JP7055981B2 - 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 and a method for manufacturing the electrochemical device.

As an electrochemical device such as a lithium ion capacitor, a winding type device in which a positive electrode and a negative electrode are wound while being separated by a separator is often used. The positive electrode and the negative electrode are each connected to the terminal via a lead member.

In electrochemical devices, it is possible to increase the capacity and reduce the resistance by lengthening the electrodes. However, when the electrode is lengthened, it becomes difficult to obtain sufficient output characteristics due to the length of the electrode. In order to solve this problem, a plurality of lead members are connected to the electrodes, and the electrodes and terminals are connected by the plurality of lead members.

For example, Patent Document 1 discloses a secondary battery in which a plurality of lead plates are overlapped at one point and the overlapped portion is connected to a sealing body. Further, Patent Document 2 discloses a method of connecting a plurality of lead plates to a sealing body via a current collector plate.

Japanese Unexamined Patent Publication No. 2007-335232 International Publication No. 2016/174811

However, it is difficult to directly connect to the sealing body by the connection method described in Patent Document 1, and the feasibility is poor. Further, the method described in Patent Document 2 may lead to an increase in the number of parts and a decrease in output performance due to the connection resistance between the current collector plate and the lead plate.

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

In order to achieve the above object, the electrochemical device according to one embodiment of the present invention includes a power storage element, a connection plate, a rupture disk, and an insulator.
The power storage element includes a positive electrode, a negative electrode, and a separator, and is a power storage element in which the positive electrode and the negative electrode are laminated via a separator and wound, and a plurality of electric power storage elements electrically connected to the positive electrode or the negative electrode. It has a lead plate.
The connection plate has a first main surface on the power storage element side and a second main surface on the opposite side of the first main surface, and the plurality of the connection plates are superposed on the first main surface. The lead plate is welded.
The rupture disk is connected to the second main surface of the connection plate.
The insulator abuts on the first region, which is the outer peripheral region of the second main surface, and insulates the connection plate and the rupture disk.
The plurality of lead plates are welded to a second region of the first main surface, which is a region opposite to the first region.

According to this structure, a rupture disk is connected to the second main surface of the connection plate, and in order to join the lead plate to the first main surface, the lead plate is hit on the first main surface side. It is necessary to perform series-type resistance welding in which a current is passed between the contacted welding electrodes. Here, when there are a plurality of lead plates to be welded, it is necessary to press the welding electrodes with a strong force to reduce the contact resistance. In the above structure, in the outer peripheral region of the second main surface, there is a first region in which the insulator that insulates the connection plate and the rupture disk abuts. Therefore, by performing resistance welding in the second region of the first main surface opposite to the first region, the connection plate is damaged even if the welding electrode is pressed with a strong force. It is prevented from occurring. Therefore, it is possible to press the welding electrode with a strong force and reliably join the lead plate to the connecting plate.

The plurality of lead plates may be welded to the connection plate at two points included in the second region.

The plurality of lead plates welded to the connection plate may be three or more.

The electrochemical device may be a lithium ion capacitor.

In order to achieve the above object, the method for manufacturing an electrochemical device according to one embodiment of the present invention 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. A power storage element having a plurality of lead plates electrically connected to the positive electrode or the negative electrode, a first main surface on the power storage element side, and a second surface on the opposite side of the first main surface. The connection plate having the main surface of the above, the rupture disk connected to the second main surface of the connection plate, and the first region which is the outer peripheral region of the second main surface are contacted with the connection plate. Prepare an insulator to insulate the rupture disk.
The plurality of lead plates are stacked and brought into contact with the first main surface.
In the electrode contact region including the second region, which is the region opposite to the first region of the first main surface, the first welding electrode and the second welding electrode are attached to the lead plate. The plurality of lead plates are welded to the connection plate in the second region by bringing them into contact with each other and applying a current between the first welding electrode and the second welding electrode.

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

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 of the negative electrode lead plate and the positive electrode lead plate of the 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 sectional drawing of the sealing body provided in the electrochemical device which concerns on embodiment of this invention. It is a top view of the sealing body included in the electrochemical device. It is sectional drawing of the connection plate provided in the enclosed opening body. It is a top view of the connection plate provided in the enclosed opening body. It is a schematic diagram which shows the method of resistance welding of the positive electrode lead plate and the connection plate in the electrochemical device which concerns on embodiment of this invention. It is a schematic diagram which shows the method of resistance welding of a positive electrode lead plate and a connection plate in the same electrochemical device. It is a schematic diagram which shows the state which the positive electrode lead plate and the connection plate are welded in the same electrochemical device.

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. The configuration of the sealing body 122 will be described later.

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 an electrochemically stable and 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 plurality of negative electrode lead plates 133. The negative electrode lead plate 133 is formed by projecting a part of the negative electrode current collector 131. The negative electrode lead plate 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 plate 133 is not limited to the one formed by projecting a part of the negative electrode current collector 131, and is a plate different from the negative electrode current collector 131 electrically connected to the negative electrode current collector 131. It may be a shaped or foil-shaped member. The number of the negative electrode lead plates 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 an electrochemically stable and 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 plate 143. The positive electrode lead plate 143 is made of a plate-shaped or foil-shaped metal, and is connected to a region on the positive electrode current collector 141 where the positive electrode active material layer 142 is not applied. The positive electrode lead plate 143 is made of the same material as the positive electrode current collector 141, and can be made of, for example, aluminum. The positive electrode lead plate 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 plate 143 may be formed by projecting a part of the positive electrode current collector 141. The number of positive electrode lead plates 143 is not limited to three shown in FIG. 5, and may be two 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 the electrical connection between the power storage element and the outer can]
In the electrochemical device 100, the power storage element 110 is electrically connected to the container 120, and the power storage element 110 is charged and discharged via the container 120.

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 plate 133 projects from the negative electrode 130 to one side (lower in FIG. 7) of the power storage element 110, and the positive electrode lead plate 143 projects to the opposite side (upper in FIG. 7) from the positive electrode 140.

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 plate 133 is joined to the outer can 121, and the positive electrode lead plate 143 is joined 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 positive electrode lead plate 143 and the sealing body 122 are joined by series-type resistance welding as described later.

[Composition of sealing body]
FIG. 9 is a cross-sectional view of the sealing body 122, and FIG. 10 is a plan view of the sealing body 122 as viewed from the power storage element 110 side.

As shown in these figures, the sealing body 122 includes a frame member 161, an external terminal 162, a connection plate 163, a rupture disk 164, and an insulator 165.

The frame member 161 is fitted to the outer can 121, and the sealing body 122 is fixed to the outer can 121. The frame member 161 can have an annular shape.

The external terminal 162 is fixed to the frame member 161 and functions as a positive electrode terminal of the electrochemical device 100.

The connection plate 163 has a disk shape, is arranged on the power storage element 110 side (lower side in the figure) in the sealing body 122, and is a portion to which the positive electrode lead plate 143 is joined.

FIG. 11 is a cross-sectional view of the connection plate 163. As shown in the figure, the connection plate 163 has a first main surface 163a and a second main surface 163b. The first main surface 163a is the surface on the power storage element 110 side, and the second main surface 163b is the surface on the opposite side of the first main surface 163a.

Further, as shown in FIG. 10, the connection plate 163 has a through hole 163c and a recess 163d. The through hole 163c communicates with the first main surface 163a and the second main surface 163b, and is a hole through which the generated gas passes when an abnormality occurs in the power storage element 110. The number and shape of the through holes 163c are not particularly limited, but they are arranged with a welding target region described later.

The recess 163d is a portion where the thickness of the connection plate 163 is thin, is provided in the central portion of the second main surface 163b, and is a portion to which the rupture disk 164 is connected.

The rupture disk 164 is connected to the recess 163d on the second main surface 163b, and electrically connects the connection plate 163 and the external terminal 162. When gas is generated from the power storage element 110, the rupture disk 164 breaks at the connection point with the recess 163d and insulates the connection plate 163 and the external terminal 162.

The insulator 165 is arranged between the rupture disk 164 and the connection plate 163 and insulates them from each other. The insulator 165 has an annular shape and abuts on the outer peripheral region of the second main surface 163b as shown in FIG. The region in contact with the insulator 165 on the second main surface 163b is referred to as the first region 163e.

FIG. 12 is a schematic view showing a region on the first main surface 163a. As shown in FIGS. 11 and 12, in the first main surface 163b, the region opposite to the first region 163e is defined as the second region 163f, and the region including the second region 163f and separated from the through hole 163c is an electrode. The contact area is 163 g.

Further, a region on the inner peripheral side of the electrode contact region 163 g and around the recess 163d is defined as a third region 163h.

The frame member 161, the external terminal 162, the connection plate 163, and the rupture disk 164 are made of a metal material, and those made of the same material are preferable. Examples of these materials include aluminum, alloys containing aluminum, and stainless steel. The insulator 165 is made of an insulating material such as resin.

[Welding of positive electrode lead plate to connection plate]
As described above, the positive electrode lead plate 143 is electrically connected to the sealing body 122. Specifically, the positive electrode lead plate 143 is welded to the connection plate 163 by resistance welding. FIG. 13 is a cross-sectional view when the positive electrode lead plate 143 is welded to the connection plate 163, and FIG. 14 is a plan view at this time.

As shown in these figures, at the time of welding, the positive electrode lead plate 143 is arranged so as to be overlapped on the first main surface 163a, and the two welding electrodes 301 are pressed on the positive electrode lead plate 143. In this state, a current is applied between the two welding electrodes 301. As a result, as shown by the arrow, a current flows between the two welding electrodes 301 via the positive electrode lead plate 143 and the connection plate 163, and between the positive electrode lead plate 143 and between the positive electrode lead plate 143 and the connection plate 163. Is welded (resistance welding).

As described above, the rupture disk 164 and the external terminal 162 are provided on the second main surface 163b side of the connection plate 163, and the welding electrode cannot be arranged on the second main surface 163b side. Therefore, it is necessary to bring two welding electrodes 301 into contact with the first main surface 163a side and pass a current between both electrodes to perform resistance welding (series method resistance welding).

Here, when there is only one positive electrode lead plate 143 to be welded, it is also possible to perform resistance welding by pressing the two welding electrodes 301 against the third region 163h (see FIG. 12). However, when there are two or more positive electrode lead plates 143 to be welded, it is necessary to press the welding electrode 301 against the positive electrode lead plate 143 with a strong force (for example, 20 N or more) in order to reduce the contact resistance with the welding electrode 301. be. At this time, since the back surface side of the third region 163h is a space, the connection plate 163 may be deformed.

On the other hand, in the present invention, the two welding electrodes 301 are pressed against the positive electrode lead plate 143 on the electrode contact region 163 g, and resistance welding is performed so that a welded portion is formed in the second region 163 g. .. Since the electrode contact region 163g has a first region 163e in which the insulator 165 abuts on the second main surface 163b which is the back surface, even if the welding electrode 301 is pressed against the positive electrode lead plate 143 with a strong force, the pressing force is applied. It is received by the insulator 165.

This prevents the connection plate 163 from being deformed, presses the welding electrode 301 with a strong force, reduces the contact resistance with the welding electrode 301, and securely connects the plurality of positive electrode lead plates 143. It is possible to weld to the plate 163. The welding electrode 301 needs to be pressed with a stronger force as the number of positive electrode lead plates 143 increases. The present invention is particularly effective when the number of positive electrode lead plates 143 to be welded is three or more.

In general, a through hole is arranged around the outer peripheral region of the connection plate. In the sealing body 122 according to the present embodiment, a portion where the through hole 163c does not exist is formed in the outer peripheral region of the connection plate 163, and the electrode contact region 163g is secured. In particular, in a lithium ion capacitor, the amount of gas generated at the time of abnormality is smaller than that of a lithium ion secondary battery or the like, and the size of the through hole 163c can be reduced.

Further, as described above, the electrode contact region 163g does not have to be a region corresponding to the second region 163f, and includes the second region 163f and is a region extending to the inner peripheral side to a certain extent from the second region 163f. be able to. This is because the welding electrode 301 has a certain thickness, so that even if the welding electrode 301 is brought into contact with the electrode contact region 163 g, a welded portion can be formed in the second region 163 g.

FIG. 15 is a schematic view showing a state in which the positive electrode lead plate 143 is welded to the connection plate 163. As shown in the figure, a welded portion R is formed on the second region 163f between the positive electrode lead plates 143 and between the positive electrode lead plates 143 and the connection plate 163.

The sealing body 122 is joined to the outer can 121 after the positive electrode lead plate 143 is welded to the connection plate 163. Further, the negative electrode lead plate 133 can be welded to the outer can 121 before or after welding the positive electrode lead plate 143. As a result, as shown in FIG. 8, the negative electrode 130 and the positive electrode 140 are electrically connected to the container 120.

[Modification example]
In the above description, the configuration in which the positive electrode lead plate 143 is joined to the sealing body 122 by resistance welding has been described, but instead of the positive electrode lead plate 143, the negative electrode lead plate 133 may be joined to the sealing body 122 by the above method. In this case, the positive electrode lead plate 143 can be joined to the outer can 121.

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 plate 140 ... Positive electrode 141 ... Positive electrode current collector 142 ... Positive electrode active material layer 143 ... Positive electrode lead plate 150 ... Separator 161 ... Frame member 162 ... External terminal 163 ... Connection plate 163a ... First main surface 163b ... Second main surface 163c ... Through hole 163d ... Recessed portion 163e ... First region 163f ... 2nd region 163g ... Electrode contact area 163h ... 3rd region 164 ... Rupture disk 165 ... Insulator

Claims (5)

A 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, and having a plurality of lead plates electrically connected to the positive electrode or the negative electrode. With the element
It has a first main surface on the power storage element side and a second main surface on the opposite side of the first main surface, and the plurality of stacked lead plates are welded to the first main surface. With the connection plate
A rupture disk connected to the second main surface of the connection plate, and
It is provided with an insulator that abuts on the first region, which is the outer peripheral region of the second main surface, and insulates the connection plate and the rupture disk.
The plurality of lead plates are electrochemical devices welded to a second region of the first main surface, which is a region opposite to the first region. The electrochemical device according to claim 1.
The plurality of lead plates are electrochemical devices welded to the connection plate at two points included in the second region. The electrochemical device according to claim 1 or 2.
An electrochemical device in which the plurality of lead plates welded to the connection plate is three or more. The electrochemical device according to any one of claims 1 to 3.
An electrochemical device that is a lithium-ion capacitor. A 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, and having a plurality of lead plates electrically connected to the positive electrode or the negative electrode. The element, a connection plate having the first main surface on the power storage element side, the second main surface on the opposite side of the first main surface, and the second main surface of the connection plate are connected to each other. A rupture disk and an insulator that abuts on the first region, which is the outer peripheral region of the second main surface, and insulates the connection plate and the rupture disk are prepared.
The plurality of lead plates are overlapped and brought into contact with the first main surface.
In the electrode contact region including the second region, which is the region opposite to the first region of the first main surface, the first welding electrode and the second welding electrode are attached to the plurality of lead plates. Electricity for welding the plurality of lead plates to the connection plate in the second region by bringing the electrodes into contact with each other and applying a current between the first welding electrode and the second welding electrode. How to make a chemical device.

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