Electrode assembly and secondary battery

Abstract

The utility model provides an electrode assembly and a secondary battery. The electrode assembly comprises at least one first pole piece, and the surfaces of the two sides, in the thickness direction, of the first pole piece are each provided with a first coating area extending in the length direction of the first pole piece; the surfaces of the two sides, in the thickness direction of the second pole piece, of the second pole piece are each provided with a second coating area extending in the length direction of the second pole piece, the second pole piece is bent in a Z shape in the length direction of the second pole piece to form at least one containing space and a plurality of second sub-coating areas, and one first pole piece is arranged in each containing space; each first coating area is opposite to one second sub-coating area, and the first coating area and the second sub-coating area which are opposite are in concave-convex fit. According to the utility model, the problem of poor use performance of the secondary battery in the prior art is solved.

Description

TECHNICAL FIELD

[0001] The utility model relates to battery technology field, specifically, relate to a kind of electrode assembly and secondary battery. BACKGROUND

[0002] In prior art, with the cycle of secondary battery, battery positive and negative pole will gradually attenuate (i.e. current flow will occur inside battery, with metal ion reciprocating transmission and deintercalation between positive and negative pole, cause battery material structure and chemical property change such as electrochemical side reaction, electrode material loss, electrolyte decomposition etc.), and gas will be generated inside battery, the generation of gas can cause the contact between positive and negative pole piece to be worse, electrode assembly internal resistance increases, so as to cause positive and negative pole to accelerate attenuation, seriously affect the rate capability and cycle performance of secondary battery.Especially in soft package battery, the larger positive and negative pole piece is, the smaller electrode assembly central stress is, and the worse the contact of positive and negative pole piece is, more easily cause impact on the rate capability and cycle performance of battery.

[0003] Therefore, there is the problem of poor performance of secondary battery in prior art. SUMMARY

[0004] The main purpose of the utility model is to provide a kind of electrode assembly and secondary battery, to solve the problem of poor performance of secondary battery in prior art.

[0005] In order to achieve the above-mentioned purpose, according to one aspect of the utility model, an electrode assembly is provided, comprising: at least one first pole piece, the surface of both sides along the thickness direction of the first pole piece has a first coating area extending along the length direction of the first pole piece; second pole piece, the surface of both sides along the thickness direction of the second pole piece has a second coating area extending along the length direction of the second pole piece, the second pole piece is bent in Z type along the length direction to form at least one accommodation space and a plurality of second sub-coating areas, one first pole piece is arranged in each accommodation space, each first coating area is arranged opposite to one second sub-coating area, and the opposite first coating area and second sub-coating area are concave-convex matched.

[0006] Further, the compaction density of each part of the first coating area of the first pole piece is the same; and / or, the compaction density of each part of the second coating area of the second pole piece is the same.

[0007] Further, the first pole piece is a positive pole piece, the second pole piece is a negative pole piece, the first coating area has a groove structure arranged along the length direction of the first pole piece, and the second sub-coating area is provided with a protruding structure corresponding to the groove structure.

[0008] Further, the groove structure is arranged corresponding to a first middle line of the first coating area extending along the length direction of the first pole piece, and the convex structure is arranged corresponding to a second middle line of the second sub-coating area extending along the length direction of the second pole piece.

[0009] Further, the first coating area further has a first equal-thickness area located on both sides of the groove structure, and the second sub-coating area further has a second equal-thickness area located on both sides of the convex structure.

[0010] Further, the width of the groove structure accounts for 50%-60% of the width of the first coating area; and / or, the width of the convex structure accounts for 50%-60% of the width of the second sub-coating area.

[0011] Further, the first pole piece further comprises a first empty-foil area extending along the length direction of the first pole piece, the first empty-foil area is located on one side of the first coating area along the width direction of the first pole piece, and the length of the first empty-foil area is the same as the length of the first pole piece; and / or the second pole piece further comprises a second empty-foil area extending along the length direction of the second pole piece, the second empty-foil area is located on one side of the second coating area along the width direction of the second pole piece, and the length of the second empty-foil area is the same as the length of the second pole piece.

[0012] Further, the first empty-foil areas of the first pole pieces in different accommodation spaces are located on the same side of the first coating area, and the first empty-foil area and the second empty-foil area are respectively located on different sides of the electrode assembly.

[0013] Further, the electrode assembly further comprises a diaphragm, and the diaphragm is arranged between the first pole piece and the second pole piece.

[0014] According to another aspect of the present application, a secondary battery is provided, comprising the above electrode assembly.

[0015] According to the technical scheme of the present application, the electrode assembly in the present application comprises at least one first pole piece and second pole piece. The surface of the first pole piece on both sides along the thickness direction thereof has a first coating area extending along the length direction of the first pole piece; the surface of the second pole piece on both sides along the thickness direction thereof has a second coating area extending along the length direction of the second pole piece, and the second pole piece is bent in a Z shape along the length direction to form at least one accommodation space and a plurality of second sub-coating areas, one first pole piece is arranged in each accommodation space, each first coating area is arranged opposite to one second sub-coating area, and the concave-convex matching of the opposite first coating area and the second sub-coating area.

[0016] When the electrode assembly in the application is applied to a secondary battery, since the first coating area of the first tab and the second sub-coating area of the second tab are in a concave-convex matching mode, the first tab and the second tab can be provided with a mutual binding force by the concave-convex matching, and the second tab is designed in an integral type with Z-shaped bending, which can also provide a constraint force, so that all the first tabs can keep close contact with the second tab as the secondary battery is cycled, thereby reducing the internal resistance of the electrode assembly to achieve the effect of prolonging the cycle life of the electrode assembly. Therefore, the electrode assembly in the application effectively solves the problem of poor performance of the secondary battery in the prior art. BRIEF DESCRIPTION OF DRAWINGS

[0017] The accompanying drawings constituting a part of the specification of the application serve to provide a further understanding of the application, and the schematic embodiments of the application and the description thereof serve to explain the application and do not constitute an improper limitation on the application. In the drawings:

[0018] Figure 1 A structural schematic view of an electrode assembly of one specific embodiment of the application is shown;

[0019] Figure 2 A structural schematic view of a first tab of the electrode assembly in Figure 1 is shown;

[0020] Figure 3 A sectional schematic view of the first tab of the electrode assembly in Figure 2 is shown;

[0021] Figure 4 A structural schematic view of a second tab of the electrode assembly in Figure 1 is shown;

[0022] Figure 5 A sectional schematic view of the second tab of the electrode assembly in Figure 4 is shown;

[0023] Figure 6 A partial structural schematic view of a secondary battery of one specific embodiment of the application is shown.

[0024] In the above drawings, the following reference signs are used:

[0025] 10, first tab; 11, first coating area; 111, first coating layer; 112, second coating layer; 12, first empty foil area; 20, second tab; 21, second coating area; 211, third coating layer; 212, fourth coating layer; 22, second empty foil area; 23, accommodating space; 30, separator; 40, shell; 50, first lug; 60, second lug; 70, adhesive tape. DETAILED DESCRIPTION

[0026] It should be noted that the embodiments and features in the embodiments of the present application can be combined with each other without conflict. The present application will be described in detail below with reference to the drawings and in combination with the embodiments.

[0027] It should be noted that, unless otherwise specified, all technical and scientific terms used in the present application have the same meaning as generally understood by those skilled in the art to which the present application belongs.

[0028] In the present application, unless otherwise stated, the orientation words such as "up, down, top, bottom" are generally directed to the direction shown in the drawings, or are directed to the vertical, perpendicular or gravity direction of the components themselves; similarly, for the convenience of understanding and description, "inner, outer" refers to the inner and outer relative to the contour of each component itself, but the above orientation words are not used to limit the present application.

[0029] In order to solve the problem of poor performance of the secondary battery in the prior art, the present application provides an electrode assembly and a secondary battery.

[0030] And, as shown in Figure 6 The secondary battery in the present application includes a shell 40 and the electrode assembly described below, and at least a part of the electrode assembly is arranged inside the shell 40. At the same time, the secondary battery in the present application can be a lithium battery, a sodium battery, etc.

[0031] As shown in Figures 1 to 5 The electrode assembly in the present application includes at least one first pole piece 10 and a second pole piece 20. The surface of the first pole piece 10 on both sides along its thickness direction has a first coating area 11 extending along the length direction of the first pole piece 10; the surface of the second pole piece 20 on both sides along its thickness direction has a second coating area 21 extending along the length direction of the second pole piece 20, and the second pole piece 20 is bent in Z shape along its length direction to form at least one accommodation space 23 and a plurality of second sub-coating areas. One first pole piece 10 is arranged in each accommodation space 23, each first coating area 11 is arranged opposite to one second sub-coating area, and the opposite first coating area 11 and the second sub-coating area are concave-convex matched, or different first pole pieces 10 are concave-convex matched with different positions of the same second pole piece 20.

[0032] When the electrode assembly in the application is applied to a secondary battery, the first coating area 11 of the first electrode sheet 10 and the second coating area 21 of the second electrode sheet 20 are in different positions and are in a concave-convex matching relationship, so that the first electrode sheet 10 and the second electrode sheet 20 can be provided with a mutual constraint force by the concave-convex matching relationship, and the second electrode sheet 20 is designed in an integral Z-shaped bending manner and can also provide a constraint force, thereby ensuring that all the first electrode sheets 10 can maintain close contact with the second electrode sheet 20 as the secondary battery is cycled, and the internal resistance of the electrode assembly can be reduced to prolong the cycle life of the electrode assembly. Therefore, the electrode assembly in the application effectively solves the problem of poor performance of the secondary battery in the prior art.

[0033] In addition, in the application, the first electrode sheet 10 can be a positive electrode sheet, and the second electrode sheet 20 can be a negative electrode sheet. In addition, in the application, one negative electrode sheet can be matched with one or more positive electrode sheets. Therefore, in the application, the length of the second electrode sheet 20 is greater than the length of the first electrode sheet 10. In addition, in the application, the second electrode sheet 20 needs to be in a concave-convex matching relationship with the two surfaces on both sides of the same first electrode sheet 10 along the thickness direction, so that the number of layers of the second electrode sheet 20 after folding is greater than the number of the first electrode sheet 10. Generally, the number of layers of the second electrode sheet 20 after folding is one more than the number of the first electrode sheet 10.

[0034] Optionally, the compaction density of the first coating area 11 of the first electrode sheet 10 is the same at different positions; and / or, the compaction density of the second coating area 21 of the second electrode sheet 20 is the same at different positions. By such a design, the distribution of the resistance of the first electrode sheet 10 and the second electrode sheet 20 at different positions can be more uniform, thereby ensuring the uniformity of the local current of the first electrode sheet 10 and the second electrode sheet 20 to ensure the performance of the secondary battery.

[0035] Optionally, the first coating area 11 has a groove structure arranged along the length direction, and the second sub-coating area is provided with a protrusion structure corresponding to the groove structure. At the same time, since the first electrode sheet 10 is a positive electrode sheet and the second electrode sheet 20 is a negative electrode sheet, by arranging the groove structure on the first electrode sheet 10 and the protrusion structure on the second electrode sheet 20, the CB value (the ratio of the capacity of the active material of the negative electrode to the capacity of the active material of the positive electrode) of the electrode assembly formed by the positive electrode sheet and the negative electrode sheet can be improved, and the low CB value can be prevented from causing lithium precipitation during the charging process, thereby improving the safety performance of the electrode assembly.

[0036] Optionally, the first coating area 11 further has a first equal-thickness area located on both sides of the groove structure, and the second coating area 21 further has a second equal-thickness area located on both sides of the protrusion structure. In this way, the constraint force can be provided while ensuring the energy density of the secondary battery.

[0037] Specifically, the width of the groove structure in the present application can be 0.5-0.6 times the width of the first coating area 11. Similarly, the width of the convex structure can be 0.5-0.6 times the width of the second coating area 21. That is, the width of the groove structure accounts for 50%-60% of the width of the first coating area 11; the width of the convex structure accounts for 50%-60% of the width of the second coating area 21. For the range value setting of 50%-60%, if the width of the groove structure and the convex structure is less than 50%, the central part of the positive and negative electrodes may still have insufficient contact in the case of a large number of cycles, increasing the contact resistance and affecting the electron transport. If the width of the groove structure and the convex structure is greater than 60%, the convex structure of the second tab will be too large, causing the thickness of the second tab to increase significantly, and the contact effect between the coating and the current collector of the second tab will be poor, thereby causing the coating of the second tab to be easily detached, affecting the cycle performance of the secondary battery, and the excessive width is not conducive to ensuring the energy density of the secondary battery. Of course, in the present application, the specific width of the groove structure and the convex structure can be adaptively adjusted according to actual design needs. And the width of the groove structure and the convex structure should be basically the same. And in the present application, the width of the first tab 10 can be slightly smaller than the width of the second tab 20.

[0038] Optionally, the groove structure is provided corresponding to a first center line of the first coating area 11 extending in the length direction of the first tab 10, and the convex structure is provided corresponding to a second center line of the second sub-coating area extending in the length direction of the second tab 20, that is, the groove structure is symmetrically arranged along the first center line, the first center line is located in the middle of the groove structure, and the convex structure is symmetrically arranged along the second center line, the second center line is located in the middle of the convex structure. By such arrangement, the stability of the cooperation between the first tab 10 and the second tab 20 can be further ensured, thereby preventing mutual deflection between the first tab 10 and the second tab 20. And since the central position of the electrode assembly in the prior art is less stressed, by arranging the groove structure and the convex structure that cooperate with each other on the length direction center lines of the first coating area 11 and the second sub-coating area respectively, the contact area of the first coating area 11 and the second sub-coating area at the central position can be effectively increased, the binding force on the middle position can be increased, and thus the contact effect of the first coating area 11 and the second sub-coating area can be improved. Therefore, the contact effect between the positive and negative electrode tabs in the electrode assembly of the present application is better than that in the electrode assembly of the prior art, thereby reducing the impact on the rate performance and cycle performance of the secondary battery.

[0039] Of course, in the present application, the specific form of the concave-convex matching of the first pole piece 10 and the second pole piece 20, a plurality of groove structures can be provided on the first pole piece 10, and correspondingly a plurality of convex structures can be provided on the second pole piece 20, so as to further increase the contact effect of the first pole piece 10 and the second pole piece 20. In addition, in the present application, convex structures and groove structures can be provided on the first pole piece 10 and the second pole piece 20 at the same time, and the convex structures of the first pole piece 10 match the groove structures of the second pole piece 20, and the groove structures of the first pole piece 10 match the convex structures of the second pole piece 20.

[0040] Optionally, as shown in FIG. 1, the first coating area 11 includes a first coating layer 111 coated on the current collector of the first pole piece 10 and a second coating layer 112 coated on the first coating layer 111, the second coating layer 112 covers a part of the first coating layer 111, and another part of the first coating layer 111 forms a groove structure with the second coating layer 112. Figure 3

[0041] Optionally, the second coating area 21 includes a third coating layer 211 coated on the current collector of the second pole piece 20 and a fourth coating layer 212 coated on the third coating layer 211, and the fourth coating layer 212 is formed as a convex structure.

[0042] In a specific embodiment of the present application, the first coating area 11 includes a first coating layer 111 coated on the current collector of the first pole piece 10 and a second coating layer 112 coated on the first coating layer 111, the second coating layer 112 covers at least a part of the first coating layer 111, and at least another part of the first coating layer 111 forms a groove structure with the second coating layer 112; the second coating area 21 includes a third coating layer 211 coated on the current collector of the second pole piece 20 and a fourth coating layer 212, and the fourth coating layer 212 is formed as a convex structure. And in this embodiment, the second coating layer 112 is provided along the two side edges of the first coating area 11 in the width direction and extends along the length direction of the first coating area 11, so that the first coating layer 111 can be exposed in the middle area of the first coating area 11 to form a groove structure by being thus provided; and the fourth coating layer 212 can be coated on the third coating layer 211 corresponding to the exposed part of the first coating layer 111 to form a convex structure.

[0043] And in the present application, the materials of the first coating layer 111 and the second coating layer 112 can be the same, and the materials of the third coating layer 211 and the fourth coating layer 212 can be the same.

[0044] ​Optionally, the first tab 10 further comprises a first empty foil area 12 extending along the length direction of the first tab 10, the first empty foil area 12 is located at one side of the first coating area 11 along the width direction of the first tab 10, and the first empty foil area 12 is an area without a coating part on the current collector of the first tab 10; the second tab 20 further comprises a second empty foil area 22 extending along the length direction of the second tab 20, the second empty foil area 22 is located at one side of the second coating area 21 along the width direction of the second tab 20, and the second empty foil area 22 is an area without a coating part on the current collector of the second tab 20.

[0045] Optionally, the length of the first empty foil area 12 is the same as the length of the first tab 10. The length of the second empty foil area 22 is the same as the length of the second tab 20. In the prior art, the empty foil area is usually die-cut to form a tab, and burrs may be generated at the die-cutting position, which may cause a short circuit problem of the battery. However, in the present application, the full-tab design of the positive and negative tabs of the secondary battery can be realized by such arrangement, that is, the empty foil area does not need to be die-cut, the problem of burrs generated in the die-cutting process can be avoided, and the yield of the secondary battery is improved.

[0046] Optionally, one first tab 10 is arranged in each accommodation space 23, the first empty foil areas 12 of the first tabs 10 in different accommodation spaces 23 are located at the same side of the length direction of the first tabs 10, and the first empty foil area 12 and the second empty foil area 22 are located at different sides of the electrode assembly.

[0047] Optionally, the electrode assembly further comprises a separator 30 arranged between the first tab 10 and the second tab 20. By such arrangement, the first tab 10 and the second tab 20 can be effectively insulated and isolated.

[0048] In the present application, as shown in Figure 6 the first tab 10 and the second tab 20 are stacked, the first tab 10 and the first empty foil area 12 on the first tab 10 are connected by welding, the second tab 20 and the second empty foil area 22 on the second tab 20 are connected by welding, and the welding area of the first tab 50 and the second tab 60 is provided with a tape 70, and the tape 70 completely covers the welding area. By sticking the tape 70 on the welding area and completely covering the welding area, an insulation effect can be achieved to prevent the occurrence of a leakage phenomenon in this area during charging and discharging.

[0049] From the above description, it can be seen that the above-mentioned embodiments of the present application achieve the following technical effects:

[0050] Since the first coating area of the first pole piece and the second sub-coating area of the second pole piece are in a concave-convex fit, the first pole piece and the second pole piece can be provided with a mutual binding force by the concave-convex fit, and the second pole piece is designed in an integral type with a Z-shaped bending, and can also provide a constraint force, so that all the first pole pieces can maintain close contact with the second pole piece as the secondary battery circulates, thereby reducing the internal resistance of the electrode assembly, and achieving the effect of prolonging the cycle life of the electrode assembly. Therefore, the electrode assembly in the application effectively solves the problem of poor use performance of the secondary battery in the prior art.

[0051] Obviously, the above-described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should belong to the scope of protection of the present application.

[0052] It should be noted that the terms used herein are only for the purpose of describing specific embodiments, and are not intended to limit the exemplary embodiments according to the present application. As used herein, the singular form is intended to include the plural form unless the context clearly indicates otherwise, and it should be understood that when the terms "comprise" and / or "include" are used in the specification, there is a feature, step, work, device, component and / or combination thereof.

[0053] It should be noted that the terms "first", "second" and the like in the specification and claims of the present application and the above-described drawings are used to distinguish similar objects, and do not necessarily have to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances, so that the embodiments of the application described herein can be implemented in an order other than those illustrated or described herein.

[0054] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. An electrode assembly, characterized by, The electrode assembly comprises: at least one first pole piece (10), the surfaces of both sides of the first pole piece (10) along its thickness direction each have a first coating area (11) extending along the length direction of the first pole piece (10); a second pole piece (20), the surfaces of both sides of the second pole piece (20) along its thickness direction each have a second coating area (21) extending along the length direction of the second pole piece (20), the second pole piece (20) is bent in a Z shape along its length direction to form at least one accommodation space (23) and a plurality of second sub-coating areas, one first pole piece (10) is arranged in each of the accommodation spaces (23), each of the first coating areas (11) is arranged opposite to one of the second sub-coating areas, and the opposite first coating area (11) and the second sub-coating area are in concave-convex matching.

2. The electrode assembly of claim 1, wherein, The compaction densities of the first coating areas (11) of the first pole piece (10) are the same everywhere; and / or the compaction densities of the second coating areas (21) of the second pole piece (20) are the same everywhere.

3. The electrode assembly of claim 1, wherein, The first pole piece (10) is a positive pole piece, the second pole piece (20) is a negative pole piece, the first coating area (11) has a groove structure arranged along the length direction of the first pole piece (10), and the second sub-coating area is provided with a protruding structure corresponding to the groove structure.

4. The electrode assembly of claim 3, wherein, The groove structure is arranged corresponding to a first median line of the first coating area (11) extending along the length direction of the first pole piece (10), and the protruding structure is arranged corresponding to a second median line of the second sub-coating area extending along the length direction of the second pole piece (20).

5. The electrode assembly of claim 3, wherein, The first coating area (11) further has a first equal-thickness area located on both sides of the groove structure, and the second sub-coating area further has a second equal-thickness area located on both sides of the protruding structure.

6. The electrode assembly of claim 5, wherein, The width of the groove structure accounts for 50%-60% of the width of the first coating area (11); and / or the width of the protruding structure accounts for 50%-60% of the width of the second sub-coating area.

7. The electrode assembly according to any one of claims 1 to 6, wherein the first pole piece (10) further comprises a first empty foil area (12) extending along the length direction of the first pole piece (10), the first empty foil area (12) is located on one side of the first coating area (11) along the width direction of the first pole piece (10), and the length of the first empty foil area (12) is the same as the length of the first pole piece (10); and / or the second pole piece (20) further comprises a second empty foil area (22) extending along the length direction of the second pole piece (20), the second empty foil area (22) is located on one side of the second coating area (21) along the width direction of the second pole piece (20), and the length of the second empty foil area (22) is the same as the length of the second pole piece (20).

8. The electrode assembly of claim 7, wherein, The first foil-free areas (12) of the first pole piece (10) in different of the accommodation spaces (23) are located on the same side of the first coated area (11), and the first foil-free area (12) and the second foil-free area (22) are located on different sides of the electrode assembly, respectively.

9. The electrode assembly of any one of claims 1 to 6, wherein, The electrode assembly further comprises a separator (30) arranged between the first pole piece (10) and the second pole piece (20).

10. A secondary battery characterized by comprising: An electrode assembly comprising any one of claims 1 to 9.

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