JP2021161455A - Method for recovering valuable metal from waste lithium-ion battery - Google Patents

Abstract

To provide a method capable of effectively utilizing dust discharged in an oxidize-roasting process, and also capable of inexpensively and efficiently recovering valuable metal.SOLUTION: A method for recovering valuable metal from a waste lithium-ion battery includes: an oxidize-roasting process to obtain an oxidize-roasted material by oxidizing and roasting the waste lithium-ion battery; a melting process to obtain a molten material by melting the oxidize-roasted material; and a slag separation process to recover an alloy including the valuable metal by separating a slag from the molten material. In the method, the dust generated in the oxidize-roasting process is recovered, and at least a portion of the recovered dust is added to a material to be treated in the melting process.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for recovering valuable metals from a waste lithium ion battery.

In recent years, lithium-ion batteries have become widespread as lightweight, high-output secondary batteries. As a lithium ion battery, a negative electrode material, a positive electrode material, a separator, an electrolytic solution, and the like are known to be enclosed in a metal outer can such as aluminum or iron. The negative electrode material is made of a negative electrode active material (graphite or the like) fixed to a negative electrode current collector (copper foil). The positive electrode material is made of a positive electrode active material (lithium nickel oxide, lithium cobalt oxide, etc.) fixed to a positive electrode current collector (aluminum foil). The separator is a polypropylene porous resin film or the like. The electrolytic solution contains an electrolyte such as lithium hexafluorophosphate (LiPF _6).

One of the main applications of lithium-ion batteries is hybrid vehicles and electric vehicles. Along with the life cycle of automobiles, a large amount of on-board lithium-ion batteries are expected to be discarded in the future, and used batteries and defective products generated during manufacturing (hereinafter, "waste lithium-ion batteries" or "waste batteries") It is desired to reuse (referred to as) as a resource. Against this background, a technique has been proposed in which valuable metals (Ni, Co, Cu, etc.) contained in the waste battery are recovered and reused by a pyrometallurgical process in which the entire amount of the waste battery is melted in a high-temperature furnace.

The waste lithium ion battery contains impurity elements such as carbon (C), aluminum (Al), fluorine (F), and phosphorus (P) in addition to valuable metals. Therefore, when recovering valuable metals from waste batteries, it is necessary to remove these impurity elements. In the pyrometallurgical process, combustible components (C, etc.) in impurity elements are burnt and removed, the remaining impurity elements are oxidized, and valuable metals are reduced and alloyed to separate them from the slag-ized oxide impurities. Has been done. Patent Documents 1 and 2 are examples of documents that disclose a pyrometallurgical process for recovering valuable metals (Ni, Co, Cu, etc.) from a waste lithium-ion battery.

Patent Document 1 describes a method for recovering cobalt from a lithium ion battery containing aluminum and carbon, which comprises a step of preparing a bath furnace provided with a means for injecting _{O 2, CaO as a slag forming agent, and CaO.} The process of preparing the metallurgical charge raw material including the lithium ion battery, the process of injecting oxygen and supplying the metallurgical raw material to the furnace, thereby reducing at least a part of the cobalt and collecting it in the metal phase, and the hot water. A method including a step of separating slag from the metal phase by dispensing is disclosed (claim 1 of Patent Document 1). Further, Patent Document 2 describes a method of recovering a valuable metal containing nickel and cobalt from a waste battery of a lithium ion battery, in which a melting step of melting the waste battery to obtain a melt and an oxidation treatment of the waste battery are performed. A method including an oxidation step, a slag separation step of separating slag from a melt to recover an alloy containing a valuable metal, and a dephosphorization step of separating phosphorus contained in the alloy is disclosed (Patent Document). 2 claim 1).

By the way, in the pyrometallurgical process of recovering valuable metals, it is important to control the degree of oxidation-reduction in the steps of reducing and alloying the valuable metals (melting step). For example, if the degree of reduction is adjusted to be excessively weak (the degree of oxidation is high), the valuable metal is oxidized and incorporated into the slag, making it difficult to recover it as a fused metal. Therefore, in order to increase the recovery rate of valuable metals, it is necessary to adjust the degree of reduction to some extent.

On the other hand, adjusting the degree of reduction to an excessively high degree (low degree of oxidation) is not preferable because the recovery rate of valuable metals is rather lowered. For example, if the degree of reduction is excessively high, the impurity carbon remains without being oxidized and removed, which may hinder the separation of the alloy (valuable metal) and the slag (impurities other than carbon). Further, if the degree of reduction is excessively high, impurities other than carbon are prevented from being oxidized and slagged, so that the impurities may be incorporated into the valuable metal alloy. In particular, among impurities, phosphorus (P) has a property of being relatively easily reduced. Therefore, if the degree of reduction is adjusted to be high, phosphorus is incorporated into the valuable metal alloy without being slagged. Therefore, in order to recover valuable metals stably and efficiently, it is desirable to appropriately control the degree of redox in the melting step.

In the conventionally proposed method for recovering valuable metals by a pyrometallurgical process, a reducing agent such as graphite is added in order to promote the reduction of valuable metals in the process of reducing and alloying the valuable metals (melting process). .. In addition, dust generated in the oxidative roasting process prior to the melting process was discharged to the outside of the furnace and discarded.

Japanese Patent No. 5818798 Japanese Patent No. 5835585

However, as a result of investigation by the present inventors, it was found that the dust discharged in the oxidative roasting process is mainly composed of carbon, which can be effectively used as a reducing agent in the subsequent melting process. It was also found that the dust contains a considerable amount of valuable metal, and that the recovery rate of the finally obtained valuable metal can be increased by using the dust as a reducing agent.

The present invention has been completed based on such knowledge, and an object of the present invention is to provide a method capable of recovering valuable metals inexpensively and efficiently by effectively utilizing the dust discharged in the oxidative roasting process. do.

The present invention includes the following aspects (1) to (3). In the present specification, the expression "-" includes the numerical values at both ends thereof. That is, "X to Y" is synonymous with "X or more and Y or less".

(1) A method of recovering valuable metals from waste lithium-ion batteries.
An oxidative roasting step of oxidatively roasting the waste lithium ion battery to obtain an oxidative roasted product,
A melting step of melting the oxidized roasted product to obtain a melt, and
It has a slag separation step of separating slag from the melt and recovering an alloy containing a valuable metal.
A method of recovering dust generated in the oxidation roasting step and adding at least a part of the recovered dust to an object to be processed in the melting step.

(2) The method of (1) above, wherein the valuable metal is at least one selected from cobalt (Co), nickel (Ni), and copper (Cu).

(3) The method according to (1) or (2) above, wherein the heating temperature in the melting step is 1300 ° C. or higher and 1500 ° C. or lower.

According to the present invention, there is provided a method capable of recovering valuable metals inexpensively and efficiently by effectively utilizing the dust discharged in the oxidative roasting process.

It is a process drawing which shows an example of the flow of the recovery method of a valuable metal.

Hereinafter, specific embodiments of the present invention (hereinafter, referred to as “the present embodiment”) will be described in detail. The present invention is not limited to the following embodiments, and various modifications can be made without changing the gist of the present invention.

≪1. Overview of valuable metal recovery method ≫
The valuable metal recovery method of the present embodiment is a method of recovering the valuable metal contained in the waste lithium ion battery. The method of recovering valuable metals from waste batteries is roughly divided into a pyrometallurgical process and a hydrometallurgical process. The recovery method of the present embodiment mainly relates to a pyrometallurgical process.

Waste lithium-ion batteries are used lithium-ion batteries, defective products generated in the manufacturing process of positive electrode materials that make up the batteries, residues inside the manufacturing process, waste materials in the battery manufacturing process such as generated waste, and these. Contains the mixture. Waste batteries contain valuable metals (Ni, Co, Cu, etc.). The amount of each valuable metal contained in the waste battery is not particularly limited, but for example, copper (Cu) may be contained in an amount of 10% by mass or more, or 20% by mass or more.

FIG. 1 is a process diagram showing an example of a flow of a method for recovering valuable metals. As shown in FIG. 1, the recovery method of the present embodiment includes a pretreatment step S1 for removing the electrolytic solution and the outer can of the waste battery as needed, and the crushed product by crushing the battery contents as needed. The crushing step S2, the oxidative roasting step S3 in which the crushed product is oxidatively roasted to obtain an oxidative roasted product, the melting step S4 in which the oxidative roasted product is melted and alloyed, and the slag is separated from the molten material to be valuable. It has a slag separation step S5 for recovering an alloy containing a metal.

≪2. About each process of collection method ≫
Hereinafter, each step of the valuable metal recovery method of the present embodiment will be specifically described.

[Pretreatment process]
In the recovery method of the present embodiment, the pretreatment step S1 may be provided if necessary. The pretreatment step S1 is performed for the purpose of preventing or detoxifying the waste lithium ion battery, removing the outer can, and the like. Waste batteries such as used lithium-ion batteries are sealed and have an electrolytic solution inside. If the crushing treatment is performed as it is, there is a risk of explosion and it is dangerous. Therefore, it is desirable to perform a discharge treatment or a removal treatment of the electrolytic solution by some method. By removing the electrolytic solution and the outer can in the pretreatment step S1, the safety can be enhanced and the recovery rate of valuable metals (Ni, Co, Cu, etc.) can be enhanced.

The specific method of the pretreatment step S1 is not particularly limited. For example, the battery may be physically opened with a needle-shaped cutting edge, and the electrolytic solution inside may be flushed out to remove the battery. Alternatively, the waste battery may be heated as it is and the electrolytic solution may be burned to make it harmless.

The outer can is often made of a metal such as aluminum (Al) or iron (Fe). By going through the pretreatment step S1, the outer can can be easily recovered as a metal. For example, aluminum and iron contained in the outer can can be recovered by crushing the removed outer can and then sieving it using a sieve shaker. Aluminum easily becomes powdery even if it is lightly pulverized, so that it can be efficiently recovered. In addition, iron contained in the outer can can be recovered by sorting by magnetic force.

[Crushing process]
In the recovery method of the present embodiment, the crushing step S2 may be provided if necessary. In the pulverization step S2, the battery contents obtained through the pretreatment step S1 are pulverized to obtain a pulverized product. By providing the pulverization step S2, the reaction efficiency in the subsequent step can be increased, and thus the recovery rate of valuable metals (Ni, Co, Cu, etc.) can be increased. The specific crushing method of the crushing step S2 is not limited. For example, a method of crushing the battery contents using a known crusher such as a cutter mixer can be mentioned.

[Oxidation roasting process]
In the oxidative roasting step S3, the pulverized product is oxidatively roasted to obtain an oxidative roasted product. By oxidative roasting, thermal decomposition components such as carbon (C) contained in the battery contents can be burned and removed. Further, impurities other than carbon (P, Fe, Mn, Al, etc.) can be made into oxides, and can be separated and removed from valuable metals as slag in a subsequent step. When the pretreatment step S1 and / or the crushing step S2 is provided, the waste lithium ion battery (battery contents, crushed product) obtained through each of the above steps becomes an object of oxidative roasting.

Since dust is generated in the oxidative roasting process, this dust is collected and effectively utilized in the subsequent melting process. That is, the waste lithium ion battery contains a large amount of carbonaceous components such as carbon and organic components. For example, carbon is often used for the negative electrode. Polypropylene is used for the separator, and plastic is used for a part of the exterior material. These carbonaceous components (carbon, organic components) are burned and removed by oxidative roasting, but some of them are incompletely burned to produce soot (carbon). This soot is discharged to the outside of the furnace and collected as dust. In addition, a part of the metal component contained in the waste lithium ion battery is volatilized and discharged to the outside of the furnace together with soot. Therefore, the recovered dust contains metal components such as valuable metals as well as soot. The dust may be recovered by a known method. For example, the dust may be discharged to the outside of the furnace together with the exhaust gas, and the dust may be separated and recovered from the exhaust gas using a dust collector.

In the oxidative roasting step S3, it is preferable to heat (oxidatively roast) at a temperature of 700 ° C. or higher. By setting the oxidative roasting temperature to 700 ° C. or higher, the efficiency of removing impurities contained in the battery can be further improved. On the other hand, the oxidative roasting temperature is preferably 900 ° C. or lower. As a result, the thermal energy cost can be suppressed and the processing efficiency can be improved.

The oxidative roasting step S3 is preferably performed in the presence of an oxidizing agent. As a result, carbon (C) among the impurities contained in the battery contents can be efficiently burned and removed, and other impurities such as aluminum (Al) can be oxidized and slagged. In particular, when carbon is burnt and removed, the molten fine particles of the valuable metal generated in the subsequent melting step S4 are likely to be aggregated and integrated without physical obstacles. Therefore, the valuable metal obtained as a melt can be easily recovered as an integrated alloy. The main elements constituting the waste battery have different affinity with oxygen, and generally, aluminum (Al)> lithium (Li)> carbon (C)> manganese (Mn)> phosphorus (P)> iron. It is easily oxidized in the order of (Fe)> cobalt (Co)> nickel (Ni)> copper (Cu).

The oxidizing agent is not particularly limited as long as it can burn off carbon and oxidize other impurities. However, oxygen-containing gases such as air, pure oxygen, and oxygen-enriched gas, which are easy to handle, are preferable. The amount of the oxidizing agent introduced can be, for example, about 1.2 times the chemical equivalent required for oxidation of each substance to be oxidized.

In the oxidative roasting step S3, a known roasting furnace can be used. However, it is preferable to use a furnace (preliminary furnace) different from the melting furnace used in the melting step S4 and perform the process in the preliminary furnace. As the roasting furnace, any type of kiln that can be oxidized by supplying oxygen while roasting the pulverized material inside the furnace can be used. As an example, a conventionally known rotary kiln and tunnel kiln (Haas furnace) can be preferably used.

[Melting process]
In the melting step S4, the oxidized roasted product is melted to obtain a molten product composed of an alloy and slag. Impurities other than carbon (P, Fe, Mn, Al, etc.) are incorporated into the slag as oxides by the melting treatment. On the other hand, valuable metals (Ni, Co, Cu, etc.) that are difficult to form oxides are melted and integrated into a fused metal, which is recovered in a subsequent step.

In the melting step S4, at least a part of the dust recovered in the oxidative roasting step S3 is added to the object to be treated (oxidized roasted product or molten product). By adding dust, the addition of a reducing agent such as graphite can be eliminated or reduced, and as a result, cost reduction can be achieved. That is, dust contains soot (carbon) as a main component and functions as a reducing agent. By adding dust to the object to be processed in the melting step S4, reduction melting is performed in the presence of carbon contained in the dust, and oxides of valuable metals (Ni, Co, Cu, etc.) contained in the object to be processed are easily formed. And it is efficiently reduced. The thermite method using a metal powder such as aluminum is known as a reduction method, but the reduction using carbon also has an advantage that it is extremely safer than the thermite method.

Moreover, dust contains metal components such as valuable metals in addition to soot (carbon). In fact, as investigated by the present inventors, dust contains carbon in an amount of about 60% by mass, and other components such as nickel (Ni) and cobalt (Co) in an amount of about 40% by mass. It was included. Therefore, by adding dust in the melting step S4, the valuable metal (Ni, Co, Cu, etc.) discharged as dust can be returned to the valuable metal alloy, and the recovery rate of the valuable metal can be improved.

A part of the recovered dust may be added to the object to be processed in the melting step S4, or all of them may be added. The amount of dust added should be adjusted so that valuable metals (Ni, Co, Cu, etc.) contained in the object to be treated can be melted and reduced to alloy them, and impurities (P, Fe, Mn, Al, etc.) are not reduced. good. Specifically, the ratio of carbon content in the dust may be analyzed in advance, and the amount of dust added may be determined based on the obtained carbon ratio and the required degree of reduction.

If necessary, a reducing agent other than dust may be added to the object to be treated in the melting step S4. That is, if dust alone is insufficient to sufficiently reduce the valuable metal in the object to be treated, another reducing agent may be additionally added. Other reducing agents include, for example, graphite capable of reducing 2 mol of valuable metal oxide with 1 mol of carbon. Further, a carbon source such as a hydrocarbon capable of reducing 2 to 4 mol of a valuable metal oxide per 1 mol of carbon and carbon monoxide capable of reducing 1 mol of a valuable metal oxide per 1 mol of carbon can be used.

In the melting step S4, flux may be added to the oxidized roasted product. The flux preferably contains an element that incorporates an impurity element to form a basic oxide having a low melting point, and among them, a flux containing a calcium compound that is inexpensive and stable at room temperature is more preferable. Since phosphorus becomes an acidic oxide when oxidized, the more basic the slag formed by the treatment in the melting step S4, the easier it is for phosphorus to be incorporated into the slag. Examples of the calcium compound include calcium oxide (CaO) and calcium carbonate (CaCO ₃ ).

When the flux is added, the dust and / or carbon as the reducing agent described above may be added in excess. In the absence of flux, excessive carbon addition may reduce the phosphorus compound in the waste battery and mix phosphorus into the fusion metal. On the other hand, when the waste battery is melted in the presence of the flux, even if the carbon is excessive, the flux takes in the phosphorus compound and suppresses the mixing into the fusion metal.

In the melting step S4, a flux component other than the calcium compound may be added. However, it is preferable that the flux is added so that the ratio of the calcium component and the silicon component in the slag after melting (mass ratio SiO _{2 / CaO) based on the oxide is 0.50 or less.} Here, the ratio is the mass ratio of silicon dioxide to calcium oxide. Silicon components such as silicon dioxide are difficult to volatilize by heating in the melting step S4, and become acidic oxides when slagged. By reducing the silicon component with respect to the calcium compound forming the basic oxide, the slag tends to be basic, so that the slag easily takes up phosphorus. That is, by adding the flux so that the mass ratio of silicon dioxide to calcium oxide becomes small, it is possible to promote the uptake of phosphorus into the slag and suppress the mixing of phosphorus into the alloy.

Further, it is preferable to add the flux so that the ratio of calcium oxide to aluminum oxide in the melted slag based on the oxide (mass ratio CaO / Al ₂ O ₃ ) is 0.30 or more and 2.00 or less. The flux may be added so that the mass ratio CaO / Al ₂ O ₃ is 0.40 or more, or the mass ratio CaO / Al ₂ O ₃ is 1.90 or less. Aluminum oxide is a component that raises the melting point of slag. Therefore, if the amount of aluminum oxide is large in the melting step S4, a sufficient amount of calcium component is required to melt the aluminum oxide. Aluminum oxide is a component that forms an amphoteric oxide, and can be either an acidic oxide or a basic oxide. Therefore, by adjusting the ratio of the amount of aluminum oxide to the amount of the calcium compound forming the basic oxide within a predetermined range, it is possible to appropriately control the melting of aluminum oxide and the acidity at the time of melting, and as a result, phosphorus. Can be easily incorporated into the slag.

When adding the flux, the mass ratio of each mass ratio in the slag after melting may be adjusted by adjusting the amount of flux added, or by adjusting the concentration of the component contained in the flux. Further, the flux may be added so that the calcium oxide contained in the melted slag is preferably 10% by mass or more, more preferably 15% by mass or more, and further preferably 21% by mass or more based on the oxide. As a result, the recovery rate of valuable metals, particularly cobalt (Co), can be increased. On the other hand, from the viewpoint of economy, the flux may be added so that the calcium oxide contained in the slag after melting is 80% by mass or less, or 60% by mass or less. The mass of each component in the "oxide standard" is the mass of the oxide when it is assumed that all the components contained in the slag after melting are changed to oxide.

The heating temperature (melting temperature) in the melting process is not particularly limited. However, the melting temperature is preferably 1300 ° C. or higher, more preferably 1350 ° C. or higher. In the melting process of 1300 ° C. or higher, the valuable metal is sufficiently melted and the fluidity of the fused metal becomes sufficiently high. Therefore, the separation efficiency between the fused metal (valuable metal) and the slag (impurities) is improved in the slag separation step S5 described later. On the other hand, if the melting temperature exceeds 1500 ° C., heat energy is wasted and the refractory materials such as the pot and the furnace wall are consumed severely, which may reduce the productivity. Therefore, it is preferable to set the melting temperature to 1500 ° C. or lower.

Dust, exhaust gas, and the like may be generated during the melting treatment, but these can be detoxified by performing a conventionally known exhaust gas treatment.

[Slag separation process]
In the slag separation step S5, the slag is separated from the melt obtained in the melting step S4, and the molten metal containing a valuable metal is recovered. Since the slag and the alloy contained in the melt have different specific densities, the slag and the alloy can be recovered by utilizing the difference in the specific densities. The treatment method for recovering the valuable metal from the alloy is not particularly limited, and a known method such as a neutralization treatment or a solvent extraction treatment may be used. In the case of an alloy composed of cobalt (Co), nickel (Ni) and copper (Cu), after leaching a valuable metal with an acid such as sulfuric acid (leaching step), copper is extracted by solvent extraction or the like (extracting step). ), A method of using the remaining nickel and cobalt solution for the production of the positive electrode active material in the battery production process can be mentioned as an example.

As described above, in the method of the present embodiment, the alloy containing a valuable metal is effective by utilizing the dust discharged in the oxidative roasting process as a reducing agent in the melting process without discarding it. Can be obtained. Further, since the addition of a reducing agent such as graphite can be eliminated or reduced, it also leads to cost reduction. Further, the valuable metal discharged as dust can be returned to the alloy, and the recovery rate of the valuable metal can be improved. As a result, valuable metals can be recovered inexpensively and efficiently.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

<Pretreatment process>
First, as waste lithium-ion batteries, 18650-inch cylindrical batteries, used batteries of square batteries for vehicles, and defective products collected in the battery manufacturing process were prepared. Then, the waste lithium ion batteries are collectively immersed in salt water to be discharged, then the water is removed, and the batteries are roasted in the air at a temperature of 260 ° C. to decompose and remove the electrolytic solution and the outer can, and the battery contents are removed. I got something. The main elemental compositions of the battery contents are as shown in Table 1 below.

<Crushing process>
The obtained battery contents were crushed by a crusher (trade name: Good Cutter, manufactured by Ujiie Seisakusho Co., Ltd.) to obtain a crushed product.

<Oxidation roasting process>
The obtained pulverized product was put into a rotary kiln and oxidatively roasted at 800 ° C. in the air for 180 minutes to obtain an oxidative roasted product.

This crushed material was roasted by introducing air into a rotating rotary kiln, and the dust generated in the furnace was collected by a dust collecting filter provided in an exhaust path. The main components in the dust were as shown in Table 2 below.

<Melting process>
Calcium oxide and silicon dioxide were added as fluxes to the obtained oxidized roasted product, and a reducing agent was added to adjust the degree of redox, and these were mixed and charged into an alumina crucible. This was heated to 1400 ° C. by resistance heating and melted for 60 minutes to obtain a melt. Valuable metals were alloyed in the melt.

As the reducing agent, dust obtained from the oxidative roasting step was used in Example 1, and graphite fine powder was used in Comparative Example 1 so that the carbonaceous components were added in the same amount. The amount of carbonaceous component was the same as the total number of moles of copper, nickel, and cobalt contained in the roasted oxidized product.

<Slag separation process>
With respect to the obtained melt, slag was separated from the melt by utilizing the difference in specific densities, and the alloy was recovered.

The recovered alloy was also subjected to elemental analysis using an ICP analyzer (Agilent5100SUDV manufactured by Agilent Technologies, Inc.) to determine the contents of copper, nickel and cobalt. Next, the obtained content was compared with the main elemental composition of the battery contents obtained in the pretreatment step, and the recovery rate of copper, nickel and cobalt to be recovered as valuable metals was calculated. The obtained results are shown in Table 3 below.

As described above, in Example 1, the dust discharged in the oxidative roasting step was used as a reducing agent in the melting step, so that it is not necessary to use the graphite fine powder used as the reducing agent in Comparative Example 1. , Cost reduction. Further, as can be seen from Table 3, in Example 1, the valuable metal discharged as dust could be returned to the alloy, so that the recovery rate of the valuable metal could be improved.

Claims (3)

A method of recovering valuable metals from waste lithium-ion batteries.
An oxidative roasting step of oxidatively roasting the waste lithium ion battery to obtain an oxidative roasted product,
A melting step of melting the oxidized roasted product to obtain a melt, and
It has a slag separation step of separating slag from the melt and recovering an alloy containing a valuable metal.
A method of recovering dust generated in the oxidation roasting step and adding at least a part of the recovered dust to an object to be processed in the melting step. The method according to claim 1, wherein the valuable metal is at least one selected from cobalt (Co), nickel (Ni), and copper (Cu). The method according to claim 1 or 2, wherein the heating temperature in the melting step is 1300 ° C. or higher and 1500 ° C. or lower.

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