JPH0696801A - Thin non-aqueous electrolyte battery - Google Patents

Abstract

PURPOSE:To obtain a battery having good high load characteristic by winding sheet-shaped positive plate and negative plate around a flat board acting as a core through a separator so as to construct a group of plates. CONSTITUTION:A separator 3 is used after cutting a porous film made of polypropylene, etc., so as to have the width wider than those of a positive plate 1 and a negative plate 2. The plates 1, 2 and the separator 3 are wound around a flat board acting as a core 7 and end of the separator 3, is fixed by an adhesive tape, thereafter the core 7 is pulled out to construct a group of pates having a elliptical cross section. The group of plates are inserted into a battery case 6, lead plates 4 and 5 of the positive and negative poles are spot-welded to the terminal of a sealing plate and no-aqueous electrolyte is poured into the case. Thus, a thin non-aqueous electrolyte battery having excellent high load characteristic and a thin non-aqueous electrolyte secondary battery having a quick charge characteristic are obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin non-aqueous electrolyte battery which is required to have high load characteristics, and more particularly to an improvement in electrode plate group structure.

In recent years, with the remarkable portable and intelligent use of cordless information / communication devices such as mobile phones and camcorders, a small, lightweight, high energy density battery has been required as a power source for driving them. Non-aqueous electrolyte batteries, especially lithium secondary batteries, are highly expected as the mainstay of next-generation batteries, and their potential market size is also very large. Further, as for its shape, there is an increasing demand for a thin sealed battery from the viewpoint of making the device thinner and effectively utilizing the space.

[0003]

2. Description of the Related Art As thin sealed batteries, nickel-cadmium storage batteries and lead storage batteries, and recently nickel-hydrogen storage batteries have been developed and put into practical use. In these battery systems, a high-concentration aqueous solution of alkali or acid is used as an electrolytic solution, and the electrode plate group is configured by stacking strip-shaped electrode plates alternately with positive and negative electrodes via separators.

[0004]

However, a battery using a non-aqueous electrolytic solution containing an organic electrolytic solution as a main component, such as a lithium battery, has a low electric conductivity of the electrolytic solution, and therefore has the same structure as the above battery system. If the electrode plate group is made up of electrode plates having a certain thickness, sufficient high load characteristics cannot be obtained, and in the case of a secondary battery, there is a problem that rapid charging cannot be performed.

In order to solve these problems, it is conceivable that the electrode plates are thinned to increase the number of sheets and increase the effective reaction area to reduce the current density, but it is difficult to handle a large number of sheet-like electrode plates. Group composition is extremely difficult.

The present invention solves the problems of the conventional methods described above, and is a thin non-aqueous electrolyte battery excellent in high load characteristics,
An object of the present invention is to provide a thin non-aqueous electrolyte secondary battery having excellent quick charging characteristics.

[0007]

In order to achieve this object, the thin non-aqueous electrolyte battery of the present invention comprises a positive electrode and a negative electrode in sheet form, with a separator interposed therebetween, and a flat plate wound as a core. This is a group of plates.

[0008]

By such a method of constructing the electrode plate group, it is possible to obtain a thin non-aqueous electrolyte battery excellent in high load characteristics and a thin non-aqueous electrolyte secondary battery excellent in rapid charging characteristics.

[0009]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a cross-sectional view of the thin lithium secondary battery of the present invention. In the figure, reference numeral 1 denotes a positive electrode plate, which has lithium cobalt oxide (LiCoO ₂ ) obtained by mixing lithium carbonate (LiCO ₃ ) and tricobalt tetroxide (Co ₃ O ₄ ) and firing the mixture in air at 900 ° C. After mixing 3% by weight of acetylene black as a conductive agent with this, and kneading 7% by weight of an aqueous dispersion of a polytetrafluoroethylene resin as a binder into a paste-like mixture, a core made of aluminum foil was used. The material is applied on both sides, dried, and rolled. Further, a part of the mixture is peeled off, and the positive electrode lead plate 4 is spot-welded. The positive electrode plate 1 has a width of 34 mm, a length of 95 mm and a thickness of 0.170 mm.

The negative electrode plate 2 is made of spherical graphite obtained by heat-treating mesophase pitch at 2800 ° C. in an argon atmosphere as an active material, and an aqueous dispersion of polytetrafluoroethylene resin as a binder is kneaded in an amount of 5% by weight. The mixture is applied to both sides of a core material made of copper foil, dried, and rolled. Further, the negative electrode lead plate 5 is spot-welded to the end portion thereof. The negative electrode plate 2 has a width of 36 mm, a length of 132 mm and a thickness of 0.205 mm.

[0012] Here, as a result of preliminary examination of various carbon materials having different physical properties and structures, carbon materials having a lattice spacing (d ₀₀₂ ) of 0.342 nm or less by the powder X-ray diffraction method have a high capacity, It was also found to be excellent in reversibility. By the way, the spherical graphite obtained by heat-treating mesophase pitch at 2800 ° C. in an argon atmosphere has a lattice spacing (d ₀₀₂ ) according to a powder X-ray diffraction method of 0.342 nm or less.

As the separator 3, a porous film made of polypropylene was used after being cut wider than the positive electrode plate 1 and the negative electrode plate 2.

The positive and negative electrode plates 1 and 2 and the separator 3 are wound with a flat plate as a winding core 7 as shown in FIG. 2, and the end of the separator 3 is fixed with an adhesive tape made of polypropylene. 7 was removed to form an electrode plate group having an oval cross section.

Next, although not shown, after inserting the lower insulating plate into the battery case 6, the electrode group was housed and the upper insulating ring was further inserted. After grooving in the upper part of the battery case 6, the positive and negative lead plates 4 and 5 are spot-welded to mutually insulated terminals provided on the sealing plate,
A non-aqueous electrolyte was injected. Non-aqueous electrolytes are ethylene carbonate (EC) and diethylene carbonate (DE
C) was mixed at a volume ratio of 1: 1 and lithium hexafluorophosphate (LiPF ₆ ) was dissolved at 1 mol / liter. After that, the battery was constructed by sealing. The size of this battery is 6 mm in thickness, 17 mm in width, and 48 mm in height.

The charge / discharge rate characteristics of the thin sealed lithium secondary battery constructed as described above were evaluated. As a comparative example, a positive electrode and a negative electrode were coated with a mixture having the same composition as that of the above-mentioned example, the positive electrode was made of aluminum expanded metal, and the negative electrode was made of copper expanded metal as a core material, which was applied on both sides, dried, and rolled into strips. After cutting into pieces, a part of the mixture was peeled off and a lead plate was spot-welded to form an electrode plate. By stacking 4 positive electrodes and 5 negative electrodes, an electrode group was simultaneously constructed and evaluated. . In the comparative example, the positive electrode thickness is 0.40 mm and the negative electrode thickness is 0.50 mm for handling. A cross-sectional view of this comparative example is shown in FIG.

FIG. 4 shows rate characteristics of discharge capacity at 20 ° C. (charging was carried out at 20 ° C. and constant current of 0.1 CmA).
Voltage is 2.5V from beginning to end). As is clear from FIG. 4, the discharge capacity of the comparative example is slightly larger than that of the example in the low load discharge, so that the discharge capacity is larger, but the discharge is reversed at the discharge rate of 70 mA or more, and the driving power source is used. As a result, the embodiment is far superior.

On the other hand, FIG. 5 shows the rate characteristic of the charge capacity at 20 ° C. (the initial voltage is 4.1 V). As is clear from FIG. 5, even in the case of charging at a low rate, the charging amount of the comparative example is larger than that of the example, so that the charging amount is larger, but the reversal occurs at the charging rate of 0.2 CmA or more. However, the embodiment is far superior to the charging of 1 CmA which has been often adopted as the rapid charging mode recently.

It is considered that these results are due to the difference in the area of the two electrode plates. That is, the area of the electrode plate of the example is about twice as large as that of the comparative example, and the current density is half even when charging and discharging with the same current, so it is considered that charging and discharging is sufficiently possible.

By adopting the structure in which the electrode plate group is constructed by winding the sheet-like positive electrode and negative electrode with the separator interposed between the flat plates as the core as described above, a thin non-aqueous solution excellent in high load characteristics is adopted. It is possible to obtain an electrolytic solution battery and a thin non-aqueous electrolytic solution secondary battery having excellent rapid charging characteristics.

In the embodiment, the lithium secondary battery using the intercalation / deintercalation of lithium ions was described, but the non- lithium secondary battery using ions of other alkali metals such as sodium and calcium and alkaline earth metals is used. It is also effective in a water electrolyte secondary battery, a non-aqueous electrolyte secondary battery having a negative electrode of an alkali metal such as lithium, sodium and calcium, or an alkaline earth metal, and a primary battery.

[0022]

As described above, according to the present invention, by constructing an electrode plate group by winding a sheet-like positive electrode and a negative electrode with a separator as a core and winding a flat plate as a core, high load performance can be achieved. It is possible to obtain an excellent thin non-aqueous electrolyte battery and a thin non-aqueous electrolyte secondary battery having excellent rapid charging characteristics.

[Brief description of drawings]

FIG. 1 (a) is a cross-sectional view showing the configuration of a thin non-aqueous electrolyte battery of the present invention (b) an enlarged view of an electrode group as above.

FIG. 2 is a schematic view showing a method of constructing an electrode plate group to be housed in the thin non-aqueous electrolyte battery of the present invention.

FIG. 3 (a) is a cross-sectional view showing the configuration of a thin non-aqueous electrolyte battery of a comparative example according to the prior art.

FIG. 4 is a diagram showing discharge rate characteristics of an example of the present invention and a comparative example.

FIG. 5 is a diagram showing charge rate characteristics of an example of the present invention and a comparative example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Positive electrode plate 2 Negative electrode plate 3 Separator 4 Positive electrode lead plate 5 Negative electrode lead plate 6 Battery case 7 Flat core

Claims (1)

[Claims] 1. A thin non-aqueous electrolyte battery, characterized in that a positive electrode group and a negative electrode in the form of a sheet are housed in an electrode plate group formed by winding a flat plate around a core with a separator interposed therebetween.