Method for preparing MXene material from fluoborate and application of MXene material
The preparation of MXene materials by fluoroborate etching solves the problems of high operational risks and long etching time in existing technologies, and realizes safe and efficient preparation of MXene materials, thereby improving their performance in lithium-ion energy storage electrodes.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-15
- Publication Date
- 2026-04-14
AI Technical Summary
Existing MXene material preparation processes suffer from high operational risks, poor environmental friendliness, long etching times, and low yields, making large-scale applications difficult.
The MXene material is formed by mixing fluoroborate with MAX phase material, heating and etching under inert gas protection, washing in acid or alkaline solution, centrifuging and freeze-drying.
A safe and rapid preparation of MXene materials was achieved, enhancing the electrochemical activity and cycle stability of the materials, making them suitable for lithium-ion energy storage electrodes.
Smart Images
Figure CN121849954A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of new materials technology, and in particular relates to a method and application for preparing MXene materials from fluoroborate. Background Technology
[0002] Two-dimensional transition metal carbides, nitrides, or carbonitrides (MXenes) are a class of graphene-like layered materials obtained by selectively etching the A-layer atoms (Al, Si, Ga, etc.) of ceramic compound MAX phases. They have high conductivity and tunable surface chemical properties, and show excellent application potential in the field of energy storage.
[0003] Currently, hydrofluoric acid etching is the most mature process for preparing MXene materials. Although it can effectively remove A-layer atoms, the use of high-concentration hydrofluoric acid is highly corrosive and toxic, posing significant operational risks, and requiring stringent wastewater treatment, resulting in poor environmental friendliness. In-situ formation hydrofluoric acid etching methods (such as LiF / HCl systems and difluoride salt systems) can reduce operational risks, but for some difficult-to-etch MAX phases, the etching time is long, and the etching products contain residual MAX phases, leading to low yields. Therefore, developing simple and rapid novel etching methods is of great significance for achieving large-scale preparation of MXene materials and promoting their widespread application. Summary of the Invention
[0004] The purpose of this invention is to provide a method and application for preparing MXene materials based on fluoroborates, overcoming the problems of production safety and operational hazards, as well as long process flows, associated with the aforementioned preparation processes. The MXene materials provided by this invention exhibit excellent cycle stability when used as lithium-ion energy storage electrode materials.
[0005] This invention is achieved through the following technical solution:
[0006] A method for preparing MXene materials from fluoroborates, wherein the chemical formula of the MXene material is M n+1 X n T x Wherein, M is a transition metal element, X is carbon, nitrogen, or carbon and nitrogen, T is a surface end group including -O, -OH, -F, -N, etc., and n is a natural number between 1 and 4; the preparation method includes the following steps:
[0007] (1) The precursor MAX phase and fluoroborate are mixed at a certain molar ratio and ground evenly to obtain a homogeneous mixture;
[0008] (2) The mixture is heated to a certain etching temperature under the protection of an inert gas, and after the reaction is held at the temperature for a certain time, it is naturally cooled to room temperature;
[0009] (3) Disperse the etched solid product in an acid or alkali solution of a certain molar concentration and stir and wash it;
[0010] (4) The product after stirring and washing was centrifuged with deionized water until the pH of the supernatant was close to 7 and then freeze-dried to obtain MXene material.
[0011] Preferably, M is one of the transition metal elements such as titanium, niobium, molybdenum, and tantalum.
[0012] Preferably, in step (1), the precursor MAX phase is Ti. n+1 AlC n 、Nb n+1 AlC n Mo n+1 AlC n and Ta n+1 AlC n One of them.
[0013] Preferably, the fluoroborate in step (1) is ammonium fluoroborate (NH4BF4).
[0014] Preferably, in step (1), the precursor MAX phase is mixed with fluoroborate at molar ratios of 1:2, 1:6 and 1:10 and then ground until homogeneous.
[0015] Preferably, the inert gas in step (2) is an argon atmosphere, the etching temperature is 250-800 ℃, and the heating rate is 4 ℃ min. –1 After reacting at a constant temperature for 2-7 hours, allow it to cool naturally to room temperature.
[0016] Preferably, the acid or alkali solution with a certain molar concentration in step (3) is 1-4 mol / L. –1 Sulfuric acid, hydrochloric acid, or sodium hydroxide solution.
[0017] Preferably, the stirring and washing conditions in step (3) are: washing temperature of 25-80 ℃ and washing reaction time of 10-180 min.
[0018] Preferably, the centrifugation washing conditions in step (4) are: first centrifuge at 10000 rpm for 3 min twice, then centrifuge at 3500 rpm for 5 min several times until the pH value of the supernatant is close to 7.
[0019] Preferably, the MXene material prepared in step (4) is Ti. n+1 C n T x 、Nb n+1 C n T x Mo n+1 Cn T x and Ta n+1 C n T x One of them.
[0020] The etching mechanism of the method for preparing MXene material provided by this invention is as follows: when the temperature is raised to 224 °C, ammonium fluoroborate (NH4BF4) begins to melt, accompanied by a violent endothermic decomposition reaction to form NH3, HF and BF3; if the temperature continues to rise, under strong heating, ammonium fluoroborate easily sublimates to form gas, and the decomposition reaction products will react with the MAX phase as gas, thereby etching away the A layer atoms to obtain MXene material.
[0021] The etching process of ammonium fluoroborate, taking the MAX phase Ti3AlC2 as an example, is shown in the following expression:
[0022] NH4BF4 → NH3↑+HF↑+BF3↑ (1)
[0023] Ti3AlC2+3HF↑ → Ti3C2+AlF3+3 / 2H2↑ (2)
[0024] Ti3C2+2HF → Ti3C2F2+H2↑ (3)
[0025] This invention also provides a nitrogen-doped MXene material and its preparation method, achieving simultaneous nitrogen doping during the MAX phase etching process. The NH3 gas generated during the etching process reacts with the end groups T on the surface of the formed MXene material at a certain temperature. x The interaction with exposed M atoms enables nitrogen doping of MXene materials.
[0026] This invention provides the application of the MXene material described in the above technical solution in lithium-ion energy storage electrode materials.
[0027] Beneficial effects:
[0028] This invention provides a method for preparing MXene materials using fluoroborate and its applications. Replacing the surface end groups of MXene materials with nitrogen atoms optimizes the surface electronic structure and enhances the electrochemical activity of the material. The introduction of nitrogen atoms provides more lithium-ion adsorption / desorption sites, enhancing the pseudocapacitive behavior of the material. The interaction between nitrogen atoms and exposed M atoms forms MN bonds, which helps stabilize transition metal atoms and improves the long-cycle stability of the material. Therefore, this material exhibits excellent cycle life when applied to lithium-ion energy storage electrodes. Attached Figure Description
[0029] Figure 1 Ti3C2T prepared in Example 1 xMaterials, Ti2CT prepared in Example 2 x Materials and Nb2CT prepared in Example 3 x XRD patterns of the materials and Comparative Example 1 untreated Ti3AlC2, Comparative Example 2 untreated Ti2AlC and Comparative Example 3 untreated Nb2AlC.
[0030] Figure 2 The Ti3C2T prepared in Examples 4, 5, 6, and 7 respectively x Materials and Ti3C2T prepared in Example 1 x XRD pattern of the material.
[0031] Figure 3 Ti3C2T prepared in Examples 8, 9, and 10 respectively x Materials and Ti3C2T prepared in Example 1 x XRD pattern of the material.
[0032] Figure 4 Ti2CTs prepared in Examples 11 and 12, respectively x XRD pattern of the material.
[0033] Figure 5 Ti3C2T prepared in Example 1 x SEM image of the material.
[0034] Figure 6 Ti3C2T prepared in Example 1 x XPS N 1s high-resolution spectrum of the material.
[0035] Figure 7 Ti3C2T prepared in Example 1 x The material is used for the electrochemical cycling performance of lithium storage anode materials. Detailed Implementation
[0036] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. However, the following embodiments are only for explaining the present invention, and the scope of protection of the present invention should include all the contents of the claims. Moreover, through the description of the following embodiments, those skilled in the art can fully implement all the contents of the claims of the present invention.
[0037] Example 1: A method for preparing MXene materials from fluoroborates, comprising the following steps:
[0038] (1) Mix 2 g of precursor Ti3AlC2 phase with ammonium fluoroborate at a molar ratio of 1:10 and grind evenly to obtain a homogeneous mixture;
[0039] (2) The mixture was heated to 550 °C under argon protection at a heating rate of 4 °C / min. –1 After reacting at the temperature for 5 hours, the mixture was allowed to cool naturally to room temperature.
[0040] (3) Disperse the etched solid product in 2 mol L –1 The sample was washed in a sodium hydroxide solution at 80 °C with stirring for 2 h.
[0041] (4) The product after stirring and washing was centrifuged with deionized water until the pH of the supernatant was close to 7 and then freeze-dried to obtain Ti3C2T x Material.
[0042] Example 2: A method for preparing MXene materials from fluoroborate, comprising the following steps:
[0043] (1) Mix 2 g of precursor Ti2AlC phase with ammonium fluoroborate at a molar ratio of 1:10 and grind evenly to obtain a homogeneous mixture;
[0044] (2) The mixture was heated to 600 °C under argon protection at a heating rate of 4 °C / min. –1 After reacting at the temperature for 5 hours, the mixture was allowed to cool naturally to room temperature.
[0045] (3) Disperse the etched solid product in 2 mol L –1 The sample was washed in a sodium hydroxide solution at 80 °C with stirring for 2 h.
[0046] (4) The product after stirring and washing was centrifuged with deionized water until the pH of the supernatant was close to 7 and then freeze-dried to obtain Ti2CT. x Material.
[0047] Example 3: A method for preparing MXene materials from fluoroborate, comprising the following steps:
[0048] (1) Mix 2 g of precursor Nb2AlC phase with ammonium fluoroborate at a molar ratio of 1:10 and grind evenly to obtain a homogeneous mixture;
[0049] (2) The mixture was heated to 550 °C under argon protection at a heating rate of 4 °C / min. –1 After reacting at the temperature for 5 hours, the mixture was allowed to cool naturally to room temperature.
[0050] (3) Disperse the etched solid product in 2 mol L –1 The sample was washed in a sodium hydroxide solution at 80 °C with stirring for 2 h.
[0051] (4) The product after stirring and washing was centrifuged with deionized water until the pH of the supernatant was close to 7 and then freeze-dried to obtain Nb2CT. xMaterial.
[0052] Example 4: A method for preparing MXene materials from fluoroborate, comprising the following steps:
[0053] (1) Mix 2 g of precursor Ti3AlC2 phase with ammonium fluoroborate at a molar ratio of 1:10 and grind evenly to obtain a homogeneous mixture;
[0054] (2) The mixture was heated to 550 °C under argon protection at a heating rate of 4 °C / min. –1 After reacting at the temperature for 5 hours, the mixture was allowed to cool naturally to room temperature.
[0055] (3) Disperse the etched solid product in 2 mol L –1 The sample was washed in a sulfuric acid solution at 60 °C with stirring for 2 h.
[0056] (4) The product after stirring and washing was centrifuged with deionized water until the pH of the supernatant was close to 7 and then freeze-dried to obtain Ti3C2T x Material.
[0057] Example 5: A method for preparing MXene materials from fluoroborate, comprising the following steps:
[0058] (1) Mix 2 g of precursor Ti3AlC2 phase with ammonium fluoroborate at a molar ratio of 1:10 and grind evenly to obtain a homogeneous mixture;
[0059] (2) The mixture was heated to 550 °C under argon protection at a heating rate of 4 °C / min. –1 After reacting at the temperature for 5 hours, the mixture was allowed to cool naturally to room temperature.
[0060] (3) Disperse the etched solid product in 2 mol L –1 The sample was washed in a sodium hydroxide solution at 60 °C with stirring for 2 h.
[0061] (4) The product after stirring and washing was centrifuged with deionized water until the pH of the supernatant was close to 7 and then freeze-dried to obtain Ti3C2T x Material.
[0062] Example 6: A method for preparing MXene materials from fluoroborate, comprising the following steps:
[0063] (1) Mix 2 g of precursor Ti3AlC2 phase with ammonium fluoroborate at a molar ratio of 1:10 and grind evenly to obtain a homogeneous mixture;
[0064] (2) The mixture was heated to 550 °C under argon protection at a heating rate of 4 °C / min. –1 After reacting at the temperature for 5 hours, the mixture was allowed to cool naturally to room temperature.
[0065] (3) Disperse the etched solid product in 2 mol L –1 Wash with stirring at 80 °C for 20 min in a sodium hydroxide solution.
[0066] (4) The product after stirring and washing was centrifuged with deionized water until the pH of the supernatant was close to 7 and then freeze-dried to obtain Ti3C2T x Material.
[0067] Example 7: A method for preparing MXene materials from fluoroborates, comprising the following steps:
[0068] (1) Mix 2 g of precursor Ti3AlC2 phase with ammonium fluoroborate at a molar ratio of 1:10 and grind evenly to obtain a homogeneous mixture;
[0069] (2) The mixture was heated to 550 °C under argon protection at a heating rate of 4 °C / min. –1 After reacting at the temperature for 5 hours, the mixture was allowed to cool naturally to room temperature.
[0070] (3) Disperse the etched solid product in 1 mol L –1 The sample was washed in a sodium hydroxide solution at 80 °C with stirring for 2 h.
[0071] (4) The product after stirring and washing was centrifuged with deionized water until the pH of the supernatant was close to 7 and then freeze-dried to obtain Ti3C2T x Material.
[0072] Example 8: A method for preparing MXene materials from fluoroborate, comprising the following steps:
[0073] (1) Mix 2 g of precursor Ti3AlC2 phase with ammonium fluoroborate at a molar ratio of 1:10 and grind evenly to obtain a homogeneous mixture;
[0074] (2) The mixture was heated to 450 °C under argon protection at a heating rate of 4 °C / min. –1 After reacting at the temperature for 5 hours, the mixture was allowed to cool naturally to room temperature.
[0075] (3) The etched solid product was dispersed in deionized water and stirred and washed, and then centrifuged and washed until the pH of the supernatant was close to 7 and freeze-dried to obtain Ti3C2T. x Material.
[0076] Example 9: A method for preparing MXene materials from fluoroborates, comprising the following steps:
[0077] (1) Mix 2 g of precursor Ti3AlC2 phase with ammonium fluoroborate at a molar ratio of 1:10 and grind evenly to obtain a homogeneous mixture;
[0078] (2) The mixture was heated to 550 °C under argon protection at a heating rate of 4 °C / min. –1 After reacting at the temperature for 5 hours, the mixture was allowed to cool naturally to room temperature.
[0079] (3) The etched solid product was dispersed in deionized water and stirred and washed, and then centrifuged and washed until the pH of the supernatant was close to 7 and freeze-dried to obtain Ti3C2T. x Material.
[0080] Example 10: A method for preparing MXene materials from fluoroborates, comprising the following steps:
[0081] (1) Mix 2 g of precursor Ti3AlC2 phase with ammonium fluoroborate at a molar ratio of 1:10 and grind evenly to obtain a homogeneous mixture;
[0082] (2) The mixture was heated to 650 °C under argon protection at a heating rate of 4 °C / min. –1 After reacting at the temperature for 5 hours, the mixture was allowed to cool naturally to room temperature.
[0083] (3) The etched solid product was dispersed in deionized water and stirred and washed, and then centrifuged and washed until the pH of the supernatant was close to 7 and freeze-dried to obtain Ti3C2T. x Material.
[0084] Example 11: A method for preparing MXene materials from fluoroborates, comprising the following steps:
[0085] (1) Mix 2 g of precursor Ti2AlC2 phase with ammonium fluoroborate at a molar ratio of 1:6 and grind evenly to obtain a homogeneous mixture;
[0086] (2) The mixture was heated to 600 °C under argon protection at a heating rate of 4 °C / min. –1 After reacting at the temperature for 5 hours, the mixture was allowed to cool naturally to room temperature.
[0087] (3) The etched solid product was dispersed in deionized water and stirred and washed, and then centrifuged and washed until the pH of the supernatant was close to 7 and freeze-dried to obtain Ti2CT. x Material.
[0088] Example 12: A method for preparing MXene materials from fluoroborates, comprising the following steps:
[0089] (1) Mix 2 g of precursor Ti2AlC2 phase with ammonium fluoroborate at a molar ratio of 1:10 and grind evenly to obtain a homogeneous mixture;
[0090] (2) The mixture was heated to 600 °C under argon protection at a heating rate of 4 °C / min. –1 After reacting at the temperature for 5 hours, the mixture was allowed to cool naturally to room temperature.
[0091] (3) The etched solid product was dispersed in deionized water and stirred and washed, and then centrifuged and washed until the pH of the supernatant was close to 7 and freeze-dried to obtain Ti2CT. x Material.
[0092] Comparative Example 1: Ti3AlC2, a MAX phase material that has not undergone any treatment.
[0093] Comparative Example 2: Ti2AlC, a MAX phase material that has not undergone any treatment.
[0094] Comparative Example 3: Untreated MAX phase material Nb2AlC.
[0095] Technical Extension: Three-dimensional MAX phases are ceramic materials, and more than 60 types of MAX materials have been reported to date. Therefore, the successful preparation of MAX materials in Examples 1, 2, and 3 can be extended to a wider range of MXenes materials prepared by fluoroborate etching, such as those based on Ti. n+1 AlC n 、Nb n+1 AlC n Mo n+1 AlC n and Ta n+1 AlC n Ti prepared by MAX phase n+1 C n T x 、Nb n+1 C n T x Mo n+1 C n T x and Ta n+1 C n T x MXene materials, etc.
[0096] Figure 1 XRD patterns of the MXene materials prepared in Examples 1, 2, and 3, and the untreated MAX phases in Comparative Examples 1, 2, and 3. The comparison shows that Ti3C2T x The disappearance of the (104) diffraction peak near 39.0°, which belongs to the Al atomic layer, indicates that the Al atomic layer was successfully etched. Furthermore, the intensity of the (002) diffraction peak corresponding to the layered features weakened and shifted to the left to near 8.3°, while the (004) diffraction peak also shifted to the left to near 17.9°, confirming that Ti3C2T x Successful preparation of the material. Ti2CTx The disappearance of the (103) diffraction peak near 39.5°, which belongs to the Al atomic layer, indicates that the Al atomic layer was successfully etched. Furthermore, the (002) diffraction peak corresponding to the layered features shifted to the left to approximately 9.5°, confirming that Ti2CT... x Successful preparation of the material. Nb2CT x The disappearance of the (103) diffraction peak near 38.7°, which belongs to the Al atomic layer, indicates that the Al atomic layer was successfully etched. The (002) diffraction peak, corresponding to the layered features, shifts to the left to approximately 8.7°. Simultaneously, (100) and (101) characteristic peaks appear at 36.1° and 40.5°, respectively, attributed to interlayer expansion and lattice distortion during the fabrication process, further confirming the Nb2CT... x Successful preparation of the material.
[0097] Figure 2 The Ti3C2T prepared in Examples 4, 5, 6, and 7 respectively x Materials and Ti3C2T prepared in Example 1 x XRD pattern of the material. As shown in the figure, the Ti3C2T prepared in Example 4... x The XRD pattern of the material shows (002) layered diffraction peaks, but the diffraction peak of TiOF2, a byproduct of etching (approximately 23.4°), is still present, indicating poor sulfuric acid washing effect. Furthermore, the presence of TiO2 diffraction peaks (25.2°, 36.0°, 47.4°, and 53.0°) suggests that sulfuric acid easily causes surface oxidation of the material. The Ti3C2T prepared in Examples 5 and 6... x The XRD pattern of the material still shows a relatively obvious diffraction peak of the byproduct TiOF2 (approximately 23.4°), indicating that sufficient washing reaction time and relatively high temperature are more conducive to the removal of reaction byproducts. Example 7 prepared Ti3C2T x The XRD pattern of the material clearly shows the diffraction peaks of the etching byproduct TiOF2, indicating that the reaction intensity of the low molar concentration sodium hydroxide solution is low and insufficient to remove the byproduct.
[0098] Figure 3 Ti3C2T prepared in Examples 8, 9, and 10 respectively x Materials and Ti3C2T prepared in Example 1 xXRD patterns of the materials. Examples 8, 9 and 10 compared the etching effects of Ti3AlC2 at different temperatures. In the XRD pattern of the material prepared in Example 8, there was still a weak (104) diffraction peak at 39.0°, indicating that the Al atomic layer etching was incomplete at this temperature. In addition, there were a large number of XRD diffraction peaks (13.9°, 24.7°) of the etching byproduct NH4AlF4 in the pattern. These were mainly formed by the reaction of the intermediate phase NH4BF4·NH4F and other fluorides and fluoroborate mixtures formed during the decomposition of NH4BF4 with AlF3. In the XRD pattern of the material prepared in Example 9, the (104) diffraction peak basically disappeared, indicating that the etching was more complete at this temperature. The XRD diffraction peak of the etching byproduct NH4AlF4 was also present. The XRD pattern of the material prepared in Example 10 showed that the Al atomic layer etching was more complete, but the oxidation degree of the material was higher. Due to the increase in etching temperature, NH4AlF4 was almost completely decomposed, and no obvious diffraction peaks appeared.
[0099] Figure 4 Ti2CT prepared for Examples 11 and 12 x XRD patterns of the material. XRD results show that the Ti2AlC etching products with different molar ratios washed only with deionized water contain byproducts NH4AlF4 and TiOF2. Furthermore, the XRD pattern of the 1:6 molar ratio etching product still shows a significant (103) diffraction peak, indicating that the Al atomic layer etching is incomplete at this molar ratio. The (103) diffraction peak disappears in the 1:10 molar ratio etching product. Therefore, a higher content of NH4BF4 etchant is needed to compensate for the volatilization during the etching process, thus satisfying the etching requirements of the MAX phase material.
[0100] Figure 5 Ti3C2T prepared in Example 1 x SEM images of the materials. The SEM images show that the MXene materials prepared in Example 1 all exhibit a distinct layered structure, consistent with the XRD results.
[0101] Figure 6 Ti3C2T prepared in Example 1 x The N 1s high-resolution spectrum of the material. The presence of nitrogen indicates that this etching method can introduce nitrogen in situ. The characteristic peaks of tetravalent nitrogen in the N 1s high-resolution spectrum mainly originate from the etchant component NH4 during the etching process. + The presence of pyrrole nitrogen also confirms nitrogen doping, and nitrogen oxides are formed due to the oxidation of alkaline detergents. These nitrogens may mainly adsorb at the material edges, which helps to improve the electrochemical activity and charge transport capacity of the material surface and improve the adsorption of the material surface. The presence of Ti-N bonds is beneficial to stabilizing the transition metal central atom.
[0102] Figure 7Ti3C2T prepared in Example 1 x The electrochemical cycling performance of the material was studied as a lithium storage anode material. Electrochemical performance was tested using a lithium metal sheet as the counter electrode in a coin cell assembly. Example 1: Ti3C2T x The material at 0.5 A g –1 It has -100 mAh g at all current densities –1 It exhibits high charge specific capacity and no capacity decay after 400 cycles, demonstrating excellent electrochemical cycling stability.
[0103] 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.
[0104] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. 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 scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.
Claims
1. A method for preparing MXene materials from fluoroborate, characterized in that, The chemical formula for this MXene material is M. n+ 1X n T x Where M is titanium, niobium, molybdenum, or tantalum, X is carbon, nitrogen, or a combination of carbon and nitrogen, T is a surface end group including -O, -OH, -F, or -N, and n is a natural number between 1 and 4; the preparation method includes the following steps: (1) The precursor MAX phase and fluoroborate are mixed and ground at a molar ratio of 1:2-1:10; (2) Etching is performed at 250-800 ℃ under inert gas protection for 2-7 hours; (3) Disperse the etching product in 1-4 mol L –1 Wash by stirring in acid or alkaline solutions; (4) Centrifuge and wash until the pH value is close to 7, then freeze dry.
2. The method according to claim 1, characterized in that, The precursor MAX phase is Ti n+1 AlC n 、Nb n+1 AlC n Mo n+1 AlC n and Ta n+1 AlC n One of them.
3. The method according to claim 1, characterized in that, The fluoroborate is ammonium fluoroborate NH4BF4.
4. The method according to claim 1, characterized in that, In step (2), the heating rate is 4 °C / min. –1 .
5. The method according to claim 1, characterized in that, In step (3), the acid or alkali solution is sulfuric acid, hydrochloric acid or sodium hydroxide solution, the washing temperature is 25-80 ℃, and the washing reaction time is 10-180 min.
6. An MXene material, characterized in that, Prepared by any one of the methods of claims 1-5, having a nitrogen-doped surface structure.
7. The MXene material according to claim 6, characterized in that, The nitrogen-doped structure includes Ti-N bonds, pyrrole nitrogen, and nitrogen oxides.
8. An application of the MXene material as described in claim 6 or 7, characterized in that, Used as a negative electrode material for lithium-ion batteries.
9. A method for preparing a nitrogen-doped MXene material, characterized in that, In the process of etching the MAX phase with ammonium fluoroborate, in-situ nitrogen doping is achieved by using NH3 generated from the decomposition.
10. A lithium-ion battery negative electrode, characterized in that, It includes the MXene material as described in any one of claims 6-7.