KR102606229B1 - Selective recovery of lithium from ternary cathode active material of spent lithium ion batteries - Google Patents

Abstract

The present invention relates to a method for selective recovery of lithium from a ternary waste cathode active material, comprising the steps of (a) leaching lithium from the waste cathode active material powder in an aqueous oxidizing agent solution; (b) adding a neutralizing agent to the lithium leaching filtrate obtained in step (a) to precipitate and remove impurities other than lithium; and (c) a lithium recovery step of heating and concentrating the lithium leach filtrate from which impurities have been removed in step (b), carbonating it, and recovering lithium carbonate; Including, it is possible to economically and efficiently recover valuable metals such as lithium (Li), as well as cobalt (Co), nickel (Ni), and manganese (Mn).

Description

Selective recovery of lithium from ternary cathode active material of spent lithium ion batteries}

The present invention relates to a method for selective recovery of lithium from a ternary waste cathode active material, and more specifically, to a method for selective recovery of lithium from a waste cathode active material powder containing nickel (Ni), cobalt (Co), manganese (Mn), and lithium (Li). This relates to a method for easily separating and recovering cobalt, nickel, and manganese contained in the residue by selectively removing lithium (Li) by leaching it.

Lithium secondary batteries are a core component of electric vehicles and power storage systems (ESS), and the demand for them is rapidly increasing as the supply of new and renewable energy without environmental pollution increases. As demand for electric vehicle batteries increases, the production of nickel (Ni)-cobalt (Co)-manganese (Mn) (NCM) cathode active materials for lithium ion batteries (LIBs) is increasing.

Accordingly, the ternary cathode active material of lithium secondary batteries generated from electric vehicles and energy storage systems (ESS) that have reached the end of their lifespan contains expensive metals such as lithium (Li), cobalt (Co), and nickel (Ni). There is a need to develop an effective and economical process to recover these valuable metals and recycle them as raw materials for lithium secondary batteries.

In order to recover valuable metals from conventional waste cathode active materials, lithium-ion battery scrap is leached in an acidic solution to recover valuable metals such as manganese, cobalt, nickel, and lithium through a step-by-step recovery process of manganese recovery, cobalt recovery, nickel recovery, and lithium recovery. there is.

However, since the removal of lithium is the final step, the loss rate of lithium is high, and the manufacturing cost increases due to the process of recovering each valuable metal with high purity.

In addition, conventionally, after leaching waste cathode active material by non-selective dissolution, valuable metals are recovered through the steps of removing impurities, removing Li by co-precipitation with NCM, and redissolving in sulfuric acid. However, since the removal of lithium is the final step, the loss rate of lithium is low. It is high, and uneconomical problems have existed since additional processes such as sulfuric acid re-dissolution and impurity removal are required to recover NCM co-precipitation products.

In addition, in order to selectively recover only lithium from conventional waste cathode active materials, dry reduction heat treatment is performed at over 600 ^o C with hydrogen, activated carbon, Na ₂ CO ₃ , etc., and wet water leaching is performed. ) is used in a step-by-step process, but this also has the problem that the process is complicated and energy consumption to recover lithium is large.

Therefore, by prioritizing the selective removal or recovery of lithium from waste cathode active materials through a wet process, it is possible to economically and efficiently recover valuable metals such as cobalt and nickel from the residue containing lithium-removed ternary materials, that is, cobalt, nickel, and manganese. There is a need for a process that can be used.

1. Republic of Korea Patent Publication No. 10-2013-0071838 (published on July 1, 2013)

The purpose of the present invention is to advance the recovery of high-purity lithium from waste cathode active material, and to selectively recover lithium from ternary waste cathode active material, which can recover valuable metals such as cobalt, nickel, and manganese from its residue, and cobalt (Co) The purpose is to provide a method for recovering valuable metals such as nickel (Ni) and manganese (Mn).

In order to achieve the above object, the present invention includes the steps of (a) leaching lithium from waste cathode active material powder in an oxidizing agent aqueous solution; (b) adding a neutralizing agent to the lithium leaching filtrate obtained in step (a) to precipitate and remove impurities other than lithium; and (c) a lithium recovery step of heating and concentrating the lithium leach filtrate from which impurities have been removed in step (b), carbonating it, and recovering lithium carbonate; Provides a method for selective recovery of lithium from a waste cathode active material containing.

In addition, the present invention provides valuable metals such as cobalt (Co), nickel (Ni), and manganese (Mn) from a composition containing the residue separated from the lithium leachate in step (a) and impurities other than lithium precipitated in step (b). Provides a method for recovering ternary valuable metals from waste cathode active material, including the step of recovering.

The method of selective recovery of lithium from the ternary system (nickel (Ni)-cobalt (Co)-manganese (Mn); NCM) waste cathode active material according to the present invention selectively recovers high-purity lithium through a leaching process of the waste cathode active material. By preceding the steps, high purity lithium can be obtained with a low lithium loss rate.

In addition, valuable metals such as cobalt, nickel, and manganese can be recovered from the lithium-removed residue obtained from the lithium recovery process, economically and efficiently producing not only lithium (Li), but also cobalt (Co), nickel (Ni), The valuable metal manganese (Mn) can be recovered.

Figure 1 is a schematic flowchart of a method for separating and recovering valuable metals from waste cathode active material powder according to the present invention.
Figure 2 is a schematic flowchart showing a method for selectively separating and recovering lithium from waste cathode active material powder according to the present invention.
Figure 3 is a diagram showing the results of XRD analysis of the waste cathode active material powder used in the present invention.
Figure 4 is a diagram showing the XRD analysis results of the residue after selective leaching of lithium (primary leaching).

Hereinafter, the present invention will be described in detail.

The present inventors can selectively recover only high-purity lithium by leaching waste cathode active material powder in an oxidizing agent and then performing a wet process to remove impurities and carbonate the lithium leaching filtrate, and from the residue from which lithium has been removed, cobalt, nickel, It was discovered that valuable metals such as manganese can be recovered economically and efficiently, and thus they can be recycled and used as cathode active materials for lithium secondary batteries. The present invention has been completed.

The waste cathode active material powder of the present invention is obtained from cathode active materials for lithium secondary batteries that are defective or discarded during the manufacturing process, and in particular, Ni-Co-Mn (NCM) ternary waste cathode active material is used. The collected waste cathode active material is prepared in the form of waste cathode active material powder through roasting and a predetermined powdering process. Waste cathode active material powder contains various components such as nickel (Ni), cobalt (Co), manganese (Mn), and lithium (Li), as well as trace amounts of aluminum (Al), copper (Cu), iron (Fe), and calcium (Ca). This is mixed.

The selective recovery method of lithium from waste cathode active material of the present invention involves leaching waste cathode active material powder in an oxidizing agent, followed by a wet process to remove impurities and carbonate the lithium leaching filtrate, thereby selectively recovering only high-purity lithium. Includes.

Afterwards, by performing a leaching and impurity removal process from the residue from which lithium has been removed, valuable metals such as cobalt, nickel, and manganese can also be recovered.

Specifically, the present invention includes the steps of (a) leaching lithium from waste cathode active material powder in an oxidizing agent aqueous solution; (b) adding a neutralizing agent to the lithium leaching filtrate obtained in step (a) to precipitate and remove impurities other than lithium; and (c) a lithium recovery step of heating and concentrating the lithium leach filtrate from which impurities have been removed in step (b), carbonating it, and recovering lithium carbonate; Provides a method for selective recovery of lithium from a waste cathode active material containing. Figure 2 is a flowchart showing a method for selective recovery of lithium according to the present invention, which will be described in detail below.

First, step (a) is a step of leaching lithium from the waste cathode active material powder in an oxidizing agent aqueous solution.

In the waste cathode active material powder, the crystal lattice of the layered structure is collapsed or transformed by an oxidizing agent, thereby enabling selective dissolution of lithium.

The oxidizing agent is one or more selected from the group consisting of KMnO ₄ , Na ₂ S ₂ O ₈ , O ₃ , and NaClO ₃ , but preferably potassium permanganate (KMnO ₄ ) is used to determine the optimal reaction temperature, pH, reaction time, and solid-liquid ratio. It is preferable to carry out the reaction under the following conditions.

The optimal reaction temperature is preferably in the range of 30 to 90 ° C. At a reaction temperature of 30 ^° C or lower, the oxidation reaction of manganese is not active, so the leaching rate of valuable metals such as cobalt and nickel increases, and the selectivity for lithium decreases. Above ^o C, the energy cost for water evaporation reaction and heating increases, which is not desirable.

In addition, the optimal pH is preferably in the range of 2 to 10. If the water leaching pH is more than 10, the oxidation reaction rate of manganese is slow and the lithium leaching rate is low, and if the pH is less than 2, the amount of alkaline agent added for neutralization increases, making it economical. There is a downside to this. Here, the pH can be adjusted by selecting one or more from the group consisting of H ₂ SO ₄ , HCl, and HNO ₃ .

In addition, the optimal reaction time is preferably in the range of 1 to 4 hours, and if it increases to more than 4 hours, it is not desirable because the improvement in leaching rate is not significant compared to the increase in operating time.

In addition, the waste cathode active material powder and the oxidizing agent aqueous solution preferably have a solid-liquid ratio in the range of 5 to 20. When the solid-liquid ratio L/S is 20 or more, the concentration of lithium in the leachate decreases, increasing the energy cost required to concentrate lithium, If L/S is 5 or less, the concentration of lithium increases to 13 g/L or more, and the precipitation reaction of lithium dominates the leaching reaction, causing a problem in that the dissolution rate is significantly slowed.

Step (b) is a step in which impurities other than lithium are precipitated and removed by filtering the lithium leaching solution from step (a) and adding a neutralizing agent to the obtained lithium leaching filtrate.

An alkaline neutralizer may be added to remove impurities (Cu, Al, Ca, etc.) other than lithium from the lithium leaching filtrate, and the neutralizer may be NaOH, NH ₄ OH, Na ₂ CO ₃ , K ₂ CO ₃ , CaO, One or more is selected from the group consisting of CaCO ₃ , MgCO ₃ and MgO, but preferably the pH is adjusted to the range of 9-10 using sodium carbonate (Na ₂ CO ₃ ).

After neutralization using a neutralizing agent as described above, the obtained precipitate contains cobalt, nickel, manganese, etc. in addition to Cu, Al, and Ca. At this time, the properties of nickel, cobalt, and manganese precipitates vary depending on the type of alkaline agent, mainly carbonate ((Co-Ni-Mn)CO ₃ ) or hydroxide ((Co-Ni-Mn)(OH) ₂ ) co-precipitation. Can be obtained with water.

Step (c) is a lithium recovery step in which the lithium leach filtrate from which impurities have been removed in step (b) is concentrated by heating, carbonated, and recovered as lithium carbonate.

The heating concentration is characterized in that it is carried out at a temperature of 50 to 95 ^o C, and can preferably be performed at a temperature of 90 ^o C.

In addition, the carbonation is characterized by adding one or more selected from the group consisting of Na ₂ CO ₃ , K ₂ CO ₃ , CaCO ₃ and MgCO ₃ , preferably sodium carbonate (Na ₂ CO ₃ ) compared to 1 mole of lithium. Lithium carbonate can be recovered by adding it at a concentration of 1 mole to 1.5 mole.

Afterwards, to remove sodium co-precipitated in lithium carbonate, high-purity lithium can be recovered by performing water washing twice at a solid-liquid ratio (lithium carbonate and water; L/S) of 3:1.

In addition, the present invention provides valuable metals such as cobalt (Co), nickel (Ni), and manganese (Mn) from a composition containing the residue separated from the lithium leachate in step (a) and impurities other than lithium precipitated in step (b). Provides a method for recovering ternary valuable metals from waste cathode active material, including the step of recovering. Figures 1 and 2 are flowcharts showing a method for selective recovery of lithium according to the present invention.

The step of recovering valuable metals such as cobalt (Co), nickel (Ni), and manganese (Mn) is obtained from a composition containing the residue separated from the lithium leachate in step (a) and impurities other than lithium precipitated in step (b). Any method that can recover valuable metals such as cobalt (Co), nickel (Ni), and manganese (Mn), such as leaching reaction and impurity removal reaction, can be used without limitation.

The lithium-free residue obtained by filtering the lithium leachate in step (a) includes MnO ₂ , LiCoO ₂ , and LiNiO ₂ , and impurities other than lithium precipitated in step (b) include cobalt, nickel, and manganese. It is characterized in that it contains carbonate ((Co-Ni-Mn)CO ₃ ) or hydroxide ((Co-Ni-Mn)(OH) ₂ ) co-precipitation products, which are hydrolysis products.

Therefore, the present invention can recover lithium by selectively leaching it at a high concentration from a ternary waste cathode active material through a wet process, and recover ternary valuable metals excluding lithium from the lithium-removed leaching residue in a simpler and more economical method than the existing process. That is, nickel, cobalt, manganese, etc. can be recovered.

Hereinafter, the present invention will be described in more detail through examples. These examples are only for illustrating the present invention in more detail, and it is understood by those skilled in the art that the scope of the present invention is not limited by these examples according to the gist of the present invention. It will be self-evident.

[Example]

[Table 1] shows an example of the raw material composition of the waste NCM cathode active material used in the experiment.

Ternary cathode active material raw material composition element Co Ni Mn Cu Ca Al Fe Li LOI(%) Content (wt%) 11.22 25.95 9.40 0.40 0.01 0.71 0.43 5.73 4.4

LOI; Loss on Ignition

[ Example One: Lithium leaching ]

The reaction proposed for leaching lithium in the present invention is as follows.

In the case of potassium permanganate (KMnO ₄ ) added as an oxidizing agent, it is converted into tetravalent manganese oxide, MnO ₂ , by obtaining 3 electrons from manganese (trivalent) contained in the NCM positive electrode active material under acidic conditions as shown in the reaction equation below, At this time, the layered crystal lattice of the ternary cathode active material Li(Ni,Co,Mn)O ₂ is partially collapsed or deformed, creating an environment in which selective dissolution of lithium is possible.

[Reaction formula]

2MnO ₄ ^- + 2H ⁺ + 3Mn ₂ O ₃ = 8MnO _{2 (s)} + H ₂ O

(3 electrons consumed per 1 mol of KMnO ₄ )

( ₄ mol of MnO ₂ produced per 1 mol of KMnO 4)

At this time, as a side reaction of the above reaction, manganese may be partially dissolved as shown in the side reaction equation below.

[Side reaction equation]

MnO ₄ ^- + 8H ⁺ + 5e ^- = Mn ^{2 +} + 4H ₂ O

The reaction variables of the following leaching experiment were optimized by changing the reaction temperature, concentration of oxidizing agent, solid-liquid ratio, etc. Sulfuric acid was used to adjust pH, and in addition to the influence of reaction temperature, the experiment was conducted under conditions of 70 ^o C. .

1-1. Reaction temperature effect

The leaching behavior of lithium according to change in reaction temperature of waste NCM cathode active material was investigated. In the leaching behavior according to the reaction temperature in Table 2 below (leaching liquid composition, unit: mg/L), when the reaction temperature was 25 ^o C, the concentration of lithium was 4,449 mg/L, showing a leaching rate of about 77%, but cobalt, The leaching rates of nickel and manganese also tended to increase at the same time, and as the temperature increased to 70 ^o C, the leaching rates of lithium improved to 86%, and the leaching rates of manganese and cobalt tended to relatively decrease.

(Unit: mg/L) Reaction temperature ( ^o C) Co Ni Mn Cu Ca Al Fe Li 25 2,265 6,696 2,326 N.D. 3.0 129.2 N.D. 4,449 70 1,730 6,367 8.8 N.D. 2.9 111.2 N.D. 4,782

1-2. Oxidizing agent ( KMnO ₄ ) Added amount

Using potassium permanganate (KMnO ₄ ) as an oxidizing agent, the leaching behavior of lithium (leaching solution composition, unit: mg/L) according to the amount of oxidizing agent added in the aqueous solution is shown in Table 3 below. As the amount of oxidizing agent added increased, the lithium leaching rate improved from 83% at 1 equivalent to 96% at 2 equivalents. On the other hand, when 1 equivalent of oxidizing agent was added, the leaching rates of cobalt and nickel were leached up to 22% and 44%, respectively, showing a tendency for the selectivity of lithium to decrease somewhat. At more than 1.5 equivalents, the leaching rates of cobalt and nickel were 22% and 44%, respectively. decreased to 9% and 23%, respectively.

(Unit: mg/L) Oxidizing agent equivalent Co Ni Mn Cu Ca Al Fe Li One 2,773 10,570 0.8 N.D. 1.9 129.2 N.D. 4,532 1.5 1,730 6,367 8.8 N.D. 2.9 111.2 N.D. 4,982 2 1,194 6,035 0.5 N.D. 2.9 147.5 N.D. 5,490

1-3. water leaching pH changes

The leaching behavior of lithium (leaching liquid composition, unit: mg/L) according to changes in water leaching pH was investigated. When the positive electrode active material powder was mixed with water, it showed alkalinity above pH 11, and sulfuric acid was added to lower the pH to acidic. As shown in Table 4 below, as the water leaching pH decreases, that is, toward the acidic region, the lithium leaching rate increases, and at pH 2.5, the lithium leaching rate improves to 96%.

In general, it is expected that the reaction between the oxidizing agent and the manganese in the cathode active material will proceed as follows in acidic and alkaline areas, and since the oxidizing power tends to increase toward the acidic area, the lithium leaching rate is improved in the acidic area with excellent oxidizing power. It is judged that

(Acidic region) MnO ₄ ^- + 4H ⁺ + 3e ^- = MnO _{2 (s)} + 2H ₂ O, E ^o = 1.70V

(Alkaline region) MnO ₄ ^- + 2H ₂ O + 3e ^- = MnO _{2 (s)} + 4OH ^- , E ^o = 0.59V

(Unit: mg/L) pH Co Ni Mn Cu Ca Al Fe Li 10.5 4.4 2.5 N.D. N.D. N.D. N.D. N.D. 1,505 5.0 N.D. 1,627 0.18 N.D. 3.8 N.D. N.D. 3,629 2.5 1,194 6,035 0.5 N.D. 2.9 147.5 N.D. 5,490

1-4. high cost change

The leaching behavior of lithium (leaching solution composition, unit: mg/L) according to changes in the solid-liquid ratio (waste NCM and aqueous solution) of water leaching was shown. As the solid-liquid ratio decreased from 10 to 5, the lithium leaching rate decreased from 86% to 83%, the cobalt leaching rate decreased from 13% to 5%, and the nickel leaching rate did not change.

(Unit: mg/L) High liquid ratio (L/S) Co Ni Mn Cu Ca Al Fe Li 10 1,730 6,367 8.8 N.D. N.D. 111.2 N.D. 4,782 5 1,391 16,630 0.5 N.D. 9.9 192.6 N.D. 10,850

Therefore, when lithium was leached from waste NCM positive electrode active material using potassium permanganate (KMnO ₄ ) as an oxidizing agent according to Example 1, reaction temperature was 70°C, 2 equivalents of oxidizing agent, pH 2.5, solid-liquid ratio (L/S) was 5. Under the conditions, the leaching rate of lithium could be recovered at more than 96%, and the leaching rate of other valuable metals, that is, cobalt, nickel, and manganese, was low at less than 28%, confirming that lithium could be selectively recovered. Cobalt, nickel, etc. leached together with lithium could be selectively recovered through the following neutralization process (Example 3).

[ Example 2: residue analyze]

After lithium leaching according to Example 1, the residue separated through reduced pressure filtration was analyzed by XRD (X-ray diffraction).

The XRD analysis results of the residue recovered after leaching of lithium are shown in Figure 4. _{Compared to the raw} material _{composition Li} ( _Ni It was analyzed that it remained in a form combined with lithium.

[ Example 3: Removal of impurities]

As in Example 1, in order to remove impurities (Co, Ni, Al, etc.) other than lithium in the lithium leach solution, 40 g of Na ₂ CO ₃ was added to 1 L of the Li leach filtrate (pH 2.2) and neutralized to a pH range of 9 to 10. . After neutralization, lithium was obtained at 99.9% without loss, and the obtained precipitate was a carbonate containing cobalt and nickel contained in the filtrate, which was treated with the residue separated after lithium leaching as in Example 2 above and was recovered without loss. It was possible to recover valuable metals such as cobalt, nickel, and manganese.

(Unit: mg/L) division Co Ni Mn Cu Ca Al Fe Li pH Leach filtrate 972 5,328 211 0.08 3.1 58.1 N.D. 5,334 2.2 After neutralization 0.2 N.D. 0.4 N.D. 5 N.D. N.D. 5,330 9.3

[ Example 4: lithium carbonate collect]

After neutralizing the lithium leach filtrate as in Example 3, it was concentrated by heating at a temperature of 90 ^o C, and Na ₂ CO ₃ was added up to 1.5 equivalents based on the concentration of lithium to recover lithium carbonate. To remove coprecipitated sodium in the recovered lithium carbonate, lithium carbonate with 98.4% purity was recovered after washing twice with water at 90 ^o C at a solid-liquid ratio (lithium carbonate and water; L/S) of 3:1.

division Co Ni Mn Cu Ca Al Fe Na Li Lithium carbonate
ingredient
(mg/kg) N.D. N.D. 1.7 N.D. 86 N.D. N.D. 8,060 184,800

The present invention can recover lithium by selectively leaching it at a high concentration from a ternary waste cathode active material through a wet process, and ternary valuable metals excluding lithium, i.e., Nickel, cobalt, manganese, etc. can be recovered.

Claims (12)

(a) leaching lithium from the waste cathode active material powder in an oxidizing agent aqueous solution;
(b) adding a neutralizing agent to the lithium leaching filtrate obtained in step (a) to precipitate and remove impurities other than lithium; and
(c) a lithium recovery step of heating and concentrating the lithium leach filtrate from which impurities have been removed in step (b), carbonating it, and recovering lithium carbonate; Including,
The aqueous oxidizing agent solution includes at least one from the group consisting of KMnO ₄ , Na ₂ S ₂ O ₈ , O ₃ , and NaClO ₃ , which are additional oxidizing agents in an aqueous acid solution,
The additional oxidizing agent is contained in an amount of 1.5 equivalents or more based on 1 equivalent of lithium,
The waste cathode active material powder includes a layered active material, and the crystal lattice of the layered structure is collapsed or transformed by the oxidizing agent. delete According to clause 1,
The neutralizing agent is a selective recovery method of lithium from a spent cathode active material, characterized in that at least one selected from the group consisting of NaOH, NH ₄ OH, Na ₂ CO ₃ , K ₂ CO ₃ , CaO, CaCO ₃ , MgCO ₃ , and MgO. According to clause 1,
Step (a) is a method for selective recovery of lithium from waste cathode active material, characterized in that leaching at a temperature of 30 to 90 ° C. According to clause 1,
Step (a) is a selective recovery method of lithium from waste cathode active material, characterized in that leaching at pH 2 to 7. According to clause 5,
The pH is H ₂ SO ₄ , HCl, HNO ₃ A selective recovery method of lithium from a spent cathode active material, characterized in that one or more selected from the group consisting of and controlled. According to clause 1,
Step (a) is a method for selective recovery of lithium from waste cathode active material, characterized in that leaching for 1 to 4 hours. According to clause 1,
A method for selective recovery of lithium from waste cathode active material, characterized in that in step (a), the waste cathode active material powder and the oxidizing agent aqueous solution are leached at a solid-liquid ratio (mg/L) of 5 to 20. According to clause 1,
In step (c), carbonation is performed by selecting at least one from the group consisting of Na ₂ CO ₃ , K ₂ CO ₃ , CaCO ₃ , and MgCO ₃ and adding lithium from the waste cathode active material in an amount of 1 to 1.5 equivalents relative to the lithium concentration. Selective recovery method. Valuable metals such as cobalt (Co), nickel (Ni), and manganese (Mn) are extracted from the residue separated from the lithium leachate in step (a) of claim 1 and the composition containing impurities other than lithium precipitated in step (b) of claim 1. A method for recovering ternary valuable metals from waste cathode active material including the step of recovering. According to clause 10,
The residue separated from the lithium leachate in step (a) is a method for recovering ternary valuable metals from a waste cathode active material, characterized in that it contains MnO ₂ , LiCoO ₂ , and LiNiO ₂ . According to clause 10,
Impurities other than lithium precipitated in step (b) are waste cathode active materials, characterized in that they include carbonate ((Co-Ni-Mn)CO ₃ ) or hydroxide ((Co-Ni-Mn)(OH) ₂ ). Method for recovering ternary valuable metals.