JP3345889B2 - Manufacturing method of alkaline storage battery and its negative electrode - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alkaline storage battery using a hydrogen storage alloy negative electrode, and an improvement in a method for manufacturing the negative electrode.

2. Description of the Related Art A hydrogen storage alloy capable of electrochemically storing and releasing hydrogen as an active material is attracting attention as an electrode material having a high energy density. Applications to hydrogen storage batteries are being pursued.

The electrode reaction in the sealed nickel-metal hydride storage battery is as follows.

Here, M is a hydrogen storage alloy.

As a method of manufacturing a hydrogen storage alloy negative electrode in this storage battery, an alkali-resistant organic polymer such as polyethylene or fluororesin is added to a powdered hydrogen storage alloy as a binder, and this mixture is used as a conductive current collector. Electrodes are formed by pressing and filling into punching metal, foam metal, etc.

When this battery is overcharged, gas generation reactions of the formulas (3) and (4) occur at the positive electrode and the negative electrode, respectively.

Positive electrode 2OH ⁻ → H ₂ O + 1 / 2O ₂ + 2e ⁻ … (3) Negative electrode 2H ₂ O + 2e ⁻ → 2OH ⁻ + H ₂ …… (4) At this time, as a method of suppressing an increase in battery internal pressure,
According to the formula (3), a method is employed in which oxygen gas generated from the positive electrode is reacted with hydrogen stored in the negative electrode to form water. In addition, in order to suppress the generation of hydrogen gas in equation (4),
A method is adopted in which the capacity of the negative electrode is made larger than the capacity of the positive electrode.

However, at the time of rapid charging, the generation rate of oxygen gas exceeds the absorption rate, and oxygen gas accumulates in the battery to increase the internal pressure of the battery. In order to solve the above-mentioned problems, a method of adding a noble metal catalyst such as platinum to the negative electrode to promote the reduction of oxygen gas (Japanese Patent Application Laid-Open No. 60-100382) and a method commonly used in gas electrodes for fuel cells have been proposed. Providing a water-repellent layer on a hydrogen storage alloy negative electrode to accelerate absorption of oxygen gas on the negative electrode
No. 118963) method.

Problems to be Solved by the Invention However, in the above-described conventional configuration, there are various problems. That is, the method of adding a noble metal to the negative electrode has a problem that the material is expensive. On the other hand, the method of providing the water-repellent layer on the negative electrode has problems in that the distribution of the electrolyte in the negative electrode is made non-uniform, and the effective surface area in the electrochemical reaction is reduced to lower the discharge voltage. In addition, in the above method, although the oxygen absorbing ability is improved, there is a problem that hydrogen is easily generated from the negative electrode during charging due to a decrease in wettability of the electrolytic solution inside the hydrogen storage alloy negative electrode, and the internal pressure of the battery increases. . This phenomenon is particularly noticeable during quick charging.

The present invention solves such a problem, by maintaining the water repellency of the surface of the hydrogen storage alloy negative electrode, and by improving the wettability to the electrolyte solution inside the negative electrode, to reduce the internal pressure of the battery during rapid charging. It is intended to prevent a voltage drop at the time of discharging.

Means for Solving the Problems In order to solve this problem, the present invention provides a new configuration of an alkaline storage battery, a hydrophilic resin inside a hydrogen storage alloy electrode which is a negative electrode thereof, and a water repellent resin on an electrode surface portion. An object of the present invention is to provide a configuration of an alkaline storage battery provided and a method of manufacturing a negative electrode thereof.

Function The present invention allows a gaseous phase catalyst to be provided and / or a water-repellent resin to be applied to the surface of a hydrogen-absorbing alloy negative electrode to absorb hydrogen gas by a gas-phase reaction according to the above-described structure and production method. In addition, by improving the wettability of the hydrogen storage alloy negative electrode inside the negative electrode with the hydrophilic resin, the hydrogen can be easily stored electrochemically, the hydrogen gas is suppressed, and the internal pressure of the battery during rapid charging is reduced. Further, the addition of the hydrophilic resin suppresses a voltage drop during discharge.

Examples Hereinafter, the present invention will be described with reference to examples. The hydrogen storage alloy composition used for the negative electrode here is MmNi _3.55 Co _0.75 Mn
_0.4 Al _0.3 . Misch metal Mm which is a mixture of rare earth elements (La: about 25 wt%, Ce: about 52 wt%, Nd: about 18 wt%, Pr: about 5
wt%) and each sample of Ni, Co, Mn, and Al were placed in an arc melting furnace, evacuated to 10 ^-4 to 10 ^-5 torr, then arc-discharged under reduced pressure under an argon gas atmosphere, and heated. Dissolved. In order to homogenize the sample, a heat treatment was performed in vacuum at 1050 ° C. for 6 hours. After coarsely pulverizing the obtained alloy, it was reduced to a fine powder of 38 μm or less by a ball mill.

Using the hydrogen storage alloy powder obtained as described above, the following 20 types of hydrogen storage alloy negative electrodes were prepared.

(Example 1) An aqueous solution of polyvinyl alcohol (hereinafter referred to as PVA), which is a hydrophilic resin, was mixed with the hydrogen storage alloy powder in an amount of 0.15 wt% as a resin amount of PVA to form a paste, and foamed with a porosity of 95%. After filling in the nickel porous body, pressure was applied and 0.8 mg / cm ^{2 of a} copolymer resin powder of ethylene tetrafluoride-propylene hexafluoride (hereinafter referred to as FEP) was applied to both surfaces of the negative electrode.

(Comparative Example 2) Water was added to the hydrogen-absorbing alloy powder to form a paste, and after filling into a foamed nickel porous body having a porosity of 95%,
Pressure was applied, and FEP was applied to the surface at 0.8 mg / cm ² . This allows
A hydrogen-absorbing alloy negative electrode containing no hydrophilic resin and having a water-repellent resin only on the surface was obtained.

(Comparative Example 3) 97 wt% of the hydrogen storage alloy powder and 3 wt% of FEP were mixed, and ethyl alcohol was added thereto to form a paste.
After filling into a foamed nickel porous body having a porosity of 95%, pressure was applied. Thereby, a hydrogen storage alloy electrode having a water-repellent resin inside was obtained. Each of these was cut into AA size battery dimensions (39 mm x 80 mm x 0.5 mm), and the chargeable / dischargeable capacity was 1
A negative electrode plate having 600 mAh and a porosity of 30 vol% was obtained.

Examples 4 to 20 were formed in the same manner as in Example 1 in principle as follows.

Comparative Example 4 A hydrogen storage alloy negative electrode in which the hydrogen storage alloy has an average particle size of 0.1 μm.

(Example 5) A hydrogen storage alloy negative electrode in which the hydrogen storage alloy has an average particle size of 75 µm.

(Example 6) A hydrogen storage alloy negative electrode in which the surface of the hydrogen storage alloy particles is provided with irregularities by immersing the hydrogen storage alloy powder in an alkaline solution.

(Comparative Example 7) A hydrogen storage alloy negative electrode having a water-repellent resin polyethylene disposed on the surface.

(Example 8) A hydrogen storage alloy negative electrode in which ethylene tetrafluoride (hereinafter referred to as M-12) having a hydrogen gas transmission coefficient of 1 × 10 ⁻⁹ cm ² / sec · atm is disposed on the surface.

(Comparative Example 9) A hydrogen storage alloy negative electrode in which a water-repellent resin is disposed on the surface by immersion in a FEP dispersion (hereinafter referred to as ND-1) solution having a surfactant in the solution.

(Example 10) Polyvinylidene fluoride having a water-repellent resin (hereinafter referred to as VD
F) Hydrogen storage alloy negative electrode with powder applied to the surface.

(Example 11) A hydrogen storage alloy negative electrode coated with FEP at a surface of 0.1 mg / cm ² .

(Example 12) A hydrogen storage alloy negative electrode coated with FEP at 2 mg / cm ² .

(Example 13) A mixture obtained by mixing platinum black and FEP having a catalytic performance with respect to a hydrogen decomposition reaction at a ratio of 2: 1 (weight ratio) was used.
Hydrogen storage alloy negative electrode applied to the surface at a rate of 4 mg / cm ² .

(Example 14) A hydrogen storage alloy negative electrode in which platinum black was applied to the surface at a rate of 1.6 mg / cm ² and then FEP was further applied to the surface at a rate of 0.8 mg / cm ² .

(Example 15) 4.0 mg / cm of a mixture obtained by changing LaNi ₄ Al: FEP to 4: 1 (weight ratio)
Hydrogen storage alloy negative electrode applied to the surface at a ratio of ² .

(Example 16) A hydrogen storage alloy in which a mixture of acetylene black and FEP, which are conductive substances, mixed at a ratio of 1: 1 (weight ratio) of acetylene black: FEP was applied to the surface at a ratio of 1.6 mg / cm ^2. Negative electrode.

(Example 17) A hydrogen storage alloy negative electrode containing 1.5 wt% of a hydrophilic resin inside the electrode.

(Comparative Example 18) A hydrogen storage alloy negative electrode in which the porosity of the electrode plate was 15 vol%.

(Example 19) 0.15 wt% of PVA was mixed with the above-mentioned hydrogen storage alloy powder to form a paste, which was filled in a foamed nickel porous body, and then FEP was applied at a rate of 0.8 mg / cm ^{2 to} the surface. A hydrogen-absorbing alloy negative electrode applied and then pressurized to a predetermined thickness.

(Example 20) A hydrogen storage alloy negative electrode in which a negative electrode was immersed in a dispersion liquid in which FEP powder was dispersed in a 1.5 wt% aqueous PVA solution, and FEP was attached at a rate of 0.8 mg / cm ² .

These 20 kinds of negative electrodes 1 and a nickel positive electrode 2 in which a known foamed metal was filled with nickel hydroxide were swirled through a polyamide nonwoven fabric separator 3 and inserted into a case 4 also serving as a negative electrode terminal. Thereafter, a predetermined amount of an alkaline electrolyte was injected and sealed to form a sealed AA-size nickel-metal hydride battery of 1000 mAh. FIG. 1 shows the structure of the prepared battery. In the figure, a safety valve 6 formed inside a positive electrode cap 5 generally operates so as to open when a pressure of 11 to 12 kg / cm ² is reached.
It was set to operate at / cm ² or more. In the figure, 7 is a sealing plate,
8 denotes an insulating gasket, 9 denotes a positive electrode current collector for electrically connecting the positive electrode 2 and the sealing plate 7. The internal pressure of the battery was measured by making a 1 mmφ hole in the bottom of the battery case and fixing the battery to a fixing device equipped with a pressure sensor. Charging at the time of measuring the battery internal pressure was performed up to 200% of the positive electrode capacity at various charging rates up to 2 CmA, and the battery internal pressure at that time was defined as the battery internal pressure at that charging rate. In addition, the generated gas in the battery was collected by a water displacement method, and the gas composition was analyzed by gas chromatography.

In the test of the discharge characteristics, the battery was charged to 150% of the positive electrode capacity with a charge current of 1 CmA under an environment of 20 ° C., and was continuously discharged to 0.8 V with a discharge current of 3 CmA.

FIG. 2 shows that the batteries including the hydrogen storage alloy negative electrodes of Example 1, Comparative Example 2 and Comparative Example 3 were charged at a charging current of 1 CmA and a positive electrode capacity of 20.
The behavior of the internal pressure of the battery with respect to the charging capacity when the battery was charged to 0% was shown. From FIG. 2, the internal pressure of the battery at the time of each 2000 mAh charge was 3.3 kg / cm ² in Example 1 and Comparative Example 2 was 3.3 kg / cm ² .
4.8 kg / cm ² , and Comparative Example 3 was 7.0 kg / cm ² . In Example 1, the internal pressure of the battery began to increase around 1000 mAh charge, whereas in Comparative Examples 2 and 3, the internal pressure of the battery began to increase after 800 mAh charge. When the gas composition in the battery at the time of 2000 mAh charge was analyzed, the oxygen partial pressure was about 1 kg / cm ² for all three types, which was almost the same. The difference in the three types of battery internal pressure was due to the difference in hydrogen partial pressure. I found it.

 This is for the following reason.

As in this experiment, with high capacity, for example, in AA size,
In a nickel-metal hydride storage battery aiming at 1000 mAh, the balance between the positive electrode capacity (1000 mAh) and the negative electrode capacity (1600 mAh) is not sufficient, and the following formulas (5) to (8) are used on the hydrogen storage alloy negative electrode during charging. The represented reaction proceeds.

M + H ₂ O + e ⁻ → MH + OH ⁻ (5) H ₂ O + e ⁻ → 1 / 2H ₂ + OH ⁻ (6) M + 1 / 2H ₂ → MH (7) MH−1 / 4O ₂ → M + 1 / 2H ₂ O (8) (where M is a hydrogen storage alloy) That is, in the portion of the negative electrode wetted with the electrolyte,
The hydrogen storage reaction of the formula (5) and the hydrogen generation reaction of the formula (6) occur competitively. The consumption reaction of the oxygen gas generated from the positive electrode represented by the formula (8) also occurs at the same time. Conversely, in a portion of the negative electrode that is not wet with the electrolytic solution, a reaction (7) for absorbing the hydrogen gas generated by the equation (6) in a gaseous state proceeds.
The FEP of the water-repellent resin controls the area of the water-repellent portion on the hydrogen storage alloy negative electrode. Comparative Example 2 and Comparative Example 3
From the results, it was found that the addition of the water-repellent resin was more effective when added to the negative electrode surface than when added to the inside of the negative electrode, and the reaction of formula (7) was mainly performed on the negative electrode surface. However, comparing these Examples and Comparative Examples, Comparative Examples 2 and 3 show that, due to the addition of the water-repellent resin, the hydrogen storage alloy negative electrode has poor wettability to the electrolytic solution, and the effective surface area during the electrochemical reaction decreases. As a result, the charging current density was increased, the hydrogen gas generation reaction of the formula (6) was promoted, the rise of the internal pressure of the battery was quick, and the internal pressure of the battery was increased. In order to solve this problem, in Example 1, PV which is a hydrophilic resin is used.
A was added inside the electrode. As a result, in particular, the wettability to the electrolyte inside the hydrogen storage alloy negative electrode was improved. Therefore, in Example 1 as compared with Comparative Examples 2 and 3, the effective surface area during the electrochemical reaction was increased, the charging current density was reduced, and the hydrogen gas generation reaction of the formula (6) was suppressed, and the internal pressure of the battery was reduced. Rises slowly and the internal pressure of the battery drops. For the above reason, the first embodiment can suppress the increase of the battery internal pressure even in the case of the quick charge of 1 CmA.

Similar effects were obtained by using carboxymethylcellulose, methylcellulose, or the like instead of PVA.

FIG. 3 shows the three types of batteries of Example 1 and Comparative Examples 2 and 3.
A discharge curve when the battery was discharged to 0.8 V at a discharge current of 3 CmA in an environment of 0 ° C. was shown. The battery voltage at the midpoint of the discharge capacity when discharging to 0.8 V was defined as the intermediate voltage, and was used as a measure of the difference between the discharge voltages of the batteries.

When the examples and the comparative examples were compared with each other, the discharge capacity was almost the same, but a remarkable difference appeared in the intermediate voltage. The intermediate voltage was 1.150 V in Example 1 and 1.10 V in Comparative Examples 2 and 3.
0 V, which was a difference of 50 mV from Example 1.

This is for the following reason. That is, in Example 1, the wettability of the electrolyte solution inside the negative electrode was improved because the hydrophilic resin PVA was added inside the negative electrode of the hydrogen storage alloy, and the effective surface area at the time of the electrochemical reaction was improved as compared with Comparative Examples 2 and 3. Increases,
Since the discharge current density decreased, the intermediate voltage of discharge increased.

For the above reason, the first embodiment can prevent a voltage drop during high-rate discharge.

Table 1 shows the internal pressures of the batteries using the 20 types of hydrogen storage alloy negative electrodes of Examples and Comparative Examples 1 to 20 when charged to 200% of the positive electrode capacity at a charging current of 1 CmA, and at 20 ° C. and 3 C.
The intermediate voltage when the battery was continuously discharged to 0.8 V with a discharge current of mA was shown.

In Comparative Example 4 and Example 5, the particle diameter of the hydrogen storage alloy was examined. According to Table 1, when the average particle diameter of the hydrogen storage alloy particles reached 0.1 μm, the internal pressure of the battery increased to 25.4 kg / cm ² . This is because the smaller the average particle diameter of the hydrogen storage alloy, the more easily the alloy surface is oxidized. As a result, the polarity of the negative electrode of the hydrogen storage alloy during charging increases, and hydrogen gas is easily generated. Further, when the average particle diameter of the hydrogen storage alloy is as large as 75 μm as in the fifth embodiment, the true electrode area is smaller than that in the first embodiment. Therefore, the intermediate voltage was reduced by 70 mV as compared with the first embodiment. For this reason, the average particle diameter of the hydrogen storage alloy is preferably 1 to 50 μm.

Further, in Example 6, when the negative electrode in which the surface of each particle of the hydrogen storage alloy powder had an uneven layer by immersion in an alkaline solution was used, the internal pressure of the battery during charging was lower than that in Example 1. Were similar, but the intermediate voltage of the discharge was 30
mV rose. For this reason, it is preferable that the surface of each particle of the hydrogen storage alloy powder has an uneven layer.

Next, in Examples and Comparative Examples 7 to 10, the water-repellent resin added to the surface of the hydrogen storage alloy negative electrode was examined. As can be seen from Table 1, Comparative Example 7 in which polyethylene was disposed on the surface, the permeability coefficient of hydrogen gas was 1 × 10 ⁻⁹ cm ² / sec · a.
Example 8 in which M-12 as tm was provided, Comparative Example 9 in which ND-1 which is a dispersion of FEP having a surfactant in the solution was provided, and Example 10 in which VDF was provided were all Example 1. The internal pressure of the battery during charging increased as compared to.

This is because, in Comparative Example 7 and Example 10, the degree of water repellency of each resin was smaller than that of FEP, and a solid-gas (solid and gas) interface was not satisfactorily formed on the hydrogen storage alloy negative electrode. This is because the hydrogen gas storage capacity was not sufficient.

In Example 8, although the solid-gas interface was sufficiently formed on the negative electrode of the hydrogen storage alloy, the permeability of the hydrogen gas generated by the electrochemical reaction on the negative electrode was poor, and the internal pressure of the battery increased. Similarly, in the negative electrode in which a water-repellent resin having a small permeability coefficient of oxygen gas was disposed on the surface of the hydrogen storage alloy negative electrode, the internal pressure of the battery at the time of charging similarly increased. In this case, when the gas composition was analyzed, the proportion of oxygen was higher than in Example 1. This is because the gas permeability of the oxygen gas on the negative electrode is poor, and the reducing ability of the oxygen gas is reduced.

In Comparative Example 9, since the surfactant present in the solvent of ND-1 was adsorbed on FEP, the solid-gas interface was satisfactory on the hydrogen-absorbing alloy negative electrode as in Comparative Example 7 and Example 10. This is because the hydrogen gas storage capacity was not sufficient.

From the viewpoint of the structure of the battery safety valve or the strength of the battery case, the battery internal pressure during charging is preferably at least 5 kg / cm ² or less. From this, the water-repellent material disposed on the surface layer of the hydrogen storage alloy negative electrode is (1) a fluororesin, (2) an oxygen gas or hydrogen gas having a permeability coefficient of 1 × 10 ^{−8 at} 25 ° C. cm ² / sec · atm or more. (3) When using a dispersion, there should be no surfactant in the solvent. Further, (4) Polytetrafluoroethylene or tetrafluoroethylene. It is preferable to use a hydrogenated ethylene-propylene hexafluoride copolymer resin. Note that the method (3) can be realized by using an organic solvent such as an alcohol as the solvent.

In Examples 11 and 12, the amount of the water-repellent resin to be disposed on the hydrogen-absorbing alloy negative electrode surface layer was examined. In Example 11, when the amount of FEP added was 0.1 mg / cm ² , the internal pressure of the battery during charging increased to 8.3 kg / cm ² . Further, when the addition amount of FEP in Example 12 was 2 mg / cm ² , since FEP was an insulating substance, the polarization of the hydrogen storage alloy negative electrode during discharge increased, and the discharge intermediate voltage decreased to 1.105 V. did. FIG. 4 shows the relationship between the amount of FEP added, the battery internal pressure during charging, and the intermediate voltage during discharging. As is clear from FIG. 4, there is an optimum value for the amount of FEP added, and the water-repellent resin is added to the surface layer of the hydrogen-absorbing alloy negative electrode from both the internal pressure of the battery during charging and the intermediate voltage of the discharging during discharging. that it is preferably added in the range of ^{0.15mg / cm 2 ~1.5mg / cm 2} .

In Examples 13 and 14, the effect of adding a material having catalytic performance on the decomposition reaction of hydrogen gas on the surface of the hydrogen storage alloy negative electrode and the method of adding the material were examined. Example 13 is a battery using a hydrogen storage alloy negative electrode on the surface of a mixture of platinum black exhibiting catalytic performance against hydrogen gas decomposition reaction and FEP as a water-repellent material, Example 14 is a platinum black This is a battery using a hydrogen-absorbing alloy negative electrode in which FEP is further disposed thereon after being disposed on the surface. Table 1 shows that, in each case, the battery internal pressure during charging was lower and the intermediate voltage during discharging was higher than in the battery using the hydrogen storage alloy negative electrode of Example 1 having only FEP on the surface. This is because the addition of platinum black accelerated the storage reaction of gaseous hydrogen of the formula (7) into the hydrogen storage alloy electrode during charging, and further promoted the dissociation reaction of hydrogen in the hydrogen storage alloy during discharge. is there. In addition, as a material exhibiting catalytic performance with respect to the decomposition reaction of hydrogen gas, platinum, palladium, palladium black, etc. may be used in addition to platinum black, and these materials show good results similarly to platinum black. Was.

Next, MnNi _3.55 Mn _0.4 Al _0.3
Example 15 examined the effect of disposing a hydrogen storage alloy powder having a lower hydrogen equilibrium pressure than Co _0.75 . MmNi _3.55 Mn
The hydrogen equilibrium pressure of _0.4 Al _0.3 Co _0.75 at 20 ° C is about 0.4 kg /
The hydrogen equilibrium pressure at 20 ° C. of LaNi ₄ Al disposed on the negative electrode surface in cm ² is 1.8 × 10 ⁻³ kg / cm ² . In this case, the battery internal pressure during charging showed better results than 3.3 kg / cm ² of 2.4 kg / cm ² next Example 1. This is MnNi _3.55 Mn _0.4 Al _0.3 Co _0.75
This is because LaNi ₄ Al has a lower hydrogen equilibrium pressure and the gaseous hydrogen storage reaction of the formula (7) proceeds more easily. In addition, LaNi ₄ Al is a hydrogen storage alloy negative electrode surface or
There was an effect even if it was arranged on any of the water repellent layers on the negative electrode surface. As a hydrogen storage alloy to be added to the negative electrode surface, LaNi ₄ Al
In addition, a hydrogen storage alloy having any composition may be used as long as the hydrogen equilibrium pressure is lower than that of MmNi _3.55 Mn _0.4 Al _0.3 Co _0.75 .

In Example 16, the effect of adding a conductive material to the water-repellent layer on the negative surface of the hydrogen storage alloy electrode was examined. The internal pressure of the battery of Example 16 at the time of charging was 2.3 kg / cm ² , and the intermediate voltage at the time of discharging was 1.200 V. The result was better than that of Example 1. This is because the addition of the conductive material improves the electron conductivity of the hydrogen storage alloy negative electrode and reduces the polarization of the hydrogen storage alloy negative electrode during charging and discharging. In Example 16, acetylene black was used as the conductive material. However, the same effect was obtained with other amorphous carbon such as carbon black and Ketchan black or graphite having a graphitized structure. Furthermore, when expandable graphite was used, the adhesion of FEP to the negative electrode was improved, and the charge / discharge cycle life was improved.

Next, the amount of the hydrophilic resin contained in the hydrogen storage alloy negative electrode was examined. Example 17 is a battery using a hydrogen-absorbing alloy negative electrode to which PVA, which is a hydrophilic resin, is added 10 times that of Example 1. As is clear from Table 1, even when added in a large amount as in Example 17, the discharge characteristics did not improve, and the internal pressure of the battery during charging increased to 8.4 kg / cm ² . Further, the more the PVA is added, the more the filling amount of the hydrogen storage alloy powder decreases, and from the viewpoint of increasing the energy density of the hydrogen storage alloy negative electrode, it is not preferable to add a large amount of PVA. Conversely, Comparative Example 2, in which no PVA was added, is not preferable from the viewpoint of charging characteristics and discharging characteristics. FIG. 5 shows the relationship between the amount of PVA added and the internal pressure of the battery during charging and the intermediate voltage during discharging. Fifth
From the results in the figure and the viewpoint of increasing the energy density of the hydrogen storage alloy negative electrode, the amount of PVA added was 0.0
5 to 1.0 wt% is optimal. In addition, as the hydrophilic material, PV
Similar effects were observed with other alkali-resistant resins such as carboxymethylcellulose other than A.

Next, the porosity of the hydrogen storage alloy negative electrode was examined. The battery internal pressure at the time of charging of the battery of Comparative Example 18 in which the porosity of the hydrogen storage alloy negative electrode was 15 vol% was 14.3 kg / cm ² , and was lower than that of the battery of Example 1 in which the porosity of the hydrogen storage alloy negative electrode was 30 vol%. Hydrogen gas absorption capacity decreased. This is for the following reason. That is, in Comparative Example 18, since the porosity of the hydrogen-absorbing alloy negative electrode was as low as 15 vol%, the wettability with the electrolytic solution inside the electrode was poor, and as a result, the electrochemical hydrogen-absorbing reaction of the formula (5) was suppressed. This is because the generation of hydrogen gas in the formula (7) is promoted. Similarly, the intermediate voltage at the time of discharge was lower than that of Example 1 due to a decrease in wettability of the electrode. However, conversely, when the porosity of the hydrogen storage alloy is increased, the charge characteristics and the discharge characteristics are improved, but this is not preferable from the viewpoint of increasing the energy density of the hydrogen storage alloy negative electrode and the battery. From the above, the porosity of the hydrogen storage alloy anode is 20 to 40 vol
% Is appropriate.

Further, a method of adding a water-repellent material to the surface of the hydrogen storage alloy negative electrode was examined. After mixing the hydrogen storage alloy powder and the PVA aqueous solution to form a paste and filling the paste into a foamed nickel porous body as a three-dimensional support, in Example 1, the support containing the paste was press-pressed. Then, a battery using a negative electrode coated with FEP on the negative electrode surface, and Example 19 shows that the surface of the paste-containing support was FE-coated.
This is a battery using a negative electrode obtained by applying P and then press-pressing the support. As apparent from Table 1, in Example 19, the internal pressure of the battery during charging was 11.2 kg / cm ^2, which was higher than that in Example 1. This means that, in the case of Example 19, FEP is also distributed inside the hydrogen storage alloy negative electrode by pressing the support with a press. As a result, the hydrophilicity inside the hydrogen storage alloy negative electrode is reduced, the electrochemical hydrogen storage reaction of the formula (5) is suppressed, and hydrogen gas is easily generated during charging. Accordingly, as a method for producing the hydrogen storage alloy negative electrode of the present invention, first, as in Example 1,
A PVA aqueous solution is mixed to form a paste, and the paste is filled into a support, press-fitted or coated, and then press-pressed,
Further, it is optimal to apply / dip or press-fit FEP on the surface. This method of producing a hydrogen storage alloy negative electrode involves the use of hydrogen storage alloy powder having a hydrogen equilibrium pressure lower than that of MmNi _3.55 Mn _0.4 Al _0.3 Co _0.75 , such as a material having a catalytic performance against the decomposition reaction of hydrogen gas, a conductive substance, or hydrogen. Similarly, in the case of having the surface of the hydrogen storage alloy negative electrode, the support containing the paste composed of the hydrogen storage alloy powder and the PVA aqueous solution is press-pressed, and then the above substance and the mixture of the substance and FEP are mixed with the hydrogen storage alloy negative electrode surface. It is preferable to apply, immerse or press-fit.

Further, as in Example 20, after filling a support comprising a hydrogen storage alloy powder and an aqueous PVA solution into a support, the hydrogen storage alloy negative electrode obtained by press-pressing the support was placed in an aqueous PVA solution containing FEP. As for the charge / discharge characteristics of the battery using the negative electrode to which FEP was added by immersion in the battery, the battery internal pressure during charging was 3.5 kg / cm ² , and the intermediate voltage during discharging was 1.175 V.
Comparing this with Example 1, it can be seen that the discharge characteristics are improved. As described above, as a method for producing the hydrogen storage alloy negative electrode of the present invention, the hydrogen storage alloy powder and the PVA aqueous solution are mixed to form a paste, and then the paste is filled, immersed, or pressed into a support, and thereafter, Alternatively, the support may be press-pressed, and a mixture of a hydrophilic material and a water-repellent material may be applied, dipped, or pressed into the surface.

Further, in order to grasp the effect of the gas phase catalyst, the following example was tried.

(Example 21) A pellet made of a sintered porous body of alumina powder having a diameter of about 1 mm and a length of about 2.5 mm was immersed in an aqueous solution of palladium chloride,
About 25 mg of palladium was precipitated, dried, and immersed in a 1.5 wt% fluororesin dispersion to impart water repellency. Next, the pellet was wrapped in a nonwoven fabric made of polypropylene, and placed on the electrode group shown in FIG. 1 while keeping both the positive electrode and the negative electrode electrically insulated, thereby forming a sealed nickel-hydrogen storage battery in the same manner as described above. The negative electrode of this battery was the same as the negative electrode according to Example 1.

When measuring the internal pressure of the battery when the battery was charged to 200% of the positive electrode capacity with a charging current of 1 CmA, similarly to the batteries using the hydrogen storage alloy negative electrodes of Examples and Comparative Examples 1 to 20,
It was 2.8 kg / cm ² . In addition, the intermediate voltage is 1.150 V and the first embodiment
It was the same as at the time.

(Example 22) An aqueous solution of chloroplatinic acid was prepared in place of the palladium chloride of Example 21, and alumina pellets were immersed in the aqueous solution to convert platinum to 25%.
When a gas phase catalyst with the same water repellency as in the previous example was deposited at the same position on the electrode group and the battery internal pressure and intermediate voltage were examined, almost the same results were obtained as with the palladium catalyst. Was.

Further, as a catalyst holding carrier, a carbon molded body could be used in addition to alumina, and as a catalyst to be provided, gold and silver could be used in addition to a platinum group metal.

Examples and phenomena to Comparative Examples 1-20 above, even in the general formula shown in A _1-x B _x C _y ranges by changing the hydrogen absorbing alloy composition to give a result comparable. However, when MmNi ₅ , which is a hydrogen storage alloy having a CaCu ₅ type crystal structure, is used, the charge / discharge cycle is repeated, the hydrogen storage alloy particles become finer, and fall off from the electrode support, resulting in a lower discharge capacity. The cycle life characteristics were poor. Therefore, T to MmNi ₅
at least one of i, Zr, Ca, Y, Hf, Co, Mn, Al, Fe, Cu, and Cr
When a kind of metal was added to form a multi-element alloy, the progress of pulverization of the hydrogen storage alloy particles due to repetition of charge / discharge cycles was suppressed, and the cycle life characteristics were improved. However, the amount of Ti, Zr, Ca, Y, Hf in the atomic ratio is 0.2 or more, Co, Cu
If the ratio is 1.0 or more, Fe and Cr are 0.3 or more, M is 0.6 or more, and Al is 0.5 or more, the alloy phase effective for hydrogen storage decreases, and the discharge capacity is undesirably reduced. Conversely, the amount of Ni is 3.
When it is 5 or less, the discharge capacity of the hydrogen storage alloy negative electrode similarly decreases. Further, when the composition of the hydrogen storage alloy greatly deviates from that of the CaCu ₅ type, and becomes CaCu _4.7 or CaCu _5.3 , the discharge capacity of the hydrogen storage alloy negative electrode is also unfavorable. As described above, the hydrogen storage alloy composition used for the hydrogen storage alloy negative electrode has the general formula A _1-x
B _x C _y (where A is La alone, a mixture of rare earth elements, or a misch metal, B is one of Ti, Zr, Ca, Y, Hf or a mixture thereof, 0 ≦ x ≦ 0.2 And C is N
i, Co, Mn, Al, Fe, Cu, Cr is a kind or a mixture thereof, in the case of Ni, y> 3.5, in the case of Co, y ≦ 1.0, in the case of Mn, y ≦ 0.6, in the case of Al, y ≦ 0.5, y ≦ 0.3 for Fe, y ≦ 1.0 for Cu, y ≦ 0.3, 4.7 ≦ y ≦ 5.3 for Cr).

In addition, the internal pressure during charging of a battery using hydrogen storage alloy MmNi _3.55 Co _0.75 Mn _0.4 Al _0.3 V _0.02 obtained by adding V to the above hydrogen storage alloy as a hydrogen storage alloy negative electrode was 2.8 kg / cm ² , and the intermediate pressure during discharge was The voltage was 1.158 V, which was improved compared to the first embodiment. This is because the addition of V increases the lattice constant of the hydrogen storage alloy, and facilitates diffusion of hydrogen in the solid phase of the hydrogen storage alloy. The effect of addition of V was recognized from an atomic ratio of 0.02 or more. However, when V becomes 0.3 or more in atomic ratio, there is a disadvantage that the alloy phase effective for hydrogen storage decreases and the discharge capacity decreases. For this reason, the addition of V is preferably in the range of 0.02 to 0.3 in atomic ratio.

Further, the internal pressure during charging of the battery using a hydrogen storage alloy _{MmNi 3.55 Co 0.75 Mn 0.4 Al 0.3} In 0.02 with the addition of In into the hydrogen absorbing alloy in the hydrogen storage alloy negative electrode, 2.5 kg / cm ^2, and the embodiment As compared with No. 1, the charging characteristics were improved. This is because the addition of In increases the hydrogen overvoltage at the time of charging the hydrogen storage alloy negative electrode, and suppresses the generation of hydrogen. The effect of addition of In was recognized from an atomic ratio of 0.02 or more. Conversely, if it was more than 0.1, the discharge capacity was disadvantageously reduced. From this
The addition of In is preferably in the range of 0.02 to 0.1 in atomic ratio. The same effect was observed when Tl or Ga was used instead of In.

Although the above description has been made with reference to a nickel-hydrogen storage battery as an example, it is needless to say that the same effect can be obtained in other alkaline storage batteries using a hydrogen storage alloy negative electrode such as a manganese dioxide-hydrogen storage battery.

Effect of the Invention As described above, according to the present invention, a gas phase catalyst is disposed,
And / or adding a hydrophilic resin to the inside of the hydrogen storage alloy negative electrode, and adding a water-repellent resin or a hydrogen storage alloy powder having a lower hydrogen equilibrium pressure than the main hydrogen storage alloy, a conductive material, and a hydrogen gas to the negative electrode surface. A negative electrode provided with a water-repellent material containing a material exhibiting catalytic performance against a decomposition reaction is first filled with a mixture of a hydrogen storage alloy powder and a hydrophilic material into a paste, filled into a support, pressed in, or coated. , Press press,
By providing a material containing a water-repellent resin on the surface and applying and immersing or manufacturing the same, it is possible to provide a sealed alkaline storage battery that suppresses an increase in battery internal pressure during overcharge and suppresses a decrease in battery voltage during discharge. The effect of making it possible is obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a nickel-metal hydride storage battery prepared by the present invention, and FIG.
FIG. 3 shows the relationship between the amount of charge and the internal pressure of the battery at a charge current of 1 ° C., and FIG. 3 shows the relationship between the amount of charge and the battery voltage at a discharge current of 3 ° C. at 20 ° C. Fig. 4 shows the relationship between the amount of FEP added and the positive electrode capacity at a charging current of 20 ° C and 1CmA when the battery was discharged to 0.8V at a battery internal pressure of 200% charging and a discharging current of 20 ° C and 3CmA. FIG. 5 shows the relationship between the PVA addition amount and the positive electrode capacity at 20 ° C., 1 CmA charging current and the internal pressure of the battery at 200% charging and 2%.
FIG. 4 is a diagram showing a relationship with an intermediate voltage when discharging to 0.8 V at a discharge current of 0 ° C. and 3 CmA. 1 ... a negative electrode, 2 ... a positive electrode, 3 ... a separator.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor: Osamu Takahashi 1006, Kadoma, Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (56) References JP-A-62-139255 (JP, A) JP-A-63-231882 (JP, A) JP-A-61-214360 (JP, A) JP-A-61-285658 (JP, A) JP-A-60-109183 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 4/24-4/62

Claims (24)

(57) [Claims] 1. A positive electrode comprising a metal oxide as a main constituent material and a hydrogen storage alloy having an average particle diameter larger than 0.1 μm capable of electrochemically storing and releasing hydrogen as an active material. An alkaline storage battery comprising a negative electrode as a material, an alkaline electrolyte, and a separator, wherein the negative electrode has a water-repellent material only in an electrode surface layer and a hydrophilic material inside the electrode. 2. A main structure comprising a positive electrode mainly composed of a metal oxide and a hydrogen storage alloy having an average particle diameter larger than 0.1 μm capable of electrochemically absorbing and releasing hydrogen as an active material. A negative electrode comprising a material, an alkaline electrolyte, and a separator, wherein the negative electrode has a water-repellent material having no surfactant adsorbed on the electrode surface, and a hydrophilic material inside the electrode. Storage battery. 3. A positive electrode mainly composed of a metal oxide, a negative electrode mainly composed of a hydrogen storage alloy capable of electrochemically storing and releasing hydrogen as an active material, and an alkaline electrolyte. And a separator, wherein the negative electrode has a water-repellent material other than polyethylene having no surfactant adsorbed on the electrode surface, and a hydrophilic material inside the electrode. 4. A positive electrode mainly composed of a metal oxide, a negative electrode mainly composed of a hydrogen storage alloy capable of electrochemically storing and releasing hydrogen as an active material, and an alkaline electrolyte. And a separator, wherein the negative electrode has a water-repellent material only in the electrode surface layer and a hydrophilic material inside the electrode, and the porosity of the negative electrode is greater than 15 vol%. 5. A positive electrode mainly composed of a metal oxide, a negative electrode mainly composed of a hydrogen storage alloy capable of electrochemically storing and releasing hydrogen as an active material, and an alkaline electrolyte. And a separator, wherein the negative electrode has a water-repellent material on which no surfactant is adsorbed on the electrode surface, and a hydrophilic material inside the electrode, and the porosity of the negative electrode at the time of battery construction is higher than 15 vol%. An alkaline storage battery characterized by being enlarged. 6. The composition of a hydrogen-absorbing alloy of a negative electrode represented by the general formula A _1-x
B _x C _y (where A is La alone, a mixture of rare earth elements, or a misch metal, B is one of Ti, Zr, Ca, Y, Hf or a mixture thereof, and 0 ≦ x ≦ 0.2 , C is Ni, C
o, Mn, one of Al, Fe, Cu, Cr or a mixture of these, y> 3.5 for Ni, y ≦ 1.0 for Co, y for Mn
≦ 0.6, y ≦ 0.5 for Al, y ≦ 0.3 for Fe, y ≦ 1.0 for Cu, y ≦ 0.3 for Cr, and 4.7 ≦ y ≦ 5.3). The alkaline storage battery according to claim 1. 7. The composition of a hydrogen storage alloy for a negative electrode according to the general formula A _1-x B _x
C _y D _z (where A is La alone, a mixture of rare earth elements, or misch metal, B is one of Ti, Zr, Ca, Y, Hf or a mixture thereof, and 0 ≦ x ≦ 0.2 , C is Ni, C
o, Mn, Al, Fe, Cu, a kind of Cr or a mixture thereof, y> 3.5 for Ni, y ≦ 1.0 for Co, y ≦ 1.0 for Mn
0.6, y ≦ 0.5 for Al, y ≦ 0.3 for Fe, y for Cu
≦ 1.0, Cr is represented by y ≦ 0.3, D is one of V, In, Tl, Ga or a mixture thereof, and V is 0.02 ≦ z
≦ 0.3, 0.02 ≦ z ≦ 0.1 for In, 0.02 ≦ z ≦ 0 for Tl.
1, Ga: 0.02 ≦ z ≦ 0.1, 4.7 ≦ y + z ≦ 5.3
The alkaline storage battery according to any one of claims 1 to 5, wherein 8. The alkaline storage battery according to claim 1, wherein the hydrogen storage alloy is in a powder state, and the surface of each particle has an innumerable uneven layer. 9. The hydrogen storage alloy has an average particle diameter of 1 to 50 μm.
The alkaline storage battery according to any one of claims 1 to 5, wherein the alkaline storage battery is in a powder state. 10. The water-repellent material of the hydrogen storage alloy negative electrode surface layer is a fluororesin.
The alkaline storage battery according to any one of the above. 11. The method according to claim 1, wherein the water-repellent material of the hydrogen-absorbing alloy negative electrode surface layer is polytetrafluoroethylene or a copolymer resin of ethylene tetrafluoride and propylene hexafluoride. The alkaline storage battery according to any one of the above. Water-repellent resin amount of 12. The hydrogen absorbing alloy negative electrode surface, claimed in claim 1, characterized in that the unit area per 0.15mg / cm ² ~1.5mg / cm ² of the anode Alkaline storage batteries. 13. The hydrogen storage alloy negative electrode surface or a water-repellent layer on the negative electrode surface, comprising a hydrogen storage alloy powder having a hydrogen equilibrium pressure lower than that of the hydrogen storage alloy. The alkaline storage battery according to the above. 14. The alkaline storage battery according to claim 1, wherein the hydrogen storage alloy negative electrode surface or the water repellent layer on the negative electrode surface contains a conductive material. 15. The alkali according to claim 1, wherein the amount of the hydrophilic resin contained in the negative electrode of the hydrogen storage alloy is 0.05 to 1.0% by weight based on the amount of the hydrogen storage alloy. Storage battery. 16. The alkaline storage battery according to claim 1, wherein the porosity of the hydrogen-absorbing alloy negative electrode in the battery configuration is 20 to 40 vol%. 17. A step of mixing a hydrogen storage alloy powder and an aqueous solution of a hydrophilic resin to form a paste, filling the support with a paste, press-fitting or applying the paste, and a support containing the paste. And press-fitting a water-repellent material not adsorbing a surfactant to the surface of the obtained electrode. 18. A process for applying or press-fitting a mixture of a water-repellent material not adsorbing a surfactant and a conductive material to the surface of a negative electrode of a hydrogen storage alloy.
18. The method for producing a negative electrode for an alkaline storage battery according to item 17. 19. A step of applying or press-fitting a mixture of a water repellent material not adsorbing a surfactant and a hydrogen storage alloy powder having a hydrogen equilibrium pressure lower than that of the hydrogen storage alloy to the surface of the hydrogen storage alloy negative electrode. 18. The method for producing a negative electrode for an alkaline storage battery according to claim 17, comprising: 20. The method according to claim 17, further comprising the step of applying or press-fitting a mixture of a water-repellent material to which no surfactant is adsorbed and a hydrophilic material onto the surface of the hydrogen-absorbing alloy negative electrode.
The method for producing a negative electrode for an alkaline storage battery according to the above. 21. A step of mixing a hydrogen storage alloy powder and an aqueous solution of a hydrophilic resin to form a paste, a step of filling, press-fitting, or applying the paste to a support, and a support containing the paste. And a step of dipping the obtained electrode in a dispersion containing a water-repellent material not adsorbing a surfactant. 22. The negative electrode for an alkaline storage battery according to claim 21, further comprising a step of immersing the electrode in a dispersion containing a mixture of a water-repellent material not adsorbing a surfactant and a conductive substance. Manufacturing method. 23. A method of immersing an electrode in a dispersion containing a mixture of a water-repellent material not adsorbing a surfactant and a hydrogen storage alloy powder having a hydrogen equilibrium pressure lower than that of the hydrogen storage alloy. 22. The method for producing a negative electrode for an alkaline storage battery according to claim 21. 24. The negative electrode for an alkaline storage battery according to claim 21, further comprising a step of immersing the electrode in a dispersion containing a mixture of a hydrophilic material and a water-repellent material not adsorbing a surfactant. Manufacturing method.