A magnesium phosphate cement supercapacitor with gradient interpenetrating interface and a preparation method thereof

Abstract

The application belongs to the technical field of cement-based supercapacitors, and specifically discloses a magnesium phosphate cement supercapacitor with a gradient interpenetrating interface and a preparation method thereof. The capacitor comprises a positive electrode conductive cement layer, a negative electrode conductive cement layer, and a solid-state electrolyte isolation layer located between the two. The positive electrode conductive cement layer and the negative electrode conductive cement layer are both composed of a conductive dense region and a porous transition region. The conductive dense region is located on the outer side, and the porous transition region is located on the inner side and is adjacent to the solid-state electrolyte isolation layer. The porosities of the solid-state electrolyte isolation layer, the porous transition region, and the conductive dense region gradually decrease to form a gradient structure. The solid-state electrolyte isolation layer comprises a porous magnesium phosphate cement skeleton and a gel electrolyte distributed in the connected pores thereof. Through the synergy between the mechanical bearing phase, the electron transport phase and the ion transport phase constructed in the capacitor, the interface stability and the ion conductivity between the electrode layer and the electrolyte layer are effectively improved.

Description

Technical Field

[0001] This invention belongs to the field of cement-based supercapacitor technology, specifically relating to a magnesium phosphate cement supercapacitor with a gradient interpenetrating interface and its preparation method. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Cement-based supercapacitors can serve both structural load-bearing and energy storage functions, and are suitable for building components such as energy storage bricks, energy storage panels, energy storage blocks, and prefabricated energy storage walls. However, current cement-based supercapacitors typically have the following problems: (1) The liquid electrolyte is prone to migration, volatilization, or loss under drying, soaking, or loading. (2) Adding polymers, gel components, or electrolytic salts directly to magnesium phosphate cement slurry can easily affect the hydration reaction of magnesium phosphate cement, leading to instability in coagulation, pore structure, and mechanical properties. (3) The interfacial ion migration impedance between the electrode layer and the electrolyte layer is relatively large, making it difficult for ions in the electrolyte to continuously enter the near-interface region of the electrode, reducing the effective energy storage interface utilization rate of the conductive material, increasing the internal resistance of the device, and decreasing the rate performance and areal capacitance. Increasing the porosity of the entire electrode region can help alleviate the above problems, but it will destroy the continuous electron transport network formed by the conductive material in the electrode region, causing a decrease in strength and an increase in the internal resistance of the electrode, which in turn makes it difficult for electron transport and ion transport to be matched in synergy, reducing the effective utilization rate of the electrode, and deteriorating the cycle stability and structural load-bearing performance of the device. Summary of the Invention

[0004] This invention provides a magnesium phosphate cement supercapacitor with a gradient interpenetrating interface and its preparation method. Through the synergy between the mechanically supporting phase, the electron transport phase, and the ion transport phase constructed within the capacitor, it effectively improves the interfacial stability, ion conductivity, and long-term service performance between the electrode layer and the electrolyte layer. Specifically, the technical solution of this invention is as follows.

[0005] First, this invention discloses a magnesium phosphate cement supercapacitor with a gradient interpenetrating interface, comprising: a positive electrode conductive cement layer, a negative electrode conductive cement layer, and a solid electrolyte isolation layer located between the two. Wherein: Both the positive electrode conductive cement layer and the negative electrode conductive cement layer are composed of a conductive dense region and a porous transition region. The conductive dense region is located on the outside, and the porous transition region is located on the inside and adjacent to the solid electrolyte isolation layer. The porosity of the solid electrolyte isolation layer, the porous transition region, and the conductive dense region gradually decreases to form a gradient structure.

[0006] The solid electrolyte isolation layer comprises a porous magnesium phosphate cement framework and a gel electrolyte distributed within its interconnected pores. The gel electrolyte comprises a polymer gel framework and phosphate compounds, potassium salts, magnesium salts, and water-retaining components distributed therein. The gel electrolyte interacts with the phosphate groups in the phosphate compounds through the Mg-containing compounds in the pore walls of the porous magnesium phosphate cement framework. 2+ The gel electrolyte is anchored at the interfacial active sites of Mg-OH or magnesium oxide clusters, thus stabilizing the gel electrolyte within the pores. Simultaneously, the pores of the porous transition zone also contain the gel electrolyte.

[0007] Furthermore, the porous magnesium phosphate cement skeleton is made of the following components in the following proportions: 100 parts by weight of reburned magnesium oxide, 25-50 parts by weight of phosphate, 2-10 parts by weight of retarder, 2-50 parts by weight of insulating filler, 5-20 parts by weight of pore-forming agent, and water at 0.18-0.35% of the total mass of the reburned magnesium oxide and potassium dihydrogen phosphate.

[0008] Optionally, the insulating filler includes at least one of the following: fly ash, silica fume, metakaolin, quartz powder, calcium carbonate powder, alumina powder, glass microspheres, ceramic micro powder, etc.

[0009] Furthermore, the proportions of the components in the gel electrolyte are as follows: 3-15 wt.% polymer gel backbone, 0.5-15 wt.% phosphate compound, 5-40 wt.% water-retaining component, and the balance being water. Simultaneously, the gel electrolyte also contains 0.1-3.0 mol / L potassium salt and 0.05-0.3 mol / L magnesium salt.

[0010] Optionally, the polymer gel skeleton is made of at least one of the following: polyvinyl alcohol, polyacrylamide, polyacrylate, polyethylene oxide, polyethylene glycol, sodium alginate, carboxymethyl cellulose, chitosan, etc.

[0011] Optionally, the phosphate-based compound includes at least one of the following: phytic acid, phytate, polyphosphate, hydroxyethylidene diphosphonic acid, aminotrimethylene phosphonic acid, etc.

[0012] Optionally, the potassium salt includes at least one of potassium sulfate, potassium chloride, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, potassium nitrate, and potassium acetate.

[0013] Optionally, the magnesium salt includes at least one of magnesium sulfate, magnesium chloride, magnesium nitrate, magnesium acetate, and magnesium dihydrogen phosphate.

[0014] Optionally, the water-retaining component includes at least one of the following: glycerin, sorbitol, ethylene glycol, polyethylene glycol, propylene glycol, betaine, urea, etc.

[0015] Furthermore, the conductive dense region is made of the following components in the following proportions: 100 parts by weight of calcined magnesium oxide, 25-50 parts by weight of phosphate, 2-10 parts by weight of retarder, 3-20 parts by weight of conductive material, and water at 0.18-0.35% of the total mass of the calcined magnesium oxide and potassium dihydrogen phosphate.

[0016] Furthermore, the porous transition zone is made of the following components in the following proportions: 100 parts by weight of calcined magnesium oxide, 25-50 parts by weight of phosphate, 2-10 parts by weight of retarder, 3-18 parts by weight of conductive material, 1-8 parts by weight of pore-forming agent, and water at 0.18-0.35% of the total mass of the calcined magnesium oxide and potassium dihydrogen phosphate.

[0017] Optionally, the aforementioned phosphates include at least one of potassium dihydrogen phosphate, ammonium dihydrogen phosphate, etc.

[0018] Optionally, the aforementioned retarder includes at least one of the following: borax, boric acid, citric acid, tartaric acid, gluconate, citrate, etc.

[0019] Optionally, the conductive materials mentioned above include at least one of activated carbon powder, carbon black powder, graphite powder, graphene, carbon nanotubes, etc.

[0020] Optionally, the aforementioned pore-forming agent includes at least one of the following: potassium sulfate particles, sodium chloride particles, polyethylene glycol particles, soluble starch particles, water-soluble polymer microspheres, etc.

[0021] Optionally, the particle size of the porogen is 80~150μm.

[0022] Furthermore, the thickness ratio of the porous transition region of the solid electrolyte isolation layer, the positive conductive cement layer or the negative conductive cement layer, and the conductive dense region of the positive conductive cement layer or the negative conductive cement layer is 1:0.1~1.0:0.5~8.

[0023] Secondly, this invention discloses a method for preparing a magnesium phosphate cement supercapacitor with a gradient interpenetrating interface, comprising the following steps: (1) Prepare the slurry for the conductive dense region, the slurry for the porous transition region, and the slurry for the porous magnesium phosphate cement skeleton, respectively, for later use.

[0024] (2) The slurry is poured into the mold in sequence using a wet contact continuous molding method. After hardening and curing, an integral bonding interface is formed between adjacent layers to obtain a cement matrix.

[0025] (3) The cement matrix is ​​immersed in water or potassium salt solution to dissolve and remove the pore-forming agent to form interconnected pores, thereby constructing a gradient structure in which the porosity gradually decreases from the solid electrolyte isolation layer and the porous transition region to the conductive dense region, thus obtaining the capacitor matrix.

[0026] (4) The gel electrolyte is injected into the porous magnesium phosphate cement skeleton of the capacitor matrix, and the magnesium phosphate cement supercapacitor is obtained after gelation.

[0027] Further, in step (4), the gelation method includes at least one of freeze-thaw crosslinking and ionic crosslinking. Optionally, when using freeze-thaw crosslinking, the capacitor substrate after injecting the gel electrolyte is sealed, then frozen at -10 to -30°C for 6 to 24 hours, and then thawed at 15 to 30°C for 2 to 8 hours, which is one freeze-thaw cycle, and repeated 1 to 5 times. When using ionic crosslinking, the capacitor substrate after injecting the gel electrolyte is immersed in a magnesium salt or calcium salt solution with a concentration of 0.02 to 0.50 mol / L for 10 to 180 minutes.

[0028] Furthermore, in step (4), after the polymer gel solidifies to form a skeleton, it can be impregnated with a post-treatment solution containing potassium and magnesium salts, and then dried to obtain the magnesium phosphate cement supercapacitor. This post-treatment helps to further enhance the coordination and anchoring effect between the gel electrolyte and the porous magnesium phosphate cement skeleton, preventing the gel electrolyte from migrating, desorbing, shrinking and cracking, and losing ion salts during immersion, wet-dry cycling, loading, and long-term charge-discharge processes.

[0029] Compared with the prior art, the technical solution of the present invention has at least the following beneficial effects: This invention utilizes a positive conductive cement layer and a negative conductive cement layer composed of a conductive dense region and a porous transition region, as well as a solid electrolyte isolation layer constructed from a porous magnesium phosphate cement framework and a gel electrolyte distributed in its interconnected pores. A gradient structure is formed by the gradual decrease in porosity of the solid electrolyte isolation layer, the porous transition region, and the conductive dense region to construct a cement-based supercapacitor with directional ion channels and a stable interface transition region. It has the characteristics of mechanical load-bearing, electron transport, and ion transport, effectively improving the interface stability, ion conductivity, and long-term service performance between the electrode layer and the electrolyte layer. This is because: the solid electrolyte isolation layer utilizes its high interconnected porosity to accommodate the gel electrolyte and form continuous ion transport channels; the porous transition region defines the entry path and distribution boundary of the gel electrolyte, thereby achieving a fully filled electrolyte layer, limited interpenetration in the interface region, and selective distribution of the conductive dense region maintaining the conductivity of the dense electronic network. This constructs an electronic network and ion network that approach each other near the interface without causing a short circuit, thereby expanding the effective contact area between the electrode active region and the ion transport phase, reducing the interfacial ion migration impedance, and improving the utilization rate of the active sites near the electrode interface. This gives the magnesium phosphate cement supercapacitor of the present invention excellent rate performance, areal capacitance, cycle stability, and structural load-bearing capacity. In addition, after the gel electrolyte enters the pores, it gels in situ to form a gel ionic phase, and utilizes the PO of the phosphate-based compound confined in this gel ionic phase. - P=O or phosphate ester groups and Mg-containing groups in the pore walls of the porous magnesium phosphate cement skeleton 2+ The interfacial active sites of Mg-OH or magnesium oxide clusters form Mg-OP coordination bonds, ion bridges or multi-point coordination structures, which makes the gel electrolyte more stably fixed in the pores. This can effectively reduce the risk of migration, desorption and loss of the gel electrolyte in the cement supercapacitor of this invention during soaking, wet and dry cycles, external loads and long-term charge and discharge. Attached Figure Description

[0030] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention and do not constitute an undue limitation of the invention.

[0031] Figure 1 The image shows a sample of a magnesium phosphate cement supercapacitor prepared in Example 1 below.

[0032] Figure 2 Electrochemical impedance spectroscopy (EIS) of the magnesium phosphate cement supercapacitor prepared in Example 1 below.

[0033] Figure 3 Electrochemical impedance spectroscopy (EIS) of the magnesium phosphate cement supercapacitor prepared in Example 2 below.

[0034] Figure 4Electrochemical impedance spectroscopy (EIS) of the magnesium phosphate cement supercapacitor prepared in Example 3 below.

[0035] Figure 5 Electrochemical impedance spectroscopy (EIS) of the magnesium phosphate cement supercapacitor prepared in Example 4 below.

[0036] Figure 6 Electrochemical impedance spectroscopy (EIS) of the magnesium phosphate cement supercapacitor prepared in Example 5 below.

[0037] Figure 7 Electrochemical impedance spectroscopy (EIS) of the magnesium phosphate cement supercapacitor prepared in Example 6 below.

[0038] Figure 8 Electrochemical impedance spectroscopy (EIS) of the magnesium phosphate cement supercapacitor prepared in Example 7 below. Detailed Implementation

[0039] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as those skilled in the art. The preferred embodiments and materials described in this invention are for illustrative purposes only. The technical solutions of the present invention will now be further described with reference to specific embodiments.

[0040] Example 1 A method for preparing a magnesium phosphate cement supercapacitor with a gradient interpenetrating interface includes the following steps: (1) Take the following components in the following proportions: 100 parts by weight of recalcined magnesium oxide powder, 35 parts by weight of potassium dihydrogen phosphate, 5 parts by weight of borax, 10 parts by weight of conductive material (including 6 parts of activated carbon, 3 parts of carbon black, and 1 part of carbon nanotubes), and water at 0.26% of the total mass of the recalcined magnesium oxide and potassium dihydrogen phosphate. Mix the above components and stir evenly to obtain slurry I for preparing the conductive dense region, for later use.

[0041] (2) Take the following components in the following proportions: 100 parts by weight of recalcined magnesium oxide powder, 35 parts by weight of potassium dihydrogen phosphate, 5 parts by weight of borax, 8 parts by weight of conductive material (including 5 parts by weight of activated carbon, 2 parts by weight of carbon black, and 1 part by weight of carbon nanotubes), 4 parts by weight of sodium sulfate particles with a particle size of 80~150μm, and water at 0.26% of the total mass of the recalcined magnesium oxide and potassium dihydrogen phosphate. Mix the above components and stir evenly to obtain slurry II for preparing the porous transition zone, for later use.

[0042] (3) Take the following components in the following proportions: 100 parts by weight of recalcined magnesium oxide powder, 35 parts by weight of potassium dihydrogen phosphate, 5 parts by weight of borax, 20 parts by weight of fly ash, 10 parts by weight of sodium sulfate particles with a particle size of 80~150μm, and water at 0.26% of the total mass of the recalcined magnesium oxide and potassium dihydrogen phosphate. Mix the above components and stir evenly to obtain slurry III for preparing porous magnesium phosphate cement skeleton, for later use.

[0043] (4) Take the following components in the following proportions: polyvinyl alcohol 8 wt.%, phytic acid 5 wt.%, glycerol 20 wt.%, with the remainder being water. The gel electrolyte also contains potassium sulfate 0.8 mol / L and magnesium sulfate 0.2 mol / L. Mix the above components thoroughly to obtain the gel electrolyte, which is then ready for use.

[0044] (5) The cement matrix structure of the magnesium phosphate cement supercapacitor in this embodiment includes: a positive conductive cement layer, a negative conductive cement layer, and a solid electrolyte isolation layer located between the two. Both the positive and negative conductive cement layers consist of a conductive dense region and a porous transition region, with the conductive dense region located on the outer side and the porous transition region located on the inner side and adjacent to the solid electrolyte isolation layer. According to the above structure and the thickness ratio of the solid electrolyte isolation layer, the porous transition region of the positive conductive cement layer, and the conductive dense region of either the positive or negative conductive cement layer being 1:0.5:3, slurry I, slurry II, and slurry III are poured into the mold at corresponding positions using a wet contact continuous molding method. After the slurry hardens and solidifies, it is sealed and naturally cured at 30°C for 48 hours to obtain the cement matrix.

[0045] (6) Soak the cement matrix in clean water for 24 hours, and change the clean water every 6 hours to dissolve and remove the pore-forming agent to form interconnected pores, thereby obtaining the capacitor matrix.

[0046] (7) The outer walls of the positive and negative conductive cement layers of the capacitor substrate are wrapped and sealed with a tetrafluoroethylene film. Then, a vacuum treatment is performed for 5 minutes to remove air from the pores. The substrate is then placed in the gel electrolyte of this embodiment and left to stand for 2 hours, allowing the gel electrolyte to penetrate and fill the pores after entering from the solid electrolyte isolation layer. After completion, the capacitor substrate is removed, wrapped and sealed with plastic wrap, and then frozen at -30°C for 6 hours, followed by thawing at 30°C for 2 hours to allow the polymer gel to solidify and form a framework. The tetrafluoroethylene film is then removed to obtain a magnesium phosphate cement supercapacitor (e.g., Figure 1 (As shown).

[0047] Performance testing: The magnesium phosphate cement supercapacitor prepared in this embodiment was subjected to electrochemical impedance spectroscopy (EIS) testing using an electrochemical workstation. Figure 2The area capacitance and cycle stability were tested, and the results are shown in Table 1 below.

[0048] Table 1 Test results of Example 1

[0049] Example 2 A method for preparing a magnesium phosphate cement supercapacitor with a gradient interpenetrating interface includes the following steps: (1) Take the following components in the following proportions: 100 parts by weight of recalcined magnesium oxide powder, 50 parts by weight of potassium dihydrogen phosphate, 10 parts by weight of boric acid, 20 parts by weight of conductive material (including 10 parts of activated carbon, 5 parts of carbon black, 4 parts of graphite powder, and 1 part of carbon nanotubes), and water is 0.35% of the total mass of the recalcined magnesium oxide and potassium dihydrogen phosphate. Mix the above components and stir evenly to obtain slurry I for preparing the conductive dense region, for later use.

[0050] (2) Take the following components in the following proportions: 100 parts by weight of recalcined magnesium oxide powder, 50 parts by weight of potassium dihydrogen phosphate, 10 parts by weight of boric acid, 18 parts by weight of conductive material (including 10 parts of activated carbon, 4 parts of carbon black, 3 parts of graphite powder, and 1 part of carbon nanotubes), 8 parts by weight of sodium chloride particles with a particle size of 80~150μm, and water at 0.35% of the total mass of the recalcined magnesium oxide and potassium dihydrogen phosphate. Mix the above components and stir evenly to obtain slurry II for preparing the porous transition zone, for later use.

[0051] (3) Take the following components in the following proportions: 100 parts by weight of recalcined magnesium oxide powder, 50 parts by weight of potassium dihydrogen phosphate, 10 parts by weight of boric acid, 50 parts by weight of silica fume, 20 parts by weight of sodium chloride particles with a particle size of 80~150μm, and water at 0.35% of the total mass of the recalcined magnesium oxide and potassium dihydrogen phosphate. Mix the above components and stir evenly to obtain slurry III for preparing porous magnesium phosphate cement skeleton, for later use.

[0052] (4) Take the following components in the following proportions: 15 wt.% polyacrylamide, 15 wt.% sodium phytate, 5 wt.% sorbitol, and the remainder being water. The gel electrolyte also contains 3 mol / L potassium chloride and 0.05 mol / L magnesium chloride. Mix the above components thoroughly to obtain the gel electrolyte, which is then ready for use.

[0053] (5) The cement matrix structure of the magnesium phosphate cement supercapacitor in this embodiment includes: a positive conductive cement layer, a negative conductive cement layer, and a solid electrolyte isolation layer located between the two. Both the positive and negative conductive cement layers consist of a conductive dense region and a porous transition region, with the conductive dense region located on the outer side and the porous transition region located on the inner side and adjacent to the solid electrolyte isolation layer. According to the above structure and the thickness ratio of the solid electrolyte isolation layer, the porous transition region of the positive or negative conductive cement layer, and the conductive dense region of the positive or negative conductive cement layer being 1:1:8, slurry I, slurry II, and slurry III are poured into the mold at corresponding positions using a wet contact continuous molding method. After the slurry hardens and solidifies, it is sealed and naturally cured at 30°C for 48 hours to obtain the cement matrix.

[0054] (6) Soak the cement matrix in clean water for 24 hours, and change the clean water every 6 hours to dissolve and remove the pore-forming agent to form interconnected pores, thereby obtaining the capacitor matrix.

[0055] (7) The outer walls of the positive and negative conductive cement layers of the capacitor substrate are wrapped and sealed with a tetrafluoroethylene film. Then, a vacuum treatment is performed for 5 minutes to remove air from the pores. Then, the substrate is placed in the gel electrolyte of this embodiment and left to stand for 2 hours, allowing the gel electrolyte to penetrate and fill the pores after entering from the solid electrolyte isolation layer. After completion, the capacitor substrate is removed, wrapped and sealed with plastic wrap, and then frozen at -10°C for 24 hours, followed by thawing at 15°C for 8 hours. This freeze-thaw cycle is repeated 5 times to allow the polymer gel to solidify and form a skeleton. Then, the tetrafluoroethylene film is removed to obtain the magnesium phosphate cement supercapacitor.

[0056] Performance testing: The magnesium phosphate cement supercapacitor prepared in this embodiment was subjected to electrochemical impedance spectroscopy (EIS) testing using an electrochemical workstation. Figure 3 The area capacitance and cycle stability were tested, and the results are shown in Table 2 below.

[0057] Table 2 Test results of Example 2

[0058] Example 3 A method for preparing a magnesium phosphate cement supercapacitor with a gradient interpenetrating interface includes the following steps: (1) Take the following components in the following proportions: 100 parts by weight of recalcined magnesium oxide powder, 25 parts by weight of ammonium dihydrogen phosphate, 2 parts by weight of sodium citrate, 3 parts by weight of conductive material (including 2 parts of activated carbon, 0.5 parts of carbon black, and 0.5 parts of graphene), and water at 0.18% of the total mass of the recalcined magnesium oxide and potassium dihydrogen phosphate. Mix the above components and stir evenly to obtain slurry I for preparing the conductive dense region, for later use.

[0059] (2) Take the following components in the following proportions: 100 parts by weight of recalcined magnesium oxide powder, 25 parts by weight of ammonium dihydrogen phosphate, 2 parts by weight of sodium citrate, 3 parts by weight of conductive material (including 2 parts of activated carbon, 0.5 parts of carbon black, and 0.5 parts of graphene), 1 part by weight of polyethylene glycol (PEG-1000) particles with a particle size of 80~150μm, and water at 0.18% of the total mass of the recalcined magnesium oxide and potassium dihydrogen phosphate. Mix the above components and stir evenly to obtain slurry II for preparing the porous transition zone, for later use.

[0060] (3) Take the following components in the following proportions: 100 parts by weight of recalcined magnesium oxide powder, 25 parts by weight of ammonium dihydrogen phosphate, 2 parts by weight of sodium citrate, 2 parts by weight of metakaolin, 5 parts by weight of polyethylene glycol (PEG-1000) particles with a particle size of 80~150μm, and water at 0.18% of the total mass of the recalcined magnesium oxide and potassium dihydrogen phosphate. Mix the above components and stir evenly to obtain slurry III for preparing porous magnesium phosphate cement skeleton, for later use.

[0061] (4) Take the following components in the following proportions: sodium alginate 3 wt.%, hydroxyethylidene diphosphonic acid 0.5 wt.%, betaine 40 wt.%, with the remainder being water. The gel electrolyte also contains potassium chloride 0.1 mol / L and magnesium chloride 0.3 mol / L. Mix the above components thoroughly to obtain the gel electrolyte, which is then ready for use.

[0062] (5) The cement matrix structure of the magnesium phosphate cement supercapacitor in this embodiment includes: a positive conductive cement layer, a negative conductive cement layer, and a solid electrolyte isolation layer located between the two. Both the positive and negative conductive cement layers consist of a conductive dense region and a porous transition region, with the conductive dense region located on the outer side and the porous transition region located on the inner side and adjacent to the solid electrolyte isolation layer. According to the above structure and the thickness ratio of the solid electrolyte isolation layer, the porous transition region of the positive or negative conductive cement layer, and the conductive dense region of the positive or negative conductive cement layer being 1:0.1:0.5, slurry I, slurry II, and slurry III are poured into the mold at corresponding positions using a wet contact continuous molding method. After the slurry hardens and solidifies, it is sealed and naturally cured at 30°C for 48 hours to obtain the cement matrix.

[0063] (6) Soak the cement matrix in clean water for 24 hours, and change the clean water every 6 hours to dissolve and remove the pore-forming agent to form interconnected pores, thereby obtaining the capacitor matrix.

[0064] (7) The outer walls of the positive and negative conductive cement layers of the capacitor substrate are wrapped and sealed with a tetrafluoroethylene film. Then, a vacuum treatment is performed for 5 minutes to remove air from the pores. Then, the substrate is placed in the gel electrolyte of this embodiment and left to stand for 2 hours to allow the gel electrolyte to penetrate and fill the pores after entering from the solid electrolyte isolation layer. After completion, the capacitor substrate is removed, wrapped and sealed with plastic wrap, and then immersed in a 0.50 mol / L calcium chloride solution for 30 minutes to allow the polymer gel to gel and form a skeleton. Then, the tetrafluoroethylene film is removed to obtain the magnesium phosphate cement supercapacitor.

[0065] Performance testing: The magnesium phosphate cement supercapacitor prepared in this embodiment was subjected to electrochemical impedance spectroscopy (EIS) testing using an electrochemical workstation. Figure 4 The area capacitance and cycle stability were tested, and the results are shown in Table 3 below.

[0066] Table 3 Test results of Example 3

[0067] Example 4 A method for preparing a magnesium phosphate cement supercapacitor with a gradient interpenetrating interface includes the following steps: (1) Take the following components in the following proportions: 100 parts by weight of recalcined magnesium oxide powder, 35 parts by weight of potassium dihydrogen phosphate, 5 parts by weight of borax, 10 parts by weight of conductive material (including 6 parts of activated carbon, 3 parts of carbon black, and 1 part of carbon nanotubes), and water at 0.26% of the total mass of the recalcined magnesium oxide and potassium dihydrogen phosphate. Mix the above components and stir evenly to obtain slurry I for preparing the conductive dense region, for later use.

[0068] (2) Take the following components in the following proportions: 100 parts by weight of recalcined magnesium oxide powder, 35 parts by weight of potassium dihydrogen phosphate, 5 parts by weight of borax, 20 parts by weight of fly ash, 10 parts by weight of sodium sulfate particles with a particle size of 80~150μm, and water at 0.26% of the total mass of the recalcined magnesium oxide and potassium dihydrogen phosphate. Mix the above components and stir evenly to obtain slurry II for preparing porous magnesium phosphate cement skeleton, for later use.

[0069] (3) Take the following components in the following proportions: polyvinyl alcohol 8 wt.%, phytic acid 5 wt.%, glycerol 20 wt.%, with the remainder being water. The gel electrolyte also contains potassium sulfate 0.8 mol / L and magnesium sulfate 0.2 mol / L. Mix the above components thoroughly to obtain the gel electrolyte, which is then ready for use.

[0070] (4) The cement matrix structure of the magnesium phosphate cement supercapacitor in this embodiment includes: a positive conductive cement layer, a negative conductive cement layer, and a solid electrolyte isolation layer sandwiched between the two. Wherein: the positive conductive cement layer and the negative conductive cement layer are composed of conductive dense regions. According to the above structure and the thickness ratio of the conductive dense regions of the solid electrolyte isolation layer, the positive conductive cement layer, or the negative conductive cement layer being 1:3.5, slurry I and slurry II are poured into the corresponding positions in the mold using a wet contact continuous molding method. After the slurry hardens and solidifies, it is sealed and naturally cured at 30°C for 48 hours to obtain the cement matrix.

[0071] (5) Soak the cement matrix in clean water for 24 hours and change the clean water every 6 hours to dissolve and remove the pore-forming agent to form interconnected pores, thereby obtaining the capacitor matrix.

[0072] (6) The outer walls of the positive and negative conductive cement layers of the capacitor substrate are wrapped and sealed with a tetrafluoroethylene film. Then, a vacuum treatment is performed for 5 minutes to remove air from the pores. Then, the substrate is placed in the gel electrolyte of this embodiment and left to stand for 2 hours, allowing the gel electrolyte to penetrate and fill the pores after entering from the solid electrolyte isolation layer. After completion, the capacitor substrate is removed, wrapped and sealed with plastic wrap, and then frozen at -30°C for 6 hours, followed by thawing at 30°C for 2 hours to allow the polymer gel to solidify and form a skeleton. Then, the tetrafluoroethylene film is removed to obtain the magnesium phosphate cement supercapacitor.

[0073] Performance testing: The magnesium phosphate cement supercapacitor prepared in this embodiment was subjected to electrochemical impedance spectroscopy (EIS) testing using an electrochemical workstation. Figure 5 The area capacitance and cycle stability were tested, and the results are shown in Table 4 below.

[0074] Table 4 Test results of Example 4

[0075] Example 5 A method for preparing a magnesium phosphate cement supercapacitor with a gradient interpenetrating interface is similar to that in Example 2 above, except that the gel electrolyte in this example is composed of the following components in the following proportions: 15 wt.% polyacrylamide, 5 wt.% sorbitol, and the balance being water. The gel electrolyte also contains 3 mol / L potassium chloride and 0.05 mol / L magnesium chloride. After mixing and stirring the above components evenly, the gel electrolyte is obtained.

[0076] Performance testing: The magnesium phosphate cement supercapacitor prepared in this embodiment was subjected to electrochemical impedance spectroscopy (EIS) testing using an electrochemical workstation. Figure 6The area capacitance and cycle stability were tested, and the results are shown in Table 5 below.

[0077] Table 5 Test results of Example 5

[0078] Example 6 A method for preparing a magnesium phosphate cement supercapacitor with a gradient interpenetrating interface is similar to that in Example 3 above, except that the gel electrolyte in this example is composed of the following components in the following proportions: 0.5 wt.% hydroxyethylidene diphosphonic acid, 40 wt.% betaine, and the balance being water. The gel electrolyte also contains 0.1 mol / L potassium chloride and 0.3 mol / L magnesium chloride. After mixing and stirring the above components evenly, the gel electrolyte is obtained.

[0079] Performance testing: The magnesium phosphate cement supercapacitor prepared in this embodiment was subjected to electrochemical impedance spectroscopy (EIS) testing using an electrochemical workstation. Figure 7 The area capacitance and cycle stability were tested, and the results are shown in Table 6 below.

[0080] Table 6 Test results of Example 6

[0081] Example 7 A method for preparing a magnesium phosphate cement supercapacitor with a gradient interpenetrating interface is the same as in Example 2 above, except that the cement matrix structure of the magnesium phosphate cement supercapacitor in this example includes: a positive conductive cement layer, a negative conductive cement layer, and a solid electrolyte isolation layer located between the two. Specifically, both the positive and negative conductive cement layers are composed of a conductive dense region and a porous transition region. The porous transition region is located on the outer side, and the conductive dense region is located on the inner side and adjacent to the solid electrolyte isolation layer.

[0082] Performance testing: The magnesium phosphate cement supercapacitor prepared in this embodiment was subjected to electrochemical impedance spectroscopy (EIS) testing using an electrochemical workstation. Figure 8 The area capacitance and cycle stability were tested, and the results are shown in Table 7 below.

[0083] Table 7 Test results of Example 7

[0084] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., should be included within the protection scope of the present invention.

Claims

1. A magnesium phosphate cement supercapacitor with a gradient interpenetrating interface, characterized in that, include: A positive conductive cement layer, a negative conductive cement layer, and a solid electrolyte separator layer located between the two; wherein: Both the positive electrode conductive cement layer and the negative electrode conductive cement layer are composed of a conductive dense region and a porous transition region. The conductive dense region is located on the outside, and the porous transition region is located on the inside and adjacent to the solid electrolyte isolation layer. The porosity of the solid electrolyte isolation layer, the porous transition region, and the conductive dense region gradually decreases to form a gradient structure. The solid electrolyte isolation layer comprises a porous magnesium phosphate cement framework and a gel electrolyte distributed in its interconnected pores; the gel electrolyte comprises a polymer gel framework and phosphate compounds, potassium salts, magnesium salts, and water-retaining components distributed therein, and the gel electrolyte interacts with the Mg-containing components in the pore walls of the porous magnesium phosphate cement framework through the phosphate groups in the phosphate compounds. 2+ The gel electrolyte is anchored at the interfacial active sites of Mg-OH or magnesium oxide clusters, thereby stabilizing the gel electrolyte within the pores; simultaneously, the pores of the porous transition zone contain the gel electrolyte.

2. The magnesium phosphate cement supercapacitor with a gradient interpenetrating interface according to claim 1, characterized in that, The porous magnesium phosphate cement skeleton is made of the following components in the following proportions: 100 parts by weight of reburned magnesium oxide, 25-50 parts by weight of phosphate, 2-10 parts by weight of retarder, 2-50 parts by weight of insulating filler, 5-20 parts by weight of pore-forming agent, and water at 0.18-0.35% of the total mass of the reburned magnesium oxide and potassium dihydrogen phosphate; Alternatively, the thickness ratio of the porous transition region of the solid electrolyte isolation layer, the positive conductive cement layer or the negative conductive cement layer, and the conductive dense region of the positive conductive cement layer or the negative conductive cement layer is 1:0.1~1.0:0.5~8.

3. The magnesium phosphate cement supercapacitor with a gradient interpenetrating interface according to claim 2, characterized in that, The phosphate includes at least one of potassium dihydrogen phosphate and ammonium dihydrogen phosphate. Alternatively, the retarder may include at least one of the following: borax, boric acid, citric acid, tartaric acid, gluconate, and citrate. Alternatively, the insulating filler includes at least one of the following: fly ash, silica fume, metakaolin, quartz powder, calcium carbonate powder, alumina powder, glass microspheres, and ceramic micro powder; Alternatively, the pore-forming agent may include at least one of the following: potassium sulfate particles, sodium chloride particles, polyethylene glycol particles, soluble starch particles, and water-soluble polymer microspheres. Alternatively, the particle size of the porogen is 80~150μm.

4. The magnesium phosphate cement supercapacitor with a gradient interpenetrating interface according to claim 1, characterized in that, The proportions of each component in the gel electrolyte are as follows: 3-15 wt.% polymer gel skeleton, 0.5-15 wt.% phosphate compound, 5-40 wt.% water-retaining component, and the balance being water; at the same time, the gel electrolyte also contains 0.1-3.0 mol / L potassium salt and 0.05-0.3 mol / L magnesium salt.

5. The magnesium phosphate cement supercapacitor with a gradient interpenetrating interface according to claim 4, characterized in that, The polymer gel skeleton is made of at least one of the following materials: polyvinyl alcohol, polyacrylamide, polyacrylate, polyethylene oxide, polyethylene glycol, sodium alginate, carboxymethyl cellulose, and chitosan. Alternatively, the phosphate-based compound may include at least one of: phytic acid, phytate, polyphosphate, hydroxyethylidene diphosphonic acid, and aminotrimethylene phosphonic acid; Alternatively, the potassium salt may include at least one of potassium sulfate, potassium chloride, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, potassium nitrate, and potassium acetate. Alternatively, the magnesium salt may include at least one of magnesium sulfate, magnesium chloride, magnesium nitrate, magnesium acetate, and magnesium dihydrogen phosphate. Alternatively, the water-retaining component may include at least one of the following: glycerin, sorbitol, ethylene glycol, polyethylene glycol, propylene glycol, betaine, and urea.

6. The magnesium phosphate cement supercapacitor with a gradient interpenetrating interface according to claim 1, characterized in that, The conductive dense region is made of the following components in the following proportions: 100 parts by weight of calcined magnesium oxide, 25-50 parts by weight of phosphate, 2-10 parts by weight of retarder, 3-20 parts by weight of conductive material, and water at 0.18-0.35% of the total mass of the calcined magnesium oxide and potassium dihydrogen phosphate.

7. The magnesium phosphate cement supercapacitor with a gradient interpenetrating interface according to claim 1, characterized in that, The porous transition zone is made of the following components in the following proportions: 100 parts by weight of reburned magnesium oxide, 25-50 parts by weight of phosphate, 2-10 parts by weight of retarder, 3-18 parts by weight of conductive material, 1-8 parts by weight of pore-forming agent, and water at 0.18-0.35% of the total mass of the reburned magnesium oxide and potassium dihydrogen phosphate; or, the particle size of the pore-forming agent is 80-150 μm.

8. The magnesium phosphate cement supercapacitor with a gradient interpenetrating interface according to claim 6 or 7, characterized in that, The phosphate includes at least one of potassium dihydrogen phosphate and ammonium dihydrogen phosphate. Alternatively, the retarder may include at least one of the following: borax, boric acid, citric acid, tartaric acid, gluconate, and citrate. Alternatively, the conductive material may include at least one of activated carbon powder, carbon black powder, graphite powder, graphene, and carbon nanotubes.

9. A method for preparing a magnesium phosphate cement supercapacitor with a gradient interpenetrating interface as described in any one of claims 1-8, characterized in that, Includes the following steps: (1) Prepare the slurry for the conductive dense region, the slurry for the porous transition region, and the slurry for the porous magnesium phosphate cement skeleton, respectively, for later use; (2) The slurry is poured into the mold in sequence using a wet contact continuous molding method, and cured after hardening. An integral bonding interface is formed between adjacent layers to obtain a cement matrix. (3) The cement matrix is ​​immersed in water or potassium salt solution to dissolve and remove the pore-forming agent to form interconnected pores, thereby constructing a gradient structure in which the porosity gradually decreases from the solid electrolyte isolation layer and the porous transition region to the conductive dense region, thus obtaining the capacitor matrix; (4) The gel electrolyte is injected into the porous magnesium phosphate cement skeleton of the capacitor matrix, and the magnesium phosphate cement supercapacitor is obtained after gelation.

10. The method for preparing the magnesium phosphate cement supercapacitor with a gradient interpenetrating interface as described in claim 9, characterized in that, In step (4), the gelation method includes at least one of freeze-thaw crosslinking and ionic crosslinking; Alternatively, in step (4), after the polymer gel solidifies to form a skeleton, it is impregnated with a post-treatment solution containing potassium and magnesium salts, and then dried to obtain the magnesium phosphate cement supercapacitor.

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