Two-dimensional high-entropy metal-organic framework material and preparation method and application thereof

Abstract

The application provides a two-dimensional high-entropy metal organic framework material and a preparation method and application thereof, wherein the central ion of the metal organic framework material is at least three of Fe 3+ , Co 2+ , Ni 2+ , Cu 2+ , Zn 2+ , Mn 2+ , Sb 3+ , and Sn 4+ , and the organic ligand is at least one of terephthalic acid, isophthalic acid, o-phthalic acid, trimesic acid and 2-hydroxyterephthalic acid; the metal organic framework material is applied to a sodium ion capacitor as a negative electrode active material, so that the sodium ion capacitor has high energy density and high power density and exhibits excellent cycle stability.

Description

Technical Field

[0001] This invention relates to the field of electrode materials technology, and more specifically, to a two-dimensional high-entropy metal-organic framework material, its preparation method, and its application. Background Technology

[0002] With the global energy shortage and increasingly severe environmental pollution, the development and utilization of new renewable energy sources is a crucial issue for the world today. However, clean and renewable energy sources such as solar, wind, and geothermal energy are characterized by uneven and discontinuous distribution. Therefore, utilizing these renewable energy sources is inseparable from energy storage, necessitating the development of advanced energy storage technologies. In recent decades, supercapacitors and secondary metal-ion batteries have been the two most widely used types of energy storage devices, but the low energy density of supercapacitors and the low power density of secondary metal-ion batteries make it difficult to meet practical needs.

[0003] Sodium-ion capacitors combine the advantages of supercapacitors and secondary metal-ion batteries, possessing high energy density, high power density, and long cycle life, making them one of the best choices for power sources. Furthermore, sodium resources, compared to lithium resources, have advantages such as high abundance, wide distribution, and low cost. Therefore, sodium-ion capacitors have a greater competitive advantage and promising application prospects. However, the mismatch between the kinetic mechanisms of battery-type anodes and capacitor-type cathodes is one of the key factors limiting the further development of sodium-ion hybrid capacitors. Among these factors, the preparation of high-rate and long-cycle anode materials has become a bottleneck in improving the energy density, power density, and cycle life of sodium-ion capacitors.

[0004] For existing anode materials, carbon-based materials such as graphite have good electrochemical performance in lithium-ion energy storage systems, but their cycle performance and rate performance are poor due to the large radius of sodium ions; metal-based materials such as Sb and Sn have relatively high specific capacity, but their large volume strain and rapid capacity decay result in poor cycle stability; organic compounds such as Na2C8H4O4 have insufficient cycle and rate performance and are not suitable for assembling sodium-ion capacitors.

[0005] Therefore, it is necessary to design and fabricate high-performance, low-cost sodium-ion capacitor anode materials to achieve high energy density and high power density in sodium-ion capacitors. Summary of the Invention

[0006] Based on the aforementioned technical problems in the existing technology, one of the objectives of this invention is to provide a two-dimensional high-entropy organic framework material. The central ion of this organic framework material is composed of a variety of metal ions and combined with specific organic ligands. When applied to capacitors, it can enable capacitors to have high energy density and high power density, and exhibit excellent cycle stability.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows:

[0008] A two-dimensional high-entropy metal-organic framework material, wherein the central ion of the metal-organic framework material is Fe. 3+ and Co 2 + and Ni 2+ Cu 2+ Zn 2+ Mn 2+ Sb 3+ Sn 4+ At least three of the organic ligands are selected, and the organic ligands are at least one of terephthalic acid, isophthalic acid, phthalic acid, pyromellitic acid, and 2-hydroxyterephthalic acid.

[0009] In some embodiments, a two-dimensional high-entropy metal-organic framework material is characterized in that the central ion is Fe. 3+ Co 2+ Ni 2+ Cu 2+ and Zn 2+ .

[0010] In some embodiments, the Fe 3+ Co 2+ Ni 2+ Cu 2+ and Zn 2+ The molar ratio is 2.92–13.6: 0.73–3.4: 1: 1: 1, and Fe 3+ Co 2+ The molar ratio is 4:1.

[0011] A second objective of this invention is to provide a method for preparing an organic framework material according to any of the above embodiments, the method comprising the following steps:

[0012] S1, Co 2+ Soluble salts, Fe 3+ Soluble salts and Ni 2+ Cu 2+ Zn 2+ Mn 2+ Sb 3+ Sn 4+ At least three soluble salts and organic ligands are added to a mixed solvent and mixed to obtain a first solution.

[0013] S2. Add a deprotonating solvent to the first solution, react, and then separate the solid and liquid phases to obtain the two-dimensional high-entropy metal-organic framework material.

[0014] In the first solution, Fe 3+and Co 2+ The molar ratio is 4:1; the mixed solvent is a mixture of a first solvent, ethanol and water; the first solvent is at least one of DMF, DMAC and NMP.

[0015] In some embodiments, the molar ratio of the organic component to all metals is 1:1.5-2.

[0016] In some embodiments, the volume ratio of the first solvent, ethanol, and water is 5-8:1:1.

[0017] In some embodiments, the deprotonating solvent includes at least one of ammonia, triethylamine, ethylenediamine, and n-butylamine.

[0018] A third objective of this invention is to provide a negative electrode material, wherein the negative electrode material comprises the organic framework material of any of the above embodiments or the organic framework material obtained by the preparation method of any of the above embodiments.

[0019] In some embodiments, the negative electrode material further includes a conductive agent and a binder.

[0020] The fourth objective of this invention is to provide a negative electrode, which includes the aforementioned negative electrode material.

[0021] The fifth objective of this invention is to provide an electrochemical energy storage device, which includes the aforementioned negative electrode.

[0022] In some embodiments, the electrochemical energy storage device further includes a positive electrode, which comprises a positive electrode material including activated carbon, a conductive agent, and a binder.

[0023] In some embodiments, the activated carbon may be commercially available, or produced by any disclosed method, or by the following preparation method:

[0024] Using alkali metal salt of terephthalic acid as the carbon source and KOH as the activator, the two are mixed and thoroughly mixed. The mixture is then calcined in an inert gas atmosphere. After calcination, the mixture is cooled, washed, filtered, and dried until the filtrate is neutral to obtain activated carbon.

[0025] In some embodiments, the mass ratio of the alkali metal salt of terephthalic acid to KOH is 1:4 to 6.

[0026] In some embodiments, the calcination temperature is 750–850°C; the calcination time is 1–3 hours.

[0027] In some implementations, the heating rate is 5–10 °C / min.

[0028] In some embodiments, the calcined product is washed with dilute hydrochloric acid and water, respectively.

[0029] In some embodiments, vacuum drying is performed at 80-100°C for 10-14 hours.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] This invention provides a method using Fe 3+ Co 2+ Ions, and Ni 2+ Cu 2+ Zn 2+ Mn 2+ Sb 3+ Sn 4+ This high-entropy metal-organic framework material uses at least three ions as central ions and at least one of phthalic acid, isophthalic acid, phthalic acid, trimesic acid, and 2-hydroxyterephthalic acid as organic ligands. The material exhibits a two-dimensional sheet-like structure with an average thickness of 1-3 nm. Due to the introduction of the high-entropy effect, the various metal centers work synergistically, resulting in high initial coulombic efficiency and good cycling stability as a sodium storage anode.

[0032] The method for preparing two-dimensional high-entropy metal-organic framework materials provided by this invention employs a simple bottom-up synthesis method with room-temperature stirring. The deprotonating agent induces effective coordination between metal ions and organic ligands, accelerating the reaction. Simultaneously, the addition of the deprotonating agent makes the resulting nanosheet structure more stable. The partial introduction of Fe(III) induces the formation of ultrathin two-dimensional nanosheet morphologies. This is because Fe... 3+ The adsorption of H2O from the solvent is more efficient, leading to the formation of hydroxides. This hinders the vertical growth of MOFs, causing them to extend horizontally and ultimately resulting in an ultrathin nanosheet morphology. Furthermore, Ni(II), Cu(II), and Zn(II) can partially replace Co(II) sites, introducing them into the 2D MOF framework. This increases the entropy of the 2D MOFs. Since these five metal ions have similar ionic radii, this reduces the influence of different ionic radii on crystal distortion. Ultimately, the high-entropy effect is brought into the 2D MOFs, forming a structurally stable two-dimensional high-entropy organic framework material. In addition, the preparation method of this invention features high yield and strong controllability, which is beneficial for practical high-throughput production. The process is simple, requires no heating, has low energy consumption, and saves operating costs. Moreover, the organic solvent can be recycled, further reducing raw material costs.

[0033] The two-dimensional high-entropy organic framework material provided by this invention, when used as a negative electrode active material in sodium-ion capacitors, exhibits ultra-high energy storage electrochemical performance. Because multiple metal ions are introduced into the central ion of the metal-organic framework material, a high-entropy effect is brought into the metal-organic framework material. This high-entropy effect is beneficial to improving electrochemical performance, with each metal element playing its own role.

[0034] Furthermore, the self-made activated carbon possesses an ultra-large specific surface area and abundant pore structure, exhibiting a large specific capacitance as a sodium-ion cathode material. Sodium-ion capacitors constructed using positive and negative electrode active materials in a specific mass ratio demonstrate excellent performance in terms of high energy density, high power output, and long-term cycle stability. Attached Figure Description

[0035] Figure 1 X-ray diffraction patterns of five MOF samples prepared in Examples 1-3 and Comparative Examples 1-2;

[0036] Figure 2 This is a scanning electron microscope image of HE-MOF-1 obtained in Example 1;

[0037] Figure 3 An atomic force microscope image of HE-MOF-1 prepared in Example 1;

[0038] Figure 4 The EDX spectrum of HE-MOF-1 prepared in Example 1;

[0039] Figure 5 The image shows a scanning electron microscope (SEM) image of HE-MOF-2 obtained in Example 2.

[0040] Figure 6 An atomic force microscope image of HE-MOF-2 prepared in Example 2;

[0041] Figure 7 The EDX spectrum of HE-MOF-2 obtained in Example 2;

[0042] Figure 8 This is a scanning electron microscope image of HE-MOF-3 obtained in Example 3;

[0043] Figure 9 An atomic force microscope image of HE-MOF-3 prepared in Example 3;

[0044] Figure 10 The EDX spectrum of HE-MOF-3 obtained in Example 3;

[0045] Figure 11 The image shows a scanning electron microscope (SEM) image of the CoFe-MOF prepared in Comparative Example 1.

[0046] Figure 12 The image shows a scanning electron microscope (SEM) image of the Co-MOF prepared in Comparative Example 2.

[0047] Figure 13 The electrochemical performance test graphs of the two-dimensional metal-organic framework materials prepared in Examples 1-3 and Comparative Examples 1-2 are shown.

[0048] Figure 14 The sodium-ion capacitors constructed in Examples 4-6 were tested at 0.2 Ag. -1 Constant current charge-discharge curves at current density;

[0049] Figure 15 Lagon plots of energy density-power density for sodium-ion capacitors constructed in Examples 4-6;

[0050] Figure 16 1Ag of the sodium-ion capacitor constructed in Example 5 -1 Long-cycle performance at current density. Detailed Implementation

[0051] Numerous specific details are set forth in the following description to provide a full understanding of the invention. However, the invention can be practiced in many other ways different from those described herein, and similar modifications can be made by those skilled in the art without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0052] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0053] Example 1

[0054] A method for preparing a two-dimensional high-entropy metal-organic framework material, the specific steps of which are as follows:

[0055] S1. Weigh 3.06 mmol Co(NO3)2·6H2O, 0.765 mmol FeCl3·6H2O, 0.225 mmol NiCl2·6H2O, 0.225 mmol CuCl2·2H2O, 0.225 mmol ZnSO4·7H2O and 3 mmol terephthalic acid into a beaker containing a mixed solvent of 50 ml DMF, 10 ml H2O and 10 ml EtOH, stir and disperse evenly to obtain a mixed solution;

[0056] S2. Add 4 ml of TEA to the mixed solution in step S1, stir at room temperature for 12 h to allow the reaction to proceed fully, and obtain a suspension.

[0057] S3. Centrifuge the suspension obtained in step S2 at 8000 r / min to separate the solid and liquid and obtain the precipitate; wash the solid with EtOH and centrifuge repeatedly for 3 times. Finally, place the washed solid in an oven and vacuum dry it at 100℃ for 24 h. After grinding the dried material, the powder material is obtained and named HE-MOF-1 with a yield of 870 mg.

[0058] The obtained materials were tested, and the test results are as follows: Figures 1-4 As shown.

[0059] Upon testing, the obtained material exhibits MOF diffraction peaks (such as...). Figure 1 ), exhibiting the morphology of ultrathin nanosheets (such as Figure 2 Its thickness is 1-3 nm (e.g.) Figure 3 Furthermore, EDX spectroscopy also confirmed the presence of five elements: Co, Fe, Ni, Cu, and Zn (e.g., Figure 4 ).

[0060] Example 2

[0061] A method for preparing a two-dimensional high-entropy metal-organic framework material, the specific steps of which are as follows:

[0062] S1. Weigh 2.52 mmol Co(NO3)2·6H2O, 0.63 mmol FeCl3·6H2O, 0.45 mmol NiCl2·6H2O, 0.45 mmol CuCl2·2H2O, 0.45 mmol ZnSO4·7H2O and 3 mmol terephthalic acid into a beaker containing 50 ml DMF, 10 ml H2O and 10 ml EtOH mixed solvent, stir and disperse evenly to obtain a mixed solution;

[0063] S2. Add 4 ml of TEA to the mixed solution in step S1, stir at room temperature for 12 h to allow the reaction to proceed fully, and obtain a suspension.

[0064] S3. Centrifuge the suspension from step S2 at 8000 r / min to separate the solid and liquid, and obtain the precipitate. Wash the precipitate with EtOH and centrifuge it. Repeat the washing and centrifugation three times. Finally, place the obtained precipitate in an oven and vacuum dry it at 100℃ for 24 h. After grinding the dried material, the powder material is obtained and named HE-MOF-2 with a yield of 850 mg.

[0065] The obtained materials were tested, and the test results are as follows: Figure 1 , Figures 5-7 As shown.

[0066] Testing revealed that the obtained material exhibited MOF diffraction peaks ( Figure 1 ), exhibiting the morphology of ultrathin nanosheets ( Figure 5Its thickness is 1-3 nm. Figure 6 Furthermore, EDX spectroscopy confirmed the presence of five elements: Co, Fe, Ni, Cu, and Zn. Figure 7 ).

[0067] Example 3

[0068] A method for preparing a two-dimensional high-entropy metal-organic framework material, the specific steps of which are as follows:

[0069] S1. Weigh 1.98 mmol Co(NO3)2·6H2O, 0.495 mmol FeCl3·6H2O, 0.675 mmol NiCl2·6H2O, 0.675 mmol CuCl2·2H2O, 0.675 mmol ZnSO4·7H2O and 3 mmol terephthalic acid into a beaker containing 50 ml DMF, 10 ml H2O and 10 ml EtOH mixed solvent, stir and disperse evenly to obtain a mixed solution;

[0070] S2. Add 4 ml of TEA to the mixed solution in step S1, stir at room temperature for 12 h to allow the reaction to proceed fully, and obtain a suspension.

[0071] S3. Centrifuge the suspension from step S2 at 8000 r / min to separate the solid and liquid, and obtain the precipitate. Wash the precipitate with EtOH and centrifuge it. Repeat the washing and centrifugation three times. Finally, place the obtained precipitate in an oven and vacuum dry it at 100℃ for 24 h. After grinding the dried material, the powder material is obtained and named HE-MOF-3 with a yield of 800 mg.

[0072] The obtained materials were tested, and the test results are as follows: Figure 1 , Figures 9-10 As shown.

[0073] Testing revealed that the obtained material exhibited MOF diffraction peaks ( Figure 1 ), exhibiting the morphology of ultrathin nanosheets ( Figure 8 Its thickness is 1-3 nm. Figure 9 Furthermore, EDX spectroscopy confirmed the presence of five elements: Co, Fe, Ni, Cu, and Zn. Figure 10 ).

[0074] Comparative Example 1

[0075] A method for preparing a two-dimensional bimetallic organic framework material, the specific steps of which are as follows:

[0076] S1. Weigh 3.6 mmol Co(NO3)2·6H2O, 0.9 mmol FeCl3·6H2O and 3 mmol terephthalic acid and add them to a beaker containing 50 ml DMF, 10 ml H2O and 10 ml EtOH mixed solvent. Stir and disperse evenly to obtain a mixed solution.

[0077] S2. Add 4 ml of TEA to the mixed solution in step S1, stir at room temperature for 12 h to allow the reaction to proceed fully, and obtain a suspension.

[0078] S3. Centrifuge the suspension obtained in step S2 at 8000 r / min to separate the solid and liquid and obtain the precipitate. Wash the precipitate with EtOH and centrifuge it. Repeat the washing and centrifugation three times. Finally, place the obtained precipitate in an oven and vacuum dry it at 100℃ for 24 h. After grinding the dried material, the powder material is obtained and named CoFe-MOF with a yield of 850 mg.

[0079] The obtained materials were tested, and the test results are as follows: Figure 1 and Figure 11 As shown.

[0080] Testing revealed that the obtained material exhibited MOF diffraction peaks ( Figure 1 ), exhibiting the morphology of ultrathin nanosheets ( Figure 11 ).

[0081] Comparative Example 2

[0082] A method for preparing a single-metal organic framework material, comprising the following specific steps:

[0083] S1. Weigh 4.5 mmol Co(NO3)2·6H2O and 3 mmol terephthalic acid and add them to a beaker containing 50 ml DMF, 10 ml H2O and 10 ml EtOH mixed solvent. Stir and disperse evenly to obtain a mixed solution.

[0084] S2. Add 4 ml of TEA to the mixed solution in step S1, stir at room temperature for 12 h to allow the reaction to proceed fully, and obtain a suspension.

[0085] S3. Centrifuge the suspension from step S2 at 8000 r / min to separate the solid and liquid and obtain the precipitate. Wash the precipitate with EtOH and centrifuge it. Repeat the washing and centrifugation three times. Finally, place the obtained precipitate in an oven and vacuum dry it at 100℃ for 24 h. After grinding the dried material, the powder material is obtained and named Co-MOF with a yield of 850 mg.

[0086] The obtained materials were tested, and the test results are as follows: Figure 1 and Figure 12 As shown.

[0087] Testing revealed that the obtained material exhibited MOF diffraction peaks ( Figure 1 ), exhibiting a stacked block-like morphology ( Figure 12 ).

[0088] In summary, this application induces the formation of ultrathin two-dimensional nanosheets by introducing Fe, while the introduction of the other three elements, Ni, Cu, and Zn, does not change the two-dimensional morphology or the space group structure of MOFs. EDX spectroscopy also confirms the effective introduction of the five elements, which reveals the successful preparation of two-dimensional high-entropy metal-organic frameworks.

[0089] Example 4

[0090] The metal-organic framework materials prepared in Examples 1-3 and Comparative Examples 1-2 were used as negative electrodes for electrochemical performance testing, as detailed below:

[0091] Preparation of the negative electrode sheet: Dissolve 15 mg of CMC in an appropriate amount of H2O and stir magnetically for at least 1 hour until completely dissolved to obtain a CMC solution with uniform viscosity; then grind 70 mg of metal-organic framework material and 15 mg of Super P in a mortar and add them to the above CMC solution. Add a small amount of H2O as needed according to the viscosity, and stir on a magnetic stirrer for 12 hours to obtain a slurry; then use a fully automatic coating machine to evenly spread the slurry on a carbon-containing copper foil and vacuum dry at 80°C for 12 hours to obtain the negative electrode sheet; cut the negative electrode sheet into a circular shape with a diameter of 14 mm for later use.

[0092] Half-cell assembly: CR2016 coin cells were assembled in a glove box with a high-purity Ar protective atmosphere (water and oxygen values ​​are both less than 0.1 ppm) using a negative electrode as the working electrode, metallic sodium as the counter electrode, glass fiber as the separator, and 1M NaPF6 DIGLYME solution as the electrolyte.

[0093] Electrochemical performance testing: The pre-sodiumized half-cell was tested at 0.3Ag. -1 After 120 charge-discharge cycles at current density, the cycling performance of various metal-organic framework materials is as follows: Figure 13 As shown.

[0094] Sodium-ion capacitors were prepared using the metal-organic framework material obtained in Example 3, and their electrochemical performance was tested, as detailed in the following examples.

[0095] Example 5

[0096] Preparation of activated carbon: Disodium terephthalate was used as the carbon source and KOH as the chemical activator. Disodium terephthalate and KOH were mixed evenly at a mass ratio of 1:4. The mixed raw materials were then placed in a tube furnace and heated to 800℃ at a heating rate of 5℃ / min under an Ar atmosphere and held at that temperature for 2h. After the reaction was completed, the mixture was cooled to room temperature. The product was washed with dilute HCl and water, filtered, and the filtrate was kept neutral. The product was then vacuum dried at 80℃ for 12h, ground, and crushed to obtain activated carbon material.

[0097] Preparation of the positive electrode: Dissolve 10 mg of PVDF in an appropriate amount of NMP and stir magnetically for at least 1 hour until completely dissolved to obtain a PVDF solution with uniform viscosity; then grind 80 mg of self-made activated carbon material and 10 mg of Super P in a mortar, and add it to the above PVDF solution. Add a small amount of NMP according to the viscosity, and stir on a magnetic stirrer for 6 hours to obtain a slurry; then use a fully automatic coating machine to evenly spread the slurry on a carbon-containing aluminum foil, and vacuum dry at 120°C for 12 hours to obtain the positive electrode. Cut the obtained positive electrode into a circular shape with a diameter of 14 mm for later use.

[0098] Preparation of the negative electrode sheet: 15 mg of CMC was dissolved in an appropriate amount of H2O and magnetically stirred for at least 1 hour until completely dissolved to obtain a CMC solution with uniform viscosity; then 70 mg of the two-dimensional high-entropy metal-organic framework prepared in Example 3 and 15 mg of Super P were ground thoroughly in a mortar and added to the above CMC solution. A small amount of H2O was added according to the viscosity, and the mixture was stirred on a magnetic stirrer for 12 hours to obtain a slurry; then the slurry was evenly spread on a carbon-containing copper foil using a fully automatic coating machine and vacuum dried at 80°C for 12 hours to obtain the negative electrode sheet; the negative electrode sheet was cut into a circular shape with a diameter of 14 mm for later use.

[0099] Electrochemical pre-sodiumization of the negative electrode was performed as follows: A half-cell was assembled using the negative electrode as the working electrode, metallic sodium as the counter electrode, glass fiber as the separator, and a 1M NaPF6 DIGLYME solution as the electrolyte. The CR2016 coin cell was assembled in a high-purity Ar protective atmosphere glove box (water and oxygen values ​​both less than 0.1 ppm); then, the negative electrode was pre-sodiumized in the half-cell at 0.1 Ag... -1 The current density was continuously charged and discharged for 3 cycles, and finally discharged again to a cutoff voltage of 0.01V to complete the electrochemical pre-sodiumization of the negative electrode. The negative electrode in the half-cell was removed in a glove box to obtain the pre-sodiumized negative electrode.

[0100] Assembly of sodium-ion capacitors: The pre-sodium-treated negative electrode, separator, electrolyte, positive electrode, gasket, and shell are assembled in sequence to form a sodium-ion capacitor, named SIC-2:1; wherein, the mass ratio of positive and negative active materials is 2:1 (i.e., the mass ratio of activated carbon to metal-organic framework material is 2:1); during the assembly process, the separator, electrolyte, gasket, and shell used are the same as those used in assembling half cells.

[0101] Example 6

[0102] A method for preparing a sodium-ion capacitor, the specific steps of which are as follows:

[0103] Preparation of the positive electrode sheet: Same as in Example 5.

[0104] Preparation of the negative electrode sheet: Same as in Example 5.

[0105] Pre-sodiuming of the negative electrode: Same as in Example 5.

[0106] Assembly of sodium-ion capacitor: Same as in Example 5, except that the mass ratio of positive and negative electrode active materials is 3:1, named SIC-3:1.

[0107] Example 7

[0108] A method for preparing a sodium-ion capacitor, the specific steps of which are as follows:

[0109] Preparation of the positive electrode sheet: Same as in Example 5.

[0110] Preparation of the negative electrode sheet: Same as in Example 5.

[0111] Pre-sodiuming of the negative electrode: Same as in Example 5.

[0112] Assembly of sodium-ion capacitor: Same as in Example 5, except that the mass ratio of positive and negative electrode active materials is 4:1, named SIC-4:1.

[0113] Electrochemical tests were performed on the sodium-ion capacitors assembled in Examples 6-8, and the test results are as follows: Figure 14-16 As shown.

[0114] like Figure 14 As shown, at 0.2Ag -1 At current density, their constant current charge-discharge curves exhibit almost symmetrical linear straight lines, indicating a mixing mechanism in sodium-ion capacitors; and SIC-3:1 has the longest charge-discharge time, indicating that a 3:1 mass ratio of positive to negative electrode active materials provides the best performance.

[0115] like Figure 15As shown, the energy density and power density of SIC-2:1, SIC-3:1, and SIC-4:1 were calculated respectively. At the same power density, SIC-3:1 has the highest energy density, with SIC-3:1 achieving a power density of 200 W / kg. -1 The energy density is 121.8 Wh / kg. -1 Even at 10000Wkg -1 Even with ultra-high power density, the energy density is still 64.4 Wh / kg. -1 .

[0116] like Figure 16 As shown, long-cycle performance tests were conducted on SIC-3:1, while SIC-1:3 exhibited excellent long-cycle stability at 1Ag. -1 After 1200 cycles at current density, the capacity retention rate is still 76.9%, demonstrating excellent cycle stability.

[0117] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0118] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing a two-dimensional high-entropy metal-organic framework material, characterized in that, Includes the following steps: S1, Co 2+ Soluble salts, Fe 3+ Soluble salts and Ni 2+ Cu 2+ Zn 2+ The soluble salt and organic ligand are added to the mixed solvent in proportion and mixed well to obtain the first solution; S2. Add the deprotonating solvent TEA to the first solution, carry out the reaction, and then separate the solid and liquid to obtain the two-dimensional high-entropy metal-organic framework material. The mixed solvent is a mixture of DMF, ethanol, and water; the volume ratio of DMF, ethanol, and water is 5:1:

1. The molar ratio of the organic ligand to all metals is 1:1.5; Co in the first solution 2+ Fe 3+ Ni 2+ Cu 2+ and Zn 2+ The molar ratio is 1.98:0.495:0.675:0.675:0.

675.

2. The two-dimensional high-entropy metal-organic framework material obtained by the preparation method of claim 1.

3. A negative electrode material, characterized in that, Including the two-dimensional high-entropy metal-organic framework material as described in claim 2.

4. Negative electrode, characterized in that, Including the negative electrode material as described in claim 3.

5. An electrochemical energy storage device, characterized in that, Includes the negative electrode as described in claim 4.

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