Electrode piece and electrode assembly

Abstract

The invention provides a pole piece and an electrode assembly, the pole piece comprises a current collector and a die-cut tab which are integrally formed, the die-cut tab is located on one side of the current collector in the length direction, an active material layer is arranged on the surface of the current collector, a tab groove is formed in the active material layer, and the pole piece further comprises a welding tab, the welding tab is welded at the tab groove and is electrically connected with the current collector; and the welding tab and the die cutting tab extend out of the same side edge of the current collector. According to the scheme, the problem that the energy density of the battery is influenced as the welding tab is welded in the empty foil area at the edge of the length direction of the current collector in the prior art can be solved.

Description

Technical Field

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

[0002] With the continuous evolution of lithium-ion battery technology and the continuous upgrading of market demand, the battery's current capacity has become a key point in technology development.

[0003] In the prior art, in wound-type battery cells, by simultaneously providing welded tabs and die-cut tabs on the same electrode sheet, more current paths are formed inside the battery to improve the battery's current capacity. Typically, the welded tabs and die-cut tabs are located on the same side of the electrode sheet. The head or tail of the wound electrode sheet has a hollow foil area where the current collector is exposed. The welded tabs are welded to the hollow foil area. Multiple die-cut tabs are provided, and the multiple die-cut tabs are located on the same side of the welded tabs. The multiple die-cut tabs are spaced apart along the length of the electrode sheet. In the wound-type battery cell, the multiple die-cut tabs overlap in the thickness direction of the battery cell. However, welding the welded tabs to the hollow foil area can easily affect the energy density of the battery. Summary of the Invention

[0004] The main purpose of the present invention is to provide a pole piece and an electrode assembly to solve the problem in the related art that the welding tab is welded to the empty foil area at the edge of the collector in the longitudinal direction, which affects the energy density of the battery.

[0005] In order to achieve the above-mentioned purpose, the present invention provides a pole piece on the one hand, which includes an integrally formed current collector and a die-cut pole ear, the die-cut pole ear is located on one side of the length direction of the current collector, the surface of the current collector is provided with an active material layer, and the active material layer is provided with a pole ear groove. The pole piece also includes a welded pole ear, which is welded at the pole ear groove and electrically connected to the current collector, and the welded pole ear and the die-cut pole ear extend out of the same side of the current collector.

[0006] Furthermore, a plurality of die-cut tabs are provided, the tab grooves are located in the middle of the length direction of the pole piece, part of the die-cut tabs are located on one side of the welded tab, and another part of the die-cut tabs are located on the other side of the welded tab.

[0007] Furthermore, the die-cut tabs are symmetrically distributed on both sides of the welded tabs.

[0008] Furthermore, the length of the die-cut tab gradually increases in a direction away from the welding tab.

[0009] Furthermore, the length of the welded tab protruding from the current collector is greater than the length of any one of the die-cut tabs.

[0010] Furthermore, a ceramic coating is coated on the surface of one end of the die-cut tab connected to the current collector.

[0011] Furthermore, the tab slots are located at the edges of the pole pieces in the length direction, and all the die-cut tabs are located on the same side of the welded tabs.

[0012] Another aspect of the present invention provides an electrode assembly, which includes a first electrode plate, a diaphragm, and a second electrode plate stacked in sequence. The electrode assembly is formed by winding the stacked first electrode plate, the diaphragm, and the second electrode plate. The polarity of the first electrode plate and the second electrode plate are different, and at least one of the first electrode plate and the second electrode plate is the above-mentioned electrode plate.

[0013] Furthermore, the first pole piece is the pole piece mentioned above, and the first pole piece is provided with multiple die-cut pole tabs, and the projections of all the die-cut pole tabs in the thickness direction of the electrode assembly overlap.

[0014] Furthermore, the welded tab and the die-cut tab are both located on the same side of a reference plane, wherein the reference plane is a center plane perpendicular to the thickness direction of the electrode assembly.

[0015] Furthermore, along the thickness direction of the electrode assembly, part of the die-cut tabs are located on one side of the plane where the welding tabs are located, and another part of the die-cut tabs are located on the other side of the plane where the welding tabs are located; or, along the thickness direction of the electrode assembly, all the die-cut tabs are located on the same side of the plane where the welding tabs are located.

[0016] Furthermore, the projection of the pole tab of the second pole piece along the thickness direction of the electrode assembly on the reference plane, and the projection of the die-cut pole tab of the first pole piece along the thickness direction of the electrode assembly on the reference plane, are staggered along the length direction of the electrode assembly; the projection of the pole tab of the second pole piece along the thickness direction of the electrode assembly on the reference plane, and the projection of the welded pole tab of the first pole piece along the thickness direction of the electrode assembly on the reference plane, are staggered along the length direction of the electrode assembly.

[0017] When the solution of the present invention is applied, when the electrode sheet includes both welded tabs and die-cut tabs, the effect on the mass energy density of the electrode assembly can be reduced by providing tab grooves on the active material layer and welding the welded tabs to the tab grooves. In the traditional technical solution, a blank foil is retained at the edge of the current collector in the longitudinal direction, and the welded tabs are welded to the blank foil. At this time, the entire area of ​​the blank foil is not coated with active material, resulting in a low mass energy density of the electrode sheet. In this solution, the entire area of ​​the current collector is coated with an active material layer, that is, the entire surface of the current collector is fully utilized. When the surface area of ​​the current collector is the same, compared with the form of leaving a blank foil area at the edge of the current collector in the longitudinal direction and welding the tabs in the empty thin area, this solution provides tab grooves on the active material layer and welds the welded tabs to the tab grooves, which can improve the utilization rate of the current collector and improve the energy density of the electrode sheet. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0019] Figure 1 A top view of a partial structure of a pole piece provided in accordance with the first embodiment of the present invention is shown;

[0020] Figure 2 A cross-sectional view showing a partial structure of a pole piece provided in accordance with the first embodiment of the present invention is shown;

[0021] Figure 3 It shows a top view of a partial structure of a pole piece provided in accordance with the second embodiment of the present invention;

[0022] Figure 4 A cross-sectional view showing a partial structure of a pole piece provided in accordance with a second embodiment of the present invention is shown;

[0023] Figure 5 A schematic structural diagram of a wound electrode assembly according to a third embodiment of the present invention is shown;

[0024] Figure 6 A schematic structural diagram of a wound electrode assembly according to a fourth embodiment of the present invention is shown;

[0025] Figure 7 A schematic structural diagram of another wound electrode assembly provided according to a fourth embodiment of the present invention is shown.

[0026] The above drawings include the following reference numerals:

[0027] 10. Current collector;

[0028] 11. Die-cutting tabs; 12. Welding tabs;

[0029] 20. Active material layer; 21. Tab groove;

[0030] 01. First pole piece; 02. Diaphragm; 03. Second pole piece; 031. Tab of the second pole piece. DETAILED DESCRIPTION

[0031] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is in no way intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0032] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0033] Unless otherwise specifically stated, the relative arrangement of the parts and steps, the numerical expressions and the numerical values ​​set forth in these embodiments do not limit the scope of the present invention. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the drawings are not drawn according to the actual proportional relationship. The techniques, methods and equipment known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, the techniques, methods and equipment should be considered as part of the authorization specification. In all examples shown and discussed here, any specific values ​​should be interpreted as being merely exemplary and not as limiting. Therefore, other examples of the exemplary embodiments may have different values. It should be noted that similar numbers and letters represent similar items in the following figures, and therefore, once an item is defined in one figure, it does not need to be further discussed in subsequent figures.

[0034] like Figure 1 and Figure 2 As shown, the first embodiment of the present invention provides a pole piece, which includes an integrally formed current collector 10 and a die-cut tab 11. The die-cut tab 11 is located on one side of the current collector 10 in the longitudinal direction. The surface of the current collector 10 is provided with an active material layer 20, and the active material layer 20 is provided with a tab groove 21. The welded tab 12 is welded at the tab groove 21 and electrically connected to the current collector 10. The welded tab 12 and the die-cut tab 11 extend from the same side of the current collector 10. The pole piece of this solution is used in a wound battery.

[0035] When the present invention is applied, when the electrode sheet includes both a welded electrode tab 12 and a die-cut electrode tab 11, the effect on the mass energy density of the electrode sheet can be reduced by providing an electrode tab groove 21 on the active material layer 20 and welding the welded electrode tab 12 to the electrode tab groove 21. In conventional technical solutions, a blank foil is retained at the edge of the current collector in the longitudinal direction, and the welded electrode tab is welded to the blank foil. In this case, the entire blank foil area is not coated with active material, resulting in a low mass energy density of the electrode sheet. In this solution, the entire area of ​​the current collector 10 is coated with the active material layer 20, that is, the entire surface of the current collector 10 is fully utilized. When the surface area of ​​the current collector 10 is the same, compared with the form of leaving a blank foil area at the edge of the current collector 10 in the longitudinal direction and welding the electrode tab to the blank foil area, the present solution provides an electrode tab groove 21 on the active material layer 20 and welds the welded electrode tab 12 to the electrode tab groove 21, which can improve the utilization rate of the current collector 10 and improve the mass energy density of the electrode sheet.

[0036] It can be understood that a tab groove 21 is provided on the active material layer 20 , and specifically part of the active material can be removed by laser to expose the current collector 10 ; that is, the bottom of the tab groove 21 is the exposed current collector, and the side wall of the tab groove 21 is the active material layer 20 .

[0037] This solution does not limit the distribution of the die-cut tabs 11 and the welded tabs 12 .

[0038] In this embodiment, multiple die-cut tabs 11 are provided, and the tab groove 21 is located in the middle of the length direction of the electrode sheet. Some die-cut tabs 11 are located on one side of the welded tab 12, and other die-cut tabs 11 are located on the other side of the welded tab 12. The above arrangement allows the current to diffuse to the surrounding areas through the multiple die-cut tabs 11 after entering the welded tab 12, thereby reducing current concentration, lowering resistance, and improving the battery's current capacity.

[0039] If the welding tab 12 is set at the starting end of the winding direction of the electrode sheet, when the battery is operating at a high current, the current is mainly input through the welding tab 12, and then diffuses to other parts of the electrode sheet through the active material layer 20. This centralized current input and diffusion will cause the heat in the area near the starting end of the electrode sheet winding to accumulate rapidly, which is not easy to dissipate effectively through the rest of the electrode assembly, and may cause local overheating, reducing the safety and service life of the battery; if the welding tab 12 is set at the end of the winding direction of the electrode sheet, in addition to the local overheating at the end of the electrode sheet winding when the battery is operating at a high current, it will also form a bad bulge on the battery surface after the electrode assembly is packaged, affecting the performance of the battery.

[0040] Furthermore, the die-cut tabs 11 are symmetrically distributed on both sides of the welded tabs 12. This arrangement can reduce the phenomenon of current concentration in a certain area, improve the uniformity of current distribution on the electrode sheet, enhance the battery's current capacity, and reduce the problem of local overheating caused by current concentration. In addition, the above arrangement can also help to maintain the overall structural balance of the electrode assembly.

[0041] Furthermore, the length of the die-cut tab 11 gradually increases in the direction away from the welded tab 12. In a wound electrode assembly, the projections of the multiple die-cut tabs 11 along the thickness direction of the battery cell overlap. This arrangement facilitates the aggregation of the multiple die-cut tabs 11 toward the middle of the distribution direction of the multiple die-cut tabs 11.

[0042] Furthermore, the length of the welded tab 12 protruding from the current collector 10 is greater than the length of any die-cut tab 11. This arrangement allows the welded tab 12 to serve as the primary current introduction point, carrying a higher current load; while the multiple shorter die-cut tabs 11 can serve as auxiliary current distribution paths, evenly directing current to the active material layer 20, reducing the local overheating and resistance increase that may be caused by concentrated current introduction. Furthermore, because the die-cut tabs 11 are relatively short, the additional volume generated during the winding process is small, preventing noticeable bulges or distortions in the packaging structure. This helps maintain the geometric consistency of the battery, improving the packaging quality and overall performance of the battery.

[0043] Furthermore, a ceramic coating is coated on the surface of one end of the die-cut tab 11 connected to the current collector 10. That is, the ceramic coating is coated on the root of the die-cut tab 11. The electrolyte inside the battery may corrode the die-cut tab 11 made of metal material, especially during long-term use or storage. The ceramic coating can resist the erosion of the electrolyte, protect the metal substrate of the die-cut tab 11, reduce the increase in resistance and the decrease in current transmission efficiency caused by corrosion, thereby maintaining the stability and consistency of battery performance; and, it can also improve the mechanical strength of the die-cut tab 11, and reduce wear or damage caused by friction or collision during battery manufacturing, assembly and use.

[0044] like Figure 3 and Figure 4 As shown, the second embodiment of this solution provides a pole piece, which differs from the first embodiment in that the tab groove 21 is located at the edge of the pole piece in the longitudinal direction, and all the die-cut tabs 11 are located on the same side of the welded tab 12. In addition, the length of the die-cut tab 11 gradually increases in the direction away from the welded tab 12; the length of the welded tab 12 protruding from the current collector 10 is greater than the length of the die-cut tab 11 farthest from the welded tab 12.

[0045] like Figure 5As shown, the third embodiment of the present invention provides an electrode assembly, which includes a first electrode piece 01, a separator 02, and a second electrode piece 03 stacked in sequence. The electrode assembly is formed by winding the stacked first electrode piece 01, the separator 02, and the second electrode piece 03. The first electrode piece 01 and the second electrode piece 03 have different polarities. The first electrode piece 01 is the electrode piece of the first embodiment. The X direction is the length direction of the electrode assembly, and the Y direction is the thickness direction of the electrode assembly.

[0046] The projections of all die-cut tabs 11 of the wound electrode assembly in the thickness direction of the electrode assembly overlap, so that it is easy to weld all die-cut tabs 11 to form a die-cut tab cluster.

[0047] Furthermore, the welded tab 12 and the die-cut tab 11 are both located on the same side of a reference plane, where the reference plane is the center plane perpendicular to the thickness of the electrode assembly. This arrangement facilitates connecting the welded tab 12 and the die-cut tab 11 via the adapter tab. The dotted line in the figure represents the reference plane.

[0048] Furthermore, along the thickness direction of the electrode assembly, part of the die-cut tabs 11 are located on one side of the plane where the welding tabs 12 are located, and the other part of the die-cut tabs 11 are located on the other side of the plane where the welding tabs 12 are located. This arrangement makes the center plane of the die-cut tab cluster in the thickness direction as close as possible to the plane where the welding tabs 12 are located, further improving the convenience of connecting the welding tabs 12 and the die-cut tab cluster through the adapter tabs.

[0049] In an embodiment of the present scheme, the second pole piece 03 has a pole ear, and the projection of the pole ear 031 of the second pole piece along the thickness direction of the electrode assembly on the reference plane, and the projection of the die-cut pole ear 11 of the first pole piece 01 along the thickness direction of the electrode assembly on the reference plane, are staggered along the length direction of the electrode assembly; the projection of the pole ear 031 of the second pole piece along the thickness direction of the electrode assembly on the reference plane, and the projection of the welded pole ear 12 of the first pole piece 01 along the thickness direction of the electrode assembly on the reference plane, are staggered along the length direction of the electrode assembly.

[0050] like Figure 6 As shown, the fourth embodiment of the present invention provides an electrode assembly, which includes a first electrode piece 01, a separator 02, and a second electrode piece 03 stacked in sequence. The electrode assembly is formed by winding the stacked first electrode piece 01, the separator 02, and the second electrode piece 03. The first electrode piece 01 and the second electrode piece 03 have different polarities. The difference from the third embodiment is that the first electrode piece 01 is the electrode piece of the second embodiment. The welded tab 12 and the die-cut tab 11 are both located on the same side of the reference plane, where the reference plane is the center plane perpendicular to the thickness direction of the electrode assembly.

[0051] The projections of the welded tabs 12 and all the die-cut tabs 11 of the wound electrode assembly in the thickness direction of the electrode assembly overlap.

[0052] Furthermore, along the thickness direction of the electrode assembly, all the die-cut tabs 11 are located on the same side of the plane where the welded tabs 12 are located.

[0053] Optionally, the welding tab 12 is close to the reference surface, and all the die-cut tabs 11 are located on a side of the welding tab 12 away from the reference surface.

[0054] like Figure 7 As shown, optionally, the welding tab 12 is away from the reference surface, that is, the welding tab 12 is close to the surface in the thickness direction of the electrode assembly, and all the die-cut tabs 11 are located on the side of the welding tab 12 close to the reference surface.

[0055] In addition, the second pole piece 03 has a pole ear, and the projection of the pole ear 031 of the second pole piece along the thickness direction of the electrode assembly in the reference plane, and the projection of the welding pole ear 12 of the first pole piece 01 along the thickness direction of the electrode assembly in the reference plane, are staggered along the length direction of the electrode assembly.

[0056] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0057] 1. Providing a tab groove 21 on the active material layer 20 and welding the welding tab 12 to the tab groove 21 can improve the utilization rate of the current collector 10 and increase the mass energy density of the electrode;

[0058] 2. The die-cut tabs 11 are symmetrically distributed on both sides of the welded tabs 12, which can improve the uniformity of current distribution in the active material layer 20, reduce local excessive current density, thereby reducing the formation of local hot spots and enhancing the thermal stability of the battery;

[0059] 3. The gradient setting of the length of the die-cut tab 11 facilitates the connection between the die-cut tab cluster and the welded tab 12 via the transfer tab in the wound electrode assembly.

[0060] In the description of the present invention, it should be understood that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "horizontal, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the device or element referred to must have a specific direction or be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the scope of protection of the present invention; the directional words "inside and outside" refer to the inside and outside relative to the outline of each component itself.

[0061] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used herein to describe the spatial positional relationship of a device or feature to other devices or features as shown in the figures. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figures. For example, if the device in the drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0062] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of the present invention.

[0063] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A pole piece, characterized in that: The pole piece comprises an integrally formed current collector (10) and a die-cut pole ear (11), wherein the die-cut pole ear (11) is located on one side of the length direction of the current collector (10), an active material layer (20) is provided on the surface of the current collector (10), and a pole ear groove (21) is provided on the active material layer (20), and the pole piece further comprises a welding pole ear (12), wherein the welding pole ear (12) is welded at the pole ear groove (21) and is electrically connected to the current collector (10), and the welding pole ear (12) and the die-cut pole ear (11) extend out of the same side of the current collector (10).

2. The pole piece according to claim 1, characterized in that: The die-cut pole tabs (11) are provided in plurality, the pole tab slots (21) are located in the middle of the length direction of the pole piece, part of the die-cut pole tabs (11) are located on one side of the welded pole tab (12), and another part of the die-cut pole tabs (11) are located on the other side of the welded pole tab (12).

3. The pole piece according to claim 2, characterized in that: The die-cut tabs (11) are symmetrically distributed on both sides of the welded tabs (12).

4. The pole piece according to claim 2, characterized in that: The length of the die-cut electrode tab (11) gradually increases in a direction away from the welding electrode tab (12).

5. The pole piece according to claim 1, characterized in that: The length of the welded electrode tab (12) protruding from the current collector (10) is greater than the length of any one of the die-cut electrode tabs (11).

6. The pole piece according to claim 1, characterized in that: A ceramic coating is coated on the surface of one end of the die-cut tab (11) connected to the current collector (10).

7. The pole piece according to claim 1, characterized in that: The tab groove (21) is located at the edge of the pole piece in the longitudinal direction, and all the die-cut tabs (11) are located on the same side of the welded tab (12).

8. An electrode assembly, characterized in that: The electrode assembly comprises a first pole piece (01), a diaphragm (02) and a second pole piece (03) stacked in sequence, and the electrode assembly is formed by winding the stacked first pole piece (01), the diaphragm (02) and the second pole piece (03), the first pole piece (01) and the second pole piece (03) having different polarities, and at least one of the first pole piece (01) and the second pole piece (03) is the pole piece according to any one of claims 1 to 7.

9. The electrode assembly according to claim 8, characterized in that The first pole piece (01) is the pole piece according to any one of claims 1 to 7, and the first pole piece (01) is provided with a plurality of die-cut pole ears (11), and the projections of all the die-cut pole ears (11) in the thickness direction of the electrode assembly overlap.

10. The electrode assembly according to claim 9, characterized in that The welded tab (12) and the die-cut tab (11) are both located on the same side of a reference plane, wherein the reference plane is a center plane perpendicular to the thickness direction of the electrode assembly.

11. The electrode assembly according to claim 10, wherein: Along the thickness direction of the electrode assembly, part of the die-cut electrode tab (11) is located on one side of the plane where the welding electrode tab (12) is located, and another part of the die-cut electrode tab (11) is located on the other side of the plane where the welding electrode tab (12) is located; or, Along the thickness direction of the electrode assembly, all of the die-cut electrode tabs (11) are located on the same side of the plane where the welded electrode tabs (12) are located.

12. The electrode assembly according to claim 10, wherein: The projection of the pole tab (031) of the second pole piece along the thickness direction of the electrode assembly on the reference plane, and the projection of the die-cut pole tab (11) of the first pole piece (01) along the thickness direction of the electrode assembly on the reference plane, are staggered along the length direction of the electrode assembly; The projection of the pole tab (031) of the second pole piece along the thickness direction of the electrode assembly within the reference plane, and the projection of the welding pole tab (12) of the first pole piece (01) along the thickness direction of the electrode assembly within the reference plane, are staggered along the length direction of the electrode assembly.

Images