JPH1126011A - Layer-built storage battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a storage battery which is capable of preventing the occurrence of the exhaustion of an electrolyte and a short circuit and preventing the occurrence of a leakage after a high-temperature storage by setting the width of a separator to be larger than the width of a positive electrode and a negative electrode, providing no fluff on the separator at the upper section of an electrode body of a layer-built structure, and providing fluff on the separator at the lower section. SOLUTION: It is preferable to set the width of a separator 2 larger than the width of a positive electrode and a negative electrode by 0.5-1.5 mm, and the both electrodes are prevented from short-circuiting in contact with each other. The separator 2 has no fluff at the portion kept in contact with the upper section of an electrode body 1 of a layer-built structure, no fluff is brought into contact with a sealing body and terminal portions, and a leakage caused by the creeping up of an electrolyte can be prevented. The separator 2 has fluffs at the lower section of the electrode body 1, and the electrolyte is easily moved in the separator 2. When the number of laminations is increased in particular, the gap between the electrodes becomes narrow, the infiltration of the electrolyte from the upper section becomes difficult, so that the effect becomes large.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated type storage battery in which a sheet-shaped positive electrode and a sheet-shaped negative electrode are laminated via a separator, and an electrode body having a laminated structure is inserted into a battery can.

[0002]

2. Description of the Related Art In recent years, high-capacity nickel-cadmium batteries, nickel-hydrogen batteries and the like have attracted attention as portable power supplies for portable equipment. In this type of battery, a sheet-shaped positive electrode and a sheet-shaped negative electrode are laminated with a separator interposed therebetween to form an electrode body having a laminated structure. After the electrode body having the laminated structure is inserted into an electrode can, an opening of the battery can is opened. The battery is assembled by sealing the battery.

[0003] By the way, characteristics required for a battery separator are generally excellent in separation of a positive electrode from a negative electrode, ability to hold an electrolyte, and ability to prevent a short circuit. In secondary batteries, there is a great demand for high capacity, and in order to increase the filling capacity of the positive electrode and the negative electrode in a battery can, the number of stacked electrodes is increased by making the electrodes thinner. Therefore, it is required that the separator be made thinner while maintaining the above characteristics.

[0004] As a method for improving the ability of the separator to hold the electrolytic solution, the separator surface is made hydrophilic, the fibers of the separator are combined, or the fibers of the separator are changed to various resins, whereby the electrolytic solution is retained. It has been proposed to improve the wettability (wetting property) and thereby enhance the ability to hold the electrolyte (Japanese Patent Laid-Open No. 7-94163).
JP-A-5-121062, JP-A-5-94811
Issue). In addition, as a method of improving short-circuit prevention ability, a separator is made larger than a positive electrode or a negative electrode, and a protruding portion is heat-formed and bent, or a thickness is increased by elongation in a winding direction using an anisotropic separator. A method of preventing the fluctuation of the separator, a method of providing an electrically insulating fine powder at the upper end of the separator, and the like have been proposed (July 7-22).
No. 853, JP-A-7-153488, JP-A-7-33
No. 5246).

[0005]

However, if the separator is made thinner in accordance with the thickness of the electrode in order to increase the capacity, the weight per unit area of the separator decreases, and the ability to hold the electrolytic solution decreases. Electrolyte depletion occurs at the part facing the electrodes, and the internal resistance increases due to the depletion of the electrolyte,
Thereby, the charge / discharge reaction is hindered, and the cycle life of the battery is shortened.

A short circuit caused by contact between the positive electrode and the negative electrode is as follows.
Most of them can occur at the upper and lower ends of the electrode, although they can occur at the electrode facing portion. This is thought to be due to the current sneaking around the electrode end. To prevent this, it is considered necessary to make the separator have the above-mentioned structure, but it has not been a complete solution yet. Furthermore, in the alkaline storage battery, the phenomenon of creeping up of the electrolytic solution occurs. This phenomenon becomes remarkable when the separator comes into contact with the sealing member or the terminal portion, and eventually, the electrolytic solution leaks out of the battery. Will occur. In particular, when the battery is stored at a high temperature, the liquid leakage phenomenon tends to be remarkable, and the reliability of the battery is impaired.

Accordingly, the present invention solves the above-mentioned problems of the prior art, and prevents the depletion of the electrolyte and the occurrence of a short circuit, as well as the occurrence of leakage even after high-temperature storage. The purpose is to provide.

[0008]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present invention provides an electrode body having a laminated structure in which a sheet-like positive electrode and a sheet-like negative electrode are laminated with a separator interposed therebetween. In the stacked storage battery inserted, short-circuit is prevented by making the width of the separator larger than the width of the positive electrode and the negative electrode, and the separator has no fuzz at the upper part of the electrode body having the above-mentioned laminated structure. This prevents the electrolyte from creeping up due to the contact between the separator and the sealing member or terminal portion, etc., and reduces the leakage. It has been found that the penetration of the electrolyte solution can be facilitated.

More specifically, in a stacked battery, as described above, a sheet-shaped positive electrode and a sheet-shaped negative electrode are stacked with a separator interposed therebetween to produce an electrode body having a stacked structure. In the present invention, by using a separator having a width larger than the electrodes such as the positive electrode and the negative electrode, it is possible to prevent short-circuiting by preventing contact between the electrodes. When the electrode body of the laminated structure approaches the sealing body, particularly when the separator is in a brushed state and has fluff, the sealing performance is reduced by the fluff being sandwiched between the swaged portions of the sealing body, and the electrolytic solution is reduced. Will result in liquid leakage. In addition, since the fluff of the separator comes into contact with the sealing member and the terminal portion, a phenomenon of creeping up of the electrolytic solution occurs, and this causes a leakage.

[0010] Therefore, in the present invention, the above problem is solved by making the separator have fluff on the lower portion of the electrode body having a laminated structure and not on the upper portion. FIG. 1 schematically shows an upper part of an electrode body having a laminated structure according to the present invention, and a separator 2 has no fluff above an electrode body 1 having a laminated structure shown in FIG.

FIG. 2 schematically shows an upper part of an electrode body having a laminated structure using a separator having fluff, which has been conventionally used generally. As shown in FIG. 2, when the separator 2 having the fluff 2 a is used also in a portion corresponding to the upper part of the electrode body 1 having a laminated structure, as described above, the fluff 2 a
When liquid comes into contact with the sealing member or the terminal portion, liquid leakage is likely to occur.

On the other hand, as shown in FIG. 1, if the portion of the separator 2 corresponding to the upper portion of the electrode body 1 having a laminated structure does not have fluff, the fluff does not contact the sealing member or the terminal portion, so that the electrolytic solution The liquid leakage due to crawling of the water can be prevented. In addition, it is particularly preferable that the fluff does not exist in the whole vicinity of the upper part of the wound body, or if it is not on the upper end face, it is sufficiently effective in preventing liquid leakage.

Although not shown in FIG. 1, since the separator has fluff 2a below the electrode body 1 having a laminated structure, the electrolyte can easily move between the separators, which is the starting point of absorption of the electrolyte. become. In particular, recently, the number of stacked electrode bodies has been increased in order to increase the battery capacity. However, in such an electrode body, a gap between the electrodes is narrowed, and it is difficult for the electrolyte to penetrate from above. Therefore, the effect of the present invention is particularly remarkably exhibited. FIG.
2 in FIG. 2 is a negative electrode, and the electrode body 1 having a laminated structure is manufactured by laminating a sheet-shaped positive electrode and a sheet-shaped negative electrode 3 with a separator 2 interposed therebetween. can not see.

Further, a portion of the above-mentioned laminated electrode body which contacts the bottom of the battery can (the width of the separator is made larger than the width of the electrode in order to prevent a short circuit between the electrodes. In the case where the lower portion comes into contact with the bottom of the battery can), a gap is formed between the electrode body and the bottom of the battery can by the separator, so that the oxygen gas generated from the positive electrode during overcharge can be easily moved, The increase in battery internal pressure is suppressed, and the cycle life can be extended.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the width of a separator is 0.5 to 0.5 times larger than the width of an electrode such as a positive electrode or a negative electrode.
It is preferable to increase the size by 1.5 mm, especially from 0.8 to
More preferably, it is increased by 1.2 mm. By making the width of the separator 0.5 mm or more larger than the width of the electrode, contact between the electrodes can be effectively prevented, and by making the width of the separator larger than the width of the electrode to 1.5 mm or less, the separator can be made smaller. Contact with the sealing member and the terminal portion can be avoided.

The removal of the fluff from the separator can be performed before the electrode body having the laminated structure is inserted into the battery can. However, the sliding of the electrode body and the battery can at the time of insertion also causes fluff. It is preferable to remove fluff after inserting the electrode body into the battery can.

The method of removing the fuzz after inserting the electrode body having the laminated structure into the battery can is not particularly limited, but air heated by an electric heater is blown to the portion of the separator from which the fuzz is to be removed. And a method of melting the fluff with an electron beam. Among them, it is preferable to employ a method in which air heated by a pipe heater, which is easy to control the temperature and causes little damage to other portions, is blown.

The separator is preferably a non-woven fabric, a woven fabric, or the like, and the constituent fibers thereof are preferably heat-fused fibers which have been conventionally used. The fiber structure thereof is a core-sheath type composite fiber or a side-by-side type fiber. Although a conjugate fiber or a single component type is mentioned, a core-sheath type conjugate fiber is preferable from the viewpoint of strength. As the type of fiber,
Nylon-based and polyolefin-based materials are preferred. Further, in consideration of the permeability of the electrolytic solution, it is preferable that the surface of the separator is subjected to a hydrophilic treatment. A specific example of such a separator is a separator whose surface is sulfonated by a sulfuric acid treatment. In particular, since the surface treatment increases the fluff of the separator, the effects of the present invention are more remarkably exhibited. The average fiber diameter of the separator is preferably 0.5 to 2 denier, and the thickness is preferably 50 to 300 μm.

[0019]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to a nickel-hydrogen battery as an example, but the present invention is not limited to only these examples.

[0020] The nickel hydroxide using a paste type nickel electrode for an active material as in Example 1 a positive electrode, using a paste type hydrogen-absorbing alloy electrode for an AB ₅ type hydrogen storage alloy as an active material as the negative electrode, respectively cut into a width 35mm did. The width of the separator is 3
A nonwoven fabric having a thickness of 130 μm, made of a composite fiber (average fiber diameter: 1.0 denier) having a core portion of polyethylene and a sheath portion of polypropylene having a thickness of 7 mm and having a surface subjected to sulfonation treatment and having fluff is used. Then, the separator was interposed between the positive electrode and the negative electrode, and was spirally wound to be laminated to produce an electrode body having a laminated structure.

The electrode body having the laminated structure is inserted into a battery can made of stainless steel in which an insulator is previously inserted at the bottom, and the insulator is inserted to form a groove having a bottom in the inner diameter direction near the open end of the battery can. After that, hot air at 200 ° C. was sprayed on the separator above the electrode body using a pipe heater for 0.5 second to remove the fluff of the separator above the electrode body. Then, inject the electrolyte into the battery can, insert the battery lid incorporating the reversible explosion-proof mechanism into the opening of the battery can via the insulating packing, and tighten the open end of the battery can in the inner diameter direction to remove the battery can. Is sealed, and the stacked nickel-hydrogen battery is
000 pieces were produced.

Comparative Example 1 In the manufacture of the battery of Example 1, 5,000 laminated nickel-metal hydride batteries were manufactured in the same manner as in Example 1 except that the hot air blowing treatment was not performed.

The battery of Example 1 and the battery of Comparative Example 1 produced as described above were subjected to a temperature of 60 ° C. and a relative humidity of 90.
% For 30 days, and the number of short circuits and liquid leaks was determined. Table 1 shows the results.

[0024]

[Table 1]

As shown in Table 1, the battery of Example 1 had a smaller number of short circuits and a smaller number of liquid leaks than the battery of Comparative Example 1.

Next, the battery of Example 1 and the battery of Comparative Example 1 were charged at 0.2 C for 6 hours.
When 2C discharge was performed and the discharge capacity until the discharge voltage reached 1.0 V was measured, the discharge capacity of Example 1 was 483 m
Ah, the discharge capacity of Comparative Example 1 was 482 mAh, there was no substantial difference between the two, and no decrease in discharge characteristics due to the specific configuration of the separator in the present invention as described above was observed. Was.

In the above embodiment, the nickel-hydrogen battery has been described as an example. However, the present invention can be applied to other stacked type storage batteries, for example, an organic electrolyte secondary battery. Further, in the embodiment, the stacked storage battery using the electrode body having a stacked structure wound in a spiral shape has been described. However, in the present invention, a sheet-shaped positive electrode and a sheet-shaped negative electrode are overlapped with a separator interposed therebetween. The present invention can be applied to a stacked storage battery using an electrode body having a stacked structure formed in a shape other than the spiral shape such as folding.

[0028]

As described above, according to the present invention, in a stacked storage battery using an electrode body having a stacked structure in which a sheet-shaped positive electrode and a sheet-shaped negative electrode are stacked with a separator interposed therebetween, the separator has the above-described specific structure. By doing
It was possible to provide a stacked storage battery that prevented the occurrence of a short circuit and generated less liquid leakage even after storage at a high temperature.

[Brief description of the drawings]

FIG. 1 is a perspective view schematically showing an upper part of an electrode body having a laminated structure according to the present invention.

FIG. 2 is a perspective view schematically showing an upper part of an electrode body having a conventional laminated structure.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Laminated electrode body 2 Separator 2a Fluff

Claims (1)

[Claims] 1. A laminated storage battery in which a sheet-shaped positive electrode and a sheet-shaped negative electrode are laminated with a separator interposed therebetween into a battery can, wherein the width of the separator is equal to the width of the positive electrode and the width of the negative electrode. A stacked storage battery, which is larger and has no fuzz in the separator above the electrode body having the stacked structure, and the separator has fuzz beneath the electrode body having the stacked structure.