Battery cell manufacturing method

Abstract

To provide a method for manufacturing a battery cell that includes an electrode body that can improve heat dissipation around the welded portion of each electrode foil before joining a large number of stacked electrode foils and current collector terminals by laser welding, thereby suppressing phenomena such as perforation and necking on the outer circumference of the welded portion of the electrode foil. [Solution] A method for manufacturing a battery cell 10S including an electrode body 10 comprising an electrode foil 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. The method comprises a first step S1 in which the electrode foils are brought into contact and fixed to each other at the active material layer non-forming portion to form a thermal resistance reduction portion RT of the electrode foil, in which the thermal resistance R1 at the contact fixing portion 121 between the electrode foils is reduced to the thermal resistance R2 at the separation portion 122 between the electrode foils; and a second step S2 in which, with the thermal resistance reduction portion and the current collector terminal in contact, the electrode foil and the current collector terminal are joined by laser welding such that the nugget boundary portion NK of the laser welding portion LY is connected to the thermal resistance reduction portion.

Description

Technical Field

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

Background Art

[0002] Conventionally, in the manufacturing process of manufacturing electrode bodies of battery cells used in hybrid vehicles, electric vehicles, and the like, when joining a large number of laminated electrode foils and current collectors, 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 current collectors 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 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. 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, it is necessary to set a large pressing force, vibration energy, etc. of the horn, and there are problems in the generation of cracks and foreign matters in the electrode foil due to vibration, etc., and the cost increase due to wear of the horn and anvil, etc.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] 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 method for manufacturing a battery cell that includes an electrode body that can improve the heat dissipation around the welded portion of each electrode foil before joining a number of stacked electrode foils and current collector terminals by laser welding, thereby suppressing phenomena such as perforation and necking on the outer circumference of the welded portion of the electrode foil. [Means for solving the problem]

[0007] (1) One aspect of the present invention for solving the above problems is a method for manufacturing 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, comprising: a first step of forming a thermal resistance reduction portion of the electrode foil by bringing the plurality of electrode foils into contact and fixing each other at the active material layer non-forming portions, thereby reducing the thermal resistance at the contact fixing portion between the active material layer non-forming portions than the thermal resistance at the separated portion where the active material layer non-forming portions are not fixed; and a second step of joining the electrode foil and the current collector terminal by laser welding, with the thermal resistance reduction portion of the electrode foil and the current collector terminal in contact, such that the nugget boundary portion of the laser-welded portion is connected to the thermal resistance reduction portion.

[0008] (2) In the method for manufacturing a battery cell described in (1), it is preferable that in the first step, the non-active material layer portions of a plurality of electrode foils are divided into predetermined numbers and brought into contact and fixed to each other, thereby forming the thermal resistance reduction portions at the contact and fixed portions between each divided non-active material layer portion, and in the second step, the thermal resistance reduction portions formed in the first step are brought into contact with the current collector terminal in a stacked state, and the electrode foil and the current collector terminal are joined by laser welding such that the nugget boundary portion of the laser-welded portion is connected to each thermal resistance reduction portion.

[0009] (3) In the method for manufacturing a battery cell described in (1) or (2), the thermal resistance reduction portion is preferably formed intermittently or continuously around the nugget boundary portion, and the sum of the circumferential lengths of the connecting portions between the nugget boundary portion and the thermal resistance reduction portion is less than or equal to the outer circumference length of the nugget boundary portion and is formed to be at least half the outer circumference length.

[0010] (4) In the method for manufacturing a battery cell described in any one of (1) to (3), it is preferable that the thermal resistance reduction portion is formed intermittently or continuously along a direction that separates it from the active material layer forming portion.

[0011] (5) In the method for manufacturing a battery cell described in any one of (1) to (4), in the second step, it is preferable to laser weld the electrode foil and the current collector terminal while the electrode foil is pressed against the current collector terminal by a cooling jig that contacts the thermal resistance reduction portion.

[0012] In the method for manufacturing a battery cell described in any one of (6)(1) to (5), it is preferable that the thermal resistance reduction portion is formed by ultrasonic bonding of the portions where the active material layer is not formed.

[0013] In the method for manufacturing a battery cell described in any one of (7)(1) to (5), it is preferable that the thermal resistance reduction portion is formed by pressure bonding the non-active material layer portions together. [Brief explanation of the drawing]

[0014] [Figure 1] Partial schematic cross-sectional view of a battery cell formed by a method for manufacturing a battery cell according to an aspect of an embodiment in the disclosed technology. [Figure 2] In part A shown in FIG. 1, it is a schematic cross-sectional view for explaining the heat dissipation state of welding heat. [Figure 3] It is an enlarged schematic cross-sectional view of part C shown in FIG. 2. [Figure 4] It is a view seen from arrow B shown in FIG. 1. [Figure 5A] In the first step of manufacturing the electrode body of the battery cell shown in FIG. 1, it is a partial schematic cross-sectional view of an ultrasonic bonding device for forming a heat resistance reduction part of an electrode foil by ultrasonic bonding. [Figure 5B] In the first step of manufacturing the electrode body of the battery cell shown in FIG. 1, it is a partial schematic cross-sectional view of a pressure bonding device for forming a heat resistance reduction part of an electrode foil by pressure bonding. [Figure 6] In the second step of manufacturing the electrode body of the battery cell shown in FIG. 1, it is a partial schematic cross-sectional view of a welding device for joining an electrode foil and a current collecting terminal by laser welding. [Figure 7] It is a view seen from arrow B in modification example 1 of the electrode body shown in FIG. 1. [Figure 8] It is a view seen from arrow B in modification example 2 of the electrode body shown in FIG. 1. [Figure 9] It is a view seen from arrow B in modification example 3 of the electrode body shown in FIG. 1. [Figure 10] It is a view seen from arrow B in modification example 4 of the electrode body shown in FIG. 1. [Figure 11] It is a view seen from arrow B in modification example 5 of the electrode body shown in FIG. 1. [Figure 12] It is a view seen from arrow B in modification example 6 of the electrode body shown in FIG. 1. [Figure 13] It is a view seen from arrow B in modification example 7 of the electrode body shown in FIG. 1.

Embodiments for Carrying Out the Invention

[0015] <Overall Description of This Battery Cell> Next, the overall configuration of the battery cell formed by the method for manufacturing a battery cell according to the embodiment of the disclosed technology (hereinafter also referred to as "this battery cell") will be described in detail while referring to the drawings (FIGS. 1 to 4). FIG. 1 shows a partial schematic cross-sectional view of a battery cell formed by the method for manufacturing a battery cell according to one aspect of the embodiment in the disclosed technology. FIG. 2 shows a schematic cross-sectional view for explaining the heat dissipation state of welding heat at portion A shown in FIG. 1. FIG. 3 shows an enlarged schematic cross-sectional view of portion C shown in FIG. 2. FIG. 4 shows a view taken in the direction of arrow B shown in FIG. 1. In each of the figures, 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 portion of the case body. Note that the Y direction is also the stacking direction of the electrode foils in the electrode body.

[0016] As shown in FIGS. 1 to 4, this battery cell 10S includes a battery cell 10S including an electrode body 10 having 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 collecting terminal 2 joined to the active material layer non-forming portion 12 of the electrode foil 1. The battery cell 10S includes a battery case 3 that houses the electrode body 10. Here, the battery case 3 includes a rectangular parallelepiped case body 31 having rectangular openings 311 at both ends in the longitudinal direction (X direction), and a flat lid body 32 that seals the openings 311. The current collecting terminal 2 includes a positive current collecting terminal 2a and a negative current collecting terminal 2b (not shown), and external connection terminals 22 of each current collecting terminal 2 are fixed to the lid body 32 via an insulating material 4. The insulating material 4 can use, for example, polyphenylene sulfide (PPS) resin. The external connection terminal 22 is electrically connected to an internal connection terminal 21 joined to the active material layer non-forming portion 12 of the electrode foil 1.

[0017] Note that the battery case 3 does not necessarily have to be limited to the above structure. For example, the battery case 3 may include a bottomed cylindrical case body 31 having an opening 311 at one end in the longitudinal direction (X direction), and a flat lid body 32 that seals the opening 311. Also, the case body 31 may be formed in a cylindrical shape. The case body 31 and the lid body 32 are both made of aluminum, but do not necessarily have to be limited to this, and for example, they may be made of stainless steel or the like.

[0018] Furthermore, the electrode foil 1 comprises a positive electrode foil 1a and a negative electrode foil 1b, both extending 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 extending from one widthwise end of the active material layer forming portion 11a, where the active material layer KTa is not coated. 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) extending from the other widthwise end of the active material layer forming portion 11b, where the active material layer KTb is not coated. The electrode foil 1 is rolled up and laminated in a flattened shape with a separator SP in between: a negative electrode active material layer forming portion 11b coated with a negative electrode active material layer KTb, and a positive electrode active material layer forming portion 11a coated with a positive electrode active material layer KTa.

[0019] Here, the separator SP is also interposed between the negative electrode active material layer forming portion 11b, to which the outermost negative electrode active material layer KTb is coated, and the case body 31. Furthermore, 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. In addition, the electrode foil 1 may 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 between them.

[0020] Although this battery cell 10S can be applied to various types of battery cells, here we will explain it using the example of a lithium-ion secondary battery. In this case, the positive electrode foil 1a is, 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.

[0021] 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.

[0022] Therefore, as shown in Figures 2 and 3, the electrode foil 1 of this battery cell 10S has a thermal resistance reduction section RT in which multiple electrode foils 1 are in contact and fixed to each other in the active material layer non-formed section 12, and the thermal resistance R1 at the contact and fixed section 121 between the active material layer non-formed sections 12 is reduced compared to the thermal resistance R2 at the separated section 122 where the active material layer non-formed sections 12 are not fixed to each other. The contact and fixed section 121 is pressurized by, for example, the tip surface and inclined surface of the projection of the horn of the ultrasonic bonding device described later, and it is sufficient that the surfaces of the electrode foils 1 are in contact with each other at least partially (preferably with a contact area ratio of 30% or more) and fixed to each other. The thermal resistance R1 at the location where the active material layer non-formed sections 12 of the electrode foil 1 are in contact and fixed to each other can be significantly reduced compared to the thermal resistance R2 of the separated section 122 where an air layer is interposed between the active material layer non-formed sections 12 of the electrode foil 1, because there is no air layer interposed as an insulating material. Furthermore, since the contact fixing portion 121 is fixed to the non-active material layer portion 12 of the electrode foil 1, it is possible to suppress the individual electrode foils 1 from becoming unstable and separating due to the heat of the laser welding portion LY. As a result, the molten heat YQ1 of one electrode foil 1 is dispersed and dissipated to the other electrode foils 1 via the thermal resistance reduction portion RT, thereby suppressing excessive heat accumulation in each individual electrode foil 1.

[0023] Furthermore, as shown in Figures 1, 2, and 4, the electrode foil 1 and the current collector terminal 2 are joined via the laser welding section LY, with the thermal resistance reduction section RT of the electrode foil 1 in contact with the current collector terminal 2, and the nugget boundary section NK of the laser welding section LY connected to the thermal resistance reduction section RT. In this case, the molten heat YQ2 that melts the electrode foil 1 by laser welding is dispersed and dissipated from the nugget boundary section NK through the thermal resistance reduction section RT, which has high thermal conductivity, to each electrode foil 1, suppressing excessive heat accumulation in each electrode foil 1, while rapidly dissipating heat to the current collector terminal 2 side, which has a larger heat capacity than the electrode foil 1. Therefore, the hole formation and necking phenomena on the outer circumference side of the laser welding section LY of the electrode foil 1 can be reduced. Note that the nugget boundary section NK of the laser welding section LY only needs to be connected to the thermal resistance reduction section RT in a heat transfer manner, so the laser welding section LY and the thermal resistance reduction section RT do not necessarily need to overlap. Furthermore, the entire circumference of the nugget boundary NK of the laser-welded section LY does not need to be connected to the thermal resistance reduction section RT. However, at the completion of laser welding, all or part of the thermal resistance reduction section RT connected to the nugget boundary NK of the laser-welded section LY must remain unmelted.

[0024] Here, in the non-active material layer portion 12, a rectangular tab portion 12T is formed, protruding in the longitudinal direction (X direction) away from the active material layer KT. Multiple (2) truncated square pyramidal thermal resistance reduction portions RT are continuously formed on the tab portion 12T, for example, by the projection of the horn of the ultrasonic bonding device described later. The nugget boundary portion NK of the laser-welded portion LY is connected to the multiple (2) thermal resistance reduction portions RT. The laser-welded portion LY is formed in a substantially circular shape in plan view. Therefore, at least half of the thermal resistance reduction portion RT connected to the nugget boundary portion NK of the laser-welded portion LY remains unmelted.

[0025] Furthermore, as shown in Figure 4, the thermal resistance reduction section RT is formed intermittently or continuously around the nugget boundary section NK, and the sum of the circumferential lengths L1 of the connecting section RS between the nugget boundary section NK and the thermal resistance reduction section RT, L(2×L1), is preferably less than or equal to the outer circumference length GL(L+2×L2) of the nugget boundary section NK, and is formed to be at least half the length of the outer circumference length GL. In this case, the excessive heat accumulation region at the nugget boundary section NK becomes the region other than the connecting section RS, which does not dissipate heat through the thermal resistance reduction section RT, and can be reduced to less than half of the total on the outer circumference of the nugget boundary section NK. Therefore, the decrease in joint strength due to perforation and necking phenomena associated with excessive heat accumulation in the electrode foil 1 around the laser welding section LY can be significantly suppressed, and the required joint strength can be easily secured.

[0026] <Manufacturing method for this battery cell> Next, a method for manufacturing a battery cell according to the embodiment of the disclosed technology described above will be explained in detail with reference to the drawings (Figures 1 to 6). Figure 5A shows a partial schematic cross-sectional view of an ultrasonic bonding apparatus used in the first step of manufacturing the electrode body of the battery cell shown in Figure 1, in which the thermal resistance reduction portion of the electrode foil is formed by ultrasonic bonding. Figure 5B shows a partial schematic cross-sectional view of a crimp bonding apparatus used in the first step of manufacturing the electrode body of the battery cell shown in Figure 1, in which the thermal resistance reduction portion of the electrode foil is formed by crimp bonding. Figure 6 shows a partial schematic cross-sectional view of a welding apparatus used in the second step of manufacturing the electrode body of the battery cell shown in Figure 1, in which the electrode foil and the current collector terminal are joined by laser welding.

[0027] The present battery cell 10S manufacturing method is a method for manufacturing a battery cell 10S that 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, as shown in Figures 1 to 6, comprising: a first step S1 in which the plurality of electrode foils 1 are brought into contact and fixed to each other at the active material layer non-forming portion 12 to form a thermal resistance reduction portion RT of the electrode foil 1 in which the thermal resistance R1 at the contact fixing portion 121 between the active material layer non-forming portions 122 is reduced to the thermal resistance R2 at the separation portion 122 where the active material layer non-forming portions 122 are not fixed to each other; and a second step S2 in which the electrode foil 1 and the current collector terminal 2 are joined by laser welding such that the nugget boundary portion NK of the laser welding portion LY is connected to the thermal resistance reduction portion RT while the thermal resistance reduction portion RT of the electrode foil 1 and the current collector terminal 2 are in contact with each other.

[0028] The manufacturing method for this battery cell 10S includes, as a pre-step to the first step S1, a coating step for coating the active material layer KT onto the electrode foil 1, a drying step, a pressing step, etc. Furthermore, as a post-step to the second step, there is a battery assembly step for housing the electrode body 10 in the battery case 3 and sealing it, and an adjustment step for initial charging and aging, etc. Since each of the above steps is a known process, a detailed explanation is omitted here.

[0029] Here, the method includes a first step S1 in which multiple electrode foils 1 are brought into contact and fixed to each other in the active material layer non-formed portions 12, thereby forming a thermal resistance reduction portion RT of the electrode foil 1 in which the thermal resistance R1 at the contact and fixed portions 121 between the active material layer non-formed portions 122 is reduced to the thermal resistance R2 at the separated portions 122 where the active material layer non-formed portions 12 are not fixed to each other. Therefore, when forming the thermal resistance reduction portion RT of the electrode foil 1, it is sufficient that the contact surfaces of the active material layer non-formed portions 12 are fixed to each other. For example, compared to ultrasonic bonding of multiple electrode foils 1 and the current collector terminal 2 simultaneously, the load (pressure, vibration energy, etc.) acting on the thin electrode foil 1 can be significantly reduced. More specifically, it is not necessary to set the vibration frequency of the horn 51 of the ultrasonic bonding apparatus 5 or the pressure applied by the horn 51 to the anvil 52 to such a high level that the electrode foil 1 is completely melted by frictional heat. Therefore, when forming the thermal resistance reduction portion RT of the electrode foil 1, the load acting on the thin electrode foil 1 can be reduced at the contact and fixing portion 121 between the non-active material layer portions 12.

[0030] Therefore, fractures and foreign matter are less likely to occur at the contact and fixing portions 121 between the non-active material layer portions 12, and a thermal resistance reduction portion RT with high thermal conductivity can be formed on the electrode foil 1 in good condition. As a result, in the second step S2 in which the electrode foil 1 and the current collector terminal 2 are joined by laser welding, the molten heat YQ1 of one electrode foil 1 is dispersed and dissipated to the other electrode foil 1 via the thermal resistance reduction portion RT with high thermal conductivity, thereby suppressing excessive heat accumulation in each electrode foil 1. In addition, the occurrence of short circuits due to foreign matter inside the electrode body 10 can be suppressed.

[0031] Furthermore, the method includes a second step S2 in which the electrode foil 1 and the current collector terminal 2 are joined by laser welding such that the nugget boundary portion NK of the laser-welded portion LY connects to the thermal resistance reduction portion RT while the thermal resistance reduction portion RT of the electrode foil 1 is in contact with the current collector terminal 2. This allows the heat of fusion YQ2 that melts the electrode foil 1 by laser welding to be dissipated more quickly from the nugget boundary portion NK through the thermal resistance reduction portion RT to the current collector terminal 2, which has a larger heat capacity. Therefore, a method for manufacturing a battery cell 10S including an electrode body 10 in which the perforation phenomenon and necking phenomenon on the outer circumference side of the laser-welded portion LY of the electrode foil 1 are reduced can be provided.

[0032] Furthermore, in the manufacturing method of this battery cell 10S, it is preferable that the thermal resistance reduction portion RT formed in the contact fixing portion 121 between the non-active material layer portions 12 is formed having at least one of the following: an anchor bonding region Z1 in which the metal surfaces KH of the electrode foil 1 are anchor-bonded, and a solid-phase bonding region Z2 in which the boundary layers KS of the electrode foil 1 are solid-phase bonded, as shown in Figure 3. In this case, the non-active material layer portions 12 of the electrode foil 1 can be more firmly bonded together, and the thermal resistance R1 can be reduced. Therefore, it is possible to suppress the separation of the non-active material layer portions 12 in the thermal resistance reduction portion RT while improving heat dissipation. As a result, the reduction in bonding strength due to perforation and necking phenomena of the electrode foil 1 around the laser-welded portion LY can be further suppressed, and the required bonding strength can be easily secured.

[0033] In the first step S1 for forming the thermal resistance reduction portion RT of the electrode foil 1, the metal surface KH of the non-active material layer portion 12 may be finely roughened by, for example, irradiating it with glass beads, without damaging it, and then brought into contact and fixed to each other to form contact and fixed portions 121 between the non-active material layer portions 12. In this case, the anchor bonding region Z1 in which the metal surfaces KH of the electrode foil 1 are anchored together can be formed more effectively. Alternatively, the metal surface KH of the non-active material layer portion 12 may be treated to remove the oxide film by etching or the like, and then brought into contact and fixed to each other to form contact and fixed portions 121 between the non-active material layer portions 12. In this case, the solid-phase bonding region Z2 in which the boundary layers KS of the electrode foil 1 are solid-phase bonded together can be formed more effectively.

[0034] Furthermore, in the manufacturing method of this battery cell 10S, the thermal resistance reduction portion RT formed in the contact fixing portion 121 is preferably formed by ultrasonic bonding of the non-active material layer portions 12 of the electrode foil 1, as shown in Figure 5A. In this case, as shown in Figure 3, the oxide film and the like are removed by ultrasonic vibration in the boundary layer KS of the contact fixing portion 121, making it easier to form a solid-phase bonding region Z2. As a result, the thermal resistance R1 of the thermal resistance reduction portion RT can be further reduced, and delamination of the electrode foils 1 is less likely to occur during laser welding. Consequently, the reduction in bonding strength due to perforation and necking of the electrode foil 1 around the laser-welded portion LY can be more effectively suppressed.

[0035] Furthermore, compared to the case where multiple electrode foils 1 and current collector terminals 2 are ultrasonically bonded simultaneously, the pressure and vibration energy of the projections 511 of the horn 51 in the ultrasonic bonding apparatus 5 can be set to a smaller value. As a result, damage to the electrode foils 1 and the generation of foreign matter due to vibration can be reduced, and wear of the horns 51 and anvils 52 in the ultrasonic bonding apparatus 5 can be reduced, thereby suppressing cost increases. Consequently, the reduction in bonding strength due to perforation and necking of the electrode foils 1 around the laser-welded area LY can be suppressed at low cost. The projections 511 of the horn 51 are formed in the shape of a pair of adjacent truncated square pyramids and are ultrasonically vibrated in a direction (X direction) perpendicular to the stacking direction (Y direction) of the electrode foils 1, so a thermal resistance reduction section RT is also formed at the location pressed by the inclined surface of the projections 511 of the horn 51.

[0036] Furthermore, in the manufacturing method of this battery cell 10S, the thermal resistance reduction portion RT formed on the contact fixing portion 121 is preferably formed by pressure bonding the non-active material layer portions 12 of the electrode foil 1, as shown in Figure 5B. In this case, as shown in Figure 3, the uneven portions on the metal surface KH of the contact fixing portion 121 are mechanically connected, making it easy to form an anchor bonding region Z1. As a result, the thermal resistance R1 of the thermal resistance reduction portion RT can be further reduced, and delamination of the electrode foils 1 is less likely to occur during laser welding. Consequently, the reduction in bonding strength due to perforation and necking of the electrode foil 1 around the laser-welded portion LY can be more effectively suppressed.

[0037] Furthermore, compared to the case where multiple electrode foils 1 and current collector terminals 2 are simultaneously crimped together, the pressing force of the crimping device 5B can be set to a smaller value. As a result, damage to the electrode foils 1 and the generation of foreign matter associated with crimping can be reduced, and wear on the punch 51B and die 52B in the crimping device 5B can be reduced, thereby suppressing cost increases. Consequently, the reduction in bonding strength due to perforation and necking of the electrode foils 1 around the laser-welded area LY can be suppressed at low cost. The punch 51B of the crimping device 5B is formed in the shape of a truncated square pyramid and applies pressure in the stacking direction (Y direction) of the electrode foils 1, so a thermal resistance reduction section RT is also formed in the area pressed by the inclined surface of the punch 51B. The method for forming the thermal resistance reduction section RT on the contact fixing portion 121 is not limited to the ultrasonic bonding or crimp bonding described above; various methods can be used.

[0038] Furthermore, in the manufacturing method of this battery cell 10S, in the second step S2, as shown in Figure 6, it is preferable to laser weld the electrode foil 1 and the current collector terminal 2 while the electrode foil 1 is pressed against the current collector terminal 2 by a cooling jig 61 that is in contact with the thermal resistance reduction section RT. In this case, the heat of fusion YQ1 and YQ2 that melts the electrode foil 1 by laser welding can be dispersed and dissipated not only from the thermal resistance reduction section RT to the current collector terminal 2 side, but also to the cooling jig 61 side. Therefore, the reduction in joint strength due to perforation and necking of the electrode foil 1 around the laser-welded section LY can be further suppressed.

[0039] The welding apparatus 6 used in the second step S2 includes a cooling jig 61 that contacts the thermal resistance reduction section RT, a laser beam irradiation section 62 that irradiates laser light, and a current collector terminal receiving jig 63 that receives the internal connection terminal 21 of the current collector terminal 2. The laser light from the laser beam irradiation section 62 is irradiated from above the electrode foil 1. The cooling jig 61 has a refrigerant flow path 611 for circulating refrigerant and a through hole 613 for transmitting laser light. The cooling jig 61 also presses the electrode foil 1 against the current collector terminal 2 via a spring member 612 or the like. It is preferable that the laser beam through hole 613 be formed along the nugget boundary NK of the laser welding section LY or its vicinity. This is because the heat of molten laser welding section LY can be more reliably dissipated from the nugget boundary NK through the thermal resistance reduction section RT to both the current collector terminal 2 and the cooling jig 61. The current collector terminal receiving jig 63 may also have a refrigerant flow path for circulating refrigerant.

[0040] <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.

[0041] (Variations in the manufacturing method of battery cells) In the battery cell manufacturing method described above, in the first step S1, multiple electrode foils 1 are brought into contact and fixed to each other in the active material layer non-formed portions 12, thereby forming a thermal resistance reduction portion RT of the electrode foil 1 in which the thermal resistance R1 at the contact and fixed portions 121 between the active material layer non-formed portions 122 is reduced to the thermal resistance R2 at the separated portions 122 where the active material layer non-formed portions 12 are not fixed to each other. In the second step S2, with the thermal resistance reduction portion RT of the electrode foil 1 and the current collector terminal 2 in contact, the electrode foil 1 and the current collector terminal 2 are joined by laser welding such that the nugget boundary portion NK of the laser welding portion LY is connected to the thermal resistance reduction portion RT. However, the method is not necessarily limited to the above method.

[0042] As a variation of the manufacturing method of this battery cell, for example, in the first step S1, the non-active material layer portions 12 of a plurality of electrode foils 1 may be divided into predetermined numbers and brought into contact and fixed to each other, thereby forming thermal resistance reduction portions RT at the contact and fixed portions 121 between each divided non-active material layer portion 12. Then, in the second step S2, the thermal resistance reduction portions RT formed in the first step S1 may be brought into contact with the current collection terminal 2 in a stacked state, and the electrode foil 1 and the current collection terminal 2 may be joined by laser welding so that the nugget boundary portion NK of the laser welding portion LY is connected to each thermal resistance reduction portion RT. In this case, when the non-active material layer portions 12 of the electrode foil 1 are brought into contact and fixed together, the load acting on the electrode foil 1 can be reduced by dividing it into predetermined groups. As a result, damage to the electrode foil 1 and the generation of foreign matter can be reduced, and a better battery cell 10S can be formed.

[0043] (Modified electrode body formed by the battery cell manufacturing method) Next, modified examples 1 to 7 of the electrode body formed by the manufacturing method of the battery cell according to the embodiment of the disclosed technology will be described in detail with reference to the drawings. Figure 7 shows a view of arrow B in modified example 1 of the electrode body shown in Figure 1. Figure 8 shows a view of arrow B in modified example 2 of the electrode body shown in Figure 1. Figure 9 shows a view of arrow B in modified example 3 of the electrode body shown in Figure 1. Figure 10 shows a view of arrow B in modified example 4 of the electrode body shown in Figure 1. Figure 11 shows a view of arrow B in modified example 5 of the electrode body shown in Figure 1. Figure 12 shows a view of arrow B in modified example 6 of the electrode body shown in Figure 1. Figure 13 shows a view of arrow B in modified example 7 of the electrode body shown in Figure 1.

[0044] (Variations of electrode bodies 1 and 2) In the electrode bodies 10B and 10C of modified examples 1 and 2 formed by the manufacturing method of the battery cell 10S, the thermal resistance reduction section RT is formed intermittently or continuously along a direction that separates it from the active material layer formation section 11, as shown in Figures 7 and 8. Therefore, the active material layer KT of the electrode foil 1 is less affected by the heat dissipated from the nugget boundary section NK through the thermal resistance reduction section RT, and the deterioration of the active material layer KT can be reduced. As a result, it is easier to ensure an even higher quality electrode body 10. The laser welding section LY may be formed continuously or intermittently. Furthermore, the welding width of the laser welding section LY, which is formed continuously, may be made narrower the closer it is to the active material layer formation section 11. In this case, the closer it is to the active material layer formation section 11, the less heat is generated at the melting point of the laser welding section LY, and the deterioration of the active material layer KT can be further reduced.

[0045] In the electrode body 10B of the modified example 1, as shown in Figure 7, a rectangular tab portion 12T is formed in the non-active material layer portion 12, protruding in the longitudinal direction (X direction) away from the active material layer KT. On the tab portion 12T, for example, in the contact fixing portion 121B recessed by the projection 511 of the horn 51 of the ultrasonic bonding device 5 described above, multiple (2) truncated square pyramidal thermal resistance reduction portions RT are formed intermittently or continuously in multiple rows (2 parallel rows) along the longitudinal direction (X direction) away from the active material layer forming portion 11. The nugget boundary portion NK of the laser welding portion LY is connected so as to connect the multiple (2) thermal resistance reduction portions RT in each row on the inner circumference side of the thermal resistance reduction portions RT. The laser welding portion LY is formed in an oval shape in plan view along the longitudinal direction (X direction). In this case, the heat dissipation to the current collection terminal 2 can be further improved, and the deterioration of the active material layer KT can be further reduced.

[0046] Furthermore, as shown in Figure 7, the thermal resistance reduction section RT is formed intermittently or continuously around the nugget boundary section NK of each row, and the sum L of the circumferential length L1 (4 × L11 + 2 × L12) of the connecting section RS between the nugget boundary section NK and the thermal resistance reduction section RT is less than or equal to the outer circumference length GL (L + 2 × L2) of the nugget boundary section NK, and is formed to be at least half the length of the outer circumference length GL. In this case, the excessive heat accumulation region at the nugget boundary section NK can be limited to the region other than the connecting section RS between the nugget boundary section NK and the thermal resistance reduction section RT, and can be reduced to less than half on the outer circumference of the nugget boundary section NK. Therefore, the reduction in bonding strength due to perforation and necking phenomena of the electrode foil 1 around the laser-welded section LY can be significantly suppressed, and the required bonding strength can be easily secured.

[0047] Furthermore, in the electrode body 10C of the modified example 2, as shown in Figure 8, a rectangular tab portion 12T is formed in the non-active material layer portion 12, protruding in the longitudinal direction (X direction) away from the active material layer KT. On the tab portion 12T, for example, in the contact fixing portion 121C which is recessed by the projection 511 of the horn 51 of the ultrasonic bonding device 5 described above, a plurality (4) of truncated rectangular pyramidal thermal resistance reduction portions RT are formed in a parallel and continuous manner (elongated) along the longitudinal direction (X direction) away from the active material layer forming portion 11. The nugget boundary portion NK of the laser welding portion LY is connected so as to connect two adjacent rows of thermal resistance reduction portions RT on the outer circumference side of the thermal resistance reduction portions RT. In this case, the welding width of the laser welding portion LY can be increased to improve the welding strength while reducing the deterioration of the active material layer KT. Furthermore, the laser-welded section LY is formed in an oval shape along the longitudinal direction (X direction) and has approximately the same length as the thermal resistance reduction section RT when viewed from above.

[0048] (Variations of electrode bodies 3, 4, 5) In the electrode bodies 10D, 10E, and 10F of modified examples 3, 4, and 5 formed by the manufacturing method of the battery cell 10S, the thermal resistance reduction portion RT is formed intermittently around the nugget boundary portion NK, as shown in Figures 9, 10, and 11. The sum of the circumferential lengths of the connecting portion RS between the nugget boundary portion NK and the thermal resistance reduction portion RT is less than or equal to the outer circumference length of the nugget boundary portion NK, and is formed to be at least half the length of the outer circumference. In this case, the excessive heat storage area at the nugget boundary portion NK can be reduced to less than half on the outer circumference of the nugget boundary portion NK. Therefore, the reduction in bonding strength due to perforation and necking phenomena of the electrode foil 1 around the laser-welded portion LY can be significantly suppressed, making it easier to secure the required bonding strength.

[0049] In the electrode body 10D of the modified example 3, as shown in Figure 9, a rectangular tab portion 12T is formed in the non-active material layer portion 12, protruding in the longitudinal direction (X direction) away from the active material layer KT. On the tab portion 12T, for example, in the contact fixing portion 121D recessed by the projection 511 of the horn 51 of the ultrasonic bonding device 5 described above, a plurality (4) truncated square pyramidal thermal resistance reduction portions RT are formed intermittently at 90-degree intervals around the nugget boundary portion NK. The sum of the circumferential lengths of the connecting portions RS between the nugget boundary portion NK and the thermal resistance reduction portions RT is less than or equal to the outer circumference length of the nugget boundary portion NK, and is formed to be at least half the outer circumference length. The nugget boundary portion NK of the laser welding portion LY is connected to the plurality (4) thermal resistance reduction portions RT. The laser welding portion LY is formed in an annular shape in plan view. In this case, the heat of fusion of the laser-welded area LY can be reduced, further reducing necking phenomena. Multiple (4) frustum-shaped thermal resistance reduction sections RT can be formed by rotating a horn 51 having two protrusions 511 by 90 degrees horizontally. Alternatively, the multiple (4) frustum-shaped thermal resistance reduction sections RT may be arranged so that the corners of the frustums are concentrated in the center of the annular laser-welded area LY.

[0050] Furthermore, in the electrode body 10E of the modified example 4, as shown in Figure 10, a tab portion 12T is formed in a rectangular shape on the non-active material layer portion 12, protruding in the longitudinal direction (X direction) away from the active material layer KT. On the tab portion 12T, for example, in the contact fixing portion 121E which is recessed by the projection 511 of the horn 51 of the ultrasonic bonding device 5 described above, a plurality (4) of square truncated pyramidal thermal resistance reduction portions RT are formed intermittently at different intervals around the nugget boundary portion NK, and the sum of the circumferential lengths of the connecting portion RS between the nugget boundary portion NK and the thermal resistance reduction portions RT is less than or equal to the outer circumference length of the nugget boundary portion NK, and is formed to be at least half the length of the outer circumference. The nugget boundary portion NK of the laser welded portion LY is connected so as to connect the plurality (4) of thermal resistance reduction portions RT. In addition, the laser welded portion LY is formed in an oval shape in plan view. In this case, the welding strength of the laser welded portion LY can be further improved.

[0051] Furthermore, in the electrode body 10F of the modified example 5, as shown in Figure 11, a tab portion 12T is formed in a rectangular shape on the non-active material layer portion 12, protruding in the longitudinal direction (X direction) away from the active material layer KT. On the tab portion 12T, for example, in the contact fixing portion 121F recessed by the punch 51B of the crimping device 5B described above, a plurality (10) of circular thermal resistance reduction portions RT are formed intermittently at approximately equal intervals around the nugget boundary portion NK, and the sum of the circumferential lengths of the connecting portions RS between the nugget boundary portion NK and the thermal resistance reduction portions RT is less than or equal to the outer circumference length of the nugget boundary portion NK, and is formed to be at least half the length of the outer circumference. The nugget boundary portion NK of the laser-welded portion LY is connected to the plurality (10) of thermal resistance reduction portions RT. The laser-welded portion LY is formed in a rectangular ring shape in plan view. In this case, the welding area of ​​the laser-welded section LY can be reduced while increasing the welding length, thus achieving both a reduction in necking phenomena and an improvement in welding strength.

[0052] (Variations of electrode bodies 6, 7) In the electrode bodies 10G and 10H of modified examples 6 and 7 formed by the manufacturing method of the battery cell 10S, the thermal resistance reduction portion RT is formed continuously around the nugget boundary portion NK, as shown in Figures 12 and 13, and the sum of the circumferential lengths of the connecting portion RS between the nugget boundary portion NK and the thermal resistance reduction portion RT is formed to be approximately the same length as the outer circumference of the nugget boundary portion NK. In this case, the excessive heat storage region at the nugget boundary portion NK can be almost eliminated. Therefore, the reduction in bonding strength due to perforation and necking phenomena of the electrode foil 1 around the laser-welded portion LY can be significantly suppressed, and the required bonding strength can be easily secured.

[0053] In the electrode body 10G of the modified example 6, as shown in Figure 12, a rectangular tab portion 12T is formed in the non-active material layer portion 12, protruding in the longitudinal direction (X direction) away from the active material layer KT. In the tab portion 12T, for example, in the contact fixing portion 121G formed in a recess by the projection 511 of the horn 51 of the ultrasonic bonding device 5 or the punch 51B of the crimping device 5B, a truncated annular thermal resistance reduction portion RT is continuously formed around the nugget boundary portion NK, and the sum of the circumferential lengths of the connecting portion RS between the nugget boundary portion NK and the thermal resistance reduction portion RT is formed to be approximately the same length as the outer circumference of the nugget boundary portion NK. The nugget boundary portion NK of the laser welding portion LY is connected to the thermal resistance reduction portion RT within the region of the truncated annular thermal resistance reduction portion RT. The laser welding portion LY is also formed in an annular shape in plan view. In this case, the heat of fusion of the laser-welded area (LY) can be reduced, further minimizing the necking phenomenon while also enabling a more compact laser-welded area (LY).

[0054] Furthermore, in the electrode body 10H of the modified example 7, as shown in Figure 13, a rectangular tab portion 12T is formed in the non-active material layer portion 12, protruding in the longitudinal direction (X direction) away from the active material layer KT. On the tab portion 12T, for example, in the contact fixing portion 121H recessed by the projection 511 of the horn 51 of the ultrasonic bonding device 5 or the punch 51B of the crimping device 5B, a truncated annular thermal resistance reduction portion RT is continuously formed around the nugget boundary portion NK, and the sum of the circumferential lengths of the connecting portion RS between the nugget boundary portion NK and the thermal resistance reduction portion RT is formed to be approximately the same length as the outer circumference of the nugget boundary portion NK. The nugget boundary portion NK of the laser welding portion LY is connected to the thermal resistance reduction portion RT within the region of the truncated annular thermal resistance reduction portion RT. The laser welding portion LY is formed in a circular shape in plan view. In this case, it becomes possible to increase the welding strength of the laser-welded section LY while also making the laser-welded section LY more compact.

[0055] In the electrode body 10 of the battery cell 10S and its modified examples 10B to 10H described in detail above, the various configurations in which the nugget boundary portion NK of the laser-welded portion LY is connected to the thermal resistance reduction portion RT are not limited to the configurations shown in Figures 4, 7 to 13, but may also be formed by creating multiple such configurations adjacent to each other. [Explanation of Symbols]

[0056] 1 Electrode foil 2 Current collector terminal 10 Electrode body 11 Active material layer forming part 12 Active material layer non-forming area 61 Cooling fixture 121 Contact fixed part 122 Separation section KH metal surface KS boundary layer LY laser welded section NK nugget boundary R1, R2 thermal resistance RS connection part RT Thermal Resistance Reduction Section S1 1st process S2 2nd process

Claims

1. A method for manufacturing 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, A first step is to form a thermal resistance reduction portion of the electrode foil by contacting and fixing a plurality of electrode foils to each other in the portion where the active material layer is not formed, thereby reducing the thermal resistance in the contact and fixing portion between the portions where the active material layer is not formed to the thermal resistance in the separated portion where the portions where the active material layer is not formed to each other. The invention comprises a second step of laser welding the electrode foil and the current collector terminal together, with the thermal resistance reduction portion of the electrode foil and the current collector terminal in contact, such that the nugget boundary portion of the laser-welded portion connects with the thermal resistance reduction portion. A method for manufacturing battery cells.

2. In the method for manufacturing a battery cell described in claim 1, In the first step, the portions of the electrode foils where the active material layer is not formed are divided into predetermined numbers and brought into contact and fixed to each other, and the thermal resistance reduction portions are formed at the contact and fixed portions between each divided portion where the active material layer is not formed. In the second step, the thermal resistance reduction portions formed in the first step are stacked and brought into contact with the current collection terminal, and the electrode foil and the current collection terminal are joined by laser welding such that the nugget boundary portion of the laser-welded portion is connected to the thermal resistance reduction portion. A method for manufacturing battery cells.

3. In the method for manufacturing a battery cell described in claim 1, The thermal resistance reduction portion is formed intermittently or continuously around the nugget boundary portion, The sum of the circumferential lengths of the connecting portion between the nugget boundary and the thermal resistance reduction portion is less than or equal to the outer circumference length of the nugget boundary, and is formed to be at least half the length of the outer circumference. A method for manufacturing battery cells.

4. In the method for manufacturing a battery cell described in claim 1, The thermal resistance reduction portion is formed intermittently or continuously along a direction that separates it from the active material layer forming portion. A method for manufacturing battery cells.

5. In the method for manufacturing a battery cell described in claim 1, In the second step, the electrode foil is pressed against the current collector terminal by a cooling jig that contacts the thermal resistance reduction portion, and the electrode foil and the current collector terminal are laser-welded together. A method for manufacturing battery cells.

6. In a method for manufacturing a battery cell according to any one of claims 1 to 5, The thermal resistance reduction portion is formed by ultrasonic bonding of the portions where the active material layer is not formed. A method for manufacturing battery cells.

7. In a method for manufacturing a battery cell according to any one of claims 1 to 5, The thermal resistance reduction portion is formed by pressure bonding the portions where the active material layer is not formed together. A method for manufacturing battery cells.

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