Method for extracting lithium from salt lake by means of electrochemical deintercalation

Abstract

Disclosed in the present application is a method for extracting lithium from salt lake by means of electrochemical deintercalation. The method comprises the following steps: (1) separately injecting a recovery liquid into an anode chamber and injecting salt lake brine into a cathode chamber, isolating same by using an anion exchange membrane, and performing a constant-voltage reaction using a lithium-rich electrode as an anode and a lithium-poor electrode as a cathode; (2) when the current density of the constant-voltage reaction is reduced to 30-40 A / m2, injecting a highly-reductive gas into the salt lake brine; and (3) when the current density is reduced to 5 A / m2, powering same off to stop the reaction, exchanging the cathode and the anode, and repeating the constant-voltage reaction, so as to obtain a lithium-rich solution. The present application introduces the reductive gas into the brine at the cathode, so as to improve the lithium intercalation rate of the cathode, thus sufficiently ensuring the adsorption capacity of electrodes and avoiding the problem of capacity attenuation during cyclic lithium extraction processes.

Description

A method for extracting lithium from salt lakes using electrochemical deintercalation 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 surged. Salt lake brines contain huge lithium resources (accounting for approximately 70% of the world's lithium reserves), so lithium extraction from salt lakes has attracted increasing attention. In order to develop salt lake lithium resources, a variety of processes have been invented, such as evaporation, adsorption, solvent extraction, electrodialysis, and membrane separation. The evaporation method is suitable for extracting lithium from low magnesium-lithium ratio solutions (Mg / Li < 6). Even so, approximately 50% of the lithium will be lost in the evaporated crystallized salt during the evaporation process, and the treatment of brines with high Mg / Li ratios is even more serious.

[0003] Although electrodialysis and membrane separation are environmentally friendly, the brine needs to be diluted with a large amount of water. + and Na + / K + It is difficult to separate by membrane, so it is necessary to separate the Na + and K + Removal by evaporation results in a large loss of lithium. Solvent extraction, however, is prone to emulsification due to the high viscosity of brine. While centrifugal extraction can alleviate this phenomenon to a certain extent, organic extractants have a certain solubility in brine, posing a potential environmental pollution risk. Ion sieving is considered a viable method for extracting lithium from brine due to its high selectivity, low cost, and non-toxicity. However, the adsorption capacity of ion sieving materials currently used in industry is low, and the brine often needs to be heated for adsorption and desorption, resulting in high energy consumption.

[0004] Increasing the operating voltage helps increase the exchange capacity of the electrode for lithium, but it also leads to a decrease in the electrode's selectivity for lithium. More impurity cations gain energy and compete with lithium ions for embedding into the electrode, which easily leads to cathode polarization and reduces the purity of the recovered lithium. Although the electrode has better selectivity for lithium when operating under low voltage conditions, the exchange capacity of the electrode for lithium is lower, resulting in a lower lithium extraction rate by electrochemical deintercalation.

[0005] Summary of the Invention

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

[0007] The present application provides a method for electrochemical deintercalation and lithium extraction from salt lakes. The present application introduces reducing gas into the cathode brine to increase the cathode lithium intercalation rate, fully ensure the adsorption capacity of the electrode, and effectively delay the capacity decay during the cyclic lithium extraction process.

[0008] In a first aspect, an embodiment of the present application provides a method for extracting lithium from a salt lake by electrochemical deintercalation, the method comprising the following steps:

[0009] (1) Recovered liquid is injected into the anode chamber and salt lake brine is injected into the cathode chamber, respectively, separated by an anion exchange membrane, with the lithium-rich electrode as the anode and the lithium-poor electrode as the cathode, to perform a constant voltage reaction;

[0010] (2) The current density of the constant voltage reaction is reduced to 30-40A / m 2 When injecting strong reducing gas into the salt lake brine;

[0011] (3) Wait until the current density drops to 5A / m 2 The power is turned off to stop the reaction, and the anode and cathode are exchanged to repeat the constant voltage reaction to obtain a lithium-rich solution.

[0012] There are a variety of coexisting cations of Na, K, and Mg in the brine. When using electrochemical deintercalation to extract lithium, as long as the voltage is properly controlled, lithium ions can be selectively separated from a variety of impurities. When the electrode potential is increased, the reaction rate of lithium extraction increases, but more impurity cations gain energy to compete with lithium ions to embed into the electrode, and cathode polarization is easily generated, resulting in a decrease in the number of lithium ions embedded in the electrode, an increase in impurity cations, a decrease in the exchange capacity of the electrode for lithium, and a decrease in the purity of recovered lithium. 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 efficiency of lithium extraction is reduced. In the lithium extraction process, the present application adds a strong reducing gas 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 crystal lattice of the electrode material to form lithium insertion products, ensuring the lithium purity of low-voltage lithium extraction while improving the lithium extraction efficiency.

[0013] Preferably, the recovery liquid in step (1) comprises a lithium chloride solution.

[0014] The lithium chloride in the recovery liquid described in the present application serves as a supporting electrolyte, and the anode and cathode are subsequently exchanged, and the lithium adsorbed on the cathode is released into the recovery liquid.

[0015] Preferably, the concentration of lithium ions in the recovery liquid is 0.03 to 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.

[0016] Preferably, the lithium-rich electrode in step (1) is prepared by the following method:

[0017] A lithium-containing active material, a conductive agent, a binder and a solvent are mixed to obtain a slurry, the slurry is coated on the surface of a carbon fiber cloth, and the mixture is dried to obtain a lithium-rich electrode.

[0018] Preferably, the coating amount is 5 to 7 mg / cm 2 , for example: 5mg / cm 2 , 5.5mg / cm 2 , 6mg / cm 2 、6.5mg / cm 2 or 7 mg / cm 2 wait.

[0019] 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 .

[0020] Preferably, the conductive agent comprises carbon black.

[0021] Preferably, the binder comprises polyvinylidene fluoride.

[0022] Preferably, the solvent comprises N-methylpyrrolidone.

[0023] Preferably, the drying temperature is 60-80°C, for example, 60°C, 65°C, 70°C, 75°C or 80°C.

[0024] Preferably, the drying time is 10 to 15 hours, for example, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours or 15 hours.

[0025] Preferably, the lithium-deficient electrode in step (1) is prepared by the following method:

[0026] The lithium-rich electrode is connected to the positive electrode, the AgCl electrode is connected to the negative electrode, and the solution is placed in a salt solution for constant voltage reaction. The reaction is stopped when the current drops to 0.1 mA to obtain the lithium-poor electrode.

[0027] Preferably, the salt solution comprises a potassium chloride solution.

[0028] 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.

[0029] Preferably, the voltage of the constant voltage reaction is 1-1.5V, for example, 1V, 1.1V, 1.2V, 1.3V, 1.4V or 1.5V.

[0030] Preferably, the voltage of the constant voltage reaction in step (1) is 0.1-0.6V, for example, 0.1V, 0.2V, 0.3V, 0.4V, 0.5V or 0.6V.

[0031] Preferably, the strong reducing gas in step (2) includes hydrogen and / or H2S, preferably H2S.

[0032] Preferably, the H2S comprises industrially generated H2S waste gas.

[0033] In the industrial production of artificial fibers, natural gas purification, sulfur dyes, petroleum refining, coal gas manufacturing, sewage treatment, papermaking and other industries, high concentrations of H2S waste gas and sulfur-containing organic compounds such as mercaptans, sulfides, disulfides, and cyclic sulfides are usually discharged. Direct discharge will cause environmental pollution and harm human health. The temperature of H2S waste gas generated by industry is usually high. The reducing gas with a higher temperature can conduct heat to the brine to increase the temperature of the brine, thereby increasing the activity of lithium ions in the solution and enabling the lithium ions at the cathode to be embedded in the electrode faster. In addition, the introduction of gas into the brine can disturb the brine and increase the convection speed of the brine, which can effectively improve the problem of concentration polarization of the solution near the surface of the lithium extraction electrode, further improve the liquid phase mass transfer efficiency of lithium ions, and enable the lithium ions in the brine to be more smoothly, quickly and fully embedded in the cathode, thereby improving the lithium extraction efficiency. The present application uses H2S discharged by industrial production as a reducing agent to effectively treat H2S waste gas and avoid environmental pollution.

[0034] Preferably, the temperature of the strong reducing gas in step (2) is 80-120°C, for example, 80°C, 90°C, 100°C, 110°C or 120°C.

[0035] Preferably, the flow rate of the strong reducing gas is 50-100 mL / min, for example, 50 mL / min, 60 mL / min, 70 mL / min, 80 mL / min, 90 mL / min or 100 mL / min.

[0036] As a preferred embodiment of the present invention, the method comprises the following steps:

[0037] (1) The anode chamber is injected with recycled liquid, and the cathode chamber is injected with salt lake brine, which are separated by an anion exchange membrane. The lithium-rich electrode is used as the anode and the lithium-poor electrode is used as the cathode, and a constant voltage reaction is carried out at a voltage of 0.1 to 0.6 V.

[0038] (2) The current density of the constant voltage reaction is reduced to 30-40A / m2 When a strong reducing gas with a temperature of 80 to 120°C is injected into the salt lake brine at a flow rate of 50 to 100 mL / min, the current density is reduced to 5 A / m 2 The reaction is stopped when the cathode and anode are exchanged and the constant voltage reaction is repeated to obtain a lithium-rich solution.

[0039] Compared with the related art, the embodiments of the present application have the following beneficial effects:

[0040] (1) The embodiment of the present application heats the brine by heating the reducing gas, thereby increasing the temperature of the brine and increasing the movement rate of lithium ions in the solution, so that the lithium ions in the cathode can be embedded in the electrode more quickly, thereby improving the liquid phase mass transfer efficiency of lithium ions, and allowing the lithium ions in the brine to be more smoothly, quickly and fully embedded in the cathode, thereby improving the lithium extraction efficiency.

[0041] (2) The lithium extraction method described in the embodiment of the present application can recover a lithium-rich solution with a lithium ion concentration of more than 3.1 g / L, an electrode adsorption capacity of more than 31.5 mg (Li) / g (LiMn2PO4), and a lithium extraction reaction time of less than 5.3 h.

[0042] Still other aspects will become apparent upon reading and understanding the detailed description. DETAILED DESCRIPTION

[0043] The technical solution of the present application is further described below through specific implementation methods. Those skilled in the art should understand that the embodiments are only used to help understand the present application and should not be regarded as specific limitations of the present application.

[0044] The lithium-rich electrodes and lithium-poor electrodes described in the examples and comparative examples of the present application are prepared by the following method:

[0045] LiMn2O4 powder was prepared by high temperature solid phase method. The obtained LiMn2O4 was mixed with carbon black and PVDF binder in a mass ratio of 9:1:1. N-methylpyrrolidone solvent was added and stirred thoroughly. Ultrasonic dispersion was performed for 10 minutes to obtain a uniformly dispersed slurry. The obtained slurry was evenly coated on carbon fiber cloth with a coating amount of about 6 mg / cm 2 After coating, it was dried at 70 ° C for 12 hours to obtain a lithium-rich electrode; the obtained lithium-rich LiMn2O4 electrode was connected to the positive electrode, and the AgCl electrode was connected to the negative electrode in a 0.05 mol / L KCl solution for a constant voltage reaction of 1.2 V. The reaction was stopped when the current dropped to 0.1 mA, and the lithium-poor Li 1-x Mn2O4 electrode.

[0046] The brine composition used is: 0.33g / L Li, 85.65g / L Na, 107.97g / L Mg, 8.45g / L K, 2.76g / L Ca, 10.54g / L SO4 2- .

[0047] Example 1

[0048] This embodiment provides a method for extracting lithium from a salt lake by electrochemical deintercalation, the method comprising the following steps:

[0049] (1) A lithium-rich electrode and its corresponding lithium-poor electrode were placed in a recovery solution and salt lake brine separated by an anion exchange membrane, respectively. The recovery solution was a 0.05 mol / L LiCl solution. The lithium-poor electrode was used as the cathode and the lithium-rich electrode was used as the anode. A constant voltage reaction was performed at 0.3 V.

[0050] (2) When the constant voltage reaction is carried out until the current density drops to 35A / m 2 When the gas injection device is used to introduce H2S gas at a flow rate of 75ml / min into the brine, the gas heating temperature is 95℃, and the current density is observed to decrease to 5A / m 2 The power is turned off to stop the reaction, and then the lithium-rich electrode and the lithium-poor electrode are taken out and cleaned, and the anode and cathode are interchanged, and the constant voltage reaction is repeated until the lithium concentration in the brine reaches the expected value to obtain a lithium-rich solution.

[0051] Example 2

[0052] This embodiment provides a method for extracting lithium from a salt lake by electrochemical deintercalation, the method comprising the following steps:

[0053] (1) placing a lithium-rich electrode and its corresponding lithium-poor electrode in a recovery solution and salt lake brine separated by an anion exchange membrane, respectively, wherein the recovery solution is a 0.05 mol / L LiCl solution, the lithium-poor electrode is used as the cathode, and the lithium-rich electrode is used as the anode, and a constant voltage reaction is performed at 0.6 V;

[0054] (2) When the constant voltage reaction is carried out until the current density drops to 30A / m 2 When the gas injection device is used to introduce H2S gas into the brine at a flow rate of 50ml / min, the gas heating temperature is 80℃, and the current density is observed to decrease to 5A / m 2 The power is turned off to stop the reaction, and then the lithium-rich electrode and the lithium-poor electrode are taken out and cleaned, and the anode and cathode are interchanged, and the constant voltage reaction is repeated until the lithium concentration in the brine reaches the expected value to obtain a lithium-rich solution.

[0055] Example 3

[0056] This embodiment provides a method for extracting lithium from a salt lake by electrochemical deintercalation, the method comprising the following steps:

[0057] (1) placing a lithium-rich electrode and its corresponding lithium-poor electrode in a recovery solution and salt lake brine separated by an anion exchange membrane, respectively, wherein the recovery solution is a 0.05 mol / L LiCl solution, the lithium-poor electrode is used as the cathode, and the lithium-rich electrode is used as the anode, and a constant voltage reaction is performed at 0.1 V;

[0058] (2) When the constant voltage reaction is carried out until the current density drops to 40A / m 2 When the current density is reduced to 5A / m, H2S gas with a flow rate of 100ml / min is introduced into the brine using a gas injection device and the gas heating temperature is 120℃. 2 The power is turned off to stop the reaction, and then the lithium-rich electrode and the lithium-poor electrode are taken out and cleaned, and the anode and cathode are interchanged, and the constant voltage reaction is repeated until the lithium concentration in the brine reaches the expected value to obtain a lithium-rich solution.

[0059] Example 4

[0060] This embodiment provides a method for extracting lithium from a salt lake by electrochemical deintercalation, the method comprising the following steps:

[0061] (1) A lithium-rich electrode and its corresponding lithium-poor electrode were placed in a recovery solution and salt lake brine separated by an anion exchange membrane, respectively. The recovery solution was a 0.05 mol / L LiCl solution. The lithium-poor electrode was used as the cathode and the lithium-rich electrode was used as the anode. A constant voltage reaction was performed at 0.3 V.

[0062] (2) When the constant voltage reaction is carried out until the current density drops to 35A / m 2 When the gas injection device is used to introduce H2 gas at a flow rate of 75 ml / min into the brine, the gas heating temperature is 120 ° C, and the current density is observed to decrease to 5 A / m 2 The power is turned off to stop the reaction, and then the lithium-rich electrode and the lithium-poor electrode are taken out and cleaned, and the anode and cathode are interchanged, and the constant voltage reaction is repeated until the lithium concentration in the brine reaches the expected value to obtain a lithium-rich solution.

[0063] Example 5

[0064] The only difference between this embodiment and embodiment 1 is that the heating temperature of the reducing gas is 70° C., and other conditions and parameters are exactly the same as those in embodiment 1.

[0065] Example 6

[0066] The only difference between this embodiment and embodiment 1 is that the heating temperature of the reducing gas is 130° C., and other conditions and parameters are exactly the same as those in embodiment 1.

[0067] Example 7

[0068] The only difference between this embodiment and embodiment 1 is that the flow rate of the reducing gas is 30 mL / min, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0069] Example 8

[0070] The only difference between this embodiment and embodiment 1 is that the flow rate of the reducing gas is 120 mL / min, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0071] Comparative Example 1

[0072] The only difference between this comparative example and Example 1 is that no reducing gas is introduced, and other conditions and parameters are exactly the same as those in Example 1.

[0073] Comparative Example 2

[0074] The only difference between this comparative example and Example 1 is that at a current density of 25 A / m 2 When the reducing gas is introduced, the other conditions and parameters are exactly the same as those in Example 1.

[0075] Comparative Example 3

[0076] The only difference between this comparative example and Example 1 is that at a current density of 45 A / m 2 When the reducing gas is introduced, the other conditions and parameters are exactly the same as those in Example 1.

[0077] Comparative Example 4

[0078] The only difference between this comparative example and Example 1 is that no reducing gas is introduced and hydrazine hydrate is added. Other conditions and parameters are exactly the same as those in Example 1.

[0079] Performance testing:

[0080] The indicators of the lithium extraction experiments described in the examples and comparative examples are shown in Table 1:

[0081] Table 1

[0082] As can be seen from Table 1, from Examples 1-4, the lithium ion concentration of the recovered liquid of the lithium extraction method described in the present application 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 is less than 5.3 h (which can be adjusted to 2.1 h according to the lithium extraction voltage).

[0083] By comparing Example 1 with Examples 5-6, it can be seen that in the lithium extraction method described in the present application, the heating temperature of the reducing gas will affect the lithium extraction effect. The lithium extraction effect is better when the heating temperature of the reducing gas is controlled at 80-120°C. 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 increase in the reaction rate is limited, and the heat conduction of the solution will be accelerated, thereby increasing the temperature of the anode liquid, which is not conducive to maintaining the consistency of the deintercalation and insertion capacity of the anode and cathode.

[0084] By comparing Example 1 with Examples 7-8, it can be seen that in the lithium extraction method described in the present application, the flow rate of the reducing gas affects the lithium extraction effect. When the flow rate of the reducing gas is controlled at 50-100 mL / min, the lithium extraction effect is better. When the flow rate of the reducing gas is too low, the reducing gas and the electrode material lithium ion sieve react insufficiently, affecting the adsorption capacity of the electrode; when the flow rate of the reducing gas is too high, the reducing gas reaches a saturated state, and the improvement in the lithium extraction efficiency is limited, and the excessive airflow affects the contact between the electrode and the solution, thereby reducing the interfacial reaction of the electrode.

[0085] By comparing Example 1 and Comparative Example 1, it can be seen that in the lithium extraction process, the present application adds a strong reducing gas 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 electrode material lattice to form lithium intercalation products, ensuring the lithium purity of low-voltage lithium extraction while improving the lithium extraction efficiency.

[0086] From the comparison between Example 1 and Comparative Examples 2-3, it can be seen that in the process of lithium extraction, the introduction time of reducing gas will significantly affect the lithium extraction effect. When the current density is reduced to 30-40A / m 2 When a strong reducing gas is injected into the salt lake brine, the lithium extraction effect is better. If the reducing gas is introduced too early, the electrochemical reaction mainly occurs on the electrode surface, and the effect of the reducing agent is small. The reaction may weaken the insertion rate of lithium ions. If the reducing gas is introduced too late, the reducing gas cannot react with the lithium ion sieve of the electrode material in time, which prolongs the lithium extraction time and reduces the lithium extraction efficiency.

[0087] By comparing Example 1 and Comparative Example 4, it can be seen that the introduction of reducing gas in the present application not only avoids the introduction of impurity ions compared to the addition of a reducing agent, but also the introduction of gas into the brine can increase the convection velocity of the brine, which can effectively improve the problem of concentration polarization of the solution near the surface of the lithium extraction electrode, further improve the liquid-phase mass transfer efficiency of lithium ions, and make the lithium ions in the brine more smoothly, quickly and fully embedded in the cathode, thereby improving the lithium extraction efficiency.

[0088] The above description is only a specific implementation method 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 replacements that can be easily thought of by those skilled in the art within the technical scope disclosed in the present application fall within the protection scope and disclosure scope of the present application.

Claims

1. A method for extracting lithium from a salt lake by electrochemical deintercalation, comprising the following steps: (1) injecting the recovered liquid into the anode chamber and injecting the salt lake brine into the cathode chamber respectively, separating them with an anion exchange membrane, using the lithium-rich electrode as the anode and the lithium-poor electrode as the cathode, and performing a constant voltage reaction; (2) The current density of the constant voltage reaction is reduced to 30-40A / m 2 When injecting strong reducing gas into the salt lake brine; (3) When the current density is reduced to 5A / m 2 The power is turned off to stop the reaction, and the anode and cathode are exchanged to repeat the constant voltage reaction to obtain a lithium-rich solution.

2. The method of claim 1, wherein: The recovery liquid in step (1) comprises a lithium chloride solution.

3. The method according to claim 1 or 2, wherein: The concentration of lithium ions in the recovery liquid is 0.03-0.08 mol / L.

4. The method according to any one of claims 1 to 3, wherein: The lithium-rich electrode in step (1) is prepared by the following method: The lithium-containing active material, the conductive agent, the binder and the solvent are mixed to obtain a slurry, the slurry is coated on the surface of the carbon fiber cloth, and the slurry is dried to obtain a lithium-rich electrode.

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

6. The method according to claim 4 or 5, wherein: 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 more combinations of; Preferably, the conductive agent comprises carbon black; Preferably, the binder comprises polyvinylidene fluoride; Preferably, the solvent comprises N-methylpyrrolidone; Preferably, the drying temperature is 60-80°C; Preferably, the drying time is 10 to 15 hours.

7. The method according to any one of claims 1 to 6, wherein: The lithium-poor electrode in step (1) is prepared by the following method: The lithium-rich electrode is connected to the positive electrode, the AgCl electrode is connected to the negative electrode, and placed in a salt solution for constant voltage reaction. The reaction is stopped when the current decreases to 0.1 mA to obtain the lithium-poor electrode.

8. The method of claim 7, wherein: The salt solution includes potassium chloride solution; Preferably, the concentration of the potassium chloride solution is 0.03-0.08 mol / L.

9. The method according to claim 7 or 8, wherein: The voltage of the constant voltage reaction is 1-1.5V.

10. The method according to any one of claims 1 to 9, wherein: The voltage of the constant voltage reaction in step (1) is 0.1 to 0.6V.

11. The method according to any one of claims 1 to 10, wherein: The strong reducing gas in step (2) includes hydrogen and / or H2S, preferably H2S; Preferably, the H2S comprises industrially generated H2S waste gas.

12. The method according to any one of claims 1 to 11, wherein: The temperature of the strong reducing gas in step (2) is 80-120°C.

13. The method according to any one of claims 1 to 12, wherein: The flow rate of the strong reducing gas is 50-100 mL / min.

14. The method according to any one of claims 1 to 13, comprising the following steps: (1) injecting the recovered liquid into the anode chamber and injecting the lithium-containing salt lake brine into the cathode chamber, respectively, separating them with an anion exchange membrane, using the lithium-rich electrode as the anode and the lithium-poor electrode as the cathode, and reacting at a constant voltage of 0.1 to 0.6 V; (2) The current density of the constant voltage reaction is reduced to 30-40A / m 2 When a strong reducing gas at 80-120°C is injected into the salt lake brine at a flow rate of 50-100 mL / min, the current density is reduced to 5 A / m 2 The reaction is stopped when the cathode and anode are switched and the constant voltage reaction is repeated to obtain a lithium-rich solution.

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