A dry electrode electrode sheet film and a method of manufacturing the same
By combining active materials with specific particle size ratios and fibrous binders, the problems of insufficient film formation and compaction density of dry electrode films were solved, and high-performance preparation of electrode films was achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- GAC AION NEW ENERGY AUTOMOBILE CO LTD
- Filing Date
- 2024-10-18
- Publication Date
- 2026-05-29
AI Technical Summary
Existing dry electrode film preparation processes struggle to balance film formation and compaction density, which negatively impacts the electrical properties of the electrode sheets.
Electrode films are prepared by using a combination of large and small particle size active materials with specific particle size, the binder is fibrous, the active material particles are arranged along the extension direction of the binder, and the films are prepared by fiberization treatment, crushing and granulation and multi-roll continuous rolling film forming treatment.
The prepared electrode film has excellent film-forming properties, high compaction density and stability, which improves the electrical performance of the electrode sheet.
Smart Images
Figure CN119324194B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of dry electrode manufacturing technology, and more specifically, to a dry electrode film and its preparation method. Background Technology
[0002] In existing technologies, the positive and negative electrode films of lithium-ion batteries are generally prepared by wet slurry coating. This wet process usually uses solvents and requires baking and drying steps, which not only has a certain negative impact on the production environment and safety, but also has the problem of high energy consumption.
[0003] Based on this, researchers proposed a dry electrode film preparation process, which eliminates the use of solvents during the electrode film preparation process. Specifically, the dry electrode film preparation process typically involves highly mixed fiberizing of electrode powder (a mixture of positive and negative electrode materials, binder, and conductive agent), followed by crushing and granulation, and finally roll pressing to obtain the dry electrode film. However, the dry electrode films prepared by existing dry processes suffer from poor film-forming properties (i.e., low tensile strength) or low compaction density, making it difficult to effectively balance excellent film-forming properties and high compaction density, thus affecting the electrical properties of the corresponding electrode sheets. Summary of the Invention
[0004] The purpose of this application is to provide a dry electrode film and its preparation method, which can have both good film-forming properties and high compaction density.
[0005] The embodiments of this application are implemented as follows:
[0006] In a first aspect, embodiments of this application provide a dry electrode film comprising active material particles, conductive agent particles, and an adhesive. The adhesive is fibrous, and the active material particles include large-diameter active material particles and small-diameter active material particles. The particle size D50 of the large-diameter active material particles is 4–10 μm, and the particle size D50 of the small-diameter active material particles is 1–2 μm. The small-diameter active material particles are arranged along the extension direction of the adhesive in the region close to and bonded to the adhesive.
[0007] In the above technical solution, the active material particles are composed of a combination of large-diameter and small-diameter active material particles of a specific size. The binder is fibrous, and the small-diameter active material particles are arranged along the extension direction of the binder in the area close to and bonded to the binder. The large particles of a specific size help the binder to become fibrous, thereby giving the corresponding electrode film excellent film-forming properties (i.e., high tensile strength). The small particles of a specific size near the binder fill the gaps between the large particles, giving the electrode film a high compaction density. At the same time, the small particles of a specific size attached to the binder can surround the large particles together with the fibrous binder, thereby improving the binding force between the active material particles in the electrode film, so as to give the electrode film high stability.
[0008] In some alternative implementations, the particle size D50 of the large-diameter active material particles is 6–8 μm, and the particle size D50 of the small-diameter active material particles is 1–1.5 μm.
[0009] In the above technical solution, the particle size D50 of the large-particle active material and the small-particle active material are respectively limited to a more suitable range, so that the electrode film has better film-forming properties and higher compaction density.
[0010] In some alternative implementations, the particle size D90 of the large-diameter active material particles is 15–20 μm, and the particle size D90 of the small-diameter active material particles is 3–4 μm.
[0011] In the above technical solution, the particle size D90 of the large-particle active material and the small-particle active material are respectively limited to a suitable range so that they have a suitable upper limit particle size, which also helps to improve the film-forming properties and compaction density of the electrode film.
[0012] In some alternative implementations, the mass of the small-diameter active material particles directly bonded to the adhesive accounts for 50-60% of the total mass of the small-diameter active material particles.
[0013] In the above technical solution, the mass of the small-diameter particles directly bonded to the adhesive accounts for 50-60% of the total mass of the small-diameter active material particles. This ensures that the small-diameter particles used to fill the pores between the large-diameter particles and the two small-diameter particles used to surround the large-diameter particles have appropriate mass proportions, thereby giving the electrode film better film-forming properties, higher compaction density, and better stability.
[0014] In some alternative embodiments, the mass ratio of large-diameter active material particles to small-diameter active material particles in the active material particles is (10-50):(50-90).
[0015] In the above technical solution, the mass ratio of large-diameter and small-diameter particles is limited to a specific range so that the two can be better mixed, thereby giving the electrode film better film-forming properties, higher compaction density and better stability.
[0016] In some alternative implementations, the mass ratio of active material particles, conductive agent particles and binder in the electrode film is (90-98):(1-3):(2-5).
[0017] In the above technical solution, the mass ratio of active material particles, conductive agent particles and binder in the electrode film is limited to a specific range so that the electrode film has superior electrical properties.
[0018] In some optional embodiments, the active material particles are positive electrode active material particles, which are selected from at least one of nickel-cobalt-manganese ternary materials, nickel-cobalt-aluminum ternary materials, lithium iron phosphate, lithium manganese oxide, lithium cobalt oxide, nickel-manganese or nickel-aluminum binary materials, and nickel-cobalt-manganese-aluminum quaternary materials.
[0019] In the above technical solution, this specific particle size matching system is particularly suitable for dry-process positive electrode membranes. The positive electrode active material particles are applicable to a wide variety of materials, providing more feasible implementation schemes, which facilitates the promotion and application of the technical solution provided in this application.
[0020] In some alternative embodiments, the conductive agent particles are selected from at least one of carbon nanotubes, conductive carbon black, carbon fibers, conductive graphite, and acetylene black; and / or, the adhesive is selected from at least one of polyvinylidene fluoride and polytetrafluoroethylene.
[0021] In the above technical solutions, the conductive agents and adhesives are applicable to a wide variety of materials, providing a large number of feasible solutions, which facilitates the promotion and application of the technical solutions provided in this application.
[0022] Secondly, embodiments of this application provide a method for preparing a dry electrode film as provided in the first aspect embodiment, comprising the following steps:
[0023] Active material particles, conductive agent particles and binder are mixed to obtain a mixture; and the mixture is then subjected to fiberization treatment, crushing and granulation treatment and multi-roll continuous rolling film treatment to obtain a dry electrode film.
[0024] By following the above process, a dry electrode film with good film-forming properties, high compaction density, and stability can be prepared.
[0025] In some alternative embodiments, the step of mixing active material particles, conductive agent particles, and binder to obtain a mixture includes: first mixing the conductive agent particles and binder to obtain a mixture intermediate; then adding active material particles to the mixture intermediate and mixing to obtain the mixture.
[0026] In the above technical solution, the conductive agent particles and the binder are mixed first, and then the intermediate mixture is mixed with the active material particles. This feeding and mixing method helps the conductive agent particles to better adhere to the fibrous binder after the fiberization treatment, thereby helping to form a more ideal conductive network.
[0027] In some alternative implementations, in the step of mixing the conductive agent particles and the binder, the linear velocity of the agitator is 5 to 20 m / s, the mixing time is 20 to 60 min, and the processing temperature is 5 to 20 °C.
[0028] In the above technical solution, in the step of mixing the conductive agent and the adhesive, the linear speed of the stirring paddle, the stirring time, and the processing temperature are limited to specific ranges so that the conductive agent can be distributed more evenly in the adhesive.
[0029] In some alternative implementations, during the fiberization step, the linear velocity of the agitator is ≥40 m / s, the agitation time is 5–30 min, and the treatment temperature is 60–80 °C.
[0030] In the above technical solution, during the fiberization process, the linear velocity of the mixing paddle, the mixing time, and the treatment temperature are each limited to a specific range to improve the fiberization effect of the adhesive.
[0031] In some alternative implementations, the screen size in the crusher during the crushing and granulation process is 8 to 20 mesh.
[0032] In the above technical solution, limiting the screen size to a specific range during the crushing and granulation step can balance good film quality and production continuity.
[0033] In some alternative implementations, the multi-roll continuous rolling film forming process includes: first, performing film forming treatment on the powder obtained after crushing and granulation to obtain an electrode film precursor; then, performing multiple thinning treatments on the electrode film precursor in sequence, wherein the gap between the rolls gradually decreases during the multiple thinning treatments until the thickness of the film reaches the preset thickness specification, thereby obtaining a dry electrode film.
[0034] In the above technical solution, the thinning process is achieved by multiple thinning steps, and the roller gap of the multiple thinning processes is set to gradually decrease, which helps to improve the thickness uniformity of the prepared electrode film. Attached Figure Description
[0035] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.
[0036] Figure 1 This is a schematic diagram of the structure of a dry electrode film provided in an embodiment of this application;
[0037] Figure 2 An electron microscope image of a dry electrode film provided in Embodiment 1 of this application.
[0038] Icons: 10 - Dry electrode film; 100 - Adhesive; 200a - Small-diameter active material particles attached to the adhesive; 200b - Small-diameter active material particles near the adhesive; 300 - Large-diameter active material particles. Detailed Implementation
[0039] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.
[0040] It should be noted that the terms "and / or" in this application, such as "feature 1 and / or feature 2", all refer to the three cases of "feature 1" alone, "feature 2" alone, and "feature 1" plus "feature 2".
[0041] In addition, in the description of this application, unless otherwise stated, "one or more" means two or more; the range of "numerical value a to numerical value b" includes the two endpoints "a" and "b"; and "unit of measurement" in "numerical value a to numerical value b + unit of measurement" represents the "unit of measurement" of both "numerical value a" and "numerical value b".
[0042] Existing dry electrode films typically struggle to combine good film-forming properties with high compaction density. Through research, the inventors discovered that the fiberization of the binder is related to the particle size of the active material. Specifically, larger particle size active materials are more conducive to binder fiberization, resulting in better film-forming properties in the prepared electrode film. However, larger particle size active materials also present the problem of lower compaction density in the formed electrode film.
[0043] Based on this, the inventors combined large-particle-size active materials and small-particle-size active materials of specific particle sizes to enable the corresponding electrode film to have both good film-forming properties and high compaction density.
[0044] The following is a detailed description of a dry electrode film and its preparation method according to an embodiment of this application.
[0045] In a first aspect, embodiments of this application provide a dry electrode film comprising active material particles, conductive agent particles, and an adhesive. The adhesive is fibrous. The active material particles include large-diameter active material particles and small-diameter active material particles. The particle size D50 of the large-diameter active material particles is 4–10 μm (e.g., but not limited to any one of 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, and 10 μm, or any range between two), and the particle size D50 of the small-diameter active material particles is 1–2 μm (e.g., but not limited to any one of 1 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm, and 2 μm, or any range between two). The small-diameter active material particles are arranged along the extension direction of the adhesive in a region close to and bonded to the adhesive.
[0046] In this application, the active material particles are composed of a combination of large-diameter and small-diameter active material particles of a specific size. The binder is fibrous, and the small-diameter active material particles are arranged along the extension direction of the binder in the region close to and bonded to the binder. The large particles of a specific size facilitate the fiberization of the binder, thereby giving the corresponding electrode film superior film-forming properties (i.e., high tensile strength). The small particles of a specific size near the binder fill the gaps between the large particles, giving the electrode film a high compaction density. At the same time, the small particles of a specific size attached to the binder can surround the large particles together with the fibrous binder, thereby improving the binding force between the active material particles in the electrode film, so as to give the electrode film high stability.
[0047] To better understand the technical solution, a schematic diagram of the dry electrode film 10 is provided here for further explanation. Please refer to [reference needed]. Figure 1 In this context, 100 represents fibrous adhesive, 200a represents small-diameter active material particles attached to the adhesive, 200b represents small-diameter active material particles close to the adhesive, and 300 represents large-diameter active material particles.
[0048] As an example, the particle size D50 of large-diameter active material particles is 6 to 8 μm (e.g., but not limited to any one of 6 μm, 6.5 μm, 7 μm, 7.5 μm and 8 μm or any range between two), and the particle size D50 of small-diameter active material particles is 1 to 1.5 μm (e.g., but not limited to any one of 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm and 1.5 μm or any range between two).
[0049] In this embodiment, the particle size D50 of the large-particle active material and the small-particle active material are respectively limited to a more suitable range, so that the electrode film has better film-forming properties and higher compaction density.
[0050] As an example, the particle size D90 of large-diameter active material particles is 15–20 μm (e.g., but not limited to any one of 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, and 20 μm, or any range between two), and the particle size D90 of small-diameter active material particles is 3–4 μm (e.g., but not limited to any one of 3 μm, 3.2 μm, 3.4 μm, 3.6 μm, 3.8 μm, and 4 μm, or any range between two).
[0051] In this embodiment, the particle size D90 of the large-particle active material and the small-particle active material are respectively limited to a suitable range so that they have a suitable upper limit particle size, which also helps to improve the film-forming properties and compaction density of the electrode film.
[0052] As an example, the mass of the small-diameter active material particles directly bonded to the adhesive accounts for 50 to 60% of the total mass of the small-diameter active material particles, for example, but not limited to any one of 50%, 52%, 54%, 56%, 58%, and 60% of the total mass, or a range between any two.
[0053] In this embodiment, the mass of the small-diameter particles directly bonded to the adhesive accounts for 50-60% of the total mass of the small-diameter active material particles. This ensures that the small-diameter particles used to fill the pores between the large-diameter particles and the two small-diameter particles used to surround the large-diameter particles have appropriate mass proportions, thereby giving the electrode film better film-forming properties, higher compaction density, and better stability.
[0054] As an example, in the active material particles, the mass ratio of large-diameter active material particles to small-diameter active material particles is (10-50):(50-90), for example, but not limited to any one of 10:90, 20:80, 30:70, 40:60 and 50:50, or any range between the two.
[0055] In this embodiment, the mass ratio of large-diameter to small-diameter particles is limited to a specific range so that the two can be better blended, thereby giving the electrode film better film-forming properties, higher compaction density and better stability.
[0056] It should be noted that the mass percentage of each functional component in the electrode membrane is not limited and can be adjusted according to actual needs.
[0057] As an example, in the electrode film, the mass ratio of active material particles, conductive agent particles and binder is (90-98):(1-3):(2-5).
[0058] In this embodiment, the mass ratio of active material particles, conductive agent particles, and binder in the electrode film is limited to a specific range so that the electrode film has superior electrical properties.
[0059] As an example, the active material particles are positive electrode active material particles, which are selected from at least one of nickel-cobalt-manganese ternary materials, nickel-cobalt-aluminum ternary materials, lithium iron phosphate, lithium manganese oxide, lithium cobalt oxide, nickel-manganese or nickel-aluminum binary materials, and nickel-cobalt-manganese-aluminum quaternary materials.
[0060] In this embodiment, the specific particle size matching system is particularly suitable for dry-process positive electrode membranes. The positive electrode active material particles are applicable to a wide variety of materials, providing more feasible implementation schemes, thereby facilitating the promotion and application of the technical solutions provided in this application.
[0061] As an example, the conductive agent particles are selected from at least one of carbon nanotubes, conductive carbon black, carbon fibers, conductive graphite, and acetylene black; and / or, the adhesive is selected from at least one of polyvinylidene fluoride and polytetrafluoroethylene.
[0062] In this embodiment, the conductive agent and adhesive are applicable to a wide variety of materials, providing a large number of feasible solutions, thereby facilitating the promotion and application of the technical solution provided in this application.
[0063] It should be noted that functional components in the dry electrode film that are not specifically described or limited can be selected and set in accordance with conventional methods in the field.
[0064] In a second aspect, embodiments of this application provide a method for preparing a dry electrode film as provided in the first aspect embodiment, comprising the following steps: mixing active material particles, conductive agent particles and binder to obtain a mixture; and sequentially subjecting the mixture to fiberization treatment, crushing and granulation treatment and multi-roll continuous rolling film forming treatment to obtain a dry electrode film.
[0065] In this application, by following the above-described process, a dry electrode film with good film-forming properties, high compaction density, and stability can be prepared.
[0066] As an example, the steps of mixing active material particles, conductive agent particles, and binder to obtain a mixture include: first mixing the conductive agent particles and binder to obtain a mixture intermediate; then adding active material particles to the mixture intermediate and mixing to obtain the mixture.
[0067] In this embodiment, the conductive agent particles and the binder are mixed first, and then the intermediate mixture is mixed with the active material particles. This additive mixing method helps the conductive agent particles to adhere better to the fibrous binder after the fiberization treatment, thereby helping to form a more ideal conductive network.
[0068] As an example, in the step of mixing the conductive agent particles and the binder, the linear velocity of the agitator is 5 to 20 m / s (e.g., but not limited to any one of 5 m / s, 10 m / s, 15 m / s and 20 m / s or any range between the two), the stirring time is 20 to 60 min (e.g., but not limited to any one of 20 min, 30 min, 40 min, 50 min and 60 min or any range between the two), and the processing temperature is 5 to 20 °C (e.g., but not limited to any one of 5 °C, 10 °C, 15 °C and 20 °C or any range between the two).
[0069] In this embodiment, in the step of mixing the conductive agent and the binder, the linear speed of the stirring paddle, the stirring time, and the processing temperature are each limited to a specific range so that the conductive agent can be distributed more evenly in the binder.
[0070] It should be noted that the steps of adding active material particles to the intermediate mixture and mixing them can also be carried out by referring to the mixing steps of conductive agent particles and binder.
[0071] As an example, in the fiberization process, the linear velocity of the agitator is ≥40 m / s (e.g., but not limited to any one of 40 m / s, 42 m / s, 45 m / s, 47 m / s, and 50 m / s, or any range between any two), the agitation time is 5 to 30 min (e.g., but not limited to any one of 5 min, 10 min, 20 min, and 30 min, or any range between any two), and the processing temperature is 60 to 80 °C (e.g., but not limited to any one of 60 °C, 65 °C, 70 °C, 75 °C, and 80 °C, or any range between any two).
[0072] In this embodiment, during the fiberization process, the linear velocity of the mixing paddle, the mixing time, and the processing temperature are each limited to a specific range to improve the fiberization effect of the adhesive.
[0073] As an example, in the crushing and granulation process, the screen size in the crusher is 8 to 20 mesh, for example, but not limited to any one of the sizes 8, 10, 12, 14, 16, 18 and 20, or any range between two.
[0074] In this embodiment, limiting the screen size to a specific range during the crushing and granulation step can balance good film quality and production continuity.
[0075] As an example, the steps of multi-roll continuous rolling film forming process include: first, the powder obtained after crushing and granulation is subjected to film forming process to obtain an electrode film precursor; then, the electrode film precursor is subjected to multiple thinning processes in sequence, wherein the gap between the rolls is gradually reduced in the multiple thinning processes until the thickness of the film reaches the preset thickness specification to obtain a dry electrode film.
[0076] In this embodiment, the thinning process is achieved through multiple thinning steps, and the roll gap of the multiple thinning processes is set to gradually decrease, which helps to improve the thickness uniformity of the prepared electrode film.
[0077] It should be noted that there is no limit to the number of thinning processes, and the specific number can be adjusted according to actual needs. This application example takes three thinning processes in sequence as an example.
[0078] Understandably, the roll gap during the three-stage thinning process is gradually reduced, and the specific roll gap size is not limited; it can be adjusted adaptively according to actual needs.
[0079] It should be noted that for the preparation methods of dry electrode films, any processes or steps not specifically described or limited can be set according to conventional methods in this field.
[0080] As an example, in the multi-roll continuous rolling film forming process, the rolling pressure of both the film forming roll and the thinning roll is 5 to 7T, and the temperature of both the film forming roll and the thinning roll is 140 to 160°C.
[0081] The features and performance of this application will be further described in detail below with reference to the embodiments.
[0082] Example 1
[0083] This application provides a method for preparing a dry electrode film, comprising the following steps:
[0084] 1% conductive carbon black (conductive agent) and 2% polytetrafluoroethylene (binder) were mixed to obtain a mixed intermediate. The linear velocity of the stirring paddle was 20 m / s, the stirring time was 20 min, and the processing temperature was 18℃. Then, 97% lithium iron phosphate material particles (positive electrode active material) were added to the mixed intermediate and mixed. The lithium iron phosphate material particles included 50% large-particle-size active material particles (D50 of 7.5 μm, D90 of 19 μm, and compaction density of 2.18 g / cm³). 3 ) and 50% small-diameter active material particles (D50 is 1.2μm, D90 is 4μm, and compaction density is 2.57g / cm³). 3 ), to obtain the mixture.
[0085] The mixture was sequentially subjected to fiberization treatment, with the linear velocity of the stirring paddle at 40 m / s, the stirring time at 15 min, and the treatment temperature at 65℃. The fiberized material was then crushed and granulated, with a 10-mesh screen in the crusher. The powder obtained after crushing and granulation was then subjected to film-forming treatment to obtain an electrode film precursor, with the film-forming roller temperature at 150℃, the roller gap at 280 μm, and the roller pressure at 6T. The electrode film precursor was then subjected to three thinning treatments, with the thinning roller temperature at 150℃, the thinning roller pressure at 6T, and the roller gaps for the three thinning treatments being 230 μm, 180 μm, and 130 μm respectively, to obtain a dry electrode film.
[0086] Comparative Example 1
[0087] This application provides a method for preparing a dry electrode film, which differs from Example 1 only in that all lithium iron phosphate material particles are large-diameter active material particles.
[0088] Comparative Example 2
[0089] This application provides a method for preparing a dry electrode film, which differs from Example 1 only in that all lithium iron phosphate material particles are small-diameter active material particles.
[0090] Experimental Example 1
[0091] Electron microscopy of electrode films
[0092] Test method:
[0093] The electrode films prepared in Example 1 were numbered, and the microstructure of the samples was tested using an electron microscope.
[0094] See Figure 2As can be seen, in the preparation process provided in the embodiments of this application, the binder in the prepared electrode film is fibrous and small-diameter active material particles are arranged along the extension direction of the binder in the area close to and bonded to the binder. Among them, some small particles of a specific diameter close to the binder fill the gaps between the large particles, and the small particles of a specific diameter attached to the binder can surround the large particles together with the fibrous binder.
[0095] Experimental Example 2
[0096] Electrode membrane performance testing
[0097] Test method:
[0098] The electrode films prepared in Example 1 and Comparative Examples 1 and 2 were numbered respectively, and the tensile strength and compaction density of each sample were tested and statistically analyzed in Table 1.
[0099] The tensile strength test procedure is as follows: cut each sample electrode film to obtain a tensile sample with a width of 6 mm, then use a tensile testing machine to clamp both sides of each tensile sample and perform a tensile test on it. The tensile speed is 250 mm / min until the tensile sample breaks, and the tensile strength at the time of breakage is recorded.
[0100] The test steps for compaction density are as follows: cut each sample electrode film into cylindrical samples with a diameter of 12mm, then test the weight of each cylindrical sample, calculate the areal density first, and then calculate the compaction density based on the areal density and the corresponding thickness.
[0101] Table 1
[0102] sample Tensile strength (MPa) <![CDATA[Compaction density (g / cm 3 )]]> Example 1 0.26 2 Comparative Example 1 0.263 1.55 Comparative Example 2 0.16 1.96
[0103] Referring to Table 1, the test results of Example 1 and Comparative Examples 1-2 show that the electrode film prepared by the preparation process provided in the embodiments of this application can have both good film-forming properties and high compaction density.
[0104] The embodiments described above are some, but not all, of the embodiments of this application. The detailed description of the embodiments of this application is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.
Claims
1. A dry-process electrode film, characterized in that, The material comprises active material particles, conductive agent particles, and an adhesive, wherein the adhesive is fibrous, and the active material particles include large-diameter active material particles and small-diameter active material particles. The particle size D50 of the large-diameter active material particles is 4~10 μm, and the particle size D50 of the small-diameter active material particles is 1~2 μm. The small-diameter active material particles are arranged along the extension direction of the adhesive in the region close to and bonded to the adhesive. The small-diameter active material particles near the adhesive fill the spaces between the large-diameter active material particles, and the small-diameter active material particles bonded to the adhesive surround the large-diameter active material particles. In the active material particles, the mass ratio of the large-diameter active material particles to the small-diameter active material particles is (10~50):(50~90), and the mass of the small-diameter active material particles directly bonded to the adhesive accounts for 50~60% of the total mass of the small-diameter active material particles.
2. The dry electrode film according to claim 1, characterized in that, The particle size D50 of the large-particle-size active material particles is 6~8 μm, and the particle size D50 of the small-particle-size active material particles is 1~1.5 μm.
3. The dry electrode film according to claim 2, characterized in that, The particle size D90 of the large-particle-size active material particles is 15~20 μm, and the particle size D90 of the small-particle-size active material particles is 3~4 μm.
4. The dry electrode film according to any one of claims 1 to 3, characterized in that, In the electrode film, the mass ratio of the active material particles, the conductive agent particles and the binder is (90~98):(1~3):(2~5).
5. The dry-process electrode film according to any one of claims 1 to 3, characterized in that, The active material particles are positive electrode active material particles, which are selected from at least one of nickel-cobalt-manganese ternary materials, nickel-cobalt-aluminum ternary materials, lithium iron phosphate, lithium manganese oxide, lithium cobalt oxide, nickel-manganese or nickel-aluminum binary materials, and nickel-cobalt-manganese-aluminum quaternary materials.
6. The dry-process electrode film according to any one of claims 1 to 3, characterized in that, The conductive agent particles are selected from at least one of carbon nanotubes, conductive carbon black, carbon fibers, conductive graphite, and acetylene black. And / or, the adhesive is selected from at least one of polyvinylidene fluoride and polytetrafluoroethylene.
7. A method for preparing a dry electrode film as described in any one of claims 1 to 6, characterized in that, Includes the following steps: The active material particles, the conductive agent particles, and the binder are mixed to obtain a mixture; and the mixture is subjected to fiberization treatment, crushing and granulation treatment, and multi-roll continuous rolling film forming treatment in sequence to obtain the dry electrode film.
8. The preparation method according to claim 7, characterized in that, The step of mixing the active material particles, the conductive agent particles and the binder to obtain the mixture includes: First, the conductive agent particles and the adhesive are mixed to obtain a mixture intermediate. The active material particles are added to the intermediate mixture and mixed to obtain the mixture.
9. The preparation method according to claim 8, characterized in that, In the step of mixing the conductive agent particles and the adhesive, the linear velocity of the stirring paddle is 5~20 m / s, the stirring time is 20~60 min, and the processing temperature is 5~20℃.
10. The preparation method according to claim 9, characterized in that, In the fiberization process, the linear velocity of the agitator is ≥40 m / s, the stirring time is 5~30 min, and the processing temperature is 60~80℃.
11. The preparation method according to claim 7, characterized in that, In the crushing and granulation process, the screen size in the crusher is 8-20 mesh.
12. The preparation method according to claim 7, characterized in that, The steps of the multi-roll continuous rolling film forming process include: First, the powder obtained after crushing and granulation is subjected to film-forming treatment to obtain an electrode film precursor; then, the electrode film precursor is subjected to multiple thinning treatments in sequence, wherein the roller gap is gradually reduced in the multiple thinning treatments until the film thickness reaches the preset thickness specification to obtain the dry electrode film.