Negative electrode material, negative electrode plate and lithium ion battery

Abstract

The invention relates to a negative electrode material, a negative electrode plate and a lithium ion 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 OmL / 100g, the specific surface area is S m < 2 > / g, the particle size concentration ratio of the negative electrode material is P1, P1 = (D80 + D50) / (D50 + D20), the physical rebound capacity of the negative electrode material is T, T = 0.01 OS / P1, and T is greater than 0.20 and less than 1.20. The negative electrode material disclosed by the invention has relatively low physical rebound capability, and the volume of a pole piece prepared from the negative electrode material is not easy to rebound after compaction, so that relatively high compaction density can be obtained, and excellent cycle performance is exerted.

Description

[0001] This application is a divisional application of the original application with the application number 202311435596.3 and the original filing date of October 31, 2023, and the entire contents of the original application are incorporated herein by reference. TECHNICAL FIELD

[0002] The present application relates to the technical field of negative electrode materials, in particular to a negative electrode material, a negative electrode sheet and a lithium ion battery. BACKGROUND

[0003] Lithium ion batteries have the advantages of high energy density, high cycle life, small environmental pollution and no memory effect, and are widely used in electric vehicles and consumer electronics. The negative electrode material is an important component of the lithium ion battery, which directly affects the key indicators such as the energy density, cycle life and safety performance of the battery. At present, the commercialized lithium ion battery mainly uses graphite-based negative electrode material, but its theoretical specific capacity is only 372 mAh / g, which is difficult to meet the demand of high energy density lithium ion battery. Silicon-based negative electrode material as a negative electrode material of lithium ion battery has very high specific capacity and is one of the candidate materials for the next generation of high energy density lithium ion battery. However, the silicon negative electrode will produce a huge volume change during the charge and discharge cycle, which will lead to the deterioration of the material / plate structure and the instability of the solid electrolyte interface film (SEI), thus causing the sharp decline of its electrochemical performance.

[0004] At present, silicon-based materials are often compounded with carbon materials, but the existing compounding method is often a simple mixing, which lacks reasonable matching of silicon-based materials and carbon materials, and has been unable to meet the market demand for obtaining negative electrode materials with high compaction density and good cycle performance. Therefore, it is necessary to explore the mechanism of the synergistic effect of various factors and develop a composite negative electrode material that meets the market demand. SUMMARY

[0005] The purpose of the present application is to provide a negative electrode material, a negative electrode sheet and a lithium ion battery. The negative electrode material has a low physical rebound ability, and the volume of the sheet made of the negative electrode material is not easy to rebound after compaction, so that a higher compaction density can be obtained, and excellent cycle performance can be achieved.

[0006] In a first aspect, the present application provides a negative electrode material, which comprises a silicon-based active material and a carbon material, the oil absorption value of the negative electrode material is O mL / 100g, the specific surface area of the negative electrode material is S m 2 / g, and the particle size concentration of the negative electrode material is P1, P1=(D 80 +D 50 ) / (D 50 +D 20), the physical rebound capability of the negative electrode material is T, T = 0.01*O*S / P1, 0.20

[0007] In some embodiments, the physical rebound capability of the negative electrode material is T, 0.70≤T<1.20.

[0008] In some embodiments, the physical rebound capability of the negative electrode material is T, 0.2

[0009] In some embodiments, the physical rebound capability of the negative electrode material is T, T is 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, 1.2 or other values within the above ranges.

[0010] In some embodiments, the negative electrode material further comprises a carbon layer, the carbon layer is located on at least part of the surface of the silicon-based active substance and / or the carbon material.

[0011] In some embodiments, the thickness of the carbon layer is 1nm-1000nm.

[0012] In some embodiments, the thickness of the carbon layer is 50nm-800nm.

[0013] In some embodiments, the thickness of the carbon layer is 100nm-500nm.

[0014] In some embodiments, at least part of the carbon material is located on the surface of the silicon-based active substance to form the carbon layer.

[0015] In some embodiments, the carbon material is located on the surface of the silicon-based active substance to form the carbon layer.

[0016] In some embodiments, the silicon-based active substance is distributed within the carbon material.

[0017] In some embodiments, the silicon-based active substance comprises at least one of elemental silicon and silicon oxide.

[0018] In some embodiments, the silicon-based active substance further comprises a doping metal M, M is selected from at least one of Mg, Li, Fe, Al, Mn and Cu.

[0019] In some embodiments, the silicon-based active substance further comprises a doping metal M, M is selected from at least one of Mg, Li, Fe, Al, Mn and Cu, M is dispersed in the silicon-based active substance in at least one of elemental, oxide or silicate form.

[0020] In some embodiments, the silicon-based active material comprises silicon oxide, and the general formula of the silicon oxide is SiOx, 0 < x < 2. x

[0021] In some embodiments, the silicon-based active material has a median particle size of 1 μm to 10 μm.

[0022] In some embodiments, the silicon-based active material comprises elemental silicon, and the elemental silicon comprises amorphous silicon.

[0023] In some embodiments, the carbon material comprises at least one of graphite, graphene, amorphous carbon, carbon nanotube, and carbon fiber.

[0024] In some embodiments, the negative electrode material has an oil absorption value of 0 mL / 100 g, 0 < 57.0.

[0025] In some embodiments, the negative electrode material has a specific surface area of S cm 2 / g, S < 3.50.

[0026] In some embodiments, the negative electrode material has a pH value of 6 to 12.

[0027] In some embodiments, the negative electrode material has a tap density of > 0.90 g / cm 3 .

[0028] In some embodiments, the negative electrode material has a mass content of water of ≤ 0.5 wt%.

[0029] In some embodiments, the negative electrode material has a mass content of silicon element of 0.5 wt% to 25 wt%.

[0030] In some embodiments, the negative electrode material has a particle size satisfying: 0.1 μm ≤ D 20 ≤ 12 μm, 0.2 μm ≤ D 50 ≤ 18 μm, and 0.3 μm ≤ D 80 ≤ 25 μm.

[0031] In some embodiments, in the negative electrode material, the silicon-based active material and the carbon material are dispersed in the form of particles.

[0032] In some embodiments, the negative electrode material has a particle size concentration degree of P1, 1.2 < P1 < 2.0.

[0033] In a second aspect, the embodiments of the present application further provide a negative electrode tab, which comprises the negative electrode material of the first aspect, and the negative electrode tab has a tab rebound rate of 2% to 10% under a rolling pressure of 3 MPa.

[0034] ​Thirdly, embodiments of this application also propose a lithium-ion battery, wherein the lithium-ion battery includes the negative electrode sheet described in the second aspect.

[0035] Compared with the prior art, the technical solution of this application has at least the following beneficial effects: The negative electrode material provided in this application comprises a silicon-based active material and a carbon material. The negative electrode material has an oil absorption value of 0 mL / 100g and a specific surface area of ​​5 m². 2 / g, particle size concentration is P1, P1=(D 80 +D 50 ) / (D 50 +D 20 The physical rebound capability of the negative electrode material is T, where T = 0.01. O S / P1, 0.20 < T < 1.20. The physical rebound capability T of the negative electrode material can be used to measure the ability of the electrode sheet made of the negative electrode material to physically rebound after rolling. In this application, controlling the balance between the oil absorption value, specific surface area and particle size concentration of the negative electrode material can make the negative electrode material have a low physical rebound capability, which can make the silicon-based active material and carbon material particles tightly bonded, which is beneficial to suppress the volume expansion of the silicon-based active material. This makes the volume of the electrode sheet less likely to rebound after compaction, thereby obtaining a high compaction density, so that the negative electrode sheet has both good cycle performance and rate performance. Attached Figure Description

[0036] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0037] Figure 1 A schematic flowchart illustrating the preparation method of the negative electrode material provided in the embodiments of this application; Figure 2 Comparison of cycle curves of the negative electrode materials prepared in Examples 2, 8 and 8 of this application; Figure 3 This is a comparison chart of the rate performance of the negative electrode materials prepared in Examples 2, 8 and Comparative Example 8 of this application. Detailed Implementation

[0038] To better understand the technical solution of the present invention, the embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0039] It should be understood that the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0040] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a,” “the,” and “the” as used in the embodiments of this invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0041] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0042] In a first aspect, this application provides a negative electrode material comprising a silicon-based active material and a carbon material, wherein the oil absorption value of the negative electrode material is 0 mL / 100g and the specific surface area is 5 m². 2 / g, the particle size distribution of the negative electrode material is P1, P1=(D 80 +D 50 ) / (D 50 +D 20 The physical rebound capability of the negative electrode material is T, where T = 0.01. O S / P1, 0.20 < T < 1.20.

[0043] The negative electrode material provided in this application comprises silicon-based active material and carbon material. The oil absorption value of the negative electrode material is 0 mL / 100g, and the specific surface area is 5 m². 2 / g, particle size concentration is P1, P1=(D 80 +D 50 ) / (D 50 +D 20 The physical rebound capability of the negative electrode material is T, where T = 0.01. O S / P1, 0.20 < T < 1.20. The physical rebound capability T of the negative electrode material can be used to measure the ability of the electrode sheet made of the negative electrode material to physically rebound after rolling. In this application, controlling the balance between the oil absorption value, specific surface area and particle size concentration of the negative electrode material can make the negative electrode material have a low physical rebound capability, which can make the silicon-based active material and carbon material particles tightly bonded, which is beneficial to suppress the volume expansion of the silicon-based active material. This makes the volume of the electrode sheet less likely to rebound after compaction, thereby obtaining a high compaction density, so that the negative electrode sheet has both good cycle performance and rate performance.

[0044] In some embodiments, the physical rebound capability of the negative electrode material is T, where 0.20 < T < 1.20. Specifically, it can be 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., and other values ​​within the above range are also possible and are not limited here. Understandably, after the negative electrode material is prepared, coated, and dried, it needs to be rolled under a certain pressure to increase the compaction density, ultimately obtaining a usable negative electrode sheet. Electrodes made from different negative electrodes will experience physical rebound after being rolled and left for a period of time, causing changes in the contact area of ​​the active material and the electrode porosity, resulting in different electrochemical performances. The physical rebound capability T of the negative electrode material can be used to measure the ability of the negative electrode material to undergo physical rebound after rolling. A smaller T value results in less rebound of the electrode sheet made of negative electrode material after rolling, leading to a tighter bond between the silicon-based active material and carbon material particles in the electrode, which is beneficial for suppressing the volume expansion of the negative electrode material during charging and discharging. When T ≥ 1.20, the electrode sheet made of negative electrode material experiences severe physical rebound after rolling, resulting in loose bonding between the silicon-based active material and carbon material particles and a significantly reduced contact area, which is detrimental to suppressing the volume expansion of the negative electrode material and the formation of good conductive channels. When T ≤ 0.2, the physical rebound of the electrode sheet made of negative electrode material after rolling is minimal, and there is a lack of suitable porosity between the silicon-based active material and carbon material particles in the electrode, which is not conducive to the wetting and transport of electrolyte, resulting in the lithium storage capacity of the negative electrode material not being fully utilized, reducing cycle performance, and severely degrading rate performance.

[0045] In some embodiments, the physical rebound capability of the negative electrode material is T, where 0.70 ≤ T < 1.20. When 0.70 ≤ T < 1.20, the electrode 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 appropriate electrode porosity, thus enabling the electrode to have both good cycle performance and rate performance.

[0046] In some implementations, the physical rebound capability of the negative electrode material is T, where 0.2 < T < 0.7. When 0.2 < T < 0.7, the electrode sheet made of the negative electrode material experiences a small physical rebound after rolling, resulting in a tight bond between the silicon-based active material and the carbon material particles. This significantly suppresses the volume expansion of the negative electrode material, thus providing superior cycle performance.

[0047] In some embodiments, the silicon-based active material includes at least one of elemental silicon and silicon oxide. Elemental silicon may be amorphous silicon and / or crystalline silicon.

[0048] In some embodiments, the silicon-based active material further includes a doped metal M, wherein M is selected from at least one of Mg, Li, Fe, Al, Mn and Cu.

[0049] In some embodiments, the silicon-based active material further includes a doped metal M, which 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 of element, oxide or silicate.

[0050] In some embodiments, the silicon-based active material includes silicon oxide (SiO2). x , 0 < x < 2. Specifically, SiO x Specifically, it could 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. are not specified here.

[0051] In some embodiments, the median 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, other values ​​within the above range are also possible, and are not limited here.

[0052] In some embodiments, silicon-based active materials and carbon materials are dispersed in the form of particles in the negative electrode material.

[0053] 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. Specifically, the silicon-based active material particles may be embedded within the carbon material, using the carbon material as a matrix.

[0054] In some embodiments, carbon material forms a carbon layer on the surface of the silicon-based active material.

[0055] In some embodiments, at least a portion of the carbon material forms a carbon layer on the surface of the silicon-based active material.

[0056] In one embodiment, the negative electrode material further includes a carbon layer located on at least a portion of the surface of the silicon-based active material and / or the carbon material. It is understood that the carbon material of the carbon layer in this application may differ from the carbon material in the core.

[0057] In some embodiments, the thickness of the carbon layer is 1 nm to 1000 nm, specifically 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., and is not limited herein. If the carbon layer is too thick, the carbon content is too high, which is not conducive to obtaining a negative electrode material with high specific capacity; if the carbon layer is too thin, it is not conducive to increasing the conductivity of the negative electrode material and has weak 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.

[0058] In some embodiments, the carbon material includes at least one selected from graphite, graphene, amorphous carbon, carbon nanotubes, and carbon fibers. The amorphous carbon can be soft carbon and / or hard carbon, and the graphite can be artificial graphite and / or natural graphite. Understandably, the carbon material can improve the conductivity of silicon-based active materials. Graphite is a material with high conductivity, low volume expansion, high initial efficiency, and stable cycle performance; preferably, the carbon material is graphite.

[0059] In some embodiments, the oil absorption value of the negative electrode material is 0 mL / 100g, where 0 < 57.0. Specifically, 0 can be 20.0, 25.0, 30.0, 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 and reflects the ability of the particle clusters to absorb binder during slurry preparation. It is one of the material properties used to measure the physical rebound ability of the electrode sheet. When the oil absorption value of the negative electrode material is 0 < 57.0 mL / 100g, the particle clusters of the negative electrode material can absorb an appropriate amount of binder during slurry preparation, which is beneficial for enhancing the bonding between the silicon-based active material and the carbon material. The resulting electrode sheet exhibits less physical rebound after rolling, making it easier to obtain an electrode sheet with high compaction density. When the oil absorption value O of the negative electrode material is ≥57.0mL / 100g, the binder content absorbed by the negative electrode material particle clusters during the slurry preparation process is too high. This is not only not conducive to the effective contact and filling of particles, but also the excess binder in the particle clusters has great elasticity, which makes the electrode sheet made to easily undergo severe physical rebound after rolling, ultimately resulting in poor cycle performance.

[0060] In some embodiments, the specific surface area of ​​the negative electrode material is S cm⁻¹ 2 / g, S < 3.50, specifically 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, 0.87, or 0.64, etc., and of course, other values ​​within the above range are also possible, without limitation. Understandably, specific surface area and surface energy are closely related and positively correlated. Anode materials with higher specific surface area have larger surface energy, and their interparticle interaction forces are also larger, easily hindering particle sliding and hindering particle close packing, which is also one of the material properties for measuring the physical rebound ability of the electrode. When S < 3.50cm² of silicon-based composite materials... 2 / g, possessing suitable surface energy, is conducive to the close packing of particles, thus making the resulting electrode less prone to rebound. When the S of the negative electrode material ≥ 3.50cm 2 / g, which has a large surface energy, makes it difficult for particles to form a dense packing, resulting in a large physical rebound of the electrode sheet.

[0061] 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 of course, other values ​​within the above range are also possible, which are not limited here. Preferably, the pH value of the negative electrode material is 6.5 to 8.5.

[0062] In some embodiments, the tap density of the negative electrode material is >0.90 g / cm³. 3 The tap density of the negative electrode material can specifically be 0.91 g / cm³. 3 0.95 g / cm 3 0.99 g / cm 3 1.0 g / cm 3 1.05 g / cm 3 1.1 g / cm 3 1.13 g / cm 3 1.18 g / cm 3 1.2 g / cm 3 1.25 g / cm 3 1.3 g / cm 3 1.38 g / cm 3 Or 1.4 g / cm 3 etc. are not specified here.

[0063] In some embodiments, the water content 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., or other values ​​within the above range, which are not limited here.

[0064] In some embodiments, the Si content in the anode material is 0.5 wt% to 25 wt%, specifically 0.5 wt%, 0.6 wt%, 0.8 wt%, 1.0 wt%, 1.2 wt%, 1.5 wt%, 3 wt%, 5.6 wt%, 7.8 wt%, 8.9 wt%, 10 wt%, 11.5 wt%, 14.6 wt%, 16.5 wt%, 18.9 wt%, 20 wt%, or 25 wt%, etc., or other values ​​within the above range, which are not limited here. When the Si content is below 0.5 wt%, the specific capacity of the anode material is low and cannot meet the requirements of high-energy-density lithium-ion batteries. When the Si content is above 20 wt%, the volume expansion of the anode material is too large, and the cycle performance deteriorates severely.

[0065] In some implementations, 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 cumulative particle size distribution based on volume standard determined using laser diffraction is D. 20 This indicates the particle size at which the cumulative particle size distribution percentage reaches 20%. (D) 50 This indicates the particle size at which the cumulative particle size distribution percentage reaches 50%. (D) 80 This indicates the particle size corresponding to a cumulative particle size distribution percentage of 80%.

[0066] 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.

[0067] D 50 Specifically, the micrometer can be 0.2μm, 0.5μm, 1μm, 1.8μm, 2.5μm, 3μm, 5μm, 8μm, 10μm, 12μm, 15μm or 18μm, etc., and is not limited here.

[0068] D 80Specifically, the micrometer can be 0.3μm, 1.5μm, 3μm, 5μm, 8μm, 10μm, 12μm, 15μm, 18μm, 20μm, 23μm or 25μm, etc., and is not limited here.

[0069] In some embodiments, the particle size distribution of the negative electrode material is P1, where 1.2 < P1 < 2.0, and 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., and is not limited here. The particle size distribution P1 of the negative electrode material is one of the material properties that affects the physical rebound capability of the negative electrode sheet. Among them, D 50 ~D 80 The range represents most of the larger particles in the anode material; D 20 ~D 50 The range represents most of the smaller particles in the material; therefore, P1 = (D 80 +D 50 ) / (D 50 +D 20 The ratio of large to small particle size in the negative electrode material is P1. A value closer to 1 indicates a more concentrated particle size distribution. When the negative electrode material satisfies 1.2 < P1 < 2.0, the particle size and quantity of large and small particles are well-matched, which is conducive to sufficient particle dispersion. Small particles tend to be embedded in the gaps between large particles, forming a compact packing structure, thus helping to reduce physical rebound after electrode rolling. When P1 ≤ 1.2, the particle sizes of large and small particles are very similar, and there are large pores in the particle contact, which is not conducive to the formation of a compact packing structure. When P1 ≥ 2.0, the particle sizes and quantities of large and small particles differ significantly. A large number of small particles tend to agglomerate and are difficult to form a matching compact packing structure with the large particles, failing to improve the physical rebound of the electrode.

[0070] Secondly, this application provides a method for preparing a negative electrode material, such as... Figure 1 As shown, it includes the following steps: Step S100: Provide a composite containing silicon-based active material and carbon material, wherein the particle size distribution of the composite is P0, 1.2 < P0 < 2.0, P0 = (D' 80 +D' 50 ) / (D' 50 +D' 20 ); Step S200: In a vacuum environment, a non-polymerizable gas is introduced to modify the surface of the composite, and then a polymerizable gas is introduced to carry out a plasma reaction to obtain the precursor. Step S300: The precursor is heat-treated to obtain the negative electrode material. The oil absorption value of the negative electrode material is 0 mL / 100g, and the specific surface area is 5 m. 2 / g, the particle size distribution of the negative electrode material is P1, P1=(D 80 +D 50 ) / (D 50 +D 20 The physical rebound capability of the negative electrode material is T, where T = 0.01. O S / P1, 0.20 < T < 1.20.

[0071] The method for preparing the negative electrode material provided in this application firstly involves controlling the particle size distribution of the raw material, namely the composite containing silicon-based active material and carbon material, to effectively achieve a tight packing between the silicon-based active material and the carbon material. This results in a better match between the particle size and quantity of large and small particles in the material, which is beneficial for the full dispersion of particles and tends to form a tight packing structure in which small particles are embedded in the contact gaps between large particles. Next, after vacuuming, a non-polymerizable gas is introduced to perform surface modification treatment on the composite, followed by the introduction of a polymerizable gas to continue the plasma reaction, obtaining the precursor. The surface-modified composite particles have active groups on their surface, which react with polymerizable gas. During the plasma reaction process, the active groups on the surface of the composite particles can combine with polymeric gas molecules to form a tightly bound polymer modification layer on the particle surface. After carbonization, the polymer modification layer undergoes structural cleavage and reorganization, effectively modifying the surface defects of the material. The reduction of surface defects in the negative electrode material leads to a decrease in the oil absorption value and specific surface area of ​​the negative electrode material. This allows the physical rebound ability of the final negative electrode material to be controlled within the range of 0.20 to 1.20, making it less prone to volume rebound after compaction. This results in a higher compaction density, giving the negative electrode a combination of good cycle performance and excellent rate performance.

[0072] The following is a detailed introduction to this plan: Step S100: Provide a composite containing silicon-based active material and carbon material, wherein the particle size distribution of the composite is P0, 1.2 < P0 < 2.0, P0 = (D' 80 +D' 50 ) / (D' 50 +D' 20 ).

[0073] In some embodiments, the specific steps of providing the composite containing silicon-based active material and carbon material include: mixing the silicon-based active material and carbon material to obtain the composite.

[0074] In some embodiments, the mass ratio of silicon-based active material to 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, other values ​​within the above range are also possible, and no limitation is made here.

[0075] In some embodiments, the silicon-based active material includes at least one of elemental silicon and silicon oxide. Elemental silicon may be amorphous silicon and / or crystalline silicon.

[0076] In some embodiments, the silicon-based active material further includes a doped metal M, wherein M is selected from at least one of Mg, Li, Fe, Al, Mn and Cu.

[0077] In some embodiments, the silicon-based active material further includes a doped metal M, selected from at least one of Mg, Li, Fe, Al, Mn, and Cu, wherein M is dispersed in the silicon-based active material in the form of an element, an oxide, or a silicate. Preferably, M is a silicate (M... x Si y O z It is dispersed in silicon-based active materials in the form of ).

[0078] In some embodiments, the silicon-based active material includes silicon oxide (SiO2). x , 0 < x < 2. Specifically, SiO x Specifically, it could 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. are not specified here.

[0079] In some embodiments, the carbon material includes at least one selected from graphite, graphene, amorphous carbon, carbon nanotubes, and carbon fibers. The amorphous carbon can be soft carbon and / or hard carbon, and the graphite can be artificial graphite and / or natural graphite. Understandably, the carbon material can improve the conductivity of silicon-based active materials. Graphite is a material with high conductivity, low volume expansion, high initial efficiency, and stable cycle performance; preferably, the carbon material is graphite.

[0080] In some embodiments, the median particle size of the silicon-based active material is 1 μm to 10 μm, specifically it can be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm or 10 μm, etc., and is not limited here.

[0081] In some embodiments, the median particle size of the carbon material is 2 μm to 20 μm. The median particle size of the carbon material can specifically be 2 μm, 5 μm, 7 μm, 8 μm, 10 μm, 12 μm, 15 μm, 16 μm, 18 μm or 20 μm, etc., and is not limited here.

[0082] In some embodiments, the mixing method includes at least one of grinding mixing, airflow mixing, and mechanical mixing.

[0083] In some embodiments, the method further includes: adjusting the particle size of the complex to control the particle size concentration of the complex to be P0, where 1.2 < P0 < 2.0, and P0 = (D' 80 +D' 50 ) / (D' 50 +D' 20 Understandably, controlling the particle size concentration P0 of the composite within the aforementioned range allows for better matching of the particle size and quantity between large and small particles in the anode material. This promotes thorough particle dispersion and tends to form a tightly packed structure where small particles are embedded in the contact gaps between large particles. Specifically, the composite is placed in an air classifier, and the particle size of the composite is classified and adjusted by the air classifier, thereby controlling the particle size concentration P0 of the composite to meet the aforementioned range.

[0084] In step S200, a non-polymerizable gas is introduced into the composite under vacuum to perform surface modification treatment, and then a polymerizable gas is introduced to perform a plasma reaction to obtain the precursor.

[0085] In some embodiments, the surface finishing 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 temperatures are not limited to the listed values, and other unlisted values ​​within this range also apply.

[0086] In some embodiments, the reaction system is evacuated before surface modification treatment. The pressure range of surface modification treatment is 50 Pa to 150 Pa, specifically 50 Pa, 60 Pa, 70 Pa, 80 Pa, 90 Pa, 100 Pa, 120 Pa or 150 Pa, etc. Of course, other values ​​within the above range are also possible and are not limited here.

[0087] In some embodiments, the non-polymerizable gas includes at least one of argon, nitrogen, and hydrogen.

[0088] During the surface modification process, the non-polymerizable gas is blown onto 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 the non-polymerizable gas.

[0089] In some embodiments, a non-polymerizable gas is introduced to modify the surface of the composite for 10 to 30 minutes, followed by a plasma reaction with a polymerizable gas for 20 to 60 minutes to obtain a precursor. Understandably, preheating and surface cleaning of the composite before introducing the polymerizable gas allows the polymerizable gas to bind with the active groups (e.g., hydroxyl, carboxyl, amino, aldehyde, imino) on the surface of the composite particles, forming a tightly bonded polymer-modified layer on the surface of the composite particles.

[0090] It should be noted that surface modification of the composite under a non-polymerizing gas atmosphere can cause slight damage to the composite surface. Specifically, prolonged surface modification can increase the specific surface area of ​​the anode material, negatively impacting its physical rebound capability. Conversely, longer plasma reaction times under a polymerizing gas atmosphere result in a thicker polymer modification layer deposited on the composite surface, leading to lower specific surface area and oil absorption value of the anode material after subsequent heat treatment. Therefore, controlling the surface modification time under a non-polymerizing gas atmosphere and the plasma reaction time under a polymerizing gas atmosphere is beneficial for balancing the specific surface area, oil absorption value, and physical rebound capability of the anode material, thereby improving its cycle performance and rate performance.

[0091] In some embodiments, the plasma reaction 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 temperatures are not limited to the listed values, and other unlisted values ​​within this range also apply.

[0092] In some embodiments, the pressure range of the plasma reaction is 50 Pa to 150 Pa, specifically 50 Pa, 60 Pa, 70 Pa, 80 Pa, 90 Pa, 100 Pa, 120 Pa or 150 Pa, etc., and of course other values ​​within the above range are also possible, which are not limited here.

[0093] In some embodiments, the polymerizing gas includes at least one of styrene, cyclohexylamine, vinyl chloride, acrylamine, and methacrylate. Exemplarily, the polymer modification layer may be polystyrene, polyacrylamine, polymethacrylate, polyvinyl chloride, etc., and is not limited thereto.

[0094] Step S300: The precursor is heat-treated to obtain the negative electrode material, wherein the oil absorption value of the negative electrode material is 0 mL / 100g and the specific surface area is 5 m. 2 / g, the particle size distribution concentration of the negative electrode material is P1, P1=(D 80 +D 50 ) / (D 50 +D 20 The physical rebound capability of the negative electrode material is T, where T = 0.01. O S / P1, 0.20 < T < 1.20.

[0095] Understandably, during the heat treatment process, the polymer modification layer undergoes structural pyrolysis and reorganization after carbonization, effectively modifying the surface defects of the material. The reduction of surface defects in the negative electrode material leads to a decrease in the oil absorption value and specific surface area of ​​the negative electrode material, allowing the physical rebound capability of the final negative electrode material to be controlled within the range of 0.20~1.20. The negative electrode material has both good cycle performance and excellent rate performance.

[0096] In some embodiments, the heat treatment temperature is 500℃~700℃, specifically 500℃, 530℃, 550℃, 580℃, 600℃, 620℃, 650℃, 670℃, 680℃ or 700℃, etc., and of course other values ​​within the above range are also possible, which are not limited here.

[0097] In some implementations, the heat treatment time is 1h to 20h, specifically 1h, 1.5h, 3h, 5h, 8h, 10h, 12h, 15h, 18h or 20h, etc. Of course, other values ​​within the above range are also possible, and no limitation is made here.

[0098] In some implementations, the heat treatment is performed under a protective atmosphere.

[0099] In some embodiments, the heat treatment is carried out under a protective atmosphere, which includes at least one of nitrogen, helium, neon, and argon.

[0100] Thirdly, this application provides a negative electrode sheet comprising the aforementioned negative electrode material. Under a rolling pressure of 3 MPa, the electrode rebound rate of the negative electrode sheet is 2% to 10%. The specific electrode rebound rate can be 2%, 2.5%, 3%, 3.8%, 5.6%, 6.7%, 7.8%, 8.9%, 9.6%, or 10%, etc., and is not limited here. Understandably, when the electrode rebound rate of the negative electrode sheet is within the above range, the electrode sheet undergoes appropriate physical rebound after rolling, resulting in good contact between the silicon-based active material and the carbon material, while also possessing appropriate electrode porosity, thereby enabling the electrode sheet to possess both good cycle performance and rate performance.

[0101] Fourthly, this application provides a lithium-ion battery, the lithium-ion battery including the above-mentioned negative electrode sheet.

[0102] Example Example 1 (1) Weigh 30g of SiO (D 50 =6μm), 970g of artificial graphite (D 50 After initial mixing (15 μm), the mixture was placed in an air jet mill for collision, crushing, and mixing to obtain the composite.

[0103] (2) The composite was placed in an air classifier for particle size adjustment, and the particle size distribution of the composite was controlled to be P0 = 1.34 ± 0.05, P0 = (D' 80 +D' 50 ) / (D' 50 +D' 20 ).

[0104] (3) Add the composite into the plasma device and evacuate; introduce argon gas and control the pressure to 100 Pa, use argon gas to perform surface modification treatment on the composite for 20 min, and the reaction temperature is 180℃; then introduce acrylamine and control the pressure to 100 Pa to perform plasma reaction for 40 min to obtain the precursor.

[0105] (4) The precursor is heat-treated in an argon atmosphere at a temperature of 500°C for 10 hours to obtain the negative electrode material.

[0106] The negative electrode material prepared in this embodiment includes a silicon-based active material and a carbon material, wherein the silicon-based active material is SiO and the carbon material is artificial graphite.

[0107] Other parameters of the negative electrode material are detailed in Table 1.

[0108] Example 2 (1) Weigh 100g SiO (D 50 =6μm), 900g of artificial graphite (D 50 After initial mixing (15 μm), the mixture was placed in an air jet mill for collision, crushing, and mixing to obtain the composite.

[0109] (2) The composite was placed in an air classifier for particle size adjustment, and the particle size distribution of the composite was controlled to be P0 = 1.45 ± 0.05, P0 = (D' 80 +D' 50 ) / (D' 50 +D' 20 ).

[0110] (3) Add the composite into the plasma device and evacuate; introduce argon gas and control the pressure to 100 Pa, use argon gas to perform surface modification treatment on the composite for 20 min, and the reaction temperature is 180℃; then introduce acrylamine and control the pressure to 100 Pa to perform plasma reaction for 40 min to obtain the precursor.

[0111] (4) The precursor is heat-treated in an argon atmosphere at a temperature of 500°C for 10 hours to obtain the negative electrode material.

[0112] The negative electrode material prepared in this embodiment includes a silicon-based active material and a carbon material, wherein the silicon-based active material is SiO and the carbon material is artificial graphite.

[0113] Other parameters of the negative electrode material are detailed in Table 1.

[0114] Example 3 (1) Weigh 300g of SiO (D 50 =6μm), 700g artificial graphite (D 50 After initial mixing (15 μm), the mixture was placed in an air jet mill for collision, crushing, and mixing to obtain the composite.

[0115] (2) The composite was placed in an air classifier for particle size adjustment, and the particle size distribution of the composite was controlled to be P0 = 1.66 ± 0.05, P0 = (D' 80 +D' 50 ) / (D' 50 +D' 20 ).

[0116] (3) Add the composite into the plasma device and evacuate; introduce argon gas and control the pressure to 100 Pa, use argon gas to perform surface modification treatment on the composite for 20 min, and the reaction temperature is 180℃; then introduce acrylamine and control the pressure to 100 Pa to perform plasma reaction for 40 min to obtain the precursor.

[0117] (4) The precursor is heat-treated in an argon atmosphere at a temperature of 500°C for 10 hours to obtain the negative electrode material.

[0118] The negative electrode material prepared in this embodiment includes a silicon-based active material and a carbon material, wherein the silicon-based active material is SiO and the carbon material is artificial graphite.

[0119] Other parameters of the negative electrode material are detailed in Table 1.

[0120] Example 4 (1) Weigh 100g of Mg-doped SiO (D 50 =6μm), 900g of artificial graphite (D50 After initial mixing (15 μm), the mixture was placed in an air jet mill for collision, crushing, and mixing to obtain the composite.

[0121] (2) The composite was placed in an air classifier for particle size adjustment, and the particle size distribution of the composite was controlled to be P0 = 1.62 ± 0.05, P0 = (D' 80 +D' 50 ) / (D' 50 +D' 20 ).

[0122] (3) Add the composite into the plasma device and evacuate; introduce argon gas and control the pressure to 100 Pa, use argon gas to perform surface modification treatment on the composite for 20 min, and the reaction temperature is 180℃; then introduce acrylamine and control the pressure to 100 Pa to perform plasma reaction for 40 min to obtain the precursor.

[0123] (4) The precursor is heat-treated in an argon atmosphere at a temperature of 500°C for 10 hours to obtain the negative electrode material.

[0124] The negative electrode material prepared in this embodiment includes a silicon-based active material and a carbon material. The silicon-based active material is SiO and Mg, wherein Mg is dispersed in the silicon-based active material in the form of magnesium silicate, and the carbon material is artificial graphite.

[0125] Other parameters of the negative electrode material are detailed in Table 1.

[0126] Example 5 (1) Weigh 100g of Li-doped SiO (D 50 =6μm), 900g of artificial graphite (D 50 After initial mixing (15 μm), the mixture was placed in an air jet mill for collision, crushing, and mixing to obtain the composite.

[0127] (2) The composite was placed in an air classifier for particle size adjustment, and the particle size distribution of the composite was controlled to be P0 = 1.58 ± 0.05, P0 = (D' 80 +D' 50 ) / (D' 50 +D' 20 ).

[0128] (3) Add the composite into the plasma device and evacuate; introduce argon gas and control the pressure to 100 Pa, use argon gas to perform surface modification treatment on the composite for 20 min, and the reaction temperature is 180℃; then introduce acrylamine and control the pressure to 100 Pa to perform plasma reaction for 40 min to obtain the precursor.

[0129] (4) The precursor is heat-treated in an argon atmosphere at a temperature of 500°C for 10 hours to obtain the negative electrode material.

[0130] The negative electrode material prepared in this embodiment includes a silicon-based active material and a carbon material. The silicon-based active material is SiO and Li, wherein Li is dispersed in the silicon-based active material in the form of lithium silicate, and the carbon material is artificial graphite.

[0131] Other parameters of the negative electrode material are detailed in Table 1.

[0132] Example 6 (1) Weigh 100g of SiO (D 50 =6μm), 900g natural graphite (D 50 After initial mixing (15 μm), the mixture was placed in an air jet mill for collision, crushing, and mixing to obtain the composite.

[0133] (2) The composite was placed in an air classifier for particle size adjustment, and the particle size distribution of the composite was controlled to be P0 = 1.73 ± 0.05, P0 = (D' 80 +D' 50 ) / (D' 50 +D' 20 ).

[0134] (3) Add the composite into the plasma device and evacuate; introduce argon gas and control the pressure to 100 Pa, use argon gas to perform surface modification treatment on the composite for 20 min, and the reaction temperature is 180℃; then introduce acrylamine and control the pressure to 100 Pa to perform plasma reaction for 40 min to obtain the precursor.

[0135] (4) The precursor is heat-treated in an argon atmosphere at a temperature of 500°C for 10 hours to obtain the negative electrode material.

[0136] The negative electrode material prepared in this embodiment includes a silicon-based active material and a carbon material, wherein the silicon-based active material is SiO and the carbon material is natural graphite.

[0137] Other parameters of the negative electrode material are detailed in Table 1.

[0138] Example 7 (1) Weigh 30g of SiO (D 50 =6μm), 970g of artificial graphite (D 50 After initial mixing (15 μm), the mixture was placed in an air jet mill for collision, crushing, and mixing to obtain the composite.

[0139] (2) The composite was placed in an air classifier for particle size adjustment, and the particle size distribution of the composite was controlled to be P0 = 1.34 ± 0.05, P0 = (D' 80 +D' 50 ) / (D' 50 +D' 20 ).

[0140] (3) Add the composite into the plasma device and evacuate; introduce argon gas and control the pressure to 100 Pa, use argon gas to perform surface modification treatment on the composite for 20 min, and the reaction temperature is 180℃; then introduce acrylamine and control the pressure to 100 Pa to carry out plasma reaction for 25 min to obtain the precursor.

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

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

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

[0144] Example 8 (1) Weigh 100g SiO (D 50 =6μm), 900g of artificial graphite (D 50 After initial mixing (15 μm), the mixture was placed in an air jet mill for collision, crushing, and mixing to obtain the composite.

[0145] (2) The composite was placed in an air classifier for particle size adjustment, and the particle size distribution of the composite was controlled to be P0 = 1.45 ± 0.05, P0 = (D' 80 +D' 50 ) / (D' 50 +D' 20 ).

[0146] (3) Add the composite into the plasma device and evacuate; introduce argon gas and control the pressure to 100 Pa, use argon gas to perform surface modification treatment on the composite for 20 min, and the reaction temperature is 180℃; then introduce acrylamine and control the pressure to 100 Pa to carry out plasma reaction for 25 min to obtain the precursor.

[0147] (4) The precursor is heat-treated in an argon atmosphere at a temperature of 500°C for 10 hours to obtain the negative electrode material.

[0148] The negative electrode material prepared in this embodiment includes a silicon-based active material and a carbon material, wherein the silicon-based active material is SiO and the carbon material is artificial graphite.

[0149] Other parameters of the negative electrode material are detailed in Table 1.

[0150] Example 9 (1) Weigh 300g SiO (D 50 =6μm), 700g artificial graphite (D 50 After initial mixing (15 μm), the mixture was placed in an air jet mill for collision, crushing, and mixing to obtain the composite.

[0151] (2) The composite was placed in an air classifier for particle size adjustment, and the particle size distribution of the composite was controlled to be P0 = 1.66 ± 0.05, P0 = (D' 80 +D' 50 ) / (D' 50 +D' 20 ).

[0152] (3) Add the composite into the plasma device and evacuate; introduce argon gas and control the pressure to 100 Pa, use argon gas to perform surface modification treatment on the composite for 20 min, and the reaction temperature is 180℃; then introduce acrylamine and control the pressure to 100 Pa to carry out plasma reaction for 25 min to obtain the precursor.

[0153] (4) The precursor is heat-treated in an argon atmosphere at a temperature of 500°C for 10 hours to obtain the negative electrode material.

[0154] The negative electrode material prepared in this embodiment includes a silicon-based active material and a carbon material, wherein the silicon-based active material is SiO and the carbon material is artificial graphite.

[0155] Other parameters of the negative electrode material are detailed in Table 1.

[0156] Example 10 Unlike Example 1: (3) Add the composite into the plasma device and evacuate; introduce argon gas and control the pressure to 100 Pa, use argon gas to perform surface modification treatment on the composite for 30 min, and the reaction temperature is 180℃; then introduce styrene and control the pressure to 100 Pa to carry out plasma reaction for 40 min to obtain the precursor.

[0157] The negative electrode material prepared in this embodiment includes a silicon-based active material and a carbon material, wherein the silicon-based active material is SiO and the carbon material is artificial graphite.

[0158] Other parameters of the negative electrode material are detailed in Table 1.

[0159] Example 11 The difference from Example 2 is: (3) Add the composite into the plasma device and evacuate; introduce argon gas and control the pressure to 100 Pa, use argon gas to perform surface modification treatment on the composite for 30 min, and the reaction temperature is 180℃; then introduce styrene and control the pressure to 100 Pa to carry out plasma reaction for 40 min to obtain the precursor.

[0160] The negative electrode material prepared in this embodiment includes a silicon-based active material and a carbon material, wherein the silicon-based active material is SiO and the carbon material is artificial graphite.

[0161] Other parameters of the negative electrode material are detailed in Table 1.

[0162] Example 12 Unlike Example 1: (1) Weigh 30g of Si (D 50 =6μm), 970g of artificial graphite (D 50 After initial mixing (15 μm), the mixture was placed in an air jet mill for collision, crushing, and mixing to obtain the composite.

[0163] The negative electrode material prepared in this embodiment includes a silicon-based active material and a carbon material, wherein the silicon-based active material is Si and the carbon material is artificial graphite.

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

[0165] Comparative Example 1 100g of carbon-coated SiO and 900g of artificial graphite were stirred and mixed to obtain a mixture. The mixture was then placed in an air classifier for particle size adjustment, and the particle size distribution concentration of the mixture was controlled to be P0=1.45±0.05 to obtain the negative electrode material.

[0166] Other parameters of the negative electrode material are detailed in Table 1.

[0167] Comparative Example 2 The difference from Example 8 is: (3) Add the composite into the plasma device and evacuate; introduce argon gas and control the pressure to 100 Pa, use argon gas to perform surface modification treatment on the composite for 40 min, and the reaction temperature is 180℃; then introduce acrylamine and control the pressure to 100 Pa to perform plasma reaction for 25 min to obtain the precursor.

[0168] The negative electrode material prepared in this embodiment includes a silicon-based active material and a carbon material, wherein the silicon-based active material is SiO and the carbon material is artificial graphite.

[0169] Other parameters of the negative electrode material are detailed in Table 1.

[0170] Comparative Example 3 The difference from Example 2 is: (3) Add the composite into the plasma device and evacuate; introduce argon gas and control the pressure to 100 Pa, use argon gas to perform surface modification treatment on the composite for 20 min, and the reaction temperature is 180℃; then introduce acrylamine and control the pressure to 100 Pa to carry out plasma reaction for 70 min to obtain the precursor.

[0171] The negative electrode material prepared in this embodiment includes a silicon-based active material and a carbon material, wherein the silicon-based active material is SiO and the carbon material is artificial graphite.

[0172] Other parameters of the negative electrode material are detailed in Table 1.

[0173] Comparative Example 4 The difference from Example 2 is: (1) Weigh 500g SiO (D50=6μm) and 500g artificial graphite (D50=15μm) and mix them to obtain a mixture. Place the mixture in an air jet mill for collision, crushing and mixing to obtain an active material.

[0174] (2) Place the active material in an air classifier for particle size adjustment and control the particle size distribution concentration P0 = 2.03 ± 0.05 in the active material.

[0175] Other parameters of the negative electrode material are detailed in Table 1.

[0176] Comparative Example 5 The difference from Example 2 is: (3) Add the complex into the plasma device and evacuate; introduce acrylamine and control the pressure to 100 Pa to carry out the plasma reaction for 40 min to obtain the precursor.

[0177] Other parameters of the negative electrode material are detailed in Table 1.

[0178] Comparative Example 6 The difference from Example 2 is: (3) Add the composite into the plasma device and evacuate; introduce argon gas and control the gas pressure to 100 Pa, use argon gas to perform surface modification treatment on the composite for 20 min, and the reaction temperature is 180℃ to obtain the precursor.

[0179] Other parameters of the negative electrode material are detailed in Table 1.

[0180] Test methods (1) Particle size of the negative electrode material: The particle size testing method refers to GB / T 19077-2016. It can be conveniently determined 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 a Malvern laser particle size analyzer (Mastersizer 3000). The volumetric cumulative particle size distribution is determined using laser diffraction. D20 represents the particle size corresponding to a cumulative particle size distribution percentage of 20%, D50 represents the particle size corresponding to a cumulative particle size distribution percentage of 50%, and D80 represents the particle size corresponding to a cumulative particle size distribution percentage of 80%.

[0181] (2) Test method for specific surface area of ​​negative electrode material: Referring to GB / T 19587-2004 "Determination of Specific Surface Area of ​​Solid Substances by Gas Adsorption BET Method", the amount of gas adsorbed on the solid surface at different relative pressures under constant temperature and low temperature is measured. Based on the Brownnor-Etter-Taylor adsorption theory and its formula (BET formula), the amount of monolayer adsorption of the sample is obtained, and the specific surface area of ​​the material is calculated.

[0182] (3) Test method for tap density of negative electrode material: Referring to GB / T 5162-2006 / ISO 3953:1993 "Determination of tap density of metal powders", the tap density was measured using a Canta DAT-4-220 tap density analyzer manufactured by Anton Paar (Shanghai) Trading Co., Ltd. The tap density T is the value after 3000 vibrations, and the unit is g / cm³. 3 .

[0183] (4) pH test of negative electrode material: Referring to Appendix C, "Determination of pH Value," of GB / T 24533-2019 "Graphite Anode Materials for Lithium-ion Batteries," a pH meter (Mettler-Toledo FE20) was used for measurement.

[0184] (5) Test method for oil absorption value of negative electrode material: Referring to GB / T 3780.2-2017 "Carbon Black Part 2: Determination of Oil Absorption Value", the oil absorption value Q was tested using an ASAHI S-500 oil absorption value 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, and the unit is mL / 100g.

[0185] (6) Test method for water content in negative electrode materials: The moisture content was measured according to Appendix B, "Determination of Moisture Content," of GB / T 24533-2019, "Graphite Anode Materials for Lithium-ion Batteries," or the equipment manual. A Mettler DL39 Karl Fischer coulometric titrator was used.

[0186] (7) Testing of the carbon layer: The material can be cross-sectioned using a dual-beam focused ion beam microscope (DIB-SEM). Ten cross-sections of negative electrode material particles are randomly selected, and ten sites are randomly selected from each particle to measure the thickness of the carbon layer. The average value is then used to calculate the thickness of the carbon layer.

[0187] (8) Electrochemical performance testing The negative electrode materials obtained in Examples 1-12 and Comparative Examples 1-3 were assembled into button cells: A negative electrode material, conductive agent (SuTer T), sodium carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) were mixed uniformly at a mass ratio of 92:2:2:2, and then coated onto a copper foil current collector. After drying, negative electrode sheets were obtained for later use. The dried negative electrode sheets were rolled under pressures of 3 MPa, 6 MPa, and 9 MPa, respectively. After rolling, the sheets were allowed to stand for 48 hours, and the thickness change rate before and after standing was measured, which is the physical rebound of the electrode sheet (electrode rebound rate). The negative electrode sheet was subjected to a 3MPa rolling pressure for rolling treatment. After standing, the negative electrode sheet was tested as a button cell. The battery assembly was carried out in an argon glove box. The negative electrode was a lithium metal sheet, the electrolyte was 1 mol / 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 tested on a battery testing instrument, and the charge and discharge voltage was 0.01–1.5 V.

[0188] Battery cycle life is the number of charge-discharge cycles performed before the capacity retention rate drops to 80%.

[0189] Initial Coulomb efficiency = First discharge capacity / First charge capacity.

[0190] The test results are detailed in Tables 2 and 3.

[0191] Table 1. Test results of negative electrode material performance

[0192] Table 2. Test results of negative electrode sheet rebound under different rolling pressures.

[0193] Table 3 Electrochemical performance test results of negative electrode materials

[0194] 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 keep the physical rebound ability T of the negative electrode material within the range of 0.2 to 1.2. This allows the silicon-based active material and carbon material particles to be tightly bonded, which helps to suppress the volume expansion of the silicon-based active material. As a result, the volume of the electrode sheet is not easily rebounded after compaction, and a high compaction density can be obtained, so that the negative electrode sheet has both good cycle performance and rate performance.

[0195] Table 2 shows the electrode rebound test results of the negative electrode sheet made of the negative electrode material prepared in this application under different rolling pressures. As shown in Table 2, the electrode rebound rate of the negative electrode sheet made of the negative electrode material prepared in the embodiments of this application is 2%~10% under rolling pressures of 3MPa, 6MPa and 9MPa. This can ensure good contact and tight 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 a suitable porosity, which is conducive to electrolyte wetting of the negative electrode material layer and improving lithium-ion transport efficiency. Thus, the electrode sheet has both good cycle performance and rate performance. However, the applicant found that as the rolling pressure increases, the electrode rebound rate of the negative electrode sheet after rolling also increases. It can be seen that when the rolling pressure is 3MPa, the electrode rebound rate after rolling treatment of the negative electrode sheet can be effectively reduced, reducing the loose bonding problem between the silicon-based active material and the carbon material caused by excessively high electrode rebound rate. It can also further reduce the volume expansion and particle pulverization effect of the negative electrode sheet during charge and discharge cycles.

[0196] The negative electrode material prepared in Comparative Example 1, such as Figure 2 and Figure 3 As shown, compared with Examples 2 and 8, the anode material was prepared by simply mixing silicon-based active material SiO with graphite and adjusting the particle size. The prepared anode material had an excessively high oil absorption value, and the relationship between the oil absorption value, specific surface area and particle size concentration of the anode material was unbalanced. The physical rebound ability of the anode material was greater than 1.2. The anode sheet made from this anode material experienced severe physical rebound after rolling, which reduced the bonding ability between the silicon-based active material and the carbon material particles. The silicon-based active material experienced severe volume expansion during cycling, resulting in the pulverization and breakage of the anode material, rapid battery cycle decay, and a significant decrease in the cycle life of the electrode sheet.

[0197] In Comparative Example 2, the surface modification treatment of the composite in the non-polymerizable gas during the preparation process was too long, which caused a certain degree of damage to the surface of the composite. This resulted in a high specific surface area of ​​the negative electrode material, an imbalance in the relationship between oil absorption value, specific surface area, and particle size concentration, and an electrode rebound capacity greater than 1.2. The negative electrode sheet made from this material experienced severe physical rebound after rolling, which loosened the bond between the silicon-based active material and the carbon material particles. The silicon-based active material experienced a severe volume expansion effect during cycling, leading to pulverization and breakage of the negative electrode material during cycling, a decrease in battery cycle performance, and a significant reduction in the cycle life of the electrode sheet.

[0198] In the negative electrode material prepared in Comparative Example 3, the plasma reaction time of the composite in the polymerizing gas was too long during the preparation process, resulting in a thick polymer modification layer deposited on the surface of the composite. After heat treatment of the composite, the oil absorption value and specific surface area of ​​the negative electrode material were low, resulting in a physical rebound ability T of less than 0.2. Therefore, the physical rebound of the negative electrode sheet made from this negative electrode material after rolling was minimal. The lack of suitable pores between the silicon-based active material and carbon material particles in the electrode was not conducive to the wetting and transport of the electrolyte, which resulted in the lithium storage capacity of the negative electrode material not being fully utilized, reducing the cycle performance and deteriorating the rate performance of the negative electrode material.

[0199] The negative electrode material prepared in Comparative Example 4 had a high content of silicon-based active material SiO during the preparation process, which significantly increased the mass content of silicon in the negative electrode material and the specific capacity of the negative electrode material. However, due to the excessive silicon content, the negative electrode material exhibited significant volume expansion during cycling, 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.

[0200] In Comparative Example 5, the negative electrode material was not surface-modified in a non-polymerizable gas during preparation. During the plasma reaction, the polymer gas could not form a tightly bonded modification layer on the surface of the composite particles, making it difficult to modify the surface defects of the negative electrode material. The negative electrode material had many surface defects and a high oil absorption value, resulting in an excessively large physical rebound ability T. The negative electrode sheet made from this material experienced severe physical rebound after rolling. The bonding force between the silicon-based active material and the carbon material particles decreased, and the silicon-based active material experienced severe volume expansion during cycling. The cycling performance of the negative electrode sheet deteriorated, and the cycle life was significantly reduced.

[0201] The negative electrode material prepared in Comparative Example 6 was not subjected to plasma treatment in a polymerizing gas during the preparation process. The surface defects of the negative electrode material were not modified, resulting in a large number of surface defects. Its oil absorption value and specific surface area were high, which led to a high physical rebound ability of the negative electrode material. The negative electrode sheet made from this negative electrode material experienced severe physical rebound after rolling. The bonding ability between the silicon-based active material and the carbon material was poor. The silicon-based active material underwent severe volume expansion during cycling, causing the negative electrode material to pulverize and break during cycling. The cycling performance of the negative electrode sheet was severely degraded, and the cycle life was significantly reduced.

[0202] The above are merely 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 within the scope of protection of the present invention.

Claims

1. A negative electrode material, characterized by, The negative electrode material includes a silicon-based active material and a carbon material, has an oil absorption value of O mL / 100 g, and a specific surface area of S m 2 / g, has a particle size concentration degree of P1, P1=(D 80 +D 50 ) / (D 50 +D 20 ), and has a physical rebound ability of 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 comprises at least one of the following features (1)-(6): (1) the physical rebounding ability of the negative electrode material is T, 0.70≤T<1.20; (2) the physical rebounding ability of the negative electrode material is T, 0.2 (3) the physical rebounding ability of the negative electrode material is T, T is 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, 1.2 or other values within the above range.

3. The negative electrode material of claim 1, wherein, The negative electrode material further comprises a carbon layer, and the carbon layer comprises at least one of the following features (1)-(5): (1) the carbon layer is located on at least part of the surface of the silicon-based active substance and / or the carbon material; (2) the thickness of the carbon layer is 1 nm-1000 nm; (3) the thickness of the carbon layer is 50 nm-800 nm; (4) the thickness of the carbon layer is 100 nm-500 nm; (5) at least part of the carbon material is located on the surface of the silicon-based active substance to form the carbon layer; (6) the carbon material is located on the surface of the silicon-based active substance to form the carbon layer.

4. The negative electrode material of claim 1, wherein, The silicon-based active substance is distributed in the carbon material.

5. The negative electrode material of claim 1, wherein, The negative electrode material comprises at least one of the following features (1)-(6): (1) the silicon-based active substance comprises at least one of elemental silicon and silicon oxide; (2) the silicon-based active substance further comprises a doped metal M, M is selected from at least one of Mg, Li, Fe, Al, Mn and Cu; (3) the silicon-based active substance further comprises a doped metal 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 substance in at least one of elemental, oxide or silicate form; (4) the silicon-based active material includes silicon oxide, the general formula of the silicon oxide is SiO x , 0 < x < 2; (5) the median particle size of the silicon-based active substance is 1 μm-10 μm; (6) the silicon-based active substance comprises elemental silicon, and the elemental silicon comprises amorphous silicon.

6. The negative electrode material of claim 1, wherein, The carbon material comprises at least one of graphite, graphene, amorphous carbon, carbon nanotube and carbon fiber.

7. The negative electrode material of claim 1, wherein, The negative electrode material comprises at least one of the following features (1)-(7): (1) the oil absorption value of the negative electrode material is O mL / 100g, O<57.0; (2) the specific surface area of the negative electrode material is S cm 2 / g, S < 3.50; (3) the pH value of the negative electrode material is 6-12; (4) the tap density of the negative electrode material is > 0.90 g / cm 3 ; (5) the mass content of water in the negative electrode material is ≤0.5 wt%; (6) the mass content of silicon element in the negative electrode material is 0.5 wt%-25 wt%; (7) the particle diameter of the negative electrode material satisfies: 0.1 μm ≤ D 20 ≤ 12 μm, 0.2 μm ≤ D 50 ≤ 18 μm, 0.3 μm ≤ D 80 ≤ 25 μm.

8. The negative electrode material according to any one of claims 1 to 3, characterized by, The negative electrode material satisfies at least one of the following features (1)-(2): (1) in the negative electrode material, the silicon-based active substance and the carbon material are dispersed in the form of particles; (2) the particle size concentration degree of the negative electrode material is P1, 1.2 9. A negative electrode sheet characterized by comprising: The negative electrode sheet comprises the negative electrode material according to any one of claims 1-8; under a rolling pressure of 3 MPa, the sheet rebounding rate of the negative electrode sheet is 2%-10%.

10. A lithium-ion battery, characterized by, The lithium ion battery comprises the negative electrode sheet according to claim 9.

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