A red mud-based capacitor electrode, capacitor, and preparation method and application

Abstract

The application discloses a kind of red mud-based capacitor electrode, capacitor and preparation method and application.Method with non-ionic polyacrylamide NPAM, deionized water, carbon nanotube, red mud as raw material, NPAM solution is prepared in turn, carbon nanotube-NPAM dispersion is prepared by ultrasonic, mixed into red mud and stirred to prepare slurry, then electrode is prepared by forming, drying, curing and impregnation treatment, and each raw material ratio interval is set.The application uses industrial solid waste red mud as matrix, realizes solid waste high-value resource utilization, solves the environmental pollution and land occupation problem caused by red mud stockpiling;By regulating and controlling the ratio of NPAM, carbon nanotube and red mud and matching preparation process, the electrode micro-pore structure is optimized, the ion transmission channel and electronic conduction network are constructed, the electrode internal resistance is reduced, the ion conductivity and electrochemical performance are improved, and the performance bottleneck of traditional red mud-based energy storage materials is broken.The performance of the prepared capacitor is improved, which can be applied to structural energy storage and building component energy storage field, and has environmental protection value and engineering application prospect.

Description

Technical Field

[0001] This invention relates to the fields of industrial solid waste resource utilization and electrochemical energy storage technology, and particularly to a red mud-based capacitor electrode, capacitor, preparation method and application. Background Technology

[0002] With the increasing demands for sustainable social development, the resource recycling and utilization of industrial solid waste has become a key research focus in the industry. Red mud is a major industrial byproduct generated during the alumina refining process from bauxite. Traditional stockpiling methods easily lead to environmental problems such as water and soil pollution and land resource occupation. Currently, developing red mud into building materials and electrochemical energy storage materials has become an important research direction for the high-value utilization of solid waste.

[0003] Existing red mud-based energy storage capacitors mostly use cement as the matrix and auxiliary molding material. Modification and control methods are limited, making it difficult to optimize the electrode's microporous structure. This generally results in uneven pore distribution and high ion transport resistance. Electrode systems prepared using this traditional method exhibit high internal resistance and low ionic conductivity, leading to limited improvements in the areal capacitance and energy density of the assembled capacitors. This restricts the potential for further electrochemical performance enhancement and fails to meet the practical application requirements of high-performance energy storage devices. Summary of the Invention

[0004] To address the environmental and resource problems caused by the large-scale stockpiling of red mud, and the technical shortcomings of existing red mud-based energy storage materials, such as uneven pore structure, high ion transport resistance, and poor electrochemical performance, this invention aims to provide a red mud-based capacitor electrode, capacitor, preparation method, and application. By controlling the ratio of nonionic polyacrylamide (NPAM), carbon nanotubes, and red mud, a continuous and low-torsion ion transport channel is constructed, reducing bulk resistance and interfacial impedance, and improving ionic conductivity and the number of electrochemical active sites. This invention aims to overcome the performance bottleneck of red mud-based materials in the energy storage field, realize the high-value green utilization of industrial solid waste red mud, and prepare red mud-based energy storage devices with high areal specific capacitance and high energy density. It provides high-performance core units for structural energy storage materials, building component energy storage systems, and other scenarios, promoting the technological integration of electrochemical energy storage and building materials.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows: This invention provides a method for preparing a red mud-based capacitor electrode, comprising the following steps: S1: Dissolve nonionic polyacrylamide (NPAM) in deionized water to obtain a homogeneous NPAM solution; S2: Add conductive carbon nanotubes to the NPAM solution obtained in S1 and disperse them by ultrasonication to obtain a conductive carbon nanotube-NPAM dispersion. S3: Add red mud to the conductive carbon nanotube-NPAM dispersion in S2 and stir to form a uniform slurry; S4: The obtained slurry is molded under constant pressure. After reaching the target pressure, it is demolded to obtain a green body. The green body is then dried, polished, and cured. S5: Immerse the cured electrode sheet in NPAM-KCl impregnation solution to obtain the red mud-based capacitor electrode; The mass ratio of the red mud to deionized water is 1:0.5; The carbon nanotubes account for 0.01%-0.2% of the mass of the red mud. The nonionic polyacrylamide accounts for 1%-5% of the red mud mass.

[0006] Furthermore, the specific steps of S4 are as follows: Weigh 3g of the slurry obtained from S3 and put it into a steel casting drum with an inner diameter of 20mm and a height of 25mm. Use a press to increase the pressure to the target pressure of 2kN at a speed of 0.2mm / min, load for 15min, and then unload the pressure to demold.

[0007] Furthermore, in the NPAM-KCl impregnation solution, NPAM accounts for 1%-5% of the mass of the KCl solution, and the molar concentration of the KCl solution is 1M.

[0008] Furthermore, the elemental content in the red mud is: C: 36.88%, O: 39.17%, Na: 4.62%, Mg: 0.18%, Al: 7.01%, Si: 1.68%, Ca: 0.15%, Ti: 1.31%, Fe: 9.01%, and the variation in elemental content is allowed not to exceed 1% of the content value.

[0009] Furthermore, the minerals in the red mud include hematite, quartz, corundum, nepheline, calcite, and perovskite.

[0010] Furthermore, the carbon nanotubes have an inner diameter of 3-5 nm, an outer diameter of 8-15 nm, a length of 3-12 μm, and a specific surface area of ​​≥250 m². 2 / g, density is 0.08g / cm³ 3 Resistivity: 80-100 mΩ·cm, Particle size: ≤7 μm.

[0011] In another aspect, the present invention provides a red mud-based capacitor electrode prepared by the method described above.

[0012] In another aspect, the present invention provides a capacitor comprising at least one pair of the aforementioned red mud-based capacitor electrodes, and an electrolyte layer disposed between the red mud-based capacitor electrodes, wherein the electrolyte layer is an alkaline electrolyte or a neutral salt electrolyte.

[0013] In another aspect, the present invention provides a method for assembling a capacitor having the aforementioned red mud-based capacitor electrodes, characterized in that: Graphite conductive paper is used as the current collector; The red mud-based capacitor electrode serves as the capacitor electrode. Glass fiber filter paper is used as the diaphragm; NPAM-KCl solution was used as the electrolyte; The red mud-based capacitor is assembled by stacking current collector-electrode-diaphragm-electrode-current collector in a layered manner.

[0014] In another aspect, the present invention provides the application of the red mud-based capacitor electrode or the red mud-based capacitor in structural energy storage materials, building component energy storage systems or concrete-based energy storage devices.

[0015] The beneficial effects of this invention are: (1) This invention uses industrial solid waste red mud as the core matrix raw material to prepare capacitor electrodes and capacitors, realizing the high-value resource utilization of red mud, effectively solving the environmental pollution and land occupation problems caused by red mud stockpiling, which is in line with the development concept of resource recycling and green and low-carbon, and provides a new technical path for the application of industrial solid waste in the field of electrochemical energy storage.

[0016] (2) By precisely controlling the ratio of nonionic polyacrylamide (NPAM), carbon nanotubes and red mud, and combining the synergistic control of ultrasonic dispersion, constant pressure molding and other processes, the present invention effectively optimizes the micropore structure of red mud-based capacitor electrodes, constructs continuous and low-torsional ion transport channels and electronic conduction networks, significantly reduces the bulk resistance of the electrodes, improves the ionic conductivity, and enables the prepared red mud-based capacitor electrodes to have excellent electrochemical transport performance, laying the structural foundation for the realization of high electrochemical performance of capacitors.

[0017] (3) The red mud-based capacitor prepared by the present invention exhibits significant advantages in electrochemical performance. Compared with the control system without optimized ratio and process, its area capacitance and energy density are greatly improved. It breaks through the technical bottleneck of uneven pore structure, large ion transport resistance and poor electrochemical performance of traditional red mud-based energy storage materials, and enhances the application value and competitiveness of red mud-based materials in the field of energy storage.

[0018] (4) The raw material system used in this invention is readily available, the preparation process and capacitor assembly process are simple to operate and the parameters are controllable. There are no special equipment requirements for each process step, and the raw material ratio range is clear, which is convenient for large-scale production and industrial application. At the same time, the core components of the capacitor and the electrolyte system are well matched, and the assembly structure is stable, providing a high-performance core energy storage unit for the research and development and application of structural energy storage materials, building component energy storage systems and concrete-based energy storage devices.

[0019] (5) This invention combines the preparation of red mud-based capacitor electrodes and capacitors with the field of building energy storage, realizing the effective integration of energy storage function and building material substrate. The prepared red mud-based capacitor can be directly applied to structural energy storage materials, building component energy storage systems and other scenarios, expanding the application field of electrochemical energy storage devices, providing new technical support for the development of building energy conservation and intelligent buildings, and has both good academic value and engineering application prospects. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 The image shows the XRD pattern of the red mud raw material used in the embodiments of the present invention. Figure 2 Here is a SEM image of the red mud raw material used in the embodiments of the present invention; Figure 3 This is an EDS image of the red mud raw material used in the embodiments of the present invention. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] The sources of some of the raw materials used in this application are shown in the table below. The remaining raw materials not listed are all commercially available conventional products.

[0024] Table 1 Source of Raw Materials

[0025] Example: Example 1: A method for preparing a red mud-based capacitor motor includes the following steps: S1: Dissolve 1.5 g of NPAM in 25 g of deionized water to obtain a homogeneous NPAM solution; S2: Add 0.005g of conductive carbon nanotubes to the NPAM solution obtained in S1, and then perform ultrasonic dispersion for 5min with an ultrasonic power of 500W to obtain carbon nanotube-NPAM dispersion. S3: Add red mud to the carbon nanotube-NPAM dispersion in S2 and mechanically stir for 5 minutes (magnetic stirrer, speed 1000 rpm) to form a uniform slurry; the mass ratio of red mud to deionized water (water-cement ratio) is 1:0.5; the mass of conductive material accounts for 0.01% of the mass of red mud, and the mass of nonionic polyacrylamide accounts for 3% of the mass of red mud; the carbon nanotubes have an inner diameter of 5 nm, an outer diameter of 15 nm, a length of 12 μm, and a specific surface area of ​​250 m². 2 / g, density is 0.08g / cm³ 3 Resistivity: 100 mΩ·cm, Particle size: 7 μm.

[0026] S4: Divide the obtained slurry into portions, weigh 3g of each portion, and put them into steel casting drums with an inner diameter of 20mm and a height of 25mm. Use a press to increase the pressure to 2kN at a speed of 0.2mm / min. After reaching the target pressure, load for 15min, then unload the pressure and demold to obtain multiple samples.

[0027] S5: Dry the demolded sample under vacuum at 60°C for 2 hours; S6: After drying the sample in S5, use 2000-grit sandpaper to polish the upper and lower surfaces to ensure that the electrode thickness is consistent (4.0 mm).

[0028] S7: Place the polished sample under standard curing conditions (temperature 20°C, relative humidity 95%) for 28 days.

[0029] S8: Place the cured electrode sheet in NPAM-KCl impregnation solution and soak it at 20℃ for 48 h to allow the electrolyte to fully penetrate the porous structure. In the NPAM-KCl impregnation solution, NPAM accounts for 5% of the mass of the KCl solution, and the molar concentration of the KCl solution is 1M.

[0030] XRD images of the red mud raw materials used are as follows: Figure 1 As shown, the main minerals in red mud include hematite, quartz, corundum, nepheline, calcite, and perovskite. SEM images of the red mud raw material are shown below. Figure 2As shown in the figure, the red mud raw material particles exhibit an irregular agglomerate morphology, composed of a large number of fine submicron-sized primary particles. The surface is rough and exhibits a distinct pore and void structure. The particle agglomerates have irregular crystal shapes and uneven size distribution. The primary particles constituting the agglomerates are mostly nanometer to submicron-sized, exhibiting a loose and porous agglomeration characteristic. This structure provides favorable pore channels for the dispersion and loading of conductive materials and the penetration of electrolytes during subsequent electrode fabrication. Figure 3 The red mud raw material shown is an EDS image. The elemental contents of the red mud raw material are: C: 36.88%, O: 39.17%, Na: 4.62%, Mg: 0.18%, Al: 7.01%, Si: 1.68%, Ca: 0.15%, Ti: 1.31%, Fe: 9.01%. In practical applications, the allowable variation of the above elements in the red mud raw material is no more than 1%.

[0031] Example 2 The difference from Example 1 is that in this example, the amount of conductive carbon nanotubes added is 0.05g (accounting for 0.1% of the red mud mass), while the other materials and preparation process are exactly the same as in Example 1.

[0032] Example 3 The difference from Example 2 is that in this example, the amount of conductive carbon nanotubes added is 0.1g (accounting for 0.2% of the red mud mass), while the other materials and preparation process are exactly the same as in Example 2.

[0033] Example 4 The difference from Example 2 is that in this example, the amount of NPAM added is 0.5g (accounting for 1% of the red mud mass), while the other materials and preparation process are exactly the same as in Example 2.

[0034] Example 5 The difference from Example 2 is that in this example, the amount of NPAM added is 2.5g (accounting for 5% of the red mud mass), while the other materials and preparation process are exactly the same as in Example 2.

[0035] Comparative Example Comparative Example 1 The difference from Example 2 is that no conductive material was added in step S2 in this comparative example.

[0036] Comparative Example 2 The difference from Example 2 is that in this comparative example, the mass of the conductive material carbon nanotubes added in step S2 is 0.2g (accounting for 0.40% of the mass of red mud).

[0037] Comparative Example 3 The difference from Example 2 is that in this comparative example, NPAM was not added in step S1, and only deionized water was prepared.

[0038] Comparative Example 4 The difference from Example 2 is that in this comparative example, the mass of NPAM in step S1 is 3.5g (accounting for 7% of the mass of red mud).

[0039] Comparative Example 5 The difference from Example 2 is that in this comparative example, the carbon nanotube-NPAM dispersion was prepared by manually stirring for 5 minutes in step S2.

[0040] Comparative Example 6 The difference from Example 2 is that in this comparative example, mechanical stirring for 5 minutes was performed in step S2 to obtain a carbon nanotube-NPAM dispersion. The mechanical stirrer was a magnetic stirrer with a rotation speed of 1000 revolutions per minute.

[0041] Comparative Example 7 The difference from Example 2 is that in this comparative example, the target pressure in step S4 is 5kN.

[0042] Comparative Example 8 The difference from Example 2 is that in this comparative example, the conductive material in step S2 is graphite powder of equal mass.

[0043] The composition of the raw materials in Examples 1-5 and Comparative Examples 1-8 is shown in Table 2.

[0044] Table 2 Composition of raw materials in Examples 1-5 and Comparative Examples 1-8

[0045] Performance testing The capacitors were assembled using the methods described below for examples 1-5 and comparative examples 1-8. A red mud-based capacitor is constructed by stacking and assembling a current collector using graphite conductive paper, a red mud-based capacitor electrode, a glass fiber filter paper membrane, and an NPAM-KCl solution as the electrolyte, according to the current collector-electrode-membrane-electrode-current collector structure.

[0046] 1. Perform the following performance tests on the provided capacitor: All electrochemical experiments were conducted in an indoor environment. A Bio-Logic SP-300 electrochemical workstation was used, and a dual-electrode system was employed to analyze the capacitors using cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS).

[0047] CV measurements were performed at five different scan rates within a potential window of 0-1V: 20mV / s. GCD measurements were performed within a voltage window of 0-1V at a current density of 1mA / cm².

[0048] EIS testing was performed at open-circuit potential, with a frequency range of 0.01 Hz to 100 kHz. Area ratio capacitance. Calculate using the following formula:

[0049] In the formula, Current (mA) The discharge time (s) is the discharge time. The electrode area is (cm²). The potential window is (V).

[0050] Integrating capacitor in cyclic voltammetry (CV) test Calculated by the following formula:

[0051] in I ( U The response current is (mA). u The scan rate for cyclic voltammetry is expressed in mV / s.

[0052] Energy density (Wh / m 2 The calculation formula for ) is as follows:

[0053] In the formula For discharge voltage window, S Let be the area of ​​the capacitor.

[0054] 2. Test Results: The test results are shown in Tables 3 to 5.

[0055] Table 3 EIS Test Data Analysis

[0056] Table 4. Integrating capacitance at a scan rate of 20mV / s

[0057] Table 5. Calculation of various performance parameters using GCD curves.

[0058] As shown in Tables 3 to 5, the material system constructed in this invention exhibits a significant synergistic effect among red mud, carbon nanotubes, and nonionic polyacrylamide. Among the various examples and comparative examples, Example 2 demonstrates the best overall performance, indicating the rationality of the selection of raw material types and their dosage ranges in this invention. Specifically, in Example 2, the amount of carbon nanotubes added was 0.05 g, accounting for 0.10% of the red mud mass, and the amount of nonionic polyacrylamide added was 1.5 g, accounting for 3.00% of the red mud mass. This optimal ratio can achieve precise matching and efficient synergy of electron transport, ion migration and interfacial energy storage in the system, and optimize the energy storage characteristics of the electrode from the microstructure. An appropriate amount of carbon nanotubes can build a continuous and stable three-dimensional electronic conductive network between the red mud particles, which greatly reduces the resistance to electron transport and realizes rapid electron conduction. An appropriate amount of nonionic polyacrylamide can fully disperse carbon nanotubes, avoid filler agglomeration, and optimize the porous structure inside the electrode, improve the liquid retention capacity of the pores, reduce the resistance to ion migration in the electrolyte, and ensure efficient ion diffusion and transport. The regular and unobstructed porous structure can fully expose the energy storage active sites of the red mud matrix, maximizing the adsorption energy storage and charge storage capacity of the electrode interface. The red mud matrix, carbon nanotubes, and nonionic polyacrylamide (NPAM) work synergistically and complementarily to effectively improve the inherent defects of traditional red mud-based electrodes, such as poor conductivity, disordered pore structure, and low energy storage site utilization. This allows the system to achieve an optimal state of unimpeded electron transport, high ion migration efficiency, and high interfacial energy storage utilization. Therefore, the material system with this ratio has an Rs of 11.18 Ω, an ionic conductivity of 14.60 mS / cm, and an areal capacitance of 45.10 mF / cm at a scan rate of 20 mV / s. 2 The GCD isoprenaline capacitance is 168.80 mF / cm². 2 The energy density is 0.0229 mWh / cm³. 2 All performance indicators are superior to those of other embodiments and comparative examples, ultimately achieving a significant improvement in the overall electrochemical performance of the red mud-based capacitor.

[0059] Comparing Example 2 with Comparative Example 1, it can be seen that when no conductive material is added in step S2, the system Rs increases to 50.52 Ω, the ionic conductivity decreases to 3.23 mS / cm, and the CV areal capacitance and GCD areal capacitance are only 18.45 mF / cm. 2 and 70.35 mF / cm 2The results were significantly lower than in Example 2. This demonstrates that the introduction of conductive materials plays a crucial role in reducing the internal resistance of the system, establishing electron transport pathways, and improving energy storage performance. Therefore, the electron transport pathways within the electrode are fully connected, significantly reducing the system's contact and transport resistance, and substantially improving charge transport efficiency and ion migration capability. The active sites for electrode energy storage are fully utilized, ultimately effectively improving the specific capacitance, ionic conductivity, and energy density of the red mud-based capacitor, resulting in a significant improvement in overall electrochemical energy storage performance. Furthermore, combining Examples 1, 2, and 3, it is evident that when the amount of carbon nanotubes added is increased from 0.005 g in Example 1 to 0.05 g in Example 2, the system impedance significantly decreases, and the areal capacitance significantly increases. However, when the amount of carbon nanotubes added is further increased to 0.1 g, the CV areal capacitance and GCD areal capacitance decrease instead. This indicates that when the amount of carbon nanotubes added is too low, it is difficult to form a continuous and effective conductive network in the red mud matrix; while when the amount added is too high, local agglomeration or accumulation is likely to occur, which is detrimental to pore structure connectivity and ion diffusion, thus weakening the energy storage performance. The optimal addition amount of carbon nanotubes is 0.10% of the red mud mass (Example 2). Comparing Example 2 with Comparative Example 8, it can be seen that, under the condition of the same amount of conductive material added, after replacing carbon nanotubes with graphite powder, the system Rs increases to 25.45 Ω, the ionic conductivity decreases to 6.42 mS / cm, and the CV areal capacitance and GCD areal capacitance decrease to 22.41 mF / cm, respectively. 2 and 83.45 mF / cm 2 The results showed that carbon nanotubes were significantly lower than those in Example 2, indicating that carbon nanotubes were more effective than graphite powder in constructing continuous conductive pathways between red mud particles. Carbon nanotubes, with their one-dimensional tubular high aspect ratio structure, could interweave and overlap between scattered red mud particles, creating a three-dimensional, interconnected conductive network with abundant contact points. This resulted in excellent continuity of the conductive pathways and extremely low transmission resistance. In contrast, graphite powder, being two-dimensional sheet-like particles, exhibited poor dispersion and random particle overlap, making it prone to conductive pathway breakage and localized conductive dead zones. This made it unsuitable for forming a stable and efficient electron transport system, leading to increased electrode internal resistance, hindered ion transport, and a significant decrease in energy storage performance. Therefore, this invention uses carbon nanotubes as the conductive material. Comparing Example 2 with Comparative Example 3, it can be seen that when nonionic polyacrylamide was not added in step S1, the system Rs increased to 37.54 Ω, the ionic conductivity decreased to 4.35 mS / cm, and the CV areal capacitance and GCD areal capacitance were only 19.85 mF / cm. 2 and 77.54 mF / cm 2The values ​​were significantly lower than in Example 2. This indicates that the introduction of nonionic polyacrylamide helps improve the charge transport conditions of the material system and enhances its energy storage performance. Further analysis of Examples 4, 2, and 5 shows that when the amount of nonionic polyacrylamide added increased from 0.5 g to 1.5 g, the system's Rs decreased from 17.54 Ω to 11.18 Ω, the ionic conductivity increased from 9.31 mS / cm to 14.60 mS / cm, and the GCD areal capacitance increased from 95.27 mF / cm. 2 Increased to 168.80 mF / cm 2 When the amount added was further increased to 2.5 g, Rs increased to 21.85 Ω, ionic conductivity decreased to 7.47 mS / cm, and GCD areal capacitance decreased to 111.54 mF / cm. 2 The results indicate that insufficient addition of nonionic polyacrylamide has limited effect on improving the dispersion state, interfacial structure, and pore liquid retention environment of the system; while excessive addition leads to increased viscosity of the system, partial coating of active interfaces, and hindrance to ion migration. Therefore, the optimal addition amount of nonionic polyacrylamide is 3.00% of the red mud mass. In this invention, nonionic polyacrylamide does not function as a conductive component, but primarily improves the dispersion of carbon nanotubes in the system, enhances slurry stability, strengthens liquid retention in pores, and optimizes the ion migration environment. Compared to charged polyacrylamide, nonionic polyacrylamide does not contain fixed ionic groups in its molecular chain. While improving dispersion and interfacial states, it is less likely to significantly disturb the existing ion transport environment of the system, making it more suitable for application in the red mud-based energy storage material system described in this invention. This demonstrates that the selection of nonionic polyacrylamide in this invention is not arbitrary, but rather based on a comprehensive consideration of material transport behavior and interfacial stability.

[0060] Comparative Examples 5 and 6 show that, under the condition that the types and proportions of raw materials are basically the same, compared with the manual stirring in Comparative Example 5, the carbon nanotube-nonionic polyacrylamide dispersion prepared by mechanical stirring in Comparative Example 6 showed that the system Rs decreased from 15.64 Ω to 13.28 Ω, the ionic conductivity increased from 10.44 mS / cm to 12.29 mS / cm, and the GCD areal capacitance increased from 121.05 mF / cm. 2 Increased to 149.56 mF / cm 2 However, the areal capacitance of Comparative Examples 5 and 6 was still lower than that of Example 2 under ultrasonic dispersion conditions, indicating that ultrasonic dispersion conditions are more conducive to the uniform distribution of carbon nanotubes in the red mud matrix and the formation of a continuous conductive network, thereby further improving the overall performance of the system. Furthermore, comparing Example 2 with Comparative Example 7, it can be seen that when the target pressure in step S4 is increased to 5 kN, the system Rs increases to 29.45 Ω, the ionic conductivity decreases to 5.54 mS / cm, and the GCD areal capacitance decreases to 90.14 mF / cm. 2 This demonstrates that excessive molding pressure leads to over-compaction of the internal pore structure of the material, hindering electrolyte penetration and ion migration, thereby affecting the effective utilization of the energy storage interface. Therefore, it can be further explained that the performance advantages obtained by this invention are not solely due to the selection of a single conductive filler or a single additive component, but rather to the combined effect of the adaptation and synergistic action of the carbon nanotube conductive component, the NPAM interface regulating component, and the ultrasonic dispersion and low-pressure molding process. In this invention, red mud mainly provides a porous framework and energy storage interface carrier, carbon nanotubes are used to construct an electron conduction network, and nonionic polyacrylamide is used to improve the dispersion state, enhance the liquid retention capacity, and optimize the ion migration environment. The three work together to enable the material system to have low impedance, high ionic conductivity, and superior energy storage performance.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a red mud-based capacitor electrode, characterized in that, Includes the following steps: S1: Dissolve nonionic polyacrylamide (NPAM) in deionized water to obtain an NPAM solution; S2: Add conductive carbon nanotubes to the NPAM solution obtained in S1 and disperse them by ultrasonication to obtain a conductive carbon nanotube-NPAM dispersion. S3: Add red mud to the conductive carbon nanotube-NPAM dispersion in S2 and stir to form a uniform slurry; S4: The obtained slurry is molded under constant pressure. After reaching the target pressure, it is demolded to obtain a green body. The green body is then dried, polished, and cured. S5: Immerse the cured electrode sheet in NPAM-KCl impregnation solution to obtain the red mud-based capacitor electrode; The mass ratio of the red mud to deionized water is 1:0.5; The carbon nanotubes account for 0.01%-0.2% of the mass of the red mud. The nonionic polyacrylamide accounts for 1%-5% of the red mud mass.

2. The method for preparing the red mud-based capacitor electrode according to claim 1, characterized in that, The specific steps of S4 are as follows: Weigh 3g of the slurry obtained from S3 and put it into a steel casting drum with an inner diameter of 20mm and a height of 25mm. Use a press to increase the pressure to the target pressure of 2kN at a speed of 0.2mm / min, load for 15min, and then unload the pressure to demold.

3. The method for preparing the red mud-based capacitor electrode according to claim 1, characterized in that, In the NPAM-KCl impregnation solution, NPAM accounts for 1%-5% of the mass of the KCl solution, and the molar concentration of the KCl solution is 1M.

4. The method for preparing the red mud-based capacitor electrode according to claim 1, characterized in that, The elemental content of the red mud is as follows: C: 36.88%, O: 39.17%, Na: 4.62%, Mg: 0.18%, Al: 7.01%, Si: 1.68%, Ca: 0.15%, Ti: 1.31%, Fe: 9.01%, and the elemental content variation is allowed not to exceed 1% of the content value.

5. The method for preparing the red mud-based capacitor electrode according to claim 1, characterized in that, The minerals in the red mud include hematite, quartz, corundum, nepheline, calcite, and perovskite.

6. The method for preparing the red mud-based capacitor electrode according to claim 1, characterized in that, The carbon nanotubes have an inner diameter of 3-5 nm, an outer diameter of 8-15 nm, a length of 3-12 μm, and a specific surface area of ​​≥250 m². 2 / g, density is 0.08g / cm³ 3 Resistivity: 80-100 mΩ·cm, Particle size: ≤7 μm.

7. A red mud-based capacitor electrode prepared by the method as described in claim 1.

8. A capacitor, characterized in that, It includes at least one pair of red mud-based capacitor electrodes as described in claim 7, and an electrolyte layer disposed between the red mud-based capacitor electrodes, wherein the electrolyte layer is an alkaline electrolyte or a neutral salt electrolyte.

9. The application of the red mud-based capacitor electrode as described in claim 7 or the red mud-based capacitor as described in claim 8 in structural energy storage materials, building component energy storage systems or concrete-based energy storage devices.

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