JP2010033888A - Lead wire for nonaqueous electrolyte battery and nonaqueous electrolyte battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lead wire for a nonaqueous electrolyte battery, made of nickel having hydrofluoric acid-resistant characteristics better than inexpensive surface treatment; and to provide a nonaqueous electrolyte battery using the lead wire. <P>SOLUTION: The nonaqueous electrolyte battery where a positive electrode, a negative electrode, and nonaqueous electrolyte are housed in an enclosing body 3 made of a laminated film 4 including a metallic foil and its lead wire are provided. The lead wire 2 is made of nickel (including nickel plating), the surface of the lead wire pulled out by firmly enclosing in the enclosing body 3 is to be a passive layer 5, and an insulator 6 firmly enclosed in the enclosing body is provided on the surface of the passive layer 5. The passive layer 5 is to be zero or a plus potential in a natural electrical potential against 0.01 wt.% hydrofluoric acid, and the electrical potential is to be 0 V or more and 0.5 V or less. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a lead wire for a non-aqueous electrolyte battery in which a positive electrode, a negative electrode, and a non-aqueous electrolyte (electrolytic solution) are housed in an encapsulant made of a laminated film.

  Along with downsizing of electronic devices, downsizing and lightening of a battery as a power source are required. There are also demands for higher energy density and higher energy efficiency, and non-aqueous electrolyte batteries such as lithium-ion batteries are known to satisfy such demands. Non-aqueous electrolyte batteries have a structure in which a positive electrode, a negative electrode, and an electrolytic solution are housed in, for example, a bag-shaped enclosure made of a laminated film including a metal foil, and lead wires connected to the electrodes are taken out in a sealed state. (For example, refer to Patent Document 1).

  A laminated film including a metal foil is a highly sealed laminated film in which a metal foil made of at least aluminum, copper, stainless steel or the like is sandwiched between an inner layer film made of a resin film and an outer layer film. It is done. Then, for example, the periphery of the inner film of the two laminated films cut into a rectangular shape is fused and sealed together by heat sealing to form a bag-shaped enclosure. The lead wire connected to the positive electrode or the negative electrode is covered with an insulator so that an electrical short circuit does not occur with respect to the metal foil of the laminated film, and is sealed at a predetermined edge of the encapsulant Removed in a sealed state.

  For example, as disclosed in Patent Document 1, the insulator of the lead wire lead-out portion surrounds the lead wire metal with a low-melting-point inner insulating layer and a heat-sealing heat of a laminated film having a higher melting point. It is formed of two outer insulating layers that do not melt at the sealing temperature. This insulator is sandwiched in the outlet of the encapsulant after the inner insulating layer is heated and melted and sealed in advance at the lead wire extraction portion. After that, the sealing portion around the laminated film is sealed by heat sealing, but the outer insulating layer is formed of a material that is not melted at the temperature at the time of this heat sealing. The metal foil is not electrically short-circuited.

However, the sealing portion and the lead wire take-out portion of the laminated film are not completely covered, and moisture enters from the outside if the sealing adhesion is insufficient. When moisture enters the battery, hydrofluoric acid is generated by reaction with the internal electrolyte. As the lead metal, aluminum, nickel (including nickel plating), copper, or the like is used, but the lead metal is subject to corrosion by the hydrofluoric acid. Even if the surface of the lead metal is hermetically sealed with an insulator, the surface is gradually corroded over a long period of time, the sealed form with the insulator is destroyed, and liquid leakage occurs and the battery does not function.
Japanese Patent No. 3505905

  As the lead metal (tab), aluminum, nickel, copper, or the like is used. Of these, nickel is most hardly corroded by hydrofluoric acid. For this reason, for example, when the lead wire metal is made of copper, it may be used after being plated with nickel (referred to as nickel-plated copper). Therefore, durability can be enhanced by using high-purity nickel (including nickel plating) for the lead wire metal. However, the surface of the lead wire metal is gradually corroded and becomes unstable with long-term use, and the sealed form may be destroyed.

  The present invention has been made in view of the above-described circumstances, and uses a lead wire for a non-aqueous electrolyte battery made of nickel (including nickel plating) having hydrogen fluoride acid resistance by an inexpensive surface treatment and the lead wire. An object is to provide a nonaqueous electrolyte battery.

A lead wire for a non-aqueous electrolyte battery according to the present invention is a lead wire for a non-aqueous electrolyte battery in which a positive electrode, a negative electrode, and a non-aqueous electrolyte are housed in an enclosure made of a laminated film including a metal foil. The lead wire is nickel. (Including nickel plating), the lead wire surface of the portion sealed and taken out by the enclosure is a passive layer, and the insulator is sealed on the surface of the passive layer. It is characterized by.
The passive layer has a natural potential with respect to 0.01% by weight of hydrofluoric acid and is set to zero or positive potential, and the potential is preferably 0 V or more and 0.5 V or less.

  The passive layer on the surface of the lead wire made of nickel (including nickel plating) in the present invention can be easily and inexpensively formed by exposing it to an oxidizing atmosphere in which humidity is controlled. In addition, the passive layer formed on the surface of the lead wire provides a lead wire seal excellent in hydrogen fluoride acid resistance, and realizes a non-aqueous electrolyte battery with stable characteristics and long life without liquid leakage. Is possible.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an external view illustrating an example of a nonaqueous electrolyte battery, FIG. 2A is a diagram illustrating a cross section of the nonaqueous electrolyte battery, and FIGS. 2B and 2C illustrate the configuration of a lead wire portion. It is a figure to do. In the figure, 1 is a lead wire, 2 is a lead wire metal, 3 is an encapsulant, 3a is a sealing part, 4 is a laminated film, 4a is a metal foil, 5 is a passive layer, 6 is an insulator, 7 is an adhesive layer, 8 is an insulating layer, 9 is a positive electrode, 9 'is a negative electrode, 10 is a diaphragm, 11, 11' are electrode conductors, and 12 and 12 'are active material layers.

  A non-aqueous electrolyte battery to which a lead wire (also referred to as a tab lead) according to the present invention is applied is, for example, as shown as an example in FIG. 3 is formed in a thin structure that is taken out from the seal portion 3a. The encapsulant 3 is formed by forming a peripheral seal portion 3a into a bag shape by heat sealing by heat sealing. In the enclosure 3, an electrochemical cell including a positive electrode, a negative electrode, a diaphragm, and the like and a nonaqueous electrolytic solution in which an electrolyte (for example, a lithium compound) is dissolved in a nonaqueous solvent (for example, an organic solvent) is hermetically stored. ing.

  The lead wire 1 has a thickness of 0.05 mm to 0.4 mm, and is led out through the seal portion 3a for electrical connection to the outside. The lead wire metal 2 of the lead wire 1 is made of nickel or nickel-plated copper, and at least a lead-out portion thereof is insulated with an insulator 6 and is not in electrical contact with the metal foil of the laminated film 4 forming the encapsulant 3. Structured. The lead wire metal 2 has a chemically stable passive layer 5 formed of an oxide film (nickel oxide) at least on the surface to be sealed with the laminated film 4, and an insulator 6 is hermetically bonded to the outer surface thereof for insulation. The laminated film 4 is sealed on the outer surface of the body 6.

  FIG. 2A shows an outline of the nonaqueous electrolyte battery according to the present invention. The lead wire metal 2 is covered with an insulator 6 and taken out from a part of the seal portion 3a of the enclosure 3 shown in FIG. The structure is shown. The enclosure 3 is formed of a laminated film 4 having a metal foil 4a in a resin film. The laminated film 4 is formed, for example, by laminating a metal foil 4a such as aluminum, copper, stainless steel or the like in a sandwich shape between the inner layer film and the outer layer film, and is accommodated in the enclosure 3 The sealing property against (electrolyte) is improved.

  In addition, the laminated film 4 of the encapsulant 3 is composed of, for example, a laminated body of 3 to 5 layers, and the innermost layer film is not dissolved by the electrolytic solution and prevents the electrolytic solution from leaking from the seal portion. For example, it is formed of an acid-modified polyolefin (eg, maleic anhydride-modified low density polyethylene). The outermost layer film has a thickness of 0.05 mm to 0.2 mm, and is formed of polyethylene terephthalate (abbreviated as PET) or the like to protect the inner metal foil 4a from damage.

Examples of the non-aqueous electrolyte accommodated in the enclosure 3 include organic solvents such as propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, 1,2-dimethoxyethane, and tetrahydrodofuran, LiClO ₄ , LiBF ₄ , and LiPF _6. A nonaqueous electrolyte in which LiAsF ₆ or the like is dissolved, a lithium ion conductive solid electrolyte, or the like is used.

  The electrode is composed of a positive electrode 9 and a negative electrode 9 'facing each other with a diaphragm 10 interposed therebetween, and has a structure in which active substance layers 12, 12' are formed on a metal base material such as a metal foil or expanded metal called a current collector. ing. The positive electrode 9 and the negative electrode 9 ′ are configured by forming active material layers 12 and 12 ′ composed of a reduced oxide powder, a carbon powder, and a binder of a binder on an electrode conductor 11. The diaphragm 10 disposed between the positive electrode 9 and the negative electrode 9 ′ is formed of a polyolefin-based porous film that maintains electrical insulation and ion conductivity.

  The positive electrode 9 and the negative electrode 9 ′ are connected to the lead wire metal 2 by spot welding, ultrasonic welding or the like by connecting pieces integrally formed from the electrode conductors 11 and 11 ′. Since the lead wire metal 2 connected to the positive electrode 9 has a positive high potential, it is formed of the same metal as the electrode conductor 11, for example, pure aluminum, or an alloy thereof so as not to be dissolved by contact with the electrolytic solution. It is preferable. The lead metal 2 connected to the negative electrode 9 'is an electrode that is liable to be corroded by lithium, hardly formed of an alloy with lithium, and difficult to be dissolved because lithium is deposited by overcharging and the potential becomes high by overdischarging. It is preferable that the conductor 11 ′ is formed of the same copper, nickel, or an alloy thereof.

  As shown in FIGS. 2B and 2C, the insulator 6 that covers the lead wire metal 2 extraction portion and electrically insulates from the metal foil 4 a of the laminated film 4 includes an adhesive layer 7 and an insulating layer 8. The two layers are preferably formed. Then, the adhesive layer 7 is formed of a resin material having a relatively low melting temperature, and is fused to a composite film layer 5 described later formed on the surface of the lead wire metal 2 to hermetically bond the insulating layer 8. For example, thermoplastic polyolefin resin, preferably low-density polyethylene, acid-modified low-density polyethylene or acid-modified polypropylene (eg, thickness 40 μm, melting point 110 ° C.) is used for the adhesive layer 7, It is heat-sealed to the dynamic layer 5.

  The insulating layer 8 is formed of a resin material that does not melt at the heat seal temperature of the encapsulant 3 and is fused to the encapsulant 3 to draw out the lead wire metal 2 in a sealed state. For this insulating layer 8, for example, a cross-linked polyolefin resin, preferably a cross-linked low density polyethylene, a cross-linked polypropylene or an ethylene-vinyl alcohol polymer (eg, ethylene ratio 44%, thickness 100 μm, melting point 165 ° C.) is used. It is done. When the innermost layer film of the encapsulant 3 is formed of acid-modified low-density polyethylene, the seal portion 3a is heat-sealed at about 110 ° C., but the insulating layer 8 is not melted at this heat-sealing temperature, and the lead wire metal The electrical insulation between the laminated film 4 and the metal foil 4a can be ensured at the two take-out portions.

  With the configuration described above, it is possible to maintain good characteristics and a long life by completely sealing and adhering the sealing portion 3a of the enclosure 3 and the lead-out metal 2 takeout portion. However, if these hermetic adhesions are insufficient, moisture enters from the outside, and hydrofluoric acid is generated by reaction with the electrolyte inside. Generally, aluminum, nickel (including nickel plating), copper, or the like is used as the lead wire metal 2 but is subject to corrosion by hydrofluoric acid. Among these metals, nickel (including nickel plating) is said to have acid resistance to hydrogen fluoride compared to other metals. However, the surface is gradually corroded by hydrofluoric acid over a long period of time, and the sealed form with the insulator 6 is destroyed, causing liquid leakage and deteriorating characteristics.

  In the present invention, in order to prevent the lead wire metal 2 made of nickel metal (including nickel-plated metal) from being corroded by hydrofluoric acid, the surface of the lead wire metal 2 is passivated with nickel oxide. Processing at layer 5. The passive layer of nickel oxide is formed by leaving nickel metal in the air or in an oxidizing atmosphere. In this case, the passive layer 5 having a predetermined thickness can be obtained by exposing the nickel metal to a controlled humidity environment. In addition, the metal passivation refers to a case where a metal that is normally at an electrochemically low level (easily corroded) approaches the behavior of an electrochemically noble metal (not easily corroded).

  The film thickness level of the passive layer 5 can be determined by measuring the natural potential. The natural potential is the energy value of a metal under a certain environment. When a passive film (oxide film) is generated by oxidation of the metal surface, it becomes a positive potential. Also, the thicker the passive film, the more the potential difference is. growing. On the other hand, when the metal surface is exposed or corrosion occurs, the potential becomes negative, and the progress of corrosion can be determined.

  The present invention actively utilizes a passive layer that is oxidized and formed on a lead wire portion made of nickel metal of a non-aqueous electrolyte battery, and by adjusting the passive layer to a predetermined natural potential or higher. The acid resistance to hydrogen fluoride is increased. As a result, hydrogen fluoride resistance equivalent to that of a lead wire in which a composite coating layer is formed by applying a conventional chromate treatment, titania treatment, or treatment solution containing a resin component containing a non-chromic polyacrylic acid and a metal salt. A nonaqueous electrolyte battery having acidity can be realized. Moreover, it can be manufactured at a low cost by a simple process of simply oxidizing the surface of the lead wire metal.

  FIG. 3 is a diagram showing Examples 1 to 4 and Comparative Examples 1 and 2 according to the present invention. The lead wire metal is nickel foil (thickness of about 0.1 mm) placed in a controlled environment with different humidity, and the state (thickness) of the passive layer made of nickel oxide is adjusted. Was made different.

  Example 1 was adjusted so that the natural potential with respect to 0.01% by weight of hydrofluoric acid was +0.5 V (potential at the moment when it was put in hydrofluoric acid), and Example 2 was adjusted to 0.01% by weight. Example 3 was adjusted so that the natural potential with respect to hydrofluoric acid was +0.3 V, Example 3 was adjusted so that the natural potential with respect to 0.01% by weight of hydrofluoric acid was +0.1 V, and Example 4 was The natural potential with respect to 0.01% by weight of hydrofluoric acid was adjusted to + 0.0V. Comparative Example 1 was adjusted so that the natural potential with respect to 0.01% by weight of hydrofluoric acid was −0.1 V, and Comparative Example 2 had a natural potential with respect to 0.01% by weight of hydrofluoric acid. It adjusted so that it might become -0.2V.

  Next, the nickel foil in which the natural potential of the surface passive layer 5 is adjusted as described above is cut into a strip having a width of 5 mm, and the insulator 6 described with reference to FIG. The lead wire for evaluation was used for about 10 seconds. The insulator 6 was formed of two layers, an adhesive layer 7 made of an inner thermoplastic polypropylene resin and an insulating layer 8 made of an outer crosslinked polypropylene resin. The lead wire for evaluation was immersed in an electrolytic solution (ethylene carbonate: diethyl carbonate: dimethyl carbonate = 1: 1: 1, 1 mol of lithium hexafluorophosphate added), and 60 ° C. in the atmosphere. It stored for 4 weeks in the thermostat, and the peeling state from the lead wire metal 2 (nickel foil) of the insulator 6 was confirmed visually.

As a result, as shown in FIG. 3, in Examples 1 to 4 in which the natural potential of the passive layer was a positive potential (with a nickel oxide film layer), there was no occurrence of peeling of the insulator even after 4 weeks had passed. Showed a good result. When the natural potential exceeded +0.5 V, the nickel oxide film became thick and it was difficult to ultrasonically bond with other nickel metal. In addition, even if it can be joined, the electrical resistance at the joint is large, which is not preferable for use as an electrical conductor.
On the other hand, in Comparative Examples 1 and 2 in which the passive layer has a natural potential of less than +0.0 V (nickel metal is exposed or corroded), peeling occurred on the third day and all leads were observed after two weeks. There was peeling at the wire. This clearly shows that it is not sufficient as acid resistance to hydrofluoric acid to simply seal and bond the insulator without performing any treatment on the lead metal made of nickel metal.

It is an external view which shows an example of the nonaqueous electrolyte battery by this invention. It is a figure explaining the structure of the nonaqueous electrolyte battery and lead wire by this invention. It is a figure explaining the Example and comparative example by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Lead wire, 2 ... Lead wire metal, 3 ... Enclosure, 3a ... Seal part, 4 ... Laminated film, 4a ... Metal foil, 5 ... Passive layer, 6 ... Insulator, 7 ... Adhesive layer, 8 ... Insulation Layer, 9 ... positive electrode, 9 '... negative electrode, 10 ... diaphragm, 11, 11' ... electrode conductor, 12, 12 '... active substance layer.

Claims (4)

A lead wire for a non-aqueous electrolyte battery in which a positive electrode, a negative electrode, and a non-aqueous electrolyte are housed in an enclosure made of a laminated film including a metal foil,
The lead wire is nickel or nickel-plated, the lead wire surface of the portion sealed and taken out by the enclosure is a passive layer, and the insulation is sealed to the enclosure on the surface of the passive layer A lead wire for a non-aqueous electrolyte battery comprising a body.   2. The lead wire for a non-aqueous electrolyte battery according to claim 1, wherein the passive layer has a natural potential with respect to 0.01 wt% hydrofluoric acid and is set to zero or a positive potential. 3.   The lead wire for a nonaqueous electrolyte battery according to claim 2, wherein the natural potential is 0 V or more and 0.5 V or less. A non-aqueous electrolyte battery in which a positive electrode, a negative electrode, and a non-aqueous electrolyte are housed in an enclosure made of a laminated film including a metal foil, and lead wires connected to the positive electrode and the negative electrode are sealed in the enclosure and taken out. And
The lead wire is nickel or nickel-plated, and a portion of the lead wire sealed and taken out by the encapsulant is used as a passive layer, and is sealed to the encapsulant on the surface of the passive layer. A nonaqueous electrolyte battery comprising an insulator.

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