Pole piece, battery cell and battery

Abstract

The invention provides a pole piece, a battery cell and a battery. The pole piece comprises a current collector, a first functional layer and a polymer adhesive layer, the current collector comprises a first region and a second region, and the second region is connected with one end, in the length direction, of the first region and extends in the length direction; n first concave structures are arranged on one side of the first area, and N is larger than or equal to 1; the first functional layer covers at least part of the functional surface of the first region and is embedded into at least part of the first sunken structure; the thickness of the first functional layer is reduced along the length direction; and the polymer glue layer covers at least part of the surface, far away from the current collector, of the first functional layer. The problem of short circuit caused by swelling and ridging of a polymer adhesive film at the edge position of the pole piece due to poor contact in the prior art can be solved, and the safety performance of the battery is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of secondary batteries, and particularly relates to a pole piece, a battery cell and a battery. BACKGROUND

[0002] Lithium ion batteries have been widely used in many fields such as electronic products, electric vehicles and energy storage due to their small size, high energy density, high platform voltage and no memory effect, and have provided great convenience for modern life and production. At the same time, lithium ion batteries also have many safety hazards. A lithium ion battery is mainly composed of four main materials, namely a positive electrode, a negative electrode, a separator and an electrolyte. The positive pole piece, the separator and the negative pole piece are usually stacked in order. In the case of a perfect separator, the positive pole piece and the negative pole piece are separated and do not come into contact with each other. However, when the edge of the active layer on the pole piece is pressed, burrs will be generated, the separator will be pierced, and a short circuit will occur. At present, a polymer adhesive film is usually attached to the edge position to cover the edge coating particles, thereby avoiding short circuit. However, due to the difference in material between the polymer adhesive film and the active material layer, it is difficult to achieve close contact, especially when the battery is assembled, the electrolyte slowly reacts with the adhesive layer in the polymer adhesive film, gas is generated, the polymer adhesive film swells and forms ridges, the structure separates, a gap is generated between the edge position of the pole piece and the separator, the lithium ion transmission is blocked, lithium dendrites are precipitated in the adjacent another pole piece area, and a short circuit risk occurs. Therefore, how to further improve the safety performance of the battery is a technical problem to be solved in the field. SUMMARY

[0003] The application provides a pole piece to solve the problem that the polymer adhesive film at the edge position of the pole piece swells and forms ridges due to poor contact in the prior art, thereby causing a short circuit, and to improve the safety performance of the battery.

[0004] The battery cell and the battery provided by the application can reduce lithium precipitation and are excellent in safety performance.

[0005] In one aspect, the application provides a pole piece, which comprises a current collector, a first functional layer and a polymer adhesive layer.

[0006] The current collector comprises a first region and a second region, wherein the second region is connected to one end of the first region in the length direction and extends along the length direction.

[0007] One side of the first region is provided with N first recessed structures, and N is greater than or equal to 1.

[0008] The first functional layer covers at least part of the functional surface of the first region and is embedded in at least part of the first recessed structures; and the thickness of the first functional layer decreases along the length direction.

[0009] The polymer adhesive layer covers at least part of the surface of the first functional layer away from the current collector.

[0010] The surface of the first functional layer away from the current collector has M second recess structures, 1≤M≤N.

[0011] The depth of the first recess structure is h1, and the depth of the second recess structure is h2.

[0012] The size of the opening end of the first recess structure is L1, and the size of the opening end of the second recess structure is L2.

[0013] Wherein, h2≤h1, L2≤L1.

[0014] Preferably, h1 is 0.5-20 μm, L1 is 10-100 μm, h2 is 0.5-20 μm, and L2 is 10-100 μm.

[0015] The first functional layer comprises a first active layer; or,

[0016] The first functional layer comprises a first security layer and a second active layer covering at least part of the surface of the first security layer in sequence along the direction away from the current collector; or,

[0017] The first functional layer comprises a third active layer and a second security layer along the length direction.

[0018] The first security layer is partially embedded in the first recess structure, the thickness of the first security layer embedded in the first recess structure is h3, h3≤h1, and h3 is 0.5-20 μm; or,

[0019] The first active layer is partially embedded in the first recess structure, the thickness of the first active layer embedded in the first recess structure is h4, h4≤h1, and h4 is 0.5-20 μm; or,

[0020] The second security layer is partially embedded in the first recess structure, the thickness of the second security layer embedded in the first recess structure is h5, h5≤h1, and h5 is 0.5-20 μm; and / or,

[0021] The third active layer is partially embedded in the first recess structure, the thickness of the third active layer embedded in the first recess structure is h6, h6≤h1, and h6 is 0.5-20 μm.

[0022] The first security layer comprises a protective layer and a first insulating layer along the length direction; or the second security layer comprises a second insulating layer.

[0023] The pole piece as described above, the first active layer comprises a first active material, a-Dv50 of the first active material satisfies: a-Dv50≤0.2L1 with the opening end aperture L1 of the first recessed structure; or,

[0024] The third active layer comprises a third active material, a-Dv50 of the third active material satisfies: a-Dv50≤0.2L1 with the opening end aperture L1 of the first recessed structure; or,

[0025] The first security layer comprises a first functional material, b-Dv50 of the first functional material satisfies: b-Dv50≤0.2L1 with the opening end aperture L1 of the first recessed structure; or,

[0026] The second security layer comprises a second functional material, b-Dv50 of the second functional material satisfies: b-Dv50≤0.2L1 with the opening end aperture L1 of the recessed structure;

[0027] The first active material and / or the third active material comprises at least one of lithium cobalt oxide, lithium nickel cobalt manganese phosphate, lithium iron phosphate, lithium manganese iron phosphate, lithium nickel cobalt aluminum phosphate, lithium manganese phosphate, lithium nickel phosphate, lithium-rich manganese lithium material;

[0028] The first functional material and / or the second functional material comprises at least one of a metal oxide, a non-metal oxide, an oxide hydrate, a non-conductive polymer;

[0029] Preferably, the a-Dv50 is 5-15 μm, and the b-Dv50 is 5-15 μm.

[0030] The pole piece as described above further comprises a second functional layer;

[0031] One side of the second region is provided with X third recessed structures, X≥1;

[0032] The second functional layer is at least partially embedded in the third recessed structure and covers at least part of the surface of the second region.

[0033] The pole piece as described above, the second functional layer is an active layer; or,

[0034] Along the direction away from the current collector, the second functional layer comprises a third security layer and an active layer arranged in a stack.

[0035] The pole piece as described above, in the length direction, the size of the first region is L3, and the size of the current collector is L4, which satisfies 1 / 1000≤L3 / L4≤1 / 100;

[0036] And / or, the opening end size of the first recessed structure is L1, the center line distance of adjacent first recessed structures is L5, and 1≤L5 / L1≤10 is satisfied;

[0037] And / or, the depth of the first recessed structure is h1, and the thickness of the current collector is H, and 1≤H / h1≤5 is satisfied.

[0038] Preferably, the L3 is 1-15 mm, the L4 is 1000-10000 mm, the L5 is 10-1000 μm, the H is 4-12 μm, the h1 is 0.5-20 μm, and the L1 is 10-100 μm.

[0039] The pole piece as described above is prepared by comprising the following steps:

[0040] The coating slurry is arranged on the first functional surface of the current collector, dried, and then the recessed structure is arranged on the second functional surface of the current collector, and then the coating slurry is coated on the second functional surface and the recessed structure, and the polymer adhesive layer is covered after drying and rolling, to obtain the pole piece.

[0041] The first functional surface and the second functional surface are distributed on both sides of the thickness direction of the current collector.

[0042] In still another aspect of the present application, an electric core is provided, comprising the pole piece as described above.

[0043] The electric core as described above is a winding core, the second region of the pole piece is located at or close to the head along the winding direction of the winding core, and the first region of the pole piece is located at the tail along the winding direction of the winding core.

[0044] The electric core as described above, the opening end of the first recessed structure of the pole piece faces away from the center of the electric core.

[0045] In still another aspect of the present application, a battery is provided, comprising the electric core as described above.

[0046] The implementation of the present application has at least the following beneficial effects:

[0047] The pole piece provided by the present application provides riveting sites for the polymer adhesive film by arranging the opposite first regions on the current collector, arranging the first recessed structure on the first region, and gradually reducing the corresponding first functional layer, so that the polymer adhesive film is tightly bonded with the first functional layer and the first region of the current collector under the joint action of the first recessed structure and the first functional layer, preventing the electrolyte from being immersed to cause the polymer adhesive film to swell and form ridges, and further avoiding the occurrence of lithium precipitation in the other pole piece region corresponding to the polymer adhesive film, thereby improving the safety performance of the battery. BRIEF DESCRIPTION OF DRAWINGS

[0048] In order to more clearly illustrate the technical solutions of the present application, the drawings needed in the following description of the embodiments of the present application will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0049] Figure 1 is a schematic diagram of the cross-sectional structure of the pole piece in an embodiment of the present application;

[0050] Figure 2 is a schematic diagram of the cross-sectional structure of the pole piece in another embodiment of the present application;

[0051] Figure 3 is a schematic diagram of the cross-sectional structure of the pole piece in still another embodiment of the present application;

[0052] Figure 4 is a schematic diagram of the cross-sectional structure of the pole piece in still another embodiment of the present application; Figure 3

[0053] Figure 5 is a schematic diagram of the cross-sectional structure of the current collector in an embodiment of the present application;

[0054] Figure 6 is a schematic diagram of the cross-sectional structure of the current collector in another embodiment of the present application;

[0055] Figure 7 is a schematic diagram of the top view structure of the current collector in an embodiment of the present application;

[0056] Figure 8 is a schematic diagram of the local structure of the thinned part region of the pole piece in Embodiment 2 of the present application;

[0057] Figure 9 is a schematic diagram of the local structure of the extended part region of the pole piece in Embodiment 1 of the present application;

[0058] Figure 10 is a schematic diagram of the local structure of the wound type battery cell in an embodiment of the present application.

[0059] Explanation of reference signs:

[0060] 1 - current collector; 11 - first functional surface; 12 - second functional surface; 2 - first functional layer; 21 - first safety layer; 22 - active layer; 201 - first active layer; 202 - second active layer; 203 - third active layer; 23 - second safety layer; 3 - protective layer; 41 - first insulating layer; 42 - second insulating layer; 5 - second functional layer; 51 - third safety layer; 6 - first recess structure; 7 - second recess structure; 8 - third recess structure; 9 - polymer adhesive layer; A - first region; B - second region. ​Detailed Implementation

[0061] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0062] In the description of this invention, terms such as "first" and "second" are used only for descriptive purposes, such as distinguishing different components to more clearly illustrate / explain the technical solution.

[0063] Figures 1 to 9 In the diagram, the X direction is the first direction, which is the length direction of the current collector, the Y direction is the width direction of the current collector, and the Z direction is the thickness direction of the current collector.

[0064] This invention provides an electrode sheet, such as... Figures 1-3 As shown, it includes a current collector 1, a first functional layer 2, and a polymer adhesive layer 9. The current collector includes a first region A and a second region B, wherein the second region B is connected to one end of the first region A in the length direction and extends along the length direction. N first recessed structures 6 are provided on one side of the first region A, where N≥1. The first functional layer 2 covers at least a portion of the functional surface of the first region A and embeds at least a portion of the first recessed structures 6. The thickness of the first functional layer 2 decreases along the length direction. The polymer adhesive layer 9 covers at least a portion of the surface of the first functional layer 2 away from the current collector 1.

[0065] The present invention does not limit the electrical properties of the electrode; it can be a negative electrode or a positive electrode.

[0066] In one specific embodiment, the electrode is a positive electrode.

[0067] The direction of extension of the current collector refers to the direction from the middle of the current collector along its length to the end.

[0068] The functional surfaces of a current collector refer to the outermost surfaces along its length and width directions, i.e., the two largest and opposite surfaces among the six surfaces of the current collector, for example... Figures 1-6 The first functional surface 11 and the second functional surface 12 in the middle.

[0069] The first recessed structure 6 of the present invention is either a cavity-forming structure created by the first functional surface 11 recessing towards the second functional surface 12, or a cavity-forming structure created by the second functional surface 12 recessing towards the first functional surface 11. Specifically, conventional methods in the art can be used to provide the first recessed structure 6 with a cavity in the current collector 1. For example, mechanical drilling, laser drilling, electro- or thermal laser melting, radiation melting, chemical etching, friction drilling, and other processing methods can be used.

[0070] The first recessed structure 6 may or may not penetrate the current collector 1 in the thickness direction. When the first recessed structure 6 penetrates the current collector 1 in the thickness direction, such as... Figure 1 , Figure 2 , Figure 3 , Figure 4 As shown, the first recessed structure 6 has two oppositely arranged ends, which intersect the first functional surface 11 and the second functional surface 12 respectively. The notches formed on the first functional surface 11 and the second functional surface 12 at this time constitute the opening of the first recessed structure 6. When the first recessed structure 6 does not penetrate the current collector 1 in the thickness direction, as... Figure 5 As shown, the opening of the first recessed structure 6 is the notch on the second functional surface 12.

[0071] The number of first recessed structures 6 can be one or more. When there are multiple first recessed structures 6, they are spaced apart along the extension direction of the current collector 1. That is, a non-hole region, i.e., a region without a first recessed structure 6, is provided between every two adjacent first recessed structures 6. It can also be understood that under incident light parallel to the thickness direction of the current collector 1, the projections of any two first recessed structures 6 onto a common plane are independent and have no overlapping or covering relationship. Here, the common plane refers to a plane parallel to the functional surface of the current collector 1. For example, multiple first recessed structures 6 are uniformly distributed in a linear array along the length or width direction of the current collector 1 (e.g., ...). Figures 5 to 7 (As shown).

[0072] It should be noted that the present invention does not impose any special limitation on the three-dimensional shape of the first recessed structure 6. When there are multiple first recessed structures 6, each of the multiple first recessed structures 6 is set independently, and its cross-sectional shape in the plane containing the thickness and width, as well as whether it penetrates the current collector 1, are independent. For example, some of the first recessed structures 6 have a triangular cross-sectional shape, and some of the first recessed structures 6 have a rectangular cross-sectional shape; some of the first recessed structures 6 penetrate the current collector 1 (in this case, the first recessed structure 6 can be understood as a through hole), and some of the first recessed structures 6 do not penetrate the current collector 1 (in this case, the first recessed structure 6 can be understood as a blind hole).

[0073] The first functional layer 2 covers at least a portion of the functional surface of the first region A and is embedded in at least a portion of the first recessed structure 6, that is, the first functional layer 2 fills part or all of the first recessed structure 6 and covers part or all of the plane on which the functional surface of the first region A is located.

[0074] In one specific implementation, such as Figure 1 As shown, the first functional layer 2 is embedded in the first recessed structure 6 and covers the part of the plane where the functional surface of the first region A is located.

[0075] In another specific implementation, such as Figure 2 , 3 As shown, the first functional layer 2 is embedded in all the first recessed structures 6 and covers the entire plane where the functional surface of the first region A is located.

[0076] like Figures 1-3 As shown, the thickness of the first functional layer 2 decreases along the extension direction of the first region. That is, in the extension direction of the first region, the side of the first functional layer 2 closer to the second end is relatively thicker, and the side farther from the second end is relatively thinner.

[0077] The thickness of the first functional layer 2 decreases along the extension direction of the first region. This decrease can be linear or non-linear. When the decrease is linear, the plane formed by the first functional layer 2 is relatively smooth. However, when the thickness of the first functional layer 2 decreases non-linearly, the plane formed by the first functional layer 2 is relatively uneven.

[0078] like Figures 1-4 As shown, the polymer adhesive layer 9 covers at least a portion of the surface of the first functional layer 2 away from the current collector 1. The polymer adhesive layer 9 is used to cover at least a portion of the surface of the first functional layer 2 away from the current collector 1, preventing burrs of the first functional layer 2 from piercing the diaphragm. When the first functional layer 2 is only disposed on one side of the current collector 1, the polymer adhesive layer 9 is only disposed on one side of the current collector 1; when the first functional layer 2 is disposed on both sides of the current collector 1, the polymer adhesive layer 9 is disposed independently on each side of the current collector 1.

[0079] By providing a first recessed structure 6 in the first region A of the current collector 1 and controlling the gradual thinning of the first functional layer 2, at least a portion of the first functional layer 2 can fill the first recessed structure 6 to create an inward recess. At this time, the surface of the first functional layer 2 away from the current collector 1 forms a curved surface that faces the recess towards the current collector 1. When there are multiple first recessed structures 6 in the first region A, multiple recesses are formed on the surface of the first functional layer 2 away from the current collector 1. At this time, these recesses provide rivet sites for the polymer adhesive layer 9 to be bonded, so that the polymer adhesive layer 9 is tightly bonded to the first functional layer 2 and the current collector 1. When assembling the battery, separation of the polymer adhesive layer 9 and the first functional layer 2 is effectively avoided, improving the reliability of the battery. Electrolyte infiltration is prevented from causing the polymer adhesive layer 9 to swell and form ridges, thereby preventing lithium plating in the other electrode area corresponding to the polymer adhesive layer 9, thus improving the safety performance of the battery.

[0080] Furthermore, in one specific embodiment of the present invention, such as Figure 1 As shown, the surface of the first functional layer 2 away from the current collector 1 has M second recessed structures 7, 1≤M≤N; the depth of the first recessed structure 6 is h1, and the depth of the second recessed structure 7 is h2; the size of the opening end of the first recessed structure 6 is L1, and the size of the opening end of the second recessed structure 7 is L2; ​​wherein, h2≤h1, L2≤L1; preferably, h1 is 0.5~20μm, L1 is 10~100μm, h2 is 0.5~20μm, and L2 is 10~100μm.

[0081] Because the first region A has a first recessed structure 6, as the thickness of the first functional layer 2 gradually decreases, a portion of the first functional layer 2 can fill into the first recessed structure 6, creating a second recessed structure 7 with its opening facing away from the current collector 1. This second recessed structure 7 is formed by a recessed surface facing closer to the current collector 1. A reference line is formed by connecting the two highest points of the recessed surface. The size L2 of the opening of the second recessed structure 7 is the size of this reference line in its extension direction. The depth h2 of the second recessed structure 7 specifically refers to the distance between the vertex of the recessed surface and this reference line in the thickness direction of the current collector 1.

[0082] The dimension L1 of the opening end of the first recessed structure 6 refers to the distance between the two points furthest apart from the edge of the opening. For example, when the opening is circular, the dimension L1 of the opening end of the first recessed structure 6 is the length of the diameter of the circle; when the opening is rectangular, the dimension L1 of the opening end of the first recessed structure 6 is the length of the diagonal of the rectangle.

[0083] The depth of the first recessed structure 6 refers to the distance between the lowest end of the first recessed structure 6 and the opening end of the first recessed structure 6 along the thickness direction of the current collector 1.

[0084] When a second recessed structure exists and the depth of the second recessed structure meets the above-mentioned range, the second recessed structure provides a sufficiently strong adhesive anchor point for the polymer adhesive layer, enabling the polymer adhesive layer to adhere more effectively to the surface of the first functional layer away from the current collector, thus giving the electrode a more superior safety performance.

[0085] Specifically, h1 includes, but is not limited to, a range of 0.5μm, 1μm, 2μm, 4μm, 6μm, 8μm, 10μm, 12μm, 14μm, 16μm, 18μm, 20μm, or any combination thereof; L1 includes, but is not limited to, a range of 10μm, 20μm, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, 90μm, 100μm, or any combination thereof. Range; h2 includes, but is not limited to, a range of 0.5μm, 1μm, 2μm, 4μm, 6μm, 8μm, 10μm, 12μm, 14μm, 16μm, 18μm, 20μm or any two of these ranges; L2 includes, but is not limited to, a range of 10μm, 20μm, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, 90μm, 100μm or any two of these ranges.

[0086] When the first and second recessed structures meet the above-mentioned range, they can not only provide sufficiently strong adhesive anchors for the polymer adhesive layer, but also improve the mechanical strength of the electrode itself, thereby further enhancing the safety performance of the electrode.

[0087] Furthermore, in a specific embodiment of the present invention, the first functional layer 2 includes a first active layer 201; or, along the direction away from the current collector 1, the first functional layer 2 sequentially includes a first safety layer 21 and a second active layer 202 covering at least a portion of the surface of the first safety layer 21; or, along the direction from the second end to the first end, the first functional layer 2 includes a third active layer 203 and a second safety layer 23.

[0088] In detail, in one specific implementation, such as Figure 1 As shown, the first functional layer is the first active layer 201.

[0089] In another specific implementation, such as Figure 3 As shown, along the direction away from the current collector 1, the first functional layer includes a first safety layer 21 and a second active layer 202 covering a portion of the surface of the first safety layer 21.

[0090] In another specific implementation, such as Figure 2 As shown, along the direction from the second end to the first end, the first functional layer 2 includes a third active layer 203 and a second security layer 23.

[0091] The first active layer 201, the second active layer 202, and the third active layer 203 include active materials, which can be common active materials in the art. For example, when the electrode is a positive electrode, the active material can include at least one of phosphate active materials, lithium nickel manganese cobalt acid active materials, oxide active materials, etc. When the electrode is a negative electrode, the active material can include at least one of graphite, amorphous carbon, carbon black, carbon nanotubes, titanium dioxide, tin oxide, silicon oxide, etc.

[0092] The composition of the first safety layer 21 and the second safety layer 23 can be the same or different. Each of the first safety layer 21 and the second safety layer 23 independently contains a functional material, which can be either inactive or active. For example, the functional material includes at least one of lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, lithium nickel cobalt manganese oxide, lithium iron phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadium oxide phosphate, lithium-rich manganese-based materials, lithium nickel cobalt aluminum oxide, lithium titanate, alumina, boehmite, titanium dioxide, zirconium oxide, zinc oxide, silicon dioxide, silicon carbide, silicon nitride, and conductive polymers, or at least one of their modifications. This ensures that the aforementioned functional particles reduce the probability of short circuits without affecting lithium-ion transport.

[0093] In addition, the first safety layer 21 and the active layer 22 each independently contain a conductive agent, which includes at least one of conductive carbon black, acetylene black, graphite, graphene, carbon nanotubes, carbon nanofibers, conductive polythiophene, conductive polypyrrole, and conductive polyaniline. In this way, while ensuring that the possibility of short circuit is reduced, a good conductive network is provided, which can ensure smooth electron conduction, so that the battery can obtain excellent safety performance and good cycle performance.

[0094] To ensure that the first safety layer 21, the second safety layer 23, the first active layer 201, the second active layer 202, or the third active layer 203 are fixedly bonded to the current collector 1, each of the first safety layer 21, the second safety layer 23, the first active layer 201, the second active layer 202, or the third active layer 203 independently contains an adhesive. The adhesive includes at least one of polyvinylidene fluoride, polyvinylidene chloride, polytetrafluoroethylene, polyhexafluoropropylene, polyacrylic acid, polyacrylate, polyamide, polyacrylonitrile, sodium carboxymethyl cellulose, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, styrene-butadiene rubber, polyethylene oxide, styrene-butadiene emulsion, styrene-acrylic emulsion, ethyl polyacrylate, polybutyl methacrylate, ethylene-vinyl acetate copolymer, polyvinyl acetate, or a modified form thereof, or at least one of the copolymers thereof. For example, copolymers of polyvinylidene fluoride include polyvinylidene fluoride-trifluoroethylene, polyvinylidene fluoride-tetrafluoroethylene, polyvinylidene fluoride-hexafluoroethylene, and polyvinylidene fluoride-hexafluoropropylene.

[0095] Furthermore, in a specific embodiment of the present invention, the first safety layer is partially embedded in the first recessed structure, and the thickness of the first safety layer embedded in the first recessed structure is h3, h3≤h1, and h3 is 0.5~20μm; or, the first active layer is partially embedded in the first recessed structure, and the thickness of the first active layer embedded in the first recessed structure is h4, h4≤h1, and h4 is 0.5~20μm; or, the second safety layer is partially embedded in the first recessed structure, and the thickness of the second safety layer embedded in the first recessed structure is h5, h5≤h1, and h5 is 0.5~20μm; or, the third active layer is partially embedded in the first recessed structure, and the thickness of the third active layer embedded in the first recessed structure is h6, h6≤h1, and h6 is 0.5~20μm.

[0096] When the embedding thickness of each coating satisfies the above relationship, it can not only fill the first recessed structure and improve the structural stability of the electrode, but also break the electrode at the location of the first recessed structure when it is damaged by external force, so that the coating can slide smoothly to the fracture surface and prevent the electrode from short-circuiting.

[0097] Furthermore, in a specific embodiment of the present invention, along the extension direction of the first region, the first safety layer 21 includes a protective layer 3 and a first insulating layer 41, or the second safety layer 23 is a second insulating layer 4.

[0098] In detail, along the direction away from the current collector 1, the first functional layer 2 sequentially includes a first safety layer 21 and an active layer 22 covering a portion of the surface of the first safety layer 21. At this point, along the extension direction of the first region, the first safety layer 21 includes a protective layer 3 and a first insulating layer 41, specifically as follows... Figure 3 As shown.

[0099] The first insulating layer 41 does not contain a conductive agent, while the protective layer 3 contains a conductive agent, which includes at least one of conductive carbon black, acetylene black, graphite, graphene, carbon nanotubes, carbon nanofibers, conductive polythiophene, conductive polypyrrole, and conductive polyaniline.

[0100] Alternatively, along the extension direction of the first region, the first functional layer 2 includes an active layer 22 and a second safety layer, wherein the second safety layer does not contain a conductive agent and is a second insulating layer 42.

[0101] By setting the first insulating layer 41 or the second insulating layer 42, not only can the electrolyte be prevented from penetrating through the first recessed structure 6, thus improving the cycle life and stability of the battery, but it can also prevent short circuits and improve safety.

[0102] Furthermore, in a specific embodiment of the present invention, the first active layer 201 includes a first active material, wherein the a-Dv50 of the first active material and the pore size L1 at the opening end of the first recessed structure satisfy the condition: a-Dv50≤0.2L1; or, the third active layer 203 includes a third active material, wherein the a-Dv50 of the third active material and the pore size L1 at the opening end of the first recessed structure satisfy the condition: a-Dv50≤0.2L1; or, the first safety layer includes a first functional material, wherein the b-Dv50 of the first functional material and the pore size L1 at the opening end of the first recessed structure satisfy the condition: b-Dv50≤0.2L1; Alternatively, the second safety layer includes a second functional material, wherein the b-Dv50 of the second functional material and the aperture L1 of the recessed structure satisfy the following condition: b-Dv50 ≤ 0.2L1; the first active material and / or the third active material include at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium iron phosphate, lithium manganese iron phosphate, lithium nickel cobalt aluminum oxide, lithium manganese oxide, lithium nickel oxide, and lithium-rich manganese lithium materials; the first functional material and / or the second functional material include at least one of metal oxide, non-metal oxide, oxide hydrate, and non-conductive polymer; preferably, a-Dv50 is 5-15 μm and b-Dv50 is 5-15 μm.

[0103] Wherein, a-Dv50 represents the particle size corresponding to the cumulative volume distribution percentage of the first active material and / or the third active material reaching 50%, and b-Dv50 represents the particle size corresponding to the cumulative volume distribution percentage of the first functional material and / or the second functional material reaching 50%, with the unit being μm.

[0104] By defining the relationship between the aperture L1 of the first recessed structure and the particle size distribution of the functional material, or the relationship between the aperture L1 of the first recessed structure and the particle size of the active material, some functional material particles or some active material can be embedded in the first recessed structure to increase the contact area. When this electrode sheet is applied to a battery, if the battery deforms or breaks due to external force, the first recessed structure makes it easier for the fracture surface of the current collector 1 to occur at the first recessed structure. The functional material or active material can slide inward and spread in accordance with the direction of damage, effectively protecting the fracture surface of the current collector 1 from exposure, thereby avoiding short circuits caused by the exposure of the fracture surface of the current collector 1 and improving the safety performance of the battery.

[0105] Furthermore, in one specific embodiment of the present invention, such as Figure 1 , Figure 2 , Figure 3 As shown, it also includes a second functional layer 5, and the second region B is provided with X third recessed structures 8, where X ≥ 1; the second functional layer 5 is at least partially embedded in the third recessed structures 8 and covers at least part of the surface of the second region B.

[0106] The morphology and distribution characteristics of the third recessed structure 8 set in the second region B are consistent with the pattern of the first recessed structure 6, that is, the morphology, quantity and distribution characteristics of the third recessed structure 8 can be set independently.

[0107] It is understandable that a portion of the polymer adhesive layer covers the surface of the second functional layer that is adjacent to the first functional layer and away from the current collector.

[0108] By setting a third recessed structure in the second region and embedding the second functional layer 5 into at least part of the third recessed structure 8 and covering at least part of the plane where the functional surface of the second region is located, when the battery is subjected to external mechanical damage, the electrode will break preferentially at the recessed structure. At this time, the second functional layer embedded in the recessed structure will slide inward and spread in the direction of damage, effectively protecting the current collector fracture surface from exposure and preventing the current collector from short-circuiting.

[0109] Furthermore, in one specific embodiment of the present invention, such as Figure 1 As shown, the second functional layer 5 is an active layer 22; or, along the direction away from the current collector 1, the second functional layer 5 sequentially includes a third safety layer 51 and an active layer 22 covering at least a portion of the surface of the third safety layer 51.

[0110] In one specific implementation, such as Figure 2 As shown, along the direction away from the current collector 1, the second functional layer 5 sequentially includes a third safety layer 51 and an active layer 22 covering the surface of the third safety layer 51.

[0111] It is understandable that when the electrode includes a first safety layer and a third safety layer, the composition and thickness of the first safety layer can be the same as those of the third safety layer.

[0112] In another specific embodiment, the third safety layer 51 is located in the third cavity of the third recessed structure 8, and the active layer 22 covers the plane where the functional surface of the third recessed structure 8 is located.

[0113] Furthermore, in one specific embodiment of the present invention, such as Figure 1 As shown, in the length direction, the size of the first region A is L3, and the size of the current collector 1 is L4, satisfying 1 / 1000≤L3 / L4≤1 / 100; and / or, the size of the opening end of the first recessed structure 6 is L1, and the centerline distance between adjacent first recessed structures 6 is L5, satisfying: 1≤L5 / L1≤10; and / or, the depth of the first recessed structure 6 is h1, and the thickness of the current collector 1 is H, satisfying 1≤H / h1≤5; preferably, L3 is 1-15mm, L4 is 1000-10000mm, L5 is 10~1000μm, H is 4~12μm, h1 is 0.5~20μm, and L1 is 10~100μm.

[0114] In detail, L3 / L4 includes, but is not limited to, a range of 1 / 1000, 1 / 900, 1 / 800, 1 / 700, 1 / 600, 1 / 500, 1 / 400, 1 / 300, 1 / 200, 1 / 100, or any two of these ranges.

[0115] When the dimensions of the first region A and the current collector 1 satisfy the above relationship, it can not only prevent the electrolyte from immersing and causing the film to swell and form ridges, thereby avoiding lithium plating in the electrode area corresponding to the edge of the film, thus improving the safety of lithium-ion batteries, but also ensure the energy density of the electrode.

[0116] In detail, in this invention, the opening end size of the first recessed structure 6 is L1, and the centerline distance L5 between adjacent first recessed structures 6 satisfies the following relationship: 1≤L5 / L1≤10. Here, the opening end size of the first recessed structure 6 refers to the diameter of the end of the first recessed structure 6 facing the polymer adhesive layer 9, i.e., the large-aperture end; the centerline distance L5 between adjacent first recessed structures 6 can be understood as the sum of the distance between two adjacent first recessed structures 6 and the radius of their opening ends. By defining the relationship between L1 and L5, a more reasonable density distribution of the first recessed structures can be achieved, thereby balancing the improvement of the mechanical strength of the current collector 1 and the safety performance of the battery.

[0117] The depth h1 of the first recessed structure 6 and the thickness H of the current collector 1 satisfy the following relationship: 1 ≤ H / h1 ≤ 5. The depth of the first recessed structure 6 is the dimension of the first recessed structure 6 in the thickness direction of the current collector 1. When H / h1 = 1, the depth of the first recessed structure 6 is consistent with the thickness of the current collector 1, that is, the first recessed structure 6 is a through hole; when 1 < H / h1 ≤ 5, the first recessed structure 6 is a blind hole, that is, it does not penetrate the current collector 1 in the thickness direction.

[0118] Furthermore, when the cross-section of the first recessed structure 6 is an isosceles triangle or an isosceles trapezoid, that is, the first recessed structure 6 is a tapered hole. The taper of the first recessed structure 6 is 1:(0.05~10), where the taper of the first recessed structure 6 refers to the ratio of the opening size to the depth of the first recessed structure. By limiting the taper of the first recessed structure 6, different sizes of the first recessed structure 6 can be achieved.

[0119] In some embodiments, L1 is 10-100 μm, for example, a range of 10 μm, 15 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm or any two of these; L5 is 10-1000 μm, for example, a range of 10 μm, 20 μm, 30 μm, 50 μm, 100 μm, 200 μm, 300 μm, 500 μm, 1000 μm or any two of these; h1 is 0.5-20 μm, for example, 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 10 μm, 15 μm, 20 μm or any two of these; The range of μm or any two thereof; H is 4 to 12 μm, for example, 4 μm, 5 μm, 10 μm, 12 μm or any two thereof; L3 is 1 to 15 mm, for example, 1 mm, 3 mm, 5 mm, 7 mm, 9 mm, 11 mm, 13 mm, 15 mm or any two thereof; L4 is 1000 to 10000 mm, for example, 1000 mm, 2000 mm, 3000 mm, 4000 mm, 5000 mm, 6000 mm, 7000 mm, 8000 mm, 9000 mm, 10000 mm or any two thereof.

[0120] When the morphological characteristics of the first recessed structure meet the above parameter range, it can not only ensure that the electrode breaks at the recessed structure when the electrode is damaged by external force, so that the coating can slide to the fracture surface and play a role in preventing short circuit, but also avoid the electrode itself from being too large or too dense, thus reducing its mechanical strength.

[0121] Furthermore, in a specific embodiment of the present invention, the electrode is prepared by the following steps: a coating slurry is provided on the first functional surface of the current collector, and after drying, a recessed structure is provided on the second functional surface of the current collector. Subsequently, a coating slurry is applied to the second functional surface and the recessed structure, and after drying and rolling, a polymer adhesive layer is covered to obtain the electrode. The first functional surface and the second functional surface are distributed on both sides of the current collector in the thickness direction.

[0122] In detail, the slurry coating needs to be applied according to the differences between the first and second zones.

[0123] Since the present invention first applies a coating slurry to the first functional surface and then applies a recessed structure to the second functional surface of the current collector, it can prevent leakage problems caused by applying the recessed structure.

[0124] In another aspect, the present invention provides a battery cell comprising the electrodes as described above.

[0125] It should be noted that the battery cell provided by the present invention is preferably suitable for lithium-ion batteries; of course, it is also suitable for battery cells such as sodium-ion batteries, and no further limitations are made here.

[0126] When the aforementioned electrode sheet is a positive electrode sheet, the battery cell of the present invention further includes a negative electrode sheet and a separator. The separator is used to separate the positive electrode sheet and the negative electrode sheet, preventing them from directly contacting each other. The battery cell can be a wound structure, a stacked structure, etc., and the present invention does not impose any limitations on it. Specifically, the battery cell can be a wound structure formed by stacking and winding positive electrode sheets, separators, and negative electrode sheets, or it can be a stacked structure formed by sequentially stacking multiple positive electrode sheets, separators, and negative electrode sheets.

[0127] Of course, if the above-mentioned electrode sheet is a negative electrode sheet, the battery cell of the present invention also includes a positive electrode sheet and a separator.

[0128] Because the battery cell of the present invention includes the electrode plates as described above, the battery cell has excellent safety performance.

[0129] Furthermore, in one specific embodiment of the present invention, the battery cell is a wound core, the second region of the electrode is located at or near the head along the winding direction of the wound core, and the first region of the electrode is located at the tail along the winding direction of the wound core.

[0130] In detail, in one specific embodiment, the electrode is a positive electrode, and the battery cell also includes a separator and a negative electrode; the positive electrode, separator, and negative electrode are stacked in sequence and wound from the end where the second region of the positive electrode is located to the end where the first region of the positive electrode is located. The first region of the positive electrode is located at the end of the battery cell, and the second region of the positive electrode is located at the beginning along the winding direction of the core.

[0131] When the first region A is located at the winding tail of the wound cell and the second region B is located at the winding tail of the wound cell, the polymer adhesive layer 9 can better fix and support the electrode sheet, improve the stability and integrity of the electrode sheet structure, and at the same time prevent the electrode active material in the electrode sheet from contacting the external environment, reducing potential safety risks.

[0132] Furthermore, in one specific embodiment of the present invention, the opening end of the first recessed structure 6 of the electrode sheet faces the side away from the center of the battery cell.

[0133] The opening end of the first recessed structure 6 faces the side away from the center of the cell, that is, the opening end of the first recessed structure 6 faces the outside of the cell. In this way, when the cell is damaged by external force and deforms or breaks inward, the functional layer material covering the inner surface of the first recessed structure 6 can slide and spread inward in the direction of damage, effectively protecting the fracture surface of the current collector 1 from exposure, thereby avoiding short circuit problems caused by the exposure of the fracture surface of the current collector 1.

[0134] The present invention further provides a battery comprising the cell described above.

[0135] The battery of the present invention is preferably a lithium-ion battery, including but not limited to pouch batteries, square batteries, cylindrical batteries, etc.

[0136] A battery for charging / discharging can be formed by mounting the battery cell and protection circuit together inside an aluminum-plastic film. The quality of the battery cell directly determines the quality of the battery. Due to the use of the aforementioned electrode plates, the battery of this invention exhibits excellent performance in terms of safety and other aspects.

[0137] The battery also includes an electrolyte. Specifically, the battery cell is packaged and then injected with an electrolyte. The battery is then produced through processes such as formation, capacity testing, and OCV.

[0138] The present invention will be further described below through specific embodiments and comparative examples.

[0139] Example 1

[0140] (1) Preparation of the first safety layer and the third safety layer slurry: Lithium iron phosphate (LFP): alumina (Al2O3): conductive carbon black (SP): polyvinylidene fluoride (PVDF) and N-methylpyrrolidone (NMP) in a mass ratio of 80:15:2:3 were mixed and stirred evenly to obtain the first safety coating slurry.

[0141] Preparation of the second safety layer slurry: Alumina (Al2O3), polyvinylidene fluoride (PVDF) and N-methylpyrrolidone (NMP) in a mass ratio of 90:10 are mixed and stirred until uniform to obtain the second safety coating slurry;

[0142] Preparation of the first active layer, second active layer and third active layer slurry: Lithium cobalt oxide (LCO): conductive carbon black (SP): polyvinylidene fluoride (PVDF) and N-methylpyrrolidone (NMP) in a mass ratio of 97.5:1:1.5 were mixed and stirred evenly to obtain the active material layer slurry.

[0143] (2) The first safety layer slurry is coated on the first surface of the aluminum foil, the aluminum foil thickness H is 9μm, and after drying, the first safety layer on the first surface is obtained; the positive electrode active layer slurry is coated on the first safety layer on the first surface of the aluminum foil, and after drying, a single-sided coated positive electrode sheet is obtained;

[0144] (3) A laser drilling device is used to drill holes at a preset position on the second surface of the aluminum foil to form a first recessed structure 6 and a third recessed structure 8. The depth of the first recessed structure 6 and the third recessed structure 8 is h1, h1 is 9μm, the size of the opening end of the first recessed structure L1 is 60μm, and the center line distance between adjacent first recessed structures L5 is 200μm.

[0145] (4)Reference Figure 3 The structure involves coating a first safety layer slurry, a second safety layer slurry, and a third safety layer slurry onto predetermined positions on the second surface of an aluminum foil, and drying them to obtain the first safety layer, the second safety layer, and the third safety layer on the second surface; then coating the surface of the first safety layer and the third safety layer with a positive electrode active layer slurry, and gradually thinning the active layer on the surface of the first safety layer along the position from the third safety layer to the second safety layer, and drying it to obtain the initial positive electrode film;

[0146] (5) After rolling and cutting the above initial positive electrode film, a polymer film 5 is attached to the preset position and the positive electrode tab is welded to obtain a positive electrode sheet, wherein the depth h2 of the second recessed structure is 6μm and the size L2 of the opening end of the second recessed structure is 50μm.

[0147] II. Preparation of the negative electrode sheet

[0148] Graphite, styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC) and deionized water were mixed in a mass ratio of 96:2:2 and stirred evenly to obtain a negative electrode coating slurry.

[0149] The negative electrode coating slurry is coated onto the surface of the negative electrode current collector, and the negative electrode sheet is obtained after drying, rolling, and slitting.

[0150] III. Battery Preparation

[0151] The positive electrode sheet, separator, and negative electrode sheet are stacked and wound in sequence to obtain a core; wherein the opening end of the first recessed structure 6 faces the side away from the center of the core.

[0152] The aluminum-plastic film is punched using a punching die, and then the core is sealed with the punched aluminum-plastic film to obtain the battery cell. The cell is baked until the moisture content is within acceptable limits, and then electrolyte is injected. The battery cell is charged and discharged using lithium-ion battery formation equipment to harden it, and the capacity of the cell is sorted. The cell is then resealed and folded to form the battery cell. After OCV testing, the K value of the battery is measured, and products with qualified K values ​​are selected to obtain lithium-ion batteries.

[0153] The battery was disassembled after undergoing 300 3C charge-discharge cycles at 25°C. The appearance of the polymer film and the lithium plating in the negative electrode area corresponding to the edge of the polymer film were observed. See Table 2 for details.

[0154] 3D microscopy was used to test a local structure of the positive electrode sheet in Example 1. The test results are shown in [Figure number missing]. Figure 8 .

[0155] Example 2

[0156] The preparation process is basically the same as in Example 1, except that: in the preparation process of the positive electrode sheet, along the direction from the second end to the first end, the first functional layer 2 sequentially includes an active layer 22 and a second safety layer, as shown in the figure. Figure 2 The structure was adjusted, and the drilling process and material particle size were modified to obtain the corresponding positive electrode sheet;

[0157] The positive electrode of Example 1 is replaced with the positive electrode of this example to obtain the battery of this example.

[0158] The battery was disassembled after undergoing 300 3C charge-discharge cycles at 25°C. The appearance of the polymer film and the lithium plating in the negative electrode area corresponding to the edge of the polymer film were observed. See Table 2 for details.

[0159] In Example 2, the local structure of the positive electrode was tested using a 3D microscope. The test results are shown in [Figure 2]. Figure 9 .

[0160] Example 3

[0161] The preparation process is basically the same as in Example 1, except that in the preparation of the positive electrode sheet, the positive electrode active layer slurry is directly coated onto the functional surface of the positive electrode current collector, i.e., no first and second safety layers are provided, as described above. Figure 1 The structure was adjusted, and the drilling process and material particle size were modified to obtain the corresponding positive electrode sheet;

[0162] The positive electrode of Example 1 is replaced with the positive electrode of this example to obtain the battery of this example.

[0163] The battery was disassembled after undergoing 300 3C charge-discharge cycles at 25°C. The appearance of the polymer film and the lithium plating in the negative electrode area corresponding to the edge of the polymer film were observed. See Table 2 for details.

[0164] Example 4

[0165] The preparation process is basically the same as in Example 1, except that: in the preparation process of the positive electrode sheet, the corresponding positive electrode sheet is obtained by adjusting the drilling parameters and the particle size of the material.

[0166] The positive electrode of Example 1 is replaced with the positive electrode of this example to obtain the battery of this example.

[0167] The battery was disassembled after undergoing 300 3C charge-discharge cycles at 25°C. The appearance of the polymer film and the lithium plating in the negative electrode area corresponding to the edge of the polymer film were observed. See Table 2 for details.

[0168] Example 5

[0169] The preparation process is basically the same as in Example 1, except that the corresponding positive electrode sheet is obtained by adjusting the drilling parameters during the preparation of the positive electrode sheet.

[0170] The positive electrode of Example 1 is replaced with the positive electrode of this example to obtain the battery of this example.

[0171] The battery was disassembled after undergoing 300 3C charge-discharge cycles at 25°C. The appearance of the polymer film and the lithium plating in the negative electrode area corresponding to the edge of the polymer film were observed. See Table 3 for details.

[0172] Example 6

[0173] The preparation process is basically the same as in Example 1, except that: in the preparation process of the positive electrode sheet, the type of slurry is adjusted while other conditions remain unchanged to obtain the corresponding positive electrode sheet;

[0174] The positive electrode of Example 1 is replaced with the positive electrode of this example to obtain the battery of this example.

[0175] The battery was disassembled after undergoing 300 3C charge-discharge cycles at 25°C. The appearance of the polymer film and the lithium plating in the negative electrode area corresponding to the edge of the polymer film were observed. See Table 2 for details.

[0176] Example 7

[0177] The preparation process is basically the same as in Example 1, except that: in the preparation process of the positive electrode sheet, the coating process is adjusted while other conditions remain unchanged to obtain the corresponding positive electrode sheet;

[0178] The positive electrode of Example 1 is replaced with the positive electrode of this example to obtain the battery of this example.

[0179] The battery was disassembled after undergoing 300 3C charge-discharge cycles at 25°C. The appearance of the polymer film and the lithium plating in the negative electrode area corresponding to the edge of the polymer film were observed. See Table 2 for details.

[0180] Example 8

[0181] The preparation process is basically the same as in Example 1, except that in the preparation process of the positive electrode sheet, the corresponding positive electrode sheet is obtained by changing the drilling parameters while keeping other conditions unchanged.

[0182] The positive electrode of Example 1 is replaced with the positive electrode of this example to obtain the battery of this example.

[0183] The battery was disassembled after undergoing 300 3C charge-discharge cycles at 25°C. The appearance of the polymer film and the lithium plating in the negative electrode area corresponding to the edge of the polymer film were observed. See Table 3 for details.

[0184] Example 9

[0185] The preparation process is basically the same as in Example 1, except that: in the preparation process of the positive electrode sheet, the corresponding positive electrode sheet is obtained by adjusting the drilling parameters and the particle size of the material.

[0186] The positive electrode of Example 1 is replaced with the positive electrode of this example to obtain the battery of this example.

[0187] The battery was disassembled after undergoing 300 3C charge-discharge cycles at 25°C. The appearance of the polymer film and the lithium plating in the negative electrode area corresponding to the edge of the polymer film were observed. See Table 2 for details.

[0188] Comparative Example 1

[0189] The preparation process is basically the same as that in Example 1, except that step (3) is omitted in the preparation process of the positive electrode, that is, the drilling process is not performed, and other conditions remain unchanged to obtain the corresponding positive electrode.

[0190] The positive electrode of Example 1 was replaced with the positive electrode of this comparative example to obtain the battery of this comparative example.

[0191] The battery was disassembled after undergoing 300 3C charge-discharge cycles at 25°C. The appearance of the polymer film and the lithium plating in the negative electrode area corresponding to the edge of the polymer film were observed. See Table 2 for details.

[0192] Comparative Example 2

[0193] The preparation process is basically the same as that in Example 2, except that step (3) is omitted in the preparation process of the positive electrode, that is, no drilling is performed, and other conditions remain unchanged to obtain the corresponding positive electrode.

[0194] The positive electrode of Example 2 was replaced with the positive electrode of this comparative example to obtain the battery of this comparative example.

[0195] The battery was disassembled after undergoing 300 3C charge-discharge cycles at 25°C. The appearance of the polymer film and the lithium plating in the negative electrode area corresponding to the edge of the polymer film were observed. See Table 3 for details.

[0196] Comparative Example 3

[0197] The preparation process is basically the same as that in Example 3, except that step (3) is omitted in the preparation process of the positive electrode, that is, no drilling is performed, and other conditions remain unchanged to obtain the corresponding positive electrode.

[0198] The positive electrode of Example 3 was replaced with the positive electrode of this comparative example to obtain the battery of this comparative example.

[0199] The battery was disassembled after undergoing 300 3C charge-discharge cycles at 25°C. The appearance of the polymer film and the lithium plating in the negative electrode area corresponding to the edge of the polymer film were observed. See Table 2 for details.

[0200] Comparative Example 4

[0201] The preparation process is basically the same as in Example 1, except that: in the preparation process of the positive electrode, the active layer thickness in the first region A is the same as that in the second region B, without thinning, and other conditions remain unchanged, thus obtaining the corresponding positive electrode.

[0202] The positive electrode of Example 1 was replaced with the positive electrode of this comparative example to obtain the battery of this comparative example.

[0203] The battery was disassembled after undergoing 300 3C charge-discharge cycles at 25°C. The appearance of the polymer film and the lithium plating in the negative electrode area corresponding to the edge of the polymer film were observed, as detailed in Table 2. The parameters of the electrode sheets provided in all embodiments and comparative examples are shown in Tables 1 and 2.

[0204] Table 1

[0205]

[0206] Table 2

[0207]

[0208]

[0209] As can be seen from the comparative examples and comparative examples, compared with conventional positive electrode sheets, the positive electrode sheet using the present invention has no swelling or ridges in the polymer film pasted on the surface of the thinned portion, and no lithium plating in the negative electrode area corresponding to the edge of the polymer film, thus improving safety performance.

[0210] It should be noted that the numerical values ​​and ranges involved in the embodiments of the present invention are approximate values. Due to the influence of the manufacturing process, there may be a certain range of errors, which can be considered negligible by those skilled in the art.

[0211] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

[0212] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A pole piece, characterized in that, The collector includes a current collector, a first functional layer, a polymer adhesive layer; The collector includes a first region and a second region, wherein the second region is connected to one end of the first region in the length direction and extends along the length direction; One side of the first region is provided with N first recess structures, N≥1; The first functional layer covers at least part of the functional surface of the first region and is embedded in at least part of the first recess structures; the thickness of the first functional layer decreases along the length direction; The polymer adhesive layer covers at least part of the surface of the first functional layer away from the collector.

2. The pole piece of claim 1, wherein The surface of the first functional layer away from the collector has M second recess structures, 1≤M≤N; The depth of the first recess structure is h1, and the depth of the second recess structure is h2; The size of the opening end of the first recess structure is L1, and the size of the opening end of the second recess structure is L2; Wherein, h2≤h1, L2≤L1; Preferably, h1 is 0.5-20 μm, L1 is 10-100 μm, h2 is 0.5-20 μm, and L2 is 10-100 μm.

3. The pole piece of claim 1, wherein The first functional layer includes a first active layer; or, Along the direction away from the collector, the first functional layer sequentially includes a first security layer and a second active layer covering at least part of the surface of the first security layer; or, Along the length direction, the first functional layer includes a third active layer and a second security layer.

4. The pole piece of claim 3, wherein The first security layer is partially embedded in the first recess structure, and the thickness of the first security layer embedded in the first recess structure is h3, h3≤h1, and h3 is 0.5-20 μm; Or, The first active layer is partially embedded in the first recess structure, and the thickness of the first active layer embedded in the first recess structure is h4, h4≤h1, and h4 is 0.5-20 μm; Or, The second security layer is partially embedded in the first recess structure, and the thickness of the second security layer embedded in the first recess structure is h5, h5≤h1, and h5 is 0.5-20 μm; and / or, The third active layer is partially embedded in the first recess structure, and the thickness of the third active layer embedded in the first recess structure is h6, h6≤h1, and h6 is 0.5-20 μm.

5. The pole piece according to claim 3 or 4, characterized in that Along the length direction, the first security layer includes a protective layer and a first insulating layer; or, the second security layer includes a second insulating layer.

6. The pole piece according to claim 3 or 4, characterized in that The first active layer includes a first active material, and the a-Dv50 of the first active material and the opening end aperture L1 of the first recess structure satisfy: a-Dv50≤0.2L1; or, The third active layer includes a third active material, and the a-Dv50 of the third active material and the opening end aperture L1 of the first recess structure satisfy: a-Dv50≤0.2L1; or, The first security layer includes a first functional material, and the b-Dv50 of the first functional material and the opening end aperture L1 of the first recess structure satisfy: b-Dv50≤0.2L1; or, The second security layer comprises a second functional material, and a b-Dv50 of the second functional material satisfies: b-Dv50≤0.2L1, wherein L1 is an opening end aperture of the recessed structure. The first active material and / or the third active material comprises at least one of lithium cobaltate, lithium nickel cobalt manganese phosphate, lithium iron phosphate, lithium manganese iron phosphate, lithium nickel cobalt aluminum phosphate, lithium manganate, lithium nickelate, and lithium-rich manganese lithium material. The first functional material and / or the second functional material comprises at least one of metal oxide, non-metal oxide, oxide hydrate, and non-conductive polymer. Preferably, the a-Dv50 is 5-15 μm, and the b-Dv50 is 5-15 μm.

7. The pole piece of any one of claims 1-6, wherein, The second functional layer is further included. One side of the second region is provided with X third recessed structures, and X≥1. The second functional layer is at least partially embedded in the third recessed structure and covers at least part of the surface of the second region.

8. The pole piece of claim 7, wherein The second functional layer is an active layer; or In a direction away from the current collector, the second functional layer comprises a third security layer and an active layer arranged in a stack.

9. The pole piece of any one of claims 1-8, wherein, In the extension direction of the current collector, the size of the first region is L3, and the size of the current collector is L4, and 1 / 1000≤L3 / L4≤1 / 100 is satisfied. And / or, the opening end size of the first recessed structure is L1, the center line distance between adjacent first recessed structures is L5, and 1≤L5 / L1≤10 is satisfied. And / or, the depth of the first recessed structure is h1, and the thickness of the current collector is H, and 1≤H / h1≤5 is satisfied. Preferably, the L3 is 1-15 mm, the L4 is 1000-10000 mm, the L5 is 10-1000 μm, the H is 4-12 μm, the h1 is 0.5-20 μm, and the L1 is 10-100 μm.

10. The pole piece of claim 1, wherein The pole piece is prepared by comprising the following steps: A coating slurry is arranged on the first functional surface of the current collector, dried, and then a recessed structure is arranged on the second functional surface of the current collector, and then a coating slurry is coated on the second functional surface and the recessed structure, and after drying and rolling, the polymer adhesive layer is covered to obtain the pole piece; The first functional surface and the second functional surface are distributed on opposite sides in the thickness direction of the current collector.

11. An electric cell characterized by The pole piece comprises any one of claims 1-10.

12. The electric cell of claim 11, wherein, The pole piece comprises any one of claims 1-10.

13. The cell of claim 11 or 12, wherein, The pole piece comprises any one of claims 1-10.

14. A battery, characterized by The pole piece comprises any one of claims 1-10.

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