Conductive carbon material for cement-based electrode and preparation method thereof, cement-based electrode and supercapacitor

Abstract

The application provides a conductive carbon material for a cement-based electrode and a preparation method of the conductive carbon material, the cement-based electrode and a super capacitor, and relates to the technical field of super capacitors. The application prepares carbon black material with specific pore size distribution through chlorination reaction, and reduces specific surface area loss through surface modification, and further improves the carbon black network connectivity. And the use of organic electrolyte greatly improves the voltage window, so that the capacitance produces qualitative leap.

Description

Technical Field

[0001] The present invention relates to the technical field of cement-based supercapacitors, and in particular to a conductive carbon material for cement-based electrodes, a preparation method thereof, a cement-based electrode, and a supercapacitor. Background Art

[0002] Cement-based electrodes are a new type of electrode material made from cement and conductive carbon black. Supercapacitors using carbon-cement electrodes have already appeared. However, the conductivity and double-layer capacity of conductive carbon black still need to be improved. Current research focuses on increasing the conductivity of carbon-cement electrodes by increasing the active material (carbon black) content or using a compaction molding method to significantly enhance the connectivity of the carbon network within the carbon-cement electrode. The double-layer storage performance of carbon-cement supercapacitors is crucially dependent on the available specific surface area of ​​the electrode composite. Due to the continuous cement hydration reaction, the carbon black surface is covered with insulating hydration products, severely reducing the available specific surface area. Furthermore, the efficient improvement of double-layer capacity is closely related to the pore size distribution within the electrode composite. Pores with a diameter of less than 200 nm provide an excellent location for double-layer storage and exhibit an extremely high specific surface area. Summary of the Invention

[0003] To address these issues, the present invention proposes a method for preparing carbon black materials with a specific pore size distribution through chlorination. Surface modification reduces the loss of specific surface area in the electrode material and further enhances the carbon black network connectivity. The use of an organic electrolyte significantly increases the voltage window, resulting in a substantial leap in capacitance.

[0004] One of the objects of the present invention is to provide a method for preparing a conductive carbon material for cement-based electrodes.

[0005] A second object of the present invention is to provide a conductive carbon material for cement-based electrodes prepared by the preparation method.

[0006] A third object of the present invention is to provide a cement-based electrode prepared from the conductive carbon material.

[0007] A fourth object of the present invention is to provide a supercapacitor comprising the cement-based electrode.

[0008] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are adopted:

[0009] In a first aspect, the present invention provides a method for preparing a conductive carbon material for a cement-based electrode, comprising the following steps:

[0010] 1) Silicon carbide powder is loaded into a quartz reaction tube and placed in a high-temperature furnace. An inert gas is first introduced to expel air, the high-temperature furnace is heated, and then chlorine is introduced to carry out a chlorination reaction. After the reaction is completed, the chlorine supply is stopped, the inert gas is continued to be introduced, and the reaction tube is cooled to room temperature to obtain carbide-derived carbon; wherein the chlorination reaction temperature is 800-1000°C and the time is 2-6 hours;

[0011] 2) Surface modification of the carbide-derived carbon obtained in step 1) is performed using a silane coupling agent to obtain a conductive carbon material for cement-based electrodes.

[0012] The following is a detailed description of each step:

[0013] Step 1):

[0014] Place the silicon carbide powder into the quartz reaction tube, spreading it as evenly as possible to avoid accumulation. Install the reaction tube loaded with silicon carbide powder into the high-temperature furnace, ensuring that the inlet and outlet of chlorine and inert gas are connected.

[0015] Before starting the chlorination reaction, an inert gas (such as argon) is introduced to purge the air in the reaction tube to prevent oxidation reaction.

[0016] Preferably, the flow rate of the inert gas is 100-200 ml / min, preferably 150 ml / min, and the ventilation is continued for 15-45 minutes, preferably about 30 minutes.

[0017] While introducing inert gas, the high temperature furnace is heated to 800-1000° C., preferably 900° C. (chlorination reaction temperature).

[0018] When the temperature reaches the set value, chlorine is gradually introduced while maintaining the flow of inert gas.

[0019] Preferably, the flow rate of chlorine gas is 50-200 ml / min, preferably 50 ml / min.

[0020] Chlorine reacts with silicon carbide to form silicon chloride (SiCl4), which leaves the reaction tube, leaving the remaining carbon in a porous structure. After the reaction is complete, the chlorine supply is stopped, and the inert gas is continued to flow, and the reaction tube is cooled to room temperature.

[0021] By regulating the temperature, flow rate and reaction time of the high-temperature chlorination reaction of silicon carbide, the size of the micropores can be changed to achieve precise control of the pore structure distribution.

[0022] In the carbide-derived carbon obtained in step 1), the pore volume of pores smaller than 200 nm accounts for more than 70% of the total pore volume, and the pore volume of pores smaller than 900 nm accounts for more than 90% of the total pore volume; the specific surface area of ​​the carbide-derived carbon is 1450-1800 m 2 / g.

[0023] It should be noted that the pore volume ratio of pores smaller than 200 nm is the pore volume of all pores smaller than 200 nm divided by the total pore volume according to BET statistics, and the pore volume ratio of pores smaller than 900 nm is the pore volume of all pores smaller than 900 nm divided by the total pore volume according to BET statistics.

[0024] Step 2):

[0025] In some embodiments, step 2) comprises:

[0026] a) cleaning and drying the carbide-derived carbon;

[0027] b) dissolving the silane coupling agent in anhydrous toluene to obtain a silane coupling agent solution;

[0028] c) placing the dried carbide-derived carbon in a reaction container, adding a silane coupling agent solution for reaction reflux, cooling to room temperature after the reaction, washing, and drying to obtain a conductive carbon material for cement-based electrodes.

[0029] Step a):

[0030] The carbide-derived carbon was ultrasonically cleaned with deionized water and ethanol to remove surface impurities. The sample was dried in a vacuum oven to ensure complete dryness to prevent moisture from affecting subsequent surface modification.

[0031] Step b):

[0032] Preferably, the silane coupling agent is trichloromethylsilane.

[0033] Step c):

[0034] Place the carbide-derived carbon in a reaction vessel and add the prepared silane coupling agent solution. Install a condensation reflux device to prevent solvent volatilization.

[0035] Preferably, the amount of the silane coupling agent is 2% to 10% by mass of the carbide-derived carbon, preferably 8%.

[0036] Preferably, the reaction reflux temperature is 80-110° C., and the reaction time is 24 hours.

[0037] After the reaction, cool the reaction vessel to room temperature and wash the sample with anhydrous toluene to remove any unreacted silane coupling agent. Wash the modified porous carbon several times with anhydrous ethanol to remove any remaining reactants. Finally, rinse with deionized water to ensure complete removal of the solvent and unreacted materials. Dry the washed sample in a vacuum oven to ensure complete dryness.

[0038] The surface of carbide-derived carbon is modified by long-chain alkyl groups in order to reduce the influence of hydration product formation on the pore structure in the subsequent preparation of cement-based materials, thereby forming a cement-based electrode material with ultra-high specific surface area.

[0039] In a second aspect, the present invention provides a conductive carbon material for cement-based electrodes prepared by the above preparation method.

[0040] In the conductive carbon material, the pore volume of pores smaller than 200 nm accounts for more than 70% of the total pore volume, and the pore volume of pores smaller than 900 nm accounts for more than 90% of the total pore volume; the specific surface area of ​​carbide-derived carbon is 1450-1800 m 2 / g.

[0041] The present invention uses specific carbides to carry out a chlorination reaction under specific conditions to control the pore structure of the prepared carbide-derived carbon to improve the conductive capacity, and performs surface modification through hydrophobic functional groups to reduce the problem of cement mixing hydration products covering the carbon material during the preparation of cement-based electrodes, causing its pores to be blocked and affecting its electrical performance.

[0042] In a third aspect, the present invention provides a cement-based electrode prepared from the above-mentioned conductive carbon material for cement-based electrodes and cement.

[0043] In some embodiments, the cement-based electrode is prepared by the following method:

[0044] The conductive carbon material and cement are mixed to obtain a dry mixture, water and a water reducer are added and mixed to obtain a cement-based slurry; the cement-based slurry is poured into a mold and vibrated, and after hardening, the slurry is demoulded, cured, cut, and polished to obtain a cement-based electrode.

[0045] Preferably, the cement is one or more selected from the group consisting of Portland cement, ordinary Portland cement, slag Portland cement, pozzolanic Portland cement, fly ash Portland cement, composite Portland cement, medium-heat Portland cement, low-heat slag Portland cement, and white Portland cement. The cement strength grade can be 425, 625, 325, 525, etc., without particular limitation.

[0046] Preferably, the mass of the conductive carbon material accounts for 8% to 13% of the mass of the cement;

[0047] Preferably, the water reducer is one or more selected from polycarboxylic acid high-efficiency water reducer and naphthalene-based high-efficiency water reducer;

[0048] Preferably, the water-cement ratio is 0.8-1.6, and the mass of the water reducer accounts for 2% to 4% of the mass of water.

[0049] Preferably, the curing temperature is 20±2° C., the relative humidity is controlled at above 95%, and the curing period is more than 28 days.

[0050] The specific surface area of ​​the obtained cement-based electrode is 300-500m 2 / g.

[0051] In a fourth aspect, the present invention provides a supercapacitor comprising the above-mentioned cement-based electrode;

[0052] The cement-based electrode is immersed in an organic electrolyte until saturated, and the cement-based electrode, the glass fiber membrane, and the cement-based electrode are packaged into a supercapacitor.

[0053] Beneficial effects:

[0054] The conductive carbon material of this invention significantly enhances the storage efficiency of the electric double layer (EDL) through its ultra-high specific surface area. This efficiency is maximized through precise control of the pore structure distribution. The tiny pores within the cement-based conductive material, which contribute primarily to the specific surface area, also provide numerous adsorption sites for charge storage. The medium and large pores act as fast pathways for ion transport and excellent locations for electrolyte storage.

[0055] The present invention has been described in detail above, but the above embodiments are merely illustrative in nature and are not intended to limit the present invention. In addition, the present invention is not limited by any theory described in the above prior art or invention summary or the following examples. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 shows an SEM image of the conductive carbon material prepared in Example 1;

[0057] Figure 2 shows the pore size distribution curve of the conductive carbon material prepared in Example 1;

[0058] Figure 3 shows the adsorption-desorption curve of the conductive carbon material prepared in Example 1;

[0059] Figure 4 The resistance-pressure curve of the cement-based electrode material prepared in Example 1 is shown. DETAILED DESCRIPTION

[0060] The present invention will be further described below with reference to the examples. It should be noted that the following examples are provided for illustrative purposes only and do not constitute a limitation on the scope of protection claimed in the present invention.

[0061] Unless otherwise specified, the raw materials, reagents, methods, etc. used in the examples are conventional raw materials, reagents, and methods in the art.

[0062] The materials and equipment used in the examples are as follows:

[0063] β-SiC powder comes from Angxing New Carbon Materials Changzhou Co., Ltd.

[0064] High-purity chlorine (>99.9%) was obtained from Shandong Yanhe Chemical Co., Ltd.

[0065] Trichloromethylsilane was obtained from Shanghai MacLean Biochemical Technology Co., Ltd.

[0066] Example 1

[0067] Preparation of cement-based conductive carbon materials:

[0068] Take 25g of high-purity β-SiC and evenly distribute it in a quartz reaction tube to avoid accumulation. Place the reaction tube filled with silicon carbide powder into a high-temperature furnace, ensuring that the inlets and outlets for chlorine and inert gas are properly connected. Purge the reaction tube with argon at 150ml / min to prevent oxidation. Continue purging for approximately 30 minutes.

[0069] While introducing inert gas, the high-temperature furnace was heated to 900° C., and high-purity chlorine gas (>99.9%) was gradually introduced. The flow rate of chlorine gas was controlled at 50 ml / min, and the reaction time was 2.5 hours.

[0070] After the reaction was completed, the chlorine supply was stopped, and the inert gas was continued to be introduced to cool the reaction tube to room temperature.

[0071] The prepared carbide derivative (about 10.4 g) was allowed to stand for 24 hours and then ultrasonically cleaned with deionized water and ethanol to remove surface impurities.

[0072] 0.5 g of trichloromethylsilane was dissolved in 100 g of anhydrous toluene to obtain a trichloromethylsilane solution. The above carbide derivative sample was placed in a reaction vessel and the prepared trichloromethylsilane solution was added. The reaction temperature was controlled at 110° C. and the reaction time was 24 hours.

[0073] The reaction vessel was cooled to room temperature and the sample was washed with anhydrous toluene to remove any unreacted silane coupling agent. The modified carbon porous structure sample was washed several times with anhydrous ethanol to remove any residual reactants. Finally, the sample was rinsed with deionized water to ensure complete removal of the solvent and unreacted substances. The washed sample was dried in a vacuum drying oven to ensure complete dryness, thereby obtaining a cement-based conductive carbon material.

[0074] The morphology of cement-based conductive carbon materials was observed using SEM. Figure 1 As shown in the figure, it can be seen that there are dispersed granular substances in the material, which are carbon black particles or cement hydration products. The accumulation between particles may provide a conductive path for electrons and ions. Some areas in the image show flaky or layered structures (such as the local area on the right), which are characteristics of carbon black agglomerates. The specific surface area was measured using BET nitrogen adsorption, and the results are shown in the figure below. Figure 2 As shown, the specific surface area of ​​the conductive carbon material is 1742.41m2 / g. The adsorption and desorption curve of the conductive carbon material was tested by nitrogen adsorption. The results are as follows Figure 3 As shown in the figure, this adsorption and desorption behavior indicates that the material has a high specific surface area and a suitable pore structure (a combination of micropores and mesopores), which is very beneficial for supercapacitor electrode materials and can improve ion storage capacity and rapid transmission capacity.

[0075] Preparation of cement-based electrode materials:

[0076] Finally, the modified porous carbon (cement-based conductive carbon material) was mixed with 100g of Portland cement powder at a mass ratio of 8%, a water-cement ratio of 1.35, and a water reducer (Qingdao Huatie Polycarboxylic Acid High-Performance Water Reducer HT-300) at a mass of 2% of the water mass. The mixture was stirred for 20 minutes until uniformly mixed. Pour the mixture into a 10cm*10cm*10cm mold and place it on a vibrating table for 10 minutes. After hardening, the mold was removed and placed in a curing box at a temperature of 20±2°C and a relative humidity of above 95% for 28 days.

[0077] The specific surface area of ​​the cement-based electrode material was determined using BET nitrogen adsorption, and the results are shown in Table 1.

[0078] The resistance of cement-based electrode materials was measured using the four-probe method. Figure 4 As shown in the figure, the resistance of the electrode material is significantly reduced under pressure, indicating that its conductive performance is relatively ideal.

[0079] Preparation of supercapacitors:

[0080] Organic Electrolyte: Add 0.94g of LiPF6 to 10mL of propylene carbonate. Stir using a magnetic stirrer until the electrolyte is completely dissolved. Typically, this takes 30 minutes to 1 hour. Filter the prepared electrolyte using a 0.2-micron syringe filter to remove any solid impurities and undissolved particles. Store the filtered electrolyte in an anhydrous environment to avoid contact with moisture from the air.

[0081] The cement-based electrode material is soaked in a 1M organic electrolyte until saturated, and the cement-based electrode material, the glass fiber membrane, and the cement-based electrode material are packaged into a supercapacitor.

[0082] The specific capacitance is the capacitance divided by the mass of the two electrodes, measured by cyclic voltammetry (CV) with a scan voltage range of -2 V to 2 V and -1 V to 1 V for aqueous electrolyte.

[0083] Scan rate: Set to 100mV / s, and test multiple scan rates to evaluate the effect of rate on performance.

[0084] Specific capacitance: Use specific capacitance to define storage performance. Use CHI760E electrochemical workstation. Specific capacitance calculation formula Where C is the specific capacitance, I is the test current, ΔV is the voltage gradient, u is the scan rate, U0 is the voltage window difference, and m is the mass of the active material (carbon black) used.

[0085] The results are shown in Table 1.

[0086] Example 2

[0087] The preparation process is basically the same as that of Example 1, except that the reaction time of the chlorination reaction is set to 6 hours. Tests were carried out according to the method of Example 1, and the results are shown in Table 1.

[0088] Example 3

[0089] The preparation process is basically the same as that of Example 1, except that the temperature of the chlorination reaction is set to 1000° C. Tests were carried out according to the method of Example 1, and the results are shown in Table 1.

[0090] Comparative Example 1

[0091] No surface modification operation was performed, and other steps were the same as in Example 1. Tests were performed according to the method of Example 1, and the results are shown in Table 1.

[0092] Comparative Example 2

[0093] The temperature of the chlorination reaction was set to 1200° C., and the other steps were the same as those in Example 1. Tests were carried out according to the method of Example 1, and the results are shown in Table 1.

[0094] Comparative Example 3

[0095] 1M potassium chloride solution was used as the electrolyte, and the other steps were the same as those in Example 1. Tests were performed according to the method in Example 1, and the results are shown in Table 1.

[0096] Table 1

[0097]

[0098] The above embodiments are intended only to illustrate the technical solutions of the present invention and are not intended to limit the same. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments may be modified, or some or all of the technical features thereof may be replaced with equivalents, without departing from the spirit and substance of the claims of the present invention; and such modifications or replacements remain within the scope of the claims of the present invention.

Claims

1. A method for preparing a conductive carbon material for cement-based electrodes, characterized in that: The following steps are involved: 1) Silicon carbide powder is loaded into a quartz reaction tube and placed in a high-temperature furnace. An inert gas is first introduced to expel air, the furnace is heated, and chlorine gas is introduced to carry out a chlorination reaction. After the reaction is completed, the chlorine supply is stopped, the inert gas is continued, and the reaction tube is cooled to room temperature to obtain carbide-derived carbon. The chlorination reaction temperature is 800-1000°C and the reaction time is 2-6 hours. 2) washing and drying the carbide-derived carbon; dissolving a silane coupling agent in anhydrous toluene to obtain a silane coupling agent solution; placing the dried carbide-derived carbon in a reaction vessel, adding the silane coupling agent solution to react and reflux, cooling to room temperature after the reaction, washing, and drying to obtain a conductive carbon material for a cement-based electrode.

2. The preparation method according to claim 1, characterized in that In step 1), the flow rate of the inert gas is 100-200 ml / min, and the ventilation is continued for 15-45 minutes.

3. The preparation method according to claim 1, characterized in that In step 1), the flow rate of chlorine gas is 50-200 ml / min.

4. The preparation method according to claim 1, characterized in that In step 1), the pore volume of the carbide-derived carbon obtained is less than 200 nm, and the pore volume of the pore volume is less than 900 nm, and the specific surface area of ​​the carbide-derived carbon is 1450-1800 m 2 / g.

5. The preparation method according to claim 1, characterized in that The silane coupling agent in step 2) is trichloromethylsilane; The amount of silane coupling agent used in step 2) is 2%-10% of the mass of the carbide-derived carbon; The reaction reflux temperature of step 2) is 80-110°C and the reaction time is 24 hours.

6. A conductive carbon material for cement-based electrodes, characterized in that: The invention is prepared by the preparation method according to any one of claims 1 to 5.

7. A cement-based electrode, characterized in that: It is prepared from the conductive carbon material for cement-based electrodes described in claim 6 and cement.

8. The cement-based electrode according to claim 7, characterized in that The cement-based electrode was prepared by the following method: The conductive carbon material and cement are mixed to obtain a dry mixture, water and a water reducer are added and mixed to obtain a cement-based slurry; the cement-based slurry is poured into a mold and vibrated, and after hardening, the slurry is demoulded, cured, cut, and polished to obtain a cement-based electrode; The specific surface area of ​​cement-based electrodes is 300-500 m 2 / g.

9. A supercapacitor, characterized in that: The supercapacitor comprises the cement-based electrode according to claim 7 or 8; The cement-based electrode is immersed in an organic electrolyte until saturated, and the cement-based electrode, the glass fiber membrane, and the cement-based electrode are packaged into a supercapacitor.

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