Symmetrical cement-based double-electric-layer supercapacitor and preparation method thereof

Abstract

The invention provides a symmetrical cement-based double-electric-layer supercapacitor and a preparation method thereof. The supercapacitor comprises a positive electrode composite electrode layer, a cement-based solid electrolyte layer and a negative electrode composite electrode layer which are arranged in a sandwich layered structure, the cement-based solid electrolyte layer is formed by hydrating and curing a cement-based material comprising dead burned magnesium oxide, phosphate, a retarder, an organic polymer and water; each of the positive electrode composite electrode layer and the negative electrode composite electrode layer comprises a current collector and a conductive slurry layer attached to one side of the current collector; the cement-based solid electrolyte layer and the positive composite electrode layer and the negative composite electrode layer on the two sides of the cement-based solid electrolyte layer are cured into an integrated structure; according to the symmetrical cement-based double-electric-layer supercapacitor, the magnesium phosphate cement-based solid electrolyte layer is adopted, so that the supercapacitor has certain mechanical strength, can be used as a non-bearing structural member, has no electrolyte leakage risk and is high in safety.

Description

Technical Field

[0001] This invention belongs to the field of building functional materials technology, specifically relating to a symmetrical cement-based double-layer supercapacitor and its preparation method. Background Technology

[0002] Building-in-the-building (BIB) energy storage is one of the main forms of user-side distributed energy storage, offering advantages such as proximity to the user end and low transmission losses. With the rise of green and smart building concepts, integrating energy storage devices into building structures has become a research hotspot. Traditional batteries or supercapacitors typically use liquid electrolytes, which suffer from problems such as easy leakage, difficult encapsulation, and inability to withstand mechanical loads, making them difficult to apply directly to the interior of building structures.

[0003] Cement, as the most widely used building material, has enormous application potential if endowed with energy storage capabilities. The development of cement-based capacitor technology has achieved an organic combination of bulk building materials and novel energy storage technologies. Furthermore, cement-based capacitors, being solid-state electrolyte capacitors, possess characteristics such as rapid storage and release, long cycle life, and safety and stability, making them highly compatible with building energy storage requirements. However, while ordinary silicate cement has high strength, its ionic conductivity is extremely low, and its pore structure is not interconnected, resulting in capacitors based on ordinary cement having extremely high internal resistance and very low specific capacitance.

[0004] Magnesium phosphate cement (MPC), as a novel cementitious material, possesses characteristics such as rapid hardening and early strength, high bonding strength, good compatibility, and easily controllable pore structure. However, the pore structure and water retention of pure MPC matrix still fall short of the requirements for high-performance solid electrolytes.

[0005] Therefore, there is an urgent need to design a supercapacitor that combines good mechanical strength and ion transport performance to solve the current technical problems. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a symmetrical cement-based double-layer supercapacitor with both good mechanical strength and ion transport performance, and a method for its preparation.

[0007] The technical solution of the present invention is: a symmetrical cement-based double-layer supercapacitor, characterized in that: it includes a positive electrode composite electrode layer, a cement-based solid electrolyte layer and a negative electrode composite electrode layer arranged in a sandwich layered structure; The cement-based solid electrolyte layer is formed by hydration and solidification of a cement-based material including calcined magnesium oxide, phosphate, retarder, organic polymer and water; Both the positive electrode composite layer and the negative electrode composite layer include a current collector and a conductive paste layer attached to one side of the current collector. The cement-based solid electrolyte layer and the positive electrode composite electrode layer and the negative electrode composite electrode layer on both sides are solidified into an integral structure.

[0008] Furthermore, the current collector is nickel foam; The conductive slurry layer is formed by uniformly coating and drying a composite conductive slurry containing activated carbon on one side of the current collector.

[0009] Furthermore, the thickness of the nickel foam is 1-2 mm, and the porosity is 60-98%.

[0010] Furthermore, the composite conductive paste is made by uniformly mixing and grinding activated carbon, conductive additives, binders and organic solvents.

[0011] Furthermore, the specific surface area of ​​the activated carbon is not less than 1500 m². 2 / g, ash content less than 0.5%; The conductive additive is one or more of conductive carbon black, carbon nanotubes, and graphene, and the dosage is 5-20% of the activated carbon mass. The binder is a polyvinylidene fluoride emulsion, and the dosage is 5-15% of the mass of activated carbon. The organic solvent is 1-methyl-2-pyrrolidone, used to adjust the activated carbon composite conductive paste to a glossy black ink-like paste.

[0012] Furthermore, the phosphate is one or a mixture of two of potassium dihydrogen phosphate or ammonium dihydrogen phosphate; The molar ratio of the recalcined magnesium oxide to phosphate is 1:1 to 5:1; The retarder is borax, and its dosage is 0.2-2.0% of the total mass of the reburned magnesium oxide and phosphate. The water-cement ratio of the magnesium phosphate cement matrix is ​​0.3~0.6.

[0013] Furthermore, the organic polymer is polyacrylic acid or polyacrylamide; The amount of polyacrylic acid added is 1-10% of the total mass of calcined magnesium oxide and phosphate; The amount of polyacrylamide added is 0.5 to 5.0% of the total mass of calcined magnesium oxide and phosphate.

[0014] The fabrication method of a symmetrical cement-based double-layer supercapacitor includes the following steps: Current collector treatment: After cleaning, the current collector is dried to remove surface oil and oxide layer; Preparation of composite conductive paste: Activated carbon, conductive additives, binders and organic solvents are uniformly mixed and ground to prepare a glossy black ink-like composite conductive paste; Composite electrode preparation: The composite conductive paste is uniformly coated onto the treated current collector, dried, and then pressurized to obtain the composite electrode layer; Preparation of cement-based electrolyte: Dry-mixed magnesium oxide, phosphate, and retarder are mixed evenly to obtain a dry mixture; polyacrylic acid or polyacrylamide is dissolved in water to obtain an organic polymer solution; the organic polymer solution is added to the dry mixture and stirred evenly to obtain a modified magnesium phosphate cement electrolyte slurry. Assembly and molding: Place a composite electrode layer with one side of conductive slurry facing up at the bottom of the mold. Pour the modified magnesium phosphate cement electrolyte slurry onto the composite electrode layer in the mold before initial setting. Vibrate to vent air and scrape it flat. Then cover the upper surface of the modified magnesium phosphate cement electrolyte slurry with another composite electrode layer with one side of conductive slurry facing down. Apply slight pressure to make the interface between the composite electrode layer and the cement-based electrolyte firm. Curing and demolding: Curing is carried out at room temperature or under constant temperature and humidity conditions until the magnesium phosphate cement hardens, and demolding yields the symmetrical cement-based double-layer supercapacitor.

[0015] Furthermore, in the composite electrode preparation step, the coating thickness of the composite conductive paste on the current collector is 100~500μm.

[0016] Furthermore, in the assembly and molding steps, the thickness of the modified magnesium phosphate cement electrolyte slurry is 2~10mm.

[0017] The beneficial effects of this invention are: (1) In this invention, the symmetrical cement-based double-layer supercapacitor uses a magnesium phosphate cement-based solid electrolyte layer, which makes the supercapacitor itself have a certain mechanical strength, can be used as a non-load-bearing structural component, and has no risk of electrolyte leakage, thus ensuring high safety. (2) Organic polymer modification effectively improves the ionic conductivity of magnesium phosphate cement, and the three-dimensional structure of nickel foam reduces the interfacial contact resistance. This supercapacitor exhibits good double-layer capacitance characteristics. (3) Symmetrical cement-based double-layer supercapacitors do not require complex packaging processes, have low raw material costs, fast molding speed, and high finished product performance stability, which is conducive to large-scale preparation and engineering application. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the symmetrical cement-based double-layer supercapacitor in this invention.

[0019] Figure 2 This is a flowchart of the preparation method of the symmetrical cement-based double-layer supercapacitor in this invention.

[0020] Figure 3The electrochemical performance test results are for an embodiment of the symmetrical cement-based double-layer supercapacitor of this invention.

[0021] Explanation of the reference numerals: 100 is the positive composite electrode layer; 110 is the positive current collector; 120 is the positive conductive paste layer; 200 is the cement-based solid electrolyte layer; 300 is the negative composite electrode layer; 310 is the negative current collector; 320 is the negative conductive paste layer. Detailed Implementation

[0022] Various exemplary embodiments of the invention will now be described in detail with reference to the accompanying drawings. The descriptions of the exemplary embodiments are merely illustrative and are in no way intended to limit the invention or its application or use. The invention can be embodied in many different forms and is not limited to the embodiments described herein. These embodiments are provided to make the invention thorough and complete, and to fully express the scope of the invention to those skilled in the art. It should be noted that, unless otherwise specifically stated, the relative arrangement of components and steps, the composition of materials, numerical expressions, and values ​​set forth in these embodiments should be interpreted as merely exemplary and not as limiting.

[0023] The terms "first," "second," and similar words used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different parts. Words such as "including" or "comprising" mean that the element preceding the word encompasses the element listed after it, without excluding the possibility of encompassing other elements. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0024] like Figure 1 As shown, the symmetrical cement-based double-layer supercapacitor includes a positive electrode composite electrode layer 100, a cement-based solid electrolyte layer 200, and a negative electrode composite electrode layer 300 arranged in a sandwich-like layered structure. The cement-based solid electrolyte layer 200 is formed by hydration and curing of cement-based materials including calcined magnesium oxide, phosphate, retarder, organic polymer and water; Both the positive electrode composite electrode layer 100 and the negative electrode composite electrode layer 300 include a current collector and a conductive paste layer attached to one side of the current collector. The cement-based solid electrolyte layer 200 is solidified into an integral structure with the positive electrode composite electrode layer and the negative electrode composite electrode layer 300 on both sides.

[0025] The symmetrical cement-based double-layer supercapacitor in this embodiment uses a magnesium phosphate cement-based solid electrolyte layer 200, which gives the supercapacitor a certain mechanical strength, allowing it to be used as a non-load-bearing structural component, and eliminating the risk of electrolyte leakage, thus ensuring high safety.

[0026] In one specific embodiment of the positive electrode composite layer 100 and the negative electrode composite layer 300, the current collector is nickel foam; the conductive slurry layer is formed by uniformly coating and drying a composite conductive slurry containing activated carbon on one side of the current collector; wherein, the positive electrode composite layer 100 includes a positive electrode current collector 110 and a positive electrode conductive slurry layer 120, and the negative electrode composite layer 300 includes a negative electrode current collector 310 and a negative electrode conductive slurry layer 320; the nickel foam has a three-dimensional network porous structure, which effectively increases the loading of active materials, provides abundant conductive channels, and can also form a mechanical interlocking effect with the cement matrix through pores, thereby enhancing the interfacial bonding force.

[0027] Organic polymer modification effectively improves the ionic conductivity of magnesium phosphate cement, and the three-dimensional structure of the nickel foam current collector reduces the interfacial contact resistance. This supercapacitor exhibits excellent double-layer capacitance characteristics.

[0028] More specifically, the thickness of the nickel foam is 1-2 mm, and the porosity is 60-98%.

[0029] As one specific embodiment of the composite conductive paste, the composite conductive paste is made by uniformly mixing and grinding activated carbon, conductive additives, binders, and organic solvents. Activated carbon has a high specific surface area, providing excellent electron adsorption and storage capabilities, while conductive additives improve electron transport efficiency.

[0030] Specifically, the specific surface area of ​​activated carbon should not be less than 1500 m². 2 / g, ash content less than 0.5%; The conductive additive is one or more of conductive carbon black, carbon nanotubes, and graphene, and the dosage is 5-20% of the activated carbon mass. The binder is polyvinylidene fluoride emulsion (PVDF), with a dosage of 5-15% of the activated carbon mass; The organic solvent is 1-methyl-2-pyrrolidone, used to adjust the activated carbon composite conductive paste to a glossy black ink-like paste.

[0031] In one specific embodiment of the cement-based solid electrolyte layer 200, the phosphate is one or a mixture of potassium dihydrogen phosphate (KH2PO4) or ammonium dihydrogen phosphate (NH4H2PO4); the molar ratio of reburned magnesium oxide to phosphate is 1:1 to 5:1; the retarder is borax, with an admixture dosage of 0.2 to 2.0% of the total mass of reburned magnesium oxide and phosphate; the water-cement ratio of the magnesium phosphate cement matrix is ​​0.3 to 0.6. Magnesium phosphate cement hardens through an acid-base reaction, and its solid phase product structure contains a large amount of water of crystallization and abundant microporous structure, which is beneficial for ion transport.

[0032] The organic polymer is polyacrylic acid or polyacrylamide; the dosage of polyacrylic acid is 1-10% of the total mass of calcined magnesium oxide and phosphate; the dosage of polyacrylamide is 0.5-5.0% of the total mass of calcined magnesium oxide and phosphate; the polyacrylamide is non-ionic or anionic; deionized water is weighed and mixed with polyacrylic acid or polyacrylamide at a water-cement ratio (W / C) of 0.45 to form an aqueous solution of polyacrylic acid or polyacrylamide. The introduction of polyacrylic acid / polyacrylamide mainly serves two purposes: firstly, as a highly absorbent resin, it can form a water-retaining network within the cement matrix, maintaining the water environment required for ion transport; secondly, the long-chain molecules of the organic polymer can improve the rheological properties of the cement paste, optimize the pore structure of the hardened body, and form channels more conducive to ion migration.

[0033] like Figure 2 As shown, a method for fabricating a symmetrical cement-based double-layer supercapacitor is disclosed, characterized by comprising the following steps: Current collector treatment: After cleaning, the current collector is dried to remove surface oil and oxide layer; Preparation of composite conductive paste: Activated carbon, conductive additives, binders and organic solvents are uniformly mixed and ground to prepare a glossy black ink-like composite conductive paste; Composite electrode preparation: The composite conductive paste is uniformly coated onto the treated current collector, dried, and then pressurized to obtain the composite electrode layer; Preparation of cement-based electrolyte: Dry-mixed magnesium oxide, phosphate, and retarder are mixed evenly to obtain a dry mixture; polyacrylic acid or polyacrylamide is dissolved in water to obtain an organic polymer solution; the organic polymer solution is added to the dry mixture and stirred evenly to obtain a modified magnesium phosphate cement electrolyte slurry. Assembly and molding: Place a composite electrode layer with one side of conductive slurry facing up at the bottom of the mold. Pour the modified magnesium phosphate cement electrolyte slurry onto the composite electrode layer in the mold before initial setting. Vibrate to vent air and scrape it flat. Then cover the upper surface of the modified magnesium phosphate cement electrolyte slurry with another composite electrode layer with one side of conductive slurry facing down. Apply slight pressure to make the interface between the composite electrode layer and the cement-based electrolyte firm. Curing and demolding: Curing is carried out at room temperature or under constant temperature and humidity conditions until the magnesium phosphate cement hardens. Demolding yields a symmetrical cement-based double-layer supercapacitor.

[0034] In the above-mentioned current collector treatment steps, the current collector is made of nickel foam. Before use, the nickel foam needs to be ultrasonically cleaned in hydrochloric acid, ethanol and deionized water respectively and then dried to remove surface oil and oxide layer.

[0035] The coating thickness of the above-mentioned composite conductive paste on the current collector is 100~500μm.

[0036] In the above assembly and molding steps, the thickness of the modified magnesium phosphate cement electrolyte slurry is 2~10mm.

[0037] The technical effects of this application will be further illustrated below through some specific embodiments and comparative examples.

[0038] Example 1: A cement-based double-layer supercapacitor was prepared using the following steps: Current collector treatment: Cut 1.0mm thick nickel foam into 5cm×5cm square sheets, and ultrasonically clean them in hydrochloric acid, anhydrous ethanol, and deionized water for 15 minutes in sequence, then dry them for later use. Preparation of composite conductive paste: Weigh 8 parts activated carbon, 10 parts conductive paste, and 1 part polyvinylidene fluoride emulsion according to the following mass ratio. Use 1-methyl-2-pyrrolidone as solvent and mix and grind thoroughly in a mortar to prepare a glossy black ink-like paste. The specific surface area of ​​the activated carbon is >2500 m². 2 / g; 10 parts of conductive paste, with a carbon material content of about 10%, the conductive paste is prepared by mixing carbon nanotubes and carbon black; as an example, the ratio of carbon nanotubes to carbon black is 1:1.

[0039] Composite electrode preparation: The composite conductive paste was uniformly coated on the treated nickel foam current collector with a coating thickness of 200 μm. After drying in a vacuum oven at 60℃ for 12 hours, it was taken out and rolled under a pressure of 2 MPa to obtain the composite electrode layer. Preparation of cement-based electrolyte: Weigh decomposed magnesium oxide and potassium dihydrogen phosphate at a molar ratio of M / P = 2:1. Weigh borax equivalent to 1.0% of the total mass of decomposed magnesium oxide and potassium dihydrogen phosphate as a retarder. Dry-mix the decomposed magnesium oxide, potassium dihydrogen phosphate, and borax evenly. Weigh polyacrylic acid equivalent to 2.0% of the total mass of decomposed magnesium oxide and potassium dihydrogen phosphate as a modifier. Weigh deionized water according to a water-cement ratio (W / C) = 0.45. Mix and stir to obtain a polyacrylic acid aqueous solution. Add the polyacrylic acid aqueous solution to the dry mixture and stir thoroughly to obtain polyacrylic acid modified magnesium phosphate cement electrolyte. Assembly and molding: Lay a prepared composite electrode layer flat on the acrylic mold base with the conductive paste layer facing upwards. Pour the prepared modified magnesium phosphate cement electrolyte slurry into the composite electrode layer in the mold, controlling the thickness to be about 4mm. Vibrate slightly to remove air bubbles. Cover the surface of the modified magnesium phosphate cement electrolyte slurry with another composite electrode layer facing downwards. After assembling the acrylic mold, press gently to ensure good contact. Curing and demolding: After curing naturally at room temperature of 25℃ and 60% relative humidity for 24 hours, demold and continue curing until 7 days of age before performance testing.

[0040] Electrochemical performance testing: After curing, the cement-based capacitor was thoroughly immersed in a 2 mol / L KOH solution for 30 minutes, then removed and dried. Electrochemical performance testing was performed using an electrochemical workstation, including cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) tests. The results showed that the capacitor with an area of ​​25 cm²... 2 The cement-based supercapacitor exhibits an approximately rectangular CV curve at a scan rate of 10 mV / s, demonstrating excellent double-layer capacitance characteristics; at a current density of 1 mA / cm², the supercapacitor also exhibits good performance. 2 At that time, the capacitance per square meter of the capacitor reached 1.07 F / cm². 2 It shows a significant performance improvement over conventional silicate cement-based supercapacitors.

[0041] Example 2: In Example 1, the polyacrylic acid in the preparation step of the cement-based electrolyte was replaced with anionic polyacrylamide, and the dosage was 2.0% of the total mass of calcined magnesium oxide and potassium dihydrogen phosphate; the other steps were the same as in Example 1.

[0042] Experiments showed that the polyacrylamide-modified magnesium phosphate cement-based electrolyte also exhibited good double-layer capacitance characteristics, although its specific capacitance was slightly lower than that of the polyacrylic acid-modified scheme, at a current density of 1 mA / cm². 2 At that time, the capacitance per unit area of ​​the capacitor reached 0.74 F / cm². 2 .

[0043] Comparative Example 1: Magnesium phosphate cement without polymer modification was used as the electrolyte, and other conditions were the same as in Example 1.

[0044] The electrochemical performance test results of each embodiment and comparative example are as follows: Figure 3 As shown. The test results show that the envelope area of ​​the CV curve is significantly reduced, and the voltage drop of Comparative Example 1 in the GCD curve is significantly higher than that of Example 1 and Example 2, indicating that its internal resistance is larger. The current density is 1 mA / cm². 2 At that time, the capacitance per square meter of the capacitor area was only 0.27 F / cm². 2 The values ​​were significantly lower than those in Examples 1 and 2, indicating that organic polymer modification plays a crucial role in enhancing ion transport capabilities.

[0045] The various embodiments of the present invention have now been described in detail. To avoid obscuring the concept of the invention, some details known in the art have not been described. Those skilled in the art will fully understand how to implement the technical solutions disclosed herein based on the above description.

[0046] The embodiments described above only illustrate some implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A symmetrical cement-based double-layer supercapacitor, characterized in that: It includes a positive electrode composite layer, a cement-based solid electrolyte layer, and a negative electrode composite layer arranged in a sandwich-like layered structure; The cement-based solid electrolyte layer is formed by hydration and solidification of a cement-based material including calcined magnesium oxide, phosphate, retarder, organic polymer and water; Both the positive electrode composite layer and the negative electrode composite layer include a current collector and a conductive paste layer attached to one side of the current collector. The cement-based solid electrolyte layer and the positive electrode composite electrode layer and the negative electrode composite electrode layer on both sides are solidified into an integral structure.

2. The symmetrical cement-based double-layer supercapacitor according to claim 1, characterized in that: The current collector is nickel foam; The conductive slurry layer is formed by uniformly coating and drying a composite conductive slurry containing activated carbon on one side of the current collector.

3. The symmetrical cement-based double-layer supercapacitor according to claim 2, characterized in that: The thickness of the nickel foam is 1-2 mm, and the porosity is 60-98%.

4. The symmetrical cement-based double-layer supercapacitor according to claim 2, characterized in that: The composite conductive paste is made by uniformly mixing and grinding activated carbon, conductive additives, binders and organic solvents.

5. The symmetrical cement-based double-layer supercapacitor according to claim 4, characterized in that: The specific surface area of ​​the activated carbon is not less than 1500 m². 2 / g, ash content less than 0.5%; The conductive additive is one or more of conductive carbon black, carbon nanotubes, and graphene, and the dosage is 5-20% of the activated carbon mass. The binder is a polyvinylidene fluoride emulsion, and the dosage is 5-15% of the mass of activated carbon. The organic solvent is 1-methyl-2-pyrrolidone, used to adjust the activated carbon composite conductive paste to a glossy black ink-like paste.

6. The symmetrical cement-based double-layer supercapacitor according to claim 1, characterized in that: The phosphate is one or a mixture of potassium dihydrogen phosphate or ammonium dihydrogen phosphate; The molar ratio of the recalcined magnesium oxide to phosphate is 1:1 to 5:1; The retarder is borax, and its dosage is 0.2-2.0% of the total mass of the reburned magnesium oxide and phosphate. The water-cement ratio of the magnesium phosphate cement matrix is ​​0.3~0.

6.

7. The symmetrical cement-based double-layer supercapacitor according to claim 1, characterized in that: The organic polymer is polyacrylic acid or polyacrylamide; The amount of polyacrylic acid added is 1-10% of the total mass of calcined magnesium oxide and phosphate; The amount of polyacrylamide is 0.5 to 5.0% of the total mass of calcined magnesium oxide and phosphate.

8. A method for preparing a symmetrical cement-based double-layer supercapacitor, characterized in that, Includes the following steps: Current collector treatment: After cleaning, the current collector is dried to remove surface oil and oxide layer; Preparation of composite conductive paste: Activated carbon, conductive additives, binders and organic solvents are uniformly mixed and ground to prepare a glossy black ink-like composite conductive paste; Composite electrode preparation: The composite conductive paste is uniformly coated onto the treated current collector, dried, and then pressurized to obtain the composite electrode layer; Preparation of cement-based electrolyte: Dry-mixed magnesium oxide, phosphate, and retarder are mixed evenly to obtain a dry mixture; polyacrylic acid or polyacrylamide is dissolved in water to obtain an organic polymer solution; the organic polymer solution is added to the dry mixture and stirred evenly to obtain a modified magnesium phosphate cement electrolyte slurry. Assembly and molding: Place a composite electrode layer with one side of conductive slurry facing up at the bottom of the mold. Pour the modified magnesium phosphate cement electrolyte slurry onto the composite electrode layer in the mold before initial setting. Vibrate to vent air and scrape it flat. Then cover the upper surface of the modified magnesium phosphate cement electrolyte slurry with another composite electrode layer with one side of conductive slurry facing down. Apply slight pressure to make the interface between the composite electrode layer and the cement-based electrolyte firm. Curing and demolding: Curing is carried out at room temperature or under constant temperature and humidity conditions until the magnesium phosphate cement hardens, and demolding yields the symmetrical cement-based double-layer supercapacitor.

9. The method for preparing a symmetrical cement-based double-layer supercapacitor according to claim 8, characterized in that: In the composite electrode preparation step, the coating thickness of the composite conductive paste on the current collector is 100~500μm.

10. The method for preparing a symmetrical cement-based double-layer supercapacitor according to claim 8, characterized in that: In the assembly and molding steps, the thickness of the modified magnesium phosphate cement electrolyte slurry is 2~10mm.

Images