JPH06310119A - Thin type battery - Google Patents

Abstract

PURPOSE:To provide a thin type lithium secondary battery excellent in reliability and safety by bonding a bridging plate inside a metallic battery jar, where the bridging plate is adapted to reinforce the battery jar together with a current collector of either of a positive electrode and a negative electrode. CONSTITUTION:A positive electrode, a negative electrode and a separator are wound in a spiral-shape, the terminal end of the separator is fixed via an adhesive tape, and then, an electrode plate group 12 is pressurized into an elliptic shape. A bridging plate 15 made of one of iron, aluminum, nickel, copper, stainless steel and nickel-plated iron is connected by welding to the tip of a negative electrode lead 17. The bridging plate 15 is adapted to reinforce a battery jar 11 in the thickness direction, where a length thereof in this direction is set the same as an inner dimension of the battery jar 11. After the electrode plate group 12 is inserted onto the battery jar 11, the lead 17 provided with the bridging plate 15 is superposed inside the jar so that the battery jar 11 is bonded to the bridging plate 15. The positive electrode lead 16 is welded to a sealing plate 13, followed by injection of an electrolyte, thus obtaining a thin type lithium secondary battery.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improving the reliability and safety of thin batteries.

[0002]

2. Description of the Related Art In recent years, cordless information and communication devices such as mobile phones and handy video devices have been remarkably portable,
With the increasing use of intelligence, small, lightweight, high energy density batteries are being sought as power sources for driving them.
Above all, lithium secondary batteries are highly expected as the mainstay of next-generation batteries, and their potential market size is also very large.

Further, from the viewpoints of thinning equipment and effective utilization of space, demands for thin and flat shapes are also increasing. 2. Description of the Related Art A rectangular nickel-hydrogen battery, which is a typical thin battery, has heretofore formed an electrode plate group by stacking a single plate (flat plate) of a positive electrode and a negative electrode with a separator interposed therebetween.

[0004]

However, a battery using a non-aqueous electrolytic solution containing an organic electrolytic solution as a main component, such as a lithium battery, has the same conductivity as the above-mentioned battery system because the conductivity of the electrolytic solution is low. If the electrode plate group is composed of the electrode plates having a certain thickness, sufficient high load characteristics cannot be obtained. Therefore, in a thin lithium battery, an electrode plate group structure similar to that of a cylindrical lithium battery, that is, a sheet-shaped positive electrode plate and a negative electrode plate are spirally wound via a separator, and the electrode plate group is formed by compression molding in an oval shape. I am configuring. And when joining the battery case and the electrode plate lead at the bottom of the metal battery case, the welding rod must be inserted through the center part of the electrode plate group to the bottom part of the electrode case. A suitable space for inserting the welding rod must be prepared in advance at the part or the peripheral part. In the case of a cylindrical battery, the electrode plate core originally has a space corresponding to the volume of the core, and it is possible to join using this space, but in the case of a thin battery, it is wound into a cylindrical shape. Since there is no space for inserting the welding rod in the winding core part due to the structure in which the electrode plate group is pressed from a certain direction and configured into an oval shape, it is necessary to make the group structure so as to have that space. The volume energy density of the thin battery is reduced accordingly, which is not preferable.

In general, a thin battery is vulnerable to stress in the thickness direction of the battery case, so that the deformation of the battery container due to compression from the outside of the battery or expansion from the inside of the battery is more likely to occur than that of the cylindrical battery. Particularly in a thin lithium battery, battery deformation is likely to occur due to expansion from the inside of the battery during charge / discharge or storage at high temperature. This easily lowers the sealing strength of the battery sealing part, and has the effect of not operating the safety mechanism such as the current cutoff mechanism in the sealing plate that should be activated by the internal pressure rise of the battery during abnormal conditions such as overcharging. It has, and it is a big negative in terms of battery safety.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a thin battery excellent in safety and productivity and having good battery performance.

[0007]

In order to achieve the above object, the present invention relates to a thin battery, any one of a group consisting of iron, aluminum, nickel, copper, stainless steel, or nickel-plated iron inside a battery case. By joining the cross-linking plate formed in step 1, and joining either one of the positive and negative lead plates to this cross-linking plate, the cross-linking plate becomes a structure that also serves as a current collector and a battery case reinforcement. is there.

[0008]

According to the present invention, it is possible to eliminate the deformation of the battery case due to the pressure increase inside the battery due to the short circuit, overcharge, high temperature storage of the battery, etc. It is possible to eliminate a decrease in sealing strength due to. This has the effect of preventing non-operation of the safety mechanism provided in the sealing portion, for example, the current interruption mechanism. At the same time, an electrical connection between the electrode plate and the battery case can be obtained by joining the bridge plate and the electrode plate lead, and a spot rod at the time of joining the battery case bottom and the electrode plate lead as in the conventional example. It is possible to eliminate the bite failure in the electrode plate group. Further, by eliminating the bottom spot process, the space for inserting the spot rod can be eliminated by design, and the power generation elements can be increased by the amount of the eliminated space, so that a thin battery with high energy density can be obtained.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. Vertical sectional views of a thin battery according to the present invention are shown in FIGS. This battery is 17mm wide, 48mm high,
It is a thin lithium secondary battery with a thickness of 6 mm and the shortest inner dimension in the thickness direction of 5.2 mm.

(Embodiment 1) In FIGS. 1 and 2, 11 is a battery case, 12 is an electrode plate group, 13 is a sealing plate, 14 is a portion of the sealing plate to be joined to the positive electrode lead, 15 is a bridge plate, and 16 is The positive electrode lead and 17 are negative electrode leads.

The positive electrode plate uses lithium cobalt oxide as an active material, and a conductive agent and a binder are mixed and kneaded to form a paste, and the mixture is applied to both sides of a core material made of aluminum foil and dried. The aluminum lead is spot-welded to the core material.

For the negative electrode plate, carbon powder is used as an active material, and a binder is mixed and kneaded to form a paste mixture.
A nickel lead is spot-welded on both sides of a copper foil core material, dried and rolled.

As the separator, a porous film made of polypropylene was used after being cut wider than the positive electrode plate and the negative electrode plate.

These positive and negative electrodes and the separator were spirally wound, and after fixing the separator end with a polypropylene adhesive tape, the electrode plate group was pressed from a certain direction to form an oval shape. At this time, the positive electrode lead and the negative electrode lead were taken out from the same (upper or lower) direction of the group.

Next, the iron bridge plate shown in FIG. 3 was joined to the tip of the negative electrode lead by spot welding. This reinforcing plate is intended to reinforce the thickness direction of the battery case 11, and the length in this direction is 5.2 mm, which is the same as the inner size of the battery case. After that, this electrode plate group was replaced with an iron / nickel-plated thin battery case 1 of the above size.
1, the negative electrode lead provided with the bridge plate is folded into the battery case, and the battery container and the bridge plate are joined to obtain the electrical connection between the negative electrode and the battery case, and then the step portion is formed at the opening of the battery case. Was formed. The step is formed by pressing and fixing the battery case with the upper and lower molds of the step forming machine, and forming the step at the opening of the battery case by pressing the roller.

After that, the positive electrode lead and the sealing plate were spot-welded, and then an electrolytic solution was injected, and the thin lithium secondary battery was constructed through the bending and sealing of the positive electrode lead.

(Embodiment 2) In order to study the effect of the present invention, in a structure without a bridge plate, that is, in the group construction of Embodiment 1, this is formed into an oval shape and inserted into a battery case, and then wound. With the same configuration as in Example 1 except that a welding rod was inserted into the core and the negative electrode lead and the battery case were joined by spot welding at the bottom of the battery case to obtain electrical connection between the negative electrode and the battery case. A thin lithium secondary battery was manufactured. This is Example 2.

In order to study the effect of the present invention, 50 batteries according to the first embodiment and 50 batteries according to the second embodiment were manufactured.

As a result, in the assembling construction of the thin lithium secondary battery, when the welding rod was inserted to the bottom of the battery case in Example 2, there were 50 defects due to damage of the welding rod to the separator and the electrode plate. 13 of them occurred. This is a defect due to the insertion of the welding rod into the core of the electrode plate group originally configured with a high tension ratio in order to increase the battery capacity. On the other hand, the battery of Example 1 had 0 defects. Next, in order to study the battery expansion of the thin battery due to charge / discharge, 50 batteries were manufactured as trials. The test was performed by charging and discharging the batteries according to Examples 1 and 2 at room temperature.
Repeated for 0 cycles, stored in a charged state at 60 ° C. for 20 days, and observed the state of battery expansion. The charging / discharging at this time was performed at a constant current for 1 hour. As a result, the battery of Example 1,
That is, there was almost no battery expansion in the battery having the crosslinked plate. On the other hand, in the batteries of Example 2, that is, the batteries having no reinforcing plate, all the batteries had large expansion, and the sealing joint portion was dislocated in 3 of 50 batteries.

From the above, it was confirmed that the present invention exhibits excellent battery characteristics and productivity. In this example,
Although the lithium battery in which the battery case also serves as the negative electrode terminal has been described as an example, the same effect can be obtained for a lithium battery in which the battery case also serves as the positive electrode terminal.

The size and material of the positive electrode plate, the negative electrode plate, the separator, and the battery case shown in the examples can be applied to the present invention even if other materials are used.

Further, the cross-linked plate was made of copper, nickel-plated iron, nickel, and aluminum in addition to the materials used in the examples, and the same test was conducted, and the same effect as this example was obtained. It was

Regarding the applicable battery, the thin lithium secondary battery has been described as an example in the embodiment, but the same effect can be obtained for other thin non-aqueous electrolyte battery, thin alkaline electrolyte battery and the like.

[0024]

INDUSTRIAL APPLICABILITY According to the present invention, in a thin battery, a crosslinked plate made of any one of the group consisting of iron, aluminum, nickel, copper, stainless steel and nickel-plated iron is joined inside a metal battery case, A thin battery excellent in reliability and safety is provided, which is characterized in that the cross-linking plate has a structure that also serves as a current collector of either the positive electrode or the negative electrode and reinforcement of the battery case.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a thin battery constructed according to an embodiment of the present invention.

[FIG. 2] Similarly, a vertical cross-sectional view in the thickness direction.

FIG. 3 is a perspective view of a bridge plate used in the examples of the present invention.

[Explanation of symbols]

 11 Battery Case 12 Electrode Plate Group 13 Sealing Plate 14 Portion of Sealing Plate to be Joined to Positive Electrode Lead 15 Crosslinked Plate 16 Positive Electrode Lead 17 Negative Electrode Lead

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroshi Fukuda 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (2)

[Claims] 1. A positive electrode plate and a negative electrode plate are spirally wound via a separator, and a group of polar plates is housed in a metal container.
A thin battery in which either the positive or negative electrode lead plate is bonded to a metal bridge plate that also serves as a current collector and reinforcement of the battery case, and both ends of the bridge plate are bonded to arbitrary positions on the inner wall of the battery case. 2. The crosslinked plate is made of iron, aluminum, nickel,
The thin battery according to claim 1, which is any one of the group consisting of copper, stainless steel, and nickel-plated iron.