JP5044814B2 - Electrochemical element - Google Patents

Description

  The present invention relates to an electrochemical element such as a nonaqueous electrolyte battery or an electric double layer capacitor.

  Electrochemical elements such as non-aqueous electrolyte batteries and electric double layer capacitors are used for clock function backup power supplies, semiconductor memory backup power supplies, standby power supplies for electronic devices such as microcomputers and IC memories, solar watch batteries, and motor drives. It is used as a power source. Furthermore, in recent years, it has attracted attention as a power source for electric vehicles and an auxiliary system for an energy conversion / storage system.

  Due to the non-volatility of semiconductor memories and the reduction in power consumption of timepiece functional elements, the need for electrochemical elements that are both large in capacity and current is decreasing. Rather, there is a strong demand for mounting on a substrate by thinning or reflow soldering.

Thus, a round electrochemical element such as a coin or a button or a rectangular electrochemical element as shown in Patent Document 1 has been proposed. Unlike a round-shaped electrochemical element, a square-shaped electrochemical element cannot be sealed by crimping (crimping) a rectangular box-shaped container. For this reason, the rectangular electrochemical element has been sealed by resistance welding with a sealing plate placed on top of a square box-shaped container. More specifically, after a counter electrode composed of a positive electrode and a negative electrode, a separator, an electrolyte, and the like are accommodated in a rectangular box-shaped container, a sealing plate is placed on the upper portion, and seam welding is performed using a resistance welding method.
JP 2001-216852 A

  By the way, when performing seam welding using the resistance welding method, the sealing plate must be accurately positioned with respect to the container in order to ensure sealing performance. However, due to the recent miniaturization of electrochemical devices accompanying the further miniaturization of electronic devices, the size has become smaller and it has become increasingly difficult to position the sealing plate on the container.

  Further, after sealing, an appropriate pressure is applied to the counter electrode composed of the positive electrode and the negative electrode, the separator, and the like by the sealing plate when sealing to ensure the distance between the electrodes. Therefore, when the sealing plate is aligned with the container, the sealing plate is lifted by the counter electrode consisting of the positive electrode and the negative electrode before sealing, a separator, etc., and placed at a position slightly away from the container, that is, in a floating state. It was in a stable state. As a result, it is difficult to accurately position the sealing plate with respect to the container. This becomes more difficult as the size becomes smaller, and has been a problem in terms of production efficiency. Moreover, if the pressing is insufficient, the internal resistance of the electrochemical element increases.

  The present invention has been made to solve the above-described problems, and its purpose is to facilitate accurate positioning of the container and the sealing plate, simplify welding of the container and the sealing plate, and improve production efficiency. It is in providing the electrochemical element which can aim at.

The invention of claim 1 comprises a container having an upper opening, a sealing plate that contacts a metal film formed in the opening of the container and welds the contact portion to seal the container, In the container sealed with a sealing plate, an electrochemical element containing at least a counter electrode composed of a positive electrode and a negative electrode, a separator, and an electrolyte, the convex portion fitting into the opening of the container on the sealing plate Is formed so that the convex portion applies pressure from the convex portion toward the counter electrode .

According to a second aspect of the present invention, in the electrochemical device according to the first aspect, the convex portion is formed by denting the upper surface of the sealing plate and projecting the lower surface.
According to a third aspect of the present invention, in the electrochemical device according to the second aspect, the protruding amount of the convex portion is 4% to 20% with respect to the depth of the container.

According to a fourth aspect of the present invention, in the electrochemical element according to the third aspect, the area of the convex portion formed on the sealing plate is 20% or more with respect to the opening area of the opening of the container.
According to a fifth aspect of the present invention, in the electrochemical element according to the fourth aspect, the planar shape of the convex portion is similar to the planar shape at the opening of the container.

  According to the first aspect of the present invention, since the convex portion is formed on the sealing plate, the convex portion serves as a guide and fits into the opening of the container, so that the sealing plate placed on the container can be easily positioned. It will be certain. As a result, the sealing plate can be easily welded to the container without causing a gap.

In addition, since an appropriate pressure can be applied to the positive electrode, the negative electrode, and the like by the convex portion, the distance between the electrodes can be maintained appropriately, and the internal resistance can be reduced.
According to the second aspect of the present invention, since the recess is formed, the rigidity of the sealing plate is increased, and it is difficult for swelling and deformation to occur during welding or reflow soldering. Further, by increasing the strength of the sealing plate, the sealing plate can be made thinner, and the material cost can be reduced and the weight can be reduced.

According to the invention of claim 3, there is no leakage, and variations in internal resistance can be suppressed.
According to the invention of claim 4, the internal resistance can be reduced, and the manufacturing variation can be suppressed low.

  According to invention of Claim 5, a pressure can be uniformly applied with respect to the counter electrode etc. in a container.

Hereinafter, a first embodiment in which an electrochemical element of the present invention is embodied in an electric double layer capacitor will be described with reference to FIGS. 1 and 2.
FIG. 1 shows a cross-sectional view of an electric double layer capacitor as a rectangular parallelepiped electrochemical element. In FIG. 1, an electric double layer capacitor 10 has a rectangular box-shaped container 11 that is open at the top, and a sealing plate 12 that is welded to the container 11 and seals the opening. In the container 11 sealed by the sealing plate 12, a capacitor cell made up of a positive electrode active material 13 constituting a counter electrode, a separator 14, a negative electrode active material 15 constituting a counter electrode, an electrolyte solution 16 and the like is disposed. It is like that. In the present embodiment, the size of the container 11 is 3.6 (vertical) × 5.6 (horizontal) × 0.7 (height) mm. In this embodiment, the size of the concave portion of the container 11 is 3 (vertical) × 5 (horizontal) × 0.5 (depth) mm.

  The container 11 has a positive electrode current collector 17 made of a tungsten layer having high voltage resistance formed on the entire inner bottom surface 11a, and Kovar (cobalt: 17, nickel: 29 on the upper surface 11c of the four side walls 11b. A metal ring 18 made of (iron: remaining ratio alloy) is formed in a square ring shape. The right side of the positive electrode current collector 17 penetrates the side wall 11b and is electrically connected to a first external terminal T1 formed on the right side of the bottom surface 11d of the container 11. On the other hand, the metal ring 18 is electrically connected to the second external terminal T2 formed on the left side of the bottom surface 11d of the container 11 through the conductive film 19 made of a tungsten layer formed on the outer surface of the left side wall 11b. Yes.

  In the present embodiment, the container 11 is made of alumina, and is formed by stacking and firing a plurality of green sheets. More specifically, the positive electrode current collector 17 and the tungsten serving as the conductive film 19 are printed on the green sheet before firing, and the Kovar serving as the metal ring 18 is placed on the upper surface 11c of the side wall 11b and fired, whereby the container 11 A positive electrode current collector 17, a metal ring 18, and a conductive film 19 are formed.

Note that the thermal expansion coefficient (5.2 × 10 ⁻¹⁶ / ° C.) of the metal ring 18 made of Kovar and the thermal expansion coefficient (6.8 × 10 ⁻¹⁶ / ° C.) of the alumina container 11 are very close values. Thus, the displacement of the volume change due to thermal expansion is very small.

  The first external terminal T1 and the second external terminal T2 are formed by applying nickel or gold plating to the fired container 11. Similarly, a bonding agent (brazing material) 20 formed by nickel and gold plating is formed on the upper portion of the metal ring 18.

  Here, the thickness of the metal ring 18 is 0.15 mm in this embodiment, and the thickness of the bonding agent (the brazing material 20) is 0.05 mm in this embodiment. Therefore, in the present embodiment and the like, the height of the outer wall of the container 11 including the metal ring 18 and the bonding agent (brazing material) 20 is 0.9 mm, and the container 11 including the metal ring 18 and the bonding agent (brazing material) 20. The depth of the recess is 0.7 mm.

  The outer shape of the sealing plate 12 is a rectangular parallelepiped, and an inner portion excluding the outer peripheral portion is recessed toward the container 11 to form a recess 21 as shown in FIG. By recessing the upper surface 12a, as shown in FIG. 2B, a convex portion 22 is formed to protrude from the lower surface 12b. Then, the planar shape of the concave portion 21 on the upper surface 12a side is a quadrangular shape with a corner portion chamfered, and the convex portion 22 on the lower surface 12b (surface on the container 11 side) side also has a planar shape as shown in FIG. The portion 22a is a chamfered square shape. The sealing plate 12 is made of Kovar made of the same material as the metal ring 18 and has the same thermal expansion coefficient as that of the metal ring 18. The sealing plate 12 is formed by plating a bonding agent (brazing material) 23 made of nickel on the entire surface (including the convex portion 22) on the container 11 side.

  In this embodiment, the size of the outer shape of the sealing plate 12 is 2 (vertical) × 4 (horizontal) × 0.10 (thickness) mm. The vertical and horizontal dimensions of the convex portion 22 are 0.05 mm shorter than the vertical and horizontal dimensions of the concave portion of the container 11 in the present embodiment and the like, respectively, and are 2.95 (vertical) × 4. 95 (width) mm. The radius of the chamfered corner portion 22a of the quadrangular convex portion 22 was 0.5 mm. Moreover, the protrusion amount from the lower surface 12b of the convex part 22 was 0.02-0.10 mm in this embodiment.

  Therefore, when sealing the sealing plate 12 and the container 11 with the convex portion 22 facing the opening of the container 11, the convex portion 22 fits into the opening of the container 11 and is positioned on the outer peripheral portion of the convex portion 22. The lower surface 12b of the sealing plate 12 contacts the upper surface 11c (bonding agent 20) of the side wall 11b. Accordingly, the sealing plate 12 is positioned and held with respect to the container 11 by fitting the convex portion 22 into the opening of the container 11. That is, the sealing plate 12 is positioned and placed on the container 11 with the convex portion 22 serving as a guide, and after being placed, the convex portion 22 easily fits into the opening of the container 11. There is no deviation from the position.

  A positive electrode active material 13 is disposed on the upper surface of the positive electrode current collector 17. The positive electrode active material 13 is bonded to the positive electrode current collector 17 via a conductive adhesive 24 containing carbon, and is electrically connected to the positive electrode current collector 17. In this embodiment, the positive electrode active material 13 uses an activated carbon sheet and has a size of 2 (vertical) × 4 (horizontal) × 0.25 (thickness) mm.

  A separator 14 having a thickness of 0.2 mm is disposed above the positive electrode active material 13, and an electrolyte solution 16 is injected into the container 11. The separator 14 is preferably a heat resistant nonwoven fabric. That is, a separator such as a roll-rolled porous film is not preferable because it has heat resistance but is shrunk in the rolling direction due to heat during seam welding using a resistance welding method and easily causes an internal short circuit. In the case of a separator using a heat-resistant resin or glass fiber, shrinkage was good with little shrinkage. As the resin, polyphenylene sulfide (PPS) and polyether ether ketone (PEEK) were good. In particular, glass fiber is effective. Alternatively, the separator 14 may be formed of a ceramic porous body.

In the present embodiment, the electrolytic solution 16 is an electrolytic solution obtained by adding 1 mol / L of (C2H5) 4NBF4 to propylene carbonate (PC), and 5 microliters thereof was injected.
A negative electrode active material 15 is disposed on the upper side of the separator 14. Specifically, the negative electrode active material 15 is bonded in advance to the flat surface 22 b (bonding agent 20) of the convex portion 22 of the sealing plate 12 via the conductive adhesive 25. Therefore, in the present embodiment, the negative electrode active material 15 is arranged on the upper side of the separator 14 by fitting the convex portion 22 of the sealing plate 12 into the opening of the container 11. In the present embodiment, the negative electrode active material 15 uses an activated carbon sheet in the same manner as the positive electrode active material 13 and has a size of 2 (vertical) × 4 (horizontal) × 0.25 (thickness) mm.

  When the sealing plate 12 is placed on the container 11, the convex portion 22 is fitted into the opening of the container 11, and the sealing plate 12 is positioned and held with respect to the container 11. From this state, the sealing plate 12 is pressed toward the container 11 so as to contact the lower surface 12b of the sealing plate 12 on the outer peripheral portion of the convex portion 22 and the upper surface 11c (bonding agent 20) of the side wall 11b. At this time, the internal resistance of the positive electrode active material 13, the separator 14, and the negative electrode active material 15 accommodated in the container 11 is reduced by an appropriate pressure.

  And the sealing board 12 is welded with respect to the container 11 in the state contact | abutted to the lower surface 12b of the sealing board 12 of the outer peripheral part of the convex part 22, and the upper surface 11c (bonding agent 20) of the side wall 11b, and the container 11 To seal. In the present embodiment, the welding is performed by simultaneously welding two opposing sides of the sealing plate 12 using a parallel seam welding machine using the principle of resistance welding. The metal ring 18 is joined to the bonding agent (brazing material) 23 of the sealing plate 12 by welding, and is electrically connected to the negative electrode active material 15 via the bonding agent (brazing material) 23 and the adhesive 25. The As a result, the negative electrode active material 15 is electrically connected to the second external terminal T2 through the conductive film 19.

  And the electric double layer capacitor 10 manufactured by welding the container 11 and the sealing board 12 is surface-mounted on the board | substrate of an electronic device. Surface mounting is performed by reflow soldering. For example, the first external terminal T1 and the second external terminal T2 are soldered by passing a substrate mounted with the electric double layer capacitor 10 through a furnace in a high temperature atmosphere set to 200 to 260 ° C. and melting the solder. The electric double layer capacitor 10 is mounted on the substrate.

  Next, a plurality of sets of 100 electric double layer capacitors of various conditions including those of the present embodiment are manufactured, and each is heated by passing through a furnace for reflow soldering at a maximum temperature of 260 ° C. Then, the presence / absence of leakage and the measurement of internal resistance were carried out by an alternating current method of 1 kHz. Then, with the voltage of 70 ° C. and 2.6 V applied, it was stored for 40 days and the change in internal resistance was measured to determine how much the electric double layer capacitor deteriorated. The results are shown in Table 1. In general, storage at 70 ° C. for 10 days is considered to correspond to one year.

表１で示した封口板の凹み量は、凸部２２の下面１２ｂからの突出量に相当する。そして、容器１１の凹部の深さは０．７ｍｍに対する封口板の凹み量の割合を％で示した。

The amount of depression of the sealing plate shown in Table 1 corresponds to the amount of protrusion from the lower surface 12 b of the convex portion 22. And the depth of the recessed part of the container 11 showed the ratio of the recessed amount of the sealing board with respect to 0.7 mm in%.

As is clear from Table 1, the internal resistance after reflow heating tends to be slightly lower as the dent amount is larger, but there is no significant difference.
In Comparative Examples 1 and 2, the leakage occurred because the level difference (projection amount) of the convex portion 22 was small, the guide for positioning was not sufficient, the position was shifted during welding, and the leakage occurred. Conceivable.

  In Comparative Example 3, the internal resistance is large despite the large dent amount. This is presumably because the amount of dent provided in the sealing plate (the amount of protrusion of the convex portion 22) was too large, and the internal volume of the electric double layer capacitor was compressed. Moreover, the dent (convex part 22) provided in the sealing plate pushed out the electrodes (the positive electrode active material 13 and the negative electrode active material 15) and the electrolyte solution 16 which were put inside, and the electrolyte solution was insufficient. it is conceivable that. In addition, it is considered that the leakage occurred because part of the electrodes (the positive electrode active material 13 and the negative electrode active material 15) protruded from the welded portion and welding was not sufficient.

From this result, it is understood that the recess provided in the sealing plate 12 is preferably 4% or more and 20% or less with respect to the depth of the recess of the concave container 11.
The internal resistance after 40 days has passed after applying a voltage of 70 ° C. and 2.6 V, and in Examples 1 to 4 where the dent amount is 0.03 mm or more, the smaller the dent amount, the lower the variation and the better. Indicated.

  On the other hand, in Comparative Examples 1 and 2 having no dent amount or a small dent pressure, the pressure due to the dent is small, and an appropriate pressure is applied to the positive electrode (positive electrode active material 13) and the negative electrode (negative electrode active material 15) to reduce the distance between the electrodes. This is probably due to the failure to maintain the appropriateness. However, in Comparative Example 3 in which the dent amount is too large, the internal resistance is high and the variation is large.

Next, Examples 5 to 8 and Comparative Example 4 were performed in the same manner as in Examples 1 to 4 except for the sealing plate. The shape of the recess provided in the sealing plate 12 (corresponding to the shape of the flat surface 22b of the convex portion 22) is similar to the square inside the opening viewed from the upper surface 12a, and is 10% to the area of the square inside the opening. Changed to 90%. The amount of dents was 0.05 mm.

  Then, a plurality of sets of 100 electric double layer capacitors under various conditions were produced, and reflow soldering at a maximum temperature of 260 ° C. was passed through the furnace for heating. Then, with the voltage of 70 ° C. and 2.6 V applied, it was stored for 40 days and the change in internal resistance was measured to determine how much the electric double layer capacitor deteriorated. The results are shown in Table 2.

７０℃、２．６Ｖの電圧を印加した状態で、４０日保管して内部抵抗は、開口部内側の四角形の面積に対する凹みの面積（平面２２ｂの面積に相当）の割合が２０％以上である実施例５〜８においては、凹み面積が大きいほど低くバラツキも小さく良好な結果を示した。凹み面積の小さい比較例４は、実効的に圧を加え電極（負極活物質１５）と接している面積が小さくなり、内部抵抗が上がったものと考えられる。

Stored for 40 days with a voltage of 70 ° C. and 2.6 V applied, the internal resistance is such that the ratio of the area of the recess (corresponding to the area of the plane 22b) to the area of the square inside the opening is 20% or more. In Examples 5 to 8, the larger the dent area, the lower the variation and the better the results. In Comparative Example 4 having a small dent area, it is considered that the area in contact with the electrode (negative electrode active material 15) by effectively applying pressure was reduced, and the internal resistance was increased.

Next, effects of the present embodiment configured as described above will be described below.
(1) In this embodiment, since the convex part 22 was formed in the lower surface 12b by denting the sealing board 12, the convex part 22 became a guide and positioning of the sealing board 12 with respect to the container 11 became easy, and the container 11 and the sealing board A sufficient sealing property can be obtained without causing a gap in the welding of 12. (2) In the present embodiment, the convex portion 22 can apply an appropriate pressure to the positive electrode and the negative electrode after sealing to keep the distance between the electrodes appropriate, and stabilize the electrical characteristics of the electric double layer capacitor 10. Can be achieved. In particular, variation in internal resistance, which is an important characteristic, can be reduced, resulting in a high yield and high productivity.

In addition, since the planar shape of the convex portion 22 is similar to the planar shape at the opening of the container 11, the negative electrode active material 15 and the like in the container 11 can be more uniformly applied, and variations in internal resistance can be achieved. It can be made smaller.
(3) In this embodiment, by forming the convex portion 22 by denting the sealing plate 12, the rigidity of the sealing plate 12 is increased, and swelling and deformation are less likely to occur during welding or reflow soldering. As a result, it is possible to solve problems such as adversely affecting the mounting substrate and other components, increasing the distance between the electrodes due to swelling, and increasing the internal resistance. Further, the strength of the sealing plate 12 can be increased, so that the sealing plate 12 can be made thinner and the material cost can be reduced and the weight can be reduced.
(3) In this embodiment, since the protrusion amount of the convex portion 22 is 4% to 20% with respect to the depth of the container 11, there is no leakage and the variation in internal resistance can be suppressed.
(4) In this embodiment, the area of the convex portion 22 formed on the sealing plate 12 is set to 20% or more with respect to the opening area of the opening of the container 11, whereby the internal resistance can be reduced and manufacturing variation is reduced. It can be kept low.

In addition, you may change the said embodiment as follows.
-In the said embodiment, the square-shaped convex part 22 which dented the sealing board 12 and was formed in the lower surface 12b was one. As shown in FIGS. 3 and 4 (a) and 4 (b), this may be carried out by forming two dents and providing two rectangular convex portions 22 on the lower surface 12b of the sealing plate 12. . According to this, the strength of the sealing plate 12 can be further increased.

  In the above embodiment, the convex portion 22 is formed on the lower surface 12b. However, as shown in FIGS. 5A and 5B, the upper surface 12a of the sealing plate 12 is recessed in a cross shape, You may implement by forming the cross-shaped convex part 22 in the lower surface 12b. Also in this case, the strength of the sealing plate 12 can be increased. Further, as shown in FIGS. 6A and 6B, the upper surface 12a of the sealing plate 12 is recessed in an “X” shape (cross shape), and the “X” shape is projected on the lower surface 12b of the sealing plate 12. The portion 22 may be formed for implementation. In this case, the strength of the sealing plate 12 can be further increased.

  In the above embodiment, the upper surface 12a of the sealing plate 12 is recessed and the quadrangular convex portion 22 is formed on the lower surface 12b. However, the sealing plate 12 is not recessed and corresponds to the quadrangular convex portion 22 of the lower surface 12b. For example, the convex portion 22 may be formed by forming a film on the region to be formed by photolithography and laminating the lower surface thereof on 12b.

  In the above embodiment, the electric double layer capacitor 10 has a rectangular parallelepiped shape. However, the shape of the container and the sealing plate is not particularly limited, and the coin-shaped or button-shaped electric double layer capacitor 10, that is, a disk-shaped sealing member. You may apply also to a board.

  In the above embodiment, the electric double layer capacitor 10 is embodied as an electrochemical element, but may be applied to a nonaqueous electrolyte battery.

Sectional drawing of the electric double layer capacitor of this embodiment. It is explanatory drawing for demonstrating a sealing board, Comprising: (a) is the perspective view which looked at the sealing board from the upper side, (b) is the perspective view which looked at the sealing board from the lower side. Sectional drawing of the electrical double layer capacitor for demonstrating another example of a sealing board. It is explanatory drawing explaining a sealing plate similarly, Comprising: (a) is the perspective view which looked at the sealing plate from the upper side, (b) is the perspective view which looked at the sealing plate from the lower side. It is explanatory drawing for demonstrating another example of a sealing board, Comprising: (a) is the perspective view which looked at the sealing board from the upper side, (b) is the perspective view which looked at the sealing board from the lower side. It is explanatory drawing for demonstrating another example of a sealing board, Comprising: (a) is the perspective view which looked at the sealing board from the upper side, (b) is the perspective view which looked at the sealing board from the lower side.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Electric double layer capacitor, 11 ... Container, 12 ... Sealing plate, 12a ... Upper surface, 12b ... Lower surface, 13 ... Positive electrode active material, 14 ... Separator, 15 ... Negative electrode active material, 16 ... Electrolytic solution, 21 ... Recessed part, 22 ... convex part, 22b ... plane.

Claims (5)

The container has an opening at the top, and a sealing plate that contacts the metal film formed at the opening of the container and welds the contact portion to seal the container, and is sealed by the sealing plate. An electrochemical element containing at least a counter electrode composed of a positive electrode and a negative electrode, a separator, and an electrolyte in the container,
On the sealing plate, a convex part that fits into the opening of the container is formed to protrude ,
The electrochemical device , wherein the convex portion applies pressure from the convex portion toward the counter electrode . The electrochemical device according to claim 1,
The electrochemical element, wherein the convex portion is formed by denting the upper surface of the sealing plate and projecting the lower surface. The electrochemical device according to claim 2,
The amount of protrusion of the convex part is 4% to 20% with respect to the depth of the container. The electrochemical device according to claim 3,
The area of the convex part formed in the said sealing board is 20% or more with respect to the opening area of the opening part of the said container, The electrochemical element characterized by the above-mentioned. The electrochemical device according to claim 4,
The electrochemical device according to claim 1, wherein the planar shape of the convex portion is similar to the planar shape at the opening of the container.

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