A kind of adhesive tape and battery

Abstract

The application belongs to the technical field of adhesive paper preparation, and particularly relates to an adhesive paper and a battery cell. The adhesive paper comprises a base material layer and a coating layer arranged on at least one side surface of the base material layer; the base material layer comprises a plurality of fibers, a plurality of the fibers are cross and / or laminated to form pores, and the coating layer is partially embedded in the pores; the coating layer comprises a first coating layer on the surface of the base material layer and a second coating layer embedded in the pores; the thickness h of the first coating layer and the average diameter m of the fibers satisfy a specific relationship, the thickness of the first coating layer is 2 micrometers to 15 micrometers; and / or the average diameter of the fibers is 1 micrometer to 15 micrometers. The adhesive paper has good flexibility, and when applied to a battery, can increase the curvature radius of the pole piece bending at the inner circle arc of the wound battery cell, reduce the stress on the pole piece during winding, and avoid the active material layer from falling off or even cracking when the pole piece is wound.

Description

Technical Field

[0001] This application belongs to the field of adhesive paper preparation technology, specifically relating to an adhesive paper and a battery cell. Background Technology

[0002] Lithium-ion batteries are widely used in mobile phones, laptops, electric vehicles, and other fields. With the gradual expansion of market demand, new requirements are constantly being placed on the energy density of lithium-ion batteries. Increasing the thickness and compaction density of the electrode sheets to achieve higher energy density is currently the most important and effective method. However, when the electrode sheet surface density or compaction density is high, the electrode sheet flexibility will significantly decrease, causing the active material layer located at the inner arc of the electrode sheet to easily crack and fall off during the winding process. This can lead to problems such as electrode powder shedding and even electrode cracking, affecting the battery's electrical performance (high K value, incomplete CV cutoff, etc.) and even causing safety risks such as internal short circuits. Summary of the Invention

[0003] Therefore, the technical problem to be solved by this application is to overcome the problems of powder shedding and cracking of the electrode sheets at the inner arc of the battery cell during the winding process, thereby providing an adhesive paper and a battery cell.

[0004] To this end, the present invention provides the following technical solution.

[0005] In a first aspect, this application provides an adhesive tape, the adhesive tape comprising a substrate layer and a coating layer disposed on at least one surface of the substrate layer; the substrate layer comprises a plurality of fibers, the plurality of fibers intersecting and / or stacking to form pores, the coating layer being partially embedded in the pores; the coating layer comprises a first coating layer located on the surface of the substrate layer and a second coating layer embedded in the pores; the thickness h of the first coating layer satisfies the relationship between the average diameter m of the fibers and the following formula:

[0006]

[0007] The thickness of the first coating layer is 2 μm to 15 μm; and / or the average diameter of the fiber is 1 μm to 15 μm.

[0008] As an optional implementation, the bending stiffness of the adhesive tape is not higher than 15mN.

[0009] As an optional implementation, the average diameter of the fiber is 3μm to 6μm.

[0010] As an optional implementation, the pore size is 0.1 μm to 50 μm; and / or,

[0011] The coating layer comprises inorganic particles and / or binders.

[0012] As an optional implementation, the pore size is 0.5 μm to 10 μm; and / or,

[0013] The first coating layer and the second coating layer contain the inorganic particles.

[0014] As an optional implementation, the substrate layer is made of at least one of polyethylene terephthalate, polyethylene, polypropylene, polyimide, polyvinyl chloride, polyethylene, and polypropylene; and / or,

[0015] The thickness of the substrate layer is 5μm to 20μm; and / or,

[0016] The thickness of the adhesive tape is 8μm to 25μm.

[0017] As an optional implementation, the inorganic particles have an average particle size of 150 nm to 1.5 μm; and / or,

[0018] Based on 100% of the total mass of the coating layer, the inorganic particle content in the coating layer is 20wt% to 70wt%; and / or,

[0019] The inorganic particles include alumina, boehmite, and Li7La3Zr2O. 12 Li 3x La (2 / 3-x) / 3 TiO3, Li 1+x Al x Ti 2-x (PO4)3, at least one of magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zirconium oxide, zinc oxide, calcium oxide, magnesium hydroxide, aluminum hydroxide, barium hydroxide, barium sulfate, calcium silicate, and titanium dioxide.

[0020] As an optional implementation, the adhesive comprises at least one selected from polyisobutylene, styrene-isoprene copolymer, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, polyhexafluoropropylene, and styrene-butadiene rubber; and / or,

[0021] The adhesive content in the coating layer is 30wt% to 80wt% based on 100% of the total mass of the coating layer.

[0022] Secondly, this application provides a battery cell, the battery cell comprising a positive electrode, a negative electrode, a separator, and the aforementioned adhesive tape, wherein the separator is disposed between the positive electrode and the negative electrode; the adhesive tape is disposed at at least a portion of at least one surface of the positive electrode; and or,

[0023] The adhesive tape is disposed at at least partially on at least one surface of the negative electrode sheet; and or,

[0024] The adhesive tape is disposed at at least a portion of at least one surface of the diaphragm.

[0025] Thirdly, this application provides a battery cell comprising a positive electrode, a negative electrode, a separator disposed between the positive and negative electrode, and the aforementioned adhesive tape. The positive electrode, separator, and negative electrode are stacked and wound multiple turns along a winding direction to form a wound battery cell. The wound battery cell includes a flat region and an arcuate region. At least a portion of the adhesive tape is located in the arcuate region, and the adhesive tape is disposed at at least one location among the positive electrode, negative electrode, and separator; and / or,

[0026] From the winding direction of the wound cell, the wound cell includes a first arc region, a first straight region, a second arc region, and a second straight region. At least a portion of the adhesive tape is located at at least one of the first arc region and the second arc region. The adhesive tape is disposed at at least one of the positive electrode, the negative electrode, and the separator.

[0027] As an optional implementation, the positive electrode sheet includes a positive current collector and a positive active material layer located on at least one surface of the positive current collector, with at least a portion of the adhesive paper covering the surface of the first end of the positive active material layer; and / or,

[0028] The negative electrode sheet includes a negative current collector and a negative active material layer located on at least one surface of the negative current collector, and at least a portion of the adhesive paper covers the surface of the first end of the negative active material layer.

[0029] The technical solution of this invention has the following advantages:

[0030] 1. The adhesive tape provided by the present invention comprises a substrate layer and a coating layer disposed on at least one surface of the substrate layer; the substrate layer comprises a plurality of fibers, which intersect and / or are stacked to form pores, and the coating layer is partially embedded in the pores; the coating layer comprises a first coating layer located on the surface of the substrate layer and a second coating layer embedded in the pores; the thickness h of the first coating layer satisfies a specific relationship with the average diameter m of the fibers, and the thickness of the first coating layer is 2 μm to 15 μm; and / or, the average diameter of the fibers is 1 μm to 15 μm. The adhesive tape of this application has good flexibility, and its application in batteries can increase the radius of curvature of the electrode at the inner arc of the wound cell, reduce the stress on the electrode during winding, and avoid the shedding of active material layer powder or even cracking of the electrode when winding the electrode. After the adhesive tape is pasted onto the electrode, it protects the active material layer in the pasting area, further reducing powder shedding at the inner arc, and improving the problem of easy cracking and detachment of the active material layer in existing technologies, thereby improving the battery's electrical performance, such as increasing capacity, cycle life and safety performance. Attached Figure Description

[0031] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0032] Figure 1 This is a schematic diagram of the structure of the adhesive tape in Embodiment 1 of this application;

[0033] Figure 2 This is an SEM image of the surface of the first coating layer of the adhesive tape in Embodiment 1 of this application;

[0034] Figure 3 This is a SEM image of the surface of the adhesive tape substrate layer in Embodiment 1 of this application;

[0035] Figure 4 A schematic diagram of the battery cell in Embodiment 1 of this application;

[0036] Figure 5 This is a topographic image of the negative electrode corresponding to the adhesive tape position after disassembling the battery in Embodiment 1 of this application;

[0037] Figure 6 These are photographs of the arc-shaped region of the positive electrode sheet in Embodiment 1 and Comparative Example 1 of this application;

[0038] Figure label:

[0039] 1-Adhesive tape; 2-First arc area; 3-Second arc area; 4-First flat area; 5-Second flat area; 6-Substrate layer; 7-Coating layer. Detailed Implementation

[0040] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0041] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0042] Existing technologies generally increase electrode thickness and compaction density to achieve higher energy density lithium-ion batteries. However, when the electrode surface density or compaction density is high, the electrode flexibility decreases, causing the active material layer located at the inner arc of the cell to easily crack and fall off during winding, resulting in problems such as electrode powder shedding and even electrode cracking. To solve the above problems, this application provides the following technical solution.

[0043] In a first aspect, this application provides an adhesive tape comprising a substrate layer and a coating layer disposed on at least one surface of the substrate layer; the substrate layer comprises a plurality of fibers, which intersect and / or overlap to form pores, and the coating layer is partially embedded in the pores; the coating layer comprises a first coating layer located on the surface of the substrate layer and a second coating layer embedded in the pores; the thickness h of the first coating layer satisfies the relationship between the average diameter m of the fibers and the following formula:

[0044]

[0045] The thickness of the first coating layer is 2 μm to 15 μm; and / or the average diameter of the fiber is 1 μm to 15 μm.

[0046] The adhesive tape of this application has good flexibility. When the tape is placed at the inner arc of the battery cell, it can increase the bending radius of the electrode at the inner arc, reduce bending stress, and provide good buffering for the stress generated by winding and bending. When the electrode has a high areal density or a large compaction density, it reduces problems such as cracking and peeling of the active material layer at the inner arc of the electrode during winding, as well as electrode powdering and cracking. In particular, it can alleviate the phenomenon of cracking and powdering of the active material layer at the edge of the electrode. After the tape is pasted onto the electrode, it can also protect the active material layer in the pasting area, further reducing powdering at the inner arc.

[0047] The larger the average diameter of the fibers, the thicker the resulting substrate layer. Based on the performance of the battery and the adhesive tape, the thickness of the substrate layer needs to be matched with the thickness of the coating layer. For example, a thicker substrate layer requires a thinner coating layer. This application adjusts the thickness of the first coating layer and the average diameter of the fibers to satisfy the above relationship, ensuring a match between the substrate layer thickness and the coating layer thickness. This improves the flexibility of the adhesive tape, provides better buffering against stress generated by winding and bending, reduces problems such as cracking and shedding of the active material layer, and electrode powder shedding and cracking, and ensures the adhesive tape has a suitable thickness, thereby improving the overall performance of the battery. The presence of pores between fibers in the substrate layer, with the coating layer partially embedded in these pores, increases the adhesion between the coating and substrate layers. This ensures a tight bond between the coating and substrate layers during cell winding, reducing the likelihood of separation during bending. By ensuring the average diameter of the first coating layer and fibers meets the aforementioned range, and by enhancing the flexibility of the adhesive paper with an appropriate thickness, stress generated during winding and bending is buffered. This allows the electrode to achieve a higher areal density or compaction density while preventing powder shedding and cracking, thereby improving the battery's cycle performance and capacity. Adjusting the thickness of the first coating layer also helps improve the adhesiveness of the adhesive paper. Adjusting the average fiber diameter to meet the aforementioned range helps reduce the bending stiffness of the adhesive paper, further improving its flexibility. When this adhesive paper is applied to the battery for bending and winding, the stress generated at the arcs provides further buffering, helping to transfer some of the stress to the adhesive paper, thus mitigating problems such as powder shedding and cracking during electrode winding and bending. Adjusting the average fiber diameter also ensures the mechanical strength of the adhesive paper.

[0048] In addition, the adhesive tape has electrolyte retention capabilities. When applied to batteries, it can improve the interfacial performance between the tape and the electrode, maintaining the electrolyte's wetting of the electrode's active layer at that location. On the one hand, this can improve the flexibility of the active layer, reducing problems such as cracking and detachment of the active material layer and electrode powder shedding and cracking. On the other hand, it allows the active material with the adhesive tape attached to it to still undergo normal lithium-ion intercalation and deintercalation during charging and discharging, without losing energy density, thus ensuring the battery's high energy density.

[0049] For example, the thickness of the first coating layer is 2 μm, 5 μm, 8 μm, 13 μm, 15 μm, or within any two of the above values. The average diameter of the fiber is 1 μm, 3 μm, 5 μm, 7 μm, 9 μm, 11 μm, 13 μm, 15 μm, or within any two of the above values.

[0050] In one optional embodiment, the bending stiffness of the adhesive tape is no higher than 15 mN. A bending stiffness of no more than 15 mN allows the adhesive tape to have better flexibility, which is beneficial for buffering stress generated during winding or bending, and helps reduce electrode powdering and cracking. It should be noted that the bending stiffness of the adhesive tape is obtained using methods known in the art. One example is the use of a stiffness meter according to the national standard GB / T22364-2018, with test parameters of a bending angle of 15° and a bending length of 10 mm. For example, the bending stiffness of the adhesive tape can be 1 mN, 3 mN, 5 mN, 8 mN, 11 mN, 15 mN, or within any two of the above values.

[0051] In one optional embodiment, the average diameter of the fiber is 3μm to 6μm. Further control of the average fiber diameter in this application facilitates the embedding of the coating layer into the substrate layer, improves the matching of the substrate layer and coating layer thicknesses, and further optimizes the flexibility and liquid retention of the adhesive tape by coordinating the average fiber diameter with the first coating layer, thus reducing electrode powder shedding and cracking.

[0052] It should be noted that the thickness of the first coating layer and the average diameter of the fibers were both obtained using methods known in the art. One method is described here: a sample of adhesive tape is taken, and 10 SEM images are obtained at different locations on the sample. The diameter of any 80 fibers in each SEM image is measured, and the average value is calculated. The average diameter of the fibers is then obtained by averaging the data from the 10 SEM images. The thickness of the first coating layer is then determined using SEM testing.

[0053] In one optional embodiment, the pore size is 0.1 μm to 50 μm; and / or,

[0054] The coating layer comprises inorganic particles and / or binders.

[0055] The pore sizes of the pores formed by the intersection and / or stacking of several fibers in this application are within the aforementioned range, further improving the softness of the adhesive paper without affecting ion conduction and the film-making and adhesive-coating process. Pore sizes that are too small will affect the ion transport rate, thus affecting the battery's electrical performance. It should be noted that the pore size refers to the pore size with the largest proportion in the pore size distribution diagram. The pore size is obtained using methods known in the art. One example is as follows: Take an adhesive paper sample, immerse it in a benzene solution for 4 hours, remove the sample, dry it, and use a pore size analyzer to measure the pore size. The pore size with the largest proportion in the pore size distribution diagram is taken as the pore size. Note that the adhesive paper can also be impregnated with organic solvents such as toluene; this application does not limit the type of impregnation solvent.

[0056] Furthermore, the average diameter of the fibers affects the pore size, which in turn affects the electrolyte retention of the adhesive tape. This application controls the average fiber diameter to be 1 μm to 15 μm and the pore size to be 0.1 μm to 50 μm, which helps to further improve the electrolyte retention of the adhesive tape and to give the fibers a suitable packing density. This facilitates the embedding of the coating layer into the substrate layer, further improving the adhesion strength and lithium-ion permeability between the coating layer and the substrate layer, and further reducing the separation of the coating layer and the substrate layer, as well as the cracking and peeling of the active material layer. In addition, pore size within the above range helps to embed an appropriate coating layer into the pores, improving the processing performance of the adhesive tape and reducing the problem of complete coating penetration. For example, the pore size is 0.1 μm, 0.5 μm, 1 μm, 3 μm, 7 μm, 11 μm, 16 μm, 23 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, or within any two of the above values.

[0057] The coating layer of this application includes inorganic particles and / or an adhesive. The inorganic particles can absorb a certain amount of electrolyte, increasing the electrolyte retention capacity of the adhesive tape and improving the permeability of lithium ions. This allows lithium ions to move freely and quickly through the area where the adhesive tape is attached, without affecting the capacity of the active material in the area where the adhesive tape is attached, thus ensuring the battery's energy density. The adhesive plays a supporting and bonding role, improving the adhesion between the coating layer and the substrate layer.

[0058] In one optional embodiment, the pore size is 0.5 μm to 10 μm; and / or,

[0059] The first coating layer and the second coating layer contain the inorganic particles.

[0060] This application further regulates the pore size, maintaining an appropriate amount of coating embedded in the substrate layer. This helps optimize the flexibility and electrolyte retention of the adhesive tape, and improves issues such as powder shedding at curved edges, cracking and peeling of the active material layer. Both the first and second coating layers of this application contain inorganic particles, which further enhances the electrolyte retention of the adhesive tape.

[0061] In one optional embodiment, the substrate layer is made of at least one of polyethylene terephthalate, polyethylene, polypropylene, polyimide, polyvinyl chloride, polyethylene, and polypropylene; and / or,

[0062] The thickness of the substrate layer is 5μm to 20μm; and / or,

[0063] The thickness of the adhesive tape is 8μm to 25μm.

[0064] The adhesive tape thickness of this application is 8μm to 25μm, which helps to improve the flexibility, ion penetration, and ion transport efficiency of the adhesive tape, thereby improving the battery's electrical performance. Furthermore, the adhesive tape thickness meeting the above range also helps to improve processing performance and reduce problems such as wrinkling during the sheet fabrication process. The substrate layer thickness of this application is 5μm to 20μm, which can optimize the flexibility of the adhesive tape. For example, the adhesive tape thickness is 8μm, 10μm, 12μm, 14μm, 16μm, 18μm, 20μm, 22μm, 25μm, or within any two of the above values. The substrate layer thickness is 5μm, 8μm, 11μm, 14μm, 17μm, 20μm, or within any two of the above values.

[0065] In one optional embodiment, the average particle size of the inorganic particles is 150 nm to 1.5 μm; and / or,

[0066] Based on 100% of the total mass of the coating layer, the inorganic particle content in the coating layer is 20wt% to 70wt%; and / or,

[0067] The inorganic particles include alumina, boehmite, and Li7La3Zr2O. 12 (LLZO), Li 3x La (2 / 3-x) / 3 TiO3(LLTO), Li 1+x Al x Ti 2-x One or more of the following: (PO4)3(LATP), magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zirconium oxide, zinc oxide, calcium oxide, magnesium hydroxide, aluminum hydroxide, barium hydroxide, barium sulfate, calcium silicate, or titanium dioxide.

[0068] The average particle size of the inorganic particles in this application is 150 nm to 1.5 μm. Meeting this average particle size range helps improve the flexibility of the adhesive film. Furthermore, the inorganic particles themselves, as well as the pores formed by their stacking, can absorb a certain amount of electrolyte, improving the interfacial performance between the adhesive film and the electrode. This maintains the wetting of the electrode's active layer by the electrolyte at that location, improving the flexibility of the active layer and reducing problems such as cracking and detachment of the active material layer, and electrode powdering and cracking. On the other hand, it allows the active material in the adhesive film-covered area to better utilize its capacity, ensuring the battery's energy density. The average particle size of the inorganic particles is obtained using methods known in the art. One method is described here: under SEM, the diameter of 100 particles is randomly measured on the surface of the adhesive film coating, and the average value is calculated. Measurements are taken 10 times at 10 different locations, and the average value is recorded as the average particle size of the inorganic particles. For example, the average particle size of the inorganic particles is 150nm, 200nm, 300nm, 500nm, 800nm, 1μm, 1.2μm, 1.5μm or within any two of the above values.

[0069] In one optional embodiment, the adhesive comprises at least one selected from polyisobutylene, styrene-isoprene copolymer, polyvinylidene fluoride, a copolymer of polyvinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, polyhexafluoropropylene, and styrene-butadiene rubber; and / or,

[0070] The adhesive content in the coating layer is 30wt% to 80wt%, based on 100% of the total mass of the coating layer.

[0071] This application regulates the mass content of adhesive and inorganic particles in the coating layer, which helps to further improve the electrolyte retention capacity and flexibility of the adhesive paper.

[0072] The method for testing the mass content of inorganic particles in the coating layer adopts a method known in the art. One example is given here: a sample of adhesive paper is weighed and recorded as M. It is then immersed in a benzene solution for 4 hours, causing the coating layer to detach from the substrate layer. The substrate layer is removed, dried, and weighed, recorded as M1. The total mass of the coating layer is M-M1. The benzene solution is filtered using filter paper with a mass of M0. The adhesive in the coating layer dissolves in the benzene, and the inorganic particles adhere to the filter paper. After drying the filter paper, it is weighed and recorded as M2. The mass of the inorganic particles is M2-M0, and the mass content of inorganic particles in the coating layer is (M2-M0) / (M-M1). Note that the adhesive paper sample can also be immersed in organic solvents such as toluene. This application does not limit the type of immersion solvent, as long as it can separate the coating layer from the substrate. Furthermore, the mass content of the adhesive in the coating layer is calculated by the following formula: Adhesive mass content = 1 - Inorganic particle mass content. It should also be noted that the mass content of inorganic particles and / or adhesive in the first coating layer and the second coating layer is the same.

[0073] Secondly, this application provides a battery cell, the battery cell comprising a positive electrode, a negative electrode, a separator, and the aforementioned adhesive tape, wherein the separator is disposed between the positive electrode and the negative electrode; the adhesive tape is disposed at at least a portion of at least one surface of the positive electrode; and or,

[0074] The adhesive tape is disposed at at least partially on at least one surface of the negative electrode sheet; and or,

[0075] The adhesive tape is disposed at at least a portion of at least one surface of the diaphragm.

[0076] Thirdly, this application provides a battery cell comprising a positive electrode, a negative electrode, a separator disposed between the positive and negative electrode, and the aforementioned adhesive tape. The positive electrode, separator, and negative electrode are stacked and wound multiple turns along a winding direction to form a wound battery cell. The wound battery cell includes a flat region and an arcuate region. At least a portion of the adhesive tape is located in the arcuate region, and the adhesive tape is disposed at at least one location among the positive electrode, negative electrode, and separator; and / or,

[0077] From the winding direction of the wound battery cell, the wound battery cell includes a first arc region, a first straight region, a second arc region, and a second straight region. At least a portion of the adhesive tape is located at at least one of the first arc region and the second arc region. The adhesive tape is disposed at at least one of the positive electrode, the negative electrode, and the separator. Figure 4As shown, the battery cell includes a first arc region 2, a second arc region 3, a first flat region 4, and a second flat region 5; wherein at least a portion of the adhesive tape 1 is located at at least one location in the first arc region and the second arc region; optionally, the adhesive tape 1 is located in the first arc region, that is, the region where the battery cell is first bent during winding. Optionally, the adhesive tape may also be located in the second arc region.

[0078] In one optional embodiment, the positive electrode sheet includes a positive current collector and a positive active material layer located on at least one surface of the positive current collector, and at least a portion of the adhesive paper covers the surface of the first end of the positive active material layer; and / or,

[0079] The negative electrode sheet includes a negative current collector and a negative active material layer located on at least one surface of the negative current collector, and at least a portion of the adhesive paper covers the surface of the first end of the negative active material layer.

[0080] It should be noted that "starting point" refers to the initial position where the battery cell begins to be wound.

[0081] In one optional embodiment, the positive electrode active material layer comprises a positive electrode active material, which is a common raw material in the art, such as at least one of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium-rich manganese-based materials, lithium cobalt oxide (LiCoO2), lithium manganese oxide, lithium manganese iron phosphate, or lithium titanate. The positive electrode active material layer also comprises additives, such as binders and conductive agents, which are common raw materials in the art. Conductive agents include at least one of conductive carbon black and carbon nanotubes; binders include at least one of PVDF, HSV, PTFE, SBR, and PAA. The positive electrode current collector is a common current collector in the art, such as aluminum foil or titanium foil.

[0082] In one optional embodiment, the negative electrode current collector can be a common current collector in the art, such as copper foil, nickel foil, iron-nickel alloy foil, or copper-nickel alloy foil. The negative electrode active material layer comprises an active material, which is a common raw material in the art, such as at least one of carbon-based materials, silicon-based materials, tin-based materials, or titanium-based materials; specifically, it includes at least one of artificial graphite, natural graphite, soft carbon, hard carbon, elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, silicon alloys, elemental tin, tin oxide compounds, tin alloys, elemental titanium, titanium oxide compounds, or titanium alloys. It is understood that the negative electrode active material layer may also include additives, such as conductive agents and binders. Conductive agents include at least one of carbon black and carbon nanotubes, and the content of the conductive agent in the negative electrode active material layer is not higher than 3 wt%. Binders include at least one of SBR binders and PAA binders, and the content of the binder in the negative electrode active material layer is not higher than 3 wt%. The active material, conductive agent, and binder in the negative electrode active material layer are mixed in conventional proportions in the art.

[0083] In one optional embodiment, the diaphragm includes a base membrane and a coating on at least one surface of the base membrane, the coating including at least one layer structure selected from ceramic and adhesive layers. The material of the base membrane is selected from materials known in the art and is not limited thereto; as an example, the material of the base membrane includes at least one selected from polyethylene, polypropylene, polyethylene terephthalate, polyphenylene sulfide, polyimide, polystyrene, polytetrafluoroethylene, polymethyl methacrylate, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, cellulose, etc. The ceramic layer comprises inorganic particles and a binder, optionally with a mass ratio of (40-95):(5-60); the inorganic particles include at least one of boehmite, alumina, barium sulfate, magnesium oxide, magnesium hydroxide, silicon dioxide, tin oxide, titanium oxide, calcium oxide, zinc oxide, zirconium oxide, yttrium oxide, nickel oxide, cerium dioxide, zirconium titanate, barium titanate, and magnesium fluoride; the binder includes at least one of polyvinylidene fluoride, a copolymer of polyvinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polytetrafluoroethylene, and polyhexafluoropropylene. The coating layer is a polymer coating; the polymer is a compound commonly used in the art; for example, the polymer includes copolymers or homopolymers formed from at least one monomer selected from acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, ethyl acrylate, butyl acrylate, ethylhexyl acrylate, styrene, α-methylstyrene, vinyltoluene, ethylene, vinyl acetate, acrylonitrile, vinylidene fluoride, hexafluoropropylene, and chlorophthalic anhydride; the polymer may also be at least one selected from polyetherimide, polyamideimide, polyimide, and vinylidene fluoride-hexafluoropropylene copolymer.

[0084] In one optional embodiment, the battery cell further includes an electrolyte comprising an electrolyte salt and a solvent. It is understood that the electrolyte is a common raw material used in battery manufacturing in the art. The electrolyte salt includes at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP). The solvent includes at least one selected from fluoroethylene carbonate (FEC), ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butyl carbonate (BC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE). The electrolyte also includes additives, the type and amount of which are determined according to requirements.

[0085] Example 1

[0086] This embodiment provides a battery, including:

[0087] Positive electrode sheet: See the structural diagram of the adhesive paper. Figure 1 The adhesive tape includes a substrate layer 6 and a coating layer 7 disposed on one side of the substrate layer 6. The coating layer 7 includes a first coating layer located on the surface of the substrate layer and a second coating layer embedded in the pores of the substrate layer. The substrate layer is made of polyethylene terephthalate and has a thickness of 10 μm. The substrate layer includes several fibers with an average diameter of 4 μm and pores formed between the fibers with a pore size of 5 μm. The coating layer includes alumina particles and styrene-isoprene copolymer adhesive in a mass ratio of 2:3. The average particle size of the inorganic particles is 0.5 μm. The thickness of the first coating layer is 3 μm. The thickness of the adhesive tape is 13 μm. Figure 2 This is an SEM image of the surface of the first coating layer. The image shows that inorganic particles and binder are distributed on the surface. Figure 3 This is a SEM image of the substrate layer surface. As can be seen from the image, the substrate layer contains several fibers, which cross-link with each other to form gaps.

[0088] Lithium cobalt oxide (CCO), PVDF binder, and conductive carbon black were dispersed in N-methylpyrrolidone at a mass ratio of 97:2:1 to obtain a uniform CCO slurry. This slurry was then uniformly coated onto both surfaces of an 8 μm thick aluminum foil. After drying and rolling, an electrode sheet with a thickness of 129 μm was obtained. The electrode sheet was then slit and welded with positive electrode tabs to obtain the positive electrode sheet. The position of the first bend of the electrode sheet was located using a test roll, and the adhesive tape was then pasted at the first bend. The adhesive tape was pasted as follows: Figure 4 As shown, it is located in the first circular arc region.

[0089] Negative electrode sheet: Graphite, styrene-butadiene rubber (SBR) binder, sodium carboxymethyl cellulose (CMC) thickener, and conductive carbon black (CCH) conductive agent are mixed and dispersed in deionized water at a mass ratio of 97:1:1.5:0.5 to obtain a negative electrode slurry. The negative electrode slurry is uniformly coated on both surfaces of a 6 μm thick copper foil. After coating, the foil is dried and rolled to obtain an electrode sheet with a thickness of 165 μm. The electrode sheet is then slit and welded with negative electrode tabs to obtain the negative electrode sheet.

[0090] Electrolyte: includes solvent and lithium salt. The solvent consists of diethyl carbonate, dimethyl carbonate and ethylene carbonate in a volume ratio of 1:1:1. The lithium salt is LiPF6 with a concentration of 1 mol / L.

[0091] The positive electrode, separator, and negative electrode are stacked in sequence, wound into a core, and encapsulated with aluminum-plastic film. The core is then baked in a vacuum for 24 hours to remove moisture, and electrolyte is injected. The battery is then formed, aged, vacuum sealed, and sorted to obtain a soft-pack lithium-ion battery.

[0092] After fully charging the lithium-ion battery, disassemble it and examine the adhesive tape. Figure 5 The negative electrode sheet at the adhesive tape-covered area is golden yellow, indicating the presence of lithium ion intercalation. This verifies that lithium ions can shuttle normally at the adhesive tape-covered area, demonstrating that the active material at the adhesive tape-covered area of ​​this invention can perform its capacity normally.

[0093] Example 2-15

[0094] Examples 2-15 each provide a battery that is basically the same as that in Example 1, except that the adhesive tape is different. The parameters of the adhesive tape are shown in Table 1.

[0095] Table 1 Parameters of Adhesive Tape

[0096]

[0097]

[0098] Comparative Example 1

[0099] Comparative Example 1 provides a battery that is basically the same as that in Example 1, except that the adhesive tape is different. The parameters of the adhesive tape are shown in Table 1.

[0100] Comparative Example 2

[0101] Comparative Example 1 provides a battery that is basically the same as that in Example 1, except that the battery is not covered with adhesive tape.

[0102] Comparative Example 3

[0103] Comparative Example 3 provides a battery that is basically the same as that in Example 1, except that rubber adhesive tape is used instead of the adhesive tape in Example 1.

[0104] Test case

[0105] This test case provides the performance test results for each embodiment and comparative battery, as follows:

[0106] Battery cycle life: ① At 25℃, charge at a constant current of 0.5C to 4.5V, then charge at a constant voltage to 0.05V (cutoff); ② Discharge at a constant current of 0.5C to 3.0V (cutoff), and record the first discharge capacity as the initial capacity Q0; ③ Repeat steps ①-②, and the resulting discharge capacity is taken as the battery capacity Q1. Calculate the capacity retention rate (%) according to the following formula. When the capacity retention rate decays to 80%, the test is stopped, and the number of cycles at this point is recorded as the battery cycle life.

[0107]

[0108] Battery energy density: The battery was fully charged at 0.2C at 25℃ and allowed to stand for 10 minutes. It was then discharged at 0.2C to 3.0V, and the battery capacity was measured. The battery energy density was calculated using the following formula.

[0109]

[0110] Processing Performance: Observe the process of applying adhesive tape to the electrode sheet and the winding process of the electrode sheet to form the battery cell. During the sheet fabrication process, observe for abnormalities such as adhesive seepage or wrinkling of the adhesive tape. Wrinkling indicates wrinkles or wavy patterns during adhesive tape application. Adhesive seepage indicates that the coating layer on one side of the adhesive tape substrate layer has penetrated to the other side, making the other side sticky. This can cause the tape to adhere to other parts of the electrode sheet or other electrodes during winding, affecting the process. During the winding process, observe for cracks or powder shedding in the active material layer of the electrode sheet, and for any breakage of the electrode strip. After winding, disassemble the battery cell to observe for electrode cracking. Cracks include breaks in both the active material layer and the current collector. Figure 6 These are photographs of the arc-shaped areas of the positive electrode sheets in Example 1 and Comparative Example 2, with 6a representing Example 1 and 6b representing Comparative Example 2. As can be seen from the figures, there is no powder shedding or cracking at the arc-shaped area of ​​the positive electrode sheet in Example 1. Comparative Example 2 shows obvious powder shedding and cracking.

[0111] The performance test results of the batteries in each embodiment and comparative example are shown in Table 2.

[0112] Table 2 Test Results

[0113]

[0114] Note: " / " in the table indicates that the value does not exist. Slight cracks indicate an occasional crack during the film-making process, which does not affect the process or adhesive tape application. Slight wrinkles indicate minor wrinkling of the adhesive tape, which does not affect the process or adhesive tape application.

[0115] Based on the above results, the application's control of the average fiber diameter m in the substrate layer and the thickness h of the first coating layer to satisfy h≤60 / m can give the adhesive paper better flexibility, and avoid problems such as powder shedding and cracking of the active material layer during the preparation of the battery cell.

[0116] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. An adhesive tape, characterized in that, The adhesive tape includes a substrate layer and a coating layer disposed on at least one surface of the substrate layer; the substrate layer comprises a plurality of fibers, which intersect and / or overlap to form pores, and the coating layer is partially embedded in the pores; the coating layer includes a first coating layer located on the surface of the substrate layer and a second coating layer embedded in the pores; the thickness h of the first coating layer satisfies the relationship between the average diameter m of the fibers and the following formula: The thickness of the first coating layer is 2 μm to 15 μm; and / or the average diameter of the fiber is 1 μm to 15 μm.

2. The adhesive tape according to claim 1, characterized in that, The bending stiffness of the adhesive tape is not higher than 15mN.

3. The adhesive tape according to claim 1, characterized in that, The average diameter of the fibers is 3μm to 6μm; and / or, The pore size is 0.1 μm to 50 μm; and / or, The coating layer comprises inorganic particles and / or binders.

4. The adhesive tape according to claim 3, characterized in that, The pore size is 0.5 μm to 10 μm; and / or, The first coating layer and the second coating layer contain the inorganic particles.

5. The adhesive tape according to claim 1, characterized in that, The substrate layer is made of at least one of polyethylene terephthalate, polyethylene, polypropylene, polyimide, polyvinyl chloride, polyethylene, and polypropylene; and / or, The thickness of the substrate layer is 5μm to 20μm; and / or, The thickness of the adhesive tape is 8μm to 25μm.

6. The adhesive tape according to claim 3, characterized in that, The inorganic particles have an average particle size of 150 nm to 1.5 μm; and / or, Based on 100% of the total mass of the coating layer, the inorganic particle content in the coating layer is 20wt% to 70wt%; and / or, The inorganic particles include alumina, boehmite, and Li7La3Zr2O. 12 Li 3x La (2 / 3-x) / 3 TiO3, Li 1+x Al x Ti 2-x (PO4)3, at least one of magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zirconium oxide, zinc oxide, calcium oxide, magnesium hydroxide, aluminum hydroxide, barium hydroxide, barium sulfate, calcium silicate, and titanium dioxide.

7. The adhesive tape according to claim 3, characterized in that, The adhesive comprises at least one of polyisobutylene, styrene-isoprene copolymer, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, polyhexafluoropropylene, and styrene-butadiene rubber; and / or, The adhesive content in the coating layer is 30wt% to 80wt% based on 100% of the total mass of the coating layer.

8. A battery cell, characterized in that, The battery cell includes a positive electrode, a negative electrode, a separator, and the adhesive tape as described in any one of claims 1 to 7, wherein the separator is disposed between the positive electrode and the negative electrode; the adhesive tape is disposed at at least a portion of at least one surface of the positive electrode; and or, The adhesive tape is disposed at at least a portion of at least one surface of the negative electrode sheet; and or, The adhesive tape is disposed at at least a portion of at least one surface of the diaphragm.

9. A battery cell, characterized in that, The battery cell includes a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and the adhesive tape as described in any one of claims 1 to 7. The positive electrode, separator, and negative electrode are stacked and wound multiple turns along the winding direction to form a wound battery cell. The wound battery cell includes a flat region and an arc region. At least a portion of the adhesive tape is located in the arc region. The adhesive tape is disposed at at least one of the positive electrode, the negative electrode, and the separator; and / or, From the winding direction of the wound cell, the wound cell includes a first arc region, a first straight region, a second arc region, and a second straight region. At least a portion of the adhesive tape is located at at least one of the first arc region and the second arc region. The adhesive tape is disposed at at least one of the positive electrode, the negative electrode, and the separator.

10. The battery cell according to claim 9, characterized in that, The positive electrode sheet includes a positive current collector and a positive active material layer located on at least one surface of the positive current collector, and at least a portion of the adhesive paper covers the surface of the first end of the positive active material layer; and / or, The negative electrode sheet includes a negative current collector and a negative active material layer located on at least one surface of the negative current collector, and at least a portion of the adhesive paper covers the surface of the first end of the negative active material layer.

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