Slurry auxiliary agent and method for preparing aqueous hard carbon negative pole piece of sodium ion battery by using slurry auxiliary agent

Abstract

The invention discloses a slurry auxiliary agent and a method for preparing a water-based hard carbon negative pole piece of a sodium-ion battery, and belongs to the technical field of sodium-ion battery manufacturing, the slurry auxiliary agent comprises a base material wetting agent and a compound defoaming agent, and the mass ratio of the base material wetting agent to the compound defoaming agent is 1: 1-1: 5. The slurry additive is applied to the water-based hard carbon negative electrode slurry formula, so that the problem that the water-based hard carbon slurry cannot uniformly form a film on an aluminum foil current collector is effectively solved, and the formula has the characteristics of high drying speed, good leveling property, no film formation, no hole formation and the like. The processing yield of the water-based hard carbon negative electrode plate is effectively improved, and a sodium ion battery prepared from the negative electrode plate realizes relatively high first coulombic efficiency and excellent cycling stability.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium-ion battery manufacturing, and particularly relates to a slurry additive and a method for preparing a water-based hard carbon negative electrode sheet of a sodium-ion battery. Background Art

[0002] Sodium-ion batteries have the characteristics of low cost and excellent high and low temperature performance, and can be used as an alternative technology to lead-acid batteries for high-safety and extreme temperature scenarios. The process of sodium-ion batteries can use lithium-ion battery equipment, but there are huge differences in the use of raw materials, such as negative current collectors, carbon materials, etc., which determine that the sodium-ion battery process needs to be improved and broken through on the basis of lithium-ion battery technology. In traditional lithium-ion batteries, copper foil with high cost and heavy weight is selected as the current collector for the negative electrode. In sodium-ion batteries, aluminum foil with low cost can be used as the current collector for both the positive and negative electrodes, and hard carbon is used as the active material. In the preparation process of water-based hard carbon slurry, the dispersion of carbon materials directly affects the smoothness, uniformity, and stability of the slurry, and bubbles are extremely likely to appear in the slurry, which will cause the bubbles to be difficult to discharge during the coating process, and then form bubble defects on the electrode sheet. The traditional methods of vacuum defoaming and adding silicone defoamers cannot completely eliminate bubbles for water-based hard carbon slurry. In addition, using aluminum foil as the negative current collector means that problems such as the hydrophobicity of aluminum foil, the change in tension after water evaporation, the uniform dispersion of hard carbon negative electrode materials and water-based binders, and the easy formation of pores in the film after hard carbon slurry coating need to be solved, resulting in more problems such as shrinkage holes and sagging during the coating and drying processes of water-based hard carbon slurry, seriously affecting the quality of the electrode sheet after drying.

[0003] To solve the above problems, the Chinese invention patent with the publication number of CN119050270A discloses a graphite negative electrode binder, a slurry mixing method, a negative electrode sheet, and a lithium-ion battery. In the mixing process, the stirring paddle of a reverse planetary mixer is used to evacuate small bubbles in the slurry, but this method cannot completely eliminate bubbles for hard carbon slurry. The Chinese invention patent with the publication number of CN117747749A discloses a sodium-ion hard carbon negative electrode sheet and a preparation method thereof, which uses a vibration defoaming method to eliminate bubbles generated by the slurry, but does not solve the problem of shrinkage holes generated during the coating and drying processes of water-based slurry. Therefore, a new method is needed to solve various problems existing when water-based hard carbon slurry is coated on an aluminum foil current collector. Summary of the Invention

[0004] The present invention aims to provide a slurry additive and a method for preparing a water-based hard carbon negative electrode sheet of a sodium-ion battery to solve the problems of shrinkage holes and sagging generated during the coating and drying processes of existing water-based hard carbon slurry.

[0005] To solve the above technical problems, the present invention provides the following technical solution: A slurry additive is composed of a substrate wetting agent and a compound defoamer, and the mass ratio is 1:1 to 1:5.

[0006] Further, the substrate wetting agent includes one or more of ethylene oxide adducts, alkynediol compounds, and organofluoropolymers.

[0007] Further, the compound defoamer is composed of a polyether defoamer and a silicone defoamer, and the mass ratio is 1:1 to 1:5.

[0008] Further, the polyether defoamer includes one or more of GP-type polyether defoamers, GPE-type polyether defoamers, and GEPS-type polyether defoamers.

[0009] Further, the silicone defoamer includes one or more of fluorosiloxane, dimethylsiloxane, and ethylene glycol siloxane.

[0010] A preparation method of a slurry additive applied to the sodium-ion battery aqueous hard carbon negative electrode sheet includes the following steps:

[0011] Step 1: Mix the slurry additive with deionized water to obtain a slurry additive solution for standby.

[0012] Step 2: Use a planetary dispersion vacuum stirring device, with deionized water as the solvent, take the binder and deionized water and mix them, and stir at medium speed for 1 - 3 h until uniform.

[0013] Step 3: Add the conductive agent, first stir at low speed for 10 - 20 min, and then stir at high speed for 1 - 3 h until uniform.

[0014] Step 4: Add the hard carbon material, first stir at low speed for 10 - 20 min, and then stir at high speed for 1 - 3 h until uniform, add deionized water, and adjust the viscosity of the slurry to 6000 - 10000 mPa·s to obtain Slurry A.

[0015] Step 5: Add the slurry additive solution under medium-speed stirring conditions and stir for 30 - 60 min.

[0016] Step 6: Add the binder, first stir at low speed for 10 - 20 min, and then stir at medium speed for 1 - 3 h until uniform, add deionized water, and adjust the viscosity of the slurry to 4000 - 5000 mPa·s to obtain Slurry B.

[0017] Step 7: Coating the Slurry B on the aluminum foil, drying it with hot air at 40 - 60 °C for 1 - 2 h, and then drying it in vacuum at 90 - 140 °C for 24 - 48 h to obtain the sodium-ion battery aqueous hard carbon negative electrode sheet.

[0018] Further, for the planetary dispersion vacuum stirring device, the revolution speed for low-speed stirring is 20 - 30 rpm, and the rotation speed for stirring is 500 - 1000 rpm; the revolution speed for medium-speed stirring is 40 - 50 rpm, and the rotation speed for stirring is 2000 - 3000 rpm; the revolution speed for high-speed stirring is 60 - 70 rpm, and the rotation speed for stirring is 3000 - 4000 rpm.

[0019] Further, the binder includes one or more of polyacrylic acid, sodium carboxymethyl cellulose, sodium alginate, styrene-butadiene rubber, and fluororubber.

[0020] Further, the conductive agent includes one or more of carbon nanotubes, conductive graphite, conductive carbon black, and graphene.

[0021] Advantages of the present invention:

[0022] 1. By adding a very small amount of compound defoamer and substrate wetting agent, the present invention has a low use cost and effectively solves problems such as shrinkage holes and sagging during the coating and drying processes of aqueous hard carbon slurries.

[0023] 2. Compared with traditional defoamers, the compound defoamer in this solution can balance defoaming performance and compatibility, quickly eliminate bubbles generated during the production process, and ensure the quality of the slurry and the smooth progress of the production process.

[0024] 3. Meanwhile, the use of the substrate wetting agent can effectively reduce the surface tension of the slurry, enabling the slurry to spread better on the surface of the aluminum foil and enhancing the adhesion between the slurry and the aluminum foil. It can adjust the imbalance of surface tension during the film-forming and drying processes of the slurry, promote the flow and leveling of the slurry, and thus effectively eliminate surface defects such as concave holes and pinholes caused by bubbles and low surface tension of the aluminum foil. The qualified rate of the aqueous hard carbon negative electrode sheet finally obtained is effectively improved, and the initial Coulomb efficiency in the battery is effectively increased, thereby improving the specific energy and cycle stability of the sodium-ion battery prototype. Description of the Drawings

[0025] In order to more clearly illustrate the technical solutions in the specific embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following described drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0026] Figure 1 Surface diagram of the aqueous hard carbon negative electrode sheet obtained without adding slurry additives;

[0027] Figure 2 Surface diagram of the aqueous hard carbon negative electrode sheet obtained by adding slurry additives in the present invention;

[0028] Figure 3First charge-discharge curves of the Na||HC half-cells prepared in the examples and comparative examples at a rate of 0.1C. Detailed implementation manners

[0029] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments. However, it should not be understood that the scope of the subject matter of the present invention is limited to the following embodiments. Without departing from the above technical idea of the present invention, all modifications, substitutions, and changes made according to ordinary technical knowledge and customary means in the art are included in the scope of the present invention.

[0030] Example 1:

[0031] A slurry additive, with a content of 0.5 wt.% in the aqueous hard carbon negative electrode slurry.

[0032] The slurry additive is composed of a substrate wetting agent and a compound defoamer, with a mass ratio of 1:4; the substrate wetting agent is an alkynediol compound (dimethyl octynediol); the compound defoamer is composed of a polyether defoamer and a silicone defoamer, with a mass ratio of 1:1.

[0033] The polyether defoamer is a GPE-type polyether defoamer; the silicone defoamer is dimethyl siloxane.

[0034] (1) Prepare the slurry additive solution: Mix 1 g of alkynediol compound (dimethyl octynediol), 2 g of GPE-type polyether defoamer, 2 g of dimethyl siloxane with 200 g of deionized water to obtain the slurry additive solution for standby.

[0035] (2) Use a planetary dispersion vacuum stirring device, with deionized water as the solvent, mix 15 g of sodium carboxymethylcellulose and 1000 g of deionized water, and stir at a revolution speed of 45 rpm and a rotation speed of 3000 rpm for 1 - 3 h until uniform.

[0036] (3) Add 20 g of carbon nanotubes, first stir at a revolution speed of 20 rpm and a rotation speed of 500 rpm for 10 min, and then stir at a revolution speed of 65 rpm and a rotation speed of 4000 rpm for 1 - 3 h until uniform.

[0037] (4) Add 940 g of hard carbon material, first stir at a revolution speed of 20 rpm and a rotation speed of 500 rpm for 10 min, and then stir at a revolution speed of 65 rpm and a rotation speed of 4000 rpm for 1 - 3 h until uniform; add deionized water to adjust the slurry viscosity to 8000 mPa·s to obtain Slurry A;

[0038] (5) Under the conditions of a revolution speed of 45 rpm and a rotation speed of 3000 rpm, add the slurry additive solution.

[0039] (6) Add 20 g of styrene-butadiene rubber, first stir for 10 min at a revolution speed of 20 rpm and a rotation speed of 500 rpm, and then stir for 1 - 3 h at a revolution speed of 45 rpm and a rotation speed of 3000 rpm until uniform; add deionized water and adjust the slurry viscosity to 5000 mPa·s to obtain Slurry B.

[0040] (7) Coat Slurry B on aluminum foil, dry it in a blast dryer at 55 °C for 2 h, and then transfer it to a vacuum dryer at 120 °C for 48 h to obtain a water-based hard carbon negative electrode sheet.

[0041] Example 2:

[0042] The difference from Example 1 is as follows:

[0043] A kind of slurry additive, with a content of 0.5 wt.% in the water-based hard carbon negative electrode slurry.

[0044] The slurry additive consists of a substrate wetting agent and a compound defoamer with a mass ratio of 1:3; the substrate wetting agent is an ethylene oxide adduct (2,4,7,9-tetramethyl-5-decyn-4,7-diol ethylene oxide adduct); the compound defoamer is composed of a polyether defoamer and a silicone defoamer with a mass ratio of 1:2.

[0045] The polyether defoamer is a GP-type polyether defoamer; the silicone defoamer is fluorosilicone.

[0046] (1) Prepare the slurry additive solution: Mix 1.5 g of ethylene oxide adduct (2,4,7,9-tetramethyl-5-decyn-4,7-diol ethylene oxide adduct), 1.5 g of GP-type polyether defoamer, 3.0 g of fluorosilicone with 200 g of deionized water to obtain the slurry additive solution for standby.

[0047] (2) Use a planetary dispersion vacuum stirring device, with deionized water as the solvent, mix 15 g of sodium carboxymethyl cellulose and 1000 g of deionized water, and stir at a revolution speed of 45 rpm and a rotation speed of 3000 rpm for 1 - 3 h until uniform.

[0048] (3) Add 20 g of conductive graphite, first stir for 10 min at a revolution speed of 20 rpm and a rotation speed of 500 rpm, and then stir for 1 - 3 h at a revolution speed of 65 rpm and a rotation speed of 4000 rpm until uniform.

[0049] (4) Add 940 g of hard carbon material, first stir for 10 min at a revolution speed of 20 rpm and a rotation speed of 500 rpm, and then stir for 1 - 3 h at a revolution speed of 65 rpm and a rotation speed of 4000 rpm until uniform; add deionized water and adjust the slurry viscosity to 8000 mPa·s to obtain Slurry A;

[0050] (5) Add the slurry additive solution under the conditions of 45 rpm of revolution and 3000 rpm of rotation.

[0051] (6) Add 20 g of styrene-butadiene rubber. First, stir for 10 min at 20 rpm of revolution and 500 rpm of rotation, and then stir for 1 - 3 h at 45 rpm of revolution and 3000 rpm of rotation until homogeneous; add deionized water and adjust the slurry viscosity to 5000 mPa·s to obtain Slurry B.

[0052] (7) Coat Slurry B on aluminum foil, dry it with forced air at 55 °C for 2 h, and then dry it in vacuum at 120 °C for 48 h to obtain the aqueous hard carbon negative electrode sheet.

[0053] Example 3:

[0054] The difference from Example 1 is:

[0055] A kind of slurry additive, with a content of 1 wt.% in the aqueous hard carbon negative electrode slurry.

[0056] The slurry additive is composed of a substrate wetting agent and a compound defoamer, with a mass ratio of 1:4; the substrate wetting agent is an alkynediol compound (dimethyl octynediol); the compound defoamer is composed of a polyether defoamer and a silicone defoamer, with a mass ratio of 1:3.

[0057] The polyether defoamer is a GEPS-type polyether defoamer; the silicone defoamer is ethylene glycol siloxane.

[0058] (1) Prepare the slurry additive solution: Mix 4 g of alkynediol compound (dimethyl octynediol), 4 g of GEPS-type polyether defoamer, 12 g of ethylene glycol siloxane with 200 g of deionized water to obtain the slurry additive solution for standby.

[0059] (2) Using a planetary dispersion vacuum stirring device, with deionized water as the solvent, mix 10 g of sodium carboxymethylcellulose and 1000 g of deionized water, and stir at 45 rpm of revolution and 3000 rpm of rotation for 1 - 3 h until homogeneous.

[0060] (3) Add 20 g of conductive carbon black, first stir for 10 min at 20 rpm of revolution and 500 rpm of rotation, and then stir for 1 - 3 h at 65 rpm of revolution and 4000 rpm of rotation until homogeneous.

[0061] (4) Add 940 g of hard carbon material, first stir for 10 min at 20 rpm of revolution and 500 rpm of rotation, and then stir for 1 - 3 h at 65 rpm of revolution and 4000 rpm of rotation until homogeneous; add deionized water and adjust the slurry viscosity to 8000 mPa·s to obtain Slurry A;

[0062] (5) Add the slurry additive solution under the conditions of 45 rpm of revolution and 3000 rpm of rotation.

[0063] (6) Add 20 g of styrene-butadiene rubber, first stir for 10 min at 20 rpm of revolution and 500 rpm of rotation, and then stir for 1 - 3 h at 45 rpm of revolution and 3000 rpm of rotation until homogeneous; add deionized water and adjust the slurry viscosity to 5000 mPa·s to obtain Slurry B.

[0064] (7) Coat Slurry B on the aluminum foil, dry it in a blast dryer at 55 °C for 2 h, and then dry it in a vacuum dryer at 120 °C for 48 h to obtain the aqueous hard carbon negative electrode sheet.

[0065] Example 4:

[0066] The difference from Example 1 is:

[0067] A kind of slurry additive, and its content in the aqueous hard carbon negative electrode slurry is 1 wt.%.

[0068] The slurry additive is composed of a substrate wetting agent and a compound defoaming agent, and the mass ratio is 1:4.5; the substrate wetting agent is an organic fluoropolymer (perfluoropolyether); the compound defoaming agent is composed of a polyether defoaming agent and a silicone defoaming agent, and the mass ratio is 1:5.

[0069] The polyether defoaming agent is a GPE-type polyether defoaming agent; the silicone defoaming agent is dimethyl silicone.

[0070] (1) Prepare the slurry additive solution: Mix 4 g of organic fluoropolymer (perfluoropolyether), 3 g of GPE-type polyether defoaming agent, 15 g of dimethyl silicone and 200 g of deionized water to obtain the slurry additive solution for standby.

[0071] (2) Use a planetary dispersion vacuum stirring device, with deionized water as the solvent, mix 10 g of sodium carboxymethylcellulose and 1000 g of deionized water, and stir at 45 rpm of revolution and 3000 rpm of rotation for 1 - 3 h until homogeneous.

[0072] (3) Add 20 g of graphene, first stir for 10 min at 20 rpm of revolution and 500 rpm of rotation, and then stir at 65 rpm of revolution and 4000 rpm of rotation for 1 - 3 h until homogeneous.

[0073] (4) Add 940 g of hard carbon material, first stir for 10 min at 20 rpm of revolution and 500 rpm of rotation, and then stir at 65 rpm of revolution and 4000 rpm of rotation for 1 - 3 h until homogeneous; add deionized water and adjust the slurry viscosity to 8000 mPa·s to obtain Slurry A;

[0074] (5) Add the slurry additive solution under the conditions of 45 rpm of revolution and 3000 rpm of rotation.

[0075] (6) Add 20 g of styrene-butadiene rubber, first stir for 10 min at 20 rpm of revolution and 500 rpm of rotation, and then stir for 1 - 3 h at 45 rpm of revolution and 3000 rpm of rotation until uniform; add deionized water and adjust the slurry viscosity to 5000 mPa·s to obtain Slurry B.

[0076] (7) Coat Slurry B on the aluminum foil, dry it in a blast dryer at 55 °C for 2 h, and then transfer it to a vacuum dryer at 120 °C for 48 h to obtain the aqueous hard carbon negative electrode sheet.

[0077] Comparative Example 1:

[0078] The difference from Example 1 is that:

[0079] No slurry additive is added.

[0080] (1) Use a planetary dispersion vacuum stirring device, with deionized water as the solvent, mix 15 g of sodium carboxymethyl cellulose and 1000 g of deionized water, and stir at 45 rpm of revolution and 3000 rpm of rotation for 1 - 3 h until uniform.

[0081] (2) Add 20 g of conductive agent, first stir for 10 min at 20 rpm of revolution and 500 rpm of rotation, and then stir for 1 - 3 h at 65 rpm of revolution and 4000 rpm of rotation until uniform.

[0082] (4) Add 940 g of hard carbon material, first stir for 10 min at 20 rpm of revolution and 500 rpm of rotation, and then stir for 1 - 3 h at 65 rpm of revolution and 4000 rpm of rotation until uniform; add deionized water and adjust the slurry viscosity to 8000 mPa·s to obtain Slurry A;

[0083] (5) Add 25 g of styrene-butadiene rubber, first stir for 10 min at 20 rpm of revolution and 500 rpm of rotation, and then stir for 1 - 3 h at 45 rpm of revolution and 3000 rpm of rotation until uniform; add deionized water and adjust the slurry viscosity to 5000 mPa·s to obtain Slurry B.

[0084] (6) Coat Slurry B on the aluminum foil, dry it in a blast dryer at 55 °C for 2 h, and then transfer it to a vacuum dryer at 120 °C for 48 h to obtain the aqueous hard carbon negative electrode sheet.

[0085] The electrode sheet obtained by coating the slurry without adding the slurry additive in Comparative Example 1 is as shown in Figure 1 shown, and the electrode sheet obtained by coating the slurry with the slurry additive in the present invention is as shown in Figure 2As shown. Through comparison, it can be seen that a large number of concave holes and sagging phenomena will appear on the electrode sheet without adding the slurry additive. While the slurry with the slurry additive has good leveling property during the coating process, and the surface of the coated electrode sheet is smooth and flat. After drying, no concave holes, pinholes, etc. are found, indicating that the method of adding the slurry additive can effectively solve the problems of shrinkage holes, sagging, etc. generated during the coating and drying processes of the aqueous hard carbon slurry.

[0086] Performance test: The aqueous hard carbon negative electrode sheets obtained in Example 2 and Comparative Example 1 were subjected to the processes of rolling and slitting, and then assembled with sodium sheets into coin cells for electrochemical performance testing. The test results are as Figure 3 shown.

[0087] It can be seen from the figure that the first Coulombic efficiency of the battery in Comparative Example 1 is 94.2% at a rate of 0.1C. The first Coulombic efficiency of the battery in Example 2 is 97.5% at a rate of 0.1C. The aqueous hard carbon negative electrode sheet coated with the slurry containing the slurry additive of the present invention achieves a better first Coulombic efficiency.

[0088] The present invention adds a very small amount of compound defoamer and substrate wetting agent, with low use cost, and effectively solves the problems of shrinkage holes, sagging, etc. generated during the coating and drying processes of the aqueous hard carbon slurry. Compared with traditional defoamers, this compound defoamer can balance defoaming property and compatibility, quickly eliminate the bubbles generated during the production process, and ensure the quality of the slurry and the smooth progress of the production process. In addition, the simultaneous use of the substrate wetting agent can effectively reduce the surface tension of the slurry, enabling the slurry to spread better on the surface of the aluminum foil and enhancing the adhesion between the slurry and the aluminum foil, adjusting the surface tension imbalance during the film-forming and drying processes of the slurry, promoting the flow and leveling of the slurry, and thus effectively eliminating surface defects such as concave holes and pinholes caused by bubbles and low surface tension of the aluminum foil. The qualified rate of the finally obtained aqueous hard carbon negative electrode sheet is effectively improved, and the first Coulombic efficiency in the battery is effectively improved, thereby improving the specific energy and cycle stability of the sodium-ion battery prototype.

[0089] The above has introduced in detail the slurry additive provided by the present invention and the method for preparing the aqueous hard carbon negative electrode sheet of the sodium-ion battery. Specific examples are used in this article to elaborate on the structure and working principle of the present invention. The description of the above embodiments is only used to help understand the method and core idea of the present invention. It should be noted that for those of ordinary skill in the art in this technical field, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A slurry additive, characterized in that: It comprises a base material wetting agent and a compound defoaming agent in a mass ratio of 1:1 to 1:

5.

2. A slurry additive according to claim 1, characterized in that: The substrate wetting agent includes one or more of ethylene oxide adducts, acetylene glycol compounds and organic fluorine polymers.

3. A slurry additive according to claim 2, characterized in that: The compound defoamer is composed of a polyether defoamer and a silicone defoamer in a mass ratio of 1:1 to 1:

5.

4. A slurry additive according to claim 3, characterized in that: The polyether defoamer includes one or more of GP type polyether defoamer, GPE type polyether defoamer and GEPS type polyether defoamer.

5. A slurry additive according to claim 4, characterized in that: The organosilicon defoaming agent includes one or more of fluorosilicone, dimethylsiloxane and ethylene glycol siloxane.

6. A method for preparing an aqueous hard carbon negative electrode sheet for a sodium ion battery according to claims 1 to 5, characterized in that: The following steps are involved: Step 1: Mix a slurry additive with deionized water to obtain a slurry additive solution for later use; Step 2: Use a planetary dispersing vacuum stirring device and deionized water as the solvent, mix the binder and deionized water, and stir at medium speed for 1-3 hours until uniform; Step 3: Add the conductive agent, stir at low speed for 10-20 minutes, then stir at high speed for 1-3 hours until uniform; Step 4: Add the hard carbon material, stir at a low speed for 10-20 minutes, then stir at a high speed for 1-3 hours until uniform, add deionized water, and adjust the slurry viscosity to 6000-10000 mPa·s to obtain slurry A; Step 5: Add the slurry additive solution under medium speed stirring and stir for 30-60 minutes; Step 6: Add a binder, stir at a low speed for 10-20 minutes, then stir at a medium speed for 1-3 hours, add deionized water, and adjust the slurry viscosity to 4000-5000 mPa·s to obtain slurry B; Step 7: The slurry B is coated on aluminum foil, dried by forced air at 40-60° C. for 1-2 h, and then dried in a vacuum at 90-140° C. for 24-48 h to obtain the aqueous hard carbon negative electrode sheet for the sodium ion battery.

7. The method for preparing a sodium ion battery aqueous hard carbon negative electrode sheet according to claim 6, characterized in that: The planetary dispersing vacuum stirring device has a low-speed stirring revolution of 20-30 rpm and a stirring rotation of 500-1000 rpm; a medium-speed stirring revolution of 40-50 rpm and a stirring rotation of 2000-3000 rpm; and a high-speed stirring revolution of 60-70 rpm and a stirring rotation of 3000-4000 rpm.

8. The method for preparing a sodium ion battery aqueous hard carbon negative electrode sheet according to claim 7, characterized in that: The binder includes one or more of polyacrylic acid, sodium carboxymethyl cellulose, sodium alginate, styrene-butadiene rubber and fluorinated rubber.

9. The method for preparing a sodium ion battery aqueous hard carbon negative electrode sheet according to claim 8, characterized in that: The conductive agent includes one or more of carbon nanotubes, conductive graphite, conductive carbon black and graphene.

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