Method for determining kneading first solidification of graphite negative electrode slurry and application thereof

Abstract

The invention provides a method for determining kneading first solidification of graphite negative electrode slurry and application of the method, and relates to the technical field of batteries. According to the method, multiple graphite negative electrode key physical and chemical data are extracted, and the kneading first fixation which is objective and difficult to quantify is digitalized in combination with the homogenate kneading first fixation and the fitting function equation, so that a green researcher can quickly formulate homogenate process parameters, and the problems of pole pieces and batteries caused by unstable slurry are avoided.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a method for determining the initial bonding of graphite negative electrode slurry and its application. Background Technology

[0002] The homogenization of graphite anode slurry for lithium-ion batteries is a crucial step in the manufacturing process, often referred to as the first step in battery production. Its quality directly determines the battery's performance, consistency, and safety. The initial kneading solidification is the first critical process node in the entire slurry preparation process. While difficult to determine precisely, its timing and state have a profound and direct impact on subsequent processes and the final battery performance. Typically, researchers determine the initial kneading solidification during the material homogenization stage based on experience, but this method is often characterized by ambiguity, lag, and unreliability. Furthermore, it is difficult for new researchers to reach a consensus with experienced researchers, potentially leading to fluctuations in production process quality. Therefore, this invention proposes a method for rapidly determining the initial kneading solidification of graphite anode slurry. By extracting key physicochemical data of graphite and combining it with functional equations, the initial kneading solidification of the homogenization slurry can be quickly determined. This allows researchers to quickly and accurately formulate homogenization parameters, avoiding electrode and battery problems caused by slurry instability.

[0003] In view of this, the present invention is hereby proposed. Summary of the Invention

[0004] The primary objective of this invention is to provide a method for determining the initial kneading of graphite negative electrode slurry, in order to solve the aforementioned technical problems.

[0005] A second objective of this invention is to provide the application of the above method in the preparation of negative electrode sheets.

[0006] The third objective of this invention is to provide a method for preparing graphite anode slurry.

[0007] To achieve the above objectives, the following technical solution is adopted: In a first aspect, the present invention provides a method for determining the initial solidification of graphite negative electrode slurry kneading, comprising the following steps: The specific surface area x1, surface defects x2, tap density x3 of different graphites and the optimal solid content y of the material after kneading during the homogenization process of graphite negative electrode slurry were obtained. Then, x1, x2, x3 and y were fitted to obtain the fitting curve. Then, the specific surface area, defects and tap density of the graphite to be tested were substituted into the fitting curve to determine the optimal kneading first solid content of the graphite to be tested. The graphite negative electrode slurry comprises water and solid components dispersed in the water; by mass percentage, the solid components comprise 1.2%-1.9% conductive agent, 0.8%-1.3% thickener, 1.5%-1.9% binder, and the balance being graphite; The homogenization process of the graphite anode slurry includes: mixing a thickener with water to obtain a slurry; then mixing a portion of the slurry with all the graphite and all the conductive agent; kneading the mixture to obtain the kneaded material; then mixing and dispersing the kneaded material with the remaining slurry; adding water to adjust the slurry viscosity; and finally adding a binder to prepare the graphite anode slurry; the solid content of the slurry is 5%-6%. The surface defect is the intensity ratio of the D peak and the G peak in graphite Raman spectroscopy.

[0008] As a further technical solution, the fitting formula is: y = ax1 + bx2 + cx3 + d; Where a, b, c, and d are constants.

[0009] As a further technical solution, the conductive agent includes one or more of acetylene black, carbon black, Ketjen black, graphene, or carbon nanotubes.

[0010] As a further technical solution, the thickener includes one or more of sodium carboxymethyl cellulose (CMC), lithium carboxymethyl cellulose (CMC-Li), polyacrylic acid (PAA), chitosan, or highly substituted guar gum.

[0011] As a further technical solution, the adhesive includes one or more of styrene-butadiene rubber (SBR) and polyvinylidene fluoride (PVDF).

[0012] Secondly, the present invention provides the application of the above method in the preparation of negative electrode sheets.

[0013] Thirdly, the present invention provides a method for preparing a graphite negative electrode slurry, comprising the following steps: Thickener and water are mixed to obtain a slurry. Then, part of the slurry is mixed with all of the graphite and all of the conductive agent. After kneading, the kneaded material is obtained. Then, the kneaded material is mixed and dispersed with the remaining slurry. Water is added to adjust the viscosity of the slurry. Finally, a binder is added to prepare a graphite negative electrode slurry. The graphite negative electrode slurry comprises water and solid components dispersed in the water; by mass percentage, the solid components comprise 1.2%-1.9% conductive agent, 0.8%-1.3% thickener, 1.5%-1.9% binder, and the balance being graphite; The optimal solids content of the kneaded material is determined by the method described above.

[0014] As a further technical solution, the conductive agent includes one or more of acetylene black, carbon black, Ketjen black, graphene, or carbon nanotubes.

[0015] As a further technical solution, the thickener includes one or more of sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, polyacrylic acid, chitosan, or highly substituted guar gum.

[0016] As a further technical solution, the adhesive includes one or more of styrene-butadiene rubber and polyvinylidene fluoride.

[0017] Compared with existing technologies, the method for determining the initial bonding of graphite negative electrode slurry provided by this invention has the following beneficial effects: This invention extracts key physicochemical data of multiple graphite anodes, combines them with homogenization and kneading first-stage solidification, and fits functional equations to digitize the objective and difficult-to-quantify kneading first-stage solidification. This allows novice researchers to quickly formulate homogenization process parameters and avoid electrode and battery problems caused by unstable slurry. Attached Figure Description

[0018] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0019] Figure 1 : This refers to the state of the kneaded graphite 1 material; Figure 2 : This refers to the slurry state of graphite 1; Figure 3 : This refers to the sieving status of graphite 1 slurry; Figure 4 : This refers to the state of the graphite 2 material after kneading; Figure 5 : This refers to the slurry state of graphite 2; Figure 6 : This refers to the sieving status of the graphite 2 slurry; Figure 7 : This refers to the state of the graphite 3 material after kneading; Figure 8 : This refers to the slurry state of graphite 3; Figure 9 : This refers to the sieving status of graphite 3 slurry; Figure 10 : This refers to the state of the graphite 4 material after kneading; Figure 11 : This refers to the slurry state of graphite 4; Figure 12 : This refers to the sieving status of graphite 4 slurry; Figure 13 : This refers to the state of the graphite 5 material after kneading; Figure 14 : This refers to the slurry state of graphite 5; Figure 15 : This refers to the sieving status of graphite 5 slurry; Figure 16 : This refers to the state of the graphite 6 material after kneading; Figure 17 : This refers to the slurry state of graphite 6; Figure 18 : This refers to the sieving status of graphite 6 slurry. Detailed Implementation

[0020] The embodiments and examples of the present invention will be described in detail below. However, those skilled in the art will understand that the following embodiments and examples are for illustrative purposes only and should not be considered as limiting the scope of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. Unless otherwise specified, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0021] In a first aspect, the present invention provides a method for determining the initial solidification of graphite negative electrode slurry kneading, comprising the following steps: The specific surface area x1, surface defects x2, tap density x3 of different graphites and the optimal solid content y of the material after kneading during the homogenization process of graphite negative electrode slurry were obtained. Then, x1, x2, x3 and y were fitted to obtain the fitting curve. Then, the specific surface area, defects and tap density of the graphite to be tested were substituted into the fitting curve to determine the optimal kneading first solid content of the graphite to be tested. The graphite negative electrode slurry comprises water and solid components dispersed in the water; by mass percentage, the solid components comprise 1.2%-1.9% conductive agent (e.g., but not limited to 1.2%, 1.6%, or 1.9%), 0.8%-1.3% thickener (e.g., but not limited to 0.8%, 1%, or 1.3%), 1.5%-1.9% binder (e.g., but not limited to 1.5%, 1.7%, or 1.9%), with the balance being graphite; The homogenization process of the graphite anode slurry includes: mixing a thickener with water to obtain a slurry; then mixing a portion of the slurry with all the graphite and all the conductive agent; kneading the mixture to obtain the kneaded material; then mixing and dispersing the kneaded material with the remaining slurry; adding water to adjust the slurry viscosity (adjusting the viscosity according to conventional requirements in the art); and then adding a binder to prepare the graphite anode slurry; the solid content of the slurry is 5%-6% (for example, it can be, but is not limited to, 5%, 5.5% or 6%). The surface defect is the intensity ratio of the D peak and the G peak in graphite Raman spectroscopy.

[0022] This invention extracts key physicochemical data of multiple graphite anodes, combines them with homogenization and kneading first-stage solidification, and fits functional equations to digitize the objective and difficult-to-quantify kneading first-stage solidification, so as to ensure the uniformity and stability of the slurry. This makes it easier for novice researchers to quickly formulate homogenization process parameters and avoid electrode and battery problems caused by slurry instability.

[0023] In some alternative implementations, the fitting formula is: y = ax1 + bx2 + cx3 + d; Where a, b, c, and d are constants.

[0024] In some alternative embodiments, the conductive agent includes, but is not limited to, one or more of acetylene black, carbon black, Ketjen black, graphene or carbon nanotubes, or other conductive agents well known to those skilled in the art.

[0025] In some alternative embodiments, the thickener includes, but is not limited to, one or more of sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, polyacrylic acid, chitosan or highly substituted guar gum, or other thickeners well known to those skilled in the art.

[0026] In some alternative embodiments, the adhesive includes, but is not limited to, one or more of styrene-butadiene rubber and polyvinylidene fluoride, or other adhesives well known to those skilled in the art.

[0027] Secondly, the present invention provides the application of the above method in the preparation of negative electrode sheets.

[0028] The method provided by this invention can accurately determine the initial solidification of graphite negative electrode slurry kneading, avoiding problems with the electrode and battery caused by slurry instability, and can be used for the preparation of battery negative electrode sheets.

[0029] Thirdly, the present invention provides a method for preparing a graphite negative electrode slurry, comprising the following steps: Thickener and water are mixed to obtain a slurry. Then, part of the slurry is mixed with all of the graphite and all of the conductive agent. After kneading, the kneaded material is obtained. Then, the kneaded material is mixed and dispersed with the remaining slurry. Water is added to adjust the viscosity of the slurry. Finally, a binder is added to prepare a graphite negative electrode slurry. The graphite negative electrode slurry comprises water and solid components dispersed in the water; by mass percentage, the solid components comprise 1.2%-1.9% conductive agent (e.g., but not limited to 1.2%, 1.6%, or 1.9%), 0.8%-1.3% thickener (e.g., but not limited to 0.8%, 1%, or 1.3%), 1.5%-1.9% binder (e.g., but not limited to 1.5%, 1.7%, or 1.9%), with the balance being graphite; The optimal solids content of the kneaded material is determined by the method provided in the first aspect of the present invention.

[0030] The slurry prepared by this method has good stability and can effectively avoid problems with electrodes and batteries caused by slurry instability.

[0031] In some alternative embodiments, the conductive agent includes, but is not limited to, one or more of acetylene black, carbon black, Ketjen black, graphene or carbon nanotubes, or other conductive agents well known to those skilled in the art.

[0032] In some alternative embodiments, the thickener includes, but is not limited to, one or more of sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, polyacrylic acid, chitosan or highly substituted guar gum, or other thickeners well known to those skilled in the art.

[0033] In some alternative embodiments, the adhesive includes, but is not limited to, one or more of styrene-butadiene rubber and polyvinylidene fluoride, or other adhesives well known to those skilled in the art.

[0034] The present invention will be further illustrated below with specific embodiments. However, it should be understood that these embodiments are merely for the purpose of more detailed illustration and should not be construed as limiting the present invention in any way.

[0035] Example 1 A method for rapidly determining the initial binding of graphite negative electrode slurry kneading includes the following steps: The specific surface area x1, defects x2, tap density x3 of different graphites and the optimal solid content y of the material after kneading during the homogenization process of graphite negative electrode slurry were obtained. Then, x1, x2, x3 and y were fitted to obtain a fitting curve. Subsequently, the specific surface area, defects and tap density of the graphite to be tested were substituted into the fitting curve to determine the optimal initial solid content of the graphite to be tested.

[0036] The homogenization process of the graphite anode slurry includes: mixing the binder with water to obtain glue, then mixing part of the glue with all of the graphite and all of the conductive agent, kneading to obtain the kneaded material, and then mixing the kneaded material with the remaining glue to prepare the graphite anode slurry.

[0037] The surface defect is the intensity ratio of the D peak and the G peak in graphite Raman spectroscopy.

[0038] Experimental Example 1 Graphite AH was collected and subjected to physicochemical tests. The results are shown in Table 1.

[0039] The negative electrode slurry was prepared according to the following steps: The graphite slurry formulation (94.5-97% graphite, 0.9-2.0% conductive agent, 0.8-1.8% thickener, 0.9-1.9% binder, wherein the slurry for graphite A is: 94.5% graphite + 2.0% acetylene black + 1.8% CMC + 1.7% SBR; the slurry for graphite B is: 96.1% graphite + 1.2% acetylene black + 0.5% CMC + 1.3% PAA + 0.9% SBR; the slurry for graphite C is: 97.05% graphite + 0.9% carbon black + 0.05% carbon nanotubes + 1.1% PAA + 0.9% SBR; the raw materials for the remaining graphite DH are the same as those for graphite A, and the amounts of each raw material are within the range of the above graphite slurry formulation). A thickener is mixed with water to obtain a slurry with a solid content of 6%. Then, a portion of the slurry is mixed with all the graphite and all the conductive agent. After kneading, the kneaded material is obtained. The kneaded material is then mixed and dispersed with the remaining slurry. Water is added to adjust the viscosity of the slurry. Finally, a binder is added to prepare a graphite negative electrode slurry.

[0040] During the preparation process, the amount of the first adhesive added was changed, and the output material after kneading and homogenization was tested. Based on the test results, the optimal kneading first strength of graphite AH was determined. The parameters of each graphite and the measured optimal kneading first strength are shown in Table 1.

[0041] Table 1

[0042] Note: The discharge solids content, discharge viscosity, and discharge fineness are all parameters of the final graphite anode slurry. The optimal kneading initial solids content is mainly evaluated based on the discharge fineness.

[0043] It should be noted that fineness refers to the degree of dispersion of solid particles in a slurry, and is a key indicator for measuring the particle size and uniformity of distribution in the slurry. The initial kneading process largely determines the particle size and distribution. During kneading, dry powder is initially mixed with some liquid to form clumps or a paste, ensuring that all dry powder is fully wetted and initially dispersed by the liquid. Improper initial kneading can result in only surface wetting of the powder, leaving the interior dry. This dry powder is extremely difficult to break up during subsequent addition of the remaining adhesive and stirring, forming hard, difficult-to-disperse agglomerates, leading to large particles in the slurry with a very high fineness.

[0044] The above slurry is considered qualified if the solid content of the output is between 49% and 52%, the viscosity of the output is between 1800 and 3000, and the fineness of the output is below 30.

[0045] The graphite AH data were then fitted using the method described in Example 1, and the fitting formula is as follows: y = ax1 + bx2 + cx3 + d; Where a, b, c, and d are constants, x1 is the specific surface area, x2 is the surface defect, and x3 is the tap density.

[0046] After fitting, the fitted curve obtained is: y=43.18-1.287x1+0.28x2+21.21x3.

[0047] To verify the accuracy of the method in Example 1, graphite 1-6 was also taken (the graphite slurry formulation was: 94.5-97% graphite, 0.9-2.0% conductive agent, 0.8-1.8% thickener, and 0.9-1.9% binder, with the same raw material selection as graphite A slurry). The specific surface area, defects, tap density, and actual optimal kneading solids content of graphite 1-6 after kneading during the homogenization process of the graphite negative electrode slurry were determined according to the method above. Then, the kneading solids content fitting value of graphite 1-6 was calculated based on the fitting curve, and the results are shown in Table 2.

[0048] Table 2

[0049] The results show that the kneading solids content (predicted) calculated by this invention is close to the actual kneading solids content. Furthermore, based on the state of the kneaded material and graphite anode slurry prepared according to the predicted kneading solids content, the overall sieving of the six graphite anode materials was smooth, with no obvious particles. Figures 1-18 The coating showed no exposed foil or scratches, and the electrode appearance was normal, indicating that this method can be used to quickly determine the initial bonding of the slurry.

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for determining the initial bonding of graphite negative electrode slurry, characterized in that, Includes the following steps: The specific surface area x1, surface defects x2, tap density x3 of different graphites and the optimal solid content y of the material after kneading during the homogenization process of graphite negative electrode slurry were obtained. Then, x1, x2, x3 and y were fitted to obtain the fitting curve. Then, the specific surface area, defects and tap density of the graphite to be tested were substituted into the fitting curve to determine the optimal kneading first solid content of the graphite to be tested. The graphite negative electrode slurry comprises water and solid components dispersed in the water; by mass percentage, the solid components comprise 1.2%-1.9% conductive agent, 0.8%-1.3% thickener, 1.5%-1.9% binder, and the balance being graphite; The homogenization process of the graphite anode slurry includes: mixing a thickener with water to obtain a slurry; then mixing a portion of the slurry with all the graphite and all the conductive agent; kneading the mixture to obtain the kneaded material; then mixing and dispersing the kneaded material with the remaining slurry; adding water to adjust the slurry viscosity; and finally adding a binder to prepare the graphite anode slurry; the solid content of the slurry is 5%-6%. The surface defect is the intensity ratio of the D peak and the G peak in graphite Raman spectroscopy.

2. The method according to claim 1, characterized in that, The fitting formula is: y = ax1 + bx2 + cx3 + d; Where a, b, c, and d are constants.

3. The method according to claim 1, characterized in that, The conductive agent includes one or more of acetylene black, carbon black, Ketjen black, graphene, or carbon nanotubes.

4. The method according to claim 1, characterized in that, The thickener includes one or more of sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, polyacrylic acid, chitosan, or highly substituted guar gum.

5. The method according to claim 1, characterized in that, The adhesive includes one or more of styrene-butadiene rubber and polyvinylidene fluoride.

6. The application of the method according to any one of claims 1-5 in the preparation of negative electrode sheets.

7. A method for preparing a graphite negative electrode slurry, characterized in that, Includes the following steps: Thickener and water are mixed to obtain a slurry. Then, part of the slurry is mixed with all of the graphite and all of the conductive agent. After kneading, the kneaded material is obtained. Then, the kneaded material is mixed and dispersed with the remaining slurry. Water is added to adjust the viscosity of the slurry. Finally, a binder is added to prepare a graphite negative electrode slurry. The graphite negative electrode slurry comprises water and solid components dispersed in the water; by mass percentage, the solid components comprise 1.2%-1.9% conductive agent, 0.8%-1.3% thickener, 1.5%-1.9% binder, and the balance being graphite; The optimal solids content of the kneaded material is determined by the method described in any one of claims 1-5.

8. The preparation method according to claim 7, characterized in that, Conductive agents include one or more of acetylene black, carbon black, Ketjen black, graphene, or carbon nanotubes.

9. The preparation method according to claim 7, characterized in that, Thickeners include one or more of sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, polyacrylic acid, chitosan, or highly substituted guar gum.

10. The preparation method according to claim 7, characterized in that, The adhesive includes one or more of styrene-butadiene rubber and polyvinylidene fluoride.

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