Negative electrode material, preparation method thereof and battery

Abstract

The invention provides a negative electrode material and a preparation method thereof, and a battery, the negative electrode material comprises a silicon-based active substance and a carbon material, the oil absorption value of the negative electrode material is O mL / 100 g, the specific surface area is S m < 2 > / g, the tap density is T g / cm < 3 >, the compaction degree of the negative electrode material is Y, Y = T / (0.01 * O * S), and Y is more than 0.6 and less than 3.0. The negative electrode material provided by the invention has relatively high compaction capability, and is easy to compact in a pole piece preparation process, so that relatively high compaction density is obtained, and the cycle performance of the battery is improved.

Description

Technical Field

[0001] The present application relates to the technical field of negative electrode materials, and in particular, to a negative electrode material and a preparation method thereof, and a battery. Background Art

[0002] Electric new energy vehicles are the future development direction of the automobile market, and their core components are lithium-ion batteries. As the market develops, the demand for high-capacity and high-density batteries is increasing. The use of new high-specific-capacity positive and negative electrode materials is one of the important methods to improve the energy density of batteries.

[0003] Silicon-based negative electrode materials are considered to be the next generation of negative electrode materials. They are highly praised for their ultra-high theoretical specific capacity (4200mAh / g) and low lithium desorption potential (<0.5V). The voltage platform of silicon is slightly higher than that of graphite. It is difficult to cause surface lithium deposition during charging, and has better safety performance. However, the silicon negative electrode has a drastic volume expansion effect during the cycle, which causes the material to pulverize and break, and the battery cycle decays quickly.

[0004] At present, silicon-based materials and carbon materials are often compounded, but the existing compounding method is often a simple mixing, lacking a reasonable combination of silicon-based materials and carbon materials. It can no longer meet the market demand for negative electrode materials with high compaction density and good cycle performance. It is necessary to explore the mechanism of action of multiple factors in coordination and develop composite negative electrode materials that meet market demand. Summary of the invention

[0005] The present application proposes a negative electrode material and a preparation method thereof, and a battery, which can improve the compaction density of the negative electrode material so that the negative electrode material has good cycle performance.

[0006] In a first aspect, the present application provides a negative electrode material comprising a silicon-based active substance and a carbon material, wherein the oil absorption value of the negative electrode material is 0 mL / 100 g and the specific surface area is S m 2 / g, tap density is T g / cm 3 The compactibility of the negative electrode material is Y, Y=T / (0.01*O*S), 0.6<Y<3.0.

[0007] In some embodiments, the silicon-based active material includes at least one of elemental silicon, silicon oxide, and silicon alloy.

[0008] In some embodiments, the silicon-based active material further includes a doping metal M, where M is selected from at least one of Li, Mg, Al, Fe, La, Zn, Ti, Cu, and Mn.

[0009] In some embodiments, the silicon-based active material further includes a doping metal M, where M is Mg and / or Li.

[0010] In some embodiments, the silicon-based active material comprises silicon oxide, and the general formula of the silicon oxide is SiO x , 0.5≤x<2.

[0011] In some embodiments, the silicon-based active material has a median particle size of 1.0 μm to 10.0 μm.

[0012] In some embodiments, the carbon material includes at least one of graphite, graphene, amorphous carbon, carbon nanotubes, and carbon fibers.

[0013] In some embodiments, the carbon material contains oxygen.

[0014] In some embodiments, the tap density of the negative electrode material is T g / cm 3 , T>0.90.

[0015] In some embodiments, the oil absorption value of the negative electrode material is 0 mL / 100 g, and O<57.0.

[0016] In some embodiments, the specific surface area of ​​the negative electrode material is S m 2 / g, S<3.50.

[0017] In some embodiments, the pH of the negative electrode material is 6-12.

[0018] In some embodiments, the particle size of the negative electrode material satisfies: 2.5≤D 10 ≤8.5μm, 12.0≤D 90 ≤28.0μm.

[0019] In some embodiments, the water content of the negative electrode material is ≤0.5 wt %.

[0020] In some embodiments, the mass content of Si element in the negative electrode material is 0.5% to 25%.

[0021] In some embodiments, in the negative electrode material, the silicon-based active material and the carbon material are dispersed with each other in the form of particles.

[0022] In some embodiments, the compactability of the negative electrode material is Y, 0.6<Y≤1.1.

[0023] In some embodiments, the compactability of the negative electrode material is Y, 1.1<Y<3.0.

[0024] In a second aspect, the present application provides a method for preparing a negative electrode material, the method comprising the following steps:

[0025] preparing a first mixed solution of a silicon-based active substance and a cationic surfactant, and a second mixed solution of a carbonaceous material and an anionic surfactant;

[0026] Mixing the first mixed solution and the second mixed solution dropwise, and drying to obtain a composite;

[0027] After evacuation, non-polymerizing gas is introduced to perform surface modification on the composite, and then polymerizing gas is introduced to perform plasma reaction to obtain a precursor;

[0028] The precursor is carbonized to obtain a negative electrode material, and the compactibility of the negative electrode material is Y, 0.6<Y<3.0.

[0029] In some embodiments, the mass ratio of the silicon-based active substance to the cationic surfactant is (12-33):1.

[0030] In some embodiments, the cationic surfactant includes at least one of polydiallyldimethylammonium chloride, hexadecyltrimethylammonium bromide, dodecyldimethylbenzylammonium chloride, octadecyl phosphate substituted amine, dodecylpyridinium chloride and polyvinylpyridinium quaternary ammonium salt.

[0031] In some embodiments, the mass ratio of the carbon material to the anionic surfactant is (12-33):1.

[0032] In some embodiments, the anionic surfactant includes at least one of ammonium dodecyl sulfate, sodium dodecyl sulfate, sodium hexadecyl sulfate, sodium octadecyl sulfate, dioctyl sodium sulfosuccinate, and sodium dodecylbenzene sulfonate.

[0033] In some embodiments, the first mixed liquid and the second mixed liquid include a solvent, and the solvent includes at least one of water, methanol, ethanol, isopropanol, acetone, petroleum ether, tetrahydrofuran, ethyl acetate, N,N-dimethylacetamide, N,N-dimethylformamide and n-hexane.

[0034] In some embodiments, the silicon-based active material includes at least one of elemental silicon, silicon oxide, and silicon alloy.

[0035] In some embodiments, the silicon-based active material further includes a doping metal M, where M is selected from at least one of Li, Mg, Al, Fe, La, Zn, Ti, Cu, and Mn.

[0036] In some embodiments, the silicon-based active material further includes a doping metal M, where M is Mg and / or Li.

[0037] In some embodiments, the silicon-based active material comprises silicon oxide SiO x, 0.5≤x<2.

[0038] In some embodiments, the silicon-based active material has a median particle size of 1.0 μm to 10.0 μm.

[0039] In some embodiments, the carbon material includes at least one of graphite, graphene, amorphous carbon, carbon nanotubes, and carbon fibers.

[0040] In some embodiments, the carbon material contains oxygen.

[0041] In some embodiments, the feed rate of the composite is 10 g / min to 20 g / min.

[0042] In some embodiments, the surface modification treatment is performed at a temperature of 50-200°C.

[0043] In some embodiments, the gas pressure range of the surface modification treatment is 50Pa to 150Pa.

[0044] In some embodiments, the surface modification treatment time is 10 min to 30 min.

[0045] In some embodiments, the non-polymerizable gas includes at least one of argon, nitrogen, and hydrogen.

[0046] In some embodiments, the temperature of the plasma reaction is 50-200°C.

[0047] In some embodiments, the gas pressure of the plasma reaction ranges from 50Pa to 150Pa.

[0048] In some embodiments, the plasma reaction time is 20 min to 60 min.

[0049] In some embodiments, the polymerizable gas includes at least one of styrene, cyclohexylamine, acrylamine, and methacrylate.

[0050] In some embodiments, the carbonization treatment is performed at a temperature of 500°C to 700°C.

[0051] In some embodiments, the carbonization treatment time is 1 h to 20 h.

[0052] In some embodiments, the carbonization process is performed under a protective atmosphere.

[0053] In some embodiments, the carbonization treatment is performed under a protective atmosphere, and the protective atmosphere includes at least one of nitrogen, argon, neon, krypton and helium.

[0054] In a third aspect, the present application provides a battery, comprising the negative electrode material described in the first aspect or the negative electrode material prepared according to the second aspect.

[0055] The technical solution of this application has at least the following beneficial effects:

[0056] First, the negative electrode material provided in the present application comprises a silicon-based active material and a carbon material, the oil absorption value of the negative electrode material is 0 mL / 100 g, and the specific surface area is S m 2 / g, tap density is T g / cm 3 , the compactability of the negative electrode material is Y=T / (0.01*O*S), 0.6<Y<3.0. The tap density of the negative electrode material can reflect the lithium ion migration rate and friction between the negative electrode material particles. The migration of lithium ions also requires the wetting ability of the electrolyte. The amount of electrolyte that the negative electrode material can absorb is related to the oil absorption value of the negative electrode material. In the present application, the balance between the specific surface area, oil absorption value and tap density of the negative electrode material is controlled so that the compactability of the negative electrode material is controlled within the above range, and the wetting ability of the electrolyte can be fully utilized to improve the transmission efficiency of lithium ions. In addition, the tap density of the negative electrode material is controlled to ensure the close combination of the silicon-based active material and the carbon material, which can be beneficial to inhibit the volume expansion of the silicon-based active material, so that the manufactured negative electrode plate has a suitable compaction density, so that the negative electrode plate has both good cycle performance and excellent rate performance.

[0057] The preparation method of the negative electrode material provided by the present application comprises the following steps: dropwise mixing a first mixed solution of a silicon-based active substance and a cationic surfactant and a second mixed solution of a carbon-containing material and an anionic surfactant, wherein the silicon-based active substance carries a positive charge under the action of the cationic surfactant, so that it achieves an excellent dispersion effect in the first mixed solution; the carbon material carries a negative charge under the action of the anionic surfactant, and achieves a better dispersion effect through electrostatic repulsion; when the two mixed solutions are mixed dropwise, the positively charged silicon-based active substance and the negatively charged carbon material combine with each other under the action of electrostatic attraction, effectively realizing a close combination of the two and stacking, and the composite particles can also maintain a high degree of dispersion, thereby helping to improve the tap density of the negative electrode material; then, after evacuation, a non- The polymerizing gas is used to modify the surface of the composite, and then the polymerizing gas is introduced to continue the plasma reaction to obtain a precursor; the surface of the composite particles after the surface modification treatment has active groups, and during the plasma reaction of the polymerizing gas, the active groups on the surface of the composite particles can be combined with the polymerizing gas molecules to form a tightly bound polymer modification layer on the particle surface; after carbonization, the polymer modification layer undergoes structural cracking and reforming, effectively modifying the surface defects of the material, reducing the surface defects of the negative electrode material, reducing the oil absorption value and specific surface area of ​​the negative electrode material, and making the final negative electrode material compactible within the range of 0.6 to 3.0, so that the prepared negative electrode plate has a suitable compaction density, so that the negative electrode plate has both good cycle performance and excellent rate performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 A schematic diagram of a process for preparing a negative electrode material provided in an embodiment of the present application.

[0059] Figure 2 A schematic diagram of the process status of the method for preparing the negative electrode material provided in an embodiment of the present application.

[0060] Figure 3 This is a comparison chart of the cycle performance of the negative electrode materials provided in Example 2 and Example 8 of the present application and Comparative Example 1.

[0061] Figure 4 This is another cycle performance comparison chart of the negative electrode materials provided in Examples 2 and 8 of the present application and Comparative Example 1. DETAILED DESCRIPTION

[0062] The following is a preferred implementation of the embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the embodiment of the present invention. These improvements and modifications are also considered to be within the scope of protection of the embodiment of the present invention.

[0063] Specifically, the present application provides a negative electrode material, the negative electrode material includes a silicon-based active substance and a carbon material, the oil absorption value of the negative electrode material is 0 mL / 100g, and the specific surface area is S m 2 / g, tap density is T g / cm 3 The compactibility of the negative electrode material is Y, Y=T / (0.01*O*S), 0.6<Y<3.0.

[0064] In the above scheme, the negative electrode material includes a silicon-based active material and a carbon material, the oil absorption value of the negative electrode material is 0 mL / 100 g, and the specific surface area is S m 2 / g, tap density is T g / cm 3 , the compactability of the negative electrode material is Y=T / (0.01*O*S), 0.6<Y<3.0. The tap density of the negative electrode material can reflect the lithium ion migration rate and friction between the negative electrode material particles. The migration of lithium ions also requires the wetting ability of the electrolyte. The amount of electrolyte that the negative electrode material can absorb is related to the oil absorption value of the negative electrode material. In the present application, the balance between the specific surface area, oil absorption value and tap density of the negative electrode material is controlled so that the compactability of the negative electrode material is controlled within the above range, and the wetting ability of the electrolyte can be fully utilized to improve the transmission efficiency of lithium ions. In addition, the tap density of the negative electrode material is controlled to ensure the close combination of the silicon-based active material and the carbon material, which can be beneficial to inhibit the volume expansion of the silicon-based active material, so that the manufactured negative electrode plate has a suitable compaction density, so that the negative electrode plate has both good cycle performance and excellent rate performance.

[0065] In some embodiments, the compactability of the negative electrode material is Y, 0.6<Y<3.0; specifically, it can be 0.61, 0.63, 0.65, 0.7, 0.85, 0.9, 1.0, 1.2, 1.5, 1.9, 2.1, 2.23, 2.39, 2.5, 2.84 or 2.9, etc., which are not limited here. The compactability Y of the negative electrode material can be used to measure the ability of the electrode sheet made of the negative electrode material to obtain a high compaction density by rolling under the same pressure. The larger the Y value, the easier it is to compact the electrode sheet made of the negative electrode material, so that the silicon-based active material and the carbon material particles in the electrode sheet are more tightly combined, which is beneficial to suppress the volume expansion of the negative electrode material during the charge and discharge process. When Y≤0.6, the compaction density of the electrode sheet made of the negative electrode material is too low, and it is difficult to exert good electrochemical performance. . When Y≥3.0, the compaction density of the electrode made of the negative electrode material is too high, and there is a lack of suitable pores between the silicon-based active substances and the carbon material particles in the electrode, which is not conducive to the infiltration and transmission of the electrolyte, resulting in serious degradation of the rate performance of the electrode made of the negative electrode material.

[0066] In some embodiments, the compactability of the negative electrode material is Y, 0.6<Y≤1.1, specifically 0.61, 0.63, 0.65, 0.7, 0.85, 0.9, 1.0 or 1.1, etc., which are not limited here. When 0.6<Y≤1.1, the electrode sheet made of the negative electrode material has a suitable compaction density and can have good cycle performance and rate performance.

[0067] In some embodiments, the compactability of the negative electrode material is Y, 1.1<Y<3.0, specifically 1.11, 1.2, 1.5, 1.9, 2.1, 2.23, 2.39, 2.5, 2.84 or 2.9, etc., which are not limited here. When 1.1<Y<3.0, the electrode sheet made of the negative electrode material can obtain a larger compaction density and has significantly improved cycle performance.

[0068] In some embodiments, the silicon-based active material includes at least one of elemental silicon, silicon oxide, and silicon alloy. The elemental silicon may be amorphous silicon and / or crystalline silicon, and the silicon alloy may be silicon-lithium alloy, silicon-magnesium alloy, silicon-nickel alloy, etc. In some cases, the silicon-based active particles include elemental silicon particles and silicon alloys.

[0069] In some embodiments, the general formula of silicon oxide is SiO x , where 0.5≤x<2. Specifically, SiO x Specifically, it can be SiO 0.5 、SiO 0.7 、SiO 0.9 、SiO、SiO 1.2 、SiO 1.5 、SiO 1.8 、SiO 1.9 Etc., no limitation is made here.

[0070] Silicon oxide can be represented by the general formula SiOx (0.5≤x<2). It can be a material formed by silicon particles dispersed in SiO2, or a material having a tetrahedral structural unit, in which the silicon atom is located at the center of the tetrahedral structural unit, and the silicon atom and oxygen atoms are located at the four vertices of the tetrahedral structural unit.

[0071] In some embodiments, the silicon-based active material further includes a doping metal M, and M is selected from at least one of Li, Mg, Al, Fe, La, Zn, Ti, Cu and Mn. It is understandable that a small amount of doping metal can be doped into the carbon material or the silicon-based active material, and the doping metal can improve the conductivity of the negative electrode material and enhance the structural strength of the negative electrode material. Preferably, M is Mg and / or Li.

[0072] In some embodiments, the median particle size of the silicon-based active material is 1.0μm to 10.0μm, specifically 1μm, 1.1μm, 1.3μ, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 4.8μm, 5μm, 6μm, 7μm, 8μm or 10μm, etc., and of course it can also be other values ​​within the above range, which is not limited here.

[0073] In some embodiments, in the negative electrode material, the silicon-based active material and the carbon material are dispersed with each other in the form of particles.

[0074] In some embodiments, the carbon material exists on the surface of the silicon-based active material and / or is dispersed between the silicon-based active material particles. Specifically, the silicon-based active material particles can be based on the carbon material and embedded in the carbon material.

[0075] In some embodiments, the carbon material is located on the surface of the silicon-based active material to form a carbon layer.

[0076] In some embodiments, the thickness of the carbon layer is 1nm to 1000nm, and can be specifically 1nm, 5nm, 10nm, 15nm, 20nm, 50nm, 80nm, 100nm, 150nm, 200nm, 400nm, 500nm, 700nm, 800nm, 900nm, 1000nm, etc., which are not limited here. If the carbon layer is too thick, the carbon content is too high, which is not conducive to obtaining a negative electrode material with a high specific capacity; if the carbon layer is too thin, it is not conducive to increasing the conductivity of the negative electrode material and has a weak performance in inhibiting the volume expansion of the material, resulting in poor long cycle performance. Preferably, the thickness of the carbon layer is 50nm to 800nm; more preferably, the thickness of the carbon layer is 100nm to 500nm.

[0077] In some embodiments, the carbon material includes at least one of graphite, graphene, amorphous carbon, carbon nanotubes and carbon fibers. Amorphous carbon can be soft carbon and / or hard carbon, and graphite can be artificial graphite and / or natural graphite. It is understandable that the carbon material can improve the conductivity of the silicon-based active material. Graphite is a material with high conductivity, small volume expansion, high first efficiency and stable cycle performance. Preferably, the carbon material is graphite.

[0078] In some embodiments, the tap density of the negative electrode material is T g / cm 3 , T>0.90, T can be 0.91, 0.94, 1.01, 1.03, 1.05, 1.08, 1.1, 1.15, 1.16, 1.19, 1.21, 1.25 or 1.3, etc., which are not limited here. The tap density reflects the stacking of the negative electrode material and is one of the indicators for measuring compactability. When T>0.90g / cm 3When T≤0.90g / cm 3 When the tap density is within the above range, it indicates that the silicon-based active material and the carbon material are not composited uniformly, and there are large particle gaps, which is not conducive to the preparation of high compaction density electrodes. Therefore, controlling the tap density within the above range is conducive to improving the energy density and rate performance of the negative electrode material.

[0079] In some embodiments, the specific surface area of ​​the negative electrode material is S m 2 / g, S<3.50; specifically it can be 3.49, 3.16, 2.52, 2.42, 2.12, 2.11, 2.05, 1.97, 1.56, 1.38, 1.37, 0.87, 0.82 or 0.81, etc., which are not limited here. It can be understood that the specific surface area is closely related to the surface energy and is positively correlated. The negative electrode material with a higher specific surface area has a larger surface energy, and the interaction force between its particles is also larger, which can easily hinder the sliding of particles and is not conducive to the dense accumulation of particles. It is also one of the indicators to measure the compactability. When the S of the negative electrode material is less than 3.50cm 2 / g, which has a suitable surface energy, is conducive to the close packing of particles, and it is easy to obtain a high compaction density electrode. When the S of the negative electrode material is ≥3.50cm 2 / g, which has a large surface energy, making it difficult for the particles to form dense packing and difficult to obtain a pole piece with a high compaction density.

[0080] In some embodiments, the oil absorption value of the negative electrode material is O mL / 100g, O<57.0; specifically, it can be 43, 44, 45, 47, 49, 51, 52, 53, 54, 55 or 56.9, etc., which are not limited here. The oil absorption value is related to the liquid absorption capacity of the negative electrode material, reflects the absorption capacity of the particle clusters to the binder during the slurry preparation process, and is one of the indicators for measuring the compactability. When the O of the negative electrode material is less than 57.0mL / 100g, the negative electrode material particle clusters can absorb an appropriate amount of binder during the slurry adjustment process, which is beneficial to enhance the bonding of the negative electrode material particles and easily obtain a high compaction density electrode. When the O of the negative electrode material is ≥57.0mL / 100g, the binder content absorbed by the negative electrode material particle clusters during the slurry adjustment process is too high, which is not conducive to effective contact and filling of the particles, and easily leads to a low compaction density of the electrode and poor cycle performance. Controlling the oil absorption value of the material within the above range is beneficial to improving the material's adsorption and wetting properties to the electrolyte and improving the electrochemical properties of the negative electrode material.

[0081] In some embodiments, the particle size of the negative electrode material satisfies: 2.5 μm ≤ D 10 ≤8.5μm, 12.0μm≤D 90 ≤28.0μm.D 10Specifically, it can be 2.5μm, 3.5μm, 4μm, 4.5μm, 5μm, 6.5μm, 7μm, 7.5μm or 8.5μm, etc. 90 Specifically, it can be 12.0 μm, 15.0 μm, 15.8 μm, 16.9 μm, 18.7 μm, 20.6 μm, 23.7 μm, 26.5 μm or 28.0 μm, etc., which are not limited here. It should be noted that the volume-based cumulative particle size distribution of the particle size distribution measured by laser diffraction method, D 10 Indicates the particle size corresponding to when the cumulative particle size distribution percentage reaches 10%. 90 It indicates the particle size corresponding to when the cumulative particle size distribution percentage reaches 90%.

[0082] In some embodiments, the mass content of Si element in the negative electrode material is 0.5% to 25%, and the mass content can specifically be 0.5%, 0.8%, 1.1%, 1.5%, 2.8%, 3.8%, 5.1%, 7%, 8.9%, 12.5%, 15.0%, 18.2%, 22.7%, 24.8% or 25%. The mass content of Si element is controlled within the above range, which is beneficial to the specific capacity and rate performance of the negative electrode material. When the mass content of Si element is less than 0.5%, the specific capacity of the negative electrode material is low and cannot meet the requirements of high energy density lithium-ion batteries. When the mass content of Si element is higher than 20%, the volume expansion of the negative electrode material is too large and the cycle performance is seriously deteriorated.

[0083] In some embodiments, the pH value of the negative electrode material is 6-12, specifically 6, 7, 8, 9, 10, 10.5, 11, 11.5 or 12, etc., which are not limited here. Preferably, the pH value of the negative electrode material is 9-11.

[0084] In some embodiments, the water content of the negative electrode material is ≤0.5wt%; specifically, it can be 0.5wt%, 0.35wt%, 0.25wt%, 0.10wt%, 0.09wt%, 0.08wt%, 0.05wt% or 0.01wt%, etc., and of course, it can also be other values ​​within the above range, which is not limited here.

[0085] The present application also provides a method for preparing a negative electrode material, such as Figure 1 As shown, the method includes the following steps S10 to S30:

[0086] S10, preparing a first mixed solution of a silicon-based active substance and a cationic surfactant, and a second mixed solution of a carbonaceous material and an anionic surfactant;

[0087] S20, mixing the first mixed solution and the second mixed solution dropwise, and drying to obtain a composite;

[0088] S30, after evacuation, introducing a non-polymerizing gas to perform surface modification on the composite, and then introducing a polymerizing gas to perform a plasma reaction to obtain a precursor;

[0089] S40, carbonizing the precursor to obtain a negative electrode material, wherein the compactability of the negative electrode material is Y, 0.6<Y<3.0.

[0090] The preparation method of the negative electrode material provided by the present application comprises the following steps: dropwise mixing a first mixed solution of a silicon-based active substance and a cationic surfactant and a second mixed solution of a carbon-containing material and an anionic surfactant, wherein the silicon-based active substance carries a positive charge under the action of the cationic surfactant, so that it achieves an excellent dispersion effect in the first mixed solution; the carbon material carries a negative charge under the action of the anionic surfactant, and achieves a better dispersion effect through electrostatic repulsion; when the two mixed solutions are mixed dropwise, the positively charged silicon-based active substance and the negatively charged carbon material combine with each other under the action of electrostatic attraction, effectively realizing a close combination of the two and stacking, and the composite particles can also maintain a high degree of dispersion, thereby helping to improve the tap density of the negative electrode material; then, after evacuation, a non- The polymerizing gas is used to modify the surface of the composite, and then the polymerizing gas is introduced to continue the plasma reaction to obtain a precursor; the surface of the composite particles after the surface modification treatment has active groups, and during the plasma reaction of the polymerizing gas, the active groups on the surface of the composite particles can be combined with the polymerizing gas molecules to form a tightly bound polymer modification layer on the particle surface; after carbonization, the polymer modification layer undergoes structural cracking and reforming, effectively modifying the surface defects of the material, reducing the surface defects of the negative electrode material, reducing the oil absorption value and specific surface area of ​​the negative electrode material, and making the final negative electrode material compactible within the range of 0.6 to 3.0, so that the prepared negative electrode plate has a suitable compaction density, so that the negative electrode plate has both good cycle performance and excellent rate performance.

[0091] The following is a detailed introduction to this program:

[0092] Step S10, preparing a first mixed solution containing silicon-based active substances and cationic surfactants, and a second mixed solution containing carbonaceous materials and anionic surfactants.

[0093] In some embodiments, the silicon-based active material includes at least one of elemental silicon, silicon oxide, and silicon alloy. The elemental silicon may be amorphous silicon and / or crystalline silicon, and the silicon alloy may be silicon-lithium alloy, silicon-magnesium alloy, silicon-nickel alloy, etc. In some cases, the silicon-based active particles include elemental silicon particles and silicon alloys.

[0094] In some embodiments, silicon oxide SiO x , where 0.5≤x<2. Specifically, SiOx Specifically, it can be SiO 0.5 、SiO 0.7 、SiO 0.9 、SiO、SiO 1.2 、SiO 1.5 、SiO 1.8 、SiO 1.9 Etc., no limitation is made here.

[0095] In some embodiments, the silicon-based active material further includes a doping metal M, where M is selected from at least one of Li, Mg, Al, Fe, La, Zn, Ti, Cu and Mn; preferably, M is Mg and / or Al.

[0096] In some embodiments, the median particle size of the silicon-based active material is 1.0μm to 10.0μm, specifically 1μm, 1.1μm, 1.3μ, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 4.8μm, 5μm, 6μm, 7μm, 8μm or 10μm, etc., and of course it can also be other values ​​within the above range, which is not limited here.

[0097] In some embodiments, the mass ratio of the silicon-based active substance to the cationic surfactant is (12-33):1, specifically 12:1, 15:1, 18:1, 20:1, 22:1, 24:1, 28:1, 30:1, 32:1 or 33:1, etc., and of course it can also be other values ​​within the above range, which is not limited here.

[0098] In some embodiments, the cationic surfactant includes at least one of polydiallyldimethylammonium chloride, hexadecyltrimethylammonium bromide, dodecyldimethylbenzylammonium chloride, octadecylphosphate-substituted amine, dodecylpyridinium chloride, and polyvinylpyridinium quaternary ammonium salt.

[0099] It can be understood that the silicon-based active substance carries a positive charge under the action of the cationic surfactant, so that it can achieve a better dispersion effect in the first mixed liquid through electrostatic repulsion.

[0100] In some embodiments, the mass ratio of carbon material to anionic surfactant is (12-33):1, specifically 12:1, 15:1, 18:1, 20:1, 22:1, 24:1, 28:1, 30:1, 32:1 or 33:1, etc., and of course it can also be other values ​​within the above range, which is not limited here.

[0101] In some embodiments, the carbon material includes at least one of graphite, graphene, amorphous carbon, carbon nanotubes and carbon fibers. Amorphous carbon can be soft carbon and / or hard carbon, and graphite can be artificial graphite and / or natural graphite. It is understandable that the carbon material can improve the conductivity of the silicon-based active material. Preferably, the carbon material is graphite.

[0102] In some embodiments, the anionic surfactant includes at least one of ammonium dodecyl sulfate, sodium dodecyl sulfate, sodium hexadecyl sulfate, sodium octadecyl sulfate, dioctyl sodium sulfosuccinate, and sodium dodecylbenzene sulfonate.

[0103] Understandably, the carbon material has a negative charge under the action of the anionic surfactant, so that it can achieve a better dispersion effect in the second mixed liquid through electrostatic repulsion.

[0104] In some embodiments, the first mixed liquid and / or the second mixed liquid also includes a solvent, and the solvent includes at least one of water, methanol, ethanol, isopropanol, acetone, petroleum ether, tetrahydrofuran, ethyl acetate, N,N-dimethylacetamide, N,N-dimethylformamide and n-hexane.

[0105] Step S20, mixing the first mixed solution and the second mixed solution dropwise, and drying to obtain a composite.

[0106] like Figure 2 As shown, when the two mixed liquids are mixed drop by drop, the positively charged silicon-based active material and the negatively charged carbon material combine with each other under the action of electrostatic attraction, effectively achieving a close combination of the two. The composite particles can also maintain a high degree of dispersion in the solution, which helps to increase the tap density of the negative electrode material.

[0107] In some embodiments, the drying temperature is 50° C. to 200° C. Specifically, the temperature may be 50° C., 60° C., 70° C., 80° C., 100° C., 120° C., 150° C., 180° C. or 200° C. It is understood that the above temperature is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0108] In some embodiments, the drying time is 5 h to 24 h, specifically 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, 12 h, 15 h, 18 h, 20 h, 24 h, etc., and of course, it can also be other values ​​within the above range, which is not limited here.

[0109] In the present application, the drying temperature and time can be set according to the situation, as long as the solvent in the composite can be fully volatilized through the drying process.

[0110] Step S30, after evacuation, non-polymerizing gas is introduced to perform surface modification treatment on the composite, and then polymerizing gas is introduced to perform plasma reaction to obtain a precursor.

[0111] In some embodiments, during the plasma reaction process, the feed rate of the composite is 10 g / min to 20 g / min, specifically 10 g / min, 11 g / min, 12 g / min, 13 g / min, 14 g / min, 15 g / min, 16 g / min, 17 g / min, 18 g / min or 20 g / min, etc., and of course, it can also be other values ​​within the above range, which are not limited here. It can be understood that if the feed rate is too fast, it will cause a certain degree of damage to the surface of the composite, so that the specific surface area of ​​the negative electrode material increases, which is not conducive to improving the tap density of the negative electrode material. If the feed rate is too slow, the plasma reaction time will increase, and the thicker the polymer modification layer deposited on the surface of the composite, the lower the specific surface area and oil absorption value of the negative electrode material after the subsequent carbonization treatment. Therefore, controlling the feed rate of the composite is conducive to controlling the balance between the specific surface area, oil absorption value and tap density of the negative electrode material, and improving the cycle performance and rate performance of the negative electrode material.

[0112] In some embodiments, the temperature of the surface modification treatment is 50-200° C., specifically 50° C., 60° C., 70° C., 80° C., 100° C., 120° C., 150° C., 180° C. or 200° C. It is understood that the above temperature is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0113] In some embodiments, before surface modification treatment, the reaction system is first evacuated, and the pressure range of the surface modification treatment is 50Pa to 150Pa, specifically 50Pa, 60Pa, 70Pa, 80Pa, 90Pa, 100Pa, 120Pa or 150Pa, etc., and of course, it can also be other values ​​within the above range, which is not limited here.

[0114] In some embodiments, the non-polymerizing gas includes at least one of argon, nitrogen, and hydrogen.

[0115] During the surface modification process, non-polymerizing gas is blown through the composite at high speed to remove impurities adsorbed on the surface of the composite. Since the carbon material in the composite contains some oxygen elements, the oxygen elements can introduce active groups such as hydroxyl, carboxyl, amino, aldehyde, and imino groups under the attack of non-polymerizing gas.

[0116] In some embodiments, a non-polymerizing gas is introduced to perform surface modification treatment on the composite for 10 to 30 minutes, and then a polymerizing gas is introduced to perform plasma reaction for 20 to 60 minutes to obtain a precursor. It can be understood that the composite introduced into the non-polymerizing gas is first fully preheated and surface cleaned, and then the polymerizing gas is introduced, so that the polymerizing gas can be combined with the active groups (such as hydroxyl, carboxyl, amino, aldehyde, and imino) on the surface of the composite particles to form a tightly bound polymer modification layer on the surface of the composite particles.

[0117] In some embodiments, the temperature of the plasma reaction is 50-200° C., specifically 50° C., 60° C., 70° C., 80° C., 100° C., 120° C., 150° C., 180° C. or 200° C. It is understood that the above temperature is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0118] In some embodiments, the gas pressure range of the plasma reaction is 50Pa to 150Pa, specifically 50Pa, 60Pa, 70Pa, 80Pa, 90Pa, 100Pa, 120Pa or 150Pa, etc., and of course, other values ​​within the above range may also be used, which are not limited here. In some embodiments, the polymerizable gas includes at least one of styrene, cyclohexylamine, vinyl chloride, acrylamine, and methacrylate. Exemplarily, the polymer modified layer may be polystyrene, polyacrylamine, polymethacrylate, polyvinyl chloride, etc., which are not limited here.

[0119] Step S40, carbonizing the precursor to obtain a negative electrode material, wherein the compactability of the negative electrode material is Y, 0.6<Y<3.0.

[0120] It can be understood that during the carbonization process, the polymer modified layer undergoes structural cracking and reforming after carbonization, which effectively modifies the surface defects of the material. The surface defects of the negative electrode material are reduced, which reduces the oil absorption value and specific surface area of ​​the negative electrode material, so that the compactibility of the final negative electrode material can be controlled within the range of 0.6 to 3.0, and the negative electrode material has both good cycle performance and excellent rate performance.

[0121] In some embodiments, the temperature of the carbonization treatment is 500°C-1000°C, and the time of the carbonization treatment is 1h-20h. The temperature of the carbonization treatment can be 500°C, 600°C, 700°C, 800°C, 900°C or 1000°C, and the time of the carbonization treatment can be 1h, 3h, 5h, 8h, 10h, 12h, 15h, 18h or 20h, etc., which are not limited here.

[0122] In some embodiments, the carbonization process is performed under a protective atmosphere.

[0123] In some embodiments, the protective atmosphere includes at least one of nitrogen, argon, neon, krypton, and helium.

[0124] Furthermore, the method also includes: screening and demagnetizing the carbonized material to obtain a negative electrode material.

[0125] In some embodiments, the screening method is any one of a fixed screen, a drum screen, a resonance screen, a roller screen, a vibrating screen and a chain screen, and the screening mesh number is 100 to 500 meshes. Specifically, the screening mesh number can be 100 mesh, 200 mesh, 250 mesh, 325 mesh, 400 mesh, 500 mesh, etc. Preferably, the screening mesh number is 250 mesh, and the particle size of the negative electrode material is controlled within the above range, which is beneficial to the improvement of the processing performance of the negative electrode material.

[0126] In some embodiments, the demagnetization equipment is any one of a permanent magnetic drum magnetic separator, an electromagnetic iron remover and a pulsating high gradient magnetic separator. The demagnetization is to ultimately control the magnetic substance content of the negative electrode material, avoid the discharge effect of the magnetic substance on the lithium-ion battery and the safety of the battery during use.

[0127] The present invention also provides a battery using the negative electrode material provided in the above embodiment of the present invention or the negative electrode material prepared by the method for preparing the negative electrode material provided in the above embodiment of the present invention. The lithium ion battery provided in the present invention has the advantages of excellent rate performance and low expansion.

[0128] Test method:

[0129] 1) Particle size of negative electrode material:

[0130] The particle size test method refers to GB / T 19077-2016. It can be conveniently measured using a laser particle size analyzer, such as the Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd., UK.

[0131] 2) Testing method for specific surface area of ​​negative electrode materials:

[0132] Refer to GB / T 19587-2004 "Determination of Specific Surface Area of ​​Solid Substances by Gas Adsorption BET Method", at constant temperature and low temperature, after measuring the amount of gas adsorbed on the solid surface at different relative pressures, the sample monolayer adsorption amount is obtained based on the Brownauer-Etter-Taylor adsorption theory and its formula (BET formula), thereby calculating the specific surface area of ​​the material. 3) Test method for the tap density of negative electrode materials:

[0133] Refer to GB / T 5162-2006 / ISO 3953:1993 "Determination of tap density of metal powders", and use the Quantachrome tap density analyzer (Quantachrome DAT-4-220) of Anton Paar (Shanghai) Trading Co., Ltd. for testing. The tap density T is the value after 3000 vibrations, and the unit is g / cm 3 .

[0134] 4) Negative electrode material pH test:

[0135] Take 10g of negative electrode material, add 10g of water, stir for 30min, and measure the pH value of the solution.

[0136] 5) Testing method of oil absorption value of negative electrode material:

[0137] With reference to GB / T 3780.2-2017 "Carbon Black Part 2: Determination of Oil Absorption", the oil absorption value Q is tested using the ASAHI S-500 oil absorption value tester of ASAHISOUKEN of Japan. The oil absorption value Q is the amount of dibutyl phthalate added when the torque generated by the change in viscosity characteristics reaches 70% of the maximum torque, and the unit is mL / 100g.

[0138] 6) Test method for compaction density of negative electrode sheet:

[0139] The pressurization method is to apply a certain pressure to the negative electrode plate and maintain the pressure for a period of time, and then test the thickness L of the powder layer in the negative electrode plate to test the compaction density.

[0140] 7) Electrochemical performance test

[0141] According to the mass ratio of negative electrode material: conductive agent (SuTer T): sodium carboxymethyl cellulose (CMC): styrene-butadiene rubber (SBR) = 92:2:2:2, the mixture is evenly mixed and coated on the copper foil current collector. After drying, the negative electrode sheet is obtained for use. The dried electrode sheet is rolled under a pressure of 3 MTa to obtain a negative electrode sheet with a certain compaction density. The button cell test is performed on the rolled negative electrode sheet. The battery assembly is carried out in an argon glove box. The metal lithium sheet is used as the negative electrode, the electrolyte is 1 mol / L lithium hexafluorophosphate + ethylene carbonate (EC) + methyl ethyl carbonate (EMC), and the diaphragm is a polyethylene / propylene composite microporous membrane. The electrochemical performance is carried out on a battery test instrument, and the charge and discharge voltage is 0.01~1.5V.

[0142] The battery cycle life is the number of charge and discharge cycles when the capacity retention rate decays to 80%.

[0143] First coulombic efficiency = first-cycle lithium removal capacity / first-cycle lithium insertion capacity.

[0144] When the lithium-free capacity of the battery is 80% of the initial lithium-free capacity, the charge-discharge cycle ends; the sum of the lithium-free capacity per week in this process is the cumulative released capacity.

[0145] Rate test method: Lithium insertion and delithiation were carried out at 0.1C, 0.2C, 0.5C, 1C and 0.2C for 3 weeks respectively. The ratio of the lithium desorption capacity at 1C to that at 0.1C is the rate performance.

[0146] The following is a further description of the embodiments of the present invention in multiple embodiments. The embodiments of the present invention are not limited to the following specific embodiments. The embodiments can be appropriately modified within the scope of the unchanged main rights.

[0147] Example 1

[0148] A method for preparing a negative electrode material comprises the following steps:

[0149] (1) Take 30 g of carbon-coated SiO, disperse it in 1 L of water, add 1.5 g of polydiallyldimethylammonium chloride, and stir for 1 hour to obtain a first mixed solution.

[0150] (2) 970 g of artificial graphite was dispersed in 2 L of water, 48.5 g of ammonium dodecyl sulfate was added, and the mixture was stirred for 1 hour to obtain a second mixed solution.

[0151] (3) The first mixed solution and the second mixed solution are mixed dropwise under stirring, and then filtered and dried to obtain a composite.

[0152] (4) Add the composite into a plasma device and evacuate it, controlling the feed rate to 15 g / min; introduce argon gas and control the gas pressure to 100 Pa, and use argon gas to perform surface modification on the composite for 20 minutes, with the reaction temperature being 180°C; then introduce acrylamine and control the gas pressure to 100 Pa for plasma reaction for 40 minutes to obtain a precursor.

[0153] (5) The precursor was carbonized in an argon atmosphere at a temperature of 500° C. for 10 hours to obtain a negative electrode material.

[0154] The negative electrode material prepared in the embodiment of the present application includes a silicon-based active substance and a carbon material, the silicon-based active substance is carbon-coated SiO, and the carbon material is artificial graphite.

[0155] The other parameters of the negative electrode materials are shown in Table 1.

[0156] Example 2

[0157] A method for preparing a negative electrode material comprises the following steps:

[0158] (1) Take 100 g of carbon-coated SiO, disperse it in 1 L of water, add 5 g of polydiallyldimethylammonium chloride, and stir for 1 hour to obtain a first mixed solution.

[0159] (2) 900 g of artificial graphite was dispersed in 2 L of water, 45 g of ammonium dodecyl sulfate was added, and the mixture was stirred for 1 hour to obtain a second mixed solution.

[0160] (3) The first mixed solution and the second mixed solution are mixed dropwise under stirring, and then filtered and dried to obtain a composite.

[0161] (4) Add the composite into a plasma device and evacuate it, controlling the feed rate to 15 g / min; introduce argon gas and control the gas pressure to 120 Pa, and use argon gas to perform surface modification on the composite for 20 minutes at a reaction temperature of 180°C; then introduce acrylamine and control the gas pressure to 120 Pa for plasma reaction for 40 minutes to obtain a precursor.

[0162] (5) The precursor was carbonized in an argon atmosphere at a temperature of 500° C. for 10 hours to obtain a negative electrode material.

[0163] The negative electrode material prepared in the embodiment of the present application includes a silicon-based active substance and a carbon material, the silicon-based active substance is carbon-coated SiO, and the carbon material is artificial graphite.

[0164] The other parameters of the negative electrode materials are shown in Table 1.

[0165] Example 3

[0166] A method for preparing a negative electrode material comprises the following steps:

[0167] (1) Take 300g carbon-coated SiO 1.2 , dispersed in 1L of water, added with 15g of polydiallyldimethylammonium chloride, stirred for 1 hour to obtain a first mixed solution.

[0168] (2) 700 g of artificial graphite was dispersed in 2 L of water, 35 g of ammonium dodecyl sulfate was added, and the mixture was stirred for 1 hour to obtain a second mixed solution.

[0169] (3) The first mixed solution and the second mixed solution are mixed dropwise under stirring, and then filtered and dried to obtain a composite.

[0170] (4) Add the composite into a plasma device and evacuate it, controlling the feed rate to 15 g / min; introduce argon and control the gas pressure to 150 Pa, use nitrogen to perform surface modification on the composite for 20 min, and the reaction temperature is 180°C; then introduce acrylamine and control the gas pressure to 150 Pa for plasma reaction for 40 min to obtain a precursor.

[0171] (5) The precursor was carbonized in an argon atmosphere at a temperature of 500° C. for 10 hours to obtain a negative electrode material.

[0172] The negative electrode material prepared in the embodiment of the present application includes a silicon-based active material and a carbon material. The silicon-based active material is a carbon-coated SiO 1.2 , the carbon material is artificial graphite.

[0173] The other parameters of the negative electrode materials are shown in Table 1.

[0174] Example 4

[0175] A method for preparing a negative electrode material comprises the following steps:

[0176] (1) 100 g of Mg-doped carbon-coated SiO was dispersed in 1 L of water, 5 g of polydiallyldimethylammonium chloride was added, and the mixture was stirred for 1 hour to obtain a first mixed solution.

[0177] (2) 900 g of artificial graphite was dispersed in 2 L of water, 45 g of ammonium dodecyl sulfate was added, and the mixture was stirred for 1 hour to obtain a second mixed solution.

[0178] (3) The first mixed solution and the second mixed solution are mixed dropwise under stirring, and then filtered and dried to obtain a composite.

[0179] (4) Add the composite into a plasma device and evacuate it, controlling the feed rate to 15 g / min; introduce argon gas and control the gas pressure to 100 Pa, and use argon gas to perform surface modification on the composite for 20 minutes, with the reaction temperature being 180°C; then introduce acrylamine and control the gas pressure to 100 Pa for plasma reaction for 40 minutes to obtain a precursor.

[0180] (5) The precursor was carbonized in an argon atmosphere at a temperature of 600° C. for 10 hours to obtain a negative electrode material.

[0181] The negative electrode material prepared in the embodiment of the present application includes a silicon-based active substance and a carbon material. The silicon-based active substance is carbon-coated SiO and Mg, and the carbon material is artificial graphite.

[0182] The other parameters of the negative electrode materials are shown in Table 1.

[0183] Example 5

[0184] A method for preparing a negative electrode material comprises the following steps:

[0185] (1) 100 g of Li-doped carbon-coated SiO was dispersed in 1 L of water, 5 g of polydiallyldimethylammonium chloride was added, and the mixture was stirred for 1 hour to obtain a first mixed solution.

[0186] (2) 900 g of artificial graphite was dispersed in 2 L of water, 45 g of ammonium dodecyl sulfate was added, and the mixture was stirred for 1 hour to obtain a second mixed solution.

[0187] (3) The first mixed solution and the second mixed solution are mixed dropwise under stirring, and then filtered and dried to obtain a composite.

[0188] (4) Add the composite into a plasma device and evacuate it, controlling the feed rate to 15 g / min; introduce argon gas and control the gas pressure to 100 Pa, and use argon gas to perform surface modification on the composite for 20 minutes, with the reaction temperature being 180°C; then introduce acrylamine and control the gas pressure to 100 Pa for plasma reaction for 40 minutes to obtain a precursor.

[0189] (5) The precursor was carbonized in an argon atmosphere at a temperature of 500° C. for 10 hours to obtain a negative electrode material.

[0190] The negative electrode material prepared in the embodiment of the present application includes a silicon-based active substance and a carbon material. The silicon-based active substance includes carbon-coated SiO and Li, and the carbon material is artificial graphite.

[0191] The other parameters of the negative electrode materials are shown in Table 1.

[0192] Example 6

[0193] A method for preparing a negative electrode material comprises the following steps:

[0194] (1) Take 100 g of carbon-coated SiO, disperse it in 1 L of water, add 5 g of polydiallyldimethylammonium chloride, and stir for 1 hour to obtain a first mixed solution.

[0195] (2) 900 g of natural graphite was dispersed in 2 L of water, 45 g of ammonium dodecyl sulfate was added, and the mixture was stirred for 1 hour to obtain a second mixed solution.

[0196] (3) The first mixed solution and the second mixed solution are mixed dropwise under stirring, and then filtered and dried to obtain a composite.

[0197] (4) Add the composite into a plasma device and evacuate it, controlling the feed rate to 15 g / min; introduce argon gas and control the gas pressure to 100 Pa, and use argon gas to perform surface modification on the composite for 20 minutes, with the reaction temperature being 180°C; then introduce acrylamine and control the gas pressure to 100 Pa for plasma reaction for 40 minutes to obtain a precursor.

[0198] (5) The precursor was carbonized in an argon atmosphere at a temperature of 500° C. for 10 hours to obtain a negative electrode material.

[0199] The negative electrode material prepared in the embodiment of the present application includes a silicon-based active substance and a carbon material. The silicon-based active substance includes carbon-coated SiO, and the carbon material is natural graphite.

[0200] The other parameters of the negative electrode materials are shown in Table 1.

[0201] Example 7

[0202] A method for preparing a negative electrode material comprises the following steps:

[0203] (1) Take 30 g of carbon-coated SiO, disperse it in 1 L of water, add 1.5 g of polydiallyldimethylammonium chloride, and stir for 1 hour to obtain a first mixed solution.

[0204] (2) 970 g of artificial graphite was dispersed in 2 L of water, 48.5 g of ammonium dodecyl sulfate was added, and the mixture was stirred for 1 hour to obtain a second mixed solution.

[0205] (3) The first mixed solution and the second mixed solution are mixed dropwise under stirring, and then filtered and dried to obtain a composite.

[0206] (4) Add the composite into a plasma device and evacuate it, controlling the feed rate to 15 g / min; introduce argon gas and control the gas pressure to 100 Pa, and use argon gas to perform surface modification on the composite for 20 minutes at a reaction temperature of 180°C; then introduce acrylamine and control the gas pressure to 100 Pa for plasma reaction for 25 minutes to obtain a precursor.

[0207] (5) The precursor was carbonized in an argon atmosphere at a temperature of 500° C. for 10 hours to obtain a negative electrode material.

[0208] Example 8

[0209] A method for preparing a negative electrode material comprises the following steps:

[0210] (1) Take 100 g of carbon-coated SiO, disperse it in 1 L of water, add 5 g of polydiallyldimethylammonium chloride, and stir for 1 hour to obtain a first mixed solution.

[0211] (2) 900 g of artificial graphite was dispersed in 2 L of water, 45 g of ammonium dodecyl sulfate was added, and the mixture was stirred for 1 hour to obtain a first mixed solution.

[0212] (3) The first mixed solution and the second mixed solution are mixed dropwise under stirring, and then filtered and dried to obtain a composite.

[0213] (4) Add the composite into a plasma device and evacuate it, controlling the feed rate to 15 g / min; introduce argon gas and control the gas pressure to 120 Pa, and use argon gas to perform surface modification on the composite for 20 minutes at a reaction temperature of 180°C; then introduce acrylamine and control the gas pressure to 120 Pa for plasma reaction for 25 minutes to obtain a precursor.

[0214] (5) The precursor was carbonized in an argon atmosphere at a temperature of 500° C. for 10 hours to obtain a negative electrode material.

[0215] Example 9

[0216] A method for preparing a negative electrode material comprises the following steps:

[0217] (1) Take 300g carbon-coated SiO x , dispersed in 1L of water, added with 15g of polydiallyldimethylammonium chloride, stirred for 1 hour to obtain a first mixed solution.

[0218] (2) 700 g of artificial graphite was dispersed in 2 L of water, 35 g of ammonium dodecyl sulfate was added, and the mixture was stirred for 1 hour to obtain a second mixed solution.

[0219] (3) The first mixed solution and the second mixed solution are mixed dropwise under stirring, and then filtered and dried to obtain a composite.

[0220] (4) Add the composite into a plasma device and evacuate it, controlling the feed rate to 15 g / min; introduce argon gas and control the gas pressure to 150 Pa, and use nitrogen to perform surface modification on the composite for 20 minutes, with the reaction temperature being 180°C; then introduce acrylamine and control the gas pressure to 150 Pa for plasma reaction for 25 minutes to obtain a precursor.

[0221] (5) The precursor was carbonized in an argon atmosphere at a temperature of 500° C. for 10 hours to obtain a negative electrode material.

[0222] Example 10

[0223] The difference from Example 1 is:

[0224] (4) Add the composite into a plasma device and evacuate it, controlling the feed rate to 15 g / min; introduce argon gas and control the gas pressure to 100 Pa, and use argon gas to perform surface modification on the composite for 20 minutes at a reaction temperature of 180°C; then introduce styrene and control the gas pressure to 100 Pa for plasma reaction for 40 minutes to obtain a precursor.

[0225] The parameters of the negative electrode materials are detailed in Table 1.

[0226] Embodiment 11

[0227] The difference from Example 2 is that:

[0228] (4) Add the composite into a plasma device and evacuate it, controlling the feed rate to 10 g / min; introduce argon gas and control the gas pressure to 100 Pa, and use argon gas to perform surface modification on the composite for 40 minutes at a reaction temperature of 180°C; then introduce styrene and control the gas pressure to 100 Pa for plasma reaction for 20 minutes to obtain a precursor.

[0229] The parameters of the negative electrode materials are detailed in Table 1.

[0230] Comparative Example 1

[0231] A method for preparing a negative electrode material comprises the following steps:

[0232] 100 g of carbon-coated SiO and 900 g of artificial graphite were stirred and mixed to obtain a negative electrode material.

[0233] The other parameters of the negative electrode materials are shown in Table 1.

[0234] Comparative Example 2

[0235] The difference from Example 2 is:

[0236] (4) Add the composite into a plasma device and evacuate it, controlling the feed rate to 10 g / min; introduce argon gas and control the gas pressure to 120 Pa, and use argon gas to perform surface modification on the composite for 20 minutes at a reaction temperature of 180°C; then introduce styrene and control the gas pressure to 120 Pa for plasma reaction for 80 minutes to obtain a precursor.

[0237] The parameters of the negative electrode materials are detailed in Table 1.

[0238] Comparative Example 3

[0239] (1) 500 g of carbon-coated SiO was dispersed in 1 L of water, 5 g of polydiallyldimethylammonium chloride was added, and the mixture was stirred for 1 hour to obtain a first mixed solution.

[0240] (2) Take 500 g of artificial graphite, disperse it in 2 L of water, add 45 g of ammonium dodecyl sulfate, and stir for 1 hour to obtain a second mixed solution.

[0241] (3) The first mixed solution and the second mixed solution are mixed dropwise under stirring, and then filtered and dried to obtain a composite.

[0242] (4) The composite was carbonized in an argon atmosphere at a temperature of 500° C. for 10 hours to obtain a negative electrode material.

[0243] The negative electrode material prepared in the embodiment of the present application includes a silicon-based active substance and a carbon material, the silicon-based active substance is carbon-coated SiO, and the carbon material is artificial graphite.

[0244] The parameters of the negative electrode materials are detailed in Table 1.

[0245] The negative electrode materials obtained in the examples and comparative examples were subjected to performance tests. The results of the above performance tests are shown in Table 1:

[0246] Table 1. Summary of negative electrode material performance test results

[0247]

[0248]

[0249] Table 2. Summary of electrochemical performance results of the electrode

[0250]

[0251]

[0252] According to the data in Table 1, by controlling the balance between the specific surface area, oil absorption value and tap density of the negative electrode material, the compactability Y of the negative electrode material can be controlled in the range of 0.6 to 3.0, and the wetting ability of the electrolyte can be fully utilized to improve the transmission efficiency of lithium ions. In addition, by controlling the tap density of the negative electrode material, the close combination of the silicon-based active material and the carbon material can be ensured, so that the manufactured negative electrode plate has a suitable compaction density, so that the negative electrode plate has both good cycle performance and excellent rate performance.

[0253] The negative electrode material prepared in Comparative Example 1 is as follows Figure 3 and Figure 4 As shown, compared with Example 2 and Example 8, the silicon-based active material in Comparative Example 1 is directly compounded with the carbon material without surface modification, and the bonding force between the two is reduced. The silicon-based active material has a drastic volume expansion effect during the cycle, resulting in pulverization and breakage of the negative electrode material, the battery cycle decays quickly, and the cycle life of the electrode is greatly reduced.

[0254] During the preparation of Comparative Example 2, the plasma reaction time was too long, resulting in an increase in carbon material on the surface of the silicon-based active substance. The final compactibility Y of the negative electrode material was too large, and the compaction density of the electrode made of the negative electrode material was too high. There was a lack of suitable pores between the silicon-based active substance and the carbon material particles in the electrode, which was not conducive to the infiltration and transmission of the electrolyte, resulting in serious degradation of the rate performance.

[0255] The mass content of carbon-coated SiO in the raw material used in Comparative Example 3 increased to 50%, resulting in a significant increase in the mass content of silicon in the negative electrode material. The specific capacity of the prepared negative electrode pole piece was significantly improved, but due to the excessively high silicon content, the volume of silicon expanded significantly during the cycle, and the cycle life of the pole piece was greatly reduced; and the compaction density of the pole piece made of the negative electrode material was too low, making it difficult to exert good electrochemical performance.

[0256] Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the claims. Any technical personnel in this field may make several possible changes and modifications without departing from the concept of the present application. Therefore, the scope of protection of the present application shall be based on the scope defined by the claims of the present application.

Claims

1. A negative electrode material, characterized in that: The negative electrode material comprises a silicon-based active material and a carbon material. The oil absorption value of the negative electrode material is 0 mL / 100 g and the specific surface area is Sm 2 / g, tap density is T g / cm 3 The compactibility of the negative electrode material is Y, Y=T / (0.01*O*S), 0.6<Y<3.

0.

2. The negative electrode material according to claim 1, characterized in that Satisfies at least one of the following characteristics (1) to (7): (1) The silicon-based active material includes at least one of elemental silicon, silicon oxide and silicon alloy; (2) The silicon-based active material further includes a doping metal M, wherein M is selected from at least one of Li, Mg, Al, Fe, La, Zn, Ti, Cu and Mn; (3) The silicon-based active material further includes a doped metal M, where M is Mg and / or Li; (4) The silicon-based active material includes silicon oxide, and the general formula of the silicon oxide is SiO x , 0.5≤x<2; (5) The median particle size of the silicon-based active material is 1.0 μm to 10.0 μm; (6) The carbon material includes at least one of graphite, graphene, amorphous carbon, carbon nanotubes and carbon fibers; (7) The carbon material contains oxygen.

3. The negative electrode material according to claim 1 or 2, characterized in that: Satisfies at least one of the following characteristics (1) to (5): (1) The tap density of the negative electrode material is T g / cm 3 , T>0.90; (2) The oil absorption value of the negative electrode material is 0 mL / 100 g, O<57.0; (3) The specific surface area of ​​the negative electrode material is Sm 2 / g, S<3.50; (4) The pH of the negative electrode material is 6 to 12; (5) The particle size of the negative electrode material satisfies: 2.5≤D 10 ≤8.5μm, 12.0≤D 90 ≤28.0μm; (6) The water content of the negative electrode material is ≤0.5wt%; (7) The mass content of Si element in the negative electrode material is 0.5% to 25%.

4. The negative electrode material according to any one of claims 1 to 3, characterized in that Satisfies at least one of the following characteristics (1) to (3): (1) In the negative electrode material, the silicon-based active material and the carbon material are dispersed in the form of particles; (2) The compactability of the negative electrode material is Y, 0.6<Y≤1.1; (3) The compactability of the negative electrode material is Y, 1.1<Y<3.

0.

5. A method for preparing a negative electrode material, characterized in that: The method comprises the following steps: preparing a first mixed solution of a silicon-based active substance and a cationic surfactant, and a second mixed solution of a carbonaceous material and an anionic surfactant; Mixing the first mixed solution and the second mixed solution dropwise, and drying to obtain a composite; After evacuation, non-polymerizing gas is introduced to perform surface modification on the composite, and then polymerizing gas is introduced to perform plasma reaction to obtain a precursor; The precursor is carbonized to obtain a negative electrode material, and the compactibility of the negative electrode material is Y, 0.6<Y<3.

0.

6. The preparation method according to claim 5, characterized in that: Contains at least one of the following features (1) to (6): (1) The mass ratio of the silicon-based active substance to the cationic surfactant is (12-33):1; (2) the cationic surfactant comprises at least one of polydiallyldimethylammonium chloride, hexadecyltrimethylammonium bromide, dodecyldimethylbenzylammonium chloride, octadecyl phosphate substituted amine, dodecylpyridinium chloride and polyvinylpyridinium quaternary ammonium salt; (3) The mass ratio of the carbon material to the anionic surfactant is (12-33):1; (4) the anionic surfactant includes at least one of ammonium dodecyl sulfate, sodium dodecyl sulfate, sodium hexadecyl sulfate, sodium octadecyl sulfate, dioctyl sodium sulfosuccinate and sodium dodecylbenzene sulfonate; (5) The first mixed liquid and the second mixed liquid include a solvent, and the solvent includes at least one of water, methanol, ethanol, isopropanol, acetone, petroleum ether, tetrahydrofuran, ethyl acetate, N,N-dimethylacetamide, N,N-dimethylformamide and n-hexane.

7. The preparation method according to claim 5, characterized in that: The invention comprises at least one of the following features (1) to (7): (1) The silicon-based active material includes at least one of elemental silicon, silicon oxide and silicon alloy; (2) The silicon-based active material further includes a doping metal M, wherein M is selected from at least one of Li, Mg, Al, Fe, La, Zn, Ti, Cu and Mn; (3) The silicon-based active material further includes a doped metal M, where M is Mg and / or Li; (4) The silicon-based active material includes silicon oxide SiO x , 0.5≤x<2; (5) The median particle size of the silicon-based active material is 1.0 μm to 10.0 μm; (6) The carbon material includes at least one of graphite, graphene, amorphous carbon, carbon nanotubes and carbon fibers; (7) The carbon material contains oxygen.

8. The preparation method according to claim 5, characterized in that: The method comprises at least one of the following features (1) to (9): (1) The feed rate of the composite is 10 g / min to 20 g / min; (2) The temperature of the surface modification treatment is 50 to 200° C.; (3) The gas pressure range of the surface modification treatment is 50Pa to 150Pa; (4) The surface modification treatment time is 10 min to 30 min; (5) The non-polymerizable gas includes at least one of argon, nitrogen, and hydrogen; (6) The temperature of the plasma reaction is 50 to 200° C.; (7) The gas pressure range of the plasma reaction is 50Pa to 150Pa; (8) The plasma reaction time is 20 min to 60 min; (9) The polymerizable gas includes at least one of styrene, cyclohexylamine, acrylamine, and methacrylate.

9. The preparation method according to claim 5, characterized in that: Contains at least one of the following features (1) to (4): (1) The temperature of the carbonization treatment is 500° C. to 700° C.; (2) The carbonization treatment time is 1h to 20h; (3) The carbonization treatment is carried out under a protective atmosphere; (4) The carbonization treatment is carried out under a protective atmosphere, and the protective atmosphere includes at least one of nitrogen, argon, neon, krypton and helium.

10. A battery, characterized in that: The invention comprises the negative electrode material according to any one of claims 1 to 4 or the negative electrode material prepared by the preparation method according to any one of claims 5 to 9.

Images