JP2024053446A - Metal recovery method - Google Patents

Abstract

To provide a metal recovery method capable of effectively recovering one or more target metals selected from a group consisting of cobalt, nickel and manganese as metal salts from lithium ion battery waste.SOLUTION: A method for recovering a metal containing one or more target metals selected from the group consisting of cobalt, nickel, and manganese from battery powder of lithium ion battery waste, the method comprising: leaching the battery powder with an acid to obtain a metal-containing solution as a post-leaching solution in which one or more target metals are dissolved; and raising the pH of the metal-containing solution to obtain a neutralized residue containing the one or more target metals, By leaching the neutralized residue together with the battery powder in the leaching step and repeating a series of steps including the leaching step and the neutralization step, a concentration of the one or more target metals in the metal-containing solution is increased, after the leaching and before the neutralization step, the one or more target metals are precipitated from the metal-containing solution to obtain a metal salt containing one or more target metals.SELECTED DRAWING: Figure 1

Description

This specification discloses a method for recovering metals.

In recent years, from the perspective of effective resource utilization, there has been widespread consideration of using wet processing to recover valuable metals such as cobalt and nickel that may be contained in waste lithium-ion secondary batteries that have been discarded due to product life, manufacturing defects, or other reasons.

In the process of recovering valuable metals from lithium-ion battery waste, for example, lithium-ion battery waste is pretreated, such as by roasting, and then the battery powder is leached with acid to obtain a metal-containing solution as a leaching liquid in which metals that may be contained in the battery powder are dissolved. Thereafter, as described in Patent Document 1, for example, the metal ions in the metal-containing solution are separated by neutralization, solvent extraction, or the like, and the valuable metals are recovered.

International Publication No. 2018/181816

In the metal recovery process described above, if the metals can be recovered in the form of metal salts containing one or more of the target metals cobalt, nickel, and manganese, it may be possible to use them directly as raw materials for manufacturing positive electrode materials for lithium-ion batteries. For example, if a mixed metal salt containing metal salts of the three target metals cobalt, nickel, and manganese is obtained, it is considered possible to use it directly as raw materials for manufacturing ternary positive electrode materials for lithium-ion secondary batteries. In this case, simplification of the process and significant cost reduction are expected.

This specification provides a metal recovery method that can effectively recover one or more target metals selected from the group consisting of cobalt, nickel, and manganese as metal salts from lithium ion battery waste.

The metal recovery method disclosed in this specification is a method for recovering metals, including one or more target metals selected from the group consisting of cobalt, nickel, and manganese, from battery powder of lithium-ion battery waste, and includes a leaching step in which the battery powder is leached with an acid to obtain a metal-containing solution as a post-leaching solution in which the one or more target metals are dissolved, and a neutralization step in which the pH of the metal-containing solution is increased to obtain a neutralization residue containing the one or more target metals. The neutralization residue is leached together with the battery powder in the leaching step, and a series of steps including the leaching step and the neutralization step are repeated to increase the concentration of the one or more target metals in the metal-containing solution, and a crystallization step in which the one or more target metals are precipitated from the metal-containing solution after the leaching step and before the neutralization step to obtain a metal salt containing the one or more target metals.

The above-mentioned metal recovery method makes it possible to effectively recover one or more target metals selected from the group consisting of cobalt, nickel, and manganese as metal salts from lithium ion battery waste.

FIG. 1 is a flow diagram showing a metal recovery method according to one embodiment. FIG. 1 is a flow diagram showing an example of a pretreatment process for obtaining battery powder from lithium ion battery waste. 1 is a graph showing the saturation concentration of each metal versus liquid temperature for verifying the effect.

Hereinafter, an embodiment of the above-mentioned metal recovery method will be described in detail.
One embodiment of the metal recovery method is a method for recovering metals from battery powder of lithium ion battery waste, the metals to be recovered including one or more target metals selected from the group consisting of cobalt, nickel, and manganese.

As shown in Figure 1, this method involves repeating a series of steps including a leaching step in which battery powder is leached with acid to obtain a metal-containing solution as a post-leaching liquid in which one or more target metals are dissolved, and a neutralization step in which the pH of the metal-containing solution is increased to obtain a neutralization residue containing one or more target metals. The neutralization residue obtained in the neutralization step is subjected to the leaching step, in which it is leached together with the battery powder. In this way, by repeating the series of steps, one or more target metals in the metal-containing solution are concentrated, and their concentration gradually increases.

Then, when the series of steps is repeated and the concentration of one or more target metals in the metal-containing solution becomes high to a certain extent, a crystallization step is carried out after the leaching step and before the neutralization step, in which one or more target metals are precipitated from the metal-containing solution to obtain a metal salt containing one or more target metals. This makes it possible to effectively recover one or more target metals as metal salts. When the crystallization step is carried out, a metal-containing solution is obtained as a post-crystallization liquid in which one or more target metals are dissolved, and this metal-containing solution is then subjected to the neutralization step.

If lithium is dissolved in the metal-containing solution as the post-leaching solution obtained after the leaching step, much of the lithium remains in the solution until after the neutralization step, and the lithium-containing solution in which lithium is dissolved is obtained in the neutralization step. In this case, a hydroxide step can be performed to obtain a lithium hydroxide solution from the lithium-containing solution. In addition, if aluminum and/or iron are dissolved in the metal-containing solution as the post-leaching solution due to the battery powder containing aluminum and/or iron, the series of steps can include an impurity removal step for removing aluminum and/or iron between the leaching step and the neutralization step (before the crystallization step if a crystallization step is performed), as necessary.

(Lithium ion battery waste)
Lithium-ion battery waste is a lithium-ion secondary battery that can be used in mobile phones and various other electronic devices, and is discarded due to the end of the battery product's life, manufacturing defects, or other reasons. From the viewpoint of effective use of resources, it is preferable to recover valuable metals from such lithium-ion battery waste. Lithium-ion battery waste refers to lithium-ion batteries that are subject to recycling, and it does not matter whether the lithium-ion batteries are traded for a value, or traded free of charge or as industrial waste.

Waste lithium-ion batteries have a housing that contains aluminum as the exterior that encases them. For example, this housing may be made of only aluminum, or may contain aluminum and iron, aluminum laminate, etc.

In addition, lithium-ion battery waste may contain, within the above-mentioned casing, a positive electrode active material made of a single metal oxide containing lithium and one selected from the group consisting of nickel, cobalt, and manganese, or a composite metal oxide containing two or more types of lithium and an aluminum foil (positive electrode substrate) to which the positive electrode active material is coated and fixed with, for example, polyvinylidene fluoride (PVDF) or other organic binder. In addition, lithium-ion battery waste may contain copper, iron, etc.

The casing of lithium-ion battery waste typically contains an electrolyte solution in which an electrolyte such as lithium hexafluorophosphate is dissolved in an organic solvent. Examples of organic solvents that may be used include ethylene carbonate and diethyl carbonate.

(Pretreatment process)
Lithium ion battery waste is often subjected to a pretreatment process before dry processing. The pretreatment process may include at least one of roasting, crushing, and sieving. Lithium ion battery waste is turned into battery powder through the pretreatment process. The roasting, crushing, and sieving processes in the pretreatment process may be performed individually as necessary, or may be performed in any order. In the example shown in FIG. 2, roasting, crushing, and sieving are performed in this order.

The term "battery powder" refers to powder in which the positive electrode material components have been separated and concentrated by subjecting lithium-ion battery waste to some kind of processing. Battery powder can also be obtained as a powder in which the positive electrode material components have been concentrated by crushing and sieving lithium-ion battery waste with or without heat treatment.

In the roasting process, the lithium ion battery waste is heated. When roasting is performed, for example, metals such as lithium and cobalt contained in the lithium ion battery waste can be converted into a form that is easily soluble. In the roasting process, it is preferable to heat the lithium ion battery waste at a temperature range of, for example, 450°C to 1000°C, or further 600°C to 800°C for 0.5 to 4 hours. Roasting can be performed in an air atmosphere or an inert atmosphere such as nitrogen, or it can be performed in both an air atmosphere and an inert atmosphere in this order or in the reverse order. The roasting furnace can be of a batch type or a continuous type. For example, a stationary furnace is used for the batch type, and a rotary kiln furnace is used for the continuous type, and various other furnaces can also be used.

During roasting, at least a portion of the electrolyte is removed from the lithium-ion battery waste by evaporating the electrolyte, etc. In many cases, when lithium-ion battery waste is heated during roasting, the electrolyte components inside the waste evaporate in order, starting with those with low boiling points. When roasting is performed, the electrolyte is removed and rendered harmless, and the organic binder is decomposed, facilitating the separation of the aluminum foil and the positive electrode active material during crushing and sieving, which will be described later. Note that the composition of the positive electrode active material changes due to roasting, but here we will refer to it as a positive electrode active material even if it has been roasted.

After roasting, the lithium-ion battery waste can be crushed to remove the positive electrode active material and other materials from the casing. In the crushing process, the casing of the lithium-ion battery waste is destroyed and the positive electrode active material is selectively separated from the aluminum foil on which it is applied.

Various known devices or equipment can be used for crushing, but it is particularly preferable to use an impact crusher that can crush the lithium ion battery waste by applying an impact while cutting it. Examples of this impact crusher include a sample mill, hammer mill, pin mill, wing mill, tornado mill, and hammer crusher. A screen can be installed at the outlet of the crusher, so that the lithium ion battery waste is discharged from the crusher through the screen when it has been crushed to a size that can pass through the screen.

After the lithium-ion battery waste is crushed, it is sieved using a sieve with appropriate mesh size. This leaves aluminum and copper on the sieve, and battery powder with aluminum and copper removed to a certain extent is obtained below the sieve.

The battery powder obtained in the pretreatment process contains one or more target metals selected from the group consisting of cobalt, nickel, and manganese. In addition, the battery powder may contain at least one metal selected from the group consisting of lithium, aluminum, iron, and copper. For example, the battery powder has a cobalt content of 1% to 30% by mass, a nickel content of 1% to 30% by mass, a manganese content of 1% to 30% by mass, a lithium content of 2% to 8% by mass, an aluminum content of 1% to 10% by mass, an iron content of 1% to 5% by mass, and a copper content of 1% to 10% by mass.

The battery powder can be brought into contact with water before the leaching step described below in order to extract essentially only lithium from the battery powder. This causes the lithium in the battery powder to leach into the water. In this case, the battery powder as the water leaching residue is subjected to the leaching step. However, when water leaching is performed, the equipment is required, and the processing time increases by performing both the water leaching and the acid leaching in the leaching step. In addition, it may be necessary to control the conditions of roasting, etc., in order to effectively leach lithium with water. Even if such control is performed, the leaching rate of lithium with water may not be increased significantly. Therefore, the battery powder obtained as described above may be subjected to acid leaching in the leaching step without water leaching. When water leaching is not performed, it is easier to maintain a high lithium ion concentration in the liquid in the wet processing after the leaching step.

(Leaching process)
In the leaching process, the battery powder is added to an acidic leaching solution containing sulfuric acid, nitric acid, hydrochloric acid or other inorganic acid, and metals including one or more target metals selected from the group consisting of cobalt, nickel and manganese contained in the battery powder are leached with the acid.

The leaching process can be carried out using known methods or conditions, but the pH may be between 0.0 and 2.0, and the oxidation-reduction potential (ORP value, silver/silver chloride potential standard) may be 0 mV or less.

The leaching residue that remains after the acid leaching can be separated from the metal-containing solution by solid-liquid separation, such as filtration, using known devices and methods, such as a filter press or thickener. In some cases, much of the copper in the battery powder can be contained in the leaching residue. This solid-liquid separation can be omitted, and the next process after leaching may be carried out without solid-liquid separation.

In the leaching process, a metal-containing solution in which one or more target metals selected from the group consisting of cobalt, nickel, and manganese are dissolved is obtained as the leaching liquid. Typically, the metal-containing solution further contains at least one metal selected from the group consisting of lithium, aluminum, iron, and copper dissolved therein.

The metal-containing solution used as the post-leaching solution may have a cobalt ion concentration of 10 g/L to 50 g/L, a nickel ion concentration of 10 g/L to 50 g/L, a manganese ion concentration of 0 g/L to 50 g/L, a lithium ion concentration of 1.0 g/L to 20 g/L, an aluminum ion concentration of 1.0 g/L to 20 g/L, an iron ion concentration of 0.1 g/L to 5.0 g/L, and a copper ion concentration of 0.005 g/L to 0.2 g/L.

(Impurity Removal Process)
When the metal-containing solution obtained as the post-leaching solution in the leaching step contains a certain amount of aluminum ions and/or iron ions as impurities, the pH of the metal-containing solution can be increased to precipitate and remove aluminum and/or iron. Here, a dealumination step and an iron removal step may be performed. However, when the metal-containing solution does not substantially contain aluminum ions or iron ions, the dealumination step or the iron removal step may be omitted. When the metal-containing solution does not substantially contain either aluminum ions or iron ions, it is also possible to omit the impurity removal step.

In the dealumination stage, the pH of the metal-containing solution is increased to precipitate at least a portion of the aluminum ions, which are then removed by solid-liquid separation. At this time, for example, if the pH is increased to within the range of 4.0 to 5.0 using a pH adjuster at a liquid temperature of 50°C to 90°C, the aluminum ions can be effectively separated while suppressing the precipitation of nickel ions and cobalt ions.

In the iron removal stage, an oxidizing agent is added, and a pH adjuster is further added to raise the pH to within a range of 4.0 to 5.0. As a result, the iron ions are oxidized from divalent to trivalent, and precipitate as solids such as iron oxide or hydroxide (Fe(OH) ₃ ), which can be removed by solid-liquid separation. The oxidation-reduction potential (ORP value, silver/silver chloride potential standard) during oxidation is preferably 300 mV to 900 mV. The oxidizing agent is not particularly limited as long as it can oxidize iron, but is preferably manganese dioxide, a positive electrode active material, and/or a manganese-containing leaching residue obtained by leaching the positive electrode active material. The manganese-containing leaching residue obtained by leaching the positive electrode active material with an acid may contain manganese dioxide.

Examples of pH adjusters used in the above-mentioned dealumination and/or iron removal stages include lithium hydroxide, sodium hydroxide, sodium carbonate, ammonia, etc., but it is preferable to use a lithium hydroxide solution obtained in the hydroxide step described below. In this case, lithium ions circulate within the wet treatment.

(Crystallization process)
When the concentration of the target metal in the metal-containing solution has increased to a certain degree by repeatedly performing a series of steps including the above-mentioned leaching step, the impurity removal step in some cases, and the neutralization step described below, a crystallization step is performed after the leaching step or after the impurity removal step and before the neutralization step. By performing the crystallization step after the target metal concentration has increased, the target metal can be selectively precipitated without precipitating lithium, etc.

The crystallization process may be carried out when, through the repetition of a series of processes, the cobalt ion concentration of the metal-containing solution after the leaching process or the impurity removal process reaches 50 g/L or more, the nickel ion concentration reaches 50 g/L or more, and/or the manganese ion concentration reaches 50 g/L or more. At this time, the lithium ion concentration may be 1.0 g/L to 30 g/L.

In the crystallization process, metal salts of one or more target metals selected from the group consisting of cobalt, nickel and manganese (cobalt salts, nickel salts and/or manganese salts) are precipitated from the metal-containing solution after the leaching process or the impurity removal process.

The one or more target metals referred to here are two or more target metals selected from the group consisting of cobalt, nickel, and manganese, and when two or more target metals selected from the group consisting of cobalt, nickel, and manganese are dissolved in the metal-containing solution, the crystallization step causes each metal salt of the two or more target metals to precipitate, and a mixed metal salt containing those metal salts is obtained.

In the example shown in FIG. 1, the one or more target metals are three target metals, cobalt, nickel, and manganese, and the three target metals, cobalt, nickel, and manganese, are dissolved in the metal-containing solution. In this example, a mixed metal salt containing a cobalt salt, a nickel salt, and a manganese salt is obtained in the crystallization process.

In the crystallization process, for example, one or more target metals dissolved in the metal-containing solution can be crystallized by heating the metal-containing solution to a temperature of 50°C to 80°C, concentrating the solution, and then cooling it.

Thereby, a metal salt corresponding to the anion of an inorganic acid, such as sulfate ion, nitrate ion, or chloride ion, contained in the metal-containing solution is obtained. For example, when the metal-containing solution contains sulfate ion, the metal salt includes one or more selected from the group consisting of cobalt sulfate, nickel sulfate, and manganese sulfate.

Of the one or more target metals contained in the metal-containing solution, those that are not precipitated in the crystallization process remain dissolved in the post-crystallization liquid. In addition, when lithium ions are contained in the metal-containing solution that is subjected to the crystallization process, the lithium ions are often not precipitated in the crystallization process and are contained in the post-crystallization liquid.

The metal-containing solution after crystallization may have a cobalt ion concentration of 140 g/L to 180 g/L, a nickel ion concentration of 100 g/L to 150 g/L, a manganese ion concentration of 100 g/L to 150 g/L, and a lithium ion concentration of 10 g/L to 35 g/L.

(Neutralization process)
In the neutralization process, a pH adjuster is added to the metal-containing solution after the leaching process, the impurity removal process, or the crystallization process to raise the pH, thereby precipitating one or more target metals dissolved therein, thereby obtaining a neutralization residue containing the target metals.

More specifically, for example, the temperature of the metal-containing solution can be set to 60°C to 90°C, the pH to 9.0 to 10.0, and the oxidation-reduction potential (ORP value, silver/silver chloride potential standard) to 0 mV to 600 mV. Examples of pH adjusters include lithium hydroxide, sodium hydroxide, sodium carbonate, and ammonia, but it is preferable to use the lithium hydroxide solution obtained in the hydroxide process described below. In this case, lithium ions circulate within the wet treatment.

In most cases, the target metals are precipitated as hydroxides (cobalt hydroxide, nickel hydroxide, and/or manganese hydroxide) in _the neutralization residue, and may also contain oxides of the target metals _{( Co3O4} , _Mn3O4 , _{Mn2O3 , Ni3O4} , _etc. ).

The neutralization residue can be separated from the solution by solid-liquid separation. In this embodiment, as shown in FIG. 1, the neutralization residue is subjected to a leaching process, in which it is leached together with the battery powder. As a result, the target metal transferred to the neutralization residue in the neutralization process is leached in the leaching process and is included again in the metal-containing solution. By repeating a series of processes including the leaching process and the neutralization process in this manner, the target metal circulating in the series of processes is added to the target metal in the newly added battery powder, thereby increasing the concentration of the target metal in the metal-containing solution. When the concentration of the target metal in the metal-containing solution has reached a certain level, a crystallization process is performed as described above to obtain a metal salt of the target metal.

In addition, since the lithium ions in the metal-containing solution are not substantially precipitated in the neutralization process, the neutralization residue contains almost no lithium. If the neutralization residue containing the target metal but not lithium is subjected to the leaching process and the series of steps is repeated, the concentration of the target metal in the metal-containing solution increases significantly in the series of steps, but the lithium ion concentration does not increase significantly. For this reason, if the above-mentioned crystallization process is performed on such a metal-containing solution, the target metal is more likely to crystallize before the lithium ions in the crystallization process. As a result, the target metal can be selectively precipitated in the crystallization process without precipitating the lithium ions.

The solution obtained by separating the neutralization residue in the neutralization process is a lithium-containing solution in which essentially only lithium is dissolved. The lithium-containing solution may have a lithium ion concentration of 10 g/L to 35 g/L. This lithium-containing solution can be subjected to the hydroxide process described below.

(Hydroxylation process)
In the hydroxide step, a lithium hydroxide solution is obtained from the lithium-containing solution such as a lithium sulfate solution. The details of the hydroxide step are not particularly limited as long as the lithium hydroxide solution can be produced, but for example, a method using electrodialysis, a chemical conversion method using barium hydroxide, a chemical conversion method using calcium hydroxide after producing lithium carbonate, etc. can be adopted.

In electrodialysis, in a bipolar membrane electrodialysis device, a lithium-containing solution is placed in the desalting chamber between the anion exchange membrane and the cation exchange membrane, while pure water is placed in the acid chamber between the bipolar membrane and the anion exchange membrane and the alkaline chamber between the cation exchange membrane and the bipolar membrane, and a voltage is applied between the electrodes. This causes the lithium ions in the metal-containing solution in the desalting chamber to move to the alkaline chamber, where the bipolar membrane breaks down the pure water into hydroxide ions, producing a lithium hydroxide solution.

In the case of the carbonation and chemical formation method, a lithium carbonate solution is first obtained by adding carbonate to a lithium-containing solution or by blowing carbon dioxide gas into the solution. Then, in the so-called chemical formation method, calcium hydroxide is added to the lithium carbonate solution to generate a _lithium hydroxide solution under the reaction formula _Li2CO3 +Ca(OH) ₂ →2LiOH+ _CaCO3 . Calcium ions that may remain in the solution can be removed by a cation exchange resin, a chelating resin, or the like.

When barium hydroxide is used, it is possible to obtain a lithium hydroxide solution by adding _barium hydroxide to a lithium-containing solution and carrying out the reaction _Li2SO4 + Ba(OH) ₂ → 2LiOH + _BaSO4 . Note that barium that may dissolve in the solution at this time can be separated and removed using a cation exchange resin, a chelating resin, or the like.

The lithium hydroxide solution obtained in this manner can be effectively used as an alkaline pH adjuster in the neutralization process, as shown in Figure 1.

After the hydroxide, lithium hydroxide may be precipitated from the lithium hydroxide solution by a crystallization procedure such as heating and concentration or vacuum distillation. In the case of heating and concentration, the higher the temperature during crystallization, the faster the process proceeds, which is preferable. However, after crystallization, the crystallized material is preferably dried at a temperature of less than 60°C, at which water of crystallization does not desorb. If water of crystallization desorbs, the resulting product becomes anhydrous lithium hydroxide, which is deliquescent and difficult to handle. The lithium hydroxide can then be subjected to a grinding process or the like to adjust the physical properties required.

(Verification of effectiveness)
The saturation concentrations of cobalt, nickel, manganese and lithium were confirmed according to the Chemical Handbook, Basic Edition, 3rd Revised Edition (published by Maruzen Publishing, June 1984, edited by the Chemical Society of Japan), and were as shown in the graph in Figure 3. Although not shown in Figure 3, the saturation concentration of manganese at 20°C was 143 g/L.

This shows that if crystallization is performed when the concentrations of cobalt, nickel, and manganese are high enough, cobalt, nickel, and manganese can be precipitated without precipitating lithium.

The above suggests that the above-mentioned metal recovery method may be able to effectively recover one or more target metals selected from the group consisting of cobalt, nickel, and manganese as metal salts from lithium-ion battery waste.

Claims (8)

A method for recovering metals, including one or more target metals selected from the group consisting of cobalt, nickel, and manganese, from battery powder of lithium ion battery waste, comprising the steps of:
The method includes a leaching step of leaching the battery powder with an acid to obtain a metal-containing solution as a leaching solution in which the one or more target metals are dissolved, and a neutralization step of increasing the pH of the metal-containing solution to obtain a neutralization residue containing the one or more target metals,
the neutralization residue is leached together with the battery powder in the leaching step, and a series of steps including the leaching step and the neutralization step are repeated to increase the concentration of the one or more target metals in the metal-containing solution;
A metal recovery method comprising a crystallization step, subsequent to the leaching step and prior to the neutralization step, of precipitating the one or more target metals from the metal-containing solution to obtain a metal salt containing the one or more target metals. The metal recovery method according to claim 1, wherein the one or more target metals are two or more target metals selected from the group consisting of cobalt, nickel, and manganese. The metal recovery method according to claim 2, wherein the one or more target metals are three target metals: cobalt, nickel, and manganese. Lithium is dissolved in the metal-containing solution as the post-leaching solution,
In the neutralization step, a lithium-containing solution in which lithium is dissolved is obtained,
The metal recovery method according to any one of claims 1 to 3, further comprising a hydroxide step of obtaining a lithium hydroxide solution from the lithium-containing solution. The metal recovery method according to claim 4, wherein the lithium hydroxide solution is used as a pH adjuster in the neutralization step. The metal recovery method according to any one of claims 1 to 3, wherein the neutralization residue contains hydroxides of the one or more target metals. The metal-containing solution as the post-leaching solution contains dissolved aluminum and/or iron,
The metal recovery method according to any one of claims 1 to 3, wherein the series of steps further includes an impurity removal step between the leaching step and the neutralization step, in which the pH of the metal-containing solution is increased to precipitate and remove aluminum and/or iron. The metal recovery method according to any one of claims 1 to 3, wherein the crystallization step is performed when the cobalt ion concentration of the metal-containing solution becomes 50 g/L or more, when the nickel ion concentration becomes 50 g/L or more, and/or when the manganese ion concentration becomes 50 g/L or more, by repeating the series of steps.