Electrochemical lithium extraction electrode based on structured packing, three-chamber electrochemical lithium extraction system and lithium extraction method

Abstract

The invention relates to an electrochemical lithium extraction electrode based on structured packing, a three-chamber electrochemical lithium extraction system and a lithium extraction method. The invention innovatively adopts a three-chamber electrochemical lithium extraction system based on a structured packing electrode. On one hand, the structured packing has multistage pore channels, the loading capacity of an electrode active material is remarkably improved due to the characteristic of high specific surface area, the complex degree of a device is simplified due to cooperative treatment of multiple pairs of electrodes, and a flow field is optimized, so that the cycling stability of electrochemical lithium extraction is effectively improved; and on the other hand, the middle buffer chamber is introduced to decouple the lithium ion embedding and releasing process in a traditional two-chamber electrochemical lithium extraction system, and independent regulation and control of lithium ion embedding and releasing potential and current are realized, so that the problems caused by dynamic unbalance are effectively solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrochemical lithium extraction, and particularly relates to an electrochemical lithium extraction electrode based on regular packing, a three-chamber electrochemical lithium extraction system and a lithium extraction method. BACKGROUND

[0002] Lithium, as a core element of global clean energy transformation, has attracted much attention due to its irreplaceable role in lithium-ion batteries for electric vehicles, portable electronic devices and energy storage systems. With the continuous rise in demand for renewable energy technologies, the global lithium market is expected to grow exponentially, which puts an urgent demand for green and efficient lithium resource extraction technologies. Lithium-containing solutions, especially salt lake brines, have the advantages of low development cost and abundant reserves, and have become a strategic development direction for lithium resource extraction. However, traditional lithium extraction technologies (such as solvent extraction, membrane separation and electrodialysis) for high magnesium-lithium ratio or high sodium-lithium ratio brines generally face problems such as low selectivity, high process energy consumption and environmental pollution caused by the use of chemical reagents, and therefore there is an urgent need to develop more advanced technology systems. The electrochemical selective lithium extraction strategy based on redox active materials shows broad application prospects due to its advantages such as high selectivity, controllability and environmental friendliness.

[0003] In the traditional two-chamber electrochemical lithium extraction system based on the electrode system of redox active materials, lithium ion intercalation occurs in the cathode activated electrochemical lithium extraction electrode, while lithium ion deintercalation occurs in the anode unactivated electrochemical lithium extraction electrode. However, there are still some bottlenecks in the practical application of this system: (1) when extracting lithium from ultra-low concentration lithium-containing solutions, severe concentration polarization occurs at the cathode, and oxygen evolution side reactions occur at the anode under low current density, leading to the co-intercalation of hydrogen ions and other side reactions, causing manganese dissolution and structural damage, and ultimately leading to continuous capacity decay, which cannot realize lithium extraction in ultra-low lithium-containing solutions; (2) the rate imbalance between rapid intercalation and slow deintercalation of lithium ions and the spontaneous intercalation behavior of the activated electrochemical lithium extraction electrode lead to the premature capacity of the activated electrochemical lithium extraction electrode and the far lagging deintercalation reaction of the unactivated electrochemical lithium extraction electrode, causing a sharp drop in current, prolonging the reaction time, and problems such as manganese dissolution at the later stage of the cycle, directly leading to electrode structure damage and rapid decay of cycle stability; (3) anion exchange membranes undergo transmembrane penetration of competing ions (such as ) driven by a large concentration difference, causing cross-contamination and reducing the purity of lithium products; (4) high operating cell voltage leads to high energy consumption, which restricts industrial application. In addition, the traditional two-chamber electrochemical lithium extraction system has complex operation and high assembly difficulty when multiple electrodes are used for collaborative treatment, and is prone to liquid leakage. In addition, uneven flow distribution leads to local over-concentration / under-concentration, exacerbating concentration polarization, which leads to manganese dissolution, affects long-term cycling and other problems. SUMMARY

[0004] In view of the problems in the prior art, the present application innovatively adopts a three-chamber electrochemical lithium extraction system based on a structured packing electrode. On the one hand, the structured packing has multiple levels of pores, and the high specific surface area feature significantly improves the loading capacity of the electrode active material, avoids the cooperative treatment of multiple pairs of electrodes, simplifies the complexity of the device, optimizes the flow field, and thus effectively improves the cycle stability of electrochemical lithium extraction. On the other hand, the introduction of the intermediate buffer chamber decouples the lithium ion intercalation and extraction processes in the traditional two-chamber electrochemical lithium extraction system, realizes independent regulation of the lithium ion intercalation and extraction potentials and currents, and thus effectively solves the problems caused by kinetic imbalance.

[0005] To achieve the object of the present application, the first aspect of the present application relates to an electrochemical lithium extraction electrode based on structured packing, which is composed of electrode active material powder uniformly loaded inside the structured packing.

[0006] According to a preferred embodiment of the present application, the structured packing is electrically conductive, and its material includes stainless steel, copper, aluminum, titanium, molybdenum-titanium alloy, or any combination thereof, and its form includes hole plate corrugated packing, plate mesh corrugated packing, spiked hole plate corrugated packing, wire mesh corrugated packing, ring-shaped corrugated packing, honeycomb packing, or any combination thereof.

[0007] The electrochemical lithium extraction electrode based on structured packing is prepared by the following method: The electrode active material powder is mixed with an organic solvent, a binder, a conductive agent, and an organic pore-forming agent to obtain a precursor solution; the structured packing is completely immersed in the precursor solution, so that the electrode active material powder is uniformly loaded inside the structured packing, thereby obtaining the electrochemical lithium extraction electrode based on structured packing.

[0008] According to a preferred embodiment of the present application, the electrode active material includes LiMn2O4, Li4Mn5O 12 , Li 1.6 Mn 1.6 O4, Li4Ti5O 12 , LiTi2O3, LiFePO4.

[0009] According to a preferred embodiment of the present application, the organic solvent includes N-methyl pyrrolidone, N-ethyl pyrrolidone, N-vinyl pyrrolidone, dimethyl formamide, dimethyl acetamide, or any combination thereof.

[0010] According to a preferred embodiment of the present application, the binder includes polyvinyl chloride, polyvinylidene fluoride, polytetrafluoroethylene, butylbenzene, water-based polyvinyl acetate, or any combination thereof.

[0011] According to a preferred embodiment of the present application, the conductive agent includes carbon black, acetylene black, graphite, carbon fiber, carbon nanotube, graphene, composite conductive paste, or any combination thereof.

[0012] According to a preferred embodiment of the present application, the organic pore forming agent comprises polystyrene, polyethylene glycol, polyvinyl chloride, polyoxymethylene, epoxy resin, polyglycolic acid, lignin, cellulose, hemicellulose, or any combination thereof.

[0013] According to a preferred embodiment of the present application, the weight ratio of the electrode active material powder, the organic solvent, the binder, the electrically conductive agent, and the organic pore-forming agent is 8 : 1-10 : 1-10 : 1-10 : 1-3. According to a further preferred embodiment of the present application, the weight ratio of the electrode active material powder, the organic solvent, the binder, the electrically conductive agent, and the organic pore-forming agent is 8 : 1 : 1-10 : 1-10 : 1-3, 8 : 2 : 1-10 : 1-10 : 1-3, 8 : 3 : 1-10 : 1-10 : 1-3, 8 : 4 : 1-10 : 1-10 : 1-3, 8 : 5 : 1-10 : 1-10 : 1-3, 8 : 6 : 1-10 : 1-10 : 1-3, 8 : 7 : 1-10 : 1-10 : 1-3, 8 : 8 : 1-10 : 1-10 : 1-3, 8 : 9 : 1-10 : 1-10 : 1-3, 8 : 10 : 1-10 : 1-10 : 1-3, 8 : 1-10 : 1 : 1-10 : 1-3, 8 : 1-10 : 2 : 1-10 : 1-3, 8 : 1-10 : 3 : 1-10 : 1-3, 8 : 1-10 : 4 : 1-10 : 1-3, 8 : 1-10 : 5 : 1-10 : 1-3, 8 : 1-10 : 6 : 1-10 : 1-3, 8 : 1-10 : 7 : 1-10 : 1-3, 8 : 1-10 : 8 : 1-10 : 1-3, 8 : 1-10 : 9 : 1-10 : 1-3, 8 : 1-10 : 10 : 1-10 : 1-3, 8 : 1-10 : 1-10 : 1 : 1-3, 8 : 1-10 : 1-10 : 2 : 1-3, 8 : 1-10 : 1-10 : 3 : 1-3, 8 : 1-10 : 1-10 : 4 : 1-3, 8 : 1-10 : 1-10 : 5 : 1-3, 8 : 1-10 : 1-10 : 6 : 1-3, 8 : 1-10 : 1-10 : 7 : 1-3, 8 : 1-10 : 1-10 : 8 : 1-3, 8 : 1-10 : 1-10 : 9 : 1-3, 8 : 1-10 : 1-10 : 10 : 1-3, 8 : 1-10 : 1-10 : 1-10 : 1, 8 : 1-10 : 1-10 : 1-10 : 2, or 8 : 1-10 : 1-10 : 1-10 : 3.

[0014] According to a preferred embodiment of the present application, the step of uniformly loading the electrode active material powder inside the structured packing is performed under the condition of water bath heating and stirring. According to a preferred embodiment of the present application, the temperature of the water bath heating is 30-90℃. According to a further preferred embodiment of the present application, the temperature of the water bath heating is 30℃, 40℃, 50℃, 60℃, 70℃, 80℃ or 90℃. According to a preferred embodiment of the present application, the stirring time is 1-10h. According to a further preferred embodiment of the present application, the stirring time is 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h or 10h.

[0015] After uniformly loading the electrode active material powder inside the structured packing, the organic solvent is removed by heating. According to a preferred embodiment of the present application, the heating temperature is 40-120℃ and the heating time is 2-24h. According to a further preferred embodiment of the present application, the heating temperature is 40℃, 50℃, 60℃, 70℃, 80℃, 90℃, 100℃, 110℃ or 120℃. According to a further preferred embodiment of the present application, the heating time is 2h, 4h, 6h, 8h, 10h, 12h, 14h, 16h, 18h, 20h, 22h or 24h.

[0016] According to a preferred embodiment of the present application, the step of removing the organic pore-forming agent to form pores is further included. According to a preferred embodiment of the present application, the organic pore-forming agent is removed to form pores by heating to 150-350℃. According to a further preferred embodiment of the present application, the organic pore-forming agent is removed to form pores by heating to 150℃, 160℃, 170℃, 180℃, 190℃, 200℃, 210℃, 220℃, 230℃, 240℃, 250℃, 260℃, 270℃, 280℃, 290℃, 300℃, 310℃, 320℃, 330℃, 340℃ or 350℃. As for the step of removing the organic pore-forming agent to form pores, detailed descriptions have been made in patent application 202210656925.6 (publication date: August 2, 2022) filed to the State Intellectual Property Office of China on June 10, 2022, the entire contents of which are incorporated herein by reference. By the type of the organic pore-forming agent and the amount, particle size of the organic pore-forming agent added, the pore diameter and porosity of the electrode can be controlled.

[0017] Before use, the electrochemical lithium extraction electrode based on the structured packing is electrochemically activated to obtain an activated electrochemical lithium extraction electrode based on the structured packing. As for the detailed electrochemical activation process, detailed descriptions have been made in patent application 202211254215.7 (publication date: December 27, 2022) filed to the State Intellectual Property Office of China on October 13, 2022, the entire contents of which are incorporated herein by reference.

[0018] To achieve the object of the present application, the second aspect of the present application relates to a three-chamber electrochemical lithium extraction system.

[0019] The three-chamber electrochemical lithium extraction system is composed of a cathode chamber, an intermediate buffer chamber and an anode chamber, the cathode chamber and the intermediate buffer chamber and the intermediate buffer chamber and the anode chamber are separated by an anion exchange membrane respectively; the anode chamber contains a salt solution and an unactivated electrochemical lithium extraction electrode based on a structured packing, which forms a first electrochemical loop with one conductive electrode in the intermediate buffer chamber; the cathode chamber contains a lithium-containing solution and an activated electrochemical lithium extraction electrode based on a structured packing, which forms a second electrochemical loop with another conductive electrode in the buffer chamber; the intermediate buffer chamber contains a solution of a redox couple.

[0020] In the present application, the term "salt solution" refers to a solution of inorganic soluble salt. According to a preferred embodiment of the present application, the salt solution includes a solution containing at least one of Cl - , SO4 2- , SO3 2- , NO3 - , NO2 - , PO4 3- , CO3 2- , chlorate, perchlorate. According to a preferred embodiment of the present application, the concentration of the salt solution is 0.1-10 mol / L. According to a further preferred embodiment of the present application, the concentration of the salt solution is 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L or 10 mol / L.

[0021] According to a preferred embodiment of the present application, the pH of the salt solution is 5-14. According to a further preferred embodiment of the present application, the pH of the salt solution is 5, 6, 7, 8, 9, 10, 11, 12, 13 or 14.

[0022] According to a preferred embodiment of the present application, the conductive electrode is an inert conductive electrode. According to a further preferred embodiment of the present application, the conductive electrode includes at least one of a carbon electrode, a graphite electrode, a carbon cloth electrode, a titanium electrode, a glassy carbon electrode, a carbon felt electrode, a platinum electrode, a gold electrode, a stainless steel electrode, a copper electrode, a silver electrode, an aluminum electrode, a metal alloy electrode.

[0023] According to a preferred embodiment of the present application, the lithium-containing solution is a naturally occurring or configured lithium-rich solution, including brine, geothermal water, gas field water, or other lithium-rich solutions. According to a preferred embodiment of the present application, the concentration of lithium ions in the lithium-containing solution is greater than 2 ppm. According to a further preferred embodiment of the present application, the concentration of lithium ions in the lithium-containing solution is 300 ppm, 200 ppm, 150 ppm, 100 ppm, 50 ppm, 10 ppm.

[0024] According to a preferred embodiment of the present application, the pH of the lithium-containing solution is 5-14. According to a further preferred embodiment of the present application, the pH of the lithium-containing solution is 5, 6, 7, 8, 9, 10, 11, 12, 13, or 14.

[0025] According to a preferred embodiment of the present application, the redox couple has no particular restrictions, and is merely an electron donor or acceptor. According to a further preferred embodiment of the present application, the redox couple includes, but is not limited to, Fe 2+ / Fe 3+ , I - / I3 - , Cu 2+ / Cu + , [Fe(CN)6] 3- / [Fe(CN)6] 4- , MnO4 - / Mn 2+ , Cr2O7 2- / Cr 3+ , Ce 4+ / Ce 3+ .

[0026] According to a preferred embodiment of the present application, the concentration of the solution of the redox couple is 0.1-10 mol / L. According to a further preferred embodiment of the present application, the concentration of the solution of the redox couple is 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L, or 10 mol / L.

[0027] According to a preferred embodiment of the present application, the pH of the solution of the redox couple is 2-4. According to a further preferred embodiment of the present application, the pH of the solution of the redox couple is 2, 3, or 4.

[0028] In the present application, the anion exchange membrane is a membrane with selective permeability to anions. According to a preferred embodiment of the present application, the anion exchange membrane includes but is not limited to AMVN, DSVN, AAM, CAM, and ASE. To achieve the object of the present application, the third aspect of the present application relates to a lithium extraction method based on a three-chamber electrochemical lithium extraction system, comprising the following steps: A constant current is applied on the first electrochemical loop and the second point chemical loop of the three-chamber electrochemical lithium extraction system respectively, and after reaching the cut-off voltage, a constant voltage is switched to independently regulate the lithium intercalation and lithium extraction processes; after the lithium intercalation and lithium extraction are completed, the electrodes in the anode chamber and the electrodes in the cathode chamber are taken out, washed and exchanged positions, and the above steps are repeated for subsequent multiple cycles.

[0029] The lithium intercalation and lithium extraction processes occurring on the two loops can be performed synchronously or distributedly.

[0030] According to a preferred embodiment of the present application, the applied constant current is 2-50 A / m 2 . According to a further preferred embodiment of the present application, the applied constant current is 2 A / m 2 , 5 A / m 2 , 10 A / m 2 , 15 A / m 2 , 20 A / m 2 , 25 A / m 2 , 30 A / m 2 , 35 A / m 2 , 40 A / m 2 , 45 A / m 2 or 50 A / m 2 .

[0031] According to a preferred embodiment of the present application, the cut-off voltage is 0.3-1.2 V. According to a further preferred embodiment of the present application, the voltage for lithium extraction is 0.3 V, 0.4 V, 0.5 V, 0.6 V, 0.7 V, 0.8 V, 0.9 V, 1.0 V, 1.1 V or 1.2 V.

[0032] According to a preferred embodiment of the present application, the time for lithium extraction is 1-100 h. According to a further preferred embodiment of the present application, the time for lithium extraction is 1 h, 5 h, 10 h, 20 h, 30 h, 40 h, 50 h, 60 h, 70 h, 80 h, 90 h or 100 h.

[0033] The number of cycles is determined according to the concentration of lithium ions in the lithium-containing solution in the cathode chamber. According to a preferred embodiment of the present application, the number of cycles can be 3-500 times.

[0034] Compared with the prior art, the present application has the following beneficial effects: 1. The regular filler itself has multiple levels of channels, has the characteristics of large specific surface area, small pressure drop and uniform fluid distribution, can significantly increase the loading capacity of electrode active material, replace the multi-pair electrode stacking architecture, solve the problems of high assembly complexity and large interface contact impedance of traditional multi-pair electrode, effectively reduce the operation difficulty of the device, optimize the flow field, significantly reduce the concentration polarization, and be easy to industrialize; 2. The three-chamber structure allows independent regulation of the current and potential of the lithium intercalation and deintercalation process, effectively solves the capacity decay and manganese capacity loss problems caused by the mismatch between adsorption and desorption rates, and significantly improves the cycle stability of the electrochemical lithium extraction electrode; 3. The three-chamber structure separates the desorption chamber from the adsorption chamber due to the introduction of the buffer chamber, which effectively solves the problem of impurity ion transmembrane pollution caused by the large concentration difference between the anode and cathode chambers, and significantly improves the purity of lithium ions in the desorption process; 4. The introduction of the redox couple in the buffer chamber effectively reduces the cell voltage and reduces the reaction energy consumption. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 A schematic diagram of the three-chamber electrochemical lithium extraction system of Example 1 is shown; Figure 2 The lithium ion adsorption and desorption capacity and manganese solution loss rate of Example 1 within 10 cycles are shown; Figure 3 The lithium ion adsorption and desorption capacity and manganese solution loss rate of Comparative Example 1 within 10 cycles are shown; Figure 4 The lithium ion adsorption and desorption capacity and manganese solution loss rate of Comparative Example 2 within 10 cycles are shown; Figure 5 The lithium ion adsorption and desorption capacity and manganese solution loss rate of Comparative Example 3 within 10 cycles are shown; Figure 6 The lithium ion adsorption and desorption capacity and manganese solution loss rate of Example 2 within 10 cycles are shown; Figure 7 The lithium ion adsorption and desorption capacity and manganese solution loss rate of Comparative Example 4 within 10 cycles are shown; Figure 8 The lithium ion adsorption and desorption capacity and manganese solution loss rate of Comparative Example 5 within 10 cycles are shown; Figure 9 The lithium ion adsorption and desorption capacity and manganese solution loss rate of Example 3 within 10 cycles are shown. DETAILED DESCRIPTION

[0036] In order to better explain the present application, the following specific examples are combined for further explanation, but the present application is not limited to the specific examples.

[0037] Example 1 LiMn2O4 powder was mixed with organic solvent N-methyl pyrrolidone, binder polytetrafluoroethylene, conductive agent acetylene black, organic pore-forming agent polyvinyl chloride in weight ratio of 8:5:1:1:2, stirred at 60°C for 2h to obtain a precursor solution; then the regular packing in the form of honeycomb packing of titanium material was completely immersed in the precursor solution, stirred at 50°C water bath temperature for 8h to make LiMn2O4 powder uniformly loaded in the regular packing; heated at 70°C for 4h to remove the organic solvent; heated at 150°C for 2h to remove the organic pore-forming agent, to obtain LiMn2O4 electrodes A and B based on regular packing.

[0038] Electrode A was placed in the anode chamber of the device for activating the electrode as an anode and 0.1 mol / L Li2SO4 solution with pH of 7; a titanium plate was placed in the cathode chamber of the device for activating the electrode as a cathode and 0.5 mol / L CuCl2 solution, the cathode chamber and the anode chamber were separated by anion exchange membrane ASE. A constant current of 20 A / m 2 The activated electrode A was obtained by constant current activation for 10h.

[0039] The activated electrode A was placed in the cathode chamber of the three-chamber electrochemical lithium extraction system as a cathode and a solution containing 200ppm lithium with pH of 7, a titanium plate in the middle buffer chamber as an anode, forming a first electrochemical circuit with the activated electrode A, the cathode chamber and the middle buffer chamber were separated by anion exchange membrane ASE; the middle buffer chamber was placed in 0.5 mol / L FeCl2 and FeCl3 solutions with pH of 3; the unactivated electrode B was placed in the anode chamber as an anode and 0.1 mol / L LiCl solution with pH of 7, another titanium plate in the buffer chamber as a cathode, forming a second electrochemical circuit with the unactivated electrode B, the middle buffer chamber and the anode chamber were separated by anion exchange membrane ASE.

[0040] A constant current of 10 A / m 2 was applied to the first electrochemical circuit until the voltage reached 0.6V, then lithium extraction was carried out at 0.6V constant voltage for 10h. A constant current of 30 A / m 2 was applied to the second electrochemical circuit until the voltage reached 0.8V, then lithium extraction was carried out at 0.8V constant voltage for 10h. After the end of lithium extraction and lithium extraction, electrode A, electrode B were taken out and the surface of the electrode was washed, then electrode B was placed in the cathode chamber of the three-chamber electrochemical lithium extraction system, electrode A was placed in the anode chamber of the three-chamber electrochemical lithium extraction system, and the second cycle was carried out, the operation conditions were the same as the first time, and the cycle was carried out for 10 times. Finally, the solution in the anode chamber was concentrated, and Na2CO3 was added to obtain lithium carbonate product.

[0041] Figure 2The lithium ion adsorption and desorption capacity and manganese dissolution rate of Example 1 within 10 cycles are shown. Li + The adsorption amount of Li can reach 35.852 mg / g, the capacity retention rate is 98.95%, the Mn dissolution rate is 0.00113%, and the overall recovery rate of Li + The overall recovery rate of Li can reach more than 98.73%.

[0042] Comparative Example 1 LiMn2O4 powder, organic solvent N-methyl pyrrolidone, binder polytetrafluoroethylene, conductive agent acetylene black, and organic pore-forming agent polyvinyl chloride were mixed in a weight ratio of 8:5:1:1:2, stirred at 60°C for 2h to obtain a precursor solution; 4g of the precursor solution was uniformly coated on two titanium plates, and the coating thickness was 2mm; the organic solvent was removed by heating at 70°C for 4h; the organic pore-forming agent was removed by heating at 150°C for 2h to obtain LiMn2O4 electrodes A and B.

[0043] Electrode A was placed in the anode chamber of the electrode activation device as the anode and 0.1 mol / L Li2SO4 solution with pH 7; a titanium plate was placed in the cathode chamber of the electrode activation device as the cathode and 0.5 mol / L CuCl2 solution, and the cathode chamber and the anode chamber were separated by an anion exchange membrane ASE. A constant current of 20A / m 2 was applied for 10h to obtain the activated electrode A.

[0044] The activated electrode A was placed in the cathode chamber of the three-chamber electrochemical lithium extraction system as the cathode and a solution containing 200ppm lithium with pH 7, and a titanium plate in the middle buffer chamber as the anode, forming a first electrochemical circuit with the activated electrode A, and the cathode chamber and the middle buffer chamber were separated by an anion exchange membrane ASE; the middle buffer chamber was placed in 0.5 mol / L FeCl2 and FeCl3 solutions with pH 3; the unactivated electrode B was placed in the anode chamber as the anode and 0.1 mol / L LiCl solution with pH 7, and another titanium plate in the buffer chamber as the cathode, forming a second electrochemical circuit with the unactivated electrode B, and the middle buffer chamber and the anode chamber were separated by an anion exchange membrane ASE.

[0045] A constant current of 10A / m 2 was applied on the first electrochemical circuit until the voltage reached 0.6V, and then lithium extraction was carried out at a constant voltage of 0.6V for 10h. A constant current of 30A / m 2constant current until the voltage reaches 0.8 V, and then constant voltage at 0.8 V for 10 h. After the lithium extraction and the end of the delithiation, electrode A and electrode B were taken out and the surface of the electrodes was rinsed, then electrode B was put into the cathode chamber of the three-chamber electrochemical lithium extraction system, and electrode A was put into the anode chamber of the three-chamber electrochemical lithium extraction system, and a second cycle was carried out, with the same operation conditions as the first cycle, for 10 times. Finally, the solution in the anode chamber was concentrated, and Na2CO3 was added to obtain a lithium carbonate product.

[0046] Figure 3 The lithium ion adsorption and desorption capacity and the manganese dissolution loss rate of Comparative Example 1 within 10 cycles are shown. Li + The adsorption capacity of Li + The overall recovery rate was only 75.53%.

[0047] Compared with Example 1, the adsorption capacity and capacity maintenance rate of Li + decreased, and the manganese dissolution loss rate increased sharply. This is because the introduction of the structured packing in Example 1 significantly improved the loading capacity of the electrode active material, while the traditional titanium plate electrode in Comparative Example 1 did not have the porous structure and high specific surface area characteristics possessed by the structured packing, and the larger electrode thickness led to low active material loading and increased lithium ion diffusion resistance; on the other hand, the introduction of the structured packing in Example 1 optimized the flow field and reduced the concentration polarization, while the flow field in Comparative Example 1 was poor, leading to an increase in concentration polarization effect during lithium extraction, resulting in a sharp increase in manganese dissolution loss and further leading to capacity decay.

[0048] Comparative Example 2 LiMn2O4 powder, organic solvent N-methyl pyrrolidone, binder polytetrafluoroethylene, conductive agent acetylene black, and organic pore-forming agent polyvinyl chloride were mixed in a weight ratio of 8:5:1:1:2, stirred at 60°C for 2 h to obtain a precursor solution; 4 g of the precursor solution was uniformly coated on two titanium plates, with a coating thickness of 2 mm; the titanium plates were heated at 70°C for 4 h to remove the organic solvent; and the titanium plates were heated at 150°C for 2 h to remove the organic pore-forming agent, to obtain LiMn2O4 electrodes A and B.

[0049] Electrode A was placed in the anode chamber of the electrode activation device as the anode and 0.1 mol / L Li2SO4 solution with a pH of 7 was placed in the cathode chamber of the electrode activation device as the cathode, and the cathode chamber and the anode chamber were separated by an anion exchange membrane ASE. The current density was 20 A / m 2 The electrode was activated at a constant current for 10 h to obtain the activated electrode A.

[0050] Activated electrode A was placed as cathode in the cathode chamber of the traditional two-chamber electrochemical lithium extraction system and the solution containing 200 ppm lithium with pH of 7 was placed as electrolyte, and unactivated electrode B was placed as anode in the anode chamber of the traditional two-chamber electrochemical lithium extraction system and the LiCl solution with concentration of 0.1 mol / L and pH of 7 was placed as electrolyte, and the anode chamber and the cathode chamber were separated by anion exchange membrane ASE.

[0051] A constant current of 20 A / m 2 was applied until the voltage reached 1.2 V, and then lithium extraction was carried out at a constant voltage of 1.2 V for 20 h. After the end, electrode A and electrode B were taken out and the surface of the electrode was rinsed, and then electrode A was placed in the anode chamber of the two-chamber electrochemical lithium extraction system and electrode B was placed in the cathode chamber of the traditional two-chamber electrochemical lithium extraction system, and the second cycle was carried out, and the operation conditions were the same as the first time, and the cycle was 10 times. Finally, the solution in the anode chamber was concentrated, and Na2CO3 was added to obtain lithium carbonate product.

[0052] Figure 4 The lithium ion adsorption and desorption capacity and manganese dissolution loss rate of Comparative Example 2 in 10 cycles are shown. Li + The adsorption amount of Li + The overall recovery rate of Li

[0053] Compared with Example 1 and Comparative Example 1, the adsorption amount of Li + and the capacity retention rate are significantly reduced. This is because, on the one hand, the traditional titanium plate electrode does not have the porous structure and high specific surface area characteristics possessed by the structured packing, and the active material loading is low and the flow field is poor; on the other hand, the traditional two-chamber electrochemical lithium extraction system cannot independently regulate the lithium intercalation and deintercalation during lithium extraction, resulting in a serious imbalance between lithium intercalation and deintercalation rates, and thus a large amount of manganese dissolution and capacity decay problems. In addition, compared with Example 1 and Comparative Example 1, the cell voltage in Comparative Example 2 increases significantly, because the redox couple cannot be introduced in this example to reduce the cell voltage.

[0054] Comparative Example 3 LiMn2O4 powder was mixed with organic solvent N-methyl pyrrolidone, binder polytetrafluoroethylene, conductive agent acetylene black, and organic pore-forming agent polyvinyl chloride at a weight ratio of 8:5:1:1:2, stirred at 60°C for 2h to obtain a precursor solution; then the structured packing in the form of titanium material honeycomb packing was completely immersed in the precursor solution, and stirred at a water bath temperature of 50°C for 8h to make the LiMn2O4 powder uniformly loaded inside the structured packing; heated at 70°C for 4h to remove the organic solvent; heated at 150°C for 2h to remove the organic pore-forming agent, to obtain LiMn2O4 electrodes A and B based on structured packing.

[0055] Electrode A and a 0.1 mol / L Li₂SO₄ solution at pH 7 were placed in the anode chamber of the device for activating the electrode; a titanium plate and a 0.5 mol / L CuCl₂ solution were placed in the cathode chamber of the device for activating the electrode. The cathode and anode chambers were separated by an anion exchange membrane (ASE). At 20 A / m 2 Electrode A was obtained by activating with a constant current for 10 hours.

[0056] In a conventional two-chamber electrochemical lithium extraction system, an activated electrode A is placed in the cathode chamber as the cathode and a solution containing 200 ppm lithium at pH 7. An unactivated electrode B is placed in the anode chamber as the anode and a LiCl solution with a concentration of 0.1 mol / L and pH 7. The anode and cathode chambers are separated by an anion exchange membrane ASE.

[0057] Apply 20A / m 2 A constant current was applied until the voltage reached 1.2V, and lithium extraction was then carried out at a constant voltage of 1.2V for 20 hours. After completion, electrodes A and B were removed and their surfaces were rinsed. Electrode A was then placed in the anode chamber of a two-chamber electrochemical lithium extraction system, and electrode B was placed in the cathode chamber of a conventional two-chamber electrochemical lithium extraction system for a second cycle, with the operating conditions the same as the first cycle, for a total of 10 cycles. Finally, the solution in the anode chamber was concentrated, and Na2CO3 was added to obtain lithium carbonate product.

[0058] Figure 5 The lithium-ion adsorption / desorption capacity and manganese dissolution rate of Comparative Example 3 over 10 cycles are shown. + The highest adsorption capacity was 22.122 mg / g, with a capacity retention of 18.13%, and a dissolution rate of 5.12% for Mn and Li. + The overall recovery rate was 62.53%.

[0059] Compared to Comparative Example 2, the introduction of structured packing increased the loading of the electrode active material and optimized the flow field, resulting in improved Li... + The adsorption capacity increased slightly, and the Mn dissolution rate decreased. However, due to the inability to independently control lithium insertion and delithiation, a severe imbalance occurred in the lithium insertion and delithiation rates during the lithium extraction process, still resulting in significant manganese dissolution and capacity decay.

[0060] Example 2 LiMn2O4 powder was mixed with organic solvent N-methylpyrrolidone, binder polytetrafluoroethylene, conductive agent acetylene black, and organic pore-forming agent polyvinyl chloride in a weight ratio of 8:5:1:1:2 and stirred at 60°C for 2 hours to obtain a precursor solution. Then, a structured packing material in the form of a titanium honeycomb filler was completely immersed in the precursor solution and stirred at 50°C for 8 hours to uniformly load the LiMn2O4 powder inside the structured packing. The organic solvent was removed by heating at 70°C for 4 hours and the organic pore-forming agent was removed by heating at 150°C for 2 hours to obtain LiMn2O4 electrodes A and B based on the structured packing.

[0061] Electrode A and a 0.1 mol / L Li₂SO₄ solution at pH 7 were placed in the anode chamber of the device for activating the electrode; a titanium plate and a 0.5 mol / L CuCl₂ solution were placed in the cathode chamber of the device for activating the electrode. The cathode and anode chambers were separated by an anion exchange membrane (ASE). At 20 A / m 2 Electrode A was obtained by activating with a constant current for 10 hours.

[0062] In a three-chamber electrochemical lithium extraction system, an activated electrode A is placed in the cathode chamber as the cathode, along with a solution containing 50 ppm lithium at pH 7. A titanium plate in the intermediate buffer chamber serves as the anode, forming the first electrochemical circuit with the activated electrode A. The cathode chamber and the intermediate buffer chamber are separated by an anion exchange membrane (ASE). The intermediate buffer chamber contains FeCl2 and FeCl3 solutions, both at a concentration of 0.5 mol / L and a pH of 3. In the anode chamber, an unactivated electrode B is placed as the anode, along with a LiCl solution at a concentration of 0.1 mol / L and a pH of 7. Another titanium plate in the buffer chamber serves as the cathode, forming the second electrochemical circuit with the unactivated electrode B. The intermediate buffer chamber and the anode chamber are separated by an anion exchange membrane (ASE).

[0063] Apply 5A / m to the first electrochemical circuit 2 A constant current was applied until the voltage reached 0.5V, and then lithium extraction was performed at a constant voltage of 0.5V for 10 hours. A current of 30A / m was applied to the second electrochemical circuit. 2 A constant current was applied until the voltage reached 0.8V, and then lithium removal was performed at a constant voltage of 0.8V for 10 hours. After lithium extraction and removal, electrodes A and B were removed and their surfaces were rinsed. Electrode B was then placed in the cathode chamber of the three-chamber electrochemical lithium extraction system, and electrode A was placed in the anode chamber for a second cycle under the same operating conditions, for a total of 10 cycles. Finally, the solution in the anode chamber was concentrated, and Na₂CO₃ was added to obtain lithium carbonate product.

[0064] Figure 6 The lithium-ion adsorption / desorption capacity and manganese dissolution rate of Example 2 over 10 cycles are shown.+ The adsorption capacity of Li+ can reach 28.762 mg / g, the capacity retention rate is 98.73%, the Mn dissolution rate is 0.00013%, and the Li + The overall recovery rate can reach more than 99.23%.

[0065] Compared with Example 1, the adsorption capacity of Example 2 slightly decreases, which is caused by the decrease of lithium ion concentration in the initial solution. The current applied in the first electrochemical circuit decreases, which is caused by the decrease of lithium ion concentration in the solution and the increase of lithium ion diffusion resistance. In order to reduce the competitive intercalation of hydrogen ions, the current is reduced.

[0066] Comparative Example 4 LiMn2O4 powder, organic solvent N-methyl pyrrolidone, binder polytetrafluoroethylene, conductive agent acetylene black, and organic pore-forming agent polyvinyl chloride were mixed in a weight ratio of 8:5:1:1:2, and stirred at 60°C for 2h to obtain a precursor solution; 4g of the precursor solution was uniformly coated on two titanium plates respectively, and the coating thickness was 2mm; the titanium plates were heated at 70°C for 4h to remove the organic solvent; and the titanium plates were heated at 150°C for 2h to remove the organic pore-forming agent, thereby obtaining LiMn2O4 electrodes A and B.

[0067] The electrode A was placed in the anode cavity of the electrode activation device as an anode and a 0.1 mol / L Li2SO4 solution with pH of 7; the titanium plate was placed in the cathode cavity of the electrode activation device as a cathode and a 0.5 mol / L CuCl2 solution, and the cathode cavity and the anode cavity were separated by an anion exchange membrane ASE. A constant current of 20 A / m 2 was applied for 10h to obtain the activated electrode A.

[0068] The activated electrode A was placed in the cathode chamber of the traditional two-chamber electrochemical lithium extraction system as a cathode and a solution containing 50ppm lithium with pH of 7, and the unactivated electrode B was placed in the anode chamber as an anode and a 0.1 mol / L LiCl solution with pH of 7, and the anode chamber and the cathode chamber were separated by an anion exchange membrane ASE.

[0069] A constant current of 5 A / m 2 was applied until the voltage reached 1.2V, and then lithium extraction was carried out at a constant voltage of 1.2V for 20h. After the end, the electrode A and the electrode B were taken out and the surface of the electrode was washed, then the electrode A was placed in the anode chamber of the two-chamber electrochemical lithium extraction system, and the electrode B was placed in the cathode chamber of the traditional two-chamber electrochemical lithium extraction system, and a second cycle was carried out, and the operation conditions were the same as the first time, and the cycle was carried out for 10 times. Finally, the solution in the anode chamber was concentrated, and Na2CO3 was added to obtain lithium carbonate product.

[0070] Figure 7The lithium ion adsorption and desorption capacity and manganese dissolution loss rate of Comparative Example 4 within 10 cycles are shown. Li + The adsorption amount of Li is 15.762 mg / g, the capacity retention rate is 10.23%, and the Mn dissolution loss rate is 8.3%. The overall recovery rate of Li + is 30.43%.

[0071] Because the lithium insertion and deintercalation of the traditional two-chamber electrochemical lithium extraction system cannot be independently regulated, when the lithium ion concentration decreases, sustainable lithium ion extraction cannot be achieved even if the current density is reduced.

[0072] Comparative Example 5 LiMn2O4 powder was mixed with organic solvent N-methyl pyrrolidone, binder polytetrafluoroethylene, conductive agent acetylene black, and organic pore-forming agent polyvinyl chloride at a weight ratio of 8:5:1:1:2, stirred at 60°C for 2 h to obtain a precursor solution; 4 g of the precursor solution was uniformly coated on two titanium plates, with a coating thickness of 2 mm; the titanium plates were heated at 70°C for 4 h to remove the organic solvent; and the titanium plates were heated at 150°C for 2 h to remove the organic pore-forming agent, obtaining LiMn2O4 electrodes A and B.

[0073] Electrode A was placed in the anode chamber of the electrode activation device as the anode and a 0.1 mol / L Li2SO4 solution with a pH of 7; a titanium plate was placed in the cathode chamber of the electrode activation device as the cathode and a 0.5 mol / L CuCl2 solution, and the cathode chamber and the anode chamber were separated by an anion exchange membrane ASE. A constant current of 20 A / m 2 was applied for 10 h to obtain the activated electrode A.

[0074] The activated electrode A was placed in the cathode chamber of the traditional two-chamber electrochemical lithium extraction system and a solution containing 50 ppm lithium with a pH of 7; the unactivated electrode B was placed in the anode chamber of the traditional two-chamber electrochemical lithium extraction system as the anode and a 0.1 mol / L LiCl solution with a pH of 7, and the anode chamber and the cathode chamber were separated by an anion exchange membrane ASE.

[0075] A constant current of 30 A / m 2 was applied until the voltage reached 1.2 V, and then lithium extraction was performed at a constant voltage of 1.2 V for 20 h. After the end, electrode A and electrode B were taken out and the surface of the electrodes was rinsed, then electrode A was placed in the anode chamber of the two-chamber electrochemical lithium extraction system and electrode B was placed in the cathode chamber of the traditional two-chamber electrochemical lithium extraction system, and a second cycle was performed, with the same operation conditions as the first cycle, for 10 cycles. Finally, the solution in the anode chamber was concentrated and Na2CO3 was added to obtain lithium carbonate product.

[0076] Figure 8 The lithium ion adsorption and desorption capacity and manganese dissolution loss rate of Comparative Example 5 within 10 cycles are shown. Li+ The adsorption capacity is 12.762 mg / g, the capacity retention rate is 8.23%, the Mn dissolution rate is 10.3%, and the Li + The overall recovery rate is 20.43%.

[0077] Compared with Comparative Example 4, the current density is increased. Since the lithium intercalation and deintercalation cannot be independently controlled, and the decrease in lithium ion concentration leads to an increase in lithium ion diffusion resistance, Lambda The electron receiving speed of the MnO2 electrode is significantly faster than the lithium ion diffusion speed, resulting in more serious concentration polarization, and thus the adsorption capacity is further reduced and the manganese dissolution is further increased, indicating that sustainable lithium ion extraction cannot be achieved at high current density.

[0078] Example 3 LiFePO4 powder, organic solvent N-methyl pyrrolidone, binder polytetrafluoroethylene, conductive agent acetylene black, and organic pore-forming agent polyvinyl chloride were mixed in a weight ratio of 8:5:1:1:2, stirred at 60°C for 2h to obtain a precursor solution; then the regular packing in the form of titanium material honeycomb packing was completely immersed in the precursor solution, and stirred at a water bath temperature of 50°C for 8h to make the LiFePO4 powder uniformly loaded inside the regular packing; the organic solvent was removed by heating at 70°C for 4h; the organic pore-forming agent was removed by heating at 150°C for 2h to obtain LiFePO4 electrodes A and B based on regular packing.

[0079] The electrode A was placed in the anode chamber of the device for activating the electrode as the anode and 0.1 mol / L Li2SO4 solution with pH of 7; the titanium plate was placed in the cathode chamber of the device for activating the electrode as the cathode and 0.5 mol / L CuCl2 solution, and the cathode chamber and the anode chamber were separated by an anion exchange membrane ASE. A constant current of 20 A / m 2 The activated electrode A was obtained by constant current activation for 10h.

[0080] The activated electrode A was placed in the cathode chamber of the three-chamber electrochemical lithium extraction system as the cathode and the solution containing 200 ppm lithium with pH of 7, and the titanium plate in the middle buffer chamber as the anode formed a first electrochemical circuit with the activated electrode A, and the cathode chamber and the middle buffer chamber were separated by an anion exchange membrane ASE; the FeCl2 and FeCl3 solutions with a concentration of 0.5 mol / L and pH of 3 were placed in the middle buffer chamber; the unactivated electrode B was placed in the anode chamber as the anode and the LiCl solution with a concentration of 0.1 mol / L and pH of 7, and the other titanium plate in the buffer chamber as the cathode formed a second electrochemical circuit with the unactivated electrode B, and the middle buffer chamber and the anode chamber were separated by an anion exchange membrane ASE.

[0081] A constant current of 10 A / m 2A constant current of 30 A / m2was applied until the voltage reached 0.5 V, and then lithium extraction was carried out at a constant voltage of 0.5 V for 10 h. 2 A constant current of 30 A / m2was applied until the voltage reached 0.7 V, and then lithium extraction was carried out at a constant voltage of 0.7 V for 10 h. After the end of lithium extraction and lithium removal, electrode A, electrode B were taken out and the surface of the electrode was rinsed, then electrode B was placed in the cathode chamber of the three-chamber electrochemical lithium extraction system, and electrode A was placed in the anode chamber of the three-chamber electrochemical lithium extraction system, and the second cycle was carried out, the operation conditions were the same as the first time, and the cycle was carried out for 10 times. Finally, the solution in the anode chamber was concentrated, and Na2CO3was added to obtain a lithium carbonate product.

[0082] Figure 9 The lithium ion adsorption and desorption capacity and manganese loss rate of Example 3 within 10 cycles are shown. Li + The adsorption amount of Li can reach 37.852 mg / g, the capacity retention rate is 98.98%, and the Mn loss rate is 0.00102%, Li + The overall recovery rate of Li can reach more than 98.93%.

Claims

1. A structured packing-based electrochemical lithium extraction electrode, which is composed of electrode active material powder uniformly loaded inside structured packing.

2. The structured packing-based electrochemical lithium extraction electrode of claim 1, wherein, The structured packing is electrically conductive, and its material includes stainless steel, copper, aluminum, titanium, molybdenum-titanium alloy or any combination thereof, and its form includes perforated plate corrugated packing, plate net corrugated packing, perforated plate corrugated packing, wire mesh corrugated packing, ring-shaped corrugated packing, honeycomb packing or any combination thereof.

3. The structured packing-based electrochemical lithium extraction electrode according to claim 1, which is prepared by the following method: mixing electrode active material powder with organic solvent, binder, conductive agent and organic pore-forming agent to obtain a precursor solution; completely immersing the structured packing in the precursor solution to uniformly load the electrode active material powder inside the structured packing, thereby obtaining the structured packing-based electrochemical lithium extraction electrode; wherein Electrode active materials include LiMn2O4, Li4Mn5O 12 , Li 1.6 Mn 1.6 O4, Li4Ti5O 12 , LiTi2O3, LiFePO4; the organic solvent includes N-methyl pyrrolidone, N-ethyl pyrrolidone, N-vinyl pyrrolidone, dimethylformamide, dimethylacetamide or any combination thereof; the binder includes polyvinyl chloride, polyvinylidene fluoride, polytetrafluoroethylene, butylphenyl, water-based polyvinyl acetate or any combination thereof; the conductive agent includes carbon black, acetylene black, graphite, carbon fiber, carbon nanotube, graphene, composite conductive paste or any combination thereof; the organic pore-forming agent includes polystyrene, polyethylene glycol, polyvinyl chloride, polyformaldehyde, epoxy resin, polyglycolic acid, lignin, cellulose, hemicellulose or any combination thereof; the weight ratio of the electrode active material powder, the organic solvent, the binder, the conductive agent and the organic pore-forming agent is 8:1-10:1-10:1-10:1-3; the step of uniformly loading the electrode active material powder inside the structured packing is carried out under the condition of water bath heating and stirring, the temperature of water bath heating is 30-90℃, and the stirring time is 1-10h.

4. A three-chamber electrochemical lithium extraction system, which is composed of a cathode chamber, an intermediate buffer chamber and an anode chamber, the cathode chamber and the intermediate buffer chamber and the intermediate buffer chamber and the anode chamber are separated by an anion exchange membrane respectively; the anode chamber contains a salt solution and an unactivated structured packing-based electrochemical lithium extraction electrode, which forms a first electrochemical loop with another conductive electrode in the intermediate buffer chamber; the cathode chamber contains a lithium-containing solution and an activated structured packing-based electrochemical lithium extraction electrode, which forms a second electrochemical loop with another conductive electrode in the buffer chamber; the intermediate buffer chamber contains a solution of a redox couple.

5. The three-compartment electrochemical lithium extraction system of claim 4, wherein, A salt solution includes a solution of at least one of Cl - , SO4 2- , SO3 2- , NO3 - , NO2 - , PO4 3- , CO3 2- , chlorate, or perchlorate. The concentration of the salt solution is 0.1-10mol / L; The pH of the salt solution is 5-14.

6. The three-compartment electrochemical lithium extraction system of claim 4, wherein, The conductive electrode includes at least one of carbon electrode, graphite electrode, carbon cloth electrode, titanium electrode, glassy carbon electrode, carbon felt electrode, platinum electrode, gold electrode, stainless steel electrode, copper electrode, silver electrode, aluminum electrode and metal alloy electrode.

7. The three-compartment electrochemical lithium extraction system of claim 4, wherein, The lithium-containing solution includes brine, geothermal water, gas field water or other lithium-rich solution; the concentration of lithium ions in the lithium-containing solution is greater than 2ppm; the pH of the lithium-containing solution is 5-14.

8. The three-compartment electrochemical lithium extraction system of claim 4, wherein, Redox couples include Fe 2+ / Fe 3+ , I - / I3 - , Cu 2+ / Cu + , [Fe(CN)6] 3- / [Fe(CN)6] 4- , MnO4 - / Mn 2+ , Cr2O7 2- / Cr 3+ , Ce 4+ / Ce 3+ ; the concentration of the solution of the redox couple is 0.1-10 mol / L; the pH of the solution of the redox couple is 2-4.

9. A lithium extraction method based on the three-chamber electrochemical lithium extraction system according to any one of claims 4 to 8, which comprises the following steps: Constant current is applied on the first electrochemical loop and the second point chemical loop of the three-chamber electrochemical lithium extraction system respectively, and constant voltage is switched after reaching the cut-off voltage, so as to independently control the lithium intercalation and lithium extraction processes; After the lithium intercalation and lithium extraction are completed, the electrode in the anode chamber and the electrode in the cathode chamber are taken out, cleaned and exchanged positions, and the above steps are repeated for subsequent multiple cycles.

10. The method for lithium extraction according to claim 9, wherein, The constant current applied is 2-50 A / m 2 ; the cut-off voltage is 0.3-1.2 V.

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