JP2002100326A - Flat-type battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve safety of a battery, especially in anti-overcharge performance. SOLUTION: With regard to the flat-type battery wherein a power generation element composed of positive and negative electrode plates and an insulator is housed in a battery sheath body, the battery sheath body is wound with a belt-shaped body having not less than 75 MPa of tensile strength so that reduction of a discharge capacity resulted from swelling of the battery is suppressed, and even in case the flat-type battery generates heat and swells at a temperature rise, deformation of the power generation element is restricted, and a local concentration of electric current is suppressed to eventually realize the highly-safe flat-type battery. A heat shrinkable resin tube, resin tape or resin coating metal laminate sheet can be used as the belt-shaped body.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a flat battery wound with a band.

[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 and thickness so as to be portable. Accordingly, the built-in battery is required to have a flat shape, a high energy density, high safety and high reliability.

[0003] A typical non-aqueous electrolyte secondary battery which satisfies such demands is a non-aqueous electrolyte secondary battery, which uses not only a non-aqueous electrolyte secondary battery using a liquid non-aqueous electrolyte but also a polymer electrolyte. The solid polymer electrolyte secondary battery and the gelled polymer electrolyte secondary battery are also being put to practical use.

The power generating elements of these nonaqueous electrolyte secondary batteries include a positive electrode plate in which a positive electrode active material such as a composite oxide of lithium and a transition metal is held by a positive electrode current collector as a support, and a lithium metal or a lithium metal. A negative electrode plate that holds a lithium alloy or a carbonaceous material capable of occluding and releasing lithium ions on the negative electrode current collector, which is its support, and intervening between the negative electrode plate and the positive electrode plate to prevent a short circuit between the two electrodes It consists of an isolator.
In a non-aqueous electrolyte secondary battery using a non-aqueous electrolyte, a microporous membrane (separator) made of a polyolefin resin or the like is used as a separator, and an aprotic organic solvent such as LiPF6 or LiClO4 is used as a non-aqueous electrolyte. Is used in which a lithium salt is dissolved. In addition, in the secondary battery using the polymer solid electrolyte, the polymer solid electrolyte was used as the separator, and in the secondary battery using the gel polymer electrolyte, the non-aqueous electrolyte was contained in the polymer solid electrolyte. A gel electrolyte is used.

The power generating element used for the flat type non-aqueous electrolyte secondary battery includes a positive electrode plate and a negative electrode plate having a laminated structure in which a positive electrode plate and a negative electrode plate are sequentially laminated via an separator, and an elliptical shape. Some have a winding-type structure wound around. Basically, a winding-type power generating element is widely used because it can increase the electrode surface area and enable high-rate charging and discharging.

[0006] In these non-aqueous electrolyte secondary batteries, such a power generation element is housed in a battery exterior body.
The battery case is made of a metal case such as stainless steel, nickel-plated iron or aluminum. Furthermore, recently, a bag-shaped battery outer package made of a metal laminate sheet in which both surfaces of a metal foil such as aluminum are coated with a resin has been put to practical use.

When such a flat battery is used as a battery for a portable electronic device (for example, a portable telephone), it is incorporated in the portable electronic device in the following form from the viewpoint of protecting the battery from insulation. (1) Connect a protection circuit with terminals to the flat battery,
-A relatively robust battery pack is housed in a housing made of ABS resin or the like. (2) A protection circuit is connected to the flat battery, and the protection circuit is housed in a thin case made of PET (polyethylene terephthalate) resin or the like. I do. (3) A protection circuit with a connector is connected to the flat battery, and the flat battery and the entire protection circuit are covered with a heat-shrinkable tube to obtain a battery with a connector. Among these, the case of the battery pack of (1) also serves as an exterior cover of the portable electronic device, and is integrated with the portable electronic device by being fitted into the battery storage section of the portable electronic device. Further, the batteries of (2) and (3) are stored in a battery storage section of the portable electronic device, and an external cover is fitted thereon, and stored in the portable electronic device. FIG. 5 shows an example of the battery with a connector of the above (3).

In the case of the battery with a connector according to the above (3),
It is generally applied to a flat battery using a metal outer can, and plays a role of insulating protection of the battery and integrally fixing the battery and the protection circuit. In a flat battery using a bag-shaped exterior body, it is difficult to cover the entire battery with a heat-shrinkable tube, and a part of the bag-shaped exterior body is exposed.

Conventionally, as materials for heat-shrinkable tubes, heat-shrinkable polymer materials such as polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, polybutylene terephthalate, ethylene propylene rubber, isoprene rubber, chloroprene rubber, styrene butadiene rubber, Heat resistant rubber materials such as nitrile butadiene rubber have been used.

In the heat shrinkable tube for covering such a battery outer can, it is important that breakage and wrinkles do not occur in the covering step. In general, if the tensile strength is low, it breaks, and abnormalities such as pinholes are likely to occur.
If the tensile strength is increased, the heat shrinkage becomes poor, and wrinkles and poor adhesion at the ends are likely to occur. Therefore, without increasing the tensile strength of the heat-shrinkable tube unnecessarily,
Those having a tensile strength of less than 5 MPa have been used.

[0011]

In a flat battery housed in a battery outer package, the electrode plate expands with the repetition of the charge / discharge cycle, and the gas generated in the battery accumulates. Will increase. In particular, in the case of a non-aqueous electrolyte battery, if the battery is left at a high temperature for a long time in a charged state, the non-aqueous electrolyte reacts with the active materials of the positive and negative electrodes to decompose, and this decomposition product gas is accumulated in the battery, and the battery is discharged. By spreading the outer package, the thickness of the battery is increased, and the discharge capacity is also reduced. In the case of a flat battery using a bag-shaped outer package, the rigidity of the outer package itself is weak, and the battery thickness tends to increase.

[0012] In order to solve such a problem, merely covering the outer periphery of the battery outer casing with the heat-shrinkable tube having a relatively low strength of less than 75 MPa as described above increases the battery thickness (battery swelling) and increases the battery thickness. The accompanying decrease in discharge capacity could not be suppressed.

In addition, a power pack for portable electronic equipment using a non-aqueous electrolyte secondary battery has sufficient safety against an unexpected situation such as malfunction of a protection circuit or misuse. is necessary. For this reason, besides the protection circuit,
Although overcharge measures such as the provision of a thermal fuse and a PTC element have been taken, it is basically important that the battery body has sufficient safety against overcharge. There are various tests for verifying this safety.For example, there is an overcharge test in which a high voltage is externally applied to the battery body and an excessive current is forced to flow continuously. There is a demand for high security that does not lead to an unsafe state such as rupture or ignition even in a severe situation.

In such an overcharge test, as the current flowing through the battery becomes excessive, the calorific value increases, and the rate of increase in the internal pressure of the battery due to the gas decomposed by the heat increases. In a non-aqueous electrolyte secondary battery, this calorific value is large, and when the battery temperature exceeds a certain temperature, the carbonaceous material that occludes lithium ions is decomposed, and the heat of decomposition causes greater heat generation. Further, the decomposition of the lithium transition metal composite oxide of the positive electrode occurs, resulting in a thermal runaway state. In the worst case where the release of gas due to the opening of the safety valve cannot follow the rise in the internal pressure, a burst or ignition will occur. .

In order to prevent the thermal runaway state even when the excessive current flows in the battery as described above, it is important to suppress the amount of heat generated in the initial stage. If local power concentration does not occur between the batteries, it is considered that the battery does not explode or ignite only by relatively mild heat generation. In other words, if the outer periphery of the battery exterior body is wound and covered with a belt-like body such as a heat-shrinkable tube, and if the current concentration that occurs between the positive electrode plate and the negative electrode plate due to the deformation of the power generation element can be avoided, the initial stage. It is considered that the calorific value can be suppressed.

However, even with respect to such a problem, merely covering the outer periphery of the battery package with the relatively low-strength heat-shrinkable tube having a strength of less than 75 MPa as described above,
The calorific value could not be suppressed, and the battery could not be prevented from exploding or firing depending on the condition of excessive current.

The present invention has been made in view of the above-described circumstances, and has as its object to suppress battery swelling and the resulting decrease in discharge capacity, and to provide an unsafe condition even in an unexpected situation. An object of the present invention is to provide a flat battery with high safety that cannot be achieved.

[0018]

According to the present invention, the outer periphery of the battery outer casing is covered with a belt having a high tensile strength and fixed in close contact with the outer casing to suppress the swelling of the battery and the accompanying decrease in the discharge capacity. Also, to provide a flat battery with high safety that suppresses deformation of the power generating element even in an unforeseen situation and does not cause an extreme heat generation state or an unsafe state without causing local current concentration. I found that I can do it.

That is, according to the first aspect of the present invention, in a flat battery in which a power generation element composed of a positive electrode plate, a negative electrode plate, and a separator is housed in a battery outer case,
It is characterized by being wound with a belt having a tensile strength of 75 MPa or more. According to the first invention of the present application, it is possible to suppress a decrease in discharge capacity due to battery swelling,
Even if the flat battery generates heat and expands due to its temperature rise, the deformation of the power generating element is restricted, and the amount of deformation is reduced.
Therefore, a large change does not occur in the distance between the positive electrode plate and the negative electrode plate, and local heat concentration is suppressed, so that excessive heat generation does not occur.

The second invention of the present application is characterized in that the belt-like body in the first invention of the present application is any one of a heat-shrinkable resin tube, a resin tape and a resin-coated metal laminate sheet. According to the second aspect of the present invention, the above effects can be obtained by using a heat-shrinkable tube having a high tensile strength, a resin tape, or a resin-coated metal laminate sheet as the belt-shaped body covering the battery exterior body. Is found. In the case of a resin tape or a resin-coated metal laminate sheet, if the adhesive or adhesive is applied to at least a part of the surface wound in contact with the battery outer casing, it is easily fixed to the battery outer casing. It is desirable in terms of work efficiency.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As an example of a flat battery, a non-aqueous electrolyte secondary battery in which a power generating element formed by winding a positive electrode plate, a negative electrode plate, and an isolator in an oval shape is housed in a bag-shaped battery outer package is shown. The structure is shown in FIG. This flat battery has a strip-shaped positive electrode plate 12.
And a negative electrode plate 13 are wound in an elliptical shape via a separator 14 (separator), the power generation element 11 is housed in the bag-shaped battery outer package 2, and the respective electrodes of the positive electrode plate 12 and the negative electrode plate 13 are separated. Connecting conductor 1 connected and fixed to the body by ultrasonic welding
5 and 16 are led out from one end face in the winding axis direction of the power generating element 1, and have a structure in which the positive electrode terminal 3 and the negative electrode terminal 4 are formed outside the battery exterior body sealing portion 5, respectively.

In the present invention, as one of the embodiments, a belt-like body 13a as shown in FIG. The belt-shaped body in the present invention does not necessarily cover the entire battery, and aims to suppress the expansion and deformation of the battery. By simply winding the main part of the power generation element, the effect can be sufficiently exerted. Things. Therefore, as another one of the embodiments, as shown in FIG. 2, a narrow band 13b divided into several parts can be wound around the outer periphery of the battery package. Further, the narrow band-shaped body can be spirally wound around the outer periphery of the battery exterior body.

Further, the flat battery to which the present invention is applied is:
It is not limited to the battery using such a bag-shaped exterior body. In the case of a battery using a metal battery exterior can, a narrow band-shaped body 13b is wound around the outer periphery of the battery exterior can, and FIG. The embodiment shown in FIG. When a heat-shrinkable tube is used as the belt-like body and the entire battery including the protection circuit is covered, the configuration is as shown in FIG. 5 and the appearance is the same as that of a conventional battery with a connector.

In the case of a flat battery having a winding-type power generating element, the direction in which the band is wound may be perpendicular or parallel to the winding axis of the power generating element. What is necessary is just to select suitably according to the shape of a pattern battery. The same applies to a flat type battery having a power generation element of a stacked type structure.

When a flat battery is to be incorporated into a battery pack housing made of PC-ABS resin or the like, it is necessary to increase the thickness of the battery pack by the thickness of the band covered with the battery outer package. I am concerned. However, in the case where the battery pack is housed in a housing, a narrow band-like body 13 as shown in FIGS.
Since b can be divided into a plurality of sections and wound around the outer periphery of the battery exterior body, it is not directly connected to increasing the thickness of the battery pack.

Examples of the belt-shaped material of the present invention include heat-shrinkable polymer materials such as polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, and polybutylene terephthalate, which are excellent in heat shrinkage, insulation, and mechanical strength; A heat-shrinkable resin tube made of a heat-resistant rubber material such as rubber, isoprene rubber, chloroprene rubber, styrene butadiene rubber, and nitrile butadiene rubber can be used. In this case, a heat-shrinkable resin tube having a tube diameter larger than that of the battery exterior body is cut into a predetermined length, a flat battery is placed inside the resin tube, and the battery is easily heated by external heating. A belt-like body can be fixed to the outer periphery of the exterior body.

Further, the belt of the present invention includes a resin tape made of a polymer material such as polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, polybutylene terephthalate, and polyimide, which has excellent insulating properties and mechanical strength, and aluminum. A metal laminate sheet obtained by coating a metal foil sheet such as these with these polymer materials can be used. Usually, such a band-shaped body is used in which an adhesive or an adhesive is applied to at least a part of a surface wound in contact with the battery exterior body. By cutting such a band into a predetermined length, winding the band around the outer periphery of the battery case, and attaching the band, the band can be easily fixed to the battery case.

Further, the strip in the present invention must have a function of suppressing the expansion and thermal deformation of the battery when the battery temperature rises, and has a certain appropriate thickness.
Mechanical strength must be maintained not only at normal temperature but also at high temperature.

As a result of various tests, when a strip having a thickness of 0.1 mm was used, its strength at a shrinkage rate of 0 to 50% was 75M.
It became clear that a tensile strength of Pa or more was necessary. If the thickness of the band-shaped body is too large, the thickness of the battery after the shrink coating is increased, which is an obstacle to the thinning of the battery pack. On the other hand, if it is too thin, the effect of suppressing swelling of the battery outer package cannot be obtained. Therefore, the practical thickness of the strip is preferably in the range of 0.08 to 0.15 mm.

The positive electrode material of the flat battery according to the present invention includes a compound capable of occluding and releasing lithium, a composition formula LixM.
O2 or LiyM2O4 (where M is a transition metal,
An inorganic compound such as a composite oxide represented by 0 ≦ x ≦ 1 and 0 ≦ y ≦ 2), an oxide having tunnel-like vacancies, and a metal chalcogenide having a layered structure can be used. Specific examples thereof include LiCoO2, LiNiO2, and LiM.
n2O4, Li2Mn2O4, MnO2, FeO2,
V2O5, V6O13, TiO2, TiS2 and the like. Examples of the organic compound include a conductive polymer such as polyaniline. In addition, regardless of an inorganic compound or an organic compound, the above-mentioned various active materials may be mixed and used.

Further, as the compound of the negative electrode material, A
Alloys of lithium with l, Si, Pb, Sn, Zn, Cd, etc., transition metal oxides such as LiFe2O3, WO2, MoO2, carbonaceous materials such as graphite, carbon, Li5
Lithium nitride such as (Li3N) or metallic lithium foil, or a mixture thereof may be used.

As the solvent of the non-aqueous electrolyte, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, sulfolane, dimethyl sulfoxide, acetonitrile, dimethylformamide, dimethylacetamide, 1,2-
A polar solvent such as dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dioxolan, methyl acetate, or a mixture thereof may be used.

The lithium salt dissolved in the organic solvent includes LiPF6, LiClO4, LiBF4, LiAs
F6, LiCF3CO2, LiCF3SO3, LiN
(SO2CF3) 2, LiN (SO2CF2CF3)
2, LiN (COCF3) 2 and LiN (COCF2)
A salt such as CF3) 2 or a mixture thereof may be used.

Further, as the separator of the flat battery according to the present invention, a separator obtained by impregnating an electrolytic solution into a microporous insulating polyethylene film, a solid polymer electrolyte, or a solid polymer electrolyte containing an electrolytic solution is used. A gel electrolyte or the like can also be used. Also,
An insulative microporous film and a solid polymer electrolyte may be used in combination. Further, when a porous solid polymer electrolyte membrane is used as the solid polymer electrolyte, the electrolyte contained in the polymer and the electrolyte contained in the pores may be different.

[0035]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to examples of a nonaqueous electrolyte secondary battery in which a power generation element is housed in a bag-shaped battery outer case. However, the present invention is not limited to the following examples. It is needless to say that the present invention can be implemented by appropriately changing the scope without changing the gist.

Example 1 (Preparation of Positive Electrode Plate) LiCoO ₂ was used as a positive electrode active material at 95%.
% Of acetylene black as a carbon-based conductive agent, and polyvinylidene fluoride (PVd) as a binder.
F) in a proportion of 3% by weight and further add N-methyl-2.
-A mixture to which pyrrolidone (NMP) was added was kneaded to obtain a positive electrode paste (coating liquid). Next, this positive electrode paste was
Intermittent coating was performed according to a predetermined coating pattern on an electrode substrate made of an aluminum foil having a thickness of 5 μm, and after drying, pressing was performed so that the porosity of the electrode mixture layer became 30%. Then, a positive electrode plate having a predetermined size was cut out from the long positive electrode plate sheet.

(Preparation of Negative Electrode Plate) Mesocarbon microbeads made from mesophase small spheres having a two-layer structure having a layer of non-graphitizable carbon on the surface generated in the carbonization process of pitch were used as a negative electrode active material at 96% by weight. Polyvinylidene fluoride (PVdF) was mixed at a ratio of 4% by weight as a binder,
The mixture to which N-methyl-2-pyrrolidone (NMP) was added was kneaded to obtain a negative electrode paste (coating liquid). Next, this positive electrode paste is intermittently applied to an electrode substrate made of a copper foil having a thickness of 15 μm according to a predetermined coating pattern, and after drying, is pressed so that the porosity of the electrode mixture layer becomes 35%. did.
Then, a negative electrode plate having a predetermined size was cut out from the long negative electrode plate sheet.

(Preparation of Power Generating Element) The above-mentioned positive electrode plate and negative electrode plate were simultaneously wound with separators to form a power generating element. As the separator, a polyethylene microporous membrane (separator) having a thickness of 25 μm and a porosity of 40% was used.

(Preparation of Test Battery) The above-mentioned power generating element was resin-coated metal laminate sheet (polyethylene resin film +
(Aluminum foil + polyethylene terephthalate resin film), and the non-aqueous electrolyte having a structure as shown in FIG. 4 is obtained by injecting a non-aqueous electrolyte and heat sealing the opening. An electrolyte secondary battery was manufactured. As the non-aqueous electrolyte, one obtained by dissolving LiPF ₆ as a lithium salt at 1 mol / liter in a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) at a volume ratio of 1: 1 was used.

(Wound coating of a band-like body)
Inserted into a heat-shrinkable tube (0.1 mm thick) made of crosslinked polyethylene having a tensile strength of 76 MPa according to the present invention,
The sample was passed through a hot-air heating tank at a temperature of 2 ° C. for 2 minutes, and the heat-shrinkable tube was covered around the battery outer casing, thereby forming a test battery of Example 1 as shown in FIG.

[Example 2] A polyimide resin tape (0.1 mm thick) having a tensile strength of 80 MPa and cut into a width of 12 mm was wound into the flat battery of the above-mentioned example 1 in three sections, and a battery was formed using an adhesive. A test battery of Example 2 as shown in FIG. 2 was fixed to the outer package.

Example 3 A resin-coated metal laminate sheet (0.1 mm thick) having a tensile strength of 100 MPa and cut to a width of 12 mm was wound around the flat battery of Example 1 in three sections, and the adhesive was used as an adhesive. Thus, a test battery of Example 3 as shown in FIG. 2 was fixed to the battery exterior body.

Comparative Example 1 A test battery of Comparative Example 1 was prepared by coating the flat battery of Example 1 with a conventionally used crosslinked polyethylene heat-shrinkable tube (0.1 mm thick) having a tensile strength of 70 MPa. Was configured.

[High-Temperature Leaving Test] A charge / discharge test was performed on each of the three batteries of Example and Comparative Example in an atmosphere at a temperature of 25 ° C. under the following charge / discharge conditions, and the initial discharge capacity and battery thickness of the battery were measured. Charging condition: 540 mA constant current / 4.2 V constant voltage × 5 h Discharging condition: 540 mA constant current, final voltage 3.0 V Next, after charging under the above charging conditions, the temperature was 80 ° C.
Was left under the atmosphere for 48 hours. Then, discharge was performed under the above-described discharge conditions in an atmosphere at a temperature of 25 ° C., and the discharge capacity and the battery thickness after being left at a high temperature were measured.

[High-Temperature Charge / Discharge Cycle Test] A charge / discharge test was performed on each of the three batteries of Example and Comparative Example in an atmosphere at a temperature of 60 ° C. under the following charge / discharge conditions. The number of cycles to decrease to% was measured. Charging conditions: 540 mA constant current, 4.2 V constant voltage × 5 h Discharging conditions: 540 mA constant current, final voltage 3.0 V

[Overcharge Test] The batteries of Examples and Comparative Examples were connected to a power supply having a load voltage of 12 V, and the following currents were passed through the batteries for 12 hours continuously to check the heat generation state of the batteries. The number of test batteries was three for each of the following test conditions. Current value: 420 mA, 480 mA, 540 mA, 6
00mA, 660mA

[Test Results] The results of the various tests described above for the batteries of the examples and the comparative examples are shown in Table 1 below. In addition,
The numerical values in Table 1 are obtained by taking an average value for three test batteries.

[0048]

[Table 1]

Regarding the battery thickness, all the test batteries swelled by being left at a high temperature of 80 ° C., but the test batteries of Examples 1 to 3 showed an increase in thickness compared to the test battery of the comparative example. It is understood that the expansion is suppressed as the strength of the belt-like body is small. In the test battery of the example having a small thickness increase, the discharge capacity after high temperature storage was high, and the electrode reaction did not proceed smoothly in the portion where the distance between the positive electrode and the negative electrode was increased due to the expansion of the battery. it is conceivable that. However, in the test battery of Example 2 in which the strip was divided into a plurality of turns and wound, the discharge capacity was slightly lower than that of the test battery in Example 1, and the unwound portion of the strip contributed to the electrode reaction. This indicates that there were some parts that did not.

Next, regarding the charge-discharge cycle life characteristics at high temperatures, the number of cycles reaching 80% of the initial capacity in the test batteries of Examples 1 to 3 is more than twice that of the battery of the comparative example. Understand. Moreover, as a whole, the higher the strength of the band, the more the number of cycles. It is considered that this also prevented the reduction of the discharge capacity by winding the high-strength band to suppress the expansion of the battery.

Regarding the overcharge resistance, the test batteries of the example and the comparative example did not ignite or burst, but the comparative example battery produced smoke when continuously supplied with a current of 600 mA or more. On the other hand, in the battery of Example 1, smoke was generated by continuous current supply of 660 mA, and in the batteries of Examples 2 and 3, no heat was generated even by continuous current supply of 660 mA. By winding the high-strength strip, the batteries of any of the examples did not reach an unsafe condition, which remained relatively mild without any local current concentration. It is thought to be due to this.

The present invention suppresses the expansion of the battery and the accompanying decrease in the discharge capacity by winding a band-shaped body having a higher tensile strength than the conventional heat-shrinkable tube around the flat-type battery, and at the same time secures the battery. , Especially improved overcharge resistance. In the above description, the nonaqueous electrolyte secondary battery has been described as an example of the flat battery, but such a problem is not necessarily limited to the nonaqueous electrolyte secondary battery. The present invention also has a common problem, and the application of the present invention can be solved in other flat batteries as in the case of the non-aqueous electrolyte secondary battery. Therefore, the battery according to the present invention is not restricted by the type, shape, and material of the outer package of the flat type battery.

[0053]

As described above, the present invention is characterized in that a belt-shaped body having a tensile strength of 75 MPa or more is wound around a battery outer casing of a flat battery containing a power generating element.

According to the present invention, even if the flat type battery generates heat and expands due to its temperature rise, the deformation of the power generating element is restrained and the amount of deformation is reduced. Therefore, a large change does not occur in the distance between the positive electrode plate and the negative electrode plate, and local heat concentration is suppressed, thereby preventing excessive heat generation. The present invention has a simple configuration in which the periphery of the battery outer body is wound around a belt-shaped body, does not cost much, and serves as an integral protection of the battery protection by the band-shaped body covering, and an accessory part such as a protection circuit. Since the safety of the battery, particularly the overcharge resistance, can be surely improved, its practicality is high.

[Brief description of the drawings]

FIG. 1 shows one of the embodiments according to the present invention, and is a perspective view of a battery in which a flat-type battery using a bag-shaped exterior body is covered with a wide band-shaped body.

FIG. 2, showing one embodiment of the present invention, is a perspective view of a battery in which a narrow band formed of a plurality of strips is wound around a flat battery using a bag-shaped exterior body.

FIG. 3 shows one of the embodiments according to the present invention, and is a perspective view of a battery in which a narrow band composed of a plurality of strips is wound around a flat battery using a metal outer can.

FIG. 4 is a perspective view of a flat battery using a bag-shaped outer package.

FIG. 5 is a perspective view of a battery with a connector in which a conventional flat battery using a metal outer can is covered with a wide band.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Flat type battery main body 2 Battery exterior body 3 Positive electrode terminal 4 Negative electrode terminal 5 Terminal formation side sealing part 6 Back sealing part 7 Bottom sealing part 8 Band 8a Heat-shrinkable resin tube 8b Resin tape or resin-coated metal laminate Sheet 11 Positive electrode plate 12 Negative electrode plate 13 Separator 14 Power generation element 15 Positive electrode connection conductor 16 Negative electrode connection conductor

Claims (2)

[Claims] 1. A flat battery in which a power generation element composed of a positive electrode plate, a negative electrode plate, and a separator is housed in a battery outer casing, wherein the battery outer casing is a belt-shaped body having a tensile strength of 75 MPa or more. A flat type battery characterized by being wound. 2. The flat battery according to claim 1, wherein the strip is any one of a heat-shrinkable resin tube, a resin tape and a resin-coated metal laminate sheet.