JPS6290865A - Substrate for alkaline battery and its manufacture - Google Patents

Abstract

PURPOSE:To aim at combining metal fibres firmly among each other, so as to obtain increased strength, by distributing a metal with low melting point at the concentration lower than 30wt% to alkaline resistive metal fibres made of Ni or steel etc. and then heating and cooling them in non-oxidizing or reducing atmosphere at the treatment over melting point of metal alloy with lower melting point and at the same time, below melting point of alkaline resistive metal. CONSTITUTION:Metal fibres with wire diameter of 5-100mum are made from an alloy consisting of Ni in 89% and P in 11%. The melting point of this alloy is 875 deg.C. these fibers are distributed uniformly in the ratio of less than 30wt% to the fibers of which wire diameter is 5-100mum, being made of material such as Ni or steel, thus forming felt like substance. When these fibres are heated at the temperature of 900 deg.C in a nn-oxidizing or reducing atmosphere, the alloy melts instantly and spreads over the surface of the main alkaline resistive fibers, thus sttaching a large amount of alloy to contact points among main fibres. Then, by cooling, the alloy is solidified instantly, thus combining firmly main fibres among each other, resulting in the dramatically increased strength as a felt.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a substrate for alkaline batteries and a method for manufacturing the same.

Between the prior art and high-performance alkaline storage batteries such as Ni-Cd batteries and Ni-Fe batteries, sintered plates have traditionally been used. This is made by sintering carbonyl nickel powder at high temperatures, and the porosity is 80.
%, and active materials such as nickel and cadmium are filled into the pores by chemical or electrolytic methods. However, it takes time to fill the active material, resulting in high costs, and there is a desire to fill more active material into the same volume of electrode plate to create a battery with higher energy density. Electrodes using electrode plates and foamed metal substrates have been proposed. However, the former can only be used as a cathode plate and requires sacrificing performance, while the latter has good performance but is unsatisfactory due to its low cost. A metal fiber electrode plate was proposed as a method that could maintain performance and reduce costs sufficiently. This is made by molding nickel or steel fibers or nickel-plated steel fibers with a diameter of 5 to 50 μm into a felt shape, with a porosity of 90 to 95%. can be filled with active materials. Furthermore, since the conductive material is uniformly and finely and continuously distributed, the properties as an electrode plate are also good.

Methods for making metal fibers include the chattering vibration cutting method, which involves cutting a metal block with a lathe, cutting metal foil into thin pieces with a rotating blade, or extruding a metal oxide paste into fibers, which are then reduced and sintered. There are various methods such as a method of cutting fibers from a steel wire, and a method of cutting fibers from a steel wire. In order to make uniform felt, it is common to make short fibers several tens of fibers long and then distribute them into a felt shape using a wet or dry process.

However, since it lacks strength in its current state, it is necessary to bond the contact points between the fibers by sintering. In order to sinter as quickly as possible, the temperature must be kept as high as possible and below the melting point of nickel or steel in a reducing atmosphere. Normally, sintering is required at about 950-1150°C for 5-15 minutes. The higher the temperature, the shorter the holding time, and therefore the shorter the length of the sintering furnace, which is more economical. However, on the other hand, the higher the temperature of the furnace, the higher the cost of the furnace materials and the shorter the life of the furnace. Also, the cost of the thermal energy (electricity or gas) consumed is high and accounts for a significant proportion of the cost. Therefore, the most important point in manufacturing fiber-based substrates is how to sinter at a low temperature and in a short time.

OBJECTS OF THE INVENTION The present invention has been made in view of the above, and an object of the present invention is to provide an inexpensive alkaline battery substrate with improved substrate strength and excellent productivity.

Composition of the invention The present invention consists of the following configuration.

(1) mH of a low melting point alloy of 3 ovt% or less is uniformly dispersed in alkali-resistant metal fibers such as nickel or steel and made into a felt shape.

(2) Heating and cooling in a non-oxidizing or reducing atmosphere to a temperature above the melting point of the low melting point alloy and below the melting point of the alkali-resistant metal.

(3) Alkali-resistant gold #! This is a substrate in which the contact points between fibers are bonded by melted material of low-melting alloy fibers.

Example The details of the present invention will be explained by examples.

Alkali-resistant fibers made of nickel or steel and having a fiber diameter of 5 to 100 μm are combined with a low melting point alloy such as nickel 8.
An alloy containing 9% phosphorus and 11% phosphorus has a melting point of 875° C., and this alloy may be made into fibers with a diameter of 5 to 100 μm by the method described above. This low melting point alloy fiber is mixed in at a ratio of 30 wt% or less and uniformly dispersed to form a felt shape. When this is heated to 900°C in a non-oxidizing or reducing atmosphere, the alloy melts instantly, spreads over the surface of the main alkali-resistant fibers, and a large amount of the alloy adheres to the contact points between the main fibers. When this is cooled, the alloy instantly solidifies, strongly bonding the main fibers to each other, and dramatically increasing the strength of the felt as a whole.

Its strength varies depending on the amount of alloy fibers mixed in, and the more light there is, the higher the strength becomes. However, if the alloy fiber foot exceeds 30%, it becomes excessive and will come loose from the felt during melting and spill out, so 30% is the upper limit.

When a 1-thickness felt with 90% porosity was made using nickel fibers with a fiber diameter of 20 μm, the sintering temperature, sintering time, and substrate strength were determined for the cases in which 10% of the above-mentioned low melting point alloy was mixed and in the case of only nickel fibers. The manufacturing cost ratios are shown in Table 1.

In the present invention, the sintering temperature is low and the sintering time is less than that of the sintering time, the substrate strength is 2.5 times higher, and the manufacturing cost is extremely high.

Effect of the invention

Claims (2)

[Claims] (1) 30% of alkali-resistant metal fibers such as nickel and copper
1. A substrate for an alkaline battery, characterized in that contact points between metal fibers are bonded by a melt of fibers of a low melting point alloy mixed in advance in an amount of wt% or less. (2) 30w for metal fibers mainly made of nickel or copper
Fibers of a low melting point alloy of t% or less are uniformly dispersed in advance and made into a felt shape, and after heating this in a non-oxidizing or reducing atmosphere to a temperature above the melting point of the alloy and below the melting point of the main metal,
A method for manufacturing an alkaline battery substrate characterized by cooling.