JP5028780B2 - Sealed battery and method for manufacturing the same - Google Patents

Description

  The present invention relates to a sealed battery having an improved sealing member for sealing a liquid injection hole provided in a sealing plate incorporated in a battery case containing a laminated or spiral electrode group and an electrolyte, and a method for manufacturing the same. Is.

In recent years, lithium secondary batteries, which are increasingly used as power sources for portable electronic devices, are sealed with high energy density and load characteristics, and are suitable for making electronic devices thinner and more efficient in space within electronic devices. Is required to have a high square. In addition, these lithium secondary batteries are required to have higher voltages, higher capacities, and thinner thicknesses as electronic devices have higher performance, higher functionality, and more compact size.
In the rectangular battery, the laser sealing method is the mainstream in comparison with the caulking sealing method which is inferior in sealing property to be a sealed type. In a laser-sealed prismatic battery, a laminated or spiral electrode plate group is stored in a battery case, and then a current collector attached to the laminated or spiral electrode plate group is welded to the sealing plate and the sealing plate and the battery are The case is laser welded, an electrolyte is injected from a liquid injection hole provided in either the sealing plate or the battery case, and then the liquid injection hole is sealed with a sealing plug to constitute a sealed battery.

  The sealing method using the sealing plug is such that the injection hole 2 for injecting the electrolyte solution opened into the battery case 4 having the configuration as shown in FIGS. A sealing method is proposed in which the injection hole 2 is sealed by irradiating the sealing plug 3 with a laser beam and welding the sealing plug 3 and the battery case 4 (for example, Patent Documents). 1).

  Further, as shown in FIG. 9, a sealing plug 3 for sealing the liquid injection hole 2 opened in the battery case 4 is provided, and the sealing plug 3 includes a metal sealing body body 3b and a rubber plug. The sealing body main body 3b has a disk shape, an elliptical shape or a polygonal shape, and the liquid injection hole 2 is fitted with the recess 2a and the rubber plug 3a. A sealing method using a sealing plug 3 configured with a hole 2b is proposed (see, for example, Patent Document 2).

Further, as another sealing method using a sealing plug, as shown in FIGS. 10A and 10B, a support member 3b fixed in a state of covering the liquid injection hole 2 and an elastic press-fitting member 3a. The support member 3b is inserted into the outer peripheral end rising portion 14 of the sealing plate 1 in a state where the configured sealing plug 3 is press-fitted into the liquid injection hole 2, and the end portion of the support member 3b and the sealing member are sealed. There has been proposed a sealing method that is fixed by laser welding between the outer peripheral end rising portion 14 of the plate 1 (see, for example, Patent Document 3).
JP 2000-48804 A JP 2001-313022 A JP 2000-268811 A

  However, in Patent Document 1 which is a conventional technique, when the electrolyte solution penetrates into the gap between the sealing plug and the injection hole for injecting the electrolyte solution, a problem of poor welding is likely to occur due to sputtering during welding. There is.

Patent Documents 2 and 3 have been invented in view of the above problems. However, in the case of Patent Document 2, the injection hole 2 for injecting the electrolyte as shown in FIG. 9 has a recess 2a for fitting with the metal sealing body 3b and a hole for fitting with the rubber plug 3a. And has a function of centering the hole 2b into which the rubber plug 3a is fitted, so that the tolerance or position of the coaxiality of the rubber plug 3a with respect to the sealing body 3b is determined. If the accuracy is insufficient, the sealing body 3b and the recess 2a of the liquid injection hole 2 interfere with each other, resulting in poor insertion.

  Moreover, the sealing plug 3 joins the sealing body 3b and the rubber plug 3a with an adhesive, and laser-welds the outer edge of the sealing body 3b. At that time, it is necessary to keep the distance between the end of the sealing body 3b and the end of the rubber plug 3a so as not to be affected by the heat at the time of laser welding. The rubber plug 3a is burnt due to the heat effect and cannot be sealed. Therefore, in the case of a thin prismatic battery, if the sealing plug 3 is downsized while keeping the distance between the end of the sealing body 3b and the end of the rubber plug 3a so as not to be affected by heat during laser welding, There arises a problem that the rubber plug 3a cannot be molded.

  Further, in the sealing method disclosed in Patent Document 3, when the support member 3b is fitted into the outer peripheral end rising portion 14 of the sealing plate 1 as shown in FIG. 10, a gap is formed to stabilize laser welding. It needs to be as small as possible. Therefore, the support member 3b of the sealing plug 3 interferes with the outer peripheral end rising portion 14 of the sealing plate 1 to cause poor insertion, which may cause sealing failure.

  Further, in a production line that performs laser welding along the boundary between the support member 3b and the outer peripheral end rising portion 14 of the sealing plate 1, a jig or laser for holding a lens barrel for condensing a laser beam of a laser welding machine is used. The position accuracy of the jig that holds the battery, which is the object to be irradiated, varies depending on the distortion caused by the heat stored in the laser, and there is a relative shift in the trajectory of the laser and the influence of the repeatability of the laser welding machine power supply and flash lamp. Variation in laser output occurs. Therefore, welding cannot be performed along the boundary between the support member 3b and the outer peripheral edge rising portion 14 of the sealing plate 1, resulting in poor welding and poor sealing.

  The present invention has been accomplished in view of the above-described conventional problems, and an object of the present invention is to provide a sealed battery that can improve the quality at the time of laser welding in manufacturing the sealed battery. To do.

In order to achieve the above-described object, the sealed battery of the present invention includes a strip-shaped positive electrode plate and a negative electrode plate, and an electrode plate group formed by laminating or spirally winding a separator between them. In the sealed battery in which the opening of the battery case is sealed with a sealing plate having a liquid injection hole for injecting a nonaqueous electrolyte, and the liquid injection hole is sealed with a sealing member. The sealing member is constituted by a sealing member press-fitted into the liquid injection hole and a plate-like support welded to the sealing plate, and the shape of the plate-like support is at least a square having an arc portion on one side to be laser-welded. It is an object to provide a configuration.

  According to the present invention, the shape of the plate-like support is a square having an arc portion, so that the deviation of the trajectory of the laser beam irradiated from the laser welding machine occurs or the output of the laser beam of the laser welding machine. Even when variations occur, the laser beam trajectory that matches the shape of the arc of the plate-like support can be drawn and the arc of the plate-like support can be welded. It is possible to improve the quality during welding. Furthermore, when sealing the liquid injection hole provided in the sealing plate, the welding strength at the time of laser welding can be ensured, and the quality of the battery can be improved. Further, the plate-like support is not fitted into the outer peripheral end rising portion of the sealing plate, but a gap is provided between the plate-like support and the outer peripheral end rising portion of the sealing plate so that it can be easily inserted on the facility.

According to a first aspect of the present invention, an opening of a battery case is configured by being sealed with a sealing plate having a liquid injection hole for injecting a non-aqueous electrolyte, and the liquid injection hole is sealed with a sealing member. In the battery, the sealing member is constituted by a sealing member press-fitted into the liquid injection hole and a plate-like support member welded to the sealing plate, and the shape of the plate-like support member is at least an arc portion on one side to be laser-welded. Due to the rectangular shape, the deviation of the trajectory of the laser beam emitted from the laser welding machine or the variation of the laser beam output of the laser welding machine can follow the arc part of the plate-like support. Can be welded.

  According to a second aspect of the present invention, the distance between the end of the plate-like support and the sealing member provided with the arc is obtained by making the shape of the plate-like support a square having arcs on opposite sides. By keeping the distance so as not to be affected by heat at the time of laser welding, the sealing member can be burnt due to the heat effect at the time of laser welding and the problem that cannot be sealed can be dealt with.

  According to a third aspect of the present invention, a depression is formed in the sealing plate, and the plate-like support is coupled to the depression, thereby providing an effect of preventing the rotation of the plate-like support and the depression in the sealing plate. Since a gap can be provided between the plate-like support member and the plate-like support member, the tolerance of the coaxiality or the positional tolerance of the sealing member relative to the plate-like support member can be absorbed.

According to a fourth aspect of the present invention, an electrode plate group is formed by stacking or spirally winding a strip-like positive electrode plate and a negative electrode plate with a separator interposed therebetween, and then the electrode plate group is placed in a battery case. A sealing member that is housed and sealed with a sealing plate having a liquid injection hole into which a non-aqueous electrolyte can be injected, and after the electrolyte is injected from the liquid injection hole, a sealing member that is press-fitted into the liquid injection hole; When sealing the liquid injection hole with a sealing member constituted by a rectangular plate-like support having an arc portion, laser welding the arc portion of the plate-like support and fixing the sealing member to the sealing plate, Since the arc portion of the plate-like support can be welded, sufficient welding strength for sealing the injection hole can be ensured.

  According to a fifth aspect of the present invention, the laser beam of laser welding draws an arc-shaped track and welds at least one arc portion provided on the plate-like support to fix the sealing member to the sealing plate. Even when the deviation of the trajectory of the laser beam irradiated from the laser welding machine occurs or when the output of the laser beam of the laser welding machine varies, it is possible to weld according to the shape of the arc part of the plate support, Sufficient welding strength can be ensured.

  According to a sixth aspect of the present invention, arc portions of opposing sides provided on a plate-like support member of a sealing member are welded so that a laser beam of laser welding draws an arc-shaped track, and the sealing member is sealed with a sealing plate. Since the arcuate portion of the plate-like support can be welded with a laser beam having an arc-shaped track even when the plate-like support of the plugging member is rotated around the plugging member, the welding failure is caused. Can be suppressed.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS The best embodiment of the present invention will be described in detail below with reference to the drawings. 1A and 1B show the overall configuration of a prismatic lithium secondary battery as a typical sealed battery according to an embodiment of the present invention, where FIG. 1A is a longitudinal side view and FIG. 1B is a plan view. FIG. 2 shows a sealing member fixed to a prismatic lithium secondary battery according to an embodiment of the present invention, (a) is a plan view of the sealing member, and (b) is a liquid injection hole in a sealing plate. And (c) is a plan view after laser-welding the sealing member sealing the sealing member to the opening of the battery case.

  The prismatic lithium secondary battery includes a battery case 4 that serves as a positive electrode terminal in a bottomed rectangular tube-shaped aluminum material in which an electrode plate group 5 that is a power generation element, which will be described in detail later, and an opening 4a of the battery case 4. A sealing plate 1 made of an aluminum material is provided. The sealing plate 1 is provided with a liquid injection hole 2 for injecting a non-aqueous electrolyte (not shown) into the battery case 4.

  The electrode plate group 5 is housed in the battery case 4 so as to be electrically insulated and separated by the lower insulating plate 10 at the bottom thereof, and the positive and negative electrode plates are interposed with a separator therebetween. After winding in a laminated state, it is produced in a flat shape by press molding. The upper end portion of the electrode plate group 5 has an upper insulating plate 6 and is electrically insulated. An external negative electrode terminal 8 is attached to the sealing plate 1 in a state where it is electrically insulated via an upper insulating gasket 7 at the center thereof. An internal negative terminal 11 that is electrically insulated from the sealing plate 1 via a lower insulating gasket 9 is connected to the lower portion of the external negative terminal 8 in an electrically connected state. The negative electrode lead 12 led out from the electrode plate group 5 is connected by welding.

  A positive electrode lead 13 led out from the electrode plate group 5 is connected to the sealing plate 1 by welding. The sealing plate 1 is joined and sealed at the opening 4a of the battery case 4 by, for example, laser welding. After injecting a predetermined non-aqueous electrolyte from the liquid injection hole 2, the sealing member 3 a constituting the sealing member 3 is pressed and pressed by the plate-like support 3 b. Thereafter, the arc portion of the plate-like support 3b is laser-welded while holding the square plate-like support 3b having the arc portion.

  The sealing member 3a preferably has non-aqueous electrolyte solution resistance. For example, the material is preferably fluororubber or EPDM. Further, the plate-like support 3b is preferably the same type of metal as the battery case 4. For example, when the battery case 4 is made of aluminum, the plate-like support 3b is also preferably made of aluminum.

  Next, FIG. 5 shows a flowchart showing manufacturing steps of the prismatic lithium secondary battery which is the sealed battery of the present invention. First, the positive electrode plate 102 and the negative electrode plate 104 are manufactured in the source step 110 for manufacturing the electrode plate, and the positive electrode plate 102, the negative electrode plate 104, and the separator 105 are used to form the electrode plate that is a power generation element in the electrode plate group forming step 111. Group 5 is manufactured. Further, after inserting the electrode plate group 5 into the battery case 4, the sealing plate 1 is welded to the opening of the battery case 4, the nonaqueous electrolyte solution 106 is injected, and the sealing member 3 is welded to the sealing plate 1. There is an assembly process 112 for manufacturing the rectangular lithium secondary battery 109.

  As a positive electrode raw material 101 in the source process 110, a positive electrode active material that is a lithium-containing composite oxide such as lithium cobaltate, a conductive agent using acetylene black, and a binder using polyvinylidene fluoride are used as a dispersion medium. Kneaded and dispersed, the positive electrode raw material 101 is applied to an aluminum foil as a positive electrode current collector, dried and rolled to produce a strip-shaped positive electrode plate 102. In addition, as the negative electrode raw material 103 in the source process 110, a negative electrode active material using natural graphite or the like, a binder using polyvinylidene fluoride or the like, and a thickener using polyethylene oxide or the like are kneaded and dispersed in a dispersion medium. Then, the negative electrode raw material 103 is coated on a copper foil as a negative electrode current collector, dried and rolled to produce a strip-shaped negative electrode plate 104.

  Next, in the electrode plate group forming step 111, the positive electrode plate 102 using a composite lithium oxide as an active material and the negative electrode plate 104 using natural graphite or the like as an active material are separators that are microporous films made of a polymer such as polyethylene. The electrode plate group 5 is formed by winding or stacking in a spiral shape via the line 105. Further, in the assembly process 112, after the lower insulating plate 10 and the electrode plate group 5 are inserted into the battery case 4, the upper insulating plate 6 is inserted, and the upper insulating gasket 7, the external negative electrode terminal 8, and the lower insulating gasket 9 are first connected. The positive electrode lead led out from the electrode plate group 5 is welded to the sealing plate 1 integrated in the process, and the negative electrode lead led out from the electrode plate group 5 is welded to the external negative electrode terminal 8.

Next, the sealing plate 1 to which the positive electrode lead and the negative electrode lead are electrically connected is inserted into the opening of the battery case 4, and the sealing plate 1 is welded to the battery case 4. Furthermore, after injecting the nonaqueous electrolyte 106 from the injection hole provided in the sealing plate 1, the sealing member constituting the sealing member 3 is pressed into the injection hole by pressing it with a plate-like support. Thereafter, while holding the rectangular plate-like support having an arc portion, the arc portion of the plate-like support is laser-welded, and the sealing member 3 is fixed to the sealing plate 1, whereby the rectangular lithium secondary battery 109 is manufactured. Is done.

  Hereinafter, a sealing member fixed to a sealing plate of a prismatic lithium secondary battery in an embodiment of the present invention will be described in detail with reference to the drawings.

  As shown in FIG. 2, the sealing member 3a constituting the sealing member 3 has a circular truncated cone shape following the cylinder and is made of EPDM. The plate-like support 3b has arc-shaped portions having a diameter of 3.2 mm on opposite sides of a square shape, and is made of an aluminum alloy material having a square width of 2.1 mm and a thickness of 0.3 mm. The injection hole 2 provided in the sealing plate 1 is on the concave surface having a rectangular length of 4.6 mm, a width of 2.3 mm, and a depth of 0.4 mm provided in the upper portion of the sealing plate 1. It has a recess 2b and a through hole 2a. The hollow portion 2b and the through hole 2a preferably have a dimensional relationship that allows the sealing member 3a to be press-fitted. The sealing plate 1 produced by press-fitting the sealing member 3 into the liquid injection hole 2 and laser welding the arc portion of the plate-like support 3b was taken as Example 1.

  FIG. 3 shows a sealing member 3 fixed to a sealing plate of a prismatic lithium secondary battery according to another embodiment of the present invention. As shown in FIG. 3, the plate-like support 3b has an arc portion having a diameter of 3.2 mm on only one of the four sides of the square shape, the width of the square is 2.1 mm, and the thickness is 0.3 mm. Aluminum alloy material. Further, the specifications are the same as those in Example 1 except for the shape of the plate-like support 3b. However, when laser welding the plate-like support 3b, the arc portion of the plate-like support 3b draws a laser beam in an arc shape. Welding was performed, and the linear portion of the plate-like support 3b was irradiated with a laser beam in a straight line to weld the sealing plate 1 and the sealing member 3, and the produced sealing plate 1 was taken as Example 2.

  FIG. 4 shows a sealing member 3 fixed to a sealing plate of a prismatic lithium secondary battery which is another embodiment of the present invention. As shown in FIG. 4, the plate-like support 3b has a circular arc part having a diameter of 3.2 mm on two sides of the four sides of the square shape, and a diameter of 9.2 mm on one side of the remaining two sides. This is an aluminum alloy material having a circular arc portion with a square width of 2.1 mm and a thickness of 0.3 mm. Further, the sealing plate 1 having the same specifications as in Example 1 except for the shape of the plate-like support 3b was taken as Example 3.

(Comparative example)
In order to compare with the embodiment of the present invention, it has the same specifications as the above embodiment except that it includes a sealing member 3 having a quadrangular support shown in FIG. 6A and laser welds a quadrangular linear portion. The sealing plate 1 was used as a comparative example.

  Laser sealing of the sealing member 3 was performed using the sealing member 3 shown in Examples and Comparative Examples as described above. As the welding quality of laser welding, whether the sealing member 3 and the sealing plate 1 were welded was determined visually, and the welding strength was measured in a welding strength measurement experiment and compared. In this welding strength measurement experiment, as shown in FIG. 7, a pressure rod 50 is applied from the injection hole 2 side to the sealing member 3a of the sealing member 3 laser welded to the sealing plate 1, and the load is applied. The welded part was damaged by peeling and the peeled load was measured.

  As is clear from Table 1, the sealing members 3 of Examples 1, 2, and 3 are all welded to the sealing plate 1, whereas the sealing member 3 of the comparative example is unwelded to the sealing plate 1. There was a part with weak welding strength between the sealing member 3 and the sealing plate 1. This is because, as shown in FIG. 6B, the plate-like support of the rectangular plug member 3 rotates around the liquid injection hole provided in the sealing plate 1, and the laser trajectory drawn in a straight line. It is considered that an unwelded portion was generated because the end of the plate-like support had an angle corresponding to the rotation.

In terms of the welding strength, the welding damage load of 0.2 kgf corresponds to the internal pressure of the battery case 4 of 15 kgf / cm ² , which is the limit value of the pressure resistance of the battery case 4. That is, it is a load that must be extinguished by a welding damage load of 0.2 kgf or more. In the comparative example, there is a welding strength with a welding breakage load of 0.2 kgf or less, and it cannot be said that the strength is sufficient.

  From the above measurement results, when the sealing member 3 characterized in that the shape of the plate-like support 3b of the sealing member 3 according to the present invention is a square having an arc portion on at least one side, the sealing member 3 is used. The laser beam is in an arc shape even when the laser beam is not in a fixed position and when the orbital deviation of the laser beam emitted from the laser welding machine occurs or when the laser beam output of the laser welding machine varies. Since the arc of the plate-like support 3b of the sealing member 3 can be welded, sufficient welding strength for sealing the injection hole can be ensured.

  According to the present invention, a sealed battery in which the opening of a battery case is sealed with a sealing plate having a liquid injection hole for injecting a non-aqueous electrolyte, and the liquid injection hole is sealed with a sealing member. The sealing member is composed of a sealing member press-fitted into the liquid injection hole and a plate-like support welded to the sealing plate, and has a square shape having an arc portion on at least one side of the shape of the plate-like support. Therefore, even when the sealing member 3 rotates and is not in a fixed position, or when the deviation of the trajectory of the laser beam irradiated from the laser welding machine occurs or when the output of the laser beam of the laser welding machine varies, Since the arc portion of the cylindrical support can be welded, it is possible to ensure the welding strength for sealing the injection hole and improve the quality at the time of laser welding when sealing the liquid injection hole.

(A) A longitudinal sectional view of a sealed battery in an embodiment of the present invention, (b) a plan view of the sealed battery. (A) A plan view of a sealing member fixed to a prismatic lithium secondary battery in one embodiment of the present invention, (b) a cross-sectional view of a liquid injection hole and a sealing member in the sealing plate, and (c) a sealing plug. Plan view after laser welding the member to the sealing plate The top view of the sealing member which shows the sealing member fixed to the sealing board of the square lithium secondary battery in another Example of this invention, and has an arc part on one side of a plate-shaped support body. The top view of the sealing member which shows the sealing member fixed to the sealing board of the square lithium secondary battery in another Example of this invention, and has an arc part on the three sides of a plate-shaped support body. Manufacturing process flowchart of prismatic lithium secondary battery in the same embodiment (A) Standard attachment state diagram of the sealing member in the comparative example, (b) Attachment state diagram at the time of rotation occurrence Schematic diagram of welding strength measurement experiment in the same example (A) Sectional view of sealing plug portion before sealing by electrolyte injection hole in conventional example, (b) Sectional view after sealing Schematic diagram of sealing plug in conventional example (A) Perspective view of sealing plug part welded to sealing plate of prismatic lithium secondary battery in conventional example, (b) AA line sectional view of the sealing plug part

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sealing plate 2 Injection hole 2a Through-hole 2b Recessed part 3 Sealing member 3a Sealing member 3b Plate-like support body 4 Battery case 4a Opening part 5 Electrode plate group (power generation element)
6 Upper Insulating Plate 7 Upper Insulating Gasket 8 External Negative Terminal 9 Lower Insulating Gasket 10 Lower Insulating Plate 11 Internal Negative Terminal 12 Negative Electrode Lead 13 Positive Electrode 14 Start Up Part 50 Pressure Bar 110 Source Process 111 Group Configuration Process 112 Assembly Process

Claims (6)

A strip-shaped positive electrode plate and a negative electrode plate, and an electrode plate group formed by stacking or spirally winding a separator between them are housed in a battery case, and the opening of the battery case injects a non-aqueous electrolyte. A sealed battery in which the liquid injection hole is sealed with a sealing member, and the sealing member is a sealing member press-fitted into the liquid injection hole; A sealed battery comprising a plate-like support member welded to a sealing plate, and having a shape having a circular arc part on at least one side to be laser-welded .   2. The sealed battery according to claim 1, wherein the shape of the plate-like support is a square having arc portions on opposite sides.   2. The sealed battery according to claim 1, wherein a recess is formed in the sealing plate, and a plate-like support is coupled to the recess. After forming the electrode plate group by laminating or winding in a striped manner with a separator interposed between the strip-like positive electrode plate and the negative electrode plate, the electrode plate group is housed in the battery case, and the opening of the battery case A rectangular plate having a circular arc part and a sealing member that is pressed into the liquid injection hole after the liquid electrolyte is injected through the liquid injection hole. When the liquid injection hole is sealed with a sealing member constituted by a cylindrical support, the arc-shaped portion of the plate-like support is laser- welded and the sealing member is fixed to the sealing plate. Battery manufacturing method.   5. The sealing according to claim 4, wherein a laser beam of laser welding draws an arc-shaped track and welds at least one arc portion provided on the plate-like support to fix the sealing member to the sealing plate. A manufacturing method of a battery. A laser beam of laser welding is welded in an arc-shaped orbit on the arcuate portions of opposing sides provided on the plate-like support of the sealing member, and the sealing member is fixed to the sealing plate. Item 5. A method for producing a sealed battery according to Item 4.

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