Pole piece, battery cell and battery

Abstract

The utility model provides a pole piece, cell and battery, the pole piece includes current collector, the current collector includes first area and second area, the first area is connected with the one end of second area in the length direction and extends along the length direction, the size of the first area in the length direction is 0.5-20mm; n first sunken structures are arranged on one side of the second area, and N is larger than or equal to 1; a first safety layer and a first active layer are stacked on at least one side of the first region in the direction away from the current collector, and a second safety layer and a second active layer are stacked on at least part of the surface of at least one side of the second region in the direction away from the current collector. The problem that the pole piece is easy to wrinkle in the prior art can be solved, and the safety performance and the yield of the battery are 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 and other fields due to their advantages such as fast charging speed, no memory effect and environmental friendliness. With the advancement of technology, people have put forward higher requirements for the safety of lithium-ion batteries. Among them, rolling is required in the process of pole piece production. During the rolling process, the pole piece is prone to wrinkling, especially at the junction of the empty foil area and the active layer area, which causes the structure of the pole piece to deform, resulting in increased process risks, serious impact on the appearance and performance of the battery cell, and affecting the safety performance and yield rate of the battery. Utility Model Content

[0003] The utility model provides a pole piece to solve the problem that the pole piece in the prior art is prone to wrinkling, thereby improving the safety performance and yield rate of the battery.

[0004] The utility model also provides a battery core and a battery, which have excellent safety performance and good product rate due to comprising the pole piece.

[0005] The utility model provides a pole piece, the pole piece comprises a current collector, the current collector comprises a first region and a second region, wherein the first region is connected to one end of the second region in the length direction and extends along the length direction, and the size of the first region in the length direction is 0.5-20 mm;

[0006] N first recessed structures are arranged on one side of the second region, where N≥1;

[0007] A first safety layer and a first active layer are stacked on at least one side of the first region in a direction away from the current collector, and a second safety layer and a second active layer are stacked on at least a portion of the surface of at least one side of the second region in a direction away from the current collector.

[0008] In the pole piece as described above, in a direction away from the current collector, the second safety layer and the second active layer are stacked in at least a portion of the first recessed structure.

[0009] The pole piece as described above is a positive pole piece.

[0010] For the pole piece as described above, along the length direction of the current collector, the first safety layer and the first active layer are stacked on both sides of the first region in a direction away from the current collector; and / or, the second safety layer and the second active layer are stacked on at least part of the surface on both sides of the second region in a direction away from the current collector.

[0011] The pole piece as described above, wherein the surface of the second region includes a first sub-region and a second sub-region adjacent to each other;

[0012] The first sub-region is stacked with the second safety layer and the second active layer in a direction away from the current collector;

[0013] The second sub-region is provided with a protective layer in a direction away from the current collector.

[0014] The pole piece as described above, the stacked second safety layer and the second active layer are provided with a groove, exposing the surface of the second region of the current collector, the first pole ear is located in the groove and is electrically connected to the current collector;

[0015] There is a distance between the first recessed structure and the groove, and the distance between the groove and the first recessed structure is not less than 1 mm.

[0016] The pole piece as described above, the current collector further comprises a third region, the third region is connected to one end of the first region in the length direction and extends along the length direction;

[0017] At least part of the third region is provided with M second recessed structures, where M≥1.

[0018] As for the pole piece as described above, the third area includes a perforated area and a pole ear area, the second recessed structure is arranged in the perforated area, the second pole ear is electrically connected to the current collector in the pole ear area, and there is a distance between the pole ear area and the perforated area, and the distance is not less than 1 mm.

[0019] For the pole piece as described above, in the length direction, the ratio of the sizes of the first region, the second region and the third region is (0.5-20): (300-2000): (8-70).

[0020] The pole piece as described above, the aperture of the opening end of the first recessed structure is L1, and the center line spacing between adjacent first recessed structures is L2, wherein 1≤L2 / L1≤10;

[0021] And / or, the depth of the first recessed structure is h, and the thickness of the current collector is H, wherein 1≤H / h≤5;

[0022] And / or, the opening end of the first recessed structure has a protrusion, the width of the protrusion is w, and the height is h1; wherein, 1 μm≤w≤L1×2, 0.1 μm≤h1≤L1×2.

[0023] For the pole piece as described above, L1 is 5-100 μm, L2 is 10-1000 μm, h is 1-12 μm, H is 4-12 μm, w is 1-600 μm, and h1 is 0.1-600 μm.

[0024] In another aspect, the utility model provides a battery core, comprising the pole piece as described above.

[0025] As described above, the battery core is a wound battery core, and the opening end of the first recessed structure faces a side away from the center of the winding core.

[0026] In the battery cell as described above, the surface of the second region includes a first sub-region and a second sub-region adjacent to each other;

[0027] The first sub-region is provided with the second safety layer and the second active layer in a stacked manner in a direction away from the current collector; the second sub-region is provided with a protective layer in a direction away from the current collector;

[0028] The protective layer is located at a tail portion along a winding direction of the wound battery core, and the first region is located at a head portion along a winding direction of the wound battery core.

[0029] The battery cell as described above, wherein the outer surface of the wound battery cell is provided with a hot melt adhesive layer;

[0030] The ratio of the orthographic projection area of ​​the hot melt adhesive layer on the second region to the area of ​​the wound battery core is greater than 5%.

[0031] In another aspect, the utility model provides a battery, comprising the battery cell as described above.

[0032] The implementation of the utility model has at least the following beneficial effects:

[0033] The pole piece provided by the utility model can effectively improve the risk of wrinkling of the pole piece with a first recessed structure having a cavity during rolling by being arranged in a first area with a size of 0.5-20 mm in the length direction, reduce process risks and the output of defective products, and thus improve the safety performance and yield rate of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] 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.

[0035] Figure 1 This is a schematic diagram of the structure of a pole piece in one embodiment of the utility model;

[0036] Figure 2 It is a schematic diagram of the structure of a pole piece in another embodiment of the utility model;

[0037] Figure 3 This is a schematic diagram of the structure of a pole piece in one embodiment of the utility model;

[0038] Figure 4 It is a schematic diagram of the structure of a pole piece in another embodiment of the utility model;

[0039] Figure 5 is a schematic diagram of the cross-sectional structure of the second region in the pole piece in one embodiment of the utility model;

[0040] Figure 6 is a schematic diagram of the cross-sectional structure of the second region in the pole piece in another embodiment of the utility model;

[0041] Figure 7 This is a schematic diagram of the top view of the second area of ​​the pole piece in one embodiment of the utility model;

[0042] Figure 8 It is a schematic diagram of a partial cross-sectional structure of the second region in a pole piece in one embodiment of the utility model;

[0043] Fig. 9 This is a schematic diagram of a top view of a winding core in one embodiment of the utility model;

[0044] Fig.10 It is a schematic diagram of the top view structure of the winding core in another embodiment of the utility model.

[0045] Description of reference numerals:

[0046] 1-winding core; 2-hot melt adhesive layer; 3-tailing end; 4-ear;

[0047] 10-current collector; 20-second safety layer; 201-first safety layer; 30-second active layer; 301-first active layer; 40-protective layer; 50-first recessed structure; 501-protrusion; 101-first region; 102-third region; 103-second region; 104-second recessed structure; 105-first sub-region; 106-second sub-region; 107-ear region;

[0048] 11 - first functional surface; 12 - second functional surface. DETAILED DESCRIPTION

[0049] 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.

[0050] In the description of the present invention, those skilled in the art can understand the specific meanings of the above-mentioned terms in the present invention in specific situations. The terms "first" and "second" are only used for descriptive purposes, such as distinguishing between components to more clearly illustrate / explain the technical solution.

[0051] Figures 1 to 7 In the figure, the X direction 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.

[0052] The utility model provides a pole piece, such as Figure 1-Figure 4 As shown, the pole piece includes a current collector 10, and the current collector 10 includes a first region 101 and a second region 103, wherein the first region 101 is connected to one end of the second region 103 in the length direction and extends along the length direction, and the size of the first region 101 in the length direction is 0.5-20 mm; N first recessed structures are arranged on one side of the second region 103, and N ≥ 1; a first safety layer 201 and a first active layer 301 are stacked on at least one side of the first region 101 in a direction away from the current collector 10, and a second safety layer 20 and a second active layer 30 are stacked on at least part of the surface of at least one side of the second region 103 in a direction away from the current collector 1.

[0053] The utility model does not limit the electrical properties of the electrode, which can be a negative electrode or a positive electrode.

[0054] The first region 101 is connected to one end of the second region 103 in the length direction and extends along the length direction. That is, the first region 101 and the second region 103 are sequentially arranged in the length direction of the current collector 10. Figure 1 , Figure 2 shown.

[0055] The size of the first area 101 in the length direction is 0.5-20 mm. For example, the size of the first area 101 in the length direction includes but is not limited to 0.5 mm, 1 mm, 2 mm, 4 mm, 6 mm, 8 mm, 10 mm, 12 mm, 14 mm, 16 mm, 18 mm, 20 mm or a range between any two of them.

[0056] The functional surface of the current collector 10 refers to the outermost surface in the length direction and the width direction of the current collector, that is, the two largest and opposite surfaces among the six surfaces of the current collector 10. Since the first region 101 and the second region 103 constitute the current collector 10, the definition of the functional surface of the first region 101 and the second region 103 is consistent with the definition of the functional surface of the current collector 10.

[0057] It can be understood that, since the first region 101 and the second region 103 are on the same plane, a functional surface of the first region 101 and a functional surface of the second region 103 may overlap after extension, and another functional surface of the first region 101 and another functional surface of the second region 103 may overlap after extension, for example. Figure 1 and Figure 2 The first functional surface 11 and the second functional surface 12 in the embodiment.

[0058] The first recessed structure 50 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 second region 103 with the first recessed structure 50 with a cavity. For example, mechanical punching, laser pore making, electric or thermal light melting, radiation melting, chemical corrosion, friction punching, and other processing methods can be used.

[0059] The first recessed structure 50 may or may not penetrate the second region 103 in the thickness direction of the second region 103. When the first recessed structure 50 penetrates the second region 103 in the thickness direction of the second region 103, as shown in FIG. Figure 1-Figure 5 as well as Figure 8 As shown, the first recessed structure 50 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 first recessed structure 50; when the first recessed structure 50 does not penetrate the second region 103 in the thickness direction of the second region 103, as shown in FIG. Figure 6 As shown, the opening of the first recessed structure 50 is a notch on the first functional surface 11 .

[0060] The number of the first recessed structures 50 may be one or more. When the number of the first recessed structures 50 is plural, the first recessed structures 50 are distributed in the extension direction of the second region 103, and any two first recessed structures 50 are independent of each other without overlapping or covering.

[0061] It should be noted that the present invention does not specifically limit the three-dimensional shape of the first recessed structure 50. When there are multiple first recessed structures 50, the multiple first recessed structures 50 are independently arranged, and their cross-sectional shapes in the plane where the thickness and width are located and whether they penetrate the second area 103 are independent. For example, the cross-sectional shape of some first recessed structures 50 is a triangle, and the cross-sectional shape of some first recessed structures 50 is a trapezoid; some first recessed structures 50 penetrate the second area 103 (in this case, the first recessed structure 50 can be understood as a through hole), and some first recessed structures 50 do not penetrate the second area 103 (in this case, the first recessed structure can be understood as a blind hole).

[0062] When there are multiple first recessed structures 50, the present invention does not limit the distance between each first recessed structure 50, and the distance between the first recessed structures 50 can be controlled according to actual needs. Similarly, the distance between each first recessed structure 50 can be the same or different.

[0063] At least one side of the first region 101 is stacked with a first safety layer 201 and a first active layer 301 in a direction away from the current collector 10. One side of the first region 101 refers to a functional surface of the first region 101. In detail, the first region 101 can have a functional surface in which the first safety layer 201 and the first active layer 301 are stacked in sequence in a direction away from the current collector 10; the first region 101 can also have two functional surfaces in which the first safety layer 201 and the first active layer 301 are stacked in sequence in a direction away from the current collector 10, such as Figure 1 shown.

[0064] At least a portion of the surface of at least one side of the second region 103 is stacked with the second safety layer 20 and the second active layer 30 in a direction away from the current collector 10. One side of the second region 103 refers to a functional surface of the second region 103. In detail, the second region 103 can be stacked with the second safety layer 20 and the second active layer 30 in a direction away from the current collector 10 on all or part of one functional surface; the second region 103 can also be stacked with the second safety layer 20 and the second active layer 30 in a direction away from the current collector 10 on all or part of two functional surfaces.

[0065] In a specific embodiment, the second safety layer 20 and the second active layer 30 are sequentially stacked on the two functional surface portions of the second region 103 in a direction away from the current collector 10, wherein the second safety layer 20 disposed on the first functional surface 11 of the second region 103 and the second safety layer 20 disposed on the second functional surface 12 may have the same or different sizes in the length direction of the current collector 10, such as Figure 4 shown.

[0066] The composition of the second safety layer 20 and the first safety layer 201 may be the same or different. The composition of the second safety layer 20 and the first safety layer 201 includes at least one of lithium iron phosphate, iron phosphate, lithium iron manganese phosphate, lithium cobalt oxide, ternary materials, lithium-rich manganese, aluminum oxide, boehmite, titanium dioxide, silicon dioxide, zirconium oxide, boron nitride and other materials.

[0067] The composition of the second active layer 30 and the first active layer 301 may be the same or different. When the electrode is a positive electrode, the composition of the second active layer 30 and the first active layer may be selected from at least one of lithium cobalt oxide, lithium iron phosphate, lithium manganese iron phosphate, nickel cobalt manganese lithium, nickel cobalt aluminum lithium, lithium manganese oxide and lithium-rich manganese-based lithium; when the electrode is a negative electrode, the composition of the second active layer 30 and the first active layer 301 may be selected from one or more of natural graphite, artificial graphite, mesophase carbon microbeads, lithium titanate, silicon negative electrode, and silicon-carbon negative electrode.

[0068] By setting a first region 101 of a certain size, the rolling wrinkling problem caused by continuous punching during the preparation of the pole piece can be effectively solved, and the yield rate of the pole piece can be improved. At the same time, the first recessed structure 50 on the second region 103 can increase the contact area between the second safety layer 20 and the second region 103, improve the adhesion between the second safety layer 20 and the second region 103, thereby avoiding the short circuit problem caused by the exposure of the functional surface of the second region 103; in addition, when the pole piece is applied to the battery, when the battery is damaged by external force and causes inward deformation or fracture, the setting of the first recessed structure 50 on the second region 103 makes it easier for the fracture of the current collector to be generated at the first recessed structure 50, at this time, the second safety layer 20 covering the second region 103 can slide and spread inward in the direction of destruction, so that the fracture surface of the current collector is covered and protected by the second safety layer 20, so that it is not exposed, and the resistance when the positive and negative electrodes are in contact with each other is increased, and the short circuit current is effectively reduced, thereby improving the safety performance of the battery, especially the safety performance of the battery under mechanical abuse.

[0069] Furthermore, in a specific embodiment of the present invention, the second safety layer 20 and the second active layer 30 are stacked in at least a portion of the first recessed structure 50 .

[0070] The stacking of the second safety layer 20 and the second active layer 30 in the first recessed structure 50 means that the orthographic projections of the second safety layer 20 and the second active layer 30 along the thickness direction of the current collector overlap with the first recessed structure 50 .

[0071] When the second safety layer 20 and the second active layer 30 are stacked in the first recessed structure 50, when the pole piece is damaged by external force, a fracture occurs at the first recessed structure, and the second active layer slides to the fracture surface of the pole piece along the force direction to prevent the fracture surfaces from contacting each other and causing a short circuit, thereby improving the safety performance of the pole piece.

[0072] Furthermore, in a specific embodiment of the present invention, the electrode sheet is a positive electrode sheet.

[0073] Furthermore, in a specific embodiment of the present invention, a first safety layer 201 and a first active layer 301 are stacked on both sides of the first region 101 in a direction away from the current collector; and / or a second safety layer 20 and a second active layer 30 are stacked on at least part of the surface on both sides of the second region 103 in a direction away from the current collector 10.

[0074] When the pole piece conforms to the above-mentioned configuration, not only can the safety layer be used to protect the pole piece, but also the active material in the active layer can be used to increase the energy density of the pole piece and avoid energy loss.

[0075] Furthermore, in a specific embodiment of the present invention, the surface of the second region 103 includes an adjacent first sub-region 105 and a second sub-region 106; the first sub-region 105 is stacked with a second safety layer 20 and a second active layer 30 in a direction away from the current collector 10; and the second sub-region 106 is provided with a protective layer 40 in a direction away from the current collector 10.

[0076] It can be understood that the current collector 10 has two relative maximum functional surfaces, and the second region 103 also has two relative maximum functional surfaces, such as Figure 1-Figure 6 The first functional surface 11 and the second functional surface 12 in the embodiment.

[0077] Along the length direction of the current collector 10 , the sizes of the first sub-region and the second sub-region in the two functional surfaces of the second region 103 may be the same or different.

[0078] In a specific embodiment, the first sub-region and the second sub-region of the two surfaces of the second region 103 have different sizes, such as Figure 1 and Figure 2 When the sizes of the first sub-region and the second sub-region are different, the requirements of the electrode manufacturing process can be met, and especially when used for a wound battery cell, the safety can be improved while the requirements of the manufacturing process are met.

[0079] The present invention does not limit the composition of the protective layer 40, as long as it can play a protective effect. The provision of the protective layer 40 can increase the internal resistance of the battery and reduce the probability of internal short circuit of the battery. Moreover, the protective layer 40 can cover the exposed functional surface of the second area 103 to prevent the short circuit problem caused by the contact between the second area 103 and the negative electrode sheet. In addition, the protective layer 40 can cover the burrs generated on the surface of the first recessed structure 50 in the single-layer area 106, reduce or eliminate the corrosion of the electrolyte to the first recessed structure 50, and reduce the gas production of the battery.

[0080] Furthermore, in a specific embodiment of the present invention, the stacked second safety layer 20 and the second active layer 30 are provided with a groove, exposing the surface of the second region 103 of the current collector 10, and the first pole ear is located in the groove and electrically connected to the current collector 10; wherein, there is a spacing between the first recessed structure 50 and the groove, and the spacing between the groove and the first recessed structure 50 is not less than 1 mm.

[0081] like Figure 4 As shown, the groove does not contain the first recessed structure 50 , the first recessed structure 50 is located at a portion of the periphery of the groove, and the distance D between the groove and the first recessed structure 50 is not less than 1 mm.

[0082] In the present invention, the groove can be set to be consistent with the width of the second region 103 along the width direction of the second region 103, or can be set to be less than the width of the second region 103 along the width direction of the second region 103. When the groove is consistent with the width of the second region 103 along the width direction of the second region 103, the distance between the edge of the first recessed structure 50 closest to the groove along the length direction and the groove is not less than 1mm. When the size of the groove along the width direction of the second region 103 is smaller than the width of the second region 103, with the groove as a ray around the groove, the distance between the edge of the first recessed structure 50 closest to the groove and the groove is not less than 1mm.

[0083] When the pole tabs in the pole piece are connected to the current collector according to the above connection method, it can not only collect current, but also ensure the stability of the pole tab connection, improve the welding strength, and avoid problems such as the pole tab falling off.

[0084] Furthermore, in a specific embodiment of the present invention, the current collector 10 also includes a third region 102, which is connected to one end of the first region 101 in the length direction and extends along the length direction; at least part of the third region 102 is provided with M second recessed structures 104, M≥1.

[0085] In detail, Figure 2 , Figure 3 As shown, in the length direction, the third region 102, the first region 101 and the second region 103 are arranged in sequence, wherein the third region 102 is provided with no less than one second recessed structure 104, and the opening end of the second recessed structure 104 is located on at least one functional surface of the third region 102.

[0086] The second recessed structure 104 and the first recessed structure 50 are arranged in the same rule.

[0087] When the current collector includes the third region 102 , when the pole piece is used to make a battery cell, the heat inside the battery cell can be dissipated through the third region 102 , and the pole piece can be further prevented from being easily broken during rolling, thereby improving the safety of the pole piece.

[0088] Furthermore, in a specific embodiment of the present invention, the third region 102 includes a perforated region and a tab region, the second recessed structure 104 is arranged in the perforated region, the second tab is electrically connected to the current collector 10 in the tab region, and there is a spacing between the tab region and the perforated region, and the spacing is not less than 1 mm.

[0089] The number of the pole lugs 4 is one or more, and the pole lugs 4 are used to lead out the circuit to achieve connectivity with the peripheral circuit. The pole lug 4 is arranged on at least one side of the third region 102, and the electrical connection can be achieved by laser welding, ultrasonic welding, etc. There is a gap between the pole lug 4 and the second recessed structure 104. By arranging the pole lug 4 in an area with relatively high mechanical strength and without a recessed structure, the welding tension of the pole lug 4 can be increased, and the welding strength can be enhanced. In addition, the thickness of the overall welding area is consistent, which can ensure the consistency of the connection area formed by welding, prevent short circuits, and thus improve the safety performance of the battery.

[0090] The spacing between the tab region and the perforated region is ≥1 mm, specifically, the edge distance between the tab region and the perforated region in the length direction or width direction of the current collector is ≥1 mm. It can also be understood that the distance between the second recessed structure 104 closest to the tab edge and the tab region 107 in the length direction or width direction of the current collector is ≥1 mm, so as to prevent the problem of poor welding of the tab 4 or excessive impedance at the welding point.

[0091] Furthermore, in a specific embodiment of the present invention, in the length direction, the ratio of the sizes of the first region 101, the third region 102 and the second region 103 is (0.5-20): (300-2000): (8-70).

[0092] When the sizes of the first region 101, the third region 102 and the second region 103 are within the above range, the relationship between the various regions can be better balanced, which can not only avoid wrinkling problems, but also ensure that the electrode does not suffer short circuit problems under mechanical damage, and prevent safety problems caused by excessive temperature.

[0093] Further, in a specific embodiment of the present invention, the aperture of the opening end of the first recessed structure 50 is L1, and the center line spacing between adjacent first recessed structures 50 is L2, wherein 1≤L2 / L1≤10; and / or, the depth of the first recessed structure 50 is h, and the thickness of the current collector is H, wherein 1≤H / h≤5; and / or, as Figure 8 As shown, the outer periphery of the opening end of the first recessed structure has a protrusion 501, and the width of the protrusion 501 is w and the height is h1; wherein, 1 μm≤w≤L1×2, 0.1 μm≤h1≤L1×2.

[0094] In detail, the aperture L1 of the opening end of the first recessed structure 50 and the centerline spacing L2 of adjacent first recessed structures 50 satisfy the following relationship: 1≤L2 / L1≤10. It should be noted that the aperture L1 of the opening end of the first recessed structure 50 refers to the diameter of the large end of the first recessed structure 50, and the centerline spacing L2 of adjacent first recessed structures 50 can also be understood as the sum of the distance between two adjacent first recessed structures 50 and the radius of the opening ends of two adjacent first recessed structures 50. By limiting the relationship between L1 and L2, the hole density can be achieved within the above range, thereby taking into account the improvement of the mechanical strength of the pole piece, the safety performance of the battery and the cycle performance.

[0095] The depth h of the first recessed structure 50 and the thickness H of the current collector satisfy the following relationship: 1≤H / h≤5; the depth of the first recessed structure 50 is the dimension of the first recessed structure 50 in the thickness direction of the current collector. When H / h=1, the depth of the first recessed structure 50 is consistent with the thickness of the current collector, that is, the first recessed structure 50 is a through hole, such as Figures 1 to 5 As shown; when 1<H / h≤5, the first recessed structure 50 is a blind hole, such as Figure 6 shown.

[0096] By limiting w, h1 and L1 to satisfy the above relationship, it is avoided that the size of the protrusion 501 is too wide or too thick, which affects the reduction of the loading amount of the second active layer 30 and the bonding force of the second safety layer 20. When the loading amount of the second active layer 30 is reduced, it will lead to a decrease in the active material content, thereby affecting the battery capacity, the stability of the electrode and the energy density of the battery.

[0097] Among them, the protrusion 501 refers to the outer circle structure formed by extending along the radial direction of the inner circle and toward the side away from the opening end of the first recessed structure in the length direction of the current collector, with the opening end of the first recessed structure as the inner circle, at this time, the inner circle and the outer circle form an annular structure, and at the same time, in the thickness direction of the current collector, with the surface where the opening end of the first recessed structure is located as the reference, the protrusion forms a protrusion structure in the direction away from the functional surface of the current collector, and the inner circle and the outer circle in the annular structure are connected by the protrusion structure. The width w of the protrusion 501 is the distance extending toward the side away from the opening end of the first recessed structure based on the inner circle; the height h1 of the protrusion 501 refers to the height of the protrusion in the thickness direction of the current collector, with the surface where the opening end of the first recessed structure is located as the reference, and the direction away from the current collector.

[0098] 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 first recessed structure, and the second edge of the annular protrusion is the edge away from the center direction of the first recessed structure and flush with the functional surface.

[0099] In a specific embodiment, the first recessed structure 50 is a tapered hole, and the taper of the first recessed structure 50 is 1:(0.05-10). The taper of the first recessed structure 50 refers to the ratio of the aperture of the opening end of the first recessed structure 50 to the depth. By limiting the taper of the first recessed structure 50, the setting of tapered holes of different sizes can be achieved.

[0100] Further, in a specific embodiment of the present invention, L1 is 5-100 μm, L2 is 10-1000 μm, h is 1-12 μm, H is 4-12 μm, w is 1-600 μm, and h1 is 0.1-600 μm.

[0101] L1 is 5 to 100 μm, for example, 5 μm, 10 μm, 15 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, or a range consisting of any two thereof; L2 is 10 to 1000 μm, for example, 10 μm, 20 μm, 30 μm, 50 μm, 100 μm, 200 μm, 300 μm, 500 μm, 1000 μm, or a range consisting of any two thereof; h is 1 to 12 μm, for example, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, or a range consisting of any two thereof; H is 4-12μm, for example 4μm, 5μm, 10μm, 12μm or a range consisting of any two thereof; w is 1-600μm, for example 1, 10, 20, 30, 40, 50, 100, 200, 300, 400, 500, 600 or a range consisting of any two thereof; h1 is 0.1-600μm, for example 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 10, 50, 100, 200, 300, 400, 500, 600 or a range consisting of any two thereof.

[0102] 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, resulting in poor protection effect of the recessed structure when external force damage occurs, but also avoid the situation where the recessed structure is too dense, resulting in a decrease in the mechanical properties of the pole piece itself, thereby ensuring the safety performance of the pole piece.

[0103] In another aspect, the utility model provides a battery core, comprising the pole piece as described above.

[0104] It should be noted that the battery cell provided by the present invention is preferably applicable to lithium-ion secondary batteries; of course, it is also applicable to batteries such as sodium-ion batteries, and no excessive limitations are made here.

[0105] 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.

[0106] Since the battery cell of the utility model comprises the pole piece as described above, the battery cell has excellent safety performance.

[0107] Furthermore, in a specific embodiment of the present invention, the battery cell is a wound battery cell, and the opening end of the first recessed structure 50 on the current collector of the pole piece faces a side away from the center of the winding core.

[0108] The opening end of the first recessed structure 50 faces the side away from the center of the battery cell, that is, the opening end of the first recessed structure 50 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 coating material covering the inner surface of the first recessed structure 50 can slide and spread inward in the direction of damage, effectively protecting the fracture surface of the current collector from exposure, thereby avoiding short circuit problems caused by the exposure of the fracture surface of the current collector.

[0109] Furthermore, in a specific embodiment of the present invention, the surface of the second region 103 includes an adjacent first sub-region 105 and a second sub-region 106; the first sub-region 105 is stacked with a second safety layer 20 and a second active layer 30 in a direction away from the current collector 10; the second sub-region 106 is provided with a protective layer 40 in a direction away from the current collector 10; the protective layer 40 is located at the tail along the winding direction of the wound battery cell, and the first region 101 is located at the head along the winding direction of the wound battery cell.

[0110] The wound battery cell of the utility model further comprises a negative electrode sheet and a diaphragm, wherein the diaphragm is used to separate the positive electrode sheet from the negative electrode sheet to avoid direct contact between the positive electrode sheet and the negative electrode sheet.

[0111] 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 first region 101 is located at the head of the winding core, and the protective layer 40 is located at the tail of the winding core.

[0112] Furthermore, in a specific embodiment of the present invention, a hot melt adhesive layer 2 is provided on the outer surface of the wound battery core; the ratio of the orthographic projection area of ​​the hot melt adhesive layer 2 in the second region 103 to the area of ​​the core 1 is greater than 5%.

[0113] like Fig. 9and Fig.10 As shown, a hot melt adhesive layer 2 is provided on the outermost surface of the core 1; at least part of the hot melt adhesive layer 2 is located on a side surface away from the center of the core 1; at least part of the hot melt adhesive layer 2 is projected orthographically on the first plane, and the orthographic projection of the second region on the first plane overlaps, and the overlapping area is B; the orthographic projection area of ​​the core 1 on the first plane is A; it satisfies: B / A×100%>5%, wherein the first plane is perpendicular to the thickness direction of the core 1.

[0114] The outermost surface of the winding core 1 refers to the outermost side away from the center of the winding core 1 , and specifically may be the outermost surface of the outermost pole piece or the outermost surface of the outermost diaphragm, for example, the outer surface of the pole piece or the outer surface of the diaphragm.

[0115] In one embodiment, the hot melt adhesive layer 2 can be arranged at the outermost side of the tail end 3 of the core 1. In this case, the hot melt adhesive layer 2 is not only used to fix the tail end 3 of the core 1, but also can fix the position of the core 1 and the aluminum-plastic film to prevent displacement.

[0116] In another embodiment, the hot melt adhesive layer 2 may not be arranged at the winding core end 3, that is, the hot melt adhesive layer 2 is entirely located on the second area 103 of the pole piece on the side surface away from the center of the winding core. In this case, the hot melt adhesive layer 2 can fix the position of the winding core 1 and the aluminum-plastic film to prevent displacement.

[0117] In the utility model, a large amount of electrolyte will be absorbed inside the first recessed structure 50 in the second area 103. By limiting the overlapping area of ​​the orthographic projection of the hot-melt adhesive layer 2 and the second area 103, the electrolyte in the protective layer of the second area 103 corresponding to the hot-melt adhesive layer 2 is reduced, thereby reducing the swelling and damage of the hot-melt adhesive layer 2 by the electrolyte, and enhancing the adhesion between the hot-melt adhesive layer 2 and the winding core 1, thereby reducing the occurrence of side reactions between the hot-melt adhesive layer 2 and the electrolyte, and at the same time, it can also improve the battery's ability to resist drop impact.

[0118] The thickness of the hot melt adhesive layer 2 is 8 to 60 μm, for example, 8 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30, 40 μm, 50 μm, 60 μm or a range consisting of any two of them. When the thickness of the hot melt adhesive layer is within the above range, it can not only effectively protect the components, have a good fixing effect, improve the stability and reliability of the battery, and thus improve the safety performance of the battery, but also avoid the problem of reduced battery capacity due to excessive thickness of the hot melt adhesive layer.

[0119] The main components of the hot melt layer 2 include at least one of SIS (polystyrene-polyisoprene-polystyrene block copolymer), EVA (ethylene-vinyl acetate copolymer), SBS (styrene-butadiene-styrene triblock copolymer), TPR (thermoplastic rubber), etc. In addition to the main components, the hot melt layer 2 also contains plasticizers, tackifying resins and additives, such as antioxidants.

[0120] In another aspect, the utility model provides a battery, comprising the battery cell as described above.

[0121] 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.

[0122] 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.

[0123] 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.

[0124] The present invention will be further described below through specific embodiments.

[0125] Example 1

[0126] 1. Preparation of positive electrode

[0127] (1) Preparation of the first safety layer slurry and the second safety layer slurry: titanium dioxide, nano-silicon dioxide, polyvinylidene fluoride (PVDF) and N-methylpyrrolidone (NMP) are mixed and stirred evenly to obtain a safety coating slurry; wherein the mass ratio of titanium dioxide, nano-silicon dioxide and PVDF is 85:10:5;

[0128] Preparation of protective layer slurry: 88 parts by mass of boehmite was added to 12 parts by mass of PVDF glue, and then an appropriate amount of solvent NMP was added, and the positive electrode tail protective layer slurry was obtained after stirring evenly.

[0129] Preparation of the first active layer and the second active layer slurry: lithium cobalt oxide (LCO), a conductive agent, polyvinylidene fluoride (PVDF) and N-methylpyrrolidone (NMP) are mixed and stirred evenly to obtain a positive electrode active material layer slurry; wherein the mass ratio of lithium cobalt oxide (LCO), the conductive agent and polyvinylidene fluoride (PVDF) is 97.6:1.05:1.35, and the conductive agent includes conductive carbon black, single-walled carbon nanotubes and multi-walled carbon nanotubes;

[0130] (2) The first safety layer slurry and the second safety layer slurry in step (1) are applied to the first region and the partial region on one side of the second region of the positive electrode collector (aluminum foil), and the first safety layer and the second safety layer are formed after drying; the protective layer slurry is then applied to the second region of the positive electrode collector away from the first region, and the protective layer is formed after drying; finally, the first active layer slurry and the second active layer slurry in step (1) are applied to the surface of the first safety layer and the second safety layer, and the first active layer and the second active layer are formed after drying.

[0131] (3) A punching device is used to punch holes at a preset position on the other side of the positive electrode current collector to form a first recessed structure, wherein the first recessed structure is a conical hole, wherein the length of the first area is 0.5 mm and no punching is performed, and a reserved groove area in the middle of the second area is not punched; wherein the punched conical hole is a through hole, the aperture is 50 μm, the hole spacing is twice the aperture, and the distance between the hole structure closest to the edge of the pole piece and the edge of the pole piece is 2 mm.

[0132] (4) applying the first safety layer slurry and the second safety layer slurry in step (1) to the partial surface of the first region and the other side of the second region of the positive electrode current collector, and forming the first safety layer and the second safety layer after drying; applying the protective layer slurry to the remaining surface of the other side of the second region of the positive electrode current collector, and forming the protective layer after drying; then applying the first active slurry and the matrix active slurry in step (1) on the surface of the first safety layer and the second safety layer, and forming the first active layer and the second active layer after drying; and obtaining the positive electrode film after drying, rolling and slitting;

[0133] (5) The positive electrode ear 4 is welded to the current collector of the groove. The distance between the conical hole closest to the edge of the positive electrode ear and the positive electrode ear is 2 mm. Figure 4 Pole piece shown.

[0134] 2. Preparation of negative electrode sheet

[0135] Graphite, conductive carbon black and carboxymethyl cellulose (CMC) are mixed with deionized water, stirred evenly, and finally a binder styrene-butadiene rubber is added and mixed evenly to obtain a negative electrode slurry; the negative electrode slurry is coated on the functional surface of the negative electrode current collector to form a negative electrode active material layer, and the negative electrode sheet is obtained after drying, rolling and slitting; wherein the mass ratio of graphite, conductive carbon black, carboxymethyl cellulose (CMC) and styrene-butadiene rubber is 97:0.5:1.3:1.2.

[0136] 3. Preparation of batteries

[0137] The positive electrode sheet, separator, and negative electrode sheet are stacked and wound in sequence. Fig. 9The structure shown is affixed with hot melt adhesive to satisfy: B / A×100%=20%, thereby obtaining a winding core; wherein the opening end of the tapered hole faces a side away from the center of the winding core;

[0138] After the core is packaged, the electrolyte is injected, and the battery is produced through processes such as formation, capacity division, and OCV.

[0139] Example 2

[0140] In the preparation process of the positive electrode sheet in this embodiment, the length of the first region is 2 mm, and the rest is the same as in Embodiment 1.

[0141] Example 3

[0142] In the preparation process of the positive electrode sheet in this embodiment, the length of the first region is 5 mm, and the rest is the same as in Embodiment 1.

[0143] Example 4

[0144] In the process of preparing the pole piece in this embodiment, the length of the first region is 10 mm, and the rest is the same as in Embodiment 1.

[0145] Example 5

[0146] In the process of preparing the positive electrode sheet in this embodiment, the parameters of the punching process are adjusted to obtain the electrode sheet, as shown in Table 1. The rest is the same as in Embodiment 3.

[0147] Example 6

[0148] In the process of preparing the positive electrode sheet in this embodiment, the parameters of the punching process are adjusted to obtain the electrode sheet, as shown in Table 1. The rest is the same as in Embodiment 3.

[0149] Example 7

[0150] In the preparation process of the positive electrode sheet of this embodiment, the functional surface of the second region of the positive electrode sheet away from the first region is not coated with a non-conductive coating, and the rest is the same as in Embodiment 3.

[0151] Example 8

[0152] In the process of preparing the positive electrode sheet in this embodiment, the parameters of the punching process are adjusted to obtain the electrode sheet, as shown in Table 1. The rest is the same as in Embodiment 1.

[0153] Example 9

[0154] In the preparation process of the battery in this embodiment, the following ratio is satisfied: B / A×100%=5%, and the rest is the same as in Embodiment 1.

[0155] Example 10

[0156] In the manufacturing process of the battery in this embodiment, the orthographic projection of the hot melt adhesive on the first plane does not overlap with the orthographic projection of the punching area on the first plane, that is, B / A×100%=0%, and the rest is the same as in Embodiment 1.

[0157] Embodiment 11

[0158] In the process of preparing the positive electrode sheet in this embodiment, the parameters and area of ​​the punching process are adjusted to obtain the following Figure 2 For the pole piece shown, the ratio of the sizes of the first region, the second region and the third region is 20:2000:70, as shown in Table 1. The rest is the same as in Example 1.

[0159] Example 12

[0160] In the process of preparing the positive electrode sheet in this embodiment, the parameters and area of ​​the punching process are adjusted to obtain the following Figure 2 For the pole piece shown, the size ratio of the first region, the second region and the third region is 0.5:300:8, as shown in Table 1 for details, and the rest is the same as in Example 1.

[0161] Comparative Example 1

[0162] In the process of preparing the positive electrode sheet of this comparative example, the positive electrode current collector is not subjected to a punching treatment, that is, the positive electrode current collector has no concave structure, and the rest is the same as in Example 1.

[0163] Comparative Example 2

[0164] In the process of preparing the positive electrode sheet in this comparative example, the first safety layer, the second safety layer and the protective layer are not provided on the surface of the positive electrode collector, and the rest is the same as in Example 3.

[0165] Comparative Example 3

[0166] In the preparation process of the positive electrode sheet of this comparative example, the length of the first non-perforated area is 0.2 mm, and the rest is the same as in Example 1.

[0167] Comparative Example 4

[0168] In the preparation process of the positive electrode sheet of this comparative example, the length of the first non-perforated area is 40 mm, and the rest is the same as in Example 1.

[0169] Comparative Example 5

[0170] In the preparation process of the positive electrode sheet of this comparative example, the first region is not set, all positions are punched, and the rest is the same as in Example 1.

[0171] The pole piece parameters provided in all embodiments and comparative examples are shown in Table 1.

[0172] Test example

[0173] 1. Wrinkle test

[0174] The wrinkle phenomenon was detected by observing the appearance of the electrode after rolling during the manufacturing process and recording whether wrinkles occurred. The test results are shown in Table 2.

[0175] 2. Drop test

[0176] Under normal temperature, the lithium-ion battery is charged at 1C constant current to a voltage of 4.5V, then charged at a constant voltage until the current drops to 0.05C, and then the charging is stopped. Then, it is discharged at 1C constant current to 3.0V, and this cycle is repeated for 5T. After the battery is fully charged for the last time, the fully charged battery is freely dropped from a height of 1m onto a concrete plate, and dropped once in each of the positive and negative directions (6 directions) of X, Y, and Z. The voltage, internal resistance, and appearance of the battery before and after the test are recorded. The battery after the test is considered to have passed if it does not catch fire, explode, smoke, or leak. The number of passes / number of tests is the pass rate of the drop test. The number of tests is 10, and the test results are shown in Table 2.

[0177] 3. Heavy object impact test

[0178] Place the battery at room temperature, charge the lithium-ion battery at a constant current of 1C to a voltage of 4.5V, then charge at a constant voltage until the current drops to 0.05C, stop charging, and then discharge at a constant current of 1C to 3.0V, repeat this cycle for 5T, and conduct a heavy object impact test within 24 hours after the battery is fully charged for the last time: place the battery cell on a plane, place a steel column with a diameter of 15.8±0.2mm at the center of the battery cell, with the longitudinal axis of the steel column parallel to the plane, and let a weight of 9.1±0.1kg fall freely from a height of 610±25mm to the steel column above the center of the battery. After the test, observe for 6 hours. If the battery does not catch fire or explode, it is considered to have passed the test. The number of passes / number of tests is the pass rate of the heavy object impact test. The number of tests is 20, and the test results are shown in Table 2.

[0179] 4. Screw extrusion test

[0180] 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 15mm / s. When the equipment pressure reaches 13KN or the stroke reaches 10mm, 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. The number of tests is 10. The test results are shown in Table 2.

[0181] Table 1

[0182]

[0183] Table 2

[0184]

[0185]

[0186] According to Table 1 and Table 2, by setting a first area of ​​0.5 to 20 mm in the length direction of the positive electrode current collector, the problem of wrinkling of the pole piece during the manufacturing process of the battery can be better solved, and the safety performance of the lithium-ion battery will not be deteriorated. In particular, by comparing Examples 1-4 and 3-5, it can be seen that the embodiment can significantly improve the wrinkling phenomenon. By comparing Examples 1-4 and 8, it can be seen that by further limiting the size of the first area to 0.5 to 10 mm, the pass rate of heavy object impact and the pass rate of screw extrusion can be further improved. In addition, by comparing Examples 3 and 5, it can be seen that the first recessed structure on the pole piece is a through hole, which significantly improves the safety performance of the battery compared to the non-through hole. By comparing Examples 1-8 and Examples 9 and 10, it can be seen that in the battery, when B / A×100%>5% is satisfied, the pass rate of the battery drop test can be significantly improved.

[0187] 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.

[0188] 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.

[0189] 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: The pole piece includes a current collector, and the current collector includes a first region and a second region, wherein the first region is connected to one end of the second region in the length direction and extends along the length direction, and the size of the first region in the length direction is 0.5-20 mm; N first recessed structures are arranged on one side of the second region, where N≥1; A first safety layer and a first active layer are stacked on at least one side of the first region in a direction away from the current collector, and a second safety layer and a second active layer are stacked on at least a portion of the surface of at least one side of the second region in a direction away from the current collector.

2. The pole piece according to claim 1, characterized in that: In a direction away from the current collector, the second safety layer and the second active layer are stacked in at least a portion of the first recessed structure.

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

4. The pole piece according to claim 1 or 2, characterized in that: Along the length direction of the current collector, a first safety layer and a first active layer are stacked on both sides of the first region in a direction away from the current collector; and / or a second safety layer and a second active layer are stacked on at least part of the surface on both sides of the second region in a direction away from the current collector.

5. The pole piece according to claim 1 or 2, characterized in that: The surface of the second region includes a first sub-region and a second sub-region that are adjacent; The first sub-region is stacked with the second safety layer and the second active layer in a direction away from the current collector; The second sub-region is provided with a protective layer in a direction away from the current collector.

6. The pole piece according to claim 1, characterized in that: The stacked second safety layer and the second active layer are provided with a groove to expose the surface of the second region of the current collector, and the first electrode tab is located in the groove and is electrically connected to the current collector; There is a distance between the first recessed structure and the groove, and the distance between the groove and the first recessed structure is not less than 1 mm.

7. The pole piece according to any one of claims 1, 2 and 6, characterized in that: The current collector further includes a third region, the third region is connected to one end of the first region in the length direction and extends along the length direction; At least part of the third region is provided with M second recessed structures, where M≥1.

8. The pole piece according to claim 7, characterized in that: The third region includes a perforated region and a tab region, the second recessed structure is arranged in the perforated region, the second tab is electrically connected to the current collector in the tab region, and there is a distance between the tab region and the perforated region, and the distance is not less than 1 mm.

9. The pole piece according to claim 8, characterized in that: In the length direction, the ratio of the sizes of the first region, the second region and the third region is (0.5-20):(300-2000):(8-70).

10. The pole piece according to any one of claims 1, 2, 6 and 8, characterized in that: The aperture of the opening end of the first recessed structure is L1, and the center line spacing between adjacent first recessed structures is L2, wherein 1≤L2 / L1≤10; And / or, the depth of the first recessed structure is h, and the thickness of the current collector is H, wherein 1≤H / h≤5; And / or, the opening end of the first recessed structure has a protrusion, the width of the protrusion is w, and the height is h1; wherein, 1 μm≤w≤L1×2, 0.1 μm≤h1≤L1×2.

11. The pole piece according to claim 10, characterized in that: L1 is 5-100μm, L2 is 10-1000μm, h is 1-12μm, H is 4-12μm, w is 1-600μm, and h1 is 0.1-600μm.

12. A battery cell, characterized in that: A pole piece comprising any one of claims 1 to 11.

13. The battery cell according to claim 12, characterized in that: The battery core is a wound battery core, and the opening end of the first recessed structure faces a side away from the center of the winding core.

14. The battery cell according to claim 13, characterized in that: The surface of the second region includes a first sub-region and a second sub-region that are adjacent; The first sub-region is provided with the second safety layer and the second active layer in a stacked manner in a direction away from the current collector; the second sub-region is provided with a protective layer in a direction away from the current collector; The protective layer is located at a tail portion along a winding direction of the wound battery core, and the first region is located at a head portion along a winding direction of the wound battery core.

15. The battery cell according to claim 13, characterized in that: The outer surface of the wound battery core is provided with a hot melt adhesive layer; The ratio of the orthographic projection area of ​​the hot melt adhesive layer on the second region to the area of ​​the wound battery core is greater than 5%.

16. A battery, characterized in that: Comprising the battery cell as claimed in claim 12.

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