JPH11297299A - Thin secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily permeate an electrolyte between plates, shorten manufacturing time, and provide stable charge/discharge characteristics by covering at least one of the layered or spiral end surface of a plate group with a tape having voids. SOLUTION: Porosity of a tape is desirable set to 5 to 90%, a tape base material is formed of a film or nonwoven fabric composed of either of polyethylene, polypropylene, polyamide, polyimide and a fluororesin, and the tape base material is formed as glass cloth. A layered plate group 1 or a wound spiral plate group 1 is formed by alternately stacking a positive electrode plate, a negative electrode plate and a separator interposed between these. The end surface 1a of the layered or spiral plate group 1 is covered with a tape 2 having voids, and is constituted so that the inside bottom surface 3a of a battery case 3 and the end surface 1a of the plate group 1 are opposed to each other. Therefore, since there is no electrolyte unpermeated space between plates, discharge capacity is increased, dispersion in capacity is reduced, and high capacity of a thin secondary battery is realized so as to be effective in stabilizing characteristics.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an improvement in characteristics of a thin secondary battery.

[0002]

2. Description of the Related Art In recent years, cordless devices such as cellular phones, camcorders, and notebook personal computers have been remarkably reduced in size, weight, and thickness. There is also a growing demand for thin and flat shapes in terms of the shape of the equipment and effective use of space.

[0003] Square nickel cadmium batteries and prismatic nickel metal hydride batteries conventionally used as such thin batteries are formed by stacking a single plate (flat plate) of a positive electrode plate and a negative electrode plate with a separator interposed therebetween to form an electrode group. Make up. In a lithium ion secondary battery which is a new battery, a thin long positive electrode plate and a thin long negative electrode plate are spirally wound via a separator to form an electrode plate group.

Further, in order to prevent an internal short circuit, the width of the separator is set wider than the width of the electrode plate. Therefore, both end surfaces of the electrode group have a laminated or spiral structure with only extra separators.

Although this extra separator is necessary for ensuring the reliability of the battery, it is difficult to handle in the manufacture of the battery. In particular, when the electrode group is inserted into the battery case, the separator may catch on the end face of the case. A problem that the separator is turned up and the electrode plate is exposed occurs.
Or shrink by heat as disclosed in Japanese Patent No. 0900,
Generally, a tape is attached and bundled as disclosed in JP-A-8-195204.

[0006]

However, in the injection of the electrolytic solution, generally, a method of replacing the air between the electrode plates and the electrolytic solution by centrifugation, decompression, and both centrifugation and decompression is used. The electrode group has a tape attached to an end face facing the bottom surface of the battery case, and the tape acts to prevent the space between the electrode plates from being replaced by the electrolyte when the electrolyte is injected. It is necessary for a long time for the electrolyte to sufficiently penetrate between the plates, or because the space between the plates remains, the reaction of the plates becomes uneven and a predetermined charge / discharge capacity cannot be secured. There was a problem on characteristics.

The present invention solves the above-mentioned problems, and facilitates the permeation of the electrolyte between the electrodes in the step of injecting a thin battery having a stacked or spiral electrode group. An object of the present invention is to provide a high-capacity thin battery with stable charge / discharge characteristics while shortening the manufacturing process time.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a thin battery using an electrode plate formed by laminating a positive electrode plate, a negative electrode plate and a separator, or by spirally winding an electrode plate group.
By covering the layered or spiral end face of the electrode group with a tape having a gap, the variation of the electrode plate is suppressed,
This is to ensure insulation from the case and to facilitate penetration of the electrolyte between the electrode plates in the liquid injection step.

[0009]

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

FIG. 1 shows a thin battery according to an embodiment of the present invention. The electrode plate group 1 is a stacked electrode plate group in which a positive electrode plate, a negative electrode plate, and a separator interposed therebetween are alternately stacked, or a positive electrode plate, a negative electrode plate, and a separator interposed therebetween. Are a group of spirally wound electrode plates.
At this time, a layered or spiral end face 1a of the electrode plate group 1 is formed.
Is covered with a tape 2 having a gap, and an inner bottom surface 3a of the battery case 3 and a layered or spiral end surface 1 of the electrode plate group 1 are covered.
a is configured to face each other.

FIG. 2 shows a typical example of a tape having voids used in a thin secondary battery according to an embodiment of the present invention.

FIG. 4 shows a conventional thin battery. In a conventional thin battery, the tape 2 covering the layered or spiral end face 1a of the electrode plate group 1 has no gap. Reference numeral 3 denotes a battery case having an inner bottom surface 3a.

In examining an embodiment of the present invention,
A lithium ion secondary battery having the following configuration was used.

A positive electrode plate in which lithium cobalt oxide as a positive electrode active material is applied to an aluminum foil, a negative electrode plate in which carbon as a negative electrode active material is applied to a copper foil, and a separator made of a porous polyethylene resin sheet are spirally wound. Configure the electrode group,
Nickel plating was performed using an organic electrolyte obtained by dissolving lithium hexafluorophosphate (1.5 mol / l) in an organic solvent in which ethylene carbonate, diethyl carbonate and methyl propionate were mixed at a predetermined ratio. After inserting the electrode group into the iron bottomed square case, an organic electrolyte solution was injected, and the sealing lid plate was crimp-sealed to form a lithium ion secondary battery.

The dimensions of this battery are 6 mm thick and 30 m wide.
m, height 48 mm. The dimensions of the electrode plate group are 5.4 mm in thickness, 29.0 mm in width, and 40 mm in height, and the end face 1 a facing the inner bottom surface 3 a of the battery case 3 has a width of 9 mm.
It is covered with a tape 2 having a base material of a polypropylene film having a length of 20 mm and a length of 20 mm, and an extra separator is bundled.

A battery formed by covering the spiral end face 1a of the spiral electrode group 1 with a tape 2 having a porosity of 50% is referred to as a battery A of the present invention.

A battery comprising the laminated end plate 1 of the laminated electrode group 1 covered with a tape 2 having a porosity of 50% is referred to as a battery B of the present invention.

A battery formed by covering the spiral end face 1a of the spiral electrode group 1 with a tape 2 having a porosity of 5% is referred to as a battery C of the present invention.

A battery formed by covering the spiral end face 1a of the spiral electrode group 1 with a tape 2 having a porosity of 90% is referred to as a battery D of the present invention.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to investigate the effects of the present invention, the following conventional examples were used.
A battery of a comparative example was manufactured by the same method as that described in the above embodiment, except for the following conditions.

A battery formed by covering the spiral end face of the spiral electrode group with a tape having no gap is referred to as a conventional battery E.

A conventional battery F is a battery in which the layered end faces of the laminated electrode group are covered with a tape having no void.

A battery in which the spiral end faces of the spiral electrode group are not covered with tape is referred to as a comparative battery G.

A battery in which the layered end faces of the laminated electrode group were not covered with tape was designated as Comparative Battery H.

(Performance Comparison Experiment 1) Wetting time of the electrode plate in the pouring process of the battery of the present invention, the conventional battery, and the comparative battery,
That is, the time from injection of the electrolytic solution to the permeation of the electrolytic solution between the electrode plates until the electrode plate surface is uniformly wetted with the electrolytic solution was examined. The results are shown in Table 1.

[0026]

[Table 1]

As can be seen from Table 1, the battery of the present invention can greatly reduce the wetting time of the electrode plate as compared with the conventional battery, and is equivalent to the comparative battery. Since the comparative battery has no tape, the separator causes various problems in battery production as described in the related art.

(Performance Comparison Experiment 2) The discharge capacity and the discharge curve of the battery of the present invention, the conventional battery, and the comparative battery were examined. The discharge capacity is shown in Table 2, and the discharge curve of the battery is shown in FIG.

The charging and discharging conditions are shown below. -Charging conditions: constant voltage constant current charging, 4.1 V, maximum current 4
20 mA, charge time 2 hours, temperature 20 ° C. Discharge conditions: constant current discharge, 120 mA, final voltage 3 V, temperature 20 ° C.

[0030]

[Table 2]

As can be seen from Table 2 and FIG. 3, the battery of the present invention has a larger discharge capacity and less variation than the conventional battery.

The effect is that the porosity of the tape is 5%.
%, 50% and 90% hardly change.

Further, it can be seen that there is no difference whether the configuration of the electrode group is a lamination or a spiral. In addition, there is no difference between the battery of the present invention and the battery of the comparative example in the performance shown in Table 2 and FIG. 3, but since the comparative example battery has no tape, the separator causes various problems in battery production. .

[0034]

According to the present invention, the layered or spiral end face of a thin or secondary spiral electrode group of a thin secondary battery is covered with a tape having a gap, so that the electrode plate during the liquid injection step is formed. This has the effect of shortening the liquid wetting time.

Further, since there is no space between the electrode plates where the electrolyte does not permeate, the discharge capacity is large and the capacity variation is small, which is effective for increasing the capacity and stabilizing the characteristics of the thin secondary battery.

Although the embodiment of the present invention has been described with respect to a lithium ion secondary battery, similar effects can be obtained in other battery systems, for example, a nickel cadmium battery or a nickel hydrogen battery.

Further, as the base material of the tape, not only polypropylene but also polyethylene, polyamide, polyimide, fluororesin, glass cloth and the like can be used.

[Brief description of the drawings]

FIG. 1A is a half sectional view of a lithium ion secondary battery according to an embodiment of the present invention. FIG.

FIG. 2 is a plan view of a representative example of a tape used in the lithium ion secondary battery according to the embodiment of the present invention.

FIG. 3 is a diagram showing discharge curves of the batteries of the present invention, a conventional example, and a comparative example.

FIG. 4 is a half sectional view of a conventional thin secondary battery.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electrode group 1a End surface 2 Tape 3 Battery case 3a Internal bottom surface

Claims (4)

[Claims] 1. A thin secondary battery using an electrode group formed by laminating a positive electrode plate, a negative electrode plate, and a separator, or spirally wound, in a layered or spiral shape of the electrode group. Characterized in that at least one of the end faces is covered with a tape having a void. 2. The thin secondary battery according to claim 1, wherein the porosity of the tape is 5% or more and 90% or less. 3. The thin secondary battery according to claim 1, wherein the base material of the tape is a film or a non-woven fabric made of any one of polyethylene, polypropylene, polyamide, polyimide and fluororesin. 4. The thin secondary battery according to claim 1, wherein the base material of the tape is a glass cloth.