JP6436479B2 - Sealing method for liquid injection part for lithium ion battery - Google Patents

Description

The present invention relates to a method for sealing a liquid injection portion for a lithium ion battery for sealing an opening after the injection of the lithium ion battery.

In order to improve the performance and size and weight of modern electronic products such as mobile notebook PCs, tablet terminals, smartphones, and portable music devices, lithium-ion batteries (Lithium Ion Battery, below) have high potential and high energy density among storage batteries. (Abbreviated as LIB) greatly contributes, and various types of LIBs such as a square shape and a pouch type are mounted on these devices. In recent years, its use has expanded to other than the above-mentioned small to medium-sized devices, and it can be used as a power source for moving bodies such as electric cars, hybrid cars, trains, and aircraft, or for emergency use in hospital facilities and communication base stations. As a power source, research and development and commercialization of large LIBs are being promoted.

Here, the configuration will be briefly described by taking, as an example, a square LIB often used for a moving body. In the rectangular LIB, an electrode plate group in which positive electrodes and negative electrodes are alternately stacked via separators is stored in a battery case, and current collecting tabs provided on the positive electrode and the negative electrode, respectively, are insulated from the battery case lid. By connecting to the electrode terminal and joining the battery case lid to the battery case can, it has a structure for extracting electric energy from the electrode plate group inside the battery to the outside.

Further, a predetermined amount of electrolyte is injected into the battery case through the through-hole formed in the battery case lid. As the electrolyte, a non-aqueous solution in which a lithium salt is dissolved in an organic solvent is used. However, since the electrolyte causes severe performance deterioration due to contact with moisture in the atmosphere, the liquid injection operation is usually performed in an inert gas atmosphere. Do. After injection, in order to cut off the contact between the electrolyte and the atmosphere, the through-hole is sealed and sealed by various means to form a sealed structure, thereby obtaining a LIB having a sealed structure of the injected part.

The sealing and sealing method for the liquid injection part is divided into a fitting process for fitting a sealing plug into the through hole and a welding process for welding the fitting part and sealing the liquid injection part. In particular, since the welding process is performed with the electrolyte solution filled in the LIB battery case, laser welding with a narrow welding range and relatively small heat generation may be selected for the purpose of preventing alteration of the electrolyte solution due to heat. is there.

The narrow welding range is also a disadvantage of laser welding. It is known that the welding strength is lowered only by having a gap of several millimeters in the welded portion, and in some cases, a defective weld such as a pinhole is generated in the welded portion. When pinholes occur in the LIB battery case, the airtightness is remarkably lowered, which may cause deterioration of the electrolyte, the electrode plate group, and the like.

In order to eliminate the welding failure at the time of laser welding as described above, the applicant previously proposed a method for sealing a battery case of LIB disclosed in Patent Document 1. As shown in FIG. 2, this product has a liquid injection plug 4 made of a hollow metal having a liquid injection hole 3 having a shape in which three through-holes of different diameters are successively connected to a through hole 2 formed in the battery case lid 1. Thus, the through-hole 2 and the liquid injection hole 3 are in communication with each other, and an annular packing 7 placed in the middle cylinder 6 with respect to the female thread portion of the lower cylinder 5 of the liquid injection hole 3 is provided. And a soft flat packing 10 is mounted in a recessed space having a desired depth surrounded by the upper surface of the screw plug head 9 and the inner peripheral surface of the middle cylinder 6 of the liquid injection plug 4. The flat plate washer 11 is slidably fitted so as to further compress the flat plate packing 10, and the outer peripheral surface of the flat plate washer 11 and the inner peripheral surface of the liquid injection stopper upper cylinder 12 are sealed by laser welding. As a result, the battery case lid 1 was sealed.
According to this method, since the position of the flat washer 11 can be freely determined with respect to the inner periphery of the upper cylinder 12, not only can the gap of the welded portion be reduced to an allowable range, but also the softness in the recessed space on the screw plug 8 can be reduced. Since the flat plate packing 10 is placed, the flat plate washer 11 and the top surface of the liquid filling tap 4 can always be kept flush with each other, so that defects in the welding process can be eliminated.

On the other hand, as a sealing plug having a shape suitable for laser welding, Patent Document 2 proposes a multi-stage cylindrical sealing plug provided with a collar. By performing laser welding along the flange, the creepage distance from the welded portion to the electrolyte surface of the injection hole can be sufficiently increased, so that the influence of welding heat on the electrolyte is reduced, leakage of the electrolyte and the associated pin Welding defects such as hole generation can be eliminated.

Japanese Patent No. 5314359 JP 2008-147069 A

However, the technique disclosed in Patent Document 1 can surely eliminate laser welding defects, but depending on the processing accuracy, the flat washer 11 is difficult to fit into the upper cylinder 12, and in that case, fraying is necessary. The process required time and there was room for improvement in terms of workability. In particular, once the flat washer 11 is firmly fitted, it is difficult to remove due to the structure. If the work is mistaken, the liquid injection part may be damaged, or in the worst case, the LIB battery case itself may be damaged. It was. Furthermore, since the number of parts is large, the structure of the liquid injection part has become complicated and large.

On the other hand, when a sealing plug having a collar as in Patent Document 2 is used, it is allowed to increase the dimensional tolerance of the sealing plug, so that the workability of the fitting process is improved. Since the fitting between the sealing plug and the liquid injection hole becomes weak, a gap is easily formed, and the airtightness is lowered. If airtightness decreases, the electrolyte easily penetrates even if the creepage distance from the injection hole to the weld is increased.Therefore, there is a risk of deterioration of the electrolyte due to welding heat, and in the worst case, ignition and rupture. Conceivable. On the other hand, when the dimensional tolerance is reduced, it becomes difficult to fit the sealing plug to the lowermost part, so that the collar part floats from the battery case lid, and when laser welding is performed in such a state, It is not difficult to predict that welding defects will occur.

In addition to the above, problems to be solved include an increase in the size of a series of sealing process facilities, an increase in manufacturing costs associated therewith, and a decrease in workability. In the method of Patent Document 2, it is necessary to carry out the process from injection to hermetic sealing in an inert gas atmosphere, and both the injection equipment and the laser welding apparatus are integrated to make various operations large. Had to be done in the glove box. Furthermore, it is difficult to perform the operation of fitting the sealing plug into the liquid injection hole in the glove box. In order to prevent inert gas from leaking to the outside, the gloves for working in the glove box are often made of thick rubber, etc., and this requires the operator to perform detailed work such as assembling parts with dimensions of several centimeters or less. When it is done, it is easy to remove parts by mistake, and there is a risk of inferior welding if the collar part with a thickness of several millimeters is damaged, which is inconvenient.

The invention of the present application provides a sealing welding method that improves the airtight structure of the liquid injection part, has better work efficiency than before, eliminates defective welding, simplifies and downsizes the structure, and significantly reduces manufacturing costs. Objective.

The invention of the present application attaches a liquid injection plug made of a hollow metal having a liquid injection hole having a shape in which two-stage cylindrical holes of different diameters are successively connected to a through-hole formed in the battery case lid of the LIB. A screw cap for sealing in which the through hole and the liquid injection hole are in communication with each other, the fitting insertion part at the lower part of the liquid injection stopper and the through hole are welded so as to be airtight, and then a flange is provided on the outer edge of the upper end The battery case can be hermetically sealed by screwing into the liquid injection hole through the flexible annular packing into the liquid injection hole, and the battery case can be hermetically sealed. The present invention relates to a method for sealing a liquid injection part for LIB, wherein the contact part is sealed by welding.

In the present invention, by screwing a screw cap for sealing through a flexible annular packing to a screw portion provided in the inner periphery of the liquid injection hole, the flange portion and the upper surface of the liquid injection plug are attached. Since the liquid injection hole can be sealed, even if the dimensional tolerance of the screw plug is increased so that it can be easily fitted, the airtightness of the liquid injection part is not impaired and the workability can be greatly improved.

LIB also decomposes the electrolyte during the initial charge after injecting the electrolyte, generating decomposition gas of the electrolyte component and causing expansion of the battery case and internal components. Since it can be removed with a screw, the degassing work is easy. On the other hand, such degassing is difficult with the technique of press-fitting a sealing plug as in Patent Document 2.

Furthermore, this means that the screwing of the screw cap for sealing is not simply simplified, and the subsequent welding of the liquid injection part can be performed outside the glove box. That is, since it is possible to separate the liquid injection device and the laser welding device, it is not necessary to increase the size of the device, and since a general-purpose welding device can be used, the manufacturing cost can be greatly reduced.

The disassembled sectional view which showed the liquid injection part for LIB of embodiment of this invention. The exploded sectional view showing the conventional LI injection part.

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

FIG. 1 is an exploded cross-sectional view of a LIB injection part according to an embodiment of the present invention. A through-hole 2 projecting downward is formed at a predetermined position of the battery case lid 1 made of metal. A hollow injection plug 20 made of metal has a cylindrical lower insertion portion formed so that the outer diameter is equal to the inner diameter of the through-hole 2 and has the same length as the height of the through-hole 2 protruding downward. 21 and an upper cylindrical portion 22 having an outer diameter larger than that of the lower fitting insertion portion 21 were processed so as to form a two-stage cylindrical shape in which the center lines were connected. Further, the hollow portion penetrates the center of the liquid filling plug 20 up and down, and the lower cylindrical hole 23 having a female screw portion on the inner peripheral surface and the upper cylindrical hole 24 having a larger inner diameter share the central plug. Then, it was produced so as to form a two-stage cylindrical hole connected in order, and this was used as the liquid injection hole 25. Reference numeral 30 denotes a circular flat packing having a hollow portion 31 at the center, which is made of polytetrafluoroethylene (PTFE) and has flexibility.

In FIG. 1, reference numeral 40 denotes a sealing screw plug made of metal, and includes a screw shaft portion 41 having a male screw portion screwed into the lower cylindrical hole 23 of the liquid injection plug 20, and an upper portion of the screw shaft portion 41. Further, a screw head 42 having an outer diameter larger than the outer diameter of the screw shaft portion 41 and smaller than the inner diameter of the upper cylindrical hole 24 of the liquid injection stopper 20 is integrally formed. Here, the sum of the height of the screw head 42 and the thickness of the annular packing 30 is processed to be larger than the depth of the upper cylindrical hole 24. Further, a flange 43 is formed on the outer edge of the upper end of the screw head 42. The flange 43 is formed over the entire periphery of the outer edge of the screw head 42, and when the screw shaft portion 41 of the sealing screw plug 40 is screwed into the lower cylindrical hole 23 of the liquid injection plug 20, the liquid injection is performed. It is sized to abut on the upper surface of the stopper 20. Reference numeral 44 denotes a groove formed on the upper surface of the sealing screw plug 40 in accordance with the shape of the working portion of a tool such as a screwdriver used when the sealing screw plug 40 is screwed.

Each member comprised in this way is assembled as follows, and seals the through-hole 2 of the battery case lid 1.

The lower insertion portion 21 of the liquid injection plug 20 is inserted into the through hole 2 of the battery case lid 1 so that the through hole 2 and the liquid injection hole 25 communicate with each other. When abutting on the upper surface of the battery case lid 1, the lower end of the through hole 2 and the lower end of the lower fitting insertion portion 21 of the injection plug 20 are flush with each other, and this flushed portion is subjected to argon arc welding or Gas injection is performed by TIG welding or the like, and the liquid injection stopper 20 is attached to the battery case lid 1 in an airtight manner. In this state, a battery case cover is applied to the upper opening portion of the battery case in which the electrode plate group in which the positive electrode and the negative electrode are alternately laminated via the separator is housed, and the non-water is supplied from the injection hole 25 of the injection stopper 20. A predetermined amount of electrolyte is poured into the battery case.

Next, the screw shaft portion 41 of the sealing screw plug 40 is inserted into the hollow portion 31 of the annular packing 30, a screwdriver is inserted into the groove 44 on the upper surface of the sealing screw plug 40, and the screw shaft portion 41 is injected. The sealing screw plug 40 was fastened to the liquid injection hole 25 through the annular packing 30 by screwing into a female screw portion of the inner peripheral surface of the lower cylindrical hole 23 of the plug 20. At this time, the annular packing 30 is crushed, and the flange 43 provided on the outer edge of the upper end of the screw head 42 of the sealing screw plug 40 contacts and adheres to the upper surface of the liquid injection plug 20 without a gap. In addition, when a slight fastening deviation occurs due to a dimensional tolerance of the sealing screw plug 40 and the liquid filling plug 20, it is adjusted by tightening firmly to ensure attachment. At this time, the airtightness is not inhibited by the flexibility of the annular packing 30. When PTFE was used as the annular packing 30, even if the flange 43 protruded from the upper surface of the liquid filling tap 20 by about 0.1 to 0.5 mm, it could be attached by compression of torque tightening.

In this state, the LIB becomes airtight, and the battery can be transported in a normal air atmosphere. The sealing operation is completed by laser welding or electron beam welding of the upper surface of the liquid injection plug 20 and the flange 43 of the sealing screw plug 40 attached thereto.

Here, the thickness of the flange portion 43 is about 0.2 to 0.5 mm, whereby good hermeticity and welding strength can be obtained.

The LIB liquid injection part sealed in this way can reduce the number of parts used compared to the conventional liquid injection part shown in FIG. 2, simplify the structure, and simultaneously reduce the size.

In addition, LIB may decompose in the initial charge after electrolyte injection, generating decomposition gas of the electrolyte component and causing expansion of the battery case and internal components. After fastening the stopper screw cap 40, it can be transported in a normal air atmosphere. Therefore, after charging, the sealing screw stopper 40 is loosened in an inert gas atmosphere such as in a glove box, and the decomposition gas is discharged. Then, the expansion of the battery case can and the internal components are restored, the screw cap 40 for sealing is fastened again, and the collar portion 43 is attached to the upper surface of the liquid injection cap 20, and is then put into a normal atmosphere. LIB can be conveyed, and the flange 43 and the upper surface of the liquid injection stopper 20 can be welded together.

Furthermore, since the liquid injection device and the laser welding device can be separated, there is no need to increase the size of the device, and a general-purpose welding device can be used, so that the manufacturing cost can be greatly reduced. It plays.

DESCRIPTION OF SYMBOLS 1 Battery case cover 2 Through-hole 20 Injection plug 23 Lower cylindrical hole 24 Upper cylindrical hole 25 Injection hole 30 Ring packing 40 Sealing screw plug 43 Butt

Claims (1)

A through hole formed in the battery case lid of the lithium ion battery is composed of a lower insertion portion that is inserted into the through hole and an upper cylindrical portion that is larger than the lower insertion portion, and a screw portion on the inner peripheral surface of the lower insertion portion. The shape of the lower cylindrical hole and the upper cylindrical part that are formed are two-stage cylindrical holes with different diameters that are connected in sequence to the upper cylindrical hole having a larger inner diameter than the lower cylindrical hole. A liquid injection stopper made of a hollow metal having a liquid injection hole is attached, so that the through hole and the liquid injection hole are in communication with each other, and the fitting insertion portion at the lower part of the liquid injection stopper and the through hole are airtight. welded so, then lithium ion sealing screw plug having a flange portion at the upper end edge, by screwing the screw portion of the liquid injection plug inner surface via an annular packing flexibility in infusion fluid hole while an airtight batteries, especially to sealing by welding Chakuse' portion of the collar portion and the infusion liquid plug Pouring part way of the sealing lithium ion batteries to.