Dry-type electrode film and its manufacturing method, electrode, and battery

Abstract

This application discloses a dry-type electrode film, a method for manufacturing the same, an electrode, and a battery, and belongs to the art of batteries. The method of this application includes mixing polytetrafluoroethylene, an active material, and a conductive agent, grinding them to obtain a pulverized mixture, performing primary airflow polishing shear on the pulverized mixture to obtain a polished shear mixture, wherein the primary shearing conditions include an airflow temperature of -10 to 10°C, an airflow pressure of 0.7 to 0.9 MPa, and a rotation speed of 8000 to 12000 rpm, performing secondary airflow polishing shear fiberization on the polished shear mixture to obtain a fibrous material, and performing a secondary fiberization treatment on the fibrous material to obtain a dry-type electrode film. The method of this application can significantly improve the tensile strength of the electrode film, improve the liquid absorption rate of the electrode, and reduce the resistivity of the electrode.

Description

Technical Field

[0001] This application claims the priority of a Chinese patent application with application number 202411922353.7 filed with the Chinese Patent Office on December 24, 2024, and the full text of the above application is incorporated herein by reference.

[0002] This application relates to the technical field of batteries, specifically to dry-process electrode films and their manufacturing methods, electrodes, and batteries.

Background Art

[0003] The manufacturing of electrodes for conventional lithium batteries usually adopts the coating method. First, an adhesive, a solvent, and a conductive agent are prepared into a conductive paste, and the electrode active material is added in batches to make a uniform paste. Finally, the paste is uniformly coated on the current collector by coating equipment, and after drying, roll pressing, and slitting, the electrode sheet is made.

Summary of the Invention

Problems to be Solved by the Invention

[0004] The above method has high requirements for the dispersity of the conductive agent, the control of paste viscosity, and coating equipment. The active material content of the electrode sheet is low, the management and control of the production process are strict, thick electrode sheets cannot be made, and the energy consumption in the solvent drying and solvent recovery processes is large, the cost is high, and it is not environmentally friendly.

[0005] To address the aforementioned shortcomings, dry electrode processes have been developed. The main steps of this process involve uniformly mixing a conductive agent, adhesive, and electrode active material, then using high-speed shearing to fibrousize the PTFE adhesive to form a fiber network that restrains the active material and conductive agent, and finally, further fibrousizing by roll pressing to produce a self-supporting electrode film which is then coated onto a current collector to obtain a double-sided electrode. Here, the fibrousization step is a crucial step in the dry electrode process, requiring uniform dispersion and fibrousization of PTFE with extremely high shearing force. Mainstream methods include airflow shearing, high-speed agitation shearing, and ball mill shearing. However, these methods typically require a high adhesive content (e.g., 8 wt% or more), demand high levels of adhesive fibrousization, high demands for shearing force of the equipment, high demands for uniformity of mixing, long production times, and difficulty in achieving large-scale production. The cause of this contradiction lies primarily in the special properties of the adhesive PTFE required for the process. For the formation of the electrode film in this process, PTFE must be uniformly dispersed between the electrode materials and form a nano-order fiber network through shear tension. The higher the molecular weight of PTFE, the more likely the fiber formation process is to occur. However, commercially available high molecular weight PTFE is often produced with secondary particle sizes of 500-700 μm to avoid aggregation during transport. In contrast, positive electrode active materials and conductive agents with particle sizes generally smaller than 30 μm are prone to segregation due to uneven mixing during the mixing process, resulting in an uneven fiber formation effect. [Means for solving the problem]

[0006] This application provides a dry electrode film, a method for manufacturing the same, an electrode, and a battery to solve the problems of non-uniform mixing of polytetrafluoroethylene adhesive in the dry electrode process, low degree of fiber formation, and low strength of the electrode film fragments.

[0007] According to aspect 1 of this application, Step S1 involves mixing polytetrafluoroethylene material, electrode active material, and conductive agent, and then grinding them to obtain a pulverized mixture. The pulverized mixture is subjected to primary airflow polishing shear to obtain the polished shear mixture, and the primary airflow polishing shear conditions include an airflow temperature of -10°C to 10°C, a compressed airflow pressure of 0.7 to 0.9 MPa, and a shearing rotation speed of 8000 to 12000 rpm, in step S2. Step S3 involves performing secondary airflow polishing and shearing fiberization on the polishing and shearing mixture to obtain a fibrous material. The process includes step S4, which involves performing a secondary fiberization treatment on a fiberized material to obtain a dry electrode film. This invention provides a method for manufacturing electrode films using a dry method.

[0008] Preferably, the airflow temperature for primary airflow polishing shear is -5°C to 5°C, and more preferably 0 to 5°C.

[0009] Preferably, the airflow temperature for secondary airflow polishing shear is 50°C to 100°C, the compressed airflow pressure is 0.7 to 0.9 MPa, and the shearing rotation speed is 8000 to 12000 rpm.

[0010] Preferably, the airflow temperature for secondary airflow polishing shear is 60 to 100°C, more preferably 70 to 100°C, and more preferably 80 to 100°C.

[0011] Preferably, the shear rotation speed of the primary airflow polishing shear is 10,000 to 11,000 rpm.

[0012] Preferably, the shear rotation speed of the secondary airflow polishing shear is 10,000 to 11,000 rpm.

[0013] Preferably, the polytetrafluoroethylene material is a polytetrafluoroethylene dispersion resin having an average particle size of 400 to 600 μm, a molecular weight of 500,000 to 8,000,000, and a compression ratio of 100 to 3,000.

[0014] Preferably, the polytetrafluoroethylene dispersion resin is kept warm at -8°C to -12°C for 8 to 12 hours before mixing.

[0015] Preferably, the specific process of step S1 includes mixing an electrode active material and a conductive agent, and pulverizing to obtain powder A, and mixing the polytetrafluoroethylene dispersion resin after heat preservation and powder A, and pulverizing to obtain a pulverized mixture.

[0016] Preferably, the electrode active material and the conductive agent are mixed by a ball mill or a high-speed mixer, and the rotation speed of the high-speed mixer is 400 to 600 rpm.

[0017] Preferably, the ball-to-material ratio of the ball mill is 1:(1 to 2).

[0018] Preferably, the polytetrafluoroethylene dispersion resin and powder A are mixed by a double motion mixer or a three-dimensional motion mixer.

[0019] Preferably, the time for mixing the polytetrafluoroethylene dispersion resin and powder A by a double motion mixer is 20 to 40 min.

[0020] Preferably, the average particle size of the pulverized mixture is 8 to 12 μm.

[0021] Preferably, the average particle size of the polished and sheared mixture is 3 to 6 μm.

[0022] Preferably, a jet mill is employed for the first airflow polishing and shearing and / or the second airflow polishing and shearing.

[0023] Preferably, the jet mill is a fluidized bed type jet mill.

[0024] Preferably, the secondary fibrillation treatment is performed by differential open roll fibrillation using a differential roll press.

[0025] Preferably, the differential roll press has a roll press temperature of 60°C to 120°C and a roll press speed ratio of 1:(1 to 1.5).

[0026] Preferably, the weight ratio of the electrode active material to the conductive agent is (90-95):(0-5).

[0027] Preferably, the weight ratio of powder A to the polytetrafluoroethylene dispersion resin after heating is (95-99):(1-3).

[0028] Preferably, the electrode active material includes a positive electrode active material and a negative electrode active material, wherein the positive electrode active material is at least one selected from lithium iron phosphate, lithium iron manganese phosphate, lithium nickel cobalt manganese oxide, lithium cobalt oxide, lithium manganese oxide, lithium nickel cobalt aluminate, and manganese dioxide, and the negative electrode active material is at least one selected from artificial graphite, natural graphite, lithium titanate, silicon-oxygen negative electrode material, and silicon-carbon.

[0029] Preferably, the conductive agent is at least one selected from conductive carbon black, graphite, graphene, carbon nanotubes, carbon fibers, acetylene black, and Ketjenblack.

[0030] According to aspect 2 of this application, The electrode film is manufactured by the above dry method manufacturing method. The present invention provides a dry-type electrode film.

[0031] Preferably, the dry-process electrode film has a thickness of 100-150 μm, a tensile strength of 0.2-0.4 MPa, and a press density of 2.50-3.30 g / cm³. 3 That is the case.

[0032] According to aspect 3 of this application, A method for manufacturing a dry electrode, comprising the step of roll-pressing a dry electrode film onto at least one side of a current collector, wherein the dry electrode film is the dry electrode film described above. This invention provides a method for manufacturing a dry electrode.

[0033] Preferably, the temperature of the roll press is between 0°C and 100°C.

[0034] Preferably, the current collector is at least one selected from copper foil, carbon-coated copper foil, aluminum foil, nickel foil, stainless steel mesh, aluminum mesh, and nickel mesh.

[0035] According to aspect 4 of this application, A battery comprising electrodes, a separator, and an electrolyte, wherein the electrodes are manufactured by the dry electrode manufacturing method described above. We provide batteries. [Effects of the Invention]

[0036] Applying the present invention, a dry method for manufacturing electrode films is provided. Based on the phase transition temperature of the adhesive PTFE, different temperature shearing methods are employed. First, low-temperature high-speed shearing reduces the particle size of the adhesive to the nano-order, resulting in a more uniform distribution. Furthermore, high-temperature high-speed shearing increases the degree of fibrous formation of the adhesive, increasing the tensile strength of the manufactured electrode film, reducing the amount of adhesive used, and lowering anisotropy after film formation. This method also breaks through the limits of electrode thickness, enabling the production of electrodes with thicknesses from 30 μm to 3 mm, making it suitable for various battery systems. Compared to conventional electrode coating processes, it eliminates the drying step, reduces the rate of electrode chip shedding, and enables the production of thicker electrodes, meeting the manufacturing needs for battery cells with higher energy density.

[0037] After reviewing and understanding the drawings and detailed descriptions, other embodiments can also be understood. [Brief explanation of the drawing]

[0038] The drawings, which constitute part of this application, are provided to provide a further understanding of this application, and the schematic embodiments and descriptions of this application are for interpretation purposes only and do not unduly limit this application.

[0039] [Figure 1] A flowchart of the manufacturing process for the dry electrode film and electrode according to the embodiment of this application is shown. [Figure 2] This image shows an SEM diagram of Example 1 of the present invention, in which PTFE covers the surface of the positive electrode active material before fiber formation. [Figure 3] This image shows the SEM diagram of the fibrous effect of PTFE in Example 1 of the present invention. [Figure 4] This shows an SEM image of the surface of the electrode film piece in Example 1 of the present invention. [Figure 5] This diagram shows a comparison of the tensile strength in the longitudinal direction of the electrode films of Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 of the present application. [Figure 6] This diagram shows a comparison of the lateral tensile strength of the electrode films of Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 of this application. [Figure 7] The following diagram shows a comparison of the resistivity of the electrodes in Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 of this application. [Figure 8] The diagram shows a comparison of the liquid absorption rates of the electrodes in Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 of this application. [Modes for carrying out the invention]

[0040] Furthermore, the embodiments and features of the embodiments in this application can be combined in any way, as long as they do not contradict each other. The present application will be described in detail below with reference to the drawings and embodiments.

[0041] In related technologies, the fiberization of PTFE adhesives is usually carried out using methods such as airflow shearing, high-speed stirring shearing, and ball mill shearing. These methods require a high amount of adhesive, such as 8 wt% or more, and the secondary particle size of the PTFE used is 500-700 μm. The mixing of the PTFE with the active material and conductive agent is uneven, which can easily lead to segregation and an uneven fiberization effect, further reducing the performance of the dry-process electrode film, such as its tensile strength. Therefore, this application adopts different temperature shearing methods based on the phase transition temperature of the PTFE adhesive to improve the mixing uniformity and degree of fiberization of the PTFE.

[0042] According to aspect 1 of this application, Step S1 involves mixing polytetrafluoroethylene material, electrode active material, and conductive agent, and then grinding them to obtain a pulverized mixture. The pulverized mixture is subjected to primary airflow polishing shear to obtain the polished shear mixture, and the primary airflow polishing shear conditions include an airflow temperature of -10°C to 10°C, a compressed airflow pressure of 0.7 to 0.9 MPa, and a shearing rotation speed of 8000 to 12000 rpm, in step S2. Step S3 involves performing secondary airflow polishing shear on the polishing shear mixture to obtain a fibrous material, The present invention provides a method for manufacturing a dry electrode film, which includes step S4, a secondary fiberization treatment of a fiberized material to obtain a dry electrode film.

[0043] The airflow temperature for primary airflow polishing shear according to this application is any value selected from -10°C, -9°C, -8°C, -7°C, -6°C, -5°C, -4°C, -3°C, -1°C, 0°C, 1°C, 2°C, 3°C, 4°C, 5°C, 6°C, 7°C, 8°C, 9°C, and 10°C, or any value within a range between the two. The airflow temperature for secondary airflow polishing shear is any value selected from 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, and 100°C. The value is either a specific value or a range between the two. For example, the primary airflow polishing temperature is -5 to 10°C, preferably -5 to 5°C, more preferably 0 to 5°C, and for example 0°C. The secondary airflow polishing temperature is 50 to 100°C, preferably 60 to 100°C, more preferably 70 to 100°C, even more preferably 80 to 100°C, and for example 80°C.

[0044] The shear rotation speed for the primary airflow polishing shear according to this application is any value selected from 8000 rpm, 8500 rpm, 9000 rpm, 9500 rpm, 10000 rpm, 10500 rpm, 11000 rpm, 11500 rpm, and 12000 rpm, or any value in any range between the two, for example, 10000 rpm. The shear rotation speed for the secondary airflow polishing shear is any value selected from 8000 rpm, 8500 rpm, 9000 rpm, 9500 rpm, 10000 rpm, 10500 rpm, 11000 rpm, 11500 rpm, and 12000 rpm, or any value in any range between the two, for example, 10000 rpm. The two shear rotation speeds may be the same or different.

[0045] The dry-type electrode film manufacturing method according to this application employs different temperature shearing methods based on the phase transition temperature of the adhesive PTFE (the phase transition temperature of PTFE is 19°C). First, a low-temperature, high-speed shearing is performed on a mixture containing PTFE to reduce the particle size of the PTFE adhesive from the micro-order to the nano-order, thereby making the dispersion of the mixture more uniform. In this low-temperature, high-speed shearing process, theoretically, PTFE hardly undergoes fiber formation because the temperature is lower than the phase transition temperature. However, heat is generated during the shearing process, and if it is necessary to achieve a predetermined fiber formation effect, it is appropriate to control the temperature of the low-temperature, high-speed shearing to -10 to 10°C. Since the shearing rate is close to the shearing rate for fiber formation, high-speed polishing shearing is employed in both cases. This allows for polishing and shearing of commonly used PTFE with large particle sizes on the micro-order to the nano-order. After the PTFE is reduced to the nano-order size, it covers the active material, which greatly improves the uniformity of the mixing of each raw material and is advantageous for subsequent fiber formation of the PTFE mixture. By fabricating a PTFE mixture to the nanoscale and then subjecting it to high-temperature, high-speed shearing, the degree of PTFE fiberization is increased, the tensile strength of the manufactured electrode film is increased, the amount of adhesive used is reduced, and the anisotropy after film formation is also reduced.

[0046] This invention employs a continuous dry roll press to manufacture electrodes, eliminating the need for solvents in the production process and eliminating the drying process, thereby reducing energy consumption during production. This invention also provides the electrode adhesive in a fibrous state, making the contact between the positive electrode active material and conductive agent particles tighter, improving the electrode press density, reducing the resistance of the electrode pieces, and lowering the rate of electrode piece powder shedding. Furthermore, this invention controls the particle size and degree of fibrous formation of the PTFE adhesive with temperature, improving the uniformity of the mixture, reducing the difficulty of forming the electrode film, and improving the tensile strength of the film pieces.

[0047] In some examples, the polytetrafluoroethylene material is a polytetrafluoroethylene dispersion resin having an average particle size of 400 to 600 μm, a molecular weight of 50 to 8 million, and a compression ratio of 100 to 3000.

[0048] The improved method of this invention primarily addresses the need to avoid aggregation of commercially available, commonly used high molecular weight PTFE during transport, by producing it as large particles with a secondary particle size of 500-700 μm. In related technologies, the large particle size PTFE is often directly mixed with the active material and conductive agent, which makes it difficult to properly mix the micro-order PTFE with other nano-order materials, and further affects the degree of PTFE fiberization and electrode film strength. By adopting the improved method of this invention, micro-order PTFE can be reduced to nano-order, and its dispersion uniformity can be further improved.

[0049] In some embodiments, the polytetrafluoroethylene dispersion resin is kept warm at -8°C to -12°C for 8 to 12 hours before mixing, for example, at -10°C for 10 hours. In this application, the reason for first warming the PTFE at the above temperature before use is to prevent further aggregation of the PTFE and increase in particle size, thereby avoiding difficulties in subsequent powder mixing.

[0050] In some embodiments, the specific process of step S1 includes mixing the electrode active material and the conductive agent, grinding them to obtain powder A, and mixing the polytetrafluoroethylene dispersion resin after heating with powder A to obtain a pulverized mixture. The present invention can further improve the uniformity of the mixture by using a stepwise mixing method.

[0051] In some embodiments, the electrode active material and conductive agent were mixed in a ball mill or high-speed mixer, with the rotation speed of the high-speed mixer being 400-600 rpm, and the ball-to-material ratio of the ball mill being 1:(1-2). The polytetrafluoroethylene dispersion resin and powder A were mixed in a dual-motion mixer or a three-dimensional-motion mixer, with a mixing time of 20-40 min in the dual-motion mixer.

[0052] This invention allows for the selection of different mixing equipment and process conditions depending on the materials being mixed, thereby correspondingly improving the dispersibility and uniformity of each mixture. When mixing PTFE and powder A in a dual-motion mixer or a three-dimensional-motion mixer, the mixing time can be controlled, for example, to 20-40 mins, or to 30 mins, thereby avoiding excessive shearing which could cause the PTFE to fibrousize before subsequent high-temperature, high-speed shearing, thus detrimental to the subsequent PTFE fibrosis effect.

[0053] In some examples, the average particle size of the pulverized mixture is 8-12 μm, and the average particle size of the abrasive sheared mixture is 3-6 μm, for example, 3-4 μm. The present invention provides a method to gradually reduce the particle size of the mixture through pulverization and abrasive shearing processes, which contributes to the subsequent airflow abrasive shearing process.

[0054] In some embodiments, a jet mill is used for the first and / or second airflow polishing shearing, for example, a fluidized bed jet mill. In this application, the above equipment is used for the two polishing shearing stages. Compared to a stirrer or ball mill, the heat generated during the polishing process of the jet mill is removed promptly by the low-temperature airflow, avoiding deformation, fiberization, and uneven distribution of PTFE due to localized heat accumulation in the cavity of the equipment. On the other hand, a high-temperature airflow (specifically, an airflow higher than the phase transition temperature of PTFE, i.e., 19°C or higher) is used during the fiberization process to induce a phase transition in PTFE, thereby promoting the fiberization of PTFE. When the temperature is lower than 19°C, the PTFE molecular chain is a 13 / 6 helix, and at 19°C, a phase transition occurs, the molecules unravel slightly to form a 15 / 7 helix, making it even easier to fiberize.

[0055] In some embodiments, the secondary fiberization process can be performed by differential open roll fiberization using a differential roll press, with a roll press temperature of 60°C to 120°C and a roll press speed ratio of 1:(1 to 1.5). In this invention, by adopting the above roll press conditions, the PTFE mixture can be sufficiently and completely fiberized to further form an electrode film.

[0056] In some examples, the weight ratio of electrode active material to conductive agent is (90-95):(0-5), for example, 92:5, and the weight ratio of powder A to polytetrafluoroethylene dispersion resin after heat retention is (95-99):(1-5), for example, 98:2. The present invention controls the PTFE content to 1-5, mixes it with other components, and then performs fiber formation, thereby improving the synergistic effect and avoiding phenomena such as cracking in the film fragments due to too much or too little PTFE content.

[0057] In some embodiments, the electrode active material comprises a positive electrode active material and a negative electrode active material, wherein the positive electrode active material is at least one selected from lithium iron phosphate, lithium iron manganese phosphate, lithium nickel cobalt manganese oxide, lithium cobalt oxide, lithium manganese oxide, lithium nickel cobalt aluminate, and manganese dioxide, and the negative electrode active material is at least one selected from artificial graphite, natural graphite, lithium titanate, silicon-oxygen negative electrode material, and silicon-carbon. The method for manufacturing electrode films of the present invention is suitable for positive electrode films and negative electrode films, and other types of positive electrode active materials, negative electrode active materials, or conductive agents can also be selected as required in practice.

[0058] The conductive agent of this invention mainly uses carbon nanotubes (CNTs) and graphite. Since carbon nanotubes have a one-dimensional linear morphology similar to PTFE fibers, a synergistic effect may occur between the two, allowing more active material particles to be connected, thereby constructing a more effective electron communication network. The effect of graphite is due to its sheet structure having good lubricity, which can contribute to the powder film formation and thinning processes.

[0059] According to aspect 2 of the present application, a dry electrode film manufactured by the above-described dry electrode film manufacturing method is provided.

[0060] In some examples, the dry electrode film had a thickness of 100-152 μm, for example, 115-152 μm, a tensile strength of 0.15-0.4 MPa, for example, 0.15-0.30 MPa, and further, for example, 0.15-0.25 MPa, and a press density of 2.50-3.30 g / cm³. 3 And furthermore, for example, 2.50~3.0 g / cm³ 3 That is the case.

[0061] The electrode film manufactured by the present invention exhibits good dispersibility and uniformity of PTFE, a high degree of fiberization, improved mechanical properties such as tensile strength of the electrode film, increased press density of the electrode film, and further increased energy density of the battery. This method is also suitable for thick electrode films.

[0062] According to aspect 3 of the present application, a method for manufacturing a dry electrode is provided, the method for manufacturing a dry electrode comprising the step of roll-pressing a dry electrode film onto at least one side of a current collector, wherein the dry electrode film is the dry electrode film described above.

[0063] In some embodiments, when bonding the current collectors, the temperature of the roll press is 0°C to 100°C, and the current collector is at least one selected from copper foil, carbon-coated copper foil, aluminum foil, nickel foil, stainless steel mesh, aluminum mesh, and nickel mesh.

[0064] The electrode film manufactured by the present invention can correspondingly coat one or both sides of a positive or negative current collector, and other types of current collectors can be selected as required by practical needs.

[0065] According to aspect 4 of the present application, a battery is provided comprising an electrode, a separator, and an electrolyte, wherein the electrode is an electrode manufactured by the dry electrode manufacturing method described above.

[0066] The present application will be described in detail below with reference to specific embodiments, and these embodiments should not be understood as limiting the scope of protection sought by the present application.

[0067] Each of the raw materials and equipment used in the embodiments of this application are products of related technologies and are commercially available. [Examples]

[0068] The manufacturing process for battery electrodes includes the following steps, as shown in Figure 1.

[0069] (1) PTFE insulation: The PTFE had a secondary particle size of 570 μm, a molecular weight of 7.7 million, and a compression ratio of 100-300. The PTFE was insulated at -10°C for 10 hours.

[0070] (2) Pre-mixing: Lithium iron phosphate (LFP), graphite, and carbon nanotubes were uniformly mixed in a ball mill in a ratio of 92:2:3 with a ball-to-material ratio of 1:1 at 500 rpm to obtain powder A. Powder A and the PTFE adhesive, which had been kept warm, were placed in a double-action mixer in a ratio of 98:2 and mixed for 30 minutes to obtain powder B, which had an average particle size of 10.4 μm. The form in which the PTFE covered the active material after mixing is shown in Figure 2.

[0071] (3) Fiber formation: Powder B was polished with a low-temperature airflow using a jet mill, with an airflow temperature of 0°C, a polishing pressure of 0.70 MPa, and a classification wheel rotation speed of 10,000 rpm to obtain powder C, which had an average particle size of 3.6 μm. The fiber formation effect of PTFE is shown in Figure 3.

[0072] Furthermore, powder C was polished using a jet mill with high-temperature airflow at an airflow temperature of 80°C, a polishing pressure of 0.90 MPa, and a classification wheel rotation speed of 10,000 rpm to obtain powder D.

[0073] (4) Film formation: Powder D was formed into open roll fibers using a multi-stage differential roll press, with a roll press speed ratio of 1:1.5 and temperatures of 120°C / 100°C / 60°C. Each temperature was roll-pressed once to obtain an electrode film. The film thickness was 120 μm, the tensile strength was 0.25 MPa, and the press density was 2.90 g / cm³. 3The membrane fragment morphology is as shown in Figure 4.

[0074] (5) Bonding to the current collector: After forming the film pieces, they were simultaneously roll-pressed onto both sides of an aluminum foil current collector to form electrodes. The roll-press temperature was 50°C, and positive electrode pieces were obtained. [Examples]

[0075] The difference between Example 2 and Example 1 is that the fiberization process in step (3) was different.

[0076] Fiberization: Powder B was polished with a low-temperature airflow using a jet mill, with an airflow temperature of -10°C, a polishing pressure of 0.80 MPa, and a classification wheel rotation speed of 10,000 rpm to obtain powder C, which has an average particle size of 4.1 μm.

[0077] Furthermore, powder C was polished using a jet mill with high-temperature airflow at an airflow temperature of 90°C, a polishing pressure of 0.90 MPa, and a classification wheel rotation speed of 10,000 rpm to obtain powder D. [Examples]

[0078] The difference between Example 3 and Example 1 is that the fiberization process in step (3) was different.

[0079] Fiberization: Powder B was polished with a low-temperature airflow using a Jetmill (model number), with an airflow temperature of -5°C, a polishing pressure of 0.90 MPa, and a classification wheel rotation speed of 10,000 rpm to obtain powder C, which has an average particle size of 3.2 μm.

[0080] Furthermore, powder C was polished using a jet mill with high-temperature airflow at a temperature of 100°C, a polishing pressure of 0.90 MPa, and a classification wheel rotation speed of 10,000 rpm to obtain powder D. [Examples]

[0081] The difference between Example 4 and Example 1 is that the fiberization process in step (3) was different.

[0082] Fiber formation: Powder B was polished with a low-temperature airflow using a jet mill, with an airflow temperature of 5°C, a polishing pressure of 0.90 MPa, and a classification wheel rotation speed of 10,000 rpm to obtain powder C, which has an average particle size of 4.0 μm.

[0083] Furthermore, powder C was polished using a jet mill with high-temperature airflow at an airflow temperature of 70°C, a polishing pressure of 0.90 MPa, and a classification wheel rotation speed of 10,000 rpm to obtain powder D. [Examples]

[0084] The difference between Example 5 and Example 1 is that the fiberization process in step (3) was different.

[0085] Fiberization: Powder B was polished with a low-temperature airflow using a jet mill, with an airflow temperature of 10°C, a polishing pressure of 0.90 MPa, and a classification wheel rotation speed of 10,000 rpm to obtain powder C, which has an average particle size of 3.5 μm.

[0086] Furthermore, powder C was polished using a jet mill with high-temperature airflow at an airflow temperature of 60°C, a polishing pressure of 0.90 MPa, and a classification wheel rotation speed of 10,000 rpm to obtain powder D. [Examples]

[0087] The difference between Example 6 and Example 1 is that the fiberization process in step (3) was different.

[0088] Fiber formation: Powder B was polished with a low-temperature airflow using a jet mill, with an airflow temperature of 3°C, a polishing pressure of 0.90 MPa, and a classification wheel rotation speed of 10,000 rpm to obtain powder C, which has an average particle size of 3.9 μm.

[0089] Furthermore, powder C was polished using a jet mill with high-temperature airflow at an airflow temperature of 50°C, a polishing pressure of 0.90 MPa, and a classification wheel rotation speed of 10,000 rpm to obtain powder D. [Examples]

[0090] The difference between Example 7 and Example 1 is that the fiberization process in step (3) was different.

[0091] Fiber formation: Powder B was polished with a low-temperature airflow using a jet mill, with an airflow temperature of 0°C, a polishing pressure of 0.70 MPa, and a classification wheel rotation speed of 8000 rpm to obtain powder C, which has an average particle size of 5.4 μm.

[0092] Furthermore, powder C was polished using a jet mill with high-temperature airflow at an airflow temperature of 80°C, a polishing pressure of 0.90 MPa, and a classification wheel rotation speed of 8000 rpm to obtain powder D. [Examples]

[0093] The difference between Example 8 and Example 1 is that the fiberization process in step (3) was different.

[0094] Fiber formation: Powder B was polished with a low-temperature airflow using a jet mill, with an airflow temperature of 0°C, a polishing pressure of 0.70 MPa, and a classification wheel rotation speed of 9000 rpm to obtain powder C, which has an average particle size of 6.1 μm.

[0095] Furthermore, powder C was polished using a jet mill with high-temperature airflow at an airflow temperature of 80°C, a polishing pressure of 0.90 MPa, and a classification wheel rotation speed of 9000 rpm to obtain powder D. [Examples]

[0096] The difference between Example 9 and Example 1 is that the fiberization process in step (3) was different.

[0097] Fiber formation: Powder B was polished with a low-temperature airflow using a jet mill, with an airflow temperature of 0°C, a polishing pressure of 0.70 MPa, and a classification wheel rotation speed of 11000 rpm to obtain powder C, which has an average particle size of 5.0 μm.

[0098] Furthermore, powder C was polished using a jet mill with high-temperature airflow at an airflow temperature of 80°C, a polishing pressure of 0.90 MPa, and a classification wheel rotation speed of 11,000 rpm to obtain powder D. [Examples]

[0099] The difference between Example 10 and Example 1 is that the fiberization process in step (3) was different.

[0100] Fiber formation: Powder B was polished with a low-temperature airflow using a jet mill, with an airflow temperature of 0°C, a polishing pressure of 0.70 MPa, and a classification wheel rotation speed of 12000 rpm to obtain powder C, which has an average particle size of 4.7 μm.

[0101] Furthermore, powder C was polished using a jet mill with high-temperature airflow at an airflow temperature of 80°C, a polishing pressure of 0.90 MPa, and a classification wheel rotation speed of 12,000 rpm to obtain powder D. [Examples]

[0102] The difference between Example 11 and Example 1 is that the fiberization process in step (3) was different.

[0103] Fiber formation: Powder B was polished with a low-temperature airflow using a jet mill, with an airflow temperature of 0°C, a polishing pressure of 0.70 MPa, and a classification wheel rotation speed of 10,000 rpm to obtain powder C, which has an average particle size of 5.6 μm.

[0104] Furthermore, powder C was polished using a jet mill with high-temperature airflow at an airflow temperature of 90°C, a polishing pressure of 0.90 MPa, and a classification wheel rotation speed of 12,000 rpm to obtain powder D. [Examples]

[0105] The difference between Example 12 and Example 1 is that the active material in step (2) was the negative electrode active material.

[0106] Pre-mixing: Artificial graphite and carbon nanotubes were uniformly mixed in a 92:6 ratio using a ball mill at a ball-to-material ratio of 1:1 and 500 rpm to obtain powder A. Powder A and the PTFE adhesive (after heating) were then mixed in a 98:2 ratio in a dual-action mixer for 30 minutes to obtain powder B. Comparative Example 1

[0107] The difference between Comparative Example 1 and Example 1 is that in Example 1, the PTFE was not subjected to low-temperature, high-speed polishing and shearing treatment, but was instead subjected to high-temperature airflow polishing and fiber formation.

[0108] (3) Fiberization: Powder B was fiberized by high-temperature airflow polishing using a jet mill, with an airflow temperature of 80°C, a polishing pressure of 0.90 MPa, and a classification wheel rotation speed of 10,000 rpm to obtain powder D. Comparative Example 2

[0109] The difference between Comparative Example 2 and Example 1 is that in step (3), powder C was fiberized at room temperature.

[0110] Powder C was air-jet polished using a jet mill at an airflow temperature of 20°C, a polishing pressure of 0.90 MPa, and a classification wheel rotation speed of 10,000 rpm to obtain powder D. Comparative Example 3

[0111] The difference between Comparative Example 3 and Example 1 is that the PTFE content in step (1) is 8 wt%, and in step (3), the PTFE was fiberized at room temperature without low-temperature high-speed polishing and shearing treatment.

[0112] Lithium iron phosphate (LFP), graphite, and carbon nanotubes were uniformly mixed in a 90:1:1 ratio using a ball mill at a ball-to-material ratio of 1:1 and 500 rpm to obtain powder A. Powder A and the PTFE adhesive, after being kept warm, were then mixed in a 90:8 ratio in a dual-action mixer for 30 minutes to obtain powder B.

[0113] Powder B was compressed into fibers using a low-temperature jet mill with airflow polishing. The airflow temperature was 20°C, the polishing pressure was 0.90 MPa, and the classification wheel rotation speed was 10,000 rpm to obtain powder D. Comparative Example 4

[0114] The difference between Comparative Example 4 and Example 1 is that in step (3), the PTFE was fiberized at room temperature without performing low-temperature high-speed polishing and shearing treatment.

[0115] Powder B was polished using a jet mill with low-temperature airflow at an airflow temperature of 20°C, a polishing pressure of 0.90 MPa, and a classification wheel rotation speed of 10,000 rpm to obtain powder D. Comparative Example 5

[0116] The difference between Comparative Example 5 and Example 1 is that the temperature at which airflow polishing shear was performed on powder B in step (3) was different.

[0117] Powder B was polished using a jet mill with low-temperature airflow at an airflow temperature of 15°C, a polishing pressure of 0.70 MPa, and a classification wheel rotation speed of 10,000 rpm to obtain powder C. Comparative Example 6

[0118] The difference between Comparative Example 6 and Example 1 is that the temperature at which airflow polishing shear was performed on powder B in step (3) was different.

[0119] Powder B was polished using a jet mill with low-temperature airflow at an airflow temperature of 19°C, a polishing pressure of 0.70 MPa, and a classification wheel rotation speed of 10,000 rpm to obtain powder C.

[0120] The thickness, tensile strength, and press density of the electrode films produced in Examples 1-12 and Comparative Examples 1-6 were measured. The tensile strength test method was based on Part 2, "Test Conditions for Molding and Extrusion of Plastics," of GB / T 1040.2-2022 Measurement of Tensile Performance of Plastics, and the results are shown in Table 1.

[0121] Electrochemical performance detection method: The resistivity of the electrode film was tested using a BER2300 electrode resistometer manufactured by Initial Energy Science & Technology.

[0122] Method for testing liquid absorption rate: Take a 10 x 3 cm membrane piece and weigh it, recording the initial weight as m1. After weighing, immerse the membrane piece in the electrolyte solution for 2 hours. Then, remove it with tweezers, wipe off the free electrolyte from the surface, weigh it again, and record the result as m2. Liquid absorption rate = (m2 - m1) / m1.

[0123] The resistivity and liquid absorption rate of electrodes manufactured using the above method were detected.

[0124] [Table 1]

[0125] According to the detection data in Table 1, the electrode films manufactured by the dry process in Examples 1 to 12 of this application had a thickness of 115 to 152 μm, a tensile strength of 0.15 to 0.22 MPa, and a press density of 2.65 to 2.90 g / cm³. 3 (In Example 12, it was a negative electrode, and the press density was 1.76), and the tensile strength, resistivity, and liquid absorption rate are as shown in Figures 5, 6, 7, and 8.

[0126] In the manufacturing method of Comparative Example 1, instead of performing low-temperature, high-speed polishing shear on the PTFE, micro-order PTFE, nano-order active material, and conductive agent were mixed, and then high-temperature airflow polishing was performed directly. Because the PTFE mixture had poor dispersibility and was non-uniform, the fiberization effect was further reduced, and the tensile strength of the manufactured electrode film was 0.14 MPa and the press density was 2.78 g / cm³. 3 As a result, the electrode film fragments were prone to cracking and tearing, and there was clearly PTFE that was not uniformly dispersed on the surface of the film fragments. By comparison, the present invention first fabricates PTFE into nano-order particles under low-temperature, high-speed polishing and shearing conditions, and then performs high-temperature, high-speed polishing and shearing fiberization treatment, thereby clearly promoting the uniformity of PTFE dispersion and a better fiberization effect, and the tensile strength of the fabricated film fragments is clearly improved.

[0127] Comparative Example 2 involved fiberizing PTFE at room temperature, but because the fiberization temperature was inappropriate, a continuous electrode film could not be obtained, and the film fragment broke during the thinning process. This means that in order to obtain a good fiberization effect when fiberizing PTFE, the fiberization temperature needs to reach a certain value.

[0128] Comparative Example 3 contained too much PTFE, and fiberization was performed at room temperature without low-temperature high-speed shearing of the PTFE. This resulted in cracking during the thinning process of the film fragments, significantly reducing the tensile strength of the film fragments.

[0129] In Comparative Example 4, PTFE was subjected to room-temperature fiber formation without low-temperature high-speed polishing and shearing treatment. During the film formation process, the powder particles interlocked and became fixed, resulting in a lack of tensile strength.

[0130] In Comparative Examples 5 and 6, low-temperature airflow polishing was performed at a temperature close to the phase transition temperature of PTFE. At this temperature, during the manufacturing process from micro-order particles to nano-order particles, some of the PTFE already became fibrous due to the heat generated during the shearing process, inhibiting and destroying the effect of manufacturing nano-order particles with PTFE. As a result, the final PTFE had poor dispersibility, poor uniformity, poor PTFE fibrosis, and reduced tensile strength of the film fragments. The comparison revealed that, in addition to manufacturing PTFE to the nano-order before PTFE fibrosis, it is necessary to avoid premature PTFE fibrosis caused by excessively high shear temperatures during the manufacturing process of nano-order particles with PTFE. Therefore, it was found that the shear temperature during the manufacturing process of nanoparticles with PTFE must be strictly controlled.

[0131] As shown in Figure 7, the resistivity of the electrode piece representing Example 1 was the lowest at 9 mΩ, the resistivity of the electrode piece of Comparative Example 3 was the highest, and the resistivity of the electrode pieces of Comparative Examples 2 and 3 was at least twice as high as that of Example 1. This means that in Example 1 of the present invention, the resistivity of the electrode manufactured after first performing low-temperature, high-speed polishing and shearing on PTFE to reach the nano-order is only about 30% of the resistivity of the electrode manufactured from micro-order PTFE.

[0132] As shown in Figure 8, the liquid absorption rate of the electrode piece representing Example 1 was the highest, reaching over 225%, while the liquid absorption rates of the electrode pieces of Comparative Examples 1, 2, and 3 decreased sequentially, with the liquid absorption rate of Comparative Example 1 reaching only about 65% of that of Example 1. In Example 1 of the present invention, the liquid absorption rate of the electrode manufactured after first performing low-temperature, high-speed polishing and shearing on PTFE to reach the nano-order was improved by more than 35% compared to the liquid absorption rate of an electrode manufactured directly from micro-order PTFE.

[0133] The above means that by manufacturing a dry electrode film using the method of this invention, the tensile strength, press density, etc., are significantly improved, the resistivity of the dry electrode is significantly reduced, and the liquid absorption rate is increased.

[0134] Furthermore, terms such as "first," "second," etc., in the specification and claims of this invention are used to distinguish similar subjects and are not necessary to describe a specific order or priority. It should be understood that such terms may be interchangeable in appropriate circumstances so that the embodiments of this application described herein may be carried out, for example, in an order other than that described herein.

Claims

1. Step S1 involves mixing a polytetrafluoroethylene material, an electrode active material, and a conductive agent, and then grinding them to obtain a pulverized mixture. Step S2 involves performing primary airflow polishing shear on the pulverized mixture to obtain a polished shear mixture, wherein the conditions for the primary airflow polishing shear include an airflow temperature of -10°C to 10°C, a compressed airflow pressure of 0.7 to 0.9 MPa, and a shearing rotation speed of 8000 to 12000 rpm. Step S3 involves performing secondary airflow polishing and shearing on the polishing and shearing mixture to obtain a fibrous material. The process includes step S4, which involves performing a secondary fiberization treatment on the fiberized material to obtain a dry electrode film. A method for manufacturing electrode films using a dry process.

2. The airflow temperature for the primary airflow polishing shear is -5°C to 5°C, preferably 0 to 5°C. and / or the conditions for the secondary airflow polishing shear include an airflow temperature of 50°C to 100°C, a compressed airflow pressure of 0.7 to 0.9 MPa, and a shear rotation speed of 8000 to 12000 rpm. Preferably, the airflow temperature for the secondary airflow polishing shear is 60 to 100°C, preferably 70 to 100°C, more preferably 80 to 100°C, and the shearing rotation speed is 10,000 to 11,000 rpm. and / or, the shear rotation speed of the primary airflow polishing shear is 10,000 to 11,000 rpm. and / or, the polytetrafluoroethylene material is a polytetrafluoroethylene dispersion resin having an average particle size of 400 to 600 μm, a molecular weight of 500,000 to 8,000,000, and a compression ratio of 100 to 3,000. Preferably, the polytetrafluoroethylene dispersion resin is kept warm at -8°C to -12°C for 8 to 12 hours before mixing. A method for manufacturing a dry electrode film according to claim 1.

3. The specific process of step S1 includes mixing the electrode active material and the conductive agent, grinding them to obtain powder A, and mixing the polytetrafluoroethylene dispersion resin after heating with powder A, grinding them to obtain the pulverized mixture. Preferably, the electrode active material and the conductive agent are mixed in a ball mill or a high-speed mixer, and the rotation speed of the high-speed mixer is 400 to 600 rpm. Preferably, the ball-to-material ratio of the ball mill is 1:(1-2), Preferably, the polytetrafluoroethylene dispersion resin and the powder A are mixed in a double-motion mixer or a three-dimensional motion mixer. Preferably, the time for mixing the polytetrafluoroethylene dispersion resin and the powder A in the double-action mixer is 20 to 40 minutes. The method for manufacturing a dry electrode film according to claim 2.

4. The average particle size of the pulverized mixture is 8 to 12 μm. and / or, the average particle size of the abrasive shear mixture is 3 to 6 μm, and / or the primary airflow polishing shear and / or the secondary airflow polishing shear employ a jet mill, Preferably, the jet mill is a fluidized bed type jet mill. A method for manufacturing a dry electrode film according to any one of claims 1 to 3.

5. The aforementioned secondary fiberization process involves performing differential open roll fiberization using a differential roll press machine. Preferably, the differential roll press has a roll press temperature of 60°C to 120°C and a roll press speed ratio of 1:(1 to 1.5). A method for manufacturing a dry electrode film according to any one of claims 1 to 4.

6. The weight ratio of the electrode active material to the conductive agent is (90-95):(0-5), and / or, the weight ratio of powder A to the polytetrafluoroethylene dispersion resin after heating is (95-99):(1-5), and / or, the electrode active material comprises a positive electrode active material and a negative electrode active material, wherein the positive electrode active material is at least one selected from lithium iron phosphate, lithium iron manganese phosphate, lithium nickel cobalt manganese oxide, lithium cobalt oxide, lithium manganese oxide, lithium nickel cobalt aluminate and manganese dioxide, and the negative electrode active material is at least one selected from artificial graphite, natural graphite, lithium titanate, silicon-oxygen negative electrode material and silicon-carbon, and / or, the conductive agent is at least one selected from conductive carbon black, graphite, graphene, carbon nanotubes, carbon fibers, acetylene black, and Ketjenblack. A method for manufacturing a dry electrode film according to any one of claims 2 to 5.

7. Manufactured by the dry electrode film manufacturing method described in any one of claims 1 to 6, Dry method electrode membrane.

8. The dry electrode film has a thickness of 100 to 152 μm, a tensile strength of 0.15 to 0.4 MPa, and a press density of 2.50 to 3.30 g / cm³. 3 That is, The dry electrode film according to claim 7.

9. A method for manufacturing a dry electrode, comprising the step of roll-pressing a dry electrode film onto at least one side of a current collector, The dry electrode film is the dry electrode film described in claim 7 or 8. A method for manufacturing a dry electrode.

10. The temperature of the roll press is between 0°C and 100°C. Preferably, the current collector is at least one selected from copper foil, carbon-coated copper foil, aluminum foil, nickel foil, stainless steel mesh, aluminum mesh, and nickel mesh. The method for manufacturing a dry electrode according to claim 9.

11. A battery comprising electrodes, a separator, and an electrolyte, The electrode is an electrode manufactured by the dry electrode manufacturing method described in claim 9 or 10. battery.

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