture is maintained at 10.5, the mass ratio of solid phase material to liquid phase material in the mixture is 1:3, and the mixture is stirred for 30 minutes, and then filtered under pressure; the solid phase material is taken out and heat-treated in a vacuum atmosphere at 60°C for 24 hours in a blower dryer, the heating rate is 1.5°C / min, and the mixture is naturally cooled, and then pulverized in a pulverizer at a linear velocity of 7 m / s and sieved through a 400 mesh screen to obtain a silicon-based negative electrode material, and the stirring device is a propeller-type agitator.

[0104] It was found by detection that the network structure of the polymer layer of the silicon-based negative electrode material prepared in Comparative Example 3 was not complete.

[0105] The silicon-based negative electrode materials produced in Examples 1 to 12 and Comparative Examples 1 to 3 were subjected to electrochemical performance tests and gas generation tests under the following test conditions, and the test results are shown in Table 1. The state of gas generation when the paste in Example 1 was left at room temperature for 268 hours is shown in Figure 2. The state of gas generation when the paste in Comparative Example 1 was left at room temperature for 2 hours is shown in Figure 3.

[0106] Electrochemical Performance Test The silicon-based anode materials prepared in Examples 1-12 and Comparative Examples 1-3 were used as the active material. They were mixed with an aqueous dispersion of acrylonitrile copolymer (LA132, 15% solids) as a binder and a conductive agent (Super-P) in a mass ratio of 70:10:20. An appropriate amount of water was added as a solvent to form a paste. This paste was then applied to copper foil, vacuum dried, and roll-pressed to form anode sheets. Metallic lithium was used as the counter electrode. A 1 mol / L LiPF6 electrolyte was mixed with a ternary solvent mixture of EC:DMC:EMC = 1:1:1 (v / v). A polypropylene microporous membrane was used as the separator. CR2032 button batteries were assembled in an inert gas-filled glove box. The charge / discharge test of the button battery was carried out using the battery test system of Wuhan Landen Electronics Co., Ltd., and the battery was charged and discharged at a constant current of 0.1C to 0.01V at room temperature, then discharged at a constant current of 0.02C to 0.005V, and finally charged at a constant current of 0.1C to 1.5V. The capacity charged to 1.5V is the initial lithium insertion capacity, and the ratio of the charge capacity to the discharge capacity is the initial coulombic efficiency.

[0107] Gas Generation Test In the electrochemical performance test step, 5 ml of the paste was taken and placed in a 20 ml syringe, the tip of the needle was sealed with hot melt, and the syringe containing the paste was sealed and then stored in an oven at 45°C under room temperature conditions. The movement of the syringe was observed, and the time difference between the time when the syringe began to move and the time when the test started was recorded, which was taken as the gas generation time of the material.

[0108] Table 1. Results of electrochemical performance tests and gas generation tests for each example and comparative example JPEG0007735361000001.jpg120170

[0109] As can be seen from the results in Table 1, the silicon-based negative electrode materials prepared in Examples 1 to 12 and Comparative Examples 1 to 3 have higher initial lithium insertion capacity and initial coulombic efficiency. Compared with Comparative Examples 1 to 3, the silicon-based negative electrode materials prepared in Examples 1 to 12 can effectively suppress gas generation, and at a pH of 10 to 11, multiple silicic acids and multiple silicic acid ions can undergo dehydration polycondensation to form large amounts of -Si-O-Si- polymer, which can then be further condensed by heat treatment to form a polymer layer with a three-dimensional network structure.

[0110] However, since there is no hydrogen-releasing agent in Comparative Example 1, the conversion of silicate ions to silicic acid and polycondensation cannot be promoted, and a polymer layer having -Si-O-Si- bonds cannot be formed. As can be seen from a comparison of Figures 2 and 3, the silicon-based negative electrode material prepared in Example 1 does not generate gas after standing at room temperature for 268 hours, whereas the silicon-based negative electrode material prepared in Comparative Example 1 generates gas at a rate of 3 mL after standing at room temperature for 2 hours.

[0111] In Comparative Example 2, the pH value of the mixed liquid was 12, and the effect of suppressing gas generation in Comparative Example 2 was poor.

[0112] In Comparative Example 3, there is no film formation accelerator, and the gas generation suppression effect in Comparative Example 3 is poor.

[0113] Finally, it should be noted that the above examples are merely for illustrating the technical solutions of the present invention and do not limit the protection scope of the present invention. Although the present invention has been described in detail through preferred embodiments, it is not limited to those listed in the embodiments. As will be understood by those skilled in the art, modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for producing a silicon-based negative electrode material, comprising: The method for producing a silicon-based core comprises mixing a silicon-based material with a lithium source and carrying out a heat treatment reaction to convert the silicon-based material into SiO ｘ or carbon-coated SiO ｘ and 0.5≦x≦1.6; and a step (II) of coating a polymer layer, comprising: preparing an aqueous dispersion of a hydrogen-releasing agent, adding it to the silicon-based core and stirring to obtain a mixed solution; maintaining the pH value of the mixed solution at 10-11; adding a film-forming accelerator containing a silicic acid group and continuing to stir; and further performing solid-liquid separation to remove a solid phase material, heat-treating it, and then dispersing it.

2. The lithium source comprises at least one of alkyl lithium, metallic lithium, lithium aluminum hydride, lithium amide, lithium carbide, lithium silicide, and lithium borohydride. The method for producing a silicon-based negative electrode material according to claim 1, characterized in that the lithium source accounts for 2 to 25% of the mass of the silicon-based material (2).

3. The temperature of the heat treatment during the production of the silicon-based core in step (I) is 300 to 1000°C (3); The duration of the heat treatment during the production of the silicon-based core in step (I) is 1 to 10 h (4); (5) The heat treatment during the production of the silicon-based core in step (I) is performed in a vacuum or a non-oxidizing atmosphere, and the non-oxidizing atmosphere is at least one of a hydrogen gas atmosphere, a nitrogen gas atmosphere, a helium gas atmosphere, a neon gas atmosphere, an argon gas atmosphere, a krypton gas atmosphere, and a xenon gas atmosphere.

2. The method for producing a silicon-based negative electrode material according to claim 1, further comprising the step (I) of washing the silicon-based core with water and drying the resulting mixture after the heat treatment reaction.

4. The method for producing a silicon-based negative electrode material according to claim 1, characterized in that the solid-liquid separation is carried out by a method selected from the group consisting of centrifugation, suction filtration, and pressure filtration (7).

5. Feature (8), wherein the temperature of the heat treatment during coating of the polymer layer in step (II) is 40 to 800°C; Feature (9), wherein the heat treatment time during coating of the polymer layer in step (II) is 5 to 60 hours; The heat treatment during the coating of the polymer layer in step (II) is carried out in a vacuum or a non-oxidizing atmosphere, and the non-oxidizing atmosphere is at least one of a hydrogen gas atmosphere, a nitrogen gas atmosphere, a helium gas atmosphere, a neon gas atmosphere, an argon gas atmosphere, a krypton gas atmosphere, and a xenon gas atmosphere. The method for producing a silicon-based negative electrode material according to claim 1, characterized in that the method further comprises the step (II) of: (11) comprising: (i) heating the polymer layer at a rate of 0.5 to 5°C / min in the heat treatment;

6. The preparation of the hydrogen sustained-release agent aqueous dispersion includes dispersing a hydrogen sustained-release agent in a solvent, and the hydrogen sustained-release agent includes at least one of silicon phosphate, silicon tripolyphosphate, magnesium phosphate, calcium phosphate, and magnesium carbonate (12). The method for producing the silicon-based negative electrode material according to claim 1, characterized in that the method for producing the hydrogen-release agent aqueous dispersion comprises dispersing the hydrogen-release agent in a solvent, and the solvent adjusts the pH value of the mixture to 10-11 (13).

7. Feature (14), wherein the film-forming accelerator comprises at least one of silica sol, potassium silicate, sodium silicate, ammonium silicate, sodium metasilicate, and potassium metasilicate. The method for producing a silicon-based negative electrode material according to claim 1, characterized in that the film-forming accelerator accounts for 0.1 to 1% of the mass of the silicon-based core (15).

8. (16) The mass ratio of the solid phase substance to the liquid phase substance in the mixture is 1:1 to 1:

5. The stirring device is a magnetic stirrer, a propeller stirrer, a turbine stirrer, or a ribbon stirrer (17). The method for producing a silicon-based negative electrode material according to claim 1, characterized in that the method further comprises the feature (18) that the duration of the stirring is 0.5 to 12 hours.

9. 10. The method for producing a silicon-based negative electrode material according to claim 1, characterized in that the dispersion comprises a feature (19) including grinding and sieving.

10. A method for using a silicon-based negative electrode material produced by the method for producing a silicon-based negative electrode material according to any one of claims 1 to 9 as a negative electrode active material for a secondary battery.

Images