JP7044676B2 - Electrochemical devices and methods for manufacturing electrochemical devices - Google Patents

Description

The present invention relates to an electrochemical device having a conduction path joined by resistance welding, a bonded body, a method for manufacturing an electrochemical device, and a method for manufacturing a bonded body.

Some electrochemical devices such as lithium ion capacitors are wound with a positive electrode and a negative electrode separated by a separator and housed in an outer can. The positive electrode and the negative electrode are each composed of a current collector coated with an active material.

Here, one of the positive electrode and the negative electrode is electrically connected to the outer can, and the outer can may be used as a conductive path of the positive electrode or the negative electrode. In electrochemical devices, further reduction in resistance is required in order to obtain high output characteristics, but the ratio of resistance due to the joining of the outer can and the electrode is large in the total resistance.

Generally, the outer can and the electrode are joined by joining the current collector to the outer can by resistance welding. (See, for example, Patent Document 1). In resistance welding, strength is ensured by welding the object to be welded one-on-one.

Japanese Unexamined Patent Publication No. 2012-216653

Here, by stacking a plurality of current collectors and directly joining them to the outer can at one point, it is possible to reduce the connection resistance between the current collector and the outer can. However, in resistance welding, it is common to weld objects to be welded one-on-one, and there is a problem that the joint strength cannot be secured when a plurality of current collectors are stacked and resistance welded to an outer can.

In view of the above circumstances, an object of the present invention is to provide an electrochemical device, a junction, a method for manufacturing an electrochemical device, and a method for manufacturing a junction, in which the resistance of the conduction path is small and high output characteristics can be obtained. To provide.

In order to achieve the above object, the electrochemical device according to one embodiment of the present invention includes an outer can, a power storage element, and a reinforcing plate.
The outer can is made of a metal containing the first metal type.
The energy storage element includes a positive electrode, a negative electrode, and a separator, and the positive electrode and the negative electrode are laminated via a separator and wound, and is electrically connected to the positive electrode or the negative electrode. It contains a second metal type different from the metal type 1 and has a lead foil made of a metal different from the outer can, and is housed in the outer can.
The reinforcing plate is made of a metal containing the first metal type.
The outer can and the reinforcing plate are welded with the lead foil sandwiched between them, and the first metal type and the second metal type coexist at the welded portion.

According to this configuration, the outer can, the lead foil and the reinforcing plate are welded with the lead foil sandwiched between the outer can and the reinforcing plate. The first metal type contained in the outer can and the reinforcing plate and the second metal type contained in the lead foil coexist at the welded portion, and the outer can, the lead foil and the reinforcing plate are joined to each other with high bonding strength. It is possible. Further, it is possible to reduce the resistance of the conduction path between the lead foil and the outer can and obtain high output characteristics.

The outer can and the reinforcing plate may be welded by sandwiching three or more lead foils.

The outer can and the reinforcing plate may be made of the same metal.

The first metal type mentioned above is iron,
The second metal type may be copper.

The outer can and the reinforcing plate may further contain nickel.

In order to achieve the above object, the bonded body according to one embodiment of the present invention includes a first member, a plurality of foils, and a second member.
The first member is made of a metal containing the first metal species.
The plurality of foils contain a second metal type different from the first metal type, and are made of a metal different from the first member.
The second member is made of a metal containing the first metal species.
The first member and the second member are welded by sandwiching the plurality of foils, and the first metal type and the second metal are welded to the welded portions of the first member and the second member. Species coexist.

In order to achieve the above object, the method for manufacturing an electrochemical device according to one embodiment of the present invention is:
An outer can made of a metal containing a first metal type, a positive electrode, a negative electrode, and a separator are provided, and the positive electrode and the negative electrode are laminated via a separator and wound, and the positive electrode or the negative electrode is wound. It has a lead foil electrically connected to the above, contains a second metal type different from the first metal type, and has a lead foil made of a metal different from the outer can, and is housed in the outer can. , Prepare a reinforcing plate made of metal containing the above-mentioned first metal type,
The lead foil is sandwiched between the outer can and the reinforcing plate,
The first welding electrode is brought into contact with the outer can.
The second welding electrode is brought into contact with the reinforcing plate, and the second welding electrode is brought into contact with the reinforcing plate.
A voltage is applied between the first welding electrode and the second welding electrode, and the outer can and the reinforcing plate are joined with the lead foil sandwiched by resistance welding.

In order to achieve the above object, the method for manufacturing a bonded body according to one embodiment of the present invention is:
A first member made of a metal containing a first metal type, a plurality of foils containing a second metal type different from the first metal type and made of a metal different from the first metal type, and the above. Prepare a second member made of metal containing the first metal species,
The plurality of foils are sandwiched between the first member and the second member.
The first welding electrode is brought into contact with the first member, and the first member is brought into contact with the first welding electrode.
The second welding electrode is brought into contact with the second member, and the second member is brought into contact with the second welding electrode.
A voltage is applied between the first welding electrode and the second welding electrode, and the first member and the second member are joined by resistance welding to sandwich the plurality of foils.

As described above, according to the present invention, it is possible to provide an electrochemical device, a junction, a method for manufacturing an electrochemical device, and a method for manufacturing a junction, which have a small resistance of a conduction path and can obtain high output characteristics. It is possible.

It is a perspective view of the electrochemical device which concerns on embodiment of this invention. It is a perspective view of a part of the structure of the electrochemical device. It is a perspective view of the power storage element included in the electrochemical device. It is sectional drawing of the power storage element. It is a top view of the negative electrode included in the power storage element. It is a top view of the positive electrode included in the power storage element. It is a schematic diagram which shows the negative electrode lead foil and the positive electrode lead foil of the electricity storage element. It is a schematic diagram which shows the mode of the electric connection with the container of the power storage element. It is a schematic diagram which shows the mode of resistance welding by the conventional method of the negative electrode lead foil and the outer can of the power storage element. It is a schematic diagram which shows the mode of resistance welding by the method of this invention of the negative electrode lead foil and the outer can of the power storage element. It is a schematic diagram which shows the mode of joining using the storage element and the reinforcing plate of the outer can. It is a schematic diagram which shows the welding part of the negative electrode lead foil of the power storage element, the outer can, and the reinforcing plate.

The electrochemical device according to the present invention will be described.

[Electrochemical device configuration]
FIG. 1 is a perspective view of the electrochemical device 100 according to the present embodiment, and FIG. 2 is a perspective view of a partial configuration of the electrochemical device 100. In the figure below, the X, Y, and Z directions are three directions orthogonal to each other.

The electrochemical device 100 may be any device that can be charged and discharged, and may be any of various electrochemical devices such as a lithium ion capacitor, an electric double layer capacitor, and a lithium ion secondary battery.

As shown in FIGS. 1 and 2, the electrochemical device 100 includes a power storage element 110 and a container 120. The electrochemical device 100 has a cylindrical shape, and can have, for example, a diameter (XY direction) of 18 mm and a length (Z direction) of 65 mm.

As shown in FIG. 1, the container 120 includes an outer can 121 and a sealing body 122.

The outer can 121 is made of metal and has a can bottom portion 121a and a side wall portion 121b. The can bottom 121a has a disk shape. The side wall portion 121b has a cylindrical shape continuous with the peripheral edge of the can bottom portion 121a. The side wall portion 121b is covered with an insulating film.

The sealing body 122 is made of metal and is joined to the side wall portion 121b to seal the internal space of the outer can 121.

As shown in FIG. 2, the storage element 110 and an electrolytic solution (not shown) are housed in the outer can 121 and sealed by the sealing body 122 to form the electrochemical device 100.

FIG. 3 is a perspective view of the power storage element 110, and FIG. 4 is an enlarged cross-sectional view of the power storage element 110. As shown in these figures, the power storage element 110 has a negative electrode 130, a positive electrode 140, and a separator 150, and is configured by winding a laminate in which these are laminated.

As shown in FIG. 4, the negative electrode 130 has a negative electrode current collector 131 and a negative electrode active material layer 132. The negative electrode current collector 131 is made of a conductive material and can be a metal foil such as a copper foil. The negative electrode current collector 131 is preferably a metal foil whose surface is chemically or mechanically roughened, or a metal foil having through holes formed therein.

The negative electrode active material layer 132 is formed on both the front and back surfaces of the negative electrode current collector 131. The material of the negative electrode active material layer 132 may be a mixture of the negative electrode active material and the binder resin, and may further contain a conductive auxiliary material. The negative electrode active material can be, for example, a carbon-based material such as hard carbon, graphite, or soft carbon.

The binder resin is a synthetic resin for bonding a negative electrode active material, for example, carboxymethyl cellulose, styrene butadiene rubber, polyethylene, polypropylene, aromatic polyamide, fluororubber, polyvinylidene fluoride, isoprene rubber, butadiene rubber and ethylene propylene rubber. And so on.

The conductive auxiliary agent is a particle made of a conductive material and improves the conductivity between the negative electrode active materials. Examples of the conductive auxiliary agent include carbon materials such as graphite and carbon black. These may be used alone or in combination of two or more. The conductive auxiliary agent may be a metal material, a conductive polymer, or the like as long as it is a conductive material.

FIG. 5 is a plan view showing the negative electrode 130 before winding. As shown in the figure, the negative electrode active material layer 132 is laminated on most of the surface of the negative electrode current collector 131. Similarly, a negative electrode active material layer 132 (not shown) is laminated on the back surface of the negative electrode current collector 131.

Further, the negative electrode 130 includes a negative electrode lead foil 133. The negative electrode lead foil 133 is formed by projecting a part of the negative electrode current collector 131. The negative electrode lead foil 133 is connected to the outer can 121 as described later, and electrically connects the outer can 121 and the negative electrode 130.

The negative electrode lead foil 133 is not limited to the one formed by projecting a part of the negative electrode current collector 131, and is a foil different from the negative electrode current collector 131 electrically connected to the negative electrode current collector 131. It may be a shaped member. The number of the negative electrode lead foil 133 is not limited to the seven shown in FIG. 5, and may be any one or more.

As shown in FIG. 4, the positive electrode 140 has a positive electrode current collector 141 and a positive electrode active material layer 142. The positive electrode current collector 141 is made of a conductive material and can be a metal foil such as an aluminum foil. The positive electrode current collector 141 is preferably a metal foil whose surface is chemically or mechanically roughened, or a metal foil having through holes formed therein.

The positive electrode active material layer 142 is formed on both the front and back surfaces of the positive electrode current collector 141. The material of the positive electrode active material layer 142 may be a mixture of the positive electrode active material and the binder resin, and may further contain a conductive auxiliary material. The positive electrode active material can be, for example, activated carbon or PAS (Polyacenic Semiconductor).

The binder resin is a synthetic resin for bonding a positive electrode active material, for example, carboxymethyl cellulose, styrene butadiene rubber, polyethylene, polypropylene, aromatic polyamide, fluororubber, polyvinylidene fluoride, isoprene rubber, butadiene rubber and ethylene propylene rubber. And so on.

The conductive auxiliary agent is a particle made of a conductive material and improves the conductivity between the positive electrode active materials. Examples of the conductive auxiliary agent include carbon materials such as graphite and carbon black. These may be used alone or in combination of two or more. The conductive auxiliary agent may be a metal material, a conductive polymer, or the like as long as it is a conductive material.

FIG. 6 is a plan view showing the positive electrode 140 before winding. As shown in the figure, the positive electrode active material layer 142 is laminated on most of the surface of the positive electrode current collector 141. Further, a positive electrode active material layer 142 (not shown) is similarly laminated on the back surface of the positive electrode current collector 141.

Further, the positive electrode 140 includes a positive electrode lead foil 143. The positive electrode lead foil 143 is connected to a region on the positive electrode current collector 141 where the positive electrode active material layer 142 is not applied, and is covered with an insulating tape (not shown). The positive electrode lead foil 143 is connected to the sealing body 122 as described later, and electrically connects the sealing body 122 and the positive electrode 140.

The positive electrode lead foil 143 may be formed by projecting a part of the positive electrode current collector 141. The number of positive electrode lead foils 143 is not limited to the three shown in FIG. 5, and may be one or more.

The separator 150 is arranged between the negative electrode 130 and the positive electrode 140, insulates the negative electrode 130 and the positive electrode 140, and allows ions contained in the electrolytic solution to pass through. The separator 150 can be a porous sheet made of a woven fabric, a non-woven fabric, a glass fiber, a cellulose fiber, a plastic fiber, or the like.

The electrochemical device 100 is configured as described above. The electrolytic solution accommodated in the container 120 together with the power storage element 110 can be arbitrarily selected according to the type of the electrochemical device 100.

[About materials]
The outer can 121 and the negative electrode lead foil 133 are made of metal. Here, the outer can 121 is made of a metal containing the first metal type. The first metal type is preferably iron, and the outer can 121 may be made of iron. Further, the outer can 121 may be made of an alloy containing iron. Further, the outer can 121 may be made of stainless steel.

Further, the outer can 121 preferably contains nickel in addition to iron, and may be made of an alloy of iron and nickel. Further, the outer can 121 may be a base material made of iron plated with nickel.

Further, the negative electrode lead foil 133 contains a second metal type and is made of a metal different from that of the outer can 121. The second metal species is a metal species different from the first metal species. Copper is suitable as the second metal type, and the negative electrode lead foil 133 may be made of copper. Further, the negative electrode lead foil 133 may be made of an alloy containing copper.

The material of the outer can 121 is preferably one having a melting point higher than that of the material of the negative electrode lead foil 133.

[About the electrical connection between the power storage element and the outer can]
In the electrochemical device 100, the negative electrode 130 is electrically connected to the outer can 121 and the positive electrode 140 is electrically connected to the sealing body 122, and the power storage element 110 is charged and discharged via the outer can 121 and the sealing body 122.

FIG. 7 is a schematic cross-sectional view of the power storage element 110. As shown in the figure, the negative electrode 130 and the positive electrode 140 are wound in a state of being separated by the separator 150. As shown in the figure, the hole at the center of winding is referred to as the central hole S. The negative electrode lead foil 133 protrudes from the negative electrode 130 to one side (lower in FIG. 7) of the power storage element 110, and the positive electrode lead foil 143 protrudes from the positive electrode 140 to the opposite side (upper in FIG. 7).

FIG. 8 is a schematic diagram showing an electrical connection between the power storage element 110 and the container 120. As shown in the figure, the negative electrode lead foil 133 is bonded to the can bottom portion 121a of the outer can 121, and the positive electrode lead foil 143 is bonded to the sealing body 122. As a result, the can bottom portion 121a of the outer can 121 functions as a negative electrode terminal, and the sealing body 122 functions as a positive electrode terminal.

Here, the negative electrode lead foil 133 and the outer can 121 are joined by resistance welding. FIG. 9 is a schematic view showing resistance welding of the negative electrode lead foil and the outer can by a general method. As shown in the figure, when a plurality of negative electrode lead foils 233 and the outer can 221 are joined by resistance welding, the negative electrode lead foil 233 is placed on the can bottom 221a of the outer can 221 and the outer can 221 is bottom welded. It is brought into contact with the electrode 301.

Further, the upper welding electrode 302 is brought into contact with the negative electrode lead foil 233, and a voltage is applied between the upper welding electrode 302 and the lower welding electrode 301.

As a result, a current flows between the upper welding electrode 302 and the lower welding electrode 301 via the negative electrode lead foil 233 and the outer can 221, and the negative electrode lead foil 233 and the outer can 221 are welded (resistance welded) by heat generated by the resistance. ..

However, when there are a plurality of negative electrode lead foils 233, the negative electrode lead foil 233 in the upper layer (upper welding electrode 302 side) is heated, but the negative electrode lead foil 233 in the lower layer (outer can 221 side) is not sufficiently heated. , The bonding strength between the negative electrode lead foil 233 and the outer can 221 becomes insufficient. In particular, when the outer can 221 and the negative electrode lead foil 233 are made of dissimilar metals, the bonding strength tends to be insufficient.

Therefore, in the electrochemical device 100, resistance welding of the negative electrode lead foil 133 and the outer can 121 is performed as follows. FIG. 10 is a schematic view showing resistance welding of the negative electrode lead foil 133 and the outer can 121 by the method according to the present invention.

As shown in the figure, in the electrochemical device 100 according to the present invention, the negative electrode lead foil 133 is placed on the outer can 121, and the lower welding electrode 301 is brought into contact with the outer can 121. Further, the reinforcing plate 160 is placed on the negative electrode lead foil 133, the negative electrode lead foil 133 is sandwiched between the outer can 121 and the reinforcing plate 160, and the upper welding electrode 302 is brought into contact with the reinforcing plate 160. The upper welding electrode 302 can be brought into contact with the negative electrode lead foil 133 via the center hole S (see FIG. 7).

The reinforcing plate 160 is a plate-shaped member made of metal, and includes the above-mentioned first metal type. The reinforcing plate 160 is preferably made of the same material as the outer can 121. Further, it is preferable that the thickness of the reinforcing plate 160 and the outer can 121 is larger than the total thickness of the negative electrode lead foil 133 to be welded.

In this state, when a voltage is applied between the upper welding electrode 302 and the lower welding electrode 301, a current is generated between the upper welding electrode 302 and the lower welding electrode 301 via the reinforcing plate 160, the negative electrode lead foil 133 and the outer can 121. It flows. At this time, the reinforcing plate 160, the negative electrode lead foil 133, and the outer can 121 are welded (resistance welded) by the heat generated by the resistance.

FIG. 11 is a schematic view of the electrochemical device 100, showing a state in which resistance welding is performed using the reinforcing plate 160. FIG. 12 is an enlarged schematic view of the electrochemical device 100 resistance welded portion. As shown in FIG. 12, a material coexistence region R is formed at the welded portion of the reinforcing plate 160, the negative electrode lead foil 133, and the outer can 121.

The material coexistence region R is a region where the materials of the reinforcing plate 160, the negative electrode lead foil 133, and the outer can 121 are partially melted by welding and coexist. As described above, the reinforcing plate 160 and the outer can 121 contain the first metal type, and the negative electrode lead foil 133 contains the second metal type. Therefore, in the material coexistence region R, the first metal species and the second metal species coexist.

By performing resistance welding with a plurality of negative electrode lead foils 133 sandwiched between the reinforcing plate 160 and the outer can 121, the plurality of negative electrode lead foils 133 are evenly heated, and the first metal type and the second metal are heated. A material coexistence region R in which species coexist is formed.

In particular, when the first metal type is iron and the second metal type is copper, iron and copper diffuse each other, and a material coexistence region R is preferably formed. Further, when nickel is contained in the reinforcing plate 160 and the outer can 121, copper and nickel are compatible with each other, and the material coexistence region R in which the metal species coexist in the order of iron-nickel-copper from the center of the material coexistence region R. It is formed.

This makes it possible to bond the reinforcing plate 160, the negative electrode lead foil 133, and the outer can 121 to each other with high bonding strength. Further, since the contact area between the reinforcing plate 160, the negative electrode lead foil 133 and the outer can 121 is expanded, it is possible to reduce the resistance of the conduction path between the negative electrode lead foil 133 and the outer can 121, which is large. It is possible to reduce heat generation and alleviate element deterioration during current input / output.

The number of negative electrode lead foils 133 that can be joined by the method according to the present invention is not particularly limited, but three or more are suitable, and up to about 12 sheets can be welded with sufficient strength.

[Modification example]
In the above description, the configuration of joining the negative electrode lead foil 133 to the outer can 121 by resistance welding has been described, but instead of the negative electrode lead foil 133, the positive electrode lead foil 143 may be joined to the outer can 121 by the above method. In this case, by sandwiching the positive electrode lead foil 143 between the outer can 121 and the reinforcing plate 160 and performing resistance welding, it is possible to join a plurality of positive electrode lead foils 143 with high bonding strength.

Further, the method according to the present invention can be applied to resistance welding other than electrochemical devices. That is, by sandwiching a plurality of metal foils between the first member and the second member, the welding electrodes are brought into contact with the first member and the second member, respectively, and a current is applied between the welding electrodes. , It is possible to produce a bonded body in which a plurality of metal foils are joined to the first member and the second member.

The first member and the second member are made of a metal containing a first metal type, and the metal foil is made of a metal containing a second metal type, so that the first metal type and the second metal A material coexistence region where seeds coexist is formed, and it is possible to bond a plurality of metal foils with high bonding strength.

100 ... Electrochemical device 110 ... Power storage element 120 ... Container 121 ... Exterior can 122 ... Seal 130 ... Negative electrode 131 ... Negative electrode current collector 132 ... Negative electrode active material layer 133 ... Negative electrode lead foil 140 ... Positive electrode 141 ... Positive electrode current collector 142 … Positive electrode active material layer 143… Positive electrode lead foil 150… Separator 160… Reinforcing plate

Claims (5)

An exterior can made of metal containing iron and
A power storage element comprising a positive electrode, a negative electrode and a separator, in which the positive electrode and the negative electrode are laminated via a separator and wound, which is electrically connected to the positive electrode or the negative electrode and contains copper , and the outer can. A power storage element having a lead foil made of a metal different from that of the outer can and housed in the outer can.
Equipped with a reinforcing plate made of metal including iron ,
An electrochemical device in which the outer can and the reinforcing plate are welded with the lead foil sandwiched between them, and iron and copper coexist at the welded portion. The electrochemical device according to claim 1.
The outer can and the reinforcing plate are electrochemical devices that are welded by sandwiching three or more lead foils. The electrochemical device according to claim 1 or 2.
The outer can and the reinforcing plate are electrochemical devices made of the same metal. The electrochemical device according to claim 1 .
The outer can and the reinforcing plate are electrochemical devices further containing nickel. An outer can made of a metal containing iron , a positive electrode, a negative electrode, and a separator are provided, and the positive electrode and the negative electrode are laminated via a separator and wound, and is electrically connected to the positive electrode or the negative electrode. A lead foil that is connected and contains copper and is made of a metal different from that of the outer can is prepared, and a power storage element housed in the outer can and a reinforcing plate made of metal containing iron are prepared.
The lead foil is sandwiched between the outer can and the reinforcing plate,
The first welding electrode is brought into contact with the outer can.
The second welding electrode is brought into contact with the reinforcing plate, and the second welding electrode is brought into contact with the reinforcing plate.
A method for manufacturing an electrochemical device in which a voltage is applied between the first welding electrode and the second welding electrode, and the lead foil is sandwiched by resistance welding to join the outer can and the reinforcing plate.

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