JPH08115752A - Method for recovering effective component from nickel-hydrogen storage alloy secondary battery - Google Patents

Abstract

PURPOSE: To recover a hydrogen storage alloy as a starting metal with a simple process to allow its recycling by removing a component included as impurities, and recovering a negative electrode active material as it is in the form of metal. CONSTITUTION: A nickel-hydrogen storage alloy secondary waste battery is disassembled to take out electrodes and remove terminal parts, and the positive electrode and negative electrode are then dipped in an alkali solution. The electrodes after dipping are crushed by a mechanical means, the crushed material is separated into an active material powder and an electrode base, and the separated active material powder and the electrode base are washed and dried. Consequently, as the hydrogen storage alloy material, zinc and others forming impurities are eluted and removed.

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 waste battery, in which the active ingredient is recovered in a metal state by a particularly simple process and reused as it is as a raw material for hydrogen storage alloy. The present invention relates to a method for recovering an active ingredient from a nickel-hydrogen storage alloy secondary waste battery that can be used.

[0002]

2. Description of the Related Art Nickel-hydrogen storage alloy secondary batteries using hydrogen storage alloys have been commercialized and widely used as environmentally clean batteries due to their high energy density, but rare metals such as cobalt, nickel and rare earths are being used. Since is the main component of the active material, its recovery and recycling are strongly desired.

In particular, this nickel-hydrogen storage alloy secondary battery is considered to occupy the mainstream of batteries for electric vehicles, which is considered as one of the measures for global environment, and therefore batteries and rare metals are recovered and recycled. Is mandatory.

As shown in Table 1, the nickel-hydrogen storage alloy secondary battery contains a wide variety of components whose properties differ significantly thermally, chemically and physically as shown in Table 1.
That is, nickel hydroxide as a positive electrode active material, hydrogen storage alloy (nickel, cobalt, rare earth (Misch metal), etc.) as a negative electrode active material, potassium hydroxide aqueous solution as an electrolytic solution, an organic separator, and a nickel plate or nickel as an electrode substrate. It consists of a wide variety of materials such as plated iron plates, copper or iron-based electrode terminal materials, and cases made of plastic or steel.

[0005]

[Table 1]

However, the recycling of the new nickel-hydrogen storage alloy secondary battery or its electrode material composed of various components is not only a new field, but also the process is complicated and the cost is expected to increase. Or, it has never been considered in earnest.

Conventionally, the treatment of waste batteries is different depending on the type of the battery. However, as seen in the treatment of dry batteries, lead batteries, and nickel-cadmium batteries, after removing the plastic case, It is industrially practiced to collectively apply constituent materials to a certain processing step. For example, lead batteries are placed in a blast furnace, and nickel-cadmium batteries are placed in a distillation furnace.

In this case, it is necessary to homogenize the raw materials to be charged in order to stabilize the operation, and the waste battery materials are mixed.

However, if the nickel-hydrogen storage alloy secondary waste battery is mixed for homogenization as described above, it has a plurality of components as raw materials for the recovery step, and it is necessary to obtain a desired purity. The recovery of the components can be a very long and complex process, resulting in an expensive recovery. In particular, if a wet process in which the active ingredient is extracted and then separated and recovered is adopted, it is possible to recover the metal as a metal by combining the existing technologies, but it is necessary to use a costly process such as solvent extraction or electrolytic extraction. It is not preferred and not preferable. In particular, the negative electrode active material is not simple cadmium but N
It is composed of many components such as i, Co, Mn, Al, and Mm (Misch metal) that have greatly different thermal and chemical properties. In particular, Al and Mm are very easily oxidizable substances, so they are recovered in a metallic state. Not easy to do.

The nickel-hydrogen storage alloy secondary battery as described above has the following problems.

(1) In order to reuse as an active material, it is necessary to prevent mixing of components other than the necessary constituent components, that is, components that become impurities.

(2) Even though it is one of the materials forming the electrode, there is a component which becomes an impurity when it is contained in the active material from the beginning. For example, it is unsuitable if the hydrogen storage alloy, which is the negative electrode active material, contains a certain amount or more of carbon in the organic material used in the separator or as the binder. Zinc in zinc oxide, which is a constituent material, also becomes an impurity.

(3) The rare earth (rare earth) metal, which is a component of the hydrogen storage alloy, is very easily oxidized, and is easily converted into an oxide or salt by ordinary heat or chemical treatment. It cannot be used as an active material.

Under these circumstances, the recycling technology for nickel-hydrogen secondary batteries has not yet been studied in earnest.

[0015]

SUMMARY OF THE INVENTION The object of the present invention is to perform a simple process from a nickel-hydrogen storage alloy secondary waste battery, in particular, for a rare metal which is a constituent component of the active material, without changing the metal state. An object of the present invention is to provide a method for recovering an active ingredient from a nickel-hydrogen storage alloy secondary battery, which is recovered and reused as a raw material metal of a hydrogen storage alloy which is one of active materials.

[0016]

In order to solve the above-mentioned problems, the inventors of the present invention have decided how to remove the components mixed in as impurities by a simple method. As a result of intensive studies based on the two viewpoints of recovering as it is, the present invention has been completed.

That is, the present invention includes the following steps: After disassembling the nickel-hydrogen storage alloy secondary waste battery, taking out the electrode and removing the terminal part, the electrode is separately or mixed with the positive electrode and the negative electrode. And then immersing in an acid or alkaline solution, crushing the electrode after immersing by mechanical means, separating the crushed material into an active material powder and an electrode substrate, and separating the active material powder A method for recovering an active ingredient from a nickel-hydrogen storage alloy secondary battery, which comprises a step of washing and drying the electrode substrate.

In the present invention, the nickel-hydrogen storage alloy secondary waste battery is disassembled to take out the electrode, the terminal portion is removed, and then the electrode is immersed in an acid or alkali solution. As a result, zinc and other components as impurities are eluted and removed from the hydrogen storage alloy raw material. The electrode may be immersed in the positive electrode and the negative electrode separately or in a mixture of both.

The acid solution used here is not particularly limited as long as it has a pH of 3 or lower and the alkaline solution has a pH of 11 or higher. However, only the desired additive such as zinc is eluted and the other components are eluted. Is a solution that does not elute, for example, an industrial and inexpensive alkaline solution such as sodium hydroxide or potassium hydroxide is preferable, and a sodium hydroxide solution is particularly preferable. The immersion time and the temperature of the solution are not particularly limited, but the longer the time and the higher the temperature, the easier the elution of the additive such as zinc is.

Next, the electrode (positive electrode or negative electrode or a mixture thereof) from which additives such as zinc have been removed is mechanically crushed by a device having a mixing and crushing function such as a ball mill or a concrete mixer, The active material is peeled off from the substrate. Wet processing using a solvent is preferable for facilitating peeling. The solvent is not particularly limited as long as it does not react with the electrode component, but is usually an aqueous solution. Although the pH of the aqueous solution is not limited, it is usually an acid or alkaline solution, but preferably the above-mentioned alkaline solution may be used, and the dipping and crushing may be carried out in the same step. Additives such as can be removed more effectively and efficiently.

The zinc is added to the negative electrode in order to improve the battery performance. Even when another metal component is used instead of this zinc, the present invention can be applied as long as it is eluted with an acid or alkali solution.

On the other hand, during this crushing operation, dust may be generated even if it is wet. This dust is mainly an organic binder powder, which is necessary when preparing an active material to be applied to an electrode substrate, and is dusty because of its high water repellency.

Since carbon in the organic matter becomes an impurity in the active material itself, it is desirable to remove dust generated during crushing by suction. For example, the dust of the organic powder contained in the electrode substrate is removed to the outside of the device by suctioning and exhausting from the upper part of the device having the mixing and crushing function. The remaining binder is discarded together with the liquid by the next separation and washing, and removed.

The slurry obtained by crushing is separated into a coarse-grained electrode substrate and a finely divided active material by a conventional method, and then washed, filtered and dried. The atmosphere from crushing to drying is preferably non-oxidizing, but may be in the air.

What is obtained at this point is a porous nickel plate or a nickel-plated iron plate as the substrate, a hydrogen storage alloy as the negative electrode active material, and nickel hydroxide as the positive electrode active material as the active material.

Since the nickel plate is almost pure nickel, it may be used as it is, or after being melted and then cast, as a raw material for the hydrogen storage alloy, or may be used for other purposes. The nickel-plated iron plate may be a raw material for a hydrogen storage alloy that may contain iron, or may be used for other purposes such as ferronickel.

Nickel hydroxide may be used as a positive electrode active material as it is, or may be reused as a nickel metal for the nickel source of the negative electrode active material by subjecting it to a reduction treatment which will be described later alone or together with the recovered negative electrode active material. Good,
Alternatively, it may be used as a nickel raw material for other purposes.

The recovered negative electrode active material may be used as a negative electrode active material as it is, or may be melted and cast into a metal lump and then used as a raw material of a hydrogen storage alloy for a negative electrode. In the latter case, the recovered nickel plate may be melted together.

Melting and casting are carried out at a temperature of 1000 ° C. or higher, preferably 1300 ° C. or higher. The melting and casting atmosphere may be non-oxidizing, and is preferably an argon gas atmosphere. A vacuum melting furnace whose atmosphere can be easily controlled is preferable as the melting device. The melting may be performed by mixing with a rare earth metal having a relatively low melting point.

The yield from the recovered negative electrode active material to the bulk metal depends on the degree of oxidation of the recovered active material, and the yield is low if the amount of oxide is large. Therefore, in the method of the present invention, a method is employed in which the oxidation is not advanced as much as possible beyond the initial oxidation state of the negative electrode active material of the waste battery.

However, depending on the conditions under which the waste battery is left unattended, some degree of oxidation of the active material, especially the negative electrode active material whose main component is rare earth, which is easily oxidized, cannot be avoided. There are two methods for metallizing the negative electrode active material in this case.

One is a method of obtaining a lumpy metal by using the above-described series of steps, and separately oxidizing the remaining oxides which do not form a lumpy metal, to metallize. The other one is a method in which the entire amount of the recovered negative electrode active material is directly dry-reduced and metallized without performing the melting treatment.

In the case of dry reduction, the same applies to both of the above two methods, and as the reducing agent, a substance having a greater oxygen affinity than rare earth, usually calcium is used. Mix the powder recovery and calcium well and mold. In addition, in the mixing, an oxide and / or a metal of a hydrogen storage alloy constituent element may be added for composition adjustment.

Calcium is added in an amount equal to or more than the equivalent required to reduce the rare earth oxide. Next, the molded body is heat-treated at a temperature of 500 ° C. or higher, preferably 1000 ° C. or higher in a non-oxidizing atmosphere, usually an argon gas atmosphere, for a certain period of time or longer.

Next, in order to remove excess calcium and generated calcium oxide, the molded body after the heat treatment is put into water or an aqueous solution containing a salt effective for decalcification such as ammonium chloride and filtered, Dehydrate and dry. Since the powder thus recovered can have properties almost the same as those required for the hydrogen storage alloy powder which is the negative electrode active material of the nickel-hydrogen storage alloy secondary battery, it should be directly used for the electrode material. It can also be reused as a raw material for a hydrogen storage alloy.

It should be noted that expensive calcium is used as the reducing agent only for the negative electrode active material containing rare earth, and for the reduction of nickel hydroxide of the positive electrode active material described above, a cheaper carbonaceous material, aluminum or the like is used. The conventional method using In the case where the positive electrode and the negative electrode are mixed and treated without being separated, therefore, it is necessary to take this point into consideration so that expensive calcium is not used for the reduction of the positive electrode active material.

In order to facilitate these simple processes, it is preferable to separate the constituent materials of the battery in advance as much as possible.

In the present invention, in the electrode substrate obtained by disassembling the battery using the hydrogen storage alloy, the type of substrate and the composition of the hydrogen storage alloy are not limited in any way. In addition to the electrode substrate obtained by disassembling the battery, the same effect can be obtained in the waste electrode substrate generated during the electrode substrate manufacturing.

[0039]

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

Example 1 Zinc oxide 1 as an electrode additive obtained by disassembling a battery
10 kg of the negative electrode plate containing wt% was immersed in 30 liters of a sodium hydroxide solution having a pH of 13 for 48 hours, and then placed in a bow mill containing 10 kg of nickel balls and 30 liters of water.
It was crushed to zero.

The obtained slurry was separated into an electrode substrate and an active material with a 1 mm screen, filtered and dried.

The separated products were the electrode substrate and the active material having a nickel content of 97%, the collection rate was 95%, and the zinc component was 0.1 wt% or less.

When the nickel substrate and the active material were separately melted and cast in a vacuum melting furnace in an argon gas atmosphere and metallized, they were recovered as metal with a yield of 90% and 75%, respectively.

Furthermore, calcium (twice the amount equivalent to the oxides contained in the recovered active material and the non-melting material) is mixed into the above-mentioned active material and the non-melting material which is not recovered as a metal when the active material is melted. Then, after molding by a press, heat treatment was performed at 1000 ° C. for 6 hours in an argon gas atmosphere.

After cooling, washing with an ammonium chloride solution, filtration and drying, a hydrogen storage alloy powder having a H / M of 0.8 or more and satisfactory hydrogen storage characteristics was obtained at a hydrogen pressure of 5 atm. Was given.

Example 2 5 kg of positive electrode plate and 5 kg of negative electrode plate obtained by disassembling the battery
After being mixed with 30 liters of a sodium hydroxide solution having a pH of 13 for 24 hours, they were put together with the sodium hydroxide solution in a ball mill containing 10 kg of nickel balls and decomposed into 90 pieces.

The obtained slurry was separated by a sieve (1 mm) into an electrode substrate and an active material, filtered, and dried to obtain an electrode substrate containing 97% nickel and the active material in a yield of 95%. The zinc content was 0.1% or less.

When the nickel substrate and the active material were melted under vacuum in an argon gas atmosphere, they were recovered as metals with a yield of 90% and 65%, respectively.

[0049]

As described above, according to the present invention,
From the nickel-hydrogen storage alloy secondary waste battery, effective components such as rare metals, which are constituent components of the active material, can be recovered by a simple process.

Therefore, the present invention is a small nickel nickel alloy for consumer use.
Not only is it suitable for the treatment of hydrogen storage alloy secondary batteries, but it is also most suitable as a method for recovering effective components of large-sized batteries such as electric vehicle batteries.

Claims (9)

[Claims] 1. The following steps: After disassembling a nickel-hydrogen storage alloy secondary waste battery to take out an electrode and removing a terminal portion, the electrode is mixed with an acid or a positive electrode and a negative electrode separately or A step of immersing in an alkaline solution, a step of crushing the electrode after the immersion by mechanical means, a step of separating the crushed material into an active material powder and an electrode substrate, washing the separated active material and the electrode substrate And a step of drying, the method for recovering an active ingredient from a nickel-hydrogen storage alloy secondary battery. 2. After the steps (1) to (3), the dried active material powder and the electrode substrate are separately or mixed and then melted at 1000 ° C. or higher in a non-oxidizing atmosphere and cast. Item 1. The method for recovering an active ingredient according to item 1. 3. The method for recovering an active ingredient according to claim 1, wherein the mechanical means is a device having a mixing and pulverizing function. 4. The method for recovering an active ingredient according to claim 3, wherein suction and exhaust are performed from an upper portion of the apparatus having the mixing and pulverizing function. 5. The method for recovering an active ingredient according to claim 1, wherein the crushing is carried out by a wet method in the presence of a solution. 6. The method for recovering an active ingredient according to claim 2, wherein the melting means is performed in a vacuum melting furnace. 7. The separated and dried active material powder or the non-melted material generated by melting is mixed with a reducing agent,
The method for recovering an active ingredient according to claim 1 or 2, wherein heat treatment is performed at 500 ° C or higher in an inert atmosphere to recover the metal state. 8. The reducing agent is calcium.
The method for recovering the active ingredient according to. 9. The recovery of the active ingredient according to claim 8, wherein the heat-treated product is put into an aqueous solution containing a salt which reacts with calcium oxide to produce a water-soluble substance, and then filtered, dehydrated and dried. Method.