Homologous heterostructure high-entropy MAX phase and preparation method and application thereof

Abstract

The invention belongs to the technical field of inorganic nonmetallic materials, and particularly relates to a homologous heterostructure high-entropy MAX phase and a preparation method and application thereof. The M site of the prepared homologous heterostructure high-entropy MAX phase material is four transition metals of Ti, V, Cr and Mo, the A site is Al, the X site is C, the molar ratio of the transition metal elements is (0.1-1): (0.1-1): (0.1-1): (0.1-1): (0.1-1), specifically, through two-step solid-phase reaction (step-by-step calcination), element ratio optimization and process parameter control, uniform solid solution and heterogeneous interface formation of the four transition metals of Ti, V, Cr and Mo are achieved for the first time, and the homologous heterostructure high-entropy MAX phase material is prepared. The homologous and heterostructure high-entropy MAX phase material has the advantages of high purity and uniform element distribution, and has excellent application prospects in the fields of aerospace and energy materials. Meanwhile, the two-step solid-phase reaction preparation method adopted by the invention is simple in process, energy-saving and environment-friendly, and the homologous heterostructure high-entropy MAX phase powder with low impurity phase content can be produced, so that the method has good practical application value.

Description

Technical Field

[0001] The present invention belongs to the technical field of inorganic non-metallic materials, and particularly relates to a homologous heterostructure high-entropy MAX phase, a preparation method thereof and an application thereof. Background Art

[0002] Disclosing the information of this background art section is only intended to enhance the understanding of the overall background of the present invention, and is not necessarily regarded as an admission or an implication in any form that this information constitutes the prior art already known to those of ordinary skill in the art.

[0003] The high-entropy MAX phase refers to a class of high-entropy materials with a MAX phase structure, which is a ternary layered compound composed of a variety of transition metals (M), A-site elements (such as Al, Si, etc.) and X-site elements (C / N), and has a hexagonal symmetric crystal structure, formed by the interleaved stacking of M n+1 X n layers and A atomic layers, where the M n+1 X n layers are connected by edge-sharing octahedra (M6X) through covalent bonds or ionic bonds, and X atoms occupy the octahedral interstitial sites, with the chemical general formula of M n+1 AX n (n = 1, 2, 3…).

[0004] The high-entropy characteristics of the high-entropy MAX phase endow the material with excellent strength, toughness, high-temperature and high-pressure stability, and electrical conductivity. The heterostructure material is a multiphase material formed by the physical or chemical coupling of multiple components, with rich heterointerfaces and accompanied by complex interfacial effects. The intrinsic characteristics of the structural units (such as the energy band structure and Fermi level difference, etc.) and the charge redistribution behavior near the heterointerfaces will have a significant impact on the overall electronic structure and electric field distribution of the heterostructure material. In addition, the homologous heterostructure can form a stronger coupling interface and induce the intensification of the synergistic effect between the components, thereby endowing the material with enhanced electrical conductivity, fast ion diffusion kinetics and excellent cycle stability. The heterostructure also plays a unique role in optimizing the stress distribution and strengthening the phase interface, making the heterostructure high-entropy material perform excellently in bearing stress and plastic deformation, having stronger high-temperature stability and antioxidant properties, and being applicable to extreme environmental conditions. However, in the prior art, the preparation of the homologous heterostructure high-entropy MAX phase faces the following problems:

[0005] (1) Phase separation: Multiple main elements lead to uneven element distribution and it is difficult to form a uniform solid solution;

[0006] (2) Complex synthesis process: Traditional methods (such as hot pressing sintering, molten salt method, SPS rapid sintering technology) require complex equipment or high-energy-consuming processes;

[0007] (3)Heterostructure deficiency: The prior art has not achieved the controllable synthesis of homologous heterostructures. Summary of the Invention

[0008] In view of the above problems, the purpose of the present invention is to provide a homologous heterostructure high-entropy MAX phase and its preparation method and application. The present invention uses transition metal element single powders as metal sources, aluminum powder and graphite powder as aluminum source and carbon source respectively. By controlling the powder calcination temperature and the addition amount of aluminum, the solid solution of each transition metal element at the M site is realized, and a homologous heterostructure high-entropy MAX phase powder with higher purity is formed, which has good practical application value.

[0009] Specifically, the present invention provides the following technical solutions:

[0010] In the first aspect of the present invention, a homologous heterostructure high-entropy MAX phase is provided, and its general formula is M n+1 AlC n , (n≥1), where M is a transition metal, including Ti, V, Cr, Mo, and the molar ratio is 0.1~1:0.1~1:0.1~1:0.1~1; the total molar ratio of the transition metals to aluminum Al and carbon C is 3:1.2~1.6:1.8~2;

[0011] The homologous heterostructure high-entropy MAX phase has a hexagonal crystal system structure, and the unit cell is composed of M n+1 C n atomic layers and Al atomic layers stacked alternately in the c-axis direction; in the M n+1 C n atomic layer, transition metal atoms are randomly distributed at the M site, forming a homologous heterointerface; the content of the impurity phase is less than 10%, and the element distribution is uniform.

[0012] Preferably, both 312 configuration and 413 configuration exist in the homologous heterostructure high-entropy MAX phase, and the ratio of the 312 and 413 configurations is x:1-x (the value range of x is 0<x<1).

[0013] Preferably, the interface spacing of the homologous heterointerface is 1.3~1.5nm.

[0014] In the second aspect of the present invention, a preparation method of the above-mentioned homologous heterostructure high-entropy MAX phase is provided, specifically: the powder mixture of titanium source, vanadium source, chromium source, molybdenum source and carbon source is pressed into a mold and then subjected to the first calcination to obtain a carbide solid solution powder; then the powder mixture of the carbide solid solution powder and aluminum source is pressed into a mold and then subjected to the second calcination to obtain the homologous heterostructure high-entropy MAX phase powder.

[0015] Preferably, the titanium source, vanadium source, chromium source, molybdenum source, and aluminum source are single powders of each metal element; the carbon source is graphite powder.

[0016] Preferably, the pressure for the press molding is 10 - 17 MPa.

[0017] Preferably, the temperature for the first calcination is 1650 °C, the heating rate is 4 - 6 °C / min, and the calcination time is 2 - 3 h; the temperature for the second calcination is 1400 - 1500 °C, the heating rate is 4 - 6 °C / min, and the calcination time is 1 - 1.5 h.

[0018] More preferably, the temperature for the first calcination is 1650 °C, the heating rate is 4 °C / min, and the calcination time is 3 h; the temperature for the second calcination is 1450 °C, the heating rate is 4 °C / min, and the calcination time is 1 h.

[0019] Preferably, both the first calcination and the second calcination are carried out in an inert atmosphere.

[0020] Preferably, the products obtained from the first calcination and the second calcination both need to be ground and dried; the grinding medium added during grinding is deionized water or absolute ethanol; the drying temperature is 60 - 80 °C.

[0021] In the third aspect of the present invention, there is provided an application of the derivative of the homologous and heterogeneous structure high-entropy MAX phase described in the first aspect in the field of energy materials.

[0022] One or more embodiments of the present invention have at least the following beneficial effects:

[0023] (1) The present invention uses four kinds of transition metal elemental powders, aluminum powder and graphite powder as raw materials, and adopts a process of two-step uniform mixing, grinding and calcination. Specifically, by adjusting the calcination temperature, the local transformation of the 312 configuration high-entropy MAX phase to the 413 configuration is controlled, realizing the construction of the mixed configuration and the heterogeneous transition region in the homologous and heterogeneous structure high-entropy MAX phase. The obtained homologous and heterogeneous structure high-entropy MAX phase material has the advantages of high purity and uniform element distribution.

[0024] (2) The two-step solid-phase reaction preparation method adopted by the present invention has a simple process, is energy-saving and environmentally friendly, and can produce homologous and heterogeneous structure high-entropy MAX phase powders with a low impurity phase content. Therefore, it has good practical application value.

[0025] (3) By selectively etching the Al atomic layer, a derivative MXene material of a homologous heterostructure high-entropy MAX phase was obtained, and its electrochemical performance was tested. The results show that the excellent electrochemical performance can be attributed to the differences in lattice parameters in different configuration regions and the formation of a heterogeneous transition region, which leads to different structural symmetries, induces a complex differential electrostatic potential field, electronic structure, and local atomic coordination, endows the internal transition metal atoms with a higher average oxidation state, enables it to obtain enhanced electrochemical reaction activity, and thus exhibits a higher specific capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings forming a part of this invention are used to provide a further understanding of the invention. The schematic embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation to the invention.

[0027] Figure 1 It is the X-ray diffraction pattern of the homologous heterostructure high-entropy MAX phase powder with four transition metals Ti, V, Cr, and Mo in the M position prepared in Example 1 of the present invention;

[0028] Figure 2 It is the atomic resolution high-angle annular dark-field scanning transmission electron microscopy image of the homologous heterostructure high-entropy MAX phase powder with four transition metals Ti, V, Cr, and Mo in the M position prepared in Example 1 of the present invention; Figure 3 It is the cyclic stability and specific capacity test images of high-entropy MXenes with different configurations prepared in Example 1 and Comparative Examples 1-2 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0030] Combined with specific embodiments below, the present invention will be further described in detail. It should be noted that the specific embodiments are explanations rather than limitations of the present invention.

[0031] Example 1 : This embodiment provides a homologous heterostructure high-entropy MAX phase and its preparation method

[0032] 1) Weigh the raw materials according to the molar ratio of the total of transition metals to carbon (C) being 3:1.9. The metal sources are titanium powder, vanadium powder, chromium powder, and molybdenum powder respectively, and the carbon source is graphite powder. Each metal element (Ti, V, Cr, Mo) weighed is 0.009 mol;

[0033] 2) Dissolve the raw materials weighed in step 1) in 10 mL of absolute ethanol, and manually grind them in an agate mortar to fully mix the raw materials;

[0034] 3) Place the mixture obtained in step 2) in a vacuum drying oven at 60 °C for drying to obtain a mixture powder;

[0035] 4) Pour the mixture powder obtained in step 3) into a mold and dry-press it at 15 MPa to obtain a cylindrical green body;

[0036] 5) Calcinate the cylindrical green body obtained in step 4) at 1650 °C for 3 h for heat preservation.

[0037] 6) After grinding the carbide solid solution obtained in step 5) into powder, weigh the carbide solid solution and aluminum powder according to the molar ratio of the total of transition metals, aluminum (Al), and carbon (C) being 3:1.4:1.9. The weighed aluminum is 0.007 mol;

[0038] 7) Dissolve the carbide solid solution and aluminum powder weighed in step 6) in 10 mL of absolute ethanol, and manually grind them in an agate mortar to fully mix the raw materials;

[0039] 8) Place the mixture obtained in step 7) in a vacuum drying oven at 60 °C for drying to obtain a mixture powder;

[0040] 9) Pour the mixture powder obtained in step 8) into a mold and dry-press it at 15 MPa to obtain a cylindrical green body;

[0041] 10) Calcinate the cylindrical green body obtained in step 9) at 1450 °C for 1 h for heat preservation.

[0042] 11) Grind the homologous and heterogeneous high-entropy MAX phase obtained in step 10) into powder.

[0043] The phase information and micro-morphology of the obtained homologous and heterogeneous high-entropy MAX phase powder are respectively referred to Figure 1 and Figure 2 the X-ray diffraction pattern and the atomic resolution high-angle annular dark field scanning transmission electron microscopy image shown.

[0044] As Figure 1As shown, a series of diffraction peaks at 9.7°, 19.6°, 29.5°, 35.4°, 40.4°, 43.3°, 50.1°, 58.2°, and 62.8° can be well indexed to the (002), (004), (006), (101), (104), (105), (107), (109), and (110) crystal planes of the 312-type MAX phase, while a series of diffraction peaks at 7.8°, 15.5°, 23.3°, 38.2°, 39.2°, 42.4°, 56.7°, and 60.2° can be well indexed to the (002), (004), (006), (104), (105), (106), (1012), and (110) crystal planes of the 413-type MAX phase. The above results indicate the successful synthesis of the high-entropy MAX phase, and the coexistence of the crystal structure characteristics of the 312 configuration and the 413 configuration.

[0045] As Figure 2 shown, under the STEM mode, the atomic brightness is positively correlated with the square of its average atomic number. Three bright atomic columns (M atomic layer) and a single dark atomic column (A atomic layer) are observed to be arranged alternately in a zigzag pattern at the lower part of the picture, indicating the existence of the 312 configuration; the upper part of the picture shows a sandwich-like arrangement of four transition metal atomic layers and one Al atomic layer, indicating the existence of the 413 configuration; a heterogeneous transition region with alternating numbers of different transition metal atomic layers is formed in the middle part of the picture. The above results prove the existence of a mixed configuration in the same high-entropy MAX phase particle, and a heterogeneous transition region is formed between the two configurations, indicating the successful synthesis of the homologous heterogeneous structure high-entropy MAX phase.

[0046] Example 2 : This example provides a homologous heterogeneous structure high-entropy MAX phase and its preparation method

[0047] 1) Weigh the raw materials according to the molar ratio of the total of transition metals to carbon (C) being 3:1.8. The metal sources are titanium powder, vanadium powder, chromium powder, and molybdenum powder respectively, and the carbon source is graphite powder. Each metal element weighed is 0.009 mol;

[0048] 2) Dissolve the raw materials weighed in step 1) in 10 mL of absolute ethanol, and manually grind them in an agate mortar to fully mix the raw materials;

[0049] 3) Place the mixture obtained in step 2) in a vacuum drying oven at 70 °C for drying to obtain a mixture powder;

[0050] 4) Pour the mixture powder obtained in step 3) into a mold and dry press it at 16 MPa to obtain a cylindrical green body;

[0051] 5) The cylindrical green body obtained in step 4) is calcined at 1650 °C for 3 h;

[0052] 6) After grinding the carbide solid solution obtained in step 5) into powder, weigh the carbide solid solution and aluminum powder according to the molar ratio of the total of transition metals to aluminum (Al) and carbon (C) of 3:1.4:1.8. The weighed aluminum is 0.007 mol;

[0053] 7) Dissolve the weighed carbide solid solution and aluminum powder in step 6) in 10 mL of absolute ethanol, and manually grind them in an agate mortar to fully mix the raw materials;

[0054] 8) Place the mixture obtained in step 7) in a vacuum drying oven at 70 °C for drying to obtain a mixture powder;

[0055] 9) Pour the mixture powder obtained in step 8) into a mold and dry-press it into a cylindrical green body at 16 MPa;

[0056] 10) The cylindrical green body obtained in step 9) is calcined at 1450 °C for 1 h.

[0057] 11) Grind the homologous and heterogeneous high-entropy MAX phase obtained in step 10) into powder.

[0058] Example 3 : This example provides a homologous and heterogeneous high-entropy MAX phase and its preparation method

[0059] 1) Weigh the raw materials according to the molar ratio of the total of transition metals to carbon (C) of 3:1.9. The metal sources are titanium powder, vanadium powder, chromium powder and molybdenum powder respectively, and the carbon source is graphite powder. Each weighed metal element is 0.009 mol;

[0060] 2) Dissolve the weighed raw materials in step 1) in 10 mL of absolute ethanol, and manually grind them in an agate mortar to fully mix the raw materials;

[0061] 3) Place the mixture obtained in step 2) in a vacuum drying oven at 60 °C for drying to obtain a mixture powder;

[0062] 4) Pour the mixture powder obtained in step 3) into a mold and dry-press it into a cylindrical green body at 12 MPa;

[0063] 5) The cylindrical green body obtained in step 4) is calcined at 1650 °C for 3 h.

[0064] 6) After grinding the carbide solid solution obtained in step 5) into powder, weigh the carbide solid solution and aluminum powder according to the molar ratio of the total of transition metals to aluminum (Al) and carbon (C) of 3:1.6:1.9. The weighed aluminum is 0.007 mol;

[0065] 7) Dissolve the carbide solid solution and aluminum powder weighed in step 6) in 10 mL of absolute ethanol, and manually grind them in an agate mortar to fully mix the raw materials;

[0066] 8) Place the mixture obtained in step 7) in a vacuum drying oven at 60 °C for drying to obtain a mixture powder;

[0067] 9) Pour the mixture powder obtained in step 8) into a mold and dry-press it into shape at 12 MPa to obtain a cylindrical green body;

[0068] 10) Calcinate the cylindrical green body obtained in step 9) at 1500 °C for 1 h.

[0069] 11) Grind the obtained homologous and heterogeneous structure high-entropy MAX phase in step 10) into powder.

[0070] Comparative Example 1 : This comparative example provides a 312 configuration high-entropy MAX phase and its preparation method

[0071] 1) Weigh the raw materials according to the molar ratio of the total of transition metals to carbon (C) of 3:1.9. The metal sources are titanium powder, vanadium powder, chromium powder and molybdenum powder respectively, and the carbon source is graphite powder. Each weighed metal element is 0.009 mol;

[0072] 2) Dissolve the raw materials weighed in step 1) in 10 mL of absolute ethanol, and manually grind them in an agate mortar to fully mix the raw materials;

[0073] 3) Place the mixture obtained in step 2) in a vacuum drying oven at 60 °C for drying to obtain a mixture powder;

[0074] 4) Pour the mixture powder obtained in step 3) into a mold and dry-press it into shape at 15 MPa to obtain a cylindrical green body;

[0075] 5) Calcinate the cylindrical green body obtained in step 4) at 1600 °C for 3 h.

[0076] 6) After grinding the carbide solid solution obtained in step 5) into powder, weigh the carbide solid solution and aluminum powder according to the molar ratio of the total of transition metals to aluminum (Al) and carbon (C) of 3:1.4:1.9. The weighed aluminum is 0.007 mol;

[0077] 7) Dissolve the carbide solid solution and aluminum powder weighed in step 6) in 10 mL of absolute ethanol, and manually grind them in an agate mortar to fully mix the raw materials;

[0078] 8) Place the mixture obtained in step 7) in a vacuum drying oven at 60 °C for drying to obtain a mixture powder;

[0079] 9) Pour the mixture powder obtained in step 8) into a mold and dry-press it at 15 MPa to form a cylindrical green body;

[0080] 10) Calcinate the cylindrical green body obtained in step 9) at 1400 °C for 1 h.

[0081] 11) Grind the 312 configuration high-entropy MAX phase obtained in step 10) into powder.

[0082] Comparative Example 2 : This comparative example provides a 413 configuration high-entropy MAX phase and its preparation method

[0083] 1) Weigh the raw materials according to the molar ratio of the total of transition metals to carbon (C) of 3:1.9. The metal sources are titanium powder, vanadium powder, chromium powder and molybdenum powder respectively, and the carbon source is graphite powder. Each weighed metal element is 0.009 mol;

[0084] 2) Dissolve the raw materials weighed in step 1) in 10 mL of absolute ethanol, and manually grind them in an agate mortar to fully mix the raw materials;

[0085] 3) Place the mixture obtained in step 2) in a vacuum drying oven at 60 °C for drying to obtain a mixture powder;

[0086] 4) Pour the mixture powder obtained in step 3) into a mold and dry-press it at 15 MPa to form a cylindrical green body;

[0087] 5) Calcinate the cylindrical green body obtained in step 4) at 1600 °C for 3 h.

[0088] 6) After grinding the carbide solid solution obtained in step 5) into powder, weigh the carbide solid solution and aluminum powder according to the molar ratio of the total of transition metals to aluminum (Al) and carbon (C) of 3:1.7:1.9. The weighed aluminum is 0.007 mol;

[0089] 7) Dissolve the carbide solid solution and aluminum powder weighed in step 6) in 10 mL of absolute ethanol, and manually grind them in an agate mortar to fully mix the raw materials;

[0090] 8) Place the mixture obtained in step 7) in a vacuum drying oven at 60 °C for drying to obtain a mixture powder;

[0091] 9) Pour the mixture powder obtained in step 8) into a mold, and dry-press it into a cylindrical green body at 15 MPa.

[0092] 10) Calcinate the cylindrical green body obtained in step 9) at 1500 °C for 1 h.

[0093] 11) Grind the 413-structured high-entropy MAX phase obtained in step 10) into powder.

[0094] Test Example 1 : In this test example, the electrochemical properties of the homologous heterostructured high-entropy MAX phase prepared in Example 1 and the derivatives MXenes of the high-entropy MAX phase prepared in Comparative Examples 1-2 were investigated.

[0095] Experimental process: First, its derivative MXenes was obtained by selectively etching the Al atomic layer. Measure 30 mL of hydrochloric acid solution with a concentration of 36 wt% in a fume hood and pour it into the inner lining of a polytetrafluoroethylene reaction kettle. Subsequently, weigh 3 g of lithium fluoride and add it to the above solution, and magnetically stir for 15 min to fully react it with hydrochloric acid. Then, slowly add 2 g of high-entropy MAX phase powder to the inner lining of the polytetrafluoroethylene reaction kettle containing the above solution, stir while adding, and seal the lid after completion. The stirring rate, temperature, and time are set to 500 rpm, 50 °C, and 48 h respectively. After the etching process is completed, repeatedly wash the clay-like solid precipitate with deionized water and centrifuge it at 3500 rpm for 10 min. Take the supernatant and ultrasonically treat it in an ice-water bath under argon protection for 30 min to obtain a well-dispersed colloidal solution of few-layer high-entropy MXenes nanosheets. Finally, put the MXenes supernatant into a vacuum drying oven and vacuum dry it at 50 °C for 24 h to obtain high-entropy MXenes powder.

[0096] The battery preparation process is as follows: Mix the active material, acetylene black, and polyvinylidene fluoride (PVDF) in an N-methylpyrrolidone (NMP) solution at a mass ratio of 8:1:1 to prepare an electrode slurry. Subsequently, magnetically stir the slurry at 80 °C for 5 h, and after full stirring, evenly coat it on the copper foil with an electrode coater, and the coating thickness is 100 μm. After the coating process, put the electrode plate into a vacuum drying oven and vacuum dry it at 120 °C for 12 h. After the drying process is completed, use a punching machine to punch the electrode plate into a circular sheet with a diameter of 12 mm, weigh it with a precision balance and mark the mass. Assemble a CR-2032 type button battery in a multifunctional glove box filled with argon. Select a lithium foil as the counter electrode, a mixed solution prepared by dissolving 1 M LiPF6 in ethylene carbonate (EC) and dimethyl carbonate (DMC) with a volume ratio of 1:1 as the electrolyte, and Celgard 2400 as the separator. Let the assembled button battery stand for 24 h for relevant electrochemical performance tests.

[0097] As Figure 3 shown, compared with the single 312 configuration and the single 413 configuration, the homologous heterogeneous structure high-entropy MXenes of Examples 1 to 3 of the present invention have more excellent electrochemical performance, such as good cycle stability and high reversible specific capacity. At a current density of 200 mA·g -1 , after 500 cycles, Example 1 can provide a specific capacity of 682.4 mAh·g -1 , the specific capacity of Example 2 is 654 mAh·g -1 , and the specific capacity of Example 3 is 661 mAh·g -1 , while the specific capacities of Comparative Examples 1 to 2 are only 189.5 mAh·g -1 and 240.2 mAh·g -1 .

[0098] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A homologous and heterogeneous structure high-entropy MAX phase, characterized in that Its general formula is M n+1 AlC n , (n≥1), where M is a transition metal, including Ti, V, Cr, Mo, and the molar ratio is 0.1-1:0.1-1:0.1-1:0.1-1; the total of the transition metals and the molar ratio of aluminum Al and carbon C is 3:1.2-1.6:1.8-2; The homologous and heterogeneous structure high-entropy MAX phase has a hexagonal crystal system structure, and the unit cell is alternately stacked by M n+1 C n atomic layers and Al atomic layers in the c-axis direction; in the M n+1 C n atomic layer, transition metal atoms are randomly distributed at the M site to form a homologous and heterogeneous interface; the impurity phase content is less than 10%, and the element distribution is uniform.

2. The high-entropy MAX phase with a homologous and heterogeneous structure as described in claim 1, wherein Both 312 configuration and 413 configuration coexist in the homologous and heterogeneous structure high-entropy MAX phase, and the ratio of the 312 configuration to the 413 configuration is x:1-x, where the value range of x is 0 < x < 1.

3. The high-entropy MAX phase with a homologous and heterogeneous structure according to claim 1, characterized in that, The interface spacing of the homologous and heterogeneous interface is 1.3 - 1.5 nm.

4. A method for preparing a homologous and heterogeneous structure high-entropy MAX phase according to any one of claims 1 to 3, characterized in that, Specifically: The powder mixture of titanium source, vanadium source, chromium source, molybdenum source and carbon source is pressed into a mold and then subjected to the first calcination to obtain carbide solid solution powder; then the powder mixture of the carbide solid solution powder and aluminum source is pressed into a mold and then subjected to the second calcination to obtain the homologous and heterogeneous structure high-entropy MAX phase powder.

5. The preparation method according to claim 4, characterized in that, The titanium source, vanadium source, chromium source, molybdenum source and aluminum source are elemental powders of each metal element; the carbon source is graphite powder.

6. The preparation method according to claim 4, characterized in that, The pressure for pressing into a mold is 10 - 17 MPa.

7. The preparation method according to claim 4, wherein, The temperature of the first calcination is 1650 °C, the heating rate is 4 - 6 °C / min, and the calcination time is 2 - 3 h; the temperature of the second calcination is 1400 - 1500 °C, the heating rate is 4 - 6 °C / min, and the calcination time is 1 - 1.5 h.

8. The preparation method according to claim 7, characterized in that, The temperature of the first calcination is 1650 °C, the heating rate is 4 °C / min, and the calcination time is 3 h; the temperature of the second calcination is 1450 °C, the heating rate is 4 °C / min, and the calcination time is 1 h.

9. The preparation method according to claim 4, wherein Both the first calcination and the second calcination are carried out in an inert atmosphere; Preferably, the products obtained from the first calcination and the second calcination need to be ground and dried; the grinding medium added during grinding is deionized water or absolute ethanol; the drying temperature is 60 - 80 °C.

10. Application of the homologous and heterogeneous structure high-entropy MAX phase and its derivative MXenes according to any one of claims 1 - 4 in the field of energy materials.

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