Expanding adhesive tape for battery encapsulation, its preparation method and application, secondary batteries and electrical devices.

Abstract

This application provides an expansion tape 7 for battery encapsulation, comprising a substrate 71, an expansion layer 72, and a base coating 73. The substrate 71 has opposing first and second surfaces. The expansion layer 72 is disposed on the first surface of the substrate 71. The expansion layer 72 comprises an organic adhesive and a temperature-expanding material. The temperature-expanding material is a material capable of volume expansion after heat treatment. The base coating 73 is disposed on the second surface of the substrate 71. The base coating 73 has adhesive properties.

Description

Technical Field

[0001] This application relates to the field of secondary batteries, specifically to an expansion tape for battery encapsulation, its preparation method and application, secondary batteries, and electrical devices. Background Technology

[0002] With the rapid development of the electric vehicle industry, the application of secondary batteries such as lithium-ion batteries in power storage has been increasing year by year, leading to a surge in research on high-power secondary batteries. Some emerging fields are placing higher demands on secondary batteries. Currently, the most widely used high-power power batteries are hard-shell batteries. However, as energy density increases, the negative electrode expands during long-term storage cycles due to charging and discharging, potentially rupturing the casing and causing safety accidents. Therefore, the battery pack margin should not be too high, resulting in a gap between the casing and the bare cell. Expansion tape can fill this gap, while also alleviating electrode expansion stress and improving battery safety. However, traditional expansion tape has a relatively small expansion rate, making it difficult to meet the requirements of low battery pack margins. Summary of the Invention

[0003] In view of the above problems, this application provides an expansion tape for battery encapsulation, its preparation method and application, a secondary battery and an electrical device, which can meet the requirements of low battery mass margin.

[0004] One aspect of this application provides an expansion tape for battery encapsulation, comprising:

[0005] The substrate has a first surface and a second surface opposite to each other;

[0006] An expansion layer, disposed on a first surface of the substrate, the expansion layer comprising an organic adhesive and a temperature-expanding material, the temperature-expanding material being a material capable of volume expansion after heat treatment; and

[0007] A base coating is disposed on the second surface of the substrate, and the base coating has adhesive properties.

[0008] The expansion tape for battery encapsulation according to this application includes a substrate, an expansion layer, and a base layer. The base layer includes an organic adhesive and a temperature-expanding material. The organic adhesive has swelling properties, and the temperature-expanding material can expand in volume after heat treatment. The expansion tape has a large expansion ratio and can be used for secondary battery encapsulation, filling the gap between the electrode assembly and the casing, thus meeting the requirements for low battery capacity.

[0009] In some embodiments, the maximum ratio of the expanded tape's thickness after expansion to its initial unexpanded thickness is ≥5, optionally 5 to 10. When the maximum ratio of the expanded tape's thickness after expansion to its initial unexpanded thickness is within the above range, the expanded tape has a large expansion ratio, enabling it to significantly expand and fill the gap between the electrode assembly and the housing.

[0010] In some embodiments, the initial unexpanded thickness of the expandable tape is 100μm to 500μm, optionally 150μm to 300μm. When the initial unexpanded thickness of the expandable tape is within this range, it can fill most of the gap between the electrode assembly and the housing after expansion, thus solving the filling problem between the electrode assembly and the housing of low-margin power batteries.

[0011] In some embodiments, the thickness of the expanded adhesive tape after expansion is 1mm to 5mm, optionally 1mm to 3mm. When the thickness of the expanded adhesive tape is within the above range, it can fill most of the gap between the electrode assembly and the housing after expansion, thus solving the filling problem between the electrode assembly and the housing of low-margin power batteries.

[0012] In some embodiments, the compression rate of the expanded tape after expansion is 10% to 75%, where the compression rate refers to the percentage reduction in thickness of the expanded tape under a preset stress. When the compression rate of the expanded tape is within the above range, the expanded tape can be compressed during battery cycling, alleviating the expansion stress on the electrode assembly during cycling.

[0013] In some embodiments, the ratio of the thickness of the substrate to the initial unexpanded thickness of the expanding tape is (2-10):100, optionally (3-6):100; when the ratio of the thickness of the substrate to the initial unexpanded thickness of the expanding tape is within the above range, the expanding tape has suitable mechanical strength.

[0014] Optionally, the thickness of the substrate is 5μm to 30μm, and optionally 5μm to 15μm.

[0015] In some embodiments, the ratio of the initial unexpanded thickness of the expanded layer to the initial unexpanded thickness of the expanded tape is (75-97):100, optionally (90-97):100. When the ratio of the initial unexpanded thickness of the expanded layer to the initial unexpanded thickness of the expanded tape is within the above range, the expanded tape has a large expansion ratio.

[0016] Optionally, the thickness of the expansion layer is 75μm to 450μm, and optionally 100μm to 200μm.

[0017] In some embodiments, the ratio of the thickness of the base coating to the initial unexpanded thickness of the expandable tape is (1-5):100, optionally (15-3):100;

[0018] Optionally, the thickness of the base coating is 2.5 μm to 20 μm, and optionally 2.5 μm to 7.5 μm.

[0019] In some embodiments, the mass ratio of the organic adhesive to the temperature-expanding material in the expansion layer is (50-80):(20-50);

[0020] Optionally, the organic adhesive in the expansion layer has a mass content of 50% to 80%, and the temperature-expanding material has a mass content of 20% to 50%. When the contents of the organic adhesive and the temperature-expanding material in the expansion layer are within the above ranges, the expansion layer has both good swelling properties and temperature-expanding properties, and the expansion ratio of the expansion tape is large and it is not easy for adhesive to overflow.

[0021] In some embodiments, the swelling ratio of the organic adhesive is 50% to 200%; the swelling ratio refers to the ratio of the volume of the organic adhesive placed in the electrolyte to the volume of the dried organic adhesive. When the swelling ratio of the organic adhesive is within the above range, the organic adhesive in the expansion layer can absorb electrolyte and expand during the secondary battery encapsulation process, resulting in a relatively large expansion ratio of the expansion tape.

[0022] In some embodiments, the glass transition temperature of the organic adhesive is -20°C to 60°C. When the glass transition temperature of the organic adhesive is within this range, the expansion ratio of the expanded tape is larger and the mechanical properties are better.

[0023] In some embodiments, the initial expansion temperature of the temperature-expanding material is 70°C to 130°C, optionally 80°C to 110°C. Since the initial expansion temperature of the temperature-expanding material is within this range, the expansion tape can be matched with traditional secondary battery encapsulation processes, completing the temperature-responsive expansion process during secondary battery encapsulation. Therefore, the expansion tape can expand synchronously during the secondary battery encapsulation process, filling the gap between the electrode plates and the casing.

[0024] In some embodiments, the organic adhesive includes at least one selected from acrylate adhesives, methyl methacrylate adhesives, acrylic adhesives, ethylene-vinyl acetate adhesives, and polypropylene adhesives; optionally, it includes acrylate adhesives. The above-mentioned organic adhesives possess both good swelling properties and adhesion, maintaining a certain adhesive strength even after absorbing electrolyte and swelling.

[0025] In some embodiments, the substrate is made of at least one of polyethylene terephthalate, polyimide, polypropylene, and polyethylene.

[0026] In some embodiments, the base coating comprises at least one of modified polypropylene, styrene-isoprene-styrene block copolymer, and hydrogenated styrene-butadiene-styrene block copolymer. The aforementioned base coating materials exhibit good adhesion and electrolyte resistance. When used for secondary battery encapsulation, the base coating maintains good adhesion after electrolyte injection, preventing the expansion tape from detaching or shifting.

[0027] In some embodiments, the expanding tape further includes:

[0028] An oriented polystyrene layer is disposed on the surface of the expanded layer away from the substrate;

[0029] Optionally, the ratio of the thickness of the oriented polystyrene layer to the thickness of the expanding tape is ≤20:100, and can be (5~20):100;

[0030] Optionally, the thickness of the oriented polystyrene layer is 15 μm to 90 μm, and more preferably 25 μm to 50 μm.

[0031] Oriented polystyrene layers have the characteristics of high strength, high rigidity, and stable shape. By setting an oriented polystyrene layer on the surface of the expansion layer away from the substrate, the stress on the two surfaces of the expansion layer is basically the same, so the expansion tape is not easy to deform or curl after expansion.

[0032] Secondly, this application also provides a method for preparing an expansion tape for battery encapsulation, comprising the following steps for preparing the expansion tape described in the first aspect:

[0033] An expanded layer is prepared on one surface of the substrate;

[0034] A base coating is prepared on the surface of the substrate away from the expansion layer.

[0035] The expansion tape prepared by the method of this application has both swelling properties and temperature-responsive expansion properties. The expansion tape has a large expansion ratio, making it particularly suitable for secondary battery encapsulation and able to meet the low margin requirements of batteries.

[0036] In some embodiments, the step of preparing the expanded layer includes:

[0037] The raw materials of organic adhesives and temperature-expanding materials are mixed to prepare a slurry precursor;

[0038] The slurry precursor is cured and reacted to prepare an expanded layer slurry.

[0039] The expanded layer slurry is coated onto the surface of the substrate.

[0040] In some embodiments, the method for preparing the expanding adhesive tape satisfies at least one of the conditions in (1) to (2):

[0041] (1) The solid content of the expanded layer slurry is 10% to 50%;

[0042] (2) The viscosity of the expansion layer slurry is 50 mPa·s to 500 mPa·s.

[0043] Thirdly, this application also provides the application of the expansion tape mentioned in the first aspect in the preparation of batteries.

[0044] Fourthly, this application also provides a method for preparing a secondary battery, comprising the following steps:

[0045] The base coating of the expansion tape described in the first aspect is attached to the surface of the electrode assembly;

[0046] The electrode assembly with the expansion tape attached is placed in the housing and vacuum dried at 70°C to 130°C, causing the expansion tape to expand once.

[0047] Seal the housing:

[0048] Electrolyte is injected into the sealed housing, causing the expansion tape, which has already expanded once, to absorb the electrolyte and expand a second time.

[0049] The secondary battery preparation method of this application adopts the expansion tape of the first aspect. By setting the expansion tape in the secondary battery packaging process, the expansion tape expands synchronously during the secondary battery packaging process, thereby filling the gap between the electrode assembly and the shell, which can meet the low margin requirement of the battery. The above-mentioned secondary battery preparation method has a simple preparation process and low production cost.

[0050] Fifthly, this application also provides a secondary battery, comprising:

[0051] A housing, the housing being filled with an electrolyte;

[0052] Electrode assemblies, disposed within the housing; and

[0053] The aforementioned expansion tape of the first aspect is disposed between the housing and the electrode assembly and fills the gap between the housing and the electrode assembly, wherein the base coating of the expansion tape is attached to the surface of the electrode assembly.

[0054] The secondary battery of this application embodiment can effectively fill the gap between the casing and the electrode assembly by providing the expansion tape of the first aspect between them, thereby meeting the low margin requirement of the battery.

[0055] Sixthly, this application also provides a battery module, including the secondary battery described in the fifth aspect above.

[0056] In a seventh aspect, this application also provides a battery pack, including the battery module described in the sixth aspect above.

[0057] Eighthly, this application also provides an electrical device, including at least one selected from the secondary battery of the fifth aspect, the battery module of the sixth aspect, or the battery pack of the seventh aspect.

[0058] Details of one or more embodiments of this application are set forth in the following drawings and description, and other features, objects and advantages of this application will become apparent from the specification, drawings and claims. Attached Figure Description

[0059] Figure 1 This is a schematic diagram of the structure of an expansion tape according to an embodiment of this application;

[0060] Figure 2 This is a schematic diagram of the structure of an expansion tape according to another embodiment of this application;

[0061] Figure 3 This is a schematic flowchart of a method for preparing an expanding adhesive tape according to an embodiment of this application;

[0062] Figure 4 This is a schematic diagram of a secondary battery according to one embodiment of this application;

[0063] Figure 5 yes Figure 4 An exploded view of a secondary battery according to an embodiment of this application is shown.

[0064] Figure 6 This is a schematic flowchart of a secondary battery preparation method according to an embodiment of this application;

[0065] Figure 7 This is a schematic diagram of a battery module according to one embodiment of this application;

[0066] Figure 8 This is a schematic diagram of a battery pack according to one embodiment of this application;

[0067] Figure 9 yes Figure 8 An exploded view of a battery pack according to one embodiment of this application is shown;

[0068] Figure 10This is a schematic diagram of an electrical device that uses a secondary battery as a power source according to one embodiment of this application;

[0069] Explanation of reference numerals in the attached figures:

[0070] 1. Battery pack; 2. Upper casing; 3. Lower casing; 4. Battery module; 5. Secondary battery; 51. Housing; 52. Electrode assembly; 53. Cover plate; 6. Electrical device; 7. Expansion tape; 71. Substrate; 72. Expansion layer; 73. Primer layer; 74. Oriented styrene layer.

[0071] To better describe and illustrate embodiments and / or examples of the inventions disclosed herein, reference may be made to one or more accompanying drawings. Additional details or examples used to describe the drawings should not be considered as limiting the scope of any of the disclosed inventions, the currently described embodiments and / or examples, or the best mode of these inventions as currently understood. Detailed Implementation

[0072] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings. Preferred embodiments of this application are shown in the drawings. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of this application.

[0073] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0074] See Figure 1 According to one embodiment of this application, an expansion tape 7 for battery encapsulation is provided, including a substrate 71, an expansion layer 72 and a base coating layer 73.

[0075] The substrate 71 has a first surface and a second surface that are opposite to each other.

[0076] An expansion layer 72 is disposed on the first surface of the substrate 71. The expansion layer 72 includes an organic adhesive and a temperature-expanding material. The temperature-expanding material is a material that can undergo volume expansion after heat treatment.

[0077] The primer coating 73 is disposed on the second surface of the substrate 71. The primer coating 73 has adhesive properties.

[0078] The aforementioned expansion tape 7 for battery encapsulation includes a substrate 71, an expansion layer 72, and a base layer 73. The base layer 73 includes an organic adhesive and a temperature-expanding material. The organic adhesive has swelling properties, and the temperature-expanding material can expand in volume after heat treatment. The aforementioned expansion tape 7 has a large expansion ratio and can be used in secondary battery encapsulation to fill the gaps between the electrode components and the casing.

[0079] In some embodiments, the maximum ratio of the expanded adhesive tape 7's thickness after expansion to its initial unexpanded thickness is ≥5. The maximum ratio of the expanded adhesive tape 7's thickness after expansion to its initial unexpanded thickness refers to the ratio of the maximum expanded thickness of the expanded adhesive tape 7 to its initial unexpanded thickness. As an example, the expanded adhesive tape 7 expands to its maximum thickness through the following process: the base coating 73 of the expanded adhesive tape 7 is adhered to the substrate and its initial unexpanded thickness is measured; then the expanded adhesive tape 7 is heat-treated at 110°C for 4 hours to induce primary expansion; next, the primary expanded adhesive tape 7 is immersed in a conventional secondary battery electrolyte for at least 48 hours to induce secondary expansion; the expanded adhesive tape 7 is then removed and its expanded thickness is measured as the maximum expanded thickness of the expanded adhesive tape 7. Specifically, the thickness of the expanded adhesive tape 7 in each state can be easily measured using a micrometer. When the maximum ratio of the expanded adhesive tape 7's thickness after expansion to its initial unexpanded thickness is within the above range, the expanded adhesive tape 7 has a large expansion ratio, enabling it to significantly expand and fill the gap between the electrode assembly and the housing. Furthermore, the maximum ratio of the expanded thickness of the adhesive tape 7 after expansion to its initial unexpanded thickness is 5 to 10. Optionally, the maximum ratio of the expanded thickness of the adhesive tape 7 after expansion to its initial unexpanded thickness can be within any of the following ranges: 5, 6, 7, 8, 9, or 10.

[0080] In some embodiments, the initial unexpanded thickness of the expanding tape 7 is 100 μm to 500 μm. With an initial unexpanded thickness within this range, the expanding tape 7 can fill most of the gap between the electrode assembly and the housing after expansion, thus solving the filling problem between the electrode assembly and the housing in low-margin power batteries. Optionally, the initial unexpanded thickness of the expanding tape 7 can be within any of the following ranges: 100 μm, 150 μm, 200 μm, 250 μm, 300 μm, 350 μm, 400 μm, 450 μm, or 500 μm. Further, the initial unexpanded thickness of the expanding tape 7 is 150 μm to 300 μm.

[0081] In some embodiments, the thickness of the expanded adhesive tape 7 after expansion is 1mm to 5mm. When the thickness of the expanded adhesive tape 7 is within this range, it can fill most of the gap between the electrode assembly and the housing after expansion, thus solving the filling problem between the electrode assembly and the housing of a low-margin power battery. Optionally, the thickness of the expanded adhesive tape 7 can be within any of the following ranges: 1mm, 2mm, 3mm, 4mm, or 5mm. Further, the thickness of the expanded adhesive tape 7 is 1mm to 3mm.

[0082] In some embodiments, the compression rate of the expanded adhesive tape 7 is 10% to 75%. The compression rate refers to the percentage reduction in thickness of the expanded adhesive tape 7 under a preset stress. In this embodiment, the compression rate of the expanded adhesive tape 7 can be tested by: first, testing the thickness of the expanded adhesive tape 7; then, applying a pressure of 1.5 MPa to the surface of the expanded adhesive tape 7 near the base coating 73, and testing its thickness under pressure, thus calculating the compression rate. When the compression rate of the expanded adhesive tape 7 is within the above range, the expanded adhesive tape 7 can be compressed during secondary battery cycling, thereby alleviating the expansion stress on the electrode assembly during cycling. Optionally, the compression rate of the expanded adhesive tape 7 can be within any of the following ranges: 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 72%, or 75%.

[0083] In some embodiments, the ratio of the thickness of the substrate 71 to the initial unexpanded thickness of the expandable tape 7 is (2-10):100. When the ratio of the thickness of the substrate 71 to the initial unexpanded thickness of the expandable tape 7 is within the aforementioned range, the expandable tape 7 possesses suitable mechanical strength. Further, the ratio of the thickness of the substrate 71 to the initial unexpanded thickness of the expandable tape 7 is (3-6):100.

[0084] In some embodiments, the thickness of the substrate 71 is 5 μm to 30 μm. Optionally, the thickness of the substrate 71 can be within any of the following ranges: 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 20 μm, 25 μm, or 30 μm. Further, the thickness of the substrate 71 is 5 μm to 15 μm.

[0085] In some embodiments, the ratio of the initial unexpanded thickness of the expanded layer 72 to the initial unexpanded thickness of the expanded tape 7 is (75-97):100. When the ratio of the initial unexpanded thickness of the expanded layer 72 to the initial unexpanded thickness of the expanded tape 7 is within the above range, the expanded tape 7 has a large expansion ratio. Further, the ratio of the initial unexpanded thickness of the expanded layer 72 to the initial unexpanded thickness of the expanded tape 7 is (90-97):100.

[0086] In some embodiments, the thickness of the expansion layer 72 is 75 μm to 450 μm. Optionally, the thickness of the expansion layer 72 is 75 μm, 80 μm, 90 μm, 100 μm, 120 μm, 150 μm, 160 μm, 180 μm, 200 μm, 250 μm, 300 μm, 350 μm, 400 μm, or 450 μm. Further, the thickness of the expansion layer 72 is 100 μm to 200 μm.

[0087] In some embodiments, the ratio of the thickness of the base coating 73 to the initial unexpanded thickness of the expanding tape 7 is (1-5):100. Further, the ratio of the thickness of the base coating 73 to the initial unexpanded thickness of the expanding tape 7 is (1.5-3):100. The base coating 73 has adhesive properties and can adhere to the surface of the electrode assembly during the secondary battery encapsulation process. By controlling the thickness of the base coating 73 within the above-mentioned range, the expanding tape 7 can achieve a good bonding effect.

[0088] In some embodiments, the thickness of the base coating 73 is 2.5 μm to 20 μm. Optionally, the thickness of the base coating 73 is 2.5 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 7.5 μm, 8 μm, 10 μm, 12 μm, 14 μm, 15 μm, 16 μm, 18 μm, or 20 μm. Further, the thickness of the base coating 73 is 2.5 μm to 7.5 μm.

[0089] In some embodiments, the mass ratio of organic adhesive to temperature-expanding material in the expansion layer 72 is (50-80):(20-50). When the mass ratio of organic adhesive to temperature-expanding material in the expansion layer 72 is within the above range, the expansion layer 72 has both good swelling properties and temperature-expanding properties, and the expansion ratio of the expansion tape 7 is large and it is not easy for adhesive to overflow.

[0090] In some embodiments, the organic adhesive content in the expansion layer 72 is 50% to 80% by mass, and the thermo-expanding material content is 20% to 50% by mass. Optionally, the organic adhesive content in the expansion layer 72 can be within any of the following ranges: 50%, 55%, 60%, 65%, 70%, 75%, or 80%. The thermo-expanding material content in the expansion layer 72 can be within any of the following ranges: 20%, 25%, 30%, 35%, 40%, 45%, or 50%.

[0091] In some embodiments, the swelling ratio of the organic adhesive is 50% to 200%. The swelling ratio refers to the ratio of the volume of the organic adhesive placed in the electrolyte to the volume of the dried organic adhesive. When the swelling ratio of the organic adhesive is within the above range, the organic adhesive in the expansion layer 72 can absorb electrolyte and expand during the secondary battery encapsulation process, resulting in a relatively large expansion ratio of the expansion tape 7. Optionally, the swelling ratio of the organic adhesive can be within any of the following ranges: 50%, 60%, 70%, 80%, 90%, 100%, 120%, 140%, 150%, 160%, 180%, or 200%.

[0092] In some embodiments, the glass transition temperature of the organic adhesive is -20°C to 60°C. The glass transition temperature is the temperature at which the organic adhesive transitions from a highly elastic state to a glassy state. Above this temperature, the organic adhesive exhibits elasticity; below this temperature, it exhibits brittleness. The glass transition temperature of the organic adhesive can be measured using methods known in the art, such as dilatometer method, refractive index method, thermomechanical method, differential thermal analysis (DTA), dynamic mechanical property analysis (DMA), nuclear magnetic resonance (NMR), etc. When the glass transition temperature of the organic adhesive is within the above range, the expansion ratio of the expanded adhesive tape is larger and the mechanical properties are better. Optionally, the glass transition temperature of the organic adhesive can be within any of the following ranges: -20°C, -10°C, 0°C, 5°C, 10°C, 20°C, 30°C, 40°C, 50°C, or 60°C.

[0093] In some embodiments, the initial expansion temperature of the temperature-expanding material is 70°C to 130°C. The initial expansion temperature of the temperature-expanding material refers to the temperature at which the material begins to expand. When the initial expansion temperature of the temperature-expanding material is within the above range, the expansion tape 7 can be matched with traditional secondary battery encapsulation processes, completing the temperature-responsive expansion process during the secondary battery encapsulation process. Therefore, the expansion tape 7 can expand synchronously during the secondary battery encapsulation process, filling the gap between the electrode sheet and the casing. Optionally, the initial expansion temperature of the temperature-expanding material can be within any of the following ranges: 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, or 130°C. Further, the initial expansion temperature of the temperature-expanding material is 80°C to 110°C.

[0094] In some embodiments, the organic adhesive includes at least one selected from acrylate adhesives, methyl methacrylate adhesives, acrylic adhesives, ethylene-vinyl acetate adhesives, and polypropylene adhesives. Optionally, the organic adhesive includes acrylate adhesives. The above-mentioned organic adhesives possess both good swelling properties and adhesion, maintaining a certain adhesive strength even after absorbing electrolyte and swelling.

[0095] In some embodiments, the temperature-expanding material includes at least one of expanded microspheres and polyurethane. The initial expansion temperature and expansion ratio of the above-mentioned temperature-expanding material are suitable, and the expanding tape 7 has a large expansion ratio. Optionally, the temperature-expanding material includes expanded microspheres. Expanded microspheres are thermoplastic hollow polymer microspheres composed of a thermoplastic polymer shell and encapsulated liquid alkane gas. When heated, the gas pressure inside the shell increases and the thermoplastic shell softens, thereby significantly increasing the volume of the expanded microspheres. When cooled, the shell of the expanded microspheres hardens again, and the volume remains fixed.

[0096] In some embodiments, the expandable microspheres may be selected from at least one of Akzo's EXPANCEL series: 551DU40, 461DU20, 461DU40, 031DU40, 053DU40, 007WUF20, and 031WUF20. The aforementioned expandable microspheres have a suitable initial expansion temperature.

[0097] In some embodiments, the expanded layer 72 may optionally include a tackifier. As an example, the tackifier includes at least one selected from C5 petroleum resin, C9 petroleum resin, hydrocarbon petroleum resin, and dicyclopentadiene DCPD resin. Further, the tackifier content in the expanded layer 72 is 5% to 30% by mass.

[0098] In some embodiments, the expansion layer 72 may optionally include an antioxidant. Further, the antioxidant content in the expansion layer 72 is 0.5% to 2% by mass.

[0099] In some embodiments, the material of the substrate 71 includes at least one of polyethylene terephthalate (PET), polyimide (PI), polypropylene (PP), and polyethylene.

[0100] In some embodiments, the base coating 73 comprises at least one of modified polypropylene, styrene-isoprene-styrene block copolymer (SIS), and hydrogenated styrene-butadiene-styrene block copolymer (SEBS). The aforementioned base coating 73 material exhibits good adhesion and electrolyte resistance. When used for secondary battery encapsulation, the base coating 73 maintains good adhesion after electrolyte injection, preventing the expansion tape 7 from detaching or shifting.

[0101] See Figure 2 In some embodiments, the expanding tape 7 further includes an oriented polystyrene layer. The oriented polystyrene layer is disposed on the surface of the expanding layer 72 away from the substrate 71. Oriented polystyrene (OPS) has the characteristics of high strength, high rigidity, and shape stability. By disposing of the oriented polystyrene layer on the surface of the expanding layer 72 away from the substrate 71, the stress on the two surfaces of the expanding layer 72 is basically the same, so the expanding tape 7 is not easily deformed or curled after expansion.

[0102] In some embodiments, the ratio of the thickness of the oriented polystyrene layer to the thickness of the expandable tape 7 is ≤20:100. When the thickness of the oriented polystyrene layer is within this range, the expandable tape 7 has suitable mechanical strength, and the expanded tape 7 is not easily deformed or curled after expansion. Further, the ratio of the thickness of the oriented polystyrene layer to the thickness of the expandable tape 7 is (5-20):100.

[0103] In some embodiments, the thickness of the oriented polystyrene layer is 15 μm to 90 μm. Optionally, the thickness of the oriented polystyrene layer is 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 60 μm, 70 μm, 80 μm, or 90 μm. Further, the thickness of the oriented polystyrene layer is 25 μm to 50 μm.

[0104] See Figure 3 In another embodiment of this application, a method for preparing an expansion tape 7 for battery encapsulation is also provided, comprising the following steps S110 to S120 for preparing the expansion tape 7 described in the first aspect:

[0105] S110: An expansion layer 72 is prepared on one surface of the substrate 71.

[0106] S120: Prepare a base coating 73 on the surface of the substrate 71 away from the expansion layer 72.

[0107] The expansion tape 7 prepared by the above-mentioned method has both swelling properties and temperature-responsive expansion properties. The expansion tape 7 has a large expansion ratio and is especially suitable for secondary battery encapsulation.

[0108] In some embodiments, step S110 includes:

[0109] S111: The raw materials of the organic adhesive and the temperature-expanding material are mixed to prepare a slurry precursor. In some embodiments, the raw materials of the organic adhesive include an adhesive matrix and a curing agent. Optionally, the adhesive matrix includes at least one selected from methyl methacrylate, vinyl acetate, ethyl acrylate, acrylate, and acrylonitrile.

[0110] In some embodiments, step S111 further includes mixing the solvent and other optional components (e.g., tackifiers and antioxidants) with the raw materials and temperature-expanding materials of the organic adhesive. Specifically, the solvent includes at least one of ethyl acetate, toluene, and xylene.

[0111] S112: The slurry precursor is cured and reacted to prepare the expansion layer 72 slurry.

[0112] S113: Apply the expansion layer 72 slurry to the surface of the substrate 71.

[0113] In some embodiments, the solid content of the expanded layer 72 slurry is 10% to 50%.

[0114] In some embodiments, the viscosity of the expanded layer 72 slurry is 50 mPa·s to 500 mPa·s.

[0115] In some embodiments, step S110 specifically involves: weighing solvent, adhesive matrix, curing agent, temperature-expanding material, and other optional components according to the preset composition of the expansion layer 72. Then, the weighed solvent, adhesive matrix, temperature-expanding material, and other optional components are stirred uniformly under vacuum to prepare a slurry precursor. Next, the curing agent is added to the slurry precursor, and stirring continues under vacuum for 10-20 minutes to prepare the expansion layer 72 slurry. The prepared expansion layer 72 slurry is uniformly coated onto the first surface of the substrate 71 to prepare the expansion layer 72.

[0116] In addition, the secondary battery, battery module, battery pack and power device of this application will be described below with appropriate reference to the accompanying drawings.

[0117] In one embodiment of this application, a secondary battery is provided.

[0118] Typically, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0119] [Positive electrode plate]

[0120] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer including the positive electrode active material of the first aspect of this application.

[0121] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0122] In some embodiments, the positive 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 substrate and a metal layer formed on at least one surface of the polymer substrate. 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 substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0123] In some embodiments, when the secondary battery is a lithium-ion battery, the positive electrode active material may be a positive electrode active material known in the art for lithium-ion batteries. As an example, the positive electrode active material may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM)523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 Al 0.05 At least one of O2 and its modified compounds. Examples of lithium phosphates with an olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0124] In some embodiments, when the secondary battery is a sodium-ion battery, the positive electrode active material can be a positive electrode active material known in the art for sodium-ion batteries. As an example, the positive electrode active material can be a single material or a combination of two or more. The positive electrode active material can be selected from sodium-iron composite oxide (NaFeO2), sodium-cobalt composite oxide (NaCoO2), sodium-chromium composite oxide (NaCrO2), sodium-manganese composite oxide (NaMnO2), sodium-nickel composite oxide (NaNiO2), and sodium-nickel-titanium composite oxide (NaNiO2). 1 / 2 Ti 1 / 2 O2), sodium nickel manganese composite oxide (NaNi) 1 / 2 Mn 1 / 2 O2), sodium iron manganese composite oxide (Na) 2 / 3 Fe 1 / 3 Mn 2 / 3 O2), sodium nickel cobalt manganese composite oxide (NaNi) 1 / 3 Co 1 / 3 Mn 1 / 3 O2), sodium iron phosphate (NaFePO4), sodium manganese phosphate (NaMn) P The present application may use materials such as O4, sodium cobalt phosphate (NaCoPO4), Prussian blue materials, and polyanionic materials (phosphates, fluorophosphates, pyrophosphates, sulfates), but this application is not limited to these materials. Other conventionally known materials that can be used as positive electrode active materials for sodium-ion batteries may also be used.

[0125] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0126] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0127] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0128] [Negative electrode plate]

[0129] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer including a negative electrode active material.

[0130] As an example, the negative electrode current collector has two surfaces opposite each other in its own 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.

[0131] 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 substrate and a metal layer formed on at least one surface of the polymer substrate. 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 substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0132] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. 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, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional 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.

[0133] In some embodiments, the negative electrode film layer may optionally include a binder. 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).

[0134] In some embodiments, the negative electrode film may optionally include a conductive agent. 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.

[0135] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0136] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0137] [Isolation membrane]

[0138] In some embodiments, the secondary battery also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0139] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven 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.

[0140] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0141] [Electrolytes]

[0142] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0143] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0144] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0145] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0146] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0147] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0148] 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. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0149] This application does not impose any particular limitation on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 4 This is an example of a square-structured secondary battery 5.

[0150] In some implementations, refer to Figure 5 The outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 can be placed over the opening to close the receiving cavity. A positive electrode, a negative electrode, and a separator can be formed into an electrode assembly 52 using a winding or stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The secondary battery 5 may contain one or more electrode assemblies 52, which can be selected by those skilled in the art according to specific practical needs.

[0151] Another embodiment of this application also provides a secondary battery 5, including: a housing 51, an electrode assembly 52, and the expansion tape 7 described in the first aspect.

[0152] The housing 51 is filled with electrolyte. The electrode assembly 52 is disposed within the housing. The expansion tape 7 is disposed between the housing 51 and the electrode assembly 52 and fills the gap between them. The base coating 73 of the expansion tape 7 is attached to the surface of the electrode assembly 52.

[0153] See Figure 6 According to one embodiment of this application, a method for preparing a secondary battery 5 is also provided, comprising the following steps S210 to S240:

[0154] S210: The base coating 73 of the expansion tape 7 described above is attached to the surface of the electrode assembly 52.

[0155] S220: The electrode assembly 52 with the expansion tape 7 attached is placed in the housing and vacuum dried at 70℃~130℃, causing the expansion tape 7 to expand once. In step S220, the electrode assembly 52 is placed in the housing 51 and vacuum dried at 70℃~130℃ to remove water and oxygen from the electrode assembly 52 and the housing 51. The temperature-expanding material in the expansion tape 7 expands synchronously during this process, causing the expansion tape 7 to expand once.

[0156] S230: Seal the housing 51. Specifically, in step S230, the housing 51 is sealed by covering the opening of the housing 51 with a cover plate 53.

[0157] S240: Electrolyte is injected into the sealed housing 51, causing the expansion tape 7, which has undergone one expansion, to absorb the electrolyte and expand a second time. In step S240, the organic adhesive in the expansion tape 7 can absorb the electrolyte and swell, thereby causing the expansion tape 7 to expand a second time.

[0158] The above-mentioned secondary battery 5 is prepared by using the expansion tape 7 of the first aspect. By setting the expansion tape 7 in the secondary battery encapsulation process, the expansion tape 7 expands synchronously during the secondary battery encapsulation process, thereby filling the gap between the electrode assembly and the shell. The above-mentioned secondary battery preparation method has a simple preparation process and low production cost.

[0159] In some implementations, the secondary batteries can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0160] Figure 7 This is battery module 4, used as an example. (See reference...) Figure 7 In battery module 4, multiple secondary batteries 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple secondary batteries 5 can be fixed in place using fasteners.

[0161] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of secondary batteries 5 are received.

[0162] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0163] Figure 8 and Figure 9 This is battery pack 1 as an example. (See reference...) Figure 8 and Figure 9 The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0164] In addition, this application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in this application. The secondary battery, battery module, or battery pack 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, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., 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.

[0165] As the electrical device, a secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0166] Figure 10 This is an example of an electrical device. The device could be 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 for this device, a battery pack or battery module can be used.

[0167] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a rechargeable battery as their power source.

[0168] Example

[0169] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0170] (1) Preparation of expanding adhesive tape:

[0171] Materials were selected based on the composition of the expanding tapes in Examples 1-29 and Comparative Example 1 in Table 1.

[0172] Preparation of the expansion layer: Ethyl acetate solvent, adhesive matrix, curing agent, and temperature-expanding material were weighed according to the preset expansion layer composition. The weighed solvent, adhesive matrix, and temperature-expanding material were then stirred uniformly under vacuum to prepare a slurry precursor. The curing agent was then added to the slurry precursor, and stirring continued under vacuum for 20 minutes to prepare the expansion layer slurry. The solid content of the expansion layer slurry was 50%, and the viscosity was 500 mPa·s. The prepared expansion layer slurry was uniformly coated onto the first surface of the substrate to prepare the expansion layer. The composition ratio of the expansion layer can be found in Table 1.

[0173] Preparation of the base coating: SIS and SEBS materials are added to a glass reactor at a mass ratio of 1:1, heated and stirred until uniform, and then coated onto the second surface of the PET substrate and wound up for later use. Specifically, in Example 13, the base coating is prepared by heating and stirring acrylic adhesive (PMMA), uniformly coating it onto the second surface of the PET substrate, and then winding it up for later use.

[0174] Preparation of oriented polystyrene layer: The oriented polystyrene film is transferred and coated onto the expanded layer.

[0175] (2) Electrode assembly fabrication:

[0176] Positive electrode preparation: Lithium iron phosphate (LiFePO4), conductive carbon black (COP), and binder are mixed and dispersed in N-methylpyrrolidone at a weight ratio of 97:1:2. Modified polyvinylidene fluoride (PVDF) is used as the binder. The resulting mixture is thoroughly stirred to form a positive electrode slurry. The slurry is then uniformly coated onto aluminum foil used as a positive electrode current collector, followed by drying, cold pressing, and slitting to obtain the positive electrode sheet.

[0177] Negative electrode preparation: The active material artificial graphite, the conductive agent carbon black, the binder styrene-butadiene rubber (SBR), and the thickener sodium carboxymethyl cellulose (CMC) are dissolved in deionized water at a weight ratio of 97:0.4:1.5:1.1 and mixed evenly to prepare a negative electrode slurry; the negative electrode slurry is evenly coated on the negative electrode current collector copper foil, and then dried, cold-pressed, and slit to obtain the negative electrode sheet.

[0178] Separating membrane: PE porous polymer film is used as the separating membrane.

[0179] Electrode assembly fabrication: The positive electrode sheet, separator and negative electrode sheet are stacked in sequence and then wound, pressed and shaped and the tabs are welded to obtain the electrode assembly.

[0180] (3) Preparation of secondary batteries:

[0181] Electrolyte: In an argon atmosphere glove box with a water content of <10ppm, equal volumes of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are mixed to obtain an organic solvent. Then, 1 mol / L of LiPF6 is uniformly dissolved in the organic solvent to obtain the electrolyte.

[0182] The base coating of the expansion tapes used in Examples 1-29 and Comparative Example 1 was applied to the surface of the electrode assembly, which was then placed in a housing and vacuum dried at 100°C to induce primary expansion of the tape. A cover plate was then placed over the opening of the housing to seal it. Electrolyte was then injected into the sealed housing at room temperature, causing the primary expansion tape to absorb the electrolyte and undergo secondary expansion. After formation and other processes, a secondary battery was obtained. It should be noted that the width of the gap between the housing and the electrode assembly was between 1 mm and 2 mm, matching the secondary expansion thickness of the expansion tape used, and the difference between the gap width and the secondary expansion thickness was within ±50 μm.

[0183] Test section:

[0184] Adhesion test:

[0185] The adhesion test was conducted according to the 180-degree peel strength test method for adhesive tape. Specifically, the adhesive tape to be tested was cut into 20*100mm samples for later use. The bottom coating side of the cut sample was attached to a steel plate and rolled back and forth twice with a 2kg roller to ensure complete adhesion. One end of the sample was then bent in the opposite direction at a bending angle of 180°. A high-speed rail tensile testing machine was used. One end of the steel plate was fixed to the lower clamp of the tensile testing machine, and the bent end of the sample was fixed to the upper clamp. The angle of the sample was adjusted to ensure that the upper and lower ends were in a vertical position. Then, the sample was stretched at a speed of 50mm / min until the sample was completely peeled off from the steel plate. The displacement and force during the process were recorded. Generally, the force at which the forces are balanced is considered to be the adhesion force of the sample.

[0186] Expansion test of expansion tape:

[0187] Cut the expanding tape into 5*5mm sheets and attach them to the substrate. Measure the initial unexpanded thickness using a micrometer. Then, heat at 100℃ for 4 hours to allow the tape to expand once; measure the thickness of the first expansion using a micrometer. Next, immerse the expanded tape in an electrolyte solution at 45℃ for 48 hours to allow for a second expansion; measure the thickness of the second expansion using a micrometer. Thickness testing is performed as follows: Prepare two 5cm*5cm*0.5cm flat PP boards. Place the PP boards on a horizontal workbench, with the tape (before and after expansion) placed flat between the boards. Measure the thickness using a micrometer, taking the average of 10 measurements. The maximum expansion ratio is the ratio of the second expansion thickness to the initial unexpanded thickness.

[0188] Compression ratio test:

[0189] A stress of 1.5 MPa is applied to the expanded tape after secondary expansion, and its thickness under stress is tested. The ratio of the reduction in thickness of the expanded tape under stress to its secondary expansion thickness is the compression ratio of the expanded tape.

[0190] Secondary battery cycle test:

[0191] The prepared battery cell is hung and tested cyclically. After the battery cell has circulated 100 times, it is removed. Then the battery cell is disassembled, the expansion tape is removed, and its thickness is tested with a micrometer. Visually observe whether there is any glue overflow around the tape.

[0192] Table 1

[0193]

[0194]

[0195]

[0196]

[0197] Table 2

[0198]

[0199]

[0200] Table 3

[0201]

[0202] As can be seen from the data in Tables 1 to 3, the adhesive force of the expanding tapes in Examples 1 to 28 ranges from 258 N to 470 N, with a maximum expansion ratio of 3.3 to 10. The compression ratio of the expanding tapes after expansion is 55% to 72%. The expanding tapes in Examples 1 to 28 have a large expansion ratio and can be compressed after expansion. Therefore, the expanding tapes in Examples 1 to 29 can effectively fill the gaps between the electrode assembly and the casing, and effectively buffer the volume expansion of the electrode assembly during cycling, thus meeting the low margin requirements of the battery. The secondary batteries made with the expanding tapes in Examples 1 to 28 showed no tape overflow within 400 cycles.

[0203] As can be seen from Examples 1-8, the expansion tape prepared using 031DU40 expansion microspheres in Example 4 has a relatively large maximum expansion ratio. Examples 4 and 14-16, by adjusting the composition ratio of the expansion layer, achieve a maximum expansion ratio of 6.2-9.4 for the expansion tape, exhibiting a large expansion ratio. Examples 1-19 and 25 all have a maximum expansion ratio ≥5, and a thickness of 100μm-200μm is sufficient to meet the encapsulation requirements of most commercially available secondary batteries.

[0204] The difference between the expansion tape of Comparative Example 1 and Example 1 is that the expansion layer does not contain temperature-expanding materials, the adhesive force of the expansion tape is 405N, and the maximum expansion ratio is 2.1, which is difficult to meet the encapsulation requirements of commercial secondary batteries; the compression rate of the expansion tape of Comparative Example 1 after expansion is 51%; and it is actually quite difficult to prepare an expansion tape with a thickness >100μm as required by Comparative Example 1, as its thickness after expansion is difficult to meet the requirements of secondary battery encapsulation.

[0205] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0206] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A secondary battery, comprising: A housing, the housing being filled with an electrolyte; Electrode assembly, disposed within the housing; as well as Expanding tape is disposed between the housing and the electrode assembly and fills the gap between the housing and the electrode assembly; The expanding tape includes: The substrate has a first surface and a second surface opposite to each other; An expansion layer is disposed on a first surface of the substrate. The expansion layer comprises an organic adhesive and a temperature-expanding material, wherein the temperature-expanding material is a material capable of volume expansion after heat treatment. The organic adhesive comprises at least one selected from acrylic adhesives, ethylene-vinyl acetate adhesives, and polypropylene adhesives. The temperature-expanding material comprises at least one selected from expanded microspheres and polyurethane. A base coating is disposed on a second surface of the substrate, and the base coating has adhesive properties; the base coating of the expanding tape is attached to the surface of the electrode assembly; The thickness of the expansion layer is 75μm to 450μm; the mass ratio of the organic adhesive to the temperature-expanding material in the expansion layer is (50~80):(20~50). The maximum ratio of the expanded tape's thickness after expansion to its initial unexpanded thickness is ≥5; the compression rate of the expanded tape after expansion is 55%~72%, where the compression rate refers to the percentage reduction in thickness of the expanded tape under a stress of 1.5MPa; the ratio of the substrate thickness to the initial unexpanded thickness of the expanded tape is (2~10):100; the swelling rate of the organic adhesive is 50%~200%; the swelling rate refers to the ratio of the volume of the organic adhesive placed in the electrolyte to the volume of the dried organic adhesive. The thickness of the expanding tape after expansion refers to the thickness after the expanding tape is kept at 100°C for 4 hours to cause the expanding tape to expand once; and then the expanded tape is soaked in an electrolyte at 45°C for 48 hours to cause the expanding tape to expand a second time. When testing the swelling rate of the organic adhesive and the thickness of the expanded tape after expansion, the electrolyte used was an organic solution containing 1 mol / L LiPF6, wherein the solvent of the organic solution was formed by mixing equal volumes of ethylene carbonate and methyl ethyl carbonate.

2. The secondary battery according to claim 1, wherein, The maximum ratio of the expanded thickness of the tape after expansion to its initial unexpanded thickness is 5 to 10.

3. The secondary battery according to claim 1, wherein, The initial unexpanded thickness of the expanding tape is 100μm~500μm.

4. The secondary battery according to claim 3, wherein, The initial unexpanded thickness of the expanding tape is 150μm~300μm.

5. The secondary battery according to claim 1, wherein, The thickness of the expanded tape after expansion is 1mm to 5mm.

6. The secondary battery according to claim 5, wherein, The thickness of the expanded tape after expansion is 1mm to 3mm.

7. The secondary battery according to claim 1, wherein, The ratio of the thickness of the substrate to the initial unexpanded thickness of the expanding tape is (3~6):

100.

8. The secondary battery according to claim 1, wherein, The thickness of the substrate is 5μm to 30μm.

9. The secondary battery according to claim 8, wherein, The thickness of the substrate is 5μm to 15μm.

10. The secondary battery according to claim 1, wherein, The ratio of the initial unexpanded thickness of the expanded layer to the initial unexpanded thickness of the expanded tape is (75~97):

100.

11. The secondary battery according to claim 10, wherein, The ratio of the initial unexpanded thickness of the expanded layer to the initial unexpanded thickness of the expanded tape is (90~97):

100.

12. The secondary battery according to claim 1, wherein, The thickness of the expansion layer is 100μm to 300μm.

13. The secondary battery according to claim 1, wherein, The ratio of the thickness of the base coating to the initial unexpanded thickness of the expanding tape is (1~5):

100.

14. The secondary battery according to claim 13, wherein, The ratio of the thickness of the base coating to the initial unexpanded thickness of the expanding tape is (1.5~3):

100.

15. The secondary battery according to claim 1, wherein, The thickness of the base coating is 2.5 μm to 20 μm.

16. The secondary battery according to claim 15, wherein, The thickness of the base coating is 2.5 μm to 7.5 μm.

17. The secondary battery according to claim 1, wherein, The organic adhesive in the expansion layer has a mass content of 50% to 80%, and the temperature-expanding material has a mass content of 20% to 50%.

18. The secondary battery according to claim 1, wherein, The glass transition temperature of the organic adhesive is -20℃ to 60℃.

19. The secondary battery according to claim 1, wherein, The initial expansion temperature of the temperature-expanding material is 70℃~130℃.

20. The secondary battery according to claim 1, wherein, The initial expansion temperature of the temperature-expanding material is 80℃~110℃.

21. The secondary battery according to claim 1, wherein, The organic adhesives include acrylate adhesives.

22. The secondary battery according to claim 1, wherein, The temperature-expanding material includes expandable microspheres.

23. The secondary battery according to claim 1, wherein, The substrate material includes at least one of polyethylene terephthalate, polyimide, polypropylene, and polyethylene.

24. The secondary battery according to claim 1, wherein, The base coating comprises at least one of modified polypropylene, styrene-isoprene-styrene block copolymer, and hydrogenated styrene-butadiene-styrene block copolymer.

25. The secondary battery according to any one of claims 1 to 24, wherein, The expansion tape also includes: An oriented polystyrene layer is disposed on the surface of the expanded layer away from the substrate.

26. The secondary battery according to claim 25, wherein, The ratio of the thickness of the oriented polystyrene layer to the thickness of the expanding tape is ≤20:

100.

27. The secondary battery according to claim 26, wherein, The ratio of the thickness of the oriented polystyrene layer to the thickness of the expanding tape is (5~20):

100.

28. The secondary battery according to claim 25, wherein, The thickness of the oriented polystyrene layer is 15 μm to 90 μm.

29. The secondary battery according to claim 28, wherein, The thickness of the oriented polystyrene layer is 25μm~50μm.

30. A method for preparing a secondary battery according to any one of claims 1 to 29, comprising the following steps: Apply the base coat of the expansion tape to the surface of the electrode assembly; The electrode assembly with the expansion tape attached is placed in the housing and vacuum dried at 70°C to 130°C, causing the expansion tape to expand once. Seal the housing; Electrolyte is injected into the sealed housing, causing the expansion tape, which has already expanded once, to absorb the electrolyte and expand a second time.

31. The method for preparing a secondary battery according to claim 30, wherein, The preparation of the expanding adhesive tape includes the following steps: An expanded layer is prepared on one surface of the substrate; A base coating is prepared on the surface of the substrate away from the expansion layer.

32. The method for preparing a secondary battery according to claim 31, wherein, The step of preparing the expanded layer includes: The raw materials of organic adhesives and temperature-expanding materials are mixed to prepare a slurry precursor; The slurry precursor is cured and reacted to prepare an expanded layer slurry. The expanded layer slurry is coated onto the surface of the substrate.

33. The method for preparing a secondary battery according to claim 32, wherein, The method for preparing the expanding adhesive tape satisfies at least one of the conditions in (1) to (2): (1) The solid content of the expanded layer slurry is 10%~50%; (2) The viscosity of the expansion layer slurry is 50 mPa·s to 500 mPa·s.

34. A battery module comprising the secondary battery as described in any one of claims 1 to 29.

35. A battery pack comprising the battery module of claim 34.

36. An electrical device comprising at least one selected from the secondary battery of any one of claims 1 to 29, the battery module of claim 34, or the battery pack of claim 35.

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