A method for extracting lithium from lithium-containing aqueous solutions

Abstract

This invention discloses a method for extracting lithium from a lithium-containing aqueous solution. A zinc or zinc alloy is used as the negative electrode, and a positive electrode current collector loaded with lithium-ion battery positive electrode material is used as the positive electrode, assembled into an electrochemical lithium extraction device based on a zinc-lithium hybrid ion battery system. When the lithium-containing aqueous solution is injected and discharged while the positive electrode is fully charged, the Li in the lithium-containing aqueous solution... + Zinc ions are embedded into the positive electrode, while an equal amount of zinc ions is generated at the negative electrode and enters the lithium-containing aqueous solution, maintaining charge conservation in the lithium-containing aqueous solution. Then, after being discharged, zinc-containing electrolyte is injected into the empty electrolytic cell and charged, and the Zn in the electrolyte... 2+ Li is reduced on the negative electrode surface, while a moderate coulombic amount of Li is present at the positive electrode. + The lithium is extracted into the electrolyte, maintaining charge balance in the electrolyte and achieving electrochemical extraction of lithium-containing aqueous solutions. This method does not require the use of ion exchange membranes and does not need to consider the type of anions in the lithium-containing aqueous solutions. It has advantages such as high production efficiency, low cost, and strong adaptability to solution composition.

Description

Technical Field

[0001] This invention belongs to the field of lithium resource recycling and relates to a method for extracting lithium from lithium-containing aqueous solutions. It can be applied to the extraction of lithium ions from lithium-ion-containing salt lake brines, groundwater, industrial wastewater, waste liquid from recycled lithium-ion batteries, and seawater concentrate. Background Technology

[0002] Lithium plays a vital role in various fields such as electroplating, alloys, electrolytic aluminum, and batteries, and is often referred to as "metal MSG." The solutions generated during and after the recycling of spent lithium-ion battery cathode materials contain a certain amount of lithium ions, but the presence of ions from metals such as Fe, Ni, and Co makes separation difficult.

[0003] Taking lithium extraction from salt lake brine as an example: To solve the problem of lithium extraction from salt lake brine with a high magnesium-to-lithium ratio in my country, various lithium extraction technologies for salt lake brine that are under research or being attempted for industrialization have been proposed, such as: extraction methods, adsorption methods, membrane methods, electrochemical methods, and reaction / separation coupling technologies. Among them, the electrochemical lithium extraction method based on lithium battery systems is a method that utilizes Li... + A novel method for lithium extraction from salt lakes via the deintercalation / intercalation reaction in lithium-ion battery cathode materials, utilizing the specific lithium intercalation / intercalation potential of the lithium-ion battery cathode material and Li... + The migration channel first discharges in the brine of the salt lake to selectively insert Li. + Then it is charged in a lithium-rich solution to release Li + To achieve Li + Extraction of, for example: LiFePO4-Ag, λ-MnO2-Ag, Li 1-x Ni 0.5 Mn 1.5 O4-Ag, Li 1-x Ni 0.33 Co 1 / 3 Mn 1 / 3 O2-Ag, λ-MnO2-AC, LiNi 0.6 Co 0.2 Mn 0.2 Systems such as O2-AC and LiFePO4-FePO4.

[0004] All of these systems involve inserting lithium ions into a lithium-containing aqueous solution while simultaneously using anion capture electrodes or anion exchange membranes to transfer an equal amount of anions to satisfy charge conservation in the lithium-containing aqueous solution. However, the anion composition varies greatly in different solutions, which reduces the adaptability of the anion exchange membranes and anion capture electrodes used in the above methods, thus greatly limiting their actual production effectiveness.

[0005] Chinese patent CN102049237A discloses a ferric phosphate ion sieve for selective lithium extraction and its application. It uses a LiFePO4-FePO4 system, placing a NaCl extract and a lithium-containing aqueous solution in two separate electrode chambers, separated by an anion exchange membrane. After charging, the Li in the LiFePO4 is extracted... + The lithium in the aqueous solution is removed by adding it to a NaCl solution. + Embedded in FePO4 to achieve Li in lithium-containing aqueous solutions + The lithium is extracted by transferring it to a NaCl extractant, thus achieving lithium extraction from a lithium-containing aqueous solution. However, this method requires both solutions to be present in the electrolyzer simultaneously, making the operation complex and necessitating the use of expensive and fragile anion exchange membranes.

[0006] Chinese patent CN112795940 discloses a method for suppressing interference from coexisting cations in the electrochemical extraction of lithium from brine. The method uses a lithium-ion sieve electrode as the working electrode, an Ag electrode as the capture electrode (counter electrode) for chloride ions, and a LiCl solution as the electrolyte to construct the electrochemical reaction system. Intermittent discharge is used to embed lithium ions in the lithium-ion sieve, while chloride ions are captured by the capture electrode. During constant current charging, lithium ions are desorbed from the lithium-ion sieve and regenerated, while chloride ions are desorbed from the capture electrode and regenerated. Although this method does not require an ion exchange membrane, it has significant limitations as it can only use LiCl solution as the electrolyte and cannot extract lithium from aqueous solutions containing any anions.

[0007] How to extract lithium ions without using expensive and fragile anion exchange membranes and without being limited by the composition of anions in lithium-containing aqueous solutions is a problem that urgently needs to be solved. Summary of the Invention

[0008] To achieve a simpler, lower-cost, lower-carbon, and more efficient method for extracting lithium from lithium-containing aqueous solutions, this invention provides a method for extracting lithium from lithium-containing aqueous solutions, using an electrochemical lithium extraction device based on a zinc-lithium hybrid ion battery system to extract lithium ions from lithium-containing aqueous solutions.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] A method for extracting lithium from a lithium-containing aqueous solution, the method comprising the following steps:

[0011] (1) Using zinc or zinc alloy as the negative electrode and a positive current collector loaded with lithium-ion battery positive electrode material as the positive electrode, the two are placed in an electrolytic cell to assemble an electrochemical lithium extraction device based on a zinc-lithium hybrid ion battery system.

[0012] (2) Inject a lithium-containing aqueous solution into the electrolytic cell until the liquid surface covers the positive and negative electrodes, discharge the electrolyte, and after the discharge is completed, evacuate the lithium-containing aqueous solution after electrolysis and clean the electrolytic cell and the positive and negative electrodes.

[0013] (3) Then inject zinc-containing electrolyte into the electrolytic cell until the liquid surface covers the positive and negative electrodes, and charge it to extract lithium from the lithium-containing aqueous solution into the electrolyte.

[0014] The lithium-containing aqueous solution includes one or more of the following: lithium-ion-containing salt lake brine, groundwater, industrial wastewater, waste liquid from recycled lithium-ion batteries, and seawater concentrate.

[0015] In step (3), after extracting lithium from the lithium-containing aqueous solution into the electrolyte, an alkaline solution is added to the electrolyte. After the precipitation is complete, the solution is filtered, and the resulting precipitate is LiOH·H2O. The alkaline solution is one or more of KOH solution and NaOH solution.

[0016] In step (1), the negative electrode is a sheet-like, rod-like, or mesh-like zinc or zinc alloy; it can undergo a stable anodic reaction in aqueous solution, and its corresponding zinc ions can be electro-reduced in aqueous solution, and its electrochemical reaction potential is lower than the lithium insertion / extraction potential of LiFePO4 and LiMn2O4 in aqueous solution.

[0017] In step (1), the positive electrode is a positive current collector loaded with FePO4, LiFePO4, Mn2O4 or LiMn2O4, and the positive electrode is wrapped with multilayer nylon.

[0018] The positive electrode is prepared by mixing the positive electrode active material, conductive agent, and binder, adding solvent and stirring evenly, then uniformly coating the mixture onto the positive electrode current collector, drying it, and then wrapping it with double-layer nylon.

[0019] The positive electrode active material is FePO4, carbon-coated LiFePO4, Mn2O4, or LiMn2O4;

[0020] The conductive agent is conductive carbon black.

[0021] The adhesive is any one or more of polyvinylidene fluoride, polytetrafluoroethylene, and adhesive LA133.

[0022] The solvent is any one or more of N-methylpyrrolidone, N,N-dimethylformamide, ethanol, and pure water.

[0023] The positive current collector is a titanium mesh, titanium plate, silver mesh, silver plate, or carbon material.

[0024] When the positive electrode is loaded with LiFePO4 or LiMn2O4 as the positive current collector, a pre-charging process is required between steps (1) and (2) to achieve pre-lithiation and activation of the positive electrode. The pre-charging method is as follows: inject zinc-ion-containing electrolyte into the electrolytic cell until the liquid surface covers the positive and negative electrodes, charge, and after charging, evacuate the zinc-ion-containing electrolyte after electrolysis, and clean the electrolytic cell and the positive and negative electrodes. The charging conditions are: control the temperature at 0-90℃ and the charging current density at 0.1-200A / m. 2 The charging continues until the charging is complete, with the charging cut-off voltage being 0.1-2.5V.

[0025] When the positive electrode is loaded with a positive current collector of FePO4 or Mn2O4, the above-mentioned pre-charging is not required.

[0026] In step (2), the discharge conditions are: the temperature is controlled at 0-90℃ for discharge, and the current density is 0.1-1200A / m. 2 The discharge continues until the discharge ends, with a discharge cutoff voltage of 0-1.5V.

[0027] In step (3), the charging conditions are: the charging temperature is controlled at 0-90℃, and the current density is 0.1-500A / m. 2 The charging continues until the charging is complete, with the charging cut-off voltage being 0.1-2.0V.

[0028] The zinc ion-containing electrolyte is an aqueous solution of any one or more of ZnCl2, ZnSO4, and Zn(NO3)2.

[0029] The zinc ion concentration in the zinc-containing electrolyte is 0.5–8 M.

[0030] Furthermore, the method further includes the following steps: repeatedly performing steps (2) and (3), repeatedly discharging the same lithium-containing aqueous solution, and / or repeatedly charging the same zinc-containing electrolyte, until the lithium ion concentration in the lithium-containing aqueous solution is extremely low or the lithium ion concentration in the zinc-containing electrolyte is significantly increased.

[0031] Furthermore, the method includes the following steps: repeatedly performing steps (2) and (3), replacing the lithium-containing aqueous solution each time, but repeatedly using the same zinc-containing electrolyte, so that all lithium ions in the lithium-containing aqueous solution are extracted into the same zinc-containing electrolyte to obtain a zinc-lithium mixed salt extract, so that the zinc-lithium mixed salt extract can be post-processed in a concentrated and efficient manner.

[0032] Alternatively, steps (2) and (3) can be repeated, with the same lithium-ion-containing aqueous solution and zinc-ion-containing electrolyte used in each repetition to fully extract lithium ions from the lithium-ion-containing aqueous solution into the same zinc-ion-containing electrolyte to obtain a zinc-lithium mixed salt extract, so that the zinc-lithium mixed salt extract can be processed in a concentrated and efficient manner in the future.

[0033] The positive and negative electrodes are at least one set. When there are multiple sets of positive and negative electrodes, the positive and negative electrodes are alternately arranged in the electrolytic cell, and multiple electrode pairs are stacked in the electrolytic cell in the form of A:B:A:B:A:B...

[0034] The positive and negative electrodes may be separated by a diaphragm or not; when a diaphragm is used, the diaphragm is a natural or artificial porous polymer membrane or polymer mesh.

[0035] The method for extracting lithium from a lithium-containing aqueous solution provided by this invention uses metallic zinc or zinc alloy, whose anode potential is lower than that of commonly used lithium-ion batteries and can discharge stably, as the negative electrode; a positive electrode current collector loaded with lithium-ion battery positive electrode material as the positive electrode; an aqueous solution containing zinc ions as the electrolyte for lithium extraction; and a lithium-containing aqueous solution as the stock solution, from which lithium is extracted. By constructing an electrolytic cell similar to a zinc-lithium hybrid ion battery system, when a lithium-containing aqueous solution is injected and discharged while the positive electrode is fully charged, the Li in the lithium-containing aqueous solution... + It will embed into the positive electrode, while the negative electrode generates an equal amount of zinc ions which enter the lithium-containing aqueous solution, maintaining charge conservation in the lithium-containing aqueous solution; then, after being discharged, a zinc-containing electrolyte is injected into the electrolytic cell and charged, the Zn in the zinc-containing electrolyte... 2+ Li is reduced on the negative electrode surface, while a moderate coulombic amount of Li is present at the positive electrode. + The lithium is extracted and enters the electrolyte, maintaining charge conservation in the extract to achieve the desired effect of removing Li from the lithium-containing aqueous solution. + The lithium is transferred to electrolysis to achieve electrochemical extraction of lithium-containing aqueous solutions.

[0036] Taking a titanium mesh loaded with FePO4 as the positive electrode as an example, the reactions that occur at the positive and negative electrodes during charging and discharging are as follows:

[0037] During discharge, the positive electrode reaction is: 2FePO4 + 2Li + +2e - =2LiFePO4; Anode: Zn-2e - =Zn 2+ That is, Li in lithium-containing aqueous solutions + While the positive electrode is embedded, the negative electrode generates an equal amount of zinc ions and enters the lithium-containing aqueous solution, thus maintaining the charge balance in the lithium-containing aqueous solution.

[0038] During charging, the positive electrode is: 2LiFePO4-2e -= 2FePO4 + 2Li + Negative electrode: Zn 2+ +2e - =Zn; that is, Zn in an electrolyte containing zinc ions. 2+ While zinc is reduced on the negative electrode surface, a moderate coulombic amount of Li is present at the positive electrode. + It is separated into the electrolyte to maintain the charge balance in the extract.

[0039] Taking a titanium mesh loaded with LiFePO4 as the positive electrode as an example, the positive electrode needs to be pre-charged before use. The reactions that occur at the positive and negative electrodes during the pre-charging process are as follows:

[0040] Positive electrode: 2LiFePO4-2e - = 2FePO4 + 2Li + Negative electrode: Zn 2+ +2e - =Zn; Thus, the active material in the positive electrode becomes FePO4 after pre-charging. During subsequent injection of a lithium-containing aqueous solution and discharge, the Li in the lithium-containing aqueous solution... + It will embed into the positive electrode, while the negative electrode generates an equal amount of zinc ions which enter the lithium-containing aqueous solution, maintaining charge conservation in the lithium-containing aqueous solution; then, after being discharged, a zinc-containing electrolyte is injected into the electrolytic cell and charged, the Zn in the zinc-containing electrolyte... 2+ Li is reduced on the negative electrode surface, while a moderate coulombic amount of Li is present at the positive electrode. + The lithium is extracted and enters the electrolyte, maintaining charge conservation in the extract to achieve the desired effect of removing Li from the lithium-containing aqueous solution. + The lithium is transferred to electrolysis to achieve electrochemical extraction of lithium-containing aqueous solutions.

[0041] Compared with the prior art, the present invention has the following advantages:

[0042] 1. The method for extracting lithium from a lithium-containing solution provided by this invention utilizes the fact that the FePO4 lattice can only embed Li. + The characteristics of Zn enable high selectivity for Li+, and then Zn is used. 2+ Li was replaced in the lithium-containing aqueous solution + The electrolytic cell has a simple structure, does not require the use of ion exchange membranes, and does not need to consider the ionic composition of lithium-containing aqueous solutions in the positive and negative electrode reactions. It has the advantages of high production efficiency (it takes about 12 hours to complete one lithium extraction in steps 3-4), low cost, and strong adaptability to solution composition.

[0043] 2. In the method for extracting lithium from a lithium-containing solution provided by the present invention, the discharge and charge processes can be repeated, the same lithium-containing aqueous solution can be repeatedly discharged, and / or the same zinc-containing electrolyte can be repeatedly charged, until the lithium ion concentration in the lithium-containing aqueous solution is extremely low or the lithium ion concentration in the zinc-containing electrolyte is significantly increased. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the electrochemical lithium extraction device based on a zinc-lithium hybrid ion battery system in this invention. Detailed Implementation

[0045] The present invention will now be described in detail with reference to the embodiments.

[0046] Example 1

[0047] A method for extracting lithium from brine in Qinghai Salt Lake includes the following steps:

[0048] (1) Use a 0.003×0.45×1.2m zinc plate as the negative electrode; mix 400g of carbon-coated LiFePO4 with polyvinylidene fluoride and conductive carbon black in a ratio of 7.5:1:1.5, add 46L of N-methylpyrrolidone and mix thoroughly, then coat evenly on a 0.4×1.2m 100-mesh titanium mesh, dry at 90℃ for 18 hours, and wrap with a double-layer nylon mesh as the positive electrode; put the positive and negative electrodes into an electrolytic cell made of polypropylene material with a length of 0.5m, a width of 0.2m and a height of 1.5m, and connect the positive and negative electrodes to the positive and negative electrodes of the external power supply respectively to assemble an electrochemical lithium extraction device based on a zinc-lithium hybrid ion battery system;

[0049] (2) Inject 4M ZnCl2 aqueous solution into the electrolytic cell until the liquid surface covers the two electrodes. Charge at room temperature, set the charging current to 10A and the charging cut-off voltage to 1.6V. After charging, remove the ZnCl2 aqueous solution after electrolysis and rinse the cell and electrodes with distilled water.

[0050] (3) Then inject Qinghai salt lake brine into the electrolytic cell until the liquid surface covers the two electrodes. Discharge at room temperature, set the discharge current to 10A and the discharge cutoff voltage to 0.8V. After the discharge is completed, remove the lithium-containing aqueous solution and rinse the cell and electrodes with distilled water.

[0051] (4) Then inject the ZnCl2 aqueous solution obtained in step (2) into the electrolytic cell until the liquid surface covers the two electrodes. Charge at room temperature, set the charging current to 20A and the charging cut-off voltage to 1.6V. After charging, remove the ZnCl2 aqueous solution after electrolysis and rinse the cell and electrodes with distilled water.

[0052] (5) Repeat steps (3)-(4) 20 times in multiple batches of Qinghai Salt Lake brine, replacing the brine each time, but repeatedly using the same ZnCl2 aqueous solution, and finally obtaining a zinc-lithium mixed salt extract.

[0053] The ICP test results of the brine from the salt lake after the first lithium extraction and the final zinc-lithium mixed extract are shown in Table 1:

[0054] Table 1

[0055]

[0056] Example 2

[0057] A method for extracting lithium from a lithium-containing aqueous solution in the recycling section of spent lithium-ion batteries includes the following steps:

[0058] (1) Use a 0.002×0.35×1m zinc plate as the negative electrode; mix 320g LiMn2O4 powder with water-washable battery binder LA133 and conductive carbon black in a ratio of 8:1:1, add 29L of distilled water and mix thoroughly, then coat evenly on a 0.3×1.0m 100-mesh titanium mesh, dry at 90℃ for 24 hours, and wrap with a double-layer nylon mesh as the positive electrode; put the positive and negative electrodes into an electrolytic cell made of polypropylene material with a length of 0.5m, a width of 0.2m and a height of 1.5m, and connect the positive and negative electrodes to the positive and negative electrodes of the external power supply respectively to assemble an electrochemical lithium extraction device based on a zinc-lithium hybrid ion battery system;

[0059] (2) Inject 3M ZnSO4 aqueous solution into the electrolytic cell until the liquid surface covers the two electrodes. Charge at room temperature, set the charging current to 2A and the charging cut-off voltage to 1.55V. After charging is completed, remove the ZnSO4 aqueous solution after electrolysis.

[0060] (3) Inject lithium-containing aqueous solution from the waste lithium-ion battery recycling section into the electrolytic cell until the liquid surface covers the two electrodes. Discharge at room temperature, set the discharge current to 2A and the discharge cutoff voltage to 0.8V. After the discharge is completed, remove the lithium-containing aqueous solution and rinse the cell and electrodes with distilled water.

[0061] (4) Then inject ZnSO4 aqueous solution until the liquid surface covers the two electrodes, charge at room temperature, set the charging current to 3A, and the charging cut-off voltage to 1.75V. After charging is completed, remove the electrolyzed ZnSO4 aqueous solution.

[0062] (5) Repeat steps (3)-(4) 25 times to extract lithium in multiple batches of lithium-ion battery recycling section lithium-containing aqueous solution. During this period, a new lithium-ion battery recycling section lithium-containing aqueous solution is used each time, but the same ZnSO4 aqueous solution is used repeatedly to finally obtain zinc-lithium mixed salt extract.

[0063] The ICP test results of the lithium-containing aqueous solution and the final zinc-lithium mixed extract after the first lithium extraction are shown in Table 2:

[0064] Table 2

[0065]

[0066] Example 3

[0067] A method for extracting lithium from brine in Qinghai Salt Lake includes the following steps:

[0068] (1) Use a 0.002×0.25×0.5m zinc plate as the negative electrode; mix 320g LiMn2O4 powder with water-washable battery binder LA133 and conductive carbon black in a ratio of 8:1:1, add 29L of distilled water and mix thoroughly, then coat evenly on a 0.2×0.5m 100-mesh titanium mesh, dry at 90℃ for 24 hours, and wrap with a double-layer nylon mesh as the positive electrode; put the positive and negative electrodes into a polytetrafluoroethylene electrolytic cell with a length of 0.3m, a width of 0.1m and a height of 0.7m, and connect the positive and negative electrodes to the positive and negative electrodes of the external power supply respectively to assemble an electrochemical lithium extraction device based on a zinc-lithium hybrid ion battery system;

[0069] (2) Inject 3M Zn(NO3)2 aqueous solution into the electrolytic cell until the liquid surface covers the two electrodes. Charge at room temperature, set the charging current to 1A and the charging cut-off voltage to 1.6V. After charging is completed, remove the Zn(NO3)2 aqueous solution after electrolysis.

[0070] (3) Then inject Qinghai salt lake brine into the electrolytic cell until the liquid surface covers the two electrodes. Discharge at room temperature, set the discharge current to 3A and the discharge cutoff voltage to 0.8V. After the discharge is completed, remove the lithium-containing aqueous solution and rinse the cell and electrodes with distilled water.

[0071] (4) Then inject Zn(NO3)2 extract into the electrolytic cell until the liquid surface covers the two electrodes. Charge at room temperature, set the charging current to 2A and the charging cut-off voltage to 1.7V. After charging is completed, remove the Zn(NO3)2 aqueous solution after electrolysis.

[0072] (5) Repeat steps (3)-(4) 20 times to extract lithium from multiple batches of Qinghai Salt Lake brine. Each time, a new Qinghai Salt Lake brine is used, but the same Zn(NO3)2 aqueous solution is used to finally obtain a zinc-lithium mixed salt extract.

[0073] The ICP test results of the lithium-containing aqueous solution and the final zinc-lithium mixed extract after the first lithium extraction are shown in Table 3:

[0074] Table 3

[0075]

[0076] Example 4

[0077] A method for extracting lithium from a lithium-containing aqueous solution in the recycling section of spent lithium-ion batteries includes the following steps:

[0078] (1) Using a 0.01×0.25×0.5m coarse-pore zinc mesh as the negative electrode, 300g of carbon-coated LiFePO4 powder, water-washable battery binder (LA133), and conductive carbon black were thoroughly mixed in a ratio of 8:1:1. After mixing thoroughly, 34L of distilled water was added and the mixture was evenly coated onto a 0.2×0.5m 100-mesh titanium mesh. After drying at 90℃ for 24 hours, it was wrapped with a double-layer nylon mesh and used as the positive electrode. The positive and negative electrodes were loaded into a polytetrafluoroethylene electrolytic cell with a length of 0.3m, a width of 0.1m, and a height of 0.7m. The positive and negative electrodes were connected to the positive and negative electrodes of an external power supply, respectively, to assemble an electrochemical lithium extraction device based on a zinc-lithium hybrid ion battery system.

[0079] (2) Inject 3M ZnCl2 aqueous solution into the electrolytic cell until the liquid surface covers the two electrodes, charge at room temperature, set the charging current to 1A and the charging cut-off voltage to 1.6V, and after charging is completed, remove the ZnCl2 aqueous solution after electrolysis.

[0080] (3) Then inject the lithium-containing aqueous solution from the waste lithium-ion battery recycling section into the electrolytic cell until the liquid surface covers the two electrodes. Discharge at room temperature, set the discharge current to 1A and the discharge cutoff voltage to 0.6V. After the discharge is completed, remove the lithium-containing aqueous solution and rinse the cell and electrodes with distilled water.

[0081] (4) Then inject ZnCl2 aqueous solution into the electrolytic cell until the liquid surface covers the two electrodes. Charge at room temperature, set the charging current to 1A and the charging cut-off voltage to 1.6V. After charging is completed, remove the ZnCl2 aqueous solution.

[0082] (5) Repeat steps (3)-(4) 30 times to extract lithium in multiple batches of lithium-ion battery recycling section lithium-containing aqueous solution. During this period, a new lithium-ion battery recycling section lithium-containing aqueous solution is used each time, but the same ZnCl2 aqueous solution is used repeatedly to finally obtain zinc-lithium mixed salt extract.

[0083] The ICP test results of the lithium-containing aqueous solution and the final zinc-lithium mixed extract after the first lithium extraction are shown in Table 4:

[0084] Table 4

[0085]

[0086] Example 5

[0087] A method for extracting lithium from brine in Qinghai Salt Lake includes the following steps:

[0088] (1) Use a 0.002×0.2×0.6m zinc plate as the negative electrode; mix 340g FePO4 powder with water-based battery binder LA133 and conductive carbon black in a ratio of 8:1:1, add 30L of distilled water and mix thoroughly, then coat evenly on a 0.2×0.6m 100-mesh silver wire mesh, dry at 90℃ for 24 hours, and wrap with a double-layer nylon mesh as the positive electrode; put the positive and negative electrodes into a polytetrafluoroethylene electrolytic cell with a length of 0.3m, a width of 0.1m and a height of 0.7m, and connect the positive and negative electrodes to the positive and negative electrodes of the external power supply respectively to assemble an electrochemical lithium extraction device based on a zinc-lithium hybrid ion battery system;

[0089] (2) Pour Qinghai salt lake brine into the electrolytic cell until the liquid surface covers the two electrodes. Discharge at room temperature. Set the discharge current to 3A and the discharge cut-off voltage to 0.75V. After the discharge is completed, remove the lithium-containing aqueous solution and rinse the cell and electrodes with distilled water.

[0090] (3) Then inject Zn(NO3)2 extract into the electrolytic cell until the liquid surface covers the two electrodes. Charge at room temperature, set the charging current to 2A and the charging cut-off voltage to 1.6V. After charging is completed, remove the Zn(NO3)2 aqueous solution after electrolysis.

[0091] (4) Repeat steps (2)-(3) 15 times to extract lithium from multiple batches of Qinghai Salt Lake brine. Each time, a new Qinghai Salt Lake brine is used, but the same Zn(NO3)2 aqueous solution is used to finally obtain a zinc-lithium mixed salt extract.

[0092] The ICP test results of the lithium-containing aqueous solution and the final zinc-lithium mixed extract after the first lithium extraction are shown in Table 5:

[0093] Table 5

[0094]

[0095] The above detailed description of the method for extracting lithium from a lithium-containing aqueous solution with reference to the embodiments is illustrative rather than limiting. Several embodiments may be listed within the defined scope. Therefore, variations and modifications without departing from the overall concept of the present invention should be within the protection scope of the present invention.

Claims

1. A method for extracting lithium from a lithium-containing aqueous solution, characterized in that, The method includes the following steps: (1) Using zinc or zinc alloy as the negative electrode and a positive current collector loaded with lithium-ion battery positive electrode material as the positive electrode, the two are placed in an electrolytic cell to assemble an electrochemical lithium extraction device based on a zinc-lithium hybrid ion battery system. (2) Inject lithium-containing aqueous solution into the electrolytic cell until the liquid surface covers the positive and negative electrodes, discharge, and after the discharge is completed, evacuate the lithium-containing aqueous solution after electrolysis and clean the electrolytic cell and positive and negative electrodes. (3) Then inject zinc ion-containing electrolyte into the electrolytic cell until the liquid surface covers the positive and negative electrodes, and charge it to extract lithium from the lithium-containing aqueous solution into the electrolyte. In step (1), the negative electrode is a sheet-like, rod-like, or mesh-like zinc or zinc alloy; the positive electrode is a positive current collector loaded with FePO4, LiFePO4, Mn2O4, or LiMn2O4, and the positive electrode is wrapped with multiple layers of nylon. When the positive electrode is loaded with a positive current collector of LiFePO4 or LiMn2O4, a pre-charging is required between steps (1) and (2). The pre-charging method is as follows: inject zinc ion-containing electrolyte into the electrolytic cell until the liquid surface covers the positive and negative electrodes, charge, and after charging, evacuate the zinc ion-containing electrolyte after electrolysis, and clean the electrolytic cell and the positive and negative electrodes.

2. The method for extracting lithium from a lithium-containing aqueous solution according to claim 1, characterized in that, In step (3), after extracting lithium from the lithium-containing aqueous solution into the electrolyte, an alkaline solution is added to the electrolyte. After the precipitation is complete, the solution is filtered, and the resulting precipitate is LiOH·H2O.

3. The method for extracting lithium from a lithium-containing aqueous solution according to claim 1, characterized in that, The pre-charging conditions are: temperature controlled between 0-90 ℃, and charging current density between 0.1-200 A / m. 2 The charging continues until the charging is complete, with the charging cut-off voltage being 0.1-2.5 V.

4. The method for extracting lithium from a lithium-containing aqueous solution according to claim 1, characterized in that, In step (2), the discharge conditions are: the temperature is controlled at 0-90 ℃ for discharge, and the current density is 0.1-1200 A / m. 2 The discharge continues until the discharge ends, with a discharge cutoff voltage of 0-1.5 V.

5. The method for extracting lithium from a lithium-containing aqueous solution according to claim 1, characterized in that, In step (3), the charging conditions are: the charging temperature is controlled at 0-90 ℃, and the current density is 0.1-500 A / m. 2 The charging continues until the charging is complete, with the charging cut-off voltage being 0.1-2.0 V.

6. The method for extracting lithium from a lithium-containing aqueous solution according to claim 1, characterized in that, The zinc ion-containing electrolyte is an aqueous solution of any one or more of ZnCl2, ZnSO4, and Zn(NO3)2.

7. The method for extracting lithium from a lithium-containing aqueous solution according to claim 1, characterized in that, The method further includes the following steps: repeatedly performing steps (2) and (3), repeatedly discharging the same lithium-containing aqueous solution, and / or repeatedly charging the same zinc-containing electrolyte.

8. The method for extracting lithium from a lithium-containing aqueous solution according to claim 1, characterized in that, The positive and negative electrodes are at least one set, and when there are multiple sets of positive and negative electrodes, the positive and negative electrodes are arranged alternately in the electrolytic cell.

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