How to recover lithium from used lithium-ion batteries

Abstract

To provide a method for recovering lithium from a waste lithium ion battery that enables lithium to be recovered with a high recovery rate and also enables salts generated during the recovery process to be reused in the process as mineral acid and alkali.SOLUTION: A method for recovering lithium from a waste lithium ion battery includes: an extraction step for dissolving active material powder, obtained by pretreating a waste lithium ion battery, with mineral acid, and adding at least one of sodium hydroxide and potassium hydroxide thereto, to obtain a solution, from which valuable metals such as manganese are to be extracted with an organic solvent; a separation step for separating a lithium salt and a sodium salt or the like from an alkali metal mixed salt aqueous solution obtained in the extraction step; and a step for carbonating the lithium salt to obtain lithium carbonate.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for recovering lithium from waste lithium-ion batteries.

Background Art

[0002] In recent years, with the widespread use of lithium-ion batteries, methods for recovering valuable metals such as cobalt, nickel, manganese, and lithium from waste lithium-ion batteries and reusing them as materials for the lithium-ion batteries have been studied.

[0003] Conventionally, when recovering the valuable metals from the waste lithium-ion batteries, cobalt, nickel, manganese, and lithium are separated and purified by a wet process from the powder containing the valuable metals obtained by heat-treating (roasting), pulverizing, classifying, etc. the waste lithium-ion batteries (see, for example, Patent Documents 1 and 2).

[0004] In the present invention, the waste lithium-ion battery means a used lithium-ion battery whose battery product life has expired, a lithium-ion battery discarded as a defective product or the like in the manufacturing process, and the remaining positive electrode material, negative electrode material, etc. used for commercialization in the manufacturing process. Further, the powder containing the positive electrode and the negative electrode obtained from the waste lithium-ion battery is used as the active material powder. Furthermore, the impurity means a metal contained in the active material powder that does not require recovery.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, existing wet processes use compounds other than lithium compounds, which are the target material to be recovered, as alkali sources. As a result, the concentration of non-lithium cations increases, while the lithium ion concentration decreases. Consequently, conventional wet processes suffer a significant decrease in the recovery rate of lithium, the target material. Furthermore, conventional wet processes have the disadvantage that the mineral acid used to dissolve the active material powder and the compounds used as alkali sources are discharged as salts, and there is no technology to recycle these mineral acids and compounds used as alkali sources. In recent years, there has been a strong demand for a method to recover lithium from waste lithium-ion batteries that overcomes these drawbacks, allows for high-rate recovery of lithium, and enables the reuse of salts generated in the recovery process as mineral acids and alkalis within the same process. However, such a method has not been provided. The problem that the present invention aims to solve is to provide a method for recovering lithium from waste lithium-ion batteries that allows for high-rate recovery of lithium and enables the reuse of salts generated in the recovery process as mineral acids and alkalis within the same process. [Means for solving the problem]

[0007] In view of the above problems, the inventors conducted extensive research and found that by dissolving the active material powder in a mineral acid to obtain a solution, adding at least one of sodium hydroxide and potassium hydroxide, further separating the lithium salt aqueous solution from the sodium and potassium salt aqueous solution, and then electrolyzing the separated sodium and potassium salt aqueous solution to obtain the mineral acid, along with at least one of sodium hydroxide and potassium hydroxide, can be reused. The present invention was completed based on these findings.

[0008] The present invention relates to a method for recovering lithium from a waste lithium-ion battery, comprising: a dissolution step of dissolving an active material powder obtained by pre-treating the waste lithium-ion battery with a mineral acid; an alkali metal hydroxide addition step of adding at least one of sodium hydroxide and potassium hydroxide to the solution obtained in the dissolution step; an extraction step of extracting at least one of iron, aluminum, manganese, cobalt, and nickel contained in the active material powder from the solution obtained in the alkali metal hydroxide addition step by solvent extraction with an organic solvent; a separation step of separating a lithium salt and at least one salt of sodium and potassium from the alkali metal mixed salt aqueous solution obtained in the extraction step; and a carbonation step of carbonizing the lithium salt aqueous solution obtained in the separation step to obtain lithium carbonate. The present invention preferably further includes an electrolysis step in which an aqueous solution of at least one salt of sodium and potassium obtained from the separation step is electrolyzed using an ion exchange membrane to obtain an aqueous solution of alkali hydroxide. In the present invention, preferably, the aqueous alkali hydroxide solution obtained in the electrolysis step is reused in at least one of the steps of the alkali hydroxide addition step, the extraction step, and the separation step. The separation step is preferably carried out by at least one of the lithium phosphate method, the evaporation concentration method, and the solvent extraction method. In the present invention, preferably, an aqueous solution of at least one sodium and potassium salt is concentrated, and the concentrated aqueous solution of at least one sodium and potassium salt is electrolyzed in the electrolysis step. The mineral acid used in the dissolution step preferably includes at least one of hydrochloric acid, sulfuric acid, and nitric acid. In the present invention, preferably, at least one of sodium hydroxide and potassium hydroxide obtained in the electrolysis step is reacted with carbon dioxide to produce at least one of sodium carbonate and potassium carbonate, which is then used in the carbonation step. Preferably, renewable energy is used as the power used in the electrolysis process. Preferably, at least one of solar power generation and wind power generation is used as the power used in the electrolysis process. [Effects of the Invention]

[0009] The present invention provides a method for recovering lithium from waste lithium-ion batteries that can recover lithium with a high recovery rate and allows the salts generated in the recovery process to be reused as mineral acids and alkalis in the same process. [Brief explanation of the drawing]

[0010] [Figure 1] This diagram illustrates the configuration of one embodiment of the method for recovering lithium from waste lithium-ion batteries according to the present invention. [Figure 2] An explanatory diagram illustrating the lithium phosphate method. [Figure 3] An explanatory cross-sectional view showing the structure of an ion exchange membrane electrolytic cell used in the lithium recovery method from waste lithium-ion batteries of the present invention. [Modes for carrying out the invention]

[0011] Next, the present invention will be described in more detail with reference to the attached drawings. As shown in Figure 1, the present invention's method for recovering lithium from waste lithium-ion batteries (hereinafter referred to as the "recovery method") uses active material powder 1 as a starting material.

[0012] The recovery method of the present invention includes a dissolution step (STEP 1) in which the pre-treated active material powder 1 is dissolved with a mineral acid. The mineral acid preferably contains at least one of hydrochloric acid, sulfuric acid, and nitric acid, more preferably at least one of hydrochloric acid, sulfuric acid, and nitric acid, even more preferably hydrochloric acid, sulfuric acid, or nitric acid, and particularly preferably hydrochloric acid. Since the active material powder 1 contains valuable metals such as lithium, iron, aluminum, cobalt, nickel, and manganese, a solution of the valuable metals contained in the active material powder 1 can be obtained by dissolving the active material powder 1 with the mineral acid.

[0013] The recovery method of the present invention includes an alkali metal hydroxide addition step (STEP 2) of adding at least one of sodium hydroxide and potassium hydroxide to the solution of the valuable metal obtained in the dissolution step. In FIG. 1, the case where only sodium hydroxide is added as the alkali metal hydroxide is shown. The addition of at least one of sodium hydroxide and potassium hydroxide may be the addition of at least one solid of sodium hydroxide and potassium hydroxide, the addition of at least one of an aqueous solution of sodium hydroxide and an aqueous solution of potassium hydroxide, or at least one of these mixed forms. The solution of the valuable metal is neutralized in the alkali metal hydroxide addition step. Furthermore, iron hydroxide and aluminum hydroxide may be sequentially precipitated by the addition of at least one of sodium hydroxide and potassium hydroxide to the solution of the valuable metal, and iron and aluminum may be separated from the solution of the valuable metal.

[0014] The recovery method of the present invention includes an extraction step (STEP 3) of extracting at least one of iron, aluminum, manganese, cobalt, and nickel contained in the active material powder 1 from the solution obtained in the alkali metal hydroxide addition step by solvent extraction with an organic solvent.

[0015] Lithium, sodium, manganese, cobalt, and nickel are contained in the solution of the valuable metal neutralized in the alkali metal hydroxide addition step. If iron and aluminum have not been removed in the alkali metal hydroxide addition step, iron and aluminum are also contained in the solution of the valuable metal.

[0016] The extraction step includes a first extraction step of extracting iron, aluminum, manganese, cobalt, or nickel from the solution of the valuable metal with a first organic solvent. The pH of the homogeneous mixture of the solution of the valuable metal and the first organic solvent is adjusted by the addition of an alkali such as at least one of sodium hydroxide and potassium hydroxide, and a first metal-containing organic phase and a first extraction residue are obtained in the first extraction step.

[0017] The extraction process may include a second extraction process of extracting valuable metals not extracted in the first extraction process from the first extraction residue with a second organic solvent. The pH of the homogeneous mixture of the first extraction residue and the second organic solvent is adjusted by adding an alkali such as at least one of sodium hydroxide and potassium hydroxide, and a second metal-containing organic phase and a second extraction residue are obtained in the second extraction process.

[0018] The extraction process may include third to fifth extraction processes of sequentially extracting the valuable metals not extracted in the first and second extraction processes from the second extraction residue.

[0019] Examples of the organic solvent used in the extraction process include bis(2-ethylhexyl) hydrogen phosphate, 2-ethylhexyl(2-ethylhexyl) phosphonate, and bis(2,4,4-trimethylpentyl) phosphinic acid. The organic solvent may be diluted with a hydrocarbon such as kerosene.

[0020] Back-extraction with sulfuric acid is carried out for each of the iron-containing organic phase, aluminum-containing organic phase, manganese-containing organic phase, cobalt-containing organic phase, and nickel-containing organic phase, and an aqueous solution 2 of metal sulfates (iron sulfate, aluminum sulfate, manganese sulfate, cobalt sulfate, and nickel sulfate) is recovered.

[0021] The recovery method of the present invention includes a separation step (STEP 4) of separating a lithium salt and each of salts of at least one of sodium and potassium from an aqueous solution of an alkali metal mixed salt containing lithium obtained in the extraction process and at least one of sodium and potassium. The separation step is not limited to a specific method, but is preferably carried out by at least one of the lithium phosphate method, evaporation concentration method, and solvent extraction method.

[0022] <Lithium Phosphate Method> The lithium phosphate method will be explained using Figure 2. The lithium phosphate method includes a phosphorylation step (STEP A) in which aluminum phosphate and an aqueous solution of at least one alkali metal hydroxide (MOH), such as sodium hydroxide and potassium hydroxide, are added to the alkali metal mixed salt aqueous solution to produce a solid containing lithium phosphate and aluminum hydroxide. Alkali metal chloride (MCl) is dissolved in the aqueous solution in which the solid is produced. The alkali metal hydroxide is preferably sodium hydroxide. Figure 2 shows the case in which only sodium hydroxide is used as the alkali metal.

[0023] The lithium phosphate method includes a first solid-liquid separation (STEP B) for separating the solid material produced in the phosphorylation step into a solid-liquid state. For example, filtration may be used as this first solid-liquid separation step.

[0024] The lithium phosphate method may include washing the solid separated in the first solid-liquid separation step. It also includes a pH adjustment step (STEP C) in which a mineral acid is added to a suspension obtained by suspending the solid in water to adjust the pH of the suspension to 2-3. The mineral acid is not limited to a specific mineral acid. The mineral acid includes at least one of hydrochloric acid, sulfuric acid, and nitric acid. Preferably, the mineral acid is at least one of hydrochloric acid, sulfuric acid, and nitric acid, more preferably hydrochloric acid, sulfuric acid, or nitric acid, and even more preferably hydrochloric acid. When the mineral acid is hydrochloric acid, the lithium salt is lithium chloride, which is illustrated in Figure 2.

[0025] The lithium phosphate method includes a second solid-liquid separation step (STEP D) for solid-liquid separation of the aluminum phosphate and lithium salt aqueous solution obtained in the pH adjustment step. For example, filtration can be used as the second solid-liquid separation step. The aluminum phosphate obtained in this second solid-liquid separation step can be separated from the solid-liquid in a short time, and the solid-liquid separated aluminum phosphate is reused in the phosphorylation step.

[0026] The pH of the lithium salt aqueous solution obtained in the second solid-liquid separation step is preferably adjusted in the pH adjustment step (STEP 5) described later. Since the pH of the suspension is adjusted to 2-3 in the pH adjustment step (STEP C), the pH of the lithium salt aqueous solution is 2-3, but in the pH adjustment step (STEP 5), the pH is preferably adjusted to 6-8. In this case, unreacted aluminum and phosphorus precipitate, and the purity of the lithium salt aqueous solution becomes higher.

[0027] Preferably, the lithium salt aqueous solution whose pH has been adjusted in the pH adjustment step (STEP 5) is carbonated to obtain lithium carbonate in a carbonation step (STEP 6) described later. The aqueous solution of at least one sodium and potassium salt produced in this carbonation step contains at least one sodium chloride and potassium chloride, a trace amount of lithium chloride, and at least one sodium carbonate and potassium carbonate, and preferably the pH of the aqueous solution of at least one sodium and potassium salt is about 12. When hydrochloric acid is added to the aqueous solution of at least one sodium and potassium salt to adjust its pH to 5 or less, at least one sodium carbonate and potassium carbonate decompose to produce carbon dioxide and water, resulting in an aqueous solution in which at least one sodium chloride and potassium chloride is dissolved. This aqueous solution may be concentrated in a concentration step (STEP 9) described later. Figure 2 shows the case in which this concentration step is performed.

[0028] In the lithium phosphate method, the filtrate containing the dissolved alkali metal chloride, separated in the first solid-liquid separation step, may be concentrated in a concentration step (STEP 9) described later.

[0029] <Evaporation concentration method> The aqueous solution of lithium and at least one alkali metal mixed salt of sodium and potassium is evaporated and concentrated, and at least one sodium salt and potassium salt, such as at least one sodium chloride and potassium chloride, are sequentially crystallized and separated from the alkali metal mixed salt aqueous solution. The separated sodium salt and potassium salt, such as at least one sodium chloride and potassium chloride, are dissolved in water, and the aqueous solution of at least one sodium and potassium salt is electrolyzed using an ion exchange membrane in an electrolysis step (STEP 7) described later. The lithium salt aqueous solution from which at least one sodium salt and potassium salt has been separated is preferably subjected to a pH adjustment step (STEP 5) described later, similar to the lithium salt aqueous solution obtained by the lithium phosphate method, and further subjected to a carbonation step (STEP 6). If the aqueous solution of at least one sodium and potassium salt produced in the carbonation step is an aqueous solution in which at least one sodium chloride and potassium chloride is dissolved as described above, the aqueous solution may be concentrated in a concentration step (STEP 9) described later.

[0030] <Solvent extraction method> The pH of a homogeneous mixture of lithium, an aqueous solution of at least one mixed salt of sodium and potassium, and an organic solvent for lithium extraction is preferably adjusted to a range of 5 to 9 by adding an alkali such as at least one of sodium hydroxide and potassium hydroxide, yielding a lithium-containing organic phase and an aqueous solution of at least one salt of sodium and potassium as the extraction residue. Examples of organic solvents for lithium extraction include bis(2-ethylhexyl) hydrogen phosphate. The lithium-containing organic phase is scrubbed with a mineral acid to recover the lithium salt aqueous solution. This lithium salt aqueous solution is preferably subjected to a pH adjustment step (STEP 5) described later, similar to the lithium salt aqueous solution obtained in the lithium phosphate method, and further subjected to a carbonation step (STEP 6). If the aqueous solution of at least one salt of sodium and potassium produced in the carbonation step is an aqueous solution in which at least one of sodium chloride and potassium chloride is dissolved as described above, this aqueous solution may be concentrated in a concentration step (STEP 9) described later.

[0031] An electrolysis step (STEP 7), described later, is performed, in which at least one of the sodium salt and potassium salt, such as sodium chloride and potassium chloride, which have been separated by lithium extraction, is dissolved in an aqueous solution of at least one sodium salt and potassium salt, and electrolysis is performed using an ion exchange membrane. The aqueous solution of at least one sodium salt and potassium salt is concentrated in a concentration step (STEP 9), described later, preferably using a reverse osmosis membrane (RO membrane) or the like.

[0032] The recovery method of the present invention may include a pH adjustment step (STEP 5) in which at least one of sodium hydroxide and potassium hydroxide is added to the lithium salt aqueous solution obtained in the separation step to adjust the pH of the lithium salt aqueous solution. The pH of the lithium salt aqueous solution is preferably adjusted to 8 to 14, more preferably to 10 to 11.

[0033] The recovery method of the present invention includes a carbonation step (STEP 6) in which the lithium salt aqueous solution obtained in the separation step is carbonated to obtain lithium carbonate. In this carbonation step, an alkali metal carbonate (excluding lithium carbonate), such as sodium carbonate and potassium carbonate, obtained in a carbon dioxide absorption step (STEP 8) in which carbon dioxide is absorbed into an aqueous solution 4 in which at least one of sodium hydroxide and potassium hydroxide obtained in the electrolysis step described later is dissolved, may be added to the lithium salt aqueous solution.

[0034] The alkali metal of the alkali metal carbonate salt is at least one of sodium, potassium, rubidium, cesium, and francium. The alkali metal is preferably at least one of sodium and potassium, and more preferably sodium.

[0035] The recovery method of the present invention preferably includes an electrolysis step (STEP 7) in which an aqueous solution of at least one sodium and potassium salt, obtained from the separation step, in which at least one of sodium chloride and potassium chloride is dissolved, is electrolyzed using an ion exchange membrane to obtain an aqueous alkali metal hydroxide solution. This electrolysis step can be carried out, for example, using the electrolytic cell 21 shown in Figure 3.

[0036] The electrolytic cell 21 is equipped with an anode plate 22 on one inner surface and a cathode plate 23 on the inner surface opposite to the anode plate 22. The anode plate 22 is connected to the anode 24 of the power supply, and the cathode plate 23 is connected to the cathode 25 of the power supply. The electrolytic cell 21 is also divided by an ion exchange membrane 26 into an anode chamber 27 equipped with the anode plate 22 and a cathode chamber 28 equipped with the cathode plate 23.

[0037] In the electrolytic cell 21, when electrolysis is performed by supplying at least one aqueous solution of sodium and potassium to the anode chamber 27, chloride ions generate chlorine gas (Cl2) on the anode plate 22. Meanwhile, at least one alkali metal ion, either sodium or potassium, moves to the cathode chamber 28 via the ion exchange membrane 26.

[0038] In cathode chamber 28, water (H2O) is converted into hydroxide ions (OH - ) and hydrogen ions (H + ) ionizes, and hydrogen ions generate hydrogen gas (H2) on the cathode plate 23, while hydroxide ions and at least one of sodium ions and potassium ions generate an alkali metal aqueous solution 4 in which at least one of sodium hydroxide and potassium hydroxide is dissolved.

[0039] For example, renewable energy, preferably at least one of solar power generation and wind power generation, is used as the electricity required for the electrolysis.

[0040] If at least one of the sodium and potassium salt aqueous solutions contains chloride ions, the hydrogen gas (H2) produced in the electrolysis step can be reacted with chlorine gas (Cl2) to obtain hydrochloric acid. If at least one of the sodium and potassium salt aqueous solutions contains sulfate ions, sulfuric acid can be obtained in the anode chamber 27. If at least one of the sodium and potassium salt aqueous solutions contains nitrate ions, nitric acid can be obtained in the anode chamber 27. In other words, mineral acid 5 can be obtained in the electrolysis step, and this mineral acid 5 is used in at least one of the dissolution of the active material powder 1 in STEP 1 and pH adjustment in STEP C.

[0041] The recovery method of the present invention may include a carbon dioxide absorption step (STEP 8) in which carbon dioxide is absorbed into an alkali metal hydroxide aqueous solution 4 in which at least one of sodium hydroxide and potassium hydroxide obtained by electrolysis is dissolved. At least one alkali metal carbonate 6, such as sodium carbonate and potassium carbonate, produced in the carbon dioxide absorption step may be used in the carbonation step.

[0042] The alkali metal hydroxide aqueous solution 4 produced in the electrolysis step is preferably reused in at least one of the following steps: the alkali metal hydroxide addition step, the extraction step, the separation step by lithium phosphate, and the separation step by solvent extraction.

[0043] In the electrolysis step, the at least one sodium and potassium salt aqueous solution is electrolyzed, resulting in the production of a sodium and potassium salt aqueous solution that is more dilute than the original sodium and potassium salt aqueous solution. Therefore, the recovery method of the present invention may include a concentration step (STEP 9) in which the dilute sodium and potassium salt aqueous solution is concentrated and added to the sodium and potassium salt aqueous solution obtained in the separation step. This concentration step can be carried out, for example, using a reverse osmosis membrane (RO membrane). [Examples]

[0044] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0045] In the examples, various physical properties were measured or calculated as follows. <Metal content in lithium and sodium mixed salt aqueous solution, and impurity content in lithium carbonate> Using a PerkinElmer Optima8300, the metal content in a lithium and sodium mixed salt aqueous solution and the impurity content in lithium carbonate were measured by inductively coupled plasma atomic emission spectroscopy (ICP-OES).

[0046] Used lithium-ion batteries, whose lifespan as battery products had reached its limit, were discharged to completely remove any remaining charge. Next, the waste lithium-ion batteries were heat-treated (roasted), then crushed in a hammer mill. The casing, current collector, and other components constituting the waste lithium-ion batteries were sieved to obtain active material powder. 500 g of this active material powder was dissolved in 3 L of 6 mol / L hydrochloric acid. 2.8 L of 2 mol / L sodium hydroxide aqueous solution was added to the resulting solution to neutralize it. 5.8 L of the neutralized solution was mixed with 5.8 L of bis(2,4,4-trimethylpentyl)phosphinic acid (Cyanex 272, kerosene as diluent) as an extractant, and cobalt was extracted using solvent extraction. 5 mol / L sodium hydroxide aqueous solution was added to the mixture to adjust the pH to 4, obtaining a cobalt-containing organic phase and the first extraction residue. The cobalt-containing organic phase was scrubbed with dilute sulfuric acid, and then back-extracted with 1.5 mol / L sulfuric acid to obtain a cobalt sulfate solution. Using the same organic solvent as used in the cobalt extraction step, nickel was extracted from the first extraction residue, and an aqueous solution of a lithium and sodium mixed salt was obtained as the extraction residue. This aqueous solution contained 3.5 g / L of lithium and 38.2 g / L of sodium.

[0047] 187 g of aluminum phosphate was added to 8.3 L of the aqueous solution, and then sodium hydroxide was added to adjust the pH of the aqueous solution to 10.5. The reaction was carried out for 2 hours to obtain white slurry A. Next, white slurry A was filtered and washed to obtain 614 g of white cake A with a water content of 55%. White cake A was suspended in 300 mL of pure water, and 35% by mass hydrochloric acid was added to adjust the pH of the suspension to 2.5. The suspension was heated to 60°C and reacted for 6 hours to obtain white slurry B. White slurry B was filtered and washed to obtain 467 g of white cake B with a water content of 60%, and a total of 1060 mL of filtrate and washing water. Sodium hydroxide was added to the 1060 mL of filtrate and washing water to adjust the pH to 7, and the filtered filtrate was mixed with 680 g of 35% by mass sodium carbonate aqueous solution. The mixture was heated to 60°C and reacted for 1 hour. The obtained solid was filtered and washed to obtain hydrated lithium carbonate. The hydrated lithium carbonate was dried at 500°C for 4 hours to obtain 129 g of lithium carbonate. The lithium recovery rate was 83.5%. The sodium content in the lithium carbonate was less than 200 ppm, the aluminum content was less than 10 ppm, the phosphorus content was less than 10 ppm, and the water content was less than 0.1 mass%.

[0048] The filtrate and washing water (10.5 L, sodium chloride concentration 98 g / L) obtained by filtration and washing of the white slurry A were concentrated using the RO membrane, and the resulting sodium chloride aqueous solution (sodium chloride concentration 300 g / L) was subjected to a current density of 40 A / dm² using an ion exchange membrane (Nafion N324, manufactured by Chemours). 2 , electrode area 1.75dm 2 Under conditions of electrolysis with an energizing time of 4 hours, 1.6 kg of 21.2% by mass sodium hydroxide was obtained. Furthermore, the reaction product of the generated chlorine gas and hydrogen gas was absorbed into water to obtain 1.04 kg of 30% by mass hydrochloric acid. The sodium hydroxide produced in the electrolysis process could be reused in the sodium hydroxide addition process (STEP 2), the extraction process (STEP 3), and the separation process (STEP 4). Furthermore, the hydrochloric acid synthesized in the electrolysis process could be reused in the dissolution process (STEP 1). The current efficiency in the electrolysis process was 81.5%.

[0049] In this example, it was found that the mineral acids and alkalis used can be regenerated and reused. Furthermore, it was found that the purity of the lithium carbonate obtained in the final stage of lithium recovery from waste lithium-ion batteries, as well as the lithium recovery rate, are very high.

[0050] In the recovery method of the present invention, sodium hydroxide can be directly obtained in an electrolytic step using an ion exchange membrane for the sodium salt aqueous solution. Since the mineral acid and alkali generated in the electrolytic step can be recycled into the recovery method of the present invention, a closed-loop recycling process can be realized. Furthermore, because the recovery method of the present invention recycles the mineral acid and alkali, it can reduce the amount of carbon dioxide emitted in the logistics process of the mineral acid and alkali compared to when the mineral acid and alkali are purchased from external sources as in the conventional method. [Explanation of Symbols]

[0051] 1…Active material powder, 2…Metal sulfate aqueous solution, 3…Lithium carbonate, 4…Sodium hydroxide solution, 5…Mineral acid, 6…Sodium carbonate, 11…Electrolytic cell, 12... Anode plate, 13... Cathode plate, 14... Anode, 15... Cathode, 16... Ion exchange membrane 17...Anode chamber, 18...Cathode chamber.

Claims

1. A method for recovering lithium from waste lithium-ion batteries, comprising: a dissolving step of dissolving the active material powder obtained by pretreating the waste lithium ion batteries in a mineral acid; an alkali hydroxide adding step of adding at least one of sodium hydroxide and potassium hydroxide to the solution obtained in the dissolving step; an extraction step of extracting at least one of iron, aluminum, manganese, cobalt, and nickel contained in the active material powder with an organic solvent by solvent extraction from the solution obtained in the alkali hydroxide addition step; a separation step of separating a lithium salt and at least one salt of sodium and potassium from the aqueous alkali mixed salt solution obtained in the extraction step; A method for recovering lithium from waste lithium-ion batteries, comprising a carbonation step of carbonate-treating the lithium salt aqueous solution obtained in the separation step to obtain lithium carbonate.

2. 2. The method for recovering lithium from waste lithium-ion batteries according to claim 1, further comprising an electrolysis step of electrolyzing the aqueous salt solution of at least one of sodium and potassium obtained from the separation step using an ion exchange membrane to obtain an aqueous alkali hydroxide solution.

3. 3. The method for recovering lithium from waste lithium-ion batteries according to claim 2, wherein the aqueous alkali hydroxide solution obtained in the electrolysis step is reused in at least one of the alkali hydroxide adding step, the extraction step, and the separation step.

4. 4. The method for recovering lithium from waste lithium-ion batteries according to claim 1, wherein the separation step is carried out by at least one of a lithium phosphate method, an evaporation concentration method, and a solvent extraction method.

5. 5. The method for recovering lithium from waste lithium-ion batteries according to claim 2, wherein an aqueous salt solution of at least one of sodium and potassium is concentrated, and the concentrated aqueous salt solution of at least one of sodium and potassium is electrolyzed in the electrolysis step.

6. 6. The method for recovering lithium from waste lithium-ion batteries according to claim 1, wherein the mineral acid used in the dissolving step includes at least one of hydrochloric acid, sulfuric acid, and nitric acid.

7. 7. The method for recovering lithium from waste lithium-ion batteries according to claim 2, wherein at least one of sodium hydroxide and potassium hydroxide obtained in the electrolysis step is reacted with carbon dioxide to produce at least one of sodium carbonate and potassium carbonate, and the produced sodium carbonate is used in the carbonation step.

8. The method for recovering lithium from waste lithium-ion batteries according to any one of claims 2 to 7, wherein renewable energy is used as the power used in the electrolysis step. A method for recovering lithium from waste lithium-ion batteries.

9. 9. The method for recovering lithium from waste lithium-ion batteries according to claim 2, wherein the electric power used in the electrolysis step is generated by at least one of solar power generation and wind power generation.

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