Negative electrode material and preparation method therefor, negative electrode sheet, and lithium ion battery

Abstract

A negative electrode material and a preparation method therefor, a negative electrode sheet, and a lithium ion battery. The negative electrode material comprises a silicon-based active substance and a carbon material, the negative electrode material has an oil absorption number of O mL / 100 g, specific surface area of Sm2 / g, and particle size concentration of P1, wherein P1=(D80+D50) / (D50+D20), and the physical rebound capability of the negative electrode material is T, wherein T=0.01*O*S / P1, and 0.20<T<1.20. The negative electrode material has a relatively low physical rebound capability, and the volume of an electrode sheet prepared from the negative electrode material is not prone to rebound after compaction, thereby obtaining a relatively high compaction density, and exerting excellent cycle performance.

Description

Negative electrode material and preparation method thereof, negative electrode sheet, and lithium-ion 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 202311435596.3 and titled “Negative electrode material and preparation method thereof, negative electrode sheet, lithium-ion battery”. Technical Field

[0003] The present application relates to the technical field of negative electrode materials, and in particular to negative electrode materials and preparation methods thereof, negative electrode sheets, and lithium-ion batteries. Background Art

[0004] Lithium-ion batteries have the advantages of high energy density, long cycle life, low environmental pollution and no memory effect, and are therefore widely used in electric vehicles and consumer electronics. The negative electrode material is an important component of lithium-ion batteries, which directly affects key indicators such as the battery's energy density, cycle life and safety performance. At present, commercial lithium-ion batteries mainly use graphite-based negative electrode materials, but its theoretical specific capacity is only 372mAh / g, which is difficult to meet the needs of high-energy-density lithium-ion batteries. Silicon-based negative electrode materials have a very high specific capacity as lithium-ion battery negative electrode materials and are one of the candidate materials for the next generation of high-energy-density lithium-ion batteries. However, the silicon negative electrode will produce huge volume changes during the charge and discharge cycle, resulting in degradation of the material / electrode structure and instability of the solid electrolyte interface film (SEI), which leads to a sharp decline in its electrochemical performance.

[0005] 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. Therefore, it is necessary to explore the mechanism of action of multiple factors in coordination and develop composite negative electrode materials that meet market demand.

[0006] Summary of the Invention

[0007] The purpose of the present application is to provide a negative electrode material and a preparation method thereof, a negative electrode plate, and a lithium-ion battery. The negative electrode material of the present application has a low physical rebound ability, and the plate made therefrom is not easy to rebound in volume after compaction, thereby obtaining a higher compaction density and exerting excellent cycle performance.

[0008] 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, the particle size concentration of the negative electrode material is P1, P1=(D 80 +D 50 ) / (D 50 +D 20 ), the physical rebound ability of the negative electrode material is T, T=0.01*O*S / P1, 0.20<T<1.20.

[0009] In some embodiments, the silicon-based active material includes at least one of elemental silicon and silicon oxide.

[0010] In some embodiments, the silicon-based active material further includes a metal M element, where M is selected from at least one of Mg, Li, Fe, Al, Mn, and Cu.

[0011] In some embodiments, the metal M element exists in at least one form of a simple substance, an oxide, or a silicate.

[0012] In some embodiments, the silicon-based active material comprises silicon oxide, and the general chemical formula of silicon oxide is SiO x , 0<x≤2.

[0013] In some embodiments, the average particle size of the silicon-based active material is 1 μm to 10 μm.

[0014] In some embodiments, the carbon material includes at least one of graphite, graphene, amorphous carbon, carbon nanotubes, and carbon fibers.

[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 cm 2 / g, S<3.50.

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

[0018] In some embodiments, the tap density of the negative electrode material is greater than 0.90 g / cm 3 .

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

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

[0021] In some embodiments, the particle size of the negative electrode material satisfies: 0.1 μm ≤ D 20 ≤12μm, 0.2μm≤D50 ≤18μm, 0.3μm≤D 80 ≤25μm.

[0022] 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.

[0023] In some embodiments, the physical rebound capability of the negative electrode material is T, 0.2<T<0.7.

[0024] In some embodiments, the physical rebound capability of the negative electrode material is T, 0.70≤T<1.20.

[0025] In some embodiments, the particle size concentration of the negative electrode material is P1, 1.2<P1<2.0.

[0026] In a second aspect, the present application provides a method for preparing a negative electrode material, comprising the following steps:

[0027] Provided is a composite containing a silicon-based active substance and a carbon material, wherein the particle size concentration of the composite is P0, 1.2<P0<2.0, P0=(D' 80 +D' 50 ) / (D' 50 +D' 20 );

[0028] In a vacuum environment, 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;

[0029] The precursor is heat-treated to obtain a negative electrode material having an oil absorption value of 0 mL / 100 g and a specific surface area of ​​5 m 2 / g, the particle size concentration of the negative electrode material is P1, P1=(D 80 +D 50 ) / (D 50 +D 20 ), the physical rebound ability of the negative electrode material is T, T=0.01*O*S / P1, 0.20<T<1.20.

[0030] In some embodiments, the specific step of providing a composite comprising a silicon-based active substance and a carbon material includes: mixing the silicon-based active substance and the carbon material to obtain the composite.

[0031] In some embodiments, the mass ratio of the silicon-based active material to the carbon material is (0.01-0.4):1.

[0032] In some embodiments, the silicon-based active material includes at least one of elemental silicon and silicon oxide.

[0033] In some embodiments, the silicon-based active material further includes a metal M element, where M is selected from at least one of Mg, Li, Fe, Al, Mn, and Cu.

[0034] In some embodiments, the silicon-based active material further includes a metal M element, where M is selected from at least one of Mg, Li, Fe, Al, Mn, and Cu, and is dispersed in the silicon-based active material in the form of at least one element, oxide, or silicate.

[0035] In some embodiments, the silicon-based active material comprises silicon oxide, and the general chemical formula of silicon oxide is SiO x , 0<x<2.

[0036] In some embodiments, the carbon material includes at least one of graphite, graphene, amorphous carbon, carbon nanotubes, and carbon fibers.

[0037] In some embodiments, the average particle size of the silicon-based active material is 1 μm to 10 μm.

[0038] In some embodiments, the average particle size of the carbon material is 2 μm to 20 μm.

[0039] In some embodiments, the mixing method includes at least one of grinding mixing, air flow mixing, and mechanical mixing.

[0040] In some embodiments, the method further comprises: adjusting the particle size of the composite to control the particle size concentration of the composite to be P0, 1.2<P0<2.0, P0=(D' 80 +D' 50 ) / (D' 50 +D' 20 ).

[0041] In some embodiments, the surface modification treatment is performed at a temperature of 50°C to 200°C.

[0042] In some embodiments, the surface modification treatment is performed at an air pressure ranging from 50 Pa to 150 Pa.

[0043] In some embodiments, the surface modification treatment lasts for 10 min to 30 min.

[0044] In some embodiments, the non-polymerizable gas includes at least one of argon, nitrogen, and hydrogen.

[0045] In some embodiments, the temperature of the plasma reaction is 50°C to 200°C.

[0046] In some embodiments, the gas pressure of the plasma reaction ranges from 50 Pa to 150 Pa.

[0047] In some embodiments, the plasma reaction time is 20 min to 60 min.

[0048] In some embodiments, the polymerizable gas includes at least one of styrene, cyclohexylamine, allylamine, and methacrylate.

[0049] In some embodiments, the heat treatment temperature is 500°C to 700°C.

[0050] In some embodiments, the heat treatment time is 1 hour to 20 hours.

[0051] In some embodiments, the heat treatment is performed under a protective atmosphere.

[0052] In some embodiments, the heat treatment is performed under a protective atmosphere comprising at least one of nitrogen, helium, neon, and argon.

[0053] In a third aspect, the present application provides a negative electrode plate, which includes the negative electrode material described in the first aspect or the negative electrode material prepared by the preparation method of the negative electrode material described in the second aspect; under a rolling pressure of 3MPa, the plate rebound rate of the negative electrode plate is 2% to 10%.

[0054] In a fourth aspect, the present application provides a lithium-ion battery, comprising the negative electrode sheet described in the third aspect.

[0055] Compared with the prior art, the technical solution of this application has at least the following beneficial effects:

[0056] The negative electrode material provided in this application 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, particle size concentration is P1, P1=(D 80 +D 50 ) / (D 50 +D 20), the physical rebound ability of the negative electrode material is T, T=0.01*O*S / P1, 0.20<T<1.20. The oil absorption value reflects the absorption capacity of the negative electrode material particle clusters on the binder during the slurry preparation process. The larger the oil absorption value, the higher the binder content absorbed by the negative electrode material particle clusters during the slurry preparation process, which is not only not conducive to the effective contact and filling of the negative electrode material particles, but also the excess binder in the negative electrode material particle clusters has greater elasticity, making the produced electrode easy to physically rebound after rolling. The specific surface area reflects the surface energy of the negative electrode material particles. The smaller the specific surface area of ​​the negative electrode material particles, the smaller its surface energy, which is more conducive to reducing the interaction force between the negative electrode material particles and is conducive to the sliding of the negative electrode material particles to form a dense stacking, and promoting the produced electrode to be less likely to rebound. The particle size characteristics affect the stacking of the negative electrode material particles. Only when P1 meets a specific range, the particle size and quantity matching of large and small particles in the negative electrode material are better, which is conducive to the full dispersion of the negative electrode material particles, tending to form small particles embedded in the contact gaps between large particles, forming a tightly packed structure, thereby helping to reduce the physical rebound of the negative electrode plate after rolling. It is understandable that the physical rebound characteristics of the negative electrode plate are also related to the ability of the negative electrode material particle clusters to absorb binders, the difficulty of slippage between particles, the degree of particle size matching between particles, etc. Judging the physical rebound 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 T can be used to measure the ability of the negative electrode material made of the plate to physically rebound after rolling. By controlling the balance between the oil absorption value, specific surface area and particle size concentration of the negative electrode material, that is, controlling T to fall within the above range, the negative electrode material can have a suitable physical rebound ability, and the resulting electrode sheet is conducive to the close combination of silicon-based active material and carbon material particles, effectively inhibiting the volume expansion of the silicon-based active material. At the same time, retaining appropriate pores in the negative electrode sheet also allows the electrolyte to penetrate into the negative electrode sheet, so that the resulting battery has both good cycle performance and excellent rate performance.

[0057] The preparation method of the negative electrode material provided by the present application, first, by controlling the particle size concentration of the raw material, that is, the composite containing the silicon-based active substance and the carbon material, the close combination and stacking between the silicon-based active substance and the carbon material can be effectively achieved, and the particle size and quantity of the large particles and the small particles in the material can be well matched, which is conducive to the full dispersion of the particles and tends to form a close stacking structure in which the small particles are embedded in the contact gaps of the large particles; then, after vacuuming, a non-polymerizing gas is introduced to perform surface modification treatment on the composite, 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, which are During the plasma reaction process, the active groups on the surface of the composite particles can combine with the polymerizable 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. The surface defects of the negative electrode material are reduced, and the oil absorption value and specific surface area of ​​the negative electrode material are reduced. The physical rebound ability of the final negative electrode material can be controlled within the range of 0.20 to 1.20, so that the volume of the manufactured negative electrode plate is not easy to rebound after compaction, thereby obtaining a higher compaction density, so that the negative electrode plate has both good cycle performance and excellent rate performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] The present invention will be further described below with reference to the accompanying drawings and examples.

[0059] FIG1 is a schematic flow chart of a method for preparing a negative electrode material according to an embodiment of the present application;

[0060] FIG2 is a comparison of cycle curves of negative electrode materials prepared in Example 2, Example 8, and Comparative Example 8 of the present application;

[0061] FIG3 is a comparison chart of the rate performance of the negative electrode materials prepared in Example 2, Example 8 and Comparative Example 8 of the present application. DETAILED DESCRIPTION

[0062] In order to better understand the technical solution of the present invention, the embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0063] It should be understood that the embodiments described are only a portion of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative work are within the scope of protection of the present invention.

[0064] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The singular forms "a", "an", "the" and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise.

[0065] It should be understood that the term "and / or" as used herein is merely a description of the relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can represent: A exists alone, A and B exist simultaneously, or B exists alone. Furthermore, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0066] In the first aspect, the present application provides a negative electrode material, 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, the particle size concentration of the negative electrode material is P1, P1=(D 80 +D 50 ) / (D 50 +D 20 ), the physical rebound capacity of the negative electrode material is T, T=0.01*O*S / P1, 0.20<T<1.20.

[0067] The negative electrode material provided in this application 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, particle size concentration is P1, P1=(D 80 +D 50 ) / (D 50 +D 20), the physical rebound ability of the negative electrode material is T, T=0.01*O*S / P1, 0.20<T<1.20. The oil absorption value reflects the absorption capacity of the negative electrode material particle clusters on the binder during the slurry preparation process. The larger the oil absorption value, the higher the binder content absorbed by the negative electrode material particle clusters during the slurry preparation process, which is not only not conducive to the effective contact and filling of the negative electrode material particles, but also the excess binder in the negative electrode material particle clusters has greater elasticity, making the produced electrode easy to physically rebound after rolling. The specific surface area reflects the surface energy of the negative electrode material particles. The smaller the specific surface area of ​​the negative electrode material particles, the smaller its surface energy, which is more conducive to reducing the interaction force between the negative electrode material particles and is conducive to the sliding of the negative electrode material particles to form a dense stacking, and promoting the produced electrode to be less likely to rebound. The particle size characteristics affect the stacking of the negative electrode material particles. Only when P1 meets a specific range, the particle size and quantity matching of large and small particles in the negative electrode material are better, which is conducive to the full dispersion of the negative electrode material particles, tending to form small particles embedded in the contact gaps between large particles, forming a tightly packed structure, thereby helping to reduce the physical rebound of the negative electrode plate after rolling. It is understandable that the physical rebound characteristics of the negative electrode plate are also related to the ability of the negative electrode material particle clusters to absorb binders, the difficulty of slippage between particles, the degree of particle size matching between particles, etc. Judging the physical rebound 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 T can be used to measure the ability of the negative electrode material made of the plate to physically rebound after rolling. By controlling the balance between the oil absorption value, specific surface area and particle size concentration of the negative electrode material, that is, controlling T to fall within the above range, the negative electrode material can have a suitable physical rebound ability, and the resulting electrode sheet is conducive to the close combination of silicon-based active material and carbon material particles, effectively inhibiting the volume expansion of the silicon-based active material. At the same time, retaining appropriate pores in the negative electrode sheet also allows the electrolyte to penetrate into the negative electrode sheet, so that the resulting battery has both good cycle performance and excellent rate performance.

[0068] In some embodiments, the physical rebound capacity of the negative electrode material is T, 0.20<T<1.20, specifically 0.21, 0.25, 0.3, 0.4, 0.45, 0.5, 0.6, 0.7, 0.75, 0.8, 0.9, 0.95, 1.0, 1.1, 1.15 or 1.2, etc., of course, it can also be other values ​​within the above range, which are not limited here. It can be understood that after the negative electrode material is slurried, coated, and dried, it needs to be rolled under a certain pressure to increase the compaction density and finally obtain a usable negative electrode pole piece. The pole pieces made of different negative electrodes will physically rebound after being placed for a period of time after rolling, causing changes in the contact area of ​​the active material and the porosity of the pole piece, and exhibiting different electrochemical properties. The physical rebound capacity T of the negative electrode material can be used to measure the ability of the pole piece made of the negative electrode material to physically rebound after rolling. The smaller the T value, the less likely the electrode sheets made of negative electrode materials will rebound during rolling, making the silicon-based active material and carbon material particles in the electrode sheets more tightly bonded, which is beneficial to suppressing the volume expansion of the negative electrode material during the charge and discharge process. When T ≥ 1.20, the electrode sheets made of negative electrode materials will experience severe physical rebound after rolling, making the bond between the silicon-based active material and the carbon material particles loose and the contact area significantly reduced, which is not conducive to suppressing the volume expansion of the negative electrode material and the formation of a good conductive channel. When T ≤ 0.2, the physical rebound of the electrode sheets made of negative electrode materials after rolling is extremely small, and there is a lack of suitable pores between the silicon-based active material and the carbon material particles in the electrode sheets, which is not conducive to the infiltration and transmission of the electrolyte, resulting in the inability to fully utilize the lithium storage capacity of the negative electrode material, reducing the cycle performance, and seriously degrading the rate performance.

[0069] In some embodiments, the physical rebound capacity of the negative electrode material is T, 0.70≤T<1.20. When 0.70≤T<1.20, the electrode sheet made of the negative electrode material undergoes appropriate physical rebound after rolling, resulting in good contact between the silicon-based active material and the carbon material particles, while also having an appropriate electrode sheet porosity, thereby enabling the electrode sheet to have excellent rate performance while maintaining relatively good cycle performance.

[0070] In some embodiments, the physical rebound capacity of the negative electrode material is T, 0.2 < T < 0.7. When 0.2 < T < 0.7, the electrode sheet made of the negative electrode material undergoes minimal physical rebound after rolling, resulting in a tight bond between the silicon-based active material and the carbon material particles, which can provide stress to the silicon-based active material, thereby significantly suppressing the volume expansion of the negative electrode material and achieving excellent cycle performance.

[0071] In some embodiments, the silicon-based active material includes at least one of elemental silicon and silicon oxide. The elemental silicon may be amorphous silicon and / or crystalline silicon.

[0072] In some embodiments, the silicon-based active material further includes a metal M element, where M is selected from at least one of Mg, Li, Fe, Al, Mn, and Cu.

[0073] In some embodiments, the metal M element exists in the form of at least one of a simple substance, an oxide, or a silicate.

[0074] In some embodiments, the silicon-based active material comprises silicon oxide SiO x , 0<x≤2. SiO x Specifically, it can be SiO 0.2 、SiO 0.5 、SiO 0.7 、SiO 0.9 、SiO、SiO 1.2 、SiO 1.5 、SiO 1.8 、SiO 1.9 , SiO2, etc., are not limited here.

[0075] In some embodiments, the average particle size of the silicon-based active material is 1 μm to 10 μm, specifically 1 μm, 1.8 μm, 2 μm, 2.5 μm, 3 μm, 3.6 μm, 5 μm, 6 μm, 6.5 μm, 7 μm, 7.8 μm, 8.5 μm, 9 μm, 9.8 μm or 10 μm, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0076] In some embodiments, in the negative electrode material, at least the silicon-based active material and the carbon material are dispersed with each other in the form of particles.

[0077] In some embodiments, the carbon material is present on the surface of the silicon-based active material.

[0078] In some embodiments, the silicon-based active material particles may be based on a carbon material and embedded in the carbon material.

[0079] In some embodiments, the carbon material is located on the surface of the silicon-based active material to form a carbon layer.

[0080] 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.

[0081] 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, small volume expansion, high initial efficiency, and stable cycle performance. Preferably, the carbon material is graphite.

[0082] In some embodiments, the oil absorption value of the negative electrode material is 0 mL / 100g, 30.0<O<57.0, and O can specifically be 33.0, 40.0, 43.0, 45.0, 46.0, 47.0, 48.0, 50.0, 52.0, 53.0, 55.0, 56.0, or 57.0, etc., and is not limited here. 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 material properties that measures the physical rebound ability of the electrode. When the oil absorption value of the negative electrode material is 0<57.0mL / 100g, the negative electrode material particle clusters can absorb an appropriate amount of binder during the slurry preparation process, which is beneficial to enhance the bonding between the silicon-based active material and the carbon material. The obtained electrode undergoes less physical rebound after rolling, and it is easy to obtain an electrode with a high compaction density.

[0083] In some embodiments, the specific surface area of ​​the negative electrode material is S cm 2 / g, 0.7<S<3.50, specifically it can be 3.49, 3.45, 3.35, 3.30, 3.25, 3.15, 3.10, 3.0, 2.85, 2.76, 2.23, 2.10, 1.98, 1.56, 1.47, 1.38, 1.24, 0.98 or 0.87, etc., of course, it can also be other values ​​within the above range, which is not limited here. It can be understood that the specific surface area is closely related to the surface energy and is positively correlated. Negative electrode materials with higher specific surface area have greater surface energy, and the interaction force between their particles is also greater, which can easily hinder the sliding of particles and is not conducive to dense accumulation of particles. It is also one of the material properties to measure the physical rebound ability of the electrode. When the S of the silicon-based composite material is less than 3.50cm 2 / g, which has appropriate surface energy, is conducive to the dense accumulation of particles, so that the pole piece produced is not easy to rebound.

[0084] In some embodiments, the pH value of the negative electrode material is 6 to 12, specifically 6, 6.5, 7, 7.8, 8, 8.5, 9, 9.6, 10, 10.5, 11, 11.3, 11.8, or 12, etc., and other values ​​within the above range are also possible, and are not limited here. Preferably, the pH value of the negative electrode material is 6.5 to 8.5.

[0085] In some embodiments, the tap density of the negative electrode material is 0.90 g / cm 3 ~1.25g / cm 3 The tap density of the negative electrode material can be specifically 0.91 g / cm 3 , 0.95g / cm 3 , 0.99g / cm 3 , 1.0g / cm 3 , 1.05g / cm 3 , 1.1g / cm 3 , 1.13g / cm 3 , 1.18g / cm 3 or 1.2 g / cm 3 etc., not limited here.

[0086] In some embodiments, the mass content of water in the negative electrode material is ≤0.5wt%, specifically 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.

[0087] In some embodiments, the mass content of Si element in the negative electrode material is 0.5wt% to 25wt%, specifically 0.5wt%, 0.6wt%, 0.8wt%, 1.0wt%, 1.2wt%, 1.5wt%, 3wt%, 5.6wt%, 7.8wt%, 8.9wt%, 10wt%, 11.5wt%, 14.6wt%, 16.5wt%, 18.9wt%, 20wt% or 25wt%, etc., and of course other values ​​within the above range can also be used, which is not limited here. Controlling the mass content of Si element within the above range 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 particle size of the negative electrode material satisfies: 0.1 μm ≤ D 20 ≤12μm, 0.2μm≤D 50 ≤18μm, 0.3μm≤D 80 ≤25μm. It should be noted that the volume-based cumulative particle size distribution of the particle size distribution was measured using the laser diffraction method, D 20 Indicates the particle size corresponding to when the cumulative particle size distribution percentage reaches 20%. 50 Indicates the particle size corresponding to when the cumulative particle size distribution percentage reaches 50%. 80 It indicates the particle size corresponding to when the cumulative particle size distribution percentage reaches 80%.

[0089] Specifically, D 20 It can be 0.1μm, 0.5μm, 1μm, 1.5μm, 3μm, 5μm, 8μm, 10μm, 11μm or 12μm, etc., and is not limited here.

[0090] D 50 Specifically, it can be 0.2μm, 0.5μm, 1μm, 1.8μm, 2.5μm, 3μm, 5μm, 8μm, 10μm, 12μm, 15μm or 18μm, etc., which is not limited here.

[0091] D 80 Specifically, it can be 0.3μm, 1.5μm, 3μm, 5μm, 8μm, 10μm, 12μm, 15μm, 18μm, 20μm, 23μm or 25μm, etc., which is not limited here.

[0092] In some embodiments, the particle size concentration of the negative electrode material is P1, 1.2<P1<2.0, P1=(D 80 +D 50 ) / (D 50 +D 20). Specifically, P1 can be 1.21, 1.26, 1.31, 1.34, 1.38, 1.43, 1.47, 1.5, 1.56, 1.67, 1.74, 1.86, 1.95, 1.98 or 1.99, etc., which are not limited here. The particle size concentration P1 of the negative electrode material is one of the material properties that affects the physical rebound ability of the negative electrode sheet. Among them, D 50 ~D 80 The range represents the majority of larger particles in the negative electrode material; D 20 ~D 50 The range represents the majority of smaller particles in the material; therefore, P1 can be used as (D 80 +D 50 ) / (D 50 +D 20 ) represents the size ratio of large to small particles in the negative electrode material. The closer the P1 value is to 1, the more concentrated the particle size distribution is. When the negative electrode material satisfies 1.2<P1<2.0, the size and quantity of large and small particles in the material are well matched, which promotes full particle dispersion and tends to form a densely packed structure with small particles embedded in the contact gaps between large particles, thus helping to reduce the physical rebound after the electrode sheet is rolled.

[0093] In a second aspect, the present application provides a method for preparing a negative electrode material, as shown in FIG1 , comprising the following steps:

[0094] Step S100: providing a composite material containing a silicon-based active substance and a carbon material, wherein the particle size concentration of the composite material is P0, 1.2<P0<2.0, P0=(D' 80 +D' 50 ) / (D' 50 +D' 20 );

[0095] Step S200, in a vacuum environment, introducing a non-polymerizable gas to perform surface modification on the composite, and then introducing a polymerizable gas to perform a plasma reaction to obtain a precursor;

[0096] Step S300: heat-treating the precursor to obtain a negative electrode material. The negative electrode material has an oil absorption value of 0 mL / 100 g and a specific surface area of ​​5 m 2 / g, the particle size concentration of the negative electrode material is P1, P1=(D 80 +D 50 ) / (D 50 +D 20 ), the physical rebound capacity of the negative electrode material is T, T=0.01*O*S / P1, 0.20<T<1.20.

[0097] The preparation method of the negative electrode material provided by the present application, first, by controlling the particle size concentration of the raw material, that is, the composite containing the silicon-based active substance and the carbon material, the close combination and stacking between the silicon-based active substance and the carbon material can be effectively achieved, and the particle size and quantity of the large particles and the small particles in the material can be well matched, which is conducive to the full dispersion of the particles and tends to form a close stacking structure in which the small particles are embedded in the contact gaps of the large particles; then, after vacuuming, a non-polymerizing gas is introduced to perform surface modification treatment on the composite, 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, which are During the plasma reaction process, the active groups on the surface of the composite particles can combine with the polymerizable 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. The surface defects of the negative electrode material are reduced, and the oil absorption value and specific surface area of ​​the negative electrode material are reduced. The physical rebound ability of the final negative electrode material can be controlled within the range of 0.20 to 1.20, so that the volume of the manufactured negative electrode plate is not easy to rebound after compaction, thereby obtaining a higher compaction density, so that the negative electrode plate has both good cycle performance and excellent rate performance.

[0098] The following is a detailed introduction to this plan:

[0099] Step S100, providing a composite material containing a silicon-based active material and a carbon material, wherein the particle size concentration of the composite material is P0, 1.2<P0<2.0, P0=(D' 80 +D' 50 ) / (D' 50 +D' 20 ).

[0100] In some embodiments, the specific step of providing a composite comprising a silicon-based active substance and a carbon material includes: mixing the silicon-based active substance and the carbon material to obtain the composite.

[0101] In some embodiments, the mass ratio of the silicon-based active substance to the carbon material is (0.01-0.4):1, specifically 0.01:1, 0.05:1, 0.1:1, 0.15:1, 0.2:1, 0.25:1, 0.3:1, 0.35:1 or 0.4:1, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0102] In some embodiments, the silicon-based active material includes at least one of elemental silicon and silicon oxide. The elemental silicon may be amorphous silicon and / or crystalline silicon.

[0103] In some embodiments, the silicon-based active material further includes a metal M element, where M is selected from at least one of Mg, Li, Fe, Al, Mn, and Cu.

[0104] In some embodiments, the silicon-based active material further comprises a metal element M, M is selected from at least one of Mg, Li, Fe, Al, Mn and Cu, and M is dispersed in the silicon-based active material in the form of at least one element, oxide or silicate. Preferably, M is in the form of silicate (M x Si y O z ) in the form of dispersed in the silicon-based active material.

[0105] In some embodiments, the silicon-based active material comprises silicon oxide SiO x , 0<x<2. Specifically, SiO x Specifically, it can be SiO 0.2 、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.

[0106] 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.

[0107] In some embodiments, the average particle size of the silicon-based active material is 1 μm to 10 μm, specifically 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm or 10 μm, etc., which is not limited here.

[0108] In some embodiments, the average particle size of the carbon material is 2 μm to 20 μm. The average particle size of the carbon material can be 2 μm, 5 μm, 7 μm, 8 μm, 10 μm, 12 μm, 15 μm, 16 μm, 18 μm or 20 μm, etc., which is not limited here.

[0109] In some embodiments, the mixing method includes at least one of grinding mixing, air flow mixing, and mechanical mixing.

[0110] In some embodiments, the method further comprises: adjusting the particle size of the complex to control the particle size concentration of the complex to be P0, 1.2<P0<2.0, P0=(D' 80 +D' 50 ) / (D' 50 +D' 20 ). It can be understood that controlling the particle size concentration P0 of the composite within the above range can achieve better matching of the particle size and quantity of large and small particles in the negative electrode material, which is conducive to sufficient dispersion of the particles and tends to form a densely packed structure in which small particles are embedded in the contact gaps between large particles. Specifically, the composite is placed in an airflow classifier, and the airflow classifier is used to classify and adjust the particle size of the composite, so that the particle size concentration P0 of the composite is controlled to meet the above range.

[0111] In step S200 , a non-polymerizable gas is introduced into the composite under a vacuum environment to perform surface modification treatment, and then a polymerizable gas is introduced into the composite to perform plasma reaction to obtain a precursor.

[0112] In some embodiments, the surface modification treatment temperature is 50° C. to 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 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.

[0114] In some embodiments, the non-polymerizable 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 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.

[0117] It should be noted that surface modification treatment of the composite under non-polymerizing gas will cause certain slight damage to the surface of the composite. That is, when the surface modification treatment time is too long, the specific surface area of ​​the negative electrode material will increase, which is not conducive to improving the physical rebound ability of the negative electrode material. The longer the plasma reaction time under polymerizing gas is, the thicker the polymer modification layer deposited on the surface of the composite will be. After subsequent heat treatment, the specific surface area and oil absorption value of the negative electrode material will be lower. Therefore, controlling the time for surface modification treatment of the composite under non-polymerizing gas and the time for plasma reaction under polymerizing gas is beneficial to controlling the balance between the specific surface area, oil absorption value and physical rebound ability of the negative electrode material, and improving the cycle performance and rate performance of the negative electrode material.

[0118] In some embodiments, the temperature of the plasma reaction is 50° C. to 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.

[0119] 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. Of course, it can also be other values ​​within the above range, which is not limited here.

[0120] In some embodiments, the polymerizable gas includes at least one of styrene, cyclohexylamine, vinyl chloride, propylene amine, and methacrylate. For example, the polymer modified layer can be polystyrene, polypropylene amine, polymethacrylate, polyvinyl chloride, etc., which are not limited here.

[0121] Step S300: heat-treating the precursor to obtain a negative electrode material having an oil absorption value of 0 mL / 100 g and a specific surface area of ​​S m 2 / g, the particle size distribution concentration of the negative electrode material is P1, P1=(D 80 +D 50 ) / (D50 +D 20 ), the physical rebound ability of the negative electrode material is T, T=0.01*O*S / P1, 0.20<T<1.20.

[0122] It can be understood that during the heat treatment process, the polymer modification 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 physical rebound ability of the final negative electrode material can be controlled within the range of 0.20 to 1.20, and the negative electrode material has both good cycle performance and excellent rate performance.

[0123] In some embodiments, the heat treatment temperature is 500°C to 700°C, specifically 500°C, 530°C, 550°C, 580°C, 600°C, 620°C, 650°C, 670°C, 680°C or 700°C, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0124] In some embodiments, the heat treatment time is 1 h to 20 h, specifically 1 h, 1.5 h, 3 h, 5 h, 8 h, 10 h, 12 h, 15 h, 18 h or 20 h, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0125] In some embodiments, the heat treatment is performed under a protective atmosphere.

[0126] In some embodiments, the heat treatment is performed under a protective atmosphere comprising at least one of nitrogen, helium, neon, and argon.

[0127] On the third aspect, the present application provides a negative electrode plate, which includes the above-mentioned negative electrode material. Under a rolling pressure of 3MPa, the plate rebound rate of the negative electrode plate is 2% to 10%. The plate rebound rate can be specifically 2%, 2.5%, 3%, 3.8%, 5.6%, 6.7%, 7.8%, 8.9%, 9.6% or 10%, etc., which is not limited here. It can be understood that the plate rebound rate of the negative electrode plate is within the above range, and the plate undergoes appropriate physical rebound after rolling, so that the silicon-based active material and the carbon material have good contact, and also have appropriate plate porosity, so that the plate has excellent rate performance while maintaining relatively good cycle performance.

[0128] In a fourth aspect, the present application provides a lithium-ion battery, which includes the above-mentioned negative electrode plate.

[0129] Example

[0130] Example 1

[0131] (1) Weigh 30g SiO(D 50 =6μm), 970g artificial graphite (D 50 =15 μm) were preliminarily mixed and then placed in a jet mill for collision, crushing and mixing to obtain a composite.

[0132] (2) Place the composite in an airflow classifier for particle size adjustment, and control the composite particle size concentration P0 = 1.34 ± 0.05, P0 = (D' 80 +D' 50 ) / (D' 50 +D' 20 ).

[0133] (3) Add the complex into the plasma equipment and evacuate it; introduce argon gas and control the gas pressure to 100 Pa, and use argon gas to perform surface modification treatment on the complex for 20 minutes at a reaction temperature of 180°C; then introduce propyleneamine and control the gas pressure to 100 Pa to perform plasma reaction for 40 minutes to obtain a precursor.

[0134] (4) The precursor was heat-treated in an argon atmosphere at a temperature of 500° C. for 10 hours to obtain a negative electrode material.

[0135] The negative electrode material prepared in this embodiment includes a silicon-based active material and a carbon material. The silicon-based active material contains SiO, and the carbon material includes artificial graphite.

[0136] Other parameters of the negative electrode materials are detailed in Table 1.

[0137] Example 2

[0138] (1) Weigh 100g SiO(D 50 =6μm), 900g artificial graphite (D 50 =15 μm) were preliminarily mixed and then placed in a jet mill for collision, crushing and mixing to obtain a composite.

[0139] (2) Place the composite in an airflow classifier for particle size adjustment, and control the composite particle size concentration P0 = 1.45 ± 0.05, P0 = (D' 80 +D' 50 ) / (D' 50 +D' 20 ).

[0140] (3) Add the complex into the plasma equipment and evacuate it; introduce argon gas and control the gas pressure to 100 Pa, and use argon gas to perform surface modification treatment on the complex for 20 minutes at a reaction temperature of 180°C; then introduce propyleneamine and control the gas pressure to 100 Pa to perform plasma reaction for 40 minutes to obtain a precursor.

[0141] (4) The precursor was heat-treated in an argon atmosphere at a temperature of 500° C. for 10 hours to obtain a negative electrode material.

[0142] The negative electrode material prepared in this embodiment includes a silicon-based active material and a carbon material. The silicon-based active material contains SiO, and the carbon material includes artificial graphite.

[0143] Other parameters of the negative electrode materials are detailed in Table 1.

[0144] Example 3

[0145] (1) Weigh 300g SiO(D 50 =6μm), 700g artificial graphite (D 50 =15 μm) were preliminarily mixed and then placed in a jet mill for collision, crushing and mixing to obtain a composite.

[0146] (2) Place the composite in an air classifier for particle size adjustment, and control the composite particle size concentration P0 = 1.66 ± 0.05, P0 = (D' 80 +D' 50 ) / (D' 50 +D' 20 ).

[0147] (3) Add the complex into the plasma equipment and evacuate it; introduce argon gas and control the gas pressure to 100 Pa, and use argon gas to perform surface modification treatment on the complex for 20 minutes at a reaction temperature of 180°C; then introduce propyleneamine and control the gas pressure to 100 Pa to perform plasma reaction for 40 minutes to obtain a precursor.

[0148] (4) The precursor was heat-treated in an argon atmosphere at a temperature of 500° C. for 10 hours to obtain a negative electrode material.

[0149] The negative electrode material prepared in this embodiment includes a silicon-based active material and a carbon material. The silicon-based active material contains SiO, and the carbon material includes artificial graphite.

[0150] Other parameters of the negative electrode materials are detailed in Table 1.

[0151] Example 4

[0152] (1) Weigh 100g of Mg-doped SiO(D 50 =6μm), 900g artificial graphite (D 50 =15 μm) were preliminarily mixed and then placed in a jet mill for collision, crushing and mixing to obtain a composite.

[0153] (2) Place the composite in an airflow classifier for particle size adjustment, and control the composite particle size concentration P0 = 1.62 ± 0.05, P0 = (D' 80 +D' 50 ) / (D' 50 +D' 20 ).

[0154] (3) Add the complex into the plasma equipment and evacuate it; introduce argon gas and control the gas pressure to 100 Pa, and use argon gas to perform surface modification treatment on the complex for 20 minutes at a reaction temperature of 180°C; then introduce propyleneamine and control the gas pressure to 100 Pa to perform plasma reaction for 40 minutes to obtain a precursor.

[0155] (4) The precursor was heat-treated in an argon atmosphere at a temperature of 500° C. for 10 hours to obtain a negative electrode material.

[0156] The negative electrode material prepared in this embodiment includes a silicon-based active material and a carbon material. The silicon-based active material contains SiO and Mg elements, wherein Mg exists in the form of magnesium silicate. The carbon material includes artificial graphite.

[0157] Other parameters of the negative electrode materials are detailed in Table 1.

[0158] Example 5

[0159] (1) Weigh 100g of Li-doped SiO(D 50 =6μm), 900g artificial graphite (D 50 =15 μm) were preliminarily mixed and then placed in a jet mill for collision, crushing and mixing to obtain a composite.

[0160] (2) Place the composite in an airflow classifier for particle size adjustment, and control the composite particle size concentration P0 = 1.58 ± 0.05, P0 = (D' 80 +D' 50 ) / (D' 50 +D' 20 ).

[0161] (3) Add the complex into the plasma equipment and evacuate it; introduce argon gas and control the gas pressure to 100 Pa, and use argon gas to perform surface modification treatment on the complex for 20 minutes at a reaction temperature of 180°C; then introduce propyleneamine and control the gas pressure to 100 Pa to perform plasma reaction for 40 minutes to obtain a precursor.

[0162] (4) The precursor was heat-treated 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 this embodiment includes a silicon-based active material and a carbon material. The silicon-based active material contains SiO and Li elements, wherein Li exists in the form of lithium silicate. The carbon material includes artificial graphite.

[0164] Other parameters of the negative electrode materials are detailed in Table 1.

[0165] Example 6

[0166] (1) Weigh 100g SiO(D 50 =6μm), 900g natural graphite (D 50 =15 μm) were preliminarily mixed and then placed in a jet mill for collision, crushing and mixing to obtain a composite.

[0167] (2) The composite was placed in an air flow classifier for particle size adjustment, and the particle size concentration of the composite was controlled to be P0 = 1.73 ± 0.05, P0 = (D' 80 +D' 50 ) / (D' 50 +D' 20 ).

[0168] (3) Add the complex into the plasma equipment and evacuate it; introduce argon gas and control the gas pressure to 100 Pa, and use argon gas to perform surface modification treatment on the complex for 20 minutes at a reaction temperature of 180°C; then introduce propyleneamine and control the gas pressure to 100 Pa to perform plasma reaction for 40 minutes to obtain a precursor.

[0169] (4) The precursor was heat-treated in an argon atmosphere at a temperature of 500° C. for 10 hours to obtain a negative electrode material.

[0170] The negative electrode material prepared in this embodiment includes a silicon-based active material and a carbon material. The silicon-based active material contains SiO, and the carbon material includes natural graphite.

[0171] Other parameters of the negative electrode materials are detailed in Table 1.

[0172] Example 7

[0173] (1) Weigh 30g SiO(D 50 =6μm), 970g artificial graphite (D 50 =15 μm) were preliminarily mixed and then placed in a jet mill for collision, crushing and mixing to obtain a composite.

[0174] (2) Place the composite in an airflow classifier for particle size adjustment, and control the composite particle size concentration P0 = 1.34 ± 0.05, P0 = (D' 80 +D' 50 ) / (D' 50+D' 20 ).

[0175] (3) Add the complex into the plasma equipment and evacuate it; introduce argon gas and control the gas pressure to 100 Pa, and use argon gas to perform surface modification treatment on the complex for 20 minutes at a reaction temperature of 180°C; then introduce propyleneamine and control the gas pressure to 100 Pa for plasma reaction for 25 minutes to obtain a precursor.

[0176] (4) The precursor was heat-treated in an argon atmosphere at a temperature of 500° C. for 10 hours to obtain a negative electrode material.

[0177] The negative electrode material prepared in this embodiment includes a silicon-based active material and a carbon material. The silicon-based active material contains SiO, and the carbon material includes natural graphite.

[0178] Other parameters of the negative electrode materials are detailed in Table 1.

[0179] Example 8

[0180] (1) Weigh 100g SiO(D 50 =6μm), 900g artificial graphite (D 50 =15 μm) were preliminarily mixed and then placed in a jet mill for collision, crushing and mixing to obtain a composite.

[0181] (2) Place the composite in an airflow classifier for particle size adjustment, and control the composite particle size concentration P0 = 1.45 ± 0.05, P0 = (D' 80 +D' 50 ) / (D' 50 +D' 20 ).

[0182] (3) Add the complex into the plasma equipment and evacuate it; introduce argon gas and control the gas pressure to 100 Pa, and use argon gas to perform surface modification treatment on the complex for 20 minutes at a reaction temperature of 180°C; then introduce propyleneamine and control the gas pressure to 100 Pa for plasma reaction for 25 minutes to obtain a precursor.

[0183] (4) The precursor was heat-treated 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 this embodiment includes a silicon-based active material and a carbon material. The silicon-based active material contains SiO, and the carbon material includes artificial graphite.

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

[0186] Example 9

[0187] (1) Weigh 300g SiO(D 50 =6μm), 700g artificial graphite (D 50 =15 μm) were preliminarily mixed and then placed in a jet mill for collision, crushing and mixing to obtain a composite.

[0188] (2) Place the composite in an air classifier for particle size adjustment, and control the composite particle size concentration P0 = 1.66 ± 0.05, P0 = (D' 80 +D' 50 ) / (D' 50 +D' 20 ).

[0189] (3) Add the complex into the plasma equipment and evacuate it; introduce argon gas and control the gas pressure to 100 Pa, and use argon gas to perform surface modification treatment on the complex for 20 minutes at a reaction temperature of 180°C; then introduce propyleneamine and control the gas pressure to 100 Pa for plasma reaction for 25 minutes to obtain a precursor.

[0190] (4) The precursor was heat-treated in an argon atmosphere at a temperature of 500° C. for 10 hours to obtain a negative electrode material.

[0191] The negative electrode material prepared in this embodiment includes a silicon-based active material and a carbon material. The silicon-based active material contains SiO, and the carbon material includes artificial graphite.

[0192] Other parameters of the negative electrode materials are detailed in Table 1.

[0193] Example 10

[0194] The difference from Example 1 is that:

[0195] (3) Add the complex into the plasma equipment and evacuate it; introduce argon gas and control the gas pressure to 100 Pa, and use argon gas to perform surface modification treatment on the complex for 30 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.

[0196] The negative electrode material prepared in this embodiment includes a silicon-based active material and a carbon material. The silicon-based active material contains SiO, and the carbon material includes artificial graphite.

[0197] Other parameters of the negative electrode materials are detailed in Table 1.

[0198] Example 11

[0199] The difference from Example 2 is that:

[0200] (3) Add the complex into the plasma equipment and evacuate it; introduce argon gas and control the gas pressure to 100 Pa, and use argon gas to perform surface modification treatment on the complex for 30 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.

[0201] The negative electrode material prepared in this embodiment includes a silicon-based active material and a carbon material. The silicon-based active material contains SiO, and the carbon material includes artificial graphite.

[0202] Other parameters of the negative electrode materials are detailed in Table 1.

[0203] Example 12

[0204] The difference from Example 1 is that:

[0205] (1) Weigh 30g Si(D 50 =6μm), 970g artificial graphite (D 50 =15 μm) were preliminarily mixed and then placed in a jet mill for collision, crushing and mixing to obtain a composite.

[0206] The negative electrode material prepared in this embodiment includes a silicon-based active substance and a carbon material. The silicon-based active substance contains Si, and the carbon material includes artificial graphite.

[0207] Other parameters of the negative electrode materials are detailed in Table 1.

[0208] Comparative Example 1

[0209] 100 g of carbon-coated SiO and 900 g of artificial graphite were stirred and mixed to obtain a mixture; the mixture was placed in an air flow classifier for particle size adjustment, and the particle size distribution concentration of the mixture was controlled to be P0=1.45±0.05, thereby obtaining a negative electrode material.

[0210] Other parameters of the negative electrode materials are detailed in Table 1.

[0211] Comparative Example 2

[0212] The difference from Example 8 is that:

[0213] (3) The composite was added into a plasma device and vacuumed; argon gas was introduced and the pressure was controlled at 100 Pa, and the composite was surface modified with argon gas for 40 minutes at a reaction temperature of 180°C; then propyleneamine was introduced and the pressure was controlled at 100 Pa for plasma reaction for 25 minutes to obtain a precursor.

[0214] The negative electrode material prepared in this embodiment includes a silicon-based active material and a carbon material. The silicon-based active material contains SiO, and the carbon material includes artificial graphite.

[0215] Other parameters of the negative electrode materials are detailed in Table 1.

[0216] Comparative Example 3

[0217] The difference from Example 2 is that:

[0218] (3) Add the complex into the plasma equipment and evacuate it; introduce argon gas and control the gas pressure to 100 Pa, and use argon gas to perform surface modification treatment on the complex for 20 minutes at a reaction temperature of 180°C; then introduce propyleneamine and control the gas pressure to 100 Pa for plasma reaction for 70 minutes to obtain a precursor.

[0219] The negative electrode material prepared in this embodiment includes a silicon-based active material and a carbon material. The silicon-based active material contains SiO, and the carbon material includes artificial graphite.

[0220] Other parameters of the negative electrode materials are detailed in Table 1.

[0221] Comparative Example 4

[0222] The difference from Example 2 is that:

[0223] (1) Weigh 500gSiO(D 50 =6μm), 500g artificial graphite (D 50 =15 μm) to obtain a mixture, and the mixture is placed in a jet mill for collision, crushing, and mixing to obtain an active material.

[0224] (2) The active material is placed in an air flow classifier for particle size adjustment, and the particle size distribution concentration of the active material is controlled to be P0 = 2.03 ± 0.05.

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

[0226] Comparative Example 5

[0227] The difference from Example 2 is that:

[0228] (3) The complex was added into a plasma device and vacuumed; propyleneamine was introduced and the gas pressure was controlled at 100 Pa to carry out plasma reaction for 40 minutes to obtain a precursor.

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

[0230] Comparative Example 6

[0231] The difference from Example 2 is that:

[0232] (3) Add the composite into the plasma equipment and evacuate it; introduce argon gas and control the gas pressure to 100 Pa, use argon gas to perform surface modification treatment on the composite for 20 minutes, and the reaction temperature is 180°C to obtain a precursor.

[0233] Other parameters of the negative electrode materials are detailed in Table 1.

[0234] Test Method

[0235] (1) Particle size of negative electrode material:

[0236] 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. The particle size distribution range of the negative electrode material is tested using the Malvern laser particle size analyzer (Mastersizer 3000). The volume-based cumulative particle size distribution of the particle size distribution is measured using the laser diffraction method. 20 Indicates the particle size corresponding to when the cumulative particle size distribution percentage of the powder reaches 20%, D 50 Indicates the particle size corresponding to when the cumulative particle size distribution percentage reaches 50%, D 80 It indicates the particle size corresponding to when the cumulative particle size distribution percentage reaches 80%.

[0237] (2) Average particle size of silicon-based active material:

[0238] 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.

[0239] (3) Mass content of Si element:

[0240] 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%.

[0241] (4) Test method for specific surface area of ​​negative electrode material:

[0242] 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.

[0243] (5) Test method for the tap density of negative electrode materials:

[0244] Refer to GB / T 5162-2006 / ISO 3953:1993 "Metal powders - Determination of tap density" and use a Quantachrome tap density analyzer (Quanttra DAT-4-220) from Anton Paar (Shanghai) Trading Co., Ltd. for testing. The tap density T is the value after 3000 vibrations and is expressed in g / cm 3 .

[0245] (6) pH value test of negative electrode material:

[0246] Refer to Appendix C "Determination of pH Value" of GB / T 24533-2019 "Graphite-based Anode Materials for Lithium-ion Batteries" and use a pH meter (Mettler-Toledo FE20) for measurement.

[0247] (7) Test method for oil absorption value of negative electrode material:

[0248] 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 characteristics reaches 70% of the maximum torque, expressed in mL / 100 g.

[0249] (8) Test method for the mass content of water in negative electrode materials:

[0250] 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.

[0251] (9) Electrochemical performance test

[0252] The negative electrode materials prepared in Examples 1-12 and Comparative Examples 1-3 were assembled into button-type batteries. After uniform mixing at a mass ratio of 92:2:2:2:2, the negative electrode material: conductive agent (SuTer T): sodium carboxymethyl cellulose (CMC): styrene-butadiene rubber (SBR) was applied to a copper foil current collector and dried to obtain negative electrode sheets. The dried negative electrode sheets were roller-pressed at pressures of 3 MPa, 6 MPa, and 9 MPa, respectively. After rolling, the sheets were allowed to rest for 48 hours. The thickness change before and after the rest period was measured, which was the physical rebound of the sheet (sheet rebound rate). The negative electrode sheet was placed under a roller pressing pressure of 3MPa for roller pressing treatment. After standing still, the negative electrode sheet was subjected to button battery testing. The battery assembly was carried out in an argon glove box. The metal lithium sheet was used as the negative electrode, the electrolyte was 1mol / L lithium hexafluorophosphate LiPF6+ethylene carbonate (EC)+methyl ethyl carbonate (EMC), and the separator was a polyethylene / propylene composite microporous membrane. The electrochemical performance was carried out on a battery testing instrument, and the charge and discharge voltage was 0.01~1.5V.

[0253] The battery cycle life is the number of charge and discharge cycles when the capacity retention rate decays to 80%.

[0254] First coulombic efficiency = first cycle discharge capacity / first cycle charge capacity.

[0255] The test results are detailed in Table 2 and Table 3.

[0256] Table 1 Negative electrode material performance test results

[0257] Table 2 Negative electrode rebound test results under different rolling pressures

[0258] Table 3 Electrochemical performance test results of negative electrode materials

[0259] According to the test data in Tables 1 to 3, controlling the balance between the oil absorption value, specific surface area and particle size concentration of the negative electrode material can control the physical rebound ability T of the negative electrode material within the range of 0.2 to 1.2, and can make the silicon-based active material and the carbon material particles tightly combined, which is beneficial to inhibiting the volume expansion of the silicon-based active material, so that the volume of the manufactured electrode is not easy to rebound after compaction, and a higher compaction density can be obtained, so that the negative electrode has both good cycle performance and excellent rate performance.

[0260] Table 2 shows the results of the electrode rebound test of the negative electrode sheet made of the negative electrode material prepared in the present application under different rolling pressures. As shown in Table 2, the electrode sheet rebound rate of the negative electrode sheet made of the negative electrode material prepared in the embodiment of the present application under rolling pressures of 3MPa, 6MPa and 9MPa is 2% to 10%, which can ensure good contact and close bonding between the silicon-based active material and the carbon material. At the same time, it can also ensure that the negative electrode material layer on the negative electrode sheet has an appropriate porosity, which is conducive to the electrolyte infiltration of the negative electrode material layer and improves the lithium ion transmission efficiency, thereby making the electrode sheet have both good cycle performance and excellent rate performance. However, the applicant found that as the rolling pressure increases, the electrode sheet rebound rate of the negative electrode sheet after rolling also increases. Therefore, when the rolling pressure is 3MPa, the electrode sheet rebound rate of the negative electrode sheet after rolling treatment can be effectively reduced, reducing the problem of loose bonding between the silicon-based active material and the carbon material caused by excessively high electrode sheet rebound rate, and further reducing the volume expansion and particle pulverization effect of the negative electrode sheet during the charge and discharge cycle.

[0261] The negative electrode material prepared in Comparative Example 1, as shown in Figures 2 and 3, is prepared by adjusting the particle size of the silicon-based active material SiO and graphite by simple stirring and mixing. The oil absorption value of the prepared negative electrode material is too high, and the relationship between the oil absorption value, specific surface area and particle size concentration of the negative electrode material is unbalanced. The physical rebound capacity of the negative electrode material is greater than 1.2. The negative electrode plate made of this negative electrode material undergoes severe physical rebound after rolling, which reduces the binding ability between the silicon-based active material and the carbon material particles. The silicon-based active material undergoes severe volume expansion during the cycle, resulting in pulverization and breakage of the negative electrode material, rapid cycle attenuation of the battery, and a significant reduction in the cycle life of the plate.

[0262] For the negative electrode material prepared in Comparative Example 2, the surface modification time of the composite in the non-polymerizing gas is too long during the preparation process, which causes a certain degree of damage to the surface of the composite, resulting in a higher specific surface area of ​​the negative electrode material, and an imbalance in the relationship between the oil absorption value, specific surface area and particle size concentration in the negative electrode material, so that the electrode sheet rebound ability of the negative electrode material is greater than 1.2. The negative electrode sheet made of the negative electrode material undergoes severe physical rebound after rolling, which loosens the bonding between the silicon-based active substance and the carbon material particles. The silicon-based active substance has a drastic volume expansion effect during the cycle, resulting in pulverization and breakage of the negative electrode material during the cycle, a decrease in the cycle performance of the battery, and a significant reduction in the cycle life of the electrode sheet.

[0263] In the negative electrode material prepared in Comparative Example 3, the time for the composite to undergo plasma reaction in the polymerizing gas is too long during the preparation process, and the polymer modification layer deposited on the surface of the composite is relatively thick. After the composite is heat-treated, the oil absorption value and specific surface area of ​​the negative electrode material are low, so that the physical rebound ability T of the negative electrode material is less than 0.2. Therefore, the physical rebound of the negative electrode pole piece made of this negative electrode material after rolling is extremely small, and there is a lack of suitable pores between the silicon-based active substance and the carbon material particles in the pole piece, which is not conducive to the infiltration and transmission of the electrolyte, resulting in the inability to fully utilize the lithium storage capacity of the negative electrode material, reducing the cycle performance, and at the same time deteriorating the rate performance of the negative electrode material.

[0264] In the negative electrode material prepared in Comparative Example 4, the content of silicon-based active material SiO2 used in the preparation process is relatively high, the mass content of silicon element in the negative electrode material is significantly increased, and the specific capacity of the negative electrode material is also significantly increased. However, due to the excessive silicon content, the negative electrode material has obvious volume expansion during the cycle process, resulting in a decrease in the cycle performance and rate performance of the negative electrode material, and a significant decrease in the cycle life of the electrode piece.

[0265] In the negative electrode material prepared in Comparative Example 5, the composite was not surface-modified in a non-polymerizing gas during the preparation process. During the plasma reaction, it was difficult for the polymer gas to form a tightly bound modification layer on the surface of the composite particles, and the surface defects of the negative electrode material were difficult to modify. The negative electrode material had many surface defects and a high oil absorption value, which made the physical rebound ability T of the negative electrode material too large. The negative electrode sheet made of this negative electrode material experienced severe physical rebound after rolling, and the binding force between the silicon-based active substance and the carbon material particles decreased. The silicon-based active substance experienced severe volume expansion during the cycle, the cycle performance of the negative electrode sheet deteriorated, and the cycle life was greatly reduced.

[0266] In the negative electrode material prepared in Comparative Example 6, the composite was not plasma-treated in a polymerizing gas during the preparation process, and the surface defects of the negative electrode material were not modified. The negative electrode material had many surface defects, and its oil absorption value and specific surface area were high, which made the physical rebound ability of the negative electrode material high. The negative electrode sheet made of this negative electrode material experienced severe physical rebound after rolling, and the bonding ability between the silicon-based active substance and the carbon material was poor. The silicon-based active substance underwent severe volume expansion during the cycle, resulting in pulverization and breakage of the negative electrode material during the cycle, severe deterioration of the cycle performance of the negative electrode sheet, and a significant reduction in the cycle life.

[0267] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

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, the particle size concentration of the negative electrode material is P1, P1 = (D 80 +D 50 ) / (D 50 +D 20 ), the physical rebound capacity of the negative electrode material is T, T = 0.01*O*S / P1, 0.20<T<1.

20.

2. The negative electrode material according to claim 1, characterized in that The negative electrode material includes at least one of the following features (1) to (2): (1) The silicon-based active material includes at least one of elemental silicon and silicon oxide; (2) The silicon-based active material further includes a metal M element, where M is selected from at least one of Mg, Li, Fe, Al, Mn and Cu.

3. The negative electrode material according to claim 2, characterized in that The negative electrode material includes at least one of the following features (1) to (2): (1) The silicon-based active material further includes a metal M element, M is selected from at least one of Mg, Li, Fe, Al, Mn and Cu, and the metal M element exists in at least one form of a simple substance, an oxide or a silicate; (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 negative electrode material includes at least one of the following features (1) to (2): (1) The average particle size of the silicon-based active material is 1 μm to 10 μm; (2) The carbon material includes at least one of graphite, graphene, amorphous carbon, carbon nanotubes and carbon fibers.

5. 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 30.0<0<57.

0.

6. The negative electrode material according to claim 1, characterized in that The specific surface area of ​​the negative electrode material is S cm 2 / g, 0.7<S<3.

50.

7. The negative electrode material according to claim 1, characterized in that The negative electrode material includes at least one of the following features (1) to (4): (1) The pH value of the negative electrode material is 6 to 12; (2) The tap density of the negative electrode material is 0.90 g / cm 3 ~1.25g / cm 3 ; (3) The mass content of water in the negative electrode material is ≤0.5wt%; (4) The mass content of silicon in the negative electrode material is 0.5wt% to 25wt%.

8. The negative electrode material according to claim 1, characterized in that The particle size of the negative electrode material satisfies: 0.1 μm ≤ D 20 ≤12μm, 0.2μm≤D 50 ≤18μm, 0.3μm≤D 80 ≤25μm.

9. The negative electrode material according to any one of claims 1 to 8, characterized in that 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.

10. The negative electrode material according to claim 1, characterized in that The physical rebound capacity of the negative electrode material is T, 0.2<T<0.

7.

11. The negative electrode material according to claim 1, characterized in that The physical rebound capacity of the negative electrode material is T, 0.70≤T<1.

20.

12. The negative electrode material according to claim 1, characterized in that The particle size concentration of the negative electrode material is P1, 1.2<P1<2.

0.

13. A method for preparing a negative electrode material, characterized in that: The following steps are involved: Provided is a composite containing a silicon-based active substance and a carbon material, wherein the particle size concentration of the composite is P0, 1.2 < P0 < 2.0, P0 = (D' 80 +D' 50 ) / (D' 50 +D' 20 ); In a vacuum environment, 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 heat treated to obtain a negative electrode material having an oil absorption value of 0 mL / 100 g and a specific surface area of ​​5 m 2 / g, the particle size concentration of the negative electrode material is P1, P1 = (D 80 +D 50 ) / (D 50 +D 20 ), the physical rebound capacity of the negative electrode material is T, T = 0.01*O*S / P1, 0.20<T<1.

20.

14. A negative electrode plate, characterized in that: The negative electrode plate comprises the negative electrode material according to any one of claims 1 to 12 or the negative electrode material prepared by the method for preparing the negative electrode material according to claim 13; under a rolling pressure of 3 MPa, the plate rebound rate of the negative electrode plate is 2% to 10%.

15. A lithium ion battery, characterized in that: The lithium-ion battery comprises the negative electrode sheet according to claim 14.

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