Sodium-ion battery anode slurry and preparation method thereof

Abstract

The invention discloses a negative electrode slurry for a sodium ion battery, comprising hard carbon, sodium carboxymethyl cellulose (CMC), a conductive agent, a polyacrylic acid emulsion, a carbonate solution, an isopropyl alcohol solvent and deionized water. Also disclosed is a method for preparing the negative electrode slurry for a sodium ion battery. The invention can reduce the hydrophilicity and compatibility between the hard carbon, the conductive agent, the glue and the polyacrylic acid binder in the negative electrode slurry, so that the slurry dispersion effect is better, and the amount of the conductive agent, the polyacrylic acid binder and the CMC used in the same product can be adjusted, thereby increasing the proportion of active substances in the negative electrode slurry in disguised form and improving the energy density of the battery.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium batteries, and specifically relates to a negative electrode slurry for a sodium-ion battery and a preparation method thereof. Background Art

[0002] Sodium is relatively abundant in the earth's crust, widely distributed, low in cost, safe and non-toxic. Sodium and lithium both belong to alkali metal elements, and sodium atoms and lithium atoms have very similar physical and chemical properties and similar deintercalation / insertion mechanisms. Compared with other energy storage technologies, sodium-ion batteries have certain advantages in terms of resource reserves, cost, energy conversion efficiency, cycle life, safety and stability, maintenance costs, etc. Therefore, the large-scale development of sodium-ion batteries has very important strategic significance. The negative electrode of the sodium-ion uses deionized water as a solvent and a water-based binder at the same time, making the entire aqueous negative electrode slurry non-toxic and pollution-free. The prepared sodium-ion battery is a truly green energy source. To reduce costs, aluminum foil is used instead of copper foil, but the bonding effect between the aluminum foil and the aqueous negative electrode is poor, and powder falling is likely to occur during the sheet making process. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide a negative electrode slurry for a sodium-ion battery and a preparation method thereof in view of the deficiencies of the prior art, which solves the problem of poor adhesion between the aqueous negative electrode slurry and the aluminum foil and improves the problem of powder falling easily occurring during the sheet making process.

[0004] To achieve the above purpose, the present invention adopts the following technical solutions:

[0005] The negative electrode slurry for a sodium-ion battery includes hard carbon, sodium carboxymethyl cellulose CMC, a conductive agent, a polyacrylic acid emulsion, a carbonic acid solution, an isopropanol solvent, and deionized water.

[0006] Preferably, the parts ratio between the hard carbon: conductive agent: CMC: polyacrylic acid emulsion: carbonic acid solution: isopropanol solvent is: 85-95: 0.3-3.0: 0.2-5.0: 0.5-5.0: 0.1-3.0: 0.1-3.0.

[0007] A preparation method for a negative electrode slurry of a sodium-ion battery includes the following steps:

[0008] (1) Weigh sodium carboxymethyl cellulose CMC according to the ratio, and then evenly sprinkle it in three times on the set area S of the stirring tank x inside, and the weight ratio of the three sprinklings is 2:3:6;

[0009] (2) Divide the deionized water into 3 equal parts according to the number of parts of CMC, and label them as M1, M2, and M3. The temperature of each part is T1, T2, and T3, where the temperature of T1 is 25 ± 5 °C, the temperature of T2 is 50 ± 5 °C, and the temperature of T3 is 75 ± 5 °C;

[0010] (3) Add the deionized water M1 to the stirring tank, and then evenly sprinkle the first portion of CMC on the liquid surface with an area of S1 in the stirring tank, and stir for 6 - 8 min;

[0011] (4) Add the deionized water M2 to the stirring tank, and then evenly sprinkle the second portion of CMC on the liquid surface with an area of S2 in the stirring tank, and stir for 8 - 10 min;

[0012] (5) Add the deionized water M3 to the stirring tank, and then evenly sprinkle the third portion of CMC on the liquid surface with an area of S3 in the stirring tank, and stir for 10 - 12 min;

[0013] (6) Add the carbonic acid solution to the stirring tank and perform ultrasonic stirring. The stirring speed is 1000 - 2000 rpm, and the stirring time is 5 - 15 min to improve the hydrophilicity of the glue solution;

[0014] Then add the polyacrylic acid emulsion and isopropyl alcohol solvent, and perform ultrasonic stirring to mix evenly. The stirring speed is 1000 - 2000 rpm, and the stirring time is 5 - 15 min to obtain the glue solution; then evacuate the glue solution to -0.085 Mpa, and then add the hard carbon powder and conductive agent in multiple batches and stir evenly to obtain the negative electrode active material liquid;

[0015] (7) Then add the modified polyacrylic acid emulsion to the negative electrode active material liquid, and stir evenly to obtain the negative electrode paste for coating on the aluminum foil

[0016] Preferably, the area S of the stirring tank in step (1) x is: S1 = π(1 / 3)R 2 、S2 = π(1 / 2)R 2 、S3 = πR 2 .

[0017] Preferably, the stirring speed of the stirring tank in step (3) is 5 - 10 rpm for the revolution and 1500 - 1600 rpm for the rotation.

[0018] Preferably, the stirring speed of the stirring tank in step (4) is 10 - 15 rpm for the revolution and 1600 - 1800 rpm for the rotation.

[0019] Preferably, the stirring speed of the stirring tank in step (5) is 15 - 20 rpm for the revolution and 1800 - 2000 rpm for the rotation.

[0020] Preferably, in step (6), the hard carbon powder and the conductive agent are added in 2 to 3 times; before the first addition of the hard carbon powder and the conductive agent, dry gas at 55 °C is passed for 5 to 10 minutes, and then when adding the hard carbon powder and the conductive agent, stirring is carried out at a rotation speed of 5 to 10 rpm for revolution and 1000 - 1200 rpm for self-rotation for 20 minutes;

[0021] Subsequently, each time when adding the hard carbon powder and the conductive agent again, the temperature of the dry gas increases in a gradient of 10 °C, the ventilation time and the stirring time increase in a gradient of 10 minutes, and the self-rotation speed and the revolution speed increase in gradients of 200 rpm and 5 rpm respectively.

[0022] The beneficial effects of the present invention are as follows:

[0023] The present invention matches the spreading of CMC according to the area of the stirring tank and the amount of CMC, which can make the CMC spread evenly, avoid the phenomenon of agglomeration and caking when CMC meets water, and improve the solubility of CMC at the same time. As CMC is added, the concentration of deionized water will become higher and higher, and the surface tension will become greater and greater. By increasing the addition temperature, stirring speed, and spreading area of deionized water in a gradient manner, the surface tension of the liquid is reduced, and the solubility and dissolution speed are improved.

[0024] When the conductive powder and the hard carbon powder are added to the glue solution, the powder is added in multiple batches, and at the same time, requirements for gradient increase are made for the temperature, stirring speed, and spreading area, so that the density difference between the two body phases adjacent to the liquid surface layer of the powder becomes smaller, and the dispersibility is improved.

[0025] In the slurry system, the surfaces of the hard carbon and conductive agent particles are hydrophobic. By adding a carbonic acid solution to the CMC glue solution, a substitution reaction occurs for the hydrophilic carboxyl groups in the CMC glue solution, improving the hydrophobicity and making the hard carbon particles adsorbed with CMC more evenly dispersed in the glue solution, thereby suppressing the sedimentation of the slurry and preventing adverse phenomena such as rapid sedimentation of the slurry leading to agglomeration.

[0026] The carboxyl group on the surface of the polyacrylic acid emulsion particles is modified to endow the polyacrylic acid with hydrophilicity, enabling it to stably suspend in water. Due to its hydrophilic characteristics, the adsorption of polyacrylic acid to hard carbon is poor, resulting in the phenomenon of emulsion floating. Therefore, the polyacrylic acid emulsion and the isopropanol solvent are ultrasonically stirred and evenly mixed for an esterification reaction to improve the compatibility of the polyacrylic acid binder and the hard carbon slurry after dispersion of CMC. Some polyacrylic acid binders do not float when the slurry is left standing, and the emulsion is evenly distributed in the slurry.

[0027] Using the polyacrylic acid emulsion binder can greatly enhance the bonding effect between the negative aluminum foil and the water-based binder, reduce the film peeling phenomenon during the production of the electrode sheet, and reduce the production cost at the same time.

[0028] The present invention can reduce the hydrophilicity and compatibility among hard carbon, conductive agent, glue and polyacrylic acid binder in negative electrode slurry, so the slurry dispersion effect is better. The dosage of conductive agent, polyacrylic acid binder and CMC can be adjusted under the same product, which increases the proportion of active material in negative electrode slurry in disguise and improves the energy density of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is the SEM picture of the present invention;

[0030] Figure 2 It is the SEM picture of comparative example;

[0031] Figure 3 The peeling conditions of the embodiments of the present invention and the comparative examples at different temperatures are shown. DETAILED DESCRIPTION

[0032] The following examples further describe the present invention.

[0033] Example 1

[0034] A sodium ion battery negative electrode slurry comprises hard carbon, sodium carboxymethyl cellulose (CMC), a conductive agent, polyacrylic acid emulsion, a carbonic acid solution, an isopropanol solvent and deionized water. The ratio of hard carbon: conductive agent: CMC: polyacrylic acid emulsion: carbonic acid solution: isopropanol solvent is 85:0.3:0.2:0.5:0.1:0.1.

[0035] Example 2

[0036] A sodium ion battery negative electrode slurry comprises hard carbon, sodium carboxymethyl cellulose (CMC), a conductive agent, polyacrylic acid emulsion, a carbonic acid solution, an isopropanol solvent and deionized water. The ratio of hard carbon: conductive agent: CMC: polyacrylic acid emulsion: carbonic acid solution: isopropanol solvent is 90:1.6:3:2.5:2:1.

[0037] Example 3

[0038] A sodium ion battery negative electrode slurry comprises hard carbon, sodium carboxymethyl cellulose (CMC), a conductive agent, polyacrylic acid emulsion, a carbonic acid solution, an isopropanol solvent and deionized water. The ratio of hard carbon: conductive agent: CMC: polyacrylic acid emulsion: carbonic acid solution: isopropanol solvent is 95:3.0:5.0:5.0:3.0:3.0.

[0039] Example 4

[0040] A method for preparing a negative electrode slurry for a sodium ion battery, using the raw material ratio in Example 1, comprises the following steps:

[0041] (1) Weigh sodium carboxymethyl cellulose (CMC) according to the ratio, and then evenly sprinkle it in three times within the set area S of the stirring tank. The weight ratio of the three sprinklings is 2:3:6. Here, multiple sprinklings can also be carried out according to the actual situation. The area S of the stirring tank is as follows: x Inside, the area S of the stirring tank is: S1 = π(1 / 3)R, x S2 = π(1 / 2)R, 2 S3 = πR, 2 where R = 50 cm. 2

[0042] (2) Divide the deionized water into three equal parts according to the number of parts of CMC, and label them as M1, M2, and M3. The temperature of each part is T1, T2, and T3. The temperature T1 is 25 ± 5°C, the temperature T2 is 50 ± 5°C, and the temperature T3 is 75 ± 5°C.

[0043] (3) Add deionized water M1 into the stirring tank, and then evenly sprinkle the first portion of CMC on the liquid surface of the area S1 of the stirring tank. The stirring speed of the stirring tank is 5 rpm for the revolution and 1500 rpm for the rotation, and stir for 8 minutes.

[0044] (4) Add deionized water M2 into the stirring tank, and then evenly sprinkle the second portion of CMC on the liquid surface of the area S2 of the stirring tank. The stirring speed of the stirring tank is 10 rpm for the revolution and 1600 rpm for the rotation, and stir for 10 minutes.

[0045] (5) Add deionized water M3 into the stirring tank, and then evenly sprinkle the third portion of CMC on the liquid surface of the area S3 of the stirring tank. The stirring speed of the stirring tank is 15 rpm for the revolution and 1800 rpm for the rotation, and stir for 12 minutes.

[0046] (6) Add carbonic acid solution into the stirring tank and carry out ultrasonic stirring. The stirring speed is 1000 rpm and the stirring time is 15 minutes to improve the hydrophilicity of the glue solution. Then add polyacrylic acid emulsion and isopropanol solvent, and carry out ultrasonic stirring to mix evenly. The stirring speed is 1000 rpm and the stirring time is 15 minutes to obtain the glue solution. Then evacuate the glue solution to -0.085 Mpa, and then add hard carbon powder and conductive agent in multiple times and stir evenly to obtain the negative electrode active material liquid.

[0047]

[0048] The hard carbon powder and the conductive agent are added in 3 portions; before the first addition of the hard carbon powder and the conductive agent, dry gas at 55 °C is introduced for 5 min. After that, when adding the hard carbon powder and the conductive agent, stirring is carried out at a rotation speed of 5 rpm for revolution and 1000 rpm for self-rotation for 20 min; each subsequent time when adding the hard carbon powder and the conductive agent, the temperature of the dry gas is increased in a gradient of 10 °C, the gas introduction time and the stirring time are increased in a gradient of 10 min, and the self-rotation speed and the revolution speed are increased in gradients of 200 rpm and 5 rpm respectively.

[0049] (7) Then, the modified polyacrylic acid emulsion is added to the negative electrode active material liquid, and after stirring evenly, a negative electrode slurry for coating on an aluminum foil is obtained.

[0050] Example 5

[0051] A method for preparing a negative electrode slurry of a sodium ion battery, using the raw material ratio in Example 1, includes the following steps:

[0052] (1) Sodium carboxymethyl cellulose CMC is weighed according to the ratio, and then evenly sprinkled in 3 portions over the set area S of the stirring tank x inside, and the weight ratio of the 3 sprinklings is 2:3:6; multiple sprinklings can also be carried out according to the actual situation; the area S of the stirring tank x is: S1 = π(1 / 3)R 2 , S2 = π(1 / 2)R 2 , S3 = πR 2 , R = 50 cm.

[0053] (2) Deionized water is evenly divided into 3 portions according to the number of parts of CMC, and denoted as M1, M2, M3, where the temperature of each portion is T1, T2, T3, the temperature T1 is 25 ± 5 °C, the temperature T2 is 50 ± 5 °C, and the temperature T3 is 75 ± 5 °C;

[0054] (3) Add deionized water M1 to the stirring tank, and then evenly sprinkle the first portion of CMC on the liquid surface of the area S1 of the stirring tank. The stirring speed of the stirring tank is 7 rpm for revolution and 1570 rpm for self-rotation, and stir for 7 min;

[0055] (4) Add deionized water M2 to the stirring tank, and then evenly sprinkle the second portion of CMC on the liquid surface of the area S2 of the stirring tank. The stirring speed of the stirring tank is 12 rpm for revolution and 1700 rpm for self-rotation, and stir for 9 min;

[0056] (5) Add deionized water M3 to the stirring tank, and then evenly sprinkle the third portion of CMC on the liquid surface of the area S3 of the stirring tank. The stirring speed of the stirring tank is 17 rpm for revolution and 1900 rpm for self-rotation, and stir for 11 min;

[0057] (6) Add a carbonic acid solution to the stirring tank and perform ultrasonic stirring at a stirring speed of 1500 rpm for 10 min to improve the hydrophilicity of the glue solution.

[0058] Then add polyacrylic acid emulsion and isopropyl alcohol solvent, and perform ultrasonic stirring to mix evenly at a stirring speed of 1500 rpm for 11 min to obtain a glue solution; then evacuate the glue solution to -0.085 Mpa, and then add hard carbon powder and conductive agent in multiple times and stir evenly to obtain the negative electrode active material liquid.

[0059] The hard carbon powder and conductive agent are added in 3 times; before the first addition of the hard carbon powder and conductive agent, dry gas at 55 °C is passed for 7 min, and then when adding the hard carbon powder and conductive agent, stir at a rotation speed of 6 rpm for revolution and 1150 rpm for self-rotation for 20 min; each subsequent time when adding the hard carbon powder and conductive agent, the temperature of the dry gas increases in a gradient of 10 °C, the ventilation time and stirring time increase in a gradient of 10 min, and the self-rotation speed and revolution speed increase in gradients of 200 rpm and 5 rpm respectively.

[0060] Then add the modified polyacrylic acid emulsion to the negative electrode active material liquid and stir evenly to obtain the negative electrode paste for coating on the aluminum foil.

[0061] Example 6

[0062] A method for preparing a negative electrode paste of a sodium-ion battery, using the raw material ratio in Example 1, including the following steps:

[0063] (1) Weigh sodium carboxymethyl cellulose CMC according to the ratio, and then evenly sprinkle it in 3 times within the set range area S of the stirring tank, and the weight ratio of the 3 sprinkles is 2:3:6; here, multiple sprinkles can also be carried out according to the actual situation; the area S of the stirring tank x is: S1 = π(1 / 3)R x 、S2 = π(1 / 2)R 2 、S3 = πR 2 ,R = 50 cm. 2

[0064] (2) Divide deionized water into 3 equal parts according to the number of parts of CMC, and denote them as M1, M2, and M3, where the temperature of each part is T1, T2, and T3, T1 temperature is 25 ± 5 °C, T2 temperature is 50 ± 5 °C, and T3 temperature is 75 ± 5 °C;

[0065] (3) Add deionized water M1 to the stirring tank, and then evenly sprinkle the first portion of CMC on the liquid surface of the area S1 of the stirring tank, and the stirring speed of the stirring tank is 10 rpm for revolution and 1600 rpm for self-rotation, and stir for 6 min.

[0066] (4) Add deionized water M2 into the stirring tank, and then evenly sprinkle the second portion of CMC on the liquid surface of the area S2 of the stirring tank. The stirring speed of the stirring tank is 15 rpm for the revolution speed and 1800 rpm for the rotation speed, and stir for 8 minutes;

[0067] (5) Add deionized water M3 into the stirring tank, and then evenly sprinkle the third portion of CMC on the liquid surface of the area S3 of the stirring tank. The stirring speed of the stirring tank is 20 rpm for the revolution speed and 2000 rpm for the rotation speed, and stir for 10 minutes;

[0068] (6) Add carbonic acid solution into the stirring tank and perform ultrasonic stirring. The stirring speed is 2000 rpm and the stirring time is 5 minutes to improve the hydrophilicity of the glue solution;

[0069] Then add polyacrylic acid emulsion and isopropanol solvent, and perform ultrasonic stirring for uniform mixing. The stirring speed is 2000 rpm and the stirring time is 5 minutes to obtain the glue solution; then evacuate the glue solution to -0.085 Mpa, and then add hard carbon powder and conductive agent in multiple times and stir evenly to obtain the negative electrode active material liquid;

[0070] The hard carbon powder and conductive agent are added in 3 times; before the first addition of the hard carbon powder and conductive agent, dry gas at 55 °C is passed for 10 minutes. Then, when adding the hard carbon powder and conductive agent, stir at a speed of 10 rpm for the revolution speed and 1200 rpm for the rotation speed for 20 minutes; each subsequent time when adding the hard carbon powder and conductive agent, the temperature of the dry gas increases at a gradient of 10 °C, the ventilation time and stirring time increase at a gradient of 10 minutes, and the rotation speed and revolution speed increase at gradients of 200 rpm and 5 rpm respectively.

[0071] Then add the modified polyacrylic acid emulsion to the negative electrode active material liquid and stir evenly to obtain the negative electrode paste for coating on the aluminum foil.

[0072] Example 7

[0073] The negative electrode paste of the sodium-ion battery prepared in this example is the same as that in Example 2, and the preparation process adopted is the same as that in Example 4.

[0074] Example 8

[0075] The negative electrode paste of the sodium-ion battery prepared in this example is the same as that in Example 3, and the preparation process adopted is the same as that in Example 4.

[0076] Perform a peeling test on the negative electrode paste of the sodium-ion battery prepared in Example 4 and the negative electrode paste purchased on the market, and the results are as Figure 3 :

[0077] Figure 3 The exfoliation situations of the embodiments and comparative examples of the present invention at different temperatures are given in Figure 3 and it can be seen from

[0078] Three negative electrode paste products randomly purchased on the market are all made into 411526 model batteries, which are respectively recorded as Comparative Examples 1-3. Then the negative electrode pastes prepared in Examples 4-8 are also made into 411526 model batteries, and their internal resistances are compared as shown in Table 1:

[0079] Table 1

[0080] Batch Average internal resistance mΩ CPK Standard deviation of internal resistance Comparative example 1 140.91 1.26 12.97 Comparative example 2 147.34 1.12 12.71 Comparative example 3 140.61 1.45 11.31 Example 4 132.84 2.18 8.73 Example 5 136.62 2.13 8.33 Example 6 134.52 2.28 8.11 Example 7 134.65 2.31 7.99 Example 8 140.88 2.35 6.97

[0081] It can be concluded from Table 1 that the internal resistance of the battery made of the negative electrode paste prepared by the present invention is reduced, so the discharge time of the battery is extended, and the control accuracy of production is also improved.

[0082] Figure 1 and 2 The SEM diagrams of the products obtained in Example 2 and Comparative Example 1 are given in

[0083] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit them. Any other modifications or equivalent replacements made by those of ordinary skill in the art to the technical solutions of the present invention shall be covered by the scope of the claims of the present invention as long as they do not depart from the spirit and scope of the technical solutions of the present invention.

Claims

1. A preparation method of a negative electrode slurry for a sodium-ion battery, the negative electrode slurry for the sodium-ion battery comprising hard carbon, sodium carboxymethyl cellulose (CMC), a conductive agent, a polyacrylic acid emulsion, a carbonic acid solution, an isopropyl alcohol solvent, and deionized water; the parts ratio among the hard carbon: conductive agent: CMC: polyacrylic acid emulsion: carbonic acid solution: isopropyl alcohol solvent is: 85-95: 0.3-3.0: 0.2-5.0: 0.5-5.0: 0.1-3.0: 0.1-3.0, and it is characterized in that: (1) Weigh sodium carboxymethyl cellulose (CMC) according to the ratio, and then evenly sprinkle it in three times within the set area S of the stirring tank. The weight ratio of the three sprinkles is 2:3:

6. Among them, S x is: S1 = π(1 / 3)R x 、S2 = π(1 / 2)R 2 、S3 = πR 2 ; 2 ​ (2) Divide the deionized water into 3 parts according to the parts of CMC, and denote them as M1, M2, and M3, wherein the temperature of each part is T1, T2, and T3, the temperature T1 is 25±5°C, the temperature T2 is 50±5°C, and the temperature T3 is 75±5°C; (3) Add the deionized water M1 into a stirring tank, and then evenly sprinkle the first part of CMC on the liquid surface of the area S1 of the stirring tank, and stir for 6-8 min; (4) Add the deionized water M2 into the stirring tank, and then evenly sprinkle the second part of CMC on the liquid surface of the area S2 of the stirring tank, and stir for 8-10 min; (5) Add the deionized water M3 into the stirring tank, and then evenly sprinkle the third part of CMC on the liquid surface of the area S3 of the stirring tank, and stir for 10-12 min; (6) Add the carbonic acid solution into the stirring tank, and perform ultrasonic stirring, the stirring speed is 1000-2000 rpm, and the stirring time is 5-15 min to improve the hydrophilicity of the glue solution; Then add the polyacrylic acid emulsion and the isopropyl alcohol solvent, and perform ultrasonic stirring to mix evenly, the stirring speed is 1000-2000 rpm, and the stirring time is 5-15 min to obtain a glue solution; then evacuate the glue solution to -0.085 Mpa, and then add the hard carbon powder and the conductive agent in multiple times, and stir evenly to obtain a negative electrode active material liquid; Among them, the hard carbon powder and the conductive agent are added in 2-3 times; before adding the hard carbon powder and the conductive agent for the first time, first pass a drying gas at 55°C for 5-10 min, and then when adding the hard carbon powder and the conductive agent, stir at a rotation speed of 5-10 rpm for revolution and 1000-1200 rpm for self-rotation for 20 min; when adding the hard carbon powder and the conductive agent each time subsequently, the temperature of the drying gas increases at a gradient of 10°C, the ventilation time and the stirring time increase at a gradient of 10 min, and the self-rotation speed and the revolution speed increase at gradients of 200 rpm and 5 rpm respectively; (7) Then add the carboxyl-modified polyacrylic acid emulsion to the negative electrode active material liquid, and stir evenly to obtain a negative electrode slurry for coating on an aluminum foil.

2. The preparation method of the negative electrode slurry for a sodium ion battery according to claim 1, wherein The stirring speed of the stirring tank in step (3) is 5-10 rpm for revolution and 1500-1600 rpm for self-rotation.

3. The preparation method of the negative electrode slurry for a sodium ion battery according to claim 1, wherein, The stirring speed of the stirring tank in step (4) is 10-15 rpm for revolution and 1600-1800 rpm for self-rotation.

4. The preparation method of the negative electrode slurry for a sodium ion battery according to claim 1, wherein The stirring speed of the stirring tank in step (5) is 15-20 rpm for revolution and 1800-2000 rpm for self-rotation.

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