Additive for preventing agglomeration of carbon-based negative electrode slurry and application thereof

Abstract

Compared with the prior art, the additive for preventing agglomeration of the carbon-based negative electrode slurry and the application thereof provided by the invention have the advantages that the non-ionic surfactant and the high-molecular active agent are used as raw materials, so that the phenomena that a carbon-based negative electrode material is extremely easy to agglomerate and poor in dispersion effect in the stirring process are improved; and agglomerated carbon surface powder material particles can be in a stable dispersed state, so that particle agglomeration is avoided in a slurry stirring and dispersing process. The dispersion effect of the slurry is improved; the stirring and dispersing time of the negative electrode powder is shortened, and the production efficiency is improved. The raw materials of the additive provided by the invention are completely used and non-toxic, so that the occupational safety of workers can be guaranteed.

Description

Technical Field

[0001] The present invention belongs to the technical field of carbon-based anodes for lithium batteries, and specifically relates to an additive for preventing agglomeration of carbon-based anode slurries and its application. Background Art

[0002] Under the background of energy conservation and environmental protection, new energy has received increasing attention, and energy storage technologies represented by lithium-ion batteries have witnessed rapid development. Due to advantages such as high energy density, small size, and long service life, lithium-ion batteries are widely used in production and life.

[0003] The main purpose of the lithium battery slurry-making process is to uniformly disperse substances such as active materials, conductive agents, and binders to obtain a uniform and stable slurry for the electrode coating process. In an ideal electrode structure, the particles of each component are uniformly dispersed without agglomeration, and the active particles are in full contact with the conductive agent and the binder, forming a good electronic conduction and ion conduction network. The macroscopic process of the slurry-making process is the dispersion and uniform mixing of different components, while the microscopic process involves the interaction between particles during the slurry-making process and the formation of a stable network structure.

[0004] However, in the actual production process of aqueous anode slurries, graphite and conductive carbon (SP) will re-agglomerate after being stirred and dispersed in water due to their non-polarity and surface hydrophobicity. The currently popular system in the industry is the combined use of sodium carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR).

[0005] Due to the phenomenon that carbon-based anode materials are extremely prone to particle agglomeration and poor dispersion during the stirring process, problems such as material blockage and pitting on the electrode after drying will occur during the extrusion coating process, resulting in quality problems of the electrode. In the subsequent rolling process, due to uneven stress at the poorly coated areas, the electrode is extremely prone to fracture and local microcracks, which cause great harm to the cycle performance, rate performance, and safety performance of the battery. Summary of the Invention

[0006] The purpose of the present invention is to provide an additive for preventing agglomeration of carbon-based anode slurries and its application. The additive uses non-ionic surfactants and polymer surfactants as raw materials to improve the phenomenon that carbon-based anode materials are extremely prone to particle agglomeration and poor dispersion during the stirring process. It can make the agglomerated carbon surface powder material particles in a stable dispersed state, avoid the occurrence of particle agglomeration during the stirring and dispersion process of the slurry, improve the dispersion effect of the slurry, shorten the time for the negative electrode powder during the stirring and dispersion process, and improve production efficiency.

[0007] The specific technical solution of the present invention is as follows:

[0008] An additive for preventing agglomeration of carbon-based anode slurries, the raw materials of which include non-ionic surfactants and polymer surfactants;

[0009] The mass percentage of the non-ionic surfactant in the additive for preventing the aggregation of the carbon-based anode slurry is 5-15%;

[0010] The non-ionic surfactant is selected from at least one of polyvinylpyrrolidone (model PVP-K15, molecular weight about 10,000), polyethylene glycol (model PEG400), and polyvinyl alcohol (model L088-20);

[0011] The mass percentage of the polymeric surfactant in the additive for preventing the aggregation of the carbon-based anode slurry is 5-15%;

[0012] The polymeric surfactant is selected from at least one of sodium polyacrylate (low molecular weight, molecular weight 1000-9000), polyacrylamide (low molecular weight, molecular weight less than 5 million), and polycarboxylic acid polymer;

[0013] The raw materials of the additive for preventing the aggregation of the carbon-based anode slurry further include water, and the balance is water, preferably 70-90%.

[0014] Preferably, for the additive for preventing the aggregation of the carbon-based anode slurry, the raw materials include 5-15% non-ionic surfactant, 5-15% polymeric surfactant, and the balance is water;

[0015] Preferably, the additive for preventing the aggregation of the carbon-based anode slurry includes the following raw materials by mass percentage: 10% polyvinylpyrrolidone (PVP), 10% sodium polyacrylate (PAAS), and 80% water.

[0016] An application of an additive for preventing the aggregation of the carbon-based anode slurry provided by the present invention is used for preparing the carbon-based anode slurry;

[0017] The specific application method is as follows:

[0018] Add the additive for preventing the aggregation of the carbon-based anode slurry into the carbon-based anode slurry according to a mass percentage of 2%. That is, if the total weight of the prepared slurry is 500 kg, 10 kg of the additive needs to be added.

[0019] Preferably, the specific application method is as follows:

[0020] 1) Stir and disperse the additive for preventing the aggregation of the carbon-based anode slurry, the anode material, conductive carbon, sodium carboxymethylcellulose, and pure water (the pure water is calculated according to the overall solid content. According to the solid content of the anode slurry being 60%, the amount of pure water to be added is 40%);

[0021] 2) Then add styrene-butadiene rubber and continue to stir and disperse.

[0022] The negative electrode material: conductive carbon: sodium carboxymethyl cellulose: styrene-butadiene rubber = 96.5:1:0.5:2.

[0023] In the present invention, the non-ionic surfactant has amphiphilicity and can effectively coat the surface of the particles through steric hindrance to prevent direct contact and aggregation between the particles; through synergistic action with the polymeric surfactant, electrostatic repulsion is generated between the particles, thereby preventing particle aggregation. At the same time, a thick steric hindrance layer is formed on the surface of the particles to further prevent direct contact between the particles.

[0024] In the present invention, PVP in the additive raw materials is a kind of polymeric compound with the characteristics of a non-ionic surfactant. It can carry a weak charge by adsorbing hydrogen ions or hydroxide ions in water in the solution, and these charges generate repulsive forces between the graphite particles, further preventing the aggregation of graphite particles; at the same time, the polar groups in the PVP molecule can interact with the polar sites on the surface of the graphite particles, so as to firmly adsorb on the surface of the graphite particles, not only enhancing the binding force between PVP and the graphite particles, but also enabling PVP to form a uniform covering layer on the surface of the graphite particles, effectively preventing the aggregation between the graphite particles.

[0025] PAAS in the additive raw materials is a kind of polymeric compound, and a large number of carboxyl (-COOH) groups are contained in its molecular chain. These carboxyl groups can be partially or completely ionized into carboxylate ions (-COO-) in water, generating repulsive forces between the graphite particles and improving the dispersion effect of the graphite slurry.

[0026] Moreover, both PVP and PAAS in the additive raw materials are water-soluble substances and can be dissolved quickly in water, making the preparation convenient.

[0027] Polyacrylamide, polycarboxylic acid polymers: These polymeric surfactants can also prevent particle aggregation through similar electrostatic repulsion and steric hindrance effects.

[0028] Compared with the prior art, the additive provided by the present invention can improve the wettability of the carbon-based negative electrode material, enhance the dispersion ability of the material, and avoid particle aggregation in the slurry; the additive provided by the present invention can optimize the slurry stirring process, shorten the stirring time, and improve production efficiency; the additive raw materials provided by the present invention are completely used and non-toxic, which can ensure the occupational safety of the staff. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is the coating effect of Comparative Example 1;

[0030] Figure 2 It is the coating effect of Comparative Example 2;

[0031] Figure 3For the coating effect of Comparative Example 3;

[0032] Figure 4 For the coating effect of Comparative Example 4;

[0033] Figure 5 For the coating effect of Example 1;

[0034] Figure 6 For the coating effect of Example 2;

[0035] Figure 7 For the coating effect of Example 3;

[0036] Figure 8 For the coating effect of Example 4;

[0037] Figure 9 For the comparison of the backscattered light intensity between Comparative Example 1 and Example 1;

[0038] Figure 10 For the comparison of the stability test between Comparative Example 1 and Example 1. Detailed implementation manners

[0039] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0040] The test materials and reagents used in the following embodiments, unless otherwise specified, can all be obtained through commercial channels.

[0041] For those not specifying specific technologies or conditions in the embodiments, they can all be carried out according to the technologies or conditions described in the literature in this field or according to the product specifications.

[0042] The raw materials used in the following examples and comparative examples are the same: the negative electrode material uses conductive graphite KS-6; the conductive carbon is acetylene black; the styrene-butadiene rubber uses styrene-butadiene rubber SBR 1502; the polyvinylpyrrolidone (model PVP-K15, molecular weight about 10,000), polyethylene glycol (model PEG400), polyvinyl alcohol (model L088-20) are used; polyacrylic acid sodium (low molecular weight, molecular weight 1000 - 9000), polyacrylamide (low molecular weight, molecular weight less than 5 million).

[0043] Comparative Example 1

[0044] A preparation process of a carbon-based negative electrode (homogenization time 4h):

[0045] 1) Prepare the ingredients according to the mass ratio of negative electrode material: conductive carbon: sodium carboxymethyl cellulose: styrene-butadiene rubber

[0046] = 96.5:1:0.5:2;

[0047] 2) Stir and disperse the negative electrode material, conductive carbon, sodium carboxymethyl cellulose and pure water for 3 h at a stirring rate of 1200 r / min, and control the water addition to make the solid content 60%;

[0048] 3) After the dispersion is completed, add styrene-butadiene rubber and continue to stir for 1 h at a stirring rate of 800 r / min;

[0049] 4) Perform coating and observe the coating effect.

[0050] Comparative Example 2

[0051] A preparation process of a carbon-based negative electrode (homogenization time: 2 h):

[0052] 1) Prepare the ingredients according to the mass ratio of negative electrode material: conductive carbon: sodium carboxymethyl cellulose: styrene-butadiene rubber = 96.5:1:0.5:2;

[0053] 2) Stir and disperse the negative electrode material, conductive carbon, sodium carboxymethyl cellulose and pure water for 1 h at a stirring rate of 1200 r / min, and control the water addition to make the solid content 60%;

[0054] 3) After the dispersion is completed, add styrene-butadiene rubber and continue to stir and disperse for 1 h at a stirring rate of 800 r / min;

[0055] 4) Perform coating and observe the coating effect.

[0056] Comparative Example 3

[0057] A preparation process of a carbon-based negative electrode (additive: 10% polyvinylpyrrolidone + 90% water, homogenization time: 2 h):

[0058] 1) Prepare the additive by mixing 10% polyvinylpyrrolidone and 90% water;

[0059] 2) Prepare the ingredients according to the mass ratio of negative electrode material: conductive carbon: sodium carboxymethyl cellulose: styrene-butadiene rubber = 96.5:1:0.5:2;

[0060] 3) Stir and disperse the negative electrode material, conductive carbon, sodium carboxymethyl cellulose, pure water and the additive for 1 h at a stirring rate of 1200 r / min, and control the water addition to make the solid content 60%; add the additive according to 2% of the mass percentage;

[0061] 4) After the dispersion is completed, add styrene butadiene rubber and continue to stir and disperse for 1 hour; the stirring rate is 800r / min;

[0062] 5) Carry out coating and observe the coating effect.

[0063] Comparative Example 4

[0064] Preparation process of a carbon-based negative electrode (additive is 10% sodium polyacrylate + 90% water, homogenization time is 2h):

[0065] 1) Prepare additives according to 10% sodium polyacrylate + 90% water;

[0066] 2) preparing the negative electrode material: conductive carbon: sodium carboxymethyl cellulose: styrene butadiene rubber in a ratio of 96.5:1:0.5:2;

[0067] 3) Stir and disperse the negative electrode material, conductive carbon, sodium carboxymethyl cellulose, pure water and additives for 1 hour; add water to control the solid content to 60%, and stir at a rate of 1200 r / min; add additives at a mass percentage of 2%;

[0068] 4) After the dispersion is completed, add styrene butadiene rubber and continue to stir and disperse for 1 hour; the stirring rate is 800r / min;

[0069] 5) Carry out coating and observe the coating effect.

[0070] Example 1

[0071] An application of an additive for preventing agglomeration of a carbon-based negative electrode slurry is used to prepare a carbon-based negative electrode slurry (the additive is 10% polyvinyl pyrrolidone + 10% sodium polyacrylate + 80% water, and the homogenization time is 2h), and the specific method is:

[0072] 1) preparing an additive according to the mass percentage of 10% polyvinyl pyrrolidone + 10% sodium polyacrylate + 80% water;

[0073] 2) preparing the negative electrode material: conductive carbon: sodium carboxymethyl cellulose: styrene butadiene rubber in a ratio of 96.5:1:0.5:2;

[0074] 3) Stir and disperse the negative electrode material, conductive carbon, sodium carboxymethyl cellulose, pure water and additives for 1 hour; add water to control the solid content to 60%, and stir at a rate of 1200 r / min; add additives at a mass percentage of 2%;

[0075] 4) After the dispersion is completed, add styrene butadiene rubber and continue to stir and disperse for 1 hour; the stirring rate is 800r / min;

[0076] 5) Carry out coating and observe the coating effect.

[0077] Example 2

[0078] An application of an additive for preventing agglomeration of a carbon-based negative electrode slurry is used to prepare a carbon-based negative electrode slurry (the additive is 10% polyethylene glycol + 10% sodium polyacrylate + 80% water, and the homogenization time is 2h), and the specific method is:

[0079] 1) preparing an additive according to the mass percentage of 10% polyethylene glycol + 10% sodium polyacrylate + 80% water;

[0080] 2) preparing the negative electrode material: conductive carbon: sodium carboxymethyl cellulose: styrene butadiene rubber in a ratio of 96.5:1:0.5:2;

[0081] 3) Stir and disperse the negative electrode material, conductive carbon, sodium carboxymethyl cellulose, pure water and additives for 1 hour; add water to control the solid content to 60%, and stir at a rate of 1200 r / min; add additives at a mass percentage of 2%;

[0082] 4) After the dispersion is completed, add styrene butadiene rubber and continue to stir and disperse for 1 hour; the stirring rate is 800r / min;

[0083] 5) Carry out coating and observe the coating effect.

[0084] Example 3

[0085] An application of an additive for preventing agglomeration of a carbon-based negative electrode slurry is used to prepare a carbon-based negative electrode slurry (the additive is 10% polyethylene glycol + 10% polyacrylamide + 80% water, and the homogenization time is 2h), and the specific method is:

[0086] 1) preparing an additive according to the mass percentage of 10% polyethylene glycol + 10% polyacrylamide + 80% water;

[0087] 2) preparing the negative electrode material: conductive carbon: sodium carboxymethyl cellulose: styrene butadiene rubber in a ratio of 96.5:1:0.5:2;

[0088] 3) Stir and disperse the negative electrode material, conductive carbon, sodium carboxymethyl cellulose, pure water and additives for 1 hour; add water to control the solid content to 60%, and stir at a rate of 1200 r / min; add additives at a mass percentage of 2%;

[0089] 4) After the dispersion is completed, add styrene butadiene rubber and continue to stir and disperse for 1 hour; the stirring rate is 800r / min;

[0090] 5) Carry out coating and observe the coating effect.

[0091] Example 4

[0092] An application of an additive for preventing agglomeration of a carbon-based negative electrode slurry is used to prepare a carbon-based negative electrode slurry (the additive is 5% polyvinyl pyrrolidone + 5% sodium polyacrylate + 90% water, and the homogenization time is 2h), and the specific method is:

[0093] 1) preparing an additive according to the mass percentage of 5% polyvinyl pyrrolidone + 5% sodium polyacrylate + 90% water;

[0094] 2) preparing the negative electrode: conductive carbon: sodium carboxymethyl cellulose: styrene butadiene rubber in a ratio of 96.5:1:0.5:2;

[0095] 3) Stir and disperse the negative electrode, conductive carbon, sodium carboxymethyl cellulose, pure water and additives for 1 hour; add water to control the solid content to 60%, and stir at a rate of 1200 r / min; add additives at a mass percentage of 2%;

[0096] 4) After the dispersion is completed, add styrene butadiene rubber and continue to stir and disperse for 1 hour; the stirring rate is 800r / min;

[0097] 5) Carry out coating and observe the coating effect.

[0098] Comparative Examples 1 to 4 and Examples 1 to 4 were subjected to the following tests:

[0099] 1. Coating result detection:

[0100] from Figures 1 - 8 The coating effect after homogenization can be seen:

[0101] In Comparative Example 1, no additives were added in the traditional way, and when the homogenization time was extended to 4 hours, no obvious particles appeared during coating;

[0102] In Comparative Example 2, particles appeared when the coating was applied after 2 hours of homogenization without adding additives in the traditional way;

[0103] In Comparative Example 3, additives were added, but sodium polyacrylate was not added. When the homogenization time was 2 hours, particles appeared during coating.

[0104] In Comparative Example 4, additives were added, but polyvinyl pyrrolidone was not added. When the homogenization time was 2 hours, particles appeared during coating.

[0105] In Example 1, which is a preferred example of the present invention, the additive of the present invention is used. When the homogenization time is 2 hours, no particles appear during coating, indicating that the additive of the present invention can effectively improve the dispersion effect of the carbon-based negative electrode material, and the homogenization efficiency (only 2 hours) is doubled;

[0106] In Examples 2, 3, and 4, the components and contents of the additives were changed, the homogenization time was 2 hours, and no particles appeared during coating, which can realize the present invention.

[0107] II. Comparison of Slurry Stability Tests:

[0108] The stability of the slurry without using additives and homogenized for 4 h (Comparative Example 1) and the slurry using additives and homogenized for 2 h (Example 1) was characterized using a multiple light scattering instrument (model Formulaction); the characterization conditions were: backscattering scanning frequency 1 time / 1 min, scanning time 1 h.

[0109] Comparison of the dispersion uniformity index:

[0110] In Comparative Example 1, without using the additive of the present invention and homogenized for 4 h, the initial dispersion uniformity index of the slurry was 0.112%.

[0111] In Example 1, using the additive of the present invention and homogenized for 2 h, the initial dispersion uniformity index of the slurry was 0.038%.

[0112] The lower the initial dispersion uniformity index, the more uniform the dispersion of the slurry.

[0113] Comparison of the backscattered light intensity:

[0114] The initial backscattered light intensity of Comparative Example 1 was lower than that of Example 1 ( Figure 9 ), and the greater the backscattered light intensity, the smaller the particles in the slurry. Therefore, the slurry prepared by homogenization using the additive of the present invention has improved uniformity and dispersion.

[0115] Comparison of stability:

[0116] The results are as Figure 10 , and it can be seen that:

[0117] Comparative Example 1 and Example 1 were subjected to a stability test within 1 h. It can be seen that the TSI index of Comparative Example 1 increased higher within 1 h than that of Example 1. TSI is the instability index of the slurry, and the higher the TSI, the more unstable the slurry. Therefore, it can be seen that the stability of the slurry prepared using the additive of the present invention has also been improved.

[0118] In summary, the slurry prepared using the additive of the present invention can shorten the homogenization time, and at the same time, the dispersion uniformity and slurry stability can be improved.

[0119] The descriptions of the above embodiments are for the convenience of those of ordinary skill in the art to understand and use the invention. Those skilled in the art can obviously make various modifications to these embodiments easily and apply the general principles described herein to other embodiments without creative labor. Therefore, the present invention is not limited to the above embodiments, and the improvements and modifications made by those skilled in the art without departing from the scope of the present invention according to the disclosure of the present invention should be within the protection scope of the present invention.

Claims

1. An additive for preventing agglomeration of carbon-based negative electrode slurry, characterized in that: The raw materials of the additive include non-ionic surfactant and high molecular active agent.

2. The additive according to claim 1, characterized in that The nonionic surfactant is selected from at least one of polyvinyl pyrrolidone, polyethylene glycol and polyvinyl alcohol.

3. The additive according to claim 1 or 2, characterized in that The polymer active agent is selected from at least one of sodium polyacrylate, polyacrylamide and polycarboxylic acid polymer.

4. The additive according to claim 1 or 2, characterized in that The non-ionic surfactant accounts for 5 to 15% by weight of the additive for preventing the agglomeration of the carbon-based negative electrode slurry.

5. The additive according to claim 1 or 3, characterized in that The polymer active agent accounts for 5 to 15% by weight of the additive for preventing the carbon-based negative electrode slurry from agglomerating.

6. The additive according to claim 1 or 2, characterized in that The raw material of the additive for preventing the carbon-based negative electrode slurry from agglomerating also includes water, which is the balance.

7. An application of the additive for preventing agglomeration of carbon-based negative electrode slurry according to any one of claims 1 to 6, characterized in that: The additive is used for preparing carbon-based negative electrode slurry.

8. The use of the additive for preventing agglomeration of carbon-based negative electrode slurry according to claim 7, characterized in that: The specific application method is: The additive for preventing the carbon-based negative electrode slurry from agglomerating is added to the carbon-based negative electrode slurry.

9. The use of the additive for preventing agglomeration of carbon-based negative electrode slurry according to claim 8, characterized in that: The additive for preventing the carbon-based negative electrode slurry from agglomerating is added at a mass percentage of 2%.

10. The use of the additive for preventing agglomeration of carbon-based negative electrode slurry according to claim 8 or 9, characterized in that: The specific application method is: 1) stirring and dispersing an additive for preventing agglomeration of a carbon-based negative electrode slurry, a negative electrode material, conductive carbon, sodium carboxymethyl cellulose and pure water; 2) Add styrene butadiene rubber and continue stirring to disperse.

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