JP2001243939A - Thin type secondary battery, lead terminal for thin type secondary battery and their manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thin type secondary battery, a lead terminal for the thin type secondary battery and their manufacturing method which prevent abnormal capacity fall. SOLUTION: An electricity generating element 1 consisting of a positive and a negative electrodes and a separator, and a part of lead wires 3, 4 which are a metal flat plate electrically connected to a non-aqueous electrolyte solution and each of, a positive and a negative electrodes are packaged with a polymer film 2a, 2b. A front surface 5a and a rear surface 5b of at least one of the lead terminals 3 (4) are concave and convex, and also sides of this terminal 3 (4) are plane.

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 capable of preventing an abnormal decrease in capacity, a lead terminal for the thin secondary battery, and a method for manufacturing the same.

[0002]

2. Description of the Related Art In today's market where portable information terminals such as notebook personal computers and mobile phones are rapidly expanding, batteries used in portable information terminals have high output and are excellent in safety. It is especially required. In order to meet this demand, development of secondary batteries using an alkali metal ion such as lithium ion as a charge carrier and utilizing an electrochemical reaction accompanying the transfer of charge has been actively performed. Non-aqueous electrolyte solutions that contribute to high output can be used for secondary batteries using such alkali metal ions,
In order to ensure safety, it is necessary to suppress outflow and evaporation of the electrolyte solution.

[0003] In order to suppress the outflow and evaporation of the electrolyte solution, a conventional secondary battery has been packaged with a metal case. However, since the metal case is heavy, the secondary battery used in the portable information terminal has a problem that the outer package must be reduced in weight. Therefore, a thin secondary battery that is packaged with a light laminated film or the like instead of a metal case is being studied. However, in order to ensure safety, it is necessary to prevent the electrolyte solution from leaking due to changes in internal pressure due to charging / discharging, deterioration with time of the exterior body, corrosion, and the like. Particularly, in the vicinity of the lead terminal, the adhesiveness between the surface of the lead terminal and the laminated film fusion layer is liable to change due to various factors. This is because when the electronic device is incorporated in the vicinity of the thin secondary battery, the electronic device is seriously damaged by an electrolyte solution or the like leaked from the laminate film.

[0004] In order to prevent the electrolyte solution from leaking, studies have been made to improve the adhesion between the lead terminal and the laminate film. For example, JP-A-11-2
Japanese Patent No. 42953 discloses a battery (thin secondary battery) in which a part of the surface of an electrode terminal (lead terminal) in contact with a laminate film made of a thermoplastic resin layer is roughened. Here, the method of roughening the surface of the electrode terminal (lead terminal) includes (i) etching with an acid, an alkali or another solution, (ii) anodic oxidation in an electrolytic solution, and (iii) electrolytic corrosion. Chemical treatment and (iv) mechanical treatment such as file, vinyl grindstone, belt sander and the like are mentioned. Since the thermoplastic resin filled in the irregularities formed by roughening a part of the surface of the electrode terminal acts as an anchor, the adhesiveness between the electrode terminal (lead terminal) and the thermoplastic resin (laminate film) is improved. I was able to.

[0005]

However, a battery (a thin secondary battery) in which a part of the surface of an electrode terminal (lead terminal) is roughened is disclosed in Japanese Patent Application Laid-Open No. H11-242953.
However, there were the following problems.

When the electrode terminals are used, not only the surface of the electrode terminals but also the side portions of the electrode terminals are used.
That is, for example, when the electrode terminals are contaminated with an etching solution, the entire electrode terminals are immersed in the etching solution to form irregularities on the surface and side portions (outer surfaces). It has been newly found that it is difficult to completely fill the irregularities on the side portions of the electrode terminals with the thermoplastic resin to the details thereof, and liquid leakage, gas permeation, and the like due to deterioration of the thermoplastic resin with time are observed. As a result, there has been a problem that the capacity is abnormally reduced during repeated charging and discharging of the thin secondary battery.

The present invention has been made in view of the above-mentioned problems in the prior art, and has a thin secondary battery capable of preventing an abnormal decrease in capacity, a lead terminal for the thin secondary battery, and manufacturing thereof. It is an object to provide a method.

[0008]

Means for Solving the Problems A first invention of the present application for solving the above problems is to electrically connect a power generating element comprising a positive electrode, a negative electrode and a separator, a non-aqueous electrolyte solution, and a positive electrode and a negative electrode respectively. In a thin secondary battery in which a part of a lead terminal which is a metal flat plate is covered with a polymer film, the surface and the back surface of at least one of the lead terminals are uneven, and A thin secondary battery characterized in that the side portions of the lead terminals are flat.

Therefore, according to the thin secondary battery of the first invention of the present application, when the battery is packaged with the polymer film, the adhesive strength between the lead terminal and the polymer film is maintained by the uneven surface, and the lead terminal has Since the side of at least one of the lead terminals is flat, the close contact between the lead terminal and the polymer film can be enhanced. Thus, liquid leakage and gas permeation from the polymer film near the side portions of the lead terminals can be prevented. As a result, there is an advantage that the capacity is not abnormally reduced in the repeated charging and discharging of the thin secondary battery.

[0010] The second invention of the present application is the thin secondary battery according to the first invention of the present application, characterized in that the polymer film is a laminate coated with a metal thin film having anti-gas barrier properties. is there.

Therefore, according to the thin secondary battery of the second invention of the present application, there are advantages of the first invention of the present application,
Gas permeation can be further prevented by the metal thin film having a fog barrier property. Thus, there is an advantage that the capacity does not abnormally decrease further in the repeated charging and discharging of the thin secondary battery.

The third invention of the present application is also characterized in that the innermost layer of the laminate is a thermoplastic resin layer and the outermost layer of the laminate is a heat-resistant resin layer. A thin secondary battery according to the invention or the second invention of the present application.

Therefore, according to the thin secondary battery of the third invention of the present application, there are advantages of the first invention of the present application or the second invention of the present application, and when the battery is packaged by heat fusion,
The adhesive strength can be further improved, and the adhesiveness can be further improved. Thereby, there is an advantage that the capacity does not abnormally decrease further in repeated charging and discharging of the thin secondary battery.

According to a fourth aspect of the present invention, the lead terminal connected to the positive electrode is made of Al or an Al alloy. A thin secondary battery according to (1).

Therefore, according to the thin secondary battery of the fourth invention of the present application, there are the advantages of any one of the first to third inventions of the present application and the lead connected to the positive electrode. Since the terminals are light, there is an advantage that the thickness of the thin secondary battery can be reduced.

Further, in the fifth invention of the present application, the uneven surface may be
The present invention is characterized by being formed by chemical etching or electric etching.
A thin secondary battery according to any one of the above aspects of the invention.

Therefore, according to the thin secondary battery of the fifth invention of the present application, there are the advantages of any one of the first to fourth inventions of the present application, and the unevenness of the lead terminals is reduced. There is an advantage that it is easily formed.

The sixth invention of the present application is a lead terminal for a thin secondary battery, characterized in that the front and back surfaces are uneven, and the sides are flat.

According to a seventh aspect of the present invention, there is provided a lead terminal for a thin secondary battery according to the sixth aspect of the present invention, which is for connecting a positive electrode and is made of Al or an Al alloy.

The eighth invention of the present application is a lead terminal for a thin secondary battery according to the sixth invention or the seventh invention of the present application, which is characterized by the following.

Therefore, according to the lead terminal for a thin secondary battery according to any one of the sixth to eighth inventions of the present application, when the lead terminal is packaged with a polymer film, the height of the lead terminal is increased by the uneven surface. Since the adhesive strength with the molecular film is maintained and at least one of the lead terminals has a flat side surface, the close contact between the lead terminal and the polymer film can be enhanced. This allows
Liquid leakage from the polymer film near the side of the lead terminal,
Gas permeation can be prevented. As a result of this,
There is an advantage that the capacity is not abnormally reduced in the repeated charging and discharging of the thin secondary battery.

The ninth invention of the present application also relates to a power generating element comprising a positive electrode, a negative electrode and a separator, a non-aqueous electrolyte solution, and a part of a lead terminal which is a metal flat plate electrically connected to each of the positive electrode and the negative electrode. In a method for manufacturing a thin secondary battery, which is covered with a polymer film, the surface and the back surface of at least one of the lead terminals are unevenly processed, and then the side portions of the one lead terminal are flattened. This is a method of manufacturing a thin secondary battery.

A tenth invention of the present application is the thin secondary battery according to the ninth invention of the present application, wherein the polymer film is a laminate coated with a metal thin film having anti-gas barrier properties. It is a manufacturing method.

In the eleventh invention of the present application, the innermost layer of the laminate is a thermoplastic resin layer, and the outermost layer of the laminate is a heat-resistant resin layer, and the laminate is packaged by heat fusion. A method for manufacturing a thin secondary battery according to the ninth invention or the tenth invention, which is a feature of the present invention.

In a twelfth aspect of the present invention, the lead terminal connected to the positive electrode is made of Al or an Al alloy. 2. The method for producing a thin secondary battery according to (1).

The thirteenth invention of the present application is the liquid crystal display device according to any one of the ninth to twelfth inventions, characterized in that the uneven surface processing is performed by chemical etching or electrical etching. 2. The method for producing a thin secondary battery according to (1).

Therefore, according to the method for manufacturing a thin secondary battery according to any one of the ninth invention to the thirteenth invention of the present application, when the package is packaged with the polymer film, the lead terminals and the polymer film are formed by the uneven surface. The adhesive strength between the lead terminal and the polymer film can be enhanced because the side surface of at least one of the lead terminals is flat, and the adhesive strength between the lead terminal and the polymer film can be increased. Thus, liquid leakage and gas permeation from the polymer film near the side portions of the lead terminals can be prevented. As a result, there is an advantage that the capacity is not abnormally reduced in the repeated charging and discharging of the thin secondary battery.

According to a fourteenth aspect of the present invention, the flat secondary processing according to any one of the ninth aspect of the present invention to the thirteenth aspect of the present invention, wherein the planar processing is performed by a cutting step. Battery manufacturing method

Therefore, according to the method for manufacturing a thin secondary battery of the fourteenth invention of the present application, there is an advantage of any one of the ninth invention to the thirteenth invention of the present application,
There is an advantage that planar processing of the lead terminal can be easily performed.

The fifteenth invention of the present application is a method for manufacturing a lead terminal for a thin secondary battery, characterized in that the top and bottom surfaces are processed to be uneven, and then the side portions are flattened.

According to a sixteenth aspect of the present invention, the lead terminal for a thin secondary battery according to the fifteenth aspect of the present invention is characterized in that the irregular surface processing is performed by chemical etching or electrical etching. It is a manufacturing method of.

According to a seventeenth aspect of the present invention, there is provided a lead for a thin secondary battery according to the fifteenth aspect of the present invention or the sixteenth aspect of the present invention, wherein the planar processing is performed by a cutting step. This is a method for manufacturing a terminal.

Therefore, according to the method of manufacturing a lead terminal for a thin secondary battery according to any one of the fifteenth invention to the seventeenth invention,
Due to the uneven surface, the adhesive strength between the lead terminal and the polymer film is maintained, and since at least one of the lead terminals has a flat side surface, the adhesion between the lead terminal and the polymer film is increased. be able to. Thus, liquid leakage and gas permeation from the polymer film near the side portions of the lead terminals can be prevented. As a result, there is an advantage that the capacity is not abnormally reduced in the repeated charging and discharging of the thin secondary battery.

[0034]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A thin secondary battery according to an embodiment of the present invention, a lead terminal for the thin secondary battery, and a method for manufacturing the same will be described below with reference to the drawings.

(Embodiment) First, a thin secondary battery according to an embodiment of the present invention, a lead terminal for the thin secondary battery, and a method of manufacturing the same will be described with reference to FIGS. . FIG. 1A is a plan view showing the structure of the thin secondary battery according to the embodiment of the present invention, and FIG. 1B is a sectional view taken on line AA of FIG.
It is sectional drawing corresponding to a line. However, the polymer film 2b in FIG. 1 (b) is omitted in FIG. 1 (a). Also,
FIG. 2 is a right side perspective view of a lead terminal for a thin secondary battery according to an embodiment of the present invention.

Referring to FIG. 1, a thin secondary battery according to an embodiment of the present invention includes a positive electrode (not shown) and a negative electrode (not shown).
, A power generating element 1 including a separator (not shown), a non-aqueous electrolyte solution (not shown), and a lead terminal 3, which is a metal flat plate electrically connected to each of a positive electrode and a negative electrode.
4 is covered with polymer films 2a and 2b. Referring to FIG. 2, the front surface 5a and the back surface 5b of at least one of the lead terminals 3 and 4 are provided.
Is an uneven surface, and the side portion of the one lead terminal 3 (4) is a flat surface.

[Lead Terminals] The lead terminals 3 and 4 are plate-shaped, and their width and thickness are not particularly limited. Generally width 1
It is selected in a shape usually used as a lead terminal having a thickness of 10 to 10 mm and a thickness of 0.01 to 0.5 mm. In the lead terminals 3 and 4 according to the embodiment of the present invention, the surface 5 of the lead terminals 3 and 4
a and the back surface 5b are etched, and the right side portion 5a and the left side portion 5b are flattened. The method of etching is not particularly limited, and (i)
Chemical etching, (ii) electrochemical etching, (iii)
Although mechanical etching and the like are performed, (i) chemical etching and (ii) electrochemical etching are particularly preferable in terms of ease of implementation. (i) Examples of etchants for chemical etching include acid or base etchants such as aqueous sodium hydroxide, dilute nitric acid, aqueous ferric chloride, and aqueous sodium phosphate. As (ii) electrochemical etching, a method of applying a direct current or an alternating current in an electrolytic solution such as ammonium chloride or the like can be used.

By the etching of (i), (ii) and (iii), irregularities are formed on the front surface 5a, the back surface 5b, the right side 5a and the left side 5b of the lead terminals 3 and 4. The degree of these etchings can be evaluated by, for example, a surface roughness meter or a step meter. A surface roughness meter or a step gauge is a device for measuring a gap between a convex portion and a concave portion within a certain range, for example, within a range of 500 μm. According to the study of the present inventors, the gap between the convex portion and the concave portion by etching is generally 0.5 μm.
m, the adhesive strength between the lead terminals 3 and 4 and the polymer film 2 was improved.

The material of the lead terminals 3 and 4 according to the embodiment of the present invention is not particularly limited, and a conventionally known lead terminal of a thin secondary battery can be used. For example, Al or an Al alloy can be used as the positive electrode lead terminal 3, and Ni, Cu, or an alloy thereof can be used as the negative electrode lead terminal 4. From the viewpoint of weight reduction, the positive electrode lead terminal 3 is made of Al or an Al alloy. Is preferred.

After the lead terminals 3 and 4 are processed to have an uneven surface, the side portions are flattened. The method for smoothing the right side portion 5a and the left side portion 5b of the lead terminals 3, 4 is not particularly limited, and can be performed by melting, polishing, bonding, cutting, or the like. Here, it is preferable to be a cutting step from the viewpoint of ease of implementation,
For example, the right side portion 5a and the left side portion 5b of the lead terminals 3, 4 can be cut using a cutting tool such as a cutting tool, a side saw, and a cutter.

[Power Supply Element] The form of the power generation element 1 composed of a positive electrode, a negative electrode and a separator is not particularly limited. From a flat plate, a laminate of two or more sets or a long one is wound. What is furthermore, what was flatly wound etc. is used. Here, from the viewpoint of high capacity, it is preferable to use a flat winding.

[Positive electrode] The positive electrode is not particularly limited as long as it absorbs positive ions or emits negative ions during discharge. (I) LiMnO ₂ , LiMn ₂ O ₄ , LiCo
Metal oxides such as O ₂ and LiNiO ₂ , (ii) conductive polymers such as polyacetylene and polyaniline, and (iii) general formula (R
-Sm) n (R is aliphatic or aromatic;
Is sulfur, and m and n are integers of m ≧ 1, n ≧ 1) (dithioglycol, 2,5-dimercapto-1,3,4-thiadiazole, S-triazine- As the positive electrode material of a secondary battery such as 2, 4, 6-trithiol, etc., a conventionally known material can be used.

The positive electrode may be formed by mixing a positive electrode active material (not shown) with an appropriate binder or a functional material. These binders include halogen-containing polymers such as polyvinylidene fluoride, and the functional materials include conductive polymers such as acetylene black, polypyrrole, and polyaniline, which secure electron conductivity, and ion conductivity. And a composite thereof.

[Negative Electrode] The negative electrode is not particularly limited as long as it can absorb and release cations. Crystalline carbon such as graphitized carbon obtained by heat-treating natural graphite, coal or petroleum pitch at a high temperature, Conventionally known negative electrode active materials for a secondary battery, such as amorphous carbon obtained by heat-treating coal, petroleum pitch coke, acetylene pitch coke, and the like, and lithium alloys such as metallic lithium and AlLi can be used.

[Non-aqueous electrolyte solution] Non-aqueous electrolyte solution
As, for example, ethylene carbonate, propylene
Carbonate, dimethyl carbonate, diethyl carbonate
Nate, methyl ethyl carbonate, γ-butyrolact
, N, N'-dimethylformamide, dimethylsulfo
Oxides, N-methylpyrrolidone, m-cresol, etc.
Highly polar basic solvent usable as electrolyte for secondary batteries
Alkali metal cations such as Li, K, and Na with ClO
₄ ⁻, BF₄ ⁻, PF₆ ⁻, CF₃SO₃ ⁻, (CF₃
SO₂)₂N ⁻, (C₂F₅SO₂)₂N⁻, (CF₃
SO₂)₃C⁻, (C₂F₅SO₂) ₃C⁻Such as haloge
Of a compound containing anion
Solvents composed of these basic solvents and electrolytes
Decomposed salts may be used alone or in combination.
it can.

[Polymer film] Polymer film 2a, 2b
Can be made into laminates 2a and 2b coated with a metal thin film having a fog barrier property. The structure of the laminates 2a and 2b and the thickness of each of the constituent layers are not particularly limited, but generally, a polyester as a heat-resistant protective layer is provided on the outermost layer 7 of the laminates 2a and 2b (polymer films 2a and 2b). The innermost layer 8 is made of a material having a thermoplastic resin layer made of polyolefin, polyolefin derivative, or the like. These laminates 2a and 2b can be formed into a multilayer by combining two or more kinds as necessary. In addition, Al, Sn, Cu, Ni, stainless steel, etc. are mentioned as a metal layer of a gas barrier property.

[Thin Secondary Battery] The form of the thin secondary battery manufactured by the method according to the embodiment of the present invention is not particularly limited, but it is generally manufactured in a rectangular shape, a coin shape, a sheet shape or the like. . Also, the power generating element 1, the non-aqueous electrolyte solution, and a part of the lead terminals 3, 4 which are metal flat plates electrically connected to the positive electrode and the negative electrode, respectively, are connected to two polymer films 2a,
After packaging with 2b, the method of sealing the polymer films 2a and 2b is not particularly limited. Polymer film 2a, 2b
When the innermost layer 8 is a thermoplastic resin which is a sealing resin, the innermost layer 8 is pressed and finished at a temperature not lower than the melting point of the thermoplastic resin.
For the outer layer, it is also possible to use a polymer film 2a pre-molded in accordance with the shape of the electrode laminate (the power generating element 1, a non-aqueous electrolyte solution) having the lead terminals 3 and 4.

[0048]

EXAMPLES Hereinafter, the details of the thin secondary battery of the present invention, the lead terminals for the thin secondary battery, and the manufacturing method thereof will be specifically described with reference to Examples, but the present invention is not limited to these Examples. It is not something to be done. (Example 1) [Unevenness processing, plane processing step] An Al plate having a thickness of 0.1 mm and a width of 5 mm was immersed in a 15% by mass aqueous sodium hydroxide solution at 60 ° C for 60 seconds. Bubbles were generated from the Al plate along with the immersion, and irregularities were generated on the entire outer surface of the Al plate. Next, this Al
After removing the plate from the aqueous sodium hydroxide solution, the plate was washed with running water for 30 minutes, dried at 60 ° C. under reduced pressure, and etched.
A plate was obtained. Next, the side part of the obtained etching flat plate was cut off using a side saw, and finally the thickness was 0.095 m.
A metal flat plate (lead terminal 3) having a front surface and a back surface having a width of 4 mm and a width of 4 mm was etched and the side portions were flattened.

FIG. 3 (a) is a view showing the result of measurement of the front surface 5a or the back surface 5b (uneven portion) of the lead terminals 3 and 4 with a surface step meter. FIG. 3B is a view showing the result of measuring the right side portion 5a or the left side portion 5b (planar processed portion) of the lead terminals 3 and 4 with a surface step meter. Referring to FIG. 3, the surface roughness of the uneven portion is 3 μm, and the surface roughness of the flat portion is estimated to be 0.2 μm.

[Power Supply Element Preparation Step] Next, the average particle size is 5 μm.
Lithium cobaltate, acetylene black, polyvinylidene fluoride, N-methyl-2-pyrrolidone
They were mixed and dispersed at a weight ratio of 1: 1: 30. This is uniformly applied on one side of aluminum foil by a wire bar method,
Vacuum dried at 2 ° C. for 2 hours to remove the solvent. The obtained thin layer was cut into an appropriate size and cut to about 25 mA.
A positive electrode layer having a capacity of h was prepared. A separator film made of polyethylene and having a thickness of 25 μm and a porosity of 50% was laminated on the positive electrode layer. A slurry in which polyvinylidene fluoride, N-methyl-2-pyrrolidone, petroleum petroleum coke, and acetylene black were mixed at a weight ratio of 1: 30: 20: 1 was cast on the laminated film (positive electrode, separator), and a wire bar was formed. 100 ° C
For 2 hours to form a negative electrode layer. Next, a copper foil having the same area as the aluminum foil of the positive electrode 3 was placed on the negative electrode layer as a current collector, wound and flattened to obtain an electrode laminate (power supply element 1) of the lithium ion secondary battery.

[Electrical Connection Step] Next, an aluminum plate (positive lead terminal 3) having a thickness of 0.095 mm and a width of 4 mm, the front and back surfaces of which are uneven, and the side portions of which are flattened, is prepared. ) On the positive electrode layer of the electrode laminate, with a thickness of 0.1 m
A rolled Ni flat plate (negative electrode lead terminal 4) having a width of 4 mm and a width of 4 mm was connected (electrically connected) to the negative electrode layer of the electrode laminate using an ultrasonic welding method.

[Exterior Package] Next, the surface protective layer 7 is covered with laminated films 2a and 2b made of a 25 μm-thick aluminum foil having a blown nylon film and a heat-sealing layer 8 with a modified polypropylene film.
A heater bar at 205 ° C. was press-bonded in a range of cm and subjected to heat fusion to obtain a thin secondary battery. At this time, before closing the last side, an electrolyte solution composed of a mixed solution of ethylene carbonate and propylene carbonate (mixing ratio 50/50) containing 1M LiPF ₆ as an electrolyte salt was impregnated.

[Evaluation] A charge / discharge test was performed on the thin secondary battery obtained in this example. As a result, the capacity was as designed and the charge / discharge efficiency was good. Further, even when the charge / discharge test was repeatedly performed, no liquid leakage was observed for 200 cycles or more, and no abnormal capacity decrease considered to be caused by evaporation of the solvent was observed. Further, when a short-circuit test was performed after charging, the internal pressure was increased and a part of the laminate film was swollen, but it was found that the sealing was maintained and the safety was excellent.

Comparative Example 1 Rolled A having a thickness of 0.1 mm and a width of 4 mm was formed on the electrode laminate of Example 1 as a positive electrode lead terminal.
Example of mounting a flat plate without etching
Similarly to 1, a rolled Ni plate was attached as a negative electrode lead terminal. Thereafter, the package was packaged with a laminate film according to the method of Example 1 to obtain a thin secondary battery. When the charge and discharge test of the obtained thin secondary battery was performed, it had an initial capacity as designed,
The charge and discharge efficiency was also good, but in repeated charge and discharge, liquid leakage occurred from the positive electrode lead portion by 50 cycles, and the capacity was drastically reduced. Further, in the short-circuit test after charging, the internal pressure increased, a part of the laminate film was peeled off, and the gas and the electrolytic solution flowed out. As a result, it was found that a thin secondary battery using an unplated Al flat plate as a lead terminal was inferior in safety and stability.

(Comparative Example 2) The etched Al flat plate of Example 1 was attached to the electrode laminate of Example 1 as a positive electrode lead terminal without separating the side portions, and a rolled Ni plate was replaced with a negative electrode lead in the same manner as in Example 1. Mounted as a terminal. afterwards,
It was packaged with a laminate film by the method of Example 1 to obtain a thin secondary battery. When a charge / discharge test was performed on the obtained thin secondary battery, it had an initial capacity as designed and good charge / discharge efficiency. However, the capacity was drastically reduced by 50 cycles in repeated charge / discharge. Observation of the interface between the sealing resin and the lead terminal of this sample revealed a void in which the resin was not filled in the side part of the positive electrode lead terminal, which seemed to evaporate the solvent via this void. . Further, in the short-circuit test after charging, the internal pressure increased, a part of the laminate film was peeled off, and the gas and the electrolytic solution flowed out. As a result, it was found that a thin secondary battery using an Al flat plate whose entire surface was etched as a lead terminal was inferior in safety and stability.

(Embodiment 2) In this embodiment, only the unevenness processing, the plane processing step, the exterior step, and the evaluation will be described, and other description will be omitted. [Roughing and flattening process] An aluminum plate having a thickness of 0.1 mm and a width of 5 mm is immersed in a 0.25 M ammonium chloride aqueous solution, and a DC voltage of 20 V and an alternating current are superimposed on the Ni plate as a counter electrode for 15 minutes. The reaction was performed. Bubbles were generated from the Al flat plate with the progress of the reaction, and irregularities were generated on the entire surface. After taking it out, it is washed with running water for 30 minutes,
It dried under reduced pressure at ° C and obtained the etching Al board. Next, the side portion of the obtained etched flat plate was cut off using a side saw, and finally the front and back surfaces having a thickness of 0.1 mm and a width of 4 mm were etched and the side portions were flattened. Terminal 3). The surface roughness of the uneven portion was 2 μm, and the surface roughness of the flat portion was 0.2 μm.

[Exterior Package] A laminate film 2a, 2b made of aluminum foil having a thickness of 25 μm and having a nylon film as the surface protective layer 7 and an ionomer film as the heat sealing layer 8 is coated with 165 in a range of 1 cm from the outer periphery.
A heater bar at a temperature of 0 ° C. was press-bonded and heat-sealed to obtain a thin battery. At this time, before closing the last side, an electrolyte solution composed of a mixed solution of ethylene carbonate and propylene carbonate (mixing ratio 50/50) containing 1M LiPF ₆ as an electrolyte salt was impregnated.

[Evaluation] A charge / discharge test was performed on the thin secondary battery obtained in this example. As a result, the battery had the capacity as designed and the charge / discharge efficiency was good. Further, even when the charge / discharge test was repeatedly performed, no liquid leakage was observed for 200 cycles or more, and no abnormal capacity decrease considered to be caused by evaporation of the solvent was observed. Further, when a short-circuit test was performed after charging, the internal pressure was increased and a part of the laminate was swollen, but it was found that the sealing was maintained and the safety was excellent.

(Embodiment 3) In this embodiment, only the unevenness processing, the plane processing step, the exterior step, and the evaluation will be described, and the other description will be omitted. [Roughing and Planar Processing Step] A Ni flat plate having a thickness of 0.1 mm and a width of 5 mm was immersed in a 10% by mass aqueous ferric chloride solution at 40 ° C. for 60 minutes. As the reaction progressed, irregularities were generated on the entire surface of the Ni plate. After taking this out, it was washed with running water for 30 minutes and dried under reduced pressure at 60 ° C. to obtain an etched Ni foil. Next, the side portion of the obtained etching foil was cut off using a side saw, and finally a metal plate (lead having a thickness of 0.1 mm and a width of 4 mm, whose front and back surfaces were etched and whose side portions were flattened). Terminal 3). The surface roughness of the uneven portion was 2.5 μm, and the surface roughness of the flat portion was 0.2 μm.

[Exterior Package] A laminated polyester film 2a, 2b having a thickness of 25 μm and having a stretched polyester film as the surface protective layer 7 and a maleic acid-modified polypropylene film as the heat-sealing layer 8 was coated 1 cm from the outer periphery. A heater bar of 210 ° C. was crimped in the range, and heat fusion was performed to obtain a thin battery. At this time, before closing the last side, an electrolyte solution composed of a mixed solution of ethylene carbonate and propylene carbonate (mixing ratio 50/50) containing 1M LiPF ₆ as an electrolyte salt was impregnated.

[Evaluation] A charge / discharge test was performed on the thin secondary battery obtained in this example. As a result, the battery had the capacity as designed and had good charge / discharge efficiency. In addition, even when the charge / discharge test was repeated, no liquid leakage was observed for 500 cycles or more, and no abnormal capacity decrease considered to be caused by evaporation of the solvent was observed. Further, when a short-circuit test was performed after charging, the internal pressure was increased and a part of the laminate was swollen, but it was found that the sealing was maintained and the safety was excellent.

(Embodiment 4) In this embodiment, only the unevenness processing, the plane processing step, the exterior step, and the evaluation will be described, and the other description will be omitted. [Roughing and Plane Processing Steps] A Cu flat plate having a thickness of 0.1 mm and a width of 5 mm was immersed in a 3% by mass aqueous solution of nitric acid for 15 minutes. As the reaction progressed, irregularities were generated on the entire surface of the Cu plate. After taking it out, it is washed with running water for 30 minutes,
Drying under reduced pressure at ℃ gave an etched Cu flat plate. Next, both sides of the obtained etched Cu flat plate were cut off using a side saw, and finally a metal flat plate having a thickness of 0.1 mm and a width of 4 mm whose front and back surfaces were etched, and whose side portions were flattened. (Lead terminal 3). The surface roughness of the uneven portion was 3.5 μm, and the surface roughness of the flat portion was 0.2 μm.

[Exterior Package] A laminated polyester film 2a, 2b having a thickness of 25 μm and having a stretched polyester film as the surface protective layer 7 and a maleic acid-modified polypropylene film as the heat-sealing layer 8 was covered with a film 1 cm from the outer periphery. A heater bar of 210 ° C. was crimped in the range, and heat fusion was performed to obtain a thin battery. At this time, before closing the last side, an electrolyte solution composed of a mixed solution of ethylene carbonate and propylene carbonate (mixing ratio 50/50) containing 1M LiPF ₆ as an electrolyte salt was impregnated.

[Evaluation] A charge / discharge test was performed on the thin secondary battery obtained in this example. As a result, the capacity was as designed and the charge / discharge efficiency was good. In addition, even when the charge / discharge test was repeated, no liquid leakage was observed for 500 cycles or more, and no abnormal capacity decrease considered to be caused by evaporation of the solvent was observed. Further, when a short-circuit test was performed after charging, the internal pressure was increased and a part of the laminate was swollen, but it was found that the sealing was maintained and the safety was excellent.

[0065]

As described above, the thin secondary battery of the present invention has the following features.
A power generation element 1 comprising a positive electrode, a negative electrode, and a separator, a non-aqueous electrolyte solution, and a part of lead terminals 3, 4 which are metal flat plates electrically connected to the positive electrode and the negative electrode respectively, are combined with polymer films 2a, 2b. And lead terminals 3,
4, the front surface 5a and the back surface 5b of at least one of the lead terminals 3 (4) are uneven surfaces, and
The side of (4) is a plane. When packaged with the polymer films 7a, 7b, the adhesive strength between the lead terminals 3, 4 and the polymer films 7a, 7b is maintained by the uneven surface, and at least one of the lead terminals 3, 4 is provided. Since the side of (4) is flat, the close contact between the lead terminal 3 (4) and the polymer films 7a and 7b can be enhanced. Thus, liquid leakage and gas permeation from the polymer film near the side portions of the lead terminals can be prevented. As a result, there is an effect that the capacity is not abnormally reduced in the repeated charging and discharging of the thin secondary battery.

[Brief description of the drawings]

FIG. 1A is a plan view showing the structure of a thin secondary battery according to an embodiment of the present invention, and FIG. 1B is a plan view of FIG.
FIG. 3 is a cross-sectional view corresponding to line A.

FIG. 2 is a right side perspective view of a lead terminal for a thin secondary battery according to an embodiment of the present invention.

FIG. 3 (a) is a diagram showing a result obtained by measuring the uneven portion with a surface step meter, and FIG. 3 (b) is a diagram showing a result obtained by measuring the flat portion with a surface step meter.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Power generation element 2a, 2b Polymer film 3 Positive electrode lead terminal 4 Negative electrode lead terminal 5a, 5b Front or back surface of lead terminal 6a, 6b Right or left side of lead terminal 7 Outermost layer of polymer film 8 Last layer of polymer film Inner layer

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hiroshi Sakauchi 5-7-1 Shiba, Minato-ku, Tokyo Inside NEC Corporation (72) Kentaro Nakahara 5-7-1 Shiba, Minato-ku, Tokyo Japan F-term in the electric company (reference)

Claims (17)

[Claims] 1. A power generation element comprising a positive electrode, a negative electrode, and a separator, a nonaqueous electrolyte solution, and a part of a lead terminal which is a metal flat plate electrically connected to each of the positive electrode and the negative electrode are covered with a polymer film. Wherein the front and back surfaces of at least one of the lead terminals are uneven, and the side portions of the one lead terminal are flat. battery. 2. The thin secondary battery according to claim 1, wherein the polymer film is a laminate coated with a metal thin film having a fuzz barrier property. 3. The thin two-layer structure according to claim 1, wherein the innermost layer of the laminate is a thermoplastic resin layer, and the outermost layer of the laminate is a heat-resistant resin layer. Next battery. 4. The lead terminal connected to a positive electrode,
The thin secondary battery according to any one of claims 1 to 3, wherein the secondary battery is l or an Al alloy. 5. The thin secondary battery according to claim 1, wherein the uneven surface is formed by chemical etching or electrical etching. 6. A lead terminal for a thin secondary battery, characterized in that the front and back surfaces are uneven, and the sides are flat. 7. The lead terminal for a thin secondary battery according to claim 6, wherein the lead terminal is for connecting a positive electrode and is made of Al or an Al alloy. 8. The lead terminal for a thin secondary battery according to claim 6, wherein the uneven surface is formed by chemical etching or electric etching. 9. A power generation element comprising a positive electrode, a negative electrode and a separator, a non-aqueous electrolyte solution, and a part of a lead terminal which is a metal flat plate electrically connected to each of the positive electrode and the negative electrode are covered with a polymer film. The method for manufacturing a thin secondary battery according to claim 1, wherein the surface and the back surface of at least one of the lead terminals are processed to have an uneven surface, and then the side portions of the one lead terminal are flat-processed. A method for manufacturing a secondary battery. 10. The method for manufacturing a thin secondary battery according to claim 9, wherein the polymer film is a laminate coated with a metal thin film having a fuzz barrier property. 11. The laminate according to claim 9, wherein the innermost layer of the laminate is a thermoplastic resin layer, and the outermost layer of the laminate is a heat-resistant resin layer, which is packaged by heat fusion.
A method for manufacturing a thin secondary battery according to claim 10. 12. The lead terminal connected to a positive electrode,
The method for manufacturing a thin secondary battery according to any one of claims 9 to 11, wherein the method is Al or an Al alloy. 13. The method for manufacturing a thin secondary battery according to claim 9, wherein the uneven surface processing is performed by chemical etching or electric etching. 14. The method for manufacturing a thin secondary battery according to claim 9, wherein the planar processing is performed by a cutting process. 15. A method of manufacturing a lead terminal for a thin secondary battery, comprising: forming a concave and convex surface on a front surface and a rear surface; and then flattening a side portion. 16. The method for manufacturing a lead terminal for a thin secondary battery according to claim 15, wherein the uneven surface processing is performed by chemical etching or electric etching. 17. The method for manufacturing a lead terminal for a thin secondary battery according to claim 15, wherein the planar processing is performed by a cutting step.