JP6047676B2 - Prismatic secondary battery - Google Patents

Description

  The present invention relates to a prismatic secondary battery used for in-vehicle applications, for example.

  In recent years, lithium ion secondary batteries with high energy density have been developed as power sources for electric vehicles and the like. In a secondary battery for in-vehicle use, since a large current flows as compared with that for a mobile phone or the like, it is important to prevent moisture from being mixed in or leakage of an electrolytic solution, and sealing is an issue. For example, Patent Document 1 discloses a structure in which a wound group is accommodated in a battery can and an electrolyte is injected, and then a lid is welded to the battery can to seal the battery casing. Patent Document 2 discloses a structure in which a convex portion is provided on the back surface of a lid in a square secondary battery.

JP 2010-97770 JP 2004-31027 A

  In patent document 1, in order to seal a battery housing | casing, the battery can and the battery cover are joined by welding. Although joining by welding improves reliability, there is a possibility that spatter generated during welding may enter the inside of the battery as a metal foreign substance and cause a short circuit.

  An object of the present invention is to provide a highly reliable prismatic secondary battery by preventing metal foreign matter from being mixed into a battery by sputtering when welding a battery lid to a metal battery can.

  The prismatic secondary battery of the present invention that solves the above problems includes a power storage unit, a battery container that houses the power storage unit and has an opening, a cover that closes the opening of the battery container and is welded to the battery container. In the secondary battery according to the aspect of the invention, the lid includes a closed portion that faces the opening, a convex portion provided on the outer peripheral end side of the lid with respect to the closed portion, and an outer peripheral end side of the convex portion. A contact portion that contacts the battery container, the side wall of the battery container has a stepped portion on the opening side, the contact portion contacts the stepped portion, and is adjacent to the stepped portion. The protrusions are arranged.

  ADVANTAGE OF THE INVENTION According to this invention, when welding a battery cover to a battery can, mixing of the metal foreign material into the battery by sputtering can be prevented, and a highly reliable square secondary battery can be provided. Problems, configurations, and effects other than those described above will be clarified by the following description of the embodiments.

1 is an external perspective view of a prismatic secondary battery according to a first embodiment. The disassembled perspective view of the square secondary battery concerning 1st Embodiment. The disassembled perspective view which shows the state which expand | deployed some electric power generation bodies. The perspective view which looked at the lid concerning a 1st embodiment from the undersurface side. The top view which shows the lower surface of the lid | cover concerning 1st Embodiment. Sectional drawing which shows the junction part of the battery can and cover concerning 1st Embodiment. Sectional drawing which shows the decomposition | disassembly state of FIG. Sectional drawing which shows the junction part of the battery can and cover concerning 2nd Embodiment. Sectional drawing which shows the decomposition | disassembly state of FIG. The figure explaining a prior art example. The figure explaining another prior art example.

  Next, embodiments of the present invention will be described in detail below with reference to the drawings.

  The prismatic secondary battery according to the present embodiment has a rectangular bottom wall, a rectangular tubular side wall rising from the bottom wall, and an opening opened upward at the upper end of the side wall. And a battery lid that is welded to the upper end of the side wall of the battery can and seals the opening. The battery lid protrudes into the battery can and protrudes into the side of the battery can. A contact portion lid that has a convex portion that faces the inner surface of the battery can and continues along the circumferential direction of the side wall portion over the entire circumference, and that contacts the upper end of the side wall portion of the battery can outside the convex portion. It is characterized in that the thickness is thicker than half of the lid thickness of the closing portion that closes the opening inside the convex portion and thinner than the lid thickness of the closing portion.

[First Embodiment]
FIG. 1 is an external perspective view of a prismatic secondary battery according to the present embodiment.

  The square secondary battery C <b> 1 includes a battery can 1 and a lid (battery lid) 6. In the battery can 1, a power generator 3 (see FIG. 2) is housed, and the opening 1 a of the battery can 1 is sealed with a lid 6. The lid 6 is joined to the battery can 1 by laser welding to constitute a battery container sealed by the battery can 1 and the lid 6. The lid 6 is provided with a positive external terminal 8A and a negative external terminal 8B. The power generator 3 (see FIG. 2) is charged via the positive external terminal 8A and the negative external terminal 8B, and power is supplied to the external load. The lid 6 is integrally provided with a gas discharge valve 10, and when the pressure in the battery container rises, the gas discharge valve 10 opens to discharge gas from the inside, and the pressure in the battery container is reduced. Thereby, the safety of the square secondary battery C1 is ensured.

  Next, with reference to FIG. 2, the structure in the battery can 1 of the square secondary battery C1 will be described.

  FIG. 2 is an exploded perspective view of the prismatic secondary battery according to the present embodiment.

  The battery can 1 of the prismatic secondary battery C1 has a so-called square shape, and is open upward at the rectangular bottom wall portion 22, the rectangular tubular side wall portion 21 rising from the bottom wall portion 22, and the upper end of the side wall portion 21. Opening 1a. A power generator 3 is accommodated in the battery can 1 via an insulating sheet 2. The power generation body 3 is an electrode group in which a positive electrode body and a negative electrode body are wound in a flat shape with a separator interposed therebetween, and an electrode to which a positive electrode mixture and a negative electrode mixture are not applied on both end surfaces in the winding axis direction. Foil exposed portions 31c and 32c are provided.

  Since the power generating body 3 is wound in a flat shape, it has a pair of curved portions facing each other in a semicircular cross section, and a plane portion formed continuously between the pair of curved portions. Yes. The power generator 3 is inserted into the battery can 1 from one curved portion side so that the winding axis direction is along the lateral width direction of the battery can 1, and the other curved portion side is disposed on the upper opening side.

  At least a part of the positive electrode connecting portion 31d and the negative electrode connecting portion 32d, which are the flat portions of the power generator 3 and the electrode foil exposed portions, are bundled into a flat plate shape, and each has a positive electrode current collector plate (current collector terminal) 4A. And one end of the negative electrode current collector plate (current collector terminal) 4B are overlapped and connected.

  The other end of the positive electrode current collector plate 4A and the other end of the negative electrode current collector plate 4B are connected to the positive electrode external terminal 8A and the negative electrode external terminal 8B, respectively. The positive current collector plate 4A is provided with a current interrupting means (fuse) 44 for interrupting the current when an excessive current flows. For example, the current interrupting means 44 is provided with a portion having a narrow width in a part of the positive electrode current collector plate 4A, and the portion is melted by an excessive current so that the positive electrode current collector plate 4A is connected to the power generator 3 side and the positive electrode external terminal 8A side. It has the structure separated into. In this embodiment, the current interrupting means 44 is provided on the positive current collector 4A, but may be provided on the negative current collector 4B, or provided on both the positive current collector 4A and the negative current collector 4B. May be. Further, the current interrupting means 44 may be any configuration as long as it interrupts the current in the event of an abnormality, and is not limited to the above configuration.

  In order to electrically insulate the positive electrode collector plate 4A and the negative electrode collector plate 4B, and the positive electrode external terminal 8A and the negative electrode external terminal 8B from the lid 6, a gasket 5 and an insulating plate 7 are provided on the lid 6, respectively. Yes. Moreover, after pouring electrolyte solution into the battery can 1 from the liquid injection port 9, the liquid injection stopper 11 is joined to the cover 6 by laser welding, the liquid injection port 9 is sealed, and the square secondary battery C1 is sealed. .

  As the material for the battery can 1 and the lid 6, aluminum or aluminum alloy, which is a metal material, is used. Aluminum or an aluminum alloy is used as a material for the positive electrode current collector plate 4A and the positive electrode external terminal 8A. Copper or copper alloy is used as a material for the negative electrode current collector plate 4B and the negative electrode external terminal 8B.

  The positive external terminal 8A and the negative external terminal 8B have weld joints that are welded to a bus bar or the like (not shown). The welded joint has a rectangular parallelepiped block shape protruding upward from the lid 6, and has a configuration in which the lower surface faces the surface of the lid 6 and the upper surface is parallel to the lid 6 at a predetermined height position. Yes.

  A positive electrode connection portion 12A for connecting the positive electrode external terminal 8A and the positive electrode current collector plate 4A is integrally provided on the lower surface of the weld joint portion of the positive electrode external terminal 8A. A negative electrode connection portion 12B for connecting the negative electrode external terminal 8B and the negative electrode current collector plate 4B is integrally provided on the lower surface of the weld joint portion of the negative electrode external terminal 8B.

  The positive electrode connecting portion 12A and the negative electrode connecting portion 12B have cylindrical shapes that protrude from the lower surfaces of the positive electrode external terminal 8A and the negative electrode external terminal 8B, respectively, and can be inserted into the through holes 6A and 6B of the lid 6, respectively. The positive electrode connecting portion 12A and the negative electrode connecting portion 12B penetrate through the lid 6 and protrude toward the inner side of the battery can 1 from the base portions 41A and 41B of the positive electrode current collector plate 4A and the negative electrode current collector plate 4B, and their tips are caulked. The positive electrode external terminal 8A, the negative electrode external terminal 8B, the positive electrode current collector plate 4A, and the negative electrode current collector plate 4B are integrally fixed to the lid 6. A gasket 5 is interposed between the positive electrode external terminal 8A and the negative electrode external terminal 8B and the lid 6, and an insulating plate 7 is interposed between the positive electrode current collector plate 4A, the negative electrode current collector plate 4B and the lid 6. Intervened.

  The positive electrode current collector plate 4A and the negative electrode current collector plate 4B are bent at the rectangular plate-like base portions 41A and 41B disposed opposite to the lower surface of the lid 6 and the side edges of the base portions 41A and 41B. The connection end portions 42A and 42B are extended toward the bottom surface side along the wide surface of the power generation body 3 and connected in a state of being overlapped with the positive electrode connection portion 31d and the negative electrode connection portion 32d of the power generator 3. . Opening holes 43A and 43B through which the positive electrode connecting portion 12A and the negative electrode connecting portion 12B are inserted are formed in the base portions 41A and 41B, respectively.

  FIG. 3 is an exploded perspective view showing a state in which a part of the power generator is developed.

  The power generation body 3 is an electrode group in which a positive electrode body 31 and a negative electrode body 32 are wound in a flat shape via a separator 33. The positive electrode body 31 is obtained by applying a positive electrode mixture 31b on both surfaces of a positive electrode foil 31a, and has an uncoated positive electrode foil exposed portion 31c on one side in the width direction of the positive electrode foil 31a.

  The negative electrode body 32 is obtained by applying a negative electrode mixture 32b on both surfaces of a negative electrode foil 32a, and has an uncoated negative electrode foil exposed portion 32c on the other side in the width direction of the negative electrode foil 32a. The positive electrode foil exposed portion 31c and the negative electrode foil exposed portion 32c are wound so as to be positioned on opposite sides in the winding axis direction.

  FIG. 4 is a perspective view of the lid as viewed from the lower surface side (inside the secondary battery), and FIG. 5 is a plan view showing the lower surface of the lid (inside the secondary battery).

  The lid 6 has a flat plate shape that is large enough to close the opening 1 a of the battery can 1. In the lid 6, through holes 6 </ b> A and 6 </ b> B, a liquid injection port 9, and a gas discharge valve 10 are arranged. The lid 6 has a closed portion 54 that expands so as to close the opening 1a with a substantially constant lid thickness, and has a cover thickness that is thinner than the closed portion 54 on the outer side of the closed portion 54 and around the outer peripheral end of the lid 6. And a contact portion 52 that extends over and contacts the end portion (upper end) of the side wall portion 21 of the battery can 1.

  And the convex part 51 which protrudes in the battery can 1 inside the contact part 52, opposes the inner surface of the side wall part 21 of the battery can 1, and continues over the perimeter along the circumferential direction of the side wall part 21 is provided. Is provided. Further, a groove 53 is provided inside the convex portion 51. The groove 53 is recessed in the closing portion 54.

  FIG. 6 is a cross-sectional view showing a joint portion between the battery can and the lid, and FIG. 7 is a cross-sectional view showing an exploded state of FIG.

  The abutting portion 52 of the lid 6 is laser-welded from the side (the left side in the drawing) outside the battery can 1 while being in contact with the end of the side wall portion 21 of the battery can 1. A welded portion 61 is formed between the contact portion 52 and the end portion of the side wall portion 21 of the battery can 1 and joined to each other. The welded portion 61 is continuously formed on the outer peripheral end of the lid 6 over the entire periphery, and seals the opening of the battery can 1.

  The convex portion 51 faces the inner surface of the side wall portion 21 of the battery can 1. At this time, the dimensional tolerance of the convex part 51 is set smaller than the inner dimension of the side wall part 21 of the battery can 1 so that the convex part 51 fits comfortably inside the side wall part 21 of the battery can 1. A gap may be formed between the convex portion 51 and the side wall portion 21 of the battery can 1.

  The contact part 52, the convex part 51, and the groove | channel 53 covering the perimeter of the lid | cover 6 can be easily shape | molded by press work. The convex portion 51 can be formed using a surplus thickness generated when the contact portion 52 and the groove 53 having a lid thickness thinner than that of the closing portion 54 are formed. The convex portion 51 is formed such that the height protruding from the contact portion 52 into the battery can 1 is a predetermined height L. Thereby, the length distance which the edge part of the side wall part 21 of the battery can 1 and the lid | cover 6 oppose can be lengthened only the height L.

  FIG. 10 is a diagram for explaining a comparative example for explaining the operational effects of the present embodiment, and corresponds to FIG.

  The prismatic secondary battery of the comparative example shown in FIG. 10 has a flat plate shape in which the lid 106 has a constant thickness Tc. Then, the contact portion 152 of the lid 106 is placed on the end portion of the side wall portion 121 of the battery can 101, and the side wall portion 121 and the contact portion 152 are laser-welded from the side. The spatter S of laser welding may pass between the end portion of the side wall portion 121 and the contact portion 152 of the lid 106 and fall into the battery can 1.

  In particular, when the distal end depth of the welded portion 161 is increased and sealing is to be performed more reliably, the end portion of the side wall portion 121 and the contact portion of the lid 6 are increased as the distal end depth of the welded portion 161 is increased. The distance H between the gaps 152 becomes shorter, and the sputter S easily enters the battery can 1.

  On the other hand, in the present embodiment, as shown in FIG. 6, the convex portion 51 is provided on the lid 6, and the length distance of the gap formed between the end portion of the side wall portion 21 of the battery can 1 is set. The length of the convex portion 51 is secured longer. Therefore, when the end portion of the side wall portion 21 and the contact portion 52 of the lid 6 are joined by laser welding from the outside of the battery can 1, the spatter is opposed to the inner wall surface 21 a or the convex portion 51 of the side wall portion 21. It is possible to positively adhere to the surface 51a and stay between the side wall portion 21 and the convex portion 51. Therefore, it is possible to effectively prevent the spatter from passing through the gap between the end portion of the side wall portion 21 and the contact portion 52 of the lid 6 and falling into the battery can 1.

  In the case of laser welding, when the distal end depth of the welded portion 61 is increased, the weld width on the proximal end side is also increased accordingly. Therefore, in order to weld more deeply and securely seal, the contact portion 52 needs to have a predetermined lid thickness. In the present embodiment, the lid thickness Tu of the contact portion 52 is set to a thickness that is thicker than half the lid thickness Tt of the closing portion 54 and thinner than the lid thickness Tt of the closing portion 54 ( Tt> Tu> (Tt / 2)), the welding allowance of the welded portion 61 is ensured as wide as possible, and the depth of the welded portion 61 can be increased.

  And when the depth of the welded portion 61 is increased, the length distance H of the gap between the end portion of the side wall portion 21 and the contact portion 52 of the lid 6 is shortened instead. A convex portion 51 is provided on the lid 6, and the length distance of the gap formed between the end portion of the side wall portion 21 of the battery can 1 is secured longer by the height L of the convex portion 51. Therefore, it is possible to effectively prevent the spatter from passing through the gap between the end portion of the side wall portion 21 and the contact portion 52 of the lid 6 and falling into the battery can 1. As described above, when the lid 6 is welded by laser from the outside of the battery can 1, it is possible to prevent metal foreign matter from being mixed into the battery can 1 due to sputtering and to provide a highly reliable square secondary battery C <b> 1. .

  In the above-described embodiment, the case where the groove 53 is provided inside the convex portion 51 has been described as an example. However, the present invention is not limited to this, and it is only necessary that the convex portion 51 can be formed at a predetermined height. Is not required.

[Second Embodiment]
Next, a second embodiment will be described below with reference to FIGS. 8, 9, and 11. FIG.

  FIG. 8 is a cross-sectional view showing a joint portion between the battery can and the lid, and FIG. 9 is a cross-sectional view showing an exploded state of FIG. The same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  What is characteristic in this embodiment is that a step 23 is provided at the end of the side wall portion 21 of the battery can 1 so that the battery lid 6 is fitted inside the side wall portion 21 of the battery can 1. In other words, the battery can 1 is sealed by laser welding from the upper side of the battery can 1 to the side wall 21 of the first battery.

  A step 23 is provided at the end of the side wall 21 of the battery can 1. The step 23 is continuously provided on the inner side of the end portion of the side wall portion 21 in a circumferential shape. The contact portion 52 of the lid 6 is in contact with the step 23, and the end portion of the side wall portion 21 and the contact portion 52 of the lid 6 are welded by laser welding from above, which is outside the battery can 1. The Thereby, the welding part 62 is formed between the edge parts of the side wall part 21 of the battery can 1. The welded portion 62 is continuously formed along the entire periphery of the lid 6 and seals the opening of the battery can 1.

  The convex portion 51 is opposed to the inner side of the side wall portion 21 of the battery can 1 over the entire circumference. At this time, the dimensional tolerance of the convex part 51 is set smaller than the inner dimension of the side wall part 21 of the battery can 1 so that the convex part 51 fits comfortably inside the side wall part 21 of the battery can 1. A gap may be formed between the convex portion 51 and the side wall portion 21 of the battery can 1.

  FIG. 11 is a diagram for explaining a comparative example for explaining the operational effects of the present embodiment, and corresponds to FIG.

  The prismatic secondary battery of the comparative example shown in FIG. 11 has a flat plate shape in which the lid 106 has a constant thickness Tc. Then, the contact part 152 of the lid 106 is placed on the step 123 at the end of the side wall part 121, and the side wall part 121 and the contact part 152 are joined by laser welding from above the cover 106. . Therefore, the length distance at which the side wall 121 and the contact part 152 face each other is short, and the laser welding spatter S passes between the step 123 of the side wall part 121 and the contact part 152 of the lid 106, thereby There is a risk of falling into the can 1.

  In laser welding, if the distal end depth of the welded portion 162 is increased, the weld width on the proximal end side is also increased accordingly. Therefore, it is desirable to arrange the welded part 162 at a position on the inner side (right side in the drawing) of the battery can 1 as much as possible. Therefore, the step 123 needs to reduce the amount of depression Ts from the inner surface of the side wall 121. Therefore, the length distance of the gap between the end portion of the side wall portion 121 and the contact portion 152 of the lid 6 is shortened, and the sputter S easily enters the battery can 1.

  On the other hand, in this embodiment, as shown in FIG. 8, the convex portion 51 is provided on the lid 6, and the length distance of the gap formed between the end portion of the side wall portion 21 of the battery can 1 is set. The length of the convex portion 51 is secured longer. Therefore, when laser welding is performed from the outside of the battery can 1 between the end portion of the side wall portion 21 and the contact portion 52 of the lid 6, spatter is actively attached to the side wall portion 21 or the convex portion 51. 21 and the convex portion 51. Therefore, it is possible to effectively prevent the spatter from passing through the gap between the end portion of the side wall portion 21 and the contact portion 52 of the lid 6 and falling into the battery can 1.

  As described above, when the lid 6 is welded by laser from the outside of the battery can 1, it is possible to prevent metal foreign matter from being mixed into the battery due to sputtering, and to provide a highly reliable square secondary battery C <b> 1.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various designs can be made without departing from the spirit of the present invention described in the claims. It can be changed. For example, the above-described embodiment has been described in detail for easy understanding of the present invention, and is not necessarily limited to one having all the configurations described. Further, a part of the configuration of an embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of an embodiment. Furthermore, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

1 Battery Can 1a Opening 3 Power Generator (Electrode Group)
4A Positive current collector (current collector terminal)
4B Negative electrode current collector plate 6 Lid (battery lid)
8A Positive external terminal (external terminal)
8B Negative electrode external terminal 12A Positive electrode connection part 12B Negative electrode connection part 21 Side wall part 22 Bottom wall part 51 Projection part 52 Contact part 53 Groove 54 Closure part 61, 62 Welding part C1 Rectangular secondary battery

Claims (2)

A power storage unit;
A battery container containing the power storage unit and having an opening;
In the secondary battery having a lid that closes the opening of the battery container and is welded to the battery container,
The lid includes a closed portion facing the opening, a convex portion provided on the outer peripheral end side of the lid with respect to the closed portion, and an outer peripheral end portion side of the convex portion. An abutting portion that contacts,
The side wall of the battery container has a step on the opening side,
The secondary battery according to claim 1, wherein the contact portion is in contact with the step portion, and the convex portion is disposed adjacent to the step portion. The secondary battery according to claim 1,
The secondary battery is characterized in that the convex portion is provided corresponding to a portion of the battery lid to be welded to the battery container.

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