High-entropy oxide and its use in the preparation of supercapacitors

Abstract

The application discloses a kind of high-entropy oxides and its application in preparation supercapacitor, belong to supercapacitor technical field.The application uses boron-doped and histidine and serine functionalized graphene quantum dots (BHS-GQD) synthesis (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4 high-entropy oxide nanocrystals, realizes the atomic average of all metal elements in solution and solid state evenly dispersed.The high-entropy oxide structure prepared by the application is long-range ordered (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4 nanocrystals, and the electrochemical performance is significantly improved, and the energy can be up to 153Wh / kg when the power density is 900W / kg.

Description

Technical Field

[0001] The present invention relates to a high entropy oxide and application thereof in preparing a supercapacitor, belonging to the technical field of supercapacitors. Background Art

[0002] In the face of increasingly serious environmental pollution and energy crisis, it is crucial to develop efficient energy storage and conversion devices. Supercapacitors are electrochemical devices that bridge the gap between batteries and traditional capacitors. Due to their high power density (2-10kW / kg), fast charge / discharge speed, and long service life (10 4 -10 6 cycle) and has attracted widespread attention.

[0003] Supercapacitors are divided into two categories: electric double-layer capacitors (EDLCs) and pseudocapacitors. The materials used in EDLCs (e.g., carbonaceous materials) significantly influence their cycling stability, while pseudocapacitors utilize transition metal oxides and conductive polymers with multiple oxidation transition states, which offer high capacitance in energy storage applications. Transition metal oxides exhibit excellent oxidation and reduction reversibility over a wider potential range, which is highly advantageous in supercapacitor applications. However, their poor electrical conductivity and severe structural disintegration during reactions hinder their application in high-performance supercapacitors.

[0004] High entropy oxides are single-phase oxides formed by solid solution of at least five metals in an equimolar or near molar ratio in the same sublattice. config )≥1.5R. High-entropy oxides break the solid solubility limits of traditional oxide elements, generating high-entropy effects, cocktail effects, slow diffusion effects, and lattice distortion effects in highly disordered combinations of diverse elements. Compared to traditional oxides, the high-entropy and slow diffusion effects jointly suppress structural phase transitions during electrochemical testing. The cocktail effect and lattice distortion produce defect engineering that synergistically provides sufficient active sites and improves electronic conductivity, respectively, leading to higher structural stability and storage capacity.

[0005] However, the poor structural uniformity and electrical conductivity of high-entropy oxides (HEOs) limit their practical application in high-performance supercapacitors. Due to the entropic interactions between the constituent elements and the random distribution of multiple elements with different atomic radii, numerous studies have shown that HEO solid solutions with random element distributions generally exhibit significant short-range ordered structural heterogeneity. This heterogeneity directly affects the distribution, abundance, and properties of electrochemically active sites, leading to different chemical environments and energy storage pathways.

[0006] Wang et al. reported a high-temperature strategy for the preparation of Mg 0.2 Co 0.2Ni 0.2 Cu 0.2 Zn 0.2 O single-phase nano high entropy oxide. Abdelhafiz et al. prepared (FeNiCoCr)acet single-phase nano high entropy oxide by pulsed photosynthesis. Although the synthesis technology of single-phase nano high entropy oxide has made significant progress, the practical application of HEO electrode materials in high-performance supercapacitors still faces four key challenges: (1) The current synthesis method is not suitable for large-scale production of HEO nanoparticles due to the requirement for special equipment, low efficiency and high cost; (2) The current synthesis method cannot achieve effective tuning of the morphology and nanostructure of HEO nanocrystals; (3) The current design of the metal element composition in HEO electrode materials is not conducive to efficient hybrid capacitor deionization; (4) Due to the lack of effective electron and ion channels, the electron / ionic conductivity of current HEO electrode materials is poor.

[0007] Therefore, developing a method that can prepare single-phase nano high-entropy oxide at a relatively low temperature and use it to prepare high-performance supercapacitors has extremely high practical and economic value. Summary of the Invention

[0008] In order to solve the above problems, the present invention uses boron doped and histidine and serine functionalized graphene quantum dots (BHS-GQD) to synthesize (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4 high entropy oxide nanocrystals achieve uniform atomic dispersion of all metal elements in solution and solid state. The high entropy oxide structure prepared by the present invention is a long-range ordered (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4 nanocrystals, and their electrochemical performance is significantly improved.

[0009] A first object of the present invention is to provide a method for preparing a high entropy oxide, the method comprising:

[0010] (1) mixing a cobalt ion salt, a tungsten ion salt, a vanadium ion salt, a niobium ion salt, and a molybdenum ion salt in a molar ratio of 0.15-0.2:0.15-0.2:0.15-0.2:0.31-0.34:0.15-0.2, dissolving the mixture in a graphene quantum dot solution, and stirring to obtain a mixed solution;

[0011] (2) using cotton to absorb the mixed solution and drying it to obtain cotton adsorbed with metal ions and graphene quantum dots; wherein the mass ratio of metal salt, graphene quantum dots and cotton is 0.8-1.2:0.6-1.2:0.9-1.3;

[0012] (3) Cotton adsorbed with metal ions and graphene quantum dots was annealed to prepare high entropy oxides.

[0013] In one embodiment, the method for preparing graphene quantum dots comprises:

[0014] One or more of citric acid, serine, histidine and boric acid are dissolved in water and heated for reaction;

[0015] Optionally, citric acid is dissolved in water, and the ratio of citric acid to water is 18-19.5 g: 45-60 mL;

[0016] Optionally, citric acid, serine and histidine are dissolved in water, and the ratio of citric acid, serine, histidine and water is 18-19.5 g: 1.8-2.4 g: 15-16 g: 45-60 mL;

[0017] Optionally, citric acid, serine, histidine and boric acid are dissolved in water, and the ratio of citric acid, serine, histidine, boric acid and water is 18-19.5 g: 1.8-2.4 g: 15-16 g: 0.8-1.5 g: 45-60 mL;

[0018] Optionally, the heating reaction is carried out at 170-200° C. for 2-4 hours.

[0019] In one embodiment, the molar ratio in step (1) is also the molar ratio of cobalt ions, tungsten ions, vanadium ions, niobium ions and molybdenum ions.

[0020] In one embodiment, the cobalt ion salt includes one or more of cobalt chloride, cobalt nitrate, and cobalt sulfate;

[0021] The tungsten ion salt includes one or more of tungsten hexachloride, sodium metatungstate, and sodium tungstate dihydrate;

[0022] The vanadium ion salt includes one or more of vanadium chloride, ammonium metavanadate, and sodium vanadate hydrate;

[0023] The niobium ion salt includes one or more of niobium chloride, niobium oxalate, and ammonium niobate oxalate hydrate;

[0024] The molybdenum ion salt includes one or more of sodium molybdate, molybdenum pentachloride, and ammonium molybdate.

[0025] In one embodiment, the annealing is carried out at 800-900° C. for 2-5 hours.

[0026] In one embodiment, the stirring is performed at 400-600 rpm for uniform stirring.

[0027] The second object of the present invention is to provide a high entropy oxide prepared by any of the above methods.

[0028] The third object of the present invention is to provide the use of any of the above methods or the above high entropy oxides in the preparation of electronic components.

[0029] In one embodiment, the electronic components include batteries and capacitors.

[0030] A fourth object of the present invention is to provide any supercapacitor, wherein the preparation method of the supercapacitor comprises:

[0031] The high entropy oxide, carbon black, and polyvinylidene fluoride are dispersed in n-methyl-2-pyrrolidone to obtain an electrode slurry; the electrode slurry is coated on the surface of a titanium sheet to obtain an electrode sheet; two electrode sheets are used as electrodes and PVA / Li2SO4 gel is used as an electrolyte to form a symmetrical solid-state supercapacitor;

[0032] Optionally, the mass ratio of high entropy oxide, carbon black and polyvinylidene fluoride is 70-90:5-15:5-15;

[0033] Optionally, the mass density of the electrode slurry on the surface of the electrode sheet is 1.5 to 2.5 mg / cm3.

[0034] In one embodiment, the PVA / Li2SO4 gel preparation method comprises:

[0035] Pour 1-3 g of polyvinyl alcohol (PVA) and 8-12 mL of 1-3 mol / L Li2SO4 solution into 10-30 mL of water, stir at 70-75°C until the solution becomes clear and transparent, and then cool to room temperature to obtain PVA / Li2SO4 gel.

[0036] A fifth object of the present invention is to provide a method for improving the performance of a supercapacitor, wherein a supercapacitor is prepared using a high entropy oxide; the method for preparing the high entropy oxide comprises:

[0037] (1) mixing a cobalt ion salt, a tungsten ion salt, a vanadium ion salt, a niobium ion salt, and a molybdenum ion salt in a molar ratio of 0.15-0.2:0.15-0.2:0.15-0.2:0.31-0.34:0.15-0.2, dissolving the mixture in a graphene quantum dot solution, and stirring to obtain a mixed solution;

[0038] (2) Using cotton to absorb the mixed solution and drying it to obtain cotton adsorbed with metal ions and graphene quantum dots; wherein the mass ratio of metal salt, graphene quantum dots and cotton is 0.8-1.2:0.6-1.2:0.9-1.3

[0039] (3) Cotton adsorbed with metal ions and graphene quantum dots was annealed to prepare high entropy oxides.

[0040] In one embodiment, a method for preparing graphene quantum dots comprises:

[0041] One or more of citric acid, serine, histidine and boric acid are dissolved in water and heated for reaction;

[0042] Optionally, citric acid is dissolved in water, and the ratio of citric acid to water is 18-19.5 g: 45-60 mL;

[0043] Optionally, citric acid, serine and histidine are dissolved in water, and the ratio of citric acid, serine, histidine and water is 18-19.5 g: 1.8-2.4 g: 15-16 g: 45-60 mL;

[0044] Optionally, citric acid, serine, histidine and boric acid are dissolved in water, and the ratio of citric acid, serine, histidine, boric acid and water is 18-19.5 g: 1.8-2.4 g: 15-16 g: 0.8-1.5 g: 45-60 mL;

[0045] Optionally, the heating reaction is carried out at 170-200° C. for 2-4 hours.

[0046] In one embodiment, the cobalt ion salt includes one or more of cobalt chloride, cobalt nitrate, and cobalt sulfate;

[0047] The tungsten ion salt includes one or more of tungsten hexachloride, sodium metatungstate, and sodium tungstate dihydrate;

[0048] The vanadium ion salt includes one or more of vanadium chloride, ammonium metavanadate, and sodium vanadate hydrate;

[0049] The niobium ion salt includes one or more of niobium chloride, niobium oxalate, and ammonium niobate oxalate hydrate;

[0050] The molybdenum ion salt includes one or more of sodium molybdate, molybdenum pentachloride, and ammonium molybdate.

[0051] In one embodiment, the annealing is carried out at 800-900° C. for 2-5 hours.

[0052] Beneficial effects of the present invention

[0053] The present invention uses boron doped and histidine and serine functionalized graphene quantum dots (BHS-GQD) to synthesize (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4 high entropy oxide nanocrystals achieve uniform atomic dispersion of all metal elements in solution and solid state. At the same time, the high entropy oxide structure prepared by the present invention is a long-range ordered (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4 nanocrystals, and their electrochemical performance is significantly improved.

[0054] Specifically, supercapacitors (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4 / / (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4 shows a higher energy density (up to 153W h / Kg at 900W / Kg). BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )SEM image of 2O4-GQD.

[0056] Figure 2 (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )SEM image of 2O4-HS-GQD.

[0057] Figure 3 (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )SEM image of 2O4-BHS-GQD.

[0058] Figure 4 (Nb 0.32 V 0.17 Mo 0.17 W0.17 Co 0.17 )XRD pattern of 2O4-GQD.

[0059] Figure 5 (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )XRD pattern of 2O4-HS-GQD.

[0060] Figure 6 (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )XRD pattern of 2O4-BHS-GQD.

[0061] Figure 7 The crystal structure of space group I-4 (PDF#081-2343).

[0062] Figure 8 This is the crystal structure of the space group P42 / mnm (PDF#075-2340).

[0063] Figure 9 (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-GQD, (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-HS-GQD and (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-BHS-GQD electrochemical impedance spectroscopy combined diagram; a is (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-BHS-GQD electrochemical impedance spectroscopy curve; b is (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-HS-GQD electrochemical impedance curve; c is (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co0.17 )2O4-GQD electrochemical impedance curve.

[0064] Figure 10 (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-GQD electrode charge and discharge curves measured at different current densities.

[0065] Figure 11 (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )The charge-discharge curves of the 2O4-HS-GQD electrode measured at different current densities.

[0066] Figure 12 (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )The charge-discharge curves of the 2O4-BHS-GQD electrode measured at different current densities.

[0067] Figure 13 (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )Cyclic voltammetry curves of the 2O4-BHS-GQD electrode measured at different scan rates.

[0068] Figure 14 For supercapacitors (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-BHS-GQD / / (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )Energy density of 2O4-BHS-GQD at different power densities. DETAILED DESCRIPTION

[0069] The following describes preferred embodiments of the present invention. It should be understood that the embodiments are for better explanation of the present invention and are not intended to limit the present invention.

[0070] Test method:

[0071] The preparation process of the electrochemical impedance spectroscopy electrode is as follows:

[0072] A mixture of high entropy oxide and polyvinylidene fluoride was dispersed in n-methyl-2-pyrrolidone in a mass ratio of 80:10 to form a uniform electrode slurry. The electrode slurry was then coated on a 1 cm × 1 cm conductive glass surface by a doctor blade method and dried in a vacuum drying oven at 80°C for 24 hours to prepare an electrochemical impedance spectroscopy electrode.

[0073] The raw materials used in the embodiment are:

[0074] Citric acid, serine, histidine, boric acid, cobalt chloride (CoCl2·6H2O) and sodium tungstate (Na2WO4·2H2O) were purchased from Shanghai Sinopharm Chemical Reagent Co., Ltd., China; ammonium metavanadate (NH4VO3) and niobium oxalate (Nb(HC2O4)5) were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; ammonium molybdate (H 24 Mo7N6O 24 2H2O) was purchased from Shanghai MacLean Biochemical Technology Co., Ltd., China.

[0075] Example 1: Preparation of graphene quantum dots doped with different elements

[0076] 1. Preparation of undoped graphene quantum dots (GQD)

[0077] 19.2 g of citric acid was weighed and ultrasonically dissolved in 50 mL of ultrapure water, poured into a 200 mL polytetrafluoroethylene reactor, and then reacted in a forced air drying oven at 175°C for 6 hours; after the reactor was cooled to room temperature, the liquid was collected and freeze-dried to obtain GQD solid.

[0078] 2. Preparation of N-doped graphene quantum dots (HS-GQD)

[0079] 19.2 g of citric acid, 2.1 g of serine, and 15.5 g of histidine were weighed and ultrasonically dissolved in 50 mL of ultrapure water, poured into a 200 mL polytetrafluoroethylene reactor, and then reacted in a forced air drying oven at 175 ° C for 6 hours; after the reactor was cooled to room temperature, the liquid was collected and freeze-dried to obtain HS-GQD solid.

[0080] 3. Preparation of N and B atom-doped graphene quantum dots (BHS-GQD)

[0081] 19.2 g of citric acid, 2.1 g of serine, 15.5 g of histidine, and 1.2 g of boric acid were respectively weighed and ultrasonically dissolved in 50 mL of ultrapure water, poured into a 200 mL polytetrafluoroethylene reactor, and then reacted in a forced air drying oven at 175 ° C for 6 hours; after the reactor was cooled to room temperature, the liquid was collected and freeze-dried to obtain BSH-GQD solid.

[0082] Example 2: Preparation of high-entropy oxide

[0083] The graphene quantum dots GQD, HS-GQD and BHS-GQD prepared in Example 1 were taken to prepare high-entropy oxide.

[0084] Preparation of (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-GQD

[0085] (1) 1 g of GQD, 10 mL of 30 wt.% H2O2 and 2 mL of ammonia were poured into 60 mL of ultrapure water, and ultrasonic treatment was performed for 20 minutes to obtain a graphene quantum dot GQD solution;

[0086] (2) 0.17 mol of CoCl2·6H2O, 0.17 mol of Na2WO4·2H2O, 0.17 mol of NH4VO3, 0.32 mol of Nb(HC2O4)5 and 0.024 mol of Mo7N6O·2H2O were weighed respectively and added to the solution (i.e., graphene quantum dot GQD solution) obtained in the above (1) process, and stirring was performed at 500 rpm for 3 hours to obtain a mixed solution; 24 Mo7N6O 24 ·2H2O were weighed respectively and added to the solution (i.e., graphene quantum dot GQD solution) obtained in the above (1) process, and stirring was performed at 500 rpm for 3 hours to obtain a mixed solution;

[0087] (3) 1 g of cotton was weighed and laid flat on a watch glass, and the solution (mixed solution) obtained in the above (2) process was poured thereon. After the cotton completely absorbed the solution, drying was performed in a drying oven at 60°C;

[0088] (4) The dried product was placed in a tube furnace under a nitrogen atmosphere for high-temperature annealing, the heating rate was 5°C / min, and the temperature was maintained at 850°C for 3 hours to obtain a high-entropy oxide, which was named (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-GQD.

[0089] On the basis of the above method, GQD was replaced by HS-GQD and BHS-GQD respectively, and high-entropy oxides (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-HS-GQD and (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17)2O4-BHS-GQD. Example 3: Morphological Detection of High Entropy Oxide Composites of Different Graphene Quantum Dots

[0090] Take the high entropy oxide (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-GQD、(Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-HS-GQD and (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-BHS-GQD and detect its morphological characteristics.

[0091] 1. Scanning electron microscopy (SEM)

[0092] (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-GQD morphological characteristics such as Figure 1 As shown;

[0093] (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-HS-GQD morphology characteristics such as Figure 2 As shown;

[0094] (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-BSH-GQD morphology characteristics such as Figure 3 shown.

[0095] SEM results showed that (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-GQD、(Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-SH-GQD and (Nb 0.32V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-BSH-GQDs have obvious differences in morphology.

[0096] (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-GQD and (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-SH-GQDs are all cubic in shape, but (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-GQD has rounded corners, while (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-SH-GQD has sharp corners.

[0097] and (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-GQD and (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-SH-GQD is different, (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 The morphology of )2O4-BSH-GQD is fish-shaped.

[0098] The above results show that undoped graphene quantum dots, N atom-doped graphene quantum dots and N and B atom-co-doped graphene quantum dots can induce high-entropy oxide complexes of different forms; among them, the morphological characteristics induced by N and B atom-co-doped graphene quantum dots are more uniform.

[0099] 2. X-ray diffraction (XDR)

[0100] (Nb 0.32 V 0.17 Mo 0.17 W 0.17Co 0.17 )2O4-GQD as shown in Figure 4 ;

[0101] (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-HS-GQD as shown in Figure 5 ;

[0102] (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-BSH-GQD as shown in Figure 6 .

[0103] The XRD results show that the space groups of (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-GQD, (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-HS-GQD and (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-BSH-GQD are obviously different.

[0104] (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-GQD and (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-SH-GQD both exist two P42 / mnm (PDF #075-2340) and I-4 (PDF #081-2343) space groups;

[0105] The ratio of P42 / mnm is much higher than I-4 in (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-HS-GQD;

[0106] In (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-BHS-GQDs only have a single P42 / mnm space group.

[0107] The above results show that undoped graphene quantum dots, N atom-doped graphene quantum dots and N and B atom-co-doped graphene quantum dots can make high-entropy oxides produce different space groups; compared with undoped graphene quantum dots and N atom-doped graphene quantum dots, N and B atom-co-doped graphene quantum dots can obtain single-phase high-entropy oxides.

[0108] Among them, the crystal structure corresponding to the space group I-4 (PDF#081-2343) is as follows Figure 7 As shown, it indicates short-range order.

[0109] The crystal structure of the space group P42 / mnm (PDF#075-2340) is as follows Figure 8 As shown, it indicates long-range order.

[0110] Combined with the crystal structure, it can be seen that (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-GQD and (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-HS-GQDs have both short-range ordered and long-range ordered crystal structures, that is, these two high entropy oxide complexes have obvious structural heterogeneity; while (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-BSH-GQD only has a long-range ordered crystal structure, that is, N, B co-doped graphene quantum dots induce a structurally homogeneous high-entropy oxide.

[0111] Example 4: Electrochemical impedance of high entropy oxide composites of different graphene quantum dots

[0112] Take the (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-GQD, (Nb 0.32 V 0.17 Mo0.17 W 0.17 Co 0.17 )2O4-HS-GQD and (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-BHS-GQD), and the electrochemical impedance spectroscopy results were as follows: Figure 9 shown.

[0113] The results show that among the three materials, (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-BHS-GQD) exhibits the smallest electron transfer resistance and the fastest ion diffusion rate, indicating that boron-doped graphene quantum dots functionalized with histidine and serine can significantly enhance the electrical conductivity of high-entropy oxide composites.

[0114] Example 5: Preparation of high entropy oxide electrodes

[0115] 1. Preparation of high entropy oxide electrodes

[0116] Take the high entropy oxide (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-GQD、(Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-HS-GQD and (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-BHS-GQD, prepare the electrode.

[0117] High entropy oxide (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-GQD, carbon black and polyvinylidene fluoride were dispersed in n-methyl-2-pyrrolidone in a mass ratio of 80:10:10 to obtain a uniform electrode slurry; the electrode slurry was coated on the surface of a 1 cm × 1 cm titanium sheet by a doctor blade method, dried in a vacuum drying oven at 80 ° C for 24 hours, and then allowed to stand at a pressure of 5 MPa for 1 minute to prepare (Nb 0.32 V 0.17 Mo0.17 W 0.17 Co 0.17 )2O4-GQD working electrode sheet; the mass density of the electrode slurry on the electrode sheet is 2 mg / cm, and the surface area of ​​the electrode sheet is 1 cm 2 .

[0118] According to the above method, the high entropy oxide composite (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-GQD is (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-HS-GQD and (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-BHS-GQD, respectively prepared (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-HS-GQD working electrode and (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-BHS-GQD working electrode sheet.

[0119] 2. Working electrode energy storage performance test

[0120] Take the (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-GQD working electrode sheet, (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-HS-GQD working electrode and (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-BHS-GQD working electrode sheets were immersed in 1 mol / L Li2SO4 electrolyte for 24 hours to obtain activated working electrodes.

[0121] The three-electrode test system consists of an activated working electrode (1cm×2cm), a platinum counter electrode (1cm×1cm) and a saturated calomel reference electrode; the three-electrode test system uses 1 mol / L Li2SO4 aqueous solution as the electrolyte.

[0122] The three-electrode test system was used to detect (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-GQD electrode sheet, (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-HS-GQD electrode and (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )The energy storage performance of 2O4-BHS-GQD electrode sheet is as follows.

[0123] (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 The charge-discharge curves of )2O4-GQD electrode measured at different current densities are shown in Figure 2. Figure 10 As shown in the figure, the results show that when the charge and discharge current density is 1A / g, it can be calculated that (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-GQD electrode has a specific capacity of up to 468F / g.

[0124] (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 The charge-discharge curves of )2O4-HS-GQD electrode measured at different current densities are shown in Figure 2. Figure 11 The results show that the specific capacity of the material is as high as 545.4F / g when the charge and discharge current density is 1A / g, which is higher than that of undoped graphene quantum dots (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 The capacity of the )2O4-GQD high-entropy oxide composite increased by 77.4F / g.

[0125] (Nb0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 The charge-discharge curves of 2O4-BHS-GQD electrode measured at different current densities are shown in Figure 2. Figure 12 The results show that when the charge and discharge current density is 1A / g, the specific capacity of the material is as high as 966F / g, which is higher than that of undoped graphene quantum dots (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-GQD high entropy oxide composites increased by 498F / g, and the capacity of N-doped graphene quantum dots (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 The capacity of the )2O4-HS-GQD high-entropy oxide composite increased by 420.6 F / g.

[0126] (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 The cyclic voltammetry curves of )2O4-BHS-GQD electrode measured at different scan rates are shown in Figure 2. Figure 13 As shown, the results show that the redox peak pair indicates that Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-BHS-GQD has pseudocapacitive characteristics, which mainly comes from the redox reaction of metal ions in high-entropy oxides.

[0127] Example 6: Preparation of supercapacitors

[0128] Take the (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-BHS-GQD electrode sheet, prepare super supercapacitor, the steps are as follows:

[0129] Two pieces (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17)2O4-BHS-GQD electrode sheets were used as the two poles of the supercapacitor, and PVA / Li2SO4 gel was used as the electrolyte to assemble into a symmetrical solid-state supercapacitor.

[0130] Preparation of PVA / Li2SO4 gel electrolyte: 2.0 g of polyvinyl alcohol (PVA) and 10 mL of 2 mol / L Li2SO4 solution were poured into 20 mL of ultrapure water and stirred on a heating mantle at 75°C until the solution became clear and transparent. After cooling to room temperature, PVA / Li2SO4 gel was obtained.

[0131] (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 )2O4-BHS-GQD / / (Nb 0.32 V 0.17 Mo 0.17 W 0.17 Co 0.17 The energy density of )2O4-BHS-GQD supercapacitors at different power densities is as follows Figure 14 As shown in the results, at a power density of 900 W / kg, its energy can reach 153 Wh / kg, which is significantly higher than the energy density of the current aqueous supercapacitors made of high-entropy oxide-based materials (Facile synthesis of high-entropy (Co0.2Cr0.2Fe0.2Mn0.2Ni0.2)3O4 nanopowders and their electrochemical properties as supercapacitor electrode; doi.org / 10.1016 / j.est.2023.109182) (at a power density of 746 W / kg, the energy density reaches 24 Wh / kg).

[0132] Although the present invention has been disclosed above in terms of preferred embodiments, it is not intended to limit the present invention. Anyone familiar with this technology can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the definition of the claims.

Claims

1. A method for preparing a high entropy oxide composite, characterized in that: The method comprises: (1) mixing a cobalt ion salt, a tungsten ion salt, a vanadium ion salt, a niobium ion salt and a molybdenum ion salt in a molar ratio of 0.15-0.2:0.15-0.2:0.15-0.2:0.31-0.34:0.15-0.2, dissolving the mixture in a graphene quantum dot solution, and stirring to obtain a mixed solution; (2) Using cotton to absorb the mixed solution and drying it to obtain cotton adsorbed with metal ions and graphene quantum dots; wherein the mass ratio of metal salt, graphene quantum dots and cotton is 0.8~1.2:0.6~1.2:0.9~1.3; (3) Cotton adsorbed with metal ions and graphene quantum dots was annealed to prepare high entropy oxides.

2. The method according to claim 1, characterized in that The preparation method of graphene quantum dots includes: One or more of serine, histidine, boric acid and citric acid are dissolved in water, and heated at 170-200° C. for 2-4 hours to react.

3. The method according to claim 2, characterized in that The preparation method of graphene quantum dots includes: Select citric acid and dissolve it in water. The ratio of citric acid to water is 18-19.5 g: 45-60 mL.

4. The method according to claim 2, characterized in that The preparation method of graphene quantum dots includes: Select citric acid, serine, and histidine and dissolve them in water. The dosage ratio of citric acid, serine, histidine, and water is 18-19.5 g: 1.8-2.4 g: 15-16 g: 45-60 mL.

5. The method according to claim 2, characterized in that The preparation method of graphene quantum dots includes: Select citric acid, serine, histidine and boric acid and dissolve them in water. The usage ratio of citric acid, serine, histidine, boric acid and water is 18-19.5 g: 1.8-2.4 g: 15-16 g: 0.8-1.5 g: 45-60 mL.

6. The method according to claim 1, characterized in that The cobalt ion salt includes one or more of cobalt chloride, cobalt nitrate, and cobalt sulfate; The tungsten ion salt includes one or more of tungsten hexachloride, sodium metatungstate, and sodium tungstate dihydrate; The vanadium ion salt includes one or more of vanadium chloride, ammonium metavanadate, and sodium vanadate hydrate; The niobium ion salt includes one or more of niobium chloride, niobium oxalate, and ammonium niobate oxalate hydrate; The molybdenum ion salt includes one or more of sodium molybdate, molybdenum pentachloride, and ammonium molybdate.

7. The method according to claim 1, wherein Annealing is performed at 800~900℃ for 2~5 hours.

8. A high entropy oxide prepared by the method according to any one of claims 1 to 7.

9. Use of the method according to any one of claims 1 to 7 or the high entropy oxide according to claim 8 in the preparation of electronic components.

10. The use according to claim 9, characterized in that The electronic components include batteries and capacitors.

11. A supercapacitor, characterized in that: The preparation method of the supercapacitor comprises: The high entropy oxide, carbon black and polyvinylidene fluoride described in claim 8 are dispersed in n-methyl-2-pyrrolidone to obtain an electrode slurry; the electrode slurry is coated on the surface of a titanium sheet to obtain an electrode sheet; two electrode sheets are used as electrodes and PVA / Li2SO4 gel is used as an electrolyte to form a symmetrical solid-state supercapacitor.

12. The supercapacitor according to claim 11, wherein The mass ratio of high entropy oxide, carbon black and polyvinylidene fluoride is 70-90:5-15:5-15; the mass density of the electrode slurry on the surface of the electrode sheet is 1.5-2.5 mg / cm.

13. A method for improving the performance of a supercapacitor, characterized in that: Preparation of supercapacitors using high entropy oxides; The preparation method of the high entropy oxide comprises: (1) mixing a cobalt ion salt, a tungsten ion salt, a vanadium ion salt, a niobium ion salt and a molybdenum ion salt in a molar ratio of 0.15-0.2:0.15-0.2:0.15-0.2:0.31-0.34:0.15-0.2, dissolving the mixture in a graphene quantum dot solution, and stirring to obtain a mixed solution; (2) Using cotton to absorb the mixed solution and drying it to obtain cotton adsorbed with metal ions and graphene quantum dots; wherein the mass ratio of metal salt, graphene quantum dots and cotton is 0.8~1.2:0.6~1.2:0.9~1.3; (3) Cotton adsorbed with metal ions and graphene quantum dots was annealed to prepare high entropy oxides.

14. The method according to claim 13, characterized in that The preparation method of graphene quantum dots includes: One or more of serine, histidine, boric acid and citric acid are dissolved in water, and heated at 170-200° C. for 2-4 hours to react.

15. The method according to claim 14, characterized in that The preparation method of graphene quantum dots includes: Select citric acid and dissolve it in water. The ratio of citric acid to water is 18-19.5 g: 45-60 mL.

16. The method according to claim 14, characterized in that The preparation method of graphene quantum dots includes: Select citric acid, serine, and histidine and dissolve them in water. The dosage ratio of citric acid, serine, histidine, and water is 18-19.5 g: 1.8-2.4 g: 15-16 g: 45-60 mL.

17. The method according to claim 14, characterized in that The preparation method of graphene quantum dots includes: Select citric acid, serine, histidine and boric acid and dissolve them in water. The usage ratio of citric acid, serine, histidine, boric acid and water is 18-19.5 g: 1.8-2.4 g: 15-16 g: 0.8-1.5 g: 45-60 mL.

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