Preparation and application of La1-xCaxCoO3 / activated carbon / cement-based electrode

Abstract

The invention discloses a preparation method of a La1-xCaxCoO3 / activated carbon / cement-based electrode. The preparation method comprises the following steps: preparing La1-xCaxCoO3 nano powder; pretreating the activated carbon; preparing cement paste, doping the La1-xCaxCoO3 nano powder and the pretreated activated carbon into the cement paste, and stirring to obtain conductive cement paste; the conductive cement paste is poured into a silica gel flexible mold, and ultrasonic vibration is carried out; and after ultrasonic vibration, soaking in deionized water for hydration, curing and demolding, and polishing the surface of the block body to obtain the La1-xCaxCoO3 / activated carbon / cement-based electrode. According to the invention, La1-xCaxCoO3 nano-powder and conductive active carbon are synergistically doped into a cement matrix to construct a ternary composite conductive system, through the complementary effect of two functional materials, the energy storage mode that a traditional cement-based electrode only depends on a double-electric-layer capacitor is broken through, the conductivity and energy storage performance of cement are improved, and the energy storage performance of the cement-based electrode is improved. A scientific basis is provided for application of the composite functional material in a cement-based system, and the composite functional material has huge application potential in the fields of green energy storage buildings, intelligent concrete and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of cement-based electrode preparation, and more particularly, the application relates to a La 1-x Ca x CoO3 / activated carbon / cement-based electrode and a preparation method and application thereof. BACKGROUND

[0002] With the continuous depletion of traditional energy, researching power resource energy storage system material technology has become a feasible method to solve the energy problem. An electrochemical energy storage system is composed of an electrode, an electrolyte and a separator, and the performance of the electrochemical energy storage system is affected by multiple factors, and the electrode material is the main factor determining the electrochemical performance. According to the charge storage mechanism, electrochemical energy storage devices can be mainly divided into three types: double-layer energy storage devices, pseudo-capacitive energy storage devices and hybrid capacitive energy storage devices. In the double-layer energy storage device, when the electrode mainly made of carbon materials such as carbon aerogel, graphene and carbon black is immersed in the electrolyte, the negative ions and positive ions in the electrolyte will be attracted to the positive and negative electrodes respectively, and a double layer is formed, so the double-layer energy storage device has a high power density. For the double-layer energy storage device, there is great research potential to improve the energy density, which depends on the specific capacitance and voltage window of the electrode material. The specific capacitance of the double-layer energy storage device depends largely on the large specific surface area of the electrode material at the nanoscale, the lightweight property, the good structural stability and the single surface or overall functionality. Compared with the double-layer energy storage device, the pseudo-capacitive energy storage device is more difficult to meet the actual demand due to its lower conductivity and ion diffusion rate, and the material itself of the pseudo-capacitive energy storage device is often greatly shortened in service life due to the oxidation-reduction reaction in the electrochemical test.

[0003] Cement can be applied to double-layer energy storage devices as an electrode or an electrolyte, and certain achievements have been made in the specific capacitance and energy density thereof. The carbon-doped electrode has the characteristics of porosity, good electrochemical stability and low price, and has been maturely applied in the electrochemical energy storage structure. The La 1-x Ca x CoO3 with a perovskite structure has structural stability and high adjustability, and belongs to a typical strong correlation electron system. The unique crystal structure and various magnetic phase transitions, Co 3+ spin state transitions and Jahn-Teller effects in the system endow the material with unique magnetic, photoelectric properties, visible light catalytic activity and other properties, and it is an electrode material with great application prospect; the unique pseudo-capacitive properties of the material endow the material with high energy storage potential, and the material also has good ion conductivity and electronic conductivity. In addition, the La 1-x Ca xThe preparation process of CoO3, such as sintering process, is relatively simple, and has low toxicity, which has wide application potential in related fields. The abundant pore structure in general building materials can accommodate metal salts and water to form a pore solution. Due to the flow of the pore solution providing sufficient paths, this ion conductor characteristic enhances the design potential of cement as a building structure electrochemical energy storage device.

[0004] In summary, there are few explorations of cement in electric energy storage devices at present, La 1-x Ca x The role of CoO3 / activated carbon composite in cement energy storage is not clear, and the exploration of La 1-x Ca x The application of CoO3 / activated carbon / cement composite system in electrochemistry not only can alleviate the energy problem, but also can combine building and electrochemistry, and propose a new development direction for the industry. SUMMARY

[0005] An object of the present application is to solve at least the above problems and / or defects, and to provide at least the advantages to be explained later.

[0006] In order to achieve these objects and other advantages of the present application, a La 1-x Ca x CoO3 / activated carbon / cement-based electrode preparation method is provided, comprising the following steps: Step one, preparing La 1-x Ca x CoO3nanopowder; Step two, pretreating activated carbon; Step three, preparing cement slurry, incorporating La 1-x Ca x CoO3nanopowder and pretreated activated carbon into the cement slurry, and stirring to obtain conductive cement slurry; Step four, pouring the conductive cement slurry into a flexible silica gel mold and performing ultrasonic vibration; Step five, after ultrasonic vibration, soaking it in deionized water for hydration, curing and demolding, and polishing the block surface to obtain La 1-x Ca x CoO3 / activated carbon / cement-based electrode.

[0007] Preferably, in the step one, La 1-x Ca x CoO3, x=0~0.5; the La 1-x Ca x CoO3nanopowder preparation method comprises the following steps: S11, La(NO3)3·6H2O, Ca(NO3)2·4H2O and Co(NO3)2·6H2O are added into deionized water to obtain a mixed solution by stirring; S12, C6H8O7·H2O is added into the mixed solution, stirring is continued for 0.5-2h, then acrylamide is added, heating is continued to 90-110℃, and stirring is continued until the solution becomes a gel, to obtain a gel; S13, the prepared gel is vacuum dried, then heat treated, and grinded to obtain a black powder precursor; S14, the black powder precursor is sintered to obtain La 1-x Ca x CoO3nanopowder.

[0008] Preferably, in S11, the molar ratio of La(NO3)3·6H2O, Ca(NO3)2·4H2O and Co(NO3)2·6H2O is 0.5-1:0-0.5:1; the molar volume ratio of La(NO3)3·6H2O and deionized water is 0.5-1mol:2-5L.

[0009] Preferably, in S12, the molar ratio of C6H8O7·H2O and La(NO3)3·6H2O in S11 is 3:0.5-1; the molar ratio of acrylamide and La(NO3)3·6H2O in S11 is 9:0.5-1.

[0010] Preferably, in S13, the vacuum drying temperature is 100-150℃, and the time is 12-36h; the heat treatment temperature is 300-500℃, and the time is 3-5h.

[0011] Preferably, in S14, the sintering temperature is 600-800℃, and the sintering time is 3-5h.

[0012] Preferably, in step two, the specific method for pretreating the activated carbon is: the activated carbon is ultrasonically cleaned in deionized water for 10-30min, and dried at 80-120℃ to constant weight to obtain the pretreated activated carbon.

[0013] Preferably, in step two, the specific method for pretreating the activated carbon comprises the following steps: S21, the activated carbon is ultrasonically cleaned in deionized water for 10-30min, then soaked in KOH solution for 4-8h, washed with deionized water to neutral pH, and dried to obtain the alkali-treated activated carbon; S22, the alkali-treated activated carbon and γ-aminopropyl triethoxysilane are added into an aqueous ethanol solution, and stirred at 70-100℃ for 20-60 min, and then cooled to room temperature, and then polyvinylpyrrolidone and ethylenediamine are added, and continuously stirred for 1-3 h, and then left to stand for 8-14 h, and then washed with deionized water, and dried to obtain the modified activated carbon; S23, the modified activated carbon is heat-treated in a nitrogen atmosphere, and naturally cooled to room temperature to obtain the pretreated activated carbon.

[0014] Preferably, in S21, the concentration of the KOH solution is 0.05-0.2 mol / L.

[0015] Preferably, in S22, the mass-volume ratio of the alkali-treated activated carbon, γ-aminopropyl triethoxysilane and the aqueous ethanol solution is 10 g:0.5-2 g:50-150 mL; the concentration of the aqueous ethanol solution is 30-80 wt%; and the mass ratio of the alkali-treated activated carbon, polyvinylpyrrolidone and ethylenediamine is 10:0.1-1:0.1-1.

[0016] Preferably, in S23, the specific method of heat treatment is to heat to 600-800℃ at a heating rate of 5-15℃ / min, and hold for 1-3 h.

[0017] Preferably, in step three, the specific method of preparing the cement paste is to mix cement and water to obtain a water-cement ratio of 0.5-0.7; the cement includes ordinary Portland cement, Portland cement, slag Portland cement, pozzolanic Portland cement, fly ash Portland cement and / or composite Portland cement; and the cement strength includes 42.5, 52.5 and / or 62.5, etc., without particular limitation.

[0018] Preferably, in La 1-x Ca x The doping amount of the CoO3 nanopowder is 3-7% of the mass of the cement; and the doping amount of the pretreated activated carbon is 3-7% of the mass of the cement.

[0019] Preferably, in step four, the ultrasonic vibration time is 20-60 min, the ultrasonic power is 80-150 W, and the ultrasonic frequency is 30-60 kHz.

[0020] Preferably, in step five, the curing temperature is 18-25℃, the curing humidity is 90-96%, and the curing time is 21-35 d.

[0021] A La 1-x Ca x CoO3 / activated carbon / cement-based electrode prepared by the preparation method.

[0022] The present application at least includes the following beneficial effects: for the problems of poor conductivity and weak energy storage of cement, the present application introduces conductive activated carbon and La 1-x Ca x CoO3nano-powder into the cement matrix to construct a ternary composite conductive system, and through the complementary effect of the two functional materials (activated carbon optimizes the conductivity and porous structure, and La 1-x Ca x CoO3can make the cement-based material produce pseudo-capacitive characteristics), and breaks through the energy storage mode of traditional cement-based electrodes which only rely on double-layer capacitance; The results show that: La 0.9 Ca 0.1 CoO3and activated carbon form a uniform porous three-dimensional network structure in cement; the prepared La 0.9 Ca 0.1 CoO3 / activated carbon / cement-based electrode has excellent electrochemical performance and can be fitted by equivalent circuit; with the increase of the content of La 0.9 Ca 0.1 CoO3 / activated carbon, the specific capacitance of the electrode shows a trend of first increasing and then decreasing (the highest can reach 1.2 F / g), and the resistance shows a trend of first decreasing and then increasing (the minimum can reach 22.6 Ω); the appropriate amount of La 0.9 Ca 0.1 CoO3can make the cement produce pseudo-capacitive characteristics and enhance its energy storage capacity; The present application significantly improves the energy storage capacity of the cement-based electrode (the highest specific capacitance can reach 1.2 F / g) by introducing the synergistic effect of pseudo-capacitance and double-layer capacitance; at the same time, the synergistic effect of La 1-x Ca x CoO3and activated carbon can simultaneously improve the conductivity and energy storage of cement, and provides a scientific basis for the application of composite functional materials in cement-based systems, and has great application potential in the fields of green energy storage buildings and intelligent concrete.

[0023] Other advantages, objects and features of the present application will be partly embodied by the following description, and will be partly understood by those skilled in the art through research and practice of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 SEM image of La-CCE3 prepared for Example 1 of the present application; Figure 2 SEM image of La-CCE6 prepared for Example 4 of the present application; Figure 3 EDS image of La-CCE6 prepared for Example 4 of the present application, a is the selected area of La-CCE6 in EDS test, and b is the distribution of C, Co, La and Si in the selected area. Figure 4 La-CCE6 prepared for the present embodiment 4 at 20, 100, 500 mV·s -1 at a scan rate; Figure 5 La prepared for the present embodiments 1-5 0.9 Ca 0.1 CoO3 / activated carbon / cement-based electrode in galvanostatic charge-discharge curves at 10 mA·cm -2 current density; Figure 6 La prepared for the present embodiments 1-5 0.9 Ca 0.1 CoO3 / activated carbon / cement-based electrode in Nyquist plots in AC impedance tests. DETAILED DESCRIPTION

[0025] The present application will be further described below in conjunction with the accompanying drawings so as to enable those skilled in the art to implement the present application according to the description herein.

[0026] It should be understood that the terms such as "have", "contain" and "include" used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0027] The raw materials used in the following examples include: activated carbon supplied by Japan KURARAY Co., Ltd., model YP-80F; cement is ordinary Portland cement (P·O42.5) produced in Mianyang, Sichuan, China; electrolyte potassium chloride (KCl) is purchased from Cologne Company.

[0028] In the following examples, the prepared La 1-x Ca x CoO3is La 0.9 Ca 0.1 CoO3, i.e. x = 0.1.

[0029] Embodiment 1 A method for preparing a La 0.9 Ca 0.1 CoO3 / activated carbon / cement-based electrode, comprising the following steps: Step one, preparing La 0.9 Ca 0.1 CoO3nanopowder, comprising the following steps: S11, 0.009 mol La(NO3)3·6H2O, 0.001 mol Ca(NO3)2·4H2O and 0.01 mol Co(NO3)2·6H2O were taken in a 250 mL round-bottom flask, 30 mL deionized water was added, and the round-bottom flask was placed in a constant-temperature water bath for continuous stirring until all the raw materials were fully dissolved to obtain a mixed solution; S12, then 0.03 mol C6H8O7·H2O was added to the mixed solution, and stirring was continued for 1 h, then 0.09 mol acrylamide was added, and the oil bath was heated to 100°C, and stirring was continued until the solution gradually became a transparent jelly-like colloid to obtain a gel; S13, the prepared gel was placed in a 120°C vacuum drying oven for drying for 24 h to remove the water inside the gel, and then heat-treated in a 400°C electric resistance furnace for 4 h to remove most of the organic matter in the gel, and then cooled to room temperature, and fully ground to obtain a black powder precursor; S14, the black powder precursor was placed in a crucible and sintered at 700°C for 4 h to obtain La 0.9 Ca 0.1 CoO3nanopowder; Step two, after the activated carbon was ultrasonically cleaned in deionized water for 15 min to remove surface impurities, it was placed in an oven and dried to constant weight at a constant temperature of 100°C to obtain pretreated activated carbon; Step three, the cement paste was accurately prepared with a water-cement ratio of 0.6, and the prepared La 0.9 Ca 0.1 CoO3nanopowder was mixed into the cement paste at the same mass percentage (3.0%), and the cement paste was stirred at 500 r / min for 30 min to ensure uniform dispersion of the conductive material in the cement matrix to obtain a conductive cement paste; Step four, the conductive cement paste was poured into a 10×10×5 (mm) cubic silicone flexible mold, which determined the geometric area of the electrode to be 1 cm 2 The mold filled with conductive cement paste was ultrasonically vibrated for 30 min at an ultrasonic power of 100 W and an ultrasonic frequency of 40 kHz to ensure uniform distribution of the mortar in the mold and to eliminate possible microcracks and bubbles; Step five, soaking in deionized water for hydration for 24 h, according to the Standard Concrete Engineering Regulations (GB50666-2011), the hardened sample was demolded after 28 days of curing, the curing temperature was 20°C, the curing humidity was 95%, and a series of abrasive particles with gradually decreasing size of silicon carbide sandpaper was used to polish the surface of the block to obtain La 0.9 Ca 0.1 CoO3 / activated carbon / cement-based electrode, denoted as La-CCE3.

[0030] Example 2-5 Example 2-5 differs from Example 1 only in that La 0.9 Ca 0.1 The dosages of CoO3 nano-powder and the pretreated activated carbon are different, and are shown in Table 1.

[0031] Example 6 This example differs from Example 4 only in that the method of pretreating the activated carbon is different; The method of pretreating the activated carbon in this example includes the following steps: S21, ultrasonic cleaning the activated carbon in deionized water for 15 min, then soaking in 0.1 mol / L KOH solution for 6 h, washing with deionized water until the pH is neutral, and placing in an oven for drying at 100℃ to obtain alkali-treated activated carbon; S22, adding 10 g of alkali-treated activated carbon and 1 g of γ-aminopropyl triethoxysilane into 100 mL of 50wt% ethanol aqueous solution, stirring at 80℃ for 30 min, then adding 0.5 g of polyvinylpyrrolidone and 0.5 g of ethylenediamine after cooling to room temperature, continuously stirring for 2 h, standing for 12 h, washing with deionized water, and placing in an oven for drying at 100℃ to obtain modified activated carbon; S23, heat treating the modified activated carbon in a nitrogen atmosphere, heating to 700℃ at a heating rate of 10℃ / min, holding for 2 h, and naturally cooling to room temperature to obtain pretreated activated carbon.

[0032] This example increases the specific surface area by alkali solution activation treatment, reduces the material internal resistance by nitrogen doping with polyvinylpyrrolidone and ethylenediamine, promotes electron transmission, optimizes the electrochemical performance of the activated carbon, and further improves the conductivity and energy storage of the cement; in addition, the use of γ-aminopropyl triethoxysilane can improve the dispersibility of the activated carbon and also introduce nitrogen elements, and subsequent heat treatment in a nitrogen atmosphere obtains activated carbon with high specific surface area and nitrogen doping.

[0033] Example 7 This example differs from Example 4 only in that the method of pretreating the activated carbon is different; The method of pretreating the activated carbon in this example includes the following steps: S21, ultrasonic cleaning the activated carbon in deionized water for 15 min, then soaking in 0.1 mol / L KOH solution for 6 h, washing with deionized water until the pH is neutral, and placing in an oven for drying at 100℃ to obtain alkali-treated activated carbon; S22, 10 g of the alkali-treated activated carbon and 1 g of γ-aminopropyl triethoxysilane were added into 100 mL of 50 wt% aqueous ethanol solution, and stirred at 80°C for 30 min. After cooling to room temperature, 1 g of ethylenediamine was added, and stirring was continued for 2 h. After standing for 12 h, the product was washed with deionized water and dried in an oven at 100°C to obtain the modified activated carbon; S23, the modified activated carbon was heat-treated in a nitrogen atmosphere, and heated to 700°C at a heating rate of 10°C / min, and kept for 2 h. After natural cooling to room temperature, the pretreated activated carbon was obtained. Compared with Example 6, this example does not use polyvinylpyrrolidone.

[0034] Example 8 The difference between this example and Example 4 is only that the method for pretreating the activated carbon is different. The method for pretreating the activated carbon in this example comprises the following steps: S21, the activated carbon was ultrasonically cleaned in deionized water for 15 min, and then soaked in 0.1 mol / L KOH solution for 6 h. After washing with deionized water to neutral pH, the product was dried in an oven at 100°C to obtain the alkali-treated activated carbon. S22, 10 g of the alkali-treated activated carbon and 1 g of γ-aminopropyl triethoxysilane were added into 100 mL of 50 wt% aqueous ethanol solution, and stirred at 80°C for 30 min. After cooling to room temperature, 1 g of ethylenediamine was added, and stirring was continued for 2 h. After standing for 12 h, the product was washed with deionized water and dried in an oven at 100°C to obtain the modified activated carbon; S23, the modified activated carbon was heat-treated in a nitrogen atmosphere, and heated to 700°C at a heating rate of 10°C / min, and kept for 2 h. After natural cooling to room temperature, the pretreated activated carbon was obtained. Compared with Example 6, this example does not use ethylenediamine.

[0035] Example 9 The difference between this example and Example 4 is only that the method for pretreating the activated carbon is different. The method for pretreating the activated carbon in this example comprises the following steps: S21, the activated carbon was ultrasonically cleaned in deionized water for 15 min, and then soaked in 0.1 mol / L KOH solution for 6 h. After washing with deionized water to neutral pH, the product was dried in an oven at 100°C to obtain the alkali-treated activated carbon. S22. Add 10g of alkali-treated activated carbon to 100mL of 50wt% ethanol aqueous solution, heat to 80℃ and stir for 30min, cool to room temperature and then add 0.5g of polyvinylpyrrolidone and 0.5g of ethylenediamine, continue stirring for 2h, let stand for 12h, wash with deionized water, put in an oven and dry at 100℃ to obtain modified activated carbon. S23. The modified activated carbon is heat-treated in a nitrogen atmosphere, heated to 700℃ at a heating rate of 10℃ / min, held at the temperature for 2 hours, and then naturally cooled to room temperature to obtain the pretreated activated carbon. Compared to Example 6, this example does not use γ-aminopropyltriethoxysilane.

[0036] Comparative Example 1 This comparative example does not contain La. 0.9 Ca 0.1 CoO3 nanoparticles were used, with only 12% activated carbon added, and the remaining steps were the same as in Example 1 to prepare an activated carbon / cement-based electrode, denoted as CCE12.

[0037] Comparative Example 2 This comparative example does not contain La. 0.9 Ca 0.1 CoO3 nanoparticles were used, with only 6% activated carbon added, and the remaining steps were the same as in Example 1 to prepare an activated carbon / cement-based electrode, denoted as CCE6.

[0038] Comparative Example 3 This comparative example does not contain activated carbon, only 6% La. 0.9 Ca 0.1 CoO3 nanoparticles were prepared using the same steps as in Example 1 to obtain La. 0.9 Ca 0.1 CoO3 / cement-based electrode, denoted as La-CE6.

[0039] Table 1 Physicochemical characterization: The surface and cross-sectional microstructure of the samples were analyzed using a field emission scanning electron microscope (FE-SEM, Carl Zeiss Ultra 55) at an accelerating voltage of 15 kV. Prior to analysis, a 5 nm thick gold film was sputtered onto the sample surface to improve conductivity. Elemental distribution maps of the samples were obtained using an energy dispersive X-ray spectroscopy (EDX) instrument (TESCAN MAIA3LMU), with a collection time of 120 s for each element. The EDX was calibrated using standard samples before testing.

[0040] Electrochemical testing: The La was studied using an electrochemical workstation (CHI660E) with a three-electrode system.0.9 Ca 0.1 Electrochemical performance of CoO3 / activated carbon / cement-based electrodes at room temperature. The electrochemical performance of the electrodes was obtained by cyclic voltammetry. All samples were first electrochemically activated by cyclic voltammetry at scan rates of 20, 100, and 500 mV·s. -1 After a 2-minute equilibration period, three consecutive cycles were recorded at each rate. The voltage window relative to the Ag / AgCl (3 mol / L KCl) reference electrode was -1 V to 0 V. Specific capacitance and other performance characteristics were obtained and calculated using constant current charge-discharge tests at a test current of 10 mA·cm⁻¹. -2 The current accuracy of this test is ±0.1%, and the voltage measurement resolution is 0.1 mV. Eight complete charge-discharge cycles were performed at each density. Based on the constant current charge-discharge (GCD) test results, the specific capacitance C was calculated using the following equation. s (F / g): In the formula, I (A) represents the current. t (s) represents the discharge time. m (g) represents the electrode mass. V (V) represents the total voltage window.

[0041] AC impedance spectroscopy provides impedance-related information. Electrochemical impedance spectroscopy (EIS) was performed with an AC frequency amplitude of 5 mV in the frequency range of 0.01 Hz to 10 kHz to study the equivalent series resistance (ESR) and phase angle. The ESR was extracted from the high-frequency intercept of the Nyquist plot, and the phase angle data were obtained from Bode plots at different frequencies. The impedance data were analyzed using Zview software. All measurements were performed in a three-electrode system to isolate the response of the working electrode.

[0042] Figure 1 This is a SEM image of La-CCE3 prepared in Example 1. Figure 2 The image shows a SEM image of La-CCE6 prepared in Example 4. Figure 1 (a) and Figure 2 (a) shows that it is mainly a blocky colloidal structure with varying block sizes, because La 0.9 Ca 0.1 CoO3 nanoparticles adhere to the surface of activated carbon, and cement hydration products firmly bind the active components together, with different types of pores existing between the blocks. Figure 1 (b) and Figure 2 (b) is a high-magnification image of the electrode sample, showing La 0.9 Ca 0.1The three-dimensional interconnected microporous structure formed by CoO3 / activated carbon and cement confirms that the cement block is formed through La 0.9 Ca 0.1 CoO3 / activated carbon material networks achieve interconnection, and La 0.9 Ca 0.1 CoO3 / activated carbon materials play an important role in inhomogeneous porous random networks, among which La-CCE6 contains La 0.9 Ca 0.1 The CoO3 / activated carbon material has a richer structure, a more complex conductive network, and more micropores. This three-dimensional microporous structure not only provides ion and electron transport channels for the electrodes, but also provides a large number of nanoscale micropores.

[0043] Figure 3 The image shown is an EDS image of La-CCE6 prepared in Example 4. Figure 3 (a) shows the regions selected for La-CCE6 in the EDS test. Figure 3 (b) shows the distribution of C, Co, La, and Si in the selected region. It can be seen that La... 0.9 Ca 0.1 The CoO3 / activated carbon / cement-based electrode contains C, Co, La, and Si, which are evenly distributed. C is widely distributed, which is related to the carbon content in the activated carbon and cement-based materials. Si is also present in the material, as it is a major component of cement-based materials. La and Co are present in relatively small amounts because these two elements are only found in La. 0.9 Ca 0.1 CoO3 nanoparticles.

[0044] Figure 4 La prepared in Example 4 0.9 Ca 0.1 CoO3 / activated carbon / cement-based electrode La-CCE6 at 20, 100, and 500 mV·s -1 Cyclic voltammetry (CV) curves at scan rates. It can be seen that even at 500 mV·s... -1 At high scan rates, the electrode still exhibits significant double-layer capacitance behavior, demonstrating its fast charge transport dynamics and suitability for high-power applications. Its CV curve shows a quasi-rectangular shape and clear cyclic reversibility, indicating that La... 0.9 Ca 0.1 The CoO3 / activated carbon doped porous structure enables the exchange of electrons and ions in the electrolyte. The addition of conductive La... 0.9 Ca 0.1 CoO3 nanopowder and activated carbon can form nanoscale micropores, which promote the transfer of electrons and ions, making the movement of electrons in the electrode smoother, enhancing the electron transfer capacity, and thus reducing the internal resistance.

[0045] Figure 5 La prepared in Examples 1-5 0.9 Ca 0.1 CoO3 / activated carbon / cement-based electrode at 10 mA·cm -2 Constant current charge-discharge (GCD) curves at current density. It can be seen that all five electrodes can charge and discharge normally, and the curves exhibit a near-isosceles triangle characteristic. However, the curves do not perfectly exhibit an isosceles triangle characteristic; this is because of the interaction between conductive activated carbon and La. 0.9 Ca 0.1 The addition of CoO3 nanoparticles results in an electrode capacitance exhibiting a hybrid form of electric double-layer capacitance and pseudocapacitance. Furthermore, the five curves show that while the charging time increases with increasing conductive material, the increase in discharging time is less than the increase in charging time. The specific capacitance C of each electrode can be calculated using the formula. s Size, La at 3-7% doping 0.9 Ca 0.1 The specific capacitances of the CoO3 / activated carbon / cement-based electrodes are 0.24 F / g, 0.28 F / g, 0.36 F / g, 1.2 F / g, and 1.08 F / g, respectively, indicating that La was added. 0.9 Ca 0.1 CoO3 / activated carbon can increase the specific capacitance of the electrode and exhibit pseudocapacitive characteristics; La at 6% doping 0.9 Ca 0.1 The CoO3 / activated carbon / cement-based electrode exhibits the highest specific capacitance, reaching 1.2 F / g, consistent with the CV curve results. La 0.9 Ca 0.1 The incorporation of CoO3 / activated carbon enables the formation of a conductive network in the electrode, increases the number of micropores, and increases the activation area, significantly improving the overall electrochemical performance of the electrode. However, excessive incorporation of conductive materials such as La... 0.9 Ca 0.1 CoO3 nanoparticles do not further enhance electrochemical performance, La 0.9 Ca 0.1 Excessive doping of CoO3 nanoparticles, which are low-conductivity materials at room temperature, will increase their internal resistance and block their micropores, thereby weakening their electron and ion transport capabilities and thus failing to improve the rate performance of the electrode.

[0046] To further analyze the kinetic properties of the electrode material, La 0.9 Ca 0.1 Electrochemical impedance spectroscopy (EIS) of the CoO3 / activated carbon / cement-based electrode was performed, and the results are as follows: Figure 6As shown. Electrochemical impedance spectroscopy (EIS) analysis can be used to determine charge transfer resistance and charge separation efficiency. The arc portion in the EIS Nyquist plot represents the high-frequency reaction region, indicating the electron transfer process. Generally, the smaller the radius of the Nyquist arc, the lower the charge transfer resistance. The straight line portion in the EIS Nyquist plot represents the low-frequency reaction region, indicating the ion transfer process. Different La doping concentrations... 0.9 Ca 0.1 The calculated arc projection dimensions of the CoO3 / activated carbon / cement-based electrode are R2=48.5Ω (3%), R2=45.1Ω (4%), R2=44.8Ω (5%), R2=22.6Ω (6%), and R2=34.8Ω (7%), respectively. This indicates that 6% La content... 0.9 Ca 0.1 The CoO3 / activated carbon / cement-based electrode exhibits lower resistance, consistent with the results of cyclic voltammetry and constant current charge-discharge tests.

[0047] The specific capacitance and resistance of the electrodes prepared in Examples 1-9 and Comparative Examples 1-3 are shown in Table 2.

[0048] In summary, this invention successfully prepared La with different doping amounts. 0.9 Ca 0.1 CoO3 / activated carbon / cement-based electrode, the C, Co, La, Si and other elements in the material are uniformly distributed, La 0.9 Ca 0.1 CoO3 and carbon form a uniformly distributed porous three-dimensional network structure in cement.

[0049] La 0.9 Ca 0.1 CoO3 / activated carbon / cement-based electrodes exhibit double-layer capacitance characteristics, with their CV curves showing an initial expansion followed by a contraction. Among these, La-CCE6 exhibits the largest CV curve area and the best cycle performance. Different La... 0.9 Ca 0.1 CoO3 / activated carbon doped electrodes can all store capacitance, up to 1.2 F / g (Example 4). The specific capacitance first increases and then decreases with increasing doping concentration. All electrodes possess both ion and electron transport capabilities, which can be fitted using equivalent circuits. 6% La doping... 0.9 Ca 0.1 The CoO3 / activated carbon / cement-based electrode has a minimum resistance R2 = 22.6Ω.

[0050] La 0.9 Ca 0.1 CoO3 nanopowder assists activated carbon in forming a three-dimensional conductive network in the electrode, helping to create nanoscale pores in the electrode, which can effectively reduce the electrode resistance and give the cement electrode a pseudocapacitive effect. By introducing the synergistic effect of pseudocapacitance and double-layer capacitance characteristics, its energy storage capacity is enhanced.

[0051] By changing the pretreatment method of activated carbon, increasing the specific surface area through alkaline solution activation treatment, reducing the internal resistance of the material through nitrogen doping, promoting electron transport, and optimizing the electrochemical performance of activated carbon, the conductivity and energy storage properties of cement can be further improved.

[0052] Table 2 Specific capacitance (F / g) Resistance (Ω) Example 1 0.24 48.5 Example 2 0.28 45.1 Example 3 0.36 44.8 Example 4 1.2 22.6 Example 5 1.08 34.8 Example 6 1.33 14.0 Example 7 1.27 18.9 Example 8 1.26 19.7 Example 9 1.3 16.8 Comparative Example 1 1.02 36.6 Comparative Example 2 0.12 88.0 Comparative Example 3 0.08 106 Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A La 1-x Ca x The method for preparing CoO3 / activated carbon / cement-based electrodes is characterized by, Includes the following steps: Step 1: Preparation of La 1-x Ca x CoO3 nanoparticles; Step 2: Pre-treat the activated carbon; Step 3: Prepare cement grout, adding La 1-x Ca x CoO3 nanoparticles and pretreated activated carbon are mixed into cement slurry and stirred to obtain conductive cement slurry. Step 4: Pour the conductive cement slurry into a flexible silicone mold and perform ultrasonic vibration; Step 5: After ultrasonic vibration, immerse it in deionized water for hydration, cure and demold, then polish the surface of the block to obtain La. 1-x Ca x CoO3 / activated carbon / cement-based electrode.

2. The La as described in claim 1 1-x Ca x The method for preparing CoO3 / activated carbon / cement-based electrodes is characterized by, In step one, La 1-x Ca x In CoO3, x = 0~0.5; the La 1-x Ca x The preparation method of CoO3 nanopowder includes the following steps: S11. Take La(NO3)3·6H2O, Ca(NO3)2·4H2O and Co(NO3)2·6H2O and add them to deionized water, stir to obtain a mixed solution; S12. Add C6H8O7·H2O to the mixed solution and stir continuously for 0.5~2h. Then add acrylamide, heat to 90~110℃, and stir continuously until the solution becomes a colloid to obtain a gel. S13. The obtained gel is vacuum dried, then heat-treated, and ground to obtain a black powder precursor. S14. Sinter the black powder precursor to obtain La. 1-x Ca x CoO3 nanoparticles.

3. The La as described in claim 2 1-x Ca x The method for preparing CoO3 / activated carbon / cement-based electrodes is characterized by, In S11, the molar ratio of La(NO3)3·6H2O, Ca(NO3)2·4H2O and Co(NO3)2·6H2O is 0.5~1:0~0.5:1; the molar volume ratio of La(NO3)3·6H2O and deionized water is 0.5~1mol:2~5L.

4. The La as described in claim 2 1-x Ca x The method for preparing CoO3 / activated carbon / cement-based electrodes is characterized by, In S12, the molar ratio of C6H8O7·H2O to La(NO3)3·6H2O in S11 is 3:0.5~1; the molar ratio of acrylamide to La(NO3)3·6H2O in S11 is 9:0.5~1.

5. The La as described in claim 2 1-x Ca x The method for preparing CoO3 / activated carbon / cement-based electrodes is characterized by, In step S13, the vacuum drying temperature is 100~150℃ and the time is 12~36h; the heat treatment temperature is 300~500℃ and the time is 3~5h. In S14, the sintering temperature is 600~800℃ and the sintering time is 3~5h.

6. The La as described in claim 1 1-x Ca x The method for preparing CoO3 / activated carbon / cement-based electrodes is characterized by, In step two, the specific method for pretreating activated carbon is as follows: ultrasonically clean the activated carbon in deionized water for 10-30 minutes, and dry it at 80-120℃ to constant weight to obtain pretreated activated carbon.

7. The La as described in claim 1 1-x Ca x The method for preparing CoO3 / activated carbon / cement-based electrodes is characterized by, In step three, the specific method for preparing the cement paste is as follows: cement and water are mixed at a water-cement ratio of 0.5 to 0.

7.

8. The La as described in claim 7 1-x Ca x The method for preparing CoO3 / activated carbon / cement-based electrodes is characterized by, The La 1-x Ca x The amount of CoO3 nanopowder is 3-7% of the cement mass; the amount of pretreated activated carbon is 3-7% of the cement mass.

9. The La as described in claim 1 1-x Ca x The method for preparing CoO3 / activated carbon / cement-based electrodes is characterized by, In step five, the curing temperature is 18~25℃, the curing humidity is 90~96%, and the curing time is 21~35 days.

10. A La prepared by the preparation method according to any one of claims 1-9 1-x Ca x Application of CoO3 / activated carbon / cement-based electrodes in electrochemical energy storage devices.

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