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 and a second pole piece which are stacked and wound, and the polarities of the first pole piece and the second pole piece are opposite; the first pole piece is provided with a first pole lug, the second pole piece is provided with a stepped groove opposite to the first pole lug, the stepped groove comprises a first groove and a second groove which are arranged away from the first pole lug and are communicated in sequence, and the projection of the second groove is located in the projection of the first groove; one side, facing the second pole piece, of the winding tail end of the first pole piece is provided with an active layer ending part and termination gummed paper, and the head of the termination gummed paper covers the active layer ending part; the head part of the termination adhesive paper and the ending part of the active layer are positioned in the second groove. The head part of the termination gummed paper and the ending part of the active layer are both positioned in the second groove, so that the thickness difference of the tab position is reduced, and the flatness of the roll core is improved, thereby reducing the non-uniform compression near the tab during formation, avoiding the generation of a gap at an interface bonding part, and relieving the lithium precipitation problem at the tab position.

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] At present, when manufacturing the roll core of some batteries, the positive electrode sheet, the separator and the negative electrode sheet are stacked together, and then wound from the head to the tail with the head of the negative electrode sheet as the center.

[0004] Among them, the center-placed lug structure has a difference in thickness between the lug position and the non-lug position due to the difference in lug thickness and paste thickness, which leads to a decrease in the flatness of the winding core. During formation, it is easy to cause uneven pressure near the lug, resulting in gaps in interface bonding, which leads to lithium deposition at the lug position, seriously affecting the cycle performance 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 problems in the related art such as uneven pressure, interface gaps, and lithium deposition at the tabs, which affect battery performance due to thickness differences.

[0006] The present application provides a winding core, comprising a first pole piece, a diaphragm and a second pole piece which are stacked and wound, wherein the polarities of the first pole piece and the second pole piece are opposite;

[0007] The first pole piece is provided with a first pole ear, and the second pole piece is provided with a stepped groove arranged opposite to the first pole ear, the stepped groove includes a first groove and a second groove arranged away from the first pole ear and connected in sequence, and along the thickness direction of the winding core, the projection of the second groove is located within the projection of the first groove;

[0008] The winding tail end of the first pole piece has an active layer tail portion and a termination tape on one side facing the second pole piece, and the head of the termination tape covers the active layer tail portion;

[0009] Among them, in the orthographic projection in the thickness direction of the winding core, the head of the termination tape and the tail of the active layer are both located in the second groove.

[0010] In a possible implementation, the first pole piece includes a first current collector and a first active layer and a second active layer respectively located on opposite sides of the first current collector in a thickness direction, and along the winding direction, in the tail portion of the active layer, the tail end of the first active layer is flush with the tail end of the second active layer; or, the tail end of the first active layer exceeds the tail end of the second active layer; or, the tail end of the second active layer exceeds the tail end of the first active layer.

[0011] In a possible implementation, the stepped groove includes a third groove that is arranged away from the first groove and connected to the second groove, and along the thickness direction of the winding core, the projection of the third groove is located within the projection of the second groove, and the first step surface of the first groove and the third step surface of the third groove are respectively located on both sides of the second step surface of the second groove;

[0012] The depth of the first step surface is h1, the depth of the second step surface is h2, and the depth of the third step surface is h3, wherein h1, h2 and h3 satisfy: 0

[0013] In a possible implementation, the first pole piece includes a first current collector and first active material layers respectively located on two opposite sides of the first current collector in a thickness direction, and the second pole piece includes a second current collector and second active material layers respectively located on two opposite sides of the second current collector in a thickness direction;

[0014] h1 satisfies: h1<h3-thickness of the first electrode tab; and / or

[0015] h2 satisfies: h2<h3-2*thickness of the first active material layer; and / or

[0016] h3 satisfies: h3 is equal to the thickness of the second active material layer.

[0017] In a possible implementation, h1 satisfies: h1=h3-1 / 2 the thickness of the first electrode tab; and / or

[0018] h2 satisfies: h2=h3-thickness of the first active material layer.

[0019] In a possible implementation, a tail groove is provided at the winding tail end of the first pole piece, and the head of the terminating tape is located in the tail groove.

[0020] In a possible implementation, the winding core also includes a first protective tape, which is arranged on the first pole piece and covers the first pole ear. The first protective tape extends along the winding direction of the winding core and at least partially covers the arc segment of the winding core on the side closest to the first pole ear.

[0021] In a possible implementation, the winding core further includes a second protective tape, the second protective tape is disposed on the second pole piece, and the second protective tape covers the step groove.

[0022] In a possible implementation manner, in the width direction of the second pole piece, there is a gap between the edge of the stepped groove and the edge of the second pole piece.

[0023] In a possible implementation, the first pole piece includes a first current collector and first active material layers respectively located on two opposite sides of the first current collector in a thickness direction, and a first recess is formed on the first active material layer; and / or,​

[0024] The second pole piece includes a second current collector and second active material layers respectively located on two opposite sides of the second current collector in the thickness direction, and a second recess is formed on the second active material layer.

[0025] The present application provides a battery, comprising a shell and the above-mentioned winding core, wherein the winding core is located in the shell.

[0026] The winding core and battery provided in the present application are characterized in that a termination tape is connected to the winding tail end of the first pole piece, and in the thickness direction of the winding core, a projection of the connection area between the termination tape and the first pole piece is located in the second groove of the step groove, so that the thickness of the first pole ear and the first pole piece at the winding tail end are accommodated in the step groove, reducing the step mutation at the end of the active layer, thereby reducing the thickness difference between adjacent positions near the pole ear position, improving the flatness of the winding core, thereby reducing the uneven pressure near the pole ear during formation, avoiding the formation of gaps at the interface bonding, and alleviating the problem of lithium plating at the pole ear position. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] 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 paying any creative work.

[0028] Figure 1 One of the structural schematic diagrams of the winding core provided in the embodiment of the present application;

[0029] Figure 2 The second structural schematic diagram of the winding core provided in the embodiment of the present application;

[0030] Figure 3 for Figure 1 A schematic diagram of the structure of the first tab position in the winding core;

[0031] Figure 4 for Figure 2 A schematic diagram of the structure of the first tab position in the winding core;

[0032] Figure 5 for Figure 3 A schematic diagram of the enlarged structure of part A;

[0033] Figure 6 A schematic diagram of the corresponding position relationship between the first pole piece and the second pole piece of the winding core provided in an embodiment of the present application;

[0034] Figure 7 Schematic diagram of the structure of the winding core of the comparative example.

[0035] Description of reference numerals:

[0036] 100-winding core; 10-first pole piece; 11-first current collector; 12-first active material layer; 121-first pole ear groove; 123-first recess; 13-first active layer; 14-second active layer; 20-diaphragm; 30-second pole piece; 31-second current collector; 32-second active material layer; 33-step groove; 331-first groove; 332-second groove; 333-third groove; 334-first step surface; 335-second step surface; 336-third step surface; 34-second recess; 40-first pole ear; 50-second pole ear; 60-termination tape; 70-first protective tape; 200-arc segment; 300-straight segment. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical scheme and advantages of the present application clearer, the technical scheme in the embodiment 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 construed 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 the present application. The embodiments of the present application are described in detail below in conjunction with the drawings.

[0038] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, or it can be an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0039] In the description of the present 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 drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0040] The terms "first", "second" and "third" (if any) in the specification 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.

[0041] In addition, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, for example, a process, method, system, product, or display comprising a series of steps or elements is not necessarily limited to those steps or elements explicitly listed, but may include other steps or elements not explicitly listed or inherent to such process, method, product, or display.

[0042] At present, in the prior art, the winding 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. Among them, the pole ear is welded to the corresponding pole sheet by laser or ultrasonic welding through the slot on the pole sheet. Due to the difference between the thickness of the pole ear and the thickness of the active material paste coating part on the pole sheet in the pole ear center structure (the pole ear is located in the middle of the pole sheet, and the pole ear is located in the middle of the winding core after winding), there is a thickness difference between the pole ear position and the non-pole ear position on the pole sheet. After winding to form a winding core, there are areas of different thickness on the surface of the winding core, which affects the flatness of the winding core. During formation, it is easy to cause uneven pressure near the pole ear position, resulting in gaps at the interface bonding, which leads to the problem of lithium precipitation at the pole ear position, affecting the cycle performance and safety of the battery finally formed.

[0043] After repeated thinking and verification, the inventor found that if a stepped groove is provided on the second pole sheet opposite to the first pole ear, so that the winding tail end of the first pole sheet at the end of the winding core does not exceed the projection area of ​​the first pole ear during winding, and is projected in the stepped groove, it is possible to reduce the problem of uneven surface of the winding core caused by the difference between the thickness of the pole sheet and the thickness of the paste, reduce the possibility of gaps at the interface, and improve the cycle performance of the battery.

[0044] In view of this, the utility model provides a winding core, comprising a first pole piece, a diaphragm and a second pole piece that are stacked and wound, the polarities of the first pole piece and the second pole piece are opposite; the first pole piece is provided with a first pole ear, and the second pole piece is provided with a step groove arranged opposite to the first pole ear, the step groove comprises a first groove and a second groove arranged away from the first pole ear and connected in sequence, and along the thickness direction of the winding core, the projection of the second groove is located within the projection of the first groove; the winding tail end of the first pole piece has an active layer tail portion and a termination tape on the side facing the second pole piece, and the head of the termination tape covers the active layer tail portion; wherein, the orthographic projection of the termination tape in the thickness direction of the winding core, the head of the termination tape and the active layer tail portion are both located in the second groove.

[0045] The winding core is connected to the termination tape at the winding tail end of the first pole piece. In the thickness direction of the winding core, the orthographic projection of the connection area between the termination tape and the first pole piece is located in the second groove of the step groove, so that the thickness of the first pole ear and the first pole piece at the winding tail end are accommodated in the step groove, reducing the step mutation at the end of the active layer, thereby reducing the thickness difference between adjacent positions near the pole ear position, improving the flatness of the winding core, thereby reducing the uneven pressure near the pole ear during formation, avoiding the formation of gaps at the interface bonding, and alleviating the problem of lithium plating at the pole ear position.

[0046] The content of the utility model will be described in detail below with reference to the accompanying drawings so that those skilled in the art can understand the content of the utility model more clearly and in detail.

[0047] Figure 1 This is one of the structural schematic diagrams of the winding core provided in the embodiment of the present application. Figure 2 The second structural schematic diagram of the winding core provided in the embodiment of the present application is as follows: Figure 3 for Figure 1 Structural diagram of the first tab position in the winding core, Figure 4 for Figure 2 Schematic diagram of the structure of the first pole ear position in the winding core.

[0048] like Figures 1 to 4 As shown, the winding core 100 provided in the embodiment of the present application includes a first pole piece 10, a diaphragm 20, and a second pole piece 30 that are stacked and wound. The first pole piece 10 and the second pole piece 30 have opposite polarities, and the diaphragm 20 is located between the adjacent first pole piece 10 and the second pole piece 30 to avoid contact short circuit between the first pole piece 10 and the second pole piece 30.

[0049] like Figure 1 As shown, the winding core 100 is provided with an arc segment 200. It can be understood that the arc segment 200 is the area 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. 1 , both ends of the winding core 100 in the left-right direction are arc segments 200 . Optionally, the winding core 100 further includes a straight segment 300 connected to the arc segment 200 .

[0050] The winding core 100 further includes a first pole ear 40, a second pole ear 50 and a termination tape 60. The first pole ear 40 is disposed on the first pole piece 10, and the second pole ear 50 is disposed on the second pole piece 30. The winding tail end of the first pole piece 10 has an active layer tail portion on the side facing the second pole piece 30. The termination tape 60 is connected to the winding tail end of the first pole piece 10, and the head of the termination tape 60 covers the active layer tail portion. In the thickness direction of the winding core 100, that is, Figure 1In the middle X direction, the orthographic projection of the connection area between the termination tape 60 and the end of the active layer of the first pole piece 10 is, relative to the first pole ear 40, away from the arc segment 200 of the winding core 100 on the side closest to the first pole ear 40, that is, located on the first pole ear 40, away from the side of the arc segment 200 of the winding core 100 on the side closest to the first pole ear 40, so that the end of the winding core 100 does not exceed the position of the first pole ear 40.

[0051] The projection of the winding tail end of the first pole piece 10 falls on the pole ear position, which can reduce the thickness difference caused by the reduction of the first pole piece 10 at the end position of the winding core 100 and improve the flatness of the winding core 100.

[0052] Preferably, the tail end of the first pole piece 10 on the surface of the winding core 100 does not exceed the position of the first pole tab 40, so that the thickness difference between adjacent positions is ≤40 μm, which can reduce the uneven pressure on the first pole tab 40 during formation and reduce the occurrence of interface gaps.

[0053] like Figure 5 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 respectively located on opposite sides of the first current collector 11 in the thickness direction, a first pole lug groove 121 is provided on the first active material layer 12, the bottom wall of the first pole lug groove 121 is the first current collector 11, and the surrounding side is the first active material layer 12, and a first pole lug 40 electrically connected to the first current collector 11 is provided in the first pole lug groove 121.

[0054] In a possible implementation, the two first active material layers 12 are respectively the first active layer 13 and the second active layer 14. Along the thickness direction of the winding core, in the active layer tail portion of the first pole piece 10, the projection of the tail end of the first active layer 13 coincides with the projection of the tail end of the second active layer 14, as shown in FIG. Figure 2 or the length of the projection of the tail end of the first active layer 13 is greater than the length of the projection of the tail end of the second active layer 14, as shown in FIG. Figure 1 As shown; or the length of the projection of the tail end of the first active layer 13 is less than the length of the projection of the tail end of the second active layer 14. That is, along the winding direction, the tail end of the first active layer 13 is flush with the tail end of the second active layer 14; or the tail end of the first active layer 13 exceeds the tail end of the second active layer 14; or the tail end of the second active layer 14 exceeds the tail end of the first active layer 13.

[0055] The first pole piece 10 includes a double-sided area, a single-sided area and an empty foil area. The double-sided area is an area where the first active material layer 12 exists on both sides of the first current collector 11. The single-sided area is an area where the first active material layer 12 exists on only one side of the first current collector 11. The empty foil area is an area where only the first current collector 11 exists. Among them, on the first pole piece 10, the double-sided area, the single-sided area and the empty foil area are connected in sequence, so that the empty foil area ends at the tail of the first pole piece 10. The tail of the termination tape 60 covers the empty foil area.

[0056] 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 respectively located on opposite sides of the second current collector 31 in the thickness direction, a second pole lug groove is provided on the second active material layer 32, the bottom wall of the second pole lug groove is the second current collector 31, and the surrounding side is the second active material layer 32, and a second pole lug 50 electrically connected to the second current collector 31 is provided in the second pole lug groove.

[0057] Exemplarily, the first electrode sheet 10 may be a positive electrode sheet, and the second electrode sheet 30 may be a negative electrode sheet; or, the first electrode sheet 10 may be a negative electrode sheet, and the second electrode sheet 30 may be a positive electrode sheet, which is not limited here. When the first electrode sheet 10 is a positive electrode sheet and the second electrode sheet 30 is a negative electrode sheet, aluminum foil may be used as the first current collector 11, and copper foil may be used as the second current collector 31.

[0058] like Figures 3 to 5 As shown, in a possible implementation, a stepped groove 33 is provided on the second pole piece 30. The stepped groove 33 is arranged opposite to the first pole tab 40. The stepped groove 33 includes a first groove 331 and a second groove 332 which are arranged away from the first pole tab 40 and are connected in sequence. Along the thickness direction of the winding core 100, the projection of the second groove 332 is located within the projection of the first groove 331.

[0059] In the orthographic projection in the thickness direction of the winding core 100 , the head of the stopper tape 60 and the tail of the active layer are both located in the second groove 332 .

[0060] By adjusting the depth of different steps of the step groove 33 , the flatness of the winding core 100 can be further reduced due to the reduction in the number of layers of the first pole ear 40 , the pole ear adhesive, and the first pole piece 10 , as well as the thickness difference caused by the termination tape 60 .

[0061] Preferably, in the thickness direction of the winding core 100, the stepped groove 33 is located between the first pole ear 40 and the tail end of the first pole piece 10, so that the pole piece stacking on the side away from the tail end of the winding core 100 is relatively flat, reducing the flatness fluctuation caused by the opening of the hole groove in the thickness direction of the winding core 100. On the other hand, after the thickness of the first pole ear 40 is accommodated in the stepped groove 33, the overall thickness of the winding core 100 can also be reduced, so that the space utilization rate of the winding core 100 is improved, thereby improving the energy density.

[0062] Preferably, the step groove 33 is opened on the second active material layer 32 adjacent to the first pole ear 40, so that the first pole ear 40 that affects the flatness of the core 100 is adjacent to the groove, thereby improving the step groove 33 to accommodate the thickness of the first pole ear 40, reducing the overall thickness of the core 100, and alleviating the flatness fluctuation caused by the setting of the first pole ear 40 in the thickness direction.

[0063] like Figure 5 As shown, the stepped groove 33 includes a third groove 333 disposed away from the first groove 331 and connected to the second groove 332. Along the thickness direction of the winding core 100, the projection of the third groove 333 is located within the projection of the second groove 332. The first step surface 334 of the first groove 331 and the third step surface 336 of the third groove 333 are respectively located on both sides of the second step surface 335 of the second groove 332. Along the length direction of the second pole piece 30, the sum of the widths of the first step surface 334, the second step surface 335 and the third step surface 336 is consistent with the width of the first pole tab 40.

[0064] like Figure 3 As shown, the width L1 of the first step surface 334 is the distance between the projection position of the first pole tab 40 close to the side of the winding core arc segment 200 and the projection position of the active layer tail portion adjacent thereto in the thickness direction of the winding core 100 .

[0065] The width L2 of the second step surface 335 is the distance between the projection position of the end of the first active layer 13 and the projection position of the end of the second active layer 14 in the thickness direction of the core 100, that is, the misalignment distance of the end coating on both sides, and a ±1mm process margin is reserved.

[0066] The width L3 of the third step surface 336 is the distance between the projection position of the first electrode tab 40 away from the arc segment 200 of the winding core and the projection position of the end of the other active layer in the thickness direction of the winding core 100 .

[0067] The connection area between the termination tape 60 and the tail end of the active layer of the first pole piece 10 is thicker than other areas of the tail end of the first pole piece 10 due to the addition of the termination tape 60. The projection of the second step surface 335 is overlapped with it, so that the increased thickness portion can be accommodated in the second step surface 335, thereby improving the flatness of this position, and can further reduce the overall thickness of the core 100, so that the space utilization of the core 100 is improved, thereby improving the energy density.

[0068] For example, due to fluctuations in the manufacturing process, the width L1 of the first step surface 334 , the width L2 of the second step surface 335 , and the width L3 of the third step surface 336 may increase the error of 2 mm to 5 mm on the basis of the above dimensions.

[0069] In a possible implementation, the depth of the first step surface 334 is h1, the depth of the second step surface 335 is h2, and the depth of the third step surface 336 is h3, wherein h1, h2, and h3 satisfy: 0

[0070] Since there are the tail ends of the first pole ear 40 and the first pole piece 10 and the starting end of the termination tape 60 at the second step surface 335 and the third step surface 336 in the thickness direction of the winding core 100, the thickness here is thicker than that in other areas. Setting h1, h2 and h3 to 0

[0071] like Figure 1 and Figure 2 As shown, the winding core 100 further includes a first protective adhesive tape 70. The first protective adhesive tape 70 is disposed on the first pole piece 10. The first protective adhesive tape 70 covers the first pole tab 40.

[0072] ​​Exemplarily, on the straight section 300, the position where the first protective tape 70 is away from the arc section 200 relative to the first pole ear 40 and the projection of the end end of the first active layer 13 overlaps with the projection of the end end of the second active layer 14 is defined as position a; the position where the first pole ear 40 is not provided in the first pole ear groove 121 and overlaps with the projection of the end tape 60 is defined as position b; the position at the third step surface 336 is defined as position c; the position at the second step surface 335 is defined as position d; the second The position where the step surface 335 overlaps with the end of the outer active layer tail portion (the active material layer tail portion relatively close to the arc segment 200 adjacent to the first pole ear 40) is defined as position e; the position at the first step surface 334 is defined as position f; the position where the first pole ear 40 is not set in the first pole ear groove 121 and is far away from position b relative to the first pole ear 40 is defined as position g; the projection of the termination tape 60 is defined, and the position overlapping with the double-sided area on the side of the first pole ear groove 121 close to the arc segment 200 is defined as position h.

[0073] The depth h1 of the first step surface 334 is a thickness step that balances the thickness of the position e and the position g. Therefore, 0

[0074] Since the thickness difference between the position e and the position g is substantially equal to the thickness of the first electrode tab 40 , the depth h1 of the first step surface 334 satisfies: 0

[0075] The depth h2 of the second step surface 335 is the thickness difference between the position c and the position g. Therefore, 0

[0076] Since the difference in thickness between the position c and the position g is approximately twice the thickness of the first active material layer 12 , the depth h2 of the second step surface 335 satisfies: h2<h3−2*the thickness of the first active material layer 12 .

[0077] The depth h3 of the third step surface 336 satisfies: h3 is equal to the thickness of the second active material layer 32 , that is, the third step surface 336 has the second current collector 31 as a bottom wall.

[0078] Preferably, h1 satisfies: h1=h3−1 / 2 the thickness of the first electrode tab 40 .

[0079] Preferably, h2 satisfies: h2=h3−thickness of the first active material layer 12 .

[0080] For example, due to fluctuations in the manufacturing process, the depth h1 of the first step surface 334 , the depth h2 of the second step surface 335 , and the depth h3 of the third step surface 336 may have an error of ±10 μm based on the above dimensions.

[0081] ​​​In a possible implementation, a tail groove is provided at the winding tail end of the first pole piece 10. The head of the terminating adhesive tape 60 is located in the tail groove.

[0082] Specifically, the tail groove is opened at the tail end of the first active material layer 12 .

[0083] The setting of the tail groove reduces the thickness of the connection area between the termination tape 60 and the first pole piece 10, thereby reducing the thickness variation of the first pole piece 10 near the tail position, reducing the thickness difference at the tail end of the first pole piece 10 caused by the reduction in the number of layers, and improving the flatness of the core 100.

[0084] Preferably, the depth of the tail groove is greater than or equal to the thickness of the termination tape 60, so that the thickness of the connection area between the termination tape 60 and the first pole piece 10 is not higher than the thickness of the first pole piece 10 near the tail, so that the thickness of the first pole piece 10 at the tail gradually decreases without a sudden increase.

[0085] like Figure 1 As shown, in a possible implementation, the first protective tape 70 extends along the winding direction of the winding core 100 and at least partially covers the arc segment 200 of the winding core 100 adjacent to the first electrode tab 40 .

[0086] The first protective tape 70 covers the arc segment 200 , which can increase the thickness of the arc segment 200 compared to the straight segment 300 , so that during the hot pressing process of the winding core 100 , the interface of the arc segment 200 is more tightly bonded after the arc segment 200 is subjected to force, thereby solving the problem of poor adhesion between the diaphragm 20 on the arc segment 200 and the positive and negative electrodes, and improving the long cycle performance of the battery.

[0087] In a possible implementation, the winding core 100 further includes a second protective tape, which is disposed on the second pole piece 30 and covers the stepped groove 33 .

[0088] like Figure 4 As shown, in a possible implementation, in the width direction of the second pole piece 30, there is a gap between the edge of the step groove 33 and the edge of the second pole piece 30 adjacent to the first pole lug 40, that is, there is a second active material layer 32 between the step groove 33 and the edge of the second pole piece 30. In the width direction of the second pole piece 30, the width of the gap is A.

[0089] Because the negative electrode of a conventional lithium-ion battery is wider than the positive electrode, that is, there is an overhang in the width direction, and this width difference is denoted as B. By setting the gap, the second active material layer 32 and the first electrode tab 40 at the gap can be closely abutted to prevent the interface gap from being too large, alleviate the problem of lithium precipitation in the electrode tab, and improve the heat conduction efficiency on the electrode.

[0090] Preferably, A≥B, so that the contact between the pole pieces at this position is wider and the combination is tighter.

[0091] In a possible implementation, a plurality of first recesses 123 are formed on the first active material layer 12. The first recesses 123 may be grooves or strip-shaped grooves.

[0092] The groove is a through hole, a blind hole or a countersunk hole on the first pole piece 10. The strip groove is a linear groove extending along the length direction of the pole piece.

[0093] The concave portion set on the positive electrode sheet can knock out some active substances and increase the CB (Cell Balance) value at the corresponding position. The pore structure can also store electrolyte, improve the wetting performance of the electrolyte on the electrode sheet, and further improve the lithium precipitation phenomenon.

[0094] Preferably, the first recess 123 is a hole, which can be opened at the edge of the first pole piece 10, the arc segment 200, the edge of the first pole ear 40, the edge of the termination tape 60, the edge of the first protective tape 70, or set on the entire surface of the first pole piece 10, which can improve the CB value of the corresponding position and improve the edge lithium deposition, arc lithium deposition, and pole ear lithium deposition on the winding core 100.

[0095] The strip grooves can be made on the first pole piece 10 by laser marking.

[0096] In a possible implementation, a plurality of second recesses 34 are formed on the second active material layer 32 .

[0097] The second recess 34 opened on the negative electrode sheet can increase the lithium insertion speed at the corresponding position, improve the negative electrode dynamics, and then increase the negative electrode surface density, thereby improving the overall energy density of the battery, and alleviate the lithium desorption problem. In addition, it can also increase the liquid storage capacity.

[0098] The second recess 34 may be a second hole formed on the second electrode sheet 30 , or a groove formed on the first active material layer 12 .

[0099] like Figure 7 The figure is a schematic diagram of the structure of a winding core of a comparative example shown in the prior art.

[0100] The difference between the comparative example and the embodiment of the present application is that, in the comparative example, there is no groove on the second pole piece 30 corresponding to the welding area of ​​the first pole ear 40, and the first active material layer 12 at the tail end of the first pole piece 10 of the winding core extends beyond the first pole ear 40 and is closer to the arc segment 200 on the side adjacent to the first pole ear 40.

[0101] As shown below, a table comparing the thickness data of the embodiment of the present application and the comparative example is provided, wherein the position of the comparative example and the position of the embodiment of the present application relative to the first electrode tab 40 are consistent.

[0102] Table 1 is a table of thickness data of each position of Example 1, Example 2 and Comparative Example (unit: μm)

[0103] Example 1 Very bad Example 2 Very bad Comparative Example Very bad a w+518 w+518 w+518 b w+434 84 w+434 84 w+410 108 c w+504 -70 w+504 -70 w+580 -170 d w+473 31 w+442 62 w+580 0 e w+442 31 w+442 0 w+580 0 f w+441 1 w+441 1 w+580 0 g w+442 -1 w+442 -1 w+480 100 h w+480 -38 w+480 -38 w+542 -62

[0104] Where w is the total thickness of other areas of the core, and the range is the thickness difference between adjacent positions.

[0105] Compared with the results of the embodiment, it can be seen that by setting the step groove 33, the range between adjacent positions in the tab area (position b-position h) can be reduced from the maximum 170μm of the comparative example to the maximum 84μm, and reduced to within 100μm, especially the range between position c and position g is significantly reduced, which improves the interface adhesion in the tab area. In addition, the thickness change at each position is also smaller, that is, it is flatter. Therefore, during formation, the pressure near the tab is more uniform, and the probability of gaps in the interface bonding is reduced, which alleviates the problem of lithium precipitation at the tab position.

[0106] The battery is not limited to lithium batteries, and in the future this technology may be applied to sodium batteries, etc. In the present embodiment, lithium-ion batteries are preferred.

[0107] In addition, the embodiment of the present application further provides a battery, including a battery housing and a winding core 100. The winding core 100 is located in the battery housing.

[0108] The specific structure, working principle and function of the winding core 100 have been described in detail in the above embodiments and will not be repeated here. It should be noted that the preparation process of the lithium-ion battery is as follows:

[0109] Step 1: Preparation of positive electrode sheet: prepare positive electrode active layer slurry, apply the positive electrode active material slurry on the surface of the current collector, and obtain the first electrode sheet 10 after baking and rolling. The first electrode sheet 10 has a thickness of 70 μm, and a certain position of the first electrode sheet 10 has a first pole ear groove 121 of fixed size, and a first pole ear 40 with a thickness of 100 μm is welded in the first pole ear groove 121 by laser or ultrasonic welding, and a first protective adhesive tape 70 with a thickness of 12 μm is respectively attached to both sides of the pole sheet in the first pole ear groove 121;

[0110] Step 2: Prepare the negative electrode active layer slurry, apply the negative electrode slurry on the carbon-coated copper foil, and obtain the second pole piece 30 after baking and rolling. The thickness of the second pole piece 30 is 105μm. A certain position of the second pole piece 30 has a second pole ear groove with a fixed size. The second pole ear 50 is welded in this groove by laser or ultrasonic welding, and a 12μm thick adhesive tape is pasted on both sides of the second pole ear groove pole piece; in addition, the second pole piece 30 corresponding to the welding area of ​​the first pole ear 40 is cleaned to form a stepped groove 33, wherein the first step surface 334 is 3mm wide and 30μm deep, the second step surface 335 is 3mm wide and 45μm deep, and the third step surface 336 is 3mm wide and 50μm deep. The copper foil is visible to the naked eye;

[0111] Step 3: After the positive and negative electrode sheets are cut and sliced, they are wound with the separator to obtain a winding core, and the paste at the tail of the positive electrode of the winding core is mapped on the first pole ear 40, and the width of the termination tape 60 covering the positive electrode paste is 3mm, and the distance between the termination tape 60 and the left and right sides of the first pole ear groove 121 is 3.5mm;

[0112] Step 4: After packaging, baking, liquid injection, formation, secondary sealing, sorting and OCV (open circuit voltage) testing, a lithium-ion battery is obtained.

[0113] The electrolyte is a commercially available conventional electrolyte, and the lithium salt therein is LiFP6.

[0114] 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 it. 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 replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A winding core, characterized in that: It comprises a first pole piece, a diaphragm and a second pole piece which are stacked and wound, wherein the first pole piece and the second pole piece have opposite polarities; The first pole piece is provided with a first pole ear, the second pole piece is provided with a stepped groove arranged opposite to the first pole ear, the stepped groove comprises a first groove and a second groove arranged away from the first pole ear and connected in sequence, and along the thickness direction of the winding core, the projection of the second groove is located within the projection of the first groove; The winding tail end of the first pole piece has an active layer tail portion and a termination tape on one side facing the second pole piece, and the head of the termination tape covers the active layer tail portion; Wherein, in the orthographic projection in the thickness direction of the winding core, the head of the termination tape and the tail of the active layer are both located in the second groove.

2. The winding core according to claim 1, characterized in that: The first pole piece includes a first current collector and a first active layer and a second active layer respectively located on opposite sides of the first current collector in a thickness direction, and along the winding direction, in the tail portion of the active layer, the tail end of the first active layer is flush with the tail end of the second active layer; or, The end of the first active layer exceeds the end of the second active layer; or The tail end of the second active layer exceeds the tail end of the first active layer.

3. The winding core according to claim 1, characterized in that: The stepped groove includes a third groove which is arranged away from the first groove and connected to the second groove, and along the thickness direction of the winding core, the projection of the third groove is located within the projection of the second groove, and the first step surface of the first groove and the third step surface of the third groove are respectively located on both sides of the second step surface of the second groove; The depth of the first step surface is h1, the depth of the second step surface is h2, and the depth of the third step surface is h3, wherein h1, h2 and h3 satisfy: 0<h1≤h2≤h3.

4. The winding core according to claim 3, characterized in that: The first pole piece includes a first current collector and first active material layers respectively located on two opposite sides of the first current collector in a thickness direction, and the second pole piece includes a second current collector and second active material layers respectively located on two opposite sides of the second current collector in a thickness direction; h1 satisfies: h1<h3-thickness of the first electrode tab; and / or h2 satisfies: h2<h3-2*thickness of the first active material layer; and / or h3 satisfies: h3 is equal to the thickness of the second active material layer.

5. The winding core according to claim 4, characterized in that: h1 satisfies: h1=h3-1 / 2 the thickness of the first electrode tab; and / or h2 satisfies: h2=h3-the thickness of the first active material layer.

6. The winding core according to claim 1, characterized in that: A tail groove is provided at the winding tail end of the first pole piece, and the head of the terminating adhesive tape is located in the tail groove.

7. The winding core according to claim 1, characterized in that: The winding core also includes a first protective tape, which is arranged on the first pole piece and covers the first pole ear. The first protective tape extends along the winding direction of the winding core and at least partially covers the arc segment of the winding core closest to the first pole ear.

8. The winding core according to claim 1, characterized in that: The winding core further includes a second protective adhesive tape, the second protective adhesive tape is arranged on the second pole piece, and the second protective adhesive tape covers the step groove.

9. The winding core according to claim 1, characterized in that: In the width direction of the second pole piece, there is a gap between the edge of the stepped groove and the edge of the second pole piece.

10. The winding core according to claim 1, characterized in that: The first pole piece includes a first current collector and first active material layers respectively located on two opposite sides of the first current collector in a thickness direction, and a first recess is formed on the first active material layer; and / or, The second pole piece includes a second current collector and second active material layers respectively located on two opposite sides of the second current collector in a thickness direction, and a second recess is formed on the second active material layer.

11. A battery, characterized in that: The invention comprises a shell and the winding core according to any one of claims 1 to 10, wherein the winding core is located in the shell.

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