Carbon nanofiber positive electrode material for aluminum ion capacitor and preparation method of carbon nanofiber positive electrode material

Abstract

The invention discloses a carbon nanofiber positive electrode material for an aluminum ion capacitor and a preparation method of the carbon nanofiber positive electrode material. The material is of a graded porous three-dimensional structure and is prepared through an electrostatic spinning technology. The preparation method comprises the following steps: (1) dissolving an N source, a P source, an S source and a polymer in N, N-dimethylformamide to prepare a spinning solution; (2) preparing nanofibers through electrostatic spinning; and (3) carrying out pre-oxidation, carbonization and activation treatment on the nanofiber to prepare the N, P and S doped porous carbon nanofiber. The prepared carbon nanofiber is large in specific surface area, the conductivity of the material is improved by element doping, and ion adsorption / desorption is facilitated. The material has good performance when being used as an aluminum ion capacitor positive electrode material.

Description

Technical Field

[0001] The invention relates to a carbon nanofiber positive electrode material prepared by electrostatic spinning technology and applied to ion capacitors. Background Art

[0002] Ion capacitors are a new type of energy storage device between batteries and traditional capacitors. They have attracted attention due to their high power density, low price, short charge and discharge time, and long cycle life. Compared with other ion capacitors (lithium, sodium, and potassium ion capacitors), aluminum ion capacitors have great development potential and application prospects in the field of energy storage due to their abundant resources, cost-effectiveness, high energy density, high safety, long life, and environmental friendliness.

[0003] The oxide positive electrode of aluminum ion capacitors has weak conductivity and specific surface area, which inhibits the rate performance and cycle stability of the material. Carbon materials are widely used in various electrochemical energy storage devices due to their advantages such as high conductivity and light weight, especially porous carbon, which has the characteristics of large specific surface area, high porosity, good symmetry and good rheology.

[0004] Among porous carbons, carbon nanofibers have a large specific surface area and excellent electrical conductivity, which are beneficial to the improvement of the rate performance and cycle stability of aluminum ion capacitors. The present invention provides a new method for the application of carbon materials in aluminum ion capacitors by preparing a hierarchical porous carbon nanofiber through electrospinning technology. Summary of the invention

[0005] The present invention relates to the preparation of carbon nanofiber positive electrode materials for aluminum ion capacitors by electrospinning, improving the conductivity and ion adsorption and desorption performance of carbon materials by element doping, and improving the ion diffusion performance by hierarchical porous carbon nanofiber structure, thereby greatly improving the electrochemical performance of ion capacitors. The technical solution for realizing the present invention is: The preparation method of carbon nanofiber positive electrode material for aluminum ion capacitor prepared by electrospinning, the steps are as follows: (1) First, place the N source, P source and S source in a container, add N,N-dimethylformamide (DMF) to ultrasonically dissolve until the solution is uniform and stable; then add the polymer and stir until it is completely dissolved to prepare a spinning solution; (2) transferring the spinning solution prepared in step (1) into a needle tube, and preparing nanofibers by electrospinning technology; (3) Placing the nanofibers in an air atmosphere for pre-oxidation to stabilize the fiber morphology and structure. Carbonizing the nanofibers in an inert atmosphere to prepare N, P, and S-doped carbon nanofibers. (4) The prepared N, P, S doped carbon nanofibers are fully mixed with an activator and activated at a certain temperature in an inert atmosphere to prepare N, P, S doped porous carbon nanofibers.

[0006] In the step (1), the N source is a mixture of one or more of urea, melamine, polyvinyl pyrrolidone, polyacrylonitrile, chitosan, ammonium persulfate, polyaniline, ethylenediamine, glutamic acid, tryptophan, etc.; the S source is a mixture of one or more of thiourea, sulfur powder, ammonium persulfate, benzene disulfonic acid, cysteine, etc.; the P source is a mixture of one or more of triphenylphosphine, tetraphenylphosphine bromide, phytic acid, sodium hypophosphite, sodium hypophosphite, etc. The polymer is a mixture of one or more of polyvinyl pyrrolidone, polyacrylonitrile, polymethyl methacrylate, etc.

[0007] In the step (1), the volume of N,N-dimethylformamide is 10 mL, the total mass of the N source, the P source, and the S source is 0.1-5.0 g, and the mass of the polymer is 0.5-5.0 g.

[0008] The carbonization temperature in step (3) is 400-1200°C.

[0009] The activator in step (4) is a mixture of potassium hydroxide, potassium carbonate or zinc chloride or the like. The activation temperature is 400-1200°C, and the mass ratio of activator to carbon nanofiber is 0.1-10.

[0010] The beneficial effects of the present invention are: (1) The porous carbon nanofibers prepared by element doping and activation with activators have good conductivity, large specific surface area and good ion adsorption / desorption performance, which greatly improves the electrochemical performance of the material.

[0011] (2) The present invention can controllably adjust the fiber diameter and morphology by changing parameters such as voltage and needle type. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0013] Figure 1 is a scanning electron microscope image of the carbon nanofiber positive electrode material prepared in Example 1; Figure 2 is the cyclic voltammogram of the carbon nanofiber positive electrode material prepared in Example 1; Figure 3 The carbon nanofiber cathode material prepared in Example 1 is 0.5 A g -1 Cyclic performance curve under current density; Figure 4 The carbon nanofiber cathode material prepared in Example 1 is 2.0 A g -1 Cyclic performance curve under current density; Figure 5 The carbon nanofiber cathode material prepared in Example 1 is 5.0 A g -1 Cyclic performance curve under current density; Figure 6 This is the rate performance curve of the carbon nanofiber positive electrode material prepared in Example 1. DETAILED DESCRIPTION

[0014] The technical solution of the present invention will be described in detail below in conjunction with the accompanying drawings and embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0015] Example 1 The steps for preparing a carbon nanofiber positive electrode material are as follows: (1) 0.2 g of urea, 0.2 g of triphenylphosphine, and 0.2 g of thiourea were placed in a container, and 10 mL of DMF was added for ultrasonic dissolution until the solution was uniform and stable; then 1.0 g of polyvinyl pyrrolidone and 0.5 g of polyacrylonitrile were added and stirred until they were completely dissolved to prepare a spinning solution; (2) transferring the spinning solution prepared in step (1) into a needle tube, and preparing nanofibers by electrospinning technology; (3) Pre-oxidizing the nanofibers prepared in step (2) at 230°C in an air atmosphere to stabilize the fiber morphology and structure. Carbonizing the nanofibers in an argon atmosphere at 800°C for 2 hours to prepare N, P, and S doped carbon nanofibers; (4) The prepared N, P, S doped carbon nanofibers were fully mixed with an activator, potassium hydroxide, with a KOH / carbon nanofiber mass ratio of 2, and activated at 800 °C for 30 min in an argon atmosphere to prepare N, P, S doped porous carbon nanofibers.

[0016] The samples in Example 1 were subjected to morphology and electrochemical performance analysis tests, respectively, and the prepared materials showed good electrochemical performance.

[0017] Figure 1This is a scanning electron microscope image of a porous carbon nanofiber cathode material. As shown in the figure, the large specific surface area of ​​the prepared carbon nanofiber is conducive to the full contact between the electrolyte and the electrode material; the graded porosity is conducive to the transmission of ions; and element doping can improve the material's conductivity and ion adsorption / desorption capabilities.

[0018] Figure 2 This is the cyclic voltammogram of the porous carbon nanofiber positive electrode material. As shown in the figure, the curve overlaps more, indicating that the material has good stability and reversibility.

[0019] like Figure 3-6 As shown in the figure, the prepared porous carbon nanofibers have enhanced their electrochemical performance as positive electrode materials for aluminum ion capacitors due to their good microstructure. As shown in the figure: in the voltage range of 0.01-2.1 V, 0.5 A g -1 At a current density of 1.34 W / m, the specific capacity of the electrode material reaches 114.7 F g -1 ; at 2.0 A g -1 At a current density of 1.5 Å, the specific capacity of the electrode material reaches 95.5 F g -1 ; at 5.0 A g -1 At a current density of 1.3 Å, the specific capacity of the electrode material reaches 45.3 F g -1 The porous carbon nanofibers exhibited excellent cycling stability, with 148.8, 89.8, 76.1, 67.6, and 59.5 F g at current densities of 0.2, 0.5, 1.0, 2.0, and 5.0, respectively. -1 The specific capacity shows good rate performance.

[0020] The porous carbon nanofiber has a large specific surface area, and can improve the conductivity and ion absorption / desorption capability of the material by element doping, thereby enhancing the electrochemical performance of the aluminum ion capacitor.

[0021] Example 2 The steps for preparing a carbon nanofiber positive electrode material are as follows: (1) 0.01 g of triphenylphosphine, 0.05 g of cysteine, 0.02 g of urea, and 0.02 g of melamine were placed in a container, and 10 mL of DMF was added for ultrasonic dissolution until the solution was uniform and stable; then 5.0 g of polymethyl methacrylate was added and stirred until it was completely dissolved to prepare a spinning solution; (2) transferring the spinning solution prepared in step (1) into a needle tube, and preparing nanofibers by electrospinning technology; (3) Pre-oxidizing the nanofibers prepared in step (2) at 230°C in an air atmosphere to stabilize the fiber morphology and structure. Carbonizing the nanofibers in an argon atmosphere at 1200°C for 2 hours to prepare N, P, and S doped carbon nanofibers; (4) The prepared N, P, S doped carbon nanofibers were fully mixed with an activator, potassium carbonate, with a potassium carbonate / carbon nanofiber mass ratio of 3, and activated at 700 °C for 120 min in an argon atmosphere to prepare N, P, S doped porous carbon nanofibers.

[0022] Example 3 The steps for preparing a carbon nanofiber positive electrode material are as follows: (1) 1.0 g of melamine, 2.0 g of phytic acid, and 1.0 g of cysteine ​​were placed in a container, 10 mL of DMF was added, and ultrasonic dissolution was performed in a cold water bath until the solution was uniform and stable; then 0.5 g of polyacrylonitrile was added and stirred until it was completely dissolved to prepare a spinning solution; (2) transferring the spinning solution prepared in step (1) into a needle tube, and preparing nanofibers by electrospinning technology; (3) The nanofibers prepared in step (2) were pre-oxidized in air at 230 °C to stabilize the fiber morphology and structure. 2 Carbonization was carried out in an atmosphere at 400 °C for 3 hours to prepare N, P, and S-doped carbon nanofibers; (4) The prepared N, P, S doped carbon nanofibers are fully mixed with the activator zinc chloride, ZnCl 2 / carbon nanofiber mass ratio is 0.1, and in N 2 The carbon nanofibers were activated at 1200°C for 60 minutes in an atmosphere to prepare N, P, and S-doped porous carbon nanofibers.

[0023] Example 4 The steps for preparing a carbon nanofiber positive electrode material are as follows: (1) 0.5 g of melamine, 1.3 g of phytic acid, and 1.2 g of thiourea were placed in a container, 10 mL of DMF was added, and ultrasonic dissolution was performed in a cold water bath until the solution was uniform and stable; then 1.0 g of polyvinyl pyrrolidone and 2.0 g of polymethyl methacrylate were added and stirred until they were completely dissolved to prepare a spinning solution; (2) transferring the spinning solution prepared in step (1) into a needle tube, and preparing nanofibers by electrospinning technology; (3) Pre-oxidizing the nanofibers prepared in step (2) at 200°C in an air atmosphere to stabilize the fiber morphology and structure. Carbonizing the nanofibers in an argon atmosphere at a constant temperature of 1000°C for 2 hours to prepare N, P, and S doped carbon nanofibers; (4) The prepared N, P, S doped carbon nanofibers were fully mixed with potassium hydroxide and zinc chloride with a (potassium hydroxide, zinc chloride) / carbon nanofiber mass ratio of 10, and activated at 400 °C for 120 min in an argon atmosphere to prepare N, P, S doped porous carbon nanofibers.

[0024] In the above embodiments, the N source is one or more of urea, melamine, polyvinyl pyrrolidone, polyacrylonitrile, chitosan, ammonium persulfate, polyaniline, ethylenediamine, glutamic acid, and tryptophan; the S source is one or more of thiourea, sulfur powder, ammonium persulfate, benzene disulfonic acid, and cysteine; the P source is one or more of triphenylphosphine, tetraphenylphosphine bromide, phytic acid, sodium hypophosphite, and sodium hypophosphite; the polymer is one or more of polyvinyl pyrrolidone, polyacrylonitrile, and polymethyl methacrylate. They can be replaced according to actual applications.

[0025] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A carbon nanofiber positive electrode material for aluminum ion capacitor and a preparation method thereof, characterized in that: Here are the steps: (1) placing a N source, a P source, and a S source in N,N-dimethylformamide, performing ultrasound until the solution is uniform and stable, then adding a polymer and stirring until it is completely dissolved to prepare a spinning solution; (2) transferring the spinning solution prepared in step (1) into a needle tube to prepare nanofibers by electrospinning; (3) The nanofibers are placed in air, pre-oxidized to stabilize the fiber morphology and structure, and then carbonized in an inert atmosphere to prepare N, P, and S-doped carbon nanofibers; (4) The N, P, S doped carbon nanofibers are fully mixed with an activator and activated in an inert atmosphere to prepare N, P, S doped porous carbon nanofibers.

2. The method for preparing the carbon nanofiber positive electrode material according to claim 1, characterized in that: In the step (1), the N source is one or more of urea, melamine, polyvinyl pyrrolidone, polyacrylonitrile, chitosan, ammonium persulfate, polyaniline, ethylenediamine, glutamic acid, and tryptophan; the S source is one or more of thiourea, sulfur powder, ammonium persulfate, benzene disulfonic acid, and cysteine; the P source is one or more of triphenylphosphine, tetraphenylphosphine bromide, phytic acid, sodium hypophosphite, and sodium hypophosphite; and the polymer is one or more of polyvinyl pyrrolidone, polyacrylonitrile, and polymethyl methacrylate.

3. The method for preparing the carbon nanofiber positive electrode material according to claim 1, characterized in that: In the step (1), based on the volume of 10 mL of N,N-dimethylformamide, the total mass of the N source, the P source, and the S source is 0.1-5.0 g, and the mass of the polymer is 0.5-5.0 g.

4. The method for preparing the carbon nanofiber positive electrode material according to claim 1, characterized in that: The carbonization temperature in step (3) is 400-1200°C.

5. The method for preparing the carbon nanofiber positive electrode material according to claim 1, characterized in that: The activator in step (4) is one or more of potassium hydroxide, potassium carbonate or zinc chloride, the activation temperature is 400-1200° C., and the mass ratio of activator to carbon nanofiber is 0.1-10.

6. Use of the carbon nanofiber positive electrode material prepared by any method as described in any one of claims 1 to 5 in an ion capacitor.

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