Iron electrode of iron-air battery and preparation method of iron electrode

Abstract

The invention discloses an iron electrode of an iron-air battery and a preparation method of the iron electrode. Porous nitrogen-doped carbon powder is prepared by mixing polyaniline and a saturated sodium chloride solution and performing high-temperature pyrolysis; mixing the porous nitrogen-doped carbon powder with iron particles subjected to surface vulcanization treatment, and performing high-energy ball milling treatment to obtain carbon-coated iron particles subjected to surface vulcanization treatment; performing ultrasonic treatment on the carbon-coated iron particles subjected to surface vulcanization treatment and carbon nanotubes in ethanol to obtain iron catalyst powder with a three-dimensional porous structure; and finally, coating the surface of a stainless steel mesh with the coating, and performing hot-pressing treatment to obtain an iron electrode product. The passivation of the iron particles in the charging and discharging process is reduced through sulfuration treatment of the iron particles, and the iron electrode is further stabilized through coating treatment of the nitrogen-doped carbon powder; and finally, through ultrasonic treatment, the carbon nanotubes and the iron catalyst powder are intertwined to form a three-dimensional porous structure, so that the overall stability of the electrode is facilitated, and a product in the charge-discharge process is fixed.

Description

Technical Field

[0001] The invention belongs to the field of iron-air batteries and other novel batteries based on iron electrodes, and in particular provides an iron electrode of an iron-air battery and a preparation method thereof. Background Art

[0002] Iron electrodes are widely used in iron-air batteries and other new batteries based on iron electrodes. During the operation of the battery, the corresponding iron electrode undergoes an oxidation reaction (discharge process) or a reduction reaction (charge process), thereby realizing the cyclic operation of the battery. Obviously, whether the substances in the iron electrode after discharge can be fully restored during charging plays a key role in the stability and durability of the battery; in addition, the iron electrode is prone to form a passivation film during discharge, thereby causing the battery performance to decline rapidly and be difficult to recover. Therefore, solving these problems of iron electrodes in actual use is of practical significance for the development of new electrochemical energy sources such as iron-air batteries. Summary of the invention

[0003] In order to solve the problems existing in the prior art, the purpose of the present invention is to overcome the problem that the iron electrode is easy to form a passivation film during discharge, and to provide an iron electrode of an iron-air battery and a preparation method thereof.

[0004] To achieve the above purpose, the technical scheme adopted by the present invention is as follows: an iron electrode of an iron-air battery, wherein porous nitrogen-doped carbon powder is prepared by mixing polyaniline with a saturated sodium chloride solution and pyrolyzing it at high temperature; the porous nitrogen-doped carbon powder is mixed with surface-sulfurized iron particles and subjected to high-energy ball milling treatment to obtain carbon-coated surface-sulfurized iron particles; the carbon-coated surface-sulfurized iron particles and carbon nanotubes are then ultrasonically treated in ethanol to obtain iron catalyst powder with a three-dimensional porous structure; and finally, the iron catalyst powder is coated on the surface of a stainless steel mesh and subjected to hot pressing treatment to obtain an iron electrode product.

[0005] A method for preparing an iron electrode of an iron-air battery comprises the following steps:

[0006] (a) polyaniline was mixed with a saturated sodium chloride solution, and then the temperature was raised to 60°C while stirring continuously and the stirring was continued until the solution was completely evaporated; the obtained solid was dried and fully ground, and then the solid was heated in a nitrogen atmosphere at 4°C / min. -1 The solid was immersed in 50°C hot water and stirred, and then filtered, and then immersed in 50°C hot water and stirred. After filtering, the solid was dried to obtain porous nitrogen-doped carbon powder;

[0007] (b) mixing iron particles with sulfur powder, adding an appropriate amount of ethanol, and then fully ball milling; then adding the porous nitrogen-doped carbon powder, and continuing to fully ball mill; then drying the obtained mixture and fully grinding it to obtain carbon-coated surface-sulfurized iron particles;

[0008] (c) mixing the carbon-coated surface-sulfurized iron particles and carbon nanotubes in ethanol, followed by ultrasonic treatment, drying, and grinding to obtain an iron catalyst powder;

[0009] (d) The stainless steel mesh is soaked in a hot sodium carbonate solution, washed with water, and dried. Finally, a viscous substance formed by ultrasonic treatment of the mixture of the iron catalyst powder and the PTFE emulsion is applied to the surface of the treated stainless steel mesh, and then covered with a piece of the same stainless steel mesh, and then hot-pressed to obtain an iron electrode product.

[0010] Preferably, the mass ratio of polyaniline to sodium chloride is 1:20.

[0011] Preferably, the diameter of the iron particles is 100 nm to 1 μm.

[0012] Preferably, the mass ratio of the iron particles to the sulfur powder is 10:(0.5-5).

[0013] Preferably, the mass ratio of the iron particles to the porous nitrogen-doped carbon powder is 4:1.

[0014] Preferably, the mass ratio of the carbon-coated surface-sulfurized iron particles to the carbon nanotubes is 5:1.

[0015] Beneficial effects of the present invention: The present invention first prepares porous nitrogen-doped carbon powder, then mixes it with surface-sulfurized iron particles and performs high-energy ball milling treatment to obtain carbon-coated surface-sulfurized iron particles; then, it is ultrasonically treated with carbon nanotubes in ethanol to obtain an iron catalyst powder with a three-dimensional porous structure; finally, it is coated on the surface of a stainless steel mesh and hot-pressed to obtain an iron electrode product. The present invention reduces the passivation of iron particles during the charge and discharge process by sulfurizing the iron particles, and further stabilizes the iron electrode by coating the nitrogen-doped carbon powder; finally, by ultrasonic treatment, the carbon nanotubes and the iron catalyst powder are entangled with each other to form a three-dimensional porous structure, which is beneficial to the overall stability of the electrode and fixes the products during the charge and discharge process. The process of the present invention is simple, and the obtained iron electrode product has important practical application significance in electrochemical energy systems such as iron-air batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a SEM image of the iron electrode product prepared in Example 1;

[0017] Figure 2 This is the SEM image of the iron electrode product prepared in Example 2.

[0018] Figure 3 This is a charge and discharge cycle diagram of an iron-air battery composed of the iron electrode product prepared in Example 1 and a Pt / C+IrO2 air electrode in a mixed solution of 4MNH4Cl and 1M KCl.

[0019] Figure 4 This is a charge and discharge cycle diagram of an iron-air battery composed of the iron electrode product prepared in Example 2 and a Pt / C+IrO2 air electrode in a mixed solution of 4MNH4Cl and 1M KCl. DETAILED DESCRIPTION

[0020] In order to further illustrate and fully describe the technical solution of the present invention, an iron electrode of an iron-air battery and a preparation method thereof provided by the present invention are described below in conjunction with embodiments. The protection scope of the present invention is not limited by the following embodiments.

[0021] Example 1

[0022] A method for preparing an iron electrode of an iron-air battery comprises the following steps:

[0023] (a) 5 g of polyaniline was mixed with 300 mL of saturated sodium chloride solution, and then the temperature was raised to 60° C. under continuous stirring and continued to be stirred until the solution was completely evaporated; the obtained solid was further placed in a 50° C. drying oven for 6 hours, then fully ground and then transferred to a tube furnace and dried at 4° C. / min in a nitrogen atmosphere. -1 The solid was immersed in 50°C hot water and stirred, and then filtered, and then immersed in 50°C hot water and stirred. The solid obtained after filtration was dried in a 50°C drying oven for 6 hours to obtain porous nitrogen-doped carbon powder.

[0024] (b) 4 g of iron particles with a diameter of 100 nm were mixed with 0.4 g of sulfur powder, placed in a high-energy ball mill, and then an appropriate amount of ethanol was added to keep the mixture completely immersed in the ethanol, and ball milling was carried out at a speed of 500 rpm for 16 hours; then 1 g of the above-mentioned porous nitrogen-doped carbon powder was added, and the ball milling was continued for 10 hours; thereafter, the obtained mixture was dried and fully ground to obtain carbon-coated surface-sulfurized iron particles.

[0025] (c) 1 g of the carbon-coated surface-sulfurized iron particles and 0.2 g of carbon nanotubes were mixed in ethanol, followed by ultrasonic treatment, drying, and grinding to obtain an iron catalyst powder.

[0026] (d) A stainless steel mesh (304 stainless steel, 300 mesh, 0.05 mm thick) was soaked in a hot sodium carbonate solution for 10 min, then washed with water and dried. Finally, a viscous substance formed by ultrasonically treating the mixture of the iron catalyst powder and PTFE emulsion was coated on the surface of the treated stainless steel mesh, and then covered with a piece of the same stainless steel mesh. After that, the mixture was hot-pressed at 150° C. and 25 kN pressure for 10 min to obtain an iron electrode product.

[0027] (e) Pt / C+IrO2 (mass ratio 1:1) mixture was mixed with polytetrafluoroethylene emulsion, and the slurry formed after ultrasonic dispersion was coated on the hydrophobic carbon paper, and then covered with a stainless steel mesh of the same shape as the carbon paper, and then hot pressed at 150°C and 25kN pressure for 10 minutes to obtain an air electrode; the air electrode and the above-mentioned iron electrode product were fixed in a battery model, and a conventional polyethylene film was used as a diaphragm to assemble an iron-air battery, and the electrolyte was a mixed solution of 4M NH4Cl and 1M KCl. At 0.3mA / cm 2 The charge and discharge test was carried out at a constant current density of , and the corresponding charge and discharge curves are shown in the attached Figure 3 .

[0028] Example 2

[0029] A method for preparing an iron electrode of an iron-air battery comprises the following steps:

[0030] (a) 5 g of polyaniline was mixed with 300 mL of saturated sodium chloride solution, and then the temperature was raised to 60° C. under continuous stirring and continued to be stirred until the solution was completely evaporated; the obtained solid was further placed in a 50° C. drying oven for 6 hours, then fully ground and then transferred to a tube furnace and dried at 4° C. / min in a nitrogen atmosphere. -1 The mixture was heated to 810°C at a heating rate of 1000°C, kept at this temperature for 2 hours, and then cooled to room temperature; the solid was soaked and stirred with 50°C hot water, then filtered, and then soaked and stirred with 50°C hot water again. The solid obtained after filtration was dried in a drying oven at 50°C for 6 hours to obtain porous nitrogen-doped carbon powder.

[0031] (b) 4 g of iron particles with a diameter of 200 nm were mixed with 1 g of sulfur powder, placed in a high-energy ball mill, and then an appropriate amount of ethanol was added to keep the mixture completely immersed in the ethanol, and ball milling was carried out at a speed of 500 rpm for 16 hours; then 1 g of the above-mentioned porous nitrogen-doped carbon powder was added, and the ball milling was continued for 10 hours; thereafter, the obtained mixture was dried and fully ground to obtain carbon-coated surface-sulfurized iron particles.

[0032] (c) 1 g of the carbon-coated surface-sulfurized iron particles and 0.2 g of carbon nanotubes were mixed in ethanol, followed by ultrasonic treatment, drying, and grinding to obtain an iron catalyst powder.

[0033] (d) A stainless steel mesh (304 stainless steel, 300 mesh, 0.05 mm thick) was soaked in a hot sodium carbonate solution for 10 min, then washed with water and dried. Finally, a viscous substance formed by ultrasonically treating the mixture of the iron catalyst powder and PTFE emulsion was coated on the surface of the treated stainless steel mesh, and then covered with a piece of the same stainless steel mesh. After that, the mixture was hot-pressed at 150° C. and 25 kN pressure for 10 min to obtain an iron electrode product.

[0034] (e) Pt / C+IrO2 (mass ratio 1:1) mixture was mixed with polytetrafluoroethylene emulsion, and the slurry formed after ultrasonic dispersion was coated on the hydrophobic carbon paper, and then covered with a stainless steel mesh of the same shape as the carbon paper, and then hot pressed at 150°C and 25kN pressure for 10 minutes to obtain an air electrode; the air electrode and the above-mentioned iron electrode product were fixed in a battery model, and a conventional polyethylene film was used as a diaphragm to assemble an iron-air battery, and the electrolyte was a mixed solution of 4M NH4Cl and 1M KCl. At 0.3mA / cm 2 The charge and discharge test was carried out at a constant current density of , and the corresponding charge and discharge curves are shown in the attached Figure 4 .

[0035] The present invention proposes corresponding solutions to the key problems existing in the practical application of iron electrodes. First, the surface of the iron particles is sulfurized with sulfur powder, and the iron sulfide formed effectively inhibits the passivation phenomenon of the iron electrode during the discharge process; then, the iron particles treated with sulfur are further coated with porous nitrogen-doped carbon powder, thereby effectively dispersing the iron particles and fixing the products after the iron electrode is discharged, which is beneficial to the recovery of the iron electrode during charging; finally, by adding carbon nanotubes with a one-dimensional structure and performing ultrasonic treatment, the carbon nanotubes with a twisted structure, the nitrogen-doped porous carbon powder and the iron particles form a stable three-dimensional porous structure. The iron electrode formed in this way forms a stable structure through the three-dimensional porous carbon skeleton, thereby effectively maintaining the high activity of the electrode during long-term operation.

[0036] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present invention.

Claims

1. An iron electrode for an iron-air battery, characterized in that: The porous nitrogen-doped carbon powder is prepared by mixing polyaniline with a saturated sodium chloride solution and pyrolyzing it at high temperature; the porous nitrogen-doped carbon powder is mixed with surface-sulfurized iron particles and subjected to high-energy ball milling treatment to obtain carbon-coated surface-sulfurized iron particles; the carbon-coated surface-sulfurized iron particles and carbon nanotubes are ultrasonically treated in ethanol to obtain iron catalyst powder with a three-dimensional porous structure; and finally, the powder is coated on the surface of a stainless steel mesh and subjected to hot pressing treatment to obtain an iron electrode product.

2. A method for preparing an iron electrode for an iron-air battery, characterized in that: The steps include: (a) polyaniline was mixed with a saturated sodium chloride solution, and then the temperature was raised to 60°C while stirring continuously and the stirring was continued until the solution was completely evaporated; the obtained solid was dried and fully ground, and then the solid was heated in a nitrogen atmosphere at 4°C / min. -1 The solid was immersed in 50°C hot water and stirred, and then filtered, and then immersed in 50°C hot water and stirred. After filtering, the solid was dried to obtain porous nitrogen-doped carbon powder; (b) mixing iron particles with sulfur powder, adding an appropriate amount of ethanol, and then fully ball milling; then adding the porous nitrogen-doped carbon powder, and continuing to fully ball mill; then drying the obtained mixture and fully grinding it to obtain carbon-coated surface-sulfurized iron particles; (c) mixing the carbon-coated surface-sulfurized iron particles and carbon nanotubes in ethanol, followed by ultrasonic treatment, drying, and grinding to obtain an iron catalyst powder; (d) The stainless steel mesh is soaked in a hot sodium carbonate solution, washed with water, and dried. Finally, a viscous substance formed by ultrasonic treatment of the mixture of the iron catalyst powder and the PTFE emulsion is applied to the surface of the treated stainless steel mesh, and then covered with a piece of the same stainless steel mesh, and then hot-pressed to obtain an iron electrode product.

3. The method for preparing an iron electrode of an iron-air battery according to claim 2, characterized in that: The mass ratio of the polyaniline to sodium chloride is 1:

20.

4. The method for preparing an iron electrode of an iron-air battery according to claim 2, characterized in that: The diameter of the iron particles is 100 nm to 1 μm.

5. The method for preparing an iron electrode of an iron-air battery according to claim 2, characterized in that: The mass ratio of the iron particles to the sulfur powder is 10:(0.5-5).

6. The method for preparing an iron electrode of an iron-air battery according to claim 2, characterized in that: The mass ratio of the iron particles to the porous nitrogen-doped carbon powder is 4:

1.

7. The method for preparing an iron electrode for an iron-air battery according to claim 2, characterized in that: The mass ratio of the carbon-coated surface-sulfurized iron particles to the carbon nanotubes is 5:1.

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