JPH11250895A - Battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase discharging capacity and to prevent rupture, ignition in overcharging and to increase a field by installing a cut line between a negative active material and the connecting part of a negative lead so as to easily cut, and cutting a negative current collector in overcharging of a battery to separate a negative electrode from the negative lead. SOLUTION: A negative electrode 1 formed by applying carbon serving as an negative active material to copper foil and a positive electrode 2 using lithium cobaltate as a positive active material are spirally wound through a separator, and one end of a negative lead 5 is connected to a part to which the negative active material is not applied, of a negative current collector 4 at the final end of the negative electrode 1. One end of a positive lead 6 is connected to the positive electrode 2. A perforated cut line 7 which is easily cut is formed between the negative lead 5 and the negative active material in the negative current collector 4 at the final end of the negative electrode 1. An electrode group formed by winding the negative electrode 1, the positive electrode 2, and the separator is put into a battery case made of a nickel-plated steel plate, an electrolyte is poured into the battery case, the battery case is sealed with a sealing cover.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to safety of a battery when overcharged.

[0002]

2. Description of the Related Art In general, a battery is inserted into a battery case in a state in which an electrode group including a positive electrode, a negative electrode, and a separator is wound.
An electrolytic solution is injected therein, and the opening of the battery case is sealed using a sealing lid. Here, in order to take out voltage to the outside, the negative electrode and the battery case are connected, and the positive electrode and the sealing lid are connected using a metal ribbon as a current collector. If the battery is continuously charged at a voltage higher than the specified voltage, the battery may be overcharged and the battery may explode or catch fire. Therefore, a charging current cutoff mechanism is provided on the sealing lid to prevent overcharging. Generally, the charging current cutoff mechanism detects a pressure rise inside the battery due to gas generation inside the battery at the time of overcharge, and cuts off the current.

[0003]

However, in a battery having a structure in which the current interrupting mechanism is installed in a sealing device, a space is required in the height direction of the battery in the sealing device.
The space for accommodating the power generating element is reduced, which is an obstacle in improving the battery capacity of the battery. Further, in order to detect the internal pressure of the battery, a complicated mechanism and production process management are required to ensure the reliability of the pressure setting, which has been a factor of lowering the yield of the production process.

[0004] In order to cope with such a problem, the present invention does not require a special space, and therefore increases the discharge capacity of the battery to prevent the battery from bursting or firing at the time of overcharging.
It is an object of the present invention to provide a battery having stable battery performance by realizing a charging current interrupting function capable of improving the yield of a production process.

[0005]

In order to solve the above-mentioned problems, the present invention is characterized in that a negative electrode current collector of an electrode group housed in a battery is cut off when overcharged. In addition, by using the structure of the present invention, an improvement in the storage space for the electrode plate group of the power generation element can be ensured, the battery capacity can be significantly improved, and the production of the sealing lid can be facilitated, and the productivity is good.

[0006]

Embodiments of the present invention will be described below.

As shown in FIG. 1, a negative electrode 1 formed by coating carbon foil as a negative electrode active material with carbon and a positive electrode 2 with lithium cobalt oxide as a positive electrode active material are spirally wound a plurality of times with a separator 3 interposed therebetween. One end of a negative electrode lead 5 made of nickel ribbon is connected to a negative electrode current collector 4 made of a copper foil on which the negative electrode active material is not applied at the terminal end of the negative electrode 1. on the other hand,
One end of a positive electrode lead 6 is connected to the positive electrode 2. In the negative electrode current collector 4 made of copper foil formed at the terminal end of the negative electrode 1, a cutting line 7, which is commonly called a perforation, is provided between the negative electrode lead 5 and the negative electrode active material. .

Then, as shown in FIG. 3, the electrode group 8 in which the negative electrode 1, the positive electrode 2, and the separator 3 are wound is charged into a battery case 9 made of a nickel-plated steel sheet, and after an electrolyte is injected. The opening of the battery case 9 is sealed by the sealing lid 10. The other end of the negative electrode lead 5 is connected to the inner bottom of the battery case 9, and the positive electrode lead 6 is connected to the sealing lid 10. Numeral 11 denotes an upper insulating plate of the electrode group 8, and 12 denotes a lower insulating plate of the electrode group 8. A groove 9 a is provided near the opening of the battery case 9, and the sealing lid 10 is placed in the groove 9 a, and the opening of the battery case 9 is swaged.

The diameter of the battery case 9 is 17.9 mm,
The inner diameter of the groove 9a is 15.0 mm, the distance from the groove 9a at the time of opening to the opening end of the battery case 9 is 5.0 mm, the distance from the bottom of the battery case 9 to the opening end of the battery case 9 is 63.2 mm,
The electrode group 8 has an outer diameter of 17.0 mm and a length of 58.2.
mm.

The battery having the above-mentioned structure was used as the battery of Example 1 of the present invention. Next, the battery of the comparative example is different from the battery of the first embodiment only in that the negative electrode current collector is not provided with a cutting line which is easily cut, and the battery having the same configuration as the battery of the first embodiment is otherwise provided. And Therefore, in the electrode group of the battery of the comparative example, the negative electrode lead 5 made of nickel ribbon was welded to the negative electrode current collector 4 of the copper foil at the end of the negative electrode 1 to be wound, and the negative electrode 1 was wound via the positive electrode 2 and the separator 3. The configuration is as shown in FIG. 4, and a cross-sectional view when assembled into a battery is as shown in FIG.

As shown in FIG. 2, a sharp edge portion 13 is provided on a negative electrode lead 5 made of nickel ribbon which is welded to a terminal end portion of a negative electrode 1 formed by coating a negative electrode active material on a copper foil. A battery having the same configuration as the battery of the comparative example described above was designated as a battery of Example 2 of the present invention.

Further, as shown in FIG.
Reference numeral 4 denotes a PTC element 15 and a metal foil 16 which are overlapped on the lower side, the periphery of which is surrounded by an internal gasket 17.
8 and the lower filter 19 were placed below, and the outer periphery thereof was entirely surrounded by an external gasket 20, and a battery airtightly fitted into an opening of a battery case (not shown) was defined as a conventional battery.

The upper filter 18 has a central portion 2
In 1, it is welded to the metal foil 16.

Therefore, the positive electrode terminal device 14 having the above-described structure is
It has a current cut-off mechanism having a TC element 15, a metal foil 16, an upper filter 18 and a lower filter 19. The positive electrode terminal device 14 seals the electrode plate group and a battery case filled with an electrolyte.

After the above-described conventional battery, the battery of Example 1 of the present invention, the battery of Example 2, and the battery of Comparative Example were fully charged, overcharge was performed to confirm safety. That is, full charge is a constant current constant voltage method, a maximum voltage of 4.2 V, a maximum current of 0.9 A, and charging at room temperature for 2 hours.
On the other hand, in the overcharging, continuous charging at a constant current of 1.3 A was performed in a normal temperature and normal humidity environment.

First, the conventional battery is charged unlimitedly beyond the upper limit voltage of 4.2 V of the constant current / constant voltage charging system, which is a normal charging system, so that it is overcharged and the active material inside the battery is charged. And the electrolytic solution is decomposed, and gas is generated inside the battery. The internal pressure inside the battery is increased by this gas, and FIG.
The metal foil 16 shown in (1) was pushed up, the current cutoff mechanism was activated, charging was stopped in about 60 minutes from the start of charging, and no explosion or ignition occurred.

On the other hand, the battery of the comparative example having no current interruption mechanism burst and ignited in about 70 minutes from the start of charging.

However, the current of the battery of Example 1 was cut off at the same time as that of the conventional battery in about 60 minutes from the start of charging. The reason is that the electrode is overcharged due to overcharging, the active material expands and the thickness of the electrode plate becomes thicker, and the electrode plate group 8 shown in FIG. And pressure in the thickness direction, the cutting line 7 shown in FIG.
Was cut off.

The battery of Example 2 had the same results as the battery of Example 1. This is because the negative electrode current collector 4 is cut by the sharp edge portion 13 shown in FIG.

Table 1 shows the evaluation results of the above-mentioned conventional battery, the battery of Example 1 of the present invention, the battery of Example 2, and the battery of the comparative example.

[0021]

[Table 1]

In Table 1, only the battery of the conventional example has a small discharge capacity because the capacity in the battery is small due to the current interruption mechanism of the positive electrode terminal device.

In the batteries of the first and second embodiments of the present invention, the negative electrode current collector 4 is made of copper foil because the copper foil is flexible and easy to be wound, and the electrode group is formed. This is because the battery of Example 1 is easily cut by the cutting line 7, and the battery of Example 2 is easily cut by the sharp edge portion 13 provided on the negative electrode lead wire.

Further, the results shown in Table 1 were found to be the same when the results were carried out for a square-shaped battery.

[0025]

As is apparent from the above description, according to the present invention, it is possible to secure an improvement in the storage space for the electrode plate group of the power generation element, to improve the battery capacity and to easily manufacture the sealing lid, and to improve the productivity. And a stable and highly reliable battery can be supplied.

[Brief description of the drawings]

FIG. 1 is a plan view showing a main part of an electrode plate group of a battery according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing a main part of a negative electrode plate of a battery according to a second embodiment of the present invention.

FIG. 3 is a half sectional view of the entire configuration of the batteries of Example 1, Example 2 and Comparative Example of the present invention.

FIG. 4 is a plan view showing a main part of an electrode group of a battery of a comparative example.

FIG. 5 is a cross-sectional view of a conventional battery positive electrode terminal device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Negative electrode 2 Positive electrode 3 Separator 4 Negative current collector 5 Negative lead 6 Positive electrode lead 7 Cutting line 8 Electrode group 9 Battery case 10 Sealing lid 11 Upper insulating plate 12 Lower insulating plate 13 Sharp edge part

Claims (3)

[Claims] At the end of a negative electrode current collector connected to a negative electrode lead at the end of a negative electrode to be wound, cutting is easier than other parts between the negative electrode active material and the connection part of the negative electrode lead. A negative electrode current collector is cut off when the battery is overcharged, the negative electrode and the negative electrode lead are separated, and the charging current is interrupted by the disconnection line. 2. A negative electrode lead connected to a negative electrode current collector at a terminal portion of a wound negative electrode, a sharp edge portion is formed at a portion in contact with the negative electrode current collector, and the sharp edge portion forms a battery. The battery is characterized in that the negative electrode current collector is cut off when the battery is overcharged, the negative electrode and the negative electrode lead are separated, and the charging current is interrupted. 3. The battery according to claim 1, wherein the negative electrode current collector is made of copper foil.