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 the lithium ion secondary battery are formed of different materials. When a bus bar including the same kind of material as that for one electrode terminal is used for connection between single cells, the conduction and the junction strength between one electrode terminal and the bus bar become relatively lower than those between the other electrode terminal and the bus bar.

In order to establish a conduction between the electrode terminal and the bus bar, Japanese Patent Application <CIT> discloses a technology of forming an electrode terminal using a cladding material matched to the metal species forming the bus bar and the collector terminal. Further, Japanese Patent Application <CIT> discloses a technology of joining connection terminals including different kinds of metals by ultrasonic welding, followed by crimping, thereby improving the conduction and the junction strength between the components. From <CIT>, an energy storage device is known includes: a terminal portion; a current collector; and a connecting portion which connects the terminal portion and the current collector, wherein the terminal portion includes a cylindrical portion which is bottomed at one end side and is open at another end side, wherein the connecting portion is inserted into and connected to the cylindrical portion, wherein, on an outer surface of the connecting portion, a concave portion of the connecting portion or a convex portion of the connecting portion is formed, and wherein, on an inner surface of the cylindrical portion, a convex portion on the inner surface of the cylindrical portion or a concave portion on the inner surface of the cylindrical portion, which is engaged with the concave portion of the connecting portion or the convex portion of the connecting portion, is formed. <CIT> furthermore discloses an electric storage device including a first conductive member having a head bulging from an inserted part inserted through a partition wall, and a second conductive member that is formed using a metal material different from a material of the first conductive member and is fixed to the head of the first conductive member by friction stir welding.

Incidentally, the electrode terminal formed using the cladding material as described in Japanese Patent Application <CIT> is generally high in manufacturing cost. Further, as described in Japanese Patent Application <CIT>, by the method in which the connection terminals are joined therebetween by ultrasonic welding, followed by crimping, the components may be deformed by the crimping. The technology for joining different kinds of metals to the electrode terminal has been required to be developed so as to reduce the cost, and to have a sufficient junction strength.

The present disclosure has been made in view of such points. It is an object of the present disclosure to provide a method for manufacturing an electrode terminal formed of different kinds of metals excellent in junction strength. In addition, it is another main object of the present disclosure to provide a terminal manufactured by such a method, and a battery using the terminal.

The present inventors found the following. When an electrode terminal formed of two kinds of metals is manufactured by joining with ultrasonic joining, one metal is drawn to and is brought into pressure contact with the other metal due to the pressure and the vibration applied to the two kinds of metals, resulting in the formation of the crimped structure.

It has been found that the connection terminal manufactured by such a method attains favorable conduction due to metal joining between two kinds of metals, and moreover due to a crimped structure thereof, whereby joining is established with a sufficient strength between a first member and a second member.

The method for manufacturing a terminal herein disclosed is a method for manufacturing a terminal forming any of a positive electrode and a negative electrode of a secondary battery. The method is defined in claim <NUM> and includes the following steps of:.

With such a manufacturing method, it is possible to manufacture a terminal including a connection terminal in which the first member and the second member are subjected to ultrasonic joining therebetween, thereby establishing a favorable conduction therebetween, and have a crimped structure, so that the first member and the second member are joined with each other with a sufficient strength.

In the method, the first member and the second member are formed of mutually different metals.

With such a manufacturing method, it is possible to manufacture a terminal with favorable junction strength and conduction even though different metal species are included therein.

In one embodiment, 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.

With such a manufacturing method, it is possible to manufacture a terminal to be brought into favorable conduction with the bus bar including aluminum or an alloy mainly containing aluminum.

As another aspect of the technology herein disclosed, a terminal forming any of the positive electrode and the negative electrode of the secondary battery according to claim is provided. The terminal being manufactured by the method as set forth above and includes a first member being formed in a sheet shape and having a concave part at one surface thereof and a second member having a flange part to be accommodated in the concave part of the first member. Herein, the first member and the flange part of the second member are at least partially joined with each other by metal joining with ultrasonic joining thereby extending the flange part and bringing a part of the extended flange part into pressure contact with an inner wall surface of the concave part, whereby an end of the flange part is crimped with an inner wall surface of the concave part not via a through hole.

For the terminal having such a configuration, the first member and the second member are subjected to ultrasonic wave joining, thereby establishing a favorable conduction therebetween, and have a crimped structure, thereby joining the first member and the second member therebetween with a sufficient strength.

In the terminal, the first member and the second member are formed of mutually different metals.

With such a configuration, even the terminal including different metal species can ensure the junction strength and the conduction.

In one preferable embodiment, the metal joining is caused at a position closer to a center of the flange part than to a part that has been crimped.

With such a configuration, the foregoing effects can be exerted better.

An interface of the metal joining present between the first member and the second member has a joint surface caused by ultrasonic joining.

With such a configuration, it is possible to establish a favorable conduction between the first member and the second member.

With such a configuration, the electrode terminal including the terminal and external connection components such as the bus bar including aluminum or an alloy mainly containing aluminum can be brought into favorable conduction with each other.

As a furthermore 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 in the inside thereof 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. At least one of the positive electrode terminal and the negative electrode terminal includes the terminal herein disclosed.

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

In a still other embodiment, for the respective plurality of single cells, a positive electrode terminal of one single cell is electrically connected with a negative electrode terminal of another single cell 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, the assembled battery in which single cells are favorably connected one another can be provided.

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 one embodiment of 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 secondary battery using a terminal in accordance with one embodiment.

A secondary battery <NUM> is a secondary battery capable of being repeatedly charged and discharged, and is, for example, a lithium ion secondary battery. A detailed description on the structure is omitted. The secondary battery <NUM> herein disclosed includes an electrode body having a structure in which a positive electrode and a negative electrode are stacked one on another via a separator 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.

The battery case <NUM> includes a positive electrode terminal <NUM> and a negative electrode terminal <NUM> to be electrically connected with the electrode body in the inside of the battery case, and to be connected with external connection components via a bus bar or the like. At least one of the positive electrode terminal <NUM> and the negative electrode terminal <NUM> has a connection terminal corresponding to the electrode terminal of a positive electrode connection terminal <NUM> and a negative electrode connection terminal <NUM>.

Incidentally, the shape of the positive electrode terminal <NUM> and the negative electrode terminal <NUM> exposed to the outside of the battery case has no particular restriction, and may be a rectangular shape as shown, and may be, for example, 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 disposed at the top of each single cell <NUM>. At least one of the positive electrode terminal <NUM> and the negative electrode terminal <NUM> has a connection terminal corresponding to the electrode terminal of the positive electrode connection terminal <NUM> and the negative electrode connection terminal <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>.

<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 secondary battery <NUM> includes an electrode body <NUM>, a battery case <NUM>, a positive electrode terminal <NUM>, and a negative electrode terminal <NUM>. Below, respective structures will be described.

The electrode body <NUM> 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. The electrode body <NUM> includes a long sheet-shaped positive electrode <NUM>, a long sheet-shaped negative electrode <NUM>, and long sheet-shaped separators <NUM> and <NUM>. Such an electrode body <NUM> is a wound electrode body including the foregoing long sheet-shaped members wound in a stacked manner.

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 one surface or 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.

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

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

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, or the like is used. As the separators <NUM> and <NUM>, those usable for a conventional common lithium ion secondary battery can be used without particular restriction, and not characterize the present disclosure, and hence will not be described in detail.

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.

In one embodiment, the positive electrode terminal <NUM> includes a positive electrode connection terminal <NUM> and a positive electrode collector terminal <NUM>. The positive electrode connection terminal <NUM> is partially exposed to the outside of the battery case <NUM> as shown in <FIG>, and is partially connected with the positive electrode collector terminal <NUM> in the inside of the battery case <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.

In one embodiment, the negative electrode terminal <NUM> includes a negative electrode connection terminal <NUM> and a negative electrode collector terminal <NUM>. The negative electrode connection terminal <NUM> is partially exposed to the outside of the battery case <NUM> as shown in <FIG>, and is partially connected with the negative electrode collector terminal <NUM> in the inside of the battery case <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.

At least one of the positive electrode terminal <NUM> and the negative electrode terminal <NUM> has a connection terminal corresponding to the electrode terminal of the positive electrode connection terminal <NUM> and the negative electrode connection terminal <NUM>. Below, based on the configuration in the case where the negative electrode terminal <NUM> has the negative electrode connection terminal <NUM>, a detailed description will be given with reference to <FIG>. The configuration when the positive electrode terminal <NUM> has the positive electrode connection terminal <NUM> is the same as the configuration when the negative electrode terminal <NUM> has the negative electrode connection terminal <NUM>, and hence will not be described in detail.

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

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 second member <NUM> by welding or the like. For the negative electrode collector terminal <NUM> to be connected with the negative electrode collector 22A, preferably, the same kind of metal as the negative electrode collector 22A is used, and for example, copper is used. As the second member <NUM> to be connected with the negative electrode collector terminal <NUM>, preferably, the same kind of metal as the negative electrode collector terminal <NUM> is used, and for example, copper is used.

As shown in <FIG>, the negative electrode connection terminal <NUM> is inserted into a lid body <NUM> having a through hole, 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.

A method for manufacturing the foregoing terminal, and a method for manufacturing a secondary battery having the terminal will be described. Below, a description will be given by taking a method for manufacturing a negative electrode terminal as an example. The method for manufacturing a positive electrode terminal is the same as the method for manufacturing a negative electrode terminal, and hence will not be described.

<FIG> is a flowchart of a method for manufacturing a secondary battery including a terminal in accordance with one embodiment.

With such a manufacturing method, first, the first member <NUM> and the second member <NUM> each made of a metal forming the connection terminal are prepared (S1).

The first member <NUM> is formed in a sheet shape, and has a concave part 56R in which a part of the second member <NUM> is fitted at one surface thereof. The second member <NUM> has a flange part 58F to be fitted with the concave part 56R of the first member <NUM>. The second member <NUM> further has a shaft part <NUM> to be inserted into the through hole of the lid body <NUM>. The second member <NUM> can have a leg part <NUM> for being connected with the negative electrode collector terminal <NUM> by welding or the like, and being fixed to the lid body <NUM> by crimping or the like. A flange part 58F in a shape spreading in a flange form from the shaft part <NUM> outward as shown in <FIG> is disposed at the end on the side of the shaft part <NUM> opposed to the concave part 56R.

The dimensions of the concave part 56R of the first member <NUM> and the flange part 58F of the second member <NUM> are appropriately set according to the metal species to be used, and the like. The dimensions have no particular restriction unless the effects of the present disclosure are impaired. For example, when the first member <NUM> is formed of aluminum, and the second member <NUM> is formed of copper, from the viewpoint of ease for bringing the two members into pressure contact in a later step, the gap between the concave part 56R and the flange part 58F formed when the flange part 58F is fitted to the concave part 56R is preferably <NUM> or less at the maximum. The gap is more preferably <NUM> or less, and further preferably <NUM> or less. From the viewpoint of ease of fitting, the gap is preferably <NUM> or more.

From the viewpoint of ease for bringing the two members into pressure contact in a later step, DR is more than <NUM> x TF, preferably more than <NUM> x TF, and more preferably more than <NUM> x TF where DR represents the depth of the concave part 56R, and TF represents the thickness of the flange part 58F. Further, DR is preferably smaller than <NUM> x TF, and more preferably smaller than <NUM> x TF.

The shape of the concave part 56R of the first member <NUM> has no particular restriction so long as the flange part 58F of the second member <NUM> is fitted thereto. For example, as shown in <FIG>, by providing a groove for allowing the end of the flange part 58F to be press-fitted thereinto at the inner wall of the concave part 56R, it is possible to join the first member <NUM> and the second member <NUM> more strongly.

Examples of the shape of the groove may include a rectangular shape in cross section as shown in, for example, <FIG>, and such a shape as to spread with approach toward the bottom surface at the side surface of the concave part.

The first member <NUM> and the second member <NUM> are formed of mutually different metals. In that case, it is preferable from the viewpoint of ensuring the conduction that the first member <NUM> and the bus bar <NUM> are formed of the same metal, and that the second member <NUM> and the negative electrode collector 22A are formed of the same metal.

For example, when the bus bar <NUM> to be connected with the negative electrode connection terminal <NUM> is formed of aluminum or an alloy mainly containing aluminum, and the negative electrode collector terminal <NUM> is formed of copper or an alloy mainly containing copper, preferably, the first member <NUM> is formed of aluminum or an alloy mainly containing aluminum, and the second member <NUM> is formed of copper or an alloy mainly containing copper.

By thus selecting the metal species of the first member <NUM> and the second member <NUM> according to the metal species of the bus bar and the collector terminal, it is possible to improve the conduction and the junction strength of external connection components such as the negative electrode terminal and the bus bar.

Then, the first member <NUM> and the second member <NUM> are fitted (S2), and the first member <NUM> and the second member <NUM> are fixed to each other by ultrasonic pressure contact (S3).

As shown in <FIG>, the flange part 58F of the second member <NUM> is fitted to the concave part 56R of the first member <NUM>, and is sandwiched by a horn <NUM> and an anvil <NUM> (S2). The shape and the like of the horn <NUM> and the anvil <NUM> have no restriction so long as the effects of the present disclosure are produced.

In one embodiment, the anvil <NUM> at which the second member <NUM> is arranged has such a concave as to allow the shaft part <NUM> of the second member <NUM> to be inserted therethrough, and as to allow the flange part 58F to be arranged therein. The horn <NUM> to be put from the top surface of the first member <NUM> has such a shape as to be able to apply a pressure with an area similar to the area of each opposing surface of the concave part 56R and the flange part 58F. The shape of the horn <NUM> is not limited thereto, and can be appropriately selected according to the shapes of the first member <NUM> and the second member <NUM>. Examples of the shape of the horn <NUM> are not limited to, but may include a cylindrical shape or such a shape that a plurality of pressurizing parts are arranged equally in the circumferential direction so as to be able to pressurize the surface of the first member <NUM> top surface supported by the anvil <NUM> via the flange part 58F.

The horn <NUM> is mounted at a press including a vibration generator (not shown). The vibration generator is a device for applying a prescribed vibration required for ultrasonic welding to the horn <NUM>. In order to extend the flange part 58F with efficiency, the horn <NUM> and the anvil <NUM> are preferably arranged so that the end of the flange part 58F is applied with a vibration due to an ultrasonic wave.

The first member <NUM> and the second member <NUM> sandwiched by the horn <NUM> and the anvil <NUM> as described above is subjected to ultrasonic pressure contact, thereby fixing the first member <NUM> and the second member <NUM> (S3).

The first member <NUM> and the second member <NUM> are applied with a pressure by a press. The pressure herein applied can be appropriately set according to the metal species and the dimensions of the first member <NUM> and the second member <NUM>, and the shape of the horn <NUM>, and the like. Although not limited thereto, the pressure to be applied to the first member <NUM> and the second member <NUM> can be set at, for example, about <NUM> to <NUM> N.

Then, with the first member <NUM> and the second member <NUM> applied with a pressure, an ultrasonic wave vibration is applied thereto via the horn <NUM>. As shown in <FIG>, before the first member <NUM> and the second member <NUM> are applied with an ultrasonic wave vibration, there is a gap between the inner wall surface of the concave part 56R and the end of the flange part 58F. By applying a vibration as shown in <FIG>, the flange part 58F is extended with respect to the inner wall surface of the concave part 56R. As a result, as shown in <FIG>, a part of the extended flange part 58F is brought into pressure contact with the inner wall surface of the concave part 56R, so that the first member <NUM> and the second member <NUM> are fixed to each other.

A metal joining can be formed at least a part of the opposing surfaces of the flange part 58F and the concave part 56R pressed against each other by being sandwiched by the horn <NUM> and the anvil <NUM>.

The conditions for ultrasonic wave vibration herein applied via the horn <NUM> 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 <NUM>, 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 applied to the first member <NUM> and the second member <NUM>, at about <NUM> to <NUM> J.

By the manufacturing method described up to this point, it is possible to manufacture a terminal including the negative electrode connection terminal <NUM> herein disclosed as a constituent element.

Using the negative electrode connection terminal <NUM> manufactured through the foregoing steps, a battery assembly can be constructed (S4).

In this step, first, the electrode body <NUM>, the nonaqueous electrolyte, the battery case <NUM>, the positive electrode terminal <NUM>, the negative electrode collector terminal <NUM>, and the negative electrode connection terminal <NUM> are prepared. The battery case <NUM> includes a battery case main body <NUM> having an opening, and a lid body <NUM> having a liquid introduction port for introducing a nonaqueous electrolyte. The lid body <NUM> has through holes for allowing the positive electrode terminal <NUM> and the negative electrode connection terminal <NUM> to be inserted therethrough, respectively.

Then, the electrode body <NUM> is accommodated in the battery case <NUM>.

The positive electrode terminal <NUM> is inserted through one through hole of the lid body <NUM> for mounting. The negative electrode connection terminal <NUM> is inserted through the other through hole of the lid body <NUM>, and is connected with the negative electrode collector terminal <NUM>, thereby mounting the negative electrode terminal <NUM> at the lid body <NUM>. The negative electrode connection terminal <NUM> and the negative electrode collector terminal <NUM> are connected with each other by a known method. Although not limited thereto, the connection between the negative electrode connection terminal <NUM> and the negative electrode collector terminal <NUM> may be established by crimping as shown in <FIG>.

The positive electrode terminal <NUM> and the negative electrode collector terminal <NUM> are welded to the positive electrode collector exposed part 21C and the negative electrode collector exposed part 22C exposed at the end of the electrode body <NUM>, respectively. Then, the electrode body <NUM> is accommodated through the opening into the inside of the main body of the battery case <NUM>, so that the main body of the battery case <NUM> and the lid body <NUM> are welded.

Subsequently, a nonaqueous electrolyte is introduced through the introduction port. After introducing the nonaqueous electrolyte, the introduction port is sealed. As a result, a battery assembly can be obtained. The battery assembly is subjected to initial charging processing. As a result, a lithium ion secondary battery can be manufactured.

The negative electrode connection terminal <NUM> manufactured by the manufacturing method herein disclosed has 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 has the concave part 56R at one surface thereof. The second member <NUM> has the flange part 58F to be accommodated in the concave part 56R of the first member <NUM>. The first member <NUM> and the flange part 58F of the second member <NUM> are at least partially joined to each other by metal joining. In addition, the end of the flange part 58F is crimped with the inner wall surface of the concave part 56R not via the through hole.

Herein, the wording "the end of the flange part 58F is crimped with the inner wall surface of the concave part 56R" represents, for example, the following state: the end of the flange part 58F is in pressure contact with the inner wall surface of the concave part 56R; as a result, the first member <NUM> is fixed to the second member <NUM>.

<FIG> is a cross sectional photograph after ultrasonic pressure contact when aluminum is used for the first member <NUM>, and copper is used for the second member <NUM>. The dashed line in the drawing represents the position of the inner wall surface of the concave part 56R before performing ultrasonic pressure contact. It can be observed as follows: the end of the flange part 58F is extended, so that the flange part 58F is press-fitted to the inner wall surface of the concave part 56R.

The metal joining is caused at the opposing surfaces of the concave part 56R and the flange part 58F at the first member <NUM> and the second member <NUM>, and, for example, can be caused at closer to a center of the flange part 58F than to the crimped part.

In the present embodiment, the fact that a metal joining is caused between the first member <NUM> and the second member <NUM> can be confirmed, for example, 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> including aluminum and the second member <NUM> including copper. The arrow in the drawing indicates the adhesion of the first member <NUM> including aluminum on the second member <NUM> including 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 first member <NUM> and the second member <NUM> forming the negative electrode connection terminal <NUM> may be formed of mutually the same kind of metal. When the negative electrode collector 22A and the bus bar <NUM> are formed of mutually different metals, or in other cases, the first member <NUM> and the second member <NUM> are preferably formed of mutually different metals. In that case, it is preferable from the viewpoint of ensuring the conduction that the first member <NUM> and the bus bar <NUM> are formed of the same metal, and that the second member <NUM> and the negative electrode collector 22A are formed of the same metal.

With such a configuration, it is possible to improve the conduction and the junction strength of the negative electrode terminal <NUM> including the negative electrode connection terminal <NUM> and the bus bar <NUM>.

For example, when the bus bar <NUM> to be connected with the negative electrode connection terminal <NUM> is formed of aluminum or an alloy mainly containing aluminum, and the negative electrode collector terminal <NUM> is formed of copper or an alloy mainly containing copper, preferably the first member <NUM> is formed of aluminum or an alloy mainly containing aluminum, and the second member <NUM> is formed of copper or an alloy mainly containing copper.

With such a configuration, it is possible to improve the conduction and the junction strength of the negative electrode terminal <NUM> including the negative electrode connection terminal <NUM>, and the bus bar <NUM> to be connected with the negative electrode terminal <NUM>.

Claim 1:
A method for manufacturing a terminal (<NUM>) forming any of a positive electrode and a negative electrode of a secondary battery (<NUM>), the method comprising the steps of:
preparing a first member (<NUM>) and a second member (<NUM>) each made of a metal and forming the terminal (<NUM>), wherein the first member (<NUM>) and the second member (<NUM>) are formed of mutually different metals,
with the first member (<NUM>) being formed in a sheet shape and having at one surface thereof a concave part (56R) for allowing a part of the second member (<NUM>) to be fitted therein, and with the second member (<NUM>) having a flange part (58F) to be accommodated in the concave part (56R); and
fixing the first member (<NUM>) and the second member (<NUM>) to each other by ultrasonic pressure contact,
with the ultrasonic pressure contact being performed by applying an ultrasonic wave vibration while applying a pressure in a direction of stacking of the first member (<NUM>) and the second member (<NUM>) in a state where the flange part (58F) of the second member (<NUM>) is arranged in the concave part (56R) of the first member (<NUM>), thereby extending the flange part (58F) and bringing a part of the extended flange part (58F) into pressure contact with an inner wall surface of the concave part (56R), thereby forming a crimped structure of the first and second member (<NUM>, <NUM>).