A coaxial gradient porous nanocore-shell structure cathode material and its preparation method

Abstract

This invention discloses a coaxial gradient porous nanocore-shell structure cathode material and its preparation method. The preparation method involves using a coaxial air-jet spinning technique to obtain an air-jet spun membrane with a nanocore-shell structure. This membrane is then chemically modified, followed by pyrolytic carbonization in an inert atmosphere, acid treatment, and finally carbonization with a strong alkali solution to obtain the coaxial gradient porous nanocore-shell structure cathode material. The cathode material prepared by this invention possesses a dual-pathway fiber structure with axial electron transport and radial ion diffusion, combined with gradient mesopores, optimizing the high energy storage and power output of carbonaceous materials. It exhibits excellent electrochemical performance and structural stability, making it suitable for high-performance zinc-ion batteries.

Description

Technical Field

[0001] This invention relates to the field of battery materials technology, specifically to a coaxial gradient porous nanocore-shell structure cathode material and its preparation method. Background Technology

[0002] With the increasing demand for energy and the growing severity of environmental problems, the development of efficient and environmentally friendly energy storage technologies has become particularly important. Zinc-ion batteries, due to their high safety, low cost, and environmental friendliness, are gradually becoming an energy storage technology with broad application prospects. Zinc, as an ideal anode material for aqueous zinc-ion batteries, exhibits rapid deposition / stripping redox reactions, enabling high power density and long service life. In the research of cathode materials for zinc-ion batteries, manganese-based compounds (such as MnO2 and Mn3O4), vanadium-based compounds (such as V2O5 and Na3V2(PO4)3), and Prussian blue-based materials have attracted considerable research attention due to their high theoretical capacity and excellent electrochemical performance.

[0003] Carbon-based materials can also be used as cathode materials for zinc-ion batteries. However, traditional carbon-based materials (such as graphite and activated carbon, which have high specific surface areas and good conductivity) often have low zinc storage capacity, limiting their application in zinc-ion batteries. Nevertheless, carbon-based materials possess unique advantages, such as light weight, low cost, environmental friendliness, and excellent conductivity. Through engineering design, particularly by introducing appropriate pore structures and functionalized surfaces, the zinc storage capacity and electrochemical performance of carbon materials can be significantly improved. For example, carbonaceous materials with high specific surface areas and appropriate pore sizes facilitate high-density zinc storage, but a single type of pore structure often cannot simultaneously achieve high energy density and high power output. Therefore, carbon materials with gradient pore structures have emerged. This structure not only improves zinc storage capacity but also optimizes electron transport and ion diffusion pathways, thereby achieving efficient energy storage and release. Therefore, developing a zinc-ion battery cathode material with a gradient porous nanostructure is of great significance for improving the performance of zinc-ion batteries.

[0004] Patent CN116722121A involves chemically modifying the surface of carbon-based materials to coat vanadium-based oxide cathode materials with redox-active carbon-based materials. It emphasizes the rate performance of vanadium-based cathode materials and the structural stability and specific surface area of ​​carbon-based materials, but does not address gradient porous structures or engineering designs for carbon-based materials to improve zinc storage capacity. Patent CN110828802A uses electrospinning to prepare a composite cathode material of graphene-coated manganese sulfide and nitrogen-doped carbon nanofibers, improving the specific capacity of the battery cathode and exhibiting excellent cycle stability, enabling high-rate charge and discharge. However, electrospinning has low production efficiency, hindering mass production and large-scale application of the cathode. Patent CN114335471A obtains manganese suboxide through Mn-MOF derivatization, followed by heat treatment under an argon atmosphere to obtain MnO / C. The material inherits the advantages of Mn-MOF, such as its porous structure and large specific surface area, which provides a significant advantage for ion diffusion and electron transfer. However, it does not improve the performance by modifying the structure of carbon-based materials, especially the effect of gradient porosity on zinc ion storage and battery performance. Summary of the Invention

[0005] To address the aforementioned technical problems, the present invention aims to provide a coaxial gradient porous nanocore-shell structure cathode material and its preparation method. Through coaxial air-jet spinning and chemical modification processes, a zinc-ion battery cathode material with excellent electrochemical performance is prepared, which can be widely used in the fields of energy storage and conversion.

[0006] The above-mentioned objective of the present invention is achieved through the following technical solution:

[0007] The first aspect of this invention provides a method for preparing a coaxial gradient porous nanocore-shell structured cathode material, comprising the following steps:

[0008] (1) A precursor solution A is obtained by dissolving conductive carbon nanomaterials and polymers in a solvent; a precursor solution B is obtained by dissolving styrene-acrylonitrile copolymer (SAN) and polymers in a solvent; precursor solution A is injected into the outer channel of a coaxial gas nozzle and precursor solution B is injected into the inner channel of the coaxial gas nozzle, or precursor solution A is injected into the inner channel of the coaxial gas nozzle and precursor solution B is injected into the outer channel of the coaxial gas nozzle, and coaxial gas-jet spinning is performed to obtain a gas-jet spun film with a nano-core-shell structure; the conductive carbon nanomaterials are selected from one or more of carbon quantum dots (CDs), graphene quantum dots (GQDs), carbon nanotubes (CNTs), fullerene (C60) and graphene oxide (GO); the polymers are selected from one or more of polyacrylonitrile (PAN), polyamic acid (PAA), polybenzimidazole (PBI), polypyrrole (PPy) and polyetherimide (PEI).

[0009] (2) The air-jet spun membrane with nano core-shell structure obtained in step (1) is immersed in 3-aminophenol solution, then methyltriethoxysilane (VTMS) and ammonia are added, and then formaldehyde solution is injected to obtain a surface-modified air-jet spun membrane with nano core-shell structure.

[0010] (3) The surface-modified gas-spun membrane with nano-core-shell structure obtained in step (2) is subjected to pyrolysis carbonization treatment in an inert atmosphere to obtain a nano-hybrid carbon fiber membrane material with porous structure.

[0011] (4) The nano-hybrid carbon fiber membrane material with porous structure obtained in step (3) is treated with an acid solution, and the treated material is mixed with a strong alkaline solution and carbonized in an inert atmosphere to obtain the coaxial gradient porous nano core-shell structure cathode material.

[0012] The preparation method provided by this invention introduces conductive carbon nanomaterials and optimized air-jet spinning technology, and constructs a gradient pore structure through chemical modification to prepare a cathode material with high specific surface area and excellent electrochemical performance, thereby significantly improving the energy storage performance and cycle stability of zinc-ion batteries.

[0013] Further, in step (1), the molecular weight of the styrene-acrylonitrile copolymer is 80,000-150,000 g / mol.

[0014] Further, in step (1), the molecular weight of the polymer is 100,000-150,000 g / mol.

[0015] Further, in step (1), the mass ratio of the conductive carbon nanomaterial to the polymer is (0.5-1):(10-15); the mass ratio of the styrene-acrylonitrile copolymer to the polymer is (5-10):(10-15).

[0016] Further, in step (1), the concentration of conductive carbon nanomaterials in precursor solution A is 10-15 wt%; and the concentration of styrene-acrylonitrile copolymer in precursor solution B is 5-20 wt%.

[0017] In a specific embodiment, in step (1), conductive carbon nanomaterials are dispersed in a solvent and ultrasonically treated to ensure uniform dispersion; PAN is dissolved in the above solution and stirred until completely dissolved to obtain a precursor solution A of CDs-doped PAN-based components with a concentration of 10-15 wt%; SAN is dissolved in a solvent and stirred until completely dissolved; PAN is added to the above solution and stirred until completely dissolved to obtain a precursor solution B of SAN-doped PAN-based components with a concentration of 5-20 wt%.

[0018] Further, in step (1), the solvent is selected from one or more of dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF) and N-methylpyrrolidone (NMP).

[0019] Furthermore, in step (1), the conductive carbon nanomaterial is preferably carbon quantum dots (CDs).

[0020] Doping CDs is more conducive to improving conductivity and the porosity distribution of the core layer.

[0021] Further, in step (1), the polymer is preferably polyacrylonitrile (PAN).

[0022] The coaxial gradient porous nanocore-shell structure cathode material prepared by this invention consists of a nanofiber porous core and a nanoshell with a gradient pore structure. The nanofiber porous core is a SAN-doped PAN-based component, and the nanoshell with a gradient pore structure is a CDs-doped PAN-based component. The nanoshell has excellent conductivity. Alternatively, it can be composed of a core with a gradient pore structure and a nanofiber porous outer shell. The core with a gradient pore structure is a CDs-doped PAN-based component, and the nanofiber porous outer shell is a SAN-doped PAN-based component. CDs, as the core, provide an efficient electronic conduction path, while SAN, as the outer shell, ensures the mechanical strength and pore structure stability of the material. This combination has good comprehensive performance, especially in the balance between electrical conductivity and mechanical strength.

[0023] Furthermore, the diameter of the porous nanofiber core is 100-500 nanometers, and the thickness of the outer nanoshell with a gradient pore structure is 150-800 nanometers.

[0024] In this invention, the precursor solution, during the subsequent coaxial air-jet spinning process, helps to form a fiber membrane material with a uniform nanostructure and excellent properties. Furthermore, air-jet spinning is more suitable for large-scale production, and the material processing capabilities of air-jet spinning are more diverse.

[0025] Further, in step (1), the process parameters of the coaxial air-jet spinning are: the jetting rate of the inner channel is 0.5-2.0 mL / h; the jetting rate of the outer channel is 1.0-5.0 mL / h.

[0026] Furthermore, in step (1), after coaxial air-jet spinning, an air-jet spun film with a nano core-shell structure is obtained on the receiver.

[0027] Further, in step (2), the concentration of 3-aminophenol in the 3-aminophenol solution is 0.1-1 mol / L.

[0028] Further, in step (2), the volume ratio of the 3-aminophenol solution, methyltriethoxysilane, ammonia and formaldehyde solution is 5:(0.5-1.5):(0.5-1.5):(0.5-1.5).

[0029] Furthermore, in step (2), the volume ratio of methyltriethoxysilane to ammonia is preferably 1:1.

[0030] Further, in step (2), the air-spun membrane with nano-core-shell structure obtained in step (1) is immersed in 3-aminophenol solution and stirred for 5-10 min. Then, methyltriethoxysilane and ammonia are added and stirred for 5-6 h. Then, formaldehyde solution is injected and stirred at 20-25℃ for 5-6 h. After drying, a surface-modified air-spun membrane with nano-core-shell structure is obtained.

[0031] Step (2) involves a multifunctional surface modification process that combines the surface functionalization of organosilicon and aminophenol groups, forming an organic-inorganic hybrid core-shell structure through the synergistic surface functionalization treatment of aminophenol and organosilicon.

[0032] Furthermore, in step (2), the concentration of the formaldehyde solution is 5-15 wt%.

[0033] Furthermore, in step (3), the temperature of the pyrolysis carbonization treatment is 750-800℃.

[0034] Furthermore, in step (3), the inert atmosphere can be argon, nitrogen, helium, neon, etc.

[0035] Furthermore, in step (4), the acid solution is a hydrofluoric acid (HF) solution with a concentration of 10%-15%.

[0036] Furthermore, in step (4), the acid solution treatment time is 2-4 hours.

[0037] Further, in step (4), the mass ratio of the treated material to the strong alkali solution is 1:(3-7).

[0038] During carbonization, strong alkalis act as activators, combining chemical reactions with physical etching to create abundant microporous and mesoporous structures within the material. During high-temperature carbonization, strong alkalis react with carbon materials in a redox reaction, generating gases such as carbon monoxide (CO) and carbon dioxide (CO2). The generation of these gases causes the expansion of the carbon structure and the formation of pores. For example, KOH can react with carbon materials to generate K2CO3, which further decomposes to produce CO2 and additional pores. These reactions occur on the pore walls, leading to surface erosion and increased pore size. Furthermore, the CO and CO2 generated during carbonization etch the internal microstructure of the material, further forming porous structures. This gas etching can disrupt the inherent structure of carbon materials, further refining and expanding the pore size, thereby optimizing the porosity of the material.

[0039] When the carbonization temperature reaches a certain level (e.g., above 750℃), KOH decomposes to produce metallic potassium. Metallic potassium has a relatively large volume and can embed itself into the interlayer spaces of carbon materials, causing expansion of the layered structure and enhancing pore formation. This embedding and expansion effectively expands the pore size distribution range, contributing to the formation of mesopores and micropores.

[0040] The presence of strong bases goes beyond simple etching; it further activates carbon-based materials during carbonization, increasing their specific surface area. This activation increases the number of reaction sites in the material, thus facilitating the electrochemical reaction of zinc ions and the construction of ion migration channels.

[0041] Strong alkalis have a dual role in high-temperature carbonization, combining chemical reaction and physical etching. Through processes such as redox reaction, gas etching and potassium metal intercalation, they significantly increase the porosity of the material and regulate the pore size and pore distribution, ultimately forming an ideal microporous-mesoporous structure to meet the requirements of zinc ion transport.

[0042] Furthermore, in step (4), the strong alkaline solution can be potassium hydroxide (KOH) solution, sodium hydroxide (NaOH) solution, etc.

[0043] Furthermore, in step (4), the concentration of the strong alkali solution is 5-10 mol / L.

[0044] Further, in step (4), the specific operation of the carbonization treatment is as follows: heat up to 700-800℃ at a heating rate of 1-3℃ / min and hold for 0.5-2h.

[0045] Furthermore, in step (4), after the carbonization process is completed, the process further includes washing with hydrochloric acid solution and water until neutral, and then performing a drying process.

[0046] Furthermore, the concentration of the hydrochloric acid solution is 1-3 mol / L.

[0047] Furthermore, the electrical conductivity of the water is less than 1 μS / cm.

[0048] Furthermore, the water is preferably deionized water.

[0049] Furthermore, the drying process is carried out at a temperature of 60-80°C for 8-12 hours.

[0050] The second aspect of this invention protects the coaxial gradient porous nanocore-shell structure cathode material prepared by the method described in the first aspect.

[0051] The cathode material prepared by this invention has a dual-pathway fiber structure of axial electron transport and radial ion diffusion, and combined with gradient mesoscopic micropores, which will further optimize the high energy storage and power output of carbonaceous materials. It has good electrochemical performance and structural stability and is suitable for high-performance zinc-ion batteries.

[0052] The coaxial gradient porous nanocore-shell structure cathode material provided by this invention can be used in zinc-ion batteries.

[0053] The beneficial effects of this invention are:

[0054] 1. The conductive carbon nanomaterials used in this invention possess excellent conductivity and high specific surface area. By doping them into polymer molecules, the conductivity and electrochemical activity of the cathode material can be significantly improved. Simultaneously, the presence of conductive carbon nanomaterials provides more active sites, facilitating the rapid adsorption and desorption of zinc ions, thereby increasing the zinc ion storage capacity and the battery's energy density. The addition of SAN enhances the mechanical strength and stability of the shell material. The SAN-doped shell not only provides structural support but also increases the material's chemical stability, extending the battery's lifespan.

[0055] 2. Compared to traditional electrospinning, the coaxial air-jet spinning method of this invention offers higher efficiency and better controllability. By precisely controlling the flow rate of the inner and outer layer solutions and the air-jet pressure, uniform formation of the core-shell structure can be achieved. Optimization of the spinning distance further ensures the quality of fiber formation and structural integrity. This invention employs multi-step chemical modification and heat treatment. Through multi-step chemical modification with 3-aminophenol, VTMS, ammonia, and formaldehyde, the shell structure is further strengthened. Subsequent pyrolysis carbonization and acid solution treatment steps endow the material with a gradient porous structure, significantly improving its electrochemical performance.

[0056] 3. This invention, by adjusting the concentration of the strong alkaline solution, enables precise control of the pore size and distribution in carbon materials, forming a gradient pore structure. This structure not only enhances the specific surface area of ​​the material but also optimizes the pore structure, making it more suitable as a cathode material for high-performance zinc-ion batteries. The gradient pore structure facilitates the rapid transport and uniform distribution of zinc ions, thereby significantly improving the electrochemical performance of the battery.

[0057] 4. The coaxial gradient porous nanostructured cathode material prepared by this invention not only provides excellent mechanical properties and structural stability, but also significantly improves the zinc ion storage capacity. The gradient porous structure facilitates the rapid transport and uniform distribution of zinc ions, reduces the ion transport resistance inside the battery, and further improves the battery's power density and cycle stability.

[0058] 5. This invention significantly improves the electrochemical performance and service life of zinc-ion battery cathode materials through the rational selection of doping materials, optimized preparation process and innovative structural design, providing new ideas and methods for the development of high-performance zinc-ion batteries. Attached Figure Description

[0059] Figure 1 The process flow diagram is shown for the preparation method of the coaxial gradient porous nanocore-shell structure cathode material provided by the present invention.

[0060] Figure 2 This is a schematic diagram of the coaxial gradient porous nanocore-shell structure cathode material prepared in Example 1. Detailed Implementation

[0061] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0062] This invention provides a method for preparing a coaxial gradient porous nanocore-shell structured cathode material, such as... Figure 1 As shown, it includes the following steps:

[0063] (1) Dissolve conductive carbon nanomaterials and polymers in a solvent to obtain precursor solution A; dissolve styrene-acrylonitrile copolymer (SAN) and polymers in a solvent to obtain precursor solution B; inject precursor solution A and precursor solution B into the outer and inner channels of a coaxial air nozzle, respectively, or inject precursor solution A and precursor solution B into the inner and outer channels of a coaxial air nozzle, respectively, and perform coaxial air-jet spinning to obtain an air-jet spun film with a nano core-shell structure;

[0064] (2) Immerse the air-jet spun membrane with nano core-shell structure obtained in step (1) into 3-aminophenol solution, then add methyltriethoxysilane and ammonia, and then inject formaldehyde solution to obtain surface-modified air-jet spun membrane with nano core-shell structure.

[0065] (3) The surface-modified gas-spun membrane with nano-core-shell structure obtained in step (2) is subjected to pyrolysis carbonization treatment in an inert atmosphere to obtain a nano-hybrid carbon fiber membrane material with porous structure.

[0066] (4) The nano-hybrid carbon fiber membrane material with porous structure obtained in step (3) is treated with an acid solution, and the treated material is mixed with a strong alkaline solution and carbonized in an inert atmosphere to obtain the coaxial gradient porous nano core-shell structure cathode material.

[0067] In a specific embodiment, the precursor solution A is prepared as follows: conductive carbon nanomaterials are dispersed in a solvent. To ensure uniform dispersion, ultrasonic treatment is employed for 30-40 minutes at a frequency of 40-50 kHz. Subsequently, PAN is slowly added to the uniformly dispersed conductive carbon nanomaterial solution, and continuous stirring is carried out to promote complete dissolution of PAN. The stirring conditions are 500-600 rpm at room temperature for 4-5 hours, ultimately yielding precursor solution A of the PAN-based component doped with conductive carbon nanomaterials.

[0068] In a specific embodiment, the precursor solution B is prepared as follows: SAN is dissolved in a solvent and magnetically stirred at room temperature until the SAN is completely dissolved. The stirring rate is 500-600 rpm, and the stirring time is 2-3 hours. Subsequently, PAN is slowly added to the completely dissolved SAN solution, and stirring continues to ensure the complete dissolution of PAN. The stirring conditions are 500-600 rpm at room temperature, and the stirring time is 4-5 hours, finally obtaining the SAN-doped PAN-based precursor solution B.

[0069] In a specific embodiment, the conductive carbon nanomaterial is selected from one or more of carbon quantum dots (CDs), graphene quantum dots (GQDs), carbon nanotubes (CNTs), fullerenes (C60), and graphene oxides (GO); the polymer is selected from one or more of polyacrylonitrile (PAN), polyamic acid (PAA), polybenzimidazole (PBI), polypyrrole (PPy), and polyetherimide (PEI).

[0070] In a specific embodiment, in step (1), the coaxial air-jet spinning operation is as follows: the precursor solution A and the precursor solution B are injected into the inner and outer channels of the coaxial air nozzle, respectively, and coaxial air-jet spinning is performed. The diameter of the fiber core and the thickness of the outer shell layer in the nanofiber are controlled by changing the spinning flow rate and the air-jet pressure. Different nanofiber core-shell structure air-jet spun films are obtained on the receiver. Then the fibers are dried in a drying oven at 60-80℃ for 10-20 hours.

[0071] In a specific implementation, in step (1), the process parameters of the coaxial air-jet spinning are: the jetting rate of the inner channel is 0.5-2.0 mL / h, the jetting rate of the outer channel is 1.0-5.0 mL / h, the air jetting pressure is 0.2-0.3 MPa, and the spinning distance is 10-20 cm.

[0072] In a specific embodiment, in step (2), the air-spun membrane with nano-core-shell structure obtained in step (1) is cut into samples of appropriate size, immersed in 3-aminophenol solution, stirred for 5-10 min, then methyltriethoxysilane and ammonia are added, stirred for 5-6 h, then formaldehyde solution is injected, stirred at 20-25℃ for 5-6 h, and then the sample is dried overnight to obtain a surface-modified air-spun membrane with nano-core-shell structure.

[0073] In a specific embodiment, in step (3), the surface-modified gas-spun membrane with a nano core-shell structure obtained in step (2) is subjected to pyrolysis carbonization treatment in an inert atmosphere, heated to 750-800℃ at a heating rate of 2-3℃ / min and held for 2-3 hours, and then naturally cooled to room temperature to obtain a nano-hybrid carbon fiber membrane material with a porous structure.

[0074] In a specific embodiment, in step (4), the nano-hybrid carbon fiber membrane material with porous structure obtained in step (3) is treated with an acid solution at room temperature for 30-40 min, and then washed with deionized water until neutral; the treated material is mixed with a strong alkaline solution and carbonized in an inert atmosphere, heated to 700-800℃ at a heating rate of 1-3℃ / min, held for 0.5-2 h, then washed with hydrochloric acid solution and deionized water until neutral, and dried overnight in a constant temperature drying oven at 70-80℃ to obtain the coaxial gradient porous nano-core-shell structure cathode material.

[0075] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0076] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the materials and reagents used are commercially available.

[0077] In the examples described below, carbon quantum dots were purchased from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd. (catalog number 102632); polyacrylonitrile was purchased from Shanghai Guchen Biotechnology Co., Ltd. (catalog number GC25168-500gA); styrene-acrylonitrile was purchased from Guangzhou Zhongxin Plastics Co., Ltd.; dimethyl sulfoxide was purchased from Shandong Jinhe Chemical Co., Ltd. (density 1.100 g / mL); 3-aminophenol was purchased from Nanjing Chemical Reagent Co., Ltd. (catalog number C0480559335); methyltriethoxysilane was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. (purity AR grade); formaldehyde was purchased from Nanjing Chemical Reagent Co., Ltd.; hydrofluoric acid was purchased from Shanghai Yi'en Chemical Technology Co., Ltd. (purity AR grade); potassium hydroxide was purchased from Xilong Scientific Co., Ltd.; hydrochloric acid was purchased from Shenzhen Bolinda Technology Co., Ltd. (concentration 2 mol / L); and argon was purchased from Shanghai Jinzhu Chemical Co., Ltd.

[0078] Example 1

[0079] A method for preparing a coaxial gradient porous nanocore-shell structure cathode material includes the following steps:

[0080] (1) 15g of CDs were dispersed in 100mL of dimethyl sulfoxide (DMSO) solution and sonicated for 30min at a frequency of 40kHz to ensure uniform dispersion. Then, 15g of PAN was slowly added to the uniformly dispersed CDs solution and stirred continuously until completely dissolved at 500rpm for 4h at room temperature, yielding a precursor solution A of the CDs-doped PAN-based component. 10g of SAN was dissolved in 100mL of DMSO solution and magnetically stirred at 500rpm for 2h at room temperature until completely dissolved. Then, 15g of PAN was slowly added to the completely dissolved SAN solution and stirred at 500rpm for 4h at room temperature, yielding a precursor solution B of the SAN-doped PAN-based component. Precursor solution A was injected into the outer channel of the coaxial air nozzle, and precursor solution B was injected into the inner channel of the coaxial air nozzle for coaxial air-jet spinning. The jetting rate of the inner channel was 0.5 mL / h, the jetting rate of the outer channel was 1.0 mL / h, the air jetting pressure was 0.2 MPa, and the spinning distance was 15 cm. An air-jet spun membrane with a CDs@SAN nanocore-shell structure was obtained on the receiver.

[0081] (2) Cut the air-jet spun membrane into 2cm×2cm samples, immerse them in 50mL of 0.1mol / L 3-aminophenol solution, stir for 10min, then add 10mL of methyltriethoxysilane and 10mL of ammonia water, stir for 6h, then inject 10mL of 10wt% formaldehyde solution, stir at 25℃ for 6h, and then dry the samples overnight to obtain an air-jet spun membrane with CDs@organosilicon@APF nano core-shell structure.

[0082] (3) The gas-spun membrane with CDs@organosilicon@APF nano core-shell structure was subjected to pyrolysis carbonization treatment in an argon atmosphere, heated to 800℃ at a heating rate of 2℃ / min and held for 2h, and then naturally cooled to room temperature to obtain a nano-hybrid carbon fiber membrane material with a porous structure.

[0083] (4) The nano-hybrid carbon fiber membrane material with porous structure was immersed in 10% HF solution and treated at room temperature for 30 min. Then it was washed with deionized water until neutral. The treated material was mixed with 6 mol / L KOH solution at a mass ratio of 1:3 and carbonized in an argon atmosphere. The temperature was increased to 750℃ at a heating rate of 2℃ / min and held for 1 h. Then it was washed with 1 mol / L hydrochloric acid solution and deionized water until neutral and dried overnight in a constant temperature drying oven at 70℃ to obtain the coaxial gradient porous nano-core-shell structure cathode material.

[0084] Figure 2This is a schematic diagram of the coaxial gradient porous nanocore-shell cathode material prepared in Example 1. The inner layer represents a porous core composed of SAN-doped PAN-based nanofibers, which provides high conductivity and structural support. The outer layer exhibits a gradient porous structure, consisting of a nanoshell composed of CDs-doped PAN-based materials. This gradient porous structure is achieved through specific treatment concentrations with KOH solution, which optimizes the transport path of zinc ions and improves the electrochemical performance of the material. The gradient pores exist on the surface of the outer carbon quantum dots, consisting of micropores and mesopores. The micropores are located on the surface of the carbon quantum dots, and the mesopores are distributed above the micropores. This invention provides an effective method for designing and realizing high-energy-density energy storage using mesoporous carbon materials.

[0085] Example 2

[0086] A method for preparing a coaxial gradient porous nanocore-shell structure cathode material includes the following steps:

[0087] (1) 15g of CDs were dispersed in 100mL of DMSO solution and sonicated for 30min at a frequency of 40kHz to ensure uniform dispersion. Then, 20g of PAN was slowly added to the uniformly dispersed CDs solution and stirred continuously until completely dissolved at 500rpm for 4h at room temperature, yielding a precursor solution A of the CDs-doped PAN-based component. 20g of SAN was dissolved in 100mL of DMSO solution and magnetically stirred at 500rpm for 2h at room temperature until completely dissolved. Then, 20g of PAN was slowly added to the completely dissolved SAN solution and stirred at 500rpm for 4h at room temperature, yielding a precursor solution B of the SAN-doped PAN-based component. Precursor solution A was injected into the outer channel of the coaxial air nozzle, and precursor solution B was injected into the inner channel of the coaxial air nozzle for coaxial air-jet spinning. The jetting rate of the inner channel was 0.7 mL / h, the jetting rate of the outer channel was 1.2 mL / h, the air jetting pressure was 0.25 MPa, and the spinning distance was 15 cm. An air-jet spun membrane with a CDs@SAN nanocore-shell structure was obtained on the receiver.

[0088] (2) Cut the air-jet spun membrane into 2cm×2cm samples, immerse them in 50mL of 0.1mol / L 3-aminophenol solution, stir for 15min, then add 10mL of methyltriethoxysilane and 10mL of ammonia water, stir for 8h, then inject 10mL of 10wt% formaldehyde solution, stir at 25℃ for 8h, and then dry the samples overnight to obtain an air-jet spun membrane with CDs@organosilicon@APF nano core-shell structure.

[0089] (3) The gas-spun membrane with CDs@organosilicon@APF nano core-shell structure was subjected to pyrolysis carbonization treatment in an argon atmosphere, heated to 800℃ at a heating rate of 2℃ / min and held for 2h, and then naturally cooled to room temperature to obtain a nano-hybrid carbon fiber membrane material with a porous structure.

[0090] (4) The nano-hybrid carbon fiber membrane material with porous structure was immersed in 10% HF solution and treated at room temperature for 30 min. Then it was washed with deionized water until neutral. The treated material was mixed with 6 mol / L KOH solution at a mass ratio of 1:5 and carbonized in an argon atmosphere. The temperature was increased to 700℃ at a heating rate of 3℃ / min and held for 2 h. Then it was washed with 1 mol / L hydrochloric acid solution and deionized water until neutral and dried overnight in a constant temperature drying oven at 80℃ to obtain the coaxial gradient porous nano-core-shell structure cathode material.

[0091] Example 3

[0092] A method for preparing a coaxial gradient porous nanocore-shell structure cathode material includes the following steps:

[0093] (1) 15g of CDs were dispersed in 100mL of DMSO solution and sonicated for 40min at a frequency of 40kHz to ensure uniform dispersion. Then, 25g of PAN was slowly added to the uniformly dispersed CDs solution and stirred continuously until completely dissolved at 500rpm for 5h at room temperature, yielding a precursor solution A of the CDs-doped PAN-based component. 25g of SAN was dissolved in 100mL of DMSO solution and magnetically stirred at 500rpm for 3h at room temperature until completely dissolved. Then, 25g of PAN was slowly added to the completely dissolved SAN solution and stirred at 500rpm for 5h at room temperature, yielding a precursor solution B of the SAN-doped PAN-based component. Precursor solution A was injected into the outer channel of the coaxial air nozzle, and precursor solution B was injected into the inner channel of the coaxial air nozzle for coaxial air-jet spinning. The jetting rate of the inner channel was 0.6 mL / h, the jetting rate of the outer channel was 1.1 mL / h, the air jetting pressure was 0.22 MPa, and the spinning distance was 14 cm. An air-jet spun membrane with a CDs@SAN nanocore-shell structure was obtained on the receiver.

[0094] (2) Cut a 2cm×2cm sample of the air-jet spun membrane, immerse it in 50mL of 0.1mol / L 3-aminophenol solution, stir for 12min, then add 10mL of methyltriethoxysilane and 10mL of ammonia water, stir for 7h, then inject 10mL of 10wt% formaldehyde solution, stir at 25℃ for 7h, and then dry the sample overnight to obtain an air-jet spun membrane with CDs@organosilicon@APF nano core-shell structure.

[0095] (3) The gas-spun membrane with CDs@organosilicon@APF nano core-shell structure was subjected to pyrolysis carbonization treatment in an argon atmosphere, heated to 800℃ at a heating rate of 2℃ / min and held for 2h, and then naturally cooled to room temperature to obtain a nano-hybrid carbon fiber membrane material with a porous structure.

[0096] (4) The nano-hybrid carbon fiber membrane material with porous structure was immersed in 10% HF solution and treated at room temperature for 30 min. Then it was washed with deionized water until neutral. The treated material was mixed with 6 mol / L KOH solution at a mass ratio of 1:7 and carbonized in an argon atmosphere. The temperature was raised to 720℃ at a heating rate of 2.5℃ / min and held for 1.5 h. Then it was washed with 1 mol / L hydrochloric acid solution and deionized water until neutral and dried overnight in a constant temperature drying oven at 75℃ to obtain the coaxial gradient porous nano-core-shell structure cathode material.

[0097] Example 4

[0098] A method for preparing a coaxial gradient porous nanocore-shell structure cathode material is basically the same as that in Example 1, except that in step (4), the treated material is mixed with a 6 mol / L KOH solution at a mass ratio of 1:1.

[0099] Example 5

[0100] A method for preparing a coaxial gradient porous nanocore-shell structure cathode material is basically the same as that in Example 1, except that in step (4), the treated material is mixed with a 6 mol / L KOH solution at a mass ratio of 1:5.

[0101] Example 6

[0102] A method for preparing a coaxial gradient porous nanocore-shell structure cathode material is basically the same as that in Example 1, except that in step (4), the treated material is mixed with a 6 mol / L KOH solution at a mass ratio of 1:7.

[0103] Example 7

[0104] A method for preparing a coaxial gradient porous nanocore-shell structure cathode material is basically the same as that in Example 1, except that in step (4), the treated material is mixed with a 6 mol / L KOH solution at a mass ratio of 1:10.

[0105] Example 8

[0106] A method for preparing a coaxial gradient porous nanocore-shell structure cathode material includes the following steps:

[0107] (1) 15g of carbon nanotubes (CNTs) were dispersed in 100mL of DMSO solution and sonicated for 30min at a frequency of 40kHz to ensure uniform dispersion. Then, 20g of PAN was slowly added to the uniformly dispersed CNTs solution and stirred continuously until completely dissolved at 500rpm for 4h at room temperature, yielding precursor solution A of the CNTs-doped PAN-based component. 20g of SAN was dissolved in 100mL of DMSO solution and magnetically stirred at 500rpm for 2h at room temperature until completely dissolved. Then, 20g of PAN was slowly added to the completely dissolved SAN solution and stirred at 500rpm for 4h at room temperature, yielding precursor solution B of the SAN-doped PAN-based component. Precursor solution A was injected into the outer channel of the coaxial air nozzle, and precursor solution B was injected into the inner channel of the coaxial air nozzle for coaxial air-jet spinning. The jetting rate of the inner channel was 0.7 mL / h, the jetting rate of the outer channel was 1.2 mL / h, the air jetting pressure was 0.25 MPa, and the spinning distance was 15 cm. An air-jet spun membrane with a CNTs@SAN nanocore-shell structure was obtained on the receiver.

[0108] (2) Cut the air-jet spun membrane into 2cm×2cm samples, immerse them in 50mL of 0.1mol / L 3-aminophenol solution, stir for 15min, then add 10mL of methyltriethoxysilane and 10mL of ammonia water, stir for 8h, then inject 10mL of 10wt% formaldehyde solution, stir at 25℃ for 8h, and then dry the samples overnight to obtain an air-jet spun membrane with CNTs@organosilicon@APF nano core-shell structure.

[0109] (3) The gas-spun membrane with CNTs@organosilicon@APF nano core-shell structure was subjected to pyrolysis carbonization treatment in an argon atmosphere, heated to 800℃ at a heating rate of 2℃ / min and held for 2h, and then naturally cooled to room temperature to obtain a nano-hybrid carbon fiber membrane material with a porous structure.

[0110] (4) The nano-hybrid carbon fiber membrane material with porous structure was immersed in 10% HF solution and treated at room temperature for 30 min. Then it was washed with deionized water until neutral. The treated material was mixed with 6 mol / L KOH solution at a mass ratio of 1:5 and carbonized in an argon atmosphere. The temperature was increased to 700℃ at a heating rate of 3℃ / min and held for 2 h. Then it was washed with 1 mol / L hydrochloric acid solution and deionized water until neutral and dried overnight in a constant temperature drying oven at 80℃ to obtain the coaxial gradient porous nano-core-shell structure cathode material.

[0111] Example 9

[0112] A method for preparing a coaxial gradient porous nanocore-shell structure cathode material includes the following steps:

[0113] (1) 15g of CDs were dispersed in 100mL of dimethyl sulfoxide (DMSO) solution and sonicated for 30min at a frequency of 40kHz to ensure uniform dispersion. Then, 15g of PAN was slowly added to the uniformly dispersed CDs solution and stirred continuously until completely dissolved at 500rpm for 4h at room temperature, yielding a precursor solution A of the CDs-doped PAN-based component. 10g of SAN was dissolved in 100mL of DMSO solution and magnetically stirred at 500rpm for 2h at room temperature until completely dissolved. Then, 15g of PAN was slowly added to the completely dissolved SAN solution and stirred at 500rpm for 4h at room temperature, yielding a precursor solution B of the SAN-doped PAN-based component. Precursor solution A was injected into the inner channel of the coaxial air nozzle, and precursor solution B was injected into the outer channel of the coaxial air nozzle for coaxial air-jet spinning. The jetting rate of the inner channel was 0.5 mL / h, the jetting rate of the outer channel was 1.0 mL / h, the air jetting pressure was 0.2 MPa, and the spinning distance was 15 cm. An air-jet spun membrane with a SAN@CDs nanocore-shell structure was obtained on the receiver.

[0114] (2) Cut the air-jet spun membrane into 2cm×2cm samples, immerse them in 50mL of 0.1mol / L 3-aminophenol solution, stir for 10min, then add 10mL of methyltriethoxysilane and 10mL of ammonia water, stir for 6h, then inject 10mL of 10wt% formaldehyde solution, stir at 25℃ for 6h, and then dry the samples overnight to obtain an air-jet spun membrane with SAN@CDs@organosilicon@APF nano core-shell structure.

[0115] (3) The gas-spun membrane with SAN@CDs@organosilicon@APF nano core-shell structure was subjected to pyrolysis carbonization treatment in an argon atmosphere, heated to 800℃ at a heating rate of 2℃ / min and held for 2h, and then naturally cooled to room temperature to obtain a nano-hybrid carbon fiber membrane material with a porous structure.

[0116] (4) The nano-hybrid carbon fiber membrane material with porous structure was immersed in 10% HF solution and treated at room temperature for 30 min. Then it was washed with deionized water until neutral. The treated material was mixed with 6 mol / L KOH solution at a mass ratio of 1:3 and carbonized in an argon atmosphere. The temperature was increased to 750℃ at a heating rate of 2℃ / min and held for 1 h. Then it was washed with 1 mol / L hydrochloric acid solution and deionized water until neutral and dried overnight in a constant temperature drying oven at 70℃ to obtain the coaxial gradient porous nano-core-shell structure cathode material.

[0117] Comparative Example 1

[0118] A method for preparing a nano-hybrid carbon fiber membrane material with a porous structure includes the following steps:

[0119] (1) 15g of CDs were dispersed in 100mL of dimethyl sulfoxide (DMSO) solution and sonicated for 30min at a frequency of 40kHz to ensure uniform dispersion. Then, 15g of PAN was slowly added to the uniformly dispersed CDs solution and stirred continuously until completely dissolved at 500rpm for 4h at room temperature, yielding a precursor solution A of the CDs-doped PAN-based component. 10g of SAN was dissolved in 100mL of DMSO solution and magnetically stirred at 500rpm for 2h at room temperature until completely dissolved. Then, 15g of PAN was slowly added to the completely dissolved SAN solution and stirred at 500rpm for 4h at room temperature, yielding a precursor solution B of the SAN-doped PAN-based component. Precursor solution A was injected into the outer channel of the coaxial air nozzle, and precursor solution B was injected into the inner channel of the coaxial air nozzle for coaxial air-jet spinning. The jetting rate of the inner channel was 0.5 mL / h, the jetting rate of the outer channel was 1.0 mL / h, the air jetting pressure was 0.2 MPa, and the spinning distance was 15 cm. An air-jet spun membrane with a CDs@SAN nanocore-shell structure was obtained on the receiver.

[0120] (2) Cut the air-jet spun membrane into 2cm×2cm samples, immerse them in 50mL of 0.1mol / L 3-aminophenol solution, stir for 10min, then add 10mL of methyltriethoxysilane and 10mL of ammonia water, stir for 6h, then inject 10mL of 10wt% formaldehyde solution, stir at 25℃ for 6h, and then dry the samples overnight to obtain an air-jet spun membrane with CDs@organosilicon@APF nano core-shell structure.

[0121] (3) The gas-spun membrane with CDs@organosilicon@APF nano core-shell structure was subjected to pyrolysis carbonization treatment in an argon atmosphere, heated to 800℃ at a heating rate of 2℃ / min and held for 2h, and then naturally cooled to room temperature to obtain a nano-hybrid carbon fiber membrane material with a porous structure.

[0122] Comparative Example 2

[0123] A method for preparing a porous nanocore-shell structured cathode material includes the following steps:

[0124] (1) 15g of CDs were dispersed in 100mL of dimethyl sulfoxide (DMSO) solution and sonicated for 30min at a frequency of 40kHz to ensure uniform dispersion. Then, 15g of PAN was slowly added to the uniformly dispersed CDs solution and stirred continuously until completely dissolved at 500rpm for 4h at room temperature, yielding a precursor solution A of the CDs-doped PAN-based component. 10g of SAN was dissolved in 100mL of DMSO solution and magnetically stirred at 500rpm for 2h at room temperature until completely dissolved. Then, 15g of PAN was slowly added to the completely dissolved SAN solution and stirred at 500rpm for 4h at room temperature, yielding a precursor solution B of the SAN-doped PAN-based component. Precursor solution A was injected into the outer channel of the coaxial air nozzle, and precursor solution B was injected into the inner channel of the coaxial air nozzle for coaxial air-jet spinning. The jetting rate of the inner channel was 0.5 mL / h, the jetting rate of the outer channel was 1.0 mL / h, the air jetting pressure was 0.2 MPa, and the spinning distance was 15 cm. An air-jet spun membrane with a CDs@SAN nanocore-shell structure was obtained on the receiver.

[0125] (2) Cut the air-jet spun membrane into 2cm×2cm samples, immerse them in 50mL of 0.1mol / L 3-aminophenol solution, stir for 10min, then add 10mL of methyltriethoxysilane and 10mL of ammonia water, stir for 6h, then inject 10mL of 10wt% formaldehyde solution, stir at 25℃ for 6h, and then dry the samples overnight to obtain an air-jet spun membrane with CDs@organosilicon@APF nano core-shell structure.

[0126] (3) The gas-spun membrane with CDs@organosilicon@APF nano core-shell structure was subjected to pyrolysis carbonization treatment in an argon atmosphere, heated to 800℃ at a heating rate of 2℃ / min and held for 2h, and then naturally cooled to room temperature to obtain a nano-hybrid carbon fiber membrane material with a porous structure.

[0127] (4) The porous nano-hybrid carbon fiber membrane material was immersed in 10% HF solution and treated at room temperature for 30 min. Then it was washed with deionized water until neutral and carbonized in an argon atmosphere. The temperature was increased to 750℃ at a heating rate of 2℃ / min and held for 1 h. Then it was washed with 1 mol / L hydrochloric acid solution and deionized water until neutral and dried overnight in a constant temperature drying oven at 70℃ to obtain the porous nano-core-shell structure cathode material.

[0128] Comparative Example 3

[0129] A method for preparing a porous nanocore-shell structured cathode material includes the following steps:

[0130] (1) 15g of CDs were dispersed in 100mL of dimethyl sulfoxide (DMSO) solution and sonicated for 30min at a frequency of 40kHz to ensure uniform dispersion. Then, 15g of PAN was slowly added to the uniformly dispersed CDs solution and stirred continuously until completely dissolved at 500rpm for 4h at room temperature, yielding a precursor solution A of the CDs-doped PAN-based component. 10g of SAN was dissolved in 100mL of DMSO solution and magnetically stirred at 500rpm for 2h at room temperature until completely dissolved. Then, 15g of PAN was slowly added to the completely dissolved SAN solution and stirred at 500rpm for 4h at room temperature, yielding a precursor solution B of the SAN-doped PAN-based component. Precursor solution A was injected into the outer channel of the coaxial air nozzle, and precursor solution B was injected into the inner channel of the coaxial air nozzle for coaxial air-jet spinning. The jetting rate of the inner channel was 0.5 mL / h, the jetting rate of the outer channel was 1.0 mL / h, the air jetting pressure was 0.2 MPa, and the spinning distance was 15 cm. An air-jet spun membrane with a CDs@SAN nanocore-shell structure was obtained on the receiver.

[0131] (2) Cut the air-jet spun membrane into 2cm×2cm samples, immerse them in 50mL of 0.1mol / L 3-aminophenol solution, stir for 10min, then add 10mL of methyltriethoxysilane and 10mL of ammonia water, stir for 6h, then inject 10mL of 10wt% formaldehyde solution, stir at 25℃ for 6h, and then dry the samples overnight to obtain an air-jet spun membrane with CDs@organosilicon@APF nano core-shell structure.

[0132] (3) The gas-spun membrane with CDs@organosilicon@APF nano core-shell structure was subjected to pyrolysis carbonization treatment in an argon atmosphere, heated to 800℃ at a heating rate of 2℃ / min and held for 2h, and then naturally cooled to room temperature to obtain a nano-hybrid carbon fiber membrane material with a porous structure.

[0133] (4) The porous nano-hybrid carbon fiber membrane material was mixed with 6 mol / L KOH solution at a mass ratio of 1:5 and carbonized in an argon atmosphere. The temperature was increased to 750℃ at a heating rate of 2℃ / min and held for 1h. Then it was washed with 1 mol / L hydrochloric acid solution and deionized water until neutral and dried overnight in a constant temperature drying oven at 70℃ to obtain the coaxial gradient porous nano-core-shell structure cathode material.

[0134] Comparative Example 4

[0135] A method for preparing a porous nanocore-shell structured cathode material includes the following steps:

[0136] (1) 15g of CDs were dispersed in 100mL of dimethyl sulfoxide (DMSO) solution and sonicated for 30min at a frequency of 40kHz to ensure uniform dispersion. Then, 15g of PAN was slowly added to the uniformly dispersed CDs solution and stirred continuously until completely dissolved at 500rpm for 4h at room temperature, yielding a precursor solution A of the CDs-doped PAN-based component. 10g of SAN was dissolved in 100mL of DMSO solution and magnetically stirred at 500rpm for 2h at room temperature until completely dissolved. Then, 15g of PAN was slowly added to the completely dissolved SAN solution and stirred at 500rpm for 4h at room temperature, yielding a precursor solution B of the SAN-doped PAN-based component. Precursor solution A was injected into the outer channel of the coaxial air nozzle, and precursor solution B was injected into the inner channel of the coaxial air nozzle for coaxial air-jet spinning. The jetting rate of the inner channel was 0.5 mL / h, the jetting rate of the outer channel was 1.0 mL / h, the air jetting pressure was 0.2 MPa, and the spinning distance was 15 cm. An air-jet spun membrane with a CDs@SAN nanocore-shell structure was obtained on the receiver.

[0137] (2) Cut the air-jet spun membrane into 2cm×2cm samples, immerse them in 50mL of 0.1mol / L 3-aminophenol solution, stir for 10min, then add 10mL of methyltriethoxysilane and 10mL of ammonia water, stir for 6h, then inject 10mL of 10wt% formaldehyde solution, stir at 25℃ for 6h, and then dry the samples overnight to obtain an air-jet spun membrane with CDs@organosilicon@APF nano core-shell structure.

[0138] (3) The gas-spun membrane with CDs@organosilicon@APF nano core-shell structure was subjected to pyrolysis carbonization treatment in an argon atmosphere, heated to 800℃ at a heating rate of 2℃ / min and held for 2h, and then naturally cooled to room temperature to obtain a nano-hybrid carbon fiber membrane material with a porous structure.

[0139] (4) The nano-hybrid carbon fiber membrane material with porous structure is immersed in 10% HF solution and treated at room temperature for 30 min, and then washed with deionized water until neutral. The treated material is mixed with 1-1.5 mol / L Na2CO3 solution at a mass ratio of 1:7 and carbonized in an argon atmosphere. The temperature is increased to 750℃ at a heating rate of 2℃ / min and held for 1 h. Then it is washed with 1 mol / L hydrochloric acid solution and deionized water until neutral, and dried overnight in a constant temperature drying oven at 70℃ to obtain the coaxial gradient porous nano-core-shell structure cathode material.

[0140] Comparative Example 5

[0141] A method for preparing an electrospun film cathode material with a V2O5 / C structure includes the following steps:

[0142] (1) 2g of vanadium-based oxide (V2O5) was dispersed in 100mL of deionized water and ultrasonically treated for 30min at a frequency of 40kHz to ensure uniform dispersion. Subsequently, 2g of polyvinyl alcohol (PVA) was slowly added to the uniformly dispersed V2O5 solution and stirred continuously until completely dissolved at 500rpm at room temperature for 4h to obtain a precursor solution of V2O5-doped PVA-based component. The precursor solution was injected into an electrospinning apparatus at a flow rate of 0.5mL / h, a voltage of 20kV, and a spinning distance of 10cm to obtain an electrospun membrane with a V2O5 / PVA structure on a receiver.

[0143] (2) Cut the air-spun membrane into 2cm×2cm samples, immerse them in 50mL of 0.1mol / L 3-aminophenol solution, stir for 15min, then add 10mL of methyltriethoxysilane and 10mL of ammonia water, stir for 8h, then inject 10mL of 10wt% formaldehyde solution, stir at 25℃ for 8h, and then dry the samples overnight to obtain electrospun membrane cathode material with V2O5 / C structure.

[0144] The cathode materials prepared in Examples 1-9 and Comparative Examples 1-5 were subjected to performance tests in terms of tensile strength, specific surface area, pore size distribution, specific capacity, energy density, cycle stability, and charge transfer resistance. The tensile strength test followed GB / T 10654-2001; the specific surface area test followed GB / T 19587-2017; the pore size distribution test followed GB / T 21650.3-2011; the specific capacity test followed SJ / T 11793-2022; the energy density test followed SJ / T 11793-2022; and the cycle stability test followed SJ / T 11793-2022. The charge transfer resistance was obtained by electrochemical impedance spectroscopy. The test results are shown in Table 1.

[0145] Table 1

[0146]

[0147]

[0148] Analysis of the data in Table 1 shows that, compared with other examples and comparative examples, the coaxial gradient porous nanostructured core-shell cathode material prepared in Example 5 exhibits significant advantages in electrochemical performance. Specifically, this cathode material achieves a specific capacity of 300 mAh / g and an energy density as high as 190 Wh / kg, demonstrating excellent energy storage capacity. Furthermore, after 500 charge-discharge cycles, its capacity retention rate remains as high as 98%, showing excellent cycle stability. Simultaneously, the charge transfer resistance is 39 Ω, indicating that the cathode material has low impedance during electrochemical reactions, further enhancing its electrochemical performance. Moreover, this cathode material also exhibits excellent mechanical properties. Its tensile strength reaches 116 MPa, indicating that while possessing excellent electrochemical performance, the cathode material can still meet high mechanical strength requirements. This characteristic makes the cathode material more reliable and durable in practical applications. Considering both electrochemical and mechanical performance, the cathode material of Example 5 clearly has significant comprehensive advantages.

[0149] The main difference between Examples 1 and 4-7 lies in the different mass ratios of the treated material to the 6 mol / L KOH solution; that is, the immersion concentration ratio of the alkali solution to the material varies from 1:1 to 1:10. This different mass ratio significantly affects the final porous structure and electrochemical performance of the material. As the KOH solution treatment ratio increases, the pore size of the material varies within a certain range. Different KOH treatment ratios affect the etching depth of the material and the degree of corrosion on the carbon fiber surface. Experiments show that Example 5 (KOH concentration of 1:5) produced the optimal pore size distribution, giving the material pores suitable for zinc ion transport. KOH solution is a strong alkaline corrosive agent; different ratios will produce different degrees of corrosion on the surface and internal structure of the material. An appropriate KOH ratio (e.g., 1:5) can form a uniform microporous or mesoporous structure on the surface and inside the material, while excessively high or low concentrations may lead to uneven pore structure, affecting the effective transport path of zinc ions. Under a 1:5 ratio, the optimized pore size distribution and structure within the material provide efficient channels for zinc ions, reducing ion transport resistance and thus enhancing the material's electrochemical performance.

[0150] Example 5 exhibits a higher specific surface area, while Example 7, with a higher treatment ratio (e.g., 1:10), shows a lower specific surface area. Increased specific surface area helps the material provide more active sites, thereby enhancing the activity of the electrode reaction. When the KOH concentration is at the optimal ratio of 1:5, the formation of pore structure and specific surface area reach an optimal balance. Excessively high concentrations (e.g., 1:10) can lead to over-corrosion, potentially causing surface irregularities and pore collapse, thus reducing the specific surface area. Lower concentrations are insufficient to form a sufficient pore structure; therefore, the optimal KOH treatment ratio provides the material surface with more active sites, increasing the specific surface area.

[0151] The highest specific capacity was achieved in Example 5, indicating that optimal pore size distribution and a large specific surface area facilitated the electrochemical reactions, particularly the insertion and extraction of zinc ions. Appropriate pore size and a uniform porous structure provide better pathways for the reversible insertion and extraction of zinc ions. Optimized pore structure ensured efficient zinc ion transport, reduced polarization effects, and thus improved specific capacity. At a mass ratio of 1:5, the material exhibited a relatively uniform pore size distribution and a good pore structure, enabling it to accommodate more zinc ions during charge and discharge, thereby enhancing specific capacity.

[0152] The KOH solution treatment ratio in Example 5 showed optimal performance in preparing coaxial gradient porous nanostructured core-shell cathode materials. The optimal KOH concentration resulted in a uniform and moderate pore distribution within the material, maximizing the specific surface area while providing an efficient zinc ion transport pathway. Appropriate KOH treatment increased porosity, improved specific capacity and energy density without damaging the material structure, and ensured high stability during long-term cycling. Low charge transfer resistance ensured high efficiency of the electrochemical reaction, resulting in good electrical conductivity.

[0153] In the comparison between Examples 5 and 8, the only variable was the change in doping material, specifically replacing carbon quantum dots (CDs) with carbon nanotubes (CNTs). According to the data, CDs generally outperformed CNTs. Example 5 (CD-doped) exhibited a more uniform pore size distribution and a higher specific surface area, while Example 8 (CNT-doped) was slightly inferior. Due to their small size and unique nanoscale effect, CDs, after doping, can be more uniformly distributed within the carbon fiber structure, resulting in a higher specific surface area for the carbon fiber film. CDs typically range in size from a few nanometers to tens of nanometers, allowing for the formation of more micropores or mesopores compared to CNTs (which typically have diameters of tens to hundreds of nanometers). These pores provide more pathways for zinc ion transport and electrolyte permeation, thereby improving the material's specific surface area and pore size uniformity. In contrast, CNTs, with their larger size and one-dimensional tubular structure, exhibit slightly inferior distribution uniformity and pore size control in the material, resulting in a slightly lower specific surface area and pore size distribution compared to CD-doped materials.

[0154] The specific capacity and energy density of Example 5 are both superior to those of Example 8. Specific capacity and energy density are significantly influenced by the active sites and electrode structure of the material. CDs exhibit a zero-dimensional structure in the material, which not only allows for the formation of more active sites but also, due to their small size, enables them to fully fill the gaps between carbon fibers, resulting in a uniform distribution of active sites on the material surface and within the material. While the tubular structure of CNTs helps improve conductivity, their one-dimensional tubular morphology restricts the insertion sites and pathways of zinc ions, leading to slightly lower specific capacity and energy density. The porous structure and increased active sites after CD doping provide more ample space for zinc ion insertion and extraction, resulting in superior specific capacity and energy density.

[0155] The zero-dimensional structure of core-shell doped materials (CDs) not only increases the porosity and specific surface area of ​​the material but also provides more active sites, effectively improving specific capacity and energy density. Compared to core-shell nanoparticles (CNTs), CDs can be more uniformly dispersed in the material, thereby optimizing pore size distribution, reducing charge transfer resistance, and improving cycling stability. While CNTs have good conductivity, in these core-shell structured materials, CDs exhibit stronger porosity control, active site provision, and structural stability. Therefore, the overall performance of CD-doped materials is superior to that of CNT-doped materials.

[0156] Example 9 involved switching the inner and outer layer materials: the outer layer was replaced with SAN-doped PAN, and the inner layer with CDs-doped PAN. SAN-doped PAN has higher molecular rigidity and tensile strength in its outer layer, while CDs-doped PAN generally offers better flexibility. Moving the SAN-doped PAN to the outer layer makes the material more resistant to external tensile forces, thus slightly increasing the tensile strength. The electrochemical performance of Example 9 decreased, possibly because CDs have a more significant effect on improving conductivity and active sites. When CDs-doped PAN is used as the outer layer, it has more direct contact with the electrolyte, providing more reaction sites and facilitating the transport and storage of zinc ions; CDs have good conductivity, and placing them in the outer layer effectively reduces charge transfer resistance. However, in Example 9, the CDs-doped PAN is in the inner layer, reducing contact with the electrolyte and decreasing the utilization of active sites, leading to a decrease in specific capacity and energy density; the SAN-doped PAN is in the outer layer, where conductivity is poor, increasing the resistance to charge transfer at the interface, thus increasing the charge transfer resistance. Because SAN-doped PAN materials are difficult to form an ideal gradient pore structure after KOH treatment, the pore distribution of the outer layer is not as effective as that of the CDs-doped PAN in the original design. This deficiency in the gradient pore structure leads to narrower zinc ion channels, affecting ion transport efficiency. At the same time, the effect of the pore structure in the inner CDs-doped PAN is weakened, affecting electrolyte penetration and ion diffusion, further reducing the material's specific capacity and cycle performance.

[0157] Compared to Example 5, Comparative Example 2 lacked the KOH treatment step, resulting in a significant performance reduction compared to other examples. The specific surface area and pore size distribution of Comparative Example 2 were significantly lower than those of other examples. KOH treatment significantly increases the controllability of specific surface area and pore structure, which is crucial for ion channels in zinc-ion batteries. KOH treatment chemically etches the material surface, creating abundant micropores and mesopores in the carbon fiber film. This etching process increases the porosity of the material, generating more effective ion channels and increasing the specific surface area. Optimization of the pore structure can improve the diffusion rate and transport efficiency of zinc ions. Comparative Example 2, lacking KOH treatment, failed to generate these pore structures, resulting in a significantly reduced specific surface area and insufficient zinc ion channels, thus limiting the ion transport capacity of the material.

[0158] Comparative Example 2 exhibits lower specific capacity and energy density compared to other examples. KOH treatment creates abundant active sites on the material surface, which play a crucial role in electrochemical reactions, thereby improving the material's specific capacity and energy density. The more active sites there are, the greater the amount of ions the material can carry during charge and discharge, thus increasing specific capacity and energy density. Comparative Example 2, lacking KOH treatment, lacks these active sites, resulting in a significant reduction in its energy storage capacity. Furthermore, the pore structure after KOH treatment provides a higher electrolyte contact area, improving electrochemical reaction efficiency and further enhancing energy density.

[0159] The charge transfer resistance of Comparative Example 2 was significantly higher than that of the other examples, indicating poor conductivity. KOH treatment generated more pores and active sites in the carbon fiber film material, reducing charge migration resistance and thus optimizing electrode conductivity. The microporous structure etched by KOH can effectively shorten the migration paths of ions and electrons, reduce internal resistance, and improve electrode reaction efficiency. However, Comparative Example 2, lacking the KOH treatment step, had a limited charge transport path, leading to increased electron migration resistance and a significantly higher charge transfer resistance. This directly affects the electrochemical performance of the material, resulting in poorer reaction efficiency during charge and discharge processes.

[0160] The above analysis demonstrates that KOH treatment has a significant impact on the pore structure, active site distribution, cycle stability, and charge transfer resistance of the material. Comparative Example 2, lacking this step, suffers from reduced porosity and specific surface area, resulting in insufficient active sites and consequently affecting the efficiency of zinc ion diffusion and electron migration, leading to a significant decrease in specific capacity, energy density, and cycle life. Furthermore, the higher charge transfer resistance further limits its electrochemical reaction rate. In conclusion, KOH treatment is a crucial step in improving the performance of this type of coaxial gradient porous nanostructured core-shell cathode material.

[0161] Compared with Example 5, the specific surface areas of Comparative Example 1 and Comparative Example 2 were significantly lower, at 700 m².2 / g and 760m 2 / g, while the specific surface area of ​​Example 5 is 880m². 2 / g. This difference is mainly attributed to the optimized design of the gradient porous structure in Example 5, which provides more active sites on the material surface, significantly improving the adsorption capacity of zinc ions. In the comparative example, the pore structure is relatively simple or coarse, failing to effectively provide more zinc ion adsorption sites, resulting in a smaller specific surface area and thus limiting the electrochemical performance.

[0162] Compared to Example 5, Comparative Examples 1 and 2 exhibit significantly wider pore size distributions, ranging from 1 to 10 nm, while Example 5 shows a narrower pore size distribution range of only 1.1 to 3.8 nm. This difference is primarily attributed to the special air-jet spinning process and the introduction of carbon nanodots employed in Example 5, which allows for more precise pore size control, thereby optimizing the Zn²⁺ storage environment. In the comparative examples, the wider pore size distribution reflects the inhomogeneity of the material's internal structure, leading to decreased electrode performance stability and potentially affecting the storage and release efficiency of zinc ions.

[0163] Compared to Example 5, Comparative Examples 1 and 2 showed significantly lower specific capacities, at 200 mAh / g and 210 mAh / g, respectively, while Example 5 achieved a specific capacity of 300 mAh / g. This difference is attributed to the optimized pore structure and higher specific surface area in Example 5, which significantly improved the Zn2+ storage capacity. In contrast, the materials in the comparative examples suffered from insufficient specific surface area and suboptimal pore structure, resulting in limited zinc ion storage capacity and consequently reduced overall electrochemical performance.

[0164] The energy densities of Examples 1, 2, 3, 5, 6, and 8 were 180 Wh / kg, 185 Wh / kg, 183 Wh / kg, 190 Wh / kg, 180 Wh / kg, and 180 Wh / kg, respectively, demonstrating the material's significant advantages in energy storage. This is attributed to the optimized pore structure, which effectively enhances the material's zinc ion storage capacity, thereby increasing the overall energy density. In contrast, Comparative Examples 1 and 2 had lower energy densities, primarily due to their poor pore structure, which limited the effective storage of zinc ions and thus affected the material's energy density performance.

[0165] Examples 1, 2, 3, 5, 6, and 8 exhibited very high cycle stability (94%-98%), demonstrating excellent performance over long cycle life. This is attributed to the porous core-shell structure effectively buffering volume changes in the electrode material during charge and discharge, ensuring stable electrochemical performance. In contrast, Comparative Examples 1 and 2 showed poorer cycle stability (85% and 87%, respectively), which may be due to insufficient material structural stability, leading to significant performance degradation after multiple charge-discharge cycles.

[0166] Compared to Example 5, Comparative Examples 1 and 2 exhibited significantly higher charge transfer resistances, at 65 Ω and 70 Ω respectively, while Example 5 showed a charge transfer resistance of only 39 Ω. This indicates that the electrode material in Example 5 possesses superior conductivity, primarily attributed to its optimized pore structure and uniformly distributed conductive paths, which effectively promote rapid charge transport within the electrode material. In contrast, Comparative Examples 1 and 2 had fewer conductive paths or pore structures that hindered charge transport, resulting in higher charge transfer resistances and consequently limiting the battery's power output and overall electrochemical performance.

[0167] Comparative Example 3 lacked HF acid treatment. HF acid treatment is used to remove certain inorganic components from the fiber membrane or to generate specific porous structures. This treatment typically forms micropores and mesopores suitable for zinc ion transport on nanofibers. The absence of HF acid treatment results in more residual inorganic impurities in the fiber membrane, leading to an uneven pore structure and a reduced overall specific surface area. This directly affects the ion transport efficiency and electrolyte permeability. Due to insufficient pore structure and the lack of support from micropores and mesopores, the diffusion path of the electrolyte in the material increases, hindering efficient zinc ion transport and thus reducing specific capacity and energy density. The uneven pore structure may lead to increased local current density during long-term cycling, further exacerbating material degradation and reducing cycle stability. Without HF acid treatment, the reduced micropore structure and smaller contact area between the electrolyte and electrode active sites result in increased charge transfer resistance.

[0168] Comparative Example 4 used a weak alkali treatment instead of concentrated KOH treatment. The strong alkalinity and corrosiveness of KOH at high temperatures etch the carbon material surface, generating abundant micropores and mesopores, thus optimizing the pore distribution and pore size of the electrode material. However, the etching ability of weak alkali treatment (such as NaHCO3 or Na2CO3) is limited, resulting in insufficient micropore formation on the material surface and an inability to effectively optimize the zinc ion channel pathway. This leads to slow electrolyte diffusion, affecting electrode reaction efficiency. Due to the reduced pore structure, the number of active sites inside the material decreases, and incomplete electrode reactions result in lower specific capacity and energy density. The suboptimal pore structure increases the electrolyte penetration resistance during cycling, leading to decreased charge transfer efficiency and increased charge transfer resistance. Furthermore, under long-term cycling, the utilization rate of active sites and the stability of the material structure are poor, exhibiting low cycling stability.

[0169] Comparative Example 5 uses vanadium-based oxide (V₂O₅) doped PAN. V₂O₅ exhibits good redox activity, but its conductivity is relatively low. Using V₂O₅-doped PAN fiber materials may lead to a decrease in the overall conductivity of the material, thus affecting the charge transfer efficiency in electrochemical reactions. The active sites of vanadium-based oxides do not perfectly match the electrochemical active sites of the electrode material, potentially forming unfavorable interactions during zinc ion insertion and extraction, resulting in a decrease in specific capacity and energy density. The vanadium-based oxide-doped PAN material after electrospinning may not form an ideal gradient pore or microporous structure, preventing the electrolyte and zinc ions from effectively distributing within the fiber membrane, thereby reducing ion transport efficiency. After V₂O₅ doping, the material structure may easily deform and experience decreased stability during long-term cycling. The electrochemical stability of vanadium-based oxides is less stable than that of carbon-based materials, leading to a decline in cycling performance.

[0170] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art should understand that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a coaxial gradient porous nanocore-shell structure cathode material, characterized in that, Includes the following steps: (1) Dissolve conductive carbon nanomaterials and polymers in a solvent to obtain precursor solution A; A precursor solution B is obtained by dissolving a styrene-acrylonitrile copolymer and a polymer in a solvent. Precursor solution A is injected into the outer channel of a coaxial gas nozzle, and precursor solution B is injected into the inner channel of the coaxial gas nozzle, or precursor solution A is injected into the inner channel of the coaxial gas nozzle, and precursor solution B is injected into the outer channel of the coaxial gas nozzle, followed by coaxial gas-jet spinning to obtain a gas-jet spun film with a nano-core-shell structure. The conductive carbon nanomaterial is selected from one or more of carbon quantum dots, graphene quantum dots, carbon nanotubes, fullerenes, and graphene oxides. The polymer is selected from one or more of polyacrylonitrile, polyamic acid, polybenzimidazole, polypyrrole, and polyetherimide. (2) The air-jet spun membrane with nano-core-shell structure obtained in step (1) is immersed in 3-aminophenol solution, then methyltriethoxysilane and ammonia are added, and then formaldehyde solution is injected to obtain a surface-modified air-jet spun membrane with nano-core-shell structure. (3) The surface-modified gas-spun membrane with nano-core-shell structure obtained in step (2) is subjected to pyrolysis carbonization treatment in an inert atmosphere to obtain a nano-hybrid carbon fiber membrane material with porous structure. (4) The nano-hybrid carbon fiber membrane material with porous structure obtained in step (3) is treated with an acid solution, and the treated material is mixed with a strong alkaline solution and carbonized in an inert atmosphere to obtain the coaxial gradient porous nano core-shell structure cathode material.

2. The preparation method according to claim 1, characterized in that, In step (1), the mass ratio of the conductive carbon nanomaterial to the polymer is (0.5-1):(10-15); the mass ratio of the styrene-acrylonitrile copolymer to the polymer is (5-10):(10-15).

3. The preparation method according to claim 1, characterized in that, In step (1), the concentration of conductive carbon nanomaterials in precursor solution A is 10-15 wt%; the concentration of styrene-acrylonitrile copolymer in precursor solution B is 5-20 wt%.

4. The preparation method according to claim 1, characterized in that, In step (1), the process parameters for coaxial air-jet spinning are: the jetting rate of the inner channel is 0.5-2.0 mL / h; and the jetting rate of the outer channel is 1.0-5.0 mL / h.

5. The preparation method according to claim 1, characterized in that, In step (2), the volume ratio of the 3-aminophenol solution, methyltriethoxysilane, ammonia and formaldehyde solution is 5:(0.5-1.5):(0.5-1.5):(0.5-1.5).

6. The preparation method according to claim 1, characterized in that, In step (3), the temperature of the pyrolysis carbonization treatment is 750-800℃.

7. The preparation method according to claim 1, characterized in that, In step (4), the mass ratio of the treated material to the strong alkali solution is 1:(3-7).

8. The preparation method according to claim 1, characterized in that, In step (4), the specific operation of the carbonization treatment is as follows: heat up to 700-800℃ at a heating rate of 1-3℃ / min and hold for 0.5-2h.

9. The coaxial gradient porous nanocore-shell structure cathode material prepared by the method according to any one of claims 1-8.

10. The application of the coaxial gradient porous nanocore-shell structure cathode material according to claim 9 in the preparation of zinc-ion batteries.

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