KR102558188B1 - Economical method removing impurities from waste phosphor-containg lithium battery materials - Google Patents

Abstract

Lithium is leached from waste phosphate-based lithium battery materials containing lithium to obtain a solution containing lithium, iron and phosphorus, and iron and phosphorus are extracted from Vivianite (Fe ₃ (PO ₄ ) ₂ 8H ₂ O) and brushite (CaHPO ₄ ). 2H ₂ O) to precipitate and separate to remove the remaining iron and phosphorus with Magnetite (Fe ₃ O ₄ ) and Hydroxyapatite (Ca ₅ (PO ₄ ) ₃ OH) to precipitate and separate to remove the second It provides a method for removing iron and phosphorus from a lithium containing solution.

Description

Method for removing impurities from waste phosphate-based lithium battery materials

It relates to a method for removing impurities from waste phosphate-based lithium battery materials.

Recently, LiFePO ₄ , an inexpensive phosphate-based material, has been increasingly used as a cathode active material for large-capacity lithium batteries for electric vehicles instead of conventional LiCoO ₂ and three-component active materials (Li(CoNiMn)O ₂ , etc.).

Lithium (Li) contained in waste phosphate-based lithium battery materials is a very expensive metal and is not produced domestically, so all of it is imported from abroad. Therefore, it is necessary to recover and reuse lithium from waste phosphate-based lithium battery materials that are discarded after use in terms of the characteristics of countries without endowed resources such as Korea and the prevention of environmental pollution by heavy metals.

In order to recover lithium from the waste phosphate-based lithium battery material, a process of leaching lithium, iron, and phosphorus from the waste phosphate-based lithium battery material and then removing impurities from it must be preceded.

Conventionally, in order to recover lithium from waste lithium battery materials, a method of eluting not only lithium but also nickel, cobalt, and manganese together using strong acids such as nitric acid, sulfuric acid, and hydrochloric acid, and then precipitating them as hydroxides to separate each has been used. . In addition, recently, the metal component is separated from the eluate by solvent extraction. This impurity removal method mainly aims at recovering cobalt and nickel and cannot be used to remove iron and phosphorus from waste phosphate-based lithium battery materials.

Recently, a method of removing iron and aluminum by precipitating them as FePO ₄ and AlPO ₄ by adding phosphoric acid to waste lithium battery material leachate has been developed. However, this method has a problem in that phosphoric acid must be additionally added and the leachate of the waste lithium battery material is contaminated with the intentionally added phosphorus. In addition, a method of dissolving waste phosphate-based positive electrode material and iron powder in phosphoric acid, removing iron in the form of iron hydroxide by adding sodium hydroxide, and then adding ethanol to extract lithium phosphate has been developed. However, this method has a problem in that impurities to be removed by additionally using iron powder increase. On the other hand, in order to avoid the process of removing impurities from the waste lithium battery material leachate, the waste lithium battery material is heat treated for a long time in a high-temperature hydrogen atmosphere of 500 ° C to 1,000 ° C, a carbon dioxide atmosphere, or a vacuum atmosphere, so that lithium present in the form of a compound with a transition metal Attempts have been made to leach only lithium by converting it into lithium carbonate, lithium hydroxide or lithium oxide and adding water. However, when using this method, a large enclosed type heating device is required, which increases the equipment investment cost, and expensive reducing gases such as hydrogen or carbon dioxide and fuel are used in large quantities, so that economic feasibility is lowered.

Accordingly, the present invention proposes a method for economically removing impurities from waste phosphate-based lithium battery materials.

One embodiment of the present invention provides a method for economically removing impurities from waste phosphate-based lithium battery materials.

In one embodiment of the present invention, preparing a waste phosphate-based lithium battery material containing lithium; Leaching lithium at a high concentration under normal pressure without a heat treatment process; firstly removing iron and phosphorus from the lithium leaching solution with Vivianite (Fe ₃ (PO ₄ ) ₂ .8H ₂ O) and brushite (CaHPO ₄ .2H ₂ O); Provides an impurity removal method comprising the step of secondarily removing iron and phosphorus from the lithium leachate from which iron and phosphorus are primarily removed with Magnetite (Fe ₃ O ₄ ) and Hydroxyapatite (Ca ₅ (PO ₄ ) ₃ OH) do.

More specifically,

The lithium content of the waste phosphate-based lithium battery material may be 1 to 5% by weight.

The impurity may be iron, manganese, phosphorus or a mixture thereof.

In the lithium leaching step, the waste phosphate-based lithium battery material may be used as it is without heat treatment.

In the lithium leaching step, the waste phosphate-based lithium battery material may be used as it is at normal pressure without pressurization.

In the step of leaching lithium from the waste phosphate-based lithium battery material under normal pressure, inorganic acid, that is, sulfuric acid, hydrochloric acid, hypochlorous acid, or nitric acid may be used to leach lithium.

In the step of leaching lithium from the waste phosphate-based lithium battery material, lithium may be leached at a high concentration.

In the lithium leaching step, the pH of the lithium leachate may be -0.05 to 2.

In the lithium leaching step, the leaching temperature may be from room temperature to 100°C.

The lithium leachate may have a lithium concentration of 3 to 5 g/L.

Iron, manganese, phosphorus, or a mixture thereof may be present in the lithium leaching solution together with lithium.

Iron and phosphorus present in the lithium leachate may be precipitated as individual phosphorus compounds to be primarily removed.

When the iron and phosphorus are primarily removed, iron and phosphorus may be removed as Vivianite (Fe ₃ (PO ₄ ) ₂ 8H ₂ O) and brushite (CaHPO ₄ 2H ₂ O), respectively.

Secondary removal may be performed by precipitating iron and phosphorus as respective phosphorus compounds from the lithium leachate from which iron and phosphorus are primarily removed.

When the iron and phosphorus are removed secondarily, iron and phosphorus may be removed by magnetite (Fe ₃ O ₄ ) and hydroxyapatite (Ca ₅ (PO ₄ ) ₃ OH), respectively.

One embodiment of the present invention provides a method for economically removing impurities from waste phosphate-based lithium battery materials.

1 shows that waste lithium battery materials containing Li, Fe, and P components are mixed with an aqueous hydrochloric acid solution in air at normal pressure, and then stirred at room temperature for 2 hours to obtain a lithium leachate and alkali to remove Fe and P from the lithium leachate. The X-ray diffraction pattern of the precipitate containing Fe and P obtained by the first injection is shown.
Figure 2 shows an X-ray diffraction pattern of a precipitate containing Fe and P obtained by adding an alkali secondly to completely remove Fe and P remaining in the lithium leachate from which Fe and P are primarily removed.

Hereinafter, embodiments of the present invention will be described in detail. However, this is presented as an example, and the present invention is not limited thereby, and the present invention is only defined by the scope of the claims to be described later.

Conventionally, in order to recover lithium from waste lithium battery materials containing lithium, lithium is leached after high-temperature heat treatment of waste lithium battery materials in a reducing atmosphere or carbon dioxide atmosphere. However, when using this method, there is a problem in that a large amount of expensive reducing gas must be used and economical efficiency is lowered due to high energy cost. Therefore, in the present invention, the waste lithium battery material is limited to being treated in a normal pressure air atmosphere without heating in a reducing atmosphere or a carbon dioxide atmosphere.

In general, in order to recover lithium from waste phosphate-based lithium battery materials, lithium is eluted using an acid. At this time, iron and lead present in the waste phosphate-based lithium battery material are eluted together. However, in order to recover lithium from the lithium leaching solution, iron and phosphorus eluted together with lithium must first be removed. In general, iron and phosphorus can be precipitated and removed at once by adding alkali to the lithium leachate, but excessive addition of alkali causes precipitation of not only iron and phosphorus but also lithium, resulting in a loss of a large amount of lithium. In the present invention, iron and phosphorus are removed in two steps to suppress the loss of lithium.

First, calcium hydroxide, a type of alkali earth metal hydroxide, is added to the lithium leaching solution to first remove iron and phosphorus. At this time, if iron and phosphorus are precipitated as Fe(PO ₄ ) ₂ 8H ₂ O (Vivianite) and CaHPO ₄ 2H ₂ O (Brushite), respectively, according to the reaction equation below, the lithium leach solution suppresses the loss due to lithium precipitation. can remove most of the iron and phosphorus present in

3Fe ²⁺ + 2HPO ₄ ^2- + 6H ⁺ + 8OH ^- --> Fe ₃ (PO ₄ ) ₂ 8H ₂ O

Ca ²⁺ + HPO ₄ ^3- + H ⁺ + 2OH ^- --> CaHPO ₄ 2H ₂ O

In order to completely remove iron and phosphorus remaining in the lithium leachate from which iron and phosphorus are primarily removed in this way, calcium hydroxide, a kind of alkaline earth metal hydroxide, is additionally added to the lithium leachate. At this time, if iron and phosphorus are secondaryly precipitated as Fe ₃ O ₄ (Magnetite) and Ca ₅ (PO ₄ ) ₃ OH (Hydroxyapatite), respectively, according to the reaction equation below, the loss due to lithium precipitation is suppressed and the lithium leachate Any iron and phosphorus present can be removed.

3Fe ³⁺ + 3Fe ²⁺ + 2H ⁺ + 10OH ^- --> 2Fe ₃ O ₄ + 2H ₂ O

5Ca ²⁺ + 3PO ₄ ^3- + OH ^- --> Ca ₅ (PO ₄ ) ₃ OH

The alkaline earth metal hydroxide may be calcium hydroxide, magnesium hydroxide, strontium hydroxide, barium hydroxide, or a combination thereof.

In general, it is also important to properly manage the temperature of the reaction solution because the precipitation and removal of impurities by adding alkaline earth metal hydroxide to the lithium leaching solution is also affected by temperature.

Therefore, in the present invention, the temperature of the carbonation reaction solution is limited to room temperature to 100°C.

In the present specification, room temperature does not mean a constant temperature, but means a temperature in a state without the addition of external energy. Therefore, the room temperature may change depending on the place and time.

Hereinafter, preferred embodiments of the present invention are described. However, the following examples are only preferred examples of the present invention, but the present invention is not limited to the following examples.

In order to leach lithium from the waste phosphate-based lithium battery material containing lithium, a cathode material for a waste phosphate-based lithium battery containing lithium, iron, and phosphorus was prepared. The chemical composition of the waste phosphate-based lithium battery cathode material is shown in Table 1. As shown in Table 2, the waste lithium battery positive electrode material was mixed with aqueous hydrochloric acid solutions of different concentrations at room temperature and stirred for 2 hours in air at normal pressure.

After the stirring was completed, the samples were filtered to measure the concentrations of lithium, iron and phosphorus in the leachate, and the results are shown in Table 2.

As shown in Table 2 and FIG. 1, when the pH of the leachate is maintained at 1.4 to -0.2, lithium can be leached from the waste phosphate-based lithium battery cathode material at a high recovery rate of 80% or more at room temperature and normal pressure. However, when the pH of the leachate is reduced to -0.2 or less by excessive use of acid, there is a problem in that the amount of acid used is excessive and thus the economic feasibility is lowered.

division Li Fe P Mg Ca B S Na content(%) 4.53 33.12 18.77 0.01 0.04 0.02 0.03 0.07

Lithium Leachate pH 1.6 1.4 1.2 0.6 0.2 -0.01 -0.2 Li leaching rate (%) 64.6 82.9 95.9 96.8 99.3 100 100 Fe leaching rate (%) 54.9 77.3 100 100 100 100 100 P leaching rate (%) 49.9 68.9 92.2 99.2 100 100 100 leachate
Lithium concentration (mg/L) 2,926 3,759 4,344 4,385 4,498 4,530 4,530

From these results, it was confirmed that when lithium is leached from the waste phosphate-based lithium battery material containing lithium, it is preferable to limit the pH of the leachate to the range of 1.4 to -0.2.

Lithium, iron, and phosphorus were leached from the above-mentioned waste phosphorus oxide-based lithium battery positive electrode material containing lithium, and calcium hydroxide was added to precipitate and remove iron and phosphorus. The lithium leachate slurry in which iron and phosphorus were precipitated was filtered to separate the iron and phosphorus primary precipitates, and then the concentrations of lithium, iron, and phosphorus in the lithium leachate were measured. This is shown in Table 3. Meanwhile, the mineral phase analysis results of primary iron and phosphorus precipitates are shown in FIG. 1 . As shown in FIG. 1, it can be seen that iron and phosphorus precipitated as Vivianite (Fe ₃ (PO ₄ ) ₂ .8H ₂ O) and brushite (CaHPO ₄ .2H ₂ O), respectively, and were removed from the leachate.

division Li concentration
(mg/L) Fe concentration
(mg/L) P concentration
(mg/L) leachate 4,530 35,062 18,483 After first removal of Fe and P
leachate 4,510 1,039 14 Li dissolved rate (%) 99.6 Fe removal rate (%) 97.0 P removal rate (%) 99.9

As shown in Table 3, when Fe and P are removed by primary precipitation with Vivianite (Fe ₃ (PO ₄ ) ₂ 8H ₂ O) and Brushite (CaHPO ₄ 2H ₂ O), Li is almost not lost and is added to the lithium leachate. It can be seen that the presence of

Calcium hydroxide was additionally added to the above-described lithium leachate from which iron and phosphorus were primarily removed to precipitate iron and phosphorus secondarily and completely removed. The lithium leachate slurry in which iron and phosphorus were secondaryly precipitated was filtered to separate the iron and phosphorus secondary precipitates, and then the concentrations of lithium, iron, and phosphorus in the lithium leachate were measured. Based on this, the lithium dissolution rate and the iron and phosphorus removal rate were calculated. . This is shown in Table 4. Meanwhile, the mineral phase analysis results of iron and phosphorus secondary precipitates are shown in FIG. 2 . As shown in FIG. 2, it can be seen that iron and phosphorus are precipitated as magnetite (Fe ₃ O ₄ ) and hydroxyapatite (Ca ₅ (PO ₄ ) ₃ OH), respectively, and removed from the lithium leachate.

division Li concentration
(mg/L) Fe concentration
(mg/L) P concentration
(mg/L) After first removal of Fe and P
lithium leachate 4,510 1,039 14 After secondary removal of Fe and P
lithium leachate 4,500 0 0 Li dissolved rate (%) 99.8 Fe removal rate (%) 100 P removal rate (%) 100

As shown in Table 4, when Fe and P are removed by secondary precipitation with Magnetite (Fe ₃ O ₄ ) and Hydroxyapatite (Ca ₅ (PO ₄ ) ₃ OH), Li is hardly lost and dissolved in the lithium leachate. there is.

The present invention is not limited to the above embodiments, but can be manufactured in various different forms, and those skilled in the art to which the present invention belongs can make other specific forms without changing the technical spirit or essential features of the present invention. It will be appreciated that it can be implemented. Therefore, the embodiments described above should be understood as illustrative in all respects and not limiting.

Claims (5)

Preparing a waste phosphate-based lithium battery material;
leaching lithium into an aqueous acid solution under normal pressure without a heat treatment process;
Injecting calcium oxide or calcium hydroxide into the lithium-containing solution to precipitate iron and phosphorus into Vivianite (Fe ₃ (PO ₄ ) ₂ 8H ₂ O) and Brushite (CaHPO ₄ 2H ₂ O), and separating and firstly removing iron and phosphorus. ; and
Secondary removal by precipitating and separating iron and phosphorus as Magnetite (Fe ₃ O ₄ ) and Hydroxyapatite (Ca ₅ (PO ₄ ) ₃ OH) from the lithium-containing solution from which the iron and phosphorus are primarily removed, ,
Method for removing iron and phosphorus from a lithium-containing solution, wherein the acid in the aqueous acid solution is sulfuric acid, hydrochloric acid, hypochlorous acid, nitric acid, or a mixture thereof. According to claim 1,
Preparing the waste phosphate-based lithium battery material containing the lithium;
Waste phosphate-based lithium battery material is lithium iron phosphate (LiFePO ₄ , LFP) Method for removing iron and phosphorus from a lithium-containing solution According to claim 1,
A method for removing iron and phosphorus from a lithium-containing solution in which the pH of the lithium-containing solution is 1.4 to 0 in the step of leaching lithium with an acid aqueous solution at atmospheric pressure without the heat treatment process; delete According to claim 1,
A method for removing iron and phosphorus from a lithium-containing solution in which the temperature of the lithium-containing solution is from room temperature to 100 ° C. in the step of leaching lithium at atmospheric pressure without the heat treatment process.