How to recover lithium from used lithium-ion batteries

Abstract

To provide a method for recovering lithium from a waste lithium ion battery which can recover lithium at a high recovery rate, and can recycle a salt generated in a recovery process as a mineral acid and alkali in the process.SOLUTION: A method for recovering lithium from a waste lithium ion battery includes: a step of extracting valuable metal such as manganese from a solution obtained by dissolving active substance powder obtained from a waste lithium ion battery with a mineral acid, and adding at least one of sodium hydroxide and potassium hydroxide thereto, by an organic solvent; a separation step of separating a lithium salt and a sodium salt from an alkali metal mixed salt aqueous solution obtained by the extraction step; and a first electrolysis step of electrolyzing a lithium salt aqueous solution.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

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

[0003] Conventionally, when recovering the valuable metals from the waste lithium-ion batteries, the waste lithium-ion batteries are subjected to a heat treatment (roasting), crushing, classification, etc. to obtain a powder containing the valuable metals, and cobalt, nickel, manganese, and lithium are separated and refined by a wet process (see, for example, Patent Documents 1 and 2).

[0004] In the present invention, the waste lithium ion batteries refer to used lithium ion batteries that have run out of life as battery products, lithium ion batteries that have been discarded as defective products in the manufacturing process, and the remaining positive and negative electrode materials used in the manufacturing process. The powder containing the positive and negative electrodes obtained from the waste lithium ion batteries is called the active material powder. Furthermore, the impurities refer to metals contained in the active material powder that do not require recovery. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6835820 [Patent Document 2] Patent No. 6869444 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the existing wet process, a compound other than the lithium compound to be recovered is used as an alkali source, so that the concentration of cations other than lithium is high and the concentration of lithium ions is low at the same time. As a result, the recovery rate of the target lithium is significantly reduced in the conventional wet process. Furthermore, in the conventional wet process, the mineral acid used to dissolve the active material powder and the compound used as the alkali source are discharged as salts, and there is a disadvantage that there is no technology to circulate and recycle the mineral acid and the compound used as the alkali source. In recent years, there has been a demand for a method for recovering lithium from used lithium ion batteries that can eliminate such inconveniences, recover lithium at a high recovery rate, and reuse the salts generated in the recovery process as mineral acids and alkalis in the process, but 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 used lithium ion batteries that can recover lithium at a high recovery rate and reuse the salts generated in the recovery process as mineral acids and alkalis in the process. [Means for solving the problem]

[0007] The present inventors have conducted extensive research in light of the above problems, and have found that it is possible to add at least one of sodium hydroxide and potassium hydroxide to a solution obtained by dissolving an active material powder in a mineral acid, separate the lithium salt aqueous solution from the at least one salt aqueous solution of sodium and potassium, and electrolyze the separated at least one salt aqueous solution of sodium and potassium, thereby obtaining a mineral acid and at least one of sodium hydroxide and potassium hydroxide, which can be reused. The present invention has been completed based on these findings.

[0008] The present invention is a method for recovering lithium from used lithium ion batteries, comprising: a dissolving step of dissolving an active material powder obtained by pretreating used lithium ion batteries with a mineral acid; an alkali metal 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 from the solution obtained in the alkali metal hydroxide adding step by solvent extraction; a separation step of separating a lithium salt and at least one salt of sodium salt and potassium from the aqueous alkali metal salt mixture obtained in the extraction step; and a first electrolysis step of electrolyzing the aqueous lithium salt solution obtained in the separation step using an ion exchange membrane to obtain an aqueous lithium hydroxide solution. and a second electrolysis step in which the 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 an alkali hydroxide. Including and reusing the aqueous alkali hydroxide solution obtained in the second electrolysis step in at least one of the alkali hydroxide adding step, the extraction step, and the separation step. , a method for recovering lithium from waste lithium-ion batteries. 。 before The separation step is preferably carried out by at least one of a lithium phosphate method, an evaporation concentration method, and a solvent extraction method. In the present invention, preferably, 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 second electrolysis step. The mineral acid used in the dissolution step preferably comprises at least one of hydrochloric acid, sulfuric acid, and nitric acid. The power used in at least one of the first electrolysis step and the second electrolysis step is preferably renewable energy. As the electric power used in at least one of the first electrolysis step and the second electrolysis step, at least one of solar power generation and wind power generation is preferably used. Effect of the Invention

[0009] The method for recovering lithium from waste lithium ion batteries of the present invention provides a method that can recover lithium with a high recovery rate and can reuse the salts generated in the recovery process as mineral acids and alkalis in the process. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is an explanatory diagram showing the configuration of one embodiment of the method for recovering lithium from used lithium ion batteries of the present invention. [Diagram 2] FIG. 2 is an explanatory diagram showing the lithium phosphate method. [Diagram 3] FIG. 2 is an explanatory cross-sectional view showing the structure of an ion exchange membrane electrolytic cell used in the first electrolysis step of the method for recovering lithium from waste lithium ion batteries of the present invention. [Figure 4] FIG. 2 is an explanatory cross-sectional view showing the structure of an ion exchange membrane electrolytic cell used in the second electrolysis step of the method for recovering lithium from waste lithium ion batteries of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The invention will now be described in more detail with reference to the accompanying drawings. As shown in FIG. 1, the method of recovering lithium from used lithium ion batteries of the present invention (hereinafter referred to as the "recovery method") starts with active material powder 1 as a starting material.

[0012] <Dissolution process> The recovery method of the present invention includes a dissolving step (STEP 1) of dissolving the active material powder 1 obtained by the pretreatment with a mineral acid. The mineral acid preferably includes 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 includes valuable metals such as lithium, iron, aluminum, cobalt, nickel, and manganese, a solution of the valuable metals included in the active material powder 1 can be obtained by dissolving the active material powder 1 with the mineral acid.

[0013] <Alkaline hydroxide addition process> The recovery method of the present invention includes an alkali metal hydroxide adding step (STEP 2) in which at least one of sodium hydroxide and potassium hydroxide is added to the solution of valuable metals obtained in the dissolution step. FIG. 1 shows a case in which only sodium hydroxide is added as the alkali metal hydroxide. The addition of at least one of sodium hydroxide and potassium hydroxide may be in the form of at least one solid of sodium hydroxide and potassium hydroxide, at least one aqueous solution of sodium hydroxide and at least one aqueous solution of potassium hydroxide, or at least one mixture thereof. The solution of valuable metals is neutralized in the alkali metal hydroxide adding step. Furthermore, iron hydroxide and aluminum hydroxide may be precipitated in sequence by the addition of at least one of sodium hydroxide and potassium hydroxide to the solution of valuable metals, and iron and aluminum may be separated from the solution of valuable metals.

[0014] <Extraction process> 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 with an organic solvent by solvent extraction from the solution obtained in the alkali metal hydroxide addition step.

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

[0016] The extraction step includes a first extraction step of extracting iron, aluminum, manganese, cobalt, or nickel from the valuable metal solution with a first organic solvent, the pH of the homogeneous mixture of the valuable metal solution and the first organic solvent being adjusted by adding 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 step may include a second extraction step in which valuable metals not extracted in the first extraction step are extracted from the first bottom solution with a second organic solvent, the pH of the homogeneous mixture of the first bottom solution and the second organic solvent being adjusted by the addition of an alkali such as at least one of sodium hydroxide and potassium hydroxide, to obtain a second metal-containing organic phase and a second bottom solution in the second extraction step.

[0018] The extraction step may include third to fifth extraction steps for sequentially extracting the valuable metals that have not been extracted in the first and second extraction steps from the second extraction residue.

[0019] The organic solvent used in the extraction step may be, for example, bis(2-ethylhexyl) hydrogen phosphate, 2-ethylhexyl(2-ethylhexyl)phosphonate, or bis(2,4,4-trimethylpentyl)phosphinic acid. The organic solvent may be diluted with a hydrocarbon, such as kerosene.

[0020] The iron-containing organic phase, the aluminum-containing organic phase, the manganese-containing organic phase, the cobalt-containing organic phase, and the nickel-containing organic phase are each subjected to back extraction with sulfuric acid, and an aqueous solution 2 of metal sulfates (iron sulfate, aluminum sulfate, manganese sulfate, cobalt sulfate, and nickel sulfate) is recovered.

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

[0022] (Lithium phosphate method) The lithium phosphate method will be described with reference to Fig. 2. The lithium phosphate method includes a phosphorylation step (STEP A) in which an aqueous solution of aluminum phosphate and at least one alkali metal hydroxide (MOH) of sodium hydroxide and potassium hydroxide is added to the aqueous solution of the alkali metal mixed salt to produce a solid material containing lithium phosphate and aluminum hydroxide. An alkali metal chloride (MCl) is dissolved in the aqueous solution in which the solid material is produced. The alkali metal hydroxide is preferably sodium hydroxide. Fig. 2 shows a 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) in which the solid produced in the phosphorylation step is separated into solid and liquid. An example of the first solid-liquid separation step is filtration.

[0024] In the lithium phosphate method, the solid matter separated in the first solid-liquid separation step may be washed. The method includes a pH adjustment step (STEP C) of adding a mineral acid to a suspension obtained by suspending the solid matter in water to adjust the pH of the suspension to 2 to 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. The mineral acid is preferably at least one of hydrochloric acid, sulfuric acid, and nitric acid, more preferably hydrochloric acid, sulfuric acid, or nitric acid, and further preferably hydrochloric acid. When the mineral acid is hydrochloric acid, the lithium salt is lithium chloride, and this case is illustrated in FIG. 2.

[0025] The lithium phosphate method includes a second solid-liquid separation step (STEP D) in which the aluminum phosphate obtained in the pH adjustment step and the lithium salt aqueous solution are subjected to solid-liquid separation. An example of the second solid-liquid separation step is filtration. The aluminum phosphate obtained in the second solid-liquid separation step can be separated into solid and liquid in a short time, and the aluminum phosphate separated from the solid and liquid 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 a pH adjustment step (STEP 5) described below. Since the pH of the suspension is adjusted to 2 to 3 in the pH adjustment step (STEP C), the pH of the lithium salt aqueous solution is 2 to 3, but the pH is preferably adjusted to 6 to 14, more preferably 6 to 8, in the pH adjustment step (STEP 5). In this case, unreacted aluminum and phosphorus are precipitated, and the purity of the lithium salt aqueous solution becomes higher.

[0027] Preferably, the lithium salt aqueous solution, the pH of which has been adjusted in the pH adjustment step (STEP 5), is electrolyzed using an ion exchange membrane to obtain a lithium hydroxide aqueous solution, in a first electrolysis step (STEP 6) described below. The lithium salt aqueous solution may be concentrated in a first concentration step (STEP E) before being subjected to the first electrolysis step. The first concentration step can be performed, for example, using a reverse osmosis membrane (RO membrane).

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

[0029] (Evaporation concentration method) The aqueous solution of the mixed alkali metal salt containing lithium and at least one of sodium and potassium is evaporated and concentrated, and at least one of sodium salt and potassium salt, such as at least one of sodium chloride and potassium chloride, is sequentially crystallized and separated from the aqueous solution of the mixed alkali metal salt. The separated at least one of sodium salt and potassium salt, such as at least one of sodium chloride and potassium chloride, is dissolved in water, and the aqueous solution of at least one of sodium and potassium salt is electrolyzed using an ion exchange membrane, in a second electrolysis step (STEP 7) described later. The aqueous solution of the lithium salt from which at least one of the sodium salt and potassium salt has been separated is preferably subjected to a pH adjustment step (STEP 5) and a first concentration step (STEP E) described later, as with the aqueous solution of the lithium salt obtained by the lithium phosphate method, and is then subjected to a first electrolysis step (STEP 6) described later.

[0030] (Solvent extraction method) The pH of the homogeneous mixture of the aqueous solution of the alkali metal mixed salt containing lithium and at least one of sodium and potassium and the organic solvent for lithium extraction is adjusted to preferably within the range of 5 to 9 by adding an alkali such as at least one of sodium hydroxide and potassium hydroxide, and a lithium-containing organic phase and an aqueous solution of at least one salt of sodium and potassium are obtained as the extraction residue. An example of the organic solvent for lithium extraction is bis(2-ethylhexyl) hydrogen phosphate. The lithium-containing organic phase is scrubbed with a mineral acid to recover an aqueous lithium salt solution. The aqueous lithium salt solution is preferably subjected to a pH adjustment step (STEP 5) and a first concentration step (STEP E) described later, as with the aqueous lithium salt solution obtained by the lithium phosphate method, and is then subjected to a first electrolysis step (STEP 6) described later.

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

[0032] <Lithium salt aqueous solution pH adjustment process> The recovery method of the present invention may include a pH adjustment step (STEP 5) of adding at least one of lithium hydroxide and an aqueous lithium hydroxide solution to the aqueous lithium salt solution obtained in the separation step to adjust the pH of the aqueous lithium salt solution. The pH of the aqueous lithium salt solution is preferably adjusted to 6 to 14, more preferably 6 to 8.

[0033] <Lithium salt aqueous solution concentration process> The recovery method of the present invention may include a first concentration step (STEP E) of concentrating the lithium salt aqueous solution obtained in the separation step and, if necessary, subjected to the pH adjustment step (STEP 5). The first concentration step can be performed using, for example, a reverse osmosis membrane (RO membrane).

[0034] <First electrolysis step> The recovery method of the present invention includes a first electrolysis step (STEP 6) of electrolyzing the aqueous lithium salt solution obtained in the separation step and, if necessary, subjected to at least one of the pH adjustment step (STEP 5) and the first concentration step (STEP E) using an ion exchange membrane to obtain an aqueous lithium hydroxide solution.

[0035] The first electrolysis step can be carried out using, for example, an electrolytic cell 11 shown in FIG. The electrolytic cell 11 is equipped with an anode plate 12 on one of its inner surfaces and a cathode plate 13 on the inner surface opposite the anode plate 12, the anode plate 12 being connected to an anode 14 of a power supply, and the cathode plate 13 being connected to a cathode 15 of the power supply. The electrolytic cell 11 is also partitioned by an ion exchange membrane 16 into an anode chamber 17 equipped with the anode plate 12 and a cathode chamber 18 equipped with the cathode plate 13.

[0036] In the electrolytic cell 11, when the lithium salt aqueous solution in which lithium chloride is dissolved is supplied to the anode chamber 17 to perform electrolysis, chloride ions generate chlorine gas (Cl2) on the anode plate 12. Meanwhile, lithium ions move to the cathode chamber 18 through the ion exchange membrane 16.

[0037] In the cathode chamber 18, water (HO) is converted into hydroxide ions (OH - ) and hydrogen ions (H + ) and the hydrogen ions generate hydrogen gas (H2) on the cathode plate 13, while the hydroxide ions and lithium ions generate a lithium hydroxide aqueous solution.

[0038] The power required for the electrolysis is, for example, renewable energy, preferably at least one of solar power generation and wind power generation.

[0039] Hydrogen gas (H2) and chlorine gas (Cl2) generated in the first electrolysis step can be reacted to obtain hydrochloric acid. Although not shown in FIG. 3, when the lithium chloride aqueous solution contains sulfate ions, sulfuric acid can be obtained in the anode chamber 17. When the lithium chloride aqueous solution contains nitrate ions, nitric acid can be obtained in the anode chamber 17. That is, mineral acid 5 can be obtained in the first electrolysis step, and the mineral acid 5 can be used for at least one of dissolving the active material powder 1 in STEP 1 and adjusting the pH in STEP C.

[0040] (Isolation of lithium hydroxide monohydrate) The recovery method of the present invention may include a crystallization step (STEP F) of crystallizing lithium hydroxide monohydrate 3 by evaporating and concentrating the lithium hydroxide aqueous solution obtained in the first electrolysis step.

[0041] (Separation of lithium carbonate) The recovery method of the present invention may include a carbonation step (STEP G) in which carbon dioxide is blown into the lithium hydroxide aqueous solution obtained in the first electrolysis step to generate lithium carbonate 6. The aqueous solution in which a lithium salt such as lithium chloride is dissolved, which is obtained by performing solid-liquid separation of the slurry obtained in the carbonation step by filtration or the like, may be concentrated in the first concentration step (STEP E). Note that Figs. 1 and 2 show a case in which the lithium salt is lithium chloride.

[0042] <Second electrolysis process> The recovery method of the present invention preferably includes a second electrolysis step (STEP 7) of electrolyzing the aqueous solution of at least one salt of sodium and potassium, in which at least one of sodium chloride and potassium chloride is dissolved, obtained from the separation step, using an ion exchange membrane to obtain an aqueous solution of an alkali metal hydroxide. The second electrolysis step can be performed, for example, using an electrolytic cell 21 shown in FIG. 4.

[0043] The electrolytic cell 21 is provided with an anode plate 22 on one of its inner surfaces and a cathode plate 23 on the inner surface opposite the anode plate 22, the anode plate 22 being connected to an anode 24 of a power supply, and the cathode plate 23 being connected to a cathode 25 of the power supply. The electrolytic cell 21 is also partitioned by an ion exchange membrane 26 into an anode chamber 27 including the anode plate 22 and a cathode chamber 28 including the cathode plate 23.

[0044] In the electrolysis cell 21, when an aqueous salt solution of at least one of sodium chloride and potassium chloride is supplied to the anode chamber 27 to perform electrolysis, chloride ions generate chlorine gas (Cl2) on the anode plate 22. Meanwhile, at least one alkali metal ion of sodium ions and potassium ions moves to the cathode chamber 28 through the ion exchange membrane 26. FIG. 4 shows a case where an aqueous sodium salt solution is supplied to the anode chamber 27.

[0045] In the cathode chamber 28, water (HO) is converted into hydroxide ions (OH - ) and hydrogen ions (H +) and the hydrogen ions generate hydrogen gas (H2) on the cathode plate 23, while the hydroxide ions and at least one of the sodium ions and potassium ions generate an alkali metal aqueous solution in which at least one of sodium hydroxide and potassium hydroxide is dissolved. Figures 1, 2 and 4 show the case where a sodium hydroxide aqueous solution 4 is generated.

[0046] The power required for the second electrolysis is, for example, renewable energy, preferably at least one of solar power generation and wind power generation.

[0047] When the aqueous solution of at least one of sodium and potassium salts contains chloride ions, hydrogen gas (H2) and chlorine gas (Cl2) generated in the second electrolysis step can be reacted to obtain hydrochloric acid. Although not shown in FIG. 4, when the aqueous solution of at least one of sodium and potassium salts contains sulfate ions, sulfuric acid can be obtained in the anode chamber 27. When the aqueous solution of at least one of sodium and potassium salts contains nitrate ions, nitric acid can be obtained in the anode chamber 27. That is, mineral acid 5 can be obtained in the second electrolysis step, and the mineral acid 5 is used for at least one of dissolving active material powder 1 in STEP 1 and adjusting pH in STEP C.

[0048] The aqueous alkali metal hydroxide solution produced in the second electrolysis step is preferably reused in at least one of the alkali metal hydroxide addition step, the extraction step, the lithium phosphate method separation step, and the solvent extraction method separation step.

[0049] In the second electrolysis step, the aqueous solution of at least one salt of sodium and potassium is electrolyzed, resulting in the production of an aqueous solution of at least one salt of sodium and potassium that is more dilute than the aqueous solution of at least one salt of sodium and potassium. Therefore, the recovery method of the present invention may include a second concentration step (STEP 9) in which the dilute aqueous solution of at least one salt of sodium and potassium is concentrated and added to the aqueous solution of at least one salt of sodium and potassium obtained in the separation step. The second concentration step can be performed, for example, using a reverse osmosis membrane (RO membrane). EXAMPLES

[0050] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these.

[0051] In the examples, various physical properties were measured or calculated as follows. <Metal content in lithium and sodium mixed salt aqueous solution, impurity content in lithium hydroxide monohydrate> The metal contents in the lithium and sodium mixed salt aqueous solution were measured by inductively coupled plasma optical emission spectrometry (ICP-OES) using an Optima 8300 manufactured by PerkinElmer.

[0052] Used lithium ion batteries that had run out of life as battery products were discharged to discharge all remaining charges. The waste lithium ion batteries were then heated (roasted) and pulverized with a hammer mill, and the casings, current collectors, etc. constituting the waste lithium ion batteries were sieved to obtain active material powder. 500 g of the active material powder was dissolved in 3 L of 6 mol / L hydrochloric acid, and 2.8 L of 2 mol / L aqueous sodium hydroxide solution was added to the obtained solution to neutralize the solution. 5.8 L of the neutralized solution was mixed with 5.8 L of bis(2,4,4-trimethylpentyl)phosphinic acid (Cyanex272, diluent kerosene) as an extractant, and cobalt was extracted with a solvent. 5 mol / L aqueous sodium hydroxide solution was added to the mixture to adjust the pH to 4, and a cobalt-containing organic phase and a first extraction residue were obtained. 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. Nickel was extracted from the first residue using the same organic solvent as that used in the cobalt extraction step, and an aqueous solution of lithium and sodium mixed salt was obtained as the residue. The aqueous solution contained 3.5 g / L of lithium and 38.2 g / L of sodium.

[0053] 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, and the reaction was carried out for 2 hours to obtain a white slurry A. Next, the white slurry A was filtered and washed to obtain 614 g of a white cake A with a water content of 55%. The white cake A was suspended in 300 mL of pure water, and 35 mass % of hydrochloric acid was added to adjust the pH of the suspension to 2.5, and the suspension was heated to 60°C and reacted for 6 hours to obtain a white slurry B. The white slurry B was filtered and washed to obtain 467 g of a white cake B with a water content of 60%, and a total of 1060 mL of filtrate and washing water. The 1,060 mL of filtrate and washing water were added with lithium hydroxide to adjust the pH to 7, and the filtrate (filtrate 1) was filtered to obtain 1,060 mL (lithium chloride concentration: 92 g / L). The filtrate was concentrated using the RO membrane, and the resulting lithium chloride aqueous solution (lithium chloride concentration: 200 g / L) was passed through an ion exchange membrane (Nafion N324 manufactured by Chemours) at a current density of 40 A / dm 2, electrode area 0.7dm 2 Electrolysis was performed under the above conditions (first electrolysis step), and 1100 g of a 6.2 mass% lithium hydroxide aqueous solution was obtained. Furthermore, the reaction product of the generated chlorine gas and hydrogen gas was absorbed in water, and 350 g of 30 mass% hydrochloric acid was also obtained. The recovery rate of lithium in the first electrolysis step was 70.3%.

[0054] 380 g of the 6.2% by mass lithium hydroxide aqueous solution was taken, and 80% by mass of the aqueous solution was crystallized to obtain 19.3 g (mass after drying) of lithium hydroxide monohydrate crystals. The sodium content in the lithium hydroxide monohydrate was less than 50 ppm, the aluminum content was less than 10 ppm, and the phosphorus content was less than 10 ppm.

[0055] The filtrate and washing water (10.5 L, sodium chloride concentration: 98 g / L) obtained by filtering and washing the white slurry A were concentrated using the RO membrane, and the resulting aqueous sodium chloride solution (sodium chloride concentration: 300 g / L) was passed through an ion exchange membrane (Nafion N324, manufactured by Chemours) at a current density of 40 A / dm 2 , electrode area 1.75dm 2 The electrolysis was carried out under the condition of current flow time of 4 hours, and 1.6 kg of 21.2 mass% sodium hydroxide was obtained. Furthermore, the reaction product of the generated chlorine gas and hydrogen gas was absorbed in water, and 1.04 kg of 30 mass% hydrochloric acid was also obtained. The sodium hydroxide produced in the electrolysis process was reusable 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 was reusable in the dissolution process (STEP 1). The current efficiency in the electrolysis process was 81.5%.

[0056] In this example, it was found that the mineral acid and alkali used could be regenerated and reused, and it was also found that the purity of the lithium hydroxide monohydrate obtained in the final stage of lithium recovery from waste lithium-ion batteries and the recovery rate of lithium were very high.

[0057] In the recovery method of the present invention, at least one of sodium hydroxide and potassium hydroxide can be directly obtained in the second electrolysis step using an ion exchange membrane of the aqueous alkali mixed salt solution. Since the mineral acid and alkali generated in the second electrolysis step can be recycled for use in the recovery method of the present invention, a closed-loop recycle process can be realized. Furthermore, since the recovery method of the present invention recycles the mineral acid and alkali, the amount of carbon dioxide emitted in the distribution process of the mineral acid and alkali can be reduced compared to the conventional case in which the mineral acid and alkali are purchased from outside. [Explanation of symbols]

[0058] 1...active material powder, 2...metal sulfate aqueous solution, 3...lithium hydroxide monohydrate, 4...sodium hydroxide solution, 5...mineral acid, 6...lithium carbonate, 11, 21...electrolytic cell, 12, 22...anode plate, 13, 23...cathode plate, 14, 24...anode, 15, 25...cathode, 16, 26...ion exchange membrane, 17, 27...Anode chamber, 18, 28...Cathode chamber.

Claims

1. A method for recovering lithium from waste lithium ion batteries, comprising the steps of: A dissolving step of dissolving the active material powder obtained by pretreating the waste lithium ion batteries with 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 the lithium salt and at least one salt of sodium and potassium from the aqueous alkali mixed salt solution obtained in the extraction step; a first electrolysis step of electrolyzing the lithium salt aqueous solution obtained in the separation step using an ion exchange membrane to obtain a lithium hydroxide aqueous solution; and a second electrolysis step of electrolyzing the aqueous solution of at least one salt of sodium and potassium obtained from the separation step using an ion exchange membrane to obtain an aqueous solution of an alkali hydroxide; a second electrolysis step of reusing the aqueous alkali hydroxide solution obtained in the second electrolysis step in at least one of the alkali hydroxide adding step, the extraction step, and the separation step.

2. 2. The method for recovering lithium from used 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.

3. 3. The method for recovering lithium from used lithium ion batteries according to claim 1 or 2, further comprising concentrating an aqueous salt solution of at least one of sodium and potassium, and electrolyzing the concentrated aqueous salt solution of at least one of sodium and potassium in the second electrolysis step.

4. The method for recovering lithium from waste lithium-ion batteries according to any one of claims 1 to 3, wherein the mineral acid used in the dissolving step includes at least one of hydrochloric acid, sulfuric acid, and nitric acid.

5. The method for recovering lithium from used lithium ion batteries according to any one of claims 1 to 4, wherein renewable energy is used as the power used in at least one of the first electrolysis step and the second electrolysis step. A method for recovering lithium from used lithium ion batteries.

6. The method for recovering lithium from waste lithium-ion batteries according to any one of claims 1 to 5, wherein at least one of solar power generation and wind power generation is used as the electric power used in the first electrolysis step and the second electrolysis step.

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