Tab glue and preparation method thereof, pole piece, battery and electric device

Abstract

The invention relates to tab glue and a preparation method thereof, a pole piece, a battery and an electric device. The tab glue comprises a magnesium fluoride layer and functional layers, and the functional layers are arranged on the surfaces of the two sides in the thickness direction of the magnesium fluoride layer; the magnesium fluoride layer comprises magnesium fluoride and a binder; the functional layer comprises magnesium fluoride, polypropylene and polyvinylidene fluoride. By selecting magnesium fluoride, the heat resistance and mechanical stress tolerance of the tab adhesive are effectively improved, and the tab adhesive can keep a stable structure in a heat sealing process. In addition, on one hand, the polyvinylidene fluoride can enhance the adhesiveness of the tab film so as to prevent the tab film from layering; and on the other hand, polypropylene molecules can be adhered or anchored, so that the problem of battery short circuit caused by polypropylene flow is effectively avoided. According to the tab adhesive provided by the invention, the conditions of liquid leakage and short circuit of a finished battery product caused by a gap at a tab packaging part of the soft package battery can be obviously reduced, the qualification rate of the battery product is effectively improved, and the risk caused by battery failure is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of tab glue films, and in particular to a tab glue and a preparation method thereof, a pole piece, a battery and an electrical device. Background Art

[0002] Power soft-pack batteries have established a dominant position in the current computer, communication and consumer electronics fields due to their light weight, high energy density and excellent safety, and also occupy a significant share in the power lithium battery market.

[0003] In the design of soft-pack batteries, the tabs play a vital role as the key conductor connecting the cathode / anode. In order to effectively prevent the tabs from contacting the metal part of the edge of the aluminum-plastic film, tab glue is usually used between the tabs and the aluminum-plastic film to achieve bonding and insulation. However, the existing tab glue technology faces many difficulties in actual heat sealing: on the one hand, when the packaging temperature is too high, the tab glue is easy to melt, resulting in partial displacement of the tab glue, which in turn causes leakage problems, and even causes the tabs to contact the metal part, resulting in a short circuit in the battery; on the other hand, if there are burrs or impurities on the surface of the tabs, they will also pierce the tab glue, which will also cause the battery to short-circuit and fail. Once a battery short-circuits, a large amount of heat energy will be released in a short period of time, which greatly increases the risk of serious safety accidents such as fire and explosion.

[0004] At present, in order to solve the above problems, the commonly used method is to use high melting point and high mechanical strength materials to compound with the ear glue to improve the melting point, heat resistance and mechanical strength of the ear glue. For example, Chinese patent application CN202110825022.1 uses metallocene to modify the ear glue; Chinese patent application CN2021110294755.7 uses inorganic metal oxide particles such as alumina to mix with the main body of the ear glue material. However, these methods have obvious disadvantages: metallocene polymer molecules have poor melt strength, which can easily lead to melt fracture and other problems during the heat sealing process, bringing new difficulties to maintaining the stability of the ear glue during the heat sealing process; and although metal oxides such as alumina are heat-resistant and have high mechanical strength, they are brittle and easily broken by external forces during hot pressing.

[0005] In summary, although some improvement measures have been taken, the existing technology still has limitations in improving the structural stability of the ear glue. Simply increasing the melting point of the ear glue increases the heat sealing setting temperature of the ear glue, which increases the cost and makes it difficult to control the heat sealing conditions. It also does not solve the problem of easy failure of the ear glue structure.

[0006] Therefore, developing a new type of ear glue that can maintain structural stability and puncture resistance during the heat sealing process is of great significance to improving the overall safety and reliability of the battery. Summary of the invention

[0007] In view of this, the embodiments of the present application provide a tab glue and a preparation method thereof, a pole piece, a battery and an electrical device to solve at least one problem existing in the background technology.

[0008] A first aspect of the present invention provides a tab glue, the tab glue comprising a magnesium fluoride layer (22) and a functional layer (21), wherein the functional layer (21) is arranged on both side surfaces along the thickness direction of the magnesium fluoride layer (22);

[0009] The magnesium fluoride layer (22) comprises magnesium fluoride and a binder; and the functional layer (21) comprises magnesium fluoride, polypropylene and polyvinylidene fluoride.

[0010] Preferably, the tab glue satisfies at least one of the following characteristics (1) to (6):

[0011] (1) The thickness of the magnesium fluoride layer (22) is 15 μm to 25 μm; the magnesium fluoride in the magnesium fluoride layer (22) is magnesium fluoride particles, and the particle size D50 of the magnesium fluoride particles is 50 nm to 500 nm;

[0012] (2) In the magnesium fluoride layer (22), the mass ratio of the magnesium fluoride to the binder is (7-9): (1-3);

[0013] (3) In the magnesium fluoride layer (22), the binder is selected from at least one of polyacrylonitrile, polyvinylidene fluoride and yellow gelatin;

[0014] (4) The thickness of the functional layer (21) is 26 μm to 44 μm;

[0015] (5) The functional layer (21) comprises a base layer (211) and a polyvinylidene fluoride layer (212) disposed on both side surfaces of the base layer (211) in a thickness direction; the base layer (211) comprises magnesium fluoride and polypropylene; the base layer (211) has a thickness of 20 μm to 30 μm; the polyvinylidene fluoride layer (212) has a thickness of 3 μm to 7 μm;

[0016] (6) In the functional layer (21), the mass ratio of magnesium fluoride, polypropylene and polyvinylidene fluoride is (1-3): (14-17): (2-3).

[0017] The second aspect of the present invention provides a method for preparing the ear glue according to the first aspect of the present invention, comprising the following steps:

[0018] S1: preparing a functional layer (21) and a magnesium fluoride layer slurry;

[0019] The step of preparing the functional layer (21) comprises: adding magnesium fluoride particles into a polypropylene melt, cooling to obtain a base layer (211), and spraying polyvinylidene fluoride on both sides of the base layer (211) in a thickness direction to obtain the functional layer (21);

[0020] The step of preparing the magnesium fluoride layer slurry comprises: adding magnesium fluoride into polyacrylonitrile to obtain the magnesium fluoride layer slurry;

[0021] S2: coating the magnesium fluoride layer slurry obtained in step S1 on the functional layer (21), drying to form a magnesium fluoride layer (22), and stacking another layer of the functional layer (21) on the magnesium fluoride layer (22) to obtain the ear glue.

[0022] Preferably, in the step of preparing the functional layer (21), the mass ratio of the magnesium fluoride to the polypropylene melt is (1-3):(14-17).

[0023] Preferably, in the step of preparing the functional layer (21), the polyvinylidene fluoride is a polyvinylidene fluoride aqueous solution, and the mass volume fraction of the polyvinylidene fluoride aqueous solution is 0.15 g / mL to 0.2 g / mL; and after the step of spraying the polyvinylidene fluoride, a drying step is also included.

[0024] Preferably, in the step of preparing the magnesium fluoride layer slurry, the polyacrylonitrile is a polyacrylonitrile aqueous solution, and the concentration of the polyacrylonitrile aqueous solution is 10wt% to 14wt%; the mass ratio of the magnesium fluoride to the polyacrylonitrile is (7 to 9): (1 to 3).

[0025] Preferably, in step S2, the coating method is gravure coating; and the stacking is hot pressing stacking.

[0026] The third aspect of the present invention provides a pole piece, the pole piece comprising a pole ear, the pole ear being provided with the pole ear glue provided by the first aspect of the present invention or the pole ear glue prepared by the preparation method provided by the second aspect of the present invention.

[0027] A fourth aspect of the present invention provides a battery, comprising the electrode provided by the third aspect of the present invention.

[0028] A fifth aspect of the present invention provides an electrical device, wherein the electrical device comprises the battery provided by the fourth aspect of the present invention.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] The present invention effectively improves the heat resistance and mechanical stress tolerance of the ear glue by selecting magnesium fluoride that is acid and alkali resistant, chemically stable, has a high melting point, and has high mechanical stress tolerance, which is beneficial for the ear glue to maintain structural stability during the heat sealing process. In addition, the binder polyvinylidene fluoride on the surface of the functional layer can enhance the adhesion of the ear glue on the one hand, and can effectively prevent the delamination of the ear glue; on the other hand, when polypropylene melts, the polypropylene molecules can be adhered or anchored by polyvinylidene fluoride, effectively avoiding the battery short circuit problem caused by the flow of polypropylene.

[0031] The tab glue provided by the present invention can significantly reduce the occurrence of gaps in the tab packaging of soft-pack batteries, leading to leakage and short circuits in finished batteries, effectively improving the qualified rate of battery products and reducing the risk of battery failure. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0033] Figure 1 A schematic diagram of the cross-sectional structure of the tab glue provided in Example 1 of the present application;

[0034] Figure 2 A schematic diagram of the cross-sectional structure of the tab glue and the tab after being connected to each other provided in Example 1 of the present application;

[0035] Figure 3 A schematic diagram of the cross-sectional structure of the functional layer (21) in the ear glue provided in Example 1 of the present application;

[0036] Figure 4 It is a line graph showing the variation of the peel strength of the tab glue obtained in Examples 1 to 3 of the present invention and Comparative Examples 1 to 2 with time in an electrolyte at 85°C.

[0037] Description of Reference Numerals

[0038] 10. Earpiece;

[0039] 21. Functional layer;

[0040] 211, basal layer;

[0041] 212, polyvinylidene fluoride layer;

[0042] 22. Magnesium fluoride layer. DETAILED DESCRIPTION

[0043] In order to make the technical scheme and beneficial effects of the present invention more obvious and easy to understand, the following is a detailed description by listing specific embodiments. Wherein, the drawings are not necessarily drawn to scale, and local features can be enlarged or reduced to more clearly show the details of local features. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. The experimental methods in the following examples that do not specify specific conditions are usually based on conventional experimental conditions. Reagents and raw materials used in the present invention are commercially available unless otherwise specified.

[0044] In the following description, a large number of specific details are given to provide a more thorough understanding of the present application. However, it is obvious to those skilled in the art that the present application can be implemented without one or more of these details. In other examples, in order to avoid confusion with the present application, some technical features known in the art are not described; that is, all features of the actual embodiments are not described here, and well-known functions and steps are not described in detail.

[0045] The purpose of the terms used herein is only to describe specific embodiments and is not intended to be limiting of the present application. When used herein, the singular forms "one", "an" and "said / the" are also intended to include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "consisting of" and / or "comprising", when used in this specification, determine the presence of the features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0046] In order to thoroughly understand the present application, detailed steps and detailed structures will be presented in the following description to illustrate the technical solution of the present application. The preferred embodiments of the present application are described in detail below, but in addition to these detailed descriptions, the present application may also have other implementation methods.

[0047] Unless otherwise defined, technical and scientific terms used in this application have the same meanings as those in the technical field to which this application belongs.

[0048] If no specific techniques or conditions are specified in the following examples, the conventional techniques or conditions described in the literature in the art, or the conditions recommended by the product instructions and the manufacturer are generally used. The numerical ranges in the following examples all include the endpoint values.

[0049] At present, the tab glue used in power batteries is generally composed of two modified polypropylene layers on the surface and a middle skeleton polypropylene layer. The modification of the polypropylene layer is generally to improve the melting point and mechanical strength of the tab glue, which does not fundamentally solve the problem of flow displacement when the tab glue is melted. In addition, the introduction of some modified materials also brings melt fracture, material breakage and other problems to the tab glue heat sealing. The increase in the melting point of the tab glue increases the set temperature of the tab glue heat sealing, which also makes it difficult to control the heat sealing conditions, and the problem of easy failure of the tab glue structure has not yet been solved.

[0050] In view of this, the present invention provides the following technical solutions:

[0051] [Ear glue]

[0052] The first aspect of the present invention provides a tab glue, the tab glue comprising a magnesium fluoride layer 22 and a functional layer 21, the functional layer 21 being arranged on both side surfaces along the thickness direction of the magnesium fluoride layer 22;

[0053] The magnesium fluoride layer 22 includes magnesium fluoride and a binder; and the functional layer 21 includes magnesium fluoride, polypropylene and polyvinylidene fluoride.

[0054] In the present invention, the ear glue is improved by selecting magnesium fluoride which is resistant to acid and alkali, chemically stable, has a high melting point and high mechanical stress tolerance, thereby effectively improving the heat resistance and mechanical stress tolerance of the functional layer 21, thereby enhancing the tensile strength at break, elongation at break and puncture resistance of the ear glue, which is beneficial for the ear glue to maintain structural stability during the heat sealing process, thereby withstanding the stress and high temperature during the heat sealing process.

[0055] In addition, the binder polyvinylidene fluoride on the surface of the functional layer 21 can, on the one hand, strengthen the adhesion between the magnesium fluoride and the polypropylene structure; on the other hand, when polyvinylidene fluoride contacts polypropylene, the fluorine atoms on the polyvinylidene fluoride molecules and the hydrogen atoms in the polypropylene molecules will have electrostatic interactions, thereby forming hydrogen bonds and van der Waals forces, thereby promoting the polyvinylidene fluoride and polypropylene to bond together, and then when the polypropylene melts, it can be adhered or anchored by the polyvinylidene fluoride, effectively avoiding the battery short circuit problem caused by the flow of polypropylene. Furthermore, polyvinylidene fluoride can also improve the adhesion between the ear glue layers, which can not only prevent the ear glue from stratifying, but also strengthen the connection between the ear and the aluminum-plastic film, which can effectively improve the stability of the battery.

[0056] Therefore, the tab glue provided by the present invention can significantly reduce the occurrence of gaps in the tab packaging of soft-pack batteries, leading to leakage and short circuits in finished batteries, effectively improving the qualified rate of battery products and reducing the risk of battery failure.

[0057] In some embodiments, the thickness of the magnesium fluoride layer 22 is 15 μm to 25 μm, for example, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm or 25 μm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0058] In some embodiments, the magnesium fluoride in the magnesium fluoride layer 22 is magnesium fluoride particles.

[0059] In certain embodiments, the particle size D50 of the magnesium fluoride particles is 50 nm to 500 nm, for example, 50 nm, 75 nm, 100 nm, 125 nm, 150 nm, 175 nm, 200 nm, 225 nm, 250 nm, 275 nm, 300 nm, 325 nm, 350 nm, 375 nm, 400 nm, 425 nm, 450 nm, 475 nm or 500 nm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0060] In some embodiments, in the magnesium fluoride layer 22, the mass ratio of the magnesium fluoride to the binder is (7-9):(1-3), for example, 7:1, 7:2, 7:3, 8:1, 8:2, 8:3, 9:1, 9:2 or 9:3, but is not limited to the listed ratios, and other unlisted values ​​within the ratio range are also applicable.

[0061] In some embodiments, in the magnesium fluoride layer 22, the binder is selected from at least one of polyacrylonitrile, polyvinylidene fluoride and yellow gelatin.

[0062] In certain embodiments, in the magnesium fluoride layer 22, the binder is selected from polyacrylonitrile.

[0063] In some embodiments, the thickness of the functional layer 21 is 26μm to 44μm, for example, 26μm, 27μm, 28μm, 29μm, 30μm, 31μm, 32μm, 33μm, 34μm, 35μm, 36μm, 37μm, 38μm, 39μm, 40μm, 41μm, 42μm, 43μm or 44μm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0064] In some embodiments, the functional layer 21 includes a base layer 211 and a polyvinylidene fluoride layer 212 disposed on both side surfaces of the base layer 211 in a thickness direction; the base layer 211 includes magnesium fluoride and polypropylene.

[0065] In some embodiments, the thickness of the base layer 211 is 20 μm to 30 μm, for example 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm or 30 μm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0066] In some embodiments, the thickness of the polyvinylidene fluoride layer 212 is 3 μm to 7 μm, such as 3 μm, 4 μm, 5 μm, 6 μm or 7 μm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0067] In some embodiments, in the functional layer 21, the mass ratio of magnesium fluoride, polypropylene and polyvinylidene fluoride is (1-3):(14-17):(2-3), for example 1:14:2, 1:14:3, 1:15:2, 1:15:3, 1:16:2, 1:16:3, 1:17:2, 1:17:3, 2:14:2, 2:14:3, 2:15:2, 2:15:3, 2:16:2, 2:16:3, 2:17:2, 2:17:3, 3:14:2, 3:14:3, 3:15:2, 3:15:3, 3:16:2, 3:16:3, 3:17:2 or 3:17:3, but is not limited to the listed ratios, and other values ​​not listed within the ratio range are also applicable.

[0068] [Preparation method of ear glue]

[0069] The second aspect of the present invention provides a method for preparing the ear glue according to the first aspect of the present invention, comprising the following steps:

[0070] S1: preparing a functional layer 21 and a magnesium fluoride layer slurry;

[0071] The step of preparing the functional layer 21 comprises: adding magnesium fluoride particles into a polypropylene melt, cooling to obtain a base layer 211, and spraying polyvinylidene fluoride on both sides of the base layer 211 in a thickness direction to obtain the functional layer 21;

[0072] The step of preparing the magnesium fluoride layer slurry comprises: adding magnesium fluoride into polyacrylonitrile to obtain the magnesium fluoride layer slurry;

[0073] S2: coating the magnesium fluoride layer slurry obtained in step S1 on the functional layer 21, drying to form a magnesium fluoride layer 22, and stacking another layer of the functional layer 21 on the magnesium fluoride layer 22 to obtain the ear glue.

[0074] In certain embodiments, in the step of preparing the functional layer 21, the mass ratio of the magnesium fluoride to the polypropylene melt is (1-3):(14-17), for example, 1:14, 1:15, 1:16, 1:17, 2:14, 2:15, 2:16, 2:17, 3:14, 3:15, 3:16 or 3:17, but is not limited to the listed ratios, and other unlisted values ​​within the ratio range are also applicable.

[0075] In certain embodiments, in the step of preparing the functional layer 21, the polyvinylidene fluoride is a polyvinylidene fluoride aqueous solution.

[0076] In certain embodiments, the mass volume fraction of the polyvinylidene fluoride aqueous solution is 0.15 g / mL to 0.2 g / mL, for example 0.15 g / mL, 0.16 g / mL, 0.17 g / mL, 0.18 g / mL, 0.19 g / mL or 0.2 g / mL, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0077] In certain embodiments, after the step of spraying polyvinylidene fluoride, a drying step is also included.

[0078] In certain embodiments, in the step of preparing the magnesium fluoride layer slurry, the polyacrylonitrile is a polyacrylonitrile aqueous solution.

[0079] In certain embodiments, the concentration of the polyacrylonitrile aqueous solution is 10 wt% to 14 wt%, for example 10 wt%, 11 wt%, 12 wt%, 13 wt% or 14 wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0080] In certain embodiments, the mass ratio of the magnesium fluoride to the polyacrylonitrile is (7-9):(1-3), for example 7:1, 7:2, 7:3, 8:1, 8:2, 8:3, 9:1, 9:2 or 9:3, but is not limited to the listed ratios, and other unlisted values ​​within the ratio range are also applicable.

[0081] In certain embodiments, in step S2, the coating method is gravure coating.

[0082] In certain embodiments, in step S2, the stacking is performed by heat pressing.

[0083] [Pole piece]

[0084] The third aspect of the present invention provides a pole piece, the pole piece comprising a pole ear, the pole ear being provided with the pole ear glue provided by the first aspect of the present invention or the pole ear glue prepared by the preparation method provided by the second aspect of the present invention.

[0085] It should be understood that since the pole piece provided in the present application includes a pole ear, the pole ear is provided with the pole ear glue provided by the first aspect of the present invention or the pole ear glue prepared by the preparation method provided by the second aspect of the present invention, so the beneficial effects of the pole ear glue and its preparation method described in any of the above embodiments are applicable to the pole piece.

[0086] [Battery]

[0087] A fourth aspect of the present invention provides a battery, comprising the electrode provided by the third aspect of the present invention.

[0088] In some embodiments, the battery may be a secondary battery or a primary battery, preferably a secondary battery. For example, the battery may be a sodium ion battery, a lithium ion battery, a potassium ion battery, etc., but is not limited thereto. The battery structure of the present application includes but is not limited to a soft-pack battery, a square hard-shell battery, or a cylindrical hard-shell battery, etc.

[0089] It should be understood that, since the battery provided in the present application includes the pole piece provided in the third aspect of the present invention, the beneficial effects of the ear glue and the preparation method thereof described in any of the above embodiments are applicable to the pole piece.

[0090] [Electrical devices]

[0091] A fifth aspect of the present invention provides an electrical device, wherein the electrical device comprises the battery provided by the fourth aspect of the present invention.

[0092] The use of the battery of the present application is not particularly limited, and it can be used for any electrical device known in the prior art. In some embodiments, the battery of the present application can be used for, but not limited to, laptop computers, pen-input computers, mobile computers, e-book players, portable phones, portable fax machines, portable copiers, portable printers, head-mounted stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini-discs, transceivers, electronic notepads, calculators, memory cards, portable recorders, radios, backup power supplies, motors, cars, motorcycles, power-assisted bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries, drones, and capacitors, etc.

[0093] It should be understood that, since the battery provided in the present application includes the battery provided in the fourth aspect of the present invention, the beneficial effects of the ear glue and the preparation method thereof described in any of the above embodiments are applicable to the electrode.

[0094] The method of the present invention is described below by means of specific examples. It should be understood that these examples are used to illustrate the basic principles, main features and advantages of the present invention, and the present invention is not limited to the scope of the following examples; the implementation conditions adopted in the examples can be further adjusted according to specific requirements, and the implementation conditions not specified are usually the conditions in routine experiments.

[0095] Example 1

[0096] Step S101

[0097] Magnesium fluoride particles with a particle size D50 of 75 nm are fully dispersed in a polypropylene melt at a mass ratio of 10%:80% (magnesium fluoride:polypropylene), and after cooling and solidification, a base layer 211 (thickness of 25 μm, the mass ratio of magnesium fluoride to polypropylene in the base layer is 1:8) is obtained; then a polyvinylidene fluoride aqueous solution with a mass volume fraction of 0.175 g / mL is sprayed on both sides of the base layer, and after drying, a functional layer 21 (thickness of 35 μm, wherein the thickness of the polyvinylidene fluoride layer 212 on one side of the functional layer is 5 μm, and the magnesium fluoride:polypropylene:polyvinylidene fluoride in the functional layer = 10%:80%:10%) is obtained;

[0098] The magnesium fluoride particles of 50nm to 500nm are dispersed in a 12wt% polyacrylonitrile aqueous solution to obtain a slurry of the magnesium fluoride layer (wherein the mass ratio of magnesium fluoride to polyacrylonitrile is 75%:25%).

[0099] Step S102

[0100] The magnesium fluoride layer slurry prepared in step S101 is coated on one side of the functional layer 21 by gravure coating, and is formed into a magnesium fluoride layer 22 (with a thickness of 20 μm) after oven drying, and then a layer of functional layer 21 is superimposed on the other side of the magnesium fluoride layer 22 by hot pressing to obtain the ear glue.

[0101] Example 2

[0102] The only difference between Example 2 and Example 1 is that the thickness of the functional layer in Example 2 is 33 μm, wherein the thickness of the polyvinylidene fluoride layer on one side of the functional layer is 4 μm.

[0103] Example 3

[0104] The only difference between Example 3 and Example 1 is that the mass ratio of the functional layer components in Example 3 is 5%:85%:10% (magnesium fluoride:polypropylene:polyvinylidene fluoride).

[0105] Comparative Example 1

[0106] The ear glue structure is stacked with three polypropylene layers from the outside to the inside, with thicknesses of 35 μm, 20 μm, and 35 μm respectively.

[0107] Comparative Example 2

[0108] The ear glue structure is stacked with three layers of polyvinylidene fluoride / polypropylene from the outside to the inside, with thicknesses of 35μm, 20μm, and 35μm respectively. The polyvinylidene fluoride / polypropylene layer is obtained by spraying a polyvinylidene fluoride aqueous solution with a mass volume fraction of 0.175g / mL on both sides of the polypropylene layer and then drying it (the single-side spray thickness of the polyvinylidene fluoride is 5μm).

[0109] Performance Testing

[0110] 1. High temperature resistance test

[0111] The ear glue obtained in Examples 1 to 3 and Comparative Examples 1 to 2 was immersed in an 85°C electrolyte (the electrolyte was a mixture of dimethyl carbonate and ethylene carbonate in a ratio of 1:1 as a solvent, and lithium hexafluorophosphate was added as a lithium salt; the concentration of lithium hexafluorophosphate in the electrolyte was 1.6M), and the ear glue was taken out at regular intervals, washed and dried to observe whether it was stratified, and the peel strength test was performed according to the national standard GB2792-1998. The results are shown in Table 1, and the peel strength change curve over time is shown in Table 1. Figure 4 shown.

[0112] Table 1

[0113] Test specimen Layering Example 1 1800 hours without delamination Example 2 1800 hours without delamination Example 3 1800 hours without delamination Comparative Example 1 Delamination occurred at 990 hours Comparative Example 2 Delamination occurred at 1740 hours

[0114] It can be seen from Table 1 that compared with the comparative example 1, in which the ear glue was stratified after 990 hours, the ear glue prepared in Examples 1 to 3 of the present application did not stratify after 1800 hours of immersion in the electrolyte. This shows that the functional layer in Examples 1 to 3 of the present application contains polyvinylidene fluoride, which can anchor the polypropylene molecules through the intermolecular force between polyvinylidene fluoride and polypropylene, thereby effectively improving the adhesion of the functional layer 21 and avoiding the problem of polypropylene melting and flowing when heated; and effectively improving the adhesion between the ear glue layers to prevent stratification between the ear glue layers.

[0115] Depend on Figure 1 It can be seen that, compared with Comparative Examples 1 to 2, the peel strength of the tab glue prepared in Examples 1 to 3 of the present application decreases more slowly over time after being immersed in the electrolyte, which indicates that the tab glue prepared in the examples of the present application has strong high temperature resistance. This is because magnesium fluoride improves the heat resistance of the functional layer, which is beneficial for the tab glue to maintain structural stability during the heat sealing process.

[0116] 2. Tensile strength at break, elongation at break and puncture resistance test

[0117] The tensile strength at break, elongation at break and puncture resistance of the tab glue obtained in Examples 1 to 3 and Comparative Examples 1 to 2 were tested. The tensile strength at break and elongation at break were tested in accordance with ASTM D638 standard; the puncture resistance test was performed at a speed of 100 mm / min, using a puncture needle with a radius of 0.5 mm and a top spherical radius of 0.5 mm to pierce the tab glue material fixed in a ring shape with a radius of 0.5 mm. The test results are shown in Table 2.

[0118] Table 2

[0119] Test specimen <![CDATA[Tensile strength at break (N / mm 2 )]]> Elongation at break <![CDATA[Puncture resistance (N / mm 2 )]]> Example 1 0.95 18.2 0.67 Example 2 0.93 17.9 0.66 Example 3 0.90 17.5 0.51 Comparative Example 1 0.89 17.3 0.51 Comparative Example 2 0.89 17.4 0.52

[0120] It can be seen from Table 2 that compared with comparative examples 1 to 2, the ear glue prepared in Examples 1 to 3 of the present application has stronger tensile strength at break, elongation at break and puncture resistance. This is because the functional layer of the ear glue of the present application contains magnesium fluoride, which acts to improve the mechanical stress resistance of the modified polypropylene layer, thereby improving the tensile strength at break, elongation at break and puncture resistance of the ear glue, which is beneficial for the ear glue to maintain structural stability during the heat sealing process and withstand the stress during the heat sealing process.

[0121] It should be understood that the above embodiments are exemplary and are not intended to include all possible implementations included in the claims. Various modifications and changes may be made on the basis of the above embodiments without departing from the scope of the present disclosure. Similarly, the various technical features of the above embodiments may be arbitrarily combined to form other embodiments of the present invention that may not be explicitly described. Therefore, the above embodiments only express several implementations of the present invention and do not limit the scope of protection of the patent of the present invention.

Claims

1. A tip glue, characterized in that: The tab glue comprises a magnesium fluoride layer (22) and a functional layer (21), wherein the functional layer (21) is arranged on both side surfaces of the magnesium fluoride layer (22) in a thickness direction; The magnesium fluoride layer (22) comprises magnesium fluoride and a binder; and the functional layer (21) comprises magnesium fluoride, polypropylene and polyvinylidene fluoride.

2. The ear glue according to claim 1, characterized in that: The tab glue satisfies at least one of the following characteristics (1) to (6): (1) The thickness of the magnesium fluoride layer (22) is 15 μm to 25 μm; the magnesium fluoride in the magnesium fluoride layer (22) is magnesium fluoride particles, and the particle size D50 of the magnesium fluoride particles is 50 nm to 500 nm; (2) In the magnesium fluoride layer (22), the mass ratio of the magnesium fluoride to the binder is (7-9): (1-3); (3) In the magnesium fluoride layer (22), the binder is selected from at least one of polyacrylonitrile, polyvinylidene fluoride and yellow gelatin; (4) The thickness of the functional layer (21) is 26 μm to 44 μm; (5) The functional layer (21) comprises a base layer (211) and a polyvinylidene fluoride layer (212) disposed on both side surfaces of the base layer (211) in a thickness direction; the base layer (211) comprises magnesium fluoride and polypropylene; the base layer (211) has a thickness of 20 μm to 30 μm; the polyvinylidene fluoride layer (212) has a thickness of 3 μm to 7 μm; (6) In the functional layer (21), the mass ratio of magnesium fluoride, polypropylene and polyvinylidene fluoride is (1-3): (14-17): (2-3).

3. A method for preparing the ear glue according to claim 1 or 2, characterized in that: The preparation method comprises the following steps: S1: preparing a functional layer (21) and a magnesium fluoride layer slurry; The step of preparing the functional layer (21) comprises: adding magnesium fluoride particles into a polypropylene melt, cooling to obtain a base layer (211), and spraying polyvinylidene fluoride on both sides of the base layer (211) in a thickness direction to obtain the functional layer (21); The step of preparing the magnesium fluoride layer slurry comprises: adding magnesium fluoride into polyacrylonitrile to obtain the magnesium fluoride layer slurry; S2: coating the magnesium fluoride layer slurry obtained in step S1 on the functional layer (21), drying to form a magnesium fluoride layer (22), and stacking another layer of the functional layer (21) on the magnesium fluoride layer (22) to obtain the ear glue.

4. The preparation method according to claim 3, characterized in that: In the step of preparing the functional layer (21), the mass ratio of the magnesium fluoride to the polypropylene melt is (1-3):(14-17).

5. The preparation method according to claim 3, characterized in that: In the step of preparing the functional layer (21), the polyvinylidene fluoride is a polyvinylidene fluoride aqueous solution, and the mass volume fraction of the polyvinylidene fluoride aqueous solution is 0.15g / mL to 0.2g / mL; after the step of spraying the polyvinylidene fluoride, a drying step is also included.

6. The preparation method according to claim 3, characterized in that: In the step of preparing the magnesium fluoride layer slurry, the polyacrylonitrile is a polyacrylonitrile aqueous solution, and the concentration of the polyacrylonitrile aqueous solution is 10wt% to 14wt%; the mass ratio of the magnesium fluoride to the polyacrylonitrile is (7 to 9): (1 to 3).

7. The preparation method according to claim 3, characterized in that: In step S2, the coating method is gravure coating; and the stacking is hot pressing stacking.

8. A pole piece, characterized in that: The pole piece includes a pole ear, and the pole ear glue according to claim 1 or 2 or the pole ear glue prepared by the preparation method according to any one of claims 3-7 is arranged on the pole ear.

9. A battery, characterized in that: The battery comprises the pole piece as claimed in claim 8.

10. An electrical device, characterized in that: The electric device comprises the battery as claimed in claim 9.

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