JP2002270251A - Air zinc battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an air zinc battery with stable discharging characteristics and high reliability. SOLUTION: For the improvement of an air electrode which is a positive electrode of an air zinc battery, when adhering a water-repellent film made of PTFE with pressure to a positive electrode catalyst sheet made by integrating a catalyst layer and current collector, the Gurley permeability number of the water-repellent film is made 2,000-15,000 in advance, and the water-repellent film is adhered to the positive electrode catalyst sheet in a state that volatile liquid is filled inside the minute holes of the water-repellent film. The air permeability can be adjusted by adding a pressure using a balanced roller. The problem of lowering of discharging capacity or liquid leakage, owing to the inadequate pressure caused by adjusting the air permeability by the pressure added when adhering, is solved by adjusting the air permeability in advance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a zinc-air battery, and more particularly, to a zinc-air battery with an improved cathode.

[0002]

2. Description of the Related Art In a zinc-air battery in which zinc is used as a negative electrode and oxygen in the air is used as a positive electrode, there is no need to pack a positive electrode active material into the battery. Is characterized by the fact that a larger capacity can be packed, and a larger capacity can be obtained as compared with alkaline manganese batteries and silver oxide batteries, and demand has been expanding.

[0003] In recent years, there has been an increasing interest in environmental issues, and there has been support for high-output hearing aids for hearing impairment, which has been using a mercury battery, and multifunctional devices such as pagers. As the demand has further increased, there has been a demand for a zinc-air battery having higher output and higher reliability.

FIG. 1 shows the structure of a conventional button-type zinc-air battery. Air hole 10 is provided on the bottom surface of the positive electrode case 7,
A step is formed. Water-repellent film 8a is on the inner surface of the upper stage,
The air electrode and the separator 3 are stored. Air electrode, activated carbon, manganese oxide, conductive material and PTFE
The positive electrode catalyst powder composed of (polytetrafluoroethylene) powder is pressure-bonded and packed into a positive electrode current collector 6 made of nickel-plated stainless steel to form a positive electrode catalyst sheet 5. Water repellent film 8a
Another water-repellent film 8b (not shown) is formed is crimped toward not the separator side of the. A negative electrode case 1 (a three-layer clad material of nickel-stainless-copper) is disposed on an upper portion of the separator 3 with an insulating gasket 4 interposed therebetween.
Usually, a sealing agent such as a polyamide resin is applied between the insulating gasket 4 and the negative electrode case 1 to prevent leakage of the alkaline electrolyte. Further, the gelled zinc negative electrode 2 is filled in the negative electrode case 1 and is in contact with the separator.

The water-repellent film 8b is made of PTFE resin,
It is pressed against the positive electrode catalyst sheet, and its water repellency prevents leakage of the electrolytic solution in the battery and supplies oxygen in the air to the catalyst layer through the fine holes.

[0006] The pressure bonding method between the water-repellent film 8b and the positive electrode catalyst sheet has conventionally been continuous pressure bonding with a balance roller. According to this method, the water-repellent film is deformed by the unevenness of the surface of the catalyst layer, and the attachment is performed without any inclusions by the anchor effect. At that time, the crimping strength is low, the interface between the water-repellent film and the catalyst layer are films of the electrolytic solution forming the oxygen supply to the catalyst is interrupted, the discharge becomes impossible. Conversely, if the pressure bonding strength is too high, the fine pores of the water-repellent film are crushed, the air permeation decreases, and the amount of air required for discharge cannot be secured, and the discharge reaction cannot be maintained. In addition, the PTFE film is embrittled by being crushed, and cracks are generated in a manufacturing process or deformation during electric discharge, which may cause liquid leakage.

To solve this, crimped equilibrium rollers in a state impregnated with volatile liquid in advance water-repellent film, then, a method of crimping by the volatile liquid volatilizes (dry) (hereinafter "The liquid impregnation method") is being studied.
According to this method, since the fine pores of the water-repellent film is filled with a volatile liquid, prevents collapse of micropores even with increased pressure, the pressure bonding strength without water repellent film becomes brittle Can be enhanced.

[0008]

[0007] However, there are the following problems in the liquid impregnation method. In an air battery, during long-term discharge, the electrolyte in the electrolyte is likely to dissipate due to the escape of moisture in the electrolyte through the air electrode and the absorption of carbon dioxide in the air.
In order to obtain a sufficient discharge characteristics while ensuring oxygen permeability required for the discharge, in order to suppress the influence, it is necessary to control the air flow rate. In this respect, in the conventional pressure bonding method, the fine pores of the water-repellent film were crushed, thereby controlling the amount of air inflow.However, in the liquid impregnation method, the pressure bonding pressure can be increased by increasing the pressure, but on the other hand, the water-repellent film can be improved. There is a problem that it is difficult to control the air permeability because the micropores are not crushed. In addition, when excessive pressure is applied, the water-repellent film is excessively crushed only in the current collector portion of the positive electrode catalyst sheet, and as a result, cracks and deformation of fine pores are caused, and liquid leakage occurs during discharge. there were.

The present invention has been made to solve such a problem. In a zinc-air battery, the pores of a water-repellent film to be pressed against a cathode catalyst sheet are maintained, the air permeability is controlled, and An object of the present invention is to prevent embrittlement due to pressure bonding, and to thereby provide a highly reliable air zinc battery having stable discharge characteristics.

[0010]

That is, the present invention comprises an air electrode formed by pressing a water-repellent film made of PTFE on one surface of a positive electrode catalyst sheet in which a catalyst layer and a current collector are integrated. In the zinc-air battery, a water-repellent film made of PTFE was used which had been previously adjusted to air permeability Gurley No. 2000 to 15000, and the water-repellent film was filled with a volatile liquid in its micropores. characterized in that it is pressed against the cathode catalyst sheet in a state.

In the above, the adjustment of the air permeability of the water-repellent film is performed by:
This is performed by pressurizing the water-repellent film with an equilibrium roller in advance before pressure bonding to the positive electrode catalyst sheet. In this case, since the pressure partially pressurized in equilibrium roller having irregularities on the surface, it is preferable to stabilize the air permeability. The water-repellent film whose air permeability has been adjusted in this way is pressure-bonded to a positive electrode catalyst sheet using an apparatus as shown in FIG. 2 described below.

In the conventional method, since the air permeability is adjusted by adjusting the pressing force at the time of pressing, it is necessary to keep the pressing force low in order to maintain good air permeability, and the pressing strength is insufficient. However, in the present invention, a water-repellent film whose air permeability is adjusted in advance is used to perform pressure bonding to the catalyst sheet by a liquid impregnation method, so it is necessary to control the air permeability during the pressure bonding. However, such a problem can be solved.

[0013] we should be noted, Gurley in the No. The air permeability those were numerically shown by JIS 8117 provisions, and the area 645 mm ² of analyte such as paper calculated by measuring using a specific device the time (in seconds) that air 100ml passes Things. The higher the value, the lower the air permeability.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the zinc-air battery of the present invention will be described below with reference to the drawings. (Example 1) A water repellent film having fine pores made of a PTFE resin was produced by a uniaxial stretching method, and this was pressed with an equilibrium roll.
By crushing the micropores of the PTFE membrane as appropriate,
Gurley No. according to IS 8117. 2000 water-repellent films were used.
This water-repellent film was pressure-bonded to the cathode catalyst sheet by a liquid impregnation method using the apparatus shown in FIG. 2 to form an air electrode.

FIG. 2 is a schematic view of an apparatus for pressing a water-repellent film on a cathode catalyst sheet. As shown in FIG. 2, the water-repellent film 11 whose air permeability has been adjusted and the catalyst layer (composed of activated carbon, manganese oxide, conductive material and PTFE powder) are pressed on a current collector composed of a metal screen. The integrated positive electrode catalyst sheet 12 is superposed and introduced into the balancing roller 13. At this time, in the present invention, the micropores of the water-repellent film 11 are impregnated with the volatile liquid 15 immediately before being introduced into the balancing roller 13,
In the impregnated state, pressure is applied to the balancing roller. Ethanol was used as the volatile liquid. The volatile liquid may be any liquid that is substantially inert to the water-repellent film and the positive electrode catalyst sheet and has good volatility (that is, does not remain). It can be selected mainly from hydrocarbons and alcohols.

The air electrode 14 subjected to pressure bonding, after complete evaporation of the volatile liquid by heating and drying, it was punched into a predetermined shape. Using this air electrode, a PR44 type zinc-air battery shown in FIG. 1 was prepared.

[0017] (Example 2) Gurley air permeability of the water-repellent film N
o. PR44 of FIG.
A zinc-air battery was fabricated.

Example 3 The air permeability of the water-repellent film was measured using Gurley N
o. PR44 of FIG.
A zinc-air battery was fabricated.

(Comparative Example 1) The air permeability of the water-repellent film was not adjusted beforehand, but the pressure was adjusted when the film was pressed against the positive electrode catalyst sheet, and the Gurley No. 2000 and it was. Also, no liquid impregnation method was used. Otherwise, the procedure of Example 1 was followed to prepare a PR44 type zinc-air battery of FIG.

(Comparative Example 2) The air permeability of the water-repellent film was not adjusted in advance, and the pressure was adjusted when the film was pressure-bonded to the positive electrode catalyst sheet. 15000 and the. Also, no liquid impregnation method was used. Otherwise, the procedure of Example 1 was followed to prepare a PR44 type zinc-air battery of FIG.

The Gurley air permeability (Comparative Example 3) water-repellent film N
o. PR44 of FIG.
A zinc-air battery was fabricated.

Comparative Example 4 The air permeability of the water-repellent film was measured using Gurley N
o. PR44 of FIG.
You create a type zinc-air battery.

[0023] Each battery of Examples and Comparative Examples, continuous discharge tests 120 Ohm, were intermittent discharge test and overdischarge test 4 hours / day 620Omu. Table 2 shows the results.
In the overdischarge test, discharge was performed at a load of 250 Ω in an atmosphere at a temperature of 25 ° C. and a relative humidity of 85%.
This is a survey of the rate of liquid leakage when a time load is applied. The numerical values of the discharge capacity in each discharge test in Table 2 are the average value (mAH) of 20 batteries and the variation σ.

[0024]

[Table 1]

In Comparative Example 1, the Gurley No. Is controlled at the time of pressure bonding to the catalyst sheet. The pressure strength is reduced in order to obtain air permeability, and a film of an electrolytic solution is formed at the interface between the water-repellent film and the catalyst layer, thereby inhibiting discharge. In particular, the effect is large when the load is 120Ω. Also, the variation in discharge capacity has increased. Meanwhile in Comparative Example 2, Gurley No. Since the pressing force at the time of pressing is increased in order to obtain the air permeability, the formation of the electrolyte solution film at the above-mentioned interface could be prevented,
Embrittlement of the PTFE resin proceeds, leakage occurs in the over-discharge test.

In Comparative Example 3, the liquid impregnation method was used. However, the air permeability was too large, so that the electrolyte solution was dissipated during intermittent discharge and the electrolyte solution was deteriorated due to absorption of carbon dioxide gas in the air. , The discharge capacity is low. Further, at the time of the overdischarge test, moisture was absorbed, and the internal pressure was increased due to the discharge, so that the electrolytic solution was pushed out, and a leak occurred. Conversely, in Comparative Example 4, the air permeability was too small, the oxygen supply amount at 120Ω discharge was insufficient, and the discharge capacity was reduced. On the other hand, in the examples of the present invention, the discharge capacity is ensured and the variation is small in any of the discharge tests. The occurrence of liquid leakage was 0.

[0027]

As described above, according to the present invention,
It is possible to provide a highly reliable air zinc battery that maintains good heavy-load discharge characteristics and prevents liquid leakage during overdischarge and deterioration during long-term discharge.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a button-type zinc-air battery which is an example of a zinc-air battery.

FIG. 2 is a schematic diagram of a water-repellent film pressure bonding apparatus used in the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Negative electrode case, 2 ... Gel zinc negative electrode, 3 ... Separator, 4 ... Insulating gasket, 5 ... Positive catalyst layer, 6 ... Positive current collector, 7 ... Positive case, 8a ... Water repellent film, 9 ... Air diffusion paper , 10 ... air holes, 11 ... water-repellent film pressed against the catalyst sheet,
12… Positive electrode catalyst sheet, 13… Balance roller, 14… Air electrode,
15 ... volatile liquid.

Continuation of the front page (72) Inventor Machiko Ohashi 3-4-10 Minamishinagawa, Shinagawa-ku, Tokyo Toshiba Battery Corporation F-term (reference) 5H032 AA01 AS03 AS11 BB04 CC00 EE05 EE09 HH00

Claims (1)

[Claims] An air zinc battery provided with an air electrode formed by pressing a water-repellent film made of PTFE on one surface of a positive electrode catalyst sheet in which a catalyst layer and a current collector are integrated,
Water-repellent film made of FE is pre-air permeable Gurley No. 2000-150
An air-zinc battery, wherein the battery adjusted to 00 is used, and the water-repellent film is pressure-bonded to a positive electrode catalyst sheet in a state in which a volatile liquid is filled in micropores.