JP6108545B2 - Square secondary battery and battery pack - Google Patents

Description

  The present invention relates to a prismatic secondary battery and an assembled battery, and more particularly, a prismatic secondary battery in which a joining member such as a bus bar is joined to positive and negative external terminals, and a set including a plurality of prismatic secondary batteries. It relates to batteries.

Secondary batteries such as lithium-ion batteries and nickel-metal hydride batteries with high energy density are used as power source batteries for vehicles such as electric vehicles. Since the secondary battery is required to have a high output voltage and a large electric power, it is connected in series by a joining member such as a bus bar to form an assembled battery.
As for the connection by the bus bar, joining by a welding method such as a laser is usually used as a method suitable for ensuring sufficient connection strength and reducing the contact resistance.

  As a junction between the prismatic secondary battery and the bus bar, a small protrusion is provided on the upper surface of the positive and negative external terminals of the prismatic secondary battery, a through hole is provided in the bus bar, and the small protrusion is fitted. There is known a structure in which a part is bonded by irradiating a laser (see, for example, Patent Document 1). This Patent Document 1 describes that positive and negative external terminals are formed by forging or cutting. If it forms by forging, productivity can be improved rather than forming by cutting.

JP 2012-248451 A

  When the size of the square secondary battery is reduced and the areas of the positive and negative external terminals are reduced, the structure described in Patent Document 1 has insufficient bonding force because the area of the boundary between the bus bar and the small protrusion is small. When the positive and negative external terminals are formed by forging, the bus bar is lifted from the upper surface of the positive and negative external terminals by the flash generated at the peripheral edge of the upper surface of the positive and negative external terminals, and the bonding force is further increased. There may be a shortage.

The prismatic secondary battery of the present invention has a positive electrode external terminal connected to the positive electrode and a negative electrode connected to one side surface of a battery container containing a power generation element having a positive electrode and a negative electrode. A negative electrode external terminal, and a plate-like bus bar is placed on the positive electrode external terminal and the negative electrode external terminal so as to face the outer peripheral side surfaces of the positive electrode external terminal and the negative electrode external terminal, respectively, and the positive electrode A prismatic secondary battery welded to the upper surface of each of the external terminal and the negative electrode external terminal, wherein each of the positive electrode external terminal and the negative electrode external terminal has an upper surface and a peripheral side surface, and the upper surface is at a central portion. A flat surface and an inclined surface that is formed at a peripheral edge of the flat surface and gradually inclines toward the lower surface. The depth of the inclined surface from the flat surface is such that the inclined surface reaches the peripheral side surface. 0. A 8Mm～0.2Mm, wherein each of the positive electrode external terminal and the negative electrode external terminal, having the burr height which does not reach a flat surface on the periphery of the top surface.
The assembled battery of the present invention includes a plurality of the rectangular secondary batteries and a bus bar connecting the positive external terminal and the negative external terminal of the adjacent square secondary battery, and the bus bar includes the The positive electrode external terminal and the negative electrode external terminal are placed on the positive electrode external terminal and the negative electrode external terminal so as to face the outer peripheral side surfaces of each of the positive electrode external terminal and the negative electrode external terminal. The other end of the bus bar and the negative electrode external terminal are bonded to each other at a melting portion that penetrates in the direction, exceeds the boundary between the bus bar and the upper surface of the positive electrode external terminal, and reaches the inside of the positive electrode external terminal. It penetrates the bus bar in the thickness direction, and is joined at a melted portion that reaches the inside of the negative electrode external terminal beyond the boundary between the bus bar and the upper surface of the negative electrode external terminal.

  According to the present invention, since the inclined surface of 0.08 mm to 0.2 mm is provided at the position where the depth from the flat surface reaches the peripheral side surface, burr is generated at the peripheral portion of the upper surface of the positive / negative external terminal. Even in this case, the positive and negative external terminals and the bus bar can be bonded with sufficient bonding strength.

1 is an external perspective view of an embodiment of a prismatic secondary battery according to the present invention. FIG. 2 is an exploded perspective view of the prismatic secondary battery shown in FIG. 1. The perspective view of the state which expand | deployed the winding termination | terminus part side of the electric power generation element accommodated in the square secondary battery. (A)-(d) is typical sectional drawing which shows the method of producing a positive / negative electrode external terminal by forging. The characteristic view which shows the relationship between the clearance gap between an external terminal material and a forge metal mold | die, and welding strength. The expanded sectional view of the upper surface peripheral part of a positive / negative electrode external terminal. Distribution chart of beam height. It is a figure for demonstrating one Embodiment of the assembled battery of this invention, (a) is a top view of an assembled battery, (b) is the VIIIb-VIIIb sectional view taken on the line in (a).

[Overall structure of prismatic secondary battery]
Hereinafter, an embodiment of a prismatic secondary battery and an assembled battery according to the present invention will be described with reference to the drawings.
FIG. 1 is an external perspective view of an embodiment of a prismatic secondary battery according to the present invention, and FIG. 2 is an exploded perspective view of the prismatic secondary battery shown in FIG.
In the following description, the square secondary battery is described as a lithium ion battery.
The square secondary battery C <b> 1 includes a battery can 1 and a battery lid 6. As a material of the battery can 1 and the battery lid 6, an aluminum-based metal such as aluminum or an aluminum alloy is used. The battery can 1 includes a rectangular bottom wall portion 22, a rectangular tubular side wall portion 21 rising from the bottom wall portion 22, and an opening 1 a (see FIG. 2) opened upward at the upper end of the side wall portion 21. have. The side wall part 21 has a pair of wide area part 21a and a pair of narrow area part 21b. In the battery can 1, a power generation element 40 (see FIG. 3) is housed, and the opening 1 a of the battery can 1 is sealed by the battery lid 6.

The battery lid 6 is joined at its peripheral edge to the peripheral edge of the opening 1 a of the battery can 1 by laser welding. A sealed battery container 10 is constituted by the battery can 1 and the battery lid 6. The battery lid 6 is provided with a positive external terminal 8A and a negative external terminal 8B.
The positive external terminal 8A and the negative external terminal 8B are formed by forging, and the formation method will be described later.
The power generation element 40 (see FIG. 3) is charged via the positive external terminal 8A and the negative external terminal 8B, and power is supplied to the external load. The battery cover 6 is integrally provided with a gas discharge valve 12. When the pressure in the battery container 10 rises, the gas discharge valve 12 opens to discharge gas from the inside, and the pressure in the battery container 10 is reduced. The Thereby, the safety of the square secondary battery C1 is ensured.

  The battery lid 6 is provided with an injection stopper 11 adjacent to the gas discharge valve 12. The power generation element 40 is housed in the battery container 10, the opening 1 a of the battery container 10 is sealed with the battery lid 6, and the nonaqueous electrolyte is injected into the battery container 10 from the liquid injection port 9 provided in the battery lid 6. After that, the liquid injection port 9 is sealed with a liquid injection stopper 11.

  As the non-aqueous electrolyte, for example, lithium hexafluorophosphate (LiPF6) was dissolved at a concentration of 1 mol / liter in a mixed solution in which ethylene carbonate and dimethyl carbonate were mixed at a volume ratio of 1: 2. Things can be used. The above is an example, and a non-aqueous electrolytic solution in which a general lithium salt is used as an electrolyte and dissolved in an organic solvent may be used, and the lithium salt and the organic solvent used in the present invention are not particularly limited.

[Power generation element]
FIG. 3 is a perspective view of the power generation element 40. In FIG. 3, the power generation element 40 is illustrated in a state where the winding end portion side is developed.
The power generation element 40 is formed in a flat rectangular parallelepiped shape by winding a positive electrode 41 and a negative electrode 42 around the axis C-C with separators 43 and 44 interposed therebetween.
The positive electrode 41 includes, for example, a positive electrode mixture coating portion 41b in which a positive electrode mixture is coated on both the front and back surfaces of a positive electrode metal foil 41a made of aluminum metal such as aluminum or an aluminum alloy. The positive electrode mixture coating portion 41b applies the positive electrode mixture to the positive electrode metal foil 41a so that the positive electrode mixture uncoated portion 41c where the positive electrode metal foil 41a is exposed is formed on one side edge of the positive electrode metal foil 41a. It is formed by coating.
The negative electrode 42 includes, for example, a negative electrode mixture coating portion 42b in which a negative electrode mixture is coated on both the front and back surfaces of a negative electrode metal foil 42a made of copper-based metal such as copper or a copper alloy. The negative electrode mixture coated portion 42b is a negative electrode mixture uncoated portion in which the negative electrode metal foil 42a is exposed on the other side edge which is the side edge opposite to the side edge where the negative electrode mixture uncoated portion 42c is disposed. The negative electrode metal foil 42a is coated with a negative electrode mixture so that 42c is formed.

  The separators 43 and 44 have a role of insulating the positive electrode metal foil 41a or the negative electrode metal foil 42a. The negative electrode mixture coating portion 42b of the negative electrode 42 is formed larger in the width direction (X direction) and the longitudinal direction (Z direction) than the positive electrode mixture coating portion 41b of the positive electrode 41, whereby the positive electrode mixture coating is performed. As for the process part 41b, the whole area | region from a start end part to a peripheral end part is covered with the negative mix coating part 42b.

As illustrated in FIG. 3, the outer shape of the power generation element 40 is an arc portion 40T formed at both ends in the height direction (Y direction) and a pair of flat portions 40P positioned between both arc portions 40T. It is a flat rectangular parallelepiped shape formed by.
The power generation element 40 is accommodated in the battery can 1 with one arc portion 40T facing downward and the axis C-C parallel to the bottom wall portion 22 of the battery can 1. In the state accommodated in the battery can 1, the pair of flat portions 40 </ b> P of the power generation element 40 face each other substantially parallel to the wide area portion 21 a of the battery can 1.

With reference to FIG. 2, the power generation element 40 is accommodated in the battery can 1 of the square secondary battery C <b> 1 via the insulating sheet 2.
As described above, the power generation element 40 is an electrode group in which the positive electrode 41 and the negative electrode 42 are wound in a flat shape via the separators 43 and 44, and the positive electrode mixture and A positive electrode mixture uncoated portion 41c and a negative electrode mixture uncoated portion 42c to which no negative electrode mixture is applied are provided.
Since the power generation element 40 is wound in a flat shape, the power generation element 40 includes a pair of opposed curved portions having a semicircular cross section and a plane portion formed continuously between the pair of curved portions. Yes. The power generation element 40 is inserted into the battery can 1 from one arcuate portion 40T side so that the winding axis direction is along the lateral width direction of the battery can 1, and the other arcuate portion 40T side is the upper opening of the insulating sheet 2 Placed on the side.

   The positive electrode mixture uncoated portion 41c and the negative electrode mixture uncoated portion 42c, which are the flat portion of the power generation element 40 and the electrode foil exposed portion, are at least partially bundled into a flat plate shape. It is overlapped and connected to one end of the electric plate 4A and one end of the negative electrode current collecting plate 4B.

   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 separated from the power generation element 40 side and the positive electrode external terminal 8A side. It has the structure which isolate | separates 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 current collecting plate 4A and the negative electrode current collecting plate 4B, and the positive electrode external terminal 8A and the negative electrode external terminal 8B from the battery lid 6, respectively, a gasket 5 and an insulating plate 7 are provided on the battery lid 6. ing.
The positive external terminal 8A is formed by integrating a weld joint 13a welded to the bus bar 50 (see FIG. 8) and a positive electrode connection 14a connected to the positive current collector plate 4A. The negative external terminal 8B is formed by integrating a weld joint 13b welded to the bus bar 50 and a negative connection 14b connected to the negative current collector plate 4B.

   Each of the positive electrode connecting portion 14a and the negative electrode connecting portion 14b protrudes from the lower surfaces of the positive electrode external terminal 8A and the negative electrode external terminal 8B, and the tips thereof can be inserted into the positive electrode side through hole 6A and the negative electrode side through hole 6B. It has a cylindrical shape. The positive electrode connecting portion 14a and the negative electrode connecting portion 14b penetrate the battery lid 6 and are inside the battery can 1 more than the positive electrode current collector plate base 41A and the negative electrode current collector plate base 41B of the positive electrode current collector plate 4A and the negative electrode current collector plate 4B. The positive electrode external terminal 8 </ b> A, the negative electrode external terminal 8 </ b> B, the positive electrode current collector plate 4 </ b> A, and the negative electrode current collector plate 4 </ b> B are integrally fixed to the battery lid 6.

  Gasket 5 is interposed between each of positive electrode external terminal 8A and negative electrode external terminal 8B and battery cover 6, and between each of positive electrode current collector plate 4 A and negative electrode current collector plate 4 B and battery cover 6. Insulating plate 7 is interposed.

  The positive electrode current collector plate 4A is bent at a rectangular plate-like positive electrode current collector plate base portion 41A disposed opposite to the lower surface of the battery lid 6 and the side end of the positive electrode current collector plate base portion 41A. It has a positive electrode side connection end 45A that extends toward the bottom wall portion 22 side along the wide area portion 21a and is connected in a state of being superimposed facing the positive electrode mixture uncoated portion 41c of the power generation element 40. doing. The negative electrode current collector plate 4B is bent at the rectangular plate-shaped negative electrode current collector plate base portion 41B disposed opposite to the lower surface of the battery lid 6 and the side end of the negative electrode current collector plate base portion 41B. A negative electrode side connection end 45B that extends toward the bottom wall portion 22 side along the wide area portion 21a and is connected in a state of being overlapped with the negative electrode mixture uncoated portion 42c of the power generation element 40 is provided. doing. Each of the positive electrode collector plate base 41A and the negative electrode collector plate base 41B is formed with a positive electrode side opening hole 43A through which the positive electrode connection part 14a is inserted and a negative electrode side opening hole 43B through which the negative electrode connection part 14b is inserted. ing.

[Positive and negative external terminals]
The positive external terminal 8A is formed of an aluminum-based metal such as aluminum or an aluminum alloy, and the negative external terminal 8B is formed of a copper-based metal such as copper or a copper alloy. The positive external terminal 8A and the negative external terminal 8B have the same structure except that the materials are different. For this reason, in the following, the positive external terminal 8A will be described as an example on behalf of both members, but this also applies to the negative external terminal 8B.
As described above, the positive external terminal 8A is formed by integrating the weld joint 13a and the positive connection 14a, and the bus bar 50 is joined to the upper surface of the weld joint 13a by welding such as laser welding. (See FIGS. 8A and 8B).

The weld joint 13a (13b) has a rectangular parallelepiped shape having a rectangular cross section of about (8.5 mm to 10.5 mm) × (10 mm to 14 mm).
FIG. 6 is an enlarged cross-sectional view of the upper side of the weld joint 13a.
The upper surface 31 of the weld joint 13a has a flat surface 32 formed at the center and an inclined surface 33 formed at the peripheral edge of the weld joint 13a. The inclined surface 33 is inclined so as to descend from the boundary with the flat surface 32 toward the lower surface side of the weld joint 13a substantially linearly toward the peripheral side surface 35 of the weld joint 13a. That is, the inclined surface 33 has the deepest depth E from the flat surface 32 at the position of the peripheral side surface 35. For reasons described later, the maximum depth E of the inclined surface 33 is 0.08 mm to 0.2 mm at the position where the inclined surface 33 reaches the peripheral side surface 35. When the length of the inclined surface 33, in other words, the length from the boundary between the flat surface 32 and the inclined surface 33 to the peripheral side surface 35 is D, the inclination of the inclined surface 33, that is, E / D is 1 / 5 or less is preferable. In order to reduce the area of the weld joint 13a, the length D of the inclined surface 33 is preferably 1.0 mm or less.

[Method for manufacturing positive and negative external terminals]
A method of manufacturing the positive external terminal 8A or the negative external terminal 8B by forging will be described with reference to FIGS. Here, the case where the positive electrode external terminal 8A is manufactured as a representative of the positive and negative electrode external terminals 8A and 8B will be described.
The external terminal material 71 for producing the positive external terminal 8A is accommodated in the forging die 81. The external terminal material 71 is a cylindrical body, and has a diameter with a gap from the inner wall surface 81 a of the forging die 81.
The forging die 81 has an upper space S1 having a cross section of the same size as the peripheral side surface 35 of the weld joint 13a and a height higher than the height of the weld joint 13a, and a lower space S2 having the same shape as the positive electrode connection portion 14a. Is formed.

  A jig 82 is arranged on the external terminal material 71 accommodated in the forging die 81. The lower end surface 83 of the jig 82 has the same shape as the upper surface 31 of the positive electrode external terminal 8A. That is, a flat surface 84 corresponding to the flat surface 32 of the positive electrode external terminal 8A and a peripheral portion of the lower end surface 83 are formed on the lower surface 83 of the jig 82, and the inclination is parallel to the inclined surface 33 of the positive electrode external terminal 8A. A surface 85 is formed.

  When the external terminal material 71 is hit with the jig 82, the external terminal material 71 is crushed by the compressive load applied by the jig 82, the cross-sectional area is enlarged, and the lower side of the external terminal material 71 is deformed. It is pushed into the lower space S2 (see FIG. 4B). Further, the upper surface 72 of the external terminal member 71 is formed with an inclined surface 74 at the peripheral edge thereof, following the shape of the lower end surface 83 of the jig 82. However, at first, a part of the inclined surface 74 corresponding to the outermost peripheral side of the external terminal material 71 is formed, and the area (width) of the inclined surface 74 in this state is that of the lower end surface 83 of the jig 82. It is smaller than the area (width) of the inclined surface 85.

Furthermore, when a compressive load is applied by the jig 82, the cross-sectional area of the external terminal material 71 is further expanded, and the inclined surface 74 of the upper surface 72 of the external terminal material 71 has the same area (width) as the inclined surface 85 of the forging die 82. And a flat surface 73 having the same area (width) as the area (width) of the flat surface 84 of the lower end surface 83 of the forging die 82 is formed at the center of the upper surface 72 of the external terminal material 71 (FIG. 4). (See (c)).
When the forging is further continued, the cross-sectional area of the external terminal material 71 becomes the same as the cross-sectional area of the upper space S1 of the forging die 81, and the positive external terminal 8A is formed (see FIG. 4D).

  During the forging process illustrated in FIGS. 4B to 4D, sagging and flashing may occur at the peripheral edge of the inclined surface 74 of the external terminal material 71. The sagging occurs when the peripheral portion of the external terminal material 71 is insufficiently filled with the external terminal material 71. The flash is mainly generated when the external terminal material 71 is filled in a gap (not shown) between the forging die 81 and the jig 82 due to excessive pressing by the jig 82.

In the present embodiment, the bus bar 50 is welded to the upper surfaces 31 of the positive / negative external terminals 8A and 8B. Therefore, as for the sagging that occurs at the peripheral edge of the upper surface 31 of the positive / negative external terminals 8A, 8B, the bonding strength can be ensured as long as it does not become too large.
However, the flash generated at the periphery of the upper surface 31 of the positive / negative external terminals 8A, 8B causes the bus bar 50 to float from the upper surface 31 of the positive / negative external terminals 8A, 8B, thus reducing the bonding strength.

[Relationship between beam and bonding strength]
FIG. 5 is a characteristic diagram showing the relationship between the gap between the external terminal material and the forging die and the welding strength.
The bonding strength in the figure is a relative value. The gap E is the depth from the flat surface 32 at the position of the peripheral side surface 35 shown in FIG. 6, that is, the maximum depth of the inclined surface 33.
The measurement of the bonding strength was performed after placing the bus bar 50 on the upper surface 31 of the positive / negative external terminals 8A and 8B, performing elliptical scanning while irradiating the bus bar 50 with laser, and laser welding. The inclination angle of the inclined surface 74 of the external terminal material 71 was 1/5, and the gap between the external terminal material 71 and the forging die 81 was constant. The upper terminal shape of the external terminal material 71 is a rectangular shape of 9.5 mm × 12.5 mm.
As shown in FIG. 5, the bonding strength between the positive / negative external terminals 8A and 8B and the bus bar 50 was almost the same as the flat case when the gap E was about 0.2 mm or less.
Thereby, the maximum depth E of the inclined surface 33 of the positive / negative external terminals 8A, 8B is, in other words, the depth E from the flat surface 32 at the position where the inclined surface 33 reaches the peripheral side surface 35 is 0. It can be seen that the positive and negative external terminals 8A and 8B and the bus bar 50 can be joined without lowering the joining strength if it is 2 mm or less.

  In the above description, the inclination angle of the inclined surface 74 of the external terminal material 71 is set to 1/5. If the inclination angle is increased beyond this, the jig 82 generates concentrated stress on the external terminal material 71, which impairs durability. It is for producing.

FIG. 7 shows the distribution of the height of the flash formed on the peripheral edge of the upper surface 31 of the positive / negative external terminals 8A and 8B formed by forging shown in FIGS. 4 (a) to 4 (d).
From FIG. 7, it can be seen that the height of the burr is 0.07 mm or less.
Therefore, if the maximum depth E of the inclined surface 33 of the positive / negative external terminals 8A, 8B is 0.08 mm or more, the beam is placed on the upper surface 31 of the positive / negative external terminals 8A, 8B. It can be seen that the bus bar 50 is not reached and the bonding strength is not lowered.

[Battery]
FIG. 8 is a diagram for explaining an embodiment of the assembled battery of the present invention, FIG. 8 (a) is a top view of the assembled battery, and FIG. 8 (b) is a diagram in FIG. 8 (a). It is a VIIIb-VIIIb line sectional view.
As shown in FIG. 8A, the assembled battery 100 is configured by arranging a plurality of rectangular secondary batteries C1 in the thickness direction. The plurality of prismatic secondary batteries C1 are arranged such that adjacent prismatic secondary batteries C1 are alternately opposed to each other with the wide area portion 21a facing each other. In other words, the different polarity external terminals of the adjacent rectangular secondary battery C1 are arranged to face each other, that is, the positive electrode external terminal 8A and the negative electrode external terminal 8B are arranged to face each other.

  The positive electrode external terminal 8A of each square secondary battery C1 and the negative electrode external terminal 8B of the adjacent square secondary battery C1 are connected in series by a bus bar 50. In FIG. 8, three rectangular secondary batteries C1 are illustrated, but by repeating the same connection, a large number of rectangular secondary batteries C1 can all be connected in series.

The bus bar 50 is formed of a clad material having a positive electrode side portion 51 formed of an aluminum-based metal and a negative electrode side portion 52 formed of a copper-based metal. The positive electrode side portion 51 of the bus bar 50 is placed on the upper surface 31 of the positive electrode external terminal 8A, the negative electrode side portion 52 is placed on the upper surface of the negative electrode external terminal 8B, and the positive electrode side portion 51 is irradiated with laser from the positive electrode side portion. Bonded to the external terminal 8A. Further, the negative electrode side portion 52 is irradiated with a laser to be bonded to the negative electrode external terminal 8B.
Each bonding is performed by scanning an ellipse while irradiating a laser.

If the cross-sectional view on the positive electrode side illustrated in FIG. 8B is described as an example, the laser R is applied to the bus bar 50 substantially perpendicularly. By irradiating the laser R, the bus bar 50 is melted in the thickness direction, and a melted part 50R is formed. The melting part 50R exceeds the upper surface 31 of the positive electrode external terminal 8A, which is a boundary surface between the bus bar 50 and the positive electrode external terminal 8A, and reaches the inside of the positive electrode external terminal 8A. By scanning the laser R on the positive electrode side portion 51 of the bus bar 50 in an elliptical shape, the bus bar 50 and the positive electrode external terminal 8A are joined at the melting portion 50R. The negative electrode external terminal 8B and the negative electrode side portion 52 of the bus bar 50 can be joined in the same manner.
The thickness of the bus bar 50 is preferably about 1.0 mm to 1.5 mm.

As described above, according to the above embodiment, the following effects can be obtained.
(1) An inclined surface 33 having a depth E from the flat surface 32 at a position reaching the peripheral side surface 35 of about 0.08 mm to 0.2 mm is formed on the peripheral edge portion of the upper surface 31 of the positive / negative external terminals 8A and 8B. did. For this reason, when the positive / negative external terminals 8A and 8B are produced by forging, even if a flash occurs on the peripheral edge of the upper surface 31 of the positive / negative external terminals 8A and 8B, the decrease in the bonding strength due to laser welding is eliminated. Can do.

(2) The inclination angle of the inclined surface 33 formed on the outer periphery of the flat surface 32 of the upper surface 31 of the positive / negative external terminals 8A and 8B is set to 1/5 or less. For this reason, the concentrated stress which arises in the peripheral part of the jig | tool 82 with the external terminal material 71 can be made small, and sufficient durability can be ensured.

(3) The inclination angle of the inclined surface 33 formed on the outer periphery of the flat surface 32 of the upper surface 31 of the positive / negative external terminals 8A and 8B is set to 1/5 or less and from the boundary between the flat surface 32 and the inclined surface 33. The length D to the peripheral side surface 35 was set to 1.0 mm or less. For this reason, although the inclination angle of the inclined surface 33 formed on the flat surface 32 is small, the area of the upper surface 31 of the positive / negative external terminals 8A and 8B can be reduced.

  In the above embodiment, the battery container 10 is constituted by the battery can 1 and the battery lid 6, and the positive electrode external terminal 8 </ b> A and the negative electrode external terminal 8 </ b> B are exemplified as the structure provided on the battery lid 6. However, the positive electrode external terminal 8A and the negative electrode external terminal 8B are provided in the narrow area portion 21b of the battery can 1, or the battery can 1 is provided with a ceiling wall surface, and the positive electrode external terminal 8A and the negative electrode external terminal 8B are provided on the ceiling wall surface. Or you may. When the battery can 1 is provided with a ceiling wall surface, the bottom surface of the battery can 1 is opened to serve as a storage opening for the power generation element 40 and the like.

  In the one embodiment, the positive / negative external terminals 8A and 8B are illustrated as a quadrangular prism shape. However, the positive / negative external terminals 8A and 8B may be formed in a columnar shape, a column shape having an upper surface of an ellipse or an ellipse, or a column shape of pentagon or more.

  In the above embodiment, the inclined surfaces 33 of the positive and negative external terminals 8A and 8B are exemplified as a shape that descends linearly, but may be a shape that descends in a curved line such as an arc shape or an elliptical shape.

  In the above embodiment, the bus bar 50 is exemplified as the clad material, but the whole of iron or the like may be formed of a single metal material. Further, a film such as chromium may be formed on a metal surface such as iron by plating or cold spray.

  In the said one Embodiment, all the square secondary batteries C1 which comprise the assembled battery 100 were illustrated as a structure connected in series. However, the present invention can also be applied to a structure in which the rectangular secondary batteries C1 are connected in parallel, in other words, via the bus bar 50, the positive external terminals 8A and the negative external terminals 8B are joined together.

  In the above embodiments, the square secondary battery C1 has been described as a lithium ion battery. However, the present invention can also be applied to a prismatic secondary battery C1 using a water-soluble electrolyte such as a nickel metal hydride battery, a nickel cadmium battery, or a lead storage battery.

In addition, the present invention can be applied with various modifications within the scope of the invention. In short, the positive external terminal is such that the plate-like bus bar faces the outer peripheral side surfaces of the positive external terminal and the negative external terminal. A prismatic secondary battery mounted on the upper and negative electrode external terminals and welded to the upper surface of each of the positive electrode external terminal and the negative electrode external terminal. Each of the positive electrode external terminal and the negative electrode external terminal is flat at the center. And has an inclined surface that gradually slopes toward the lower surface side at the periphery of the flat surface, and the depth of the inclined surface from the flat surface is 0.08 mm to a position where the inclined surface reaches the peripheral side surface. It is 0.2 mm, and each of the positive electrode external terminal and the negative electrode external terminal only has to have a height flash that does not reach a flat surface at the periphery of the upper surface.

DESCRIPTION OF SYMBOLS 1 Battery can 6 Battery cover 8A Positive electrode external terminal 8B Negative electrode external terminal 10 Battery container 13a, 13b Welding connection part 14a Positive electrode connection part 14b Negative electrode connection part 21 Side wall part 21a Wide area part 21b Narrow area part 31 Upper surface 32 Flat surface 33 Inclination Surface 35 Peripheral side surface 40 Power generation element 41 Positive electrode 42 Negative electrode 50 Bus bar 50R Melting part 71 External terminal material 81 Forging die 82 Jig 100 Battery assembly C1 Rectangular secondary battery S1 Upper space S2 Lower space

Claims (11)

A positive electrode external terminal connected to the positive electrode and a negative electrode external terminal connected to the negative electrode are provided on one side surface of a battery container in which a power generation element having a positive electrode and a negative electrode is stored, Plate-shaped bus bars are placed on the positive external terminal and the negative external terminal so as to face the outer peripheral side surfaces of the positive external terminal and the negative external terminal, respectively. A prismatic secondary battery welded to the upper surface ,
Each of the positive electrode external terminal and the negative electrode external terminal has an upper surface and a peripheral side surface, and the upper surface is formed with a flat surface at the center and a slope formed gradually at the periphery of the flat surface toward the lower surface. And the depth of the inclined surface from the flat surface is 0.08 mm to 0.2 mm at a position where the inclined surface reaches the peripheral side surface,
Each of the positive electrode external terminal and the negative electrode external terminal is a prismatic secondary battery having a flash having a height that does not reach the flat surface at a peripheral portion of the upper surface. The prismatic secondary battery according to claim 1,
The bus bar is a prismatic secondary battery that covers the entire upper surface of each of the positive external terminal and the negative external terminal and is placed on the positive external terminal and the negative external terminal. The prismatic secondary battery according to claim 1,
The rectangular secondary battery, wherein a length between the flat surface of the inclined surface and the peripheral side surface is 1.0 mm or less. The prismatic secondary battery according to claim 3 ,
A prismatic secondary battery, wherein the inclined surface has an inclination angle of 1/5 or less. The prismatic secondary battery according to claim 4 ,
The prismatic secondary battery, wherein the positive external terminal is formed of an aluminum-based metal and the negative external terminal is formed of a copper-based metal. The prismatic secondary battery according to claim 4 ,
Each of the positive electrode external terminal and the negative electrode external terminal is a rectangular secondary battery having a rectangular shape in plan view. The prismatic secondary battery according to claim 4 ,
A prismatic secondary battery in which a height of a flash formed on a peripheral portion of the upper surface of each of the positive electrode external terminal and the negative electrode external terminal is 0.07 mm or less. A plurality of prismatic secondary batteries according to any one of claims 1 to 7 , and a bus bar connecting the positive electrode external terminal and the negative electrode external terminal of the adjacent prismatic secondary battery,
The bus bar is placed on the positive external terminal and the negative external terminal so as to face the outer peripheral side surfaces of the positive external terminal and the negative external terminal,
One end of the bus bar and the positive external terminal are a melting part that penetrates the bus bar in the thickness direction, exceeds a boundary between the bus bar and the upper surface of the positive external terminal, and reaches the inside of the positive external terminal. Joined and
The other end of the bus bar and the negative electrode external terminal penetrate through the bus bar in the thickness direction, cross the boundary between the bus bar and the upper surface of the negative electrode external terminal, and reach the inside of the negative electrode external terminal The battery pack is joined by The assembled battery according to claim 8,
The assembled battery, wherein the bus bar covers the entire upper surface of each of the positive external terminal and the negative external terminal and is placed on the positive external terminal and the negative external terminal. The assembled battery according to claim 8 ,
The battery pack has a thickness of 1.5 mm or less. The assembled battery according to claim 8 ,
The bus bar is an assembled battery in which the one end is a clad material formed of an aluminum-based metal and the other end of a copper-based metal.

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