Process for separating Li ions and Na ions

Abstract

The present invention relates to a process for separating lithium ions and sodium ions from a sulfate-containing solution, and to an apparatus for carrying out the process.

Description

[Technical Field]

[0001] The present invention relates to a process for separating lithium ions and sodium ions from a sulfate-containing solution, and to an apparatus for carrying out this process. [Background technology]

[0002] Electric vehicles powered by low-emission electricity are considered to have the highest climate protection potential among land transport technologies throughout their entire lifecycle. Therefore, electric vehicles are seen as an important component of a sustainable and climate-friendly transportation system based on renewable energy. While lithium-ion / polymer batteries are a promising energy storage system for electric drive systems, their lifespan is limited. In this regard, the desired level of electrification can only be achieved through a combination with a sustainable recycling concept. In particular, the plan to ban the sale of new vehicles with internal combustion engines necessitates the comprehensive recovery of valuable metals such as cobalt, nickel, and manganese contained in used batteries, as well as lithium, which can only be obtained through long processes.

[0003] Conventional technologies describe numerous methods for recovering useful metals from used lithium-ion / polymer batteries.

[0004] U.S. Patent Application Publication No. 2017 / 0077564 relates to a lithium-ion battery recycling process, which includes: (i) determining the molar ratio of cathode material for new batteries; (ii) forming a leachate by mixing crushed battery material from a lithium battery recycling stream with an acidic leachate and hydrogen peroxide (H2O2) to separate the cathode material from the undissolved material; (iii) filtering the undissolved material from the formed leachate, leaving the dissolved salts of the cathode material in the leachate; and (iv) determining the molar ratio of the dissolved cathode material salts in the leachate. (v) Determining the composition of the leaching solution; (v) Adding Ni, Co, Mn or Al salts as sulfates (xSO4) based on the determined composition to adjust the molar ratio of dissolved positive electrode material salts in the leaching solution to correspond to a specific molar ratio of the regenerated battery, including the addition of aluminum sulfate solution and chelating agents; and (vi) Raising the pH of the leaching solution to at least 10 to precipitate metal ions of the positive electrode material, removing them by filtration, and forming pCAM, which is a precursor of the actual positive electrode active material CAM, in which case the Ni, Co, Mn and Al salts remaining in the solution 、 It exists as hydroxide (OH)2 or carbonate (CO3) bonded in the molar ratio required for the new CAM. Subsequently, the precursor is thoroughly mixed with LiOH*H2O or Li2CO3. 、 The positive electrode active material is obtained by reacting it at a temperature higher than 800°C.

[0005] U.S. Patent Application Publication No. 2013 / 0302226 discloses a method for recycling batteries, which involves preparing a solution of aggregated battery material from used cells, precipitating impurities from the prepared solution, adjusting a predetermined ratio of the desired material in the solution, and precipitating the desired material to further form it into a positive electrode material for a new battery.

[0006] However, the methods described in the prior art have a drawback: due to the nature of process control, the lithium to be recovered exists in the solution as Li2SO4 along with Na2SO4, and therefore can only be recovered as sparingly soluble Li2CO3 at the end of the process chain. 3、And the relationship between the solubility of Na2SO4 and Li2SO4 、 The separation of Na ions and Li ions is highly complex and intricate, making the quantitative recovery of lithium virtually impossible from an economic standpoint. [Overview of the project] [Problems that the invention aims to solve]

[0007] Therefore, in order to achieve sustainable and complete value recycling of used lithium-ion / polymer batteries, there is still a need for improved processes for lithium recovery from sodium-containing sulfate solutions. Accordingly, the object of the present invention is to satisfy this need. [Means for solving the problem]

[0008] Within the scope of the present invention, it has been surprisingly found that the poor separation of Li ions and Na ions from sulfate-containing solutions can be avoided by their conversion to the corresponding hydroxides.

[0009] Therefore, the present invention first relates to a process for separating Na ions and Li ions, in which an aqueous solution A containing Na2SO4 and Li2SO4 is electrolyzed to produce solution B, and the produced solution B is treated with a carbonate source to form Li2CO3.

[0010] Those skilled in the art are aware that the compounds Na2SO4, Li2SO4, Na2CO3, Li2CO3, and all other salts exist in ionic form in solution. Therefore, unless otherwise specified, these are used interchangeably with their corresponding ions, and explicit references are omitted.

[0011] Surprisingly, the difference in solubility between Li2CO3 and Na2CO3 is 、The difference in solubility between Na2SO4 and Li2SO4 is significant, and it was found that this difference can be utilized to achieve more effective separation. While the difference in solubility between Na2SO4 and Li2SO4 is only about twice, Li2CO3 is clearly less soluble than Na2CO3. 、 This allows for a more effective separation of the two metals. Therefore, in a preferred embodiment of the process of the present invention, Li2CO3 is separated to produce a filtrate containing Na2CO3. [Brief explanation of the drawing]

[0012] [Figure 1] A schematic diagram illustrating the concept of the process according to the present invention. [Figure 2a] A schematic diagram showing the method for obtaining solution A. [Figure 2b] A scheme in which solution X is further treated with H2SO2. [Figure 3] A diagram illustrating the general procedure of the process according to the present invention. [Modes for carrying out the invention]

[0013] Within the scope of the process according to the present invention, a number of compounds can be used as carbonate sources. Preferably, the carbonate source is selected from the group consisting of Na2CO3, CO2, NaHCO3, (NH4)3CO3, (NH4)3CO3, and mixtures thereof. The use of CO2 as a carbonate source has been found to be particularly advantageous and is therefore preferred. CO2 can be recovered, for example, from the exhaust gas of other processes, and thus CO2 emissions can be reduced by leading to sustainable use.

[0014] The process according to the present invention involves electrolysis of a solution of Na and Li sulfates, in which the sulfates are expected to be converted into the corresponding hydroxides, which are more easily separated. In this regard, membrane electrolysis, particularly electrodialysis, and more specifically electrodialysis using a bipolar membrane are preferred. Particularly preferred is multi-compartment electrolysis using a cation exchange membrane and an anion exchange membrane.

[0015] Within the scope of the process according to the present invention, lithium is recovered as Li2CO3, which can be taken out as a solid from the solution in a further step. Preferably, Li2CO3 is separated by at least one method selected from the group consisting of sedimentation, filtration, and centrifugation. The separation may include a short washing step where the washing liquid can be recycled at an appropriate location throughout the process.

[0016] The process according to the present invention enables effective separation of Na and Li. If the purity of the obtained Li2CO3 is determined to be insufficient, the Li2CO3 may be subjected to a further purification step. In a preferred embodiment, the obtained Li2CO3 is treated with CO2 in a further step to convert it into soluble LiHCO3. By heating the solution containing LiHCO3, high-purity Li2CO3 can be obtained from this solution 。 Therefore, an embodiment in which the solution containing LiHCO3 is heated to form Li2CO3 is preferred 。 This purification step has the advantage that the mother liquor obtained from the separation of Li2CO3 and the CO2 discharged from the reaction mixture during the production process of Li2CO3 can be recycled to the process to form a sustainable cycle.

[0017] The starting solution A in the process according to the present invention can be obtained by a number of methods applied in the recycling process. The aqueous sulfate-containing solution A is preferably obtained by treating solution X. Here, this solution X contains Li2SO4 and at least one compound MSO4, where M is a transition metal, preferably selected from the group consisting of Ni, Co, Mn, Al, and mixtures thereof. For example, this treatment can be carried out using NaOH, and H2SO4 may be further added if necessary. By treating solution X with NaOH, metal M is converted into a hydroxide 、It is considered that Na2SO4 is produced as a by-product. Alternatively, first, the metal is transferred to the organic phase by reactive extraction in the presence of an organic extractant, and then it is possible to recycle the metal to a further value-added cycle by re-extracting it from the organic phase to the aqueous phase as MSO4 using sulfuric acid.

[0018] Preferably, within the scope of the process according to the present invention, solution X is obtained by treating suspension Y containing at least compound LiMO2 with H2SO4 and a reducing agent. Here, M is a transition metal, preferably selected from the group consisting of Ni, Co, Mn, Al, and mixtures thereof. Preferably, the reducing agent is selected from the group consisting of H2O2 and SO2.

[0019] The process according to the present invention is particularly aimed at the recovery of Li from lithium-ion / polymer batteries. Therefore, embodiments of obtaining a suspension containing LiMO2 from used lithium-ion batteries and / or manufacturing waste from their manufacturing processes are preferred. Thus, the process according to the present invention provides an inclusive recycling cycle that enables the efficient recovery of lithium incorporated in lithium-ion / polymer batteries, and thus makes a valuable contribution to the success of the required concept of electric mobility.

[0020] Within the scope of an inclusive recycling approach, the transition metal hydroxide obtained by treating solution X can also be further processed, for example, for reuse as a cathode active material for a new battery. Therefore, in one preferred embodiment of the process according to the present invention, the treatment of solution X is carried out by adjusting the stoichiometric ratio of the transition metal and precipitating it using NaOH to obtain a transition metal mixed hydroxide Ni x Co y Mn zIt is carried out so that (OH)₂ is still obtained. The adjustment of the above-mentioned stoichiometric ratio is achieved, for example, by selectively separating or selectively adding one or more of the components of the above transition metal mixed hydroxide. By this method, it becomes possible to preliminarily adjust the ratio of Ni:Co:Mn desired in the subsequent cathode material in the transition metal mixed hydroxide. Within the range of conversion to the current nickel-enriched cathode active material, it is preferable to adjust the stoichiometry by selectively separating one or more of the components of the transition metal mixed hydroxide. In a preferred embodiment, the ratio of Ni:Co:Mn in the transition metal mixed hydroxide is 1:1:1, or preferably 8:1:1.

[0021] In addition to the recovery of the materials used, especially useful metals, another aspect of a sustainable recycling strategy is the environmentally friendly treatment of resources. In particular, this means recovering or recycling, if possible, the chemicals required for the recycling process. In this process, this applies especially to the sulfuric acid required to obtain solution X. Therefore, as an embodiment of the process according to the invention, it is preferable to use at least a part of the sulfuric acid obtained by electrolysis for the preparation of solution X.

[0022] The present invention further relates to an apparatus for carrying out the process according to the present invention. This apparatus includes at least one electrolysis unit having at least one supply part for introducing solution A and at least one discharge part for discharging solution B.

[0023] The present invention is further illustrated by the following examples, which should in no way be construed as limiting the gist of the invention.

[0024] Figure 1 schematically illustrates the concept of the process according to the present invention. According to this, solution A, obtained from the recycling of lithium-ion / polymer batteries and containing Li2SO4 and Na2SO4, is subjected to electrolysis, thereby converting sulfates into their corresponding hydroxides. Treatment with CO2 as a carbonate source separates Li as Li2CO3, while Na2CO3 remains in the solution.

[0025] Figure 2a schematically shows how solution A is obtained from a suspension Y containing Li in the form of lithium / transition metal oxide LiMO2, which is obtained in the processing of lithium-ion / polymer batteries. The lithium / transition metal oxide is converted to Li2SO4 and the corresponding transition metal sulfate MSO4 (solution X) by treatment with H2SO4 and a reducing agent, preferably H2O2 or SO2. 。 The transition metal sulfate is converted to the corresponding hydroxide M(OH)2 by treating solution X with NaOH and then separated. This yields a solution containing Na2SO4 and Li2SO4, which serves as starting solution A for the process according to the present invention.

[0026] By further treating solution X with H2SO2 according to the scheme shown in Figure 2b, 、 Transition metals can be obtained in the form of sulfates.

[0027] Figure 3 shows a schematic procedure of the process according to the present invention, in which solution A of Li2SO4 and Na2SO4 is electrolyzed to produce solution B, and Li2CO3 can be separated from solution B by treatment with a carbonate source. In this way, effective separation of the two ions can be achieved.

Claims

1. Na ２ SO ４ and Li ２ SO ４ An aqueous solution A containing Li is electrolyzed to obtain solution B, and the obtained solution B is treated with a carbonate source to obtain Li ２ CO ３ A process for separating Na ions and Li ions, characterized by forming [a specific structure / component].

2. where the carbonate source is Na ２ CO ３ 、CO ２ 、NaHCO ３ 、(NH ４ ) ２ CO ３ 、(NH ４ )HCO ３ and the process according to claim 1, characterized in that it is selected from the group consisting of these and mixtures thereof.

3. The process according to at least one prior claim, characterized in that the electrolysis is multi-compartment electrolysis using a cation exchange membrane and an anion exchange membrane, particularly electrodialysis, preferably electrodialysis using a bipolar membrane.

4. Formed Li ２ CO ３ The process according to at least one of the preceding claims, characterized in that the material is separated by at least one method selected from the group consisting of sedimentation, filtration, and centrifugation.

5. Obtained Li ２ CO ３ CO ２ By processing with this, soluble LiHCO ３ A process according to at least one prior claim, characterized by converting to

6. The aqueous solution A is obtained by treating solution X, and solution X is 、 Li ２ SO ４ and at least one compound MSO ４ The process according to at least one of the preceding claims, comprising, wherein M is a transition metal, preferably selected from the group consisting of Ni, Co, Mn, Al, and mixtures thereof.

7. The solution X contains at least the compound LiMO ２ A suspension Y containing H ２ SO ４ The process according to claim 6, characterized in that it is obtained by treatment with a reducing agent, wherein M is selected from the group consisting of transition metals, preferably Ni, Co, Mn, Al, and mixtures thereof.

8. The aforementioned compound LiMO ２ The process according to claim 7, characterized in that it is obtained from used lithium-ion / polymer batteries and / or manufacturing waste from their manufacture.

9. When processing the aforementioned solution X, transition metal mixed hydroxide Ni ｘ Mn ｙ Co ｚ (OH) ２ The present invention is characterized by the production of the transition metal mixed hydroxide Ni ｘ Mn ｙ Co ｚ (OH) ２ The process according to at least one of claims 6 to 8, characterized in that the generation is carried out by adjusting the stoichiometric ratio of the transition metal and precipitating it with an aqueous sodium hydroxide solution.

10. The process according to claim 9, characterized in that the adjustment of the stoichiometric ratio of the transition metal is carried out by selectively separating or adding one or more components of the transition metal mixed hydroxide.

11. The process according to at least one prior claim, characterized in that at least a portion of the sulfuric acid obtained by the electrolysis is used in the preparation of the solution X.

12. An apparatus for performing the process according to at least one of the preceding claims, comprising an electrolytic unit having at least one supply unit for introducing the solution A and at least one discharge unit for discharging the solution B.

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