JPH06333552A - Nonaqueous secondary battery - Google Patents

Abstract

PURPOSE:To facilitate manufacture and enhance capacity by welding a plurality of electrode plates of the same polarity protruded from a separator, and rewelding them. CONSTITUTION:In an nonaqueous secondary battery formed of a positive electrode 4, a negative electrode 2, and a separator 3, a plurality of electrode plates of the same polarity protruded from the separator 3 are welded together, and their welding parts 12, 13 are then plurally rewelded. Namely, positive electrode lugs 11 are spot-welded two by two, and the welded lugs 11 are welded to an aluminum plate by use of a comb shaped jig. Negative electrode lugs 10 are welded in the same manner. In the welding of the lugs 10, after three lugs 10 from the end are first spot-welded, the remaining lugs 10 are spot-welded two by two, and then rewelding is carried out by use of the comb jig. Thus, an nonaqueous secondary battery with high capacity having a number of electrode plates can be provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of a non-aqueous electrolyte secondary battery, and provides a high-capacity non-aqueous electrolyte secondary battery with a simple manufacturing method.

[0002]

2. Description of the Related Art Due to the recent miniaturization and portability of various electronic devices, development of compact and lightweight high energy density secondary batteries has been demanded, and due to environmental problems such as air pollution and carbon dioxide, electric vehicles have become early stages. Practical application is desired, and development of a new secondary battery having features such as high output, high efficiency, and high energy density is desired. In particular, a secondary battery using a non-aqueous electrolytic solution has an energy density several times higher than that of a battery using a conventional aqueous electrolytic solution, and therefore its practical application is awaited.

Various positive electrode active materials for non-aqueous electrolyte secondary batteries such as titanium disulfide, lithium cobalt composite oxide, lithium manganese oxide, vanadium pentoxide, molybdenum disulfide and the like have been investigated. ing.

As the non-aqueous electrolyte, a solution in which a metal salt serving as an electrolyte is dissolved in an aprotic organic solvent is used. For example, for lithium salts, LiCl O ₄ , LiP
_{F 6, LiBF 4, LiAs F} 6, propylene carbonate LiCF ₃ SO ₃ or the like, ethylene carbonate, 1,2-dimethoxyethane, .gamma.-butyrolactone, dioxolane, 2-methyltetrahydrofuran, diethyl carbonate, dimethyl carbonate, alone sulfolane What is dissolved in a solvent or a mixed solvent is used. These non-aqueous electrolytes are used by injecting them into a battery container, but impregnating them into a porous separator, adding a high molecular weight resin to make them highly viscous, and gelating them to lose fluidity. It is sometimes used in the state.

Various materials have been studied as a negative electrode active material for non-aqueous electrolyte batteries, but a lithium-based negative electrode has been attracting attention as a material expected to have a high energy density. Particularly, as a negative electrode of a non-aqueous electrolyte secondary battery, lithium metal, lithium alloy, carbon having lithium ions retained, and the like have been studied.

Lithium metal has a high electromotive force and can be expected to have a high energy density, but due to its high reactivity, there is a problem in battery safety, and particulate lithium metal is likely to be generated in the charging reaction. It has a big problem that internal short circuit and charge / discharge efficiency decrease.

Lithium alloys can prevent the generation of metallic lithium that is not involved in the discharge reaction, but due to the characteristics, the potential of the alloy shifts to the noble direction relative to the lithium potential, and the discharge voltage decreases. There was a flaw. Further, since the component contains metallic lithium, there was a problem in safety.

In order to improve the safety problem, a carbon negative electrode has been studied as a host material that holds lithium ions. The charged carbon negative electrode holds lithium ions between the layers of the crystal lattice, and easily discharges lithium ions by the discharge reaction. The carbon negative electrode is highly safe because it does not use metallic lithium, and is less prone to deterioration due to charge and discharge, making it possible to provide a long-life non-aqueous electrolyte secondary battery.

The use of carbon as the host material has enabled the use of alkali metal ions other than lithium. Potassium and sodium are cheaper than lithium, are stable as long as they are used in the ionic state, and are not dangerous.

As the carbon used for the negative electrode, various pyrolytic carbons and natural and synthetic graphite are well known. Polyacrylonitrile-based, pitch-based, or rayon-based carbon fibers, vapor-grown carbon from benzene, propane, etc. as raw materials, carbon by thermal decomposition of polymer compounds such as phenolic resins, pitch or tar as raw materials Various carbons such as carbon can be used.

Carbon itself has electrical conductivity, and since the change in electrical conductivity due to charge / discharge is small, the method of collecting current from the electrodes has not been considered so much. Also, since it was premised on use in a non-aqueous electrolyte with low electrical conductivity, carbon-based negative electrodes are generally limited to low current, small capacity electrodes, and large capacity or large size electrodes can be created. Was not done.

However, from the viewpoints of environmental protection of the earth and effective use of energy, there is an increasing demand for high capacity, high output batteries for storage of nighttime electric power and for electric vehicles, and a high safety carbon negative electrode is used. Development of a non-aqueous electrolyte secondary battery having a large capacity has been desired.

Further, in a high capacity battery, the number of electrode plates increases, but the terminal connection method in that case is not well established.
A simple and reliable terminal connection method has been desired.

[0014]

Conventionally, a plurality of polar plates having the same polarity in a non-aqueous electrolyte secondary battery having a small number of polar plates are shown in FIG.
As shown in (3), after the polar plates of the same polarity protruding from the separator were superposed on each other, they were integrated by spot welding or the like. However, when the number of electrode plates is large as in the case of a large capacity battery as well as in the case of a small capacity battery as in the case of a small number of electrode plates, it is difficult to perform welding by such a spot welding method. Therefore, it is conceivable to install the electrode plate in the recess of the comb-shaped jig as shown in FIG. 6 (FIG. 7) and weld the electrode plate of the same polarity protruding above the comb-shaped jig. The work of setting the electrode plates on the comb-shaped jig becomes very difficult because the electrode plate base is thin, the distance between the electrode plates is narrow, and the number of electrode plates is large.

[0015]

The present invention provides a high-capacity non-aqueous electrolyte secondary battery, which comprises a rechargeable positive electrode,
In a non-aqueous electrolyte secondary battery comprising a separator impregnated with a non-aqueous electrolyte containing an alkali metal ion, and a negative electrode, a plurality of same-polarity electrode plates protruding from the separator are welded, and further these welded parts It is characterized by welding a plurality of.

[0016]

Since a plurality of polar plates of the same polarity are welded and then these are re-welded, it is possible to provide a high capacity battery which is easy to manufacture.

[0017]

1 is a cross-sectional view of a main part of a prismatic battery according to an embodiment of the present invention.

Reference numeral 1 denotes a square container made of stainless steel, in which a negative electrode 2, a separator 3 and a positive electrode 4 are housed. The negative electrode 2 is formed by holding spherical carbon powder in foamed nickel, and is alternately inserted with the LiCoO ₂ positive electrode through the porous separator 3 made of polypropylene impregnated with the nonaqueous electrolytic solution. Reference numeral 5 denotes a container lid, which is welded to the opening of the container 1 at the peripheral edge. A stopper 7 is fixed to the center of the container lid 5 via a gasket 6, and a safety valve 8
However, the opening of the eyelet 7 is sealed. Reference numeral 9 denotes an exhaust port when the internal pressure rises when the battery is abnormal and the safety valve 8 operates.

Reference numeral 10 is a negative electrode ear provided on the negative electrode 2, and 11 is a positive electrode ear provided on the positive electrode 4. Negative electrode ears 10 and positive electrode ears 11 are spot-welded on a plurality of ears, respectively, as described later, and then re-welded using a comb-shaped jig so that the negative pole 1 is provided above the re-welded portions 12 and 13, respectively.
6, the positive pole 17 is welded.

Further, these poles are welded to a negative electrode bushing 14 and a positive electrode bushing 15 which are fixed to the container lid 5 via a gasket 6 to form a negative electrode terminal 18 and a positive electrode terminal 19.

The negative electrode 2 used in the batteries of the examples of the present invention was manufactured as follows. In a weight ratio, 98 parts of spherical carbon having an average particle size of 30 μm, 2 parts of polyvinylidene fluoride as a binder and 30 parts of N-methyl-2-pyrrolidone as a solvent were kneaded to form a paste. The thickness of this paste is the negative electrode plate support 2 '.
An electrode substrate was prepared by applying a nickel foam having a diameter of 1.0 mm, an average cell opening diameter of 300 μm and a porosity of 98%, followed by drying and rolling. Note that the paste was not applied to the portion that would become the ear in the subsequent punching process.

This electrode substrate is punched out to a thickness of 0.48 mm,
A flat negative electrode plate having a width of 100 mm and a height of 100 mm was obtained. Negative electrode 1
The weight of the active material carbon mixture per sheet was 6.3 g. The spherical carbon used here is obtained by thermally decomposing a spherical phenol resin. The physical property values determined by X-ray diffractometry are a crystal interlayer distance (d ₀₀₂ ) of 3.36 Å and a crystallite length (Lc) of 39 Å.

The unipolar characteristics of the negative electrode plate were measured. Using lithium as a counter electrode, a charge / discharge test was carried out in an equal volume mixture of ethylene carbonate and diethyl carbonate in which 1 molar concentration of LiPF ₆ was dissolved. The battery was charged to 0 V at a lithium potential of 250 mA and then discharged at the same 250 mA. It was possible to discharge for 4.2 hours until it showed 1.0 V against the lithium potential. The discharge capacity of this negative plate is 1,05
It was 0 mAh.

The positive electrode 4 was manufactured as follows. 85 parts of LiCoO ₂ which is the positive electrode active material, 8 parts of acetylene black which is a conductive agent and 34 parts of a PTFE dispersion aqueous solution (containing 15% of polytetrafluoroethylene resin) which is a binder are kneaded, and a pair of these is mixed. After passing between rolls to form a sheet, the positive electrode plate support 4 ′ was pressure-bonded to both sides of an aluminum expanded metal core material to prepare a positive electrode substrate having a thickness of 0.62 mm. This substrate was punched out to obtain a flat positive electrode having a width of 100 mm and a height of 100 mm. The active material was not pressure-bonded to the ears during punching. The weight of the active material in one positive electrode is 19.2g, and the discharge capacity is 1,500mAh.

The separator 3 has a thickness of 0.18 mm and a basis weight
A polypropylene non-woven fabric of 50 g / m ² was used.

While inserting the separator made of the above polypropylene nonwoven fabric between the positive electrode plate and the negative electrode plate, the positive electrode plate 5
After stacking 0 sheets and 51 sheets of negative electrodes alternately, the periphery of this stacked electrode group was covered with a polypropylene film (not shown in FIG. 1) and fixed. FIG. 2 is a schematic view showing a state in the middle of stacking.

Next, as shown in FIG. 3, two positive electrode ears were spot-welded. After that, the spot-welded ears are shown in FIG.
It was welded to an aluminum plate as shown in FIG. A positive pole is welded to this aluminum plate. The positive electrode plate support has a thickness of about 0.6 m.
Since it is very thin, the mechanical strength is weak and it is very difficult to set it on the comb jig one by one, but this time, two pieces were spot welded, so set it on the comb jig. Was easy.

Similarly, the negative electrode ear was welded. However, in the case of welding the negative electrode ears, first, three negative electrode ears from the end were spot-welded, and then the remaining negative electrode ears were spot-welded two by two. Next, they were welded again using the comb jig shown in FIG.
The negative electrode ear was welded to a nickel plate. Similarly to the case of the positive electrode, the welding of the negative electrode ear was performed by spot welding two or three pieces in advance, so that it was easy to set the ear on the comb jig.

It is impossible to spot-weld such a number of electrode plates at a time, and it is very difficult to set and weld them one by one in a comb-shaped jig. It was not applicable to the production of.

After that, the container was inserted into the container, a lid was placed thereon, and the lid and the container were laser-welded.

As the electrolyte, 1 mol / liter of LiPF ₆ was added to a 1: 1 mixed solvent of ethylene carbonate and diethyl carbonate.
What was melt | dissolved in the ratio of liter was used as a non-aqueous electrolyte, and the predetermined amount was inject | poured from the electrolyte injection port provided in the lid. The inlet was then completely sealed by laser welding.

The battery of Example was charged at a current of 12.75 A until the terminal voltage showed 4.1 V, and then discharged at a current of 12.75 A, and the battery could be discharged for 4.1 hours until the terminal voltage dropped to 2.8 V. And the discharge capacity of this battery was 53 Ah.

In the above embodiment, two or three electrode plate ears having the same polarity were first spot-welded. However, when the number of electrode plates constituting the battery is larger, spot-welding is first performed. It is also possible to increase the number of ears to be used to 5 to 6. Further, the number of ears to be spot-welded first may naturally vary depending on the thickness of the electrode plate support and the capability of the machine for spot-welding.

Further, the aluminum plate and the nickel plate used for the re-welding may be made of materials other than these as long as they have corrosion resistance at each electrode.

[0035]

According to the present invention, a non-aqueous electrolyte secondary battery comprising a rechargeable positive electrode, a separator impregnated with a non-aqueous electrolyte containing an alkali metal ion, and a negative electrode protrudes from the separator. It is characterized by welding a plurality of polar plates of the same polarity, and then re-welding these plates. It is possible to provide, and the industrial value is extremely large.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing the structure of a battery according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing a state during stacking

FIG. 3 is a schematic view showing a state (a part) in which two positive electrode ears are spot-welded together.

FIG. 4 is a schematic cross-sectional view showing a state (a part near the pole) where the spot-welded positive electrode ear is welded again.

FIG. 5 is a diagram in which polar plates of the same polarity are overlapped for spot welding.

FIG. 6 is a top view of the comb jig.

FIG. 7 is a diagram in which an electrode plate is installed in the recess of the comb-shaped jig.

[Explanation of symbols]

 1 Container 2 Negative Electrode 3 Separator 4 Positive Electrode 5 Container Lid 10 Negative Electrode Ear 11 Positive Electrode Ear 12 Welding Part (Negative Electrode) 13 Welding Part (Positive Electrode) 20 Comb Jig

Claims (1)

[Claims] 1. A non-aqueous electrolyte secondary battery comprising a rechargeable positive electrode, a separator impregnated with a non-aqueous electrolyte containing an alkali metal ion, and a negative electrode, and a plurality of same polarities protruding from the separator. A non-aqueous electrolyte secondary battery, characterized in that the electrode plate of (1) is welded, and a plurality of these welded portions are welded.