A kind of battery cell adhesive tape and its preparation method and application

Abstract

The application relates to a tape for an electric core and a preparation method and application thereof. The tape is a multilayer composite structure, comprising a glue layer, a core layer, an induced activation layer and a limiting layer which are sequentially stacked; wherein the glue layer is the innermost layer close to the electric core, and the limiting layer is the outermost layer away from the electric core; the tape has an expansion rate of not less than 24% in the thickness direction and a compression permanent deformation rate of not more than 10%. The thickness of the tape can change adaptively with the expansion and contraction of the electric core, can compress and absorb energy when the winding core expands, can rebound and compensate when the winding core contracts, and can always maintain the optimal interface pressure, so that the cycle life and safety of the battery are significantly improved.

Description

Technical Field

[0001] This article relates to the field of lithium-ion battery materials technology, specifically to a smart tape for large cylindrical lithium batteries, its preparation method, and its application. Background Technology

[0002] Large cylindrical lithium batteries (such as the 4680, 4695, 46115, and 46120 series models) have become a key development direction for electric vehicles and energy storage systems due to their high energy density and structural efficiency. However, during charging and discharging, the battery active materials undergo significant volume expansion and contraction (the expansion rate of silicon-carbon anodes can reach 10%-20%), leading to the accumulation of mechanical stress between the cell and the casing. Traditional solutions often use ordinary termination tape or swelling tape for fixation and cushioning, but these have the following significant shortcomings: 1) Limited fixing ability: Ordinary tapes (such as PET tapes) are rigid and cannot adapt to the continuous volume changes of the battery cell, which can easily lead to bonding failure or interface peeling. 2) Insufficient buffering performance: Although traditional swelling tape can provide some buffering, its compression set rate is high (often >30%), and its resilience decreases significantly after multiple cycles. At the same time, the swelling process absorbs electrolyte, which is easy to dissolve, age or fail in the complex chemical environment inside the battery. 3) Lack of active response: Existing tapes are all passive structures, which cannot dynamically adjust their mechanical properties according to the internal state of the battery (such as temperature and voltage changes), making it difficult to cope with extreme conditions such as fast charging and thermal abuse.

[0003] Therefore, there is an urgent need for a new type of tape that can intelligently adapt to changes in cell volume, dynamically maintain interface pressure, and withstand harsh environments. Summary of the Invention

[0004] The following is an overview of the subject matter described in detail herein. This overview is not intended to limit the scope of protection of this application.

[0005] This application provides a thickness-oriented stretchable tape for large cylindrical lithium batteries, its preparation method, and its application. The tape, based on the intelligent response characteristics of shape memory polymers and combined with a gradient pore structure and inductive activation mechanism, adaptively stretches and contracts along the thickness direction during battery charging and discharging to cope with changes in cell volume, thereby improving the battery's interface stability, safety performance, and cycle life, effectively solving the problems in the prior art.

[0006] The first aspect of this application provides a tape for battery cells, the tape having a multi-layer composite structure, including an adhesive layer, a core layer, an induction activation layer, and a confinement layer stacked sequentially; wherein the adhesive layer is the innermost layer closest to the battery cell, and the confinement layer is the outermost layer furthest from the battery cell.

[0007] In one exemplary embodiment, the adhesive layer is made of an electrolyte-resistant acrylic pressure-sensitive adhesive or a rubber-based adhesive.

[0008] In one exemplary embodiment, the thickness of the adhesive layer is 50-100 μm.

[0009] In one exemplary embodiment, the raw material of the core layer includes a shape memory polymer, selected from one or two of thermoplastic polymers and thermosetting polymers.

[0010] In one exemplary embodiment, the shape memory polymer is selected from one or more of polyurethane (TPU), polycaprolactone (PCL), and polyimide (PI).

[0011] In one exemplary embodiment, the glass transition temperature (Tg) of the shape memory polymer is 45 to 65°C.

[0012] In one exemplary embodiment, the core layer is a porous structure with a gradient aperture, wherein the gradient aperture is configured to increase from the side closer to the cell to the side farther away from the cell along the thickness direction.

[0013] In one exemplary embodiment, the gradient aperture is configured such that the aperture increases linearly from the side closer to the cell to the side farther away from the cell along the thickness direction.

[0014] In one exemplary embodiment, the aperture of the core layer near the cell side is 50-100 μm, and the aperture of the core layer away from the cell side is 150-300 μm.

[0015] In one exemplary embodiment, the ratio of the aperture of the core layer near the cell side to the aperture of the core layer away from the cell side is 1:3.

[0016] In one exemplary embodiment, the thickness of the core layer is 200-500 μm.

[0017] In one exemplary embodiment, a conductive material may also be added to the adhesive layer and / or the core layer; Optionally, the conductive material is selected from one or more of conductive carbon black, carbon nanotubes, graphene, graphene oxide (GO), reduced graphene oxide, and graphite.

[0018] In one exemplary embodiment, after the addition of the conductive material, the volume resistivity of the adhesive layer is 1-100 Ω·cm.

[0019] In one exemplary embodiment, the amount of conductive material added to the core layer is 1wt%-3wt% of the mass of the core layer.

[0020] In one exemplary embodiment, the inductively activated layer is capable of changing its modulus in response to voltage or temperature changes inside the battery or cell.

[0021] In one exemplary embodiment, the raw material of the inductive activation layer includes one or both of an electroresponsive material and a thermally responsive material.

[0022] In one exemplary embodiment, the electroresponsive material comprises a polymer composite containing an ionic liquid, such as polyethylene oxide containing 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt.

[0023] In one exemplary embodiment, the electrical response trigger voltage of the electrical response material is >4.25V.

[0024] In one exemplary embodiment, the thermally responsive material includes one or both of poly(N-isopropylacrylamide) and vanadium dioxide.

[0025] In one exemplary embodiment, the thermal response trigger temperature of the thermal response material is >45°C.

[0026] In one exemplary embodiment, the thickness of the inductive activation layer is 50-150 μm.

[0027] In one exemplary embodiment, the limiting layer is a polyester nonwoven fabric or a glass fiber mesh; Preferably, the limiting layer is a polyester fiber nonwoven fabric or glass fiber mesh that has been oriented and stretched along the length and width directions.

[0028] In one exemplary embodiment, the tensile strength of the confinement layer is greater than 50 MPa.

[0029] In one exemplary embodiment, the thickness of the confinement layer is 50-100 μm.

[0030] In one exemplary embodiment, the tape has a stretch rate of not less than 24% in the thickness direction and a compression set of not more than 10%.

[0031] The second aspect of this application provides a method for preparing the above-mentioned adhesive tape for battery cells, comprising the following steps: A core layer with gradient pore size is formed by thermally induced phase separation, 3D printing technology or template sintering. An induction activation layer is formed on one side of the core layer by coating or deposition process; The confinement layer and the sensor activation layer are combined; An adhesive layer is applied to the other side of the core layer and then cured.

[0032] The third aspect of this application provides an adhesive tape for battery cells prepared by the above method.

[0033] A fourth aspect of this application provides a large cylindrical lithium battery, including a casing, a cell, and the aforementioned adhesive tape, wherein the cell is disposed inside the casing, and the adhesive tape is attached to the cell.

[0034] In one exemplary embodiment, after the large cylindrical lithium battery completes 1000 charge-discharge cycles, the interfacial pressure fluctuation of the tape is within ±15%.

[0035] Compared with existing related technologies, this application has the following technical effects: 1) The tape of this application has a multi-layer composite structure, including an adhesive layer, a core layer, an induction activation layer, and a restraint layer stacked sequentially: The adhesive layer is used to provide adhesion to the surface of the battery cell; The core layer is made of shape memory polymer and adopts a gradient aperture design, with smaller apertures (50-100μm) near the core side to distribute stress evenly, and larger apertures (150-300μm) near the shell side to provide more compression space. The sensing activation layer can sense changes in battery voltage or temperature, dynamically adjust its modulus, and enhance its elastic deformation response capability. The limiting layer ensures that the tape deforms only in the thickness direction.

[0036] 2) The triggering mechanism of the inductive activation layer is: Temperature response: When the battery temperature is >45℃, the material modulus decreases, the flexibility increases, and compression buffering is promoted; Voltage response: When the battery voltage is abnormal (such as overcharge > 4.25V), the material undergoes a redox reaction, and the modulus is dynamically adjusted.

[0037] The tape thickness of this application can adaptively change with the expansion and contraction of the battery cell. When the core expands, it compresses and absorbs energy, and when it contracts, it rebounds and compensates, always maintaining the optimal interface pressure, thereby significantly improving the cycle life and safety of the battery.

[0038] Other features and advantages of this application will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the application. Other advantages of this application can be realized and obtained by means of the embodiments described in the description and the accompanying drawings. Attached Figure Description

[0039] The accompanying drawings are used to provide an understanding of the technical solutions of this application and constitute a part of the specification. They are used together with the embodiments of this application to explain the technical solutions of this application and do not constitute a limitation on the technical solutions of this application.

[0040] Figure 1 This is a schematic diagram of the structure of the tape used in this application.

[0041] Explanation of reference numerals in the attached figures: 1. Adhesive layer; 2. Core layer; 3. Sensing and activating layer; 4. Confinement layer. Detailed Implementation

[0042] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be arbitrarily combined with each other.

[0043] This application provides a tape for battery cells, the tape having a multi-layer composite structure, comprising the following layers stacked sequentially: The adhesive layer, located at the innermost layer, is in direct contact with the surface of the battery cell and is used to provide initial adhesion and electrical connection with the surface of the battery cell, ensuring interface wettability. The core layer is made of shape memory polymer and has a gradient aperture design, which is used to achieve reversible deformation in the thickness direction based on the shape memory effect and triggered by temperature / voltage. The inductive activation layer can change its modulus in response to voltage or temperature changes inside the battery or cell, adjusting the mechanical properties of the tape in real time, enhancing its self-adaptability, and changing its modulus in response to voltage or temperature changes inside the battery; and The restraining layer is used to constrain the tape so that it deforms mainly along the thickness direction. By limiting the deformation of the tape in the length and width directions through high in-plane stiffness, it ensures that the stretching and contraction only occur in the thickness direction. The adhesive layer is the innermost layer closest to the battery cell, and the limiting layer is the outermost layer furthest from the battery cell.

[0044] In the embodiments of this application, the adhesive layer is made of an electrolyte-resistant acrylic pressure-sensitive adhesive or a rubber-based adhesive (e.g., polyisobutylene-based).

[0045] In the embodiments of this application, the thickness of the adhesive layer is 50-100μm; for example, it can be 50μm, 60μm, 70μm, 80μm, 90μm or 100μm, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0046] In this embodiment, the thickness of the adhesive layer is 80 μm.

[0047] In the embodiments of this application, the raw material of the core layer is a shape memory polymer, selected from one or more of thermoplastic polymers and thermosetting polymers.

[0048] In the embodiments of this application, the shape memory polymer is selected from one or more of polyurethane TPU, polycaprolactone PCL, and polyimide PI.

[0049] In the embodiments of this application, the glass transition temperature (Tg) of the shape memory polymer is 45 to 65°C (e.g., 50°C or 55°C) to adapt to the normal operating temperature of the battery; for example, it can be 45°C, 50°C, 55°C, 60°C or 65°C, but is not limited to the listed values, and other unlisted values ​​within the above range are also applicable.

[0050] In this embodiment, the core layer is a porous structure with gradient pore size. The gradient pore size is set such that the pore size increases from the side closer to the battery cell (i.e. the side adjacent to the adhesive layer) to the side farther away from the battery cell (i.e. the side adjacent to the induction activation layer) along the thickness direction, so as to achieve the dual effect of uniform stress distribution and efficient compression energy absorption.

[0051] In this embodiment of the application, the gradient aperture is set such that the aperture increases linearly from the side closer to the cell to the side farther away from the cell along the thickness direction.

[0052] In this embodiment, the core layer has a pore size of 50-100 μm near the battery cell side, which has a high pore density to uniformly distribute stress and avoid local overload; the pore size away from the battery cell side is 150-300 μm, which has a low pore density to provide greater compression space and absorb expansion energy. For example, the pore size near the battery cell side is 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, or 100 μm, and the pore size away from the battery cell side is 150 μm, 180 μm, 200 μm, 220 μm, 240 μm, 260 μm, 280 μm, or 300 μm, but is not limited to the listed values; other unlisted values ​​within the above range are also applicable. This gradient pore size design allows the tape to provide a uniform stress distribution near the core side, avoiding local overload; and provides greater compression space near the shell side, absorbing expansion energy.

[0053] In this embodiment, the aperture of the core layer near the cell side is 80 μm, and the aperture of the core layer away from the cell side is 250 μm; or the aperture of the core layer near the cell side is 70 μm, and the aperture of the core layer away from the cell side is 210 μm; or the aperture of the core layer near the cell side is 90 μm, and the aperture of the core layer away from the cell side is 270 μm.

[0054] In this embodiment of the application, the ratio of the aperture of the core layer near the cell side to the aperture of the core layer away from the cell side is 1:3.

[0055] In the embodiments of this application, the thickness of the core layer is 200-500μm; for example, it can be 200μm, 250μm, 300μm, 350μm, 400μm, 450μm or 500μm, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0056] In the embodiments of this application, the thickness of the core layer is 300μm, 350μm, or 400μm.

[0057] In this embodiment of the application, conductive materials may also be added to the adhesive layer and / or the core layer to enhance conductivity; Optionally, the conductive material is selected from one or more of conductive carbon black, carbon nanotubes, graphene, graphene oxide (GO), reduced graphene oxide, and graphite.

[0058] In this embodiment of the application, the step of adding conductive material to the adhesive layer includes: surface-activating the conductive material with a silane coupling agent, ultrasonically dispersing it in an organic solvent, then mixing it with an electrolyte-resistant acrylic pressure-sensitive adhesive or a rubber-based adhesive, high-speed shearing dispersion, vacuum degassing, coating, and drying and curing to obtain a conductive modified adhesive layer.

[0059] In the embodiments of this application, after adding the conductive material, the volume resistivity of the adhesive layer is 1-100 Ω·cm; for example, it can be 1 Ω·cm, 10 Ω·cm, 20 Ω·cm, 30 Ω·cm, 40 Ω·cm, 50 Ω·cm, 60 Ω·cm, 70 Ω·cm, 80 Ω·cm, 90 Ω·cm or 100 Ω·cm, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0060] In this embodiment, the volume resistivity of the adhesive layer is 8 Ω·cm.

[0061] In the embodiments of this application, the amount of conductive material added to the core layer accounts for 1-3 wt% of the mass of the core layer; for example, 3 wt% of carbon nanotubes are added.

[0062] In this embodiment, the raw material of the inductive activation layer includes one or both of electrical responsive materials and thermal responsive materials.

[0063] In the embodiments of this application, the electroresponsive material includes a polymer composite material containing an ionic liquid, such as polyethylene oxide containing 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt.

[0064] In this embodiment of the application, the electrical response trigger voltage of the electrical response material is >4.25V.

[0065] In the embodiments of this application, the thermally responsive material includes one or both of poly(N-isopropylacrylamide) and vanadium dioxide.

[0066] In this embodiment of the application, the thermal response trigger temperature of the thermal response material is >45°C.

[0067] In the embodiments of this application, the thickness of the inductive activation layer is 50-150 μm; for example, it can be 50 μm, 80 μm, 100 μm, 120 μm, 140 μm or 150 μm, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0068] In the embodiments of this application, the thickness of the inductive activation layer is 100μm, 120μm, or 130μm.

[0069] In this embodiment, the limiting layer is a polyester fiber nonwoven fabric or a glass fiber mesh; preferably, the limiting layer is a polyester fiber nonwoven fabric or a glass fiber mesh that has been oriented and stretched along the length and width directions.

[0070] In this embodiment, the tensile strength of the limiting layer is greater than 50 MPa.

[0071] In the embodiments of this application, the thickness of the limiting layer is 50-100μm; for example, it can be 50μm, 60μm, 70μm, 80μm, 90μm or 100μm, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0072] In this embodiment of the application, the thickness of the limiting layer is 80 μm.

[0073] In this embodiment of the application, the tape has a stretch rate of not less than 24% in the thickness direction and a compression set of not more than 10%.

[0074] This application also provides a method for preparing the above-mentioned adhesive tape for battery cells, comprising the following steps: A core layer with gradient pore size is formed by thermally induced phase separation, 3D printing technology or template sintering. An induction activation layer is formed on one side of the core layer by coating or deposition process; The confinement layer and the sensor activation layer are combined; An adhesive layer is applied to the other side of the core layer and then cured.

[0075] This application also provides a battery cell tape prepared by the above method.

[0076] This application also provides a large cylindrical lithium battery, including a casing, a cell, and the aforementioned adhesive tape, wherein the cell is disposed inside the casing, and the adhesive tape is attached to the cell.

[0077] In this embodiment of the application, after the large cylindrical lithium battery completes 1000 charge-discharge cycles, the interfacial pressure fluctuation range of the tape is within ±15%.

[0078] The present application will be further described in detail below with reference to specific embodiments, but these embodiments should not be construed as limiting the present application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this invention.

[0079] The raw materials used in this application are all conventional products on the market.

[0080] Unless otherwise specified, all materials and reagents used in the embodiments of this invention are commercially available.

[0081] Experimental methods not specified in the examples are generally performed under standard conditions or as recommended by the manufacturer.

[0082] Example 1: Heat-triggered stretchable tape The tape structure in this embodiment is as follows: (1) Adhesive layer Material: Polyisobutylene-based, volume resistivity 8 Ω·cm; Thickness: 80μm.

[0083] The conductive modification step of the adhesive layer: 1.1 Raw material ratio (based on 100 parts of polyisobutylene liquid with a solid content of 40%) Matrix adhesive: Polyisobutylene rubber liquid (40% solids), 100 parts; Conductive material: Multi-walled carbon nanotubes, 2.5 parts; Surface activator: KH-550 aminosilane coupling agent, 0.0075 parts (0.3% of the mass of carbon nanotubes); Organic solvent: lithium battery grade anhydrous ethyl acetate, prepared into a dispersion with a filler solid content of 15%.

[0084] 1.2 Carbon Nanotube Activation and Dispersion Process Add carbon nanotubes and KH-550 to ethyl acetate and stir for 5 minutes to premix. Ultrasonic dispersion: The power was 300W, the frequency was 40kHz, and the temperature was 25℃. The mixture was sonicated for 30 minutes to obtain an activated conductive dispersion.

[0085] 1.3 Degassing of adhesive blending Homogenize the PIB solution by stirring at 300 rpm for 5 minutes in the autoclave. The carbon nanotube dispersion was added dropwise at a uniform rate over a period of 15 minutes. High-speed shearing: 1800 r / min, 30℃, shearing for 40 min; Vacuum degassing: vacuum degree -0.095MPa, 35℃, degassing for 20min.

[0086] 1.4 Coating and Curing Micro-recessed blade coating, wet film thickness 200μm, dry adhesive layer thickness 80μm; Step drying: 60℃×8min → 85℃×12min; Curing conditions: 25℃, 50% RH, constant temperature for 24h; to obtain a conductive modified adhesive layer.

[0087] (2) Core layer: Material: Polyurethane TPU-based shape memory polymer, Tg=55℃, gradient pore size formed by thermally induced phase separation method; Near-core side aperture: 80μm Near-shell side aperture: 250μm; Thickness: 350μm.

[0088] (3) Induction activation layer: Material: Poly(N-isopropylacrylamide) microcapsule dispersion layer, with an inductive activation layer formed on the core layer through a coating process; The temperature response is triggered at 50℃. Thickness: 100μm.

[0089] (4) Restriction layer: Material: Polyester fiber nonwoven fabric that has been oriented and stretched along its length and width; Thickness: 80μm.

[0090] Example 2: Electrically triggered stretchable tape The difference between the tape structure in this embodiment and that in Embodiment 1 is: (2) Core layer: Material: Polycaprolactone (PCL)-based shape memory polymer, doped with carbon nanotubes (3wt%) to enhance conductivity; gradient pore size formed by 3D printing; Tg=50℃. Near-core side aperture: 70μm Near-shell side aperture: 210 μm; Thickness: 300μm.

[0091] (3) Induction activation layer: Material: Polyethylene oxide layer containing ionic liquid (1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt); Trigger voltage for electrical response: 4.3V Thickness: 120μm.

[0092] Example 3: High-temperature resistant stretchable tape (for fast-charging batteries) The difference between the tape structure in this embodiment and that in Embodiment 1 is: (2) Core layer: Material: Polyimide (PI)-based shape memory polymer, long-term temperature resistance up to 180℃, gradient pore size formed by template sintering; Tg=60℃. Near-core side aperture: 90μm Near-shell side aperture: 270μm; Thickness: 400μm.

[0093] (3) Induction activation layer: Material: Vanadium dioxide nanowire coating; temperature response trigger temperature 65℃ (phase transition temperature). Thickness: 130μm.

[0094] Comparative Example 1 The difference from Example 1 is that the inductive activation layer in Example 1 is missing, while the rest of the structure and parameters are exactly the same as in Example 1.

[0095] Comparative Example 2 The difference from Example 1 is that the core layer adopts a uniform pore size design with a uniform pore size of 180μm, while the rest of the structure and parameters are exactly the same as those in Example 1.

[0096] Comparative Example 3 The difference from Example 1 is that the core layer material is replaced with ordinary polyurethane (non-shape memory type), which has no shape memory effect, while the rest of the structure and parameters are exactly the same as those in Example 1. Comparative Example 4 The difference from Example 1 is that the limiting layer is made of ordinary polyester fiber nonwoven fabric (without directional stretching in the length and width directions), with a tensile strength of 35MPa. The rest of the structure and parameters are exactly the same as those in Example 1.

[0097] Performance testing: 1. Test Subject: (1) The tapes of Examples 1-3 and Comparative Examples 1-4; (2) The tapes from Examples 1-3 and Comparative Examples 1-4 were assembled into a 46115 large cylindrical lithium battery, wherein the 46115 large cylindrical lithium battery is: a positive electrode of 7-series ternary lithium, a negative electrode of graphite doped with 5% SiC, and a conventional lithium salt electrolyte of LiPF6. The average cell capacity is 42Ah, and the cell voltage plateau voltage is 2.75V-4.25V.

[0098] 2. Test items: (1) Tests of the mechanical properties of the tape itself: elongation and compression set. Thickness-direction stretching test: According to GB / T 1040.3-2006 standard, take each tape sample (size 10mm×10mm), use a universal testing machine, apply 500N pressure to the tape until it is compressed by 50% under the conditions of 25℃, 50℃ (trigger temperature of Examples 1 and 3), and 4.3V (trigger voltage of Example 2), hold for 10min and then unload, measure the difference between the thickness after unloading and the initial thickness, and calculate the stretching rate (stretching rate = (thickness after unloading - initial thickness) / initial thickness × 100%).

[0099] Compression set test: According to GB / T 7759-2015 standard, take each tape sample, keep it at 25℃ and 50% compression rate for 24h, unload and place it for 30min, measure the difference between the thickness after unloading and the initial thickness, and calculate the compression set (compression set = (initial thickness - thickness after unloading) / initial thickness × 100%).

[0100] The test results are shown in Table 1.

[0101] Table 1 (2) Battery performance testing: interface stability, safety performance, cycle life Interface pressure fluctuation test: Each tape was assembled into a 4680 type large cylindrical lithium battery and cyclically charged and discharged 1000 times under 25℃ and 1C conditions. The interface pressure between the cell and the tape was monitored in real time using a pressure sensor, and the pressure fluctuation range after the cycle was calculated (fluctuation range = (maximum pressure - minimum pressure) / initial pressure × 100%).

[0102] Safety performance testing: The needle penetration test (according to GB 38031-2021 standard) is adopted, with a needle penetration speed of 5mm / s, and the battery is observed to see if it catches fire or explodes; the overcharge test (charging voltage rises to 5.0V, 1C charging) is adopted, and the battery is observed to see if it leaks or catches fire.

[0103] Cycle life test: Under the conditions of 25℃ and 1C charge and discharge (charge to 4.25V and discharge to 2.75V), the number of cycles when the battery capacity decays to 80% of the initial capacity is measured is the battery cycle life.

[0104] The test results are shown in Table 2.

[0105] Table 2 In summary, the tape thickness of this application can adaptively change with the expansion and contraction of the battery cell. It absorbs energy during expansion and rebounds to compensate during contraction, thus maintaining the optimal interface pressure and significantly improving the cycle life and safety of the battery.

[0106] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A tape for battery cells, the tape having a multi-layer composite structure, comprising an adhesive layer, a core layer, an induction activation layer and a confinement layer stacked sequentially, wherein the adhesive layer is the innermost layer closest to the battery cell and the confinement layer is the outermost layer furthest from the battery cell; in, The core layer is made of shape memory polymer and the core layer is a porous structure with gradient pore size. The inductive activation layer can change its own modulus in response to changes in voltage or temperature inside the battery or cell. The tape has a stretch rate of not less than 24% in the thickness direction and a compression set of not more than 10%.

2. The tape for battery cells according to claim 1, wherein, The adhesive layer is an electrolyte-resistant acrylic pressure-sensitive adhesive or a rubber-based adhesive; and / or The shape memory polymer is selected from one or two of thermoplastic polymers and thermosetting polymers; and / or The raw material of the inductive activation layer includes one or both of electroresponsive materials and thermally responsive materials; and / or The limiting layer is a polyester fiber nonwoven fabric or a glass fiber mesh.

3. The tape for battery cells according to claim 2, wherein, The shape memory polymer is selected from one or more of polyurethane, polycaprolactone, and polyimide; and / or The gradient aperture is configured such that the aperture increases from the side closer to the cell to the side farther away from the cell along the thickness direction; and / or The electroresponsive material includes a polymer composite material containing ionic liquid; and / or The thermally responsive material includes one or two of poly(N-isopropylacrylamide) and vanadium dioxide; and / or The limiting layer is a polyester fiber nonwoven fabric or glass fiber mesh that has been oriented and stretched along its length and width.

4. The tape for battery cells according to claim 3, wherein, The glass transition temperature of the shape memory polymer is 45 to 65°C; and / or The gradient aperture is configured such that the aperture increases linearly from the side closer to the cell to the side farther away from the cell along the thickness direction; and / or The tensile strength of the confinement layer is greater than 50 MPa.

5. The tape for battery cells according to claim 4, wherein, The core layer has pores with a diameter of 50-100 μm near the cell side and 150-300 μm away from the cell side; and / or The ratio of the aperture size of the core layer near the cell side to the aperture size away from the cell side is 1:

3.

6. The tape for battery cells according to any one of claims 1 to 5, wherein, Conductive materials are also added to the adhesive layer and / or the core layer; Optionally, the conductive material is selected from one or more of conductive carbon black, carbon nanotubes, graphene, graphene oxide, reduced graphene oxide, and graphite. Optionally, after adding the conductive material, the volume resistivity of the adhesive layer is 1-100 Ω·cm; Optionally, in the core layer, the amount of the conductive material added accounts for 1wt%-3wt% of the mass percentage of the core layer.

7. The tape for battery cells according to any one of claims 1 to 5, wherein, The thickness of the adhesive layer is 50-100 μm; and / or The core layer has a thickness of 200-500 μm; and / or The thickness of the inductive activation layer is 50-150 μm; and / or The thickness of the confinement layer is 50-100 μm.

8. A method for preparing a battery cell tape according to any one of claims 1 to 7, comprising the following steps: A core layer with gradient pore size is formed by thermally induced phase separation, 3D printing technology or template sintering. An inductive activation layer is formed on one side of the core layer by a coating or deposition process; The confinement layer is combined with the sensing activation layer; An adhesive layer is applied to the other side of the core layer and then cured.

9. A large cylindrical lithium battery, comprising a casing, a cell, and a cell tape according to any one of claims 1 to 7 or a cell tape prepared by the method of claim 8, wherein, The battery cell is disposed inside the housing, and the battery cell is attached with the battery cell tape.

10. The large cylindrical lithium battery according to claim 9, wherein, After the large cylindrical lithium battery completes 1000 charge-discharge cycles, the interfacial pressure fluctuation range of the cell tape is within ±15%.

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