LiAlO2 modified LiFePO4 composite material, preparation method thereof, lithium extraction electrode and application

Abstract

The invention relates to the technical field of salt lake lithium extraction, and discloses a LiAlO2 modified LiFePO4 composite material, a preparation method thereof, a lithium extraction electrode and application. The preparation method comprises the following steps: dispersing lithium iron phosphate powder in a dopamine hydrochloride solution, stirring and treating to obtain polydopamine coated lithium iron phosphate; and adding the prepared polydopamine coated lithium iron phosphate, an aluminum source and a lithium source into ethanol, stirring, and calcining to obtain the LiAlO2 modified LiFePO4 composite material. The LiAlO2 modified LiFePO4 composite material prepared by the invention has excellent lithium ion conductivity and structural stability, can realize high-efficiency lithium ion adsorption under electrochemical driving, shows high ion selectivity and cycling stability in simulated saline water, is suitable for efficiently and selectively extracting lithium from complex salt lake brine, and can be used for preparing a lithium ion battery. Good application prospects and social and economic benefits are shown in the field of extracting lithium from the salt lake brine through electrochemical driving.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion adsorption materials technology, and in particular to a LiAlO2-modified LiFePO4 composite material, its preparation method, lithium extraction electrode, and its application. Background Technology

[0002] With the rapid development of the new energy vehicle industry, global demand for lithium resources continues to grow. Salt lake brines account for approximately 64% of global lithium reserves, possessing enormous mining potential. However, the high concentration of sodium in salt lake brines... + K + Mg 2+ Ca 2+ Competing cations pose a significant challenge to the selective extraction of lithium. While technologies such as precipitation-evaporation, solvent extraction, membrane separation, and lithium-ion sieve adsorption have been applied to lithium extraction from salt lakes, they still generally suffer from low energy efficiency, heavy pollution, and insufficient selectivity. Hybrid capacitive deionization (HCDI), as an emerging electrochemical separation technology, achieves selective electroadsorption of ions through an electric field, offering a green and efficient potential solution for lithium extraction from salt lakes.

[0003] LiFePO4 is considered an ideal candidate material for lithium extraction electrodes due to its high theoretical adsorption capacity, excellent structural stability, and environmental friendliness. However, the inherent low electronic conductivity and slow lithium-ion diffusion rate of LiFePO4 severely limit its practical application performance. Summary of the Invention

[0004] Based on this, the purpose of this invention is to provide a LiAlO2-modified LiFePO4 composite material, its preparation method, lithium extraction electrode, and its application, so as to improve the problems of low lithium-ion adsorption capacity and poor cycle stability of existing LiFePO4 electrode materials.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a method for preparing LiAlO2-modified LiFePO4 composite materials, which includes the following steps: S1. Disperse lithium iron phosphate powder in a dopamine hydrochloride solution, stir, and then perform post-treatment to obtain polydopamine-coated lithium iron phosphate. S2. The polydopamine-coated lithium iron phosphate obtained in step S1 is added to ethanol along with an aluminum source and a lithium source, stirred, and calcined to obtain a LiAlO2-modified LiFePO4 composite material.

[0006] As a further improvement to the above-described scheme of the present invention, in step S1, the concentration of the dopamine hydrochloride solution is 0.1wt%~0.5wt%; And / or, in step S1, the stirring is performed at room temperature for 12 to 48 hours; And / or, in step S1, the post-processing includes filtration and drying in sequence, wherein the drying is performed in a forced-air drying oven at 60~100℃.

[0007] As a further improvement to the above-mentioned solution of the present invention, in step S2, the aluminum source is at least one of aluminum isopropoxide, aluminum nitrate, and aluminum chloride; And / or, in step S2, the lithium source is at least one of lithium hydroxide monohydrate and lithium carbonate.

[0008] As a further improvement to the above-mentioned solution of the present invention, in step S2, the amounts of the aluminum source and the lithium source satisfy the following: the molar ratio of lithium element to aluminum element is 1~1.1:1.

[0009] As a further improvement to the above-mentioned solution of the present invention, in step S2, the stirring is carried out at 60~80℃ for 2-8 hours.

[0010] As a further improvement to the above-mentioned solution of the present invention, in step S2, the calcination is carried out under a protective atmosphere, with the temperature increased to 500-700°C at a heating rate of 2-10°C / min for 2-5 hours.

[0011] The present invention also provides a LiAlO2-modified LiFePO4 composite material, which is prepared by the preparation method described above.

[0012] The present invention also provides a lithium extraction electrode, which is prepared by using the LiAlO2-modified LiFePO4 composite material prepared by the preparation method described above.

[0013] As a further improvement to the above-mentioned solution of the present invention, the preparation method of the lithium extraction electrode includes: dissolving the LiAlO2-modified LiFePO4 composite material, conductive carbon black and polyvinylidene fluoride in N-methylpyrrolidone, stirring in a sealed container, coating the resulting slurry onto a titanium sheet, and drying it to obtain the lithium extraction electrode.

[0014] This invention also provides an application of the LiAlO2-modified LiFePO4 composite material prepared by the preparation method described above for the selective extraction of lithium ions in a lithium-containing solution.

[0015] Compared with the prior art, the present invention has the following beneficial effects: This invention proposes a polydopamine-assisted sol-gel synthesis method to construct a uniform and dense LiAlO2 fast ion conductor modification layer on the surface of LiFePO4, thus obtaining a LiAlO2-modified LiFePO4 composite material. The LiAlO2 modification layer significantly improves the lithium-ion transport rate and structural stability at the material's surface, achieving high lithium adsorption capacity and cycle stability. Furthermore, thanks to the selective conduction of lithium ions and the blocking effect of competing ions by the LiAlO2 layer, the composite material exhibits excellent lithium-ion selectivity in complex simulated salt lake brine.

[0016] The LiAlO2-modified LiFePO4 composite material prepared by this invention has high adsorption capacity, excellent selectivity and long cycle stability. It has excellent lithium-ion conductivity and structural stability, and can achieve efficient lithium-ion adsorption under electrochemical drive. It exhibits high ion selectivity and cycle stability in simulated brine, and is suitable for efficient and selective extraction of lithium from complex salt lake brines. It shows good application prospects and social and economic benefits in the field of electrochemically driven lithium extraction from salt lake brines.

[0017] The synthesis process of this invention is mild, controllable, easy to operate, environmentally friendly, and easy to scale up in a controlled manner. The resulting material has excellent properties and good application prospects. Attached Figure Description

[0018] Figure 1 The XRD patterns of Examples 1-3 of the present invention and lithium iron phosphate are shown below. Figure 2 The X-ray photoelectron spectrum of the LiAlO2-modified LiFePO4 composite material prepared in Example 2 of this invention is shown below. Figure 3 This is a graph showing the lithium adsorption capacity of lithium iron phosphate in Example 2 of the present invention; Figure 4 The diagram shows the separation coefficient of the LiAlO2-modified LiFePO4 composite material prepared in Example 2 of this invention during lithium selective adsorption experiments. Figure 5 The graph shows the changes in the concentration of each cation in the receiving solution during a lithium selective adsorption experiment using the LiAlO2-modified LiFePO4 composite material prepared in Example 2 of this invention. Detailed Implementation

[0019] To facilitate understanding of the present invention, a more comprehensive description will be given below with reference to specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of the present invention.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0021] Example 1 This embodiment proposes a LiAlO2-modified LiFePO4 composite material, the preparation method of which includes the following steps: S1. 2.0 g of lithium iron phosphate (LiFePO4) powder was dispersed in 50 ml of a 0.1 wt% dopamine hydrochloride aqueous solution and stirred vigorously at room temperature for 24 h. The mixture was then filtered, and the solid obtained was dried in an 80 °C forced-air drying oven to obtain a polydopamine-modified LiFePO4 intermediate. S2. 0.1 g aluminum isopropoxide, 0.02 g lithium hydroxide monohydrate, and the polydopamine-modified LiFePO4 intermediate obtained in step S1 were placed together in 50 ml of ethanol solution and stirred continuously at 80 °C for 4 h. After drying, the mixture was placed in a tube furnace and heated to 600 °C at a heating rate of 2 °C / min under a nitrogen atmosphere and held at 600 °C for 3 h to obtain the LiAlO2-modified LiFePO4 composite material, denoted as LFP@1.5PLAO.

[0022] Example 2 This embodiment proposes a LiAlO2-modified LiFePO4 composite material, the preparation method of which includes the following steps: S1. 2.0 g of lithium iron phosphate (LiFePO4) powder was dispersed in 50 ml of a 0.1 wt% dopamine hydrochloride aqueous solution and stirred vigorously at room temperature for 24 h. The mixture was then filtered, and the solid obtained was dried in an 80 °C forced-air drying oven to obtain a polydopamine-modified LiFePO4 intermediate. S2. 0.2 g aluminum isopropoxide, 0.04 g lithium hydroxide monohydrate, and the polydopamine-modified LiFePO4 intermediate obtained in step S1 were placed together in 50 ml of ethanol solution and stirred continuously at 80 °C for 4 h. After drying, the mixture was placed in a tube furnace and heated to 600 °C at a heating rate of 2 °C / min under a nitrogen atmosphere and held at 600 °C for 3 h to obtain the LiAlO2-modified LiFePO4 composite material, denoted as LFP@3PLAO.

[0023] Example 3 This embodiment proposes a LiAlO2-modified LiFePO4 composite material, the preparation method of which includes the following steps: S1. 2.0 g of lithium iron phosphate (LiFePO4) powder was dispersed in 50 ml of a 0.1 wt% dopamine hydrochloride aqueous solution and stirred vigorously at room temperature for 24 h. The mixture was then filtered, and the solid obtained was dried in an 80 °C forced-air drying oven to obtain a polydopamine-modified LiFePO4 intermediate. S2. 0.3 g aluminum isopropoxide, 0.06 g lithium hydroxide monohydrate, and the polydopamine-modified LiFePO4 intermediate obtained in step S1 were placed together in 50 ml of ethanol solution and stirred continuously at 80 °C for 4 h. After drying, the mixture was placed in a tube furnace and heated to 600 °C at a heating rate of 2 °C / min under a nitrogen atmosphere and held at 600 °C for 3 h to obtain the LiAlO2-modified LiFePO4 composite material, denoted as LFP@5PLAO.

[0024] Test case (1) The LiAlO2-modified LiFePO4 composite materials and lithium iron phosphate LiFePO4 materials (LFP) prepared in Examples 1-3 were characterized to obtain the following results: Figure 1 The X-ray diffraction pattern shown is from... Figure 1 It can be seen that the LiAlO2-modified LiFePO4 composite materials prepared in Examples 1-3 are consistent with the standard card of LiFePO4 (LiFePO4PDF#00-040-1499), proving that the LiAlO2 modification process did not destroy the crystal form of LiFePO4.

[0025] The X-ray photoelectron spectrum of the LiAlO2-modified LiFePO4 composite material prepared in Example 2 is as follows: Figure 2 As shown, from Figure 2 The successful synthesis of the LiAlO2 modified layer can be seen.

[0026] (2) The LFP@3PLAO and lithium iron phosphate (LiFePO4) materials obtained in Example 2 were used to prepare lithium extraction electrodes: LFP@3PLAO or lithium iron phosphate, conductive carbon black and polyvinylidene fluoride (PVDF) were dissolved in N-methylpyrrolidone (NMP) at a mass ratio of 8:1:1, and stirred in a sealed container for 8 hours to form a slurry. The slurry was coated on a titanium sheet and dried at 60°C for 8 hours to obtain the lithium extraction electrode. Then, the lithium extraction electrode was used to conduct lithium extraction experiments: The lithium extraction electrode was first immersed in 0.1M Na2S2O8 solution at 40°C for 2 hours to obtain a delithiated electrode; an electrochemical adsorption method was used with an asymmetric capacitor deionization device, with the lithium extraction electrode as the negative electrode and activated carbon as the positive electrode, at a current density of 100-300 mA g. -1 Lithium adsorption experiments were conducted in 30 ml of 10 mM LiCl solution under the following conditions: voltage window 0 to -1.2 V. The lithium adsorption capacity is as follows: Figure 3 As shown.

[0027] from Figure 3 It can be seen that LFP@3PLAO exhibits higher lithium adsorption capacity at various current densities.

[0028] (3) The lithium-extraction electrode prepared using LFP@3PLAO obtained in Example 2 was subjected to lithium selective adsorption experiments: the lithium-extraction electrode was first immersed in 0.1M Na2S2O8 solution at 40℃ for 2h to obtain a delithiated electrode; an electrochemically driven adsorption method was adopted, using an asymmetric capacitor deionization device, with the lithium-extraction electrode as the negative electrode and activated carbon as the positive electrode, at a current density of 200mA g. -1 The simulated brine from a salt lake, with a voltage window of 0 to -1.2V and a volume of 30ml (wherein Li...) + The concentration was 0.26 g / L. -1 Na + The concentration was 102.4 g / L. -1 K + The concentration was 8.44 g / L. -1 Mg 2+ The concentration was 15.36 g / L. -1 Ca 2+ The concentration was 0.72 g / L. -1 Lithium selective adsorption experiments were conducted using the following formula. Calculate the lithium separation factor, where x represents other metal cations (Li). + Mg 2+ Na + , K + and Ca 2+ ), and This represents the cation concentration of the simulated saline solution before adsorption. and This represents the cation concentration in the simulated saline solution after adsorption.

[0029] After the adsorption process is complete, a reverse voltage is applied to the electrodes, i.e., the lithium extraction electrode is used as the positive electrode and the activated carbon as the negative electrode, causing the cations adsorbed inside the electrodes to desorb and release into the receiving solution. The changes in the concentration of each cation in the receiving solution are monitored and recorded. The results of lithium selective adsorption are as follows: Figure 4 As shown, the concentration changes of each cation in the receiving solution are as follows: Figure 5 As shown.

[0030] from Figure 4 It can be seen that LFP@3PLAO exhibits excellent lithium-ion selectivity in simulated salt lake brine.

[0031] from Figure 5It can be seen that the purity of lithium ions in the receiving liquid is 81.5%.

[0032] In summary, the LiAlO2-modified LiFePO4 composite material of the present invention has high lithium-ion adsorption capacity and cycling stability, and exhibits excellent lithium-ion selectivity in complex salt lake brines, showing great application potential.

[0033] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0034] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing a LiAlO2 modified LiFePO4 composite material, characterized in that, It comprises the following steps: S1. Dispersing lithium iron phosphate powder in a dopamine hydrochloride solution, stirring, post-treatment, to obtain polydopamine-coated lithium iron phosphate; S2. Adding the polydopamine-coated lithium iron phosphate prepared in step S1, an aluminum source, and a lithium source to ethanol, stirring, and calcining to obtain a LiAlO2-modified LiFePO4 composite material.

2. The method of claim 1, wherein the LiAlO2 modified LiFePO4 composite is prepared by the steps of: (a) mixing LiFePO4 and LiAlO2 in a solvent; (b) drying the mixture; (c) calcining the dried mixture; and (d) milling the calcined mixture. In step S1, the concentration of the dopamine hydrochloride solution is 0.1wt%-0.5wt%; And / or, in step S1, the stirring is stirring at room temperature for 12-48h; And / or, in step S1, the post-treatment comprises, in sequence, suction filtration and drying, and the drying is drying in a blast drying oven at 60-100℃.

3. The method of claim 1, wherein the LiAlO2 modified LiFePO4 composite is prepared by the steps of: (a) mixing LiFePO4 and LiAlO2 in a solvent; (b) drying the mixture; and (c) sintering the mixture. In step S2, the aluminum source is at least one of aluminum isopropoxide, aluminum nitrate, and aluminum chloride; And / or, in step S2, the lithium source is at least one of lithium hydroxide monohydrate and lithium carbonate.

4. The method of claim 1, wherein the LiAlO2 modified LiFePO4 composite is prepared by the steps of: (a) mixing LiFePO4 and LiAlO2 in a solvent; (b) drying the mixture; (c) calcining the dried mixture; and (d) milling the calcined mixture. In step S2, the amount of the aluminum source and the lithium source satisfies that the molar ratio of lithium element to aluminum element is 1-1.1:

1.

5. The method of claim 1, wherein the LiAlO2 modified LiFePO4 composite is prepared by the steps of: (a) mixing LiFePO4 and LiAlO2 in a solvent; (b) drying the mixture; and (c) sintering the mixture. In step S2, the stirring is stirring at 60-80℃ for 2-8h.

6. The method of claim 1, wherein the LiAlO2 modified LiFePO4 composite is prepared by the steps of: a) mixing LiFePO4 and LiAlO2 in a solvent; b) drying the mixture; and c) sintering the mixture. In step S2, the calcining is calcining under a protective atmosphere, at a temperature rising rate of 2-10℃ / min, to 500-700℃ for 2-5h.

7. A LiAlO2 modified LiFePO4 composite material, characterized in that, It is prepared by the preparation method of any one of claims 1-6.

8. A lithium extraction electrode, characterized by, It is prepared by the preparation method of any one of claims 1-6.

9. The lithium extraction electrode of claim 8, wherein, The preparation method of the lithium extraction electrode comprises: dissolving the LiAlO2-modified LiFePO4 composite material, conductive carbon black, and polyvinylidene fluoride in N-methylpyrrolidone, sealing and stirring, coating the obtained slurry on a titanium sheet, and drying to obtain a lithium extraction electrode.

10. Use of a LiAlO2-modified LiFePO4 composite material prepared by the preparation method of any one of claims 1-6 for selectively extracting lithium ions in a lithium-containing solution.

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