JPH0971825A - Method for recovering effective component from nickel hydrogen-storing alloy secondary cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily recover valuable metals in a negative pole at a low cost by treating a negative pole alloy of a waste secondary cell of nickel hydrogen- storing alloy by the combination of an arc fusing method and a fused-salt electrolysis method. SOLUTION: An alloy powder recovered from a negative pole of a waste nickel hydrogen-storing alloy secondary cell is press formed and fused as the consumable electrode of arc discharge to form an alloy layer and a slug layer. The alloy layer essentially consists of Ni, Co, etc., and contains light rare earth elements so that it can be used as it is as an alloy for a nickel hydrogen-storing secondary cell. The slug layer essentially consists of oxides of light rare earth elements and contains a small amt. of Ni and Co. Therefore, the slug is electrolyzed and reduced by using an electrolytic bath containing, by mass %, 50-90% light rare earth fluorides, 0-50 % lithium fluoride, 0-50% barium fluoride and 0-30% calcium fluoride, a carbon electrode as an anode and Ni or Co as a cathode which is the structural component of an hydrogenstoring alloy for a cell. Thus, not only light rare earth elements but valuable metals such as Ni and Co are recovered.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for recovering an active ingredient from a nickel-hydrogen storage alloy secondary battery, which combines an arc melting method and a molten salt electrolysis method to obtain the active ingredient in a simple and inexpensive process. The present invention relates to a method for recovering an active ingredient from a nickel-hydrogen storage alloy secondary battery that can be recovered in a metal state and reused as it is as a raw material for a hydrogen storage alloy.

[0002]

2. Description of the Related Art Nickel-hydrogen storage alloy secondary batteries using rare earth-based hydrogen storage alloys are widely used because of their high energy density. The active material components thereof are rare earth, cobalt and nickel. Since rare metals are used, their recovery and recycling are required. In particular, it is expected that this nickel-hydrogen storage alloy secondary battery will become the mainstream of batteries for electric vehicles, which is considered as one of the measures for global environment, so the recovery and recycling of rare metals contained in batteries is not possible. Required. However, the hydrogen storage alloys for nickel-hydrogen storage alloy secondary batteries have a wide variety of constituent elements such as rare earths, nickel, cobalt, manganese, and aluminum, and the physical characteristics of these are also large.

Further, in the case where the alloy recovered from the negative electrode of these waste batteries is melted and the active ingredient is recovered as a metal by a conventional process such as atmosphere melting with an inert gas by induction heating. However, since the alloy recovered from the waste negative electrode contains a large amount of carbon and oxygen, there is a problem that a high-purity alloy that can be used as a raw material for a hydrogen storage alloy for batteries cannot be obtained. Further, when the alloy recovered from the negative electrode of the waste battery is melted in the atmosphere melting as described above, a large amount of dross containing concentrated oxide is generated in the melting crucible, which causes a problem. There was also. There is also a step of dissolving the alloy recovered from this waste negative electrode with an acid or the like, and separating and recovering it as a rare earth compound or an aqueous solution thereof or other active ingredient compound or an aqueous solution by using a wet process. Has a complicated process and has a problem in terms of processing cost.

[0004]

An object of the present invention is to use a negative electrode alloy recovered from a nickel-hydrogen storage alloy secondary waste battery as a raw material for a hydrogen storage alloy for a secondary battery in a simple and inexpensive process. An object of the present invention is to provide a method of recovering and reusing as high-purity raw material metal as possible.

[0005]

In order to solve the above-mentioned problems, the present inventor diligently studied an inexpensive and efficient process, and as a result, without using a wet process, in the alloy recovered from the waste negative electrode. The present invention has been accomplished to remove impurities and recover a high-purity raw material alloy that can be used for nickel-hydrogen storage alloy secondary batteries. That is, the present invention is a step of decomposing a nickel-hydrogen storage alloy secondary battery and melting the negative electrode alloy recovered from the negative electrode by arc melting to make the rare earth component an oxide and the other alloy components a metal. A nickel / hydrogen storage alloy characterized by comprising a step of crushing a mixture to separate it into a rare earth oxide and another alloy, and a step of electrolytically reducing the rare earth oxide by a molten salt electrolysis method to obtain a rare earth metal. It is a method of recovering the active ingredient from the secondary battery.

Hereinafter, the present invention will be described specifically. First,
The nickel-hydrogen storage alloy secondary battery is disassembled, the alloy powder collected from the negative electrode is molded by a press, and this is arc-melted. At this time, either the so-called consumable electrode type in which the molded alloy powder itself is used as an electrode or the button melting type in which an electrode made of tungsten or the like is used may be used. The ingot obtained by arc melting is crushed by mechanical means, and separated into a slag portion containing a rare earth oxide as a main component and a refined alloy portion.
The alloy portion is returned as it is to the manufacturing process as a raw material for the nickel / hydrogen storage alloy secondary battery alloy, and the slag portion is used as a raw material for the following molten salt electrolysis step. In this molten salt electrolysis step, an electrolytic bath made of rare earth fluoride, lithium fluoride, barium fluoride, and calcium fluoride is used. For example, rare earth fluoride 50 to 90 mass%, lithium fluoride 10 to 50 mass. %, Barium fluoride 0-3
It is composed of 0 mass% and 0 to 30 mass% of calcium fluoride.

In this molten salt electrolysis step, a metal, which is a constituent of a nickel-hydrogen storage alloy secondary battery alloy, is used as a cathode on which a metal to be electrolytically reduced is deposited and recovered as a low-melting rare earth alloy. Is also possible. The rare earth alloy recovered by the molten salt electrolysis method has reduced carbon and oxygen,
As it is, it can be returned to the manufacturing process as a raw material of an alloy for a nickel-hydrogen storage alloy secondary battery.

In the present invention, a sample obtained by pressing the alloy powder recovered from the waste negative electrode of the nickel-hydrogen storage alloy secondary battery into a briquette shape by pressing is set in an arc melting furnace and is set in the furnace by a rotary pump or the like. After being evacuated to a vacuum, argon gas is introduced into the arc melting furnace up to atmospheric pressure, the briquette is melted by arc melting, and after cooling, an ingot consisting of two phases of a metal part and a slag part is obtained. When a so-called consumable electrode type is used for arc melting, press molding is performed into a predetermined shape as an electrode when molding the above alloy powder. This molded electrode is installed in an arc melting furnace, the arc melting furnace is evacuated to a vacuum with a rotary pump, and then argon gas is introduced to atmospheric pressure to perform arc discharge and melt the alloy powder molded as an electrode. At the very least, drop it. The dripping alloy is received by a water-cooled mold placed under the electrode and continuously solidified, and the slag portion with a lighter specific gravity is floated above and separated to collect it as an ingot in which the alloy portion and the slag portion are separated. By mechanically crushing the ingot obtained by arc melting, it is possible to easily separate the alloy part and the slag part, so separate this and separate the rare earth such as refined nickel and cobalt after arc melting. The alloy whose main component is is recovered. In addition, the slag portion recovered at the same time is in a state in which a rare earth metal and a metal other than the rare earth are mixed with the rare earth oxide as a main component.

The slag portion is electrolytically reduced by molten salt electrolysis to recover an effective component as a rare earth metal or an alloy of a rare earth metal and a metal which is a constituent component of an alloy for a nickel-hydrogen storage alloy secondary battery. In the molten salt electrolysis step at this time, a fluoride-based electrolytic bath composed of rare earth fluoride consisting of rare earth components constituting the alloy to be recovered and lithium fluoride, barium fluoride, calcium fluoride or the like is used. Used, the slag recovered in the arc melting step is added to this electrolytic bath to carry out electrolytic reduction. The composition of this electrolytic bath is, for example, 50 to 90 mass% of rare earth fluoride, 10 to 50 mass% of lithium fluoride, and 0 to 30 of barium fluoride.
mass% and calcium fluoride 0 to 30 mass%. These are dissolved in an atmosphere of an inert gas such as argon or the atmosphere, and a carbon electrode is used as an anode, and titanium or tungsten that does not form an alloy with a rare earth element is used as a cathode for electrolysis.

If nickel or cobalt, which is a constituent of the alloy for nickel-hydrogen storage alloy secondary battery, is used as the cathode in the molten salt electrolysis step, the rare earth metal deposited on the surface of the cathode and the metal constituting the cathode are used. Has the property of forming an alloy with a low melting point, it is possible to set the operating temperature of this molten salt electrolysis step to a low value. Rare earth metals or rare earth alloys that have accumulated in the bottom of the electrolytic cell in a molten state in the electrolysis process are pumped out to the mold outside the electrolytic cell by ladle every certain operating time and collected as an ingot. Further, while keeping the alloy produced by this electrolysis in a molten state, a nickel pipe can be inserted into the molten state and the molten alloy can be taken out of the system by vacuum suction. Either recovery method enables continuous electrolysis operation without cooling the electrolysis cell. The rare earth metal or rare earth alloy recovered by molten salt electrolysis has carbon and oxygen contents that can be used as raw materials for nickel / hydrogen storage alloy secondary battery alloys, so it can be used as it is as raw materials. .

[0011]

EXAMPLES The present invention will be specifically described below based on examples.

Example 1 A sample obtained by briquetting 100 g of negative electrode alloy powder recovered from a nickel-hydrogen storage alloy secondary battery was placed in an arc melting furnace, and the rotary furnace pumped the inside of the arc melting furnace to 0.1 to.
After evacuation to rr, argon gas was introduced into the furnace up to atmospheric pressure. The sample was taken out after 10 minutes of melting at a melting current of 700 A and cooling for 10 minutes. When the obtained sample was crushed, alloy 85.2g, slag 7.5g
Could be recovered. Table 1 shows the analysis results of these alloys, the slag, and the alloy powder before arc melting.

Example 2 250 g of negative electrode alloy powder recovered from a waste battery of a nickel-hydrogen storage alloy secondary battery was briquetted, put in an arc melting furnace, and the inside of the arc melting furnace was 0.5 torr by a rotary pump. After vacuum evacuation to, argon gas was introduced into the furnace up to atmospheric pressure. 15 at a melting current of 1000 A
The sample was taken out after 30 minutes of melting and cooling for 30 minutes. When the obtained sample was crushed, alloy 225.1
g, and 16.2 g of slag could be recovered. Table 1 shows the analysis results of these alloys, the slag, and the alloy powder before arc melting.

Example 3 Using the slag recovered in Example 1, reduction was performed by a molten salt electrolysis method. As an electrolytic bath, light rare earth (La, Ce, P
r, Nd) Fluoride 70 mass%, lithium fluoride 3
Using a fluoride bath containing 0 mass%, graphite as the anode,
Using nickel for the cathode, the temperature of the electrolytic bath is 900 ± 5
Electrolysis was carried out in an argon gas atmosphere while maintaining the temperature at ℃. The electrolytic current at this time was 10 A, the slag was crushed, and the whole amount was dissolved in the electrolytic bath before electrolysis. The slag concentration in the electrolytic bath at this time corresponds to 3.5%. After passing an electrolytic current for 1 hour, the electrolytic cell was cooled, the electrolytic cell was taken out and disassembled, and 5.8 g of an alloy was recovered from the inside.
Table 1 shows the analytical values of the alloys recovered at this time.

Example 4 Using the slag recovered in Example 2, reduction was carried out by a molten salt electrolysis method. Light rare earth (La, Ce, P
r, Nd) Fluoride 70 mass%, lithium fluoride 2
Electrolysis was carried out in an argon gas atmosphere while using a fluoride bath composed of 5 mass% and 5 mass% of barium fluoride, using graphite for the anode and nickel for the cathode while keeping the temperature of the electrolytic bath at 900 ± 10 ° C. . The electrolytic current at this time was set to 25 A, and the slag obtained as a raw material, which was obtained by the above-described arc melting, was pulverized, and all the samples were dissolved in the electrolytic bath before electrolysis. The raw material concentration in the electrolytic bath at this time corresponds to 3.5%. After passing the electrolytic current for 30 minutes, the electrolytic cell was cooled, and when the temperature reached 50 ° C. or lower, the electrolytic cell was taken out and decomposed, and 11.5 g of the alloy was recovered from the inside. Table 1 shows the analytical values of the alloys recovered at this time.

[0016]

[Table 1]

[0017]

As described above, according to the method of the present invention, nickel / hydrogen in which a large amount of carbon and oxygen contained in the alloy recovered from a waste battery is removed without using a complicated wet process. The alloy for the storage alloy secondary battery can be recovered.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Sadayuki Komatsu 652-15 Takehara-cho, Takehara-shi, Hiroshima Mitsui Kinzoku Kurohama company house

Claims (5)

[Claims] 1. A step of decomposing a nickel-hydrogen storage alloy secondary battery and dissolving the negative electrode alloy recovered from the negative electrode by arc melting to obtain a rare earth component as an oxide and other alloy components as a metal. Nickel / hydrogen storage characterized by a step of crushing the mixture to separate it into a rare earth oxide and other alloys, and a step of electrolytically reducing the rare earth oxide by a molten salt electrolysis method to obtain a rare earth metal A method for recovering active ingredients from an alloy secondary battery. 2. The nickel-hydrogen storage alloy secondary according to claim 1, wherein the anode alloy recovered from the anode by decomposing the nickel-hydrogen alloy secondary battery is used as a consumable electrode in the arc melting step. Method of recovering active ingredients from batteries. 3. The nickel-hydrogen storage alloy according to claim 1, wherein an electrolytic bath of rare earth fluoride, lithium fluoride, barium fluoride and calcium fluoride is used in the molten salt electrolysis step. How to recover active ingredients from secondary batteries. 4. Rare earth fluoride 50 to 90 mass%, lithium fluoride 10 to 50 mass%, barium fluoride 0 to
30 mass%, calcium fluoride 0-30 mass%
The method for recovering an active ingredient from a nickel-hydrogen storage alloy secondary battery according to claim 3, characterized in that an electrolytic bath consisting of 5. The method for recovering an effective component from a nickel-hydrogen storage alloy secondary battery according to claim 1, wherein a metal which is a constituent component of the hydrogen storage alloy for a battery is used for the cathode of the molten salt electrolysis.