JPH08273674A - Battery electrode substrate and manufacturing method thereof - Google Patents

Abstract

(57) [Summary] [Object] To provide an electrode substrate having low electric resistance, high output capability, and excellent corrosion resistance, which is particularly suitable for alkaline secondary batteries. [Structure] It is composed of a metal porous body, and the inside of its skeleton is Cu.
(Alloy), the surface portion is made of Ni (alloy), and Cu is formed in the exposed portion of Cu (alloy) generated during the cutting process.
An electrode substrate coated with a third metal having a smaller ionization tendency than (alloy).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode substrate used in alkaline secondary batteries such as nickel-cadmium batteries, nickel-zinc batteries and nickel-hydrogen batteries.

[0002]

2. Description of the Related Art Lead-acid batteries and alkaline batteries are used as storage batteries used as various power sources. Among them, the alkaline storage battery can be expected to have high reliability and can be made compact and lightweight. For this reason, the small battery has been widely used for various portable devices and the large battery for industrial use. In this alkaline storage battery, zinc, iron, hydrogen, etc. are used as the negative electrode in addition to cadmium. However, as the positive electrode, an air electrode, a silver oxide electrode, and the like are partially taken up, but in most cases, it is a nickel electrode. The characteristics have been improved from the pocket type to the sintering type, and the sealing has been made possible and the use has expanded.

However, in the ordinary powder sintering method, when the porosity of the substrate is 85% or more, the strength is significantly lowered, so that there is a limit to the filling of the active material, and therefore, there is a limit to increase the capacity of the battery. Therefore, as a substrate having a higher porosity of 90% or more, a foamed substrate or a fibrous substrate has been picked up and put into practical use instead of the sintered substrate. As a method for producing such a porous metal substrate having a high porosity, Japanese Patent Application Laid-Open No. S5-5200 is known.
There is a plating method disclosed in JP-A No. 7-174484 and a sintering method disclosed in JP-B-38-17554. In the plating method, carbon powder or the like is applied to the skeleton surface of a foamed resin such as urethane foam to carry out a conductive treatment, and Ni is electrodeposited on the skeleton surface by electroplating, after which the foamed resin and carbon are eliminated, The method is to obtain a metal porous body. On the other hand, in the sintering method, slurry metal powder is impregnated and applied on the skeleton surface of foamed resin such as urethane foam, and then heated to sinter the metal powder. As a porous metal body using these methods, "Celmet" (trade name: manufactured by Sumitomo Electric Industries, Ltd.) made of Ni metal is already on the market and used as an electrode substrate for an alkaline secondary battery.

[0004]

As described in the prior art, the use of a metal porous body as an electrode substrate for a battery makes a large contribution to increasing the capacity of the battery. However, in a large alkaline secondary battery intended for an electric vehicle or the like, since the electrode area of the battery electrode substrate using the Ni porous body of the prior art is large, the electrode substrate is used as an electrode substrate and in the surface of the electrode plate. A potential distribution occurs and charging efficiency also decreases.

Under these circumstances, an object of the present invention is to provide an electrode substrate suitable for alkaline secondary batteries, which has a low electric resistance, a high output and a high corrosion resistance, and a method for producing the same. Is.

[0006]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that the above problems can be achieved by an electrode substrate made of a specific metal porous body, and have completed the present invention.

That is, according to the present invention, (1) in a battery electrode substrate for forming an active material holder used as a current collector for a battery, the inside of the skeleton is Cu or a Cu alloy and the surface is Ni.
Alternatively, a third porous metal having a three-dimensional network structure made of Ni alloy and having a smaller ionization tendency than Cu or Cu alloy in the exposed portion of Cu or Cu alloy
An electrode substrate for a battery, which is coated with the metal of (2), for a battery comprising (2) a skeleton inside of Cu or a Cu alloy and a surface portion of a porous metal body having a three-dimensional network structure of Ni or a Ni alloy In the method for producing an electrode substrate, the metal porous body is cut into a final shape and then processed into cyanide A
Cu or C by immersion in g potassium solution and substitution reaction
This is a method for manufacturing a battery electrode substrate, characterized in that the exposed portion of the u alloy is coated with Ag.

In the present invention, the internal skeleton of Cu or Cu alloy has a specific resistance of about 1/4 that of Ni, so that the electric resistance as a porous metal body can be reduced and when used as a battery electrode plate. The above problems of can be solved. Also,
Since Cu or Cu alloy easily elutes in the alkaline electrolyte in the battery, Ni is coated on the surface thereof to avoid elution of Cu, improve corrosion resistance as an electrode plate, and improve life characteristics of the battery. Improve. However, in the actual battery manufacturing process, the electrode plate is prepared by cutting the metal porous body into a predetermined size and then filling it with an active material, or by filling the active material and then cutting it into a predetermined size. However, in any case, an exposed portion of Cu or Cu alloy is generated on the cut end surface. Also, N
Even when coating i, it is difficult to completely cover the surface of Cu or Cu alloy, and some pinholes or the like are present. In order to eliminate such Cu elution from the partially exposed Cu or Cu alloy portion, a metal having a smaller ionization tendency than Cu is coated. Examples of such a metal element include Ag, Pt, Pd, and Au.
Ag is preferable in consideration of cost. These third metals themselves do not elute at the charge / discharge potential of ordinary alkaline secondary batteries. As described above, according to the electrode substrate structure of the present invention, a battery electrode plate having low resistance and excellent corrosion resistance can be realized, and when applied to an alkaline secondary battery,
High output and efficient charge / discharge become possible. As the third metal coating method in the present invention, the inside of the skeleton is Cu or C.
A method of immersing a metal porous body having a three-dimensional network structure of Ni alloy or Ni alloy whose surface portion is made of Ni alloy in a solution of potassium potassium cyanide and performing Ag plating only on the exposed portion of Cu or Cu alloy by a substitution reaction is used. preferable. Since the ionization tendency of these metals has a relationship of Ni>Cu> Ag, in a solution in which Ag ions are present (cyanide Ag
When a metal consisting of Ni / Cu is immersed in a potassium solution), the reaction of Ni → Ni ²⁺ + 2e ~ occurs on the Ni surface and Ni is melted out, while the electrons and Ag ions collected on the Cu side by the local cell reaction are Bonded and Ag ⁺ + on Cu surface
Ag precipitates due to the reaction e ~ → Ag. According to this method, Ag coating can be selectively carried out only on the surface of Cu or Cu alloy in an extremely simple process, and Cu or C
Since the exposed area of the u alloy is much smaller than the area of Ni or the surface of the Ni alloy, the amount of Ag consumed is small, and the amount of Ni to be eluted can be suppressed to a level at which there is no practical problem.

As a more preferred embodiment of this method, the free KCN concentration of the potassium potassium cyanide solution is set to 1
The concentration is 0 g / liter or more and the Ag concentration is 5 g / liter or more. If the free KCN concentration is less than 10 g / liter or if the Ag concentration is less than 5 g / liter, it is difficult to obtain a uniform Ag coating stably even if the Ag concentration, bath temperature or immersion time is adjusted.

In the present invention, the Cu or Cu alloy portion inside the skeleton is coated with carbon on the porous resin core and electroless C
Formed by electroplating after conductive undercoating such as u-plating or electroless Ni plating.
The alloy can be formed by electroplating.

The Cu or Cu alloy portion is formed by coating and sintering a slurry containing Cu or Cu alloy powder on a porous resin core, and the Ni or Ni alloy on the surface is formed by electroplating. You can also do it. By these methods, a metal porous body having a skeletal metal of Cu and Ni can be obtained.

As the porous resin core, polyurethane foam resin is typically used. Alternatively, woven or non-woven fabric made of resin fibers may be used.

[0013]

【Example】

Preparation of metal porous body A polyurethane foam having a thickness of 2.5 mm and about 50 pores per inch was subjected to a conductive treatment in a plating bath (Sulcup ELC-SR, manufactured by Uemura Kogyo Co., Ltd.) with a bath temperature of 55 ° C. Immerse for 10 minutes, electroless plating Cu 10g /
After m ^{2 was} deposited, electroplating was performed at 3 A / dm ² in a copper sulfate plating bath to form Cu at 450 g / m ² . Then, heat treatment is performed at 800 ° C. for 5 minutes at a rising temperature of 40 ° C./min in a hydrogen gas flow. The Cu porous body having a three-dimensional network structure is plated with Ni at a current density of 10 A / dm ² in a watt bath for electric Ni plating. 100 g / m ² of Ni was formed.

The metal porous body thus obtained has a 10 mm width of 100.
The electric resistance at a length of mm was 12 mΩ / 100 mm. This metal porous body is referred to as Sample A.

Also, 50% by weight of Cu powder having an average particle size of 10 μm, 10% of acrylic resin, 2% of carboxymethyl cellulose and 38% of water are mixed and mixed for 5 hours to form Cu.
A slurry liquid was prepared. Next, after impregnating the slurry liquid with a polyurethane foam having a thickness of 2.5 mm and about 50 pores per inch, the excess impregnated coating was removed with a squeezing roll, and the mixture was allowed to stand at room temperature for 1 hour. And dried. Then, the coated product was heated to 850 ° C. at a heating rate of 30 ° C./min in a hydrogen stream and heat-treated at 850 ° C. for 10 minutes to obtain a Cu porous body having a three-dimensional network structure. The surface density of this Cu porous body was 450 g / m ² . Then this C
u Current density of 10 in watt bath for electro-Ni plating on porous body
Ni plating was performed at 100 g / m ² with A / dm ² . The electrical resistance of the obtained porous metal body at a length of 10 mm is 11 mΩ / 1
It was 00 mm. This metal porous body is referred to as Sample B.

Next, as a comparative example, a porous metal body of Ni alone (Celmet manufactured by Sumitomo Electric Industries, Ltd.) was prepared as a sample C. The surface density of this Ni porous body is 550 g / m ²
The electrical resistance was 43 mΩ.

Example 1 The samples A, B and C obtained as described above were cut into a size of 150 mm × 120 mm as a battery electrode substrate.

Here, with respect to a part of Samples A and B, KAg (CN) ₂ 10 was added to 1000 g of water in order to coat the exposed Cu portion formed by cutting with Ag.
g, KCN 12 g were mixed, stirred and dissolved to obtain an Ag concentration of 6 g / liter, a free KCN concentration of 12 g / liter,
The sample was immersed in a potassium potassium cyanide solution having a bath temperature of 30 ° C. for 10 seconds. As a result of evaluating the sample subjected to this treatment, it was confirmed that about 0.2 μm of Ag was coated only on the Cu exposed portion.

Among the samples A and B which have been cut, the samples exposed to the end faces of Cu and coated with Ag are referred to as samples A1 and B1, respectively.

Example 2 A positive electrode of a Ni-hydrogen secondary battery was manufactured by the following procedure using each of the porous metal sample A, B, C, A1 and B1 as a current collector. A porous metal body is press-filled with an active material paste containing nickel hydride as a main component, smoothed, and then 12
After drying at 0 ° C. for 1 hour, the obtained electrode plate was pressed at a pressure of 1 ton / cm ² to adjust the thickness to 0.7 mm.

10 sheets of this positive electrode and MmN known as a negative electrode
i (Misch metal nickel) -based hydrogen storage alloy electrode 10
A square sealed Ni-hydrogen battery was constructed using a single piece of hydrophilically treated polypropylene nonwoven fabric separator. As an electrolytic solution, 25 g / liter of lithium hydroxide was dissolved in an aqueous caustic potash solution having a specific gravity of 1.25 and used. The batteries obtained by the above procedure were taken as A-D, B-D, C-D, A1-D and B corresponding to the metal porous body samples A, B, C, A1 and B1, respectively.
1-D.

The discharge voltage and capacity of each battery at discharge currents of 10 A and 150 A were examined. As a life test, 10A
The capacity retention rate after 500 cycles in discharge was evaluated. The results are shown in Table 1.

[0023]

[Table 1]

As is clear from these results, A of the present invention
1-D and B1-D show excellent battery characteristics.

Example 3 With respect to the sample A, Ag coating after cutting was carried out under various conditions to evaluate Ag coating thickness and uniformity.
The evaluation is shown in Table 2.

[0026]

[Table 2]

[0027]

[0028]

According to the present invention, a battery electrode substrate having low resistance and excellent corrosion resistance can be realized, and particularly when applied to an alkaline secondary battery, high output and efficient charge / discharge can be realized.

Claims (6)

[Claims] 1. A battery electrode substrate for forming an active material holder used as a current collector for a battery, wherein a metal porous body having a three-dimensional network structure in which a skeleton has Cu or a Cu alloy inside and a surface has Ni or a Ni alloy. Composed of body and Cu
Alternatively, an electrode substrate for a battery, wherein the exposed portion of the Cu alloy is coated with Cu or a third metal having a smaller ionization tendency than that of the Cu alloy. 2. The electrode plate for a battery according to claim 1, wherein the third metal is Ag. 3. A method for producing an electrode substrate for a battery, which comprises a porous metal body having a three-dimensional network structure in which the skeleton is made of Cu or Cu alloy and the surface portion is made of Ni or Ni alloy, and the porous metal body is formed into a final shape. A method for manufacturing a battery electrode substrate, comprising cutting and processing, immersing this in a solution of potassium potassium cyanide, and coating the exposed portion of Cu or Cu alloy with Ag by a substitution reaction. 4. The potassium potassium cyanide solution is free KC.
The method for producing a battery electrode plate according to claim 3, wherein the N concentration is 10 g / liter or more and the Ag concentration is 5 g / liter or more. 5. The Cu or Cu alloy portion inside the skeleton is formed by electroplating after a conductive base treatment such as carbon coating, electroless Cu plating, or electroless Ni plating on the porous resin core, The method for producing a battery electrode plate according to claim 3, wherein the Ni or Ni alloy is formed by electroplating. 6. The Cu or Cu alloy portion inside the skeleton is formed by applying and sintering a slurry containing Cu or Cu alloy powder on a porous resin core body, and the Ni or Ni alloy on the surface portion is formed by electroplating. The method for manufacturing a battery electrode plate according to claim 3, wherein the electrode plate is formed by plating.