Preparation method of micron-sized dry-method electrode particles

Abstract

The invention relates to a preparation method of micron-sized dry-method electrode particles. The preparation method comprises the following steps: premixing an electrode active material and a conductive agent to obtain a mixture A; carrying out secondary mixing treatment on the mixture A and binder powder to obtain a mixture B; the obtained mixture B is put into a high-speed mixer to be subjected to multi-stage fibration treatment, and a fibration material C is obtained after fibration of the material is completed; and adding the fiberized material C into a granulator for granulation treatment to obtain the micron-sized dry electrode particles. The dry-method electrode premixed material obtained by the mixing method of the dry-method electrode material is better in fibrosis degree in the subsequent process, and more uniform micron-sized powder particles are obtained after granulation.

Description

Technical Field

[0001] This invention relates to the field of battery electrode manufacturing technology, and in particular to a method for preparing micron-sized dry electrode particles. Background Technology

[0002] Currently, wet coating technology dominates the manufacturing process of lithium-ion battery electrodes. However, this process has several major drawbacks: First, it consumes a large amount of energy in the drying and solvent recovery stages, significantly increasing production costs. Second, its ability to control coating thickness is limited, making it difficult to meet the demands of high-energy-density batteries. Furthermore, the process involves the use of toxic solvents, posing environmental pollution and safety hazards. In contrast, dry film deposition technology offers significant advantages: it not only effectively reduces energy consumption and improves production efficiency but also allows for a wider range of coating thickness control, while avoiding the use of toxic solvents, thus aligning better with the development concept of green manufacturing.

[0003] In the dry electrode manufacturing process, the fiberization of polytetrafluoroethylene (PTFE) is a key technological step that determines electrode performance. Currently, the mainstream PTFE fiberization processes include: shear fiberization via high-speed mixers, impact fiberization using air jet mills, and the preparation of fiberized materials using twin-screw extruders. Among these three processes, the high-speed mixer process allows for continuous premixing and fiberization, making it more convenient and efficient than the other two. However, due to the tendency of PTFE to agglomerate and fiberize at high temperatures, it is difficult to obtain a uniformly mixed material by directly using a high-speed mixer for premixing. Therefore, it is difficult to obtain micron-sized powder particles in the subsequent granulation process, and the agglomerated PTFE particles adhere to the hot rollers during calendering, affecting electrode integrity. Summary of the Invention

[0004] To address the technical problem in existing dry electrode powder premixing processes using high-speed mixers that lead to electrode material agglomeration and premature PTFE fiberization, resulting in decreased electrode performance, this invention provides a method for preparing micron-sized dry electrode particles. The dry electrode premix material obtained by the mixing method of this invention exhibits better fiberization in subsequent processes and yields more uniform micron-sized powder particles after granulation.

[0005] The purpose of this invention is to provide a method for preparing micron-sized dry electrode particles, comprising the following steps: The electrode active material and the conductive agent are premixed to obtain mixture A; The mixture A is mixed with the binder powder a second time to obtain mixture B; The resulting mixture B is placed in a high-speed mixer for multi-stage fiberization treatment. Once the fiberization is complete, fiberized material C is obtained. The fibrous material C is added to a granulator for granulation to obtain micron-sized electrode particles.

[0006] In some embodiments of the present invention, the premixing process and the secondary mixing process are each independently performed using at least one of a high-speed mixer and a plow mixer.

[0007] In this invention, the premixing and secondary mixing processes are non-destructive mixing processes.

[0008] In some embodiments of the present invention, during the secondary mixing process, the mixing temperature is 0–20°C, which can be exemplarily 0°C, 5°C, 10°C, 15°C, 20°C, etc., or any range between any two values. Other unlisted values ​​within this range are also applicable. The mixing speed is 100–1200 rpm, which can be exemplarily 100 rpm, 400 rpm, 800 rpm, 1000 rpm, 1200 rpm. However, it is not limited to the listed values ​​or any range between any two values; other unlisted values ​​within this range are also applicable.

[0009] In some embodiments of the present invention, the electrode active material includes at least one of NCM ternary material, LFP, graphite and silicon carbide.

[0010] In some embodiments of the present invention, the conductive agent includes at least one of SP, ECP, KS-6, CNT and VGCF.

[0011] In some embodiments of the present invention, the binder includes at least one of PTFE, PVDF, CMC, and PAA. The order of addition of the binder is crucial in this invention because binders (such as PTFE) are prone to fibrosis under shear force, forming a network structure. If added too early, they will preferentially encapsulate other components, leading to uneven mixing (such as the formation of PTFE clumps), making it difficult to disperse the active material and conductive agent subsequently. By premixing the electrode active material and conductive agent, it is ensured that the conductive agent fully encapsulates the active material particles, avoiding interference from the subsequent binder (such as PTFE). Mixture A is mixed with the binder (such as PTFE) powder at low temperature to avoid insufficient mixing caused by the fibrosis of the binder (such as PTFE) during the mixing process.

[0012] In some embodiments of the present invention, the mass ratio of the electrode active material, conductive agent and binder is (90-98):(1-5):(1-5), which can be exemplarily 90:5:5, 95:2:3 or 97:1:2, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable, or any interval between any two values.

[0013] In some embodiments of the present invention, the D50 of the electrode active material is <20 μm. Further, it is preferably 1 to 20 μm, and can be exemplarily 1 μm, 5 μm, 10 μm or 15 μm, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable, or any interval between any two values.

[0014] In some embodiments of the present invention, the granulator speed is 800–1500 rpm, and the screen aperture is 0.6–2.5 mm. The granulation process in this invention provides sufficient shear force and pressure to transform the fibrous material C into micron-sized electrode particles through the screen; electrode particles of different sizes can be obtained by adjusting the screen size.

[0015] In some embodiments of the present invention, the multi-stage fiberization process includes three heating stages. The first stage involves heating the mixture in a high-speed mixer to 40°C–60°C, with the impeller speed set to 100–1200 rpm during the heating process. Exemplarily, the heating temperature can be 40°C, 45°C, 50°C, 55°C, or 60°C, but is not limited to the listed values; other unlisted values ​​within this range are also applicable. Exemplarily, the impeller speed can be 100 rpm, 400 rpm, 800 rpm, 1000 rpm, 1200 rpm, etc., but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0016] The second stage involves increasing the impeller speed to 2000–2500 rpm, raising the material temperature to 60°C–80°C through high-speed shearing of mixture B by the impeller. For example, the impeller speed can be 2000 rpm, 2100 rpm, 2200 rpm, 2300 rpm, 2400 rpm, or 2500 rpm, but is not limited to the listed values; other unlisted values ​​within this range are also applicable. For example, the material temperature can be 60°C, 65°C, 70°C, 75°C, or 80°C, etc., but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0017] The third stage: After the high-speed mixer reaches a temperature of 60℃~80℃, the impeller speed is increased again to 2500~3500rpm. Once the material temperature rises to 80℃~100℃, the material fiberization is complete. For example, the impeller speed can be 2500rpm, 3000rpm, or 3500rpm, but is not limited to the listed values; other unlisted values ​​within this range are also applicable. For example, the material temperature can be 80℃, 90℃, or 100℃, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0018] In this invention, when the high-speed mixer operates at a speed of 2000–2500 rpm, the mixing is a destructive, high-shear mixing process, during which mixture B undergoes fibrosis. When the speed is increased to 2500–3500 rpm, the mixing also becomes a destructive, high-shear mixing process, the purpose of which is to enhance the degree of fibrosis in the material.

[0019] In some embodiments of the present invention, the heating method of the high-speed mixer is selected as hydrothermal or oil-heated.

[0020] The technical solution of the present invention has the following advantages compared with the prior art: 1. The mixing method of the dry electrode material of the present invention involves first mixing the electrode active material and the conductive agent evenly to avoid premature addition of the binder, which would lead to uneven dispersion of the conductive agent; mixing mixture A with the binder at low temperature to avoid fiberization of the binder during the mixing process, which would cause material agglomeration and insufficient mixing; and combining low-speed mixing or non-destructive mixing methods such as plow mixers with low temperature to obtain mixture B with better fiberization in subsequent processes.

[0021] 2. The method for manufacturing micron-sized electrode particles of the present invention, through low-temperature premixing, segmented fiberization, and shear granulation, can obtain micron-sized electrode particles, resulting in better film formation during subsequent calendering. The size of the electrode particles can be adjusted by the aperture of the sieve in the granulator. Applying this method to prepare dry electrode sheets is beneficial for improving cell performance and quality. Attached Figure Description

[0022] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein... Figure 1 This is a SEM image of mixture B obtained in Example 1 of the present invention.

[0023] Figure 2 This is an SEM image of the fibrous material C in Embodiment 2 of the present invention.

[0024] Figure 3 , 4 This is an SEM image of the granulated material in Example 2 of the present invention.

[0025] Figure 5 This is an SEM image of the fibrous material C in Embodiment 3 of the present invention.

[0026] Figure 6 This is a SEM image of mixture B in Comparative Example 1 of this invention.

[0027] Figure 7 This is a SEM image of mixture B in Comparative Example 2 of this invention.

[0028] Figure 8 This is a SEM image of the fibrous material C in Comparative Example 3 of this invention. Detailed Implementation

[0029] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0030] Example 1 This embodiment provides a method for mixing dry electrode materials and a method for preparing micron-sized dry electrode particles, wherein the mass ratio of NCM, SP, and PTFE is 97:1:2, as detailed below: 1. Add lithium-ion battery positive electrode powder NCM and conductive agent SP to a high-speed mixer at a mass ratio to obtain mixture A. The high-speed mixer speed is 1000 rpm and the stirring time is 30 min. The mixture is uniform and the angle of repose is close to that of the positive electrode active material.

[0031] 2. Mix the mixture A obtained in step 1 and the binder PTFE in a high-speed mixer. Set the mixer cavity temperature to 8°C, the rotation speed to 1000 rpm, and the mixing time to 20 min to obtain mixture B. Characterize the structure of mixture B; the results are shown below. Figure 1 As shown in the figure, after low-temperature slow premixing, the active material, conductive agent and binder are evenly dispersed without agglomeration. Mixture B is in the form of flour and does not agglomerate.

[0032] 3. The high-speed mixer is then heated to 60°C, with the impeller speed at 400 rpm during heating to ensure uniform heating of mixture B. Once the high-speed mixer reaches 60°C, the heating module is set to heat preservation mode, and the impeller speed is increased to 2000 rpm to pre-fiberize mixture B.

[0033] 4. Then, (due to the heat generated by friction during high-speed mixing) the temperature of the high-speed mixer chamber rises to 70°C, the speed of the paddle is increased to 3000 rpm, and fiberization is stopped when the temperature of the high-speed mixer reaches 85°C, resulting in a loose, clay-like fibrous material C.

[0034] 5. The fibrous material C obtained in step 4 is added to a granulator for granulation. The granulator speed is 1000 rpm and the screen aperture is 2 mm to obtain micron-sized electrode particles. The granulated product is dense and soft with micron-sized particles, which is easy to calender into a film.

[0035] Example 2 This embodiment provides a method for mixing dry electrode materials and a method for preparing micron-sized dry electrode particles, wherein the mass ratio of LFP, SP, and PTFE is 97:1:2, as detailed below: 1. Add lithium-ion battery cathode powder LFP and conductive agent SP to a high-speed mixer at a mass ratio to obtain mixture A. The high-speed mixer speed is 1000 rpm and the stirring time is 30 min. The mixture is uniform and the angle of repose is close to that of the cathode active material.

[0036] 2. Mix the mixture A obtained in step 1 and the binder PTFE in a high-speed mixer. Set the temperature inside the high-speed mixer to 8°C, the rotation speed to 1000 rpm, and the mixing time to 20 min to obtain mixture B. The actual temperature of mixture B is approximately 10°C, and it has a flour-like consistency with no agglomeration.

[0037] 3. The high-speed mixer is then heated to 60°C, with the impeller speed at 400 rpm during heating to ensure uniform heating of mixture B. Once the high-speed mixer reaches 60°C, the heating module is set to heat preservation mode, and the impeller speed is increased to 2000 rpm to pre-fiberize mixture B.

[0038] 4. Subsequently, (due to heat generated by friction during high-speed mixing) the temperature of the high-speed mixer chamber rises to 70°C, and the impeller speed is increased to 3000 rpm until the high-speed mixer temperature reaches 85°C, at which point fiberization stops, yielding a fibrous material C resembling putty. The resulting fibrous material C is characterized structurally; the results are shown below. Figure 2 As shown in the figure, the materials are tightly bound together by the adhesive.

[0039] 5. The fibrous material C obtained in step 4 was added to a granulator for granulation. The granulator speed was 1000 rpm and the screen aperture was 2 mm to obtain micron-sized electrode particles. The structure was then characterized, and the results are shown in [Figure number missing]. Figure 3 and Figure 4 As shown in the figure, the granulated electrode particles have a particle size of approximately 1 μm. The internal binder bonds the conductive agent and active material together, and the contact method is point-to-line contact. The granulated product is dense and soft, with particle sizes in the micrometer range, making it easy to subsequently calender and form a film.

[0040] Example 3 This embodiment provides a method for mixing dry electrode materials and a method for preparing micron-sized dry electrode particles, wherein the mass ratio of graphite, SP, and PTFE is 98:1:1, as detailed below: 1. Add graphite powder and conductive agent SP to a high-speed mixer at a mass ratio to obtain mixture A. The speed of the high-speed mixer is 1000 rpm and the stirring time is 30 min. After mixing, mixture A is uniform and the angle of repose is close to that of the positive electrode active material.

[0041] 2. Mix the mixture A obtained in step 1 and the binder PTFE in a high-speed mixer. Set the temperature inside the high-speed mixer to 8°C, the rotation speed to 1000 rpm, and the mixing time to 20 min to obtain mixture B. The actual temperature of mixture B is approximately 10°C, and it has a flour-like consistency with no agglomeration.

[0042] 3. Heat the high-speed mixer to 60℃, with the impeller speed at 400 rpm during heating to ensure uniform heating of mixture B. Once the high-speed mixer reaches 60℃, set the heating module to heat preservation mode and increase the impeller speed to 2000 rpm to pre-fiberize mixture B.

[0043] 4. Then, (due to the heat generated by friction during high-speed mixing) the temperature of the high-speed mixer chamber rises to 70°C, the speed of the paddle is increased to 3000 rpm, and fiberization is stopped when the temperature of the high-speed mixer reaches 85°C, resulting in a fibrous material C in the form of putty.

[0044] 5. The fibrous material C obtained in step 4 was added to a granulator for granulation. The granulator speed was 1000 rpm and the screen aperture was 2 mm to obtain micron-sized electrode particles. The structure was then characterized, and the results are shown in [Figure number missing]. Figure 5 As shown in the figure, the granulated product is dense and soft, with particle size in the micrometer range, making it easy to form a film by subsequent calendering.

[0045] Comparative Example 1 (compared to Example 1, except that the temperature of the high-speed mixer cavity in step 2 is room temperature) This comparative example provides a method for mixing dry electrode materials and a method for preparing micron-sized dry electrode particles, with a mass ratio of NCM, SP, and PTFE of 97:1:2, as shown below: 1. Add lithium-ion battery positive electrode powder NCM and conductive agent SP to a high-speed mixer at a mass ratio to obtain mixture A. The high-speed mixer speed is 1000 rpm and the stirring time is 30 min. The mixture is uniform and the angle of repose is close to that of the positive electrode active material.

[0046] 2. Mixture A obtained in step 1 and binder PTFE were mixed in a high-speed mixer at 1000 rpm for 20 min to obtain mixture B. The structure of this mixture was then characterized, and the results are shown below. Figure 6 As shown in the figure, since the premixing process was not carried out at low temperature, PTFE agglomerates due to its own characteristics. Mixture B is in the form of flour and has a small amount of agglomeration.

[0047] 3. The high-speed mixer is then heated to 60°C, with the impeller speed at 400 rpm during heating to ensure uniform heating of mixture B. Once the high-speed mixer reaches 60°C, the heating module is set to heat preservation mode, and the impeller speed is increased to 2000 rpm to pre-fiberize mixture B.

[0048] 4. Then, (due to the heat generated by friction during high-speed mixing) the temperature of the high-speed mixer chamber rises to 70°C, the speed of the paddle is increased to 3000 rpm, and fiberization is stopped when the temperature of the high-speed mixer reaches 85°C, resulting in a loose, clay-like fibrous material C.

[0049] 5. The fibrous material C obtained in step 4 is added to a granulator for granulation. The granulator speed is 1000 rpm and the screen aperture is 2 mm to obtain micron-sized dry electrode particles. The granulated product is dense and soft with a particle size in the micron range. However, during the subsequent calendering process, some sticky particles peel off from the film and adhere to the rollers.

[0050] Comparative Example 2 This comparative example provides a method for mixing dry electrode materials and a method for preparing micron-sized dry electrode particles, wherein the mass ratio of NCM, SP, and PTFE is 97:1:2. The preparation method includes: 1. Add lithium-ion battery positive electrode powder NCM and conductive agent SP to a high-speed mixer at a mass ratio to obtain mixture A. The high-speed mixer speed is 1000 rpm and the stirring time is 30 min. After mixing, mixture A is uniform and the angle of repose is close to that of the positive electrode active material.

[0051] 2. Mixture A obtained in step 1 and binder PTFE were mixed in a high-speed mixer. The mixer cavity temperature was set to 8℃, the rotation speed to 2000rpm, and the mixing time to 20min to obtain mixture B. The structure was then characterized, and the results are shown in [Figure number missing]. Figure 7 As shown in the figure, due to the excessive speed of the high-speed mixer during the premixing process, PTFE has already undergone fibrosis and agglomerated with some active substances, resulting in mixture B being in the form of putty and exhibiting agglomeration.

[0052] 3. The high-speed mixer is then heated to 60°C, with the impeller speed at 400 rpm during heating to ensure uniform heating of mixture B. Once the high-speed mixer reaches 60°C, the heating module is set to heat preservation mode, and the impeller speed is increased to 2000 rpm to pre-fiberize mixture B.

[0053] 4. Then, (due to the heat generated by friction during high-speed mixing) the temperature of the high-speed mixer chamber rises to 70°C, the speed of the paddle is increased to 3000 rpm, and fiberization is stopped when the temperature of the high-speed mixer reaches 85°C, resulting in a loose, clay-like fibrous material C.

[0054] 5. The fibrous material C obtained in step 4 is added to a granulator for granulation. The granulator speed is 1000 rpm and the screen aperture is 2 mm to obtain micron-sized electrode particles. The granulated product is mostly micron-sized particles, with a small number of millimeter-sized particles. During the subsequent calendering process, some particles peel off from the film and adhere to the rollers.

[0055] Comparative Example 3 This comparative example provides a method for mixing dry electrode materials and a method for preparing micron-sized dry electrode particles, wherein the mass ratio of graphite, SP, and PTFE is 98:1:1, as shown below: 1. Add graphite powder and conductive agent SP to a high-speed mixer at a mass ratio to obtain mixture A. The speed of the high-speed mixer is 1000 rpm and the stirring time is 30 min. After mixing, mixture A is uniform and the angle of repose is close to that of the positive electrode active material.

[0056] 2. Mix the mixture A obtained in step 1 and the binder PTFE in a high-speed mixer. Set the temperature inside the high-speed mixer to 8°C, the rotation speed to 1000 rpm, and the mixing time to 20 minutes. The resulting mixture B has an actual temperature of approximately 10°C, is in the form of flour, and shows no agglomeration.

[0057] 3. The high-speed mixer was heated to 60℃, with the impeller speed at 400 rpm during heating to ensure uniform heating of mixture B. The 60℃ mixture B was then added to an air jet mill for fiberization treatment to obtain material C. Structural characterization was performed, and the results are shown in [Figure number missing]. Figure 8 As shown in the figure, the use of air jet mill for fiberization resulted in some PTFE not being sheared and remaining in granular form, leading to a significant decrease in electrode strength. The resulting material C after air jet mill fiberization had a certain viscosity, but it still appeared as flour, indicating a poor degree of fiberization.

[0058] 4. Add the fibrous material C to the granulator for granulation. The granulator speed is 1000 rpm and the screen aperture is 2 mm. The granulated product is dense and soft with a particle size in the micrometer range, but the subsequent calendering effect is poor, the film is brittle and the thickness is difficult to reduce.

[0059] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing micron-sized dry electrode particles, characterized in that, Includes the following steps: The electrode active material and the conductive agent are premixed to obtain mixture A; The mixture A is mixed with the binder powder a second time to obtain mixture B; The resulting mixture B is placed in a high-speed mixer for multi-stage fiberization treatment. Once the fiberization is complete, fiberized material C is obtained. The fibrous material C is added to a granulator for granulation to obtain micron-sized dry electrode particles.

2. The preparation method according to claim 1, characterized in that, The premixing and secondary mixing processes are each carried out independently using at least one of a high-speed mixer and a plow mixer.

3. The preparation method according to claim 1, characterized in that, During the secondary mixing process, the mixing temperature is 0–20℃ and the mixing speed is 100–1200 rpm.

4. The preparation method according to claim 1, characterized in that, The electrode active material includes at least one of NCM ternary material, LFP, graphite, and silicon carbide.

5. The preparation method according to claim 1, characterized in that, The conductive agent includes at least one of SP, ECP, KS-6, CNT and VGCF.

6. The preparation method according to claim 1, characterized in that, The adhesive includes at least one of PTFE, PVDF, CMC, and PAA.

7. The preparation method according to claim 1, characterized in that, The mass ratio of the electrode active material, conductive agent and binder is (90-98):(1-5):(1-5).

8. The preparation method according to claim 1, characterized in that, The D50 of the electrode active material is less than 20 μm.

9. The preparation method according to claim 1, characterized in that, The granulator speed is 800-1200 rpm, and the screen aperture is 0.6-2.5 mm.

10. The preparation method according to claim 1, characterized in that, The specific process of the multi-stage fiberization treatment includes heating the mixture in a high-speed mixer to 40℃~60℃, setting the blade speed to 100~1200rpm during the heating process; increasing the blade speed to 2000~2500rpm, and raising the material temperature to 60℃~80℃ through high-speed shearing of the mixture B by the blades; after the high-speed mixer temperature reaches 60℃~80℃, increasing the blade speed again to 2500~3500rpm, and completing the fiberization of the material after the material temperature rises to 80℃~100℃.

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