JP4354028B2 - Battery case with safety valve - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a battery case for forming a battery by storing battery constituent materials, and is particularly suitable for a sheet-like battery case such as a lithium polymer battery, and is light, thin, tough, water vapor and other gas barriers. The present invention relates to a battery case having a safety valve structure and excellent safety as well as excellent performance such as safety.
[0002]
[Prior art]
Conventionally, a metal case is usually used as a battery case for storing battery constituent materials. However, along with the development and widespread use of various electronic devices such as notebook computers and mobile phones, their weight and thickness have been reduced, and the batteries used for these have been made as light as possible and used. There is a demand for weight reduction and thinning so that the battery space in the device can be reduced.
[0003]
In order to meet such a demand, for example, various sheet-like batteries that are light and thin in sheet form by introducing a polymer material into battery electrodes and electrolytes have been researched and developed.
In such a sheet-like battery, the battery case serving as the outer wall material is also preferably a thin and light film, for example, a base film layer such as plastic, a barrier layer, and a thermal adhesive resin layer. Using a laminated film laminated with (sealant layer), etc., a bag-shaped battery case with one end opened is prepared, the battery components are housed inside, and the electrode terminals are extended from the inside to the outside through the openings. A sheet-shaped battery is manufactured by sealing the opening by thermal bonding.
[0004]
The laminated film used in such battery cases has various properties such as lightness and thinness, various strengths and durability, water vapor and other gas barrier properties, heat sealing properties, and thermal adhesion to electrode terminals. Is needed.
For this purpose, for example, a metal foil such as water vapor or other gas barrier excellent in gas barrier properties is used for the intermediate layer, and various strengths and resistances are imparted to both sides of the metal foil, and the metal foil is protected to protect the metal foil. A method has been adopted in which a biaxially stretched plastic film is laminated as a material film, and a laminated film is formed by laminating polyethylene and other polyolefin-based resin as a heat-adhesive resin layer (sealant layer) as the innermost layer. .
[0005]
By using such a laminated film in the case of a sheet-like battery such as a lithium polymer battery, a sheet-like battery that is almost satisfactory in terms of performance such as various strengths and durability and water vapor and other gas barrier properties is produced. be able to.
[0006]
On the other hand, in a lithium ion battery using a metal deep-drawn container for the battery case, there is a risk of explosion due to an increase in internal pressure due to an abnormal rise in temperature inside the battery, so a pressure release valve must be provided to prevent explosion. It has been.
In this regard, in a polymer battery using a laminated film for a battery case, a pressure release valve has generally been unnecessary.
However, even in the case of a polymer battery, in order to further enhance safety, it is preferable to provide a pressure release valve, and it has been desired to provide some kind of safety valve.
[0007]
From such a background, there was a polymer battery in which a degassing valve (trade name: Aroma Fin Valve, manufactured by BOSCH), which was developed for a roasted coffee packaging bag, was attached to a battery case made of laminated film as a pressure release valve. .
However, such a gas vent valve is configured such that when the internal pressure reaches a certain level due to the gas generated in the bag, excess gas is released and the internal pressure is maintained within a certain range. Although it has the effect of preventing the internal pressure from rising above a certain value, the valve itself does not have so much gas barrier properties, and when used in a polymer battery, water vapor and other gas barrier properties decrease, and the battery performance There was a problem of lowering.
[0008]
[Problems to be solved by the invention]
The present invention has been made in order to solve such problems. The object of the present invention is to provide a thin and light battery case such as a polymer battery with various strengths and resistances, water vapor and the like. When a certain internal pressure is generated in the case due to misuse, etc., without damaging its water vapor and other gas barrier properties, while forming with a laminated film having gas barrier properties and heat sealing properties. By providing a safety valve structure that automatically disconnects the charge / discharge circuit, stops temperature rise and internal pressure rise, and prevents the case from rupturing, it excels in the above-mentioned various performances and also in safety. It is to provide a battery case.
[0009]
[Means for Solving the Problems]
The above problems can be solved by the following present invention.
That is, the invention described in claim 1 comprises a bag body made of a laminated film having an opening at one end, containing the constituent material of the battery inside, and extending the electrode lead from the inside to the outside to seal the opening. In the battery case of the type, the opening of the bag body through which the electrode lead passes is sealed in two stages of the inner partition seal part and the outer seal part, and the main chamber and the electrode lead in which the constituent materials of the battery are stored And the partition seal portion has a weak seal portion, and the electrode lead of the dependent chamber is provided with a shutdown mechanism that is disconnected by an increase in internal pressure. It consists of a battery case with a safety valve.
[0010]
By adopting such a configuration, for example, an aluminum foil layer is used as an intermediate layer for a laminated film forming a battery case, and biaxially stretched plastics such as a biaxially stretched polyethylene terephthalate film or a biaxially stretched nylon film are provided on both sides thereof. By using a laminated film in which films are laminated and a polyolefin resin layer with excellent heat sealing properties is laminated on the innermost layer, the battery case has various strengths and resistances, as well as water vapor and other gas barrier properties. It will be excellent.
[0011]
The battery case has an opening through which the electrode lead passes, which is sealed in two stages, that is, an inner partition seal portion and an outer seal portion. In addition to being divided into a subordinate chamber through which the lead passes, a weak seal portion is provided in the partition seal portion, and a shutdown mechanism is provided in the electrode lead of the subordinate chamber to disconnect the connection due to an increase in internal pressure.
In such a safety valve structure, the main chamber and the subordinate chamber are completely shut off from the outside, so that water vapor and other gas barrier properties are well maintained.
[0012]
In addition, with such a safety valve structure, when the temperature inside the main compartment of the battery case rises due to misuse, etc., and the internal pressure of this part rises, it is provided in the inner partition seal part when a certain internal pressure is reached. As a result, the internal pressure is released to the subordinate chamber and the internal pressure rises and expands as a result of the shutdown mechanism operating and disconnecting the electrode leads, so charging or discharging stops. The increase in internal pressure is also stopped. Therefore, the outer seal portion is not broken, and explosion can be prevented, and a battery case excellent in safety can be provided.
[0013]
The invention described in claim 2 is characterized in that the weak seal portion of the partition seal portion is formed by a narrow width seal portion in which the width of the partition seal portion is narrowed in a region including a portion where the electrode lead is interposed. The battery case with a safety valve according to claim 1.
[0014]
By adopting such a configuration, the thermal adhesiveness between the electrode lead and the innermost surface layer of the battery case is not so strong from the beginning, so it is easy to adjust the peel strength of the weak seal part formed by the narrow width seal part. Therefore, it is possible to provide a battery case with a safety valve in which the shutdown mechanism operates more reliably due to an increase in internal pressure.
[0015]
In the invention described in claim 3, the weak seal portion of the partition seal portion is formed of a heat seal portion of an easy peel resin layer provided in a pattern in a region including the partition seal portion. The battery case with a safety valve according to claim 1.
[0016]
By adopting such a configuration, it is possible to adjust the peel strength of the weak seal portion provided in the partition seal portion to a desired strength, and thus to provide a battery case with a safety valve that can more reliably operate the shutdown mechanism due to an increase in internal pressure. it can.
[0017]
According to a fourth aspect of the present invention, there is provided the shutdown mechanism in which the connection is disconnected due to the internal pressure increase provided in the electrode lead of the subordinate chamber divided into the external output side and the battery side, and in the subordinate chamber, The battery case with a safety valve according to any one of claims 1 to 3, wherein the battery case is formed of an electrode lead having a split structure in which end edges overlap and connect.
[0018]
Such a shutdown mechanism provided in the electrode lead in the subordinate chamber may be provided in one of the positive electrode lead and the negative electrode lead, or may be provided in both electrode leads.
The electrode lead divided into the inner side (battery side) and the outer side is bonded to the inner surface of the battery case on the opposite side facing each other in the dependent chamber by thermal bonding or the like, thereby operating the shutdown mechanism. When the sub chamber expands due to an increase in internal pressure, the overlapping portion (connecting portion) of the divided electrode leads is surely cut off and the charge / discharge circuit is cut off.
[0019]
Therefore, by adopting such a configuration, when the temperature in the main chamber of the battery case rises due to misuse or the like, and the internal pressure of this part rises, when the internal pressure reaches a certain internal pressure, the inner partition seal part As a result, the internal pressure is released to the subordinate chamber and the internal pressure of the subordinate chamber rises and expands. As a result, the shutdown mechanism operates reliably and the electrode lead connection portion of the split structure is disconnected. As a result, the increase in internal pressure is stopped, and the battery case can be prevented from exploding.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the battery case with a safety valve of the present invention, such as materials and processing methods, will be described.
The laminated film used in the battery case with a safety valve of the present invention is not particularly limited. For example, a metal foil layer such as an aluminum foil layer is used as a water vapor or other gas barrier layer as an intermediate layer, and various strengths and resistances are provided on both sides thereof. Biaxially stretched polyethylene terephthalate film (hereinafter referred to as PET film), biaxially stretched nylon film (hereinafter referred to as ON film), biaxially stretched plastic film (hereinafter referred to as OPP film), etc. It is preferable that the base film layer also serves as a base film layer, and further, a polyolefin resin layer having excellent heat sealability is laminated on the innermost layer.
[0021]
For the biaxially stretched plastic film as the base film laminated on both sides of the metal foil layer, the PET film, ON film, OPP film, etc. can be used, and these may be used alone, A laminated film laminated with another film may be used.
[0022]
Among the biaxially stretched plastic films, especially the PET film has low hygroscopicity, is excellent in rigidity, tensile strength, bending strength, impact strength, scratch resistance, heat resistance, water resistance, etc., and is well balanced. It can be suitably used because it has performance and is relatively inexpensive and economical.
ON film is slightly higher in hygroscopicity than PET film, but it is rich in flexibility and excellent in piercing strength, impact strength, bending strength, cold resistance, etc. Can be used.
The OPP film is excellent in not only moisture resistance, water resistance and chemical resistance, but also in tensile strength, bending strength and the like, and is particularly advantageous in that it is inexpensive.
[0023]
The method for laminating such a biaxially stretched plastic film on both sides of the intermediate layer such as an aluminum foil layer is not particularly limited, and it can be laminated by a known dry lamination method, extrusion lamination method, or the like. In particular, when it is desired to increase the laminate strength, it is preferable to use a dry lamination method.
The thickness of such a biaxially stretched plastic film is preferably 8 to 80 μm and more preferably 12 to 40 μm when used on the outside of the metal foil layer. Moreover, when using it inside a metal foil layer, it is not necessary to make it so thick, and about 8-30 micrometers is suitable.
[0024]
Next, aluminum foil, copper foil, etc. can be used for the metal foil layer of the intermediate layer. However, aluminum foil is more widely used and is easily available in various thicknesses, lightweight, workability and economy. It is preferable in that it has excellent properties.
In the case of using an aluminum foil, the thickness is suitably about 7 to 25 μm.
If the thickness of the aluminum foil layer is less than 7 μm, pinholes increase and water vapor and other gas barrier properties decrease, which is not preferable. A thickness exceeding 25 μm already has sufficient gas barrier properties. This is not desirable because it is not necessary and rather disadvantageous in terms of economy.
[0025]
For example, when an aluminum foil having a thickness of 9 μm is used as the intermediate layer, the water vapor permeability is easily 0.01 g / (m ² · 24 hrs), (40 ° C., 90% RH) or less. As a result, it is easy to further improve the level.
[0026]
The innermost layer of the laminated film is laminated with a polyolefin resin layer having excellent heat sealing properties as a heat-adhesive resin layer (sealant layer). Specifically, in addition to polyethylene, it is a copolymer thereof. Ethylene-α / olefin copolymer resin, ethylene-vinyl acetate copolymer resin, ethylene-acrylic acid ester copolymer resin, ethylene-methacrylic acid ester copolymer resin, ethylene-acrylic acid copolymer resin, ethylene- Methacrylic acid copolymer resins, other acid-modified polyolefin resins, ionomers, and the like can be used. These may be used alone or in a blend of two or more.
[0027]
Among these, a suitable material can be appropriately selected and used in consideration of the material (surface presence / absence of surface coating) of the electrode lead.
In particular, when the electrode lead is formed of a bare metal foil or the like with no surface coating, the polyolefin resin layer has an ethylene-acrylic acid copolymer resin, an ethylene-methacrylic acid copolymer resin, and other acid-modified. Use of a polyolefin-based resin, an ionomer, or the like is preferable because thermal adhesiveness can be improved.
The thickness of the innermost polyolefin-based resin layer is preferably 15 to 100 μm, and more preferably 30 to 80 μm.
[0028]
As a method of laminating the innermost polyolefin resin layer, it is easy to adopt a known extrusion coating method, but a polyolefin resin film previously formed into a film is laminated by a dry lamination method or an extrusion lamination method. You can also.
[0029]
The following structures are mentioned as a typical example of a structure of such a laminated | multilayer film. However, the pretreatment and adhesive layer used for lamination are omitted.
(1) PET film (thickness 16 μm) / aluminum foil (thickness 9 μm) / PET film (thickness 12 μm) / polyolefin resin layer (thickness 40 μm) [innermost layer]
(2) ON film (thickness 15 μm) / aluminum foil (thickness 9 μm) / PET film (thickness 12 μm) / polyolefin resin layer (thickness 40 μm) [innermost layer]
(3) OPP film (thickness 20 μm) / aluminum foil (thickness 9 μm) / PET film (thickness 12 μm) / polyolefin-based resin layer (thickness 40 μm) [innermost layer]
(4) PET film (thickness 16 μm) / aluminum foil (thickness 9 μm) / OPP film (thickness 20 μm) / polyolefin resin layer (thickness 40 μm) [innermost layer]
(5) PET film (thickness 16 μm) / aluminum foil (thickness 9 μm) / ON film (thickness 15 μm) / polyolefin resin layer (thickness 40 μm) [innermost layer]
[0030]
(6) ON film (thickness 15 μm) / PET film (thickness 12 μm) / aluminum foil (thickness 9 μm) / PET film (thickness 12 μm) / polyolefin resin layer (thickness 40 μm) [innermost layer]
(7) PET film (thickness 12 μm) / ON film (thickness 15 μm) / aluminum foil (thickness 9 μm) / PET film (thickness 12 μm) / polyolefin resin layer (thickness 40 μm) [innermost layer]
(8) PET film (thickness 12 μm) / OPP film (thickness 20 μm) / aluminum foil (thickness 9 μm) / PET film (thickness 12 μm) / polyolefin resin layer (thickness 40 μm) [innermost layer] is there.
[0031]
The battery case with a safety valve of the present invention is formed by heat-sealing the laminated film as described above into a bag shape having one open end, but the shape is free and can be formed into a bag body having a desired shape. .
When the battery constituent material is housed in the bag body and the electrode lead is extended from the inside to the outside to seal the opening, the opening through which the electrode lead passes is divided into the inner partition seal portion and the outer seal. In addition to providing a main chamber in which the constituent materials of the battery are stored and a subordinate chamber through which the electrode leads pass, a weak seal portion is provided in the inner partition seal portion. A safety valve is provided on the electrode lead by providing a shutdown mechanism that is disconnected by an increase in internal pressure.
[0032]
As such an electrode lead shutdown mechanism, for example, as described above, the electrode lead is divided into the inner battery side and the outer external output side, and the end edges of the two are normal. When the subordinate chambers are overlapped and connected in the subchamber and the subchamber expands due to internal pressure, the electrode leads of both are adhered to the inner surface of the opposite battery case and the connection of the overlapping portion is cut off. -It can be set as the structure where a discharge circuit is cut | disconnected.
[0033]
As another method, the electrode lead passing through the subordinate chamber is not divided, and the ribbon-like electrode lead is provided with a notch cut on the side, or intermittent cut such as a perforation. As a structure in which a line of sight is provided to make it easy to cut and the notch or both sides of the cut line are bonded to the inner surface of the opposite battery case opposite to each other, when the dependent chamber is inflated by internal pressure, it is pulled to the opposite side Then, the electrode lead can be cut at the notch or cut line, and the charge / discharge circuit can be cut off.
[0034]
【Example】
Hereinafter, the present invention will be described more specifically with reference to the drawings of the embodiments. However, the present invention is not limited to these drawings.
[0035]
FIG. 1 is a schematic plan view showing an example of a sheet-like battery produced by the battery case with a safety valve of the present invention.
2 is an enlarged cross-sectional view taken along line AA in FIG. 1. (A) is a cross-sectional view when the electrode lead is connected (normal state), and (B) is when the safety valve is operating (when the shutdown mechanism is operating). FIG.
[0036]
In FIG. 1, the outer periphery of a sheet-like battery 200 is formed by a battery case 100. The battery case 100 is folded at the bottom 2 so that the innermost layers are in contact with each other, and edge portions on both sides are formed. Is formed into a bag body having an upper opening.
In the present invention, when the battery constituent material is housed in the battery case 100 and the positive and negative electrode leads are extended and sealed from the inside to the outside through the opening, the safety valve structure is configured as follows. Is added.
[0037]
That is, one of the positive and negative electrode leads extending from the inside to the outside through the opening after housing the battery constituent material in the battery case 100 is the same as the case of a normal sheet battery. 7 and the other electrode lead is divided into a battery-side electrode lead 7b and an external output-side electrode lead 7a.
Then, the heat seal of the opening is divided into two stages of an inner partition seal portion 4 and an outer seal portion 6, and the main chamber 9 in which the battery constituent material is stored and the subordinate chamber through which the electrode lead passes. There will be 10 2 rooms.
[0038]
The partition seal portion 4 is provided with a narrow seal portion 5 in which the width of the partition seal portion is narrowed at a position where the electrode lead 7b is interposed to form a weak seal portion.
In the dependent chamber 10, the battery-side electrode lead 7b and the external output-side electrode lead 7a are formed so that their edge portions overlap each other and are electrically connected, and each electrode lead 7a. 7b are bonded to the inner surfaces of opposite battery cases opposite to each other by thermal bonding or the like.
[0039]
At this time, a non-thermal adhesive electrode lead separator 8 is formed between the electrode lead 7a and the electrode lead 7b as needed, with the overlapped portion of the both notched. It can be temporarily attached and fixed by biting into a part.
By providing such an electrode lead separator 8, work such as thermal bonding of the electrode leads 7a, 7b to the inner surface of the battery case is facilitated, and the electrode leads 7a, 7b when the dependent chamber 10 is inflated by internal pressure. The connection and disconnection can be easily performed.
[0040]
Further, in order to ensure normal connection of the overlapping portions of the electrode lead 7a and the electrode lead 7b, it is preferable to perform heat sealing of the outer seal portion 6 by a vacuum sealing method or a degassing sealing method. An embossed shape or the like can be applied to the superposed portion.
[0041]
By providing such a safety valve structure in the battery case 100, the sheet-like battery 200 has a cross section taken along the line AA in FIG. 1 in a normal state, as shown in the enlarged sectional view of FIG. Although the edge portions of the electrode leads 7a and 7b are in close contact with each other, they are connected to each other. However, when heat is generated due to misuse or the like and the internal pressure of the main chamber 9 rises, the electrode seals are provided in the partition seal portion 4 with a constant internal pressure. The narrow-width seal portion 5 (weak seal portion) is peeled off, the internal pressure is released to the subordinate chamber 10, the internal pressure of the subordinate chamber 10 is increased, and the subordinate chamber 10 is shown in FIG. Since the connection between the electrode lead 7a and the electrode lead 7b is cut off, the charge / discharge circuit is cut off, the heat generation and the internal pressure increase are stopped, and the battery case can be prevented from rupture.
[0042]
【The invention's effect】
As described above in detail, according to the present invention, it is thin, light, flexible, has various strengths and resistances, and has excellent performance such as water vapor and other gas barrier properties, heat sealing properties, and misuse. Even if the internal pressure in the battery case rises, the charge / discharge circuit is automatically disconnected at the specified pressure, the internal pressure rise stops, and the battery with a safety valve that is excellent in safety can prevent the battery case from bursting The effect which can provide a case is produced.
[Brief description of the drawings]
FIG. 1 is a schematic plan view showing an example of a sheet-like battery manufactured by a battery case with a safety valve of the present invention.
2 is an enlarged cross-sectional view taken along line AA in FIG. 1. (A) is a cross-sectional view when the electrode lead is connected (normal state), and (B) is when the safety valve is operating (when the shutdown mechanism is operating). It is sectional drawing.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Laminated film 2 Bottom part 3 Trunk part seal part 4 Inner partition seal part 5 Narrow width seal part 6 Outer seal part 7, 7a, 7b Electrode lead 8 Electrode lead separator 9 Main room 10 Subordinate room 100 Battery case 200 Sheet shape battery

Claims (4)

A battery case of a type consisting of a laminated film bag with one end open, containing battery constituent materials inside, and extending the electrode lead from the inside to the outside to seal the opening. The opening of the bag body is sealed in two stages of an inner partition seal portion and an outer seal portion, and a main chamber in which battery constituent materials are stored and a subordinate chamber through which the electrode leads pass are provided. A battery case with a safety valve, wherein the partition seal portion has a weak seal portion, and the electrode lead of the subordinate chamber is provided with a shutdown mechanism that is disconnected by an increase in internal pressure. 2. A safety valve according to claim 1, wherein the weak seal portion of the partition seal portion is formed by a narrow width seal portion in which the width of the partition seal portion is narrowed in a region including a portion where the electrode lead is interposed. Battery case. 2. The safety valve according to claim 1, wherein the weak seal portion of the partition seal portion is formed by a heat seal portion of an easy peel resin layer provided in a pattern in a region including the partition seal portion. Battery case. A shutdown mechanism in which the connection is disconnected due to an increase in internal pressure provided in the electrode lead of the dependent chamber is divided into an external output side and a battery side, and the edge portions overlap and connect in the dependent chamber The battery case with a safety valve according to claim 1, wherein the battery case is formed of an electrode lead.

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