Electrochemical deintercalation lithium enrichment device and lithium extraction method thereof

Abstract

The present disclosure provides an electrochemical deintercalation lithium enrichment device and a lithium extraction method thereof, the device comprises a power supply, a cathode chamber, an anode chamber and an anion exchange membrane arranged between the cathode chamber and the anode chamber, a heteroion adsorption layer is arranged on the surface of the side close to the cathode chamber of the anion exchange membrane, a lithium ion sieve electrode in a lithium-lean state is arranged in the cathode chamber, a lithium ion sieve electrode in a lithium-rich state is arranged in the anode chamber, the lithium ion sieve cathode electrode in a lithium-lean state is connected to the negative electrode of the power supply, and the lithium ion sieve electrode in a lithium-rich state is connected to the positive electrode of the power supply. The device of the present disclosure can avoid the penetration of impurity cations through the anion exchange membrane due to the osmotic effect during the electrochemical lithium extraction process, reduce the impurity removal step, and reduce the cost of the subsequent production process.

Description

Technical Field

[0001] This disclosure pertains to the field of lithium extraction technology from salt lakes, such as an apparatus for electrochemical deintercalation and enrichment of lithium and a method for lithium extraction. Background Technology

[0002] The main processes for developing lithium resources from salt lakes include salt drying, adsorption, solvent extraction, electrodialysis, and electrochemical deintercalation. Among these, electrochemical deintercalation utilizes electrochemical reactions to achieve the adsorption and extraction of lithium ions from solid materials. This reduces the use of chemicals and is characterized by being environmentally friendly, having high lithium ion selectivity, and good adaptability to brine. It has been extensively studied.

[0003] CN115818801A discloses a method for extracting lithium from salt lake brine. This method involves two processes: lithium insertion and lithium removal. During lithium insertion, lead is used as the anode, and a conductive substrate coated with an ion sieve is used as the cathode. An anion exchange membrane separates the anode and cathode. A sulfate solution is added to the anode, and salt lake brine is added to the cathode. During lithium removal, the electrode polarities of the anode and cathode are reversed. Simultaneously, the solution on the lead electrode side of the previous cycle remains unchanged, and fresh sulfate solution replaces the brine as the supporting electrolyte. Electrolysis is then applied again to release lithium sulfate.

[0004] CN115612838A discloses a device for selective lithium extraction from salt lakes and its application. The device includes: a power source, an anion exchange membrane, a current collector grid, an inlet, an outlet, and an adsorbent. The current collector grid is divided into a first current collector grid and a second current collector grid, which are respectively disposed in a first electrolysis chamber and a second electrolysis chamber. The first current collector grid and the second current collector grid are three-dimensional structures with several layers of mesh arranged in parallel. The first current collector grid or the second current collector grid is electrically connected to the positive or negative electrode of the power source.

[0005] In the lithium extraction methods from salt lakes described above, an anion exchange membrane is added between the cathode and the anode to intercept sodium and magnesium ions. However, in actual use, the permeation effect causes some sodium, magnesium, and other impurity ions in the cathode chamber to diffuse into the anode chamber, increasing the content of impurity ions in the anode chamber. This requires additional impurity removal steps, which lengthens the production process and increases costs. Summary of the Invention

[0006] The following is an overview of the subject matter described in detail herein. This overview is not intended to limit the scope of the claims.

[0007] The purpose of this disclosure is to provide an electrochemical lithium extraction and enrichment device and a lithium extraction method thereof. This disclosure utilizes the principle of liquid gravity stratification to set a layer of impurity ion adsorption between the cathode brine and the anion exchange membrane, which prevents impurity cations from penetrating the anion exchange membrane during the electrochemical lithium extraction process due to permeation, and prevents some sodium ions, magnesium ions and other impurity ions in the cathode chamber from diffusing into the anode chamber, thereby reducing the impurity removal steps and lowering the cost of subsequent production processes.

[0008] To achieve this purpose of disclosure, the following technical solution is adopted:

[0009] In a first aspect, embodiments of this disclosure provide an apparatus for electrochemical lithium deintercalation and enrichment. The apparatus includes a power source, a cathode chamber, an anode chamber, and an anion exchange membrane disposed between the cathode chamber and the anode chamber. A heterogeneous ion adsorption layer is disposed on the surface of the anion exchange membrane near the cathode chamber. A lithium-poor lithium-ion sieve electrode is disposed in the cathode chamber, and a lithium-rich lithium-ion sieve electrode is disposed in the anode chamber. The lithium-poor lithium-ion sieve electrode is connected to the negative electrode of the power source, and the lithium-rich lithium-ion sieve electrode is connected to the positive electrode of the power source.

[0010] In this embodiment, a heterogeneous ion adsorption layer is added near the anion exchange membrane on the cathode chamber side. Since the density of the heterogeneous ion adsorption layer differs significantly from that of the brine in the salt lake, the liquid layer is positioned on the side of the anion exchange membrane near the brine in the cathode chamber, based on the principle of liquid stratification by gravity. This allows cations that are about to pass through the anion exchange membrane due to osmosis to be complexed by the complexing agent in the heterogeneous ion adsorption layer. This prevents impurity cations from penetrating the anion exchange membrane during the electrochemical lithium extraction process, thereby improving the purity of cations in the anode chamber and reducing the difficulty of subsequent impurity removal steps.

[0011] In one embodiment, the lithium-poor lithium-ion sieve electrode and the lithium-rich lithium-ion sieve electrode are arranged laterally parallel.

[0012] In one embodiment, the thickness of the heteroion adsorption layer is 1 / 50 to 1 / 100 of the thickness of the brine in the cathode chamber, for example: 1 / 50, 1 / 60, 1 / 70, 1 / 80, 1 / 90 or 1 / 100, etc.

[0013] In one embodiment, the density of the heteroion adsorption layer is less than the density of the brine, the anode chamber is located above, and the cathode chamber is located below.

[0014] In one embodiment, the heteroion adsorption layer comprises an ethylenediamine solution and / or an ethylenediamine salt solution.

[0015] In one embodiment, the ethylenediamine salt solution comprises any one or a combination of at least two of the following: an aqueous solution of ethylenediaminetetraacetic acid, an aqueous solution of disodium ethylenediaminetetraacetic acid, or an aqueous solution of tetrasodium ethylenediaminetetraacetic acid.

[0016] In one embodiment, the concentration of ethylenediamine and / or ethylenediamine salt in the heteroion adsorption layer is 0.1~10 mmol / L, for example: 0.1 mmol / L, 0.5 mmol / L, 1 mmol / L, 2 mmol / L, 5 mmol / L or 10 mmol / L, etc.

[0017] In one embodiment, the density of the heteroion adsorption layer is greater than the density of the brine, and the anode chamber is located below and the cathode chamber is located above.

[0018] In one embodiment, the heteroion adsorption layer comprises an ethylenediamine solution and / or an ethylenediamine salt solution, as well as a sodium salt and / or a potassium salt.

[0019] In one embodiment, the sodium salt comprises sodium chloride and / or sodium sulfate.

[0020] In one embodiment, the potassium salt comprises potassium chloride and / or potassium sulfate.

[0021] In one embodiment, the concentration of ethylenediamine and / or ethylenediamine salt in the heteroion adsorption layer is 0.1~10 mmol / L, for example: 0.1 mmol / L, 0.5 mmol / L, 1 mmol / L, 2 mmol / L, 5 mmol / L or 10 mmol / L, etc.

[0022] In one embodiment, the concentration of sodium and / or potassium salts in the heteroion adsorption layer is 2 to 10 mol / L, for example: 2 mol / L, 4 mol / L, 6 mol / L, 8 mol / L, or 10 mol / L, etc.

[0023] In a second aspect, embodiments of this disclosure provide a lithium extraction method using the apparatus described in the first aspect, the method comprising the following steps:

[0024] (1) The positions of the cathode chamber, anode chamber and anion exchange membrane are set according to the concentration of the salt lake brine. A lithium-poor lithium ion screen electrode is installed in the cathode chamber, a lithium-rich lithium ion screen electrode is installed in the anode chamber, and an anion exchange membrane is installed between the cathode chamber and the anode chamber to obtain a lithium extraction tank in which the cathode and anode are arranged in a horizontal parallel manner.

[0025] (2) Salt lake brine is injected into the cathode chamber of the vertical lithium extraction tank, a heterogeneous ion adsorption layer is slowly injected into the side of the anion exchange membrane near the cathode chamber, a salt solution is injected into the anode chamber, and a constant voltage is applied to the anode and cathode for lithium extraction.

[0026] In one embodiment, the lithium-rich lithium-ion sieve electrode of step (1) is prepared by the following method:

[0027] The lithium-ion sieve, conductive agent, pore-forming agent, PVDF and N-methylpyrrolidone are mixed evenly in a mass ratio of 100:(10~15):(10~30):(5~15):(150~250). The mixed slurry is coated on the current collector and dried at 50~80℃ for 3~10h to obtain the lithium-rich lithium-ion sieve electrode.

[0028] In one embodiment, the lithium-ion sieve comprises any one or a combination of at least two of lithium manganese phosphate, lithium titanate, lithium manganese oxide, lithium iron phosphate, or lithium manganese iron phosphate.

[0029] In one embodiment, the pore-forming agent comprises ammonium bicarbonate and / or ammonium carbonate.

[0030] In one embodiment, the conductive agent includes any one or a combination of at least two of conductive carbon black, conductive acetylene black, graphene, or carbon nanotubes.

[0031] In one embodiment, the current collector comprises any one or a combination of at least two of the following: titanium mesh, graphite plate, carbon cloth, carbon paper, or aluminum foil.

[0032] In one embodiment, the lithium-poor lithium-ion sieve anode is prepared by the following method:

[0033] A lithium-rich lithium-ion sieve electrode was used as the positive electrode, and an AgCl electrode was used as the negative electrode. The electrodes were placed in a salt solution and delithiation was carried out at a constant voltage of 0.3~1.2V. The reaction was stopped when the current dropped to 0.2mA, thus obtaining a lithium-poor lithium-ion sieve electrode.

[0034] In one embodiment, the density of the salt lake brine in step (2) is 1.1~1.8 g / cm³. 3 For example: 1.1 g / cm³ 3 1.2 g / cm 3 1.4 g / cm 3 1.6 g / cm 3 Or 1.8 g / cm 3 wait.

[0035] In one embodiment, the salt solution in step (2) comprises a sulfate solution and / or a chloride solution.

[0036] In one embodiment, the concentration of metal ions in the salt solution is 0.05~2 mol / L, for example: 0.05 mol / L, 0.1 mol / L, 0.5 mol / L, 1 mol / L or 2 mol / L, etc.

[0037] In one embodiment, the voltage in step (2) is 0.3~1.2V, for example: 0.3V, 0.5V, 0.8V, 1V or 1.2V, etc.

[0038] In one embodiment, during the constant-voltage lithium extraction process in step (2), when the current drops to 0.2mA, the power is stopped and the cathode and anode are reversed before the power is resumed. This process is repeated 2 to 5 times to obtain a lithium-rich solution.

[0039] This disclosure has the following beneficial effects:

[0040] (1) This disclosure utilizes the principle of liquid gravity stratification to set a layer of impurity ion adsorption between the cathode brine and the anion exchange membrane, which avoids impurity cations from penetrating the anion exchange membrane due to permeation during the electrochemical lithium extraction process, and avoids some sodium ions, magnesium ions and other impurity ions in the cathode chamber from diffusing into the anode chamber, thereby reducing the impurity removal steps and lowering the cost of subsequent production processes.

[0041] (2) The electrochemical deintercalation and enrichment method for lithium described in this disclosure, after lithium extraction, the Li in the anode chamber solution... + Concentrations can reach above 0.253 mol / L, Na + The concentration can reach below 0.508 mol / L (remaining essentially unchanged before and after), Mg 2+ Concentrations can reach below 0.001 mol / L, K + The concentration can reach below 0.012 mol / L, which improves the purity of cations in the anode chamber and reduces the difficulty of subsequent impurity removal steps.

[0042] After reading and understanding the accompanying diagrams and detailed descriptions, the other aspects can be understood. Attached Figure Description

[0043] The accompanying drawings are used to provide a further understanding of the technical solutions in this paper and form part of the specification. They are used together with the embodiments of this application to explain the technical solutions in this paper and do not constitute a limitation on the technical solutions in this paper.

[0044] Figure 1 This is a schematic diagram of the apparatus for the electrochemical lithium enrichment method described in Embodiment 1 of this disclosure, where 1-lithium-rich lithium-ion sieve, 2-lithium-poor lithium-ion sieve, 3-anion exchange membrane, and 4-hetero-ion adsorption layer.

[0045] Figure 2 This is a schematic diagram of the apparatus for the electrochemical lithium enrichment method described in Embodiment 2 of this disclosure, where 1-lithium-rich lithium-ion sieve, 2-lithium-poor lithium-ion sieve, 3-anion exchange membrane, and 4-hetero-ion adsorption layer.

[0046] Figure 3This is a schematic diagram of the apparatus for the electrochemical lithium enrichment method described in Comparative Example 1, where 1-lithium-rich lithium-ion sieve, 2-lithium-poor lithium-ion sieve, and 3-anion exchange membrane. Detailed Implementation

[0047] The technical solutions of this disclosure will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of this disclosure and should not be construed as specific limitations thereof.

[0048] The lithium-rich lithium-ion sieve electrode described in this embodiment and comparative example is prepared by the following method: lithium iron phosphate lithium-ion sieve, conductive carbon black, ammonium bicarbonate, PVDF and N-methylpyrrolidone are mixed uniformly in a mass ratio of 100:12:20:10:200. The mixed slurry is coated onto a current collector and dried at 60°C for 5 hours to obtain the lithium-rich lithium-ion sieve electrode. The lithium-rich lithium-ion sieve anode is prepared by the following method: the above-mentioned lithium-rich lithium-ion sieve electrode is used as the positive electrode, and an AgCl electrode is used as the negative electrode. The electrode is placed in a salt solution and delithiation is performed at a constant voltage of 0.8V. The reaction is stopped when the current drops to 0.2mA to obtain a lithium-poor lithium-ion sieve electrode.

[0049] Example 1

[0050] This embodiment provides an electrochemical lithium deintercalation / enrichment method, and a schematic diagram of the apparatus for the electrochemical lithium deintercalation / enrichment method is shown below. Figure 1 As shown, the method includes the following steps:

[0051] (1) The density of the hetero ion adsorption layer is less than the density of the brine. The lithium ion screen in the lithium-poor state is used as the cathode and the lithium ion screen in the lithium-rich state is used as the anode. The anode and cathode chambers are separated by an anion exchange membrane. The anode chamber is located above and the cathode chamber is located below. The hetero ion adsorption layer is located below the anion exchange membrane and the cathode chamber is at the top of the brine.

[0052] (2) Salt lake brine is injected into the cathode chamber of a vertical lithium extraction tank. The thickness of the impurity ion adsorption layer is 1 / 90 of the thickness of the brine in the cathode chamber. Finally, a 0.5 mol / L sodium chloride solution is injected into the anode chamber above the anion exchange membrane. The impurity ion adsorption layer is an aqueous solution of ethylenediamine with a concentration of 0.5 mmol / L and a brine density of 1.5 g / cm³. 3 A constant voltage of 0.8V is applied to the anode and cathode for lithium extraction. When the current drops to 0.2mA, the reaction is stopped and the anode and cathode are reversed. After the lithium-intercalated lithium ion sieve is detached, the lithium-depleted lithium ion sieve is restored, and lithium ions are enriched in the anode chamber. The above steps are repeated 3 times to obtain a lithium-rich solution.

[0053] Example 2

[0054] This embodiment provides an electrochemical lithium deintercalation / enrichment method, and a schematic diagram of the apparatus for the electrochemical lithium deintercalation / enrichment method is shown below. Figure 2 As shown, the method includes the following steps:

[0055] (1) The density of the hetero ion adsorption layer is greater than the density of the brine. The lithium ion screen in the lithium-poor state is used as the cathode and the lithium ion screen in the lithium-rich state is used as the anode. The anode and cathode chambers are separated by an anion exchange membrane. The anode chamber is located below and the cathode chamber is located above. The hetero ion adsorption layer is located above the anion exchange membrane and the cathode chamber is at the bottom of the brine.

[0056] (2) Salt lake brine is injected into the cathode chamber of a vertical lithium extraction tank. The thickness of the impurity ion adsorption layer is 1 / 80 of the thickness of the brine in the cathode chamber. Finally, a 0.5 mol / L sodium chloride solution is injected into the anode chamber above the anion exchange membrane. The impurity ion adsorption layer is a mixed aqueous solution of disodium ethylenediaminetetraacetate (EDTA) and sodium chloride. The concentration of EDTA is 3 mmol / L, the concentration of sodium chloride is 6 mol / L, and the density of the brine is 1.5 g / cm³. 3 A constant voltage of 0.9V is applied to the anode and cathode for lithium extraction. When the current drops to 0.2mA, the reaction is stopped and the anode and cathode are reversed. After the lithium-intercalated lithium ion sieve is detached, the lithium-depleted lithium ion sieve is restored, and lithium ions are enriched in the anode chamber. The above steps are repeated 3 times to obtain a lithium-rich solution.

[0057] Example 3

[0058] The only difference between this embodiment and Embodiment 1 is that the thickness of the heterogeneous ion adsorption layer is 1 / 30 of the cathode chamber brine; all other conditions and parameters are exactly the same as in Embodiment 1.

[0059] Example 4

[0060] The only difference between this embodiment and Embodiment 1 is that the thickness of the heteroion adsorption layer is 1 / 120 of the cathode chamber brine; all other conditions and parameters are exactly the same as in Embodiment 1.

[0061] Comparative Example 1

[0062] The only difference between this comparative example and Example 1 is that the lithium extraction tank is placed horizontally, and the lithium-poor lithium-ion sieve electrode and the lithium-rich lithium-ion sieve electrode are arranged longitudinally parallel to each other. A schematic diagram of the device is shown below. Figure 3 As shown.

[0063] Comparative Example 2

[0064] The only difference between this comparative example and Example 1 is that no heteroion adsorption layer is added; all other conditions and parameters are exactly the same as in Example 1.

[0065] Performance testing:

[0066] The concentrations of various major elements in the anode chamber solution of the electrochemical lithium extraction and enrichment apparatus described in the examples and comparative examples before and after lithium extraction are shown in Table 1:

[0067] Table 1

[0068]

[0069] As can be seen from Table 1, as obtained from Examples 1-2, the electrochemical lithium extraction and enrichment method of this disclosure results in a lower concentration of Li in the anode chamber solution after lithium extraction. + Concentrations can reach above 0.253 mol / L, Na + The concentration can reach below 0.508 mol / L (remaining essentially unchanged before and after), Mg 2+ Concentrations can reach below 0.001 mol / L, K + The concentration can reach below 0.012 mol / L, which avoids impurity cations from penetrating the anion exchange membrane during the electrochemical lithium extraction process, improves the purity of cations in the anode chamber, and reduces the difficulty of subsequent impurity removal steps.

[0070] A comparison of Examples 1 and 3-4 shows that the thickness of the hetero-ion adsorption layer described in this disclosure significantly affects the lithium enrichment effect. Controlling the thickness of the hetero-ion adsorption layer to 1 / 50 to 1 / 100 of the brine thickness in the cathode chamber results in a better lithium enrichment effect. If the thickness of the hetero-ion adsorption layer is too small, it will reduce the purity of the cations in the cation chamber.

[0071] As can be seen from the comparison between Example 1 and Comparative Example 1, when a heterogeneous ion adsorption layer is added to a conventional electrolytic cell, it is impossible to place the heterogeneous ion adsorption layer on the cathode chamber side of the anion exchange membrane through the principle of liquid gravity stratification. Therefore, it cannot filter out impurity ions that penetrate the anion exchange membrane through permeation.

[0072] As can be seen from the comparison between Example 1 and Comparative Example 2, the present disclosure adds a heterogeneous ion adsorption layer near the anion exchange membrane on the cathode chamber side, which prevents impurity cations from penetrating the anion exchange membrane during the electrochemical lithium extraction process, thereby improving the purity of cations in the anode chamber and reducing the difficulty of subsequent impurity removal steps.

Claims

1. An apparatus for electrochemically deintercalating lithium enrichment, the apparatus comprising a power supply, a cathode chamber, an anode chamber, and an anion exchange membrane disposed between the cathode chamber and the anode chamber, the anion exchange membrane being provided with a heteroion adsorption layer on the surface close to the cathode chamber, a lithium ion sieve electrode in a lithium-depleted state being disposed in the cathode chamber, a lithium ion sieve electrode in a lithium-enriched state being disposed in the anode chamber, the lithium ion sieve electrode in the lithium-depleted state being connected to the negative electrode of the power supply, and the lithium ion sieve electrode in the lithium-enriched state being connected to the positive electrode of the power supply. The thickness of the heteroion adsorption layer is 1 / 50 to 1 / 100 of the thickness of the brine in the cathode chamber. The heteroion adsorption layer comprises an ethylenediamine solution and / or an ethylenediamine salt solution.

2. The apparatus of claim 1, wherein, The lithium ion sieve electrode in the lithium-depleted state and the lithium ion sieve electrode in the lithium-enriched state are arranged in a horizontal and parallel manner.

3. The apparatus of claim 1, wherein, The density of the heteroion adsorption layer is less than the density of the brine, the anode chamber is located above, and the cathode chamber is located below.

4. The apparatus of claim 1, wherein, The ethylenediamine salt solution comprises any one or a combination of at least two of an ethylenediamine tetraacetic acid aqueous solution, an ethylenediamine tetraacetic acid disodium salt aqueous solution, or an ethylenediamine tetraacetic acid tetrasodium salt aqueous solution.

5. The apparatus of claim 1, wherein, The concentration of ethylenediamine and / or ethylenediamine salt in the heteroion adsorption layer is 0.1 to 10 mmol / L.

6. The apparatus of claim 1, wherein, The density of the heteroion adsorption layer is greater than the density of the brine, the cathode chamber is located above, and the anode chamber is located below.

7. The apparatus of claim 6, wherein, The heteroion adsorption layer comprises an ethylenediamine solution and / or an ethylenediamine salt solution and a sodium salt and / or a potassium salt.

8. The apparatus of claim 7, wherein, The sodium salt comprises sodium chloride and / or sodium sulfate.

9. The apparatus of claim 7, wherein, The potassium salt comprises potassium chloride and / or potassium sulfate.

10. The apparatus of claim 6, wherein, The concentration of ethylenediamine and / or ethylenediamine salt in the heteroion adsorption layer is 0.1 to 10 mmol / L.

11. The apparatus of claim 7, wherein, The concentration of sodium salt and / or potassium salt in the heteroion adsorption layer is 2 to 10 mol / L. 12.A method for extracting lithium using the apparatus of any one of claims 1 to 11, the method comprising the following steps: (1) arranging the positions of the cathode chamber, the anode chamber, and the anion exchange membrane according to the concentration of the salt lake brine, installing the lithium ion sieve electrode in the lithium-depleted state in the cathode chamber, installing the lithium ion sieve electrode in the lithium-enriched state in the anode chamber, and installing the anion exchange membrane between the cathode chamber and the anode chamber to obtain an extraction lithium tank in which the cathode and the anode are arranged in a horizontal and parallel manner; (2) injecting the salt lake brine into the cathode chamber of the vertical extraction lithium tank, slowly injecting the heteroion adsorption layer close to the cathode chamber side of the anion exchange membrane, injecting the salt solution into the anode chamber, and applying voltage to the cathode and the anode for constant voltage lithium extraction.

13. The method of claim 12, wherein, The lithium ion sieve electrode in the lithium-enriched state in step (1) is prepared by the following method: Lithium ion sieve, conductive agent, pore-forming agent, PVDF, and N-methyl pyrrolidone are uniformly mixed according to a mass ratio of 100:(10-15):(10-30):(5-15):(150-250), the mixed slurry is coated on a current collector, and the coated current collector is dried at 50-80℃ for 3-10 h to obtain the lithium ion sieve electrode in the lithium-enriched state.

14. The method of claim 13, wherein, The lithium ion sieve comprises any one or a combination of at least two of lithium manganese phosphate, lithium titanate, lithium manganate, lithium iron phosphate, or lithium manganese iron phosphate.

15. The method of claim 13, wherein, The pore-forming agent comprises ammonium bicarbonate and / or ammonium carbonate.

16. The method of claim 13, wherein, The conductive agent includes any one or a combination of at least two of conductive carbon black, conductive acetylene black, graphene, or carbon nanotubes.

17. The method of claim 13, wherein, The current collector includes any one or a combination of at least two of titanium mesh, graphite plate, carbon cloth, carbon paper, or aluminum foil.

18. The method of claim 12, wherein, The lithium-ion-sieve electrode in a lithium-lean state is prepared by the following method: The lithium-ion-sieve electrode in a lithium-lean state is obtained by taking the lithium-ion-sieve electrode in a lithium-rich state as a positive electrode, taking an AgCl electrode as a negative electrode, placing them in a salt solution, and performing lithium extraction at a constant voltage of 0.3-1.2 V, and stopping the reaction when the current is as low as 0.2 mA.

19. The method of claim 12, wherein, The density of the salt lake brine in step (2) is 1.1-1.8 g / cm 3 .

20. The method of claim 12, wherein, The salt solution in step (2) includes a sulfate salt solution and / or a chloride salt solution.

21. The method of claim 20, wherein, The concentration of metal ions in the salt solution is 0.05-2 mol / L.

22. The method of claim 12, wherein, The voltage in step (2) is 0.3-1.2 V.

23. The method of claim 12, wherein, In the process of constant-voltage lithium extraction in step (2), the power supply is stopped when the current is as low as 0.2 mA, and the power supply is continued after the negative and positive electrodes are reversed, and the process is repeated 2-5 times to obtain a lithium-rich solution.

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