Dry electrode mixture, preparation method, electrode plate, secondary battery and electric device

Abstract

The invention provides a dry electrode mixture, which comprises an active material, a binder and a conductive agent, the active material comprises graphite, the flow energy of the dry electrode mixture is 1 J / 100 g to 3 J / 100 g, and the Dv50 particle size of the graphite in the dry electrode mixture is 8 [mu] m to 18 [mu] m. The electrode mixture has excellent flowability and can be free of loss in the conveying process, so that the stability of production and manufacturing is guaranteed, meanwhile, the prepared dry electrode film is high in flatness, thickness consistency and component uniformity, and the electrochemical performance of the dry electrode is improved.

Description

Technical Field

[0001] This application belongs to the field of battery technology, specifically relating to a dry electrode mixture, a preparation method, an electrode sheet, a secondary battery, and an electrical device. Background Technology

[0002] To improve battery energy density and reduce production costs, dry electrode technology has been proposed. On one hand, dry electrode technology can reduce process steps and solvent recovery, thus lowering production costs. On the other hand, it can increase electrode compaction density, thereby improving energy density. However, unlike wet electrodes which form a film through slurry flow, dry electrodes are completely solvent-free in their manufacturing process. This has a significant impact on the production and properties of dry electrode sheets, which in turn affects the performance of the battery cell. Summary of the Invention

[0003] Addressing the issue of the impact of solvent-free processes on processability and electrode properties in dry electrode manufacturing, this application provides a dry electrode mixture, a preparation method, an electrode sheet, a secondary battery, and an electrical device. By controlling the flow energy of the graphite-containing dry electrode mixture, this application obtains an electrode mixture with excellent flowability. This ensures no loss of powder during transport and prevents localized accumulation upon entering the film-forming equipment, thereby guaranteeing production stability, improving the yield of dry electrode films, and facilitating the production of flat, uniformly thick, and evenly distributed dry electrode sheets.

[0004] The first aspect of this application provides a dry electrode mixture comprising an active material, a binder, and a conductive agent, wherein the active material comprises graphite, the flow energy of the dry electrode mixture is 1J / 100g to 3J / 100g, and the Dv50 particle size of the graphite in the dry electrode mixture is 8μm-18μm.

[0005] The second aspect of this application provides a method for preparing a dry electrode mixture, comprising the following steps:

[0006] (I) The active material particles, binder particles and conductive agent particles are mixed to obtain mixture A; the active material particles include graphite particles with a Dv50 particle size of 8μm-18μm, the mixing temperature is 15℃-30℃, and the mixing linear velocity is 20m / s-45m / s.

[0007] (II) The mixture A is subjected to fiberization treatment to obtain a dry electrode mixture; the temperature of the fiberization treatment is 70℃-80℃, the linear velocity of the fiberization treatment is 30m / s-45m / s, and the flow energy of the dry electrode mixture is 1J / 100g~3J / 100g.

[0008] A third aspect of this application provides a dry electrode film, which is obtained by roll forming of a dry electrode mixture prepared by the method described in the first aspect or the preparation method described in the second aspect.

[0009] The fourth aspect of this application provides an electrode sheet which is formed by combining a dry electrode film and a current collector as described in the third aspect.

[0010] The fifth aspect of this application provides a secondary battery comprising electrode sheets as described in the fourth aspect.

[0011] The sixth aspect of this application provides an electrical device comprising the secondary battery described in the fifth aspect.

[0012] The beneficial effects of this application are as follows: By controlling the flow energy of the graphite-containing dry electrode mixture, this application improves the flowability of the mixed powder, so that the mixture is not lost during the transportation process and there is no local accumulation when it enters the film forming equipment, thus ensuring the stability of production and manufacturing. Furthermore, the prepared dry electrode film has high flatness, high thickness consistency, and high composition uniformity, thereby improving the electrochemical performance of the dry electrode. Detailed Implementation

[0013] For the sake of brevity, this application only specifically discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, just as any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and be combined with any other point or single value or with other lower or upper limits to form an unspecified range.

[0014] Unless otherwise stated, the terms used in this application have their common meanings as commonly understood by those skilled in the art. Unless otherwise stated, the values ​​of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art (e.g., they can be tested according to the methods given in the embodiments of this application).

[0015] The term "dry electrode mix" refers to a mixed powder containing active materials and binders but without solvents, used in the preparation of dry electrodes. "Without solvents" means that the dry electrode mix does not contain detectable processing solvents, processing solvent residues, or processing solvent impurities. These processing solvents include, but are not limited to, water, pyrrolidone, acetates, ketones, alcohols, diols, toluene, and xylene.

[0016] The term "dry electrode film" refers to an electrode film incorporating an adhesive matrix structure sufficient to support the film and maintain its shape, allowing the electrode film to operate independently without any external support elements, such as current collectors. For example, without other support elements, a dry electrode film can have sufficient strength to be rolled up, handled, and unrolled during electrode sheet manufacturing.

[0017] The term "flow energy" refers to the ability of a dry electrode mixture to flow under external force, determined by the rotation of precision-machined blades along a helical path through the dry electrode mixture. Specifically, it refers to the resistance exerted by a unit mass of dry electrode mixture on the blades during the counterclockwise downward movement of the blades. This resistance can be obtained by combining the radial torque and axial force acting on the blades by the dry electrode mixture over the distance of action, and is usually expressed as the flow energy of the dry electrode mixture sample when it reaches a steady state. In this application, the "flow energy" is measured at room temperature, i.e., 23±2℃. In this application, the "flow energy" can be measured using, for example, an FT4 powder rheometer.

[0018] The term "bulk density" refers to the ratio of the volume of a given mass of dry electrode mixture poured into a container and allowed to flow freely to the mass of the dry electrode mixture. In this application, the "bulk density" is measured at room temperature, i.e., 23 ± 2 °C. In this application, the "bulk density" can be measured using methods conventional in the art, such as according to ASTM B329-06.

[0019] The term "tap density" refers to the ratio of the volume formed when a certain mass of dry electrode mixture is poured into a container and the particles are compacted by vibration or tapping, to the mass of the dry electrode mixture. In this application, the "tap density" is measured at room temperature, i.e., 23 ± 2 °C. In this application, the "tap density" can be measured using methods conventional in the art, such as according to ASTM B527-06.

[0020] The term "graphite" is not specifically limited and can refer to both synthetic and / or natural graphite.

[0021] The present application will be further described below with reference to specific embodiments. It should be understood that these specific embodiments are for illustrative purposes only and are not intended to limit the scope of the present application.

[0022] The first aspect of this application provides a dry electrode mixture comprising an active material, a binder, and a conductive agent, wherein the active material comprises graphite, the flow energy of the dry electrode mixture is 1J / 100g to 3J / 100g, and the Dv50 particle size of the graphite in the dry electrode mixture is 8μm-18μm.

[0023] In some embodiments, the flow energy of the dry electrode mixture is exemplarily 1 J / 100g, 1.2 J / 100g, 1.5 J / 100g, 1.8 J / 100g, 2 J / 100g, 2.2 J / 100g, 2.5 J / 100g, 2.8 J / 100g, 3 J / 100g, or a range of any two of these values. Excessively high flow energy in some electrode mixtures can lead to breakage or deformation of the active material particles, resulting in an uneven and non-uniform dry electrode film, which in turn affects the electrochemical performance of the electrode, such as its initial efficiency. Conversely, excessively low flow energy in some electrode mixtures reduces the fluidity of the mixture, causing losses during transport, with some material remaining in the mixing or fiberization equipment, and even affecting film formation performance.

[0024] In some embodiments, the Dv50 particle size of the graphite in the dry electrode mixture is exemplary to be 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, or a range of any combination of these values. The Dv50 particle size of the graphite affects the flow energy of the dry electrode mixture, as well as the processability and film quality of the dry electrode.

[0025] In some embodiments, the Dv10 particle size of the graphite in the dry electrode mixture is 6 μm-11 μm, exemplarily a range of 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, or any combination of these values. In some embodiments, the Dv90 particle size of the graphite in the dry electrode mixture is 20 μm-26 μm, exemplarily a range of 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, or any combination of these values.

[0026] In some embodiments, when the composition distribution image of the dry electrode mixture is obtained by measuring the surface of the dry electrode mixture using an energy dispersive spectroscopy (EDS) instrument, the area of ​​100 adjacent particles is 4 × 10⁻⁶. -4 mm 2 The standard deviation of the area ratio of fluorine in the region is <0.6, preferably ≤0.5, and more preferably ≤0.4. When the standard deviation of the area ratio of fluorine in adjacent regions is <0.6, the good in-plane dispersion of the binder can ensure the stability of the manufacturing process, resulting in a dry electrode film with high flatness, high thickness consistency, and high compositional uniformity, thereby improving the electrochemical performance of the dry electrode, such as its first-efficiency.

[0027] In some embodiments, the bulk density of the dry electrode mixture is 0.4 g / cm³. 3 -0.8g / cm 3For example, it is 0.4 g / cm³. 3 0.45g / cm 3 0.5g / cm 3 0.55g / cm 3 0.6g / cm 3 0.65g / cm 3 0.7g / cm 3 0.75g / cm 3 0.8g / cm 3 Or a range of any two of these values. A bulk density within the above range further facilitates the flowability of the electrode mixture, ensuring production stability and resulting in a dry electrode film with high flatness, consistent thickness, and high component uniformity. If the bulk density of some electrode mixtures is too high, it will reduce the flowability of the mixture, leading to losses during transport, with some material remaining in the mixing or fiberizing equipment, and even affecting film-forming performance. If the bulk density of some electrode mixtures is too low, it will result in excessively high flowability, which is not conducive to obtaining a flat and uniform dry electrode film.

[0028] In some embodiments, the tap density of the dry electrode mixture is 1.00 g / cm³. 3 -1.14g / cm 3 For example, it is 1.00 g / cm³. 3 1.02g / cm 3 1.04 g / cm 3 1.06 g / cm 3 1.08g / cm 3 1.10 g / cm 3 1.12 g / cm 3 1.14 g / cm 3 Or a range of any two of these values. A tap density of the dry electrode mixture within the above range is more conducive to ensuring production stability and obtaining dry electrode films with high flatness, high thickness consistency, and high compositional uniformity. If the tap density of some electrode mixtures is too high, it indicates that the particle size of the mixture is too small, posing a risk of particle breakage and hindering the preparation of a flat, uniform, or electrochemically superior dry electrode film. If the tap density of some electrode mixtures is too low, it indicates that the mixture dispersion contains large particle agglomerations, posing a risk of uneven lithium intercalation.

[0029] In some embodiments, the binder is selected from one or more of polytetrafluoroethylene (PTFE), polyethylene, polyvinylidene fluoride (PVDF), and acrylic-modified PTFE. In some embodiments, the binder comprises a fibrous binder and a non-fibrous binder; the fibrous binder comprises fibrous PTFE and / or fibrous acrylic-modified PTFE, and the non-fibrous binder comprises polyethylene and / or PVDF. In some embodiments, the binder comprises fibrous PTFE and / or fibrous acrylic-modified PTFE. Here, "fibrous" refers to a state in which fibrous binder particles become fibrous under thermal or shear conditions.

[0030] In some embodiments, the binder constitutes 0.2%-3% of the dry electrode mixture by mass, exemplarily a range of 0.2%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%, or any combination of these values. In some embodiments, the binder constitutes 0.3%-2.5% of the dry electrode mixture by mass. In some embodiments, the binder comprises fibrous and non-fibrous binders; the fibrous binder comprises fibrous polytetrafluoroethylene and / or fibrous acrylic-modified polytetrafluoroethylene; the non-fibrous binder comprises polyethylene and / or polyvinylidene fluoride; the fibrous binder constitutes 0.1%-2.5% of the dry electrode mixture by mass, the non-fibrous binder constitutes 0.1%-1% of the dry electrode mixture by mass, and the binder constitutes 0.2%-3% of the dry electrode mixture by mass.

[0031] In some embodiments, the graphite comprises synthetic graphite and / or natural graphite. In some embodiments, the active material constitutes 95%-99.5% of the dry electrode mixture by mass, exemplarily a range of 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, 99.5%, or any combination of these values.

[0032] In some embodiments, the conductive agent constitutes 0.3% to 2% of the dry electrode mixture by mass, exemplarily a range of 0.3%, 0.5%, 0.7%, 1%, 1.3%, 1.5%, 1.7%, 2%, or any combination thereof. In some embodiments, the conductive agent constitutes 0.3% to 1.5% of the dry electrode mixture by mass. This application does not impose any particular limitation on the conductive agent, which may be any technology disclosed in the prior art, including but not limited to carbon nanotubes, natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, graphene, carbon fiber, or any combination thereof.

[0033] In some embodiments, the dry electrode mixture is prepared by a method comprising the following steps:

[0034] (I) The active material particles, binder particles and conductive agent particles are mixed to obtain mixture A; the mixing temperature is 15℃-30℃ and the dispersion linear velocity of the mixture is 20m / s-45m / s;

[0035] (II) The mixture A is subjected to fiberization treatment; the temperature of the fiberization treatment is 70℃-80℃, and the dispersion linear velocity of the fiberization treatment is 30m / s-45m / s.

[0036] In some implementations, the mixing in step (I) is carried out in a high-speed, high-intensity mixer.

[0037] In some embodiments, the fiberization process described in step (II) is carried out in a high-speed, high-intensity mixer.

[0038] A second aspect of this application provides a method for preparing a dry electrode mixture, comprising the steps of:

[0039] (I) The active material particles, binder particles and conductive agent particles are mixed to obtain mixture A; the active material particles have a Dv50 particle size of 8μm-18μm, the mixing temperature is 15℃-30℃, and the mixing linear velocity is 20m / s-45m / s.

[0040] (II) The mixture A is subjected to fiberization treatment to obtain a dry electrode mixture; the temperature of the fiberization treatment is 70℃-80℃, the linear velocity of the fiberization treatment is 30m / s-45m / s, and the flow energy of the dry electrode mixture is 1J / 100g~3J / 100g.

[0041] In some implementations, the mixing in step (I) is carried out in a high-speed, high-intensity mixer.

[0042] In some implementations, the mixing temperature in step (I) is exemplary to be 15°C, 17°C, 20°C, 22°C, 25°C, 28°C, 30°C, or a range of any two of these values.

[0043] In some implementations, the linear velocity of the mixture described in step (I) is exemplary to be 20 m / s, 22 m / s, 25 m / s, 28 m / s, 30 m / s, 32 m / s, 35 m / s, 38 m / s, 40 m / s, 42 m / s, 45 m / s, or a range of any two of these values.

[0044] In some embodiments, the fiberization process described in step (II) is carried out in a high-speed, high-intensity mixer.

[0045] In some embodiments, the temperature of the fiberization treatment in step (II) is exemplary to be 70°C, 72°C, 74°C, 75°C, 76°C, 78°C, 80°C, or any combination of these values.

[0046] In some embodiments, the linear velocity of the fiberization process in step (II) is exemplary to be 30 m / s, 32 m / s, 34 m / s, 35 m / s, 36 m / s, 38 m / s, 40 m / s, 42 m / s, 44 m / s, 45 m / s, or a range of any two of these values.

[0047] In some embodiments, the Dv50 particle size of the graphite particles in step (I) is exemplary to be 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm or a range of any two of these values.

[0048] In some embodiments, in step (I), the active material particles account for 95%-99.5% of the mass percentage of the mixture A, the binder particles account for 0.2%-3% of the mass percentage of the mixture A, and the conductive agent particles account for 0.3% to 2% of the mass percentage of the mixture A.

[0049] In some embodiments, in step (I), the adhesive particles are selected from one or more of polytetrafluoroethylene, polyethylene, polyvinylidene fluoride, and acrylic acid-modified polytetrafluoroethylene.

[0050] In some embodiments, in step (I), the conductive agent particles are selected from carbon black particles and carbon nanotubes.

[0051] A third aspect of this application provides a dry electrode film, which is obtained by roll forming of a dry electrode mixture prepared as described in the first aspect or by the preparation method described in the second aspect. The roll forming of this application can employ conventional forming methods and processes in the field of dry electrodes, such as roll forming the electrode mixture into a film using pressure rollers at 30°C-120°C.

[0052] The fourth aspect of this application provides an electrode sheet, which is formed by combining a dry electrode film and a current collector as described in the third aspect. The composite process in this application can employ conventional methods and processes for combining dry electrode films and current collectors in the field of dry electrodes, such as rolling the dry electrode film and current collector together at 60°C-150°C using a pressure roller.

[0053] The fifth aspect of this application provides a secondary battery comprising electrode sheets as described in the fourth aspect.

[0054] In some embodiments, the secondary battery includes a positive electrode and a negative electrode, wherein the negative electrode is an electrode sheet as described in the third aspect.

[0055] In some embodiments, the secondary battery may include an outer packaging, which may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc.; or it may be a soft pack, such as a pouch-type soft pack. The material of the soft pack is not limited, for example, polypropylene, polybutylene terephthalate, polybutylene succinate. In this application, the shape of the secondary battery is not particularly limited, and it may be cylindrical, square, or any other arbitrary shape.

[0056] In some embodiments, this application also provides a battery module. This battery module includes the aforementioned secondary battery. The battery module of this application uses the aforementioned secondary battery, and therefore has at least the same advantages as the aforementioned secondary battery. The battery module of this application can contain multiple secondary batteries, and the specific number can be adjusted according to the application and capacity of the battery module.

[0057] In some embodiments, this application also provides a battery pack including the aforementioned battery modules. The number of battery modules included in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0058] The sixth aspect of this application provides an electrical device comprising at least one of the above-described secondary batteries, battery modules, or battery packs.

[0059] In some embodiments, the electrical device includes, but is not limited to, electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and energy storage systems. To meet the high power and high energy density requirements of the electrical device, battery packs or battery modules may be used.

[0060] In other embodiments, the power device can be a mobile phone, tablet computer, laptop computer, etc. This power device is typically required to be thin and light, and can use a rechargeable battery as its power source.

[0061] Example

[0062] Unless otherwise specified, all raw materials used in this application are commonly used in the art, and the methods in the embodiments are conventional methods in the art unless otherwise specified.

[0063] Test methods

[0064] 1. Graphite particle size determination

[0065] The particle size distribution was measured using a laser diffraction particle size distribution measuring instrument (Mastersizer 3000) according to the particle size distribution laser diffraction method GB / T19077-2016. For the volume distribution, the particle sizes at cumulative frequencies of 10%, 50%, and 90% starting from the side with the smallest particle size are D10, D50, and D90, respectively.

[0066] 2. Determination of the flow energy of dry electrode mixtures

[0067] The flow energy of the dry electrode mixtures in each embodiment and comparative example was determined using an FT4 powder rheometer at room temperature (23±2℃). Flow energy is the energy required to move 100g of dry electrode mixture sample under a fixed flow mode and flow rate, and is obtained by dividing the flow energy at steady state by the mass of the sample after splitting. The test conditions were as follows: sample mass 100g, helix angle -5°, blade tip linear velocity 100mm / s. The blade rotated from the sample surface downwards to the bottom, and then from the bottom back to the surface, which was recorded as one rotation. The flow energy at steady state was determined by the flow energy of the seventh test.

[0068] 3. Determination of the bulk density of the dry electrode mixture

[0069] The bulk density test steps for the dry electrode mixtures in each embodiment and comparative example are as follows: Place a 100mL graduated cylinder on a balance and adjust it to zero. Then add the dry electrode mixture to the graduated cylinder. Then measure the volume by reading the mark at eye level and measuring the weight of the dry electrode mixture with the balance. Then calculate the bulk density using the following formula.

[0070] Bulk density (g / cm³) 3 = Weight of dry electrode mixture (g) / Volume of dry electrode mixture (cm³) 3 )

[0071] 4. Determination of tap density of dry electrode mixture

[0072] The tap density test steps for the dry electrode mixtures in each embodiment and comparative example are as follows: Place a 100mL graduated cylinder on a balance and adjust it to zero. Then add the dry electrode mixture to the graduated cylinder. Measure the volume by reading the mark at eye level and measuring the weight of the dry electrode mixture with the balance. After gently tapping the graduated cylinder 3000 times on the table, read the mark on the graduated cylinder to measure the volume. Then calculate the tap density according to the following formula.

[0073] Tap density (g / cm³) 3 = Weight of dry electrode mixture (g) / (Volume of dry electrode mixture after 100 taps (cm³)) 3 5. Determination of fluorine content in dry electrode mixtures

[0074] The dry electrode mixtures of each embodiment and comparative example were attached to the sample stage, sputter-coated with gold, and their surfaces were photographed using a scanning electron microscope (SEM) at 500x magnification. The observable sample area was 0.04 mm². 2 Then, the energy dispersive spectroscopy (EDS) mapping of the sample surface was measured using an energy dispersive spectroscopy (EDS) instrument to obtain the distribution images of each element. The fluorine distribution image was obtained through big data processing, specifically by processing a 0.04 mm... 2 The observation area was divided into 100 regions. By analyzing the differences in color contrast, the area occupied by fluorine in each region was statistically determined. The standard deviation of the area data for the 100 regions was calculated to obtain the Sigma value. If the standard deviation Sigma value is less than 0.6, the fluorine in the electrode mixture is considered to be uniformly distributed.

[0075] 6. Determination of the thickness uniformity of dry electrode film

[0076] The thickness of the dry electrode films in each embodiment and comparative example was measured using a laser thickness gauge. If the thickness tolerance of the film is less than 0.35%, the thickness consistency of the film is considered excellent; if the thickness tolerance of the film is in the range of 0.35%-0.45%, the thickness consistency of the film is considered moderate; if the thickness tolerance of the film is greater than 0.45%, the thickness consistency of the film is considered poor.

[0077] 7. Determination of the uniformity of conductive agent in dry electrode film

[0078] The surfaces of the dry electrode samples in each embodiment and comparative example were observed using SEM. If conductive agent particles with a diameter greater than 5 μm were observed on the electrode surface, it was considered that the conductive agent was unevenly dispersed and agglomerated, indicating poor uniformity of the conductive agent in the dry electrode film. If conductive agent particles with a diameter of 3 μm-5 μm were observed on the electrode surface, it was considered that the uniformity of the conductive agent in the dry electrode film was moderate. If the diameter of the conductive agent particles on the electrode surface was all less than 3 μm, it was considered that the uniformity of the conductive agent in the dry electrode film was excellent.

[0079] 8. Determination of the component uniformity of the binder in the dry electrode film

[0080] The cross-sections of the dry electrode samples in each embodiment and comparative example were observed using SEM, with the entire dry electrode membrane above the current collector falling within the SEM field of view. The thickness of the membrane falling within the field of view was denoted as h. The upper region was cut from the top surface of the membrane, with a thickness of h × 15%. The lower region, avoiding the current collector and its carbon coating, was cut from the area near the current collector towards the membrane surface, with a thickness of h × 15%. The mass ratio of fluorine in the upper region of the dry electrode membrane, a1%, and the mass ratio of fluorine in the lower region, a2%, were determined using EDS. If a1 / a2 is greater than 0.8 and less than 1.1, it indicates that the binder distribution in the membrane cross-section is uniform, and the binder distribution in the dry electrode membrane is considered to be uniform and has good uniformity. If a1 / a2 is in the range of 0.7-0.8 or 1.1-1.2, the binder uniformity in the dry electrode membrane is considered to be moderate. If a1 / a2 is less than 0.7 or greater than 1.2, the binder uniformity in the dry electrode membrane is considered to be poor.

[0081] 9. First-efficiency determination of dry electrodes

[0082] Using the electrode sheets prepared in each embodiment and comparative example as working electrodes and the lithium metal sheet as counter electrodes, a coin cell was assembled, and the first efficiency of the coin cell was tested using a blue electric test cabinet.

[0083] The coin cell half-cell is prepared as follows: steel sheet, electrode sheet, separator, lithium metal sheet, steel sheet, and spring are stacked in sequence, and electrolyte is injected to obtain the coin cell half-cell ...

[0084] During the test, the coin cell was first discharged at 25°C with a constant current of 0.1C to 0.005V, left to stand for 5 minutes, then discharged at 0.05C to 0.005V, left to stand for 5 minutes, and then charged at a constant current of 0.1C to 1.5V. The initial efficiency of the coin cell is calculated as: initial charge capacity / (0.1C discharge specific capacity + 0.05C discharge specific capacity) × 100%.

[0085] Example 1

[0086] Active material graphite particles, binder PTFE particles, conductive agent carbon black particles, and carbon nanotubes were mixed uniformly at a weight ratio of 96:2.6:1:0.4 using a high-speed, high-intensity mixer at 30°C and a dispersion velocity of 40 m / s to form mixture A. Mixture A was then subjected to fiberization treatment using a high-speed, high-intensity mixer at 80°C and a dispersion velocity of 45 m / s to obtain a dry electrode mixture. This dry electrode mixture was then rolled into a film using a roller mill, resulting in a dry electrode film with high surface smoothness. This dry electrode film was then composited with a current collector to obtain a dry electrode sheet. The flow energy, bulk density, tap density, and EDS fluorine element distribution of the obtained dry electrode mixture are shown in Table 1.

[0087] Example 2

[0088] Example 2 is based on Example 1, achieved by adjusting the Dv50 particle size of the active material graphite particles, process parameters, and the standard deviation of the flow energy, bulk density, tap density, and area ratio of EDS fluorine in the dry electrode mixture. The resulting dry electrode film has high surface smoothness. Specific adjustment measures and detailed data are shown in Table 1.

[0089] Example 3

[0090] Example 3 is based on Example 1, achieved by adjusting the Dv50 particle size of the active material graphite particles, process parameters, and the standard deviation of the flow energy, bulk density, tap density, and area ratio of EDS fluorine in the dry electrode mixture. The resulting dry electrode film exhibits moderate surface smoothness. Specific adjustment measures and detailed data are shown in Table 1.

[0091] Comparative Example 1

[0092] Comparative Example 1 was achieved by adjusting the Dv50 particle size of the active material graphite particles, process parameters, and the standard deviation of the flow energy, bulk density, tap density, and area ratio of EDS fluorine in the dry electrode mixture, based on Example 1. The resulting dry electrode film had poor surface smoothness. Specific adjustment measures and detailed data are shown in Table 1.

[0093] Comparative Example 2

[0094] Comparative Example 2 was developed based on Example 1 by adjusting the Dv50 particle size of the active material graphite particles, process parameters, and the standard deviation of the flow energy, bulk density, tap density, and area ratio of EDS fluorine in the dry electrode mixture. The resulting dry electrode film exhibited high surface smoothness. Specific adjustment measures and detailed data are shown in Table 1.

[0095] Table 1

[0096]

[0097] The test results of the dry electrode films and electrodes of each embodiment and comparative example are shown in Table 2. It can be seen that the dry electrode films of Examples 1-3 of the present invention exhibit excellent thickness consistency and compositional uniformity, and show significantly improved first-time efficiency. The dry electrode film of Comparative Example 1 has poor thickness consistency and compositional uniformity, while the dry electrode film of Comparative Example 2, although exhibiting excellent thickness consistency and compositional uniformity, suffers from severe particle breakage during preparation, resulting in low first-time efficiency. Furthermore, the electrode mixture in the dry electrode films of Examples 1-3 of the present invention is not lost during the entire transport process, and there is no local accumulation when it enters the film-forming equipment, ensuring the stability of the production process.

[0098] Table 2

[0099]

[0100]

[0101] While some exemplary embodiments of this application have been described and illustrated, this application is not limited to the disclosed embodiments. Rather, those skilled in the art will recognize that modifications and changes may be made to the described embodiments without departing from the spirit and scope of this application as described in the appended claims.

Claims

1. A dry electrode mixture comprising an active material, a binder, and a conductive agent, wherein the active material comprises graphite, characterized in that, The flow energy of the dry electrode mixture is 1J / 100g to 3J / 100g, and the Dv50 particle size of the graphite in the dry electrode mixture is 8μm-18μm.

2. The dry electrode mixture according to claim 1, characterized in that, In the composition distribution image obtained by measuring the surface of the dry electrode mixture using an energy dispersive spectroscopy (EDS) instrument, the area of ​​100 adjacent samples is 4 × 10⁻⁶. -4 mm 2 The standard deviation of the area ratio of fluorine in the region is <0.

6.

3. The dry electrode mixture according to claim 1 or 2, characterized in that, The bulk density of the dry electrode mixture is 0.4 g / cm³. 3 -0.8g / cm 3 .

4. The dry electrode mixture according to claim 1 or 2, characterized in that, The tap density of the dry electrode mixture is 1.00 g / cm³. 3 -1.14g / cm 3 .

5. The dry electrode mixture according to claim 1 or 2, characterized in that, The adhesive is selected from one or more of polytetrafluoroethylene, polyethylene, polyvinylidene fluoride, and acrylic acid-modified polytetrafluoroethylene.

6. A method for preparing a dry electrode mixture, characterized in that, Includes the following steps: (I) The active material particles, binder particles and conductive agent particles are mixed to obtain mixture A; the active material particles include graphite particles with a Dv50 particle size of 8μm-18μm, the mixing temperature is 15℃-30℃, and the mixing linear velocity is 20m / s-45m / s. (II) The mixture A is subjected to fiberization treatment to obtain a dry electrode mixture; the temperature of the fiberization treatment is 70℃-80℃, the linear velocity of the fiberization treatment is 30m / s-45m / s, and the flow energy of the dry electrode mixture is 1J / 100g~3J / 100g.

7. A dry electrode film, which is obtained by roll forming of a dry electrode mixture as described in any one of claims 1-5 or a dry electrode mixture prepared by the preparation method as described in claim 6.

8. An electrode sheet formed by combining a dry electrode film as described in claim 7 with a current collector.

9. A secondary battery comprising the electrode sheet as described in claim 8.

10. An electrical device comprising the secondary battery of claim 9.

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