Negative electrode material, preparation method and lithium ion battery

Abstract

This application relates to the field of battery anode materials technology. This application discloses an anode material, a preparation method, and a lithium-ion battery. The porosity X1, compaction density X2, oil absorption value X3, and number median particle size Dn50 of the anode material satisfy the following relationship: Y = 4 × X1 × X2 2 +e Dn50 -0.1×X3, and 15≤Y≤90; where Y represents the comprehensive performance value of the negative electrode material characterized by X1, X2, X3 and Dn50. The negative electrode material according to the embodiments of this application has good comprehensive performance.

Description

Technical Field

[0001] This application generally relates to the field of battery anode materials technology. More specifically, this application relates to an anode material, a preparation method thereof, and a lithium-ion battery. Background Technology

[0002] With the increasing demand for consumer electronics, the need for lithium-ion batteries is also growing. Developing high-performance lithium-ion batteries has become a top priority. Currently, the main anode materials used in lithium-ion batteries are graphite-based and silicon-based materials. Silicon-based materials have the advantage of high capacity, but silicon's poor conductivity leads to high internal resistance, which is detrimental to their application as anode materials. Graphite-based materials are favored due to their wide availability, abundant reserves, relatively stable electrochemical performance, and high safety profile. Graphite-based materials are mainly divided into artificial graphite and natural graphite. Natural graphite has high capacity and high compaction density, but poor cycle performance; while artificial graphite has excellent cycle performance and is suitable for energy storage and power battery projects, but its capacity needs improvement.

[0003] In view of this, there is an urgent need to provide a solution for anode materials in order to improve the overall performance of anode materials. Summary of the Invention

[0004] In order to at least solve one or more of the technical problems mentioned above, this application proposes a negative electrode material, a method for preparing the negative electrode material, and a scheme for a lithium-ion battery in several aspects.

[0005] In a first aspect, this application provides a negative electrode material, wherein the porosity X1, compaction density X2, oil absorption value X3, and number median particle size Dn50 of the negative electrode material satisfy the following relationship: Y = 4 × X1 × X2 2 +e Dn50 -0.1×X3, and 15≤Y≤90; where Y represents the comprehensive performance value of the negative electrode material characterized by X1, X2, X3 and Dn50.

[0006] In some embodiments, the negative electrode material also satisfies at least one of the following: (1) 10% ≤ X1 ≤ 28%; (2) 1.8 g / cm³ 3 ≤X2≤2.1g / cm 3 ; (3)31mL / 100g≤X3≤55mL / 100g; (4)2.7μm≤Dn50≤4.5μm.

[0007] In other embodiments, the negative electrode material also satisfies: 1.5≤(Dn90-Dn10) / Dn50≤2; where Dn90 represents the particle size corresponding to a cumulative particle size distribution percentage of 90%, and Dn10 represents the particle size corresponding to a cumulative particle size distribution percentage of 10%.

[0008] In some other embodiments, the negative electrode material also satisfies: And 10≤Z≤30; where Z represents the structural characterization index of the negative electrode material, A represents the average pore size of the negative electrode material, and B represents the specific surface area of ​​the negative electrode material.

[0009] In some embodiments, the negative electrode material further satisfies at least one of the following conditions: (1) the volume median particle size Dv50 of the negative electrode material is 5 μm to 30 μm; (2) the tap density of the negative electrode material is 0.9 g / cm³. 3 ~1.15g / cm 3 (3) The specific surface area of ​​the negative electrode material is 1m². 2 / g~4m 2 / g; (4) The average pore size of the negative electrode material is 20nm~60nm; (5) In the Raman spectrum of the negative electrode material, the peak area ratio of the D peak and the G peak is 0.4~1.6; (6) The capacity of the negative electrode material is ≥350mAh / g.

[0010] In other embodiments, the negative electrode material comprises a carbon material; the carbon material comprises artificial graphite.

[0011] In a second aspect, this application provides a method for preparing a negative electrode material, comprising: carbonizing a carbon precursor to obtain a carbonized material; using silicon carbide powder as a target material, performing a deposition treatment on the surface of the carbonized material using physical vapor deposition to obtain a silicon-carbon material with a silicon carbide coating layer; and graphitizing the silicon-carbon material to obtain the negative electrode material.

[0012] In some embodiments, the preparation method further includes at least one of the following conditions: (1) controlling the deposition time of the deposition treatment to be 5 min to 60 min; (2) controlling the sputtering power per unit target area in the deposition treatment to be 45 W / cm². 2 ~75W / cm 2 (3) The deposition process is performed using a magnetron sputtering apparatus, and the vacuum level inside the magnetron sputtering apparatus is controlled to be 2 × 10⁻⁶. -3 Pa~2×10 -5Pa; (4) The deposition treatment and / or the carbonization treatment are carried out in a protective gas atmosphere, wherein the protective gas includes one or more of nitrogen, helium, and argon; (5) The deposition treatment is carried out in a protective gas atmosphere, wherein the gas flow rate of the protective gas in the deposition treatment is 15 sccm to 80 sccm and the ventilation time is 100 min to 450 min; (6) The mass percentage of silicon carbide coating layer in the silicon-carbon material is 2 wt% to 18 wt%; (7) The carbonization treatment temperature is controlled to be 600℃ to 1400℃ and the carbonization treatment time is 8 h to 50 h; (8) The graphitization treatment temperature is controlled to be 2800℃ to 3200℃ and the graphitization treatment time is 24 h to 72 h; (9) The carbon precursor includes pulverized coke raw material and / or carbon-coated material obtained by carbon coating treatment of the pulverized material.

[0013] In other embodiments, when the carbon precursor comprises a pulverized coke feedstock, the pulverized feedstock satisfies at least one of the following conditions: (1) the volume median particle size Dv50 of the pulverized feedstock is 5 μm to 30 μm; (2) the number median particle size Dn50 of the pulverized feedstock is 2 μm to 7 μm; (3) 0.5 ≤ (Dn10 × Dn90) / Dn50 2 ≤4, where Dn90 represents the particle size corresponding to a cumulative particle size distribution percentage of 90%, Dn10 represents the particle size corresponding to a cumulative particle size distribution percentage of 10%, and Dn50 represents the median particle size of the crushed material; (4) 1.5≤Dv50 / Dn50≤2.5; (5) The tapped density of the crushed material is ≥0.55g / cm³. 3 ; and / or when the carbon precursor includes the carbon coating material, the preparation method further includes: coating and granulating the mixture of the pulverized material and the coating agent to obtain the carbon coating material, and also satisfies at least one of the following conditions: (1) the mass percentage of the coating agent in the mixture is 3wt% to 15wt%; (2) the coating agent includes at least one of asphalt, phenolic resin, and polyimide; (3) the coating time of the coating treatment is 1h to 4h, and the mixing speed is 10r / min to 30r / min; (4) the granulation temperature of the granulation treatment is 400℃ to 700℃, and the granulation time is 4h to 10h.

[0014] In a third aspect, this application provides a lithium-ion battery comprising the negative electrode material described in any one of the first aspects of this application or the negative electrode material prepared according to any one of the preparation methods described in the second aspect of this application.

[0015] In the above-mentioned anode material scheme, the comprehensive performance value Y of the anode material of the present application embodiment can satisfy 15≤Y≤90, and the comprehensive performance value Y is obtained by jointly characterizing the porosity X1, compaction density X2, oil absorption value X3 and number median particle size Dn50. This shows that the anode material of the present application embodiment has good comprehensive performance and has good performance in terms of rate performance, capacity, cycle performance and processing performance. Attached Figure Description

[0016] The above and other objects, features, and advantages of exemplary embodiments of this application will become readily understood by reading the following detailed description with reference to the accompanying drawings. In the drawings, several embodiments of this application are illustrated by way of example and not limitation, and the same or corresponding reference numerals denote the same or corresponding parts, wherein:

[0017] Figure 1 A schematic diagram of a battery in a discharged state, i.e., during operation, is shown.

[0018] Figure 2 An exemplary flowchart of a method for preparing a negative electrode material according to some embodiments of this application is shown;

[0019] Figure 3 An exemplary flowchart of a method for preparing a negative electrode material according to other embodiments of this application is shown;

[0020] Figure 4 A scanning electron microscope image of the negative electrode material prepared in Example 1 is shown;

[0021] Figure 5 A scanning electron microscope image of the negative electrode material prepared in Comparative Example 2 is shown;

[0022] Figure 6 A comparison diagram of the pore size distribution of the negative electrode materials prepared in Example 1 and Comparative Example 1 is shown. Detailed Implementation

[0023] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0024] It should be understood that the terms "comprising" and "including" used in the specification and claims of this application indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0025] It should also be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application. As used in this specification and claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used in this specification and claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes such combinations.

[0026] As used in this specification and claims, the term "if" may be interpreted, depending on the context, as "when," "once," "in response to determination," or "in response to detection." Similarly, the phrase "if determined" or "if [described condition or event] is detected" may be interpreted, depending on the context, as "once determined," "in response to determination," "once [described condition or event] is detected," or "in response to detection of [described condition or event]."

[0027] The specific embodiments of this application are described in detail below with reference to the accompanying drawings. Unless otherwise specified, the materials, reagents and equipment used in the embodiments of this application are obtained through conventional commercial channels.

[0028] One embodiment of this application provides a secondary battery (such as a lithium-ion battery, sodium-ion battery, etc.), including a casing, an electrode assembly, and an electrolyte / electrolyte. Both the electrode assembly and the electrolyte / electrolyte are located within the casing.

[0029] The outer casing can be a packaging bag sealed with an encapsulating film (such as aluminum-plastic film), for example, a pouch battery for a secondary battery. In other embodiments, the secondary battery can also be a steel-cased battery, an aluminum-cased battery, etc.

[0030] Figure 1 This diagram shows a battery in a discharged state, i.e., during operation. Figure 1 As shown, the electrode assembly includes a positive electrode 110, a negative electrode 120, and a separator 130, with the separator 130 disposed between the positive electrode 110 and the negative electrode 120. The electrode assembly can be a stacked structure, formed by alternately stacking the positive electrode 110, the separator 130, and the negative electrode 120. In other embodiments, the electrode assembly can also be a wound structure, formed by sequentially stacking and winding the positive electrode, the separator, and the negative electrode.

[0031] Positive electrode tablets:

[0032] The positive electrode 110 includes a positive current collector 111 and a positive active layer 112 disposed on at least one surface of the positive current collector. The positive current collector 111 can be aluminum foil or nickel foil, or any composite current collector disclosed in the prior art, such as, but not limited to, a current collector formed by combining a conductive foil and a polymer substrate. The positive active layer 112 contains a positive active material, which includes compounds that reversibly insert and extract metal ions. In some embodiments, the positive active material may include lithium transition metal composite oxides, sodium transition metal composite oxides, etc. The lithium transition metal composite oxide contains lithium and at least one element selected from cobalt, manganese, and nickel. In some embodiments, the positive active material may include, but is not limited to, lithium cobalt oxide (LiCoO2), lithium nickel manganese cobalt ternary materials (NCM), lithium manganese oxide (LiMn2O4), and lithium nickel manganese oxide (LiNi). 0.5 Mn 1.5 At least one of lithium iron phosphate (LiFePO4) or lithium iron phosphate (LiFePO4).

[0033] Negative electrode plate:

[0034] The negative electrode 120 includes a negative electrode current collector 121 and a negative electrode active material layer 122 disposed on at least one surface of the negative electrode current collector. The negative electrode current collector 121 can be at least one of copper foil, nickel foil, stainless steel foil, titanium foil, or carbon-based current collectors, or any composite current collector disclosed in the prior art, such as, but not limited to, current collectors formed by combining the aforementioned conductive foil and polymer substrate. The negative electrode active material layer 122 includes a negative electrode material.

[0035] During battery operation, i.e. when the battery is in a discharge state, metal ions 140 (e.g., lithium ions) in the negative electrode are released from the lattice of the negative electrode material, pass through the electrolyte / electrolyte through the separator 130, and are embedded in the lattice of the positive electrode material.

[0036] Conversely, when the battery is charged by applying an external circuit, the oxidation of the positive electrode material causes metal ions (such as lithium ions) in the positive electrode to be released from the lattice of the positive electrode material, pass through the electrolyte / electrolyte through the separator 130, and move to the negative electrode; at the same time, the negative electrode material undergoes a reduction reaction, causing metal ions to be embedded in the lattice of the negative electrode material.

[0037] As metal ions move back and forth between the positive and negative electrodes, the battery can achieve the discharge and charge process in thousands of cycles.

[0038] In some implementations, the negative electrode material may include silicon-based materials and / or graphite-based materials.

[0039] In other embodiments, the silicon-based material may include at least one of amorphous silicon, crystalline silicon, silicon oxide, and silicate.

[0040] In some embodiments, the silicon-based material includes silicon oxide, which includes silicon and oxygen elements in an atomic ratio of 1:0 to 2, excluding 0.

[0041] In some embodiments, the silicon-based material includes silicon oxide, which has the general chemical formula SiOx, where 0 < x ≤ 2. Specifically, SiOx can be SiO 0.5 SiO 0.7 SiO 0.9 SiO, SiO 1.2 SiO 1.5 SiO 1.8 SiO 1.9 The terms are not limited here. Silicon oxides can be represented by the general formula SiOx (0 < x ≤ 2). It can be a material formed by silicon dispersed in SiO2; or it can be a material with tetrahedral structural units, where silicon atoms are located at the center of the tetrahedral structural units, and oxygen atoms and / or silicon atoms are located at the four vertices of the tetrahedral structural units.

[0042] In some embodiments, the graphite material in the negative electrode material may include at least one of natural graphite, artificial graphite, expanded graphite, and graphite oxide.

[0043] In some embodiments, the negative electrode material includes a carbon material, which includes at least one of amorphous carbon and graphitized carbon.

[0044] In a first aspect, this application provides a negative electrode material whose porosity X1, compaction density X2, oil absorption value X3, and number median particle size Dn50 satisfy the following relationship: Y = 4 × X1 × X2 2 +e Dn50 -0.1×X3, and 15≤Y≤90; where Y represents the comprehensive performance value of the anode material characterized by X1, X2, X3 and Dn50.

[0045] In some embodiments, the negative electrode material may be in powder or particulate form before being processed into a negative electrode sheet. In other embodiments, the negative electrode material may include a carbon material. This carbon material may include one or more of artificial graphite, natural graphite, amorphous carbon, carbon nanotubes, and / or mesophase carbon microspheres. In some preferred embodiments, the carbon material may include artificial graphite.

[0046] Generally speaking, porosity is the percentage of the total pore volume of a material to its total volume in its natural state. The porosity (X1) of a negative electrode material has a certain impact on its rate performance; the higher the porosity, the higher the rate performance. Therefore, porosity (X1) can be used to evaluate and reflect the rate performance of a negative electrode material. Compacted density refers to the density of a material during the compaction process and is commonly used to describe the compactness of battery materials. In some embodiments, the unit of compacted density (X2) can be g / cm³. 3 In the manufacturing process of lithium-ion batteries, compaction density has a significant impact on battery performance. Generally, the higher the compaction density, the higher the battery capacity; therefore, compaction density x² is also considered one of the reference indicators for material energy density.

[0047] Oil absorption value refers to a material's ability to absorb oil. It is typically quantified by measuring the minimum volume of oil required to completely wet 100 grams of powder under certain conditions with linseed oil. This volume is expressed in milliliters (mL), so the unit can be mL / 100g. Oil absorption value X3 is an important indicator of battery performance, affecting discharge performance, cycle performance, safety performance, and processing performance. The number median particle size (Dn50) represents the particle size corresponding to a cumulative particle size distribution percentage of 50% for the material. Dn50 reflects the amount of fine powder in the material. The amount of fine powder in the negative electrode material affects its processing performance and cycle performance. Too much fine powder will make the negative electrode material difficult to process. Too little fine powder will affect the battery's cycle performance.

[0048] Based on the above, the comprehensive performance value Y, characterized by porosity X1, compaction density X2, oil absorption value X3, and number median particle size Dn50, can comprehensively and fully reflect the overall capabilities of the anode material in terms of rate performance, capacity, cycle performance, and processing performance. In existing technologies, it is often difficult to obtain anode materials with high overall performance; often, improving one electrochemical performance aspect results in a decrease in others. Furthermore, the porosity X1, compaction density X2, oil absorption value X3, and number median particle size Dn50 of the anode material in the embodiments of this application satisfy Y = 4 × X1 × X2 2 +e Dn50 -0.1×X3, the weights of X1, X2, X3 and Dn50 in this formula are not evenly distributed, but have different coefficients, exponents or forms of expression according to the degree of influence on the overall performance of the material, so as to more realistically reflect the actual overall performance of the negative electrode material of the present application.

[0049] The applicant, through extensive experimentation and research, summarized the aforementioned index patterns. Based on the comprehensive performance value Y of the negative electrode material in this application's embodiments, which is within the range of 15 to 90, it possesses excellent rate performance, high capacity performance, high cycle performance, and good processing performance, ensuring that lithium-ion batteries prepared using this negative electrode material can meet the required performance requirements in all aspects. In some embodiments, the comprehensive performance value Y of the negative electrode material in this application's embodiments can be 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, or other values ​​within the range of 15 to 90. If the comprehensive performance value of the negative electrode material is lower than 15, it indicates that the porosity X1, compaction density X2, and / or the number median particle size Dn50 of the negative electrode material are too small, or the oil absorption value X3 is too large, all reflecting deficiencies in at least one aspect of the negative electrode material's performance. If the comprehensive performance value of the negative electrode material is higher than 90, it may be due to an excessively large number median particle size Dn50, thereby affecting the cycle performance of the negative electrode material.

[0050] In some embodiments, the negative electrode material can also satisfy the following condition: 10% ≤ X1 ≤ 28%. For example, the porosity X1 of the negative electrode material can reach 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, etc., or can be other values ​​within the range of 10% to 28%. If the porosity X1 is too small, it will result in poor rate performance of the negative electrode material. If the porosity X1 is too large, it will easily lead to low initial efficiency of the negative electrode material.

[0051] In other embodiments, the compaction density X2 of the negative electrode material satisfies: 1.8 g / cm³ 3 ≤X2≤2.1g / cm 3 For example, the compaction density X2 of the negative electrode material can be 1.8 g / cm³. 3 1.85g / cm 3 1.9g / cm 3 1.95g / cm 3 2.0g / cm 3 2.05g / cm 3 2.1g / cm 3 etc., or it could be 1.8 g / cm 3 ~2.1g / cm 3 Other values ​​within the range. If the compaction density X2 is too small, the capacity of the negative electrode material will be too small. If the compaction density X2 is too large, it may increase the internal resistance of the battery, thereby affecting the battery's charge and discharge efficiency.

[0052] In some other embodiments, the oil absorption value X3 of the negative electrode material satisfies: 31 mL / 100g ≤ X3 ≤ 55 mL / 100g. For example, the oil absorption value X3 can be 31 mL / 100g, 32 mL / 100g, 33 mL / 100g, 34 mL / 100g, 35 mL / 100g, 36 mL / 100g, 37 mL / 100g, 38 mL / 100g, 39 mL / 100g, 40 mL / 100g, 41 mL / 100g, 42 mL / 100g, 43 mL / 100g, 44 mL / 100g, etc. 00g, 45mL / 100g, 46mL / 100g, 47mL / 100g, 48mL / 100g, 49mL / 100g, 50mL / 100g, 51mL / 100g, 52mL / 100g, 53mL / 100g, 54mL / 100g, 55mL / 100g, etc., or other values ​​within the range of 31mL / 100g to 55mL / 100g. If the oil absorption value X3 is too small, it may reduce the adsorption capacity of the negative electrode material, affecting the stability of the electrolyte, and thus affecting the cycle stability and safety of the battery; it may also reduce the effective charge transport area of ​​the negative electrode material, reducing the charge and discharge performance of the battery. If the oil absorption value X3 is too large, it will increase the viscosity of the slurry, thereby affecting the coating performance and processing performance; it may also mean that the material dispersion performance is poor, which will affect the electrochemical performance of the battery.

[0053] In some implementations, the number median particle size Dn50 of the negative electrode material satisfies the following condition: 2.7 μm ≤ Dn50 ≤ 4.5 μm. For example, the number median particle size Dn50 of the negative electrode material can be 2.7 μm, 2.9 μm, 3 μm, 3.2 μm, 3.4 μm, 3.6 μm, 3.8 μm, 4 μm, 4.2 μm, 4.4 μm, 4.5 μm, or other values ​​within the range of 2.7 μm to 4.5 μm. If the number median particle size Dn50 is too small, it indicates that there is too much fine powder in the negative electrode material, which may mean that more material volume is occupied by fine particles. This will reduce the effective volume of the battery, thereby reducing the energy density of the battery. Too much fine powder is also prone to detaching from the electrode surface during battery charging and discharging, leading to internal micro-short circuits in the battery and affecting the cycle stability and lifespan of the battery. In addition, excessive fine powder will also increase the processing difficulty and cost of the material, as more processes are required to handle or separate the fine powder. If the median particle size Dn50 is too large, it indicates that there is too little fine powder and too many large particles in the negative electrode material. This may mean that during charging and discharging, the volume expansion and contraction of the electrode material will be more severe, accelerating the wear of the electrode material and affecting the cycle life of the battery. In addition, during battery manufacturing, too little fine powder may affect the rheological properties of the slurry, thereby affecting the uniformity of coating and the manufacturing quality of the battery. Furthermore, large particles may pose a risk of puncturing the separator, affecting the safety performance of the battery.

[0054] In other embodiments, the negative electrode material may also satisfy: 1.5≤(Dn90-Dn10) / Dn50≤2; where Dn90 represents the particle size corresponding to a cumulative particle size distribution percentage of 90%, and Dn10 represents the particle size corresponding to a cumulative particle size distribution percentage of 10%.

[0055] (Dn90-Dn10) / Dn50 measures the width of the particle size distribution of the negative electrode material, i.e., the ratio of the difference between the maximum particle size (Dn90) and the minimum particle size (Dn10) to the number median particle size (Dn50). In some embodiments, the number ratio of the negative electrode material 1.5≤(Dn90-Dn10) / Dn50≤2 can be, for example, 1.5, 1.6, 1.7, 1.8, 1.9, 2, or other values ​​within the range of 1.5 to 2. It reflects the dispersion and uniformity of the particle size distribution. When the (Dn90-Dn10) / Dn50 of the negative electrode material is within the range of 1.5 to 2, it indicates that the particle size distribution of the negative electrode material powder is relatively uniform, which is beneficial for more efficient space utilization and more uniform volume change during charge and discharge, reducing stress concentration, thereby helping to improve the energy density and cycle stability of the battery. Materials with uniform particle size distribution also make the rheological properties of the slurry more stable and the coating more uniform, thereby helping to improve the processing performance of the negative electrode material. If (Dn90-Dn10) / Dn50 is too large, it indicates that the particle size distribution of the negative electrode material is uneven or dispersed, which may lead to a decrease in the packing density of the battery material, thereby reducing the battery's energy density. Dispersed particle size distribution can also cause uneven volume changes of particles of different sizes during charging and discharging, resulting in stress concentration and affecting the battery's cycle stability and lifespan. If (Dn90-Dn10) / Dn50 is too small, it may be due to an excessively large Dn50, which will affect the processing performance and safety performance of the negative electrode material.

[0056] In some other embodiments, the negative electrode material also satisfies: Furthermore, 10 ≤ Z ≤ 30; in some embodiments, the comprehensive performance Z of the negative electrode material can be, for example, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, or other values ​​within the range of 10 to 30. Here, Z represents the structural characterization index of the negative electrode material, A represents the average pore size of the negative electrode material, and B represents the specific surface area of ​​the negative electrode material. When Z is within the range of 10 to 30, it indicates that the average pore size and specific surface area of ​​the negative electrode material are both within a suitable range, thereby enabling the negative electrode material to have good rate performance, expansion performance, and processing performance. If Z < 10, the average pore size of the negative electrode material powder particles is small and / or the specific surface area is large, which is not conducive to lithium ion intercalation, leading to poor expansion performance and affecting the rate performance of the negative electrode material. If Z > 30, the average pore size of the negative electrode material powder particles is larger, which leads to a decrease in the strength of the negative electrode material powder particles and affects the processing performance of the negative electrode material.

[0057] In some embodiments, the average pore size of the negative electrode material is 20nm to 60nm, such as 20nm, 21nm, 22nm, 23nm, 24nm, 25nm, 26nm, 27nm, 28nm, 29nm, 30nm, 31nm, 32nm, 33nm, 34nm, 35nm, 36nm, 37nm, 38nm, 39nm, 40nm, 42nm, 44nm, 46nm, 48nm, 50nm, 52nm, 54nm, 56nm, 58nm, 60nm, or other values ​​within the range of 20nm to 60nm.

[0058] In other embodiments, the specific surface area of ​​the negative electrode material is 1 m². 2 / g~4m 2 / g, for example, 1m 2 / g, 1.2m 2 / g, 1.4m 2 / g, 1.6m 2 / g, 1.8m 2 / g、2m 2 / g, 2.2m 2 / g, 2.4m 2 / g, 2.6m 2 / g, 2.8m 2 / g、3m 2 / g, 3.2m 2 / g, 3.4m 2 / g, 3.6m 2 / g, 3.8m 2 / g、4m 2 / g, or 1m 2 / g~4m 2Other values ​​within the / g range.

[0059] In some other embodiments, the volumetric median particle size Dv50 of the negative electrode material can be 5 μm to 30 μm, for example, 5 μm, 8 μm, 10 μm, 12 μm, 14 μm, 16 μm, 18 μm, 20 μm, 22 μm, 24 μm, 26 μm, 28 μm, 30 μm, or other values ​​within the range of 5 μm to 30 μm. The volumetric median particle size Dv50 represents the particle size corresponding to a cumulative particle size distribution volume percentage of 50%.

[0060] In some embodiments, the tap density of the negative electrode material is 0.9 g / cm³. 3 ~1.15g / cm 3 For example, 0.9 g / cm 3 0.95g / cm 3 1.0g / cm 3 1.05g / cm 3 1.10 g / cm 3 1.15g / cm 3 Wait, or 0.9 g / cm 3 ~1.15g / cm 3 Other values ​​within the range. Tap density refers to the mass per unit volume of powder in a container after it has been tapped under specified conditions. Tap density reflects the compactness of the material particles; a high tap density is beneficial for improving the volumetric energy density of the battery. Both excessively high and low tap densities are detrimental to the processing performance of the negative electrode material.

[0061] In other embodiments, the peak area ratio of the D peak to the G peak (referred to as the "Raman D / G(A) value") in the Raman spectrum of the negative electrode material is 0.4 to 1.6, for example, it can be 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, etc. Typically, in the Raman spectrum, the D peak (approximately 1350 cm⁻¹) is... -1 The peak (G) represents the disordered structure or defects in carbon materials, while the peak (G peak, approximately 1580 cm⁻¹) represents the disordered structure or defects in carbon materials. -1 The () represents the ordered graphite structure in carbon materials. The Raman D / G(A) value can reflect the defect density and surface smoothness of the anode material. When the Raman D / G(A) value is in the range of 0.4 to 1.6, it indicates that the anode material has fewer defects and a relatively smooth surface.

[0062] In some embodiments, the capacity of the negative electrode material is ≥350 mAh / g. In other embodiments, the capacity of the negative electrode material can reach 350 mAh / g to 372 mAh / g, for example, 350 mAh / g, 352 mAh / g, 354 mAh / g, 356 mAh / g, 358 mAh / g, 360 mAh / g, 362 mAh / g, 364 mAh / g, 366 mAh / g, 368 mAh / g, 370 mAh / g, 372 mAh / g, etc. The negative electrode material according to the embodiments of this application has a high capacity.

[0063] The above describes the anode material according to the embodiments of this application. In order to obtain the anode material with the above-mentioned excellent comprehensive properties, this application provides a new preparation method in a second aspect, which will be described in detail below with reference to the accompanying drawings.

[0064] Figure 2 An exemplary flowchart of a method for preparing a negative electrode material according to some embodiments of this application is shown. Figure 2 As shown, the preparation method 200 may include: step S202, carbonizing the carbon precursor to obtain a carbonized material; step S204, using silicon carbide powder as a target, performing a deposition treatment on the surface of the carbonized material using physical vapor deposition to obtain a silicon-carbon material with a silicon carbide coating layer; and step S206, graphitizing the silicon-carbon material to obtain a negative electrode material.

[0065] In some embodiments, the carbon precursor can be prepared from coke. In other embodiments, in step S202, the carbonization temperature can be controlled to be 600℃ to 1400℃, and the carbonization time to be 8h to 50h. For example, the carbonization temperature can be 600℃, 650℃, 700℃, 750℃, 800℃, 850℃, 900℃, 950℃, 1000℃, 1050℃, 1100℃, 1150℃, 1200℃, 1250℃, 1300℃, 1350℃, 1400℃, etc., or other values ​​within the range of 600℃ to 1400℃. The carbonization time can be 8h, 10h, 15h, 20h, 25h, 30h, 35h, 40h, 45h, 50h, etc., or other values ​​within the range of 8h to 50h.

[0066] In some embodiments, the carbonization process in step S202 is carried out in a protective gas atmosphere, which may include one or more of nitrogen, helium, argon, etc. In other embodiments, the carbon precursor may be placed in a carbonization device such as a tunnel kiln or roller kiln for the above-mentioned carbonization process.

[0067] Understandably, the carbonization process in step S202 effectively removes volatile components from the carbon precursor, resulting in carbonized material. This helps prevent the risk of production accidents caused by excessive gas escape from the material during subsequent graphitization. If the carbonization temperature is too low and / or the carbonization time is too short, volatile components may not be completely removed. If the carbonization temperature is too high and / or the carbonization time is too long, energy consumption and production costs will increase.

[0068] After obtaining the carbide material, the process can proceed to step S204 for deposition. Specifically, Physical Vapor Deposition (PVD) is a technique that uses physical methods to vaporize the coating material into atoms or molecules and deposit them onto the substrate surface to form a film. This method mainly includes vacuum evaporation deposition, sputtering deposition, and ion plating. In the embodiments of this application, sputtering deposition technology is mainly used, with silicon carbide powder as the target material (or target source). In a vacuum environment, by applying a magnetic field and an electric field, the target material is ionized, and these ions (i.e., sputtered atoms or molecules) are sputtered and deposited onto the carbide material to obtain a silicon-carbon material with a core-shell structure, consisting of a carbide core and a silicon carbide coating layer.

[0069] In some implementations, a magnetron sputtering apparatus can be used for deposition, and the vacuum level within the magnetron sputtering apparatus can be controlled to be 2 × 10⁻⁶. -3 Pa~2×10 -5 Pa. In other embodiments, the deposition process can be carried out in a protective gas atmosphere, which may include one or more of nitrogen, helium, and argon.

[0070] For example, carbide material is placed on a sample vibration stage in a magnetron sputtering apparatus (e.g., a magnetron sputtering furnace), and silicon carbide powder with a median volume particle size of, for example, 15 μm to 90 μm is placed as a target on the cathode within the magnetron sputtering apparatus. The target is typically positioned relative to the sample vibration stage. Specific operations may include: evacuating the magnetron sputtering apparatus to a preset vacuum level, then introducing a protective gas; once the magnetron sputtering apparatus is in a stable protective gas atmosphere, the sample vibration stage frequency can be set to, for example, 5 Hz to 60 Hz, and then the RF power supply is turned on to control the thermocouple heating, thus initiating magnetron sputtering.

[0071] In other embodiments, step S204 may further control the sputtering power per unit target area during the deposition process to be 45 W / cm². 2 ~75W / cm 2 For example, the sputtering power per unit target area during deposition can be controlled to 45 W / cm². 250W / cm 2 55W / cm 2 60W / cm 2 65W / cm 2 70W / cm 2 75W / cm 2 Wait, or 45W / cm 2 ~75W / cm 2 Other values ​​within the range.

[0072] Higher sputtering power per unit target area generally means a higher sputtering rate, because more energy is transferred to the target, resulting in more atoms or molecules being sputtered. Sputtering power per unit target area also affects the adhesion between the coating and the substrate. Appropriate sputtering power per unit target area can help improve adhesion, while excessively high or low sputtering power may reduce adhesion.

[0073] In some embodiments, in step S204, the deposition time of the deposition treatment can be controlled to be 5 min to 60 min, such as 5 min, 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min, or other values ​​within the range of 5 min to 60 min.

[0074] In some other embodiments, in step S204, the mass percentage of the silicon carbide coating layer in the obtained silicon-carbon material is 2 wt% to 18 wt%. For example, the mass percentage of the silicon carbide coating layer in the silicon-carbon material can be 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, or other values ​​within the range of 2 wt% to 18 wt%.

[0075] Controlling the appropriate sputtering power and deposition time per unit target area can effectively control the thickness, uniformity, and coating ratio of the silicon carbide coating. The sputtering power per unit target area was controlled at 45 W / cm². 2 ~75W / cm 2 By controlling the deposition time within 5 min to 60 min, a uniformly distributed and thick silicon carbide coating layer can be formed, and the silicon carbide coating layer can have strong adhesion to the substrate. At the same time, the mass percentage of the silicon carbide coating layer in the silicon-carbon material can be controlled within the range of 2 wt% to 18 wt%.

[0076] Insufficient sputtering power per unit target area and / or excessively short deposition time will prevent the formation of a silicon carbide coating that completely covers the substrate (i.e., the carbide material) surface. Alternatively, the resulting silicon carbide coating may be too thin or have a mass percentage below 2 wt%, affecting its catalytic effect in subsequent graphitization and its protective function against the substrate structure. This, in turn, will impact the graphitization process and the capacity and other properties of the prepared anode material. Conversely, excessively high sputtering power per unit target area and / or excessively long deposition time will result in an excessively thick or uneven silicon carbide coating, or a silicon carbide coating mass percentage exceeding 18 wt%. While this will not significantly improve the performance of the prepared anode material, it will increase production costs, hindering industrialization and commercial value.

[0077] Furthermore, in some embodiments, the deposition process can be carried out in a protective gas atmosphere. The flow rate of the protective gas during deposition can be controlled to be between 15 sccm and 80 sccm, for example, 15 sccm, 20 sccm, 25 sccm, 30 sccm, 35 sccm, 40 sccm, 45 sccm, 50 sccm, 55 sccm, 60 sccm, 65 sccm, 70 sccm, 75 sccm, 80 sccm, or other values ​​within the range of 15 sccm to 80 sccm. In some embodiments, the aeration time of the protective gas during deposition can be controlled to be between 100 min and 450 min, for example, 100 min, 150 min, 200 min, 250 min, 300 min, 350 min, 400 min, 450 min, or other values ​​within the range of 100 min to 450 min. The aeration time of the protective gas is longer than the deposition time, ensuring that the atmosphere is always sufficiently protective during the deposition process to avoid side reactions. After obtaining the aforementioned silicon-carbon material, the preparation method 200 can proceed to step S206 for graphitization to obtain the negative electrode material. Graphitization is a process that utilizes thermal activation to transform thermodynamically unstable carbon atoms from a disordered layer structure to an ordered graphite crystal structure. In some embodiments, one or more graphitization devices, such as an Atchison furnace, a box furnace, an internal furnace, or a continuous graphitization furnace, can be used to perform the graphitization process in step S206.

[0078] In other embodiments, the graphitization temperature can be controlled to be between 2800℃ and 3200℃, for example, 2800℃, 2850℃, 2900℃, 2950℃, 3000℃, 3050℃, 3100℃, 3150℃, 3200℃, or other values ​​within the range of 2800℃ to 3200℃. In other embodiments, the graphitization time (i.e., the power supply duration) can be controlled to be between 24h and 72h, for example, 24h, 30h, 35h, 40h, 45h, 50h, 55h, 60h, 65h, 70h, 72h, or other values ​​within the range of 24h to 72h.

[0079] If the graphitization temperature is too low, it will be difficult to remove magnetic impurities such as nickel and / or nickel compounds, which can easily lead to short circuits in the resulting battery and affect its safety performance. If the graphitization temperature is too high, it will not significantly improve the performance of the prepared negative electrode material, but it will increase the production cost of the negative electrode material and the lifespan of the graphitization equipment, which is not conducive to the industrialization and commercial value of the product.

[0080] It is important to understand that, firstly, in the embodiments of this application, silicon carbide is deposited on the surface of the carbide material. In the subsequent graphitization process, the reaction between silicon carbide and the carbide material at high temperatures, and the entry of silicon atoms from the gaseous phase of silicon carbide into the carbon lattice at high temperatures, increase the interaction between graphite layers, disrupting the original stable mechanical structure of the graphite layers and promoting the rearrangement of carbon atoms, thereby accelerating the graphitization process. Therefore, the silicon carbide coating layer can act as a catalyst in the graphitization process.

[0081] Secondly, since silicon carbide has good high-temperature resistance, its melting point is around 2700℃, while the temperature of graphitization transformation (i.e., the process by which carbon atoms achieve an ordered transformation from a disordered layer structure to a graphite crystal structure) is between 2200℃ and 3000℃, compared with catalysts or dopants with lower boiling points such as boric acid, the silicon carbide coating layer in this application embodiment can volatilize later during the graphitization transformation process, thereby maintaining the catalytic effect for a longer period of time.

[0082] Furthermore, compared to coating silicon carbide or other coating agents with carbide materials through solid-phase mixing or sintering, the embodiments of this application use silicon carbide as the target material and employ physical vapor deposition to deposit the carbide material. This allows silicon carbide to be uniformly coated on the surface of the carbide material, avoiding the uneven mixing phenomenon that may be caused by solid-phase mixing or liquid-phase mixing. It also allows the generated silicon carbide coating layer to have stronger adhesion to the carbide material, similar to growing on the surface of the carbide material, which strengthens the recombination of C-C bonds during graphitization. As a result, it is not easy to fall off in subsequent graphitization treatment, can continue to play a catalytic role, and can protect the graphite crystal structure and morphology during the graphitization transformation process.

[0083] Furthermore, due to the excellent thermal conductivity of silicon carbide, it facilitates rapid heating of the carbon source (carbon material) during graphitization, which helps improve the graphitization degree and capacity of the prepared anode material. After silicon carbide coating, the volatilization of silicon carbide during graphitization also plays a role in pore formation, increasing the average pore size and porosity of the prepared anode material, which is beneficial to improving the rate performance of the battery. In particular, after using physical vapor deposition to coat the carbon material with silicon carbide, silicon carbide also acts as a binder during graphitization, reducing the amount of fine powder in the prepared anode material and improving the compaction density and tap density.

[0084] The above combination Figure 2 The preparation method of the negative electrode material according to the embodiments of this application has been described exemplarily. It is understood that the above preparation method 200 is beneficial to improve various aspects of the performance of the negative electrode material, thereby obtaining a negative electrode material with a comprehensive performance value Y of 15 to 90 as described in the first aspect of this application. It is also understood that the above description is exemplary and not restrictive. For example, in some embodiments, the carbon precursor may include pulverized coke raw material and / or carbon-coated material obtained by carbon coating treatment of the pulverized material. When the carbon precursor includes pulverized coke raw material, before step S202, the preparation method 200 may further include: pulverizing the coke raw material to obtain pulverized material. For ease of understanding, the following will be combined with Figure 3 An exemplary description is provided.

[0085] Figure 3 An exemplary flowchart of a method for preparing a negative electrode material according to other embodiments of this application is shown. Figure 3As shown, the preparation method 300 may include: step S302, pulverizing the coke raw material to obtain pulverized material; step S306, carbonizing the carbon precursor to obtain carbonized material; step S308, using silicon carbide powder as a target material, depositing it on the surface of the carbonized material to obtain silicon-carbon material; and step S310, graphitizing the silicon-carbon material to obtain anode material. Steps S306, S308, and S310 are combined with the above description. Figure 2 Steps S202, S204, and S206 are the same or similar, and will not be repeated here. Step S302 will be described in detail below.

[0086] Coke raw materials are widely available and readily obtained. In some embodiments, the coke raw materials may include one or more of petroleum coke, needle coke, and pitch coke. In some embodiments, the volume median particle size (Dv50) of the pulverized material is 5 μm to 30 μm, for example, it can be 5 μm, 7 μm, 10 μm, 12 μm, 14 μm, 16 μm, 18 μm, 20 μm, 22 μm, 24 μm, 26 μm, 28 μm, 30 μm, etc., or it can be other values ​​within the range of 5 μm to 30 μm. Pulverizing the coke raw material into a powder with a Dv50 in the range of 5 μm to 30 μm for use in the preparation of anode materials helps to ensure that the Dv50 of the prepared anode material is within a suitable range, which is beneficial for the processing of anode materials.

[0087] In other embodiments, the median particle size Dn50 of the pulverized material is 2μm to 7μm, for example, it can be 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, 5.5μm, 6μm, 6.5μm, 7μm, etc., or it can be other values ​​within the range of 2μm to 7μm. Pulverizing the coke raw material into a pulverized material with a Dn50 in the range of 2μm to 7μm for use in the preparation of anode materials is beneficial to reducing the amount of fine powder in the prepared anode material.

[0088] In some other embodiments, the pulverized material can satisfy the following condition: 0.5 ≤ (Dn10 × Dn90) / Dn50 2 ≤4, where Dn90 represents the particle size corresponding to a cumulative particle size distribution percentage of 90%, Dn10 represents the particle size corresponding to a cumulative particle size distribution percentage of 10%, and Dn50 represents the median particle size of the crushed material. Here, (Dn10×Dn90) / Dn50 2 It can be used to characterize the particle size distribution space of pulverized materials. A reasonable particle size distribution space can ensure the uniformity of particle size distribution and avoid large differences in particle size. Controlling the (Dn10×Dn90) / Dn50 of the pulverized material... 2Within the range of 0.5 to 4, such as 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, etc., the particle size distribution of the pulverized material can be made more uniform, which is beneficial to forming uniformly distributed negative electrode material particles in subsequent steps.

[0089] In some embodiments, the pulverized material can satisfy the following condition: 1.5 ≤ Dv50 / Dn50 ≤ 2.5. Here, Dv50 / Dn50 represents the ratio between the volume median particle size and the number median particle size, reflecting the characteristics of particle size distribution. Specifically, it indicates whether the particle size distribution is uniform and the shape characteristics of the particles. The closer Dv50 / Dn50 is to 1, the closer the particle shape is to spherical. Dv50 / Dn50 within the range of 1.5 to 2.5 indicates that the particle size distribution of the pulverized material is relatively uniform and the shape is relatively regular, which is beneficial for subsequent preparation of anode material particles with uniform particle size distribution and regular shape. Dv50 / Dn50 can be, for example, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, or other values ​​within the range of 1.5 to 2.5.

[0090] In other embodiments, the tapped density of the pulverized material is ≥0.55 g / cm³. 3 For example, 0.55g / cm 3 0.60g / cm 3 0.65g / cm 3 0.70g / cm 3 The high compaction density of the pulverized material is beneficial for increasing the material loading per unit volume, which in turn facilitates subsequent carbonization and graphitization processes to obtain high-capacity anode materials.

[0091] like Figure 3 As further shown in the figure, in some other embodiments, when the carbon precursor includes a carbon coating material, the preparation method 300 according to the embodiments of this application may further include: step S304 (shown in dashed box), coating and granulating the mixture of pulverized material and coating agent to obtain carbon coating material.

[0092] In some embodiments, the coating agent may include at least one of asphalt, phenolic resin, polyimide, etc. In other embodiments, the coating process can be carried out in a mixing device, for example, the pulverized material and the coating agent can be placed in a mixing tank for solid-phase mixing. In still other embodiments, the mixing speed of the mixing device during the coating process can be controlled to be between 10 r / min and 30 r / min, for example, 10 r / min, 11 r / min, 12 r / min, 13 r / min, 14 r / min, 15 r / min, 16 r / min, 17 r / min, 18 r / min, 19 r / min, 20 r / min, 21 r / min, 22 r / min, 23 r / min, 24 r / min, 25 r / min, 26 r / min, 27 r / min, 28 r / min, 29 r / min, 30 r / min, etc., or other values ​​within the range of 10 r / min to 30 r / min. In other embodiments, the coating time (i.e., mixing time) of the coating treatment is 1h to 4h, for example, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, or other values ​​within the range of 1h to 4h.

[0093] In some embodiments, the mass percentage of the coating agent in the mixture of pulverized material and coating agent can be controlled to be 3wt% to 15wt%, for example, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, 11wt%, 12wt%, 13wt%, 14wt%, 15wt%, etc., or other values ​​within the range of 3wt% to 15wt%. If the mass percentage of the coating agent in the mixture is too low, it is difficult to achieve the purpose of modifying the pulverized material, and the improvement effect on the rate performance and fast charging performance of the negative electrode material is not significant. If the mass percentage of the coating agent in the mixture is too high, since the coating agent is a soft carbon material with a lower degree of graphitization than the coke raw material, too much soft carbon coating agent will affect the degree of graphitization and capacity of the negative electrode material. Therefore, controlling the mass percentage of the coating agent in the mixture within the range of 3wt% to 15wt% is beneficial for achieving the fast charging function of the negative electrode material (e.g., 1.5C fast charging) and improving the rate performance of the negative electrode material, while also reducing the impact on the capacity of the negative electrode material.

[0094] In other embodiments, the coated material can be placed in a granulation device for the aforementioned granulation process, and the granulation speed of the granulation device can be controlled to be 10 r / min to 60 r / min, for example, 10 r / min, 15 r / min, 20 r / min, 25 r / min, 30 r / min, 35 r / min, 40 r / min, 45 r / min, 50 r / min, 55 r / min, 60 r / min, or other values ​​within the range of 10 r / min to 60 r / min. In some embodiments, the granulation device may include one or more of, for example, a vertical reactor, a horizontal reactor, or a continuous granulation reactor.

[0095] In some other embodiments, the granulation temperature can be 400℃ to 700℃, and the granulation time can be 4h to 10h. For example, the granulation temperature can be 400℃, 420℃, 450℃, 470℃, 500℃, 520℃, 550℃, 570℃, 600℃, 620℃, 650℃, 670℃, 700℃, etc., or other values ​​within the range of 400℃ to 700℃. The granulation time can be, for example, 4h, 4.5h, 5h, 5.5h, 6h, 6.5h, 7h, 7.5h, 8h, 8.5h, 9h, 9.5h, 10h, etc., or other values ​​within the range of 4h to 10h.

[0096] The above description, in conjunction with several accompanying drawings, details the negative electrode material and its preparation method according to embodiments of this application. It is understood that the above description is exemplary and not restrictive. For example, in some embodiments, the carbon precursor may not be limited to only pulverized material or carbon-coated material, but may also be a mixture of pulverized material and carbon-coated material.

[0097] In yet another aspect, this application provides a lithium-ion battery comprising the negative electrode material described in any one of the preceding first aspects of this application, or the material described in the foregoing combination. Figure 2 and Figure 3 The negative electrode material prepared by any of the described preparation methods. The lithium-ion battery embodiments of this application also include, for example... Figure 1 The electrode components shown, such as the positive electrode and the separator, will not be described in detail here.

[0098] Example:

[0099] To better understand the performance of the negative electrode material and its preparation method according to the embodiments of this application, specific examples will be described below. Several comparative examples are also provided below to further illustrate the advantages of the negative electrode material according to the embodiments of this application.

[0100] Example 1:

[0101] Step 1) Crush the coke raw material into a powder with a median volumetric particle size Dv50 of 14 μm and Dn10, Dn50 and Dn90 of 3.2 μm, 6.9 μm and 16.4 μm respectively.

[0102] Step 2) Place the crushed material in a tunnel kiln, introduce N2 as a protective gas, and carbonize it at a carbonization temperature of 1150℃ for 12 hours to obtain carbonized material, which is then cooled to room temperature for later use.

[0103] Step 3) Place the carbonized material in the sample vibration table and evacuate the magnetron sputtering furnace to a vacuum level of 2×10⁻⁶. -3 ~2×10 -5 At Pa, He gas was introduced at a flow rate of 25 sccm for a total duration of 140 min. Using silicon carbide powder with a Dv50 of 45 μm as the target, the sample vibration stage frequency was set to 20 Hz, the RF power supply was turned on, and the thermocouple was used for heating to begin magnetron sputtering. The sputtering power per unit target area was set to 60 W / cm². 2 The deposition time is 20 min; after the sample cools to room temperature, it is taken out, which is a silicon carbide coated material; compared with the carbonized material obtained in step 2), the total weight of the material after discharge in step 3) increases by 5 wt%, which means that the mass ratio (or mass proportion) of the silicon carbide coated layer in the silicon carbide material is considered to be 5 wt%.

[0104] Step 4) The silicon-carbon material obtained in Step 3) is graphitized at a temperature of 3000℃ for 48 hours. The graphitized product is then sieved and demagnetized to obtain the negative electrode material.

[0105] Example 2:

[0106] Step 1) Crush the coke raw material into a powder with a median volumetric particle size Dv50 of 14 μm and Dn10, Dn50 and Dn90 of 3.5 μm, 6.8 μm and 16.1 μm respectively.

[0107] Step 2) Place the crushed material in a tunnel kiln, introduce Ar as a protective gas, and perform carbonization treatment at a carbonization temperature of 1200℃ for 12 hours to obtain carbonized material, and then cool it to room temperature for later use.

[0108] Step 3) Place the carbonized material in the sample vibration table and evacuate the magnetron sputtering furnace to a vacuum level of 2×10⁻⁶. -3 ~2×10 -5At Pa, Ar gas was introduced at a flow rate of 25 sccm for a total duration of 180 min. Using silicon carbide powder with a Dv50 of 45 μm as the target, the sample vibration stage frequency was set to 30 Hz, the RF power supply was turned on, and the thermocouple was heated to begin magnetron sputtering. The sputtering power per unit target area was set to 60 W / cm². 2 The deposition time is 40 min; after the sample cools to room temperature, it is taken out and it is a silicon carbide coated material; compared with the carbonized material obtained in step 2), the total weight of the material after discharge in step 3) increases by 8 wt%, which means that the mass ratio (or mass proportion) of the silicon carbide coated layer in the silicon carbide material is considered to be 8 wt%.

[0109] Step 4) The silicon-carbon material obtained in Step 3) is graphitized at a temperature of 3000℃ for 48 hours. The graphitized product is then sieved and demagnetized to obtain the negative electrode material.

[0110] Example 3:

[0111] Step 1) Crush the coke raw material into a powder with a median volumetric particle size Dv50 of 14 μm and Dn10, Dn50 and Dn90 of 3.4 μm, 6.9 μm and 16.5 μm respectively.

[0112] Step 2) Place the crushed material in a tunnel kiln, introduce N2 as a protective gas, and carbonize it at a carbonization temperature of 1250℃ for 12 hours to obtain carbonized material, which is then cooled to room temperature for later use.

[0113] Step 3) Place the carbonized material in the sample vibration table and evacuate the magnetron sputtering furnace to a vacuum level of 2×10⁻⁶. -3 ~2×10 -5 At Pa, Ar gas was introduced at a flow rate of 40 sccm for a total duration of 220 min. Using silicon carbide powder with a Dv50 of 35 μm as the target, the sample vibration stage frequency was set to 30 Hz, the RF power supply was turned on, and the thermocouple was heated to begin magnetron sputtering. The sputtering power per unit target area was set to 60 W / cm². 2 The deposition time is 60 min; after the sample cools to room temperature, it is taken out and it is a silicon carbide coated material; compared with the carbonized material obtained in step 2), the total weight of the material after discharge in step 3) increases by 15 wt%, which means that the mass ratio (or mass proportion) of the silicon carbide coated layer in the silicon carbide material is considered to be 15 wt%.

[0114] Step 4) The silicon-carbon material obtained in Step 3) is graphitized at a temperature of 3000℃ for 48 hours. The graphitized product is then sieved and demagnetized to obtain the negative electrode material.

[0115] Example 4:

[0116] Step 1) Crush the coke raw material into a powder with a median volumetric particle size Dv50 of 7 μm and Dn10, Dn50 and Dn90 of 1.2 μm, 2.9 μm and 7.6 μm respectively.

[0117] Step 2) The pulverized material and medium-temperature asphalt powder with Dv50 = 5μm are mixed at a mass ratio of medium-temperature asphalt:coke raw material = 8:92. The mixture is carried out in a mixing device at a mixing speed of 20r / min for 2h. Then, the temperature is raised to 450℃ and stirred and granulated for 4h to obtain carbon-coated material.

[0118] Step 3) Place the carbon-coated material in a tunnel kiln, introduce N2 as a protective gas, and perform carbonization treatment at a carbonization temperature of 1150℃ for 8 hours to obtain carbonized material, and then cool it to room temperature for later use.

[0119] Step 4) Place the carbonized material in the sample vibration table and evacuate the magnetron sputtering furnace to a vacuum level of 2×10⁻⁶. -3 ~2×10 -5 At Pa, Ar gas was introduced at a flow rate of 60 sccm for a total duration of 300 min. Using silicon carbide powder with a Dv50 of 35 μm as the target, the sample vibration stage frequency was set to 20 Hz, the RF power supply was turned on, and the thermocouple was used for heating to begin magnetron sputtering. The sputtering power per unit target area was set to 60 W / cm². 2 The deposition time is 20 min; after the sample cools to room temperature, it is taken out, which is the silicon carbide coating material; compared with the carbonized material obtained in step 3), the total weight of the material after discharge in step 4) increases by 5 wt%, which means that the mass ratio (or mass proportion) of the silicon carbide coating in the silicon carbide material is considered to be 5 wt%.

[0120] Step 5) The silicon-carbon material obtained in Step 4) is graphitized at a temperature of 3000℃ for 36 hours. The graphitized product is then sieved and demagnetized to obtain the negative electrode material.

[0121] Example 5:

[0122] Step 1) Crush the coke raw material into a powder with a median volumetric particle size Dv50 of 7 μm and Dn10, Dn50 and Dn90 of 1.1 μm, 2.9 μm and 7.4 μm respectively.

[0123] Step 2) The pulverized material and phenolic resin powder with Dv50 = 5μm are mixed at a mass ratio of phenolic resin: coke raw material = 15:85. The mixture is mixed at a mixing speed of 30r / min in a mixing device for 2h. Then, the temperature is raised to 450℃ and stirred and granulated for 6h to obtain carbon-coated material.

[0124] Step 3) Place the carbon-coated material in a tunnel kiln, introduce N2 as a protective gas, and perform carbonization treatment at a carbonization temperature of 1150℃ for 48 hours to obtain carbonized material, and then cool it to room temperature for later use.

[0125] Step 4) Place the carbonized material in the sample vibration table and evacuate the magnetron sputtering furnace to a vacuum level of 2×10⁻⁶. -3 ~2×10 -5 At Pa, Ar gas was introduced at a flow rate of 80 sccm for a total duration of 380 min. Using silicon carbide powder with a Dv50 of 35 μm as the target, the sample vibration stage frequency was set to 20 Hz, the RF power supply was turned on, and the thermocouple was used for heating to begin magnetron sputtering. The sputtering power per unit target area was set to 60 W / cm². 2 The deposition time is 20 min; after the sample cools to room temperature, it is taken out, which is the silicon carbide coating material; compared with the carbonized material obtained in step 3), the total weight of the material after discharge in step 4) increases by 5 wt%, which means that the mass ratio (or mass proportion) of the silicon carbide coating in the silicon carbide material is considered to be 5 wt%.

[0126] Step 5) The silicon-carbon material obtained in Step 4) is graphitized at a temperature of 3000℃ for 24 hours. The graphitized product is then sieved and demagnetized to obtain the negative electrode material.

[0127] Example 6:

[0128] The only difference from Example 5 is that the deposition time in step 4) is 40 min, and the sputtering power per unit target area is set to 45 W / cm². 2 The silicon carbide coating layer in this silicon-carbon material accounts for 8 wt% of the total mass.

[0129] Example 7:

[0130] The difference from Example 5 is that: in step 2), the granulation auxiliary material used is polyimide, and the granulation temperature is 680°C; the mass percentage (or mass ratio) of the silicon carbide coating layer in this silicon-carbon material is 5 wt%.

[0131] Example 8:

[0132] The difference from Example 5 is that in step 2), the granulation auxiliary material used is polyimide, and the granulation temperature is 680℃; in step 4), the sputtering power per unit target area is set to 75W / cm². 2 The deposition time was 20 minutes, and the mass percentage (or mass ratio) of the silicon carbide coating in the silicon-carbon material was 6 wt%.

[0133] Example 9:

[0134] The difference from Example 5 is that in step 3), the carbonization temperature is 1350℃ and the carbonization time is 36h; in step 4), the sputtering power per unit target area is set to 75W / cm². 2 The deposition time was 15 minutes, and the graphitization temperature in step 5) was 2800℃. The mass percentage (or mass ratio) of the silicon carbide coating in this silicon-carbon material was 3 wt%.

[0135] Example 10:

[0136] The difference from Example 5 is that the graphitization time in step 5) is 72 hours, and the mass percentage (or mass ratio) of the silicon carbide coating layer in the silicon-carbon material is 5 wt%.

[0137] Example 11:

[0138] The difference from Example 3 is that in step 4), the sputtering power per unit target area is set to 45 W / cm². 2 The deposition time was 15 min, and the mass percentage (or mass ratio) of the silicon carbide coating in the silicon-carbon material was 2.5 wt%.

[0139] Comparative Example 1:

[0140] The only difference from Example 3 is that step 3) in Comparative Example 1 does not involve physical vapor deposition; instead, step 3) is replaced with the following operation:

[0141] The carbonized material and silicon carbide powder with Dv50 = 14μm were mixed in a solid phase at a mass ratio of 92:8 for 30 minutes. The resulting material is silicon carbide-coated silicon-carbon material.

[0142] Comparative Example 2:

[0143] Step 1) Crush the coke raw material into a powder with a median particle size Dv50 of 14μm.

[0144] Step 2) Place the crushed material in a tunnel kiln, introduce N2 as a protective gas, and carbonize it at a carbonization temperature of 1150℃ for 8 hours to obtain carbonized material, and then cool it to room temperature for later use.

[0145] Step 3) The carbonized material obtained in Step 2) is subjected to graphitization treatment at a temperature of 3000℃ for 24 hours. The graphitized product is then screened and demagnetized to obtain the negative electrode material.

[0146] Comparative Example 3:

[0147] Step 1) Crush the coke raw material into pulverized material with a median particle size Dv50 of 7μm.

[0148] Step 2) The pulverized material and phenolic resin powder with Dv50 = 7μm are mixed at a mass ratio of phenolic resin: coke raw material = 7:93. The mixture is mixed at a mixing speed of 10r / min in a mixing device for 2h. Then, the mixture is heated to a granulation temperature of 550℃ and stirred and granulated for 6h to obtain carbon-coated material.

[0149] Step 3) Place the carbon-coated material in a tunnel kiln, introduce N2 as a protective gas, and carbonize at 1150℃ for 36 hours to obtain the carbonized material. Then cool it to room temperature for later use. Mix the carbonized material with silicon carbide powder with Dv50 = 14μm at a mass ratio of 85:15 for 30 minutes. The resulting material is silicon carbide-coated silicon-carbon material.

[0150] Step 4) The carbonized material obtained in Step 3) is subjected to graphitization treatment at a temperature of 3000℃ for 24 hours. The graphitized product is then screened and demagnetized to obtain the negative electrode material.

[0151] Performance testing methods:

[0152] This application also conducted the following performance tests on the anode materials prepared in the above embodiments and comparative examples:

[0153] (1) Test method for particle size of negative electrode material:

[0154] The particle size distribution range of the negative electrode material was tested using a Malvern laser particle size analyzer (Mastersizer 3000). The cumulative particle size distribution based on volume was determined by laser diffraction. Dv10 represents the particle size corresponding to a cumulative particle size distribution volume percentage of 10%, Dv50 represents the particle size corresponding to a cumulative particle size distribution volume percentage of 50%, and Dv90 represents the particle size corresponding to a cumulative particle size distribution volume percentage of 90%. Dn10 represents the particle size corresponding to a cumulative particle size distribution number percentage of 50%, Dn50 represents the particle size corresponding to a cumulative particle size distribution number percentage of 50%, and Dn90 represents the particle size corresponding to a cumulative particle size distribution number percentage of 90%.

[0155] (2) Test method for tap density of negative electrode material:

[0156] Place the negative electrode material in the sample chamber of the tap density meter, vibrate it 1000 times, and record the sample volume at this time. The tap density can then be calculated according to the mass-volume ratio.

[0157] (3) Test method for specific surface area of ​​negative electrode material:

[0158] After measuring the amount of gas adsorbed on the solid surface at different relative pressures under constant temperature and low temperature, the amount of monolayer adsorption of the sample is obtained based on the Brownnor-Etter-Taylor adsorption theory and its formula (BET formula), thereby calculating the specific surface area of ​​the material.

[0159] (4) Test method for compaction density of negative electrode material:

[0160] The compaction density was tested according to the test method of GB / T 24533-2009 for graphite anode materials of lithium-ion batteries, with a test pressure of 5 tons.

[0161] (5) Test methods for average pore size and porosity:

[0162] Using the iPore620 pore size analyzer from Phyto-Chemistry, the pore size distribution data of the material was obtained through DFT simulation analysis using the isothermal adsorption characteristic curve of nitrogen, and then the average pore size and pore volume of the material were obtained.

[0163] (6) Test method for oil absorption value of negative electrode material:

[0164] The oil absorption value was tested using an ASAHI S-500 oil absorption value tester from ASAHISOUKEN, Japan. The oil absorption value is the amount of linseed oil added when the torque generated by the change in viscosity characteristics reaches 70% of the maximum torque, and the unit is mL / 100g.

[0165] (7) Raman test method:

[0166] The tests were conducted using an XPLORA laser confocal Raman spectrometer manufactured by HORIBA. Thirty data points were collected during the tests, and the test data were processed and analyzed using spectroscopic instrument software to obtain Raman values.

[0167] (8) Graphitization degree test method: The interlayer spacing d002 of the crystal structure of the negative electrode material is determined by XRD diffraction, and then the graphitization degree is obtained by using the Franklin formula G = (0.3440 - d002) / 0.0086 × 100%. X-ray diffraction can directly determine the interlayer spacing d002 of the crystal structure of the negative electrode material, and then substitute it into the formula to calculate the graphitization degree.

[0168] (9) Electrochemical performance testing method: The negative electrode materials prepared in each example and each comparative example were dissolved in deionized water at a mass ratio of 96.5:1.5:1, carboxymethyl cellulose and styrene-butadiene rubber, respectively, with the solid content controlled at 50%. The solutions were coated on copper foil current collectors, vacuum dried, and negative electrode sheets were obtained. A lithium metal sheet was used as the counter electrode, and the cells were assembled into coin cells in an argon-filled glove box. Charge and discharge tests were conducted at a current density of 0.1C, with a charge and discharge range of 0.01-1.5V. After 300 charge and discharge cycles, the initial reversible specific capacity (hereinafter referred to as initial capacity), the initial charge capacity, the initial discharge capacity, and the 300-cycle performance (i.e., the capacity retention rate after 300 cycles at 0.1C) were obtained. Initial coulombic efficiency (hereinafter referred to as initial efficiency) = initial discharge capacity / initial charge capacity. After completing the above tests, the charging current density is set to 2C, and a discharge lithium intercalation test is performed to obtain the rate performance under 2C conditions (i.e., the capacity retention rate of 2C rate discharge (lithium intercalation)).

[0169] To facilitate the description of the differences between the above embodiments and comparative examples, and the test results of each embodiment and comparative example, further explanation will be provided below with reference to Tables 1 and 2. Tables 1 and 2 respectively present the test results of the negative electrode material samples prepared in each embodiment and comparative example. Furthermore, Figure 4 A scanning electron microscope image of the negative electrode material prepared in Example 1 is shown. Figure 5 A scanning electron microscope image of the negative electrode material prepared in Comparative Example 2 is shown. Figure 6 A comparison diagram of the pore size distribution of the negative electrode materials prepared in Example 1 and Comparative Example 1 is shown.

[0170] Table 1:

[0171]

[0172]

[0173] Table 2:

[0174]

[0175] The data in Tables 1 and 2 above show that:

[0176] (1) As can be seen from Table 2, the comprehensive performance values ​​Y of the negative electrode material samples of Examples 1 to 11 are all between 15 and 90, while the comprehensive performance values ​​Y of Comparative Example 1 and Comparative Example 2 are all below 10. Furthermore, the cycle performance (i.e., capacity retention rate after 300 cycles at 0.1C), rate performance, degree of graphitization, initial capacity, and initial efficiency of the negative electrode materials of Examples 1 to 11 are all superior to those of Comparative Example 1 and Comparative Example 2. Therefore, compared with the silicon carbide coating method used in Comparative Example 1 and the preparation scheme without silicon carbide deposition or coating in Comparative Example 2, the negative electrode materials of the present application have superior comprehensive performance.

[0177] (2) As can be seen from Table 1, compared with Comparative Example 1 and Comparative Example 2, the Dn50 of Examples 1 to 11 is significantly increased, indicating that the amount of fine powder of the negative electrode material according to the embodiments of this application is significantly reduced.

[0178] (3) As can be seen from Table 1, compared with the negative electrode material in Comparative Example 2, the compaction density of Examples 1 to 11 is significantly improved, with an improvement of ≥2.1%.

[0179] (4) As can be seen from Table 2, compared with Comparative Examples 1 to 3, the graphitization degree and initial capacity of Examples 1 to 11 are improved, and the initial capacity of all examples reaches more than 350 mAh / g. This indicates that the step of silicon carbide deposition in the embodiments of this application is beneficial to improving the graphitization degree and capacity of the anode material. In particular, compared with Comparative Example 2, the initial capacity of Examples 1 to 11 can be increased by about 6 mAh / g to 13 mAh / g, with an improvement of more than 1.9%.

[0180] (5) As can be seen from Tables 1 and 2, compared with Comparative Examples 1 and 2, the average pore size and Z value of Examples 1 to 11 have increased significantly, the rate performance has been significantly improved, and the combination of Figure 6 As can be seen from the pore size distribution comparison diagram, the mesopore volume (pore size of 2nm to 50nm) of the negative electrode material in this application embodiment is significantly improved, which is beneficial to improving the rate performance of the negative electrode material.

[0181] (6) As can be seen from Table 2, the Raman D / G(A) value of the negative electrode material in Comparative Example 2 is less than 0.4, while the Raman D / G(A) values ​​of Examples 1 to 11 are all greater than 0.4. Furthermore, the first-time efficiency of Examples 1 to 11 is significantly higher than that of Comparative Example 2. Meanwhile, combined with... Figure 4 and Figure 5It can be seen that the surface of the negative electrode material in Example 1 is smoother than that in Comparative Example 2. This indicates that, compared to the negative electrode material prepared by the preparation method without silicon carbide deposition in Comparative Example 2, the use of physical vapor deposition to coat silicon carbide in this embodiment of the application is beneficial to making the surface of the negative electrode material smoother, reducing defects, and thus improving the first-efficiency performance of the negative electrode material.

[0182] (7) As can be seen from Table 2, compared with the negative electrode material in Comparative Example 2, the tap density of Examples 1 to 11 is significantly improved, with an improvement of ≥2.3%.

[0183] (8) As can be seen from Tables 1 and 2, the comprehensive performance value Y of the negative electrode material of Comparative Example 3 is greater than 90 and the Z value is greater than 30. Its Dn50 > 4.5 leads to the comprehensive performance value Y of the negative electrode material being greater than 90. Excessive Dn50 will reduce the rate performance and cycle performance of the negative electrode material. At the same time, the average pore size of Comparative Example 3 is greater than 60 nm and the porosity is greater than 28%, which is significantly greater than that of Examples 1 to 11. The higher porosity and average pore size lead to an increase in the specific surface area of ​​the negative electrode material, resulting in an increase in the number of lithium ions consumed when forming the SEI film. These lithium ions are irreversibly consumed in the formation process of the SEI film and cannot participate in the subsequent charge and discharge reaction, resulting in the battery's first coulombic efficiency being lower than that of Examples 1 to 11.

[0184] In summary, the embodiments of this application provide a negative electrode material with good overall performance, wherein its porosity X1, compaction density X2, oil absorption value X3, and number median particle size Dn50 satisfy the relationship: Y = 4 × X1 × X2 2 +e Dn50 With a value of -0.1×X3 and 15≤Y≤90, this anode material exhibits excellent performance in terms of capacity, cycle performance, rate performance, and processing performance, meeting the diverse performance requirements of batteries in practical applications.

[0185] This application also provides a method for preparing a negative electrode material. By using physical vapor deposition to deposit silicon carbide onto the surface of a carbon material, the catalytic effect is prolonged during high-temperature graphitization, and the graphitization transformation process is accelerated, thereby improving the degree of graphitization and capacity of the product. It also enhances the bonding between carbon material particles, thus reducing the amount of fine powder in the prepared negative electrode material. Therefore, the negative electrode material prepared based on the method of this application can improve various aspects of the negative electrode material's performance, enabling its comprehensive performance value Y to reach the range of 15 to 90.

[0186] While numerous embodiments of this application have been shown and described herein, it will be apparent to those skilled in the art that such embodiments are provided by way of example only. Many modifications, alterations, and alternatives will arise for those skilled in the art without departing from the spirit and intent of this application. It should be understood that various alternatives to the embodiments of this application described herein may be employed in the practice of this application. The appended claims are intended to define the scope of protection of this application and therefore cover equivalents or alternatives within the scope of these claims.

Claims

1. A negative electrode material, characterized in that, The porosity X1, compaction density X2, oil absorption value X3, and number median particle size Dn50 of the negative electrode material satisfy the following relationship: Y = 4 x X1x X2 2 + e Dn50 - 0.1 x X3, and 15 < Y < 90; Wherein, Y represents the comprehensive performance value of the negative electrode material characterized by X1, X2, X3 and Dn50.

2. The negative electrode material according to claim 1, characterized in that, The negative electrode material also satisfies at least one of the following: (1)10％≤X1≤28％； (2)1.8g / cm 3 ≤X2≤2.1g / cm 3 ; (3)31mL / 100g≤X3≤55mL / 100g; (4) 2.7μm≤Dn50≤4.5μm.

3. The negative electrode material according to claim 1, characterized in that, The negative electrode material also satisfies: 1.5≤(Dn90-Dn10) / Dn50≤2; Wherein, Dn90 represents the particle size corresponding to a cumulative particle size distribution percentage of 90%, and Dn10 represents the particle size corresponding to a cumulative particle size distribution percentage of 10%.

4. The negative electrode material according to claim 1, characterized in that, The negative electrode material also satisfies: And 10≤Z≤30; Wherein, Z represents the structural characterization index of the negative electrode material, A represents the average pore size of the negative electrode material, and B represents the specific surface area of ​​the negative electrode material.

5. The negative electrode material according to any one of claims 1-4, characterized in that, The negative electrode material also satisfies at least one of the following conditions: (1) The volume median particle size Dv50 of the negative electrode material is 5μm to 30μm; (2) The tap density of the negative electrode material is 0.9 g / cm³. 3 ~1.15g / cm 3 ; (3) The specific surface area of ​​the negative electrode material is 1m². 2 / g~4m 2 / g; (4) The average pore size of the negative electrode material is 20 nm to 60 nm; (5) In the Raman spectrum of the negative electrode material, the peak area ratio of the D peak to the G peak is 0.4 to 1.6; (6) The capacity of the negative electrode material is ≥350mAh / g.

6. The negative electrode material according to any one of claims 1-4, characterized in that, The negative electrode material includes carbon materials; the carbon materials include artificial graphite.

7. A method for preparing a negative electrode material, characterized in that, include: Carbon precursors are carbonized to obtain carbonized materials. Using silicon carbide powder as a target material, a physical vapor deposition method is used to deposit the silicon carbide material on the surface of the carbide material to obtain a silicon carbide coated material. The silicon-carbon material is graphitized to obtain the negative electrode material.

8. The preparation method according to claim 7, characterized in that, It also includes at least one of the following conditions: (1) The deposition time of the deposition treatment is controlled to be 5 min to 60 min; (2) The sputtering power per unit target area during the deposition process is controlled to be 45 W / cm². 2 ~75W / cm 2 ; (3) The deposition process is performed using a magnetron sputtering apparatus, and the vacuum level inside the magnetron sputtering apparatus is controlled to be 2 × 10⁻⁶. -3 Pa~2×10 -5 Pa; (4) The deposition process and / or the carbonization process are carried out in a protective gas atmosphere, wherein the protective gas includes one or more of nitrogen, helium, and argon; (5) The deposition process is carried out in a protective gas atmosphere, wherein the gas flow rate of the protective gas in the deposition process is 15 sccm to 80 sccm and the ventilation time is 100 min to 450 min; (6) The mass percentage of the silicon carbide coating layer in the silicon-carbon material is 2wt% to 18wt%; (7) The carbonization temperature of the carbonization process is controlled to be 600℃~1400℃ and the carbonization time is 8h~50h; (8) The graphitization temperature of the graphitization process is controlled to be 2800℃~3200℃, and the graphitization time is 24h~72h; (9) The carbon precursor includes pulverized coke raw material and / or carbon-coated material obtained by carbon coating treatment of the pulverized material.

9. The preparation method according to claim 8, characterized in that, When the carbon precursor comprises pulverized coke feedstock, the pulverized feedstock satisfies at least one of the following conditions: (1) The median particle size Dv50 of the pulverized material is 5μm to 30μm; (2) The median particle size Dn50 of the pulverized material is 2μm to 7μm; (3) 0.5 ≤ (Dn10 × Dn90) / Dn50 2 ≤4, where Dn90 represents the particle size corresponding to a cumulative particle size distribution percentage of 90%, Dn10 represents the particle size corresponding to a cumulative particle size distribution percentage of 10%, and Dn50 represents the median particle size of the pulverized material. (4) 1.5≤Dv50 / Dn50≤2.5; (5) The tapped density of the pulverized material is ≥0.55 g / cm³. 3 ; and / or When the carbon precursor includes the carbon-coated material, the preparation method further includes: subjecting the mixture of the pulverized material and the coating agent to coating and granulation treatment to obtain the carbon-coated material, and also satisfies at least one of the following conditions: (1) The mass percentage of the coating agent in the mixture is 3wt% to 15wt%; (2) The coating agent includes at least one of asphalt, phenolic resin, and polyimide; (3) The coating time of the coating treatment is 1h to 4h, and the mixing speed is 10r / min to 30r / min; (4) The granulation temperature of the granulation process is 400℃~700℃ and the granulation time is 4h~10h.

10. A lithium-ion battery, characterized in that, The lithium-ion battery includes the negative electrode material according to any one of claims 1-6 or the negative electrode material prepared by the preparation method according to any one of claims 7-9.

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