JP6019593B2 - Non-aqueous electrolyte battery lead wire and non-aqueous electrolyte battery using the same - Google Patents

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.

  Patent Document 3 discloses a lead wire for a non-aqueous electrolyte battery in which a composite film layer is formed on a lead conductor metal surface by applying a treatment liquid containing a resin component containing polyacrylic acid and a metal salt. Although this method does not use a chromium-based material, there is no environmental problem. However, in order to extend the life of the battery, it is necessary to further improve the electrolytic solution resistance.

Japanese Patent No. 3562129 JP 2009-99527 A JP 2006-128096 A

  In view of such problems, the present invention provides a lead wire for a non-aqueous electrolyte battery that is excellent in resistance to an electrolytic solution and does not peel off even when contacted with an electrolytic solution for a long time, and a non-aqueous electrolyte battery using the same. This is the issue.

The present invention provides a lead conductor having a composite film layer formed of a reaction product of polyacrylic acid and an oxazoline group-containing polymer on the entire surface or a part thereof, and is in contact with the composite film layer and covers at least a part of the lead conductor. A lead wire for a non-aqueous electrolyte battery having a heat fusion layer, wherein a mixing ratio (mass ratio) of the polyacrylic acid and the oxazoline group-containing polymer is 1: 0.1 to 1:10, A lead wire for a non-aqueous electrolyte battery in which the composite coating layer does not contain a chromium compound .

  When polyacrylic acid and an oxazoline group-containing polymer are reacted, the carboxyl group of polyacrylic acid and the oxazoline group of the oxazoline group-containing polymer react to form a crosslinked structure. By providing the composite film made of such a reactant on the surface of the lead conductor, the resistance of the lead wire to electrolyte, particularly the resistance to electrolyte in a high temperature atmosphere can be improved. Further, by providing the heat-sealing layer, the seal part of the non-aqueous electrolyte battery can be favorably bonded, and the sealing performance of the non-aqueous electrolyte battery can be improved.

As the oxazoline group-containing polymer, an acrylate copolymer containing an oxazoline group is preferable . The mixing ratio (mass ratio) of the polyacrylic acid and the oxazoline group-containing polymer is preferably in the range of 1: 0.1 to 1:10 . A more preferable range is 1: 0.1 to 1: 1. When the mixing ratio of the oxazoline group-containing polymer is less than this range, the polyacrylic acid is not sufficiently cross-linked and the resistance to electrolytic solution is lowered. Moreover, even if the mixing ratio of the oxazoline group-containing polymer exceeds this range, the oxazoline group-containing polymer does not sufficiently react with the carboxyl group of polyacrylic acid, and the electrolytic solution resistance decreases.

By providing such a composite coating layer on the surface, particularly when the lead conductor is nickel or a metal plated with nickel on the surface, the effect of improving the resistance to electrolytic solution is enhanced .

Furthermore, the present invention provides a sealed container having a metal layer, a lead conductor extending from the inside of the sealed container, a nonaqueous electrolyte sealed in the sealed container and the sealed container, and the lead A non-aqueous electrolyte battery having an electrode connected to an end portion of a conductor, wherein the enclosure and the lead conductor are heat-sealed at a seal portion, and polyacrylic acid is formed on the surface of the lead conductor While having a composite film layer made of a reaction product with an oxazoline group-containing polymer, a mixing ratio (mass ratio) of the polyacrylic acid and the oxazoline group-containing polymer is 1: 0.1 to 1:10, and the composite Provided is a nonaqueous electrolyte battery characterized in that the coating layer does not contain a chromium compound . Since the non-aqueous electrolyte battery having such a configuration has a high resistance to an electrolytic solution, the adhesiveness and the sealing performance can be maintained even if time elapses in use. This non-aqueous electrolyte battery can be manufactured using the above lead wires. Moreover, it can also produce in combination with an enclosure container etc. using the lead conductor which has the composite film layer which consists of a reaction material of polyacrylic acid and an oxazoline group containing polymer on the surface.

  ADVANTAGE OF THE INVENTION According to this invention, the lead wire for nonaqueous electrolyte batteries which can improve the adhesiveness in an initial state and a contact state with electrolyte solution, and sealing performance, and a nonaqueous electrolyte battery using the same can be provided. .

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 enclosing container 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. A composite film layer 14 made of a reaction product of polyacrylic acid and an oxazoline group-containing polymer is provided on the surface of the plate-like lead conductor 3, and both surfaces of the lead conductor 3 are covered with the heat-sealing layer 4. The heat sealing layer 4 is made to correspond to the seal part of the nonaqueous electrolyte battery. The composite coating layer does not need to be provided on the entire surface of the lead conductor 3, and may be provided at least between the heat-sealing layer 4 and the lead conductor. Furthermore, it is preferable that the lead conductor 3 is provided so as to cover the front surface of the portion in contact with the non-aqueous electrolyte. The lead wire is sometimes called a tab lead.

  Polyacrylic acid is a polymer of acrylic acid, which is an unsaturated carboxylic acid, and has a number of carboxyl groups in the molecule. Polyacrylic acid having a molecular weight of about 1,000 to 100,000, more preferably about 10,000 to 50,000 can be used from the viewpoint of ease of handling and adhesive strength with the lead conductor.

  As the oxazoline group-containing polymer, a polymer having two or more oxazoline groups in the molecule can be used. The polyacrylic acid is crosslinked by the reaction of the oxazoline group in the polymer with the carboxyl group of the polyacrylic acid. 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 preferably used because of its excellent compatibility with polyacrylic acid.

The polyacrylic acid and the oxazoline group-containing polymer are mixed and used at an appropriate blending ratio. Since polyacrylic acid is water-soluble, a composite film layer is formed on the surface of the lead conductor when a solution obtained by dissolving both in water is applied to the lead conductor and then dried. The polyacrylic acid and the oxazoline group-containing polymer react with each other by heating during drying to crosslink the polyacrylic acid. The coating amount of the composite coating layer is preferably 10 mg / m ^{2 to} 100 mg / m ² (about 10 nm to 100 nm in terms of thickness). 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.

  As the lead conductor 3, a metal such as aluminum, nickel, copper, or nickel-plated copper is used. 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 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.

  For the heat-fusible layer 4, any resin that can be melted by the heat at the time of heat sealing to bond the sealed container and the lead conductor can be used. For example, polyolefin resin, acid-modified styrene elastomer, etc. can be 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 excellent in adhesion to metal and sealing properties.

  In addition to these resins, 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 heat-fusible 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 1-4)
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 are 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 in parts by mass as shown in Table 1, and a mixed solution in which 0.01 parts by mass of 25% aqueous ammonia is added as a pH adjuster is 0.2 mm in thickness, 35 mm in width, and length. After coating on the surface of 45 mm nickel-plated copper (lead conductor), it was dried at 120 ° C. for 5 minutes to form a composite coating layer. A maleic anhydride-modified polypropylene film (heat fusion layer) having a thickness of 50 μm was coated on both surfaces of the lead conductor, and pressed and adhered at 260 ° C. for 30 seconds to produce a lead wire.

(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.

(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.

(Comparative Example 1)
A series of evaluations were performed in the same manner as in Example 1 except that only the polyacrylic acid was used without mixing the oxazoline group-containing polymer.

(Comparative Examples 2 to 4)
A series of evaluations were performed in the same manner as in Example 1 except that ammonium zirconium carbonate was used as a crosslinking agent instead of the oxazoline group-containing polymer.

(Comparative Example 5)
A series of evaluations were performed in the same manner as in Example 1 except that sodium polyacrylate (molecular weight: 170,000) was used instead of polyacrylic acid. The above results are shown in Tables 1 and 2.

  The lead wires of Examples 1 to 4 are excellent in initial adhesive strength and maintain adhesive strength even after being immersed in an electrolyte solution for 8 weeks, and are resistant to any mixing ratio of polyacrylic acid and oxazoline group. It turns out that it is excellent in electrolyte solution property. On the other hand, the lead wires of Comparative Example 1 using no cross-linking agent and Comparative Examples 2 to 4 using ammonium zirconium carbonate as the cross-linking agent have good initial adhesive strength, but have an adhesive strength even after being immersed in an electrolyte for 1 week. It is falling. Similarly in Comparative Example 5 using sodium polyacrylate instead of polyacrylic acid, the adhesive strength after immersion in the electrolytic solution is reduced, and the resistance to electrolytic solution is poor.

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 (4)

A lead conductor having a composite film layer made of a reaction product of polyacrylic acid and an oxazoline group-containing polymer over the entire surface or a part thereof, and a heat-sealing layer in contact with the composite film layer and covering at least part of the lead conductor A lead wire for a non-aqueous electrolyte battery,
The mixing ratio (mass ratio) of the polyacrylic acid and the oxazoline group-containing polymer is
A lead wire for a non-aqueous electrolyte battery, which is 1: 0.1 to 1:10 and does not contain a chromium compound in the composite coating layer .   The lead wire for a nonaqueous electrolyte battery according to claim 1, wherein the oxazoline group-containing polymer is an acrylic acid copolymer containing an oxazoline group. The lead wire for a non-aqueous electrolyte battery according to claim 1 or 2 , wherein the lead conductor is made of nickel or a metal plated with nickel on the surface. A sealed container having a metal layer; a lead conductor extending from the inside of the sealed container; and a nonaqueous electrolyte sealed in the sealed container and the sealed container; A non-aqueous electrolyte battery having a connected electrode, wherein the enclosing container and the lead conductor are heat-sealed at a seal portion, and a polyacrylic acid and an oxazoline group-containing polymer on the surface of the lead conductor And having a composite film layer made of the reaction product of
The mixing ratio (mass ratio) of the polyacrylic acid and the oxazoline group-containing polymer is
A non-aqueous electrolyte battery having a ratio of 1: 0.1 to 1:10 and containing no chromium compound in the composite coating layer .

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