An alkaline full-iron flow battery and a preparation method of an electrode material

Abstract

The application discloses a kind of alkaline full iron liquid flow batteries and preparation method of electrode material.Its characteristics are: the positive electrolyte of the alkaline full iron liquid flow battery is with ferrocyanide as active substance, one or both of NaOH and KOH as supporting electrolyte, the negative electrolyte is with 3-[N-N-bis (2-hydroxyethyl) amino]-2-hydroxypropane sulfonic acid and ferric chloride reaction to form complex iron as active substance, one or both of NaOH and KOH as supporting electrolyte to form the alkaline full iron liquid flow battery.The application increases the reaction active site of positive and negative electrode electrolyte active substance on the surface of electrode respectively, so as to improve the charge-discharge capacity of liquid flow battery.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of liquid flow batteries, and particularly relates to a kind of alkaline full-iron liquid flow batteries and a preparation method of electrode material. BACKGROUND

[0002] As a long-time, large-scale electrochemical energy storage technology, liquid flow batteries have the advantages of intrinsic safety, capacity and power that can be independently designed, and are a reliable choice for sustainable utilization of fluctuating wind, light and other new energy sources. As the most mature liquid flow battery at present, the full-vanadium liquid flow battery has gradually realized large-scale demonstration application, but is subject to the high cost of vanadium materials, which poses certain challenges in large-scale commercial application. Alkaline full-iron liquid flow batteries, such as the patent document CN113764714, use iron ions and organic complexes as raw materials, which are widely available and low in price, and have a strong application prospect.

[0003] The electrode is the place of electrochemical reaction of the liquid flow battery, and can provide corresponding adsorption sites for the positive and negative active materials. Different positive and negative active materials have different requirements for the reaction active sites on the electrode. For alkaline full-iron batteries, different preparation methods of positive and negative electrode materials are needed according to the differences between the positive and negative electrolytes to meet the demand for high efficiency of full battery charging and discharging. The existing liquid flow battery has the defects of low electrochemical reaction activity and low charging and discharging capacity of the liquid flow battery. SUMMARY

[0004] In order to improve the electrochemical reaction activity of the positive and negative active materials of the alkaline full-iron liquid flow battery on the electrode material, the application provides a preparation method of an alkaline full-iron liquid flow battery and electrode material. The positive electrode material is activated by high-temperature treatment after being immersed in thiocyanate solution, and the negative electrode material is activated by hydrothermal method or high-temperature thermal decomposition method, which respectively increases the reaction active sites of the positive and negative electrolyte active materials on the electrode surface. The raw materials used in the preparation method are easy to obtain, the operation is simple, and the method can be applied to the alkaline full-iron liquid flow battery and improve its charging and discharging capacity.

[0005] In order to achieve the above object, the technical scheme adopted by the application is:

[0006] An alkaline full-iron liquid flow battery, characterized in that: the positive electrolyte of the alkaline full-iron liquid flow battery is composed of ferrocyanide as the active material, one or both of NaOH and KOH as the supporting electrolyte, and the negative electrolyte is composed of complex iron formed by the reaction of 3-[N-N-bis(2-hydroxyethyl)amino]-2-hydroxypropanesulfonic acid and ferric chloride as the active material, and one or both of NaOH and KOH as the supporting electrolyte.

[0007] The positive electrode material of the alkaline all-iron flow battery of the present invention is prepared by the following method:

[0008] (1) The carbon electrode is activated at high temperature of 200-400℃ for 3-10 hours in air atmosphere, and then naturally cooled to room temperature;

[0009] (2) The material obtained in step (1) is immersed in a solution of thiocyanate and subjected to ultrasonic treatment for 5 to 30 minutes. The electrode is then removed and dried at 60 to 100°C for 6 to 12 hours.

[0010] (3) The electrode after step (2) is placed under an inert atmosphere and subjected to high-temperature heat treatment at 600-800℃ for 30-150 min;

[0011] (4) The electrode obtained after the above step (3) is placed in a 0.05-1 mol / L hydrochloric acid solution and ultrasonically treated for 30 min. Then the acid-treated electrode is washed with a large amount of deionized water and finally dried at 60-100℃ for 6-12 h to obtain the electrode positive electrode material.

[0012] The preparation methods of the negative electrode material of this invention include hydrothermal method and high-temperature thermal decomposition method:

[0013] The hydrothermal preparation step described herein involves immersing the carbon-based electrode material in a urea aqueous solution with a concentration of 50–200 g / L, followed by ultrasonic treatment for 5–30 min (the ultrasonic cleaner has an ultrasonic frequency of 20–50 kHz), then placing it in a hydrothermal reactor and reacting at 180–220 °C for 10–24 h. Finally, the material is washed with deionized water and dried to obtain the negative electrode material.

[0014] The high-temperature thermal decomposition method preparation steps are as follows: carbon-based electrode material is immersed in a urea aqueous solution with a concentration of 50-200 g / L, and then subjected to ultrasonic treatment for 5-30 min. The ultrasonic frequency of the ultrasonic cleaner is 20-50 kHz. After drying, it is placed in an inert atmosphere and activated at a high temperature of 600-1000℃ for 30-180 min. Finally, it is cooled to room temperature to obtain the negative electrode material.

[0015] The carbon-based electrode material is one of carbon felt, graphite felt, or carbon paper. The thiocyanate is one of potassium thiocyanate, sodium thiocyanate, and ammonium thiocyanate, and the concentration of thiocyanate is 10–300 g / L.

[0016] The beneficial effects of this invention are:

[0017] (1) Based on the different adsorption characteristics of the active substances in the positive and negative electrode electrolytes, the present invention performs different functionalization doping modification treatments on the positive and negative electrode materials, which greatly increases the adsorption sites of the positive and negative electrode materials for the active substances in the positive and negative electrode electrolytes, improves the corresponding adsorption capacity, and thus enhances the electrochemical activity of the active substances in the positive and negative electrode electrolytes on the corresponding electrode materials.

[0018] (2) When the positive and negative electrode materials prepared by the method of the present invention are applied to alkaline all-iron flow batteries, the alkaline all-iron flow batteries exhibit higher charge and discharge capacity in charge and discharge tests due to the increased reaction rate of the active materials of the positive and negative electrolytes on the positive and negative electrode materials.

[0019] (3) The preparation method of positive and negative electrode materials provided by the present invention is simple to operate, the raw materials are readily available, the price is low, and the effect is significant. It can be widely used in alkaline all-iron flow batteries with ferrocyanide as the positive electrode active material and Fe-DIPSO as the negative electrode active material. Attached Figure Description

[0020] Figure 1 The graph shows a comparison of cyclic voltammetry between the positive electrode graphite felt electrode and the positive electrode graphite felt electrode obtained in Examples 1-3 of this invention in the positive electrode electrolyte potassium ferrocyanide electrolyte.

[0021] Figure 2 The graph shows a comparison of the cyclic voltammetry of the negative electrode graphite felt electrode and the negative electrode graphite felt electrode obtained in Examples 1-3 of this invention in the negative electrode electrolyte DIPSO-Fe electrolyte.

[0022] Figure 3 The graph shows a comparison of the charge and discharge capacities of the positive and negative graphite felt electrodes and the positive and negative graphite felt electrodes obtained in Example 4 of this invention when applied to an alkaline all-iron flow battery at different current densities. Detailed Implementation

[0023] The present invention will be further described in detail below with specific embodiments of the results.

[0024] The electrolyte composition in the following examples is as follows: The positive electrode electrolyte is a mixed solution of 0.1 mol / L potassium ferrocyanide and 3 mol / L NaOH, and the negative electrode electrolyte is a mixed solution of 0.1 mol / L Fe-DIPSO and 3 mol / L NaOH formed by the complexation reaction of 0.1 mol / L FeCl3 and 0.1 mol / L DIPSO (3-[NN-bis(2-hydroxyethyl)amino]-2-hydroxypropanesulfonic acid).

[0025] Example 1

[0026] (1) Positive electrode: The graphite felt electrode, after being activated at 300℃ for 6 hours in air, was immersed in a 10 g / L potassium thiocyanate solution, ultrasonically dispersed for 10 min, and then placed in an oven to dry at 60℃ for 12 h. The ultrasonic cleaning frequency was 40 kHz. The electrode was then removed, placed in a tube furnace, purged with nitrogen, and then heated to 600℃ at a nitrogen atmosphere at a heating rate of 5℃ / min and held for 30 min. After cooling to room temperature, the electrode material was ultrasonically treated with 0.1 mol / L hydrochloric acid solution for 30 min, then rinsed thoroughly with a large amount of deionized water, and finally placed in an oven to dry at 60℃ for 12 h to obtain the positive electrode material.

[0027] (2) Negative electrode: The graphite felt electrode material was immersed in a urea aqueous solution with a concentration of 50 g / L, ultrasonically treated for 15 min, the ultrasonic frequency of the ultrasonic cleaner was 40 kHz, and then placed in a hydrothermal reactor and reacted at 220 °C for 8 h. Finally, it was washed clean with deionized water and dried at 80 °C for 8 h to obtain the negative electrode material.

[0028] The above-prepared positive electrode graphite felt electrode material is used in the positive electrode electrolyte with ferrocyanide as the active material and one or two of NaOH and KOH as the supporting electrolyte. The modified negative electrode graphite felt electrode material is used in the negative electrode electrolyte in an alkaline all-iron flow battery composed of complex iron formed by the reaction of 3-[NN-bis(2-hydroxyethyl)amino]-2-hydroxypropanesulfonic acid with ferric chloride as the active material and one or two of NaOH and KOH as the supporting electrolyte.

[0029] Example 2

[0030] (1) Positive electrode: The graphite felt electrode, after being activated at 200℃ for 10h in air, was immersed in a 100g / L potassium thiocyanate solution, ultrasonically dispersed for 20min, and then placed in an oven to dry at 100℃ for 6h. The ultrasonic cleaning frequency was 50kHz. The electrode was then removed, placed in a tube furnace, purged with nitrogen, and then heated to 700℃ at a rate of 10℃ / min under an argon atmosphere and held for 60min. After cooling to room temperature, the electrode material was ultrasonically treated with 0.1mol / L hydrochloric acid solution for 30min. The ultrasonic cleaning frequency was 50kHz. Then it was rinsed with a large amount of deionized water and finally placed in an oven to dry at 100℃ for 6h to obtain the positive electrode material.

[0031] (2) Negative electrode: The graphite felt electrode material was immersed in a urea aqueous solution with a concentration of 150 g / L, ultrasonically treated for 20 min, the ultrasonic cleaner had an ultrasonic frequency of 50 kHz, dried at 75 ℃ for 10 h, and then placed under an argon atmosphere for high-temperature treatment at 800 ℃ for 1 h. Finally, it was cooled to room temperature to obtain the negative electrode material.

[0032] The above-prepared positive electrode graphite felt electrode material is used in the positive electrode electrolyte with ferrocyanide as the active material and one or two of NaOH and KOH as the supporting electrolyte. The modified negative electrode graphite felt electrode material is used in the negative electrode electrolyte in an alkaline all-iron flow battery composed of complex iron formed by the reaction of 3-[NN-bis(2-hydroxyethyl)amino]-2-hydroxypropanesulfonic acid with ferric chloride as the active material and one or two of NaOH and KOH as the supporting electrolyte.

[0033] Example 3

[0034] (1) Positive electrode: The graphite felt electrode, after being activated at 400℃ for 3 hours in air, was immersed in a 300 g / L potassium thiocyanate solution, ultrasonically dispersed for 30 min, and then placed in an oven to dry at 80℃ for 8 hours. The ultrasonic cleaning frequency was 30 kHz. The electrode was then removed, placed in a tube furnace, purged with nitrogen, and then heated to 1000℃ at a rate of 5℃ / min under a helium atmosphere and held for 180 min. After cooling to room temperature, the electrode material was ultrasonically treated with 0.1 mol / L hydrochloric acid solution for 30 min, then rinsed thoroughly with a large amount of deionized water, and finally placed in an oven to dry at 80℃ for 8 hours to obtain the positive electrode material.

[0035] (2) Negative electrode: The graphite felt electrode material was immersed in a urea aqueous solution with a concentration of 200 g / L, ultrasonically treated for 15 min, the ultrasonic frequency of the ultrasonic cleaner was 30 kHz, and then placed in a hydrothermal reactor and reacted at 180 °C for 10 h. Finally, it was washed clean with deionized water and dried at 80 °C for 8 h to obtain the negative electrode material.

[0036] The above-prepared positive electrode graphite felt electrode material is used in the positive electrode electrolyte with ferrocyanide as the active material and one or two of NaOH and KOH as the supporting electrolyte. The modified negative electrode graphite felt electrode material is used in the negative electrode electrolyte in an alkaline all-iron flow battery composed of complex iron formed by the reaction of 3-[NN-bis(2-hydroxyethyl)amino]-2-hydroxypropanesulfonic acid with ferric chloride as the active material and one or two of NaOH and KOH as the supporting electrolyte.

[0037] Example 4

[0038] (1) Positive electrode: The graphite felt electrode, after being activated at 400℃ for 3 hours in air, was immersed in a 200 g / L potassium thiocyanate solution, ultrasonically dispersed for 30 min, and then placed in an oven to dry at 80℃ for 8 hours. The ultrasonic cleaning frequency was 30 kHz. The electrode was then removed, placed in a tube furnace, purged with nitrogen, and then heated to 800℃ for 150 min at a heating rate of 5℃ / min under an argon atmosphere. After cooling to room temperature, the electrode material was ultrasonically treated with 0.1 mol / L hydrochloric acid solution for 30 min, then rinsed thoroughly with a large amount of deionized water, and finally placed in an oven to dry at 80℃ for 8 hours to obtain the positive electrode material.

[0039] (2) Negative electrode: The graphite felt electrode material was immersed in a urea aqueous solution with a concentration of 100 g / L, ultrasonically treated for 30 min, the ultrasonic frequency of the ultrasonic cleaner was 30 kHz, dried at 80 ℃ for 8 h, and then placed under argon atmosphere protection for high temperature treatment at 600 ℃ for 2 h. Finally, it was cooled to room temperature to obtain the negative electrode material.

[0040] The above-prepared positive electrode graphite felt electrode material is used in the positive electrode electrolyte with ferrocyanide as the active material and one or two of NaOH and KOH as the supporting electrolyte. The modified negative electrode graphite felt electrode material is used in the negative electrode electrolyte in an alkaline all-iron flow battery composed of complex iron formed by the reaction of 3-[NN-bis(2-hydroxyethyl)amino]-2-hydroxypropanesulfonic acid with ferric chloride as the active material and one or two of NaOH and KOH as the supporting electrolyte.

[0041] The untreated graphite felt electrode and the graphite felt electrode prepared as the positive electrode in Examples 1-3 of this invention were subjected to cyclic voltammetry tests in a mixed solution of potassium ferrocyanide and NaOH. The results are as follows: Figure 1 As shown. From Figure 1 As can be seen, the peak current density of the electrode material treated with thiocyanate was increased, while the peak potential difference was reduced, indicating that the electrode material treated with thiocyanate exhibited higher electrochemical performance for the ferrocyanide active material in the positive electrode electrolyte.

[0042] The untreated graphite felt electrode and the graphite felt electrode prepared as the negative electrode in Examples 1-3 of this invention were subjected to cyclic voltammetry tests in a mixed solution of Fe-DIPSO and NaOH as the negative electrode. The results are as follows: Figure 2 As shown. From Figure 2 As can be seen, the peak current value of the electrode material after urea impregnation followed by hydrothermal treatment and vapor phase chemical deposition was significantly increased, while the peak potential difference was reduced, indicating that the active material of the negative electrode electrolyte has excellent electrochemical activity on the modified electrode material.

[0043] The untreated graphite felt electrode and the graphite felt electrodes prepared in Example 4 of this invention were respectively applied to the positive and negative electrodes of an alkaline all-iron flow battery. The positive electrode electrolyte was a mixed solution of 0.1 mol / L potassium ferrocyanide and 3 mol / L NaOH, and the negative electrode electrolyte was a mixed solution of 0.1 mol / L FeCl3 and 0.1 mol / L DIPSO (3-[NN-bis(2-hydroxyethyl)amino]-2-hydroxypropanesulfonic acid) complexed with 0.1 mol / L Fe-DIPSO and 3 mol / L NaOH. The alkaline all-iron flow battery was assembled at 60 mA / cm². 2 80mA / cm 2 and 100mA / cm 2 Charge-discharge tests were performed at current density. Results are as follows: Figure 3 As shown. By Figure 3 The results show that, compared with the charge and discharge capacity of batteries using untreated electrode materials as positive and negative electrodes, batteries using electrode materials modified by the method of this invention exhibit higher charge and discharge capacity at different current densities, especially at high current densities.

Claims

1. An alkaline all-iron flow battery, characterized in that: The alkaline all-iron flow battery described herein uses ferrocyanide as the active material and one or both of NaOH and KOH as the supporting electrolyte in its positive electrode electrolyte, and one or both of NaOH and KOH as the supporting electrolyte in its negative electrode electrolyte. The positive electrode material of the alkaline all-iron flow battery is prepared using the following method: (1) The carbon electrode is activated at high temperature in air at 200-400℃ for 3-10 hours, and then naturally cooled to room temperature; (2) The material obtained in step (1) is immersed in a solution of thiocyanate and subjected to ultrasonic treatment for 5 to 30 minutes. The electrode is then removed and dried at 60 to 100°C for 6 to 12 hours. The thiocyanate is one of potassium thiocyanate, sodium thiocyanate and ammonium thiocyanate, and the concentration of thiocyanate is 10 to 300 g / L. (3) The electrode after step (2) is placed under an inert atmosphere and subjected to high-temperature heat treatment at 600-800℃ for 30-150 min; (4) The electrode obtained after the above step (3) is placed in a 0.05-1 mol / L hydrochloric acid solution and ultrasonically treated for 30 min. Then the acid-treated electrode is washed with a large amount of deionized water and finally dried at 60-100℃ for 6-12 h to obtain the positive electrode material. The negative electrode material of the alkaline all-iron flow battery is prepared by the following method: carbon electrode material is immersed in a urea aqueous solution with a concentration of 50-200 g / L, and then subjected to ultrasonic treatment for 5-30 min. After drying, it is placed under an inert atmosphere and activated at a high temperature of 600-1000℃ for 30-180 min. Finally, it is cooled to room temperature to obtain the negative electrode material.

2. The alkaline all-iron flow battery according to claim 1, characterized in that: The carbon-based electrode material is one of carbon felt, graphite felt, or carbon paper.

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