Battery

Abstract

The battery comprises a shell and an electrode assembly located in the shell, and the electrode assembly comprises a negative plate, a diaphragm and a positive plate which are sequentially stacked and wound; a foil leaking groove is formed in the surface of the negative plate, a part of the negative current collector is exposed out of the bottom wall of the foil leaking groove, the negative plate further comprises a negative lug and first protection glue, a part of the negative lug is located in the foil leaking groove and electrically connected with the negative current collector, and the negative lug extends in the second direction and exceeds the first edge of the negative plate; the first protection glue covers part of the negative tab in the foil leakage groove, gaps are formed between the two side edges of the first protection glue and the side walls of the foil leakage groove in the first direction, and gaps are formed between the bottom edge of the first protection glue and the lower wall, away from the first edge, of the foil leakage groove in the second direction; the lithium ion battery further comprises a hot melt adhesive, the hot melt adhesive is located on the outer surface of the electrode assembly, the hot melt adhesive is connected with the inner side wall of the shell and the electrode assembly, and in the orthographic projection of the third direction, the two sides of the first protection adhesive do not exceed the two sides of the hot melt adhesive in the width direction of the negative tab.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a battery. Background Art

[0002] After the tabs and the battery cell are welded, protective glue needs to be pasted on the tabs to prevent the burrs at the welding points or the edges of the tabs from piercing the diaphragm and avoiding the danger of short circuit between the positive and negative electrodes. However, the protective glue will overlap with the active layer around the tabs, which will not only affect the flatness of the pole piece, but also make the thickness of the final electrode assembly larger, affecting the energy density of the battery.

[0003] In the related art, the protective glue is reduced in size and embedded in the leakage foil groove of the electrode piece to solve the problem of thick electrode assembly. However, it is easy to cause the copper foil to break, increasing the safety risk. Summary of the invention

[0004] To solve the above problems, the present invention aims to provide a battery, the battery comprising a housing and an electrode assembly located inside the housing, the electrode assembly comprising a negative electrode sheet, a separator and a positive electrode sheet stacked and wound in sequence;

[0005] The negative electrode sheet comprises a negative electrode current collector and a negative electrode active layer disposed on at least one side of the surface of the negative electrode current collector, a leakage foil groove is disposed on the surface of the negative electrode sheet, a bottom wall of the leakage foil groove exposes a portion of the negative electrode current collector, and the negative electrode active layer is disposed on the surrounding side of the leakage foil groove;

[0006] The negative electrode sheet further includes a negative electrode ear and a first protective glue, a portion of the negative electrode ear is located in the leakage foil groove and is electrically connected to the negative electrode current collector, and the negative electrode ear extends along the second direction and exceeds the first edge of the negative electrode sheet;

[0007] The first protective glue covers part of the negative electrode ear in the leakage foil groove, and along the first direction, both sides of the first protective glue have gaps with the side walls of the leakage foil groove, and along the second direction, the bottom edge of the first protective glue has a gap with the lower wall of the leakage foil groove away from the first edge;

[0008] The battery includes a hot melt adhesive, which is located on the outer surface of the electrode assembly. The hot melt adhesive respectively connects the inner wall of the shell and the electrode assembly. In the orthographic projection in the third direction, along the width direction of the negative electrode ear, the two sides of the first protective adhesive do not exceed the two sides of the hot melt adhesive.

[0009] As an optional embodiment of the present invention, in the orthographic projection in the third direction, the upper edge of the hot melt adhesive exceeds the lower edge of the negative electrode ear on the negative electrode current collector away from the first edge; and / or,

[0010] In the orthographic projection of the third direction, along the first direction, two sides of the hot melt adhesive exceed two sides of the foil leakage groove.

[0011] As an optional embodiment of the present invention, a chamfered portion is provided on the lower edge of the negative electrode tab and on at least one side edge of the electrode tab.

[0012] As an optional embodiment of the present invention, the electrode assembly includes a straight section and a first arc segment and a second arc segment respectively located on both sides of the straight section, the negative electrode ear is arranged close to the first arc segment, and the chamfered portion is located at the side edge of the negative electrode ear close to the first arc segment.

[0013] As an optional implementation manner of the present invention, the chamfered portion is an arc chamfer.

[0014] As an optional implementation manner of the present invention, the leakage foil groove is configured to be U-shaped.

[0015] As an optional embodiment of the present invention, the gap between the bottom edge of the first protective glue and the lower wall of the leakage foil groove away from the first edge is A, and the gap between the two side edges of the first protective glue and the side walls of the leakage foil groove is B, and A and B satisfy:

[0016] 0.1≤A / B≤1.2;

[0017] Preferably, 0.4≤A / B≤0.8; and / or,

[0018] A≥0.15mm.

[0019] As an optional embodiment of the present invention, the positive electrode sheet is provided with a positive electrode ear, and the hot melt adhesive includes two, and in the orthographic projection in the third direction, the two hot melt adhesives are arranged at intervals, and the two hot melt adhesives respectively cover at least part of the negative electrode ear and at least part of the positive electrode ear.

[0020] As an optional embodiment of the present invention, along the first direction, the width of the hot melt adhesive is D, and the width of the leakage foil groove is W. 1 , D and W 1 satisfy:

[0021] 1<D / W 1 <1.9;

[0022] Preferably, 1.2<D / W 1 <1.7.

[0023] As an optional embodiment of the present invention, the positive electrode sheet comprises a positive electrode current collector and a positive electrode active layer provided on at least one side surface of the positive electrode current collector, the positive electrode sheet is provided with a thinning groove, the depth of the bottom wall of the thinning groove from the positive electrode current collector is less than the thickness of the positive electrode active layer, and the thinning groove is arranged opposite to the negative electrode ear;

[0024] Along the first direction, the width of the thinning groove is greater than the width of the foil leakage groove.

[0025] As an optional embodiment of the present invention, the thinning groove includes a first groove and a second groove that are interconnected;

[0026] The first groove is located on a side of the second groove away from the positive electrode current collector, and along the first direction, the width of the first groove is greater than the width of the leakage foil groove, and the width of the first groove is greater than the width of the second groove;

[0027] The negative electrode ear surface has a welding mark, and in the orthographic projection in the third direction, two sides of the width of the second groove exceed two sides of the width of the welding mark.

[0028] As an optional embodiment of the present invention, the negative electrode sheet is provided with a plurality of wire grooves, and the plurality of wire grooves are arranged on the negative electrode active layer at intervals along the first direction.

[0029] The beneficial effects of the present invention are as follows: by attaching hot melt adhesive at the positions corresponding to the positive and negative tabs on the outside of the electrode assembly, and making the width of the hot melt adhesive greater than the width of the corresponding protective adhesive. When the battery cell undergoes a high-temperature hot pressing process, the hot melt adhesive here will partially melt, and the hot melt adhesive in a molten state will fill the cavity formed by the leakage foil groove and the surrounding active layer and the protective adhesive under pressure, which not only improves the flatness of the electrode piece and reduces the thickness of the electrode assembly, but also avoids the danger of copper foil breakage, thereby improving the safety performance of the battery cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor.

[0031] Figure 1 It is a partial structural schematic diagram of a negative electrode sheet according to an exemplary embodiment of the present invention.

[0032] Figure 2 A cross-sectional view of an electrode assembly according to an exemplary embodiment of the present invention.

[0033] Figure 3 for Figure 2 Enlarged view of point A in the middle.

[0034] Figure 4 It is a front view of an electrode assembly according to an exemplary embodiment of the present invention.

[0035] Figure 5 for Figure 4 A rear view of the electrode assembly.

[0036] Figure 6 It is a schematic diagram of the partial structure of the negative electrode sheet in the related technology.

[0037] In the figure,

[0038] 10. Leakage foil groove; 20. First protective glue; 30. Negative ear; 31. Welding point; 40. Positive electrode sheet; 41. Thinning groove; 411. First groove; 412. Second groove; 413. First insulating glue; 50. Negative electrode sheet; 51. Starting end; 52. First edge; 53. Second edge; 54. Negative active layer; 60. Second insulating glue; 70. Positive ear; 80. Hot melt glue; 90. Diaphragm; 101. First arc segment; 102. Second arc segment; 103. Straight segment. DETAILED DESCRIPTION

[0039] It is known that some batteries have an electrode assembly (also called a winding core) wound into a flat structure. The electrode assembly includes a negative electrode sheet, a separator and a positive electrode sheet stacked and wound in sequence, and the negative electrode sheet and the positive electrode sheet are wound through the separator to form an electrode assembly. Among them, the negative electrode sheet includes a negative electrode collector and a negative electrode active layer 54 arranged on at least one side surface of the negative electrode collector. For example, the negative electrode collector includes a first surface and a second surface arranged oppositely, and the negative electrode active layer 54 is coated on the first surface, or coated on the second surface, or coated on the first surface and the second surface.

[0040] In related technologies, such as Figure 6 As shown, Figure 6 It is a schematic diagram of the structure of the electrode assembly in the related art. The electrode assembly includes a negative electrode ear 30, a first protective glue 20 and a leakage foil groove 10. Among them, the leakage foil groove 10 is formed by cleaning the negative electrode active layer 54 at the corresponding position on the first surface and / or the second surface to expose the negative electrode collector. Afterwards, at the corresponding position of the leakage foil groove 10 (that is, the position where the negative electrode active layer 54 is cleaned), the negative electrode ear 30 is fixed to the exposed negative electrode collector by welding, and a plurality of welding points 31 are formed between the negative electrode collector and the negative electrode ear 30. The first protective glue 20 is pasted on the first surface and the second surface corresponding to the negative electrode ear 30, and is used to cover the plurality of welding points 31 to prevent the welding points 31 from piercing the diaphragm to cause a short circuit between the positive and negative electrode sheets and the positive electrode sheets.

[0041] For ease of understanding, Figure 6 The V-axis direction is the width direction of the electrode assembly, that is, the length direction of the positive / negative electrode sheet; the R-axis direction is the height direction of the electrode assembly, that is, the width direction of the positive / negative electrode sheet. Figure 6 As can be seen from the figure, the width W of the first protective glue 20 is 2 Greater than the width W of the foil slot 10 1 , the distance Y between the bottom edge of the first protective glue 20 and the top edge of the negative electrode ear 30 2 Greater than the distance Y between the bottom edge of the leakage foil slot 10 and the top edge of the negative electrode ear 30 1 .

[0042] The resulting problem is that the thickness of the tab region in the electrode assembly is the sum of the thickness of the negative tab 30 and the thickness of the first protective glue 20; the thickness of the non-tab region is the thickness of the first protective glue 20; or the thickness of the first protective glue 20 and the thickness of the negative electrode active layer 54. As a result, the thickness of the tab region and the non-tab region are inconsistent during the winding process of the electrode assembly, resulting in poor flatness of the final electrode assembly.

[0043] In addition, due to the width W of the first protective glue 20 2 Greater than the width W of the foil slot 10 1 , the distance Y between the bottom edge of the first protective glue 20 and the top edge of the negative electrode ear 30 2 Greater than the distance Y between the bottom edge of the leakage foil slot 10 and the top edge of the negative electrode ear 30 1 Another problem is that the portion of the first protective glue 20 that exceeds the leakage foil groove 10 will overlap with the negative electrode active layer 54, so that the thickness of this portion increases unexpectedly, eventually leading to an increase in the thickness of the electrode assembly, affecting the energy density of the battery.

[0044] Continue to see Figure 6 , the width W of the first protective glue 20 2 Greater than the width W of the foil slot 10 1 , that is, the two sides of the first protective glue 20 in the width direction exceed the two sides of the leakage foil groove 10 in the width direction. It is possible that the two sides of the negative electrode ear 30 in the width direction are in contact with the negative electrode active layer 54, resulting in increased heat generation at this position and severe temperature rise.

[0045] In order to solve the above problems, the inventors have found through research that by reducing the size of the first protective glue 20 accordingly so that the first protective glue 20 does not overlap with the negative electrode active layer 54, the problem of thickening of the electrode assembly can be solved. At the same time, the process steps can be simplified to a certain extent. The negative electrode active layer 54 only needs to be cleaned once to form the leakage foil groove 10, thereby improving production efficiency.

[0046] However, since the first protective glue 20 after the embedded treatment does not cover part of the negative electrode current collector in the leakage foil groove 10, that is, there is a large thickness difference between the leakage foil and the surrounding negative electrode active layer 54 or the first protective glue 20, a cavity is formed here. During the charge and discharge process of the battery cell, the expansion and contraction of the negative electrode active layer 54 during the charge and discharge cycle will cause this part of the negative electrode current collector to be squeezed or stretched, causing the negative electrode current collector not covered by the first protective glue 20 to break, increasing the internal resistance and heat generation at the negative electrode ear 30, and the broken negative electrode current collector will pierce the diaphragm and short-circuit the positive electrode during the expansion and stretching process, causing safety risks. At the same time, due to the changeable expansion and stretching direction of the negative electrode sheet 50, especially at the angle position of the lower edge of the rectangular leakage foil groove 10, the negative electrode current collector is prone to fatigue fracture after multiple cycles, which greatly advances the time for the negative electrode current collector to break.

[0047] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0048] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0049] In addition, in the description of the present invention, the terms used are only for illustrative purposes and are not intended to limit the scope of the present invention. The terms "include" and / or "comprise" are used to specify the existence of the elements, steps, operations and / or components, but do not exclude the existence or addition of one or more other elements, steps, operations and / or components. The terms "first", "second" and the like may be used to describe various elements, do not represent the order, and do not limit these elements. In addition, in the description of the present invention, unless otherwise specified, the meaning of "multiple" is two and more than two. These terms are only used to distinguish one element from another element. In conjunction with the following drawings, these and / or other aspects become apparent, and it is easier for a person of ordinary skill in the art to understand the description of the embodiments of the present invention. The accompanying drawings are used to describe the embodiments of the present invention for illustrative purposes only. Those skilled in the art will easily recognize from the following description that, without departing from the principles of the present invention, alternative embodiments of the structures and methods shown in the present invention can be adopted.

[0050] See also Figure 2 and Figure 4 ,in Figure 2 is a schematic cross-sectional view of an exemplary electrode assembly taken along the height direction; Figure 4 : is a front view of the exemplary electrode assembly. For ease of understanding, the V-axis direction in the figure is the width direction of the electrode assembly, that is, the first direction, that is, the length direction of the negative electrode sheet 50 and the positive electrode sheet 40; the R-axis direction is the height direction of the electrode assembly, that is, the second direction, that is, the width direction of the negative electrode sheet 50 and the positive electrode sheet 40; the U-axis direction is the thickness direction of the electrode assembly, that is, the third direction, that is, the thickness direction of the negative electrode sheet 50 and the positive electrode sheet 40; wherein the first direction, the second direction and the third direction are perpendicular to each other.

[0051] like Figure 2 and Figure 4 As shown, a battery described in this embodiment includes a shell (not shown) and an electrode assembly located inside the shell, and the electrode assembly includes a negative electrode sheet 50, a separator 90 and a positive electrode sheet 40 stacked and wound in sequence. Among them, the negative electrode sheet 50 includes a negative electrode collector and a negative electrode active layer 54 provided on at least one side of the negative electrode collector. A leakage foil groove 10 is provided on the surface of the negative electrode sheet 50, and a portion of the negative electrode collector is exposed on the bottom wall of the leakage foil groove 10, and a negative electrode active layer 54 is provided on the surrounding side of the leakage foil groove 10.

[0052] For details, see Figure 1 , Figure 1 Schematic diagram of the structure of the negative electrode sheet 50 in the electrode assembly. As described above, the negative electrode sheet 50 includes a negative electrode current collector and a first negative electrode active layer 54 and a second negative electrode active layer 54 coated on the negative electrode current collector. The first negative electrode active layer 54 is, for example, located on the first surface of the negative electrode sheet 50 in the thickness direction, the second negative electrode active layer 54 is, for example, located on the second surface of the negative electrode sheet 50 in the thickness direction, and the negative electrode current collector is, for example, located between the first surface and the second surface.

[0053] The leakage foil groove 10 can be, for example, disposed on the first surface, or the second surface, or the first surface and the second surface of the negative electrode sheet 50. The leakage foil groove 10 can be formed by washing away the first negative electrode active layer 54, the second negative electrode active layer 54, or the first negative electrode active layer 54 and the second negative electrode active layer 54 at the corresponding position thereof to expose the current collector in the leakage foil groove 10, which facilitates welding the negative electrode ear 30 to the current collector. In use, the leakage foil groove 10 can be disposed on the first surface and / or the second surface according to the arrangement position of the negative electrode ear 30, which is not specifically limited in the present application.

[0054] See also Figure 1 In the orthographic projection of the negative electrode sheet 50 in the thickness direction, the dotted frame in the figure is a schematic diagram of the projection position relationship between the hot melt adhesive 80 and the fold where the negative electrode ear 30 is located.

[0055] Continue to see Figure 1 The negative electrode sheet 50 further includes a negative electrode ear 30 and a first protective glue 20. A portion of the negative electrode ear 30 is located in the leakage foil groove 10 and is electrically connected to the negative electrode current collector. The negative electrode ear 30 extends along the second direction and exceeds the first edge 52 of the negative electrode sheet 50. The first edge 52 is, for example, the upper edge of the negative electrode sheet 50 in the second direction. For example, the negative electrode ear 30 is fixedly connected to the negative electrode sheet 50 by welding.

[0056] Specifically, a portion of the negative electrode ear 30 is located in the leakage foil groove 10, and the connection between the negative electrode ear 30 and the negative electrode sheet 50 is achieved by welding with the current collector in the leakage foil groove 10, and the other portion of the negative electrode ear 30 extends along the width direction of the negative electrode sheet 50 beyond the first edge 52 of the negative electrode sheet 50 located above, so as to be electrically connected to other battery cells.

[0057] It should be noted that, along the width direction of the negative electrode sheet 50 , the negative electrode sheet 50 has a first edge 52 and a second edge 53 that are arranged opposite to each other, the negative electrode ear 30 extends out of the electrode assembly through the first edge 52 , and the leakage foil groove 10 is arranged close to the first edge 52 .

[0058] The first protective glue 20 covers part of the negative electrode ear 30 in the leakage foil groove 10. Along the first direction, both side edges of the first protective glue 20 have gaps with the side walls of the leakage foil groove 10. Along the second direction, the bottom edge of the first protective glue 20 has a gap with the lower wall of the leakage foil groove 10 away from the first edge 52.

[0059] Specifically, the first protective glue 20 is attached to the leakage foil slot 10 and completely covers the negative electrode ear 30 located in the leakage foil slot 10. On the one hand, the first protective glue 20 can cover all the welding points 31 between the negative electrode ear 30 and the negative electrode sheet 50, so as to prevent the welding points 31 from piercing the diaphragm 90 and causing a short circuit between the negative electrode sheet 50 and the positive electrode sheet 40; at the same time, the first protective glue 20 can also cover the edges of both sides of the negative electrode ear 30, so as to prevent the burrs on the edges of the negative electrode ear 30 from piercing the diaphragm 90 and causing a short circuit between the negative electrode sheet 50 and the positive electrode sheet 40.

[0060] by Figure 1 Take this as an example to illustrate:

[0061] W 1 is the width of the foil slot 10, W 2 is the width of the first protective glue 20, Y 1 Y is the distance between the bottom edge of the leakage foil groove 10 and the top edge of the negative electrode sheet 50, 2 is the distance between the bottom edge of the first protective glue 20 and the top edge of the negative electrode sheet 50 .

[0062] The first protective glue 20 satisfies the following relationship: 2 <W 1 And Y 2 <Y1 That is, the width of the first protective glue 20 is smaller than the width of the leakage foil groove 10, and the distance between the bottom edge of the first protective glue 20 and the top edge of the negative electrode sheet 50 is also smaller than the distance between the bottom edge of the leakage foil groove 10 and the top edge of the negative electrode sheet 50. In other words, the positive projection of the first protective glue 20 on the current collector of the negative electrode sheet 50 is smaller than the positive projection of the leakage foil groove 10 on the current collector of the negative electrode sheet 50.

[0063] In this way, not only can the thickness of the electrode assembly be reduced and the energy density of the battery be improved, but also the first protective glue 20 can be directly bonded to the current collector in the leakage foil groove 10 (avoiding the first protective glue 20 from bonding to the active layer), thereby improving the adhesion of the first protective glue 20.

[0064] See also Figure 2 or Figure 4 The battery described in this embodiment also includes a hot melt adhesive 80, which is located on the outer surface of the electrode assembly. The hot melt adhesive 80 connects the inner wall of the shell and the electrode assembly respectively. In the orthographic projection in the third direction, along the width direction of the negative electrode ear 30, the two sides of the first protective adhesive 20 do not exceed the two sides of the hot melt adhesive 80.

[0065] It can be understood that the hot melt adhesive 80 is located on the outer surface of the electrode assembly, and its position corresponds to the position of the first protective adhesive 20, that is, in the projection in the third direction, the width of the hot melt adhesive 80 can be equal to the width of the first protective adhesive 20, or the width of the hot melt adhesive 80 can be greater than the width of the first protective adhesive 20. In use, it can be selected according to specific circumstances, and this application does not specifically limit it.

[0066] It is easy to understand that the hot melt adhesive 80 can fix the electrode assembly and the shell through the viscosity it generates during the high-temperature hot pressing process of the battery cell assembly; more importantly, under the combined action of high temperature and pressure, part of the hot melt adhesive 80 will be in a molten state, and the hot melt adhesive 80 in a molten state will be filled in the recessed area formed on the outer surface of the electrode assembly due to the gap between the first protective adhesive 20 and the leakage foil groove 10 under the action of extrusion. It can not only overcome the problem of overall unevenness of the electrode assembly caused by the gap between the first protective adhesive 20 and the leakage foil groove 10, but also overcome the stress concentration problem caused by the recessed area, thereby improving the safety of the battery cell.

[0067] It should be noted that during the formation stage, due to the extrusion of the hot melt adhesive 80 , the edge of the hot melt adhesive 80 will form an imprint with a nearly uniform width on the surface of the electrode assembly, that is, the imprint on the outer surface of the electrode assembly can be regarded as the outer dimension of the hot melt adhesive 80 .

[0068] Furthermore, a gap A is formed between the bottom edge of the first protective adhesive 20 and the lower wall of the foil drain groove 10 away from the first edge 52 , and a gap B is formed between the two side edges of the first protective adhesive 20 and the corresponding side walls of the foil drain groove 10 .

[0069] like Figure 1 As shown in FIG. 1 , the size of the gap A can be understood as Y 1 With Y 2 The size of the gap B can be understood as W 1 With W 2 The difference is half. A and B satisfy 0.1≤A / B≤1.2.

[0070] In this way, the difference between the gap A and the gap B is small, which can effectively improve the flatness of the casting surface of the hot melt adhesive 80 and improve the flatness of the battery cell.

[0071] Preferably, A<B and / or 0.4≤A / B≤0.8, for example, the value of A / B is 0.5, 0.6 or 0.7, etc.

[0072] Because the length of gap A is much larger than gap B, the gap A between the bottom edge of the first protective glue 20 and the lower wall of the leakage foil groove 10 is set smaller, which can reduce the amount of hot melt adhesive 80 used to fill the recessed area formed on the surface of the electrode assembly due to gap A, avoid the existence of a large width mutation area in the width direction of the negative electrode sheet, and improve the overall flatness of the electrode assembly.

[0073] Furthermore, A≥0.15 mm, for example, A may be 0.18 mm, 0.19 mm, 0.22 mm, 0.25 mm, 0.26 mm or 0.27 mm, etc. The gap A meeting the above range can not only reduce the amount of hot melt adhesive 80 used, but also maintain a sufficient gap size to prevent the first protective adhesive 20 from adhering to the negative active layer 54 of the negative electrode sheet 50.

[0074] In an optional embodiment, in the orthographic projection in the third direction, the upper edge of the hot melt adhesive 80 exceeds the lower edge of the negative electrode ear 30 on the negative electrode collector away from the first edge 52; and / or, along the first direction, both sides of the hot melt adhesive 80 exceed both sides of the leakage foil groove.

[0075] like Figure 4As shown, in the orthographic projection in the third direction, the upper edge of the hot melt adhesive 80 exceeds the lower edge of the negative electrode ear 30. It can be understood that in the orthographic projection in the third direction, the lower edge of the negative electrode ear 30 is covered by the upper edge of the hot melt adhesive 80, that is, the hot melt adhesive 80 is sufficient to cover the lower edge of the negative electrode ear 30 in the second direction of the electrode assembly. The hot melt adhesive 80 can increase the strength and toughness of the position near the lower edge of the negative electrode ear 30, and can effectively alleviate the fracture problem of the current collector at this position caused by the deformation near the lower edge of the negative electrode ear 30 being greater than the deformation on both sides of the negative electrode ear 30.

[0076] Preferably, in the orthographic projection in the third direction, both sides of the hot melt adhesive 80 exceed both sides of the leakage foil groove. In other words, the hot melt adhesive 80 not only covers the lower edge of the negative electrode ear 30 in the second direction of the electrode assembly, but also covers the two side edges of the negative electrode ear 30 in the first direction of the electrode assembly. Not only can the stress concentration problem of the current collector at the lower edge of the negative electrode ear 30 be alleviated, but also the stress concentration problem at the two side edges of the negative electrode ear 30 can be alleviated. In this way, the problem of the current collector at the peripheral side of the negative electrode ear 30 being broken due to stress concentration is avoided.

[0077] In an optional embodiment, a chamfer is provided at the lower edge of the negative electrode ear 30 and at least one side edge of the negative electrode ear 30. For example, the chamfer may be an arc chamfer, a C-shaped chamfer, a U-shaped chamfer, or a linear chamfer, etc. In use, an adaptive selection may be made according to factors such as processing conditions, and the present application does not specifically limit it.

[0078] Preferably, continue to see Figure 1 Along the second direction of the electrode assembly, the lower edge of the negative electrode ear 30 is set to be an arc-shaped chamfer, so that during the charging and discharging process of the battery, the deformation of the negative electrode ear 30 due to the expansion or contraction of the negative electrode sheet 50 is curved, avoiding stress concentration caused by the right angle between the lower edge of the negative electrode ear 30 and the side, affecting the service life of the negative electrode ear 30 and its corresponding current collector, and improving the safety of the battery.

[0079] Furthermore, the electrode assembly includes a straight section and a first arc section and a second arc section respectively located on both sides of the straight section, the negative electrode ear 30 is arranged close to the first arc section, and the chamfered portion is located at the side edge of the negative electrode ear 30 close to the first arc section.

[0080] It is known that the battery cell is flat as a whole, and the two sides located in the first direction thereof are arc-shaped transitions called arc segments, namely the first arc segment 101 and the second arc segment 102. The first arc segment 101 is located on the right side of the electrode assembly, and the second arc segment 102 is located on the left side of the electrode assembly. The negative electrode ear 30 is, for example, arranged at a position close to the first arc segment 101. The portion located between the first arc segment 101 and the second arc segment 102 is flat and is called a straight segment 103. The first arc segment 101 and the second arc segment 102 are bent and subjected to a greater pressing force than the straight segment. When the negative electrode sheet 50 is deformed during the battery cycle, the deformation is difficult to be transmitted to the other side of the arc segment, resulting in a larger deformation amount on one side of the arc segment than on the other side. The arc chamfer is arranged on the side close to the first arc segment 101, so that the deformation of the negative electrode ear 30 can be gradually transitioned along the arc chamfer to avoid stress concentration at a certain point.

[0081] In an optional embodiment, the leakage foil slot 10 is configured to be U-shaped.

[0082] like Figure 1 As shown, the angle of the leakage foil slot 10 can be understood as, for example, the angle between the bottom edge of the leakage foil slot 10 and the two side edges adjacent to the bottom edge in the second direction. Setting a chamfer at the angle of the leakage foil slot 10 can be understood as setting the transition between the bottom edge and the two side edges of the leakage foil slot 10 as an arc transition, so that the leakage foil slot 10 presents a U-shaped structure as a whole. In this way, stress concentration can be avoided at the angle between the bottom edge and the two side edges of the leakage foil slot 10, thereby avoiding the problem of the current collector breaking at this position due to stress concentration.

[0083] In an optional embodiment, a positive electrode tab 70 is provided on the positive electrode sheet 40, and two hot melt adhesives 80 are included. In the orthographic projection in the third direction, the two hot melt adhesives 80 are arranged at intervals, and the two hot melt adhesives 80 respectively cover at least part of the negative electrode tab 30 and at least part of the positive electrode tab 70.

[0084] like Figure 4 As shown, two hot melt adhesives 80 correspond to the negative electrode ear 30 and the positive electrode ear 70, respectively, that is, one hot melt adhesive 80 is attached to the position of the electrode assembly surface corresponding to the negative electrode ear 30, and the other hot melt adhesive 80 is attached to the position of the electrode assembly surface corresponding to the positive electrode ear 70. While the hot melt adhesive 80 plays a bonding and filling role, the area of ​​the hot melt adhesive 80 can be minimized as much as possible, and the bubbles generated by the hot melt adhesive 80 during the hot pressing process can be discharged in time, avoiding the accumulation of bubbles inside the hot melt adhesive 80 due to the large area of ​​the hot melt adhesive 80, thereby affecting the effective filling of the hot melt adhesive 80 into the concave area on the surface of the electrode assembly.

[0085] Preferably, along the first direction, the width of the hot melt adhesive 80 is D, and the width of the leaking foil slot 10 is W. 1 , D and W1 Satisfy: 1<D / W 1 <1.9.

[0086] It is easy to understand that the width D of the hot melt adhesive 80 can be understood as, for example, the distance between the left side and the right side of the hot melt adhesive 80 in the first direction, and the width of the leaking foil slot 10 is W. 1 For example, it can be understood as the distance between the left side and the right side of the foil drain slot 10 in the first direction. 1 is greater than 1, that is, the width of the hot melt adhesive 80 is greater than the width of the leakage foil groove 10. In the orthographic projection in the third direction, it can be ensured that both sides of the hot melt adhesive 80 can cover the two sides of the leakage foil groove 10, thereby ensuring that a sufficient amount of hot melt adhesive 80 can be filled into the concave area corresponding to the leakage foil groove 10 on the surface of the electrode assembly in a molten state. At the same time, D / W 1 When the ratio is less than 1.9, the area of ​​the hot melt adhesive 80 will not be too large, which may affect the generation of a large number of bubbles in the hot melt adhesive 80 during the hot pressing state.

[0087] More preferably, 1.2<D / W 1 <1.7. For example, D / W 1 It can be 1.3, 1.4, 1.5 or 1.6, etc. The width of the hot melt adhesive 80 and the width of the leakage foil slot 10 that meet the above range can, on the one hand, offset the error in the pasting process of the hot melt adhesive 80, and on the other hand, even in the case of the maximum error, there can still be about 1mm of hot melt adhesive 80 remaining, and this part of the excess hot melt adhesive 80 is sufficient to cover both sides of the leakage foil slot 10 in the molten state. Thus, it can be avoided that the hot melt adhesive 80 covers too much area on both sides of the leakage foil slot 10, and the thickness of the electrode assembly will not increase due to overlap. Finally, the flatness and energy density of the electrode assembly are improved.

[0088] In an optional embodiment, the positive electrode sheet 70 includes a positive electrode current collector and a positive electrode active layer arranged on the surface of at least one side of the positive electrode current collector. A thinning groove 41 is provided on the positive electrode sheet 40. The depth of the bottom wall of the thinning groove 41 from the positive electrode current collector is less than the thickness of the positive electrode active layer. The thinning groove is arranged opposite to the negative electrode ear 30. Along the first direction, the width of the thinning groove 41 is greater than the width of the leakage foil groove 10.

[0089] Among them, the thinning groove 41 includes a first groove 411 and a second groove 412 which are connected to each other; the first groove 411 is located on the side where the second groove 412 is located away from the positive electrode current collector, and along the first direction, the width of the first groove 411 is greater than the width of the leakage foil groove 10, and the width of the first groove 411 is greater than the width of the second groove 412; the surface of the negative electrode ear 30 has a weld mark, and in the orthographic projection in the third direction, the width of the first groove exceeds the width of the weld mark on both sides.

[0090] like Figure 2 and Figure 3 As shown, it can be understood that the positive electrode sheet 40 includes a positive electrode collector and a positive electrode active layer. Among them, the positive electrode active material is coated on one surface of the positive electrode collector in the thickness direction, or coated on two surfaces of the positive electrode collector in the thickness direction. The thickness of the single-sided active layer is, for example, the thickness of the positive electrode active layer on any one surface of the positive electrode collector. The thinning groove 41 is, for example, arranged at the corresponding position of the two positive electrode sheets 40 adjacent to the negative electrode ear 30, and the position is, for example, the projection position of the negative electrode ear 30 on the adjacent positive electrode sheet 40. The thinning groove 41 is described below by taking the positive electrode sheet 40 located below the negative electrode ear 30 as an example.

[0091] The thinning groove 41 includes a first groove 411 close to the negative electrode ear 30 and a second groove 412 away from the negative electrode ear 30, that is, the first groove 411 is located above the second groove 412. The width L of the first groove 411 is 1 Greater than the width W of the foil slot 10 1 , the amount of negative electrode active material on the negative electrode sheet 50 corresponding to the portion of the first groove 411 that exceeds the leakage foil groove 10 is greater than the amount of positive electrode active material on the positive electrode sheet 40, so that there is enough space on the negative electrode sheet 50 to accommodate the ions released from the positive electrode sheet 40. The negative electrode active material on the negative electrode sheet 50 is, for example, graphite, and the positive electrode active material on the positive electrode sheet 40 is, for example, a lithium-containing compound. When the width L of the first groove 411 is 1 Greater than the width W of the foil slot 10 1 When the negative electrode sheet 50 is filled with graphite, there is enough graphite on the negative electrode sheet 50 to accommodate the lithium ions released from the positive electrode sheet 40, thereby avoiding the problem of lithium deposition during the charge and discharge process of the battery.

[0092] Preferably, 1<L 1 / W 1 ≤2.5. For example, L 1 / W 1 is 1.2, 1.5, 1.6, 1.8, 2 or 2.3, etc. Among them, L 1 is the width of the first groove 411, W 1 The first groove 411 that meets the above range can not only ensure that there is enough graphite on the negative electrode sheet 50 to accommodate the lithium ions released from the positive electrode sheet 40, thereby avoiding the problem of lithium precipitation during the charge and discharge process of the battery; at the same time, it can also avoid the width of the first groove 411 being too large, resulting in waste of the capacity of the positive electrode sheet 40 and loss of the energy density of the battery.

[0093] Continue to see Figure 3, the electrode assembly also includes a first insulating glue 413, and the first insulating glue 413 is located in the first groove 411. The weld mark on the surface of the negative ear 30 can be understood as a mark or pattern formed by welding the negative ear 30 to the multiple welding points 31 formed on the current collector of the negative electrode sheet 50. The width of the second groove 412 is greater than the width of the mark or pattern formed by the multiple welding points 31, so that the first insulating glue 413 can further block all the welding points 31 between the negative electrode sheet 50 and the negative ear 30. The outer side of the welding point 31 is at least covered with a double layer of the first protective glue 20 and the first insulating glue 413. Even if the first protective glue 20 is punctured by the welding point 31, the first insulating glue 413 can also play a blocking role, further avoiding a short circuit between the negative ear 50 and the positive ear 40. It is easy to understand that by placing the first insulating glue 413 in the first groove 411, the first groove 411 can offset the thickness of the first insulating glue 413, thereby preventing the first insulating glue 413 from increasing the thickness of the electrode assembly and thus affecting the energy density of the battery. It should be noted that the first insulating glue 413 can be an insulating adhesive tape, or an insulating liquid or semi-solid coating formed by curing.

[0094] In an optional embodiment, the first groove 411 and the second groove 412 satisfy:

[0095] h 3 ≤h 1 ≤h 2 ≤h 4 , where h 1 is the depth of the first groove 411, h 2 is the depth of the second groove 412, h 3 is the thickness of the first insulating adhesive 413, h 4 is the thickness of the single-sided active layer on the positive electrode sheet 40.

[0096] As described above, the first insulating glue 413 is arranged in the first groove 411, so that the first groove 411 can offset the thickness of the first insulating glue 413, and the thickness of the first insulating glue 413 is less than or equal to the depth of the first groove 411, ensuring that the thickness of the first insulating glue 413 is completely offset by the first groove 411, and the first insulating glue 413 will not increase the thickness of the electrode assembly.

[0097] The second groove 412 can be used to offset the height of the welding spot 31. For example, when the height of the welding spot 31 is high and exceeds the negative electrode sheet 50, the portion of the welding spot 31 that exceeds the negative electrode sheet 50 can be accommodated in the second groove 412, thereby preventing the welding spot 31 from being too high and increasing the thickness of the electrode assembly, which has an adverse effect on the battery density. At the same time, the depth of the second groove 412 is less than or equal to the thickness of the single-sided active layer on the positive electrode sheet 40, which can prevent the second groove 412 from affecting the positive current collector of the positive electrode sheet 40.

[0098] Preferably, the sum of the depths of the first groove 411 and the second groove 412 is equal to the thickness of the single-sided active layer on the positive electrode sheet 40. At this time, the positive electrode collector at the corresponding position of the second groove 412 is exposed, so that the first insulating glue 413 here is directly bonded to the positive electrode collector, thereby improving the adhesion between the first insulating glue 413 and the positive electrode sheet 40 and reducing the risk of the first insulating glue 413 falling off.

[0099] See also Figure 2 and Figure 4-5 The electrode assembly further includes a second insulating glue 60 , which is wound from one side of the electrode assembly to the other side of the electrode assembly, and the second insulating glue 60 is located between the negative electrode tab 30 and the positive electrode tab 70 .

[0100] As shown in the figure, the second insulating glue 60 is arranged at the upper end of the electrode assembly and is in contact with the outer side of the electrode assembly. The first end of the second insulating glue 60 is, for example, located on the front side of the electrode assembly, and the second end of the second insulating glue 60 is, for example, located on the rear side of the electrode assembly. And the portion between the first end and the second end of the second insulating glue 60 is located between the negative electrode ear 30 and the positive electrode ear 70. In this way, during the formation hot pressing process, the area between the negative electrode ear 30 and the positive electrode ear 70 is thicker than other areas of the electrode assembly, and the second insulating glue 60 can apply a pressing force to the area between the negative electrode ear 30 and the positive electrode ear 70, thereby playing a role in pressing the electrode assembly.

[0101] It is easy to understand that the negative electrode sheet 50 has a starting end 51 during the winding process, and the first starting end 51 is located at the innermost part of the electrode assembly. Preferably, the projection of the second insulating glue 60 on the electrode assembly overlaps with the starting end 51, that is, the second insulating glue 60 can exert a certain pressing force on the starting end 51 to prevent the starting end 51 of the negative electrode sheet 50 from breaking and moving inside the electrode assembly, affecting the normal use of the battery.

[0102] In an optional embodiment, the negative electrode sheet is provided with a plurality of wire grooves, and the plurality of wire grooves are arranged on the negative electrode sheet along the first direction, and the extension direction of the wire grooves is the width direction of the electrode sheet.

[0103] The wire grooves may be, for example, wrinkles provided on the negative electrode sheet 50 or grooves formed in the thickness direction of the negative electrode sheet 50. The wire grooves are grooves formed in the thickness direction of the negative electrode sheet 50 as an example for explanation: for example, the wire grooves may be implemented in any process step such as rolling, laser cleaning, die cutting, and winding of the negative electrode sheet 50.

[0104] Preferably, the negative electrode sheet 50 is cleaned to form a wire groove. During the battery cycle, the negative electrode sheet 50 will expand and contract. The provision of the wire groove can effectively alleviate the stress concentration existing at certain positions of the negative electrode sheet 50, improve the tensile and compressive resistance of the negative electrode sheet 50, thereby avoiding the problem of the current collector being broken due to the expansion and contraction of the negative electrode sheet 50, and can also improve the electrolyte infiltration ability of the negative electrode sheet 50.

[0105] In the description provided herein, a large number of specific details are described. However, it is understood that embodiments of the present invention can be practiced without these specific details. In some instances, well-known methods, structures and techniques are not shown in detail so as not to obscure the understanding of this description.

[0106] Furthermore, persons of ordinary skill in the art will appreciate that although some embodiments described herein include certain features included in other embodiments but not other features, the combination of features from different embodiments is meant to be within the scope of the present invention and to form different embodiments.

[0107] It will be appreciated by those skilled in the art that, although the present invention has been described with reference to exemplary embodiments, various changes may be made and its elements may be replaced with equivalents without departing from the scope of the present invention. In addition, many modifications may be made to adapt specific situations or materials to the teachings of the present invention without departing from the essential scope of the present invention.

Claims

1. A battery, characterized in that: It comprises a shell and an electrode assembly located inside the shell, wherein the electrode assembly comprises a negative electrode sheet, a separator and a positive electrode sheet which are stacked and wound in sequence; The negative electrode sheet comprises a negative electrode current collector and a negative electrode active layer disposed on at least one side of the surface of the negative electrode current collector, a leakage foil groove is disposed on the surface of the negative electrode sheet, a bottom wall of the leakage foil groove exposes a portion of the negative electrode current collector, and the negative electrode active layer is disposed on the surrounding side of the leakage foil groove; The negative electrode sheet further includes a negative electrode ear and a first protective glue, a portion of the negative electrode ear is located in the leakage foil groove and is electrically connected to the negative electrode current collector, and the negative electrode ear extends along the second direction and exceeds the first edge of the negative electrode sheet; The first protective glue covers part of the negative electrode ear in the leakage foil groove, and along the first direction, both sides of the first protective glue have gaps with the side walls of the leakage foil groove, and along the second direction, the bottom edge of the first protective glue has a gap with the lower wall of the leakage foil groove away from the first edge; The battery includes a hot melt adhesive, which is located on the outer surface of the electrode assembly. The hot melt adhesive respectively connects the inner wall of the shell and the electrode assembly. In the orthographic projection in the third direction, along the width direction of the negative electrode ear, the two sides of the first protective adhesive do not exceed the two sides of the hot melt adhesive.

2. The battery according to claim 1, characterized in that In the orthographic projection in the third direction, the upper edge of the hot melt adhesive exceeds the lower edge of the negative electrode ear on the negative electrode current collector away from the first edge; and / or, In the orthographic projection in the third direction, along the first direction, two sides of the hot melt adhesive exceed two sides of the foil leakage groove.

3. The battery according to claim 1, characterized in that A chamfered portion is provided on the lower edge of the negative electrode ear and at least one side edge of the negative electrode ear.

4. The battery according to claim 3, characterized in that The electrode assembly includes a straight section and a first arc section and a second arc section respectively located on both sides of the straight section, the negative electrode ear is arranged close to the first arc section, and the chamfered portion is located at the side edge of the negative electrode ear close to the first arc section.

5. The battery according to claim 3, characterized in that The chamfered portion is a circular arc chamfer.

6. The battery according to claim 1, characterized in that The foil drain slot is arranged in a U shape.

7. The battery according to claim 1, characterized in that The gap between the bottom edge of the first protective glue and the lower wall of the foil drain groove away from the first edge is A, and the gap between the two side edges of the first protective glue and the side walls of the foil drain groove is B. A and B satisfy: 0.1≤A / B≤1.2; Preferably, 0.4≤A / B≤0.8; and / or, A≥0.15mm.

8. The battery according to claim 1, characterized in that The positive electrode sheet is provided with a positive electrode ear, and the hot melt adhesives include two. In the orthographic projection in the third direction, the two hot melt adhesives are arranged at intervals, and the two hot melt adhesives respectively cover at least part of the negative electrode ear and at least part of the positive electrode ear.

9. The battery according to claim 1, characterized in that Along the first direction, the width of the hot melt adhesive is D, the width of the foil leakage slot is W1, and D and W1 satisfy: 1<D / W1<1.9; Preferably, 1.2<D / W1<1.

7.

10. The battery according to claim 1, characterized in that The positive electrode sheet comprises a positive electrode current collector and a positive electrode active layer disposed on at least one side of the positive electrode current collector, the positive electrode sheet is provided with a thinning groove, the depth of the bottom wall of the thinning groove from the positive electrode current collector is less than the thickness of the positive electrode active layer, and the thinning groove is disposed opposite to the negative electrode ear; Along the first direction, the width of the thinning groove is greater than the width of the foil leakage groove.

11. The battery according to claim 10, characterized in that The thinning groove includes a first groove and a second groove that are interconnected; The first groove is located on a side of the second groove away from the positive electrode current collector, and along the first direction, the width of the first groove is greater than the width of the leakage foil groove, and the width of the first groove is greater than the width of the second groove; The negative electrode ear surface has a welding mark, and in the orthographic projection in the third direction, two sides of the width of the second groove exceed two sides of the width of the welding mark.

12. The battery according to claim 1, characterized in that The negative electrode sheet is provided with a plurality of wire grooves, and the plurality of wire grooves are arranged on the negative electrode active layer at intervals along the first direction.

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