A high-efficiency composite electrode for supercapacitor negative electrode and a preparation method thereof

Abstract

The application discloses a kind of supercapacitor negative high-efficiency composite electrode and preparation method thereof, including the block body iron of substrate and the outer layer PrNi x Fe 1‑x O3 conductive active layer, and Fe2O3 active layer between the two, by wet chemical etching and transient high temperature joule heat method in-situ synthesis active layer, and further utilize wet chemical brush coating and transient high temperature joule heat method in-situ synthesis conductive active layer, two are asymmetric sandwich structure, it is favorable to build charge transport path, improve charge transport efficiency, at the same time, can effectively relieve the volume change generated in the process of charge and discharge of iron oxide, unlike the characteristics of particle composite structure easy to collapse, inhibit the occurrence of electrode material pulverization, wherein, using transient high temperature joule heat preparation technology, layered in-situ build heterostructure, not only simple and fast, also make the structure compact and dense, maintain the stability of overall electrode structure, improve the long-period cycle charge and discharge capacity of electrode.

Description

Technical Field

[0001] This invention relates to the field of supercapacitor technology, specifically to a high-efficiency composite electrode for the negative electrode of a supercapacitor and its preparation method. Background Technology

[0002] Supercapacitors, as a novel type of energy storage device, combine the characteristics of traditional capacitors and batteries, making them indispensable in the field of high-power-density energy storage. The negative electrode, in particular, is a core component of supercapacitors because it can broaden the operating voltage window and significantly improve energy density. However, the overall development of negative electrode materials for supercapacitors in my country is currently lagging behind, with average capacitance far lower than that of positive electrode materials, becoming a bottleneck restricting the technological development of supercapacitors in my country. Among the many supercapacitor negative electrode materials, Fe2O3 has the highest theoretical capacitance, reaching 3625 F / g, which is 10-100 times higher than that of carbon materials. However, Fe2O3 has poor conductivity (~10⁻¹⁴ S / cm), resulting in high energy consumption during energy storage and a lower actual capacitance.

[0003] Currently, when Fe2O3 is used as the negative electrode of supercapacitors, conductive agents are usually added to improve the transport of electrons between Fe2O3 particles. In addition, researchers mainly use the method of constructing composite electrodes with conductive materials and Fe2O3 to overcome the problem of poor conductivity of Fe2O3 materials. Various conductive materials have been used to improve the conductivity of Fe2O3-based anode materials, mainly conductive polymers or carbon materials. For example, patent CN106558423A discloses the synthesis of a Fe2O3 and polypyrrole composite electrode; patent CN105244484A discloses the synthesis of a Fe2O3 and graphene-polyimide-based carbon aerogel composite electrode; patent CN110136978A discloses the synthesis of a reduced graphene and Fe2O3 composite electrode; patent CN110429246A discloses the synthesis of a graphitic carbon nitride and Fe2O3 composite electrode; patent CN106449157A discloses the synthesis of a Fe2O3 and graphene composite electrode; and patent CN103903873A discloses the synthesis of a Fe2O3 and multi-walled carbon nanotube / conductive carbon cloth composite electrode.

[0004] However, the composite electrodes of Fe2O3 and highly conductive materials generally have the following problems: (1) Although conductive polymer materials and carbon materials have high conductivity, their own capacitance is low, which dilutes the capacitance of the negative electrode of the composite supercapacitor and makes it difficult to obtain high energy density and continuous charge and discharge capability; (2) During preparation, 20-30% of conductive agent and binder mixture needs to be added, but these conductive agents and binders contribute very little to the capacitance and energy density of the supercapacitor and account for a large proportion, which inhibits the electrochemical performance of the composite electrode; (3) The preparation process is complicated and it is difficult to achieve mass production; (4) The electrode lacks a fixed electrode structure, which makes it difficult for Fe2O3 to form effective contact with other materials, and the randomness is large, making it difficult to obtain an effective charge transport path.

[0005] On the other hand, metal-based materials have also been used to construct composite electrodes with Fe2O3. For example, patent CN103366970A discloses the synthesis of a composite electrode of MnO2 and Fe2O3, and patent CN110391091A discloses the synthesis of Mn7O2. 13 Composite electrodes of Cu9S5 and Fe2O3 have been synthesized, as disclosed in patent CN113764196A and Co3O4 and Fe2O3 composite electrodes, respectively. However, while these metal-based materials offer high capacitance and can improve the energy density of the composite electrodes, their inherent poor conductivity leads to high resistance and significant energy consumption during energy storage. Therefore, providing a Fe2O3-based supercapacitor anode that simultaneously improves the conductivity and capacitance of Fe2O3, requires no conductive agents or binders, has a simple composite process, is easy to mass-produce, and possesses an effective composite structure is a pressing technical problem that needs to be solved. Summary of the Invention

[0006] This invention provides a high-efficiency composite electrode for supercapacitor negative electrodes that combines high conductivity and high capacitance, is synthesized in situ without conductive agents and binders, has a simple manufacturing method, and is easy to process in batches, in order to solve the above-mentioned problems.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a high-efficiency composite electrode for the negative electrode of a supercapacitor, comprising a bulk iron substrate and an outer PrNi layer. x Fe 1-x The O3 conductive active layer, and the Fe2O3 active layer located between them, wherein the bulk iron and the outer PrNi x Fe 1-x The O3 conductive active layer encapsulates the Fe2O3 active layer in the middle through an asymmetric clamping method.

[0008] Preferably, the Fe2O3 active layer and PrNi x Fe 1-x The thickness ratio of the O3 conductive active layer is 1:1 to 1:1.2.

[0009] A method for preparing a high-efficiency composite electrode for the negative electrode of a supercapacitor includes the following steps:

[0010] S1. The bulk iron substrate is rapidly sintered by a combination of wet chemical etching and instantaneous high-temperature Joule heating process, so that the iron chloride on its surface is converted into an active layer of Fe2O3 in situ.

[0011] S2, Configure PrNi x Fe 1-x The precursor solution of O3 was uniformly brushed onto the Fe2O3 active layer.

[0012] S3. Then, rapid sintering is performed using instantaneous high-temperature Joule heating technology, followed by cooling to obtain Fe\Fe2O3\PrNi. x Fe 1-x O3 composite electrode.

[0013] Preferably, in step S1, the bulk iron is pretreated by ultrasonically cleaning it with ethanol to remove organic matter and impurities from the surface of the bulk iron, and then dried.

[0014] Preferably, in step S1, a certain concentration of HCl solution is used to etch the bulk iron substrate, so that iron chloride is generated in situ on the surface of the bulk iron.

[0015] Preferably, in step S1, a DC power supply is used as the output source, and a current density of 9.3 A / cm is applied. 2 A DC power supply generates instantaneous high-temperature Joule heating to rapidly sinter the corroded bulk iron substrate. The process lasts 10-25 seconds, causing the iron chloride on the surface of the bulk iron to be converted in situ into an Fe2O3 active layer.

[0016] Preferably, in step S2, in PrNi x Fe 1-x In the O3 precursor solution, the molar ratio of Pr to Ni-Fe is 1:1, and the molar amount of Ni is 10%-30% of the sum of Ni-Fe molar amounts.

[0017] Preferably, the projected area of ​​the precursor solution coating is larger than that of the Fe2O3 active layer but smaller than that of the bulk iron.

[0018] Preferably, in step S3, a DC power supply is used as the output source, and a current density of 9.3 A / cm is applied. 2A DC power supply is used to generate instantaneous high-temperature Joule heating to rapidly sinter the corroded bulk iron substrate. The process lasts 10-15 seconds, resulting in an outer PrNi layer. x Fe 1-x O3 conductive active layer.

[0019] Among them, the repeated instantaneous high-temperature Joule heating technology controls the Fe2O3 active layer and PrNi x Fe 1-x Thickness of the O3 conductive active layer.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] In this invention, PrNi is used x Fe 1-x A heterojunction composite electrode is constructed using O3 and Fe2O3. The interface symmetry breaking effect of the heterojunction induces holes within Fe2O3, increasing the charge carrier concentration and lowering the charge migration barrier to enhance the conductivity of Fe2O3. Simultaneously, PrNi... x Fe 1-x O3 exhibits internal ion double exchange interactions and possesses excellent electron and ion transport properties, several orders of magnitude higher than traditional transition metal oxides, making Fe2O3 / PrNi... x Fe 1-x The conductivity of the O3 composite electrode is significantly improved; and PrNi x Fe 1-x O3 material contains three metal centers with high pseudocapacitive activity, and its capacitance is much higher than that of traditional carbon materials and conductive polymer materials, thus achieving high conductivity, high capacitance and high energy density characteristics of the negative electrode for supercapacitors.

[0022] In addition, the asymmetric clamping method can effectively alleviate the volume change of iron oxide during charging and discharging, which is different from the tendency of particulate composite structures to collapse and inhibits the pulverization of electrode materials.

[0023] In this invention, the electrode uses bulk iron as a substrate and is synthesized in two in-situ processes. No additional conductive agents or binders are required, which helps to improve the overall capacitance and energy density of the electrode. Furthermore, the composite materials are closely connected and have an ordered interface structure, which helps to reduce the interfacial contact resistance of the composite materials.

[0024] Among them, the instantaneous high-temperature Joule heating preparation technology is simple, fast, easy to process in batches, has controllable material layer thickness, low cost, and high commercial application value. Moreover, the oxide material prepared by the instantaneous high-temperature Joule heating preparation technology has a compact and dense structure, maintains the stability of the overall electrode structure, and improves the long-cycle charge and discharge capability of the electrode. Attached Figure Description

[0025] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof.

[0026] In the attached diagram:

[0027] Figure 1 This invention relates to Fe\Fe2O3\PrNi x Fe 1-x Schematic diagram of the asymmetric clamping structure of the O3 composite electrode;

[0028] Figure 2 This invention relates to Fe\Fe2O3\PrNi x Fe 1-x Flowchart of O3 composite electrode preparation;

[0029] Figure 3 This invention relates to Fe\Fe2O3\PrNi 0.1 Fe 0.9 SEM image of the O3 composite electrode;

[0030] Figure 4 This invention relates to Fe\Fe2O3\PrNi 0.1 Fe 0.9 Cyclic voltammetry (CV) curves of O3 composite electrode at different scan rates;

[0031] Figure 5 This invention relates to Fe\Fe2O3\PrNi 0.1 Fe 0.9 Constant current charge-discharge curves of O3 composite electrode at different rates;

[0032] Figure 6 This invention relates to Fe\Fe2O3\PrNi 0.1 Fe 0.9 Capacitance diagram of O3 composite electrode at different rates;

[0033] Figure 7 This invention relates to Fe\Fe2O3\PrNi 0.1 Fe 0.9 A schematic diagram of the capacitance retention rate of the O3 composite electrode after 20,000 charge-discharge cycles at a current density of 10 A / g.

[0034] Figure 8 These are XRD spectrum comparison diagrams of the comparative example and various embodiments of the present invention;

[0035] Figure 9 This is a comparison diagram of EIS spectra of the comparative examples and various embodiments of the present invention. Detailed Implementation

[0036] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0037] like Figure 1 As shown, a high-efficiency composite electrode for the negative electrode of a supercapacitor includes a bulk iron substrate and an outer PrNi layer. x Fe 1-x The O3 conductive active layer and the Fe2O3 active layer located between them, the Fe2O3 active layer in the middle is smooth and dense, and the Fe2O3 active layer and PrNi x Fe 1-x The thickness ratio of the O3 conductive active layer is 1:1 to 1:1.2;

[0038] Among them, bulk iron with high conductivity is used as the substrate, and PrNi with high conductivity and corrosion resistance is used as the substrate. x Fe 1-x The O3 conductive active layer serves as the outer layer, with the Fe2O3 active layer sandwiched in the middle by an asymmetric sandwich structure. The Fe2O3 active layer has the smallest projected area. In this asymmetric sandwich structure, the middle Fe2O3 active layer establishes a charge transport path with the outer conductive active layer through the heterojunction interface. The outer conductive active layer is also connected to the current collector-bulk iron substrate. The combination of the two forms a highly efficient charge transport path, achieving high conductivity of the composite electrode. At the same time, it effectively avoids direct contact between the middle Fe2O3 active layer and the electrolyte, improving the cycle stability of the composite electrode.

[0039] In addition, the asymmetric sandwich heterojunction electrode structure can effectively alleviate the volume change of the Fe2O3 active layer during charging and discharging, which is superior to the easy collapse of the particulate composite structure and inhibits the pulverization of the electrode material.

[0040] The performance characteristics of this composite electrode in supercapacitors are as follows: with the total weight of the composite material as the weight of the active material, the highest specific capacity can reach 940 F / g under constant current charge-discharge at 1 A / g within a voltage window of -1.0 to 0 V, exhibiting good rate performance. At currents of 4, 6, 8, 10, 12, and 15 A / g, the specific capacities can reach 873, 834, 796, 754, 711, and 645 mAh / g, respectively, demonstrating good capacity characteristics and rate performance.

[0041] refer to Figure 2 As shown, a method for preparing a high-efficiency composite electrode for the negative electrode of a supercapacitor includes the following steps:

[0042] S1. Pre-treat the bulk iron. The bulk iron can be any form of iron, such as foamed iron, iron sheet, iron mesh and other macroscopic bulk iron. Clean the bulk iron with ethanol ultrasonically to remove organic matter and impurities from the surface of the bulk iron, and then dry it.

[0043] S2. Use a certain concentration of HCl solution to etch the bulk iron substrate, so that iron chloride is generated in situ on the surface of the bulk iron.

[0044] S3. Using a DC power supply as the output source, connect the positive and negative terminals to the two ends of the block iron, turn on the power, and apply a current density of 9.3 A / cm². 2 The DC power supply generates instantaneous high-temperature Joule heating to rapidly sinter the corroded bulk iron substrate. The process lasts for 10-25 seconds, causing the iron chloride on the surface of the bulk iron to be converted in situ into an Fe2O3 active layer.

[0045] S4, Configure PrNi x Fe 1-x The precursor solution of O3 is uniformly brushed onto the Fe2O3 active layer with a Pr molar ratio of 1:1 and a Ni molar ratio of 10%-30% of the Ni molar ratio of the Ni-Fe molar ratio. The amount of nickel doped is continuously adjustable within this ratio.

[0046] S5. Then, using a DC power supply as the output source, apply a current density of 9.3 A / cm². 2 A DC power supply generates instantaneous high-temperature Joule heating to rapidly sinter the corroded bulk iron substrate. The process lasts 10-15 seconds, and after cooling, Fe\Fe2O3\PrNi is obtained. x Fe 1-x O3 composite electrode.

[0047] Specifically, by repeating steps S3 and S5 respectively, the Fe2O3 active layer and PrNi can be treated. x Fe 1-x The thickness of the O3 conductive active layer is controlled.

[0048] Example 1:

[0049] (1) Commercial foam iron (4cm×1.5cm) was ultrasonically treated in anhydrous ethanol for 15min, rinsed with deionized water for 1min, and then dried for later use;

[0050] (2) Use 1M HCl solution to brush the foam iron, with a brushing area of ​​3cm×1.5cm (leave a blank area of ​​0.5cm×1.5cm at each end of the substrate), place it in an oven at 80℃ for 1 hour to dry. During this process, the substrate surface is corroded and FeCl3 is generated in situ.

[0051] (3) Using a spark plasma sintering system with a DC power supply as the output source, the positive and negative terminals are connected to the two ends of the foamed iron, respectively. The power supply is turned on, and a DC current of 55.8A (current density of 9.3A / cm³) is applied. 2 The energizing time is 10-25 seconds, generating instantaneous high-temperature Joule heating, resulting in an electrode with a Fe2O3 active layer supported on foamed iron.

[0052] (4) Configure PrNi 0.1 Fe 0.9 The O3 precursor solution consists of 870 mg praseodymium(III) nitrate hexahydrate (2 mmol), 727.2 mg ferric(III) nitrate nonahydrate (0.9 mmol), and 58.2 mg nickel(II) nitrate hexahydrate (0.1 mmol), dissolved in 15 ml n-butanol solution. The molar amount of Ni is 10% of the sum of the molar amounts of Ni and Fe.

[0053] (5) The above precursor solution was brushed onto the Fe2O3 active layer electrode supported on the foamed iron obtained in step 3. The brushing size was 3.5cm × 1.5cm (with the Fe2O3 active layer as the center, the projected area was larger than the Fe2O3 active layer but smaller than the bulk iron, and a blank area of ​​0.25cm × 1.5cm was left at each end of the substrate). The electrode was then sintered again using a discharge plasma sintering system with a DC power supply as the output source. The positive and negative terminals were connected to the two ends of the foamed iron, respectively. The power supply was turned on and a DC power supply with a current of 55.8A (current density of 9.3A / cm) was applied. 2 The energizing time is 10-15 seconds, generating instantaneous high-temperature Joule heating for in-situ growth of the outer PrNi layer. 0.1 Fe 0.9 The O3 conductive active layer yields Fe\Fe2O3\PrNi 0.1 Fe 0.9 O3 composite electrode.

[0054] The composite material was observed using scanning electron microscopy (SEM), and the obtained SEM images are as follows: Figure 3 As shown in the figure, the foamed iron substrate, the middle Fe2O3 active layer, and the outer PrNi layer can be seen. 0.1 Fe 0.9 The O3 conductive active layer exhibits an asymmetric sandwich structure, with a smooth and dense intermediate Fe2O3 active layer that is integrated with the foamed iron substrate and the outer PrNi layer. 0.1 Fe 0.9 The O3 conductive active layer fits tightly;

[0055] refer to Figure 4 The figure shows the CV curves tested at different scan rates. From the figure, we can see that Fe\Fe2O3\PrNi 0.1 Fe0.9 The O3 composite electrode exhibits significant redox peaks; at a scan rate of 5 mV / s, the redox potentials are -0.375 and -0.439 V relative to the Hg / HgO electrode; the low redox potential makes it suitable for use as a negative electrode material in supercapacitors.

[0056] refer to Figure 5 As shown, the constant current charge-discharge curves are displayed at different rates. It can be seen from the figure that there is a very obvious charge-discharge plateau at low current density; and at high current density, a clear charge-discharge plateau can still be seen, proving that the composite electrode has excellent supercapacitor performance.

[0057] refer to Figure 6 The figure shows the rate performance of the composite electrode. As can be seen from the figure, the capacitance can reach 1008.6, 1000.4, 992.3, 985.4, and 988.5 F / g at currents of 1, 2, 3, 5, and 10 A / g, respectively. The composite electrode exhibits excellent rate performance.

[0058] refer to Figure 7 The figure shows the stability test curve of the composite electrode in Example 1 under constant current density; as shown in the figure, Fe\Fe2O3\PrNi 0.1 Fe 0.9 The O3 composite electrode operates stably for 20,000 cycles at a current density of 10 A / g, and maintains a performance retention rate of 92%.

[0059] Example 2:

[0060] (1) An electrode with a Fe2O3 active layer supported on foamed iron was obtained by the same operation as in Example 1;

[0061] (2) Configure PrNi 0.2 Fe 0.8 The O3 precursor solution consists of 870 mg praseodymium(III) nitrate hexahydrate (2 mmol), 646.4 mg ferric(III) nitrate nonahydrate (0.8 mmol), and 116.4 mg nickel(II) nitrate hexahydrate (0.2 mmol), dissolved in 15 ml n-butanol solution. The molar amount of Ni is 20% of the sum of the molar amounts of Ni and Fe.

[0062] (3) The above precursor solution was brushed onto the Fe2O3 active layer electrode supported on iron foam obtained in step 2, and the same operation as in Example 1 was performed to obtain Fe\Fe2O3\PrNi. 0.2 Fe 0.8 O3 composite electrode.

[0063] Example 3:

[0064] (1) An electrode with a Fe2O3 active layer supported on foamed iron was obtained by the same operation as in Example 1;

[0065] (2) Configure PrNi 0.3 Fe 0.7 The O3 precursor solution specifically weighs 870 mg praseodymium(III) nitrate hexahydrate (2 mmol), 565.6 mg ferric(III) nitrate nonahydrate (0.7 mmol), and 174.6 mg nickel(II) nitrate hexahydrate (0.3 mmol), and dissolves it in 15 ml of n-butanol solution. The molar amount of Ni is 30% of the sum of the molar amounts of Ni and Fe.

[0066] (3) The above precursor solution was brushed onto the Fe2O3 active layer electrode supported on iron foam obtained in step 2, and the same operation as in Example 1 was performed to obtain Fe\Fe2O3\PrNi. 0.3 Fe 0.7 O3 composite electrode.

[0067] Example 4:

[0068] (1) An electrode with a Fe2O3 active layer supported on foamed iron was obtained by the same operation as in Example 1;

[0069] (2) Configure PrNi 0.4 Fe 0.6 The O3 precursor solution consists of 870 mg praseodymium(III) nitrate hexahydrate (2 mmol), 484.8 mg ferric(III) nitrate nonahydrate (0.6 mmol), and 232.8 mg nickel(II) nitrate hexahydrate (0.4 mmol), dissolved in 15 ml n-butanol solution. The molar amount of Ni is 40% of the sum of the molar amounts of Ni and Fe.

[0070] (3) The above precursor solution was brushed onto the Fe2O3 active layer electrode supported on iron foam obtained in step 2, and the same operation as in Example 1 was performed to obtain Fe\Fe2O3\PrNi. 0.4 Fe 0.6 O3 composite electrode.

[0071] Comparative example:

[0072] (1) Commercial foam iron (4cm×1.5cm) was ultrasonically treated in anhydrous ethanol for 15min, rinsed with deionized water for 1min, and then dried for later use;

[0073] (2) Use 1M HCl solution to brush the foam iron, with a brushing area of ​​3cm×1.5cm (leave a blank area of ​​0.5cm×1.5cm at each end of the substrate), place it in an oven at 80℃ for 1 hour to dry. During this process, the substrate surface is corroded and FeCl3 is generated in situ.

[0074] (3) Using a spark plasma sintering system with a DC power supply as the output source, the positive and negative terminals are connected to the two ends of the foamed iron, respectively. The power supply is turned on, and a DC current of 55.8A (current density of 9.3A / cm³) is applied. 2 The energizing time is 10-25s, which generates instantaneous high temperature Joule heat, and the Fe2O3 active layer supported by foamed iron is synthesized in situ, thus obtaining the Fe\Fe2O3 composite electrode.

[0075] The samples obtained from Examples 1, 2, 3, 4, and the comparative example were analyzed by X-ray diffraction (XRD). The obtained XRD patterns are shown below. Figure 8 As shown, the composite electrodes corresponding to Examples 1, 2, 3, and 4 contain Fe2O3 and PrNi. x Fe 1-x XRD patterns of O3 (x = 0.1, 0.2, 0.3, 0.4) powder and Fe2O3 powder in the comparative composite electrode.

[0076] Fe, Fe2O3, and PrNi were tested in a three-electrode system. 0.1 Fe 0.9 O3 composite electrode, Fe\Fe2O3\PrNi 0.2 Fe 0.8 O3 composite electrode, Fe\Fe2O3\PrNi 0.3 Fe 0.7 O3 composite electrode, Fe\Fe2O3\PrNi 0.4 Fe 0.6 The electrochemical performance of the O3 composite electrode and the Fe\Fe2O3 composite electrode was investigated. Each of these composite electrodes was used as the working electrode, with a Hg / HgO electrode and a platinum sheet electrode used as the reference and counter electrodes, respectively. The electrolyte was a 6M KOH solution. Cyclic voltammetry (CV) curves and AC impedance were measured using a CHI660e electrochemical workstation, and constant current charge-discharge tests were performed using a Blue Electric supercapacitor analyzer. The total weight of the composite material was used as the weight of the active material.

[0077] The capacitance and cycle stability of the composite electrode in each of the above embodiments, as well as the equivalent series resistance and charge transfer resistance, are shown in the table below:

[0078]

[0079] As shown in the table above, the Ni doping ratios from high to low electrochemical performance are 30%, 20%, 10%, and 40%, respectively.

[0080] The capacitance and cycle stability of the composite electrode in the above comparative examples, as well as the equivalent series resistance and charge transfer resistance, are shown in the table below:

[0081]

[0082] From the results in the two tables above, it can be concluded that when the core material PrNi x Fe 1-x When O3 and the corresponding heterojunction are absent, the electrochemical performance of the composite electrode is worse than that of the composite electrode with Ni doping ratios of 10%, 20%, and 30%.

[0083] refer to Figure 9 As shown, the composite electrodes Fe\Fe2O3\PrNi corresponding to Examples 1, 2, 3, and 4 are shown. x Fe 1-x Comparison of EIS (electrochemical impedance spectroscopy) lines of O3 (x = 0.1, 0.2, 0.3, 0.4) and the composite electrode Fe\Fe2O3 of Comparative Example 1.

[0084] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a high-efficiency composite electrode for the negative electrode of a supercapacitor, characterized in that: High-efficiency composite electrode, comprising bulk iron substrate and outer PrNi layer x Fe 1-x The O3 conductive active layer, and the Fe2O3 active layer located between them, wherein the bulk iron and the outer PrNi x Fe 1-x The O3 conductive active layer encapsulates the Fe2O3 active layer in an asymmetric sandwich configuration; the preparation method includes the following steps: S1. The bulk iron substrate is rapidly sintered by a combination of wet chemical etching and instantaneous high-temperature Joule heating process, so that the iron chloride on its surface is converted into an active layer of Fe2O3 in situ. S2, Configure PrNi x Fe 1-x The precursor solution of O3 was uniformly brushed onto the Fe2O3 active layer. In PrNi x Fe 1-x In the O3 precursor solution, the molar ratio of Pr to Ni-Fe is 1:1, and the molar amount of Ni is 10%-30% of the sum of Ni-Fe molar amounts. S3. Then, rapid sintering is performed using instantaneous high-temperature Joule heating technology, followed by cooling to obtain Fe\Fe2O3\PrNi. x Fe 1-x O3 composite electrode.

2. The method for preparing a high-efficiency composite electrode for the negative electrode of a supercapacitor according to claim 1, characterized in that: Fe2O3 active layer and PrNi x Fe 1-x The thickness ratio of the O3 conductive active layer is 1:1 to 1:1.

2.

3. The method for preparing a high-efficiency composite electrode for the negative electrode of a supercapacitor according to claim 1, characterized in that: In step S1, the bulk iron is pretreated by ultrasonically cleaning it with ethanol to remove organic matter and impurities from its surface, followed by drying.

4. The method for preparing a high-efficiency composite electrode for the negative electrode of a supercapacitor according to claim 3, characterized in that: In step S1, a certain concentration of HCl solution is used to etch the bulk iron substrate, causing iron chloride to be generated in situ on the surface of the bulk iron.

5. The method for preparing a high-efficiency composite electrode for the negative electrode of a supercapacitor according to claim 4, characterized in that: In step S1, a DC power supply is used as the output source, and a current density of 9.3 A / cm is applied. 2 A DC power supply generates instantaneous high-temperature Joule heating to rapidly sinter the corroded bulk iron substrate. The process lasts 10-25 seconds, causing the iron chloride on the surface of the bulk iron to be converted in situ into an Fe2O3 active layer.

6. The method for preparing a high-efficiency composite electrode for the negative electrode of a supercapacitor according to claim 1, characterized in that: The projected area of ​​the precursor solution coating is larger than that of the Fe2O3 active layer but smaller than that of the bulk iron.

7. The method for preparing a high-efficiency composite electrode for the negative electrode of a supercapacitor according to claim 1, characterized in that: In step S3, a current density of 9.3 A / cm is applied using a DC power supply as the output source. 2 A DC power supply is used to generate instantaneous high-temperature Joule heating to rapidly sinter the corroded bulk iron substrate. The process lasts 10-15 seconds, resulting in an outer PrNi layer. x Fe 1-x O3 conductive active layer.

8. A method for preparing a high-efficiency composite electrode for a supercapacitor negative electrode according to claim 5 or 7, characterized in that: Repeated instantaneous high-temperature Joule heating technology to control the Fe2O3 active layer and PrNi x Fe 1-x Thickness of the O3 conductive active layer.

Images