An adhesive structure, an electrochemical device including the adhesive structure, and an electronic device

Abstract

The application provides a kind of adhesive structure, electrochemical device and electronic device comprising the adhesive structure, adhesive structure includes swelling layer, setting on the adhesive layer of at least one surface of the swelling layer;Swelling layer includes acrylonitrile-butadiene-styrene copolymer.The three-dimensional volume expansion rate of adhesive structure can reach 180% to 500% when the adhesive structure of the application is soaked at 85 DEG C for 4h, which can effectively fill the gap between the shell and the electrode assembly, while having good elasticity and adhesion, buffering the stress generated by falling, roller, etc., maintaining its good binding effect. By using the adhesive structure in the electrochemical device, the safety performance of the electrochemical device can be effectively improved. The electronic device of the application comprises the electrochemical device of the application, so the electronic device has good safety performance.

Description

Technical Field

[0001] This application relates to the field of electrochemistry, and more specifically to an adhesive structure, an electrochemical device comprising the adhesive structure, and an electronic device. Background Technology

[0002] Lithium-ion batteries, as a typical example of devices that convert electrical energy into chemical energy, are increasingly widely used in various fields.

[0003] Existing cylindrical lithium-ion batteries suffer from voltage drop failure, electrode breakage, and tab breakage due to the gap between the electrode assembly and the casing during drop or roller tests, caused by relative movement between the electrode assembly and the casing. To address these issues, those skilled in the art have developed a method using swollen adhesive paper soaked in electrolyte. This adhesive paper extends three-dimensionally along its length, width, and thickness to fill the gap between the electrode assembly and the casing, thereby restraining the vibration and shaking of the electrode assembly within the casing. This, in turn, buffers the stress from drops and roller tests, improving the safety of lithium-ion batteries.

[0004] However, currently used swellable adhesive paper has several disadvantages in application. For example, it is rigid and has poor conformability, making it unsuitable for electrode components with various curvatures, and it tends to curl up before being placed into the casing. During ball rolling tests, its initial tack is low, hindering rapid adhesion and fixation of the object, making it unsuitable for high-speed production lines. Furthermore, after swelling, it relies solely on filling and bonding for fixation, which can lead to failure in applications with high requirements such as rollers and vibration. Due to these disadvantages, lithium-ion batteries using the aforementioned swellable adhesive paper often exhibit poor safety performance. Summary of the Invention

[0005] This application provides an adhesive structure, an electrochemical device including the adhesive structure, and an electronic device to improve the safety performance of the electrochemical device.

[0006] It should be noted that, in the following explanation, lithium-ion batteries are used as an example of electrochemical devices to illustrate this application; however, the electrochemical devices of this application are not limited to lithium-ion batteries. The specific technical solution is as follows:

[0007] The first aspect of this application provides an adhesive structure including a swollen layer and an adhesive layer disposed on at least one surface of the swollen layer; the swollen layer includes acrylonitrile-butadiene-styrene copolymer (ABS).

[0008] The adhesive layer effectively bonds the electrode assembly to the housing. The binding force of this adhesive structure on the electrode assembly is stronger than that of existing technologies using abutment fixation, making it suitable for electrode assemblies with various curvatures requiring high vibration or roller resistance. The acrylonitrile-butadiene-styrene copolymer in the swelling layer possesses excellent chemical resistance, heat resistance, and hardness; butadiene exhibits high elasticity and toughness; and styrene demonstrates thermoplastic processing characteristics. The swelling layer formed by this acrylonitrile-butadiene-styrene copolymer, due to the synergistic effect between acrylonitrile, butadiene, and styrene, gives the adhesive structure excellent flexibility and conformability, enabling rapid adhesion of the electrode assembly to the housing and suitable for insulating and fixing the termination parts of the electrode assembly. After being placed in a cold-drying system at 2°C to 10°C for 24 hours, the adhesive structure remained free of warping. The adhesive structure of this application, when immersed in electrolyte at 85°C for 4 hours, experiences amplification of the relatively fixed molecular positions of the acrylonitrile-butadiene-styrene copolymer in the swelling layer under the action of the electrolyte. This weakens the intermolecular forces, causing the adhesive structure to extend three-dimensionally along its length, width, and thickness directions. The three-dimensional volume expansion rate of the adhesive structure reaches 180% to 500%. Therefore, the adhesive structure of this application can effectively fill the gap between the shell and the electrode assembly in three dimensions, while possessing good elasticity and adhesion. It effectively buffers the stress generated by drops, rollers, etc., to maintain the good binding effect of the adhesive structure on the electrode assembly, thereby effectively improving the safety performance of the electrochemical device.

[0009] This application does not impose any particular limitation on the weight-average molecular weight of the acrylonitrile-butadiene-styrene copolymer, as long as it achieves the purpose of this application. For example, the weight-average molecular weight of the acrylonitrile-butadiene-styrene copolymer can be from 50,000 to 700,000.

[0010] In some embodiments of this application, the mass proportion of the acrylonitrile-butadiene-styrene copolymer is between 85% and 98% based on the total mass of the swollen layer. For example, the mass proportion of the acrylonitrile-butadiene-styrene copolymer can be 85%, 90%, 95%, 98%, or any value within a range thereof. If the mass proportion of the acrylonitrile-butadiene-styrene copolymer is too low (e.g., below 85%), the three-dimensional volume expansion rate of the adhesive structure decreases, and the binding effect of the adhesive structure on the electrode assembly will deteriorate; if the mass proportion of the acrylonitrile-butadiene-styrene copolymer is too high (e.g., above 98%), the three-dimensional volume expansion rate of the adhesive structure is too high, which will affect the expansion performance of the electrochemical device. Controlling the mass proportion of the acrylonitrile-butadiene-styrene copolymer in the swollen layer within the above-mentioned range is more conducive to the effective filling of the space between the electrode assembly and the shell by the adhesive structure, thereby more effectively improving the safety performance of the electrochemical device.

[0011] In some embodiments of this application, based on the total mass of the acrylonitrile-butadiene-styrene copolymer, the mass ratio of acrylonitrile, butadiene, and styrene in the acrylonitrile-butadiene-styrene copolymer is (5-20):(55-80):(5-25). For example, the mass ratio of acrylonitrile, butadiene, and styrene is 5:65:25, 5:80:15, 10:75:15, 18:60:22, 20:75:5, or any value within a range thereof. By controlling the mass ratio of acrylonitrile, butadiene, and styrene within the above range, it is more beneficial to improve the effective filling of the adhesive structure between the electrode assembly and the housing, thereby more effectively improving the safety performance of the electrochemical device.

[0012] In some embodiments of this application, the swelling layer further includes a functional resin, which includes at least one selected from styrene-ethylene-butene-styrene block copolymer (SEBS), ethylene-vinyl acetate copolymer (EVA), polyurethane elastomer, thermoplastic elastomer (TPE / TPR), polyurethane acrylate (PUA), polyisobutylene, or polybutadiene. Further addition of a functional resin to the swelling layer allows the adhesive structure to maintain its intact swelling shape even after prolonged immersion (>4h) in the electrolyte at high temperatures (>60°C), effectively improving the safety performance of the electrochemical device.

[0013] This application does not impose any particular limitation on the weight-average molecular weight of SEBS and EVA, as long as the purpose of this application can be achieved. For example, the weight-average molecular weight of SEBS can be between 80,000 and 150,000, and the molecular weight of EVA can be 342.43.

[0014] This application does not impose any particular limitation on the mass ratio of functional resin in the swollen layer, as long as the purpose of this application can be achieved. For example, based on the total mass of the swollen layer, the mass ratio of functional resin can be from 2% to 15%. Within this range, the mass ratio of functional resin is more conducive to improving the expansion morphology of the adhesive structure after prolonged immersion in electrolyte at high temperatures, thereby effectively improving the safety performance of the electrochemical device.

[0015] In some embodiments of this application, the thickness of the adhesive structure is between 20 μm and 50 μm. For example, the thickness of the adhesive structure can be 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, or any value within a range thereof. By controlling the thickness of the adhesive structure within the above range, the adhesive structure can effectively fill the gap between the electrode assembly and the housing through its three-dimensional extension along its length, width, and thickness directions. This is beneficial for improving the binding effect of the adhesive structure on the electrode assembly and for reducing the volume of the lithium-ion battery, thereby increasing the energy density of the electrochemical device.

[0016] In some embodiments of this application, the thickness of the swelling layer is from 10 μm to 30 μm. For example, the thickness of the swelling layer can be 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, or any value within a range thereof. If the thickness of the swelling layer is too small (e.g., less than 10 μm), the swelling effect of the adhesive structure is affected; if the thickness of the swelling layer is too large (e.g., greater than 30 μm), the thickness of the adhesive structure increases, and the distance between the electrode assembly and the housing needs to be increased accordingly to meet the gap required by the adhesive structure, which will increase the volume of the electrochemical device and thus reduce the energy density of the electrochemical device.

[0017] In some embodiments of this application, the thickness of the adhesive layer is from 5 μm to 10 μm. For example, the thickness of the adhesive layer can be 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, or any value within a range thereof. If the thickness of the adhesive layer is too small (e.g., less than 5 μm), the adhesion between the adhesive structure and the electrode assembly or housing is reduced, and the adhesion effect of the adhesive structure to the electrode assembly or housing will be worse. If the thickness of the adhesive layer is too large (e.g., greater than 10 μm), the thickness of the adhesive structure increases, and the distance between the electrode assembly and the housing needs to be increased accordingly to meet the gap required by the adhesive structure, which will increase the volume of the electrochemical device and thus reduce the energy density of the electrochemical device.

[0018] It should be noted that the adhesive layer can be disposed on one surface of the swollen layer or on both surfaces of the swollen layer. In some embodiments, the adhesive layer is disposed on both surfaces of the swollen layer. The adhesive layers on both sides of the swollen layer can be the same or different.

[0019] In some embodiments of this application, the adhesive layer material includes at least one selected from polymethyl methacrylate, polypropylene (PP), hot-melt styrene-isoprene-styrene rubber (SIS), polyethylene, or polyamide. Using these materials as the adhesive layer material is beneficial for improving the adhesion between the adhesive structure and the electrode assembly.

[0020] In some embodiments of this application, the adhesive force of the adhesive layer is from 0.15 N / mm to 0.5 N / mm. This indicates that the adhesive layer has excellent adhesion to the electrode assembly and / or the housing, which can effectively improve the binding effect of the adhesive structure on the electrode assembly, thereby improving the safety performance of the electrochemical device.

[0021] In some embodiments of this application, the adhesive structure is immersed in the electrolyte at 85°C for 4 hours. The three-dimensional volume expansion rate of the adhesive structure is 180% to 500%, preferably 200% to 450%. This indicates that after being immersed in the electrolyte at high temperature, the adhesive structure can extend in three dimensions along its length, width and thickness directions, and has a good expansion rate. This effectively fills the gap between the electrode assembly and the shell, thus fixing the electrode assembly and effectively improving the safety performance of the electrochemical device.

[0022] In some embodiments of this application, the initial tack of the adhesive-bonded balls is ≥8#, indicating that the adhesive structure has good initial tack performance and can effectively improve the binding effect of the adhesive structure on the electrode assembly, thereby improving the safety performance of the electrochemical device. In this application, the size of the steel balls used to test the initial tack is numbered according to 32 times the imperial diameter of the steel ball. Specifically, the ball diameter is 1 / 32 inch and the ball number is 1#, the ball diameter is 2 / 32 inch and the ball number is 2#, and so on, the ball diameter is 8 / 32 inch and the ball number is 31#, the ball diameter is 32 / 32 inch (i.e., 1 inch) and the ball number is 32#.

[0023] In some embodiments of this application, the tensile strength of the adhesive structure is 0.2 N / mm to 0.5 N / mm, indicating that the adhesive structure has good tensile strength, which can effectively improve the service life of the adhesive structure and thus improve the safety performance of the electrochemical device.

[0024] In this application, after immersing the adhesive structure of any of the aforementioned schemes in electrolyte at 85°C for 24 hours, the color number of the electrolyte was compared with that of the blank electrolyte under the same conditions using the Pantone international standard color chart. The color numbers remained consistent, and the morphology of the adhesive structure remained intact. This indicates that the adhesive structure provided in this application has good electrolyte resistance, thereby improving the safety performance of electrochemical devices and extending their service life.

[0025] In this application, the adhesive structure also includes an anti-adhesive layer disposed on the outer surface of the adhesive layer. It is understood that the inner surface of the adhesive layer is bonded to the surface of the swelling layer; therefore, the anti-adhesive layer is disposed on the outer surface of the adhesive layer. The anti-adhesive layer prevents the adhesive layer from adhering to non-target bonding objects during winding and packaging, thus facilitating the storage and transportation of the adhesive structure.

[0026] In this application, the release layer includes release paper or release film. This application does not impose any particular limitation on the type of release paper or release film, as long as it achieves the purpose of this application.

[0027] This application does not impose any particular limitation on the preparation method of the adhesive structure, as long as it can achieve the purpose of this application. For example, this application uses an example of disposing adhesive layers on two surfaces of the swollen layer, with the two adhesive layers being a first adhesive layer and a second adhesive layer. The first adhesive layer and the second adhesive layer can be the same or different. Specifically, the following method can be used to prepare the adhesive structure, which includes the following steps:

[0028] (1) The acrylonitrile-butadiene-styrene copolymer is subjected to melt extrusion, casting, cooling molding, traction and heat treatment at 150°C to 200°C for 1 to 2 hours to relieve stress and obtain a swollen layer of 10 μm to 30 μm.

[0029] (2) Coating one side of the swollen layer with the material of the first adhesive layer to obtain a first adhesive layer of 5 μm to 10 μm;

[0030] (3) Coating the other side of the swollen layer with the material of the second adhesive layer to obtain a second adhesive layer of 5 μm to 10 μm; that is, obtaining the adhesive structure of this application.

[0031] A second aspect of this application provides an electrochemical device comprising an electrode assembly, a housing, and an adhesive structure as described in any of the foregoing embodiments, wherein the adhesive layer is bonded to the outer surface of the electrode assembly and / or the housing. Specifically, the first adhesive layer of the adhesive structure is bonded to the outer surface of the electrode assembly, and the adhesive structure expands after immersion in the electrolyte, while the second adhesive layer of the adhesive structure contacts and bonds to the housing. In this way, the adhesive structure effectively fills the gap between the housing and the electrode assembly, tightly binding the electrode assembly. Therefore, when the electrochemical device is dropped or rolled, relative movement between the electrode assembly and the housing can be effectively prevented, avoiding serious consequences such as voltage drop failure, electrode breakage, or tab breakage, thereby effectively improving the safety performance of the electrochemical device.

[0032] This application does not impose any particular limitations on the structure of the electrode assembly, which may include a wound structure or a stacked structure. In this application, the electrode assembly includes a separator, a positive electrode, and a negative electrode. The separator separates the positive and negative electrode to prevent short circuits within the electrochemical device, while allowing electrolyte ions to pass freely, thus facilitating the electrochemical charge-discharge process. This application does not impose any particular limitations on the number or type of the separator, positive electrode, and negative electrode, as long as the purpose of this application is achieved.

[0033] The positive electrode sheet of this application includes a positive current collector and a positive active material layer. This application does not impose any particular limitations on the positive current collector and the positive active material layer, as long as the purpose of this application is achieved. It should be noted that the positive active material layer can be disposed on one surface or on two surfaces along the thickness direction of the positive current collector. Here, "surface" can refer to the entire area of ​​the positive current collector or only a portion thereof; this application does not impose any particular limitations, as long as the purpose of this application is achieved.

[0034] The negative electrode sheet of this application includes a negative electrode current collector and a negative electrode active material layer. This application does not impose any particular limitations on the negative electrode current collector and the negative electrode active material layer, as long as the purpose of this application is achieved. It should be noted that the negative electrode active material layer can be disposed on one surface or on two surfaces along the thickness direction of the negative electrode current collector. Here, "surface" can refer to the entire area of ​​the negative electrode current collector or only a portion thereof; this application does not impose any particular limitations, as long as the purpose of this application is achieved.

[0035] In some embodiments of this application, the electrode assembly is a stacked or wound structure, and the adhesive structure is disposed between the outer surface of the electrode assembly and the housing. This effectively reduces the risk of decreased binding effect of the adhesive structure on the electrode assembly due to abutment fixation. Based on the total area of ​​the outer surface of the electrode assembly, the bonding area of ​​the adhesive structure accounts for 10% to 100%.

[0036] Based on the distance between the electrode assembly and the housing, the proportion of the adhesive structure's bonding area on the outer surface of the electrode assembly is selected within the aforementioned range to fully fill the gap between the electrode assembly and the housing, thereby improving the fixation effect of the electrode assembly. By controlling the proportion of the adhesive structure's bonding area on the outer surface of the electrode assembly within the aforementioned range, the high-temperature safety performance of the electrochemical device can be effectively improved. It should be noted that the outer surface of the electrode assembly can be any one of the following: a positive electrode current collector, a positive electrode active material layer, a negative electrode current collector, a negative electrode active material layer, or a separator.

[0037] This application does not impose any particular restrictions on the casing, as long as it achieves the purpose of this application. For example, the casing may include an inner layer and an outer layer. In this application, there are no particular restrictions on the material of the inner layer, as long as it achieves the purpose of this application. For example, the material of the inner layer may include at least one of PP, polyester, p-hydroxybenzaldehyde, polyamide, polyphenylene ether, or polyurethane. In this application, there are no particular restrictions on the material of the outer layer, as long as it achieves the purpose of this application. For example, the material of the outer layer may include at least one of aluminum foil, an alumina layer, or a silicon nitride layer. Furthermore, the casing may also be an aluminum-plastic film, which includes a nylon layer, an aluminum foil layer, a PP layer, and / or a matte layer.

[0038] In this application, there is no particular limitation on the thickness of the casing, as long as it achieves the purpose of this application. For example, the thickness of the casing can be from 50 μm to 500 μm, preferably from 50 μm to 300 μm, and more preferably from 50 μm to 200 μm. Casings within the above thickness range can effectively protect the internal structure of the electrochemical device.

[0039] This application does not impose any particular limitation on the type of electrolyte, as long as it can achieve the purpose of this application. For example, an organic solution can be obtained by mixing at least one of ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), ethyl propionate (EP), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), or fluoroethylene carbonate (FEC) in a certain mass ratio, followed by adding lithium salt to dissolve and mixing thoroughly. This application does not impose any limitation on the type of lithium salt, as long as it can achieve the purpose of this application. For example, the lithium salt may include at least one of LiPF6, LiBF4, LiAsF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, LiSiF6, LiBOB, or lithium difluoroborate. Preferably, LiPF6 can be selected as the lithium salt because it can provide high ionic conductivity and improve cycle characteristics.

[0040] The electrochemical device described in this application is not particularly limited and may include, but is not limited to, lithium metal secondary batteries, lithium-ion secondary batteries (lithium-ion batteries), lithium polymer secondary batteries, or lithium-ion polymer secondary batteries.

[0041] The fabrication process of electrochemical devices is well known to those skilled in the art, and this application does not impose any particular limitations. For example, it may include, but is not limited to, the following steps: stacking the positive electrode, separator, and negative electrode in sequence, and performing operations such as winding and folding as needed to obtain a wound electrode assembly; placing the electrode assembly into a packaging shell; injecting electrolyte into the packaging shell and sealing it to obtain the electrochemical device; or stacking the positive electrode, separator, and negative electrode in sequence, and then fixing the four corners of the entire stacked structure with tape to obtain a stacked electrode assembly; placing the electrode assembly into a packaging shell; injecting electrolyte into the packaging shell and sealing it to obtain the electrochemical device. In addition, overcurrent protection elements, conductive plates, etc., may be placed in the packaging shell as needed to prevent pressure rise and overcharging / discharging inside the electrochemical device.

[0042] A third aspect of this application provides an electronic device that includes the electrochemical device provided in the second aspect of this application. This electronic device has good safety performance.

[0043] The electronic devices covered by this application are not particularly limited and may include, but are not limited to: laptops, pen-based computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries, and lithium-ion capacitors, etc.

[0044] This application provides an adhesive structure, an electrochemical device incorporating the adhesive structure, and an electronic device. The adhesive structure includes a swollen layer and an adhesive layer disposed on at least one surface of the swollen layer; the swollen layer comprises an acrylonitrile-butadiene-styrene copolymer. When immersed at 85°C for 4 hours, the adhesive structure exhibits a three-dimensional volume expansion rate of 180% to 500%, effectively filling the gap between the housing and the electrode assembly. It also possesses good elasticity and adhesion, buffering stresses generated by drops, rollers, etc., and maintaining its excellent binding effect. Using this adhesive structure in an electrochemical device can effectively improve the safety performance of the device. The electronic device of this application includes the electrochemical device of this application; therefore, the electronic device has excellent safety performance. Attached Figure Description

[0045] To more clearly illustrate the technical solutions of the embodiments of this application and the prior art, the drawings used in the embodiments and the prior art are briefly introduced below. Obviously, the drawings described below are only some embodiments of this application.

[0046] Figure 1 This is a schematic diagram of the adhesive structure of some embodiments of this application;

[0047] Figure 2 This is a schematic diagram illustrating the working principle of the adhesive structure in an electrochemical device according to some embodiments of this application;

[0048] Figure 3 This is a schematic diagram illustrating the working principle of the acrylonitrile-butadiene-styrene copolymer in the electrolyte in some embodiments of this application;

[0049] Figure 4 This is a schematic diagram of the structure of an electrochemical device according to some embodiments of this application.

[0050] Reference numerals: 10. Electrode assembly; 20. Adhesive structure; 21. First adhesive layer; 22. Swelling layer; 23. Second adhesive layer; 30. Housing. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are merely some embodiments of this application, and not all embodiments. All other technical solutions obtained by those skilled in the art based on the embodiments of this application fall within the scope of protection of this application.

[0052] It should be noted that, in the specific embodiments of this application, lithium-ion batteries are used as an example of electrochemical devices to explain this application, but the electrochemical devices of this application are not limited to lithium-ion batteries.

[0053] The adhesive structure of some embodiments of this application includes a swollen layer and an adhesive layer disposed on at least one surface of the swollen layer. The accompanying drawings and the following embodiments illustrate an adhesive layer disposed on both surfaces of the swollen layer.

[0054] Figure 1 A schematic diagram of the adhesive structure according to some embodiments of this application is shown. The adhesive structure 20 includes a first adhesive layer 21, a swollen layer 22, and a second adhesive layer 23, with the swollen layer 22 located between the first adhesive layer 21 and the second adhesive layer 23. The first adhesive layer 21 and the second adhesive layer 23 may be the same or different.

[0055] Figure 2 A schematic diagram illustrating the working principle of the adhesive structure according to some embodiments of this application in an electrochemical device is shown. Figure 2 (a) in the text refers to electrode assembly 10. Figure 2 (b) is a schematic diagram of the principle of wrapping the adhesive structure 20 around the electrode assembly 10. Figure 2 (c) is a schematic diagram of the structure after the adhesive structure 20 is attached to the electrode assembly 10. Figure 2 (d) in the diagram is a schematic diagram of the structure of the electrode assembly 10 after the adhesive bonding structure 20 in (c) is installed into the housing 30. Figure 2 (e) in the diagram is a schematic representation of the expansion of the adhesive structure 20 after the electrolyte is injected into the electrochemical device. Figure 2 As shown, the adhesive structure 20 is attached to the outer surface of the electrode assembly 10. After the electrolyte is injected into the electrochemical device, the adhesive structure 20 expands and extends in three dimensions along its length, width and thickness directions. The volume of the adhesive structure 20 increases and it fills the gap between the electrode assembly 10 and the shell 30 in three dimensions.

[0056] Figure 3 This is a schematic diagram illustrating the working principle of the acrylonitrile-butadiene-styrene copolymer in the electrolyte in some embodiments of this application. Figure 3(f) is a schematic diagram of the structure of the acrylonitrile-butadiene-styrene copolymer before immersion in the electrolyte. Figure 3 (g) in the diagram represents the structure of the acrylonitrile-butadiene-styrene copolymer after immersion in the electrolyte. For example... Figure 3 As shown, after the acrylonitrile-butadiene-styrene copolymer is immersed in the electrolyte, the relatively fixed positions between the acrylonitrile-butadiene-styrene copolymer molecules are squeezed and enlarged under the action of the electrolyte, the intermolecular forces are weakened, and the adhesive structure is extended in three dimensions along its length, width and thickness directions, resulting in an increase in the volume of the adhesive structure.

[0057] Figure 4 This is a schematic diagram of the structure of an electrochemical device according to some embodiments of this application. Figure 4 (h) in the diagram is a cross-sectional view of the electrochemical device along the CC direction. Figure 4 In the diagram, (i) is a top view taken along the height of the electrochemical device itself. For example... Figure 4 As shown, the adhesive structure 20 is disposed between the outer surface A of the electrode assembly 10 and the housing 30, and the adhesive structure 20 is bonded to the outer surface A of the electrode assembly 10.

[0058] The embodiments and comparative examples provided below illustrate the implementation of this application in more detail. Various tests and evaluations were conducted according to the methods described below. Furthermore, unless otherwise specified, "%" represents a quality standard.

[0059] Test methods and equipment:

[0060] Adhesion strength test:

[0061] According to GB / T 2792-2014 peel force test method, a high-speed rail tensile testing machine was used to test at a 180° angle: (1) The adhesive structure of each embodiment and comparative example was attached to Al foil and cut into strips of 20mm×60mm. The length and width values ​​can be adjusted proportionally according to the actual situation; (2) The sample was hot-pressed for 40min at a temperature of 85℃ and a pressure of 1MPa, and then immersed in the electrolyte of the corresponding embodiment or comparative example at 85℃ for 4h. Along the length of the sample, the Al foil surface was adhered to the steel plate with double-sided adhesive (Japan 5000NS), and the adhesion length was not less than 40mm; (3) The steel plate was fixed in the corresponding position of the high-speed rail tensile testing machine, and the other end of the sample that was not adhered to the steel plate was pulled up. The sample was clamped in the clamp by means of a connector or directly, and the angle between the pulled sample part and the steel plate in space was 180°. The clamp pulls the sample at a speed of 50±0.2 mm / min, and the average tensile force in the stable area is recorded as the adhesive force.

[0062] Expansion rate test:

[0063] The adhesive structures of each embodiment and comparative example were bonded to 50μm release paper and pressed back and forth 3 times with a 2kg rubber roller to ensure flatness and no wrinkles. The dimensions were cut to be 20mm x 100mm (width x length). The structures were then immersed in the electrolyte of the corresponding embodiment or comparative example at 85℃ for 4 hours. The expansion was then observed, and the thickness of the adhesive structure after expansion was measured with a micrometer.

[0064] Expansion rate = (Thickness after expansion / Thickness before expansion) × 100%.

[0065] Heat dryness test:

[0066] After placing the glued structure in an 80℃ oven for 4 hours, remove it and observe whether it shrinks or deforms.

[0067] Cold drying test:

[0068] After placing the adhesive structure in a cold drying system at 2°C to 10°C for 24 hours, remove it and observe its appearance for any curling edges.

[0069] Initial tack test of rolling ball:

[0070] The rolling ball method initial tack tester is an instrument that evaluates the initial tack of an adhesive structure by rolling a steel ball over the adhesive surface (i.e., the adhesive layer of the adhesive structure) of the adhesive structure placed flat on an inclined plate. The instrument assesses the initial tack based on the maximum size of the steel ball that can be adhered to by the adhesive surface of a specified length.

[0071] ① Inclined ball rolling device: This device mainly consists of an inclined plate, a ball releaser, a support, a base, and a ball receiving box.

[0072] ② Steel balls: Steel balls made of GCr15 bearing steel with a precision not lower than grade 0 as specified in GB 308-77 "Steel Balls" and a diameter of 1 / 32 inch to 1 inch can be used as test steel balls.

[0073] The steel balls are numbered according to a multiple of 32 of their imperial diameter. Specifically, a steel ball with a diameter of 1 / 32 inch is numbered 1#, a steel ball with a diameter of 2 / 32 inch is numbered 2#, and so on, with a steel ball with a diameter of 8 / 32 inch being numbered 8#, a steel ball with a diameter of 3 1 / 32 inch being numbered 31#, and a steel ball with a diameter of 32 / 32 inch (i.e., 1 inch) being numbered 32#. A set of steel balls with consecutive numbers should be used for testing.

[0074] Steel balls should be stored in rust-preventive oil. Balls with rust or scratches must be replaced promptly.

[0075] Adjustable tilt angle: 0° to 60°; table width: 120mm; test area width: 80mm; standard steel ball: 1 / 32 inch to 1 inch.

[0076] Take three samples and perform a rolling ball test on each sample using a steel ball with the largest ball size. If a sample cannot stick to the steel ball, replace it with a steel ball with a smaller ball size and perform another rolling ball test until it sticks. The ball size that sticks is the result of the initial rolling ball adhesion test.

[0077] Tensile strength test:

[0078] The tensile strength of the adhesive structures in each embodiment and comparative example was tested using a universal testing machine.

[0079] Roller test:

[0080] After the lithium-ion battery was left to stand at 25℃ for 60 minutes, its voltage, internal resistance, and capacity were tested. Then, the lithium-ion battery was placed in a fixture with a roller height of 1m and the roller contact surface with the lithium-ion battery being a metal contact surface. The roller was rolled for 5 minutes per revolution, for a total of 500 revolutions. The voltage and internal resistance were tested and recorded every 100 revolutions. The appearance was then checked and photographed.

[0081] Judgment criteria: No smoke, no fire, no explosion, no leakage, voltage drop <50mV, and internal resistance <18mΩ indicate that the system is not in failure.

[0082] Failure rate = (Number of failures / Total number of tests) × 100%.

[0083] Drop test:

[0084] After the lithium-ion battery was left to stand at 25°C for 60 minutes, its voltage, internal resistance, and capacity were tested. Then, the lithium-ion battery was placed in a special fixture and dropped freely using a drop tester. The lithium-ion battery was placed 1.9m above the ground and dropped 300 times. The voltage and internal resistance were measured and recorded every 100 drops. The appearance was then inspected and photographed.

[0085] Judgment criteria: No smoke, no fire, no explosion, no leakage, voltage drop <50mV, and internal resistance <18mΩ indicate that the system is not in failure.

[0086] Failure rate = (Number of failures / Total number of tests) × 100%.

[0087] Example 1-1

[0088] <Preparation of Negative Electrode Sheets>

[0089] Graphite powder (negative electrode active material), conductive carbon black (Super P) (conductive agent), and styrene-butadiene rubber (SBR) (binder) were mixed in a mass ratio of 96:1.5:2.5. Deionized water was then added as a solvent to prepare a slurry with a solid content of 70%, and the mixture was stirred thoroughly. The slurry was uniformly coated onto one surface of an 8 μm thick copper foil used as a negative electrode current collector, and dried at 110°C to obtain a single-sided coated negative electrode sheet with a coating thickness of 130 μm. This completes the single-sided coating of the negative electrode sheet. The above steps were then repeated on the other surface of the negative electrode sheet to obtain a double-sided coated negative electrode sheet. After coating, the negative electrode sheet was cold-pressed and cut for later use.

[0090] <Preparation of the positive electrode>

[0091] Lithium cobalt oxide (LiCoO2), a positive electrode active material, nano-conductive carbon black, and polyvinylidene fluoride (PVDF), a binder, were mixed in a mass ratio of 97.5:1.0:1.5. N-methylpyrrolidone (NMP) was added as a solvent to prepare a slurry with a solid content of 75%, and the mixture was stirred evenly. The slurry was uniformly coated onto one surface of a 9 μm thick aluminum foil used as a positive electrode current collector, and dried at 90°C to obtain a positive electrode sheet with a coating thickness of 110 μm. This completes the single-sided coating of the positive electrode sheet. The above steps were then repeated on the other surface of the positive electrode sheet to obtain a double-sided coated positive electrode sheet. After coating, the positive electrode sheet was cold-pressed and cut for later use.

[0092] <Preparation of Electrolyte>

[0093] In a dry argon atmosphere, ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a mass ratio of 30:50:20 to obtain an organic solvent. Then, lithium hexafluorophosphate was added to the organic solvent to dissolve and mix evenly to obtain an electrolyte with a lithium salt concentration of 1.15 mol / L.

[0094] <Preparation of the diaphragm>

[0095] Alumina and polyvinylidene fluoride were mixed at a mass ratio of 90:10 and dissolved in deionized water to form a ceramic slurry with a solid content of 50%. The ceramic slurry was then uniformly coated onto one side of a porous substrate (polyethylene, 7 μm thick, average pore size 0.073 μm, porosity 26%) using a microgravure coating method. After drying, a bilayer structure of ceramic coating and porous substrate was obtained, with the ceramic coating having a thickness of 50 μm.

[0096] Polyvinylidene fluoride (PVDF) and polyacrylate were mixed at a mass ratio of 96:4 and dissolved in deionized water to form a polymer slurry with a solid content of 50%. The polymer slurry was then uniformly coated onto both surfaces of the above-mentioned ceramic coating and porous substrate bilayer structure using a microgravure coating method. After drying, a diaphragm was obtained, wherein the thickness of the single-layer coating formed by the polymer slurry was 2 μm.

[0097] <Preparation of Adhesive Structures>

[0098] The adhesive structure includes a swollen layer, a first adhesive layer, and a second adhesive layer disposed on two surfaces of the swollen layer. The swollen layer comprises 98% by mass of an acrylonitrile-butadiene-styrene copolymer and 2% by mass of a functional resin styrene-ethylene-butene-styrene block copolymer. The first adhesive layer comprises SIS, and the second adhesive layer comprises PP. The mass ratio of acrylonitrile, butadiene, and styrene in the acrylonitrile-butadiene-styrene copolymer is 10:75:15. The weight-average molecular weight of the acrylonitrile-butadiene-styrene copolymer is 400,000, and the weight-average molecular weight of the styrene-ethylene-butene-styrene block copolymer is 120,000. The adhesive structure has a thickness of 36 μm, the swollen layer has a thickness of 20 μm, the first adhesive layer has a thickness of 8 μm, and the second adhesive layer has a thickness of 8 μm.

[0099] <Preparation of Lithium-ion Batteries>

[0100] The prepared positive electrode sheet, separator, and negative electrode sheet are stacked sequentially, with the separator positioned between the positive and negative electrodes to provide isolation. The stacked electrodes are then wound to obtain a wound electrode assembly. After the first adhesive layer of the adhesive structure is bonded to the outer surface of the electrode assembly, the assembly is placed into an aluminum-plastic film housing. Moisture is removed at 80°C, and a prepared electrolyte is injected. The assembly undergoes vacuum sealing, settling, formation, and degassing processes to obtain a lithium-ion battery. The projected area of ​​the adhesive structure on the outer surface of the electrode assembly accounts for 50% of the total area.

[0101] In Examples 1-2 to 1-4 and Examples 1-12, except for adjusting the mass ratio of acrylonitrile-butadiene-styrene copolymer and the mass ratio of functional resin according to Table 1, the rest are the same as in Example 1-1.

[0102] In Examples 1-5 to 1-8, the mass ratios of acrylonitrile, butadiene, and styrene were adjusted according to Table 1, and the rest were the same as in Examples 1-2.

[0103] In Examples 1-9, the only difference from Examples 1-2 is that the types of functional resins are adjusted according to Table 1.

[0104] In Examples 1-10, the only difference from Examples 1-2 is that the material of the first adhesive layer is adjusted according to Table 1.

[0105] In Examples 1-11, the only difference from Examples 1-2 is that the material of the second adhesive layer is adjusted according to Table 1.

[0106] In Examples 2-1 to 2-2, the thickness of the swelling layer was adjusted according to Table 2, and the rest were the same as in Examples 1-4.

[0107] In Examples 2-3 to 2-4, the thickness of the first adhesive layer was adjusted according to Table 2, and the rest were the same as in Examples 1-4.

[0108] In Examples 2-5 to 2-6, the thickness of the second adhesive layer was adjusted according to Table 2, and the rest were the same as in Examples 1-4.

[0109] In Examples 2-7 to 2-8, the thicknesses of the swelling layer, the first adhesive layer, and the second adhesive layer are adjusted according to Table 2, and the rest are the same as in Examples 1-4.

[0110] In Examples 2-9 to 2-10, except for adjusting the bonding area ratio according to Table 2, the rest are the same as in Examples 1-4.

[0111] In Comparative Example 1-1, except that the swelling layer in <Preparation of Adhesive Structure> includes 100% polyurethane (a composition of butanediol polyol and diphenylmethane-4,4′-diisocyanate in a mass ratio of 1:1) and no first adhesive layer is provided, the rest is the same as in Example 1-1.

[0112] In Comparative Examples 1-2, except that the swelling layer in the <Preparation of Adhesive Structure> includes 100% polyurethane acrylic (a composition prepared by mixing and defoaming 40 parts by weight of polyurethane acrylate, 70 parts by weight of isoborneol acrylate, and 0.5 parts by weight of photoinitiator) and no first adhesive layer is provided, the rest are the same as in Examples 1-1.

[0113] In Comparative Examples 1-3, except that in the <Preparation of Adhesive Structure>, the swelling layer includes 100% epoxy acrylic acid (a composition prepared by mixing and defoaming 60 parts by weight of epoxy acrylate, 38 parts by weight of isoborneol acrylate, and 1.2 parts by weight of photoinitiator) and no first adhesive layer is provided, the rest are the same as in Examples 1-1.

[0114] In Comparative Examples 1-4, except that in the <Preparation of Adhesive Structure> the swelling layer includes 100% cellulose (made of cellulose acetate propionate compound with a number average molecular weight of 70,000) by mass percentage and no first adhesive layer is provided, the rest are the same as in Examples 1-1.

[0115] The changes in preparation parameters for Examples 1-1 to 1-12 and Comparative Examples 1-1 to 1-4 are shown in Table 1; the changes in preparation parameters for Examples 2-1 to 2-10 are shown in Table 2; and the performance parameters for Examples 1-1 to 1-12, Examples 2-1 to 2-10, and Comparative Examples 1-1 to 1-4 are shown in Table 3.

[0116] Table 1

[0117]

[0118] Note: In Table 1, "\" indicates that there is no corresponding parameter.

[0119] Table 2

[0120]

[0121]

[0122]

[0123] As can be seen from Examples 1-1 to 1-4, Examples 1-12, and Comparative Example 1-1, the safety performance of lithium-ion batteries varies with the composition of the swelling layer. The composition of the swelling layer in lithium-ion batteries within the scope of this application exhibits good safety performance.

[0124] The mass ratio of acrylonitrile-butadiene-styrene copolymer also typically affects the safety performance of lithium-ion batteries. As can be seen from Examples 1-1 to 1-4 and Examples 1-12, lithium-ion batteries with a mass ratio of acrylonitrile-butadiene-styrene copolymer within the scope of this application exhibit good safety performance.

[0125] The mass ratio of acrylonitrile, butadiene, and styrene in the acrylonitrile-butadiene-styrene copolymer also typically affects the safety performance of lithium-ion batteries. As can be seen from Examples 1-4 to 1-8, the lithium-ion batteries with the appropriate mass ratio of acrylonitrile, butadiene, and styrene within the scope of this application exhibit good safety performance.

[0126] The type of functional resin also typically affects the safety performance of lithium-ion batteries. As can be seen from Examples 1-4 and 1-9, the types of functional resins used in the lithium-ion batteries within the scope of this application demonstrate good safety performance.

[0127] The type of material used in the first adhesive layer also typically affects the safety performance of lithium-ion batteries. As can be seen from Examples 1-4 and 1-10, the type of material used in the first adhesive layer of the lithium-ion battery within the scope of this application exhibits good safety performance.

[0128] The type of material used in the second adhesive layer also typically affects the safety performance of lithium-ion batteries. As can be seen from Examples 1-4 and 1-11, the type of material used in the second adhesive layer in the lithium-ion batteries within the scope of this application exhibits good safety performance.

[0129] The thickness of the swelling layer, the first adhesive layer, the second adhesive layer, and the adhesive structure also typically affect the safety performance of lithium-ion batteries. As can be seen from Examples 1-4 and Examples 2-1 to 2-8, the lithium-ion batteries within the scope of this application exhibit good safety performance due to the thicknesses of the swelling layer, the first adhesive layer, the second adhesive layer, and the adhesive structure.

[0130] The proportion of the adhesive structure's bonding area on the outer surface of the electrode assembly also typically affects the high-temperature safety performance of lithium-ion batteries. As can be seen from Examples 1-4, 2-9 to 2-10, the lithium-ion batteries within the scope of this application exhibit good safety performance due to the proportion of the adhesive structure's bonding area on the outer surface of the electrode assembly.

[0131] The above description is only a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. An adhesive structure comprising a swollen layer and an adhesive layer disposed on at least one surface of the swollen layer; The swelling layer comprises an acrylonitrile-butadiene-styrene copolymer and a functional resin; Based on the total mass of the swollen layer, the acrylonitrile-butadiene-styrene copolymer accounts for 85% to 98% by mass, and the functional resin accounts for 2% to 15% by mass. Based on the total mass of the acrylonitrile-butadiene-styrene copolymer, the mass ratio of acrylonitrile, butadiene and styrene in the acrylonitrile-butadiene-styrene copolymer is (5-20):(55-80):(5-25). The functional resin includes at least one of styrene-ethylene-butene-styrene block copolymer, ethylene-vinyl acetate copolymer, polyurethane elastomer, thermoplastic elastomer, and polyurethane acrylate.

2. The adhesive structure according to claim 1, wherein, The thickness of the adhesive structure is 20 μm to 50 μm.

3. The adhesive structure according to claim 1, wherein, The adhesive structure satisfies at least one of the following characteristics: (a) The thickness of the swollen layer is 10 μm to 30 μm; (b) The thickness of the adhesive layer is 5 μm to 10 μm.

4. The adhesive structure according to claim 1, wherein, The adhesive layer is made of at least one of polymethyl methacrylate, polypropylene, hot-melt styrene-isoprene-styrene rubber, polyethylene, or polyamide.

5. The adhesive structure according to claim 1, wherein, The adhesive strength of the adhesive layer is from 0.15 N / mm to 0.5 N / mm.

6. The adhesive structure according to claim 1, wherein, The adhesive structure satisfies at least one of the following conditions: (1) The adhesive structure is immersed in an electrolyte at 85°C for 4 hours, and the three-dimensional volume expansion rate of the adhesive structure is 180% to 500%; (2) The initial tack of the ball in the adhesive structure is ≥8#; (3) The tensile strength of the adhesive structure is 0.2 N / mm to 0.5 N / mm.

7. The adhesive structure according to claim 1, wherein, The adhesive structure further includes an anti-adhesion layer, which is disposed on the outer surface of the adhesive layer; The anti-stick layer includes release paper or release film.

8. An electrochemical device comprising an electrode assembly, a housing, and an adhesive structure according to any one of claims 1 to 7, wherein the adhesive layer is bonded to an outer surface of the electrode assembly and / or an inner surface of the housing.

9. The electrochemical device according to claim 8, wherein, Based on the total area of ​​the outer surface of the electrode assembly, the bonding area of ​​the adhesive structure accounts for 10% to 100%.

10. An electronic device comprising the electrochemical device of claim 8 or 9.

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