Electric storage device and method of manufacture thereof

This application is a continuation of International Application No. PCT/JP2012/007969, filed on Dec. 13, 2012, which in turn claims the benefit of Japanese Application No. 2011-274178, filed on Dec. 15, 2011, Japanese Application No. 2011-274179, filed on Dec. 15, 2011, Japanese Application No. 2011-274180, filed on Dec. 15, 2011 and Japanese Application No. 2011-274181, filed on Dec. 15, 2011, the disclosures of which Applications are incorporated by reference herein.

1. Technical Field

The present technical field relates to electric storage devices typically used for regeneration or power storage in a range of electronic devices and hybrid vehicles, and manufacturing methods thereof.

2. Background Art

FIG. 21 is a front sectional view of an electric double-layer capacitor, which is an example of a conventional electric storage device. This capacitor includes capacitor element 101 , two collector plates 102 , tubular metal case 105 with bottom 105 A, terminal plate 103 partially exposed to the outside of case 105 , and sealing rubber 106 .

Capacitor element 101 includes positive electrode end 101 A and negative electrode end 101 B (hereafter referred to as ends 101 A and 101 B) at opposed positions. Collector plates 102 are welded to ends 101 A and 101 B, respectively. Capacitor element 101 is housed in case 105 such that collector plate 102 welded to end 101 B faces bottom 105 A. Collector plate 102 welded to end 101 A is disposed at an opening of case 105 , and is coupled to terminal plate 103 . Sealing rubber 106 is provided between terminal plate 103 and the opening of case 105 to insulate them. Horizontally drawn part 105 B is formed from the outside to inside of the opening of case 105 against sealing rubber 106 so that sealing rubber 106 is compressed to seal the opening. In addition, an end of the opening of case 105 is bent inward to form bent part 105 C.

Capacitor element 101 includes a positive electrode, a negative electrode, and a separator (none of them are illustrated). Each of the positive electrode and the negative electrode is configured by applying an electrode layer containing carbon material to a strip of collector except for one end. In capacitor element 101 , these positive and negative electrodes face each other and are shifted such that portions without electrode layers on their collectors protrude in the opposite directions, and are wound with the separator therebetween. Accordingly, the portions without electrode layers of the electrodes configure ends 101 A and 101 B, respectively.

Terminal plate 103 is provided with a through hole for linking inside and outside case 105 . Pressure-adjusting valve 104 for preventing pressure rise inside case 105 is provided so as to cover this through hole in.

In this structure, sheet-like electrodes and collectors 102 are in plane contact, respectively, to take out current from capacitor element 101 . Accordingly, power can be collected at low resistance inside electric double-layer capacitor (e.g., Japanese Patent Unexamined Publication No. 2009-194131).

The present disclosure relates to an electric storage device with improved workability for setting a sealing member, and a manufacturing method thereof.

An electric storage device of various embodiments includes an electric storage element, electrolyte with which the electric storage element is impregnated, a terminal plate, an outer jacket, and a sealing member. The electric storage element includes a first electrode, second electrode, and first end where the first electrode is led out. The terminal plate includes an element-connecting part electrically connected to the first electrode at the first end, and an external terminal connected to the element-connecting part. The outer jacket includes a bottom and a tubular side wall extending from the bottom, and having an opening located opposite to the bottom. The outer jacket is formed of a conductive material, and houses the electric storage element together with the electrolyte such that the terminal plate located nearer the opening than the bottom. The sealing member is disposed on the element connecting part, and is provided with an insertion hole where the external terminal is inserted. The sealing member seals the opening of the outer jacket together with the external terminal. The external terminal is a columnar or tubular body with a tapered part on an outer periphery at a tip thereof. A part of the external terminal is exposed from the sealing member. The tapered part includes a first end and a second end further away from the element connecting part than the first end. An edge of the side wall at the opening of the outer jacket is disposed between the first end and the second end of the tapered part in a first direction extending from the bottom to the opening of the outer jacket.

The electric storage device of the embodiments is manufactured according to the following steps:

fabricating an electric storage element including the first electrode, second electrode, and first end where the first electrode is led out,

electrically connecting an element connecting part of a terminal plate and the first electrode at the first end of the electric storage element, the terminal plate including the element connecting part and the external terminal connected to the element connecting part,

housing the electric storage element connected to the terminal plate together with an electrolyte in an outer jacket formed of conductive material and including a bottom and a tubular side wall with an opening disposed opposite to the bottom, such that the terminal plate is located nearer the opening than the bottom,

inserting the external terminal into an insertion hole of the sealing member so as to dispose the sealing member on the element connecting part, while housing the sealing member into the outer jacket, and

sealing the outer jacket by the sealing member and the external terminal.

The external terminal is a columnar or tubular body, and includes a tapered part provided on an outer periphery thereof, and a sealing part linked to the tapered part. When the sealing member is housed inside the outer jacket, at least a part of the outer periphery of the sealing member is housed inside the outer jacket before a sealing portion of the external terminal comes in contact with the insertion hole of the sealing member. Then, after the sealing member is housed in the outer jacket, a part of the external terminal is exposed from the sealing member.

According to this manufacturing method, an end of the open of the outer jacket comes in contact with the sealing member before the untapered sealing part of the external terminal when the external terminal is inserted into the insertion hole of the sealing member as the sealing member is housed inside the outer jacket. Therefore, the position of the outer wall of the sealing member inside the outer jacket is determined with reference to the position of inner wall at the end of the opening that comes in contact first. Accordingly, the sealing member can be further inserted into the outer jacket even after the position of the outer wall of the sealing member is determined. Aforementioned electric storage device of the embodiments is configured by setting dimensional relationship of the external terminal, sealing member, and outer jacket such that at least a part of the outer periphery of the sealing member can be housed inside the outer jacket before the sealing part of the external terminal comes in contact with the insertion hole of the sealing member.

FIG. 1A is a top view of an electric double layer capacitor in accordance with a first exemplary embodiment.

FIG. 1B is a front sectional view of the electric double layer capacitor shown in FIG. 1A .

FIG. 2A is a top view of a terminal plate used in the electric double layer capacitor shown in FIG. 1B .

FIG. 2B is a front sectional view of the terminal plate shown in FIG. 2A .

FIG. 3A is a top view of a sealing member used in the electric double layer capacitor shown in FIG. 1B

FIG. 3B is a front sectional view of the sealing member shown in FIG. 3A .

FIG. 3C is a bottom view of the sealing member shown in FIG. 3A .

FIG. 4A is a schematic sectional view illustrating the state of inserting an external terminal of the terminal plate shown in FIG. 2B into the sealing member shown in FIG. 3B while the sealing member is housed in an outer jacket.

FIG. 4B is a schematic sectional view illustrating the state of inserting the external terminal of the terminal plate shown in FIG. 2B into the sealing member shown in FIG. 3B while the sealing member is housed in the outer jacket.

FIG. 4C is a schematic sectional view illustrating the state of inserting the external terminal of the terminal plate shown in FIG. 2B into the sealing member shown in FIG. 3B while the sealing member is housed in the outer jacket.

FIG. 4D is a schematic sectional view illustrating the state of inserting the external terminal of the terminal plate shown in FIG. 2B into the sealing member shown in FIG. 3B while the sealing member is housed in the outer jacket.

FIG. 5 shows an extracted image of the state of the external terminal of the terminal plate shown in FIG. 2B and the sealing member shown in FIG. 3B when the sealing member and the external terminal are in contact.

FIG. 6A is a top view of a collector plate of the electric double layer capacitor shown in FIG. 1B .

FIG. 6B is a front sectional view of the collector plate shown in FIG. 6A .

FIG. 7 is a plan view illustrating the inner side of a bottom of the outer jacket in the electric double layer capacitor shown in FIG. 1B .

FIG. 8 is an enlarged front sectional view illustrating a joining state of the outer jacket and the collector plate in the electric double layer capacitor shown in FIG. 1B .

FIG. 9 is a perspective bottom view illustrating the bottom of the outer jacket passing through the collector plate in the electric double layer capacitor shown in FIG. 1B .

FIG. 10A is a front sectional view of an electric double layer capacitor in accordance with a second exemplary embodiment.

FIG. 10B is a side sectional view of the electric double layer capacitor shown in FIG. 10A .

FIG. 11 is a perspective view of a terminal plate used in the electric double layer capacitor shown in FIG. 10A .

FIG. 12A is a top view of a terminal plate shown in FIG. 11 .

FIG. 12B is a front sectional view of the terminal plate shown in FIG. 11 .

FIG. 13 is a perspective view of a collector plate used in the electric double layer capacitor shown in FIG. 10A .

FIG. 14 is a bottom view of the collector plate shown in FIG. 13 .

FIG. 15A is a top perspective view of a terminal plate holder or collector plate holder used in the electric double layer capacitor shown in FIG. 10A .

FIG. 15B is a bottom perspective view of the terminal plate holder or collector plate holder shown in FIG. 15A .

FIG. 16A is a top view of the terminal plate holder or collector plate holder shown in FIG. 15A .

FIG. 16B is a front sectional view of the terminal plate holder or collector plate holder shown in FIG. 15A .

FIG. 17A is an enlarged partial sectional view of another outer jacket in the electric double layer capacitor shown in FIG. 10A .

FIG. 17B is an enlarged partial sectional view of still another outer jacket in the electric double layer capacitor shown in FIG. 10A .

FIG. 18A is a bottom view of another collector plate in the electric double layer capacitor in accordance with the second exemplary embodiment.

FIG. 18B is a front sectional view of the collector plate shown in FIG. 18A .

FIG. 18C is a side sectional view of the collector plate shown in FIG. 18A .

FIG. 19 is a bottom view of still another collector plate in the electric double layer capacitor in accordance with the second exemplary embodiment.

FIG. 20A is a front partial sectional view illustrating a bottom part of the outer jacket before connection for illustrating another connecting method of the collector plate and the outer jacket used in the electric double layer capacitor in accordance with the second exemplary embodiment.

FIG. 20B is a front partial sectional view illustrating the bottom part of the outer jacket after connection for illustrating the other connecting method of the collector plate and the outer jacket used in the electric double layer capacitor in accordance with the second exemplary embodiment.

FIG. 21 is a front sectional view of the electric double layer capacitor as an example of a conventional electric storage device.

Before describing exemplary embodiments, disadvantages in a conventional structure is described. An electric double layer capacitor shown in FIG. 21 certainly has low resistance. However, case 105 and terminal plate 103 from which a pair of electrodes are led out, respectively, need to be insulated from each other in order to lead out one of the electrodes from an opening of case 105 via terminal 103 . In addition, annular or tubular sealing rubber 106 needs to be provided such that it covers the outer periphery of terminal plate 103 , in order to seal the opening of case 105 .

In this case, sealing rubber 106 is generally disposed inside case 105 while a part of electrode plate 103 is inserted into a through hole created in sealing rubber 106 . When terminal plate 103 is inserted into sealing rubber 106 , an inner wall of sealing rubber 106 slides against terminal plate 103 , and an outer wall thereof slides against case 105 . Since a friction resistance on the surface of sealing rubber 106 is large, this friction resistance may degrade workability at inserting terminal plate 103 .

An electric storage device in the exemplary embodiments is described hereinafter with reference to drawings. However, the present disclosure is not limited in anyway by the exemplary embodiments.

First Exemplary Embodiment

FIG. 1A is a top view of an electric double layer capacitor that is an example of the electric storage device in the first exemplary embodiment. FIG. 1B is a front sectional view of this electric double layer capacitor. This electric double layer capacitor includes capacitor element 1 as an electric storage element, electrolyte (not illustrated) with which capacitor element 1 is impregnated, terminal plate 2 , collector plate 3 , outer jacket 4 with bottom 4 A, and sealing member 5 .

Capacitor element 1 includes a positive electrode as a first electrode, and a negative electrode as a second electrode. Capacitor element 1 has element end 1 A as a first end from which the positive electrode is led out, and element end 1 B as a second end opposite to the first end.

In this exemplary embodiment, capacitor element 1 has a wound structure, and has element end 1 A for leading out the positive electrode and element end 1 B for leading out the negative electrode at its both ends in the winding axis direction. In this way, the electrodes with different polarities from each other are led out from a pair of opposed ends, respectively. The positive electrode and the negative electrode may be at reverse ends. The structure of capacitor element is also not limited to the wound structure. As long as the electrodes are lead out from both opposed ends, respectively, the structure is not particularly limited. For example, the capacitor element may have a multilayer structure in which the positive electrode, negative electrode, and separator are laminated one after another, or a structure in which positive and negative electrodes face each other and are folded in a zigzag manner.

Capacitor element 1 includes the positive electrode and negative electrode which face each other and a separator between these electrodes (none of them are illustrated). Each of the positive electrode and the negative electrode includes a metal-foil collector, such as aluminum, and an electrode layer containing carbon material formed on the surface of this collector except for one edge (none of them are illustrated). The separator is typically formed of cellulose.

The positive electrode and the negative electrode face each other such that their portions without electrode layers protrude in opposite directions. These electrodes and the separator between them are wound to configure capacitor element 1 . In other words, capacitor element 1 is a wound body. Since the positive electrode, negative electrode, and separator are wound, hollow 1 C that is a space is formed after winding so as to penetrate in the winding axis direction. The portions without positive and negative electrode layers are respectively bundled together to form element ends 1 A and 1 B at both ends in the winding axis direction. As described above, capacitor element 1 is substantially cylindrical and has hollow 1 C at its center.

As for electrolyte, an electrolytic solution prepared, for example, by dissolving ethyltrimethyl ammonium tetrafluoroborate as a supporting electrolyte in γ-butyrolactone as a solvent may be used. The concentration is, for example, 1.0 mol/l.

Terminal plate 2 includes plate-shaped element connecting part 2 A and external terminal 2 B connected to element connecting part 2 A and also to outside. Element connecting part 2 A is electrically connected to the positive electrode at element end 1 A of capacitor element 1 . External terminal 2 B is provided on rear side of the face of element connecting part 2 A connected to capacitor element 1 . Terminal plate 2 is, for example, made of aluminum.

Collector plate 3 is joined to the negative electrode at element end 1 B. Collector plate 3 is made of a conductive plate-shaped metal, such as aluminum plate.

Outer jacket 4 is tubular (cylindrical) and has bottom 4 A and side wall 4 K provided with an opening opposite to bottom 4 A. Outer jacket 4 is made of a conductive material, such as metal. Outer jacket 4 houses capacitor element 1 together with terminal plate 2 , collector plate 3 , and electrolyte such that terminal plate 2 is positioned nearer aforementioned opening than bottom 4 A. Outer jacket 4 is, for example, made of aluminum.

Sealing member 5 is disposed on element connecting part 2 A, and is provided with insertion hole 5 A to which external terminal 2 B is inserted. Sealing member 5 seals the opening in outer jacket 4 together with external terminal 2 B. Sealing member 5 is, for example, made of butyl rubber.

Terminal plate 2 and sealing member 5 are detailed below with reference to FIGS. 2A to 3C . FIG. 2A is a top view of terminal plate 2 , and FIG. 2B is a front sectional view of terminal plate 2 . FIGS. 3A , 3 B, and 3 C are a top view, a front sectional view, and a bottom view of sealing member 5 , respectively.

Terminal plate 2 is formed of a conductive material, such as metal. As described above, terminal plate 2 includes disk-like element connecting part 2 A and columnar external terminal 2 B that leads out the electrode provided on the outer surface of element connecting part 2 A. As shown in FIG. 2B , external terminal 2 B is columnar or tubular (cylindrical), and tapered part 2 C whose tip is the narrowest is formed on the outer periphery at the tip of external terminal 2 B. To impregnate capacitor element 1 with the electrolytic solution from outside, pouring holes 2 D and 2 d are created in the thickness direction of element connecting part 2 A. The thickness direction is a first direction extending from bottom 4 A to the opening of outer jacket 4 . In other words, the thickness direction is a vertical direction when bottom 4 A of outer jacket 4 is placed on a horizontal plane.

As shown in FIGS. 3A to 3C , sealing member 5 is formed with at least a cylindrical elastic material. As described above, insertion hole 5 A is formed at the center of sealing member 5 . Sealing member 5 is disposed on element connecting part 2 A of terminal plate 2 in the state that external terminal 2 B of terminal plate 2 is inserted in insertion hole 5 A.

The outer wall of sealing member 5 faces the inner wall of the opening of outer jacket 4 . The inner wall of sealing member 5 is a face exposed on insertion hole 5 A. To seal this opening, drawn part 4 C protruding inward of outer jacket 4 is processed on the outer face at side wall 4 K of outer jacket 4 where the inner face of side wall 4 K faces the outer wall of sealing member 5 . The opening in outer jacket 4 is sealed by compressing sealing member 5 with drawn part 4 C.

The end of the opening of outer jacket 4 is bent inward of outer jacket 4 , and curled part 4 D is processed to make side fall edge 4 J come in contact with the top face of sealing member 5 . Curled part 4 D suppresses displacement of sealing member 5 in the vertical direction (in particular, upward direction) relative to element connecting part 2 A when an inner pressure of outer jacket 4 increases.

The top face of sealing member 5 is provided with protrusion 5 E formed by thickening and rising sealing member 5 between external terminal 2 B of terminal plate 2 partially exposed from insertion hole 5 A and curled part 4 D.

The electric double layer capacitor in the exemplary embodiment is configured as described above.

The electric double layer capacitor in the exemplary embodiment has the following characteristics. First, external terminal 2 B of terminal plate 2 is columnar or tubular, and includes tapered part 2 C provided on the top face at the tip and the outer periphery, and sealing part 2 H linked to tapered part 2 C. Tapered part 2 C has first end 2 F and second end 2 G that is farther from element connecting part 2 A than first end 2 F. For example, in the exemplary embodiment, first end 2 F is at the bottom end of tapered part 2 C, and second end 2 G is at the top end of tapered part 2 C, as shown in FIG. 1B . A part of external terminal 2 B protrudes outside from sealing member 5 . At least a part of the outer periphery of sealing member 5 is housed inside outer jacket 4 before sealing part 2 H of external terminal 2 B comes in contact with insertion hole 5 A of sealing member 5 when sealing member 5 is housed inside outer jacket 4 while external terminal 2 B is inserted into insertion hole 5 A of sealing member 5 . This structure can increase workability of insertion of sealing member 5 that is gradually housed in outer jacket 4 as external terminal 2 B is inserted.

As shown in FIG. 1B , side wall edge 4 J refers to an edge sharpened by the wall face of side wall 4 K. Therefore, if curled part 4 C is processed at the top end of the opening of outer jacket 4 , a curved portion formed at the top end of outer jacket 4 does not fall under side wall edge 4 J. In this case, side wall edge 4 J refers to an end of a part extended inward of outer jacket 4 . The position (height) of side wall edge 4 J of outer jacket 4 is specified by at least one of the height of side wall edge 4 J of outer jacket 4 after drawn part 4 C is processed on side wall 4 K and the height of side wall edge 4 J of outer jacket 4 before drawn part 4 C is formed. In particular, to specify the position of side wall edge 4 J before processing based on the structure after processing, a length of a part protruded inward of outer jacket 4 is not considered as drawn part 4 C of outer jacket 4 . If drawn part 4 C is provided, a shortest distance connecting bottom end 4 L where deformation for protruding inward of outer jacket 4 starts to top end 4 U where deformation completes is the height of drawn part 4 C.

Next is described procedures for inserting external terminal 2 B into sealing member 5 while sealing member 5 is housed inside outer jacket 4 , with reference to FIGS. 4A to 4D and FIG. 5 . FIG. 4A to 4D are schematic sectional views when external terminal 2 B is inserted into sealing member 5 while sealing member 5 is housed inside outer jacket 4 . FIG. 5 is an extracted image of the state that external terminal 2 B is in contact with sealing member 5 .

FIG. 4A illustrates the state that capacitor element 1 is fabricated, element connecting part 2 A of terminal plate 2 is connected to element end 1 A, and capacitor element 1 to which terminal plate 2 is connected is housed in outer jacket 4 together with the electrolyte such that terminal plate 2 is located nearer the opening than the bottom. As shown in FIG. 4A , a tip of external terminal 2 B is at a position higher than side wall edge 4 J, and is protruded outside of outer jacket 4 . When sealing member 5 is moved close to outer jacket 4 and external terminal 2 B, the tip of external terminal 2 B enters insertion hole 5 A of sealing member 5 first, as shown in FIG. 4B . This tentatively positions sealing member 5 relative to external terminal 2 B. In other words, the tip of external terminal 2 B and insertion hole 5 A function as guides.

Aforementioned first end 2 F close to element connecting part 2 A in tapered part 2 C is at a position closer to element connecting part 2 A than the position of side wall edge 4 J of outer jacket 4 . Therefore, the outer wall of sealing member 5 is inserted into outer jacket 4 before an untapered sealing part 2 H of external terminal 2 B enters the narrowest part of insertion hole 5 A, as shown in FIG. 4C , when external terminal 2 B is inserted into sealing member 5 while sealing member 5 is further housed inside outer jacket 4 .

When external terminal 2 B is further inserted into sealing member 5 as well as sealing member 5 is housed inside outer jacket 4 , sealing part 2 H is inserted into the narrowest part of insertion hole 5 A, as shown in FIG. 4D . At last, most of tapered part 2 C of external terminal 2 B protrudes from sealing member 5 .

In this way, when external terminal 2 B is inserted into sealing member 5 while sealing member 5 is housed inside outer jacket 5 , side wall edge 4 J comes in contact with sealing member 5 earlier than sealing part 2 H that will actively come in contact with sealing member 5 . Accordingly, the position of outer wall of sealing member 5 inside outer jacket 4 is determined based on the position of the inner wall of side wall edge 4 J that comes in contact first. Since sealing member 5 is already in contact with the inner wall of side wall edge 4 J, which is inside outer jacket 4 , sealing member 5 can be continuously inserted into outer jacket 4 even after the position of the outer wall of sealing member 5 is determined.

On the other hand, if first end 2 F of tapered part 2 C is at a position higher than side wall edge 4 J, sealing member 5 actively comes in contact with sealing part 2 H of external terminal 2 B in insertion hole 5 A before the outer wall thereof comes in contact with the inner wall of outer jacket 4 . In this case, the position of the outer wall of sealing member 5 is determined based on the position of the outer wall of sealing part 2 H. Then, after the position of the outer wall of sealing member 5 is determined, sealing member 5 comes in contact with side wall edge 4 J.

If external terminal 2 B is displaced from the center axis in the height direction of cylindrical outer jacket 4 , the position of the outer wall of sealing member becomes deviated in line with positional deviation of external terminal 2 B. This positional deviation of sealing member 5 may cause a part of the outer wall of sealing member 5 protrude outside of outer jacket 4 from the position of the inner wall of side wall edge 4 J. In this case, a part of sealing member 5 in contact with the end face of outer jacket 4 hinders further progress of sealing member 5 . Housing of sealing member 5 inside outer jacket 4 thus becomes difficult.

On the other hand, the position of sealing member 5 is determined by the contact condition with the inner periphery of the opening of outer jacket 4 in this exemplary embodiment. In other words, feasibility of housing sealing member 5 inside outer jacket 4 is firstly confirmed by continuously inserting external terminal 2 B. Thereafter, sealing member 5 can come in contact with sealing part 2 H at insertion hole 5 A. Therefore, as described above, the disadvantage that housing of sealing member 5 inside outer jacket 4 becomes difficult due to the protruded part can be suppressed. This structure can easily house sealing member 5 without separately preparing a guide jig for housing sealing member 5 inside outer jacket 4 .

As shown in FIG. 5 , if the position of external terminal 2 B is deviated from the center axis of outer jacket 4 , the opening of insertion hole 5 A comes in contact with a sloped face of tapered part 2 C before reaching sealing part 2 H. In this case, the opening of insertion hole 5 A receives a stress indicated by arrow A in the direction perpendicular to this sloped face, depending on an angle of slope of tapered part 2 C.

The stress shown by arrow A can be decomposed to a stress indicated by arrow B in the horizontal direction relative to element connecting part 2 A of terminal plate 2 and a stress indicated by arrow C in the vertical direction relative to element connecting part 2 A. Generation of the stress of arrow B applies a compression stress in the horizontal direction to insertion hole 5 A. This broadens the opening area of insertion hole 5 A. As a result, even if the position of external terminal 2 B is slightly deviated, external terminal 2 B can be inserted while absorbing this deviation to a compression limit of sealing member 5 .

However, if sealing member 5 comes in contact with side wall edge 4 J of outer jacket 4 in the state that external terminal 2 B is not inserted into sealing member 5 , the tip of external terminal 2 B and the bottom of sealing member 5 may contact, depending on a degree of positional deviation of external terminal 2 B. In this case, insertion of external terminal 2 B into insertion hole 5 A also becomes difficult. Accordingly, as described above, the position of the tip of external terminal 2 B is preferably higher than that of side wall edge 4 J of outer jacket 4 .

The above positional relationship results in establishing the following positional relationship in a state after drawn part 4 C and curled part 4 D are processed. Specifically, side wall edge 4 J at the opening of outer jacket 4 is positioned between first end 2 F and second end 2 G of tapered part 2 C in the first direction extending from bottom 4 A to the opening of outer jacket 4 . As described above, the first direction is a vertical direction relative to bottom 4 A when bottom 4 A is placed horizontally. It is a direction along which side wall 4 K of outer jacket 4 extends.

In a structure that does not satisfy the above positional relationship, side wall edge 4 J is, for example, positioned above second end 2 G. In this case, the top end of side wall 4 K of outer jacket 4 is always at a position higher than that of the top end of terminal plate 2 . If these electric double layer capacitors are electrically connected, using a connector (not illustrated), this connector needs to be processed into a shape that can connect one of external terminals 2 B across the top end (in particular, curled part) of side wall 4 K between two electric double layer capacitors disposed in parallel. This decreases connection flexibility. In addition, if side wall edge 4 J is positioned lower than first end 2 F, sealing part 4 H becomes tall due to the need of a certain space between side wall edge 4 J and element connecting part 2 A for forming drawn part 4 C. As a result, external terminal 2 B tends to become tall. This may enlarge the size of the electric double layer capacitor.

As shown in FIG. 1B , it is defined that the bottom end of the inner wall of insertion hole 5 A of sealing member 5 is first end 5 F, and the top end farther from element connecting part 2 A than first end 5 F in the above first direction is second end 5 G. In this definition, it is preferable that first end 2 F of tapered part 2 C is positioned above bottom end 4 L of drawn part 4 C, i.e., farther from element connecting part 2 A; and below second end 5 G of the inner wall of insertion hole 5 A, i.e., close to element connecting part 2 A. Compared to the structure that first end 2 F of tapered part 2 C is not positioned in this range, a stress is unevenly generated on external terminal 2 B in the height direction in the structure that first end 2 F of tapered part 2 C is positioned in this aforementioned range. As a result, a sealing stress applied to the outer wall of external terminal 2 B is concentrated and locally increased. This can increase reliability of sealing at the opening of outer jacket 4 . One of forms of time degradation of sealing member 5 is a decrease in sealing stress. However, this structure can maintain good sealing stress. The sealing stress to be applied to external terminal 2 B from sealing member 5 can be calculated by measuring in advance the relationship of distortion and stress of the sealing member that will be a specimen, setting the sealing structure of the opening to be used for stress analysis of this specimen, and analyzing the stress using known simulation software. In the front sectional view of outer jacket 4 as shown in FIG. 1B , a cross section of side wall 4 K of outer jacket 4 is formed substantially straight to a predetermined height from bottom 4 A. There is a point of changing from substantially straight to curved line (changed point) in this cross section. In the description, a portion where this changed point is provided is defined as bottom end 4 L of drawn part 4 C. In other words, bottom end 4 L of drawn part 4 C is an end farther from side wall edge 4 J in the first direction.

In sealing member 5 , circular skirt 5 B that extends toward bottom 4 A of outer jacket 4 is preferably formed on the outer-peripheral end of the bottom facing element connecting part 2 A of terminal plate 2 . Skirt 5 B is circular or tubular (cylindrical), and is formed of an insulating material same as or different from the main part of sealing member 5 . Skirt 5 B has a function to insulate the outer peripheral end of element connecting part 2 A of terminal plate 2 and the confronting inner wall of outer jacket 4 . Reliability improves by providing skirt 5 B between the outer peripheral end of element connecting part 2 A and the inner wall of outer jacket 4 in this way.

Meanwhile, levelness of sealing member 5 in outer jacket 4 may degrade due to some reasons, while external terminal 2 B is being inserted into sealing member 5 . In this case, a protruding direction of skirt 5 B also changes in an oblique direction, depending on an angle that sealing member 5 is tilted from the direction perpendicular to element connecting part 2 A. On the other hand, a space between element connecting part 2 A and outer jacket 4 extends in the direction perpendicular to element connecting part 2 A. Therefore, it becomes difficult to insert skirt 5 B into this space. In some cases, sealing member 5 may be housed in outer jacket 4 without skirt 5 B being inserted into this space. Therefore, as shown in FIG. 3B , it is further preferable to provide tapered part 5 C on skirt 5 B at the inner side.

By providing tapered part 5 C, a sloped face of tapered part 5 C becomes parallel to the outer peripheral end of element connecting part 2 A or this sloped face comes in contact with element connecting part 2 A even if sealing member 5 is tilted to the extent of a tapering angle of tapered part 5 C. Accordingly, compared to the structure without tapered part 5 C, flexibility in inserting skirt 5 B into the above space improves. Skirt 5 B is not limited to a circular shape. It may be provided intermittently on the outer peripheral end.

Still more, as shown in FIG. 3B , tapered part 5 D is preferably provided on the inner periphery of the opening at the bottom (a face confronting terminal plate 2 ) in sealing member 5 . Tapered part 5 D broadens the distance between the outer wall of external terminal 2 B and the inner wall at insertion hole 5 A. This can more reliably avoid contact of external terminal 2 B and the inner wall at insertion hole 5 A. A friction resistance can thus be reduced.

The opening of outer jacket 4 is sealed with sealing member 5 and external terminal 2 B of terminal plate 2 . In this case, gas generated inside outer jacket 4 is discharged through sealing member 5 . This structure eliminates the need of a pressure-adjusting valve (not illustrated), and thus the electric double layer capacitor can be used in the state it is laid sideways. In addition, a space for providing the pressure-adjusting valve on the opening face of outer jacket 4 can be eliminated. Accordingly, the overall electric double layer capacitor is downsized.

Next, a structure of collector plate 4 , bottom 4 A of outer jacket 4 , and terminal plate 2 is described with reference to FIGS. 6A to 9 in addition to FIG. 2A . FIGS. 6A and 6B are a plan view and a front sectional view of collector plate 3 . FIG. 7 is a plan view illustrating the inner side of bottom 4 A of outer jacket 4 . FIG. 8 is a front sectional view partially magnifying the joined state of outer jacket 4 and collector plate 3 . FIG. 9 is a bottom perspective view of bottom 4 A of outer jacket 4 seeing through collector plate 3 .

As described above, collector plate 3 is formed of a conductive plate, such as metal. As shown in FIGS. 6A and 6B , collector plate 3 includes disk plate 3 D and protrusion 3 E provided at the center of disk plate 3 D. As shown in FIG. 8 , protrusion 3 E is disposed facing hollow 1 C of capacitor element 1 . Disk plate 3 D and protrusion 3 E are provided with pouring holes 3 B and disk plate 3 D is provided with notch 3 C on the outer periphery thereof. Disk plate 3 D includes element connecting part 3 A and outer jacket connecting part 3 G as shown in FIGS. 8 and 9 . Element connecting part 3 A is joined to element end 1 B. Outer jacket connecting part 3 G comes in contact with joining part 4 G on bottom 4 A of outer jacket 4 , and welded together.

On the other hand, as shown in FIG. 7 , contact part 4 E that protrudes toward the opening and contacts collector plate 3 is formed on the inner face of bottom 4 A of outer jacket 4 . In addition, as shown in FIG. 8 , external connecting part 4 B protruding outward for connecting with a connection bar (not illustrated) is formed on the outer face of bottom 4 A. A recess is formed on the outer face of bottom 4 A at a position different from external connecting part 4 B. For example, a cross cut is created at the bottom of this recess. Mechanical strength at this cut is weaker compared to a portion without cut. When the inner pressure in outer jacket 4 exceeds a predetermined level, outer jacket 4 opens from this cut. Valve 4 F is provided in this way.

As shown in FIG. 8 , a space is created between a portion, of collector plate 3 , not in contact with contact part 4 E and bottom 4 A of outer jacket 4 by contact of contact part 4 E and collector plate 3 . Outer jacket connecting part 3 G of collector plate 3 and the inner face of bottom 4 A are welded at this space where collector plate 3 and outer jacket 4 are not in contact. This portion in bottom 4 A is joining part 4 G.

As shown in FIG. 2A , terminal plate 2 is provided with notch 2 E on the outer peripheral end of element connecting part 2 A thereof. Collector plate 3 is provided with notch 3 C at a position facing notch 2 E via capacitor element 1 . In other words, notch 3 C of collector plate 3 and notch 2 E of element connecting part 2 A face each other in a direction extending from bottom 4 A to the opening of outer jacket 4 , i.e., a direction perpendicular to bottom 4 A. Such a structure is preferable.

By making these notches face each other, notch 2 E serves a reference for positioning element connecting part 2 A and collector plate 3 in a rotating direction with reference to an axis of external terminal 2 B. In other words, the position of collector plate 3 in the rotating direction can be determined by determining the position of notch 2 E. Accordingly, the position of connecting part of collector plate 3 relative to capacitor element 1 can be determined with reference to notch 2 E.

In other words, the position of collector plate 3 at the bottom of outer jacket 4 can be judged by looking at the position of notch 2 E. Accordingly, double melting of element connecting part 3 A that is a connecting part of collector plate 3 and capacitor element 1 is preventable when welding outer jacket-connecting part 3 G of collector 3 and joining part 4 G of outer jacket 4 from outside of outer jacket 4 . When a positioning reference is provided as described above, it is preferable that a structure has no rotation symmetry with reference to the center of the face where the reference is provided.

As described above, positioning parts are preferably provided at positions of terminal plate 2 and collector plate 3 where they face each other via capacitor element 1 . This enables to know the state of collector plate 3 housed in outer jacket 4 , which is difficult to see, based on other members, and avoid welding the position of element connecting part 3 A where collector plate 3 and capacitor element 1 are connected together when outer jacket 4 and collector plate 3 is welded. The positioning part may be, for example, a hole with different size from pouring hole 3 B, protrusion, or partially-colored part instead of the notch. In other words, each of collector plate 3 and element connecting part 2 A is set rotationally asymmetric to be used as a positioning part.

However, it is preferable to provide the positioning parts on the outer peripheral ends of element connecting part 2 A and collector plate 3 , such as notches 2 E and 3 C. In this structure of positioning by the outer peripheral ends, the relative position in the rotating direction can be confirmed after joining terminal plate 2 and collector plate 3 to capacitor element 1 just by looking at capacitor element 1 from the side face. As a result, productivity can be improved. Accordingly, each of the outer shape of collector plate 3 and outer shape of element connecting part 2 A is preferably rotationally asymmetric.

When the positioning part is provided inside the outer periphery, a protrusion protruding from capacitor element 1 that is higher than the outer peripheral end needs to be provided, in order to enable to visually recognize the positioning part. In this case, the shape of element connecting part 2 A may become complicated or the weight may be increased.

By the use of a jig (not illustrated) that has a pair of insertion parts that fit into spaces in notches 2 E and 3 C, terminal plate 2 and collector plate 3 can be positioned at once in capacitor element 1 when terminal plate 2 and collector plate 3 are disposed on and welded to element ends 1 A and 1 B of capacitor element 1 . This also improves productivity.

Still more, burr may exist on the surface of welded portion. In other words, burr may exist at a connecting part of collector plate 3 to capacitor element 1 . If contact parts 4 E come in contact with this connecting part in the state containing burr, height of collector plate 3 varies among contact parts 4 E and the levelness of collector plate 3 may decrease. Therefore, as shown in FIG. 9 , it is preferable to dispose the notch of collector plate 3 above contact part 4 E of outer jacket 4 , and make a portion of collector plate 3 contact with contact part 4 E, except for the connected part (welded part) with capacitor element 1 .

Still more, valve 4 F may be used for positioning collector plate 3 and bottom 4 A of outer jacket 4 . Valve 4 F is a component without rotation symmetry to the center of bottom 4 A, and is provided at the position off the center of bottom 4 A of outer jacket 4 . In this case, bottom 4 A of outer jacket 4 is rotationally asymmetric. For example, three of contact parts 4 E are provided on the outer peripheral end of the inner face of bottom 4 A at interval such that the inner angle formed by straight lines connecting the center of bottom 4 A and contact parts 4 E is 120°. The position of joining part 4 G can be determined with reference to the positional relationship of a straight line connecting the center of bottom 4 A and the position of valve 4 F and a straight line connecting the above center and contact part 4 E.

Here, to facilitate identification of the positional condition of collector plate 3 , the position of joining collector plate 3 to outer jacket 4 is preferably determined with reference to the positional relationship of a straight line linking contact part 4 E in contact with notch 3 C of collector plate 3 in three contact parts 4 E and the center of bottom 4 A and a straight line linking the center of bottom 4 A and valve 4 F. Here, the center of bottom 4 A, valve 4 F, and the notch lie on one straight line when the above two straight lines mutually point the same direction or opposite directions The position of the joining part of collector plate 3 with capacitor element 1 can be easily determined based on the position of the straight lines. In other words, the position of notch 3 C can be easily identified based on the position of valve 4 F.

The position of joining part 4 G on bottom 4 A of outer jacket 4 can be set with reference to the positions of the above straight lines such that the position of the joining part with capacitor element 1 is avoided. With this structure, an overlap of the position of joining part 4 G with element connecting part 3 A can be easily avoided at bottom 4 A. As a result, the possibility of re-melting the part of collector plate 3 connected to capacitor element 1 can be reduced.

In the above description, valve 4 F is used as a positioning part without rotation symmetry with reference to the center of bottom 4 A. However, aforementioned positioning part may be formed separately on bottom 4 A.

When the inner pressure in outer jacket 4 rises, bottom 4 A may swell. In this case, swelling gradually progresses from the center of bottom 4 A in the radial direction. In other words, displacement at the center of bottom 4 A will be the largest due to swelling. Therefore, joining part 4 G is preferably formed around the center of bottom 4 A of outer jacket 4 . This structure improves reliability of welding compared to the structure of radially forming joining part 4 G from the center. In other words, formation of joining part 4 G at a predetermined interval from the center can delay the peeling timing of outer jacket connecting part 3 G from joining part 4 G that may occur due to displacement of bottom 4 A due to swelling, compared to radial joining parts. Joining reliability between collector plate 3 and outer jacket 4 is thus improved and an increase of resistance on the joining boundary face can be suppressed.

Still more, the opening areas of pouring hole 2 D and pouring hole 2 d are preferably different. Pouring hole 2 D is a first through hole and pouring hole 2 d is a second through hole both provided on element connecting part 2 A. Or, assuming that notch 2 E is not created and element connecting part 2 A is a disk plate, distances from the center of element connecting part 2 A to pouring hole 2 D and to pouring hole 2 d are preferably different. This structure enables the open areas of pouring holes 2 D and 2 d to come in contact with capacitor element 1 at diversifying points. The electrolytic solution can thus be poured from diversifying points in capacitor element 1 .

The electrolytic solution also passes through between capacitor element 1 and side wall 4 K of outer jacket 4 and is also supplied to capacitor element 1 from the side near collector plate 3 . Therefore, the opening areas of pouring hole 3 B and pouring hole 3 B, both created in collector plate 3 , are preferably different. Or, assuming that notch 3 C is not created and collector plate 3 is a disk plate, distances from the center of collector plate 3 to pouring hole 3 B and to pouring hole 3 b are preferably different.

Still more, pouring holes 2 D and 2 d created in terminal plate 2 and pouring holes 3 B and 3 b created in collector plate 3 preferably have portions not facing each other. In other words, pouring holes 2 D and 2 d that are terminal plate through holes and pouring holes 3 B and 3 b that are collector plate through holes preferably do not coincident in a direction extending from bottom 4 A to the opening of outer jacket 4 . That is to say, a part of the open areas preferably have opposed portions. These partially opposed portions establish a path where the electrolytic solution poured into collector plate 3 from terminal plate 2 via capacitor element 1 passes through. The electrolytic solution passes through this path and further enters into capacitor element 1 through non-corresponding portions provided at different positions. By setting different positions for non-corresponding portions of pouring holes 2 D, 2 d , 3 B, and 3 b , the electrolytic solution can be poured into diversifying portions in capacitor element 1 . As a result, the pouring efficiency of entire capacitor element 1 increases.

Second Exemplary Embodiment

FIG. 10A is a front sectional view of an electric double layer capacitor as an example of an electric storage device in the second exemplary embodiment. FIG. 10B is a side sectional view thereof. Major points where this exemplary embodiment differ from that of the first exemplary embodiment is terminal plate 32 instead of terminal plate 2 , collector plate 33 instead of collector plate 3 , and that terminal plate holder 6 and collector plate holder 7 are added. In addition, sealing member 5 does not have skirt 5 B. Other than these points, the basic structure is same as that of the first exemplary embodiment, and thus its detailed description may be omitted.

More specifically, terminal plate 32 joined to element end 1 A of capacitor element 1 is housed and fixed inside terminal plate holder 6 . Collector plate 33 joined to element end 1 B of capacitor element 1 is housed and fixed inside collector plate holder 7 . On the inner face of bottom 4 A of outer jacket 4 , collector plate connecting part 4 H is formed so as to protrude toward the opening of outer jacket 4 , be fixed to collector plate holder 7 , and be in contact with collector plate 33 .

Next, terminal plate 32 is described with reference to FIGS. 11 to 12B . FIG. 11 is a perspective view of terminal plate 32 , FIG. 12A is a top view of terminal plate 32 , and FIG. 12B is a front sectional view of terminal plate 32 .

Terminal plate 32 is formed of a conductive material, such as metal. Terminal plate 32 includes disk-shaped element connecting part 32 A and external terminal 32 B. Element connecting part 32 A is connected (joined) to element end 1 A of capacitor element 1 . External terminal 32 B is provided on the outer surface of element connecting part 32 A, and is columnar for leading out an electrode. Element connecting part 32 A is provided with element joining part 32 C so as to protrude toward element end 1 A for being welded onto element end 1 A. Element connecting part 32 A is also provided with slit holes 32 D between external terminal 32 B and element joining part 32 C. External terminal 32 B is provided with tapered part 32 E on the outer periphery at a tip thereof. Terminal plate 32 is formed of aluminum, for example.

Next, collector plate 33 is described with reference to FIGS. 13 and 14 . FIG. 13 is a perspective view of collector plate 33 and FIG. 14 is a bottom view of collector plate 33 .

Collector plate 33 is formed of a conductive plate, such as metal. Collector plate 33 includes element connecting part 33 A and outer jacket connecting part 33 B. Element connecting part 33 A protrudes toward element end 1 B so that it can be welded onto element end 1 B. Outer jacket connecting part 33 B is provided at a position facing hollow 1 C of capacitor element 1 . Outer jacket connecting part 33 B comes in contact with collector plate connecting part 4 H in bottom 4 A of outer jacket 4 , as shown in FIGS. 10A and 10B , and is welded. Slit holes 33 C are formed between element connecting part 33 A and outer jacket connecting part 33 B. Pouring hole 33 D is formed at a position different from element connecting part 33 A and outer jacket connecting part 33 B. Collector plate 33 is, for example, formed of aluminum. Outer jacket connecting part 33 B is welded onto collector plate connecting part 4 H by inserting an electrode tool of a resistance welder from hollow 1 C of capacitor element 1 from the opposite side.

Next, terminal plate holder 6 and collector plate holder 7 are described with reference to FIGS. 15A to 16B . FIG. 15A is a top perspective view of terminal plate holder 6 , and FIG. 15B is a bottom perspective view of terminal plate holder 6 . FIG. 16A is a top view of terminal plate holder 6 , and FIG. 16B is a front sectional view of terminal plate holder 6 . Since collector plate holder 7 has a structure same as that of terminal plate holder 6 , reference marks in brackets are indicated in the drawings. Terminal plate holder 6 and collector plate holder 7 are formed of insulating material, such as polypropylene.

Terminal plate holder 6 includes tubular (columnar) part 6 A and fixing part 6 B. Tubular part 6 A covers and houses an outer peripheral end of terminal plate 32 . Fixing part 6 B is provided on an inner wall of tubular part 6 A, and supports terminal plate 32 housed in tubular part 6 A.

More specifically, fixing part 6 B is formed of two components that are flat part 6 C and protrusion 6 D. Flat part 6 C is formed such that it partially covers tubular part 6 A from one end of an opening thereof to the outer peripheral end on a face of the opening. Protrusion 6 D is formed on the inner side of tubular part 6 A at a predetermined distance with flat part 6 C. Protrusion 6 D and tubular part 6 A establishes a snap-fit structure to sandwich and fix terminal plate 32 between flat part 6 C and protrusion 6 D. In this structure, tubular part 6 A proves effective same as skirt 5 B of sealing member 5 in the first exemplary embodiment.

In the same way, collector plate holder 7 includes tubular (columnar) part 7 A and fixing part 7 B. Tubular part 7 A covers and houses an outer peripheral end of collector plate 33 . Fixing part 7 B is provided on an inner wall of tubular part 7 A, and supports collector plate 33 housed inside tubular part 7 A.

More specifically, fixing part 7 B is formed of two components that are flat part 7 C and protrusion 7 D. Flat part 7 C is formed such that it partially covers tubular part 7 A from one end of an opening thereof to the outer peripheral end on a face of the opening. Protrusion 7 D is formed on the inner side of tubular part 7 A at a predetermined distance with flat part 7 C. Protrusion 7 D and tubular part 7 A establish a snap-fit structure to sandwich and fix collector plate 33 between flat part 7 C and protrusion 7 D.

Positions and dimensional relationship of sealing member 5 , tapered part 32 E of external terminal 32 B, and outer jacket 4 are same as the relationship of sealing member 5 , tapered part 2 C of external terminal 2 B, and outer jacket 4 in the first exemplary embodiment. the electric double layer capacitor in this exemplary embodiment is configured as above.

In the above structure, outer jacket connecting part 33 B of collector plate 33 joined to element end 1 B of capacitor element 1 and collector plate connecting part 4 H of outer jacket 4 can be joined by resistance welding from the collector plate 33 side. In this case, collector plate 33 is melted ahead of outer jacket 4 , and thus piercing in outer jacket 4 can be suppressed. Collector plate connecting part 4 H is provided at a position (connecting part) facing hollow 1 C, where collector plate 33 does not face capacitor element 1 . As a trace of welding, a welding mark is exposed at least on the top face of outer jacket connecting part 33 B. In addition, collector plate connecting part 4 H is thicker than outer jacket connecting part 33 B. In other words, collector plate 33 is thicker than bottom 4 A of outer jacket 4 at the above-mentioned connecting part. Therefore, a reaction force from thick collector plate connecting part 4 H to outer jacket connecting part 33 B can be applied against a pressure in the resistance welding that applies pressure to outer jacket connecting part 33 B and welds this pressurized part. Accordingly, reliability at welding can be increased.

Still more, collector plate connecting part 4 H is formed protruding from bottom 4 A of outer jacket 4 . In other words, collector plate connecting part 4 H is preferably provided as a protrusion protruding from the inner side of bottom 4 A at the connecting part of bottom 4 A of outer jacket 4 and collector plate 33 . Therefore, a contact area with outer jacket connecting part 33 B is smaller compared to the structure of applying resistance welding to a bottom formed thicker than collector plate 33 . Accordingly, a stronger reaction force (stress) can be achieved.

As an example, resistance welding is applied, using a DC resistance equipment, to 0.6-mm thick outer jacket connecting part 33 B and 5.00-mm thick collector plate connecting part 4 H (1.0 mm at a portion excluding collector plate connecting part 4 H). As an example, conditions of the resistance equipment are 9.6 V, 7.8 kA, and 8 ms. A curvature radius at the electrode tip is 30 mm.

Next, a further preferable example of collector plate connecting part 4 H is described with reference to FIGS. 17A and 17B . FIGS. 17A and 17 B are enlarged partial sectional view of outer jacket 4 . In a structure shown in FIG. 17A , an end face of the tip of collector plate connecting part 4 H is a spherical face and not flat face. In a structure in FIG. 17B , the outer periphery of collector plate connecting part 4 H is tapered. These structures further decrease a contact area, and can thus further increase reaction force to outer jacket connecting part 33 B.

Alternatively, the reaction force may be increased by decreasing the contact area by providing a protrusion, i.e., a projection, on the joining face of outer jacket connecting part 33 B. Or, a protrusion protruding outward may be provided on the outer side of bottom 4 A of outer jacket 4 at a portion where the connecting part for collector plate 33 is formed. In this case, external connecting part 4 B shown in FIG. 10B can be used as the protrusion.

Still more, in the electric double layer capacitor in this exemplary embodiment, collector plate 33 and outer jacket 4 come in contact and are electrically connected only at outer jacket connecting part 33 B and collector plate connecting part 4 H. In other words, a portion in collector plate 33 except for outer jacket connecting part 33 B is not in contact with outer jacket 4 formed of a conductive material. Therefore, the current that should be consumed in outer jacket connecting part 33 B can be prevented from dispersing. In other words, energy input for welding is concentrated on a part to be welded. As a result, highly-reliable welding can be achieved.

Still more, the protrusion of collector plate connecting part 4 H from bottom 4 A enables to determine a position of collector plate 33 based on the height of collector plate connecting part 4 H and insulate collector plate 33 at a position away from bottom 4 A. In addition, flat part 7 C of collector plate holder 7 is positioned at a part other than the contact part of collector plate 33 and bottom 4 A of outer jacket 4 . Since flat part 7 C is made of an insulating material, physical and electrical insulation accuracy can be reliably improved at a portion other than the joining part.

Instead of collector plate holder 7 , an insulating sheet with a through hole large enough to house collector plate connecting part 4 H may be disposed on the inner face of bottom 4 A, or an insulating film may be formed on a portion on bottom 4 A, excluding collector plate connecting part 4 H. By providing an insulating material to insulate between at least a part of a portion excluding collector plate connecting part 4 H and the inner face of bottom 4 A of outer jacket 4 , the above effect can be achieved.

Next is described an effect of slit holes 32 D in terminal plate 32 shown in FIG. 11 and a slit hole in collector plate 33 shown in FIG. 13 .

As described above, slit holes 32 D are provided between element connecting part 32 C and external terminal 32 B. Therefore, external terminal 32 B can be displaced in the first direction (vertical direction) extending from bottom 4 A to the opening of outer jacket 4 , independently of element connecting part 32 C. Element connecting part 32 A can thus act as a damper with slit holes 32 D.

In the same way, slit holes 33 C are provided between element connecting part 33 A and outer jacket connecting part 33 B. Therefore, outer jacket connecting part 33 B can be displaced in the first direction (vertical direction) extending from bottom 4 A to the opening of outer jacket 4 , independently of element connecting part 33 A. Collector plate 33 can thus act as a damper with slit holes 33 C.

When sealing the opening of outer jacket 4 , or when an inner pressure of outer jacket 4 increases, sealing member 5 may swell. If sealing member 5 swells, a stress is applied to capacitor element 1 joined to terminal plate 32 and collector plate 33 , in the winding axis direction thereof. By absorbing the stress with the effect of the damper, application of a stress to element connecting part 32 C and element connecting part 33 A can be suppressed. As a result, an increase of resistance in element ends 1 A and 1 B can be suppressed. Long-term reliability can be secured by providing slit holes 32 D in terminal plate 32 and slit holes 33 C in collector plate 33 .

To increase the function of this damper, it is preferable to form slit holes 32 D around (but not completely in a ring shape) one of external terminal 32 B and element connecting part 32 C. In the same way, it is preferable to form slit holes 33 C around (but not completely in a ring shape) one of outer jacket connecting part 33 B and element connecting part 33 A.

Next is described a collector plate with a structure different from that of collector plate 33 with reference to FIGS. 18A to 19 . FIG. 18A is a bottom view of another collector plate, collector plate 13 , used in the electric double layer capacitor in the exemplary embodiment. FIG. 18B is a front sectional view of collector plate 13 , and FIG. 18C is a side sectional view of collector plate 13 . FIG. 19 is a bottom view of still another collector plate.

First, collector plate 13 is described. Collector plate 13 includes element connecting part 13 A connected to element end 1 B of capacitor element 1 , and outer jacket connecting part 13 B connected to collector plate connecting part 4 H of outer jacket 4 . Element connecting part 13 A and outer jacket connecting part 13 B has a flat shape and are provided on a same plane. Flange 13 E is provided around flat element connecting part 13 A and outer jacket connecting part 13 B. Flange 13 E protrudes from around element connecting part 13 A and outer jacket connecting part 13 B toward bottom 4 A of outer jacket 4 , and its edge extends in the horizontal direction relative to bottom 4 A.

Since element connecting part 13 A and outer jacket connecting part 13 B are on the same plane, a position of end face in element end 1 B of a portion in contact with element connecting part 13 A is fixed by the height of the top end of collector plate connecting part 4 H. On the other hand, in element end 1 B, a portion not in contact further protrudes toward bottom 4 A. Flange 13 E comes in contact with this end face not in contact with element connecting part 13 A. Therefore, the position of end face not in contact with element connecting part 13 A can also be fixed by the position of flange 13 E. As a result, a space is provided in collector plate 33 and outer jacket 4 between at least a part of the portion excluding the connecting part and the inner face of bottom 4 A of outer jacket 4 . In collector plate 33 , at least a part of a portion excluding the connecting part is insulated with outer jacket 4 by this space. Accordingly, flange 13 E enables to control the position of the end face of element end 1 B at a portion not in contact with element connecting part 13 A.

By adjusting the position of flange 13 E to the position that does not come in contact with bottom 4 A, element end 1 B can be prevented from contacting with bottom 4 A. As a result, flow of current supplied to parts other than outer jacket connecting part 13 B can be suppressed at applying resistance welding to outer jacket connecting part 13 B and collector plate connecting part 4 H. In other words, electric energy required for welding can be concentrated on outer jacket connecting part 13 B.

On the other hand, collector plate 23 shown in FIG. 19 is configured as an integrated plate having areas only required as elements of element connecting part 23 A and outer jacket connecting part 23 B, respectively, as a simple structure. This enables to reduce material costs, and achieve a low-cost electric storage device.

Next, a connecting structure using other collector plate and outer jacket is described with reference to FIGS. 20A and 20B . FIGS. 20A and 20B are partial front sectional views illustrating structures before and after joining collector plate 43 to the inner bottom of outer jacket 14 by cold welding.

In the structure shown in FIGS. 10A and 10B , the bottom of outer jacket 4 and outer jacket connecting part 33 B at the center of collector plate 33 are joined by resistance welding. In contrast, in the structure shown in FIGS. 20A and 20B , collector plate 43 joined to element end 1 B of electric storage element 1 is joined to the bottom of cylindrical outer jacket 14 with bottom by cold welding.

As shown in FIG. 20A , collector plate 43 is formed of a conductive material such as metal, and includes flat element connecting part 43 A and outer jacket connecting part 43 B provided at the center of element connecting part 43 A and protruding toward the bottom of outer jacket 14 . Outer jacket connecting part 43 B is formed thicker than element connecting part 43 A in order to be connected to the bottom of outer jacket 14 by cold welding. Collector plate 43 is typically made of aluminum.

Outer jacket 14 is formed of a conductive material such as metal, and includes bottom 14 A whose inner face is protruded and collector plate connecting part 14 H provided at the center of bottom 14 A. Collector plate connecting part 14 H is a recess for housing outer jacket connecting part 43 B.

This structure, as shown in FIG. 20B , enables to join collector plate 43 and outer jacket 14 by forming pressure-joining part 43 C where outer jacket connecting part 43 B digs into the bottom of collector plate connecting part 14 H. In other words, pressure-joining part 43 C is configured with outer jacket connecting part 43 B and collector plate connecting part 14 H. Since this joining method does not require melting for joining, piercing and the like can be reduced, compared to laser welding.

For cold welding, it is preferable that a thickness ratio of pressure-joining part 43 C after pressure-joining to the sum of thickness of collector plate connecting part 14 H and outer jacket connecting part 43 B before pressure-joining is 0.3 or less. Still more, if this ratio is 0.2 or less, change of resistance at the connecting part over time also becomes small. The sum of thicknesses for collector plate connecting part 14 H and outer jacket connecting part 43 B before pressure-joining can be identified by thicknesses of non-pressure-joined portion of collector plate connecting part 14 H and outer jacket connecting part 43 excluding pressure-joined part 43 C after cold welding.

Still more, a ratio of a diameter of a hole bottom of pressure-joined part 43 C to an inner diameter of collector plate connecting part 14 H or an outer diameter of outer jacket connecting part 43 B is preferably 0.6 or less. Still more, if this ratio is 0.4 or less, change of resistance at the connecting part over time also becomes small.

For the electrolytic solution used in the first and second exemplary embodiments, the following materials can be used in addition to aforementioned compositions. As the solvent, at least one of propylene carbonate (PC), ethylene carbonate (EC), and dimethyl carbonate (DMC) can be used. As the supporting electrolyte, at least one of tetraethyl ammonium tetrafluoroborate (TEABF 4 ), triethylmethyl ammonium tetrafluoroborate (TEMABF 4 ), 1-ethyl-3-methyl imidazolium tetrafluoroborate (EMIBF 4 ), 1-ethyl-2,3-dimethyl imidazolium tetrafluoroborate (EDMIBF 4 ), 1,2,3-trimethyl imidazolium tetrafluoroborate (TMIBF 4 ), and 1,3-dimethyl imidazolium tetrafluoroborate (DMIBF 4 ) can be used. The solvent and electrolyte are not particularly limited.

Other than electrolytic solution, a gel electrolyte containing binder in the solvent or solid electrolyte may be used as electrolyte.

Materials used for collector plate 3 and terminal plate 2 are not limited to aforementioned aluminum. Titanium, zirconium, hafnium, niobium, tantalum, chrome, molybdenum, tungsten, manganese, silicon, iron, silver, lead, nickel, copper, platinum, and gold, and their alloys may be used.

The electrode layers of positive electrode and negative electrode may contain a binder such as ammonium salt of carboxylmethyl cellulose and polytetrafluoroethylene, and/or conductive agent such as acetylene black, in addition to a carbon material such as activated carbon. Addition of these materials can shorten a distance between active carbons or improve conductivity, and thus capacitor element 1 can have lower resistance.

Still more, the present disclosure is not limited to the electric double layer capacitor. The present configuration is also applicable to storage batteries mainly using metal material as a collector member of each electrode layer, such as electrochemical capacitors and lithium secondary batteries. In an electrochemical capacitor, lithium ion is used as cation of electrolyte. Lithium is absorbed in a carbon material or metal that can make alloy with cation. Such material is contained in the electrode layer of the negative electrode. The positive electrode is the same as the positive electrode of the electric double layer capacitor. The present disclosure demonstrates an outstanding effect of improving reliability of sealing as aforementioned electric storage device also when applied to electrochemical capacitors and storage batteries.

The electric storage device of the present disclosure improves workability of inserting the sealing member into the outer jacket, and thus productivity in manufacturing an electric storage device can be improved. Accordingly, the use of the present disclosure in various electronic devices that require storing electricity is expected.