ENERGY STORAGE APPARATUS AND METHOD FOR MANUFACTURING ENERGY STORAGE APPARATUS

In the embodiment, an energy storage apparatus includes: an energy storage device including a metal external terminal; and a metal bus bar that is laminated on the external terminal and welded to the external terminal. A welded portion that welds the bus bar and the external terminal is formed on the bus bar, the welded portion is extended from the bus bar to the external terminal, the external terminal includes a clad material including a first metal layer adjacent to the bus bar and a second metal layer adjacent to the first metal layer, the welded portion welds the bus bar and the first metal layer, and an end of the welded portion does not reach an interface between the first metal layer and the second metal layer.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority to Japanese Patent Application No. 2020-082644, the contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to an energy storage apparatus including an energy storage device having an external terminal and a bus bar, and a method for manufacturing the energy storage apparatus.

BACKGROUND ART

Conventionally, an assembled battery including a plurality of prismatic secondary batteries including external terminals is known (for example, see Patent Document 1). The assembled battery includes a negative electrode terminal, a positive electrode terminal, the external terminal (a negative electrode external terminal or a positive electrode external terminal), and a bus bar connecting between the negative electrode external terminals or between the positive electrode external terminals. In this assembled battery, the external terminal and the bus bar are connected by laser welding. In this assembled battery, the negative electrode terminal is made of a copper material, and the bus bar is made of an aluminum material. The negative electrode external terminal includes a clad region including a copper material portion and an aluminum material portion.

By the way, in order to secure the connection strength between the external terminal and the bus bar, when a welding joining width is secured during the laser welding of the external terminal and the bus bar, a depth of penetration of the external terminal and the bus bar increases. On the other hand, when penetration by welding reaches an interface between different metal layers of the external terminal during the welding of the external terminal having the clad region and the bus bar, bonding strength at this interface (bonding strength between adjacent metal layers) decreases.

PRIOR ART DOCUMENT

Patent Document

SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

An object of an embodiment is to provide an energy storage apparatus including an energy storage device in which an external terminal is formed of a clad material and a bus bar is connected to the external terminal, the energy storage apparatus in which a decrease in bonding strength between metal layers constituting the clad material is prevented, and a method for manufacturing the energy storage apparatus.

Means for Solving the Problems

An energy storage apparatus of the embodiment includes: an energy storage device including a metal external terminal; and a metal bus bar that is laminated on the external terminal and welded to the external terminal. A welded portion that welds the bus bar and the external terminal is formed on the bus bar, the welded portion is extended from the bus bar to the external terminal, the external terminal includes a clad material including a first metal layer adjacent to the bus bar and a second metal layer adjacent to the first metal layer, the welded portion welds the bus bar and the first metal layer, and an end of the welded portion does not reach an interface between the first metal layer and the second metal layer.

In the energy storage apparatus, the welded portion may include a first welded portion and a second welded portion that partially overlap each other.

In the energy storage apparatus, in a section of the external terminal and the bus bar in a laminating direction of the external terminal and the bus bar, a dimension of the welded portion at a boundary position between the external terminal and the bus bar in a direction orthogonal to the laminating direction may be larger than a thickness of the first metal layer.

In the energy storage apparatus, the welded portion when viewed from the laminating direction of the external terminal and the bus bar may have an annular shape having no corner or an arc shape having no corner.

An energy storage apparatus of the embodiment includes: an energy storage device including a metal external terminal; and a bus bar that is formed of a metal containing aluminum, the aluminum being laminated on the external terminal and welded to the external terminal. A welded portion that welds the bus bar and the external terminal is formed on the bus bar, the welded portion is extended from the bus bar to the external terminal, the external terminal includes a positive electrode external terminal and a negative electrode external terminal, the positive electrode external terminal is made of a metal containing aluminum, the negative electrode external terminal includes a clad material including a first metal layer adjacent to the bus bar and a second metal layer adjacent to the first metal layer, the first metal layer is formed of a metal containing aluminum, the second metal layer is formed of a metal containing copper, the welded portion welds the bus bar and the first metal layer, and an end of the welded portion does not reach an interface between the first metal layer and the second metal layer.

A method for manufacturing an energy storage apparatus of the embodiment includes: laminating a metal bus bar on a metal external terminal of an energy storage device; applying heat to the bus bar from a side opposite to the external terminal to weld the bus bar and the external terminal; and forming a welded portion that welds the bus bar and the external terminal to each other on the bus bar. The welded portion is extended from the bus bar to the external terminal, the external terminal includes a clad material including a first metal layer adjacent to the bus bar and a second metal layer adjacent to the first metal layer, the welded portion welds the bus bar and the first metal layer, and an end of the welded portion does not reach an interface between the first metal layer and the second metal layer.

In the method for manufacturing the energy storage apparatus, the welded portion may be formed in an annular shape having no corner or an arc shape having no corner when viewed from a laminating direction of the external terminal and the bus bar.

MODE FOR CARRYING OUT THE INVENTION

An energy storage apparatus of the embodiment includes: an energy storage device including a metal external terminal; and a metal bus bar that is laminated on the external terminal and welded to the external terminal. A welded portion that welds the bus bar and the external terminal is formed on the bus bar, the welded portion is extended from the bus bar to the external terminal, the external terminal includes a clad material including a first metal layer adjacent to the bus bar and a second metal layer adjacent to the first metal layer, the welded portion welds the bus bar and the first metal layer, and an end of the welded portion does not reach an interface between the first metal layer and the second metal layer.

According to the above configuration, the welded portion does not reach the interface between the metal layers constituting the clad material, so that the bonding strength of each metal layer constituting the clad material can be secured.

In the energy storage apparatus, the welded portion may include a first welded portion and a second welded portion that partially overlap each other.

According to the above configuration, the bonding strength between the bus bar and the external terminal can be ensured by ensuring a wide bonding width of the welded portion.

In the energy storage apparatus, in a section of the external terminal and the bus bar in a laminating direction of the external terminal and the bus bar, a dimension in a direction orthogonal to the laminating direction at a boundary position between the external terminal and the bus bar may be larger than a thickness of the first metal layer.

According to the above configuration, because the dimension (dimension in the direction orthogonal to the laminating direction) of the welded portion is secured at the boundary position between the external terminal and the bus bar, the bonding strength between the bus bar and the external terminal can be secured, whereby the bonding strength between the bus bar and the external terminal can be secured while the bonding strength between the metal layers of the clad material is secured.

In the energy storage apparatus, the welded portion when viewed from the laminating direction of the external terminal and the bus bar may have an annular shape having no corner or an arc shape having no corner.

According to the above configuration, since the welded portion has an annular shape or an arc shape without a corner portion, even if a force is applied to the welded portion, the force is less likely to concentrate on a part of the welded portion.

An energy storage apparatus of the embodiment includes: an energy storage device including a metal external terminal; and a bus bar that is formed of a metal containing aluminum, the aluminum being laminated on the external terminal and welded to the external terminal. A welded portion that welds the bus bar and the external terminal is formed on the bus bar, the welded portion is extended from the bus bar to the external terminal, the external terminal includes a positive electrode external terminal and a negative electrode external terminal, the positive electrode external terminal is made of a metal containing aluminum, the negative electrode external terminal includes a clad material including a first metal layer adjacent to the bus bar and a second metal layer adjacent to the first metal layer, the first metal layer is formed of a metal containing aluminum, the second metal layer is formed of a metal containing copper, the welded portion welds the bus bar and the first metal layer, and an end of the welded portion does not reach an interface between the first metal layer and the second metal layer.

According to the above configuration, the welded portion does not reach the interface between the metal layers constituting the clad material, so that the bonding strength of each metal layer constituting the clad material can be secured.

A method for manufacturing an energy storage apparatus of the embodiment includes: laminating a metal bus bar on a metal external terminal of an energy storage device; applying heat to the bus bar from a side opposite to the external terminal to weld the bus bar and the external terminal; and forming a welded portion that welds the bus bar and the external terminal to each other on the bus bar. The welded portion is extended from the bus bar to the external terminal, the external terminal includes a clad material including a first metal layer adjacent to the bus bar and a second metal layer adjacent to the first metal layer, the welded portion welds the bus bar and the first metal layer, and an end of the welded portion does not reach an interface between the first metal layer and the second metal layer.

According to the above configuration, the welded portion does not reach the interface between the metal layers constituting the clad material, the energy storage apparatus in which the bonding strength of each metal layer constituting the clad material is ensured can be manufactured.

In the method for manufacturing the energy storage apparatus, the welded portion may be formed in an annular shape having no corner or an arc shape having no corner when viewed from a laminating direction of the external terminal and the bus bar.

According to the above configuration, when the welding is performed with a general welding width, an annular or arc-shaped welded portion having no corner where force is hardly concentrated on one portion can be formed.

From the above, the energy storage apparatus including the energy storage device in which the external terminal is formed of the clad material and the bus bar is connected to the external terminal, the energy storage apparatus in which the decrease in bonding strength between metal layers constituting the clad material is prevented, and a method for manufacturing the energy storage apparatus can be provided.

Hereinafter, an embodiment of the present invention will be described with reference toFIGS.1to7B. In the embodiment, a chargeable and dischargeable secondary battery will be described as an example of the energy storage device. Names of the constituent members (constituent elements) of the embodiment are those in the embodiment, and are sometimes different from the names of the constituent members (constituent elements) in the background art.

As illustrated inFIG.1, an energy storage apparatus11includes an energy storage device1including a metal external terminal4and a metal bus bar6that is laminated on the external terminal4and welded to the external terminal4. As illustrated inFIG.6B, in the bus bar6of the energy storage apparatus11, a welded portion7that welds the external terminal4and the bus bar6is formed at a joining position between the external terminal4and the bus bar6. The energy storage apparatus11of the embodiment includes a plurality of energy storage devices1(seeFIG.1).

The plurality of energy storage devices1are arranged in a predetermined direction (first direction). For example, the first direction is a direction orthogonal to a laminating direction of the external terminal4and the bus bar6. Each of the plurality of energy storage devices1is a primary battery, a secondary battery, a capacitor, or the like. The energy storage device1of the embodiment is a nonaqueous electrolyte secondary battery that can be charged and discharged. More specifically, the energy storage device1is a lithium ion secondary battery utilizing electron transfer caused by transfer of the lithium ion. The energy storage device1is what is called a prismatic lithium ion secondary battery.

As illustrated inFIGS.2to5, the energy storage device1includes an electrode assembly2including a positive electrode and a negative electrode, a case3accommodating the electrode assembly2, and the external terminal4that is disposed outside the case3and electrically connected to the electrode assembly2. In addition to the electrode assembly2, the case3and the external terminal4, the energy storage device1includes a current collector5that makes the electrode assembly2and the external terminal4conductive with each other.

The electrode assembly2includes a winding core21and a layered product22in which a positive electrode and a negative electrode are insulated from each other and laminated, the layered product22being wound around a winding core21(seeFIG.5). When the lithium ion moves between the positive electrode and the negative electrode in the electrode assembly2, the energy storage device1is charged and discharged.

For example, the positive electrode includes a strip-shaped metal foil and a positive active material layer formed on the metal foil. For example, the negative electrode includes a strip-shaped metal foil and a negative active material layer formed on the metal foil.

In the electrode assembly2of the embodiment, the positive electrode and the negative electrode are wound while being insulated from each other by a separator. That is, in the electrode assembly2of the embodiment, the layered product of the positive electrode, the negative electrode, and the separator is wound. The separator is a member having an insulating property. The separator is disposed between the positive electrode and the negative electrode. Thus, in the electrode assembly2(particularly; the layered product), the positive electrode and the negative electrode are insulated from each other. The separator holds the electrolyte solution in the case3. Thus, during charge-discharge of the energy storage device1, the lithium ion moves between the positive electrode and the negative electrode that are alternately layered with the separator interposed therebetween.

The case3includes a case body31including an opening, and a lid plate32that closes the opening of the case body31. The case3accommodates the electrolyte solution in an internal space33together with the electrode assembly2, the current collector5, and the like. The case3is made of metal having resistance to the electrolyte solution. For example, the case3of the embodiment is formed of aluminum or a metal material containing aluminum such as an aluminum alloy. The case3may be formed of a metal material such as stainless steel and nickel, a composite material obtained by bonding resin such as nylon to aluminum, or the like.

The electrolyte solution is a non-aqueous solution electrolytic solution. The electrolyte solution is obtained by dissolving an electrolyte salt in an organic solvent. Examples of the organic solvent include cyclic carbonate esters such as propylene carbonate and ethylene carbonate, and chain carbonates such as dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. Examples of the electrolyte salt include LiClO4, LiBF4, and LiPF6.

The case3is formed by overlapping and joining an opening peripheral edge of the case body31and a peripheral edge of the lid plate32(seeFIG.4). The case3includes an internal space33defined by the case body31and the lid plate32. In the embodiment, the opening peripheral edge of the case body31and the peripheral edge of the lid plate32are joined by welding.

The case body31includes a closing portion311that has a plate shape and includes an inner surface facing the inside of the case3and an outer surface facing the outside of the case3, and a cylindrical body portion312that is connected to a peripheral edge of the closing portion311, extends to the inner surface side of the closing portion311, and surrounds the inner surface of the closing portion311(seeFIG.2).

The closing portion311is a member positioned at a lower end of the case body31(that is, a bottom wall of the case body31is formed when the opening looks upward) when the case body31is disposed such that the opening looks upward. The closing portion311has a rectangular shape as viewed in a normal direction of the closing portion311. The four corners of the closing portion311have an arc shape.

Hereinafter, as illustrated inFIG.2, a long side direction of the closing portion311is defined as an X-axis direction, a short side direction of the closing portion311is defined as a Y-axis direction, and the normal direction of the closing portion311is defined as a Z-axis direction.

The lid plate32is a plate-like member that closes the opening of the case body31. Specifically, the lid plate32abuts on the case body31so as to close the opening of the case body31. More specifically, the peripheral edge of the lid plate32overlaps with the opening peripheral edge of the case body31such that the lid plate32closes the opening. A boundary portion between the lid plate32and the case body31laminated in this manner is welded. Thus, the case3is configured.

The lid plate32includes a gas release valve321capable of discharging gas in the case3to the outside (seeFIG.3). The gas release valve321discharges the gas from the inside of the case3to the outside when internal pressure of the case3increases to a predetermined pressure.

The external terminal4is a member that is electrically connected to an external terminal of another energy storage device, an external device, or the like. The external terminal4of the embodiment has an outer surface40that is a surface to which the bus bar or the like can be welded. The outer surface40of the embodiment is a flat surface. The external terminal4has a plate shape expanding along the lid plate32. Particularly, a flange of the external terminal4has a rectangular plate shape as viewed in the Z-axis direction.

The external terminal4has a flange that extends along the case3outside the case3, and a shaft that extends from the flange, penetrates the case3, and is electrically connected to the electrode assembly2(seeFIG.4). Furthermore, the external terminal4includes an external terminal (positive electrode external terminal)4aconnected to the positive electrode and an external terminal (negative electrode external terminal)4bconnected to the negative electrode.

In the external terminal4a, a flange401aand a shaft402aare integrated. The external terminal4ais formed of aluminum or a metal material containing aluminum such as an aluminum alloy.

In the external terminal4b, a flange401band a shaft402bare separate bodies (separate members). The flange401band the shaft402bare connected by swaging the shaft402b.

The external terminal4bhas a clad material including a plurality of (two layers in the example of the embodiment) metal layers laminated in the laminating direction (Z-axis direction) of the bus bar6and the external terminal4. Specifically, in the external terminal4b, the flange401bis made of a clad material. The metal layers adjacent to each other in the plurality of metal layers are made of different kinds of metals.

For example, as illustrated inFIG.6B, the plurality of metal layers included in the flange401b(external terminal4b) include a first metal layer41located closest to the bus bar6in the Z-axis direction (that is, adjacent to the bus bar6), and a second metal layer42adjacent to the first metal layer41. The flange401bof the embodiment is configured of the first metal layer41and the second metal layer42. For example, the thickness of the first metal layer41of the embodiment ranges from 0.2 mm to 1.0 mm, and the thickness of the second metal layer42ranges from 0.2 mm to 3.0 mm. The thickness of the first metal layer41and the thickness of the second metal layer42are not limited to these ranges.

For example, the first metal layer41is formed of aluminum or a metal material containing aluminum such as an aluminum alloy. For example, the second metal layer42is formed of a metal material containing copper such as copper or a copper alloy.

The current collector5is disposed in the case3and directly or indirectly connected to the electrode assembly2in a conductive manner (seeFIGS.4and5). The current collector5is formed of a member having conductivity.

The bus bar6connects the different energy storage devices1to each other or connects the energy storage device1to an external input and output terminal or the like in a conductive manner (seeFIG.1). The bus bar6of the embodiment is overlapped on the outer surface40of the external terminal4and welded to the external terminal4(seeFIG.6B). In addition, the bus bar6of the embodiment is made of the same material as the external terminal4a. Furthermore, the bus bar6of the embodiment is made of the same material as the first metal layer41of the external terminal4b. Specifically, the bus bar6is formed of aluminum or a metal material containing aluminum such as an aluminum alloy.

The welded portion7is a member formed by welding the external terminal4b(particularly, the flange401b) and the bus bar6(seeFIGS.6A and6B). The welded portion7is extended from the bus bar6to the external terminal4b, namely, formed between the bus bar6and the external terminal4b. In other words, the welded portion7is formed continuously from the bus bar6to the external terminal4b. The welded portion7of the embodiment is formed by laser welding between the external terminal4band the bus bar6. The welded portion7of the embodiment includes welding tracks710,720that are a mark of a laser irradiation position (specifically, a mark due to a center of the laser irradiation position). The width of the laser beam with which the bus bar6is irradiated in the laser welding of the embodiment is less than or equal to 1.0 mm.

The method for manufacturing the energy storage apparatus11includes a process of forming the welded portion7when the external terminal4band the bus bar6are welded to each other. Specifically, the method for manufacturing the energy storage apparatus11includes: laminating the metal bus bar6on the metal external terminal4bof the energy storage device1; applying heat to the bus bar6from the side opposite to the external terminal4bto weld the bus bar6and the external terminal4bto each other; and forming the welded portion7where the bus bar6and the external terminal4bare welded to each other at the welding position between the external terminal4band the bus bar6, namely, forming the welded portion7between the external terminal4band the bus bar6. In other words, the welded portion7is formed continuously from the bus bar6to the external terminal4b.

In the Z-axis direction, an end70of the welded portion7does not reach an interface43between the first metal layer41and the second metal layer42. Specifically, the end70of the welded portion7exists in the first metal layer41. More specifically, the end70of the welded portion7is located closer onto the side of the bus bar6than the interface43between the first metal layer41and the second metal layer42(seeFIG.6B). That is, in the Z-axis direction, the end70is located in front of the interface43between the first metal layer41and the second metal layer42.

The end70of the welded portion7is an end on the side of the external terminal4bout of both ends of the welded portion7in the Z-axis direction. That is, the end70of the welded portion7becomes a lower end of the welded portion7when the case body31is disposed such that the opening looks upward (that is, when the bus bar6is disposed above the external terminal4b).

The welded portion7of the embodiment includes a first welded portion71and a second welded portion72partially overlapping each other. Specifically, the first welded portion71and the second welded portion72overlap each other at least at a boundary position between the external terminal4band the bus bar6(the outer surface40of the external terminal4b). The first welded portion71includes a first welding track710, and the second welded portion72includes a second welding track720(seeFIG.6A).

In the dimension (width W1) of the welded portion7in the direction along the boundary at the boundary position (particularly, the outer surface40of the flange401bof the external terminal4b) between the external terminal4band the bus bar6in the Z-axis direction, namely, in the section (seeFIG.6B) in the direction crossing the welding tracks710and720, the dimension W1of the welded portion7in the direction orthogonal to the Z-axis direction at the boundary position between the external terminal4band the bus bar6is larger than the thickness T1of the first metal layer41(seeFIG.6B). That is, the width W1of the welded portion7at this boundary position is larger than the thickness T1of the first metal layer41.

Furthermore, the shape of the welded portion7viewed from the Z-axis direction is an annular shape without a corner (for example, an elliptic shape or a circular shape). That is, the welded portion7is formed in an annular shape having no corner when viewed from the Z-axis direction. In the welded portion7of the embodiment, the shape of the first welding track710and the shape of the second welding track720are both annular without corner (in the example ofFIG.6A, whet is called a racetrack type). In the welded portion7of the embodiment, the welding track is formed in a plurality of concentric circles (for example, a double circle shape).

The first welding track710is separated from the second welding track720. Specifically, the first welding track710and the second welding track720are separated from each other in the range where the first welded portion71and the second welded portion72overlap each other at the boundary position between the bus bar6and the external terminal4b. The first welding track710is disposed inside the second welding track720.

In the conventional energy storage apparatus, when the external terminal4band the bus bar6are welded by the laser welding such that the welding track is formed around the bus bar6, as illustrated inFIGS.7A and7B, the depth of the penetration between the external terminal4band the bus bar6is increased in order to increase the width of the welded portion7at the boundary position between the external terminal4band the bus bar6(the upper surface40of the external terminal4b) for the purpose of securing the bonding strength between the external terminal4band the bus bar6. Consequently, in the conventional energy storage apparatus, the end70of the welded portion7reaches the interface43between the first metal layer41and the second metal layer42that constitute the clad material, and sometimes the bonding strength between the metal layers41and42is not secured.

On the other hand, in the energy storage apparatus11of the embodiment, because the end70of the welded portion7is positioned in front of the interface43between the first metal layer41and the second metal layer42(seeFIG.6B), namely, because the welded portion7does not reach the interface43between the first metal layer41and the second metal layer42that constitute the clad material of the external terminal4b, the bonding strength between the metal layers41and42that constitute the clad material is secured. The details are as follows.

In the case where the laser beam having a small spot diameter (less than or equal to 1.0 mm) is used for welding the bus bar6and the external terminal4b, when the width of the welded portion7is small, the welding strength between the external terminal4band the bus bar6cannot be secured. On the other hand, when the penetration depth in the welded portion7is increased in order to secure the welding strength, the end70of the welded portion7reaches the interface between the first metal layer41and the second metal layer42of the external terminal (clad material)4bto generate an alloy of copper and aluminum, so that the strength of the external terminal4b(particularly, the flange401bformed of the clad material) decreases. Therefore, like the method for manufacturing the energy storage apparatus11of the embodiment, the end70of the welded portion7does not reach the interface43between the first metal layer41and the second metal layer42of the clad material (external terminal4b) as a method for welding the external terminal4b(flange401b) and the bus bar6with the laser beam having the small spot diameter so as not to lower the interface strength of the clad material. At this point, the spot diameter of the laser welding in the embodiment is the width of the laser beam focused by the laser beam being narrowed at the focal position. That is, the width of the laser that focuses on the upper surface of the bus bar6is the spot diameter.

For example, specifically, like the energy storage apparatus11of the embodiment, the first welded portion71and the second welded portion72partially overlap with each other to secure the wide bonding width of the welded portion7, so that the bonding strength between the bus bar6and the external terminal4bcan be secured. That is, as compared with the case where the first welded portion71and the second welded portion72are welded while being separated from each other (in the state where the first welded portion71and the second welded portion72do not overlap each other), when the first welded portion71and the second welded portion72partially overlap each other like the energy storage apparatus11of the embodiment, an area (the size of the width W1, seeFIG.6(b)) of the welded portion7is secured, and the sufficient connection strength can be obtained at the connection (welding) member between the bus bar6and the external terminal4b.

In the energy storage apparatus11of the embodiment, the width. W1at the boundary position between the external terminal4bof the welded portion7and the bus bar6is larger than the thickness T1of the first metal layer41, so that the dimension of the welded portion7is sufficiently secured at the boundary position. Consequently, the bonding strength between the bus bar6and the external terminal4bcan be secured. Thus, the bonding strength between the bus bar6and the external terminal4bcan be secured while the bonding strength between the metal layers41and42constituting the clad material is secured.

Like the energy storage apparatus11of this embodiment, when the clad material including the first metal layer41made of aluminum and the second metal layer42made of the copper is made to constitute the external terminal4b(particularly, the flange401b), the electric resistance of the external terminal4bcan be restrained by making the width W1of the welded portion7at the boundary position between the bus bar6and the external terminal4blarger than the thickness T1of the first metal layer41. That is, when the width W1at the boundary position of the welded portion7is made larger than the thickness T1of the first metal layer41while the end70of the welded portion7does not reach the interface43between the first metal layer41and the second metal layer42, the layer of aluminum (first metal layer41) having electrical conductivity higher than that of copper is thinned while the welding strength between the external terminal4band the bus bar6is sufficiently secured, so that the electric resistance of the entire external terminal4bcan be restrained.

In the energy storage apparatus11of the embodiment, the bus bar6and the external terminal4bare cut at the position where the bus bar6and the external terminal4bcross the welded portion7(welding tracks710,720), and the section (the section along the laminating direction) of the bus bar6and the external terminal4bis etched, so that the penetration depth (the position of the end70in the Z-axis direction), the shape, the width W1, and the like of the welded portion7can be checked because a corrosion speed is different between the welded portion7and other portions.

Furthermore, in the energy storage apparatus11of the embodiment, because the welded portion7has the annular shape without the corner, force is hardly concentrated on a portion of the welded portion7even when the force is applied to the welded portion7. In other words, the welded portion7has the annular shape without the corner, so that stress concentration in the welded portion7can be restrained.

In the method for manufacturing the energy storage apparatus11described above, the welded portion7does not reach the interface between the metal layers41,42that constitute the clad material of the external terminal4b, so that the energy storage apparatus11in which the bonding strength between the metal layers41,42constituting the clad material is secured can be manufactured.

In the method for manufacturing the energy storage apparatus11of the embodiment, when the welding is performed with a general welding width, the annular welded portion7having no corner where the force is hardly concentrated on one portion can be formed.

In the energy storage apparatus11of the embodiment, the energy storage devices1are arranged in the direction orthogonal to the laminating direction of the external terminals4band the bus bars6. Thus, the laminated portion between the external terminal4band the bus bar6in each energy storage device1is not hidden by another energy storage device, so that the welding between the external terminal4band the bus bar6can be easily performed. In addition, the laminated portion of the external terminal4band the bus bar6is not hidden by another energy storage device, so that alignment of the bus bar6and the external terminal4bbefore the welding is easy to perform.

It is needless to say that the energy storage apparatus and the method for manufacturing the energy storage apparatus of the present invention are not limited to the above-mentioned embodiment, and various modifications can be made without departing from the gist of the present invention. For example, the configuration of another embodiment can be added to the configuration of one embodiment, and a part of the configuration of one embodiment can be replaced with the configuration of another embodiment. Furthermore, a part of the configuration of an embodiment can be deleted.

In the embodiment, the welded portion7viewed from the Z-axis direction has the shape without the corner, but may be a shape with the corner (for example, a polygonal shape having the corner, a linear shape, and a polygonal line shape).

The welded portion7viewed from the Z-axis direction preferably has the shape without the corner, and may be an arc shape without the corner. Even in this case, because the welded portion7has the shape without the corner, the force does not concentrate on a part of the welded portion7even when the force is applied to the welded portion7. When the welded portion7has the arc shape, the arc shape having a length greater than or equal to a semicircle is more preferable from the viewpoint of ensuring the bonding strength between the external terminal4bconstituting the clad material and the bus bar6.

Furthermore, the shape of the welded portion7viewed from the Z-axis direction may be a spiral shape without a corner or the like. The shape of the welded portion7as viewed from the Z-axis direction may be a curved shape or the like.

Although the welded portion7includes the first welding track710and the second welding track720as two welding tracks, the welded portion7may include one welding track or at least three welding tracks. When the welded portion7includes the plurality of welding tracks, the plurality of welding tracks may be separated from each other or partially overlap each other. When the plurality of welding tracks overlap each other in the welded portion7, the output of the welding may be limited (adjusted) such that the end70of the welded portion7does not reach the interface43between the metal layers41,42.

The dimension (dimension of the width W1) of the welded portion7at the boundary position between the external terminal4band the bus bar6in the Z-axis direction (the outer surface40of the external terminal4) in the direction along this boundary is larger than the thickness T1of the first metal layer41, but may be the same as the thickness T1of the first metal layer41or be smaller than the thickness T1of the first metal layer41.

In the embodiment, the flange (clad material)401bof the external terminal4bis constituted of two metal layers, but may be constituted of a plurality of metal layers of at least three layers. Also in this case, the end70of the welded portion7is positioned closer to the bus bar6than the interface between the first metal layer41adjacent to the bus bar6and the second metal layer42adjacent to the first metal layer41in the flange (clad material)401bof the external terminal4b, so that the configuration in which the welded portion7does not reach the interface43between the metal layers41,42constituting the clad material can be implemented.

Furthermore, in the embodiment, the energy storage apparatus11includes the plurality of energy storage devices1. However, the energy storage apparatus11may include one energy storage device1.

In the embodiment, the case where the energy storage device is used as the nonaqueous electrolyte secondary battery (for example, the lithium ion secondary battery) that can be charged and discharged has been described. However, the type and the size (capacity) of the energy storage device are arbitrary. In the embodiment, the lithium ion secondary battery has been described as an example of the energy storage device, but the present invention is not limited thereto. For example, the present invention is also applicable to various secondary batteries, primary batteries, and energy storage devices of capacitors such as an electric double layer capacitor.

In order to express the present invention, the present invention has been appropriately and sufficiently described above through the embodiment with reference to the drawings, but it should be recognized that a person skilled in the art can easily modify and/or improve the embodiment. Accordingly, as long as the modification or improvement implemented by those skilled in the art are not at a level departing from the scope of the claims described in the claims, the modification or improvement is interpreted to be included in the scope of the claims.

DESCRIPTION OF REFERENCE SIGNS

1: energy storage device

4,4a,4b: external terminal

5: current collector

6: bus bar

11: energy storage apparatus

22: layered product

31: case body

33: internal space

71: first welded portion

72: second welded portion

311: closing portion

312: body portion

321: gas release valve

710: first welding track

720: second welding track