JP2002056828A - Nonaqueous electrolyte secondary battery, and electric double layer capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery that does not cause liquid leakage or degradation of a characteristic during storage. SOLUTION: A standing part in a groove of a gasket made of fluororesin having a U or J shaped groove is provided with a plurality of projections that do not reach a plat plane positioned on the lowest part or the bottom of the groove. The plat plane is formed on the bottom of the U or J shaped groove, and an angle between the plat plane and a standing surface standing from the plat plane is taken as radius 0.1 mm or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery in which a gasket interposed between a positive electrode case and a negative electrode case is compressed and sealed by caulking either the positive electrode case or the negative electrode case. . It is mainly a coin-type (button-type) battery, but the shape is not limited to a circle.

[0002]

2. Description of the Related Art Conventionally, coin-type (button-type) batteries, particularly non-aqueous electrolyte secondary batteries, are characterized by their high energy density and light weight, and their use as backup power supplies for equipment is increasing.

In a conventional coin-type (button-type) non-aqueous electrolyte secondary battery, the material of the gasket for maintaining the airtightness and liquid-tightness of the battery and the insulation of the positive and negative electrode cans is extremely important.

[0004] When used as a memory backup power supply, a soldering terminal is often welded to a printed circuit board together with a memory element after the terminal is soldered to the battery.

When soldering is performed on a printed circuit board using a soldering iron, the gasket material is excellent in chemical resistance, elasticity, and creep resistance, has good moldability, is injection-moldable, and is inexpensive. PP (polypropylene) has been used.

[0006] Solder cream or the like is applied in advance to a portion on the printed circuit board where soldering is to be performed, and a component is placed on the portion, or after placing the component, small solder balls are supplied to the soldered portion. A reflow process in which the solder is melted and soldered by passing the printed board on which the components are mounted in a furnace in a high-temperature atmosphere set so that the soldered portion has a temperature equal to or higher than the melting point of the solder, for example, 200 to 260 ° C. In soldering, fluorine resin has been studied as a gasket material in consideration of heat resistance.

[0007]

Since the airtightness between the gasket and the metal case is not always sufficient, it has been conventionally practiced to provide a U or J-shaped groove in the gasket and apply a liquid sealant to the groove in advance. I have been. PP
In a gasket using, there was no problem because the liquid sealant was sufficiently distributed, but when a fluororesin was used, the fluororesin had the property of repelling the liquid sealant,
The sealant was uneven, and the gasket and the metal case were not sufficiently airtight.

For this reason, there have been problems that the electrolyte inside the battery leaks to the outside and that the characteristics deteriorate during storage.

FIG. 2 shows a conventional PFA gasket coated with a sealant obtained by dissolving a butyl rubber-based adhesive in toluene. As the sealant uniformly applied at the beginning dries, places with a narrow coating width appear as shown in FIG. As time goes on, the place where the coating width is narrow expands, as shown in Figure 3.
A discontinuous portion is formed in the sealant applied in an annular shape. The electrolytic solution leaks from the discontinuous portion, or external moisture enters the inside of the battery, and significantly degrades battery characteristics.

[0010]

A plurality of projections or grooves are formed at the rising portions inside the grooves of a fluorine resin gasket having U or J-shaped grooves. The plurality of protrusions or grooves did not reach a flat surface located at the bottom or bottom of the U or J-shaped groove.

The U- or J-shaped groove has a flat surface at the bottom, and an angle with a surface rising from the flat surface is a radius of 0.1.
mm or less.

[0012]

FIG. 4 shows a gasket 108 according to the present invention in which a plurality of grooves 111 are provided at the rising portion inside the gasket groove, and a sealant 110 in which a butyl rubber-based adhesive is dissolved in toluene is applied. Was. In this case, the sealant enters the groove, and it is possible to suppress the spread of a narrow coating width as in the case of the conventional gasket. After more time, the solvent can be dried before the discontinuity is formed as shown in FIG. Desirably, the plurality of grooves located at the rising portion inside the gasket groove do not reach the flat surface located at the lowest portion or the bottom of the U or J-shaped groove. This is because the gasket is compressed most at the bottom portion and becomes an important position for maintaining airtightness.

As a result of various studies, it has been found that the number of grooves is more than five. When the number is five or less, the place where the coating width is narrow is widened due to vibration or the like, and a discontinuous portion is sometimes formed.

FIG. 6 shows a gasket according to the present invention in which a plurality of projections 112 are provided at the rising portion inside the gasket groove, and a sealant obtained by dissolving a butyl rubber-based adhesive in toluene is applied. In this case, the sealing agent enters on both sides of the projection, and it is possible to suppress the spread of the place where the coating width is small as in the case of the conventional gasket. After more time, the solvent can be dried before the discontinuous surface is formed as shown in FIG. It is also desirable that the plurality of times located at the rising portion inside the gasket groove does not reach the flat surface located at the lowest portion or the bottom of the U or J-shaped groove. As for the number of projections, 5 or more were good as in the case of the grooves.

FIG. 8 shows a flat surface 1 at the bottom of a U or J-shaped groove.
13 and an angle with a surface rising from a flat surface having a radius of 0.1.
The case where a sealant obtained by dissolving a butyl rubber-based adhesive in toluene was applied to a gasket of 05 mm was shown. The sealant accumulates at the corner between the bottom flat surface and the surface rising from the flat surface, and a discontinuous portion of the sealant was not formed unlike the conventional gasket. According to the results of the experiment, the corner radius was preferably 0.2 mm or less, more preferably 0.1 mm or less.

Hereinafter, the present invention will be described in more detail by way of examples.

[0017]

(Examples 1 to 3) In this example, MoO3 is used as a positive electrode active material and WO2 is used as a negative electrode active material. The positive electrode, the negative electrode, and the electrolyte prepared as described below were used. The battery had an outer diameter of 4.8 mm and a thickness of 1.4 mm. A cross-sectional view of the battery is shown in FIG.

In Example 1, a positive electrode was manufactured as follows. Commercially available MoO3 is pulverized with graphite as a conductive agent and polyacrylic acid as a binder in a weight ratio of MoO3: graphite: polyacrylic acid = 53: 4.
The mixture was mixed at a ratio of 5: 2 to form a positive electrode mixture, and then 5 mg of the positive electrode mixture was press-formed at 2 ton / cm 2 into pellets having a diameter of 2.4 mm. Thereafter, the positive electrode pellet 101 thus obtained is bonded to and integrated with the positive electrode case 103 using the electrode current collector 102 made of a conductive resin adhesive containing carbon (a positive electrode unit). The resultant was dried by heating under reduced pressure for 8 hours.

The negative electrode was manufactured as follows. Commercial W
The crushed O2 was used as the active material of the working electrode. This active material was mixed with graphite as a conductive agent and polyacrylic acid as a binder at a weight ratio of 45:40:15 to obtain a negative electrode mixture. 2.6mg of mixture in 2 to
A pellet formed by pressing into a 2.4 mm diameter pellet at n / cm 2 was used. Thereafter, the negative electrode pellet 104 thus obtained is bonded to and integrated with the negative electrode case 105 using the electrode current collector 2 made of a conductive resin adhesive containing carbon as a conductive filler (a negative electrode unit). 8 at 250 ° C
It was dried by heating under reduced pressure for hours. Further, a punched lithium foil 106 having a diameter of 2 mm and a thickness of 0.22 mm was pressed on the pellet to obtain a lithium-negative electrode pellet laminated electrode.

A nonwoven fabric made of glass fiber having a thickness of 0.2 mm was dried and punched out to a diameter of 3 mm to form a separator 109. The gasket 108 is made of PFA, and is a sealant 110 obtained by dissolving a butyl rubber-based adhesive in toluene.
Was applied. The electrolyte solution 107 has a volume ratio of ethylene carbonate (EC): γ-butyrolactone (γBL) of 1:
6 μL of 1 mol / l lithium borofluoride (LiBF 4) dissolved in one mixed solvent was placed in a battery can. A battery was produced by stacking and closing the positive electrode unit and the negative electrode unit.

A battery manufactured by this method, using the gasket having the conventional structure shown in FIG.
Example 1 used a gasket in which a plurality of grooves were provided at the rising portion inside the gasket grooves shown in FIG.

The second embodiment uses a gasket provided with a plurality of projections at the rising portion inside the gasket groove shown in FIG. Example 3 used a gasket having a corner radius of 0.05 mm between the bottom flat surface and the surface rising from the flat surface shown in FIG.

In order to check whether the batteries can withstand the reflow temperature for each of the ten batteries manufactured as described above,
A reflow test was performed by heating at 180 ° C. for 10 minutes and at 240 ° C. for 1 minute. The heated sample was measured for battery height, internal resistance, and cycle characteristics to check for swelling. Height was measured using a dial gauge. The internal resistance was measured by an AC method (1 kHz). The charge and discharge conditions in the cycle characteristics are as follows: charge is a maximum current of 0.05 mA, a constant voltage value of 3.3 V, and a charge time of 2
0 hour constant current constant voltage method, discharge is 0.025 m
The test was performed at a constant current of A and a final voltage of 1.8 V. Leakage was visually performed using a 5 × stereo microscope.

The results are shown in Table 1.

[0025]

[Table 1]

In Table 1, ◎ indicates good characteristics, は indicates no problem in practical use, △ indicates slight swelling of the battery and increases internal resistance, and × indicates problems in characteristics and is on a practical level. Not something.

The swelling of the batteries of Examples 1 to 3 was all 0.
The level was no problem at 03 mm or less. After the reflow test, the internal resistance was within the range of ± 20% before the test and was at a level without any problem. Good results were also shown in the cycle test. No liquid leakage was observed.

On the other hand, in the battery of the comparative example, liquid leakage was observed, and although there was no swelling of the battery, there were some batteries which were not at practical levels in all characteristics. It is considered that when the discontinuous portion is formed on the sealant-applied surface, moisture and the like enter into the inside and the characteristics are deteriorated. (Examples 4 to 6) Next, examples using an electric double layer capacitor will be described. The size of the electric double layer capacitor is 4.8m in outer diameter
m, and the thickness was 1.4 mm. The sectional view is almost the same as FIG. 1 except for the lithium foil 106.

The positive electrode and the negative electrode were produced as follows. Activated carbon 80% by weight, conductive carbon black 10
% By weight and 10% by weight of polytetrafluoroethylene as a binder, and a powder compact is obtained at a molding pressure of 500 kg / cm <2>.

A mixture of 80% by weight of activated carbon, 10% by weight of carbon black as a conductive material, and 10% by weight of polytetrafluoroethylene as a binder was pressed at a molding pressure of 500 kg / cm 2 to obtain a thickness of 0.4.
A positive electrode pellet 101 having a diameter of 2.4 mm and a diameter of 2.4 mm was obtained.
Thereafter, the positive electrode pellet 101 thus obtained is bonded to and integrated with the positive electrode case 103 using the electrode current collector 102 made of a conductive resin adhesive containing carbon (a positive electrode unit). The resultant was dried by heating under reduced pressure for 8 hours.

Similarly, 80% by weight of activated carbon, 10% by weight of carbon black as a conductive material, and polytetrafluoroethylene 1 as a binder
0 wt% was mixed and subjected to a molding pressure of 500 kg / cm 2 to obtain a negative electrode pellet 104 having a thickness of 0.4 mmt and a diameter of 2.1 mm.

Thereafter, the negative electrode pellet 104 thus obtained was bonded and integrated with a negative electrode case 105 using an electrode current collector 2 made of a conductive resin adhesive containing carbon as a conductive filler (a negative electrode unit). ), And dried by heating under reduced pressure at 250 ° C for 8 hours. After drying a non-woven fabric made of glass fiber having a thickness of 0.2 mm, the separator
It was set to 9. The gasket 108 was made of PFA, and a sealant 110 in which a butyl rubber-based adhesive was dissolved in toluene was applied. The electrolyte 107 has a boiling point of about 240
6 μL of 1 mol / L tetraalkylammonium tetrafluoroborate dissolved in a propylene carbonate (abbreviated PC) solvent at a temperature of 6 ° C. was placed in an electric double layer capacitor can. The electric double layer capacitor was manufactured by stacking and closing the positive electrode unit and the negative electrode unit.

An electric double layer capacitor manufactured by this method, which uses the gasket having the conventional structure shown in FIG. Example 4 used a gasket in which a plurality of grooves were provided at the rising portion inside the gasket grooves shown in FIG. Example 5 used a gasket provided with a plurality of protrusions at the rising portion inside the gasket groove shown in FIG. Example 6 used a gasket having a corner radius of 0.05 mm between the bottom flat surface and the surface rising from the flat surface shown in FIG.

In order to check whether each of the ten electric double layer capacitors manufactured as described above can withstand the reflow temperature, preheating was performed at 180 ° C. for 10 minutes, heating was performed at 240 ° C.
A reflow test was performed by heating for 1 minute. The heated sample was subjected to a height measurement, an internal resistance measurement, and a cycle characteristic measurement in order to examine the swelling. Height was measured using a dial gauge. Internal resistance is AC method (1kHz)
Was performed. The charge and discharge conditions in the cycle characteristics are as follows: charge is a maximum current of 0.5 mA, a constant voltage value of 2.5 V, and a charge time of 5
Discharge was performed at a constant current of 0.05 mA and a final voltage of 0 V using a constant current constant voltage method for a time. Leakage was visually performed using a 5 × stereo microscope.

The results are shown in Table 2.

[0036]

[Table 2]

In Table 2, ◎ indicates good characteristics, は indicates no problem in practical use, △ indicates slight swelling of the battery and increases internal resistance, and × indicates problems in characteristics and is on a practical level. Not something.

The swelling of the electric double layer capacitors of Examples 4 to 6 was 0.03 mm or less, which was a level without any problem. After the reflow test, the internal resistance was within the range of ± 20% before the test and was at a level without any problem. Good results were also shown in the cycle test. No liquid leakage was observed.

On the other hand, in the electric double layer capacitor of Comparative Example 2, although liquid leakage was observed and there was no swelling, there were some which were not at practical levels in all characteristics. It is considered that when a discontinuous portion was formed on the sealant-applied surface, moisture or the like penetrated into the inside similarly to Comparative Example 1, and the characteristics were deteriorated.

When the sealant was applied such that a discontinuous portion was formed as in the comparative example, the characteristics were more deteriorated than when the sealant was not applied.

Further, by applying a sealant to the gasket, the reaction between the negative electrode and the fluororesin could be suppressed, and the reliability in long-term storage could be improved.

[0042]

As described above in detail, according to the present invention, by devising the shape of the gasket, it is possible to uniformly apply the liquid sealant which could not be applied uniformly to the conventional fluorine-based gasket. became. As a result, the characteristics of batteries and capacitors after reflow and the characteristics after storage can be significantly improved.

[Brief description of the drawings]

FIG. 1 is a sectional view of a coin-type lithium secondary battery of the present invention.

FIG. 2 shows a conventional gasket.

FIG. 3 shows a conventional gasket.

FIG. 4 shows a gasket of the present invention.

FIG. 5 shows a gasket of the present invention.

FIG. 6 shows a gasket of the present invention.

FIG. 7 shows a gasket of the present invention.

FIG. 8 shows a gasket of the present invention.

FIG. 9 shows a gasket of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 101 Positive electrode pellet 102 Electrode collector 103 Positive electrode case 104 Negative electrode pellet 105 Negative electrode case 106 Lithium foil 107 Electrolyte solution 108 Gasket 109 Separator 110 Sealant 111 Groove 112 Projection 113 Flat surface

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shinichi Takasugi 45-1 Matsubara, Kami-Aiko, Aoba-ku, Sendai, Miyagi Prefecture Within SII Microparts Co., Ltd. 45-1 Matsubara, Kami-Aiko Character F-term (reference) in SII Micro Parts Co., Ltd. 5H011 AA17 DD15 FF03 GG02 GG05 HH02 JJ04 JJ15 KK03

Claims (7)

[Claims] 1. A battery in which a gasket interposed between a positive electrode case and a negative electrode case is compressed and sealed by caulking one of the positive electrode case and the negative electrode case. A battery having a J-shaped groove, wherein a plurality of protrusions or grooves are formed at a rising portion inside the gasket groove. 2. The battery according to claim 1, wherein the fluororesin is PFA (tetrafluoroethylene-perfluoroalkylvinyl ether copolymer resin). 3. The U-shaped gasket made of a fluororesin.
2. The battery according to claim 1, wherein a liquid sealant is previously applied to the J-shaped groove. 4. A plurality of protrusions or grooves located at a rising portion inside the gasket groove do not reach a flat surface located at a lowermost portion or a bottom of a U-shaped or J-shaped groove. Item 7. The battery according to Item 1. 5. The battery according to claim 1, wherein the number of the plurality of protrusions or grooves located at the rising portion inside the gasket groove is five or more. 6. In a battery in which a gasket interposed between a positive electrode case and a negative electrode case is compressed and sealed by caulking either the positive electrode case or the negative electrode case, the gasket made of fluororesin is U or A battery having a J-shaped groove, a flat surface at the bottom of the U-shaped or J-shaped groove, and a corner with a surface rising from the flat surface having a radius of 0.2 mm or less. 7. The U-shaped gasket made of a fluororesin.
7. The battery according to claim 6, wherein a liquid sealant is previously applied to the J-shaped groove.