A preparation method of cement-based supercapacitor based on static pressure molding

Abstract

The present invention belongs to the technical field of supercapacitors, and specifically relates to a method for preparing cement-based supercapacitors based on static pressure molding. The present invention achieves physical compaction and optimization of high-carbon content slurry by applying uniform static pressure, ensuring the connectivity of the conductive network of the carbon cement matrix electrode and the optimization of its pore structure. The final electrode material exhibits excellent energy storage performance and mechanical strength, achieving a balance between capacitance performance and mechanical properties. After treatment by this method, when the molding pressure is 4 MPa, the area specific capacitance can reach 817.3 mF / cm 2 The mechanical strength of the electrode after 28 days of curing was 12.7 MPa. Compared with traditional processes, this method significantly balances the electrochemical and mechanical properties of cement-based supercapacitors, meeting the practical application requirements of integrated building-energy storage functions.

Description

Technical Field

[0001] The present invention belongs to the technical field of supercapacitors, and in particular relates to a preparation method of a cement-based supercapacitor based on static pressure molding. Background Art

[0002] The information disclosed in the background of the invention is only intended to enhance understanding of the overall background of the invention and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] Currently, the global energy transition is accelerating from fossil fuels to green renewable energy sources such as wind, solar, and hydropower. In this transition process, efficiently storing unstable renewable energy power has become a core challenge in achieving its large-scale application. Existing mainstream energy storage technologies each have limitations: lithium battery energy storage systems face problems such as high production costs, short cycle life, and environmental pollution; mechanical energy storage methods such as pumped storage are subject to geographical constraints and ecological impacts; and technologies such as thermal energy storage still have room for improvement in energy conversion efficiency. In contrast, supercapacitors, which combine fast charging and discharging characteristics, ultra-long cycle life, and environmental friendliness, are expected to become a new solution to break through the bottleneck of renewable energy storage.

[0004] Cement-based supercapacitors are a novel electrochemical energy application technology designed by combining hardened cement paste as a solid electrolyte with traditional supercapacitor technology. As a novel energy storage device, the performance of cement-based supercapacitors depends primarily on the performance of the electrodes and the ion transport properties within the cement matrix. By utilizing the pore fluid within the cement as the electrolyte, they can avoid environmental contamination caused by electrolyte leakage.

[0005] In existing cement-based supercapacitor technology, structural designs are primarily categorized into two types: layered and embedded. The layered structure employs a top-down pouring of the anode, electrolyte, and cathode, with both cathode and cathode constructed from cement-based composite materials. Embedded structures, on the other hand, embed the anode and cathode electrode materials within an electrolyte matrix. Current research and development of cement-based supercapacitors primarily relies on layered structures. Their conductive properties typically rely on incorporating a specific proportion of carbon materials (such as graphite, carbon black, or activated carbon) into the cement matrix to create an effective conductive network. In existing cement-based supercapacitor fabrication processes, the incorporation of large amounts of carbon materials into the cement paste significantly increases paste viscosity and reduces fluidity, leading to uneven molding and weakening structural density, significantly reducing mechanical strength after curing. Furthermore, water absorption by the carbon material makes it difficult to precisely control the porosity and pore size distribution of the carbon-cement electrode, which can easily lead to pore occlusion or collapse, restricting ion diffusion within the electrode and reducing capacitance performance. Furthermore, existing pressure forming processes only consider the impact on the mechanical properties of cement materials, without considering the impact of pressure-induced changes in pore structure on the energy storage performance of supercapacitors. Currently, cement-based supercapacitors can only choose between high strength and high capacitance, making it difficult to achieve a balance between mechanical and energy storage performance, limiting their application and promotion. Summary of the Invention

[0006] In response to the shortcomings of the prior art, the present invention aims to provide a method for preparing cement-based supercapacitors using static pressure molding. By applying uniform static pressure, physical compaction and optimization of the high-carbon content slurry are achieved, ensuring the conductive network connectivity and pore structure optimization of the carbon-cement matrix electrode. Without changing the composition of the carbon-cement matrix electrode, the mechanical strength of the carbon-cement matrix electrode is increased, while the energy storage performance of the carbon-cement matrix electrode is improved, thereby achieving the desired balance between high strength and high capacitance for cement-based supercapacitors.

[0007] In order to achieve the above object, the technical solution of the present invention is:

[0008] The present invention provides a method for preparing a cement-based supercapacitor based on static pressing, comprising the following steps:

[0009] (1) mixing carbon black powder and cement to obtain a uniform premix, adding water to the premix and mixing uniformly to obtain a water-containing premix;

[0010] (2) Pour the water-containing premix into the mold and apply a pressure of 2-8 MPa for static pressure molding. After demolding, the formed cement matrix is ​​obtained. After curing and shaping, it is dried and polished;

[0011] (3) The two polished cement substrates are immersed in the electrolyte to allow them to absorb the electrolyte. After saturation, they are taken out and used as the positive electrode and negative electrode respectively. The positive electrode and negative electrode are combined with the glass fiber membrane soaked in the electrolyte and the conductive graphite paper to make a cement-based supercapacitor.

[0012] In some embodiments, in step (1), the carbon black powder is acetylene black or Ketjen black, with a specific surface area of ​​200m 2 / g to 1400m 2 / g; the cement is silicate cement or sulphoaluminate cement with a strength grade of 425 or above.

[0013] In some embodiments, in step (1), the stirring is mechanical stirring, and the stirring time is 5-10 min.

[0014] In some embodiments, in step (1), the water-cement ratio is the mass ratio of water to cement, and the water-cement ratio is between 0.2 and 0.4. The water-cement ratio can be any value between 0.2 and 0.4, such as 0.21, 0.22, 0.23, 0.24, 0.25, ... 0.3, 0.31, 0.32, ... 0.37, 0.38, 0.39, etc. The carbon-ash ratio is the mass ratio of carbon black to cement, and the carbon-ash ratio does not exceed 0.2, and is preferably between 0.15 and 0.2. For example, the carbon-ash ratio can be 0.19, 0.18, 0.17, 0.16, etc. If the water-cement ratio is too low, the cement hydration reaction is restricted, and the structural strength is reduced. If the water-cement ratio is too high, the porosity increases and the strength is reduced. If the carbon-ash ratio is too high, it will interfere with the continuity and density of cement hydration products, weaken the bonding ability between matrix phases, and ultimately lead to a decrease in strength; if the carbon-ash ratio is too low, it will be difficult to form a continuous conductive network inside the material, reducing the charge transfer efficiency and weakening the electrochemical energy storage capacity.

[0015] In some embodiments, in step (2), the static pressing time is 10-30 s; the pressing thickness is 0.4-2 cm. The static pressing pressure can be any value in the range of 2-8 MPa, such as 3 MPa, 4 MPa, 5 MPa, 6 MPa, 7 MPa, 8 MPa, etc. Applying uniform static pressure can achieve physical compaction and optimization of high-carbon content slurry, uniform molding and structural density improvement of high-carbon content electrodes, ensure the conductive network connectivity, pore structure and ion diffusion of the carbon cement matrix electrode, and exhibit excellent energy storage performance and mechanical strength.

[0016] In some embodiments, in step (2), the curing process is as follows: the formed cement matrix is ​​cured in water at 20±1°C for 25-30 days. This ensures that the cement is fully hydrated and improves its structural stability. If the curing temperature is too low, the hydration reaction is slow and the early strength development is insufficient. If the curing temperature is too high, the hydration reaction is accelerated, but it may lead to uneven microstructure and affect long-term strength.

[0017] In some embodiments, in step (3), the electrolyte is a 1-3 mol / L potassium chloride solution, and the soaking time is 10-15 hours.

[0018] In some embodiments, in step (3), the glass fiber membrane has a thickness of 0.5-1 mm; and the conductive graphite paper has a thickness of 0.5-1.5 mm.

[0019] In some embodiments, the specific operation of step (3) is as follows: immersing two polished cement substrates in an electrolyte to allow them to fully absorb the electrolyte, removing them after saturation, removing excess electrolyte from the surface of the cement substrate, and then affixing conductive graphite paper to one side of the surface of each cement substrate and connecting them to the other side of the conductive graphite paper with a wire, so that the two cement substrates serve as the positive electrode and the negative electrode, respectively. The positive electrode and the negative electrode are combined with the glass fiber membrane soaked in the electrolyte and the conductive graphite paper to form a cement-based supercapacitor.

[0020] The beneficial effects of the present invention are:

[0021] The present invention proposes a preparation method for cement-based supercapacitors based on static pressure molding, which uses a static pressure molding process to achieve stable molding and production of carbon cement electrodes, proving that pressure not only improves the mechanical properties of carbon cement matrix electrodes, but also improves the energy storage performance of carbon cement matrix electrodes. This technology achieves uniform molding and structural density improvement of high-carbon content electrodes by applying uniform static pressure, ensuring the connectivity of the conductive network, pore structure and diffusion path of ions in the carbon cement matrix electrode, achieving an effective balance between mechanical properties and energy storage performance, and showing excellent energy storage performance and mechanical strength. After treatment by this process, when the molding pressure is 4 MPa, the area specific capacitance can reach 817.3 mF / cm 2 The mechanical strength of the electrode after 28 days of curing is 12.7 MPa. Compared with the traditional non-static pressing process, this technology significantly balances the electrochemical and mechanical properties of cement-based supercapacitors, meeting the practical application requirements of building-energy storage integration. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0023] Figure 1 Schematic diagram of the process for preparing cement-based supercapacitors based on static pressure process.

[0024] Figure 2 This is a graph showing the compressive strength of the carbon cement matrix electrodes prepared in Examples 1-4 at different curing periods.

[0025] Figure 3 The pore distribution diagram of the carbon cement matrix electrodes prepared in Examples 1-4 under different pressures.

[0026] Figure 4 The constant current charge and discharge curves of the cement-based supercapacitors prepared in Examples 1-4 are shown.

[0027] Figure 5 The area specific capacitance diagram of the cement-based supercapacitors prepared in Examples 1-4.

[0028] Figure 6 The cyclic voltammetry curves of the cement-based supercapacitors prepared in Examples 1-4 are shown.

[0029] Figure 7 This is a constant current charge and discharge curve of the cement-based supercapacitor prepared in Example 5.

[0030] Figure 8 This is the cyclic voltammetry curve of the cement-based supercapacitor prepared in Example 5.

[0031] Figure 9 This is a constant current charge and discharge curve of the cement-based supercapacitor prepared in Comparative Example 1.

[0032] Figure 10 This is the cyclic voltammetry curve of the cement-based supercapacitor prepared in Comparative Example 1.

[0033] Figure 11 This is a constant current charge and discharge curve of the cement-based supercapacitor prepared in Comparative Example 2.

[0034] Figure 12 This is the cyclic voltammetry curve of the cement-based supercapacitor prepared in Comparative Example 2. DETAILED DESCRIPTION

[0035] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0036] The present invention will be further described below with reference to the embodiments.

[0037] Example 1:

[0038] The process of preparing cement-based supercapacitors based on static pressure process is as follows Figure 1 As shown, the specific steps include:

[0039] (1) Uniform mixing of carbon black and cement:

[0040] The specific surface area is selected as 250 m 2 / g of acetylene black and PI 525 Portland cement were mixed in a mass ratio of 1:5 and mechanically stirred for 10 minutes to fully mix to obtain a uniform premix. Water was added to the premix to control the water-cement ratio to 0.2 and mixed uniformly to obtain a water-containing premix.

[0041] (2) Static pressure forming:

[0042] The aqueous premix was poured into a mold and statically pressed to a thickness of 1 cm, applying a pressure of 2 MPa for 30 seconds. The molded carbon-cement matrix was then removed and cured in water at 20°C for 28 days. After 28 days of curing, the matrix was dried and the surface smoothed using 1000-grit sandpaper.

[0043] (3) Electrode assembly and packaging:

[0044] Two polished carbon cement substrates and a 0.6 mm thick glass fiber separator were immersed in a 1 mol / L potassium chloride electrolyte for 12 hours to allow for sufficient electrolyte absorption. The carbon cement substrates were then removed from the electrolyte and the residual solution wiped dry. Conductive graphite paper was then attached to one side of each carbon cement substrate and connected to the other side of the conductive graphite paper with a wire, with the two cement substrates serving as the positive and negative electrodes, respectively. The positive and negative electrodes, along with the electrolyte-soaked glass fiber membrane and 1 mm thick conductive graphite paper, were combined to form a cement-based supercapacitor, which was tested using a Gamry Interface 1010 electrochemical workstation.

[0045] Example 2

[0046] The operation was the same as in Example 1, but static pressure molding was performed by applying a pressure of 4 MPa.

[0047] Example 3

[0048] The operation was the same as in Example 1, but static pressure molding was performed by applying a pressure of 6 MPa.

[0049] Example 4

[0050] The operation was the same as in Example 1, but static pressure molding was performed by applying a pressure of 8 MPa.

[0051] Example 5

[0052] (1) Uniform mixing of carbon black and cement:

[0053] The specific surface area is selected as 250 m 2 / g acetylene black and PI 525 Portland cement were mixed at a mass ratio of 3:20 and mechanically stirred for 10 minutes to fully mix to obtain a uniform premix. Water was added to the premix to control the water-cement ratio to 0.4 and mixed uniformly to obtain a water-containing premix.

[0054] (2) Static pressure forming:

[0055] The aqueous premix was poured into a mold and statically pressed to a thickness of 1 cm, applying a pressure of 2 MPa for 10 seconds. The molded carbon-cement matrix was then removed and cured in water at 20°C for 28 days. After 28 days of curing, the matrix was dried and the surface smoothed using 1000-grit sandpaper.

[0056] (3) Electrode assembly and packaging:

[0057] Two polished carbon cement substrates and a 0.6mm-thick glass fiber separator were immersed in a 3mol / L potassium chloride electrolyte for 15 hours to allow for sufficient electrolyte absorption. The carbon cement substrates were then removed from the electrolyte and the residual solution on the surface wiped dry. Conductive graphite paper was then attached to one side of each carbon cement substrate and connected to the other side of the conductive graphite paper with a wire, with the two cement substrates serving as the positive and negative electrodes, respectively. The positive and negative electrodes, along with the electrolyte-soaked glass fiber membrane and 1mm-thick conductive graphite paper, were combined to form a cement-based supercapacitor, which was tested using a Gamry Interface 1010 electrochemical workstation.

[0058] Comparative Example 1

[0059] The operation was the same as in Example 1, but static pressure molding was performed by applying a pressure of 10 MPa.

[0060] Comparative Example 2

[0061] (1) Uniform mixing of carbon black and cement:

[0062] The specific surface area is selected as 250 m 2 / g acetylene black and PI 525 Portland cement were mixed at a mass ratio of 1:5 and mechanically stirred for 10 minutes to fully mix to obtain a uniform premix. Water was added to the premix to control the water-cement ratio to 1.4 and mixed uniformly to obtain a water-containing premix.

[0063] (2) Traditional molding:

[0064] The aqueous slurry was poured into a 2 × 2 × 1 cm mold in two separate batches. After each pour, the sample was vibrated 60 times to remove air bubbles and ensure sample density and structural consistency. The molded carbon-cement matrix was then removed and cured in 20°C water for 28 days. After 28 days of curing, the matrix was dried and the surface smoothed using 1000-grit sandpaper.

[0065] (3) Electrode assembly and packaging:

[0066] Two polished carbon cement substrates and a 0.6 mm thick glass fiber separator were immersed in a 1 mol / L potassium chloride electrolyte for 12 hours to allow for sufficient electrolyte absorption. The carbon cement substrates were then removed from the electrolyte and the residual solution on the surface wiped dry. Graphite paper was then attached to one side of each carbon cement substrate and connected to the other side of the graphite paper with a wire, with the two cement substrates serving as the positive and negative electrodes, respectively. The positive and negative electrodes, along with the electrolyte-soaked glass fiber membrane and 1 mm thick conductive graphite paper, were combined to form a cement-based supercapacitor, which was tested using a Gamry Interface 1010 electrochemical workstation.

[0067] The effect data of Examples 1-5 and Comparative Examples 1-2 are shown in Table 1 below:

[0068] Table 1 Effect data table of various embodiments and comparative examples

[0069]

[0070] Performance Comparison

[0071] The compressive strength of the carbon cement matrix electrodes prepared in Examples 1-4 at different curing periods is as follows: Figure 2 As shown in the figure, the longer the curing time, the stronger the compressive properties of the carbon-cement-based electrode. Furthermore, as the molding pressure increases, the compressive properties of the carbon-cement-based electrode also increase, showing a clear trend towards structural densification. After 28 days of curing and a pressure of 8 MPa, the compressive strength of the electrode increases to 17.8 MPa, fully demonstrating the effectiveness of the static pressing process in enhancing the mechanical properties of carbon-cement-based electrodes.

[0072] The pore distribution of the carbon cement matrix electrodes prepared in Examples 1-4 under different pressures is shown in FIG. Figure 3 As shown in the figure, it can be seen that with the gradual increase in molding pressure, the overall porosity of the carbon-cement matrix electrode shows a downward trend, especially the number of pores with a pore size greater than 50 nm decreases significantly. This shows that molding pressure has a significant regulatory effect on the electrode pore structure. Higher molding pressure helps optimize the pore distribution of carbon-cement matrix electrodes and improves structural density, but it also hinders the diffusion of electrolyte ions and affects the electrochemical performance of the material.

[0073] The charge and discharge curves of the cement-based supercapacitors prepared in Examples 1-4 are as follows: Figure 4 As shown, the area specific capacitance of the cement-based supercapacitors prepared in Examples 1-4 is as follows Figure 5 As shown. Figure 4 It can be observed that the cement-based supercapacitor based on the static pressing process has a stable charging and discharging process. Figure 5 It can be observed that with the increase of applied pressure, the area specific capacitance of cement-based supercapacitor shows a trend of first increasing and then decreasing, and finally tends to be stable. When the molding pressure is 4 MPa, the area specific capacitance is the highest at 817.3 mF / cm 2 This change indicates that appropriate static pressing pressure helps optimize the microstructure of the electrode and improve its energy storage performance. However, excessive pressure may lead to excessive compaction of the electrode pore structure, limiting the effective transport of ions and thus reducing the capacitance performance. Therefore, it is necessary to control the appropriate molding pressure to achieve a balance between the mechanical properties and energy storage performance of cement-based supercapacitors.

[0074] The cyclic voltammetry curves of the cement-based supercapacitors prepared in Examples 1-4 are as follows: Figure 6 At a scan rate of 10 mV / s, the cyclic voltammetry curve of the cement-based supercapacitor exhibits a typical spindle-shaped characteristic, with a steep slope at the end of charge and at the potential reversal point, indicating good electrochemical response and rapid charge transfer. This characteristic reflects its excellent kinetic performance and high reversibility, making it suitable for high-power output scenarios such as rapid charge and discharge.

[0075] The carbon cement matrix electrode prepared in Example 5 had a compressive strength of 9.7 MPa and an area specific capacitance of 672.2 mF / cm after 28 days of curing. 2 The charge-discharge curves and cyclic voltammetry curves of the cement-based supercapacitor prepared in Example 5 are as follows: Figure 7 、 Figure 8 shown.

[0076] The carbon cement matrix electrode prepared in Comparative Example 1 has a compressive strength of 20.5 MPa after 28 days of curing (which is somewhat improved compared to Examples 1-4), but the area specific capacitance of the cement-based supercapacitor is 615.6 mF / cm 2 (lower than Examples 1-4), the charge-discharge curves and cyclic voltammetry curves of the cement-based supercapacitor prepared in Comparative Example 1 are as follows: Figure 9 、 Figure 10 The carbon cement matrix electrode prepared in Comparative Example 2 has a compressive strength of 4.8 MPa after 28 days of curing (significantly lower than that of Examples 1-4), and the area specific capacitance of the cement-based supercapacitor is 311.9 mF / cm 2(Comparative Example 1-4 is greatly reduced), the charge-discharge curve and cyclic voltammetry curve of the cement-based supercapacitor prepared in Comparative Example 2 are as follows: Figure 11 、 Figure 12 Therefore, this technology significantly improves the electrochemical and structural properties of cement-based supercapacitors.

[0077] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for preparing a cement-based supercapacitor based on static pressure molding, characterized in that: The following steps are involved: (1) mixing carbon black powder and cement to obtain a uniform premix, adding water to the premix and mixing uniformly to obtain a water-containing premix; wherein the carbon-to-ash ratio is 0.15-0.2; (2) Pour the water-containing premix into the mold and apply a pressure of 2-8 MPa for static pressure molding. After demolding, the formed cement matrix is ​​obtained. After curing and shaping, it is dried and polished. The static pressure molding time is 10-30s. (3) The two polished cement substrates are immersed in the electrolyte to allow them to absorb the electrolyte. After saturation, they are taken out and used as the positive electrode and negative electrode respectively. The positive electrode and negative electrode are combined with the glass fiber membrane soaked in the electrolyte and the conductive graphite paper to prepare a cement-based supercapacitor.

2. The method according to claim 1, characterized in that In step (1), the carbon black powder is acetylene black or Ketjen black.

3. The method according to claim 1, characterized in that In step (1), the cement is silicate cement or sulphoaluminate cement.

4. The method according to claim 1, wherein In step (1), the stirring is mechanical stirring, and the stirring time is 5-10 minutes.

5. The method according to claim 1, wherein In step (1), the water-cement ratio is 0.2-0.

4.

6. The method according to claim 1, characterized in that In step (2), the pressing thickness is 0.4-2 cm.

7. The method according to claim 1, characterized in that In step (2), the formed cement matrix is ​​cured in water at 20±1°C for 25-30 days.

8. The method according to claim 1, characterized in that In step (3), the electrolyte is a 1-3 mol / L potassium chloride aqueous solution, and the soaking time is 10-15 h.

9. The method according to claim 1, characterized in that In step (3), the thickness of the glass fiber membrane is 0.5-1 mm; the thickness of the conductive graphite paper is 0.5-1.5 mm.

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