JP2000030675A - Secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high quality secondary battery, which is provided with a high sealing property and durable against long-term use, by accomplishing hermetically sealing structure between a base cylindrical part inside a cylindrical metallic case and a cylindrical part outside a lid and between a case opening end curling in an expanded tube cylindrical stepped part and a flange part of the lid. SOLUTION: A cylindrical metallic case 20 is formed of a base cylindrical part 20a and an expanded tube cylindrical part 20b formed by expanding an opening end side in diameter, while in a plastic lid 21, a cylindrical part 21b provided with a disc type flange part 21a and a groove 21c is arranged. In this structure, the lid 21 is inserted through an opening end of the metallic case 20 so as to be press-fitted inside the base cylindrical part 20a of the metallic case 20 via an elastic body O-ring 17 arranged inside the groove 21c in the cylindrical part 21b of the lid 21, so that the metallic case 20 and the lid 21 are sealed together hermetically by means of compressing force of the O-ring 17. In addition, the disc type flange part 21a of the lid 21 is arranged in a stepped part 20d in the expanded tube cylindrical part 20b of the metallic case 20, and the case 20 and the lid 21 are compressedly sealed together hermetically via an elastic packing 18 by means of a curling 20e in the case opening end.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply for a mobile device such as an electric car or an electric cart, a backup device at the time of a power failure, a power storage device, and a security device. The present invention relates to a sealed structure for preventing electrolyte from leaking from a battery case of a medium-sized and large-sized electrolyte-filled secondary battery.

[0002]

2. Description of the Related Art As shown in FIG. 2, a conventional battery case of an electrolyte secondary battery has a sealed structure in which a wound electrode group 30 composed of a positive electrode, a negative electrode and a separator is provided in a cylindrical metal case 32, as shown in FIG. A stepped portion 32a is formed by necking near the opening end of the cylindrical metal case, and a metal sealing plate 33 with a safety device connected to one electrode is made of a gasket 34 of a polymer material such as polypropylene (PP). With the stepped portion and the crimp 32b at the end of the case opening being compressed and fixed.

[0003] For medium and large-sized batteries, see Japanese Patent Application Laid-Open No. 9-9 / 1997.
As described in Japanese Patent Publication No. 2241, referring to FIG. 3, a metal perforated cap 43 as a sealing plate is welded all around the open end of the cylindrical metal case 42, and the periphery of the cap hole is made of polypropylene or the like. Through a ring 44 of polymeric material,
The both sides of the hole are electrically insulated by being sandwiched by a washer 45 made of a ceramic material.
6 is inserted through the cap hole, and a nut 48 is screwed into the mandrel male screw portion 46b of the electrode terminal penetrating through the O-ring 47 between the internal disk portion 46a of the electrode terminal and the cap from the external ceramic washer side. The part was pressed against the cap to compress and seal the O-ring.

[0004]

However, in the method of crimping the sealing plate through a gasket made of a polymer material, as shown in the above-mentioned example of the small battery, the gasket made of a plastic material such as PP having a small elastic range is made of an elastic material. Since the plastic is held in a compressed state, the plastic may creep due to long-term use, or the difference in the thermal expansion coefficient between the plastic material and the metal case or sealing plate in the normal operating temperature range, for example, -30 ° C to 60 ° C. As a result, a gap was formed in the seal portion, and the electrolyte sometimes leaked. Also, after inserting the wound electrode group into the case in the battery assembling process, the stepped portion holding the sealing plate is necked, and the case opening end is crimped, so that the electrode group is not damaged. The sealing work was troublesome, and it was also difficult to control the processing of the compressed size of the gasket as the sealing member.

Japanese Patent Application Laid-Open No. 9-92241 discloses a non-elastic metal sealing plate cap and a ceramic washer sandwiching the cap, which are screw-fastened to a disc-shaped electrode terminal with a mandrel via an O-ring and a nut. In addition, the sealing property of the battery case is left only to the fastening frictional force of the screw. Therefore, there is a concern that the screw fastening portion may be loosened due to vibration during use or repeated heat and cold, and the electrolyte may leak. Furthermore, there is a problem in that the O-ring is swelled and deformed by being eroded by the electrolytic solution due to use for a long period of time, and loses elasticity and impairs the sealing property. When the electrolyte leaks and the electrolyte in the battery runs short, the charging capacity is reduced and the battery life is shortened. In addition, the leaked electrolyte is corrosive and corrodes the battery container and peripheral devices. Occurs.

The present invention has been made in view of the above-mentioned problems of the prior art, and has as its object to provide a highly productive and highly sealable battery case and lid sealing structure for long-term use. An object of the present invention is to provide a high quality secondary battery that can withstand.

[0007]

According to the present invention, in order to achieve the above object, a power generating element comprising an electrode group formed by winding a strip-shaped positive electrode and a negative electrode through a separator and an electrolytic solution is placed in a cylindrical metal case. In a secondary battery that is housed and sealed with a plastic lid via a sealing material, the cylindrical metal case is provided with a base cylindrical part and an expanded tubular part near the opening end of the power generation element storage part, while the plastic lid is placed inside. A cylindrical portion and a disk-shaped flange on its outer periphery are compression-sealed through an elastic O-ring between the inside of the base cylindrical portion of the case and the outside of the cylindrical portion of the lid. The lid is fixed by compression-sealing with a lid flange and an elastic packing interposed between the part and the case opening end curling.

Further, the secondary battery of the present invention is the secondary battery having the above-described structure in which a groove for accommodating an elastic O-ring is formed in a cylindrical outer peripheral portion of a plastic lid.

Further, the secondary battery of the present invention is the secondary battery having the above-mentioned configuration, wherein the elastic O-ring and the elastic packing are made of ethylene propylene diene rubber (EPDM) or fluorine rubber.

According to the present invention, O is radially provided between the inside of the base cylindrical portion of the cylindrical metal case and the outside of the cylindrical portion of the lid.
Independent double sealing structure with a first sealing structure in which the ring is compressed by a compression seal and a second sealing structure in which the flange of the lid is axially compressed between the expanded cylindrical step portion and the case opening end curling via packing. As a result, a secondary battery having improved sealing properties and withstanding long-term use can be provided.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a secondary battery according to the present invention will be described below with reference to the drawings, taking a lithium ion secondary battery as an example. FIG. 1 is a structural vertical sectional view showing an embodiment of a secondary battery of the present invention, and a dashed line in the figure is a sectional view before curling an open end of a cylindrical metal case. In FIG. 1, reference numeral 1 denotes a positive electrode, and a positive electrode mixture 3 (for example, as an active material) using an inorganic lithium intercalation / deintercalation material as a positive electrode active material on both surfaces of a positive electrode current collector 2 made of a strip-shaped aluminum foil. LiMn ₂ O ₄ ,
Carbon as a conductive material such as LiCoO ₂ and LiNiO ₂ ;
(Polyvinylidene fluoride mixed and adjusted as a binder) is applied and pressed and held.

Reference numeral 4 denotes a negative electrode, and a negative electrode mixture 6 (for example, as an active material) using a lithium intercalation / deintercalation carbon material as a negative electrode active material on both surfaces of a negative electrode current collector 5 made of a strip-shaped copper foil. A mixture of graphite, amorphous carbon, and polyvinylidene fluoride as a binder)
Is applied and pressed.

Reference numeral 7 denotes a separator made of a microporous thin film or a nonwoven fabric of a thermoplastic resin such as polyethylene or polypropylene. When the temperature of the polyethylene film rises, the shutdown start temperature at which the micropores close due to melting of the film itself is about 130 ° C., and the shutdown start temperature of the polypropylene film is about 150 ° C. In other words, when the temperature of the battery rises due to an abnormal state such as an internal short circuit or an external short circuit, the thermoplastic resin of the separator melts, causing microporous or nonwoven fabric to be clogged, thereby blocking the movement of ions between the positive and negative electrodes. Has the function of interrupting the battery current and protecting the battery.

The positive electrode 1 and the negative electrode 4 are spirally wound in a state where they face each other with a separator 7 interposed therebetween, thereby forming an electrode group 10. In this case, the separator 7 is composed of the positive electrode 1 and the negative electrode 4
The separator 7 is wound a few times more at the core and the end of the winding to provide electrical insulation between the positive electrode and the negative electrode and around the electrode group. The electrode group 10 is immersed in an electrolytic solution (not shown) to become a power generating element.

The above-mentioned electrolytic solution is composed of LiPF ₆ , LiBF ₄ , L
A solution in which a lithium salt such as iClO ₄ or LiAsF _{6 is} dissolved as an electrolyte in an organic solvent (single or a mixture of propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, etc.) is used.

20 is stainless steel, nickel-plated iron,
A cylindrical metal case made of a metal such as nickel-plated copper or aluminum, a base cylindrical portion 20a in which the electrode group 10 and a power generation element made of an electrolytic solution are housed, and an expanded cylindrical portion 20b having a larger diameter at the opening end. Has formed. Further, a safety valve 22 having a weak portion such as a cut groove is provided at the bottom 20c of the case. The safety valve 22 is opened when the pressure inside the battery case becomes high due to an abnormal temperature rise. To prevent.

The operating pressure of the safety valve 22 is determined by the temperature inside the sealed battery case and the pressure resistance of the sealed case / lid structure, and is preferably about 10 kg / cm ² at which the safety valve is opened first. Reference numeral 21 denotes a plastic lid, which has a disk-shaped flange 21a on the outside, a cylindrical portion 21b on the inside, and a cylindrical portion 2b.
There is a groove 21c for installing the O-ring 17 on the outer periphery of 1b. The lid 21 needs heat resistance and electrolytic solution resistance, and is preferably made of thermosetting phenol resin or thermoplastic resin polyphenylene sulfide (PPS).

The lid 21 is inserted from the opening end of the cylindrical metal case 20 and is inserted into the base cylindrical portion 20a of the case 20 through an elastic O-ring 17 installed in the groove 21c of the cylindrical portion 21b of the lid 21. The case 20 and the lid 21 are sealed by press-fitting and the compressive force of the O-ring. Further, the disc-shaped flange 21 a of the lid 21 is provided with the stepped portion 20 of the expanded tubular portion of the case 20.
The case 20 and the cover 21 are compressed and hermetically sealed by the curling 20e at the open end of the case via the elastic packing 18. The elastic O-ring 17 and the packing 18 are preferably made of a rubber material such as ethylene-propylene-diene rubber (EPDM) or fluorine-based rubber which has an electrolytic solution resistance and a large elasticity range.

The injection tube 16 for injecting the electrolytic solution consisting of the positive electrode terminal 14, the negative electrode terminal 15 and the copper tube penetrates the lid 21 and is hermetically sealed by insert molding. In addition, an insulating plate 13 is provided on the side of the can bottom portion 20c in the case 20 in order to maintain electrical insulation between the battery charging section and the case. The insulating plate is perforated where the safety valve is located so as not to hinder the operation of the safety valve.

Reference numeral 8 denotes a strip-shaped positive electrode lead of aluminum material, which is connected to the positive electrode current collector 2 of the positive electrode 1 and the positive electrode terminal 14 of aluminum material by welding or the like. Reference numeral 9 denotes a strip-shaped nickel or copper negative electrode lead, which is connected to the negative electrode current collector 5 of the negative electrode 4 and the nickel or copper negative electrode terminal 15 by welding or the like. It should be noted that a single positive electrode lead 8 and a negative electrode lead 9 cannot provide a sufficient current capacity for a medium or large battery, so that a plurality of lead wires must be connected.

Reference numeral 12 denotes a cylindrical insulating destant;
A separating plate 12a for insulating and separating the positive electrode lead 8 and the negative electrode lead 9 is provided in the cylinder between the electrode group 10 and the lid 21 to secure an independent space for accommodating each electrode lead wire, and the electrode group 10 is provided inside the battery case. And hold it so that it does not move.
Therefore, the plurality of positive electrode leads 8 and negative electrode leads 9 are separated from each other by the separation plate 12a, and the insulation is maintained without contact.

Next, a method for manufacturing and assembling the secondary battery according to the present invention will be described. The cylindrical metal case 20 is made into a bottomed cylindrical can by impact molding or deep drawing, and then the opening end is expanded by pressing or the like, and the dimensions from the stepped portion to the opening end are determined and the end surface is cut. . Further, the weak point is stamped on the bottom 20c of the can with a press to release the safety valve 2.
Make 2. In other words, since all cases other than curling are processed in the state of the raw can, a case having high dimensional accuracy and good assembling efficiency can be obtained.

The lid 21 is formed by plastic insert molding with the positive and negative electrode terminals 14 and 15 and the injection tube 16 penetrating both sides of the lid 21 to seal and fix the electrode terminal and the injection tube. That is, the positive / negative electrode terminals 14 and 15 and the injection tube 16 maintain the hermeticity with the plastic lid 21 and are manufactured at low cost by integral injection molding. An O-ring 17 is provided in a groove provided on the outer periphery of the cylindrical portion 21b of the lid.

The battery is assembled by a strip-shaped positive electrode 1 and a negative electrode 4.
Are wound spirally through the separator 7 and the positive electrode lead 8 and the negative electrode lead 9 are attached to the current collector of each electrode by spot welding or ultrasonic welding, and are wound up. The outer periphery of the wound electrode group 10 is fixed with a tape or the like, and the positive electrode lead and the negative electrode lead are bundled in one row, respectively, and connected to the positive terminal 14 and the negative terminal 15 fixed to the lid 21 by welding or the like.

Next, the insulating plate 13 and the electrode group 1 are placed in the case.
0, insert the insulated distant 12 and cover 21
The flange 21a is pressed into the open end of the cover until the flange 21a hits the step 20d, and is sealed and fixed to the disc-shaped flange 21a of the lid via the packing 18 only by curling.

Therefore, there is little fear of damaging the electrode group insulated by the thin separator in the operation after the electrode group 10 is placed in the case 20, and the work yield is good.
Finally, an electrolytic solution is injected from the injection pipe 16, the end of the injection pipe is crushed by a press to close the end, and the tip of the injection pipe is welded and sealed.

[0027]

As described above, according to the present invention, since the cylindrical metal case 20 is provided with the expanded cylindrical portion 20b having a larger diameter in the base cylindrical portion 20a by the expanding tube press, the cover 21 for fixing the lid 21 is provided. Since the stepped portion 20d is already formed in a raw can state, in the assembling process, it is not necessary to perform a necking process for reducing the diameter of the cylindrical case for fixing the lid after inserting the electrode group 10 into the case 20. Furthermore, since the length of the expanded tubular portion for curling the lid in the raw can state is determined and cut, the dimensional accuracy of the curling is good and the sealing quality of the curling portion is improved.

The lid 21 is provided with a cylindrical portion 21b on the inner side and a disk-shaped flange portion 21a on the outer side. The first seal is made between the case 20 and the lid 21 by the inner side of the case base cylindrical portion 20a and the lid cylindrical portion 21b. The elastic O-ring 17 is compressed in the radial direction between them, and the second sealing is performed by installing the disc-shaped flange 21a on the case step 20d and curling the expanded cylindrical portion 20b via the elastic packing 18 with the curling 20e. Since it is processed and compressed and sealed in the axial direction, the sealing structure becomes an independent double structure, and the sealing reliability is improved. Since the electrolyte is sealed by the seal of the first O-ring, and the electrolyte does not normally come into contact with the second packing seal portion, the proof life of the rubber elastic body with respect to the electrolyte is greatly extended. Even if the first O-ring seal is broken, the sealing performance is maintained only by the second packing seal, and there is no problem in battery characteristics.

Further, an O-ring 1 is provided on the outer periphery of the lid cylindrical portion 21b.
Since the groove 21c for accommodating the O-ring 7 is provided, the O-ring can be prevented from coming off the cylindrical portion of the lid, and the wall of the groove 21c functions as a backup ring even when the O-ring is swollen and deformed by the electrolytic solution. And has the function of preventing deformation of the O-ring and maintaining the seal by elasticity.

Further, since the metal case is deformed by plastic working curling and the lid is fixed, the metal case does not loosen due to vibration or the like due to long-term use. In addition, the material of the elastic O-ring and the elastic packing is made of ethylene-propylene-diene rubber (EPD) having a wide elastic range and resistance to electrolyte.
Since M) or fluorine rubber is used, a large allowable range of the compression dimension can be taken, and the seal is hardly swelled in the electrolytic solution, and a stable elasticity with little creep deformation can be obtained for a long period of time. Therefore, the hermeticity of the electrolyte secondary battery used for a long time is remarkably improved, the life of the battery is extended, and stable battery characteristics are obtained.

[Brief description of the drawings]

FIG. 1 is a structural sectional view showing one embodiment of a secondary battery of the present invention.

FIG. 2 is a cross-sectional view showing a conventional example of a closed structure by a clamp method via a gasket.

FIG. 3 is a cross-sectional view showing a conventional example of a hermetically sealed structure formed by screwing an O-ring.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Positive electrode, 2 ... Positive electrode collector, 3 ... Positive electrode mixture, 4 ... Negative electrode,
5 ... negative electrode current collector, 6 ... negative electrode mixture, 7 ... separator, 8 ...
Positive electrode lead, 9 ... Negative electrode lead, 10 ... Electrode group, 12 ... Insulating distant, 12a ... Separating plate, 13 ... Insulating plate, 14 ...
Positive electrode terminal, 15: negative electrode terminal, 16: injection tube, 17, 47
... O-ring, 18 ... Packing, 20 ... Case, 20a ...
Base cylindrical part, 20b ... expanded cylindrical part, 20c ... can bottom part, 20
d step, 20e curling, 21 lid, 21a disk-shaped flange, 21b cylindrical part, 21c groove part, 22 safety valve, 30, 40 wound electrode group, 31, 41 lead, 3
2, 42 ... cylindrical metal case, 32a ... necking stepped portion, 32b ... crimp, 33 ... sealing plate, 34 ... gasket, 43 ... cap, 44 ... ring, 45 ... ceramic washer, 46 ... electrode terminal, 46a ... circle Plate part, 46b ...
Mandrel male thread, 48 nut.

Claims (3)

[Claims] 1. A secondary battery in which a power generating element comprising an electrode group formed by winding a strip-shaped positive electrode and a negative electrode with a separator interposed therebetween and an electrolytic solution is housed in a cylindrical metal case and sealed with a plastic lid. In the above, the cylindrical metal case is provided with a base cylindrical portion of the power generation element storage portion and an expanded tube portion near the opening end, while the plastic lid is formed of a cylindrical portion on the inside and a disk-shaped flange on the outer periphery thereof, The inside of the base cylindrical portion and the cylindrical portion of the lid are compressed and hermetically sealed via an elastic O-ring, and further, the flange portion of the lid and the elastic portion are provided between the stepped portion of the expanded tubular portion of the case and the curling at the end of the case opening. A secondary battery comprising a body packing, compression-sealing, and a lid fixed. 2. The secondary battery according to claim 1, wherein a groove for accommodating an elastic O-ring is formed in a cylindrical outer peripheral portion of the plastic lid. 3. The secondary battery according to claim 1, wherein the elastic O-ring and the elastic packing are made of ethylene propylene diene rubber (EPDM) or fluorine rubber.