JPH0620707A - Spiral lithium battery - Google Patents

Abstract

(57) [Abstract] [Purpose] Equipped with a spirally wound electrode body formed by winding a strip-shaped negative electrode made of lithium or a lithium alloy and a strip-shaped positive electrode having a positive electrode mixture held on a metal current collector through a separator. In the spiral lithium battery, a short circuit due to a burr of the metal current collector at the end of the strip positive electrode is prevented. [Structure] An inorganic coating agent in which a metal oxide such as zirconia oxide or alumina oxide is dispersed in an organic solvent together with a binder is applied to the end portion of the strip-shaped positive electrode 3, and the organic solvent is removed by drying to remove the binder. To cure the inorganic coating film 3
By forming c, the end of the strip-shaped positive electrode 3 is covered with the inorganic coating film 3c containing a metal oxide such as zirconia oxide or alumina oxide.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spiral lithium battery, and more particularly to improvement of a strip positive electrode thereof.

[0002]

2. Description of the Related Art A strip-shaped positive electrode used in a spiral lithium battery has a positive electrode mixture composed of a mixture of a positive electrode active material, a conductive additive and a binder, on a metal current collector made of plain woven wire mesh or expanded metal. Hold the positive electrode mixture on the metal current collector by pressing it with a rolling roller etc.
It is made by cutting it to a predetermined size.

[0003]

However, the above-mentioned cutting causes a burr of the metal current collector at the end of the strip-shaped positive electrode, which causes a short circuit due to contact with the negative electrode during spiral winding. was there.

Therefore, it has been proposed to use a laser beam to cut the metal current collector to reduce the occurrence of burrs, but it has been possible to completely eliminate the occurrence of burrs and the occurrence of short circuits. Not in.

Further, the short circuit due to the burr of the metal current collector may occur due to vibration or shock after the battery is assembled, and abnormal heat may be generated due to the short circuit, which may lead to ignition in the worst case. .

Therefore, the present invention solves the problems in the conventional spiral lithium battery, prevents the occurrence of a short circuit due to the burr of the metal current collector at the end of the strip positive electrode, and improves the safety of the spiral lithium battery. The purpose is to provide a battery.

[0007]

According to the present invention, an end portion of a strip positive electrode is coated with an inorganic coating film containing a metal oxide such as zirconia oxide or alumina oxide.
The above object is achieved.

That is, according to the present invention, by covering the end portion of the strip-shaped positive electrode with an inorganic coating film containing a metal oxide such as zirconia oxide or alumina oxide, a metal current collector generated at the end portion of the strip-shaped positive electrode is formed. The burr is suppressed, the burr is prevented from penetrating the separator and coming into contact with the negative electrode, and thereby the occurrence of a short circuit can be prevented.

The inorganic coating film is formed by applying an inorganic coating agent, in which a metal oxide such as zirconia oxide or alumina oxide is dispersed in an organic solvent together with a binder, to the end portion of the strip-shaped positive electrode and drying to remove the organic solvent. Then, it is formed by curing the binder.

Specific examples of such an inorganic coating agent include, for example, 3 commercially available from Three Bond Co.
7X-025, 37X-030, 37X-034 (all are brand names) etc. are mentioned.

Since the above inorganic coating film is mainly composed of zirconia oxide or alumina oxide, and its binder is also an inorganic substance, it is less likely to be affected by the organic solvent used in the electrolytic solution, and after the battery is assembled. Also in this case, since the burr of the metal current collector at the end of the strip-shaped positive electrode is suppressed, the occurrence of a short circuit due to the burr can be prevented even when the battery is subjected to vibration or impact.

As described above, the inorganic coating film effectively acts to prevent the occurrence of a short circuit due to the burr of the metal current collector, but on the other hand, it hinders the reaction of the positive electrode, so that it is wider than necessary. It is not preferable to form too much, and since it is sufficient that it is formed at least in the vicinity of the end face, it is preferable to form the strip positive electrode within about 1 mm from the end face.

[0013]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 is a partial vertical cross-sectional view showing an embodiment of the spiral lithium battery of the present invention, FIG. 2 is an enlarged view of part A of FIG. 1, and FIG. 3 is a belt shape before being spirally wound. It is a front view which shows a positive electrode typically.

In the figure, reference numeral 1 denotes a battery case having a bottomed cylindrical shape made of nickel-plated iron or the like and having a constricted portion 1a at the upper part thereof, and a strip-shaped negative electrode 2 and a strip-shaped positive electrode 3 made of lithium or a lithium alloy therein. A spirally wound electrode body 5 formed by spirally winding and through the separator 4 is loaded.

As shown in FIG. 2, the band-shaped positive electrode 3 has a positive electrode mixture 3a held on a metal current collector 3b.
As shown in FIG. 3, the longitudinal upper and lower ends of the strip-shaped positive electrode 3 are covered with an inorganic coating film 3c.

Now, FIG. 3 will be described in detail. FIG. 3 is a front view schematically showing a state before the strip-shaped positive electrode 3 is spirally wound. The strip-shaped positive electrode 3 has a central portion in the longitudinal direction. The positive electrode mixture 3a is not pressure-bonded to the metal current collector 3b, and there is a part that is composed only of the metal current collector 3b. Then, the positive electrode tab 3d is spot-welded to a portion constituted only by the metal current collector 3b, and the adhesive tape 3e having an electric insulation property is attached to the surface thereof from both sides.

In FIG. 3, the shaded portions of the upper and lower ends of the strip-shaped positive electrode 3 in the longitudinal direction indicate not the cross section but the inorganic coating film 3c covering the portions.

The above-mentioned inorganic coating film 3c is an inorganic coating agent in which a metal oxide such as zirconia oxide or alumina oxide is dispersed in an organic solvent together with a binder, for example, 37X-025, 37X-030, 3X manufactured by ThreeBond Co., Ltd.
7X-034 or the like is applied to the end portion of the strip-shaped positive electrode 3 with a width of about 1 mm from the end surface, dried, and cured.

The separator 4 is made of a non-woven fabric such as polypropylene fiber in the shape of a bag, and the strip-shaped positive electrode 3 is wrapped inside the separator 4 with a margin left above.

Reference numeral 6 denotes a disk-shaped sealing plate made of SUS430 or the like having a hole 6a in the center, and this sealing plate 6 has an inwardly curved portion 1b at the upper edge of the battery case 1 at the peripheral portion folded back to the upper surface side. It is fitted inside by means of insulating packing 7.

Reference numeral 8 denotes a positive electrode terminal plate obtained by press-forming a nickel-plated iron plate or the like into a hat shape. The positive electrode terminal plate 8 has a cutting edge 8a formed by cutting and raising the central portion of the positive electrode terminal plate in a diagonally downward direction. The ring-shaped packing 9 is fitted between the flange-shaped peripheral portion and the peripheral edge portion of the sealing plate 6.

Reference numeral 10 denotes an explosion-proof film of titanium or the like having a thickness of about 15 μm, which is arranged on the sealing plate 6, and the explosion-proof film 10 is sandwiched between the sealing plate 6 and the positive electrode terminal plate 8 at the outermost peripheral edge portion. When the internal pressure of the battery rises, it bulges upward and is broken by contact with the cutting edge 8a of the positive electrode terminal plate 8 to release the gas inside the battery to the outside, and the battery bursts under high pressure (so-called explosion). It has a function to prevent it.

Reference numeral 11 denotes an annular heat-deformable member made of polyethylene or the like loaded in the space between the explosion-proof film 10 and the positive electrode terminal plate 8. The heat-deformable member 11 has a function of preventing malfunction of the explosion-proof film 10. is doing. Reference numeral 12 is an insulating ring arranged on the spiral electrode body 5, and 13 is an insulator mounted between the lower surface of the spiral electrode body 5 and the inner bottom surface of the battery case 1.

Reference numeral 14 is a strip-shaped positive electrode lead made of a SUS plate or the like. The positive electrode lead 14 is in contact with the sealing plate 6 at its upper end, and the strip-shaped positive electrode 3 is processed at the lower end with polytetrafluoroethylene glass. It is attached via an adhesive insulating tape having a fiber cloth as a base material.

Reference numeral 15 denotes a strip-shaped negative electrode lead made of a nickel plate or the like. Although not shown in detail due to space limitations, the negative electrode lead 15 has a strip-shaped negative electrode in a vertical piece bent into an L shape. 2 is attached to the central portion of the battery case 2 via the same adhesive insulating tape as described above, and at the same horizontal portion, the center hole 5a of the spiral electrode body 5 and the central hole 13a of the insulating plate 13 are used to Spot welded on the bottom. Then, an electrolyte solution obtained by dissolving a lithium salt in a non-aqueous solvent is injected into the battery case 1.

Table 1 shows the results of examining the open circuit voltage drop conditions of the battery of the embodiment of the present invention and the battery of the conventional configuration (conventional example).

The details of the battery of the embodiment of the present invention are as follows.

Manganese dioxide was used as the positive electrode active material, graphite was used as the conduction aid, and polytetrafluoroethylene was used as the binder. These manganese dioxide, graphite and polytetrafluoroethylene were mixed at a weight ratio of 100: 10: 2. A positive electrode mixture is prepared, and the obtained positive electrode mixture is pressed onto a metal current collector made of SUS316 net with a rolling roller to form a sheet having a thickness of 0.4 mm. Hold it on your body and hold it to a specified size of 190 mm x
It was cut into 30 mm to obtain a strip positive electrode.

A positive electrode tab made of a SUS plate was spot-welded to the center of the strip-shaped positive electrode in the longitudinal direction, and an adhesive tape was attached to the surface of the positive electrode tab. Then, 37X-025 manufactured by ThreeBond Co., Ltd. as an inorganic coating agent is applied to the upper end and the lower end in the longitudinal direction of the strip-shaped positive electrode 1 m from the end surface.
m, apply at room temperature for 10 minutes and then 2
An inorganic coating film was formed by heating to 00 ° C. or higher and curing.

The band-shaped positive electrode is wrapped in a bag-shaped separator, the opening edge of the separator is heat-sealed, and the band-shaped negative electrode made of lithium is superposed and spirally wound to prepare a spirally wound electrode body. It was inserted in the battery case.

As the electrolytic solution, a solution obtained by dissolving lithium perchlorate at a concentration of 1 mol / l in a mixed solvent of propylene carbonate and 1,2-dimethoxyethane in a volume ratio of 1: 1 is used in a battery case. It was injected and finished into a spiral lithium battery having the structure shown in FIG.

The battery of the conventional example has the same structure as the battery of the example except that the end portion of the strip positive electrode is not covered with the inorganic coating film.

The measurement of the decrease in open circuit voltage was carried out by preparing 500 batteries of the example of the present invention and 500 batteries of the conventional example, dropping the open circuit voltage, and dropping it on the concrete 20 times from a height of 2 m. After that, the open circuit voltage was measured again, and the battery in which the open circuit voltage dropped to 3.1 V or less was examined. In Table 1, the number of batteries used in the test is shown in the denominator, and the number of batteries with a reduced open circuit voltage is shown in the numerator.

[0035]

[Table 1]

As shown in Table 1, in the conventional example, five of the 500 batteries used for the test had a reduced open circuit voltage, but in the examples of the present invention, none of them had a reduced open circuit voltage. None, the occurrence of a short circuit was completely prevented.

[0037]

As described above, according to the present invention, the end portion of the strip-shaped positive electrode is coated with the inorganic coating film containing the metal oxide such as zirconia oxide and alumina oxide, so that the metal of the end portion of the strip-shaped positive electrode is It was possible to suppress the burr of the current collector and prevent the occurrence of a short circuit due to the burr.

[Brief description of drawings]

FIG. 1 is a partial sectional view showing an embodiment of a spiral lithium battery of the present invention.

FIG. 2 is an enlarged view of part A in FIG.

FIG. 3 is a front view schematically showing a belt-shaped positive electrode before being spirally wound.

[Explanation of symbols]

 2 band-shaped negative electrode 3 band-shaped positive electrode 3a positive electrode mixture 3b metal current collector 3c inorganic coating film 4 separator 5 spiral electrode body

Claims (2)

[Claims] 1. A spiral-shaped spiral electrode formed by spirally winding a strip-shaped negative electrode 2 made of lithium or a lithium alloy and a strip-shaped positive electrode 3 in which a positive electrode mixture 3a is held on a metal current collector 3b with a separator 4 in between. A spiral lithium battery provided with an electrode body 5, wherein the end of the strip-shaped positive electrode 3 is covered with an inorganic coating film 3c containing a metal oxide. 2. The spiral lithium battery according to claim 1, wherein the metal oxide contained in the inorganic coating film 3c is zirconia oxide or alumina oxide.