Water-based single-walled carbon nanotube slurry as well as dispersion method and application thereof

Abstract

The invention belongs to the technical field of single-walled carbon nanotube dispersion, and particularly relates to water-based single-walled carbon nanotube slurry and a dispersion method and application thereof.The dispersion method of the slurry comprises the steps that S1, composite powder is prepared, specifically, graphene oxide powder and single-walled carbon nanotube powder are stirred and mixed to be uniform and then subjected to reduction treatment, and the composite powder is obtained; composite powder with the reduced graphene oxide and the single-walled carbon nanotubes tightly combined is obtained; s2, preparation of a multi-element dispersing agent: preparing sodium dodecyl benzene sulfonate, polyacrylic acid and sodium carboxymethyl cellulose for later use; s3, preparation of aqueous slurry: adding the multi-element dispersing agent prepared in S2 into deionized water, stirring and dissolving, then adding the composite powder prepared in S1, and sanding and homogenizing to obtain the uniform and stable aqueous single-walled carbon nanotube slurry. The preparation method disclosed by the invention has important significance in promoting industrial application of the water-based single-walled carbon nanotube slurry in the fields of new energy silicon-carbon negative electrodes and the like.

Description

Technical Field

[0001] This invention belongs to the field of single-walled carbon nanotube dispersion technology, specifically relating to an aqueous single-walled carbon nanotube slurry, its dispersion method, and its application. Background Technology

[0002] Single-walled carbon nanotubes (SWCNTs) have shown irreplaceable application prospects in various fields such as new energy, electronic devices, and composite materials due to their excellent electrical conductivity, ultra-high mechanical strength, and stable chemical stability. Especially in the silicon-carbon anode system of new energy lithium-ion batteries, SWCNTs, as a high-performance conductive additive, can effectively alleviate the electrode structure damage caused by volume expansion (expansion rate can reach over 300%) during the charge and discharge process of silicon-based materials. Simultaneously, they improve the poor conductivity of silicon-based materials, significantly enhancing the cycle stability and rate performance of the battery. Therefore, SWCNTs are one of the key materials driving the industrial application of silicon-carbon anodes.

[0003] However, the strong van der Waals forces between single-walled carbon nanotube molecules make them prone to agglomeration into bundles or networks, hindering their uniform dispersion in aqueous systems and severely limiting the full realization of their superior properties. Existing aqueous dispersion technologies for single-walled carbon nanotubes suffer from several technical bottlenecks, such as insufficient dispersion stability, significant loss of conductivity, and short storage periods (generally no more than 3 months). Summary of the Invention

[0004] To address the problems of poor dispersion stability, significant loss of conductivity, and short storage period in existing aqueous single-walled carbon nanotube slurries, this invention provides an aqueous single-walled carbon nanotube slurry, its dispersion method, and its application. This achieves the goal of providing aqueous single-walled carbon nanotube slurry with high dispersion stability, excellent conductivity, and a long storage period, which is of great significance for promoting the industrial application of aqueous single-walled carbon nanotube slurry in fields such as new energy silicon-carbon anodes.

[0005] The technical problem solved by this invention is achieved by the following technical solution:

[0006] The present invention aims to provide a method for dispersing aqueous single-walled carbon nanotube slurry, comprising the following steps:

[0007] S1. Preparation of composite powder: Graphene oxide powder and single-walled carbon nanotube powder are stirred and mixed, and then reduced to obtain a composite powder in which reduced graphene oxide and single-walled carbon nanotubes are tightly bonded.

[0008] S2. Preparation of multi-component dispersants: Prepare sodium dodecylbenzenesulfonate, polyacrylic acid and sodium carboxymethyl cellulose for later use;

[0009] S3. Preparation of aqueous slurry: The multi-component dispersant prepared in S2 is added to deionized water and stirred to dissolve. Then, the composite powder prepared in S1 is added and homogenized by sand milling to obtain a uniform and stable aqueous single-walled carbon nanotube slurry.

[0010] While small molecule surfactants (such as sodium dodecyl sulfate) can achieve initial dispersion of aqueous single-walled carbon nanotubes, their dispersion stability is insufficient, and secondary agglomeration is prone to occur when the slurry is left for a long time (usually within 1 month). If only polymeric dispersants (such as polyvinylpyrrolidone) are used, the dispersant is prone to forming an excessively thick coating layer on the surface of carbon nanotubes, which hinders the construction of the conductive network between carbon nanotubes and results in a significant loss of conductivity (usually a reduction of 20%-30%).

[0011] Graphene oxide (GO), a carbon material with a two-dimensional sheet structure, is rich in hydrophilic groups such as hydroxyl and carboxyl groups on its surface. Its sheet structure can form a stable bond with single-walled carbon nanotubes (SUVs) through π-π stacking, which can aid in the dispersion of SUVs. However, simply mechanically mixing graphene oxide and SUVs without effective reduction treatment and synergistic dispersion system design fails to fully utilize the hydrophilic groups of graphene oxide, thus failing to solve the core problem of long-term stable dispersion and efficient retention of conductivity of SUVs. This invention achieves efficient and long-term stable dispersion of SUVs in aqueous systems through composite modification of graphene oxide and SUVs, synergistic effects of multi-component dispersants, and a dual dispersion process of "sand milling + high-pressure homogenization." Furthermore, applying this slurry to a new energy silicon-carbon anode system significantly improves the conductivity, cycle stability, and structural integrity of the silicon-carbon anode.

[0012] Furthermore, the mass of the graphene oxide powder is 5%-10% of the mass of the single-walled carbon nanotube powder.

[0013] Furthermore, the purity of the single-walled carbon nanotube powder is ≥99%, and the tube diameter is 1-2 nm.

[0014] Furthermore, in S1, the graphene oxide powder and the single-walled carbon nanotube powder are mechanically stirred at a speed of 800-1200 r / min for 30-60 min to mix them evenly.

[0015] Furthermore, in S1, the reduction process is carried out in a microwave heating device, with the microwave power set to 500-800W and the heating time set to 10-20min.

[0016] Furthermore, the amount of composite powder added is 30%-50% of the total solid content of the slurry, the amount of sodium dodecylbenzenesulfonate added is 5%-15% of the total solid content of the slurry, the amount of polyacrylic acid added is 15%-30% of the total solid content of the slurry, the amount of sodium carboxymethyl cellulose added is 20%-40% of the total solid content of the slurry, and the amount of deionized water added is 98%-99.5% of the total mass of the slurry.

[0017] Furthermore, in S3, the multi-component dispersant is added to deionized water and stirred at 500-800 r / min for 20-30 min until the dispersant is completely dissolved.

[0018] Furthermore, in S3, the grinding is carried out at a speed of 1000-1500 r / min for 60-120 min, and homogenization is carried out 5-8 times at a pressure of 800-1200 bar.

[0019] An aqueous single-walled carbon nanotube slurry was prepared by a dispersion method.

[0020] An aqueous single-walled carbon nanotube slurry dispersion method is used to prepare an aqueous single-walled carbon nanotube slurry for use in a new energy silicon-carbon anode system. The aqueous single-walled carbon nanotube slurry is used as a conductive additive and mixed with silicon-carbon anode active materials to prepare silicon-carbon anode sheets. The amount of aqueous single-walled carbon nanotube slurry added is 0.02%-0.1% of the mass of silicon-carbon anode active materials.

[0021] A method for dispersing an aqueous single-walled carbon nanotube slurry includes the following steps:

[0022] 1. Preparation of composite powder:

[0023] Single-walled carbon nanotube (SWCNT) powder with a purity ≥99% and a diameter of 1-2 nm and graphene oxide (GO) powder were selected as raw materials. Graphene oxide was added to a high-speed stirring device at 5%-10% (preferably 8%) of the SWCNT powder mass, and mechanically stirred at 800-1200 r / min for 30-60 min to ensure uniform mixing. The mixed powder was then transferred to a microwave heating device for reduction treatment. The microwave power was set to 500-800 W (preferably 650 W) and the heating time was 10-20 min (preferably 15 min). Rapid microwave heating reduced the graphene oxide, resulting in a composite powder in which reduced graphene oxide (rGO) and SWCNTs were tightly bonded. The sheet-like structure of the reduced graphene oxide can encapsulate the SWCNTs through π-π stacking, effectively weakening their agglomeration tendency.

[0024] 2. Preparation of multi-component dispersants:

[0025] Three dispersants are prepared in the following proportions: sodium dodecylbenzenesulfonate (SDBS), a small molecule surfactant; polyacrylic acid (PAA, molecular weight 5000-10000), a polymeric dispersant; and sodium carboxymethyl cellulose (CMC, viscosity 200-500 mPa·s). The amount of SDBS added is 5%-15% (preferably 10%) of the total solids content of the subsequent slurry; the amount of PAA added is 15%-30% (preferably 20%) of the total solids content of the subsequent slurry; and the amount of CMC added is 20%-40% (preferably 30%) of the total solids content of the subsequent slurry. The three dispersants work synergistically: SDBS reduces the surface tension of the system and improves wetting; PAA inhibits particle agglomeration through steric hindrance; and CMC further enhances the viscosity stability of the slurry and extends the storage period.

[0026] 3. Preparation of water-based slurry:

[0027] Add the multi-component dispersant prepared in step 2 to deionized water and stir at 500-800 r / min for 20-30 min until the dispersant is completely dissolved. Then add the composite powder prepared in step 1, controlling the raw material ratio: the amount of composite powder added is 30%-50% (preferably 40%) of the total solid content of the slurry, the amount of dispersant added is 50%-70% (preferably 60%) of the total solid content of the slurry, and the amount of deionized water added is 98%-99.5% of the total mass of the slurry. Transfer the mixture to a sand mill. In the process, the material is milled at a speed of 1000-1500 r / min (preferably 1200 r / min) for 60-120 min (preferably 90 min) to break up the initial agglomerates through the impact and shearing action of the milling beads. Then, the milled system is transferred to a high-pressure homogenizer and homogenized 5-8 times (preferably 6 times) under a pressure of 800-1200 bar (preferably 1000 bar) to further refine the particles through the cavitation and shearing effects under high pressure, and finally obtain a uniform and stable aqueous single-walled carbon nanotube slurry.

[0028] Application of the aqueous single-walled carbon nanotube slurry prepared by the above dispersion method in new energy silicon-carbon anode systems:

[0029] The aqueous single-walled carbon nanotube slurry prepared in this invention is used as a conductive additive and mixed with silicon-carbon anode active material, binder, and deionized water in a certain proportion. The silicon-carbon anode sheet is prepared by stirring, coating, drying, rolling and other processes. The amount of aqueous single-walled carbon nanotube slurry added is 0.02%-0.1% (preferably 0.05%) of the mass of silicon-carbon anode active material.

[0030] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0031] 1. This invention completely solves the technical problem of poor dispersion stability of single-walled carbon nanotubes in aqueous systems by combining "reduced graphene oxide composite modification + multi-element dispersant synergy + dual dispersion process". The prepared slurry has no obvious agglomeration after being sealed and stored at room temperature for more than 6 months, and the dispersion uniformity retention rate is ≥90%.

[0032] 2. The synergistic design of multiple dispersants avoids the loss of conductivity caused by a single dispersant. The composite structure of reduced graphene oxide and single-walled carbon nanotubes further enhances the construction of the conductive network. The resistivity of the slurry can be as low as 10 mΩ·cm, which is 30%-50% higher than that of slurries prepared by traditional single dispersants.

[0033] 3. The dispersion process is mild and controllable, requiring no extreme conditions such as high temperature or high pressure, resulting in low production costs and suitability for large-scale production.

[0034] 4. When applied to silicon-carbon anode systems, it can simultaneously improve the conductivity, structural stability, and cycle life of the electrode, providing key material support for the research and development of high-performance lithium-ion batteries and having broad prospects for industrial application.

[0035] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention, it can be implemented according to the contents of the specification. Furthermore, in order to make the above contents, objectives, features and advantages of the present invention more obvious and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0036] Figure 1 This is a SEM image of an aqueous single-walled carbon nanotube slurry prepared by a dispersion method of the present invention.

[0037] Figure 2 The graph shows the viscosity change of the slurries prepared in Examples 1, 2, Comparative Example 1 and Comparative Example 2 after 60 days of standing. Detailed Implementation

[0038] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0039] In addition, unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be obtained by purchasing from the market or prepared by existing methods.

[0040] Example 1

[0041] Preparation of composite powder: 100g of single-walled carbon nanotube powder with a purity of 99.5% and a diameter of 1-2nm was selected, and 8g of graphene oxide powder was added. The mixture was mechanically stirred at 1000r / min for 45min to mix evenly. The mixed powder was placed in a microwave heating device, and the microwave power was set to 650W and the heating time was 15min to obtain reduced graphene oxide-single-walled carbon nanotube composite powder.

[0042] Preparation of multi-component dispersant: Prepare 1.0g of SDBS, 2.0g of PAA, and 3.0g of CMC (calculated based on a total solids content of 10g in the subsequent slurry), mix them evenly and set aside.

[0043] Preparation of aqueous slurry: The above-mentioned multi-component dispersant was added to 990g of deionized water and stirred at 600r / min for 25min until completely dissolved; 4.0g of composite powder was added, stirred evenly, and then transferred to a sand mill and sand milled at 1200r / min for 90min; then it was homogenized under high pressure at 1000bar for 6 times to obtain an aqueous single-walled carbon nanotube slurry with a solid content of 1.0%.

[0044] Application testing: The slurry was added at a ratio of 0.05% by mass of silicon-carbon active material to prepare silicon-carbon negative electrode sheets and assemble them into coin cells; the test results showed that the capacity retention rate was 97.2% after 50 cycles.

[0045] Example 2

[0046] Preparation of composite powder: 100g of single-walled carbon nanotube powder with a purity of 99% and a diameter of 1-2nm was selected, and 5g of graphene oxide powder was added. The mixture was mechanically stirred at 800r / min for 60min to mix evenly. The mixed powder was placed in a microwave heating device, and the microwave power was set to 500W and the heating time was 20min to obtain reduced graphene oxide-single-walled carbon nanotube composite powder.

[0047] Preparation of multi-component dispersant: Prepare 1.5g of SDBS, 3.0g of PAA, and 4.0g of CMC (calculated based on a total solids content of 10g in the subsequent slurry), mix them evenly and set aside.

[0048] Preparation of aqueous slurry: The above-mentioned multi-component dispersant was added to 985.5g of deionized water and stirred at 500r / min for 30min until completely dissolved; 6.0g of composite powder was added, stirred evenly, and then transferred to a sand mill and sand milled at 1000r / min for 120min; then it was homogenized under high pressure at 800bar for 8 times to obtain an aqueous single-walled carbon nanotube slurry with a solid content of 1.45%.

[0049] Application testing: The slurry was added at a ratio of 0.05% by mass of silicon-carbon active material to prepare silicon-carbon negative electrode sheets and assemble them into coin cells; the test results showed that the capacity retention rate was 96.7% after 50 cycles.

[0050] Comparative Example 1

[0051] Take 4.0g of the same single-walled carbon nanotube powder as in Example 1, add it to 990g of deionized water containing 6.0g of PVP, stir evenly, and then transfer it to a sand mill. Sand mill at 1200r / min for 90min to obtain an aqueous single-walled carbon nanotube slurry.

[0052] Application testing: Silicon-carbon anode sheets were prepared by adding the same proportions and the batteries were assembled; the test results showed that the slurry showed obvious agglomeration after 2 months of storage, and the battery capacity retention rate was 88.2% after 50 cycles.

[0053] Comparative Example 2

[0054] Take 4.0g of the same single-walled carbon nanotube powder as in Example 1 and 5.0g of graphene oxide powder, add them to 990g of deionized water containing 1.0g of SDBS, stir evenly, and then transfer to a sand mill. Sand mill at 1200r / min for 90min to obtain an aqueous single-walled carbon nanotube slurry.

[0055] Application testing: Silicon-carbon anode sheets were prepared by adding the same proportion and the battery was assembled; the test results showed that the slurry still showed obvious agglomeration after 2 months of storage, and the battery capacity retention rate was 90.3% after 50 cycles.

[0056] Table 1: Cycle performance of button cells

[0057] category Initial specific capacity (mAh / g) 50-week specific capacity (mAh / g) 50-week retention rate (%) Example 1 559 543 97.2 Example 2 550 532 96.7 Comparative Example 1 543 479 88.2 Comparative Example 2 548 511 90.3

[0058] As can be seen from the comparison of the examples and comparative examples, as shown in Table 1, the aqueous single-walled carbon nanotube slurry prepared by the present invention is significantly better than other methods in terms of dispersion stability, conductivity and application effect, and has outstanding technical advantages and practical value.

[0059] The slurry of this invention has the following advantages in silicon-carbon anode systems:

[0060] Uniform dispersion of single-walled carbon nanotubes in slurry can build a continuous conductive network between silicon-carbon particles, reducing the electronic resistivity of silicon-carbon anode to below 1.0 Ω·cm and significantly reducing electrode internal resistance.

[0061] The composite structure formed by reduced graphene oxide and single-walled carbon nanotubes has excellent mechanical toughness, which can effectively buffer the volume expansion of silicon-based materials during charging and discharging, suppress electrode structure cracking, and improve the capacity retention rate of the battery to more than 85% after 1000 cycles.

[0062] The aqueous system is highly compatible with existing silicon-carbon anode production processes, requiring no additional equipment adjustments and reducing the cost of industrial application.

[0063] The sequence numbers of the above embodiments of the present invention are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0064] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A method for dispersing an aqueous single-walled carbon nanotube slurry, characterized in that, Includes the following steps: S1. Preparation of composite powder: Graphene oxide powder and single-walled carbon nanotube powder are stirred and mixed, and then reduced to obtain a composite powder in which reduced graphene oxide and single-walled carbon nanotubes are tightly bonded. S2. Preparation of multi-component dispersants: Prepare sodium dodecylbenzenesulfonate, polyacrylic acid and sodium carboxymethyl cellulose for later use; S3. Preparation of aqueous slurry: The multi-component dispersant prepared in S2 is added to deionized water and stirred to dissolve. Then, the composite powder prepared in S1 is added and homogenized by sand milling to obtain a uniform and stable aqueous single-walled carbon nanotube slurry.

2. The dispersion method of an aqueous single-walled carbon nanotube slurry as described in claim 1, characterized in that: The mass of graphene oxide powder is 5%-10% of the mass of single-walled carbon nanotube powder.

3. The dispersion method of an aqueous single-walled carbon nanotube slurry as described in claim 1, characterized in that: The purity of the single-walled carbon nanotube powder is ≥99%, and the tube diameter is 1-2 nm.

4. The dispersion method of an aqueous single-walled carbon nanotube slurry as described in claim 1, characterized in that: In S1, graphene oxide powder and single-walled carbon nanotube powder are mechanically stirred at a speed of 800-1200 r / min for 30-60 min to mix them.

5. The dispersion method of an aqueous single-walled carbon nanotube slurry as described in claim 4, characterized in that: In S1, the reduction process is carried out in a microwave heating device, with the microwave power set to 500-800W and the heating time set to 10-20min.

6. The dispersion method of an aqueous single-walled carbon nanotube slurry as described in claim 1, characterized in that: The amount of composite powder added is 30%-50% of the total solid content of the slurry, the amount of sodium dodecylbenzenesulfonate added is 5%-15% of the total solid content of the slurry, the amount of polyacrylic acid added is 15%-30% of the total solid content of the slurry, the amount of sodium carboxymethyl cellulose added is 20%-40% of the total solid content of the slurry, and the amount of deionized water added is 98%-99.5% of the total mass of the slurry.

7. The dispersion method of an aqueous single-walled carbon nanotube slurry as described in claim 1, characterized in that: In S3, the multi-component dispersant is added to deionized water and stirred at 500-800 r / min for 20-30 min until the dispersant is completely dissolved.

8. The dispersion method of an aqueous single-walled carbon nanotube slurry as described in claim 7, characterized in that: In S3, the sand mill is run at a speed of 1000-1500 r / min for 60-120 min, and then homogenized 5-8 times under a pressure of 800-1200 bar.

9. An aqueous single-walled carbon nanotube slurry prepared by the dispersion method of an aqueous single-walled carbon nanotube slurry as described in any one of claims 1-8.

10. The application of the aqueous single-walled carbon nanotube slurry prepared by the dispersion method of any one of claims 1-8 in a new energy silicon-carbon anode system, characterized in that: Aqueous single-walled carbon nanotube slurry was used as a conductive additive and mixed with silicon-carbon anode active material to prepare silicon-carbon anode sheets. The amount of aqueous single-walled carbon nanotube slurry added is 0.02%-0.1% of the mass of the silicon-carbon anode active material.

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