JPH03159074A - Cell - Google Patents

Abstract

PURPOSE:To prevent the drop and separation of a positive electrode bonding agent, the occurrence of internal shortcircuit, a capacity loss and a cycle life drop by covering the whole external edge of a strip-shaped positive electrode. CONSTITUTION:A positive electrode bonding agent 4 is applied to a stainless steel net 5 and a positive electrode tab 1 used as the positive electrode power collector of a press fitted strip-shaped positive electrode in common, is spot welded to a strip-shaped positive electrode portion where the bonding agent 4 is removed, and covered with an insulation tape 2 except for a partial area. Also, the whole external edge of the strip-shaped positive electrode is covered with an insulation tape 3. According to the aforesaid construction, the separation and drop of the positive electrode bonding agent 4 from the external edge of the strip shaped positive electrode can be prevented, thereby preventing the occurrence of internal shortcircuit and a drop in the capacity and cycle life of the cell.

Description

[Detailed Description of the Invention] [Industrial Application Field 1] The present invention relates to a cylindrical battery or a prismatic battery, and more specifically to a battery using a strip-shaped positive electrode whose entire outer periphery is covered with tape. be.

[Summary of the Invention] The present invention provides a battery having an electrode group in which a strip-shaped positive electrode and a strip-shaped negative electrode are spirally wound or squarely folded with a separator interposed therebetween, and in which a tape is formed on the entire outer periphery of the strip-shaped positive electrode. This coating prevents the positive electrode mixture from falling off and peeling, and prevents internal short circuits, capacity loss, and shortened cycle life.

[Conventional technology] BACKGROUND ART Conventionally, batteries using a strip-shaped positive electrode are known.

JP-A-53-39435, JP-A-59-4278
Such conventional batteries are disclosed in Japanese Patent Publication No. 3 and Japanese Patent Laid-Open No. 59-112582.

[Problems to be Solved by the Invention] Conventional batteries do not cover the entire outer periphery of the strip-shaped positive electrode with tape, and therefore have the disadvantage that the positive electrode mixture peels off and falls off from the outer periphery of the strip-shaped positive electrode.

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention covers the entire outer periphery of the strip-shaped positive electrode with tape, so that the positive electrode mixture is peeled off from the outer periphery of the strip-shaped positive electrode. It was possible to provide a battery that can prevent falling off, internal short circuits, capacity loss, and cycle life reduction.

[Function] In the present invention, a tape is attached to the entire outer periphery of the strip-shaped positive electrode of the battery.
Since it is subjected to rH, it is possible to prevent the positive electrode mixture from spilling, peeling, falling off, etc. from the strip positive electrode.

That is, the strip-shaped positive electrode is produced by applying a positive electrode mixture slurry to a strip-shaped metal net or expanded metal, drying it, and rolling it to an appropriate thickness. When used for batteries, cut to a certain length. For example, for AA size (AA size), the width is 38 mm.
mm x length 220 mm x thickness 0.22 mm. The outer peripheral edge of this strip-shaped positive electrode has become brittle due to rolling and cutting, and the positive electrode mixture is likely to peel off and fall off.

If you perform a battery drop test even immediately after battery assembly.

The positive electrode mixture peels off and falls off from the outer periphery of this strip-shaped positive electrode,
An internal short circuit is formed between the positive and negative electrodes of the electrode group, causing a short circuit in the battery. If this internal short circuit occurs, not only will the capacity of the battery decrease (but it may also generate heat).

Moreover, if the positive electrode mixture peels off or falls off from the strip-shaped positive electrode, the capacity of the battery will also decrease.

Further, as described on page 2 of JP-A No. 63-150855, as the positive electrode absorbs electrolyte and swells during discharge, the outer peripheral edge of the strip-shaped positive electrode becomes more prone to collapse.

If this battery is a secondary battery, the charging and discharging efficiency of the positive electrode will be poor, and the cycle life of the battery will be shortened.

【Example] Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a front view showing an embodiment of a strip-shaped positive electrode to which the present invention is applied.

In the figure, the positive electrode mixture 4 is applied to a stainless steel net, and the positive electrode mixture 4 is applied to the 0-width 38 mm stainless steel net that is crimped using a belt roll. This strip-shaped positive electrode has a thickness of 0.22 mm including the net, and a length of 220 mm.
Cut in mm.

1 is a stainless steel positive electrode tab with a thickness of 0.1 mm, a width of 3 mm, and a length of 60 mm, which also serves as a positive electrode current collector. This positive electrode tab 1 is spot welded to the band-shaped positive electrode portion from which the positive electrode mixture 4 has been removed. Furthermore, this positive electrode tab 1 is covered with an insulating tape 2 except for a portion thereof. 3 covers the outer peripheral edge of the strip-shaped positive electrode with a coating tape according to the present invention. The width of the covering tape 3 was 3 mm.

FIG. 2 shows a cross section taken along line A-A' in the front view of FIG.

In the figure, reference numeral 3 denotes a covering tape according to the present invention, which is installed on the outer peripheral edge of the strip-shaped positive electrode. 5 is a stainless steel net to which positive electrode mixture 4 is applied.

[Example 21] FIG. 3 shows an example of a battery to which the present invention is applied, and shows a cross-sectional view. The battery is AA size.

In the figure, l is a positive electrode tab that is welded to the strip-shaped positive electrode of the present invention and also to the inner surface of the positive electrode cap 13. 3
is a coated tape according to the present invention with a thickness of 0.03 mm, and is the outer periphery of a strip-shaped positive electrode! It is installed in tffl. 4 is a positive electrode mixture, which is mainly composed of BiaOs. 6 is a negative electrode active material, and lithium was used. 8 is a separator, and positive electrode mixture 4. It is spirally wound together with the negative electrode active material 6. 7
is a negative electrode tab which also serves as a current collector for the negative electrode active material 6 and is welded to the negative electrode case 11 at the bottom. 9. IO is an insulating ring made of plastic. 12 is a gasket, which connects the negative electrode case 11 and the positive electrode cap 13.
It is sealed between.

Next, the open-circuit voltage of the battery of the present invention and a conventional battery without a covering tape installed on the outer peripheral edge of the strip-shaped positive electrode were compared after a drop test.

In the drop test, the battery was dropped onto concrete from a height of 1 m with the negative electrode case 11 facing downward and the positive electrode cap 1 facing upward.

After dropping the battery 10 times, the open circuit voltage of the battery was determined to be 2.0v.
The following batteries were judged to be defective. A normal crystal voltage is 2°4V, and a voltage below 2.4V indicates that the battery has an internal short circuit.

Table 1 shows a comparison of the defective rate between the battery of the present invention and the conventional battery.
Each test cell had n=100 pieces.

Table 1 As is clear from Table 1, the battery of the present invention has a lower defective rate than the conventional battery.

The reason for this is that in the present invention, since the outer peripheral edge of the strip-shaped positive electrode is covered with tape, the positive electrode mixture does not peel off or fall off from the stainless steel net.

Therefore, even if the negative electrode active material and the positive electrode mixture are spirally wound through a thin separator, the fallen positive electrode mixture will not jump over the outer periphery of the separator and cause an internal short circuit between the positive electrode and the negative electrode.

Further, in the present invention, since the positive electrode mixture does not peel off or fall off from the strip-shaped positive electrode, there is no loss of battery capacity or decrease in the charging/discharging efficiency of the positive electrode.

Furthermore, even when the strip-shaped positive electrode is folded into a square like in a prismatic battery, it is possible to prevent the positive electrode mixture from falling off from the outer edge of the strip-shaped positive electrode, thereby preventing internal short circuits, capacity loss, and reduction in cycle life.

[Effect of the Invention 1] As described in detail above, the present invention can prevent internal short circuits, capacity loss, decrease in cycle life, etc. of the battery by covering the entire outer periphery of the strip-shaped positive electrode with tape.

The present invention can be applied to cylindrical or prismatic primary batteries and secondary batteries, and has great industrial value.

[Brief explanation of the drawing]

FIG. 1 is a front view showing an embodiment of a strip-shaped positive electrode to which the present invention is applied, and FIG. 2 is a sectional view. FIG. 3 is a sectional view showing an embodiment of a battery to which the present invention is applied. l...Positive electrode tab 2...Insulating tape 3...Covering tape 4 ・ ・ ・ 5 ・ ・ 6 ・ 7 ・ 8 ・ 9, l 1 ・ l 2 ・ 13 ・ Positive electrode combination agent Stainless steel net negative electrode active material negative electrode tab separator insulation ring negative electrode case gasket positive electrode cap 1 Diagram above

Claims (1)

[Claims] 1. A battery having an electrode group in which a strip-shaped positive electrode and a strip-shaped negative electrode are spirally wound or squarely folded with a separator in between, characterized in that the outer peripheral edge of the strip-shaped positive electrode is covered with tape.