JP2000119769A - Manufacture of spongy porous nickel metallic sheet excellent in thermal and electric conductivity - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a spongy porous metallic sheet excellent in thermal and electric conductivities and suitable for an electrode plate for a nickel-hydrogen battery. SOLUTION: The spongy porous nickel metallic sheet can be manufactured by adding a surfactant and a volatile organic solvent to slurry consisting of powdered raw material, water-soluble resin binder, plasticizer, and water to form foaming slurry, forming this foaming slurry into sheet-like state, foaming it into spongy state and applying drying to prepare a spongy green sheet, and then degreasing and burning this spongy green sheet. In this case, the powdered raw material is composed of a powder mixture of NiO powder of 0.1-10 μm average particle size and 2.0 to 4.0 g/cm3 underwater bulk density and Ni powder of 1-15 μm average particle size and 1.5 to 5.0 g/cm3 underwater bulk density.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a sponge-like porous nickel metal sheet having excellent heat and electric conductivity, and a sponge-like porous sheet having excellent heat and electric conductivity produced by this method. Quality nickel metal plate
It is used for producing a high temperature filter, a filter for an air purifier, and an electrode substrate of an alkaline secondary battery, and is particularly suitable for producing an electrode substrate of an alkaline secondary battery, particularly a nickel hydride battery.

[0002]

2. Description of the Related Art Generally, various filters, electrode substrates of alkaline secondary batteries, and the like have a sponge-like porous material having pores opened on the surface and continuous with internal pores (hereinafter referred to as open continuous pores). Nickel metal plates are used. This sponge-like porous nickel metal plate is made of nickel oxide powder (hereinafter, referred to as NiO powder) and nickel powder (hereinafter, N
i) and a slurry comprising a water-soluble resin binder, a plasticizer, and water, to which a surfactant and a volatile organic solvent are added to form a foamed slurry. The foamed slurry is formed into a thin plate. A sponge-like green plate is prepared by foaming into a sponge shape by utilizing the vapor pressure of the volatile organic solvent and the foaming property of the surfactant, and then dried to prepare a sponge-like green plate. The sponge-like green plate is degreased and fired. It is manufactured by This method of producing a sponge-like porous nickel metal plate is called a "slurry foaming method".
The sponge-like porous nickel metal plate produced by the slurry foaming method is used for a high temperature filter, a filter for an air purifier, an electrode substrate of an alkaline secondary battery, particularly a nickel hydrogen battery, and the like.

Conventionally, an alkaline secondary battery such as a lead storage battery or a nickel-cadmium battery has been used as a power source for an electric vehicle or a power tool. Industrial waste disposal has become a problem since it is used in large quantities and is discarded as it ages. In particular, when a lead storage battery or a nickel-cadmium battery is used as a power source for an electric vehicle, a large lead storage battery or a nickel-cadmium battery is used because a large capacity is required. Therefore, a large amount of lead or cadmium is used. As lead-acid batteries and nickel-cadmium batteries age with the spread of electric vehicles, large lead-acid batteries containing lead and cadmium and nickel-cadmium batteries
Cadmium batteries have to be discarded, and their disposal is becoming a serious problem. However, nickel-metal hydride batteries do not use harmful metals such as lead and cadmium, and have therefore attracted attention as alternative batteries to electric vehicles and power tools.

[0004]

However, when a large nickel-metal hydride battery is rapidly charged and discharged, heat is trapped inside the battery and the internal temperature of the battery easily rises. Since the negative electrode of the battery is made of a hydrogen-absorbing alloy, the hydrogen-absorbing ability is reduced, and accordingly, the battery characteristics of the nickel-metal hydride battery are reduced. One of the causes of the temperature rise inside the nickel-metal hydride battery is that the electrode substrate of the nickel-metal hydride battery is made of a sponge-like porous nickel metal plate, so that its thermal conductivity and electrical conductivity are low, and therefore heat dissipation However, it is said that the temperature inside the nickel-metal hydride battery rises, and there is a need for a sponge-like porous nickel metal plate having more excellent thermal conductivity and electric conductivity.

Further, nickel-metal hydride batteries used for electric vehicles and the like are large in size, and therefore, a sponge-like porous nickel metal plate which is much thicker than a normal nickel-metal hydride battery is used as an electrode substrate. N for producing a thick sponge-like porous nickel metal plate
In the step of forming a foamed slurry containing iO powder and Ni powder into a thin plate and foaming the foamed slurry into a sponge-like green plate to produce a sponge-like green plate, the NiO powder and the Ni powder contained in the foamed slurry precipitate by their own weight, The concentration distribution of Ni becomes uneven on the front and back sides, and a thick sponge-like porous nickel metal plate having a uniform porosity over the entire thickness cannot be obtained as an electrode substrate.

[0006]

Means for Solving the Problems Accordingly, the present inventors have:
As a result of conducting research to solve this problem, (a) Ni
The density of a raw material powder composed of a mixed powder of O powder and Ni powder includes bulk density, tap density, bulk density in water, and the like. The density of the raw material powder used for producing a sponge-like porous nickel metal plate is the bulk density in water. The raw material powder used for producing the sponge-like porous nickel metal plate has an average particle diameter of 0.1 to 10 μm and a bulk density in water of:
2.0-4.0 g / cm ³ NiO powder and average particle size:
1 to 15 μm and bulk density in water: 1.5 to 5.0 g /
preferably made of mixed powder of Ni powder cm ^3, (b) the raw material powder has an average particle size: 0.1～10Myu
m and an underwater bulk density of 2.0 to 4.0 g / cm ³
iO powder: containing 10 to 90% by weight, the balance having an average particle size of 1 to 15 µm and a bulk density in water of 1.5 to 5.0.
g / cm ³ Ni powder is more preferably a mixed powder. (c) The raw material powder comprising the mixed powder is:
It has been found that it is even more preferable to use a foamed slurry containing 40 to 80% by weight.

The present invention has been made on the basis of this finding. (1) A surfactant and a volatile organic solvent are added to a slurry composed of raw material powder, a water-soluble resin binder, a plasticizer and water. Into a foamed slurry, formed into a thin plate, foamed into a sponge utilizing the vapor pressure of the volatile organic solvent and the foaming properties of the surfactant, and then dried to form a sponge-like green plate. In the method for producing a sponge-like porous nickel metal plate by degreasing and firing this sponge-like green plate, the raw material powder has an average particle size of 0.1 to 10 μm.
Ni with a bulk density of 2.0 to 4.0 g / cm ^{3 in} water
A sponge-like porous nickel metal excellent in heat and electric conductivity, comprising a mixed powder of an O powder and a Ni powder having an average particle diameter of 1 to 15 µm and a bulk density in water of 1.5 to 5.0 g / cm ^3. (2) a surfactant and a volatile organic solvent are added to a slurry composed of raw material powder, a water-soluble resin binder, a plasticizer and water to form a foamed slurry, and the foamed slurry is formed into a thin plate. By using a vapor pressure of the volatile organic solvent and a foaming property of a surfactant to foam into a sponge, and then drying to produce a sponge-like green plate, the sponge-like green plate is degreased and fired. In the method for producing a sponge-like porous nickel metal plate, the raw material powder has an average particle diameter of 0.1.
10 to 10 µm and bulk density in water 2.0 to 4.0 g / c
NiO powder m ^3: containing 10 to 90 wt%, the rest is an average particle size: 1 to 15 m a and 1.5 underwater bulk density
A method for producing a sponge-like porous nickel metal plate excellent in heat and electric conductivity, which is a mixed powder composed of 5.0 g / cm ³ Ni powder, (3) The raw powder composed of the mixed powder is mixed in a foamed slurry The method for producing a sponge-like porous nickel metal sheet having excellent heat and electric conductivity according to the above (1) or (2), which is contained in an amount of 40 to 80% by weight.

[0008] The reason why the average particle diameter and the bulk density in water of the NiO powder and the Ni powder, which are the raw material powders composed of the mixed powder of the NiO powder and the Ni powder, are limited as described above will be described. (A) Average particle size of NiO powder and Ni powder As the particle size of NiO powder and Ni powder contained in the foamed slurry becomes finer, the organic binder component in the foamable slurry is used in order to obtain the handling strength of the foamed slurry. On the other hand, when the amount of the organic binder component increases, the viscosity of the foaming slurry increases, and it becomes impossible to form the foaming slurry into a plate shape. To 0.
The lower limit of the average particle size of the Ni powder was set to 1 μm, and the foamable slurry was successfully prepared. On the other hand, the average particle size of the NiO powder contained in the foamed slurry is 10 μm.
When the average particle size of the Ni powder exceeds 15 μm, the concentration distribution of the NiO powder and the Ni powder in the sponge-like green plate formed from the foamed slurry becomes non-uniform,
Even if the obtained sponge-like green plate is fired, fired pores remain in the skeleton and do not densify, so that a sponge-like porous nickel metal plate having desired heat conductivity cannot be obtained, which is not preferable. Therefore, the N constituting the raw material powder of the present invention
The average particle size of the iO powder is 0.1 to 10 μm (more preferably 1 to 5 μm), and the average particle size of the Ni powder is 1 to 1 μm.
It was determined to be within the range of 5 μm (more preferably 2 to 10 μm).

(B) Underwater bulk density of NiO powder and Ni powder The underwater bulk density is measured by placing a certain amount of powder in a graduated cylinder filled with water and leaving it until the bulk becomes constant (over the day and night). The scale of the powder is measured by reading the scale of the measuring cylinder, and the bulk density of the powder can be calculated from the formula of bulk density in water = (bulk weight of powder) / (weight of powder). This is the most appropriate index for determining how much powder can be dispersed in the powder. When the bulk density in water of the NiO powder is less than 2.0 g / cm ³ and the bulk density in water of the Ni powder is less than 1.5 g / cm ³ , sintering shrinkage becomes too large, and cracks may occur during sintering. Is not preferred. On the other hand, NiO
When the underwater bulk density of the powder exceeds 4.0 g / cm ³ and the underwater bulk density of the Ni powder exceeds 5.0 g / cm ³ , the powder having a wide particle size distribution from the average particle size to the fine powder side. Such a powder is not preferable because a foamable slurry cannot be successfully prepared. Therefore, N
The iO powder has a bulk density of 2.0 to 4.0 g / cm ³ (more preferably 2.5 to 3.5 g / cm ³ ), and the Ni powder has a bulk density of 1.5 to 5.0 g / cm ³ (more preferably 2.0 to 4.0 g / cm ³ ).

(C) Compounding ratio of NiO powder to Ni powder NiO powder is added in a small amount to improve sinterability, lower electric resistance, and improve thermal conductivity. However, the electric resistance is low and the thermal conductivity is not improved. On the other hand, if NiO powder is added to the raw material mixed powder in an amount exceeding 90% by weight, the strength of the degreased body becomes weak at the time of degreasing, and cracks are caused by slight vibration, which is not preferable. Therefore, the mixing ratio of the NiO powder with respect to the Ni powder is set to 10 to 90% by weight. When the compounding ratio of the NiO powder to the Ni powder is 30 to 70% by weight,
Cracking hardly occurs in the degreased body, the electric resistance is further reduced, and the thermal conductivity is further improved.
More preferably, it is 70% by weight.

(D) Ratio of NiO-Ni mixed raw material powder in slurry NiO powder: The ratio of mixed raw material powder containing 10 to 90% by weight and the balance of Ni powder in the slurry is as follows:
If the content is less than 40% by weight, cracks may occur during sintering, so it is necessary that the content be 40% by weight or more.
If it is added in excess of 0% by weight, the viscosity of the slurry becomes too high and molding becomes difficult. Therefore, the proportion of the mixed raw material powder in the slurry was set to 40 to 80% by weight. A more preferred range is 50-70% by weight.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS NiO powder and Ni powder having the average particle diameter and the bulk density in water shown in Tables 1 to 4 are blended so as to have the blending ratios shown in Tables 1 to 4 and mixed. To prepare a NiO-Ni mixed powder, and the mixed powders were blended so as to have a blending composition shown in Tables 1 to 4 and mixed, thereby obtaining Table 1
-Expandable slurries A to L shown in Table 4 were prepared.

[0013]

[Table 1]

[0014]

[Table 2]

[0015]

[Table 3]

[0016]

[Table 4]

The foamable slurries A to A shown in Tables 1 to 4
L is blade gap: 0.4 mm, molding speed: 200
Each of the foamed slurries was formed into a thin plate by a doctor blade method under the condition of mm / min, and the obtained thin plate of the foamable slurry was foamed under the conditions of humidity: 90%, temperature: 40 ° C., and holding for 30 minutes, and then air Atmosphere, temperature: 80 ° C, 15
A sponge-like green plate was prepared by drying under the condition of holding for a minute, and the sponge-like green plate was further degreased in an air atmosphere at a temperature of 600 ° C. for 20 minutes.
A method for producing a sponge-like porous metal plate of the present invention having continuous open pores by firing in a 5% H ₂ -N ₂ atmosphere at a temperature of 1100 ° C. for 10 minutes (hereinafter referred to as the present method). 1 to 7 and Comparative Sponge-like Porous Metal Plate Manufacturing Methods (hereinafter referred to as Comparative Methods) 1 to 5 were performed.

For the sponge-like porous metal plates obtained by the methods 1 to 7 of the present invention and the comparative methods 1 to 5, the basis weight was measured, and the electric resistance was measured by a four-terminal method. The results are shown in Table 6. Further, the cross sections of the sponge-like porous metal plates obtained by the methods 1 to 7 of the present invention and the comparative methods 1 to 5 were examined with a metallographic microscope, and no unevenness in the concentration distribution of the raw material powder was found.

Further, methods 1 to 7 of the present invention and comparative methods 1 to 5
Ni (OH) ₂ powder: 70% by weight, CoO powder: 7% by weight, PTFE (polytetrafluoroethylene) dispersion solution: 13
% Of water: 10% by weight of water.
The sponge-like porous metal plate was passed between the vertical filling rolls while supplying the active material slurry by using a vertical filling roll having a thickness of 0.7 mm. The electrode substrate of the alkaline secondary battery was prepared by rolling and pressing to obtain the active material filling amount of the obtained electrode substrate of the alkaline secondary battery shown in Tables 5 to 6, and the obtained alkaline The thermal conductivity of the electrode substrate of the secondary battery was measured by the laser flash method and the temperature gradient method, and the results are shown in Tables 5 to 6.

[0020]

[Table 5]

[0021]

[Table 6]

[0022]

As is evident from the results shown in Tables 1 to 6, the sponge-like porous metal plates obtained by the methods 1 to 7 of the present invention are similar to the sponge-like porous metal plates obtained by the comparison methods 1 to 5. The electrical conductivity is smaller than that of the porous metal plate, and the thermal conductivity of the electrode substrate of the alkaline secondary battery manufactured using the sponge-like porous metal plate obtained by the methods 1 to 7 of the present invention is determined by the comparative method. It can be seen that the thermal conductivity of the electrode substrate of the alkaline secondary battery manufactured using the sponge-like porous metal plate obtained in each of Examples 1 to 5 is larger than that of the electrode substrate.

As described above, according to the method of the present invention,
A sponge-like porous metal plate having a small electric resistance and a large thermal conductivity can be provided, and this sponge-like porous metal plate having a small electric resistance and a large thermal conductivity is used as a positive electrode substrate of an alkaline secondary battery. Alkaline secondary battery with excellent heat dissipation can be manufactured.Alkaline secondary battery with excellent heat dissipation suppresses the temperature rise of the battery, so that rapid charging and efficient discharging can be performed efficiently. Since a higher performance alkaline secondary battery can be provided, it can greatly contribute to the development of the battery industry.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Saburo Wakita 1-297 Kitabukuro-cho, Omiya-shi, Saitama Mitsubishi Materials Co., Ltd. F-term (reference) 5H017 AA02 BB04 BB06 BB10 BB12 BB14 BB16 CC28 DD08 EE04 EE09 HH01 HH03 HH06

Claims (3)

[Claims] 1. A foaming slurry obtained by adding a surfactant and a volatile organic solvent to a slurry comprising raw material powder, a water-soluble resin binder, a plasticizer and water, forming the foaming slurry into a thin plate, The sponge-like green plate is prepared by foaming into a sponge shape by utilizing the vapor pressure of the organic solvent and the foaming property of the surfactant, and then dried to produce a sponge-like green plate. In the method for producing a porous nickel metal plate, the raw material powder has a mean particle size of 0.1 to 10 μm and a bulk density in water of 2.0 to 4.0 g / cm ³ , which is hereinafter referred to as NiO powder. ) And average particle size: 1-1
5 μm and a bulk density in water of 1.5 to 5.0 g / cm ³
A method for producing a sponge-like porous nickel metal plate having excellent thermal and electrical conductivity, comprising a mixed powder with a nickel powder (hereinafter referred to as Ni powder). 2. The raw material powder is NiO powder: 10-9.
The method for producing a sponge-like porous nickel metal sheet having excellent heat and electric conductivity according to claim 1, wherein the powder is a mixed powder containing 0% by weight and the balance being Ni powder. 3. The sponge-like porous nickel metal plate excellent in heat and electric conductivity according to claim 1, wherein the raw material powder contained in the foamed slurry is 40 to 80% by weight. Production method.