Carbon slurry for sodium salt solid-state energy storage battery and preparation method and application thereof

Abstract

The present application relates to a kind of carbon slurry for sodium salt solid-state energy storage battery and its preparation method and application.The carbon slurry includes modified carbon black, dispersant and solvent, wherein the modification method of the modified carbon black includes introducing hydrophilic functional group in carbon black, and the solvent includes water and organic solvent.The slurry prepared based on the modified carbon black, under the premise of keeping solid content substantially stable, viscosity is significantly reduced, and storage stability is significantly improved.At process level, the slurry has good brushability and construction adaptability, not only improves coating efficiency, but also reduces the high-precision requirement of automatic spraying equipment, thereby reducing the difficulty and cost of process development and introduction.

Description

Technical Field

[0001] This invention relates to the field of new energy technology, and in particular to a sodium salt solid-state energy storage battery carbon slurry, its preparation method, and its application. Background Technology

[0002] Sodium-ion batteries (also known as sodium chloride batteries or Zehra batteries) are a novel electrochemical energy storage system that has garnered widespread attention in the energy storage field due to their advantages such as being environmentally friendly, highly safe, having high specific energy, long cycle life, and good weather resistance. Among the various sodium-based battery technologies, sodium-ion batteries are most similar to lithium-ion batteries in terms of working principle and material system, while sodium-ion batteries belong to the high-temperature solid-state battery system; the two technologies take different paths. Given the increasing emphasis on energy security and environmental protection worldwide, sodium-ion batteries are expected to become an important supplement to lithium-ion batteries, especially in the field of large-scale energy storage, where they have promising application prospects.

[0003] Carbon slurry is one of the key materials in sodium-ion batteries. Its main function is to uniformly coat a conductive carbon layer onto the surface of the solid electrolyte membrane during battery assembly. This coating promotes the uniform precipitation and adhesion of metallic sodium to the membrane surface during battery charging, thereby ensuring the uniformity of sodium deposition and the cycle stability of the battery.

[0004] Currently, the typical formulations of carbon slurry for traditional sodium salt batteries are shown in Table 1.

[0005] Table 1

[0006] Its preparation process mainly includes the following steps: 1) Mix sodium hexametaphosphate with deionized water at room temperature and stir to form a homogeneous solution; 2) Add carbon black powder and acetone to the solution obtained from the above operation according to the formula; 3) Under vacuum conditions, a homogenizer is used to homogenize the slurry and obtain a uniformly dispersed slurry. 4) Sample and test key parameters of the slurry, such as viscosity, moisture content, and solid content; 5) Transfer the qualified slurry to a storage tank and seal it for later use in production.

[0007] However, this traditional carbon slurry has the following main problems in practical applications: 1. During storage and use, slurry is prone to phase separation, with solid phase sedimentation and liquid phase supernatant, which leads to a decrease in slurry uniformity and difficulty in maintaining performance consistency. Second, the high viscosity of the slurry makes it difficult to control the coating thickness during manual coating, resulting in poor coating uniformity, low production efficiency, and difficulty in adapting to the production cycle of automated production lines. At the same time, the high viscosity of the slurry easily causes the nozzles of the spraying equipment to become clogged, resulting in uneven coating thickness, which restricts the development and widespread application of automated spraying technology.

[0008] Therefore, it is of great significance to develop a new sodium salt solid-state energy storage battery carbon slurry. Summary of the Invention

[0009] To address the above technical problems, this invention provides a carbon slurry for sodium salt solid-state energy storage batteries, which exhibits significantly reduced viscosity at room temperature (20-30°C). The carbon slurry of this application is used as the negative electrode in solid-state sodium salt batteries, not lithium batteries. It eliminates the need for coating-slitting-winding-cell assembly processes. The slurry is directly coated onto a ceramic separator without contacting any liquid. During battery discharge, only metallic sodium passes through the ceramic separator, and the space between the ceramic separator and the cell casing remains a vacuum.

[0010] The present invention also provides a method for preparing the above-mentioned carbon slurry.

[0011] The present invention also provides applications of the above-mentioned carbon slurry.

[0012] In some embodiments of the present invention, a carbon slurry for sodium salt solid-state energy storage batteries is proposed. The carbon slurry includes modified carbon black, a dispersant, and a solvent. The modification method of the modified carbon black includes immersing the modified carbon black in nitric acid to introduce hydrophilic functional groups. The solvent includes water and an organic solvent.

[0013] In some embodiments of the present invention, the hydrophilic functional group includes oxygen-containing and / or nitrogen-containing functional groups.

[0014] In some embodiments of the present invention, the hydrophilic functional group includes at least one of hydroxyl, carboxyl, or amino groups.

[0015] In some embodiments of the present invention, the modification method of the modified carbon black further includes introducing oxygen-containing and / or nitrogen-containing linking groups into the carbon black. By introducing oxygen-containing functional groups onto the surface of carbon black, the present invention improves its wettability and dispersibility in polar solvents to a certain extent, aiming to reduce its viscosity and thereby optimize the current manual carbon coating process to an automated spray coating process.

[0016] In some embodiments of the present invention, the linking group includes an ether bond or an amide bond.

[0017] In some embodiments of the present invention, the modified carbon black contains hydrophilic functional groups and amide bonds.

[0018] In some embodiments of the present invention, the viscosity of the carbon slurry is above 38P (i.e., above 38 Pa·s).

[0019] In some embodiments of the present invention, the viscosity of the carbon slurry is 39P or higher (i.e., 39 Pa·s or higher).

[0020] In some embodiments of the present invention, the dispersant is sodium hexametaphosphate, and the molar ratio of modified carbon black to sodium hexametaphosphate is 30~40:1.

[0021] In some embodiments of the present invention, the mass ratio of the modified carbon black, dispersant, and solvent is 20-40:60:140-150, wherein the mass of the modified carbon black is based on the weight of the carbon black before modification. No drying treatment is performed after modification.

[0022] In some embodiments of the present invention, the carbon black has an average particle size of 90-100 nm and a specific surface area of ​​10-30 m². 2 / g, oil absorption value 40ml-50ml / 100g.

[0023] In some embodiments of the present invention, the dispersant comprises sodium hexametaphosphate.

[0024] In some embodiments of the present invention, the organic solvent includes at least one of acetone, methyl ethyl ketone, or isopropanol.

[0025] In some embodiments of the present invention, the organic solvent includes acetone. Acetone facilitates the wetting of carbon black powder, promotes better extension and adsorption of sodium hexametaphosphate on the carbon black surface, reduces the initial mixing viscosity, and promotes wetting and defoaming.

[0026] In some embodiments of the present invention, the organic solvent is acetone, and the mass ratio of acetone to water is 1:82.5~85.5.

[0027] In some embodiments of the present invention, a method for preparing carbon slurry for sodium salt solid-state energy storage batteries is also proposed, comprising the following steps: S1. Modified carbon black is prepared by soaking carbon black in nitric acid solution; S2. Mix the dispersant with water to prepare a dispersant solution; mix the modified carbon black and organic solvent obtained in step S1 with the dispersant solution to obtain the final product.

[0028] In some embodiments of the present invention, the molar ratio of nitric acid to carbon black is 4:1 or higher. An excess of liquid is used to ensure sufficient modification of the carbon black.

[0029] In some embodiments of the present invention, the mass concentration of nitric acid in the nitric acid solution is 8.5-17.5%.

[0030] In some embodiments of the present invention, the mass concentration of nitric acid in the nitric acid solution is 8.625~17.25%.

[0031] In some embodiments of the present invention, the soaking time is 20-28 hours, such as 24 hours.

[0032] In some embodiments of the present invention, step S1 further includes rinsing the soaked carbon black with water to remove residual nitric acid solution from the surface of the carbon black.

[0033] In some embodiments of the present invention, the preparation process of modified carbon black in step S1 further includes a step of forming amide bonds in the washed carbon black.

[0034] In some embodiments of the present invention, the preparation process of modified carbon black in step S1 further includes further oxidation of the washed carbon black using the (NH4)2S2O8-H2SO4 system.

[0035] In some embodiments of the present invention, step S2 further includes a step of homogenizing the mixed materials under vacuum.

[0036] In some embodiments of the present invention, the vacuum degree of the vacuum state is below 1 Pa.

[0037] In some embodiments of the present invention, the homogenization process refers to stirring with a homogenizer for 15-30 minutes, such as 20 minutes.

[0038] In some embodiments of the present invention, a sodium battery is also proposed, wherein the raw materials for preparing the sodium battery include the above-mentioned carbon slurry.

[0039] In some embodiments of the present invention, the sodium battery includes a positive electrode, a negative electrode, and a separator. The separator includes a base film and a coating on the surface of the base film. The coating is prepared from the carbon slurry. The slurry is used to coat the surface of the sodium salt battery ceramic separator and is baked at a high temperature >180°C to form a solid coating.

[0040] In this invention, carbon slurry is coated on the outer surface of a ceramic tube, and the interior of the ceramic tube is filled with positive electrode material and melt. During charging, sodium ions pass through the ceramic diaphragm; during discharging, sodium ions pass through the ceramic diaphragm and enter the interior of the ceramic tube. The carbon slurry does not come into contact with substances other than sodium metal.

[0041] Compared with the prior art, the above-mentioned technical solution of the present invention has the following advantages: The present invention effectively improves the hydrophilicity and dispersibility of carbon black by introducing hydrophilic functional groups or connecting structures such as hydroxyl, carboxyl, or ether bonds onto its surface through surface modification. The slurry prepared based on this modified carbon black exhibits significantly reduced viscosity and significantly improved storage stability while maintaining a basically stable solid content. At the process level, this slurry has good brushability and application adaptability, which not only improves coating efficiency but also reduces the high-precision requirements of automated spraying equipment, thereby reducing the difficulty and cost of process development and implementation. Attached Figure Description

[0042] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein... Figure 1 This is a schematic diagram of the preparation process of carbon slurry in Embodiments 1 and 2 of the present invention.

[0043] Figure 2 This is a scatter plot of solid content test results for Embodiments 1-2 and Comparative Example 1 of the present invention.

[0044] Figure 3 These are scatter plots of viscosity tests from Embodiments 1-2 and Comparative Example 1 of the present invention. Detailed Implementation

[0045] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0046] Example 1 provides a carbon slurry for sodium salt solid-state energy storage batteries. The raw materials and their weight proportions are as follows: 15.7 parts modified carbon black, 0.007 parts acetone, 23.9 parts sodium hexametaphosphate, and 59.7 parts deionized water. The molar ratio of modified carbon black to sodium hexametaphosphate is 33.5:1. The mass ratio of modified carbon black, dispersant, and solvent is 39.4:60:149.9176.

[0047] Its preparation process is as follows Figure 1 As shown, the details are as follows: Take carbon black (average particle size 95nm, specific surface area 20m²) 2 15.7 portions of carbon black powder (with an oil absorption value of 40-50 ml / 100 g) were soaked in an 8.625% nitric acid solution (the solution completely covered the carbon black powder, with a nitric acid:carbon = 4 mol:1 mol ratio) for 24 hours to oxidize and modify the carbon black powder. The modified carbon black was then rinsed with deionized water to remove the nitric acid from its surface, yielding the modified carbon black for later use.

[0048] 23.9 parts of sodium hexametaphosphate and 59.7 parts of deionized water were mixed and stirred into a solution using a stirring device to obtain a sodium hexametaphosphate solution. 15.7 parts of modified carbon black and 0.007 parts of acetone prepared in the above operation were added to the sodium hexametaphosphate solution. Under a vacuum degree of less than 1 Pa, the slurry was thoroughly stirred for 20 minutes using a homogenizer to form a uniform slurry.

[0049] The slurry obtained by the above operation is transferred from the mixing equipment to a slurry storage tank, sealed and stored for later use.

[0050] Example 2: This example provides a carbon slurry for sodium salt solid-state energy storage batteries. The raw materials and their weight proportions are as follows: 15.7 parts modified carbon black, 0.007 parts acetone, 23.9 parts sodium hexametaphosphate, and 59.7 parts deionized water. The molar ratio of modified carbon black to sodium hexametaphosphate is 33.5:1. The mass ratio of modified carbon black, dispersant, and solvent is 39.4:60:149.9176.

[0051] Its preparation process is as follows: Take 15.7 parts of carbon black (source same as in Example 1) and soak it in a 17.25% nitric acid solution (the solution covers the carbon black powder, nitric acid: carbon > 4 mol: 1 mol) for 24 hours to oxidize and modify the carbon black powder. Rinse the modified carbon black with deionized water to remove the nitric acid from the surface of the carbon black, and the modified carbon black is ready for use.

[0052] 23.9 parts of sodium hexametaphosphate and 59.7 parts of deionized water were mixed and stirred into a solution using a stirring device to obtain a sodium hexametaphosphate solution. 15.7 parts of modified carbon black and 0.007 parts of acetone prepared in the above operation were added to the sodium hexametaphosphate solution. Under a vacuum degree of less than 1 Pa, the slurry was thoroughly stirred for 20 minutes using a homogenizer to form a uniform slurry.

[0053] The slurry obtained by the above operation is transferred from the mixing equipment to a slurry storage tank, sealed and stored for later use.

[0054] Comparative Example 1 This example provides a carbon slurry for sodium salt solid-state energy storage batteries, the raw materials for which are prepared and their weight parts are as follows: 15.7 parts carbon black, 0.007 parts acetone, 23.9 parts sodium hexametaphosphate and 59.7 parts deionized water.

[0055] Its preparation process is as follows: 23.9 parts of sodium hexametaphosphate were mixed with 59.7 parts of deionized water and stirred into a solution using a stirring device to obtain a sodium hexametaphosphate solution.

[0056] Take 15.7 parts of carbon black (from the same source as in Example 1) and 0.007 parts of acetone into a sodium hexametaphosphate solution. Under a vacuum of less than 1 Pa, use a homogenizer to thoroughly stir the slurry for 20 minutes to form a uniform slurry.

[0057] The slurry obtained by the above operation is transferred from the mixing equipment to a slurry storage tank, sealed and stored for later use.

[0058] Test example: 1) Solid content test: Take 5.0~6.0g of the carbon slurry prepared in the above examples and comparative examples, and test its solid content at 150℃ for 10min.

[0059] 2) Viscosity test: Take 100ml of the carbon slurry prepared in each example or comparative example and measure the viscosity of the slurry (room temperature around 25℃, viscometer using a No. 4 rotor, 30rpm).

[0060] 3) Stability testing: Take 50g of the carbon slurry prepared in each example or comparative example, store it at room temperature (20-30℃), and observe whether segregation and solid-liquid separation occur after 7 days of storage.

[0061] The performance test results are shown in Table 2 below: Table 2

[0062] To facilitate observation and comparison, the solid content test results of Examples 1-2 and Comparative Example 1 are plotted as a scatter plot as follows: Figure 2 As shown, the viscosity test results are plotted as a scatter plot. Figure 3 As shown.

[0063] From Table 2 and Figures 2-3 As can be seen from Table 2 and Figures 2-3 It can be seen that the viscosity of traditional carbon slurry is usually as high as 300P or more (some can reach 500P), while the viscosity of the slurry obtained in the embodiments of the present invention can be as low as 38.79P, a reduction of 87.07%. The significant reduction in viscosity greatly alleviates the process difficulty of developing and implementing carbon slurry in automated spraying equipment.

[0064] The hydrophilicity of carbon black can be improved through chemical methods such as nitration, acylation, and alkylation. These methods introduce hydrophilic functional groups such as hydroxyl, carboxyl, and amino groups onto its surface, thereby improving the dispersibility of carbon black in water. Based on this method, the embodiments of the present invention, while maintaining a basically stable solid content in the carbon slurry, not only effectively reduce the viscosity but also significantly enhance the storage stability of the slurry. For example, at room temperature of 20-30°C, the comparative carbon slurry showed obvious segregation and stratification after 24 hours of storage, while the carbon slurry of the embodiments of the present invention showed no stratification after 7 days of storage.

[0065] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A carbon slurry for sodium salt solid-state energy storage batteries, characterized in that, The carbon slurry comprises modified carbon black, a dispersant, and a solvent. The modification method of the modified carbon black includes immersing the modified carbon black in nitric acid to introduce hydrophilic functional groups. The solvent includes water and organic solvents.

2. The sodium salt solid-state energy storage battery carbon slurry according to claim 1, characterized in that, The hydrophilic functional groups include oxygen-containing and / or nitrogen-containing functional groups.

3. The sodium salt solid-state energy storage battery carbon slurry according to claim 1, characterized in that, The hydrophilic functional group includes at least one of hydroxyl, carboxyl, or amino groups.

4. The sodium salt solid-state energy storage battery carbon slurry according to claim 1, characterized in that, The modified carbon black further includes the introduction of oxygen- and / or nitrogen-containing linking groups into the carbon black.

5. The sodium salt solid-state energy storage battery carbon slurry according to claim 4, characterized in that, The modified carbon black contains hydrophilic functional groups and amide bonds.

6. The sodium salt solid-state energy storage battery carbon slurry according to claim 1, characterized in that, The viscosity of the carbon slurry is above 38 Pa·s; the dispersant is sodium hexametaphosphate, and the molar ratio of the modified carbon black to sodium hexametaphosphate is 20~40:1; the mass ratio of the modified carbon black, dispersant and solvent is 20~40:60:140~150, wherein the mass of the modified carbon black is based on the weight of the carbon black before modification.

7. The method for preparing sodium salt solid-state energy storage battery carbon slurry according to any one of claims 1 to 6, characterized in that: Includes the following steps: S1. Modified carbon black is prepared by soaking carbon black in nitric acid solution; S2. Mix the dispersant with water to prepare a dispersant solution; mix the modified carbon black and organic solvent obtained in step S1 with the dispersant solution to obtain the final product.

8. A sodium battery, characterized in that, The raw materials for preparing the sodium battery include the carbon slurry as described in any one of claims 1 to 6.

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