Pole piece, battery cell and battery

Abstract

The utility model provides a pole piece, cell and battery, including current collector, the current collector includes first area and second area, wherein the first area is connected with the one end of second area in the length direction and extends along the length direction; n sunken structures are arranged on the first side of the second area, and N is larger than or equal to 1; the first side of the second area is covered with a first safety bottom coating in the direction away from the current collector, and the first area is provided with a second safety bottom coating and an active layer in a stacked mode in the direction away from the current collector. According to the pole piece provided by the utility model, internal heat generated during thermal runaway of the battery assembled by the pole piece can be reduced, and the thermal runaway probability of the battery is reduced while the energy density is ensured.

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] The wide application of lithium-ion batteries in many fields such as electronic products, power vehicles and energy storage has greatly improved people's social life and production. With the advancement of technology, people have continuously put forward higher requirements for the energy density and power density of lithium-ion batteries. At present, most of them reduce the mass of the pole piece by making holes in the current collector to improve the mass energy density, but at the same time, the hole making can easily cause serious damage to the current collector, resulting in low battery liquid retention, and then lead to electrolyte leakage inside the battery. These internal reasons may cause the battery to generate a lot of heat during charging or discharging, thereby causing thermal runaway. Therefore, how to provide a pole piece that reduces the probability of thermal runaway of the battery is a technical problem that needs to be solved urgently in this field. Utility Model Content

[0003] The utility model provides a pole piece to solve the problem of serious current collector damage caused by hole formation in the prior art, reduce the internal heat generation of a battery assembled with the pole piece, and reduce the probability of thermal runaway of the battery while ensuring energy density.

[0004] The utility model also provides a battery cell and a battery, which include the above-mentioned pole piece, and can reduce the probability of thermal runaway behavior of the battery while ensuring energy density.

[0005] The utility model provides a pole piece, comprising a current collector, wherein 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 a length direction and extends along the length direction;

[0006] The first side of the second region is provided with N recessed structures, where N≥1;

[0007] A first safety primer layer is disposed on the first side of the second region in a direction away from the current collector.

[0008] The first region is stacked with a second safety primer layer and an active layer in a direction away from the current collector.

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

[0010] The pole piece as described above, the size of the opening end of the recessed structure is L1, and the center distance between any two adjacent recessed structures is L2, wherein 1:10<L1:L2<1:1; the current collector includes two largest and opposite surfaces, and the two surfaces include a first functional surface and a second functional surface;

[0011] And / or, the depth of the concave structure is h, and the thickness of the current collector is H, satisfying: 1 ≤ H / h ≤ 5;

[0012] And / or, the edge of the opening of the concave structure has a convex structure, the width of the convex structure is w, and the height is h1, where h1 and w satisfy 1 μm ≤ w ≤ L2 × 2 and 0.1 μm ≤ h1 ≤ L2 × 2;

[0013] Or, the concave structure includes a groove, the opening direction of the groove is flush with the first functional surface, and the outer wall of the groove protrudes from the second functional surface, and the protruding part has a height of h1, and the thickness of the first safety bottom coating is h2, and h1 and h2 satisfy h1:h2 = 1:(2 - 15).

[0014] For the pole piece as described above, L1 is 5 - 100 μm, L2 is 10 - 1000 μm, h is 1 - 6 μm, H is 5 - 20 μm, w is 1 - 600 μm, h1 is 0.01 - 4 μm, and h2 is 0.1 - 50 μm.

[0015] For the pole piece as described above, in the length direction, the size of the first region is b1, and the size of the second region is a1, satisfying b1:a1 = (6 - 15):1.

[0016] For the pole piece as described above, in the length direction, the first side of the second region includes a first sub-region and a second sub-region;

[0017] The first sub-region is adjacent to the first region, and the second sub-region is away from the first region;

[0018] The concave structure is located in the first sub-region;

[0019] The size of the first sub-region in the length direction is l1, and the size of the second sub-region in the length direction is l2, satisfying l1:l2 = (5 - 9):1.

[0020] For the pole piece as described above, in the length direction, the second side that overlaps with the positive projection of the first side includes a third sub-region and a fourth sub-region;

[0021] The third sub-region is adjacent to the first region, and the fourth sub-region is away from the first region;

[0022] The second safety bottom coating and the active layer are stacked in the direction away from the current collector in the third sub-region, and at least part of the surface of the fourth sub-region is covered with the third safety bottom coating in the direction away from the current collector;

[0023] The size of the third sub-region in the length direction is d1, and the size of the fourth sub-region in the length direction is d2, satisfying d1:d2 = (4 - 8):1.

[0024] The pole piece as described above further includes adhesive tape;

[0025] The adhesive tape partially covers the active layer and partially covers the first safety undercoat;

[0026] Wherein, the area of the adhesive tape covering the first safety undercoat is A, the total area of the adhesive tape is B, and A / B×100% = 75% - 95%;

[0027] The overlapping area of the adhesive tape and the projection of the concave structure on the current collector is C, and C / B×100% = 60 - 90%.

[0028] On the other hand, the present invention provides an electric core, including the pole piece as described above.

[0029] For the electric core as described above, the opening of the concave structure faces away from the center of the electric core.

[0030] For the electric core as described above, the electric core is a wound core, the first region is located at the head along the winding direction of the wound core, and the second region is located at the tail along the winding direction of the wound core.

[0031] On the other hand, the present invention provides a battery, including the electric core as described above.

[0032] The implementation of the present invention has at least the following beneficial effects:

[0033] The pole piece provided by the present invention includes a second region of a concave structure at least partially filled and covered by a first safety undercoat, which can not only ensure the loading amount of the first safety undercoat and help to ensure the energy density of the battery, but also avoid problems such as low liquid retention amount and electrolyte leakage of the battery caused by serious damage to the current collector by setting the second region at the end of the current collector. Therefore, while ensuring the energy density, the probability of thermal runaway of the battery is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions of the present invention, the drawings required for describing the embodiments of the present invention will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0035] Figure 1 It is a schematic cross-sectional structure diagram of a pole piece in an embodiment of the present invention;

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

[0037] Figure 3 It is a schematic cross-sectional structure diagram of a pole piece in another embodiment of the present utility model;

[0038] Figure 4 is Figure 2 a schematic top view structure diagram of the pole piece in

[0039] Figure 5 a schematic structure diagram of the pole piece in a core in one embodiment of the present utility model;

[0040] Figure 6 a schematic top view structure diagram of the current collector in the pole piece in one embodiment of the present utility model;

[0041] Figure 7 a schematic cross-sectional structure diagram of the current collector in the pole piece in another embodiment of the present utility model;

[0042] Figure 8 a schematic cross-sectional structure diagram of the current collector in the pole piece in yet another embodiment of the present utility model;

[0043] Figure 9 a schematic cross-sectional structure diagram of the current collector in the pole piece in another embodiment of the present utility model;

[0044] Figure 10 a schematic cross-sectional structure diagram of the current collector in the pole piece in yet another embodiment of the present utility model;

[0045] Figure 11 a schematic cross-sectional structure diagram of the pole piece in yet another embodiment of the present utility model;

[0046] Figure 12 a schematic cross-sectional structure diagram of the pole piece in yet another embodiment of the present utility model;

[0047] Figure 13 a schematic partial cross-sectional structure diagram of the pole piece in one embodiment of the present utility model.

[0048] Explanation of reference numerals:

[0049] 1 - Current collector; 101 - First functional surface; 102 - Second functional surface; 2 - Active layer; 31 - First safety undercoat; 32 - Second safety undercoat; 4 - Protrusion structure; 5 - Depression structure; 6 - Adhesive tape; A1 - Second region; B1 - First region; A11 - First sub-region; A12 - Second sub-region; A21 - Third sub-region, A22 - Fourth sub-region. Detailed embodiments

[0050] To make the objectives, technical solutions, and advantages of the embodiments of the present utility model clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present utility model with reference to the accompanying drawings in the embodiments of the present utility model. Obviously, the described embodiments are some, but not all, of the embodiments of the present utility model. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present utility model without making creative efforts fall within the scope of protection of the present utility model.

[0051] In the description of the present utility model, terms such as "first" and "second" are only used for descriptive purposes, for example, to distinguish each component to more clearly illustrate / explain the technical solution.

[0052] The first aspect of the present utility model provides a pole piece, as Figures 1-3 shown, which includes a current collector 1. The current collector 1 includes a first region B1 and a second region A1. Among them, one end of the first region B1 and the second region A1 are connected in the length direction and extend along the length direction; N recessed structures are provided on the first side of the second region A1, where N≥1; a first safety bottom coating 31 is provided on the first side of the second region A1 in a direction away from the current collector, and a second safety bottom coating 32 and an active layer 2 are stacked on the first region B1 in a direction away from the current collector.

[0053] The present utility model does not limit the polarity of the pole piece, which can be a positive pole piece or a negative pole piece.

[0054] The first side of the first region A1 refers to one side of the first functional surface of the current collector 1. Among them, the functional surface of the current collector refers to the outermost surface where the length direction and the width direction of the current collector are located, that is, the two largest and opposite surfaces among the six surfaces of the current collector. For example Figure 1 and Figure 2 the first functional surface 101 and the second functional surface 102 in

[0055] As Figure 1 shown, the current collector 1 is provided with a second region A1 and a first region B1. Among them, recessed structures 5 are provided on at least a part of the first functional surface of the second region A1. The recessed structures 5 are recessed in a direction away from the first functional surface 101 and the openings are flush with the first functional surface 101 in the length direction.

[0056] The recessed structures 5 are through holes or blind holes, that is, the recessed structures 5 penetrate or do not penetrate the current collector 1 in the thickness direction of the current collector 1. When the recessed structures 5 are blind holes, as Figure 7 、 Figure 9 shown, the ends of the recessed structures 5 are only connected to the first functional surface 101; when the recessed structures 5 are through holes, as Figures 1 to 2 、 Figure 7 、Figure 9 and Figure 10 As shown in Figure 10 , the recessed structure 5 has two oppositely arranged ends, and these two ends are respectively communicated with the first functional surface 101 and the second functional surface 102. Among them, the open end is communicated with the second functional surface 101.

[0057] The number of the recessed structures 5 is one or more. When the number of the recessed structures 5 is multiple, as Figure 6 shown in Figure 6 , the multiple recessed structures 5 are arranged at intervals in the extending direction of the current collector 1. It can also be understood that under the incident light parallel to the thickness direction of the current collector 1, the projections of any two recessed structures 5 on the common plane are independent of each other and have no overlapping relationship or covering relationship. Among them, the common plane refers to the plane parallel to the functional surface of the current collector 1. For example, the multiple recessed structures 5 are uniformly distributed in a linear array in the length direction or the width direction of the current collector 1.

[0058] It should be noted that the present invention does not make special limitations on the three-dimensional shape of the recessed structure 5. When the number of the recessed structures 5 is multiple, the multiple recessed structures 5 are independently arranged, and their cross-sectional shapes in the plane where the thickness and width are located and whether they penetrate the current collector 1 are all independent. For example, the cross-sectional shapes of some of the recessed structures 5 are triangular, and the cross-sectional shapes of some of the recessed structures 5 are rectangular; some of the recessed structures 5 penetrate the current collector 1 (at this time, it can be understood that the recessed structure 5 is a through hole), and some of the recessed structures 5 do not penetrate the current collector 1 (at this time, it can be understood that the recessed structure 5 is a blind hole).

[0059] When the number of the recessed structures 5 is multiple, the multiple recessed structures 5 are independently through holes or blind holes.

[0060] In the second region A1, the first safety bottom coating 31 is filled in the cavity and at least covers part of the plane where the functional surface of the second region A1 is located. In this way, on the basis of maintaining the overall thickness of the electrode sheet unchanged, the second region A1 can enhance the cohesive force of the first safety bottom coating 31 by means of the recessed structure 5, strengthen the adhesion between the first safety bottom coating 31 and the first functional surface 101 on the first functional surface 101, prevent the first safety bottom coating 31 from falling off and causing the first functional surface 101 to be exposed and resulting in internal short circuit, thereby improving the safety performance of the battery, especially improving the passing rate of the battery in mechanical abuse tests, such as foreign object extrusion tests and needle puncture tests.

[0061] Among them, the first safety bottom coating 31 at least covers part of the plane where the functional surface of the second region A1 is located. In one embodiment, in the length direction of the current collector 1, the distance that the first safety bottom coating 31 covers the second region A1 is not less than 1 mm.

[0062] The present utility model provides a recessed structure 5 on the second region A1, which can ensure the loading capacity of the first safety bottom coating 31, ensure the energy density of the battery, and at the same time avoid problems such as low liquid retention capacity of the battery and electrolyte leakage caused by severe damage to the current collector 1, improve the overall thermal stability of the electrode sheet, and thus reduce the probability of thermal runaway of the battery.

[0063] As Figures 1 to 3 shown, the first region B1 is not provided with the recessed structure 5. In this way, the recessed structure 5 is only provided on the second region A1, preventing the slurry from leaking from the recessed structure 5 during the coating process and improving the yield rate of the electrode sheet.

[0064] The first safety bottom coating 31 does not contain a conductive agent, and the material of the first safety bottom coating 31 may include at least one of lithium cobaltate, lithium manganate, lithium nickelate, lithium nickel cobalt manganate, lithium iron phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadium oxyphosphate, lithium-rich manganese-based materials, lithium nickel cobalt aluminate, lithium titanate, alumina, boehmite, titanium dioxide, zirconium oxide, zinc oxide, silicon dioxide, silicon carbide, silicon nitride, conductive polymers and their modified substances.

[0065] The first safety bottom coating 31 may further include a binder, specifically including at least one of polyvinylidene fluoride, polyvinylidene chloride, polytetrafluoroethylene, hexafluoropropylene, polyacrylic acid, polyacrylate, polyamide, polyacrylonitrile, carboxymethyl cellulose sodium, polyvinylpyrrolidone, polyethylene ether, polymethyl methacrylate, styrene-butadiene rubber, polyethylene oxide, styrene-butadiene latex, styrene-acrylic latex, ethyl polyacrylate, butyl polymethacrylate, ethylene-vinyl acetate copolymer, polyvinyl acetate and at least one of their modified substances or copolymers. For example, copolymers of polyvinylidene fluoride include polyvinylidene fluoride-trifluoroethylene, polyvinylidene fluoride-tetrafluoroethylene, polyvinylidene fluoride-hexafluoroethylene, polyvinylidene fluoride-hexafluoropropylene.

[0066] The active layer 2 includes an active material. The present utility model does not limit the specific type of the active material. For example, when the electrode sheet is a positive electrode sheet, the active material may include at least one of lithium cobaltate, lithium manganate, lithium nickelate, lithium nickel cobalt manganate, lithium iron phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadium oxyphosphate, lithium-rich manganese-based materials, lithium nickel cobalt aluminate; when the electrode sheet is a negative electrode sheet, the active material may include at least one of graphite, hard carbon, and silicon-based materials.

[0067] Furthermore, in a specific embodiment of the present utility model, the electrode sheet is a positive electrode sheet.

[0068] Further, in a specific embodiment of the present utility model, the size of the opening end of the recessed structure 5 is L1, and the center distance between any two adjacent recessed structures 5 is L2, where 1:10 < L1:L2 < 1:1; and / or, the depth of the recessed structure 5 is h, and the thickness of the current collector 1 is H, satisfying 1 ≤ H / h ≤ 5; and / or, the edge of the opening of the recessed structure 5 has a raised structure 4, the width of the raised structure 4 is w, and the height is h1, where h1 and w satisfy 1 μm ≤ w ≤ L2×2, 0.1 μm ≤ h1 ≤ L2×2; or, the recessed structure 4 includes a groove, the opening direction of the groove is flush with the first functional surface 101, and the outer wall of the groove protrudes from the second functional surface 102, and the protruding part has a height of h1, and the thickness of the first safety bottom coating 31 is h2, and h1 and h2 satisfy h1:h2 = 1:(2 - 15).

[0069] Further, in a specific embodiment of the present utility model, as Figures 7-11 shown, the size of the opening end of the recessed structure 5 is L1, and the center distance between any two adjacent recessed structures 5 is L2, where 1:10 < L1:L2 < 1:1.

[0070] Wherein, the size L1 of the opening end of the recessed structure 5 refers to the distance between the two points with the farthest distance on the opening edge. For example, when the opening is circular, the size L1 of the opening end of the recessed structure 5 is the length of the diameter of the circle; when the opening is rectangular, the size L1 of the opening end of the recessed structure 5 is the length of the diagonal of the rectangle.

[0071] It can be understood that when there are recessed structures 5 with different three-dimensional shapes in the same current collector 1, the size L1 of the opening of the recessed structure 5 at this time is the maximum value of the opening sizes of all the recessed structures 5.

[0072] Similarly, the distance L2 between the centers of the openings of the adjacent recessed structures 5 is the maximum value among the distances between the centers of the openings of all the adjacent recessed structures 5.

[0073] When the recessed structure 5 is a hole structure, the size L1 of the recessed structure 5 refers to the diameter of the recessed structure 5 on the second functional surface 101; the center line distance L2 between the adjacent recessed structures 5 can be understood as the sum of the distance between the adjacent two recessed structures 5 and the radii of the opening ends of the adjacent two recessed structures 5. By limiting the relationship formula of L1 and L2, the hole density can be within the above range, so as to balance the improvement of the mechanical strength of the current collector 1, the safety performance and the cycle performance of the battery.

[0074] In one embodiment, the depth h of the recessed structure 5 and the thickness H of the current collector 1 satisfy the following relationship: 1 ≤ H / h ≤ 5. The depth of the recessed structure 5 is the dimension of the recessed structure 5 in the thickness direction of the current collector 1. When H / h = 1, at this time, the depth of the recessed structure 5 is the same as the thickness of the current collector 1, that is, the recessed structure 5 is a through hole, as shown in Figure 9 , Figure 10 and Figure 11 ; when 1 < H / h ≤ 5, as shown in Figure 7 and 9 .

[0075] By defining the relationship between the depth of the recessed structure and the thickness of the current collector, on the one hand, when the battery including the above-mentioned electrode sheet is damaged by an external force, the current collector 1 is more likely to break along the position of the recessed structure 3, reducing the probability of the exposure of the current collector cross-section in the current collector 1. When the current collector 1 breaks, the first safety bottom coating can slide along the fracture to the fracture surface of the current collector 1 to provide protection for the fracture surface.

[0076] As shown in Figure 13 , the edge of the opening of the recessed structure 5 has a raised structure 4. The width of the raised structure 4 is w, and the height is h1. Among them, h1 and w satisfy 1 μm ≤ w ≤ L2 × 2, 0.1 μm ≤ h1 ≤ L2 × 2; or, as shown in Figure 12 , the recessed structure 5 includes a groove. The opening direction of the groove is flush with the first functional surface, and the outer wall of the groove protrudes from the second functional surface 102. The protruding part has a height of h1, and the thickness of the first safety bottom coating is h2. h1 and h2 satisfy h1:h2 = 1:(2 - 15).

[0077] The height of the raised structure 4 is h1, and the thickness of the first safety bottom coating 31 is h2, satisfying h1:h2 = 1:(2 - 15). By regulating the relationship between the height of the raised structure 4 and the thickness of the first safety bottom coating 31, it is avoided that the protrusion is too thick and affects the loading amount and adhesion of the first safety bottom coating 31 on the second functional surface 102, so as to ensure the thermal stability of the electrode sheet and the energy density of the battery when the electrode sheet is damaged by an external force.

[0078] Furthermore, in a specific embodiment of the present invention, L1 is 5 - 100 μm; L2 is 10 - 1000 μm; h is 1 - 6 μm, H is 5 - 20 μm, w is 1 - 600 μm, h1 is 0.1 - 4 μm, and h2 is 0.1 - 50 μm.

[0079] Specifically, L1 includes but is not limited to 5μm, 10μm, 20μm, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, 90μm, 100μm or a range composed of any two of them; L2 includes but is not limited to 10μm, 50μm, 100μm, 200μm, 300μm, 400μm, 500μm, 600μm, 700μm, 800μm, 900μm, 1000μm or a range composed of any two of them; h includes but is not limited to 1μm, 1.5μm, 2.0μm, 2.5μm, 3.0μm, 3.5μm, 4.0μm, 4.5μm, 5.0μm, 5.5μm, 6.0μm or a range composed of any two of them; H includes but is not limited to a range between 5μm, 8μm, 10μm, 13μm, 15μm, 18μm, 20μm or any two of them, w includes but is not limited to a range between 1μm, 5μm, 10μm, 50μm, 100μm, 200μm, 300μm, 400μm, 500μm, 600μm or any two of them, h1 includes but is not limited to a range between 0.1μm, 0.5μm, 1μm, 2μm, 3μm, 4μm, 5μm or any two of them, and h2 includes but is not limited to a range between 0.1μm, 1μm, 5μm, 10μm, 20μm, 30μm, 40μm, 50μm or any two of them.

[0080] When the size of the recessed structure meets the above range, it is possible to prevent the electrolyte from directly contacting the foil, thereby avoiding side reactions. A reasonable spacing and recess depth are beneficial to the slurry distribution in the second region and improve the safety performance of the battery cell.

[0081] Furthermore, in a specific embodiment of the present invention, in the length direction, the size of the first region B1 is b1, and the size of the second region A1 is a1, satisfying b1:a1=(6 - 15):1.

[0082] Specifically, the size of the second region A1 in the length direction refers to the size of the second region A1 in the length direction of the current collector 1.

[0083] Similarly, the size of the first region B1 in the length direction refers to the size of the first region B1 in the length direction of the current collector 1.

[0084] The ratio of the size of the second region A1 to the size of the first region B1 in the length direction is (6 - 15):1. For example, the ratio of the sizes includes but is not limited to b1:a1 = 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 or a range composed of any two of them.

[0085] When the dimensions of the second region A1 and the first region B1 in the length direction conform to the above rules, not only can the electrode have excellent safety performance, but also the energy density of the electrode can be maintained, and the electrochemical performance of the electrode can be improved.

[0086] Further, in a specific embodiment of the present invention, in the length direction, the first side of the second region A1 includes a first sub-region A11 and a second sub-region A12; the first sub-region A11 is adjacent to the first region B1, and the second sub-region A12 is away from the first region B1; the concave structure 5 is located in the first sub-region A11; the dimension of the first sub-region A11 in the length direction is l1, and the dimension of the second sub-region A12 in the length direction is l2, satisfying l1:l2=(5-9):1.

[0087] When the second region A1 of the electrode satisfies the above conditions, the electrode is covered with an appropriate first safety bottom coating, and the safety performance of the battery cell is improved.

[0088] Further, in a specific embodiment of the present invention, as Figure 1 、 Figure 3 shown, in the length direction, the second side that overlaps with the positive projection of the first side includes a third sub-region A21 and a fourth sub-region A22; the third sub-region A21 is adjacent to the first region B1, and the fourth sub-region A22 is away from the first region B1; the second safety bottom coating 32 and the active layer 2 are stacked in the direction away from the current collector 1 in the third sub-region A21, and at least part of the surface of the fourth sub-region A22 is covered with a third safety bottom coating 33 in the direction away from the current collector; the dimension of the third sub-region A21 in the length direction is d1, and the dimension of the fourth sub-region A22 in the length direction is d2, satisfying d1:d2=(4-8):1.

[0089] Wherein, the second side that overlaps with the positive projection of the first side refers to the plane where the second functional surface of the current collector 1 is located.

[0090] In a specific embodiment, the length dimension of the overlapping part of the positive projection of the third sub-region A21 in the thickness direction of the current collector and the third sub-region A11 is not less than 1 mm.

[0091] Specifically, the dimension ratio of the third sub-region to the fourth sub-region includes, but is not limited to, d1:d2 = 4:1, 5:1, 6:1, 7:1, 8:1 or the range composed of any two of them.

[0092] When the dimension relationship between the third sub-region and the fourth sub-region satisfies the above conditions, the proportion of the active layer can be guaranteed, the energy density of the battery cell can be improved, and the situation of energy density decrease caused by insufficient proportion of the active layer can be avoided.

[0093] Further, in a specific embodiment of the present invention, asFigure 1 and Figure 4 As shown, it further includes an adhesive tape 6; the adhesive tape 6 partially covers the active layer 2 and partially covers the first safety undercoat 31; wherein, the area of the adhesive tape 6 covering the first safety undercoat 31 is A, the total area of the adhesive tape is B, and A / B×100% = 75% - 95%; the overlapping area of the adhesive tape 6 and the concave structure 5 in the projection on the current collector 1 is C, and C / B×100% = 60 - 90%.

[0094] As Figure 1 shown, on the surface of the part of the first safety undercoat 31 away from the current collector 1, the surface of the part of the active layer away from the current collector 1, and the non-overlapping end face of the active layer close to the first safety undercoat 31, the adhesive tape 6 is continuously arranged.

[0095] By arranging the adhesive tape 6, it can prevent the burrs at the ends of the active layer and the first safety undercoat 31 from piercing the separator and causing a short-circuit problem, thereby further improving the yield rate of the battery. At the same time, connecting the active layer and the first safety undercoat 31 with the adhesive tape can ensure that the adhesive tape 6 completely covers the second area A1 and the first area B1.

[0096] Under the incident light along the thickness direction of the current collector 1, the projected area of the adhesive tape 6 on the current collector 1 is B, and the area of the overlapping region between the projection of the first safety undercoat 31 on the current collector 1 and the projection of the adhesive tape 6 on the current collector 1 is A. In some embodiments, A / B×100% = 75% - 95%.

[0097] By defining A / B×100% = 75% - 95%, it is ensured that 75% - 95% of the adhesive tape 6 is pasted on the surface of the first safety undercoat 31. Correspondingly, the remaining adhesive tape 6 is pasted on the surface of the active layer.

[0098] Under the incident light along the thickness direction of the current collector 1, the overlapping area of the projection of the adhesive tape 6 and the concave structure 5 on the current collector 1 is C.

[0099] In some embodiments, the overlapping area of the orthographic projection of the adhesive tape 6 and the concave structure 5 on the current collector 1 is C, the projected area of the adhesive tape 6 on the current collector 1 is B, and C / B×100% = 60% - 90%.

[0100] By defining C / B×100% = 60% - 90%, the adhesive tape 6 can further avoid the exposure of the burrs of the concave structure 5, resulting in the corrosion of the concave structure 5 by the electrolyte and reducing the gas generation of the battery.

[0101] On the other hand, the present utility model provides a battery cell including the electrode sheet as described above.

[0102] It should be noted that the battery cell provided by the present utility model is preferably applicable to lithium-ion batteries; of course, it is also applicable to battery cells such as sodium-ion batteries, etc., and no excessive limitations are made here.

[0103] The wound core of the present utility model further includes a positive electrode sheet and a separator. The separator is used to separate the positive electrode sheet and the negative electrode sheet to prevent the positive electrode sheet and the negative electrode sheet from coming into direct contact.

[0104] The positive electrode sheet can be of a conventional structure or an ear-centered structure. Among them, the conventional structure means that the positive ear is located at one end of the positive electrode sheet, and the ear-centered structure means that the positive ear is located in the middle of the positive electrode sheet. The present utility model does not make excessive limitations here.

[0105] Furthermore, in a specific embodiment of the present utility model, the opening of the concave structure faces away from the center of the battery cell.

[0106] When the opening of the concave structure in the battery cell faces away from the center of the battery cell, when the battery cell is damaged by an external force and causes inward deformation or fracture, the first safety bottom coating covering the concave structure can slide and spread towards the inside along the direction of the damage, effectively protecting the fracture surface of the current collector 1 from being exposed, thereby avoiding the short-circuit problem caused by the exposure of the fracture surface of the current collector 1.

[0107] Furthermore, in a specific embodiment of the present utility model, as Figure 5 shown, the battery cell is a wound core, the first region is located at the head along the winding direction of the wound core, and the second region is located at the tail along the winding direction of the wound core.

[0108] Specifically, the positive electrode sheet, the separator, and the negative electrode sheet are stacked in sequence to obtain a stacked body, and the stacked body is wound along the winding direction to obtain the wound core provided by the present utility model. During the winding process, one end of the stacked body is used as the starting end until the winding operation is completed. At this time, the first region is located inside the wound core, the second region is outside the wound core, that is, the end of the winding, and the protective layer is located at the end of the winding of the wound core.

[0109] Setting the second region on the outermost layer can protect the internal wound core to the greatest extent; when a short circuit occurs inside the wound core, the particles in the second region can extend to all short-circuit points to the greatest extent.

[0110] On the other hand, the present utility model provides a battery including the battery cell as described above.

[0111] The battery of the present utility model is preferably a lithium-ion battery, including but not limited to soft-pack batteries, square batteries, cylindrical batteries, etc.

[0112] A battery for charging / discharging can be formed by installing the battery cell and the protection circuit together inside the aluminum-plastic film. The quality of the battery cell directly determines the quality of the battery. Due to the adoption of the above-mentioned electrode sheets, the battery of the present utility model performs excellently in terms of safety performance and the like.

[0113] The above battery further includes an electrolyte. Specifically, after the battery cell is encapsulated, the electrolyte is injected, and the battery is obtained through processes such as formation, grading, and OCV.

[0114] The present utility model will be further described below through specific examples and comparative examples. Unless otherwise specified, the reagents, materials, and instruments used below are all conventional reagents, conventional materials, and conventional instruments, which can be commercially purchased, and the reagents and materials involved can also be synthesized by conventional synthesis methods.

[0115] Example 1

[0116] I. Preparation of Electrode Sheets

[0117] (1) Preparation of the first safety bottom coating and the second safety bottom coating slurries: Mix titanium dioxide: conductive carbon black (SP): polyvinylidene fluoride (PVDF) with N-methylpyrrolidone (NMP), and after stirring evenly, obtain the protective layer slurry; wherein, the mass ratio of titanium dioxide: conductive carbon black (SP): polyvinylidene fluoride (PVDF) is 95:1:4;

[0118] Preparation of the active layer slurry: Mix lithium cobalt oxide (LCO), conductive carbon black (SP), polyvinylidene fluoride (PVDF) with N-methylpyrrolidone (NMP), and after stirring evenly, obtain the positive electrode active material layer slurry; wherein, the mass ratio of LCO, SP, and PVDF is 97.5:1:1.5;

[0119] Preparation of the third safety coating slurry: Mix aluminum oxide (Al2O3): polyvinylidene fluoride (PVDF) with N-methylpyrrolidone (NMP), and after stirring evenly, obtain the first safety coating slurry; wherein, the mass ratio of Al2O3 and PVDF is 90:10;

[0120] (2) Use a punching device to perform punching treatment on a preset position of the current collector 1 to form a concave structure 5, and the specific parameters are shown in Table 1;

[0121] (3) Coating the first safety bottom coating slurry and the third safety coating in step (1) on the first functional surface 201, the second functional surface 202 of the first area of the current collector 1 and the second functional surface 202 of the second area respectively, and drying to form the first safety bottom coating and the third safety coating; coating the first safety bottom coating slurry on the first functional surface 101 of the second area, and drying to form the first safety bottom coating 31; coating the active layer slurry on the surfaces of the first safety bottom coating and the second safety bottom coating (as Figure 2 shown), drying to form the active layer, and obtaining the electrode sheet after rolling and slitting.

[0122] II. Preparation of the negative electrode sheet

[0123] Mix graphite, styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC) and deionized water, and stir evenly to obtain the negative electrode slurry; coat the negative electrode slurry on the surface of the negative electrode current collector, and obtain the negative electrode sheet after drying, rolling and slitting; among them, the mass ratio of graphite, styrene-butadiene rubber (SBR), and carboxymethyl cellulose (CMC) is 97:1.5:1.5.

[0124] III. Preparation of the battery

[0125] Stack and wind the electrode sheet, the separator, and the negative electrode sheet in sequence to obtain the wound core; among them, the first area is located at the head along the winding direction of the wound core, the second area is located at the tail along the winding direction of the wound core, and the open end of the concave structure 5 is far from the winding center.

[0126] Example 2

[0127] The preparation process of this example is basically the same as that of Example 1, the difference is that: in the preparation of the electrode sheet, coat the first safety bottom coating slurry and the third safety bottom coating slurry on the first functional surface 101 and the second functional surface 102 of the second area A1 (as Figure 1 shown), under other unchanged conditions, obtain the electrode sheet of this example;

[0128] In the preparation process of the battery, replace the electrode sheet of Example 1 with the electrode sheet of this example.

[0129] Example 3

[0130] The preparation process of this example is basically the same as that of Example 1, the difference is that; in the preparation of the electrode sheet, punch holes in both the first functional surface 101 and the second functional surface 102, under other unchanged conditions, obtain the electrode sheet of this example, and the specific parameters are shown in Table 1;

[0131] In the preparation process of the battery, replace the electrode sheet of Example 1 with the electrode sheet of this example.

[0132] Example 4

[0133] The preparation process of this example is basically the same as that of Example 1, except that in the preparation of the electrode sheet, no adhesive tape is used to cover the junction between the first safety bottom coating and the active layer, and other conditions remain unchanged, thus obtaining the electrode sheet of this example. For specific parameters, see Table 1;

[0134] During the preparation of the battery, the electrode sheet of Example 1 is replaced with the electrode sheet of this example.

[0135] Example 5

[0136] The preparation process of this example is basically the same as that of Example 1, except that in the preparation of the electrode sheet, the overlapping projection size of the first safety bottom coating 31 and the first sub-region A11 in the second region A1 is set to be <1 mm, and other conditions remain unchanged, thus obtaining the electrode sheet of this example. For specific parameters, see Table 1;

[0137] During the preparation of the battery, the electrode sheet of Example 1 is replaced with the electrode sheet of this example.

[0138] Example 6

[0139] The preparation process of this example is basically the same as that of Example 1, except that in the preparation of the electrode sheet, the overlapping projection size of the second active functional layer 21 and the first sub-region A11 in the second region A1 is set to be <1 mm, and other conditions remain unchanged, thus obtaining the electrode sheet of this example. For specific parameters, see Table 1;

[0140] During the preparation of the battery, the electrode sheet of Example 1 is replaced with the electrode sheet of this example.

[0141] Example 7

[0142] The preparation process of this example is basically the same as that of Example 1, except that in the preparation of the electrode sheet, A / B = 30% and C / B = 5% are set, and other conditions remain unchanged, thus obtaining the electrode sheet of this example. For specific parameters, see Table 1;

[0143] During the preparation of the battery, the electrode sheet of Example 1 is replaced with the electrode sheet of this example.

[0144] Example 8

[0145] The preparation process of this example is basically the same as that of Example 1, except that in the preparation of the electrode sheet, L2 / L1 = 15% is set, and other conditions remain unchanged, thus obtaining the electrode sheet of this example. For specific parameters, see Table 1;

[0146] During the preparation of the battery, the electrode sheet of Example 1 is replaced with the electrode sheet of this example.

[0147] Example 9

[0148] The preparation process of this example is basically the same as that of Example 1, except that in the preparation of the electrode sheet, H / h = 10 is set, and other conditions remain unchanged to obtain the electrode sheet of this example. For specific parameters, see Table 1;

[0149] In the process of preparing the battery, the electrode sheet of Example 1 is replaced with the electrode sheet of this example.

[0150] Example 10

[0151] The preparation process of this example is basically the same as that of Example 1, except that in the preparation of the electrode sheet, h2 / h1 = 18 is set, and other conditions remain unchanged to obtain the electrode sheet of this example. For specific parameters, see Table 1;

[0152] In the process of preparing the battery, the electrode sheet of Example 1 is replaced with the electrode sheet of this example.

[0153] Example 11

[0154] The preparation process of this example is basically the same as that of Example 1, except that in the preparation of the electrode sheet, h1 / w = 0.01 is set, and other conditions remain unchanged to obtain the electrode sheet of this example. For specific parameters, see Table 1;

[0155] In the process of preparing the battery, the electrode sheet of Example 1 is replaced with the electrode sheet of this example.

[0156] Example 12

[0157] The preparation process of this example is basically the same as that of Example 1, except that in the preparation of the electrode sheet, a1 / b1 = 20 is set, and other conditions remain unchanged to obtain the electrode sheet of this example. For specific parameters, see Table 1;

[0158] In the process of preparing the battery, the electrode sheet of Example 1 is replaced with the electrode sheet of this example.

[0159] Example 13

[0160] The preparation process of this example is basically the same as that of Example 1, except that in the preparation of the electrode sheet, l1:l2 = 2 is set, and other conditions remain unchanged to obtain the electrode sheet of this example. For specific parameters, see Table 1;

[0161] In the process of preparing the battery, the electrode sheet of Example 1 is replaced with the electrode sheet of this example.

[0162] Example 14

[0163] The preparation process of this example is basically the same as that of Example 1, except that in the preparation of the electrode sheet, d1:d2 = 1 is set, and other conditions remain unchanged to obtain the electrode sheet of this example. For specific parameters, see Table 1;

[0164] During the preparation of the battery, the electrode sheet of Example 1 was replaced with the electrode sheet of this example.

[0165] Example 15

[0166] The preparation process of this example is basically the same as that of Example 1, except that the punching parameters and punching positions are adjusted, and other conditions remain unchanged, to obtain the electrode sheet of this example. The specific parameters are shown in Table 1;

[0167] During the preparation of the battery, the electrode sheet of Example 1 was replaced with the electrode sheet of this example.

[0168] Comparative Example 1

[0169] The preparation process of this example is basically the same as that of Example 1, except that in the preparation of the electrode sheet, step (2) is omitted, that is, no punching treatment is performed, and other conditions remain unchanged, to obtain the electrode sheet of this example;

[0170] During the preparation of the battery, the electrode sheet of Example 1 was replaced with the electrode sheet of this example.

[0171] Comparative Example 2

[0172] The preparation process of this example is basically the same as that of Example 2, except that in the preparation of the electrode sheet, step (2) is omitted, that is, no punching treatment is performed, and other conditions remain unchanged, to obtain the electrode sheet of this example;

[0173] During the preparation of the battery, the electrode sheet of Example 1 was replaced with the electrode sheet of this example.

[0174] Comparative Example 3

[0175] The preparation process of this example is basically the same as that of Example 1, except that in the preparation of the electrode sheet, the first safety bottom coating is cancelled, and only the protective layer is retained, and other conditions remain unchanged, to obtain the electrode sheet of this example. The specific parameters are shown in Table 1;

[0176] During the preparation of the battery, the electrode sheet of Example 1 was replaced with the electrode sheet of this example.

[0177] Comparative Example 4

[0178] The preparation process of this example is basically the same as that of Example 1, except that in the preparation of the electrode sheet, the protective layer slurry is not coated, that is, the electrode sheet does not have a protective layer, and other conditions remain unchanged, to obtain the electrode sheet of this example. The specific parameters are shown in Table 1;

[0179] During the preparation of the battery, the electrode sheet of Example 1 was replaced with the electrode sheet of this example.

[0180] Comparative Example 5

[0181] The preparation process of this example is basically the same as that of Example 1, with the difference that; in the preparation of the electrode sheet, the second region is not set, and the first region is extended along the length direction to replace the second region, and other conditions remain unchanged, obtaining the electrode sheet of this example. For specific parameters, see Table 1;

[0182] During the preparation process of the battery, the electrode sheet of Example 1 is replaced with the electrode sheet of this example.

[0183] For the specific parameters of the electrode sheets in the examples and comparative examples, see Table 1.

[0184] Test Example

[0185] 1. Foreign Object Extrusion Pass Rate Test

[0186] Fully charge the battery, keep the test environment temperature at 25 ± 2 °C, place a screw with a diameter of 2 mm and a length of 3.5 mm in the middle of the battery, and use an extruder to extrude the battery vertically at a speed of 15 mm / s. Stop when the pressure reaches 13 KN or the extrusion stroke reaches 10 mm, and keep it for 100 s. If the battery does not catch fire or explode, it is considered a pass. The pass rate is calculated as the number of passes / the number of tests, and the number of tests is 10.

[0187] 2. Needle Penetration Pass Rate Test

[0188] Fully charge the battery, keep the test environment temperature at 25 ± 2 °C, use a 4 mm steel needle to pierce the center of the battery vertically at a speed of 30 mm / s, and keep it for 5 min. If the battery does not catch fire or explode, it is considered a pass. The pass rate is calculated as the number of passes / the number of tests, and the number of tests is 10.

[0189] 3. Energy Density Test

[0190] Charge the lithium-ion battery to the upper limit voltage of 4.45 V, then discharge it at 0.2 C to the lower limit voltage of 3.0 V. Record the discharge energy as E, and then calculate the energy density of the lithium-ion battery through the following formula:

[0191] Energy density = E / (length × width × height of the lithium-ion battery); or,

[0192] Use a battery charge and discharge tester to charge the battery at a constant current of 0.5 C to 4.25 V at 25 °C, then charge it at a constant voltage until the current drops to 0.02 C. After standing for 5 min, discharge the battery at a constant current of 0.5 C to 2.5 V, and record the first discharge capacity Q 放 and the first discharge energy E 放 , weigh the battery mass and record it as W, and calculate the mass energy density ED = E 放 / W.

[0193] 4. Cycle Performance Test

[0194] Test method: At 25°C, charge and discharge the lithium-ion battery at a rate of 1.5C charge / 0.5C discharge, and record the discharge capacity Q2 of its 500th charge and discharge and the discharge capacity Q1 of its first charge and discharge. The capacity retention rate = Q2 / Q1 × 100%.

[0195] 5. Test on the expansion rate of the battery after 500 cycles

[0196] Test method: At 25°C, measure the battery thickness D1 before the battery undergoes cyclic testing; after 500 cycles, measure the battery thickness D2 again, and compare the change in the cell thickness, that is, the battery expansion rate T = (D2 - D1) / D1.

[0197] The test results are shown in Table 2.

[0198] Table 1

[0199]

[0200]

[0201] Table 2

[0202]

[0203]

[0204] By comparing the examples and comparative examples, it can be seen that for the pole piece provided by the present utility model, by providing a concave structure in the second region and in cooperation with the first region, it is possible to significantly reduce the probability of thermal runaway of the battery while ensuring the energy density, electrochemical performance, and expansion rate of the battery.

[0205] The preferred specific embodiments of the present utility model and the experimental verification have been described in detail above. It should be understood that those of ordinary skill in the art can make many modifications and variations according to the concept of the present utility model without creative labor. Therefore, all technical solutions that can be obtained by those skilled in the art in the technical field based on the concept of the present utility model through logical analysis, reasoning, or limited experiments on the basis of the prior art should fall within the protection scope of the present utility model.

Claims

1. A pole piece, characterized in that: A current collector is included, wherein 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 a length direction and extends along the length direction; The first side of the second region is provided with N recessed structures, N ≥ 1; A first safety primer layer is disposed on the first side of the second region in a direction away from the current collector. The first region is stacked with a second safety primer layer and an active layer in a direction away from the current collector.

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 size of the opening end of the recessed structure is L1, and the center distance between any two adjacent recessed structures is L2, wherein 1:10<L1:L2<1:1; the current collector includes two largest and opposite surfaces, and the two surfaces include a first functional surface and a second functional surface; And / or, the depth of the recessed structure is h, the thickness of the current collector is H, and the following conditions are satisfied: 1≤H / h≤5; And / or, the edge of the opening of the recessed structure has a convex structure, the width of the convex structure is w, and the height is h1, wherein h1 and w satisfy, 1 μm≤w≤L2×2, 0.1 μm≤h1≤L2×2; Or, the recessed structure includes a groove, the opening direction of the groove is flush with the first functional surface, and the outer wall of the groove protrudes from the second functional surface, the height of the protruding part is h1, the thickness of the first safety primer layer is h2, and h1 and h2 satisfy, h1:h2=1:(2-15).

4. The pole piece according to claim 3, characterized in that: L1 is 5-100μm, L2 is 10-1000μm, h is 1-6μm, H is 5-20μm, w is 1-600μm, h1 is 0.01-4μm, and h2 is 0.1-50μm.

5. The pole piece according to claim 1, characterized in that: In the length direction, the size of the first area is b1, and the size of the second area is a1, satisfying b1:a1=(6-15):

1.

6. The pole piece according to claim 1, characterized in that: In the length direction, the first side of the second region includes a first sub-region and a second sub-region; The first sub-region is adjacent to the first region, and the second sub-region is far away from the first region; The recessed structure is located in the first sub-region; The size of the first sub-region in the length direction is l1, and the size of the second sub-region in the length direction is l2, satisfying l1:l2=(5-9):

1.

7. The pole piece according to claim 1, characterized in that: In the length direction, the second side overlapping with the orthographic projection of the first side includes a third sub-region and a fourth sub-region; The third sub-region is adjacent to the first region, and the fourth sub-region is far away from the first region; The third sub-region is stacked with a second safety primer layer and an active layer in a direction away from the current collector, and at least a portion of the surface of the fourth sub-region is covered with a third safety primer layer in a direction away from the current collector; The size of the third sub-region in the length direction is d1, and the size of the fourth sub-region in the length direction is d2, satisfying d1:d2=(4-8):

1.

8. The pole piece according to claim 1, characterized in that: Also includes adhesive tape; The adhesive tape partially covers the active layer and partially covers the first safety primer layer; The area of ​​the adhesive tape covered on the first safety primer layer is A, the total area of ​​the adhesive tape is B, and A / B×100%=75% to 95%; The projected overlapping area of ​​the adhesive tape and the recessed structure on the current collector is C, where C / B×100%=60-90%.

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

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

11. The battery cell according to claim 9 or 10, characterized in that: The battery core is a winding core, the first region is located at the head portion along the winding direction of the winding core, and the second region is located at the tail portion along the winding direction of the winding core.

12. A battery, characterized in that: Comprising the battery cell as claimed in claim 9.

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