Roll core and battery

Abstract

The utility model relates to the technical field of battery energy, in particular to a roll core and a battery. The roll core comprises a first pole piece, a diaphragm, a second pole piece, a first pole lug and first pole lug gummed paper, the first pole lug is arranged on the first pole piece, and the first pole lug gummed paper is arranged on the first pole piece and covers the first pole lug; wherein the roll core is provided with a first arc area, a straight area and a second arc area, the first arc area and the second arc area are respectively positioned on two sides of the straight area, the first tab gummed paper covers at least part of the first arc area, and the tail part of the diaphragm covers at least part of the second arc area. The first tab gummed paper on the first tab and the ending position of the diaphragm are arranged on the arc area, so that the thickness of the arc area is increased, the stress of the arc area is more uniform, the interface gap is reduced, the combination is tighter in the subsequent hot pressing process, the problem of poor adhesion between the diaphragm and the positive and negative electrodes in the arc area is solved, the infiltration effect of the pole piece is improved, and the service life of the pole piece is prolonged. The long cycle life of the battery is prolonged; and the safety performance of the battery is improved.

Description

Technical Field

[0001] The present application relates to the field of battery energy technology, and in particular to a winding core and a battery. Background Art

[0002] With the rapid development of battery technology, people have put forward higher requirements on battery energy density, fast charging capability and charge and discharge rate. High energy density fast charging battery is also the development trend of consumer batteries.

[0003] Currently, some battery cells are manufactured by stacking the positive electrode, separator, and negative electrode together, then winding the negative electrode from the head to the tail, creating a circular arc. To increase battery energy density, the electrodes are increasingly being manufactured with higher density and thicker thickness.

[0004] However, the current battery has the problem of lithium deposition in the arc area, which seriously affects the long cycle life and safety of the battery. Utility Model Content

[0005] Based on this, the present application provides a winding core and a battery to solve the problem of lithium plating in the arc area in the related art, which affects the long cycle life and safety of the battery.

[0006] On the one hand, the present application provides a winding core, comprising a first pole piece, a separator, a second pole piece, a first pole tab and a first pole tab adhesive tape, wherein the first pole piece, the separator and the second pole piece are sequentially stacked and wound, the first pole tab is provided on the first pole piece, the first pole tab adhesive tape is provided on the first pole piece, and the first pole tab adhesive tape covers the first pole tab;

[0007] Among them, the winding core has a first arc area, a straight area and a second arc area. The first arc area and the second arc area are respectively located on both sides of the straight area. The first tab tape covers at least part of the first arc area, and the tail of the diaphragm covers at least part of the second arc area.

[0008] In a possible implementation, the winding core further includes a positive electrode termination glue, which is connected to the tail of the first electrode sheet; the positive electrode termination glue covers at least a portion of the second arc area.

[0009] In a possible implementation, the tail of the separator and the tail of the positive electrode termination glue are located in the second arc area; or,

[0010] The tail of the diaphragm and the tail of the positive electrode termination glue are located in the flat area, and in the thickness direction of the core, there is a gap between the orthographic projection of the tail of the diaphragm and the orthographic projection of the tail of the positive electrode termination glue and the orthographic projection of the tail of the first pole piece.

[0011] In one possible implementation, the first electrode sheet includes a first current collector and two first active material layers, the two first active material layers are respectively located on opposite sides of the first current collector in the thickness direction, the first electrode sheet includes a double-sided area, a single-sided area and a hollow foil area, the double-sided area, the single-sided area and the hollow foil area are connected in sequence, and the positive electrode termination glue includes a first positive electrode termination glue and a second positive electrode termination glue, the first positive electrode termination glue and the second positive electrode termination glue are respectively located on both sides of the tail of the second electrode sheet;

[0012] The first positive electrode termination glue is connected to the tail of the double-sided area on the first electrode piece, and the second positive electrode termination glue is connected to the tail of the single-sided area on the first electrode piece.

[0013] In a possible implementation, along the winding direction, the length of the tail of the separator extending beyond the tail of the second electrode piece is L1, and the length of the tail of the first positive electrode termination glue extending beyond the tail of the second electrode piece is L2;

[0014] The positive electrode termination glue is a rubber tape, L1, L2 meet: 1<L1 / L2≤3; or,

[0015] The positive electrode termination glue is acrylic tape, and L1 and L2 meet the following conditions: 0.2≤L1 / L2<1.

[0016] In one possible implementation, the winding core further includes a finishing tape and a second pole tab, the second pole tab is arranged on the second pole piece, and in the thickness direction of the winding core, the orthographic projection of the finishing tape covers the orthographic projection of the first pole tab and / or the second pole tab.

[0017] In a possible implementation, the finishing tape includes a first portion covering the empty foil area and a second portion covering the single-sided area;

[0018] The length of the first part is X1, the length of the second part is X2, and X1 and X2 satisfy: 0.3≤X1 / X2≤2.

[0019] In one possible implementation, in the thickness direction of the core, the distance between the orthographic projection of the finishing tape and the first arc area or the second arc area is X3, the width of the core is W, and X3 and W satisfy: 0.03≤X3 / W<0.5, and X3≥3mm.

[0020] In a possible implementation, in the thickness direction of the winding core, there is a gap between the orthographic projection of the tail of the double-sided area of ​​the first pole piece and the orthographic projection of the tail of the single-sided area of ​​the first pole piece.

[0021] In one possible implementation, the second electrode includes a second current collector and a second active material layer, the second active material layer is located on one side of the second current collector in the thickness direction, the second active material layer includes a first material layer and a second material layer, the first material layer and the second material layer are stacked in sequence along the thickness direction of the second current collector, wherein the second material layer is located on the side of the first material layer away from the second current collector.

[0022] In a possible implementation, a plurality of recesses are provided on a surface of the second active material layer away from the second current collector.

[0023] On the other hand, the present application provides a battery, comprising a shell and the above-mentioned winding core, wherein the winding core is located in the shell.

[0024] The winding core and battery provided by the present application have the first tab tape covering the first arc region along the winding direction, and the tail of the diaphragm covering the second arc region. By forming the first tab tape and the diaphragm on the first tab in an arc shape, the thickness of the arc region is increased, and the first tab tape and the diaphragm are respectively located on the arc regions on both sides of the straight region, which reduces the tension of the pole piece, thereby improving the cycle life of the pole piece. During the subsequent hot pressing process of the winding core, the arc region is subjected to more uniform force, the interface gap is reduced, and the bonding is tighter, thus solving the problem of poor adhesion between the diaphragm and the positive and negative electrodes in the arc region, improving the wetting effect of the pole piece, and improving the long cycle life and safety performance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0026] Figure 1 This is one of the structural schematic diagrams of the winding core provided in an embodiment of the present application;

[0027] Figure 2 for Figure 1 Schematic diagram of the enlarged structure at A in the middle;

[0028] Figure 3 for Figure 1 Schematic diagram of the enlarged structure at B in the middle;

[0029] Figure 4 This is the second structural diagram of the winding core provided in the embodiment of the present application;

[0030] Figure 5 This is one of the structural schematic diagrams of the winding core tail area provided in an embodiment of the present application;

[0031] Figure 6 This is the second structural diagram of the winding core tail area provided in an embodiment of the present application;

[0032] Figure 7 A schematic structural diagram of a second pole piece cross section provided in an embodiment of the present application.

[0033] Description of reference numerals:

[0034] 100-winding core; 10-first pole piece; 11-first current collector; 12-first active material layer; 13-double-sided area; 14-single-sided area; 15-empty foil area; 20-diaphragm; 30-second pole piece; 31-second current collector; 32-second active material layer; 321-first material layer; 322-second material layer; 33-recess; 40-first tab; 50-second tab; 60-first tab adhesive tape; 70-positive electrode termination adhesive; 71-first positive electrode termination adhesive; 72-second positive electrode termination adhesive; 80-finishing adhesive tape; 200-first arc area; 300-straight area; 400-second arc area. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solutions and advantages of the present application clearer, the technical solutions in the embodiments of the present application will be described in more detail below in conjunction with the drawings in the preferred embodiments of the present application. In the drawings, the same or similar reference numerals throughout represent the same or similar parts or parts with the same or similar functions. The described embodiments are part of the embodiments of the present application, not all of the embodiments. The embodiments described below with reference to the drawings are exemplary and are intended to be used to explain the present application, and should not be understood as limitations on the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application. The embodiments of the present application are described in detail below in conjunction with the drawings.

[0036] In the description of this application, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood broadly. For example, they may refer to a fixed connection, an indirect connection via an intermediate medium, internal communication between two components, or an interaction between two components. Those skilled in the art will understand the specific meanings of these terms in this application based on specific circumstances.

[0037] In the description of this application, it should be understood that the terms "upper", "lower", "front", "back", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are orientations or positional relationships based on the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on this application.

[0038] The terms "first", "second" and "third" (if any) in the description and claims of this application and the above drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0039] In addition, the terms "comprises" and "having" and any variations thereof are intended to cover a non-exclusive inclusion, for example, a process, method, system, product or display that includes a series of steps or elements is not necessarily limited to those steps or elements expressly listed but may include other steps or elements not expressly listed or inherent to such process, method, product or display.

[0040] At present, in the existing technology, the core is formed by stacking the positive electrode sheet, the diaphragm and the negative electrode sheet together, and then winding from the head to the tail with the head of the negative electrode sheet as the center. In order to improve the energy density of the battery, the electrode sheet is gradually developed in the direction of high compaction and thick electrodes. However, since the core-structured battery is formed by winding the electrode sheet and the diaphragm, there is deformation in the bent part (arc area) due to the stretching of the electrode sheet and the diaphragm, resulting in a decrease in the thickness of each arc area, thereby generating an interface gap in the arc area. During the hot pressing process, the force on the arc area is uneven, resulting in poor adhesion between the diaphragm and the positive and negative electrodes after hot pressing, which easily causes the problem of lithium precipitation in the arc area, reducing the life of the electrode sheet, and seriously affecting the long cycle life and safety of the battery.

[0041] After repeated thinking and verification, the inventors found that if the flat area remains basically unchanged, by arranging structural parts that may adjust their positions, such as the positive electrode termination glue, the diaphragm at the end, and the protective glue inside the core in the arc area, the thickness of the arc area of ​​the core can be increased. During the hot pressing process of the core, the gap in the arc area will become smaller after the force is applied, the bonding between the interfaces will become tighter, the adhesion between the diaphragm and the positive and negative electrodes will be improved, the problem of lithium plating in the arc area will be improved, the life of the electrode will be extended, thereby improving the long cycle life of the battery and improving the safety performance of the battery.

[0042] In view of this, the present application provides a winding core, comprising a first pole piece, a diaphragm, a second pole piece, a first pole ear and a first pole ear tape, the first pole piece, the diaphragm and the second pole piece are stacked and wound in sequence, the first pole ear is arranged on the first pole piece, the first pole ear tape is arranged on the first pole piece, and the first pole ear tape covers the first pole ear; wherein, the winding core has a first arc area, a straight area and a second arc area, the first arc area and the second arc area are respectively located on both sides of the straight area, the first pole ear tape covers at least part of the first arc area, and the tail of the diaphragm covers at least part of the second arc area.

[0043] The first tab tape and the tail diaphragm on the first tab are both arc-shaped, which increases the thickness of the arc area of ​​the winding core (relatively straight area), and the first tab tape and the diaphragm are respectively located on the arc areas on both sides of the straight area, which reduces the tension of the pole piece, thereby improving the cycle life of the pole piece. During the hot pressing process of the battery, the arc area is subjected to more uniform force, the interface gap is reduced, and the combination is tighter, which solves the problem of poor adhesion between the diaphragm and the positive and negative electrodes in the arc area, improves the wetting effect of the pole piece, improves the long cycle life of the battery, and improves the safety performance of the battery.

[0044] The contents of this application will be described in detail below with reference to the accompanying drawings so that those skilled in the art can understand the contents of this application more clearly and in detail.

[0045] Figure 1 This is one of the structural diagrams of the winding core provided in the embodiment of the present application. Figure 2 for Figure 1 The enlarged structural diagram at A in the middle is shown. Figure 3 for Figure 1 The enlarged structural diagram at B in the middle is shown. Figure 4 This is the second structural schematic diagram of the winding core provided in an embodiment of the present application. Figure 5 This is one of the structural diagrams of the winding core tail area provided in the embodiment of the present application. Figure 6 This is the second structural schematic diagram of the winding core tail area provided in an embodiment of the present application. Figure 7 A schematic structural diagram of a second pole piece cross section provided in an embodiment of the present application.

[0046] like Figure 1 and Figure 4 As shown, the winding core 100 provided in an embodiment of the present application includes a wound first pole piece 10, a diaphragm 20, and a second pole piece 30. The first pole piece 10 and the second pole piece 30 have opposite polarities, and the diaphragm 20 is located between adjacent first pole pieces 10 and second pole pieces 30 to prevent contact short circuits between the first pole piece 10 and the second pole piece 30.

[0047] Specifically, the winding core 100 is formed by stacking the first pole piece 10, the diaphragm 20, and the second pole piece 30 together, and then winding it from one side of the length direction to the other side of the length direction along the length direction of the pole piece with a partial area on one side of the length direction of the second pole piece 30 as the center.

[0048] The core 100 has a winding head and a winding tail. The winding head is the middle part of the core 100, and the winding tail is the part that ends on the outside of the core 100. The first pole piece 10, the diaphragm 20, the second pole piece 30, etc. have a head and a tail along the length direction. Among them, the head of the second pole piece 30 is one side of the length direction of the second pole piece 30, and the tail of the second pole piece 30 is the other side of the length direction of the second pole piece 30. The first pole piece 10, the diaphragm 20, and the second pole piece 30 are wound from the head to the tail to form the core 100. The length direction of the first pole piece 10, the diaphragm 20, and the second pole piece 30 is the direction in which winding occurs, that is, the winding direction of the core 100 is from the head in the length direction to the tail in the length direction of the first pole piece 10, the diaphragm 20, and the second pole piece 30.

[0049] It is understood that after the first pole piece 10, the diaphragm 20, and the second pole piece 30 are wound to form the winding core 100, the winding core 100 includes a first arc area 200, a straight area 300, and a second arc area 400. The first arc area 200 and the second arc area 400 are respectively located on both sides of the straight area 300. It is understood that the first arc area 200 and the second arc area 400 are the areas where the first pole piece 10, the diaphragm 20, and the second pole piece 30 are bent when they are wound. Figure 1 As shown in FIG, the winding core 100 includes, from right to left, a first arc region 200, a straight region 300, and a second arc region 400. The tails of the first pole piece 10, the diaphragm 20, and the second pole piece 30 are all close to the second arc region 400.

[0050] The winding core 100 further includes a first tab 40, a second tab 50, and a first tab tape 60. The first tab 40 is disposed on the first pole piece 10, the second tab 50 is disposed on the second pole piece 30, and the first tab tape 60 is disposed on the first pole piece 10. The first tab tape 60 covers the first tab 40.

[0051] Please also see Figure 2 and Figure 3 Along the winding direction, the first tab tape 60 covers at least part of the first arc region 200 of the winding core 100 adjacent to the first tab 40, and the tail of the diaphragm 20 covers at least part of the second arc region 400 of the winding core.

[0052] In some embodiments, the first tab tape 60 completely covers the first arc region 200 , and the tail portion of the diaphragm 20 completely covers the second arc region 400 .

[0053] The first tab tape 60 on the first tab 40 and the tail of the diaphragm 20 are both arc-shaped, which increases the thickness of the arc area (compared to the straight area 300), and the first tab tape 60 and the diaphragm 20 are respectively located on the arc areas on both sides of the straight area 300, which reduces the tension of the electrode, thereby improving the cycle life of the electrode, making the force in the arc area more uniform during the subsequent hot pressing process, reducing the interface gap, and making the combination tighter, solving the problem of poor adhesion between the diaphragm 20 and the positive and negative electrodes in the arc area, and improving the long cycle life of the battery.

[0054] like Figure 5 and Figure 6 As shown, the first pole piece 10 includes a first current collector 11 and two first active material layers 12. The two first active material layers 12 are located on opposite sides of the thickness direction of the first current collector 11. The second pole piece 30 includes a second current collector 31 and two second active material layers 32. The two second active material layers 32 are located on opposite sides of the thickness direction of the second current collector 31.

[0055] A first tab groove is provided on the first active material layer 12. Its bottom wall forms the first current collector 11, and its surrounding area is the first active material layer 12. A first tab 40, electrically connected to the first current collector 11, is located in the first tab groove. First tab tape 60 is affixed to both sides of the first active material layer 12 at the opening of the first tab groove, covering the first tab groove from both sides. A second tab groove is provided on the second active material layer 32. Its bottom wall forms the second current collector 31, and its surrounding area is the second active material layer 32. A second tab 50, electrically connected to the second current collector 31, is located in the second tab groove.

[0056] In some embodiments, the winding core 100 further includes a second tab tape, which covers the second tab 50 and is disposed on the second electrode sheet 30 , and the first tab tape 60 completely covers the second tab tape.

[0057] For example, the first electrode sheet 10 can be a positive electrode sheet, and the second electrode sheet 30 can be a negative electrode sheet; alternatively, the first electrode sheet 10 can be a negative electrode sheet, and the second electrode sheet 30 can be a positive electrode sheet, without limitation. When the first electrode sheet 10 is a positive electrode sheet and the second electrode sheet 30 is a negative electrode sheet, aluminum foil can be used as the first current collector 11, and copper foil can be used as the second current collector 31.

[0058] The winding core 100 further includes a positive electrode end cap 70. The positive electrode end cap 70 is connected to the tail of the first electrode sheet 10. Along the winding direction, the positive electrode end cap 70 covers at least a portion of the second arc region 400 adjacent to the winding tail of the first electrode sheet 10.

[0059] In some embodiments, the positive electrode termination adhesive 70 completely covers the second arc region 400 . Specifically, the positive electrode termination adhesive 70 is connected to the tail of the first active material layer 12 on the first electrode sheet 10 .

[0060] The first arc area 200 on the positive electrode termination glue 70 can also increase the thickness of the first arc area 200, so that in the subsequent hot pressing process, the force on the first arc area 200 is more uniform, the interface gap is improved, and the first arc area 200 is more tightly bonded, solving the problem of poor adhesion between the diaphragm 20 and the positive and negative electrodes in the first arc area 200, improving the wetting effect of the electrode, improving the long cycle life of the battery and improving the safety performance of the battery.

[0061] Preferably, the tail of the separator 20 and the tail of the positive electrode termination glue 70 are located in the second arc region 400. This prevents thickness stacking on the straight region 300, resulting in thickness difference and unevenness, and reduces the yield reduction caused by the appearance of interface gaps.

[0062] The tail of the separator 20 and the tail of the positive electrode termination glue 70 can also be located on the straight area 300, as long as they are in the thickness direction of the winding core 100, that is, Figure 1 In the middle Y direction, the orthographic projections of the tail of the diaphragm 20 and the tail of the positive electrode termination glue 70 are not within the orthographic projection of the tail of the positive electrode termination glue first electrode piece 10, that is, there is a gap between the orthographic projection of the tail of the diaphragm 20 and the orthographic projection of the tail of the positive electrode termination glue 70 and the orthographic projection of the tail of the first electrode piece 10.

[0063] Exemplarily, the distance between the orthographic projection of the tail of the diaphragm 20 in the thickness direction of the core 100 and the orthographic projection of the tail of the first electrode piece 10 of the positive electrode termination glue in the thickness direction of the core 100 is X, and X satisfies: X>0.

[0064] When there is a gap between the projection of the tail of the diaphragm 20 and the projection of the connection area between the positive termination glue 70 and the first pole piece 10, the thickness stacking of the straight area 300 can be reduced, thereby reducing the thickness difference and the occurrence of the interface gap.

[0065] In some embodiments, as Figure 5 and Figure 6 As shown, the first electrode sheet 10 includes a double-sided area 13, a single-sided area 14, and a hollow foil area 15. The double-sided area 13 is the area where the first active material layer 12 exists on both sides of the first current collector 11. The single-sided area 14 is the area where the first active material layer 12 exists on only one side of the first current collector 11. The hollow foil area 15 is the area where only the first current collector 11 exists. On the first electrode sheet 10, the double-sided area 13, the single-sided area 14, and the hollow foil area 15 are connected in sequence, so that the hollow foil area 15 ends at the end of the first electrode sheet 10.

[0066] Specifically, the positive electrode termination glue 70 includes a first positive electrode termination glue 71 and a second positive electrode termination glue 72. The first positive electrode termination glue 71 and the second positive electrode termination glue 72 are respectively located on both sides of the tail of the second electrode sheet 30. Among them, the first positive electrode termination glue 71 is connected to the tail of the double-sided area 13 on the first electrode sheet 10 (i.e., the end close to the single-sided area 14). The second positive electrode termination glue 72 is connected to the tail of the single-sided area 14 on the first electrode sheet 10 (i.e., the end close to the empty foil area 15).

[0067] Preferably, the material of the positive electrode termination adhesive 70 is rubber adhesive tape or acrylic adhesive tape.

[0068] In some embodiments, a relief groove is provided at the tail of the double-sided region 13 and the single-sided region 14 on the first electrode sheet 10. The first positive electrode termination adhesive 71 is connected to the double-sided region 13 in the relief groove. The second positive electrode termination adhesive 72 is connected to the single-sided region 14 in the relief groove. The provision of the relief groove can reduce the thickness at the connection between the first positive electrode termination adhesive 71 and the second positive electrode termination adhesive 72, thereby reducing the thickness difference of the winding core 100 in the straight region 300, improving the flatness of the winding core 100, and thus reducing the occurrence of interfacial gaps.

[0069] Preferably, along the winding direction, the tail length of the separator 20 is greater than the tail length of the second electrode piece 30 , and the tail length of the positive electrode termination glue 70 is equal to the tail length of the second electrode piece 30 .

[0070] In some embodiments, the tail of the diaphragm 20 extends beyond the tail of the second electrode piece 30 by a dimension L1 , and the tail of the first positive electrode termination glue 71 extends beyond the tail of the second electrode piece 30 by a dimension L2 .

[0071] like Figure 1 and Figure 5 As shown, when the positive electrode termination adhesive 70 is made of rubber tape, L1 and L2 satisfy the following: 1<L1 / L2≤3, forming a state where the end section of the separator 20 covers the positive electrode termination adhesive 70 .

[0072] Because the steel plate peel strength of rubber-based terminators is 0.01kgf / mm-0.024kgf / mm (test method using JIS Z0237 pressure-sensitive adhesive tape and pressure-sensitive adhesive sheet), the positive electrode terminator 70 has a strong bond with the first current collector 11 (aluminum foil). This can easily pull the first current collector 11 when subjected to stress, causing the electrode sheet to break. Therefore, to prevent contact short circuits between the positive and negative electrode sheets after a break, the separator 20 tail should be longer than the first positive electrode terminator 71. This prevents contact short circuits by allowing the separator 20 tail to cover the first positive electrode terminator 71.

[0073] like Figure 4 and Figure 6As shown, when the positive electrode termination adhesive 70 is acrylic tape, L1 and L2 satisfy: 0.2≤L1 / L2<1.

[0074] Since the steel plate peeling strength of the acrylic terminator glue is 0.01kgf / mm-0.018kgf / mm (using the test method of JISZ0237 pressure-sensitive adhesive tape and pressure-sensitive adhesive sheet), the positive electrode terminator glue 70 has poor adhesion to the first current collector 11 (aluminum foil). After being soaked in electrolyte, the positive electrode terminator glue 70 is easily separated from the first current collector 11. Therefore, the tail length of the diaphragm 20 is shorter than that of the acrylic first positive electrode terminator glue 71, avoiding the increase in the thickness of the core 100 due to the excessive length of the diaphragm 20, resulting in a decrease in space utilization and energy density.

[0075] Furthermore, when the positive electrode termination adhesive 70 is made of acrylic tape, the length of the first positive electrode termination adhesive 71 must exceed the projection range of the empty foil area 15 .

[0076] Since the winding core 100 is closed with a closing tape 80, and the pasting range of the closing tape 80 (usually hot melt adhesive) covers the range of the acrylic first positive electrode termination adhesive 71, and compared with the acrylic tape, the closing tape 80 has greater adhesion to the first current collector 11 (aluminum foil), in order to prevent the closing tape 80 from directly contacting the first current collector 11 provided with the first active material layer 12 and causing tearing of the first electrode 10, the length of the first positive electrode termination adhesive 71 must exceed the projection range of the empty foil area 15.

[0077] In a possible implementation, in the thickness direction of the winding core 100 , the orthographic projection of the finishing tape 80 covers the orthographic projection of the first electrode tab 40 and / or the second electrode tab 50 .

[0078] Preferably, the area of ​​the finishing tape 80 occupies 20%-70% of the area of ​​the straight area 300 on one side of the winding core 100 .

[0079] like Figure 1 and Figure 4 As shown, the finishing tape 80 includes a first portion covering the blank foil area 15 and a second portion covering the single-sided area 14. Along the winding direction of the winding core 100, the length of the first portion covering the blank foil area 15 is X1. The length of the second portion covering the single-sided area 14 is X2, where X1 and X2 satisfy the following relationship: 0.3 ≤ X1 / X2 ≤ 2.

[0080] When X1 / X2>2, most of the closing tape 80 is attached to one side of the empty foil area 15. Since the empty foil area 15 has no adhesion to the entire core 100, the first current collector 11 will be torn when subjected to force, and the core 100 cannot be fixed. When X1 / X2<0.3, most of the closing tape 80 is attached to one side of the single-sided area 14. Since the closing tape 80 has a high adhesion to the first current collector 11 (aluminum foil), the single-sided area 14 is easily torn when subjected to force, causing a significant drop in the voltage of the core 100.

[0081] In one possible implementation, in the thickness direction of the core 100, the distance between the orthographic projection of the finishing tape 80 and the first arc area 200 or the second arc area 400 is X3, the width of the core 100 is W, and X3 and W satisfy: 0.03≤X3 / W<0.5, and X3≥3mm.

[0082] Preferably, in the thickness direction of the winding core 100 , there is a gap between the orthographic projection of the tail of the double-sided area 13 of the first pole piece 10 and the orthographic projection of the tail of the single-sided area 14 of the first pole piece 10 .

[0083] When the tail of the double-sided area 13 and the tail of the single-sided area 14 are aligned in the thickness direction of the core 100, there will be an excessively large thickness difference at the end in the straight area 300, resulting in a reduction in the flatness of the core 100 and the appearance of interface gaps. During the circulation process, the core will be deformed. Therefore, the tail of the double-sided area 13 and the tail of the single-sided area 14 are misaligned to reduce the thickness difference at the end.

[0084] Exemplarily, the distance between the projection of the tail of the double-sided area 13 and the projection of the tail of the single-sided area 14 is m, and m satisfies: -5 mm < m ≤ 5 mm.

[0085] like Figure 5 and Figure 6 As shown, in some optional embodiments, there is an area at the tail of the second pole piece 30 that does not contain the second active material layer 32 and only has the second current collector 31 (empty foil), that is, it includes an uncoated area. The second pole piece 30 ends with an empty foil, which can improve the safety of the end side.

[0086] Based on the electrode short-circuiting mechanism, the heat generated by the contact between the second electrode sheet 30 with the second active material layer 32 and the bare foil area 15 of the first electrode sheet 10 is much greater than the heat generated by the contact between the second current collector 31 and the bare foil area 15. Therefore, the tail of the second electrode sheet 30 ends with the second current collector 31 without the second active material layer 32. Even if a short-circuit such as a needle puncture occurs here, the voltage of the core 100 can be quickly reduced with minimal heat generation, thus ensuring the safety of the battery cell.

[0087] Exemplarily, the length of the uncoated area at the tail of the second pole piece 30 is n, and n satisfies: 0<n≤5mm.

[0088] like Figure 7 As shown, in some optional embodiments, the second active material layer 32 includes a first material layer 321 and a second material layer 322, and the first material layer 321 and the second material layer 322 are stacked in sequence along the thickness direction of the second current collector 31, wherein the second material layer 322 is located on the side of the first material layer 321 away from the second current collector 31.

[0089] It should be noted that the second active material layer 32 has a double-layer structure, wherein the materials used for the first material layer 321 and the second material layer 322 can be the same or different.

[0090] In some optional embodiments, the second active material layer 32 is a double-layer graphite structure, wherein the particle size of the graphite particles in the first material layer 321 is larger than the particle size of the graphite particles in the second material layer 322 .

[0091] In some optional embodiments, at least one of the first material layer 321 and the second material layer 322 is made of graphite-doped silicon material.

[0092] The ratio of the thickness of the second material layer 322 to the thickness of the second active material layer 32 is greater than or equal to 20% and less than or equal to 60%.

[0093] The graphite in the second material layer 322 has a larger porosity and more surface coatings, making it more susceptible to side reactions and heat generation.

[0094] Preferably, a plurality of recesses 33 are formed on a surface of the second active material layer 32 away from the second current collector 31 .

[0095] While retaining the double-layer graphite design, a recess 33 is opened on the surface of the second pole piece 30 to further reduce the impedance of the negative electrode side and improve the dynamic performance of the negative electrode side.

[0096] The recess 33 includes a hole and / or a groove. The hole is opened along the thickness direction of the second pole piece 30. The groove extends along the width direction of the second pole piece 30.

[0097] The hole may be a blind hole provided on the second active material layer 32 , or a through hole penetrating the second electrode plate 30 .

[0098] The holes can be arranged on the entire surface of the second active material layer 32 along the winding direction, or on the edge of the second electrode sheet 30 in the width direction, or in the middle of the second electrode sheet 30 in the width direction, or on the first arc area 200 and the second arc area 400.

[0099] The groove can be formed on the second pole piece 30 by laser marking.

[0100] Preferably, the depth h of the groove is smaller than the thickness of the second material layer 322 .

[0101] It should be noted that the second active material layer 32 is a double-layer graphite design, in which the lower layer is large-particle graphite and the upper layer is small-particle graphite. The thickness of the upper layer of small-particle graphite accounts for 20%-60% of the total thickness of the second active material layer 32. A linear recess 33 is punched out on the second electrode 30 using a laser. The depth of the recess 33 is less than the thickness of the second material layer 322. The upper layer of small-particle graphite has a larger porosity and is more conducive to air and heat conduction.

[0102] In some embodiments, holes are further provided on the first electrode sheet 10. The holes provided on the positive electrode sheet can knock out part of the active material and improve the CB (Cell Balance) value of the corresponding position. The hole structure can also store electrolyte, improve the wetting performance of the electrolyte on the electrode sheet, and improve the problems of edge lithium deposition and arc lithium deposition.

[0103] It should be noted that the following is a table comparing multiple sets of example data.

[0104] Table 1 is a data table of multiple groups of examples and comparative examples cycle test

[0105]

[0106] In the first embodiment, the positive electrode termination adhesive 70 is made of rubber adhesive tape.

[0107] The difference between the comparative example and the embodiment 1 is that the first tab tape 60 of the comparative example does not cover the first arc region 200 and the second arc region 400 .

[0108] The difference between Example 2 and Example 1 is that the finishing tape 80 covers the blank foil area 15 with an area X1 = 5 mm and covers the single-sided area 14 with an area X2 = 17 mm.

[0109] The difference between Example 3 and Example 1 is that the finishing tape 80 covers the blank foil area 15 with an area X1 = 17 mm and covers the single-sided area 14 with an area X2 = 5 mm.

[0110] The difference between Example 4 and Example 1 is that the positive electrode termination adhesive 70 is made of acrylic tape, which exceeds the dimension L2 of the second electrode 30 by 30 mm, and the finishing tape 80 covers X1 = 5 mm of the empty foil area 15 and X2 = 17 mm of the single-sided area 14.

[0111] The difference between Example 5 and Example 1 is that, during winding, the end section of the double-sided area 13 is flush with the end section of the single-sided area 14 , that is, m=0.

[0112] The difference between Example 6 and Example 1 is that the tail of the second pole piece 30 is provided with a second active material layer 32 , and there is no empty second current collector 31 at the end, that is, n=0.

[0113] The difference between Example 7 and Example 1 is that no recess 33 is provided on the second active material layer 32 .

[0114] Among them, the test method of the cycle test is:

[0115] 1. Cycle 50T at 25℃: In a constant temperature room at 25℃, cycle the battery for 50T using the charge and discharge method specified in the specification, then disassemble the battery after fully charging it.

[0116] 2. End-side acupuncture: Perform 5 room temperature cycles before acupuncture (1C constant current and constant voltage charging to the upper limit voltage, 0.05C cut-off, 0.5C discharge), and complete the acupuncture test within 2 days after the cycle. The test should be carried out within 24 hours after the battery cell is fully charged (1C constant current and constant voltage charging to the upper limit voltage, 0.05C cut-off); use a 4mm diameter iron nail to pierce the left, center and right positions of the battery cell respectively, with a needle speed of 30mm / s. The nail should remain in the battery for 1 minute and then be removed. Test 5pcs of battery cells.

[0117] The judgment criteria are: no explosion and no fire.

[0118] 3. Simulate a drop of the entire device: After cycling the cell / battery five times at room temperature, fully charge it (charging method: 1C constant current and constant voltage charging to the upper limit voltage, 0.05C cut-off; discharging method: 0.5C discharge to 3.0V), and perform the following tests:

[0119] 1) Place the cell / battery in a drop fixture with double-sided tape and drop it from a height of 1.5m.

[0120] 2) Drop in the order of "front - back - bottom - top - left - right - upper left corner - upper right corner - lower left corner - lower right corner". Each side / corner drops once for one round, for a total of 6 rounds.

[0121] Judgment criteria: After completing 2 rounds of drop tests, the battery cell / battery has no heat problems and the voltage drop is less than 15mV; after completing 6 rounds of drop tests, the battery cell / battery must not leak, swell, or catch fire.

[0122] As shown in Table 1, the comparison between the comparative example and the embodiment shows that the first tab tape 60 is located on the arc area, which can reduce the tension of the electrode, make the arc area more evenly stressed, reduce the interface gap, and make the combination tighter, thereby solving the problem of poor adhesion between the diaphragm and the positive and negative electrodes in the arc area, improving the wetting effect of the electrode, and improving the problem of lithium deposition in the arc area.

[0123] Comparison between Example 1 and Example 2 shows that when X1 / X2 is less than 0.3, most of the closing tape 80 is attached to one side of the single-sided area 14. Due to the high viscosity between the closing tape 80 and the first current collector 11, the single-sided area 14 is easily torn when subjected to force, resulting in a significant voltage drop in the winding core 100.

[0124] A comparison between Example 1 and Example 3 shows that when X1 / X2>2, most of the finishing tape 80 is attached to one side of the empty foil area 15. Since the empty foil area 15 has no adhesion to the entire core 100, the first current collector 11 will be torn when subjected to force, and will not be able to fix the core 100.

[0125] Comparison between Example 1 and Example 4 shows that when acrylic tape is used for the positive electrode termination glue 70, 0.2≤L1 / L2<1, ensuring that the length of the positive electrode termination glue 70 is greater than the length of the separator 20, can prevent the problem of the core tearing after being subjected to force due to the poor adhesion between the positive electrode termination glue 70 and the first current collector 11.

[0126] Comparison between Example 1 and Example 5 shows that the end section of the double-sided area 13 is flush with the end section of the single-sided area 14, which will reduce the flatness of the winding core 100, thereby causing interface gaps and causing deformation of the battery cell after cycling.

[0127] Comparison between Example 1 and Example 6 shows that the second active material layer 32 at the tail of the second electrode 30 will come into contact with the empty foil area 15 of the first electrode 10 during acupuncture, generating a large amount of heat and causing a short circuit.

[0128] Comparison between Example 1 and Example 7 shows that the recess 33 formed on the surface of the second electrode 30 can reduce the impedance of the negative electrode side, store electrolyte, improve the wettability of the electrolyte to the electrode, improve edge lithium deposition, and enhance the kinetic performance of the negative electrode side.

[0129] The winding core 100 provided in the embodiment of the present application includes a first electrode piece 10, a diaphragm 20, a second electrode piece 30, a first electrode tab 40 and a first electrode tab tape 60. The first electrode piece 10, the diaphragm 20 and the second electrode piece 30 are stacked and wound in sequence. The first electrode tab 40 is arranged on the first electrode piece 10, the first electrode tab tape 60 is arranged on the first electrode piece 10, and the first electrode tab tape 60 covers the first electrode tab 40; wherein, the winding core 100 has a first arc area 200, a straight area 300 and a second arc area 400, and the first arc area 200 and the second arc area 400 are respectively located on both sides of the straight area 300, the first electrode tab tape 60 covers at least part of the first arc area 200, and the tail of the diaphragm 20 covers at least part of the second arc area 400.

[0130] The first tab tape 60 and the diaphragm 20 on the first tab 40 are both arc-shaped, which increases the thickness of the arc area (compared to the straight area 300), and the first tab tape 60 and the diaphragm 20 are respectively located on the arc areas on both sides of the straight area 300, which reduces the tension of the pole piece, thereby improving the cycle life of the pole piece, making the force in the arc area more uniform during the subsequent hot pressing process, reducing the interface gap, and combining more tightly, solving the problem of poor adhesion between the diaphragm 20 and the positive and negative electrodes in the arc area, improving the problem of lithium deposition in the arc area, extending the life of the pole piece, improving the long cycle life of the battery, and improving the safety performance of the battery. At the same time, at the end of the winding core 100, the end form of the second pole piece 30 is adjusted, and the end tape 80 gluing method related to the category of the positive terminal glue 70 is set to ensure the safety of the battery cell and improve the safety performance.

[0131] In addition, an embodiment of the present application further provides a battery, comprising a battery housing and a winding core 100. The winding core 100 is located in the battery housing.

[0132] The battery is not limited to lithium batteries, and in the future this technology may be applied to sodium batteries, etc. In the embodiment of the present application, lithium-ion batteries are preferred.

[0133] The specific structure, working principle and function of the winding core 100 have been described in detail in the previous embodiment and will not be repeated here. It should be noted that the preparation process of the lithium-ion battery is as follows:

[0134] Step 1: Positive electrode sheet preparation: Prepare the positive electrode active layer slurry, apply the positive electrode active material slurry to the surface of the first current collector 11, and obtain the first electrode sheet 10 after baking and roller pressing. A certain position of the first electrode sheet 10 has a first electrode tab groove of fixed size. The first electrode tab 40 is welded in the first electrode tab groove by laser or ultrasonic welding. First electrode tab tape 60 is affixed to both sides of the electrode sheet at the groove position. A second electrode tab tape is affixed to the negative electrode sheet. The projection of the first electrode tab tape 60 completely covers the second electrode tab tape.

[0135] Step 2: Preparation of negative electrode sheet: Two different negative electrode active layer slurries are prepared and coated on carbon-coated copper foil at the same time. After baking and rolling, a second electrode sheet 30 is obtained, wherein the second material layer 322 has a thickness of 20 μm and the first material layer 321 has a thickness of 70 μm. A certain position of the second electrode sheet 30 has a second electrode tab groove of fixed size. The second electrode tab 50 is welded in the second electrode tab groove by laser or ultrasonic welding, and second electrode tab tape is affixed to both sides of the electrode sheet at the slot position, and a first electrode tab tape 60 is affixed to the projected first electrode sheet 10. The projection of the first electrode tab tape 60 completely covers the second electrode tab tape. A uniform linear recess 33 is punched on the surface of the negative second electrode sheet 30 using a laser of a certain intensity. The depth h of the recess 33 is 10 μm.

[0136] Step 3: After the positive and negative electrode sheets are cut and sheeted, they are wound with the separator 20 to obtain a roll core 100. During winding, the end section of the double-sided area 13 and the end section of the single-sided area 14 are not flush with the paste, with a misalignment of m=5mm. The first positive electrode termination glue 71 and the second positive electrode termination glue 72 are both made of rubber adhesive tape, wherein the first positive electrode termination glue 71 exceeds the second electrode sheet 30 by a dimension L2=5mm; the end separator 20 exceeds the second electrode sheet 30 by a dimension L1=8mm, and the tail of the second electrode sheet 30 is terminated with the second current collector 31 without the second active material layer 32, and the empty foil length n=2mm; the end adhesive tape 80 is a rubber-based end adhesive tape with a length of 22mm, wherein the length X1 of one side covering the empty foil area 15 is 11mm, and the length X2 of one side covering the single-sided area 14 is 11mm;

[0137] Step 4: After packaging, baking, liquid filling, formation, secondary sealing, sorting and OCV (open circuit voltage) testing, a lithium-ion battery is obtained.

[0138] The electrolyte is a conventional commercially available electrolyte, and the lithium salt therein is LiFP6.

[0139] In the battery provided by the embodiment of the present application, the first tab tape 60 on the first tab 40 and the end position of the diaphragm 20 are both arc-shaped, which increases the thickness of the arc area (compared to the straight area 300), and the first tab tape 60 and the diaphragm 20 are respectively located on the arc areas on both sides of the straight area 300, which reduces the tension of the pole piece, thereby improving the cycle life of the pole piece, making the force in the arc area more uniform during the subsequent hot pressing process, reducing the interface gap, and combining more tightly, solving the problem of poor adhesion between the diaphragm 20 and the positive and negative electrodes in the arc area, improving the problem of lithium deposition in the arc area, extending the life of the pole piece, and improving the long cycle life of the battery. At the same time, at the end of the winding core 100, the end form of the second pole piece 30 is adjusted, and the end tape 80 gluing method related to the category of the positive terminal glue 70 is set to ensure the safety of the battery cell and improve the safety performance.

[0140] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A winding core, characterized in that: The invention comprises a first pole piece (10), a diaphragm (20), a second pole piece (30), a first pole ear (40) and a first pole ear adhesive paper (60), wherein the first pole piece (10), the diaphragm (20) and the second pole piece (30) are sequentially stacked and wound, the first pole ear (40) is arranged on the first pole piece (10), the first pole ear adhesive paper (60) is arranged on the first pole piece (10), and the first pole ear adhesive paper (60) covers the first pole ear (40); The winding core (100) comprises a first arc region (200), a straight region (300) and a second arc region (400); the first arc region (200) and the second arc region (400) are respectively located on both sides of the straight region (300); the first tab tape (60) covers at least a portion of the first arc region (200); and the tail of the diaphragm (20) covers at least a portion of the second arc region (400).

2. The winding core according to claim 1, characterized in that: The winding core (100) further comprises a positive electrode termination glue (70), wherein the positive electrode termination glue (70) is connected to the tail of the first pole piece (10); the positive electrode termination glue (70) covers at least a portion of the second arc region (400).

3. The winding core according to claim 2, characterized in that: The tail of the separator (20) and the tail of the positive electrode termination glue (70) are located in the second arc region (400); or, The tail of the diaphragm (20) and the tail of the positive electrode termination glue (70) are located in the straight area (300), and in the thickness direction of the winding core (100), there is a gap between the orthographic projection of the tail of the diaphragm (20) and the orthographic projection of the tail of the positive electrode termination glue (70) and the orthographic projection of the tail of the first electrode sheet (10) of the positive electrode termination glue.

4. The winding core according to claim 2, characterized in that: The first pole piece (10) comprises a first current collector (11) and two first active material layers (12), the two first active material layers (12) are respectively located on opposite sides of the first current collector (11) in a thickness direction, the first pole piece (10) comprises a double-sided area (13), a single-sided area (14) and a hollow foil area (15), the double-sided area (13), the single-sided area (14) and the hollow foil area (15) are connected in sequence, the positive electrode termination glue (70) comprises a first positive electrode termination glue (71) and a second positive electrode termination glue (72), the first positive electrode termination glue (71) and the second positive electrode termination glue (72) are respectively located on two sides of the tail of the second pole piece (30); The first positive electrode termination glue (71) is connected to the tail of the double-sided area (13) on the first pole piece (10), and the second positive electrode termination glue (72) is connected to the tail of the single-sided area (14) on the first pole piece (10).

5. The winding core according to claim 4, characterized in that: Along the winding direction, the tail of the separator (20) exceeds the tail of the second pole piece (30) by a dimension L1, and the tail of the first positive electrode termination glue (71) exceeds the tail of the second pole piece (30) by a dimension L2; The positive electrode termination glue (70) is a rubber adhesive tape, and L1 and L2 satisfy: 1<L1 / L2≤3; or, The positive electrode termination glue (70) is an acrylic adhesive tape, and L1 and L2 satisfy: 0.2≤L1 / L2<1.

6. The winding core according to claim 4, characterized in that: The winding core (100) further comprises a finishing tape (80) and a second pole ear (50), wherein the second pole ear (50) is arranged on the second pole piece (30), and in the thickness direction of the winding core (100), the orthographic projection of the finishing tape (80) covers the orthographic projection of the first pole ear (40) and / or the second pole ear (50).

7. The winding core according to claim 6, characterized in that: The finishing tape (80) comprises a first portion covering the empty foil area and a second portion covering the single-sided area; The length of the first part is X1, the length of the second part is X2, and X1 and X2 satisfy: 0.3≤X1 / X2≤2.

8. The winding core according to claim 6, characterized in that: In the thickness direction of the winding core (100), the distance between the orthographic projection of the finishing tape (80) and the first arc area (200) or the second arc area (400) is X3, the width of the winding core is W, and X3 and W satisfy: 0.03≤X3 / W<0.5, and X3≥3mm.

9. The winding core according to claim 4, characterized in that: In the thickness direction of the winding core (100), there is a gap between the orthographic projection of the tail of the double-sided area (13) of the first pole piece (10) and the orthographic projection of the tail of the single-sided area (14) of the first pole piece (10).

10. The winding core according to claim 1, characterized in that: The second pole piece (30) comprises a second current collector (31) and a second active material layer (32), wherein the second active material layer (32) is located on one side of the second current collector (31) in the thickness direction, and the second active material layer (32) comprises a first material layer (321) and a second material layer (322), wherein the first material layer (321) and the second material layer (322) are stacked in sequence along the thickness direction of the second current collector (31), wherein the second material layer (322) is located on a side of the first material layer (321) away from the second current collector (31).

11. The winding core according to claim 10, characterized in that: A plurality of recesses (33) are provided on a surface of the second active material layer (32) away from the second current collector (31).

12. A battery, characterized in that: It comprises a shell and a winding core as claimed in any one of claims 1 to 11, wherein the winding core is located in the shell.

Images