A nickel-iron prussian blue supercapacitor electrode material, a preparation method thereof and a supercapacitor

Abstract

The application belongs to the technical field of capacitors, and discloses a nickel-iron Prussian blue supercapacitor electrode material, a preparation method thereof and a supercapacitor, which comprises the following steps: dissolving nickel chloride hexahydrate, iron trichloride hexahydrate and trisodium citrate dihydrate in water to obtain reagent A, dissolving potassium ferricyanide in water to prepare a solution to obtain reagent B; slowly adding reagent B into reagent A under room temperature, stirring, and then placing the mixed solution under room temperature, washing, centrifuging, collecting the precipitate, and vacuum drying to obtain a nickel-iron Prussian blue material PBA; by adjusting the amount of trisodium citrate and the ratio of nickel to iron, the two play a synergistic role to achieve the effect of high specific capacitance (140.25 F·g ‑1 ) and cycle stability (84.35% retention rate after 2000 cycles), and when the two synergistically act, the structural stability and redox activity of the material can be effectively enhanced, and finally the balance between high specific capacitance and excellent cycle stability is achieved.

Description

Technical Field

[0001] This invention belongs to the field of capacitor technology, specifically relating to a nickel-iron Prussian blue supercapacitor electrode material, its preparation method, and a supercapacitor. Background Technology

[0002] Supercapacitors (SCs) are a new type of energy storage device with high power density, good charge and discharge efficiency, and excellent cycle life. Their energy storage level is between that of traditional capacitors and batteries. Low energy density is a key factor hindering their widespread application. Based on different charge storage mechanisms, supercapacitors are broadly classified into three categories: electric double-layer capacitors (EDLCs), pseudocapacitive capacitors, and hybrid capacitors. EDLCs rely on electrostatic interactions at the electrode interfaces to store charge; pseudocapacitive capacitors, on the other hand, rely on redox reactions occurring on the electrode surface. Because Faraday reactions have inherent time delays, the power density of pseudocapacitors is generally lower than that of EDLCs, and their electrodes constantly expand and contract during redox reactions, leading to a significant reduction in cycle life. Hybrid supercapacitors combine the advantages of both types of capacitors. Faraday electrodes achieve high energy density through redox reactions, while non-Faraday electrodes provide excellent power output and long-term stability. The appropriate selection of electrode materials is one of the key factors in manufacturing high-performance supercapacitors.

[0003] In recent years, metal-organic frameworks (MOFs) have emerged as promising candidates in electrochemistry due to their large specific surface area and flexibly tunable structures. Prussian blue and its analogues (PBAs) belong to the MOF family. Their relatively simple preparation, open three-dimensional structure, and unique mixed valence states have led to their widespread application in supercapacitors. However, traditional Prussian blue suffers from low electronic conductivity, resulting in poor electrical conductivity in capacitors. Furthermore, the slow ion insertion and extraction rates significantly limit the capacitance and rate performance of PBA materials. Currently, synthesizing PBAs with substances possessing good electrical conductivity can indeed greatly optimize electrode performance. Among various PBA materials, [Fe(CN)6] stands out. 3- FeHCF is one of the most widely used and lowest-cost ligands among PBAs. However, existing research reports have mentioned that FeHCF suffers from poor cycling stability, which affects its practical application. Summary of the Invention

[0004] One object of the present invention is to solve at least the above-mentioned problems and / or defects, and to provide at least the advantages described below.

[0005] To achieve these objectives and other advantages of the present invention, a method for preparing a nickel-iron Prussian blue supercapacitor electrode material is provided, comprising the following steps:

[0006] Step 1: Dissolve nickel chloride hexahydrate, ferric chloride hexahydrate, and trisodium citrate dihydrate in water to obtain reagent A; dissolve potassium ferricyanide in water to prepare a solution to obtain reagent B.

[0007] Step 2: Slowly add reagent B to reagent A at room temperature while stirring continuously. After stirring, let the mixed solution stand at room temperature, then wash with ethanol and deionized water and centrifuge. Collect the precipitate, dry it under vacuum, and obtain nickel-iron Prussian blue material PBA.

[0008] Preferably, in step one, the ratio of nickel chloride hexahydrate, ferric chloride hexahydrate, trisodium citrate dihydrate to water is 0.004~0.006 mol:0.001 mol:0.003~0.007 mol:50mL, and the ratio of potassium ferricyanide to water is 0.005 mol:50mL.

[0009] Preferably, in step two, the volume ratio of reagent B to reagent A is 1:1, the mixture is stirred for 2-4 hours, allowed to stand for 24-36 hours, and then vacuum dried at 60-80°C for 24-36 hours.

[0010] Preferably, in step two, the washing process involves washing with deionized water and ethanol 3 to 5 times each.

[0011] Preferably, in step one, a cobalt-doped carbon quantum dot solution is added to reagent A. The cobalt-doped carbon quantum dot solution is prepared by adding tartaric acid, cobalt acetate and triethylamine to deionized water, then transferring the mixture to a hydrothermal reactor for hydrothermal reaction, and cooling the reactor after the reaction is completed to obtain the cobalt-doped carbon quantum dot solution.

[0012] Preferably, in step one, the volume ratio of cobalt-doped carbon quantum dot solution to reagent A is 1:0.4~0.6, the ratio of tartaric acid, cobalt acetate, triethylamine and deionized water is 0.5~1g:0.01~0.02g:5~10mL:50mL, the hydrothermal reaction temperature is 150~200℃, and the reaction time is 18~24h.

[0013] Preferably, the nickel-iron Prussian blue material obtained in step two undergoes post-treatment, the method being as follows:

[0014] S21. Potassium hydroxide, N,N-dimethylformamide, ethylene glycol, oleylamine and heptanol were mixed and then nickel acetylacetonate and iron acetylacetonate were added to obtain a reaction solution. After stirring at room temperature overnight, the solution was transferred to a hydrothermal reactor for hydrothermal synthesis. After the reaction was completed, the solution was centrifuged and washed to obtain nano-nickel-iron material. The nano-nickel-iron alloy material was dispersed in water, and then dilute hydrochloric acid was added. The solution was ultrasonically reacted for a period of time to obtain a modified solution.

[0015] S22. Disperse the nickel-iron Prussian blue material in deionized water, add 2-hydroxysuccinic acid and the modification solution, stir and react at room temperature, let stand after stirring, then centrifuge, wash the obtained solid and freeze dry to obtain the modified nickel-iron Prussian blue material.

[0016] Preferably, in step S21, the ratio of potassium hydroxide, N,N-dimethylformamide, ethylene glycol, oleylamine, heptanol, nickel acetylacetonate, and iron acetylacetonate is 0.3~0.5g:10~20mL:5~10mL:10~20mL:5~10mL:0.03~0.05g:0.03~0.05g, the hydrothermal reaction temperature is 120~160℃, and the hydrothermal reaction is carried out for 12~24h; the ratio of nano-nickel-iron alloy material, water, and dilute hydrochloric acid is 10~15mg:10~20mL:1~2mL, the concentration of dilute hydrochloric acid is 0.1~0.5M, and the reaction is carried out under ultrasonication at 20~40kHz for 1~2h.

[0017] Preferably, in step S22, the ratio of nickel-iron Prussian blue material, deionized water, 2-hydroxysuccinic acid, and the modified solution is 2~5g:50mL:0.2~0.5g:5~10mL, the stirring speed is 300~400rpm, the stirring time is 1~2h, the standing time is 0.5~1h, the centrifugation speed is 6000~8000rpm, the centrifugation time is 10~15min, the freeze-drying temperature is -30~-40℃, and the freeze-drying time is 12~24h.

[0018] A nickel-iron Prussian blue supercapacitor electrode material is prepared by the above-mentioned method for preparing nickel-iron Prussian blue supercapacitor electrode materials.

[0019] A supercapacitor, wherein the positive electrode material of the supercapacitor is the aforementioned nickel-iron Prussian blue supercapacitor electrode material, and the negative electrode material of the supercapacitor is activated carbon.

[0020] This invention has the following beneficial effects: By adjusting the amount of trisodium citrate and the ratio of nickel to iron, the properties of FeNiHCF materials can be regulated. Trisodium citrate improves the ion transport pathway by controlling the pore structure, while the nickel-iron ratio (5:1) enhances the reversibility of redox reactions by forming an ordered crystal framework and active site distribution. The combined effect of these two factors achieves a high specific capacitance (140.25 F·g). -1The material achieves a balance between high specific capacitance and excellent cycling stability (84.35% retention after 2000 cycles). By adjusting the amount of trisodium citrate and the ratio of nickel to iron, the synergistic effect of both can effectively enhance the structural stability and redox activity of the material, ultimately achieving a balance between high specific capacitance and excellent cycling stability.

[0021] The asymmetric supercapacitor constructed using PBA5 (with optimal performance) as the positive electrode and activated carbon (AC) as the negative electrode exhibits excellent device performance: within a voltage window of 0-1.4 V, at a power density of 700 W·kg⁻¹ -1 At that time, the energy density can reach 6.65 Wh∙kg. -1 Of particular note is the presence of 100 mV∙s -1 After 2000 cycles at the scan rate, the capacity retention rate was as high as 135.13%, and the retention rate increased with the number of cycles, which clearly indicates that there is a significant electrode activation effect during the cycling process.

[0022] This invention also improves the electronic conductivity within and between particles of Prussian blue by dispersing carbon quantum dot materials inside the Prussian blue material. Furthermore, the cobalt-doped carbon quantum dot material added in this invention is prepared from tartaric acid, cobalt acetate, and triethylamine, and has a high surface carboxyl group density, enabling it to bind more tightly to PBA and improve the performance and capacity of the Prussian blue material. This invention also introduces 2-hydroxysuccinic acid and nano-nickel-iron alloy materials to modify the surface of PBA; the carboxyl groups of 2-hydroxysuccinic acid interact with the exposed Ni on the PBA surface. 2+ Fe 3+ Complexation optimizes the interfacial compatibility between the material and the electrolyte, reduces interfacial polarization of ion transport, and provides a small number of additional capacitive active sites to further enhance capacity. The nano-nickel-iron alloy material also reacts with 2-hydroxysuccinic acid under acidic conditions, which is equivalent to loading nickel-iron alloy onto nickel-iron Prussian blue, effectively reducing electron transfer resistance and improving the conductivity of the prepared material. Attached Figure Description

[0023] Figure 1 XRD patterns of the materials prepared in Examples 2 and 5;

[0024] Figure 2 The image shows the SEM image of the material obtained in Example 1 at a magnification of 5000x.

[0025] Figure 3 The image shows the SEM image of the material prepared in Example 1 at a magnification of 10,000.

[0026] Figure 4 The image shows the SEM image of the material prepared in Example 1 at a magnification of 20,000.

[0027] Figure 5 The image shows the SEM image of the material obtained in Example 2 at a magnification of 5000x.

[0028] Figure 6 The image shows the SEM image of the material obtained in Example 2 at a magnification of 10,000.

[0029] Figure 7 The image shows the SEM image of the material obtained in Example 2 at a magnification of 20,000.

[0030] Figure 8 The image shows the SEM image of the material obtained in Example 2 at a magnification of 5000x.

[0031] Figure 9 The image shows the SEM image of the material obtained in Example 2 at a magnification of 10,000.

[0032] Figure 10 The image shows the SEM image of the material obtained in Example 2 at a magnification of 20,000.

[0033] Figure 11 After the materials prepared in Examples 1-3 were fabricated into electrodes, the electrode temperature was 10 mV∙s. -1 The CV curve below;

[0034] Figure 12 After the materials prepared in Examples 1-3 were fabricated into electrodes, the scanning density was 1 A∙g -1 The GCD curve below;

[0035] Figure 13 After the materials prepared in Examples 1-3 were fabricated into electrodes, the scanning density was 1 A∙g. -1 The EIS curve below;

[0036] Figure 14 After the materials prepared in Examples 4-6 were fabricated into electrodes, the electrode temperature was 10 mV·s. -1 The CV curve below;

[0037] Figure 15 After the materials prepared in Examples 4-6 were fabricated into electrodes, the scanning density was 1 A∙g -1 The GCD curve below;

[0038] Figure 16 After the materials prepared in Examples 4-6 were fabricated into electrodes, the scanning density was 1 A∙g -1 The EIS curve below;

[0039] Figure 17 The material prepared in Example 2 was used to make an electrode, which was then subjected to a voltage of 100 mV∙s. -1 The following is a diagram of a long-cycle charge-discharge test;

[0040] Figure 18The material prepared in Example 5 was used to fabricate an electrode at 100 mV∙s. -1 The following is a diagram of a long-cycle charge-discharge test;

[0041] Figure 19 The materials prepared in Examples 2 and 5 were used to fabricate electrodes, which were then subjected to a voltage of 100 mV·s. -1 Capacity retention rate at the following levels;

[0042] Figure 20 The CV curves of the supercapacitor in Example 4 at different scan rates;

[0043] Figure 21 The GCD curves of the supercapacitor in Example 4 at different current densities are shown.

[0044] Figure 22 The curves showing the relationship between specific capacitance and current density for the supercapacitor in Application Example 4 at different current densities are shown.

[0045] Figure 23 The curve showing the relationship between energy density and power density of the supercapacitor in Example 4;

[0046] Figure 24 The EIS curve of the supercapacitor in Example 4 is shown.

[0047] Figure 25 For the supercapacitor in Application Example 4 at 100 mV∙s -1 Long-cycle charge-discharge curves;

[0048] Figure 26 For the supercapacitor in Application Example 4 at 100 mV∙s -1 The capacity retention rate. Detailed Implementation

[0049] The present invention will now be described in further detail with reference to the embodiments and accompanying drawings, so that those skilled in the art can implement it based on the description.

[0050] Example 1

[0051] A method for preparing a nickel-iron Prussian blue supercapacitor electrode material includes the following steps:

[0052] Step 1: Dissolve 0.004 mol nickel chloride hexahydrate, 0.001 mol ferric chloride hexahydrate, and 0.003 mol trisodium citrate dihydrate in 50 mL of water to obtain reagent A; dissolve 0.005 mol potassium ferricyanide in 50 mL of water to prepare a solution to obtain reagent B.

[0053] Step 2: Slowly add 50 mL of reagent B to 50 mL of reagent A at room temperature and stir continuously for 2 hours. After stirring, let the mixed solution stand at room temperature for 24 hours, then wash with ethanol and deionized water and centrifuge. Collect the precipitate and dry it in a vacuum drying oven at 60°C for 24 hours to obtain the nickel-iron Prussian blue supercapacitor electrode material, denoted as PBA1.

[0054] Example 2

[0055] The difference between this embodiment and Embodiment 1 is that the amount of trisodium citrate dihydrate used in step one is 0.005 mol, while the other steps are the same as in Embodiment 1, resulting in a nickel-iron Prussian blue supercapacitor electrode material, denoted as PBA2.

[0056] Example 3

[0057] The difference between this embodiment and Embodiment 1 is that the amount of trisodium citrate dihydrate used in step one is 0.007 mol, while the other steps are the same as in Embodiment 1, resulting in a nickel-iron Prussian blue supercapacitor electrode material, denoted as PBA3.

[0058] Example 4

[0059] A method for preparing a nickel-iron Prussian blue supercapacitor electrode material includes the following steps:

[0060] Step 1: Dissolve 0.004 mol nickel chloride hexahydrate, 0.001 mol ferric chloride hexahydrate, and 0.005 mol trisodium citrate dihydrate in 50 mL of water to obtain reagent A. Dissolve 0.005 mol potassium ferricyanide in 50 mL of water to prepare a solution to obtain reagent B.

[0061] Step 2: Slowly add 50 mL of reagent B to 50 mL of reagent A at room temperature and stir continuously for 2 hours. After stirring, let the mixed solution stand at room temperature for 24 hours, then wash with ethanol and deionized water and centrifuge. Collect the precipitate and dry it in a vacuum drying oven at 60°C for 24 hours to obtain the nickel-iron Prussian blue supercapacitor electrode material, denoted as PBA4.

[0062] Example 5

[0063] The difference between this embodiment and embodiment 4 is that the amount of nickel chloride hexahydrate used in step one is 0.005 mol, while the other steps are the same as in embodiment 4, resulting in a nickel-iron Prussian blue supercapacitor electrode material, denoted as PBA5.

[0064] Example 6

[0065] The difference between this embodiment and embodiment 4 is that the amount of nickel chloride hexahydrate used in step one is 0.006 mol, while the other steps are the same as in embodiment 41, resulting in a nickel-iron Prussian blue supercapacitor electrode material, denoted as PBA6.

[0066] Example 7

[0067] A method for preparing a nickel-iron Prussian blue supercapacitor electrode material includes the following steps:

[0068] Step 1: Dissolve 0.005 mol nickel chloride hexahydrate, 0.001 mol ferric chloride hexahydrate, and 0.005 mol trisodium citrate dihydrate in 50 mL of water to obtain reagent A. Then, add 20 mL of cobalt-doped carbon quantum dot solution to reagent A and dissolve 0.005 mol potassium ferricyanide in 50 mL of water to prepare a solution to obtain reagent B. The cobalt-doped carbon quantum dot solution is prepared by adding 0.5 g tartaric acid, 0.01 g cobalt acetate, and 5 mL triethylamine to 50 mL of deionized water, then transferring the solution to a hydrothermal reactor and hydrothermally reacting at 150 °C for 18 h. After the reaction is complete, cool the solution to obtain the cobalt-doped carbon quantum dot solution.

[0069] Step 2: At room temperature, slowly add 50 mL of reagent B to a mixture of 50 mL of reagent A and 20 mL of cobalt-doped carbon quantum dot solution and stir continuously for 2 hours. After stirring, let the mixture stand at room temperature for 24 hours, then wash with ethanol and deionized water and centrifuge to obtain carbon quantum dot-nickel iron Prussian blue material (C-PBA).

[0070] Step 3: Mix 0.5g potassium hydroxide, 10mL N,N-dimethylformamide, 5mL ethylene glycol, 10mL oleylamine, and 5mL heptanol evenly, then add 0.05g nickel acetylacetone and 0.05g iron acetylacetone. Stir overnight at room temperature, then transfer to a hydrothermal reactor and react hydrothermally at 160℃ for 12 hours. Centrifuge and wash to obtain nano-nickel-iron alloy material. Disperse 10mg of nano-nickel-iron alloy material in 10mL of water, then add 1mL of 0.1M dilute hydrochloric acid and sonicate at 20kHz for 2 hours to obtain the modified solution.

[0071] Step 4: Disperse 5g C-PBA in 50mL of deionized water, add 0.5g 2-hydroxysuccinic acid and 10mL of modification solution, stir at 300rpm for 2h at room temperature, let stand for 1h, centrifuge at 8000rpm for 10min, wash the obtained solid and freeze dry at -30℃ for 12h to obtain modified nickel-iron Prussian blue material (G-PBA).

[0072] Example 8

[0073] A method for preparing a nickel-iron Prussian blue supercapacitor electrode material includes the following steps:

[0074] Step 1: Dissolve 0.005 mol nickel chloride hexahydrate, 0.001 mol ferric chloride hexahydrate, and 0.005 mol trisodium citrate dihydrate in 50 mL of water to obtain reagent A; dissolve 0.005 mol potassium ferricyanide in 50 mL of water to prepare a solution to obtain reagent B.

[0075] Step 2: Slowly add 50 mL of reagent B to 50 mL of reagent A at room temperature and stir continuously for 2 hours. After stirring, let the mixed solution stand at room temperature for 24 hours, then wash with ethanol and deionized water and centrifuge to obtain nickel-iron Prussian blue material (PBA).

[0076] Step 3: Mix 0.5g potassium hydroxide, 10mL N,N-dimethylformamide, 5mL ethylene glycol, 10mL oleylamine, and 5mL heptanol evenly, then add 0.05g nickel acetylacetone and 0.05g iron acetylacetone. Stir overnight at room temperature, then transfer to a hydrothermal reactor and react hydrothermally at 160℃ for 12 hours. Centrifuge and wash to obtain nano-nickel-iron alloy material. Disperse 10mg of nano-nickel-iron alloy material in 10mL of water, then add 1mL of 0.1M dilute hydrochloric acid and sonicate at 20kHz for 2 hours to obtain the modified solution.

[0077] Step 4: Disperse 5g PBA in 50mL of deionized water, add 0.5g 2-hydroxysuccinic acid and 10mL of modification solution, stir at 300rpm for 2h at room temperature, let stand for 1h, centrifuge at 8000rpm for 10min, wash the obtained solid and freeze dry at -30℃ for 12h to obtain nickel-iron Prussian blue material (C-free-PBA).

[0078] Example 9

[0079] A method for preparing a nickel-iron Prussian blue supercapacitor electrode material includes the following steps:

[0080] Step 1: Dissolve 0.005 mol nickel chloride hexahydrate, 0.001 mol ferric chloride hexahydrate, and 0.005 mol trisodium citrate dihydrate in 50 mL of water to obtain reagent A. Then, add 20 mL of cobalt-doped carbon quantum dot solution to reagent A and dissolve 0.005 mol potassium ferricyanide in 50 mL of water to prepare a solution to obtain reagent B. The cobalt-doped carbon quantum dot solution is prepared by adding 0.5 g tartaric acid, 0.01 g cobalt nitrate, and 5 mL triethylamine to 50 mL of deionized water, then transferring the solution to a hydrothermal reactor and hydrothermally reacting at 150 °C for 18 h. After the reaction is complete, cool the solution to obtain the cobalt-doped carbon quantum dot solution.

[0081] Step 2: At room temperature, slowly add 50 mL of reagent B to a mixture of 50 mL of reagent A and 20 mL of carbon quantum dot solution and stir continuously for 2 hours. After stirring, let the mixture stand at room temperature for 24 hours, then wash with ethanol and deionized water and centrifuge to obtain carbon quantum dot-nickel iron Prussian blue material (C-PBA).

[0082] Step 3: Mix 0.5g potassium hydroxide, 10mL N,N-dimethylformamide, 5mL ethylene glycol, 10mL oleylamine, and 5mL heptanol evenly, then add 0.05g nickel acetylacetone and 0.05g iron acetylacetone. Stir overnight at room temperature, then transfer to a hydrothermal reactor and react hydrothermally at 160℃ for 12 hours. Centrifuge and wash to obtain nano-nickel-iron alloy material. Disperse 10mg of nano-nickel-iron alloy material in 10mL of water, then add 1mL of 0.1M dilute hydrochloric acid and sonicate at 20kHz for 2 hours to obtain the modified solution.

[0083] Step 4: Disperse 5g C-PBA into 50mL deionized water, add 10mL of modification solution, stir at 300rpm for 2h at room temperature, let stand for 1h, centrifuge at 8000rpm for 10min, wash the obtained solid and freeze dry at -30℃ for 12h to obtain nickel-iron Prussian blue material (N-PBA).

[0084] Example 10

[0085] A method for preparing a nickel-iron Prussian blue supercapacitor electrode material includes the following steps:

[0086] Step 1: Dissolve 0.005 mol nickel chloride hexahydrate, 0.001 mol ferric chloride hexahydrate, and 0.005 mol trisodium citrate dihydrate in 50 mL of water to obtain reagent A. Then, add 20 mL of cobalt-doped carbon quantum dot solution to reagent A and dissolve 0.005 mol potassium ferricyanide in 50 mL of water to prepare a solution to obtain reagent B. The cobalt-doped carbon quantum dot solution is prepared by adding 0.5 g tartaric acid, 0.01 g cobalt acetate, and 5 mL triethylamine to 50 mL of deionized water, then transferring the solution to a hydrothermal reactor and hydrothermally reacting at 150 °C for 18 h. After the reaction is complete, cool the solution to obtain the cobalt-doped carbon quantum dot solution.

[0087] Step 2: At room temperature, slowly add 50 mL of reagent B to a mixture of 50 mL of reagent A and 20 mL of cobalt-doped carbon quantum dot solution and stir continuously for 2 hours. After stirring, let the mixture stand at room temperature for 24 hours, then wash with ethanol and deionized water and centrifuge to obtain carbon quantum dot-nickel iron Prussian blue material (C-PBA).

[0088] Step 3: Disperse 5g C-PBA into 50mL of deionized water, add 0.5g 2-hydroxysuccinic acid, stir at 300rpm for 2h at room temperature, let stand for 1h, centrifuge at 8000rpm for 10min, wash the obtained solid and freeze dry at -30℃ for 12h to obtain nickel-iron Prussian blue material (CA-PBA).

[0089] Example 11

[0090] A method for preparing a nickel-iron Prussian blue supercapacitor electrode material includes the following steps:

[0091] Step 1: Dissolve 0.005 mol nickel chloride hexahydrate, 0.001 mol ferric chloride hexahydrate, and 0.005 mol trisodium citrate dihydrate in 50 mL of water to obtain reagent A. Then, add 20 mL of cobalt-doped carbon quantum dot solution to reagent A and dissolve 0.005 mol potassium ferricyanide in 50 mL of water to prepare a solution to obtain reagent B. The cobalt-doped carbon quantum dot solution is prepared by adding 0.5 g tartaric acid, 0.01 g cobalt nitrate, and 5 mL triethylamine to 50 mL of deionized water, then transferring the solution to a hydrothermal reactor and hydrothermally reacting at 150 °C for 18 h. After the reaction is complete, cool the solution to obtain the cobalt-doped carbon quantum dot solution.

[0092] Step 2: At room temperature, slowly add 50 mL of reagent B to a mixture of 50 mL of reagent A and 20 mL of carbon quantum dot solution and stir continuously for 2 hours. After stirring, let the mixture stand at room temperature for 24 hours, then wash with ethanol and deionized water and centrifuge to obtain carbon quantum dot-nickel iron Prussian blue material (C-PBA).

[0093] Figure 1 The XRD patterns of the materials prepared in Examples 2 and 5 are shown below. Figure 1 As shown, the strong diffraction peaks at 2θ = 17.3°, 24.6°, 35.1°, 39.4°, 43.3°, 50.4°, 53.7°, and 56.9° correspond to (200), (220), (400), (420), (422), (440), (600), and (620) of FeNiHCF. The (200) peak, being the strongest peak, is a typical characteristic of Prussian blue analogues, proving that the main diffraction peaks of the synthesized FeNiHCF powder are in good agreement with those of Prussian blue material (JCPDS No. 86-0501). This demonstrates that the sample has not undergone severe lattice distortion or phase transformation. Furthermore, the sharp and narrow half-width of the strong diffraction peaks in the figure suggest that the sample may have good crystallinity and a large grain size.

[0094] Figures 2-4 The material prepared in Example 1 was examined at different magnifications ( Figure 2 5000 times Figure 2 10,000 times Figure 2 SEM image at 20000x magnification, such as Figures 2-4 As shown, large particles can be observed in PBA1, indicating that the low concentration of trisodium citrate has insufficient complexing ability, and crystal growth dominates, resulting in large particles. However, excessively large particles will lead to low specific surface area, insufficient active sites, and limited capacity. The dense structure will hinder ion transport and may lead to poor rate performance. Figures 5-7 The material prepared in Example 2 was examined at different magnifications ( Figure 5 5000 times Figure 6 10,000 times Figure 7 SEM image at 20000x magnification, such as Figures 5-7 As shown, in PBA2, the material exhibits moderate particle size and good distribution uniformity; among them, the smaller particle size effectively shortens the ion diffusion path, while the uniform particle distribution significantly suppresses agglomeration, which may improve the utilization rate of active sites of the electrode material. Figures 8-10 The material prepared in Example 1 was examined at different magnifications ( Figure 8 5000 times Figure 9 10,000 times Figure 10 SEM image at 20000x magnification, such as Figures 8-10 As shown, severe particle agglomeration was observed in PBA3, forming irregular masses. This may be due to the high concentration of trisodium citrate leading to excessive nucleation sites, excessively small particles, and a decrease in the actual effective surface area. Furthermore, agglomeration hinders ion transport pathways, resulting in decreased structural stability. Therefore, PBA2 may be able to effectively control the material morphology, optimize its ion transport kinetics, and ultimately exhibit superior electrochemical performance.

[0095] The materials prepared in Examples 1-6 and Examples 7-11 were mixed with acetylene black and polyvinylidene fluoride in a mass ratio of 8:1:1. The mixture was then placed in a mortar and thoroughly ground and mixed. Approximately 3-4 drops of N-methylpyrrolidone as a solvent were added, and the mixture was stirred to obtain an electrode paste. The electrode paste was then evenly spread onto a 1 cm² area. 2 Electrode paste was coated onto nickel foam and placed in a vacuum oven to dry under vacuum at 60°C for 24 hours to obtain the working electrode. The supercapacitive characteristics of the electrode were detected using a three-electrode method, with Ag / AgCl as the reference electrode, a platinum sheet electrode as the counter electrode, and a 0.5 M Na₂SO₄ solution as the electrolyte solution.

[0096] Application Example 1

[0097] Cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) were performed on the working electrodes made from the materials obtained in Examples 1-3 using a three-electrode system. Figure 11 After the materials prepared in Examples 1-3 were fabricated into electrodes, the voltage was 10 mV·s. -1 The CV curve below, from Figure 11 As can be seen, in the CV test, the scan rate was 10 mV∙s -1 When the voltage range is 0~1V, the CV curves of PBA1, PBA2 and PBA3 samples all show obvious redox peaks, indicating that the material has typical pseudocapacitive energy storage characteristics. By comparing the integral area, it can be found that the integral area of ​​PBA2 is significantly higher than that of other samples, and the energy storage performance is better. Figure 12 After the materials prepared in Examples 1-3 were fabricated into electrodes, the scanning density was 1 A∙g. -1 The GCD curve below, such as Figure 12 As shown, the GCD test results indicate that the current density is 1 A∙g -1 At that time, the sample curves all exhibited an approximate triangular shape, indicating that the pseudocapacitive mechanism was dominant. The specific capacitance values ​​corresponding to the three samples were 34.38 F∙g. -1 , 94.38 F∙g -1 and 30.00 F∙g -1 Therefore, it can be seen that PBA2 performed the best among the selected samples, with a specific capacitance that was 2.7-3.1 times that of the other samples. Figure 13 After the materials prepared in Examples 1-3 were fabricated into electrodes, the scanning density was 1 A∙g. -1 In the EIS curves below, the diameter of the semicircle in the high-frequency region is positively correlated with the charge transfer resistance, while the slope of the straight line in the low-frequency region represents the kinetics of ion diffusion. Figure 13 It can be seen that the slope of the straight line in the low-frequency region of the PBA2 sample is the largest, indicating that the PBA2 sample has the best ion transport performance and has a significant advantage over other samples, which verifies the charge transfer capability of the PBA2 material in the electrochemical reaction process.

[0098] The above tests show that PBA2 exhibits the best electrochemical performance, with superior energy storage capacity, larger specific capacitance, and faster ion diffusion rate. In comparison, PBA1 and PBA3 have relatively poor performance. This indicates that the amount of trisodium citrate added can significantly alter the energy storage of the material. By adjusting the amount of trisodium citrate added, the microstructure of FeNiHCF can be controlled, thereby affecting its electrochemical performance.

[0099] Application Example 2

[0100] The working electrodes made from the materials obtained in Examples 4-6 and 7-11 were subjected to cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) tests using a three-electrode system. Figure 14 After the materials prepared in Examples 4-6 were fabricated into electrodes, the electrode temperature was 10 mV·s. -1 The CV curves below, as shown in Figure 14, all exhibit a pair of clear redox peaks, indicating that their energy storage mechanism is dominated by surface redox pseudocapacitance. Among them, PBA5 has the largest CV curve integral area, indicating that it has a higher active site density and reversibility of reaction, suggesting that its specific capacitance performance is better than the other ratios. Figure 15 After the materials prepared in Examples 4-6 were fabricated into electrodes, the scanning density was 1 A∙g -1 The GCD curve below, Figure 15 This demonstrates a classic pseudocapacitive process, with specific capacitances of 83.75 F∙g for PBA4, PBA5, and PBA6. -1 140.25 F∙g -1 83.63 F∙g -1 The specific capacitance of PBA5 is 1.7 times that of PBA4 and PBA6, indicating that it has higher energy storage efficiency and better pseudocapacitive characteristics at the same current density. Figure 16 After the materials prepared in Examples 4-6 were fabricated into electrodes, the scanning density was 1 A∙g -1 The EIS curve below, from Figure 16 It can be seen that PBA6 and PBA4 have similar slopes in the low-frequency region, and PBA4 is better than PBA5, indicating that the two perform better in terms of ion diffusion ability. In contrast, although PBA5 is slightly inferior in the low-frequency region slope, its high-frequency region is still better than PBA6 and PBA4, indicating that its charge transfer ability remains at a high level.

[0101] Based on the CV and GCD test results, although PBA6 and PBA4 showed outstanding performance in ion diffusion, PBA5 exhibited the highest specific capacitance (140.25 F∙g). -1 ), is PBA4 (83.75 F∙g -1 ) and PBA6 (83.63 F∙g -1 The efficiency of PBA5 is 1.7 times that of other nickel-iron compounds. This significant difference suggests that PBA5 has unique advantages in electrochemical energy storage, possibly due to its optimized nickel-iron ratio resulting in higher utilization of active sites and better reaction reversibility.

[0102] Example 7 improves the electronic conductivity within and between particles of the Prussian blue-like compound by dispersing cobalt-doped carbon quantum dots inside the Prussian blue material; it also introduces 2-hydroxysuccinic acid and nickel-iron nanowires to modify the surface of PBA, with the carboxyl groups of 2-hydroxysuccinic acid reacting with the exposed Ni nanowires on the PBA surface. 2+ Fe 3+ Complexation optimizes the interfacial compatibility between the material and the electrolyte, reduces interfacial polarization during ion transport, and provides a small number of additional capacitive active sites. The nano-nickel-iron alloy material also reacts with 2-hydroxysuccinic acid under acidic conditions, essentially loading nickel-iron alloy onto nickel-iron Prussian blue. This effectively reduces electron transfer resistance, improves the conductivity of the prepared material, and further enhances the capacity, resulting in a specific capacitance of 185.17 F∙g for G-PBA. -1 Example 8: No carbon quantum dot material was introduced into the PBA; only the surface was modified with a modifying liquid and 2-hydroxysuccinic acid. The specific capacitance of the resulting C-free-PBA was 163.25 F∙g. -1 Compared to Example 7, the specific capacitance decreased; in Example 9, carbon quantum dots and nano-nickel-iron alloy materials were introduced into Prussian blue material. Because 2-hydroxysuccinic acid was not used, the nano-nickel-iron alloy material could not react, and the specific capacitance of the resulting N-PBA was only 152.45 F∙g. -1 In Example 10, after incorporating carbon quantum dots, only 2-hydroxysuccinic acid was used for surface modification, resulting in CA-PBA with a specific capacitance of 176.60 F∙g. -1 This is similar to Example 7; Example 11 only introduced carbon quantum dots into the Prussian blue material, and the resulting C-PBA had a capacity of 148.65 F∙g. -1 The material showed the lowest increase in specific capacitance.

[0103] Application Example 3

[0104] The working electrodes made from the materials obtained in Examples 2 and 5 were tested at 100 mV / s. -1 Under the scanning speed, 2000 long-term cycle tests were carried out. Figure 17 The material prepared in Example 2 was used to make an electrode, which was then subjected to a voltage of 100 mV∙s. -1 The following is a long-cycle charge-discharge test diagram. Figure 18 The material prepared in Example 5 was used to fabricate an electrode at 100 mV∙s. -1 The following is a long-cycle charge-discharge test diagram. Figure 19 The materials prepared in Examples 2 and 5 were used to fabricate electrodes, which were then subjected to a voltage of 100 mV·s. -1 The capacity retention rate below, from Figures 17-19As shown in Table 1, at the beginning of cycling, the active material gradually comes into complete contact with the electrolyte, and the integral area slowly increases. As the number of cycles increases, the integral area decreases. The capacity of the two groups of materials decreases from 83.80% and 95.54% of the initial capacity to 71.55% and 84.35%, respectively. After 2000 cycles, the capacity retention of PBA5 is much better than that of PBA2, and the total decay is also smaller for PBA5. This indicates that the improved nickel-iron ratio does indeed enhance the structural stability of the material. This result is consistent with the conclusions obtained from the previous electrochemical tests, and it further confirms that the improved nickel-iron ratio is crucial for improving the overall performance of FeNiHCF materials. Excellent cycling stability will allow it to have a longer service life in practical energy storage applications.

[0105] Table 1

[0106] parameter <![CDATA[Example 2 (PBA2)]]> <![CDATA[Example 5 (PBA5)]]> Capacity retention after 100 cycles 83.80% 95.54% Capacity retention after 2000 cycles 71.55% 84.35% Total attenuation 12.55% 11.19%

[0107] Application Example 4

[0108] A supercapacitor is provided, wherein the positive electrode material of the supercapacitor is FeNiHCF (PBA5) prepared in Example 5, and the negative electrode material of the supercapacitor is AC (activated carbon YP50). Cyclic voltammetry (CV), constant current charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS) are performed on the supercapacitor. Figure 20 To illustrate the CV curves of the supercapacitor in Example 4 at different scan rates; from Figure 20 FeNiHCF can be clearly seen in the AC range of 10~100 mV∙s. -1 Redox peaks appeared in the scanning rate range, indicating that the energy storage of FeNiHCF mainly relies on pseudocapacitance, while AC achieves rapid charge transfer through double-layer capacitance. The two complement each other, enabling the operating voltage range to reach 1.4 V. Figure 21 To illustrate the GCD curves of the supercapacitor in Example 4 at different current densities, the specific capacitance of FeNiHCF / / AC at the five current densities is 24.43 F∙g. -1 13.71 F∙g -1 11.36 F∙g -1 7.86 F∙g -1 2.86 F∙g -1 . Figure 22 To apply the capacitance-current density ratio curves of the supercapacitor in Example 4 at different current densities, from... Figure 22 As can be seen from this, as the current density increases from 1 A∙g -1 Increased to 10A∙g -1 The specific capacitance is 24.43 F∙g -1 It dropped sharply to 2.86 F∙g-1 (The retention rate is only 11.7%), mainly because the microporous structure of FeNiHCF hinders the rapid migration of ions under high current. Figure 23 To apply the energy density vs. power density curve of the supercapacitor in Example 4, from... Figure 23 It can be seen from this that at 700 W∙kg -1 1400W∙kg -1 2100W∙kg -1 3500W∙kg -1 7000W∙kg -1 At a power density of , the energy density is 6.65 Wh∙kg⁻¹. -1 3.77Wh∙kg -1 3.10Wh∙kg -1 2.14Wh∙kg -1 0.78Wh∙kg -1 When the power density is 700 Wh·kg -1 Increased to 7000 W∙kg -1 At that time, the energy density also increased from 6.65 Wh∙kg⁻¹ -1 Reduced to 0.78Wh∙kg -1 This indicates that the device is suitable for low-power, short-term high-energy demand scenarios, but its efficiency decreases significantly at high power. Figure 24 To apply the EIS curve of the supercapacitor in Example 4, from Figure 24 As can be seen, the slope of the straight line in the low-frequency region is relatively large, indicating that FeNiHCF / / AC has good ion transport performance. Figure 25 For the supercapacitor in Application Example 4 at 100 mV∙s -1 The long-cycle charge-discharge curves are shown below. Figure 26 For the supercapacitor in Application Example 4 at 100 mV∙s -1 The capacity retention rate below, from Figures 25-26 It can be seen that FeNiHCF / / AC at 100 mV∙s -1 At different scan rates, the capacity retention increased from 88.55% to 135.13% with increasing cycle count. The reason for the 135.13% capacity retention after 2000 cycles may be due to: first, the electrode activation effect, where the electrolyte gradually penetrates the material pores during cycling, activating more hidden active sites; second, structural self-repair, where the Prussian blue framework of FeNiHCF undergoes slight reconstruction during cycling, improving reaction reversibility. The increased area under the CV curve after cycling corroborates the improved utilization of active sites, but the risk of structural collapse during long-term cycling should be noted.

[0109] In summary, this invention achieves the regulation of FeNiHCF material properties by adjusting the amount of trisodium citrate and the nickel-iron ratio. Trisodium citrate improves the ion transport pathway by controlling the pore structure, while the nickel-iron ratio (5:1) enhances the reversibility of redox reactions by forming an ordered crystal framework and active site distribution. The combined effect of these two factors results in a high specific capacitance (140.25 F·g). -1 The desired effect is to achieve both good cyclic stability (84.35% retention after 2000 cycles). While modifying only trisodium citrate improves the pore structure, the lack of improvement in the nickel-iron ratio leads to uneven distribution of active sites, causing lattice distortion and metal dissolution during cycling, thus limiting stability improvement (71.55% retention). Optimizing the nickel-iron ratio strengthens the crystal structure, harmonizes the pore network, and enhances Fe... 3+ / Ni 2+ The synergistic effect of these parameters improves the stability of the material, which demonstrates the necessity of multi-parameter collaborative design for the integrated regulation of "structure-interface-dynamics" and provides an improved paradigm that balances performance and stability for the development of energy storage materials.

[0110] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A method for preparing a nickel-iron Prussian blue supercapacitor electrode material, characterized in that, Includes the following steps: Step 1: Dissolve nickel chloride hexahydrate, ferric chloride hexahydrate, and trisodium citrate dihydrate in water to obtain reagent A; dissolve potassium ferricyanide in water to prepare a solution to obtain reagent B. Step 2: Slowly add reagent B to reagent A at room temperature while stirring continuously. After stirring, let the mixed solution stand at room temperature, then wash with ethanol and deionized water and centrifuge. Collect the precipitate, vacuum dry, and obtain nickel-iron Prussian blue material PBA. The nickel-iron Prussian blue material obtained in step two undergoes post-processing as follows: S21. Disperse the nano-nickel-iron alloy material in water, add dilute hydrochloric acid, and sonicate for a period of time to obtain the modified solution; S22. Disperse the nickel-iron Prussian blue material in deionized water, add 2-hydroxysuccinic acid and the modification solution, stir and react at room temperature, let stand after stirring, then centrifuge, wash the obtained solid and freeze dry to obtain the modified nickel-iron Prussian blue material.

2. The method for preparing the nickel-iron Prussian blue supercapacitor electrode material as described in claim 1, characterized in that, In step one, the ratio of nickel chloride hexahydrate, ferric chloride hexahydrate, trisodium citrate dihydrate to water is 0.004~0.006 mol:0.001 mol:0.003~0.007 mol:50mL, and the ratio of potassium ferricyanide to water is 0.005 mol:50mL.

3. The method for preparing the nickel-iron Prussian blue supercapacitor electrode material as described in claim 1, characterized in that, In step two, the volume ratio of reagent B to reagent A is 1:1, stirring is performed for 2-4 hours, the mixture is allowed to stand for 24-36 hours, and the vacuum drying temperature is 60-80℃ for 24-36 hours.

4. The method for preparing the nickel-iron Prussian blue supercapacitor electrode material as described in claim 1, characterized in that, In step two, the washing process involves washing with deionized water and ethanol 3 to 5 times each.

5. The method for preparing the nickel-iron Prussian blue supercapacitor electrode material as described in claim 1, characterized in that, In step one, a cobalt-doped carbon quantum dot solution is added to reagent A. The cobalt-doped carbon quantum dot solution is prepared by adding tartaric acid, cobalt acetate and triethylamine to deionized water, then transferring it to a hydrothermal reactor for hydrothermal reaction, and cooling after the reaction is completed to obtain the cobalt-doped carbon quantum dot solution.

6. The method for preparing the nickel-iron Prussian blue supercapacitor electrode material as described in claim 5, characterized in that, In step one, the volume ratio of cobalt-doped carbon quantum dot solution to reagent A is 1:0.4~0.6, the ratio of tartaric acid, cobalt acetate, triethylamine and deionized water is 0.5~1g:0.01~0.02g:5~10mL:50mL, the hydrothermal reaction temperature is 150~200℃, and the reaction time is 18~24h.

7. The method for preparing the nickel-iron Prussian blue supercapacitor electrode material as described in claim 1, characterized in that, In step S21, the ratio of nano-nickel-iron alloy material, water, and dilute hydrochloric acid is 10-15 mg: 10-20 mL: 1-2 mL, the concentration of dilute hydrochloric acid is 0.1-0.5 M, and the reaction is carried out under ultrasonication at 20-40 kHz for 1-2 hours. In S22, the ratio of nickel-iron Prussian blue material, deionized water, 2-hydroxysuccinic acid, and modification solution is 2~5g:50mL:0.2~0.5g:5~10mL. The stirring speed is 300~400rpm, stirring time is 1~2h, standing time is 0.5~1h, centrifugation speed is 6000~8000rpm, centrifugation time is 10~15min, freeze-drying temperature is -30~-40℃, freeze-drying time is 12~24h.

8. A nickel-iron Prussian blue supercapacitor electrode material, characterized in that, It is prepared by the method for preparing nickel-iron Prussian blue supercapacitor electrode material according to any one of claims 1-7.

9. A supercapacitor, characterized in that, The positive electrode material of the supercapacitor is the nickel-iron Prussian blue supercapacitor electrode material as described in claim 8, and the negative electrode material of the supercapacitor is activated carbon.

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