JP3085018B2 - Thin battery - Google Patents

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 a thin battery.

[0002]

2. Description of the Related Art In recent years, remarkable portability of cordless information and communication devices such as mobile phones and handy videos,
With the advancement of intelligence, small and lightweight batteries with high energy density are required 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 very large.

[0003] Further, from the viewpoint of making equipment thinner and effective use of space, there is a growing demand for thin and flat shapes. BACKGROUND ART A square nickel-metal hydride battery, which is a typical example of a thin battery, has a structure in which a positive electrode and a negative electrode of a single plate (flat plate) have a laminated structure with a separator interposed therebetween.

[0004]

However, a battery using a non-aqueous electrolyte containing an organic electrolyte as a main component, such as a lithium battery, has a low conductivity of the electrolyte, so that it is the same as the above battery system. If the electrode plate group is made of an electrode plate having a sufficient thickness, sufficient high load characteristics cannot be obtained. Therefore, in the case of a thin lithium battery, the electrode plate group configuration is the same as that of a cylindrical lithium battery, that is, a sheet-like positive electrode plate and a negative electrode plate are spirally wound via a separator and compression-molded into an oblong shape to form the electrode group. Make up. And when joining the battery case and the electrode plate lead at the bottom of the metal battery case, it is necessary to insert the welding rod through the center of the electrode plate group and insert it to the bottom of the battery case. A suitable space for the insertion of a welding rod must be prepared in advance or in the periphery. A cylindrical battery originally has a space corresponding to the volume of the core in the core of the electrode plate, and can be joined using this space.However, in the case of a thin battery, the battery is wound into a cylindrical shape. Since the electrode plate group is pressurized from a certain direction and formed into an elliptical shape, there is no space for inserting a welding rod in the core, and it is not possible to configure the group so as to have that space. The volume energy density of the thin battery is reduced by that much, which is not preferable.

In general, a thin battery has a structure that is less susceptible to stress in the thickness direction of the battery case, and the battery case is more easily deformed than a cylindrical battery due to compression from the outside of the battery or expansion from the inside of the battery. Particularly in a thin lithium battery, battery deformation is likely to occur due to expansion from inside the battery during charge / discharge or storage at high temperatures. This has the effect of easily lowering the sealing strength of the battery sealing part and disabling safety mechanisms such as the current cutoff mechanism in the sealing plate that should be activated due to an increase in the internal pressure of the battery in the event of an abnormality such as overcharging. It is a big negative in terms of battery safety.

An object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to provide a thin battery having excellent battery performance and excellent safety and productivity.

[0007]

In order to achieve the above-mentioned object, the present invention relates to a thin battery, which comprises a battery case having any one of the group consisting of iron, aluminum, nickel, copper, stainless steel or nickel-plated iron. The cross-linking plate is formed by joining the cross-linking plate and either the positive or negative lead plate to form a cross-linking plate that functions as both a current collector and a battery case reinforcement. is there.

[0008]

According to the present invention, deformation of the battery case due to an increase in pressure inside the battery due to short-circuiting, overcharging, or high-temperature storage of the battery, and in particular, expansion and deformation near the sealing portion can be eliminated, and the battery can be expanded. This can eliminate a decrease in sealing strength due to the above. This has an effect of preventing a safety mechanism provided in the sealing portion, for example, a current cutoff mechanism from being inoperative. By joining the bridge plate and the electrode plate lead, an electrical connection between the electrode plate and the battery case can be obtained. Defective biting into the electrode plate group can be eliminated. Furthermore, by eliminating the bottom spot process, the insertion space for the spot bar can be eliminated in design, the number of power generation elements can be increased by the eliminated space, and a thin battery with high energy density can be obtained.

[0009]

An embodiment of the present invention will be described below with reference to the drawings. 1 and 2 are longitudinal sectional views of a thin battery according to the present invention. This battery is 17mm wide, 48mm high,
This is a thin lithium secondary battery having a thickness of 6 mm and a minimum inner dimension of 5.2 mm in the thickness direction.

(Embodiment 1) In FIGS. 1 and 2, reference numeral 11 denotes a battery case, 12 denotes an electrode plate group, 13 denotes a sealing plate, 14 denotes a portion of the sealing plate to be joined to the positive electrode lead, 15 denotes a cross-linking plate, and 16 denotes a bridge plate. A positive electrode lead 17 indicates a negative electrode lead.

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

The negative electrode plate is prepared by mixing carbon powder as an active material, mixing a binder with the active material, kneading the mixture, and forming a paste.
A core material made of copper foil is coated on both sides, dried, rolled, and spot-welded with a nickel lead.

As the separator, a porous film made of polypropylene was cut more widely than the positive electrode plate and the negative electrode plate.

The positive electrode, the negative electrode, and the separator were spirally wound, and the end of the separator was fixed with an adhesive tape made of polypropylene. Then, the electrode plate group was pressed in 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, an 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 battery case 11 in the thickness direction, and the length in this direction is 5.2 mm, which is the same as the internal size of the battery case. Thereafter, this electrode plate group is placed in an iron / nickel-plated thin battery case 1 of the above-mentioned size.
After inserting the negative electrode lead with the bridge plate into the battery case, the battery case and the bridge plate are joined to obtain an electrical connection between the negative electrode and the battery case, and then a stepped portion is formed in the battery case opening. Was formed. The step portion is formed by pressing and fixing the battery case with an upper mold and a lower mold of a step forming machine, and forming a step portion at an opening of the battery case by pressing a roller.

Then, after the positive electrode lead and the sealing plate were spot-welded, an electrolytic solution was injected, and the positive electrode lead was bent and sealed to form a thin lithium secondary battery.

(Embodiment 2) In order to examine the effect of the present invention, in a structure without a cross-linking plate, that is, in the group configuration of Embodiment 1, this was formed into an oblong shape, inserted into a battery case, and then wound. The same configuration as in Example 1 except that an electric connection between the negative electrode and the battery case was obtained by inserting a welding rod into the core and joining the negative electrode lead and the battery case by spot welding at the bottom of the battery case. A thin lithium secondary battery was manufactured. This is Example 2.

In order to examine the effects of the present invention, 50 batteries each of the first embodiment and the second embodiment were fabricated.

As a result, at the time of assembling the thin lithium secondary battery, when the welding rod is inserted to the bottom of the battery case in the second embodiment, the defect caused by the breakage of the welding rod between the separator and the electrode plate is 50%. 13 of them occurred. This is a defect caused by inserting a welding rod into the core of the electrode plate group having a high tension ratio in order to increase the battery capacity. On the other hand, the battery of Example 1 had 0 failure. Next, in order to examine the battery expansion of the thin battery due to charging / discharging, another 50 batteries were prototyped. The test was performed by charging and discharging the batteries according to Examples 1 and 2 at room temperature for 1
Zero cycles were repeated, the battery was stored at 60 ° C. for 20 days in a charged state, and the state of battery expansion was observed. At this time, charging and discharging were performed at a constant current of 1 hour. As a result, the battery of Example 1
That is, in the battery having the cross-linked plate, there was almost no battery expansion. On the other hand, in the battery of Example 2, that is, the battery having no reinforcing plate, all of the batteries had a large expansion, and three out of fifty batteries had a missing sealing joint.

From the above, it was confirmed that the present invention exhibited excellent battery characteristics and productivity. In this embodiment,
Although a lithium battery in which the battery case also serves as the negative electrode terminal has been described as an example, a similar effect is obtained with a lithium battery in which the battery case also serves as the positive electrode terminal.

The present invention can be applied to the sizes and materials of the positive electrode plate, the negative electrode plate, the separator, and the battery case shown in the examples other than these.

Further, in addition to the materials used in the present embodiment, the crosslinked plate was made of copper, nickel-plated iron, nickel and aluminum, and the same test was carried out. The same effect as in the present embodiment was obtained. Was.

In the embodiment, a thin lithium secondary battery has been described as an example of applicable batteries, but similar effects can be obtained with other thin nonaqueous electrolyte batteries, thin alkaline electrolyte batteries, and the like.

[0024]

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. It is characterized in that the cross-linked plate has a structure that also functions as a current collector for one of the positive electrode and the negative electrode and for reinforcing the battery case, and provides a thin battery excellent in reliability and safety.

[Brief description of the drawings]

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

FIG. 2 is a longitudinal sectional view in the same thickness direction.

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Battery case 12 Electrode group 13 Sealing plate 14 Portion of sealing plate which joins with a positive electrode lead 15 Cross-linking plate 16 Positive electrode lead 17 Negative electrode lead

Continuation of the front page (72) Inventor Hiroshi Fukuda 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References JP-A-63-264863 (JP, A) JP-A-3-84852 (JP) JP-A-4-206142 (JP, A) JP-A-4-135162 (JP, U) JP-B-38-10555 (JP, Y1) JP-B-41-14028 (JP, Y1) (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01M 2/20-2/34 H01M 10/40

Claims (2)

(57) [Claims] An electrode plate group in which a positive electrode plate and a negative electrode plate are spirally wound via a separator is housed in a metal battery case,
A thin battery in which either one of the positive and negative electrode lead plates is joined to a metal bridge plate that serves both as a current collector and as a reinforcement of the battery case, and both end portions of the bridge plate are joined 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, wherein the battery is one of the group consisting of copper, stainless steel, and nickel-plated iron.