JP2014107176A - Lead wire for nonaqueous electrolyte battery use and nonaqueous electrolyte battery using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a lead wire for nonaqueous electrolyte battery use which enables the reduction in cost, and has good resistance against electrolyte; and a nonaqueous electrolyte battery.SOLUTION: A lead wire for nonaqueous electrolyte battery use comprises: a lead conductor made of copper; a composite coating layer which covers the surface of the lead conductor; and a heat-seal layer which covers at least part of the composite coating layer. The composite coating layer which covers the surface of the lead conductor is made of a polyacrylic acid copolymer or polymethacrylic acid copolymer, or a hardened material thereof. The heat-seal layer is made of a resin composition including 0.05 pts.mass or more of a copper inhibitor to 100 pts.mass of a polyolefin-based resin.

Description

  The present invention relates to a non-aqueous electrolyte battery used as a power source for a small electronic device and the like, and a lead wire for a non-aqueous electrolyte battery which is a member constituting the non-aqueous electrolyte battery.

As electronic devices become smaller and lighter, electric components such as batteries and capacitors used in these devices are also required to be smaller and lighter. For this reason, for example, a nonaqueous electrolyte battery in which a bag body is used as an enclosure and a nonaqueous electrolyte (electrolyte), a positive electrode, and a negative electrode are enclosed therein is employed. As the nonaqueous electrolyte, an electrolytic solution in which a lithium salt containing fluorine such as LiPF ₆ or LiBF ₄ is dissolved in propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate or the like is used.

  The sealed container is required to have a property of preventing permeation of the electrolyte and gas and moisture from the outside. For this reason, a laminate film in which a metal layer such as an aluminum foil is coated with a resin is used as a material for the enclosure, and the ends of the two laminate films are heat-sealed to form an enclosure.

  One end of the enclosure is an opening, and a nonaqueous electrolyte, a positive electrode plate, a negative electrode plate, a separator, and the like are enclosed in the inside. Furthermore, a lead conductor having one end connected to the positive electrode plate and the negative electrode plate is arranged so as to extend from the inside of the enclosure to the outside, and finally the opening of the enclosure is heat-sealed (heat fusion). Is closed and the enclosure and the lead conductor are bonded to seal the opening. This last part to be heat-sealed is called a seal part.

  At this time, the sealed container and the lead conductor are bonded (heat-sealed) via the heat-sealing layer. The heat-sealing layer is provided in advance in a portion corresponding to the seal portion of the lead conductor, or is provided in a portion corresponding to the seal portion of the enclosure, so that it is interposed between the metal layer of the enclosure and the lead conductor. Let If the fluidity of the heat-fusible layer is high at the time of heat sealing, the adhesive force between the enclosing container and the lead conductor can be increased. However, if it flows too much at the time of heat fusion, the metal layer and the lead conductor are short-circuited. For this reason, the seal portion is required to have a characteristic that the adhesiveness and the sealing property (sealing property) can be maintained without causing a short circuit between the metal layer and the lead conductor.

  Patent Document 1 discloses a battery enclosing bag and lead wires used in such a non-aqueous electrolyte battery. It is described that a maleic acid-modified polyolefin layer is provided directly on the conductor of the lead conductor to form a heat-sealing layer, whereby the sealing performance of the seal portion can be improved.

  The seal part requires adhesion and sealing between the enclosing container and the lead conductor, but even if the adhesion immediately after sealing is sufficient, the adhesive force gradually decreases over time, and the metal layer Another problem is that peeling occurs at the interface with the lead conductor. This is because moisture permeates from the seal portion with the passage of time, and hydrofluoric acid is generated by the reaction between the electrolyte enclosed in the enclosure and the water, and the lead conductor (metal) is corroded. In particular, electrical components used in automobile applications need to be usable for a long period of time, and it is an issue to further improve the electrolyte resistance of the heat fusion part. In particular, peeling at the interface with nickel or a nickel plating layer used as a negative electrode lead conductor is likely to occur, and improvement in resistance to electrolytic solution is required.

  In order to improve the electrolytic solution resistance, Patent Document 2 discloses a battery tab in which a composite film layer of an aminated phenol polymer, a trivalent chromium compound and a phosphorus compound is formed on the surface and side of a lead conductor whose surface is nickel. Has been. It is described that by forming a composite coating layer, corrosion of the nickel layer by hydrofluoric acid generated by the electrolyte and moisture can be prevented, and elution of the nickel layer can be prevented. However, this method uses chromium, which is a heavy metal, and is not preferable in terms of environment.

  In Patent Document 3, it is proposed to provide a layer made of an acid-modified styrene-based elastomer at a portion of the seal portion in contact with the lead conductor.

Japanese Patent No. 3562129 JP 2009-99527 A JP 2010-92631 A

  In a nonaqueous electrolyte battery such as a lithium ion battery, aluminum is used for the positive electrode and nickel or nickel-plated copper is used for the negative electrode as the lead conductor. Although copper is a material having higher conductivity than nickel, it is more easily corroded by hydrofluoric acid than nickel, so the resistance to electrolytic solution is poor, and it is difficult to use copper alone as a lead conductor. For this reason, the surface is plated with a metal such as nickel. However, since the cost is increased by performing the plating process, there is a demand to use copper having good conductivity as a single lead conductor.

  In view of such a problem, the present invention reduces the cost by using copper that does not have a metal plating layer such as nickel as a lead conductor and has a good electrolytic solution resistance, and a lead wire for a non-aqueous electrolyte battery, It is another object of the present invention to provide a nonaqueous electrolyte battery using the same.

  The present invention is a lead wire for a non-aqueous electrolyte battery comprising a lead conductor made of copper, a composite coating layer covering the surface of the lead conductor, and a heat-sealing layer covering at least a part of the composite coating layer. The composite film layer covering the surface of the lead conductor is an acrylic acid copolymer and / or a methacrylic acid copolymer, or a cured product thereof, and the thermal fusion layer is based on 100 parts by mass of the polyolefin resin. A lead wire for a non-aqueous electrolyte battery comprising a resin composition containing 0.05 parts by mass or more of a copper damage inhibitor.

  The surface of the lead wire is covered with an acrylic acid copolymer and / or methacrylic acid copolymer, or a composite film layer that is a cured product thereof to prevent copper corrosion and resistance to electrolyte solution (acid resistance to hydrogen fluoride) ) Can be good. Therefore, it is possible to use a lead wire whose copper surface is not plated with a metal such as nickel, and the cost can be reduced. The acrylic acid copolymer includes a homopolymer of acrylic acid and a copolymer of acrylic acid and acrylic acid ester, methacrylic acid, methacrylic acid ester or the like. The methacrylic acid copolymer includes a homopolymer of methacrylic acid and a copolymer of methacrylic acid and methacrylic acid ester, acrylic acid, acrylic acid ester and the like.

  When copper used for the lead wire and the polyolefin resin used for the fusion layer are in contact with each other for a long time, copper ions diffuse into the polyolefin resin and the polyolefin resin deteriorates. By using a resin composition containing 0.05 parts by mass or more of a copper damage inhibitor as a heat-sealable layer with respect to 100 parts by mass of a polyolefin-based resin, deterioration of the heat-sealable layer can be prevented.

  Furthermore, the present invention provides a nonaqueous electrolyte battery using the lead wire for a nonaqueous electrolyte battery. The non-aqueous electrolyte battery having such a configuration can be manufactured at low cost and can have good resistance to electrolytic solution.

  According to the present invention, there is provided a lead wire for a non-aqueous electrolyte battery and a non-aqueous electrolyte battery that can reduce cost and can have good electrolytic solution resistance by using copper having no metal plating layer such as nickel as a lead conductor. Can be obtained.

It is a front view of the nonaqueous electrolyte battery which concerns on one Embodiment of this invention. It is a fragmentary sectional view of the nonaqueous electrolyte battery concerning one embodiment of the present invention. It is a fragmentary sectional view of the lead wire concerning one embodiment of the present invention.

  FIG. 1 is a front view schematically showing an embodiment of a nonaqueous electrolyte battery, and FIG. 2 is a partial cross-sectional view taken along line A-A ′ of FIG. 1. This nonaqueous electrolyte battery 1 has a substantially rectangular enclosure 2 and a lead conductor 3 extending from the inside of the enclosure 2 to the outside.

  As shown in FIG. 2, the enclosure 2 includes a three-layer laminate film 8 including a metal layer 5, a resin layer 6 that covers the metal layer 5, and a resin layer 7. The metal layer 5 is formed from a metal such as an aluminum foil. As the resin layer 6 positioned outside the enclosure, polyamide resin such as 6,6-nylon and 6-nylon, polyester resin, polyimide resin, or the like can be used. In addition, it is preferable to use an insulating resin that does not dissolve in the non-aqueous electrolyte and melts when heated, for the resin layer 7 located inside the enclosing container 2, and is a polyolefin resin, an acid-modified polyolefin resin, an acid-modified styrene. Examples are based on elastomers. The enclosure 2 is produced by superposing two laminated films 8 and heat-sealing three sides other than the side through which the lead conductor passes. At the outer peripheral portion of the enclosure, the two metal layers 5 are bonded via the resin layer 7.

  In the seal portion 9, the lead conductor 3 is bonded (heat-sealed) to the sealed container (laminate film 8) via the heat-sealing layer 4. Further, inside the nonaqueous electrolyte battery, a positive electrode current collector 10 and a negative electrode current collector 11, a nonaqueous electrolyte 13, and a separator 12 connected to the end of the lead conductor 3 are enclosed.

  FIG. 3 is a schematic cross-sectional view of a lead wire. The surface of the plate-like lead conductor 3 has a composite coating layer 14 made of an acrylic acid copolymer and / or methacrylic acid copolymer, or a cured product thereof. Furthermore, it has the heat sealing | fusion layer 4 which coat | covers both surfaces of the lead conductor 3. As shown in FIG. The heat sealing layer 4 is made to correspond to the seal part of the nonaqueous electrolyte battery. The composite coating layer is provided so as to cover the entire surface of the portion where the lead conductor 3 is in contact with the non-aqueous electrolyte. The lead wire is sometimes called a tab lead.

  An acrylic acid copolymer and a methacrylic acid copolymer are polymers of acrylic acid, methacrylic acid or esters thereof, which are unsaturated carboxylic acids, and have a number of carboxyl groups in the molecule. The monomer composition is not particularly limited as long as it has water solubility, and acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, phenyl acrylate, 2-hydroxyethyl acrylate , 2-aminoethyl acrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, 2-hydroxyethyl methacrylate, 2-aminoethyl methacrylate Among them, a copolymer using one or more of these monomers or a mixture of the copolymers can be used. An acrylic acid copolymer or a methacrylic acid copolymer having a molecular weight of about 1,000 to 100,000, more preferably about 10,000 to 50,000 is used from the viewpoint of ease of handling and adhesion to the lead conductor. it can. An acrylic acid copolymer and a methacrylic acid copolymer may be used alone, but curing with a curing agent is preferable because the resistance to electrolytic solution is further improved.

  As the curing agent for the acrylic acid copolymer and / or methacrylic acid copolymer, any one capable of reacting with the carboxyl group of the acrylic acid copolymer or methacrylic acid copolymer can be used. Examples of the curing agent include metal salts such as zirconium salts, titanium salts, and molybdenum salts, and oxazoline group-containing polymers. Zirconium fluoride salt, zirconium carbonate salt, zirconium phosphate salt, etc. as zirconium salt, titanium diisopropoxybis (triethanolaminate), titanium lactate ammonium salt, titanium lactate etc. as molybdenum salt as titanium salt For example, orthomolybdate, paramolybdate, metamolybdate, and phosphomolybdate can be used. In addition, a hardening | curing agent is not limited to what was illustrated here.

  As the oxazoline group-containing polymer, a polymer having two or more oxazoline groups in the molecule can be used. The oxazoline group in the polymer reacts with the carboxyl group of the acrylic acid copolymer or methacrylic acid copolymer to crosslink the acrylic acid copolymer or methacrylic acid copolymer. The oxazoline group-containing polymer includes an unsaturated bond having addition polymerizability and an oxazoline group, such as 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, and 2-isophenyl-2-oxazoline. It is obtained by polymerizing or copolymerizing monomers. An acrylic ester copolymer containing an oxazoline group in the molecule is excellent in compatibility with an acrylic acid copolymer and a methacrylic acid copolymer, and thus can be preferably used.

The above curing agent and acrylic acid copolymer or / and methacrylic acid copolymer are mixed and used at an appropriate ratio. Since acrylic acid copolymer and methacrylic acid copolymer are water-soluble, a solution obtained by dissolving both in water or an aqueous solution of acrylic acid copolymer or methacrylic acid copolymer alone is applied to the lead conductor and then dried. Then, a composite film layer is formed on the surface of the lead conductor. The acrylic acid copolymer or / and the methacrylic acid copolymer reacts with the curing agent by heating at the time of drying to cure the acrylic acid copolymer or / and the methacrylic acid copolymer. The coating amount of the composite coating ^{layer, 1mg / m 2 ~300mg / m} 2, and more (in the thickness in terms of about 1 nm~100 nm) preferably 10mg ^{/ m 2} ~100mg ^/ m 2 is preferably set to. When the coating amount of the composite coating layer is too large, the weldability of the conductor is deteriorated or the resistance to the electrolytic solution is lowered. Moreover, management will become difficult when there is too little coating amount.

  Copper is used for the lead conductor 3. In the case of a lithium ion battery, aluminum is often used for the positive electrode, and nickel or nickel-plated copper is often used for the negative electrode. The lead wire of this invention is used suitably as a negative electrode of a lithium ion battery. The shape of the lead conductor is not particularly limited, but a flat metal having a thickness of 50 μm to 500 μm, a width of 1 mm to 200 mm, and a length of 5 mm to 200 mm can be preferably used.

  The heat-sealing layer 4 contains 0.05 parts by mass or more of a copper damage preventing agent with respect to 100 parts by mass of the polyolefin resin that can be melted by heat at the time of heat sealing and can adhere the sealed container and the lead conductor. A resin composition is used. Examples of the polyolefin resin include polyethylene, polypropylene, ionomer resin, and acid-modified polyolefin. In particular, an acid-modified polyolefin having an adhesive functional group modified with maleic acid, acrylic acid, methacrylic acid, maleic anhydride or the like is preferable. Of these, maleic anhydride-modified polyolefin resin is preferable because of its excellent adhesion to metal and sealing properties.

  There are no particular limitations on the copper damage inhibitor, and any conventionally known one can be used. 3- (N-salicyloyl) amino 1,2,4-triazole, 2,3-bis [[3- (3,5-di-tert-butyl-4-hydroxyphenyl] propionyl] propionyl] propiononohydrazide, salicyl Hydrazide, 2 ′, 3-bis [[3- [3,5-di-tert-butyl-4-hydroxyphenyl] propionyl] propiohydrazide and the like can be preferably used.

  In addition, various additives such as a flame retardant, an ultraviolet absorber, a light stabilizer, a heat stabilizer, a lubricant, and a colorant can be mixed in the resin composition constituting the heat fusion layer. These resin materials and additives are mixed using a known mixing device such as an open roll, a pressure kneader, a single-screw mixer, or a twin-screw mixer, and then a film-like heat-fusible layer is produced by extrusion molding or the like. . Although the thickness of the heat sealing | fusion layer is dependent on the thickness of a lead conductor, 30 micrometers-200 micrometers are preferable.

  The heat-fusible layer can also be used after being crosslinked by irradiation with ionizing radiation such as an accelerated electron beam or γ-ray. By cross-linking, the heat resistance can be increased, and a decrease in adhesive strength when the temperature during use is increased and a short circuit between the lead conductor and the metal layer can be prevented. The entire heat-sealing layer may be crosslinked, or the heat-sealing layer may have a multilayer structure, and a non-crosslinked layer and a crosslinked layer may be laminated.

  Next, the present invention will be described in more detail based on examples. The examples are not intended to limit the scope of the invention.

(Examples 1 to 3, Comparative Example 1)
Polyacrylic acid (manufactured by Nippon Shokubai Co., Ltd., molecular weight (Mw) 10,000) in an aqueous solution in which 87 parts by weight of water was dissolved in 87.77 parts by weight of water, an oxazoline group-containing polymer (manufactured by Nippon Shokubai Co., Ltd., Epocross (registered trademark)) ) WS-700, molecular weight 20,000) is added 1 part by mass, and a mixed solution obtained by adding 25% ammonia water as a pH adjuster so that the pH is 9 is 0.2 mm thick, 35 mm wide, 45 mm long. After being applied to the surface of copper (lead conductor), it was dried at 120 ° C. for 5 minutes to form a composite coating layer.

  A resin composition in which a polyolefin resin (acid-modified polypropylene: Mitsui Chemicals, Admer QF551), copper damage inhibitor (ADK STAB CDA1), and antioxidant (Irganox 1010) are mixed at a ratio shown in Table 1 is molded to a thickness of 50 μm. A heat-sealing layer was prepared. A heat-sealable layer was coated on both surfaces of the lead conductor having a composite coating layer formed on the surface, and pressed and adhered at 260 ° C. for 10 seconds to produce a lead wire.

(Reference Example 1)
Using a nickel-plated copper having a thickness of 0.2 mm, a width of 35 mm, and a length of 45 mm as the lead conductor, a composite coating layer was formed in the same manner as in Examples 1 to 3 and Comparative Example 1, and heat fusion at the ratios shown in Table 1 A lead wire was prepared using the layer.

(Evaluation of initial adhesive strength)
The produced lead wire was cut into a width of 10 mm, and the adhesive force between the heat-fusible layer and the lead conductor was measured by a 180 ° peel test. The tensile speed was 100 mm / min. When the adhesive force was 6 N / cm or more, it was judged that the adhesive was good.

(Evaluation of electrolyte resistance)
Ethylene carbonate (EC), diethyl carbonate (DEC), and dimethyl carbonate (DMC) are mixed at a volume ratio of 1: 1: 1, so that lithium hexafluorophosphate (LiPF ₆ ) is 1.0 mol / l as an electrolyte. Thus, the melted electrolyte solution was prepared. A lead wire is immersed in this electrolytic solution, adjusted so that the moisture content of the electrolytic solution becomes 1000 ppm, and left in a 60 ° C. thermostatic bath for the period shown in Table 1, and then heat-melted in the same manner as in the evaluation of the initial adhesive strength. The adhesion force between the deposition layer and the lead conductor was measured.

(Evaluation of long-term heat resistance)
After the produced lead wire was left in a thermostat bath at 136 ° C., 130 ° C., and 125 ° C., the number of days until a crack was generated in a state bent at 180 ° was observed. The results are shown in Table 1.

  The lead wires of Examples 1 to 3 have better long-term heat resistance than the lead wires of Comparative Example 1. In particular, Example 3 containing 2 parts by mass of copper damage inhibitor with respect to 100 parts by mass of polyolefin resin has long-term heat resistance equivalent to Reference Example 1 using nickel-plated copper. When this result is Arrhenius-plotted, it is estimated that in Examples 1 to 3, the battery can be used for more than 10 years, which is the useful life of the battery, at 95 ° C. In addition, in all of Examples 1 to 3, the initial adhesive strength and the electrolytic solution resistance are good.

DESCRIPTION OF SYMBOLS 1 Nonaqueous electrolyte battery 2 Enclosed container 3 Lead conductor 4 Thermal fusion layer 5 Metal layer 6 Resin layer 7 Resin layer 8 Laminate film 9 Sealing part 10 Positive electrode current collector 11 Negative electrode current collector 12 Separator 13 Nonaqueous electrolyte 14 Composite film layer

Claims (5)

A lead conductor for a non-aqueous electrolyte battery comprising a lead conductor made of copper, a composite coating layer covering the surface of the lead conductor, and a thermal fusion layer covering at least a part of the composite coating layer;
The composite film layer covering the surface of the lead conductor is an acrylic acid copolymer or / and a methacrylic acid copolymer, or a cured product thereof.
The said heat-fusion layer is a lead wire for non-aqueous electrolyte batteries which consists of a resin composition which contains 0.05 mass part or more of copper damage inhibitors with respect to 100 mass parts of polyolefin resin.   The copper damage inhibitor is 3- (N-salicyloyl) amino 1,2,4-triazole, 2,3-bis [[3- (3,5-di-tert-butyl-4-hydroxyphenyl] propionyl]. One or more selected from the group consisting of propionyl] propiononohydrazide, salicylhydrazide, 2 ′, 3-bis [[3- [3,5-di-tert-butyl-4-hydroxyphenyl] propionyl] propiohydrazide The lead wire for a nonaqueous electrolyte battery according to claim 1.   The lead wire for a non-aqueous electrolyte battery according to claim 1, wherein the composite coating layer is a cured product of an acrylic acid copolymer and / or a methacrylic acid copolymer.   The lead wire for a nonaqueous electrolyte battery according to any one of claims 1 to 3, wherein the polyolefin resin is polypropylene or acid-modified polypropylene.   The nonaqueous electrolyte battery using the lead wire for nonaqueous electrolyte batteries of any one of Claims 1-4.

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