JP2000353502A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To quickly detect the trouble of a battery due to the deterioration of airtightness of a laminate sheet by housing an electrode body in a battery case formed of a laminate sheet of metal and resin, and electrically connecting the metal part of the laminate sheet to a positive electrode. SOLUTION: In this battery, aluminum laminate film constituting a battery case 6 is formed of a PET film provided on the outermost layer as a surface protecting layer 15, an aluminum foil adhered to the lower side thereof through an urethane adhesive as a barrier layer 16, and an acid modified LDPE provided on the lower side thereof as a thermally fused layer 17. Aluminum is used as the positive electrode, and nickel is used as the negative electrode. The surface protecting layer 15 on the battier layer 16 located on a sealing part is partially peeled and exposed to form a battery case surface connection part, and a conductive adhesive tape is stuck to the exposed part so as to perfectly cover it and connect the exposed part to a positive electrode lead 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a non-aqueous electrolyte secondary battery.

[0002]

2. Description of the Related Art In recent years, electronic devices such as a portable radio telephone, a portable personal computer, and a portable video camera have been developed, and various electronic devices have been reduced in size to be portable. Along with this, a battery having a high energy density and a light weight is also adopted as a built-in battery. A typical battery that satisfies such a requirement is an active material such as lithium metal or lithium alloy, or a host material containing lithium ions (here, a host material refers to a material that can occlude and release lithium ions). Lithium intercalation compound occluded in a certain carbon is used as a negative electrode material, and LiC
This is a non-aqueous electrolyte secondary battery using an aprotic organic solvent in which a lithium salt such as l04 and LiPF6 is dissolved as an electrolyte.

This non-aqueous electrolyte secondary battery has a negative electrode plate in which the above-mentioned negative electrode material is held on a negative electrode current collector as a support, and a reversible electrochemical reaction with lithium ions such as a lithium-cobalt composite oxide. The positive electrode plate, which holds the positive electrode active material that reacts on the positive electrode current collector that is the support, from the separator that holds the electrolytic solution and intervenes between the negative electrode plate and the positive electrode plate to prevent a short circuit between the two electrodes Has become.

[0004] In the case of a non-cylindrical battery, the positive electrode plate and the negative electrode plate are each formed into a thin sheet or foil and wound spirally and non-circularly in section through a separator. The outermost circumference of the body is wrapped with tape. Then, the completed electrode body is housed in a battery container made of a metal such as stainless steel, nickel-plated iron, or aluminum. After the electrolyte is injected, the battery is assembled by hermetically sealing with a cover plate.

[0005]

A battery container made of a metal which has been conventionally used has the advantages of high airtightness and excellent mechanical strength, but has the advantage of reducing the weight of the battery and reducing the weight of the battery. The selection of the container material and the design of the battery have great restrictions. Therefore, as a new battery container that solves such a problem, a battery container formed of an aluminum laminate sheet has been proposed and put into practical use. However, due to some abnormality such as burrs of the electrode current collector or mixing of foreign metal into the inside of the battery, the inner surface resin of the aluminum laminate sheet penetrates, and the aluminum foil in the aluminum laminate sheet comes into contact with the negative electrode to reach the negative electrode potential. If this occurs, a lithium-aluminum alloy will be generated, and aluminum foil will be pulverized, causing a reduction in the airtightness of the aluminum laminate sheet.
It turned out that the problem that the reliability of a battery falls arises. And, since this phenomenon progresses over time due to repetition of charge and discharge, even if such contact occurs during production, it cannot be detected immediately after production, or if such contact occurs during use. However, there is a problem that this cannot be detected.

[0006] In view of the above, the present invention quickly solves the above-mentioned problem when a non-aqueous electrolyte secondary battery contained in a battery container formed of a laminated sheet of metal and resin is generated. An object of the present invention is to enable detection and improve the reliability of use of a battery.

[0007]

According to the present invention, there is provided a non-aqueous electrolyte secondary battery in which an electrode body is housed in a battery container formed of a laminated sheet of metal and resin, The metal of the laminate sheet is electrically connected to the positive electrode. When the laminate sheet is used as a battery container, since the inner surface of the container is formed of a resin, the laminated metal has a structure that is not electrically connected to the electrodes. With this configuration, the potential of the laminated metal becomes equal to the potential of the positive electrode, and when the laminated metal comes into contact with the negative electrode or the like, this can be detected as a change in the terminal voltage of the battery. The metal constituting the laminate sheet of the metal and the resin is exemplified by aluminum or an alloy thereof, and may be any material as long as it is stable with respect to the potential of the positive electrode. Further, the resin layer and the metal foil layer of the metal laminate sheet are not limited to one layer each, and may be two or more layers.

Further, the present invention is a battery which is particularly useful when the battery is a lithium battery and the metal constituting the laminate sheet contains an element such as aluminum, gold or lead. The electrode body is provided with a positive electrode, a negative electrode, and a separator, and has a structure in which the electrode body is laminated or wound in a non-circular cross section in that the advantage of using a laminated sheet as a battery can be maximized. This is especially useful if you have Further, in the case where a structure in which the negative electrode is located outside the electrode body is provided, the probability of occurrence of the above-described inconvenience increases, and thus the battery having such a structure is more useful.

[0009]

FIG. 1 is an external perspective view showing one embodiment of a non-aqueous electrolyte secondary battery according to the present invention. Hereinafter, the battery of the present invention will be described in more detail while describing this embodiment.

As shown in FIG. 1, in a battery 1, an electrode body composed of a positive electrode plate, a negative electrode plate and a separator is accommodated in a battery container 6 together with a non-aqueous electrolyte, and a positive electrode lead 5 and a negative electrode lead 5 ' This is a thin lithium secondary battery having a structure pulled out from one end of a container.
It has a structure in which a part of the PET layer on the surface is peeled off and the battery case surface connection part (located at the sealing part) where aluminum is exposed is connected by the conductive adhesive tape 4.

In the present battery, the positive electrode plate is a current collector in which a lithium-cobalt composite oxide is held as an active material. As the current collector, an aluminum foil having a thickness of 20 μm was used. The positive electrode plate was prepared by mixing 8 parts of polyvinylidene fluoride as a binder and 5 parts of acetylene black as a conductive agent together with 87 parts of an active material, and adding N-methylpyrrolidone as needed to prepare a paste. It was manufactured by applying and drying both surfaces of the current collector material.

As the negative electrode plate, a copper foil having a thickness of 14 μm was used as a current collector, and 86 parts of graphite (graphite) as a host material and 14 parts of polyvinylidene fluoride as a binder were provided on both surfaces of the current collector. Was prepared by mixing and preparing a paste, followed by coating and drying.

[0013] The separator is a polyethylene microporous membrane. The electrolyte was ethylene carbonate: diethyl carbonate = 1: 1 containing LiPF6 at 1 mol / l.
(Volume ratio).

FIG. 3 is a perspective view showing a schematic structure of the electrode body. The dimensions of each electrode body are as follows.
m, width 45 mm, separator thickness 25 μm, width 50
mm, the negative electrode plate has a thickness of 170 μm and a width of 47 mm, and lead terminals are welded to the positive electrode plate and the negative electrode plate, respectively. The electrode body 2 is formed by superposing these in order and winding them around the rectangular core of polyethylene so that the long side is parallel to the winding axis of the electrode body, in a spiral shape around the periphery, and has a non-circular cross section. It is. Then, using a winding-stopping tape 3 made of polypropylene (here, an adhesive is applied to one side), the terminal edge portion of the electrode is set to a length corresponding to the electrode width (the length of the electrode body parallel to the winding axis). The electrode body 2 is wound and fixed by being attached to the side wall of the electrode body parallel to the winding axis.

The battery container 6 is made of an aluminum laminated film having the structure described below. The battery 1 is formed by molding the aluminum laminated film into a cylindrical shape.
The electrode body 2 is housed therein, and at one end of the open end, the cylindrical body is closed by heat-sealing the laminate sheet together with the separator protruding from the winding surface where the electrode lead is not exposed. Electrodes and separators are sufficiently wetted, and an amount of free electrolyte solution outside the electrode group is vacuum-injected into this, and finally, lamination is performed at the open end on the winding surface side where the electrode leads are provided. It is produced by heat-sealing a sheet.

FIG. 2 is a schematic cross-sectional structure diagram showing a cross-sectional structure of a sealing portion of a lead portion of the positive electrode lead 5. The aluminum laminate film constituting the battery case 6 has a surface protective layer 15 as an outermost layer as shown in FIG.
μm thick PET film, under which a barrier layer 16
Is a 9 μm-thick aluminum foil bonded with a urethane-based adhesive, and further has a structure having a 60 μm-thick acid-modified LDPE (low-density polyethylene) as a heat sealing layer 17 thereunder.

The lead terminals 5, 5 'are
Acid-modified LD having a thickness of 50 μm as an adhesive layer 18 for bonding a metal conductor such as copper, aluminum, nickel or the like of 00 μm to a metal
PE resin and 50 μm thick LDPE resin layer 1 on the outside
The present battery uses aluminum for the positive electrode and nickel for the negative electrode. The conductive adhesive tape 4 is not shown, but a part of the surface protective layer 15 on the barrier layer 16 located on the sealing portion is peeled off to expose the surface protective layer 15 to form a battery container surface connection portion. It is attached so as to completely cover the exposed portion and connect this portion to the positive electrode lead 5.

The method of connecting the metal layer of the metal laminate film to the positive electrode is not limited to this, and the connection may be made, for example, in a battery container or inside the sealing portion. Also, even if the battery itself is not a connected structure, for example, a terminal portion that is electrically connected to the metal layer in the metal laminate film is provided on the surface of the battery container,
When the battery is installed in the tester or inserted into the equipment to be used, this terminal section and the battery's positive terminal are in contact with each other, so that the positive electrode and the metal of the laminate sheet are electrically connected. Is also good.

[Tests and Results] Ten batteries (A) as described above were produced. This battery has a width of 35 m
m, length = 60mm, thickness = 3.6mm Design capacity 5
It is a battery of 00 mAh. Further, the conductive adhesive tape 4
And the above battery (A) except that it does not have a battery container surface connection.
Ten comparative batteries (B) having the same structure as that of (B) were produced. Each of these 10 batteries A (battery according to the present invention) and 10 batteries B (comparative battery) was charged at a constant current of 100 mA to 3.8 V at a constant current. Thereafter, when the lead-out portion of the negative electrode was hit several times with a hammer, the open circuit voltage of the battery A was reduced in the battery A, but no change was observed in the open circuit voltage of the comparative battery B.

Further, the battery B was charged at a constant current and a constant voltage of up to 4.1 V at 500 mA for 3 hours, and a charge / discharge cycle test of discharging the battery B at a constant current of 500 mA to 2.75 V was performed. Of the aluminum foil and leakage of the electrolyte were observed. Analysis of the breakage of the aluminum foil showed that the cause was aluminum pulverization due to lithium aluminum alloy formation. From the above, it can be seen that in both of the batteries A and B, the aluminum metal layer of the laminate film and the negative electrode lead came into contact at the lead lead-out portion of the negative electrode by hitting with a hammer. In the case of the battery A, this appeared in the form of a decrease in the open circuit voltage, and it was found that the occurrence of this problem could be easily detected without dismantling the battery. On the other hand, this defect could not be detected in the battery B, and the defect was not recognized until the battery was destroyed to the extent that it could be visually recognized.

[0021]

According to the present invention, since the metal of the laminated film is electrically connected to the positive electrode, even if the metal of the laminated film and the negative electrode are short-circuited during manufacturing or use, this can be easily performed. And a highly reliable non-aqueous electrolyte secondary battery can be provided.

[Brief description of the drawings]

FIG. 1 is an external perspective view showing one embodiment.

FIG. 2 is a schematic cross-sectional structure diagram showing a cross-sectional structure of a sealing portion.

FIG. 3 is a perspective view showing a schematic structure of an electrode body.

[Explanation of symbols]

1: Battery 2: Electrode body 4: Conductive adhesive tape
5: Positive electrode lead 5 ': Negative electrode lead 6: Battery container 16: Barrier layer (aluminum foil)

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Tetsuya Murai No. 1 Nishinosho Inono Babacho, Kichijoin, Minami-ku, Kyoto-shi, Japan F-term (reference) 5H011 AA12 CC02 CC06 CC10 DD13 EE04 5H022 AA09 AA18 BB27 CC02 CC12 CC19 CC21 CC30 5H029 AJ12 AJ14 AK03 AL06 AM01 BJ04 BJ12 BJ14 CJ05 DJ02 DJ05 EJ01 EJ12

Claims (3)

[Claims] 1. A non-aqueous electrolyte secondary battery in which an electrode body is housed in a battery container formed of a laminate sheet of a metal and a resin, wherein the metal of the laminate sheet is electrically connected to a positive electrode. Non-aqueous electrolyte secondary battery characterized by the above-mentioned. 2. The non-aqueous electrolyte secondary battery according to claim 1, wherein the electrode body includes a positive electrode, a negative electrode, and a separator, and is wound in a laminated or non-circular cross section. 3. The non-aqueous electrolyte secondary battery according to claim 2, wherein the negative electrode is located outside the electrode body.