Electrode piece, electrode assembly, battery monomer and electric device

Abstract

The invention relates to a pole piece, an electrode assembly, a battery monomer and an electric device, and the pole piece comprises a current collector which comprises a main body part and a convex part protruding out of the main body part; the active material layer is arranged on at least one side surface of the main body part along the thickness direction of the current collector; a lug is formed in the region, where the active material layer is not arranged, of the convex part; the active material layer is provided with a first area and a second area which are located on the main body part, the thickness of the first area is smaller than that of the second area in the thickness direction, the first area is close to the convex part relative to the second area in the first direction, and the second area is close to the convex part relative to the second direction in the second direction. The first direction is the direction in which the main body part points to the convex part; in the thickness direction, the surface of at least one side of the tab is provided with a first reinforcing part, the active substance layer on the surface of at least one side of the main body part is provided with a second reinforcing part, and the second reinforcing part is located on the surface, deviating from the main body part, of the first area.

Description

Technical Field

[0001] The present invention relates to the field of new energy technology, and in particular to a pole piece, an electrode assembly, a battery cell and an electrical device. Background Art

[0002] As new energy vehicles continue to increase their demand for battery energy density and power, battery cell design is trending towards larger, multi-tab designs. Tabs are formed by the protruding area of ​​the current collector that bulges outward. Large tabs are prone to folding during assembly.

[0003] The folding of the tab will bring many adverse effects. For example, the tab will not be effectively connected or contacted with the main area of ​​the current collector and / or the external terminal, resulting in increased internal resistance; or the folding of the tab may be inserted into the core and cause short circuit or lithium deposition of the battery cell.

[0004] In order to solve the problem of tab folding, traditional technologies focus on optimizing the tab thickness or using tab glue. However, increasing the tab thickness will sacrifice the battery energy density, and the tab glue process is costly and has limited improvement effects. Summary of the Invention

[0005] Based on this, it is necessary to address the problem that the tabs are easily folded and provide a pole piece, electrode assembly, battery cell and electrical device that can reduce the risk of tab folding.

[0006] In one aspect, the present application provides a pole piece, comprising:

[0007] A current collector comprising a main body and a convex portion extending outward from the main body;

[0008] An active material layer is provided on at least one side surface of the main body along the thickness direction of the current collector; an area of ​​the protrusion where the active material layer is not provided forms a tab;

[0009] The active material layer includes a first region and a second region located on the main body, wherein the thickness of the first region is smaller than the thickness of the second region along the thickness direction, and the first region is closer to the protrusion than the second region along the first direction, wherein the first direction is the direction from the main body to the protrusion;

[0010] Along the thickness direction, at least one surface of the tab has a first reinforcement portion, and the active material layer on at least one surface of the main body has a second reinforcement portion, which is located on a surface of the first region away from the main body.

[0011] In one embodiment, along the thickness direction, the first reinforcement portion and the second reinforcement portion are both located on the same side surface of the pole piece.

[0012] In one embodiment, along the thickness direction, one side surface of the tab is concave and the other side surface is correspondingly convex, forming the first reinforcement portion; one side surface of the first region is concave and the other side surface is correspondingly convex, forming the second reinforcement portion.

[0013] In one embodiment, along the first direction, the first reinforcement portion and the second reinforcement portion are connected to each other to form a reinforcement portion; and the cross-sectional shape of the reinforcement portion is a long strip extending along the first direction.

[0014] In one embodiment, along a direction opposite to the first direction, the recessed depth of the reinforcement portion along the thickness direction decreases.

[0015] In one embodiment, the reinforcement portion and the first direction have a first angle θ, 0°≤θ≤20°.

[0016] In one embodiment, the reinforcement portion has a bottom wall and side walls connected to each other, and a smooth transition is formed between the bottom wall and the side walls.

[0017] In one embodiment, it is characterized in that:

[0018] Along the thickness direction, the convex portion has a first thickness c, the first reinforcement portion has a first depth recess H1, the sum of the thicknesses of the main portion and the entire first region is a second thickness T2, and the second reinforcement portion has a second recess depth H2; wherein,

[0019] H1=(1-100)c;

[0020] and / or, H2=(0.05-1)T2;

[0021] and / or, H2

[0022] and / or, 5 μm ≤ H1 ≤ 500 μm;

[0023] And / or, 5μm≤H2≤100μm.

[0024] In one embodiment, it is characterized in that:

[0025] There are multiple first reinforcing portions, and the cross-section of each first reinforcing portion is a long strip extending along the first direction, and there is a third distance D1 between each two adjacent first reinforcing portions along the second direction; the first direction, the thickness direction, and the second direction intersect each other;

[0026] ​Each of the first reinforcement portions has a first recessed depth H1 along the thickness direction, the convex portion has a third height a along the first direction, the convex portion has a first thickness c along the thickness direction, and the convex portion has a first width b along the first direction;

[0027] H1 / D1=k*a / (b*c);

[0028] Among them, 5μm≤H1≤500μm, 1mm≤D1≤10mm, 1*10 -7 ≤k≤0.08.

[0029] In one embodiment, along the thickness direction, the average thickness of the first region is smaller than the average thickness of the second region by Δt;

[0030] 4μm≤△t≤6μm.

[0031] In one embodiment, the first region includes a first sub-region and a second sub-region sequentially arranged along the first direction, and the first sub-region is arranged closer to the convex portion relative to the second sub-region;

[0032] The second reinforcement portion is provided in the first sub-region.

[0033] In one embodiment, along the first direction, the first sub-region has a first height M1, and the second sub-region has a second height M2;

[0034] M2=(0.1-0.9)M1, or 1mm≤M1≤10mm.

[0035] In one embodiment, along the first direction, the first region has a total height M3;

[0036] Along the first direction, the second reinforcement portion has a first edge away from the protrusion; the first area and the second area have a boundary line; along the first direction, there is a fifth distance L3 between the first edge and the boundary line, L3 = (0.1-0.9)M3.

[0037] In one embodiment, the protrusion includes a connecting portion and the electrode tab arranged in sequence along the first direction, the connecting portion connects the main body and the electrode tab, and the active material layer is also arranged on the connecting portion; the second reinforcement portion extends to the connecting portion.

[0038] In one embodiment, along the first direction, the second reinforcement portion has a first edge away from the protrusion, and the first region has a second edge close to the protrusion;

[0039] Along the first direction, a first distance L1 is defined between the first edge and the second edge, where 1 mm ≤ L1 ≤ 10 mm.

[0040] In one embodiment, the main body has a third edge connected to the protrusion;

[0041] Along the first direction, a second distance L2 is formed between the first edge and the third edge, 1 mm ≤ L2 ≤ 10 mm;

[0042] And / or, L1=L2.

[0043] On the other hand, the present application also provides an electrode assembly, comprising the electrode piece as described above.

[0044] In one embodiment, the electrode assembly includes a positive electrode sheet, a negative electrode sheet and a separator, the separator is arranged between the positive electrode sheet and the negative electrode sheet, the negative electrode sheet is the electrode sheet as described above, one side surface of the first area is concave, and the other side surface is correspondingly convex to form the second reinforcement portion.

[0045] In one embodiment, the second reinforcement portion has a second recessed depth H2 along the thickness direction, the first region of the negative electrode sheet has a third thickness t1, and the first region of the positive electrode sheet has a fourth thickness t2;

[0046] t1≤H2≤(t1+t2).

[0047] On the other hand, the present application provides a battery cell, including the pole piece as described above, or including the electrode assembly as described above.

[0048] On the other hand, the present application also provides an electrical device comprising the battery cell as described above.

[0049] Compared with the prior art, this application has the following beneficial effects:

[0050] In the aforementioned pole piece, electrode assembly, battery cell, and electrical device, since the extension length of the reinforcement along the first direction is positively correlated with the tab tensile strength and stress dispersion capability, providing a first reinforcement on at least one side of the tab and providing a second reinforcement on the surface of the first region of the active material layer on at least one side of the current collector body facing away from the main body effectively increases the length of the first reinforcement along the first direction, further increasing the tab tensile strength. Compared to providing only the first reinforcement on the tab, this reduces the risk of tab collapse and, consequently, the risk of tab folding. Compared to optimizing tab thickness, providing both the first and second reinforcements does not increase tab thickness, thereby sacrificing battery energy density. Compared to using tab glue to mitigate tab folding, the process cost is low and the effect of improving tab folding is superior. Furthermore, providing the second reinforcement on the surface of at least one first region facing away from the main body enhances the strength of the first region and reduces the risk of the pole piece wrinkling.

[0051] In addition, the thickness of the first region is smaller than that of the second region, so that a thinned region is formed at the edge of the active material layer. In this way, even if the thinned region produces a bulge during drying, since the thinned region is thin, the bulge will not be rolled during rolling, thereby reducing the risk of cracking of the active material layer. In addition, the second reinforcement portion can increase the compaction density of the active material in the thinned region, reduce the risk of material falling, and further reduce the risk of lithium deposition in the thinned region (because the thinned region is thin, the gap between the positive and negative electrode sheets corresponding to this region is larger, and the interlayer gap can easily cause poor electrolyte infiltration and poor ion transmission performance. During high-power charging, lithium deposition is prone to occur in the thinned region, that is, the thinned region is a region prone to lithium deposition). BRIEF DESCRIPTION OF THE DRAWINGS

[0052] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0053] Figure 1 A structural diagram of a pole piece provided in one embodiment of the present application;

[0054] Figure 2 for Figure 1 The structure diagram of the current collector of the pole piece shown in ;

[0055] Figure 3 for Figure 1 An enlarged view of point A of the pole piece shown in FIG;

[0056] Figure 4A structural diagram of a pole piece provided in another embodiment of the present application;

[0057] Figure 5 for Figure 4 An enlarged view of point A of the pole piece shown in FIG;

[0058] Figure 6 A structural diagram of a pole piece provided in yet another embodiment of the present application;

[0059] Figure 7 for Figure 6 An enlarged view of point C of the pole piece shown in FIG;

[0060] Figure 8 A cross-sectional view of a pole piece provided in yet another embodiment of the present application;

[0061] Figure 9 A structural diagram of a pole piece provided in another embodiment of the present application;

[0062] Figure 10 for Figure 9 A cross-sectional view of the pole piece B shown in FIG;

[0063] Figure 11 A longitudinal cross-sectional view of a pole piece provided in another embodiment of the present application;

[0064] Figure 12 A longitudinal cross-sectional view of a pole piece provided in yet another embodiment of the present application;

[0065] Figure 13 A structural diagram of a pole piece provided in another embodiment of the present application;

[0066] Figure 14 A structural diagram of a pole piece provided in yet another embodiment of the present application;

[0067] Figure 15 A structural diagram of a pole piece provided in yet another embodiment of the present application;

[0068] Figure 16 A structural diagram of a pole piece provided in yet another embodiment of the present application;

[0069] Figure 17 A structural diagram of a pole piece provided in another embodiment of the present application;

[0070] Figure 18 A structural diagram of a pole piece provided in yet another embodiment of the present application;

[0071] Figure 19 A structural diagram of a pole piece provided in yet another embodiment of the present application;

[0072] Figure 20 A structural diagram of a pole piece provided in yet another embodiment of the present application;

[0073] Figure 21 The structure of the electrode assembly provided in one embodiment of the present application.

[0074] Description of reference numerals:

[0075] 1000, electrode assembly; 100, electrode sheet; 100a, positive electrode sheet; 100b, negative electrode sheet; 10, current collector; 11, main body; 12, protrusion; 121, electrode tab; 122, connecting portion; 20, active material layer; 21, first region; 211, first sub-region; 212, second sub-region; 22, second region; 30, first reinforcement; 40, second reinforcement; 41, second bottom wall; 42, second side wall; 50, boundary line; 60, first edge; 70, second edge; 80, third edge; 200, diaphragm. DETAILED DESCRIPTION

[0076] To make the above-mentioned objects, features, and advantages of the present invention more readily apparent, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings. The following description sets forth numerous specific details to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways than those described herein, and those skilled in the art may make similar modifications without departing from the scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0077] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0078] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0079] In the present invention, unless otherwise specified or limited, the terms "installed," "connected," "connect," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection, electrical connection; direct connection, or indirect connection through an intermediate medium; internal communication between two components, or interaction between two components, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0080] In the present invention, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediary. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0081] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it may be directly on the other element or there may be an intermediate element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be an intermediate element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only implementation methods.

[0082] See Figure 1 and Figure 2 In one embodiment of the present application, a pole piece 100 is provided. The pole piece 100 may be a positive pole piece 100a or a negative pole piece 100b, which is not limited here. The pole piece 100 includes a current collector 10, which is usually prepared by using a metal foil. For example, some negative current collectors 10 may be prepared by using copper foil, while other negative current collectors 10 (such as the negative current collector 10 of a sodium ion battery) may also be prepared by using aluminum foil. Some positive current collectors 10 may be prepared by using aluminum foil. Of course, in other embodiments, there is no limitation on the type of foil selected for the current collector 10.

[0083] Continue reading Figure 2The current collector 10 includes a main body 11 and a protrusion 12. The protrusion 12 is provided to protrude from the main body 11. That is, the protrusion 12 serves as an extension of the current collector 10 extending outward from the main body 11. Optionally, the protrusion 12 is provided on one side of the main body 11. In other embodiments, the protrusions 12 may be provided on two opposite sides of the main body 11, which is not limited here.

[0084] Continue reading Figure 1 The electrode 100 further includes an active material layer 20, along the thickness direction of the current collector 10 ( Figure 1 In the direction perpendicular to the paper surface), the active material layer 20 is provided on at least one side surface of the main body 11. The area of ​​the protrusion 12 where the active material layer 20 is not provided forms a pole ear 121. The current collector 10 is used to conduct the current generated by the active material layer 20, and the pole ear 121 is used as the current output end of the current collector 10. For the wet method of preparing the pole piece 100, usually, in the process of preparing the pole piece 100, the active material, the binder, the conductive agent and the solvent are mixed to form an active slurry, and then the active slurry is coated on the current collector 10 to form the active material layer 20. The active material layer 20 is prepared to form the pole piece 100 through processes such as drying and rolling. For the dry method of preparing the pole piece 100, the active material layer 20 prepared in advance is set on the current collector 10 by dry pressing.

[0085] It should be noted that since the thickness direction of the entire pole piece 100 is parallel to the thickness direction of the current collector 10 , the thickness direction mentioned below refers to the thickness direction of the current collector 10 or the pole piece 100 .

[0086] Continue reading Figure 1 , the active material layer 20 has a first region 21 and a second region 22. Along the first direction, the first region 21 is arranged closer to the protrusion 12 relative to the second region 22. The first direction is the direction from the main body 11 to the protrusion 12. It can be seen that the first direction is the protrusion direction of the protrusion 12 protruding from the main body 11. The first direction intersects with the thickness direction. Specifically, the first direction is perpendicular to the thickness direction. In some embodiments, when the protrusion 12 is arranged to protrude from the main body 11 along the width direction of the current collector 10, the first direction is parallel to the width direction. Figure 1 and Figure 2 The Y direction is the first direction.

[0087] Continue reading Figure 1, along the thickness direction, at least one side surface of the pole tab 121 has a first reinforcement portion 30. The provision of the first reinforcement portion 30 can enhance the strength of the pole tab 121. Moreover, along the thickness direction, the active material layer 20 on at least one side surface of the main body 11 has a second reinforcement portion 40, and the second reinforcement portion 40 is located on the surface of the first region 21 facing away from the main body 11. Specifically, the second reinforcement portion 40 is provided on the first portion of the first region 21 that is opposite to the pole tab 121 along the first direction. More specifically, when the pole piece 100 has multiple pole tabs 121, the first region 21 is provided with a first portion that is opposite to each pole tab 121 along the first direction, and each first portion is provided with a second reinforcement portion 40.

[0088] Because the extension length of the reinforcement portion along the first direction is positively correlated with the tensile strength and stress dispersion capability of the tab 121, providing a first reinforcement portion 30 on at least one side of the tab 121 and providing a second reinforcement portion 40 on the surface of the first region 21 of the active material layer 20 on at least one side facing away from the main body 11 is equivalent to increasing the length of the first reinforcement portion 30 along the first direction, further increasing the tensile strength of the tab 121. Compared to providing only the first reinforcement portion 30 on the tab 121, the risk of the tab 121 collapsing can be reduced, thereby reducing the risk of the tab 121 folding. Compared to optimizing the thickness of the tab 121, the provision of the first reinforcement portion 30 and the second reinforcement portion 40 does not increase the thickness of the tab 121, thereby not sacrificing the battery energy density. Compared to using tab glue to improve the folding of the tab 121, the process cost is low and the effect of improving the folding of the tab 121 is better. On the other hand, a second reinforcement portion 40 is provided on the surface of at least one side of the first region 21 facing away from the main body 11 , thereby increasing the strength of the first region 21 and reducing the risk of wrinkling of the pole piece 100 .

[0089] It should be noted that in this application, the second reinforcement 40 is disposed on the surface of the first region 21 facing away from the main body 11. That is, if the surface where the first region 21 and the main body 11 meet is defined as the inner surface, the second reinforcement 40 is located on the outer surface of the first region 21. During the preparation of the electrode 100, after the active material is formed on the current collector 10, necessary steps such as drying and rolling are required. Drying is to remove organic solvents in the active material, and rolling is to reduce gaps between the active material, shorten the current path, and improve the adhesion between the active material and the current collector 10. To avoid affecting the second reinforcement 40, the second reinforcement 40 should be formed on the outer surface of the first region 21 of the active material layer 20 after the active material layer 20 is formed on the main body 11. If the second reinforcement 40 is formed on the main body 11 before the active material layer 20 is formed, the second reinforcement 40 may be flattened during the rolling process, and the flattened second reinforcement 40 will not provide any reinforcement.

[0090] In some embodiments, see Figure 1 , and see Figure 3 The entire convex portion 12 serves as the tab 121. In this case, the entire convex portion 12 is not provided with the active material layer 20, that is, the active material area is not cut when the convex portion 12 is formed by die cutting, thus reducing the use of active materials and saving resources.

[0091] In other embodiments, see Figure 4 and Figure 5 The protrusion 12 includes a connecting portion 122 and a tab 121 arranged in sequence along the first direction. The connecting portion 122 connects the main body 11 and the tab 121. The active material layer 20 is also disposed on the connecting portion 122. In this way, when die-cutting, the active material area is cut to form the protrusion 12. Compared with the case where the active material area is not cut, the generation of burrs can be reduced.

[0092] Further, see Figure 5 , the second reinforcing portion 40 extends to the connecting portion 122. It should be noted here that the second reinforcing portion 40 extending to the connecting portion 122 means that the second reinforcing portion 40 provided in the first region 21 is also provided on the surface of the active material layer 20 on the connecting portion 122 facing away from the connecting portion 122. The second reinforcing portion 40 can be extended to the active material layer 20 on the connecting portion 122 in a continuous manner, or in a discontinuous manner. When the second reinforcing portion 40 is extended to the active material layer 20 on the connecting portion 122 in a continuous manner, the second reinforcing portion 40 on the first region 21 is connected to the second reinforcing portion 40 on the active material layer 20 on the connecting portion 122 as a whole. When the second reinforcing portion 40 is extended to the active material layer 20 on the connecting portion 122 in a discontinuous manner, the second reinforcing portion 40 on the first region 21 is spaced apart from the second reinforcing portion 40 on the active material layer 20 on the connecting portion 122.

[0093] In some embodiments, continue to refer to Figure 3 Along the first direction, the first region 21 has a second edge 70 close to the protrusion 12, and the main body 11 has a third edge 80 connected to the protrusion 12. The second edge 70 is flush with the third edge 80. In this case, the edge of the active material layer 20 on the main body 11 is the edge of the main body 11, and there is no area of ​​the main body 11 near the protrusion 12 without the active material layer 20.

[0094] In other embodiments, see Figure 6As with 7, the second edge 70 is located inside the third edge 80. At this time, the edge of the active material layer 20 located on the main body 11 is located on the inner side of the edge of the main body 11, and there is an area of ​​the main body 11 near the protrusion 12 where the active material layer 20 is not provided.

[0095] Continue reading Figure 3 and Figure 7 Along the first direction, the second reinforcing portion 40 has a first edge 60 away from the protrusion 12 (the first edge 60 is also the end of the second reinforcing portion 40. When there are multiple second reinforcing portions 40, the end of all the second reinforcing portions 40 farthest from the protrusion 12 is the first edge 60). There is a first distance L1 between the first edge 60 and the second edge 70, 1mm≤L1≤10mm.

[0096] Specifically, the first spacing is obtained as follows: the straight-line distance between the first end surface of the second reinforcement portion 40 away from the protrusion 12 in the first direction (when one side surface of the first region 21 is recessed and the other side surface is correspondingly convex or non-convex to form the second reinforcement portion 40 (described below), the first end surface is the wall surface of the groove of the second reinforcement portion 40 away from the protrusion 12 along the first direction) and the second edge 70. If the first end surface is not perpendicular to the first direction, the first spacing can be the average distance between each location of the first end surface and the second edge 70, the minimum distance between the first end surface and the second edge 70, or the maximum distance between the first end surface and the second edge 70. If the second edge 70 is not perpendicular to the first direction, the first spacing can be the average distance between each location of the first edge 60 and the second edge 70, the minimum distance between the first edge 60 and the second edge 70, or the maximum distance between the first edge 60 and the second edge 70.

[0097] If L1 is too large, the end of the second reinforcement 40 away from the protrusion 12 will extend far above the first region 21. When the electrode sheet 100 with the second reinforcement 40, which is recessed on one side and raised on the other, is used as the negative electrode sheet 100b and / or the positive electrode sheet 100a to form the electrode assembly 1000, the gap between the positive and negative electrodes will increase, potentially affecting the interfacial adhesion between the positive and negative electrodes. Because the active material in the negative electrode sheet 100b has weaker viscosity than that in the positive electrode sheet 100a, if L1 is too large, using the electrode sheet 100 with the second reinforcement 40 as the negative electrode sheet 100b may easily cause the active material to fall off.

[0098] When 1 mm ≤ L1 ≤ 10 mm, the extension position of the second reinforcement portion 40 on the active material layer 20 is limited, which is beneficial to the interface bonding of the positive and negative electrode sheets and prevents the active material from falling off.

[0099] In some specific implementations, 2 mm ≤ L1 ≤ 6 mm. Of course, in other implementations, L1 can be selected as needed and is not limited here.

[0100] Further, see Figure 3 and Figure 7 Along the first direction, the first edge 60 and the third edge 80 have a second spacing L2, where 1mm≤L2≤10mm. This further limits the extension of the second reinforcement 40 on the active material layer 20, further facilitating interfacial bonding between the positive and negative electrode sheets and preventing active material dropout. It should be noted that the method for obtaining the second spacing L2 can be similar to the method for obtaining the first spacing L1, and will not be further described here.

[0101] Optionally, continue to Figure 3 , when the second edge 70 is flush with the third edge 80, L1 = L2. Figure 7 When the second edge 70 and the third edge 80 are not flush, L1 < L2.

[0102] See Figure 8 The first region 21 includes a first sub-region 211 and a second sub-region 212 arranged sequentially along the first direction. The first sub-region 211 is located closer to the protrusion 12 than the second sub-region 212. The second reinforcement 40 is provided in the first sub-region 211. Since the second reinforcement 40 is provided in the first sub-region 211, the extension position of the second reinforcement 40 on the active material layer 20 is indirectly limited, which can facilitate the interface bonding of the positive and negative electrode sheets and prevent the active material from falling off.

[0103] Optionally, continue to Figure 8 Along the first direction, the first subregion 211 has a first height M1, and the second subregion 212 has a second height M2; M2 = (0.1-0.9) M1, or 1mm≤M1≤10mm. This further limits the extension of the second reinforcement 40 on the active material layer 20, further facilitating interfacial bonding between the positive and negative electrode sheets and preventing active material dropout.

[0104] Specifically, the first sub-region 211 and the second sub-region 212 are divided by the end of the second reinforcing portion 40. If the second reinforcing portion 40 extends to the edge of the first sub-region 211 (when there are multiple second reinforcing portions 40, at least one second reinforcing portion 40 extends to the edge of the first sub-region 211), and the height of the second reinforcing portion 40 along the first direction is M4, then M4 = M1. Furthermore, when the second edge 70 is flush with the third edge 80, M4 = M1 = L1 = L2.

[0105] Continue reading Figure 8, along the first direction, the first region 21 has a total height M3. There is a boundary line 50 between the first region 21 and the second region 22, and along the first direction, there is a fifth spacing L3 between the first edge 60 and the boundary line 50 (the method for obtaining the fifth spacing L3 can refer to the method for obtaining the first spacing L1). L3 = (0.1-0.9) M3. In this way, the second reinforcement 40 is distributed within a suitable range, which limits the extension position of the second reinforcement 40 on the active material layer 20, so as to further facilitate the interface bonding of the positive and negative electrodes and prevent the active material from falling off. If the end of the second reinforcement 40 extends to the edge position of the first sub-region 211, L3 = M2.

[0106] The above M1, M2 and M3 can be the average height of the area, or the maximum height or minimum height of the area, which is not limited here and can be set as needed. Similarly, L3 can be the average spacing, or the maximum spacing or the minimum spacing, which is also not limited here.

[0107] In some embodiments, see Figure 8 , along the thickness direction ( Figure 8 In the Z direction), the thickness of the first region 21 is less than the thickness of the second region 22. In this case, the first region 21 can also be defined as a thinned region, and the second region 22 can be positioned as a main region. Figure 8 The thickness of the first region 21 gradually decreases.

[0108] Typically, the active material is a water-based slurry. If the active material is applied in a uniform thickness, the fluidity and surface tension of the active material will cause protrusions to form at the edges of the active material layer 20 during drying. These protrusions will be directly compressed during rolling, causing cracks to form at the edges of the active material layer 20. Therefore, by setting the thickness of the first region 21 to be smaller than that of the second region 22, a thinned region is formed at the edge of the active material layer 20. Even if the thinned region produces protrusions during drying, the thinner the region is, the protrusions will not be compressed during rolling, thereby reducing the risk of cracking in the active material layer 20. At the same time, since the thinned area has a second reinforcement part 40, that is, the second reinforcement part 40 will not exceed the thinned area, while increasing the length of the first reinforcement part 30 in the first direction, it will not cause loss to the actual capacity of the battery, and the second reinforcement part 40 can increase the compaction density of the active material in the thinned area, reduce the risk of material falling, and thus reduce the risk of lithium deposition in the thinned area (because the thinned area is thinner, the gap between the positive and negative electrode sheets corresponding to this area is larger, and the interlayer gap is easy to cause poor electrolyte infiltration and poor ion transmission performance. During high-power charging, lithium deposition is prone to occur in the thinned area, that is, the thinned area is an area prone to lithium deposition).

[0109] Furthermore, the average thickness of the first region 21 is smaller than the average thickness of the second region 22 by a value Δt, 4 μm ≤ Δt ≤ 6 μm. When Δt is within this range, the difference in average thickness between the first region 21 and the second region 22 is not too small, which can improve lithium deposition in the thinned region. At the same time, the difference between the two is not too large. Even if protrusions are formed in the thinned region, the protrusions are not pressed during rolling, thereby reducing the risk of cracking in the active material layer 20.

[0110] In some specific embodiments, Δt may be defined as the difference between the average thickness of the active material in the middle (1 / 2 position) of the second region 22 along the first direction and the average thickness of the active material in the first region 21 at a position 703 mm from the second edge.

[0111] Optionally, Δt is 5 μm. Of course, in other implementations, there is no limitation on the specific value of Δt, for example, Δt may also be 4 μm, 4.5 μm, 5.5 μm or 6 μm.

[0112] In other embodiments, the thickness of the first region 21 can be set equal to the thickness of the second region 22. In this way, the thickness of the active material layer 20 located in various parts of the main body 11 is equal, which is convenient for processing. At the same time, the thickness of the first region 21 and the second region 22 are equal. At this time, the gap between the positive and negative electrodes will not increase, the electrolyte infiltration is good, the ion transmission performance is good, and lithium precipitation is not easy to occur in the first region 21. In addition, when the first region 21 is a thinned area, the resistance to lithium ion migration in the pole piece 100 increases, the battery polarization increases, and ultimately causes the battery capacity to decay too quickly, the battery cycle performance deteriorates, and the life of the battery cell is greatly shortened. By setting the thickness of the first region 21 to be equal to the thickness of the second region 22, the problems caused by the thin thickness can be improved and the life of the battery cell can be increased.

[0113] In some further embodiments, the thickness of the first region 21 may be slightly greater than the thickness of the second region 22, or the thickness of a portion of the first region 21 may be less than the thickness of the second region 22, while the thickness of the remaining portion of the first region 21 may be greater than or equal to the thickness of the second region 22. This is not limited herein. For example, in some specific embodiments, the thickness of a portion of the first region 21 adjacent to the protrusion 12 along the first direction may be less than the thickness of the second region 22, while the thickness of the remaining portion of the first region 21 may be greater than or equal to the thickness of the second region 22. In this case, the first region 21 includes not only the thinned region but also a portion of the unthinned region.

[0114] In some embodiments, first reinforcements 30 are provided on both sides of the tab 121 along the thickness direction to further enhance the strength of the tab 121. Furthermore, second reinforcements 40 are provided on both sides of the main body 11 along the thickness direction on the surfaces of the first regions 21 facing away from the main body 11 to further enhance the strength of the tab 121 and reduce the risk of wrinkling of the pole piece 100.

[0115] In some other embodiments, along the thickness direction, a first reinforcement portion 30 is provided on one surface of the tab 121 , and a second reinforcement portion 40 is provided on a surface of the first region 21 on one side of the main body 11 facing away from the main body 11 .

[0116] In some further embodiments, it is also possible to provide a first reinforcement portion 30 on one side surface of the tab 121 along the thickness direction, and a second reinforcement portion 40 on the surface of the first region 21 on both sides of the main body 11 facing away from the main body 11; or it is possible to provide a first reinforcement portion 30 on both side surfaces of the tab 121 along the thickness direction, and a second reinforcement portion 40 on the surface of the first region 21 on one side of the main body 11 facing away from the main body, which is not limited here.

[0117] Optionally, see Figure 9 Along the thickness direction, the first reinforcement portion 30 and the second reinforcement portion 40 are both located on the same side surface of the pole piece 100 , so that the first reinforcement portion 30 and the second reinforcement portion 40 can be prepared and formed at the same time, thereby improving operation efficiency.

[0118] In some embodiments, see Figure 10 Along the thickness direction, one side of the tab 121 is concave, and the other side is convex, forming a first reinforcement portion 30. Figure 11 and Figure 12 Along the thickness direction, one side of the surface of the first region 21 is concave, while the other side is correspondingly convex, forming the second reinforcement portion 40. This arrangement, on the one hand, allows the first reinforcement portion 30 and the second reinforcement portion 40 to be formed without thinning the thickness of the tab 121 and the first region 21, facilitating their formation on a thinner pole piece 100 and reducing processing difficulty; on the other hand, it allows the first reinforcement portion 30 and the second reinforcement portion 40 to appear wavy in appearance, dispersing bending stress concentration points, reducing the accumulation of plastic deformation in the tab 121, and thereby reducing the risk of tab 121 folding.

[0119] In other embodiments, along the thickness direction, one side surface of the tab 121 is recessed, while the other side surface remains unchanged relative to other regions, forming a first reinforcement portion 30. This is equivalent to the tab 121 being compacted and thinned to form the first reinforcement portion 30. One side surface of the first region 21 is recessed, while the other side surface remains unchanged relative to other regions, forming a second reinforcement portion 40. This is equivalent to the first region 21 being compacted and thinned to form the second reinforcement portion 40. This arrangement, equivalent to forming a reinforcement portion by concavely forming one side surface and correspondingly protruding the other side surface, does not increase the overall thickness of the pole piece 100.

[0120] Optionally, to form the first and second reinforcing portions 30 and 40, a roller with a convex surface is typically used to roll the area of ​​the electrode sheet 100 where the reinforcement is to be formed, thereby forming an indentation or impression. This indentation or impression serves as the corresponding reinforcement. Selecting rollers of different shapes allows for the formation of first and second reinforcing portions 30 and 40 of different shapes. The first and second reinforcing portions 30 and 40 can be formed using the same roller or different rollers.

[0121] The cross-sectional shape of the first and second reinforcing portions 30 and 40 can be elongated, circular, diamond-shaped, elliptical, arc-shaped, wavy, or V-shaped, among others. The longitudinal cross-sectional shape of the first and second reinforcing portions 30 and 40 can be rectangular, circular, semicircular, trapezoidal, and among others. When different cross-sectional and longitudinal cross-sectional shapes are desired for the first and second reinforcing portions 30 and 40, this can be achieved by selecting rollers of different shapes. The cross-sectional and longitudinal cross-sectional shapes of the first and second reinforcing portions 30 and 40 can be the same or different, depending on the needs.

[0122] It should be noted that the first direction and the second direction intersect to form a first plane, and the cross section is the surface formed by the first plane cutting the first reinforcement part 30 and the second reinforcement part 40. The second direction and the thickness direction intersect to form a second plane, and the longitudinal section is the surface formed by the second plane cutting the first reinforcement part 30 and the second reinforcement part 40. Among them, the first direction, the second direction and the thickness direction intersect with each other. Specifically, the first direction, the second direction and the thickness direction are perpendicular to each other. The second direction is Figure 1 and Figure 2 When the first direction is parallel to the width direction of the current collector 10 , the second direction is parallel to the length direction of the current collector 10 .

[0123] The first reinforcement portion 30 has a first bottom wall and a first side wall connected to each other, and a smooth transition between the first bottom wall and the first side wall. Figure 12The second reinforcement portion 40 includes a second bottom wall 41 and a second side wall 42 connected to each other, with a smooth transition between the second bottom wall 41 and the second side wall 42. This configuration can reduce the risk of active material falling in the area where the second reinforcement portion 40 is located. For example, when the longitudinal cross-section of the second reinforcement portion 40 is rectangular or trapezoidal, the corners of the rectangle and trapezoid are rounded.

[0124] It should be noted here that when the first reinforcement part 30 and the second reinforcement part 40 are connected to form an integral reinforcement part, the first bottom wall and the second bottom wall together form the bottom wall of the entire reinforcement part, and the first side wall and the second side wall together form the side wall of the entire reinforcement part, and there is a smooth transition between the bottom wall and the side wall of the entire reinforcement part.

[0125] Continue reading Figure 9 , a plurality of first reinforcement portions 30 are correspondingly provided on the tab 121, and a plurality of second reinforcement portions 40 are provided on the first portion corresponding to the tab 121. The shapes of the plurality of first reinforcement portions 30 on each tab 121 can be the same or different, and the shapes of the plurality of second reinforcement portions 40 on the first region 21 can be the same or different, and are not limited here. The first reinforcement portion 30 and the second reinforcement portion 40 can be independent of each other or connected as one. It should be noted here that regardless of whether the groove shapes of the first reinforcement portion 30 and the second reinforcement portion 40 are the same or different, the first reinforcement portion 30 and the second reinforcement portion can be connected as one, or can be set independently of each other.

[0126] See Figure 13-15 Along the second direction, a third spacing D1 is defined between each pair of adjacent first reinforcements 30, and a fourth spacing D2 is defined between each pair of adjacent second reinforcements 40. Where D2 ≥ D1. When D2 is greater than or equal to D1, the distribution density of the second reinforcements 40 along the second direction is less than or equal to the distribution density of the first reinforcements 30 along the second direction, thereby achieving both improved tab 121 folding and prevention of active material dropout. It should be understood that in other embodiments, D2 < D1 can also be configured.

[0127] It should be noted that the third spacing refers to the spacing between two adjacent first reinforcing portions 30 on their sides that are closer to each other along the second direction. This spacing may be the average spacing between the two first reinforcing portions 30, or the maximum spacing or minimum spacing between the two first reinforcing portions 30. The fourth spacing refers to the spacing between two adjacent second reinforcing portions 40 on their sides that are closer to each other along the second direction. This spacing may be the average spacing between the two second reinforcing portions 40, or the maximum spacing or minimum spacing between the two second reinforcing portions 40.

[0128] When D1 and D2 are too large, the effect of improving the tab 121 folding is limited, and when they are too small, the tab 121 is easily torn. Optionally, 1mm≤D1≤10mm, 1mm≤D2≤20mm, so that D1 and D2 are neither too large nor too small, can achieve both improvement of the tab 121 folding and reduction of the tab 121 tearing; at the same time, D2 can be greater than or equal to D1, which can not only improve the tab 121 folding but also prevent the active material from falling.

[0129] Optionally, continue to Figure 3 、 Figure 7 、 Figure 9 and Figure 13 , a plurality of first reinforcement portions 30 are correspondingly provided on the tab 121, and the cross section of the first reinforcement portion 30 is a long strip extending along the first direction. Figure 8 and Figure 9 The protrusion 12 has a third height a along the first direction. If a is too large, the tab 121 is at a high risk of folding. If a is too small, it will make it difficult to connect to the electrode terminal. The protrusion 12 has a first width b along the second direction. If b is too large, the tab 121 is prone to cracking during rolling. If b is too small, the welding area is insufficient. The protrusion 12 has a first thickness c along the thickness direction. If c is too large, it wastes space. If c is too small, the tab 121 lacks strength and is prone to sagging and folding.

[0130] The above-mentioned third height, first width and first thickness can be average values, or can be maximum values ​​or minimum values, etc., and can be set as needed. In some specific embodiments, the cross-sectional shape of the protrusion 12 is an isosceles trapezoid, and the long side of the isosceles trapezoid is connected to the main body 11. The third height is the height of the isosceles trapezoid, the first width is the length of the long side of the isosceles trapezoid, and the thickness of the protrusion 12 is equal at all places, then the first thickness is the thickness of any position of the isosceles trapezoid. It is understandable that in other embodiments, the cross-sectional shape of the protrusion 12 is not limited, for example, the cross-sectional shape of the protrusion 12 can also be a rectangle.

[0131] Continue reading Figure 10 Each first reinforcement portion 30 has a first recessed depth H1 along the thickness direction. The first recessed depth H1 may be a maximum recessed depth or an average recessed depth.

[0132] H1 / D1=k*a / (b*c);

[0133] Among them, 5μm≤H1≤500μm, 1mm≤D1≤10mm, 1*10 -7 ≤k≤0.08.

[0134] Taking into account that the larger a is, the smaller b is, and the smaller c is, the more likely the tab 121 is to fold over, in this application, H1 / D1=k*a / (b*c) is set to limit the third height, first thickness and first width of the protrusion 12, the first recess depth of the first reinforcement 30, and the third spacing between two adjacent first reinforcements 30 to a suitable range, so as to reduce the risk of the tab 121 folding over.

[0135] Optionally, 5mm≤a≤50mm, 10mm≤b≤80mm, and 3μm≤c≤8μm are set to avoid the third height, first width, and first thickness of the protrusion 12 from being too large or too small, thereby reducing adverse effects caused by being too large or too small.

[0136] Too many layers in the tab 121 can easily cause cold solder joints, while too few layers can lead to insufficient current carrying capacity. The number of tab 121 layers (and convex 12 layers) can be set within a range of 5-100 to reduce the adverse effects of too many or too few layers.

[0137] It is understandable that in some other embodiments, a, b, c and the number of layers of the tab 121 can also be selected from other ranges, which are not limited here.

[0138] Because excessive H1 can easily tear the tab 121, while a small H1 has limited effect in improving tab 121 folding, H1 can be set to (1-100)c to limit H1 to an appropriate range, reducing tab 121 folding while also preventing tab 121 tearing. Specifically, 5 μm ≤ H1 ≤ 500 μm.

[0139] The sum of the thicknesses of the main body 11 and all first regions 21 is the second thickness T2. For example, if the first region 21 is provided on one side of the main body 11, the second thickness is the sum of the thicknesses of the main body 11 and the first region 21 on that side. If the first region 21 is provided on both sides of the main body 11 along the thickness direction, the second thickness is the sum of the thicknesses of the main body 11 and the second regions 22 on both sides. The second reinforcement 40 has a second recessed depth H2. The second thickness can be a maximum thickness, a minimum thickness, or an average thickness, and the second recessed depth can be a maximum recessed depth or an average recessed depth.

[0140] While excessive H2 can easily cause active material dropout, a too small depth has limited effectiveness in preventing lithium deposition in the chipped area and wrinkling of the electrode 100. Optionally, setting H2 = (0.05-1)T2 limits H2 to an appropriate range. This reduces both active material dropout and lithium deposition in the chipped area, as well as wrinkling of the electrode 100. Specifically, 5μm ≤ H2 ≤ 100μm.

[0141] It should be noted that H1 can be equal to or different from H2. In some specific embodiments, H2 is less than H1, so as to improve the folding of the electrode 100 and prevent the active material from falling off.

[0142] In some embodiments, see Figure 3 、 Figure 5 、 Figure 7 and Figure 13 Along the first direction, the first reinforcement portion 30 and the second reinforcement portion 40 are connected to each other to form a reinforcement portion. In this way, the first reinforcement portion 30 continuously extends from the tab 121 to the first region 21, thereby improving the reinforcement effect of the tab 121 and reducing the folding of the tab 121.

[0143] Specifically, the cross-section of the entire reinforcement portion is in the shape of a long strip extending along the first direction, so as to increase the length of the reinforcement portion along the first direction and enhance the reinforcement effect on the tab 121 .

[0144] Optionally, continue to Figure 13 The reinforcement portion has a first angle θ with the first direction, 0°≤θ≤20°. In this way, the reinforcement portion is parallel to the first direction or has an inclined angle with the first direction, so as to increase the length of the reinforcement portion and improve the reinforcement effect.

[0145] In some specific embodiments, 0°≤θ≤10°, and specifically, θ is 8°. Of course, in other embodiments, the specific value of θ is not limited, and for example, θ can also be 0°, 1°, 2°, 3°, 4°, 5°, 6°, 7°, 9°, and 10°.

[0146] Further, see Figure 10 In a direction opposite to the first direction, the depth of the concave portion of the reinforcement portion in the thickness direction decreases. Specifically, in a direction opposite to the first direction, the depth of the concave portion decreases in a gradient or gradually decreases.

[0147] Specifically, along the direction opposite to the first direction, H1 and a satisfy the relationship:

[0148]

[0149] Where g and h are constants, and 2≤g≤10, 5≤h≤100;

[0150] The second reinforcement portion 40 has a second recessed depth H2 along the thickness direction.

[0151] H2 and L1 satisfy the relationship:

[0152]

[0153] Where i and j are constants, 2≤i≤10, 5≤j≤100.

[0154] In some embodiments, see Figure 16 Along the first direction, the first reinforcement portion 30 and the second reinforcement portion 40 are spaced apart. Specifically, the cross-sectional shape of the first reinforcement portion 30 is an elongated strip extending along the first direction (the elongated strip extends along a straight line and is wider along the second direction), while the cross-sectional shape of the second reinforcement portion 40 is circular. Compared to the elongated strip, the circular shape has a smaller pressure-bearing area, thereby reducing deformation and damage to the region of the pole piece 100 where the second reinforcement portion 40 is located.

[0155] In some embodiments, see Figure 14 and Figure 15 The groove of the first reinforcement portion 30 is hemispherical in shape. The first reinforcement portion 30 has a first spherical diameter R1, and the second reinforcement portion 40 has a second spherical diameter R2, where R2 ≤ R1. Specifically, R2 < R1. This makes the area of ​​the second reinforcement portion 40 smaller than that of the first reinforcement portion 30, thereby achieving both improved tab 121 folding and prevention of active material dropout. It is understood that in other embodiments, R2 = R1 can also be set.

[0156] Specifically, 0.5 mm ≤ R1 ≤ 5 mm; and / or 0.5 mm ≤ R2 ≤ 5 mm, so that the ball diameters of the first reinforcement portion 30 and the second reinforcement portion 40 are neither too large nor too small, thereby achieving both improvement in the folding of the tab 121 and prevention of the active material from falling off.

[0157] The first reinforcement portion 30 has a first opening radius r1, where r1 ≤ R1; and / or the second reinforcement portion 40 has a second opening radius r2, where r2 ≤ R2. In this case, the grooves of the first reinforcement portion 30 and the second reinforcement portion 40 can be complete or incomplete spherical. Since r1 ≤ R1 and / or r2 ≤ R2, the grooves of the first reinforcement portion 30 and the second reinforcement portion 40 are formed more easily than when r1 > R1 and / or r2 > R2.

[0158] In other embodiments, the groove shape of the first reinforcement part 30 is semi-ellipsoidal, the first major semi-axis range of the first reinforcement part 30 is 0.5mm-20mm, and the first minor semi-axis range of the first reinforcement part 30 is 0.2mm-5mm. In this way, it is possible to take into account both improving the folding of the tab 121 and preventing the active material from falling off.

[0159] The groove shape of the second reinforcement part 40 is semi-ellipsoidal, the second major semi-axis range of the second reinforcement part 40 is 0.5mm-20mm, and the second minor semi-axis range of the second reinforcement part 40 is 0.2mm-5mm. In this way, it is possible to take into account both improving the folding of the tab 121 and preventing the active material from falling off.

[0160] The semi-ellipsoid can be a complete semi-ellipsoid or an incomplete semi-ellipsoid, that is, the semi-major axis of the opening of the groove is less than or equal to the semi-major axis of the ellipsoid, and the semi-minor axis of the opening of the groove is less than or equal to the semi-minor axis of the ellipsoid.

[0161] In some other embodiments, see Figure 17 The first reinforcement portion 30 and / or the second reinforcement portion 40 is in an arc shape extending along the first direction, and the central angle of the arc ranges from 1° to 180°.

[0162] In some other embodiments, see Figure 18 and Figure 19 The first reinforcement portion 30 and / or the second reinforcement portion 40 are wavy lines extending along the first direction. The wavy lines have a wavelength ranging from 1 mm to 20 mm and an amplitude ranging from 0.1 mm to 5 mm. The wavelength refers to the distance a wave travels during one vibration cycle, and the amplitude refers to the distance between the peak and trough of the wave.

[0163] In some other embodiments, see Figure 20 The first reinforcement portion 30 and the second reinforcement portion 40 are connected to form a V-shape, with the V-shaped opening facing away from the second region 22, and the sharp corner of the V located in the first region 21. When the sharp corner of the V is located in the first region 21, excessive pressure on the active material area is avoided, and the degree of deformation and damage to the electrode 100 area corresponding to the second reinforcement portion 40 is reduced. Specifically, the angle of the sharp corner of the V-shape can be 10°-90°, and the sharp corner can be rounded.

[0164] Although several shapes of the grooves of the first reinforcing portion 30 and the second reinforcing portion 40 are exemplified above, the shapes of the grooves of the first reinforcing portion 30 and the second reinforcing portion 40 are not limited thereto, and other conceivable shapes may be used, all of which are included in the scope of protection of this application.

[0165] In addition, see Figure 21 The present application also provides an electrode assembly 1000. The electrode assembly 1000 is the core component of the battery cell. The electrode assembly 1000 can be formed by winding or laminating a positive electrode sheet 100a, a negative electrode sheet 100b, and a separator 200 that insulates the negative electrode sheet 100b and the positive electrode sheet 100a. The electrode tabs 121 of the electrode assembly 1000 are divided into positive electrode tabs 121 and negative electrode tabs 121. The positive electrode tabs 121 and the negative electrode tabs 121 are respectively extended from the positive electrode sheet 100a and the negative electrode sheet 100b. The positive electrode sheet 100a and / or the negative electrode sheet 100b are the electrode sheets 100 mentioned above.

[0166] In some embodiments, the negative electrode sheet 100b is the electrode sheet 100 described above. In the negative electrode sheet 100b, one side of the first region 21 is recessed, while the other side is correspondingly raised, forming a second reinforcement portion 40. This configuration allows the raised portion to fill the gap between the positive and negative electrodes, effectively reducing the interlayer gap between the positive and negative electrode sheets 100a and 100b. This improves electrolyte wetting and ion transport performance, reduces the risk of lithium plating, lowers lithium ion migration resistance, and reduces battery polarization, thereby reducing the risk of rapid battery capacity decay and improving battery cycling performance and cycle life.

[0167] Optionally, both the positive electrode sheet 100a and the negative electrode sheet 100b are provided with a thinned region. The thickness of the first region 21 is less than that of the second region 22, in which case the first region 21 is the thinned region. One side of the thinned region is concave, while the other side is convex, forming a second reinforcement portion 40. This convex portion fills the gap between the thinned regions of the positive and negative electrodes, further reducing the risk of lithium plating.

[0168] Furthermore, the thinned area of ​​the negative electrode sheet 100b has a third thickness t1 along the thickness direction, and the thinned area of ​​the positive electrode sheet 100a has a fourth thickness t2 along the thickness direction; t1≤H2≤(t1+t2). When H2≥t1, the position of the negative electrode sheet 100b provided with the second reinforcement 40 protrudes toward the positive electrode sheet 100a to fill the gap between the thinned areas of the positive electrode sheet 100a and the negative electrode sheet 100b to reduce the risk of lithium plating. If H2 is greater than t1+t2, the groove depth of the second reinforcement 40 is too deep, the active material layer 20 is prone to falling off, and it also causes the interface between the positive electrode sheet 100a and the negative electrode sheet 100b to be uneven, resulting in wavy edges, causing problems such as wrinkling of the electrode sheet 100. Setting H2≤(t1+t2) can not only reduce the falling of the active material layer 20, but also prevent the electrode sheet 100 from wrinkling.

[0169] Furthermore, H2 / D2 = f*(t1+t2), where f is a constant. This arrangement ensures that H2, D2, t1, and t2 satisfy a specific functional relationship, thereby reducing the gap between the thinned areas of the positive and negative electrode sheets 100a, 100b, and mitigating the risk of lithium deposition. This also maintains a smooth interface between the support of the positive and negative electrode sheets 100a, 100b, minimizing the shedding of the active material layer 20 and preventing wrinkling of the electrode sheet 100.

[0170] In some specific embodiments, 0.001 ≤ f ≤ 0.9, 5 μm ≤ H2 ≤ 100 μm, 1 mm ≤ D2 ≤ 20 mm, 0 μm ≤ t1 ≤ 50 μm, and 0 μm ≤ t1 ≤ 80 μm. This allows each parameter to fall within an optimized range, reducing the risk of lithium plating, minimizing the dropout of the active material layer 20, and preventing wrinkling of the electrode 100.

[0171] The present application also provides a battery cell, which includes a top cover assembly, a shell, and the above-mentioned electrode assembly 1000.

[0172] The housing is a hollow structure with an internal space for accommodating the electrode assembly 1000, electrolyte, and other components. At least one end of the housing is provided with an opening through which the electrode assembly 1000 can be installed. A top cover assembly is mounted to the housing and covers the opening, thereby forming a relatively closed environment within the housing to isolate the electrode assembly 1000 from the external environment.

[0173] The battery cells may be lithium-ion batteries, sodium-ion batteries or magnesium-ion batteries, and their outer contours may be cylindrical, flat, rectangular or other shapes, but are not limited thereto.

[0174] The present application also provides a battery, including the above-mentioned battery cells. The battery can be a battery pack or a battery module. When the above-mentioned battery is a battery pack, the battery pack specifically includes a battery management system (BMS) and a plurality of the above-mentioned battery cells. The multiple battery cells can be electrically connected in series, in parallel, or in a combination of series and parallel, and communicated with the battery management system, which controls and monitors the working status of each battery cell. In addition, the multiple battery cells can also first form a battery module with the module management system, and then the multiple battery modules are electrically connected in series, in parallel, or in a combination of series and parallel, and together with the battery management system, form a battery pack.

[0175] Multiple battery cells can be installed on a supporting structure such as a box, a frame, or a bracket. The battery cells and the battery management system can be electrically connected through electrical connectors, which can be busbars.

[0176] The present application also provides an electrical device, which includes the above-mentioned battery cell or battery and can be provided with electrical energy by the above-mentioned battery cell or battery. Among them, the above-mentioned electrical device can be a vehicle, a mobile phone, a portable device, a laptop computer, a ship, a spacecraft, an electric toy, an electric tool, an energy storage device, an amusement equipment, an elevator and a lifting equipment, etc. Electric toys include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys or electric airplane toys, etc.; electric tools include metal cutting electric tools, grinding electric tools, assembly electric tools and railway electric tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators and electric planers, etc.; energy storage equipment can be energy storage walls, base station energy storage, container energy storage, etc.; amusement equipment can be carousels, bungee jumping machines, etc.

[0177] The vehicle may be a fuel-powered vehicle, a gas-powered vehicle, or a new energy vehicle. A new energy vehicle may be a pure electric vehicle, a hybrid vehicle, or an extended-range vehicle. For new energy vehicles, the battery may serve as a driving power source, thereby replacing fossil fuels in providing driving power. This application does not impose any specific restrictions on the electrical device.

[0178] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0179] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A pole piece, characterized in that: include: A current collector (10) comprises a main body (11) and a convex portion (12) protruding from the main body (11); An active material layer (20) is provided on at least one side surface of the main body (11) along the thickness direction of the current collector (10); a region of the convex portion (12) where the active material layer (20) is not provided forms a tab (121); The active material layer (20) comprises a first region (21) and a second region (22) located on the main body (11); along the thickness direction, the thickness of the first region (21) is smaller than the thickness of the second region (22); along the first direction, the first region (21) is closer to the convex portion (12) relative to the second region (22); the first direction is the direction from the main body (11) to the convex portion (12); Along the thickness direction, at least one side surface of the electrode tab (121) has a first reinforcement portion (30), and the active material layer (20) on at least one side surface of the main body (11) has a second reinforcement portion (40), and the second reinforcement portion (40) is located on the surface of the first region (21) away from the main body (11).

2. The pole piece according to claim 1, characterized in that: Along the thickness direction, the first reinforcement portion (30) and the second reinforcement portion (40) are both located on the same side surface of the pole piece.

3. The pole piece according to claim 2, characterized in that: Along the thickness direction, one side surface of the tab (121) is concave, and the other side surface is correspondingly convex, forming the first reinforcement portion (30); one side surface of the first region (21) is concave, and the other side surface is correspondingly convex, forming the second reinforcement portion (40).

4. The pole piece according to claim 3, characterized in that: Along the first direction, the first reinforcement portion (30) and the second reinforcement portion (40) are connected to each other to form a reinforcement portion; the cross-sectional shape of the reinforcement portion is a long strip extending along the first direction.

5. The pole piece according to claim 4, characterized in that: In a direction opposite to the first direction, a recessed depth of the reinforcing portion in the thickness direction decreases.

6. The pole piece according to claim 4, characterized in that: The reinforcement portion and the first direction have a first angle θ, 0°≤θ≤20°.

7. The pole piece according to claim 4, characterized in that: The reinforcement portion has a bottom wall and side walls connected to each other, and a smooth transition is formed between the bottom wall and the side walls.

8. The pole piece according to claim 3, characterized in that: Along the thickness direction, the convex portion (12) has a first thickness c, the first reinforcement portion (30) has a first depth recess H1, the sum of the thicknesses of the main portion (11) and the entire first region (21) is a second thickness T2, and the second reinforcement portion (40) has a second recess depth H2; wherein, H1=(1-100)c; and / or, H2=(0.05-1)T2; and / or, H2<H1; and / or, 5 μm ≤ H1 ≤ 500 μm; And / or, 5μm≤H2≤100μm.

9. The pole piece according to claim 3, characterized in that: There are a plurality of first reinforcing portions (30), and the cross-sectional shape of each first reinforcing portion (30) is a long strip extending along the first direction, and two adjacent first reinforcing portions (30) have a third spacing D1 along the second direction; the first direction, the thickness direction, and the second direction intersect each other; Each of the first reinforcement portions (30) has a first recessed depth H1 along the thickness direction, the convex portion (12) has a third height a along the first direction, the convex portion (12) has a first thickness c along the thickness direction, and the convex portion (12) has a first width b along the first direction; H1 / D1=k*a / (b*c); Among them, 5μm≤H1≤500μm, 1mm≤D1≤10mm, 1*10 -7 ≤k≤0.

08.

10. The pole piece according to any one of claims 1 to 9, characterized in that: Along the thickness direction, the average thickness of the first region (21) is smaller than the average thickness of the second region (22) by Δt; 4μm≤△t≤6μm.

11. The pole piece according to any one of claims 1 to 9, characterized in that: The first region (21) comprises a first sub-region (211) and a second sub-region (212) sequentially arranged along the first direction, wherein the first sub-region (211) is arranged closer to the convex portion (12) relative to the second sub-region (212); The second reinforcement portion (40) is provided in the first sub-region (211).

12. The pole piece according to claim 11, characterized in that: Along the first direction, the first sub-region (211) has a first height M1, and the second sub-region (212) has a second height M2; M2=(0.1-0.9)M1, or 1mm≤M1≤10mm.

13. The pole piece according to any one of claims 1 to 9, characterized in that: Along the first direction, the first region (21) has a total height M3; Along the first direction, the second reinforcement portion (40) has a first edge (60) away from the protrusion (12); the first area (21) and the second area (22) have a boundary line (50); along the first direction, a fifth distance L3 is present between the first edge (60) and the boundary line (50), where L3 = (0.1-0.9)M3.

14. The pole piece according to any one of claims 1 to 12, characterized in that: The convex portion (12) includes a connecting portion (122) and the tab (121) arranged in sequence along the first direction, the connecting portion (122) connects the main body (11) and the tab (121), and the active material layer (20) is also arranged on the connecting portion (122); the second reinforcing portion (40) extends to the connecting portion (122).

15. The pole piece according to any one of claims 1 to 12, characterized in that: Along the first direction, the second reinforcement portion (40) has a first edge (60) away from the convex portion (12), and the first region (21) has a second edge (70) close to the convex portion (12); Along the first direction, a first distance L1 is provided between the first edge (60) and the second edge (70), and 1 mm ≤ L1 ≤ 10 mm.

16. The pole piece according to claim 15, characterized in that: The main body (11) has a third edge (80) connected to the convex portion (12); Along the first direction, the first edge (60) and the third edge (80) have a second distance L2, 1mm≤L2≤10mm; And / or, L1=L2.

17. An electrode assembly, characterized in that: Comprising a pole piece as described in any one of claims 1-16.

18. The electrode assembly according to claim 17, characterized in that The electrode assembly comprises a positive electrode sheet (100a), a negative electrode sheet (100b) and a separator (200), wherein the separator (200) is arranged between the positive electrode sheet (100a) and the negative electrode sheet (100b), and the negative electrode sheet (100b) is a plate according to any one of claims 1 to 16, wherein one side surface of the first region (21) is concave and the other side surface is correspondingly convex, forming the second reinforcement portion (40).

19. The electrode assembly according to claim 18, wherein The second reinforcing portion (40) has a second recessed depth H2 along the thickness direction, the first region (21) of the negative electrode sheet (100b) has a third thickness t1, and the first region (21) of the positive electrode sheet (100a) has a fourth thickness t2; t1≤H2≤(t1+t2).

20. A battery cell, characterized in that: It comprises the pole piece as described in any one of claims 1 to 16, or comprises the electrode assembly as described in any one of claims 17 to 19.

21. An electrical device, characterized in that: Comprising the battery cell as claimed in claim 20.

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