JPH04332461A - Closed type battery - Google Patents

Abstract

PURPOSE:To provide a highly safe closed type battery capable of preventing outside short circuit beforehand even if contact or connection occurs between outside terminals and the armor surface. CONSTITUTION:A heat resistant insulating layer 13 is arranged on the armor surface of a closed type battery having outside terminals 19 and 20.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sealed battery, and more particularly to a sealed battery that prevents external short circuits.

0002

BACKGROUND OF THE INVENTION In recent years, advances in electronic technology have led to higher performance, smaller size, and more portable electronic equipment, and there has been an increasing demand for high energy density secondary batteries used in these electronic equipment. Traditionally, secondary batteries used in these electronic devices include nickel-cadmium batteries and lead batteries, but these batteries have a low discharge potential and are still difficult to obtain in terms of producing batteries with high energy density. Not enough.

[0003]Recently, therefore, non-conductive materials have been developed in which a material that can be doped and dedoped with lithium ions, such as lithium, lithium alloy, or carbon material, is used as the negative electrode, and a lithium composite oxide such as lithium cobalt composite oxide is used as the positive electrode. Research and development of water electrolyte secondary batteries is underway. This battery has high battery voltage and high energy density,
It has little self-discharge and excellent cycle characteristics.

0004

[Problem to be Solved by the Invention] In recent years, various electrical devices have been developed to be more compact, and due to this situation, batteries and related parts incorporated into the devices are also being developed to save space. Increasingly, there is a growing demand for designs that can be used in a variety of ways. Normally, the batteries incorporated in such devices are sealed batteries with external terminals connected to the positive and negative electrodes, but in response to the above-mentioned space savings, the sealed batteries are also being used. , it has become necessary to have a structure in which the external terminal and the exterior surface of the battery are very close to each other.

However, in a sealed battery, if the external terminals and the exterior surface are configured to be close to each other, the external terminals and the exterior surface will come into contact and generate heat, causing the insulating film provided on the exterior surface to melt. Therefore, there is a high possibility that an external short circuit will occur. Furthermore, when incorporating a battery into a device, solder welding is used to join the battery's external terminals and other electronic component terminals, but if the battery's external terminals and the exterior surface are close to each other,
During solder welding, there is a high possibility that the solder will reach the battery exterior surface, increasing the frequency of melting of the insulating film and causing external short circuits.

[0006] When a battery suffers from an external short circuit like this, especially in the case of a high energy density battery as described above, a large current flows through the external short circuit, generating heat inside the battery, which may damage the battery. , there is a risk of damaging electronic components and equipment due to large currents and light heat. Furthermore, if a battery that has experienced an external short circuit is used as is, there will be a problem in that no matter how high the energy density of the battery is, it will hardly be able to demonstrate its performance.

[0007]The present invention has been proposed in view of the above-mentioned conventional circumstances, and is a sealed type that can prevent external short circuits even if there is contact or bonding between the external terminal and the exterior surface. The purpose is to provide batteries.

[0008] 3,

[Detailed description of the invention]

[Means for Solving the Problem] As a result of various studies conducted by the present inventors in order to achieve the above object, the problem was solved by providing at least one layer having heat-resistant insulation performance on the exterior surface. I found out that it can be done.

The present invention has been proposed based on such findings, and is characterized in that, in a sealed battery having an external terminal, a heat-resistant insulating layer is provided on the exterior surface of the battery adjacent to the external terminal. It is something to do.

[0010] In the sealed battery of the present invention, a heat-resistant heat-shrinkable tube, a heat-resistant adhesive tape, a heat-resistant film, a heat-resistant paint, etc. can be used for the layer having heat-resistant insulation performance. The material for these heat-resistant insulating layers is 200°C.
As mentioned above, it is preferable to use a material that does not undergo chemical or physical changes such as decomposition, melting, or deformation even in an environment of 250°C or higher. Products using crosslinked polyolefins (polypropylene, polyethylene, etc.) as materials, heat-resistant adhesive tapes As the base film material, polyimide, fluororesin, aramid fiber, glass cloth, etc. can be used, and as the heat-resistant paint, silicone resin, fluororesin, etc. can be used as the material.

The thickness of the heat-resistant insulating layer is preferably 5 to 500 μm, more preferably 10 to 200 μm, in order to sufficiently prevent external short circuits. Further, the heat-resistant insulating layer may have a single-layer structure, but may also have a two-layer or more structure using a plurality of heat-resistant materials.

0012

[Function] In a sealed battery having an external terminal, if a heat-resistant insulating layer is provided on the exterior surface near the external terminal, for example, even if solder flows out onto the battery surface when soldering the external terminal, the above-mentioned heat-resistant The insulating layer protects and insulates the exterior surface, thereby preventing external short circuits.

[0013]

EXAMPLES Preferred examples of the present invention will be described below based on experimental results.

Example 1 FIG. 1 shows a longitudinal sectional view of a sealed battery prepared in this example.

First, a negative electrode was prepared as follows. As the negative electrode active material, petroleum pitch is used as a starting material, and after introducing 10 to 20% of oxygen-containing functional groups (so-called oxygen crosslinking), it is fired at 1000°C in an inert gas stream.
A non-graphitic carbon material with properties close to glassy carbon was obtained. As a result of performing X-ray diffraction on this material, the interplanar spacing of the (002) plane was 3.76 Å, and the true specific gravity was 1.58 g/cm 3 . This material was pulverized to obtain carbon material powder with an average particle size of 10 μm. 90 parts by weight of the carbon material powder thus obtained and polyvinylidene fluoride (PVDF) as a binder.
This negative electrode mixture was dispersed in a solvent N-methyl 2-pyrrolidone to form a slurry. and,
This negative electrode slurry was applied as a negative electrode current collector uniformly onto both sides of a strip-shaped copper foil having a thickness of 10 μm, and after drying, compression molding was performed using a roll press machine to produce a strip-shaped negative electrode 1.

Next, a positive electrode was produced in the following manner. Lithium carbonate and cobalt carbonate are used as the positive electrode active material.
Mix so that (molar ratio)=1 and heat at 900℃ in air.
, using LiCoO2 obtained by firing for 5 hours, 99.5 parts by weight of LiCoO2 obtained, 0 parts by weight of lithium carbonate.
．． A positive electrode mixture was prepared by mixing 91 parts by weight of a mixture containing 5 parts by weight, 6 parts by weight of graphite as a conductive agent, and 3 parts by weight of polyvinylidene fluoride (PVDF) as a binder. was dispersed in N-methyl-2-pyrrolidone, a solvent, to form a slurry. The positive electrode slurry thus obtained was used as a positive electrode current collector to a thickness of 20 μm.
The mixture was uniformly applied to both sides of a strip-shaped aluminum foil of 50 mm, and after drying, compression molding was performed using a roll press machine to produce a strip-shaped positive electrode 2.

A microporous polypropylene film was prepared as a separator. When the strip-shaped negative electrode 1, strip-shaped positive electrode 2, and separator 3 are respectively spiral electrode elements,
The length and width of the electrode were adjusted in advance so that it could fit into the battery can 5 having an outer diameter of 20 mm and a height of 51 mm, and a spiral electrode as shown in FIG. 1 was produced.

The spiral electrode thus produced was housed in a nickel-plated iron battery can 5. Insulating plates 4 are arranged on both the upper and lower sides of the spiral electrode, an aluminum positive electrode lead 12 is led out from the positive electrode current collector and attached to the battery lid 7, and a nickel negative electrode lead 11 is led out from the negative electrode current collector to the battery can 5.
Welded to. Next, an electrolytic solution containing 1 mol/l of LiPF6 dissolved in a mixed solvent of 50 parts by volume of propylene carbonate and 50 parts by volume of dipropyl carbonate was injected into the battery can 5.

The battery lid 7 was fixed by caulking the battery can 5 through an insulating sealing gasket coated with asphalt, thereby producing a cylindrical non-aqueous electrolyte secondary battery with a diameter of 20 mm and a height of 50 mm. This is called a unit cell.

Next, the device is inserted into a polyvinyl chloride heat-shrinkable tube (manufactured by Gunze Polymer) 13, and with the insulating washer 14 installed on the positive electrode side, the tube is passed through a hot air oven until it reaches the outside diameter of the unit cell. Heat-shrinked. This battery 15, 16
I prepared two.

A polyimide adhesive tape 17 (manufactured by Nitto Denko Corporation, trade name No. 360UL) having a width of 10 mm was attached to the positive electrode side of the battery side of the unit cell 15 to the same length as the circumference. In order to produce a series-connected assembled battery, the positive electrodes of the unit cells 15 and 16 were connected via the polyswitch 18. Subsequently, external terminals 19 and 20 were resistance welded to the positions shown in the figure.

[0022] This assembled battery has a maximum voltage of 8.20V and a current of 1A.
After constant current charging for 8 hours, molten solder was dropped onto the tip of the external terminal 18 until it contacted the surface of the polyimide tape. After that, when I measured the open circuit voltage of the assembled battery, it was 8.
．． It was 18V and no abnormality was found in the battery.

Example 2 An assembled battery was prepared in the same manner as in Example 1, except that the polyimide binding tape was replaced with a glass cloth adhesive tape (manufactured by Nitto Denko Corporation, trade name No. 188UL), and charged and soldered in the same manner. dripping was done. Thereafter, when the open circuit voltage of the assembled battery was measured, it was 8.18V, and no abnormality was observed in the battery.

Example 3 Except for changing the polyimide adhesive tape to an aramid fiber adhesive tape (manufactured by Nitto Denko Corporation, trade name No. 403),
A battery pack similar to that in Example 1 was prepared, and charged and solder dripped in the same manner. Thereafter, when the open circuit voltage of the assembled battery was measured, it was 8.18V, and no abnormality was observed in the battery.

Example 4 An assembled battery was prepared in the same manner as in Example 1, except that the polyimide adhesive tape was replaced with a fluororesin adhesive tape (manufactured by Nitto Denko Corporation, product name No. 453), and charged and soldered in the same manner. I did it. Thereafter, when the open circuit voltage of the assembled battery was measured, it was 8.18V, and no abnormality was observed in the battery.

Example 5 A perfluoro-alkoxy resin heat-shrinkable tube (manufactured by Gunze) was used instead of a polyvinyl chloride heat-shrinkable tube.
In addition, an assembled battery was prepared in the same manner as in Example 1, except that no polyimide adhesive tape was attached, and charging and solder dripping were performed in the same manner. After that, when the open circuit voltage of the assembled battery was measured, it was 8.1.
The voltage was 8V, and no abnormality was found in the battery.

Example 6 A unit cell was prepared in the same manner as in Example 1, and a fluororesin paint (LF-100 manufactured by Asahi Glass Co., Ltd.) was applied in advance to the area where the polyimide adhesive tape was attached to the unit cell 15 and to the surface of the battery can. An assembled battery was prepared in the same manner as in Example 1, except that no tape was attached, and charging and solder dripping were performed in the same manner. Although the polyvinyl chloride heat shrink tube melted immediately, the open circuit voltage of the assembled battery was 8.18 V, and no abnormality was observed in the battery.

Comparative Example 1 A battery pack was prepared in the same manner as in Example 1, except that no polyimide adhesive tape was attached, and charging and solder dripping were carried out in the same manner. The polyvinyl chloride heat-shrinkable tube in the solder droplet melted immediately, and when the assembled battery open circuit voltage was measured, it dropped to 4.15V, the unit cell 15 generated heat, and the polyvinylchloride heat-shrinkable tube melted. .

Comparative Example 2 Except for changing the polyimide adhesive tape to a polyester adhesive tape (manufactured by Nitto Denko Corporation, trade name No. 337),
A battery pack similar to that in Example 1 was prepared, and charged and solder dripped in the same manner. Thereafter, when the open circuit voltage of the assembled battery was measured, it was found to have decreased to 4.20 V, and the unit cell 15 gradually generated heat, and the polyvinyl chloride heat-shrinkable tube melted.

In the batteries of Comparative Example 1 and Comparative Example 2 in which the heat-resistant insulating layer was not provided on the exterior surface as described above,
When the circuit voltage was measured after the solder had flowed out to the battery surface 2, abnormalities such as heat generation and voltage drop were observed. Even if the solder flows out onto the battery surface, no abnormalities such as heat generation or voltage drop are observed. Therefore, from this, it was found that providing a heat-resistant insulating layer on the exterior surface is effective in preventing external short circuits caused by solder flowing out onto the battery surface.

[0031]

[Effects of the Invention] As is clear from the above description, the sealed battery of the present invention is provided with a heat-resistant insulating layer on the exterior surface close to the external terminal, so that the heat-resistant insulating layer is provided in the process of assembling the battery into a device. It is possible to prevent the external terminal from joining/contacting with the other terminal's exterior, so-called external short circuit, and its industrial value is enormous.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view showing an example of the configuration of a unit cell produced in this example.

FIG. 2 is a schematic perspective view showing an example of a configuration in which a unit cell is provided with an external terminal and a heat-resistant insulating layer to form an assembled battery.

[Explanation of symbols]

1... Negative electrode 2... Positive electrode 3... Separator 13... Heat shrink tubes 19, 20...
・External terminal

Claims (1)

[Claims] 1. A sealed battery having an external terminal, characterized in that a heat-resistant insulating layer is provided on the exterior surface close to the external terminal.