Patent Description:
A nonaqueous electrolyte secondary battery such as a lithium ion secondary battery is more lightweight and has a higher energy density as compared with existing batteries. For this reason, in recent years, the nonaqueous electrolyte secondary battery has been used as a power supply to be mounted on a vehicle that uses electricity as a driving source, or a power supply to be mounted on electric products such as a personal computer and a portable terminal. Particularly, an assembled battery including as a single cell a closed type lithium ion secondary battery, which is lightweight and provides a high energy density, has been preferably used as a high output power supply for driving a vehicle such as an electric vehicle (EV), a plug-in hybrid vehicle (PHV), or a hybrid vehicle (HV).

Such a closed type secondary battery forming an assembled battery includes a battery case for accommodating an electrode body, and electrode terminals of a positive electrode and a negative electrode. One end of the electrode terminal forming the secondary battery is exposed to the outside of the battery case, and the other end is connected with the electrode body inside the battery case via a collector.

A plurality of such secondary batteries (which will be hereinafter also referred to as "single cells") are arrayed along a prescribed array direction, and the electrode terminal of one single cell is electrically connected with another single cell via a bus bar, thereby constructing an assembled battery.

Generally, the electrode terminals of the positive electrode and the negative electrode of this type of secondary battery are formed of different metal materials, respectively. When a bus bar formed of the same kind of material as that for one of the electrode terminals is used for connection between single cells, the conduction and the junction strength between the other of the electrode terminals and the bus bar become relatively lower as compared with those for the one of the electrode terminals.

In order to ensure the conduction and the junction strength between the electrode terminal and the bus bar, Japanese Patent Application <CIT> and Japanese Patent Application <CIT> disclose a technology of joining an intermediate member formed of the same kind of material as that for the bus bar to an electrode terminal formed of a different kind of material from that for the bus bar by ultrasonic joining. A method for producing battery packs is furthermore known from Japanese Patent Application <CIT>. A secondary battery terminal including a lid to block an opening part of a vessel for accommodating an electrode body, an internal terminal joined to the electrode body, an external tie bolt having a polygonal head contacting to an external side face of the internal terminal, and an external contact terminal having an annular shape to insert the head into the inner peripheral side and being inserted into an arrangement hole formed on the lid, through an outer insulation material, is known from <CIT>. In the secondary battery terminal of <CIT>, an outer rim portion on the tip side of the external contact terminal of the secondary battery terminal is crimped to the periphery of the arrangement hole on the lid through the outer insulation material, in a state that the polygonal head is prevented from rotation by an inner peripheral face of the external contact terminal.

However, when an electrode terminal and an intermediate member are subjected to ultrasonic joining, in order to ensure the junction strength between the electrode terminal and the intermediate member, a large junction energy is required to be applied to the junction surface. When the junction surface is applied with a large junction energy, roughness or deformation is caused at the surface of the intermediate member, namely, the connection surface between the intermediate member and the bus bar. This requires a post treatment for flattening the surface. In <CIT>, after ultrasonic joining, a treatment for reducing the surface roughness by the surface treatment such as a cutting treatment, a polishing treatment, or a melting treatment is performed. In Japanese Patent Application <CIT>, a step of removing foreign matters generated accordingly after ultrasonic joining is provided.

Such steps cause hindrance in easy assembly of a battery and further in the production of a battery. There has been a demand for the development of a technology so as to establish a favorable conduction between an electrode terminal and an external connection terminal such as a bus bar, and to ensure the junction strength between the members, and moreover to eliminate the necessity of a complicated post treatment.

The present disclosure has been made in view of such points. It is a main object of the present disclosure to provide a terminal excellent in conduction with an external connection terminal such as a bus bar. In addition, it is another main object to provide a battery using such a terminal, and a technology of manufacturing the terminal without requiring a post treatment.

The present inventors focused on the following: two members each made of a metal and forming a terminal are crimped to each other, which can strengthen the mechanical strength between the members. Further, the present inventors found the following: by elaborating the form of the crimped structure, it is possible to apply metal-joining between the two members without further affecting the crimped structure, and as a result, it is possible to attain both the junction strength and the conduction with more ease than ever. As a result, the present inventors completed the present disclosure, with the invention given by the claims.

The terminal herein disclosed is a terminal forming any of a positive electrode and a negative electrode of a secondary battery, and has a first member and a second member each made of a metal, wherein the first member and the second member are formed of mutually different metals. The first member is formed in a sheet shape and has a concave part, and the second member has a crimped part and a shaft part. Herein, the crimped part of the second member is provided in a convex shape or a flange shape at a surface of the shaft part opposed to the first member, fitted into the concave part of the first member and crimped with the first member at one surface of the first member not via a through hole, and the first member and the second member have metal junction surfaces metal-joined to each other at opposing surfaces thereof after the first member and the second member have been previously crimped, wherein the metal joining is performed by ultrasonic joining, diffusion joining, frictional pressure contact, or laser welding.

With normal crimping, a part of one member passes through a through hole previously formed in the other member, and the part of the passed one member is crimped at the periphery of the through hole of the other member. As a result, a crimped structure is formed. However, for such a crimped structure via the through hole, the formation of the through hole causes the crimped structure itself to occupy a large area. For this reason, it is difficult to ensure the region suitable for separately performing metal joining.

On the other hand, for the terminal for a secondary battery herein disclosed, the first member and the second member are crimped with each other not via a through hole, thereby ensuring the mechanical strength of the terminal. This can ensure the region for forming metal-joining at mutually opposing surfaces of the first member and the second member after crimping. Further, the first member and the second member are crimped with each other not via a through hole. For this reason, it is possible to suppress the change in shape due to the crimped structure at the surface of the first member on an opposite side thereof to the second member.

Further, for the terminal herein disclosed, the mechanical strength is ensured by the crimped structure not via a through hole, and metal junction surfaces metal joined to each other are formed at the opposing surfaces of the first member and the second member. As a result, a favorable conduction between the first member and the second member is ensured. Moreover, with the technology herein disclosed, both the crimped structure not via a through hole and metal joining are attained. Even when the first member and the second member are formed of mutually different metals, favorable mechanical strength and conduction are implemented.

In a preferable embodiment, the area of the metal junction surface is <NUM>% or less of an area of each opposing surface of the first member and the second member.

With such a configuration, it is possible to reduce the effects exerted by metal joining on the surface of the first member. As a result, it is possible to keep the initial flatness of the surface of the sheet-shaped first member on an opposite side to the surface, which is opposed to the second member (i.e., the surface of the first member which can be connected with an external connection component).

In a more preferable embodiment, the first member has a concave part at a surface thereof on an opposite side to a surface is opposed to the second member, and the metal junction surface is formed at a part opposed to the concave part.

With such a configuration, it is possible to keep the flatness of the part except for the concave part at the surface of the sheet-shaped first member on an opposite side to the surface opposed to the second member.

In another preferable embodiment, an arithmetic average roughness Sa at a surface of the first member on an opposite side to the opposing surface is <NUM> or less.

With such a configuration, it is possible to keep the initial flatness of the surface of the sheet-shaped first member on an opposite side to the surface, which is opposed to the second member (i.e., the surface of the first member which can be connected with an external connection component).

For example, mention may be made of the case where the first member is formed of aluminum or an alloy mainly containing aluminum, and the second member is formed of copper or an alloy mainly containing copper.

In one embodiment, the metal junction surfaces present between the first member and the second member have junction surfaces caused by ultrasonic joining.

With such a configuration, the first member and the second member can be brought into conduction with each other more favorably.

As another aspect of the technology herein disclosed, a secondary battery is provided which includes: an electrode body including a positive electrode and a negative electrode; a battery case accommodating therein the electrode body; and a positive electrode terminal and a negative electrode terminal electrically connected with the positive electrode and the negative electrode in the electrode body, respectively, in which at least one of the positive electrode terminal and the negative electrode terminal includes the terminal herein disclosed.

As a still other aspect of the technology herein disclosed, an assembled battery is provided which includes a plurality of single cells electrically connected to one another and arrayed therein, in which the secondary battery including the terminal herein disclosed as at least one of the positive electrode terminal and the negative electrode terminal is used as each of the plurality of single cells.

As a still other preferable embodiment, for the respective plurality of single cells, a positive electrode terminal of one single cell and a negative electrode terminal of another single cell are electrically connected with each other by a prescribed bus bar, and the bus bar is formed of the same metal as a metal forming the first member of the terminal.

With such a configuration, an assemble battery is provided in which a favorable connection is established between the single cells.

As a still other aspect of the technology herein disclosed, a method for manufacturing a terminal is provided.

Namely, the method for manufacturing a terminal herein disclosed includes the following steps of:.

With such a manufacturing method, it is possible to manufacture a terminal including the terminal herein disclosed as a constituent element.

In a preferable embodiment, the step of metal joining is carried out so that a junction surface of metal joining formed by the step may have an area of <NUM>% or less of an area of each opposing surface of the first member and the second member.

With such a manufacturing method, it is possible to reduce the effects exerted by metal joining on the first member surface. As a result, it is possible to manufacture a terminal kept in flatness of the surface of the first member to be connected with an external connection component.

In a preferable embodiment, the step of metal joining is carried out so that an arithmetic average roughness Sa at a surface opposite to the opposing surface of the first member after the metal joining becomes <NUM> or less.

Such a manufacturing method is implemented by the following: the mechanical strength between the members is ensured by the crimping; as a result, the junction energy given by metal joining can be made weaker than ever. As a result, it is possible to manufacture a terminal with the roughness of the surface of the first member to be connected with an external connection component suppressed to the foregoing value.

Below, appropriately referring to the accompanying drawings, a terminal herein disclosed, a secondary battery including the terminal, an assembled battery including a single cell having the terminal as a constituent element, and the method for manufacturing the terminal will be described in details by taking a rectangular lithium ion secondary battery including a wound electrode body as an example. The following embodiments naturally should not be construed as particularly limiting the technology herein disclosed.

The secondary battery herein disclosed is not limited to the lithium ion secondary battery described below. For example, a sodium ion secondary battery, a magnesium ion secondary battery, or a lithium ion capacitor included in a so-called physical battery is also the example included in the secondary battery herein referred to. Further, herein, a description will be given using a lithium ion secondary battery including a wound electrode body having a structure in which a plurality of electrode bodies of positive electrodes and negative electrodes are wound via separators. Not limited to such a configuration, the electrode body may be configured such that a plurality of electrode bodies of positive electrodes and negative electrodes are stacked via separators.

Incidentally, matters necessary for executing the present disclosure, except for matters specifically referred to in the present specification can be grasped as design matters of those skilled in the art based on the related art in the present field. The present disclosure can be executed based on the contents disclosed in the present specification, and the technical common sense in the present field.

In the following drawings, the members/parts producing the same effect are given the same reference sign and numeral, and the overlapping description thereon may be omitted or simplified. The dimensional relation of length, width, or the like in each following drawing does not necessarily reflect the actual dimensional relation.

When the numerical value range is described as A to B (where A or B is a given numerical value) in the present specification, it is assumed that the range means A or more and B or less. Further, the term "main body" in the present specification represents the component accounting for <NUM>% by weight or more based on the total amount of all the components.

<FIG> is a perspective view schematically showing the outline of a lithium ion secondary battery using a terminal in accordance with one embodiment.

A lithium ion secondary battery <NUM> in accordance with the present embodiment includes an electrode body having a structure in which a positive electrode and a negative electrode are stacked via separators in the inside of a battery case <NUM>. Such an electrode body is accommodated together with a nonaqueous electrolyte (not shown) in a battery case main body <NUM>. The edge part of a lid body <NUM> is sealed while the inside being reduced in pressure by welding or the like, resulting in a hermetically sealed state. For the battery case <NUM>, a metal material which is lightweight, and has good thermal conductivity such as aluminum is used. The shape of the battery case <NUM> is not limited to the rectangular shape as described in <FIG>, and may be, for example, a cylindrical shape.

As shown in <FIG> and <FIG>, the lithium ion secondary battery <NUM> in accordance with the present embodiment includes a positive electrode terminal <NUM> and a negative electrode terminal <NUM> electrically connected with the electrode body <NUM> (<FIG>) inside the battery case <NUM>, and connected with an external connection component via a bus bar or the like. As shown in <FIG>, the positive and negative electrode terminals <NUM> and <NUM> are provided in such a manner as to penetrate through a lid body <NUM> of the battery case <NUM>. In the present embodiment, the negative electrode terminal <NUM> has a terminal structure including the first member and the second member herein disclosed. This will be described later.

Incidentally, each shape of the positive electrode terminal <NUM> and the negative electrode terminal <NUM> exposed to the outside of the battery case <NUM> has no particular restriction, and may be, for example, a rectangular shape as shown, or may be a circular shape including an elliptic shape.

<FIG> is a perspective view schematically showing an assembled battery including single cells using the terminals in accordance with one embodiment.

In an assembled battery <NUM> including a plurality of single cells <NUM> arrayed therein shown in <FIG>, the single cells <NUM> are arrayed via spacers <NUM>. At further outside of the spacer <NUM> arranged on the outermost side, a pair of end plates <NUM> are arranged. These are bound by fastening beam materials <NUM> mounted for cross-linking the end plates <NUM>, and the end of the fastening beam material <NUM> is fastened and fixed by a vis screw <NUM>.

The positive electrode terminal <NUM> and the negative electrode terminal <NUM> are electrically connected with respective adjacent single cells <NUM> via bus bars <NUM>. As the bus bar <NUM>, a metal having high electric conductivity and high mechanical strength is generally used. For example, aluminum, copper, or the like is used.

The internal structure of a secondary battery using the terminal herein disclosed will be described with reference to <FIG> is a cross sectional view of the broad surface schematically showing the structure of a secondary battery using the terminal in accordance with one embodiment.

The electrode body <NUM> herein disclosed is a power generating element accommodated in the inside of the battery case <NUM> while being covered with an insulating film or the like not shown, and is a so-called wound electrode body including a long sheet-shaped positive electrode <NUM> and a long sheet-shaped negative electrode <NUM> wound in a manner stacked one on another with two similarly long sheet-shaped separators <NUM> and <NUM> interposed therebetween.

The positive electrode <NUM> includes a foil-shaped positive electrode collector 21A, and a positive electrode active material layer 21B formed along the longitudinal direction on each opposite surface of the positive electrode collector 21A. Further, at one side edge part of the electrode body <NUM> in the width direction of the secondary battery <NUM>, a positive electrode collector exposed part 21C at which the positive electrode active material layer 21B is not formed, and the positive electrode collector 21A is exposed is disposed. The positive electrode active material layer 21B includes various materials such as a positive electrode active material, a binder, and a conductive material. Incidentally, as for the materials included in the positive electrode active material layer 21B, those usable in a conventional common lithium ion secondary battery can be used without particular restriction, and do not characterize the present disclosure, and hence will not be described in detail.

As the positive electrode collector terminal <NUM>, for example, aluminum foil is used.

The negative electrode <NUM> includes a foil-shaped negative electrode collector 22A, and a negative electrode active material layer 22B formed along the longitudinal direction on one surface or each opposite surface of the negative electrode collector 22A. Further, at the other side edge part of the electrode body <NUM> in the width direction, a negative electrode collector exposed part 22C at which the negative electrode active material layer 22B is not formed, and the negative electrode collector 22A is exposed is disposed. As with the positive electrode active material layer 21B, the negative electrode active material layer 22B includes various materials such as a negative electrode active material and a binder. As for the materials included in the negative electrode active material layer 22B, those usable in a conventional common lithium ion secondary battery can be used without particular restriction, and do not characterize the present disclosure, and hence will not be described in detail.

As the negative electrode collector terminal <NUM>, for example, copper foil is used.

The separators <NUM> and <NUM> are each interposed between the positive electrode <NUM> and the negative electrode <NUM>, and prevent the direct contact between the electrodes. Although not shown, a plurality of fine holes are formed at the separators <NUM> and <NUM>. The fine holes are configured such that electric charge carriers (lithium ions for a lithium ion secondary battery) transfer between the positive electrode <NUM> and the negative electrode <NUM>.

For the separators <NUM> and <NUM>, a resin sheet having a desirable heat resistance (e.g., a sheet made of polyolefin such as polypropylene or polystyrene), or the like is used.

As the nonaqueous electrolyte to be accommodated in the battery case <NUM>, typically, those including a nonaqueous solvent and a support salt, and usable for a conventional common lithium ion secondary battery can be used without particular restriction, and do not characterize the present disclosure, and hence will not be described in details.

As shown in <FIG> and <FIG>, the positive electrode terminal <NUM> includes a positive electrode collector terminal <NUM> connected to the electrode body <NUM> inside the battery case <NUM>, and a positive electrode connection terminal <NUM> connected with the collector terminal <NUM>, and partially exposed through a through hole <NUM> of the lid body <NUM> to the outer surface of the lid body <NUM>. The positive electrode collector terminal <NUM> is arranged in the inside of the battery case <NUM>, and is connected with the positive electrode <NUM> via the positive electrode collector exposed part 21C.

As shown in <FIG> and <FIG>, the negative electrode terminal <NUM> includes a negative electrode collector terminal <NUM> connected to the electrode body <NUM> inside the battery case <NUM>, and a negative electrode connection terminal <NUM> connected with the collector terminal <NUM>, and partially exposed through the through hole <NUM> of the lid body <NUM> to the outer surface of the lid body <NUM>. The negative electrode collector terminal <NUM> is arranged in the inside of the battery case <NUM>, and is connected with the negative electrode <NUM> via the negative electrode collector exposed part 22C.

Below, based on the configuration of the negative electrode terminal <NUM> embodying the terminal structure herein disclosed, a detailed description will be given with reference to <FIG>. Incidentally, the configuration in the case where the positive electrode terminal <NUM> has the terminal structure herein disclosed is the same as the configuration in the case where the negative electrode terminal <NUM> has the negative electrode connection terminal <NUM>, and hence, a detailed description thereon is omitted.

<FIG> is a cross sectional view schematically showing the essential structure of the terminal in accordance with one embodiment.

As described above, the negative electrode terminal <NUM> includes the negative electrode connection terminal <NUM> and the negative electrode collector terminal <NUM>. The negative electrode connection terminal <NUM> includes a first member <NUM> and a second member <NUM>.

The negative electrode collector terminal <NUM> is connected with the part present inside the battery case <NUM> in the second member <NUM> of the negative electrode connection terminal <NUM> by crimping, welding, or the like. In the present embodiment, as described later, the negative electrode collector terminal <NUM> and the negative electrode connection terminal <NUM> are connected with each other by the crimped structure formed between the negative electrode collector terminal <NUM> and a leg part <NUM> of the second member <NUM> of the negative electrode connection terminal <NUM>, thereby forming the negative electrode terminal <NUM> in accordance with the present embodiment (see <FIG>).

For the negative electrode collector terminal <NUM> to be connected with the negative electrode collector 22A, preferably, the same kind of metal as that of the negative electrode collector 22A is used, and for example, copper is used. For the second member <NUM> of the negative electrode connection terminal <NUM> to be connected with the negative electrode collector terminal <NUM>, preferably, the same kind of metal as that of the negative electrode collector terminal <NUM> is used, and for example, copper is used. On the other hand, in the present embodiment, the first member <NUM> of the negative electrode connection terminal <NUM> is made of aluminum.

As shown in <FIG>, the negative electrode connection terminal <NUM> is inserted through the through hole <NUM> formed in the lid body <NUM>, and the lid body <NUM> and the negative electrode connection terminal <NUM> are insulated therebetween by a gasket <NUM>.

The gasket <NUM> is formed of a material having insulation property. For example, a fluorine resin such as perfluoroalkoxy alkane (PFA) is used.

Further, as shown, the negative electrode collector terminal <NUM> is insulated by an insulator <NUM>. The insulator <NUM> is formed of a material having an insulation property. For example, a resin material such as polyphenylene sulfide resin (PPS) is used.

The negative electrode connection terminal <NUM> reflects the terminal structure herein disclosed, and includes the first member <NUM> and the second member <NUM> each made of a metal. The first member <NUM> is formed in a sheet shape, and the second member <NUM> has a crimped part 58C opposed to the first member <NUM>. Herein, at one surface of the first member <NUM>, the crimped part 58C of the second member <NUM> is crimped with the first member <NUM> not via any through hole, and the first member <NUM> and the second member <NUM> have metal junction surfaces mutually metal joined to opposing surfaces <NUM>. A surface <NUM> of the first member <NUM> opposite to the opposing surface thereof is connected with the outside by, for example, being at least partially welded with the bus bar <NUM>.

The shapes of the first member <NUM> and the second member <NUM> have no particular restriction unless the effects of the present disclosure are impaired. Although not limited thereto, the first member <NUM> is in a sheet shape, and has a concave part 56R in which the crimped part 58C of the second member <NUM> is fitted. Although not limited thereto, the second member <NUM> has, for example, the crimped part 58C to be crimped with the first member <NUM>, and a shaft part <NUM> to be inserted though the through hole <NUM> of the lid body <NUM>. The second member <NUM> may have the leg part <NUM> to be connected with the negative electrode collector terminal <NUM> by welding or the like, and, to be fixed to the lid body <NUM> by crimping or the like. Namely, as shown in <FIG>, the negative electrode connection terminal <NUM> in accordance with the present embodiment is fixed by crimping the leg part <NUM> of the second member <NUM> which has passed through the through hole <NUM> of the lid body <NUM> inside the battery case <NUM> to the periphery of the crimping through hole <NUM> provided in the opposing negative electrode collector terminal <NUM>.

The shapes of the crimped part 58C of the second member <NUM> and the concave part 56R of the first member <NUM>, and the like have no particular restriction so long as the first member <NUM> and the second member <NUM> are crimped and joined with each other with a sufficient strength.

As shown in <FIG>, the crimped part 58C of the second member <NUM> may be provided in a convex shape at the surface of the shaft part <NUM> opposed to the first member <NUM>. As shown in <FIG>, the crimped part 58C of the second member <NUM> may be provided in a flange shape at the surface of the shaft part <NUM> opposed to the first member <NUM>.

Joining between the first member <NUM> and the second member <NUM> is performed by ultrasonic joining. However, the method for joining the first member <NUM> and the second member <NUM> by metal joining is not limited to ultrasonic joining, and may also be performed by, for example, diffusion joining, frictional pressure contact or laser welding.

For the negative electrode connection terminal <NUM> herein disclosed, as described above, the crimped part 58C of the second member <NUM> is crimped with the first member <NUM>, and hence the junction strength between both the members is favorable, and joining is performed by metal joining, thereby ensuring a favorable conduction.

The junction strength between the members is ensured by the crimping. For this reason, metal joining between the first member <NUM> and the second member <NUM> may be performed within a small region on the opposing surfaces of the first member <NUM> and the second member <NUM>.

Although not limited thereto, the area of the surface at which the first member <NUM> and the second member <NUM> are metal joined is preferably <NUM>% or less, and more preferably, for example, <NUM>% or less of the area of each opposing surface of the first member <NUM> and the second member <NUM>. Such an area may be a still narrower area, and may be, for example, <NUM>% or less, and <NUM>% or less so long as the effects of the present disclosure are produced. Further, as shown in <FIG>, the first member <NUM> may have a concave part 56R2 at a surface <NUM> opposed to the surface <NUM> opposed to the second member <NUM>, and the metal junction surface may be formed inside the region corresponding to the opening of the concave part 56R2. Herein, the wording "the area of each opposing surface of the first member <NUM> and the second member <NUM>" represents the area of the surface formed when each opposing surface <NUM> of the first member <NUM> and the second member <NUM> is projected onto the surface horizontal with the surface <NUM>.

Even when metal joining is attained only in such a narrow region, previous crimping between the first member <NUM> and the second member <NUM> results in a favorable junction strength between the members. Further, the effect exerted by the metal joining on the first member surface is small. As a result, the flatness of the surface of the first member to be connected with an external connection component is kept, which eliminates the necessity of a post treatment for flattening.

Further, metal joining between the first member <NUM> and the second member <NUM> can be performed with a weak joining energy so as to suppress the surface roughness of the surface of the first member <NUM> opposite to the surface thereof opposed to the second member <NUM>. For example, the arithmetic average roughness Sa of the surface after metal joining is preferably <NUM> or less, more preferably <NUM> or less, and further preferably, for example, <NUM> or less.

Thus, the surface opposite to the opposing surfaces of the first member <NUM> and the second member <NUM> is flat. As a result, without performing a post treatment such as flattening, the negative electrode connection terminal <NUM> is favorably connected with an external connection component such as a bus bar.

In the present embodiment, the bus bar <NUM> to be connected with the negative electrode connection terminal <NUM> is formed of aluminum or an alloy mainly containing aluminum. Therefore, in the present embodiment, the first member <NUM> made of aluminum and the metal species forming the bus bar are matched with each other. This can improve the conduction and the junction strength between the negative electrode terminal and the bus bar.

As described above, in the present embodiment, the first member <NUM> and the second member <NUM> have metal junction surfaces formed by ultrasonic joining.

The first member <NUM> and the second member <NUM> having such junction surfaces can be confirmed by causing rupture at the interface between the first member <NUM> and the second member <NUM>, and observing the ruptured surface. <FIG> is a SEM image of the surface resulting from rupture of the first member <NUM> formed of aluminum and the second member <NUM> formed of copper. The arrow in the drawing indicates the adhesion of the first member <NUM> formed of aluminum on the second member <NUM> formed of copper. When at least one ruptured surface of the first member <NUM> and the second member <NUM>, adhesion of the other metal can be thus observed, it can be confirmed that there has been the joined surface.

The secondary battery <NUM> having the terminal herein disclosed (in the present embodiment, a negative electrode terminal) can be brought into favorable conduction with an external connection component such as the bus bar <NUM>. Further, with an assembled battery <NUM> using the secondary battery <NUM> as a single cell, the bus bar <NUM> is formed of the same metal as the metal species forming the first member <NUM> of the terminal herein disclosed (particularly, a connection terminal). This can establish a better conduction between single cells <NUM>.

Below, a method for manufacturing the terminal herein disclosed, and a method for manufacturing a secondary battery having the terminal will be described again.

Incidentally, below, the manufacturing method will be described by taking a method for manufacturing a negative electrode terminal having the terminal herein disclosed as an example. For the method for manufacturing a positive electrode terminal having the terminal herein disclosed, manufacturing can be performed by the same method as that for the case of a negative electrode terminal having the terminal, and hence a description thereon is omitted.

<FIG> is a flowchart of a method for manufacturing a terminal.

First, the first member <NUM> and the second member <NUM> forming the terminal are prepared (S1).

Then, the first member <NUM> and the second member <NUM> are crimped via the crimped part 58C and the concave part 56R (S2). Crimping can be performed by, for example, fixing any one of the first member <NUM> and the second member <NUM>, and pressurizing the other against one. This operation deforms and press-fits one member of the first member <NUM> and the second member <NUM> with respect to the other member. As a result, the crimped part 58C and the concave part 56R can be fixed.

Then, the opposing surfaces of the first member <NUM> and the second member <NUM> are at least partially metal joined to each other (S3).

The metal joining between the first member <NUM> and the second member <NUM> is performed by ultrasonic joining as described above. Ultrasonic joining is preferably performed by, for example, sandwiching the first member <NUM> and the second member <NUM> by a horn and an anvil, and applying an ultrasonic wave vibration thereto while pressing the first member <NUM> and the shaft part <NUM> of the second member <NUM>.

For example, the conditions for the ultrasonic wave vibration to be applied via the horn can be appropriately set according to the metal species and the dimensions of the first member <NUM> and the second member <NUM>, the shape of the horn, and the like. Although not limited thereto, for example, the amplitude can be set at about <NUM> to <NUM>; the frequency, at about <NUM> to <NUM>; and the energy amount to be given to the first member <NUM> and the second member <NUM>, at about <NUM> to <NUM> J.

Incidentally, not limited to the present embodiment, the method for joining the first member <NUM> and the second member <NUM> by metal joining may be performed by, for example, diffusion joining, frictional pressure contact, or laser welding.

Herein, although the step of metal joining the first member <NUM> and the second member <NUM> (S3) is carried out so that the metal junction surface may have an area of <NUM>% or less of the area of each normal opposing surface of the first member <NUM> and the second member <NUM> as described above, there is no particular restriction thereon. Such an area may be, for example, the region having an area exceeding <NUM>% of the area of the each opposing surface (e.g., <NUM>% to <NUM>% of the total area). The step may be carried out so that such an area may become a still narrower area, and may be carried out so that such an area may become <NUM>% or less or <NUM>% or less.

The first member <NUM> and the second member <NUM> have been previously crimped. As a result, the junction strength between the members is ensured. For this reason, even when the region for metal joining is narrowed, the junction strength and the conduction between the members can be both attained. By narrowing the region for metal joining, it is also possible to suppress the region to be roughened of the surface to be connected with an external connection component. The terminal manufactured with this method eliminates the necessity of a post treatment such as flattening of the surface to be connected with an external connection component, and is also preferable from the viewpoint of the productivity.

Claim 1:
A terminal (<NUM>) forming any of a positive electrode and a negative electrode of a secondary battery (<NUM>), the terminal (<NUM>) comprising:
a first member (<NUM>) and a second member (<NUM>) each made of a metal,
the first member (<NUM>) and the second member (<NUM>) being formed of mutually different metals,
the first member (<NUM>) being formed in a sheet shape and having a concave part (56R), and
the second member (<NUM>) having a crimped part (58C) and a shaft part (<NUM>),
wherein:
the crimped part (58C) of the second member (<NUM>) is provided in a convex shape or a flange shape at a surface of the shaft part (<NUM>) opposed to the first member (<NUM>), fitted into the concave part (56R) of the first member (<NUM>) and crimped with the first member (<NUM>) at one surface of the first member (<NUM>) not via a through hole, and
the first member (<NUM>) and the second member (<NUM>) have metal junction surfaces metal-joined to each other at opposing surfaces thereof after the first member (<NUM>) and the second member (<NUM>) have been previously crimped, wherein the metal joining is performed by ultrasonic joining, diffusion joining, frictional pressure contact, or laser welding.