Battery production method

A method for producing a battery comprises a deformation step for moving a first metal foil forming a pair of perpendicularly intersecting portions of a first metal, respectively, toward the outside in a second radial direction while enlarging the inside diameter, in the second radial direction, of a first metal winding part by making a force act on the pair of perpendicularly intersecting portions of a first metal toward the outside in the second radial direction, and a resistance welding step for pressing a pair of first metal welding portions toward the inside in a first radical direction under a state where the first terminal welding part of a first current collecting terminal member is arranged on the radial by inside of the first metal winding part after the first metal winding part is deformed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national phase application of International Application No. PCT/JP2008/072907, filed Dec. 17, 2008, and claims the priority of Japanese Application No. 2008-011851, filed Jan. 22, 2008, the contents of both of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a battery and a production method therefor.

BACKGROUND ART

There have been proposed various types of batteries each including an electrode body having: a power generating part made by laminating a first electrode-forming portion having a first electrode mixture layer of a first electrode sheet and a second electrode sheet by interposing a separator therebetween and winding such a laminated body about an axis line into a cylindrical form; and a first metal winding part (a portion formed with no electrode mixture layer) constituted of only a first metal portion made of a first metal foil in a wound form, the first metal winding part being adjacent to the power generating part (for example, see Patent Literature 1). A cylindrical battery disclosed in Patent Literature 1 is provided with a current collecting terminal (a first current collecting terminal member) for collecting electric charge of a first electrode sheet, the current collecting terminal including a portion (a first terminal welding part) being located on the radial inside of the portion with no electrode mixture layer (the first metal winding part) and welded to the first metal winding part.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

Meanwhile, Patent Literature 1 discloses a method achieved by radially inward pressing a pair of first metal welding portions of a cylindrical first metal winding part respectively, and welding the first metal welding portions and a first terminal welding part placed on the radial inside of the first metal winding part while holding the first metal welding portions in pressure contact with the first terminal welding part. According to this method, when the first metal welding portions are pressed radially inward to press against the first terminal welding part, parts of the first metal foil may buckle at first metal perpendicularly intersecting portions of the first metal winding part and hence the buckled part of the metal foil may contact an adjacent part of the metal foil. It is to be noted that the first metal winding part does not include a second electrode plate and a separator between the parts of the first metal foil and thus the parts of the first metal foil forming the first metal winding part are apart from each other before pressing.

If the parts of the first metal foil forming the first metal perpendicularly intersecting portion buckle, the parts caused to contact with each other due to buckling are apt to generate spatters during resistance welding, causing a part (foreign matters) of the first metal foil to scatter and adhere to the electrode body. Thus, the foreign matters may enter in a battery, leading to a decrease in reliability of the battery. Furthermore, a shunt of welding current at the contact portions resulting from buckling may cause welding failures between the first metal winding part and the first terminal welding part. This also may deteriorate the battery reliability.

The present invention has been made to solve the above problems and has a purpose to provide a highly reliable battery produced by preventing entrance of foreign matters in the battery and including a first metal winding part and a first terminal welding part both being appropriately welded to each other, and a production method therefor.

Solution to Problem

To achieve the above purpose, the present invention provides a method of producing a battery comprising an electrode body and a first current collecting terminal member, the electrode body being provided with: a first electrode sheet having a first electrode mixture layer provided on a surface of a strip-shaped first metal foil, the sheet including: a first electrode-forming portion extending along one side of the first metal foil extending in a longitudinal direction and including the first metal foil and the first electrode mixture layer; and a first metal portion extending adjacently to the first electrode-forming portion and along the one side along the longitudinal direction and consisting of the first metal foil without having the first electrode mixture layer; a strip-shaped second electrode sheet; and a strip-shaped separator, the electrode body including: a power generating part in which the first electrode-forming portion of the first electrode sheet and the second electrode sheet are laminated by interposing the separator therebetween and wound around an axis line into a cylindrical form; and a first metal winding part in which the first metal portion is wound, the first metal winding part being adjacent to the power generating part, and the first current collecting terminal member being configured to collect electric charge of the first electrode sheet and provided with a first terminal welding part placed on a radial inside of the first metal winding part and welded to the first metal winding part, the method comprising: a deforming step of deforming the first metal winding part of the electrode body including: the power generating part; and the first metal winding part in which the first metal portion is wound in a cylindrical form, the deforming step including: when a pair of portions of the first metal winding part to be welded to the first terminal welding part of the first current collecting terminal member, the portions being opposed to each other in a first radial direction of the first metal winding part, is a pair of first metal welding portions, and a pair of portions of the first metal winding part opposed to each other in a second radial direction perpendicular to the first radial direction is a pair of first metal perpendicularly intersecting portions, exerting an outward force in the second radial direction on the pair of metal perpendicularly intersecting portions to enlarge the inside diameter of the first metal winding part in the second radial direction and move parts of the first metal foil forming the pair of first metal perpendicularly intersecting portions outward in the second radial direction respectively, and a resistance welding step of pressing the pair of first metal welding portions inward in the first radial direction while the first terminal welding part of the first current collecting terminal member is placed on the radial inside of the deformed first metal winding part, and resistance-welding the first metal welding portions and the first terminal welding part to each other while holding the pair of first metal welding portions in pressure contact with the first terminal welding part.

According to the production method of the invention, before the pair of first metal welding portions are pressed against the first terminal welding part in the resistance welding step, an outward force in the second radial direction is applied in advance to the pair of first metal perpendicularly intersecting portions in the deforming step to move the parts of the first metal foil forming the pair of first metal perpendicularly intersecting portions outward in the second radial direction respectively. In the later resistance welding step, accordingly, when the pair of first metal welding portions are pressed inward in the first radial direction to bring the pair of first metal welding portions in pressure contact with the first terminal welding part, the parts of the first metal foil forming the pair of metal perpendicularly intersecting portions are allowed to easily move together outward in the second radial direction.

According to such deforming technique, the first metal winding part is unlikely to buckle during deforming. Furthermore, the parts of the first metal foil forming the pair of first metal perpendicularly intersecting portions are respectively moved outward in the second radial direction, thus moving the pair of metal welding portions inward in the first radial direction, bringing the first metal winding part closer to the first terminal welding part.

In the resistance welding step, accordingly, when the pair of first metal welding portions are pressed inward in the first radial direction to bring the pair of first metal welding portions in pressure contact with the first terminal welding part, the parts of the first metal foil forming the first metal winding part can be prevented from buckling. This makes it possible to prevent adhesion of foreign matters to the electrode body caused by the occurrence of spatters, thereby avoiding entrance of the foreign matters into the battery. It is further possible to prevent welding failures between the first metal welding portions and the first terminal welding part due to the influence of a shunt of welding current. Therefore, the production method of the invention can produce a highly reliable battery.

One example of the deforming step is achieved by deforming the cylindrical first metal winding part into an elliptic form having an inside diameter in the first radial direction shorter than an inside diameter in the second radial direction.

Furthermore, in the above battery production method, preferably, the first terminal welding part has a shape having such a cross section, taken along a direction perpendicular to the axis line while the first terminal welding part is placed on the radial inside of the first metal winding part, as that a maximum size in the second radial direction is larger than the inside diameter of the first metal winding part before deformed and a maximum size in the first radial direction is smaller than the inside diameter of the first metal winding part before deformed, and the deforming step including inserting the first terminal welding part in the radial inside of the first metal winding part.

In the production method of the invention, the first terminal welding part is inserted in the radial inside of the first metal winding part to exert an outward force in the second radial direction on the pair of first metal perpendicularly intersecting portions, thereby enlarging the inside diameter of the first metal winding part in the second radial direction and moving the parts of the first metal foil forming the pair of metal perpendicularly intersecting portions respectively outward in the second radial direction. This method is therefore more preferable because easier and faster deforming of the first metal winding part can be achieved as compared with deforming of the first metal winding part using an additional deforming jig and the like.

Furthermore, in the above battery production method, preferably, the first terminal welding part has a cross section taken along the second radial direction so as to pass the axis line while the first terminal welding part is placed on the radial inside of the first metal winding part, the cross section having such a size in the second radial direction as that the size at a side closest to the power generating part is equal to or less than the inside diameter of the first metal winding part before deformed, the size increases as farther from the power generating part in the axis line direction, and the size at a farthermost side from the power generating part in the axis line direction is larger than the inside diameter of the first metal winding part before deformed.

Because of the use of the first current collecting terminal member including the first terminal welding part having the above shape, the first terminal welding part can be smoothly inserted in the radial inside of the first metal winding part. Furthermore, as the first terminal welding part is inserted in the first metal winding part, the force applied on the first metal winding part gradually increases. Therefore, the parts of the first metal foil forming the first metal winding part are less likely to break than the case where a large force is applied abruptly.

Furthermore, one of the above battery production methods, preferably, further comprises: after the deforming step and before the resistance welding step, a foil collecting step of pressing the pair of first metal welding portions inward in the first radial direction while the first terminal welding part is placed on the radial inside of the deformed first metal winding part to collect parts of the first metal foil forming the first metal welding portions inward in the first radial direction while decreasing clearances between the parts of the first metal foil in the first radial direction.

Before resistance welding, the parts of the first metal foil forming the first metal welding portions are collected in advance inward in the first radial direction while reducing the clearances or spaces between the parts of the first metal foil in the first radial direction, thereby allowing more appropriate resistance welding. In particular, in the later resistance welding step, the first metal winding part is unlikely to be deformed when the first metal welding portions are pressed inward in the first radial direction. Accordingly, this method is more preferable in further preventing buckling of the first metal foil.

In the deforming step, before the foil collecting step, the parts of the first metal foil forming the first metal perpendicularly intersecting portions are moved outward in the second radial direction. In the foil collecting step, therefore, when the first metal welding portions are pressed inward in the first radial direction, the parts of the first metal foil forming the first metal perpendicularly intersecting portions are easily moved together outward in the second radial direction. Accordingly, it is also possible to prevent the first metal foil from buckling even in the foil collecting step.

Furthermore, in the above battery production method, preferably, the first terminal welding part has a shape formed with a portion recessed inward in the first radial direction as compared with other portions in a cross section taken along the direction perpendicular to the axis line while the first terminal welding part is placed on the radial inside of the first metal winding part, the recessed portion being to be welded to the first metal welding portions of the first metal winding part, and the foil collecting step includes pressing the first metal welding portions inward in the first radial direction to bring the first metal welding portions in pressure contact with the recessed portion of the first terminal welding part.

In the foil collecting step, even when the first metal welding portions are pressed inward in the first radial direction to collect the parts of the first metal foil forming the first metal welding portions inward in the first radial direction while reducing the clearances between the parts of the first metal foil in the first radial direction, the parts of the first metal foil forming the first metal welding portions are apt to elastically move outward in the first radial direction due to spring back.

However, according to the production method of the invention, the first current collecting terminal member includes the first terminal welding part shaped to have the portion recessed inward in the first radial direction as compared with other portions, the recessed portion being to be welded to the first metal welding portions of the first metal winding part when the first terminal welding part is taken along the direction perpendicular to the axis line while the first terminal welding part is placed on the radial inside of the first metal winding part. Then, the first metal welding portions are pressed inward in the first radial direction to bring the first metal welding portions in pressure contact with the recessed portion of the first terminal welding part. Thus, even when the first metal foil causes outward spring back in the first radial direction, the parts of the first metal foil forming the first metal welding portions can appropriately be collected inward in the first radial direction.

Another aspect of the invention provides a battery comprising an electrode body and a first current collecting terminal member, the electrode body being provided with: a first electrode sheet having a first electrode mixture layer provided on a surface of a strip-shaped first metal foil, the sheet including: a first electrode-forming portion extending along one side of the first metal foil extending in a longitudinal direction and including the first metal foil and the first electrode mixture layer; and a first metal portion extending adjacently to the first electrode-forming portion and along the one side along the longitudinal direction and consisting of the first metal foil without having the first electrode mixture layer; a strip-shaped second electrode sheet; and a strip-shaped separator, the electrode body including: a power generating part in which the first electrode-forming portion of the first electrode sheet and the second electrode sheet are laminated by interposing the separator therebetween and wound around an axis line into a cylindrical form; and a first metal winding part in which the first metal portion is wound, the first metal winding part being adjacent to the power generating part, and the first current collecting terminal member being configured to collect electric charge of the first electrode sheet and provided with a first terminal welding part placed on a radial inside of the first metal winding part and welded to the first metal winding part, wherein when a pair of portions of the first metal winding part welded to the first terminal welding part of the first current collecting terminal member and opposed to each other in a first radial direction of the first metal winding part is a pair of first metal welding portions, and a pair of portions of the first metal winding part opposed to each other in a second radial direction perpendicular to the first radial direction is a pair of first metal perpendicularly intersecting portions, in a cross section taken along a direction perpendicular to the axis line to pass the first metal welding portions, the first metal winding part has an outside diameter in the first radial direction smaller than an outside diameter in the second radial direction, and each part of the first metal foil forming the first perpendicularly intersecting portions is curved to bulge outward in the second radial direction.

The battery of the invention is configured such that the first terminal welding part placed on the radial inside of the first metal winding part and the first metal welding portions of the first metal winding part are resistance-welded to each other. Furthermore, in the cross section of the first metal winding part taken along the direction perpendicular to the axis line to pass the first metal welding portions, the outside diameter of the first metal winding part in the first radial direction in which the pair of metal welding portions are opposed to each other is determined to be smaller than the outside diameter of the first metal winding part in the second radial direction perpendicular to the first radial direction.

Such battery is produced in such a manner that the pair of first metal welding portions are pressed respectively radially inward while the first terminal welding part is placed on the radial inside of the first metal winding part and the first metal welding portions are resistance-welded to the first terminal welding part while holding the pair of first metal welding portions in pressure contact with the first terminal welding part. However, when the first metal welding portions are pressed radially inward to press against the first terminal welding part, conventionally, a part or parts of the first metal foil might buckle at the first metal perpendicularly intersecting portions of the first metal winding part and hence come into contact with an adjacent part or parts of the metal foil. If the part of the first metal foil at the first metal perpendicularly intersecting portion buckles, the parts caused to contact with each other due to buckling may generate spatters during the resistance welding, causing a part (foreign matters) of the first metal foil to scatter and adhere to the electrode body. Furthermore, a shunt of welding current in the portions resulting from buckling may cause welding failures between the first metal winding part and the first terminal welding part. This also may deteriorate the battery reliability.

On the other hand, in the battery of the invention, each of the parts of the first metal foil forming the first metal perpendicularly intersecting portions is curved to bulge outward in the second radial direction. Specifically, the first metal foil does not buckle at the first metal perpendicularly intersecting portions. Thus, the first metal welding portions and the first terminal welding part are resistance-welded to each other while preventing adhesion of foreign matters to the electrode body caused by the occurrence of spatters and welding failures due to a shunt of welding current between the first metal welding portions and the first terminal welding part. From the above, the battery of the invention can be achieved as a highly reliable battery by restraining entrance of the foreign matters into the battery and appropriately welding the first metal winding part and the first terminal welding part to each other.

REFERENCE SIGNS LIST

DESCRIPTION OF EMBODIMENTS

A detailed description of a preferred embodiment of a battery1embodying the present invention will now be given referring to the accompanying drawings.

As shown inFIG. 1, a first electrode sheet10in which a first electrode mixture layer12is provided on a surface of a strip-shaped first metal foil11is first prepared. This first electrode sheet10includes a first electrode-forming portion14and a first metal portion13adjacent to the first electrode-forming portion14. The first electrode-forming portion14extends along one side10bof the first metal foil11extending in a longitudinal direction (a lateral direction inFIG. 1) and is constituted of a part of the first metal foil11and a first electrode mixture layer12. The first metal portion13is made of the first metal foil11without including the first electrode mixture layer12and extends along the side10bin the longitudinal direction.

The first metal foil11is for example made of copper. The first electrode mixture layer12is constituted of a first electrode active material, a binder, and others. The first electrode active material is for example lithium nickel oxide.

As shown inFIG. 2, furthermore, a second electrode sheet20in which a second electrode mixture layer22is provided on a surface of a strip-shaped second metal foil21is prepared. This second electrode sheet20includes a second electrode-forming portion24and a second metal portion23adjacent to the second electrode-forming portion24. The second electrode-forming portion24extends along one side20bof the second metal foil21extending in a longitudinal direction (a lateral direction inFIG. 2) and includes a second metal foil21and a second electrode mixture layer22. The second metal portion23is made of the second metal foil21without including the second electrode mixture layer22and extends along the side20bin the longitudinal direction.

The second metal foil21is for example made of aluminum. The second electrode mixture layer22is constituted of a second electrode active material, a binder, and others. The second electrode active material is for example natural graphite.

As shown inFIG. 3, successively, the first electrode sheet10, a separator30, the second electrode sheet20, and another separator30are laminated in this order. Concretely, they are laminated in such a manner that the first metal portion13of the first electrode sheet10and the second metal portion23of the second electrode sheet20are located opposite in a width direction (a vertical direction inFIG. 3) so that the first metal portion13does not overlap the separators30and the second electrode sheet20and the second metal portion23does not overlap the separators30and the first electrode sheet10. Then, the laminated first electrode sheet10, separator30, second electrode sheet20, and separator30are wound in a cylindrical form around a cylindrical winding core45.

After the above winding, the winding core45is removed. As shown inFIG. 4, the electrode body40is thus formed to include a power generating part42, a first metal winding part44, and a second metal winding part46. The power generating part42includes the first electrode-forming portion14of the first electrode sheet10and the second electrode-forming portion24of the second electrode sheet20, both electrode-forming portions14and24being laminated by interposing the separator30therebetween and wound around the axis line P into a cylindrical form. The first metal winding part44is adjacent to the power generating part42on one side (on a right side inFIG. 4) in the axis direction and is constituted of the wound first metal portion13. The second metal winding part46is adjacent to the power generating part42on the other side (on a left side inFIG. 4) in the axis direction and is constituted of the second metal portion23.

As shown inFIG. 5, a first current collecting terminal member (a “terminal member”)50is prepared for collecting electric charge of the first electrode sheet10. This terminal member50includes a first terminal welding part53to be placed on the radial inside of the first metal winding part44and welded to the first metal winding part44, a screw part55formed with male threads, and a flange part57located between the first terminal welding part53and the screw part55. The terminal member50is preferably made of the same material as that of the first metal foil11. For example, when the first metal foil11is made of a copper foil, the terminal member50is also preferably made of copper.

In a deforming step, subsequently, as shown inFIG. 6, the first terminal welding part53of the terminal member50is inserted in the radial inside of the first metal winding part44, thereby deforming the first metal winding part44.

Herein,FIG. 7is a sectional view (taken along a line B-B inFIG. 6) of the first metal winding part44taken along a direction perpendicular to the axis line P, in which the first terminal welding part53is placed inside in the radial direction of the winding part44(seeFIG. 6). As shown inFIG. 7, the winding part44includes a pair of first metal welding portions44band44cto be welded to the first terminal welding part53. The first metal welding portion44band the first metal welding portion44care opposed to each other in a first radial direction X of the winding part44. Furthermore, the winding part44includes a pair of first metal perpendicularly intersecting portions44dand44eopposed to each other in a second radial direction Y perpendicular to the first radial direction X.

FIG. 8shows a sectional view taken along a line C-C inFIG. 6. InFIGS. 7 and 8, the inner periphery C1of the first metal winding part44in which the first terminal welding part53is not yet placed on the radial inside of the winding part44(i.e., before deformation thereof) is indicated by a broken line.

As shown inFIG. 7, when the first terminal welding part53placed on the radial inside of the first metal winding part44is viewed in section taken along a perpendicular direction to the axis line P, the first terminal welding part53has a shape including a section53bhaving a maximum size Q in the second radial direction Y is larger than an inside diameter D1of the not-yet-deformed winding part44and a maximum size R in the first radial direction X is smaller than the inside diameter D1of the not-yet-deformed winding part44. As shown inFIG. 8, furthermore, when the first terminal welding part53placed on the radial inside of the winding part44is viewed in section taken along in a perpendicular direction to the axis line P, the first terminal welding part53has a shape including a section53chaving a maximum size H in the second radial direction Y is larger than the inside diameter D1of the not-yet-deformed winding part44and a maximum size K in the first radial direction X is smaller than the inside diameter D1of the not-yet-deformed winding part44.

Accordingly, the first terminal welding part53having the above shape is inserted in the radial inside of the first metal winding part44, exerting a radially-outward force on the first metal perpendicularly intersecting portion44din the second radial direction (upward inFIG. 7) and exerting a radially-outward force on the first metal perpendicularly intersecting portion44ein the second radial direction (downward inFIG. 7). This can enlarge the inside diameter of the first metal winding part44in the second radial direction. Thus, the parts of the first metal foil11forming the perpendicularly intersecting portion44dcan be moved outward in the second radial direction (upward inFIG. 7) and the parts of the first metal foil11forming the perpendicularly intersecting portion44ecan be moved outward in the second radial direction (downward inFIG. 7).

In a foil collecting step and a resistance welding step mentioned later, when the pair of first metal welding portions44band44care pressed inward in the first radial direction to bring the pair of first metal welding portions44band44cin pressure contact with the first terminal welding part53, the above deformed state allows the parts of the first metal foil11forming the pair of first metal perpendicularly intersecting portions44dand44eto easily move together outward in the second radial direction.

According to the deforming method in the present embodiment, the first metal winding part44is unlikely to buckle during deformation. In addition, when the parts of the first metal foil11forming the pair of first metal perpendicularly intersecting portions44dand44eare moved outward together in the second radial direction, the pair of first metal welding portions44band44care moved inward in the first radial direction. Thus, the first metal welding portions44band44ccan be brought close to the first terminal welding part53.

In the foil collecting step and the resistance welding step mentioned later, while the pair of first metal welding portions44band44care pressed inward in the first radial direction to be pressed against the first terminal welding part53, the first metal foil11forming the first metal winding part44can be prevented from buckling. In the deforming step in the present embodiment, the cylindrical first metal winding part44can be deformed into an elliptic form having an inside diameter in the first radial direction X shorter than an inside diameter in the second radial direction Y (seeFIGS. 7 and 8).

Herein,FIG. 9shows a section53dof the first terminal welding part53placed on the radial inside of the first metal winding part44and taken along the second radial direction so as to pass the axis line P. As shown inFIG. 9, the size of the section53din the second radial direction Y is determined such that a size F at a side53eclosest to the power generating part42is equal to or less than the inside diameter D1of the not-yet-deformed first metal winding part44. The size of the section53din the second radial direction Y is larger as it is farther from the power generating part42in the axis direction (it is closer to a right side along the axis line P inFIG. 9). A size H at a farthest side53ffrom the power generating part42in the axis direction is larger than the inside diameter D1of the not-yet-deformed first metal winding part44.

The use of the first current collecting terminal member50including the first terminal welding part53having the above shape makes it easy to smoothly insert the welding part53in the radial inside of the first metal winding part44. Additionally, as the welding part53is inserted in the winding part44, the force acting on the winding part44is gradually increased. Accordingly, the parts of the first metal foil11forming the winding part44are less broken as compared with when a large force is abruptly applied thereon.

In the foil collecting step, thereafter, while the first terminal welding part53is placed on the radial inside of the deformed first metal winding part44, the first metal welding portions44b,44care pressed inward in the first radial direction.

Concretely, as shown inFIG. 10, a press part4cof the foil collecting device3placed outside of the first metal welding portion44cin the first radial direction (on an upper side inFIG. 10) is moved inward in the first radial direction (downward inFIG. 10) toward the first metal winding part44. In sync with this, a press part4bof the foil collecting device3placed outside of the first metal welding portion44bin the first radial direction (on a lower side inFIG. 10) is moved inward in the first radial direction (upward inFIG. 10).

As shown inFIG. 11, accordingly, the pair of first metal welding portions44band44care pressed inward in the first radial direction, thereby closely collecting parts of the first metal foil11forming the first metal welding portions44band44cinward in the first radial direction by decreasing clearances between the parts of the first metal foil11in the first radial direction X.

Before the resistance welding mentioned later, therefore, the parts of the first metal foil11forming each of the first metal welding portions44b,44care collected inward in the first radial direction by decreasing the clearances between the parts of the metal foil11in the first radial direction X, so that the resistance welding can be appropriately performed. In the later resistance welding step, particularly, when the first metal welding portions44band44care respectively pressed inward in the first radial direction, the first metal winding part44is unlikely to be deformed and therefore the first metal foil11can be further prevented from buckling.

In the deforming step, before the foil collecting step, the parts of the first metal foil11forming each of the first metal perpendicularly intersecting portions44dand44eare moved outward in the second radial direction. In the foil collecting step, accordingly, when the first metal welding portions44band44care pressed inward in the first radial direction, the parts of the first metal foil11forming the first metal perpendicularly intersecting portions44dand44ecan be easily moved together outward in the second radial direction. Therefore, even in the foil collecting step, the first metal foil11can be prevented from buckling.

Meanwhile, in the foil collecting step, when the first metal welding portions44band44care respectively pressed inward in the first radial direction, decreasing the clearances between the parts of the first metal foil11forming each of the first metal welding portions44band44cin the first radial direction X to collect the parts of the first metal foil11inward in the first radial direction, the parts of the first metal foil11forming each of the first metal welding portions44band44care apt to elastically move outward in the first radial direction due to spring back. Thus, the clearances between the parts of the first metal foil11are widened in the first radial direction.

In the present embodiment, however, as shown inFIG. 10, the first terminal welding part53is designed such that a portion to be welded to the first metal welding portions44band44cof the first metal winding part44is formed as a recess53grecessed inward in the first radial direction than other portions when viewed in section taken along a direction perpendicular to the axis line P while the first terminal welding part53is placed on the radial inside of the first metal winding part44. As shown inFIG. 11, the first metal welding portions44band44care pressed inward in the first radial direction to be brought in pressure contact with the recess53gof the first terminal welding part53. Even after the first metal foil11causes outward spring-back in the first radial direction, the parts of the first metal foil11forming each of the first metal welding portions44band44ccan be appropriately collected inward in the first radial direction.

In the foil collecting step of the present embodiment, furthermore, not only the first metal welding portions44band44cbut also the entire of recess-corresponding metal portions44g(a region hatched with broken lines inFIG. 6) and 44hof the first metal winding part44each of which faces the recess53gof the first terminal welding part53in the first radial direction X are pressed under pressure against the recess53gof the first terminal welding part53. Concretely, the press parts4band4cof the foil collecting device3press the recess-corresponding metal portions44gand44hagainst the recess53gof the first terminal welding part53and also the press parts4band4care moved in a direction along the axis line P (in a direction perpendicular to a drawing sheet ofFIG. 11). In this way, the parts of the first metal foil11forming the first metal welding portions44band44ccan be more appropriately collected inward in the first radial direction and also the parts of the first metal foil11forming the recess-corresponding metal portions44gand44hcan be collected inward in the first radial direction. In the later resistance welding step, accordingly, when the first metal welding portions44band44care pressed inward in the first radial direction, the first metal winding part44is more unlikely to be deformed. This can further prevent the first metal foil11from buckling.

In the resistance welding step, subsequently, the first metal winding part44and the first terminal welding part53are resistance-welded to each other. Concretely, as shown inFIG. 12, a first electrode7and a second electrode8of a resistance welding machine6press the first metal welding portions44band44cinward in the first radial direction to bring the first metal welding portions44band44cin pressure contact with the recess53gof the first terminal welding part53. In this state, electric current is supplied between the first electrode7and the second electrode8, thereby resistance-welding the first metal welding portions44band44cto the first terminal welding part53.

In the present embodiment, as mentioned above, in the deforming step and the foil collecting step, the parts of the first metal foil11forming the first metal winding part44are prevented from buckling. In the resistance welding step, furthermore, even when the first metal welding portions44band44care brought into pressure contact with the recess53gof the first terminal welding part53, the parts of the first metal foil11forming the first metal winding part44can be prevented from buckling. This can prevent the occurrence of spatters during resistance welding and hence avoid adhesion of foreign matters to the electrode body40caused by the occurrence of spatters. The use of this electrode body40can therefore restrain entrance of the foreign matters into the battery. Moreover, it is possible to prevent welding failures between the first metal welding portions44band44cand the first terminal welding part53due to a shunt of welding current.

As shown inFIG. 13, thereafter, a disc-shaped lid member61is prepared and placed on the flange part57of the first current collecting terminal member50so that the screw part55of the terminal member50is inserted in a through hole61bof the lid member61. In this state, a nut65is threaded on the screw part55of the terminal member50to fasten the lid member61to the flange part57of the terminal member50. Then, an electrolyte is poured in a battery case62.

Subsequently, the electrode body40is inserted in the battery case62having a bottom-closed cylindrical shape and also the lid member61is put on an open end face62cof the battery case62to close the opening of the battery case62. It is to be noted that an electrical insulating member not shown is placed between the open end face62cof the battery case62and the lid member61to electrically insulate between the lid member61and the battery case62. When the opening of the battery case62is closed with the lid member61, a second current collecting terminal member (not shown) welded to the second metal winding part46contacts with a bottom62bof the battery case62. Accordingly, the battery case62serves as a second electrode.

Thereafter, the lid member61and the battery case62are welded to each other. The battery in this embodiment is thus completed.

In relation to the battery1of the present embodiment,FIG. 14shows a sectional view of the first metal winding part44taken along a direction perpendicular to the axis line P so as to pass the first metal welding portion44c. This view corresponds to a sectional view taken along a line L-L inFIG. 13. As shown inFIG. 14, the first terminal welding part53placed on the radial inside of the first metal winding part44and the first metal welding portions44band44cof the first metal winding part44are resistance-welded to each other. In addition, an outside diameter N of the first metal winding part44in the first radial direction X in which the first metal welding portion44bfaces the first metal welding portion44cis determined to be smaller than an outside diameter M of the first metal winding part44in the second radial direction Y perpendicular to the first radial direction X. In such battery, conventionally, a first metal foil would buckle at first metal perpendicularly intersecting portions (portions opposed to each other in the second radial direction perpendicular to the first radial direction) of the first metal winding part.

On the other hand, in the battery1of the present embodiment, as shown inFIG. 14, each part of the first metal foil11forming the first metal perpendicularly intersecting portions44dand44eis curved to outward bulge in the second radial direction Y. In other words, in the first metal perpendicularly intersecting portions44dand44e, the first metal foil11does not buckle. Accordingly, when the first metal welding portions44band44care resistance-welded to the first terminal welding part53, it is possible to prevent adhesion of foreign matters to the electrode body40caused by the occurrence of spatters and prevent welding failures between the first metal welding portions44band44cand the first terminal welding part53due to a shunt of welding current. Consequently, the battery1of the present embodiment can be provided as a highly reliable battery by restraining entrance of foreign matters into the battery and appropriately welding the first metal winding part44and the first terminal welding part53to each other.

Example 1 and Comparative Example 1

In Example 1, as mentioned in the embodiment, the deforming step, the foil collecting step, and the resistance welding step are sequentially performed to produce a hundred samples (Samples1to100) in each of which the first metal winding part44and the first terminal welding part53are welded to each other, thereby welding the first current collecting terminal member50and the electrode body40. The battery1is then produced in the manner described in the embodiment.

It is to be noted that, in Example 1, the first metal winding part44is designed to have fifty winding turns. The resistance welding step is conducted under the condition that a welding current value is 7000 A, a welding current application time is 116 ms, and a contact pressure between the first electrode7and the second electrode8is 100 kgf (980 N).

In Comparative example 1, a first metal winding part having fifty winding turns as with that in Example 1 is not subjected to the deforming step but is subjected to a foil collecting step different from Example 1 and then the resistance welding step as in Example 1. In this way, a hundred samples (Samples101to200) in each of which the first current collecting terminal member and the electrode body are welded to each other are produced.

Concretely, a first current collecting terminal member150used in Comparative example 1 has a first terminal welding part153having an almost square pole shape whose cross section is almost square (its maximum size is equal to or less than the inside diameter of a first metal winding part144) in a direction perpendicular to the axis line of the first metal winding part144wound in a cylindrical form, as shown inFIG. 15. Accordingly, even when the first terminal welding part153is inserted in the radial inside of the first metal winding part144, the first metal winding part144will not be deformed.

In the foil collecting step in Comparative example 1, furthermore, press parts104band104ceach having a flat plate shape and constituting a foil collecting device103are moved radially inward while the first terminal welding part153is placed on the radial inside of the first metal winding part144as shown inFIG. 15. Accordingly, as shown inFIG. 16, a pair of first metal welding portions144band144care pressed inward in the first radial direction, thereby collecting parts of the first metal foil forming the first metal welding portions144band144cby decreasing clearances between the parts of the first metal foil in the first radial direction X. Then, the resistance welding step is conducted in the same manner as in Example 1 to produce samples101to200.

The samples101to200in Comparative example 1 are examined about each welded state between each of the first metal welding portions144band144cand the first terminal welding part153. The result thereof shows that every welded state is appropriate. However, each electrode body140was examined about adhesion of foreign matters resulting from welding spatters, and adhesion of foreign matters was found in five samples.

On the other hand, the samples1to100in Example 1 are examined about each welded state between each of the first metal welding portions44band44cand the first terminal welding part53. The result thereof shows that every welded state is appropriate. Each electrode body40was examined about adhesion of foreign matters resulting from welding spatters, and no adhesion of foreign matters was found in each sample.

It is clear from the above results that the production method according to Example 1 can produce a highly reliable battery by preventing entrance of foreign matters into the battery and appropriately welding the first metal winding part and the first terminal welding part to each other. Furthermore, the battery1of Example 1 can be achieved as a highly reliable battery produced by preventing entrance of foreign matters into the battery and the first metal winding part and appropriately welding the first terminal welding part to each other.

The present invention is explained in the above embodiment and Example 1 but is not limited thereto. It should be understood that the present invention may be embodied in other specific forms without departing from the essential characteristics thereof.