JP2000243401A - Collector for battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polymer battery of excellent performance by using a collector etched with a metallic foil base material and by assembling cells used with an isolating material consisting of a polymer and a plasticizer to substitute the plasticizer with an electrolytic solution. SOLUTION: In the base material of a collector 1, an aluminum foil for a positive electrode and a copper foil for a negative electrode are usually used. The collector 1 has a plurality of openings; preferably a honeycomb shape of a hexagon for enhancing impedance characteristics of a battery or capacitance utilization ratio. The average diameter of the opening is preferably 0.5-2 mm. No opening is provided in a lead wire part 2. A positive electrode material formed in a sheet shape is integrated with a positive electrode collector, a negative electrode material is integrated with a negative electrode collector and an isolating material film is sandwiched therebetween to integrate these three. This integrated product is immersed in an extraction solvent to extract a plasticizer. The solvent is preferably a low boiling point solvent such as a methanol compatible with the plasticizer and inert to a polymer. Then, the integrated product is immersed in an electrolyte, the plasticizer is substituted with the electrolyte, the lead wire 2 is removed and sealed to be a polymer electrode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a current collector for a polymer secondary battery and a method for producing the same. More specifically, the present invention relates to a current collector having excellent performance for a secondary battery and a method for producing the same. The current collector of the present invention is useful for a polymer battery obtained by assembling a cell using an isolating material composed of a polymer and a plasticizer and then replacing the plasticizer with an electrolyte solution.

[0002]

2. Description of the Related Art In a polymer battery, a positive electrode material and a negative electrode material are integrated by sandwiching a polymer electrolyte as an isolating material, and the positive electrode material and the negative electrode material have respective current collectors. Since a polymer battery uses a polymer electrolyte instead of a liquid electrolyte, it can be made thin and has excellent safety, and is expected as a battery for small portable electronic devices.

There are two types of polymer electrolytes, one consisting only of a polymer and an electrolyte salt, and the other gel type consisting of a combination of a polymer, an electrolyte and an electrolyte salt. The former is not always satisfactory in terms of battery performance. At present, gel-type polymer batteries are being put to practical use. However, the gel-type polymer battery has problems such as poor film-forming properties and the need for a special environment due to the problem of moisture absorption of the lithium electrolyte salt when assembling the cell.

In order to solve the above-mentioned problems, US Pat. No. 5,460,904 discloses a method of forming a film of a composition comprising a polymer and a plasticizer to form a separator, and assembling a cell after assembling the cell. Polymer batteries are manufactured by replacing the agent with an electrolyte. However, the practical performance of the battery manufactured by this method has not been sufficient yet.

[0005]

As a result of various studies on the effects on the performance of the polymer battery, the present inventor has found that
It was discovered that the current collector had a significant effect. In such a polymer battery, in order to replace the plasticizer with the electrolyte after the cell is assembled, the current collector must be in a mesh shape having a large number of openings through which the solvent and the electrolyte move. Conventionally, an expanded metal manufactured by a method in which slits are alternately cut in a metal sheet and the resultant is stretched as a current collector has been used. However, expanded metal is not strong enough.
The tension may be insufficient for coating or laminating the positive and negative electrode materials, which is not suitable for line production, and the performance of the obtained batteries, such as impedance characteristics and capacity utilization, is insufficient. There was found.

Accordingly, an object of the present invention is to form a separator comprising a composition comprising a polymer and a plasticizer to form a separator, and replace the plasticizer in the polymer with an electrolyte after assembling the cell. An object of the present invention is to provide a polymer battery having excellent performance. Another object of the present invention is to provide a current collector which is extremely suitable for such a battery.

[0007]

SUMMARY OF THE INVENTION The object of the present invention is to replace a plasticizer with an electrolyte solution after assembling a cell using an isolating material comprising a polymer and a plasticizer, which is obtained by etching a metal foil substrate. The present invention can be achieved by a current collector for a polymer battery obtained by the above method, and a polymer secondary battery incorporating such a current collector.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In a polymer secondary battery of the present invention, a separator is integrally formed by sandwiching a positive electrode material and a negative electrode material provided with respective current collectors. The separator is obtained by replacing the plasticizer with an electrolytic solution after assembling a cell with a film made of a polymer and a plasticizer.

Examples of the polymer used for the isolating material include polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride, and copolymers thereof. As the plasticizer, any of those conventionally used as plasticizers for plastics, such as dibutyl phthalate, diethyl phthalate, dioctyl phthalate, tributoxyethyl phosphate and tricresyl phosphate, can be used. The plasticizer has a function of giving the polymer a film-forming property and also making the electrolyte more easily absorbed by the polymer by replacing the electrolyte with the electrolyte after assembling the cell. A solvent such as acetone, methyl ethyl ketone, or tetrahydrofuran may be used as needed for viscosity adjustment or the like. A polymer, a plasticizer, a solvent used as required, and the like are uniformly mixed by a conventional method to form a film. For example, after mixing with a blender, apply evenly with a doctor blade on the release film of the plastic film, remove the solvent by drying,
The film can be peeled off to form a film.

As a positive electrode material, an active material usable in a conventional lithium ion secondary battery, for example, LiCoO ₂ , Li
A film obtained by mixing a Li salt such as NiO ₂ or LiMn ₂ O ₄ with a polymer similar to the separator and a plasticizer and, if necessary, a solvent or the like can be used. As the negative electrode material, an active material that can be used in a conventional lithium ion secondary battery, for example, a material formed by mixing graphite with a polymer and a plasticizer similar to the separator and a solvent or the like as necessary can be used. .
These film forming methods can be performed in the same manner as the separator.

The current collector used in the present invention has a large number of openings. FIG. 1 shows a current collector with a lead wire according to the present invention, wherein 1 is a current collector body and 2 is a lead wire.

The current collector of the present invention is manufactured by etching. As a substrate, an aluminum foil is usually used for a positive electrode, and a copper foil is used for a negative electrode. The thickness of the metal foil substrate is not particularly limited as long as it can be used as a current collector. It is usually from 5 to 100 μm, preferably from 20 to 100 μm, more preferably from 20 to 50 μm.

As a manufacturing method, for example, the following method can be mentioned. As shown in FIGS. 2 and 3, one surface of the metal foil substrate 11 is masked over the entire surface with the etching resist 12, and the other surface is masked in the shape of a current collector body with leads. Then, after the etching resist 12 is cured by heat, ultraviolet rays, electron beams, or the like, it is treated with an etching solution to dissolve the metal in the unmasked portion. Next, the etching resist is peeled off with a peeling agent, whereby a current collector can be manufactured.

As another method, as shown in FIG. 4, one surface of the metal foil substrate is entirely masked with an etching resist, and the other surface is entirely masked while leaving a mesh space. Then, curing, etching and etching resist removal are performed in the same manner as described above. Finally, the outer shape of the current collector with leads may be cut by a known method.

As still another method, instead of masking the entire surface of one side of the metal foil substrate with an etching resist,
A laminate of a metal foil substrate and a film or sheet having resistance to an etchant such as polyester, polyethylene, or polypropylene may be used. The film or sheet is peeled off and removed after etching as necessary.

As the etching resist used in the present invention, any etching resist that can be masked into a desired pattern and has resistance to an etching solution can be used. Typically, various etching resist inks and dry films used in the production of printed circuit boards can be used. As the etching resist ink, a thermosetting or ultraviolet curable ink is often used. Masking with an etching resist ink can be typically performed by screen printing. For example, screen printing is performed on the entire surface of one side of the metal foil substrate, and after drying, a pattern is screen-printed in a desired shape on the other side. When a laminate of a metal foil substrate and a resin film or sheet is used, printing on one side is unnecessary.

In the case of dry film, the film is adhered to both surfaces of a metal foil substrate in close contact, and a masking film having a desired pattern is adhered to one surface of the substrate, and irradiated with light such as ultraviolet rays, and the entire surface is covered on one surface. The other side cures the pattern. Then, the latent image is developed with a weak alkaline solution or the like, and one surface can be masked to the entire surface and the other surface can be masked to a desired pattern. The above is a typical example of the etching resist,
Of course, it is not limited to these.

The etching solution may be any solution that dissolves the metal but does not dissolve the etching resist. For example, a solution of ferric chloride or cupric chloride, or an acidic solution such as hydrochloric acid or sulfuric acid is used. In the case of an aluminum foil substrate, an alkaline solution such as a caustic soda solution can be used when the etching resist has alkali resistance.

After the etching, the remaining resist ink is removed by peeling or the like. The stripping may be performed by using a stripping solution suitable for the etching resist, and an alkali solution such as caustic soda is often used. When a metal foil and a laminated material such as a film or a sheet are used as the base material, this may be peeled off as necessary. Thus, the current collector of the present invention can be manufactured.

Although the current collector of the present invention has a large number of openings,
The shape is preferably a substantially hexagonal honeycomb shape, and it has been found that using such a current collector improves the impedance characteristics and the capacity utilization of the battery. In this case, the honeycomb-shaped opening is provided at a portion in contact with the positive and negative electrode films, and no opening is provided at the lead wire portion. The average diameter of the opening is preferably 0.1 to 5 mm,
More preferably, it is 0.5 to 2 mm. Here, the diameter of the opening refers to a distance (a in FIG. 5) between opposing vertices of a regular hexagon. The average diameter is an arithmetic average diameter of a number of openings of the current collector. However, in the case of a honeycomb structure, since the size of each opening is almost equal, the average diameter is almost equal to the diameter of each opening. In addition, the width of an adjacent opening and the side of the opening (FIG. 5)
B) has a honeycomb structure, so that all parts are substantially equal, preferably 0.1 to 5 mm, more preferably 0.5 to 5 mm.
２2 mm. In this case, the thickness of the current collector is preferably 5 to 100 μm, more preferably 20 to 50 μm.
Is

The polymer battery of the present invention can be manufactured as follows. The positive electrode material obtained by forming the above into a sheet shape is integrated with a positive electrode current collector, and the negative electrode material is integrated with a negative electrode current collector to obtain a positive electrode and a negative electrode, respectively. The integration can be performed by, for example, thermal lamination. Alternatively, a mixture of positive and negative electrode materials may be directly applied to the current collector and dried, and the method of integration is not limited.

Next, a separator film is sandwiched between the positive electrode and the negative electrode thus manufactured, and the three members are laminated and integrated. The integration can be performed by, for example, thermal lamination. Next, this laminate is immersed in a plasticizer extraction solvent to extract a part or all, preferably all, of the plasticizer. As the solvent, a low-boiling solvent that is compatible with the plasticizer and inert to the polymer is preferable. Examples of such a solvent include methanol, diethyl ether, hexane, cyclohexane and the like. After extraction, the solvent is removed by evaporation.

Next, the laminate is immersed in an electrolytic solution. The electrolytic solution is obtained by dissolving a supporting electrolyte in a solvent having a high dielectric constant, and may be one which can be used in a conventional lithium ion secondary battery. Examples of the solvent include propylene carbonate, ethylene carbonate, dimethyl carbonate, dimethyl sulfoxide, γ-butyl lactone, sulfolane,
Examples thereof include 2-dimethoxyethane, tetrahydrofuran, dioxolan, and diethyl carbonate, and one or more of these can be used. Examples of the electrolyte include LiCF ₃ SO ₃ , LiAsF ₆ , LiBF ₄ , and LiClO.
₄ , LiPF _{6 and the} like, and one or more of these can be used. The concentration of the electrolyte is usually 0.5 to 5M. In this way, part or all, and preferably all, of the plasticizer of the laminate is replaced with the electrolyte. Next, a polymer battery can be obtained by sealing except for the lead wires of the positive electrode and the negative electrode.

[0024]

The present invention will be described below with reference to examples. Example 1 An alkali-soluble etching resist was screen-printed on the entire surface of one side of a 50-μm aluminum foil, and 120
Dried at 2 ° C. for 2 minutes. Then, the etching resist was printed on the other surface as shown in FIG. 2 and dried at 120 ° C. for 20 minutes.
Next, treatment with an etching solution (ferric chloride) was carried out to elute aluminum in portions where no etching resist was printed. After washing, the substrate was treated with an alkaline solution to remove the etching resist, thereby obtaining a current collector as shown in FIG.

Example 2 An aluminum foil having a thickness of 40 μm was etched in the same manner as in Example 1 to prepare a test piece having a honeycomb shape and an elliptical shape with a 15 mm × 200 mm opening, and a tensile test was performed. And proof stress were measured. As a comparison,
The measurement was also performed on an expanded metal having a similar shape having a thickness of 60 μm. The results are shown in Table 1. Also, 40μ × 50
The tensile strength and proof stress when converted to 0 mm are also shown. From this table, it can be said that the current collector of the present invention having the honeycomb type openings can apply a line tension about 10 times that of the expanded metal.

[0026]

[Table 1]

Example 3 (1) Production of honeycomb-shaped current collector An etching resist was applied to the aluminum foil surface of a laminated film of 20 μm of aluminum foil and 50 μm of polyester, and a honeycomb-shaped lead was formed in the same manner as in Example 1. A positive electrode current collector of an aluminum foil with a wire was manufactured. The diameter of all the openings of the honeycomb is 1.0 mm, and the width of the side is 0.3 mm. Similarly, a copper foil of 20 μm and 50
A negative electrode current collector having a similar shape was produced using a μm polyester laminated film.

(2) Production of positive electrode LiCoO ₂ / conductive carbon Ensaco250 (MMM
Carbon Company / KYNAR2801 (Polyvinylidene fluoride and polyhexafluoropropylene copolymer, ELF
Atochem) / Dibutyl phthalate = 70/5/8 /
Acetone 11 as a solvent using 100 g of a raw material having a ratio of 17
The mixture was mixed with 0 g in a blender (4000 rpm) for 10 minutes, the mixture was applied to a uniform thickness with a doctor blade, and acetone was evaporated and dried to produce a positive electrode film having a thickness of 130 μm. The above aluminum current collector is
The laminate was thermally laminated at 0 ° C. to form a positive electrode.

(3) Manufacture of Negative Electrode A mesophase carbon material (MCMB25-28 manufactured by Osaka Gas Co., Ltd.) widely used for lithium batteries is used as a negative electrode material.
MCMB / conductive carbon Ensaco250 / KYNAR2801 / weight ratio by weight
Dibutyl phthalate = 69.4 / 2.2 / 8.6 / 1
Acetone 2 as a solvent using 100 g of a raw material having a ratio of 9.8
And a uniform thickness with a doctor blade, and acetone was evaporated to dryness to form a film having a thickness of 15 g.
A 0 μm negative electrode film was produced. The above-mentioned copper current collector was thermally laminated at about 120 ° C. to obtain a negative electrode.

(4) Production of separator SiO ₂ / KYNAR2801 / dibutyl phthalate = 2 by weight
100 g of a raw material having a ratio of 2/33/44 was added to 225 of acetone.
g and a blender, and this mixture was applied to a uniform thickness with a doctor blade, and the acetone was evaporated and dried to produce a 70 μm thick separator.

(5) Assembly of Cell The above three films were heat-laminated at 130 ° C. and integrated. After the work was immersed in methanol to extract dibutyl phthalate as a plasticizer, the work was allowed to absorb an electrolytic solution (1 M LiPF ₆ in a mixture of ethylene carbonate and dimethyl carbonate = 2: 1). This work was placed in an airtight bag, and the work was sealed with the positive and negative lead electrodes protruding from the mouth of the bag to obtain a battery cell.

Comparative Example 1 A battery cell was manufactured in the same manner as in Example 3 except that an expanded metal of aluminum was used as the current collector for the positive electrode and an expanded metal of copper was used as the negative electrode.

Evaluation Example 1 The impedance characteristics of the two types of cells manufactured as described above were measured by changing the frequency with an impedance analyzer. The results are shown in FIG. From FIG. 6, it can be seen that Example 2 has lower impedance and better initial impedance characteristics than Comparative Example 1. In addition, load characteristics were measured by a charge / discharge tester. FIG. 7 shows the results. From FIG. 7, it can be seen that Example 2 is superior to Comparative Example 1 in the capacity utilization rate at a high discharge rate.

[0034]

The polymer battery using the current collector manufactured by the etching of the present invention, particularly the polymer battery using the current collector having a honeycomb-shaped opening has excellent impedance characteristics and load characteristics. Although it is not clear, it is considered that the contact portion with the carbon film is relatively small, the combined resistance is small, and the average current moving distance in the current collector is shortened.

[Brief description of the drawings]

FIG. 1 is a diagram showing a current collector with a lead wire of the present invention.

FIG. 2 is a diagram showing a state in which an etching resist is masked in a pattern of a current collector with leads on a metal foil substrate.

FIG. 3 is a sectional view of the state of FIG. 2;

FIG. 4 is a diagram showing a state in which the entire surface of the metal foil substrate is masked with an etching resist except for a space in a mesh portion.

FIG. 5 is a diagram illustrating a structure of a current collector having a honeycomb-shaped opening.

FIG. 6 is a diagram showing impedance characteristics.

FIG. 7 is a diagram showing load characteristics.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Current collector main body 2 Lead wire 11 Metal foil substrate 12 Etching resist

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[Procedure amendment]

[Submission date] May 31, 2000 (2005.3
1)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claim 5

[Correction method] Change

[Correction contents]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0003

[Correction method] Change

[Correction contents]

There are two types of polymer electrolytes, one consisting only of a polymer and an electrolyte salt, and the other gel type consisting of a combination of a polymer, an electrolyte and an electrolyte salt. The former is not always satisfactory in terms of battery performance. At present, gel-type polymer batteries are being put to practical use. However, the gel type polymer battery has problems such as inferior film-forming properties and a special environment due to the problem of hygroscopicity of the lithium electrolyte salt when assembling the cell.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0029

[Correction method] Change

[Correction contents]

(3) Manufacture of Negative Electrode A mesophase carbon material (MCMB25-28 manufactured by Osaka Gas Co., Ltd.) widely used for lithium batteries is used as a negative electrode material.
MCMB / conductive carbon Ensaco250 / KYNAR2801 / weight ratio by weight
Dibutyl phthalate = 69.4 / 2.2 / 8.6 / 1
Acetone 2 as a solvent using 100 g of a raw material having a ratio of 9.8
It was mixed with 00g and blender, was applied to a uniform thickness by a doctor blade, film thickness 150 dried by evaporation of acetone
A μm negative electrode film was manufactured. The above copper current collector is
The laminate was thermally laminated at 20 ° C. to form a negative electrode.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0033

[Correction method] Change

[Correction contents]

Evaluation Example 1 The impedance characteristics of the two types of cells manufactured as described above were measured by changing the frequency with an impedance analyzer. The results are shown in FIG. From FIG. 6, it can be seen that Example 3 has lower impedance and better initial impedance characteristics than Comparative Example 1. In addition, load characteristics were measured by a charge / discharge tester. FIG. 7 shows the results. FIG. 7 shows that Example 3 is superior to Comparative Example 1 in the capacity utilization rate at a high discharge rate.

[Procedure amendment 5]

[Document name to be amended] Drawing

[Correction target item name] Fig. 6

[Correction method] Change

[Correction contents]

FIG. 6

[Procedure amendment 6]

[Document name to be amended] Drawing

[Correction target item name] Fig. 7

[Correction method] Change

[Correction contents]

FIG. 7

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Toshiaki Watanabe 1994-26 Yoshihama, Yugawara-machi, Ashigarashimo-gun, Kanagawa Prefecture F-term (reference) 2-10-1 Toranomon, Minato-ku, Tokyo 5H017 AA03 BB14 BB16 CC01 CC05 DD08 EE01 EE05 EE08 5H029 AJ03 AJ06 AK03 AL07 AM02 AM03 AM04 AM05 AM07 AM16 BJ04 BJ12 CJ12 CJ12 EJ01 EJ12

Claims (5)

[Claims] The present invention relates to a polymer battery obtained by assembling a cell using an isolating material comprising a polymer and a plasticizer, obtained by etching a metal foil substrate, and then replacing the plasticizer with an electrolyte solution. Current collector. 2. The current collector according to claim 1, wherein the current collector and the lead wire are integrally formed by a metal foil base material. 3. The current collector according to claim 1, which has a honeycomb-shaped opening. 4. The current collector according to claim 1, wherein the metal foil substrate is an aluminum foil substrate or a copper foil substrate. 5. A polymer secondary battery in which the current collector according to claim 1 is incorporated.