WO2014196230A1

WO2014196230A1 - Electrochemical device

Info

Publication number: WO2014196230A1
Application number: PCT/JP2014/054611
Authority: WO
Inventors: 裕樹河井; 直人萩原; 響太郎真野
Original assignee: 太陽誘電株式会社
Priority date: 2013-06-07
Filing date: 2014-02-26
Publication date: 2014-12-11
Also published as: JPWO2014196230A1

Abstract

[Problem] To provide a securely welded electrochemical device. [Solution] This electrochemical device is provided with a case, a welding ring, a lid, a melt-solidified portion, a power storage element, and an electrolyte. The case has a bottom and frame-shape walls along the outer periphery of the bottom. The welding ring is joined to the case and forms a liquid chamber together with the case. The lid seals the liquid chamber. The melt-solidified portion of the welding ring and the lid is formed from the lid to the welding ring but without reaching the case, and, in a cross-section passing through and perpendicular to the wall, the shape of the melt-solidified portion gradually narrows with the melting depth. The power storage element is housed in the liquid chamber. The electrolyte is housed in the liquid chamber.

Description

Electrochemical devices

The present invention relates to an electrochemical device in which a storage element is accommodated.

An electrochemical device such as an electric double layer capacitor or a lithium ion capacitor is generally configured by storing a storage element or an electrolyte in a case. Such an electrochemical device is manufactured by housing a power storage element or the like in a case and then bonding a lid (lid) to the case.

For joining the lid to the case, seam welding, which is welding by resistance heating using a seam (welding terminal), has been the mainstream so far. However, in recent years, electrochemical devices have been miniaturized, and laser welding that can cope with the miniaturization of electrochemical devices has attracted attention.

For example, Patent Document 1 discloses a technique for sealing a battery case and a lid by laser welding. In this document, in order to enable good welding, the depth with respect to the width of the weld solidified portion is defined. Patent Document 2 discloses laser welding of different materials. Also in this document, the depth of the weld solidification part is prescribed | regulated.

JP 2005-040853 A Japanese Patent Laid-Open No. 11-239888

Here, the strength and sealing performance of the welding depend on the melting degree of the material (the shape of the weld solidified portion), and it becomes a problem whether the melting is insufficient or excessive. As an indicator of the degree of melting in laser welding, since the cross section of the melted and solidified portion is a triangle with the width irradiated with the laser as the base, it is common to define the ratio of the base to the height. For example, Patent Document 1 also defines the height of a triangle with respect to the base. However, since the welding strength is determined by the amount to be melted (penetration width), there is a possibility that the welding width is insufficient to maintain the sealing performance according to the provisions of the technology.

Also, in order to securely join the lid and the case, it is necessary for both to melt together, so the melted and solidified part must penetrate through the part irradiated with the laser. However, in the above-described defining method, the welding width and the depth of the melt-solidified portion are regulated, and welding may not be possible depending on the size of the case and the thickness of the part.

In view of the above circumstances, an object of the present invention is to provide an electrochemical device that is reliably welded.

In order to achieve the above object, an electrochemical device according to an embodiment of the present invention includes a case, a welding ring, a lid, a melt-solidified part, a power storage element, and an electrolytic solution.
The case has a bottom and a frame-like wall along the outer edge of the bottom.
The welding ring is joined to the case and forms a liquid chamber together with the case.
The lid seals the liquid chamber.
The melt-solidified portion is a melt-solidified portion of the lid and the weld ring, and is formed from the lid to the weld ring, does not reach the case, and is cross-sectionally orthogonal to the wall portion. The shape of the solidified part gradually decreases in width with the melting depth.
The power storage element is accommodated in the liquid chamber.
The electrolytic solution is accommodated in the liquid chamber.

1 is a perspective view of an electrochemical device according to an embodiment of the present invention. FIG. 3 is a cross-sectional view taken along line S11-S11 of the same electrochemical device. It is a disassembled perspective view of the case of the same electrochemical device. It is sectional drawing which shows the fusion | melting solidification part of the same electrochemical device. It is a top view which shows the fusion | melting solidification part of the same electrochemical device. It is a schematic diagram which shows the melt solidification part of the same electrochemical device. It is a schematic diagram which shows the melt solidification part of the same electrochemical device. It is a schematic diagram which shows the laser welding which forms the fusion | melting solidification part of the same electrochemical device.

An electrochemical device according to an embodiment of the present invention includes a case, a welding ring, a lid, a melt-solidified portion, a power storage element, and an electrolytic solution.
The case has a bottom and a frame-like wall along the outer edge of the bottom.
The welding ring is joined to the case and forms a liquid chamber together with the case.
The lid seals the liquid chamber.
The melt-solidified portion is a melt-solidified portion of the lid and the weld ring, and is formed from the lid to the weld ring, does not reach the case, and is cross-sectionally orthogonal to the wall portion. The shape of the solidified part gradually decreases in width with the melting depth.
The power storage element is accommodated in the liquid chamber.
The electrolytic solution is accommodated in the liquid chamber.

When the melt-solidified part is formed from the lid to the weld ring, the lid and the weld ring are welded. On the other hand, when the weld solidified portion reaches the case, the case is damaged by heat during welding, and the airtightness of the liquid chamber may be insufficient. That is, the melted and solidified portion is formed from the lid to the weld ring, and can reliably join the lid and the weld ring when it does not reach the case.

When the width at the widest position is the first width and the width at the half of the melt depth is the second width, the second width is the first width. The cross-sectional shape is 0.3 times or more and 0.9 times or less.

If the penetration by laser welding is insufficient and the second width is less than 0.3 times the first width, the weld will be destroyed by a slight impact, the airtightness of the liquid chamber will be reduced, and the resistance of the electrochemical device will increase. And capacity reduction occurs. In addition, when reflow soldering or overcharge occurs, gas is generated due to decomposition of the electrolytic solution, etc., the pressure in the liquid chamber rises, the welded portion is destroyed, and the contents may jump out. On the other hand, if there is too much penetration by laser welding and the second width exceeds 0.9 times the first width, ambient air will be taken in during welding to create a burrow, from which the pin pole will be vacated and the liquid chamber The airtightness of the is reduced. If the penetration due to welding is excessive, the welded portion protrudes outside the case, and the lid is cut at the boundary between the welded portion and the lid. On the other hand, the melt-solidified portion having the above-described cross-sectional shape has an appropriate amount of penetration, and the lid and the weld ring can be reliably joined.

The melt-solidified part may have a funnel-like cross-sectional shape.

By making the melt-solidified part into a funnel-shaped cross section, the weld bead can be deepened without being exposed to the inside of the liquid chamber, and the weld strength can be increased without exposing the weld bead. be able to. Moreover, since the distortion of the weld ring can be suppressed by reducing the amount of penetration of the weld ring, it is possible to prevent poor welding due to deformation of the weld ring or the like.

The case is made of ceramic,
The weld ring and the lid are made of Kovar,
The welding ring may be brazed to the case.

According to this configuration, the case and the weld ring are joined by brazing, and the weld ring and the lid are joined by laser welding, so that the airtightness of the liquid chamber is maintained. Note that the welding ring may be plated with Au plating, Ni plating, or the like.

The melt-solidified part may be formed by laser irradiation of a fiber laser.

¡The weld ring and lid can be welded by irradiating a fiber laser onto the lid area overlapping the weld ring.

[Configuration of electrochemical device]
FIG. 1 is a perspective view of an electrochemical device 10 according to this embodiment, and FIG. 2 is a cross-sectional view of the electrochemical device 10 taken along line S11-S11 (FIG. 1). As shown in these drawings, the electrochemical device 10 includes a case 11, a lid 12, a power storage element 13, a positive electrode wiring 14, a positive electrode terminal 15, a negative electrode wiring 16, a negative electrode terminal 17, a welding ring 18, a positive electrode adhesive layer 19, and a negative electrode. It has an adhesive layer 20 and a melt-solidified part 21.

As shown in FIG. 2, the electrochemical device 10 includes a lid 12 and a weld ring 18 that are welded by a melt-solidified portion 21, and an electric storage element 13 and an electrolysis element in a liquid chamber 11 a formed by the case 11, the weld ring 18 and the lid 12. The liquid is enclosed. The positive electrode wiring 14 electrically connects the positive electrode of the power storage element 13 and the positive electrode terminal 15, and the negative electrode wiring 16 electrically connects the negative electrode of the power storage element 13 and the negative electrode terminal 17.

The case 11 forms a liquid chamber 11 a together with the lid 12 and the welding ring 18. FIG. 3 is an exploded perspective view of the case 11. As shown in the figure, the case 11 includes a bottom portion 11b and a wall portion 11c. The bottom portion 11b is a plate-like portion constituting the bottom of the liquid chamber 11a, and a via 11d for the positive electrode wiring 14 is provided. The wall part 11c is a frame-shaped part which comprises the side wall of the liquid chamber 11a and follows the outer edge of the bottom part 11b.

The case 11 may be made of a ceramic such as HTCC (High Temperature Co-fired Ceramics) or LTCC (Low Temperature Co-fired Ceramics). The case 11 can be formed in a concave shape so as to constitute the liquid chamber 11a. For example, the case 11 can have other shapes such as a rectangular parallelepiped shape or a cylindrical shape as shown in FIG.

The lid 12 is joined to the case 11 via the welding ring 18 to seal the liquid chamber 11a. The lid 12 can be made of a conductive material such as various metals, and can be made of, for example, Kovar (iron-nickel-cobalt alloy). The lid 12 is welded to the weld ring by the melted and solidified portion 21, and details thereof will be described later.

The electricity storage element 13 is accommodated in the liquid chamber 11a, and accumulates (accumulates) electric charge or releases (discharges) electric charge. As shown in FIG. 2, the storage element 13 has a first electrode sheet 13a, a second electrode sheet 13b, and a separate sheet 13c, and the separate sheet 13c is sandwiched between the first electrode sheet 13a and the second electrode sheet 13b. It can be.

The constituent materials of the first electrode sheet 13a, the second electrode sheet 13b, and the separate sheet 13c can be appropriately selected according to necessary characteristics. For example, the first electrode sheet 13a and the second electrode sheet 13b are made of a material containing an active material selected from activated carbon, graphite, PAS (Polyacenic Semiconductor), and the separate sheet 13c is made of glass. It can be a porous sheet mainly composed of fiber, cellulose fiber, plastic fiber or the like.

The materials of the first electrode sheet 13 a, the second electrode sheet 13 b, and the separate sheet 13 c may be the same or different depending on the type of the electrochemical device 10. For example, when the electrochemical device 10 is an electric double layer capacitor, the first electrode sheet 13a and the second electrode sheet 13b can be made of the same material. When the electrochemical device 10 is a lithium ion capacitor, the first electrode is used. The material of the sheet 13a and the second electrode sheet 13b can be different.

The electrolyte solution accommodated in the liquid chamber 11a together with the electricity storage element 13 can be arbitrarily selected. For example, when the electrochemical device 10 is an electric double layer capacitor, the electrolytic solution can be an electrolytic solution in which an electrolyte salt is dissolved in a solvent. When the electrochemical device 10 is a lithium ion capacitor, the lithium salt is dissolved in a solvent. Electrolyte solution.

The positive electrode wiring 14 electrically connects the positive electrode (first electrode sheet 13a) of the power storage element 13 and the positive electrode terminal 15. The positive electrode wiring 14 can be made of any conductive material. Specifically, the positive electrode wiring 14 passes through the inside of the case 11 from the positive electrode terminal 15 to immediately below the power storage element 13, contacts the positive electrode adhesive layer 19 via the via 11 d, and stores electricity via the positive electrode adhesive layer 19. It can be electrically connected to the element 13.

The positive electrode terminal 15 is connected to the positive electrode of the electricity storage element 13 by the positive electrode wiring 14, and is used for connection to the outside, for example, a mounting substrate. The positive electrode terminal 15 can be made of an arbitrary conductive material, and can be formed from the side surface of the case 11 toward the lower surface side as shown in FIG.

The negative electrode wiring 16 electrically connects the power storage element 13 (second electrode sheet 13b) and the negative electrode terminal 17. Specifically, the negative electrode wiring 16 can be formed from the negative electrode terminal 17 along the outer periphery of the case 11 and connected to the welding ring 18. The negative electrode wiring 16 is electrically connected to the second electrode sheet 13b through the conductive welding ring 18, the lid 12, and the negative electrode adhesive layer 20. The negative electrode wiring 16 can be made of any conductive material.

The negative electrode terminal 17 is connected to the negative electrode of the electricity storage element 13 by the negative electrode wiring 16, and is used for connection to the outside, for example, a mounting substrate. The negative electrode terminal 17 can be made of an arbitrary conductive material, and can be formed from the side surface of the case 11 toward the lower surface side as shown in FIG.

The welding ring 18 connects the case 11 and the lid 12 to seal the liquid chamber 11a, and electrically connects the lid 12 and the negative electrode wiring 16. The welding ring 18 is joined to the case 11 by bonding (brazing) with a brazing material (gold-copper alloy or the like), and is welded to the lid 12 by a melt-solidified portion 21. The welding ring 18 can be made of a conductive material such as Kovar (iron-nickel-cobalt alloy). The welding ring 18 may be plated with Ni plating, Au plating, or the like.

The positive electrode adhesive layer 19 bonds the first electrode sheet 13 a to the case 11 and electrically connects the first electrode sheet 13 a and the positive electrode wiring 14. The positive electrode adhesive layer 19 is obtained by curing a conductive adhesive, and the conductive adhesive can be a synthetic resin containing conductive particles. The conductive particles are, for example, carbon particles (carbon black), graphite particles (graphite particles), and the like, and the synthetic resin can be a thermosetting resin such as a phenol resin or an epoxy resin.

The negative electrode adhesive layer 20 adheres the second electrode sheet 13 b to the lid 12 and electrically connects the second electrode sheet 13 b and the lid 12. The negative electrode adhesive layer 20 is obtained by curing a conductive adhesive, and the conductive adhesive can be a synthetic resin containing conductive particles, like the positive electrode adhesive layer 19. The negative electrode adhesive layer 20 and the positive electrode adhesive layer 19 can be made of the same type of conductive adhesive, or can be made of other types of conductive adhesive.

[Melting and solidification part]
As described above, the lid 12 and the weld ring 18 are welded by the melt-solidified portion 21. The melt-solidified portion 21 is a portion where the constituent materials of the lid 12 and the weld ring 18 are melted and solidified, and can be formed by laser welding described later.

FIG. 4 is an enlarged view of the melt-solidified portion 21 in FIG. 2, and is a cross-sectional view orthogonal to the wall portion 11c. As shown in FIG. 4A or FIG. 4B, the melt-solidified portion 21 is formed from the lid 12 to the welding ring 18. If the melted and solidified portion 21 does not reach the weld ring 18, the effect of joining the lid 12 to the weld ring 18 does not occur. On the other hand, when the melted and solidified portion 21 reaches the case 11, the case 11 is damaged. Specifically, the melting depth of the melt-solidified portion 21 is preferably half or less of the thickness of the weld ring 18.

FIG. 5 is a plan view showing a region where the melt-solidified portion 21 is formed. As shown in the figure, the melt-solidified portion 21 can be formed in a region where the weld ring 18 and the lid 12 overlap, that is, can be formed in an annular shape around the liquid chamber 11a.

The melt-solidified part 21 has a shape in which the width of the cross section gradually decreases with the melting depth. FIG. 6 is a cross-sectional view showing a cross-sectional shape of the melt-solidified portion 21. As shown in FIG. 6A, the melt-solidified portion 21 can have a cross-sectional shape that has a triangular shape with the surface of the lid 12 as a base. In addition, as shown in FIG. 6B, the melt-solidified portion 21 has a cross-sectional shape in which the width reduction ratio at the shallow melting depth (the width reduction amount with respect to the melting depth) is larger than the width reduction ratio at the deep melting depth. It can be a shape (funnel shape).

By forming the melted and solidified portion 21 into the shape shown in FIG. 6B, the weld bead can be deepened without being exposed to the inside of the liquid chamber 11a, and welding can be performed without exposing the weld bead. Strength can be increased. Moreover, since the distortion of the welding ring 18 can be suppressed by reducing the amount of penetration of the welding ring 18, it becomes possible to prevent poor welding due to deformation of the welding ring 18 or the like. The shape of the melt-solidified portion 21 is formed by performing laser irradiation on the surface of the lid 12, and the shape of the melt-solidified portion 21 varies depending on the laser irradiation conditions.

FIG. 7 is a plan view showing the width of the melt-solidified portion 21, and is a partially enlarged view of FIG. As shown in FIG.6 and FIG.7, let the width | variety in the widest position of the fusion | melting solidification part 21 be 1st width | variety T1. In these figures, the width of the melt-solidified portion 21 is the widest on the surface of the lid 12, but the width of the melt-solidified portion 21 may be the widest at a position deeper than the surface of the lid 12. Further, as shown in FIG. 6, the width of the melt-solidified portion 21 at the half of the welding depth is defined as a second width T2. Here, the melt-solidified portion 21 has a shape in which the width T2 is not less than 0.3 times and not more than 0.9 times the width T1.

When the penetration due to welding is insufficient and the width T2 is less than 0.3 times the width T1, the welding is broken by a slight impact, the airtightness of the liquid chamber 11a is lowered, the resistance of the electrochemical device 10 is increased, and the capacity is decreased. Occurs. Also, when reflow soldering or overcharge occurs, gas is generated due to decomposition of the electrolytic solution, etc., the pressure in the liquid chamber rises, the welded portion is destroyed, and the contents may jump out. On the other hand, if there is too much penetration due to welding and the width T2 exceeds 0.9 times the width T1, the surrounding outside air is taken in during welding to form a burrow, from which a pin pole is opened, and the liquid chamber 11a is airtight. descend. When the penetration due to welding is excessive, the welded portion protrudes outside the case 11, and the lid 12 is cut at the boundary between the welded portion and the lid 12. On the other hand, when the width T2 is not less than 0.3 times and not more than 0.9 times the width T1, penetration by welding becomes appropriate, and these problems do not occur.

[Method for forming melt-solidified part]
The melt-solidified part 21 can be formed as follows. It is assumed that the storage element 13 and the electrolytic solution are accommodated in the liquid chamber 11a before welding. FIG. 8 is a schematic diagram showing a method for forming the melt-solidified portion 21. As shown in the figure, the laser L is irradiated to the lid 12 placed on the welding ring 18. By moving (scanning) the region (spot) irradiated with the laser L at a predetermined speed, the melted and solidified portion 21 is formed on the scanning path.

The fiber laser can be used as the laser to irradiate. The shape of the melt-solidified portion 21 can be adjusted by the output of the laser to be irradiated, the scanning speed, and the focal length (spot diameter). Specifically, in the case of a fiber laser, the melt-solidified portion 21 can be formed by setting the output to 300 W and the irradiation time to 60 ms.

As described above, in the present embodiment, the lid 12 is welded to the weld ring 18 by the melt-solidified portion 21. By welding so that the melt-solidified portion 21 has the shape described above, it is possible to ensure the airtightness of the liquid chamber 11a and improve the reliability of the electrochemical device 10. Furthermore, since the melt-solidified portion 21 is formed by laser welding, this embodiment is suitable for downsizing the electrochemical device 10.

DESCRIPTION OF SYMBOLS 10 ... Electrochemical device 11 ... Case 12 ... Lid 13 ... Power storage element 18 ... Welding ring 21 ... Welding part

Claims

A case having a bottom and a frame-like wall along the outer edge of the bottom;
A welding ring joined to the case and forming a liquid chamber with the case;
A lid for sealing the liquid chamber;
In the melt-solidified part of the lid and the weld ring, which is formed from the lid to the weld ring, does not reach the case, and in a cross section that passes through the wall and is orthogonal, the shape of the weld-solidified part is: A melt-solidified portion whose width gradually decreases with the melting depth;
A power storage element housed in the liquid chamber;
An electrochemical device comprising: an electrolytic solution housed in the liquid chamber.
The electrochemical device according to claim 1,
When the width at the widest position is the first width and the width at the half of the melt depth is the second width, the second width is the first width. An electrochemical device having a cross-sectional shape that is not less than 0.3 times and not more than 0.9 times.
The electrochemical device according to claim 1 or 2,
The melt-solidified part is an electrochemical device having a funnel-shaped cross-sectional shape.
The electrochemical device according to any one of claims 1 to 3,
The case is made of ceramic,
The welding ring and the lid are made of Kovar,
The welding ring is an electrochemical device brazed to the case.
The electrochemical device according to any one of claims 1 to 4,
The melt-solidified part is an electrochemical device formed by laser irradiation of a fiber laser.