Negative electrode material and preparation method therefor, and battery

Abstract

A negative electrode material and a preparation method therefor, 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 / 100g, the specific surface area is S m2 / g, the tap density is T g / cm 3, the degree of compaction of the negative electrode material is Y, Y=T / (0.01*O*S), and 0.6<Y<3.0. The negative electrode material has relatively high compaction capability, which allows for easy compaction during the preparation of electrode sheets, thereby achieving higher compaction density, and improving the cycle performance of batteries.

Description

Negative electrode material and preparation method thereof, and battery

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to the Chinese patent application filed on October 31, 2023, with application number 202311436252.4 and titled “Negative electrode material, preparation method thereof, and battery”. Technical Field

[0003] The present application relates to the technical field of negative electrode materials, and in particular, to a negative electrode material, a preparation method thereof, and a battery. Background Art

[0004] Electric new energy vehicles are the future of the automotive market, and their core component is the lithium-ion battery. As the market develops, the demand for high-capacity batteries is increasing. Using new high-specific-capacity cathode and cathode materials is one of the key methods for increasing battery energy density.

[0005] Silicon-based anode materials are considered the next generation of anode materials. They are highly regarded for their ultra-high theoretical specific capacity (4200mAh / g), low delithiation potential (<0.5V), slightly higher voltage platform than graphite, less prone to surface lithium deposition during charging, and improved safety. However, silicon anodes experience significant volume expansion during cycling, leading to material pulverization and fragmentation, resulting in rapid battery degradation.

[0006] 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, and 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 the coordinated action of multiple factors and develop composite negative electrode materials that meet market demand.

[0007] Summary of the Invention

[0008] The present application proposes a negative electrode material, 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.

[0009] In a first aspect, the present application provides a negative electrode material, wherein the negative electrode material comprises 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.

[0010] In some embodiments, the silicon-based active material includes at least one of elemental silicon, silicon oxide, and silicon alloy.

[0011] In some embodiments, the silicon-based active material further includes a metal M element, where M is selected from at least one of Li, Mg, Al, Fe, La, Zn, Ti, Cu, and Mn.

[0012] In some embodiments, the silicon-based active material further includes a metal element M, where M is Mg and / or Li.

[0013] In some embodiments, the chemical formula of the silicon oxide is SiO x , 0<x≤2.

[0014] In some embodiments, the average particle size of the silicon-based active material is 1.0 μm to 10.0 μm.

[0015] In some embodiments, the carbon material includes at least one of graphite, graphene, amorphous carbon, carbon nanotubes, and carbon fibers.

[0016] In some embodiments, the carbon material contains oxygen.

[0017] In some embodiments, the tap density of the negative electrode material is T g / cm 3 , T>0.90.

[0018] In some embodiments, the oil absorption value of the negative electrode material is 0 mL / 100 g, and O<57.0.

[0019] In some embodiments, the specific surface area of ​​the negative electrode material is S m 2 / g, S<3.50.

[0020] In some embodiments, the pH value of the negative electrode material is 6-12.

[0021] In some embodiments, the particle size of the negative electrode material satisfies: 2.5≤D 10 ≤8.5μm, 12.0≤D 90 ≤28.0μm.

[0022] In some embodiments, the water content of the negative electrode material is ≤0.5 wt %.

[0023] In some embodiments, the mass content of Si element in the negative electrode material is 0.5% to 25%.

[0024] In some embodiments, in the negative electrode material, at least a portion of the silicon-based active material and the carbon material are dispersed with each other in the form of particles.

[0025] In some embodiments, the negative electrode material has a compactibility Y, 0.6<Y≤1.1.

[0026] In some embodiments, the negative electrode material has a compactibility Y, 1.1<Y<3.0.

[0027] In a second aspect, the present application provides a method for preparing a negative electrode material, the method comprising the following steps:

[0028] 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;

[0029] mixing the first mixed solution and the second mixed solution dropwise, and drying to obtain a composite;

[0030] After vacuuming, 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;

[0031] The precursor is carbonized to obtain a negative electrode material, wherein the negative electrode material has a compactibility Y, 0.6<Y<3.0.

[0032] In some embodiments, the mass ratio of the silicon-based active material to the cationic surfactant is (12-33):1.

[0033] In some embodiments, the cationic surfactant includes at least one of polydiallyldimethylammonium chloride, cetyltrimethylammonium bromide, dodecyldimethylbenzylammonium chloride, octadecyl phosphate-substituted amine, dodecylpyridinium chloride, and polyvinylpyridinium quaternary ammonium salt.

[0034] In some embodiments, the mass ratio of the carbon material to the anionic surfactant is (12-33):1.

[0035] In some embodiments, the anionic surfactant includes at least one of ammonium lauryl sulfate, sodium lauryl sulfate, sodium hexadecyl sulfate, sodium octadecyl sulfate, dioctyl sodium sulfosuccinate, and sodium dodecylbenzenesulfonate.

[0036] 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.

[0037] In some embodiments, the silicon-based active material includes at least one of elemental silicon, silicon oxide, and silicon alloy.

[0038] In some embodiments, the silicon-based active material further includes a metal M element, where M is selected from at least one of Li, Mg, Al, Fe, La, Zn, Ti, Cu, and Mn.

[0039] In some embodiments, the silicon-based active material further includes a metal element M, where M is Mg and / or Li.

[0040] In some embodiments, the chemical formula of the silicon oxide is SiO x , 0<x≤2.

[0041] In some embodiments, the average particle size of the silicon-based active material is 1.0 μm to 10.0 μm.

[0042] In some embodiments, the carbon material includes at least one of graphite, graphene, amorphous carbon, carbon nanotubes, and carbon fibers.

[0043] In some embodiments, the carbon material contains oxygen.

[0044] In some embodiments, the feed rate of the composite is 10 g / min to 20 g / min.

[0045] In some embodiments, the surface modification treatment is performed at a temperature of 50-200°C.

[0046] In some embodiments, the surface modification treatment is performed at an air pressure ranging from 50 Pa to 150 Pa.

[0047] In some embodiments, the surface modification treatment lasts for 10 min to 30 min.

[0048] In some embodiments, the non-polymerizable gas includes at least one of argon, nitrogen, and hydrogen.

[0049] In some embodiments, the temperature of the plasma reaction is 50-200°C.

[0050] In some embodiments, the gas pressure of the plasma reaction ranges from 50 Pa to 150 Pa.

[0051] In some embodiments, the plasma reaction time is 20 min to 60 min.

[0052] In some embodiments, the polymerizable gas includes at least one of styrene, cyclohexylamine, allylamine, and methacrylate.

[0053] In some embodiments, the temperature of the carbonization treatment is 500°C to 700°C.

[0054] In some embodiments, the carbonization treatment time is 1 hour to 20 hours.

[0055] In some embodiments, the carbonization treatment is performed under a protective atmosphere.

[0056] 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.

[0057] 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.

[0058] The technical solution of this application has at least the following beneficial effects:

[0059] First, the negative electrode material provided by the present application includes a silicon-based active material and a carbon material, and 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 negative electrode materials is Y = T / (0.01*O*S), with 0.6 < Y < 3.0. The tap density reflects the packing of negative electrode material particles. A higher tap density indicates better particle size matching, which facilitates the formation of smaller gaps and a high-density electrode sheet. The specific surface area reflects the surface energy of the negative electrode material particles. A smaller specific surface area reduces surface energy, which reduces the interaction between the negative electrode material particles and facilitates the sliding and dense packing of the negative electrode material particles, promoting the preparation of high-density electrode sheets. The oil absorption value reflects the ability of negative electrode material particle clusters to absorb binder during the slurry preparation process. A higher oil absorption value indicates that the negative electrode material particle clusters absorb too much binder during the slurry preparation process, hindering effective contact and packing of the negative electrode material particles and potentially resulting in a lower tap density of the negative electrode sheet. The tap density of a negative electrode sheet is the density achieved after the binder-absorbed negative electrode material particles slide and rearrange under pressure. It is understandable that the compaction density of the negative electrode plate is related to the degree of matching of the particle size of the negative electrode material, the difficulty of slippage between the particles of the negative electrode material, the bridging effect of the binder, etc., and judging the compaction ability of the negative electrode material by a single indicator has limitations. To this end, the applicant has verified through a large number of experiments that the compaction ability of the material can be evaluated by the compaction degree Y. When Y is controlled within the above range, the silicon-based active material and the carbon material can be tightly combined and stacked, and the obtained electrode has a suitable compaction density. While suppressing the volume expansion stress, it also improves the penetration of the electrolyte in the electrode, so that the prepared battery has both good cycle performance and excellent rate performance.

[0060] The preparation method of the negative electrode material provided by the present application comprises the following steps: dropwise mixing a first mixed liquid containing a silicon-based active substance and a cationic surfactant, and a second mixed liquid containing a carbon 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 liquid; 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 liquids 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 and stacking of the two, 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 vacuuming, a non-polymerizing gas is introduced to the composite. The composite is surface-modified, and then a 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, thereby 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 compactibility of the final negative electrode material controllable within the range of 0.6 to 3.0, so that the prepared negative electrode plate has a suitable compaction density, and thus the battery containing the negative electrode material has both good cycle performance and excellent rate performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] FIG1 is a schematic flow chart of a method for preparing a negative electrode material provided in an embodiment of the present application.

[0062] FIG2 is a schematic diagram of the process state of the method for preparing the negative electrode material provided in an embodiment of the present application.

[0063] FIG3 is a comparison chart of the cycle performance of the negative electrode materials provided in Example 2, Example 8, and Comparative Example 1 of the present application.

[0064] FIG4 is another comparison chart of the cycle performance of the negative electrode materials provided in Example 2, Example 8, and Comparative Example 1 of the present application. DETAILED DESCRIPTION

[0065] The following is a preferred implementation of the embodiment of the present invention. It should be noted 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.

[0066] Specifically, the present application provides a negative electrode material, which 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 compactibility of the negative electrode material is Y, Y=T / (0.01*O*S), 0.6<Y<3.0.

[0067] 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 negative electrode materials is Y = T / (0.01*O*S), with 0.6 < Y < 3.0. The tap density reflects the packing of negative electrode material particles. A higher tap density indicates better particle size matching, which facilitates the formation of smaller gaps and a high-density electrode sheet. The specific surface area reflects the surface energy of the negative electrode material particles. A smaller specific surface area reduces surface energy, which reduces the interaction between the negative electrode material particles and facilitates the sliding and dense packing of the negative electrode material particles, promoting the preparation of high-density electrode sheets. The oil absorption value reflects the ability of negative electrode material particle clusters to absorb binder during the slurry preparation process. A higher oil absorption value indicates that the negative electrode material particle clusters absorb too much binder during the slurry preparation process, hindering effective contact and packing of the negative electrode material particles and potentially resulting in a lower tap density of the negative electrode sheet. The tap density of a negative electrode sheet is the density achieved after the binder-absorbed negative electrode material particles slide and rearrange under pressure. It is understandable that the compaction density of the negative electrode plate is related to the degree of matching of the particle size of the negative electrode material, the difficulty of slippage between the particles of the negative electrode material, the bridging effect of the binder, etc., and judging the compaction ability of the negative electrode material by a single indicator has limitations. To this end, the applicant has verified through a large number of experiments that the compaction ability of the material can be evaluated by the compaction degree Y. When Y is controlled within the above range, the silicon-based active material and the carbon material can be tightly combined and stacked, and the obtained electrode has a suitable compaction density. While suppressing the volume expansion stress, it also improves the penetration of the electrolyte in the electrode, so that the prepared battery has both good cycle performance and excellent rate performance.

[0068] 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, 1.1, 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 negative electrode material to obtain a high compaction density electrode sheet by rolling under the same pressure, and still have good cycle performance and excellent rate performance at a high compaction density. 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 can provide stress for the silicon-based active material, thereby helping to suppress the volume expansion of the negative electrode material during the charge and discharge process. When Y≤0.6, the compaction density that can be achieved for the electrode made of the negative electrode material is too low, the bonding between the silicon-based active material and the carbon material is not tight, and it is difficult to suppress volume expansion, making it easy for the conductive channel in the electrode to be cut off due to dislocation and lose its capacity contribution, that is, rapid capacity decay occurs. When Y≥3.0, although the electrode made of the negative electrode material can achieve a higher compaction density, the lack of suitable pores between the silicon-based active material and the carbon material particles in the electrode is not conducive to the infiltration and transmission of the electrolyte, resulting in a serious deterioration of the rate performance of the electrode made of the negative electrode material.

[0069] In some embodiments, the negative electrode material has a compactibility Y, where 0.6 < Y ≤ 1.1, and specifically can be 0.61, 0.63, 0.65, 0.7, 0.85, 0.9, 1.0, or 1.1, etc., without limitation herein. When 0.6 < Y ≤ 1.1, the electrode sheet made of the negative electrode material has an appropriate compaction density, thereby enabling the electrode sheet to have superior rate performance while maintaining relatively good cycle performance.

[0070] In some embodiments, the negative electrode material has a compactibility Y, where 1.1 < Y ​​< 3.0, and specifically can be 1.11, 1.2, 1.5, 1.9, 2.1, 2.23, 2.39, 2.5, 2.84, or 2.9, etc., without limitation herein. When 1.1 < Y ​​< 3.0, the electrode sheet made of the negative electrode material can achieve a greater compaction density, resulting in significantly improved cycle performance.

[0071] In some embodiments, the silicon-based active material includes at least one of elemental silicon, silicon oxide, and a silicon alloy. The elemental silicon may be amorphous silicon and / or crystalline silicon, and the silicon alloy may be a silicon-lithium alloy, a silicon-magnesium alloy, a silicon-nickel alloy, or the like. In some cases, the silicon-based active particles include elemental silicon particles and silicon alloys.

[0072] In some embodiments, the chemical formula of silicon oxide is SiO x , where 0<x≤2. SiO x Specifically, it can be SiO0.1 、SiO 0.3 、SiO 0.5 、SiO 0.7 、SiO 0.9 、SiO、SiO 1.2 、SiO 1.5 、SiO 1.8 、SiO 1.9 etc., not limited here.

[0073] Silicon oxide can be represented by the chemical formula SiO x (0<x≤2). It can be a material formed by dispersing silicon particles in SiO2, or a material having a tetrahedral structural unit, with the silicon atom located at the center of the tetrahedral structural unit and silicon atoms and / or oxygen atoms located at the four vertices of the tetrahedral structural unit.

[0074] In some embodiments, the silicon-based active material further includes a metal element M, where M is selected from at least one of Li, Mg, Al, Fe, La, Zn, Ti, Cu, and Mn. It is understood that the metal element M can be doped into either the carbon material or the silicon-based active material. The metal element M 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.

[0075] In some embodiments, the metal M element in the negative electrode material exists in at least one form of M element, M oxide, or M silicate.

[0076] In some embodiments, the average particle size of the silicon-based active material is 1.0 μm to 10.0 μm, specifically 1 μm, 1.1 μm, 1.3 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 4.8 μm, 5 μm, 6 μm, 7 μm, 8 μm or 10 μm, etc., and of course it can also be other values ​​within the above range, which is not limited here.

[0077] In some embodiments, in the negative electrode material, at least a portion of the silicon-based active material and the carbon material are dispersed with each other in the form of particles.

[0078] In some embodiments, the carbon material is present on the surface of the silicon-based active material and / or dispersed between the silicon-based active material particles.

[0079] In some embodiments, the silicon-based active material particles may be based on a carbon material and embedded in the carbon material.

[0080] In some embodiments, at least a portion of the carbon material is located on the surface of the silicon-based active material to form a carbon layer.

[0081] In some embodiments, the thickness of the carbon layer is 1 nm to 1000 nm, and can specifically be 1 nm, 5 nm, 10 nm, 15 nm, 20 nm, 50 nm, 80 nm, 100 nm, 150 nm, 200 nm, 400 nm, 500 nm, 700 nm, 800 nm, 900 nm, 1000 nm, etc., without limitation herein. A carbon layer that is too thick and has too high a carbon content is not conducive to obtaining a negative electrode material with a high specific capacity; a carbon layer that is too thin is not conducive to increasing the conductivity of the negative electrode material and has poor performance in suppressing the volume expansion of the material, resulting in poor long-cycle performance. Preferably, the thickness of the carbon layer is 50 nm to 800 nm; more preferably, the thickness of the carbon layer is 100 nm to 500 nm.

[0082] 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 understood that the carbon material can improve the conductivity of the silicon-based active material. Graphite is a material with high conductivity, low volume expansion, high initial efficiency, and stable cycle performance. Preferably, the carbon material is graphite.

[0083] 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 3 When the tap density is within the above range, it indicates that the silicon-based active material and carbon material particles are evenly dispersed, which is conducive to obtaining a high tap density electrode. Controlling the tap density within the above range is beneficial to improving the energy density and rate performance of the negative electrode material.

[0084] 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 appropriate surface energy, is conducive to the dense packing of particles and is easy to obtain a pole piece with high compaction density.

[0085] In some embodiments, the oil absorption value of the negative electrode material is 0 mL / 100g, where O is less than 57.0; specifically, it can be 43, 44, 45, 47, 49, 51, 52, 53, 54, 55, or 56.9, etc., without limitation herein. The oil absorption value is related to the liquid absorption capacity of the negative electrode material, reflecting the ability of the particle clusters to absorb the binder during the slurry preparation process and is one of the indicators for measuring compactability. When O is less than 57.0 mL / 100g, the negative electrode material particle clusters can absorb an appropriate amount of binder during the slurry preparation process, which is beneficial for enhancing the cohesiveness of the negative electrode material particles and facilitating the production of a high compaction density electrode sheet. Controlling the oil absorption value of the negative electrode material within the above range is beneficial for improving the material's adsorption and wettability to the electrolyte, thereby enhancing the electrochemical performance of the negative electrode material.

[0086] 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 10 Specifically, 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 determination is 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%.

[0087] In some embodiments, the mass content of Si element in the negative electrode material is 0.5% to 25%, specifically 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%, etc., which are not limited here. The mass content of Si element is controlled within the above range, which is beneficial to improving the specific capacity and rate performance of the negative electrode material, reducing the volume expansion of the negative electrode material, and thus improving the cycle performance.

[0088] 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.

[0089] 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. Of course, it can also be other values ​​within the above range, which is not limited here.

[0090] The present application also provides a method for preparing a negative electrode material, as shown in FIG1 , the method comprising the following steps S10 to S30:

[0091] 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;

[0092] S20, mixing the first mixed solution and the second mixed solution dropwise, and drying to obtain a composite;

[0093] 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;

[0094] S40, carbonizing the precursor to obtain a negative electrode material, wherein the negative electrode material has a compactibility Y, 0.6<Y<3.0.

[0095] 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 and stacking of the two, 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 vacuuming, a non-polymerizing gas is introduced. The surface of the composite is modified by a surface modification treatment, and then a 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 surface of the particles. After carbonization, the polymer modification layer undergoes structural cracking and reforming, effectively modifying the surface defects of the material, thereby reducing the surface defects of the negative electrode material, and reducing 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, so that the prepared negative electrode plate has a suitable compaction density, and thus the negative electrode plate has both good cycle performance and excellent rate performance.

[0096] The following is a detailed introduction to this plan:

[0097] Step S10 , preparing a first mixed solution containing a silicon-based active substance and a cationic surfactant, and a second mixed solution containing a carbonaceous material and an anionic surfactant.

[0098] In some embodiments, the silicon-based active material includes at least one of elemental silicon, silicon oxide, and a silicon alloy. The elemental silicon may be amorphous silicon and / or crystalline silicon, and the silicon alloy may be a silicon-lithium alloy, a silicon-magnesium alloy, a silicon-nickel alloy, or the like. In some cases, the silicon-based active particles include elemental silicon particles and silicon alloys.

[0099] In some embodiments, the chemical formula of silicon oxide is SiO x , where 0<x≤2. SiO x Specifically, it can be SiO 0.1 、SiO 0.3 、SiO 0.5 、SiO 0.7 、SiO 0.9 、SiO、SiO 1.2 、SiO 1.5 、SiO1.8 、SiO 1.9 etc., not limited here.

[0100] In some embodiments, the silicon-based active material further includes a metal element 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.

[0101] In some embodiments, the average particle size of the silicon-based active material is 1.0 μm to 10.0 μm, specifically 1 μm, 1.1 μm, 1.3 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 4.8 μm, 5 μm, 6 μm, 7 μm, 8 μm or 10 μm, etc., and of course it can also be other values ​​within the above range, which is not limited here.

[0102] 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. Of course, it can also be other values ​​within the above range, which is not limited here.

[0103] In some embodiments, the cationic surfactant includes at least one of polydiallyldimethylammonium chloride, cetyltrimethylammonium bromide, dodecyldimethylbenzylammonium chloride, octadecylphosphate-substituted amine, dodecylpyridinium chloride, and polyvinylpyridinium quaternary ammonium salt.

[0104] 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.

[0105] 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.

[0106] In some embodiments, the carbon material includes at least one of graphite, graphene, amorphous carbon, carbon nanotubes, and carbon fibers. The amorphous carbon may be soft carbon and / or hard carbon, and the graphite may be artificial graphite and / or natural graphite. It is understood that the carbon material can improve the conductivity of the silicon-based active material. Preferably, the carbon material is graphite.

[0107] In some embodiments, the anionic surfactant includes at least one of ammonium lauryl sulfate, sodium lauryl sulfate, sodium hexadecyl sulfate, sodium octadecyl sulfate, dioctyl sodium sulfosuccinate, and sodium dodecylbenzenesulfonate.

[0108] It can be understood that 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.

[0109] In some embodiments, the first mixed liquid and / or the second mixed liquid further 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.

[0110] Step S20: mixing the first mixed liquid and the second mixed liquid dropwise, and drying to obtain a composite.

[0111] As shown in Figure 2, when the two mixed liquids are mixed dropwise, 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 tight stacking of the two. The composite particles can also maintain a high degree of dispersion in the solution, thereby helping to improve the tap density of the negative electrode material.

[0112] In some embodiments, the drying temperature is 50° C. to 200° C. Specifically, the temperature can 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.

[0113] 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. Of course, it can also be other values ​​within the above range, which is not limited here.

[0114] 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.

[0115] In step S30 , after vacuuming, 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.

[0116] 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 other values ​​within the above range can also be used, which is 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, causing the specific surface area of ​​the negative electrode material to increase, 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 beneficial 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.

[0117] In some embodiments, the surface modification treatment temperature 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, before performing the surface modification treatment, the reaction system is first vacuumed, and the pressure range of the surface modification treatment is 50Pa~150Pa, specifically 50Pa, 60Pa, 70Pa, 80Pa, 90Pa, 100Pa, 120Pa or 150Pa, etc., of course, it can also be other values ​​within the above range, which is not limited here.

[0119] In some embodiments, the non-polymerizable gas includes at least one of argon, nitrogen, and hydrogen.

[0120] 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.

[0121] In some embodiments, a non-polymerizing gas is introduced into the composite for surface modification for 10 to 30 minutes, and then a polymerizing gas is introduced for plasma reaction for 20 to 60 minutes to obtain a precursor. It is understood that the composite introduced into the non-polymerizing gas is first fully preheated and surface cleaned before the polymerizing gas is introduced, so that the polymerizing gas can bind to the active groups (e.g., hydroxyl, carboxyl, amino, aldehyde, and imino) on the surface of the composite particles, forming a tightly bound polymer modification layer on the surface of the composite particles.

[0122] 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.

[0123] In some embodiments, the plasma reaction pressure ranges from 50 Pa to 150 Pa, specifically 50 Pa, 60 Pa, 70 Pa, 80 Pa, 90 Pa, 100 Pa, 120 Pa, or 150 Pa, and may also be other values ​​within the above range, without limitation. In some embodiments, the polymerizable gas includes at least one of styrene, cyclohexylamine, vinyl chloride, allylamine, and methacrylate. For example, the polymer modified layer may be polystyrene, polyacrylamine, polymethacrylate, polyvinyl chloride, etc., without limitation.

[0124] 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.

[0125] It can be understood that during the carbonization process, the polymer modified layer undergoes structural cracking and reforming after carbonization, effectively modifying the surface defects of the material. The surface defects of the negative electrode material are reduced, resulting in a decrease in 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, thereby enabling the negative electrode material to have both good cycle performance and excellent rate performance.

[0126] In some embodiments, the carbonization treatment temperature is 500° C. to 1000° C., and the carbonization treatment time is 1 hour to 20 hours. The carbonization treatment temperature can be 500° C., 600° C., 700° C., 800° C., 900° C., or 1000° C., and the carbonization treatment time can be 1 hour, 3 hours, 5 hours, 8 hours, 10 hours, 12 hours, 15 hours, 18 hours, or 20 hours, etc., without limitation herein.

[0127] In some embodiments, the carbonization process is performed under a protective atmosphere.

[0128] In some embodiments, the protective atmosphere includes at least one of nitrogen, argon, neon, krypton, and helium.

[0129] Furthermore, the method further comprises: screening and demagnetizing the carbonized material to obtain a negative electrode material.

[0130] 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 improving the processing performance of the negative electrode material.

[0131] 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 purpose of demagnetization is to ultimately control the magnetic material content of the negative electrode material, avoid the discharge effect of the magnetic material on the lithium-ion battery, and the safety of the battery during use.

[0132] The present invention also provides a battery using the negative electrode material provided in the above embodiments of the present invention or the negative electrode material prepared using the method for preparing the negative electrode material provided in the above embodiments of the present invention. The lithium-ion battery provided in the present invention has the advantages of excellent rate performance and low expansion.

[0133] Test method:

[0134] 1) Particle size of negative electrode material:

[0135] 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.

[0136] 2) Average particle size of silicon-based active material:

[0137] The average particle size of the silicon-based active material was characterized using SEM-EDS. The EDS elemental distribution pattern confirmed the presence of silicon-based active particles in the negative electrode material. The average particle size of the silicon-based active material was obtained by randomly measuring the maximum diameter of 50 silicon-based active particles and taking the average value.

[0138] 3) Mass content of Si element:

[0139] The carbon content (C%) of the material was measured using an infrared carbon-sulfur analyzer. The oxygen content (O%) was measured using an oxygen, nitrogen, and hydrogen analyzer. The total metal content (M%) was measured using the total dissolution ICP method. Refer to the equipment manual or industry-standard methods for testing methods. The Si content of the material = 1-C%-O%-M%.

[0140] 4) Test method for specific surface area of ​​negative electrode material:

[0141] With reference to GB / T 19587-2004 "Determination of the Specific Surface Area of ​​Solid Substances by Gas Adsorption BET Method", the adsorption amount of gas on the solid surface at different relative pressures is measured at constant temperature and low temperature. Based on the Brownauer-Etter-Taylor adsorption theory and its formula (BET formula), the adsorption amount of the sample monolayer is obtained, thereby calculating the specific surface area of ​​the material.

[0142] 5) Test method for the tap density of negative electrode materials:

[0143] Reference is made to GB / T 5162-2006 / ISO 3953:1993 "Metal powders - Determination of tap density". Tests were performed using a Quantachrome tap density analyzer (Quanttra DAT-4-220) from Anton Paar (Shanghai) Trading Co., Ltd. The tap density T is the value after 3000 vibrations and is expressed in g / cm². 3 .

[0144] 6) pH value test of negative electrode material:

[0145] Take 10g of negative electrode material, add 10g of water, stir for 30min, and then measure the pH value of the solution.

[0146] 7) Test method for oil absorption value of negative electrode material:

[0147] With reference to GB / T 3780.2-2017, "Carbon Black - Part 2: Determination of Oil Absorption," the oil absorption value, Q, is measured using an ASAHI S-500 oil absorption tester from ASAHISOUKEN, Japan. The oil absorption value, Q, is the amount of dibutyl phthalate added when the torque generated by the change in viscosity reaches 70% of the maximum torque, expressed in mL / 100g.

[0148] 8) Test method for compaction density of negative electrode:

[0149] After uniformly mixing the negative electrode material, conductive agent (SuTer T), sodium carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) in a mass ratio of 92:2:2:2, the mixture was coated onto a copper foil current collector and dried to obtain a negative electrode sheet. A pressure was applied to the negative electrode sheet using a pressurization method and maintained for a period of time. The thickness L of the powder layer in the negative electrode sheet was then measured to determine the compaction density.

[0150] 9) Test method for water content in negative electrode materials:

[0151] Refer to Appendix B, "Determination of Moisture Content," of GB / T 24533-2019, "Graphite-Based Anode Materials for Lithium-Ion Batteries," or the equipment manual. Measured using a Mettler DL39 Karl Fischer Coulometric Titrator.

[0152] 10) Electrochemical performance test

[0153] After uniformly mixing the negative electrode material, conductive agent (SuTer T), sodium carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) in a mass ratio of 92:2:2:2, the mixture was coated onto a copper foil current collector and dried to obtain a negative electrode sheet. The dried sheet was roller-pressed under a pressure of 3 MTa to obtain a negative electrode sheet with a certain compaction density. The rolled negative electrode sheet was then tested in button cells. The cells were assembled in an argon glove box. The negative electrode was a lithium metal sheet, the electrolyte was 1 mol / L lithium hexafluorophosphate, ethylene carbonate (EC), and ethyl methyl carbonate (EMC), and the separator was a polyethylene / propylene composite microporous membrane. Electrochemical performance was measured on a battery tester with charge and discharge voltages ranging from 0.01 to 1.5 V.

[0154] The battery cycle life is the number of charge and discharge cycles when the capacity retention rate decays to 80%.

[0155] First coulombic efficiency = first-cycle lithium removal capacity / first-cycle lithium insertion capacity.

[0156] When the delithiation capacity of the battery is 80% of the initial delithiation capacity, the charge and discharge cycle ends; the sum of the weekly delithiation capacity in this process is the cumulative release capacity.

[0157] Rate test method: Lithium insertion and delithiation were carried out at 0.1C, 0.2C, 0.5C, 1C, and 0.2C for 3 weeks. The ratio of the delithiation capacity at 1C to the delithiation capacity at 0.1C is the rate performance.

[0158] The following further describes the embodiments of the present invention in multiple embodiments. The embodiments of the present invention are not limited to the following specific embodiments. Within the scope of the unchanged main rights, appropriate changes can be made to the implementation.

[0159] Example 1

[0160] A method for preparing a negative electrode material comprises the following steps:

[0161] (1) 30 g of carbon-coated SiO was dispersed in 1 L of water, 1.5 g of polydiallyldimethylammonium chloride was added, and the mixture was stirred for 1 hour to obtain a first mixed solution.

[0162] (2) 970 g of artificial graphite was dispersed in 2 L of water, 48.5 g of lauryl ammonium sulfate was added, and the mixture was stirred for 1 hour to obtain a second mixed solution.

[0163] (3) The first mixed solution and the second mixed solution are mixed dropwise under stirring, and then filtered and dried to obtain a composite.

[0164] (4) The composite was added into a plasma device and vacuumed, with the feed rate controlled at 15 g / min; argon was introduced and the pressure was controlled at 100 Pa, and the composite was surface modified with argon for 20 min at a reaction temperature of 180°C; then propyleneamine was introduced and the pressure was controlled at 100 Pa for a plasma reaction for 40 min to obtain a precursor.

[0165] (5) The precursor was carbonized in an argon atmosphere at a temperature of 500° C. for 10 hours to obtain a negative electrode material.

[0166] 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 contains SiO, and the carbon material is artificial graphite.

[0167] Other parameters of the negative electrode materials are detailed in Table 1.

[0168] Example 2

[0169] A method for preparing a negative electrode material comprises the following steps:

[0170] (1) 100 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.

[0171] (2) 900 g of artificial graphite was dispersed in 2 L of water, 45 g of ammonium lauryl sulfate was added, and the mixture was stirred for 1 hour to obtain a second mixed solution.

[0172] (3) The first mixed solution and the second mixed solution are mixed dropwise under stirring, and then filtered and dried to obtain a composite.

[0173] (4) The composite was added into a plasma device and vacuumed, with the feed rate controlled at 15 g / min; argon was introduced and the pressure was controlled at 120 Pa, and the composite was surface modified with argon for 20 min at a reaction temperature of 180°C; then propyleneamine was introduced and the pressure was controlled at 120 Pa for a plasma reaction for 40 min to obtain a precursor.

[0174] (5) The precursor was carbonized in an argon atmosphere at a temperature of 500° C. for 10 hours to obtain a negative electrode material.

[0175] 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 contains SiO, and the carbon material is artificial graphite.

[0176] Other parameters of the negative electrode materials are detailed in Table 1.

[0177] Example 3

[0178] A method for preparing a negative electrode material comprises the following steps:

[0179] (1) Take 300g carbon-coated SiO 1.2 , dispersed in 1 L of water, added 15 g of polydiallyldimethylammonium chloride, stirred for 1 hour to obtain a first mixed solution.

[0180] (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.

[0181] (3) The first mixed solution and the second mixed solution are mixed dropwise under stirring, and then filtered and dried to obtain a composite.

[0182] (4) The composite was added into a plasma device and vacuumed, with the feed rate controlled at 15 g / min; argon was introduced and the pressure was controlled at 150 Pa, and the composite was surface modified with nitrogen for 20 min at a reaction temperature of 180°C; then propyleneamine was introduced and the pressure was controlled at 150 Pa for a plasma reaction for 40 min to obtain a precursor.

[0183] (5) The precursor was carbonized in an argon atmosphere at a temperature of 500° C. for 10 hours to obtain a negative electrode material.

[0184] 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 contains SiO 1.2 , the carbon material is artificial graphite.

[0185] Other parameters of the negative electrode materials are detailed in Table 1.

[0186] Example 4

[0187] A method for preparing a negative electrode material comprises the following steps:

[0188] (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.

[0189] (2) 900 g of artificial graphite was dispersed in 2 L of water, 45 g of ammonium lauryl sulfate was added, and the mixture was stirred for 1 hour to obtain a second mixed solution.

[0190] (3) The first mixed solution and the second mixed solution are mixed dropwise under stirring, and then filtered and dried to obtain a composite.

[0191] (4) The composite was added into a plasma device and vacuumed, with the feed rate controlled at 15 g / min; argon was introduced and the pressure was controlled at 100 Pa, and the composite was surface modified with argon for 20 min at a reaction temperature of 180°C; then propyleneamine was introduced and the pressure was controlled at 100 Pa for a plasma reaction for 40 min to obtain a precursor.

[0192] (5) The precursor was carbonized in an argon atmosphere at a temperature of 600° C. for 10 hours to obtain a negative electrode material.

[0193] 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 contains SiO and Mg elements, and the carbon material is artificial graphite.

[0194] Other parameters of the negative electrode materials are detailed in Table 1.

[0195] Example 5

[0196] A method for preparing a negative electrode material comprises the following steps:

[0197] (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.

[0198] (2) 900 g of artificial graphite was dispersed in 2 L of water, 45 g of ammonium lauryl sulfate was added, and the mixture was stirred for 1 hour to obtain a second mixed solution.

[0199] (3) The first mixed solution and the second mixed solution are mixed dropwise under stirring, and then filtered and dried to obtain a composite.

[0200] (4) The composite was added into a plasma device and vacuumed, with the feed rate controlled at 15 g / min; argon was introduced and the pressure was controlled at 100 Pa, and the composite was surface modified with argon for 20 min at a reaction temperature of 180°C; then propyleneamine was introduced and the pressure was controlled at 100 Pa for a plasma reaction for 40 min to obtain a precursor.

[0201] (5) The precursor was carbonized in an argon atmosphere at a temperature of 500° C. for 10 hours to obtain a negative electrode material.

[0202] 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 contains SiO and Li elements, and the carbon material is artificial graphite.

[0203] Other parameters of the negative electrode materials are detailed in Table 1.

[0204] Example 6

[0205] A method for preparing a negative electrode material comprises the following steps:

[0206] (1) 100 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.

[0207] (2) 900 g of natural graphite was dispersed in 2 L of water, 45 g of ammonium lauryl sulfate was added, and the mixture was stirred for 1 hour to obtain a second mixed solution.

[0208] (3) The first mixed solution and the second mixed solution are mixed dropwise under stirring, and then filtered and dried to obtain a composite.

[0209] (4) The composite was added into a plasma device and vacuumed, with the feed rate controlled at 15 g / min; argon was introduced and the pressure was controlled at 100 Pa, and the composite was surface modified with argon for 20 min at a reaction temperature of 180°C; then propyleneamine was introduced and the pressure was controlled at 100 Pa for a plasma reaction for 40 min to obtain a precursor.

[0210] (5) The precursor was carbonized in an argon atmosphere at a temperature of 500° C. for 10 hours to obtain a negative electrode material.

[0211] 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 contains SiO, and the carbon material is natural graphite.

[0212] Other parameters of the negative electrode materials are detailed in Table 1.

[0213] Example 7

[0214] A method for preparing a negative electrode material comprises the following steps:

[0215] (1) 30 g of carbon-coated SiO was dispersed in 1 L of water, 1.5 g of polydiallyldimethylammonium chloride was added, and the mixture was stirred for 1 hour to obtain a first mixed solution.

[0216] (2) 970 g of artificial graphite was dispersed in 2 L of water, 48.5 g of lauryl ammonium sulfate was added, and the mixture was stirred for 1 hour to obtain a second mixed solution.

[0217] (3) The first mixed solution and the second mixed solution are mixed dropwise under stirring, and then filtered and dried to obtain a composite.

[0218] (4) The composite was added into a plasma device and vacuumed, with the feed rate controlled at 15 g / min; argon was introduced and the pressure was controlled at 100 Pa, and the composite was surface modified with argon for 20 min at a reaction temperature of 180°C; then propyleneamine was introduced and the pressure was controlled at 100 Pa for plasma reaction for 25 min to obtain a precursor.

[0219] (5) The precursor was carbonized in an argon atmosphere at a temperature of 500° C. for 10 hours to obtain a negative electrode material.

[0220] Example 8

[0221] A method for preparing a negative electrode material comprises the following steps:

[0222] (1) 100 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.

[0223] (2) 900 g of artificial graphite was dispersed in 2 L of water, 45 g of ammonium lauryl sulfate was added, and the mixture was stirred for 1 hour to obtain a first mixed solution.

[0224] (3) The first mixed solution and the second mixed solution are mixed dropwise under stirring, and then filtered and dried to obtain a composite.

[0225] (4) The composite was added into a plasma device and vacuumed, with the feed rate controlled at 15 g / min; argon was introduced and the pressure was controlled at 120 Pa, and the composite was surface modified with argon for 20 min at a reaction temperature of 180°C; then propyleneamine was introduced and the pressure was controlled at 120 Pa for a plasma reaction for 25 min to obtain a precursor.

[0226] (5) The precursor was carbonized in an argon atmosphere at a temperature of 500° C. for 10 hours to obtain a negative electrode material.

[0227] Example 9

[0228] A method for preparing a negative electrode material comprises the following steps:

[0229] (1) Take 300g carbon-coated SiO x , dispersed in 1 L of water, added 15 g of polydiallyldimethylammonium chloride, stirred for 1 hour to obtain a first mixed solution.

[0230] (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.

[0231] (3) The first mixed solution and the second mixed solution are mixed dropwise under stirring, and then filtered and dried to obtain a composite.

[0232] (4) The composite was added into a plasma device and vacuumed, with the feed rate controlled at 15 g / min; argon was introduced and the pressure was controlled at 150 Pa, and the composite was surface modified with nitrogen for 20 min at a reaction temperature of 180°C; then propyleneamine was introduced and the pressure was controlled at 150 Pa for plasma reaction for 25 min to obtain a precursor.

[0233] (5) The precursor was carbonized in an argon atmosphere at a temperature of 500° C. for 10 hours to obtain a negative electrode material.

[0234] Example 10

[0235] The difference from Example 1 is that:

[0236] (4) The composite was added into a plasma device and vacuumed, with the feed rate controlled at 15 g / min; argon was introduced and the pressure was controlled at 100 Pa, and the composite was surface modified with argon for 20 min at a reaction temperature of 180°C; styrene was then introduced and the pressure was controlled at 100 Pa for a plasma reaction for 40 min to obtain a precursor.

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

[0238] Example 11

[0239] The difference from Example 2 is that:

[0240] (4) The composite was added into a plasma device and vacuumed, with the feed rate controlled at 10 g / min; argon was introduced and the pressure was controlled at 100 Pa, and the composite was surface modified with argon for 40 min at a reaction temperature of 180°C; styrene was then introduced and the pressure was controlled at 100 Pa for a plasma reaction for 20 min to obtain a precursor.

[0241] The parameters of the negative electrode materials are detailed in Table 1.

[0242] Comparative Example 1

[0243] A method for preparing a negative electrode material comprises the following steps:

[0244] 100 g of carbon-coated SiO and 900 g of artificial graphite were stirred and mixed to obtain a negative electrode material.

[0245] Other parameters of the negative electrode materials are detailed in Table 1.

[0246] Comparative Example 2

[0247] The difference from Example 2 is that:

[0248] (4) The composite was added into a plasma device and vacuumed, with the feed rate controlled at 10 g / min; argon was introduced and the pressure was controlled at 120 Pa, and the composite was surface modified with argon for 20 min at a reaction temperature of 180°C; styrene was then introduced and the pressure was controlled at 120 Pa for a plasma reaction for 80 min to obtain a precursor.

[0249] The parameters of the negative electrode materials are detailed in Table 1.

[0250] Comparative Example 3

[0251] (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.

[0252] (2) 500 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.

[0253] (3) The first mixed solution and the second mixed solution are mixed dropwise under stirring, and then filtered and dried to obtain a composite.

[0254] (4) The composite was carbonized in an argon atmosphere at a temperature of 500° C. for 10 hours to obtain a negative electrode material.

[0255] 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 contains SiO, and the carbon material is artificial graphite.

[0256] The parameters of the negative electrode materials are detailed in Table 1.

[0257] The performance tests were performed on the negative electrode materials obtained in the examples and comparative examples. The results of the above performance tests are shown in Table 1:

[0258] Table 1. Summary of negative electrode material performance test results

[0259] Table 2. Summary of electrochemical performance results of the electrode

[0260] 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 compactibility Y of the negative electrode material can be controlled in the range of 0.6 to 3.0, which can fully utilize the wetting ability of the electrolyte 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 sheet has a suitable compaction density, thereby making the negative electrode sheet have both good cycle performance and excellent rate performance.

[0261] The negative electrode material prepared in Comparative Example 1 is shown in Figures 3 and 4. Compared with Example 2 and Example 8, the silicon-based active material in Comparative Example 1 is directly compounded with the carbon material without undergoing surface modification treatment. The bonding force between the two decreases, and 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.

[0262] 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 material. 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 material 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.

[0263] The mass content of carbon-coated SiO in the raw materials 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 plate was significantly improved. However, due to the high silicon content, the volume of silicon expanded significantly during the cycle, and the cycle life of the plate was greatly reduced. In addition, the compaction density of the plate made of the negative electrode material was too low, making it difficult to exert good electrochemical performance.

[0264] Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the claims. Any person skilled in the art 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 (2): (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 metal M element, wherein M is selected from at least one of Li, Mg, Al, Fe, La, Zn, Ti, Cu and Mn.

3. The negative electrode material according to claim 2, characterized in that Satisfies at least one of the following characteristics (1) to (2): (1) The silicon-based active material further includes a metal M element, where M is Mg and / or Li; (2) The silicon-based active material includes silicon oxide, and the chemical formula of the silicon oxide is SiO x , 0<x≤2.

4. The negative electrode material according to claim 1, characterized in that The average particle size of the silicon-based active material is 1.0 μm to 10.0 μm.

5. The negative electrode material according to claim 1, characterized in that Satisfies at least one of the following characteristics (1) to (2): (1) The carbon material comprises at least one of graphite, graphene, amorphous carbon, carbon nanotubes and carbon fibers; (2) The carbon material contains oxygen.

6. The negative electrode material according to claim 1 or 2, characterized in that: The tap density of the negative electrode material is Tg / cm 3 , T>0.

90.

7. The negative electrode material according to claim 1, characterized in that The oil absorption value of the negative electrode material is 0 mL / 100 g, and O is less than 57.

0.

8. The negative electrode material according to claim 1, characterized in that The specific surface area of ​​the negative electrode material is Sm 2 / g, S<3.

50.

9. The negative electrode material according to claim 1, characterized in that Satisfies at least one of the following characteristics (1) to (2): (1) The pH value of the negative electrode material is 6 to 12; (2) The particle size of the negative electrode material satisfies: 2.5≤D 10 ≤8.5μm, 12.0≤D 90 ≤28.0μm.

10. The negative electrode material according to claim 1, characterized in that Satisfies at least one of the following characteristics (1) to (2): (1) The water content of the negative electrode material is ≤0.5wt%; (2) The mass content of Si element in the negative electrode material is 0.5% to 25%.

11. The negative electrode material according to claim 1, characterized in that At least a portion of the silicon-based active material and the carbon material are dispersed with each other in the form of particles.

12. The negative electrode material according to claim 1, characterized in that The compactability of the negative electrode material is Y, 0.6<Y≤1.

1.

13. The negative electrode material according to claim 1, characterized in that The compactibility of the negative electrode material is Y, 1.1<Y<3.

0.

14. 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.

15. A battery, characterized in that: The invention comprises the negative electrode material according to any one of claims 1 to 13 or the negative electrode material prepared by the preparation method according to claim 14.

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