JP4375148B2 - Nonaqueous electrolyte battery and lead wire for nonaqueous electrolyte battery - Google Patents

Description

  The present invention relates to a nonaqueous electrolyte battery having a structure in which a positive electrode, a negative electrode, and an electric field liquid are housed in an encapsulating bag and a lead wire connected to the electrode is taken out, and a lead wire therefor.

  Along with downsizing of electronic devices, downsizing and lightening of a battery as a power source are required. In addition, there are also demands for higher energy density and higher energy efficiency, and expectations for non-aqueous electrolyte batteries such as lithium ion batteries are increasing to meet such demands. As a nonaqueous electrolyte battery, one having a structure in which a positive electrode, a negative electrode, and an electrolytic solution are housed in an encapsulating bag made of a laminated film including a metal foil and a lead wire connected to the electrode is taken out to the outside is known ( For example, see Patent Document 1 and Patent Document 2).

  FIG. 4 is a diagram showing an outline of the nonaqueous electrolyte battery disclosed in Patent Document 1. In the figure, 1 and 1 'are lead wires, 2 is an insulator, 3 is an encapsulating bag, 4 is a seal portion, 5 is a positive electrode, 5' is a negative electrode, 6 is a diaphragm, and 7 and 7 'are electrode conductors, 8, 8 'is an active substance, 9 is a metal foil, 10 and 11 are insulating layers, 12 is an innermost layer film, 13 is an outermost layer film, and 14 is a laminated film.

  In the non-aqueous electrolyte battery shown in FIG. 4A, the positive electrode 5 and the negative electrode 5 ′, the diaphragm 6, the electrolytic solution, and the like are accommodated in a bag-like encapsulating bag 3 and connected to the positive and negative electrodes 5 and 5 ′. In this structure, the lead wires 1 and 1 'are sealed and taken out. The encapsulating bag 3 uses a highly sealed laminated film 14 in which a metal foil 9 made of at least a metal such as aluminum, copper, and stainless steel is sandwiched between an innermost layer film 12 and an outermost layer film 13. It is formed. Then, with respect to the two laminated films 14 cut into a rectangular shape, the inner peripheral layer film 12 is fused and sealed to each other by sealing the peripheral seal portion 4 with a heat seal to form a bag-shaped encapsulating bag 3. . The lead wires 1 and 1 ′ connected to the positive and negative electrodes 5 and 5 ′ are covered with the insulator 2 so that an electrical short circuit does not occur with respect to the metal foil 9 of the laminated film 14 and the encapsulating bag 3. And are taken out in a sealed state.

  As shown in FIG. 4B, the insulator 2 covering the lead wire 1 and 1 'take-out portion has, for example, a low-melting-point insulating layer 10 and a heat-sealing temperature of the encapsulating bag 3 having a higher melting point. It is formed of two layers of the insulating layer 11 which does not melt. The insulator 2 is sandwiched in the takeout port of the encapsulating bag 3 after the inner insulating layer 10 is previously heated and melted and sealed and bonded to the takeout portion of the lead wires 1 and 1 ′. Thereafter, the sealing portion 4 around the laminated film 14 is sealed by heat sealing. However, since the insulating layer 11 is formed of a material that is not melted at the temperature at the time of this heat sealing, the lead wires 1, 1 ′ And the metal foil 9 in the laminated film 14 is not worried about being electrically short-circuited.

In addition, it is said that the sealing reliability can be improved by providing an insulating layer as shown by a chain line that melts at the heat seal temperature on the outside of the insulator 2 and melting and integrating with the encapsulating bag 3. Yes. Further, the positive electrode 5 and the negative electrode 5 ′ have a structure in which an active material layer is formed on a metal base material such as a current collector called a metal foil or an expanded metal, and the lead wires 1 and 1 ′ and the positive electrode 5 and the negative electrode 5 ′ can be connected by using a method of connecting the electrode conductors 7 and 7 ′ serving as the electrode base and the conductors of the lead wires 1 and 1 ′ by spot welding, ultrasonic welding, or the like. Has been.
Japanese Patent No. 3505905 Japanese Patent Laid-Open No. 2001-102016

As shown in Patent Document 1, generally, welding means such as spot welding or ultrasonic welding are used for the lead wire and electrode of the nonaqueous electrolyte battery. However, since the connection part by welding the lead wire and the electrode has a shape having a metal protrusion and is positioned so as to face the encapsulating bag, the encapsulating bag may be damaged due to contact with the encapsulating bag. May also be a cause of lowering reliability.
The present invention has been made in view of the above-described circumstances, and is excellent in electrical insulation and sealing performance at the lead wire lead-out portion, and the encapsulating bag is not damaged by the connection portion between the lead wire and the electrode. It is an object to provide a reliable nonaqueous electrolyte battery and a lead wire therefor.

  The nonaqueous electrolyte battery according to the present invention has a structure in which a positive electrode, a negative electrode, and an electrolytic solution are housed in an encapsulating bag made of a laminated film including a metal foil, and lead wires connected to the positive and negative electrodes are taken out. The insulator fused to the encapsulating bag extends to a position covering the connecting portion between the lead wire and the positive and negative electrodes, and prevents the enclosing bag from directly touching the connecting portion. The insulator is provided with an adhesive layer that adheres to the lead wire conductor and an insulating layer that is fused to the encapsulating bag, and the lead wire is electrically insulated and taken out in a sealed state. To prevent contact with the encapsulating bag.

  According to the present invention, it is possible to cover the connecting portion between the lead wire and the electrode by using the insulator that insulates the lead wire lead-out portion so that the metal projection does not directly contact the encapsulating bag. As a result, it is possible to prevent the metal projections from scratching and damaging the inner surface of the encapsulating bag, and it is possible to improve reliability without reducing productivity.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an external view showing an example of a nonaqueous electrolyte battery according to the present invention. FIG. 2 is a diagram for explaining the outline of the nonaqueous electrolyte battery according to the present invention. FIG. 2 (A) is a sectional view, FIG. 2 (B) is a partial view seen from the aa direction, and FIG. It is the partial view seen from -b direction. FIG. 3 is a view showing an example of a lead wire for a nonaqueous electrolyte battery according to the present invention. In the figure, 20 is an insulator, 20a is an extended portion, 21 is an adhesive layer, 22 is an insulating layer, and 23 is a connection portion.

  In the nonaqueous electrolyte battery according to the present invention, as shown as an example in FIG. 1, the take-out portions of the pair of lead wires 1 and 1 ′ are respectively covered with an insulator 20 and taken out from the seal portion 4 of the encapsulating bag 3. It is formed with a thin structure. The encapsulating bag 3 is a bag in which the peripheral seal portion 4 is heat-sealed by heat sealing. In the encapsulating bag 3, a single electrochemical cell including a positive electrode, a negative electrode, a diaphragm and the like and a non-aqueous electrolyte solution in which an electrolyte (for example, a lithium compound) is dissolved in a non-aqueous solvent (for example, an organic solvent). Is sealed and stored. The lead wires 1 and 1 ′ are taken out from the seal portion 4 for electrical connection to the outside, and the lead-out portion is covered and insulated with an insulator 20 to electrically connect with the metal foil in the laminated film forming the encapsulating bag 3. In order to avoid contact.

  FIG. 2 is a diagram schematically showing a nonaqueous electrolyte battery according to the present invention. Lead wires 1 and 1 ′ are covered with an insulator 20 from a part of the seal portion 4 of the encapsulating bag 3 shown in FIG. The structure to take out is shown. Although schematically shown in the figure, the encapsulating bag 3 is formed of a laminated film 14 including a metal foil layer therein as described with reference to FIG. The laminated film 14 is formed by sandwiching at least a metal foil such as aluminum, copper, stainless steel or the like in a sandwich shape between the innermost layer film and the outermost layer film, and with respect to the electrolytic solution stored in the encapsulating bag 3. Increases sealing performance.

  Moreover, the laminated film 14 of the encapsulating bag 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 is suitable for preventing leakage of the electrolytic solution from the seal portion. As a thing, it is formed with an acid-modified polyolefin (eg, maleic anhydride-modified low density polyethylene). The outermost layer film is formed of polyethylene terephthalate (abbreviated as PET) or the like to protect the inner metal foil from damage.

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

  The electrode is composed of a positive electrode 5 and a negative electrode 5 ′ facing each other with the diaphragm 6 interposed therebetween, and has a structure in which active substance layers 8 and 8 ′ are formed on a metal base material called a current collector or an expanded metal base. is doing. The positive electrode 5 is configured by forming an active substance 8 composed of a reduced oxide powder, a carbon powder, and a binder of a binder on an electrode conductor 7 of an aluminum foil. The negative electrode 5 'is formed by forming an active substance 8' made of carbon powder and a binder of a binder on an electrode conductor 7 'made of copper foil. The diaphragm 6 disposed between the positive electrode 5 and the negative electrode 5 'is formed of a polyolefin-based porous film that retains electrical insulation and ion conductivity.

  The positive and negative electrodes 5 and 5 ′ are formed by connecting the connecting pieces 7a and 7a ′ formed integrally with the electrode conductors 7 and 7 ′ to the lead wires 1 and 1 ′ by spot welding, ultrasonic welding, or the like. 23, and is electrically extracted to the outside. Since the lead wire 1 connected to the positive electrode 5 has a positive high potential, it is formed of the same aluminum or titanium as the electrode conductor 7 or an alloy thereof so as not to be dissolved by contact with the electrolytic solution. Is preferred. The lead wire 1 ′ connected to the negative electrode 5 ′ is liable to be corroded by lithium, hardly formed of an alloy with lithium, and has a high potential because lithium is deposited by overcharge and the potential becomes high by overdischarge. It is preferable that the electrode conductor 7 'which is hardly dissolved is formed of the same copper, nickel, or an alloy thereof.

  For the lead wires 1 and 1 ′, a round conductor or a single conductor of a rectangular conductor can be used. However, in the case of a round conductor, if the battery capacity is large, the diameter becomes large, so that the portion taken out from the encapsulating bag 3 is sealed. May be reduced. For this reason, even when the battery capacity is increased, it is possible to take out without reducing the sealing performance by using a rectangular conductor that does not increase the thickness by increasing the width dimension. In addition, when welding the connection pieces 7a and 7a ', the lead wire using the flat conductor can increase the contact area, and a connection with excellent reliability can be performed.

  It is preferable to form the insulator 20 that covers the lead-out portions of the lead wires 1 and 1 ′ and electrically insulates from the metal foil of the encapsulating bag 3 with two layers of an adhesive layer 21 and an insulating layer 22. The adhesive layer 21 is formed of a resin material having a relatively low melting temperature, and the insulator 20 is adhered to the conductors of the lead wires 1 and 1 ′ by melt bonding. For this adhesive layer 21, for example, a thermoplastic polyolefin resin or the like, preferably low density polyethylene or acid-modified low density polyethylene (eg, thickness 40 μm, melting point 110 ° C.) is used. It is heat-sealed on the conductor.

  The insulating layer 22 is formed of a resin material that does not melt at the heat sealing temperature of the encapsulating bag 3, and is fused to the encapsulating bag 3 to draw out the lead wires 1 and 1 'in a sealed state. For this insulating layer 22, for example, a cross-linked polyolefin resin, preferably a cross-linked low-density polyethylene or ethylene-vinyl alcohol polymer (eg, ethylene ratio 44%, thickness 100 μm, melting point 165 ° C.) is used. When the innermost layer film of the encapsulating bag 3 is formed of acid-modified low-density polyethylene, the sealing portion 4 is heat-sealed at about 110 ° C., but the insulating layer 22 is not melted at this heat-sealing temperature, and the lead wire 1 , 1 ′, electrical insulation from the metal foil of the encapsulating bag 3 can be ensured. Note that by providing an insulating layer that melts at the heat sealing temperature of the encapsulating bag 3 on the outside of the insulating layer 22, the sealing reliability at the lead-out portion of the lead wires 1, 1 ′ can be enhanced.

  In the above lead wire structure, the connecting portion 23 between the lead wires 1 and 1 'and the connecting pieces 7a and 7a' has a metal corner on the surface of the connecting portion, or a connection is formed particularly by welding. In some cases, the shape may have a metal protrusion. For this reason, if the soft encapsulating bag 3 comes into contact with the connecting portion 23 due to reduced pressure or an external force, there is a risk of scratching and damage.

  In the present invention, in the lead wires 1 and 1 ′ described above, the insulator 20 is provided with the extension portion 20 a in the direction extending from the lead wire extraction portion to the inside. The extended portion 20a extends so as to completely cover the connection portion 23 between the lead wires 1 and 1 'and the connection pieces 7a and 7a' of the electrode conductors 7 and 7 '. By covering the connection portion 23 with the extended portion 20 a of the insulator 20, it is possible to prevent the encapsulating bag 3 from coming into direct contact with the connection portion 23. As a result, it is possible to prevent the encapsulating bag 3 from being damaged by the protrusions present in the connection portion 23, and to improve the reliability of the product.

  FIG. 3 is a diagram showing various configuration examples of the extended portion 20a, and FIGS. 3A and 3B show examples in which the extended portion 20a does not have the adhesive layer 21. FIG. If the insulator 20 is provided before the connection pieces 7a and 7a 'are connected to the lead wires 1 and 1', the extended portion 20a is in a state of obstructing the connection. For this reason, it is necessary to prevent the extended portion 20a from being bonded onto the conductor of the lead wire, and it is preferable to have a structure in which the adhesive layer 21 is limitedly provided at the lead wire extraction portion.

  However, as shown in FIGS. 3C and 3D, the insulator 20 including the extended portion 20a may be formed of a two-layer structure of an adhesive layer 21 and an insulating layer 22. In this case, a sheet member made of a material that does not melt at the melting temperature of the adhesive layer 21 may be attached to the extended portion 20a to form a non-adhesive surface. Note that the sheet member may be removed after the connection pieces 7a and 7a 'are connected. In this way, by forming the entire insulator 20 in a two-layer structure, it is not necessary to identify in manufacturing that the adhesive layer 21 is partially removed or not provided, and productivity can be improved. .

  3B and 3D show an example in which the extended portion 20a is formed only on one side of the lead wire. The extension portion 20a may be provided between the connection portion 23 and the enclosing bag 3 so as to prevent contact between the extension portion 20a and the extension portion 20a on the side where the lead wires 1, 1 'and the connection pieces 7a, 7a' are connected. That's fine. However, it may be provided on both sides of the lead wire as shown in FIGS. 3 (A) and 3 (C). In the latter case, either one of the extended portions is not used, but it is not necessary to consider the mounting direction of the lead wires 1 and 1 'by providing them on both sides of the lead wire. Further, the connection pieces 7 and 7 'and the lead wires 1 and 1' can be connected from any direction, and it is not necessary to consider these directions, so that production is not troublesome. Can be improved.

  Further, as shown in FIG. 3D, not only the extended portion 20a of the insulator 20 exists between the connecting portion 23 and the surface of the enclosing bag 3, but also the adhesive layer 21 of the extended portion 20a is bonded. Thus, the connection portion 23 may be completely covered and protected. The extension 20a can be easily bonded by melting the adhesive layer 21 by connecting the connecting pieces 7a, 7a 'to the lead wires 1, 1' and then applying heat and pressure. In this way, the extension piece 20a is also bonded and fixed, so that when the extension piece 20a is inserted into the encapsulating bag 3, the extension piece 20a does not bend at the portion of the insertion port, improving workability, Product reliability can be increased.

It is an external view which shows an example of the nonaqueous electrolyte battery by this invention. It is a figure explaining the outline of the nonaqueous electrolyte battery by this invention. It is a figure which shows the various structural examples of the lead wire for nonaqueous electrolyte batteries by this invention. It is a figure explaining the prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,1 '... Lead wire, 2 ... Insulator, 3 ... Encapsulation bag, 4 ... Seal part, 5 ... Positive electrode, 5' ... Negative electrode, 6 ... Diaphragm, 7, 7 '... Electrode conductor, 7a, 7a '... connecting piece, 8, 8' ... active substance, 9 ... metal foil, 10,11 ... insulating layer, 12 ... innermost layer film, 13 ... outermost layer film, 14 ... laminated film, 20 ... insulator, 20a ... extension Part, 21 ... adhesive layer, 22 ... insulating layer, 23 ... connection part.

Claims (6)

  A nonaqueous electrolyte battery having a structure in which a positive electrode, a negative electrode, and an electrolytic solution are housed in an encapsulating bag made of a laminated film including a metal foil, and lead wires connected to the positive and negative electrodes are taken out to the outside. The non-aqueous electrolyte battery, wherein an insulator to be attached extends to a position covering a connection portion between the lead wire and the positive and negative electrodes.   The non-aqueous electrolyte battery according to claim 1, wherein the insulator includes an adhesive layer that adheres to a lead wire conductor and an insulating layer that is fused to the encapsulating bag.   The nonaqueous electrolyte battery according to claim 1, wherein a connection portion between the lead wire and the positive and negative electrodes is covered with the insulator.   The non-aqueous electrolyte battery according to claim 1, wherein the connection between the lead wire and the positive / negative electrode is formed by welding.   A lead electrode for a nonaqueous electrolyte battery having a structure in which a positive electrode, a negative electrode, and an electrolytic solution are housed in an encapsulating bag made of a laminated film including a metal foil, and a lead wire connected to the positive and negative electrodes is taken out to the outside. A lead wire for a non-aqueous electrolyte battery, comprising an insulator fused to the encapsulating bag, wherein the insulator has an extended portion extending in a non-adhered state on a part of the lead wire conductor.   The non-aqueous material according to claim 5, wherein the insulator includes an adhesive layer that adheres to a lead wire conductor and an insulating layer that is fused to the encapsulant at least at a portion where the lead wire is taken out. Lead wire for electrolyte battery.

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