A three-dimensional flower-like multi-level structure of metaphosphate micro-nano material, a preparation method and application thereof

Abstract

The application belongs to the technical field of nanometer material synthesis, and particularly relates to a three-dimensional flower-like multi-level structure metaphosphate micro-nano material and a preparation method and application thereof. The micro-nano material has a three-dimensional flower-like multi-level structure formed by assembling metaphosphate nanosheets; the three-dimensional flower-like multi-level structure has a size of 5-8 microns, and the nanosheet has a thickness of 20-50 nm. The preparation method is to first prepare a precursor material through a solvothermal method, and then to obtain the micro-nano material through a high-temperature oxidation reaction and a phosphating reaction, and has the advantages of simple and controllable synthesis process and low cost. The multi-level structure metaphosphate micro-nano material prepared by the application has a large specific surface area and good structural stability, can shorten the ion and charge transmission path and expose more electrochemical active sites, has good electrochemical performance, can be used for preparing supercapacitor electrode materials and oxygen evolution reaction electrocatalysts, and has a good potential application prospect in the field of energy storage and conversion.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of nanomaterial synthesis, and particularly relates to a three-dimensional flower-like multi-level structure metaphosphate micro-nano material and a preparation method and application thereof. BACKGROUND

[0002] Transition metal phosphates have unique physical and chemical properties and are widely used in the field of energy storage and conversion. Among them, transition metal metaphosphates (such as nickel metaphosphate, cobalt metaphosphate, manganese metaphosphate and iron metaphosphate) are also favored by researchers as an important class of metal phosphates. Due to their special structure and catalytic behavior, high theoretical capacity, high redox activity and high safety, they have gradually emerged in the field of energy storage and conversion. So far, transition metal metaphosphates with unique morphology and crystal structure have been proven to be ideal candidates for supercapacitor electrode materials and non-noble metal water splitting electrocatalysts. For example, Liu et al. reported the synthesis of hierarchical Ni(PO3)2 nanosheet arrays deposited on activated carbon cloth by a hydrothermal method, which produced a specific capacity of 2237 F / g at 1 A / g (J. Mater. Chem. A, 2017, 5, 1421-1427); Zhang et al. designed ultrathin porous Mn(PO3)2 nanosheets anchored on nitrogen and phosphorus co-doped graphene, which showed a specific capacity of 2073.4 F / g at 1 A / g (Chem. Eng. J., 2021, 403, 126379); Xiong et al. reported the synthesis of nickel metaphosphate (Ni2P4O 12 ) nanocrystals in alkaline medium, which had high catalytic activity and stability as OER electrocatalysts (Adv. Mater., 2018, 30, 1705045). However, the energy density, catalytic activity and cycle stability of these transition metal metaphosphates as electrode materials and catalysts still cannot meet the requirements of high-performance devices.

[0003] Therefore, it is of great scientific significance and potential application prospect to develop a simple and feasible method to obtain transition metal metaphosphate micro-nano materials with specific stoichiometric composition and multi-level structure. SUMMARY

[0004] In view of the deficiencies of the prior art, the first object of the present application is to provide a three-dimensional flower-like multi-level structure metaphosphate micro-nano material, which has the characteristics of uniform product morphology and uniform size distribution.

[0005] The second object of the present application is to provide a preparation method of the above-mentioned micro-nano material, which is simple and feasible in process and has good controllability.

[0006] The third object of the present application is to provide the application of the above-mentioned micro-nano material, which can be used as an electrochemical oxygen evolution reaction electrocatalyst or a supercapacitor electrode material.

[0007] To achieve the above-mentioned objects, the technical solutions adopted by the present application are as follows:

[0008] A three-dimensional flower-like multi-level structure metaphosphate micro-nano material, wherein the structure of the micro-nano material is a three-dimensional flower-like multi-level structure formed by assembling metaphosphate nanosheets.

[0009] Further, the size of the three-dimensional flower-like multi-level structure is 5-8 μm, and the thickness of the nanosheet is 20-50 nm.

[0010] Further, the metaphosphate is nickel metaphosphate, cobalt metaphosphate or nickel-cobalt metaphosphate.

[0011] The preparation method of the above-mentioned three-dimensional flower-like multi-level structure metaphosphate micro-nano material is as follows: first, a three-dimensional flower-like nickel-cobalt precursor is prepared by a solvothermal method, and then a three-dimensional flower-like multi-level structure metaphosphate micro-nano material is obtained by further high-temperature oxidation reaction and phosphating reaction.

[0012] Further, the preparation method adopts the following steps:

[0013] (1) Dissolve a nitrate and urea in ethanol, heat, separate, wash and dry to obtain a precursor material;

[0014] (2) Perform high-temperature oxidation reaction on the precursor material obtained in step (1) to obtain an oxide;

[0015] (3) Mix the oxide obtained in step (2) with sodium hypophosphite to perform phosphating reaction to obtain the three-dimensional flower-like multi-level structure metaphosphate micro-nano material.

[0016] Further, in step (1), the molar volume ratio of the nitrate, urea and ethanol is 1 mmol:(2-4) mmol:(5-10) mL.

[0017] Further, the nitrate is at least one of nickel nitrate and cobalt nitrate.

[0018] Further, when the nitrate is nickel nitrate and cobalt nitrate, the molar ratio of nickel nitrate to cobalt nitrate is (1-2):(1-2).

[0019] Further, in step (1), the heating temperature is 120°C, and the heating time is 6 h.

[0020] Further, in step (2), the high-temperature oxidation reaction temperature is 400°C, the high-temperature oxidation reaction time is 2 h, and the temperature rising rate is 5°C / min.

[0021] Further, in step (3), the phosphating reaction is carried out in an argon environment, at a temperature of 350 DEG C, for 2 hours, and at a temperature increasing rate of 5 DEG C / min.

[0022] Further, in step (3), the mass ratio of the oxide to sodium hypophosphite is 1:(40-100).

[0023] The three-dimensional flower-like multi-level structure metaphosphate micro-nano material can be used for preparing supercapacitors or electrocatalysts.

[0024] The high-temperature oxidation step adopted in the application plays a key role in forming the final three-dimensional flower-like multi-level structure, and the direct high-temperature phosphating of the hydroxide prepared by the solvothermal method cannot obtain the three-dimensional flower-like multi-level structure, and the final product is a solid spherical structure; and the amount of sodium hypophosphite plays a crucial role in the phase composition of the final product, and too much or too little sodium hypophosphite cannot obtain nickel-cobalt metaphosphate.

[0025] The application introduces another metal ion into the single-metal metaphosphate to form a double-metal metaphosphate with adjustable structure and electronic properties. Due to the synergistic effect of the two kinds of metal ions, the double-metal metaphosphate has increased redox active sites and enhanced electronic / ionic conductivity, and will exhibit better electrochemical performance than the single-metal metaphosphate. In addition, the design and synthesis of the multi-level structure metaphosphate can shorten the ion and charge transmission path and expose more electrochemical active sites, thereby improving the electrochemical performance.

[0026] Advantages:

[0027] 1. The three-dimensional flower-like multi-level structure provided by the application is assembled by metaphosphate nanosheets, the size of the flower-like structure is 5-8 microns, the thickness of the nanosheet is 20-50 nanometers, and the structure has the characteristics of uniform morphology and uniform size distribution.

[0028] 2. The preparation method adopted by the application has the advantages of simple and controllable synthesis process and low cost, the multi-level structure metaphosphate micro-nano material prepared has a large specific surface area and good structural stability, can shorten the ion and charge transmission path and expose more electrochemical active sites, can be used for preparing supercapacitor electrode materials and oxygen evolution reaction electrocatalysts, and exhibits excellent electrochemical performance. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 SEM image of the nickel-cobalt precursor material prepared in Example 1;

[0030] Figure 2XRD pattern of the nickel cobalt precursor material prepared for Example 1 ;

[0031] Figure 3 SEM image of the oxide prepared for Example 1, Figure 3 (a) is a low magnification SEM image, Figure 3 (b) is a high magnification SEM image;

[0032] Figure 4 XRD pattern of the oxide prepared for Example 1 ;

[0033] Figure 5 SEM image of the nickel cobalt double-metal phosphonate micro-nano material prepared for Example 1,

[0034] Figure 5 (a) is a low magnification SEM image, Figure 5 (b) is a high magnification SEM image;

[0035] Figure 6 XRD pattern of the nickel cobalt double-metal phosphonate micro-nano material prepared for Example 1 ;

[0036] Figure 7 Super capacitor performance test chart of the nickel cobalt double-metal phosphonate micro-nano material prepared for Example 1, Figure 7 (a) is a cyclic voltammetry curve, Figure 7 (b) is a constant current charge-discharge curve;

[0037] Figure 8 Electrochemical oxygen evolution performance test chart of the nickel cobalt double-metal phosphonate micro-nano material prepared for Example 1, Figure 8 (a) is a linear sweep voltammetry curve, Figure 8 (b) is a Tafel curve;

[0038] Figure 9 SEM image of the nickel cobalt double-metal phosphonate micro-nano material prepared for Example 2,

[0039] Figure 9 (a) is a low magnification SEM image, Figure 9 (b) is a high magnification SEM image;

[0040] Figure 10 SEM image of the nickel cobalt double-metal phosphonate micro-nano material prepared for Example 3,

[0041] Figure 10 (a) is a low magnification SEM image, Figure 10 (b) is a high magnification SEM image;

[0042] Figure 11SEM image of the nickel-cobalt double metallo-metaphosphate material prepared for Comparative Example 1;

[0043] Figure 12 Constant current charge-discharge curve of the cobalt double metallo-metaphosphate material prepared for Comparative Example 1;

[0044] Figure 13 Electrochemical oxygen evolution performance test graph of the cobalt double metallo-metaphosphate material prepared for Comparative Example 1, Figure 13 (a) is a linear sweep voltammetry curve, Figure 13 (b) is a Tafel curve;

[0045] Figure 14 XRD spectrum of the nickel-cobalt double metallo-metaphosphate material prepared for Comparative Example 2. DETAILED DESCRIPTION

[0046] In the following description, specific details of the application are further explained for the full understanding of the application. The terms used in the specification of the application are only for the purpose of illustrating the advantages and features of the application, and are not intended to limit the application.

[0047] Unless otherwise defined, all professional and scientific terms used in the application are the same as understood by those skilled in the art of the application. Unless otherwise specified, the drugs or reagents used in the application are used according to the product instructions or using conventional methods in the art. The process of the application is further described according to the specification and specific embodiments.

[0048] Example 1

[0049] (1) 1.5 mmol of nickel nitrate, 1.5 mmol of cobalt nitrate and 6.0 mmol of urea were added to 30 mL of ethanol, and the solution was transferred to a 50 mL capacity reaction kettle after stirring to complete dissolution. The solution was heated to 120℃ in an oven, and the reaction was kept for 6 h. After the reaction was completed, the product was centrifuged, washed with deionized water and ethanol for 3 times each, and then dried to obtain a nickel-cobalt precursor material;

[0050] (2) The above nickel-cobalt precursor material was placed in a muffle furnace for high-temperature oxidation reaction, the reaction temperature was 400℃, the heating rate was 5℃ / min, and the reaction was kept for 2 h. After the reaction was completed, a nickel-cobalt oxide was obtained, which was a black powder;

[0051] (3) 2.0 g of sodium hypophosphite and 50 mg of the above nickel-cobalt oxide were respectively placed in the upstream and downstream positions of a tube furnace, and argon was introduced for phosphating reaction, the reaction temperature was 350℃, the heating rate was 5℃ / min, and the reaction was kept for 2 h. After the reaction was completed, a nickel-cobalt double metallo-metaphosphate micro-nano material was obtained.

[0052] Figure 1SEM image of the nickel-cobalt precursor material prepared in Example 1, the results show that the structure of the nickel-cobalt precursor material prepared in Example 1 is a three-dimensional flower-like structure composed of nanosheets.

[0053] Figure 2 XRD spectrum of the nickel-cobalt precursor material prepared in Example 1, the results show that the nickel-cobalt precursor material prepared in Example 1 is a nickel-cobalt double metal hydroxide.

[0054] Figure 3 SEM image of the oxide prepared in Example 1, Figure 3 (a) is a low magnification SEM image, Figure 3 (b) is a high magnification SEM image, the results show that the microstructure is retained and is still a three-dimensional flower-like structure.

[0055] Figure 4 XRD spectrum of the oxide prepared in Example 1, the results show that the oxide is a nickel-cobalt oxide.

[0056] Figure 5 SEM image of the nickel-cobalt double metal metaphosphate micro-nano material prepared in Example 1, Figure 5 (a) is a low magnification SEM image, Figure 5 (b) is a high magnification SEM image; the results show that the microstructure of the nickel-cobalt double metal metaphosphate micro-nano material is a three-dimensional flower-like hierarchical structure assembled by nanosheets, the morphology is uniform, the size of the flower-like structure is about 8 μm, and the thickness of the nanosheet is about 50 nm.

[0057] Figure 6 XRD spectrum of the nickel-cobalt double metal metaphosphate micro-nano material prepared in Example 1, the results show that the phase of the product after phosphating is consistent with the nickel metaphosphate (Ni2P4O 12 ) of monoclinic system.

[0058] The cyclic voltammetry test was carried out in a three-electrode system by using an electrochemical working station, the constant current charge and discharge test was carried out by using a LAND battery test system, the electrolyte was 3 mol / L KOH aqueous solution, the counter electrode was a platinum sheet electrode, and the reference electrode was a mercury / mercury oxide electrode. The working electrode was prepared as follows: the prepared sample was an active material, acetylene black was a conductive agent, and PVDF was a binder, which were mixed in a mass ratio of 8:1:1. N-methyl pyrrolidone was used as a solvent to uniformly grind the above mixture to prepare a slurry. The slurry was uniformly coated on a foamed nickel (1 cm 2 ) and dried, and then a tablet press was used to press the tablet at 10 MPa to prepare a working electrode.

[0059] Figure 7 Super capacitor performance test graph of the nickel-cobalt double metal metaphosphate micro-nano material prepared in Example 1, Figure 7(a) is a cyclic voltammogram, a pair of wide redox peaks appear, indicating a typical pseudocapacitive energy storage mechanism. Figure 7 (b) is a galvanostatic charge-discharge curve, the results show that the specific discharge capacity of the nickel-cobalt double metal metaphosphate micro-nano material prepared in Example 1 is greater than 1500 F / g at a current density of 10 A / g.

[0060] The electrochemical working station was used for testing in a three-electrode system, the electrolyte was 1 mol / L KOH aqueous solution, the counter electrode was a graphite rod, and the reference electrode was an Ag / AgCl electrode. The working electrode was prepared as follows: 2 mg of the sample was dispersed in 1 mL of solution (containing 990 μL of ethanol and 10 μL of 5% Nafion solution), and after ultrasonic treatment for 30 min, 5 μL of the above dispersion was coated on a polished glassy carbon electrode, and after drying, the working electrode was prepared. Figure 8 The electrochemical oxygen evolution performance test diagram of the nickel-cobalt double metal metaphosphate micro-nano material prepared in Example 2 is shown in Figure 8 (a) is a linear sweep voltammogram, Figure 8 (b) is a Tafel curve, in 1 mol / L KOH solution, the overpotential at a current density of 10 mA / cm 2 < 300 mV (a), and the Tafel slope is 96.7 mV / dec (b). Figure 8 Figure 8

[0061] Example 2

[0062] (1) 2.0 mmol of nickel nitrate, 1.0 mmol of cobalt nitrate and 12 mmol of urea were added to 30 mL of ethanol, and after stirring until completely dissolved, the solution was transferred to a reaction kettle with a capacity of 50 mL, heated to 120°C in an oven, and kept for 6 h. After the reaction was completed, the product was centrifuged, washed with deionized water and ethanol three times each, and dried to obtain a nickel-cobalt precursor material;

[0063] (2) The above nickel-cobalt precursor material was placed in a muffle furnace for high-temperature oxidation reaction, the reaction temperature was 400°C, the heating rate was 5°C / min, and the holding time was 2 h. After the reaction was completed, a nickel-cobalt oxide was obtained.

[0064] (3) 2.0 g of sodium hypophosphite and 50 mg of the above nickel-cobalt oxide were placed in the upstream and downstream positions of a tubular atmosphere furnace respectively, and argon was introduced for phosphating reaction, the reaction temperature was 350°C, the heating rate was 5°C / min, and the holding time was 2 h. After the reaction was completed, a nickel-cobalt double metal metaphosphate micro-nano material was obtained.

[0065] Figure 9 The SEM diagram of the nickel-cobalt double metal metaphosphate micro-nano material prepared in Example 2 is shown in Figure 9 ​​(a) is a low magnification SEM image, Figure 9 (b) is a high magnification SEM image, the results show that the microstructure of the nickel-cobalt double metal phosphite micro-nano material prepared in Example 2 is a three-dimensional flower-like hierarchical structure assembled by nanosheets, the size of the flower-like structure is about 8 μm, and the thickness of the nanosheet is about 20 nm.

[0066] Example 3

[0067] (1) 2.0 mmol of nickel nitrate, 4.0 mmol of cobalt nitrate and 12 mmol of urea were added to 30 mL of ethanol, and after stirring until completely dissolved, the solution was transferred to a reaction kettle with a capacity of 50 mL, heated to 120°C in an oven, and kept for 6 h. After the reaction was completed, the product was centrifuged, washed with deionized water and ethanol for 3 times respectively, and dried to obtain a nickel-cobalt precursor material;

[0068] (2) The above nickel-cobalt precursor material was placed in a muffle furnace for high-temperature oxidation reaction, the reaction temperature was 400°C, the heating rate was 5°C / min, and the holding time was 2 h. After the reaction was completed, a nickel-cobalt oxide was obtained.

[0069] (3) 2.0 g of sodium hypophosphite and 50 mg of the above nickel-cobalt oxide were respectively placed in the upstream and downstream positions of a tube furnace, and argon was introduced for phosphating reaction, the reaction temperature was 350°C, the heating rate was 5°C / min, and the holding time was 2 h. After the reaction was completed, a nickel-cobalt double metal phosphite micro-nano material was obtained.

[0070] Figure 10 SEM image of the nickel-cobalt double metal phosphite micro-nano material prepared in Example 3, Figure 10 (a) is a low magnification SEM image, Figure 10 (b) is a high magnification SEM image, the results show that the microstructure of the nickel-cobalt double metal phosphite micro-nano material prepared in Example 3 is a three-dimensional flower-like hierarchical structure assembled by nanosheets, the size of the flower-like structure is about 5 μm, and the thickness of the nanosheet is about 40 nm.

[0071] Example 4

[0072] (1) 1.5 mmol of nickel nitrate, 1.5 mmol of cobalt nitrate and 6.0 mmol of urea were added to 30 mL of ethanol, and after stirring until completely dissolved, the solution was transferred to a reaction kettle with a capacity of 50 mL, heated to 120°C in an oven, and kept for 6 h. After the reaction was completed, the product was centrifuged, washed with deionized water and ethanol for 3 times respectively, and dried to obtain a nickel-cobalt precursor material;

[0073] (2), the nickel-cobalt precursor material is placed in a muffle furnace to perform a high-temperature oxidation reaction, the reaction temperature is 400°C, the heating rate is 5°C / min, and the temperature is kept for 2 hours. After the reaction is completed, a nickel-cobalt oxide is obtained;

[0074] (3), 2.0g of sodium hypophosphite and 20mg of the nickel-cobalt oxide are respectively placed in the upstream and downstream positions of a tube furnace, and argon is introduced to perform a phosphating reaction, the reaction temperature is 350°C, the heating rate is 5°C / min, and the temperature is kept for 2 hours. After the reaction is completed, a nickel-cobalt bimetallic metaphosphate micro-nano material is obtained.

[0075] The microstructure of the nickel-cobalt bimetallic metaphosphate micro-nano material prepared in Example 4 is a three-dimensional flower-like multi-level structure formed by the assembly of nanosheets, the size of the flower-like structure is about 5-8μm, and the thickness of the nanosheet is about 20-50nm.

[0076] Example 5

[0077] (1), 3.0mmol of nickel nitrate and 6.0mmol of urea are added to 30mL of ethanol, the solution is transferred to a reaction kettle with a capacity of 50mL after stirring to completely dissolve, heated to 120°C in an oven, and kept for 6 hours. After the reaction is completed, the product is centrifuged, washed with deionized water and ethanol for 3 times respectively, and dried to obtain a nickel precursor material;

[0078] (2), the nickel precursor material is placed in a muffle furnace to perform a high-temperature oxidation reaction, the reaction temperature is 400°C, the heating rate is 5°C / min, and the temperature is kept for 2 hours. After the reaction is completed, a nickel-cobalt oxide is obtained;

[0079] (3), 2.0g of sodium hypophosphite and 50mg of the oxide are respectively placed in the upstream and downstream positions of a tube furnace, and argon is introduced to perform a phosphating reaction, the reaction temperature is 350°C, the heating rate is 5°C / min, and the temperature is kept for 2 hours. After the reaction is completed, a nickel metaphosphate micro-nano material is obtained.

[0080] The microstructure of the nickel metaphosphate micro-nano material prepared in Example is a three-dimensional flower-like multi-level structure formed by the assembly of nanosheets, the size of the flower-like structure is about 5-8μm, and the thickness of the nanosheet is about 20-50nm.

[0081] Comparative Example 1

[0082] (1), the preparation method of the nickel-cobalt precursor material is consistent with that of Example 1;

[0083] (2), the difference from Example 1 is that the high-temperature oxidation reaction step is removed, and the nickel-cobalt precursor material is directly subjected to a phosphating reaction at high temperature to obtain a nickel-cobalt bimetallic metaphosphate material. The amount of sodium hypophosphite and the phosphating reaction parameters are consistent with those of Example 1.

[0084] Figure 11 The SEM image of the nickel-cobalt double metal phosphite material prepared for Comparative Example 1 shows that the three-dimensional flower-like hierarchical structure disappears and becomes a solid spherical structure, indicating that the high-temperature oxidation step plays a key role in the formation of the final three-dimensional flower-like hierarchical structure.

[0085] Figure 12 The constant current charge-discharge curve of the nickel-cobalt double metal phosphite material prepared for Comparative Example 1 shows that the specific discharge capacity of the product as a supercapacitor electrode material in a 3 mol / L KOH electrolyte is 750 F / g at a current density of 10 A / g, and the test process is the same as in Example 1.

[0086] Figure 13 The electrochemical oxygen evolution performance test diagram of the cobalt double metal phosphite material prepared for Comparative Example 1, Figure 13 (a) is a linear sweep voltammetry curve, Figure 13 (b) is a Tafel curve, and the results show that the overpotential of the cobalt double metal phosphite material prepared for Comparative Example 1 in a 1 mol / L KOH solution is 368 mV 2 at a current density of 10 mA / cm Figure 13 (a)), and the Tafel slope is 120 mV / dec Figure 13 (b)), and the test process is the same as in Example 1. Compared with the three-dimensional flower-like hierarchical nickel-cobalt phosphite prepared in Example 1, the electrochemical performance of the product prepared in Comparative Example 1 shows a large degree of decline, which indicates the advantage of the three-dimensional hierarchical structure in improving the performance of supercapacitors and electrocatalysis.

[0087] Comparative Example 2

[0088] (1) The preparation method of the nickel-cobalt precursor is consistent with Example 1;

[0089] (2) The high-temperature oxidation step is consistent with Example 1;

[0090] (3) 0.5 g of sodium hypophosphite and 50 mg of nickel-cobalt oxide are placed at the upstream and downstream positions of the tube furnace, respectively, and other reaction parameters are consistent with Example 1, to obtain a nickel-cobalt double metal phosphite material. The difference between the phosphating reaction and Example 1 is that the amount of sodium hypophosphite is reduced.

[0091] Figure 14 The XRD spectrum of the nickel-cobalt double metal phosphite material prepared for Comparative Example 2 shows that the phase of the product is a composite of nickel phosphide and cobalt phosphide, which indicates that the amount of sodium hypophosphite plays a crucial role in the formation of the final nickel-cobalt phosphite.

[0092] It should be noted that the above-mentioned embodiments only illustrate some but not all of the preferred ways for implementing the present application. Obviously, based on the above-mentioned embodiments of the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work should belong to the protection scope of the present application.

Claims

1. A three-dimensional flower-like hierarchical structure of a micro-nano material of a phosphite, characterized in that, The micro-nano material is a three-dimensional flower-like multi-level structure assembled by nano-sheets of metaphosphate; The preparation method of the three-dimensional flower-like multi-level structure metaphosphate micro-nano material comprises the following steps: (1) dissolving a nitrate and urea in ethanol, heating, separating, washing and drying to obtain a precursor material; (2) performing high-temperature oxidation reaction on the precursor material obtained in step (1) to obtain an oxide; (3) mixing the oxide obtained in step (2) with sodium hypophosphite to perform phosphating reaction to obtain the three-dimensional flower-like multi-level structure metaphosphate micro-nano material; In step (3), the mass ratio of the oxide to sodium hypophosphite is 1:40-100.

2. The three-dimensional flower-like hierarchical structure of the phosphite micro-nano materials according to claim 1, characterized in that, The size of the three-dimensional flower-like multi-level structure is 5-8 μm, and the thickness of the nano-sheets is 20-50 nm.

3. A method for preparing the three-dimensional flower-like hierarchical structure of the micro-nano material of the phosphite salt according to claim 1 or 2, characterized in that, The preparation method comprises the following steps: (1) dissolving a nitrate and urea in ethanol, heating, separating, washing and drying to obtain a precursor material; (2) performing high-temperature oxidation reaction on the precursor material obtained in step (1) to obtain an oxide; (3) mixing the oxide obtained in step (2) with sodium hypophosphite to perform phosphating reaction to obtain the three-dimensional flower-like multi-level structure metaphosphate micro-nano material; In step (3), the mass ratio of the oxide to sodium hypophosphite is 1:40-100.

4. The production method according to claim 3, characterized by, In step (1), the molar volume ratio of the nitrate, urea and ethanol is 1 mmol:2-4 mmol:5-10 mL; the nitrate is at least one of nickel nitrate and cobalt nitrate; the heating temperature is 120°C, and the heating time is 6 h.

5. The preparation method according to claim 3, characterized in that, In step (2), the high-temperature oxidation reaction is performed at a temperature of 400°C for 2 h, and the temperature rising rate is 5°C / min.

6. The preparation method according to claim 3, characterized in that, In step (3), the phosphating reaction is performed in an argon environment at a temperature of 350°C for 2 h, and the temperature rising rate is 5°C / min.

7. The preparation method according to claim 4, characterized in that, When the nitrate is nickel nitrate and cobalt nitrate, the molar ratio of nickel nitrate to cobalt nitrate is 1-2:1-2.

8. Use of the three-dimensional flower-like hierarchical structure of metaphosphate micro-nano materials according to claim 1 or 2 or the three-dimensional flower-like hierarchical structure of metaphosphate micro-nano materials prepared by the method according to any one of claims 4-7, characterized in that, The three-dimensional flower-like multi-level structure metaphosphate micro-nano material is used for preparing supercapacitors or electrocatalysts.

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