Flexible electrode film and preparation method and processing equipment thereof

Abstract

The invention discloses a flexible electrode film and a preparation method and processing equipment thereof, and belongs to the technical field of electrochemistry and environmental engineering. The thickness of the flexible electrode film is 40-1000 [mu] m, the flexible electrode film is provided with a fiberized three-dimensional network, an active material is adhered in the fiberized three-dimensional network, the interior of the flexible electrode film is also provided with a pore structure which is distributed with the fiberized three-dimensional network in a mutually interlaced manner, the pore structure is composed of a plurality of pores, and the pores are distributed in an interlaced manner. And the holes are in through or semi-through pore morphology. Soluble salt is introduced as a temporary structure regulation component, a uniformly distributed pore structure is formed in the electrode after subsequent removal, ion transmission conditions in the thick electrode are improved, and the utilization rate of active substances is increased. The fiberized three-dimensional network structure and a pore structure formed by salt pore forming cooperate with each other, so that the electrode achieves higher effective capacity and energy density in a unit area.

Description

Technical Field

[0001] This invention relates to the fields of electrochemistry and environmental engineering technology, and in particular to a flexible electrode film, its preparation method, and processing equipment. Background Technology

[0002] With the rapid development of energy storage technology, lithium-ion batteries, as a green and environmentally friendly energy storage and release device, have become the mainstream energy storage device in today's society due to their high energy density (≥200Wh / kg), good cycle stability (>1000 cycles) and mature production and manufacturing processes.

[0003] In the rapid development of the new energy industry, society's demands for the ongoing electrification revolution are increasing. The N-methylpyrrolidone (NMP) required in traditional wet electrode fabrication processes is highly toxic and volatile, resulting in high costs and severe pollution. Furthermore, when manufacturing thick electrodes using wet processes, the evaporation of solvents during the drying of high-quality loading slurry disrupts the distribution of the binder on the electrode, causing internal cracks and hindering the industrialization of lithium-ion batteries. Compared to traditional wet electrodes, dry electrode fabrication processes introduce no solvents, avoiding the highly polluting and energy-intensive steps of wet processes. It offers advantages such as smaller equipment footprint, lower investment, and lower costs, with overall costs reduced by more than 18% compared to wet processes. This is an essential path for the industrialization and upgrading of lithium-ion batteries.

[0004] Traditional coating processes involve mixing active materials with conductive agents and binders to create a slurry, which is then applied to a current collector using a coating device. After drying, the electrode is formed. However, due to volume shrinkage and stress during the drying process, traditional wet electrode technology is limited by the critical cracking thickness. According to the formula for calculating the critical cracking thickness (CCT), it is difficult to fabricate electrodes exceeding 200 μm.

[0005] ,

[0006] Among them, h max Where G is the critical cracking thickness, G is the shear modulus of the particle, and M is the number of covalent bonds. R is the volume fraction of particles in random close packing, where R is the particle radius. This refers to the air-solvent interfacial tension. For example, the thickness of a wet-processed lithium nickel cobalt manganese oxide ternary electrode is no more than 175 μm, the thickness of a wet-processed silicon-carbon anode is no more than 100 μm, and the thickness of a wet-processed activated carbon electrode is no more than 160-200 μm. Therefore, a dry electrode process is required to prepare thick electrodes.

[0007] Existing dry electrode fabrication processes include electrode powder mixing, fiberization, self-supporting film formation, and hot-pressing lamination. The main process relies on the fibrillation of polytetrafluoroethylene (PTFE) as a binder to bond the active electrode material and conductive agent together, forming self-supporting films for both positive and negative electrodes. This process is complex, and the uniformity of powder mixing and the degree of fiberization are uncontrollable. Compared to existing wet coating processes, dry film formation is less efficient. Furthermore, due to limitations in thickness, hardness, and density, it is difficult to calender the self-supporting film to the designed thickness. During calendering, excessive internal stress in the electrode film leads to defects such as fracture, cracking, and surface particle breakage, resulting in increased costs. In addition, the long ion diffusion path of thick films and the hydrophobic nature of the binder in dry electrodes result in prolonged wetting time, causing significant electrochemical polarization of the electrode in the electrolyte. Summary of the Invention

[0008] To address the aforementioned technical problems, this invention provides a flexible electrode film and its preparation method. The flexible electrode film possesses a fibrous three-dimensional network and a porous structure interwoven with this fibrous network. The porous structure can accelerate the transport of ions, liquid phase, and gas phase, thereby solving the problem of large electrochemical polarization in thick electrode films.

[0009] A further technical problem to be solved by the present invention is to provide a processing device for flexible electrode films.

[0010] To achieve the above objectives, the present invention adopts the following technical solution:

[0011] A flexible electrode membrane with a thickness of 40~1000μm has a fibrous three-dimensional network, in which an active material is adhered. The flexible electrode membrane also has a pore structure that is interwoven with the fibrous three-dimensional network inside, and the pore structure is composed of multiple pores, which are through or semi-through pores.

[0012] The thickness of the flexible electrode film of the present invention is preferably 40~300μm.

[0013] The diameter of the pores in the fibrous three-dimensional network is no greater than 1 mm, and the size of the pores is smaller than the overall thickness of the flexible electrode film.

[0014] The above-mentioned method for preparing the flexible electrode film includes the following steps:

[0015] S1: Add 0.01~10% of soluble salt by mass of raw materials to the raw materials to obtain a raw material mixture; wherein the raw materials include active materials, conductive additives and fiber-forming binders, and the mass ratio of the active materials, the conductive additives and the fiber-forming binders is 60~96:2~20:2~20.

[0016] S2: Premix the raw material mixture;

[0017] S3: The mixture obtained in step S2 is subjected to fiberization treatment to obtain fiberized powder;

[0018] S4: The fibrous powder is subjected to film-forming treatment to obtain a shaped electrode film;

[0019] S5: The molded electrode film is washed with water to obtain a washed electrode film;

[0020] S6: The flexible electrode film can be obtained by drying and winding the water-washed electrode film.

[0021] The soluble salt is one or more of the following: sodium chloride, potassium chloride, magnesium chloride, sodium sulfate, potassium sulfate, magnesium nitrate, magnesium sulfate, sodium nitrate, sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, ammonium carbonate, and ammonium bicarbonate.

[0022] The particle size of the soluble salt is no greater than 1 mm.

[0023] The active material is one or more of carbon-based active materials and lithium-ion intercalation materials; the fiberizable binder is polytetrafluoroethylene or a mixture of polytetrafluoroethylene and carboxymethyl cellulose salt; and the conductive additive is one or more of conductive carbon black, carbon aerogel, carbon nanotubes and graphene.

[0024] The volume percentage of moisture in the gas used in the fiberization process is no more than 1%.

[0025] The pressure in the cavity during the fiberization process is not less than 0.4 MPa.

[0026] The water washing process involves washing the molded electrode film with water for 1 to 10 minutes to dissolve the soluble salts in the molded electrode film in the water. The water washing process can be static immersion, slow-flow rinsing, or a combination thereof.

[0027] The drying process is low-disturbance drying, including vacuum drying, hot air drying, or infrared heating drying.

[0028] A processing device for a flexible electrode film includes a material premixing device, a fiberizing device, a rolling device, a washing device, a drying device, and a winding device connected in sequence.

[0029] The material premixing device is used to mix raw materials to obtain a raw material mixture.

[0030] The fiberization device is used to complete the fiberization process of the raw material mixture to obtain fiberized powder.

[0031] The roller pressing device is used to complete the film-forming process of the fibrous powder to obtain a shaped electrode film.

[0032] The water washing device is used to wash out the soluble salts that serve as temporary structural phases in the molded electrode film, so as to form a through-hole structure while maintaining the integrity of the fibrous three-dimensional network structure of the molded electrode film.

[0033] The drying device is used to dry the formed electrode film after it has been washed with water.

[0034] The winding device is used to wind up the dried shaped electrode film.

[0035] The fiberizing device is also connected to an air supply device, which ensures that the pressure inside the fiberizing device is not lower than 0.4 MPa.

[0036] The fiberizing device and the gas supply device are further divided into a water removal device, which ensures that the volume percentage of water in the gas entering the fiberizing device is no more than 1%.

[0037] The water removal device is a multi-stage water removal device, specifically a combination of one or more of the following: a refrigerated dryer, an adsorption dryer, and a refrigerated-adsorption combined dryer.

[0038] The beneficial effects of this invention are as follows:

[0039] (1) The flexible electrode membrane of the present invention exhibits extremely high cycling stability and considerable specific capacity. It can store higher energy per unit area. The flexible electrode membrane of the present invention forms a continuous fibrous three-dimensional network structure through binder fibrosis, stably fixing the active material and conductive additives within the three-dimensional continuous framework. This allows the thick electrode to maintain good structural integrity and ductility during cycling, thereby significantly improving cycling stability. Simultaneously, soluble salts are introduced as temporary structural control components, forming a uniformly distributed pore structure inside the electrode after subsequent removal, improving ion transport conditions inside the thick electrode and increasing the utilization rate of the active material. The aforementioned fibrous three-dimensional network structure and the pore structure formed by salt pore formation synergistically enable the electrode to achieve higher effective capacity and energy density per unit area.

[0040] (2) The porous structure formed after the removal of soluble salts further improves the ion transport and electrolyte wettability inside the thick electrode, enabling the electrode to achieve higher utilization of active materials while maintaining structural stability.

[0041] (3) The method for preparing the flexible electrode film of the present invention enables the binder to be uniformly dispersed and fiberized to form a fiberized three-dimensional network, in which the active material is adhered. The fiberized three-dimensional network has extremely strong extensibility and can stably prepare electrode films of 40~1000μm.

[0042] (4) In the fiberization process, the present invention performs multi-stage dehydration treatment on the gas source used, so that the gas entering the fiberization process is in a low moisture state. This effectively avoids the premature dissolution of soluble salts due to moisture and the resulting agglomeration and local structural failure without changing the fiberization mechanism of the binder. Through the above-mentioned gas source dehydration control measures, the uniformity and continuity of the fiberized structure inside the electrode can be significantly improved.

[0043] (5) The flexible electrode film prepared by the preparation method and processing equipment of the present invention has a wider range of applications and can be used in lithium-ion batteries, solid-state batteries, lithium-ion capacitors, supercapacitors and carbon dioxide adsorption fields. Attached Figure Description

[0044] Figure 1 This is a process flow diagram of the method for preparing the flexible electrode film of the present invention.

[0045] Figure 2 This is an overall schematic diagram of an embodiment of the fiberization apparatus of the processing equipment for the flexible electrode film of the present invention.

[0046] Figure 3 for Figure 2 The diagram shows an explosion of a fiberizing device.

[0047] Figure 4 The image is a scanning electron microscope (SEM) image of the flexible electrode film prepared in Example 1 of the present invention at a scale of 50 μm.

[0048] Figure 5 The image is a scanning electron microscope (SEM) image of the flexible electrode film prepared in Example 1 of the present invention, obtained at a scale of 5 μm.

[0049] Figure 6 This is a scanning electron microscope image of the flexible electrode film prepared in Comparative Example 1 of the present invention.

[0050] Figure 7 This is a scanning electron microscope image of the flexible electrode film prepared in Comparative Example 2 of the present invention.

[0051] The attached figures are labeled as follows: 21-first adapter; 22-feeding port; 23-second adapter; 24-first discharge hole; 25-first feed port; 26-second feed port; 27-rotating component; 28-rubber ring; 29-second discharge hole. Detailed Implementation

[0052] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0053] See Figure 1 This invention provides a method for preparing a flexible electrode film, which includes the following steps:

[0054] S1: Add 0.01~10% of soluble salt by mass of raw materials to the raw materials to obtain a raw material mixture; wherein the raw materials include active materials, conductive additives and fiber-forming binders, and the mass ratio of the active materials, the conductive additives and the fiber-forming binders is 60~96:2~20:2~20.

[0055] S2: Premix the raw material mixture; premixing can also achieve prefiberization.

[0056] S3: The mixture obtained in step S2 is subjected to fiberization treatment to obtain fiberized powder;

[0057] S4: The fibrous powder is subjected to film-forming treatment to obtain a shaped electrode film;

[0058] S5: The molded electrode film is washed with water to obtain a washed electrode film;

[0059] S6: The flexible electrode film can be obtained by drying and winding the water-washed electrode film.

[0060] The preparation method of this invention introduces a soluble salt as a temporary structure-regulating component. After the soluble salt is subsequently removed, a uniformly distributed pore structure is formed inside the flexible electrode membrane, improving the ion transport conditions inside the flexible electrode membrane and increasing the utilization rate of the active material. The aforementioned fibrous network structure and the pore structure formed by salt pore formation work synergistically to enable the flexible electrode membrane to achieve higher effective capacity and energy density per unit area.

[0061] Because the porous structure improves ion transport conditions inside the thick electrode, this invention can prepare flexible electrode films with a thickness greater than 200 μm. Of course, in flexible electrode films with a thickness less than 200 μm, the porous structure can also improve ion transport conditions inside the thick electrode, thereby increasing the utilization rate of the active material. In this embodiment, the thickness of the flexible electrode film is 40–1000 μm; particularly 100–1000 μm. More specifically, it can be 40μm, 50μm, 60μm, 70μm, 80μm, 90μm, 100μm, 110μm, 120μm, 130μm, 140μm, 150μm, 160μm, 170μm, 180μm m, 190μm, 200μm, 210μm, 220μm, 230μm, 240μm, 250μm, 260μm, 270μm, 280μm, 290μm, 300μm, 500μm, 1000μm.

[0062] The soluble salt is one or more of the following: sodium chloride, potassium chloride, magnesium chloride, sodium sulfate, potassium sulfate, magnesium nitrate, magnesium sulfate, sodium nitrate, sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, ammonium carbonate, and ammonium bicarbonate. The particle size of the soluble salt is not greater than 1 mm, preferably 1~100 μm.

[0063] The active material is one or more of carbon-based active materials and lithium-ion intercalation materials; the carbon-based active material is selected from one or more of activated carbon, mesoporous carbon, activated carbon fiber, carbon aerogel, and graphene oxide; the lithium-ion intercalation material is selected from natural flake graphite, natural microcrystalline graphite, artificial graphite, mesophase carbon microspheres, LiFePO4, LiMn2O4, LiCoO2, LiNiO2, and LiCo. 1 / 3 Ni 1 / 3 Mn 1 / 3 O2, Li4Ti5O 12 One or more of the following; when the active material is a mixture of carbon-based active material and lithium-ion intercalation material, the mass ratio of carbon-based active material to lithium-ion intercalation material is 1~50:50~99.

[0064] The fiberizable binder is polytetrafluoroethylene or a mixture of polytetrafluoroethylene and carboxymethyl cellulose salt; specifically, the fiberizable binder is a mixture of polytetrafluoroethylene and sodium carboxymethyl cellulose in a mass ratio of 1:3 to 3:1, or a mixture of polytetrafluoroethylene and lithium carboxymethyl cellulose in a mass ratio of 1:3 to 3:1.

[0065] The conductive additive is one or more of conductive carbon black, carbon aerogel, carbon nanotubes, and graphene.

[0066] During the fiberization process, the pressure in the cavity must not be lower than 0.4 MPa.

[0067] The water washing process involves immersing the molded electrode membrane in water for 1-10 minutes to dissolve the soluble salts in the membrane. The water washing process can be static immersion, slow-flow rinsing, or a combination thereof.

[0068] The drying process is a low-disturbance drying process, including vacuum drying, hot air drying, or infrared heating drying. The drying temperature is 60°C to 100°C, and the time is 4 to 24 hours.

[0069] Preferably, the premixing process is completed by ball milling.

[0070] The present invention also provides a processing device for flexible electrode films, which includes a material premixing device, a fiberizing device, a rolling device, a washing device, a drying device and a winding device connected in sequence.

[0071] The material premixing device includes a machine with multi-stage mixing capabilities to ensure uniform mixing of the binder, conductive carbon, and active materials. Optionally, the material premixing system can employ a planetary ball mill or a mixer with equivalent capabilities.

[0072] The fiberization unit includes a device that provides sufficient shear force to complete the fiberization of the binder and adhere the active material powder. This includes, but is not limited to, equipment such as air jet mills, fluidized beds, etc.

[0073] The rolling device includes a set of rollers that can meet the requirements for film preparation, in order to prepare dry electrode films that meet the thickness and width requirements.

[0074] Preferably, the fiberizing device is also connected to an air supply device, which ensures that the internal pressure of the fiberizing device is not less than 0.4 MPa. The air supply system includes an air pump or air compressor to provide sufficient air pressure to meet the energy requirements of the fiberizing equipment, generate sufficient shear force internally, and provide airflow channels. The air pump is required to have an air flow rate higher than 720 m³ / h. 2 / L, the air compressor requires an air pressure higher than 0.4MPa.

[0075] In actual processing, moisture in the gas source can easily cause premature dissolution of soluble salts in the system, leading to the formation of liquid bridges in localized areas. This results in material agglomeration, uneven fiber distribution, or fiber structure failure. Because the technical solution adopted in this invention introduces soluble salts as part of the structural composition, the fiberization process becomes more sensitive to moisture in the processing environment. If the gas source contains moisture during the fiberization stage, soluble salts are prone to premature dissolution, forming liquid bridges locally. This causes powder agglomeration and disrupts the uniform distribution of binder fibers, making it difficult for the fibrous structure to further develop into a continuous network. Therefore, compared to traditional dry fiberization processes that do not contain soluble salts, this invention requires stricter control over the moisture content of the gas source used in the fiberization process.

[0076] Therefore, the gas source used for air jet milling must undergo dehydration treatment before entering the fiberization unit to ensure that the moisture content of the gas entering the fiberization unit is less than 1%. Preferably, the gas undergoes multi-stage dehydration treatment, more preferably three-stage dehydration treatment, to significantly reduce the moisture content in the gas stream. Through the above dehydration treatment, soluble salts can be effectively prevented from contacting moisture during the fiberization process and dissolving or agglomerating, thereby preventing material clumping.

[0077] The water washing device is used to wash out the soluble salts that serve as temporary structural phases in the electrode film, so as to form a through-pore structure while maintaining the integrity of the fibrous three-dimensional network structure of the electrode film.

[0078] The drying process is low-disturbance drying, including vacuum drying, hot air drying, or infrared heating drying.

[0079] Example 1

[0080] This invention provides a method for preparing a flexible electrode film, which includes the following steps:

[0081] S1: Weigh 5g of polytetrafluoroethylene powder (purchased from Shenzhen Kejing), 90g of activated carbon and 5g of conductive carbon black as raw materials, and then add 2% potassium chloride salt powder (particle size 20~100μm, D90 is 70μm).

[0082] S2: The raw material mixture is premixed using a planetary ball mill. Specifically, the proportioned raw material mixture is added to the ball mill jar, which is then fixed to the ball mill support. Program conditions are entered on the ball mill control panel. In this embodiment, the ball-to-material ratio is 1:1. The rotation speed is set to 300 rpm on the ball mill control panel, and the rotation mode is set to alternate directions every 5 minutes (clockwise for forward rotation, counter-clockwise for reverse rotation), alternating 6 times for a total milling time of 60 minutes. The ball mill jar revolves around the turntable axis while simultaneously rotating in a reverse planetary motion around its own axis. The grinding balls and materials in the jar collide and rub against each other during high-speed motion, achieving uniform mixing and pre-fiberization. After premixing, the material is inspected; no obvious binder agglomeration is observed. If a small amount of binder agglomeration is detected after premixing, adjustments can be made by extending the milling time or performing low-intensity mixing again to restore the uniform dispersion of the material.

[0083] S3: The mixture obtained in step S2 is subjected to fiberization treatment using a fiberization device to obtain fiberized powder. After the fiberization treatment is completed, fiberized powder is obtained. This powder will spontaneously agglomerate together, indicating that the binder has completed the fiberization process.

[0084] For details, see Figure 2 and Figure 3 In this embodiment, the fiberization device is an airflow pulverizer, powered by an air supply device. One air supply pipe connects to the first adapter 21, which creates negative pressure at the feed inlet 22, allowing the powder to be smoothly drawn into the cavity. Another air supply pipe connects to the second adapter 23, and airflow enters the cavity through the second feed inlet 26, driving the rotating component 27 to rotate at high speed. The airflow passes through small holes on the component and enters the cavity, creating a strong shearing effect that fully fiberizes the binder. The fiberized powder is then discharged from the cavity through the first discharge hole 24 by the airflow. The first feed inlet 25, the rubber ring 28, and the second discharge hole 29 are all ceramic components of the airflow pulverizer, installed in corresponding positions inside the pulverizer. These ceramic components work together to create a three-dimensional air field under the drive of the airflow, causing the material entering the equipment to undergo multi-angle collisions and shearing effects in different directions, thereby achieving full dispersion and uniform processing of the material. This step is crucial in the fiberization process. The air pressure inside the chamber must meet the fiberization requirements for the binder (i.e., the internal pressure must not be lower than 0.4 MPa) to prevent incomplete fiberization, which would affect the subsequent film formation process. For this fiberization device alone, the air supply system must include a dehumidification and drying device. Excessive moisture entering the chamber will cause the material to clump together, clogging the internal pores, resulting in a drop in air pressure and hindering the completion of the fiberization process.

[0085] Specifically, the air supply device in this embodiment includes an air pump body and a filter / dehumidifier. The air pump body provides an airflow that meets the pressure requirements using compressed air. The filter / dehumidifier removes moisture from the high-pressure airflow to prevent it from interfering with the normal operation of the fiberization system.

[0086] S4: The fibrous powder is processed into a film using a roller pressing device to obtain a shaped electrode film. Specifically, a manual roller pressing device can be used. The roller pressing film forming device includes, but is not limited to, this device; any roller pressing device that meets the roller gap requirements can be used after debugging. The method of using a manual roller pressing device: Before using the manual roller pressing device, the gap between the roller shafts needs to be adjusted by adjusting the knob. Specifically, the distance between the roller shafts can be determined by moving the baffle connected to the roller shaft and changing the reading of the range gauge. After adjusting the gap distance, the roller shafts can be rotated by turning the rocker arm to press the powder into a film. Place the fibrous powder between the rollers, adjust the roller shaft gap, and then turn the handle to obtain the shaped electrode film. It is required that the relative distance between the roller shafts remain strictly constant; otherwise, the electrode film thickness will be inconsistent with the reading on the range gauge.

[0087] S5: The formed electrode film is washed with water to obtain a washed electrode film; specifically, the electrode film is soaked in water for 1 to 10 minutes to dissolve the salt.

[0088] S6: The flexible electrode film can be obtained by drying and winding the water-washed electrode film.

[0089] Comparative Example 1: Flexible electrode membrane without added soluble salts.

[0090] The preparation method of Comparative Example 1 is basically the same as that of Example 1, except that: in step S1, no soluble salt is added, and the remaining raw material ratios, premixing conditions, fiberization treatment, film formation and drying steps are the same as those of Example 1.

[0091] Comparative Example 2: Flexible electrode membrane without dehydration treatment of the fibrous gas source.

[0092] The preparation method of Comparative Example 2 is basically the same as that of Example 1, except that: in the fiberization process of step S3, the gas source used by the fiberization device has not undergone multi-stage dehydration treatment, and the remaining steps and process parameters are kept the same.

[0093] Test results:

[0094] Figure 4 and Figure 5The image shows a scanning electron microscope (SEM) image of the flexible electrode film prepared in Example 1. As can be seen from the image, the binder is uniformly dispersed and undergoes fibrosis, forming a fibrous three-dimensional network that adheres the active material within this network. After washing away soluble salts, a large number of uniformly distributed pores are formed inside the electrode. These pores, under the SEM, exhibit a continuous or semi-continuous pore morphology, with a scale significantly smaller than the overall electrode thickness, and are interwoven with the fibrous three-dimensional network. This pore structure, while maintaining the continuity of the fibrous three-dimensional network, provides an effective channel for electrolyte wetting and ion transport within the thick electrode.

[0095] Figure 6 The image shows a scanning electron microscope (SEM) image of the flexible electrode film prepared in Comparative Example 1. SEM observation revealed that although a certain degree of fibrous structure could be formed inside the electrode prepared in Comparative Example 1, the number of pores inside the electrode was significantly reduced, the pore distribution was uneven, and the electrode exhibited a relatively dense structural morphology. This structure is not conducive to sufficient electrolyte wetting and ion transport under thick electrode conditions, indicating that it is difficult to simultaneously achieve structural stability and transport performance by relying solely on fibrous treatment.

[0096] Figure 7 The image shows a scanning electron microscope (SEM) image of the flexible electrode membrane prepared in Comparative Example 2. During the fiberization process, varying degrees of agglomeration were observed, indicating uneven fiberization. The resulting electrode membrane, under SEM, exhibited a discontinuous fiber structure with localized collapse or structural damage, and the pore structure was unevenly distributed after water washing. This demonstrates that in a salt-containing system, if the moisture content of the gas source used in the fiberization process is not controlled, soluble salts are prone to dissolution or localized structural failure during the fiberization stage, thus affecting the formation of the three-dimensional fiber network and pore structure.

[0097] Example 2

[0098] A method for preparing a flexible electrode film includes the following steps:

[0099] S1: Weigh 20g of polytetrafluoroethylene powder (purchased from Shenzhen Kejing), 60g of activated carbon and 20g of conductive carbon black as raw materials, and then add 0.01% of potassium carbonate powder (particle size 20~100μm, D90 is 70μm).

[0100] S2: The raw material mixture is premixed using the same planetary ball mill and similar process parameters as in Example 1; premixing can also achieve prefiberization during the premixing process;

[0101] S3: The mixture obtained in step S2 is subjected to fiberization treatment to obtain fiberized powder;

[0102] S4: The fibrous powder is subjected to film-forming treatment to obtain a shaped electrode film;

[0103] S5: The molded electrode film is washed with water to obtain a washed electrode film;

[0104] S6: The flexible electrode film can be obtained by drying and winding the water-washed electrode film.

[0105] Example 3

[0106] This invention provides a method for preparing a flexible electrode film, which includes the following steps:

[0107] S1: Weigh 2g of polytetrafluoroethylene powder (purchased from Shenzhen Kejing), 96g of activated carbon and 2g of conductive carbon black as raw materials, and then add 10% sodium sulfate powder (particle size 20~100μm, D90 70μm).

[0108] S2: The raw material mixture is premixed using the same planetary ball mill and similar process parameters as in Example 1; premixing can also achieve prefiberization during the premixing process;

[0109] S3: The mixture obtained in step S2 is subjected to fiberization treatment to obtain fiberized powder;

[0110] S4: The fibrous powder is subjected to film-forming treatment to obtain a shaped electrode film;

[0111] S5: The molded electrode film is washed with water to obtain a washed electrode film;

[0112] S6: The flexible electrode film can be obtained by drying and winding the water-washed electrode film.

[0113] The electrode films prepared in Examples 1, 2, 3, Comparative Example 1, and Comparative Example 2, along with lithium metal electrodes, were used as positive and negative electrodes to assemble half-cells. The electrolyte was a 1 mol / L LiPF6 solution, with ethylene carbonate, propylene carbonate, and diethyl carbonate mixed in a 1:1:1 volume ratio as the solvent. The half-cells were first charged and discharged at a low rate of 0.2C, and the coulombic efficiency of the first cycle was calculated. Then, the electrochemical performance of the half-cells was tested at a high rate of 5C. The results are shown in Table 1.

[0114] Table 1 shows the first-cycle coulombic efficiency and 5C discharge specific capacity of the half-cells assembled from the samples prepared in Examples 1-3, Comparative Example 1, and Comparative Example 2.

[0115] Table 1

[0116]

[0117] Table 1 shows the test results of the first-cycle coulombic efficiency and 5C discharge specific capacity of the assembled half-cells prepared from Examples 1, Comparative Example 1, and Comparative Example 2. As can be seen from the test results in Table 1, the first-cycle coulombic efficiency and 5C discharge specific capacity of Examples 1-3 are significantly better than those of Comparative Example 1 and Comparative Example 2.

[0118] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0119] The parts of this invention not described in detail are well-known in the art. The above embodiments are provided merely for the purpose of describing the invention and are not intended to limit the scope of the invention. The scope of the invention is defined by the appended claims. All equivalent substitutions and modifications made without departing from the spirit and principles of the invention should be covered within the scope of the invention.

Claims

1. A flexible electrode film, characterized in that, The flexible electrode film has a thickness of 40~1000μm and has a fibrous three-dimensional network. The active material is adhered in the fibrous three-dimensional network. The interior of the flexible electrode film also has a pore structure that is interwoven with the fibrous three-dimensional network. The pore structure is composed of multiple pores, and the pores are through or semi-through pores.

2. The flexible electrode film according to claim 1, characterized in that, The diameter of the pores in the fibrous three-dimensional network is no greater than 1 mm, and the size of the pores is smaller than the overall thickness of the flexible electrode film.

3. The method for preparing the flexible electrode film according to claim 1 or 2, characterized in that, The preparation method includes the following steps: S1: Add 0.01~10% of soluble salt by mass of raw materials to the raw materials to obtain a raw material mixture; wherein, the raw materials include active materials, conductive additives and fiber-forming binders, and the mass ratio of the active materials, the conductive additives and the fiber-forming binders is 60~96:2~20:2~20; S2: Premix the raw material mixture; S3: The mixture obtained in step S2 is subjected to fiberization treatment to obtain fiberized powder; S4: The fibrous powder is subjected to film-forming treatment to obtain a shaped electrode film; S5: The molded electrode film is washed with water to obtain a washed electrode film; S6: The flexible electrode film can be obtained by drying and winding the water-washed electrode film.

4. The method for preparing the flexible electrode film according to claim 3, characterized in that, The soluble salt is one or more of the following: sodium chloride, potassium chloride, magnesium chloride, sodium sulfate, potassium sulfate, magnesium nitrate, magnesium sulfate, sodium nitrate, sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, ammonium carbonate, and ammonium bicarbonate. The particle size of the soluble salt is no greater than 1 mm.

5. The method for preparing the flexible electrode film according to claim 3, characterized in that, The active material is one or more of carbon-based active materials and lithium-ion intercalation materials; the fiberizable binder is polytetrafluoroethylene or a mixture of polytetrafluoroethylene and carboxymethyl cellulose salt; the conductive additive is one or more of conductive carbon black, carbon aerogel, carbon nanotubes and graphene.

6. The method for preparing the flexible electrode film according to claim 3, characterized in that, The volume percentage of moisture in the gas used in the fiberization process is no more than 1%. The pressure in the cavity during the fiberization process is not less than 0.4 MPa.

7. The method for preparing the flexible electrode film according to any one of claims 3 to 6, characterized in that, The water washing process involves washing the molded electrode film with water for 1 to 10 minutes to dissolve the soluble salts in the molded electrode film in the water. The water washing process can be static immersion, slow-flow rinsing, or a combination thereof. The drying process is low-disturbance drying, including vacuum drying, hot air drying, or infrared heating drying.

8. A processing device for a flexible electrode film, characterized in that, The processing equipment for the flexible electrode film includes a material premixing device, a fiberizing device, a rolling device, a washing device, a drying device, and a winding device connected in sequence. The material premixing device is used to mix raw materials to obtain a raw material mixture; The fiberization device is used to complete the fiberization process of the raw material mixture to obtain fiberized powder. The roller pressing device is used to complete the film-forming process of the fibrous powder to obtain a shaped electrode film. The water washing device is used to wash out the soluble salts that serve as temporary structural phases in the molded electrode film, so as to form a through-hole structure while maintaining the integrity of the fibrous three-dimensional network structure of the molded electrode film. The drying device is used to dry the formed electrode film after it has been washed with water. The winding device is used to wind up the dried shaped electrode film. The fiberizing device is also connected to an air supply device, which ensures that the pressure inside the fiberizing device is not lower than 0.4 MPa.

9. The processing equipment for the flexible electrode film according to claim 8, characterized in that, A water removal device is also included between the fiberizing device and the gas supply device, which ensures that the volume percentage of water in the gas entering the fiberizing device is no more than 1%.

10. The processing equipment for the flexible electrode film according to claim 9, characterized in that, The dehydration device is a multi-stage dehydration device, specifically a combination of one or more of the following: a refrigerated dryer, an adsorption dryer, and a refrigeration-adsorption combined dryer.

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