Method for separating and extracting lithium from salt lake by electrochemical deintercalation

Abstract

This invention discloses an electrochemical method for separating and extracting lithium from magnesium in salt lakes, belonging to the field of extraction metallurgy technology. In the method provided by this invention, a conductive substrate coated with a lithium-intercalated ion sieve is placed as the anode in a lithium salt chamber, and a conductive substrate coated with MnO2 is placed as the cathode in a brine chamber. Driven by an external potential, magnesium removal from the brine and the release of lithium in the lithium salt chamber are achieved. + Subsequently, by swapping the electrode positions, lithium extraction from the brine and the release of Mg from the magnesium salt chamber were achieved under an external potential. 2+ This invention employs an intermittent method for magnesium removal and lithium extraction in brine, successfully reducing the amount of magnesium near the ion sieve electrode during the lithium extraction process. 2+ The concentration was adjusted to avoid a significant increase in the magnesium-to-lithium ratio in the solution, especially near the electrodes, thereby improving the ion sieve's ability to filter Li. + The adsorption efficiency is high. Furthermore, the method provided by this invention is simple to operate, makes full use of resources, achieves high efficiency and energy saving, and is beneficial for practical production applications.

Description

Technical Field

[0001] This invention belongs to the field of extraction metallurgy technology, and in particular relates to an electrochemical method for separating and extracting magnesium-lithium from salt lakes. Background Technology

[0002] In recent years, with the maturity of lithium battery technology, energy storage devices and mobile devices such as mobile phones, new energy vehicles, electric vehicles, and home appliances have been widely used, leading to a large consumption of lithium resources. my country has become a major lithium consumer, making lithium resources a crucial strategic resource for national industrial development. In nature, ore and brine are the two main forms of lithium, with over 80% of lithium primarily found in salt lake brines. Therefore, developing "salt lake lithium extraction" technology is particularly critical. In brine, lithium coexists with a large number of alkaline earth metal ions, and Mg... 2+ and Li + The chemical properties of magnesium and lithium are very similar, and the separation of magnesium and lithium is one of the current challenges. Currently, researchers use lithium-ion sieves to extract lithium from brine. However, during the extraction process, as lithium ions are continuously extracted from the solution, the magnesium-to-lithium ratio in the solution (especially the solution near the electrode) increases, causing the adsorption rate of lithium by the lithium-ion sieve to gradually decrease. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide an electrochemical method for separating and extracting magnesium and lithium ions from salt lakes, which can effectively separate magnesium and lithium ions in salt lakes, reduce the magnesium content of the solution near the electrode, and improve the adsorption efficiency of lithium ions.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a method for electrochemical deintercalation and extraction of magnesium-lithium from salt lakes, the method comprising the following steps:

[0005] (1) The electrodialysis tank of the electrodialysis device is vertically divided into three areas: brine chamber, lithium salt chamber and magnesium salt chamber by anion exchange membrane. The brine chamber is filled with salt lake brine, and the lithium salt chamber and magnesium salt chamber are filled with deionized water.

[0006] (2) A conductive substrate coated with MnO2 is placed in a brine chamber as a cathode, and a conductive substrate coated with a lithium-intercalated ion sieve is placed in a lithium salt chamber as an anode. An electrochemical reaction occurs under the drive of an external potential.

[0007] (3) The anode driven by the external potential in step (2) is placed in the brine chamber as the cathode, and the cathode is placed in the magnesium salt chamber as the anode. A voltage is applied between the two electrodes to carry out an electrochemical reaction.

[0008] (4) Repeat steps (2)-(3) to add Li to the brine in the brine chamber. +If the content is ≤50mg / L, drain the liquid from the lithium salt chamber to obtain a lithium-rich solution.

[0009] This invention provides a method for electrochemical separation and lithium extraction of magnesium-lithium from salt lakes. A conductive substrate coated with a lithium-intercalated ion sieve is placed as the anode in a lithium salt chamber, and a conductive substrate coated with MnO2 is placed as the cathode in a brine chamber. An electrochemical reaction occurs under the drive of an external potential. Specifically, the magnesium in the brine chamber... 2+ and the OH produced by electrolysis - Mg(OH)₂ precipitate forms on the cathode surface, MnO₂ is converted to MnO(OH), and Li₂ is released from the lithium-intercalated ion sieve in the lithium salt chamber. + An ion sieve is formed, thereby enabling the removal of magnesium from the brine and the release of Li from the pure water in the lithium salt chamber. + And enrich Li + The purpose is to subsequently change the electrode positions or reverse the brine and lithium salt chambers, while replacing the lithium salt chamber with a magnesium salt chamber accordingly, and then conduct an electrochemical reaction using an external potential. Specifically, the Mg(OH)2 precipitate in the magnesium salt chamber reacts with the H2 produced by the electrolysis of MnO(OH)2. + After combining, it becomes Mg 2+ MnO(OH) is converted to MnO2, thereby enabling lithium extraction from the brine and the release of Mg from the pure water in the magnesium salt chamber. 2+ For the purpose of magnesium removal, the present invention provides a method for magnesium-lithium separation and lithium extraction from salt lakes. This method employs an intermittent magnesium removal and lithium extraction process in brine, successfully reducing the amount of magnesium near the ion sieve electrode during the adsorption and lithium extraction process. 2+ The concentration was adjusted to avoid a significant increase in the magnesium-to-lithium ratio in the solution, especially near the electrodes, thereby improving the ion sieve's ability to filter Li. + The adsorption efficiency is high. Furthermore, the method provided by this invention employs a continuous cyclic magnesium-lithium separation and lithium extraction approach, which simplifies operations and fully utilizes resources, achieving high efficiency and energy saving.

[0010] Specifically, taking lithium iron phosphate ion sieve as an example, the reaction process at the anode and cathode in steps (2)-(3) is described.

[0011] In step (2), the reactions occurring at the anode and cathode are as follows:

[0012] Cathode: MnO2 + H2O + e - →MnO(OH)+OH -

[0013] Anode: LiFePO4-e - →FePO4+Li +

[0014] Total: MnO2+H2O+LiFePO4→MnO(OH)+FePO4+Li+ +OH -

[0015] Mg 2+ +2OH - →Mg(OH)2↓

[0016] In step (3), the reactions occurring at the anode and cathode are as follows:

[0017] Cathode: Li + +FePO4+e - →LiFePO4

[0018] Anode: MnO(OH)-e - →MnO2+H +

[0019] Total: MnO(OH) + FePO4 + Li + →MnO2+LiFePO4+H +

[0020] Mg(OH)2 + 2H + →Mg 2+ +2H2O

[0021] In a preferred embodiment of the electrochemical deintercalation and lithium extraction method for magnesium-lithium separation and extraction from salt lakes according to the present invention, in step (2), the external potential is 0.8-1.1V and the electrochemical reaction time is 14.5-15h.

[0022] The inventors discovered that, given the magnitude of the external potential and the time of the electrochemical reaction, the Li in the lithium-intercalated ion sieve... + This allows for maximum release of Mg into the lithium salt chamber and the brine chamber. 2+ It can also react with the OH- produced by electrolysis to the greatest extent. - They combine to form Mg(OH)2 precipitate.

[0023] As a preferred embodiment of the electrochemical deintercalation and deintercalation method for separating and extracting lithium from magnesium and lithium in salt lakes according to the present invention, in step (2), the lithium-intercalated ion sieve is any one of lithium iron phosphate ion sieve, lithium cobalt oxide ion sieve, lithium manganese oxide ion sieve, lithium nickel cobalt manganese oxide ion sieve, lithium titanate ion sieve, lithium vanadium fluorophosphate ion sieve, lithium vanadium phosphate ion sieve, and lithium vanadate ion sieve.

[0024] Preferably, in step (2), the lithium-intercalated ion sieve is a lithium iron phosphate ion sieve.

[0025] In a preferred embodiment of the electrochemical deintercalation and lithium extraction method for magnesium-lithium separation and extraction from salt lakes according to the present invention, in step (3), the voltage is 0.8-1.1V and the electrochemical reaction time is 15-20h.

[0026] The inventors discovered that, given the voltage and electrochemical reaction time, the ion sieve can yield optimal Li. + The adsorption efficiency also allows the Mg(OH)2 precipitate in the magnesium salt chamber to be fully converted into Mg. 2+ .

[0027] In a preferred embodiment of the electrochemical deintercalation / intercalation method for separating and extracting lithium from magnesium in salt lakes according to the present invention, step (3) further includes enriching Mg in the magnesium salt chamber after the applied voltage is applied and maintained. 2+ The liquid is drained and deionized water is added back in.

[0028] The inventors discovered that if Mg is not enriched in the magnesium salt chamber... 2+ The discharge of liquid will affect the conversion of Mg(OH)2 to Mg during the second cycle. 2+ The conversion rate affects the subsequent conductivity of the MnO2-coated conductive substrate for Mg in the brine. 2+ The adsorption rate of Li is reduced, thereby decreasing the overall adsorption of Li. + The adsorption efficiency.

[0029] In a preferred embodiment of the electrochemical deintercalation / intercalation method for separating and extracting lithium from magnesium and lithium in salt lakes according to the present invention, in step (4), when Li in the brine chamber... + When the content is ≤50mg / L, replace the brine and repeat steps (2)-(3).

[0030] In a preferred embodiment of the electrochemical deintercalation and lithium extraction method for magnesium-lithium separation and extraction from salt lakes according to the present invention, in step (1), the anion exchange membrane is an AMX anion exchange membrane.

[0031] Anion exchange membranes can prevent the migration of cations between the three regions of brine chamber, lithium salt chamber, and magnesium salt chamber. However, anions can pass through the anion exchange membrane from the brine chamber into the lithium salt chamber or magnesium salt chamber, thereby maintaining the charge balance of the lithium salt chamber and magnesium salt chamber.

[0032] As a preferred embodiment of the electrochemical deintercalation and lithium extraction method for magnesium-lithium separation and extraction in salt lakes according to the present invention, in step (2), the conductive substrate is any one of graphite plate, Pt group metals and their alloy foils, carbon fiber cloth, graphite paper, and ruthenium-coated titanium mesh.

[0033] Preferably, in step (2), the conductive substrate is a graphite plate.

[0034] As a preferred embodiment of the electrochemical deintercalation and lithium extraction method for magnesium-lithium separation and extraction from salt lakes according to the present invention, in step (2), the method for preparing the conductive substrate coated with MnO2 is as follows: MnO2, polyvinylidene fluoride (PVDF) and graphite are mixed evenly in a mass ratio of 20:1:1, and then N-methylpyrrolidone (NMP) is added and ground into a slurry and coated onto the conductive substrate, and then dried to obtain the conductive substrate coated with MnO2;

[0035] The method for preparing a conductive substrate coated with a lithium-intercalated ion sieve is as follows: a lithium-intercalated ion sieve, polyvinylidene fluoride, and graphite are mixed evenly in a mass ratio of 20:1:1, and then N-methylpyrrolidone is added and ground into a slurry. This slurry is then coated onto a conductive substrate and subsequently dried to obtain a conductive substrate coated with a lithium-intercalated ion sieve.

[0036] Preferably, the graphite is high-purity graphite with a carbon content greater than 99.99%.

[0037] In a preferred embodiment of the electrochemical deintercalation and lithium extraction method for magnesium-lithium separation and extraction from salt lakes according to the present invention, in step (1), the volume ratio of brine to deionized water is 2L:(450-550)mL.

[0038] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0039] The electrochemical deintercalation and lithium extraction method for magnesium-lithium separation in salt lakes provided by this invention successfully reduces the amount of magnesium near the ion sieve electrode during the adsorption lithium extraction process by employing an intermittent magnesium removal and lithium extraction method in brine. 2+ The concentration was adjusted to avoid a significant increase in the magnesium-to-lithium ratio in the solution, especially near the electrodes, thereby improving the ion sieve's ability to filter Li. + The adsorption efficiency is high. Furthermore, the method provided by this invention is simple to operate, makes full use of resources, achieves high efficiency and energy saving, and is beneficial for practical production applications. Attached Figure Description

[0040] Figure 1 The ion sieves in Example 1 and Comparative Example 1 are for Li + The graph shows the relationship between the adsorption rate and time. Detailed Implementation

[0041] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0042] Unless otherwise specified, the reagents, methods and equipment used in this invention are all conventional reagents, methods and equipment in the field.

[0043] In this invention, the relative sizes of the three regions vertically divided into the electrodialysis tank by the anion exchange membrane have no practical impact on the effectiveness of the invention. For example, based on the total volume of the electrodialysis tank, the volume of the vertically divided brine chamber accounts for 60%, and the volumes of the magnesium salt chamber and lithium salt chamber each account for 20%, or the volume of the vertically divided brine chamber accounts for 40%, the volume of the magnesium salt chamber accounts for 40%, and the volume of the lithium salt chamber accounts for 20%, or the volume of the vertically divided brine chamber accounts for 20%, the volume of the magnesium salt chamber accounts for 50%, and the volume of the lithium salt chamber accounts for 30%, etc. That is, the volumes of the vertically divided brine chamber, lithium salt chamber, and magnesium salt chamber can be adjusted according to the actual volume of added salt lake brine and deionized water. In the embodiments and comparative examples of this invention, an equal division method is used, that is, the anion exchange membrane vertically divides the tank into three regions of equal volume, which are named brine chamber, lithium salt chamber, and magnesium salt chamber, respectively.

[0044] Example 1

[0045] This invention provides a method for electrochemical separation and lithium extraction of magnesium-lithium from salt lakes, comprising the following steps:

[0046] (1) The electrodialysis tank of the electrodialysis device is vertically divided into three areas of equal volume: brine chamber, lithium salt chamber and magnesium salt chamber using anion exchange membrane. 2L of salt lake brine is filled into the brine chamber, and 500mL of deionized water is filled into the lithium salt chamber and magnesium salt chamber respectively.

[0047] (2) Preparation of conductive substrate coated with MnO2: 20g MnO2, 1g PVDF and 1g high-purity graphite were mixed evenly and then 20g NMP was added and ground into a slurry and coated on a graphite plate. Then the slurry was placed in a vacuum oven at 100℃ and dried for 15h to obtain conductive substrate coated with MnO2.

[0048] (3) Preparation of conductive substrate coated with LiFePO4: 20g lithium iron phosphate, 1g PVDF and 1g high-purity graphite were mixed evenly and then 20g NMP was added and ground into a slurry and coated on a graphite plate. Then it was placed in a vacuum oven at 100℃ and dried for 12h to obtain a conductive substrate coated with LiFePO4.

[0049] (4) A conductive substrate coated with MnO2 was placed in the brine chamber as the cathode, and a conductive substrate coated with LiFePO4 was placed in the lithium salt chamber as the anode. An electrochemical reaction was carried out by applying a voltage of 1.1V across the electrodes for 15 hours. Under the drive of the external potential, Mg in the brine chamber... 2+ and the OH produced by electrolysis - Mg(OH)₂ precipitate forms on the cathode surface, MnO₂ is converted to MnO(OH), and LiFePO₄ in the lithium salt chamber releases Li₂. +Formation of FePO4 ion sieves;

[0050] (5) The anode driven by the external potential in step (4) is placed in the brine chamber as the cathode, and the cathode is placed in the magnesium salt chamber as the anode. A voltage of 1.1V is applied between the two electrodes to induce an electrochemical reaction. The reaction time is 15h. The Li in the brine chamber... + The Mg(OH)₂ precipitate in the FePO₄ ion sieve forms LiFePO₄, and the H₂ produced by electrolysis of MnO(OH)₂ in the magnesium salt chamber reacts with the H₂ produced by electrolysis of MnO(OH). + After combining, it becomes Mg 2+ MnO(OH) is converted to MnO2; subsequently, Mg is enriched in the magnesium salt chamber. 2+ After filling the liquid, refill with 500mL of deionized water;

[0051] (6) Repeat steps (4)-(5) to add Li to the brine in the brine chamber. + If the content is ≤50mg / L, drain the liquid from the lithium salt chamber to obtain a lithium-rich solution.

[0052] Example 2

[0053] This invention provides an electrochemical method for separating and extracting magnesium-lithium from salt lakes. The only difference between this method and Example 1 is that in step (4), a voltage of 0.8V is applied across the electrodes and the reaction time is 14.5h.

[0054] Example 3

[0055] This invention provides an electrochemical method for separating and extracting magnesium-lithium from salt lakes. The only difference between this method and Example 1 is that in step (5), a voltage of 0.8V is applied across the electrodes and the reaction time is 20h.

[0056] Comparative Example 1

[0057] This invention provides a comparative example of a method for the electrochemical separation and lithium extraction of magnesium and lithium from salt lakes, the method comprising the following steps:

[0058] (1) The electrodialysis tank of the electrodialysis device is vertically divided into two regions of equal volume, namely brine chamber and lithium salt chamber, by anion exchange membrane. 2L of salt lake brine is filled into the brine chamber and 500mL of deionized water is filled into the lithium salt chamber.

[0059] (2) Preparation of conductive substrate coated with FePO4: 20g of iron phosphate, 1g of PVDF and 1g of high-purity graphite were mixed evenly and then 20g of NMP was added and ground into a slurry and coated on a graphite plate. Then the slurry was placed in a vacuum oven at 100℃ and dried for 12h to obtain conductive substrate coated with FePO4.

[0060] (3) Preparation of conductive substrate coated with LiFePO4: 20g lithium iron phosphate, 1g PVDF and 1g high-purity graphite were mixed evenly and then 20g NMP was added and ground into a slurry and coated on a graphite plate. Then it was placed in a vacuum oven at 100℃ and dried for 12h to obtain a conductive substrate coated with LiFePO4.

[0061] (4) A conductive substrate coated with FePO4 was placed in the brine chamber as the cathode, and a conductive substrate coated with LiFePO4 was placed in the lithium salt chamber as the anode. An electrochemical reaction was carried out by applying a voltage of 1.1V across the electrodes for 20 hours. Under the drive of the external potential, FePO4 in the brine chamber was converted to LiFePO4, and LiFePO4 in the lithium salt chamber released Li + Formation of FePO4 ion sieves;

[0062] (5) Swap the cathode and anode after the external potential drive in step (4), and repeat step (4) until the Li in the brine in the brine chamber is filled with Li. + If the content is ≤50mg / L, drain the liquid from the lithium salt chamber to obtain a lithium-rich solution.

[0063] Comparative Example 2

[0064] This invention provides a comparative example of an electrochemical method for separating and extracting magnesium and lithium from salt lakes. The only difference between this method and Example 1 is that in step (5), the magnesium salt chamber enriched with Mg is not removed. 2+ The process involves refilling the liquid with 500mL of deionized water.

[0065] Example of effect

[0066] In the effect study of this invention, Li in the brine chamber during the circulation process in Examples 1-3 and Comparative Examples 1-2 + and Mg 2+ The content of Li in the lithium salt chamber + The cumulative amount of MnO2 on Mg 2+ The adsorption capacity of FePO4 and the effect of FePO4 on Li + The adsorption amount is shown in Table 1-3 for Examples 1 and Comparative Examples 1-2. For the corresponding number of cycles, 'a' in Examples 1 and Comparative Examples 2 refers to the data measured after step (4) to remove magnesium from the brine, and 'b' refers to the data measured after step (5) to adsorb lithium from the brine. Since the Li in the brine was measured after step (5) in the third cycle... +The concentration was already 50 mg / L, therefore, step (5) was not performed in the fourth cycle; in Comparative Example 1, c refers to the data obtained after step (4), and d refers to the data obtained after step (5). Similarly, since the Li in the brine was measured after step (5) in the third cycle, + The concentration was already 50 mg / L, therefore, step (5) was not performed in the fourth cycle; in addition, the effects of FePO4 on Li in Example 1 and Comparative Example 1 were recorded simultaneously in the first cycle. + The adsorption rate was obtained as follows: Figure 1 As shown;

[0067] Table 1: Li in the brine chamber during the circulation process in Example 1 + and Mg 2+ The content of Li in the lithium salt chamber + The cumulative amount of MnO2 on Mg 2+ The adsorption capacity of FePO4 and the effect of FePO4 on Li + Adsorption data recording table

[0068]

[0069] Table 2: Li in the brine chamber during the cycle of Comparative Example 1 + and Mg 2+ The content of Li in the lithium salt chamber + The cumulative amount and FePO4 on Li + Adsorption data recording table

[0070]

[0071] Table 3: Li in the brine chamber during the cycle of Comparative Example 2 + and Mg 2+ The content of Li in the lithium salt chamber + The cumulative amount of MnO2 on Mg 2+ The adsorption capacity of FePO4 and the effect of FePO4 on Li + Adsorption data recording table

[0072]

[0073] As can be seen from Table 1, after multiple cycles using the method of Example 1, the Li in the lithium salt chamber... + The content of Li in the brine chamber continues to increase. + and Mg 2+ The content of Mg is decreasing, and 2+ The rate of decrease in content was much greater than that of Li. +The rate of decrease in content can significantly suppress the abnormal increase in the magnesium-lithium ratio, thereby reducing the amount of Mg in the solution, especially in the solution near the electrode, to a certain extent. 2+ The content of [Li], thereby enhancing the ion sieve's resistance to Li. + The adsorption efficiency of MnO2 on Mg; Table 1 also shows that MnO2 adsorbs Mg 2+ The adsorption capacity is constant, around 56.3 mg / g, but the Mg in the brine chamber... 2+ The reduction in Mg content exceeds the adsorption of MnO2 because when the applied potential is driven for a sufficiently long time, most of the Mg... 2+ It precipitates in the brine in the form of Mg(OH)2; the results obtained in Examples 2-3 are almost the same as those in Example 1.

[0074] As can be seen from Table 2, although the method of Comparative Example 1 was used, after multiple cycles, the Li in the lithium salt chamber... + The content also continued to increase, and the Li in the brine chamber + The content also continued to decrease, but the Mg content in the brine chamber... 2+ The content of [Li] did not change significantly, resulting in a significant increase in the magnesium-to-lithium ratio in the brine chamber with increasing cycle number, which in turn affected the ion sieve's ability to filter Li. + The adsorption efficiency decreases.

[0075] This point is from Figure 1 As can also be seen from the example, in the first cycle of Example 1, FePO4 has a significant effect on Li. + The adsorption efficiency of FePO4 was relatively high, reaching near saturation within 12 hours. In contrast, in the first cycle of Comparative Example 1, FePO4 showed higher adsorption efficiency for Li. + The adsorption efficiency decreased significantly, requiring approximately 18 hours to reach saturation adsorption. In other words, compared to Example 1, only Li in the brine chamber of Comparative Example 1 showed a significantly lower adsorption efficiency. + The content decreased, while Mg 2+ The content remained unchanged, resulting in increased Mg levels in the solution, especially near the electrodes. 2+ Excessive content can damage the Li content. + The adsorption of FePO4 leads to the adsorption of Li + The adsorption efficiency of FePO4 on Li decreased significantly in Example 1 and Comparative Example 1 during the second cycle. + The adsorption rate was basically the same as in the first cycle. In the third cycle, due to the fact that most of the Li in the brine chamber of Example 1 was in a lower concentration, the adsorption rate decreased. + The adsorption has already occurred, preventing saturation adsorption; therefore, no corresponding adsorption rate diagram is provided. The adsorption rate of FePO4 on Li in the third cycle of Comparative Example 1 is not shown. + The adsorption rate was basically the same as the first time.

[0076] A comparison of Tables 1 and 3 also shows that when magnesium salts are not discharged in step (5), Mg accumulates in the chamber. 2+ During the operation of refilling the brine chamber with 500 mL of deionized water after the initial liquid phase, the Mg in the brine chamber... 2+ The decrease in Mg content was significantly less than in Example 1; under the same number of cycles, the Mg content in the brine chamber... 2+ The content was significantly higher than in Example 1, which in turn led to FePO4 affecting Li + The adsorption efficiency decreased significantly.

[0077] Finally, it should be noted that the above embodiments are used to illustrate the technical solutions of the present invention and not to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for electrochemical deintercalation / intercalation separation and lithium extraction from magnesium and lithium in salt lakes, characterized in that, The electrochemical deintercalation / intercalation method for separating and extracting lithium from magnesium-lithium in salt lakes includes the following steps: (1) The electrodialysis tank of the electrodialysis device is vertically divided into three areas: brine chamber, lithium salt chamber and magnesium salt chamber by anion exchange membrane. The brine chamber is filled with salt lake brine, and the lithium salt chamber and magnesium salt chamber are filled with deionized water. (2) A conductive substrate coated with MnO2 is placed in a brine chamber as a cathode, and a conductive substrate coated with a lithium-intercalated ion sieve is placed in a lithium salt chamber as an anode. An electrochemical reaction occurs under the drive of an external potential. (3) Place the anode driven by the external potential in step (2) as the cathode in the brine chamber, and place the cathode as the anode in the magnesium salt chamber. Apply and maintain a voltage between the two electrodes. The Li in the brine chamber... + They are embedded in ion sieves to form lithium-intercalated ion sieves, which then undergo electrochemical reactions. (4) Repeat steps (2)-(3) to add Li to the brine in the brine chamber. + If the content is ≤50mg / L, drain the liquid from the lithium salt chamber to obtain a lithium-rich solution.

2. The method for electrochemical deintercalation / intercalation separation and lithium extraction from magnesium and lithium in salt lakes according to claim 1, characterized in that, In step (2), the external potential is 0.8-1.1V and the electrochemical reaction time is 14.5-15h.

3. The method for electrochemical deintercalation / intercalation separation and lithium extraction from magnesium and lithium in salt lakes according to claim 1, characterized in that, In step (2), the lithium-intercalated ion sieve is any one of lithium iron phosphate ion sieve, lithium cobalt oxide ion sieve, lithium manganese oxide ion sieve, lithium nickel cobalt manganese oxide ion sieve, lithium titanate ion sieve, lithium vanadium fluorophosphate ion sieve, lithium vanadium phosphate ion sieve, and lithium vanadium oxide ion sieve.

4. The method for electrochemical deintercalation / intercalation separation and lithium extraction from magnesium and lithium in salt lakes according to claim 1, characterized in that, In step (3), the voltage is 0.8-1.1V and the electrochemical reaction time is 15-20h.

5. The method for electrochemical deintercalation / intercalation separation and lithium extraction from magnesium and lithium in salt lakes according to claim 1, characterized in that, Step (3) further includes enriching Mg in the magnesium salt chamber after the voltage is applied and maintained. 2+ The liquid is drained and deionized water is added back in.

6. The method for electrochemical deintercalation / intercalation separation and lithium extraction from magnesium and lithium in salt lakes according to claim 1, characterized in that, In step (4), when Li in the brine chamber + When the content is ≤50mg / L, replace the brine and repeat steps (2)-(3).

7. The method for electrochemical deintercalation / intercalation separation and lithium extraction from magnesium and lithium in salt lakes according to claim 1, characterized in that, In step (1), the anion exchange membrane is an AMX anion exchange membrane.

8. The method for electrochemical deintercalation / intercalation separation and lithium extraction from magnesium and lithium in salt lakes according to claim 1, characterized in that, In step (2), the conductive substrate is any one of graphite plate, Pt group metals and their alloy foils, carbon fiber cloth, graphite paper, and ruthenium-coated titanium mesh.

9. The method for electrochemical deintercalation / intercalation separation and lithium extraction from magnesium and lithium in salt lakes according to claim 1, characterized in that, In step (2), the method for preparing the conductive substrate coated with MnO2 is as follows: MnO2, polyvinylidene fluoride and graphite are mixed evenly in a mass ratio of 20:1:1, and then N-methylpyrrolidone is added and ground into a slurry and coated on the conductive substrate. After drying, the conductive substrate coated with MnO2 is obtained. The method for preparing a conductive substrate coated with a lithium-intercalated ion sieve is as follows: a lithium-intercalated ion sieve, polyvinylidene fluoride, and graphite are mixed evenly in a mass ratio of 20:1:1, and then N-methylpyrrolidone is added and ground into a slurry. This slurry is then coated onto a conductive substrate and subsequently dried to obtain a conductive substrate coated with a lithium-intercalated ion sieve.

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