Negative electrode sheet, method for producing negative electrode sheet, electrochemical device, and vehicle

Abstract

The application discloses a negative electrode sheet, a preparation method of the negative electrode sheet, an electrochemical device and a vehicle. The negative electrode sheet comprises a negative electrode current collector and an active coating. The active coating comprises an active material, a conductive agent, a first binder and a second binder. The first binder and the second binder are both polyacrylic binders. The tensile elongation at break of the first binder is less than 10%, and the tensile elongation at break of the second binder is 30%-70%. The negative electrode sheet provided by the application has the advantages of good processability and good power performance.

Description

Technical Field

[0001] This invention relates to the field of battery technology, specifically to a negative electrode, a method for preparing the negative electrode, an electrochemical device, and a vehicle. Background Technology

[0002] Lithium-ion batteries have advantages such as high energy density, high operating voltage, and low self-discharge, and are widely used in consumer electronics, electric vehicles, and energy storage. As new energy sources replace traditional energy sources, higher demands are being placed on the energy density, power density, safety performance, and cost of lithium batteries.

[0003] The four main materials of a lithium-ion battery include the positive electrode, negative electrode, electrolyte, and separator. The negative electrode active material is generally graphite. During the processing of the negative electrode activation layer, binders are typically a combination of CMC (sodium carboxymethyl cellulose) and SBR (styrene-butadiene rubber). In silicon-doped negative electrode systems, a linear polymer, PAA (polyacrylic acid binder), is also introduced. PAA exhibits better low-temperature performance than the SBR+CMC system and can better suppress the expansion of silicon materials. However, the flexibility and processability of PAA-based electrodes are relatively poor, limiting their use to achieve better power performance in the battery cell. Therefore, providing a negative electrode that combines excellent power performance and flexibility is a pressing issue. Summary of the Invention

[0004] The present invention aims to at least partially solve one of the technical problems in the related art.

[0005] Therefore, embodiments of the present invention provide a negative electrode sheet that has the advantages of good processability and good power performance.

[0006] Embodiments of the present invention also provide a method for preparing a negative electrode, an electrochemical device, and a vehicle.

[0007] The negative electrode sheet of this invention includes a negative current collector and an active coating. The active coating includes an active material, a conductive agent, a first binder, and a second binder. Both the first binder and the second binder are polyacrylic binders. The tensile elongation at break of the first binder is less than 10%, and the tensile elongation at break of the second binder is 30%-70%.

[0008] According to embodiments of the present invention, the negative electrode sheet uses polyacrylic acid binders as the first and second binders in the active coating. The first binder has a tensile elongation at break of less than 10%, and the second binder has a tensile elongation at break of 30%-70%, resulting in different levels of flexibility between the first and second binders. This combination of first and second binders with varying flexibility ensures adhesion between the active coating and the negative electrode current collector while effectively improving the hardness and brittleness of the negative electrode sheet, thus enhancing its processability. Furthermore, the excellent low-temperature performance of the first and second binders themselves contributes to the improved dynamic performance of the negative electrode sheet.

[0009] In some embodiments, the weight of the first adhesive accounts for 65%-80% of the total weight of the first adhesive and the second adhesive.

[0010] In some embodiments, the first binder comprises an olefinic unsaturated carboxylic acid monomer, and further comprises at least one of an aliphatic conjugated diene monomer, an aliphatic vinyl monomer, an aromatic vinyl monomer, a cyanide monomer, a hydroxyalkyl-containing unsaturated monomer, and an unsaturated amide monomer.

[0011] In some embodiments, the molar ratio of olefinic unsaturated carboxylic acid monomers in the first adhesive is 30%-50%.

[0012] In some embodiments, the second binder comprises olefinic unsaturated carboxylic acid monomers and acrylate monomers, and further comprises at least one of aliphatic conjugated diene monomers, aliphatic vinyl monomers, aromatic vinyl monomers, cyanide monomers, hydroxyalkyl-containing unsaturated monomers, and unsaturated amide monomers.

[0013] In some embodiments, the molar ratio of olefinic unsaturated carboxylic acid monomers in the second adhesive is 50%-70%, and the molar ratio of acrylate monomers is 20%-30%.

[0014] In some embodiments, the first adhesive or the second adhesive comprises at least one of lithium unsaturated carboxylate, sodium unsaturated carboxylate, and potassium unsaturated carboxylate.

[0015] The method for preparing a negative electrode sheet according to embodiments of the present invention is used to prepare a negative electrode sheet as described in any of the above embodiments, wherein the negative electrode sheet further includes a negative electrode binder and carbon nanotubes, and the negative electrode binder includes CMC-Na or CMC-Li, and the preparation method includes:

[0016] The active material, conductive agent, first binder, second binder, negative electrode binder and carbon nanotubes are mixed in deionized water at a weight ratio of 95.1:1:x:3.5-x:0.3:0.1 and stirred evenly to form an active coating.

[0017] An active coating is applied to the negative electrode current collector, and the negative electrode sheet is prepared by cold pressing, cutting, and slitting.

[0018] According to the method for preparing the negative electrode sheet of the present invention, by using a first binder and a second binder, the adhesion between the active coating and the negative electrode current collector is ensured, while the formed negative electrode sheet has better flexibility and thus better processability. Simultaneously, based on the good low-temperature performance of the first and second binders themselves, the negative electrode sheet exhibits better dynamic performance.

[0019] In some embodiments, the active material comprises artificial graphite and silicon oxide, wherein the weight ratio of artificial graphite to silicon oxide is 9:1.

[0020] And / or, the conductive agent includes conductive carbon;

[0021] And / or, the negative current collector comprises copper foil.

[0022] An electrochemical device according to an embodiment of the present invention includes a positive electrode, a separator, and a negative electrode as described in any of the above embodiments, wherein the positive electrode, the separator, and the negative electrode are stacked sequentially.

[0023] The technical advantages of the electrochemical device according to the embodiments of the present invention are the same as the technical advantages of the negative electrode sheet in the above embodiments, and will not be repeated here.

[0024] The vehicle according to an embodiment of the present invention includes an electrochemical device as described in the above embodiments.

[0025] The technical advantages of the vehicle according to the embodiments of the present invention are the same as those of the electrochemical device in the above embodiments, and will not be repeated here. Attached Figure Description

[0026] Figure 1 This is a cross-sectional view of the negative electrode sheet according to an embodiment of the present invention.

[0027] Figure label:

[0028] 100. Negative electrode sheet; 1. Negative current collector; 2. Active coating. Detailed Implementation

[0029] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0030] The following is combined with Figure 1 A negative electrode 100 according to an embodiment of the present invention is described.

[0031] The negative electrode sheet 100 of this invention includes a negative electrode current collector 1 and an active coating 2. The active coating 2 includes an active material, a conductive agent, a first binder and a second binder. Both the first binder and the second binder are polyacrylic binders. The tensile elongation at break of the first binder is less than 10%, and the tensile elongation at break of the second binder is 30%-70%.

[0032] According to an embodiment of the present invention, the negative electrode 100 uses polyacrylic acid binders as the first and second binders in the active coating 2. The first binder has a tensile elongation at break of less than 10%, and the second binder has a tensile elongation at break of 30%-70%, giving the first and second binders different flexibility. By using the first and second binders with different flexibility in combination, the adhesion between the active coating 2 and the negative electrode current collector 1 can be ensured while significantly improving the hardness and brittleness of the negative electrode, thus resulting in better processability. Furthermore, based on the good low-temperature performance of the first and second binders themselves, the negative electrode 100 exhibits better dynamic performance.

[0033] It should be noted that both the first adhesive and the second adhesive are polyacrylic adhesives, meaning that both the first adhesive and the second adhesive contain polyacrylic acid. The tensile elongation at break of the first adhesive can be 5%, 7%, and 10%, and the tensile elongation at break of the second adhesive can be 30%, 50%, and 70%.

[0034] In some embodiments, the weight of the first adhesive accounts for 65%-80% of the total weight of the first adhesive and the second adhesive.

[0035] That is, the weight ratio of the first binder to the second binder is between 13 / 7 and 4. Under this ratio, the negative electrode sheet 100 formed thereby has better dynamic performance, as well as better flexibility and processability compared with the negative electrode sheet using SBR as a binder in related technologies.

[0036] Specifically, the weight of the first adhesive can account for 65%, 70%, 75%, and 80% of the total weight of the first and second adhesives.

[0037] In some embodiments, the first binder comprises an olefinic unsaturated carboxylic acid monomer, and further comprises at least one of an aliphatic conjugated diene monomer, an aliphatic vinyl monomer, an aromatic vinyl monomer, a cyanide monomer, a hydroxyalkyl-containing unsaturated monomer, and an unsaturated amide monomer.

[0038] The first binder, by containing olefinically unsaturated carboxylic acid monomers, has good low-temperature performance and can effectively suppress the expansion of silicon materials, so that the negative electrode 100 has good dynamic performance.

[0039] Specifically, the first binder comprises an olefinically unsaturated carboxylic acid monomer, an aliphatic conjugated diene monomer, and an aliphatic vinyl monomer. Alternatively, the first binder comprises an olefinically unsaturated carboxylic acid monomer, an aromatic vinyl monomer, a cyanide monomer, a hydroxyl-containing unsaturated monomer, and an unsaturated amide monomer. Or, the first binder comprises an olefinically unsaturated carboxylic acid monomer, an aliphatic conjugated diene monomer, an aliphatic vinyl monomer, an aromatic vinyl monomer, a cyanide monomer, a hydroxyl-containing unsaturated monomer, and an unsaturated amide monomer.

[0040] In some embodiments, the molar ratio of olefinic unsaturated carboxylic acid monomers in the first binder is 30%-50%.

[0041] The first binder containing the above-mentioned proportion of olefinic unsaturated carboxylic acid monomers ensures good bonding performance, while also exhibiting better low-temperature performance and a better effect on suppressing the expansion of silicon materials, thereby resulting in better dynamic performance of the negative electrode 100.

[0042] Specifically, the molar ratio of olefinic unsaturated carboxylic acid monomers in the first binder can be 30%, 40%, and 50%.

[0043] In some embodiments, the second binder comprises an olefinic unsaturated carboxylic acid monomer and an acrylate monomer, and further comprises at least one of an aliphatic conjugated diene monomer, an aliphatic vinyl monomer, an aromatic vinyl monomer, a cyanide monomer, a hydroxyalkyl-containing unsaturated monomer, and an unsaturated amide monomer.

[0044] The second binder, by comprising olefinically unsaturated carboxylic acid monomers and acrylate monomers, exhibits excellent low-temperature performance and effectively suppresses the expansion of silicon materials, thereby enabling the negative electrode 100 to possess good dynamic performance. Simultaneously, the inclusion of acrylate monomers allows the second binder to have a higher elongation at break, effectively improving the hardness and brittleness of the negative electrode 100 and thus enhancing its processability.

[0045] Specifically, the second binder includes olefinically unsaturated carboxylic acid monomers, acrylate monomers, aliphatic conjugated diene monomers, and aliphatic vinyl monomers. Alternatively, the second binder includes olefinically unsaturated carboxylic acid monomers, acrylate monomers, aromatic vinyl monomers, vinyl cyanide monomers, hydroxyl-containing unsaturated monomers, and unsaturated amide monomers. Alternatively, the second binder includes olefinically unsaturated carboxylic acid monomers, acrylate monomers, aliphatic conjugated diene monomers, aliphatic vinyl monomers, aromatic vinyl monomers, vinyl cyanide monomers, hydroxyl-containing unsaturated monomers, and unsaturated amide monomers.

[0046] In some embodiments, the molar ratio of olefinic unsaturated carboxylic acid monomers in the second binder is 50%-70%, and the molar ratio of acrylate monomers is 20%-30%.

[0047] The second binder containing the aforementioned proportion of olefinically unsaturated carboxylic acid monomers ensures good bonding performance while also exhibiting better low-temperature performance and a better suppression effect on the expansion of silicon materials, thereby resulting in better dynamic performance of the negative electrode 100. The second binder containing the aforementioned proportion of acrylate monomers ensures good tensile elongation at break, thereby giving the negative electrode 100 better processability.

[0048] Specifically, in the second binder, the molar ratio of olefinic unsaturated carboxylic acid monomers is 50%, and the molar ratio of acrylate monomers is 20%. Alternatively, in the second binder, the molar ratio of olefinic unsaturated carboxylic acid monomers is 60%, and the molar ratio of acrylate monomers is 25%. Alternatively, in the second binder, the molar ratio of olefinic unsaturated carboxylic acid monomers is 70%, and the molar ratio of acrylate monomers is 30%.

[0049] It should be noted that the first binder or the second binder comprises at least one of lithium unsaturated carboxylate, sodium unsaturated carboxylate, and potassium unsaturated carboxylate. For example, both the first binder and the second binder comprise an olefinically unsaturated carboxylic acid monomer, which comprises any one of lithium unsaturated carboxylate, sodium unsaturated carboxylate, and potassium unsaturated carboxylate.

[0050] According to the method for preparing a negative electrode sheet according to an embodiment of the present invention, a negative electrode sheet 100 as described in any of the above embodiments is prepared. The negative electrode sheet 100 further includes a negative electrode binder and carbon nanotubes. The negative electrode binder includes CMC-Na or CMC-Li. The preparation method includes: mixing active material, conductive agent, first binder, second binder, negative electrode binder and carbon nanotubes in deionized water at a weight ratio of 95.1:1:x:3.5-x:0.3:0.1, stirring evenly to form an active coating 2; coating the active coating 2 onto the negative electrode current collector 1, and preparing the negative electrode sheet 100 by cold pressing, cutting and slitting.

[0051] According to the method for preparing the negative electrode sheet of the present invention, by using a first binder and a second binder to prepare the negative electrode sheet 100, the adhesion between the active coating 2 and the negative electrode current collector 1 is ensured, while the formed negative electrode sheet 100 has better flexibility and thus better processability. At the same time, based on the good low-temperature performance of the first and second binders themselves, the negative electrode sheet 100 has better dynamic performance.

[0052] It should be noted that the negative electrode binder is used not only as a binder but also as a dispersant and thickener. The active materials include artificial graphite and silicon oxide, with a weight ratio of 9:1. The conductive agent includes conductive carbon. The negative electrode current collector 1 includes copper foil.

[0053] To facilitate understanding of the effect of the negative electrode 100 in the embodiments of the present invention, the inventors of the present invention conducted the following comparative experiments:

[0054] Example:

[0055] (1) Preparation of negative electrode 100

[0056] Artificial graphite / silicon oxide = 9:1, conductive carbon (SP), first binder, second binder, CMC-Na / CMC-Li, and carbon nanotubes are mixed in deionized water at a weight ratio of 95.1:1:x:3.5-x:0.3:0.1 and stirred evenly to form an active coating 2. Copper foil is used as the negative electrode current collector 1, and the active coating 2 is coated on the copper foil. Then, cold pressing, cutting and slitting are performed to prepare the negative electrode sheet 100.

[0057] (2) Preparation of positive electrode

[0058] NCM523, conductive carbon (SP), and PVDF were mixed in the solvent N-methylpyrrolidone at a weight ratio of approximately 96:2:2 and stirred until homogeneous to obtain a positive electrode slurry. Then, aluminum foil was used as the positive electrode current collector, and the positive electrode current collector coated with the slurry was baked at 120°C for 1 hour. Subsequently, it was cold-pressed, cut, and slit to prepare the positive electrode sheet.

[0059] (3) Assemble bare battery cells

[0060] The positive electrode, separator, negative electrode 100, and four layers of separator are stacked in sequence, with the separator positioned between the positive and negative electrode 100 to provide isolation. Then, the cells are wound up, and tape is applied at the winding point to obtain the bare cell.

[0061] (4) Preparation of electrolyte

[0062] In an argon atmosphere, ethylene carbonate / ethyl methyl carbonate (3:7) is mixed and then lithium hexafluorophosphate is added at a concentration of 1.0 mol / L to obtain an electrolyte.

[0063] (5) Assemble lithium-ion batteries

[0064] The bare battery cell is placed into an aluminum shell, dried at 100°C, and then injected with the prepared electrolyte. After vacuum sealing, settling, formation, and shaping, the lithium-ion battery is completed.

[0065] (6) Test DCR performance after assembling the battery

[0066] Test procedure: (1) Stand at 25℃ for 60 min; (2) Charge at 25℃ with 1C constant current to 4.3V, and charge at 0.05C constant voltage; (3) Stand at 25℃ for 5 min; (4) Discharge at 25℃ with 1C constant current to 50% SOC; (5) Stand at 25℃ for 60 min, and record the end voltage U1; (6) Discharge at 25℃ with 4C constant current for 10 s, and record the end voltage U2; Wherein, DCR (power performance) = (U2-U1) / 4C.

[0067] (7) The flexibility of the cold-pressed negative electrode 100 is tested by the needle winding method. By observing the surface state of the negative electrode 100 under different curvature radii, the flexibility of the negative electrode 100 is evaluated. The smaller the curvature radius of the crack, the softer the negative electrode 100 is and the better its processability.

[0068] Comparative example:

[0069] (1) Preparation of negative electrode

[0070] Artificial graphite / silicon oxide = 9:1, conductive carbon (SP), SBR, CMC-Na / CMC-Li, and carbon nanotubes were mixed in deionized water at a weight ratio of 95.1:1:2.3:1.5:0.1 and stirred evenly to form an active coating. Copper foil was used as the negative electrode current collector, and the active coating was coated on the copper foil. Then, the negative electrode sheet was prepared by cold pressing, cutting and slitting.

[0071] (2) Other aspects are the same as in the embodiments.

[0072] Anode 100 Adhesion Test: Take the cold-pressed anode sheet and cut it into a rectangle of 150mm*20mm. Take a 25mm wide stainless steel plate, apply 21mm wide double-sided tape, and attach the cut electrode sheet to the double-sided tape on the stainless steel plate. Roll it back and forth 3 times with a pressure roller. Fix the prepared sample on a universal tensile testing machine, clamp the stainless steel plate below the testing machine, and clamp the electrode sheet above. Test at 100mm / min, and perform a 180-degree peel force test to peel the activated coating from the anode current collector 1. Take the average value after stabilization as the peel force F. The adhesion force of anode 100 F1 = F / 0.02.

[0073] In the preparation of the negative electrode 100 in the above embodiment, nine sets of experiments were conducted according to the parameters shown in Table 1 below: X value, ratio of the first binder to the second binder, tensile elongation at break of the first binder, and tensile elongation at break of the second binder. At the same time, one set of experiments was conducted on the negative electrode 100 of the comparative example. The data in Table 1 are as follows:

[0074]

[0075]

[0076] As shown in Table 1, in Example 4, when the ratio of the first binder to the second binder in the negative electrode 100 is 60:40, the peel force of the negative electrode 100 is relatively small, indicating poor adhesion between the first and second binders. In Example 5, when the ratio of the first binder to the second binder in the negative electrode 100 is 85:15, the negative electrode 100 exhibits poor flexibility and poor processability. In Example 8, when the elongation at break of the second binder is 20%, the negative electrode 100 exhibits poor flexibility and poor processability. In Example 8, when the elongation at break of the second binder is 100%, the adhesion between the first and second binders is poor.

[0077] In summary, by setting the ratio of the first binder to the second binder between 65:35 and 80:20, with the first binder having a tensile elongation at break of less than 10% and the second binder having a tensile elongation at break between 30% and 70%, the prepared negative electrode sheet 100 can be guaranteed to have both good processability and good dynamic performance.

[0078] An electrochemical device according to an embodiment of the present invention includes a positive electrode, a separator, and a negative electrode 100 as described in any of the above embodiments, wherein the positive electrode, the separator, and the negative electrode 100 are stacked sequentially.

[0079] The technical advantages of the electrochemical device according to the embodiments of the present invention are the same as those of the negative electrode 100 in the above embodiments, and will not be repeated here.

[0080] The vehicle according to an embodiment of the present invention includes an electrochemical device as described in the above embodiments.

[0081] The technical advantages of the vehicle according to the embodiments of the present invention are the same as those of the electrochemical device in the above embodiments, and will not be repeated here.

[0082] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0083] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0084] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0085] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0086] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0087] Although the above embodiments have been shown and described, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Any changes, modifications, substitutions and variations made to the above embodiments by those skilled in the art are within the protection scope of the present invention.

Claims

1. A negative electrode sheet characterized by comprising: include: The negative electrode current collector and the active coating, wherein the active coating comprises an active material, a conductive agent, a first binder and a second binder, wherein both the first binder and the second binder are polyacrylic binders, the tensile elongation at break of the first binder is less than 10%, and the tensile elongation at break of the second binder is 30%-70%.

2. The negative electrode sheet according to claim 1, characterized by The weight of the first adhesive accounts for 65%-80% of the total weight of the first adhesive and the second adhesive.

3. The negative electrode sheet according to claim 1, characterized by The first binder includes an olefinic unsaturated carboxylic acid monomer, and further includes at least one of an aliphatic conjugated diene monomer, an aliphatic vinyl monomer, an aromatic vinyl monomer, a cyanide monomer, a hydroxyalkyl-containing unsaturated monomer, and an unsaturated amide monomer.

4. The negative electrode sheet according to claim 3, characterized in that, The molar ratio of olefinic unsaturated carboxylic acid monomers in the first binder is 30%-50%.

5. The negative electrode sheet according to claim 1, characterized in that, The second binder includes olefinic unsaturated carboxylic acid monomers and acrylate monomers, and further includes at least one of aliphatic conjugated diene monomers, aliphatic vinyl monomers, aromatic vinyl monomers, cyanide monomers, hydroxyalkyl-containing unsaturated monomers, and unsaturated amide monomers.

6. The negative electrode sheet according to claim 5, characterized in that, In the second adhesive, the molar ratio of olefinic unsaturated carboxylic acid monomers is 50%-70%, and the molar ratio of acrylate monomers is 20%-30%.

7. The negative electrode sheet according to claim 1, characterized in that, The first adhesive or the second adhesive comprises at least one of lithium unsaturated carboxylate, sodium unsaturated carboxylate, and potassium unsaturated carboxylate.

8. A method for preparing a negative electrode sheet, characterized in that, The method for preparing the negative electrode sheet according to any one of claims 1-7, wherein the negative electrode sheet further comprises a negative electrode binder and carbon nanotubes, and the negative electrode binder comprises CMC-Na or CMC-Li, the preparation method comprising: The active material, conductive agent, first binder, second binder, negative electrode binder and carbon nanotubes are mixed in deionized water at a weight ratio of 95.1:1:x:3.5-x:0.3:0.1 and stirred evenly to form an active coating. An active coating is applied to the negative electrode current collector, and the negative electrode sheet is prepared by cold pressing, cutting, and slitting.

9. The method for preparing the negative electrode sheet according to claim 8, characterized in that, The active material includes artificial graphite and silicon oxide, and the weight ratio of artificial graphite to silicon oxide is 9:

1. And / or, the conductive agent includes conductive carbon; And / or, the negative current collector comprises copper foil.

10. An electrochemical device, characterized in that, It includes a positive electrode, a separator, and a negative electrode according to any one of claims 1-7, wherein the positive electrode, the separator, and the negative electrode are stacked in sequence.

11. A vehicle, characterized in that, Includes the electrochemical device according to claim 10.

Images