A diaphragm, a method for manufacturing the same, a battery, a battery pack, and an electric device

Abstract

This application provides a separator and its preparation method, a battery, a battery pack, and an electrical device. The separator includes a base membrane and an aramid coating disposed on at least one side of the base membrane. The aramid coating includes aramid fibers and pores, and any 100μm of the aramid coating... 2 The region satisfies: A ≤ 64; where R is the 100μm 2 The chord length of the holes in the region with a chord length ≥ 0.3 μm, in μm, and R ≥ 0.3 μm; N is the chord length of the 100 μm hole. 2 The number of pores with a chord length ≥ 0.3 μm in the region; x is the diameter of the aramid fiber in nm; u is the diameter of 100 μm. 2 The average diameter of the aramid fibers in the region is expressed in nm. This application can simultaneously improve the high-temperature resistance, structural stability, and thermal safety performance of the diaphragm.

Description

Technical Field

[0001] This application relates to the field of batteries, and more particularly to a separator and its preparation method, a battery, a battery pack, and an electrical device. Background Technology

[0002] With the widespread application of rechargeable batteries in electric vehicles, energy storage, and other fields, higher requirements are being placed on battery safety and stability. As one of the key components of rechargeable batteries, the performance of the separator directly affects the battery's safety performance and cycle life.

[0003] While traditional polyolefin separators possess excellent mechanical and electrochemical properties, they exhibit poor thermal stability at high temperatures. When temperatures rise, polyolefin separators are prone to shrinkage and pore formation, leading to direct contact between the positive and negative electrodes, potentially causing thermal runaway and severely threatening the safe operation of the battery.

[0004] Therefore, existing diaphragms generally suffer from the inability to simultaneously achieve high-temperature resistance, structural stability, and thermal safety, which urgently needs to be addressed. Summary of the Invention

[0005] This application provides a separator and its preparation method, a battery, a battery pack, and an electrical device, which can improve the high temperature resistance, structural stability, and thermal safety performance of the separator.

[0006] In a first aspect, embodiments of this application provide a diaphragm, comprising a base membrane and an aramid coating disposed on at least one side of the base membrane, the aramid coating comprising aramid fibers and pores, wherein any 100 μm of the aramid coating... 2 The region satisfies:

[0007] A≤64;

[0008] ,

[0009] Where R is the 100μm 2 The chord length of the holes in the region with a chord length ≥ 0.3 μm, in μm, and R ≥ 0.3 μm; N is the chord length of the 100 μm hole. 2 The number of pores with a chord length ≥ 0.3 μm in the region; x is the diameter of the aramid fiber in nm; u is the diameter of 100 μm. 2 The average diameter of the aramid fibers in the region, expressed in nm.

[0010] In one possible implementation, 5.4 ≤ A ≤ 64; and / or, 2 ≤ N ≤ 8; and / or, 0.3 μm ≤ R ≤ 0.9 μm; and / or, 30 nm ≤ x ≤ 85 nm; and / or, 51 nm ≤ u ≤ 56 nm.

[0011] In one possible embodiment, the aramid fiber comprises polyphenylene phthalamide; preferably, the polyphenylene phthalamide comprises poly(p-phenylene terephthalamide) and / or poly(m-phenylene isophthalamide); preferably, the ratio of the weight-average molecular weight to the number-average molecular weight of the polyphenylene phthalamide is 1 to 3.

[0012] In one possible implementation, the aramid fiber in the aramid coating has a mass percentage content of 65% to 95%.

[0013] In one possible implementation, the aramid coating further includes a ceramic material; preferably, the ceramic material includes one or more of alumina, silicon dioxide, titanium dioxide, zirconium dioxide, barium titanate, barium sulfate, magnesium oxide, calcium oxide, aluminum hydroxya, and silicon carbide.

[0014] In one possible embodiment, the surface of the base film has oxygen-containing groups; and / or, the base film comprises a polyolefin; preferably, the weight-average molecular weight of the polyolefin is 100W~200W; and / or, the peel strength between the aramid coating and the base film is 70 N / m~130 N / m.

[0015] Secondly, embodiments of this application provide a method for preparing the above-mentioned diaphragm, comprising the following steps: coating at least one side of the base membrane to form the aramid coating, thereby obtaining the diaphragm.

[0016] In one possible implementation, the process of coating at least one side of the base film to form the aramid coating includes: applying a coating slurry containing the aramid fibers to at least one side of the base film; passing the base film coated with the coating slurry through a multi-stage coagulation bath and then drying it to form the aramid coating on at least one side of the base film; wherein each stage of the coagulation bath independently includes an organic solvent and an inorganic electrolyte; for any two adjacent stages of the coagulation bath, the mass concentration of the organic solvent in the preceding stage of the coagulation bath is greater than the mass concentration of the organic solvent in the following stage of the coagulation bath.

[0017] In one possible implementation, the difference between the mass concentration of the organic solvent in the preceding coagulation bath and the mass concentration of the organic solvent in the following coagulation bath is 15% to 40%; and / or, each coagulation bath also independently includes water; and / or, the time for the base film coated with the coating slurry to pass through each coagulation bath is 3 to 5 minutes.

[0018] In one possible implementation, the process of passing the base film coated with the coating slurry through a multi-stage coagulation bath includes: passing the base film coated with the coating slurry sequentially through a first coagulation bath, a second coagulation bath, and a third coagulation bath, wherein the mass concentration of the organic solvent in the first coagulation bath is 60% to 90%; and / or, the mass concentration of the organic solvent in the second coagulation bath is 30% to 50%; and / or, the mass concentration of the organic solvent in the third coagulation bath is 10% to 20%.

[0019] In one possible implementation, the organic solvent includes one or more of N-methylpyrrolidone, dimethyl sulfoxide, and N,N-dimethylformamide; and / or, the inorganic electrolyte includes one or more of lithium chloride, calcium chloride, magnesium chloride, and sodium chloride; and / or, in each stage of the coagulation bath, the mass concentration of the inorganic electrolyte is independently 0.5% to 2%.

[0020] In one possible implementation, the base film is surface-treated with hydrogen peroxide solution under ultraviolet light, and then the aramid coating is applied to at least one side of the base film to form the diaphragm.

[0021] Thirdly, embodiments of this application provide a battery including the above-described separator or a separator prepared according to the above-described separator preparation method.

[0022] Fourthly, embodiments of this application provide a battery pack comprising at least two batteries as described above.

[0023] Fifthly, embodiments of this application provide an electrical device, including the battery or battery pack described above.

[0024] This application provides a separator and its preparation method, a battery, a battery pack, and an electrical device. The separator includes a base membrane and an aramid coating disposed on at least one side of the base membrane. The aramid coating includes aramid fibers and pores, and any 100μm of the aramid coating... 2 The region satisfying A≤64 indicates that the aramid fibers in the aramid coating possess a unique molecular structure with high orientation, high crystallinity, and anisotropy, exhibiting excellent mechanical strength and high-temperature resistance. This enhances the high-temperature resistance and safety of the diaphragm under high-temperature environments. Furthermore, A≤64 indicates uniform aramid fiber diameter, meaning a uniform stress distribution within the aramid coating. Under tension or compression, stress concentration due to excessively fine local aramid fibers prevents cracking or tearing of the aramid coating, thus improving the bonding force between the aramid fibers and the base membrane and enhancing the structural stability of the diaphragm. Attached Figure Description

[0025] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0026] Figure 1 This is a schematic diagram of the surface structure of the aramid coating;

[0027] Figure 2 This is a SEM image of the aramid coating in Example 4.

[0028] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0029] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0030] The inventors have researched and invented a method to improve the high-temperature resistance of a diaphragm by coating it with a high-temperature resistant material. However, this method generally has the following problems: First, the coating has insufficient adhesion to the base membrane: under high temperature or mechanical stress, the coating is prone to peeling off from the base membrane surface, resulting in a decrease in the high-temperature resistance and mechanical properties of the diaphragm. Second, the overall high-temperature resistance of the diaphragm is uneven: there are significant differences in the high-temperature resistance of different areas of the diaphragm, and under local high-temperature conditions, some areas are prone to premature membrane rupture.

[0031] In view of this, embodiments of the present invention provide a diaphragm, comprising a base membrane and an aramid coating disposed on at least one side of the base membrane, the aramid coating comprising aramid fibers and pores, wherein any 100 μm of the aramid coating... 2 The region satisfies: A≤64; Where R is 100 μm 2 The chord length of holes with a chord length ≥ 0.3 μm in the region, in μm, and R ≥ 0.3 μm; N is 100 μm. 2 The number of pores with a chord length ≥ 0.3 μm in the region; x is the diameter of the aramid fiber in nm; u is 100 μm. 2 The average diameter of the aramid fibers in the region, expressed in nm.

[0032] According to the inventors' research, a separator with the above-mentioned structure and composition can simultaneously improve the separator's high-temperature resistance, structural stability, and thermal safety. The reason for this is that the aramid fibers in the aramid coating have a unique molecular structure with high orientation, high crystallinity, and anisotropy, exhibiting excellent mechanical strength, which helps improve the mechanical stability and safety performance of the battery. Simultaneously, aramid fibers have good high-temperature resistance, with a glass transition temperature of around 280℃ and a thermal decomposition temperature greater than 400℃, allowing the separator's rupture temperature to reach around 400℃, thus enhancing the separator's high-temperature resistance and safety in high-temperature environments.

[0033] According to further research by the inventors, any 100μm of aramid coating... 2 The region that satisfies A≤64 indicates that the aramid fiber surface is uniform and without obvious defects. This makes the size and number of pores in the aramid coating and the uniformity of the aramid fibers appropriate. Uniform aramid fiber diameter means that the stress distribution inside the aramid coating is uniform. When subjected to tension or compression, stress concentration will not occur due to excessively fine local aramid fibers, which would lead to cracking or tearing of the aramid coating. This can improve the bonding force between the aramid fibers and the base membrane and improve the structural stability of the diaphragm. Controlling the size and number of pores is equivalent to ensuring the integrity of the aramid coating, so that the base membrane is covered by the aramid coating, which can improve the overall thermal stability of the diaphragm and improve the safety performance of the diaphragm.

[0034] Specifically, such as Figure 1 As shown, any 100μm 2 The region can be square, with a side length of 10 μm; R is 100 μm. 2 The chord length of holes with a chord length ≥ 0.3 μm in the region, i.e., R is the chord length of the 100 μm hole. 2 The chord length of the holes in the region; x is the diameter of the aramid fiber.

[0035] For example, A can be a range of 5.4, 9, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 64 or any two of them.

[0036] Specifically, an aramid coating can be provided on one side of the base film, or an aramid coating can be provided on both sides of the base film in the thickness direction.

[0037] In this embodiment of the invention, A can be tested as follows: Scanning electron microscopy (SEM) can be used. Take the prepared diaphragm, randomly select a clean area from the diaphragm, and cut a small sample with an area of ​​0.5cm × 0.5cm. Lay the cut sample, coating side up, flat on the adhesive tape of the sample stage. Sputter a thin film of gold or platinum, several nanometers to tens of nanometers, onto the sample surface. Switch from low magnification (500X) to high magnification for observation. Randomly select a 10μm × 10μm area; different fields of view can be selected for each sample. At 10,000x magnification, randomly select a 10μm × 10μm square area and find holes with a chord length ≥ 0.3μm, the number of which is denoted as N; the chord length of each hole with a chord length ≥ 0.3μm is denoted as R1, R... 2… R N The diameters of five aramid fibers were selected and denoted as x1, x2, x3, x4, and x5, and the average value was denoted as u.

[0038] Then according to Calculate the value of A.

[0039] In some embodiments, 5.4 ≤ A ≤ 64 is more conducive to balancing the improvement of the diaphragm's high-temperature resistance, structural stability, and thermal safety performance.

[0040] In some embodiments, 2 ≤ N ≤ 8, for example, it can be a range of 2, 3, 4, 5, 6, 7, 8 or any two of them. This is more conducive to avoiding direct exposure of the base film, improving the overall high-temperature resistance of the separator, and enhancing the safety performance of the battery.

[0041] In some embodiments, 0.3 μm ≤ R ≤ 0.9 μm, for example, it can be a range of 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, or any combination thereof. This is more conducive to reducing the exposed area of ​​the base membrane, improving the local high-temperature resistance of the diaphragm, and enhancing the safety performance of the diaphragm.

[0042] In some embodiments, 30nm ≤ x ≤ 85nm, for example, can be a range of 30nm, 35nm, 40nm, 45nm, 50nm, 55nm, 60nm, 65nm, 70nm, 75nm, 80nm, 85nm, or any combination thereof. This is more conducive to improving the uniformity of aramid fiber diameter, resulting in a more uniform stress distribution within the aramid coating, improving the adhesion between the aramid coating and the base film, and enhancing the structural stability of the diaphragm.

[0043] In some embodiments, 51nm ≤ u ≤ 56nm, for example, it can be a range of 51nm, 52nm, 53nm, 54nm, 55nm, 56nm, or any combination thereof. This can further ensure the uniformity of the aramid fiber diameter and improve the peel strength of the diaphragm.

[0044] In some embodiments, the aramid fiber includes polyphenylene phthalamide, which is more conducive to improving the high temperature resistance, mechanical stability and safety performance of the diaphragm.

[0045] In some embodiments, polyphenylene phthalamide includes poly(p-phenylene terephthalamide) and / or poly(m-phenylene isophthalamide), which can further improve the performance of the membrane.

[0046] In some embodiments, the ratio of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn) of polyphenylene phthalamide is 1 to 3, for example, it can be a range of 1, 1.5, 2, 2.5, 3, or any combination thereof. When the ratio of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn) of polyphenylene phthalamide is 1 to 3, the interactions between molecular chains (hydrogen bonds, van der Waals forces) are more uniform, the molecular chain length is more uniform, and there are fewer internal defects, which can further improve the high-temperature resistance and mechanical properties of the separator, and improve the battery life.

[0047] In this embodiment of the invention, the ratio of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn) of polyphenylene phthalamide can be determined by gel permeation chromatography (GPC), which is a conventional testing method in the art and is not limited thereto.

[0048] In some embodiments, the aramid fiber content in the aramid coating is 65% to 95% by mass, for example, it can be a range of 65%, 70%, 75%, 80%, 85%, 90%, 95%, or any combination thereof. A mass percentage of aramid fiber not less than 65% is more beneficial for improving the high-temperature resistance of the diaphragm; a mass percentage of aramid fiber not greater than 95% is more beneficial for improving the mechanical strength of the diaphragm. Therefore, a mass percentage of aramid fiber in the aramid coating of 70% to 95% can further improve the performance of the diaphragm.

[0049] In this embodiment of the invention, the mass percentage of aramid fibers in the aramid coating can be determined by the following method: Specifically, thermogravimetric analysis (TGA) can be used. Take the above-mentioned diaphragm, scrape off the aramid coating powder, dry it in an oven to remove adsorbed water and residual solvent, and record the mass as m1; put the dried powder into a crucible, place it in a TGA instrument, heat it according to the set conditions, record the weight loss rate-temperature curve (DTG curve), and keep the mass basically constant. Record the remaining mass as m2. Then, the mass percentage of aramid fibers in the aramid coating = (m1-m2) / m1×100%.

[0050] In some embodiments, the aramid coating also includes ceramic materials, which further enhance the hardness and rigidity of the aramid coating, thereby improving the puncture strength and tensile strength of the diaphragm.

[0051] In some embodiments, the ceramic material includes one or more of alumina, silicon dioxide, titanium dioxide, zirconium dioxide, barium titanate, barium sulfate, magnesium oxide, calcium oxide, aluminum hydroxya, and silicon carbide. This can further improve the performance of the diaphragm.

[0052] In some embodiments, the presence of oxygen-containing groups on the surface of the base membrane is more conducive to strengthening the chemical bonds or hydrogen bonds between the base membrane and the aramid coating, thereby improving the structural stability of the diaphragm.

[0053] In some embodiments, the base membrane can be a conventional membrane material in the art, and the base membrane may include polyolefins, such as polyethylene (PE) and / or polypropylene (PP), which is more conducive to improving the high temperature resistance and safety performance of the membrane.

[0054] In some embodiments, the weight-average molecular weight of the polyolefin is 100W to 200W, for example, it can be a range of 100W, 125W, 150W, 175W, 200W, or any combination thereof. This is more conducive to balancing the flexibility and mechanical properties of the base membrane, and improving the structural stability, high-temperature resistance, and safety performance of the diaphragm.

[0055] In some embodiments, the peel strength between the aramid coating and the base film is 70 N / m to 130 N / m, for example, it can be a range of 70 N / m, 75 N / m, 80 N / m, 85 N / m, 90 N / m, 95 N / m, 100 N / m, 105 N / m, 110 N / m, 115 N / m, 120 N / m, 125 N / m, 130 N / m, or any combination thereof. This is more conducive to improving the structural stability of the separator and improving the cycle life and safety performance of the battery.

[0056] In this embodiment of the invention, the peel strength between the aramid coating and the base film can be measured by the following method:

[0057] S1. Sample preparation: Take the above-mentioned diaphragm and cut it into 100×15mm samples using a strip cutter;

[0058] S 2. Apply 15mm wide double-sided tape vertically and horizontally to the board, extending 1cm beyond the line. Roll it back and forth evenly twice with a roller. Then, attach the coated side of the sample strip from the edge to the scale line to the double-sided tape and roll it back and forth evenly three times with a roller. Each roll should be evenly 10 seconds.

[0059] S 3. The peel strength between the aramid coating and the base film was tested at 180° using a tensile testing machine (model: TST-02H), with a tensile speed of 50 mm / min and a displacement spacing of 100 mm.

[0060] The present invention also provides a method for preparing the above-mentioned diaphragm, comprising the following steps: coating at least one side of a base membrane to form an aramid coating, thereby obtaining a diaphragm.

[0061] In some embodiments, the process of coating at least one side of a base film to form an aramid coating includes: applying a coating slurry containing aramid fibers to at least one side of the base film; passing the base film coated with the coating slurry through a multi-stage coagulation bath and then drying it to form an aramid coating on at least one side of the base film; wherein each stage of the coagulation bath independently includes an organic solvent and an inorganic electrolyte; for any two adjacent stages of the coagulation bath, the mass concentration of the organic solvent in the preceding stage of the coagulation bath is greater than the mass concentration of the organic solvent in the following stage of the coagulation bath.

[0062] According to the inventors' research, multi-stage coagulation baths can improve the uniformity of the local high-temperature resistance of the separator, that is, improve the overall high-temperature resistance of the separator. The reason for this is that by using multi-stage coagulation bath gradient treatment (i.e., for any two adjacent coagulation baths, the mass concentration of the organic solvent in the previous coagulation bath is greater than the mass concentration of the organic solvent in the next coagulation bath), the phase transfer process of the aramid coating slurry can be precisely controlled, forming a dense and uniform honeycomb porous structure. This makes the internal structure of the separator uniform, and under local high-temperature environments, the difference in high-temperature resistance of each region is minimal. This can effectively avoid the problem of local membrane rupture and further improve the safety of the battery under complex operating conditions.

[0063] Meanwhile, each coagulation bath independently includes an inorganic electrolyte. The inorganic electrolyte stabilizes the aramid molecular chains through charge action, slows down the phase separation rate, promotes the orderly arrangement of molecular chains, reduces internal defects in the diaphragm, and is more conducive to improving the high-temperature resistance of the diaphragm.

[0064] Specifically, the coating slurry containing aramid fibers, i.e., the aramid coating slurry, can be prepared by uniformly mixing aramid fibers, ceramic materials, and solvents. The solvents include, for example, N-methylpyrrolidone (NMP).

[0065] In some embodiments, the time for the base membrane coated with the coating slurry to pass through each coagulation bath is 3 to 5 minutes, for example, it can be a range of 3 minutes, 3.5 minutes, 4 minutes, 4.5 minutes, 5 minutes, or any combination thereof. This is more conducive to slowing down the phase separation rate, promoting the orderly arrangement of molecular chains, reducing internal defects in the membrane, and further improving the high-temperature resistance of the membrane.

[0066] In practice, the time it takes for the base film coated with the coating slurry to pass through each coagulation bath can be controlled by controlling the length of each coagulation bath to be 3 m to 6 m and the speed of the base film to be 10 m / min to 20 m / min.

[0067] Drying is a standard practice in this field and is not subject to any restrictions.

[0068] In some embodiments, the difference in mass concentration of the organic solvent between any two adjacent coagulation baths is 15% to 40%. For example, it can be a range of 15%, 20%, 25%, 30%, 35%, 40%, 40%, or any combination thereof. A ratio of not less than 15% ensures the coagulation effect of each coagulation bath and prevents uneven thickness of the aramid coating. A ratio of not more than 40% further slows down the phase separation rate and ensures uniform internal and external structure of the coating. Therefore, a ratio of 15% to 40% is more conducive to achieving a moderate phase separation rate and ensuring a good coagulation effect.

[0069] In some specific embodiments, in any two adjacent coagulation baths in a multi-stage coagulation bath, the difference in the mass concentration of the organic solvent in the preceding coagulation bath is equal to the difference in the mass concentration of the organic solvent in the following coagulation bath, which is more conducive to improving the performance of the diaphragm.

[0070] In some embodiments, the process of passing a base film coated with a coating slurry through a multi-stage coagulation bath includes: passing the base film coated with the coating slurry sequentially through a first coagulation bath, a second coagulation bath, and a third coagulation bath.

[0071] In specific implementation, the mass concentration of the organic solvent in the first coagulation bath is 60% to 90%, for example, it can be 60%, 65%, 70%, 75%, 80%, 85%, 90%, or any combination thereof. This is more conducive to achieving initial phase separation of the aramid coating, avoiding the formation of large-pore or porous defects in the aramid coating due to rapid phase separation, and allowing the aramid molecular chains to slowly arrange and form a uniform internal structure.

[0072] In specific implementation, the mass concentration of the organic solvent in the second coagulation bath is 30% to 50%, for example, it can be 30%, 35%, 40%, 45%, 50%, or any combination thereof. This can further cure the aramid coating, while retaining the air permeability and mechanical toughness of the aramid coating through appropriate solvent exchange, avoiding excessive density that could lead to coating embrittlement.

[0073] In specific implementation, the mass concentration of the organic solvent in the third coagulation bath is 10% to 20%, for example, it can be 10%, 15%, 20%, or any combination thereof. This can wash away residual organic solvents, reduce chemical residues in the aramid coating, and further improve its stability in environments such as high temperature and electrolytes.

[0074] In some embodiments, the organic solvent includes one or more of N-methylpyrrolidone, dimethyl sulfoxide, and N,N-dimethylformamide, which can further control the phase transfer process of the aramid coating slurry, improve the uniformity of the internal structure of the diaphragm, and improve the high temperature resistance and safety performance of the diaphragm.

[0075] In practice, NMP can be used as the organic solvent. It has good solubility for aramid slurry and is easy to volatilize and remove during subsequent drying, which is environmentally friendly. At the same time, it can better meet the requirements of solvent performance in multi-stage coagulation baths and is more conducive to forming a more ideal membrane structure.

[0076] In some embodiments, the inorganic electrolyte includes one or more of lithium chloride (LiCl), calcium chloride (CaCl2), magnesium chloride (MaCl2), and sodium chloride (LiCl), which is more conducive to improving the uniformity of the internal structure of the diaphragm.

[0077] In practical implementation, LiCl can be used as the inorganic electrolyte because Li... + With a small ionic radius and strong charge interaction, it is more conducive to stabilizing aramid molecular chains, slowing down phase separation rate and promoting orderly arrangement of molecular chains, which can more effectively reduce internal defects of the diaphragm and improve diaphragm performance.

[0078] In some embodiments, the mass concentration of the inorganic electrolyte in each coagulation bath is independently 0.5% to 2%. For example, the mass concentration of the inorganic electrolyte in the first coagulation bath is 0.5% to 2%; the mass concentration of the inorganic electrolyte in the second coagulation bath is 0.5% to 2%; and the mass concentration of the inorganic electrolyte in the third coagulation bath is 0.5% to 2%.

[0079] For example, it can be a range of 0.5%, 1%, 1.5%, 2%, or any two of them.

[0080] Specifically, an inorganic electrolyte concentration of not less than 0.5% is more conducive to slowing down the solidification rate of the aramid coating and avoiding the formation of a large number of micropore defects; an inorganic electrolyte concentration of not more than 2% is more conducive to ensuring the hydrogen bonding between aramid fiber molecules and improving the high temperature resistance and structural stability of the diaphragm.

[0081] Specifically, each coagulation bath also independently includes water, which is more conducive to phase separation of the aramid coating.

[0082] In this embodiment of the invention, the mass concentration of the organic solvent = mass of the organic solvent / (mass of the organic solvent + mass of the inorganic electrolyte + mass of water); the mass concentration of the inorganic electrolyte = mass of the inorganic electrolyte / (mass of the organic solvent + mass of the inorganic electrolyte + mass of water).

[0083] In some embodiments, after surface treatment of the base film with hydrogen peroxide (H2O2) solution under ultraviolet light (UV), an aramid coating is then applied to at least one side of the base film to form a separator.

[0084] Specifically, after the base membrane surface is treated with hydrogen peroxide solution combined with UV irradiation, OH free radicals are generated to oxidize the base membrane surface and form active groups. These active groups then form strong chemical or hydrogen bonds with the aramid coating, further improving the structural stability of the separator under high temperature and mechanical stress. This means increasing the adhesion between the aramid coating and the base membrane, and improving the separator's peel strength. This allows the separator to maintain stable performance during long-term use, extending the battery's cycle life.

[0085] Specifically, the mass concentration of the hydrogen peroxide solution is 2% to 30%, for example, it can be 2%, 5%, 10%, 15%, 20%, 25%, 30%, or any combination thereof. This is more conducive to the generation of OH free radicals to oxidize the surface of the base film and form active groups, thereby improving the adhesion between the aramid coating and the base film.

[0086] Specifically, the wavelength of the ultraviolet light is 100nm~300nm, for example, it can be a range of 100nm, 150nm, 200nm, 250nm, 300nm or any combination thereof. This is more conducive to the formation of strong chemical bonds or hydrogen bonds between the base film and the aramid coating, improving the peel strength of the separator.

[0087] Specifically, the surface treatment time (i.e., the time for irradiation under ultraviolet light after coating the base film with hydrogen peroxide solution) is 10 min to 30 min, for example, it can be a range of 10 min, 15 min, 20 min, 25 min, 30 min or any combination thereof.

[0088] Specifically, the above preparation process is simple and cost-controllable. The cost of hydrogen peroxide solution and inorganic electrolyte is low, and the processing technology is easy to operate, making it suitable for large-scale industrial production. This reduces production costs while ensuring the high performance of the diaphragm.

[0089] This invention also provides a battery comprising the above-described separator or a separator prepared according to the above-described separator preparation method. This battery has advantages corresponding to the above-described separator, which will not be elaborated further.

[0090] Generally, a battery includes a cell and a casing that encapsulates the cell. Electrolyte is injected into the cell within the casing. The cell includes a positive electrode, a negative electrode, and a separator located between the positive and negative electrodes. The cell can be a stacked cell, meaning it is composed of alternating layers of positive electrode, separator, and negative electrode; or it can be a wound cell, meaning it is composed of positive electrode, separator, and negative electrode layers stacked sequentially and then wound together.

[0091] The separator is used to separate the positive and negative electrodes to prevent them from short-circuiting. It also allows active ions such as lithium ions to pass through, enabling them to intercalate and deintercalate between the positive and negative electrodes, thus facilitating the charging and discharging process of the battery.

[0092] In this embodiment of the invention, the battery cell can be packaged using conventional housing materials in the art, such as flexible packaging materials like aluminum-plastic film, but is not limited thereto.

[0093] The electrolyte in this embodiment of the invention can be a conventional electrolyte in the art. For example, the electrolyte is a non-aqueous electrolyte, which may specifically include organic solvents, additives and electrolyte salts. Organic solvents include one or more of ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC) and propylene carbonate (PC). Additives include, for example, fluoroethylene carbonate (FEC) and / or vinylene carbonate (VC). Electrolyte salts may include lithium salts, such as lithium hexafluorophosphate (LiPF6), but are not limited thereto.

[0094] Generally, the positive electrode active layer may include a positive electrode active material (positive electrode active substance), a positive electrode conductive agent, and a positive electrode binder, all of which can be conventional materials in the art. For example, the positive electrode active material may include one or more of lithium nickel oxide, lithium iron phosphate (LFP), lithium cobalt oxide, lithium manganese oxide, and positive electrode ternary materials. The positive electrode ternary material may include nickel cobalt manganese ternary materials (NCM) and / or nickel cobalt aluminum ternary materials (NCA). The positive electrode conductive agent may include one or more of carbon black, conductive carbon black, carbon nanotubes (CNT), acetylene black, graphene, Ketjen black, and carbon fiber. The positive electrode binder may include one or more of polyvinylidene fluoride (PVDF), polyvinyl fluoride, polyethylene, polypropylene, polyvinyl alcohol, polyvinyl chloride, carboxylated polyvinyl chloride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, etc.

[0095] Generally, in the positive electrode active layer, the mass percentage of the positive electrode active material (i.e., the ratio of the mass of the positive electrode active material to the total mass of the positive electrode active layer) can be 70% to 99%, for example, 70%, 75%, 80%, 85%, 90%, 93%, 95%, 97%, 99%, or any combination thereof. The mass percentage of the positive electrode conductive agent can be 0.5% to 15%, for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 8%, 10%, 13%, 15%, or any combination thereof. The mass percentage of the positive electrode binder can be 0.5% to 15%, for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 8%, 10%, 13%, 15%, or any combination thereof.

[0096] The embodiments of the present invention may employ conventional positive current collectors in the art, for example, positive current collectors may include aluminum foil.

[0097] In this embodiment of the invention, the positive electrode sheet can be prepared by conventional methods in the art, such as by coating. Specifically, the positive electrode active material, conductive agent, binder, and other components used to form the positive electrode active layer can be dispersed in a solvent, such as N-methylpyrrolidone (NMP), to prepare a positive electrode slurry. This slurry is then coated onto the surface of the positive electrode current collector, and after drying, rolling, and other processes, the positive electrode sheet is obtained. The coating, drying, and rolling processes involved are conventional operations for preparing positive electrode sheets using the coating method, and are not particularly limited thereto.

[0098] Generally, a negative electrode sheet includes a negative current collector and a negative active layer located on at least one side surface of the negative current collector. Specifically, the negative active layer can be provided on one side surface of the negative current collector, or negative active layers can be provided on both opposite sides of the negative current collector in the thickness direction.

[0099] Specifically, the negative electrode active layer may include a negative electrode active material, a negative electrode conductive agent, and a negative electrode binder, all of which can be conventional materials in the art. For example, the negative electrode active material may include graphite; the negative electrode conductive agent may include one or more of carbon black, conductive carbon black, carbon nanotubes (CNT), acetylene black, graphene, Ketjen black, and carbon fiber; and the negative electrode binder may include one or more of polyvinylidene fluoride (PVDF), sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide-imide, polyvinyl alcohol, and sodium polyacrylate.

[0100] Generally, in the negative electrode active layer, the mass percentage of the negative electrode active material (i.e., the ratio of the mass of the negative electrode active material to the total mass of the negative electrode active layer) can be 70% to 99%, for example, 70%, 75%, 80%, 85%, 90%, 93%, 95%, 97%, 99%, or any combination thereof; the mass percentage of the conductive agent can be 0.5% to 15%, for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 8%, 10%, 13%, 15%, or any combination thereof; and the mass percentage of the binder can be 0.5% to 15%, for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 8%, 10%, 13%, 15%, or any combination thereof.

[0101] The embodiments of the present invention may employ conventional negative electrode current collectors in the art, for example, negative electrode current collectors include copper foil.

[0102] In this embodiment of the invention, the negative electrode sheet can be prepared by conventional methods in the art, such as by coating. Specifically, the components used to form the negative electrode active layer, such as the negative electrode active material, conductive agent, and binder, can be dispersed in a solvent, such as NMP, to prepare a negative electrode slurry. This slurry is then coated onto the surface of the negative electrode current collector, and after drying, rolling, and other processes, the negative electrode sheet is obtained. The coating, drying, and rolling processes involved are conventional operations for preparing negative electrode sheets using the coating method, and are not particularly limited thereto.

[0103] The embodiments of the present invention can assemble components such as positive electrode, separator and negative electrode into a battery using conventional methods in the art. For example, positive electrode, separator and negative electrode can be stacked in sequence to obtain a battery cell. Then the battery cell is placed in a casing (outer packaging) and after conventional battery assembly processes such as baking, electrolyte injection, aging, formation and secondary aging, a battery is obtained. In the battery preparation process, the baking, electrolyte injection, aging, formation and secondary aging processes are all conventional operations in the art and are not particularly limited.

[0104] This invention also provides a battery pack comprising at least two batteries as described above. This battery pack offers advantages corresponding to the batteries described above, which will not be elaborated further.

[0105] Generally, a battery pack includes multiple batteries as individual cells, which are connected to form the battery pack. These batteries can be electrically connected using methods conventional in the art, such as series connection, parallel connection, or a combination of these connection methods, without any particular limitation.

[0106] This invention also provides an electrical device, including the battery or battery pack described above. This electrical device has advantages corresponding to the battery pack described above, which will not be elaborated further.

[0107] The electrical equipment used in the embodiments of the present invention can be conventional electrical equipment in the art, such as power equipment (e.g., electric vehicles, electric cars), electronic equipment (e.g., mobile phones, tablets, laptops, digital cameras, etc.), wearable devices (e.g., watches, bracelets, VR glasses, etc.), energy storage power stations, etc., and there are no particular limitations on this.

[0108] The present invention will be further described below through specific embodiments.

[0109] 1. Preparation of the diaphragm

[0110] S1. Coating a coating slurry containing aramid fibers onto at least one side of a polyethylene base film with a molecular weight of 120w; irradiating the base film with a 20% hydrogen peroxide solution under a UV lamp with a wavelength of 254nm for 30 minutes.

[0111] S2. Prepare a mixture of poly(p-phenylene terephthalamide) with Mw / Mn=1 and solvent NMP with a solid content of 15wt% (i.e., the mass ratio of poly(p-phenylene terephthalamide) to the mixture is 15%). Add Al2O3 to the mixture, wherein the mass ratio of Al2O3 to poly(p-phenylene terephthalamide) is 1:2 (i.e., the mass percentage of poly(p-phenylene terephthalamide) is 66.7%), and prepare an aramid coating slurry.

[0112] An aramid coating slurry is applied to both sides of a surface-treated base film, passed through a three-stage coagulation bath, and then dried to form an aramid coating, thus producing a separator. The first coagulation bath consists of 60 wt% NMP, 2 wt% LiCl, and 38 wt% water; the second coagulation bath consists of 40 wt% NMP, 2 wt% LiCl, and 58 wt% water; and the third coagulation bath consists of 15 wt% NMP, 2 wt% LiCl, and 83 wt% water.

[0113] 2. Battery manufacturing

[0114] (1) Preparation of positive electrode

[0115] Lithium iron phosphate, PVDF, and carbon black were mixed in a mass ratio of 90:5:5 and dispersed in the solvent NMP. The mixture was stirred evenly to prepare a positive electrode slurry.

[0116] The positive electrode slurry is coated on both sides of the carbon-coated aluminum foil. After drying and rolling, a positive electrode coating is formed on both sides of the carbon-coated aluminum foil, thus producing a positive electrode sheet.

[0117] (2) Preparation of negative electrode

[0118] Graphite, CMC, carbon black, and water are mixed evenly in a mass ratio of 100:5:5:125 to prepare a negative electrode slurry.

[0119] The negative electrode slurry is coated on both the front and back surfaces of a copper foil. After drying and rolling, a negative electrode coating is formed on both the front and back surfaces of the copper foil, thus producing a negative electrode sheet.

[0120] (3) Battery assembly

[0121] In a glove box, the above-mentioned positive electrode sheet, the above-mentioned separator and the above-mentioned negative electrode sheet are stacked in sequence and arranged to form a stacked cell. The cell is then encapsulated with aluminum-plastic film and processed through processes such as electrolyte injection and formation to obtain a battery.

[0122] The electrolyte is an organic solvent containing lithium salt (specifically lithium hexafluorophosphate), with a LiPF6 concentration of 1 mol / L. The organic solvent includes ethylene carbonate, methyl ethyl carbonate, dimethyl carbonate, and vinylene carbonate. The mass ratio of ethylene carbonate, methyl ethyl carbonate, and dimethyl carbonate in the organic solvent is 3:6:1, and the mass fraction of vinylene carbonate is 1% (i.e., vinylene carbonate accounts for 1% of the mass fraction of the electrolyte).

[0123] Following the process of Example 1, the diaphragms of Examples 2 to 11 were prepared.

[0124] The differences between Examples 2 to 11 and Example 1 are as follows: the ratio of weight-average molecular weight to number-average molecular weight of polyphenylene phthalamide, the mass concentration of organic solvent in the first coagulation bath, the mass concentration of organic solvent in the second coagulation bath, the mass concentration of organic solvent in the third coagulation bath, the mass concentration of inorganic electrolyte, and the time of ultraviolet irradiation are different, as detailed in Table 2. The remaining steps and conditions are the same as in Example 1.

[0125] Comparative Example 1

[0126] The difference from Example 1 is that, in step S1, the surface treatment of the base film by irradiating it with a 20% hydrogen peroxide solution under a UV lamp with a wavelength of 254 nm for 30 minutes is not performed; in step S2, the weight-average molecular weight to number-average molecular weight ratio of polyphenylene phthalamide is 3.5, and after passing through a two-stage coagulation bath, it is dried to form an aramid coating and obtain a separator; wherein, the first coagulation bath includes 60 wt% NMP and 40 wt% water; the second coagulation bath includes 15 wt% NMP and 85 wt% water;

[0127] See Table 2 for details. The remaining steps and conditions are the same as in Example 1.

[0128] Comparative Example 2

[0129] The difference from Example 1 is that in step S1, the 20% hydrogen peroxide solution is not used to irradiate the base film under a UV lamp with a wavelength of 254nm for 30 minutes for surface treatment.

[0130] In step S2, the ratio of the weight-average molecular weight to the number-average molecular weight of polyphenylene phthalamide is 1.5. After passing through a two-stage coagulation bath, it is dried to form an aramid coating and obtain a diaphragm. The first coagulation bath includes 30 wt% NMP and 70 wt% water; the second coagulation bath includes 15 wt% NMP and 85 wt% water.

[0131] See Table 2 for details. The remaining steps and conditions are the same as in Example 1.

[0132] Comparative Example 3

[0133] The difference from Example 1 is that in step S2, the membrane is obtained only through the first coagulation bath; wherein, the first coagulation bath includes 60 wt% NMP, 2 wt% LiCl and 38 wt% water.

[0134] See Table 2 for details. The remaining steps and conditions are the same as in Example 1.

[0135] Test case

[0136] (1) Test method for A of the diaphragm: It can be measured by scanning electron microscopy (SEM). Take the diaphragm prepared above, randomly select a clean area from the diaphragm, and cut a small sample with an area of ​​0.5cm × 0.5cm. Lay the small sample with the coating facing up on the adhesive tape on the sample stage. Sputter a 10-nanometer platinum film on the sample surface. Switch from low magnification (500X) to high magnification for observation. Randomly select a 10-micrometer × 10-micrometer area, and select different fields of view for each sample for observation. At 10,000x, randomly select a 10-micrometer × 10-micrometer square area, find holes with a chord length > 0.3 micrometers, and record the number as N; the chord length of each hole is recorded as R1, R 2… R N The diameters of five aramid fibers were selected and denoted as x1, x2, x3, x4, and x5, and the average value was denoted as u.

[0137] according to Calculate the value of A; see Table 1 for the specific results;

[0138] like Figure 2 The image shown is a SEM image of the aramid coating of Example 4.

[0139] (2) Test method for peel strength (structural stability) of aramid coating:

[0140] S1. Sample preparation: Take the diaphragm prepared above and cut it into 100×15mm sample strips using a strip cutter;

[0141] S 2. Apply 15mm wide double-sided tape vertically and horizontally to the board, extending 1cm beyond the line. Roll it back and forth evenly twice with a roller. Then, attach the coated side of the sample strip from the edge to the scale line to the double-sided tape and roll it back and forth evenly three times with a roller. Each roll should be evenly 10 seconds.

[0142] S 3. The peel strength was tested at 180° using a tensile testing machine (model: TST-02H), with a tensile speed of 50 mm / min and a displacement interval of 100 mm; the specific results are shown in Table 3.

[0143] (3) Test method for the temperature of the suspended hot nail puncture hole of the diaphragm (high temperature resistance): Using the Chuanyuan Technology diaphragm tester 1.0, take the above-mentioned diaphragm, cut it into a 10cm×10cm square, and clamp it between two stainless steel rings to ensure that the diaphragm completely covers the stainless steel ring. The probe diameter is 3mm, the stroke is set to 29mm, and the suspension method is used for 3s. Starting from 200℃, test whether the diaphragm is punctured. Increase the temperature by 5℃ at a time until the diaphragm is punctured. Record the highest temperature without puncture as: the temperature of the suspended hot nail puncture hole of the diaphragm T; test the temperature of the suspended hot nail puncture hole at 5 different locations in parallel, and record the highest temperature of the suspended hot nail puncture hole as T. max The lowest temperature at which the suspended hot nail punctures the hole is T.min The average value is calculated as T. ave .

[0144] The percentage of temperature deviation when the hot nail punctures the membrane: (T) max -T min ) / T ave The specific results are shown in Table 3.

[0145] (4) Test method for TMA rupture temperature (high temperature resistance and structural stability) of the separator: The thermomechanical analysis (TMA) method is used. Take the separator prepared above, cut the separator into a sample with a length of 8 mm and a width of 2 mm, put the sample into the dynamic thermal analyzer (TMA instrument), clamp the two sides of the sample with clamps to simulate the tension of the separator in the battery, apply a tension of 0.03 N to the sample, start heating from room temperature, and heat up at a rate of 5 °C / min until the separator breaks. Record the temperature at which it breaks as the TMA rupture temperature; the specific results are shown in Table 3.

[0146] (5) Test method for battery needle penetration thermal runaway time (thermal safety performance): Take the battery prepared above and charge it to 100% SOC (state of charge); the test battery is clamped to ensure restraint and 1.5mm aerogel is added; use a φ5mm high temperature resistant steel needle (the cone angle of the needle tip is 45°) to penetrate the battery perpendicularly to the direction of the battery electrode during the needle penetration. The steel needle stays in the battery and the time of needle insertion is recorded. The time of sudden temperature rise and sudden voltage drop is recorded as the end time. The battery needle penetration thermal runaway time is the end time minus the start time. The longer the time from the insertion of the steel needle to the battery runaway, the better the thermal safety performance of the battery. The specific results are shown in Table 3.

[0147] Table 1. Parameters of the diaphragm

[0148]

[0149] Table 2. Parameters and preparation parameters of the diaphragm

[0150]

[0151] Table 3. Performance of the diaphragm

[0152]

[0153] Compared to Comparative Examples 1-3, the diaphragms in Examples 1-11 comprise a base membrane and an aramid coating disposed on at least one side of the base membrane. The aramid coating comprises aramid fibers and pores, with any aramid coating having a diameter of 100 μm. 2 The region satisfies: A≤64, which can simultaneously improve the high temperature resistance, structural stability and thermal safety performance of the diaphragm.

[0154] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A diaphragm, characterized in that, The substrate includes a base film and an aramid coating disposed on at least one side of the base film, the aramid coating comprising aramid fibers and pores, wherein any 100 μm of the aramid coating... 2 The region satisfies: 5.4≤A≤64； ， Where R is the 100μm 2 The chord length of the holes in the region with a chord length ≥ 0.3 μm, in μm, and 0.3 ≤ R ≤ 0.9; N is the chord length of the 100 μm hole. 2 The number of pores with a chord length ≥ 0.3 μm in the region, 2 ≤ N ≤ 8; x is the diameter of the aramid fiber in nm, 30 ≤ x ≤ 85; u is the diameter of the 100 μm pore. 2 The average diameter of the aramid fibers in the region, in nm, is 51 ≤ u ≤ 56; The aramid fiber in the aramid coating has a mass percentage content of 65% to 95%.

2. The diaphragm according to claim 1, characterized in that, The aramid fiber includes polyphenylene phthalamide.

3. The diaphragm according to claim 2, characterized in that, The polyphenylene phthalamide includes poly(p-phenylene terephthalamide) and / or poly(m-phenylene isophthalamide); And / or, the ratio of the weight-average molecular weight to the number-average molecular weight of the polyphenylene phthalamide is 1 to 3.

4. The diaphragm according to claim 1 or 2, characterized in that, The aramid coating also includes ceramic materials.

5. The diaphragm according to claim 4, characterized in that, The ceramic material includes one or more of the following: alumina, silicon dioxide, titanium dioxide, zirconium dioxide, barium titanate, barium sulfate, magnesium oxide, calcium oxide, aluminum hydroxya, and silicon carbide.

6. The diaphragm according to claim 1 or 2, characterized in that, The surface of the base film contains oxygen-containing groups; And / or, the base film comprises a polyolefin; And / or, the peel strength between the aramid coating and the base film is 70 N / m ~ 130 N / m.

7. The diaphragm according to claim 6, characterized in that, The weight-average molecular weight of the polyolefin is 100W~200W.

8. A method for preparing a diaphragm according to any one of claims 1-7, characterized in that, Includes the following steps: The aramid coating is formed by coating at least one side of the base film to obtain the diaphragm.

9. The preparation method according to claim 8, characterized in that, The process of coating at least one side of the base film to form the aramid coating includes: The coating slurry containing the aramid fibers is applied to at least one side of the base film; The base film coated with the coating slurry is passed through a multi-stage coagulation bath and then dried to form the aramid coating on at least one side of the base film; wherein each stage of the coagulation bath independently includes an organic solvent and an inorganic electrolyte; for any two adjacent stages of the coagulation bath, the mass concentration of the organic solvent in the previous stage of the coagulation bath is greater than the mass concentration of the organic solvent in the subsequent stage of the coagulation bath.

10. The preparation method according to claim 9, characterized in that, For any two adjacent coagulation baths, the difference in the mass concentration of the organic solvent in the preceding coagulation bath and the mass concentration of the organic solvent in the following coagulation bath is 15% to 40%. And / or, each coagulation bath also independently comprises water; And / or, the time for each coagulation bath of the base film coated with the coating slurry is 3 min to 5 min.

11. The preparation method according to claim 9 or 10, characterized in that, The process of passing the base film coated with the coating slurry through a multi-stage coagulation bath includes: passing the base film coated with the coating slurry sequentially through a first coagulation bath, a second coagulation bath, and a third coagulation bath, wherein the mass concentration of the organic solvent in the first coagulation bath is 60%~90%; And / or, the mass concentration of the organic solvent in the second coagulation bath is 30% to 50%; And / or, the mass concentration of the organic solvent in the third coagulation bath is 10% to 20%.

12. The preparation method according to claim 9 or 10, characterized in that, The organic solvent includes one or more of N-methylpyrrolidone, dimethyl sulfoxide, and N,N-dimethylformamide; And / or, the inorganic electrolyte includes one or more of lithium chloride, calcium chloride, magnesium chloride, and sodium chloride; And / or, in each stage of the coagulation bath, the mass concentration of the inorganic electrolyte is independently 0.5% to 2%.

13. The preparation method according to claim 10, characterized in that, The diaphragm is prepared by surface treatment of the base film with hydrogen peroxide solution under ultraviolet light, followed by coating at least one side of the base film to form the aramid coating.

14. A battery, characterized in that, This includes the diaphragm according to any one of claims 1-7 or the diaphragm prepared according to the method for preparing the diaphragm according to any one of claims 8-13.

15. A battery pack, characterized in that, It includes at least two batteries as described in claim 14.

16. An electrical appliance, characterized in that, Includes the battery of claim 14 or the battery pack of claim 15.

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