Bipolar electrodialysis apparatus for producing lithium hydroxide

Abstract

Provided is a bipolar electrodialysis apparatus for producing lithium hydroxide, including, in sequence, an anode, a first bipolar membrane, an anion-selective ion exchange membrane, a cation-selective ion exchange membrane, a second bipolar membrane, and a cathode, the apparatus comprising: an acidic solution compartment which is formed between the first bipolar membrane and the anion-selective ion exchange membrane and in which an acidic solution is generated; a basic solution compartment which is formed between the second bipolar membrane and the cation-selective ion exchange membrane and in which a basic solution is generated; and a salt solution compartment which is formed between the anion-selective ion exchange membrane and the cation-selective ion exchange membrane, wherein a lithium salt aqueous solution is introduced into the salt solution compartment, water is introduced into each of the acidic solution compartment and the basic solution compartment, an electrode solution is introduced between the anode and the first bipolar membrane and between the cathode and the second bipolar membrane, and the electrode solution includes a redox compound.

Description

Bipolar electrodialysis device for lithium hydroxide production

[0001] The present invention relates to a bipolar electrodialysis device for the production of lithium hydroxide.

[0002] The global electric vehicle market is projected to grow from 2.3 million units in 2019 to 21.9 million units in 2030. Battery performance is also continuously improving through increased capacity and longer lifespan. Regarding cathode active materials for secondary batteries, the market share of high-energy-density High-Ni batteries is also predicted to rise to 76% by 2030. Consequently, the demand for lithium hydroxide, a raw material for High-Ni cathode active materials, is also expected to increase.

[0003] Lithium, which serves as a raw material for lithium-ion batteries, has conventionally been produced by extracting lithium carbonate from salt lakes, reacting it with lime to obtain a lithium hydroxide solution, and then crystallizing it. However, the lime process generates limestone as a byproduct, and the operation of kilns to recycle the limestone produces large amounts of carbon dioxide, posing an environmental problem. Alternatively, a lithium hydroxide solution can be produced using an electrodialysis method utilizing a bipolar membrane.

[0004] The objective of the present invention is to provide a bipolar electrodialysis device for producing lithium hydroxide that can improve current efficiency and increase the productivity of lithium hydroxide.

[0005] The objects of the present invention are not limited to those mentioned above, and other unmentioned objects and advantages of the present invention may be understood from the following description and will be more clearly understood by the embodiments of the present invention. Furthermore, it will be readily apparent that the objects and advantages of the present invention can be realized by the means and combinations thereof set forth in the claims.

[0006] In one embodiment of the present invention, a bipolar electrodialysis device comprising sequentially an anode, a first bipolar membrane, an anion-selective ion exchange membrane, a cation-selective ion exchange membrane, a second bipolar membrane, and a cathode, wherein an acidic solution compartment formed between the first bipolar membrane and the anion-selective ion exchange membrane and in which an acidic solution is generated; and a basic solution compartment formed between the second bipolar membrane and the cation-selective ion exchange membrane and in which a basic solution is generated; The present invention provides a bipolar electrodialysis apparatus for producing lithium hydroxide comprising: a salt solution compartment formed between the anion-selective ion exchange membrane and the cation-selective ion exchange membrane; wherein an aqueous lithium salt solution is introduced into the salt solution compartment, water is introduced into the acidic solution compartment and the basic solution compartment, respectively, an electrode solution is introduced between the anode and the first bipolar membrane and between the cathode and the second bipolar membrane, an aqueous sulfuric acid solution obtained including sulfate ions separated from the aqueous lithium salt solution by the anion-selective ion exchange membrane and hydrogen ions generated by the decomposition of water by electrodialysis in the first bipolar membrane is discharged from the acidic solution compartment, and an aqueous lithium hydroxide solution obtained including lithium ions separated from the aqueous lithium salt solution by the cation-selective ion exchange membrane and hydroxide ions generated by the decomposition of water by electrodialysis in the second bipolar membrane is obtained from the basic solution compartment, and the electrode solution comprises a redox compound.

[0007] The above redox compound can act as an oxidizing agent or a reducing agent.

[0008] The above redox compound may be a compound containing a cyanide transition metal and an alkali metal.

[0009] The above alkali metal may include at least one selected from Group 1 elements.

[0010] The above alkali metal may, specifically, be Li, Na, or K.

[0011] The above cyanide transition metal may include at least one selected from the group consisting of iron (Fe), copper (Cu), vanadium (V) and combinations thereof.

[0012] The above redox compounds are K3Fe(CN)6, K4Fe(CN)6, Na3Fe(CN)6, Na4Fe(CN)6, Li3Fe(CN)6, Li4Fe(CN)6, FeCl2, FeCl3, Fe2SO4, Fe2(SO4)3, CuCl, CuCl2, VO 2+ Containing compound, V 3+ It may include at least one selected from the group consisting of containing compounds and combinations thereof.

[0013] The above redox compound may include a redox compound couple.

[0014] The above electrode solution may further include water, an acidic solution, or a basic solution.

[0015] In the above-described bipolar electrodialysis device for producing lithium hydroxide, if the lithium salt aqueous solution is an aqueous lithium sulfate solution, the lithium hydroxide aqueous solution can be produced together with an aqueous sulfuric acid solution by the following chemical formula 1 in the bipolar electrodialysis device.

[0016] <Chemical Formula 1>

[0017] Li2SO4 + 2H2O → H2SO4 + 2LiOH

[0018] The above-described bipolar electrodialysis device for lithium hydroxide production can improve current efficiency and increase the productivity of lithium hydroxide. In addition, the bipolar electrodialysis device for lithium hydroxide production is also advantageous in terms of cost.

[0019] In addition to the effects described above, the specific effects of the present invention are described together with the specific details for implementing the invention below.

[0020] FIG. 1 schematically shows an exemplary structure of a bipolar electrodialysis device according to one embodiment of the present invention.

[0021] FIG. 2 schematically shows an exemplary structure of a bipolar electrodialysis device according to one embodiment of the present invention.

[0022] FIG. 3 schematically shows an exemplary structure of a bipolar electrodialysis device according to one embodiment of the present invention.

[0023] FIG. 4 is a graph showing the change in current over time for a bipolar electrodialysis device according to one embodiment of the present invention and a device manufactured for comparison therewith.

[0024] FIG. 5 is a graph showing the electrical conductivity over time in a salt solution compartment for a bipolar electrodialysis device according to one embodiment of the present invention and a device manufactured for comparison therewith.

[0025] FIG. 6 is a graph showing the electrical conductivity over time in an acidic solution compartment for a bipolar electrodialysis device according to one embodiment of the present invention and a device manufactured for comparison therewith.

[0026] FIG. 7 is a graph showing the electrical conductivity over time in a basic solution compartment for a bipolar electrodialysis device according to one embodiment of the present invention and a device manufactured for comparison therewith.

[0027] FIG. 8 is a graph showing the concentration over time in an acidic solution compartment for a bipolar electrodialysis device according to one embodiment of the present invention and a device manufactured for comparison therewith.

[0028] FIG. 9 is a graph showing the concentration of a basic solution compartment over time for a bipolar electrodialysis device according to one embodiment of the present invention and a device manufactured for comparison therewith.

[0029] FIG. 10 is a graph showing the current efficiency calculated for a bipolar electrodialysis device according to one embodiment of the present invention and a device manufactured for comparison therewith.

[0030] The aforementioned objectives, features, and advantages are described in detail below with reference to the attached drawings, thereby enabling those skilled in the art to easily implement the technical concept of the present invention. In describing the present invention, detailed descriptions of known technologies related to the present invention are omitted if it is determined that such descriptions would unnecessarily obscure the essence of the invention. Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the attached drawings. In the drawings, the same reference numerals are used to indicate the same or similar components.

[0031] In the following, the statement that any configuration is placed on the "upper (or lower)" of a component or on the "upper (or lower)" of a component may mean not only that any configuration is placed in contact with the upper (or lower) surface of said component, but also that another configuration may be interposed between said component and any configuration placed on (or below) said component.

[0032] In addition, where it is stated that one component is "connected," "combined," or "connected" to another component, it should be understood that while the components may be directly connected or connected to each other, another component may be "interposed" between each component, or each component may be "connected," "combined," or "connected" through another component.

[0033] In this specification, lithium, sulfur, magnesium, calcium, sodium, potassium, etc., may be in a form that exists in raw materials, extracts, or precipitates, and are collectively referred to as types of elements without being limited to a specific form, such as metal atoms, atoms, ions, or salts, and when distinction is necessary, they may be understood as being in a state that exists according to the laws of nature.

[0034] In one embodiment of the present invention,

[0035] A bipolar electrodialysis device comprising, in sequence, an anode, a first bipolar membrane, an anion-selective ion exchange membrane, a cation-selective ion exchange membrane, a second bipolar membrane, and a cathode is provided, and lithium hydroxide can be produced using the bipolar electrodialysis device.

[0036] The bipolar electrodialysis device comprises: an acidic solution compartment formed between the first bipolar membrane and the anion-selective ion exchange membrane, in which an acidic solution is generated; a basic solution compartment formed between the second bipolar membrane and the cation-selective ion exchange membrane, in which a basic solution is generated; and a salt solution compartment formed between the anion-selective ion exchange membrane and the cation-selective ion exchange membrane.

[0037] A lithium salt aqueous solution is introduced into the above salt solution compartment.

[0038] Water is introduced into the acidic solution compartment and the basic solution compartment, respectively.

[0039] Electrode solution is introduced between the anode and the first bipolar membrane and between the cathode and the second bipolar membrane.

[0040] An aqueous sulfuric acid solution obtained by separating sulfate ions from the above lithium salt aqueous solution by the above anion-selective ion exchange membrane and hydrogen ions generated by the decomposition of water by electrodialysis in the above first bipolar membrane is discharged from the above acidic solution compartment.

[0041] The lithium hydroxide aqueous solution obtained from the basic solution compartment comprises lithium ions separated by the cation-selective ion exchange membrane in the above lithium salt aqueous solution and hydroxide ions generated by the decomposition of water by electrodialysis in the second bipolar membrane.

[0042] The above electrode solution may contain a redox compound.

[0043] The above-described bipolar electrodialysis device for lithium hydroxide production can improve current efficiency and increase the productivity of lithium hydroxide.

[0044] Figure 1 schematically shows an exemplary structure of the bipolar electrodialysis device.

[0045] Specifically, the bipolar electrodialysis device comprises: an anode (1), a first bipolar membrane (3), an anion-selective ion exchange membrane (4), a cation-selective ion exchange membrane (5), a second bipolar membrane (6) and a cathode (2) in sequence; an acidic solution compartment (11) formed between the first bipolar membrane (3) and the anion-selective ion exchange membrane (4) and in which an acidic solution is generated; a basic solution compartment (12) formed between the second bipolar membrane (6) and the cation-selective ion exchange membrane (5) and in which a basic solution is generated; and a salt solution compartment (13) formed between the anion-selective ion exchange membrane (4) and the cation-selective ion exchange membrane (5).

[0046] The lithium salt aqueous solution (10) can be introduced into the salt solution compartment (13). Water (90) is introduced into the acidic solution compartment (11) and the basic solution compartment (12). An electrode solution (80) is introduced between the anode (1) and the first bipolar membrane (3) and between the cathode (2) and the second bipolar membrane (6). The electrode solution (80) may be water or an aqueous solution.

[0047] In one embodiment, the lithium salt aqueous solution (10) may be an aqueous solution of lithium sulfate (Li2SO4).

[0048] When the above lithium salt aqueous solution (10) is introduced, lithium ions (Li) in the above lithium salt aqueous solution + ) passes through the cation-selective ion exchange membrane (5) and sulfate ions (SO4 2- Anions such as ) pass through the anion-selective ion exchange membrane (4), and the desalinated lithium salt aqueous solution (10') is discharged from the salt solution compartment (13).

[0049] When voltage is applied to the positive electrode (1) and the negative electrode (2), water is converted into hydrogen ions (H₂) by electrodialysis in the first bipolar membrane (3) and the second bipolar membrane (6). + ) and hydroxide ions (OH - It is decomposed into ) and hydrogen ions (H) into the acidic solution compartment (11) by electric force. + ) moves, and hydroxide ions (OH) move to the basic solution compartment (12). - ) will move.

[0050] Lithium ions (Li) that have passed through the cation-selective ion exchange membrane (5) above + ) and hydroxide ions (OH) formed from water by electrodialysis in the second bipolar membrane (6) - An aqueous lithium hydroxide (LiOH) solution (30) formed including ) is discharged from the basic solution compartment (12). At least a portion of the aqueous lithium hydroxide (LiOH) solution (30) discharged from the basic solution compartment (12) can be reintroduced into the basic solution compartment (12) and circulated. In FIG. 1, the aqueous lithium hydroxide (LiOH) solution (31) represents the aqueous lithium hydroxide (LiOH) solution that is circulated and introduced.

[0051] Anions that have passed through the above anion-selective ion exchange membrane (4), for example, sulfate ions (SO4 2- ) and hydrogen ions (H) formed from water by electrodialysis in the first bipolar membrane (3) +An acidic aqueous solution (20) formed including ) is discharged from the acidic solution compartment (11) as a byproduct. For example, if the lithium salt aqueous solution (10) is a lithium sulfate (Li2SO4) aqueous solution, the acidic aqueous solution (20) may be a sulfuric acid (H2SO4) aqueous solution (20). At least a portion of the sulfuric acid (H2SO4) aqueous solution (20) discharged from the acidic solution compartment (11) may be reintroduced into the acidic solution compartment (11) and circulated. In FIG. 1, the sulfuric acid (H2SO4) aqueous solution (21) represents the sulfuric acid (H2SO4) aqueous solution that is circulated and introduced.

[0052] For example, if the lithium salt aqueous solution (10) is an aqueous solution of lithium sulfate (Li2SO4), an aqueous solution of lithium hydroxide (30) is discharged from the basic solution compartment (12), and an aqueous solution of sulfuric acid (H2SO4) (20) is discharged from the acidic solution compartment (11). At this time, the reaction in the bipolar electrodialysis device can be represented by the following chemical formula 1. That is, in the bipolar electrodialysis device, the aqueous solution of lithium hydroxide (LiOH) is produced together with the aqueous solution of sulfuric acid (H2SO4) by the following chemical formula 1.

[0053] <Chemical Formula 1>

[0054] Li2SO4 + 2H2O → H2SO4 + 2LiOH

[0055]

[0056] In one embodiment, the bipolar electrodialysis device may be included as a unit comprising a pair of acidic solution compartments (11), salt solution compartments (13), and basic solution compartments (12) formed by a first bipolar membrane (3), an anion-selective ion exchange membrane (4), a cation-selective ion exchange membrane (5), and a second bipolar membrane (6), and may be included in a structure in which a plurality of pairs are repeated.

[0057] The above-described bipolar electrodialysis device may include at least 2 pairs, for example, 2 to 100 pairs, for example, 2 to 50 pairs, for example, 2 to 20 pairs, for example, 2 to 10 pairs.

[0058] FIG. 2 schematically illustrates an exemplary structure of the bipolar electrodialysis device comprising a plurality (n) of pairs.

[0059] In FIG. 1, the bipolar membranes (3, 6) are named 'first' or 'second' for convenience of explanation, but the bipolar membranes (3, 6) are hydrogen ions (H) generated from water by electrodialysis. + ) and hydroxide ions (OH - Since it performs the same function of moving according to the direction of voltage application, it is not distinguished as the 1st to nth order bipolar film in FIG. 2 but is indicated as a bipolar film (3 / 6).

[0060] In FIG. 2, for example, if the bipolar electrodialysis device comprises n pairs, it may include n anion-selective ion exchange membranes (4), n cation-selective ion exchange membranes (5), and n+1 bipolar membranes (3 / 6).

[0061] FIG. 3 schematically illustrates an exemplary structure of the bipolar electrodialysis device that can be used in one embodiment of the present invention.

[0062]

[0063] In one embodiment, when the bipolar electrodialysis device includes two or more pairs, the membrane facing the outermost anode (1) and the cathode (2) may be a bipolar membrane (3 / 6), an anion-selective ion exchange membrane (4), or a cation-selective ion exchange membrane (5). For example, depending on the structural design of the bipolar electrodialysis device, the compartment following the compartment through which the electrode solution (80) passes may be any one of an acidic solution compartment (11), a salt solution compartment (13), and a basic solution compartment (12), and accordingly, the type of membrane facing the electrode may be determined.

[0064] In one embodiment, a cation-selective ion exchange membrane (5) is placed after the anode (1) to form an acidic solution compartment (11), and then the pair is repeated sequentially, and finally a basic solution compartment (12) is formed, and an anion-selective ion exchange membrane (4) and a cathode (2) can be placed sequentially.

[0065]

[0066] The bipolar electrodialysis device of Fig. 1 corresponds to the case where n=1 in Fig. 2, and the previously described explanation with reference to Fig. 1 may be applicable not only to the cases of Figs. 2 and 3, but also to cases where the type of membrane facing the electrode is not a bipolar membrane but a cation-selective ion exchange membrane or an anion-selective exchange membrane.

[0067]

[0068] The above redox compound is a substance that facilitates oxidation / reduction and can act as an oxidizing agent or a reducing agent, and can facilitate electron transfer at both ends of the bipolar electrodialysis device for producing lithium hydroxide. Specifically, the current is improved because electron transfer becomes easier due to the excellent oxidation-reduction power of the above redox compound. This is because, according to Ohm's law, the current in the bipolar electrodialysis device for producing lithium hydroxide increases over time when the resistance is low under constant voltage. As a result, the productivity of lithium hydroxide and current efficiency can be improved in the bipolar electrodialysis device for producing lithium hydroxide.

[0069] Because the above-described bipolar electrodialysis device for producing lithium hydroxide uses the electrode solution (80) containing the above-described redox compound, the degree of improvement in electrical conductivity over time in the basic solution compartment (12) is increased. High electrical conductivity in the basic solution compartment (12) means that the concentration of lithium hydroxide (LiOH) can be performed more smoothly.

[0070] Since the above-described bipolar electrodialysis device for producing lithium hydroxide uses the electrode solution (80) containing the above-described redox compound, the degree of improvement in electrical conductivity over time in the acidic solution compartment (11) can also be increased. High electrical conductivity in the acidic solution compartment (11) means that the concentration of sulfuric acid (H2SO4) can be performed more smoothly.

[0071] In the salt solution compartment (13), a sulfuric acid (H2SO4) solution remains, and each ion must rapidly reach the basic solution compartment (12) and the acidic solution compartment (11) of the bipolar membrane through the cation or anion selective exchange membrane (4, 5) to improve productivity. Sulfate ions (SO4) in the acidic solution compartment (11) that have thus rapidly moved 2-) indicates that sulfuric acid (H2SO4) can be rapidly produced along with the water splitting of the bipolar membrane, resulting in increased electrical conductivity. Likewise, lithium ions (Li) rapidly escape from the salt solution compartment (13) + ) is made of lithium hydroxide (LiOH) along with the water decomposition of the bipolar membrane of the basic solution compartment (12), and as a result, the electrical conductivity of the basic solution compartment (12) increases rapidly.

[0072] Sulfate ions (SO4) in the acidic solution compartment (11) 2- The concentration of ) is hydrogen ions (H + It depends on the concentration of sulfate ions (SO4). That is, 2- It must be in the state ) so that it can be produced into sulfuric acid (H2SO4) through the water decomposition of the bipolar membrane (3, 6, 3 / 6). In the above-mentioned bipolar electrodialysis device for producing lithium hydroxide, sulfate ions (SO4) in the acidic solution compartment (11) 2- Because the concentration of ) is high, the production of sulfuric acid (H2SO4) also increases. Likewise, in the above-mentioned bipolar electrodialysis device for producing lithium hydroxide, lithium ions (Li) in the basic solution compartment (12) + Because the concentration of ) is high, the production of lithium hydroxide (LiOH) increases.

[0073] The redox compound included in the electrode solution (80) may be a compound containing a transition metal cyanide and an alkali metal, or a transition metal compound.

[0074] The above alkali metal may include at least one selected from Group 1 elements such as Li, Na, or K, for example.

[0075] The above cyanide transition metal may include at least one selected from the group consisting of iron (Fe), copper (Cu), vanadium (V) and combinations thereof.

[0076] The electrode solution (80) may be one in which the redox compound is added to water, an acidic solution, or a basic solution. Accordingly, the electrode solution (80) may further include water, an acidic solution, or a basic solution in addition to the redox compound.

[0077] In one embodiment, the basic solution may be an aqueous solution of lithium hydroxide.

[0078] If one wishes to achieve the current efficiency achievable with an electrode solution (80) containing the redox compound while using an electrode solution that does not contain the redox compound, for example, the amount used must be much higher in the case of an electrode solution of an aqueous lithium hydroxide solution. On the other hand, using an electrode solution (80) containing the redox compound increases current efficiency, so the amount used can be reduced, which is advantageous in terms of cost.

[0079] The molar concentration of the redox compound in the electrode solution (80) may be 0.1 M to 1 M. By using the electrode solution (80) containing the redox compound at a concentration within the above numerical range, the current efficiency of the bipolar electrodialysis device can be increased.

[0080] If the above electrode solution (80) is an aqueous solution obtained by mixing the above redox compound with water, the above redox compound must be soluble in water.

[0081] If the above electrode solution (80) is an aqueous solution obtained by mixing the above redox compound with an acidic solution, the above redox compound must be soluble in water.

[0082] If the above electrode solution (80) is an aqueous solution obtained by mixing the above redox compound with a basic solution, the above redox compound must be soluble in an alkaline solution.

[0083] In one embodiment, the redox compound is K3Fe(CN)6, K4Fe(CN)6, Na3Fe(CN)6, Na4Fe(CN)6, Li3Fe(CN)6, Li4Fe(CN)6, FeCl2, FeCl3, Fe2SO4, Fe2(SO4)3, CuCl, CuCl2, VO 2+ Containing compound, V 3+ It may include at least one selected from the group consisting of containing compounds and combinations thereof, and a substance known as a redox compound may be used, but is not limited thereto.

[0084] Since all of the exemplified redox compounds are soluble in water or an acidic solution, the electrode solution (80) may be an aqueous solution of the exemplified redox compounds or a solution in which the redox compounds are added to an acidic solution.

[0085] If the electrode solution (80) is a hydroxyl group-containing basic solution, it may be a compound containing a cyanide transition metal and an alkali metal that is soluble in the hydroxyl group-containing basic solution among the exemplified redox compounds.

[0086] In one embodiment, the electrode solution (80) may comprise at least one selected from the group consisting of an aqueous lithium hydroxide solution and K3Fe(CN)6, K4Fe(CN)6, and combinations thereof that can be dissolved in the aqueous lithium hydroxide solution.

[0087] In one embodiment, the electrode solution (80) may include a redox couple. By including a suitable redox couple in the electrode solution (80), smoother oxidation and reduction reactions can be induced, thereby facilitating electron transfer and improving current efficiency.

[0088] For example, the above redox compound couple may be K3Fe(CN)6 and K4Fe(CN)6.

[0089] For example, the above redox compound couple may be FeCl2 and FeCl3.

[0090] For example, the above redox compound couple may be Fe2SO4 and Fe2(SO4)3.

[0091] For example, the above redox compound couple may be CuCl and CuCl2.

[0092] For example, the above redox compound couple is VO 2+ Containing compounds and V 3+ It may be a contained compound.

[0093]

[0094] Examples and comparative examples of the present invention are described below. The following examples are merely embodiments of the present invention, and the present invention is not limited to the following examples.

[0095]

[0096] (Example)

[0097] Example 1

[0098] A bipolar electrodialysis device having a structure with n=3 in Fig. 2 was manufactured, and an aqueous lithium sulfate (Li2SO4) solution at a concentration of 66 mS / cm was introduced into the salt solution compartment, and deionized water at a concentration of 0.02 mS / cm was introduced into the acidic solution compartment and the basic solution compartment, respectively. The electrode solution was a mixture of an aqueous solution of 0.5M K3Fe(CN)6 and 0.5M K4Fe(CN)6 and an aqueous solution of 0.25M lithium hydroxide, and an aqueous solution of lithium hydroxide was obtained from the basic solution compartment.

[0099]

[0100] Comparative Example 1

[0101] A bipolar electrodialysis apparatus identical to that in Example 1 was prepared, except that a 0.25 M LiOH aqueous solution was used as the electrode solution, and an aqueous lithium sulfate (Li2SO4) solution at a concentration of 66 mS / cm was introduced into the salt solution compartment, and into the acidic solution compartment and the basic solution compartment at 0.02 mS / cm, respectively. 2Deionized water was added, and a 0.75M LiOH aqueous solution was added as the electrode solution to obtain an aqueous lithium hydroxide solution.

[0102]

[0103] Experimental Example 1

[0104] The change in current over time was measured for the bipolar electrodialysis devices according to Example 1 and Comparative Example 1, and the results are shown in FIG. 4.

[0105] Measuring device: Changjo Tech, CJT-055B

[0106]

[0107] Experimental Example 2

[0108] The electrical conductivity over time in the salt solution compartment, acid solution compartment, and basic solution compartment of the bipolar electrodialysis device according to Example 1 and Comparative Example 1 was measured and is shown in FIGS. 5 to 7.

[0109] Measuring devices: Orion (A2215), Endless-Hauser (CML18)

[0110]

[0111] In Fig. 5, it was confirmed that the lithium sulfate salt solution in Example 1 was rapidly desalinated compared to Comparative Example 1, resulting in lower electrical conductivity; in Fig. 6, it was confirmed that the electrical conductivity of the aqueous sulfuric acid solution in Example 1 was higher compared to Comparative Example 1; and in Fig. 7, it was confirmed that the electrical conductivity of the aqueous lithium hydroxide solution in Example 1 was higher compared to Comparative Example 1. That is, in Example 1, the electrical conductivity of the salt solution compartment decreased rapidly, and ions rapidly moved to the basic solution compartment and the acidic solution compartment. In the acidic solution compartment, sulfuric acid was rapidly generated along with the water splitting of the bipolar membrane, causing an increase in electrical conductivity (see Fig. 6), and in the basic solution compartment, lithium hydroxide was rapidly generated along with the water splitting of the bipolar membrane, causing an increase in electrical conductivity (see Fig. 7).

[0112]

[0113] Experimental Example 3

[0114] For the bipolar electrodialysis device according to Example 1 and Comparative Example 1, the concentrations over time in the acidic solution compartment and the basic solution compartment were measured and are shown in FIGS. 8 and 9.

[0115] Measuring device: SPECTRO AMETEK (Spectro Arcos ICP-OES)

[0116]

[0117] Sulfate ions (SO4) generated in the acidic solution compartment of Example 1 in Fig. 8 2- It was confirmed that the concentration of ) was high, and in particular, lithium ions (Li generated in the basic solution compartment of Example 1 in Fig. 9) + It was confirmed that the concentration of ) increased rapidly compared to Comparative Example 1.

[0118]

[0119] Experimental Example 4

[0120] The current efficiency of the bipolar electrodialysis device according to Example 1 and Comparative Example 1 was calculated according to the following formula 1, and the results are shown in FIG. 10.

[0121] <Formula 1>

[0122]

[0123] η: Current efficiency

[0124] F: Faraday constant

[0125] C f : Lithium ions (Li in the final basic solution compartment + ) concentration or sulfate ions (SO4) in the final acidic solution compartment 2- ) concentration

[0126] V f : Final volume of the basic solution compartment or acidic solution compartment after operating the bipolar electrodialysis unit

[0127] C i: Lithium ions (Li in the initial basic solution compartment + ) concentration or sulfate ions (SO4) in the initial acidic solution compartment 2- ) concentration

[0128] V i : Final volume of the basic solution compartment or acidic solution compartment before operating the bipolar electrodialysis unit

[0129] N: Number of pairs of bipolar electrodialysis devices

[0130] I: Current

[0131] t: time

[0132] z: electric charge

[0133]

[0134] Referring to FIG. 10, it can be seen that the current efficiency of Example 1 has increased compared to Comparative Example 1.

[0135]

[0136] Although the present invention has been described above with reference to embodiments, the present invention is not limited by the embodiments disclosed in this specification, and it is obvious that various modifications can be made by a person skilled in the art within the scope of the technical concept of the present invention. Furthermore, even if the effects of the configuration of the present invention were not explicitly described while describing the embodiments of the present invention above, it is natural to acknowledge that the effects predictable by said configuration should also be recognized.

[0137]

[0138] [Explanation of the symbol]

[0139] 1: Positive electrode

[0140] 2: Cathode

[0141] 3: First bipolar membrane

[0142] 4: Anion-selective ion exchange membrane

[0143] 5: Cation-selective ion exchange membrane

[0144] 6: Second bipolar membrane

[0145] 3 / 6: Bipolar membrane

[0146] 10: Aqueous solution of lithium salt

[0147] 10': Aqueous solution of lithium salt

[0148] 11: Acidic solution compartment

[0149] 12: Basic solution compartment

[0150] 13: Salt solution compartment

[0151] 20: Aqueous solution of sulfuric acid (H2SO4)

[0152] 21: Aqueous solution of sulfuric acid (H2SO4)

[0153] 30: Aqueous solution of lithium hydroxide (LiOH)

[0154] 31: Aqueous solution of lithium hydroxide (LiOH)

[0155] 80: Electrode solution

[0156] 90: Water

Claims

1. A bipolar electrodialysis device comprising, in sequence, an anode, a first bipolar membrane, an anion-selective ion exchange membrane, a cation-selective ion exchange membrane, a second bipolar membrane, and a cathode, and An acidic solution compartment formed between the first bipolar membrane and the anion-selective ion exchange membrane, in which an acidic solution is generated; a basic solution compartment formed between the second bipolar membrane and the cation-selective ion exchange membrane, in which a basic solution is generated; and a salt solution compartment formed between the anion-selective ion exchange membrane and the cation-selective ion exchange membrane; comprising A lithium salt aqueous solution is introduced into the above salt solution compartment, and Water is introduced into the acidic solution compartment and the basic solution compartment, respectively, and Electrode solution is introduced between the anode and the first bipolar film and between the cathode and the second bipolar film, and A sulfuric acid aqueous solution obtained by including sulfate ions separated from the above lithium salt aqueous solution by the above anion-selective ion exchange membrane and hydrogen ions generated by the decomposition of water by electrodialysis in the above first bipolar membrane is discharged from the above acidic solution compartment, and A lithium hydroxide aqueous solution obtained by including lithium ions separated by the cation-selective ion exchange membrane in the lithium salt aqueous solution and hydroxide ions generated by the decomposition of water by electrodialysis in the second bipolar membrane is obtained from the basic solution compartment, and The above electrode solution contains a redox compound. Bipolar electrodialysis device for lithium hydroxide production.

2. In Paragraph 1, The above redox compound acts as an oxidizing or reducing agent. Bipolar electrodialysis device for lithium hydroxide production.

3. In Paragraph 1, The above redox compound is a compound comprising a cyanide transition metal and an alkali metal. Bipolar electrodialysis device for lithium hydroxide production.

4. In Paragraph 1, The above alkali metal comprises at least one selected from Group 1 elements. Bipolar electrodialysis device for lithium hydroxide production.

5. In Paragraph 1, The above alkali metal is Li, Na, or K. Bipolar electrodialysis device for lithium hydroxide production.

6. In Paragraph 1, The above cyanide transition metal comprises at least one selected from the group consisting of iron (Fe), copper (Cu), vanadium (V), and combinations thereof. Bipolar electrodialysis device for lithium hydroxide production.

7. In Paragraph 1, The above redox compounds are K3Fe(CN)6, K4Fe(CN)6, Na3Fe(CN)6, Na4Fe(CN)6, Li3Fe(CN)6, Li4Fe(CN)6, FeCl2, FeCl3, Fe2SO4, Fe2(SO4)3, CuCl, CuCl2, VO 2+ Containing compound, V 3+ Comprising at least one selected from the group consisting of containing compounds and combinations thereof Bipolar electrodialysis device for lithium hydroxide production.

8. In Paragraph 1, The above redox compound includes a redox compound couple. Bipolar electrodialysis device for lithium hydroxide production.

9. In Paragraph 1, The above electrode solution further comprises water, an acidic solution, or a basic solution. Bipolar electrodialysis device for lithium hydroxide production.

10. In Paragraph 1, The above lithium salt aqueous solution is a lithium sulfate aqueous solution, and In the above-described bipolar electrodialysis device, the aqueous lithium hydroxide solution is produced together with the aqueous sulfuric acid solution according to the following chemical formula 1. Bipolar electrodialysis device for lithium hydroxide production. <Chemical Formula 1> Li2SO4 + 2H2O → H2SO4 + 2LiOH

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