Selective lithium extraction electrode material, preparation method, lithium extraction device and lithium enrichment method

Abstract

The invention relates to a selective lithium extraction electrode material, a preparation method, a lithium extraction device and a lithium enrichment method. The selective lithium extraction electrode material comprises an etched nanopore MXene material and LiMn2O4 loaded on the etched nanopore MXene material, and the diameter of the nanopore of the etched nanopore MXene material is 7 nm to 40 nm. An etched nanopore MXene material is adopted as a carrier, the obtained etched nanopore MXene / LiMn2O4 selective lithium extraction electrode material serves as a lithium ion adsorption electrode to be combined with a mixed capacitance deionization lithium extraction device, lithium ions are extracted through the oxidation-reduction reaction of the electrode material, and adsorption and desorption of Li < + > are driven through electrochemical potential. The selective lithium extraction electrode material provided by the invention can obviously improve the adsorption capacity and adsorption rate of lithium ions, and has good selectivity and cycling stability.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium resource extraction, and particularly relates to a selective lithium extraction electrode material, a preparation method, a lithium extraction device, and a lithium enrichment method. Background Art

[0002] Due to the rapid development of new energy technologies, the global market demand for lithium resources has been growing explosively and continuously. The stable and continuous extraction of lithium resources has gradually attracted people's attention. The total amount of lithium resources in brines accounts for more than 60% of the global lithium reserves, almost 2400 times that of ore lithium reserves. At the same time, traditional lithium ore resources are increasingly difficult to meet the expanding market demand. Non-traditional lithium sources such as brines have larger reserves and are less restricted by geography, making them a new source for obtaining lithium resources. Therefore, they have great prospects and are the key to the sustainable supply of lithium resources in the future.

[0003] Currently, the extraction of lithium mainly relies on technologies such as ore leaching, solvent extraction, membrane separation, ion exchange, and electrochemical adsorption. Among them, the HCDI lithium extraction technology, which belongs to electrochemical technology, has become one of the most promising resource recovery methods due to its advantages such as high selectivity, low energy consumption, and environmental friendliness. The HCDI lithium extraction technology achieves the reversible insertion and extraction of target ions by regulating the redox state of the electrode, thereby achieving the purpose of efficient separation. However, at present, the technology for Li+ extraction is still in the development stage. In existing methods, most lithium adsorption electrodes have low adsorption capacity and slow adsorption rate, making it difficult to efficiently extract lithium from salt lake brines.

[0004] CN119553098A discloses an electrochemical method for removing magnesium and enriching lithium in salt lake brines, which includes feeding salt lake brines into a single-chamber electrolysis chamber and carrying out an electrolysis reaction in the single-chamber electrolysis chamber; the anolyte after electrolysis is sent out of the single-chamber electrolysis chamber and collected, and the collected anolyte is sent back into the single-chamber electrolysis chamber to participate in the electrolysis reaction again; the catholyte after electrolysis is sent out of the single-chamber electrolysis chamber and filtered, so that the hydroxide ions in the catholyte after electrolysis react with the magnesium ions in the salt lake brines to form magnesium hydroxide precipitates, and the lithium-rich salt lake brines obtained after filtration are evaporated and concentrated to obtain a concentrated lithium-rich brine; sodium carbonate is added to the concentrated lithium-rich brine for lithium precipitation reaction to obtain lithium carbonate precipitates, and the lithium carbonate precipitates are centrifuged, washed, and dried to obtain lithium carbonate. However, this method has a relatively complex process and low adsorption capacity, making it difficult to efficiently extract lithium resources.

[0005] Therefore, developing an efficient, low-cost, and environmentally friendly HCDI lithium extraction technology to achieve the efficient extraction of lithium resources is of great significance for improving resource utilization efficiency and reducing environmental pollution. Summary of the Invention

[0006] To solve the above technical problems, the object of the present invention is to provide a selective lithium extraction electrode material, a preparation method, a lithium extraction device and a lithium enrichment method. The selective lithium extraction electrode material of the present invention, as a lithium ion adsorption electrode, has both high adsorption capacity and rate, good selectivity and good cycle stability performance.

[0007] To achieve this purpose, the present invention adopts the following technical solutions:

[0008] In the first aspect, the present invention provides a selective lithium extraction electrode material, which includes an etched nanoporous MXene material and LiMn2O4 loaded on the etched nanoporous MXene material.

[0009] The nanopore diameter of the etched nanoporous MXene material is 7 nm - 40 nm.

[0010] The selective lithium extraction electrode material provided by the present invention includes an etched nanoporous MXene material and lithium manganate (EtchingMXene / LiMn2O4). Among them, on the one hand, the etched nanoporous MXene material can improve the conductivity of the LiMn2O4 lithium extraction electrode material, reduce the energy consumption during the application of the selective lithium extraction electrode material, and the MXene material has hydrophilicity, which can further enhance the ion transportability; on the other hand, the porous structure of the etched nanoporous MXene material can further increase the loading sites of LiMn2O4, and then increase the adsorption sites of lithium ions during the application, thereby increasing the lithium ion adsorption capacity; at the same time, the etched nanoporous MXene material can also improve the lithium-magnesium selectivity of LiMn2O4 and the adsorption efficiency of the selective lithium extraction electrode material. The selective lithium extraction electrode material provided by the present invention, as a lithium ion adsorption electrode, has both high adsorption capacity and rate, good selectivity and good cycle stability performance.

[0011] The following are the preferred technical solutions of the present invention, but not a limitation to the technical solutions provided by the present invention. Through the following preferred technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved.

[0012] Preferably, the mass ratio of the etched nanoporous MXene material to LiMn2O4 is 1:(20 - 30).

[0013] In the second aspect, the present invention provides a preparation method of the selective lithium extraction electrode material as described in the first aspect, and the preparation method includes the following steps:

[0014] Mix the MXene solution with the etching agent, and perform etching treatment to obtain the etched nanoporous MXene material;

[0015] Mix the etched nanoporous MXene material solution and the lithium manganate suspension, react, and obtain the selective lithium extraction electrode material;

[0016] The etchant includes any one or a combination of at least two of sulfuric acid, nitric acid, or hydrogen peroxide.

[0017] In the preparation method of the selective lithium extraction electrode material provided by the present invention, first, a mild and controllable oxidative etching is carried out on MXene nanosheets with an etchant, a large number of nanopores are successfully introduced onto the MXene nanosheets, and the structural integrity of the etched nanoporous MXene material (EM x material) decreases, forming an obvious fragmented morphology. Etching MXene not only increases the specific surface area of the material, but also optimizes its layer spacing and pore structure, providing more channels for the rapid transport of Li+, improving the lithium adsorption performance of the electrode material. The etched nanoporous MXene material (EM x material) can provide additional channels for ion transport due to its abundant nanopores and expanded layer spacing, thereby increasing the lithium adsorption capacity and rate.

[0018] However, through research, it is found that if hydrochloric acid or other non-oxidizing acids are used in the etching process, the above effects cannot be achieved. This is because non-oxidizing acids such as hydrochloric acid cannot weaken C-Ti that constitutes MXene, and thus cannot play a role in creating pores in the oxidative etching of MXene nanosheets.

[0019] Preferably, the etchant preferred in the present invention is sulfuric acid. After mixing the MXene solution with sulfuric acid, the concentration of sulfuric acid is 0.1 mol / L - 0.5 mol / L.

[0020] Preferably, the temperature of the etching treatment is 50°C - 70°C.

[0021] Preferably, the time of the etching treatment is 2 h - 5 h.

[0022] Preferably, the MXene solution includes an aqueous solution of Ti3C2T x of.

[0023] Preferably, the concentration of the MXene solution is 5 mg / mL - 20 mg / mL.

[0024] Preferably, the lithium manganate suspension includes lithium manganate and a solvent.

[0025] Preferably, the concentration of the solvent is 1 mg / mL - 2 mg / mL.

[0026] Preferably, the solvent includes cetyltrimethylammonium bromide (CTAB).

[0027] In a third aspect, the present invention provides a hybrid capacitive deionization lithium extraction device, and the hybrid capacitive deionization lithium extraction device includes the selective lithium extraction electrode material described in the first aspect.

[0028] Preferably, the material of the cathode includes the selective lithium extraction electrode material.

[0029] In a fourth aspect, the present invention provides a lithium enrichment method using the hybrid capacitive deionization lithium extraction device described in the third aspect, and the lithium enrichment method includes the following steps:

[0030] (1) Electrode material pretreatment: Mix the selective lithium extraction electrode material and hydrochloric acid solution to obtain a MXene / Li 1-x Mn2O4 composite membrane electrode material, which is used as the cathode in the hybrid capacitive deionization lithium extraction device, where 0 < x < 1;

[0031] (2) Lithium extraction: Apply a voltage to the hybrid capacitive deionization lithium extraction device until the electrode reaction reaches equilibrium to obtain an electrode with saturated adsorption.

[0032] (3) Lithium desorption: Apply a voltage opposite to that in step (2) to obtain a Li + enriched solution.

[0033] The lithium enrichment method provided by the present invention based on HCDI technology uses an etched nanohole MXene / LMO (Etching nanoholey MXene / LiMn2O4) composite membrane electrode material as the electrode material, and under the action of an external electric field, high-efficiency extraction and recovery of lithium are achieved through redox reactions.

[0034] Preferably, the magnitudes of the voltages in steps (2) and (3) are independently 0.2 V - 1.2 V, preferably 0.8 V - 1 V.

[0035] The numerical ranges described in the present invention not only include the above-listed point values, but also any point values between the above numerical ranges not listed. Due to space limitations and for the sake of brevity, the present invention does not exhaustively list the specific point values included in the ranges.

[0036] Compared with the prior art, the present invention has at least the following beneficial effects:

[0037] (1) The selective lithium extraction electrode material provided by the present invention comprises etched nanoporous MXene material and lithium manganate (Etching MXene / LiMn2O4). Among them, the etched nanoporous MXene material can not only improve the conductivity of the LiMn2O4 lithium extraction electrode material, enhance ion transport, increase the adsorption sites of lithium ions, and improve the lithium ion adsorption capacity; at the same time, the etched nanoporous MXene material can also improve the lithium / magnesium selectivity of LiMn2O4 and enhance the adsorption efficiency of the selective lithium extraction electrode material. The selective lithium extraction electrode material provided by the present invention, as a lithium ion adsorption electrode, has both high adsorption capacity and rate, good selectivity and good cycle stability performance.

[0038] (2) The hybrid capacitive deionization lithium extraction device provided by the present invention extracts lithium ions through the redox reaction of the electrode material, relies on the electrochemical potential to drive the adsorption and desorption of Li+, realizes low-energy consumption and high-efficiency recovery, improves resource utilization rate, and the selective lithium extraction electrode material can significantly improve the lithium ion adsorption capacity and adsorption rate, and has good selectivity and good cycle stability.

[0039] (3) The lithium enrichment method provided by the present invention has the advantages of high lithium adsorption capacity, fast rate, high selectivity, high cycle stability, no membrane operation during adsorption and wide applicability. The present invention is applicable to halogen water environments with low concentration and complex coexisting ions, especially applicable to the resource utilization of salt lake brine resources with a high magnesium / lithium ratio, and promotes the stable and sustainable supply of lithium. Description of the Drawings

[0040] Figure 1 is the SEM image of the etched nanoporous MXene material obtained after step (Ⅰ) of Example 1 of the present invention;

[0041] Figure 2 is the SEM image of the etched nanoporous MXene material obtained after step (Ⅰ) of Example 2 of the present invention;

[0042] Figure 3 is the SEM image of the etched nanoporous MXene material obtained after step (Ⅰ) of Example 3 of the present invention;

[0043] Figure 4 is the N2 adsorption-desorption isotherm of the lithium extraction electrode materials provided by Example 1 and Comparative Example 1 of the present invention;

[0044] Figure 5 is the pore size distribution diagram of the lithium extraction electrode materials provided by Example 1 and Comparative Example 1 of the present invention;

[0045] Figure 6 is the adsorption capacity diagram of the lithium extraction electrode materials provided by Example 1, Example 2, Example 3, Example 5, Example 6 and Comparative Example 1, Comparative Example 2 of the present invention;

[0046] Figure 7 It is an exploded view of the hybrid capacitive deionization lithium extraction device provided in Application Example 1 of the present invention; wherein, 1 - fixing plate, 2 - silica gel gasket, 3 - titanium plate, 4 - cathode, 5 - silica gel gasket, 6 - separator, 7 - anion exchange membrane, 8 - silica gel gasket, 9 - anode, 10 - titanium plate, 11 - silica gel gasket and 12 - fixing plate. Specific embodiments

[0047] The technical solution of the present invention will be further described below in conjunction with the drawings and through specific embodiments. However, the following examples are only simple examples of the present invention and do not represent or limit the scope of the protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0048] An embodiment of the present invention provides a selective lithium extraction electrode material, which includes an etched nanoporous MXene material and LiMn2O4 loaded on the etched nanoporous MXene material.

[0049] The nanopore diameter of the etched nanoporous MXene material is 7nm - 40nm, for example, it can be 7nm, 10nm, 12nm, 15nm, 18nm, 20nm, 22nm, 25nm, 28nm, 33nm, 37nm or 40nm, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable, and preferably 12nm - 20nm.

[0050] The selective lithium extraction electrode material provided by the present invention includes an etched nanoporous MXene material and lithium manganate (EtchingMXene / LiMn2O4). Among them, on the one hand, the etched nanoporous MXene material can improve the conductivity of the LiMn2O4 lithium extraction electrode material, reduce the energy consumption during the application of the selective lithium extraction electrode material, and the MXene material has hydrophilicity, which can further enhance the ion transportability; on the other hand, the porous structure of the etched nanoporous MXene material can further increase the LiMn2O4 loading sites, thereby increasing the lithium ion adsorption sites during the application process, and thus increasing the lithium ion adsorption capacity; at the same time, the etched nanoporous MXene material can also improve the lithium / magnesium selectivity of LiMn2O4 and improve the adsorption efficiency of the selective lithium extraction electrode material. The selective lithium extraction electrode material provided by the present invention, as a lithium ion adsorption electrode, has both high adsorption capacity and rate, good selectivity and good cycle stability performance.

[0051] The present invention further controls the nanopore diameter of the etched nanoporous MXene material to be 7 nm - 40 nm. It is found that if the nanopore diameter of the etched nanoporous MXene material is too large, the integrity of the etched nanoporous MXene nanosheets will be significantly reduced, and an interconnected conductive network cannot be formed after compounding with LMO, resulting in a decline in lithium extraction performance; if the nanopore diameter of the etched nanoporous MXene material is too small, there will be too few ion transport pathways in the etched nanoporous MXene nanosheets, and the Li + attachment active sites will be reduced, resulting in a decrease in lithium extraction capacity and rate.

[0052] The following are the preferred technical solutions of the present invention, but do not limit the technical solutions provided by the present invention. Through the following preferred technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

[0053] In some embodiments, the mass ratio of the etched nanoporous MXene material to LiMn2O4 is 1:(20 - 30), for example, it can be 1:10, 1:15, 1:20, 1:25, or 1:30, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0054] The present invention further controls the mass ratio of the etched nanoporous MXene material to LiMn2O4 to be 1:(20 - 30). When within this mass ratio range, the selective lithium extraction electrode material has higher lithium extraction capacity and rate. If the mass ratio of the etched nanoporous MXene material to LiMn2O4 is too large, that is, the content of LiMn2O4 is too small, while the lithium adsorption capacity is limited, the self-stacking of excessive etched nanoporous MXene nanosheets will also reduce the lithium transport channels and slow down the lithium adsorption rate; if the mass ratio of the etched nanoporous MXene material to LiMn2O4 is too small, that is, the content of the etched nanoporous MXene material is too small, not only can an effective interconnected conductive network not be formed in the selective lithium extraction electrode material, resulting in a decrease in electrode conductivity, but also it cannot effectively isolate the Mn 2+ from the external electrolyte, resulting in a decline in the cycle stability of the selective lithium extraction electrode material. In addition, the reduction in electrode conductivity will also increase the lithium extraction energy consumption and decrease the current efficiency. In addition, the reduction in the content of the etched nanoporous MXene will also reduce the ion transport pathways and significantly reduce the content of lithium attachment active sites. At the same time, due to the lack of the assistance of the layered structure of the etched nanoporous MXene for screening, the lithium-magnesium selectivity of the selective lithium extraction electrode material will also be significantly reduced.

[0055] An embodiment of the present invention provides a preparation method of the selective lithium extraction electrode material according to any one of the embodiments, and the preparation method includes the following steps:

[0056] Mix the MXene solution with the etchant, and perform an etching treatment to obtain an etched nanoporous MXene material;

[0057] Mix the solution of the etched nanoporous MXene material and the lithium manganate suspension, and react to obtain the selective lithium extraction electrode material;

[0058] The etchant includes any one or a combination of at least two of sulfuric acid, nitric acid, or hydrogen peroxide.

[0059] In the preparation method of the selective lithium extraction electrode material provided by the present invention, first, mild and controllable oxidative etching is performed on MXene nanosheets with sulfuric acid, and a large number of nanopores are successfully introduced on the MXene nanosheets, making the structure integrity of the etched nanoporous MXene material (EM x material) decrease, forming an obvious fragmented morphology. Etching MXene not only increases the specific surface area of the material, but also optimizes its layer spacing and pore structure, providing more channels for the rapid transport of Li+, improving the lithium adsorption performance of the electrode material. The rich nanopores and expanded layer spacing in the etched nanoporous MXene material (EM x material) can provide additional channels for ion transport, thereby increasing the lithium adsorption capacity and rate.

[0060] However, through research, it is found that if hydrochloric acid or other types of non-oxidizing acids are used in the etching process, the above effects cannot be achieved. This is because non-oxidizing acids such as hydrochloric acid do not have an oxidative etching effect and cannot weaken C-Ti that constitutes MXene, and thus cannot perform oxidative etching to create pores on MXene nanosheets.

[0061] After mixing the MXene solution with sulfuric acid, the concentration of sulfuric acid is 0.1 mol / L - 0.5 mol / L. For example, it can be 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, or 0.5 mol / L, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0062] In the present invention, by further controlling the concentration of sulfuric acid to be 0.1 mol / L - 0.5 mol / L after mixing the MXene solution with sulfuric acid, the amount of added sulfuric acid affects the size and number of etched pores, EM xThe abundant nanopores and expanded interlayer spacing in the nanosheets can provide additional channels for ion transport. As the concentration of H2SO4 increases, the degree of fragmentation of the nanosheets gradually intensifies, oxidizing the Ti atoms on the surface of MXene, weakening the Ti-C bonds, and forming surface nanopores; if the addition amount of sulfuric acid is too high, more Ti-C bonds in the MXene nanosheets break, increasing the etched pores of the nanosheets or causing them to rupture, and the integrity of the MXene nanosheets will decrease significantly, and they may even be etched into quantum dots, losing the ability to form an interconnected conductive network; if the addition amount of sulfuric acid is too low, the MXene nanosheets cannot be effectively etched, and rich lithium transport channels and lithium attachment active sites cannot be obtained, reducing the lithium adsorption capacity and rate of the selective lithium extraction electrode material.

[0063] In some embodiments, before mixing the MXene solution with sulfuric acid, the concentration of the sulfuric acid used is 2 mol / L - 4 mol / L. For example, it can be 2 mol / L, 2.2 mol / L, 2.5 mol / L, 2.8 mol / L, 3 mol / L, 3.2 mol / L, 3.5 mol / L, 3.8 mol / L, or 4 mol / L, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0064] In some embodiments, the temperature of the etching treatment is 50°C - 70°C. For example, it can be 50°C, 55°C, 60°C, 65°C, or 70°C, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0065] In some embodiments, the time of the etching treatment is 2 h - 5 h. For example, it can be 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, or 5 h, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0066] In some embodiments, the MXene solution includes Ti3C2T x aqueous solution.

[0067] In some embodiments, the concentration of the MXene solution is 5 mg / mL - 20 mg / mL. For example, it can be 5 mg / mL, 8 mg / mL, 10 mg / mL, 12 mg / mL, 15 mg / mL, 18 mg / mL, or 20 mg / mL, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0068] In the present invention, in order to make Ti3C2T x more uniformly dispersed in the aqueous solution, ultrasonic dispersion can be used, and the ultrasonic time is 6 min - 10 min.

[0069] In some embodiments, after the etching treatment, before obtaining the etched nanoporous MXene material, solid-liquid separation, washing, and drying are also included.

[0070] In some embodiments, the drying includes freeze-drying.

[0071] In some embodiments, the temperature of the freeze-drying is from -5°C to -40°C, for example, it can be -5°C, -10°C, -15°C, -18°C, -20°C, -25°C, -30°C, or -40°C, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0072] In some embodiments, the time of the freeze-drying is 10h - 72h, for example, it can be 10h, 12h, 14h, 15h, 18h, 20h, 22h, 25h, 30h, 35h, 40h, 45h, 50h, 60h, or 72h, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0073] In some embodiments, the etched nanoporous MXene material solution includes the etched nanoporous MXene material and water.

[0074] In some embodiments, the lithium manganate suspension includes lithium manganate and a surfactant solution.

[0075] In some embodiments, the surfactant includes cetyltrimethylammonium bromide (CTAB).

[0076] In some embodiments, the concentration of the CTAB surfactant solution is 1mg / mL - 2mg / mL, for example, it can be 1mg / mL, 1.2mg / mL, 1.5mg / mL, 1.8mg / mL, or 2mg / mL, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0077] As a preferred technical solution of the preparation method of the present invention, the preparation method includes the following steps:

[0078] (Ⅰ), Mix an aqueous solution of Ti3C2T with a concentration of 5mg / mL - 20mg / mL x with sulfuric acid with a concentration of 2mol / L - 4mol / L to obtain a mixed solution with a sulfuric acid concentration of 0.1mol / L - 0.5mol / L, perform an etching treatment at 50°C - 70°C for 2h - 5h, wash by centrifugation until the supernatant is neutral, and obtain the etched nanoporous MXene material after freeze-drying at -5°C to -40°C for 10h - 72h;

[0079] (II), Mix an aqueous solution of etched nanoporous MXene material and a lithium manganate suspension with a concentration of 1 mg / mL - 2 mg / mL (the solvent is CTAB) according to the mass ratio of the etched nanoporous MXene material to LiMn₂O₄ of 1:(20 - 30), stir and react for 1 h - 5 h, and after centrifugal washing and drying at 50 °C - 70 °C for 10 h - 24 h, the selective lithium extraction electrode material MXene / LiMn₂O₄ is obtained.

[0080] A certain embodiment of the present invention provides a hybrid capacitive deionization lithium extraction device, and the hybrid capacitive deionization lithium extraction device includes the selective lithium extraction electrode material described in any embodiment.

[0081] The hybrid capacitive deionization lithium extraction device provided by the present invention extracts lithium ions through the redox reaction of the electrode material, relies on the electrochemical potential to drive the adsorption and desorption of Li⁺, realizes low-energy consumption and high-efficiency recovery, improves resource utilization rate, and the selective lithium extraction electrode material can significantly improve the adsorption capacity and adsorption rate of lithium ions, and has good selectivity and good cycle stability.

[0082] In some embodiments, the material of the cathode includes the selective lithium extraction electrode material.

[0083] The hybrid capacitive deionization lithium extraction device provided by the present invention mainly includes a cathode, an anode, and a selective anion exchange membrane. Among them, the cathode is used for reversibly adsorbing and releasing Cl - , and the anode is used for reversibly adsorbing and releasing Li + , and the selective anion exchange membrane is used to prevent Li + from being adsorbed by the cathode during the desorption stage. Through the application of an external power supply to provide potential drive, a peristaltic pump is also included in the device, and the peristaltic pump is used to realize the circulation of the raw material liquid in the hybrid capacitive deionization lithium extraction device.

[0084] In some embodiments, the material of the anode includes activated carbon.

[0085] In some embodiments, the schematic diagram of the hybrid capacitive deionization lithium extraction device is as Figure 7 shown, including a fixed plate 1, a silica gel gasket 2, a titanium plate 3, a Faraday electrode 4, a silica gel gasket 5, a separator 6, an anion exchange membrane 7, a silica gel gasket 8, an anode 9, a titanium plate 10, a silica gel gasket 11, and a fixed plate 12 arranged in sequence.

[0086] The specific connection method and functions are as follows: The fixing plates 1 and 12 are made of insulating polyvinyl chloride material, with holes drilled around for fastening screws to pass through, and a water inlet or outlet hole is left at the top; 2, 5, 8, and 11 are silicone gaskets cut from silicone sheets. The outer silicone gaskets 2 and 11 have the same size and shape as the fixing plates; The inner silicone gaskets 5 and 8 have holes drilled around for fastening screws to pass through, with the size being the same as that of the fixing plates. There is an inner frame inside for placing electrodes and holes for water flow, with the size being the same as that of the electrodes; Titanium plates 3 and 10 are used to load the active material electrodes, and the size of the active material electrodes is 4 cm 2 , and there are holes for water flow at the corresponding flow channels of the fixing plates. The size of the holes and the aperture of the water inlet and outlet holes of the fixing plates are the same as those of the fastening plates; A plastic separator, which is placed between two electrodes during use to prevent short-circuiting between the electrodes and serves as a water channel for water flow. The Faraday electrode 4 and the activated carbon electrode 9 are placed into the device, assembled in the order shown in the figure, and fastened with titanium screws.

[0087] Between the inner silicone gasket 8 and the plastic separator 6 on the side where the activated carbon electrode 9 is placed, an anion exchange membrane 7 is placed. Like the silicone gasket, it has holes around for fastening screws to pass through, with the size being the same as that of the fixing plates and having holes for water flow.

[0088] The main purpose of covering the anion exchange membrane on the surface of the activated carbon electrode is to prevent the target cations from being adsorbed by the activated carbon anode during the process of deintercalation from the Faraday electrode material and enrichment in the recovery solution, which may lead to a decrease in the recovery efficiency of the target cations. This design can significantly improve the recovery rate of the target ions and thus enhance the efficiency of the overall separation process by blocking the non-selective adsorption of the target cations on the activated carbon electrode.

[0089] Any embodiment of the present invention provides a lithium enrichment method using the hybrid capacitive deionization lithium extraction device described in any embodiment. The lithium enrichment method includes the following steps:

[0090] (1) Electrode material pretreatment: Mix the hybrid selective lithium extraction electrode material and hydrochloric acid solution to obtain the MXene / Li 1-x Mn2O4 composite membrane electrode material, which is used as the cathode in the hybrid capacitive deionization lithium extraction device, where 0 < x < 1;

[0091] (2) Lithium extraction: Apply a voltage to the hybrid capacitive deionization lithium extraction device until the electrode reaction reaches equilibrium to obtain an electrode with saturated adsorption;

[0092] (3) Lithium desorption: Apply a voltage opposite to that in step (2) to obtain a Li + enriched solution.

[0093] The lithium enrichment method based on HCDI technology provided by the present invention uses an etched nanoporous MXene / LMO (Etching nanoholey MXene / LiMn2O4) composite membrane electrode material as the electrode material. Under the action of an external electric field, efficient extraction and recovery of lithium are achieved through redox reactions.

[0094] The lithium enrichment method provided by the present invention has the following advantages: (1) High lithium adsorption capacity and fast rate: The present invention uses the hybrid capacitive deionization (HCDI) lithium extraction technology to achieve a high Li+ adsorption capacity. Compared with traditional methods such as ore leaching, solvent extraction, membrane separation, and ion exchange, the process flow is reduced and the extraction efficiency is improved; (2) High selectivity: By using the principle of electrochemical redox, high-selectivity extraction of target ions is achieved, reducing the impact on the environment; (3) High cycle stability: Using an etched nanoporous MXene / LMO composite membrane electrode as the lithium extraction electrode and AC (activated carbon) as the counter electrode, it can still maintain nearly 90% of the adsorption capacity after multiple adsorption / desorption cycles; (4) No membrane operation during adsorption: The present invention avoids the membrane fouling problem of traditional membrane technologies, simplifies the equipment structure, and reduces the maintenance cost; (5) Wide applicability: The present invention is applicable to halogen environments with low concentrations and complex coexisting ions, especially suitable for the resource utilization of salt lake brine with a high magnesium-lithium ratio, promoting the stable and sustainable supply of lithium.

[0095] In some embodiments, the magnitudes of the voltages in steps (2) and (3) are independently 0.2V - 1.2V respectively. For example, they can be 0.2V, 0.4V, 0.5V, 0.6V, 0.8V, 1.0V, or 1.2V, but are not limited to the listed values. Other unlisted values within the numerical range are equally applicable, and preferably 0.8V - 1V.

[0096] In some embodiments, the concentration of the hydrochloric acid solution in step (1) of the lithium enrichment method is 0.1mol / L - 0.6mol / L. For example, it can be 0.1mol / L, 0.2mol / L, 0.3mol / L, 0.4mol / L, 0.5mol / L, or 0.6mol / L, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0097] In some embodiments, the ratio of the selective lithium extraction electrode material to the hydrochloric acid solution is 10mg - 22mg / 5mL - 15mL. For example, it can be 10mg / 6mL, 12mg / 8mL, or 22mg / 15mL, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0098] In some embodiments, during the lithium extraction process in step (2), the solution in the hybrid capacitive deionization lithium extraction device is a LiCl solution.

[0099] In some embodiments, the concentration of the LiCl solution is 0.004 mol / L - 0.5 mol / L. For example, it can be 0.004 mol / L, 0.01 mol / L, 0.03 mol / L, 0.05 mol / L, 0.07 mol / L, 0.1 mol / L, 0.15 mol / L, 0.2 mol / L, 0.25 mol / L, 0.3 mol / L, 0.35 mol / L, 0.4 mol / L, 0.45 mol / L or 0.5 mol / L. However, it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0100] In some embodiments, after obtaining the adsorption-saturated electrodes in step (2) and before applying the reverse voltage in step (3), it further includes: taking out the adsorption-saturated cathode and anode, and cleaning to remove the adsorption-saturated cathode and anode and the solution in the hybrid capacitive deionization lithium extraction device.

[0101] In some embodiments, during the lithium desorption process in step (3), the solution in the hybrid capacitive deionization lithium extraction device is a KCl solution.

[0102] In some embodiments, the concentration of the KCl solution is 0.05 mol / L - 0.5 mol / L. For example, it can be 0.05 mol / L, 0.1 mol / L, 0.15 mol / L, 0.2 mol / L, 0.25 mol / L, 0.3 mol / L, 0.35 mol / L, 0.4 mol / L, 0.45 mol / L or 0.5 mol / L. However, it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0103] As a preferred technical solution of the preparation method of the present invention, the preparation method includes the following steps:

[0104] (1) Pretreatment of the electrode material: Mix the selective lithium extraction electrode material MXene / LiMn₂O₄ and hydrochloric acid solution to obtain the MXene / Li 1-x Mn₂O₄ composite film electrode material, which is used as the cathode in the hybrid capacitive deionization lithium extraction device;

[0105] (2) Lithium extraction: Use the MXene / Li 1-x Mn₂O₄ composite film electrode material obtained in step (1) as the cathode, use activated carbon as the anode and place them into the hybrid capacitive deionization lithium extraction device (HCDI). Introduce a LiCl solution with a concentration of 0.004 mol / L - 0.5 mol / L into the device, and apply a voltage of 0.2 V - 1.2 V to the hybrid capacitive deionization lithium extraction device, so that the lithium-depleted etched nanoporous MXene / Li 1-xThe Mn2O4 electrode undergoes a reduction reaction and selectively adsorbs Li + , achieving the selective extraction of Li + . It becomes an etched nanoporous MXene / LiMn2O4 composite membrane electrode in a lithium-rich state. As the reaction progresses, the concentrations of Li + and Cl - in the feed solution continuously decrease until the electrode reaction reaches equilibrium, obtaining an electrode with saturated adsorption;

[0106] (3) Lithium desorption: Take out the electrode with saturated adsorption, wash and remove the solution on the surface of the electrode with saturated adsorption and in the hybrid capacitive deionization lithium extraction device, put the electrode with saturated adsorption back into the HCDI device, introduce a KCl solution with a concentration of 0.05 mol / L - 0.5 mol / L, and apply a voltage of 0.2 V - 1.2 V in the reverse direction of step (2) to obtain a Li + enrichment solution.

[0107] In the following examples and comparative examples, unless otherwise specified, all reagents and consumables are purchased from conventional reagent manufacturers in the field; unless otherwise specified, the experimental methods and technical means used are conventional methods and means in the field.

[0108] Example 1

[0109] This example provides a selective lithium extraction electrode material, which includes an etched nanoporous MXene material and LiMn2O4 loaded on the etched nanoporous MXene material. The average nanopore diameter of the etched nanoporous MXene material is 16 nm, and the mass ratio of the etched nanoporous MXene material to LiMn2O4 is 1:30;

[0110] The preparation method of the selective lithium extraction electrode material provided in this example includes the following steps:

[0111] (Ⅰ) Mix an aqueous solution of Ti3C2T x with a concentration of 10 mg / mL and sulfuric acid with a concentration of 3 mol / L to obtain a mixed solution with a sulfuric acid concentration of 0.3 mol / L. Keep it at 60 °C for 3 h, centrifuge and wash until the supernatant is neutral, and vacuum freeze-dry at -40 °C for 10 h to obtain the etched nanoporous MXene material;

[0112] (Ⅱ) Mix the etched nanoporous MXene material aqueous solution and the lithium manganate suspension treated with 5 mL of CTAB with a concentration of 1.2 mg / mL according to the mass ratio of the etched nanoporous MXene material to LiMn2O4 of 1:30, stir and react for 1 h, centrifuge and wash, and vacuum dry at 60 °C for 12 h to obtain the selective lithium extraction electrode material MXene / LiMn2O4, denoted as ENMLC 0.3-1:30 .

[0113] The SEM image of the etched nanoporous MXene material obtained after step (Ⅰ) is as Figure 1 shown. It can be seen from the figure that the degree of fragmentation of the nanosheets is more severe compared to Example 2. The Ti atoms on the surface of the oxidized MXene are oxidized, weakening the Ti-C bond and forming surface nanopores.

[0114] The N2 adsorption-desorption isotherm curve of the prepared selective lithium extraction electrode material is as Figure 4 shown. It can be seen from the figure that the material exhibits a typical Type-IV isotherm and has a hysteresis loop in the relative pressure range of 0.6 to 0.9, indicating that its structure is rich in micropores and mesopores. The specific surface area of Example 1 is 15.52 m 2 / g, which is significantly higher than that of Comparative Example 1 with a specific surface area of 4.10 m 2 / g. This increase in specific surface area may be due to the expansion of the MXene nanosheet interlayer spacing or the generation of nanopores during the etching process.

[0115] The pore size distribution diagram of the prepared selective lithium extraction electrode material is as Figure 5 shown. It can be seen from the figure that compared with Comparative Example 1 with a main pore size of 3.77 nm, Example 1 contains more etched nanopores with pore sizes in the range of 12 - 20 nm. These nanopores effectively reduce the self-stacking phenomenon of MXene nanosheets, increase new Li+-selective attachment active sites and ion transport channels, and provide more efficient transport paths for the transport of Li+, thereby improving the lithium adsorption capacity and rate of the membrane electrode material in Example 1. In addition, the content of pores with pore sizes in the range of 2 nm - 3 nm in the material of Example 1 is reduced compared to Comparative Example 1, which further indicates that etching increases the interlayer spacing of MXene nanosheets and alleviates their self-stacking phenomenon. Etching MXene not only increases the specific surface area of the material but also optimizes its interlayer spacing and pore structure, providing more channels for the rapid transport of Li+ and improving the lithium adsorption performance of the electrode material.

[0116] The adsorption capacity diagram of the prepared selective lithium extraction electrode material is as Figure 6 shown. It can be seen from the figure that as the etching concentration increases, the adsorption rate and adsorption capacity of the ENMLC membrane electrode show a trend of first increasing and then decreasing. Specifically, after moderate etching of MXene and composite with LMO, the Li+ adsorption capacity and rate of the composite material are significantly improved; although MXene etched at too low and too high concentrations can also increase the lithium adsorption rate, the improvement amplitude is significantly lower than that of moderately etched MXene.

[0117] Example 2

[0118] This embodiment provides a selective lithium extraction electrode material, which includes an etched nanoporous MXene material and LiMn2O4 loaded on the etched nanoporous MXene material. The average nanopore diameter of the etched nanoporous MXene material is 12 nm, and the mass ratio of the etched nanoporous MXene material to LiMn2O4 is 1:30;

[0119] The preparation method of the selective lithium extraction electrode material provided in this embodiment includes the following steps:

[0120] (Ⅰ) Mix an aqueous solution of Ti3C2T with a concentration of 6 mg / mL and sulfuric acid with a concentration of 2 mol / L to obtain a mixed solution with a sulfuric acid concentration of 0.1 mol / L. Etch at 60 °C for 3 h, centrifuge and wash until the supernatant is neutral, and freeze-dry at -5 °C for 72 h to obtain the etched nanoporous MXene material; x After step (Ⅰ), the SEM image of the etched nanoporous MXene material is as

[0121] (Ⅱ) Mix the etched nanoporous MXene material aqueous solution and the lithium manganate suspension treated with 5 mL of CTAB with a concentration of 1.2 mg / mL according to the mass ratio of the etched nanoporous MXene material to LiMn2O4 of 1:30, stir and react for 1 h, centrifuge and wash, and vacuum dry at 60 °C for 12 h to obtain the selective lithium extraction electrode material MXene / LiMn2O4, denoted as ENMLC 0.1-1:30 .

[0122] As shown, it can be seen from the figure that mild and controllable oxidative etching of MXene nanosheets is carried out with low-concentration H2SO4, and a large number of nanopores are successfully introduced on the MXene nanosheets, resulting in a decrease in the structural integrity of the EM Figure 2 material and the formation of an obvious fragmented morphology. x

[0123] Example 3

[0124] This embodiment provides a selective lithium extraction electrode material, which includes an etched nanoporous MXene material and LiMn2O4 loaded on the etched nanoporous MXene material. The nanopore diameter of the etched nanoporous MXene material is 20 nm, and the mass ratio of the etched nanoporous MXene material to LiMn2O4 is 1:30;

[0125] The preparation method of the selective lithium extraction electrode material provided in this embodiment includes the following steps:

[0126] (Ⅰ) Mix an aqueous solution of Ti3C2T with a concentration of 20 mg / mL and x ​An aqueous solution was mixed with sulfuric acid at a concentration of 4 mol / L to obtain a mixed solution with a sulfuric acid concentration of 0.5 mol / L. It was etched at 60 °C for 3 h, centrifuged and washed until the supernatant was neutral, and freeze-dried at -15 °C for 24 h to obtain the etched nanoporous MXene material;

[0127] (II), The etched nanoporous MXene material aqueous solution and the lithium manganate suspension treated with 5 mL of CTAB at a concentration of 1.2 mg / mL were mixed according to the mass ratio of the etched nanoporous MXene material to LiMn₂O₄ of 1:30, stirred and reacted for 1 h, centrifuged and washed, and vacuum-dried at 60 °C for 12 h to obtain the selective lithium extraction electrode material MXene / LiMn₂O₄, denoted as ENMLC 0.5-1:30 。

[0128] The SEM image of the etched nanoporous MXene material obtained after step (I) is as Figure 3 shown. It can be seen from the figure that due to the increase in etching concentration, more Ti-C bonds in the MXene nanosheets are broken, resulting in an increase in etched pores or rupture of the nanosheets. EM x The abundant nanopores and expanded interlayer spacing in the nanosheets can provide additional channels for ion transport.

[0129] Example 4

[0130] This example provides a selective lithium extraction electrode material, which is only different from Example 1 in that the mass ratio of the etched nanoporous MXene material to LiMn₂O₄ is 1:10.

[0131] Example 5

[0132] This example provides a selective lithium extraction electrode material, which is only different from Example 1 in that when preparing this selective lithium extraction electrode material, after mixing the MXene solution with sulfuric acid in step (I), the concentration of sulfuric acid is 0.05 mol / L.

[0133] Example 6

[0134] This example provides a selective lithium extraction electrode material, which is only different from Example 1 in that when preparing this selective lithium extraction electrode material, after mixing the MXene solution with sulfuric acid in step (I), the concentration of sulfuric acid is 1 mol / L.

[0135] Comparative Example 1

[0136] This comparative example provides a lithium extraction electrode material, which is only different from Example 1 in that when preparing this lithium extraction electrode material, the MXene material was not etched in step (I), and the MXene material was directly used for the reaction in step (II), that is, the MXene does not contain etched nanopores, MLC 1:30 。

[0137] The N2 adsorption-desorption curves of the prepared lithium extraction electrode materials are as Figure 4 shown. It can be known from the BET test that the specific surface area of Comparative Example 1 is 4.10 m 2 / g, which is much lower than 15.52 m 2 / g in Example 1.

[0138] The pore size distribution diagram of the prepared lithium extraction electrode materials is as Figure 5 shown. It can be seen from the figure that the main pore size is 3.77 nm, which is lower than that in Example 1, and there are more etched nano-pores with pore sizes of 12 nm - 20 nm. The pores with pore sizes of 2 nm - 3 nm play a negligible role in improving the Li+ transmission rate.

[0139] Comparative Example 2

[0140] This comparative example provides a lithium extraction electrode material, which is different from Example 1 only in that when preparing this lithium extraction electrode material, step (Ⅰ) is not carried out, that is, the lithium extraction electrode material is LiMn2O4.

[0141] Comparative Example 3

[0142] This comparative example provides a lithium extraction electrode material, which is different from Example 1 only in that when preparing this lithium extraction electrode material, step (Ⅰ) is not carried out, and in step (Ⅱ), the etched nano-pore MXene material is replaced with an equal amount of GO, and then high-temperature thermal annealing is carried out, that is, the rGO / LiMn2O4 lithium extraction electrode material is prepared.

[0143] Application Example 1

[0144] This application example provides a hybrid capacitive deionization lithium extraction device. The explosion diagram of the hybrid capacitive deionization lithium extraction device is as Figure 7 shown, including a fixed plate 1, a silica gel gasket 2, a titanium plate 3, a cathode 4, a silica gel gasket 5, a separator 6, an anion exchange membrane 7, a silica gel gasket 8, an anode 9, a titanium plate 10, a silica gel gasket 11 and a fixed plate 12 arranged in sequence.

[0145] The lithium enrichment method using the hybrid capacitive deionization lithium extraction device provided in this application example includes the following steps:

[0146] (1) Electrode material pretreatment: Mix the selective lithium extraction electrode material MXene / LiMn2O4 prepared in Example 1 and a hydrochloric acid solution with a concentration of 0.2 mol / L to obtain the MXene / Li 1-x Mn2O4 composite membrane electrode material as the cathode in the hybrid capacitive deionization lithium extraction device;

[0147] (2) Lithium extraction: The MXene / Li obtained in step (1) 1-xThe Mn2O4 composite membrane electrode material is used as the cathode, and activated carbon is used as the anode and placed into the hybrid capacitive deionization lithium extraction device (HCDI). A LiCl solution with a concentration of 0.05 mol / L is introduced into the device, and a voltage of 1 V is applied to the hybrid capacitive deionization lithium extraction device, causing the etched nanoporous MXene / Li 1-x Mn2O4 electrode to undergo a reduction reaction and selectively adsorb Li + , achieving the selective extraction of Li + . The etched nanoporous MXene / LiMn2O4 composite membrane electrode becomes rich in lithium. As the reaction proceeds, the concentrations of Li + and Cl - in the feed solution continuously decrease until the electrode reaction reaches equilibrium, and an electrode saturated with adsorption is obtained;

[0148] (3) Lithium desorption: The electrode saturated with adsorption is taken out, and the solution on the surface of the electrode saturated with adsorption and in the hybrid capacitive deionization lithium extraction device is removed by washing. The electrode saturated with adsorption is put back into the HCDI device, and a KCl solution with a concentration of 0.05 mol / L is introduced, and a voltage of 1 V opposite to that in step (2) is applied to obtain a Li + -enriched solution.

[0149] Application Example 2

[0150] The hybrid capacitive deionization lithium extraction device provided in this application example has the same structure as that in Application Example 1.

[0151] The lithium enrichment method using the hybrid capacitive deionization lithium extraction device provided in this application example includes the following steps:

[0152] (1) Electrode material pretreatment: The selective lithium extraction electrode material MXene / LiMn2O4 prepared in Hybrid Example 1 and a hydrochloric acid solution with a concentration of 0.4 mol / L are mixed to obtain the MXene / Li 1-x Mn2O4 composite membrane electrode material, which is used as the cathode in the hybrid capacitive deionization lithium extraction device;

[0153] (2) Lithium extraction: The MXene / Li 1-x Mn2O4 composite membrane electrode material obtained in step (1) is used as the cathode, and activated carbon is used as the anode and placed into the hybrid capacitive deionization lithium extraction device (HCDI). A LiCl solution with a concentration of 0.5 mol / L is introduced into the device, and a voltage of 0.6 V is applied to the hybrid capacitive deionization lithium extraction device, causing the etched nanoporous MXene / Li 1-x Mn2O4 electrode to undergo a reduction reaction and selectively adsorb Li + , achieving the selective extraction of Li +The selective extraction turns into an etched nanoporous MXene / LiMn2O4 composite film electrode in a lithium-rich state. As the reaction progresses, Li in the feed solution + , Cl - concentrations continuously decrease until the electrode reaction reaches equilibrium, obtaining an electrode saturated with adsorption;

[0154] (3) Lithium desorption: Take out the electrode saturated with adsorption, wash and remove the solution on the surface of the electrode saturated with adsorption and in the hybrid capacitive deionization lithium extraction device, put the electrode saturated with adsorption back into the HCDI device, pass in a KCl solution with a concentration of 0.1 mol / L, and apply a voltage of 0.6 V in the reverse direction of step (2) to obtain a Li + enriched solution.

[0155] Application Example 3

[0156] The hybrid capacitive deionization lithium extraction device provided in this application example has the same structure as that in Application Example 1.

[0157] The lithium enrichment method using the hybrid capacitive deionization lithium extraction device provided in this application example includes the following steps:

[0158] (1) Electrode material pretreatment: Mix the selective lithium extraction electrode material MXene / LiMn2O4 prepared in Hybrid Example 1 and a hydrochloric acid solution with a concentration of 0.6 mol / L to obtain a MXene / Li 1-x Mn2O4 composite film electrode material as the cathode in the hybrid capacitive deionization lithium extraction device;

[0159] (2) Lithium extraction: Use the MXene / Li 1-x Mn2O4 composite film electrode material obtained in step (1) as the cathode, use activated carbon as the anode and place them in the hybrid capacitive deionization lithium extraction device (HCDI). Pass in a LiCl solution with a concentration of 0.1 mol / L into the device, apply a voltage of 0.2 V to the hybrid capacitive deionization lithium extraction device, and make the etched nanoporous MXene / Li 1-x Mn2O4 electrode in a lithium-poor state undergo a reduction reaction to selectively adsorb Li + , realizing the selective extraction of Li + , turning into an etched nanoporous MXene / LiMn2O4 composite film electrode in a lithium-rich state. As the reaction progresses, Li in the feed solution + , Cl - concentrations continuously decrease until the electrode reaction reaches equilibrium, obtaining an electrode saturated with adsorption;

[0160] (3) Lithium desorption: Take out the electrode saturated with adsorption, wash and remove the solution on the surface of the electrode saturated with adsorption and in the hybrid capacitive deionization lithium extraction device, put the electrode saturated with adsorption back into the HCDI device, introduce a KCl solution with a concentration of 0.05 mol / L, and apply a voltage of 0.2 V in the reverse direction of step (2) to obtain Li + enriched solution.

[0161] Application Example 4 - Application Example 8

[0162] Application Example 4 - Application Example 8 respectively provide a hybrid capacitive deionization lithium extraction device, the structural difference from the device in Application Example 1 is only that the cathode in Application Example 1 is replaced with the selective lithium extraction electrode materials prepared in Examples 2 - 6.

[0163] The difference between the lithium enrichment method using the hybrid capacitive deionization lithium extraction device provided in this application example and that in Application Example 1 is only that in step (1), the selective lithium extraction electrode materials prepared in Examples 2 - 6 are used respectively.

[0164] Comparative Application Example 1 - Comparative Application Example 3

[0165] Comparative Application Example 1 - Comparative Application Example 3 respectively provide a hybrid capacitive deionization lithium extraction device, the structural difference from the device in Application Example 1 is only that the cathode in Application Example 1 is replaced with the lithium extraction electrode materials prepared in Comparative Examples 1 - 3.

[0166] The difference between the lithium enrichment method using the hybrid capacitive deionization lithium extraction device provided in this application example and that in Application Example 1 is only that in step (1), the selective lithium extraction electrode materials prepared in Comparative Examples 1 - 3 are used respectively.

[0167] Testing method: Use the devices and methods in the application examples and comparative application examples to conduct Li + adsorption capacity tests, and the test results are shown in Table 1 and Figure 6 as follows.

[0168] From Figure 6 the adsorption capacity graph of the lithium extraction electrode materials, it can be seen that: ENMLC 0.1-1:30 has an adsorption capacity similar to that of MLC 1:30 This phenomenon may be due to the fact that under low - concentration etching conditions, although the interlayer spacing of MXene nanosheets has increased compared with the unetched state, it is still relatively narrow, resulting in a relatively limited increase in the new active attachment sites for Li+ between MXene sheets. At the same time, low - concentration etching will cause a partial decrease in the integrity of MXene nanosheets, and the increase in the interlayer spacing to obtain active attachment sites for Li+ ions cancels out the active sites lost due to the decrease in the integrity of the nanosheets. This is EMLC 0.1-1:30The main reason for the lack of significant improvement in the adsorption capacity of the membrane electrode. Under the combined action of these factors, its adsorption rate is significantly increased compared with the unetched MXene composite LMO electrode, because the etched nanopores in the etched MXene nanosheets provide an efficient ion transport channel for the diffusion of Li+.

[0169] When etched at an appropriate concentration, the self-stacking phenomenon of the EM 0.3 nanosheets is significantly alleviated, and the interlayer spacing is further enlarged. This not only increases the Li+ attachment sites between and on the surface of the etched MXene nanosheets, but also provides more efficient channels for Li+ transport, thus greatly improving the Li+ adsorption capacity and rate of the ENMLC 0.3-1:30 membrane electrode. However, when the etching concentration is too high, the electrical conductivity of the overly fragmented MXene nanosheets decreases significantly, making it difficult to construct a complete and interconnected conductive network. In addition, excessive etching will cause the interlayer spacing of the MXene nanosheets to be too large, which instead reduces the originally abundant Li+ attachment sites. This may be the reason for the decrease in the Li+ adsorption capacity and rate of the ENMLC 0.5-1:30 membrane electrode relative to the ENMLC 0.3-1:30 membrane electrode.

[0170] Table 1

[0171] <![CDATA[Li + Adsorption capacity (mg / g)]]> <![CDATA[Li + Adsorption rate (mg / g / min)]]> Application Example 1 36.08 6.67 Application Example 2 30.93 4.77 Application Example 3 23.20 4.30 Application Example 4 23.31 4.32 Application Example 5 18.90 3.47 Application Example 6 20.67 1.89 Application Example 7 19.84 3.44 Application Example 8 16.32 3.18 Comparative Application Example 1 22.83 1.33 Comparative Application Example 2 15.46 0.64 Comparative Application Example 3 23.39 1.94

[0172] It can be seen from the test results that:

[0173] (1) It can be seen from Application Example 1 - Application Example 5 that the selective lithium extraction electrode material provided by the present invention, as a lithium ion adsorption electrode combined with a hybrid capacitive deionization lithium extraction device, extracts lithium ions through the redox reaction of the electrode material, relies on the electrochemical potential to drive the adsorption and desorption of Li+, and realizes low-energy consumption and high-efficiency recovery. The selective lithium extraction electrode material can significantly improve the lithium ion adsorption capacity and adsorption rate, and has good selectivity and good cycle stability. The lithium enrichment method provided by the present invention has the advantages of high lithium adsorption capacity, fast rate, high selectivity, high cycle stability and low energy consumption in a lower voltage range. Moreover, the lithium enrichment method provided by the present invention has no membrane operation, realizes the efficient separation and recovery of lithium ions, and has a wider applicability.

[0174] (2) It can be seen from the comparison between Application Example 1 and Application Example 6 that by further controlling the mass ratio of the etched nanoporous MXene material to LiMn2O4 to be 1:(20 - 30), within this mass ratio range, the selective lithium extraction electrode material has higher lithium extraction capacity and rate. If the mass ratio of the etched nanoporous MXene material to LiMn2O4 is too large, that is, the content of LiMn2O4 is too small, while the lithium adsorption capacity is restricted, the self-stacking of excessive etched nanoporous MXene nanosheets will also reduce the lithium transport channels and slow down the lithium adsorption rate. If the mass ratio of the etched nanoporous MXene material to LiMn2O4 is too small, that is, the content of the etched nanoporous MXene material is too small, not only can an effective interconnected conductive network not be formed in the selective lithium extraction electrode material, resulting in a decrease in electrode conductivity, but also it cannot effectively isolate Mn 2+ from the external electrolyte, leading to a decrease in the cycle stability of the selective lithium extraction electrode material. In addition, the decrease in electrode conductivity will also increase the lithium extraction energy consumption and decrease the current efficiency. Moreover, the reduction in the content of the etched nanoporous MXene will also reduce the ion transport pathways and significantly decrease the content of lithium attachment active sites. At the same time, due to the lack of the assistance of the layered structure of the etched nanoporous MXene for sieving, the lithium / magnesium selectivity of the selective lithium extraction electrode material will also be significantly reduced.

[0175] (3) It can be seen from the comparison between Application Example 1 and Application Examples 7 - 8 that by further controlling the concentration of sulfuric acid to be 0.1 mol / L - 0.5 mol / L after mixing the MXene solution with sulfuric acid, the amount of sulfuric acid added affects the size and number of etched pores. EM x The abundant nanopores and expanded interlayer spacing in the nanosheets can provide additional channels for ion transport. As the concentration of H2SO4 increases, the fragmentation degree of the nanosheets gradually intensifies, oxidizing the Ti atoms on the surface of MXene, weakening the Ti - C bonds, and forming surface nanopores. However, if the addition amount of sulfuric acid is too high, more Ti - C bonds in the MXene nanosheets will break, increasing the etched pores or causing the nanosheets to rupture, and the integrity of the MXene nanosheets will be significantly reduced, and even etched into quantum dots, losing the ability to form an interconnected conductive network. If the addition amount of sulfuric acid is too low, the MXene nanosheets cannot be effectively etched, and rich lithium transport channels and lithium attachment active sites cannot be obtained, resulting in a decrease in the lithium adsorption capacity and rate of the selective lithium extraction electrode material.

[0176] (4) It can be seen from Application Example 1 and Comparative Application Example 1 that the porous structure of the etched nanoporous MXene material in the present invention can further increase the loading sites of LiMn2O4, thereby increasing the adsorption sites of lithium ions during the application process, and thus increasing the lithium ion adsorption capacity. At the same time, the etched nanoporous MXene material can also improve the lithium / magnesium selectivity of LiMn2O4 and increase the adsorption efficiency of the selective lithium extraction electrode material. The selective lithium extraction electrode material provided by the present invention, as a lithium ion adsorption electrode, has both high adsorption capacity and rate, good selectivity, and good cycle stability.

[0177] (5) It can be seen from Application Example 1 and Comparative Application Example 2 that the etched nanoporous MXene material in the present invention can improve the conductivity of the LiMn2O4 lithium extraction electrode material, reduce the energy consumption during the application of the selective lithium extraction electrode material, and the MXene material has hydrophilicity, which can further enhance ion transport.

[0178] (6) It can be seen from Application Example 1 and Comparative Application Example 3 that by using the etched nanoporous MXene material as a carrier in the present invention, a better synergistic cooperation with the LiMn2O4 material can be achieved, and the lithium extraction capacity, rate, and stability of the selective lithium extraction electrode material can be better improved, which cannot be achieved by using other carriers.

[0179] In summary, by using the etched nanoporous MXene material as a carrier in the present invention, the obtained etched nanoporous MXene / LiMn2O4 selective lithium extraction electrode material, as a lithium ion adsorption electrode combined with a hybrid capacitive deionization lithium extraction device, extracts lithium ions through the redox reaction of the electrode material, and relies on the electrochemical potential to drive the adsorption and desorption of Li+, realizing low-energy consumption and high-efficiency recovery. The selective lithium extraction electrode material can significantly increase the lithium ion adsorption capacity and adsorption rate, and has good selectivity and good cycle stability.

[0180] In addition, the lithium enrichment method provided by the present invention has the advantages of high lithium adsorption capacity, fast rate, high selectivity, high cycle stability, and low energy consumption in a lower voltage range. Moreover, the lithium enrichment method provided by the present invention has no membrane operation, realizes the efficient separation and recovery of lithium ions, and has a wider applicability.

[0181] The applicant declares that the above description is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and disclosure scope of the present invention.

Claims

1. A selective lithium extraction electrode material, characterized in that, The selective lithium extraction electrode material includes an etched nanoporous MXene material and LiMn₂O₄ loaded on the etched nanoporous MXene material; the nanopore diameter of the etched nanoporous MXene material is 7 nm - 40 nm.

2. The selective lithium extraction electrode material according to claim 1, wherein The mass ratio of the etched nanoporous MXene material to LiMn₂O₄ is 1:(20 - 30).

3. A method for preparing the selective lithium extraction electrode material according to claim 1 or 2, characterized in that, The preparation method includes the following steps: Mix the MXene solution and the etching agent, and perform etching treatment to obtain the etched nanoporous MXene material; Mix the etched nanoporous MXene material solution and the lithium manganate suspension, and react to obtain the selective lithium extraction electrode material; The etching agent includes any one or a combination of at least two of sulfuric acid, nitric acid, or hydrogen peroxide.

4. The preparation method according to claim 3, characterized in that, After mixing the MXene solution and the etching agent, the concentration of the etching agent is 0.1 mol / L - 0.5 mol / L; Preferably, the temperature of the etching treatment is 50 °C - 70 °C; Preferably, the time of the etching treatment is 2 h - 5 h.

5. The preparation method according to claim 3 or 4, characterized in that, The MXene solution includes an aqueous solution of Ti3C2T x ; Preferably, the concentration of the MXene solution is 5 mg / mL - 20 mg / mL.

6. The preparation method according to any one of claims 3 to 5, characterized in that, The lithium manganate suspension includes lithium manganate and a surfactant; Preferably, the surfactant includes cetyltrimethylammonium bromide; Preferably, the concentration of the surfactant is 1 mg / mL - 2 mg / mL.

7. A hybrid capacitive deionization lithium extraction device, characterized in that, The hybrid capacitive deionization lithium extraction device includes the selective lithium extraction electrode material according to claim 1 or 2.

8. The hybrid capacitive deionization lithium extraction device according to claim 7, wherein, The hybrid capacitive deionization lithium extraction device includes a cathode, an anode, and a selective anion exchange membrane; Preferably, the material of the cathode includes the selective lithium extraction electrode material according to claim 1 or 2.

9. A lithium enrichment method using the hybrid capacitive deionization lithium extraction device according to claim 7 or 8, characterized in that, The lithium enrichment method includes the following steps: (1) Electrode material pretreatment: Mix the selective lithium extraction electrode material and hydrochloric acid solution to obtain the MXene / Li 1-x Mn2O4 composite membrane electrode material, which serves as the cathode in the hybrid capacitive deionization lithium extraction device, where 0 < x < 1; (2) Lithium extraction: Apply a voltage to the hybrid capacitive deionization lithium extraction device until the electrode reaction reaches equilibrium to obtain an electrode with saturated adsorption; (3) Lithium desorption: Apply a voltage opposite to that in step (2) to obtain a Li + enriched solution.

10. The lithium enrichment method according to claim 9, wherein, The magnitudes of the voltages in step (2) and step (3) are independently 0.2 V - 1.2 V, preferably 0.8 V - 1 V.

Images