Graphene concentrated slurry as well as preparation method and application thereof

Abstract

The invention relates to the field of graphene materials, in particular to graphene concentrated slurry and a preparation method and application thereof. The graphene concentrated slurry with high solid content is obtained based on concentration of the small-size graphene dispersion liquid. The high-solid-content graphene concentrated slurry is a shear thickening liquid, according to the shear thickening effect, a certain network structure can be formed between graphene nanoplatelets in the slurry and a long molecular chain of a dispersing agent, and the network structure can hinder flowing of the liquid, so that the viscosity of the liquid is remarkably increased. The graphene has a special sheet structure, and the dispersing agent has a long chain structure, so that once stirring is stopped, although the external force disappears, the special network structure is not damaged, the viscosity of the slurry is not reduced, and the stability of the slurry is kept very good. The graphene concentrated slurry prepared by the method has the characteristics of high graphene content, low dispersant content, small graphene size, high stability, difficulty in sedimentation and the like.

Description

Technical Field

[0001] The present invention relates to the field of graphene materials, in particular to a graphene concentrated slurry and a preparation method and application thereof. Background Art

[0002] Graphene aqueous slurry is a graphene-based liquid material whose solvent is water. This slurry has high electrical and thermal conductivity, and therefore has a wide range of applications in new energy, lithium batteries, electric heating elements, coatings, or inks. However, traditional graphene aqueous slurries have a low graphene content, a high dispersant content, poor stability, and are prone to sedimentation, making them unsuitable for long-term storage. High-concentration graphene aqueous slurries, on the other hand, have a high graphene content, good stability, and are not prone to sedimentation. Currently, the preparation methods for high-concentration graphene aqueous slurries include ultrasonic concentration, centrifugal concentration, and evaporative concentration. Ultrasonic concentration is only suitable for dispersing graphene dispersions in low-viscosity media and cannot produce a uniform and stable graphene dispersion; the maximum single-time processing volume of centrifugal concentration is relatively small, and the equipment and maintenance costs are high; and evaporative concentration cannot remove the dispersant from the solution, resulting in a high dispersant content in the finished product. Summary of the Invention

[0003] In view of this, the technical problem to be solved by the present invention is to provide a graphene concentrated slurry, a preparation method and application thereof. The preparation method provided by the present invention can prepare a graphene concentrated slurry with high graphene content, low dispersant content, small graphene size, high stability and not easy to settle.

[0004] The present invention provides a method for preparing a graphene concentrated slurry, comprising the following steps:

[0005] S1) preparing a graphene dispersion having a particle size D50 ≤ 4 μm by using a long-chain polymer dispersant and graphite powder;

[0006] S2) The graphene dispersion obtained in step S1) is concentrated, emulsified, dispersed and stirred to obtain a graphene concentrated slurry.

[0007] The inventors of this application have creatively discovered that by using a long-chain polymer as a dispersant and preparing graphite powder into a graphene dispersion with a particle size D50 ≤ 4 μm, the graphene dispersion can be subsequently concentrated to a high solid content, thereby obtaining a high-solids graphene concentrated slurry with the characteristics of high graphene content, low dispersant content, small graphene size, high stability, and low sedimentation resistance. The present invention preferably prepares a graphene dispersion with a particle size D50 of 0.5 μm to 4 μm using a long-chain polymer dispersant and graphite powder. The long-chain polymer dispersant of the present invention is selected from one or more of polyvinyl pyrrolidone, alkali lignin, polyethylene glycol, or polyvinyl alcohol.

[0008] The present invention first prepares a graphene dispersion with a particle size D50 ≤ 4 μm by combining a long-chain polymer dispersant and graphite powder. Specifically, the long-chain polymer dispersant and graphite powder are dispersed in water and thoroughly mixed through emulsification and stirring to obtain a graphene mixture. The resulting graphene mixture is then ground until the graphene dispersion has a particle size D50 ≤ 4 μm. More specifically, the long-chain polymer dispersant is dissolved in water, graphite powder is added, and thoroughly mixed through emulsification and stirring to obtain a graphene mixture. The resulting graphene mixture is then ground until the graphene dispersion has a particle size D50 ≤ 4 μm. The emulsification and stirring time is 20 to 40 minutes. The graphite powder is selected from one or more of expanded graphite and flake graphite. The mass ratio of the long-chain polymer dispersant to the graphite powder is 1:(5-30), preferably 1:(5-15), and more preferably 1:(7-13). The solid content of the graphene dispersion of the present invention is 0.5% to 3%.

[0009] After obtaining a graphene dispersion with a particle size of D50 ≤ 4 μm, the present invention concentrates the obtained graphene dispersion, emulsifies, disperses, and stirs it to obtain a concentrated graphene slurry. Specifically, the obtained graphene dispersion with a particle size of D50 ≤ 4 μm is first concentrated to a solid content of 4% to 20% through a concentration and filtration system. In step S1), the present invention achieves efficient exfoliation of graphene through fluid dynamics such as shear, collision, and cavitation to obtain a small-sized graphene dispersion with a particle size of D50 ≤ 4 μm. The small-sized graphene dispersion is separated from the dispersant aqueous solution through the concentration and filtration system to obtain a concentrated graphene slurry with a solid content of 4% to 20%. If the particle size D50 of the prepared graphene dispersion is greater than 4 μm, the obtained graphene dispersion cannot be concentrated to this solid content range.

[0010] The present invention concentrates a graphene dispersion with a particle size D50 ≤ 4 μm through a concentration and filtration system to a solid content of 4% to 20%. The concentrated material is then emulsified and dispersed through an emulsifier pump. The concentrated material is homogenized and emulsified by the emulsifier pump to eliminate large particles that agglomerated during the concentration process.

[0011] The present invention is to emulsify and disperse the concentrated material by an emulsifying pump, and then subject the emulsified and dispersed material to stirring and shear thickening to obtain a graphene concentrated slurry. Specifically, the emulsified and dispersed material is stirred at a speed of 20 r / min~50 r / min, and the material is obviously thickened. The material is stirred until the viscosity of the emulsified and dispersed material is 2000mPa.s or more, and a graphene concentrated slurry with a viscosity of ≥2000mPa·s is obtained. It is preferably stirred until the viscosity of the emulsified and dispersed material is 4000mPa·s~15000mPa·s, and a graphene concentrated slurry with a viscosity of 4000mPa·s~15000mPa·s is obtained. The high-solids graphene concentrated slurry is a shear thickening liquid. According to the shear thickening effect, a shear stress is applied to the concentrated slurry by stirring, and a certain network structure is formed between the graphene microplatelets in the slurry and the long molecular chains of the dispersant. This network structure hinders the flow of the liquid and significantly increases its viscosity.

[0012] The present invention provides a concentrated graphene slurry obtained by the preparation method described in any of the above technical solutions. During the preparation process, due to the unique flaky structure of graphene and the long chain structure of the dispersant, once stirring is stopped, although the external force disappears, this unique network structure is not destroyed, so the viscosity of the slurry does not decrease, thereby maintaining excellent stability of the concentrated graphene slurry obtained by the above preparation method.

[0013] The present invention provides the application of the graphene concentrated slurry obtained by the preparation method described in any of the above technical solutions in the fields of lithium batteries, electric heating elements, coatings or inks. For the field of lithium batteries, specifically, it provides the application of the graphene concentrated slurry obtained by the preparation method described in any of the above technical solutions in the preparation of lithium battery positive electrode materials and graphite negative electrodes, silicon-based negative electrode materials for coating and modification. For the field of electric heating elements, specifically, it provides the application of the graphene concentrated slurry obtained by the preparation method described in any of the above technical solutions in the preparation of thermal conductive materials for electric heating elements. For the field of coatings, specifically, it provides the application of the graphene concentrated slurry obtained by the preparation method described in any of the above technical solutions in the preparation of thermally conductive and anti-corrosion coatings. For the field of inks, specifically, it provides the application of the graphene concentrated slurry obtained by the preparation method described in any of the above technical solutions in the preparation of graphene inks. Graphene inks can be used in printed electronics, flexible electronics, sensors, conductive coatings and other fields.

[0014] The present invention provides a graphene concentrated slurry, a preparation method thereof, and an application thereof. The present invention realizes efficient exfoliation of graphene through fluid dynamic effects such as shear, collision, and cavitation, thereby obtaining a small-sized graphene dispersion liquid. The small-sized graphene dispersion liquid is then concentrated to obtain a graphene concentrated slurry with a high solid content. The high-solid-content graphene concentrated slurry is a shear-thickening liquid. According to the shear-thickening effect, a shear stress is applied to the concentrated slurry by stirring, and a certain network structure is formed between the graphene microsheets in the slurry and the long molecular chains of the dispersant. This network structure hinders the flow of the liquid and significantly increases its viscosity. Since graphene has a special flaky structure and the dispersant has a very long chain structure, once stirring is stopped, although the external force disappears, this special network structure is not destroyed, so the viscosity of the slurry does not decrease, thereby allowing the slurry to maintain good stability. The preparation method provided by the present invention has the advantages of simple operation and good effect. The graphene concentrated slurry prepared by this method has the characteristics of high graphene content, low dispersant content, small graphene size, high stability and not easy to settle. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A process flow chart of the method for preparing the graphene concentrated slurry provided by the present invention;

[0016] Figure 2 This is a photo of the finished product of the graphene concentrated slurry according to Example 1 of the present invention;

[0017] Figure 3 The concentrated slurry product prepared in Example 1 of the present invention is shown in a photograph after standing for 30 days and in a redispersed state in an aqueous solution;

[0018] Figure 4 The concentrated slurry product prepared in Example 2 of the present invention is shown in a photograph after standing for 30 days and in a redispersed state in an aqueous solution;

[0019] Figure 5 The concentrated slurry product prepared in Example 3 of the present invention is shown in a photograph after standing for 30 days and in a redispersed state in an aqueous solution;

[0020] Figure 6 The concentrated slurry product prepared in Example 4 of the present invention is shown in a photograph after standing for 30 days and in a redispersed state in an aqueous solution;

[0021] Figure 7 The concentrated slurry product prepared in Comparative Example 1 of the present invention is shown in a photograph after standing for 30 days and in a redispersed state in an aqueous solution;

[0022] Figure 8 These are photos of the concentrated slurry product prepared in Comparative Example 2 of the present invention after standing for 30 days and its redispersed state in an aqueous solution. DETAILED DESCRIPTION

[0023] The present invention discloses a graphene concentrated slurry, a preparation method thereof, and an application thereof. Those skilled in the art may refer to the contents of this invention and appropriately improve the process parameters for implementation. It should be noted in particular that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in the present invention. The methods and applications of the present invention have been described through preferred embodiments, and relevant personnel can obviously modify or appropriately change and combine the methods and applications herein without departing from the content, spirit, and scope of the present invention to implement and apply the technology of the present invention.

[0024] The present invention is based on Figure 1 The process shown is used to prepare the graphene concentrated slurry. Figure 1 This is a process flow chart of the method for preparing the graphene concentrated slurry provided by the present invention.

[0025] The present invention will be further described below with reference to the embodiments:

[0026] Example 1

[0027] 40 g of polyvinyl pyrrolidone (PVP) dispersant was added to 19.56 kg of pure water and stirred until the dispersant was completely dissolved. Then 400 g of expanded graphite was added and emulsified and stirred for 30 min to fully mix the mixture to obtain a graphene mixture. The graphene mixture was ground and crushed several times by a grinding device to obtain a small-sized graphene dispersion with a particle size D50 of 3.20 μm. The graphene dispersion was concentrated to a solid content of 5.50% by a concentration and filtration system, and its viscosity was 324 mPa·s. The 5.50% graphene dispersion was emulsified once by an emulsification pump, and then stirred by a stirrer at 30 r / min until it became significantly thickened. Its viscosity was 7649 mPa·s. Figure 2 As shown, Figure 2 This is a photo of the finished product of the graphene concentrated slurry according to Example 1 of the present invention.

[0028] like Figure 3 As shown, Figure 3 The concentrated slurry product prepared in Example 1 of the present invention is in a state after being left to stand for 30 days and in a photo of its redispersion in an aqueous solution. Figure 3 (a) It can be seen that after the concentrated slurry product was left standing for 30 days, no stratification occurred, indicating that the slurry had good stability. Figure 3 (b) It can be seen that the concentrated slurry has good redispersibility in aqueous solution and no particles are found.

[0029] Example 2

[0030] 40 g of PVP dispersant was added to 19.56 kg of pure water and stirred until the dispersant was completely dissolved. 400 g of expanded graphite was then added and stirred for 30 minutes to thoroughly mix the mixture. This yielded a graphene mixture. The mixture was then ground several times using a grinding machine to produce a small-sized graphene dispersion with a particle size D50 of 2.04 μm. The graphene dispersion was concentrated to a solids content of 6.28% using a concentration and filtration system, with a viscosity of 432 mPa·s. The 6.28% graphene dispersion was emulsified once using an emulsifier pump and then stirred in a blender at 30 rpm until noticeably thickened. The viscosity was 8679 mPa·s.

[0031] like Figure 4 As shown, Figure 4 The following are photos of the concentrated slurry product prepared in Example 2 of the present invention after standing for 30 days and its redispersed state in an aqueous solution. Figure 4 (a) It can be seen that after the concentrated slurry product was left standing for 30 days, no stratification occurred, indicating that the slurry had good stability. Figure 4 (b) It can be seen that the concentrated slurry has good redispersibility in aqueous solution and no particles are found.

[0032] Example 3

[0033] 40 g of PVP dispersant was added to 19.56 kg of pure water and stirred until the dispersant was completely dissolved. 400 g of expanded graphite was then added and stirred for 30 minutes to thoroughly mix the mixture. This yielded a graphene mixture. The mixture was then ground several times using a grinding machine to produce a small-sized graphene dispersion with a particle size D50 of 0.93 μm. The graphene dispersion was concentrated to a solids content of 19.23% using a concentration and filtration system, with a viscosity of 862 mPa·s. The 19.23% graphene dispersion was emulsified once using an emulsifier pump and then stirred in a blender at 30 rpm until noticeably thickened. The viscosity was 10358 mPa·s.

[0034] like Figure 5 As shown, Figure 5 The photo shows the concentrated slurry product prepared in Example 3 of the present invention after standing for 30 days and its redispersed state in aqueous solution. Figure 5 (a) It can be seen that after the concentrated slurry product was left standing for 30 days, no stratification occurred, indicating that the slurry had good stability. Figure 5 (b) It can be seen that the concentrated slurry has good redispersibility in aqueous solution and no particles are found.

[0035] Example 4

[0036] 40 g of alkali lignin dispersant was added to 19.56 kg of pure water and stirred until the dispersant was completely dissolved. 400 g of expanded graphite was then added and stirred for 30 minutes to thoroughly mix the mixture. This yielded a graphene mixture. The mixture was then ground several times using a grinding machine to produce a small-sized graphene dispersion with a particle size D50 of 2.94 μm. The graphene dispersion was concentrated to a solids content of 10.23% using a concentration and filtration system, with a viscosity of 362 mPa·s. The 10.23% graphene dispersion was emulsified once using an emulsifier pump and then stirred in a blender at 30 rpm until noticeably thickened. The viscosity was 9568 mPa·s.

[0037] like Figure 6 As shown, Figure 6 The concentrated slurry product prepared in Example 4 of the present invention is in a state after being left to stand for 30 days and in a photo of its redispersion in an aqueous solution. Figure 6 (a) It can be seen that after the concentrated slurry product was left standing for 30 days, no stratification occurred, indicating that the slurry had good stability. Figure 6 (b) It can be seen that the concentrated slurry has good redispersibility in aqueous solution and no particles are found.

[0038] Comparative Example 1

[0039] 40 g of PVP dispersant was added to 19.56 kg of pure water and stirred until the dispersant was completely dissolved. 400 g of expanded graphite was then added and stirred for 30 minutes to thoroughly mix the mixture. This yielded a graphene mixture. The mixture was then ground several times using a grinding machine to produce a small-sized graphene dispersion with a particle size D50 of 4.32 μm. The graphene dispersion was concentrated to a solids content of 3.58% using a concentration and filtration system. At this point, the viscosity of the material in the concentration and filtration system was very high, reaching 3551 mPa·s, and further concentration was impossible. The 3.58% solids graphene dispersion was emulsified once using an emulsifier pump and then stirred evenly in a blender at 30 rpm.

[0040] like Figure 7 As shown, Figure 7 The concentrated slurry product prepared in Comparative Example 1 of the present invention is in a state after being left to stand for 30 days and in a photo of its redispersion in an aqueous solution. Figure 7 (a) It can be seen that after the concentrated slurry product was left standing for 30 days, no stratification occurred, indicating that the slurry had good stability. Figure 7 (b) It can be seen that a small amount of particles are found in the concentrated slurry in the aqueous solution, indicating that the redispersibility of the concentrated slurry is poor and there is obvious agglomeration.

[0041] Comparative Example 2

[0042] 40 g of polynaphthalene formaldehyde sulfonic acid sodium salt (MF) dispersant was added to 19.56 kg of pure water and stirred until the dispersant was completely dissolved. 400 g of expanded graphite was then added and stirred for 30 minutes to thoroughly mix the mixture. This yielded a graphene mixture. The mixture was then ground several times using a grinding machine to produce a small-sized graphene dispersion with a particle size D50 of 2.69 μm. The graphene dispersion was concentrated to a solids content of 12.56% and a viscosity of 486 mPa·s using a concentration and filtration system. The 12.56% graphene dispersion was emulsified once using an emulsifier pump and then stirred in a blender at 30 rpm for 16 hours. The material exhibited no signs of shear thickening.

[0043] like Figure 8 As shown, Figure 8 The concentrated slurry product prepared in comparative example 2 of the present invention is in a state after standing for 30 days and in a photo of its redispersion in an aqueous solution. Figure 8 (a) It can be seen that after the concentrated slurry product was left standing for 30 days, obvious stratification occurred, indicating that the stability of the slurry was very poor. Figure 8 (b) It can be seen that the concentrated slurry has good redispersibility in aqueous solution and no particles are found.

[0044] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A method for preparing a graphene concentrated slurry, characterized in that: The following steps are involved: S1) preparing a graphene dispersion having a particle size D50 ≤ 4 μm by using a long-chain polymer dispersant and graphite powder; S2) The graphene dispersion obtained in step S1) is concentrated, emulsified, dispersed and stirred to obtain a graphene concentrated slurry.

2. The preparation method according to claim 1, characterized in that In step S1), a long-chain polymer dispersant and graphite powder are prepared into a graphene dispersion having a particle size D50 of 0.5 μm to 4 μm.

3. The preparation method according to claim 1, characterized in that In step S1), the long-chain polymer dispersant is selected from one or more of polyvinyl pyrrolidone, alkali lignin, polyethylene glycol or polyvinyl alcohol.

4. The preparation method according to claim 1, characterized in that In step S1), the graphite powder is selected from one or more of expanded graphite and flake graphite.

5. The preparation method according to claim 1, characterized in that In step S1), the mass ratio of the long-chain polymer dispersant to the graphite powder is 1:(5-30).

6. The preparation method according to claim 1, characterized in that In step S1), the solid content of the graphene dispersion is 0.5% to 3%.

7. The preparation method according to claim 1, characterized in that In step S2), the graphene dispersion obtained in step S1) is concentrated to a solid content of 4% to 20%.

8. The preparation method according to claim 7, characterized in that In step S2), the mixture is stirred until the viscosity of the emulsified and dispersed material is greater than 2000 mPa·s.

9. The graphene concentrated slurry obtained by the preparation method described in any one of claims 1 to 8.

10. Use of the graphene concentrated slurry obtained by the preparation method according to any one of claims 1 to 8 in the fields of lithium batteries, electric heating elements, coatings or inks.

Images