Composite metal oxide electrode material, preparation method thereof and supercapacitor

Abstract

This invention discloses a composite metal oxide electrode material, its preparation method, and a supercapacitor, belonging to the field of capacitor technology. The preparation method includes: dissolving cobalt chloride and trisodium citrate in deionized water to prepare solution A; dissolving potassium ferricyanide in deionized water to prepare solution B; adding solution B dropwise to solution A and allowing the reaction to proceed to obtain a CoHCF precursor; calcining the CoHCF precursor to obtain the composite metal oxide electrode material. This invention utilizes a Prussian blue analogue-derived composite metal oxide to effectively enhance the pseudocapacitive properties and cycle stability of the material. Trisodium citrate is used as a complexing agent to control the metal ion release rate, enabling cobalt and iron ions to form a more stable complex. Furthermore, this invention optimizes the electrochemical performance of the electrode material by adjusting the cobalt-iron ratio, the amount of trisodium citrate, additives, and calcination, thereby improving the specific capacitance, energy density, and cycle life of the supercapacitor.

Description

Technical Field

[0001] This invention belongs to the field of capacitor technology, and more specifically, this invention relates to a composite metal oxide electrode material, its preparation method, and a supercapacitor. Background Technology

[0002] Supercapacitors are a new type of high-quality energy storage device with huge market potential. However, they currently face a series of challenges, such as poor cycle stability, low energy density, and significant self-discharge. Since the choice of electrode materials plays a decisive role in the electrochemical characteristics of supercapacitors, it has become the key to solving these problems.

[0003] Transition metal oxides (PBAs) are important pseudocapacitive electrode materials, but their main morphological defects stem from the structural heterogeneity that is difficult to avoid during traditional synthesis. High-temperature calcination easily leads to excessive grain growth and pore structure collapse, resulting in a significant reduction in specific surface area and obstruction of ion diffusion pathways. Simultaneously, the spontaneous aggregation of nanoparticles due to their high surface energy reduces the exposure of active sites, weakening interfacial charge transport efficiency. Prussian blue analogues (PBAs), as metal-organic framework materials, possess tunable three-dimensional open frameworks, low-cost preparation, and diverse metal combinations (such as Fe, Co, Ni, Mn, Zn, Cu, and Mg), making them ideal precursors for preparing high-performance transition metals. Through calcination, PBAs can be transformed into transition metal oxides (TMOs) that inherit their porous structures, such as Fe₂O₃, Co₃O₄, and NiO. Due to their high theoretical specific capacity, abundant redox active sites, and environmental friendliness, they are considered highly promising electrode materials.

[0004] The study of the structure-performance relationship between the electronic configuration, lattice arrangement, and micro-coordination environment of TMOs and their energy storage properties has become an important scientific proposition for the development of novel energy storage systems. Based on the characteristic differences of different charge storage mechanisms, it is necessary to optimize the performance of electrode materials through multi-dimensional regulation strategies, and then design advanced electrode material cathode systems with high specific capacity and long cycle stability, which constitutes the key breakthrough in this field. Summary of the Invention

[0005] 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.

[0006] To achieve these objectives and other advantages of the present invention, a method for preparing a composite metal oxide electrode material is provided, comprising the following steps:

[0007] Step 1: Dissolve cobalt chloride and trisodium citrate in deionized water to prepare solution A; dissolve potassium ferricyanide in deionized water to prepare solution B;

[0008] Step 2: Add solution B dropwise to solution A and stir continuously to obtain a mixture. Let the mixture stand at room temperature, centrifuge to collect the precipitate, wash and vacuum dry to obtain the CoHCF precursor.

[0009] Step 3: The CoHCF precursor is calcined to obtain the composite metal oxide electrode material.

[0010] Preferably, in step one, the molar ratio of cobalt chloride to trisodium citrate in solution A is 2~8:9~11.

[0011] Preferably, in step one, the molar volume ratio of cobalt chloride to deionized water in solution A is 2 mmol to 8 mmol: 100 mL to 300 mL.

[0012] Preferably, in step one, the molar volume ratio of potassium ferricyanide to deionized water in solution B is 1 mmol: 50 mL to 150 mL.

[0013] Preferably, in step two, the molar ratio of cobalt chloride in solution A to potassium ferricyanide in solution B is 1 to 4:1.

[0014] Preferably, in step two, the stirring speed is 200 r / min to 600 r / min; the dripping rate is 100 mL / h to 300 mL / h; and the mixture is allowed to stand at room temperature for 12 h to 36 h.

[0015] Preferably, in step two, the washing process involves alternating between anhydrous ethanol and deionized water 3 to 5 times; the vacuum drying temperature is 60°C to 100°C, and the time is 8 to 16 hours.

[0016] Preferably, in step three, the specific method of calcination is as follows: the temperature is increased to 400℃~600℃ at a rate of 1℃ / min~3℃ / min and then held for 1h~3h.

[0017] Preferably, step three is replaced with:

[0018] (1) Mix the CoHCF precursor and the additive, the amount of the additive is 1%~5% of the mass of the CoHCF precursor, and heat it to 150℃~250℃ at a rate of 1℃ / min~3℃ / min under a nitrogen atmosphere and hold for 0.5h~2h to obtain the pre-sintered product.

[0019] (2) Mix the pre-sintered product and the additive. The amount of the additive is 1% to 5% of the mass of the CoHCF precursor in step (1). Heat the mixture to 400℃ to 600℃ at a rate of 1℃ / min to 3℃ / min and hold it for 1h to 3h to obtain the composite metal oxide electrode material.

[0020] Preferably, the method for preparing the additive includes the following steps:

[0021] S31. Dissolve MnCl2 and Na3C6H5O7·2H2O in deionized water to prepare solution C; dissolve K3Fe(CN)6 in deionized water to prepare solution D; uniformly disperse activated carbon and polyethylene glycol 600 in deionized water to prepare solution E.

[0022] S32. Add solutions C and D dropwise into solution E simultaneously while stirring continuously to obtain a mixture. Let the mixture stand at room temperature, centrifuge to collect the precipitate, wash and vacuum dry to obtain the additive.

[0023] Preferably, in S31, the molar volume ratio of MnCl2, Na3C6H5O7·2H2O and deionized water in solution C is 2mmol~6mmol:4mmol~8mmol:30mL~80mL.

[0024] Preferably, in S31, the molar volume ratio of K3Fe(CN)6 to deionized water in solution D is 1mmol~3mmol:30mL~80mL.

[0025] Preferably, in step S31, the mass-to-volume ratio of activated carbon, polyethylene glycol 600, and deionized water in solution E is 1g:0.2g~1g:50mL~150mL.

[0026] Preferably, in S32, the molar mass ratio of MnCl2 in solution C, K3Fe(CN)6 in solution D, and activated carbon in solution E is 2mmol~6mmol:1mmol~3mmol:0.5g~2g.

[0027] Preferably, in step S32, the stirring speed is 200 r / min to 600 r / min; the dropping speed is 30 mL / h to 100 mL / h; the standing time is 12 h to 36 h at room temperature; the washing is performed by alternating washing with anhydrous ethanol and deionized water 3 to 5 times; and the vacuum drying temperature is 60℃ to 100℃ for 8 h to 16 h.

[0028] A composite metal oxide electrode material is prepared by the method described above.

[0029] A supercapacitor, wherein the positive electrode material of the supercapacitor is the aforementioned composite metal oxide electrode material.

[0030] The present invention has at least the following beneficial effects:

[0031] This invention uses Prussian blue analogues as precursors, which are calcined to transform them into composite metal oxides that inherit their porous structure, exhibiting excellent electrochemical performance. Both Fe2O3 and Co3O4 possess pseudocapacitive properties and can store charge through Faraday redox reactions. When combined, they generate more redox active sites due to a synergistic effect, improving pseudocapacitive performance and thus enhancing the energy storage capacity and cycle stability of the supercapacitor. Trisodium citrate, as a complexing agent, can control the release rate of metal ions, enabling cobalt and iron ions to form more stable complexes.

[0032] This invention employs a co-precipitation method to prepare the precursor CoHCF, which is then calcined at high temperature to obtain a composite metal oxide electrode material. The electrochemical performance was analyzed in depth using cyclic voltammetry, constant current charge-discharge testing, and AC impedance spectroscopy. It was found that when potassium ferricyanide was used as the ligand, the amount of trisodium citrate as the complexing agent was 10 mmol, and the cobalt-iron molar ratio was 3:1, the Fe2O3 / Co3O4 exhibited the best electrochemical performance, achieving a specific capacitance of 92 F / g at 1 A / g, which is 1.80 times that of Co3O4 alone. The constructed asymmetric supercapacitor was tested and found to have an energy density of 12.23 Wh / kg at a power density of 775 W / kg, and a capacitance retention rate of 108.45% after 2000 long-cycle tests (at 100 mV / s). This invention provides a feasible approach for adjusting and optimizing Prussian blue-derived transition metal oxide electrode materials for use in supercapacitors.

[0033] This invention utilizes manganese salts, activated carbon, and polyethylene glycol to prepare additives, which are then subjected to segmented calcination together with a CoHCF precursor. This process not only modulates lattice defects in the electrode material, improving its structural stability, but also increases active sites, enhances charge transport efficiency, and reduces internal resistance, thereby further optimizing the overall performance of the electrode material. The segmented calcination process—pre-sintering at 150℃~250℃ followed by sintering at 400℃~600℃—effectively removes impurities such as water of crystallization from the material, preventing the calcination process from affecting particle size distribution and morphology, thus impacting electrochemical performance. During calcination, the additives regulate crystal morphology, inhibit CoHCF agglomeration, and prevent excessive grain growth and pore structure collapse, resulting in a more uniform morphology and more stable structure in the final product. The stepwise addition allows the additives to be uniformly incorporated into the material lattice and surface. Through the synergistic effect of bulk and surface doping, the conductivity and energy storage properties of the electrode material are improved, further enhancing the specific capacitance and cycle stability of the composite metal oxide electrode material.

[0034] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0035] Figure 1 The XRD pattern of the CoHCF precursor in Example 1;

[0036] Figure 2 XRD patterns of Fe2O3 / Co3O4 prepared in Example 1 and Co3O4 prepared in Comparative Example 1;

[0037] Figure 3 SEM image of Co3O4 prepared in Comparative Example 1;

[0038] Figure 4 SEM image of Fe2O3 / Co3O4 prepared in Example 5;

[0039] Figure 5 SEM image of Fe2O3 / Co3O4 prepared in Example 1;

[0040] Figure 6 CV curves of Fe2O3 / Co3O4 prepared in Example 1 and Co3O4 prepared in Comparative Example 1 at a scan rate of 30 mV / s;

[0041] Figure 7 GCD curves of Fe2O3 / Co3O4 prepared in Example 1 and Co3O4 prepared in Comparative Example 1 at a current density of 1 A / g;

[0042] Figure 8 EIS curves of Fe2O3 / Co3O4 prepared in Example 1 and Co3O4 prepared in Comparative Example 1;

[0043] Figure 9 The capacity retention diagrams for Fe2O3 / Co3O4 prepared in Example 1 and Co3O4 prepared in Comparative Example 1 after 2000 cycles at a scan rate of 100 mV / s are shown.

[0044] Figure 10 The GCD curves of Fe2O3 / Co3O4 prepared in Examples 1 to 3 at a current density of 1 A / g are shown.

[0045] Figure 11 The GCD curves of Fe2O3 / Co3O4 prepared in Examples 1, 4 to 6 are shown at a current density of 1 A / g.

[0046] Figure 12 The CV curves of Fe2O3 / Co3O4 prepared in Example 1 at different scan rates;

[0047] Figure 13 The graph shows the relationship between the specific capacitance and current density of the Fe2O3 / Co3O4 prepared in Example 1.

[0048] Figure 14 The capacity retention of the composite metal oxide electrode materials prepared in Examples 1 and 7 after 2000 cycles at a scan rate of 100 mV / s is shown in the graph.

[0049] Figure 15 The CV curves of Fe2O3 / Co3O4 and AC prepared in Example 1 at a scan rate of 30 mV / s are shown.

[0050] Figure 16 The CV curves of the asymmetric supercapacitor Fe2O3 / Co3O4 / / AC at different scan rates;

[0051] Figure 17 GCD curves of the asymmetric supercapacitor Fe2O3 / Co3O4 / / AC at different current densities;

[0052] Figure 18 EIS curve of Fe2O3 / Co3O4 / / AC asymmetric supercapacitor;

[0053] Figure 19 The capacitance retention of the asymmetric supercapacitor Fe2O3 / Co3O4 / / AC after 2000 cycles at a scan rate of 100 mV / s is shown in the figure.

[0054] Figure 20 The capacitance retention of the asymmetric supercapacitor Fe2O3 / Co3O4-MnC / / AC after 2000 cycles at a scan rate of 100 mV / s is shown in the figure. Detailed Implementation

[0055] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0056] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0057] Example 1

[0058] A method for preparing a composite metal oxide electrode material includes the following steps:

[0059] Step 1: Weigh 6 mmol CoCl2·6H2O and 10 mmol Na3C6H5O7·2H2O and dissolve them in 200 mL of deionized water to prepare solution A; weigh 2 mmol K3Fe(CN)6 and dissolve it in 200 mL of deionized water to prepare solution B.

[0060] Step 2: Add solution B dropwise to solution A and turn on the magnetic stirrer to stir the mixture at 400 r / min for 1 h. After the addition is complete, let the mixture stand at room temperature for 24 h to fully react. After the reaction is complete, centrifuge to collect the precipitate. Wash it with anhydrous ethanol and then wash it with deionized water 4 times alternately to ensure that the impurities are removed. Then dry the washed precipitate in a vacuum environment at 80℃ for 12 h to obtain the CoHCF precursor.

[0061] Step 3: Spread the CoHCF precursor evenly in a crucible and place it in a muffle furnace. Heat the crucible to 500℃ at a rate of 2℃ / min and hold for 2 h to obtain the composite metal oxide electrode material Fe2O3 / Co3O4.

[0062] Example 2

[0063] In this embodiment, the amount of trisodium citrate dihydrate (Na3C6H5O7·2H2O) used was 9 mmol, and the remaining steps were the same as in Example 1.

[0064] Example 3

[0065] In this embodiment, the amount of trisodium citrate dihydrate (Na3C6H5O7·2H2O) used was 11 mmol, and the remaining steps were the same as in Example 1.

[0066] Example 4

[0067] In this embodiment, the amount of CoCl2·6H2O used is 2 mmol, and the remaining steps are the same as in Example 1.

[0068] Example 5

[0069] In this embodiment, the amount of CoCl2·6H2O used is 4 mmol, and the remaining steps are the same as in Example 1.

[0070] Example 6

[0071] In this embodiment, the amount of CoCl2·6H2O used is 8 mmol, and the remaining steps are the same as in Example 1.

[0072] Example 7

[0073] A method for preparing a composite metal oxide electrode material includes the following steps:

[0074] Step 1: Weigh 6 mmol CoCl2·6H2O and 10 mmol Na3C6H5O7·2H2O and dissolve them in 200 mL of deionized water to prepare solution A; weigh 2 mmol K3Fe(CN)6 and dissolve it in 200 mL of deionized water to prepare solution B.

[0075] Step 2: Add solution B dropwise to solution A and turn on the magnetic stirrer to stir the mixture at 400 r / min for 1 h. After the addition is complete, let the mixture stand at room temperature for 24 h to fully react. After the reaction is complete, centrifuge to collect the precipitate. Wash it with anhydrous ethanol and then wash it with deionized water 4 times alternately to ensure that the impurities are removed. Then dry the washed precipitate in a vacuum environment at 80℃ for 12 h to obtain the CoHCF precursor.

[0076] Step 3: Prepare additives, including:

[0077] S31. Dissolve 4 mmol MnCl2 and 6 mmol Na3C6H5O7·2H2O in 50 mL of deionized water to prepare solution C; dissolve 2 mmol K3Fe(CN)6 in 50 mL of deionized water to prepare solution D; uniformly disperse 1 g activated carbon powder and 0.5 g polyethylene glycol 600 in 100 mL of deionized water to prepare solution E.

[0078] S32. Add solutions C and D dropwise into solution E simultaneously and turn on the magnetic stirrer to stir the mixture at 400 r / min for 1 h. After the addition is complete, let the mixture stand at room temperature for 24 h, centrifuge to collect the precipitate, wash it with anhydrous ethanol and then wash it with deionized water 4 times alternately, and dry it in a vacuum environment at 80℃ for 12 h to obtain the additive.

[0079] Step 4: Mix the CoHCF precursor and additives evenly in a crucible and place it in a muffle furnace. Under a nitrogen atmosphere, heat the mixture to 200℃ at a rate of 2℃ / min and hold for 1 h to obtain the pre-sintered product. The amount of additive used is 3% of the mass of the CoHCF precursor.

[0080] Step 5: Mix the pre-sintered product and additives evenly in a crucible and place it in a muffle furnace. Heat the crucible to 500℃ at a rate of 2℃ / min and hold for 2 h to obtain the composite metal oxide electrode material Fe2O3 / Co3O4-MnC. The amount of additives used is 2% of the mass of the CoHCF precursor in Step 4.

[0081] Example 8

[0082] In this embodiment, the method for preparing the additive includes:

[0083] S31. Dissolve 4 mmol MnCl2 and 6 mmol Na3C6H5O7·2H2O in 50 mL of deionized water to prepare solution C; dissolve 2 mmol K3Fe(CN)6 in 50 mL of deionized water to prepare solution D; uniformly disperse 1 g of activated carbon powder in 100 mL of deionized water to prepare solution E.

[0084] S32. Add solutions C and D dropwise into solution E simultaneously and turn on the magnetic stirrer to stir the mixture at 400 r / min for 1 h. After the addition is complete, let the mixture stand at room temperature for 24 h, centrifuge to collect the precipitate, wash it with anhydrous ethanol and then wash it with deionized water 4 times alternately, and dry it in a vacuum environment at 80℃ for 12 h to obtain the additive.

[0085] The remaining steps are the same as in Example 7;

[0086] Compared to Example 7, polyethylene glycol is not added when preparing the additive in this example.

[0087] Example 9

[0088] In this embodiment, the method for preparing the additive includes:

[0089] 1 g of activated carbon powder and 0.5 g of polyethylene glycol 600 were uniformly dispersed in 100 mL of deionized water. The magnetic stirrer was turned on and stirred at 400 r / min for 1 h. The mixture was then allowed to stand at room temperature for 24 h. The precipitate was collected by centrifugation, washed with anhydrous ethanol and then washed with deionized water four times alternately. The mixture was dried under vacuum at 80 °C for 12 h to obtain the additive.

[0090] The remaining steps are the same as in Example 7;

[0091] Compared to Example 7, this example uses only activated carbon and polyethylene glycol to prepare the additive.

[0092] Example 10

[0093] In this embodiment, the method for preparing the additive includes:

[0094] S31. Dissolve 4 mmol MnCl2 and 6 mmol Na3C6H5O7·2H2O in 50 mL of deionized water to prepare solution C; dissolve 2 mmol K3Fe(CN)6 in 50 mL of deionized water to prepare solution D;

[0095] S32. Add solution D dropwise to solution C and turn on the magnetic stirrer to stir the mixture at 400 r / min for 1 h. After the addition is complete, let the mixture stand at room temperature for 24 h, centrifuge to collect the precipitate, wash it with anhydrous ethanol and then wash it with deionized water 4 times alternately, and dry it in a vacuum environment at 80℃ for 12 h to obtain the additive.

[0096] The remaining steps are the same as in Example 7;

[0097] Compared to Example 7, in this example, activated carbon and polyethylene glycol are not added when preparing the additive.

[0098] Example 11

[0099] A method for preparing a composite metal oxide electrode material includes the following steps:

[0100] Step 1: Same as Example 7;

[0101] Step 2, same as in Example 7;

[0102] Step 3, same as in Example 7;

[0103] Step 4: Mix the CoHCF precursor and additives evenly in a crucible and place it in a muffle furnace. Heat the crucible to 500℃ at a rate of 2℃ / min and hold for 2 hours to obtain the composite metal oxide electrode material. The amount of additive is 5% of the mass of the CoHCF precursor.

[0104] Compared to Example 7, this example does not involve pre-sintering.

[0105] Example 12

[0106] A method for preparing a composite metal oxide electrode material includes the following steps:

[0107] Step 1: Same as Example 7;

[0108] Step 2, same as in Example 7;

[0109] Step 3, same as in Example 7;

[0110] Step 4: Spread the CoHCF precursor evenly in the crucible and place it in the muffle furnace. Under a nitrogen atmosphere, heat the crucible to 200℃ at a rate of 2℃ / min and hold for 1 h to obtain the pre-sintered product.

[0111] Step 5: Mix the pre-sintered product and additives evenly in a crucible and place it in a muffle furnace. Heat the crucible to 500℃ at a rate of 2℃ / min and hold for 2 hours to obtain the composite metal oxide electrode material. The amount of additive used is 5% of the mass of the CoHCF precursor in Step 4.

[0112] Compared to Example 7, this example does not use additives in the pre-sintering stage.

[0113] Example 13

[0114] A method for preparing a composite metal oxide electrode material includes the following steps:

[0115] Step 1: Same as Example 7;

[0116] Step 2, same as in Example 7;

[0117] Step 3, same as in Example 7;

[0118] Step 4: Mix the CoHCF precursor and additives evenly in a crucible and place it in a muffle furnace. Under a nitrogen atmosphere, heat the mixture to 200℃ at a rate of 2℃ / min and hold for 1 h to obtain the pre-sintered product. The amount of additive used is 5% of the mass of the CoHCF precursor.

[0119] Step 5: Spread the pre-sintered product evenly in the crucible and place it in the muffle furnace. Heat the crucible to 500℃ at a rate of 2℃ / min and hold for 2 hours to obtain the composite metal oxide electrode material.

[0120] Compared to Example 7, this example does not use additives in the secondary calcination stage.

[0121] Comparative Example 1

[0122] A method for preparing a single metal oxide electrode material includes the following steps:

[0123] Step 1: Weigh 4 mmol CoCl2·6H2O and 10 mmol Na3C6H5O7·2H2O and dissolve them in 200 mL of deionized water to prepare solution A; weigh 2 mmol K3Co(CN)6 and dissolve it in 200 mL of deionized water to prepare solution B.

[0124] Step 2: Add solution B dropwise to solution A and turn on the magnetic stirrer to stir the mixture at 400 r / min for 1 h. Then let the mixture stand at room temperature for 24 h to fully react. After the reaction is complete, centrifuge to collect the precipitate. Wash it with anhydrous ethanol and then wash it repeatedly with deionized water 4 times to ensure that the impurities are removed. Then dry the washed precipitate in a vacuum environment at 80℃ for 12 h to obtain the CoHCC precursor.

[0125] Step 3: Spread the CoHCC precursor evenly in a crucible and place it in a muffle furnace. Heat the crucible to 500℃ at a rate of 2℃ / min and hold for 2 h to obtain the single metal oxide electrode material Co3O4.

[0126] XRD testing can be used to analyze the phase composition and crystal structure of a sample. Figure 1 The XRD pattern of the precursor CoHCF shows obvious sharp peaks, which correspond to the strong diffraction peaks at 2θ=14.9°, 17.2°, 24.4°, 34.8°, 39.0°, 50.1°, 53.3°, and 56.5° of Co3[Fe(CN)6]2·10H2O (PDF#46-0907) on the (111), (200), (220), (400), (420), (440), (600), and (620) crystal planes, indicating that the precursor was successfully synthesized.

[0127] After calcination, the precursor yielded metal oxides. Figure 2 The XRD patterns of Fe2O3 / Co3O4 prepared in Example 1 and Co3O4 prepared in Comparative Example 1 are shown in the figure. As shown in the figure, the strong diffraction peaks of the CoHCC sample at 2θ=19.0°, 31.3°, 36.8°, 38.5°, 44.8°, 55.7°, 59.4°, 65.2° and 68.6° correspond to the (110), (220), (311), (222), (422), (511), (400) and (531) crystal planes after calcination, which are completely matched with the standard card PDF#74-2120, indicating that it is Co3O4. The CoHCF sample after calcination not only has the diffraction peaks of Co3O4, but also the diffraction peaks at 2θ=23.9°, 35.1°, 42.9°, 57.2°, 62.9°, and 68.9° corresponding to the standard card Fe2O3PDF#74-2120, which indicates that it is a Fe2O3 / Co3O4 mixed metal oxide.

[0128] SEM can be used to characterize the morphology of electrode materials. Figures 3-5 Images of Co3O4 and Fe2O3 / Co3O4 by SEM. Among them, Figure 3 The SEM image of Co3O4 prepared for Comparative Example 1 shows a cubic structure with an uneven and irregular shape. The surface is rough and some particles are stuck together, which may have an adverse effect on its electrochemical performance. Figure 4 The image shows an SEM image of Fe2O3 / Co3O4 (10 mmol of trisodium citrate and a molar ratio of cobalt chloride to potassium ferricyanide of 2:1) prepared in Example 5. The cubic crystals are relatively uniformly arranged and the nanocubes are relatively fine, but there are still a small number of particles that are agglomerated. Figure 5 The image shows an SEM image of Fe2O3 / Co3O4 (10 mmol of trisodium citrate, and a molar ratio of cobalt chloride to potassium ferricyanide of 3:1) prepared in Example 1. It can be seen that the material has a regular framework structure, fine nanocube volume, uniform cubic crystal arrangement, and no obvious agglomeration, which provides favorable conditions for the full occurrence of redox reactions.

[0129] Application examples

[0130] Application of a composite metal oxide electrode material in supercapacitors

[0131] The electrode is prepared using the aforementioned composite metal oxide electrode material. The specific method is as follows: Electrode material, acetylene black, and polyvinylidene fluoride (PVDF) binder are weighed in a mass ratio of 8:1:1 and thoroughly mixed in an agate mortar. Then, 3-4 drops of N-methylpyrrolidone (NMP) are slowly added while vigorously stirring to ensure all components are uniformly combined, forming an electrode slurry. The slurry is then gently applied with a brush and evenly spread over a 1 cm area. 2 After coating the surface of the nickel foam, place the nickel foam in a vacuum oven at 80°C for 12 hours to dry completely. The electrode preparation is then complete.

[0132] Electrochemical testing is performed using a three-electrode system based on 2M KOH, comprising an Hg / HgO electrode, an auxiliary platinum sheet electrode, and a working electrode (the electrode prepared in this invention).

[0133] Figure 6 The figures show the cyclic voltammetry (CV) curves of Fe2O3 / Co3O4 prepared in Example 1 and Co3O4 prepared in Comparative Example 1. The scan rate was 30 mV / s within a voltage window of 0V to 0.55V. It is clear that Fe2O3 / Co3O4 has a larger integral area and more obvious redox peak pairs, exhibiting a typical pseudocapacitive energy storage mechanism. Figure 7 The graphs show the constant current charge-discharge (GCD) curves of Fe2O3 / Co3O4 prepared in Example 1 and Co3O4 prepared in Comparative Example 1. Within a voltage window of 0V to 0.5V, the current density is 1 A / g. It is clear that Fe2O3 / Co3O4 has a longer discharge time. Calculations show that the specific capacitances of Co3O4 and Fe2O3 / Co3O4 are 51.2 F / g and 92 F / g, respectively, indicating that Fe2O3 / Co3O4 has superior performance. Figure 8 This is an electrochemical impedance spectroscopy (EIS) curve of Fe2O3 / Co3O4 prepared in Example 1 and Co3O4 prepared in Comparative Example 1 (the horizontal axis Z' is the real part of the impedance, and the vertical axis -Z'' is the imaginary part of the impedance). The diameter of the semicircle in the high-frequency region corresponds to the charge transfer resistance (R). st The smaller the diameter, the lower the charge transfer resistance; the slope of the straight line in the low-frequency region corresponds to the ion diffusion characteristics (Warburg impedance), the larger the slope, the smaller the diffusion resistance. Figure 8 It can be seen that Fe2O3 / Co3O4 has a lower Warburg impedance.

[0134] To further investigate the effects of different metal ions on the performance of electrode active materials, two materials, Co3O4 from Comparative Example 1 and Fe2O3 / Co3O4 from Example 1, were subjected to a long-cycle test of 2000 cycles at a scan rate of 100 mV / s. The change in capacity retention was recorded every 100 cycles. The results are as follows: Figure 9As shown, the capacity retention rates of Co3O4 and Fe2O3 / Co3O4 reached 147.48% and 149.64%, respectively. This unusual capacity improvement can be attributed to the combined effects of electrode activation, deep electrolyte penetration, and reversible surface oxidation state transformation. The Fe2O3 / Co3O4 composite material reached a peak capacity (156.55%) at 700 cycles, then decreased to 149.64%, while Co3O4 reached a peak capacity (153.10%) at 600 cycles and then dropped to 147.48%. This indicates that Fe2O3 / Co3O4 still exhibits superior capacity retention at higher cycle counts, demonstrating that its composite structure effectively improves its cycling stability.

[0135] In summary, Fe2O3 / Co3O4 exhibits superior electrochemical performance compared to Co3O4.

[0136] The effect of the amount of trisodium citrate (9 mmol, 10 mmol, and 11 mmol) on the electrochemical performance was investigated using Fe2O3 / Co3O4 prepared in Examples 1-3. At a scan rate of 30 mV / s within the range of 0V to 0.55V, the C6H5Na3O7-10 mmol group exhibited the largest area of ​​integration of the CV curve, directly reflecting its optimal charge storage capacity. Figure 10 The GCD curves of Fe2O3 / Co3O4 prepared in Examples 1-3 at a current density of 1 A / g fully illustrate a classic pseudocapacitive process. The C6H5Na3O7-10 mmol group had the longest discharge time. Calculations showed that the specific capacitances of the three materials (9, 10, and 11 mmol) were 76.2 F / g (Example 2), 92 F / g (Example 1), and 58.8 F / g (Example 3), respectively. The C6H5Na3O7-10 mmol group exhibited the highest specific capacitance, further confirming that 10 mmol showed better performance. Electrochemical impedance spectroscopy (EIS) tests showed that the C6H5Na3O7-10 mmol group had lower ion diffusion resistance. Based on the above test results, it can be confirmed that when the amount of trisodium citrate (C6H5Na3O7) is 10 mmol, the prepared Fe2O3 / Co3O4 composite material (Example 1) has the best electrochemical performance.

[0137] The effect of the cobalt-iron ratio on electrochemical performance was investigated using Fe2O3 / Co3O4 prepared in Examples 1, 4-6, where the molar ratios of cobalt salt to potassium ferricyanide were 2 mmol:2 mmol, 4 mmol:2 mmol, 6 mmol:2 mmol, and 8 mmol:2 mmol, denoted as (1:1, 2:1, 3:1, 4:1). At 30 mV / s within the range of 0 V to 0.55 V, the 3:1 group showed a significantly larger integrated area than the other ratios, and exhibited the smoothest and most symmetrical redox peaks, with a clear pair of redox peaks, indicating higher capacity. Figure 11 The GCD curves of Fe2O3 / Co3O4 prepared in Examples 1, 4-6, at a current density of 1 A / g are shown. According to the discharge curves, the 3:1 group has the longest discharge time and the best specific capacitance. Electrochemical impedance spectroscopy (EIS) tests show that the 3:1 group has relatively low impedance. Based on the above test results, it can be confirmed that the Fe2O3 / Co3O4 prepared at a ratio of 3:1 (Example 1) exhibits the best electrochemical performance.

[0138] The CV curves of Fe2O3 / Co3O4 prepared in Example 1 at different scan rates (10 mV / s, 20 mV / s, 30 mV / s, 50 mV / s, 100 mV / s) within a potential window of 0 V to 0.55 V are shown below. Figure 12 As shown, all curves have a pair of distinct redox peaks, and no peak distortion was observed even at high scan rates, indicating that the reaction has good reversibility. Figure 13 The graph shows the relationship between the specific capacitance and current density of the Fe2O3 / Co3O4 prepared in Example 1. The specific capacitances at 1 A / g, 2 A / g, 3 A / g, 5 A / g, and 10 A / g are 92 F / g, 81.2 F / g, 72 F / g, 60 F / g, and 48 F / g, respectively. Even at a high rate of 10 A / g, the material can still maintain 52.17% of the initial specific capacitance, indicating that it has rapid charge transport capability and good structural stability. This good electrochemical performance may be attributed to the relatively ideal material morphology and structural characteristics obtained under optimized synthesis conditions.

[0139] The composite metal oxide electrode materials prepared in Examples 7 to 13 exhibited specific capacitances of 125.4 F / g, 121 F / g, 104.3 F / g, 114.7 F / g, 113.5 F / g, 118 F / g, and 120 F / g at a current density of 1 A / g, respectively, all higher than that of Example 1, with Example 7 showing the highest specific capacitance. The composite metal oxide electrode material prepared in Example 7 also exhibited specific capacitances of 125.4 F / g, 117 F / g, 108.3 F / g, 97 F / g, and 86 F / g at 1 A / g, 2 A / g, 3 A / g, 5 A / g, and 10 A / g, respectively. Even at a high rate of 10 A / g, the material maintained 68.58% of its initial specific capacitance, superior to Example 1. Furthermore, the composite metal oxide electrode materials prepared in Examples 7 to 13 showed better capacity retention after 2000 cycles at a scan rate of 100 mV / s than Example 1, with Example 7 showing the best performance. like Figure 14 As shown, Example 1 reached a peak capacity of 156.55% at 700 cycles and then dropped to 149.64%, while Example 7 reached a peak capacity of 166.37% at 900 cycles and then dropped to 160.65%. It can be seen that Example 7 still exhibits better capacity retention capability at higher cycle counts.

[0140] The performance test of the asymmetric supercapacitor was conducted in a dual-electrode system. The positive electrode was prepared using a composite metal oxide electrode material (Example 1), and the negative electrode was prepared using activated carbon YP50 (AC). The activated carbon YP50, acetylene black, and binder PVDF were thoroughly mixed in a mass ratio of 8:1:1 and placed in an agate mortar for thorough mixing. Then, 3-4 drops of NMP were slowly added and vigorously stirred to ensure uniform fusion of all components, forming an electrode slurry. This slurry was then gently dipped into a brush and evenly spread over a 1 cm area. 2 The surface of the foamed nickel was coated and then placed in a vacuum oven at 80°C for 12 hours to dry completely, thus completing the preparation of the negative electrode. The electrolyte was a 2M KOH solution, and the separator was a polypropylene separator. The asymmetric supercapacitor Fe2O3 / Co3O4 / / AC was assembled.

[0141] The test voltage range is set to -1V to 0.55V. Figure 15At a scan rate of 30 mV / s, a clear comparison of the cyclic voltammetry (CV) curves of Fe2O3 / Co3O4 and AC can be observed, demonstrating the ingenious combination of the double-layer and pseudo-layer mechanisms. Under a current density of 1 A / g, the specific capacitance of AC was calculated to be 100.4 F / g. Based on the charge balance principle of asymmetric supercapacitors, the required mass of the positive electrode active material was calculated. A two-electrode system was constructed to comprehensively evaluate the electrochemical performance. Constant current charge-discharge tests at different voltages (1.40 V, 1.45 V, 1.50 V, 1.55 V) determined the optimal voltage window to be 1.55 V. Based on this optimal voltage window, subsequent cyclic voltammetry and constant current charge-discharge tests were conducted to further understand its electrochemical characteristics.

[0142] Figure 16 The CV curves of Fe2O3 / Co3O4 / / AC at different scan rates (10 mV / s, 20 mV / s, 30 mV / s, 50 mV / s, 100 mV / s) all retain obvious redox peaks. Figure 17 The GCD curves of Fe2O3 / Co3O4 / / AC at different current densities (1 A / g, 2 A / g, 3 A / g, 5 A / g, 10 A / g) are shown. The five curves are roughly symmetrical, indicating that the electrode material has a stable structure and no obvious side reactions during charge and discharge. The specific capacitances of Fe2O3 / Co3O4 / / AC at the five current densities are 36.64 F / g, 34.58 F / g, 30.96 F / g, 26.13 F / g, and 20.64 F / g, respectively. Under the high rate condition of 10 A / g, it retains 56.33% of the initial capacitance.

[0143] Figure 18 The EIS curve of Fe2O3 / Co3O4 / / AC (the horizontal axis Z' represents the real part of the impedance, and the vertical axis -Z'' represents the imaginary part of the impedance) shows good resistance. At power densities of 775 W / kg, 1550 W / kg, 2325 W / kg, 3875 W / kg, and 7750 W / kg, the energy densities of Fe2O3 / Co3O4 / / AC are 12.23 Wh / kg, 11.54 Wh / kg, 10.33 Wh / kg, 8.72 Wh / kg, and 6.89 Wh / kg, respectively. Figure 19 The figure shows the capacity retention of Fe2O3 / Co3O4 / / AC after 2000 cycles at a scan rate of 100 mV / s. The capacity retention after 2000 cycles is 108.45%, which shows that Fe2O3 / Co3O4 / / AC has good rate tolerance and cycle enhancement effect. This verifies the unique advantage of this asymmetric system in energy supply balance in dynamic energy storage scenarios and provides experimental basis for the development of new high-power energy storage devices.

[0144] Using the same method, an asymmetric supercapacitor Fe2O3 / Co3O4-MnC / / AC was assembled using an electrode prepared from a composite metal oxide electrode material (Example 7) as the positive electrode, and its performance was tested based on the optimal voltage window of 1.55 V. The specific capacitance of Fe2O3 / Co3O4-MnC / / AC at different current densities (1 A / g, 2 A / g, 3 A / g, 5 A / g, 10 A / g) were 57.32 F / g, 55.78 F / g, 52.29 F / g, 48.03 F / g, and 43.61 F / g, respectively. Under the high rate condition of 10 A / g, it maintained 76.08% of the initial capacity, and the energy density was also correspondingly improved. Figure 20 The graph shows the capacity retention of Fe2O3 / Co3O4-MnC / / AC after 2000 cycles at a scan rate of 100 mV / s. The capacity retention after 2000 cycles is 120.06%, which is better than that of Example 1.

[0145] In summary, this invention prepared the precursor CoHCF via co-precipitation, which was then calcined to obtain a mixed metal oxide Fe2O3 / Co3O4. The effects of different metal ions, the amount of trisodium citrate as a complexing agent, and the cobalt-iron ratio on the material properties were investigated. This invention also utilized manganese salts, activated carbon, and polyethylene glycol to prepare additives, which were then co-calcined with the CoHCF precursor in stages. The effects of the additives and staged calcination on the material properties were investigated. The material was characterized using X-ray diffraction and scanning electron microscopy, and its electrochemical performance was studied using cyclic voltammetry, constant current charge-discharge testing, and electrochemical impedance spectroscopy. The main conclusions are as follows:

[0146] (1) By comparing the diffraction peaks and crystal planes with the standard cards through XRD testing, it was proven that the precursor CoHCF and the calcined product Fe2O3 / Co3O4 were successfully prepared.

[0147] (2) In the three-electrode system, Fe2O3 / Co3O4 has better electrochemical performance than Co3O4. At a current density of 1 A / g, the specific capacitance of Fe2O3 / Co3O4 prepared in Example 1 reaches 92 F / g, which is better than that of Co3O4 (51.2 F / g).

[0148] (3) The test results of the assembled asymmetric supercapacitor Fe2O3 / Co3O4 / / AC are as follows: when the power density is 775W / kg, it can provide an energy density of 12.23 Wh / kg. After 2000 long cycle tests, the capacity retention rate is 108.45%.

[0149] (4) The present invention utilizes manganese salt, activated carbon and polyethylene glycol to prepare additives, and performs segmented calcination together with CoHCF precursor to further improve the specific capacity and cycle stability of composite metal oxide electrode materials; under the three-electrode system, the specific capacitance of Fe2O3 / Co3O4-MnC prepared in Example 7 reaches 125.4 F / g at a current density of 1 A / g, which is better than 92 F / g in Example 1; after being assembled into an asymmetric supercapacitor Fe2O3 / Co3O4-MnC / / AC, the specific capacitance reaches 57.32 F / g at a current density of 1 A / g, and the capacity retention rate is 120.06% after 2000 long cycle tests.

[0150] 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 composite metal oxide electrode material, characterized in that, Includes the following steps: Step 1: Dissolve cobalt chloride and trisodium citrate in deionized water to prepare solution A; dissolve potassium ferricyanide in deionized water to prepare solution B; Step 2: Add solution B dropwise to solution A and stir continuously to obtain a mixture. Let the mixture stand at room temperature, centrifuge to collect the precipitate, wash and vacuum dry to obtain the CoHCF precursor. Step 3: Prepare composite metal oxide electrode materials using CoHCF precursors, including: (1) Mix the CoHCF precursor and the additive, the amount of the additive is 1%~5% of the mass of the CoHCF precursor, and heat it to 150℃~250℃ at a rate of 1℃ / min~3℃ / min under a nitrogen atmosphere and hold for 0.5h~2h to obtain the pre-sintered product. (2) Mix the pre-sintered product and the additive. The amount of the additive is 1% to 5% of the mass of the CoHCF precursor in (1). Heat the mixture to 400℃ to 600℃ at a rate of 1℃ / min to 3℃ / min and hold it for 1h to 3h to obtain the composite metal oxide electrode material. The preparation method of the additive includes the following steps: S31. Dissolve MnCl2 and Na3C6H5O7·2H2O in deionized water to prepare solution C; dissolve K3Fe(CN)6 in deionized water to prepare solution D; uniformly disperse activated carbon and polyethylene glycol 600 in deionized water to prepare solution E. S32. Add solutions C and D dropwise into solution E simultaneously while stirring continuously to obtain a mixture. Let the mixture stand at room temperature, centrifuge to collect the precipitate, wash and vacuum dry to obtain the additive.

2. The method for preparing a composite metal oxide electrode material as described in claim 1, characterized in that, In step one, the molar ratio of cobalt chloride to trisodium citrate in solution A is 2~8:9~11, and the molar volume ratio of cobalt chloride to deionized water is 2mmol~8mmol:100mL~300mL; the molar volume ratio of potassium ferricyanide to deionized water in solution B is 1mmol:50mL~150mL.

3. The method for preparing a composite metal oxide electrode material as described in claim 1, characterized in that, In step two, the molar ratio of cobalt chloride in solution A to potassium ferricyanide in solution B is 1 to 4:

1.

4. The method for preparing a composite metal oxide electrode material as described in claim 1, characterized in that, In step two, the stirring speed is 200 r / min to 600 r / min; the dripping rate is 100 mL / h to 300 mL / h; the mixture is allowed to stand at room temperature for 12 h to 36 h; the washing is performed by alternating between anhydrous ethanol and deionized water 3 to 5 times; and the vacuum drying temperature is 60℃ to 100℃ for 8 h to 16 h.

5. The method for preparing a composite metal oxide electrode material as described in claim 1, characterized in that, In S31, the molar volume ratio of MnCl2, Na3C6H5O7·2H2O and deionized water in solution C is 2mmol~6mmol:4mmol~8mmol:30mL~80mL; the molar volume ratio of K3Fe(CN)6 and deionized water in solution D is 1mmol~3mmol:30mL~80mL; and the mass-volume ratio of activated carbon, polyethylene glycol 600 and deionized water in solution E is 1g:0.2g~1g:50mL~150mL. In S32, the molar ratio of MnCl2 in solution C, K3Fe(CN)6 in solution D, and activated carbon in solution E is 2 mmol~6 mmol:1 mmol~3 mmol:0.5 g~2 g; the stirring speed is 200 r / min~600 r / min; the dropping rate is 30 mL / h~100 mL / h; the solution is allowed to stand at room temperature for 12 h~36 h; the solution is washed 3~5 times with alternating washing of anhydrous ethanol and deionized water; and the vacuum drying temperature is 60℃~100℃ for 8 h~16 h.

6. A composite metal oxide electrode material, characterized in that, It is prepared by the method for preparing the composite metal oxide electrode material according to any one of claims 1-5.

7. A supercapacitor, characterized in that, The positive electrode material of the supercapacitor is the composite metal oxide electrode material as described in claim 6.

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