Electrode tab, welding structure of electrode tab and sealing material, and secondary battery

Abstract

To improve sealing performance.SOLUTION: With an electrode tab 20, a base end portion 21 is joined to a laminated electrode body 10 in which a plurality of electrode plates 11, 12 is laminated, a tip end portion 22 is led out to the outside of a sheet-like exterior body 16 surrounding the laminated electrode body 10 together with an electrolytic solution 18, and a sealing material 17 is welded for sealing a gap relative to the sheet-like exterior body 16. A recess 24 is formed on a welded surface 23 on which the sealing material 17 is welded. A rough surface unit 27 with an uneven shape is formed on inner surfaces 26B, 26F, and 26R of the recess 24.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an electrode tab, a welding structure between the electrode tab and a sealing material, and a secondary battery. [Background technology]

[0002] Patent Document 1 discloses a laminate pack type lithium ion battery in which a heat seal layer is disposed between a laminate film covering an electrode laminate formed by laminating a negative electrode layer, an insulating layer, and a positive electrode layer, and a lead tab whose base end is joined to the electrode laminate and whose tip end protrudes outside the laminate film. In this seal structure, a plurality of recesses and / or protrusions are provided at the joint between the lead tab and the heat seal layer as a means for preventing leakage of the electrolyte stored in the laminate film. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Publication No. 2005-222788 Summary of the Invention [Problem to be solved by the invention]

[0004] The recesses and protrusions are bent at obtuse angles, which results in a weak anchoring effect, and therefore there is a problem in that peeling easily occurs between the lead tab and the heat seal layer.

[0005] The present disclosure was made in light of the above circumstances, and aims to improve sealing performance. [Means for solving the problem]

[0006] The electrode tab of the first disclosure comprises: The base end is joined to a laminated electrode body in which a plurality of electrode plates are stacked, The tip end is led out of the sheet-like outer casing that surrounds the laminated electrode body together with the electrolyte, An electrode tab to which a sealing material for sealing between the electrode tab and the sheet-like outer casing is welded, A recess is formed on the welding surface to which the sealing material is welded, A rough surface having an uneven shape is formed on the inner surface of the recess.

[0007] The welding structure of the electrode tab and the sealing material of the second disclosure is as follows: an electrode tab having a base end joined to a laminated electrode body formed by laminating a plurality of electrode plates and a tip end led out to the outside of a sheet-like outer casing that surrounds the laminated electrode body together with an electrolyte; a sealing material that is welded to the electrode tab to seal between the sheet-like exterior body and the electrode tab, a recess is formed on the surface of the electrode tab that is welded to the sealing material; A rough surface having an uneven shape is formed on the inner surface of the recess.

[0008] The secondary battery of the third disclosure comprises: a laminated electrode body formed by stacking a plurality of electrode plates; a sheet-like outer casing that surrounds the laminated electrode body together with an electrolytic solution; an electrode tab having a base end joined to the laminated electrode body and a tip end extending to the outside of the sheet-like outer casing; a sealing material that is welded to the electrode tab to seal between the sheet-like exterior body and the electrode tab, a recess is formed on the surface of the electrode tab that is welded to the sealing material; A rough surface having an uneven shape is formed on the inner surface of the recess. [Effects of the Invention]

[0009] According to the first to third disclosures, the sealing performance can be improved. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a perspective view of a secondary battery according to a first embodiment; [Figure 2] Exploded perspective view of a laminated electrode body [Figure 3] Schematic cross-sectional view showing the welding structure between the electrode tab and the sealing material [Figure 4] Schematic enlarged cross-sectional view showing the recessed portion and rough surface of the electrode tab DETAILED DESCRIPTION OF THE INVENTION

[0011] Here, preferred embodiments of the present disclosure will be described. Any combination of the following embodiments without causing any contradiction is also included in the embodiments for carrying out the invention.

[0012] The electrode tab of the first disclosure comprises: (1) An electrode tab having a base end that is joined to a laminated electrode body formed by stacking multiple electrode plates, a tip end that is led out to the outside of a sheet-like outer casing that surrounds the laminated electrode body together with an electrolyte, and a sealing material that seals between the electrode tab and the sheet-like outer casing is welded, and a recess is formed on the welding surface to which the sealing material is welded, and an uneven rough surface portion is formed on the inner surface of the recess.

[0013] According to the configuration of the first disclosure, a part of the sealing material welded to the electrode tab penetrates into the rough surface portion, thereby exerting an anchor effect due to the engagement between the sealing material and the rough surface portion. This anchor effect improves the peel strength (welding strength) between the electrode tab and the sealing material. According to the first disclosure, it is possible to improve sealing performance.

[0014] (2) In (1), it is preferable that the rough surface portion is formed on the inner surface of the recess along the overlapping direction of the sealing material and the electrode tab. With this configuration, the peaks and valleys constituting the rough surface portion are arranged alternately in a direction intersecting the direction in which the sealing material and the electrode tab separate, thereby providing a high anchor effect.

[0015] (3) In paragraph (1) or (2), The recessed portion is preferably in the form of a groove extending in a direction intersecting a direction connecting the base end portion and the tip end portion.

[0016] At the interface between the welding surface of the electrode tab and the sealing material, the path from the base end side of the electrode tab toward the tip end side of the electrode tab is defined as a potential leakage path for the electrolyte. When the recess is configured as a groove extending in a direction intersecting the direction connecting the base end and the tip end, the potential leakage path is longer than when the recess is configured as a groove extending parallel to the direction connecting the base end and the tip end. Therefore, even if the electrolyte inside the sheet-like exterior body leaks into the potential leakage path, the electrolyte is less likely to leak out of the sheet-like exterior body.

[0017] (4)(3) The recess preferably has an undercut portion in which the cross-sectional area of ​​the electrode tab cut parallel to the welding surface decreases toward the welding surface.

[0018] According to this configuration, the undercut shape provides a high anchor effect.

[0019] The welding structure of the electrode tab and the sealing material of the second disclosure is as follows: (5) An electrode tab having a base end joined to a laminated electrode body formed by stacking a plurality of electrode plates and a tip end led out to the outside of a sheet-like outer casing that surrounds the laminated electrode body together with an electrolyte, and a sealing material that is welded to the electrode tab to seal between the sheet-like outer casing and the electrode tab, wherein a recess is formed on the surface of the electrode tab that is welded to the sealing material, and an unevenly roughened surface portion is formed on the inner surface of the recess. According to the configuration of the second disclosure, sealing performance can be improved by the same action as in the first disclosure.

[0020] The secondary battery of the third disclosure comprises: (6) A battery comprising: a laminated electrode body formed by stacking a plurality of electrode plates; a sheet-like outer casing that surrounds the laminated electrode body together with an electrolyte; an electrode tab having a base end joined to the laminated electrode body and a tip end extending to the outside of the sheet-like outer casing; and a sealant that seals between the sheet-like outer casing and the electrode tab by welding to the electrode tab, wherein a recess is formed on the surface of the electrode tab that is welded to the sealant, and an unevenly shaped rough surface portion is formed on the inner surface of the recess. According to the configuration of the third disclosure, sealing performance can be improved by the same action as in the first and second disclosures.

[0021] <Embodiment 1> A first embodiment of the present disclosure will be described with reference to FIGS. 1 to 4. Note that the present invention is not limited to these examples, but is defined by the claims, and all modifications within the meaning and scope of the claims are intended to be included. In this first embodiment, with respect to the front-to-rear direction, the F direction in FIGS. 1 to 4 is defined as the front. With respect to the up-down direction, the H direction in FIGS. 1 to 4 is defined as the up. With respect to the left-to-right direction, the R direction in FIGS. 1 and 2 is defined as the right. The left-to-right direction and the width direction are used synonymously. Note that FIG. 2 omits the thickness of each component. In FIGS. 3 and 4, the size and proportions of each component and part are exaggerated.

[0022] As shown in Fig. 1, the secondary battery A of the first embodiment is configured to include a laminated electrode body 10, a sheet-like outer casing 16 that, together with the laminated electrode body 10, encloses an electrolyte solution 18, a pair of electrode tabs 20, and a sealant 17 that provides a liquid-tight seal between the electrode tabs 20 and the sheet-like outer casing 16. As shown in Fig. 2, the laminated electrode body 10 is configured by alternately stacking a plurality of negative electrode plates 11 and a plurality of positive electrode plates 12 with a plurality of separators 13 sandwiched therebetween. The separators 13 are made of PAN (polyacrylonitrile), nonwoven fabric, or the like.

[0023] The negative electrode plate 11 is of a well-known configuration, configured by applying a negative electrode slurry (not shown) to both the front and back surfaces of a sheet-like negative electrode substrate (not shown) having an overall rectangular shape. The negative electrode substrate has one protruding negative electrode connection portion 14. The negative electrode connection portion 14 is an uncoated portion to which the negative electrode slurry is not applied. The positive electrode plate 12 is of a well-known configuration, configured by applying a positive electrode slurry (not shown) to both the front and back surfaces of a sheet-like positive electrode substrate (not shown) having an overall rectangular shape. The positive electrode substrate has one protruding positive electrode connection portion 15. The positive electrode connection portion 15 is an uncoated portion to which the positive electrode slurry is not applied.

[0024] When the negative electrode plates 11 and positive electrode plates 12 are stacked with separators 13 sandwiched between them, a plurality of stacked negative electrode connection portions 14 and a plurality of stacked positive electrode connection portions 15 are arranged at intervals on the left and right sides of the front long side. Electrode tabs 20 are electrically connected to the negative electrode connection portions 14 and the positive electrode connection portions 15, respectively. The negative electrode tab 20 and the positive electrode tab 20 are flat and protrude horizontally toward the front of the stacked electrode assembly 10.

[0025] The sheet-like outer casing 16 has a sheet-like substrate (not shown) made of a metal such as aluminum or an aluminum alloy, and an insulating layer (not shown) coated on the inner surface of the sheet-like substrate (the opposing surfaces of the pair of sheet-like outer casings 16). The insulating layer is intended to prevent the sheet-like substrate from coming into contact with the electrolyte solution 18. The two sheet-like outer casings 16 are arranged to sandwich from above and below the entire laminated electrode body 10 and the base end portions 21 of the electrode tabs 20 (the portions of the electrode tabs 20 that are fixed to the negative electrode connection portion 14 and the positive electrode connection portion 15). The tip end portions 22 (front end portions) of the electrode tabs 20 protrude forward (outside the sheet-like outer casing 16) beyond the outer peripheral edge portion 16S of the sheet-like outer casing 16. The electrolyte solution 18 is sealed inside the two sheet-like outer casings 16.

[0026] A sealing material 17 made of insulating synthetic resin is laminated in a firmly fixed state on the outer peripheral edge portion 16S on the inner surface of the sheet-like exterior body 16. The peel strength between the sheet-like exterior body 16 and the sealing material 17 is higher than the peel strength between the electrode tab 20 and the sealing material 17. The sealing material 17 is a member for providing a liquid-tight seal between the sheet-like exterior body 16 and the electrode tab 20. For example, modified PP (polypropylene) is used as the material for the sealing material 17. The sealing material 17 is welded to the electrode tab 20 by a heat welding process described below.

[0027] The regions of the upper and lower surfaces of the electrode tab 20 to which the sealing material 17 is welded are defined as welding surfaces 23. A plurality of recesses 24 are formed on both the upper and lower welding surfaces 23. The recesses 24 are groove-shaped and extend in a direction perpendicular to the direction from the base end 21 to the tip end 22 of the electrode tab 20 (front-rear direction). The region in which the recesses 24 are formed in the left-right direction is the entire widthwise region of the electrode tab 20. Therefore, both left and right ends of the recess 24 open to both left and right outer surfaces of the electrode tab 20. The plurality of recesses 24 are arranged at intervals in the front-rear direction.

[0028] 4 is a schematic cross-sectional view of the electrode tab 20 cut perpendicularly to the recess 24. As shown in the figure, the groove width Gn (dimension in the front-to-rear direction) of the recess 24 on the welding surface 23 is smaller than the groove width Gw (dimension in the front-to-rear direction) at a position of the recess 24 deeper than the welding surface 23. The region of the recess 24 from the position where it opens onto the welding surface 23 to a position deeper than the welding surface 23 is defined as an undercut portion 25. The cross-sectional area of ​​the undercut portion 25, when the electrode tab 20 is cut parallel to the welding surface 23, becomes smaller the closer it is to the welding surface 23. The depth dimension (dimension in the vertical direction) of the recess 24 is 50 to 100 μm.

[0029] A rough surface portion 27 is formed on the inner surface of each recess 24. The rough surface portion 27 is formed on the front inner surface 26F and the rear inner surface 26R of the inner surface of the recess 24, which extend in a direction intersecting with the welding surface 23, and on the groove bottom surface 26B at the innermost part of the recess 24. The rough surface portions 27 on the front inner surface 26F and the rear inner surface are arranged so that elongated peaks 27M and valleys 27V extending in the left-right direction are alternately arranged in the up-down direction. The rough surface portion 27 on the groove bottom surface 26B is arranged so that elongated peaks 27M and valleys 27V extending in the left-right direction are alternately arranged in the front-rear direction. The surface roughness of the rough surface portion 27 is coarser than the surface roughness of the welding surface 23 in a region where the recess 24 is not formed. For example, the surface roughness Ra of the rough surface portion 27 is 1.4±1.2 μm, and the surface roughness Ra of the area of ​​the welding surface 23 where the recesses 24 are not formed is less than 1.0 μm. The recesses 24 and the rough surface portion 27 are formed by laser processing.

[0030] Next, the lamination process after the electrode tabs 20 are fixed to the laminated electrode body 10 in the manufacturing process of the secondary battery A of the first embodiment will be described. The laminated electrode body 10 and the portions of the electrode tabs 20 to which the laminated electrode body 10 is fixed are arranged between a pair of sheet-like exterior bodies 16. At this time, the sealing material 17 is brought into contact with both the upper and lower welding surfaces 23 of the electrode tabs 20. In this state, a thermal welding process is performed. In the thermal welding process, the outer peripheral edge portions 16S of the pair of sheet-like exterior bodies 16 are pressed from above and below and heated. The heating melts the sealing material 17, and the molten sealing material 17 is pressed against the welding surfaces 23 of the electrode tabs 20. A portion of the molten sealing material 17 fills the entire interior of the recesses 24 and also fills the valley portions 27V of the rough surface portions 27. After the welding process, the sealing material 17 is cooled and solidified. This completes the manufacturing of the secondary battery A.

[0031] When the internal pressure of the sheet-like exterior body 16 increases, a force acts on the outer peripheral edge 16S of the sheet-like exterior body 16, tending to peel the sealing material 17 from the welding surface 23 of the electrode tab 20. The recess 24 has an undercut shape in which the opening dimension (groove width Gn) in the front-rear direction at the welding surface 23 is smaller than the dimension (Gw) in the front-rear direction of the recess 24 at a position separated from the welding surface 23. This undercut shape allows the sealing material 17 to be caught on the opening edge of the recess 24, thereby achieving a high anchor effect. This anchor effect increases the welding strength (peel strength) between the electrode tab 20 and the sealing material 17.

[0032] Within the recess 24, a portion of the sealing material 17 enters the valley portion 27V of the rough surface portion 27, thereby exerting an anchor effect. This anchor effect makes it difficult for the sealing material 17 to move relative to the electrode tab 20 in a direction from inside the recess 24 to outside the recess 24. In particular, on the front inner surface 26F and the rear inner surface 26R, the valley portions 27V are recessed in a direction intersecting the depth direction of the recess 24 (the direction in which the sealing material 17 leaves the recess 24), thereby achieving a high anchor effect. This anchor effect increases the welding strength (peel strength) between the electrode tab 20 and the sealing material 17.

[0033] If the secondary battery A is a lithium-ion battery, there is a concern that if moisture penetrates into the sheet-like exterior body 16, hydrofluoric acid will be generated by a chemical reaction between the moisture and the electrolyte 18 inside the sheet-like exterior body 16, and the hydrofluoric acid will cause peeling at the interface between the electrode tab 20 and the sealing material 17. The path from the base end 21 to the tip end 22 of the electrode tab 20 along the interface between the welding surface 23 of the electrode tab 20 and the sealing material 17 is defined as a potential leakage path 28. If peeling occurs at the interface between the electrode tab 20 and the sealing material 17, a small gap will be created in the potential leakage path 28, and there is a concern that the electrolyte 18 filled in the sheet-like exterior body 16 will leak through the potential leakage path 28 to the outside of the sheet-like exterior body 16.

[0034] However, since multiple recesses 24 extending in a direction perpendicular to the path 28 of potential leakage are formed at intervals along the length of the path 28 of potential leakage, the path 28 of potential leakage is longer than when the recesses 24 are not formed. Furthermore, a rough surface portion 27 is formed within the recess 24 (path 28 of potential leakage), and the rough surface portion 27 has many (multiple) valleys 27V extending in a direction perpendicular to the path 28 of potential leakage and formed at intervals along the length of the path 28 of potential leakage. Therefore, the path 28 of potential leakage is longer than when the rough surface portion 27 is not formed. This prevents the electrolyte 18 from leaking out of the sheet-like exterior body 16.

[0035] Table 1 shows the results of tests conducted to examine whether there is leakage (leakage of electrolyte 18) in the leakage risk path 28 and whether there is peeling between the electrode tab 20 and the sealing material 17 for the present embodiment 1 in which the recesses 24 and the rough surface portion 27 are formed in the electrode tab 20, and comparative embodiments 1 to 3 in which neither the recesses 24 nor the rough surface portion 27 are formed in the electrode tab 20. The laminated electrode body 10, electrolyte 18, sheet-like exterior body 16, and sealing material 17 used in comparative embodiments 1 to 3 are the same as those in the first embodiment.

[0036] [Table 1]

[0037] In the first embodiment, recesses 24 and a rough surface portion 27 are formed on the welding surface 23. The groove width Gn (opening dimension in the front-to-back direction) of the recesses 24 on the welding surface 23 is 45±25 μm, and the depth dimension (dimension in the up-down direction) of the recesses 24 from the welding surface 23 is 75±25 μm. The rough surface portion 27 has an Ra of 1.4±1.2 μm. The welding surface 23 in the first embodiment is not surface treated, and the Ra of the welding surface 23 is 1 μm.

[0038] Comparative Form 1 is a form in which no surface treatment is performed on the welding surface 23. The Ra of the welding surface 23 of Comparative Form 1 is less than 1.0 μm, similar to Embodiment 1. Comparative Form 2 is a form in which the welding surface 23 is Ni-plated, and the Ra of the Ni-plated welding surface 23 is less than 1.0 μm, similar to Embodiment 1 and Comparative Form 1. Comparative Form 3 is a form in which treatment is performed to roughen the welding surface 23. The Ra of the welding surface 23 of Comparative Form 3 is 4.3 μm. The measured values ​​of Ra in Embodiment 1 and Comparative Forms 1 to 3 are values ​​measured by line roughness measurement after performing 3D shape measurement in high-quality depth stacking mode.

[0039] In the leakage test, 1000 ppm of water was mixed into the electrolyte 18, and the samples were left in an environment of 85°C for 120 hours, after which the presence or absence of leakage was observed. In none of the first embodiment and comparative examples 1 to 3 did leakage (leakage of the electrolyte 18) occur in the leakage risk path 28. After the leakage test, a tensile test was performed in which, with the electrode tab 20 fixed, the outer peripheral edge portion 16S of the sheet-like exterior body 16 and the sealing material 17 were pulled in a peeling direction, and it was observed whether peeling occurred at the interface between the electrode tab 20 (welding surface 23) and the sealing material 17. In the tensile test, first, in comparative examples 1, 2, and 3, the tensile strength was increased until peeling occurred at the interface between the electrode tab 20 (welding surface 23) and the sealing material 17. In embodiment 1, the outer peripheral edge portion 16S of the sheet-like exterior body 16 and the sealing material 17 were pulled in a direction to peel them apart with a force that exceeded the strength that caused peeling in comparative embodiments 1 to 3. As a result, in embodiment 1, peeling did not occur at the interface between the electrode tab 20 and the sealing material 17, and the sealing material 17 itself was destroyed. From this test result, it was discovered that by forming the recess 24 and the rough surface portion 27 in the electrode tab 20, the peel strength at the interface between the welding surface 23 and the sealing material 17 is increased.

[0040] The secondary battery A of the first embodiment includes a laminated electrode body 10, a pair of sheet-like outer casings 16, an electrode tab 20, and a sealing material 17. The laminated electrode body 10 is a member formed by stacking multiple electrode plates (positive electrode plate 12 and negative electrode plate 11). The sheet-like outer casing 16 is a member that surrounds the laminated electrode body 10 together with an electrolyte 18. The electrode tab 20 and the sealing material 17 form a welding structure for sealing the outer peripheral edge portions 16S of the pair of sheet-like outer casings 16. The electrode tab 20 is a member that has a base end 21 joined to the laminated electrode body 10 and a tip end 22 extending outside the sheet-like outer casing 16. The sealing material 17 is welded to the electrode tab 20 to seal between the sheet-like outer casing 16 and the electrode tab 20. A recess 24 is formed on a welding surface 23 of the electrode tab 20 that is welded to the sealing material 17. On the inner surface of the recess 24, a rough surface portion 27 having an uneven shape with a surface roughness smaller than that of the recess 24 is formed.

[0041] According to the secondary battery A, electrode tab 20, and welding structure between the electrode tab 20 and the sealing material 17 of the first embodiment, a portion of the sealing material 17 welded to the electrode tab 20 penetrates into the rough surface portion 27, thereby exerting an anchor effect due to the engagement between the sealing material 17 and the rough surface portion 27. This anchor effect improves the peel strength (welding strength) between the electrode tab 20 and the sealing material 17. Therefore, according to the secondary battery A, electrode tab 20, and welding structure between the electrode tab 20 and the sealing material 17 of the first embodiment, it is possible to improve sealing performance. Furthermore, the penetration of a portion of the sealing material 17 into the rough surface portion 27 increases the contact area between the electrode tab 20 and the sealing material 17. This increased contact area lengthens the potential leakage path 28 of the electrolyte 18 within the sheet-like outer casing 16. This prevents the electrolyte 18 from leaking outside the sheet-like outer casing 16.

[0042] The recess 24 has an undercut portion 25 in which the cross-sectional area of ​​the electrode tab 20 cut parallel to the welding surface 23 becomes smaller the closer it is to the welding surface 23. With this configuration, the undercut shape provides a high anchor effect.

[0043] Rough surface portion 27 is formed on front inner surface 26F and rear inner surface 26R of the inner surface of recess 24 along the overlapping direction (vertical direction) of sealing material 17 and electrode tab 20. With this configuration, peaks 27M and valleys 27V constituting rough surface portion 27 are alternately arranged in a direction intersecting the direction in which sealing material 17 and electrode tab 20 separate, thereby providing a high anchor effect.

[0044] The recess 24 is groove-shaped and extends in a direction (left-right direction) intersecting the direction (front-rear direction) connecting the base end 21 of the electrode tab 20 and the tip end 22 of the electrode tab 20. At the interface between the welding surface 23 of the electrode tab 20 and the sealing material 17, a path from the base end 21 side of the electrode tab 20 toward the tip end 22 side of the electrode tab 20 is defined as a potential leakage path 28 of the electrolyte 18. When the recess 24 is groove-shaped and extends in a direction intersecting the direction connecting the base end 21 and the tip end 22, the potential leakage path 28 is longer than when the recess 24 is groove-shaped and extends parallel to the direction connecting the base end 21 and the tip end 22. Therefore, even if the electrolyte 18 in the sheet-like outer casing 16 leaks into the potential leakage path 28, the electrolyte 18 is less likely to leak out of the sheet-like outer casing 16.

[0045] <Other Examples> The present invention is not limited to the embodiments described above and illustrated in the drawings, and the following embodiments are also included within the technical scope of the present invention. The rough surface portion may be formed only on a part of the inner surface of the recess. The recess may be a groove extending parallel to the direction connecting the base end and the tip end of the electrode tab. The recess may be a groove that does not open to the side surface of the electrode tab. The recess is not limited to a groove shape, but may be a closed window opening (for example, a circle or a square) that opens around the entire periphery of the welding surface. The recess may be configured such that the opening dimensions at the portion close to the welding surface are the same as those at the portion far from the welding surface, or the opening dimensions at the portion close to the welding surface are larger than those at the portion far from the welding surface. [Explanation of symbols]

[0046] A…Secondary battery 10...Laminated electrode body 11...Negative electrode plate (electrode plate) 12...Positive electrode plate (electrode plate) 16...Sheet-shaped exterior body 17...Sealing material 18...Electrolyte 20...Electrode tab 21...Proximal end of electrode tab 22...Tip of electrode tab 23…Welding surface 24...recess 25...Undercut section 26B... Groove bottom surface (inner surface of recess) 26F...Front inner surface (inner surface of the recess) 26R...Rear inner surface (inner surface of the recess) 27...Rough surface area

Claims

1. The base end is joined to a laminated electrode body in which a plurality of electrode plates are stacked, The tip end is led out of the sheet-like outer casing that surrounds the laminated electrode body together with the electrolyte, An electrode tab to which a sealing material for sealing between the electrode tab and the sheet-like outer casing is welded, A recess is formed on the welding surface to which the sealing material is welded, The electrode tab has an inner surface of the recess formed with a roughened surface having an uneven shape.

2. The electrode tab according to claim 1 , wherein the rough surface portion is formed on an inner surface of the recess along an overlapping direction of the sealing material and the electrode tab.

3. 3. The electrode tab according to claim 1, wherein the recess is a groove extending in a direction intersecting a direction connecting the base end and the tip end.

4. 4. The electrode tab according to claim 3, wherein the recess has an undercut portion in which the cross-sectional area of ​​the electrode tab cut parallel to the welding surface decreases toward the welding surface.

5. an electrode tab having a base end joined to a laminated electrode body formed by stacking a plurality of electrode plates and a tip end led out of a sheet-like outer casing that surrounds the laminated electrode body together with an electrolyte; a sealing material that is welded to the electrode tab to seal between the sheet-like exterior body and the electrode tab, a recess is formed on the surface of the electrode tab that is welded to the sealing material; A welding structure for the electrode tab and the sealing material, in which a rough surface portion with an uneven shape is formed on the inner surface of the recess.

6. a laminated electrode body formed by stacking a plurality of electrode plates; a sheet-like outer casing that surrounds the laminated electrode body together with an electrolytic solution; an electrode tab having a base end joined to the laminated electrode body and a tip end extending to the outside of the sheet-like outer casing; a sealing material that is welded to the electrode tab to seal between the sheet-like exterior body and the electrode tab, a recess is formed on the surface of the electrode tab that is welded to the sealing material; The secondary battery has an inner surface of the recess formed with a roughened surface having an uneven shape.

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