A coating slurry, a separator, a method for manufacturing a separator, and a battery

Abstract

This invention provides a coating slurry, a separator, a method for preparing the separator, and a battery. The separator includes a substrate and a coating layer disposed on at least one surface of the substrate. By weight, the coating layer includes 1.5–11.5 parts of a first binder, 1.5–25 parts of a second binder, and 50–95 parts of a ceramic material. The particle size of the second binder is 2.5–7.5 μm, and the ratio of the average particle size of the ceramic material to the average particle size of the second binder is 0.12–0.16. In this invention, the separator exhibits excellent heat resistance and adhesion; it also possesses good air permeability and ion conductivity.

Description

Technical Field

[0001] This invention belongs to the field of battery separator material technology, specifically relating to a coating slurry, a separator, a method for preparing the separator, and a battery. Background Technology

[0002] The separator is a crucial component of lithium-ion batteries. Its main function is to separate the positive and negative electrodes, preventing short circuits caused by contact between the electrodes, and allowing ions in the electrolyte to pass through. The performance of the separator directly affects the battery's capacity, cycle performance, and safety performance. Therefore, using a high-performance separator is one of the effective ways to obtain high-performance batteries.

[0003] In the prior art, heat resistance and adhesion performance are improved by sequentially setting ceramic coating and adhesive coating on the surface of the substrate, but this will affect the hardness of the battery, the adhesion between the separator and the electrode needs to be further improved, and it is not conducive to the air permeability of the separator.

[0004] Therefore, developing a diaphragm with good heat resistance, high adhesion, good air permeability, simple process, and good thickness uniformity is an urgent problem to be solved in this field. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a coating slurry, a separator, a method for preparing the separator, and a battery. The separator exhibits good heat resistance and high adhesion; it also possesses excellent air permeability and ion conductivity; thus, the lithium-ion battery incorporating the separator demonstrates superior performance.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a diaphragm comprising a substrate and a coating layer disposed on at least one surface of the substrate, the coating layer comprising 1.5 to 11.5 parts of a first adhesive material, 1.5 to 25 parts of a second adhesive material, and 50 to 95 parts of a ceramic material; the particle size of the second adhesive material is 2.5 to 7.5 μm, and the ratio of the average particle size of the ceramic material to the average particle size of the second adhesive material is 0.12 to 0.16.

[0008] In this invention, the coating layer of the separator is made by compounding a second binder material with a specific particle size and a ceramic material in a specific amount, and controlling the ratio of the average particle size of the ceramic material to the average particle size of the second binder material within a specific range. This is beneficial to improving the heat resistance, adhesion, and thickness uniformity of the separator, and can ensure the air permeability and ionic conductivity of the separator. In addition, the second binder material is not easy to fall off, which is beneficial to obtaining a lithium-ion battery with better overall performance and safety.

[0009] In this invention, the coating layer comprises 1.5 to 11.5 parts of a first adhesive material, for example, it can be a range of 1.5 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts, 5 parts, 5.5 parts, 6 parts, 6.5 parts, 7 parts, 7.5 parts, 8 parts, 8.5 parts, 9 parts, 9.5 parts, 10 parts, 10.5 parts, 11 parts, 11.5 parts, or any combination thereof.

[0010] In this invention, the coating layer comprises 1.5 to 25 parts of a second adhesive material, for example, it can be a range of 1.5 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts, 5 parts, 5.5 parts, 6 parts, 6.5 parts, 7 parts, 7.5 parts, 8 parts, 8.5 parts, 9 parts, 9.5 parts, 10 parts, 10.5 parts, 11 parts, 11.5 parts, 12 parts, 12.5 parts, 13 parts, 13.5 parts, 14 parts, 14.5 parts, 15 parts, 16 parts, 18 parts, 20 parts, 22 parts, 24 parts, 25 parts, or any combination of both.

[0011] In this invention, the content of the second adhesive material within the above-mentioned range can effectively achieve high adhesion and good air permeability; if too much is added, the air permeability is poor, the lithium ion permeation of the separator is reduced, and the internal resistance of the battery is increased; if too little is added, the separator adhesion is low, the battery cell adhesion is insufficient, and the battery is too soft.

[0012] In this invention, the coating layer comprises 50 to 95 parts of ceramic material, for example, a range of 50 parts, 52 parts, 54 parts, 56 parts, 58 parts, 60 parts, 62 parts, 64 parts, 66 parts, 68 parts, 70 parts, 72 parts, 74 parts, 76 parts, 78 parts, 80 parts, 82 parts, 84 parts, 85 parts, 86 parts, 88 parts, 90 parts, 92 parts, 94 parts, 95 parts, or any combination thereof.

[0013] In this invention, the particle size of the second adhesive material is 2.5–7.5 μm, for example, it can be 2.5 μm, 2.6 μm, 2.8 μm, 3 μm, 3.1 μm, 3.2 μm, 3.3 μm, 3.4 μm, 3.5 μm, 3.6 μm, 3.7 μm, 3.8 μm, 3.9 μm, 4 μm, 4.1 μm, 4.2 μm, 4.3 μm, 4.4 μm, 4.5 μm, 4.6 μm, 4.7 μm, 4. The range of values ​​is 8μm, 4.9μm, 5μm, 5.1μm, 5.2μm, 5.3μm, 5.4μm, 5.5μm, 5.6μm, 5.7μm, 5.8μm, 5.9μm, 6μm, 6.1μm, 6.2μm, 6.3μm, 6.4μm, 6.5μm, 6.6μm, 6.7μm, 6.8μm, 6.9μm, 7μm, 7.2μm, 7.4μm, 7.5μm, or any combination thereof.

[0014] In this invention, if the particle size of the second adhesive material is too small, the bonding effect will be poor; if the particle size is too large, it will result in a large separator thickness, which will affect the energy density of the battery.

[0015] In this invention, the ratio of the average particle size of the ceramic material to the average particle size of the second binder is 0.12 to 0.16, for example, it can be a range of 0.12, 0.122, 0.125, 0.128, 0.13, 0.132, 0.135, 0.138, 0.14, 0.142, 0.145, 0.148, 0.15, 0.152, 0.155, 0.158, 0.16, or any combination of both.

[0016] Preferably, the particle size distribution of the second adhesive material satisfies the following relationship:

[0017] D99-D10 ≤ 4.0 μm, for example, can be a range of values ​​including 0.1 μm, 0.2 μm, 0.4 μm, 0.6 μm, 0.8 μm, 1 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm, 2 μm, 2.2 μm, 2.4 μm, 2.6 μm, 2.8 μm, 3 μm, 3.2 μm, 3.4 μm, 3.6 μm, 3.8 μm, 4 μm or any combination of both; and / or, 0.6 ≤ (D (99-D10) / D50≤1.0, and the ratio of (D99-D10) / D50 can be, for example, a range of 0.6, 0.62, 0.64, 0.66, 0.68, 0.7, 0.72, 0.74, 0.76, 0.78, 0.8, 0.82, 0.84, 0.86, 0.88, 0.9, 0.92, 0.94, 0.96, 0.98, 1, or any combination thereof, more preferably 0.6 to 0.85.

[0018] In this invention, the D10, D50, and D99 particle sizes of the second adhesive material satisfy the above-mentioned relationship, resulting in a diaphragm with higher adhesion, better air permeability, and better heat resistance.

[0019] Preferably, the monomer of the second adhesive material is selected from any one or at least two of acrylonitrile, methyl methacrylate, methyl acrylate, butyl acrylate, glycidyl methacrylate, divinylbenzene, vinyl acetate, acrylamide, butadiene, or acrylic acid.

[0020] In this invention, the second adhesive material comprises a copolymer formed from at least two of the above-mentioned monomers, such as butadiene-acrylonitrile copolymer; and / or homopolymers of the above-mentioned monomers, such as polyacrylonitrile, polymethyl methacrylate, polyvinyl acetate, polyacrylamide, polyacrylic acid, polymethyl methacrylate, etc.

[0021] Preferably, the glass transition temperature (Tg) of the second adhesive material is 0 to 92°C, for example, it can be a range of 0°C, 5°C, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C or any combination thereof, more preferably 30 to 90°C.

[0022] Preferably, the melting point of the second adhesive material is ≥160°C, for example, it can be a range of 160°C, 165°C, 170°C, 175°C, 180°C, 185°C, 190°C, 195°C, 200°C, 205°C, 210°C, 215°C, 220°C, 225°C, 230°C, 235°C, 240°C, 245°C, 250°C or any combination thereof; more preferably, it is 180°C to 250°C.

[0023] In this invention, the Tg and melting point of the second adhesive material are within the above-mentioned range, which can ensure the effective bonding of the diaphragm to the electrode under hot pressing conditions, while preventing pore blockage due to melting, thus avoiding affecting the air permeability and ionic conductivity of the diaphragm.

[0024] Preferably, the average particle size (D50 particle size) of the ceramic material is 0.6 to 0.8 μm, for example, it can be a range of 0.6 μm, 0.61 μm, 0.62 μm, 0.63 μm, 0.64 μm, 0.65 μm, 0.66 μm, 0.67 μm, 0.68 μm, 0.69 μm, 0.7 μm, 0.71 μm, 0.72 μm, 0.73 μm, 0.74 μm, 0.75 μm, 0.76 μm, 0.77 μm, 0.78 μm, 0.79 μm, 0.8 μm, or any combination thereof.

[0025] In this invention, if the average particle size of the ceramic material is too small, the membrane will have poor air permeability; if the average particle size is too large, the heat resistance will be poor and the thermal shrinkage rate will be large.

[0026] Preferably, the ceramic material includes at least one of alumina, boehmite, barium sulfate, calcium oxide, silicon carbide, or silicon dioxide.

[0027] Preferably, the first adhesive material comprises a polymer material formed from acrylate monomers.

[0028] Preferably, the acrylate monomers include at least one of methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, n-propyl acrylate, cyclohexyl acrylate, lauryl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, isobornyl methacrylate, lauryl methacrylate, 2-hydroxyethyl methacrylate, or 2-hydroxypropyl methacrylate.

[0029] Preferably, the thickness of the coating layer is 1.6 to 2.7 μm, for example, it can be a range of 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.7 μm or any combination thereof.

[0030] Preferably, the surface of the coating layer has a raised structure.

[0031] Preferably, the height of the protrusion structure is 0.4–5.3 μm, for example, it can be a range of 0.4 μm, 0.6 μm, 0.8 μm, 1 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm, 2 μm, 2.2 μm, 2.4 μm, 2.6 μm, 2.8 μm, 3 μm, 3.2 μm, 3.4 μm, 3.6 μm, 3.8 μm, 4 μm, 4.2 μm, 4.4 μm, 4.6 μm, 4.8 μm, 5 μm, 5.2 μm, 5.3 μm or any combination thereof; more preferably, it is 1–5 μm.

[0032] In this invention, the raised structure is formed by a second adhesive material in the coating layer; the height of the raised structure is related to the thickness of the coating layer and the particle size of the second adhesive material; the particle size distribution of the second adhesive material is relatively uniform, resulting in good consistency of the raised structure on the surface of the coating layer, more effective bonding particles with the electrode, and a larger contact area, which is beneficial to improving the adhesion between the diaphragm and the electrode; and the height of the raised structure is within the above range, so the second adhesive material is not easy to fall off from the coating layer, the air permeability of the diaphragm is better, and the service life is longer.

[0033] Preferably, the thickness of the substrate is 3 to 16 μm.

[0034] Preferably, the substrate includes at least one of polypropylene (PP) substrate, polyethylene (PE) substrate, and polypropylene / polyethylene (PP / PE) multilayer composite film.

[0035] Preferably, the substrate includes at least one coated membrane with an inorganic ceramic coating or a polymer coating on its surface.

[0036] In a second aspect, the present invention provides a coating slurry, comprising, by mass percentage, 60-80% solvent, 0.3-5% first binder, 0.3-10% second binder, and 10-38% ceramic material; the particle size of the second binder is 2.5-7.5 μm; and the ratio of the average particle size of the ceramic material to the average particle size of the second binder is 0.12-0.16.

[0037] In this invention, the coating slurry comprises 60-80% solvent, for example, a range of values ​​consisting of 60%, 62%, 64%, 66%, 68%, 70%, 72%, 74%, 76%, 78%, 80%, or any combination thereof.

[0038] In this invention, the coating slurry comprises 0.3% to 5% of a first binder material, for example, it can be a range of 0.3%, 0.4%, 0.5%, 0.6%, 0.8%, 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, 2.2%, 2.4%, 2.6%, 2.8%, 3%, 3.2%, 3.4%, 3.5%, 3.6%, 3.8%, 4%, 4.2%, 4.4%, 4.6%, 4.8%, 5%, or any combination thereof.

[0039] In this invention, the coating slurry comprises 0.3% to 10% of a second binder, for example, a range of values ​​including 0.3%, 0.4%, 0.5%, 0.6%, 0.8%, 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, 2.2%, 2.4%, 2.6%, 2.8%, 3%, 3.2%, 3.4%, 3.5%, 3.6%, 3.8%, 4%, 4.2%, 4.4%, 4.6%, 4.8%, 5%, 5.2%, 5.5%, 5.8%, 6%, 6.2%, 6.5%, 6.8%, 7%, 7.2%, 7.5%, 7.8%, 8%, 8.2%, 8.5%, 8.8%, 9%, 9.2%, 9.5%, 9.8%, 10%, or any combination of both.

[0040] In this invention, the coating slurry comprises 10-38% ceramic material, for example, it can be 10%, 12%, 14%, 15%, 15.5%, 16%, 16.5%, 17%, 17.5%, 18%, 18.5%, 19%, 19.5%, 20%, 20.5%, 21%, 21.5%, 22%, 22.5%, 23%, 23.5%, 24%. The range of values ​​consisting of %, 24.5%, 25%, 25.5%, 26%, 26.5%, 27%, 27.5%, 28%, 28.5%, 29%, 29.5%, 30%, 30.5%, 31%, 31.5%, 32%, 32.5%, 33%, 33.5%, 34%, 34.5%, 35%, 36%, 37%, 38%, or any combination thereof.

[0041] Preferably, the second adhesive material satisfies at least one of the following conditions:

[0042] 1) The particle size distribution of the second adhesive material satisfies the following relationship: D99-D10≤4.0μm, and / or, 0.6≤(D99-D10) / D50≤1.0;

[0043] 2) The monomers of the second adhesive material are selected from any one or at least two of acrylonitrile, methyl methacrylate, methyl acrylate, butyl acrylate, glycidyl methacrylate, divinylbenzene, vinyl acetate, acrylamide, butadiene, or acrylic acid;

[0044] 3) The glass transition temperature of the second adhesive material is 0–92°C;

[0045] 4) The melting point of the second adhesive material is ≥160℃, more preferably 180~250℃.

[0046] Preferably, the solvent includes at least one of water, acetone, ethanol, and N-methylpyrrolidone (NMP).

[0047] Preferably, the coating slurry further includes 0.3 to 0.7% other additives by weight percentage, for example, a range of 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, or any combination thereof.

[0048] Preferably, the other additives include at least one of dispersants, wetting agents, leveling agents, thickeners, or suspending agents.

[0049] Thirdly, the present invention provides a method for preparing a diaphragm, comprising:

[0050] S1. Provide substrate;

[0051] S2. Prepare the coating slurry as described in the second aspect and coat it on at least one surface of the substrate;

[0052] S3. Dry the slurry at a temperature of 50-80°C to obtain a diaphragm.

[0053] In this invention, the method for preparing the coating slurry includes: mixing a solvent, a first adhesive material, a second adhesive material, a ceramic material, and optional other additives evenly to obtain the coating slurry.

[0054] Existing coated diaphragms with ceramic and adhesive coatings have complex manufacturing processes, requiring two slurry preparations and two coating processes. This results in poor thickness uniformity and high control difficulty. Furthermore, the adhesive coating uses materials with a wide particle size distribution (0.1–50 μm), making it difficult to control the thickness of the finished diaphragm, leading to low consistency and large thickness tolerances (above ±2 μm). In contrast, the diaphragm preparation method of this invention requires only one slurry preparation and one coating process, simplifying the production process. Moreover, the slurry has high particle size uniformity, making it easier to control the coating thickness uniformity, with tolerances controllable within ±0.8 μm, resulting in good thickness uniformity of the diaphragm.

[0055] Fourthly, the present invention provides a battery comprising at least one of the following: 1) a separator according to the first aspect; 2) a separator prepared by the preparation method of the third aspect; and 3) a coating layer prepared by the coating slurry of the second aspect.

[0056] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of brevity, this invention will not exhaustively list the specific point values ​​included in the range.

[0057] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0058] The diaphragm provided by the present invention has a coating layer made by compounding a second adhesive material with a specific particle size and a ceramic material in a specific amount, and controlling the ratio of the average particle size of the ceramic material to the average particle size of the second adhesive material within a specific range. This is beneficial to improving the heat resistance, adhesion, and thickness uniformity of the diaphragm, and can also ensure that the diaphragm has good air permeability and simplify the diaphragm production process. Attached Figure Description

[0059] Figure 1 This is a 3000x scanning electron microscope image of the second adhesive material A1 in this invention.

[0060] Figure 2 This is a particle size distribution diagram of the second adhesive material A1 in this invention.

[0061] Figure 3This is a differential scanning calorimetry curve of the second adhesive material A1 in this invention.

[0062] Figure 4 This is a 2000x scanning electron microscope image of the coating surface of the diaphragm provided in Embodiment 1 of the present invention.

[0063] Figure 5 This is a schematic diagram of the diaphragm provided in Embodiment 1 of the present invention.

[0064] Wherein, 1-substrate; 2-coating layer; 21-protrusion structure of different heights. Detailed Implementation

[0065] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention.

[0066] All materials used in this invention are commercially available or prepared using conventional methods. Unless otherwise specified, the materials used in this invention are as follows:

[0067] First adhesive material (acrylate polymer): Guangzhou Rongdong New Materials Co., Ltd., brand name 858.

[0068] Wetting and dispersing agent: Dongguan Yingcheng Chemical Co., Ltd., brand name YC-207.

[0069] In this invention, the particle size distribution, Tg, and melting point of the second adhesive material (A) are shown in Table 1; wherein, the second adhesive materials A1 to A9 are polymers synthesized by the following preparation method:

[0070] The preparation methods of A1 include:

[0071] (1) Add 558 parts of deionized water and 1 part of sodium persulfate initiator to the reactor and stir evenly; mix 67 parts of acrylonitrile, 28 parts of butyl acrylate, 3 parts of acrylic acid and 2 parts of divinylbenzene evenly and add them to the reactor, purge with nitrogen for 30 min, and heat to 70℃ for 5 h.

[0072] (2) Mix 67 parts acrylonitrile, 28 parts butyl acrylate, 1.5 parts acrylic acid, 1.5 parts glycidyl methacrylate and 2 parts divinylbenzene evenly to obtain a solution for later use; after the reaction in step (1) is completed, continuously add the solution to the reaction system dropwise for 8 hours, and finally raise the temperature to 75°C and keep it warm for 2 hours to obtain a suspension of uniformly sized adhesive microsphere particles, which is the second adhesive material A1.

[0073] A2

[0074] The only difference between the preparation method of A1 and that of A1 is that the heating reaction temperature in step (1) is adjusted to 4h and the dropping time in step (2) is adjusted to 7h. The other formulations and steps are the same as those of A1.

[0075] A3

[0076] The difference from the preparation method of A1 is that the heating reaction temperature in step (1) is adjusted to 6h; the dropping time in step (2) is adjusted to 9h, and the other formulations and steps are consistent with A1.

[0077] A4

[0078] The difference from the preparation method of A1 is that the heating reaction temperature in step (1) is adjusted to 3h; the dropping time in step (2) is adjusted to 6h, and the other formulations and steps are consistent with A1.

[0079] A5

[0080] The difference from the preparation method of A1 is that the heating reaction temperature in step (1) is adjusted to 5h; the dropping time in step (2) is adjusted to 7h, and the other formulations and steps are consistent with A1.

[0081] A6

[0082] The difference from the preparation method of A1 is that the heating reaction temperature in step (1) is adjusted to 2.5h; the dropping time in step (2) is adjusted to 9h, and the other formulations and steps are consistent with A1.

[0083] A7

[0084] The difference from the preparation method of A1 is that the heating reaction temperature in step (1) is adjusted to 2h; the dropping time in step (2) is adjusted to 10h, and the other formulations and steps are consistent with A1.

[0085] A8

[0086] The difference from the preparation method of A1 is that the monomer raw materials in step (1) include: 75 parts acrylonitrile, 21 parts butyl acrylate, 2.5 parts acrylic acid and 1.5 parts divinylbenzene; the monomer raw materials in step (2) include: 75 parts acrylonitrile, 21 parts butyl acrylate, 1.25 parts acrylic acid, 1.25 parts glycidyl methacrylate and 1.5 parts divinylbenzene; other formulations and steps are consistent with A1.

[0087] A9

[0088] The difference from the preparation method of A1 is that the monomer raw materials in step (1) include: 55 parts acrylonitrile, 38 parts butyl acrylate, 4.5 parts acrylic acid and 2.5 parts divinylbenzene; the monomer raw materials in step (2) include: 55 parts acrylonitrile, 38 parts butyl acrylate, 2.25 parts acrylic acid, 2.25 parts glycidyl methacrylate and 2.5 parts divinylbenzene; other formulations and steps are consistent with A1.

[0089] In this invention, the morphology of the second adhesive material A1 was characterized using scanning electron microscopy, and the results are as follows: Figure 1 As shown, by Figure 1 It can be seen that the particle size distribution of the second adhesive material A1 is relatively uniform; the particle size distribution of the second adhesive material A1 was tested using a particle size analyzer, and the results are as follows. Figure 2 As shown, by Figure 2 It can be seen that the second binder material A1 has a D10 particle size of 3.36 μm, a D50 particle size of 4.77 μm, a D90 particle size of 5.4 μm, and a D99 particle size of 6.51 μm, exhibiting a relatively narrow particle size distribution. The differential scanning calorimetry (DSC) curve of the second binder material A1 is shown below. Figure 3 As shown, by Figure 3 It is known that the glass transition temperature of the second adhesive material A1 is 59.52℃.

[0090] Table 1

[0091] A1 A2 A3 A4 A5 A6 A7 A8 A9 Particle size (μm) 3-7 3-7 3-7 3-7 3-7 3-7 2.5-7.5 3-7 3-7 D10 particle size (μm) 3.36 3.15 3.52 3.05 3.24 3.01 2.88 3.26 3.29 D50 particle size (μm) 4.77 4.82 4.96 4.43 5.38 3.75 5.41 4.82 4.52 D90 particle size (μm) 5.4 5.2 5.6 5.1 5.90 4.96 6.23 5.31 5.34 D99 particle size (μm) 6.51 6.8 6.53 7 6.31 6.95 7.21 6.45 6.56 D99-D10 3.15 3.65 3.01 3.95 3.07 3.94 4.33 3.19 3.27 (D99-D10) / D50 0.66 0.76 0.61 0.89 0.57 1.05 0.8 0.74 0.72 Tg (°C) 59.52 58.91 59.01 60.31 57.64 56.2 63.02 91.51 40 Melting point (°C) 190 189 189 192 185 180 195 260 150

[0092] Example 1

[0093] This embodiment provides a diaphragm, the structural schematic diagram of which is shown below. Figure 5 As shown, the material includes a substrate 1 (7 μm thick, made of Xingyuan material SW807C) and a coating layer 2 disposed on one surface of the substrate. By weight, the coating layer includes 6.67 parts of a first adhesive material, 8.33 parts of a second adhesive material A1, and 83 parts of alumina (average particle size 0.65 μm, made of Shenzhen Xinke Zhonglian Technology Co., Ltd. XKA245N). The ratio of the D50 particle size of the alumina to the D50 particle size of A1 is 0.136. The thickness of the coating layer is 2 μm. The surface of the coating layer has raised structures 21 with different heights, the height of which is 1.36 to 4.51 μm. The raised structures are formed by the second adhesive material.

[0094] This embodiment provides a method for preparing the diaphragm, specifically including the following steps:

[0095] (1) According to the amount of solid content of the coating, the first adhesive material, the second adhesive material Al, alumina, wetting and dispersing agent and deionized water are mixed to obtain a coating slurry with a solid content of 30%; the mass percentage of wetting and dispersing agent in the coating slurry is 0.5%;

[0096] (2) The coating slurry obtained in step (1) is coated on one surface of the substrate and dried at 60°C to obtain the diaphragm.

[0097] In this invention, scanning electron microscopy was used to characterize the surface morphology of the coating layer of the diaphragm, and the results are as follows: Figure 4 As shown; by Figure 4 It can be seen that the surface particles of the diaphragm have high uniformity in particle size and good uniformity in thickness.

[0098] Example 2

[0099] This embodiment provides a diaphragm, the diaphragm comprising a substrate (7 μm thick, Xingyuan material SW807C) and a coating layer disposed on one surface of the substrate; by weight, the coating layer comprises 8.6 parts of a first binder, 6.33 parts of a second binder A2 and 83.5 parts of boehmite (average particle size 0.6 μm, Shandong Guoci Functional Materials Co., Ltd. BG611); the ratio of the D50 particle size of the boehmite to the D50 particle size of A2 is 0.124; the thickness of the coating layer is 1.7 μm; the surface of the coating layer has raised structures of different heights, the height of the raised structures being 1.45–5.1 μm, and the raised structures are formed by the second binder.

[0100] This embodiment provides a method for preparing the diaphragm, which differs from Example 1 in that a slurry with a solid content of 39.5% is prepared, which contains 0.6% wetting and dispersing agent, while the other steps are the same as in Example 1.

[0101] Example 3

[0102] This embodiment provides a diaphragm, which differs from Embodiment 1 only in that, by weight, the coating layer comprises 3.6 parts of a first adhesive material, 21.8 parts of a second adhesive material A1, and 72.7 parts of alumina.

[0103] This embodiment provides a method for preparing the diaphragm, which differs from Example 1 in that a slurry with a solid content of 22% is prepared, containing 0.4% wetting and dispersing agent, while the other steps are the same as in Example 1.

[0104] Examples 4-10

[0105] Examples 4 to 10 each provide a diaphragm, which differs from Example 1 only in that the second adhesive material A1 in the coating layer is replaced with equal masses of second adhesive materials A3, A4, A5, A6, A7, A8, and A9; the other structures and preparation methods are the same as in Example 1.

[0106] Example 11

[0107] This embodiment provides a diaphragm, which differs from Embodiment 1 only in that the thickness of the coating layer is 3 μm and the height of the raised structure is 0.36–3.51 μm. The other structures and preparation methods are the same as in Embodiment 1.

[0108] Example 12

[0109] This embodiment provides a diaphragm, which differs from Embodiment 1 only in that the thickness of the coating layer is 1.2 μm and the height of the raised structure is 2.16–5.31 μm. The other structures and preparation methods are the same as in Embodiment 1.

[0110] Comparative Example 1

[0111] This comparative example provides a diaphragm that differs from Example 1 only in that the second adhesive material A1 in the coating layer has a weight ratio of 0.67 parts, and the slurry solid content in the preparation method is 27.7%. Other structures and preparation methods are the same as in Example 1.

[0112] Comparative Example 2

[0113] This comparative example provides a diaphragm that differs from Example 1 only in that the second adhesive material A1 in the coating layer has a weight of 30 parts, the slurry solid content in the preparation method is 22.5%, and the other structures and preparation methods are the same as in Example 1.

[0114] Comparative Example 3

[0115] This comparative example provides a diaphragm that differs from Example 1 only in that, in the coating layer, alumina is replaced with an equal mass of alumina with an average particle size of 0.4 μm, and the ratio of the D50 particle size of the alumina to the D50 particle size of Al is 0.084; the other structures and preparation methods are the same as in Example 1.

[0116] Comparative Example 4

[0117] This comparative example provides a diaphragm that differs from Example 1 only in that the alumina with an average particle size of 0.65 μm in the coating layer is replaced with alumina with an average particle size of 0.8 μm, and the ratio of the D50 particle size of the alumina to the D50 particle size of Al is 0.168; the other structures and preparation methods are the same as in Example 1.

[0118] Performance testing

[0119] (1) Adhesion: A 25×60mm positive electrode sheet and a 25×150mm separator were cut. The separator and the positive electrode sheet (purchased from Guangdong Zhuguang New Energy Technology Co., Ltd.; NCM523 electrode, where NCM523: carbon black: PVDF = 97.5:1:1.5) were pressed together under hot pressing conditions of 350kgf / 70℃ / 3 seconds to form a sample. The adhesion was measured by peeling the sample at 180° using a stretching machine.

[0120] (2) Heat resistance: According to GB / T36363-2018, the diaphragm was placed in an oven at 130℃ and baked for 1 hour. The dimensional change rate in the MD direction of the diaphragm before and after baking was tested. The larger the value, the worse the performance.

[0121] (3) Air permeability: Refer to GB / T36363-2018 and use an air permeability meter to test the time it takes for 100 mL of gas to pass through the diaphragm.

[0122] (4) Thickness uniformity: The difference between the maximum and minimum thickness values ​​measured according to the test method of thickness deviation in GB / T36363-2018.

[0123] The specific test results are shown in Table 2:

[0124] Table 2

[0125]

[0126]

[0127] As shown in Table 2, the diaphragm provided by the present invention has a coating layer made of a second binder material with a specific content and particle size, which is compounded with the first binder material and ceramic material. The resulting diaphragm has a high adhesion to the positive electrode sheet, with an adhesion force ≥3.66 N / m. After being placed at 130°C for 1 hour, it has a low dimensional change rate, as low as 1.46% or less. It also has good air permeability and good thickness uniformity.

[0128] As can be seen from Comparative Examples 1 to 4, too much or too little content of the second adhesive material, and the D50 particle size ratio of the ceramic material to the second adhesive material not being within a specific range, will lead to a deterioration in the adhesion performance, thermal shrinkage performance, air permeability, or thickness uniformity of the diaphragm.

[0129] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A diaphragm, comprising a substrate and a coating layer disposed on at least one surface of the substrate, characterized in that, By weight, the coating layer comprises 1.5 to 11.5 parts of a first adhesive material, 1.5 to 25 parts of a second adhesive material, and 50 to 95 parts of a ceramic material; the particle size of the second adhesive material is 2.5 to 7.5 μm, and the ratio of the average particle size of the ceramic material to the average particle size of the second adhesive material is 0.12 to 0.

16.

2. The diaphragm according to claim 1, characterized in that, The particle size distribution of the second adhesive material satisfies the following relationship: D99-D10≤4.0μm, and / or, 0.6≤(D99-D10) / D50≤1.

0.

3. The diaphragm according to claim 1 or 2, characterized in that, The monomers of the second adhesive material are selected from any one or at least two of acrylonitrile, methyl methacrylate, methyl acrylate, butyl acrylate, glycidyl methacrylate, divinylbenzene, vinyl acetate, acrylamide, butadiene, or acrylic acid; Preferably, the glass transition temperature of the second adhesive material is 0–92°C; Preferably, the melting point of the second adhesive material is ≥160°C, more preferably 180~250°C.

4. The diaphragm according to any one of claims 1 to 3, characterized in that, The ceramic material has an average particle size of 0.6–0.8 μm; Preferably, the ceramic material includes at least one of alumina, boehmite, barium sulfate, calcium oxide, silicon carbide, or silicon dioxide.

5. The diaphragm according to any one of claims 1 to 4, characterized in that, The first adhesive material comprises a polymer material formed from acrylate monomers; Preferably, the acrylate monomers include at least one of methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, n-propyl acrylate, cyclohexyl acrylate, lauryl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, isobornyl methacrylate, lauryl methacrylate, 2-hydroxyethyl methacrylate, or 2-hydroxypropyl methacrylate.

6. The diaphragm according to claim 5, characterized in that, The thickness of the coating layer is 1.6 to 2.7 μm.

7. The diaphragm according to claim 6, characterized in that, The surface of the coating layer has a raised structure; Preferably, the height of the protrusion structure is 0.4 to 5.3 μm, more preferably 1 to 5 μm.

8. The diaphragm according to any one of claims 1 to 7, characterized in that, The thickness of the substrate is 3–16 μm; Preferably, the substrate includes at least one of a polypropylene substrate, a polyethylene substrate, and a multilayer composite film of polypropylene and polyethylene; Preferably, the substrate includes at least one coated membrane with an inorganic ceramic coating or a polymer coating on its surface.

9. A coating slurry, characterized in that, The coating slurry comprises, by weight percentage, 60-80% solvent, 0.3-5% first binder, 0.3-10% second binder, and 10-38% ceramic material; The particle size of the second adhesive material is 2.5–7.5 μm; the ratio of the average particle size of the ceramic material to the average particle size of the second adhesive material is 0.12–0.

16. Preferably, the second adhesive material satisfies at least one of the following conditions: 1) The particle size distribution of the second adhesive material satisfies the following relationship: D99-D10≤4.0μm, and / or, 0.6≤(D99-D10) / D50≤1.0; 2) The monomers of the second adhesive material are selected from any one or at least two of acrylonitrile, methyl methacrylate, methyl acrylate, butyl acrylate, glycidyl methacrylate, divinylbenzene, vinyl acetate, acrylamide, butadiene, or acrylic acid; 3) The glass transition temperature of the second adhesive material is 0–92°C; 4) The melting point of the second adhesive material is ≥160℃, more preferably 180~250℃; Preferably, the solvent includes at least one of water, acetone, ethanol, and N-methylpyrrolidone; Preferably, the coating slurry further includes 0.3 to 0.7% other additives by weight percentage; Preferably, the other additives include at least one of dispersants, wetting agents, leveling agents, thickeners, or suspending agents.

10. A method for preparing a diaphragm, characterized in that, include: S1. Provide substrate; S2. Prepare the coating slurry as described in claim 9 and coat it on at least one surface of the substrate; S3. Dry the slurry at a temperature of 50-80°C to obtain a diaphragm.

11. A battery, characterized in that, The battery includes at least one of the following: 1) a separator according to any one of claims 1 to 8; 2) a separator prepared by the preparation method according to claim 10; 3) a coating layer prepared by the coating slurry according to claim 9.

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