A battery

Abstract

The application discloses a battery, which comprises a shell and an electrode assembly located in the shell, the electrode assembly comprising a negative electrode sheet, a diaphragm and a positive electrode sheet which are sequentially stacked and wound; the negative electrode sheet is provided with a leakage foil groove, the bottom wall of the leakage foil groove exposes a part of the negative electrode current collector, the negative electrode sheet further comprises a negative electrode lug and a first protective adhesive, a part of the negative electrode lug is located in the leakage foil groove and is electrically connected with the negative electrode current collector, the negative electrode lug extends along a second direction and exceeds the first edge of the negative electrode sheet; the first protective adhesive covers the part of the negative electrode lug in the leakage foil groove, the two side edges of the first protective adhesive are both provided with a gap with the side wall of the leakage foil groove along a first direction, and the bottom edge of the first protective adhesive is provided with a gap with the lower wall of the leakage foil groove away from the first edge along the second direction; the battery further comprises hot melt adhesive, the hot melt adhesive is located on the outer surface of the electrode assembly, and the hot melt adhesive is connected with the inner side wall of the shell and the electrode assembly; in the orthographic projection along a third direction, the two sides of the first protective adhesive do not exceed the two sides of the hot melt adhesive along the width direction of the negative electrode lug.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a battery. BACKGROUND

[0002] After the tab and the battery cell are welded, a protective glue needs to be pasted on the tab to prevent the burr on the edge of the welding point or the tab from piercing the diaphragm, thereby avoiding the risk of short circuit between the positive and negative electrodes. However, the protective glue will overlap with the active layer around the tab, which not only affects the flatness of the tab, but also makes the thickness of the final electrode assembly larger, thereby affecting the energy density of the battery.

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

[0004] To solve the above problems, the purpose of the present application is to provide a battery, which comprises a shell and an electrode assembly located inside the shell, and the electrode assembly comprises a negative tab, a diaphragm and a positive tab which are sequentially stacked and wound.

[0005] The negative tab comprises a negative current collector and a negative active layer arranged on at least one side surface of the negative current collector, and the negative tab is provided with a leakage foil groove, the bottom wall of the leakage foil groove exposes part of the negative current collector, and the leakage foil groove is provided with the negative active layer on the side.

[0006] The negative tab further comprises a negative tab and a first protective glue, part of the negative tab is located in the leakage foil groove and is electrically connected with the negative current collector, and the negative tab extends along a second direction and beyond the first edge of the negative tab.

[0007] The first protective glue covers part of the negative tab in the leakage foil groove, and the two sides of the first protective glue have gaps with the side walls of the leakage foil groove along the first direction, and 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 along the second direction.

[0008] The battery comprises a hot melt glue, and the hot melt glue is located on the outer surface of the electrode assembly and is connected with the inner side wall of the shell and the electrode assembly respectively. In the orthographic projection in the third direction, along the width direction of the negative tab, the two sides of the first protective glue do not exceed the two sides of the hot melt glue.

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

[0010] In the positive 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 application, the lower edge of the negative tab is provided with a chamfering part, and at least one side edge of the tab is provided with a chamfering part.

[0012] As an optional embodiment of the present application, the electrode assembly comprises a flat section and a first circular arc section and a second circular arc section located on both sides of the flat section respectively, the negative tab is arranged close to the first circular arc section, and the chamfering part is located at the side edge of the negative tab close to the first circular arc section.

[0013] As an optional embodiment of the present application, the chamfering part is a circular arc chamfering part.

[0014] As an optional embodiment of the present application, the foil leakage groove is provided in a U shape.

[0015] As an optional embodiment of the present application, the gap between the bottom edge of the first protective glue and the lower wall of the foil leakage groove away from the first edge is A, the gap between the two side edges of the first protective glue and the side wall of the foil leakage 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 application, the positive tab is provided on the positive electrode sheet, the hot melt adhesive comprises two, in the positive projection of the third direction, the two hot melt adhesives are arranged at intervals, and the two hot melt adhesives cover at least part of the negative tab and at least part of the positive tab respectively.

[0020] As an optional embodiment of the present application, along the first direction, the width of the hot melt adhesive is D, the width of the foil leakage groove is W1, and D and W1 satisfy:

[0021] 1<D / W1<1.9;

[0022] Preferably, 1.2<D / W1<1.7.

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

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

[0025] As an optional embodiment of the present application, the thinning groove comprises a first groove and a second groove in communication with each other;

[0026] The first groove is located on the side of the second groove away from the positive current collector, and in 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 tab surface has a welding mark, and in the orthogonal projection in the third direction, the width of the second groove exceeds the width of the welding mark on both sides.

[0028] As an optional embodiment of the present application, the negative tab is provided with a plurality of wire grooves, which are arranged on the negative active layer in the first direction.

[0029] The beneficial effects of the present application are: by adhering hot melt adhesive at the positions corresponding to the positive and negative tabs on the outer side 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 is subjected to high-temperature hot pressing process, the hot melt adhesive at this position will partially melt, and the hot melt adhesive in the molten state will fill the cavity formed by the leakage foil groove, the surrounding active layer and the protective adhesive under the action of pressure. Not only improves the flatness of the tab, reduces the thickness of the electrode assembly, but also can avoid the danger of copper foil fracture, improves the safety performance of the battery cell. BRIEF DESCRIPTION OF DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0031] Figure 1 A partial structure diagram of a negative tab according to an exemplary embodiment of the present application.

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

[0033] Figure 3 For Figure 2 An enlarged view of A in FIG.

[0034] Figure 4 A front view of an electrode assembly according to an exemplary embodiment of the present application.

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

[0036] Figure 6 This is a partial structural diagram of the negative electrode in related technologies.

[0037] In the picture,

[0038] 10. Foil groove; 20. First protective adhesive; 30. Negative electrode tab; 31. Solder joint; 40. Positive electrode sheet; 41. Thinning groove; 411. First groove; 412. Second groove; 413. First insulating adhesive; 50. Negative electrode sheet; 51. Starting end; 52. First edge; 53. Second edge; 54. Negative electrode active layer; 60. Second insulating adhesive; 70. Positive electrode tab; 80. Hot melt adhesive; 90. Separator; 101. First arc segment; 102. Second arc segment; 103. Straight segment. Detailed Implementation

[0039] It is known that some batteries have electrode assemblies (also called cores) wound into a flat structure. The electrode assembly includes a negative electrode sheet, a separator, and a positive electrode sheet sequentially stacked and wound, with the negative and positive electrode sheets wound through the separator to form the electrode assembly. The negative electrode sheet includes a negative current collector and a negative active layer 54 disposed on at least one surface of the negative current collector. For example, the negative current collector includes a first surface and a second surface disposed opposite to each other, and the negative active layer 54 is coated, for example, on the first surface, or on the second surface, or on both the first and second surfaces.

[0040] In related technologies, such as Figure 6 As shown, Figure 6 This is a schematic diagram of the electrode assembly in the related technology. The electrode assembly includes a negative electrode tab 30, a first protective adhesive 20, and a foil drain trough 10. The foil drain trough 10 is formed by cleaning away the negative electrode active layer 54 at corresponding positions on the first and / or second surfaces to expose the negative electrode current collector. Then, at the corresponding positions in the foil drain trough 10 (i.e., where the negative electrode active layer 54 has been cleaned), the negative electrode tab 30 is fixed to the exposed negative electrode current collector by welding, forming multiple solder joints 31 between the negative electrode current collector and the negative electrode tab 30. The first protective adhesive 20 is adhered to the first and second surfaces corresponding to the negative electrode tab 30 to cover the multiple solder joints 31, preventing the solder joints 31 from piercing the separator and causing a short circuit between the positive and negative electrode plates.

[0041] For ease of understanding, Figure 6 The V-axis direction represents the width of the electrode assembly, i.e., the length direction of the positive / negative electrode; the R-axis direction represents the height of the electrode assembly, i.e., the width direction of the positive / negative electrode. From Figure 6As can be seen, the width W2 of the first protective adhesive 20 is greater than the width W1 of the tab slot 10, and the distance Y2 between the bottom edge of the first protective adhesive 20 and the top edge of the negative tab 30 is greater than the distance Y1 between the bottom edge of the tab slot 10 and the top edge of the negative tab 30.

[0042] The problem caused thereby is that the thickness of the tab area in the electrode assembly is the sum of the thickness of the negative tab 30 and the thickness of the first protective adhesive 20, the thickness of the non-tab area is the thickness of the first protective adhesive 20, or the thickness of the first protective adhesive 20 and the thickness of the negative active layer 54. This results in the thickness of the tab area and the non-tab area being inconsistent during the winding process, and the flatness of the final electrode assembly is poor.

[0043] In addition, since the width W2 of the first protective adhesive 20 is greater than the width W1 of the tab slot 10, and the distance Y2 between the bottom edge of the first protective adhesive 20 and the top edge of the negative tab 30 is greater than the distance Y1 between the bottom edge of the tab slot 10 and the top edge of the negative tab 30. The problem caused thereby is that the part of the first protective adhesive 20 that exceeds the tab slot 10 will overlap the negative active layer 54, resulting in an undesirable increase in the thickness of this part, ultimately leading to an increase in the thickness of the electrode assembly, affecting the energy density of the battery.

[0044] Continuing to refer to Figure 6 , the width W2 of the first protective adhesive 20 is greater than the width W1 of the tab slot 10, i.e. the two side edges of the first protective adhesive 20 in the width direction exceed the two side edges of the tab slot 10 in the width direction. The possible situation is that the two side edges of the negative tab 30 in the width direction are in contact with the negative active layer 54, resulting in an increase in heat generation and a serious temperature rise at this location.

[0045] To solve the above problems, the inventors have found that by appropriately reducing the size of the first protective adhesive 20, the first protective adhesive 20 does not overlap the negative active layer 54, i.e. the problem of thickening of the electrode assembly can be solved, and the process steps can also be simplified to some extent, i.e. only one cleaning of the negative active layer 54 is required to form the tab slot 10, improving the production efficiency.

[0046] But since the first protective glue 20 after the inlaying process does not cover the negative current collector in the part of the foil leakage groove 10, that is, there is a large thickness difference between the foil leakage and the surrounding negative active layer 54 or the first protective glue 20, a cavity is formed at this position. During the charging and discharging process of the battery cell, the negative current collector at this position will be squeezed or stretched due to the expansion and contraction of the negative active layer 54 during the charging and discharging cycle, causing the negative current collector not covered by the first protective glue 20 to break, increasing the internal resistance and heat generation at the negative tab 30, and the broken negative current collector will pierce the separator and short the positive electrode during the expansion and stretching process, causing safety risks. At the same time, due to the variable expansion and stretching direction of the negative plate 50, especially at the position of the included angle of the lower edge of the rectangular foil leakage groove 10, the negative current collector is prone to fatigue fracture after multiple cycles, greatly shortening the time of negative current collector fracture.

[0047] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of the present application.

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

[0049] In addition, in the description of the present application, the terms used are only for illustrative purposes, and are not intended to limit the scope of the present application. The terms "include" and / or "contain" are used to specify the existence of the described 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", etc. can be used to describe various elements, which do not represent the order and do not limit these elements. In addition, in the description of the present application, unless otherwise specified, the meaning of "multiple" is two and more than two. These terms are only used to distinguish one element from another. These and / or other aspects become apparent from the following drawings, and those skilled in the art can more easily understand the description of the embodiments described in the present application. The drawings are used to depict the embodiments described in the present application only for illustrative purposes. Those skilled in the art will easily realize from the following description that alternative embodiments of the structures and methods shown in the present application can be employed without departing from the principles described in the present application.

[0050] Referring to Figure 2 and Figure 4 , whereinFigure 2 is a schematic view of a cross section of an exemplary electrode assembly taken along a 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, i.e., the first direction, which is also the length direction of the negative tab 50 and the positive tab 40; the R-axis direction is the height direction of the electrode assembly, i.e., the second direction, which is also the width direction of the negative tab 50 and the positive tab 40; the U-axis direction is the thickness direction of the electrode assembly, i.e., the third direction, which is also the thickness direction of the negative tab 50 and the positive tab 40; wherein the first direction, the second direction, and the third direction are perpendicular to each other.

[0051] As shown in Figure 2 and Figure 4 , a battery according to the present embodiment includes a housing (not shown in the figure) and an electrode assembly inside the housing, the electrode assembly including a negative tab 50, a separator 90, and a positive tab 40 stacked and wound in sequence. The negative tab 50 includes a negative current collector and a negative active layer 54 provided on at least one side surface of the negative current collector. The negative tab 50 is provided with a leakage foil groove 10, the bottom wall of which exposes part of the negative current collector, and the negative active layer 54 is provided on the circumferential side of the leakage foil groove 10.

[0052] Specifically, reference can be made to Figure 1 , Figure 1 is a schematic view of the structure of the negative tab 50 part of the electrode assembly. As described above, the negative tab 50 includes a negative current collector and a first negative active layer 54 and a second negative active layer 54 coated on the negative current collector. The first negative active layer 54 is, for example, located on a first surface of the negative tab 50 in the thickness direction, the second negative active layer 54 is, for example, located on a second surface of the negative tab 50 in the thickness direction, and the negative current collector is, for example, located between the first surface and the second surface.

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

[0054] Reference can be made to Figure 1 , in the orthographic projection of the negative tab 50 in the thickness direction, the dashed box in the figure is a schematic view of the projection position relationship of the hot melt adhesive 80 and the negative tab 30.

[0055] Continuing to refer to Figure 1The negative electrode sheet 50 also includes a negative electrode tab 30 and a first protective adhesive 20. Part of the negative electrode tab 30 is located in the foil groove 10 and is electrically connected to the negative electrode current collector. The negative electrode tab 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 tab 30 is fixedly connected to the negative electrode sheet 50 by welding.

[0056] Specifically, a portion of the negative electrode tab 30 is located within the foil groove 10, and the connection between the negative electrode tab 30 and the negative electrode sheet 50 is achieved by welding with the current collector in the foil groove 10. The other portion of the negative electrode tab 30 extends beyond the first edge 52 above the negative electrode sheet 50 along the width direction of the negative electrode sheet 50, so as to facilitate electrical connection with 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 disposed opposite to each other, the negative electrode tab 30 extends out of the outside of the electrode assembly through the first edge 52, and the foil groove 10 is disposed close to the first edge 52.

[0058] The first protective adhesive 20 covers part of the negative electrode tab 30 in the foil trough 10. Along the first direction, both sides of the first protective adhesive 20 have gaps with the sidewalls of the foil trough 10. Along the second direction, the bottom edge of the first protective adhesive 20 has a gap with the lower wall of the foil trough 10 away from the first edge 52.

[0059] Specifically, the first protective adhesive 20 is adhered to the foil groove 10 and completely covers the negative electrode tab 30 located within the foil groove 10. On one hand, the first protective adhesive 20 can cover all the solder joints 31 between the negative electrode tab 30 and the negative electrode sheet 50, preventing the solder joints 31 from piercing the separator 90 and causing a short circuit between the negative electrode sheet 50 and the positive electrode sheet 40; at the same time, it can also cover the two side edges of the negative electrode tab 30, preventing the burrs on the edges of the negative electrode tab 30 from piercing the separator 90 and causing a short circuit between the negative electrode sheet 50 and the positive electrode sheet 40.

[0060] by Figure 1 Let's take an example to illustrate:

[0061] W1 is the width of the foil groove 10, W2 is the width of the first protective adhesive 20, Y1 is the distance between the bottom edge of the foil groove 10 and the top edge of the negative electrode 50, and Y2 is the distance between the bottom edge of the first protective adhesive 20 and the top edge of the negative electrode 50.

[0062] The first protective adhesive 20 satisfies the following relationship: W2 < W1 and Y2 < Y1. That is, the width of the first protective adhesive 20 is smaller than the width of the foil slot 10, and the distance between the bottom edge of the first protective adhesive 20 and the top edge of the negative plate 50 is also smaller than the distance between the bottom edge of the foil slot 10 and the top edge of the negative plate 50. In other words, the orthographic projection of the first protective adhesive 20 on the current collector of the negative plate 50 is smaller than the orthographic projection of the foil slot 10 on the current collector of the negative plate 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 adhesive 20 is directly attached to the current collector in the foil slot 10 (avoiding the first protective adhesive 20 being attached to the active layer), thereby improving the adhesion of the first protective adhesive 20.

[0064] Referring to Figure 2 or Figure 4 The battery described in the embodiment further includes a hot melt adhesive 80, which is located on the outer surface of the electrode assembly and connected to the inner side wall of the shell and the electrode assembly, respectively. In the orthographic projection in the third direction along the width direction of the negative tab 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 the position thereof corresponds to the position of the first protective adhesive 20, that is, in the orthographic 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 conditions, and the present application does not make a specific limitation thereto.

[0066] It can be easily understood that the hot melt adhesive 80 can fix the electrode assembly and the shell through the adhesion thereof during the high-temperature hot-pressing formation process of the electrode assembly. More importantly, under the combined action of high temperature and pressure, part of the hot melt adhesive 80 can be in a molten state, and the hot melt adhesive 80 in the molten state can 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 foil slot 10 under the extrusion action, thereby not only overcoming the problem of unevenness of the electrode assembly as a whole due to the gap between the first protective adhesive 20 and the foil slot 10, but also improving 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, the edges of the hot melt adhesive 80 can form a pressure mark with a width tending to be uniform on the surface of the electrode assembly, that is, the pressure mark on the outer surface of the electrode assembly can be regarded as the external dimension of the hot melt adhesive 80.

[0068] Furthermore, the bottom edge of the first protective adhesive 20 has a gap A with the lower wall of the foil trough 10 away from the first edge 52, and the two sides of the first protective adhesive 20 have gaps B with the corresponding side walls of the foil trough 10.

[0069] like Figure 1 As shown, the size of gap A can be understood, for example, as the difference between Y1 and Y2; the size of gap B can be understood, for example, as half the difference between W1 and W2. The condition 0.1 ≤ A / B ≤ 1.2 is satisfied between A and B.

[0070] Thus, the difference between gap A and gap B is small, which can effectively improve the flatness of the hot melt adhesive 80 casting surface 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 greater than that of gap B, by setting the gap A between the bottom edge of the first protective adhesive 20 and the lower wall of the foil groove 10 to be smaller, 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 can be reduced, thus avoiding a large width abrupt change area in the width direction of the negative electrode sheet and improving the overall flatness of the electrode assembly.

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

[0074] In one alternative implementation, in a third-direction orthogonal projection, the upper edge of the hot melt adhesive 80 extends beyond the lower edge of the negative electrode tab 30 on the negative electrode current collector away from the first edge 52; and / or, along the first direction, both sides of the hot melt adhesive 80 extend beyond both sides of the foil groove.

[0075] like Figure 4 As shown, in the orthographic projection in the third direction, the upper edge of the hot melt adhesive 80 extends beyond the lower edge of the negative electrode tab 30. This can be understood as the lower edge of the negative electrode tab 30 being covered by the upper edge of the hot melt adhesive 80 in the orthographic projection in the third direction. In other words, the hot melt adhesive 80 is sufficient to cover the lower edge of the negative electrode tab 30 in the second direction of the electrode assembly. The hot melt adhesive 80 can increase the strength and toughness near the lower edge of the negative electrode tab 30, effectively mitigating the problem of current collector breakage at this location due to the deformation near the lower edge of the negative electrode tab 30 being greater than the deformation on both sides of the negative electrode tab 30.

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

[0077] In an alternative embodiment, the lower edge of the negative tab 30 and at least one side edge of the negative tab 30 are provided with a chamfered portion. For example, the chamfered portion can be a circular arc chamfer, a c-shaped chamfer, a u-shaped chamfer, or a linear chamfer, etc. In use, it can be adaptively selected according to factors such as processing conditions, which are not specifically limited in the present application.

[0078] Preferably, continuing to refer to Figure 1 , in the second direction of the electrode assembly, the lower edge of the negative tab 30 is provided with a circular arc chamfer, so that the deformation of the negative tab 30 under the expansion or contraction of the negative plate 50 during the charging and discharging of the battery is a curved transition, avoiding the stress concentration caused by the right angle between the lower edge and the side edge of the negative tab 30, affecting the service life of the negative tab 30 and its corresponding current collector, and improving the safety of the battery.

[0079] Further, the electrode assembly includes a flat section and first and second circular arc sections located on both sides of the flat section, respectively, the negative tab 30 is located close to the first circular arc section, and the chamfered portion is located at the side edge of the negative tab 30 close to the first circular arc section.

[0080] It is known that the overall structure of the battery cell is flat, and the two sides in the first direction are curved and are called circular arc sections, i.e. the first and second circular arc sections 101 and 102. For example, the first circular arc section 101 is located on the right side of the electrode assembly, and the second circular arc section 102 is located on the left side of the electrode assembly. The negative tab 30 is located close to the first circular arc section 101. The part between the first and second circular arc sections 101 and 102 is flat and is called a flat section 103. The first and second circular arc sections 101 and 102 are bent and subjected to greater compression than the flat section. When the negative plate 50 deforms during the battery cycle, the deformation is difficult to conduct to the other side of the circular arc section, resulting in a larger deformation on one side of the circular arc section than on the other side. The circular arc chamfer is provided on the side close to the first circular arc section 101, which can make the deformation of the negative tab 30 gradually transition along the circular arc chamfer, avoiding stress concentration at a certain point.

[0081] In an alternative embodiment, the leakage foil groove 10 is provided in a U shape.

[0082] As shown in Figure 1 The included angle of the leakage foil groove 10 can be understood as, for example, in the second direction, the included angle between the bottom edge of the leakage foil groove 10 and the two side edges adjacent to the bottom edge. The chamfering at the included angle of the leakage foil groove 10 can be understood as the overhanging of the bottom edge and the two side edges of the leakage foil groove 10 being arc-shaped, so that the overall structure of the leakage foil groove 10 is similar to a U-shaped structure. In this way, stress concentration can be avoided at the included angle between the bottom edge and the two side edges of the leakage foil groove 10, thereby avoiding the problem of the current collector breaking at this position due to stress concentration.

[0083] In an optional embodiment, the positive tab 70 is provided on the positive electrode tab 40, and the hot melt adhesive 80 includes two, which are spaced apart in the third direction, and the two hot melt adhesives 80 cover at least part of the negative tab 30 and at least part of the positive tab 70, respectively.

[0084] As shown in Figure 4 The two hot melt adhesives 80 correspond to the negative tab 30 and the positive tab 70, respectively, that is, one hot melt adhesive 80 is attached to the position on the surface of the electrode assembly corresponding to the negative tab 30, and the other hot melt adhesive 80 is attached to the position on the surface of the electrode assembly corresponding to the positive tab 70. While the hot melt adhesive 80 plays a role in bonding and filling, the area of the hot melt adhesive 80 is minimized. During the hot pressing process, the bubbles generated by the hot melt adhesive 80 can be promptly discharged, avoiding the accumulation of bubbles inside due to the excessive area of the hot melt adhesive 80, which in turn affects the effective filling of the hot melt adhesive 80 into the recessed area of the surface of the electrode assembly.

[0085] Preferably, in the first direction, the width of the hot melt adhesive 80 is D, and the width of the leakage foil groove 10 is W1, and D and W1 satisfy: 1

[0086] As can be easily understood, the width D of the hot melt adhesive 80 can be understood as, for example, in the first direction, the distance between the left side edge and the right side edge of the hot melt adhesive 80, and the width W1 of the leakage foil groove 10 can be understood as, for example, in the first direction, the distance between the left side edge and the right side edge of the leakage foil groove 10. D / W1 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, which can ensure that both side edges of the hot melt adhesive 80 can cover both side edges of the leakage foil groove 10 in the third direction, thereby ensuring that there is enough amount of hot melt adhesive 80 to fill into the recessed area of the surface of the electrode assembly corresponding to the leakage foil groove 10 in the molten state. At the same time, making D / W1 less than 1.9 can make the area of the hot melt adhesive 80 not too large, which can affect the generation of a large amount of bubbles by the hot melt adhesive 80 in the hot pressing state.

[0087] More preferably, 1.2 < D / W1 < 1.7. For example, D / W1 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 foil groove 10, satisfying the above range, can, on the one hand, compensate for errors during the hot melt adhesive 80 application process; on the other hand, even under the maximum error condition, approximately 1 mm of hot melt adhesive 80 remains. This excess hot melt adhesive 80, in its molten state, is sufficient to cover both sides of the foil groove 10. Therefore, excessive coverage of the foil groove 10 by the hot melt adhesive 80 is avoided, and the electrode assembly does not increase in thickness due to overlap. Ultimately, this improves the flatness and energy density of the electrode assembly.

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

[0089] The thinning groove 41 includes a first groove 411 and a second groove 412 that are interconnected. The first groove 411 is located on the side of the second groove 412 that is away from the positive current collector. Along the first direction, the width of the first groove 411 is greater than the width of the 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 tab 30 has solder marks. In the orthogonal projection of the third direction, the width of the first groove extends beyond the width of the solder marks on both sides.

[0090] like Figure 2 and Figure 3 As shown, it can be understood that the positive electrode 40 includes a positive current collector and a positive active layer. The positive active material is coated on one surface of the positive current collector in the thickness direction, or on both surfaces of the positive current collector in the thickness direction. The thickness of the single-sided active layer is, for example, the thickness of the positive active layer on any one surface of the positive current collector. Thinning grooves 41 are, for example, provided at corresponding positions of two positive electrode sheets 40 adjacent to the negative electrode tab 30, such that the position is, for example, the projected position of the negative electrode tab 30 on its adjacent positive electrode sheet 40. The thinning groove 41 will be described below using the positive electrode sheet 40 located below the negative electrode tab 30 as an example.

[0091] The thinning groove 41 includes a first groove 411 close to the negative tab 30 and a second groove 412 away from the negative tab 30, that is, the first groove 411 is located above the second groove 412. The width L1 of the first groove 411 is greater than the width W1 of the leakage foil groove 10. The amount of negative active material on the negative plate 50 corresponding to the part of the first groove 411 beyond the leakage foil groove 10 is greater than the amount of positive active material on the positive plate 40, so that there is enough space on the negative plate 50 to accommodate the ions released by the positive plate 40. The negative active material on the negative plate 50 is, for example, graphite, and the positive active material on the positive plate 40 is, for example, a lithium-containing compound. When the width L1 of the first groove 411 is greater than the width W1 of the leakage foil groove 10, there is enough graphite on the negative plate 50 to accommodate the lithium ions released by the positive plate 40, avoiding the problem of lithium precipitation during charging and discharging of the battery.

[0092] Preferably, 1 < L1 / W1 ≤ 2.5. For example, L1 / W1 is 1.2, 1.5, 1.6, 1.8, 2 or 2.3, etc. Wherein L1 is the width of the first groove 411, and W1 is the width of the leakage foil groove 10. The first groove 411 satisfying the above range not only enables there to be enough graphite on the negative plate 50 to accommodate the lithium ions released by the positive plate 40, avoiding the problem of lithium precipitation during charging and discharging of the battery; but also avoids the width of the first groove 411 being too large, causing waste of the capacity of the positive plate 40 and loss of the energy density of the battery.

[0093] Continuing to refer to Figure 3 , the electrode assembly further comprises a first insulating glue 413 located in the first groove 411. The surface of the negative tab 30, for example, can be understood as the mark or pattern formed by a plurality of welding points 31 formed by welding the negative tab 30 to the current collector of the negative plate 50. Making the width of the second groove 412 greater than the width of the mark or pattern formed by the plurality of welding points 31 can make the first insulating glue 413 further block all the welding points 31 between the negative plate 50 and the negative tab 30. The outside of the welding points 31 is at least double-protected by the first protective glue 20 and the first insulating glue 413, so that even if the first protective glue 20 is pierced by the welding points 31, the first insulating glue 413 can still play a blocking role, further avoiding short circuit between the negative tab 50 and the positive tab 40. It is easy to understand that arranging the first insulating glue 413 in the first groove 411 can make the first groove 411 offset the thickness of the first insulating glue 413, avoiding the first insulating glue 413 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 insulating paper, or it can be an insulating liquid or semi-solid after coating and solidification.

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

[0095] h3≤h1≤h2≤h4, wherein h1 is the depth of the first groove 411, h2 is the depth of the second groove 412, h3 is the thickness of the first insulating adhesive 413, and h4 is the thickness of the single-sided active layer on the positive plate 40.

[0096] As described above, the first insulating adhesive 413 is arranged in the first groove 411, so that the first groove 411 offsets the thickness of the first insulating adhesive 413. The thickness of the first insulating adhesive 413 is less than or equal to the depth of the first groove 411, so as to ensure that the thickness of the first insulating adhesive 413 is completely offset by the first groove 411, and the first insulating adhesive 413 does not increase the thickness of the electrode assembly.

[0097] The second groove 412 can be used to offset the height of the welding point 31. For example, when the height of the welding point 31 is relatively high and exceeds the negative plate 50, the part of the welding point 31 that exceeds the negative plate 50 can be accommodated in the second groove 412, so as to avoid the welding point 31 from increasing the thickness of the electrode assembly due to its excessive height, and adversely affecting the density of the battery. 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 plate 40, so as to avoid the second groove 412 from affecting the positive current collector of the positive plate 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 plate 40. In this case, the positive current collector at the position corresponding to the second groove 412 is exposed, so that the first insulating adhesive 413 at this position directly adheres to the positive current collector, thereby improving the adhesion between the first insulating adhesive 413 and the positive plate 40, and reducing the risk of the first insulating adhesive 413 falling off.

[0099] Referring to Figure 2 and Figures 4-5 , the electrode assembly further comprises a second insulating adhesive 60, the second insulating adhesive 60 extends from one side of the electrode assembly to the other side of the electrode assembly, and the second insulating adhesive 60 is located between the negative tab 30 and the positive tab 70.

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

[0101] It is easy to understand that the negative plate 50 has a starting end 51 during the winding process, and the first starting end 51 is located at the innermost of the electrode assembly. Preferably, the projection of the second insulating adhesive 60 on the electrode assembly overlaps the starting end 51, that is, the second insulating adhesive 60 can exert a certain pressing force on the starting end 51 to avoid the starting end 51 of the negative plate 50 from moving in the electrode assembly after being broken, thereby affecting the normal use of the battery.

[0102] In an alternative embodiment, the negative plate is provided with a plurality of wire grooves arranged on the negative plate in the first direction, and the wire grooves extend in the width direction of the plate.

[0103] The wire groove can be, for example, a wrinkle provided on the negative plate 50 or a groove formed in the thickness direction of the negative plate 50. Taking the groove formed in the thickness direction of the negative plate 50 as an example, the groove can be formed, for example, during any process step such as rolling, laser cleaning, die cutting, winding, etc.

[0104] Preferably, the negative plate 50 is cleaned to form the wire groove. During the battery cycle, the negative plate 50 will expand and contract, and the wire groove can effectively alleviate the stress concentration at some positions of the negative plate 50, improve the tensile and compressive capacity of the negative plate 50, thereby avoiding the problem of current collector breakage caused by expansion and contraction of the negative plate 50, and also improving the electrolyte infiltration capacity of the negative plate 50.

[0105] In the specification provided herein, a large number of specific details are described. However, it can be understood that the embodiments of the present application can be practiced without these specific details. In some examples, well-known methods, structures and techniques are not shown in detail in order not to obscure the understanding of the present specification.

[0106] In addition, those skilled in the art can understand that although some embodiments described herein include certain features included in other embodiments but not others, the combination of features of different embodiments means within the scope of the present application and forms different embodiments.

[0107] Those skilled in the art will understand that although the present application has been described with reference to exemplary embodiments, various changes and substitutions can be made without departing from the scope of the present application, and elements thereof can be replaced with equivalents. In addition, many modifications can be made to adapt specific situations or materials to the teachings of the present application without departing from the essential scope of the present application.

Claims

1. A battery, characterized by, The battery comprises a shell and an electrode assembly located inside the shell, and the electrode assembly comprises a negative electrode sheet, a separator and a positive electrode sheet which are sequentially stacked and wound. The negative electrode sheet comprises a negative electrode current collector and a negative electrode active layer arranged on at least one side surface of the negative electrode current collector, and the negative electrode sheet is provided with a leakage foil groove, the bottom wall of the leakage foil groove exposes part of the negative electrode current collector, and the side wall of the leakage foil groove is provided with the negative electrode active layer. The negative electrode sheet further comprises a negative electrode tab and a first protective adhesive, part of the negative electrode tab is located in the leakage foil groove and is electrically connected with the negative electrode current collector, and the negative electrode tab extends along a second direction and beyond the first edge of the negative electrode sheet. The first protective adhesive covers part of the negative electrode tab in the leakage foil groove, along a first direction, both sides of the first protective adhesive have gaps with the side wall of the leakage foil groove, along the second direction, the bottom edge of the first protective adhesive has a gap with the lower wall of the leakage foil groove away from the first edge. The battery comprises hot melt adhesive located on the outer surface of the electrode assembly, and the hot melt adhesive is connected with the inner side wall of the shell and the electrode assembly respectively, in the orthographic projection of the third direction, along the width direction of the negative electrode tab, both sides of the first protective adhesive do not exceed both sides of the hot melt adhesive, and the hot melt adhesive covers at least part of the negative electrode tab in the orthographic projection of the third direction. The first direction is the width direction of the electrode assembly, the second direction is the height direction of the electrode assembly, and the third direction is the thickness direction of the electrode assembly.

2. The battery of claim 1, wherein, In the orthographic projection of the third direction, the upper edge of the hot melt adhesive exceeds the lower edge of the negative electrode tab on the negative electrode current collector away from the first edge; and / or, In the orthographic projection of the third direction, along the first direction, both sides of the hot melt adhesive exceed both sides of the leakage foil groove.

3. The battery of claim 1, wherein the cathode comprises a lithium metal oxide. The lower edge of the negative electrode tab is provided with a chamfered portion, and at least one side edge of the negative electrode tab is provided with a chamfered portion.

4. The battery of claim 3, wherein the cathode is a lithium cobalt oxide cathode. The electrode assembly comprises a flat section and first and second circular arc sections located on both sides of the flat section respectively, the negative electrode tab is arranged close to the first circular arc section, and the chamfered portion is located on the side edge of the negative electrode tab close to the first circular arc section.

5. The battery of claim 3, wherein the cathode comprises a lithium cobalt oxide. The chamfered portion is a circular arc chamfer.

6. The battery of claim 1, wherein the cathode comprises a lithium metal oxide. The leakage foil groove is arranged in a U shape.

7. The battery of claim 1, wherein the cathode comprises a lithium metal oxide. The gap between the bottom edge of the first protective adhesive 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 adhesive and the side wall of the leakage foil groove is B, A and B satisfy: 0.1≤A / B≤1.

2.

8. The battery of claim 1, wherein the cathode comprises a lithium metal oxide. The gap between the bottom edge of the first protective adhesive 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 adhesive and the side wall of the leakage foil groove is B, A and B satisfy: 0.4≤A / B≤0.8; and / or, A≥0.15mm.

9. The battery of claim 1, wherein the cathode comprises a lithium metal oxide. The positive electrode sheet is provided with a positive electrode tab, the hot melt adhesive comprises two, in the orthographic projection of the third direction, the two hot melt adhesives are arranged at intervals, and the two hot melt adhesives cover at least part of the negative electrode tab and at least part of the positive electrode tab respectively.

10. The battery of claim 1, wherein the cathode comprises a lithium metal oxide. Along the first direction, the width of the hot melt adhesive is D, and the width of the leakage foil groove is W1, D and W1 satisfy: 1 < D / W1 < 1.

9.

11. The battery of claim 1, wherein the cathode comprises a lithium metal oxide. In the first direction, the width of the hot melt adhesive is D, the width of the leakage foil groove is W1, and D and W1 satisfy: 1.2 < D / W1 < 1.

7.

12. The battery of claim 1, wherein, The positive plate comprises a positive current collector and a positive active layer arranged on at least one side surface of the positive current collector, and a thinning groove is arranged on the positive plate, the depth of the bottom wall of the thinning groove from the positive current collector is less than the thickness of the positive active layer, and the thinning groove is arranged opposite to the negative tab; In the first direction, the width of the thinning groove is greater than the width of the leakage foil groove.

13. The battery of claim 12, wherein the cathode comprises a lithium metal oxide. The thinning groove comprises a first groove and a second groove in communication with each other; The first groove is located on the side of the second groove away from the positive current collector, and in 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 surface of the negative tab has a welding mark, and in the orthogonal projection in the third direction, the width of both sides of the second groove exceeds the width of both sides of the welding mark.

14. The battery of claim 1, wherein the cathode comprises a lithium metal oxide. The negative plate is provided with a plurality of wire grooves, and a plurality of wire grooves are arranged on the negative active layer in the first direction.

Images