JP3460529B2 - Non-aqueous electrolyte battery - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous electrolyte battery used as a power source for electronic equipment. In more detail, the positive electrode, the negative electrode, the electrolyte solution is sealed in a sealing bag, and has a structure in which the lead wires of the positive electrode and the negative electrode are respectively taken out,
The present invention also relates to a non-aqueous electrolyte battery characterized by high reliability in sealing an electrolyte. 2. Description of the Related Art Along with the miniaturization of electronic devices, there is an increasing demand for miniaturization and weight reduction of batteries as power sources. On the other hand, batteries are also required to have higher energy density and higher energy efficiency, and expectations for secondary batteries such as Li-ion batteries are increasing. In response to such demands, for example, as seen in JP-A-61-240564, a group of electrode plates is inserted into a bag made of an acid-resistant thermoplastic resin, and a large number of the electrode groups are formed into a film or sheet. There has been proposed an attempt to form a sealed lead-acid battery by enclosing it in a bag-like outer body made of a tubular or tubular synthetic resin. Also, Japanese Patent Laid-Open No.
As disclosed in Japanese Patent No. 2447 and Japanese Patent Application Laid-Open No. 57-115820, there is also an attempt to improve the sealing performance by forming a structure in which a metal layer is sandwiched between plastic films in a sheet of an enclosing bag. [0003] The provision of a metal layer greatly improves the sealing performance. However, it is difficult to eliminate the leakage of the electrolyte from the sealing portion. In some cases, such as when the battery is exposed to a nearby high temperature atmosphere, the battery life may be shortened due to leakage of the electrolyte. The inventors of the present invention have conducted various studies to solve the above-mentioned problems and to improve the reliability of sealing. As a result, the present inventors have found that a positive electrode, a negative electrode, and an electrolytic solution are sealed in a sealing bag. ,
The structure of taking out the lead wires of the positive electrode and the negative electrode respectively to the outside,
After heat-sealing the battery including the portion where the lead wire is taken out to form a battery, it has been found that by applying radiation treatment to this battery, there is a remarkable effect in preventing leakage of the electrolyte, and the present invention has been completed. did. Hereinafter, the present invention will be described in detail with reference to the drawings. In a battery of a type in which an electrode, an electrolyte, a diaphragm, and the like are inserted into an encapsulation bag, as shown in FIG. 3, the encapsulation is performed by fusing the innermost heat seal layer 10 inside the encapsulation bag in direct contact. A bag has been made. Then, as shown in FIG. 2, a positive electrode, a negative electrode, a diaphragm, and an electrolytic solution are stored in the encapsulating bag, and as shown in FIG. The insulator 2 of the lead wire is integrated by fusing, the lead wire is taken out, and the lead wire is connected to the positive and negative electrode plates inside the enclosing bag. The lead wire and the electrode are connected in advance and sealed in a sealing bag. The positive and negative electrode plates have a structure in which an active material layer is formed on a metal substrate called a current collector, such as a metal foil or an expanded metal. The method of connecting the lead wire to the positive and negative electrode plates is not particularly limited, but a method of connecting the metal base material of the electrode plate and the conductor of the lead wire by spot welding, ultrasonic welding, or the like can be preferably used. [0007] Since a very high potential is applied to the positive electrode connection, a material that does not melt at a high potential is desirable for the material of the lead wire conductor. Aluminum for that,
Alternatively, titanium or an alloy of these metals can be preferably used. For the connection of the negative electrode, lithium is precipitated by overcharging, and in overdischarge, the potential is high, so the shape is not easily changed when lithium is precipitated, that is, it is difficult to form an alloy with lithium, and it is dissolved at a relatively high potential. A material that is difficult to work is preferable. From the above viewpoints, nickel or copper, or an alloy of these metals can be preferably used as the material of the conductor. As for the shape of the conductor, a single wire of a round shape or a rectangular conductor can be preferably used. However, in the case of a round shape, the diameter of the round shape increases when the battery capacity is large. Since the thickness of the lead wire interposed between the heat seal layers 10 becomes large, a gap is easily generated in a fusion portion between the insulator 2 as the outermost layer of the lead wire and the heat seal layer 10 as the innermost layer of the encapsulating bag. As a result, there is a problem that the reliability of sealing at the fusion portion between the lead wire and the sealing bag is lowered. On the other hand, when a rectangular conductor is used, it is possible to increase the cross-sectional area by increasing the width of the conductor without increasing the thickness of the conductor to increase the battery capacity. There is no reduction in the reliability with respect to the sealing of the fused portion of the lead wire sandwiched between the layer 10 and the insulator 2. Further F
When connecting to an external circuit using a PC (flexible printed circuit board) or the like, or to the electrode plate, the rectangular conductor has a larger contact area, and more reliable connection can be performed by spot welding or ultrasonic welding. It becomes possible. The electrolyte includes propylene carbonate, γ
LiCl in organic solvents such as butyrolactone, ethylene carbonate, diethyl carbonate, dimethyl carbonate, 1.2-dimethoxyethane, tetrahydrofuran, etc.
A non-aqueous electrolyte such as 10 ₄ , LiBF ₄ , LiPF ₆ , LiAsF ₆ or a solid electrolyte having lithium ion conductivity can be used. The encapsulating bag is preferably made of a material that is bonded to a metal foil such as an aluminum foil or a plastic in which a metal deposition layer is inserted in a sandwich shape. At least the inner plastic must not dissolve in the electrolyte. . An important feature of the present invention is that a positive electrode, a negative electrode, and an electrolytic solution are sealed in an enclosing bag, and the lead wires of the positive electrode and the negative electrode are respectively taken out to the outside. And then subjecting the battery to radiation treatment. As a method of performing radiation treatment, for example, there is a method in which a battery is packed in a predetermined cardboard box and then the entire cardboard box is exposed to γ-rays using cobalt as a radiation source for a predetermined time. A similar effect can be expected by processing with an electron beam using an electron beam accelerator having a large transmission power. Of course, instead of packing batteries in a cardboard box or the like, individual batteries can be arranged directly on a conveyor and subjected to radiation treatment. The radiation dose is 50KG
y to 300 KGy was a preferable range. 50KGy
If the irradiation is less than this, the effect of improving the sealing reliability is not sufficient,
On the other hand, if the irradiation amount is too large, the economic efficiency is poor, and there is a possibility that the performance of the heat seal portion may be deteriorated, for example, the plastic may be brittle. An embodiment will be described below. First, Li
100 parts by weight of CoO ₂ powder (manufactured by Nippon Chemical Industry), 10 parts by weight of graphite and 10 parts by weight of polyvinylidene fluoride were mixed and dissolved in N-methyl-2-pyrrolidone.
Paste. Next, this paste was applied to a thickness of 20 μm.
Was coated on one side of an aluminum foil, dried and then roller-pressed. Thus, an electrode plate having a thickness of 0.1 mm, a width of 50 mm, and a length of 105 mm (5 mm is an uncoated portion) was prepared and used as a positive electrode. Next, 20 parts by weight of polyvinylidene fluoride was mixed with 100 parts by weight of phosphorous natural graphite powder, dissolved in N-methyl-2-pyrrolidone, and then made into a paste. This paste was applied on both sides of a copper foil having a thickness of 20 μm, dried, and then roller-pressed. Thus, an electrode plate (5 mm thick, 50 mm wide, 105 mm long)
mm is an uncoated part) to prepare a negative electrode. An aluminum foil (positive electrode) on which an active material layer of an electrode plate is not coated is sandwiched between a fine and porous film of polypropylene having a thickness of 25 μm between the positive electrode and the negative electrode thus obtained. Each foil (negative electrode) was connected to the conductor portion of the lead wire by ultrasonic welding, inserted into a sealed bag as shown in FIG. 2, injected with 8 cc of an electrolytic solution, impregnated under reduced pressure, and then inserted into the sealed bag. The inner layer of the sealed bag and the insulator outside the lead wire were heat-sealed (sealing width: 10 mm) with a sealing machine at 200 ° C. for 5 seconds to form a test battery. As the electrolytic solution, a solution obtained by mixing ethylene carbonate and diethyl carbonate at a volume ratio of 1: 1 and dissolving lithium hexafluorophosphate at 1 mol / liter was used. The enclosing bag is prepared by cutting a sheet having the structure shown in Table 1 into two rectangular shapes (70 mm × 135 mm).
It was obtained by heat-sealing the three sides of the rectangle with a width of 3 mm, with the PET faces facing outward and facing each other. [Table 1] The positive electrode, the negative electrode, and the electrolytic solution are sealed in the encapsulating bag thus obtained, and the positive electrode and the negative electrode lead wires are respectively taken out to the outside. Battery. The battery was irradiated with γ-rays at 100 KGy, and the sealing reliability was compared with a non-irradiated product. The comparison of the sealing reliability was performed by leaving the battery sample in an atmosphere at 100 ° C. and tracing a change in the current capacity of the battery and a decrease in weight. The results of the sealing reliability test are as shown in Tables 2 and 3. Irradiated products are 10 times less than non-irradiated products
It was found that the weight loss in the 0 ° C. atmosphere was small, and the current capacity of the battery was not much reduced, and the irradiation significantly improved the sealing reliability. [Table 2] [Table 3]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a non-aqueous electrolyte battery using an encapsulation bag and a lead wire of the present invention. FIG. 2 schematically shows the inside of an enclosing bag. FIG. 3 shows a cross section of an enclosing bag. FIG. 4 is an enlarged view of a heat sealing portion of the enclosing bag. [Description of Signs] 1, 1 ': Conductor of lead wire 2, 2': Insulation of lead wire 3: Encapsulation bag 4: Seal portion of encapsulation bag (example) 5, 5 ': Electrode 6: Diaphragm 7: Positive electrode collection Current collector 7 ': negative electrode current collector 8: positive electrode active material 8': negative electrode active material 9: aluminum foil 10: heat seal layer 11: PET layer

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-7-78604 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 2/00-2/08

Claims (1)

(1) A non-aqueous electrolyte battery having a structure in which a positive electrode, a negative electrode, an electrolytic solution, and the like are sealed in an encapsulating bag, and leads of the positive electrode and the negative electrode are respectively taken out. Non-aqueous electrolyte characterized in that the bag is composed of a laminated sheet of a metal layer and a plastic layer composed of one or more layers, and the sealed bag is heat-sealed to form a battery and then subjected to radiation treatment. battery.