JP6318985B2 - Power storage device - Google Patents

Description

  The present invention relates to a power storage device.

  2. Description of the Related Art Some power storage devices used for in-vehicle power supplies include a case that houses an electrode assembly and an electrode terminal that protrudes outside the case through a through hole in the case. Conventionally, in Patent Document 1, a seal ring (seal packing) is interposed between the opposing surfaces of the electrode terminal and the case in the protruding direction of the electrode terminal from the case, and the gap between the opposing surfaces is sealed by the seal ring. A power storage device is described. The case of the power storage device of the document includes a groove for holding the seal ring at a contact portion with the seal ring.

JP 2006-324178 A

  When the pressure in the case increases due to overcharging, the electrolyte may flow into the radially outer portion of the seal ring between the opposing surfaces of the electrode terminal and the case. In this state, when a high voltage is applied between the electrode terminals, conduction between the electrode terminal and the case via the flowing electrolyte solution, a so-called liquid junction may occur. When a liquid junction occurs and the electrolytic solution is electrolyzed, the decomposition product adheres to the surface of a seal ring or the like, and there is a possibility that a short circuit due to tracking may occur.

  The present invention has been made in view of such circumstances, and a problem to be solved is to provide a power storage device that can suitably suppress a liquid junction between an electrode terminal and a case.

  A power storage device that solves the above problems includes a case in which an electrode assembly is accommodated, a through hole in the case, a terminal head that exists in the case and has an outer diameter larger than the inner diameter of the through hole. And an electrode terminal having a terminal shaft protruding from the terminal head to the outside of the case through the through hole, and an opposing surface of the case and the terminal head in the axial direction of the terminal shaft An annular seal ring that seals between the opposing surfaces, and a case and the terminal head that are interposed in a radially outer portion of the seal ring between the opposing surfaces. And a terminal insulating member that insulates the portion, and a radially outer side than a contact position between the case and the seal ring, and an inner peripheral side radially inward of the outer periphery of the seal ring Side of the position The annular groove inner circumferential surface of the outer peripheral side surface radially outward than the terminal insulating member is located, are provided on a facing surface of said terminal head portion in the case.

  Further, another power storage device that solves the above problems includes a case in which an electrode assembly is accommodated, a through hole in the case, an outer diameter that is present in the case and is larger than an inner diameter of the through hole. An electrode terminal having a terminal shaft protruding from the terminal head to the outside of the case through the through-hole, and the case and the terminal head in the axial direction of the terminal shaft A seal ring that is interposed between the facing surfaces of the seal portion and seals between the facing surfaces; and a case that is interposed between the facing surfaces on a radially outer portion of the seal ring, And a terminal insulating member that insulates the terminal head, wherein the terminal head has a radially outer side than a contact position with the seal ring and a radially inner side than the outer periphery of the seal ring. Within Located the side of the side, the inner annular groove side surface of outer peripheral side is located radially outward from the circumference of the terminal insulating member includes a facing surface of said casing in the pin head.

  In such a power storage device, the insulation distance between the facing surfaces of the case and the terminal head is increased by the groove provided in the case or the terminal head. Therefore, the insulation resistance between the case and the electrode terminal increases.

  About the said electrical storage apparatus, it is desirable that the outer peripheral side surface of the said groove | channel is along the outer periphery of the contact part with the said seal ring in the said opposing surface. In such a case, a longer insulation distance can be ensured between the facing surfaces of the case and the terminal head.

  Regarding the power storage device, the seal ring has a circular cross section, and the distance from the outer peripheral side surface of the groove to the inner periphery of the terminal insulating member, and the depth of the groove are both It is desirable to be equal to or more than a value obtained by subtracting the radius of the cross section of the seal ring from a quarter of the circumferential length of the cross section of the seal ring. In such a case, the effect of suppressing the liquid junction due to the provision of the groove is theoretically maximized.

  Regarding the power storage device, the seal ring has a circular cross section, and the distance from the outer peripheral side surface of the groove to the inner periphery of the terminal insulating member and the depth of the groove are both the seal. It is preferably equal to a value obtained by subtracting the radius of the cross section of the seal ring from a quarter of the circumferential length of the ring cross section. In such a case, the reduction in strength of the case or the terminal head due to the provision of the groove can be suppressed while theoretically maximizing the effect of suppressing the liquid junction due to the provision of the groove.

  The power storage device can be applied to a secondary battery.

  According to the present invention, the liquid junction between the electrode terminal and the case can be suitably suppressed.

The perspective view which shows the external appearance of 1st Embodiment of the secondary battery as an electrical storage apparatus. The exploded perspective view of an electrode assembly. The exploded perspective view of a secondary battery. The disassembled perspective view which shows the joining structure of an electroconductive member and an electrode terminal. (A) is sectional drawing around a positive electrode terminal, (b) is sectional drawing around a negative electrode terminal. The expanded sectional view of the opposing part of the terminal head of an electrode terminal, and the cover of a case. (A) is sectional drawing of the periphery of the positive electrode terminal about the secondary battery of 2nd Embodiment, (b) is sectional drawing of the periphery of the negative electrode terminal.

(First embodiment)
Hereinafter, 1st Embodiment of an electrical storage apparatus is described in detail with reference to FIGS. The power storage device of this embodiment is configured as a rectangular lithium ion secondary battery.

  As shown in FIG. 1, a secondary battery 10 as a power storage device includes a rectangular parallelepiped case 11. The case 11 includes a bottomed box-shaped case main body 12 that is open on one side, and a rectangular flat plate-shaped lid 13 that closes an opening portion of the case main body 12. The case body 12 and the lid 13 are joined by welding or the like.

  The secondary battery 10 includes an electrode assembly 14 and an electrolyte solution (not shown) housed in the case 11, and electrode terminals on the positive electrode side and the negative electrode side (positive electrode terminal 15, which exchange power with the electrode assembly 14. A negative electrode terminal 16) is provided. The electrode terminals 15 and 16 are provided on the lid 13 of the case 11 and are arranged in a state of penetrating the lid 13. Each electrode terminal 15, 16 protrudes from the lid 13 of the case 11 to the outside. In the following description, the protruding direction of the electrode terminals 15 and 16 with respect to the lid 13 is the upper side of the secondary battery 10, and the opposite direction is the lower side of the secondary battery 10.

  As shown in FIG. 2, the electrode assembly 14 has a structure in which positive electrodes 21 and negative electrodes 22 are alternately stacked via separators 23, which are porous films that can transmit ions related to electrical conduction. The positive electrode 21, the negative electrode 22, and the separator 23 are rectangular sheets.

  The positive electrode 21 includes, for example, a rectangular positive metal foil 21a made of aluminum, and positive electrode active material layers 21b on both surfaces of the positive metal foil 21a. The negative electrode 22 includes, for example, a rectangular negative metal foil 22a made of copper, and negative electrode active material layers 22b on both surfaces thereof. In the state constituting the electrode assembly 14, the positive electrode active material layer 21 b is covered with the negative electrode active material layer 22 b, and the electrodes 21 and 22 are covered with the separator 23. Further, the positive electrode 21 has a positive electrode tab 31 having a shape protruding from the end 21c. The negative electrode 22 has a negative electrode tab 32 protruding from the end 22c. The electrodes 21 and 22 are stacked so that the same polarities of the tabs 31 and 32 are arranged in a row.

  As shown in FIG. 3, each negative electrode tab 32 is gathered near one side in the stacking direction of the electrodes 21, 22 and folded back to the other in the gathered state. Similarly, the positive electrode tabs 31 are gathered together in one of the stacking directions of the electrodes 21 and 22, and are folded back to the other in the gathered state. In the present embodiment, the positive electrode tab 31 and the negative electrode tab 32 are folded back in the same direction. The electrode assembly 14 is accommodated in the case 11 with the end surface 14a where the tabs 31 and 32 are present and the inner surface 13a of the lid 13 where the electrode terminals 15 and 16 are opposed.

  The secondary battery 10 includes a positive electrode conductive member 40 used to electrically connect the positive electrode tab 31 and the positive electrode terminal 15. The positive electrode conductive member 40 exists between the lid 13 of the case 11 and the electrode assembly 14, and is bonded to both the positive electrode tab 31 and the positive electrode terminal 15.

  The positive electrode conductive member 40 is composed of a single metal plate, for example, an aluminum plate. The positive electrode conductive member 40 includes a positive electrode tab bonding portion 41 bonded to the positive electrode tab 31 and a terminal bonding portion 42 bonded to the positive electrode terminal 15. The positive electrode conductive member 40 includes a positive electrode curved portion 43 that is continuous with both the positive electrode tab joint portion 41 and the terminal joint portion 42 and is curved (bent) in a crank shape.

  The positive electrode terminal 15 includes a prismatic terminal head 51 and a cylindrical terminal shaft portion 52 that extends upward from the upper surface 51 a of the terminal head 51 and has a thread groove on the outer peripheral surface. The terminal shaft portion 52 protrudes to the outside of the case 11 through the through hole 13 b provided in the lid 13.

  The terminal head 51 exists in the case 11 and protrudes from the inner surface 13 a of the lid 13 toward the electrode assembly 14. The terminal head 51 has an outer diameter larger than the inner diameter of the through hole 13b. A seal ring 53 is interposed between the opposing surfaces of the terminal head 51 and the lid 13 in the axial direction (vertical direction) of the terminal shaft portion 52. The seal ring 53 is a ring-shaped seal ring having a circular cross section, and the terminal shaft portion 52 is inserted through the inner diameter portion thereof.

  The terminal shaft portion 52 is fitted with the through hole 13b, and an insulating flanged ring 54 is inserted therethrough. A nut 55 is screwed onto the terminal shaft portion 52 from above the flanged ring 54, and the positive terminal 15 and the lid 13 are unitized.

  As shown in FIGS. 3 and 4, the secondary battery 10 includes a positive terminal insulating member (positive terminal insulating member 57) that covers a part of the terminal head 51, a terminal joint 42, and the electrode assembly 14. And a junction insulating member 58 interposed between the end face 14a of the first and second end surfaces 14a. The positive terminal insulating member 57 has an insulating property and covers the upper surface 51 a of the terminal head 51 and a part of the outer peripheral surface of the terminal head 51. The junction insulating member 58 has an insulating property and regulates contact between the terminal junction 42 and the end surface 14 a of the electrode assembly 14.

  The secondary battery 10 includes a negative electrode conductive member 60 that is used to electrically connect the negative electrode tab 32 and the negative electrode terminal 16. The negative electrode conductive member 60 exists between the lid 13 of the case 11 and the electrode assembly 14, and is bonded to both the negative electrode tab 32 and the negative electrode terminal 16.

  As shown in FIG. 3 or FIG. 4, the negative electrode conductive member 60 is composed of a single metal plate, for example, a copper plate. The negative electrode conductive member 60 has a negative electrode tab joint portion 61 joined to the negative electrode tab 32 and a cut-off joint portion 62 joined to the current cut-off portion 80. Furthermore, the negative electrode conductive member 60 has a negative electrode curved portion 63 that is continuous with both the negative electrode tab joint portion 61 and the blocking joint portion 62 and is curved (bent) in a crank shape.

  The negative electrode terminal 16 includes a cylindrical terminal head portion 71 and a cylindrical terminal shaft portion 72 that extends upward from the upper surface 71a of the terminal head portion 71 and has a thread groove on the outer peripheral surface. The terminal shaft portion 72 protrudes out of the case 11 through the through hole 13 b provided in the lid 13.

  The terminal head 71 exists in the case 11 and protrudes from the inner surface 13 a of the lid 13 toward the electrode assembly 14. The terminal head 71 has an outer diameter larger than the inner diameter of the through hole 13b. A seal ring 73 is interposed between the opposing surfaces of the terminal head 71 and the lid 13 in the axial direction (vertical direction) of the terminal shaft 72. The seal ring 73 is a ring-shaped seal ring having a circular cross section, and a terminal shaft portion 72 is inserted through an inner diameter portion thereof.

  The terminal shaft portion 72 is fitted with the through hole 13b, and an insulating flanged ring 74 is inserted therethrough. A nut 75 is screwed onto the terminal shaft portion 72 from above the flanged ring 74, and the negative electrode terminal 16 and the lid 13 are unitized.

  The secondary battery 10 includes a current interrupting unit 80. The current interrupting unit 80 is integrated with the lower surface of the terminal head 71. The current interrupting unit 80 electrically connects the negative electrode terminal 16 and the negative electrode conductive member 60 and electrically connects the negative electrode terminal 16 and the negative electrode conductive member 60 when the pressure in the case 11 exceeds a specified pressure. To make a bad connection. That is, when the pressure in the case 11 is equal to or lower than the specified pressure, the current interrupting unit 80 constitutes a part of the energization path between the negative electrode terminal 16 and the negative electrode tab 32, while the pressure in the case 11 exceeds the specified pressure. In such a case, the energization path is interrupted.

  As shown in FIG. 4, the secondary battery 10 includes an insulating negative electrode terminal insulating member (negative electrode terminal insulating member 77) that covers the upper surface 71 a and the outer peripheral surface of the terminal head 71, and a terminal head. 71 and a caulking member 88 that unitizes the current interrupting unit 80. The negative terminal insulating member 77 is attached to the terminal head 71 from above and restricts contact between the lid 13 and the terminal head 71. The caulking member 88 includes a cylindrical portion 88a, and an upper flange portion 88b and a lower flange portion 88c that are located at both ends in the axial direction of the cylindrical portion 88a and extend radially inward. The caulking member 88 has the upper collar portion 88b engaged with the negative terminal insulating member 77 and the lower collar portion 88c engaged with the stepped portion present on the outer peripheral surface of the support member 86, thereby Unitized.

  As shown in FIG. 3, the secondary battery 10 includes an insulating cover 100 disposed between the positive electrode tab joint 41 and the negative electrode tab joint 61 and the lid 13. The insulating cover 100 is made of, for example, resin. The insulating cover 100 includes a rectangular plate-shaped main body portion 101 and an upright portion 102 that rises downward from an end portion of the main body portion 101 in the short direction.

  In addition, there is a pressure release valve 103 that is opened when the pressure in the case 11 exceeds the open pressure at the center portion of the lid 13, and a portion of the body portion 101 of the insulating cover 100 facing the pressure release valve 103. Has a communication hole 101a. The pressure release valve 103 and the communication hole 101a are disposed between the positive electrode tab joint portion 41 and the negative electrode tab joint portion 61 as viewed from above.

Next, details of the structure relating to the insulation between the case 11 and the electrode terminals 15 and 16 in the secondary battery 10 will be described.
As shown in FIG. 5A, in the secondary battery 10, contact between the lid 13 of the case 11 and the positive terminal 15 is regulated by the seal ring 53, the flanged ring 54, and the positive terminal insulating member 57. Yes.

  The flanged ring 54 is protruded vertically downward from an annular plate-shaped ring portion 54a, a circular tube-shaped flange portion 54b protruding vertically upward from an outer diameter portion of the ring portion 54a, and an inner diameter portion of the ring portion 54a. A fitting portion 54c is provided. The ring portion 54a is interposed between opposing surfaces of the lower surface of the nut 55 and the outer surface 13c (surface exposed to the outside) of the lid 13. The flange portion 54 b covers the periphery of the nut 55 and is interposed between the outer side surface and the outer surface 13 c of the lid 13. The fitting portion 54c is fitted to the inner peripheral surface of the through hole 13b through which the terminal shaft portion 52 of the positive electrode terminal 15 is inserted, and the outer peripheral surface of the terminal shaft portion 52 and the inner peripheral surface of the through hole 13b. It is interposed between the opposing surfaces.

  The positive electrode side terminal insulating member 57 includes a cylindrical tube portion 57a and an annular plate-like flange portion 57b protruding radially inward from the upper end portion of the tube portion 57a. The cylindrical portion 57 a covers the outer periphery of the terminal head 51 of the positive electrode terminal 15 and is interposed between the outer peripheral surface and the inner surface 13 a of the lid 13. On the other hand, the flange portion 57 b covers a radially outer portion of the upper surface 51 a of the terminal head 51 and is interposed in a radially outer portion between the opposed surfaces of the upper surface 51 a and the inner surface 13 a of the lid 13.

  The seal ring 53 is disposed on the inner diameter portion of the flange portion 57 b between the opposed surfaces of the upper surface 51 a of the terminal head 51 and the inner surface 13 a of the lid 13. The seal ring 53 is interposed between the opposed surfaces in a state of being elastically compressed by tightening the nut 55. The contact surfaces of the seal ring 53 and the lid 13 have an annular shape.

  The lid 13 includes an annular groove 90 that circulates around the through hole 13b in a portion of the inner surface 13a facing the upper surface 51a of the terminal head 51. The groove 90 has a rectangular cross-sectional shape. The inner surface 13 a of the lid 13 is a surface facing the terminal heads 51 and 71 in the case 11.

  As shown in FIG. 5B, in the secondary battery 10, contact between the lid 13 of the case 11 and the negative electrode terminal 16 is regulated by the seal ring 73, the flanged ring 74, and the negative electrode side terminal insulating member 77. Yes.

  The flanged ring 74 is protruded vertically downward from an annular plate-shaped ring portion 74a, a circular tube-shaped flange portion 74b protruding vertically upward from an outer diameter portion of the ring portion 74a, and an inner diameter portion of the ring portion 74a. A fitting portion 74c is provided. The ring portion 74 a is interposed between the opposing surfaces of the lower surface of the nut 75 and the outer surface 13 c of the lid 13. The flange portion 74 b covers the periphery of the nut 75 and is interposed between the outer side surface and the outer surface 13 c of the lid 13. The fitting portion 74c is fitted to the inner peripheral surface of the through hole 13b through which the terminal shaft portion 72 of the negative electrode terminal 16 is inserted, and the outer peripheral surface of the terminal shaft portion 72 and the inner peripheral surface of the through hole 13b. It is interposed between the opposing surfaces.

  The negative terminal insulating member 77 includes a cylindrical tube portion 77a and an annular plate-shaped flange portion 77b protruding radially inward from the upper end portion of the tube portion 77a. The cylindrical portion 77 a covers the outer periphery of the terminal head 71 of the negative electrode terminal 16 and is interposed between the outer peripheral surface and the inner surface 13 a of the lid 13. On the other hand, the flange portion 77 b covers a radially outer portion of the upper surface 71 a of the terminal head 71 and is interposed in a radially outer portion between the opposed surfaces of the upper surface 71 a and the inner surface 13 a of the lid 13.

  The seal ring 73 is disposed on the inner diameter portion of the flange portion 77 b between the opposed surfaces of the upper surface 71 a of the terminal head 71 and the inner surface 13 a of the lid 13. The seal ring 73 is interposed between the opposing surfaces in an elastically compressed state by tightening the nut 75. The contact surface between the seal ring 73 and the lid 13 has an annular shape.

The lid 13 also includes an annular groove 91 that circulates around the through hole 13b in a portion of the inner surface 13a that faces the upper surface 71a of the terminal head 71. The groove 91 has a rectangular cross-sectional shape.
As shown in FIG. 6, the side surfaces 94 on the inner peripheral side of the grooves 90 and 91 are along the outer periphery Y of the contact portion X between the lid 13 and the seal ring 53, which has an annular shape. Further, the outer peripheral side surface 95 of the groove 90 is positioned radially outward from the inner peripheral surfaces 57c and 77c of the flange portions 57b and 77b of the terminal insulating members 57 and 77.

Then, the effect | action and effect of the secondary battery 10 of this embodiment are demonstrated.
(1) In the secondary battery 10, the seal rings 53, 73 between the facing surfaces of the terminal heads 51, 71 and the lid 13 of the case 11 when the pressure in the case 11 is increased due to overcharging, etc. It is conceivable that the electrolyte flows into the radially outer portion. As described above, when the pressure in the case 11 rises above the specified pressure, the current interrupting unit 80 interrupts the energization path between the negative electrode terminal 16 and the negative electrode tab 32, but the terminal heads 51 and 71 and the lid 13 are opposed to each other. The electrolyte may remain between the surfaces even after the blocking. When a high voltage is applied between the electrode terminals 15 and 16 in this state, a short circuit between the electrode terminals 15 and 16 and the lid 13 via the electrolytic solution, that is, a liquid junction may occur. Further, when a liquid junction occurs, a decomposition product of the electrolytic solution may accumulate on the surfaces of the seal rings 53 and 73 and the terminal insulating members 57 and 77, and the electrode terminals 15 and 16 may re-conduct.

  In that respect, in the secondary battery 10 of the present embodiment, the grooves 90 and 91 are present in the portion of the inner surface 13a of the lid 13 that faces the terminal heads 51 and 71, so that the terminal heads 51 and 71 and the lid 13 The insulation distance becomes longer. Therefore, the liquid junction between the electrode terminals 15 and 16 and the case 11 can be suitably suppressed.

  (2) Even if the distance between the facing surfaces of the terminal heads 51 and 71 and the lid 13 is simply increased, the insulation distance between these facing surfaces can be increased. However, it is necessary to increase the thickness of the seal rings 53 and 73 and the terminal insulating members 57 and 77 interposed between the facing surfaces, and this increases the weight and material cost of these components. . In addition, the compression ratio of the seal rings 53 and 73 between the opposing surfaces is reduced, leading to a decrease in sealing performance. In that respect, in the secondary battery 10 of the present embodiment, the insulation distance can be increased without increasing the distance between the opposing surfaces.

  (3) As shown in FIG. 6, in the secondary battery 10 provided with the grooves 90 and 91, the shortest conduction path between the facing surfaces of the terminal heads 51 and 71 and the lid 13 is the following path (A). To (C).

  Path (A): From the outer peripheral side surface 95 of the grooves 90, 91 to the upper surfaces 51a, 71a of the terminal heads 51, 71 along the upper surfaces 57a, 77a of the terminal insulating members 57, 77 and the inner peripheral surfaces 57c, 77c. Route.

Path (B): A path directly from the bottom surface 96 of the grooves 90 and 91 to the upper surfaces 51a and 71a of the terminal heads 51 and 71 at the shortest distance.
Path (C): Position of the outermost radial direction of the seal rings 53 and 73 along the surface of the seal rings 53 and 73 from the radially outer portion of the contact position between the inner surface 13a of the lid 13 and the seal rings 53 and 73 To the upper surfaces 51a and 71a of the terminal heads 51 and 71 at the shortest distance.

  Here, the distance from the outer peripheral side surface 95 of the grooves 90 and 91 to the inner peripheral surfaces 57c and 77c of the terminal insulating members 57 and 77 (the flange portions 57b and 77b) is “a”, and the depth of the grooves 90 and 91 is the same. “B”, and the radius of the cross section of the seal rings 53 and 73 is “r”. The distance of each path | route (A)-(C) at this time is as follows.

  The distance La of the path (A) is the distance a from the outer peripheral side surface 95 of the grooves 90, 91 to the inner peripheral surfaces 57c, 77c of the terminal insulating members 57, 77, the inner surface 13a of the lid 13 and the terminal head 51, 71 is the sum of the shortest distance between the upper surfaces 51a and 71a of 71. On the other hand, the shortest distance between the opposing surfaces is the diameter (2r) of the cross section of the seal rings 53 and 73. Therefore, the distance La of the route A is “La = a + 2r”. Similarly, since the distance Lb of the path (B) is the sum of the depth b of the grooves 90 and 91 and the shortest distance between the opposing surfaces, “Lb = b + 2r”. Further, the distance Lc of the path (C) is a quarter of the circumferential length of the cross section of the seal rings 53 and 73 (2πr / 4 = πr / 2) and the radius r of the cross section of the seal rings 53 and 73. Since it is the sum, “Lc = (π / 2 + 1) r”.

  Among these, the distances La and Lb of the path (A) and the path (B) vary depending on the shape dimensions of the grooves 90 and 91, but the distance Lc of the path (C) is related to the shape dimensions of the grooves 90 and 91. Does not have. Therefore, if the grooves 90 and 91 are set so that both the distances La and Lb of the route (A) and the route (B) are equal to or greater than the distance Lc of the route (C), theoretically, the terminal heads 51 and 71 and The insulation distance between the surface facing the lid 13 can be set to the maximum length that can be achieved by setting the grooves 90 and 91. Specifically, if both the distance a and the depth b are equal to or greater than “(π / 2-1) r”, the liquid junction suppression effect can be maximized. That is, the effect of suppressing the liquid junction is maximized by the distance a from the outer peripheral side surface 95 of the grooves 90 and 91 to the inner peripheral surfaces 57c and 77c of the terminal insulating members 57 and 77, and the depth of the grooves 90 and 91. This is when both of b are equal to or greater than a value obtained by subtracting the radius of the cross section of the seal rings 53, 73 from one-fourth of the circumferential length of the cross section of the seal rings 53, 73.

  (4) In the portion where the grooves 90 and 91 are present, the lid 13 becomes thin and the strength thereof decreases. Therefore, the distance a from the outer peripheral side surface 95 of the grooves 90 and 91 to the inner periphery of the terminal insulating members 57 and 77 and the depth b of the grooves 90 and 91 are the circumferential lengths of the cross sections of the seal rings 53 and 73. It is desirable to make it equal to a value obtained by subtracting the radius of the cross section of the seal rings 53 and 73 from ¼ of the above. In this way, the cross-sectional areas of the grooves 90 and 91 are the minimum value when the insulation distance is the theoretical maximum length. Therefore, it is possible to suppress the liquid junction more efficiently by suppressing the strength reduction of the lid 13 due to the provision of the grooves 90 and 91.

  (5) As shown by a one-dot chain line in FIG. 6, when the side surface 94 on the inner peripheral side of the grooves 90, 91 is located radially outside the outer periphery Y of the contact portion between the lid 13 and the seal ring 73, The route (C) becomes a route (C ′) indicated by a dotted line in the figure, and the distance becomes shorter. Therefore, in order to suppress the liquid junction, the side surface 94 on the inner peripheral side of the grooves 90 and 91 is along the outer periphery Y of the contact portion X between the lid 13 and the seal ring 73 as in this embodiment. desirable.

(Second Embodiment)
Next, a second embodiment of the power storage device will be described with reference to FIG. In the present embodiment, the same components as those in the above embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIGS. 7A and 7B, the secondary battery of the present embodiment is also opposed to the upper surfaces 51a and 71a of the terminal heads 51 and 71 and the inner surface 13a of the lid 13 as in the first embodiment. Between them, seal rings 53 and 73 and terminal insulating members 57 and 77 are interposed. However, in the secondary battery of this embodiment, the terminal heads 51 and 71 are provided with annular grooves 92 and 93 on the upper surface 51a. In addition, the upper surfaces 51a and 71a where the grooves 92 and 93 are located are surfaces facing the case 11 in the terminal head portions 51 and 71, respectively.

  The grooves 92 and 93 circulate around the terminal shaft portions 52 and 72 on the upper surfaces 51 a and 71 a of the terminal heads 51 and 71. The side surfaces 94 on the inner peripheral side of the grooves 92 and 93 are along the outer periphery of the contact portion between the terminal head portions 51 and 71 and the seal rings 53 and 73. In addition, the side surfaces 95 on the outer peripheral side of the grooves 92 and 93 are located on the radially outer side than the inner peripheral surfaces 57c and 77c of the flange portions 57b and 77b of the terminal insulating members 57 and 77.

  Also in this embodiment, the grooves 92 and 93 increase the insulation distance between the terminal heads 51 and 71 and the lid 13, and the liquid junction between the electrode terminals 15 and 16 and the case 11 and the facing surface is suppressed. . Also in this case, both the distance a from the side surface on the outer peripheral side of the grooves 92 and 93 to the inner periphery of the terminal insulating members 57 and 77 and the depth b of the grooves 92 and 93 are in the cross section of the seal rings 53 and 73. The insulation distance secured by the setting of the grooves 92 and 93 as long as it is equal to or larger than the value obtained by subtracting the radius of the cross section of the seal rings 53 and 73 from the quarter of the circumferential length (πr / 2−r). Can be the theoretical maximum length.

  Furthermore, if both the distance a and the depth b are equal to the above value (πr / 2−r), the cross-sectional areas of the grooves 92 and 93 are the minimum values when the insulation distance is the theoretical maximum length. . Therefore, the liquid junction can be suppressed more efficiently by suppressing the strength reduction of the lid 13 due to the provision of the grooves 92 and 93.

In addition, the said embodiment can also be changed and implemented as follows.
The side surfaces on the inner peripheral side of the grooves 90 to 93 may be positioned in a portion radially outside the outer periphery of the contact portion between the inner surface 13a of the lid 13 and the seal rings 53 and 73. Even in such a case, the inner surface 13a of the lid 13 and the terminal heads 51 and 71 are opposed to each other if the inner peripheral side surfaces of the grooves 90 to 93 are positioned radially inward from the outer periphery of the seal rings 53 and 73. The insulation distance between the surfaces is longer than when there are no grooves 90-93. Therefore, also in such a case, the insulation distance between the opposing surfaces of the lid 13 and the terminal heads 51 and 71 becomes long, and the liquid junction is suppressed.

The cross-sectional shape of the grooves 90 to 93 may be a shape other than a rectangle.
The grooves 90 to 93 may be provided only on either the positive electrode side or the negative electrode side. That is, one of the grooves 90 and 91 in the first embodiment and one of the grooves 92 and 93 in the second embodiment may be omitted.

  Both the lid 13 and the terminal heads 51 and 71 may be provided with grooves 90 to 93. That is, the grooves 92 and 93 in the second embodiment may be added to the secondary battery 10 of the first embodiment. In such a case, compared to the case where only one of the lid 13 and the terminal heads 51 and 71 is provided with the grooves 90 to 93, the lid 13 and the terminal heads 51 and 71 when the equivalent liquid junction suppression effect is obtained. The decrease in strength of each is less.

As the seal rings 53 and 73, those having a cross-sectional shape other than circular may be adopted.
As the electrode assembly 14, a wound electrode assembly in which a belt-like positive electrode and a negative electrode are wound through a belt-like separator to form a laminated structure may be used.

The shape of the case 11 may be changed to an arbitrary shape such as a cylindrical shape.
The secondary battery 10 may be a secondary battery other than a lithium ion secondary battery. The power storage device of the above embodiment may be configured as an electric double layer capacitor.

  DESCRIPTION OF SYMBOLS 10 ... Secondary battery (electric storage apparatus), 11 ... Case, 12 ... Case main body, 13 ... Cover, 13a ... Inner surface (opposite surface), 13b ... Through-hole, 14 ... Electrode assembly, 15 ... Positive electrode terminal (electrode terminal) , 16 ... negative electrode terminal (electrode terminal), 51 ... terminal head, 51a ... upper surface (opposing surface), 52 ... terminal shaft portion, 53 ... seal ring, 54 ... ring with flange, 55 ... nut, 57 ... positive terminal Insulating member (terminal insulating member), 71 ... terminal head, 71a ... upper surface (opposing surface), 72 ... terminal shaft portion, 73 ... seal ring, 74 ... ring with flange, 75 ... nut, 77 ... negative terminal insulating member (Terminal insulating member), 90 to 93... Groove, 94... Side surface on the inner peripheral side of the groove, 95.

Claims (6)

A case in which the electrode assembly is accommodated, a through hole in the case, a terminal head that exists in the case and has an outer diameter larger than an inner diameter of the through hole, and the terminal head from the terminal head The electrode terminal having a terminal shaft portion protruding to the outside of the case through a through hole, and the opposing surface interposed between the facing surfaces of the case and the terminal head in the axial direction of the terminal shaft portion A ring-shaped seal ring that seals between the surfaces, and a terminal insulation that insulates the case and the terminal head from the radially outer portion of the seal ring between the opposing surfaces A power storage device comprising:
The side surface on the inner peripheral side is located radially outside the contact position between the case and the seal ring and radially inner than the outer periphery of the seal ring, and more radially than the inner peripheral surface of the terminal insulating member An electrical storage device comprising an annular groove having an outer peripheral side surface located on an outer surface of the case facing the terminal head. A case in which the electrode assembly is accommodated, a through hole in the case, a terminal head that exists in the case and has an outer diameter larger than an inner diameter of the through hole, and the terminal head from the terminal head The electrode terminal having a terminal shaft portion protruding to the outside of the case through a through hole, and the opposing surface interposed between the facing surfaces of the case and the terminal head in the axial direction of the terminal shaft portion A seal ring that seals between the surfaces, and a terminal insulating member that is interposed in a radially outer portion of the seal ring between the opposing surfaces to insulate the case from the terminal head; In a power storage device comprising:
A side surface on the inner peripheral side is located radially outside the contact position with the seal ring at the terminal head and radially inner than the outer periphery of the seal ring, and has a diameter larger than the inner periphery of the terminal insulating member. An electrical storage device comprising an annular groove having an outer peripheral side surface positioned on the outer side in a direction on a surface of the terminal head facing the case.   The power storage device according to claim 1, wherein a side surface on an outer peripheral side of the groove is along an outer periphery of a contact portion with the seal ring on the facing surface. The seal ring has a circular cross section;
Both the distance from the outer peripheral side surface of the groove to the inner periphery of the terminal insulating member, and the depth of the groove are from a quarter of the circumferential length of the cross section of the seal ring to the cross section of the seal ring. The power storage device according to any one of claims 1 to 3, wherein the power storage device is equal to or greater than a value obtained by subtracting the radius. The seal ring has a circular cross section;
Both the distance from the outer peripheral side surface of the groove to the inner periphery of the terminal insulating member, and the depth of the groove are from a quarter of the circumferential length of the cross section of the seal ring to the cross section of the seal ring. The power storage device according to claim 1, which is equal to a value obtained by subtracting the radius of.   The power storage device according to claim 1, wherein the power storage device is a secondary battery.