Pole piece, battery cell and battery

Abstract

The utility model provides a pole piece, a battery cell and a battery. The pole piece comprises a current collector and a functional coating, the functional coating is arranged on the surface of at least one side of the current collector; the current collector is provided with N sunken structures, the opening ends of the sunken structures are located on the functional surface of the current collector, and N is larger than or equal to 1; the functional coating is embedded into at least part of the sunken structure; the size of the opening end of the sunken structure is L1; protrusions are arranged on the periphery of the opening end of the concave structure, the distance between every two adjacent protrusions is L3, and L3 is larger than or equal to L1. The pole piece can solve the problem of short circuit caused by weak mechanical performance and exposure of the fracture surface of the current collector in the prior art, so that the safety performance of the battery is further improved.

Description

Technical Field

[0001] The utility model belongs to the technical field of secondary batteries, and specifically relates to a pole piece, a battery core and a battery. Background Art

[0002] Lithium-ion batteries are widely used in portable electronic devices, electric vehicles, energy storage and other fields due to their small size, high energy density, high platform voltage and no memory effect. With the advancement of technology, people have continuously put forward higher requirements for the energy density and safety performance of lithium-ion batteries.

[0003] When the battery is mechanically damaged (puncture, extrusion, etc.), the pole piece ruptures, resulting in a fracture in the current collector. The fracture of the current collector and the pole piece short-circuit, posing a major safety hazard and possibly causing the battery to catch fire and fail.

[0004] Therefore, it is urgent to improve the safety performance of the electrode to avoid battery short circuit failure. Utility Model Content

[0005] The utility model provides a pole piece to solve the short circuit problem caused by mechanical damage of the pole piece in the prior art, thereby further improving the safety performance of the battery.

[0006] The utility model provides an electric core and a battery. As the electric core and the battery include the pole piece, the battery composed of the pole piece has excellent safety performance.

[0007] The utility model provides a pole piece, comprising a current collector and a functional coating; the functional coating is arranged on at least one side surface of the current collector;

[0008] The current collector is provided with N recessed structures, the opening ends of the recessed structures are located on the functional surface of the current collector, and N≥1; the functional coating is embedded in at least a portion of the recessed structures;

[0009] The size of the opening end of the recessed structure is L1;

[0010] The outer periphery of the opening end of the recessed structure comprises protrusions, and the distance between two adjacent protrusions is L3, wherein L3≥L1.

[0011] The pole piece as described above is a positive pole piece.

[0012] In the pole piece as described above, the protrusion is an annular protrusion.

[0013] The pole piece as described above, the width of the protrusion is w, and the height is h1, wherein 1 μm≤w≤L1×2, and / or; 0.1 μm≤h1≤L1×2;

[0014] And / or, the size L1 of the opening end of the recessed structure and the thickness d1 of the current collector satisfy: 0.1d1≤L1≤100d1;

[0015] And / or, the thickness of the current collector is d1, and the depth of the recessed structure is d2, wherein 0.2≤d2 / d1≤1;

[0016] And / or, the thickness of the pole piece is D, wherein L3≤D×10;

[0017] And / or, the distance between the center lines of adjacent recessed structures is L4, and L4 / L1≤10.

[0018] For the pole piece as described above, L1 is 5-100 μm, d2 is 1-10 μm, d1 is 4-12 μm, L3 is 10-2000 μm, D is 40-200 μm, w is 1-600 μm, and h1 is 0.1-600 μm.

[0019] The pole piece as described above, wherein the functional coating comprises a safety primer layer and an active layer stacked on the surface of the current collector;

[0020] The thickness of the safety primer layer is 0.5-5 μm, and the thickness of the active layer is 30-60 μm.

[0021] The pole piece as described above, the current collector comprises a first region and a second region adjacent to each other, the first region is provided with M1 recessed structures, the second region is provided with M2 recessed structures, M1≥1, M2≥1;

[0022] The functional coating covering the first area includes a safety primer layer and an active layer which are stacked, and the functional coating covering the second area includes a protective layer.

[0023] In another aspect, the utility model provides a battery core, comprising the pole piece as described above.

[0024] The battery cell as described above, wherein the battery cell is a wound battery cell, and the current collector includes a first region and a second region adjacent to each other;

[0025] The functional coating covering the first area includes a safety primer layer and an active layer stacked in layers, and the functional coating covering the second area includes a protective layer;

[0026] The protective layer is located at the tail portion along the winding direction of the wound battery core.

[0027] In the battery cell as described above, the opening end of the recessed structure of the pole piece faces a side away from the center of the wound battery cell.

[0028] In another aspect, the utility model provides a battery, comprising the battery cell as described above.

[0029] The implementation of the utility model has at least the following beneficial effects:

[0030] The pole piece provided by the utility model avoids a large reduction in the tensile strength of the pole piece, which affects the manufacturability of the pole piece, and avoids the occurrence of band breakage during the rolling process and the charging and discharging process by limiting the relationship between the aperture L1 of the open end of the recessed structure on the current collector and the protrusion spacing L3. In addition, by providing the recessed structure and the functional coating, even when the battery is damaged by external force and causes inward deformation or fracture, the fracture of the current collector is more likely to occur at the recessed structure. At this time, the functional coating covering the recessed structure can slide and spread inward in the direction of damage, so that the fracture surface of the current collector is covered and protected by the coating material so that it is not exposed, and the resistance of the positive and negative electrodes when they are in short circuit contact is increased, effectively reducing the short-circuit current, thereby improving the safety performance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solution of the present invention, the following is a brief introduction to the drawings required for use in the description of the embodiments of the present invention. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0032] Figure 1 This is a schematic diagram of the cross-sectional structure of a pole piece in one embodiment of the utility model;

[0033] Figure 2 It is a schematic diagram of the cross-sectional structure of the current collector in the pole piece in one embodiment of the utility model;

[0034] Figure 3 This is a schematic diagram of a top view of a current collector in a pole piece in one embodiment of the utility model;

[0035] Figure 4 This is a SEM image of a pole piece in one embodiment of the utility model;

[0036] Figure 5 It is a schematic diagram of the cross-sectional structure of the current collector in the pole piece in one embodiment of the utility model.

[0037] Description of reference numerals:

[0038] 1-current collector; 2-safety bottom coating; 3-active layer; 11-first functional surface; 12-second functional surface; 101-recessed structure; 102-protrusion; A-functional coating; 4-protective layer. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solution and advantages of the embodiment of the utility model clearer, the technical solution in the embodiment of the utility model will be clearly and completely described below in conjunction with the drawings in the embodiment of the utility model. Obviously, the described embodiment is a part of the embodiment of the utility model, not all of the embodiments. Based on the embodiment of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0040] In the description of the present utility model, terms such as "first" and "second" are only used for descriptive purposes, such as distinguishing various components to more clearly illustrate / explain the technical solution.

[0041] Figures 1 to 4 , the X direction is the length direction of the current collector 1 , the Y direction is the width direction of the current collector 1 , and the Z direction is the thickness direction of the current collector 1 .

[0042] like Figure 1 , Figure 2 , Figure 3 As shown, on the one hand, the utility model provides a pole piece, including a current collector 1 and a functional coating A; the functional coating is arranged on at least one side surface of the current collector 1, and the current collector 1 is provided with N recessed structures 101, and the opening end of the recessed structure 101 is located on the functional surface of the current collector, N≥1; the functional coating A is embedded in at least part of the recessed structure 101, and the size of the opening end of the recessed structure 101 is L1; the outer periphery of the opening end of the recessed structure 101 is provided with a protrusion 102, and the distance between two adjacent protrusions 102 is L3, wherein L3≥L1.

[0043] The pole piece of the utility model can be a negative pole piece or a positive pole piece.

[0044] The functional surface of the current collector refers to the outermost surface in the length direction and width direction of the current collector, that is, the two largest and opposite surfaces among the six surfaces of the current collector, such as Figure 1 and Figure 2 The first functional surface 11 and the second functional surface 12 in the embodiment.

[0045] The recessed structure 101 of the utility model is a structure with a cavity formed by the first functional surface 11 being recessed toward the second functional surface 12, or a structure with a cavity formed by the second functional surface 12 being recessed toward the first functional surface 11. Specifically, conventional methods in the art can be used to provide the current collector 1 with the recessed structure 101 with a cavity. For example, laser drilling, mechanical drilling, electric or thermal light melting, radiation melting, chemical corrosion, friction drilling and other processing methods can be used.

[0046] The recessed structure 101 may or may not penetrate the current collector 1 in the thickness direction of the current collector 1. When the recessed structure 101 penetrates the current collector 1 in the thickness direction of the current collector 1, the recessed structure 101 has two oppositely disposed ends, which intersect the first functional surface 11 and the second functional surface 12 respectively. At this time, the notch formed on the first functional surface 11 and the second functional surface 12 is the opening of the recessed structure 101; when the recessed structure 101 does not penetrate the current collector 1 in the thickness direction of the current collector 1, such as Figure 1 or Figure 2 As shown, the opening of the recessed structure 101 is a notch on the second functional surface 12 .

[0047] The number of the recessed structures 101 may be one or more. When the number of the recessed structures 101 is multiple, the multiple recessed structures 101 are distributed in the extension direction of the current collector 1, and any two recessed structures are independent of each other without overlapping or covering each other.

[0048] It should be noted that the present invention does not specifically limit the three-dimensional shape of the recessed structure 101. When there are multiple recessed structures 101, the multiple recessed structures 101 are independently arranged, and their cross-sectional shapes in the planes where the thickness and width are located, as well as whether they penetrate the current collector 1, are independent. For example, the cross-sectional shapes of some recessed structures 101 are triangular, and the cross-sectional shapes of some recessed structures 101 are isosceles trapezoids; some recessed structures 101 penetrate the current collector 1 (in this case, the recessed structure 101 can be understood as a through hole), and some recessed structures 101 do not penetrate the current collector 1 (in this case, the recessed structure 101 can be understood as a blind hole).

[0049] The present invention does not limit the material type of the current collector, and a common current collector type in the art can be selected according to the polarity of the pole piece. For example, in a specific embodiment, the current collector is aluminum foil.

[0050] The utility model does not limit the specific selection of the functional coating A, as long as it can prevent the functional surface of the current collector 1 from being exposed and causing a short circuit.

[0051] The periphery of the opening end of the recessed structure 101 can also be understood as the periphery of the functional surface where the opening end is located. Figure 1 , Figure 2 and Figure 4 As shown, the protrusion 102 refers to an outer circle structure formed by extending along the radial direction of the inner circle and toward a side away from the opening end of the recessed structure 101 in the extension direction of the current collector 1, with the opening end of the recessed structure 101 as the inner circle. At this time, the structure composed of the inner circle and the outer circle, at the same time, in the thickness direction of the current collector 1, with the surface where the opening end of the recessed structure 101 is located as a reference, protrudes toward the direction away from the functional surface of the positive electrode current collector 1 to form a protrusion structure.

[0052] Among them, Figure 1 , Figure 2 As shown, the distance L3 between two adjacent protrusions 102 refers to the minimum distance between two adjacent protrusions 102 in the length direction or width direction of the current collector 1. By limiting L3 ≥ L1, it is avoided that the area where the recessed structure 101 is distributed is too large, resulting in a large reduction in the tensile strength of the pole piece, affecting the manufacturability of the pole piece, and avoiding the occurrence of belt breakage during the rolling process and the charging and discharging process.

[0053] In addition, through the mutual cooperation between the recessed structure 101 and the functional coating A, the functional coating A covers the inner surface of the recessed structure 101. When the pole piece including the functional coating A and the recessed structure 101 is applied to the battery, and the open end of the recessed structure 101 is facing the side away from the center of the battery cell, even when the battery is damaged by external force and causes inward deformation or fracture, the setting of the recessed structure 101 will make it easier for the fracture of the current collector 1 to occur at the recessed structure 101. At this time, the functional coating A covering the recessed structure 101 can slide and spread inward in the direction of destruction, so that the fracture surface of the current collector 1 is covered and protected by the coating material, so that it is not exposed, and the resistance of the positive and negative electrodes when they are in short circuit contact is increased, effectively reducing the short-circuit current, thereby improving the safety performance of the battery.

[0054] Furthermore, in a specific embodiment of the present invention, the electrode sheet is a positive electrode sheet.

[0055] When the electrode is a positive electrode, the functional coating A can be 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 phosphate, lithium manganese-rich based material, lithium nickel cobalt aluminum oxide, lithium titanate, aluminum oxide, boehmite, titanium dioxide, zirconium oxide, zinc oxide, silicon dioxide, silicon carbide, silicon nitride, conductive polymers and their modified products.

[0056] Furthermore, in a specific embodiment of the present invention, the protrusion is an annular protrusion, the first edge of the annular protrusion is the opening end edge of the recessed structure, and the second edge of the annular protrusion is the edge away from the center direction of the recessed structure and flush with the functional surface.

[0057] When the protrusion is an annular protrusion, it can not only avoid the occurrence of belt breakage during the rolling process and the charging and discharging process, but also effectively control the impact of the protrusion on the loading amount of the current collector, thereby ensuring the safety performance and electrochemical performance of the electrode.

[0058] like Figure 1-Figure 3 As described above, the centerline spacing between adjacent recessed structures in the present invention is L4, wherein the centerline spacing L4 can be understood as the sum of the distance between two adjacent recessed structures 101 and the radius of the opening ends of two adjacent recessed structures 101.

[0059] In one specific embodiment, L4 / L1≤10.

[0060] By defining the relationship between L1 and L4, the pore density can be achieved within the above range, thereby improving both the mechanical strength of the current collector 1 and the safety performance of the battery.

[0061] Further, in a specific embodiment of the present invention, Figure 1 and Figure 2 As shown, the width of the protrusion 102 is w, and the height is h1, wherein 1 μm≤w≤L1×2, 0.1 μm≤h1≤L1×2.

[0062] In detail, the width w of the protrusion 102 is the distance extending toward the side away from the opening end of the recessed structure 101 based on the inner circle; the height h1 of the protrusion 102 refers to the height of the protrusion in the thickness direction of the current collector 1, based on the surface where the opening end of the recessed structure 101 is located, toward the direction away from the current collector 1.

[0063] Further, in a specific embodiment of the present invention, Figure 1 and Figure 2 As shown, the size L1 of the opening end of the recessed structure 101 is equal to the thickness d1 of the current collector 1 , wherein 0.1d1≤L1≤100d1.

[0064] The thickness d1 of the current collector 1 refers to the distance between the first functional surface 11 and the second functional surface 12 where no recessed structure 101 exists in the thickness direction of the current collector 1 .

[0065] In some specific embodiments, the thickness of the current collector 1 is d1, and the depth of the recessed structure 101 is d2, wherein 0.2≤d2 / d1≤1.

[0066] In the present invention, the depth of the recessed structure 101 is the dimension of the recessed structure 101 in the thickness direction of the current collector 1, that is, the dimension from the plane where the opening section is located to the bottom of the recessed structure.

[0067] When d2 / d1 = 1, the depth of the recessed structure 101 is consistent with the thickness of the current collector 1 , that is, the recessed structure 101 is a through hole, and the recessed structure 101 penetrates the current collector 1 .

[0068] When 0.2≤d2 / d1<1, the recessed structure 101 is a blind hole, that is, the recessed structure 101 does not penetrate the current collector 1 in the thickness direction of the current collector 1.

[0069] By limiting 0.2≤d2 / d1≤1, on the one hand, it is ensured that when the battery containing the above-mentioned electrode is damaged by external force, the current collector 1 is more likely to break along the position of the recessed structure 101; on the other hand, due to the setting of the recessed structure 101 and the functional coating A, when a break occurs, the functional coating A corresponding to the recessed structure 101 can slide along the fracture to the fracture surface of the current collector 1 to provide protection for the fracture surface.

[0070] Furthermore, in a specific embodiment of the present invention, the thickness of the pole piece is D, wherein L3≤D×10.

[0071] In the present invention, the thickness D of the pole piece refers to the thickness of the pole piece along the thickness direction of the current collector.

[0072] It can be understood that a functional coating may be provided on the functional surface of the current collector 1 , and in this case, the thickness of the pole piece refers to the sum of the thickness of the current collector 1 and the thickness of the functional coating.

[0073] In one specific embodiment, L3≤D×5.

[0074] By limiting L3≤D×10, it is helpful to ensure that the broken opening of the positive electrode sheet during mechanical damage is located at the position of the recessed structure 101, thereby improving the safety of the battery and improving both the safety performance and the cycle performance of the battery.

[0075] Further, in a specific embodiment of the present invention, L1 is 5-100 μm, d2 is 1-10 μm, d1 is 4-12 μm, L3 is 10-2000, D is 40-200 μm, w is 1-600 μm, h1 is 0.1-600 μm, and L4 is 10-2000 μm.

[0076] In detail, L1 includes but is not limited to 5μm, 10μm, 20μm, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, 90μm, 100μm or any range between two thereof. d2 includes but is not limited to 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm or any range between two thereof. d1 includes but is not limited to 4μm,

[0077] 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm or any range between two of them. L3 includes but is not limited to 10μm, 20μm, 30μm, 40μm, 50μm, 100μm, 200μm, 300μm, 400μm, 500μm, 600μm, 700μm, 800μm,

[0078] 900 μm, 1000 μm, 2000 μm or any range therebetween; D includes but is not limited to 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 100 μm, 150 μm, 200 μm or any range therebetween; w includes but is not limited to 1 μm, 5 μm, 10 μm, 50 μm, 100 μm, 200 μm, 300 μm, 400 μm, 500 μm, 600 μm or any range therebetween. h1 includes but is not limited to 0.1μm, 1μm, 5μm, 10μm, 50μm, 100μm, 200μm, 300μm, 400μm, 500μm, 600μm or a range between any two of them; L4 includes but is not limited to 10μm, 50μm, 100μm, 500μm, 1000μm, 1500μm, 2000μm or a range between any two of them.

[0079] When the relevant parameters are within the above range, it can not only avoid the situation where the recessed structure is too sparse or the depth is too small, or the protrusion parameters lead to poor protection effect of the recessed structure when external force damage occurs, but also avoid the situation where the recessed structure is too dense and the mechanical properties of the electrode itself are reduced, thereby ensuring the safety performance of the electrode.

[0080] Further, in a specific embodiment of the present invention, Figure 1 , Figure 2 As shown, the functional coating A includes a safety primer layer 2 and an active layer 3 stacked on the surface of the current collector 1; the thickness of the safety primer layer 2 is 0.5-5 μm, and the thickness of the active layer 3 is 30-60 μm.

[0081] The material of the safety primer layer 2 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 phosphate, lithium manganese-rich based material, lithium nickel cobalt aluminum oxide, lithium titanate, aluminum oxide, boehmite, titanium dioxide, zirconium oxide, zinc oxide, silicon dioxide, silicon carbide, silicon nitride, conductive polymers and their modifications.

[0082] The material of the active layer 3 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 phosphate, lithium rich manganese-based material, and lithium nickel cobalt aluminum oxide.

[0083] Furthermore, the active layer 3 and the safety primer layer 2 each independently contain a conductive agent, wherein the conductive agent 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 given to the active layer 3 and the safety primer layer 2, which can ensure smooth electronic conduction between the active layer 3, the safety primer layer 2 and the current collector 1, so that the battery has excellent safety performance and good cycle performance.

[0084] The active layer 3 and the safety primer layer 2 each independently contain a binder, and the binder includes at least one of polyvinylidene fluoride, polyvinylidene chloride, polytetrafluoroethylene, polyhexafluoropropylene, polyacrylic acid, polyacrylate, polyamide, polyacrylonitrile, carboxymethyl cellulose sodium, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, styrene-butadiene rubber, polyethylene oxide, styrene-butadiene emulsion, styrene-acrylic emulsion, polyethyl acrylate, polybutyl methacrylate, ethylene-vinyl acetate copolymer, polyvinyl acetate or at least one of its modified products and copolymers, for example, the copolymer of polyvinylidene fluoride includes polyvinylidene fluoride-trifluoroethylene, polyvinylidene fluoride-tetrafluoroethylene, polyvinylidene fluoride-hexafluoroethylene, and polyvinylidene fluoride-hexafluoropropylene. In this way, the active layer 3 and the safety primer layer 2 are fixedly bonded to the current collector 1.

[0085] The thickness of the safety primer layer refers to the average thickness of the safety primer layer, and the thickness of the active layer also refers to the average thickness of the active layer. Specifically, the thickness of the safety primer layer includes but is not limited to 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, or any range between two thereof; the thickness of the active layer includes but is not limited to 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 60 μm, or any range between two thereof.

[0086] When the thickness of the safety bottom coating and the thickness of the active layer are within the above range, not only can there be sufficient safety bottom coating sliding fingers to protect the fracture surface when the pole piece is damaged by external force and broken, but also the energy loss of the pole piece caused by excessive thickness of the safety bottom coating can be avoided, thereby ensuring the energy density of the pole piece.

[0087] The utility model does not limit the preparation process of the stacked safety primer layer 2 and the active layer 3 .

[0088] In a specific embodiment, the preparation method includes: preparing a safety primer layer 2 slurry and uniformly coating it on the first functional surface 11 of the current collector 1, obtaining the first safety primer layer 2 after drying, preparing an active layer 3 slurry and coating it on the first safety primer layer 2, and after drying, using a punching device to process the second functional surface 12 of the current collector 1 to obtain the current collector 1 including the recessed structure 101, preparing a safety primer layer 2 slurry and uniformly coating it on the inner surface of the recessed structure 101 of the current collector 1 and the second functional surface 12 of the current collector 1, obtaining the second safety primer layer 2 after drying, preparing an active layer 3 slurry and coating it on the second safety primer layer 2, and obtaining the pole piece after drying.

[0089] Furthermore, if Figure 5 As shown, in a specific embodiment of the utility model, along the length direction, the current collector 1 includes a first region and a second region adjacent to each other, the first region is provided with M1 recessed structures, and the second region is provided with M2 recessed structures, M1≥1, M2≥1; the functional coating covering the first region includes a safety bottom coating 2 and an active layer 3 which are stacked, and the functional coating covering the second region includes a protective layer 4.

[0090] It can be understood that the sum of the number M1 of the recessed structures in the first region and the number M2 of the recessed structures in the second region is N.

[0091] By providing the second region covered with the protective layer 4 on the current collector, it is possible to avoid the empty foil of the current collector being exposed and causing a short circuit, thereby further improving the safety performance of the pole piece.

[0092] In another aspect, the utility model provides a battery core, comprising the pole piece as described above.

[0093] It should be noted that the battery cell provided by the present invention is preferably applicable to lithium-ion batteries; of course, it is also applicable to sodium-ion batteries and other battery cells, and no excessive limitations are made here.

[0094] The battery cell of the present invention further includes a negative electrode sheet and a separator, and the separator is used to separate the positive electrode sheet and the negative electrode sheet to avoid direct contact between the positive electrode sheet and the negative electrode sheet. The battery cell can be a winding structure, a laminated structure, etc., and the present invention does not make too many restrictions here. Specifically, the battery cell can be a winding structure formed by stacking and winding a positive electrode sheet, a separator and a negative electrode sheet, or a laminated structure formed by stacking a plurality of positive electrode sheets, separators and negative electrode sheets in sequence.

[0095] Since the battery cell of the utility model comprises the pole piece as described above, the battery cell has excellent safety performance.

[0096] Furthermore, in a specific embodiment of the present invention, the battery cell is a wound battery cell, and the current collector includes an adjacent first region and a second region; the functional coating covering the first region includes a stacked safety primer layer and an active layer, and the functional coating covering the second region includes a protective layer; the protective layer is located at the tail along the winding direction of the wound battery cell.

[0097] In detail, the positive electrode sheet, the separator, and the negative electrode sheet are stacked in sequence to obtain a laminate, and the laminate is wound along the winding direction to obtain the winding core provided by the utility model. During the winding process, one end of the laminate is used as the starting end until the winding operation is completed. At this time, the protective layer is located at the tail of the winding core.

[0098] Furthermore, in a specific embodiment of the present invention, the opening end of the recessed structure of the pole piece faces a side away from the center of the battery cell.

[0099] The opening end of the recessed structure 101 faces the side away from the center of the battery cell, that is, the opening end of the recessed structure 101 faces the outside of the battery cell. In this way, when the battery cell is damaged by external force and causes inward deformation or fracture, the functional coating A covering the inner surface of the recessed structure 101 can slide and spread inward in the direction of damage, effectively protecting the fracture surface of the current collector 1 from exposure, thereby avoiding the short circuit problem caused by the exposure of the fracture surface of the current collector 1.

[0100] In another aspect, the utility model provides a battery, comprising the battery cell as described above.

[0101] The battery of the present invention is preferably a lithium-ion battery, including but not limited to a soft-pack battery, a square battery, a cylindrical battery, etc.

[0102] By installing the battery core and the protection circuit together inside the aluminum-plastic film, a battery for charging / discharging can be formed. The quality of the battery core directly determines the quality of the battery. Due to the use of the above-mentioned pole piece, the battery of the utility model has excellent performance in safety performance and other aspects.

[0103] The above-mentioned battery also includes an electrolyte. Specifically, the electrolyte is injected into the battery cell after packaging, and the battery is manufactured through processes such as formation, capacity separation, and OCV.

[0104] The present invention will be further described below through specific embodiments.

[0105] Example 1

[0106] (1) Preparation of safety primer coating slurry and protective layer slurry: Alumina (Al4O3), conductive carbon black (SP), polyvinylidene fluoride (PVDF) and N-methylpyrrolidone (NMP) in a mass ratio of 94:3:3 are mixed, and stirred to obtain safety primer coating slurry and protective layer slurry;

[0107] Preparation of positive electrode active material 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 are mixed, and after stirring and mixing evenly, a positive electrode active material layer slurry is obtained;

[0108] (2) applying the safety primer layer slurry and the protective layer slurry to the first surface of the aluminum foil, and drying to obtain the safety primer layer 2 and the protective layer 4 on the first surface; applying the positive electrode active material layer slurry to the safety primer layer 2 on the first surface of the aluminum foil, and drying to obtain a single-sided coated positive electrode sheet;

[0109] (3) using a laser drilling device to perform a drilling process on the second surface of the aluminum foil to form a recessed structure 101;

[0110] (4) applying the safety primer layer slurry and the protective layer slurry to the second surface of the aluminum foil, and drying to obtain the safety primer layer 2 and the protective layer 4 on the second surface; applying the positive electrode active material layer slurry to the safety primer layer 2 on the second surface of the aluminum foil, and drying to obtain the initial positive electrode film;

[0111] (5) After rolling and slitting the initial positive electrode film, the positive electrode ears are welded at the preset positions to obtain the positive electrode sheets.

[0112] 2. Preparation of negative electrode sheet

[0113] Graphite, styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC) and deionized water in a mass ratio of 97:1.5:1.5 were mixed and stirred evenly to obtain a negative electrode coating slurry;

[0114] The negative electrode coating slurry is coated on the surface of the negative electrode current collector, and the negative electrode sheet is obtained after drying, rolling and cutting.

[0115] 3. Preparation of batteries

[0116] The positive electrode sheet, the separator, and the negative electrode sheet are stacked and wound in sequence to obtain a winding core; wherein the opening end of the recessed structure 101 faces a side away from the center of the winding core;

[0117] Use a punching die to punch out the aluminum-plastic film, then use the punched aluminum-plastic film to package the roll core to obtain the battery cell, bake it until the moisture content is qualified, and inject the electrolyte; use lithium-ion battery formation equipment to charge and discharge the battery cell to harden the battery cell and sort out the capacity of the battery cell; perform a secondary sealing on the battery cell and fold the edge to form the battery cell, and perform an OCV test to test the K value of the battery, select the products with qualified K value, and obtain the lithium-ion battery.

[0118] Embodiments 2 to 8

[0119] The preparation process is basically the same as that of Example 1, except that the parameters of the laser drilling equipment are adjusted during the preparation of the positive electrode sheet to obtain recessed structures 101 of different sizes. The specific size parameters are shown in Table 1. Other conditions remain unchanged to obtain the corresponding positive electrode sheet.

[0120] The positive electrode sheet of Example 1 is replaced with the positive electrode sheets of Examples 2 to 8 to obtain batteries corresponding to Examples 2 to 8.

[0121] Comparative Example 1

[0122] The preparation process is basically the same as that of Example 1, except that no punching process is performed during the preparation of the positive electrode sheet, that is, the positive electrode current collector 1 used is a homogeneous aluminum foil, to obtain the positive electrode sheet of this comparative example.

[0123] The positive electrode sheet of Example 1 is replaced by the positive electrode sheet of this comparative example to obtain a battery of this comparative example.

[0124] Comparative Example 2

[0125] The preparation process is basically the same as that of Example 1, except that no protrusions are generated during the preparation of the positive electrode sheet, thereby obtaining the positive electrode sheet of this comparative example.

[0126] The positive electrode sheet of Example 1 is replaced by the positive electrode sheet of this comparative example to obtain a battery of this comparative example.

[0127] Comparative Example 3

[0128] The preparation process is basically the same as that of Example 1, except that the parameters of the laser drilling equipment are adjusted during the preparation of the positive electrode sheet to obtain recessed structures 101 of different sizes. The specific size parameters are shown in Table 1. Other conditions remain unchanged to obtain the corresponding positive electrode sheet.

[0129] The positive electrode sheet of Example 1 is replaced by the positive electrode sheet of this comparative example to obtain a battery of this comparative example.

[0130] Test example

[0131] 1. Screw extrusion test

[0132] Fully charge the lithium-ion battery and then place it on the test bench of the extrusion equipment. Place a screw with a screw diameter of 2mm and a screw length of 4mm in the middle of the battery, start the extrusion equipment, and squeeze the screw into the battery at a speed of 0.1mm / s. When the equipment pressure reaches 13KN, stop the test. If the battery does not catch fire or explode, the test is considered to have passed. The number of passes / the number of tests is the screw extrusion pass rate, and the number of tests is 30.

[0133] 2. Heavy object impact test:

[0134] Fully charge the lithium-ion battery and then place it on the test bench of the heavy object impact test equipment. Place a steel rod with a diameter of 15.8mm in the middle of the battery cell, start the equipment, and a heavy hammer weighing 9.1kg falls freely from a height of 610mm from the battery and hits the steel rod. The battery is considered to have passed the test if it does not catch fire or explode. The number of passes / number of tests is the pass rate of the heavy object impact test, and the number of tests is 30.

[0135] 3. Energy density test:

[0136] Energy density = battery discharge energy / (battery length * height * width)

[0137] The test results are shown in Table 1.

[0138] Table 1

[0139]

[0140]

[0141] By comparing Examples 1 to 8 with Comparative Example 1, it can be seen that the pass rates of the screw extrusion test and the heavy object impact test of the batteries of Examples 1 to 8 are much higher than those of Comparative Example 1.

[0142] By comparing Examples 1 to 4, 6, and 7 with Example 5, it can be seen that by limiting L3≤D×10, the pass rate of the screw extrusion test and the pass rate of the heavy object impact test can be further improved to more than 66%. However, in Example 5, L3>D×10, the ring spacing is too large, and the safety is reduced.

[0143] By comparing Examples 1 to 4, 6, 7 and Example 8, it can be seen that by limiting d2≥0.2d1, the pass rate of the screw extrusion test and the pass rate of the heavy object impact test can be further improved to more than 50%. In Example 8, d2<0.2d1, the hole depth is small, and the safety is reduced.

[0144] In Comparative Example 3 compared to Example 1, L3<L1, the tensile strength of the positive electrode sheet is greatly affected, resulting in reduced rolling resistance, the electrode sheet cannot be rolled to the designed thickness, and the energy density of the battery is significantly reduced.

[0145] It should be noted here that the numerical values ​​and numerical 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.

[0146] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the utility model, rather than to limit it. Although the utility model has been described in detail with reference to the aforementioned embodiments, ordinary technicians in this field should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not make the essence of the corresponding technical solution deviate from the scope of the technical solution of the embodiments of the utility model.

[0147] The above describes the implementation methods of the present invention. However, the present invention is not limited to the above implementation methods. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A pole piece, characterized in that: It comprises a current collector and a functional coating; the functional coating is arranged on at least one side surface of the current collector; The current collector is provided with N recessed structures, the opening ends of the recessed structures are located on the functional surface of the current collector, and N≥1; The functional coating is embedded in at least a portion of the recessed structure; The size of the opening end of the recessed structure is L1; The outer periphery of the opening end of the recessed structure comprises protrusions, and the distance between two adjacent protrusions is L3, wherein L3≥L1.

2. The pole piece according to claim 1, characterized in that: The pole piece is a positive pole piece.

3. The pole piece according to claim 1, characterized in that: The protrusion is an annular protrusion.

4. The pole piece according to claim 1, characterized in that: The width of the protrusion is w, and the height is h1, wherein 1 μm≤w≤L1×2, and / or; 0.1 μm≤h1≤L1×2; And / or, the size L1 of the opening end of the recessed structure and the thickness d1 of the current collector satisfy: 0.1d1≤L1≤100d1; And / or, the thickness of the current collector is d1, and the depth of the recessed structure is d2, wherein 0.2≤d2 / d1≤1; And / or, the thickness of the pole piece is D, wherein L3≤D×10, And / or, the distance between the center lines of adjacent recessed structures is L4, and L4 / L1≤10.

5. The pole piece according to claim 4, characterized in that: L1 is 5-100μm, d2 is 1-10μm, d1 is 4-12μm, L3 is 10-2000μm, D is 40-200μm, w is 1-600μm, h1 is 0.1-600μm, and L4 is 10-2000μm.

6. The pole piece according to any one of claims 1 to 5, characterized in that: The functional coating comprises a safety primer layer and an active layer stacked on the surface of the current collector; The thickness of the safety primer layer is 0.5-5 μm, and the thickness of the active layer is 30-60 μm.

7. The pole piece according to any one of claims 1 to 5, characterized in that: The current collector includes a first region and a second region adjacent to each other, the first region is provided with M1 recessed structures, the second region is provided with M2 recessed structures, M1≥1, M2≥1; The functional coating covering the first area includes a safety primer layer and an active layer which are stacked, and the functional coating covering the second area includes a protective layer.

8. A battery cell, characterized in that: A pole piece comprising any one of claims 1 to 5.

9. The battery cell according to claim 8, characterized in that: The battery cell is a wound battery cell, and the current collector includes a first region and a second region adjacent to each other; The functional coating covering the first area includes a safety primer layer and an active layer stacked in layers, and the functional coating covering the second area includes a protective layer; The protective layer is located at the tail portion along the winding direction of the wound battery core.

10. The battery cell according to claim 9, characterized in that: The opening end of the recessed structure of the pole piece faces a side away from the center of the wound battery core.

11. A battery, characterized in that: Comprising the battery cell as claimed in claim 8.

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