Adhesion substance, adhesive composition, positive electrode sheet, secondary battery, and electrical apparatus

Abstract

Provided in the present application are an adhesion substance, an adhesive composition, a positive electrode sheet, a secondary battery and an electrical apparatus. The adhesion substance comprises an adhesive, the adhesive comprising structural units A, structural units B, structural units C and structural units D. At least part of the structural units A are cross-linked with at least part of the structural units D, the structural units A being of formula (1). The structural units B are each independently any one or more of formula (2), formula (3), formula (4), formula (5) or formula (6), and optionally, the structural units B are formula (1) or formula (2). The structural units C are each independently any one of formula (7) or formula (8), m1 and m2 being each independently an integer of 1-20, and optionally, m1 being independently an integer of 2-12, and m2 being independently an integer of 8-12. The structural units D are each independently any one or more of formula (9), n1 being independently an integer of 1-20, optionally, n1 being any integer from 1 to 12, and further optionally, n1 being any integer from 1 to 6.

Description

Adhesive material, adhesive composition, positive electrode sheet, secondary battery and electrical device

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese patent application No. 202311027156.4 filed on August 15, 2023, entitled “Adhesive material, adhesive composition, positive electrode sheet, secondary battery and electrical device,” the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present application relates to the field of battery technology, and in particular to an adhesive material, an adhesive composition, a positive electrode sheet, a secondary battery, and an electrical device. Background Art

[0004] Secondary-ion batteries (such as lithium-ion or sodium-ion batteries) are new energy batteries with advantages such as high operating voltage, high specific capacity, long charge-discharge life, and no memory effect. At the same time, the safety of secondary-ion batteries is becoming a growing concern. During the routine secondary-ion battery manufacturing process, abnormal cells may appear, such as zero resistance during assembly short-circuit testing, low formation voltage, high self-discharge, and large module voltage differential. Disassembling finished batteries reveals punctures in the diaphragm corresponding to the blank area at the edge of the cell's positive electrode. Analysis reveals that metal particles generated during the laser cutting process are sputtered into the blank area, causing foreign matter to penetrate the corresponding diaphragm. This can lead to a large voltage differential in the cell at best, and even a short circuit, resulting in serious accidents. Furthermore, when the cell is inserted into the shell, the bending of the tab can cause the base of the tab to contact the blank area at the edge of the positive electrode, which can also cause a short circuit.

[0005] To solve the above problems, providing an insulating rubber layer on the edge of the positive electrode of the battery cell is very helpful in avoiding the occurrence of the above short circuit problem.

[0006] Summary of the Invention

[0007] The present application provides an adhesive material, an adhesive composition, a positive electrode plate, a secondary battery and an electrical device to solve the problem of poor wear resistance of insulating glue at the edge of the positive electrode plate.

[0008] The first aspect of the present application provides an adhesive material, comprising an adhesive, wherein the adhesive comprises a structural unit A, a structural unit B, a structural unit C and a structural unit D, at least part of the structural unit A is cross-linked with at least part of the structural unit D, wherein the structural unit A is The structural units B are each independently Any one or more of, optionally, structural unit B is The structural units C are each independently Any one of, each m1 and each m2 are independently any integer from 1 to 20, optionally, m1 are independently any integer from 2 to 12, m2 are independently any integer from 8 to 12; the structural unit D is independently Any one or more of, n1 is each independently any integer from 1 to 20, optionally, n1 is any integer from 1 to 12, further optionally n1 is any integer from 1 to 6.

[0009] Structural unit B is provided by acrylonitrile monomer, which is a hard monomer that can enhance the strength of the insulating adhesive layer; structural unit C is provided by acrylate monomer, which is a soft monomer that can improve the flexibility of the insulating adhesive layer and enhance the adhesion between the insulating adhesive layer and the current collector.

[0010] Structural units A and D form a three-dimensional cross-linked network through hydrogen bonding, which makes the resulting insulating adhesive layer have excellent wear resistance. It can isolate the effective contact and friction between the base of the tab and the edge of the positive electrode sheet caused by the bending of the tab when the battery cell is placed in the shell, effectively controlling the problem of short circuit between the tab and the positive electrode film layer. On the other hand, the above-mentioned structural units A, C and D are all polymers of acrylic monomers. The acrylic substances therein are resistant to high temperatures and are not easy to decompose. Therefore, the insulating adhesive layer formed can prevent the current collector of the positive electrode sheet from being directly cut by the laser, effectively resisting the splash of metal particles. In addition, the laser cutting in the insulating adhesive layer is not easy to produce metal molten beads, effectively alleviating the problem of metal particles splashing and penetrating the diaphragm caused by direct laser cutting of the current collector. At the same time, the above-mentioned three-dimensional cross-linked network further enhances the resistance to laser cutting, better realizing the protection of the diaphragm.

[0011] In any embodiment of the first aspect of the present application, at least part of the structural unit A, at least part of the structural unit B, at least part of the structural unit C and at least part of the structural unit D are chain-linked to form a first chain structure, and at least part of the structural unit A, at least part of the structural unit C and at least part of the structural unit D are chain-linked to form a second chain structure; at least part of the structural unit A in the first chain structure is cross-linked with at least part of the structural unit D in the second chain structure; and at least part of the structural unit D in the first chain structure is cross-linked with at least part of the structural unit A in the second chain structure.

[0012] The first chain structure and the second chain structure contain structural units A and D at the same time, providing more sites for the cross-linking of structural units A and structural units D, thereby further improving the density of the formed three-dimensional network and better improving the wear resistance of the adhesive; the first chain structure contains structural units A, structural units B, structural units C and structural units D at the same time, which is more conducive to adjusting the strength provided by the chain structure by utilizing the content of structural units B and structural units C; the second chain structure contains structural units A, structural units C and structural units D at the same time, and has better flexibility, which can be used to more flexibly adjust the content of structural unit C, and thus more flexibly adjust the bonding force of the adhesive.

[0013] In any embodiment of the first aspect of the present application, the adhesive material satisfies any one or more of the following conditions: 1) the wear resistance of the insulating adhesive layer with a thickness of 3μm-7μm formed by the adhesive material meets the following requirements: tested by an RCA paper tape wear tester, using a 55g weight and a flat tape for 300mm and 2 turns to form an experimental area, taking n test points in the experimental area and the spacing between the test points is not less than 2cm, the number of non-leaking points in the experimental area accounts for more than 30%, where 5≤n≤100, or the area of ​​non-leaking points in the experimental area is more than 60% of the total area of ​​the experimental area; 2) the cohesive force of the insulating adhesive layer formed by the adhesive material is 620N / m-750N / m, optionally 660N / m-725N / m; 3) the Shore hardness of the insulating adhesive layer formed by the adhesive material is 45HA-80HA, optionally 50HA-65HA; 4) the bonding force of the insulating adhesive layer formed by the adhesive material is 30N / m-90N / m, optionally 40N / m-80N / m.

[0014] In any embodiment of the first aspect of the present application, in the adhesive, the molar ratio of structural unit D to structural unit A is 0.5:1-5:1, optionally 0.5:1-3:1, and further optionally 1:1-3:1; optionally, the molar content of structural unit A is 4%-50%, optionally 4%-10%, and the molar content of structural unit D is 1%-50%, optionally 5%-30%, and further optionally 5%-15%. This maximizes the crosslinking of structural units A and D to improve the wear resistance of the insulating adhesive layer formed by the adhesive.

[0015] In any embodiment of the first aspect of the present application, in the adhesive, the molar ratio of structural unit C to structural unit B is 1:1-300:1, optionally 5:1-50:1; optionally, the molar content of structural unit B is 0.2%-20%, optionally 1%-5%; optionally, the molar content of structural unit C is 1%-90%, optionally 55%-90%, and further optionally 75%-80%. By controlling the ratio of structural unit B to structural unit C, the bonding strength of the adhesive can be improved as much as possible.

[0016] In any embodiment of the first aspect of the present application, the adhesive substance further comprises an insulating filler and / or a dispersant. The carboxyl groups in the adhesive substance can form hydrogen bonds with the insulating filler to improve the adhesion of the formed insulating adhesive layer.

[0017] In any embodiment of the first aspect of the present application, the weight ratio of the insulating filler, the binder, and the dispersant is (70-90):(10-25):0.4. This reduces costs by utilizing the insulating filler, and the dispersant improves the dispersion of the insulating filler in the binder while preventing interference with subsequent cross-linking of the binder. Furthermore, sufficient binder is available to provide good adhesion.

[0018] In any embodiment of the first aspect of the present application, the insulating filler includes any one or more of alumina, magnesium oxide, silicon dioxide, titanium dioxide, barium titanate, aluminum nitride, silicon nitride, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, mica, talc, boehmite, zeolite, apatite, kaolin, or glass powder. The aforementioned insulating fillers have different hardnesses, with boehmite having a more moderate hardness, thereby improving the stability of the insulating adhesive layer without negatively impacting the battery separator due to its hardness.

[0019] In any embodiment of the first aspect of the present application, the volume average particle size D of the insulating filler is V 50≤1μm. Insulating fillers within this particle size range can be completely embedded in an insulating layer of conventional thickness, thereby effectively controlling the friction of the insulating filler on the diaphragm.

[0020] In any embodiment of the first aspect of the present application, the adhesive substance further includes a solvent; optionally, the solid content of the adhesive substance is 20%-40%; optionally, the solvent of the adhesive substance includes water; optionally, the viscosity of the adhesive substance measured at 25°C and 12rpm is 350mPa·s-900mPa·s.

[0021] The second aspect of the present application provides an adhesive composition, comprising an adhesive, wherein the adhesive comprises a first adhesive and a second adhesive, wherein the first adhesive is a polymer, comprising a structural unit A, a structural unit B, a structural unit C and a structural unit D, and the second adhesive is a polymer, comprising a structural unit A, a structural unit C and a structural unit D, wherein the structural unit A is The structural units B are each independently Any one or more of, optionally, structural unit B is The structural unit C of the first binder and the structural unit C of the second binder are each independently Each m1 and each m2 are independently any integer from 1 to 20, for example, m1 is 1, 2, 3, 4, 5, 6, 8, 10, 12, 13, 14, 15, 16, 18 or 20, and m1 is 1, 2, 3, 4, 5, 6, 8, 10, 12, 13, 14, 15, 16, 18 or 20; alternatively, m1 is independently any integer from 2 to 12, and m2 is independently any integer from 8 to 12; the structural unit D of the first adhesive and the structural unit D of the second adhesive are independently n1 is each independently any integer from 1 to 20, optionally n1 is each independently any integer from 1 to 12; further optionally n1 is each independently any integer from 1 to 6.

[0022] When the adhesive composition is applied to the positive electrode plate to prepare the insulating adhesive layer, the structural unit B in the first adhesive is provided by an acrylonitrile monomer, which is a hard monomer and can enhance the strength of the insulating adhesive layer; the structural unit C in the first adhesive and the second adhesive is provided by an acrylate monomer, which is a soft monomer and can improve the flexibility of the insulating adhesive layer and enhance the bonding force between the insulating adhesive layer and the current collector.

[0023] At the same time, on the one hand, the structural unit A in the first adhesive and the structural unit D in the second adhesive, as well as the structural unit D in the first adhesive and the structural unit A in the second adhesive, interact through hydrogen bonds to form a three-dimensional cross-linked network, so that the formed insulating adhesive layer has excellent wear resistance, can isolate the effective contact and friction between the base of the tab and the edge of the positive electrode sheet caused by the bending of the tab when the battery cell is placed in the shell, and effectively control the problem of short circuit between the tab and the positive electrode film layer. On the other hand, the first adhesive and the second adhesive of the adhesive composition are both polymers of acrylic monomers, and the acrylic substances therein are resistant to high temperatures and are not easy to decompose. Therefore, the insulating adhesive layer formed can prevent the current collector of the positive electrode sheet from being directly cut by the laser, effectively resisting the splash of metal particles. Moreover, the laser cutting in the insulating adhesive layer is not easy to produce metal molten beads, effectively alleviating the problem of metal particles splashing and penetrating the diaphragm caused by direct laser cutting of the current collector; at the same time, the above-mentioned three-dimensional cross-linked network further enhances the resistance to laser cutting, and better realizes the protection of the diaphragm.

[0024] In any embodiment of the second aspect, the weight ratio of the first adhesive to the second adhesive is 1:2.5-1:20, and can optionally be 1:5-1:17.5. The second adhesive provides the insulating adhesive layer with good adhesion and flexibility, while an appropriate amount of the first adhesive enhances the strength of the insulating adhesive layer, thereby better aligning it with the strength of the insulating filler in the adhesive composition and the strength of the positive electrode current collector, thereby fully maximizing the adhesion. Furthermore, the aforementioned weight ratio is used to regulate the density of the cross-linked network of the insulating adhesive layer, providing sufficient network support for wear resistance and protection of the current collector.

[0025] In any embodiment of the second aspect, the first adhesive satisfies any one or more of the following conditions: 1) the molar content of structural unit A in the first adhesive is 5%-30%; 2) the molar content of structural unit B in the first adhesive is 5%-85%; 3) the molar content of structural unit C in the first adhesive is 5%-85%; and 4) the molar content of structural unit D in the first adhesive is 5%-15%. The hardness of the first adhesive is adjusted by adjusting the content of structural unit B and structural unit C to meet the hardness requirements of the insulating adhesive layer for different designs and different processing methods. The content of the above-mentioned structural unit A and structural unit D is relatively small among all the structural units, mainly used to form a cross-linked network with the second adhesive, while also effectively controlling the self-crosslinking of the two in the first adhesive.

[0026] In any embodiment of the second aspect, the second binder satisfies any one or more of the following conditions: 1) the molar content of structural unit A in the second binder is 5%-10%; 2) the molar content of structural unit C in the second binder is 70%-85%; and 3) the molar content of structural unit D in the second binder is 5%-20%. Structural unit C constitutes a major proportion of the second binder, thereby providing the second binder with greater flexibility and adhesion, thereby improving the adhesion of the insulating adhesive layer formed by the binder composition to the insulating filler and the positive electrode current collector.

[0027] In any embodiment of the second aspect, the first adhesive has a weight-average molecular weight of 500,000 to 1.5 million; further, optionally, the difference in weight-average molecular weight between the first adhesive and the second adhesive is 100,000 to 1.5 million. This effectively suspends the insulating filler, effectively preventing the insulating filler from settling and enhancing the bonding strength of the insulating adhesive layer.

[0028] In any embodiment of the second aspect, the adhesive material further comprises an insulating filler and / or a dispersant. The carboxyl groups of the first adhesive and the second adhesive can form hydrogen bonds with the insulating filler to improve the adhesion of the formed insulating adhesive layer.

[0029] In any embodiment of the second aspect of the present application, the weight ratio of the insulating filler, the binder, and the dispersant is (70-90):(10-25):0.4. This reduces costs by utilizing the insulating filler, and the dispersant improves the dispersion of the insulating filler in the binder while preventing interference with subsequent cross-linking of the binder. Furthermore, sufficient binder is available to provide good adhesion.

[0030] In any embodiment of the second aspect, the insulating filler includes any one or more of alumina, magnesium oxide, silicon dioxide, titanium dioxide, barium titanate, aluminum nitride, silicon nitride, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, mica, talc, boehmite, zeolite, apatite, kaolin or glass powder; optionally, the volume average particle size D of the insulating filler is V 50≤1μm. Insulating fillers within this particle size range can be completely embedded in an insulating layer of conventional thickness, thereby effectively controlling the friction of the insulating filler on the diaphragm.

[0031] In any embodiment of the second aspect, the dispersant includes one or more of polyacrylate compounds, fatty alcohol polyether compounds, or polyether-modified silicone compounds.

[0032] In any embodiment of the second aspect, the adhesive composition further comprises a solvent; optionally, the solid content of the adhesive composition is 20%-40%; further optionally, the solvent of the adhesive composition comprises water.

[0033] In a third aspect of the present application, a positive electrode plate is provided, comprising: a positive electrode current collector, at least one side of the positive electrode current collector having a positive electrode film layer region and a hollow foil region; a positive electrode film layer, arranged in the positive electrode film layer region of the positive electrode current collector; and an insulating adhesive layer, arranged in the hollow foil region of the positive electrode current collector, wherein the insulating adhesive layer is formed by using any one of the adhesive materials of the first aspect above, or is formed by curing any one of the adhesive compositions of the second aspect above.

[0034] The insulating adhesive layer exhibits excellent wear resistance, isolating the tab base from contact and friction with the positive electrode edge caused by the tab bending during cell insertion, effectively preventing short circuits between the tab and the positive electrode film. Furthermore, the insulating adhesive layer protects the positive electrode current collector from direct laser cutting, effectively preventing metal particle splash. Furthermore, laser cutting through the insulating adhesive layer is less likely to produce metal molten beads, effectively mitigating the risk of metal particles penetrating the separator due to direct laser cutting of the current collector. Furthermore, the three-dimensional cross-linked network further enhances resistance to laser cutting, further protecting the separator.

[0035] In any embodiment of the third aspect, the thickness of the insulating adhesive layer is less than or equal to the thickness of the positive electrode film layer. Optionally, the thickness of the insulating adhesive layer is 3 μm-7 μm.

[0036] The fourth aspect of the present application provides a method for preparing a positive electrode plate, including a process of setting a positive electrode film layer and an insulating adhesive layer on at least one side or both sides of a positive electrode current collector, wherein the process of setting the insulating adhesive layer includes: mixing the components of any one of the adhesive compositions of the first aspect to form an adhesive solution; coating the adhesive solution on the empty foil area of ​​the positive electrode current collector to obtain a preform with the adhesive solution; heating the preform with the adhesive solution to obtain an insulating adhesive layer, and the heating temperature is optionally 90°C-120°C to accelerate the removal of the solvent therein.

[0037] In any embodiment of the fourth aspect, the process of mixing the components of the adhesive composition to form a slurry comprises: mixing the dispersant in the adhesive composition with water to form a first dispersion, optionally, mixing as a first stirring, the first stirring time is 5min-30min, and the stirring speed is 200rpm-400rpm; mixing the first dispersion with the insulating filler in the adhesive composition to form a second dispersion, optionally, mixing as a second stirring, the second stirring time is 30min-120min, and the stirring speed is 1200rpm-1800rpm; mixing the second dispersion with the first adhesive in the adhesive composition to form a third dispersion, optionally, mixing as a third stirring, the third stirring time is 15min-60min, and the stirring speed is 400rpm-700rpm; mixing the third dispersion with the second adhesive in the adhesive composition to form a glue, optionally, mixing as a fourth stirring, the fourth stirring time is 5min-30min, and the stirring speed is 200rpm-400rpm.

[0038] The fifth aspect of the present application provides a secondary battery, comprising a positive electrode plate, wherein the positive electrode plate comprises any one of the positive electrode plates provided in the third aspect or a positive electrode plate prepared by any one of the preparation methods provided in the fourth aspect.

[0039] A sixth aspect of the present application provides an electrical device including a secondary battery, wherein the secondary battery includes any one of the secondary batteries provided in the fifth aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the drawings without creative work.

[0041] FIG1 is a side view of a positive electrode sheet provided in one embodiment of the present application.

[0042] FIG. 2 is a schematic diagram of a secondary battery according to an embodiment of the present application.

[0043] FIG. 3 is an exploded view of the secondary battery according to the embodiment of the present application shown in FIG. 2 .

[0044] FIG4 is a schematic diagram of a battery module according to an embodiment of the present application.

[0045] FIG5 is a schematic diagram of a battery pack according to an embodiment of the present application.

[0046] FIG. 6 is an exploded view of the battery pack shown in FIG. 5 according to an embodiment of the present application.

[0047] FIG. 7 is a schematic diagram of an electric device using a secondary battery as a power source according to an embodiment of the present application.

[0048] In the drawings, the drawings are not drawn to scale.

[0049] Description of reference numerals:

[0050] 10 positive electrode sheet; 11 positive electrode current collector; 12 positive electrode film layer; 13 insulating rubber layer;

[0051] 1 battery pack; 2 upper case; 3 lower case; 4 battery module; 5 secondary battery; 51 housing; 52 electrode assembly; 53 top cover assembly. DETAILED DESCRIPTION

[0052] The following detailed description of the embodiments of the present application is provided in conjunction with the accompanying drawings and examples. The following detailed description of the embodiments and the accompanying drawings are used to illustrate the principles of the present application, but are not intended to limit the scope of the present application, that is, the present application is not limited to the described embodiments.

[0053] Below, the embodiments of the adhesive material, adhesive composition, positive electrode sheet, secondary battery and electrical device of the present application are described in detail with appropriate reference to the drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0054] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0055] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0056] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0057] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0058] If there is no special explanation, the "include" and "comprising" mentioned in this application are open-ended. For example, the "include" and "comprising" may mean that other components not listed may also be included or comprised.

[0059] Unless otherwise specified, the term "or" is inclusive in this application. For example, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0060] [Adhesive material]

[0061] Secondary-ion batteries are subject to vibration during operation. This vibration causes relative movement between the tabs in the battery cell, leading to internal friction. However, conventional insulating adhesive layers are not sufficiently wear-resistant, and this relative movement can cause coating wear and electrode foil leakage, potentially leading to internal short circuits in the battery cell.

[0062] In order to solve the above problems, in the first embodiment of the present application, an adhesive material is provided, including an adhesive, the adhesive including structural unit A, structural unit B, structural unit C and structural unit D, at least part of structural unit A is cross-linked with at least part of structural unit D, wherein structural unit A is The structural units B are each independently Any one or more of, optionally, structural unit B is The structural units C are each independently Any one of, each m1 and each m2 are independently any integer from 1 to 20, optionally, m1 are independently any integer from 2 to 12, m2 are independently any integer from 8 to 12; the structural unit D is independently Any one or more of, n1 is each independently any integer from 1 to 20, optionally, n1 is any integer from 1 to 12, further optionally n1 is any integer from 1 to 6.

[0063] In the adhesive of the above-mentioned adhesive material, structural unit B is provided by acrylonitrile monomer, which is a hard monomer that can enhance the strength of the insulating adhesive layer; structural unit C is provided by acrylate monomer, which is a soft monomer that can improve the flexibility of the insulating adhesive layer and enhance the bonding force between the insulating adhesive layer and the current collector.

[0064] At the same time, structural units A and D interact through hydrogen bonds to form a three-dimensional cross-linked network, which makes the resulting insulating adhesive layer have excellent wear resistance. This can isolate the effective contact and friction between the base of the tab and the edge of the positive electrode sheet caused by the bending of the tab when the battery cell is placed in the shell, effectively controlling the problem of short circuit between the tab and the positive electrode film layer. On the other hand, the above-mentioned structural units A, C and D are all polymers of acrylic monomers. The acrylic substances therein are resistant to high temperatures and are not easy to decompose. Therefore, the insulating adhesive layer formed can prevent the current collector of the positive electrode sheet from being directly cut by the laser, effectively resisting the splash of metal particles. In addition, the laser cutting in the insulating adhesive layer is not easy to produce metal molten beads, effectively alleviating the problem of metal particles splashing and penetrating the diaphragm caused by direct laser cutting of the current collector. At the same time, the above-mentioned three-dimensional cross-linked network further enhances the resistance to laser cutting, better realizing the protection of the diaphragm.

[0065] In some embodiments, at least part of the structural unit A, at least part of the structural unit B, at least part of the structural unit C and at least part of the structural unit D are linked in a chain to form a first chain structure, and at least part of the structural unit A, at least part of the structural unit C and at least part of the structural unit D are linked in a chain to form a second chain structure; at least part of the structural unit A in the first chain structure is cross-linked with at least part of the structural unit D in the second chain structure; at least part of the structural unit D in the first chain structure is cross-linked with at least part of the structural unit A in the second chain structure.

[0066] The first chain structure and the second chain structure contain structural units A and D at the same time, providing more sites for the cross-linking of structural units A and structural units D, thereby further improving the density of the formed three-dimensional network and better improving the wear resistance of the adhesive; the first chain structure contains structural units A, structural units B, structural units C and structural units D at the same time, which is more conducive to adjusting the strength provided by the chain structure by utilizing the content of structural units B and structural units C; the second chain structure contains structural units A, structural units C and structural units D at the same time, and has better flexibility, which can be used to more flexibly adjust the content of structural unit C, and thus more flexibly adjust the bonding force of the adhesive.

[0067] In some embodiments of the present application, the adhesive material meets any one or more of the following conditions: 1) the wear resistance of the insulating adhesive layer with a thickness of 5 μm formed by the adhesive material meets the following requirements: tested using an RCA paper tape wear tester, using a 55g weight and a flat tape for 300mm and 2 turns to form an experimental area, taking n test points in the experimental area and the spacing between the test points is not less than 2cm, the number of non-leaking points in the experimental area accounts for more than 30%, where 5≤n≤100, or the area of ​​non-leaking points in the experimental area is more than 60% of the total area of ​​the experimental area; 2) the cohesive force of the insulating adhesive layer formed by the adhesive material is 620N / m-750N / m, optionally 660N / m-725N / m; 3) the Shore hardness of the insulating adhesive layer formed by the adhesive material is 45HA-80HA, optionally 50HA-65HA; 4) the bonding force of the insulating adhesive layer formed by the adhesive material is 30N / m-90N / m, optionally 40N / m-80N / m.

[0068] The test method for the above cohesion is as follows:

[0069] The adhesive substance was prepared into a slurry and applied to the carbon-coated layer of the carbon-coated copper foil. After drying, a sample sheet was obtained. One side of the sample sheet was copper foil, and the other side was an adhesive layer formed by the adhesive substance. The sample sheet was then cut into strips sized 2 cm wide and 6 cm long. The copper foil side of the strip was adhered to the surface of a hard substrate (steel plate) using 3M-55230H double-sided tape (taking care to avoid bubbles during the adhesion process). The adhesive layer of the fixed strip was adhered to the 3M-55230H double-sided tape, and the surface of the double-sided tape was covered with copper foil of the same size as the double-sided tape (taking care to avoid bubbles during the adhesion process). The double-sided tape used was the same size as the strip to obtain the test sample.

[0070] Manually peel the copper foil and double-sided tape from the first end of the test sample in a 180° angle, leaving a distance extending 1 cm beyond the first end (i.e., the second end) of the entire test sample. Use a clamp on one end of the tensile testing machine to secure the first end (hard substrate, carbon-coated copper foil, and adhesive layer); use a clamp on the other end of the tensile testing machine to secure the second end.

[0071] The tensile testing machine was set to a tensile speed of 50 mm / min and a tensile length of 100 mm for testing. The peel force data obtained during the test is the cohesive force of the coating material.

[0072] The test method for the above hardness is as follows: the hardness of the surface of the insulating rubber layer is tested using a Shore A hardness tester.

[0073] The test method for the above-mentioned adhesion is as follows:

[0074] Specifically:

[0075] Take the positive electrode to be tested. The positive electrode must be in good appearance. No products with bad appearance are allowed. Use a blade to cut a sample of the positive electrode with an insulating adhesive layer that is 20mm wide and 100-160mm long. Stick the special double-sided tape NITTO.NO5000NS on the steel plate. The tape is 10mm wide and 90-150mm long. Fix a paper tape with a width equal to the width of the sample and a length 80-200mm greater than the length of the sample on the double-sided tape, and set wrinkle adhesive on the paper tape. Stick the fixed-size sample cut above on the wrinkle adhesive with the insulating adhesive layer facing down. Then use a 3kg pressure roller to roll the sample surface in the same direction three times to obtain the test sample. Fix the test sample on the testing machine. Use the lower clamp to fix the end of the steel plate without the electrode. Fold the paper tape upward and fix it with the upper clamp. Keep the sample axis consistent with the direction of the force. Load the sample at a peeling speed of 10mm / min until the sample breaks. Stop the test and record the maximum load force as F (unit: N). The sample width L = 20mm. Based on f1 = F / L, calculate the peel strength f1 (unit: N / m). Peel strength is the adhesive force.

[0076] In some embodiments of the present application, in the above-mentioned adhesive, the molar ratio of structural unit D to structural unit A is 0.5:1-5:1, such as: 0.5:1, 1:1, 1.1:1, 2:1, 2.1:1, 2.2:1, 2.5:1, 2.7:1, 2.8:1, 2.9:1, 3:1, 3.2:1, 3.5:1, 3.8:1, 4:1, 4.5:1 or 5:1, optionally 0.5:1-3:1, further optionally 1:1-3:1; optionally, the molar content of structural unit A is The molar content of the structural unit D is 4%-50%, such as 4%, 4.5%, 4.8%, 5%, 5.3%, 5.5%, 6%, 6.2%, 6.4%, 6.8%, 7%, 10%, 15%, 20%, 30%, 40%, or 50%, and can be optionally 4%-10%. The molar content of the structural unit D is 1%-50%, such as 1%, 4%, 5%, 6%, 8%, 10%, 13%, 14%, 15%, 20%, 30%, 40%, or 50%, and can be optionally 5%-30%, and further can be optionally 5%-15%. In this way, the crosslinking of the structural units A and D is utilized as much as possible to improve the wear resistance of the insulating adhesive layer formed by the adhesive material.

[0077] In some embodiments of the present application, in the above-mentioned adhesive, the molar ratio of structural unit C to structural unit B is 1:1-300:1, such as: 1:1, 5:1, 10:1, 15:1, 20:1, 25:1, 30:1, 35:1, 40:1, 45:1, 50:1, 60:1, 100:1, 150:1, 200:1, 250:1, 280:1, 290:1 or 300:1; optionally 5:1-50:1; the molar content of the structural unit B is 0.2%-20%, such as 0.2%, The molar content of structural unit C is 1%-90%, such as 5%, 10%, 20%, 30%, 40%, 45%, 50%, 55%, 58%, 60%, 68%, 70%, 75%, 77%, 78%, 80%, 85% or 90%, and can be 55%-90%, further 75%-80%. The ratio of structural unit B to structural unit C is controlled to improve the adhesion of the adhesive material as much as possible.

[0078] In some embodiments of the present application, the above-mentioned adhesive material also includes an insulating filler and / or a dispersant. The use of the insulating filler reduces the cost, and the dispersant promotes the dispersion effect of the insulating filler in the adhesive; and the carboxyl group of the above-mentioned structural unit A can form hydrogen bonds with the insulating filler to improve the adhesion of the formed insulating adhesive layer.

[0079] In some embodiments of the present application, the ratio of insulating filler, adhesive, and dispersant can be referenced to the composition of conventional adhesives. In some embodiments, the weight ratio of insulating filler, adhesive, and dispersant is (70-90):(10-25):0.4. This reduces costs by utilizing the insulating filler, while the dispersant improves the dispersion of the insulating filler in the adhesive while preventing subsequent cross-linking of the adhesive. Furthermore, sufficient adhesive is present to provide good bonding strength.

[0080] The insulating filler can be the insulating filler commonly used in adhesives. Considering that the adhesive composition is used in the positive electrode plate and needs to withstand laser radiation later, the insulating filler can be selected from a heat-resistant and electrochemically stable inorganic material that does not soften or melt at a temperature above 600°C, typically above 700°C, for example, above 900°C, and can insulate the positive electrode from the negative electrode.

[0081] In some embodiments, the insulating filler includes one or more of alumina, magnesium oxide, silicon dioxide, titanium dioxide, barium titanate, aluminum nitride, silicon nitride, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, mica, talc, boehmite, zeolite, apatite, kaolin, or glass powder. These insulating fillers have varying hardnesses, with boehmite having a more moderate hardness, which improves the stability of the insulating adhesive layer without negatively impacting the battery separator due to its hardness.

[0082] In some embodiments, in order to further improve the dispersion effect of the insulating filler in the adhesive while avoiding the influence of the filler particle size being too large on the diaphragm, optionally, the D of the insulating filler V 50 Particle size ≤ 1 μm. Insulating fillers within this particle size range can be completely embedded in an insulating layer of conventional thickness, effectively controlling the friction of the insulating filler on the diaphragm. The above-mentioned Dv50 represents the volume average particle size, which refers to the particle size corresponding to the cumulative volume distribution percentage of the material reaching 50%. The testing method can refer to the standard GB / T 19077-2016 and be measured using a laser particle size analyzer (such as the Malvern Master Size 3000).

[0083] The dispersant used in the adhesive material of this application can be selected from conventional dispersants that facilitate the dispersion of insulating fillers. In some embodiments, the dispersant includes one or more of polyacrylate compounds, fatty alcohol polyether compounds, and polyether-modified silicone compounds, such as Chemadd-6004 from Yueyang Kaimen Waterborne Additive Co., Ltd. and Elaecpure LW-10 from Dow Chemical. When no solvent is included, the adhesive material is more convenient to package and transport; when a solvent is included, the adhesive material is more convenient to use. Different solid content adhesives have different viscosities, different application properties, and different curing conditions. Those skilled in the art can select the solid content based on the application requirements. In some embodiments, the solid content of the adhesive material can optionally be 20%-40% to improve application and curing efficiency. Optionally, the adhesive material has a viscosity of 550 mPa·s measured at 25°C and 12 rpm.

[0084] In some embodiments, in order to save costs and improve the safety of the operating environment, the solvent of the adhesive material further optionally includes water, that is, a water-based adhesive is provided.

[0085] [Adhesive composition]

[0086] In a second embodiment of the present application, an adhesive composition is provided, comprising an adhesive, wherein the adhesive comprises a first adhesive and a second adhesive, the first adhesive is a polymer comprising structural unit A, structural unit B, structural unit C, and structural unit D, the second adhesive is a polymer comprising structural unit A, structural unit C, and structural unit D,

[0087] Among them, the structural unit A is

[0088] The structural units B are each independently Any one or more of, optionally, structural unit B is The structural unit C of the first adhesive and the structural unit C of the second adhesive are each independently Each m1 and each m2 are independently an integer of 1-20, for example, m1 is 1, 2, 3, 4, 5, 6, 8, 10, 12, 13, 14, 15, 16, 18 or 20, and m1 is 1, 2, 3, 4, 5, 6, 8, 10, 12, 13, 14, 15, 16, 18 or 20; optionally, m1 is independently any integer of 2 to 12, and m2 is independently any integer of 8 to 12; the structural unit D of the first adhesive and the structural unit D of the second adhesive are independently n1 is each independently any integer from 1 to 20, for example, n1 is 1, 2, 3, 4, 5, 6, 8, 10, 12, 13, 14, 15, 16, 18 or 20, and optionally, n1 is each independently any integer from 1 to 12; further optionally, n1 is each independently any integer from 1 to 6.

[0089] When the adhesive composition is applied to the positive electrode plate to prepare the insulating adhesive layer, the structural unit B in the first adhesive is provided by an acrylonitrile monomer, which is a hard monomer and can enhance the strength of the insulating adhesive layer; the structural unit C in the first adhesive and the second adhesive is provided by an acrylate monomer, which is a soft monomer and can improve the flexibility of the insulating adhesive layer and enhance the bonding force between the insulating adhesive layer and the current collector.

[0090] At the same time, on the one hand, the structural unit A in the first adhesive and the structural unit D in the second adhesive, as well as the structural unit D in the first adhesive and the structural unit A in the second adhesive, interact through hydrogen bonds to form a three-dimensional cross-linked network, so that the formed insulating adhesive layer has excellent wear resistance, can isolate the effective contact and friction between the base of the tab and the edge of the positive electrode sheet caused by the bending of the tab when the battery cell is placed in the shell, and effectively control the problem of short circuit between the tab and the positive electrode film layer. On the other hand, the first adhesive and the second adhesive of the adhesive composition are both polymers of acrylic monomers, and the acrylic substances therein are resistant to high temperatures and are not easy to decompose. Therefore, the insulating adhesive layer formed can prevent the current collector of the positive electrode sheet from being directly cut by the laser, effectively resisting the splash of metal particles. Moreover, the laser cutting in the insulating adhesive layer is not easy to produce metal molten beads, effectively alleviating the problem of metal particles splashing and penetrating the diaphragm caused by direct laser cutting of the current collector; at the same time, the above-mentioned three-dimensional cross-linked network further enhances the resistance to laser cutting, and better realizes the protection of the diaphragm.

[0091] In some embodiments of the present application, in order to further improve the overall performance of the insulating adhesive layer formed by the adhesive composition, the weight ratio of the first adhesive to the second adhesive can be selected to be 1:2.5-1:20, for example, 1:17.5, 2:17.5, 4:17.5, 1:5, 2:12.5, 2:15, or 1:10; or optionally 1:5-1:17.5. The amount of the second adhesive used is relatively large relative to the amount of the first adhesive, and the first adhesive is used to provide better adhesion and flexibility to the insulating adhesive layer. At the same time, an appropriate amount of the second adhesive is used to increase the strength of the insulating adhesive layer, thereby better adapting to the strength of the insulating filler in the adhesive composition and the strength of the positive electrode current collector, so that the adhesion is fully exerted. Moreover, the above weight ratio is used to regulate the density of the cross-linked network of the insulating adhesive layer, providing sufficient network support for wear resistance and protection of the current collector.

[0092] The first and second adhesives in the adhesive composition of the present application can both be polymerized from acrylic monomers and acrylic acid derivative monomers corresponding to the aforementioned structural units. The properties of the adhesives vary depending on the content of each structural unit. To adjust the properties of each adhesive and achieve a better synergistic effect between the two adhesives, in some embodiments of the present application, the first adhesive is a copolymer. Optionally, the first adhesive satisfies any one or more of the following conditions: 1) the molar content of structural unit A in the first adhesive is 5%-30%; 2) the molar content of structural unit B in the first adhesive is 5%-85%, optionally 5%-55%; 3) the molar content of structural unit C in the first adhesive is 5%-85%, optionally 35%-85%; and 4) the molar content of structural unit D in the first adhesive is 5%-15%. The hardness of the first adhesive is adjusted by adjusting the content of structural units B and C to meet the hardness requirements of the insulating adhesive layer for different designs and processing methods. The content of structural units A and D is relatively small relative to the total content of all structural units, primarily serving to form a crosslinked network with the second adhesive and also effectively controlling the self-crosslinking of the two structural units in the first adhesive.

[0093] In some embodiments of the present application, the second binder is a copolymer. Optionally, the second binder satisfies any one or more of the following conditions: 1) the molar content of structural unit A in the second binder is 5%-10%; 2) the molar content of structural unit C in the second binder is 70%-85%; and 3) the molar content of structural unit D in the second binder is 5%-20%. Structural unit C constitutes the majority of the second binder, thereby providing the second binder with greater flexibility and adhesion, thereby improving the adhesion of the insulating adhesive layer formed by the binder composition to the insulating filler and the positive electrode current collector.

[0094] The first and second adhesives in the adhesive composition of this application are intended to bond insulating fillers and substrates. Due to gravity, the insulating fillers in the adhesive solution formed by the adhesive composition may settle. Severe settling can affect the adhesion of the insulating adhesive layer to the substrate. In some embodiments of this application, the first adhesive has a weight-average molecular weight of 500,000 to 1.5 million. Having such a weight-average molecular weight results in a high viscosity, effectively suspending the insulating fillers and preventing them from settling, thereby improving the adhesion of the insulating adhesive layer.

[0095] The second adhesive has better flexibility and fluidity, and its suspension effect on the insulating filler is not as good as the first adhesive. However, the second adhesive also has the characteristics of a conventional polymer, that is, its viscosity increases with the increase of molecular weight. In some embodiments, the adhesive liquid formed by the adhesive composition still using the second adhesive provides sufficient fluidity to facilitate construction. Further, optionally, the difference in weight average molecular weight between the first adhesive and the second adhesive is 0-1.5 million. The above difference can be the difference when the weight average molecular weight of the first adhesive is greater than the weight average molecular weight of the second adhesive, or it can be the difference when the weight average molecular weight of the first adhesive is less than the weight average molecular weight of the second adhesive.

[0096] In some embodiments, the adhesive material further comprises an insulating filler and / or a dispersant. The use of the insulating filler in the adhesive composition of the present application reduces the cost of the composition, and the dispersant promotes the dispersion of the insulating filler in the adhesive. In addition, the carboxyl groups can form hydrogen bonds with the insulating filler, thereby improving the adhesion of the resulting insulating adhesive layer.

[0097] The ratio of insulating filler, binder, and dispersant can be referenced to the composition of conventional adhesive compositions. In some embodiments, the weight ratio of insulating filler, binder, and dispersant is (70-90):(10-25):0.4. This reduces costs by utilizing the insulating filler, while the dispersant improves the dispersion of the insulating filler in the adhesive while preventing interference with subsequent cross-linking of the adhesive. Furthermore, sufficient adhesive is available to provide good bonding strength.

[0098] The insulating filler can be the insulating filler commonly used in adhesives. Considering that the adhesive composition is used in the positive electrode plate and needs to withstand laser radiation later, the insulating filler can be selected from a heat-resistant and electrochemically stable inorganic material that does not soften or melt at a temperature above 600°C, typically above 700°C, for example, above 900°C, and can insulate the positive electrode from the negative electrode.

[0099] In some embodiments, the insulating filler includes one or more of alumina, magnesium oxide, silica, titanium dioxide, barium titanate, aluminum nitride, silicon nitride, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, mica, talc, boehmite, zeolite, apatite, kaolin, or glass frit. These insulating fillers have varying hardnesses, with boehmite having a more moderate hardness, which improves the stability of the insulating adhesive layer without negatively impacting the battery separator.

[0100] In some embodiments, in order to further improve the dispersion effect of the insulating filler in the adhesive while avoiding the influence of the filler particle size being too large on the diaphragm, optionally, the D of the insulating filler V50 Particle size ≤ 1μm. Insulating fillers within this particle size range can be completely embedded in an insulating layer of conventional thickness, thereby effectively controlling the friction of the insulating filler on the diaphragm.

[0101] The dispersant used in the adhesive composition of the present application can be selected from conventional dispersants that are conducive to the dispersion of insulating fillers. In some embodiments, the above-mentioned dispersant includes one or more of polyacrylate compounds, fatty alcohol polyether compounds, and polyether-modified silicone compounds, such as Chemadd-6004 of Yueyang Kaimen Water-based Additive Co., Ltd. and Elaecpure LW-10 of Dow Chemical.

[0102] In some embodiments, the adhesive composition further comprises a solvent. When no solvent is included, the packaging and transportation of the adhesive composition are more convenient. When a solvent is included, the adhesive composition is more convenient to use. Adhesive compositions with different solid contents have different viscosities, different coating properties during construction, and different curing conditions. Those skilled in the art can select the solid content based on construction requirements. In some embodiments, the solid content of the adhesive composition is optionally 20%-40% to improve construction and curing efficiency. In some embodiments, in order to save costs and improve the safety of the operating environment, the solvent of the adhesive composition further optionally comprises water, i.e., to provide a water-based adhesive.

[0103] In some embodiments, the wear resistance, cohesion, hardness and adhesion of the adhesive composition also meet the requirements of the above-mentioned adhesive material, which will not be repeated here.

[0104] The first adhesive and the second adhesive used in the adhesive composition of the present application can be prepared by referring to the preparation methods of the prior art or using known materials. In order to facilitate those skilled in the art to implement the present application, the following preparation methods are provided for reference.

[0105] First binder: Dissolve the surfactant in water at 10-30°C, and add monomer A CH2=CHCOOH, monomer B CH2=CHCN, and monomer C CH2=CHCOO(CH2) in sequence. m1 CH3 and monomer D CH2=CHCOO(CH2) n1OH and a chain transfer agent (such as n-dodecyl mercaptan) are uniformly blended, while nitrogen is introduced for deoxygenation protection to form a pre-emulsion. The pre-emulsion is heated to 80°C-90°C to obtain a pre-emulsion. A surfactant (such as dialkyl sulfosuccinate salt M-30S) is dissolved in deionized water, added to a reactor, stirred, deoxygenated with nitrogen, and heated to 80°C-90°C to obtain a reactive surfactant solution. An ammonium persulfate solution is prepared with deionized water as the first initiator solution. The pre-emulsion and the first initiator solution are simultaneously and continuously added dropwise to the reactive surfactant solution in the reactor. After the addition is complete, the mixture is incubated to obtain an acrylic acid (ester) copolymer seed solution. An ammonium persulfate solution is prepared with deionized water as the second initiator solution. The concentration of the second initiator solution is greater than that of the first initiator solution. The second initiator solution is added dropwise to the acrylic acid (ester) copolymer seed solution for 100-150 minutes. After the addition is complete, the mixture is incubated for 1-3 hours to obtain an acrylic acid (ester) copolymer solution. The acrylic acid (ester) copolymer solution in the reactor is cooled to 60-70°C, then cooled naturally to room temperature, and the vacuum is evacuated to a vacuum degree of less than 0.09 MPa for 10-50 minutes. The vacuum is then vented to atmospheric pressure and filtered to obtain a water-based adhesive emulsion. The pH is then adjusted to 7-8.

[0106] Second binder: Dissolve the surfactant in water at 10-30°C, and add monomer A CH2=CHCOOH, monomer C CH2=CHCOO(CH2) in sequence. m1 CH3, monomer D CH2=CHCOO(CH2) n1OH and a chain transfer agent (such as n-dodecyl mercaptan) are uniformly blended, while nitrogen is introduced for deoxygenation protection to form a pre-emulsion. The pre-emulsion is heated to 80°C-90°C to obtain a pre-emulsion. A surfactant (such as dialkyl sulfosuccinate salt M-30S) is dissolved in deionized water, added to a reactor, stirred, deoxygenated with nitrogen, and heated to 80°C-90°C to obtain a reactive surfactant solution. An ammonium persulfate solution is prepared with deionized water as the first initiator solution. The pre-emulsion and the first initiator solution are simultaneously and continuously added dropwise to the reactive surfactant solution in the reactor. After the addition is complete, the mixture is incubated to obtain an acrylic acid (ester) copolymer seed solution. An ammonium persulfate solution is prepared with deionized water as the second initiator solution. The concentration of the second initiator solution is greater than that of the first initiator solution. The second initiator solution is added dropwise to the acrylic acid (ester) copolymer seed solution for 100-150 minutes. After the addition is complete, the mixture is incubated for 1-3 hours to obtain an acrylic acid (ester) copolymer solution. The acrylic acid (ester) copolymer solution in the reactor is cooled to 60-70°C, then cooled naturally to room temperature, and the vacuum is evacuated to a vacuum degree of less than 0.09 MPa for 10-50 minutes. The vacuum is then vented to atmospheric pressure and filtered to obtain a water-based adhesive emulsion. The pH is then adjusted to 7-8.

[0107] [Secondary battery]

[0108] Secondary batteries, also known as rechargeable batteries or storage batteries, are batteries that can be recharged to activate the active materials after discharge and continue to be used.

[0109] Typically, a secondary battery includes a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte. During the battery's charge and discharge process, active ions (such as lithium ions) are embedded and released back and forth between the positive and negative electrode sheets. The separator is set between the positive and negative electrode sheets, mainly to prevent the positive and negative electrodes from short-circuiting, while allowing active ions to pass through. The electrolyte is between the positive and negative electrode sheets, mainly to conduct active ions.

[0110] The adhesive composition can be used in a secondary battery where an adhesive is needed, or as a raw material for a separator. In some embodiments, the adhesive composition is used in a positive electrode sheet.

[0111] [Positive electrode]

[0112] As shown in FIG1 , the positive electrode sheet 10 generally includes a positive electrode current collector 11 and a positive electrode film layer 12 disposed on at least one side of the positive electrode current collector 11 . The positive electrode film layer 12 includes a positive electrode active material.

[0113] As an example, the positive electrode current collector 11 has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer 12 is disposed on either or both of the two opposite surfaces of the positive electrode current collector 11 .

[0114] As shown in FIG1 , in addition to the positive electrode film layer 12, the positive electrode current collector 11 also has a hollow foil region around the positive electrode film layer 12. In some embodiments of the present application, the positive electrode plate 10 further includes an insulating adhesive layer 13 disposed in the hollow foil region of the positive electrode current collector 11. The insulating adhesive layer 13 is formed by curing the adhesive composition provided in any of the above embodiments. The specific location of the insulating adhesive layer 13 in the hollow foil region can be based on existing technology, such as avoiding the base of the open tab.

[0115] The insulating adhesive layer 13 in the positive electrode sheet 10 is formed by curing the adhesive composition described above in the present application. On the one hand, the structural unit A in the first adhesive and the structural unit D in the second adhesive, as well as the structural unit A in the first adhesive and the second adhesive, interact through hydrogen bonds to form a three-dimensional cross-linked network, which makes the insulating adhesive layer have excellent wear resistance and can isolate the effective contact and friction between the base of the tab and the edge of the positive electrode sheet caused by the bending of the tab when the battery cell is placed in the shell, effectively controlling the problem of short circuit between the tab and the positive electrode film layer. On the other hand, the first adhesive and the second adhesive of the adhesive composition are both polymers of acrylic monomers, and the acrylic substances therein are resistant to high temperatures and are not easy to decompose. Therefore, the insulating adhesive layer can prevent the current collector of the positive electrode sheet from being directly cut by the laser, effectively resisting the splash of metal particles. In addition, the laser cutting in the insulating adhesive layer is not likely to produce metal molten beads, effectively alleviating the problem of metal particles splashing and penetrating the diaphragm caused by direct laser cutting of the current collector. At the same time, the above-mentioned three-dimensional cross-linked network further enhances the resistance to laser cutting, better protecting the diaphragm.

[0116] Furthermore, the carboxyl groups of the first and second adhesives can form hydrogen bonds with the insulating filler, thereby improving the adhesion of the insulating adhesive layer. The structural unit B in the first adhesive is provided by acrylonitrile monomer, a hard monomer that enhances the strength of the insulating adhesive layer. The structural unit C in the first and second adhesives is provided by acrylate monomers, a soft monomer that increases the flexibility of the insulating adhesive layer and strengthens the adhesion between the insulating adhesive layer and the current collector.

[0117] The thickness of the insulating adhesive layer 13 of the positive electrode sheet 10 can be based on conventional thicknesses of insulating adhesive layers, or can be set according to the design requirements of the battery. In some embodiments, the thickness of the insulating adhesive layer 13 is less than or equal to the thickness of the positive electrode film layer 12. Optionally, the thickness of the insulating adhesive layer 13 is 3 μm to 7 μm. This can protect the positive electrode current collector 11 while preventing an increase in battery cell volume due to an excessively thick insulating adhesive layer 12.

[0118] The insulating adhesive layer can be formed by conventional techniques, such as coating. In some embodiments, the insulating adhesive layer comprises: mixing an adhesive composition to form an adhesive solution; coating the adhesive solution on the hollow foil area of ​​the positive electrode current collector to form a preform having the adhesive solution; and heating the preform having the adhesive solution to form the insulating adhesive layer, optionally at a temperature of 90°C to 120°C to accelerate solvent removal.

[0119] In some embodiments, in order to improve the uniformity of mixing of the components in the adhesive composition, the process of mixing the adhesive composition to form a slurry includes:

[0120] Mixing the dispersant in the adhesive composition with water to form a first dispersion, optionally, mixing is a first stirring, the first stirring time is 5 min-30 min, and the stirring speed is 200 rpm-400 rpm;

[0121] Mixing the first dispersion with the insulating filler in the adhesive composition to form a second dispersion, optionally, mixing is a second stirring, the second stirring time is 30 min-120 min, and the stirring speed is 1200 rpm-1800 rpm;

[0122] Mixing the second dispersion with the first adhesive in the adhesive composition to form a third dispersion, optionally, mixing is a third stirring, the third stirring time is 15 min-60 min, and the stirring speed is 400 rpm-700 rpm;

[0123] The third dispersion is mixed with the second adhesive in the adhesive composition to form an adhesive solution. Optionally, the mixing is performed as a fourth stirring step, wherein the fourth stirring step has a time of 5 min to 30 min and a stirring speed of 200 rpm to 400 rpm.

[0124] In the above process, the stirring time and speed do not need to be adjusted according to the objects to be mixed, and stirring is used to improve the mixing effect of the components.

[0125] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0126] In some embodiments, the positive electrode active material may adopt the positive electrode active material for batteries that is well known in the art. As an example, when the secondary battery is a lithium ion secondary battery, the positive electrode active material may include at least one of the following materials: lithium phosphates containing olivine structure, lithium transition metal oxides and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Among them, examples of lithium transition metal oxides may include but are not limited to lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O2) and its modified compounds. Examples of olivine-structured lithium-containing phosphates may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

[0127] When the secondary battery is a sodium-ion secondary battery, as an example, the positive electrode active material of the sodium-ion secondary battery may include at least one of the following materials: a sodium transition metal oxide, a polyanionic compound, and a Prussian blue compound. However, the present application is not limited to these materials, and other conventionally known materials that can be used as positive electrode active materials for sodium-ion batteries may also be used.

[0128] As an optional technical solution of the present application, in the sodium transition metal oxide, the transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce. Sodium transition metal oxide is, for example, Na x MO2, wherein M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr and Cu, and 0<x≤1.

[0129] As an optional technical solution of the present application, the polyanionic compound can be a compound having sodium ions, transition metal ions and tetrahedral (YO4) n‐ A class of compounds with anionic units. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce; Y can be at least one of P, S and Si; n represents (YO4) n‐ valence.

[0130] Polyanionic compounds can also be sodium ions, transition metal ions, tetrahedral (YO4) n‐ A class of compounds containing anion units and halogen anions. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be at least one of P, S, and Si, and n represents (YO4) n‐ valence state; the halogen may be at least one of F, Cl and Br.

[0131] Polyanionic compounds can also be sodium ions, tetrahedral (YO4) n‐ Anion unit, polyhedron unit (ZO y ) m+ and an optional halogen anion. Y can be at least one of P, S and Si, and n represents (YO4) n‐ valence state; Z represents a transition metal, which may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce, and m represents (ZO y ) m+ valence state; the halogen may be at least one of F, Cl and Br.

[0132] Polyanionic compounds include NaFePO4, Na3V2(PO4) (sodium vanadium phosphate, abbreviated as NVP), Na4Fe3(PO4)2(P2O7), NaM'PO4F (M' is one or more of V, Fe, Mn and Ni) and Na3(VO y )2(PO4)2F 3‐2y At least one of (0≤y≤1).

[0133] Prussian blue compounds can be compounds containing sodium ions, transition metal ions, and cyanide ions (CN-). The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. Prussian blue compounds are, for example, Na a Me b Me' c (CN)6, wherein Me and Me' are each independently at least one of Ni, Cu, Fe, Mn, Co and Zn, 0<a≤2, 0<b<1, 0<c<1.

[0134] In some embodiments, the positive electrode film layer may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0135] In some embodiments, the positive electrode film layer may further include a conductive agent. For example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0136] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0137] [Negative electrode]

[0138] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.

[0139] As an example, the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0140] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base material. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0141] In some embodiments, the negative electrode active material may be a negative electrode active material for a battery that is well known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material may be selected from at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0142] In some embodiments, the negative electrode film layer may further include a binder. For example, the binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0143] In some embodiments, the negative electrode film layer may further include a conductive agent. For example, the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0144] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0145] In some embodiments, the negative electrode sheet can be prepared by the following method: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0146] [Electrolytes]

[0147] The electrolyte conducts ions between the positive and negative electrodes. This application does not specify the type of electrolyte, and the electrolyte can be selected based on the needs. For example, the electrolyte can be liquid, gel, or solid.

[0148] In some embodiments, the electrolyte is liquid and includes an electrolyte salt and a solvent.

[0149] In some embodiments, the electrolyte salt for the lithium ion secondary battery may include one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl imide), lithium bis(trifluoromethanesulfonyl imide), lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, or lithium tetrafluorooxalatophosphate. The electrolyte salt for the sodium ion secondary battery may include one or more of sodium hexafluorophosphate (NaPF6), sodium tetrafluoroborate (NaBF4), sodium hexafluoroarsenate (NaAsF6), sodium trifluoroacetate (CF3COONa), sodium trifluoromethanesulfonate (CF3NaO3S, NaOTf), or sodium tetraphenylborate (NaBPh4).

[0150] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0151] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0152] [Isolation film]

[0153] In some embodiments, the secondary battery further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical and mechanical stability can be selected.

[0154] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0155] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0156] In some embodiments, the secondary battery includes a secondary battery cell, or includes a battery module and a battery pack.

[0157] In some embodiments, the secondary battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0158] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the outer packaging of the secondary battery can be a soft shell, such as a pouch-type soft shell. The soft shell can be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0159] The present application has no particular limitation on the shape of the secondary battery cell, which can be cylindrical, square, or any other shape. For example, FIG2 shows a secondary battery cell 5 with a square structure as an example.

[0160] In some embodiments, referring to Figure 3, the outer packaging may include a shell 51 and a cover plate 53. The shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can be formed into an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the secondary battery cell 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0161] In some embodiments, secondary battery cells may be assembled into a battery module. The battery module may contain one or more secondary battery cells. The specific number may be selected by those skilled in the art based on the application and capacity of the battery module.

[0162] Figure 4 shows an example battery module 4. Referring to Figure 4 , within the battery module 4, multiple secondary battery cells 5 may be arranged sequentially along the length of the battery module 4. Of course, they may also be arranged in any other manner. Furthermore, the multiple secondary battery cells 5 may be secured together using fasteners.

[0163] Optionally, the battery module 4 may further include a housing having an accommodation space, and the plurality of secondary battery cells 5 are accommodated in the accommodation space.

[0164] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art based on the application and capacity of the battery pack.

[0165] Figures 5 and 6 illustrate an example battery pack 1. Referring to Figures 5 and 6 , the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box comprises an upper case 2 and a lower case 3. The upper case 2 can be positioned over the lower case 3 to form an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0166] In addition, the present application also provides an electrical device, which includes the secondary battery provided in the present application. The secondary battery can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but is not limited thereto.

[0167] As the electrical device, a secondary battery cell, a battery module or a battery pack can be selected according to its usage requirements.

[0168] Figure 7 shows an example of an electric device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery, a battery pack or battery module can be used.

[0169] [Example]

[0170] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0171] The first binder (structural unit B is ) is prepared as follows:

[0172] At a working temperature of 20°C, 5.4g of reactive surfactant containing double bond group bisalkyl sulfosuccinate salt M-30S was dissolved in 62g of deionized water, and monomer A CH2=CHCOOH, monomer B CH2=CHCN, monomer C CH2=CHCOO(CH2) were added in sequence. m1CH3 and monomer D CH2=CHCOO(CH2) n1 OH, 0.058g of chain transfer agent n-dodecyl mercaptan, were uniformly blended at 350 rpm for 25 minutes, with nitrogen protection at a flow rate of 110 mL / min. This formed a pre-emulsion, which was then heated to 85°C at a rate of 2°C / min and held at this temperature for 30 minutes to obtain a pre-emulsion. 3.8g of the reactive surfactant, dialkylsulfosuccinate salt M-30S, containing a double bond, was dissolved in 61.3g of deionized water and added to a reactor. The mixture was heated at 300 rpm, using nitrogen deoxygenation at a rate of 100 mL / min, and heated to 88°C at a rate of 2°C / min for 30 minutes to obtain a reactive surfactant solution. 3.5g of ammonium persulfate solution was prepared in deionized water as the first initiator solution. The pre-emulsion and first initiator solution were simultaneously and continuously added dropwise to the reactive surfactant solution in the reactor over 160 minutes. The mixture was then held at this temperature for 0.5 hours to obtain a seed solution. Prepare 1.0g of ammonium persulfate initiator solution in deionized water as the second initiator solution. Add the second initiator solution dropwise to the seed solution over a continuous 120-minute dropwise addition. After completion, incubate for 2 hours to obtain an acrylic acid copolymer solution. Cool the acrylic acid copolymer in the reactor to 65°C at a rate of 2°C / min, incubate for 30 minutes, and then naturally cool to room temperature. Vacuum the reactor to a vacuum level below 0.09 MPa for 30 minutes, then vent to atmospheric pressure and filter through a 300-mesh filter cloth to obtain a second adhesive emulsion with a solids content of 50%. The pH is then adjusted to 7-8. The solids content of the first adhesive is 15%.

[0173] The composition of the first adhesive was adjusted by adjusting the composition or amount of each monomer, and the compositions of the obtained first adhesives 1 to 21 are recorded in Table 1-1.

[0174] The first adhesive 22 (structural unit B is ) is prepared as follows:

[0175] At a working temperature of 20°C, 5.4g of reactive surfactant containing double bond group dialkyl sulfosuccinate salt M-30S was dissolved in 62g of deionized water, and monomer A CH2=CHCOOH, monomer B styrene, monomer C CH2=CHCOO(CH2) were added in sequence. m1 CH3 and monomer D CH2=CHCOO(CH2) n1OH, 0.058g of chain transfer agent n-dodecyl mercaptan, were uniformly blended at 350 rpm for 25 minutes, with nitrogen protection at a flow rate of 110 mL / min. This formed a pre-emulsion, which was then heated to 85°C at a heating rate of 2°C / min and held for 30 minutes to obtain a pre-emulsion. 3.8g of the reactive surfactant, dialkylsulfosuccinate salt M-30S, containing a double bond, was dissolved in 61.3g of deionized water and added to a reactor. The mixture was heated at 300 rpm, using nitrogen deoxygenation protection, at a flow rate of 100 mL / min, to 88°C at a heating rate of 2°C / min, and held for 30 minutes to obtain a reactive surfactant solution. 3.5g of ammonium persulfate solution was prepared in deionized water as the first initiator solution. The pre-emulsion and first initiator solution were simultaneously and continuously added dropwise to the reactive surfactant solution in the reactor over 160 minutes, and the mixture was held for 0.5 hours to obtain a seed solution. Prepare 1.0g of ammonium persulfate initiator solution in deionized water as the second initiator solution. Add the second initiator solution dropwise to the seed solution over a continuous 120-minute dropwise addition. After completion, incubate for 2 hours to obtain an acrylic acid copolymer solution. Cool the acrylic acid copolymer in the reactor to 65°C at a rate of 2°C / min, incubate for 30 minutes, and then naturally cool to room temperature. Vacuum the reactor to a vacuum level below 0.09 MPa for 30 minutes, then vent to atmospheric pressure and filter through a 300-mesh filter cloth to obtain a second adhesive emulsion with a solids content of 50%. The pH is then adjusted to 7-8. The solids content of the first adhesive is 15%.

[0176] The first adhesive 23 (structural unit B is ) is prepared as follows:

[0177] At a working temperature of 20°C, 5.4g of reactive surfactant containing double bond group dialkyl sulfosuccinate salt M-30S was dissolved in 62g of deionized water, and monomer A CH2=CHCOOH, monomer B methyl methacrylate, monomer C CH2=CHCOO(CH2) were added in sequence. m1 CH3 and monomer D CH2=CHCOO(CH2) n1OH, 0.058g of chain transfer agent n-dodecyl mercaptan, were uniformly blended at 350 rpm for 25 minutes, with nitrogen protection at a flow rate of 110 mL / min. This formed a pre-emulsion, which was then heated to 85°C at a rate of 2°C / min and held at this temperature for 30 minutes to obtain a pre-emulsion. 3.8g of the reactive surfactant, dialkylsulfosuccinate salt M-30S, containing a double bond, was dissolved in 61.3g of deionized water and added to a reactor. The mixture was heated at 300 rpm, using nitrogen deoxygenation at a rate of 100 mL / min, and heated to 88°C at a rate of 2°C / min for 30 minutes to obtain a reactive surfactant solution. 3.5g of ammonium persulfate solution was prepared in deionized water as the first initiator solution. The pre-emulsion and first initiator solution were simultaneously and continuously added dropwise to the reactive surfactant solution in the reactor over 160 minutes. The mixture was then held at this temperature for 0.5 hours to obtain a seed solution. Prepare 1.0g of ammonium persulfate initiator solution in deionized water as the second initiator solution. Add the second initiator solution dropwise to the seed solution over a continuous 120-minute dropwise addition. After completion, incubate for 2 hours to obtain an acrylic acid copolymer solution. Cool the acrylic acid copolymer in the reactor to 65°C at a rate of 2°C / min, incubate for 30 minutes, and then naturally cool to room temperature. Vacuum the reactor to a vacuum level below 0.09 MPa for 30 minutes, then vent to atmospheric pressure and filter through a 300-mesh filter cloth to obtain a second adhesive emulsion with a solids content of 50%. The pH is then adjusted to 7-8. The solids content of the first adhesive is 15%.

[0178] First adhesive 24 (structural unit C is lauryl methacrylate CH3CH2=CHCOO(CH2) 12 CH3) is prepared as follows:

[0179] At a working temperature of 20°C, 5.4g of reactive surfactant containing double bond group bisalkyl sulfosuccinate salt M-30S was dissolved in 62g of deionized water, and monomer A CH2=CHCOOH, monomer B CH2=CHCN, monomer C CH3CH2=CHCOO(CH2) were added in sequence. 12 CH3 and monomer D CH2=CHCOO(CH2) n1OH, 0.058g of chain transfer agent n-dodecyl mercaptan, were uniformly blended at 350 rpm for 25 minutes, with nitrogen protection at a flow rate of 110 mL / min. This formed a pre-emulsion, which was then heated to 85°C at a rate of 2°C / min and held at this temperature for 30 minutes to obtain a pre-emulsion. 3.8g of the reactive surfactant, dialkylsulfosuccinate salt M-30S, containing a double bond, was dissolved in 61.3g of deionized water and added to a reactor. The mixture was heated at 300 rpm, using nitrogen deoxygenation at a rate of 100 mL / min, and heated to 88°C at a rate of 2°C / min for 30 minutes to obtain a reactive surfactant solution. 3.5g of ammonium persulfate solution was prepared in deionized water as the first initiator solution. The pre-emulsion and first initiator solution were simultaneously and continuously added dropwise to the reactive surfactant solution in the reactor over 160 minutes. The mixture was then held at this temperature for 0.5 hours to obtain a seed solution. Prepare 1.0g of ammonium persulfate initiator solution in deionized water as the second initiator solution. Add the second initiator solution dropwise to the seed solution over a continuous 120-minute dropwise addition. After completion, incubate for 2 hours to obtain an acrylic acid copolymer solution. Cool the acrylic acid copolymer in the reactor to 65°C at a rate of 2°C / min, incubate for 30 minutes, and then naturally cool to room temperature. Vacuum the reactor to a vacuum level below 0.09 MPa for 30 minutes, then vent to atmospheric pressure and filter through a 300-mesh filter cloth to obtain a second adhesive emulsion with a solids content of 50%. The pH is then adjusted to 7-8. The solids content of the first adhesive is 15%.

[0180] Table 1-1

[0181] The molecular weights in Table 1-1 are weight-average molecular weights rounded to the nearest ten thousand. The test method can refer to standard GB / T 21863-2008 and be measured using an ultra-high performance polymer chromatograph.

[0182] The preparation process of the second adhesive is as follows:

[0183] At a working temperature of 20°C, 4.2g (4.2%) of the reactive surfactant containing double bond groups, dialkyl sulfosuccinate salt M-30S, was dissolved in 58g (116%) of deionized water, and monomer A CH2=CHCOOH, monomer C CH2=CHCOO(CH2) were added in sequence. m1 CH3, monomer D CH2=CHCOO(CH2) n1OH, 0.048 g (0.096%) of chain transfer agent n-dodecyl mercaptan, were mixed uniformly at a rotation speed of 300 rpm for 30 minutes, during which nitrogen was introduced for deoxygenation protection at a flow rate of 100 mL / min to form a pre-emulsion, which was then heated to 85°C at a heating rate of 2°C / min and kept warm for 30 minutes to obtain a pre-emulsion. 2.8 g (2.8%) of reactive surfactant M-30S, a double-bond-containing dialkyl sulfosuccinate salt, was dissolved in 51.3 g (102.6%) of deionized water and added to a reactor. The mixture was heated at a rotation speed of 300 rpm, using nitrogen for deoxygenation protection at a flow rate of 100 mL / min, and heated to 86°C at a heating rate of 2°C / min and kept warm for 30 minutes to obtain a reactive surfactant solution. 3g (0.15wt%) of ammonium persulfate solution was prepared with deionized water as the first initiator solution. The pre-emulsion and the first initiator solution were simultaneously and continuously added dropwise to the reactive surfactant solution in a reactor over 150 minutes. The mixture was incubated for 0.5 hours to obtain an acrylic acid copolymer seed solution. 1.0g (0.1wt%) of ammonium persulfate initiator solution was prepared with deionized water as the second initiator solution. The second initiator solution was added dropwise to the acrylic acid copolymer seed solution over 120 minutes. The mixture was incubated for 2 hours to obtain an acrylic acid copolymer solution. The acrylic acid copolymer in the reactor was cooled to 65°C at a rate of 2°C / min, incubated for 30 minutes, and then naturally cooled to room temperature. The reactor was evacuated under reduced pressure to a vacuum of less than 0.09 MPa for 30 minutes, then vented to atmospheric pressure and filtered through a 300-mesh filter cloth to obtain a second adhesive emulsion with a solids content of 50%. The pH was then adjusted to 7-8.

[0184] The composition of the second adhesive was adjusted by adjusting the composition and amount of each monomer, and the compositions of the obtained second adhesives 1 to 12 are recorded in Table 1-2.

[0185] Table 1-2

[0186] The molecular weights in Table 1-2 are weight-average molecular weights rounded to the nearest ten thousand. The test method can refer to the standard GB / T21863-2008 and be measured using an ultra-high performance polymer chromatograph.

[0187] Example 1

[0188] The dispersant was added to deionized water and stirred at 300 rpm for 15 minutes to obtain a first dispersion;

[0189] Add the insulating filler to the first dispersion, and stir at 1500 rpm for 75 minutes to obtain a second dispersion;

[0190] The first adhesive emulsion was added to the second dispersion, and the mixture was dispersed and stirred at 1500 rpm for 60 minutes to obtain a third dispersion;

[0191] The second adhesive emulsion was added to the third dispersion and dispersed at 500 rpm for 60 min to obtain an adhesive solution. The specific materials and amounts of the dispersant, insulating filler, first adhesive, and second adhesive used are recorded in Table 2.

[0192] Examples 2 to 47:

[0193] The corresponding adhesive solution was prepared by referring to the process of Example 1. The specific substances and amounts of the dispersant, insulating filler, first adhesive (dry matter) and second adhesive (dry matter) used in each example are recorded in Table 2.

[0194] Comparative Example 1

[0195] The dispersant was added to deionized water and stirred at 300 rpm for 15 minutes to obtain a first dispersion;

[0196] Add the insulating filler to the first dispersion, and stir at 1500 rpm for 75 minutes to obtain a second dispersion;

[0197] The first adhesive emulsion was added to the above dispersion and stirred at 1500 rpm for 60 min to obtain an adhesive solution. The specific materials and amounts of the dispersant, insulating filler, and first adhesive used are recorded in Table 2.

[0198] Comparative Example 2

[0199] The dispersant was added to deionized water and stirred at 300 rpm for 15 minutes to obtain a first dispersion;

[0200] Add the insulating filler to the first dispersion, and stir at 1500 rpm for 75 minutes to obtain a second dispersion;

[0201] The second adhesive emulsion was added into the second dispersion, and the mixture was dispersed and stirred at 1500 rpm for 60 min to obtain a glue solution.

[0202] The specific materials and amounts of the dispersant, insulating filler and second adhesive used are recorded in Table 2.

[0203] The dispersant used in each embodiment and comparative example is Chemadd-6004 produced by Yueyang Kaimen Waterborne Additive Co., Ltd., with a mass fraction of 0.4 parts.

[0204]

[0205]

[0206]

[0207] Viscosity test: The rotational viscosity of the glue was tested at 25°C and 12 rpm. The results are recorded in Table 3.

[0208] Abrasion resistance test: Use a 5μm scraper to scrape each of the above adhesives onto a 13μm aluminum foil, transfer it to a 100℃ oven for drying, and prepare the insulating adhesive layer to be tested.

[0209] RCA Paper Tape Abrasion Tester (BGD 530, Biugeda Precision Instruments (Guangzhou) Co., Ltd.); Test Principle: A motor drives a paper tape across an area of ​​the test sample surface at a constant speed, applying a certain pressure to abrade the test surface. Test Method: After a 5μm-thick insulating layer is tested and a 55g weight is applied to the flat surface, the tape travels 300mm (two turns). The number of points in the test area that remain intact (a total of 10 points tested) is recorded in Table 3. The area of ​​the leaking points is also recorded to calculate the ratio of the area of ​​the non-leaking points to the total area of ​​the test area.

[0210] Evaluation criteria: Under the same pressure, the longer the paper tape passes without polishing the aluminum foil, the more wear-resistant it is; or under the same tape length, the number of unpolished aluminum foil points tested is the greater the number, the more wear-resistant it is.

[0211] Test of cohesion:

[0212] The adhesive substance was prepared into a slurry and applied to the carbon-coated layer of the carbon-coated copper foil. After drying, a sample sheet was obtained. One side of the sample sheet was copper foil, and the other side was an adhesive layer formed by the adhesive substance. The sample sheet was then cut into strips sized 2 cm wide and 6 cm long. The copper foil side of the strip was adhered to the surface of a hard substrate (steel plate) using 3M-55230H double-sided tape (taking care to avoid bubbles during the adhesion process). The adhesive layer of the fixed strip was adhered to the 3M-55230H double-sided tape, and the surface of the double-sided tape was covered with copper foil of the same size as the double-sided tape (taking care to avoid bubbles during the adhesion process). The double-sided tape used was the same size as the strip to obtain the test sample.

[0213] Manually peel the copper foil and double-sided tape from the first end of the test sample in a 180° angle, leaving a distance extending 1 cm beyond the first end (i.e., the second end) of the entire test sample. Use a clamp on one end of the tensile testing machine to secure the first end (hard substrate, carbon-coated copper foil, and adhesive layer); use a clamp on the other end of the tensile testing machine to secure the second end.

[0214] The tensile testing machine was set to a tensile speed of 50 mm / min and a tensile length of 100 mm. The peel force data obtained during the test is the cohesive force of the coating material. The results are recorded in Table 3.

[0215] Hardness test: The hardness of the insulation layer surface was tested using a Shore A hardness tester. The results are recorded in Table 3.

[0216] Adhesion test:

[0217] The above adhesive solutions were respectively coated on 13 μm aluminum foil using a 5 μm scraper, and then transferred to a 100° C. oven for drying to prepare the insulating adhesive layer to be tested.

[0218] Use a razor blade to cut the aforementioned insulating adhesive layer specimen, 20mm wide and 100-160mm long. Apply NITTO.NO5000NS double-sided tape (20mm wide and 90-150mm long) to the steel plate. Secure a paper tape, the same width as the specimen and 80-200mm longer than the specimen, to the double-sided tape, using corrugated adhesive. Apply the fixed-size specimen to the corrugated adhesive, insulating adhesive layer facing downward. Finally, use a 3kg roller to roll the specimen surface three times in the same direction to obtain the test sample. The test specimen was mounted on a testing machine. The end of the steel plate not attached to the electrode was secured with the lower fixture. The paper tape was folded upward and secured with the upper fixture. The specimen axis was aligned with the direction of the applied force. The test machine applied force at a peeling speed of 10 mm / min until the specimen broke. The test was then stopped. The maximum load force was recorded as F (in Newtons). The specimen width, L, was 20 mm. Based on f1 = F / L, the peel strength, f1 (in Newtons / meter), was calculated. The peel strength is the bond strength. The results are recorded in Table 3.

[0219] Heat resistance test: The TG-DSC technique was used to perform thermogravimetric analysis on the test coating samples, and the thermal decomposition temperatures were recorded in Table 3.

[0220] Table 3

[0221] According to the comparison of each embodiment and the comparative example, it can be seen that the wear resistance of the insulating adhesive layer formed by the adhesive composition of the present application is significantly better than the wear resistance when the first adhesive 1 or the second adhesive 1 is used alone; and the viscosity of the first adhesive 1 is too high, which is not conducive to construction when used alone and the bonding force is too low; the viscosity of the second adhesive 1 is too low, which affects the construction performance and thus affects the film-forming effect.

[0222] It can be seen from the comparison of Example 2, Examples 4 and 5, and the comparison of Example 1, Examples 6 to 9 that when the content of structural unit B in the first adhesive increases and the content of structural unit C decreases, that is, the content of hard monomer structural units in the first adhesive increases, the bonding force of the corresponding adhesive composition decreases.

[0223] Although the present application has been described with reference to preferred embodiments, various modifications may be made thereto and components may be substituted with equivalents without departing from the scope of the present application. In particular, the various technical features described in the various embodiments may be combined in any manner as long as there are no structural conflicts. The present application is not limited to the specific embodiments disclosed herein, but encompasses all technical solutions within the scope of the claims.

Claims

1. An adhesive material, comprising an adhesive, wherein: The adhesive comprises structural unit A, structural unit B, structural unit C and structural unit D, and at least part of the structural unit A is cross-linked with at least part of the structural unit D; Wherein, the structural unit A is Wherein, the structural units B are each independently Any one or more of, optionally, the structural unit B is The structural units C are each independently Any one of the above, each m1 and each m2 are independently any integer from 1 to 20, optionally, each m1 is independently any integer from 2 to 12, and each m2 is independently any integer from 8 to 12; The structural units D are each independently Any one or more of n1 is each independently any integer from 1 to 20, optionally, n1 is any integer from 1 to 12, further optionally n1 is any integer from 1 to 6.

2. The adhesive material according to claim 1, wherein At least part of the structural unit A, at least part of the structural unit B, at least part of the structural unit C and at least part of the structural unit D are connected in a chain to form a first chain structure, At least part of the structural unit A, at least part of the structural unit C and at least part of the structural unit D are connected in a chain to form a second chain structure; At least a portion of the structural unit A in the first chain structure is cross-linked with at least a portion of the structural unit D in the second chain structure; At least a portion of the structural unit D in the first chain structure is cross-linked with at least a portion of the structural unit A in the second chain structure.

3. The adhesive material according to claim 1 or 2, wherein The adhesive material satisfies any one or more of the following conditions: 1) The wear resistance of the insulating adhesive layer with a thickness of 3 μm-7 μm formed by the adhesive substance meets the following requirements: tested by an RCA paper tape wear tester, using a 55g weight and a flat tape for 300mm and 2 turns to form a test area, taking n test points in the test area and the spacing between the test points is not less than 2cm, the number of non-leaking points in the test area accounts for more than 30%, where 5≤n≤100, or the area of ​​non-leaking points in the test area is more than 60% of the total area of ​​the test area; 2) The cohesive force of the insulating adhesive layer formed by the adhesive substance is 620N / m-750N / m, and can be 660N / m-725N / m; 3) The Shore hardness of the insulating adhesive layer formed by the adhesive material is 45HA-80HA, and can be 50HA-65HA; 4) The bonding force of the insulating adhesive layer formed by the adhesive substance is 30N / m-90N / m, and can be optionally 40N / m-80N / m.

4. The adhesive material according to any one of claims 1 to 3, wherein In the adhesive, the molar ratio of the structural unit D to the structural unit A is 0.5:1-5:1, optionally 0.5:1-3:1, and further optionally 1:1-3:1; optionally, the molar content of the structural unit A is 4%-50%, optionally 4%-10%, and the molar content of the structural unit D is 1%-50%, optionally 5%-30%, and further optionally 5%-15%.

5. The adhesive material according to any one of claims 1 to 4, wherein In the adhesive, the molar ratio of the structural unit C to the structural unit B is 1:1-300:1, and can be optionally 5:1-50:1; optionally, the molar content of the structural unit B is 0.2%-20%, and can be optionally 1%-5%; optionally, the molar content of the structural unit C is 1%-90%, and can be optionally 55%-90%, and can further be optionally 75%-80%.

6. The adhesive material according to any one of claims 1 to 5, wherein: The adhesive material also includes an insulating filler and / or a dispersant; optionally, the weight ratio of the insulating filler, the adhesive and the dispersant is (70-90):(10-25):0.

4.

7. The adhesive material according to claim 6, wherein The insulating filler includes any one or more of alumina, magnesium oxide, silicon dioxide, titanium dioxide, barium titanate, aluminum nitride, silicon nitride, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, mica, talc, boehmite, zeolite, apatite, kaolin or glass powder; optionally, the volume average particle size D of the insulating filler is V 50≤1μm.

8. The adhesive material according to any one of claims 1 to 7, wherein The adhesive substance further comprises a solvent; optionally, the solid content of the adhesive substance is 20%-40%; Optionally, the solvent of the adhesive substance includes water; Optionally, the viscosity of the adhesive material measured at 25° C. and 12 rpm is 350 mPa·s-900 mPa·s.

9. An adhesive composition comprising an adhesive, wherein: The adhesive comprises a first adhesive and a second adhesive, The first adhesive is a polymer, including structural unit A, structural unit B, structural unit C and structural unit D, The second binder is a polymer, comprising a structural unit A, a structural unit C and a structural unit D, Wherein, the structural unit A is The structural units B are each independently Any one or more of, optionally, the structural unit B is The structural unit C of the first adhesive and the structural unit C of the second adhesive are each independently Each m1 and each m2 are independently any integer from 1 to 20; optionally, each m1 is independently any integer from 2 to 12, and each m2 is independently any integer from 8 to 12; The structural unit D of the first adhesive and the structural unit D of the second adhesive are each independently n1 is each independently any integer from 1 to 20, optionally n1 is each independently any integer from 1 to 12; further optionally n1 is each independently any integer from 1 to 6.

10. The adhesive composition according to claim 9, wherein The weight ratio of the first adhesive to the second adhesive is 1:2.5-1:20, and can be optionally 1:5-1:17.

5.

11. The adhesive composition according to claim 9 or 10, wherein The first adhesive satisfies any one or more of the following conditions: 1) The molar content of the structural unit A in the first adhesive is 5%-30%; 2) The molar content of the structural unit B in the first adhesive is 5%-85%; 3) The molar content of the structural unit C in the first adhesive is 5%-85%; 4) The molar content of the structural unit D in the first adhesive is 5%-15%.

12. The adhesive composition according to any one of claims 9 to 11, wherein The second adhesive satisfies any one or more of the following conditions: 1) The molar content of the structural unit A in the second adhesive is 5%-10%; 2) The molar content of the structural unit C in the second adhesive is 70%-85%; 3) The molar content of the structural unit D in the second adhesive is 5%-20%.

13. The adhesive composition according to any one of claims 9 to 12, wherein The weight average molecular weight of the first adhesive is 500,000-1.5 million; further optionally, the difference between the weight average molecular weights of the first adhesive and the second adhesive is 100,000-1.5 million.

14. The adhesive composition according to any one of claims 9 to 13, wherein The adhesive composition further comprises an insulating filler and / or a dispersant; optionally, the weight ratio of the insulating filler, the adhesive and the dispersant is (70-90):(10-25):0.

4.

15. The adhesive composition according to claim 14, wherein The insulating filler includes any one or more of alumina, magnesium oxide, silicon dioxide, titanium dioxide, barium titanate, aluminum nitride, silicon nitride, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, mica, talc, boehmite, zeolite, apatite, kaolin or glass powder; optionally, the volume average particle size D of the insulating filler is V 50≤1μm.

16. The adhesive composition according to claim 14 or 15, wherein The dispersant includes one or more of polyacrylate compounds, fatty alcohol polyether compounds or polyether-modified siloxane compounds.

17. The adhesive composition according to any one of claims 9 to 16, wherein The adhesive composition further comprises a solvent; optionally, the solid content of the adhesive composition is 20%-40%; further optionally, the solvent of the adhesive composition comprises water.

18. A positive electrode sheet, comprising: A positive electrode current collector (11), wherein at least one side of the positive electrode current collector (11) has a positive electrode film layer region and a hollow foil region; A positive electrode film layer (12), arranged in the positive electrode film layer region of the positive electrode current collector (11); An insulating adhesive layer (13) is arranged in the empty foil area of ​​the positive electrode current collector (11), wherein the insulating adhesive layer (13) is formed by using the adhesive material described in any one of claims 1 to 8, or is formed by curing the adhesive composition described in any one of claims 9 to 17.

19. The positive electrode sheet according to claim 18, wherein: The thickness of the insulating adhesive layer (13) is less than or equal to the thickness of the positive electrode film layer (12). Optionally, the thickness of the insulating adhesive layer (13) is 3 μm-7 μm.

20. A method for preparing a positive electrode sheet, comprising the process of arranging a positive electrode film layer and an insulating adhesive layer on at least one side or both sides of a positive electrode current collector (11), wherein: The process of providing the insulating adhesive layer (13) comprises: Mixing the components of the adhesive substance according to any one of claims 1 to 8 or the adhesive composition according to any one of claims 9 to 17 to form an adhesive solution; Applying the glue solution on the empty foil area of ​​the positive electrode current collector to obtain a preform with the glue solution; The preform with the glue is heated to obtain the insulating glue layer, and the heating temperature is optionally 90°C-120°C.

21. The preparation method according to claim 20, wherein: The process of mixing the components of the adhesive composition to form a slurry comprises: Mixing the dispersant in the adhesive composition with water to form a first dispersion, optionally, the mixing is a first stirring, the first stirring time is 5 min-30 min, and the stirring speed is 200 rpm-400 rpm; Mixing the first dispersion with the insulating filler in the adhesive composition to form a second dispersion, optionally, the mixing is a second stirring, the second stirring time is 30 min-120 min, and the stirring speed is 1200 rpm-1800 rpm; Mixing the second dispersion with the first adhesive in the adhesive composition to form a third dispersion, optionally, the mixing is a third stirring, the third stirring time is 15 min-60 min, and the stirring speed is 400 rpm-700 rpm; The third dispersion is mixed with the second adhesive in the adhesive composition to form the adhesive solution. Optionally, the mixing is a fourth stirring, and the fourth stirring time is 5 min-30 min and the stirring speed is 200 rpm-400 rpm.

22. A secondary battery, comprising a positive electrode sheet, wherein: The positive electrode sheet includes the positive electrode sheet according to claim 18 or 19, or the positive electrode sheet obtained by the preparation method according to claim 20 or 21.

23. An electrical device comprising a secondary battery, wherein: The secondary battery includes the secondary battery according to claim 22.

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