Manufacturing process of an electrical storage device and electrical storage device

Abstract

Method for manufacturing an electrical storage device, comprising the following steps: Arranging a metal foil extending outwards from an electrode plate between a first metal element and a second metal element; and Causing an ultrasonic vibration to act on a plurality of points of action from the side of the first metal element in order to bond the metal foil to the first metal element and the second metal element, whereby the first metal element has a Vickers hardness of at least 40 Hv and not more than 75 Hv.

Description

CROSS-REFERENCE TO RELATED REGISTRATION

[0001] This application claims priority over Japanese patent application number 2012-187154, the disclosure of which is incorporated herein by reference in its entirety. AREA

[0002] The present invention relates to a method for manufacturing an electrical storage device by arranging a metal foil extending outwards from an electrode plate, which is stacked in a layered manner to form an electrode arrangement, between a first metal element and a second metal element, and causing an ultrasonic vibration to act on a plurality of contact points from the side of the first metal element in order to bond the metal foil to the metal elements. The present invention also relates to an electrical storage device. BACKGROUND OF THE INVENTION

[0003] In general, an electrical storage element of an electrical storage device contains electrode plates stacked in a layered manner to improve electrical storage performance and efficiency. The wiring configuration of this electrical storage element consists of bundled metal foils extending outwards from the corresponding electrode plates, often connected directly or indirectly to wiring elements.

[0004] In this case, ultrasonic welding technology is widely used as the technique described above for joining metal foils.

[0005] The aforementioned metal foils are not simply ultrasonically welded by applying ultrasonic vibration to them. Specifically, the ultrasonic welding process is as follows. As described in the patent literature cited below, a metal element (first metal element) is positioned between a tool (the front end of a so-called "horn" or sonotrode), which is used to apply ultrasonic vibration to the metal foil, and the metal foil itself. A second metal element (second metal element) is also positioned on the opposite surface of the bundled sections of the metal foil. As described above, the bundled sections of the metal foil are positioned between the first and second metal elements, and under this condition, the metal foil is welded together.The condition is caused by an ultrasonic vibration acting on the first metal element to bond the metal foil to the metal elements, thereby protecting the metal foil.

[0006] In addition, ultrasonic welding is performed at multiple points to secure a connection area while avoiding an increase in the size of the front end section of the sonotrode.

[0007] However, in the conventional configuration described above, the metal element (first metal element) used to protect the metal foil may, in some cases, be damaged as a result of ultrasonic welding being carried out at multiple points.

[0008] This means that when an ultrasonic vibration is applied to the first metal element, the first metal element deforms in a wave-like manner near each position or point where the ultrasonic vibration acts upon it. Consequently, the aforementioned deformations, originating from adjacent positions or points on either side, overlap between the two points of application of the ultrasonic vibration.

[0009] This superposition of deformations can, in some cases, lead to such a degree of deformation that cracks or fissures are created, attributable to the stress on the first metal element. When such cracks or fissures occur, the relative positional ratio between the first metal element and the metal foil shifts from a preferred positional ratio, which can, for example, lead to a decrease in yield. Consequently, productivity can deteriorate in some cases. Counter-arguments list Patent literature

[0010] Patent Literature 1: JP 2004-071199 A

[0011] US 2012 / 0135285A1 describes a non-aqueous electrolyte battery wound or laminated with a separator in between. The electrodes are each equipped with electrode leads whose ends are attached to the electrodes and positioned so that they are not directly opposite each other to prevent short circuits and damage to the separator. The leads may be beveled or insulated.

[0012] US 2012 / 0070720A1 describes a non-aqueous electrolyte secondary battery comprising a housing, an electrode assembly consisting of positive and negative electrodes, several current-collecting tabs extending from one electrode and overlapping, and a conductor attached to it by ultrasonic bonding. The conductor has an enlarged cross-sectional area between the bonded area and the external terminal. A lid closes the housing, and external terminals are attached to the lid. SUMMARY Technical Problem

[0013] One object of the present invention, which is addressed in view of such circumstances, is to prevent damage to a metal element as far as possible, even when ultrasonic welding is carried out at a plurality of locations, while a metal foil to be welded to the metal element is protected. Solution to the problem

[0014] A method for manufacturing an electrical storage device according to the present invention comprises the following steps: arranging a metal foil extending outwards from an electrode plate stacked in a layered manner between a first metal element and a second metal element; and causing an ultrasonic vibration to act on a plurality of points of action from the side of the first metal element in order to bond the first metal foil to the first metal element and the second metal element, wherein the first metal element has a Vickers hardness of at least 40 Hv and not more than 75 Hv.

[0015] One aspect of the method for manufacturing an electrical storage device according to the present invention may include a configuration in which, in the joining step, a vibration tool is used which has a contact surface capable of contacting the first metal element and causes an ultrasonic vibration to act on the first metal element, and the contact surface is formed by one or a plurality of projections.

[0016] Another aspect of the method for manufacturing an electrical storage device according to the present invention can include a configuration in which end edges of the first metal element and the second metal element are connected to each other by a connecting section and in the step of arranging between or sandwiching the metal foil is arranged between the first metal element and the second metal element, such that an end edge of the metal foil is in contact with the connecting section.

[0017] An electrical storage device according to the present invention comprises the following: an electrical storage element comprising: an electrode plate stacked in a layered manner and having a metal foil extending on one end side; and an additional plate for ultrasonic welding, having a plurality of connecting sections joined to the metal foil by ultrasonic vibration and placed against the bundled metal foil, wherein the additional plate has a Vickers hardness of at least 40 Hv and not more than 75 Hv. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a perspective external view of an electrical storage device according to an embodiment of the present invention. Fig. Figure 2 is a perspective view showing the internal configuration of the electrical storage device according to the embodiment of the present invention. Fig. Figure 3 is a cross-sectional view of an essential part of the electrical storage device according to the embodiment of the present invention. Fig. Figure 4 is an enlarged view of an additional plate for ultrasonic welding according to the embodiment of the present invention in an unfolded state. Fig. Figure 5 is an enlarged perspective view of the additional plate for ultrasonic welding according to the embodiment of the present invention. Fig. Figure 6 is a cross-sectional view showing an ultrasonic welding operation according to the embodiment of the present invention. Fig. Figure 7 is a perspective view showing the work to assemble an electrical storage element according to the embodiment of the present invention before the additional plates are attached. Fig. Figure 8 is a perspective view showing the work to assemble the electrical storage element according to the embodiment of the present invention, after the electrical storage element has been fitted with the additional plates. Fig. Figure 9 is a perspective view showing the work to assemble the electrical storage element according to the embodiment of the present invention, after the electrical storage element has been equipped with a current collector. Fig. Figure 10 is a graph showing the initial characteristics of ultrasonic welding. Fig. Figure 11 is a graph showing the relationship between the hardness of additional plates for ultrasonic welding and crack frequency. Fig. Figure 12 is a cross-sectional view showing an ultrasonic welding operation according to another embodiment of the present invention. Fig. Figure 13 is a cross-sectional view showing an ultrasonic welding operation according to another embodiment of the present invention. DESCRIPTION OF THE EXECUTION FORMS

[0018] A method for manufacturing an electrical storage device according to the present invention comprises the following steps: arranging a metal foil extending outwards from an electrode plate stacked in a layered manner between a first metal element and a second metal element; and causing an ultrasonic vibration to act on a plurality of contact points from the side of the first metal element in order to bond the metal foil to the first metal element and the second metal element, wherein the first metal element has a Vickers hardness of at least 40 Hv and not more than 75 Hv.

[0019] In this way, it is possible to largely prevent damage to the first metal element by appropriately determining its Vickers hardness, even when ultrasonic welding is performed at multiple points on the first metal element, which protects the metal foil to be welded. A specific description follows below.

[0020] The bundled metal foil is placed between the second metal element and the first metal element to protect the metal foil to be welded, which has a Vickers hardness of at least 40 Hv and not more than 75 Hv, and an ultrasonic vibration is caused to act on the metal foil from the side of the first metal element to join the metal foil to the first and second metal elements.

[0021] If the Vickers hardness of the first metal element is less than 40 Hv, the first metal element is excessively soft, so that stress increases due to a relative displacement between each point of action subjected to ultrasonic vibration and the surrounding environment. Therefore, damage, such as cracks, may occur at the interface between the point of action subjected to ultrasonic vibration and the surrounding environment.

[0022] Therefore, a vibration at the point of action, on which an effect of ultrasonic vibration is caused, propagates adequately peripherally (to the surroundings) by setting the Vickers hardness of the first metal element to 40 Hv or more, and consequently it is possible to largely prevent the occurrence of damage at the boundary between the point of action, on which an effect of ultrasonic vibration is caused, and the surroundings of the point.

[0023] Even if deformations due to ultrasonic welding overlap around adjacent points of action of an ultrasonic vibration in the centers of the same from the application or contact points on both sides, so that the deformations become significant, it is on the other hand possible to prevent the occurrence of damage at the deformed points, since the Vickers hardness of the first metal element is set at 75 Hv or less and the first metal element is therefore adequately soft.

[0024] One aspect of the method for manufacturing an electrical storage device according to the present invention may include a configuration in which, in the joining step, a vibration tool is used which has a contact surface capable of contacting the first metal element and causes an ultrasonic vibration to act on the first metal element, and the contact surface is formed by one or a plurality of projections.

[0025] With such a configuration, and because the Vickers hardness of the first metal element is appropriately determined, damage to the first metal element when using a vibratory tool with a contact surface of a protruding shape can be largely prevented by avoiding the application of excess ultrasonic vibration energy to the first metal element. A specific description follows below.

[0026] When performing ultrasonic welding using a vibrating tool that has a contact surface (for example, the front end of a sonotrode) with the first metal element, which is in the form of one or more protrusions, it is difficult to transfer the protruding shape of the vibrating tool to the first metal element if the first metal element has high hardness. Therefore, in the initial stage of ultrasonic welding, the surface of the first metal element on the side facing the metal foil is almost flat. Furthermore, if the protruding shape is not fully transferred to the first metal element, it is difficult to transfer the protruding shape to the metal foil located further inside it. Therefore, the surface of the metal foil is also almost flat. Consequently, slippage occurs in the initial stage of ultrasonic welding.Slipping occurs on at least the contact surface between the first metal element and the metal foil, the contact surface of the metal foil with the same and / or the contact surface between the metal foil and the second metal element, resulting in a decrease in the degree of transmission of an ultrasonic vibration.

[0027] The ultrasonic welding process then continues, and the protruding shape of the vibrating tool is gradually transferred to the first metal element. This increases the degree of energy transfer from the ultrasonic vibration to the first metal element or metal foil, thereby increasing its contribution to the joining energy. In other words, the transfer of the protruding shape to the first metal element changes the degree of energy transfer from a low to a high level.

[0028] In this way, the energy from the ultrasonic vibration of the vibration tool does not effectively contribute to the joining process, and the time required for the first metal element and others to be reliably joined by ultrasonic welding is extended. This results in excess energy from the ultrasonic vibration being applied to the first metal element.

[0029] In contrast, if the first metal element has a sufficiently low hardness (is soft), the protruding shape of the vibrating tool is readily transferred to the first metal element. Therefore, from the initial stage of ultrasonic welding, the protruding shape of the vibrating tool is transferred to the first metal element. Consequently, energy from the ultrasonic vibration is effectively transferred to the first metal element and the metal foil, thus effectively contributing to the joining energy.

[0030] Consequently, the time required to reliably join the first metal element and others via ultrasonic welding can be reduced. As a result, the application of excess energy from ultrasonic vibration to the first metal element is prevented.

[0031] The aforementioned phenomenon occurs either in the case of a single projection or in the case of multiple projections provided on the vibratory tool.

[0032] The aforementioned relationship will be explained using a specific experimental example.

[0033] Fig. Figure 10 illustrates the relationship between welding time and control output when an additional plate, formed by bending a thin, plate-shaped metal element that arranges a bundled metal foil between it, is ultrasonically welded with a current collector. That is to say, Fig. Figure 10 illustrates the case in which the first metal element and the second metal element consist of a single thin, plate-shaped metal element and are subjected to an ultrasonic vibration from the side of the first metal element opposite the side of the current collector, with the metal foil positioned between them.

[0034] The "control output" on the vertical axis in Fig. 10 is the output (power) required to make the front end of the sonotrode vibrate, which causes the ultrasonic vibration to act on the first metal element, while maintaining a specific amplitude. The ratio is such that as the load applied to the front end of the sonotrode from the side of the first metal element increases, the aforementioned control output also increases.

[0035] Fig. Figure 10 shows the experimental results of the first metallic element formed from C1020-O (material code specified in JIS H 3100) (soft material), represented by curve L. Here, C1020 is copper with a purity of 99% or higher. Specifically, it is defined as follows: C1020 contains more than 99.96% Cu by mass.

[0036] Fig. Figure 10 also shows the experimental results of the first metallic element formed from C1020-1 / 4H (hard material) by curve M. Here, C1020-O has a Vickers hardness of 50 Hv and C1020-1 / 4H has a Vickers hardness of 85 Hv.

[0037] In the measurement results shown by curve M, which use the first metal element with a high Vickers hardness, the control output rises up to point "p" and does not rise as much thereafter to point "q". This means that slippage has occurred between the first metal element and the metal foil, and consequently, the load applied to the front end of the sonotrode has not increased.

[0038] The transfer of the protruding shape of the sonotrode's front end to the first metal element then proceeds, and the load applied to the sonotrode's front end increases up to point "r" and point "s" (i.e., the ultrasonic welding continues). Consequently, the welding is completed at point "t".

[0039] In contrast, the measurement results shown by curve L, which use the first metal element with a low Vickers hardness, show that the load applied to the front end of the sonotrode increases rapidly from point "a" to point "b". This indicates that the transfer of the protruding shape of the front end of the sonotrode to the first metal element and the ultrasonic welding process progress rapidly from the initial stage of ultrasonic welding.

[0040] As from the in Fig. As is evident from the comparison shown in Figure 10 between the characteristics of curve L and the characteristics of curve M, for the first metal element, which has a high Vickers hardness, the time required to complete the welding at point "t" increases due to the delay in the transfer of the protruding shape in the initial stage of ultrasonic welding or the subsequent reduction in the increasing degree of control power. This causes excess energy from the ultrasonic vibration to be applied to the first metal element with a high Vickers hardness. Consequently, in the first metal element with a high Vickers hardness, at the point (time) indicated by arrow N in Figure 10, the time required to complete the welding at point "t" increases. Fig. As shown in 10, cracks have appeared.

[0041] In contrast, with the first metal element, which has a low Vickers hardness, the time required to complete the weld at point "c" is short, and consequently, the applied energy of the ultrasonic vibration is used effectively for joining. Therefore, no damage, such as cracking, occurs.

[0042] Another aspect of the method for manufacturing an electrical storage device according to the present invention may include a configuration in which end edges of the first metal element and the second metal element are connected to each other by a connecting section and, in the step of sandwich-like arrangement, the metal foil is arranged between the first metal element and the second metal element to have an end edge that is in contact with the connecting section.

[0043] According to such a configuration, the metal elements located on both sides of the metal foil to be welded can be treated as a single unit, and the metal foil to be welded can be positioned relative to the first and second metal elements using the aforementioned connecting section. A specific description follows below.

[0044] Since the first and second metal elements are connected by the connecting section, the metal elements located on both sides of the metal foil to be welded can be treated as a single, continuous element. Furthermore, the metal foil to be welded, the first metal element, and the second metal element can be positioned at the desired location using the connecting section.

[0045] When the first and second metal elements, acting as a single unit, are attached to the metal foil to be welded, the unit and the metal foil can be positioned by arranging the front end of the metal foil to face the inside of the joint. Consequently, it is easy to position the metal foil, the first metal element, and the second metal element relative to each other and to determine the positions or locations for ultrasonic vibration to act upon them.

[0046] Furthermore, an electrical storage device according to the present invention comprises an electrical storage element comprising: an electrode plate having a metal foil extending on one end side and formed by stacking the same in a layered manner; and an additional plate for ultrasonic welding, having a plurality of connecting sections joined to the metal foil by ultrasonic vibration and placed against the bundled metal foil, wherein the additional plate has a Vickers hardness of at least 40 Hv and not more than 75 Hv.

[0047] With such a configuration, as described above, damage to an additional plate used for ultrasonic welding, which protects the metal foils of the electrode assembly, can be avoided when the metal foils are welded using ultrasonic welding. This allows for an improvement in the quality of the electrical storage device.

[0048] The following describes embodiments of an electrical storage device to which the present invention is applied, with reference to the accompanying drawings.

[0049] In this embodiment, a battery cell, in particular a secondary cell with anhydrous electrolyte (more precisely a lithium-ion battery cell), which is an example of secondary battery cells, is listed and described as an example of an electrical storage device. [Secondary battery cell configuration]

[0050] As in the perspective view of the Fig. As shown in Figure 1, a cell RB of a secondary battery with anhydrous electrolyte of the present first embodiment comprises a cell housing BC (hereinafter simply referred to as "housing BC"). The housing BC includes a cylindrical (more precisely, rectangular-cylindrical) container body 1 with a bottom and a cover 2, which is placed on the open surface of the container body 1. The housing BC is configured by placing the cover 2 on the open surface of the container body 1 and welding the cover 2 to it. The cover 2 is formed from a sheet-shaped rectangular sheet material. A terminal bolt 5, which is the electrode terminal of a positive electrode, and a terminal bolt 7, which is the electrode terminal of a negative electrode, are provided on the surface of the cover 2 on the outside of the housing BC.

[0051] The container body 1 is a flattened rectangular parallelepiped corresponding to the shape of the cover part 2. Accordingly, the housing BC as a whole has a flattened, essentially rectangular parallelepiped shape.

[0052] In Fig. 2 are an electrical storage element 3 and plate-shaped current collectors 4 and 6, which are shown schematically by colon-dash lines, housed on the inside of the casing BC. Fig. Figure 2 is a perspective view of the inside of the housing BC, taken by looking at the housing BC from the bottom of the same upwards, excluding the container body 1.

[0053] The current collectors 4 and 6 are elements used to electrically connect the electrical storage element 3 and the connecting bolts 5 and 7.

[0054] Note that in the present embodiment, the electrical storage element 3 will be referred to below as the “power generating element 3”, since the secondary battery cell RB is listed as an example of the electrical storage device.

[0055] Both current collector 4 and current collector 6 are electrical conductors and have essentially the same shape. These current collectors 4 and 6 are arranged symmetrically. The materials of current collector 4 and current collector 6 differ. Current collector 4, on the positive electrode side, is made of aluminum, while current collector 6, on the negative electrode side, is made of copper.

[0056] The current collectors 4 and 6 are formed into a predetermined shape by bending plate-shaped elements made of the aforementioned metal materials. The current collectors 4 and 6 each contain a horizontally positioned section and a vertically positioned section and have an essentially L-shaped curved form in which these horizontally and vertically positioned sections are aligned. The horizontally positioned section extends along the surface of the cover part 2, which is the surface on which the connecting bolts 5 and 7 are located. The vertically positioned section bends downwards at a 90° angle (towards the opposite side of the surface on which the connecting bolts 5 and 7 are located) near the end section of the cover part 2 in its longitudinal direction and extends in the normal direction of the surface of the cover part 2 on the inside of the housing BC.Connecting sections 4a and 6a, used for connecting to the power generating element 3, are formed by bending portions of the vertically positioned sections towards the side of the power generating element 3. Connecting sections 4a and 6a are formed as described below. A pair of upper and lower through-holes 4c and 4d and a pair of upper and lower through-holes 6c and 6d are formed in the vertically positioned sections of the power collectors 4 and 6 in a state where they are flat plates. Incisions are also formed between the through-holes 4c and 4d and between the through-holes 6c and 6d. These incisions are then extruded by pressing or similar means to form connecting sections 4a and 6a.

[0057] The current collectors 4 and 6 have a narrow, rectangular shape in accordance with the flattened shape of the housing BC. The current collectors 4 and 6 are curved as a whole and are arranged along the short side of the housing BC.

[0058] Power generating element 3 is a winding-type power generating element. Power generating element 3 consists primarily of an electrode assembly. The electrode assembly includes a foil-shaped electrode plate serving as a positive electrode, a foil-shaped electrode plate serving as a negative electrode, and a separator in the form of a long belt. The foil-shaped electrode plate serving as a positive electrode is formed by coating an underlying metal foil in the form of a long belt, made of aluminum, with an active material for the positive electrode. The foil-shaped electrode plate serving as a negative electrode is formed by coating an underlying metal foil in the form of a long belt, made of copper, with an active material for the negative electrode.The electrode arrangement has a structure in which the separator is arranged between the foil-shaped electrode plate serving as a positive electrode and the foil-shaped electrode plate serving as a negative electrode, and these components are wound into a flattened shape in the longitudinal direction of the same, thereby stacking a pair of the foil-shaped electrode plate serving as a positive electrode and the foil-shaped electrode plate serving as a negative electrode in a layered manner.

[0059] The electrode arrangement formed by this winding-type power generating element 3 is provided with uncoated parts 3a and 3b, in which the underlying metal foil is exposed at one end of each part in a lateral direction for electrical connection with the current collectors 4 and 6, within the foil-shaped electrode plates serving as positive and negative electrodes, respectively. The uncoated part 3a on the positive electrode side and the uncoated part 3b on the negative electrode side are located on opposite sides of each other across their respective widths. In the wound state described above, the uncoated part 3a on the positive electrode side extends outwards from one end of the power generating element 3 in the direction of its winding axis (lateral direction of the foil-shaped electrode plate).Likewise, the uncoated part 3b of the side of the negative electrode extends outwards from the other end side (opposite side of the uncoated part 3a) of the power generating element 3 in the winding axis of the same (broad direction of the foil-shaped electrode plate).

[0060] The power generating element 3 and the current collectors 4 and 6 are connected as described below. Overlapping sections of the uncoated part 3a of the power generating element 3, which is the metal foil extending outwards from the foil-shaped electrode plate serving as the positive electrode, are bundled by ultrasonic welding and connected to the current collector 4. Similarly, overlapping sections of the uncoated part 3b of the power generating element 3, which is the metal foil extending outwards from the electrode plate serving as the negative electrode, are bundled by ultrasonic welding and connected to the current collector 6.

[0061] Note, however, that not only the bundled sections of metal foil and the current collectors 4 and 6 described above are ultrasonically welded. The bundled sections of metal foil and the current collectors 4 and 6 described above are ultrasonically welded using the additional plates 21 for ultrasonic welding, as shown in Fig. 4 and Fig. 5 shown.

[0062] These additional plates 21 for ultrasonic welding will be discussed in detail in the process for manufacturing the secondary battery cell RB described later.

[0063] As described above, the connecting bolt 5 on the positive electrode side, which is mounted on the metal (in particular, for example, aluminum) cover part 2, is electrically connected to the current collector 4 on the positive electrode side. Furthermore, the connecting bolt 7 on the negative electrode side, which is mounted on the metal cover part 2, is electrically connected to the current collector 6 on the negative electrode side.

[0064] The structure for attaching the terminal bolt 5 to the cover part 2 and the structure for connecting the terminal bolt 5 to the current collector 4 are essentially the same as the structure for attaching the terminal bolt 7 to the cover part 2 and the structure for connecting the terminal bolt 7 to the current collector 6. Thus, the terminal bolts 5 and 7 are arranged symmetrically. The following section primarily describes the configuration of the positive electrode side.

[0065] As shown in the cross-sectional view of the Fig. As shown in Figure 3, the connecting bolt 5 is electrically connected to the current collector 4 by a rivet 8 and a metal plate 9. The rivet 8 is made of a metal material. More precisely, the rivet 8 on the positive electrode side, like other metal elements on the positive electrode side, is made of aluminum. The metal plate 9 is made, for example, of nickel-plated copper.

[0066] The head of the rivet 8 secures the metal plate 9 by clamping the metal plate 9 downwards.

[0067] A retaining frame 10 is arranged on the cover part 2. The retaining frame 10 is open on its upper surface and contains a cup-shaped concave section corresponding to the shape of a head 5b of the connecting bolt 5 (right-angled shape in the example of the present embodiment). The head 5b of the connecting bolt 5 fits with the concave section to prevent rotation of the connecting bolt 5.

[0068] The retaining frame 10 is formed from a resin that is an electrical insulating material to ensure electrical insulation between the connecting bolt 5 and the cover part 2.

[0069] In a current path from the current collector 4 to the connecting bolt 5, electrical insulation with respect to the cover part 2 is ensured by an upper seal 11 and a lower seal 12. Furthermore, the current path from the current collector 4 to the connecting bolt 5 is hermetically sealed at the point on the cover part 2 where the rivet 8 penetrates it, by the upper seal 11 and the lower seal 12. Both the upper seal 11 and the lower seal 12 are made of an electrical insulating material (specifically, resin) and serve as sealing elements.

[0070] The upper seal 11 has a structure in which a tubular part 11a, designed to fit into an opening in the cover part 2, is attached to the bottom section of a shell-shaped, rectangular parallelepiped container, which is open at its upper section. The upper seal 11 holds the rivet 8 at a point near the head of the shell-shaped, rectangular parallelepiped container. The rivet 8 is also fitted into the interior of the tubular part 11a.

[0071] Provided that the connecting bolt 5 and the like are attached to the cover part 2, the bottom section of the upper seal 11 is arranged between the head of the rivet 8 and the cover part 2.

[0072] Provided that the current collector 4 and the like are mounted on the cover part 2, the lower seal 12 is arranged between the horizontally positioned section of the current collector 4 and the cover part 2.

[0073] The rivet 8 is compressed as it is forced through the tubular part 11a of the upper seal 11, the cover part 2, the lower seal 12, and the horizontally positioned section of the current collector 4. Consequently, the rivet 8 fixes the horizontally positioned section of the current collector 4 to the cover part 2 and electrically connects the current collector 4 and the metal plate 9. As a result, the current collector 4 and the connecting bolt 5 are electrically connected.

[0074] As in the perspective view of the Fig. As shown in Figure 2, the configuration of the negative electrode side is symmetrical to the configuration of the positive electrode side across the center of the cover part 2. On the outside of the housing BC, a retaining frame 14 arranged on the cover part 2 holds the head of the connecting bolt 7, and a metal plate 16 attached to the rivet 15 electrically connects the rivet 15 and the connecting bolt 7.

[0075] The rivet 15 is compressed, with its head being held on the upper seal 17, while the upper seal 17, the cover part 2, the lower seal 18 and the current collector 6 are clamped downwards.

[0076] Like the current collector 6, the rivet 15 is made of copper and electrically connects the current collector 6 and the connecting bolt 7 through the metal plate 16. [Manufacturing process of the secondary battery cell RB]

[0077] Next, a process for manufacturing the secondary battery cell RB will be described, with a focus on the assembly of the power generation element 3.

[0078] The foil-shaped electrode plate of the positive electrode is produced, for example, by applying a layer of an active material of the positive electrode, such as lithium iron phosphate or the like, to both the front and back sides of an underlying metal foil of aluminum (in particular A1085 (material code specified in JIS H4000)) in the shape of a long strip, and then performing a pressing operation or the like on the metal foil. A1085 is aluminum with a purity of 99% or more. In particular, it is specified as follows: A1085 contains 0.10% or less Si, 0.12% or less Fe, 0.03% or less Cu, 0.02% or less Mn, 0.02% or less Mg, 0.03% or less Zn, 0.03% or less Ga, 0.05% or less V, 0.02% or less Ti, and 99.85% or more Al, by mass fraction.

[0079] As described above, an exposed area is formed at one end in the width direction, where the belt-shaped underlying metal layer is exposed without being coated with the active material of the positive electrode. This exposed area serves as the uncoated part 3a.

[0080] The foil-shaped electrode plate of the negative electrode is produced, for example, by applying a layer of an active material of the negative electrode made of graphite or the like to both the front and back sides of an underlying metal foil made of copper (especially C1020-1 / 4H (material code specified in JIS H 3100)) in the shape of a long belt and then performing a pressing operation or the like on the metal foil.

[0081] In the case of the foil-shaped electrode plate of the negative electrode, an exposed area is formed at one end in the width direction, in which the belt-shaped underlying metal layer is exposed without being coated with the active material of the negative electrode. This exposed area serves as the uncoated part 3b.

[0082] The foil-shaped electrode plate of the positive electrode, with a predetermined length, and the foil-shaped electrode plate of the negative electrode, with a predetermined length, are wound around a flat-plate-shaped winding axis, with a separator positioned between them. At this time, the foil-shaped electrode plate of the positive electrode, the foil-shaped electrode plate of the negative electrode, and the separator are positioned such that the uncoated part 3a protrudes on one side of the winding axis, while the uncoated part 3b protrudes on the other side of the winding axis.

[0083] In power generation element 3, the separator is wound around its outermost circumference.

[0084] Next, as a preliminary arrangement for ultrasonic welding of the uncoated parts 3a and 3b and the connecting sections 4a and 6a of the current collectors 4 and 6, the additional plates 21 for ultrasonic welding, which are in Fig. 4 and Fig. 5 are shown, attached to the uncoated parts 3a and 3b.

[0085] As in Fig. As shown in Figure 5, each additional plate 21 contains a pair of metal elements 21a and 21b arranged opposite each other, and a connecting section 21c for connecting end edges of this pair of metal elements 21a and 21b together.

[0086] The corresponding additional plates 21 arrange the bundled sections of the uncoated parts 3a and 3b by means of the pair of metal elements 21a and 21b between them and are consequently attached to the uncoated parts 3a and 3b.

[0087] During ultrasonic welding of the uncoated parts 3a and 3b and the like, an ultrasonic vibration is caused to act on the metal elements 21a of the pair of metal elements 21a and 21b, which are consequently fixed.

[0088] For the sake of simplicity, the metal element 21a of the pair of metal elements 21a and 21b, which is subjected to an ultrasonic vibration, is referred to below as the “first metal element”, while the other metal element 21b is referred to as the “second metal element”.

[0089] The additional plate 21 attached to the uncoated part 3a of the positive electrode side and the additional plate 21 attached to the uncoated part 3b of the negative electrode side are formed in almost the same shape. The additional plates 21 attached to the uncoated part 3a of the positive electrode side are made of aluminum, which is the same material as the uncoated section 3a.

[0090] The additional plate 21 for ultrasonic welding, attached to the uncoated section 3b of the negative electrode side, is made of copper, as is the uncoated section 3b. The uncoated section 3b of the negative electrode side is formed from a copper plate (in particular, consisting of C1020-O (material code specified in JIS H3100)) that has not been work-hardened. Therefore, the uncoated section 3b of the negative electrode side has a Vickers hardness of at least 40 HV and not more than 75 HV. This serves to prevent damage to the additional plates 21 during ultrasonic welding. A specific description will follow below. "Vickers hardness" here is an index indicating the surface hardness of an element.The Vickers hardness can be measured on the surface of a target element at the center of the area to be subjected to ultrasonic welding, using a test method specified as the Vickers hardness test in JIS Z 2244. Specifically, the Vickers hardness can be determined by pressing an indenter made of a four-sided diamond pyramid against the surface of a test piece to create an indentation, measuring a diagonal line of the indentation to determine its area, and dividing the pressing force by the area.

[0091] The first metal element 21a, the second metal element 21b, and the connecting section 21c, which are components of the additional plate 21, are formed from a single thin, plate-shaped metal element. The thin, plate-shaped metal element (an aluminum plate for the positive electrode and a copper plate for the negative electrode) is inserted into the Fig. The shape shown in section 4 is processed. This processed element is then attached to a [unclear text]. Fig. 4. Center line A shown is folded twice to fold the element into the Fig. The additional plate 21, formed by double folding of this thin metal plate element, is configured to arrange the bundled uncoated section 3a or 3b in or between it.

[0092] A description of a method for attaching the additional plates 21 to, for example, the uncoated parts 3a and 3b of the negative electrode side will be given. In the case of the power generating element 3 wound in a flattened shape, the uncoated part 3b is unfolded into two bundles by applying a pressing, expanding force to the flattened uncoated part from the center in the lateral direction to the left and right sides thereof, as shown in Fig. 7 shown. Then each of the two bundles is arranged between an additional plate 21, as shown in Fig. 8 shown. At this time, an end edge of the uncoated part 3b is placed against the inside of the connecting section 21c to position the additional plate 21, and the additional plate 21 is attached so that the end edge of the uncoated part 3b rests against the connecting section 21c.

[0093] Furthermore, the two additional plates 21 are crimped and firmly attached to the uncoated part 3b. Consequently, the additional plates 21 are firmly positioned against the weld surfaces of the uncoated part 3b, which is a foil-shaped object to be welded. A surface of the first metal element 21a on the opposite side of a surface of the same in contact with the uncoated part 3b is a surface on which an ultrasonic vibration acts.

[0094] On the side of the positive electrode, two additional plates 21 are attached to the uncoated part 3a in the same way as described above.

[0095] On the positive electrode side of a sub-arrangement on the side of the cover part 2, the metal plate 9, mounted on the rivet 8, is arranged, with the threaded section 5a of the connecting bolt 5, held in the retaining frame 10, penetrating the metal plate 9. Furthermore, the rivet 8 is mounted in the cover part 2, penetrating the upper seal 11, the cover part 2, the lower seal 12, and the current collector 4, and is secured by upsetting the end section of the rivet 8 on the inside of the housing BC.

[0096] The metal plate 16, mounted on the rivet 15, is also arranged on the negative electrode side, with the threaded section 7a of the connecting bolt 7, held in the retaining frame 14, penetrating the metal plate 16. Furthermore, the rivet 15 is mounted in the cover part 2, penetrating the upper seal 17, the cover part 2, the lower seal 18, and the current collector 6, and is secured by upsetting the end section of the rivet 15 on the inside of the housing BC.

[0097] Note that although the connecting sections 4a and 6a were already formed in the current collectors 4 and 6 under this condition, the current collectors 4 and 6 do not have an L-shaped curved form. That is, the points on the current collectors 4 and 6 where the connecting sections 4a and 6a are formed (points to serve as the aforementioned vertically positioned sections) also have an essentially linear shape extending along the longitudinal direction of the cover part 2.

[0098] As described above, the power generating element 3, equipped with the additional plates 21, is located directly below a surface of the sub-assembly on the side of the cover part 2 where the lower seals 12 and 18 are attached. At this time, the power generating element 3 is positioned such that the winding axis of the foil-shaped electrode plate is parallel to the longitudinal direction of the cover part 2, and the flat surfaces of the power generating element 3 are positioned orthogonally to the cover part 2. Next, the positive and negative current collectors 4 and 6 are bent into an L-shape, as shown in Fig. 2 shown, and the connecting sections 4a and 6a fitted into a space between the pair of additional plates 21, as shown in Fig. 9 shown. Note that Fig. 9 only the side of the negative electrode accordingly, for example Fig. Figure 7 shows, but the side of the positive electrode is similar in layout to the side of the negative electrode.

[0099] Provided that the sub-assembly on the side of the cover part 2 and the power generating element 3 are mounted in this manner, the uncoated parts 3a and 3b of the power generating element 3 and the connecting sections 4a and 6a of the current collectors 4 and 6 are joined by ultrasonic welding.

[0100] At the time of this ultrasonic welding, an ultrasonic vibration is applied from the side of the additional plate 21 for welding the additional plates 21, into which the uncoated parts 3a and 3b are inserted, and the connecting sections 4a and 6a of the current collectors 4 and 6, while the corresponding additional plates 21 and the connecting sections 4a and 6a are placed against each other.

[0101] In particular, as in Fig. Figure 6 shows an approximate arrangement at the time of ultrasonic welding, with an anvil 31 placed against the current collectors 4 and 6 and the front end section 32 of the sonotrode, which is a vibration tool for applying ultrasonic vibration, placed against surfaces of the filler plates 21 on the opposite side from surfaces of the same in contact with the current collectors 4 and 6 (front surface of the first metal element 21a). Then, ultrasonic vibration is applied along a direction (longitudinal direction of the uncoated parts 3a and 3b) indicated by a double-sided arrow B. Fig. Figure 6 shows the uncoated parts 3a and 3b arranged between the additional plates 21 and the current collectors 4 and 6.

[0102] That is, the additional plates 21 and the current collectors 4 and 6 are connected, with the additional plates and the current collectors being placed in contact with each other, by applying an ultrasonic vibration from a side surface (front surface of the first metal element 21a) that is positioned on a side surface of a pair of side surfaces of the curved additional plates 21 on the opposite side of the surface on which the current collectors 4 and 6 are located.

[0103] A surface of the front end section 32 of the sonotrode in contact with the additional plates 21 has a thin, long rectangular shape that extends into the area indicated by the double-sided arrow B in Fig. The front end section 32 of the sonotrode extends in the direction shown in Figure 6. The front end section 32 of the sonotrode is placed against the additional plates 21, while the sonotrode itself is positioned such that the longitudinal direction of the front end section 32 of the sonotrode coincides with the longitudinal direction of the uncoated parts 3a and 3b of the flat surfaces of the power generating element 3. The areas of the additional plates 21 on which the ultrasonic vibration acts are indicated by double-dotted lines C in Figure 6. Fig. 4, Fig. 5 and Fig. Figure 9 shows that after ultrasonic welding, weld traces remain at the locations shown by the double-dotted lines C.

[0104] The contact surface of the front end 32 of the sonotrode with the additional plate 21 and the contact surface of the anvil 31 with the current collector 4 or 6 are each formed in a so-called knurled pattern (knurling), in which a plurality of projections are arranged in the form of a square pyramid, as shown schematically in Fig. 6 shown. The projections on the front end 32 of the sonotrode are larger than the projections on the side of the anvil 31.

[0105] In Fig. 4 and Fig. 5 For example, the points of action of an ultrasonic vibration, which are shown by colon-dash lines C, are defined in a plurality of locations (three locations in the present first embodiment) for each additional plate 21. In the Fig. In the embodiment shown in Figure 6, the uncoated section 3a or 3b is connected to the current collector 4 or 6 by ultrasonic welding of the effective points of the ultrasonic welding in the sequence in the additional plate 21.

[0106] At this time, deformations due to ultrasonic welding around adjacent points of action of an ultrasonic vibration of the additional plate 21, which is attached to the uncoated section 3b on the side of the negative electrode, overlap in the middles of the points of action on both sides, so that the deformations become considerable.

[0107] As described above, the additional plates 21 attached to the uncoated section 3b of the negative electrode side each have a Vickers hardness of at least 40 Hv and not more than 75 Hv. Therefore, even in the case of significant deformation due to ultrasonic welding, the occurrence of damage, such as cracks, can be prevented.

[0108] Such prevention of damage to the additional plates 21 is described by means of a specific experimental example.

[0109] Copper auxiliary plates 21, which are to be attached to the uncoated section 3b of the negative electrode side, are prepared. Specifically, 100 pieces of auxiliary plates 21, formed by varying the Vickers hardness of copper plates, are prepared for each hardness. Then, the auxiliary plates 21, the uncoated section 3b, and the current collector 6 are ultrasonically welded together in the same manner as the previously mentioned assembly procedure. The occurrence of damage, such as cracks, in the auxiliary plates 21 as a result of this process is Fig. 11 shown. In Fig. Figure 11 indicates the Vickers hardness along the horizontal axis and the frequency of damage, such as cracks, along the vertical axis. Here, the frequency of damage, such as cracks, shows the number of pieces out of 100 pieces of the additional plates 21 that exhibited damage, such as cracks.

[0110] As from Fig. As is evident from section 11, the crack frequency is “0%” when the Vickers hardness is 40 Hv or more and 75 Hv or less. This indicates that even if deformations occur in the additional plates 21, as mentioned above, the occurrence of damage, such as cracks, can be prevented.

[0111] If the Vickers hardness is less than 40 Hv, the additional plates 21 are excessively soft, and damage, such as cracks, occurs around the points of application of ultrasonic vibration. This is likely because the additional plates 21 have deformed more than necessary due to compression caused by welding.

[0112] As described above, the power generating element 3, in which the ultrasonic welding of two additional plates 21 on each side of the positive electrode side and the negative electrode side has been completed, is mounted. Subsequently, the assembly is inserted into the container body 1 on the side of the cover 2, and the end edges of the cover 2 and the opening ends of the container body 1 are welded together by laser welding.

[0113] After the secondary battery cell RB has undergone the processes of injecting an electrolyte solution, initial charging, and the like, it is completed. <Andere Ausführungsformen>

[0114] Other embodiments of the present invention are listed below. Note that the same reference numerals and symbols are used for components corresponding to those of the embodiment described above.

[0115] (1) In the embodiment described above, a case is presented in which the uncoated parts 3a and 3b are arranged between the additional plates 21 for ultrasonic welding, the end edges of the first metal element 21a and the second metal element 21b being connected to each other by the connecting section 21c, the sandwich-like components being overlapped by the connecting sections 4a and 6a of the current collectors 4 and 6, and the overlapped components being ultrasonically welded together. However, the ultrasonic welding of the uncoated parts 3a and 3b and the like, and the joining of the current collectors 4 and 6, can be carried out at separate times.

[0116] For example, the procedure described above is as follows. As shown in the cross-sectional view of the Fig. 12 shown, which the Fig. 6 in the embodiment described above is a sub-arrangement in which the uncoated parts 3a and 3b are arranged between the additional plates 21 for ultrasonic welding, which are shown and crimped in the first to third embodiments; that is, a sub-arrangement in which the uncoated parts 3a and 3b are simply arranged between the first metal element 21a and the second metal element 21b that form each additional plate 21, between the front end section 32 of the sonotrode and the anvil 31. Under this condition, ultrasonic welding can be carried out by causing an ultrasonic vibration to act on areas that are, for example, in Fig. 4 are shown by colon-dash lines C.

[0117] In this case, the additional plates 21 are not limited to a structure in which the first metal element 21a and the second metal element 21b are connected by the connecting section 21c. The first metal element 21a, which is subjected to an ultrasonic vibration, and the second metal element 21b, which is positioned on the opposite side of the first metal element 21a across the uncoated parts 3a and 3b, can be separate components.

[0118] The components welded in this way and the connecting sections 4a and 6a of the current collectors 4 and 6 can be joined, for example, by resistance welding of the additional plates 21 and the connecting sections 4a and 6a of the current collectors 4 and 6.

[0119] (2) In the embodiment described above, a case is given in which each additional plate 21, formed from a thin, plate-shaped metal element, is folded in half twice, the end edges of the first metal element 21a and the second metal element 21b are connected to each other by the connecting section 21c, and the uncoated parts 3a and 3b are arranged between the additional plates 21. As shown in the cross-sectional view of the Fig. 13 shown, which the Fig. 6 in the first embodiment, however, it can be caused that an ultrasonic vibration acts on a sub-arrangement in which the bundled sections of the uncoated parts 3a and 3b, which are arranged between the additional plates 21, which are formed as substantially flat plate materials, and the current collectors 4 and 6, from the side of the additional plate 21, thereby ultrasonically welding the additional plates 21 and the current collectors 4 and 6.

[0120] In this case, each additional plate 21 consists solely of the first metal element 21a. Furthermore, the current collectors 4 and 6 serve as the second metal element for sandwich-like arrangement of the uncoated parts 3a and 3b together with the first metal element 21a.

[0121] (3) In the aforementioned embodiment, the points of action for ultrasonic vibration are defined at three locations for an additional plate 21 for ultrasonic welding. Alternatively, however, the points of action can be defined at two locations or four or more locations.

[0122] (4) In the aforementioned embodiment, a cell RB of a secondary battery with anhydrous electrolyte is given as an example of an electrical storage device to which the present invention is applied. The present invention is also applicable to various types of electrical storage devices, including capacitors.

[0123] (5) For the additional plates 21 of the aforementioned embodiment, a copper plate that has not been cold-worked (C1020-O) is used. However, the material for the additional plates 21 is not limited to this. For example, materials with reduced hardness due to annealing of C1020-1 / 2H or -1 / 4H may be used. Furthermore, the material is not limited to C1020, and copper such as C1100 may be used. An "O" material made of a copper alloy may also be used. Furthermore, the material is not limited to such copper materials as long as the Vickers hardness is at least 40 Hv and not more than 75 Hv, and an aluminum alloy with a comparatively high hardness, such as A5000s, may be used.

[0124] (6) The embodiment mentioned above describes, for example, the case in which the present invention is applied to the side of the negative electrode. However, the present invention can be applied to the side of the positive electrode in the same way.

[0125] (7) In the aforementioned embodiment, an electrical storage element 3 of the winding type is given as an example, in which an electrode plate on the positive electrode side is in the shape of a long belt and an electrode plate on the negative electrode side is in the shape of a long belt with a separator held between them. However, the present invention is applicable to any electrical storage devices, provided that the electrical storage devices are provided with an electrical storage element in which an electrode plate on the positive electrode side and an electrode plate on the negative electrode side are stacked in a layered manner. That is to say, there is no restriction to the electrical storage element of the wound type.For example, the present invention is also applicable to an electrical storage device with a stackable electrical storage element in which a plurality of electrode plates on the positive electrode side and a plurality of electrode plates on the negative electrode side are stacked alternately with separators held between them. As another example, an electrical storage element can have a configuration in which an electrode plate on the positive electrode side, an electrode plate on the negative electrode side, and a separator are stacked in a layered manner, with at least one of these components being folded in a zigzag pattern. Reference symbol list 3 Electrical storage element 4, 6 power collector 21 Additional plate for ultrasonic welding 21a First metal element 21b Second metal element 21c Connection section 32 Vibration tool

Claims

[1] Method for manufacturing an electrical storage device, comprising the following steps: Arranging a metal foil extending outwards from an electrode plate between a first metal element and a second metal element; and Causing an ultrasonic vibration to act on a plurality of points of action from the side of the first metal element in order to connect the metal foil to the first metal element and the second metal element, whereby the first metal element has a Vickers hardness of at least 40 Hv and not more than 75 Hv. [2] Method for manufacturing an electrical storage device according to claim 1, wherein In the joining step, a vibration tool is used which has a contact surface capable of contacting the first metal element and causes an ultrasonic vibration to act on the first metal element, and the contact surface is formed by one or more protrusions. [3] Method for manufacturing an electrical storage device according to claim 1 or 2, wherein The end edges of the first metal element and the second metal element are connected to each other by a connecting section, and In the step of sandwich-like arrangement, the metal foil is arranged between the first metal element and the second metal element in such a way that an end edge of the metal foil is in contact with the connecting section. [4] Electrical storage device comprising: an electrical storage element comprising: an electrode arrangement having a metal foil extending on one end side; and an additional plate for ultrasonic welding having a plurality of connecting sections connected to the metal foil by ultrasonic vibration and placed against the metal foil, wherein The additional plate has a Vickers hardness of at least 40 Hv and not more than 75 Hv.

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