JP2000182603A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery which is remarkably improved in its productivity with shortened time for pouring of an electrolyte, and is excellent in its charging discharging cycle characteristics. SOLUTION: In a battery which is constructed by spirally winding a positive and a negative electrode plates via separators, one or more of a swelling-up part of a negative electrode material 9 is formed on a negative electrode 6, and the thickness of the swelling-up part is set to be less than 104% and not more than 125% on average for the negative electrode plate 6. It is therefore possible to attain shortening of an electrolyte pouring time and an improvement in charging/discharging cycle characteristics of the battery with the formation of an electrolyte passage at the pouring time in a spirally wound group.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous electrolyte secondary battery, and more particularly to an improvement in the permeation state of an electrolyte in a group of electrodes.

[0002]

2. Description of the Related Art In recent years, portable electronic devices have become more portable.
Cordless technology is rapidly advancing. In the past, nickel-cadmium batteries, nickel-metal hydride batteries, or small sealed lead-acid batteries played the role of power sources for driving these electronic devices. There is an increasing demand for higher energy density, smaller size and lighter weight of a secondary battery as a power source for use. In recent years, there has been a demand for batteries capable of high-rate charging and discharging, as represented by the rapid expansion of the market for small personal computers and communication devices.

Such a battery generally has a spiral structure in which, for example, a positive electrode plate and a negative electrode plate are wound with a separator interposed therebetween in order to realize high-rate charge / discharge, thereby reducing the electrode area. The device is designed to be as large as possible.

However, in these batteries, since the positive electrode plate, the negative electrode plate, and the separator are very closely opposed to each other, it is difficult to impregnate the electrode plate and the separator with the electrolytic solution during the injection of the electrolytic solution during battery assembly. It took a lot of time to inject the required amount, and the productivity was very poor.

Further, in the non-aqueous electrolyte secondary battery constructed as described above, when charge and discharge are repeated many times, the electrolyte is absorbed by the electrode plates, the amount of free electrolyte decreases, and the internal resistance of the battery increases. In some cases, the battery capacity decreases.

[0006]

In order to solve such a problem, attempts have been made to divide the electrolyte solution into small portions several times and to perform vacuum injection or to perform a centrifugal impregnation method. Time was long and production efficiency remained poor.

Further, as disclosed in Japanese Patent Application Laid-Open No. 8-29813, attempts have been made to add a nonionic surfactant to the battery material. There was a problem that it was difficult and the cost was high.

On the other hand, to solve the problem that the capacity deteriorates during repeated charging and discharging, studies have been made to increase the amount of the electrolytic solution. Even when the maximum amount of liquid that could be injected was impregnated, the electrolyte was exhausted during the repetition of the charge / discharge cycle, and the battery capacity was reduced.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and greatly improves the productivity of a battery by shortening the time for injecting an electrolytic solution, and improves the permeation state of the electrolytic solution in an electrode plate group. Accordingly, a non-aqueous electrolyte secondary battery having excellent charge / discharge cycle characteristics is provided.

[0010]

DETAILED DESCRIPTION OF THE INVENTION In order to achieve the above object, the present invention relates to a battery provided with a group of electrode plates formed by spirally winding a separator between a long positive and negative electrode plates. At least one raised portion is formed on the negative electrode plate in a direction perpendicular to the length direction of the electrode plate, and the thickness of the raised portion is 104% or more and 125% or less with respect to the average thickness of the negative electrode plate. A certain negative electrode plate is used. As a result, a passage for the electrolytic solution at the time of liquid injection is formed inside the electrode group wound in a spiral shape, thereby shortening the liquid injection time,
The improvement of the cycle characteristics of the battery can be achieved.

The reason why the thickness of the raised portion is limited to 104% or more and 125% or less of the average thickness is that if the thickness is less than this, there is not a sufficient effect on the improvement of the liquid injection property. This is because these effects are not further improved, and the negative electrode material is dropped off, which deteriorates the yield of the electrode plate.

When the position of the raised portion is within 30 mm from the end of the electrode plate on the winding core side, a flow path for the electrolyte is formed at the center, so that the injectability is improved. At this time, although the length of the electrode plate differs depending on the battery size, the thickness of the core of the electrode group is substantially equal regardless of the battery size. By providing the raised portion, a similar effect can be obtained regardless of the battery size. Further, when the two raised portions are arranged within 15 mm, the passage of the electrolyte is more firmly secured, so that the injectability is further improved.

Hereinafter, the present invention will be described in more detail with reference to examples.

[0014]

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

Embodiment 1 FIG. 1 is a longitudinal sectional view of a cylindrical non-aqueous electrolyte secondary battery used in Embodiment 1. In FIG. 1, reference numeral 1 denotes a battery case formed by processing a stainless steel sheet having resistance to organic electrolyte, 2 denotes a sealing plate provided with a safety valve, and 3 denotes an insulating packing. Reference numeral 4 denotes an electrode plate group in which a positive electrode plate 5 and a negative electrode plate 6 are spirally wound a plurality of times via a separator 7. Then, a positive electrode lead 5 a is pulled out from the positive electrode plate 5 and connected to the sealing plate 2, and a negative electrode lead 6
a is pulled out and connected to the bottom of the battery case 1. Reference numeral 8 denotes an insulating ring provided on the upper and lower portions of the electrode plate group 4, respectively.

Hereinafter, the positive electrode plate 5, the negative electrode plate 6, the electrolyte and the like will be described in detail. The negative electrode plate 6 was prepared by mixing 100 parts by weight of carbon powder obtained by heat-treating coke with 10 parts by weight of a fluororesin-based binder, and suspending the mixture in an aqueous solution of carboxymethyl cellulose to form a paste. Then, the paste was applied to the surface of the copper foil, dried, and then further partially applied to form a protruding portion.
Rolled to 1mm, width 37mm, length 430
The negative electrode plates 1 to 5 were cut out to a size of mm.

FIG. 2 is a schematic view of a cross section of the electrode plate obtained at this time. Table 1 shows values obtained by measuring the average thickness M of the electrode plate in FIG. 2, the average thickness m of the material layer, the height of the bulge t, and the distance a of the bulge from the core side.

[0018]

[Table 1]

However, the average thickness referred to here is an average of a portion excluding a raised portion. The positive electrode plate 5 opposed thereto is mixed with 100 parts by weight of LiCoO ₂ powder as an active material and 3 parts by weight of acetylene black, and mixes it with an aqueous solution of carboxymethylcellulose and a fluororesin-based binder (dispersion) solid. It was diluted to 7 parts by weight to form a paste. This paste was applied to both sides of an aluminum foil, dried, rolled to 0.18 mm by a roll press, and cut into a width of 35 mm and a length of 350 mm.

Then, leads 5a,
6a was attached and spirally wound through a 0.03 mm thick separator, and housed in a battery case 1 having a diameter of 17 mm and a height of 50 mm.

Thereafter, a predetermined amount of the electrolytic solution was injected into the electrode group 4 while measuring the time required for injection. Thereafter, the battery was sealed, and the battery 1 corresponding to each of the negative electrodes 1 to 5 was inserted.
To 5.

Each of these batteries was charged and discharged.
FIG. 3 shows the cycle life characteristics. Charging was performed for 2 hours while controlling the constant voltage of 4.2 V and the maximum current value to 600 mA, and discharging was performed under the conditions of discharging at a current value of 850 mA until the voltage became 3 V. FIG. 3 shows the charge / discharge cycle characteristics of each battery. Table 2 shows the battery injection time and the maintenance rate (5
The value obtained by dividing the battery capacity at the time of the 00 cycle by the initial capacity)
Is described.

[0023]

[Table 2]

From this (Table 2), it can be seen that Battery 1 and Battery 2 have a long injection time and poor cycle characteristics. Looking at the battery 5, it was found that although the characteristics were not different from those of the battery 4, the material layer formed on about half of the electrode plates among the trial-made negative electrodes fell off during the group formation, which was not practical.

(Example 2) Similar tests were conducted with batteries of other sizes. The size of the battery was 18 mm in diameter and 65 mm in height. The dimensions of the positive electrode plate used were 51 mm in width, 410 mm in length and 0.18 mm in thickness, and the width of the negative electrode plate was 53 mm in length and 495 mm in length. 0.23 mm.
The test was performed using the negative electrode plate shown in (Table 3).

[0026]

[Table 3]

Charging is performed at a constant voltage of 4.2 V and a maximum current value of 8
The discharge was performed at a current value of 135 for 2 hours while controlling to 50 mA.
The discharge was performed at 0 mA until the voltage reached 3 V. Other conditions were the same as those described in (Example 1). The results were obtained in the same manner as in Example 1 (Table 4).
Shown in

[0028]

[Table 4]

From this result and the result of (Example 1), the improvement of the liquid pouring properties and the cycle characteristics shows that the thickness of the raised portion is 104% to 1% of the average thickness of the active material regardless of the battery size.
It turned out that a favorable result is shown when it is 25%.

Example 3 In order to examine this effect in more detail, the position and the number of the protruding portions were changed and examined. Here, the negative electrode shown in (Table 5) was used, and a battery was prepared and evaluated under the other conditions in the same manner as in (Example 1).

[0031]

[Table 5]

In Table 5, when there are two raised portions, the positions of the raised portions are indicated by a1 and a2, and the height of the two raised portions is commonly t. The evaluation results at this time are shown in (Table 6).

[0033]

[Table 6]

As shown in Table 6, the position of the raised portion from the batteries 1 to 3 becomes shorter as the position closer to the end on the core side, the shorter the injection time.
In particular, it was found that the effect of improving the cycle characteristics was high when the distance was within 30 mm. In addition, comparing the batteries 4 to 6 with the battery 1, the number of swelling is two and the distance between them is 15
It was found that the effect of improving the liquid injection property and the cycle characteristics was particularly high when the distance was within mm.

The present invention is not particularly limited to a cylindrical battery. For example, a square battery may be formed by winding an electrode plate and satisfying the above-described conditions. It shows.

Further, the presence of the raised portion is not limited to only one side of the electrode plate, and the same effect is exhibited when it is present on both sides.

[0037]

As apparent from the above description, according to the present invention, in a battery in which the positive and negative electrode plates are spirally wound with a separator interposed therebetween, the raised portion of the negative electrode material is formed on the negative electrode plate. By forming a non-aqueous electrolyte battery using one or more formed electrode plates characterized by having one or more, a passage for the electrolyte at the time of injection is formed in a spirally wound group, This has the effect of shortening the injection time and improving the cycle characteristics of the battery.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a cylindrical non-aqueous electrolyte secondary battery of the present invention.

FIG. 2 is a schematic view of a cross section of the negative electrode plate of the present invention.

FIG. 3 is a diagram showing charge / discharge cycle characteristics of the battery of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Battery case 2 Sealing plate 3 Insulating packing 4 Electrode plate group 5 Positive electrode plate 5a Positive electrode lead 6 Negative electrode plate 6a Negative electrode lead 7 Separator 8 Insulating ring 9 Negative electrode material 10 Copper foil collector M Negative electrode plate average thickness m Negative electrode material layer Average thickness t Climbing height a Distance from the winding core side of the climax

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kenichi Oshima 1006 Kazuma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.F-term (reference) AJ14 AK03 AL06 AM01 BJ02 BJ14 CJ07 DJ04 HJ04

Claims (3)

[Claims] 1. A battery comprising an electrode group formed by spirally winding a separator between a long positive and negative electrode plates, and having a length of the electrode plate on the negative electrode plate. At least one raised portion of the negative electrode material is formed in a direction perpendicular to the direction, and the thickness of the raised portion is 104% or more and 125% or less with respect to the average thickness of the negative electrode plate. battery. 2. The raised portion formed on the negative electrode plate,
The non-aqueous electrolyte secondary battery according to claim 1, wherein the non-aqueous electrolyte secondary battery is disposed within 30 mm from an end of the electrode plate group on a winding core side. 3. The non-aqueous electrolyte secondary battery according to claim 1, wherein two or more raised portions are formed on the negative electrode plate, and a distance between adjacent raised portions is within 15 mm.