JPH11269506A - Manufacture of high strength spongy porous nickel metal sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a high strength spongy porous metal sheet suitable for an electrode substrate of alkali secondary battery. SOLUTION: The spongy porous nickel metal sheet is manufactured by adding a surfactant and a volatile organic solvent to a slurry consisting of powder of raw materials, a water-soluble resin binder, a plasticizer, and water, forming the resultant foaming slurry into sheet-like state, foaming the sheet into spongy state by utilizing the vapor pressure of the volatile organic solvent and the foaming property of the surfactant, drying it to form a spongy green sheet, and then degreasing and baking this spongy green sheet. In this case, as the powder of raw materials, a powder mixture of NiO powder and Ni powder having the following characteristics is used: (i)The grain size distribution of the NiO powder has two peaks consisting of a peak 4 on the smaller grain size side and a peak 4' on the larger grain size side, and the grain size distribution of the Ni powder has one peak 5; (ii) The one peak of the grain size distribution of the Ni powder is located in the position between the two peaks of the grain size distribution of the NiO powder.

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 high-strength sponge-like porous nickel metal plate, and a method for producing a high-strength sponge-like porous nickel metal plate produced by this method. It is used for producing an electrode substrate of an alkaline secondary battery, and is particularly suitable for producing an electrode substrate of an alkaline secondary 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. As the sponge-like green plate for producing the sponge-like porous nickel metal plate, an apparatus shown in the sectional view of FIG. 3 is used. In FIG. 3, 6 is a carrier sheet, 7 is a doctor blade, 8 is a foamed slurry, 9 is a high-temperature and high-humidity tank, 11 is a drying tank, 12 is a hopper, 13 is a rewind reel, 14 is a take-up reel, 15, Reference numeral 16 denotes a support roll.

In order to manufacture the sponge-like green plate, first, a water-soluble resin binder is added to a raw material powder comprising a mixed powder of nickel oxide powder (hereinafter, referred to as NiO powder) and nickel powder (hereinafter, referred to as Ni powder). , A plasticizer and water are added to form a slurry, and a surfactant and a volatile organic solvent are added to the slurry to form a foamed slurry. The foamed slurry 8 is stored in a hopper 12 as shown in FIG. 3, and the foamed slurry 8 is formed into a thin plate shape on a carrier sheet 6 having a release agent coating layer (not shown) by a doctor blade 7, In the high-temperature and high-humidity tank 9, the foam is sponge-formed using the vapor pressure of the volatile organic solvent and the foaming property of the surfactant, and then dried in the drying tank 11 to form a sponge having continuous open pores. The green plate 10 is manufactured. As the carrier sheet having the release agent coating layer, a sheet obtained by applying a silicone release agent to a polyethylene film is usually used.

When the obtained sponge-like green plate 10 is degreased and fired, a sponge-like porous metal plate having continuous open pores is obtained.

[0005]

However, the conventional sponge-like porous nickel metal plate does not show satisfactory values of strength, thermal conductivity and electric conductivity. This can be achieved by bonding or heat-welding the strip to a sponge-like porous nickel metal plate, but is not preferable as an electrode substrate for an alkaline secondary battery because the filling rate of the active material is reduced.

[0006]

Means for Solving the Problems Accordingly, the present inventors have:
As a result of conducting various tests and researches to develop a method for more easily manufacturing a high-strength sponge-like porous nickel metal plate suitable as a material plate for an electrode substrate of an alkaline secondary battery,
(A) A foaming slurry is obtained by adding a surfactant and a volatile organic solvent to a slurry comprising a raw material powder composed of a mixed powder of NiO powder and Ni powder, a water-soluble resin binder, a plasticizer, and water. Is sponge-like foamed on a carrier sheet having a release agent coating layer by utilizing the vapor pressure of the volatile organic solvent and the foaming property of a surfactant by a doctor blade method or the like, and then dried to form a sponge-like green. In a method for producing a sponge-like porous metal plate by preparing a plate, degreased and firing this sponge-like green plate, as shown in FIG. 1 as a raw material powder composed of a mixed powder of NiO powder and Ni powder. A NiO powder having two peaks, a peak 4 having a small particle size distribution and a peak 4 'having a large particle size distribution, and having a particle size distribution of 1
Powder mixed with Ni powder having two peaks 5,
By using a mixed powder in which the peak 5 of the particle size distribution of the i-powder is between the peak 4 of the smaller particle size and the peak 4 'of the larger particle size distribution of the NiO powder, a sponge-like porous nickel having higher strength than the conventional one A metal plate can be obtained, (b)
As a raw material powder composed of a mixed powder of the NiO powder and the Ni powder, the peak 4 having a smaller particle size distribution has an average particle diameter of:
A NiO powder having two peaks within a range of 0.1 to 2 μm and a large peak 4 ′ within a range of an average particle diameter of 5 to 20 μm;
Between the two peaks 4, 4 'of the iO powder and the average particle size:
When a mixed powder with Ni powder in the range of 1 to 15 μm is used, a sponge-like porous nickel metal plate having higher strength than before can be obtained. (C) The mixed powder is expressed in weight%, It has been found that NiO powder: 10-90%, and a mixed powder having a composition composed of the remaining Ni powder is more preferable.

The present invention has been made based on this finding, and (1) a slurry comprising a raw material powder composed of a mixed powder of NiO powder and Ni powder, a water-soluble resin binder, a plasticizer, and water. A foaming slurry is obtained by adding a surfactant and a volatile organic solvent to the foamed slurry. The foamed slurry is formed into a thin plate, and the foamed slurry is formed into a sponge shape by utilizing the vapor pressure of the volatile organic solvent and the foaming property of the surfactant. A method of producing a sponge-like porous metal plate by foaming and then drying to produce a sponge-like green plate, and degreasing and firing the sponge-like green plate.
As raw material powder consisting of mixed powder of powder and Ni powder,
NiO powder having a particle size distribution having two peaks, and N 2 having a particle size distribution peak between the two peaks of the NiO powder.
Method for producing high-strength sponge-like porous nickel metal plate using mixed powder with i powder, (2) NiO powder and Ni
As a raw material powder composed of a mixed powder with a powder, one peak of the particle size distribution is in the range of 0.1 to 2 μm in average particle size, and the other peak is in the range of 5 to 20 μm in average particle size. (1) using a mixed powder of a NiO powder having certain two peaks and a Ni powder having a particle size distribution peak between the two peaks of the NiO powder and having an average particle size within a range of 1 to 15 μm. The method for producing a high-strength sponge-like porous nickel metal plate as described in (3), wherein the raw material powder composed of a mixed powder of the NiO powder and the Ni powder is expressed in terms of% by weight,
NiO powder: a method for producing a high-strength sponge-like porous nickel metal plate according to the above (1) or (2), which is a mixed powder having a compounding composition of 10 to 90% and the remaining Ni powder. is there.

The reason why the particle size distribution and the mixing ratio of the NiO powder and the Ni powder of the raw material powder composed of the mixed powder of the NiO powder and the Ni powder are limited as described above will be described. (A) Particle Size Distribution of Ni Powder When the peak of the particle size distribution of the Ni powder is less than 1 μm in average particle size, the distribution state does not lie between the two peaks of the NiO powder. It is not preferable because the effect of increasing the density becomes small and a desired sintering density cannot be obtained. On the other hand, when the peak of the particle size distribution of the Ni powder is larger than the average particle size: 15 μm, sintering tends to be insufficient. Absent. Therefore, Ni
The peak of the particle size distribution of the powder was determined to be within the range of average particle size: 1 to 15 μm.

(B) Particle size distribution of NiO powder The peak on the smaller side of the particle size distribution of the NiO powder is the average particle size:
If it is less than 0.1 μm, the slurry floats and separates during slurry preparation, making it difficult to prepare a homogeneous slurry, which is not preferable. On the other hand, the peak on the smaller side of the particle size distribution of the NiO powder is the average particle size. When the diameter is larger than 2 μm, the distribution state in the slurry is not in a desirable arrangement, and the effect of oxidizing and expanding the Ni powder during degreasing and increasing the density of the degreased body is reduced, and a desired sintered density cannot be obtained. It is not preferable. Therefore, the peak of the particle size distribution on the smaller side of the NiO powder is defined as the average particle size: 0.1 to 2 μm
m. Furthermore, if the peak on the side with a large particle size distribution of the NiO powder is less than 5 μm in average particle size, the distribution state is not in a desirable arrangement, and the effect of increasing the density of the degreased body by oxidative expansion of the Ni powder during degreasing is small. Thus, it is not preferable because a desired sintered density cannot be obtained. On the other hand, if the peak having a large particle size distribution of the NiO powder is larger than the average particle size: 20 μm, the desired sintered density cannot be obtained, which is not preferable. . Therefore, N
The peak with the larger particle size distribution of the iO powder is the average particle size: 5
It was determined to be within the range of ２０20 μm.

(C) Mixing ratio of NiO powder to Ni powder NiO powder improves sinterability and improves electrical resistance and thermal conductivity with a small amount. The resistance does not decrease and the thermal conductivity does not improve. 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 NiO powder to Ni powder is 10
９０90% by weight. When the compounding ratio of the NiO powder to the Ni powder is 30 to 70% by weight, cracks hardly occur in the degreased body, the electric resistance is further reduced, and the thermal conductivity is improved.
The mixing ratio of the powder is more preferably 30 to 70% by weight.

Next, when producing the sponge-like porous nickel metal plate of the present invention, a NiO powder having a particle size distribution having two peaks as a raw material powder and one peak having a particle size distribution and two peaks of the NiO powder being used as a raw material powder. The reason why a sponge-like porous nickel metal plate having excellent strength, low electric resistance, and improved thermal conductivity can be obtained by using a mixed powder with Ni powder located between the two is described in detail with reference to the drawings. I do.

FIG. 2 shows a mixed powder of a NiO powder having a particle size distribution having two peaks and a Ni powder having one peak of the particle size distribution and located between the two peaks of the NiO powder used in the method of the present invention. This is a model. In FIG. 2, reference numeral 1 denotes NiO powder having a smaller particle size distribution peak, 2 denotes NiO powder having a larger particle size distribution peak, and 3 denotes Ni powder.

When such a mixed powder is used as a raw material powder, the Ni powder 3 is distributed at a position sandwiched between the NiO powder 2 having a large particle size distribution peak and the NiO powder 1 having a small particle size distribution peak. The foamed slurry containing the raw material powder is formed into a thin plate, and is foamed into a sponge using the vapor pressure of the volatile organic solvent and the foaming property of the surfactant, and then dried to form a sponge green. When a sponge-like green plate is prepared and degreased in an oxidizing atmosphere, the surface of the Ni powder is oxidized and the volume expands during degreasing, whereby the distance between adjacent powders is increased, and the powder between the powders becomes denser. It is considered that the contact is improved and the degreased body has such a strength that a crack is not generated by a slight vibration. Even if this degreased body is sintered in a non-oxidizing atmosphere, it does not crack, and therefore, a sponge-like porous nickel metal plate having excellent strength, low electric resistance, and improved thermal conductivity can be obtained. Conceivable.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS NiO powder having two particle size distribution peaks in which the peak on the smaller side of the particle size distribution is 0.2 μm and the peak on the larger side is 8 μm, and the peak of the particle size distribution is 2 μm. A Ni powder having a certain peak of the particle size distribution was prepared. The NiO powder and the Ni powder are blended in the proportions shown in Table 1 and mixed to produce raw material powders. The raw material powders are used to produce foamable slurries A to E having the component compositions shown in Table 1, The hopper 12 was filled.

[0015]

[Table 1]

A 100 μm-thick polyethylene sheet coated with a silicone release agent is prepared as a carrier sheet and wound on a rewind reel 13 of the apparatus shown in FIG. Table 1 which was set so that it was wound up by
The foamable slurries A to E shown in FIG.
, And foamed into a sponge under the conditions shown in Table 2 in the high-temperature and high-humidity tank 9 under the conditions shown in Table 2, and then shown in Table 2 in the drying tank 11. The sponge-like green plate 10 was produced by drying under conditions.

[0017]

[Table 2]

The sponge-like green plate 10 is degreased under the conditions shown in Table 3 while passing through a degreasing device (not shown), and is then passed through a firing device (not shown). By performing firing under the following conditions, methods for producing a sponge-like porous metal plate of the present invention having continuous open pores (hereinafter, referred to as the present invention method) 1 to 5 were carried out.

[0019]

[Table 3]

The sponge-like porous metal plate obtained by the methods 1 to 5 of the present invention is measured for the basis weight, the electric resistance is measured by a four-terminal method, and the sponge obtained by the methods 1 to 5 of the present invention is further measured. -Shaped porous metal plate is subjected to JI by electric discharge machine
SZ2201 (metallic material tensile test piece) was cut into a shape of No. 13A to form a tensile test piece, and a tensile test was performed using this tensile test piece to determine the tensile strength. The results are shown in Table 4.

Further, the sponge-like porous metal plate obtained by the methods 1 to 5 of the present invention is prepared by adding 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 obtained by the present invention methods 1 to 5 is passed between the vertical filling rolls while supplying the active material slurry using a vertical filling roll of 105 mm.
After drying for 1 hour with a drier, an electrode substrate of an alkaline secondary battery was manufactured by rolling and pressing to 0.7 mm. The active material loading of the electrode substrate of the alkaline secondary battery thus obtained is shown in Table 4, and the thermal conductivity of the obtained electrode substrate of the alkaline secondary battery was measured by a temperature gradient method. Are shown in Table 4.

Conventional Example NiO powder having one particle size distribution peak with a particle size distribution peak of 5 μm, and a particle size distribution peak of 5 μm
A Ni powder having one particle size distribution peak of m was prepared. The NiO powder and the Ni powder were blended in the same proportions as shown in Table 1 of the Examples and mixed to produce a raw powder, and this raw powder was foamed to have the same composition as the composition shown in Table 1. Slurries a to e were prepared.

The foamable slurry a thus obtained
To e, a sponge-like green plate is produced in the same manner as in the embodiment, and the sponge-like green plate is degreased under the same conditions as in the embodiment, fired, and fired to form a conventional sponge-like porous metal plate having continuous open pores. Manufacturing method (hereinafter referred to as conventional method)
1 to 5 were performed. For the sponge-like porous metal plates obtained by the conventional methods 1 to 5, the basis weight, the electric resistance and the tensile strength were measured in the same manner as in the examples, and the results are shown in Table 5.

Further, an electrode substrate of an alkaline secondary battery filled with an active material was prepared in the same manner as in the example, and the active material filling amount and thermal conductivity of the obtained electrode substrate of the alkaline secondary battery were measured. Table 5 shows the results.

[0025]

[Table 4]

[0026]

[Table 5]

[0027]

As is clear from the results shown in Tables 4 and 5, the sponge-like porous metal plates obtained by the methods 1 to 5 of the present invention are different from those of the sponge-like porous metal plates obtained by the conventional methods 1 to 5. The electrode substrate of the alkaline secondary battery produced using the sponge-like porous metal plate obtained by the methods 1 to 5 of the present invention has higher tensile strength and lower electric resistance than the porous metal plate. It can be seen that the conductivity is larger than the thermal conductivity of the electrode substrate of the alkaline secondary battery manufactured using the sponge-like porous metal plates obtained by the conventional methods 1 to 5.

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.

[Brief description of the drawings]

FIG. 1 is a particle size distribution explanatory diagram showing a particle size distribution of a NiO powder having two peaks, a small peak and a large peak, used in the present invention, and a particle size distribution of a Ni powder having one peak. .

FIG. 2 is an explanatory diagram schematically showing a mixed powder of NiO powder having a particle size distribution having two peaks and Ni powder having one peak used in the method of the present invention.

FIG. 3 is an explanatory sectional view of a conventional apparatus for producing a sponge-like green plate used for producing a high-strength sponge-like porous metal plate.

[Explanation of symbols]

 1 NiO powder having a smaller particle size distribution peak, 2 NiO powder having a larger particle size distribution peak, 3 Ni powder, 4 peak having a smaller particle size distribution of 4 NiO powder, 4 'NiO powder having a smaller particle size distribution. 5 Peak of particle size distribution of Ni powder, 6 Carrier sheet 7 Doctor blade 8 Foaming slurry 9 High temperature / high humidity tank 10 Sponge-like green plate 11 Drying tank 12 Hopper 13 Rewind reel 14 Take-up reel 15 Support roll 16 Support roll

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 particle size distribution of two peaks, a nickel oxide powder (hereinafter referred to as NiO powder) and a particle size distribution of 1
Powder mixed with nickel powder having two peaks (hereinafter referred to as Ni powder), wherein one peak of the particle size distribution of the Ni powder is located between two peaks of the particle size distribution of the NiO powder. A method for producing a high-strength sponge-like porous nickel metal plate, comprising: 2. The NiO powder constituting the raw material powder,
One peak of the particle size distribution is in the range of average particle size: 0.1 to 2 μm and the other peak is the average particle size: 5-2.
NiO powder having two peaks within a range of 0 μm, and the Ni powder constituting the raw material powder has a particle size distribution peak within a range of 1 to 15 μm in average particle size and 2% of the NiO powder. 2. The method for producing a high-strength sponge-like porous nickel metal plate according to claim 1, wherein the Ni powder is located between two peaks. 3. The raw material powder is a mixed powder having a composition of 10 to 90% by weight of NiO powder and the balance of Ni powder in weight%.
A method for producing a high-strength sponge-like porous nickel metal plate as described above.