JPH01292754A - Electrode for alkaline storage battery and manufacture thereof - Google Patents

Abstract

PURPOSE:To increase the filling capability of an active material and mechanical strength by specifying mean pore size in the plane direction and that in the thickness direction of a substrate made of porous metal having three-dimensional net structure. CONSTITUTION:In an electrolyte for an alkaline storage battery obtained by filling active material powder in a substrate made of porous metal having three-dimensional net structure, the substrate is formed so that a mean pore size in the plane direction is 130-200mum and a mean pore size in the thickness direction is 1/2-4/5 that in the plane direction. This substrate is manufactured by rolling a metal substrate thicker than specified thickness. Active material filling capability is increased, energy density is heightened, high electrode conductivity is maintained, and mechanical strength is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION Fields of Industrial Application The present invention has recently been developed using a three-dimensional network structure made of foamed metal, etc. as an electrode for alkaline storage batteries.
A non-sintering method has been proposed in which a mat-like sintered body of foamed metal or metal fiber is used as a support for an active material. The outline of this manufacturing method is as follows. An active material mixture consisting of nickel hydroxide as an active material, to which cobalt hydroxide as an additive, metal nickel as a conductive agent, etc. is kneaded with a paste liquid to form a beinet-like material. This paste is filled into the metal porous body (hereinafter referred to as the base body) using a jig such as a rubbing tool, and after drying, the paste is compressed to a predetermined thickness by pressure to obtain a finished electrical value.

Compared to the conventional sintering method, this method has manufacturing advantages such as easier rolling, fewer steps, and smaller equipment space. Furthermore, if we compare t@, in the following case,
Compared to sintered electrodes, it also has the advantage of being easier to measure high energy density.

However, as mentioned above, in order to directly fill the powdered active material into the substrate, the pore diameter of the substrate must be made 10 times larger than that of a sintered electrode. Therefore, there is a problem that the conductivity of the living substance is low and the discharge performance of the electrode is poor. Furthermore, this electrode contains a perforated iron plate with a core plated with nickel plating, which serves as a sintered L-shaped support, and deformation such as elongation occurs during the final pressurization process. This electrode has very low mechanical strength and tends to break easily during the winding process during assembly of wt ultra-polymers.

Conventionally, as a means to solve these problems, for the former, 7 tons of conductive material was added as described in JP-A-60-1760, and after filling the active material, [[K plating was performed to make it conductive. The latter method is described in Japanese Unexamined Patent Publication No. 57-34
No. 665, No. 55-39181, No. 55-2
As in Japanese Patent No. 8240, attempts have been made to give directionality to the irregular shape of the base body or to add reinforcing materials.

However, in either case, there are new problems such as complicating the process and deteriorating the polar properties, so essential countermeasures are required.

(, J Problems to be Solved by the Invention The present invention has been developed in view of the above-mentioned problems. It is intended to provide a large alkaline storage battery [[and a manufacturing method thereof].

B) Means for Solving the Problems The present invention provides an electrode for an alkaline storage battery with a tL ratio, in which a metal porous body having a three-dimensional network structure is used as a base, and the base is filled with active material powder, the electrode having the three-dimensional network structure. The substrate made of a porous metal body has an average pore diameter in the plane direction of 130 to 20
0 μm, and the average pore diameter in the thickness direction is 1/2 to 415 of the average pore diameter in the planar direction.

7 can be manufactured by rolling the metal base made in advance to a thickness greater than a predetermined thickness on the base made of the metal porous body having the three-dimensional network structure.

On the other hand, the n-age substrate is manufactured by plating a sponge-like resin.
When the sponge-like resin is expanded in the planar direction or compressed in the thickness direction, the holes are deformed and the electrode is manufactured using the sponge-like resin.

(E) Effect Based on the study conducted by the present inventor, when a base made of a metal porous body having a three-dimensional network structure is filled with active material powder, the average pore diameter in the plane direction of the base is 130 to 200 pm. Yes, the average pore diameter in the thickness direction is 1 of the average pore diameter in the plane direction.
/2 to 415, the filling property of the active material powder is excellent during the process, and [[(7) 4 electric power can be maintained, resulting in great mechanical strength! It becomes possible to provide [.

(f) Example The present inventor has made sponge-like nickel (foamed nickel) t-
The effect of the pore size of the substrate used as a substrate on battery customization and productivity in a non-sintering manufacturing method was investigated.

The results are detailed below: 1゜■ Filling properties of active material Average particle size 8 μm 1 Maximum particle size 405 m, minimum particle size 3 μm When nickel hydroxide is used as active material powder, substrates with various pore sizes are evaluated. The filling amount of active material t- was investigated. The results are shown in Table 1.

The particle size of nickel hydroxide is determined by taking into account reactivity and filling properties, etc. The density of the paste used for optical filling was 1.6597♂, and the thickness of the substrate was 1.6597♂. Qm.

If the pore diameter of the substrate is less than 100p, clogging occurs during filling with the active material, resulting in poor filling properties. On the other hand, the larger the pore diameter is, the easier it is to fill, but the more the pore size is removed (for example, the pore diameter is 310 am or more), so it can be said that 130 to 200 #L is practically the best pore diameter for the substrate.

■ The utilization rate of the active material ■ is used, and the electrode is pressurized to increase the density of the active material to 2.2 y/
As ess -vold, Kadmi';'mu'la
Four combined nickel-cadmium ponds are formed.
! The active material utilization rate at a current of 15C was measured and the IC
Comparison was made with the time of 12C. The results are shown in Table 2.

Note that the values at 1G and 2C are relative values calculated with the value at 1/SC as 100.

It can be seen that as the pore diameter of the substrate in Table 2 increases, both the utilization rate and high rate discharge characteristics decrease. ■、■ Comparing both characteristics,
It can be seen that it is difficult to violate Article V + Th, which satisfies both parties.

Therefore, we attempted to improve both properties by making the pore diameter smaller in the thickness direction of the substrate and larger in the planar direction. Here, the hole diameter used as the base material was 170 μm.
The following method is used to change the pore size in the thickness direction: A substrate made of foamed nickel with a large thickness is passed through a calender roll before the active material is compressed to a predetermined thickness. In the nickel plating process, resin such as polyurethane, which is the starting material for nickel foam, is compressed to a predetermined thickness and plated while waiting on the floor.

As mentioned above, the electrode is compressed after being filled with active material, but
The compression amount in this process is 4096. The results are shown in Table 3.

Margins below In Table 3, the type of substrate vI4i refers to the method of adjusting the pore diameter in the thickness direction of the substrate. Further, the discharge characteristic is shown as a utilization rate, and l[ in brackets] represents the ratio to the 115C rate discharge capacity.

As a result, it can be seen that the larger the initial thickness and the larger the difference from the final electrode thickness, the higher the utilization rate and the better the high rate discharge characteristics. The active material filling of the casing tends to be higher as the initial thickness is thinner, but the difference is slight and does not affect workability during the process.

By adjusting the pore diameter in the thickness direction in this way, we were able to change the ratio of the diameter in the plane direction and the diameter in the thickness direction, and obtain good results in both the filling property of the active material and the discharge characteristics of the electrode. This is thought to be due to the following reasons. The relationship between the pore diameter of the substrate and the particle diameter of the active material, which determines the quality of filling, is determined by the pore diameter in the planar direction, so even if the pore diameter in the thickness direction becomes smaller, the amount of filling does not decrease. On the other hand, it goes without saying that the smaller the initial pore diameter, the better the conductivity of the substrate, which determines the utilization rate of the active material. Furthermore, if the initial thickness of the substrate is increased and the IEiI ratio is sufficiently large, even if the pore diameter in the planar direction is large, the distance between the substrate lattice and the active material in the thickness direction will be short, so that sufficient conductivity can be achieved as an electrode. 1 bed, and a high utilization rate can be obtained.

Also,#! As shown in Table 4, the discharge characteristics of the electrodes differ depending on the method of adjusting the hole diameter in the thickness direction.

Ta. The reason for this is not clear, but it is thought to be as follows. When the completed nickel foam is compressed, the lattice in the thin part of the plating film becomes large and diamond-shaped, and the thick lattice in the child film remains undeformed, resulting in uneven pore sizes and a uniform conductive matrix. Can not. However, if the substrate is deformed beforehand during plating, it is believed that a well-organized discharge customization can be obtained in which the pores of the entire substrate are of uniform size.

Next, we examined the strength of the electrodes and found that troubles such as M and breakage of the base body that occur during battery assembly, especially when configuring the spiral electrode body, are mainly due to the strength of the base body. [The key point of improvement is how to make the material high in gi during the fissure construction stage. As a result of the inventor's study, tF
It was found that it is effective to minimize the electrode deformation (elongation) and suppress its variation at the Ij18Eii1 stage.For this purpose, the filling I in the active material filling process
It was found that the packing density should be as close as possible to the active material density of the Optical 11L electrode, and the amount of compression in the pressurization process should be kept small.

Next, the electrode according to the present invention and that of a comparative example will be specifically compared and explained in more detail.

[Example 1] Nickel hydroxide powder with an average particle size of 8 μm was used as an active material powder, and a methylcellulose (MC) aqueous solution as a paste was added to form a slurry. The average pore diameter of the substrate is 130μ
Foamed nickel was used with an initial thickness of 1.6111 m1 and a thickness of 1.0 mm by rolling.

The average pore diameter in the thickness direction of this substrate was rtso μm.

This base was filled with the slurry, dried, and then pressurized to a thickness of 0.6 Iawl to obtain a completed IE electrode.

[Example 2] Urethane foam with an initial thickness of 5 m and an average pore diameter of 130 μm was compressed to 1.0 μm and nickel plated, and foamed nickel of the same thickness was used. The average pore diameter in the thickness direction of this substrate is 80 μm. Then, using this as a substrate, a substrate was obtained in the same manner as in Example 1 [Example 3] using urethane foam having an initial thickness of 1, 5 m, and an average pore diameter of 170 μm. The average pore diameter in the plane direction of this substrate was 170 μm, and the average pore diameter in the thickness direction was 110 μm. Song. This substrate was then used to form an electrode in the same manner as in Example 2.

[5j! Example 4 The entire substrate was prepared using urethane foam with an initial thickness of 1, 6 m, and an average pore diameter of 200 μm. The average pore diameter in the plane direction of this substrate was 200 μm, and the average pore diameter in the thickness direction was 13 Qsm. This substrate was then used to form an electrode in the same manner as in Example 2.

[Comparative example]

Cretan foam with an initial thickness of 1.6 m and an average pore diameter of 130 μm was used, and nickel plating was applied so that the initial thickness was reduced, and NH foamed nickel was used as the substrate. Other conditions were the same as in Example 1, and electric current m was obtained. However, in order to achieve the same filling amount, the slurry density of the active material is adjusted and the active material is filled.

The electrodes of these Examples and Comparative Examples were compressed under pressure using rolling rolls to form completed poles, and then combined with a cadmium electrode to form a nickel-power domicium battery, and the utilization rate was measured. ′! After applying pressure, the XW deformation (elongation) and tensile strength &1- were measured.The results are shown in Table m4.

Examples 17'1 to 4 in Table 4 all exhibited a flat welding rate and high mechanical strength. In Example 4, the diameter in the thickness direction was small, especially L, so the removal of the filled active material was suppressed and the filling amount was increased.

It was also confirmed that the elongation caused in the compression process was greatly improved in Examples 1 to 4 compared to the comparative example. Therefore, it provides uninvented products with stable performance and quality and specific characteristics.

(G) Effects of the Invention According to the electrode for alkaline batteries and the manufacturing method thereof of the present invention, the filling property of the active material is excellent, so the energy density can be increased, and the electrical conductivity of the electrode can be maintained at a high level. Therefore, the utilization rate of the active material can be measured as well as the mechanical strength can be increased, so that it is advantageous in manufacturing processes, and has various effects, and its industrial value is extremely large.

Claims (2)

[Claims] (1) A porous metal material having a three-dimensional network structure is used as a base,
The electrode is an electrode in which the base is filled with active material powder, and the base made of the metal porous body having the three-dimensional network structure has an average pore diameter of 130 to 200 μm in the planar direction and an average pore diameter of 130 to 200 μm in the thickness direction. 1/2~ of the average pore diameter in the plane direction
An electrode for an alkaline storage battery characterized by a ratio of 4/5. (2) The electrode for an alkaline storage battery according to claim 1, wherein the base made of a metal porous body having a three-dimensional network structure is manufactured by rolling the metal base made in advance to a thickness greater than a predetermined thickness. manufacturing method. 2. The substrate made of a metal porous body having a three-dimensional network structure is manufactured by plating a sponge-like resin, and the sponge-like resin is spread in a planar direction or compressed in a thickness direction. 2. The method of manufacturing an electrode for an alkaline storage battery according to claim 1, wherein an electrode whose pores have been deformed is used.