battery cell

Abstract

To provide a battery cell that includes an electrode body capable of improving the heat absorption capacity of the electrode foil in the laser-welded area and its vicinity, where a large number of stacked electrode foils and a current collector terminal are laser-welded, thereby suppressing phenomena such as perforation and necking on the outer periphery of the laser-welded area of ​​the electrode foil. [Solution] The battery cell 10S includes an electrode body 10 comprising a plurality of electrode foils 1 having an active material layer forming portion 11 and an active material layer non-forming portion 12, and a current collector terminal 2 joined to the active material layer non-forming portion of the electrode foil by laser welding. The active material layer non-forming portion of the electrode foil is provided with a thickened portion 121 in the laser-welded region LR and its outer peripheral region GR, where the thickness t1 is greater than the thickness t0 of the adjacent non-thickened portion 122.

Description

Technical Field

[0001] The disclosed technology relates to battery cells used in hybrid vehicles, electric vehicles, and the like.

Background Art

[0002] Conventionally, in the manufacturing process of manufacturing an electrode body of a battery cell used in a hybrid vehicle, an electric vehicle, or the like, when joining a large number of laminated electrode foils and a current collector terminal, for example, a method using ultrasonic bonding is adopted (see, for example, Patent Document 1).

[0003] However, when performing overlapping bonding of a large number of electrode foils and a current collector terminal by ultrasonic bonding, usually, the protrusion of the horn is abutted against the electrode foil with a thin thickness, and the anvil is abutted against the current collector terminal with a thick thickness, and the horn is ultrasonically vibrated to bond the electrode foils to each other and at the same time bond the electrode foil and the current collector terminal. In this case, since the ultrasonic vibration of the horn is difficult to be transmitted to the joint portion between the electrode foil and the current collector terminal close to the anvil, it is necessary to set a large pressure of the horn, vibration energy, etc., and there are problems in the breakage of the electrode foil due to vibration or the generation of foreign matter, and the increase in cost due to wear of the horn and anvil.

Prior Art Documents

Patent Documents

[0004] [[ID=2​​​​​​​​​​​​Therefore, in recent years, laser welding has been considered for the overlapping joining of multiple electrode foils and current collector terminals. However, since the electrode foils are much thinner than the current collector terminals, and the stacked electrode foils are separated from each other, when multiple electrode foils are joined together by laser welding, excessive welding heat tends to accumulate around the welded area of ​​each electrode foil. As a result, problems such as hole formation (melting and tearing) of the outer circumference of the welded area of ​​the electrode foil, a decrease in plate thickness due to softening and shrinkage of the molten metal at the completion of welding, or necking (breakage) are likely to occur.

[0006] The present invention has been made in view of the above problems, and aims to provide a battery cell that includes an electrode body that can improve the heat absorption capacity of the electrode foil in the laser-welded area and its vicinity, where a large number of stacked electrode foils and a current collector terminal are laser-welded, thereby suppressing phenomena such as perforation and necking on the outer circumference of the laser-welded area of ​​the electrode foil. [Means for solving the problem]

[0007] (1) One aspect of the present invention for solving the above problems is a battery cell including an electrode body comprising a plurality of electrode foils having an active material layer forming portion and an active material layer non-forming portion, and a current collector terminal joined to the active material layer non-forming portion of the electrode foil by laser welding, wherein the active material layer non-forming portion of the electrode foil is provided with a thickened portion in the laser-welded region and its outer peripheral region, the thickness of which is greater than the thickness of the non-thickened portion.

[0008] (2) In the battery cell described in (1), it is preferable that the thickened portion is formed to a size that can absorb the excess heat generated by laser welding.

[0009] (3) In the battery cell described in (1) or (2), it is preferable that the thickened portion is formed integrally with the non-thickened portion.

[0010] (4) In the battery cell described in (1) or (2), it is preferable that the thickened portion is formed by joining a thick plate of a predetermined width to the non-thickened portion.

[0011] In the battery cell described in (5)(3) or (4), the electrode foil comprises two types of electrode foils in which the thickened portion is formed at different positions in the width direction, wherein the two types of electrode foils are alternately stacked in the thickness direction, and the thickened portions are arranged in parallel adjacent to each other in the width direction, and both of the parallel-arranged thickened portions are joined to the current collector terminal by laser welding.

[0012] (6) In the battery cell described in (1) or (2), it is preferable that the thickened portion is formed by joining the overlapping folded portions of the non-thickened portion formed at the widthwise end of the electrode foil.

[0013] (7) In the battery cell described in (1) or (2), it is preferable that the thickened portion is formed as a common thickened portion for each electrode foil by joining overlapping folded portions formed by overlapping and folding the non-thickened portions in a state where tab portions formed at the widthwise ends of a plurality of electrode foils are stacked together.

[0014] (8) In the battery cell described in (1) or (2), the electrode body is a laminated electrode body formed by laminating a plurality of rectangular sheet-shaped electrode foils of constant thickness with a separator in between, and the thickened portion is preferably formed by joining tab portions formed at the widthwise ends of the non-active material layer portion of the electrode foil to each other at a predetermined width, forming a plurality of thickened portions common to the tab portions, and the electrode foil is preferably joined to the current collector terminal by laser welding in a state in which the plurality of thickened portions are laminated. [Brief explanation of the drawing]

[0015] [Figure 1] This is a partial schematic cross-sectional view of a battery cell according to one embodiment of the present disclosed technology. [Figure 2] Figure 1 is an enlarged cross-sectional view of section A, which is a schematic cross-sectional view illustrating the state in which excess welding heat is absorbed in the laser-welded section of the thick-walled portion. [Figure 3] This is a view from arrow B shown in Figure 1. [Figure 4] It is a schematic cross-sectional view of part A in modification example 1 of the electrode body shown in FIG. 1. [Figure 5] It is a schematic cross-sectional view of part A in modification example 2 of the electrode body shown in FIG. 1. [Figure 6] It is a schematic cross-sectional view of part A in modification example 3 of the electrode body shown in FIG. 1. [Figure 7] It is a schematic cross-sectional view of part A in modification example 4 of the electrode body shown in FIG. 1. [Figure 8] It is a schematic cross-sectional view of part A in modification example 5 of the electrode body shown in FIG. 1. [[ID=十七]]

Embodiments for Carrying Out the Invention

[0016] <Overall Description of the Battery Cell> Next, the overall configuration of a battery cell (hereinafter also referred to as "the present battery cell") according to an embodiment of the above-disclosed technology will be described in detail while referring to the drawings (FIGS. 1 to 3). FIG. 1 shows a partial schematic cross-sectional view of a battery cell according to one aspect of an embodiment of the present disclosure technology. FIG. 2 shows an enlarged cross-sectional view of part A shown in FIG. 1, which is a schematic cross-sectional view for explaining a state of absorbing excessive welding heat of a laser welding part in a thick part. FIG. 3 shows a view taken in the direction of arrow B shown in FIG. 1. In each figure, the X direction indicates the longitudinal direction (axial direction) of the case body, the Y direction indicates the short-side direction of the case body, and the Z direction indicates the width direction of the long-side surface part in the case body. Note that the X direction is also the width direction of the electrode foil, the Y direction is also the stacking direction of the electrode foil, and the Z direction is also the longitudinal direction of the electrode foil.

[0017] As shown in Figures 1 to 3, the battery cell 10S includes an electrode body 10 comprising a plurality of electrode foils 1 having an active material layer forming portion 11 and an active material layer non-forming portion 12, and a current collector terminal 2 joined to the active material layer non-forming portion 12 of the electrode foil 1. The battery cell 10S is equipped with a battery case 3 for housing the electrode body 10. Here, the battery case 3 comprises a rectangular cylindrical case body 31 having rectangular openings 311 at both ends in the longitudinal direction (X direction), and a flat plate-shaped lid 32 that seals the openings 311. The current collector terminal 2 comprises a positive electrode current collector terminal 2a and a negative electrode current collector terminal 2b (not shown), and the external connection terminals 22 of each current collector terminal 2 are fixed to the lid 32 via an insulating material 4. The insulating material 4 can be, for example, polyphenylene sulfide (PPS) resin. The external connection terminal 22 is electrically connected to the internal connection terminal 21, which is joined to the non-active material layer portion 12 of the electrode foil 1.

[0018] The battery case 3 is not necessarily limited to the structure described above. For example, the battery case 3 may comprise a bottomed cylindrical case body 31 having an opening 311 at one end in the longitudinal direction (X direction), and a flat plate-shaped lid 32 that seals the opening 311. The case body 31 may also be formed in a cylindrical shape. Both the case body 31 and the lid 32 are made of aluminum, but are not necessarily limited to this; for example, they may be made of stainless steel or the like.

[0019] Further, the electrode foil 1 includes a positive electrode foil 1a and a negative electrode foil 1b that extend in a strip shape with a predetermined width. The positive electrode foil 1a has a positive electrode active material layer forming portion 11a coated with the positive electrode active material layer KTa, and an active material layer non-forming portion 12a that extends to one end in the width direction of the active material layer forming portion 11a and is not coated with the active material layer KTa. The negative electrode foil 1b has a negative electrode active material layer forming portion 11b coated with the negative electrode active material layer KTb, and an active material layer non-forming portion 12b (not shown) that extends to the other end in the width direction of the active material layer forming portion 11b and is not coated with the active material layer KTb. The electrode foil 1 is wound and flatly laminated with a separator SP sandwiched between the negative electrode active material layer forming portion 11b coated with the negative electrode active material layer KTb and the positive electrode active material layer forming portion 11a coated with the positive electrode active material layer KTa.

[0020] Here, the separator SP is also interposed between the negative electrode active material layer forming portion 11b coated with the outermost negative electrode active material layer KTb and the case body 31. The positive electrode active material layer non-forming portion 12a and the negative electrode active material layer non-forming portion 12b (not shown) are arranged to face each other in the longitudinal direction (X direction) of the case body 31, but they may also be arranged in the same direction in the longitudinal direction (X direction) of the case body 31. The electrode foil 1 may also be formed by laminating a rectangular sheet-shaped positive electrode foil 1a and a negative electrode foil 1b with a rectangular sheet-shaped separator SP sandwiched therebetween.

[0021] This battery cell 10S can be applied to various types of battery cells, but here, an example of a lithium-ion secondary battery will be described. In this case, the positive electrode foil 1a uses, for example, an aluminum foil with a thickness of about 10 to 15 μm, and the active material layer KTa coated thereon is, for example, a lithium transition metal oxide (LiNi 1 / 3 Co 1 / 3 Mn 1 / 3Materials such as O2 and LiNiO2 can be used. The negative electrode foil 1b can be, for example, a copper foil with a thickness of about 10-15 μm, and the active material layer KTb coated thereon can be, for example, graphite, hard carbon, or soft carbon. The positive electrode current collector terminal 2a can be an aluminum plate with a thickness of about 1-2 mm, and the negative electrode current collector terminal 2b (not shown) can be a copper plate with a thickness of about 1-2 mm. The separator SP can be, for example, a porous sheet such as polypropylene or polyethylene. The electrolyte can be a known non-aqueous electrolyte.

[0022] As described above, for example, when using aluminum foil with a thickness of about 10-15 μm for the positive electrode foil 1 (1a), the melting point of aluminum is about 660°C, and aluminum foil with a thickness of about 10-15 μm is soft and easily deformed by heat. Therefore, when laser welding the electrode foil 1 and the current collector terminal 2, the individual electrode foils 1, which have accumulated excessive heat on the outer circumference of the laser-welded area LY, tend to become unstable, causing phenomena such as hole formation and necking.

[0023] Therefore, as shown in Figures 1 and 2, the non-active material layer portion 12 of the electrode foil 1 of this battery cell 10S is provided with a thick portion 121 in the laser welding region LR and its outer peripheral region GR, where the thickness t1 is greater than the thickness t0 of the adjacent non-thick portion 122. As a result, the heat absorption capacity NC with respect to the heat quantity Q1 of the welding heat of the laser welding region LY of the electrode foil 1 equipped with the thick portion 121 is improved in the laser welding region LY and its vicinity. Consequently, excessive temperature rise associated with laser welding can be suppressed in the non-thick portion 122 adjacent to the thick portion 121. As a result, perforation and necking phenomena caused by laser welding can be reduced in the non-thick portion 122 adjacent to the thick portion 121. Thus, a battery cell 10S including an electrode body 10 that reduces perforation and necking phenomena on the outer peripheral side (non-thick portion 122) of the laser welding region LY of the electrode foil 1 can be provided.

[0024] In this battery cell 10S, it is preferable that the thickened portion 121 is formed to a size that can absorb the excess heat ΔQ associated with laser welding. Here, the excess heat ΔQ refers to the difference in heat amount obtained by subtracting the heat amount Q2 that is dissipated to the non-thickened portion 122 adjacent to the thickened portion 121 without causing perforation or necking from the heat amount Q1 that is dissipated from the laser-welded portion LY to the thickened portion 121. In this case, the thickness t1 and predetermined width w1 of the thickened portion 121 can be formed to the minimum necessary size according to the amount of heat dissipated by laser welding to the electrode foil 1. Therefore, while suppressing an increase in the weight of the electrode foil 1, perforation and necking phenomena on the outer circumference side (non-thickened portion 122) of the laser-welded portion LY can be effectively reduced.

[0025] For example, at the widthwise end 1T of the non-active material layer portion 12 of the electrode foil 1, a rectangular tab portion TB is formed, projecting in a direction away from the active material layer KT (in the widthwise direction (X direction) of the electrode foil 1), as shown in Figure 3. Furthermore, a thickened portion 121 with a predetermined width w1 is formed near the tip of the tab portion TB. An oval-shaped laser-welded portion LY is formed in the center of the thickened portion 121. The length d1 of the thickened portion 121 in the longitudinal direction (Z direction) of the electrode foil 1 is the same as the length d1 of the tab portion TB in the same direction (Z direction), and is slightly larger (for example, about 1.0 to 3.0 mm) than the length d2 of the current collector terminal 2 in the same direction (Z direction) and the length d3 of the laser-welded portion LY in the same direction (Z direction). The predetermined width w1 of the thickened portion 121 is slightly larger (for example, about 1.0 to 3.0 mm) than the predetermined width w2 of the laser-welded portion LY. In other words, the thickened portion 121 only needs to extend slightly (for example, about 1.0 to 3.0 mm) from the nugget boundary NK of the laser-welded portion LY. In this case, the size of the thickened portion 121 can be minimized, reducing the weight of the electrode body 10 while also reducing perforation and necking phenomena caused by laser welding.

[0026] Furthermore, a non-thick portion 122 may be formed at the tip of the tab portion TB, protruding from the thick portion 121 in the width direction (X direction) of the electrode foil 1. This non-thick portion 122 can act as a heat dissipation fin, dissipating the heat Q2 radiated from the thick portion 121 to the outside. However, this non-thick portion 122 is not necessarily required. In addition, the boundary portion 123 between the thick portion 121 and the non-thick portion 122 may be formed in a tapered shape so that the thickness changes gradually. By forming this boundary portion 123 in a tapered shape, temperature changes at the boundary portion 123 can be mitigated, and hole formation and necking phenomena caused by laser welding can be reduced in the non-thick portion 122 adjacent to the boundary portion 123.

[0027] Furthermore, the thickness t1 of the thickened portion 121 is preferably about 4 to 6 times the thickness t0 of the non-thickened portion 122. For example, if the electrode foil 1 is aluminum foil and the thickness t0 of the non-thickened portion 122 is 10 to 15 μm, then the thickness t1 of the thickened portion 121 is preferably about 40 to 90 μm. This is an example where aluminum foil with a thickness of about 10 to 15 μm is used for the positive electrode foil 1 (1a), but even when copper foil with a thickness of about 10 to 15 μm is used for the negative electrode foil 1 (1b), the hole-punching and necking phenomena caused by laser welding can be reduced by appropriately adjusting the thickness t1 of the thickened portion 121.

[0028] Furthermore, it is preferable that the thick-walled portion 121 is formed integrally with the non-thick-walled portion 122 of the electrode foil 1. In this case, the thermal conductivity between the thick-walled portion 121 and the non-thick-walled portion 122 is improved, and heat accumulation at the boundary portion 123 between the thick-walled portion 121 and the non-thick-walled portion 122 can be suppressed. Therefore, excessive temperature rise near the boundary portion 123 between the thick-walled portion 121 and the non-thick-walled portion 122 can be reduced, and the perforation and necking phenomena on the outer circumference (boundary portion 123) of the laser-welded portion LY can be reduced even more effectively. Here, one method for integrally forming the thick-walled portion 121 and the non-thick-walled portion 122 of the electrode foil 1 is, for example, a method in which the thick-walled portion 121 and the non-thick-walled portion 122 are integrally formed in a process of rolling or extruding molten metal obtained by melting the metal (such as aluminum) that will be the raw material for the electrode foil 1.

[0029] <Variation> The embodiments described in detail above are merely illustrative and do not limit the disclosed technology in any way. Therefore, the disclosed technology can be improved and modified in various ways without departing from its essence. Next, modified examples 1 to 5 of the electrode body of the battery cell according to the above-disclosed technology will be described in detail with reference to the drawings. Figure 4 shows a schematic cross-sectional view of part A in modified example 1 of the electrode body shown in Figure 1. Figure 5 shows a schematic cross-sectional view of part A in modified example 2 of the electrode body shown in Figure 1. Figure 6 shows a schematic cross-sectional view of part A in modified example 3 of the electrode body shown in Figure 1. Figure 7 shows a schematic cross-sectional view of part A in modified example 4 of the electrode body shown in Figure 1. Figure 8 shows a schematic cross-sectional view of part A in modified example 5 of the electrode body shown in Figure 1.

[0030] (Variation 1 of the electrode body) In the electrode body 10B of the modified example 1 of the battery cell 10BS, the thickened portion 121B is formed by joining a thick plate 124 of a predetermined width w1 to the non-thickened portion 122 of the electrode foil 1, as shown in Figure 4. At the widthwise end 1T of the non-active material layer portion 12 of the electrode foil 1, a rectangular tab portion TB is formed, as shown in Figure 3, protruding in a direction away from the active material layer KT (the widthwise direction (X direction) of the electrode foil 1). Furthermore, a thickened portion 121B of a predetermined width w1 is formed near the tip of the tab portion TB. In this case, a general electrode foil 1 consisting of a non-thickened portion 122 with a constant thickness t0 can be used, and the excess heat ΔQ associated with laser welding can be absorbed by the thick plate 124 joined to the non-thickened portion 122.

[0031] This thick plate 124 can be easily joined to the non-thick portion 122 of the non-active material layer 12 by roll pressure or the like, for example, before coating the active material layer KT onto the active material layer forming portion 11 of the electrode foil 1. In this case, as shown in Figure 2, compared to the method of integrally forming the thick portion 121 and the non-thick portion 122, it is possible to suppress the cost increase associated with forming the thick portion 121B of the electrode foil 1 while effectively reducing the perforation and necking phenomena on the outer circumference side (non-thick portion 122) of the laser-welded portion LY. Furthermore, as shown in Figure 4, it is preferable to join the thick plate 124 to the upper surface side of the non-active material layer 12 that is irradiated by the laser beam LK of the laser welding apparatus 5. Since the laser beam LK is irradiated onto the thick plate 124 first, evaporation and scattering of the electrode foil 1 can be suppressed, and the electrode foil 1 and the current collector terminal 2 can be joined in a better condition.

[0032] (Difference in electrode structure 2) In the electrode body 10C of the modified example 2 of the battery cell 10CS, the electrode foil 1 comprises two types of electrode foils 1x and 1y, as shown in Figure 5, in which thickened portions 121x and 121y are formed at different positions in the width direction (X direction). The two types of electrode foils 1x and 1y have thickened portions 121x and 121y and non-thickened portions 122x and 122y alternately stacked in the thickness direction (Y direction), and the thickened portions 121x and 121y are arranged in parallel adjacent to each other in the width direction (X direction). The parallel-arranged thickened portions 121x and 121y are both joined to the current collector terminal 2 by laser welding. Furthermore, as shown in Figure 3, a rectangular tab portion TB is formed at the widthwise end 1T of the non-active material layer portion 12 of the electrode foil 1, protruding in a direction away from the active material layer KT (in the width direction (X direction) of the electrode foil 1). Furthermore, thickened sections 121x and 121y are formed near the tip of the tab section TB, with a predetermined width w1.

[0033] In this case, because the thick-walled sections 121x and 121y and the non-thick-walled sections 122x and 122y are alternately stacked in the thickness direction (Y direction), as shown in Figure 2, the thickness of the laser-welded portion LY of the electrode foil 1 can be significantly reduced compared to the case where the thick-walled sections 121 are stacked together in the thickness direction (Y direction) and laser-welded. Furthermore, the thick-walled sections 121x and 121y, which are in contact with the non-thick-walled sections 122x and 122y above and below, can absorb the excess heat ΔQ in the non-thick-walled sections 122x and 122y that occurs during laser welding, thereby effectively reducing the perforation and necking phenomena on the outer periphery (non-thick-walled sections 122x and 122y) of the laser-welded portion LY.

[0034] In this embodiment, the thickened portions 121x and 121y are formed integrally with the non-thickened portions 122x and 122y, respectively, as shown in Figure 2. However, this is not necessarily the only option. For example, the thickened portions 121x and 121y may be formed by joining a thick plate 124 of a predetermined width to the non-thickened portions 122x and 122y of the electrode foil 1, as shown in Modification 1 in Figure 4.

[0035] (Variation 3 of the electrode body) In the electrode body 10D of the modified example 3 of the battery cell 10DS, the thickened portion 121D is formed by joining the overlapping folded portion KM1 of the non-thickened portion 122D formed at the widthwise end 1T of the electrode foil 1, as shown in Figure 6. Furthermore, as shown in Figure 3, a rectangular tab portion TB is formed at the widthwise end 1T of the non-active material layer portion 12 of the electrode foil 1, protruding in the direction away from the active material layer KT (the widthwise direction (X direction) of the electrode foil 1). In addition, a thickened portion 121D with a predetermined width w1 is formed near the tip of the tab portion TB. In this case, the thickened portion 121D can be formed by bending the widthwise end 1T of a general electrode foil 1 with a constant thickness t0, thereby suppressing the cost increase associated with the manufacture of the thickened portion 121D. Moreover, since the thickened portion 121D is formed by joining the overlapping folded portion KM of the thin non-thickened portion 122D with a constant thickness t0, the bending force of the electrode foil 1 is small, and it can be easily joined. Therefore, when forming the thickened portion 121D, it is possible to reduce breakage of the electrode foil 1 and generation of foreign matter due to overlapping, folding, and joining.

[0036] This thickened portion 121D can be formed, for example, by repeatedly applying roll bending and roll pressing to the widthwise end 1T of the non-thickened portion 122D of the non-active material layer-formed portion 122D in the step before applying the active material layer KT to the active material layer-forming portion 11 of the electrode foil 1. This creates an overlapping folded portion KM1 of the non-thickened portion 122D, and the overlapping folded portion KM1 can be pressed and joined together by applying pressure from above and below. Therefore, while suppressing the cost increase associated with forming the thickened portion 121D of the electrode foil 1, the perforation and necking phenomena on the outer circumference side (non-thickened portion 122D) of the laser-welded portion LY can be effectively reduced.

[0037] In Figure 6, the thickened portion 121D is formed by wrapping the widthwise end 1T of the non-thickened portion 122D inward to form an overlapping folded portion KM1, but this is not necessarily the only method. For example, the thickened portion 121D may be formed by folding the widthwise end 1T of the non-thickened portion 122D in a zigzag pattern to form an overlapping folded portion KM1, and then joining the overlapping folded portions KM1 together by applying pressure from above or below.

[0038] (Difference in electrode body modification 4) In the electrode body 10E of the modified example 4 of the battery cell 10ES, as shown in Figure 7, the thickened portion 121E is formed by joining overlapping folded portions KM2, where the non-thickened portions 122E are overlapped and folded, with tab portions TB formed on the widthwise ends 1T of multiple electrode foils 1 stacked together, thereby forming a thickened portion 121E common to all electrode foils 1. The thickened portion 121E is formed with a predetermined width w1 on the tip side of the tab portion TB. In this case, a common thickened portion 121E that can conduct heat between each electrode foil 1 can be formed at the overlapping folded portion KM2 of the non-thickened portion 122E. Therefore, the thickened portion 121E common to all electrode foils 1 can absorb the excess heat ΔQ in the non-thickened portion 122E due to laser welding, and the hole-punching and necking phenomena on the outer circumference side (non-thickened portion 122E) of the laser-welded portion LY can be effectively reduced.

[0039] This thickened portion 121E can be formed, for example, by the following method. That is, an active material layer KT is applied to the active material layer forming portion 11 of the electrode foil 1 and dried, then a separator SP is sandwiched between the layers and the electrode foil 1 is rolled up and pressed into a flat shape to form a laminate of electrode foil 1. Then, in the portion 12 of the flattened laminated electrode foil 1 where the active material layer is not formed, a tab portion TB is cut and formed at the widthwise end 1T, and the overlapping folded portions KM2 of the non-thickened portion 122E are joined together by cam bending and vertical pressing on the tab portion TB to form the thickened portion 121E. Therefore, the cost increase associated with forming the thickened portion 121E of the electrode foil 1 can be suppressed while effectively reducing the perforation and necking phenomena on the outer circumference side (non-thickened portion 122E) of the laser-welded portion LY.

[0040] In addition, the thickened portion 121E shown in Figure 7 is formed by overlapping and folding the tab portion TB of the non-active material layer portion 12 in the entire laminated electrode foil 1 toward the inner circumference, but this is not necessarily the only method. For example, the thickened portion 121E may be formed by dividing the tab portion TB of the non-active material layer portion 12 into a predetermined number of parts and overlapping and folding each divided tab portion TB toward the inner circumference. In this case, multiple thickened portions 121E may be joined together by applying pressure from above or below while they are laminated.

[0041] (5 variations of the electrode body) The electrode body 10F of the modified example 5 of the battery cell 10FS is a laminated electrode body 10F formed by laminating multiple rectangular sheet-shaped electrode foils 1F with a constant thickness t0, sandwiching a separator SP between them. In this electrode body 10F, as shown in Figure 8, multiple thickened portions 121F are formed as common thickened portions 121F for the electrode foil 1F by joining tab portions TB formed on the widthwise end 1T of the non-active material layer portion 12 of the electrode foil 1F with a predetermined width w1, and the electrode foil 1F is joined to the current collector terminal 2 by laser welding in a state where multiple thickened portions 121F are laminated.

[0042] In this case, a thickened portion 121F can be formed simply by stacking a predetermined number of tab portions TB formed on the widthwise end 1T of the non-active material layer portion 12 of a general rectangular sheet-shaped electrode foil 1F with a constant thickness t0, and joining them together, thereby suppressing the cost increase associated with the manufacture of the thickened portion 121F. Furthermore, the thickened portion 121F common to the predetermined number of stacked electrode foils 1F can absorb the excess heat ΔQ in the electrode foil 1F due to laser welding, effectively reducing the perforation and necking phenomena of the electrode foil 1F on the outer circumference side of the laser-welded portion LY. [Explanation of Symbols]

[0043] 1 Electrode foil 1T width end 2 Current collector terminal 10 Electrode body 10S battery cell 11 Active material layer forming part 12 Active material layer non-forming area 121 Thick wall part 122 Non-thick section 124 Thick Plate GR outer area KM1, KM2 overlapping folded section LR laser welding area TB tab section

Claims

1. A battery cell comprising an electrode body having a plurality of electrode foils having an active material layer forming portion and an active material layer non-forming portion, and a current collector terminal joined to the active material layer non-forming portion of the electrode foil by laser welding, The portion of the electrode foil in which the active material layer is not formed includes a thickened portion in the laser-welded region and its outer peripheral region, the thickened portion being greater than the thickness of the adjacent non-thickened portion. Battery cell.

2. In the battery cell described in claim 1, The aforementioned thickened portion is formed to a size that can absorb the excess heat generated during laser welding. Battery cell.

3. In the battery cell described in claim 1, The thickened portion is formed integrally with the non-thickened portion. Battery cell.

4. In the battery cell described in claim 1, The thickened portion is formed by joining a thick plate of a predetermined width to the non-thickened portion. Battery cell.

5. In the battery cell described in claim 3 or claim 4, The electrode foil comprises two types of electrode foils in which the thickened portion is formed at different positions in the width direction. The two types of electrode foils are arranged such that the thick-walled portion and the non-thick-walled portion are alternately laminated in the thickness direction, and the thick-walled portions are arranged in parallel adjacent to each other in the width direction. The parallel-arranged thick sections are both joined to the current collector terminal by laser welding. Battery cell.

6. In the battery cell described in claim 1, The thickened portion is formed by joining together the overlapping folded portions of the non-thickened portion formed at the widthwise end of the electrode foil. Battery cell.

7. In the battery cell described in claim 1, The aforementioned thickened portion is formed by joining overlapping folded portions, where the non-thickened portions overlap and bend, with tab portions formed at the widthwise ends of multiple electrode foils stacked together, thereby forming a thickened portion common to all electrode foils. Battery cell.

8. In the battery cell described in claim 1, The electrode body is a laminated electrode body formed by stacking a plurality of rectangular sheet-shaped electrode foils of constant thickness with a separator in between. The aforementioned thickened portion is formed by joining together tab portions formed at the widthwise ends of the non-active material layer portion of the electrode foil at a predetermined width, thereby creating a plurality of thickened portions common to the tab portions. The electrode foil is joined to the current collector terminal by laser welding, with multiple thick sections stacked together. Battery cell.

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