A method for extracting lithium from salt lakes by electrochemical deintercalation

Abstract

A method for extracting lithium from salt lakes by electrochemical deintercalation is disclosed. The method comprises the following steps: (1) injecting a recovery solution into the anode chamber and injecting salt lake brine into the cathode chamber respectively, separating them with an anion exchange membrane, using a lithium-rich electrode as the anode and a lithium-poor electrode as the cathode, and performing a constant voltage reaction; (2) when the current density of the constant voltage reaction decreases to 30-40 A / m 2 , injecting a strongly reducing gas into the salt lake brine; (3) stopping the reaction by cutting off the power when the current density decreases to 5 A / m 2 , reversing the anode and cathode and repeating the constant voltage reaction to obtain a lithium-rich solution. By introducing a reducing gas into the cathode brine, the present application improves the lithium intercalation rate of the cathode, fully ensures the adsorption capacity of the electrode, and avoids the problem of capacity decay during the cyclic lithium extraction process.

Description

Technical Field

[0001] The embodiments of the present application relate to the technical field of lithium extraction from salt lakes, for example, a method for extracting lithium from salt lakes by electrochemical deintercalation. Background Art

[0002] In recent years, with the rapid development of new energy vehicles and chemical energy storage, the demand for lithium has increased sharply. Salt lake brine contains huge amounts of lithium resources (about 70% of the global lithium resource reserves), so lithium extraction from salt lakes has attracted more and more attention. For the development of salt lake lithium resources, a variety of processes have been invented, such as evaporation method, adsorption method, solvent extraction method, electrodialysis method and membrane separation method. The evaporation method is suitable for extracting lithium from solutions with a low magnesium-lithium ratio (Mg / Li < 6). Even so, about 50% of the lithium will be lost in the evaporation crystallization salt during the evaporation process, and the treatment of brine with a high Mg / Li ratio is even more serious.

[0003] Although the electrodialysis method and the membrane separation method are environmentally friendly, the brine needs to be diluted with a large amount of water. Since Li + and Na + / K + are difficult to be separated by membrane, it is necessary to remove Na + and K + in the brine by the evaporation method, resulting in a large loss of lithium. For the solvent extraction method, due to the high viscosity of the brine, emulsification is likely to occur. Although this phenomenon can be alleviated to a certain extent by centrifugal extraction technology, the organic extractant has a certain solubility in the brine, bringing potential pollution to the environment. The ion sieve adsorption method is considered to be one of the feasible methods for lithium extraction from brine due to its high selectivity, low cost, non-toxicity, etc. However, the adsorption capacity of the ion sieve materials currently used in industry is low, and it often requires heating the brine for adsorption and desorption, resulting in high energy consumption.

[0004] Increasing the operating voltage is beneficial to improving the lithium exchange capacity of the electrode, but it will also lead to a decrease in the selectivity of the electrode for lithium. More impurity cations obtain energy to compete with lithium ions for embedding into the electrode, which is likely to cause cathode polarization and reduce the purity of the recovered lithium. Although the selectivity of the electrode for lithium is better under low voltage conditions, the lithium exchange capacity of the electrode is relatively low, resulting in a low extraction rate of lithium by the electrochemical deintercalation method. Summary of the Invention

[0005] The following is an overview of the subject matter described in detail in this article. This overview is not intended to limit the scope of protection of the claims.

[0006] The present application provides a method for extracting lithium from salt lakes by electrochemical deintercalation. By introducing a reducing gas into the cathode brine, the present application improves the lithium intercalation rate of the cathode, fully ensures the adsorption capacity of the electrode, and effectively delays the attenuation of the capacity during the cyclic lithium extraction process.

[0007] In a first aspect, an embodiment of the present application provides a method for electrochemical extraction and intercalation of lithium from salt lakes, and the method includes the following steps:

[0008] (1) Inject the recovery liquid into the anodic chamber and the salt lake brine into the cathodic chamber respectively, separate them with an anion exchange membrane, use the lithium-rich electrode as the anode and the lithium-poor electrode as the cathode, and conduct a constant voltage reaction;

[0009] (2) When the current density of the constant voltage reaction decreases to 30 - 40 A / m 2 , inject a strongly reducing gas into the salt lake brine;

[0010] (3) Stop the reaction by cutting off the power supply when the current density decreases to 5 A / m 2 , exchange the anode and the cathode and repeat the constant voltage reaction to obtain a lithium-rich solution.

[0011] There are multiple coexisting cations of Na, K, and Mg in the brine. When using electrochemical extraction and intercalation to extract lithium, as long as the voltage is appropriately controlled, lithium ions can be selectively separated from various impurities. When the electrode potential is increased, the reaction rate of lithium extraction increases, but more impurity cations obtain energy to compete with lithium ions for intercalation into the electrode, and it is easy to generate cathode polarization, resulting in a decrease in the lithium ions intercalated into the electrode, an increase in impurity cations, a decrease in the lithium exchange capacity of the electrode, and a decrease in the purity of the recovered lithium. Conducting lithium extraction at a lower potential is beneficial to the separation of lithium ions and impurity cations, but the required lithium extraction time is longer and the lithium extraction efficiency is reduced. In the process of lithium extraction in the present application, a strongly reducing gas is added to the brine, which promotes the reduction rate of the lithium ion sieve of the electrode material, thereby accelerating the entry of lithium ions into the lattice of the electrode material to form an intercalated lithium product, ensuring the lithium purity of low-voltage lithium extraction while improving the lithium extraction efficiency.

[0012] Preferably, the recovery liquid in step (1) includes a lithium chloride solution.

[0013] Lithium chloride in the recovery liquid of the present application serves as a supporting electrolyte, and after subsequently exchanging the anode and the cathode, the lithium adsorbed on the cathode is released into the recovery liquid.

[0014] Preferably, the concentration of lithium ions in the recovery liquid is 0.03 - 0.08 mol / L, for example: 0.03 mol / L, 0.04 mol / L, 0.05 mol / L, 0.06 mol / L, 0.07 mol / L, or 0.08 mol / L, etc.

[0015] Preferably, the lithium-rich electrode in step (1) is prepared by the following method:

[0016] Mix a lithium-containing active substance, a conductive agent, a binder, and a solvent to obtain a slurry, coat the slurry on the surface of a carbon fiber cloth, and dry it to obtain a lithium-rich electrode.

[0017] Preferably, the coating amount is 5-7 mg / cm 2 , for example: 5 mg / cm 2 , 5.5 mg / cm 2 , 6 mg / cm 2 , 6.5 mg / cm 2 or 7 mg / cm 2 and so on.

[0018] Preferably, the lithium-containing active material includes LiMn2O4, LiFePO4, Li2TiO3, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 or Li7Ti5O 12 any one or a combination of at least two of them.

[0019] Preferably, the conductive agent includes carbon black.

[0020] Preferably, the binder includes polyvinylidene fluoride.

[0021] Preferably, the solvent includes N-methylpyrrolidone.

[0022] Preferably, the drying temperature is 60-80 °C, for example: 60 °C, 65 °C, 70 °C, 75 °C or 80 °C and so on.

[0023] Preferably, the drying time is 10-15 h, for example: 10 h, 11 h, 12 h, 13 h, 14 h or 15 h and so on.

[0024] Preferably, the lithium-deficient electrode in step (1) is prepared by the following method:

[0025] Connect the lithium-rich electrode to the positive electrode and the AgCl electrode to the negative electrode, and place them in a salt solution for a constant voltage reaction. Stop the reaction when the current drops to 0.1 mA to obtain the lithium-deficient electrode.

[0026] Preferably, the salt solution includes potassium chloride solution.

[0027] Preferably, the concentration of the potassium chloride solution is 0.03-0.08 mol / L, for example: 0.03 mol / L, 0.04 mol / L, 0.05 mol / L, 0.06 mol / L, 0.07 mol / L or 0.08 mol / L and so on.

[0028] Preferably, the voltage of the constant voltage reaction is 1-1.5 V, for example: 1 V, 1.1 V, 1.2 V, 1.3 V, 1.4 V or 1.5 V and so on.

[0029] Preferably, the voltage of the constant-voltage reaction in step (1) is 0.1 - 0.6 V, such as 0.1 V, 0.2 V, 0.3 V, 0.4 V, 0.5 V, or 0.6 V, etc.

[0030] Preferably, the strongly reducing gas in step (2) includes hydrogen and / or H2S, preferably H2S.

[0031] Preferably, the H2S includes H2S waste gas generated industrially.

[0032] In industrial production such as artificial fiber, natural gas purification, sulfur dyes, petroleum refining, gas manufacturing, sewage treatment, and papermaking, high-concentration H2S waste gas, as well as sulfur-containing organic compounds such as mercaptans, thioethers, disulfides, and cyclic sulfides, are usually emitted. Direct emission will cause environmental pollution and harm to human health. The temperature of the H2S waste gas generated industrially is usually relatively high. The reducing gas with a relatively high temperature can conduct heat to the brine to increase the temperature of the brine, so as to increase the activity of lithium ions in the solution, enabling the lithium ions at the cathode to be embedded into the electrode faster. In addition, introducing gas into the brine can disturb the brine and increase the convection rate of the brine, effectively improving the problem of concentration polarization of the solution near the surface of the lithium extraction electrode, further improving the liquid-phase mass transfer efficiency of lithium ions, making the lithium ions in the brine more smoothly, quickly, and fully embedded into the cathode, and improving the lithium extraction efficiency. The present application uses the H2S emitted from industrial production as a reducing agent, which can effectively treat the H2S waste gas and avoid environmental pollution.

[0033] Preferably, the temperature of the strongly reducing gas in step (2) is 80 - 120 °C, such as 80 °C, 90 °C, 100 °C, 110 °C, or 120 °C, etc.

[0034] Preferably, the flow rate of the strongly reducing gas is 50 - 100 mL / min, such as 50 mL / min, 60 mL / min, 70 mL / min, 80 mL / min, 90 mL / min, or 100 mL / min, etc.

[0035] As a preferred embodiment of the present application, the method includes the following steps:

[0036] (1) Inject the recovery liquid into the anode chamber, inject the salt lake brine into the cathode chamber, separate them with an anion exchange membrane, use the lithium-rich electrode as the anode and the lithium-poor electrode as the cathode, and perform a constant-voltage reaction at a voltage of 0.1 - 0.6 V;

[0037] (2) When the current density of the constant-voltage reaction decreases to 30 - 40 A / m 2 inject a strongly reducing gas at 80 - 120 °C into the salt lake brine at a flow rate of 50 - 100 mL / min. When the current density decreases to 5 A / m 2Stop the reaction when the time is up, swap the anode and cathode, and repeat the constant voltage reaction to obtain a lithium-rich solution.

[0038] Compared with the related art, the embodiments of the present application have the following beneficial effects:

[0039] (1) By heating the reducing gas in the embodiments of the present application, heat conduction can be carried out on the brine to increase the temperature of the brine, so as to increase the movement rate of lithium ions in the solution, enable the lithium ions at the cathode to be embedded into the electrode faster, improve the liquid-phase mass transfer efficiency of lithium ions, make the lithium ions in the brine embed into the cathode more smoothly, quickly and fully, and improve the lithium extraction efficiency.

[0040] (2) In the lithium extraction method of the embodiments of the present application, the lithium ion concentration in the recovered lithium-rich solution can reach more than 3.1 g / L, the electrode adsorption capacity can reach more than 31.5 mg(Li) / g(LiMn2PO4), and the lithium extraction reaction time can be shortened to less than 5.3 h.

[0041] Other aspects can be understood after reading and understanding the detailed description. Detailed Embodiments

[0042] The technical solutions of the present application will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present application and should not be regarded as specific limitations on the present application.

[0043] The lithium-rich electrodes and lithium-poor electrodes in the embodiments of the present application and the comparative examples are prepared by the following methods:

[0044] Prepare LiMn2O4 powder by the high-temperature solid-phase method. Mix the obtained LiMn2O4 with carbon black and PVDF binder in a mass ratio of 9:1:1, add N-methylpyrrolidone solvent and stir well, and ultrasonically disperse for 10 min to obtain a uniformly dispersed paste. Coat the obtained paste evenly on the carbon fiber cloth, and the coating amount is about 6 mg / cm 2 , after coating, dry at 70 °C for 12 h to obtain a lithium-rich electrode; connect the obtained lithium-rich LiMn2O4 electrode to the positive electrode and the AgCl electrode to the negative electrode, place them in a 0.05 mol / L KCl solution for a constant voltage reaction of 1.2 V, and stop the reaction when the current drops to 0.1 mA, that is, obtain a lithium-poor Li 1-x Mn2O4 electrode.

[0045] The composition of the brine used is: 0.33 g / L Li, 85.65 g / L Na, 107.97 g / L Mg, 8.45 g / L K, 2.76 g / L Ca, 10.54 g / L SO4 2- .

[0046] Example 1

[0047] This embodiment provides a method for electrochemical extraction of lithium from salt lakes by deintercalation, and the method includes the following steps:

[0048] (1) Place the lithium-rich electrode and its corresponding lithium-poor electrode in the recycling solution and salt lake brine isolated by an anion exchange membrane respectively. The recycling solution is 0.05 mol / L LiCl solution. Use the lithium-poor electrode as the cathode and the lithium-rich electrode as the anode, and conduct a constant voltage reaction at 0.3 V.

[0049] (2) When the constant voltage reaction proceeds until the current density decreases to 35 A / m 2 , use an air injection device to introduce H2S gas into the brine at a flow rate of 75 ml / min, and the gas heating temperature is 95 °C. Observe until the current density decreases to 5 A / m 2 , then cut off the power supply to stop the reaction. Subsequently, take out the lithium-rich electrode and the lithium-poor electrode and clean them, then interchange the cathode and anode, and repeat the constant voltage reaction until the lithium concentration in the brine reaches the expected value to obtain a lithium-rich solution.

[0050] Example 2

[0051] This embodiment provides a method for electrochemical extraction of lithium from salt lakes by deintercalation, and the method includes the following steps:

[0052] (1) Place the lithium-rich electrode and its corresponding lithium-poor electrode in the recycling solution and salt lake brine isolated by an anion exchange membrane respectively. The recycling solution is 0.05 mol / L LiCl solution. Use the lithium-poor electrode as the cathode and the lithium-rich electrode as the anode, and conduct a constant voltage reaction at 0.6 V.

[0053] (2) When the constant voltage reaction proceeds until the current density decreases to 30 A / m 2 , use an air injection device to introduce H2S gas into the brine at a flow rate of 50 ml / min, and the gas heating temperature is 80 °C. Observe until the current density decreases to 5 A / m 2 , then cut off the power supply to stop the reaction. Subsequently, take out the lithium-rich electrode and the lithium-poor electrode and clean them, then interchange the cathode and anode, and repeat the constant voltage reaction until the lithium concentration in the brine reaches the expected value to obtain a lithium-rich solution.

[0054] Example 3

[0055] This embodiment provides a method for electrochemical extraction of lithium from salt lakes by deintercalation, and the method includes the following steps:

[0056] (1) Place the lithium-rich electrode and its corresponding lithium-poor electrode separately in the recovery solution and the salt lake brine isolated by an anion exchange membrane. The recovery solution is a 0.05 mol / L LiCl solution. Use the lithium-poor electrode as the cathode and the lithium-rich electrode as the anode, and conduct a constant voltage reaction at 0.1 V.

[0057] (2) When the constant voltage reaction proceeds until the current density decreases to 40 A / m 2 , use an air injection device to introduce H2S gas into the brine at a flow rate of 100 ml / min, and the gas heating temperature is 120 °C until the current density decreases to 5 A / m 2 . Then cut off the power to stop the reaction. Subsequently, take out the lithium-rich electrode and the lithium-poor electrode, clean them, swap the anode and cathode, repeat the constant voltage reaction until the lithium concentration in the brine reaches the expected value, and obtain a lithium-rich solution.

[0058] Example 4

[0059] This example provides a method for electrochemical extraction of lithium from salt lakes. The method includes the following steps:

[0060] (1) Place the lithium-rich electrode and its corresponding lithium-poor electrode separately in the recovery solution and the salt lake brine isolated by an anion exchange membrane. The recovery solution is a 0.05 mol / L LiCl solution. Use the lithium-poor electrode as the cathode and the lithium-rich electrode as the anode, and conduct a constant voltage reaction at 0.3 V.

[0061] (2) When the constant voltage reaction proceeds until the current density decreases to 35 A / m 2 , use an air injection device to introduce H2 gas into the brine at a flow rate of 75 ml / min, and the gas heating temperature is 120 °C. Observe until the current density decreases to 5 A / m 2 . Then cut off the power to stop the reaction. Subsequently, take out the lithium-rich electrode and the lithium-poor electrode, clean them, swap the anode and cathode, repeat the constant voltage reaction until the lithium concentration in the brine reaches the expected value, and obtain a lithium-rich solution.

[0062] Example 5

[0063] The difference between this example and Example 1 is only that the heating temperature of the reducing gas is 70 °C, and other conditions and parameters are exactly the same as those in Example 1.

[0064] Example 6

[0065] The difference between this example and Example 1 is only that the heating temperature of the reducing gas is 130 °C, and other conditions and parameters are exactly the same as those in Example 1.

[0066] Example 7

[0067] The difference between this embodiment and Embodiment 1 is only that the flow rate of the reducing gas is 30 mL / min, and other conditions and parameters are exactly the same as those in Embodiment 1.

[0068] Example 8

[0069] The difference between this embodiment and Embodiment 1 is only that the flow rate of the reducing gas is 120 mL / min, and other conditions and parameters are exactly the same as those in Embodiment 1.

[0070] Comparative Example 1

[0071] The difference between this comparative example and Embodiment 1 is only that no reducing gas is introduced, and other conditions and parameters are exactly the same as those in Embodiment 1.

[0072] Comparative Example 2

[0073] The difference between this comparative example and Embodiment 1 is only that when the current density is 25 A / m 2 the reducing gas is introduced, and other conditions and parameters are exactly the same as those in Embodiment 1.

[0074] Comparative Example 3

[0075] The difference between this comparative example and Embodiment 1 is only that when the current density is 45 A / m 2 the reducing gas is introduced, and other conditions and parameters are exactly the same as those in Embodiment 1.

[0076] Comparative Example 4

[0077] The difference between this comparative example and Embodiment 1 is only that no reducing gas is introduced and hydrazine hydrate is added, and other conditions and parameters are exactly the same as those in Embodiment 1.

[0078] Performance test:

[0079] The indicators of the lithium extraction experiments described in the examples and comparative examples are shown in Table 1:

[0080] Table 1

[0081]

[0082]

[0083] As can be seen from Table 1, from Examples 1-4, it can be obtained that for the lithium extraction method described in this application, the lithium ion concentration in the recovery liquid can reach 3.1 g / L or more, the electrode adsorption capacity can reach 31.5 mg(Li) / g(LiMn2PO4) or more, and the lithium extraction reaction time is below 5.3 h (which can be adjusted to 2.1 h according to the lithium extraction voltage).

[0084] Comparing Example 1 with Examples 5 - 6, it can be obtained that in the lithium extraction method described in this application, the heating temperature of the reducing gas affects the lithium extraction effect. Controlling the heating temperature of the reducing gas at 80 - 120 °C results in better lithium extraction effect. If the heating temperature of the reducing gas is too low, the reaction rate decreases, and the time required for lithium extraction increases. Increasing the heating temperature of the reducing gas accelerates the reaction. If the heating temperature of the reducing gas is too high, the improvement in the reaction rate is limited, and the heat conduction of the solution will be accelerated, thereby increasing the temperature of the anolyte, which is not conducive to maintaining the same deintercalation capacity of the anode and cathode.

[0085] Comparing Example 1 with Examples 7 - 8, it can be obtained that in the lithium extraction method described in this application, the flow rate of the reducing gas affects the lithium extraction effect. Controlling the flow rate of the reducing gas at 50 - 100 mL / min results in better lithium extraction effect. When the flow rate of the reducing gas is too low, the reaction between the reducing gas and the lithium ion sieve of the electrode material is insufficient, affecting the adsorption capacity of the electrode; when the flow rate of the reducing gas is too high, since the reducing gas reaches a saturated state, the improvement in the lithium extraction efficiency is limited, and the excessive gas flow will affect the contact between the electrode and the solution, thereby reducing the interfacial reaction of the electrode.

[0086] Comparing Example 1 with Comparative Example 1, it can be obtained that during the lithium extraction process of this application, adding a strongly reducing gas to the brine promotes the reduction rate of the lithium ion sieve of the electrode material, thereby accelerating the entry of lithium ions into the lattice of the electrode material to form a lithium-inserted product, ensuring the lithium purity of low-voltage lithium extraction and improving the lithium extraction efficiency at the same time.

[0087] Comparing Example 1 with Comparative Examples 2 - 3, it can be obtained that during the lithium extraction process of this application, the introduction time of the reducing gas significantly affects the lithium extraction effect. When the current density is reduced to 30 - 40 A / m 2 ², injecting a strongly reducing gas into the salt lake brine results in better lithium extraction effect. If the reducing gas is introduced too early, at this time, the electrochemical reaction mainly occurs on the electrode surface, and the role of the reducing agent is small, and its reaction may weaken the lithium ion insertion rate. If the reducing gas is introduced too late, the reducing gas cannot react with the lithium ion sieve of the electrode material in time, prolonging the lithium extraction time and reducing the lithium extraction efficiency.

[0088] Comparing Example 1 with Comparative Example 4, it can be obtained that introducing the reducing gas in this application not only avoids the introduction of impurity ions compared with adding a reducing agent, but also injecting gas into the brine can increase the convection velocity of the brine, effectively improving the problem of concentration polarization of the solution near the surface of the lithium extraction electrode, further improving the liquid mass transfer efficiency of lithium ions, making the lithium ions in the brine more smoothly, quickly and fully inserted into the cathode, and improving the lithium extraction efficiency.

[0089] The above are only specific embodiments of the present application, but the protection scope of the present application is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present application fall within the protection scope and the disclosure scope of the present application.

Claims

1. A method for electrochemical extraction and insertion of lithium from salt lakes, comprising the following steps: (1) Inject the recycling solution into the anodic chamber and the salt lake brine into the cathodic chamber respectively, separate them with an anion exchange membrane, use the lithium-rich electrode as the anode and the lithium-poor electrode as the cathode, and conduct a constant voltage reaction; (2) When the constant voltage reaction current density is reduced to 30 - 40 A / m 2 , a strongly reducing gas is injected into the salt lake brine; (3) When the current density is reduced to 5 A / m 2 , power off to stop the reaction, swap the anode and cathode and repeat the constant voltage reaction to obtain a lithium-rich solution; In step (2), the strongly reducing gas includes H2S, and the temperature of the strongly reducing gas is 80-120 °C.

2. The method according to claim 1, wherein The recycling solution in step (1) includes a lithium chloride solution.

3. The method according to claim 1, wherein, The concentration of lithium ions in the recycling solution is 0.03-0.08 mol / L.

4. The method according to claim 1, wherein, The lithium-rich electrode in step (1) is prepared by the following method: Mix a lithium-containing active material, a conductive agent, a binder and a solvent to obtain a slurry, coat the slurry on the surface of a carbon fiber cloth, and dry it to obtain the lithium-rich electrode.

5. The method according to claim 4, wherein The coating amount of the coating is 5-7 mg / cm 2 .

6. The method according to claim 4, wherein The lithium-containing active material includes any one or a combination of more than one of LiMn2O4, LiFePO4, Li2TiO3, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 or Li7Ti5O 12 in the combination of any one or more thereof.

7. The method according to claim 4, wherein, The conductive agent includes carbon black.

8. The method according to claim 4, wherein The binder includes polyvinylidene fluoride.

9. The method according to claim 4, wherein The solvent includes N-methylpyrrolidone.

10. The method according to claim 4, wherein The drying temperature is 60-80 °C.

11. The method according to claim 4, wherein, The drying time is 10-15 h.

12. The method according to claim 1, wherein, The lithium-poor electrode in step (1) is prepared by the following method: Connect the lithium-rich electrode to the positive electrode and the AgCl electrode to the negative electrode, place them in a salt solution, conduct a constant voltage reaction, and stop the reaction when the current drops to 0.1 mA to obtain the lithium-poor electrode.

13. The method according to claim 12, wherein, The salt solution includes a potassium chloride solution.

14. The method according to claim 13, wherein, The concentration of the potassium chloride solution is 0.03-0.08 mol / L.

15. The method according to claim 12, wherein, The voltage of the constant voltage reaction is 1-1.5 V.

16. The method according to claim 1, wherein, The voltage of the constant voltage reaction in step (1) is 0.1-0.6 V.

17. The method according to claim 1, wherein The H2S includes H2S waste gas generated industrially.

18. The method according to claim 1, wherein, The flow rate of the strongly reducing gas is 50-100 mL / min.

19. The method according to claim 1, comprising the following steps: (1) Inject the recycling solution into the anodic chamber and the lithium-containing salt lake brine into the cathodic chamber respectively, separate them with an anion exchange membrane, use the lithium-rich electrode as the anode and the lithium-poor electrode as the cathode, and conduct a constant voltage reaction at a voltage of 0.1-0.6 V; (2) When the constant voltage reaction current density is reduced to 30 - 40 A / m 2 When it reaches 2 , a strongly reducing gas at 80 - 120 °C is injected into the salt lake brine at a flow rate of 50 - 100 mL / min, and the current density is reduced to 5 A / m 2 When it reaches 2 , the reaction is stopped, the anode and cathode are swapped, and the constant voltage reaction is repeated to obtain a lithium-rich solution.

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