KR20120021256A - Method of leaching cathode active material - Google Patents

Abstract

An object of the present invention is to efficiently leach nickel, cobalt, manganese and lithium from the positive electrode active material of a lithium ion secondary battery, thereby obtaining a liquid solution suitable for separating each metal.
The present invention is a method for recovering a valuable metal from a positive electrode active material of a lithium ion battery composed of a complex oxide composed of a transition metal containing at least manganese, wherein the aqueous solution to which sulfuric acid is added is soluble in a sulfuric acid solution in the positive electrode active material. And a second step of dissolving the component and a second step of further leaching the unleached component remaining in the sulfuric acid leaching slurry by adding hydrogen peroxide to the sulfuric acid leaching slurry solution without solid-liquid separation after the first step. It is a leaching method of the positive electrode active material.

Description

Leaching method of positive electrode active material {METHOD OF LEACHING CATHODE ACTIVE MATERIAL}

The present invention relates to a method for leaching valuable metals from a positive electrode active material of a lithium ion battery composed of a complex oxide composed of a transition metal containing at least manganese.

As a method of leaching the positive electrode active material, Japanese Patent Application Laid-open No. Hei 10-287864 (Patent Document 1) has a leaching method using an inorganic acid and hydrogen peroxide, but an inorganic acid and hydrogen peroxide of 1 to 5 times in molar ratio with respect to the metal in the positive electrode active material. We use each. In this method, since inorganic acid and hydrogen peroxide are excessive, a large amount of acid or hydrogen peroxide will remain in the leaching liquid after leaching. Therefore, when further providing a separation process such as solvent extraction in a later step, it is necessary to add a neutralizing agent in order to neutralize the remaining acid. In addition, the residual hydrogen peroxide may deteriorate by oxidizing the extraction solvent in solvent extraction. For this reason, although it is preferable to remove beforehand solvent extraction, the chemical | medical agent which removes hydrogen peroxide from a leach liquid is needed.

In Japanese Patent Application Laid-Open No. 2007-122885 (Patent Document 2), valuable metals such as lithium, nickel, and cobalt contained in a positive electrode active material and the like are leached using sulfuric acid during recycling of a lithium ion battery. Techniques for promoting leaching with a fixed carbon content such as are described.

Japanese Patent Application Laid-Open No. 11-167936 (Patent Document 3) describes a method of leaching a positive electrode active material using hydrochloric acid as a specific form in which desired problems are solved.

In Japanese Patent Application Laid-Open No. 2008-231522 (Patent Document 4), after leaching manganese, cobalt, and nickel with hydrochloric acid or sulfuric acid from waste lithium battery residues, solvent extraction is carried out from this leaching solution to form manganese and cobalt-nickel. A method of separating is disclosed.

Japanese Patent Application Laid-open No. Hei 10-287864 Japanese Patent Application Publication No. 2007-122885 Japanese Patent Application Laid-open No. Hei 11-167936 Japanese Patent Application Publication No. 2008-231522

According to the method described in Patent Literature 1, in order to leach the positive electrode active material, an acid, hydrogen peroxide, or the like is excessively required, and there is a problem that treatment with a neutralizing agent and a reducing agent is necessary separately before handling the leached solution. . In addition, according to the method described in Patent Document 2, it is necessary to use a fixed carbon content as an adsorbent material, and the leaching promoting effect by this content is not applied to all of the positive electrode active materials, but can be adsorbed onto the fixed carbon content. Since it is limited, there exists a subject that the positive electrode active material which is collect | recovered is limited. Moreover, when hydrochloric acid is used at the time of leaching of a positive electrode active material like the method specifically described in patent document 3, there exists a possibility that chlorine gas may generate | occur | produce during a leaching reaction, and there exists a problem that it is not preferable.

In addition, when the leaching liquor is used for solvent extraction as in the method described in Patent Literature 4, high valence manganese ions are difficult to back-extract, and may remain in the organic phase during back-extraction, in which case manganese ions remain. The organic phase is repeatedly used for extraction, and there is a problem that it may not be very desirable from the viewpoint of recovery of precious metals.

In view of these problems, an object of the present invention is to provide a method for efficiently leaching valuable metals from a positive electrode active material of a lithium ion secondary battery. In another aspect, an object of the present invention is to provide a method for preparing a liquid solution suitable for separating each ionic species without using a medicament.

MEANS TO SOLVE THE PROBLEM This inventor discovers that after leaching a positive electrode active material with sulfuric acid and using hydrogen peroxide, it can achieve high leaching efficiency, reducing the quantity of sulfuric acid and hydrogen peroxide required for leaching, compared with a conventional technique. By adding a positive electrode active material to the solution after leaching, manganese ions in the solution are reduced to divalent and the remaining acid is consumed without adding a chemical agent such as a neutralizing agent or a reducing agent. A method of obtaining a preferred liquid solution was found.

This invention is completed based on the said knowledge, and is a method of leaching the positive electrode active material of the lithium ion battery provided with the following characteristic.

(1) A method of leaching a valuable metal from a positive electrode active material of a lithium ion battery composed of a complex oxide composed of a transition metal containing at least manganese,

1st process which melt | dissolves the component which is soluble in the sulfuric acid solution in the said positive electrode active material in the aqueous solution which added sulfuric acid,

And a second step of adding hydrogen peroxide to the sulfuric acid leaching slurry solution to further leach out the unleached component remaining in the sulfuric acid leaching slurry after the first step, without solid-liquid separation.

(2) In the leaching method of the positive electrode active material according to (1),

In addition, the third step of lowering the redox potential of the leachate after-treatment obtained in the second step, raising the pH,

After the solid-liquid separation of the reaction liquid obtained in the 3rd process, manganese is extracted with an organic phase by solvent extraction, and then the organic phase is back-extracted with an acidic aqueous solution, and the 4th process of obtaining an aqueous solution of manganese consists of the positive electrode active material characterized by the above-mentioned. Leaching method.

(3) In the leaching method of the positive electrode active material according to (2),

At the said 3rd process, the positive electrode active material is added to the leaching liquid obtained by the said 2nd process, The leaching method of the positive electrode active material characterized by the above-mentioned.

(4) The leaching method of the positive electrode active material according to any one of (1) to (3), wherein the positive electrode active material contains oxides of nickel, cobalt, manganese, and lithium contained in the positive electrode active material as main components, and The amount of sulfuric acid is used in an amount less than the total number of moles of the number of moles of nickel, cobalt, manganese and lithium, the leaching method of the positive electrode active material.

(5) In the leaching method of the positive electrode active material according to (4),

The amount of hydrogen peroxide added is used in an amount of 0.8 to 1.2 times the amount of nickel, cobalt, and manganese contained in the positive electrode active material not dissolved in the sulfuric acid solution in the first step of the positive electrode active material. Leaching method.

(6) The leaching method of the positive electrode active material according to any one of (1) to (5),

The positive electrode active material is added to the leaching liquor by sulfuric acid and hydrogen peroxide, and the value of the redox potential is adjusted to 700 Pa (vs. Ag / AgCl) or less, and the back extraction of manganese from the organic phase of solvent extraction is promoted. Leaching method of a positive electrode active material.

(7) In the leaching method of the positive electrode active material according to any one of (1) to (6), the positive electrode active material is added and stirred to the leaching liquid obtained in the second step, and the pH of the leaching liquid is 2.5 or more. It raises, The leaching method of the positive electrode active material characterized by the above-mentioned.

According to the present invention, in leaching of the positive electrode active material of a lithium ion battery,

1) Sulfuric acid is used during leaching, so no chlorine gas is generated.

2) Since the positive electrode active material soluble in sulfuric acid is first leached with sulfuric acid, the amount of hydrogen peroxide used can be reduced.

3) The manganese ions in the solution after leaching can be reduced to divalent, and a liquid solution suitable for separation of ionic species such as solvent extraction can be prepared.

The effect to be obtained is acquired and nickel, cobalt, manganese, and lithium can be leached efficiently from the positive electrode active material of a lithium ion battery.

1 is a diagram illustrating a flow up to extraction of manganese.
2 is a view showing a leaching flow of a positive electrode active material.
3 is a graph showing ORP and pH change of a leach solution during leaching of a positive electrode active material.
4 is a diagram schematically illustrating a color comparison of an organic phase after back extraction by solvent extraction from a leaching liquid.

One embodiment of the present invention is shown in FIG. 1. The material used as a leach treatment object is a non-standard positive electrode active material (off-spec) produced during the manufacturing process of a lithium ion battery, a positive electrode active material, the quality control of the extraction inspection processed product, the residue obtained by the method of this invention. And so on. A positive electrode active material is a composite oxide containing lithium nickelate, lithium cobalt acid, lithium manganate, and nickel, cobalt, manganese, and lithium in various ratios.

Since the positive electrode active material contains components which can be leached with sulfuric acid, first, leaching is carried out using sulfuric acid for these components to obtain a sulfuric acid leaching slurry solution (first step). At this time, the amount of sulfuric acid added is conventionally higher than the total number of moles of the valuable metals in consideration of total leaching, equivalent amount, and efficiency. However, in the present invention, nickel, cobalt, and manganese in the positive electrode active material are common. Less than the sum of the number of moles of lithium and the viewpoint of the efficiency of dissolution, nickel, [(the sum of the number of moles of cobalt, manganese, lithium)-(number of moles of lithium x 0.5)] is preferable. For example, when nickel, cobalt, and manganese contain 0.1 mol and 0.3 mol of lithium, respectively, in the positive electrode active material, the amount of sulfuric acid used for the leaching treatment is usually 0.1 + 0.1 + 0.1 + 0.3 = 0.6 It is less than mole, and considering the efficiency of leaching, 0.1 + 0.1 + 0.1 + 0.3 * 0.5 = 0.45 mol or more is preferable. The reason for using sulfuric acid in this amount is not to leach valuable metals completely by using excess sulfuric acid, but to allow almost all of the acid to be leached in the leaching treatment in the second step even if less sulfuric acid is used. In addition to lowering the cost by suppressing the amount of used, the neutralization treatment after leaching is no longer necessary or is not necessary to be performed under severe conditions. In addition, even if liquid temperature is normal temperature, reaction advances.

Next, after the first step, hydrogen peroxide is added to the sulfuric acid leaching slurry solution without solid-liquid separation (second step). Under the present circumstances, hydrogen peroxide may be added continuously after sulfuric acid addition and stirring, and may be performed again, changing time or place. By first leaching the positive electrode active material with sulfuric acid, the amount of hydrogen peroxide used decreases. This is the first reason for leaching with sulfuric acid. The amount which can be leached with sulfuric acid depends on the composition of the positive electrode active material. For this reason, when hydrogen peroxide is added at the same time as sulfuric acid, the excess and deficiency of hydrogen peroxide generate | occur | produce. First, by leaching with sulfuric acid and adding hydrogen peroxide to the undissolved powder, the amount of hydrogen peroxide can be reduced since hydrogen peroxide is not used up to the component soluble in sulfuric acid.

In the positive electrode active material leached by sulfuric acid, nickel, cobalt, manganese, and lithium which are not completely leached remain. In order to leach them, hydrogen peroxide is added. The amount of hydrogen peroxide added is about 0.8 to 1.2 times the molar amount relative to the total molar amount of nickel, cobalt, manganese and the like, and the total molar amount of nickel, cobalt and manganese, which are not dissolved in sulfuric acid. For example, when 0.06 mol of nickel, 0.06 mol of cobalt, and 0.06 mol of manganese are contained in the positive electrode active material leached by sulfuric acid, the amount of hydrogen peroxide used for a leaching process is 0.06 + 0.06 + 0.06 = It will be about 0.18 mol, for example, 0.144 (0.18 * 0.8)-0.216 (0.18 * 1.2) mol. The addition of more hydrogen peroxide is disadvantageous in cost. In addition, the residual hydrogen peroxide may adversely affect the extraction solvent when the ionic species are separated by solvent extraction in a later step. By addition of hydrogen peroxide, leaching of nickel, cobalt, manganese and lithium, which could not be leached with sulfuric acid alone, proceeds, and sulfuric acid remaining in the solution is consumed in addition to leaching with sulfuric acid.

Usually, the solution after leaching with sulfuric acid and hydrogen peroxide is used for the separation treatment of the next metal ion, but the redox potential of the leaching solution may be lowered to increase the pH. Thereby, it is thought that the ionic species which became high-oxidation state are reduced to bivalent ions. The redox potential of the leaching liquid at this time is 700 kV (vs. Ag / AgCl) or less. This makes it possible to promote back extraction of manganese from the organic phase of solvent extraction. The reaction proceeds even at room temperature (20 to 30 ° C).

As a method of lowering the redox potential of a leachate after solution, addition of a positive electrode active material is mentioned, for example. As a positive electrode active material to add, the same effect is acquired even if it uses the leaching residue shown in FIG. Alternatively, an unleached positive electrode active material may be added, or both of the unleached positive electrode active material and the leached positive electrode active material may be added.

A method of separating metal ions from a solution, comprising: solid-liquid separation of a leaching after-liquid or a leaching after-treatment with adjusted redox potential and pH, and then using an organic solvent in the presence of an extractant to assist extraction of a given metal ion. Solvent extraction is used. The organic phase before the extraction of the metal ions is colorless, but the organic phase after the extraction of the metal ions showing color in the solution is colored. The organic phase later returns to colorlessness. Thereby, the movement between phases of a metal ion can be confirmed.

As such an extractant, a phosphoric acid extractant, a phosphonic acid extractant, etc. are mentioned, More specifically, di (2-ethylhexyl) phosphoric acid etc. are mentioned.

In the leaching process, manganese or the like may have a valence higher than divalent. Even in the same kind of metal, the phenomenon in which a plurality of metal ions having different valences are mixed in this manner becomes a problem when the solvent extraction method is performed as a method of separating each ionic species after leaching. When solvent extraction is carried out in the presence of high valence manganese ionic species in the leaching liquor, some of the manganese ions introduced into the extractant may remain in the organic phase even after the back extraction. As a result, purple color may be seen in the solvent after back extraction. This is thought to be the color of manganese ions whose valence is higher than divalent.

Although the amount of manganese remaining in the organic solvent is a small amount of several tens of mg of manganese per 1 L of the organic solvent, in the solvent extraction, the organic solvent after back extraction is generally repeated again by extraction, and the extraction is continuously performed. Manganese not accumulated is accumulated. In addition, since manganese ions having a high valence have an oxidizing power, an organic solvent may be oxidized in solvent extraction. For these reasons, it is ideal to extract all the metal ions from the organic phase by back extraction, and it is important to remove metal ions that cannot be back extracted in advance, or to adjust the valence or the like to make the ionic species capable of back extraction. Become.

As a method, when the positive electrode active material is added to the leaching liquor, the valence of manganese ions is lowered and it is easier to extract back, so that the amount of manganese remaining in the organic phase after the reverse extraction is lowered. The organic phase after back extraction is colorless.

By adding a positive electrode active material, residual sulfuric acid and hydrogen peroxide are consumed. Thereby, the pH of the leaching liquid rises. In the case of separating nickel, cobalt, manganese and lithium from the leachate after solvent extraction, weak acidity to neutrality is suitable. This is because the extraction pH of the solvent for extracting nickel, cobalt, manganese, and lithium is in a weakly acidic to neutral region. Therefore, it is not suitable when the acid concentration of a leachate liquor is high. However, if the pH after leaching is increased by a neutralizing agent such as an alkali chemical agent, a drug cost is required separately. However, if a positive electrode active material as a raw material is added, a neutralizing agent is unnecessary.

If the extraction of manganese is carried out using a phosphate extractant and a phosphonic acid extractant from the leaching liquor, it is necessary that the extraction equilibrium pH is 2.5 or more to obtain a certain amount of extraction. For this reason, it is preferable that the pH of extraction whole liquid is also close to or more than this pH, and it is preferable to make pH of a leaching liquid into 2.5 or more. This is because if the extraction is to be performed at the total extraction pH lower than the extraction equilibrium pH, in order to maintain the extraction equilibrium pH, it is necessary to simultaneously neutralize the protons released from the extraction agent and neutralize the extraction total liquid in order to maintain the extraction equilibrium pH. It is because a large amount of pH adjuster must be added at the time, and extraction pH control becomes difficult.

Herein, the extraction of manganese has been described in detail, but other valuable metals such as cobalt, nickel and lithium can be extracted by a conventionally known method.

Most of the added positive electrode active material becomes a leaching residue. However, if the residue is used repeatedly for leaching or after leaching, the added positive electrode active material does not become a loss out of the process.

[Example]

(First Example: Effect of Adding Hydrogen Peroxide After Leaching with Sulfuric Acid)

As shown in FIG. 2, the positive electrode active material 1 (31.3dry-g) was added to 0.5 L (0.5 mol of sulfuric acid) of 1 mol / L sulfuric acid solution, and it stirred at 600 rpm without heating. The amount of sulfuric acid added is the total amount of nickel, cobalt, manganese and equimolar amount of sulfuric acid in the positive electrode active material, and 0.5 sulfuric acid in a molar ratio relative to lithium. The composition of the added positive electrode active material is shown in Table 1. Solution temperature was 20-30 degreeC. Moreover, according to Table 2 which shows the composition of the sulfuric acid leaching residue 2, 37 wt% of nickel, cobalt, and manganese contained in the positive electrode active material before leaching were leached, and lithium was leached 66wt% by leaching only sulfuric acid.

Hydrogen peroxide was added to the slurry solution of sulfuric acid leaching, without carrying out solid-liquid separation after leaching only by sulfuric acid of the preceding claim. To nickel, cobalt and manganese contained in the positive electrode active material not dissolved in sulfuric acid, 35 wt% hydrogen peroxide solution containing an equimolar amount of hydrogen peroxide was added and stirred at 600 rpm without heating. The composition of the positive electrode active material not dissolved in sulfuric acid is a composition shown in Table 2. As a result, according to Table 3 showing the composition of the leaching liquor 3, 96 wt% or more of nickel, cobalt, manganese, and lithium were leached in the positive electrode active material before leaching by first leaching with sulfuric acid and then leaching with hydrogen peroxide.

Example 2 Manganese Solvent Extraction by Addition of Positive Electrode Active Material and Leachate after Addition

The positive electrode active material (10 dry-g) was added to 0.5 L of the solution after leaching with sulfuric acid and hydrogen peroxide, and the mixture was stirred at room temperature (20 to 30 ° C.) at 600 rpm. The oxidation-reduction potential ORP of the solution was 700 kV (vs. Ag / AgCl) was lowered. In addition, the pH of the solution rose to 3 or more. This result is shown in FIG. The composition of the added positive electrode active material is the same as that of the positive electrode active material shown in Table 1. The time to which the positive electrode active material was added is when reaction time 6.5 hours in a figure. Then, continuing stirring, the fall of redox potential ORP and the raise of pH were seen. 8.5 hours after adding the positive electrode active material (15 hours after the start of leaching), the ORP of the leaching liquid became 700 Pa or less. pH rose to 3.8.

After leaching liquid obtained by adding this positive electrode active material and adjusting the redox potential ORP and pH, solid-liquid separation, manganese solvent extraction was performed from the filtrate, and manganese of the leaching liquid was extracted as an organic phase. Next, an aqueous sulfuric acid solution was added to the organic phase, and manganese was back extracted from the organic phase into the aqueous solution. The manganese extraction solvent used here is a mixed solvent of 25 volume% of di (2-ethylhexyl) phosphoric acid (D2EHPA by LANXESS) and a diluent shell sol D70 (Shell Chemical Co., Ltd.). Extraction conditions and back extraction conditions are shown in Table 4. As a result, the color of the organic phase after back extraction was colorless, and manganese in the organic phase after back extraction was analyzed. As a result, the manganese concentration of 1 L of the organic phase was nearly 30 mg / L, and the extracted manganese could be almost back extracted (Table 5).

(About comparison of back extraction amount of manganese with or without addition of positive electrode active material to leaching liquid)

Let the conditions of the second embodiment be "condition A". The filtrate obtained by solid-liquid separation after leaching the positive electrode active material under the same conditions other than the second embodiment except that the positive electrode active material was not added to the conditions of the first embodiment, that is, the leaching liquor was subjected to manganese under the same conditions as in Table 4 of the second embodiment. Solvent extraction and back extraction were performed. Let this be "condition B". When the color of the organic phase after back extraction in condition A and B was compared, on the condition which added the positive electrode active material after leaching (condition A), on the condition which an organic phase was colorless, on the condition which did not add a positive electrode active material (condition B), The organic phase was colored purple. This result is shown to FIG. 4 (a), (b). As shown in Table 6, the manganese concentration remaining in the organic phase after the back extraction is lower in the condition (condition A) in which the positive electrode active material is added after leaching than in the condition in which the positive electrode active material is not added after leaching (condition B). After the leaching, more manganese could be extracted by adding the positive electrode active material.

Claims (7)

A method of leaching a valuable metal from a positive electrode active material of a lithium ion battery composed of a composite oxide composed of a transition metal containing at least manganese,
1st process which melt | dissolves the component which is soluble in the sulfuric acid solution in the said positive electrode active material in the aqueous solution which added sulfuric acid,
And a second step of further leaching the unleached component remaining in the sulfuric acid leaching slurry by adding hydrogen peroxide to the sulfuric acid leaching slurry solution without solid-liquid separation after the first step. The third process according to claim 1, wherein the redox potential of the leaching liquid obtained in the second step is lowered and the pH is increased.
And separating the reaction liquid obtained in the third step into solid-liquid, and then extracting the manganese organic phase by solvent extraction, followed by a fourth step of back extracting the organic phase with an acidic aqueous solution to obtain a manganese aqueous solution. Leaching method of the active material. The leaching method of the positive electrode active material according to claim 2, wherein in the third step, a positive electrode active material is added to the leaching liquid obtained in the second step. The said positive electrode active material is an oxide of nickel, cobalt, manganese, and lithium contained in a positive electrode active material as a main component, and the quantity of sulfuric acid added is nickel, cobalt, and manganese in any one of Claims 1-3. A leaching method of the positive electrode active material, characterized by being used in an amount less than the total number of moles of the number of moles of lithium. The amount of hydrogen peroxide added is used in an amount of 0.8 to 1.2 times molar amount based on the total molar amount of nickel, cobalt, and manganese contained in the positive electrode active material not dissolved in the sulfuric acid solution in the first step of the positive electrode active material. A leaching method of a positive electrode active material, characterized by the above-mentioned. The positive electrode active material is added to the leaching liquor by sulfuric acid and hydrogen peroxide, and the value of a redox potential is adjusted to 700 kV (vs. Ag / AgCl) or less, characterized by the above-mentioned. Leaching method of the positive electrode active material. The positive electrode active material according to any one of claims 1 to 3, wherein the positive electrode active material is added and stirred to the leaching liquid obtained in the second step, and the pH of the leaching liquid is raised to 2.5 or more. Leaching method.

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