Preparation method and application of O, P doped ultra-microporous carbon nanomicrospheres applied to quasi-solid flexible capacitor

Abstract

The application belongs to the technical field of supercapacitors, and discloses a preparation method of O and P doped super-microporous carbon nanomicrosphere and application of the super-microporous carbon nanomicrosphere in quasi-solid flexible capacitors. The method comprises adding sodium dodecyl diphenyl ether disulfonate, acrylonitrile, potassium persulfate and acetic acid in deionized water, performing emulsion polymerization reaction at 72 DEG C for 10 hours, and preparing carbide by pre-oxidation and carbonization of the powder after demulsification, and further performing concentrated phosphoric acid impregnation to dope P and O elements to obtain the final product. The application applies super-microporous carbon material to aqueous zinc ion hybrid capacitors for the first time. The limited action of super-microporous channels on hydrated zinc ions and the promoting action of O and P doping on desolvation of hydrated zinc ions realize 262 Wh kg ‑1 of battery level high energy density. The application is simple in operation and friendly to the environment, and proves the great potential of heteroatom doped super-microporous carbon based material in the application of aqueous zinc ion hybrid capacitors.

Description

Technical Field

[0001] This invention belongs to the field of supercapacitor technology. Specifically, it relates to the technical field of aqueous zinc ion hybrid capacitors. In particular, it relates to a method for preparing O and P-doped ultraporous carbon nanospheres and their application in quasi-solid-state flexible capacitors. Background Technology

[0002] With the increasing demand for portable electronic devices and hybrid electric vehicles, there is a growing need for an excellent energy storage device that combines high energy density, high power capability, safety, reliability, and long lifespan. As a result, aqueous hybrid capacitors, composed of batteries, capacitive electrodes, and aqueous electrolytes, have emerged. In recent years, aqueous zinc-ion hybrid capacitors have attracted considerable attention from researchers due to their abundant materials, low manufacturing costs, high operating voltage, and superior safety, and they hold particular promise as energy storage components for wearable electronic devices. Furthermore, the use of aqueous electrolytes further ensures more environmentally friendly manufacturing conditions, higher safety, and better ionic conductivity. A typical aqueous zinc-ion hybrid capacitor usually consists of zinc metal as the anode and a carbon electrode as the cathode. Its working principle involves Zn on the zinc metal... 2+ The stripping / deposition and adsorption / desorption of ions in carbon materials. Due to the high mass of the zinc anode, the total capacitance is determined by the capacitance of the carbon cathode, thus energy storage is limited to the adsorption / desorption capacity of the carbon cathode for electrolyte ions. Therefore, most zinc-ion hybrid capacitors can only provide a limited energy density (<150 Wh kg). -1 This limits its further application.

[0003] To achieve higher energy storage capacity, current research focuses on optimizing pore structures and introducing heteroatoms into carbon materials to improve their capacitance. For pore design, researchers tend to employ a strategy of coexisting macropores, mesopores, and micropores, with pore sizes all larger than those of solvated electrolyte ions. Notably, in electrolytes, ions carrying a dynamic sheath of specific adsorbed solvent molecules become solvated ions. Gogotsi et al. experimentally observed an anomalous increase in capacitance in organic electrolytes with pore sizes smaller than 1 nm, overturning the long-held axiom that pore sizes smaller than those of solvated electrolyte ions cannot promote charge storage. Recently, Cao Yuancheng's research group confirmed that ions lose their electrostatic shielding solvent shell under sub-nanometer finite domain conditions, leading to a significant increase in embedding capacitance. C. Preal et al. also demonstrated a similar desolvation process in CsCl aqueous solutions and found that ion desolvation positively contributes to capacitance. In aqueous zinc ion mixed capacitors, Zn... 2+ It typically forms an octahedral coordination with six water molecules ([Zn(H₂O)₆)). 2+The diameter can reach 0.80 nm. Furthermore, some pioneering works have shown that carbon-based materials modified with doped heteroatoms (N, O, P, B) not only increase pseudocapacitance but also significantly enhance the capacitance to Zn. 2+ The adsorption of zinc ions ([Zn(H₂O)₆)) can be achieved in ultraporous carbon (pore size less than 0.7 nm). 2+ Successful desolvation of carbon nanospheres (n=1-6) is expected to increase the capacitance of the carbon cathode, thereby breaking the energy density bottleneck. However, the preparation of ultraporous carbon nanospheres with a single pore size is one challenge, and heteroatom doping, especially the introduction of oxygen-containing functional groups, is another. Furthermore, there is no precedent for using ultraporous carbon materials in zinc-ion hybrid capacitors.

[0004] Based on the above analysis, the problems and defects of the existing technology are as follows: the aqueous zinc ion hybrid capacitor is difficult to obtain a high energy density due to the limited ion adsorption capacity of the carbon cathode material. The capacitance of hydrated zinc ions in the ultra-micropore can be improved by desolvation, but there is a desolvation energy barrier.

[0005] The challenges in addressing these issues and shortcomings lie in the difficulty of designing ultramicropores with a single pore size distribution. Additionally, introducing heteroatoms using simple methods is another hurdle that needs to be overcome.

[0006] The significance of solving the above problems and defects is as follows: Through emulsion polymerization, the initial formation of ultraporous structures is eliminated by the pyrolysis of surfactants. Furthermore, the successful introduction of O and P heteroatoms and corresponding functional groups through phosphoric acid impregnation lowers the desolvation energy barrier, promotes the desolvation of hydrated zinc ions, and ultimately increases the energy density. This work sets a precedent for the application of ultraporous carbon materials in zinc-ion mixed capacitors, providing a completely new approach to overcoming the bottleneck of low energy density. Summary of the Invention

[0007] To overcome the problems existing in related technologies, this invention provides a method for preparing O and P doped ultraporous carbon nanospheres and their application in quasi-solid-state flexible capacitors.

[0008] This invention is achieved as follows: the method for preparing the O and P-doped ultraporous carbon nanospheres includes:

[0009] Preparation of polyacrylonitrile microspheres: First, 0.1 g of sodium dodecyl diphenyl ether disulfonate (SLDED) was completely dissolved in 10 mL of deionized water. Then, 0.65 g of acrylonitrile (AN), 0.02 g of potassium persulfate (KPS), and 6 drops of acetic acid were continuously added to the system, and the mixture was heated to 40 °C. o Pre-stir at C for 60 min, then at 72°C. o The emulsion polymerization process was carried out at C for 10 hours to form a milky white emulsion;

[0010] The resulting emulsion was heated at 6000 r / min -1 Centrifuge at a speed of [speed] to break the emulsion and wash twice with ethanol, then at 80 [speed]. o The polyacrylonitrile microspheres were dried in an oven at C for 24 hours to obtain a white powder.

[0011] The white powder was pre-oxidized and carbonized in a tube furnace: first in an air atmosphere at 0.5... o C min -1 The product is heated to 250 degrees Celsius at a rate that allows it to reach its maximum temperature. o After maintaining at C for 5 hours and cooling to room temperature, it is then incubated under a N2 atmosphere at 2... o C min -1 The rate continues to heat to 850 o C was maintained for 1 h to obtain carbonized products;

[0012] In a 25 mL round-bottom flask, polyacrylonitrile carbonized microspheres were immersed in concentrated phosphoric acid (1 g of product corresponds to 20 mL of concentrated phosphoric acid). After thorough mixing, the mixture was incubated at 180°C. oC Reflux for 1 h, cool to room temperature, wash repeatedly with deionized water, centrifuge until neutral, and finally centrifuge at 80 °C. o Dry in oven C for 12 hours to obtain the final product.

[0013] Another objective of this invention is to provide a quasi-solid-state flexible capacitor device, which is composed of an electrode material made of polished zinc foil (thickness: 0.1 mm), polyacrylamide (PAM) / ZnSO4 hydrogel (thickness: 1.5 mm) and O and P doped ultramicroporous carbon nanospheres coated on carbon paper, and finally encapsulated with polyimide tape.

[0014] Combining all the above technical solutions, the advantages and positive effects of this invention are as follows:

[0015] Ultraporous carbon nanospheres were synthesized via a convenient and efficient emulsion polymerization-thermal treatment method. The emulsion polymerization method ensured uniform microsphere size distribution, while the high-temperature decomposition of surfactant micelles resulted in a uniform pore size distribution within the microspheres. Polyacrylonitrile was used as the carbon precursor, exhibiting a high nitrogen self-doping content. The formation of ultrapores was controlled by adjusting the amount of surfactant, and subsequent phosphoric acid impregnation successfully achieved O and P doping and promoted further formation of ultrapores without damaging the microsphere morphology. Nitrogen self-doping enhances the electron transfer activity and conductivity of the carbon framework. Exogenous O doping alters the polarity of the carbon surface, thereby improving wettability and enriching lattice defects. P also alters the charge distribution of the carbon framework, increasing electrochemical active centers. Furthermore, these heteroatoms typically introduce pseudocapacitance through rapid redox reactions of specific electroactive groups (such as C=O, COOH / COOR). More importantly, this significantly enhances the adsorption capacity for zinc ions, promoting the desolvation of hydrated zinc ions and thus enhancing capacitance. The successful electrochemical performance of the quasi-solid-state flexible device assembled based on the prepared O and P-doped ultraporous carbon nanosphere electrode material demonstrates its great potential for application in flexible electronic products. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a flowchart of the preparation method of O and P doped ultraporous carbon nanospheres provided in the embodiments of the present invention.

[0018] Figure 2 This is a pore size distribution diagram of the material prepared according to the embodiments of the present invention.

[0019] Figure 3 These are scanning electron microscope (SEM) images and transmission electron microscope (TEM) images of the prepared materials provided in the embodiments of the present invention.

[0020] Figure 4 This is an X-ray photoelectron spectrum of the prepared material provided in the embodiments of the present invention.

[0021] Figure 5 This is a schematic diagram of the assembly of the quasi-solid-state flexible capacitor prepared according to the embodiments of the present invention, and a region diagram showing the energy density and power density of the corresponding performance. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0023] To address the problems existing in the prior art, this invention provides a method for preparing O and P-doped ultraporous carbon nanospheres and their application in quasi-solid-state flexible capacitors. The invention is described in detail below with reference to the accompanying drawings.

[0024] like Figure 1 As shown, the method for preparing O and P-doped ultraporous carbon nanospheres provided by the present invention includes the following steps:

[0025] S101: 1 g of sodium dodecyl diphenyl ether disulfonate was completely dissolved in 10 mL of deionized water. Then, 0.65 g of acrylonitrile, 0.02 g of potassium persulfate, and 6 drops of acetic acid were continuously added to the system to form a homogeneous solution. The solution was then heated at 40 °C. o Pre-stir at C for 60 minutes, then at 72°C. o The emulsion polymerization process was carried out at C for 10 h to form a milky white emulsion. After demulsification and drying, a white polyacrylonitrile powder was obtained.

[0026] S102: The resulting white powder is pre-oxidized and carbonized in a tube furnace: first in an air atmosphere at 0.5... o Cmin -1 The product is heated to 250 degrees Celsius at a rate that allows it to reach its maximum temperature. o After maintaining at C for 5 hours and cooling to room temperature, it is then incubated under a N2 atmosphere at 2... o C min -1 The rate continues to heat to 850 o C was maintained for 1 h to obtain carbonized products;

[0027] S103: Impregnate the carbonized product in concentrated phosphoric acid, with 1 g of product corresponding to 20 mL of concentrated phosphoric acid. Mix thoroughly and then heat at 180°C. o Reflux at C for 1 h, wash repeatedly with deionized water, centrifuge until neutral, and dry to obtain the final product.

[0028] The method for preparing O and P-doped ultraporous carbon nanospheres provided by this invention can also be implemented by those skilled in the art using other steps. Figure 1 The method for preparing O and P-doped ultraporous carbon nanospheres provided by this invention is merely a specific embodiment.

[0029] The invention will be further described below with reference to experimental data and results.

[0030] Figure 2 This is a pore size distribution diagram of the material prepared according to the embodiments of the present invention.

[0031] Figure 3 These are scanning electron microscope (SEM) images and transmission electron microscope (TEM) images of the prepared materials provided in the embodiments of the present invention.

[0032] Figure 4 This is an X-ray photoelectron spectrum of the prepared material provided in the embodiments of the present invention.

[0033] Figure 5 This is a schematic diagram of the assembly of the quasi-solid-state flexible capacitor provided in the embodiments of the present invention, and the corresponding energy density and power density Ragone plots characterizing its performance.

[0034] The pore size distribution diagram of this invention shows that the prepared O and P-doped ultraporous carbon microspheres have a narrow distribution at 0.59 nm, confirming the successful design of the ultraporous pores. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) characterization show that the carbon microspheres have a regular spherical geometry with a size of approximately 100 nm. Furthermore, high-resolution transmission electron microscopy (HRTEM) images reveal that the carbon microspheres possess a highly disordered amorphous carbon structure, with randomly distributed curved and closed structures suggesting the presence of micropores. X-ray photoelectron spectroscopy (XPS) indicates that the material has abundant N and O doping and the introduction of P. The N comes from the N content of polyacrylonitrile itself, while the O and P come from phosphoric acid impregnation.

[0035] This invention disperses the prepared material, acetylene black, and polyvinylidene fluoride in a 1-methyl-2-pyrrolidone solvent at a mass ratio of 8:1:1. The mixture is then coated onto carbon paper to form an electrode material, which serves as the cathode. Polished zinc foil is used as the anode, and PAM / ZnSO4 is used as the electrolyte to form a flexible quasi-solid-state capacitor. Finally, it is encapsulated with polyimide tape. Ultimately, at a medium power density (900 W / kg), the capacitor is successfully tested. -1 It exhibits a battery-level energy density (262 Wh kg). -1 It also exhibits excellent cycle stability.

[0036] The above description is merely a specific embodiment of the present invention intended to demonstrate the practical application of the technical solution provided by the present invention, and should not be construed as a limitation on the scope of protection of the present invention. However, the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions, and improvements made by any person skilled in the art within the scope of the technology disclosed in the present invention, within the spirit and principles of the present invention, should be included within the scope of protection of the present invention.

Claims

1. A method for preparing O and P-doped ultraporous carbon nanospheres, characterized in that, Sodium dodecyl diphenyl ether disulfonate, acrylonitrile, potassium persulfate, and acetic acid were added to deionized water, and emulsion polymerization was carried out at 72°C for 10 h. After demulsification, the powder was pre-oxidized and carbonized, and then impregnated with concentrated phosphoric acid to dope P and O elements to obtain the final product.

2. The method for preparing O and P-doped ultraporous carbon nanospheres as described in claim 1, characterized in that, Preparation of polyacrylonitrile microspheres: First, 0.1 g of sodium dodecyl diphenyl ether disulfonate was completely dissolved in 10 mL of deionized water. Then, 0.65 g of acrylonitrile, 0.02 g of potassium persulfate and 6 drops of acetic acid were continuously added to the system and pre-stirred at 40 °C for 60 min. Subsequently, the temperature was increased to 72 °C for emulsion polymerization for 10 h to form a milky white emulsion.

3. The method for preparing O and P-doped ultraporous carbon nanospheres as described in claim 1, characterized in that, The resulting emulsion was heated at 6000 r / min -1 The mixture was centrifuged at a speed of [speed value] to break the emulsion and washed twice with ethanol. Then it was dried in an oven at 80°C for 24 hours to obtain a white powder of polyacrylonitrile microspheres.

4. The method for preparing O and P-doped ultraporous carbon nanospheres as described in claim 1, characterized in that, Preparation of carbonized microspheres: First, in an air atmosphere, at 0.5℃ for min... -1 The product was heated to 250°C and held for 5 hours at a certain rate, then cooled to room temperature and incubated at 2°C / min under a N2 atmosphere. -1 The temperature was continued to rise to 850°C and held for 1 hour to obtain the carbonized product.

5. The method for preparing O and P-doped ultraporous carbon nanospheres as described in claim 1, characterized in that, The carbonized microspheres were immersed in concentrated phosphoric acid, with 1g of product corresponding to 20 mL of concentrated phosphoric acid. After mixing evenly, the mixture was refluxed at 180℃ for 1 h. The microspheres were washed repeatedly with deionized water and centrifuged until neutral. After drying, the final product was obtained.

6. An electrode, characterized in that, The electrode is prepared by dispersing O and P doped ultraporous carbon nanospheres, which are prepared by any one of claims 1 to 5, with acetylene black and polyvinylidene fluoride in a mass ratio of 8:1:1 in a 1-methyl-2-pyrrolidone solvent, and then coating them onto carbon paper.

7. A quasi-solid-state flexible capacitor device, characterized in that, The electrode described in claim 6 is used as the cathode, polished zinc foil as the anode, PAM / ZnSO4 as the electrolyte, and finally encapsulated with polyimide tape.

8. An electric vehicle energy system equipped with the quasi-solid-state flexible capacitor device of claim 7.

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