JPH08102313A - Nonaqueous electrolytic secondary battery - Google Patents

Abstract

PURPOSE: To reduce material cost and enhance the reliability of a positive terminal by using a material having austenite and ferrite structure at normal temperature in the positive terminal and fixing a positive electrode to a battery cover or a battery can by caulking. CONSTITUTION: A positive terminal 23 is made of two phase stainless steel comprising austenite and ferrite structure at normal temperature, and enveloped together with a negative electrode 3 and a separator 8. The negative electrode 3, the separator 8, a positive electrode 2, and the separator 8, and the negative electrode 3 are mutually stacked in order to form an electrode stacked body. The positive electrode 2 is fixed to a battery cover 21 or a battery can by caulking. Then they are put in a flat type battery container 10 and an electrolyte prepared by dissolving a lithium salt serving as an electrolyte in an organic solvent is poured in the container 10. Since two phase stainless steel is used and the positive electrode is fixed by caulking, cost is reduced, leakage resistance is ensured to the shock such as falling down, and a battery with high reliability can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous electrolyte secondary battery suitable for use as a power source for portable electronic equipment such as laptop computers, cellular phones, 8 mm video and audio equipment.

[0002]

2. Description of the Related Art In recent years,
The development of portable electronic devices such as laptop computers, cellular phones, 8 mm video and audio devices has been remarkable, and due to the progress of electronic technology, these portable electronic devices have become smaller, lighter and thinner. As devices become smaller, lighter, and thinner, batteries used as power sources are required to be smaller, lighter, thinner, and have higher energy density. Up to now, aqueous secondary batteries such as lead batteries and nickel-cadmium batteries have been used, but they cannot be said to be sufficient for the demands for weight reduction and high energy.

Recently, it has a high energy density and
There is great interest and expectation for lithium secondary batteries as clean batteries.

As a non-aqueous electrolyte secondary battery which has been put into practical use at present, a carbon material capable of doping and dedoping lithium Li is used as a negative electrode, and lithium composite oxide such as lithium cobalt oxide and lithium nickel oxide is used. There is a lithium-ion secondary battery using an object as a positive electrode, and in recent years, active research and development has been conducted.

By optimizing the capacity design of the positive and negative electrodes, this lithium ion secondary battery is free from the formation of Li dendrite seen in a battery system using lithium metal, and has excellent cycle characteristics and safety, Furthermore, it has excellent low-temperature characteristics, load characteristics, and quick charging characteristics, and is highly anticipated, and it is used as a power source for portable electronic devices such as laptop computers, cellular phones, 8 mm video, and audio devices. .

The non-aqueous electrolyte secondary battery such as the lithium ion secondary battery is characterized in that the operating voltage of the battery is high. This is a factor that has a higher energy density than the conventional aqueous battery. However, in a battery with a high operating voltage, the positive electrode terminal has a problem of electrochemical dissolution, and usable materials are limited to noble metals such as aluminum Al, stainless steel SUS and platinum.

It is not preferable to use the noble metal such as platinum for the positive electrode terminal because the noble metal such as platinum is expensive and practical.

On the other hand, the structure of the positive electrode terminal is generally a hermetically sealed system, but this hermetically sealed system has a disadvantage that it is expensive.

As a structure of this positive electrode terminal, a method of crimping an Al pin to a battery lid via an insulator has been proposed. In the case of this crimping method, by crimping the Al pin, the insulator interposed between the Al pin and the battery lid is compressed to prevent liquid leakage from the positive electrode terminal portion.

When an Al material is used as the positive electrode terminal, the Al material is soft and excellent in workability, but inferior in impact resistance due to the softness, and is partially damaged by the impact such as dropping. There is an inconvenience in that the compressibility is lowered and liquid leakage is often caused, and there is a problem in reliability.

In view of the above point, the present invention proposes a non-aqueous electrolyte secondary battery having a highly reliable positive electrode terminal structure made of a practical material.

[0012]

In the non-aqueous electrolyte secondary battery of the present invention, as shown in FIGS. 1 and 2, for example, the material of the positive electrode terminal 23 is a duplex stainless steel composed of austenite and a ferrite structure at room temperature. The positive electrode terminal 23 is attached to the battery lid 21 or the battery can via the insulator 22 by the caulking method.

[0013]

According to the present invention, the positive electrode terminal 23 is made of a duplex stainless steel composed of austenite and a ferrite structure at room temperature, and the positive electrode terminal 23 is attached to the battery lid 21 or the battery can by the caulking method. Moreover, it is possible to obtain a highly reliable liquid leak.

[0014]

Embodiments of the non-aqueous electrolyte secondary battery of the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 10 designates a closed oblong battery container made of, for example, a stainless steel plate having a thickness of 300 μm and having a thickness of 8.3 mm, a width of 34 mm and a height of 48 mm.
A predetermined number of positive electrodes 2 and negative electrodes 3 are placed in the separator 8
The laminated body alternately laminated is accommodated.

As the negative electrode 3, as shown in FIGS. 1 and 3, a copper Cu foil (or nickel Ni foil) having a rectangular thickness of about 10 μm and having a predetermined size corresponding to the internal shape of the flat rectangular battery container 10 is used. Lithium Li on both sides of the current collector 7 composed of
A carbon material capable of doping and dedoping is deposited as the negative electrode active material 6.

The carbon material as the negative electrode active material 6 may be any material that can be doped with lithium Li and dedoped.
Pyrolytic carbons, cokes (pitch cokes, needle cokes, petroleum cokes, etc.), natural graphites, artificial graphites, glassy carbons, organic polymer compound sintered bodies, carbon fibers, activated carbon and the like can be used. Preferably, a carbon material having a (002) plane spacing of 3.70 Å or more and a true density of less than 1.70 g / cc and having no exothermic peak at 700 ° C. or more in a differential thermal analysis in an active air stream is used.

As a specific example of the negative electrode 3, petroleum pitch is used as a starting material, and a functional group containing oxygen is added to the negative electrode 3.
A non-graphite carbon material obtained by introducing 0 to 20% (oxygen crosslinking) and then firing at 1000 ° C. in an inert gas stream is used as a negative electrode active material. 90 parts by weight of the powder of the non-graphite carbon material and 10 parts by weight of polyvinylidene fluoride as a binder were mixed, and the mixture was dispersed in N-methyl-2-pyrrolidone to form a slurry, which was used as a negative electrode active material. As No. 6, the negative electrode 3 was obtained by coating, drying, and pressing on both sides of a current collector 7 made of Cu foil having a thickness of about 10 μm and cutting into a predetermined shape.

As the positive electrode 2, as shown in FIGS. 1 and 3, both sides of a current collector 5 made of aluminum Al foil having a width and height slightly smaller than the negative electrode 3 and a thickness of about 20 μm. In addition, a complex oxide of lithium Li and a transition metal, for example, a carbonate of lithium, cobalt, or nickel is used as a starting material, and these carbonates are mixed according to the composition and mixed in an oxygen-existing atmosphere.
What is obtained by firing in the temperature range of 0 to 1000 ° C. is applied as the positive electrode active material 4. In this case, the starting material is not limited to carbonate, but may be oxide or hydroxide.

As a specific example of the positive electrode 2, LiCoO ₂ prepared by mixing cobalt carbonate and lithium carbonate so that Li: Co becomes 1: 1 and firing in air at 900 ° C. for 5 hours. 91 parts by weight, 6 parts by weight of graphite as a conductive agent, and 3 parts by weight of polyvinylidene fluoride as a binder were mixed, and the mixture was dispersed in N-methyl-2-pyrrolidone to form a slurry. About 20μ
The positive electrode 2 was obtained by coating, drying, and pressing on both sides of a current collector 5 made of Al foil of m.

In this example, as shown in FIG. 4, separators 8 having the same width W as the width of the negative electrode 3 on both sides of the positive electrode 2 and made of a microporous polyethylene film having a thickness of 25 μm, for example, are respectively provided. The positive electrode 2 is placed and the two separators 8 sandwiching the positive electrode 2 are partially heat-sealed as shown in FIG. 4, and the positive electrode 2 is sealed in the separator 8. In FIG. 4, 8a indicates a heat-sealed portion.

In FIG. 4, reference numeral 2a denotes a positive electrode lead, and the positive electrode lead 2a is a part of an Al foil which is a current collector 5 extended, and the positive electrode active material 4 is not applied to the positive electrode lead 2a. I shall.

Thereafter, the negative electrode 3 and the positive electrode 2 sealed by the separator 8 are alternately stacked as shown in FIG. 1 to obtain a laminated body of electrodes. The stacking positional relationship of the positive electrode 2, the negative electrode 3 and the separator 8 of this stacked body is as shown in FIG. 1, the negative electrode 3, the separator 8, the positive electrode 2, the separator 8, the negative electrode 3 ... The separator 8 and the negative electrode 3. Make it in order.

As shown in FIG. 1, a laminated body in which the negative electrode 3 and the positive electrode 2 sealed with the separator 8 are laminated in this manner is shown in FIG.
It is sandwiched by a pair of stainless steel plates 11 and 11, and an adhesive tape 12 is wound on and fixed to the stainless steel plates 11 and 11.

Further, the positive electrode leads 2a of each positive electrode 2 of this laminated body are bundled, and the sub lead 1 is attached to the bundled positive electrode leads 2a.
Weld one end of 3 and attach. On the other hand, bundle the negative electrode leads 3a provided extending from each negative electrode 3 in the same manner as the positive electrode 2,
The bundled negative electrode leads 3a are attached to the stainless steel plate 1
Weld to one of 1 and 11.

An insulating sheet 14 is laid on the lower surface of the flat rectangular battery container 10 as shown in FIG. 1, and then the laminated body is inserted into the flat rectangular battery container 10 together with the spring plate 15. After that, the two stainless steel plates 11 and 11 on both sides of this laminated body are welded to the flat rectangular battery container 10, respectively.

The other end of the sub lead 13 is welded and connected to a positive electrode terminal 23 previously attached to the battery lid 21 via a gasket 22. In this example, the positive electrode terminal 23 is provided with a gasket 22 made of polypropylene in order to obtain insulation and sealing property between the battery lid 21 and the positive electrode terminal 23 as shown in FIGS. 2A, B, C and D. The positive electrode terminal 23 is attached to the. Figure 2A
Shows a sectional view of the battery lid 21, and first, a cylindrical gasket 22 having a collar is inserted into the terminal mounting hole 21a of the battery lid 21 as shown in FIG. 2B. Next, as shown in FIG. 2C, a cylindrical positive electrode terminal 23 having a brim is inserted into the center hole of the gasket 22, and then the positive electrode terminal 23 is swaged by spin caulking as shown in FIG. To make.

In this case, the material of the positive electrode terminal 23 is duplex stainless steel SUS329J4L consisting of austenite and ferrite structure at room temperature. This material is C
r (24.0 to 26.00 wt%), Ni (5.50)
~ 7.50 wt%), Mo (2.50-3.50 wt%)
%) And the other is duplex stainless steel containing iron as a main component. The battery lid 21 was attached to the flat rectangular battery container 10, and the periphery of the battery lid 21 was laser-welded to produce a lithium ion secondary battery before injection of the electrolytic solution.

Thereafter, the closed flat rectangular battery container 1
Electrolyte solution 9 is injected into 0. As the electrolytic solution 9, an electrolytic solution in which a lithium salt is used as an electrolyte and this is dissolved in an organic solvent is used. Here, the organic solvent is not particularly limited, but propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, tetrahydrofuran, γ-butyrolactone, methyl ethyl carbonate and the like can be used alone or in combination of two or more kinds. Is. LiPF6 as the electrolyte
₆ , LiBF ₄ , LiClO ₄ , LiAsF _{6 and the} like can be used.

According to the present example, the material of the positive electrode terminal 23 is a duplex stainless steel composed of austenite and a ferrite structure at room temperature, and the positive electrode terminal 23 is used as the battery lid 21.
Since it is attached by the caulking method, there is an advantage that an inexpensive and highly reliable liquid leak can be obtained.

By the way, as Comparative Example 1, a lithium ion secondary battery was produced by the same method as in the above-mentioned example except that the material of the positive electrode terminal 23 was Al (A5056).

Further, as Comparative Example 2, a lithium ion secondary battery was manufactured by the same method as in the above-mentioned Example except that the material of the positive electrode terminal 23 was austenitic SUS304.

In Comparative Example 3, the material of the positive electrode terminal 23 is
A lithium ion secondary battery was produced by the same method as in the above-described example except that the austenitic SUS317 was used.

Further, as Comparative Example 4, a lithium ion secondary battery was manufactured by the same method as in the above-mentioned Example except that the material of the positive electrode terminal 23 was ferrite SUS430.

Further, as Comparative Example 5, a lithium ion secondary battery was produced by the same method as in the above-mentioned Example except that the material of the positive electrode terminal 23 was ferrite SUS447J1.

Regarding the above-mentioned Examples and Comparative Examples 1-5,
Charging was performed in an environment of 23 ° C. This charging was carried out at a constant current of 300 mA for 7 hours with the charging voltage set to 4.2V. This charging is 30V up to 4.2V which is the set voltage.
Charging is performed with a constant current of 0 mA, and when the set voltage is reached, the current droops and the constant current and constant voltage are charged.

After the completion of charging, float charging was carried out for 200 hours at a charging voltage of 4.2 V in an environment of 60 ° C. After this float charging, the test battery was disassembled, the positive electrode terminal 23 was taken out from the battery, and the surface state was observed with a scanning electron microscope to examine the presence or absence of dissolution.

As a result of this observation, in Example and Comparative Example 1, there was no dissolution, but in Comparative Examples 2 to 4, there was dissolution.

From these results, it is clear that the duplex stainless steels of the above-mentioned examples and Al of the comparative example 1 have excellent dissolution resistance when used as the positive electrode terminal.

Next, a leak confirmation test by a temperature / humidity cycle was conducted on the above-mentioned Example and Comparative Example 1 in which there was no problem in the dissolution resistance. This is kept in an atmosphere having a temperature of 85 ° C. and a humidity of 60% for 2 hours, and then cooled to −40 ° C. in 6 hours. When the temperature reaches -40 ° C, the temperature is maintained for 2 hours, then the temperature is raised to 85 ° C again over 6 hours, and the temperature is maintained at 85 ° C for 2 hours. After repeating this cycle three times, liquid leakage from the positive electrode terminal 23 was investigated. This leakage was confirmed by a microscope, and the number of batteries in which the leakage of the electrolyte from the positive electrode terminal portion was recognized was checked.

This investigation was carried out for 20 pieces each in the example and the comparative example 1, but no leakage of the electrolytic solution was found.

In addition, the set voltage of 4.2V, 3 for each of 20 pieces of the above-mentioned example and the comparative example 1 in the environment of 23 ° C.
After charging at a constant current of 00 mA for 7 hours, a total of 7 drops of 6 faces and 1 corner from a height of 2.0 m were performed on the plastic tile.

When the number of batteries in which electrolyte leakage from the positive electrode terminal portion was found in the dropped batteries was examined in the same manner as described above, none of the examples was found, but the one of Comparative example 1 was found. Leakage of the electrolytic solution was observed in eight of them.

From the above results, when Al is used for the positive electrode terminal, there is no problem of liquid leakage when there is no shock, but it is confirmed that there is a problem of liquid leakage when shocked such as dropping. In the example, there is no liquid leakage even after dropping, and it is clear that it has excellent reliability against impact such as dropping.

In the above-mentioned embodiment, the example in which the positive electrode terminal is attached to the battery lid has been described, but it goes without saying that the present invention can be applied to the case where the positive electrode terminal is attached to the battery can. In addition, although the above-mentioned embodiment describes the example in which the present invention is applied to the lithium ion secondary battery, it is needless to say that the present invention can be applied to other non-aqueous electrolyte secondary batteries. Further, the present invention is not limited to the above-described embodiments, and needless to say, various other configurations can be adopted without departing from the gist of the present invention.

[0045]

As described above, according to the present invention, as the material of the positive electrode terminal 23, duplex stainless steel composed of austenite and ferrite structure is used at room temperature, and the positive electrode terminal is attached by the caulking method, which is inexpensive. so,
Moreover, there is an advantage that it is possible to obtain a highly reliable non-aqueous electrolyte secondary battery that is excellent in retaining liquid leakage against impact such as dropping.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of a non-aqueous electrolyte secondary battery of the present invention.

FIG. 2 is a cross-sectional view for explaining the main part of the present invention.

FIG. 3 is a diagram provided for explaining a lithium ion secondary battery.

FIG. 4 is a diagram for explaining FIG.

[Explanation of symbols]

 2 Positive electrode 2a Positive electrode lead 3 Negative electrode 8 Separator 21 Battery lid 22 Gasket 23 Positive electrode terminal

Front page continuation (72) Inventor Masayuki Endo 1-1, Shimosugi, Takakura, Hiwada-cho, Koriyama, Fukushima Prefecture Sony Energy Tech Co., Ltd. Koriyama Plant (72) Inventor, Ayaki Watanabe Takakura, Hiwada-cho, Koriyama, Fukushima Prefecture 1-1 Shimodusugi Sony Energy Tech Koriyama Factory

Claims (1)

[Claims] 1. The material of the positive electrode terminal is made of a duplex stainless steel composed of austenite and a ferrite structure at room temperature, and the positive electrode terminal is attached to a battery lid or a battery can via an insulator by a caulking method. Non-aqueous electrolyte secondary battery.