Geopolymer-based supercapacitor and preparation method of electrode of geopolymer-based supercapacitor

Abstract

The invention discloses a geopolymer-based supercapacitor, and the supercapacitor comprises a current collector which is made of a corrosion-resistant material with good conductivity; the first structure electrode takes a geopolymer as a gel material, a carbon material as a conductive reinforcing material and a metal oxide as an active substance of the electrode, and the carbon material and the metal oxide form a conductive grid and provide a pseudocapacitance effect; the second structure electrode comprises a geopolymer and a carbon material so as to form an ion conduction and energy storage channel; and the ion transmission diaphragm is arranged between the first structure electrode and the second structure electrode and is used for preventing electron conduction but allowing ions to pass through. The invention also discloses a preparation method of the geopolymer-based supercapacitor electrode. By introducing the high-conductivity carbon material and combining a layered pressure applying process, the conductive material is ensured to be uniformly distributed in the electrode, so that the conductive material forms a tight conductive network, the internal resistance of the electrode is reduced, the conductivity of the electrode is improved, and the power density and the charge-discharge speed of the supercapacitor are enhanced.

Description

Technical Field

[0001] The invention belongs to the technical field of supercapacitors, and in particular relates to a geopolymer-based supercapacitor and a method for preparing an electrode thereof. Background Art

[0002] With the increasing global attention to sustainable development and energy efficiency, the new building sector is also facing increasing energy demand and environmental challenges. Traditional building energy systems often cannot meet these needs, so seeking innovative energy solutions has become key. Supercapacitors are energy storage devices that are widely used in electronic devices and systems that require high power and long life. Traditional supercapacitor electrodes usually use carbon materials, transition metal oxides, and conductive polymers. These materials have advantages in conductivity and electrochemical properties, but there are also problems such as high cost, poor electrochemical stability, environmental impact, and resource scarcity. With the development of materials science, supercapacitors based on geopolymers have gradually attracted the attention of researchers. Geopolymers are an inorganic material composed of silicon aluminum oxide tetrahedral structural units with good mechanical properties, corrosion resistance, and thermal stability. Through the use of alkaline activators, free ions in geopolymers can move in a directional manner under an applied electric field to realize the function of charge storage. The application of structural supercapacitors based on building materials such as geopolymers can not only supply electricity to buildings, but also have the hope of storing and utilizing renewable energy such as solar energy and wind energy.

[0003] CN117727570A proposes a supercapacitor solution based on cement materials, using activated carbon fibers as electrode materials and improving the conductivity and ion transmission capacity of the geopolymer matrix through alkaline activators. This design enables cement materials to partially replace traditional supercapacitor electrodes and improve energy storage efficiency. However, the uneven distribution of electrode materials affects the formation of conductive paths, and the optimization of electrode spacing is insufficient, which limits the improvement of electrochemical performance of this design. CN215220531U further optimizes the structure of geopolymer supercapacitors, embeds metal mesh, and uses the directional movement of free ions in geopolymers to achieve charge storage. This solution is simple in design and suitable for environmentally friendly building materials. However, the conductivity mainly depends on the physical structure of the metal mesh, and the conductive potential of the internal structure of the geopolymer is not fully utilized, which limits the improvement of the overall electrochemical performance. CN113666654A proposes a conductive material based on a combination of modified fly ash, alkaline activators and ion enhancers by improving the formula of conductive slurry, which significantly enhances the energy storage performance of the material. However, this design still has certain challenges in terms of mechanical strength and long-term conductive stability after curing. CN113436907A simplifies the structure of traditional supercapacitors and proposes a geopolymer-based supercapacitor that does not require an ion permeable membrane. By using the geopolymer matrix itself to provide electrolyte functions, the need for additional components is reduced, and the material is applied to the construction field. This technology uses a combination of modified fly ash and an alkali activator to improve the conductivity of the geopolymer matrix. However, due to the difficulty in controlling the pore structure, the ion transmission efficiency is not optimal, which limits the overall performance of the capacitor. CN113436899A proposes a new solution for the application of supercapacitors in building materials. By adjusting the proportion of conductive materials in geopolymers, a balance between high mechanical strength and electrochemical performance is achieved. The complexity of this technology in material design increases the difficulty of the production process, especially for consistency and cost control in large-scale applications.

[0004] In summary, existing technologies have made initial progress in improving the energy storage performance of geopolymer-based supercapacitors, but they still face some technical bottlenecks:

[0005] 1. Insufficient distribution and connectivity of conductive materials, resulting in poor conductivity of the electrode;

[0006] 2. It is difficult to control the pore structure of geopolymer-based materials, which affects the ion transmission efficiency;

[0007] 3. It is difficult to balance mechanical strength and long-term stability while improving electrochemical performance;

[0008] 4. There are still technical barriers to cost control and production consistency in large-scale applications.

[0009] In order to solve the limitations of the prior art, the present invention proposes a method for preparing a geopolymer-based supercapacitor using a segmented pressing method, which improves the conductivity, ion migration capacity and energy storage efficiency of the electrode by adopting a staged pressure application process. The present invention further enhances the connectivity of the conductive network and the mechanical properties of the material by improving the material combination and preparation process, and is suitable for large-scale production and application. Summary of the invention

[0010] The prior art geopolymer-based supercapacitors have deficiencies in conductivity, energy storage efficiency and mechanical properties, and cannot meet the requirements of high-performance energy storage devices. In order to solve these problems, the present invention provides a method for preparing a geopolymer-based supercapacitor and its electrode based on an optimized electrode formula and a layered pressure application process to improve the conductivity, energy storage performance and mechanical strength of the electrode.

[0011] The technical solution adopted by the present invention to solve the technical problem is: a geopolymer-based supercapacitor, comprising:

[0012] The current collector is made of a material with good electrical conductivity and corrosion resistance;

[0013] The first structure electrode uses geopolymer as gel material, carbon material as conductive reinforcing material, and metal oxide as active material of the electrode, and the carbon material and metal oxide form a conductive grid and provide pseudocapacitance effect;

[0014] The second structure electrode includes a geopolymer and a carbon material to form an ion conduction and energy storage channel;

[0015] The ion transport membrane is arranged between the first structure electrode and the second structure electrode, and is used for preventing electron conduction but allowing ions to pass through.

[0016] The first structure electrode and the second structure electrode of the present invention have different compositions, thereby providing different electrochemical reaction mechanisms, thereby improving the overall performance; geopolymer is used as a gelling material, carbon material is used as a conductive reinforcing material, and metal oxide is used as the active material of the electrode. The carbon material and the metal oxide form a stable conductive network and provide a pseudocapacitive effect. The second structure electrode is composed only of geopolymer and carbon material, forming a fast ion conduction and energy storage channel; the ion transport membrane is used as a diaphragm to prevent electron conduction but allow ions to pass through. Pseudocapacitive metal oxides can undergo Faraday redox reactions during charging and store charges on the electrode surface or near the surface; metal oxides have a higher specific capacitance and can store more charges, and are used as positive electrodes of supercapacitors; carbon material electrodes mainly rely on the double layer effect to store charges due to their strong conductivity and fast ion diffusion rate; when used as negative electrodes, they provide fast charging and discharging performance by physically adsorbing charges.

[0017] The current collector is used to collect and conduct current and is arranged between the structural electrode and the external circuit to ensure efficient transmission of current between the internal electrode of the supercapacitor and the external circuit; the current collector is made of a material with good conductivity and corrosion resistance, preferably selected from aluminum foil, copper foil, nickel foil or a high-strength material coated with a conductive coating to ensure conductivity during high-power charging and discharging and stability in long-term use; preferably, the surface of the current collector is roughened or coated with a conductive polymer to improve the bonding force with the electrode material and reduce the contact resistance, thereby improving the overall performance of the supercapacitor.

[0018] Furthermore, the carbon material is selected from one or more of carbon fiber, carbon nanotube, activated carbon, graphene and carbon black, the specific surface area of ​​the carbon material is 50-3000 square meters / gram, and in the first structure electrode and the second structure electrode, the carbon material accounts for 1%-20% of the weight of the structure electrode material. The conductivity and surface area of ​​the electrode are improved, thereby increasing the electrochemical activity; the carbon material is used to enhance the conductivity in both electrodes.

[0019] Furthermore, the metal oxide in the first structure electrode is one or two or more of MnO2, NiO, Co3O4, Fe2O3, V2O5, ZnO, SnO2 or TiO2, and the mass of the metal oxide accounts for 5%-30% of the total weight of the first electrode. The metal oxide provides a pseudocapacitive effect as an active material, significantly improving the specific capacitance and energy density of the electrode.

[0020] Furthermore, the geopolymer is prepared by mixing a geopolymer precursor and an alkaline activator, wherein the geopolymer precursor is one or more of metakaolin, slag, fly ash or steel slag, and the alkaline activator is an aqueous solution of potassium hydroxide and potassium silicate, with a modulus of 2.0-3.5 and a dosage of 50%-200% of the mass of the geopolymer precursor, providing good ionic conductivity and mechanical strength, and ensuring the structural stability of the electrode.

[0021] Furthermore, the ion transport membrane is a glass fiber membrane, an ion exchange membrane, an electrolyte impregnated membrane or a polymer electrolyte membrane.

[0022] Furthermore, the thickness of the first structure electrode is 2 mm-20 mm.

[0023] The present invention also discloses a method for preparing a geopolymer-based supercapacitor electrode, comprising the following steps:

[0024] S1, dry-mixing a geopolymer precursor and a carbon material according to a set carbon / geopolymer ratio, and stirring them sufficiently to obtain a mixture;

[0025] S2, adding pseudocapacitive metal oxide to the mixture, and adding alkaline activator and water under continuous stirring;

[0026] S3, during the stirring process, adding a water reducing agent and a dispersant, and continuing stirring until the slurry has a uniform and stable color to obtain a geopolymer slurry;

[0027] S4, pouring fresh geopolymer slurry into a hard tableting mold, leveling the slurry by vibration, and then applying a low pressure of 1MPa-5MPa for preforming for 2-5 minutes;

[0028] S5, after completing the low-pressure preforming, continue to apply a high pressure of 5MPa-50MPa for press forming, the duration is 5-10 minutes;

[0029] S6, curing the formed electrode material at room temperature or at elevated temperature, preferably for 7-28 days, or accelerating curing at 60° C. to 100° C. for 3-28 days;

[0030] S7, the electrode material after curing is surface trimmed, cut to the target thickness, and polished until both ends of the electrode are flat and smooth. The trimmed electrode is placed in a drying oven at 60°C to 100°C and dried for 24 hours until the electrode weight no longer changes;

[0031] S8, completing the preparation of the first structure electrode;

[0032] S9, repeating the above steps S1, S3 to S7 to complete the preparation of the second structure electrode;

[0033] S10, preparing an alkaline electrolyte with a concentration of 1M to 6M, and soaking the dried first structure electrode material, second structure electrode material and ion transport membrane in the alkaline electrolyte for 12 to 24 hours until the electrodes completely absorb the electrolyte and reach a saturated state;

[0034] S11, placing an ion transport membrane between the first structure electrode and the second structure electrode, and assembling the supercapacitor using a sandwich stacking structure.

[0035] Further, the following steps are included:

[0036] S1, dry-mixing a geopolymer precursor (such as fly ash or slag) and a carbon material (such as carbon black, carbon fiber or carbon nanotube) according to a selected carbon / geopolymer ratio, and stirring the mixture thoroughly to ensure a good balance of electrical conductivity and mechanical properties;

[0037] S2, adding pseudocapacitive metal oxides to the mixture of step S1. These pseudocapacitive metal oxides can significantly increase the specific capacitance and energy density of the electrode, and improve the energy storage capacity of the electrode through the Faraday redox reaction; under continuous stirring, adding an appropriate amount of alkaline activator and water to the obtained powder. This step is used to activate the geopolymer matrix to form a gel material with excellent ionic conductivity;

[0038] S3, during the stirring process, add high-efficiency water reducer and dispersant. Continue stirring until the slurry color is uniform and stable, ensuring that the carbon material is evenly distributed and prevents agglomeration. This step helps to improve the fluidity of the slurry and reduce the phenomenon of uneven internal dispersion;

[0039] S4, pouring fresh geopolymer slurry into a hard tabletting mold of a certain diameter. The slurry is leveled by vibration, and then low pressure is applied for preforming, preferably 1MPa-5MPa, for 2 to 5 minutes. This step ensures uniform distribution of the conductive material in the slurry and preliminarily forms the structural electrode;

[0040] S5, after low-pressure preforming, continue to apply high pressure for compression molding, preferably 5MPa-50MPa, for 5 to 10 minutes to further compact the electrode material. High pressure application can significantly improve the density of the electrode material, enhance the connectivity of the conductive network, and improve the mechanical strength of the electrode;

[0041] S6, curing the formed electrode material at room temperature or elevated temperature, preferably for 7-28 days, or accelerating curing at 60° C. to 100° C. for 3-28 days; the curing process ensures that the mechanical and electrochemical properties of the electrode are stable;

[0042] S7, the electrode material after curing is surface trimmed, cut to the target thickness, and polished with sandpaper of gradually increasing mesh count until both ends of the electrode are flat and smooth to reduce contact resistance. The trimmed electrode is placed in a drying oven, preferably at a temperature of 60°C to 100°C, and dried for 24 hours until the electrode weight no longer changes, ensuring that there is no excess moisture inside the electrode;

[0043] S8, completing the preparation of the first structure electrode;

[0044] S9, repeating the above steps S1, S3 to S7 to complete the preparation of the second structure electrode;

[0045] S10, prepare an appropriate amount of alkaline electrolyte, preferably potassium hydroxide, potassium chloride or potassium carbonate solution, with a concentration of 1M to 6M. Soak the dried electrode material and ion transport membrane in an alkaline electrolyte, preferably for 12 to 24 hours, until the electrode completely absorbs the electrolyte and reaches a saturated state. By using an alkaline electrolyte, the chemical stability of the electrode material and the electrolyte can be better maintained, while enhancing the conductivity of the OH- ions, and effectively improving the electrochemical properties of the electrode. This process ensures sufficient contact between the electrode material and the electrolyte interface, thereby improving the ion transfer efficiency and the specific capacitance of the electrode, and enhancing the overall energy storage capacity of the supercapacitor;

[0046] S11, a sandwich structure is used to assemble the supercapacitor. An ion transport membrane is placed between two electrodes as an isolation layer to prevent short circuit. Preferably, the outer ends of the electrodes are covered with conductive graphite paper, and a moderate prestressing pressure is applied to ensure that the contact resistance between the conductive graphite paper and the electrode is minimized, thereby improving the conductive performance of the capacitor.

[0047] Furthermore, the water reducer is one or two or more of naphthalene water reducer, polycarboxylate water reducer, lignin water reducer, protein water reducer and calcium chloride water reducer, and the added amount is 0.1%-2% of the amount of geopolymer precursor. The water reducer is used to improve the fluidity of the electrode slurry, facilitate the uniform distribution of the slurry and subsequent molding.

[0048] Furthermore, the dispersant is one or two or more of hexadecyltrimethylammonium chloride, polyacrylamide, polystyrene, polyethylene oxide and polyurethane, and the added amount is 0.5%-5% of the carbon material. The dispersant is used to effectively disperse the carbon material, prevent the carbon material from agglomerating, and ensure its uniform distribution in the matrix.

[0049] The beneficial effects of the present invention are:

[0050] 1. Electrode conductivity is significantly improved:

[0051] The present invention introduces highly conductive carbon materials and combines the process of applying pressure in layers to ensure that the conductive materials are evenly distributed in the electrode. This process enables the conductive materials to form a tight conductive network, greatly reducing the internal resistance of the electrode and improving the conductivity of the electrode, thereby enhancing the power density and charge and discharge speed of the supercapacitor.

[0052] 2. Energy storage efficiency is significantly improved:

[0053] The introduction of pseudocapacitive materials significantly improves the specific capacitance and energy density of the electrode. Pseudocapacitive materials provide additional Faradaic charge storage capacity through redox reactions, effectively enhancing the energy storage capacity of supercapacitors. In addition, the nanostructure and high specific surface area of ​​the electrode material further promote ion transport and improve the rapid charge and discharge performance of the electrode.

[0054] 3. Enhanced mechanical properties:

[0055] The application of the layered pressure application process allows the electrode material to be processed in two stages, low pressure and high pressure, during the molding process, effectively improving the density and structural integrity of the electrode. High pressure pressing not only improves the mechanical strength of the electrode, enhances its stress resistance and crack resistance, but also ensures the structural stability of the electrode during long-term use and multiple charge and discharge cycles, extending the service life of the supercapacitor.

[0056] 4. Electrolyte compatibility optimization:

[0057] The use of alkaline electrolytes is highly compatible with alkali-activated geopolymer materials, further improving the ionic conductivity and electrochemical reaction efficiency of the electrode. The chemical compatibility of alkaline electrolytes with electrode materials helps to improve the electrochemical stability of the electrode and reduce performance degradation, thereby improving the overall life and cycle performance of supercapacitors.

[0058] 5. Reduce Carbon Footprint:

[0059] The geopolymer material used in the present invention uses industrial byproducts such as fly ash and slag as raw materials, replacing traditional cement materials, significantly reducing carbon emissions. Through alkali-activated geopolymer technology, the present invention not only reduces energy consumption in the preparation process, but also effectively reduces the recycling of construction waste. The environmental advantages of this process meet the needs of sustainable development, especially in reducing carbon footprint and waste management.

[0060] 6. Suitable for large-scale production:

[0061] The preparation process adopted by the present invention is simple and easy to implement, can be easily integrated into the existing industrial production line, has low material cost, and is suitable for large-scale batch production. Especially in the field of building materials, the process can be applied to building integrated energy storage systems to achieve efficient use of energy and promote the storage and distribution of renewable energy, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 Schematic diagram of a supercapacitor based on a carbon material / geopolymer-based composite material structure in the present invention.

[0063] Figure 2 This is a cyclic voltammetry scanning curve of the supercapacitor prepared in Example 1 of the present invention.

[0064] Figure 3 This is a constant current charge and discharge curve diagram of the supercapacitor prepared in Example 1 of the present invention.

[0065] Description of the accompanying figures: 1 is a current collector, 2 is a structural electrode, and 3 is an ion transport membrane. DETAILED DESCRIPTION

[0066] In order to enable those skilled in the art to better understand the solutions of the present invention, the following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0067] Example 1

[0068] The first structure electrode and the second structure electrode are prepared respectively according to the following method:

[0069] Weigh 5 parts of fly ash as geopolymer precursor, add 1 part of carbon black and 0.5 parts of carbon fiber as conductive material, dry mix these powders, stir them thoroughly for 5 minutes to obtain a powder mixture; add 2 parts of MnO2 to the mixture, and under continuous stirring, add an alkaline activator solution with a modulus of 3.0 composed of potassium hydroxide and potassium silicate, and the amount of alkaline activator added is 8 parts. During the stirring process, add 0.05 parts of polycarboxylate water reducer and 0.1 parts of polyethylene oxide, stir thoroughly until the color of the slurry is uniform and stable, and obtain the first structure electrode slurry. The obtained first structure electrode slurry is poured into a square hard mold with a size of 2cm×2cm, and the slurry is vibrated and leveled using a vibration table. Apply a low pressure of 1MPa to the slurry for 2 minutes for pre-pressing. Then apply a high pressure of 20MPa for 5 minutes to ensure the densification of the material and form a stable conductive network. After the pressing is completed, the electrode material in the mold is placed at 60℃ for 28 days to ensure that the material is fully cured. After the curing, the electrode was demoulded and the surface was trimmed. Sandpaper was used to polish the electrode to a thickness of 5 mm, and the surface was smooth to reduce the contact resistance. The trimmed electrode was placed in a drying oven and dried at 60°C for 24 hours to ensure that the electrode material was completely dry. The dried electrode was immersed in a 3M potassium hydroxide (KOH) electrolyte for 12 hours to ensure that the electrode completely absorbed the electrolyte and reached a saturated state, thereby obtaining the first structure electrode.

[0070] Weigh 5 parts of fly ash as geopolymer precursor, add 1 part of carbon black and 0.5 parts of carbon fiber as conductive materials, dry mix these powders, stir them thoroughly for 5 minutes, and then add an alkaline activator solution with a modulus of 3.0 composed of potassium hydroxide and potassium silicate, and the amount of alkaline activator added is 8 parts. During the stirring process, add 0.05 parts of polycarboxylate water reducer and 0.1 parts of polyethylene oxide, stir thoroughly until the slurry color is uniform and stable, and obtain the second structure electrode slurry. The obtained second structure electrode slurry is poured into a square hard mold with a size of 2cm×2cm, and the slurry is vibrated and leveled using a vibration table. Apply a low pressure of 1MPa to the slurry for 2 minutes for pre-pressing. Then apply a high pressure of 20MPa for 5 minutes to ensure the densification of the material and form a stable conductive network. After the pressing is completed, the electrode material in the mold is placed at 60°C for 28 days to ensure that the material is fully cured. After curing, the electrode was demoulded and surface trimmed. Sandpaper was used to polish the electrode to a thickness of 5 mm, while ensuring that the surface was smooth to reduce contact resistance. The trimmed electrode was placed in a drying oven and dried at 60°C for 24 hours to ensure that the electrode material was completely dry. The dried electrode was immersed in a 3M potassium hydroxide (KOH) electrolyte for 12 hours to ensure that the electrode completely absorbed the electrolyte and reached a saturated state to obtain a second structure electrode.

[0071] The ion transport membrane is placed between the first structure electrode and the second structure electrode, and the current collectors connected to the external circuit are placed outside the two electrodes respectively to form a sandwich stacking structure to form an assembly of a supercapacitor.

[0072] In this embodiment, the current collector is aluminum foil.

[0073] The electrochemical performance of the electrode was tested by cyclic voltammetry (CV) and constant current charge-discharge (GCD) with an operating voltage range of 1 V, a scan rate of 20-500 mV / s, and a test current density of 2-50 mA / cm 2 , in order to evaluate its key performance indicators such as specific capacitance, energy density and surface capacitance. In this test, the prepared electrode area is 2cm×2cm and the thickness is 5mm. In the cyclic voltammetry test, the specific capacitance of the electrode was measured to be 5F / cm 2 As the electrode is thicker, the ion transport path increases, resulting in a slightly lower specific capacitance than the thinner electrode. At the same time, constant current charge and discharge tests show that the energy density of this electrode is about 2.5mWh / cm 2 , which is consistent with the expected performance of alkali-activated geopolymer-based supercapacitors.

[0074] The electrochemical test results show that it exhibits relatively stable electrochemical behavior during rapid charge and discharge. Due to its large thickness, the mechanical strength of the electrode is enhanced, the cycle stability is good, and it can adapt to multiple charge and discharge cycles, but due to the extension of the ion diffusion path, the response speed of the electrode is reduced. After multiple charge and discharge cycles, the structure of the electrode remains intact, the mechanical strength is excellent, and there is no significant performance degradation, indicating that the electrode material is suitable for high energy density energy storage applications, with certain stability and good durability.

[0075] Example 2

[0076] A geopolymer-based supercapacitor is prepared. The method of this embodiment is basically the same as that of embodiment 1, except that the type and proportion of the pseudocapacitive metal oxide are optimized.

[0077] In this embodiment, the preparation process of the first structure electrode slurry is as follows:

[0078] Weigh 5 parts of fly ash as a geopolymer precursor, add 1 part of carbon black and 0.5 parts of carbon fiber as conductive materials, dry mix these powders, and stir them for 5 minutes to obtain a powder mixture; add 0.5 parts of MnO2, 0.75 parts of NiO and 0.75 parts of Co3O4 to the mixture, and add 8 parts of an alkaline activator solution with a modulus of 3.0 composed of potassium hydroxide and potassium silicate under continuous stirring. During the stirring process, add 0.05 parts of polycarboxylate water reducer and 0.1 parts of polyethylene oxide, stir them until the slurry color is uniform and stable, and obtain the first structure electrode slurry.

[0079] The pressing, curing and post-processing of the first structure electrode and the preparation process of the second structure electrode are the same as those in Example 1.

[0080] Through this optimized combination, electrochemical test results show that the specific capacitance of the electrode is increased to 6F / cm 2 , the surface energy density reaches 3mWh / cm 2 The combination significantly enhances the electrochemical reaction activity of the electrode and exhibits better cycle stability and energy density over multiple charge and discharge cycles. The optimized electrode has a significant improvement in energy storage performance and is particularly suitable for high energy density energy storage applications.

[0081] Example 3

[0082] A geopolymer-based supercapacitor is prepared. The method of this embodiment is basically the same as that of embodiment 1, except that the type and concentration of the electrolyte are optimized in this embodiment.

[0083] In this embodiment, the slurry preparation, pressing and curing process of the first structure electrode and the second structure electrode are the same as those in Example 1. After the curing is completed, the electrode is demolded and the surface is trimmed. Sandpaper is used to polish the electrode to a thickness of 5 mm, while ensuring that the surface is smooth to reduce the contact resistance. The trimmed electrode is placed in a drying oven and dried at 60°C for 24 hours to ensure that the electrode material is completely dry. The dried electrode is immersed in a mixed solution electrolyte of 4M potassium hydroxide and 1M sodium hydroxide for 12 hours to ensure that the electrode completely absorbs the electrolyte and reaches a saturated state, and the first structure electrode and the second structure electrode are obtained respectively.

[0084] By using a higher concentration of alkaline electrolyte and Na + , K + The synergistic effect of ions makes the electrode show better performance in electrochemical tests. The electrochemical test results show that the specific capacitance of the electrode is increased to 6.5F / cm 2 , the surface energy density reaches 3.2mWh / cm 2 Compared with Example 1 and Example 2, the optimized electrolyte further improves the ion transfer rate and charge-discharge efficiency of the electrode, and also has significant improvements in cycle life and energy density.

[0085] Example 4

[0086] A geopolymer-based supercapacitor is prepared. The method of this embodiment is basically the same as that of embodiment 1, except that the ratio and modulus of the alkaline activator are optimized in this embodiment.

[0087] The first structure electrode and the second structure electrode are prepared respectively according to the following method:

[0088] Weigh 5 parts of fly ash as a geopolymer precursor, add 1 part of carbon black and 0.5 parts of carbon fiber as conductive materials, dry mix these powders, and stir them for 5 minutes to obtain a powder mixture; add 2 parts of MnO2 to the mixture, and under continuous stirring, add an alkaline activator solution with a modulus of 2.0 composed of potassium hydroxide and potassium silicate, and the amount of the alkaline activator added is 8 parts. During the stirring process, add 0.05 parts of polycarboxylate water reducer and 0.1 parts of polyethylene oxide, stir them until the slurry color is uniform and stable, and obtain the first structure electrode slurry.

[0089] Weigh 5 parts of fly ash as a geopolymer precursor, add 1 part of carbon black and 0.5 parts of carbon fiber as conductive materials, dry mix these powders, stir them thoroughly for 5 minutes, and then add an alkaline activator solution with a modulus of 2.0 composed of potassium hydroxide and potassium silicate, and the amount of the alkaline activator added is 8 parts. During the stirring process, add 0.05 parts of polycarboxylate water reducer and 0.1 parts of polyethylene oxide, stir thoroughly until the slurry color is uniform and stable, and obtain the second structure electrode slurry.

[0090] The pressing, curing and post-processing of the first structure electrode and the second structure electrode are the same as those in Example 1.

[0091] By reducing the modulus and increasing the alkali content, the ionic conductivity of the alkali-activated system was improved. The optimized alkali activator significantly improved the conductivity and energy storage capacity of the geopolymer electrode. The electrochemical test results showed that the specific capacitance of the electrode was increased to 6.5F / cm 2 , the surface energy density reaches 3.2mWh / cm 2 Compared with Example 1, the optimized alkaline activator increases the ion transfer rate of the electrode, further improves the charge and discharge efficiency, and shows significant improvements in cycle life and energy density.

[0092] Example 5

[0093] A preparation of a geopolymer-based supercapacitor. The method of this embodiment is basically the same as that of Example 1, except that in this embodiment, the geopolymer precursor material is replaced by metakaolin instead of fly ash.

[0094] The first structure electrode and the second structure electrode are prepared respectively according to the following method:

[0095] Weigh 5 parts of metakaolin as a geopolymer precursor, add 1 part of carbon black and 0.5 parts of carbon fiber as conductive materials, dry mix these powders, and stir them for 5 minutes to obtain a powder mixture; add 2 parts of MnO2 to the mixture, and under continuous stirring, add an alkaline activator solution with a modulus of 3.0 composed of potassium hydroxide and potassium silicate, and the amount of the alkaline activator added is 8 parts. During the stirring process, add 0.05 parts of polycarboxylate water reducer and 0.1 parts of polyethylene oxide, stir them until the slurry color is uniform and stable, and obtain the first structure electrode slurry.

[0096] Weigh 5 parts of metakaolin as a geopolymer precursor, add 1 part of carbon black and 0.5 parts of carbon fiber as conductive materials, dry mix these powders, stir them thoroughly for 5 minutes, and then add an alkaline activator solution with a modulus of 3.0 composed of potassium hydroxide and potassium silicate, and the amount of the alkaline activator added is 8 parts. During the stirring process, add 0.05 parts of polycarboxylate water reducer and 0.1 parts of polyethylene oxide, stir thoroughly until the slurry color is uniform and stable, and obtain the second structure electrode slurry.

[0097] The pressing, curing and post-processing of the first structure electrode and the second structure electrode are the same as those in Example 1.

[0098] Metakaolin has a high silicon and aluminum content and forms a dense three-dimensional network structure under the action of alkaline activators. Compared with fly ash, metakaolin has higher chemical activity, which helps to improve the mechanical strength and ionic conductivity of the electrode. The electrochemical test results show that the specific capacitance of the electrode using metakaolin as a precursor is increased to 6.8F / cm 2 , the surface energy density reaches 3.5mWh / cm 2 Compared with the fly ash in Example 1, the use of metakaolin significantly improves the electrochemical performance of the electrode, especially showing better cycle stability under rapid charge and discharge conditions. The electrode using metakaolin as a precursor material has higher specific capacitance and energy density, and is suitable for high-efficiency energy storage applications.

[0099] Example 6

[0100] A preparation method of a geopolymer-based supercapacitor. The method of this embodiment is basically the same as that of embodiment 1, except that the pressure and time of segmented pressing are optimized in this embodiment.

[0101] In this embodiment, the slurry preparation, curing and post-treatment process of the first structure electrode and the second structure electrode are the same as those in Example 1. After obtaining the slurries of the first structure electrode and the second structure electrode respectively, the obtained second structure electrode slurry is poured into a square hard mold with a size of 2 cm×2 cm, and the slurry is vibrated and leveled using a vibration table. A low pressure of 2 MPa is applied to the slurry for 3 minutes for pre-pressing. Then a high pressure of 25 MPa is applied for 8 minutes to ensure the densification of the material and form a stable conductive network.

[0102] The test results show that the specific capacitance of the electrode reaches 7.0F / cm 2 , the surface energy density is 3.6mWh / cm 2 Compared with Example 1, the optimized segmented pressing pressure and time further enhance the compactness, conductivity and electrochemical performance of the electrode. By increasing the pressure and time of pre-pressing and high pressure, the conductive network of the electrode material is more uniform, and the electrode exhibits higher specific capacitance and energy density.

[0103] Comparative Example 1

[0104] The preparation method of this comparative example is substantially the same as that of Example 1, except that no pseudocapacitive metal oxide is used in this comparative example.

[0105] Weigh 5 parts of fly ash as geopolymer precursor, add 1 part of carbon black and 0.5 parts of carbon fiber as conductive materials, dry mix these powders, stir them thoroughly for 5 minutes, and then add an alkaline activator solution with a modulus of 3.0 composed of potassium hydroxide and potassium silicate, and the amount of alkaline activator added is 8 parts. During the stirring process, add 0.05 parts of polycarboxylate water reducer and 0.1 parts of polyethylene oxide, stir thoroughly until the slurry color is uniform and stable, and obtain the first structure electrode slurry. The obtained first structure electrode slurry is poured into a square hard mold with a size of 2cm×2cm, and the slurry is vibrated and leveled using a vibration table. Apply a low pressure of 1MPa to the slurry for 2 minutes for pre-pressing. Then apply a high pressure of 20MPa for 5 minutes to ensure the densification of the material and form a stable conductive network. After the pressing is completed, the electrode material in the mold is placed at 60°C for 28 days to ensure that the material is fully cured. After the curing, the electrode was demoulded and the surface was trimmed. Sandpaper was used to polish the electrode to a thickness of 5 mm, and the surface was smooth to reduce the contact resistance. The trimmed electrode was placed in a drying oven and dried at 60°C for 24 hours to ensure that the electrode material was completely dry. The dried electrode was immersed in a 3M potassium hydroxide (KOH) electrolyte for 12 hours to ensure that the electrode completely absorbed the electrolyte and reached a saturated state, thereby obtaining the first structure electrode.

[0106] The preparation process of the second structure electrode is the same as that of Example 1.

[0107] Electrochemical test results show that the specific capacitance of the electrode without pseudocapacitive materials is significantly reduced to only 2.5F / cm 2 , the surface energy density is only 1.2mWh / cm 2 Due to the lack of pseudocapacitive effect, the energy storage performance of the electrode is significantly reduced. Although the electrode exhibits stable mechanical strength during the charge and discharge cycle, the overall electrochemical performance is low and the energy storage capacity is insufficient, which is especially unsuitable for high energy density application scenarios.

[0108] Comparative Example 2

[0109] The preparation method of this comparative example is substantially the same as that of Example 1, except that the layered pressure application process is not used in this comparative example.

[0110] In Comparative Example 2, the slurry preparation, curing and post-treatment of the first structure electrode and the second structure electrode are the same as those in Example 1. After obtaining the slurries of the first structure electrode and the second structure electrode, the obtained slurries are poured into a square hard mold with a size of 2 cm×2 cm, and the slurries are vibrated and leveled using a vibration table. A pressure of 5 MPa is applied to the slurry for 3 minutes for pressing.

[0111] The electrochemical test results show that the specific capacitance of the electrode without the layered pressure process drops to 3F / cm 2 , the surface energy density is 1.8mWh / cm 2 . Due to the failure to form a uniform and dense conductive network, the ion transmission path of the electrode increases, and the conductivity and energy storage performance are reduced. In addition, the mechanical strength of the electrode is also slightly weakened, especially in multiple charge and discharge cycles, the performance of the electrode decays rapidly, indicating that the layered pressure process plays an important role in improving the density and mechanical stability of the electrode.

[0112]

[0113]

[0114] The above specific implementation modes are used to explain the present invention rather than to limit the present invention. Any modification and change made to the present invention within the spirit of the present invention and the protection scope of the claims shall fall within the protection scope of the present invention.

Claims

1. A geopolymer-based supercapacitor, characterized in that: include: The current collector is made of a material with good electrical conductivity and corrosion resistance; The first structure electrode uses geopolymer as gel material, carbon material as conductive reinforcing material, and metal oxide as active material of the electrode, and the carbon material and metal oxide form a conductive grid and provide pseudocapacitance effect; The second structure electrode includes a geopolymer and a carbon material to form an ion conduction and energy storage channel; The ion transport membrane is arranged between the first structure electrode and the second structure electrode, and is used for preventing electron conduction but allowing ions to pass through.

2. The geopolymer-based supercapacitor according to claim 1, characterized in that: The carbon material is selected from one or two or more of carbon fiber, carbon nanotube, activated carbon, graphene and carbon black. The specific surface area of ​​the carbon material is 50-3000 square meters / gram. In the first structure electrode and the second structure electrode, the carbon material accounts for 1%-20% of the weight of the structural electrode material.

3. The geopolymer-based supercapacitor according to claim 1, characterized in that: The metal oxide in the first structure electrode is one or two or more of MnO2, NiO, Co3O4, Fe2O3, V2O5, ZnO, SnO2 or TiO2, and the mass of the metal oxide accounts for 5%-30% of the total weight of the first electrode.

4. The geopolymer-based supercapacitor according to claim 1, characterized in that: The geopolymer is prepared by mixing a geopolymer precursor and an alkali activator. The geopolymer precursor is one or more of metakaolin, slag, fly ash or steel slag. The alkali activator is an aqueous solution of potassium hydroxide and potassium silicate, with a modulus of 2.0-3.5 and a dosage of 50%-200% of the mass of the geopolymer precursor.

5. The geopolymer-based supercapacitor according to claim 1, characterized in that: The ion transport membrane is a glass fiber membrane, an ion exchange membrane, an electrolyte impregnated membrane or a polymer electrolyte membrane.

6. The geopolymer-based supercapacitor according to claim 1, characterized in that: The thickness of the first structure electrode is 2 mm-20 mm.

7. A method for preparing a geopolymer-based supercapacitor electrode according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1, dry-mixing a geopolymer precursor and a carbon material according to a set carbon / geopolymer ratio, and stirring them sufficiently to obtain a mixture; S2, adding pseudocapacitive metal oxide to the mixture, and adding alkaline activator and water under continuous stirring; S3, during the stirring process, adding a water reducing agent and a dispersant, and continuing stirring until the slurry has a uniform and stable color to obtain a geopolymer slurry; S4, pouring fresh geopolymer slurry into a hard tableting mold, leveling the slurry by vibration, and then applying a low pressure of 1MPa-5MPa for preforming for 2-5 minutes; S5, after completing the low-pressure preforming, continue to apply a high pressure of 5MPa-50MPa for press forming, the duration is 5-10 minutes; S6, curing the formed electrode material at room temperature or at elevated temperature, preferably for 7-28 days, or accelerating curing at 60° C. to 100° C. for 3-28 days; S7, the electrode material after curing is surface trimmed, cut to the target thickness, and polished until both ends of the electrode are flat and smooth. The trimmed electrode is placed in a drying oven at 60°C to 100°C and dried for 24 hours until the electrode weight no longer changes; S8, completing the preparation of the first structure electrode; S9, repeating the above steps S1, S3 to S7 to complete the preparation of the second structure electrode; S10, preparing an alkaline electrolyte with a concentration of 1M to 6M, and soaking the dried first structure electrode material, second structure electrode material and ion transport membrane in the alkaline electrolyte for 12 to 24 hours until the electrodes completely absorb the electrolyte and reach a saturated state; S11, placing an ion transport membrane between the first structure electrode and the second structure electrode, and assembling the supercapacitor using a sandwich stacking structure.

8. The method for preparing a geopolymer-based supercapacitor electrode according to claim 7, characterized in that: The water reducer is one or two or more of naphthalene water reducer, polycarboxylate water reducer, lignin water reducer, protein water reducer and calcium chloride water reducer, and the added amount is 0.1%-2% of the amount of the geopolymer precursor.

9. The method for preparing a geopolymer-based supercapacitor electrode according to claim 7, characterized in that: The dispersant is one or two or more of hexadecyltrimethylammonium chloride, polyacrylamide, polystyrene, polyethylene oxide and polyurethane, and the added amount is 0.5%-5% of the carbon material.

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