Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Tape or flexible-type cell including tape fuel cells or...
Reexamination Certificate
1998-02-20
2001-02-13
Kalafut, Stephen (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Tape or flexible-type cell including tape fuel cells or...
C429S211000, C429S061000, C429S133000, C429S161000, C429S057000
Reexamination Certificate
active
06187472
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a light weight small-sized thin battery to be mounted in portable electronic apparatus. The present invention relates to, e.g., lithium ion secondary battery which needs to be sealed so that it is free of water content, particularly a thin battery comprising a safety mechanism which can work when the battery body is simply sealed in the form of bag.
2. Description of the Related Art
FIG. 30
illustrates a schematic diagram of a prior art thin secondary battery disclosed in publications (e.g., “Kouseino Denchi no saishin manyuaru (Modern manual of high performance battery)”, Sogo Gijutsu Center, page 185, 1989). In this drawing, the reference numeral
1
indicates a positive electrode, the reference numeral
2
indicates a negative electrode, the reference numeral
3
indicates a separator, the reference numeral
4
indicates a positive electrode collector tab, the reference numeral
5
indicates a negative electrode collector tab, the reference numeral
6
indicates an encapsulating bag, the reference numeral
7
indicates a bag sealing portion, the reference numeral
8
indicates a coating portion for metal bonding, the reference numeral
9
indicates a silicone oil, and the reference numeral
10
indicates a reinforcing resin plate.
In the foregoing example, the bag sealing portion
7
is bonded to the majority of the periphery of a small-sized sealed lead storage battery to seal a battery body
19
composed of the positive electrode
1
, the negative electrode
2
, the separator
3
and an electrolyte in the encapsulating bag
6
made of an insulating material for the purpose of reducing the size and weight of the case of the small-sized sealed lead storage battery. The collector tabs
4
and
5
are conductors for making electrical input/output between the internal electrode and the external circuit and are connected to the positive electrode
1
and the negative electrode
2
, respectively. The coating for metal bonding
8
is provided to connect the collector tabs
4
and
5
to the encapsulating bag
6
. Finally, the electrolyte is injected into the encapsulating bag
6
through the unsealed opening at the top of the battery body as viewed in FIG.
30
. The opening is then sealed with the silicone oil
9
and the reinforcing resin plate
10
. However, this battery is not equipped with a safety mechanism for blocking current passage upon the occurrence of troubles such as overcharging and shortcircuiting or relaxing the inner pressure of the encapsulating bag
6
.
FIG. 31
is a sectional view illustrating a prior art hermetically-sealed can battery as disclosed in JP-A-6-140012 (The term “JP-A” as used herein means an “unexamined published Japanese patent application”). In the drawing, the reference numeral
11
indicates a positive electrode terminal plate, the reference numeral
12
indicates a negative electrode terminal plate, the reference numeral
14
indicates a safety valve, the reference numeral
15
indicates a spring, the reference numeral
16
indicates a gasket, the reference numeral
17
indicates an electrolyte, and the reference numeral
18
indicates a casing.
In the foregoing example, a cylindrical lithium ion battery comprising a positive electrode
1
, a negative electrode
2
, a separator
3
and the electrolyte
17
assembled into a battery body comprises a rubber elastic safety valve
14
supported by a spring
15
and provided interposed between the positive electrode terminal plate
11
and the sealing plate
13
. The valve hole is normally closed. The pressure at which the valve begins to open is set to a predetermined value. In this arrangement, any accidents such as rupture due to the rise in the inner pressure of the battery can be prevented. Further, the deterioration of the battery body due to the opening of the battery can be inhibited.
FIG. 32
is a sectional view illustrating a prior art sealed can battery as disclosed in JP-A-6-96803. In this drawing, the reference numeral
21
indicates a positive electrode lead which electrically connects a positive electrode
1
to a sealing plate
13
. The reference numeral
22
indicates an explosion-proof switch which normally is electrically connected to the sealing plate
13
at its point
22
b
. The reference numeral
23
indicates an insulating sheet. The reference numeral
24
indicates an insulating material.
In normal operation, the electrical connection between the positive electrode
1
and the positive electrode terminal plate
11
is secured by the positive electrode lead
21
, the sealing plate
13
and the explosion-proof switch
22
to allow the battery body to act as a battery. When gas is produced from the interior of the battery due to overcharging or shortcircuiting, the inner pressure of the battery rises to cause the central part
22
a
of the explosion-proof switch
22
to deform. When the inner pressure of the battery reaches the predetermined value, the contact point
22
b
is released from electrical connection to the sealing plate
13
. In this arrangement, current passage is blocked upon overcharging or shortcircuiting to prevent ignition or rupture of the battery.
In general, when gas is produced from the electrolyte or active material due to overcharging or shortcircuiting in a sealed battery encapsulating a battery body, the inner pressure of the sealed portion rises to possibly cause troubles such as ignition or rupture. Therefore, a safety valve for relaxing inner pressure as shown in
FIG. 31
or a current blocking device as shown in
FIG. 32
is needed. As in the conventional examples shown in
FIGS. 31 and 32
, various safety devices have been proposed for sealed can batteries comprising a casing prepared from a difficultly-deformable material such as metal and ABS.
In recent years, with the spread of portable electronic apparatus, further reduction of the weight, size and thickness of these portable electronic apparatus have been required. In order to simplify the casing or electrode terminal, a sealed battery comprising a battery body
19
simply sealed in the form of bag with an insulating coating material as shown in
FIG. 30
has been developed. However, any small-sized light safety mechanism which makes the best use of this simple sealing has been little studied.
The secondary lithium battery which is under extensive development at present comprises lithium metal or lithium ion as a positive electrode active material. In this arrangement, a battery having a lighter weight which supplies a higher voltage than ever can be obtained. However, since such a positive electrode active material is weak to the invasion of water from the air, it is necessary that the entire battery body be completely sealed. Further, since lithium batteries have a high energy density, further care must be taken against accidents such as shortcircuiting.
SUMMARY OF THE INVENTION
The present invention has been worked out to eliminate these problems. An object of the present invention is to realize in a form as light and small as possible in a simple way a safety mechanism for blocking current passage, relaxing the rise in the inner pressure of the battery and preventing electrolyte leakage during overcharging or shortcircuiting in a thin battery sealed in the form of bag with a flexible insulating coating material such as heat-fused laminated film by making the use of the characteristics of such a simple encapsulating bag.
The first aspect of the present invention concerns a thin battery comprising a flat battery body having a positive electrode and a negative electrode laminated with an ionically-conducting layer provided interposed therebetween, a flexible encapsulating bag for sealing said battery body with a sealing portion, and positive electrode collector tab and negative electrode collector tab connected to said positive electrode and said negative electrode, respectively, and penetrating a part of said encapsulating bag to make an electrical input/output to the external circuit, wherein said p
Aihara Shigeru
Shiota Hisashi
Shiraga Syo
Yokoyama Tetsuhide
Alejandro Raymond
Kalafut Stephen
Mitsubishi Denki & Kabushiki Kaisha
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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