Arrayed nanosheet lithium manganate material for lithium extraction and preparation method and application thereof

Abstract

This invention relates to the field of lithium extraction technology from salt lakes, specifically to an array-type nanosheet lithium manganese oxide material for lithium extraction, its preparation method, and its application. The preparation method includes a three-electrode chemical system consisting of carbon cloth as the working electrode, a graphite plate as the counter electrode, and Ag / AgCl as the reference electrode. This system is immersed in a mixed solution of manganese acetate and sodium sulfate, and an array-type nanosheet manganese hydroxide is prepared by electrolysis. The array-type nanosheet manganese hydroxide is oxidized to manganese tetroxide at room temperature, and then subjected to hydrothermal lithiation to obtain the array-type nanosheet lithium manganese oxide material. The array-type nanosheet lithium manganese oxide material prepared by this invention has high crystallinity, is dense and uniform, and exhibits more active sites, higher lithium uptake capacity, and lower manganese dissolution rate in lithium extraction from salt lakes, demonstrating better lithium extraction performance compared to existing commercial lithium manganese oxide materials.

Description

Technical Field

[0001] This invention relates to the field of lithium extraction technology from salt lakes, specifically to an array-type nanosheet lithium manganese oxide material for lithium extraction, its preparation method, and its application. Background Technology

[0002] Lithium, as an important strategic resource, is an indispensable raw material for modern high-tech products. With the rapid development of my country's lithium battery industry, market demand for lithium is increasing. Currently, most lithium salts in China are extracted from ores, but with the continuous depletion of high-quality lithium ore and the rising cost of ore extraction, lithium extraction from salt lakes, which has lower extraction costs, is gradually attracting attention.

[0003] Salt lakes are rich in lithium. Existing lithium extraction technologies require increased voltage, leading to higher costs. Alternatively, chemical reagents can be used to extract lithium ions, but these pollute the environment, and the residue can cause secondary pollution. CDI / FCDI devices are also used, but their extraction capacity is limited, and significant manganese leaching occurs during selective lithium extraction. This is primarily due to the low active sites and high manganese leaching issues associated with lithium manganese oxide materials used in CDI / FCDI. Finding a superior lithium manganese oxide material is a pressing technical challenge. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention first provides a method for preparing array-type nanosheet lithium manganese oxide materials for lithium extraction from salt lakes. The lithium manganese oxide materials prepared by this method have high active sites, low manganese dissolution rate, large specific capacity, and stable cycling performance.

[0005] The present invention adopts the following technical solution:

[0006] A method for preparing an array-type nanosheet lithium manganese oxide material for lithium extraction includes the following steps:

[0007] S1. A three-electrode chemical system was formed by using carbon cloth as the working electrode, graphite plate as the counter electrode, and Ag / AgCl as the reference electrode. This system was immersed in a mixed solution of manganese acetate and sodium sulfate, and an array of nanosheet manganese hydroxide was prepared by passing an electric current through it.

[0008] S2. The arrayed nanosheet manganese hydroxide is oxidized to manganese tetroxide at room temperature, and then subjected to hydrothermal lithiation to obtain arrayed nanosheet lithium manganese oxide material.

[0009] Preferably, the carbon cloth is pretreated with plasma before use. Specifically, a plasma cleaner uses nitrogen gas to treat both sides of the carbon cloth for 500-700 seconds.

[0010] Preferably, the concentrations of manganese acetate and sodium sulfate are both 15 mM, and the molar ratio of manganese acetate to sodium sulfate in the mixed solution is 1:1.

[0011] Preferably, the specific operation of energizing is as follows: at room temperature, operating in a constant voltage mode of -1.4V on an electrochemical workstation for 2500s.

[0012] Preferably, the oxidation process involves placing the sample at room temperature (20–25°C) and humidity (35–50% RH) for 12–20 hours.

[0013] Preferably, the hydrothermal lithiation uses 20mM lithium hydroxide as the lithiation solution, the hydrothermal reaction temperature is 180-220℃, and the reaction time is 12-22h.

[0014] The present invention also provides an array-type lithium manganese oxide material prepared by the above-mentioned method for preparing array-type nanosheet lithium manganese oxide material for lithium extraction from salt lakes.

[0015] The present invention provides an array of nanosheets and / or conductive electrodes made of the above-mentioned array of nanosheet lithium manganese oxide material for lithium extraction from salt lakes; and also provides a salt lake lithium extraction device for electro-adsorption desalination comprising a conductive electrode made of the above-mentioned array of nanosheet lithium manganese oxide material for lithium extraction from salt lakes.

[0016] The beneficial effects of this invention are as follows:

[0017] The array-structured nanosheet lithium manganese oxide material prepared by this invention exhibits high crystallinity and dense uniformity, preventing lattice expansion during adsorption and desorption processes and thus reducing manganese dissolution. This invention also provides a high specific capacity, resulting in more active sites for lithium extraction from salt lakes and an increased lithium extraction capacity of approximately 32 mg / g. Existing commercial lithium manganese oxide dissolves by 1% per ten cycles, while the array-structured nanosheet lithium manganese oxide material of this invention dissolves only 0.3% of manganese in the same number of cycles, thereby improving the cycling stability of the material. Furthermore, the array-structured nanosheet lithium manganese oxide material prepared by this invention demonstrates significantly better lithium extraction performance than existing commercial lithium manganese oxide materials, achieving an effect approximately five times greater.

[0018] The array-type nanosheet lithium manganese oxide material prepared in this invention employs electro-adsorption desalination technology. The prepared array-type nanosheet lithium manganese oxide material is used to make a conductive electrode to charge the lithium extraction device. When brine enters the lithium extraction device, the forward voltage causes ions in the brine to migrate into the array-type nanosheet lithium manganese oxide material. However, after the array-type nanosheet lithium manganese oxide material becomes saturated with adsorption, the reverse voltage causes the ions stored in the array-type nanosheet lithium manganese oxide material to migrate into the concentrate, thus realizing the lithium extraction cycle. Attached Figure Description

[0019] Figure 1The image shown is a SEM image of the surface of the array-type nanosheet lithium manganese oxide material of this invention, magnified 20,000 times.

[0020] Figure 2 The image shows the XRD pattern of the array-type nanosheet lithium manganese oxide material prepared in this invention.

[0021] Figure 3 A schematic diagram of the operating device structure of the array-type nanosheet lithium manganese oxide material prepared in this invention;

[0022] Figure 4 To illustrate the lithium absorption performance of the array-type nanosheet lithium manganese oxide material prepared in this invention, in the figure: 1-outer protective plate, 2-silicone pad, 3-conductive titanium plate, 4-brine flow channel plate, 5-anion exchange membrane;

[0023] Figure 5 The selectivity of the array-type nanosheet lithium manganese oxide material prepared in this invention to different ions;

[0024] Figure 6 This is the data from ten adsorption-desorption cycles of the array-type nanosheet lithium manganese oxide material prepared in Example 2 of this invention;

[0025] Figure 7 This is data from ten adsorption-desorption cycles of the commercial lithium manganese oxide material used in Example 2;

[0026] Figure 8 The continuous change of current in the array-type nanosheet lithium manganese oxide material prepared in this invention during the experimental period;

[0027] Figure 9 The continuous change of current in commercial lithium manganese oxide materials during the experimental period;

[0028] Figure 10 The manganese leaching rate of the arrayed nanosheet lithium manganese oxide material of this invention and commercial lithium manganese oxide material was compared after ten adsorption-desorption cycles. Detailed Implementation

[0029] The technical solution of the present invention will be described in more detail below with reference to the embodiments and accompanying drawings.

[0030] Example 1

[0031] A method for preparing arrayed nanosheet lithium manganese oxide material includes the following steps:

[0032] S1. The carbon cloth, after plasma pretreatment, was cut into 4×4cm pieces to serve as the working electrode. A 4×4cm graphite plate was used as the counter electrode, and Ag / AgCl was used as the reference electrode, forming a three-electrode chemical system. The plasma pretreatment was performed using an 80W plasma cleaner with nitrogen gas, treating both sides of the carbon cloth for 500–700 seconds each. After treatment, the carbon cloth surface exhibited radially distributed grooves, which not only increased the specific surface area of ​​the carbon cloth, thus improving the adhesion of Mn(OH)₂, but also enhanced the bonding force of the product on the carbon cloth surface, improving the interaction between the two components in the composite material.

[0033] The above system was immersed in 100 ml of a mixed solution of 15 mM manganese acetate and sodium sulfate in a 1:1 ratio. The solution was operated at room temperature in a constant voltage mode of -1.4 V on an electrochemical workstation for 2500 s to perform cathodic deposition of self-supporting Mn(OH)2 on a carbon cloth substrate, thus completing the preparation of arrayed nanosheet manganese hydroxide.

[0034] S2. The prepared arrayed nanosheet manganese hydroxide is placed at room temperature (20-25℃) and humidity (35-50% RH) for 12-20 hours to oxidize it to manganese tetroxide. Then, it is subjected to hydrothermal lithiation to obtain arrayed nanosheet lithium manganese oxide material. The hydrothermal lithiation uses 20 mM lithium hydroxide as the lithiation solution and is carried out in a Teflon-lined stainless steel container. The hydrothermal reaction temperature is 180-220℃ and the reaction time is 12-22 hours to obtain arrayed nanosheet lithium manganese oxide (LiMn2O4) material.

[0035] In this invention, the carbon cloth, carbon plate, and reference electrode are all conventional materials in the art. In this embodiment, the carbon cloth is the Taiwan Carbon Energy Carbon Cloth WOS1011 hydrophilic model. Before each use, the carbon cloth needs to be washed with deionized water on both sides 2-3 times. In S2, the lithium hydroxide used as the lithium source has an analytical purity greater than 98%, and it is added slowly with a glass plate as a guide.

[0036] The morphology of the prepared array-type nanosheet lithium manganese oxide material was observed using transmission electron microscopy, such as... Figure 1 As shown, it exhibits a nanosheet structure with high crystallinity, regular arrangement, and uniform morphology. This will result in the lithium manganese oxide material of this invention possessing more active sites, higher lithium uptake capacity, and lower manganese dissolution during lithium extraction from salt lakes. The XRD pattern obtained using an X-ray diffractometer is shown below. Figure 2 As shown, it can be seen that manganese tetroxide and arrayed nanosheet lithium manganese oxide materials have high crystallinity, and the conversion between them is relatively complete.

[0037] The array-type nanosheet lithium manganese oxide material prepared by this invention is used in electro-adsorption desalination technology. In the electro-adsorption desalination and lithium extraction device, a conductive electrode made of the array-type nanosheet lithium manganese oxide material is used to charge the lithium extraction device. When brine enters the lithium extraction device, the forward voltage migrates the ions in the brine into the array-type nanosheet lithium manganese oxide material. After the array-type nanosheet lithium manganese oxide material is saturated with adsorption, the reverse voltage allows the ions stored in the array-type nanosheet lithium manganese oxide material to migrate into the concentrate, thereby realizing the lithium extraction cycle.

[0038] In one implementation, such as Figure 3 The diagram shows a schematic of the operating device for an array-type nanosheet lithium manganese oxide material. The lithium manganese oxide material prepared according to this invention is coated onto the inner side of one of the conductive titanium plates 3 in the lithium extraction device to form a cathode electrode, positioned close to the brine. On the other side, activated carbon or similar materials are coated onto the inner side of the conductive titanium plate 3 to form an anode electrode, positioned close to the anion exchange membrane 5. When the lithium extraction device is running, the lithium manganese oxide material absorbs and stores cations, while the activated carbon absorbs and stores anions, achieving the purpose of lithium extraction. In the device, the outer protective plate 1 serves as the outermost end of the lithium extraction device, protecting it. The silicone pad 2 is the intermediate component between the outer protective plate 1 and the conductive titanium plate 3, ensuring a tighter fit between them and preventing brine leakage during lithium extraction. The brine flow channel plate 4 stores the brine, facilitating ion absorption by both sets of conductive titanium plates 3. The anion exchange membrane 5 allows only anions from the brine to pass through and enter the anode conductive titanium plate 3, thereby allowing the cathode conductive titanium plate 3 to better absorb cations.

[0039] Example 2

[0040] The lithium extraction device was energized by using a conductive electrode made of prepared arrayed lithium manganese oxide nanosheets. Specifically, referring to Example 1, CDI was used as the lithium extraction device, the prepared lithium manganese oxide nanosheets were used as the anode, activated carbon as the cathode, and a 0.2 mm thick titanium sheet was used as the current collector. An anion exchange membrane was used to divide the device into two chambers, with a silicone rubber gasket serving as a water channel and seal. The experiment was conducted at a constant flow rate (15 mL / min). -1 ), constant voltage (1.2V) and 150mg·L -1 The experiment was conducted in a lithium-ion concentration solution at the initial concentration.

[0041] When the brine enters the CDI, the forward voltage causes the ions in the brine to migrate into the arrayed nanosheet lithium manganese oxide material. When the arrayed nanosheet lithium manganese oxide material is saturated with adsorption, the reverse voltage causes the ions stored in the arrayed nanosheet lithium manganese oxide material to migrate into the concentrate, completing a single adsorption-desorption cycle.

[0042] The control group was tested using commercial lithium manganese oxide material.

[0043] Figure 4 The lithium adsorption performance of the array-type nanosheet lithium manganese oxide material is shown, and it can be seen that the adsorption amount gradually increases with the increase of lithium ion concentration.

[0044] Figure 5 The selectivity of arrayed nanosheet lithium manganese oxide materials to different ions was shown. It can be seen that as the lithium ion concentration increases, the selectivity coefficient of arrayed nanosheet lithium manganese oxide materials to lithium ions first increases and then decreases.

[0045] Cyclic experiments were conducted using a Blue Electricity testing system in a 150 mg / L lithium chloride solution, employing a repetitive charge-discharge mode. For convenient ion concentration monitoring, a Rayleigh magnetic conductivity meter was used to monitor and record the solution in real time. The capacity retention data of the arrayed nanosheet lithium manganese oxide material during 10 adsorption-desorption cycles are shown below. Figure 6 As shown, data for commercial lithium manganese oxide materials are as follows: Figure 7 As shown, after 10 cycles, the capacity retention rate of the arrayed nanosheet lithium manganese oxide material is 97%, indicating that the material has good stability. Commercial lithium manganese oxide materials, after 10 adsorption-desorption cycles, only retain 76.59% of their capacity, which is significantly inferior to the lithium manganese oxide material prepared in this invention.

[0046] The array-type nanosheet lithium manganese oxide material and commercial lithium manganese oxide material were tested using the Blue Electric testing system. Figure 8 The data shows the continuous change of current within 3.5 cycles (20 min each for adsorption and desorption) of the arrayed nanosheet lithium manganese oxide material. The results indicate that the current trend remains essentially constant within each cycle, demonstrating the structural stability of the arrayed nanosheet lithium manganese oxide material of this invention. Experimental data for commercial lithium manganese oxide materials under the same experimental conditions are shown below. Figure 9 As shown, it can be clearly observed that the periodic variation is unstable, and the peak current continues to increase with the increase of the period, indicating that the commercial lithium manganese oxide material has poor structural stability and has an activation process in the early stage.

[0047] Lithium chloride solution samples were taken after 10 adsorption-desorption cycles of both the array-type nanosheet lithium manganese oxide electrode and the commercial lithium manganese oxide electrode. These samples were named DSLMO (array-type nanosheet lithium manganese oxide electrode) and CLMO (commercial lithium manganese oxide electrode), respectively. Inductively coupled plasma atomic emission spectrometry (ICP-AES) was used to monitor the samples and examine manganese dissolution. The results are as follows: Figure 10 As shown, the manganese leaching rate of the arrayed nanosheet lithium manganese oxide material of this invention is 0.35%, which is only 1 / 5 of the 1.77% manganese leaching rate of commercial lithium manganese oxide materials. The arrayed nanosheet lithium manganese oxide material of this invention can greatly improve the structural stability by inhibiting the dissolution of manganese.

[0048] Therefore, the array-type nanosheet lithium manganese oxide material prepared by this invention has a high lithium absorption capacity and a low manganese dissolution rate, and good stability during use, which has significant advantages over existing commercial lithium manganese oxide materials.

[0049] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing an array-type nanosheet lithium manganese oxide material for lithium extraction, characterized in that, Includes the following steps: S1. A three-electrode chemical system was formed by using carbon cloth as the working electrode, graphite plate as the counter electrode, and Ag / AgCl as the reference electrode. This system was immersed in a mixed solution of manganese acetate and sodium sulfate, and an array of nanosheet manganese hydroxide was prepared by passing an electric current through it. The concentrations of manganese acetate and sodium sulfate are both 15 mM, and the molar ratio of manganese acetate to sodium sulfate in the mixed solution is 1:

1. The specific operation of the energization is as follows: at room temperature, it operates in a constant voltage mode of -1.4V on an electrochemical workstation for 2500 s. S2. The arrayed nanosheet manganese hydroxide is oxidized to manganese tetroxide at room temperature, and then subjected to hydrothermal reaction lithiation to obtain arrayed nanosheet lithium manganese oxide material; The hydrothermal lithiation uses 20 mM lithium hydroxide as the lithiation solution, and the hydrothermal reaction temperature is 180~220℃, with a reaction time of 12~22 h.

2. The method for preparing an array-type nanosheet lithium manganese oxide material for lithium extraction as described in claim 1, characterized in that, The carbon cloth undergoes plasma pretreatment before use. Specifically, a plasma cleaner uses nitrogen gas to treat both sides of the carbon cloth for 500-700 seconds.

3. The method for preparing an array-type nanosheet lithium manganese oxide material for lithium extraction as described in claim 1, characterized in that, The specific oxidation process involves placing the product at room temperature (20-25°C) and humidity (35-50%RH) for 12-20 hours.

4. An array-type nanosheet lithium manganese oxide material prepared by the preparation method according to any one of claims 1-3.

5. A conductive electrode, characterized in that, It is made of an array of lithium manganese oxide nanosheets prepared by the preparation method according to any one of claims 1-3.

6. A lithium extraction device for salt lakes using electroadsorption desalination, characterized in that, The conductive electrodes in this device are made of arrayed nanosheet lithium manganese oxide material prepared by the preparation method described in any one of claims 1-3.

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