JPH0221566A - Electrode substrate for battery - Google Patents

Abstract

PURPOSE:To obtain a substrate whose porosity is high, active material filling capability is good, and shape holding capability is good by sintering a nickel fiber aggregate and a porous nickel plate. CONSTITUTION:A nickel fiber aggregate 3 and a porous nickel plate 4 are sintered. Nickel fiber manufactured by stick-slip vibration are preferable as raw material in terms of less oxide film. 25-40mm long nickel fibers are preferable since they are easily formed in a sheet before sintering. The porous nickel plate 4 sandwiched between nickel fiber aggregates 3 is put in a sintering container 1 and a heavy cover 2 is put on the container 1. A substrate having high porosity and good shape holding capability can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an electrode substrate for batteries, and more specifically, to an electrode substrate for batteries useful as nickel plating in batteries such as NiCd batteries and molten salt fuel cells. This relates to an electrode substrate.

(Prior art) Nickel electrode plates, which have been widely used as electrode substrates for batteries, are generally porous substrates made by sintering fine nickel powder onto a nickel-based metal plate such as a nickel-plated steel plate. In the case of NiCd batteries, such porous substrates are filled with active materials such as cadmium hydroxide, nickel hydroxide, and metal cadmium and used as electrodes. In addition, there is also a battery electrode substrate made by sintering an aggregate of nickel fibers formed into a sheet as a battery electrode substrate with a high porosity that can meet the high capacity density demands of NiCd batteries in recent years. There is.

(Problems to be solved by the invention) However, what about battery electrode plates made by sintering fine nickel powder onto nickel-based metal plates, which have been commonly used in the past?
It is difficult to achieve a porosity greater than the θ factor, there are problems with strength and bending workability, and the substrate has a drawback that the diameter of the micropores is small, requiring a great deal of effort to fill with the active material.

In addition, a battery electrode plate made by sintering an aggregate of nickel fibers formed into a sheet has satisfactory quality in terms of porosity and ease of filling with active material, but has the disadvantage that it easily loses its shape. There is.

As a result of intensive studies to solve these shortcomings, the inventors of the present invention have developed a nickel-based metal plate, which had previously been recognized only as a substrate for sintering nickel powder, into a battery electrode made by sintering nickel fibers. My father came up with the idea of using it as a core metal to maintain the nickel fiber, and decided to use short fibers with a special shape that are easy to sinter as nickel fibers and/or form a special coating on the surface as a sintering jig. It was discovered that the core metal and the nickel fiber aggregate could be more easily sintered by combining the use of a graphite jig, and the present invention was achieved based on this finding.

That is, an object of the present invention is to obtain an industrially advantageous battery electrode substrate that has high porosity, is easy to fill with an active material, and has good shape retention.

(Means for Solving the Problems) Therefore, the object of the present invention can be easily achieved by a battery electrode substrate formed by sintering an aggregate of nickel fibers and a nickel-based porous metal plate.

(for production) The present invention will be explained in detail below.

The battery electrode substrate of the present invention is formed by sintering an aggregate of nickel fibers and a nickel-based porous γ metal plate.

In general, unless the powder is very fine, fibrous metal has more contact points between fibers per weight than powdered metal, so it is easier to sinter, and in the case of the battery electrode substrate of the present invention However, any nickel fiber, regardless of length, thickness, shape, manufacturing method, etc., can be used as a raw material that can be easily sintered in place of conventional nickel fine powder.
-! Nickel fibers manufactured by the Nodotori vibration method as shown in Publication No. 10ta No. 0 are preferable as raw materials because they have less oxide film that inhibits sintering, and in particular, they are easy to form into sheets before sintering. Nickel fibers having a length of about 25 to μOttrm are preferred. Although it is a previously unknown material, curled short nickel fibers as shown schematically in FIG. 7 are most preferable as the raw material of the present invention.

In this specification, the aggregate of curled nickel short fibers is substantially about 7 to 7.5, which is classified as short fibers.
m or less, preferably about O0! An aggregate of minute nickel fibers, preferably curled into a semicircle or more, with a length of σ or less, more preferably about In an aggregate, it is possible that most of the countless nickel fibers that make up the aggregate are curled to a clearly recognizable degree. It can be clearly distinguished from an aggregate.

In addition, such curled nickel short fibers are distinguished from other nickel fibers in terms of their manufacturing method, which preferably involves a process that has some effect of curling the manufactured nickel short fibers into a semicircle or more. It is included during the manufacturing process.

To give one specific example, there is a method in which a rotating abrasive material to which abrasive grains are fixed is pressed against the surface of a nickel base material in a non-oxidizing atmosphere, and the short nickel fibers are removed from the surface. Here, the non-oxidizing atmosphere is oxidized by flowing an inert gas such as nitrogen, argon, or helium into the atmosphere, or by cooling the metal surface with a solvent such as water, water-soluble grinding oil, or inert grinding oil. This refers to the condition in which the grinding conditions are any, as long as the nickel fibers can be removed, but the circumferential speed of the abrasive material must be controlled! 00-2000 m/'a
Preferably, the surface of the nickel substrate to be polished moves at a rate of 3 to 30 m/pnin with respect to the abrasive material.

FIG. 7 is a schematic diagram for explaining the shape of curled short nickel fibers obtained using the method of scraping off nickel fibers from the surface of a nickel base material using the above-mentioned abrasive material.
2 and 13 represent the tip and center portions of the curled nickel short fibers, respectively; /≠ represents the outer diameter of the curled nickel short fibers. The curled short nickel fibers produced by the above method vary in size and shape depending on the rotational speed of the abrasive in the manufacturing process, the strength of the pressure of the abrasive on the metal surface, the diameter of the abrasive grain, the depth of cut, etc. , the wall thickness of the tip 12 is approximately θ
, 5 to μm, and the thickness of the central part 13 is approximately 5 to 1000 μm.
The outer diameter m1 can vary in the range of about 250 to /jt00 μm, but each is characterized in that the thickness of the central portion 13 is larger than that of the tip portion /2.

Such curled short nickel fibers, especially those so small, may look like powder in appearance, and they are easier to sinter than other nickel fibers or fine nickel powder, and can be sintered at lower temperatures or under less pressure. Can be sintered.

The ease with which this curled nickel short fiber can be sintered is due to the compression stress being different at each location of the fiber due to the excessive force applied during the manufacturing process.
This is thought to be due to an increase in ink (bending of dislocations).

The above-mentioned nickel fiber aggregate may be formed into a sheet shape and subjected to sintering with a porous metal plate, if necessary. In the case of an aggregate of nickel fibers obtained by the chatter vibration method, after defibration, in the case of an aggregate of random fibers, after defibration, in addition to the method of making a nonwoven fabric using a random weber or card, there are two methods: C
It can be formed into a sheet by dispersing it in a dispersion medium such as MC (carboxymethyl cellulose), PVA (polyvinyl alcohol), and PE0 (polyethylene oxide) and forming it into a sheet, but it can be formed into a sheet at a lower temperature and pressure than other nickel fibers. By taking advantage of the property that it can be sintered in a vacuum, it is also possible to spray it on a porous metal plate without preforming and sinter it without applying pressure or under a light pressure of about the weight of the lid plate.

It is preferable to select a combination as shown in Table 1 below and mix this with an aggregate of curled short nickel fibers to form a paper. It is preferable to adjust the viscosity, and according to this method, a thin, uniform, and hard-to-break nickel fiber sheet can be obtained.

Table 1 Conventional battery electrode substrates made using fine nickel powder as a raw material are made of materials that cannot be immersed in battery liquid, especially concentrated alkalis, such as nickel-plated ordinary steel or high-nickel stainless steel as a sintered substrate. Porous thin plates, wire mesh, expanded metal, punched metal, etc., have been used, and their thickness, porosity, pore diameter, etc. have been selected from a very wide range. As for the nickel-based porous metal plate used as the electrode, any of the same materials as the conventionally used sintered substrate mentioned above can be used. The choice may be made depending on the type of battery, taking into consideration the ease of distribution of the battery, etc. For example, for a normal NiCd battery, a thickness of JO~700 am and a pore diameter of 0.
A thin plate of ordinary steel with a porosity of about 10N20% and a nickel plating is used.

The battery electrode substrate of the present invention may use a component made by sintering an aggregate of nickel fibers formed into a sheet according to the above needs with the above nickel-based porous metal plate. It is excellent in that it generates few impurities that adversely affect the object to be sintered, has high thermal conductivity, can be used in multiple stages, and has excellent durability. A graphite jig comprising a coating mainly composed of zirconium silicate on the area to be obtained, especially ■ The number of carbon atoms in the alkoxyl group is 1 to 1! at least seven types of 7-ranan compounds selected from the group consisting of tetraalkoxysilanes, hydrolysates of the tetraalkoxysilanes, and partial polycondensates of the hydrolysates; (1) the number of carbon atoms in the alkoxyl group is / to! at least seven zirconium compounds selected from the group consisting of a zirconium tetraalkoxide, a hydrolyzate of the zirconium tetraalkoxide, and a partial polycondensate of the hydrolyzate; ■ an organic solvent; and ■ a suspension containing zirconium silicate powder. It is preferable to use a graphite jig made by coating or impregnating a graphite molded body with a liquid and drying it.

Next, the mode of actual sintering will be explained based on the drawings. 1 and 2 are vertical cross-sectional explanatory diagrams illustrating the sintering jig used to manufacture the battery electrode substrates of the present invention one by one and its usage, and FIG. , FIG. 2 shows the state immediately after sintering. FIG. 3 is a vertical cross-sectional explanatory diagram illustrating a sintering jig used to simultaneously sinter and manufacture a plurality of battery electrode substrates of the present invention and its usage, and FIG. FIG. 5 is an explanatory side view of an apparatus for continuously manufacturing substrates, and FIGS. 5 and 6 are explanatory cross-sectional views of two examples of the apparatus taken along line AA in FIG. In each figure, l is a sintered container, C is a top lid, 3 is an aggregate of nickel fibers, ≠ is a nickel-based porous metal plate, j is a hole in the porous metal plate, and B is a nickel fiber formed into a sheet. Aggregation,
7 is a sintering jig, r is a sintering furnace, RI is a roll for adjusting thickness, 1
0 represents a battery electrode substrate, // represents a chain or mesh conveyor.

When manufacturing the battery electrode substrates of the present invention by sintering them one by one, it is preferable to use a sintering jig consisting of a sintering container/and an upper lid 2 as shown in FIG. If a sintering container L is loaded with a nickel-based porous metal material ≠ in a sintering container L with a nickel fiber aggregate 3 sandwiched between both sides in a sashidite-like manner, and a sufficiently heavy lid is used, the nickel fibers will shrink during sintering. Due to the weight of the nickel fiber aggregate and the pressure applied from the top cover, the manufactured battery electrode substrate contracts, and its thickness becomes equal to the thickness of the gap shown in FIG.

Pressure applied by the upper lid 2 is essential for sintering the nickel fiber aggregate 3 and the nickel-based porous metal plate, and is applied at least 10? /cr/l, but as mentioned earlier, nickel fibers are easier to sinter than the fine nickel powder conventionally used in this field, so the pressure during sintering is less than 1o14/d. When the nickel fibers are curled short nickel fibers, it is sufficient that the ratio is less than r/cr/l.

When sintering and manufacturing a plurality of battery electrode substrates at the same time, sintering containers L each having a bottom opening smaller than the top opening may be stacked and used as shown in FIG.

In addition, a device as shown in the side view diagram in Fig. 1 is used to sinter a material to be sintered, in which both sides of a nickel-based porous metal plate are sandwiched between aggregates of nickel fibers formed into sheets. A jig 7, preferably a graphite sintering jig formed by forming a coating mainly composed of zirconium silicate on the parts that can come into contact with the object to be sintered, is sandwiched from above and below with a chain or a mesh conveyor l/. By using a device that simultaneously feeds the material into the sintering furnace g and sinters it, the battery electrode substrate 10 of the present invention can be manufactured continuously.

Hereinafter, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof.

(Example/) A porous metal plate made by plating the surface of a punched metal (hole diameter/+m, pitch 2 Yugogo) of ordinary steel (C content 0.1%) with a thickness of 7 μm using nickel. A curled short nickel fiber having a shape as shown in FIG.
The average wire diameter of the end indicated as 72 in the figure is / -, -j
'μm, the average wire diameter at the center is expressed as /3! ~30μ
The average curl diameter expressed in m, /4t is 200 to 3j
Areal density 30 consisting of curled nickel short fibers of r0μm
0? /rr? The non-woven fabrics of the above were put together on both sides in the shape of a sandwich, and this was made into a graphite container having the shape shown in Fig. 1, and a coating mainly composed of zirconium silicate was formed on the surface in contact with the object to be sintered. A reducing atmosphere (hereinafter simply referred to as a zircon-coated graphite container)
Under the ammonia decomposition gas dew point -36'C), the pressure of the top lid on the nonwoven fabric! As 09/cdt, 7020℃
After sintering for 7 hours, a battery electrode substrate with a porosity of 73 was obtained. In the battery electrode substrate, the nickel plating and the nickel fibers were strongly sintered, and even when a chisel test was performed, the nickel fibers were always separated from the core metal together with the nickel plating.

(Example λ~Hiro) The same procedure as Example 1 was carried out except that the sintering temperature was changed as shown in Table 2. A battery electrode substrate having a porosity shown in Table 2 was obtained, and a chisel test was performed. The results of Example 1
0 (Example!~!r) As a sintering jig, a ceramic container containing more than r% of alumina was used instead of a zircon-coated graphite container, and the sintering temperatures were as shown in Table 2. When the same procedure as in Example 1 was carried out except as shown, a battery electrode substrate having a porosity as shown in Table 2 was obtained. Furthermore, when the obtained battery electrode substrate was subjected to a chisel test, the sintering temperature was 10!0.
When the sintering temperature was below 0.5°C, there were a few places where the nickel fibers were peeled off from the core metal without nickel plating, but when the sintering temperature was above 070'C, good cohesion was obtained.

(Examples 7 and 10) A nonwoven fabric made of nickel fibers produced by the chatter vibration method (hereinafter simply referred to as chatter) was used instead of a nonwoven fabric made of curled short nickel fibers, and the sintering temperature was as shown in Table λ. The same procedure as in Example 1 was carried out except that the porosity of the obtained battery electrode substrate was as shown in Table 2, and the results of the chisel test were also good as in Example 1.

(Example // and /2) Example except that a nonwoven fabric made of chatter was used instead of the nonwoven fabric made of curled nickel staple fibers, and the sintering temperature was set as shown in Table 1! The porosity of the obtained battery electrode substrate and the results of the chisel test were as shown in Table 2. As a result of the chisel test, when the sintering temperature was set to /OjO''C, there were some areas where the nickel fibers were peeled off without nickel plating, whereas when the sintering temperature was set to 1ioo°C, the nickel fibers were peeled off without nickel plating. The number of places where the fibers peeled off without nickel plating was smaller than when the sintering temperature was 1 oso℃, and could only be seen. Although metal plates with a thickness of
The pore size, porosity, etc. can be selected from a very wide range, and it is noted in this specification that the core metal for ordinary NiCd batteries is much thinner than that used in the examples. As described in.

Further, the porosity in Table 1 is the value for the portion excluding the nickel-based porous metal plate used as the core metal.

(Effects) The battery electrode substrate of the present invention has high porosity and excellent shape retention, and also uses curled short nickel fibers as a raw material and/or a zircon-coated graphite jig as a sintering jig. If this method is adopted, it can be manufactured with great industrial advantage compared to any conventional battery electrode substrate, and it will provide great industrial benefits.

[Brief explanation of the drawing]

1 and 2 are vertical cross-sectional explanatory diagrams illustrating the sintering jig used to manufacture the battery electrode substrates of the present invention one by one and its usage, and FIG. , FIG. 2 shows the state immediately after sintering. Fig. 3 is a vertical cross-sectional explanatory diagram illustrating a sintering jig used to simultaneously sinter and manufacture a plurality of battery electrode substrates of the present invention and its usage; FIG. 5 is an explanatory side view of an apparatus for continuously manufacturing substrates, and FIGS. 5 and 6 are cross-sectional views taken along line AA in FIG. μ of two examples of the apparatus. Further, FIG. 7 is a schematic diagram illustrating the shape of curled short nickel fibers suitable as a raw material for the battery electrode substrate of the present invention. f...Sintered container, λ...Top lid, 3...Nickel fiber aggregate, μ...
Nickel-based porous metal plate, j... Holes of nickel-based porous metal plate, 6... Aggregate of nickel fibers formed into a sheet, 7... Sintering jig , r...Sintering furnace, Ri...Thickness adjustment roll, 10...Battery electrode substrate, l/...Chain or Hamesh conveyor 1
2... Point end of curled short nickel fiber, /3
・・・・・・Central part of curled short nickel fiber, /l'
・・・・・・Outer diameter of curled short nickel fiber.

Claims (1)

[Claims] (1) A battery electrode substrate formed by sintering a nickel fiber aggregate and a nickel-based porous metal plate.