WO2024128429A1 - Method for removing impurities from waste phosphate-based lithium battery materials - Google Patents

Abstract

Provided is a method for removing impurities from waste phosphate-based lithium battery materials, the method comprising: a step (step 1) for preparing a first leachate, containing lithium, iron, and phosphorus, from waste phosphate-based lithium battery materials at atmospheric pressure without heat treatment; a step (step 2) for performing primary removal of some of iron and phosphorus as Vivianite and Brushite, respectively, from the first leachate containing lithium, iron, and phosphorus; and a step (step 3) for performing secondary removal of some of iron and phosphorus as Magnetite and Hydroxyapatite, respectively, from a second leachate, containing lithium, iron, and phosphorus, subjected to the primary removal of some of iron and phosphorus.

Description

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

The present invention relates to a method for removing impurities from spent phosphorus lithium battery materials.

Recently, the use of LiFePO _{4 ,} an inexpensive phosphorus-based material, has been increasing 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 contained in waste phosphate-based lithium battery materials is a very expensive metal. Lithium is not produced domestically, so it is entirely imported and used from overseas. Therefore, in view of the characteristics of a country like Korea with no natural resources and the prevention of environmental pollution caused by heavy metals, it is necessary to recover and reuse lithium from waste phosphorus lithium battery materials that are discarded after use.

In order to recover lithium from waste phosphate-based lithium battery materials, a process of leaching lithium, iron, and phosphorus in the waste phosphate-based lithium battery materials and then removing impurities therefrom must be performed.

Conventionally, to recover lithium from waste lithium battery materials, a method has been used to elute not only lithium but also nickel, cobalt, and manganese together using strong acids such as nitric acid, sulfuric acid, and hydrochloric acid, and then separate them by precipitating them with hydroxide. . Additionally, in recent years, metal components have been separated from the eluate using solvent extraction. This impurity removal method is mainly aimed at recovering cobalt and nickel, and cannot be used to remove iron and phosphorus from spent phosphorus phosphate-based lithium battery materials.

Recently, a method has been developed to remove iron and aluminum by adding phosphoric acid to the leachate of waste lithium battery materials to precipitate them as FePO ₄ and AlPO ₄ . However, this method not only requires the addition of phosphoric acid, but also has the problem that the waste lithium battery material leachate is contaminated with the intentionally added phosphorus. In addition, a method was developed to dissolve waste phosphate-based cathode material and iron powder in phosphoric acid, add sodium hydroxide to remove iron in the form of iron hydroxide, and add ethanol to extract lithium phosphate. However, using this method has the problem of increasing impurities to be removed by additional use of iron powder. Meanwhile, in order to avoid the process of removing impurities from the waste lithium battery material leachate, the waste lithium battery material is heat-treated in a high temperature hydrogen atmosphere, carbon dioxide atmosphere, or vacuum atmosphere at 500 to 1000°C for a long time to remove lithium present in the form of a compound with a transition metal. There have been attempts to leach only lithium by converting it to lithium carbonate, lithium hydroxide or lithium oxide and adding water. However, this method has not been able to overcome the problems of requiring a large enclosed heating device, increasing facility investment costs, and reducing economic feasibility due to the use of large quantities of expensive reducing gases and fuels such as hydrogen or carbon dioxide.

Accordingly, the present invention provides a method for economically removing impurities from waste phosphorus lithium battery materials.

[Prior art literature]

(Patent Document 0001) Korean Patent Publication No. 10-2022-0031997

(Patent Document 0002) Korean Patent No. 10-1178769

(Patent Document 0003) Korean Patent No. 10-1497041

(Patent Document 0004) Korean Patent Publication No. 10-2021-0066418

(Patent Document 0005) Korean Patent Publication No. 10-2021-0009133

(Patent Document 0006) Korean Patent No. 10-2332465

(Patent Document 0007) Korean Patent Publication No. 10-2022-0022171

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

One embodiment of the present invention provides a method for recovering lithium from waste phosphate-based lithium battery materials at a high recovery rate and economically.

One aspect of the present invention is a method for removing impurities from waste phosphorus-based lithium battery materials.

Methods for removing impurities from spent lithium phosphate-based battery materials include:

Preparing a first leachate containing lithium, iron and phosphorus from waste phosphate-based lithium battery material at normal pressure without heat treatment;

Firstly removing some of the iron and phosphorus from the first leachate containing lithium, iron, and phosphorus using Vivianite and Brushite, respectively; and

It includes the step of secondarily removing some of the iron and phosphorus using Magnetite and Hydroxyapatite, respectively, from the second leachate containing lithium, iron, and phosphorus from which some of the iron and phosphorus were first removed.

The waste phosphate-based lithium battery material may contain one or more complex oxides among lithium, iron, and phosphorus.

The waste phosphate-based lithium battery material may include one or more of lithium iron phosphorus oxide and lithium manganese iron oxide.

The waste phosphate-based lithium battery material may further include one or more of lithium nickel cobalt manganese oxide, lithium manganese oxide, lithium nickel manganese spinel, lithium nickel cobalt aluminum oxide, lithium cobalt oxide, and lithium titanium oxide.

Among the above materials, lithium may be contained in an amount of 1% by weight or more, iron may be contained in an amount of 20% by weight or more, and phosphorus may be contained in an amount of 5% by weight or more.

The pH of the first leachate may be -0.2 to 1.4.

Step 2 may be performed by adding an alkaline earth metal hydroxide to the first leachate, stirring it to prepare a slurry, filtering the slurry, and separating the liquid second leachate and the solid first precipitate.

The hydroxide of the alkaline earth metal may be calcium hydroxide.

Among the first precipitates, Vivianite and Brushite may be contained in an amount of 95% by weight or more.

Step 3 may be performed by adding an alkaline earth metal hydroxide to the second leachate, stirring it to prepare a slurry, filtering the slurry, and separating the liquid third leachate and the solid second precipitate.

Among the second precipitates, Magnetite and Hydroxyapatite may be contained in more than 95% by weight.

The hydroxide of the alkaline earth metal may be calcium hydroxide.

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

One embodiment of the present invention provides a method for recovering lithium from waste phosphate-based lithium battery materials at a high recovery rate and economically.

Figure 1 shows the X-ray diffraction pattern of the first precipitate obtained in Example 2.

Figure 2 shows the X-ray diffraction pattern of the second precipitate obtained in Example 3.

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.

The terminology used herein is for the purpose of describing example implementations only and is not intended to limit the invention. Singular expressions include plural expressions unless the context clearly dictates otherwise.

In this specification, the contents of lithium and various components (e.g., impurities) such as iron, phosphorus, magnesium, calcium, boron, sulfur, sodium, etc. are measured using atomic emission spectroscopy, such as inductively coupled plasma atomic emission spectroscopy (ICP- It may be measured by AES (inductively coupled plasma atomic emission spectroscopy), but is not limited to this.

In this specification, lithium and various components (e.g., impurities) such as iron, phosphorus, magnesium, calcium, boron, sulfur, sodium, manganese, etc. are not only the elements themselves, but also monovalent or higher cations derived from the elements or monovalent It can also mean negative ions above.

For example, lithium can mean not only lithium metal itself but also the monovalent cation (Li ⁺ ) of lithium. For example, iron may refer to not only iron metal itself but also divalent or trivalent cations of iron (eg, Fe ²⁺ , Fe ³⁺ , etc.). For example, phosphorus may mean not only the phosphorus non-metal itself but also a monovalent or higher anion of phosphorus.

In this specification, when indicating a numerical range, “X to Y” means greater than X and less than or equal to Y (X≤ and ≤Y).

Conventionally, in order to recover lithium from waste lithium battery materials containing lithium and impurities, the waste lithium battery materials were heat-treated at high temperature in a reducing atmosphere or carbon dioxide atmosphere to leach lithium. However, this method not only requires the use of a large amount of expensive reducing gas, but also has the problem of low economic feasibility due to high energy costs. Additionally, this method had limitations in removing impurities from waste lithium battery materials at a high removal rate. Therefore, in the present invention, waste lithium battery materials, especially waste phosphorite-based lithium battery materials, are treated in a reducing atmosphere or carbon dioxide atmosphere at normal pressure and in an air atmosphere without heat treatment or pressurization. This provides the effect of economically removing impurities from waste lithium battery materials.

Generally, in order to recover lithium from waste phosphate-based lithium battery materials, acid is used to leach the lithium. At this time, it is leached together with the iron and lithium indium present in the waste phosphate-based lithium battery materials. However, in order to recover lithium from this lithium leach solution, iron and phosphorus must first be removed. Iron and phosphorus can be removed by adding alkali to the lithium leach solution and precipitating it at once. However, if excessive alkali is added, not only iron and phosphorus but also lithium is precipitated, resulting in the loss of a large amount of lithium. In the present invention, iron and phosphorus are removed in two steps to suppress this loss of lithium. This provides a method for removing impurities from spent phosphate-based lithium battery materials at a high removal rate. Of course, in order to suppress the loss of lithium, the removal of iron and phosphorus can be performed in more than two stages, but the present inventor divides iron and phosphorus into two stages to remove iron and phosphorus from Vivianite (e.g. Fe ₃ (PO ₄ ) ₂ ·8H ₂ O ) and Brushite (e.g. CaHPO ₄ ·2H ₂ O) for primary removal, and Magnetite (e.g. Fe ₃ O ₄ ) and Hydroxyapatite (e.g. Ca ₅ (PO ₄ ) ₃ OH) for secondary removal, pulmonary phosphorylation. It was confirmed that among water-based lithium battery materials, iron and phosphorus were removed at a high removal rate.

The method for removing impurities from the waste phosphate-based lithium battery material of the present invention is

Preparing a first leachate containing lithium, iron and phosphorus from waste phosphate-based lithium battery material at normal pressure without heat treatment (step 1);

Primary removal of some of the iron and phosphorus from the first leachate containing lithium, iron, and phosphorus using Vivianite and Brushite, respectively (step 2); and

It includes a step (step 3) of secondarily removing some of the iron and phosphorus with Magnetite and Hydroxyapatite, respectively, from the first leachate containing lithium, iron, and phosphorus from which some of the iron and phosphorus were first removed.

Hereinafter, the present invention will be described in detail.

(Step 1)

Step 1 is a step of preparing a first leachate containing lithium, iron, and phosphorus from waste phosphate-based lithium battery materials at normal pressure without heat treatment.

Waste phosphorite-based lithium battery materials can be obtained from phosphorite-based lithium batteries. There are no particular restrictions on waste phosphorus lithium batteries as long as they are collected after the lithium batteries are used up. The material can be obtained through a pre-treatment process including removing the negative electrode substrate, positive substrate, separator, etc. from a spent phosphorus lithium battery. The material can be obtained from a cathode material in a spent phosphate-based lithium battery.

Waste phosphate-based lithium battery materials may contain lithium, iron, and phosphorus. In one embodiment, the waste phosphate-based lithium battery material may include one or more complex oxides among lithium, iron, and phosphorus. The complex oxide may be a complex oxide containing lithium and iron, a complex oxide containing lithium and phosphorus, or a complex oxide containing lithium, iron and phosphorus. In addition to lithium, iron, and phosphorus, the complex oxide may further include one or more of manganese, magnesium, calcium, boron, sulfur, sodium, nickel, cobalt, titanium, and aluminum.

For example, waste phosphate-based lithium battery materials include one or more of lithium iron phosphorus oxide (e.g., LiFePO ₄ , LFP) and lithium manganese iron oxide (e.g., LiFe _1-x Mn _x PO ₄ , LiFeMnPO ₄ , LMFP). can do. Waste phosphorus lithium battery materials include lithium nickel cobalt manganese oxide (LiNiCoMnO ₂ , NCM), lithium manganese oxide (LiMn ₂ O ₄ , LMO), lithium nickel manganese spinel (LiNi _0.5 Mn _1.5 O ₄ , LNMO), and lithium nickel cobalt aluminum. It may additionally include one or more of oxide (LiNiCoAlO ₂ , NCA), lithium cobalt oxide (LiCoO ₂ , LCO), and lithium titanium oxide (Li ₄ Ti ₁₅ O ₁₂ , LTO).

Among the materials, lithium may be contained in an amount of 1% by weight or more. In this range, the recovery rate of lithium from the material can be significantly higher. For example, among the above materials, lithium is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15% by weight, 1 to 15% by weight, 2 to 13%. It may be contained in weight%, 2 to 10% by weight, or 1 to 5% by weight.

Among the above materials, iron may be contained in an amount of 20% by weight or more. In this range, the recovery rate of lithium from the material can be significantly higher. For example, among the above materials, iron is 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40. , 41, 42, 43, 44, 45, 46, 47,48, 49, 50% by weight, 20 to 50% by weight, 25 to 50% by weight, 30 to 45% by weight, 30 to 40% by weight. there is.

Phosphorus in the above materials may be contained in an amount of 5% by weight or more. In this range, lithium recovery from the material can be high. For example, in the above materials, phosphorus is 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25. , 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50 It may be contained in weight%, 5 to 50% by weight, 5 to 45% by weight, 5 to 40% by weight, 5 to 35% by weight, 10 to 30% by weight, 10 to 25% by weight, and 15 to 20% by weight.

Among the above materials, magnesium may be contained in an amount of 0.0001% by weight or more. In this range, lithium recovery from the material can be high. For example, magnesium is 0.0001, 0.001, 0.01, 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 of the above materials. , 17, 18, 19, 20% by weight, 0.0001 to 20% by weight, 0.01 to 20% by weight, 0.01 to 10% by weight, and 0.01 to 5% by weight.

Among the above materials, calcium may be contained in an amount of 0.0001% by weight or more. In this range, lithium recovery from the material can be high. For example, calcium is 0.0001, 0.001, 0.01, 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 of the above materials. , 17, 18, 19, 20% by weight, 0.0001 to 20% by weight, 0.01 to 20% by weight, 0.01 to 10% by weight, and 0.01 to 5% by weight.

Among the materials, boron may be contained in an amount of 0.0001% by weight or more. In this range, lithium recovery from the material can be high. For example, boron is present in 0.0001, 0.001, 0.01, 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 of the above materials. , 17, 18, 19, 20% by weight, 0.0001 to 20% by weight, 0.01 to 20% by weight, 0.01 to 10% by weight, and 0.01 to 5% by weight.

Among the above materials, sulfur may be contained in an amount of 0.0001% by weight or more. In this range, lithium recovery from the material can be high. For example, sulfur is 0.0001, 0.001, 0.01, 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, It may be contained at 17, 18, 19, 20% by weight, 0.0001 to 20% by weight, 0.01 to 20% by weight, 0.01 to 10% by weight, and 0.01 to 5% by weight.

Among the above materials, sodium may be contained in an amount of 0.0001% by weight or more. In this range, lithium recovery from the material can be high. For example, sodium is 0.0001, 0.001, 0.01, 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 of the above materials. , 17, 18, 19, 20% by weight, 0.0001 to 20% by weight, 0.01 to 20% by weight, 0.01 to 10% by weight, and 0.01 to 5% by weight.

The total amount of iron and phosphorus in the above materials may be 40% by weight or more. Even in this case, the method of the present invention provided a significantly low iron and phosphorus removal rate of 1% or less from the material. In one embodiment, the total amount of iron and phosphorus in the materials is 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58. , 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80% by weight, 40 to 80 Weight%, may be 45 to 80% by weight, 50 to 80% by weight, or 50 to 70% by weight.

Among the materials, the total amount of metal or non-metal elements, or cations or anions derived therefrom, excluding lithium, iron and phosphorus, may be 0.01% by weight or more, for example, 0.01 to 50% by weight, 0.05 to 10% by weight. The present invention provides the effect of significantly lowering the removal rate of iron and phosphorus from the above materials to 1% or less even within the above-mentioned total range. Here, 'metallic or non-metallic element, or cation or anion derived therefrom' may mean one or more of calcium, boron, sulfur, manganese, cobalt, nickel, titanium, or sodium, or a cation or anion derived therefrom. .

In one embodiment, the waste phosphate-based lithium battery material may be in a solid phase or a liquid phase.

The first leachate containing lithium, iron and phosphorus is prepared by treating waste phosphorus lithium battery material at normal pressure without heat treatment. Specifically, lithium, iron, and phosphorus are leached by applying an acid aqueous solution to waste phosphate-based lithium battery materials. The aqueous acid solution is an aqueous solution of an inorganic acid and may be sulfuric acid, hydrochloric acid, hypochlorous acid, nitric acid, a mixture thereof, or an aqueous solution thereof. Preferably, the aqueous acid solution may be an aqueous hydrochloric acid solution.

When extracting lithium, iron and phosphorus from the material, an aqueous acid solution may be added to the material and left to stand without stirring, but stirring is performed to economically leach the lithium, iron and phosphorus. At this time, stirring can be performed at normal pressure and in air without heat treatment and without pressurization. This allows economical extraction of lithium, iron and phosphorus since it does not require a conventional reducing atmosphere or carbon dioxide atmosphere.

The temperature of the introduced aqueous acid solution may be substantially the same as the stirring temperature described below. That is, the temperature of the introduced aqueous acid solution may be room temperature to 100°C, 50 to 100°C, 50 to 90°C, 60 to 90°C, and 70 to 90°C. Within the above range, it can be easy to implement the effects of the present invention.

The stirring temperature can be carried out at room temperature to 100°C. In this temperature range, lithium, iron and phosphorus can leach from the material at high leaching rates. For example, stirring may be performed at 20 to 100°C, 25 to 100°C, 50 to 90°C, 60 to 90°C, or 70 to 90°C. Here, 'room temperature' does not mean a constant temperature, but rather a temperature without the addition of external energy. Therefore, room temperature may change depending on location and time.

The stirring time may vary depending on the content of the waste phosphate-based lithium battery material to be treated, the content of the acid aqueous solution, etc., but may be 1 to 5 hours, for example, 1 to 3 hours.

Stirring can be performed by conventional methods known to those skilled in the art by adding an aqueous acid solution to the material. For example, stirring may be performed using a stirrer with a stirring blade or a stirring bar, but is not limited thereto.

In the present invention, an aqueous acid solution was added to the waste phosphorite-based lithium battery material and stirred to leach lithium, iron, and phosphorus from the material, and the pH of the finally prepared first leach solution was -0.2 to 1.4. As the pH of the first leach liquid ranges from -0.2 to 1.4, lithium, iron, and phosphorus can each be leached from the material at a high leaching rate. For example, the pH of the first leachate may be -0.2, -0.1, 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4.

In one embodiment, the lithium leaching rate is greater than 80%, such as 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, It can be 97, 98, 99, 100%, 80 to 100%. Here, the lithium leaching rate can be calculated by Equation 1 below:

[Equation 1]

Lithium leaching rate = B/A x 100

(In Equation 1 above,

A is the concentration of lithium in waste phosphate-based lithium battery materials (unit: weight %)

B is the concentration of lithium in the first leachate (unit: weight %))

In one embodiment, the iron leaching rate is greater than 65%, such as 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100%, 70% or more, 70 to 100% there is. Here, the iron leaching rate can be calculated by equation 2:

[Equation 2]

Iron leaching rate = D/C x 100

(In Equation 2 above,

C is the concentration of iron in the waste phosphate-based lithium battery material (unit: weight %)

D is the concentration of iron in the first leachate (unit: weight%)

In one embodiment, the phosphorus leaching rate is greater than 65%, such as 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, It can be 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100%, 65 to 100%. Here, the phosphorus leaching rate can be calculated by equation 3:

[Equation 3]

Phosphorus leaching rate = F/E x 100

(In Equation 3 above,

E is the concentration of phosphorus in waste phosphate-based lithium battery materials (unit: weight %)

F is the concentration of phosphorus in the first leachate (unit: weight %)

The pH of the first leach solution is -0.2 to 1.4, depending on the content of lithium, iron and/or phosphorus in the material, the concentration and/or temperature of the aqueous acid solution added to the material, the content of the aqueous acid solution added and/or the stirring temperature during stirring, etc. It may be adjusted accordingly, but is not limited thereto.

In step 1, lithium is leached at a high concentration, and the lithium concentration in the first leach liquid is 3000 mg/L or more, for example 3000, 3500, 4000, 4500, 5000, 5500, 6000 mg/L, for example 3000 to 6000 mg/L. , 3500 to 5500 mg/L, 3000 to 5000 mg/L, 3500 to 5000 mg/L. In the above range, the recovery rate of lithium in the first leachate may be high.

(Step 2)

Step 2 converts some of the iron and phosphorus from the first leachate containing lithium, iron, and phosphorus into Vivianite (e.g., Fe ₃ (PO ₄ ) ₂ ·8H ₂ O) and Brushite (e.g., CaHPO ₄ ·2H ₂ O), respectively. This is the step of removing the car. From the first leachate, iron and phosphorus are first removed by precipitating into Vivianite and Brushite according to Reaction Formula 1 below: If iron and phosphorus are precipitated into Vivianite and Brushite, respectively, according to Reaction Formula 1 below, the loss due to precipitation of lithium is reduced. It is possible to remove most of the iron and phosphorus present in the first leachate while inhibiting:

[Scheme 1]

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 the present invention, iron and phosphorus are not removed from the first leachate in a single step, but are removed in two steps, Step 2 and Step 3 described below. Through this, the present invention can prevent the loss of a large amount of lithium by precipitating not only iron and phosphorus but also lithium from the first leachate. This can increase the removal rate of impurities such as iron and phosphorus from the first leachate while increasing the recovery rate of lithium.

By adding an alkaline substance to the first leachate, some of the iron and phosphorus are first removed using Vivianite (Fe ₃ (PO ₄ ) ₂ ·8H ₂ O) and Brushite (CaHPO ₄ ·2H ₂ O), respectively. The alkaline substance may be one or more of alkaline earth metal hydroxides and alkaline earth metal oxides. For example, the alkaline earth metal hydroxide may be calcium hydroxide, magnesium hydroxide, strontium hydroxide, barium hydroxide, or a combination thereof. For example, the oxide of an alkaline earth metal may be calcium oxide. Preferably, it may be calcium hydroxide to facilitate precipitation of CaHPO ₄ ·2H ₂ O (Brushite).

In one embodiment, step 2 may be performed by adding an alkaline earth metal hydroxide to the first leachate, stirring it to prepare a slurry, filtering the prepared slurry, and separating the liquid second leachate and the solid first precipitate. there is. This can increase the dissolution rate of lithium in the second leachate while also increasing the removal rate of iron and phosphorus.

The liquid second leachate may contain lithium, iron, and phosphorus.

The first precipitate of the solid phase may contain Vivianite (Fe ₃ (PO ₄ ) ₂ ·8H ₂ O) and Brushite (CaHPO ₄ ·2H ₂ O). Among the first precipitates, Vivianite (Fe ₃ (PO ₄ ) ₂ ·8H ₂ O) and Brushite (CaHPO ₄ ·2H ₂ O) may be contained at 95% by weight or more, for example, 99 to 100% by weight.

In one embodiment, the lithium dissolution rate can be calculated by Equation 4 below, and the lithium dissolution rate is 80% or more, for example, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90. , 91, 92, 93, 94, 95, 96, 97, 98, 99, 100%, 80% to 100%:

[Equation 4]

Lithium dissolution rate = H/G x 100

(In Equation 4 above,

G is the concentration of lithium in the first leachate (unit: mg/L)

H is the concentration of lithium in the second leachate (unit: mg/L)

In one embodiment, the iron removal rate can be calculated by Equation 5 below, where the iron removal rate is greater than or equal to 90%, such as 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100%, Can be 95 to 100%:

[Equation 5]

Iron removal rate = (I-J)/I x 100

(In Equation 5 above,

I is the concentration of iron in the first leachate (unit: mg/L)

J is the concentration of iron in the second leachate (unit: mg/L))

In one embodiment, the phosphorus removal rate can be calculated by Equation 6 below, and the phosphorus removal rate is 90% or more, such as 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100%, Can be 95 to 100%:

[Equation 6]

Phosphorus removal rate = (K-L)/K x 100

(In Equation 6 above,

K is the concentration of phosphorus in the first leachate (unit: mg/L)

L is the concentration of phosphorus in the second leachate (unit: mg/L))

The amount of alkaline earth metal hydroxide may be adjusted depending on the content of lithium, iron, and phosphorus, and the content of calcium in the first leachate.

For example, the hydroxide of alkaline earth metal is 0.1 to 0.25 mol, for example, 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.2, based on 1 mol of lithium content in the first leach liquid. It can be added in amounts of 0.21, 0.22, 0.23, 0.24, 0.25 mol, and 0.15 to 0.2 mol. For example, the hydroxide of an alkaline earth metal is 0.1 to 0.25 mol, for example, 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.2, based on 1 mol of iron content in the first leach liquid. It may be added at 0.21, 0.22, 0.23, 0.24, 0.25 mol, for example, 0.15 to 0.2 mol. For example, the hydroxide of alkaline earth metal is 0.1 to 0.25 mol, for example, 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.2, 0.21, based on 1 mol of phosphorus content in the first leach liquid. , 0.22, 0.23, 0.24, 0.25 mol, for example, 0.15 to 0.2 mol. In the above range, iron and phosphorus are not eluted at once through step 2, so the removal rate of iron and phosphorus can be increased.

The stirring may be performed at a stirring temperature of 30 to 100°C. In the above temperature range, iron and phosphorus may be precipitated from the material as Vivianite (Fe ₃ (PO ₄ ) ₂ ·8H ₂ O) and Brushite (CaHPO ₄ ·2H ₂ O), respectively. For example, stirring may be performed at 50 to 100°C, 50 to 90°C, 60 to 90°C, or 70 to 90°C.

(Step 3)

Step 3 is to remove some of the iron and phosphorus from the first leachate by first removing some of the iron and phosphorus from the second leachate containing lithium, iron, and phosphorus, respectively, into Magnetite (e.g., Fe ₃ O ₄ ) and Hydroxyapatite (e.g., This is the secondary removal step with Ca ₅ (PO ₄ ) ₃ OH). Iron and phosphorus are removed from the second leachate by precipitating into Fe ₃ O ₄ (Magnetite) and Ca ₅ (PO ₄ ) ₃ ·OH (Hydroxyapatite), respectively, according to Scheme 2 below: Accordingly, if Fe ₃ O ₄ (Magnetite) and Ca ₅ (PO ₄ ) ₃ ·OH (Hydroxyapatite) are precipitated respectively, all iron and phosphorus present in the first leachate can be removed while suppressing loss due to precipitation of lithium. :

[Scheme 2]

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

By adding an alkaline substance to the second leach solution, all iron and phosphorus that were not removed in step 2 are completely removed as Fe ₃ O ₄ (Magnetite) and Ca ₅ (PO ₄ ) ₃ ·OH (Hydroxyapatite), respectively. The alkaline substance may be one or more of alkaline earth metal hydroxides and alkaline earth metal oxides. For example, the alkaline earth metal hydroxide may be calcium hydroxide, magnesium hydroxide, strontium hydroxide, barium hydroxide, or a combination thereof. For example, the oxide of an alkaline earth metal may be calcium oxide. Preferably, it may be calcium hydroxide to facilitate precipitation of Ca ₅ (PO ₄ ) ₃ ·OH (Hydroxyapatite).

In one embodiment, step 3 may be performed by adding a hydroxide of an alkaline earth metal to the second leachate, stirring it to prepare a slurry, filtering the prepared slurry, and separating the liquid third leachate and the solid second precipitate. there is. This can increase the dissolution rate of lithium in the second leachate while also increasing the removal rate of iron and phosphorus.

The third leachate may contain lithium. Iron and phosphorus in the third leachate may each be contained at 1% by weight or less, for example, 0 to 1% by weight.

The second precipitate may contain Fe ₃ O ₄ (Magnetite) and Ca ₅ (PO ₄ ) ₃ ·OH (Hydroxyapatite). Among the second precipitates, Fe ₃ O ₄ (Magnetite) and Ca ₅ (PO ₄ ) ₃ ·OH (Hydroxyapatite) may be contained in an amount of 80% by weight or more, for example, 80 to 100% by weight.

In one embodiment, the lithium dissolution rate can be calculated by Equation 7 below, and the lithium dissolution rate is 80% or more, for example, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90. , 91, 92, 93, 94, 95, 96, 97, 98, 99, 100%, 80% to 100%:

[Equation 7]

Lithium dissolution rate = N/M x 100

(In Equation 7 above,

M is the concentration of lithium in the second leachate (unit: mg/L)

N is the concentration of lithium in the third leachate (unit: mg/L))

In one embodiment, the iron removal rate can be calculated by Equation 8 below, and the iron removal rate can be greater than 95%, for example, 95, 96, 97, 98, 99, 100%, 99 to 100%:

[Equation 8]

Iron removal rate = (P-Q)/P x 100

(In Equation 8 above,

P is the concentration of iron in the second leachate (unit: mg/L)

Q is the concentration of iron in the third leachate (unit: mg/L))

In one embodiment, the phosphorus removal rate can be calculated by Equation 9 below, and the phosphorus removal rate can be greater than 95%, for example, 95, 96, 97, 98, 99, 100%, 99 to 100%:

[Equation 9]

Phosphorus Removal Rate = (R-S)/R x 100

(In Equation 9 above,

R is the concentration of phosphorus in the second leachate (unit: mg/L)

S is the concentration of phosphorus in the third leachate (unit: mg/L))

The amount of alkaline earth metal hydroxide can be adjusted depending on the content of lithium, iron, and phosphorus, and the content of calcium in the second leachate.

For example, the hydroxide of an alkaline earth metal is 0.05 to 0.2 mol, for example, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, based on 1 mol of lithium content in the second leach liquid. It can be added in amounts of 0.16, 0.17, 0.18, 0.19, 0.2 mol, and 0.05 to 0.1 mol. For example, the hydroxide of an alkaline earth metal is 0.05 to 0.2 mol, for example, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, based on 1 mol of iron content in the second leach liquid. It can be added in amounts of 0.16, 0.17, 0.18, 0.19, 0.2 mol, and 0.05 to 0.1 mol. For example, the hydroxide of an alkaline earth metal is 0.05 to 0.2 mol, for example, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, based on 1 mol of phosphorus content in the second leachate. , 0.17, 0.18, 0.19, 0.2 mol, 0.05 to 0.1 mol. Within the above range, iron and phosphorus in the second leachate are completely removed, and there is no problem of excessive alkaline earth metal hydroxides being added, so economic efficiency can be high.

The stirring may be performed at a stirring temperature of 30 to 100°C. In the above temperature range, iron and phosphorus may be precipitated from the material as Fe ₃ O ₄ (Magnetite) and Ca ₅ (PO ₄ ) ₃ ·OH (Hydroxyapatite), respectively. For example, stirring may be performed at 50 to 100°C, 50 to 90°C, 60 to 90°C, or 70 to 90°C.

Hereinafter, preferred embodiments of the present invention will be described. However, the following example is only a preferred example of the present invention and the present invention is not limited to the following example.

[Example 1]

A spent phosphorus phosphorus-based lithium battery cathode material containing lithium, iron, and phosphorus was prepared. The waste phosphate-based lithium battery cathode material contains the ingredients in Table 1 below in the amounts in Table 1 below.

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

Hydrochloric acid aqueous solutions of different concentrations were mixed with the spent phosphorus lithium battery cathode material and stirred for 2 hours at normal pressure and in air without heat treatment. After stirring was completed, it was filtered to obtain a first leachate containing lithium, iron, and phosphorus. The pH of the first leachate is shown in Table 2 below. The lithium leaching rate, iron leaching rate, and phosphorus leaching rate for the first leachate having the corresponding pH were calculated according to Equation 1, Equation 2, and Equation 3, respectively, and are shown in Table 2 below. The lithium concentration in the leachate was measured for the first leachate having the corresponding pH, and is shown in Table 2 below.

pH of first leachate 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 In the first leachate
Concentration of lithium (mg/L) 2926 3759 4344 4385 4498 4530 4530

As shown in Table 2, when the pH of the first leach liquid is -0.2 to 1.4, lithium can be leached from the spent phosphorus lithium battery cathode material at room temperature and pressure at a high leaching rate of over 80%. However, if the acid is used excessively and the pH of the first leachate becomes less than -0.2, there is a problem in that the amount of acid used is excessive and economic efficiency is reduced. In addition, if the pH of the first leach solution is greater than 1.4 due to the use of less acid, the lithium leaching rate is too low, less than 80%, and thus the recovery efficiency of lithium is poor.

[Example 2]

The concentrations of lithium, iron, and phosphorus in the first leachate containing lithium, iron, and phosphorus obtained in Example 1 were measured and shown in Table 2 below. Some of the iron and phosphorus were first removed from the first leachate. Specifically, calcium hydroxide was added to the first leachate and stirred to prepare a slurry, and the prepared slurry was filtered to separate the second leachate and the first precipitate.

The concentrations of lithium, iron, and phosphorus in the second leachate were measured, and the results are shown in Table 3 below. The lithium dissolution rate, iron removal rate, and phosphorus removal rate were calculated according to Equation 4, Equation 5, and Equation 6 above, respectively, and are shown in Table 3 below.

division Li concentration
(mg/L) Fe concentration
(mg/L) P concentration
(mg/L) first leachate 4530 35062 18483 secondary leachate 4510 1039 14 Li dissolved rate (%) 99.6 Fe removal rate (%) 97.0 P removal rate (%) 99.9

As shown in Table 3, it can be seen that while iron and phosphorus were removed from the first leachate at a high removal rate, lithium remained in the second leachate at a high dissolved rate.

The first precipitate was washed and dried, and an X-ray diffraction pattern was measured, and the results are shown in Figure 1. As shown in Figure 1, it can be seen that iron and phosphorus were removed from the first leachate by precipitating as Vivianite (Fe ₃ (PO ₄ ) ₂ ·8H ₂ O) and Brushite (CaHPO ₄ ·2H ₂ O), respectively. .

[Example 3]

In Example 2, the concentrations of lithium, iron, and phosphorus in the second leachate were measured and shown in Table 3 below. Some of the iron and phosphorus were secondaryly removed from the second leachate. Specifically, calcium hydroxide was added to the second leachate and stirred to prepare a slurry, and the prepared slurry was filtered to separate the third leachate and the second precipitate.

The concentrations of lithium, iron, and phosphorus in the third leachate were measured, and the results are shown in Table 4 below. The lithium dissolution rate, iron removal rate, and phosphorus removal rate were calculated according to Equation 7, Equation 8, and Equation 9, respectively, and are shown in Table 4 below.

division Li concentration
(mg/L) Fe concentration
(mg/L) P concentration
(mg/L) secondary leachate 4510 1039 14 Tertiary leachate 4500 0 0 Li dissolved rate (%) 99.8 Fe removal rate (%) 100 P removal rate (%) 100

As shown in Table 4, it can be seen that iron and phosphorus were completely removed from the second leachate with a high removal rate, and lithium remained in the third leachate at a high dissolved rate.

The second precipitate was washed and dried, and an X-ray diffraction pattern was measured, and the results are shown in FIG. 2. As shown in Figure 2, it can be seen that iron and phosphorus were removed from the second leachate by precipitating as Magnetite (Fe ₃ O ₄ ) and Hydroxyapatite (Ca ₅ (PO ₄ ) ₃ OH), respectively.

The present invention is not limited to the above-mentioned embodiments, but can be manufactured in various different forms, and those skilled in the art may manufacture the present invention in other specific forms without changing the technical idea or essential features of the present invention. You will understand that it can be done. Therefore, the embodiments described above should be understood in all respects as illustrative and not restrictive.

Claims (12)

A method for removing impurities from spent phosphorus lithium battery materials, comprising: Preparing a first leachate containing lithium, iron, and phosphorus from waste phosphate-based lithium battery material at normal pressure without heat treatment (step 1); Primary removal of some of the iron and phosphorus from the first leachate containing lithium, iron, and phosphorus using Vivianite and Brushite, respectively (step 2); Comprising the step (step 3) of secondary removal of some of the iron and phosphorus with Magnetite and Hydroxyapatite, respectively, from the second leachate containing lithium, iron, and phosphorus from which some of the iron and phosphorus were first removed, Method for removing impurities from spent phosphorus lithium battery materials. The method of claim 1, wherein the spent phosphorite-based lithium battery material includes one or more complex oxides of lithium, iron, and phosphorus. The method of claim 1, wherein the spent phosphorus-based lithium battery material includes at least one of lithium iron phosphorus oxide and lithium manganese iron oxide. The method of claim 3, wherein the waste phosphate-based lithium battery material further includes one or more of lithium nickel cobalt manganese oxide, lithium manganese oxide, lithium nickel manganese spinel, lithium nickel cobalt aluminum oxide, lithium cobalt oxide, and lithium titanium oxide. How to. The method according to claim 1, wherein the material contains 1% by weight or more of lithium, 20% by weight or more of iron, and 5% by weight or more of phosphorus. The method of claim 1, wherein the pH of the first leachate is -0.2 to 1.4. The method of claim 1, wherein step 2 is performed by adding a hydroxide of an alkaline earth metal to the first leachate, stirring it to prepare a slurry, filtering the slurry, and separating the liquid second leachate and the solid first precipitate. How to become. The method of claim 7, wherein the hydroxide of an alkaline earth metal is calcium hydroxide. The method of claim 7, wherein the Vivianite and Brushite in the first precipitate are contained in an amount of 95% by weight or more. The method of claim 7, wherein step 3 is performed by adding an alkaline earth metal hydroxide to the second leachate, stirring it to prepare a slurry, filtering the slurry, and separating the liquid third leachate and the solid second precipitate. How to become. The method of claim 10, wherein Magnetite and Hydroxyapatite among the second precipitates are contained in an amount of 95% by weight or more. 11. The method of claim 10, wherein the hydroxide of an alkaline earth metal is calcium hydroxide.

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