Preparation method of high-entropy MXene modified lithium metal negative electrode based on solution coating

Abstract

The invention discloses a preparation method of a high-entropy MXene modified lithium metal negative electrode based on solution coating, and belongs to the technical field of lithium metal battery electrode materials, and the preparation method comprises the following steps: adding a high-entropy MAX material into a hydrofluoric acid solution to etch and strip Al to obtain a high-entropy MXene single-layer solution, and then performing vacuum freeze drying to obtain high-entropy MXene powder; the method comprises the following steps: dissolving high-entropy MXene powder in an N-methyl pyrrolidone solvent to prepare a solution of 80mg / ml, and adding a 5% pvdf solution as a binder to prepare a mixed solution; according to the three-dimensional multi-layer high-active-site composite electrode prepared by the preparation method disclosed by the invention, the capacity of a battery can be remarkably improved, and the long cycle life of the battery can be remarkably prolonged.

Description

Technical Field

[0002] This invention belongs to the field of lithium metal battery electrode material technology, specifically relating to a method for preparing a high-entropy MXene-modified lithium metal anode based on solution coating. Background Technology

[0003] High-entropy MXenes are novel functional materials combining two-dimensional materials and high-entropy alloy concepts. They are composed of five or more transition metal elements in equimolar or near-equimolar proportions, forming a stable crystal structure with maximum configurational entropy. Common representative materials include TiVNbMoC. These materials inherit the excellent conductivity, tunable surface properties, and ion intercalation capabilities of traditional MXenes. Simultaneously, their high-entropy characteristics generate lattice distortion effects, slow diffusion effects, and cocktail effects, exhibiting unique advantages in the field of electrochemical energy. x TiVCrMoC3T x Lithium metal batteries, due to their high energy density (theoretical capacity of 3860 mAh / g, 10 times that of graphite anodes), can significantly improve the range of electric vehicles (up to 800 kilometers or more) and support fast charging (e.g., charging to 70% in 12 minutes), and are considered a key direction for next-generation battery technology. Their development is rapid, and the market prospects are broad. However, lithium metal battery anode technology still faces key challenges such as poor interface stability, dendrite growth, short cycle life, and volume expansion during charging and discharging.

[0004] While existing MXene-modified layers can improve lithium deposition behavior, their single transition metal composition limits further performance enhancement, particularly in suppressing volume changes. Specifically, patent CN114512660A proposes a method for preparing an MXene / polymer composite modified layer, but this technology has significant limitations: First, the surface chemical properties of traditional MXenes (such as Ti) are limited, resulting in limited lithium-ion guidance; second, the polymer matrix may hinder the rapid transport of ions and electrons; third, this method has limited effectiveness in suppressing volume expansion during the charging and discharging of the lithium metal anode; furthermore, the preparation process requires precise control of the reaction conditions of the monomers and initiators, leading to high process complexity. 3C2T x Therefore, there is an urgent need for an electrode material and its preparation method that is simple to operate, can ensure uniform lithium-ion deposition, effectively suppress volume expansion, and guarantee battery performance. Summary of the Invention

[0006] To address the aforementioned issues, this invention proposes a method for preparing a high-entropy MXene-modified lithium metal anode based on solution coating.

[0007] The technical solution of the present invention is as follows: A method for preparing a high-entropy MXene-modified lithium metal anode based on solution coating, characterized by comprising the following steps: S1. Add the high-entropy MAX material to the hydrofluoric acid solution and stir at a constant temperature. Then centrifuge and wash with water until it is neutral to obtain a high-entropy MXene dispersion. Then freeze-dry under vacuum to obtain high-entropy MXene powder A. S2. Dissolve powder A in N-methylpyrrolidone solvent and add PVDF binder to prepare mixed solution A; S3. Add the mixed solution A onto the lithium sheet using a pipette, and then vacuum dry to obtain an electrode containing a protective layer.

[0008] Furthermore, the high-entropy MAX material in S1 is TiVCrMoAlC3 or TiVNbMoAlC3, with a mass of 1–3 g.

[0009] Furthermore, the hydrofluoric acid in S1 has a mass fraction of 20% to 60% and a volume of 20 to 60 mL.

[0010] Furthermore, the temperature of the constant-temperature stirring in S1 is 20-30°C, and the time is 36-48 hours.

[0011] Furthermore, in the mixed solution B of S2, the concentration of powder A is 60~100mg / ml.

[0012] Furthermore, in the mixed solution B of S2, the volume fraction of PVDF is 5%.

[0013] Furthermore, the dropping operation in S3 is at a rate of 0.3–0.5 ml / cm³. 2 The concentration was added dropwise.

[0014] Furthermore, the drying method in S3 is vacuum drying at 30~40℃ for 24~48h.

[0015] The high-entropy MXene-modified lithium metal anode material prepared by the above method based on solution coating is also within the scope of protection of this invention.

[0016] Compared with the prior art, the present invention has the following advantages and beneficial effects: (1) The high-entropy MXene material used in this invention has a unique layered structure and excellent mechanical elasticity, which can well adapt to the huge volume change of lithium metal during charging and discharging. As a buffer layer, it effectively suppresses the volume expansion of the electrode (>60%), thereby maintaining the integrity of the electrode structure and extending the battery cycle life.

[0017] (2) The high-entropy MXene-modified lithium metal anode material prepared in this invention is applied to lithium metal batteries. Its multi-principal synergistic "cocktail effect" and rich surface chemical properties provide a large number of uniform lithiophilic sites for lithium ions, which can effectively guide the uniform deposition of lithium ions, reduce the overpotential of lithium deposition by about 25%, and fundamentally inhibit the growth of lithium dendrites.

[0018] (3) The solution coating method provided by this invention is simple and low in cost: This invention uses a solution coating method, which overcomes the limitations of complex in-situ polymerization or magnetron sputtering processes in existing technologies such as CN114512660A. This method does not require complex equipment or harsh reaction conditions, is easy to operate, has a short process flow, is very suitable for large-scale industrial production, and has significant cost advantages. Attached Figure Description

[0019] Figure 1 This is a SEM image of the solution-coated high-entropy MXene lithium metal anode material obtained in Specific Example 1; Figure 2 This is the EDS image of the solution-coated high-entropy MXene lithium metal anode material obtained in Specific Example 1; Figure 3 This is a full-cell performance diagram of the solution-coated high-entropy MXene lithium metal anode material obtained in Specific Example 1 at a current density of 1C. Figure 4 This is a rate performance diagram of a lithium metal battery based on a solution-coated high-entropy MXene lithium metal anode material obtained in Specific Example 1; Figure 5 The graph shows the full cell performance at a 1C current density for the pure lithium sheet as the negative electrode obtained in Test Example 2. Detailed Implementation

[0020] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0021] Example 1 A method for preparing a high-entropy MXene-modified lithium metal anode based on solution coating, characterized by comprising the following steps: S1. Add 2g of high-entropy TVCrMoAlC3 powder to 40ml of hydrofluoric acid solution, stir magnetically at 30℃ for 48h, then centrifuge and wash with water multiple times until the dispersion is neutral, and freeze dry under vacuum for 24h to obtain high-entropy mxene powder A. S2. Dissolve powder A in N-methylpyrrolidone solvent to obtain a solution with a high entropy mxene concentration of 80 mg / ml, and add 5% PVDF binder by volume. Sonicate for 1 hour to obtain mixed solution A. S3. Solution A is pipetted onto a lithium sheet with a diameter of 1.6 cm. The amount of solution A added to each lithium sheet is 250 μl. The solution is then vacuum dried for 24 h to obtain a lithium metal composite electrode containing a high-entropy MXene protective layer.

[0022] Example 2 A method for preparing a high-entropy MXene-modified lithium metal anode based on solution coating, characterized by comprising the following steps: S1. Add 2g of high-entropy TVCrMoAlC3 powder to 40ml of hydrofluoric acid solution, stir magnetically at 30℃ for 48h, then centrifuge and wash with water multiple times until the dispersion is neutral, and freeze dry under vacuum for 24h to obtain high-entropy mxene powder A. S2. Dissolve powder A in N-methylpyrrolidone solvent to obtain a solution with a high entropy mxene concentration of 50 mg / ml, and add 5% PVDF binder by volume. Sonicate for 1 hour to obtain mixed solution A. S3. Solution A is pipetted onto a lithium sheet with a diameter of 1.6 cm. The amount of solution A added to each lithium sheet is 250 μl. The solution is then vacuum dried for 24 h to obtain a lithium metal composite electrode containing a high-entropy MXene protective layer.

[0023] Experimental Example 3 A method for preparing a high-entropy MXene-modified lithium metal anode based on solution coating, characterized by comprising the following steps: S1. Add 2g of high-entropy TVCrMoAlC3 powder to 40ml of hydrofluoric acid solution, stir magnetically at 30℃ for 48h, then centrifuge and wash with water multiple times until the dispersion is neutral, and freeze dry under vacuum for 24h to obtain high-entropy mxene powder A. S2. Dissolve powder A in N-methylpyrrolidone solvent to obtain a solution with a high entropy mxene concentration of 100 mg / ml, and add 5% PVDF binder by volume. Sonicate for 1 hour to obtain mixed solution A. S3. Solution A is pipetted onto a lithium sheet with a diameter of 1.6 cm. The amount of solution A added to each lithium sheet is 250 μl. The solution is then vacuum dried for 24 h to obtain a lithium metal composite electrode containing a high-entropy MXene protective layer.

[0024] Experiment Example 4 A method for preparing a high-entropy MXene-modified lithium metal anode based on solution coating, characterized by comprising the following steps: S1. Add 2g of high-entropy TVCrMoAlC3 powder to 40ml of hydrofluoric acid solution, stir magnetically at 30℃ for 48h, then centrifuge and wash with water multiple times until the dispersion is neutral, and freeze dry under vacuum for 24h to obtain high-entropy mxene powder A. S2. Dissolve powder A in DMSO dimethyl sulfoxide solvent to obtain a solution with a high entropy mxene concentration of 80 mg / ml, and add 5% PVDF binder by volume. Sonicate for 1 hour to obtain mixed solution A. S3. Solution A is pipetted onto a lithium sheet with a diameter of 1.6 cm. The amount of solution A added to each lithium sheet is 250 μl. The solution is then vacuum dried for 24 h to obtain a lithium metal composite electrode containing a high-entropy MXene protective layer.

[0025] Experimental Example 5 A method for preparing a high-entropy MXene-modified lithium metal anode based on solution coating, characterized by comprising the following steps: S1. Add 2g of high-entropy TVCrMoAlC3 powder to 40ml of hydrofluoric acid solution, stir magnetically at 30℃ for 48h, then centrifuge and wash with water multiple times until the dispersion is neutral, and freeze dry under vacuum for 24h to obtain high-entropy mxene powder A. S2. Dissolve powder A in N-methylpyrrolidone solvent to obtain a solution with a high entropy mxene concentration of 80 mg / ml, and add 5% PVDF binder by volume. Sonicate for 1 hour to obtain mixed solution A. S3. Solution A is pipetted onto a lithium sheet with a diameter of 1.6 cm. The amount of solution A added to each lithium sheet is 150 μl. The solution is then vacuum dried for 24 h to obtain a lithium metal composite electrode containing a high-entropy MXene protective layer.

[0026] Experimental Example 6 A method for preparing a high-entropy MXene-modified lithium metal anode based on solution coating, characterized by comprising the following steps: S1. Add 2g of high-entropy TVCrMoAlC3 powder to 40ml of hydrofluoric acid solution, stir magnetically at 30℃ for 48h, then centrifuge and wash with water multiple times until the dispersion is neutral, and freeze dry under vacuum for 24h to obtain high-entropy mxene powder A. S2. Dissolve powder A in N-methylpyrrolidone solvent to obtain a solution with a high entropy mxene concentration of 80 mg / ml, and add 5% PVDF binder by volume. Sonicate for 1 hour to obtain mixed solution A. S3. Solution A is pipetted onto a lithium sheet with a diameter of 1.6 cm. The amount of solution A added to each lithium sheet is 350 μl. The solution is then vacuum dried for 24 h to obtain a lithium metal composite electrode containing a high-entropy MXene protective layer.

[0027] Experimental Example 7 A method for preparing a high-entropy MXene-modified lithium metal anode based on solution coating, characterized by comprising the following steps: S1. Add 2g of high-entropy TVCrMoAlC3 powder to 40ml of hydrofluoric acid solution, stir magnetically at 30℃ for 48h, then centrifuge and wash with water multiple times until the dispersion is neutral, filter with MCE water-washed filter mixed fiber filter membrane, and then vacuum dry for 24h to obtain high-entropy mxene powder A. S2. Dissolve powder A in N-methylpyrrolidone solvent to obtain a solution with a high entropy mxene concentration of 80 mg / ml, and add 5% PVDF binder by volume. Sonicate for 1 hour to obtain mixed solution A. S3. Solution A is pipetted onto a lithium sheet with a diameter of 1.6 cm. The amount of solution A added to each lithium sheet is 250 μl. The solution is then vacuum dried for 24 h to obtain a lithium metal composite electrode containing a high-entropy MXene protective layer.

[0028] Example 8 A method for preparing a high-entropy MXene-modified lithium metal anode based on solution coating, characterized by comprising the following steps: S1. Add 2g of high-entropy TVCrMoAlC3 powder to 40ml of hydrofluoric acid solution, stir magnetically at 30℃ for 48h, then centrifuge and wash with water multiple times until the dispersion is neutral, and freeze dry under vacuum for 24h to obtain high-entropy mxene powder A. S2. Dissolve powder A in N-methylpyrrolidone solvent to obtain a solution with a high entropy mxene concentration of 80 mg / ml. Without adding binder, sonicate for 1 hour to obtain mixed solution A. S3. Solution A is pipetted onto a lithium sheet with a diameter of 1.6 cm. The amount of solution A added to each lithium sheet is 250 μl. The solution is then vacuum dried for 24 h to obtain a lithium metal composite electrode containing a high-entropy MXene protective layer.

[0029] Test Example 1 Based on Example 1, the morphology and electrochemical performance of the obtained high-entropy MXene (TiVCrMoC3) composite lithium metal electrode material were tested, as follows: I. Morphological Detection The obtained TiVCrMoC3 composite lithium metal electrode material was analyzed by SEM scanning electron microscopy and EDS energy-dispersive X-ray spectroscopy, and the results are as follows: Figure 1 , Figure 2 As shown, by Figure 1Yes, high-entropy MXene exhibits a three-dimensional layered structure on the lithium sheet surface. This structure possesses excellent mechanical elasticity, effectively accommodating the significant volume changes of lithium metal during charging and discharging. As a buffer layer, it effectively suppresses electrode volume expansion (>60%), thereby maintaining the integrity of the electrode structure and extending battery cycle life. Furthermore, the gaps between the layers provide numerous active sites, inducing lithium-ion deposition during charging and discharging, inhibiting dendrite growth, and further improving battery cycle life. Figure 2 The EDS spectrum confirmed that high-entropy elements were successfully deposited on the lithium wafer surface.

[0030] II. Electrochemical Performance Testing 1. Using the TiVCrMoC3 composite lithium metal electrode material obtained in Example 1 as the negative electrode and NCM811 as the positive electrode, a full cell was assembled. The cycle stability was tested at a current density of 1C, and the results are as follows: Figure 3 As shown: Depend on Figure 3 It can be seen that after 200 charge-discharge cycles, the battery capacity retention rate is still above 80%, the coulombic efficiency is always above 90%, and the average coulombic efficiency is 97.3%. This indicates that the composite of TiVCrMoC3 high-entropy MXene material and lithium metal can effectively reduce the side reactions of the electrodes during charge and discharge and improve the cycle life of the battery.

[0031] 2. Using the TiVCrMoC3 composite lithium metal electrode material obtained in Example 1 as the negative electrode and NCM811 as the positive electrode, a full cell was assembled. Its rate performance at current densities of 0.1C, 0.2C, 0.5C, 1C, 2C, and 0.1C was tested. The results are as follows: Figure 4 As shown: Depend on Figure 4 It can be seen that as the rate increases, the battery capacity exhibits a gradient decrease; even at a high rate of 2C, it still has a capacity of 50mAh. -1 The capacity remains above 90% even after returning to the initial rate of 0.1C, indicating that the battery material of this invention, when used as a negative electrode in lithium metal full batteries, can withstand a large power limit and has a wide range of applications.

[0032] Test Example 2 The negative electrode material used in Example 1 of Test Example 1 was replaced with pure lithium foil, and NCM811 was used as the positive electrode to assemble a full cell. Cycle stability was tested at a 1C current density as a comparison with Test Example 1. The results are as follows: Figure 5 As shown: Depend on Figure 5It can be seen that the full cell assembled with pure lithium wafers without high-entropy MXene as the negative electrode experiences rapid capacity reduction at a current density of 1C. After 50 charge-discharge cycles, the capacity decreases by 50%, and after 200 charge-discharge cycles, the capacity decreases to 0%, verifying that Example 1 significantly improves the cycle life and cycle stability of lithium metal batteries.

[0033] Those skilled in the art will recognize that the embodiments described herein are intended to help the reader understand the principles of the invention, and should be understood that the scope of protection of the invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific modifications and combinations based on the technical teachings disclosed in this invention without departing from the spirit of the invention, and these modifications and combinations are still within the scope of protection of this invention.

Claims

1. A method for preparing a high-entropy MXene-modified lithium metal anode based on solution coating, characterized in that, Includes the following steps: S1. Add the high-entropy MAX material to the hydrofluoric acid solution and stir at a constant temperature. Then centrifuge and wash with water until it is neutral to obtain a high-entropy MXene dispersion. Then freeze-dry under vacuum to obtain high-entropy MXene powder A. S2. Dissolve powder A in N-methylpyrrolidone solvent and add PVDF binder to prepare mixed solution A; S3. Add the mixed solution A onto the lithium sheet using a pipette, and then vacuum dry to obtain an electrode containing a protective layer.

2. The method for preparing a high-entropy MXene-modified lithium metal anode based on solution coating according to claim 1, characterized in that: The high-entropy MAX material in S1 is an MXene precursor powder containing five or more elements, with a mass of 1 to 3 g.

3. The method for preparing a high-entropy MXene-modified lithium metal anode based on solution coating according to claim 1, characterized in that: The hydrofluoric acid in S1 has a mass fraction of 20% to 60% and a volume of 20 to 60 mL.

4. The method for preparing a high-entropy MXene-modified lithium metal anode based on solution coating according to claim 1, characterized in that: The constant temperature stirring in S1 is 20-30°C, and the time is 36-48 hours.

5. The method for preparing a high-entropy MXene-modified lithium metal anode based on solution coating according to claim 1, characterized in that: In the mixed solution A in S2, the concentration of powder A is 60~100mg / ml.

6. The method for preparing a high-entropy MXene-modified lithium metal anode based on solution coating according to claim 1, characterized in that: In the mixed solution A in S2, the volume fraction of PVDF is 5%.

7. The method for preparing a high-entropy MXene-modified lithium metal anode based on solution coating according to claim 1, characterized in that: The dropping operation in S3 is at a rate of 0.3–0.5 ml / cm³. 2 The concentration was added dropwise.

8. The method for preparing a high-entropy MXene-modified lithium metal anode based on solution coating according to claims 1-7, characterized in that: The drying method in S3 is vacuum drying at 30~40℃ for 24~48h.

9. A high-entropy MXene-modified lithium metal anode material based on solution coating is obtained by any one of the preparation methods according to claims 1-8, and is applied to the anode of lithium metal batteries.

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