JP2002075320A - Thin secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small, light and thin secondary battery having excellent safety and high energy density. SOLUTION: In this thin secondary battery, a power generating element having a positive electrode, a negative electrode, and a separator is stored in a bag-shaped battery case body, and connection conductors connected to the positive electrode and the negative electrode of the power generating element respectively is derived to the outside of the battery case body in order to form an electrode terminal at the case body sealing part. At least one connection conductor is extended opposite to the sealing part on the terminal forming part, and is combined at the battery case body sealing part on the opposite side to the terminal forming side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin secondary battery in which a power generation element of a battery is housed in a flexible bag-shaped battery case.

[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. Along with this, a high energy density is required for the built-in battery.

[0003] Non-aqueous electrolyte secondary batteries are batteries that satisfy such requirements, and polymer solid electrolyte secondary batteries and gel polymer electrolyte secondary batteries are also being put into practical use. In these secondary batteries, 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 serving as a support thereof, and a lithium metal, a lithium alloy, or a lithium ion. A negative electrode plate holding a releasable carbonaceous material on a negative electrode current collector as a support thereof, and a separator interposed between the negative electrode plate and the positive electrode plate to prevent a short circuit between the two electrodes. I have. In a non-aqueous electrolyte secondary battery, a microporous membrane made of a polyolefin resin or the like is used as a separator, and LiClO4, LiP
A non-aqueous electrolyte in which a lithium salt such as F6 is dissolved is used. In the polymer solid electrolyte secondary battery, a polymer solid electrolyte is used as an isolator, and a non-aqueous electrolyte is not used.
In a gel polymer electrolyte secondary battery, a gel electrolyte in which a non-aqueous electrolyte is contained in a polymer solid electrolyte is used.

[0004] Such non-aqueous electrolyte secondary batteries, polymer solid electrolyte secondary batteries, and gel polymer electrolyte secondary batteries exhibit a high voltage of 4 V or more, so that the energy density per unit weight is low. It is high, compact and lightweight, has excellent charge-discharge cycle characteristics, and can be used after repeated charging and discharging, making this battery pack with a built-in secondary battery the most suitable power source for various portable electronic devices. .

[0005] These secondary batteries are formed into a thin sheet or foil, and the cut positive electrode plate and negative electrode plate are sequentially laminated via a separator (laminated type) or spirally wound. (Winding type), which constitutes a power generating element. In the latter case, in particular, by forming the cross section of the power generating element into a non-circular or elliptical power generating element shape, the electrode surface area can be increased, and a high efficiency Charge and discharge.

Conventionally, a cylindrical or rectangular battery outer casing made of a metal such as stainless steel, nickel-plated iron or aluminum is used for these secondary batteries, but has high airtightness. On the other hand, while the mechanical strength is excellent, the heavy metal material imposes great restrictions on reducing the weight of the battery.

Therefore, in order to solve this problem and further reduce the weight and thickness, a method of accommodating the power generating element in a bag-shaped battery outer casing has been put to practical use. The use of a metal-laminated resin film having an airtight structure for the bag-shaped battery outer casing eliminates the leakage of electrolyte and the intrusion of moisture from the outside of the battery, and is a lightweight battery with a high energy density per unit weight. Can be obtained.

Here, the structure of a thin secondary battery in which a power generating element having a positive electrode plate, a negative electrode plate, and a separator is housed in a bag-shaped battery outer casing is described with reference to FIGS. The case where elements are used will be described as an example.

In this thin secondary battery, a power generating element 1 in which a strip-shaped positive electrode plate and a negative electrode plate are wound in an elliptical shape with a separator interposed therebetween is housed in a bag-shaped battery outer package 4, and the positive electrode plate and The connection conductors 2 and 3 connected and fixed to the respective electrodes of the negative electrode plate by ultrasonic welding are led out from one end face in the winding axis direction of the power generation element 1, and are connected to the electrode terminals outside the battery exterior body sealing portion 5. 8 and 9 are formed.

The battery package 4 is made of a flexible metal laminated resin film formed by fusing and laminating each layer represented by a PET (polyethylene terephthalate) layer, an aluminum foil layer, and a PE (polyethylene) layer. It is bent with the layer inside, and the back sealing part 7 and the bottom sealing part 6 are formed by heat fusion to form a bag.

Next, the power generating element 1 is inserted through the opening of the exterior body 4, and at this time, the connection conductors 2, 3 derived from the power generating element 4 are projected from the opening. Then, after injecting the electrolytic solution into the interior of the outer package 4, the opening is thermally fused to form the terminal forming side sealing portion 5, which is sealed to obtain a thin secondary battery. The connection conductors 2 and 3 protruding from the opening of the exterior body 4 are made of a thermoplastic resin that is well adapted to metal by heat fusion so that the connection between the connection conductors 2 and 3 and the metal laminate resin film of the exterior body 4 can be completely sealed. Is interposed.

[0012]

However, in a thin secondary battery using such a bag-shaped battery outer package,
Unlike a battery using a metal battery case, the metal laminate resin film itself has flexibility, so if a strong shock or stress is applied from the outside of the battery case, the battery case may be deformed or the inside of the battery case may be deformed. The position of the power generating element 1 may be shifted. For example, when the battery pack containing the thin secondary battery is dropped with the positive electrode / negative electrode terminals 8 and 9 facing down, the exterior body 4 is deformed as shown in FIG. The element 1 moves to the terminal 8 or 9 side. As a result, the connection conductors 2 and 3 inside the battery outer body 4 are also deformed, and although extremely rare, the connection conductors 2 and 3 and the electrodes exposed from the power generation element 1 come into contact with each other, If the polarities of the electrodes and the connection conductors 2 and 3 are different, there is a problem that a short circuit occurs.

The present invention has been made in order to cope with such a situation. By preventing the power generating element from being displaced even when the battery pack is dropped, the short circuit phenomenon described above is prevented, and the safety is excellent. Another object of the present invention is to provide a small and lightweight thin secondary battery having a high energy density.

[0014]

According to a first aspect of the present invention, a power generating element having a positive electrode plate, a negative electrode plate, and an isolator is housed in a bag-shaped battery outer package, and each of the positive electrode plate and the negative electrode plate of the power generating element is mounted on the battery element. In a thin secondary battery in which the connected connection conductor is led out of the bag-shaped battery outer package to form an electrode terminal at the outer package sealing portion, at least one of the connecting conductors is opposite to the terminal-forming side sealing portion. And is fixed at the exterior body sealing portion located on the side opposite to the terminal forming side.

According to the first aspect of the invention, the battery power generating element is fixed to the sealing portion located on the terminal forming side and the opposite side thereof via the connection conductor, so that the position inside the exterior body is fixed. Therefore, even if the battery receives a strong shock, the position of the battery power generating element does not shift, and a short circuit due to the contact between the connection conductor and the electrode can be prevented.

According to a second aspect of the present invention, a resin coating is applied to a portion of the connection conductor located at the sealing portion of the battery exterior body, and the connection conductor and the battery exterior body are hermetically sealed by heat fusion. It is characterized by the following.

According to the second aspect of the present invention, the resin coated on the connection conductor at the sealing portion of the battery outer casing and the resin film of the innermost layer of the metal laminate resin film of the outer casing are completely fused by heat fusion. Thereby, airtightness can be maintained and leakage of the electrolyte can be prevented.

[0018]

Embodiments of the present invention will be described below with reference to the drawings.

As one embodiment of the present invention, a thin secondary battery in which a power generating element 1 in which a strip-shaped positive electrode plate and a negative electrode plate are wound in an oval shape with a separator interposed therebetween is housed in a bag-shaped battery outer body 4. In the battery, the power generating element 1 is connected to the terminal forming side sealing portion 5 via the connection conductors 2 and 3 and the bottom sealing portion 6 located on the opposite side.
1 and 2 show an embodiment of the present invention. FIG. 1 shows the external appearance of a thin secondary battery using a bag-shaped battery outer package, and FIG. 2 shows an AA ′ vertical cross-sectional structure of the thin secondary battery.

In this thin secondary battery, the connection conductors 2 and 3 are led out from both end faces in the winding axis direction of the power generating element 1,
The connection conductors 2 and 3 protruding from one surface are fixed to the terminal forming side sealing portion 5 to form electrode terminals 8 and 9, and the connection conductors 2 ′ and 3 ′ protruding from the other surface are connected to the terminal forming side. By fixing the power generating element 1 at the bottom sealing portion 6 located on the opposite side of the sealing portion 5, the position of the power generation element 1 does not shift inside the exterior body 4. Also, connection conductors 2, 3 and 2 ', 3'
The portions located at the terminal forming side sealing portion 5 and the bottom sealing portion 6 are coated with a polyethylene layer so that the sealing portions 5 and 6 are completely hermetically sealed during heat sealing.

The battery case 4 is made of a metal laminated resin film obtained by fusing a PET layer and a PE layer with an aluminum foil layer interposed therebetween, as in the case described above.
Into a cylindrical shape by heat fusion. And
After inserting the power generating element 1 through the opening, the bottom sealing portion 6 is heat-sealed to fix the connection conductors 2 ′ and 3 ′. Then, after the electrolyte is injected, the opening is heat-sealed. Thus, the terminal forming side sealing portion 5 is formed, and the connection conductors 2 and 3 are fixed. By sealing the battery outer casing 4 in this manner, a thin secondary battery is obtained. However, there is no particular limitation on which of the bottom sealing portion 6 and the terminal forming side sealing portion 5 is heat-sealed first from the viewpoint of the battery structure.

As shown in the cross-sectional structure of FIG. 2, the portion of the bottom sealing portion 6 to which the connection conductors 2 'and 3' are fixed is such that the ends of the connection conductors 2 'and 3' It is desirable to have a structure that fits within the depth dimension of, and does not protrude outside. However, when this thin secondary battery is finally housed in a battery pack case and used, the end 2 ′ of the connection conductor,
Even if the 3 ′ is located on the end face of the bottom sealing portion 6 or protrudes from the sealing portion 6, there is no danger of causing a short circuit and there is no problem.

Further, as shown in FIG. 1, it is not always necessary that both the connection terminals 2 'and 3' are fixed by heat sealing at the bottom sealing portion 6, and the position of the power generating element 1 is changed. If not, only one of the connection terminals 2 ′ or 3 ′ may be extended and fixed at the bottom sealing portion 6.

The power generating element used in the present invention is not limited to an oval cross section, but may be a wound type having a circular or non-circular cross section. Further, any type of power generating element can be used, such as a stacked type in which flat electrode plates are stacked via an isolator, and a folding type in which sheet electrode plates are folded and stacked via an isolator.

The portions 2, 3 and 2 ', 3' located at the terminal forming side sealing portion and the bottom sealing portion of the connection conductor led out from the power generating element 1 are provided with the metal laminate resin film of the exterior body 4. In order to completely seal the gap, a resin coating layer that is well adapted to metal by heat fusion is interposed. In the above embodiment, the connection conductors 2 and 3 are coated with the acid-modified polyethylene layer. However, the adhesion to the connection conductors 2 and 3 and 2 ′ and 3 ′ is sufficiently ensured, and the leakage of the electrolyte may occur. It is not limited to this as long as it is a thermoplastic resin having no resin. Further, if the airtightness of the sealing portion is ensured by other means, the present invention is not necessarily limited to resin coating.

As shown in the above-described embodiment, when an elliptical wound type is used as the shape of the power generating element 1, the oval wound type power generating element 1
Is housed so that the winding axis is perpendicular to the opening surface of the bag-shaped battery case 4, the connection conductors 2, 3 derived from the power generating element 1 can be taken out as the electrode terminals 8, 9 as they are, It is advantageous in a manufacturing method.

The positive electrode material of the thin secondary battery according to the present invention includes, as a compound capable of occluding and releasing lithium, a composition formula Lix
Inorganic compounds such as MO2 or LiyM2O4 (where M is a transition metal, 0 ≦ x ≦ 1, 0 ≦ y ≦ 2), oxides having tunnel-like vacancies, layered metal chalcogenides, etc. Compounds can be used. As specific examples, LiCoO 2, LiNiO
2, LiMn2O4, 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 a compound as a 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 salts dissolved in the organic solvent include 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.

As the separator of the thin secondary battery according to the present invention, an insulating polyethylene microporous membrane impregnated with an electrolytic solution, a solid polymer electrolyte, or a solid polymer electrolyte containing an electrolytic solution may be used. A gel electrolyte or the like can also be used. Further, an insulating 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.

In the above embodiment, the case of a non-aqueous electrolyte secondary battery using a metal laminated resin film composed of each layer of PET, aluminum foil, and PE has been described. if there is,
The material is not particularly limited. In addition, the present invention is not limited to the type of battery as long as it is a thin secondary battery using such a flexible exterior body, and may be applied to the above-described polymer solid electrolyte secondary battery and gel polymer electrolyte secondary battery. Can be used.

As described above, the battery power generating element 1 of the thin secondary battery is connected to both sides of the bag-shaped battery outer body 4 via the connecting conductors 2, 3 and 2 ', 3' derived from both end faces. By being attached to the sealing portions 5 and 6, the position of the power generating element 1 does not shift inside the battery outer body 4 even if the thin secondary battery receives a strong external shock. The conductors 2 and 3 are not deformed and do not come into contact with the electrodes exposed from the power generating element 1, and as a result, a short circuit between the connection conductors 2 and 3 and the electrodes can be reliably prevented.

[0034]

As is apparent from the above description, a power generating element having a positive electrode plate, a negative electrode plate, and a separator is housed in a bag-shaped battery outer package, and connected to each of the positive electrode plate and the negative electrode plate of the power generating element. In the thin battery in which the connection conductor is led out of the bag-shaped battery exterior to form an electrode terminal at the exterior sealing portion, at least one of the connection conductors is extended in a direction opposite to the sealing portion on the terminal formation side. Then, since the position of the power generation element is fixed inside the bag-shaped battery outer package by being fixed at the outer package sealing portion located on the side opposite to the terminal forming side, even if a strong impact force is applied from the outside, power generation is performed. The connection conductor can be prevented from being broken or short-circuited by contact with the electrode without the element being displaced. As a result, a small, lightweight, thin battery with excellent safety and reliability, high energy density, and the like can be obtained.

According to the present invention, the connecting conductor is simply stretched and cut, and the sealing is performed only by sandwiching the connecting conductor when sealing the battery exterior body. In particular, a manufacturing process is added. Without this, it is possible to provide a thin battery with excellent safety and reliability.

[Brief description of the drawings]

FIG. 1 is a perspective view showing the appearance of a thin secondary battery according to the present invention.

FIG. 2 is a cross-sectional view showing a cross-sectional structure along line AA ′ of the thin secondary battery according to the present invention.

FIG. 3 is a perspective view showing the appearance of a conventional thin secondary battery.

FIG. 4 is a cross-sectional view showing a cross-sectional structure along line AA ′ of a conventional thin secondary battery.

FIG. 5 is a cross-sectional view showing a cross-sectional structure taken along the line AA ′ when an external force is applied in the direction of the winding axis of the power generating element in the conventional thin secondary battery.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Battery power generation element 2 Positive electrode connection conductor 3 Negative electrode connection conductor 4 Bag-shaped battery exterior body 5 Terminal forming side sealing part 6 Bottom sealing part 7 Back sealing part 8 Positive terminal 9 Negative terminal

Claims (2)

[Claims] 1. A power generating element having a positive electrode plate, a negative electrode plate, and a separator is housed in a bag-shaped battery outer package, and connection conductors connected to each of the positive electrode plate and the negative electrode plate of the power generating element are formed in a bag-shaped battery package. In a thin secondary battery that is led out to form an electrode terminal at an outer package sealing portion, at least one connection conductor extends in a direction opposite to the terminal forming side sealing portion, and is opposite to the terminal forming side. A thin secondary battery, which is fixed at an exterior body sealing portion located at a position indicated by (a). 2. A resin coating is applied to a portion of the connection conductor located at the battery outer package sealing portion, and the connection conductor and the battery outer package are hermetically sealed by heat fusion. The thin secondary battery according to claim 1.