Silicon-based composite material and preparation method therefor, negative electrode sheet and lithium ion battery

Abstract

The present application belongs to the technical field of lithium ion battery negative electrode materials, and particularly relates to a silicon-based composite material and a preparation method therefor, a negative electrode sheet and a lithium ion battery. The silicon-based composite material comprises a silicon-based material and a composite binding agent coating the surface of the silicon-based material, the composite binding agent being a cross-linked polymer of a first polymer and a second polymer, the first polymer being selected from polyacrylates, and the second polymer being selected from at least one of polyvinyl alcohol, polymethylacrylic acid, carboxymethyl cellulose or polyaniline. In the silicon-based composite material provided by the present application, the surface of the silicon-based material is coated with the composite binding agent, on one hand, the inhibition effect on silicon expansion can be improved, and on the other hand, polyacrylic acid binding agents can directionally act on the silicon-based material, so as to reduce the content and costs of polyacrylic acid binding agents in negative electrode pastes, thus improving the processing performance of the negative electrode pastes while increasing the use amount of main materials, improving the energy density and prolonging the cycle life of lithium ion batteries.

Description

Silicon-based composite material, preparation method thereof, negative electrode sheet and lithium-ion battery

[0001] This application claims priority to the Chinese patent application filed with the Patent Office of China on March 21, 2024, with application number 202410330357.X and entitled “A silicon-based composite material, its preparation method, negative electrode sheet and lithium-ion battery”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application belongs to the technical field of negative electrode materials for lithium-ion batteries, and in particular relates to a silicon-based composite material and a preparation method thereof, a negative electrode sheet, and a lithium-ion battery. Background Art

[0003] Lithium-ion batteries have been widely used due to their high energy density, long cycle life, and environmental friendliness. Currently, graphite, the most commonly used negative electrode material in lithium-ion batteries, has a theoretical specific capacity of 372 mAh / g, limiting the development of lithium-ion batteries towards higher energy densities. Silicon, on the other hand, has a theoretical specific capacity of up to 4200 mAh / g and an actual specific capacity exceeding 3000 mAh / g. To increase the energy density of lithium-ion batteries, adding silicon to negative electrode materials is an industry trend.

[0004] However, the only drawback is that the silicon-based negative electrode has a high expansion rate and the traditional CMC / SBR has weak adhesion, which cannot bring out the performance advantages of the silicon-based negative electrode. Studies have shown that PAA (polyacrylic acid) binders have stronger adhesion, and silicon-based negative electrodes are more suitable for new PAA binders. At present, a high content of polyacrylic acid (PAA) binders needs to be added to the slurry of the silicon-based negative electrode system. On the one hand, the cost of this type of binder is significantly higher than that of the graphite system binder; on the other hand, because the polyacrylic acid binder in the slurry cannot act on the silicon material in a directionally, it is necessary to increase the content of polyacrylic acid binder in the entire electrode, resulting in a decrease in the proportion of the main material and a deterioration in the energy density; in addition, the content of polyacrylic acid binder increases with the increase of silicon content in the electrode, but the free carboxyl groups in the PAA binder are extremely hydrophilic and form hydrogen bonds, which will lead to deterioration of the processing performance of the high-silicon system slurry, and prone to problems such as coating bubbles and cracking, especially in thick-coated electrodes.

[0005] Therefore, it is of great significance to provide a new silicon-based material to reduce the expansion rate of silicon-based negative electrodes and improve their processing performance and cycle performance. Summary of the Invention

[0006] To address the above technical issues, this application provides a silicon-based composite material, a preparation method thereof, a negative electrode plate, and a lithium-ion battery. The silicon-based composite material provided in this application can effectively improve the processing performance of silicon-based negative electrode plates, reduce the plate expansion rate, and increase the energy density and cycle life of lithium-ion batteries.

[0007] In a first aspect, the present application provides a silicon-based composite material, which includes a silicon-based material and a composite binder coated on the surface of the silicon-based material, wherein the composite binder is a cross-linked polymer of a first polymer and a second polymer, wherein the first polymer is selected from polyacrylate, and the second polymer is selected from at least one of polyvinyl alcohol (PVA), polymethacrylic acid (PMA), carboxymethyl cellulose (CMC) or polyaniline (PANI).

[0008] The silicon-based composite material provided by this application, by coating the surface of the silicon-based material with a composite binder, can, on the one hand, enhance the inhibitory effect on silicon expansion, and on the other hand, enable the polyacrylic acid binder to act in a targeted manner on the silicon-based material, thereby reducing the content and cost of the polyacrylic acid binder in the negative electrode slurry, improving its processing performance, and at the same time increasing the amount of main materials used, thereby increasing the energy density and cycle life of lithium-ion batteries. Specifically:

[0009] The composite binder provided in the present application cross-links a second polymer on the basis of a polyacrylic acid binder, and can form a polymer network on the surface of a silicon-based material, increase the bonding points between the polyacrylic acid binder and the silicon-based material, thereby enhancing the inhibitory effect on silicon expansion. Moreover, the composite binder can act on the silicon-based material in a directionally directed manner, effectively reducing the amount of polyacrylic acid binder in the negative electrode slurry, solving processing problems such as high surface tension of the negative electrode slurry, high brittleness of the electrode, and easy cracking, thereby improving its processing performance and reducing costs. In addition, reducing the amount of polyacrylic acid binder in the negative electrode slurry can also reduce the hydrogen bonding effect between free carboxyl groups and water in the electrode, further improving the processing performance of the electrode, while increasing the main material content, and improving the energy density and cycle life of the lithium-ion battery.

[0010] As a preferred technical solution of the present application, the mass ratio of the first polymer to the silicon-based material is 0.5% to 0.8%:1, for example, 0.5%:1, 0.6%:1, 0.7%:1, 0.8%:1, etc.

[0011] As a preferred technical solution of the present application, the mass ratio of the first polymer to the second polymer is 0.33 to 2.01:1, for example, 0.33:1, 0.5:1, 1:1, 1.5:1, 2:1, 2.01:1, etc.

[0012] By limiting the mass ratio of the first polymer, the second polymer and the silicon-based material to within this range, the present application can effectively improve the inhibitory effect on silicon expansion, while reducing the amount of polyacrylic acid binder in the negative electrode slurry, effectively improving the processing performance of the electrode, and increasing the energy density and cycle life of the lithium-ion battery.

[0013] As a preferred technical solution of the present application, the polyacrylate includes at least one of sodium polyacrylate, lithium polyacrylate, calcium polyacrylate or magnesium polyacrylate.

[0014] The polyacrylate provided in the present application can form a cross-linked polymer composite binder with a second polymer through hydrogen bonding or covalent interaction, wherein the introduction of the second polymer can form a polymer network structure on the surface of the silicon-based material, increase the bonding points with the silicon-based material, and enhance the inhibitory effect on silicon expansion, while polyacrylic acid can act on the silicon-based material in a directionally manner, effectively reducing the amount of polyacrylic acid binder in the negative electrode slurry, improving processing performance, and at the same time increasing the amount of main material used, thereby improving the energy density and cycle life of the lithium-ion battery.

[0015] As a preferred technical solution of the present application, the silicon-based material includes a silicon-oxygen material and / or a silicon-carbon material. The silicon-oxygen material includes silicon dioxide, silicates, silicon-oxygen colloids, etc. The silicon-carbon material includes silicon carbide, silicon-carbon nanotubes, silicon-carbon films, silicon-carbon nanomaterials, etc.

[0016] In a second aspect, the present application provides a method for preparing the silicon-based composite material according to the first aspect, the preparation method comprising:

[0017] (1) mixing a silicon-based material and a first polymer solution, and drying the mixture to obtain a silicon-based material coated with the first polymer;

[0018] (2) The silicon-based material coated with the first polymer is mixed with the second polymer solution, dried, and kept warm to obtain the silicon-based composite material.

[0019] The preparation method of the silicon-based composite material provided in this application has a simple process and is suitable for mass production.

[0020] As a preferred technical solution of the present application, the insulation temperature is 100-150°C, for example, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, etc.

[0021] As a preferred technical solution of the present application, the insulation time is 1 to 3 hours, for example, 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, etc.

[0022] As a preferred technical solution of the present application, the heat preservation is carried out in a vacuum environment.

[0023] In step (2) of the present application, the temperature is kept at 100-150° C. after drying, so that the first polymer and the second polymer can fully react and cross-link to form a more stable polymer network, so that the prepared silicon-based composite material has more excellent performance.

[0024] The present application does not impose too many restrictions on the solvent in the first polymer solution. Any solvent that can dissolve the first polymer is applicable to the present application.

[0025] The present application does not impose too many restrictions on the solvent in the second polymer solution. Any solvent that can dissolve the second polymer is applicable to the present application.

[0026] The present application does not impose too many restrictions on the drying methods described in step (1) and step (2). As long as the drying method can achieve the purpose of the present application, it is applicable to the present application. For example, the drying method can be spray drying.

[0027] As a preferred technical solution of the present application, the mass ratio of the first polymer to the silicon-based material is 0.5% to 0.8%:1, for example, 0.5%:1, 0.6%:1, 0.7%:1, 0.8%:1, etc.

[0028] As a preferred technical solution of the present application, the mass ratio of the first polymer to the second polymer is 0.33 to 2.01:1, for example, 0.33:1, 0.5:1, 1:1, 1.5:1, 2:1, 2.01:1, etc.

[0029] By limiting the mass ratio of the silicon-based material, the first polymer, and the second polymer to the above-mentioned range, the present application can achieve excellent performance in the prepared silicon-based composite material. If the amount of the first polymer is too small, the amount of polyacrylic acid binder in the slurry needs to be increased, resulting in poor processing performance and a lower energy density of the prepared lithium-ion battery. If the amount of the first polymer is too large, it will lead to increased costs, and excessive first polymer will lead to a lower energy density of the lithium-ion battery. If the amount of the second polymer is too small, the degree of crosslinking is low and there are fewer bonding points with the silicon-based material, which cannot effectively improve the inhibitory effect on silicon expansion. If the amount of the second polymer is too large, it will lead to a lower energy density of the lithium-ion battery.

[0030] As a preferred technical solution of the present application, the polyacrylate includes at least one of sodium polyacrylate, lithium polyacrylate, calcium polyacrylate or magnesium polyacrylate.

[0031] As a preferred technical solution of the present application, the silicon-based material includes silicon-oxygen material and / or silicon-carbon material.

[0032] In a third aspect, the present application provides a negative electrode plate, which includes a negative electrode current collector and a negative electrode active material layer, and the negative electrode active material layer includes the silicon-based composite material described in the first aspect.

[0033] As a preferred technical solution of the present application, based on the total mass of the negative electrode active material layer as 100%, the content of the silicon-based composite material is 3% to 30%, for example, 3%, 5%, 10%, 15%, 20%, 25%, 30%, etc., preferably 3% to 25%, and more preferably 3% to 10%.

[0034] Since the silicon-based composite material provided in the present application contains a composite binder, the negative electrode active material layer of the negative electrode plate provided in the present application may not contain a polyacrylic acid binder, or may contain a small amount of a polyacrylic acid binder.

[0035] As a preferred technical solution of the present application, the negative electrode active material layer includes a polyacrylic acid binder. Based on the total mass of the negative electrode active material layer as 100%, the content of the polyacrylic acid binder is 0.01% to 0.3%, for example, 0.01%, 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, etc. To meet the energy density requirements of the battery cell, the amount of polyacrylic acid binder in the negative electrode slurry of the present application decreases accordingly as the amount of silicon-based material decreases.

[0036] A small amount of polyacrylic acid binder in the negative electrode active material layer can work together with the composite binder to form multi-point interactions between the composite binder and the surface of the silicon-based material, effectively preventing the detachment of silicon particles and further improving the cycle stability of the lithium-ion battery.

[0037] This application uses a pre-coating method to target the polyacrylic acid binder to the silicon-based material, effectively reducing the content and cost of this type of binder in the negative electrode slurry and effectively improving the cycling performance of lithium-ion batteries. If the content of polyacrylic acid binder in the negative electrode active material layer is too high, the battery's cycling performance will not be further improved, but will instead lead to poor processing performance and increased costs.

[0038] As a preferred technical solution of the present application, the preparation method of the negative electrode plate includes: mixing a silicon-based composite material, graphite, a conductive agent, a binder, a dispersant and a solvent to obtain a negative electrode slurry, applying it to at least one side of a current collector, drying and rolling to obtain the negative electrode plate.

[0039] The binder may be a polyacrylic acid binder or not according to actual conditions. The purpose of the roller pressing in this application is to adjust the negative electrode active material coated on the negative electrode sheet to have a suitable compaction density.

[0040] In a fourth aspect, the present application provides a lithium-ion battery, which includes the silicon-based composite material described in the first aspect or the negative electrode sheet described in the third aspect.

[0041] The lithium-ion battery provided in this application has a lower pole piece expansion rate and a prolonged cycle life.

[0042] The technical solution provided by the embodiments of the present application has the following advantages compared with the prior art:

[0043] The silicon-based composite material provided in the present application can, by coating the surface of the silicon-based material with a composite binder, on the one hand enhance the inhibitory effect on silicon expansion, and on the other hand enable the polyacrylic acid binder to act in a directional manner on the silicon-based material, thereby reducing the content and cost of the polyacrylic acid binder in the negative electrode slurry, improving its processing performance, and at the same time increasing the amount of main materials used, thereby increasing the energy density and cycle life of lithium-ion batteries. Specific embodiments

[0044] In order to more clearly understand the above-mentioned objectives, features and advantages of the present application, the scheme of the present application will be further described below. It should be noted that, in the absence of conflict, the embodiments of the present application and the features therein can be combined with each other.

[0045] In the following description, many specific details are set forth to facilitate a full understanding of the present application, but the present application can also be implemented in other ways different from those described herein; it is obvious that the embodiments in the specification are only part of the embodiments of the present application, not all of the embodiments.

[0046] Preparation Example 1

[0047] This preparation example provides a silicon-based composite material and a preparation method thereof, wherein the silicon-based composite material comprises SiO2 and a composite binder coated on the surface of the SiO2, wherein the composite binder is a cross-linked polymer of sodium polyacrylate and polyvinyl alcohol, wherein the mass ratio of sodium polyacrylate to SiO2 is 0.5%:1, and the mass ratio of sodium polyacrylate to polyvinyl alcohol is 1.78:1;

[0048] The preparation method comprises the following steps:

[0049] (1) mixing SiO2 with sodium polyacrylate solution, stirring evenly, and spray drying to obtain a polyacrylic acid-coated silicon-based material;

[0050] (2) The polyacrylic acid-coated silicon-based material is mixed with the polyvinyl alcohol solution, stirred evenly, spray-dried and kept warm at 120° C. for 2 h to obtain the silicon-based composite material, wherein the mass ratio of sodium polyacrylate to SiO2 is 0.5%:1, and the mass ratio of sodium polyacrylate to polyvinyl alcohol is 1.78:1.

[0051] Preparation Example 2

[0052] This preparation example provides a silicon-based composite material and a preparation method thereof, wherein the silicon-based composite material comprises SiC and a composite binder coated on the surface of the SiC, wherein the composite binder is a cross-linked polymer of magnesium polyacrylate and polymethacrylic acid, wherein the mass ratio of magnesium polyacrylate to SiC is 0.8%:1, and the mass ratio of magnesium polyacrylate to polymethacrylic acid is 1.84:1;

[0053] The preparation method comprises the following steps:

[0054] (1) mixing SiC with magnesium polyacrylate solution, stirring evenly, and spray drying to obtain a polyacrylic acid-coated silicon-based material;

[0055] (2) The polyacrylic acid-coated silicon-based material is mixed with the polymethacrylic acid solution, stirred evenly, spray-dried, and kept warm at 150° C. for 1 hour to obtain the silicon-based composite material, wherein the mass ratio of magnesium polyacrylate to SiC is 0.8%:1, and the mass ratio of magnesium polyacrylate to polymethacrylic acid is 1.84:1.

[0056] Preparation Example 3

[0057] This preparation example provides a silicon-based composite material and a preparation method thereof, wherein the silicon-based composite material comprises SiO2 and a composite binder coated on the surface of the SiO2, wherein the composite binder is a cross-linked polymer of calcium polyacrylate and carboxymethyl cellulose, wherein the mass ratio of calcium polyacrylate to SiO2 is 0.7%:1, and the mass ratio of calcium polyacrylate to carboxymethyl cellulose is 2.01:1;

[0058] The preparation method comprises the following steps:

[0059] (1) mixing SiO2 with calcium polyacrylate solution, stirring evenly, and spray drying to obtain a polyacrylic acid-coated silicon-based material;

[0060] (2) The polyacrylic acid-coated silicon-based material is mixed with a carboxymethyl cellulose solution, stirred evenly, spray-dried, and kept warm at 100° C. for 3 h to obtain the silicon-based composite material, wherein the mass ratio of calcium polyacrylate to SiO2 is 0.7%:1, and the mass ratio of calcium polyacrylate to carboxymethyl cellulose is 2.01:1.

[0061] Preparation Example 4

[0062] This preparation example provides a silicon-based composite material and a preparation method thereof. The preparation method is the same as that of Preparation Example 1, except that the mass ratio of sodium polyacrylate to SiO2 in this preparation example is 0.8%:1.

[0063] Preparation Example 5

[0064] This preparation example provides a silicon-based composite material and a preparation method thereof. The preparation method is the same as that of Preparation Example 1, except that the mass ratio of sodium polyacrylate to polyvinyl alcohol in this preparation example is 0.33:1.

[0065] Preparation Example 6

[0066] This preparation example provides a silicon-based composite material and a preparation method thereof. The preparation method is the same as that of Preparation Example 4, except that the mass ratio of sodium polyacrylate to SiO2 in this preparation example is 0.3%:1.

[0067] Preparation Example 7

[0068] This preparation example provides a silicon-based composite material and a preparation method thereof. The preparation method is the same as that of Preparation Example 4, except that the mass ratio of sodium polyacrylate to SiO2 in this preparation example is 1%:1.

[0069] Preparation Example 8

[0070] This preparation example provides a silicon-based composite material and a preparation method thereof. The preparation method is the same as that of Preparation Example 4, except that the mass ratio of sodium polyacrylate to polyvinyl alcohol in this preparation example is 5.93:1.

[0071] Preparation Example 9

[0072] This preparation example provides a silicon-based composite material and a preparation method thereof. The preparation method is the same as that of Preparation Example 4, except that the mass ratio of sodium polyacrylate to polyvinyl alcohol in this preparation example is 0.2:1.

[0073] Examples 1-11

[0074] This embodiment provides a negative electrode sheet, a lithium-ion battery, and a preparation method thereof, wherein the preparation method comprises the following steps:

[0075] (1) Preparation of negative electrode sheet: The silicon-based composite material obtained in the preparation example is mixed according to the ratio of each material: graphite: carbon black (SP): single-walled carbon nanotube (SWCNT): PAA: styrene-butadiene rubber (SBR): dispersant (CMC) = 9.63%: 86.69%: 1.2%: 0.08%: 1.65%: 0.55%: 0.2% to obtain a negative electrode slurry, which is applied to both sides of the current collector, dried, and roll-pressed to obtain the negative electrode sheet;

[0076] (2) Preparation of positive electrode sheet: NCM811, Super-P, and polyvinylidene fluoride (PVDF) are mixed in a weight ratio of 8:1:1, and an appropriate amount of N-methyl-2-pyrrolidone (NMP) is added thereto to form a uniform slurry. The slurry is uniformly and evenly applied to both sides of the aluminum foil, dried, and rolled to obtain a positive electrode sheet;

[0077] (3) Electrolyte: Silicon-based electrolyte containing 5% FEC;

[0078] (4) Assembly: After cutting the positive and negative electrode sheets, stack them with the separator to assemble into a 2Ah battery cell.

[0079] The silicon-based composite material, the amount of binder in the negative electrode slurry, the coating rate, etc. corresponding to each embodiment are shown in Table 1.

[0080] Comparative Example 1-2

[0081] This comparative example provides a negative electrode sheet, a lithium-ion battery, and a preparation method thereof. Steps (2), (3), and (4) in the preparation method are the same as those in Example 1. The difference from Example 1 is that the silicon-based material used in step (1) in this comparative example is SiO2, and the content of the PAA binder in the slurry is different, as shown in Table 1.

[0082] Performance Testing

[0083] (1) The thickness of the negative electrode sheets obtained in the examples and comparative examples was measured after rolling, and the sheets were fully charged and disassembled after formation to measure the thickness of the sheets and calculate the full charge expansion rate. The results are shown in Table 1.

[0084] (2) The lithium-ion batteries obtained in the examples and comparative examples were subjected to a 1C / 1C charge-discharge cycle test at 25°C. The test results are shown in Table 1.

[0085] The types, amounts and test results of the raw materials in the examples and comparative examples are shown in Table 1:

[0086] Table 1

[0087] From the comparison between Example 1 and Example 4, it can be found that as the amount of PAA binder in the silicon-based composite material increases, the amount of PAA binder used in the negative electrode slurry also increases, and the cycle performance of the prepared lithium-ion battery is better;

[0088] From the comparison between Example 4 and Examples 6-7, it can be found that when the amount of the first polymer polyacrylic acid is too small, it cannot effectively increase the bonding points with the silicon-based material and cannot significantly inhibit the expansion of silicon, resulting in poor cycle performance; when the amount of the first polymer polyacrylic acid is too large, it will lead to poor cycle performance and increased costs.

[0089] From the comparison between Example 4 and Examples 8 to 9, it can be found that when the mass ratio of the first polymer to the second polymer is too large or too small, the cycle performance will deteriorate;

[0090] From the comparison of Examples 4, 10, and 11, it can be found that when the amount of PAA binder in the negative electrode slurry is within 0.3%, as the amount of PAA binder in the negative electrode slurry increases, the cycle performance of the lithium-ion battery improves. When the amount of PAA binder in the negative electrode slurry is too high, the battery cycle performance will not be significantly enhanced.

[0091] From the comparison between Example 1 and Comparative Examples 1-2, it can be found that when the silicon-based material is not coated and modified, the amount of PAA binder in the negative electrode slurry is above 2%, which is relatively high, and the cycle performance of the prepared lithium-ion battery is relatively poor.

[0092] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or device comprising the element.

[0093] The foregoing description is intended only to provide specific embodiments of the present application, which will enable those skilled in the art to understand and implement the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application is not limited to the embodiments described herein, but is intended to be construed in the broadest manner consistent with the principles and novel features disclosed herein.

Claims

1. A silicon-based composite material, wherein: The silicon-based composite material includes a silicon-based material and a composite binder coated on the surface of the silicon-based material, wherein the composite binder is a cross-linked polymer of a first polymer and a second polymer, wherein the first polymer is selected from polyacrylate, and the second polymer is selected from at least one of polyvinyl alcohol, polymethacrylic acid, carboxymethyl cellulose or polyaniline.

2. The silicon-based composite material according to claim 1, wherein The mass ratio of the first polymer to the silicon-based material is 0.5% to 0.8%:1; And / or, the mass ratio of the first polymer to the second polymer is 0.33 to 2.01:

1.

3. The silicon-based composite material according to claim 1 or 2, wherein: The polyacrylate comprises at least one of sodium polyacrylate, lithium polyacrylate, calcium polyacrylate or magnesium polyacrylate; And / or, the silicon-based material includes silicon-oxygen material and / or silicon-carbon material.

4. The method for preparing the silicon-based composite material according to any one of claims 1 to 3, wherein: The preparation method comprises: (1) mixing a silicon-based material and a first polymer solution, and drying the mixture to obtain a silicon-based material coated with the first polymer; (2) The silicon-based material coated with the first polymer is mixed with the second polymer solution, dried, and kept warm to obtain the silicon-based composite material.

5. The preparation method according to claim 4, wherein The insulation temperature is 100-150°C; And / or, the insulation time is 1 to 3 hours; And / or, the heat preservation is performed under a vacuum environment.

6. The preparation method according to claim 4, wherein The mass ratio of the first polymer to the silicon-based material is 0.5% to 0.8%:1; And / or, the mass ratio of the first polymer to the second polymer is 0.33 to 2.01:

1.

7. The preparation method according to claim 4, wherein The polyacrylate comprises at least one of sodium polyacrylate, lithium polyacrylate, calcium polyacrylate or magnesium polyacrylate; And / or, the silicon-based material includes silicon-oxygen material and / or silicon-carbon material.

8. A negative electrode sheet, wherein: The negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer, and the negative electrode active material layer comprises the silicon-based composite material according to any one of claims 1 to 3.

9. The negative electrode sheet according to claim 8, wherein: Based on the total mass of the negative electrode active material layer being 100%, the content of the silicon-based composite material is 3% to 30%; And / or, the negative electrode active material layer includes a polyacrylic acid binder, and based on the total mass of the negative electrode active material layer being 100%, the content of the polyacrylic acid binder is 0.01% to 0.3%.

10. A lithium-ion battery, wherein: The lithium-ion battery comprises the silicon-based composite material according to any one of claims 1 to 3 or the negative electrode sheet according to claim 8 or 9.

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