JP2015133300A - power storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power storage device capable of preventing welding heat generated during bonding a case body and a lid by welding from being transmitted to an insulation member disposed between a terminal and the lid.SOLUTION: In a secondary battery 10, a positive electrode terminal 36 and a negative electrode terminal 37 which transfer electricity to and from an electrode assembly 12 project outside a case 11. Insulation members 38, 39 are disposed between the lid 14 and the positive electrode terminal 36 and the negative electrode terminal 37. The lid 14 and the case body 13 are bonded by welding in a state where a rear surface 14b of the lid 14 and end surfaces of side walls forming an opening portion 13x of the case body 13 are in contact with each other. A thin portion 46 positioned at an end of the lid 14 has a thickness in a thickness direction of the lid 14 smaller than a thickness of a portion which has largest area in the lid 14 in a planar view. The lid 14 has a gap 40 between projection portions of the positive electrode terminal 36 and the negative electrode terminal 37 and the thin portion 46 in region portions outside the positive electrode terminal 36 and the negative electrode terminal 37.

Description

  The present invention relates to a power storage device in which an insulating member is disposed between a lid and a terminal.

  A vehicle such as an EV (Electric Vehicle) or a PHV (Plug in Hybrid Vehicle) is equipped with a secondary battery such as a lithium ion battery as a power storage device that stores power supplied to an electric motor serving as a prime mover. This type of secondary battery is disclosed in Patent Document 1, for example. In the secondary battery disclosed in Patent Document 1, battery elements such as an electrode assembly and an electrolytic solution are accommodated in a case body, and an opening of the case body is closed with a lid. A terminal for transferring electricity to and from the electrode assembly protrudes from the lid.

JP 2010-86776 A

  By the way, an insulating member may be disposed between the terminal of the secondary battery and the lid for the purpose of ensuring the insulation of the terminal. In such a secondary battery, there is a possibility that welding heat generated when the case body and the lid are joined by welding is transmitted to the insulating member via the lid.

  The present invention has been made paying attention to such problems existing in the prior art, and the purpose of the invention is to generate welding heat generated when welding the case body and the lid body between the terminal and the lid body. It is in providing the electrical storage apparatus which can suppress transmitting to the insulation member arrange | positioned between.

  A power storage device that solves the above problem is a power storage device that includes a case that houses an electrode assembly, and the case includes a case main body having an opening and a plate-like lid that closes the opening of the case main body. A terminal for transferring electricity to and from the electrode assembly protrudes from the cover body to the outside of the case, and an insulating member is disposed between the cover body and the terminal. In the power storage device, the lid and the case main body are joined by welding in a state where the surface located inside the case and the end surface of the case wall forming the opening of the case main body are in contact with each other. Of the region outside the terminal of the lid body, the joint portion to be joined to the case body has a thickness direction of the lid body as compared with the thickness of the largest area of the lid body in plan view. The size of is small.

  In addition, a power storage device that solves the above problem is a power storage device including a case that accommodates an electrode assembly, and the case includes a case main body having an opening and a plate-like lid that closes the opening of the case main body. A terminal for transferring electricity to and from the electrode assembly protrudes from the case to the outside of the case, and an insulating member is disposed between the cover and the terminal. In the power storage device, the lid body and the case body are joined by welding in a state where the surface located inside the case and the lid body are in contact with each other among the both surfaces of the case wall forming the opening of the case body. The joint part that joins the case body in the region outside the terminal of the lid body is orthogonal to the thickness direction of the lid body compared to the thickness of the largest area of the lid body in plan view. The size of the direction is small.

  According to each of the above-described configurations, since the joint portion is easily welded by reducing the size of the joint portion, the heat capacity input to the joint portion during welding can be reduced. Therefore, it is possible to make it difficult for the welding heat to be transmitted from the joint portion to the insulating member via the lid.

For example, it is preferable that the lid body has a groove in at least a portion where the distance between the protruding portion of the terminal and the joint portion is the smallest in the region outside the terminal.
According to the said structure, a groove | channel is located in the part where the space | interval of the protrusion part of a terminal in a cover body and a junction part is the smallest, and a heat-transfer path | route can be narrowed in the formation position of the groove | channel in a cover body. Therefore, it is possible to make it difficult for the welding heat to be transmitted from the joint portion to the insulating member via the lid.

For example, the groove is preferably along the joint.
According to the said structure, transmission of the welding heat from a junction part to an insulating member can be suppressed more appropriately.

  For example, in the case where the joining portion is formed by cutting out one of the two surfaces of the lid, the groove is positioned on the other surface of the both surfaces of the lid. Is preferred.

  According to the above configuration, for example, compared to the case where the notch and the groove for forming the joint portion are located on the same surface of both sides of the lid body, heat is transferred from the joint portion in the lid body by the groove. The route to the narrowed portion becomes longer. Accordingly, the welding heat can be made difficult to be transmitted to the insulating member by the length of the path.

  In the above power storage device, a preferable example of the power storage device is a secondary battery.

  ADVANTAGE OF THE INVENTION According to this invention, it can suppress that the welding heat produced at the time of joining by welding with a case main body and a cover body is transmitted to the insulation member arrange | positioned between a terminal and a cover body.

The disassembled perspective view which shows a secondary battery. The perspective view which shows the external appearance of a secondary battery. The exploded perspective view of an electrode assembly. Sectional drawing which shows the cross-section of a secondary battery. The top view of a lid. Sectional drawing which expanded a part of secondary battery. The top view of the cover in another example. The top view of the cover in another example. The top view of the cover in another example. Sectional drawing which shows the cross-section of the secondary battery in another example. Sectional drawing which expanded a part of secondary battery in another example.

Hereinafter, an embodiment embodying a power storage device will be described with reference to FIGS.
As shown in FIG. 1, in a secondary battery 10 as a power storage device, an electrode assembly 12 is accommodated in a case 11. The case 11 includes a bottomed cylindrical case body 13 and a plate-like lid body 14 that closes an opening 13x into which the electrode assembly 12 is inserted into the case body 13. Both the case body 13 and the lid body 14 are made of metal such as aluminum. The secondary battery 10 of this embodiment is a lithium ion battery.

  As shown in FIG. 2, the case body 13 has a bottomed rectangular tube shape, a rectangular flat plate-like bottom wall 13a, and side walls 13b, 13c, 13d as case walls erected from four sides of the bottom wall 13a. , 13e. The bottom wall 13 a faces the lid body 14 that closes the opening 13 x of the case body 13. Of the four sides of the bottom wall 13a, two sides on which the side walls 13c and 13e facing each other are erected are long sides, and two sides on which the side walls 13b and 13d facing each other are erected are short sides. The lid body 14 has a rectangular plate shape, and in a state in which the opening 13x of the case body 13 is closed, the two sides located on the opening end side of the side walls 13c and 13e of the case body 13 are long sides, and the side walls 13b, Two sides located on the opening end side of 13d are short sides. The secondary battery 10 of this embodiment is a prismatic battery whose appearance is square.

  In the secondary battery 10, the case main body 13 and the lid body 14 are joined by welding (for example, laser welding), so that the welded portion W is located on the entire circumference of the case main body 13 and the lid body 14. The welding part W is formed in the edge part which comprises 4 sides of the cover body 14, and the edge part of each side wall 13b-13e which comprises the opening part 13x of the case main body 13. As shown in FIG.

  As shown in FIG. 3, the electrode assembly 12 includes a positive electrode 20 and a negative electrode 24. The positive electrode 20 includes a positive metal foil 21 (for example, an aluminum foil) and a positive electrode active material layer 22 formed by applying a positive electrode active material on both surfaces thereof. The negative electrode 24 has a negative electrode metal foil 25 (for example, copper foil) and a negative electrode active material layer 26 formed by applying a negative electrode active material on both surfaces thereof. The electrode assembly 12 has a layered structure in which a separator 28 is interposed between the positive electrode 20 and the negative electrode 24 to form a layered structure.

  A positive electrode tab 23 made of the positive electrode metal foil 21 is provided so as to protrude from a part of the edge 20 a of the positive electrode 20. A negative electrode tab 27 made of a negative electrode metal foil 25 is provided so as to protrude from a part of the edge 24 a of the negative electrode 24.

  As shown in FIG. 1, the positive electrode tabs 23 are gathered in the range from one end to the other end of the electrode assembly 12 in the stacking direction, and a positive electrode tab group 23 a is provided at the edge of the electrode assembly 12. Yes. Similarly, the negative electrode tabs 27 are also provided at the edge of the electrode assembly 12 in a range from one end to the other end of the electrode assembly 12 in the stacking direction. A positive electrode conductive member 31 made of metal (made of aluminum in the present embodiment) for electrically connecting the electrode assembly 12 and the positive electrode terminal 36 is joined to the positive electrode tab group 23a. A negative electrode conductive member 32 made of metal (copper in this embodiment) for electrically connecting the electrode assembly 12 and the negative electrode terminal 37 is joined to the negative electrode tab group 27a. The positive electrode conductive member 31 and the negative electrode conductive member 32 have a rectangular flat plate shape.

  As shown in FIG. 1, the positive electrode terminal 36 that transmits and receives electricity to and from the electrode assembly 12 includes a pole column portion 36 a and a prism-shaped base portion 36 b provided at an end portion in the axial direction of the pole column portion 36 a. have. By joining the positive electrode conductive member 31 to the base portion 36 b of the positive electrode terminal 36, the positive electrode conductive member 31 and the positive electrode terminal 36 are integrally bonded. Similarly, the negative electrode terminal 37 that transmits and receives electricity to and from the electrode assembly 12 also includes a pole column portion 37a and a prismatic base portion 37b provided at an end portion in the axial direction of the pole column portion 37a. ing. By joining the negative electrode conductive member 32 to the base portion 37 b of the negative electrode terminal 37, the negative electrode conductive member 32 and the negative electrode terminal 37 are integrally bonded.

  As shown in FIG. 4, the secondary battery 10 includes an insulating member 38 that covers the base portion 36 b and the positive electrode conductive member 31 of the positive electrode terminal 36, and the base portion 37 b and the negative electrode conductive member 32 of the negative electrode terminal 37. The insulating member 38 is fitted to the base portions 36b and 37b and the pole column portions 36a and 37a in a state where the surfaces of the positive electrode conductive member 31 and the negative electrode conductive member 32 on the electrode assembly 12 side are covered. Thus, the insulating member 38 is located between the lid body 14 and the positive electrode terminal 36 and the negative electrode terminal 37.

  Further, the pole column part 36 a of the positive electrode terminal 36 and the pole column part 37 a of the negative electrode terminal 37 are exposed so as to protrude from the hole 11 c of the lid body 14 to the outside of the case 11. Ring-shaped insulating members 39 are attached to the pole column portion 36 a of the positive electrode terminal 36 and the pole column portion 37 a of the negative electrode terminal 37, respectively. The insulating member 39 is located between the lid 14 and the positive terminal 36 and the negative terminal 37 to insulate the positive terminal 36 and the negative terminal 37 from the lid 14 of the case 11. An insulating sheet 50 is interposed between the bottom wall 13 a and the side walls 13 b to 13 e of the case body 13 and the electrode assembly 12.

  As shown in FIG. 5, a groove 40 is formed in a region outside the positive electrode terminal 36 and the negative electrode terminal 37 in the lid body 14 of the case 11. The groove 40 of this embodiment is open to the surface 14a located on the outer side of the case 11 out of both surfaces of the lid body 14 of the case 11, and has a rectangular cross section. And the groove | channel 40 is formed in the rectangular ring shape in the surface 14a of the cover body 14 so that the positive electrode terminal 36 and the negative electrode terminal 37 may be enclosed in the cover body 14, respectively. Further, the groove 40 is along the four sides of the lid body 14. That is, the groove 40 is located between the end portions forming the four sides of the lid body 14 and the protruding portions of the positive terminal 36 and the negative terminal 37. In addition, a region portion outside the positive electrode terminal 36 and the negative electrode terminal 37 in the surface 14 a of the lid body 14 is divided by the groove 40.

  As shown in FIG. 6, due to the arrangement of the groove 40, the lid body 14 is positioned inside the case 11 among the bottom of the groove 40 that is a part of the surface 14 a of the lid body 14 and both surfaces of the lid body 14. A thin portion 41 having a thickness smaller than the thickness of the lid body 14 is provided between the back surface 14b and the back surface 14b. In the present embodiment, when the lid body 14 is viewed in a plan view, the thickness of the portion having the largest area is defined as the thickness of the lid body 14. Further, when the thickness of the lid 14 is T1 and the thickness of the thin portion 41 is T2, the thin portion 41 is so small that the size T2 is smaller than 1/3 of the size T1. Is preferably formed.

  In this embodiment, the gap between the projecting portions of the positive electrode terminal 36 and the negative electrode terminal 37 and the short sides of the lid body 14 of the lid body 14 is the same as the projecting portion of the positive electrode terminal 36 and the negative electrode terminal 37 and the lid. It is smaller than the gap between each long side of the body 14. For this reason, in the groove 40, the portion of the groove 40 located between the protruding portion of the positive electrode terminal 36 and the negative electrode terminal 37 on the surface 14 a of the lid body 14 and each short side of the lid body 14 is Among them, the gap between the protruding portions of the positive electrode terminal 36 and the negative electrode terminal 37 and the four sides of the lid body 14 is located in the smallest portion.

  As shown in FIG. 6, the lid 14 of the case 11 is provided with a recess 45 at the end along the four sides of the lid 14. The recess 45 opens to the back surface 14 b of the lid 14 of the case 11 and is recessed toward the front surface 14 a of the lid 14. Further, the recess 45 is formed by cutting out the back surface 14 b of the lid body 14 so as to open at the end surfaces constituting the four sides of the lid body 14. Due to the recesses 45, the lid 14 has a thickness larger than the thickness of the lid 14 between the bottom of the recess 45 that is a part of the back surface 14 b of the lid 14 and the surface 14 a of the lid 14. Small thin portion 46 is provided. Note that when the thickness of the lid 14 is T1 and the thickness of the thin portion 46 is T3, the thin portion 46 is such that the size T3 is smaller than 2/3 of the size T1. Is preferably formed. Further, in the lid body 14, a region between the formation position of the groove 40 and the formation position of the recess 45 is thicker than the thin portions 41 and 46.

Hereinafter, the operation of the present embodiment will be described.
In the secondary battery 10, the electrode assembly 12 is accommodated in the case main body 13 through the opening 13 x of the case main body 13, and then the opening 13 x of the case main body 13 is closed with the lid 14. When closing the opening 13x of the case body 13 with the lid 14, the bottom of the recess 45 of the lid 14 is in contact with the end surfaces of the side walls 13b to 13e forming the opening 13x of the case body 13. A lid 14 is disposed on the case body 13.

  And the cover body 14 is joined to the opening part 13x of the case main body 13 by welding. At this time, by irradiating the thin part 46 of the lid 14 and the end portions of the side walls 13b to 13e forming the opening 13x of the case body 13 from a direction orthogonal to the thickness direction of the lid 14 The case body 13 and the lid body 14 are joined. By such welding, a welded portion W is provided on the entire circumference of the case main body 13 and the lid body 14. The welded portion W joins the side walls 13b to 13e of the case body 13 and the lid body 14, and extends in the longitudinal direction and the short direction of the case 11, respectively. That is, in this embodiment, the thin portion 46 of the lid body 14 and the end portions of the side walls 13b to 13e forming the opening 13x of the case main body 13 function as a joint portion joined by the welded portion W. Yes. Further, the bonding interface between the case body 13 and the lid body 14 includes a bottom portion of the recess 45 on the back surface 14 b of the lid body 14 and end faces of the side walls 13 b to 13 e that form the opening 13 x of the case body 13.

  At the time of welding the case body 13 and the lid body 14, welding heat diffuses from the joining portion to the side walls 13 b to 13 e of the case body 13 and the lid body 14. And in the cover body 14, heat | fever is transmitted toward the center of the cover body 14 from the edge part which comprises the four sides. The heat transmitted to the lid body 14 is transmitted from the end of the lid body 14 toward the positive terminal 36 and the negative terminal 37. Thus, the heat transmitted to the positive terminal 36 and the negative terminal 37 may be transmitted to the insulating members 38 and 39 located between the lid 14 and the positive terminal 36 and the negative terminal 37 via the lid 14. As described above, the gap between the projecting portions of the positive electrode terminal 36 and the negative electrode terminal 37 and the short sides of the lid body 14 of the lid body 14 is such that the projecting portions of the positive electrode terminal 36 and the negative electrode terminal 37 and the lid body. It is smaller than the gap between each of the 14 long sides. That is, in the lid body 14, the heat transfer path from each short side of the lid body 14 to the protruding portion of the positive electrode terminal 36 and the negative electrode terminal 37 is projected from each long side of the lid body 14. Shorter than the heat transfer path to the part. For this reason, the welding heat is easily transmitted to the insulating members 38 and 39 from each short side of the lid body 14.

  However, in this embodiment, the thin part 46 is provided in the edge part along the four sides of the cover body 14. As described above, the thin portion 46 is easily welded because the thickness in the thickness direction of the lid body 14 is smaller than the thickness of the lid body 14. For this reason, the cover 14 and the case main body 13 are compared with the case where the end of the cover 14 where the welded portion W is formed is not the thin portion 46 and has the same thickness as the thickness of the cover 14. The input heat capacity required for the joining with becomes small.

  Further, a groove 40 is provided in a region outside the positive electrode terminal 36 and the negative electrode terminal 37 in the lid body 14 of the case 11. As described above, the thin portion 41 formed in the lid body 14 by the groove 40 has a size in the thickness direction of the lid body 14 smaller than the thickness of the lid body 14. For this reason, the cross-sectional area in the thickness direction of the cover body 14 becomes small in the part in which the groove 40 is formed in the cover body 14. When welding heat is transmitted from the thin portion 46 to the region between the formation position of the groove 40 and the formation position of the recess 45 in the lid body 14, the thickness of this region is the thickness of the lid body 14 in the thin portion 46. By being larger than the size in the vertical direction, the welding heat is once diffused. However, when welding heat is transmitted from this region to the thin portion 41 of the lid body 14, the size of the thin portion 41 in the thickness direction of the lid body 14 is small, so that the heat transfer path of the welding heat is narrowed. .

Therefore, according to the present embodiment, the following effects can be obtained.
(1) Since the thin portion 46 that functions as a joint portion in the thickness direction of the lid body 14 is smaller than the thickness of the lid body 14, the thin portion 46 is easily welded. The heat capacity input to the can be reduced. Therefore, it is possible to make it difficult for welding heat to be transmitted from the thin portion 46 to the insulating members 38 and 39 via the lid body 14.

  (2) The grooves 40 are located along the four sides of the lid body 14 including the short side of the lid body 14 having the smallest gap between the protruding portions of the positive electrode terminal 36 and the negative electrode terminal 37 and the thin portion 46 in the lid body 14. ing. Accordingly, the heat transfer path can be narrowed at the position where the groove 40 is formed in the lid body 14. This also makes it difficult for welding heat to be transmitted from the thin portion 46 to the insulating members 38 and 39 via the lid 14.

  (3) The groove 40 is along the four sides of the lid body 14, that is, along the thin portion 46 of the lid body 14. For this reason, transmission of welding heat from the thin portion 46 to the insulating members 38 and 39 can be more appropriately suppressed.

  (4) Of both surfaces of the lid body 14, the recess 45 that is a notch for forming the thin portion 46 is located on the back surface 14 b of the lid body 14, and the groove 40 is located on the front surface 14 a of the lid body 14. . For this reason, compared with the case where the recessed part 45 and the groove | channel 40 are located in the same surface among both surfaces of the cover body 14, from the thin part 46 in the cover body 14 to the part by which the heat transfer path was narrowed by the groove | channel 40 The route becomes longer. Accordingly, the welding heat can be made difficult to be transmitted to the insulating members 38 and 39 by the length of the path.

(5) The thin portion 46 is provided by the recess 45 provided in the back surface 14 b of the lid body 14. For this reason, the thin part 46 can be provided easily.
(6) The groove 40 has an annular shape that surrounds the area outside the positive electrode terminal 36 and the negative electrode terminal 37 in the lid body 14. Therefore, the heat transfer path can be narrowed over a wide range in the lid 14, and the welding heat can be made difficult to be transmitted by the insulating members 38 and 39.

In addition, you may change each said embodiment as follows.
As shown in FIG. 7, the groove 140 may have a shape that surrounds the positive electrode terminal 36 and the negative electrode terminal 37 in common. The groove 140 is along the three sides of the lid 14 close to the positive terminal 36 in the region outside the positive terminal 36 in the lid 14. Further, the groove 140 is along the three sides of the lid body 14 close to the negative electrode terminal 37 in the region outside the negative electrode terminal 37 in the lid body 14. Such a groove 140 can appropriately suppress the transfer of welding heat from the thin portion 46 adjacent to the positive electrode terminal 36 and the negative electrode terminal 37 to the insulating members 38 and 39.

  As shown in FIG. 8, the groove 240 does not have to be annular. The groove 240 is along the three sides of the lid 14 close to the positive terminal 36 in the region outside the positive terminal 36 in the lid 14. Further, the groove 240 is along the three sides of the lid body 14 close to the negative electrode terminal 37 in the region outside the negative electrode terminal 37 in the lid body 14. Such a groove 240 can also appropriately suppress the transfer of welding heat from the thin portion 46 adjacent to the positive electrode terminal 36 and the negative electrode terminal 37 to the insulating members 38 and 39.

  As shown in FIG. 9, the groove 340 extends along one side of the lid body 14 adjacent to the positive electrode terminal 36 and the negative electrode terminal 37 in the region outside the positive electrode terminal 36 and the negative electrode terminal 37 in the lid body 14. Also good. In the lid body 14 illustrated in FIG. 9, the gaps between the protruding portions of the positive electrode terminal 36 and the negative electrode terminal 37 and the short sides of the lid body 14 are such that the protruding portions of the positive electrode terminal 36 and the negative electrode terminal 37 and the lid body 14 It is smaller than the gap between each long side. For this reason, as described above, the welding heat is easily transmitted from the short sides of the lid body 14 to the insulating members 38 and 39. In FIG. 9, among the regions outside the positive electrode terminal 36 and the negative electrode terminal 37 in the lid body 14, between the protruding portions of the positive electrode terminal 36 and the negative electrode terminal 37 and the short sides of the lid body 14, that is, the positive electrode. The groove 340 is positioned in a portion where the gap between the protruding portion of the terminal 36 and the negative electrode terminal 37 and the thin portion 46 is the smallest. Therefore, it is possible to lengthen the heat transfer path of the portion of the lid body 14 where the welding heat is easily transmitted.

  ○ Depending on the shape of the lid body 14 and the positions of the protruding portions of the positive electrode terminal 36 and the negative electrode terminal 37 on the lid body 14, the gap between the protruding portion of the positive electrode terminal 36 and the negative electrode terminal 37 and the short side of the lid body 14 may be larger. The gap between the protruding portions of the positive electrode terminal 36 and the negative electrode terminal 37 and the long side of the lid body 14 may be small. Also in the lid 14 of such a form, a groove is formed between the protruding portion of the positive terminal 36 and the negative terminal 37 and the long side of the lid 14 in the region outside the positive terminal 36 and the negative terminal 37 in the lid 14. If 340 is positioned, the heat transfer path of the portion of the lid 14 where the welding heat is easily transmitted can be lengthened.

  O When welding the case main body 13 and the lid body 14, the thickness direction of the lid body 14 may be welded as the irradiation direction. In such a form, the welded portion W includes a range from the front surface 14a to the back surface 14b of the lid 14 in the thin portion 46 of the lid 14, the end portions of the side walls 13b to 13e of the case body 13 that are in contact with the thin portion 46, and Will be formed.

  As shown in FIG. 10 and FIG. 11, the case 11 has the case body 13 in a state where the inner surface located inside the case 11 and the lid body 14 are in contact with each other on both sides of the side walls 13 b to 13 e of the case body 13. The opening 13x may be closed by the lid 14. In this embodiment, a concave portion 445 having a rectangular cross section is formed by cutting out a region portion outside the positive electrode terminal 36 and the negative electrode terminal 37 in the surface 14 a of the lid body 14. As shown in FIG. 11, the recess 445 has a rectangular annular shape on the lid body 14 so as to surround the positive electrode terminal 36 and the negative electrode terminal 37 in the lid body 14 like the groove 40 in the embodiment illustrated in FIG. 5. Is formed. By providing the concave portion 445, the end of the lid body 14, which is a portion between the formation position of the concave portion 445 of the lid body 14 and the four sides of the lid body 14, is orthogonal to the thickness direction of the lid body 14. A thin portion 446 having a size smaller than the thickness of the lid 14 is provided. In this modification, when the lid body 14 is viewed in a plan view, the thickness of the portion having the largest area is defined as the thickness of the lid body 14. In addition, when the thickness of the lid 14 is T1, and the size of the thin portion 446 in the direction orthogonal to the thickness direction of the lid 14 is T4, the size T4 is 2/2 of the size T1. It is preferable to form the thin portion 446 so as to be smaller than 3. In addition, a groove 440 having a rectangular cross section is located in a region outside the positive electrode terminal 36 and the negative electrode terminal 37 in the back surface 14 b of the lid body 14. Like the groove 40 in the embodiment illustrated in FIG. 5, the groove 440 is formed in a rectangular ring shape in the lid body 14 so as to surround the positive electrode terminal 36 and the negative electrode terminal 37 in the lid body 14. The groove 440 extends along the four sides of the lid body 14 and is located between the thin portion 446 of the lid body 14 and the protruding portions of the positive electrode terminal 36 and the negative electrode terminal 37. Due to the arrangement of the groove 440, the lid 14 has a thickness larger than the thickness of the lid 14 between the bottom of the groove 440 that is a part of the back surface 14 b of the lid 14 and the surface 14 a of the lid 14. A small thin portion 441 is provided. The groove 440 is preferably formed so that the bottom of the groove 440 is located closer to the surface 14 a of the lid 14 than the bottom of the recess 445 of the lid 14. When the case body 13 and the lid body 14 are welded, the thickness direction of the lid body 14 is welded as an irradiation direction. By such welding, a welded portion W is provided on the entire circumference of the case main body 13 and the lid body 14. In this modification, the thin portion 446 of the lid body 14 and the end portions of the side walls 13b to 13e that form the opening portion 13x of the case main body 13 function as a joint portion joined by the welded portion W. . Further, the joining interface between the case body 13 and the lid body 14 includes an end surface of the lid body 14 that forms the thin portion 446 and inner surfaces of the side walls 13b to 13e that form the opening 13x of the case body 13. In such a modification, a thin portion 446 is provided at an end portion along the four sides of the lid body 14. As described above, the thin portion 446 is easily welded because the size in the direction orthogonal to the thickness direction of the lid body 14 is smaller than the thickness of the lid body 14. For this reason, the cover 14 and the case main body 13 are compared with the case where the end of the cover 14 where the welded portion W is formed is not the thin portion 446 and has the same thickness as the cover 14. The input heat capacity required for the joining with becomes small. Further, in the lid body 14 of the case 11, a groove 440 is provided in a region outside the positive electrode terminal 36 and the negative electrode terminal 37. As described above, the thin portion 441 formed in the lid body 14 by the groove 440 has a size in the thickness direction of the lid body 14 smaller than the thickness of the lid body 14. For this reason, the cross-sectional area in the thickness direction of the cover body 14 becomes small in the part in the cover body 14 where the groove 440 is formed. Thereby, when joining the case main body 13 and the cover body 14, the heat transfer path of welding heat becomes narrow. Therefore, this modification can also provide the same effects as those obtained in the above embodiment.

  The concave portion 445 illustrated in FIG. 10 is limited to a region in which the entire outer periphery of the positive electrode terminal 36 and the negative electrode terminal 37 is arranged in the region outside the positive electrode terminal 36 and the negative electrode terminal 37 in the lid body 14. Absent. For example, the arrangement range of the recesses 445 in the lid body 14 can be changed like the arrangement range of the groove 140 in the lid body 14 illustrated in FIG. 7 and the groove 240 in the lid body 14 illustrated in FIG.

In the modification illustrated in FIG. 10, the recess 445 may have a shape other than a rectangular cross section such as a U-shaped cross section.
The grooves 40, 140, 240, 340, 440 may be arranged in the lid body 14 in a larger number than the number illustrated in FIGS. 5 and 7 to 10.

  The grooves 40, 140, 240, and 340 illustrated in FIGS. 5 and 7 to 9 may be provided on the back surface 14 b of the lid body 14. The grooves 40, 140, 240, 340 on the back surface 14 b of the lid body 14 may be provided together with the grooves 40, 140, 240, 340 on the surface 14 a of the lid body 14, or on the surface 14 a of the lid body 14. The grooves 40, 140, 240, and 340 may be provided instead.

  The groove 440 illustrated in FIG. 10 may be provided on the surface 14 a of the lid body 14. The groove 440 on the front surface 14 a of the lid body 14 may be provided together with the groove 440 on the back surface 14 b of the lid body 14, or may be provided in place of the groove 440 on the back surface 14 b of the lid body 14.

The grooves 40, 140, 240, 340, 440 may be provided only in a region outside the positive electrode terminal 36 or the negative electrode terminal 37 in the lid body 14.
The grooves 40, 140, 240, 340, 440 may not be along the short side or the long side of the lid body 14. That is, it does not have to be along the thin portions 46 and 446 that function as joint portions in the lid body 14. The grooves 40, 140, 240, 340, and 440 having such a form have a shape that extends in a direction different from the direction along the short side or the long side of the lid body 14.

The grooves 40, 140, 240, 340, 440 may have a shape outside the rectangular section, such as a U-shaped section.
O Formation of the grooves 40, 140, 240, 340, 440 in the lid 14 may be omitted.

○ The appearance of the case 11 may be changed. For example, the case 11 may have a rectangular shape, a rectangular parallelepiped shape, a cubic shape, or a cylindrical shape.
The electrode assembly 12 is not limited to the laminated type, and may be a wound type in which a belt-like positive electrode and a belt-like negative electrode are wound and laminated in layers.

  The secondary battery 10 is a lithium ion secondary battery, but is not limited thereto, and may be another secondary battery. In short, any ion may be used as long as ions move between the positive electrode active material layer and the negative electrode active material layer and transfer charge. Further, a capacitor may be used as the power storage device.

  (Circle) the secondary battery 10 may be mounted in a motor vehicle as a vehicle power supply device, and may be mounted in an industrial vehicle. Further, the present invention may be applied to a stationary power storage device.

  DESCRIPTION OF SYMBOLS 10 ... Secondary battery, 11 ... Case, 12 ... Electrode assembly, 13 ... Case main body, 13a ... Bottom wall, 13b-13e ... Side wall, 13x ... Opening, 14 ... Cover, 14a ... Front surface, 14b ... Back surface, 36 ... Positive electrode terminal, 37 ... Negative electrode terminal, 38, 39 ... Insulating member, 40, 140, 240, 340, 440 ... Groove, 45, 445 ... Recess, 46, 446 ... Thin part, W ... Welded part.

Claims (6)

A power storage device including a case for accommodating an electrode assembly,
The case is composed of a case body having an opening and a plate-like lid that closes the opening of the case body.
A terminal for transferring electricity to and from the electrode assembly protrudes from the case out of the case;
An insulating member is disposed between the lid and the terminal,
The lid and the case main body are joined by welding in a state in which a surface located on the inner side of the case out of both surfaces of the lid and an end surface of the case wall forming the opening of the case main body are in contact with each other. Has been
Of the region outside the terminal in the lid body, the joint portion to be joined to the case main body has a thickness of the lid body compared to the thickness of the largest area of the lid body in plan view. A power storage device having a small size in a direction. A power storage device including a case for accommodating an electrode assembly,
The case is composed of a case body having an opening and a plate-like lid that closes the opening of the case body.
A terminal for transferring electricity to and from the electrode assembly protrudes from the case out of the case;
An insulating member is disposed between the lid and the terminal,
The lid body and the case body are joined by welding in a state in which the surface located inside the case and the lid body are in contact with each other among both surfaces of the case wall forming the opening of the case body. And
Of the region outside the terminal in the lid body, the joint portion to be joined to the case main body has a thickness of the lid body compared to the thickness of the largest area of the lid body in plan view. A power storage device having a small size in a direction orthogonal to the direction.   3. The power storage device according to claim 1, wherein the lid has a groove in at least a portion where a distance between the protruding portion of the terminal and the joint portion is the smallest among the region portions outside the terminal.   The power storage device according to claim 3, wherein the groove is along the joint. The joint is formed by cutting out one of the two surfaces of the lid,
The power storage device according to claim 3 or 4, wherein the groove is located on one of the two surfaces of the lid.   The power storage device according to any one of claims 1 to 5, wherein the power storage device is a secondary battery.