Adhesive tape, preparation method of adhesive tape, electrochemical device and electric equipment

Abstract

The invention provides an adhesive tape, a preparation method of the adhesive tape, an electrochemical device and electric equipment. The adhesive tape comprises a bonding layer and a liquid absorption layer. And a plurality of through holes are formed in the bonding layer. The liquid absorbing layer is arranged on one side of the bonding layer, and the liquid absorbing layer is provided with a pore structure. And one side, deviating from the liquid absorption layer, of the bonding layer is used for bonding a corner region of a pole piece in the electrode assembly. The adhesive tape can protect the corner area of the pole piece, and the risks of pole piece breakage and material falling caused by large inner ring pressure in the hot pressing process are reduced. The multiple through holes in the bonding layer and the pore structure of the liquid absorption layer can provide channels for ion movement, the risk that active substances on the pole piece in the corner area lose activity is reduced, the liquid absorption layer can also absorb and store a certain amount of electrolyte, the electrolyte is provided for later circulation, the dynamic performance of the battery is guaranteed, and the phenomena of lithium precipitation and black spots at the corner are improved.

Description

Technical Field

[0001] The present application relates to the technical field of batteries, and in particular, to a tape, a preparation method of the tape, an electrochemical device, and an electrical device. Background Art

[0002] As a secondary battery that can be repeatedly charged and discharged, the working principle of a lithium-ion battery is based on the reversible insertion and extraction process of lithium ions between the positive and negative electrodes. This process enables the lithium-ion battery to store more energy under the same volume or mass, thereby achieving a high energy density. It also has advantages such as a long cycle life, no memory effect, and no pollution. It is widely used in the fields of consumer electronics, power, energy storage, and other fields.

[0003] The lithium-ion battery structures most commonly used in the current market are mainly divided into two categories. One is the laminated cell structure, and the other is the wound cell structure. During the winding process of the wound lithium-ion battery cell structure, a flat area and arc-shaped corner areas located at both ends of the core will be formed. After the cell winding is completed, a hot pressing operation will be carried out. During the hot pressing process, the pressure inside the cell is large, which is likely to cause the pole piece to break. During the long-term charge and discharge cycle process, lithium deposition is likely to occur in the arc-shaped corner areas, which has a greater impact on the safety performance of the cell. Summary of the Invention

[0004] The present application provides a tape, a preparation method of the tape, an electrochemical device, and an electrical device to solve the above technical problems.

[0005] An embodiment of the present application is implemented as follows: A tape includes an adhesive layer and a liquid-absorbing layer. A plurality of through holes are provided on the adhesive layer. The liquid-absorbing layer is disposed on one side of the adhesive layer, and the liquid-absorbing layer has a pore structure. The side of the adhesive layer facing away from the liquid-absorbing layer is used to bond the corner area of the pole piece in the electrode assembly.

[0006] The tape of the present application can be pasted on the pole piece in the corner area of the wound cell structure to protect the corner area of the pole piece and reduce the risks of pole piece breakage and material loss caused by the large pressure inside the cell during the hot pressing process. In addition, in the tape, the plurality of through holes on the adhesive layer and the pore structure of the liquid-absorbing layer can provide channels for ion movement, reduce the risk of the active material on the pole piece in the corner area losing its activity, and the liquid-absorbing layer can also absorb and store a certain amount of electrolyte to provide electrolyte for the later cycle and ensure the kinetic performance of the battery. At the same time, the liquid-absorbing layer with a pore structure can also slow down the extrusion of the pole piece in the corner area on the adjacent pole pieces due to expansion, enhance the infiltration and reflux of the electrolyte in the corner area, and greatly improve the lithium deposition and black spot phenomena in the corner.

[0007] In a possible implementation, the tape further includes a protective film, which is disposed on the side of the liquid absorbing layer away from the adhesive layer, and the protective film can be dissolved in the electrolyte. In this way, during the winding process of the pole piece, the protective film can prevent the liquid absorbing layer from being damaged, and after the electrolyte is poured, the protective film can be dissolved to expose the liquid absorbing layer, so as not to hinder the lithium insertion and extraction process between the pole pieces in the corner area.

[0008] In a possible implementation manner: the protective film includes a substrate layer and an adhesive layer, both of which can be dissolved in the electrolyte, and the adhesive layer is arranged between the liquid absorbing layer and the substrate layer.

[0009] In a possible implementation, the material of the liquid absorption layer includes a lithium supplement, and the percentage of the lithium supplement added to the total mass of the liquid absorption layer is a, where 0 < a ≤ 0.9%. The lithium supplement in the liquid absorption layer can reduce the battery impedance in the corner area, improve the dynamic performance of the corner area, and thus improve the lithium deposition phenomenon in the corner area, thereby improving the safety performance of the battery.

[0010] The embodiment of the present application also provides a method for preparing an adhesive tape, comprising: The adhesive layer is applied to the release film, and after curing, a punching operation is performed to prepare an adhesive layer; Providing a polymer solution, subjecting the polymer solution to electrostatic spinning to form a fiber layer, so as to prepare a liquid-absorbing layer; wherein the polymer material of the polymer solution includes one or more of an organic solvent-soluble synthetic polymer, a water-soluble synthetic polymer, and a degradable polymer; and the solvent material of the polymer solution includes one or more of an acid, an alcohol, an ester, an ether, a sulfoxide, and an amide solvent; The adhesive layer and the liquid absorbing layer are compounded together to obtain an adhesive tape.

[0011] The liquid-absorbing layer of the fiber layer structure produced by electrospinning can utilize its high specific surface area, porosity and permeability characteristics to store electrolyte, increase the ion transfer rate in the corner area, provide electrolyte for the battery cell cycle and improve the ion transfer capacity, avoiding the serious black spot lithium precipitation phenomenon.

[0012] In a possible implementation manner: the method for preparing the adhesive tape further includes: Prepare an adhesive that can be dissolved in an electrolyte; wherein the material of the adhesive includes polyacrylate, polyvinyl acetate, and polystyrene resin; Applying an adhesive to a substrate layer that is soluble in an electrolyte to form an adhesive layer on the substrate layer, and performing a curing treatment to obtain a protective layer; The protective layer and the liquid absorbing layer are compounded.

[0013] In a possible implementation: a lithium supplement agent is further added to the polymer solution, and the percentage of the mass of the lithium supplement agent in the total mass of the liquid absorption layer is a, where 0 < a ≤ 0.9%.

[0014] An embodiment of the present application further provides an electrochemical device, including a first electrode, a second electrode, a separator, and the tape described in the above embodiment or the tape prepared by the preparation method of the tape described in the above embodiment. The polarities of the first electrode and the second electrode are opposite, the separator is disposed between the first electrode and the second electrode, and the first electrode, the separator, and the second electrode are wound to form an electrochemical device. The first electrode has a first flat region and a first corner region in the winding structure, the tape is at least partially disposed in the first corner region, and the adhesive layer is attached to the surface of the first electrode.

[0015] In a possible implementation: the first electrode includes a first current collector and a first active material layer, and the first active material layer is disposed on the surface of the first current collector; the thickness of the first active material layer in the first flat region is t1, and the thickness of the first active material layer in the first corner region is t2, where 1 μm ≤ t1 - t2 ≤ 30 μm.

[0016] In the electrochemical device of the present application, by reducing the coating thickness of the active material layer of the first electrode in the corner region, the capacity utilization of the first electrode in the corner region can be reduced, so that the total capacity at the corner position ≤ the flat region. Then, by pasting the liquid absorption layer material containing the lithium supplement agent in the corner region of the first electrode, and utilizing the high specific capacity utilization ability of the lithium supplement agent, it is possible to neither reduce the active material capacity of the first electrode in the corner region nor improve the kinetic performance in the corner region, thereby improving the lithium deposition situation.

[0017] An embodiment of the present application further provides an electrical device, including an electrical component and the electrochemical device described in the above embodiment, and the electrical component is electrically connected to the electrochemical device. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the accompanying drawings in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0019] Figure 1 It is a schematic structural diagram of the tape according to an embodiment of the present application.

[0020] Figure 2 It is a schematic structural diagram of the tape in another embodiment.

[0021] Figure 3 It is a schematic structural diagram of the electrochemical device in an embodiment.

[0022] Figure 4 is Figure 3 a partially enlarged view of the electrochemical device shown.

[0023] Figure 5 is Figure 3 a partially enlarged view of the electrochemical device shown after the protective layer of the tape is dissolved.

[0024] Figure 6 is a schematic structural diagram of the electrochemical device in an embodiment.

[0025] Figure 7 is Figure 6 a partially enlarged view of the electrochemical device shown.

[0026] Figure 8 is Figure 6 a partially enlarged view of the electrochemical device shown after the protective layer of the tape is dissolved.

[0027] Figure 9 is a schematic structural diagram of the electrochemical device of a comparative example of the present application.

[0028] Figure 10 is Figure 9 a partially enlarged view of the electrochemical device in the comparative example shown.

[0029] Figure 11 is Figure 9 a partially enlarged view of the electrochemical device shown after the protective layer of the tape in the comparative example is dissolved.

[0030] Figure 12 is a schematic structural diagram of the electrochemical device of another comparative example of the present application.

[0031] Figure 13 is Figure 12 a partially enlarged view of the electrochemical device in the comparative example shown.

[0032] Figure 14 is a schematic structural diagram of the electrical equipment in an embodiment.

[0033] Figure 15 is a schematic flow chart of the method for preparing the tape in an embodiment of the present application.

[0034] Figure 16 is a schematic flow chart of the method for preparing the tape in another embodiment of the present application.

[0035] Description of main component symbols: Tapes 100, 100a, 100b Adhesive layer 11 Through hole 111 Liquid absorption layer 12 Protective film 13 Base material layer 131 Adhesive layer 132 Electrochemical devices 200, 200a, 200b First electrode sheet 21 First current collector 211 First active material layer 212 First flat region 213 First corner region 214 Second electrode sheet 22 Second current collector 221 Second active material layer 222 Separator 23 Electrical equipment 300 Electrical component 301 The following specific embodiments will further illustrate the present application in conjunction with the above-mentioned drawings. Specific embodiments

[0036] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments.

[0037] It should be noted that when an element is referred to as being "fixed to" another element, it can be directly on the other element or there may also be a middle element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be a middle element at the same time. When an element is considered to be "disposed on" another element, it can be directly disposed on the other element or there may be a middle element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are only for the purpose of illustration.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs. The terms used in the specification of this application are only for the purpose of describing specific embodiments, and are not intended to limit this application. The term "or / and" used herein includes any and all combinations of one or more of the related listed items.

[0039] Some embodiments of the present application will be described in detail. Without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0040] See Figure 1, this embodiment provides a tape 100, which includes an adhesive layer 11 and a liquid absorption layer 12. A plurality of through holes 111 are provided on the adhesive layer 11. The liquid absorption layer 12 is disposed on one side of the adhesive layer 11, and the liquid absorption layer 12 has a pore structure. The side of the adhesive layer 11 facing away from the liquid absorption layer 12 is used to bond the corner area of the pole piece in the electrode assembly.

[0041] The tape 100 of the present application is used to be pasted on the pole piece in the corner area of the wound battery cell structure to protect the corner area of the pole piece and reduce the risks of pole piece fracture and material loss caused by the large inner ring pressure during the hot pressing process of the battery cell. In addition, in the tape 100, the plurality of through holes 111 on the adhesive layer 11 and the pore structure of the liquid absorption layer 12 can provide channels for ion movement, reduce the risk of loss of activity of the active material on the pole piece in the corner area, and the liquid absorption layer 12 can also absorb and store a certain amount of electrolyte to provide electrolyte for later cycles and ensure the kinetic performance of the battery. At the same time, the liquid absorption layer 12 with a pore structure can also slow down the extrusion of the pole piece expansion in the corner area on the adjacent pole pieces, enhance the infiltration and reflux of the electrolyte in the corner area, and greatly improve the lithium deposition and black spot phenomena in the corner.

[0042] In one embodiment, the through holes 111 on the adhesive layer 11 are formed by die-cutting, so that the adhesive layer 11 has a porous structure. The shapes of the plurality of through holes 111 can be circular holes, rectangles, squares, ellipses, etc., and the present application is not limited thereto. The maximum directional width or inner diameter of each through hole 111 is 0.5 mm - 5 mm, specifically it can be 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm; or a range between any values of 0.5 mm - 5 mm. The spacing distance between adjacent through holes 111 can be 0.05 - 5 mm, specifically it can be 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm; or a range between any values of 0.5 mm - 5 mm.

[0043] In one embodiment, the liquid absorption layer 12 is a fiber layer, which is prepared by electrospinning. The pore structure in the liquid absorption layer 12 is a three-dimensional network structure. The fiber layer prepared by electrospinning can utilize the characteristics of high specific surface area, high porosity and high permeability of the spinning network, can achieve high liquid retention characteristics, can fully store and absorb the electrolyte, and provide electrolyte for the corner area of the wound battery cell structure during the later cycle process, avoiding the attenuation and deterioration of the battery cell life caused by the dryness of the electrolyte in the corner area.

[0044] Please refer to Figure 2, In a possible implementation, the tape 100 further includes a protective film 13. The protective film 13 is disposed on the side of the liquid absorption layer 12 away from the adhesive layer 11, and the protective film 13 can be dissolved in the electrolyte. In this way, during the winding process of the electrode sheet, the protective film 13 can prevent the liquid absorption layer 12 from being damaged during the winding process of the electrode sheet. After the electrolyte is poured, the protective film 13 can be dissolved to expose the liquid absorption layer 12, without hindering the lithium deintercalation process between the electrode sheets in the corner area. In addition, after the protective film 13 is dissolved, a certain gap space can be formed in the corner area, which is beneficial to the infiltration of the electrolyte into the corner area of the battery cell and can also reduce the extrusion and stress of the electrode sheets in the corner area.

[0045] In one implementation, the material of the protective film 13 includes but is not limited to resin materials such as polyacrylate, polyvinyl acetate, and polystyrene resin, and can be dissolved in carbonate solvents. In other embodiments, the material of the protective film 13 can be adjusted according to the material of the electrolyte, as long as the protective film 13 can be dissolved in the electrolyte, and this application is not limited thereto.

[0046] In one implementation, the protective film 13 includes a substrate layer 131 and an adhesive layer 132. Both the substrate layer 131 and the adhesive layer 132 can be dissolved in the electrolyte. The adhesive layer 132 is disposed between the liquid absorption layer 12 and the substrate layer 131 to fix the protective film 13 on the surface of the liquid absorption layer 12. Among them, the material of the adhesive layer 132 includes one or more of polyacrylate, polyvinyl acetate, and polystyrene resin. The substrate layer 131 can be a release film treated with a silicone release agent and can also be dissolved in the electrolyte. The thickness of the adhesive layer 132 is 0μm - 10μm, and the thickness of the substrate layer 131 can also be 0μm - 10μm. The total thickness of the protective film 13 is 0μm - 20μm. After the protective film 13 is compounded with the liquid absorption layer 12, the total thickness of the tape 100 is 0μm - 40μm. When the thickness of the protective film 13 is 0μm, no protective film 13 is provided on the surface of the liquid absorption layer 12 of the tape 100.

[0047] In one implementation, the material of the liquid absorption layer 12 can further include a lithium supplement agent. The addition amount of the lithium supplement agent accounts for a percentage a of the total mass of the liquid absorption layer 12, where 0 < a ≤ 0.9%; specifically, it can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%; or a range of any value between 0 - 0.9%.

[0048] The liquid absorption layer 12 prepared by the electrospinning method can make the lithium supplement agent evenly distributed in the network structure. The lithium supplement agent in the liquid absorption layer 12 can reduce the battery impedance in the corner area, improve the kinetic performance in the corner area, and further improve the lithium deposition phenomenon in the corner area, thereby enhancing the safety performance of the battery.

[0049] Please refer to Figures 3 to 8, An embodiment of the present application further provides an electrochemical device 200, which includes a first electrode sheet 21, a second electrode sheet 22, a separator 23, and the tape 100 described in the above embodiment. The polarities of the first electrode sheet 21 and the second electrode sheet 22 are opposite, the separator 23 is disposed between the first electrode sheet 21 and the second electrode sheet 22, and the first electrode sheet 21, the separator 23, and the second electrode sheet 22 are wound to form the electrochemical device 200. The first electrode sheet 21 has a first flat region 213 and a first corner region 214 in the winding structure. The tape 100 is at least partially disposed in the first corner region 214, and the adhesive layer 11 is attached to the surface of the first electrode sheet 21.

[0050] The tape 100 is disposed in the corner region of the first electrode sheet 21. On the one hand, it can protect the electrode sheet, reduce the risk of electrode sheet fracture and material loss caused by the large inner ring pressure during the hot pressing process of the battery cell. Moreover, the adhesive layer 11 having a plurality of through holes 111 and the liquid absorption layer 12 having a pore structure will not block the active material layer in the corner region of the first electrode sheet 21, and can provide a channel for ion movement, reducing the risk of the active material on the electrode sheet in the corner region losing activity. On the other hand, the tape 100 can also absorb and store a certain amount of electrolyte to provide electrolyte for later cycles and ensure the kinetic performance of the battery. At the same time, the liquid absorption layer 12 having a pore structure can also slow down the extrusion of the electrode sheet in the corner region on the adjacent electrode sheets, enhance the infiltration and reflux of the electrolyte in the corner region, and greatly improve the lithium deposition and black spot phenomena in the corner.

[0051] Please refer to Figure 3 , Figure 4 and Figure 5 , In one embodiment, the first electrode sheet 21 is a positive electrode sheet, and the second electrode sheet 22 is a negative electrode sheet. The liquid absorption layer 12 material of the tape 100 does not contain a lithium supplement agent. The first electrode sheet 21 includes a first current collector 211 and a first active material layer 212, and the first active material layer 212 is disposed on the surface of the first current collector 211. The thickness of the first active material layer 212 is the same in the first flat region 213 and the first corner region 214. The tape 100 is disposed on the side of the first electrode sheet 21 facing the inner circle of the core, and the tape 100 is at least partially disposed in the first corner region 214. Specifically, the middle section region of the tape 100 is disposed in the first corner region 214, and a small amount of the end region of the tape 100 is disposed in the first flat region 213, so as to allow the tape 100 to fully cover the first corner region 214 and reduce the problem of incomplete coverage of the electrode sheet in the corner region caused by factors such as winding error and tape 100 setting deviation. In other embodiments, the tape 100 can also be entirely disposed in the corner region, as long as the design requirements are met, and the present application is not limited thereto. In other embodiments, the first electrode sheet 21 can also be a negative electrode sheet, and the second electrode sheet 22 can be a positive electrode sheet, and the present application is not limited thereto.

[0052] In Figure 3 and Figure 4In the illustrated embodiment, the tape 100 has a four-layer structure. A protective film 13 is provided on the surface of the liquid absorption layer 12. During the winding process of the electrode sheet, the protective film 13 can prevent the fiber structure in the liquid absorption layer 12 from being damaged and maintain the integrity of the liquid absorption layer 12. After the wound electrode assembly is fabricated, when the electrolyte is poured, the two-layer structure of the protective film 13 dissolves, exposing the adhesive layer 11 and the liquid absorption layer 12 in the electrolyte, as Figure 5 shown. The liquid absorption layer 12 can fully absorb and store a certain amount of electrolyte, providing electrolyte for later cycles and ensuring the kinetic performance of the battery.

[0053] In other embodiments, the tape 100 can also be Figure 1 in the same structure as the illustrated embodiment, with a two-layer structure and no protective film 13 on the surface of the liquid absorption layer 12. When the tape 100 is disposed in the first corner region 214 of the first electrode sheet 21, the structure is Figure 5 similar to that of the illustrated embodiment.

[0054] Please refer to Figure 6 , Figure 7 and Figure 8 . In another embodiment, the first electrode sheet 21 is a positive electrode sheet and the second electrode sheet 22 is a negative electrode sheet. In the arc corner region of the winding structure, the first electrode sheet 21 is wrapped outside the second electrode sheet 22. The material of the liquid absorption layer 12 of the tape 100 contains a lithium supplement agent, and the percentage of the mass of the lithium supplement agent in the total mass of the liquid absorption layer 12 is a, where 0 < a ≤ 0.9%.

[0055] The thickness of the first active material layer 212 in the first straight region 213 is t1, and the thickness of the first active material layer 212 in the first corner region 214 is t2, where 1 μm ≤ t1 - t2 ≤ 30 μm. The value of t1 - t2 can specifically be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, 30 μm; or any value within the range of 1 μm - 30 μm.

[0056] In other words, the active material layer materials of the first flat region 213 and the first corner region 214 are the same. The thickness t1 of the first active material layer 212 in the first flat region 213 is smaller than the thickness t2 of the first active material layer 212 in the first corner region 214. By thinning the coating thickness of the active material layer of the first electrode tab 21 in the corner region, the capacity utilization of the first electrode tab 21 in the corner region can be reduced, so that the total capacity at the corner position ≤ the flat region. Then, by pasting the liquid absorption layer 12 material containing a lithium supplement agent in the corner region of the first electrode tab 21, and utilizing the high specific capacity utilization ability of the lithium supplement agent, it is possible to neither reduce the active material capacity of the first electrode tab 21 in the corner region nor improve the kinetic performance of the corner region, thereby improving the lithium plating situation. The first electrode tab 21 can be formed by slot die coating to have a structure in which the thicknesses of the active material layers in the first flat region 213 and the first corner region 214 are different.

[0057] The thickness of the tape 100 is t3. In Figure 6 the illustrated embodiment, t3 < t1 - t2 to reduce the influence of the tape 100 on the surface flatness of the electrode tab. In other embodiments, the thickness t3 of the tape 100 can also be greater than or equal to t1 - t2, that is, t3 ≥ t1 - t2, so that the tape 100 can absorb more electrolyte, improve the kinetic performance, and provide a buffer space for the expansion of the electrode tab, reducing the extrusion and stress of the electrode tab.

[0058] In Figure 6 and Figure 7 the illustrated embodiment, the tape 100 has a four-layer structure. A protective film 13 is provided on the surface of the liquid absorption layer 12, and the material of the liquid absorption layer 12 also contains a lithium supplement agent. After the wound electrode assembly is fabricated, when the electrolyte is poured, the two-layer structure of the protective film 13 dissolves, exposing the adhesive layer 11 and the liquid absorption layer 12 in the electrolyte, as shown in Figure 8 the figure. The liquid absorption layer 12 can fully absorb and store a certain amount of electrolyte, providing electrolyte for the later cycle and ensuring the kinetic performance of the battery. The uniformly distributed lithium supplement agent in the liquid absorption layer 12 can also reduce the impedance of lithium insertion into the negative electrode, being more conducive to lithium deintercalation and reducing the risk of lithium plating.

[0059] In other embodiments, the tape 100 can also have a two-layer structure without a protective film 13 on the surface of the liquid absorption layer 12. When the tape 100 is disposed in the first corner region 214 of the first electrode tab 21, the structure is similar to that in Figure 8 the illustrated embodiment.

[0060] In the electrochemical device 200 of the present application, the wound electrode assembly has a flat region and corner arc regions located at both ends of the core. The first electrode sheet 21 is coated with slurry coatings of different thicknesses in the flat region and the corner region of the core by a simple gap coating method using the same slurry. The purpose of reducing the thickness is on the one hand to leave a certain gap for later electrolyte storage, and on the other hand to balance with the lithium supplement agent, reduce the coating thickness of the positive electrode at the corner, reduce its capacity utilization, so that the total capacity at the corner position ≤ the flat region. Then, by pasting the liquid-absorbing layer 12 containing the lithium supplement agent in the corner region of the first electrode sheet 21, and utilizing the high specific capacity utilization ability of the lithium supplement agent, a method is realized that can neither reduce the capacity of the positive active material in the corner region nor improve the lithium deposition kinetics at the corner of the negative electrode.

[0061] In some embodiments, the tape 100 includes a protective film 13 that can be dissolved in the electrolyte, which can achieve the peeling off of the outer substrate layer 131 and the adhesive layer 132 during the soaking process in the electrolyte, without hindering the lithium intercalation and deintercalation between the positive electrode sheet and the negative electrode sheet at the corner, and without sacrificing the capacity at the corner position, that is, without sacrificing the energy density of the battery cell to improve lithium deposition in the battery cell. After the protective film 13 is dissolved, the liquid-absorbing layer 12 prepared by electrospinning can be exposed to the electrolyte. The liquid-absorbing layer 12 can absorb and store a certain amount of electrolyte to provide electrolyte for later cycles and ensure the kinetic performance of the battery. There is also a uniformly doped lithium supplement agent in the liquid-absorbing layer 12, which can participate in the formation of SEI during the first charge and discharge process, can optimize the SEI structure, make the inorganic-organic blending structure of the SEI film more reasonable, can improve the impedance of the negative electrode, and improve the lithium ion transport kinetics. It can also utilize the high specific capacity utilization ability of the lithium supplement agent to achieve neither reducing the capacity of the positive active material in the corner region nor achieving a lower coating thickness by using the higher specific capacity of the corner lithium supplement agent, and can provide a buffer space for the expansion of the electrode sheet.

[0062] The formation of the SEI film is mainly during the charge and discharge process of a lithium-ion battery. The reducing substances and oxides generated by the decomposition of the solute in the electrolyte react on the electrode surface to form a thin film, which has a certain conductivity and stability and can prevent the further decomposition of the solute in the electrolyte, thereby protecting the electrode material inside the battery.

[0063] Please refer to Figure 14 , the embodiment of the present application further provides an electrical device 300, including an electrical component 301 and the electrochemical device 200 described in the above embodiment, and the electrical component 301 is electrically connected to the electrochemical device 200.

[0064] Please refer to Figure 15 , the embodiment of the present application further provides a preparation method of a tape 100, including: Coating an adhesive layer on a release film, and after curing treatment, performing a punching operation to prepare the bonding layer 11; Provide a polymer solution, and perform electrospinning on the polymer solution to form a fiber layer for preparing the liquid absorption layer 12; wherein, the polymer material of the polymer solution includes one or more of an organic solvent-soluble synthetic polymer, a water-soluble synthetic polymer, and a biodegradable polymer; the solvent material of the polymer solution includes one or more of acids, alcohols, esters, ethers, sulfoxides, and amide solvents; Compound the adhesive layer 11 with the liquid absorption layer 12 to obtain the tape 100.

[0065] The liquid absorption layer 12 with a fiber layer structure prepared by electrospinning can utilize its high specific surface area, porosity, and permeability characteristics to store the electrolyte, improve the ion transport rate in the corner area, provide the electrolyte for the cell cycle, and improve the ion transport ability, avoiding the occurrence of serious black spot lithium deposition phenomenon.

[0066] Please refer to Figure 16 , in a possible implementation manner: the preparation method of the tape 100 further includes: Prepare an adhesive that can be dissolved in the electrolyte; wherein, the material of the adhesive includes polyacrylate, polyvinyl acetate, and polystyrene resin; Coat the adhesive on the substrate layer 131 that can be dissolved in the electrolyte to form an adhesive layer 132 on the substrate layer 131, and obtain a protective layer after curing treatment; Compound the protective layer with the liquid absorption layer 12.

[0067] In a possible implementation manner: a lithium supplement agent is further added to the polymer solution, and the mass percentage of the lithium supplement agent in the total mass of the liquid absorption layer 12 is a, where 0 < a ≤ 0.9%.

[0068] Figure 15 and Figure 16 The shown preparation step sequence is only an example. In other embodiments, the preparation steps can be adjusted according to design requirements, and this application is not limited thereto.

[0069] The following content will specifically describe the tape, the preparation method of the tape, and the electrochemical device in detail with reference to specific embodiments.

[0070] Example 1 Refer to Figure 6 As shown in the structural schematic diagram, when preparing the first electrode 21, a dressing layer with a normal designed thickness is coated on the flat area of the first current collector 211 by means of gap coating, and a slurry of an active material layer with a thinner thickness is coated in the corner area.

[0071] The active material slurry with a relatively thin coating thickness in the corner area is to ensure that the total capacity of the active material and the lithium supplement agent in the corner area of the positive electrode sheet ≤ that in the straight area. The implementation method listed here is to use gap coating to coat a relatively thin active material layer in the corner area, but it is also possible to clean a certain thickness of the active material layer by laser cleaning. The thickness of the first active material layer 212 in the first corner area 214 is 1 μm - 30 μm thinner than the thickness of the first active material layer 212 in the first straight area 213.

[0072] During the cycling process, the gap at this corner position can be fully utilized to provide stress deformation space for the later expansion of the electrode sheet, and can also store the electrolyte to a certain extent, enabling the electrolyte to be fully absorbed and stored in the electrospun fibers at the corner. Provide electrolyte for the later cycle and improve the black spot lithium deposition situation at the corner position.

[0073] In the preparation process of the first electrode sheet 21 in this application, it is simple, without changing the existing production line and process. Only gap coating is required during the coating process, and the slurry for gap coating is also the same slurry, without the need to separately configure a formula slurry. Only by changing the coating pressure or flow rate can the thickness of the coating slurry be adjusted, without major changes to the existing process, equipment, and process. Moreover, in the tape 100 attached to the corner area later, the lithium supplement agent in the liquid absorption layer 12 can provide capacity, combined with the active material capacity in the corner area, to ensure that the total capacity is not less than that in the straight area, without reducing the energy density of the battery cell.

[0074] The preparation process of the electrochemical device 200 specifically includes: Preparation of the first electrode sheet 21: Provide a mixed slurry of the first active material, and then coat the mixed slurry on the first current collector 211 aluminum foil of about 10 μm by gap coating. The blank area of the gap coating is the corner arc area, and the coating area of the gap coating is the straight area. After coating, the electrode sheet is dried. Then, use the same slurry to coat a slurry with a relatively thin thickness in the corner area by gap coating. The coating thickness is about 1 μm - 30 μm smaller than that in the straight area, and the specific ratio can be adjusted according to design requirements. It can make the total capacity in the corner area slightly smaller than that in the straight area, or make the total capacity in the corner area equal to that in the straight area. After the gap coating process is completed, it is dried, and then slit to obtain the first electrode sheet 21.

[0075] Preparation of the second electrode sheet 22: Provide a mixed slurry of the second active material: uniformly coat the mixed slurry on the second current collector 221 copper foil of about 5 μm, and after drying, perform die cutting and slitting to obtain the second electrode sheet 22. Preparation of the tape 100: 1. Preparation of the protective film 13: In the adhesive formulation of the adhesive layer 132, the protective film 13 selects a combination of solvent-based polyacrylate, polyvinyl acetate, and polystyrene resin as the main resin, which can be dissolved in carbonate solvents. In this way, the tape 100 can protect the first pole piece 21 in the first corner area 214, and after its dissolution, the liquid absorption layer 12 can be exposed, enabling normal lithium ion insertion and extraction, and also storing the electrolyte. The specific steps are as follows: Heat and stir polyvinyl acetate to dissolve it in solvent-based polyacrylate, and control the temperature at 90 - 100 °C; Dissolve 30% benzoyl peroxide initiator in 30% toluene, and then slowly add it dropwise to step 1. After the dropwise addition is completed, keep the temperature for reaction; Dissolve the remaining benzoyl peroxide initiator in the remaining toluene, slowly add it dropwise to step 1. After the dropwise addition is completed, keep the temperature for reaction; Cool down to room temperature, add ethyl acetate and stir to mix evenly, then add the curing agent toluene diisocyanate and polystyrene resin and stir until completely dissolved to prepare the adhesive; Coat the adhesive on a 0 - 10 μm thick PET release film treated with a silicon release agent, and obtain the adhesive layer 132 after curing and drying. The thickness of the adhesive layer 132 is 0 - 10 μm, and the total thickness of the protective film 13 is 0 - 20 μm.

[0076] 2. Preparation of the liquid absorption layer 12: In a drying room with humidity control, where the relative humidity ≤ 10%RH, dissolve 1 g of polyacrylonitrile (PAN) in a mixed solvent of 15 mL of N,N - dimethylformamide (DMF) and N - methyl - 2 - pyrrolidone (NMP), then stir magnetically at room temperature for 24 h, and then perform defoaming treatment by ultrasonic for 20 min to obtain a solution with uniformly dispersed PAN; then add 0.5 g of a lithium supplement agent to the above solution.

[0077] The lithium supplement agent can be selected from lithium - rich materials LixNiyMnzOp, Li2NiO2, Li5FeO4, LiO, LiF, Li2S, Li2O2, Li2O, Li3N, sacrificial lithium salts (azides), carbon oxides, dicarboxylic compounds, hydrazide compounds, and substances obtained by modifying traditional lithium supplement agents through methods such as surface modification, coating, doping with metal elements / non - metal elements, etc. to improve properties such as the stability, safety, economy, conductivity, impedance, and specific capacity of the lithium supplement agent.

[0078] Example 1 Taking Li5FeO4 as an example, continue magnetic stirring for 20 min, perform ultrasonic defoaming to obtain the target electrospinning solution. Then use grounded aluminum foil as the electrospinning receiving substrate, transfer this electrospinning solution into a 20 mL syringe, replace the syringe needle with a 22G needle, evacuate the air inside the needle and syringe barrel, set the electrospinning voltage to 12 kV, the distance between the needle tip and the grounded aluminum foil to 10 cm, the relative environmental humidity ≤ 10%, the temperature to 25 ± 3 °C, and the injection solution rate to 0.03 mL / min. After 50 min, an electrospinning fiber layer with a thickness of about 2 μm is obtained, and then it is transferred to a vacuum oven for vacuum drying for 24 h to obtain an electrospinning fiber layer with the lithium supplement agent uniformly dispersed, that is, the liquid absorption layer 12 containing the lithium supplement agent.

[0079] The setting parameters of electrospinning are adjusted accordingly due to the equipment, the solvent system, and the characteristics of the electrospinning fiber membrane to be prepared. In other embodiments, the electrospinning voltage can be 10 - 15 kV, the receiving distance can be 5 - 30 cm, the needle size can be specifications such as 16 - 30G, and the injection rate can be 0.01 - 0.1 mL / min, so as to obtain an electrospinning fiber membrane with better morphological dimensions and achieve the effect of uniformly doping and dispersing the lithium supplement agent.

[0080] The polymer for preparing the electrospinning fiber layer can be an organic solvent-soluble synthetic polymer, a water-soluble synthetic polymer, a biodegradable polymer, and a natural polymer. The solvent for electrospinning can be a low-boiling solvent or a high-boiling solvent used alone, or a low-boiling solvent and a high-boiling solvent can be blended and used. The solvent can be acids, alcohols, esters, ethers, sulfoxides, amide solvents such as NMP, DMF, DMAc, toluene, dichloromethane, acetone, ethanol, DMSO, THF, ethyl acetate (EA), etc.

[0081] Organic solvent-soluble synthetic polymers include but are not limited to: polybenzimidazole, poly(p-phenyleneterephthalamide), polycarbonate (PC), poly(m-phenyleneterephthalamide) (PMIA), polyetherimide (PEI), polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT), polysulfone (PSF), polyvinylcarbazole, polyacrylonitrile (PAN), polyetheretherketone (PEEK), polystyrene (PS), polymethyl methacrylate (PMMA), polyvinyl chloride (PVC), polyvinylidene fluoride (PVDF), polyurethane, polyvinyl acetate (PVAc), polyvinyl butyral (PVB), poly(ferrocenyldimethylsilane) (PEDS), polyimide (PI), polypyrrole (PPy), polyoxymethylene (POM), etc.

[0082] Water-soluble synthetic polymer includes but is not limited to: polyvinyl alcohol (PVA), polyethylene oxide (PEO), polyacrylic acid (PAA), polyvinylpyrrolidone (PVP), polyethyleneimine (PEI), polyacrylamide (PAM), polyethylene glycol / polyethylene oxide (PEG / PEO), etc.

[0083] Degradable polymer includes but is not limited to: polylactic acid (PLLA), polycaprolactone (PCL), polyglycolic acid (PGA), polyhydroxyalkanoates (PHA), polybutylene succinate (PBS), etc.

[0084] Natural polymer includes but is not limited to: cellulose, cellulose acetate (CA), ethyl cellulose (EC), hydroxypropyl methyl cellulose (HPC), chitin, chitosan, collagen, gelatin, lecithin, silk fibroin (SF), zein, wheat protein, etc.

[0085] In different embodiments, different lithium supplement additive contents can be achieved by controlling the solution concentration, and different spinning layer thicknesses can be achieved by controlling the injection solution rate or even time.

[0086] In Example 1, the percentage of the lithium supplement additive amount in the liquid absorption layer 12 to the total mass of the liquid absorption layer 12 is 0.3%.

[0087] The test method is as follows: Take 500 mg of the prepared electrospun layer sample (liquid absorption layer 12 sample). The Li and Fe element contents therein can be measured by ICP test. According to the measured Li and Fe element contents and the sample mass, the lithium supplement additive content in the liquid absorption layer 12 is calculated to be 0.3%.

[0088] 3. Preparation of the adhesive layer 11: Coat a conventional adhesive layer such as acrylate pressure-sensitive adhesive on a PET release film with a thickness of 0 - 10 μm treated with a silicone release agent, and then dry and cure it under the curing conditions of 125°C / 1 min to obtain an adhesive layer 11 with a thickness of 1 - 10 μm. Then, through a simple die-cutting method, the obtained PET-based adhesive layer 132 is die-cut and punched to form a plurality of through holes 111. The shape of the through holes 111 can be circular holes, rectangles, squares, ellipses, etc. The maximum direction width or inner diameter of each through hole 111 is 0.5 - 5 mm, and the spacing distance between adjacent through holes 111 can be 0.05 - 5 mm.

[0089] Then, by bonding the adhesive layer 11 onto the composite layer that has already bonded the soluble adhesive layer 132 and the liquid absorption layer 12 together, a composite tape 100 is finally formed, with an outer layer being a soluble protective film 13, a middle layer being an electrospun fiber layer (liquid absorption layer 12), and an inner layer being a die-cut and punched adhesive layer 11, and the total thickness is 0 - 40 μm.

[0090] Please refer to Figure 6 、 Figure 7 and Figure 8 to prepare the electrode assembly by winding the first pole piece 21, the second pole piece 22 and the separator 23 prepared above. The tape 100 is realized by pasting it on the surface of the pole piece on the equipment before winding. The tape 100 can be pasted on the inner circle of the bobbin where the bending is the most serious and the risk of lithium deposition is the highest. Because as the number of winding turns increases, the arc radius increases accordingly, and the influence of the positive electrode arc length is already small. At the same time, it is also for the uniformity of the bobbin thickness. Then, the electrode assembly is sealed into an aluminum-plastic film, baked, injected with electrolyte, formed, aged, capacity-fractionated, and finally sealed to obtain the final finished electrochemical device. After the tape 100 is soaked in the electrolyte, the outer protective film 13 can be dissolved to form a two-layer tape 100 with only the liquid absorption layer and the inner bonding layer.

[0091] Example 2: It is substantially the same as Example 1, except that in Example 2, the doping content of the lithium supplement agent in the liquid absorption layer 12 is 0.6%, and the thickness of the liquid absorption layer 12 is 4 μm. That is, the lithium supplement agent content of the liquid absorption layer 12 of the tape 100 is increased to twice that of Example 1, and the total thickness of the tape 100 in Example 2 is 0 - 34 μm.

[0092] Example 3: It is substantially the same as Example 1, except that in Example 3, the doping content of the lithium supplement agent in the liquid absorption layer 12 is 0.9%, and the thickness of the liquid absorption layer 12 is 6 μm. That is, the lithium supplement agent content of the liquid absorption layer 12 of the tape 100 is increased to three times that of Example 1, and the total thickness of the tape 100 is 0 - 36 μm.

[0093] Example 4: It is substantially the same as Example 1, except that in Example 3, the doping content of the lithium supplement agent in the liquid absorption layer 12 is 1.2%, and the thickness of the liquid absorption layer 12 is 8 μm. That is, the lithium supplement agent content of the liquid absorption layer 12 of the tape 100 is increased to four times that of Example 1, and the total thickness of the tape 100 is 0 - 38 μm.

[0094] Example 5: It is substantially the same as Example 1, except that in Example 5, the doping content of the lithium supplement agent in the liquid absorption layer 12 is 1.5%, and the thickness of the liquid absorption layer 12 is 10 μm. That is, the lithium supplement agent content of the liquid absorption layer 12 of the tape 100 is increased to five times that of Example 1, and the total thickness of the tape 100 is 0 - 40 μm.

[0095] Comparative Example 1: Please refer to Figure 9 、 Figure 10 and Figure 11, the difference between Comparative Example 1 and Example 1 is that in Comparative Example 1, the adhesive layer 11a of the tape 100a was not die-cut and perforated. The un-die-cut and un-perforated adhesive layer 11a will affect the insertion and extraction of lithium ions in the inner first active material, resulting in the inability of lithium ions in the first active material to freely pass through the adhesive layer 11a, thus affecting the insertion and extraction.

[0096] Comparative Example 2: Please refer to Figure 12 and Figure 13 , the difference between Comparative Example 2 and Example 1 is that in Comparative Example 2, the tape 100b used is an ordinary tape, that is, a tape with an ordinary PET substrate coated with acrylate pressure-sensitive adhesive, which is not die-cut and perforated, does not have the liquid absorption ability, and does not contain a lithium supplement agent.

[0097] The liquid absorption rate of the liquid absorption layer 12 of the tape 100 in the above Examples 1-5 was tested: In the glove box, the liquid absorption layer 12 prepared in Examples 1-5 after vacuum drying was cut into circular pieces with a diameter of 20 cm, weighed, and then soaked in the electrolyte for 8 h, and then the electrolyte on the surface was blotted dry with lint-free paper and weighed again. The liquid absorption rate was calculated according to the formula: liquid absorption rate = (W2 - W1) / W1. Wherein, W2 is the weight of the electrospun fiber layer after soaking in the electrolyte for 8 h, and W1 is the weight of the dry electrospun fiber layer. The test data are shown in the following table: Table 1 The air permeability values of the liquid absorption layer 12 and the adhesive layer 11 of the tape 100 in the above Examples 1-5 were tested, and the test data are shown in the following table: Table 2 The electrical performance of the electrochemical devices 200 in Examples 1-5 was tested: At 25 ± 3°C, it was charged at a constant current and constant voltage of 1C to 3.65V at a constant rate, cut off at a rate of 0.05C, left standing for 1 h, then discharged at a constant current of 1C to 2.0V, left standing for 1 h, and the charge and discharge rate was cycled 600 times. The improvement effect of the tape 100 on the performance of the electrochemical device was judged by the cycle capacity retention rate and the analysis of lithium deposition by disassembly. The test data are shown in the following table: Table 3 It can be found from the experimental results in the comparison table that the tape 100 in Examples 1-5 has good liquid absorption performance and air permeability. The tape 100 is arranged in the corner area of the electrode plate, which can fully absorb and store a certain amount of electrolyte, provide electrolyte for the later cycle, ensure the kinetic performance of the battery, and will not block the active material layer in the corner area of the first electrode plate 21, and can provide a channel for ion movement, reducing the risk of the active material on the electrode plate in the corner area losing its activity.

[0098] In the liquid absorption layer 12, when the content of LiFe 5 O 4 is in the range of 0.3-0.6%, with the increase of the content, the capacity retention rate is significantly improved, and the interface is also good after disassembly, without lithium deposition and black, purple or black spots. When the content of LiFe 5 O 4 in the liquid absorption layer 12 exceeds 0.9%, the cycle retention rate of the electrochemical device decreases significantly, and gas spots gradually appear. This is caused by the generation of gas due to the excessive content of the lithium supplement agent, resulting in poor contact between the electrode plates and the generation of gas spots. It shows that only when the lithium supplement agent is doped in an appropriate amount can an ideal improvement effect be obtained.

[0099] It can be seen from Comparative Example 1 that when the same 0.3% of the lithium supplement agent LiFe 5 O 4 is doped, if the bottom bonding layer 11 is not perforated, the lithium ions in the corresponding first electrode plate cannot or are very difficult to deintercalate to the position of the corresponding second electrode plate, because the bonding layer 11 hinders the deintercalation of lithium ions in the first active material, and only the lithium supplement agent in the liquid absorption layer 12 can react through the absorbed electrolyte, and the reaction degree and range are limited. It can be seen from Comparative Example 2 that the ordinary tape hinders the deintercalation of lithium ions in the first active material and cannot provide a lithium supplement agent for reaction. In Comparative Example 1 and Comparative Example 2, the setting of the tape fails to achieve the expected improvement in the electrochemical performance.

[0100] The beneficial effects of the tape 100, the preparation method of the tape, the electrochemical device 200 and the electrical equipment 300 of the present application are as follows: 1) The tape 100 pasted at the corner position can improve the problem of hot pressing fracture and material dropping of the inner ring electrode plate, greatly improve the stability of the corner electrode plate, and reduce the safety risk caused by material dropping and cracking at the corner. The liquid absorption layer 12 is an electrospun fiber layer with a loose network pore structure. The liquid absorption layer 12 cooperates with the bonding layer 11 having a plurality of through holes, which can fully absorb and store a certain amount of electrolyte, improve the ion transport rate at the corner, provide electrolyte for the later cycle, ensure the kinetic performance of the battery, avoid the occurrence of serious black spot and lithium deposition phenomena, and will not block the active material layer in the corner area of the first electrode plate 21, and can provide a channel for ion movement, reducing the risk of the active material on the electrode plate in the corner area losing its activity.

[0101] 2) Adding a lithium supplement agent in the liquid absorption layer 12 can reduce the battery impedance in the corner area, improve the kinetic performance in the corner area, thereby improving the lithium deposition phenomenon in the corner area and enhancing the safety performance of the battery.

[0102] 3) The first electrode sheet 21 of the electrochemical device 200 can also be coated with slurry coatings of different thicknesses in the straight area and the corner area by a simple gap coating method using the same slurry. On the one hand, the reduced thickness is beneficial for storing the electrolyte, and on the other hand, it can contribute capacity to the first charge and discharge of the lithium supplement agent in the tape 100. By utilizing the high specific capacity of the lithium supplement agent in the tape 100 and combining with the low coating thickness, it is possible to balance the capacity utilization and capacity loss of the electrode sheet in the corner area, ensuring that the total capacity at the corner position is not less than that in the straight area. It can effectively improve the lithium deposition at the corner of the battery cell and the black spot phenomenon caused by the dryness of the electrolyte in the later stage of cycling without sacrificing the energy density of the system. At the same time, it can also utilize the lower thickness in the corner area and the structural characteristics of the liquid absorption layer 12 to relieve the extrusion and stress deformation of the electrode sheet expansion in the corner area on the adjacent layers, and also enhance the infiltration and reflux of the electrolyte in the corner area, greatly improving the lithium deposition and black spot phenomena at the corner.

[0103] 4) In the electrochemical device 200 of the present application, the usage amount of the tape 100 is also very small, and it only needs to be coated in the corner area. The coated area can be the corner positions of several inner layers close to the winding center. Because when the number of winding turns gradually increases, the problem of insufficient CB value caused by the unequal lengths of the positive and negative electrode sheets in the corner area is no longer significant.

[0104] The above embodiments are only used to illustrate the technical solutions of the present application and not to limit them. Although the present application has been described in detail with reference to the above preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present application can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present application.

Claims

1. An adhesive tape, characterized in that: include: An adhesive layer, wherein a plurality of through holes are provided on the adhesive layer; The liquid absorbing layer is arranged on one side of the bonding layer and has a porous structure; the side of the bonding layer away from the liquid absorbing layer is used for bonding the corner area of ​​the pole piece in the electrode assembly.

2. The adhesive tape according to claim 1, characterized in that: The invention also comprises a protective film, which is arranged on the side of the liquid absorbing layer away from the adhesive layer, and the protective film can be dissolved in the electrolyte.

3. The adhesive tape according to claim 2, characterized in that: The protective film comprises a substrate layer and a glue layer, both of which can be dissolved in an electrolyte, and the glue layer is arranged between the liquid absorbing layer and the substrate layer.

4. The adhesive tape according to claim 1, characterized in that: The material of the liquid absorbing layer includes a lithium supplement, and the mass of the lithium supplement accounts for a percentage of the total mass of the liquid absorbing layer, wherein 0<a≤0.9%.

5. A method for preparing an adhesive tape, characterized in that: include: The adhesive layer is applied to the release film, and after curing, a punching operation is performed to prepare an adhesive layer; Providing a polymer solution, and subjecting the polymer solution to electrostatic spinning to form a fiber layer to prepare a liquid-absorbing layer; wherein the polymer material of the polymer solution includes one or more of an organic solvent-soluble synthetic polymer, a water-soluble synthetic polymer, and a degradable polymer; and the solvent material of the polymer solution includes one or more of an acid, an alcohol, an ester, an ether, a sulfoxide, and an amide solvent; The adhesive layer and the liquid absorbing layer are compounded together to obtain an adhesive tape.

6. The method for preparing the adhesive tape according to claim 5, characterized in that: Also includes: Prepare an adhesive that can be dissolved in an electrolyte; wherein the material of the adhesive includes polyacrylate, polyvinyl acetate, and polystyrene resin; Applying an adhesive to a substrate layer that is soluble in an electrolyte to form an adhesive layer on the substrate layer, and performing a curing treatment to obtain a protective layer; The protective layer is compounded with the liquid absorbing layer.

7. The method for preparing the adhesive tape according to claim 5, characterized in that: A lithium supplement is also added to the high molecular polymer solution, and the percentage of the mass of the lithium supplement to the total mass of the liquid absorbing layer is a, wherein 0<a≤0.9%.

8. An electrochemical device, characterized in that: include: A first pole piece, a second pole piece, a diaphragm, and a tape according to any one of claims 1 to 4 or a tape made by the method for making a tape according to any one of claims 5 to 7; The first pole piece and the second pole piece have opposite polarities, the diaphragm is disposed between the first pole piece and the second pole piece, and the first pole piece, the diaphragm and the second pole piece are wound to form an electrode assembly; The first pole piece has a first straight region and a first corner region in the winding structure, the tape is at least partially disposed in the first corner region, and the adhesive layer is attached to the surface of the first pole piece.

9. The electrochemical device according to claim 8, characterized in that: The first pole piece includes a first current collector and a first active material layer, and the first active material layer is arranged on the surface of the first current collector; the thickness of the first active material layer in the first straight area is t1, and the thickness of the first active material layer in the first corner area is t2, wherein 1μm≤t1-t2≤30μm.

10. An electrical device, characterized in that: include: An electrical component and the electrochemical device according to claim 8 or 9, wherein the electrical component is electrically connected to the electrochemical device.

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