CN116864720A - Preparation method and application of high-performance carbon felt electrode for iron-based liquid flow battery - Google Patents

Abstract

The present invention relates to the technical field of flow batteries, specifically a preparation method and application of high-performance carbon felt electrodes for iron-based flow batteries. The method is as follows: 1) Use a fluidized bed dryer to efficiently and uniformly load metal oxide powder onto the surface of the carbon felt fiber; 2) Take out the carbon felt and put it into a tube furnace, pass in protective gas, and heat up at a constant rate After reaching the target temperature, keep it for 1 to 2 hours, and then naturally cool to room temperature; 3) Take out the carbon felt, pickle it, rinse it with deionized water and dry it to prepare a high-performance carbon felt electrode. From the perspective of easy engineering preparation, the present invention prepares a carbon felt electrode with a porous structure with high carbon defects on the surface, which can simultaneously reduce the polarization of the positive and negative side electrodes of the iron-based liquid flow battery and improve the Coulombic efficiency and efficiency of the battery. cycle life.

Description

Preparation method and application of high-performance carbon felt electrode for iron-based liquid flow battery

Technical field

The present invention relates to the technical field of flow batteries, specifically to a preparation method and application of high-performance carbon felt electrodes for iron-based flow batteries.

Background technique

With the development of productivity, energy demand has surged. However, traditional fossil energy resources are limited and cause serious damage to the environment, prompting people to conduct research on renewable energy sources such as wind energy and solar energy. Due to the inherent instability of renewable energy power generation, corresponding large-scale energy storage facilities must be configured for regulation to ensure sustainable development and utilization. Among many energy storage technologies, flow batteries have been vigorously developed due to their intrinsic safety and high degree of freedom.

The all-vanadium redox flow battery, which is currently the most mature industrial technology, has faced the problem of vanadium resource constraints in recent years. The cost is high and further development has been hindered. Iron-based flow batteries, represented by iron-chromium flow batteries and hybrid all-iron flow batteries, use Fe as the active component and have the advantages of wide sources of active materials, low cost, and high energy density. They are widely used in distributed applications. The field of energy storage has good application prospects. However, during battery operation, due to the low specific surface area and poor electrochemical activity of commonly used carbon felt electrodes, the electrochemical reaction kinetics is slow, which easily leads to higher polarization and lower energy efficiency of the battery. In addition, during the charging process, for the all-iron flow battery system, the iron on the negative electrode side easily forms a cluster-like uneven deposition morphology on the electrode, making the negative electrode deposition and dissolution reaction poor reversibility, which greatly reduces the battery's performance. cycle life.

Faced with the above problems, in the Chinese invention patent application with the publication number CN116154191A, Beijing University of Chemical Technology proposed a method of doping iron and tin atomic level active sites on the surface of carbon-based materials to reduce the negative electrode polarization of the battery and at the same time make the iron uniform. deposited on the electrode surface, thus improving the cycle life of the battery. However, the preparation of this method is complicated and difficult to prepare on a large scale. Moreover, this method only improves the battery negative electrode to a certain extent and has a small scope of application.

Contents of the invention

In order to solve the above problems, the purpose of the present invention is to provide a preparation method and application of a high-performance carbon felt electrode for iron-based liquid flow batteries. From the perspective of easy engineering preparation, a kind of carbon felt electrode with high carbon defects on the surface is prepared. The porous structure of the carbon felt electrode can simultaneously reduce the polarization of the positive and negative electrodes of the iron-based redox flow battery and improve the Coulombic efficiency and cycle life of the battery.

In order to achieve the above objects, the present invention is achieved through the following technical solutions:

A method for preparing high-performance carbon felt electrodes for iron-based liquid flow batteries, including the following steps:

Step 1) Put a sufficient amount of metal oxide powder and raw carbon felt into a fluidized bed dryer, dry and mix thoroughly, so that the surface of the carbon felt fiber is fully loaded with metal oxide powder;

Step 2) Take out the carbon felt and place it in a quartz tube furnace. Under a protective atmosphere, raise the temperature to 1000-1500°C at a constant rate. Keep it at this temperature for 1-2 hours, perform carbothermal reduction treatment, and then naturally cool to room temperature;

Step 3) Soak the treated carbon felt in a sulfuric acid solution, perform ultrasonic vibration treatment, rinse with deionized water, and dry to prepare a high-performance carbon felt electrode for iron-based redox flow batteries.

In the preparation method of high-performance carbon felt electrodes for iron-based redox flow batteries, in step 1), the metal oxide powder is one or more of FeO, Fe ₃ O ₄ , Cr ₂ O ₃ and CuO, and the metal oxide powder is The particle size of the oxide powder is 10 to 105 μm.

In the preparation method of high-performance carbon felt electrodes for iron-based redox flow batteries, in step 1), the average pore diameter of the original carbon felt is 3 to 6 nm, the average fiber diameter is 8 to 12 μm, and the average BET specific surface area is 5 to 5 nm. 20㎡/g.

In the preparation method of high-performance carbon felt electrodes for iron-based liquid flow batteries, in step 1), the fluidized bed drying and mixing time is 20 to 40 minutes.

In the method for preparing high-performance carbon felt electrodes for iron-based liquid flow batteries, in step 2), the protective atmosphere is one or two mixed gases of nitrogen and argon, and the heating rate is 5 to 10°C/min.

In the preparation method of high-performance carbon felt electrodes for iron-based liquid flow batteries, in step 3), the concentration of the sulfuric acid solution is 4.0-7.0 mol/L, and the ultrasonic vibration treatment time is 20-40 minutes.

The described preparation method of high-performance carbon felt electrodes for iron-based liquid flow batteries improves the BET specific surface area of the carbon felt and the contact angle of the carbon felt electrode by etching an irregular hole structure rich in edge carbon defects on the surface of the carbon felt fiber. is 0°, effectively improving the polarization of the positive and negative electrodes of the battery, giving the negative electrode iron a uniform and dense deposition morphology, and improving the energy efficiency and cycle life of the battery.

The high-performance carbon felt electrode prepared by the method is used in iron-based liquid flow batteries.

It can be seen from the above that the technical route and design ideas of the present invention are:

First, the metal oxide is evenly loaded on the carbon felt by using fluidization, and then through heat treatment, the metal oxide and the carbon felt undergo a carbothermal reduction reaction, thereby etching the surface of the carbon felt. Finally, the reduced metal and metal oxides are dissolved in a sulfuric acid solution, thereby introducing an irregular hole structure on the surface of the carbon fiber of the carbon felt material to obtain a high-performance carbon felt electrode material.

The present invention uses a high-performance carbon felt electrode prepared based on metal oxide etching for the operation of iron-based liquid flow batteries. By etching a hole structure rich in edge carbon defects on the surface of the carbon felt fiber, it obtains a High performance carbon felt electrode with high specific surface area and high electrochemical activity. It can not only improve the polarization of the positive and negative electrodes of the battery, but also make the negative electrode iron have a uniform and dense deposition morphology, so as to improve the energy efficiency and cycle life of the battery and further optimize the performance of the iron-based flow battery.

Compared with the existing technology, the present invention has the following advantages and beneficial effects:

1) The present invention uses a fluidized bed to load metal oxide powder onto carbon felt fibers uniformly and efficiently, which is beneficial to large-scale production and preparation.

2) During the heat treatment and etching process, the present invention not only forms a hole structure on the electrode surface, but also increases the specific surface area of the carbon felt, making the BET specific surface area of the carbon felt reach more than 44m ² /g, which is higher than the BET specific surface area of the original carbon felt. About 3 times. In addition, the heat treatment process introduces a large number of oxygen-containing functional groups on the surface of the carbon felt, which enhances the surface wettability and electrochemical activity of the electrode. Using this electrode with a porous structure as the positive and negative electrodes of iron-based batteries can effectively reduce the battery life. change.

3) For hybrid all-iron flow batteries, more microscopic edge carbon defects will be produced at the holes during the etching process of the present invention. When this kind of hole electrode rich in microscopic defects is used as a negative electrode, its carbon fiber The edge carbon defects on the electrode can provide nucleation sites for iron deposition, and prevent iron from aggregating to form clusters and evenly distributed on the electrode surface, which greatly improves the reversibility of the negative electrode reaction and effectively extends the cycle life of the battery. .

4) Compared with the existing electrode modification methods, the method of the present invention has a simple and easy process, significant improvement effect, good stability, wide application range, and can be extended to other flow battery systems.

Description of the drawings

Figure 1 is an SEM comparison picture of the surface of b) high-performance carbon felt electrode prepared in Example 1 of the present invention and a) original carbon felt electrode.

Figure 2 is a comparison result of the contact angle in aqueous solution between b) high-performance carbon felt electrode prepared in Example 1 of the present invention and a) original carbon felt electrode.

Figure 3 is a SEM comparison picture of the surface of b) high-performance carbon felt electrode prepared in Example 2 of the present invention and a) original carbon felt electrode.

Figure 4 is a SEM comparison picture of the iron deposition morphology in the hybrid all-iron flow electrolytic cell of b) high-performance carbon felt electrode and a) original carbon felt electrode prepared in Example 4 of the present invention.

Figures 5(a) to 5(b) are comparison charts of cyclic voltammetry tests between the high-performance carbon felt electrode prepared in Example 4 of the present invention and the original carbon felt electrode in a hybrid all-iron liquid flow electrolytic cell. Figure 5(a) is the positive electrode, and Figure 5(b) is the negative electrode. In the figure, the abscissa Potential is the potential (V vs. SCE), and the ordinate Current is the current (A).

Figures 6(a) to 6(b) are comparison charts of cyclic voltammetry tests between the high-performance carbon felt electrode prepared in Example 5 of the present invention and the original carbon felt electrode in an iron-chromium flow electrolytic cell. Figure 6(a) is the positive electrode, and Figure 6(b) is the negative electrode. In the figure, the abscissa Potential is the potential (V vs. SCE), and the ordinate Current is the current (A).

Figure 7 is a long cycle comparison diagram of the high-performance carbon felt electrode prepared in Example 6 of the present invention and the original carbon felt electrode installed in a hybrid all-iron flow battery. In the figure, the abscissa Cycle number is the number of cycles, and the ordinate Capacity is the capacity (mAh).

Detailed ways

During the specific implementation process, the present invention proposes a method for preparing high-performance carbon felt electrodes for iron-based liquid flow batteries. The method is as follows: 1) Use a fluidized bed dryer to efficiently and uniformly load metal oxide powder onto the carbon felt Fiber surface; 2) Take out the carbon felt and put it into a tube furnace, and pass in protective gas. After heating to the target temperature at a constant rate, keep it warm for 1 to 2 hours, and then naturally cool to room temperature; 3) Take out the carbon felt and conduct Acid washing, followed by rinsing with deionized water and drying, produced high-performance carbon felt electrodes.

Below, the present invention will be further described in detail through examples and drawings.

Example 1

In this embodiment, a method for preparing high-performance carbon felt electrodes for iron-based liquid flow batteries includes the following steps:

1) Weigh a sufficient amount of FeO and Cr ₂ O ₃ (particle size 44 ~ 105 μm) powder. The mass ratio of FeO powder and Cr ₂ O ₃ powder is 1:1. Put the original carbon felt and powder together into the fluidizer. In the bed dryer, after fluidized drying for 20 minutes, take out the carbon felt.

In this embodiment, the average pore diameter of the original carbon felt is 5.4 nm, the average fiber diameter is 10.5 μm, and the average BET specific surface area is 16.4529 m ² /g.

2) Place the carbon felt in a tube furnace with nitrogen as the protective gas, raise the furnace temperature to 1000°C at a constant rate of 10°C/min, and keep it at this temperature for 60 minutes to allow the metal oxide to fully react with the carbon. The felt undergoes a carbothermal reduction reaction, and then is naturally cooled to room temperature, and the carbon felt is taken out for later use.

3) Prepare a 6.0 mol/L sulfuric acid aqueous solution, put the carbon felt into the solution, and vibrate ultrasonically for 30 minutes to remove metal impurities on the carbon felt.

4) Take out the carbon felt, wash it with deionized water, and place it in a drying box to dry at 50°C for 60 minutes to prepare a high-performance carbon felt electrode for use in battery assembly.

The prepared high-performance carbon felt and original carbon felt were characterized by SEM morphology, and the results are shown in Figure 1. It can be clearly seen from Figure 1 that compared with the smooth surface of the original carbon felt (a), the surface of the prepared carbon felt shows a uniform and dense hole structure (b). This structure can significantly increase the specific surface area of the carbon felt electrode. In this embodiment, the specific surface area of the carbon felt electrode reaches 44.4386 m2/g, which facilitates the transmission of active materials. As shown in Figure 2, the contact angles of the high-performance carbon felt (a) prepared in this example and the original carbon felt (b) in aqueous solution. Through comparison, it is found that the contact angle of the original carbon felt is 126° and has poor wettability; while the contact angle of the high-performance carbon felt electrode prepared in this example is 0°, which has extremely excellent hydrophilicity and excellent wettability. Hydrophilicity is one of the requirements for high-performance electrode materials for flow batteries.

Example 2

In order to simplify the description and enhance the contrast, the preparation process of Example 2 is the same as that of Example 1, except that CuO powder (particle size is 44-105 μm) is evenly loaded onto the carbon felt to prepare high-performance carbon felt electrodes. The specific surface area of the carbon felt electrode in the embodiment reaches 49.7624m ² /g. The SEM morphology of the prepared electrode was characterized. The results showed that the surface of the high-performance carbon felt electrode prepared in this example still showed a uniform and dense pore morphology (Figure 3), so it has electrochemical activity and good iron deposition morphology. .

Example 3

To simplify the description, the preparation process of Example 3 is the same as that of Example 1. The prepared high-performance carbon felt and original carbon felt were tested by XPS, and their elemental composition and relative content were analyzed, as shown in Table 1. It can be seen from Table 1 that compared with the original carbon felt, the high-performance carbon felt prepared in this example has more oxygen-containing functional groups and edge carbon defects. These abundant oxygen-containing functional groups can effectively improve the hydrophilicity of the carbon felt, making it have better electrochemical activity. The edge carbon defects provide abundant nucleation sites for iron deposition, avoiding the formation of cluster-like deposition morphology on the iron negative electrode.

Table 1: Comparison of atomic fractions between the high-performance carbon felt electrode prepared in Example 1 and the original carbon felt electrode

carbon felt O 1s C 1s C SP ² C SP ³ C-O C＝O C＝O-O Example 1 9.61% 90.39% 66.6% 20.9% 6.8% 2.3% 3.4% Raw carbon felt 27.42% 67.95% 78.5% 6% 7% 5.5% 3%

Example 4

To simplify the description, the preparation process of Example 4 is the same as that of Example 1. The prepared high-performance carbon felt and original carbon felt were used to characterize the deposition morphology and electrochemical performance in a hybrid all-iron flow battery electrolytic cell: first, the prepared high-performance carbon felt electrode was constructed as the working electrode, and A three-electrode system electrolytic cell consisting of an iron plate as the counter electrode and a saturated calomel electrode as the reference electrode; then prepare an electrolyte aqueous solution: 0.1mol/L Fe ²⁺ +2mol/LNH ₄ Cl, in which 20mA/cm ² constant The deposition experiment and cyclic voltammetry scanning experiment of flow deposition for 15 minutes were carried out to obtain the iron deposition morphology (Figure 4) and cyclic voltammetry curve (Figure 5) of the prepared high-performance carbon felt and the original carbon felt respectively. As shown in Figure 4, the metallic iron deposited on the surface of the original carbon felt shows an uneven deposition morphology of obvious clusters, while the surface of the high-performance carbon felt prepared in this example shows a uniform and dense iron deposition morphology. It shows that the high-performance carbon felt electrode prepared by the method of the present invention can effectively improve the iron deposition morphology. At the same time, as shown in Figure 5, it can be seen from the redox peak potential difference and peak current in the cyclic voltammetry curve that the prepared high-performance carbon felt electrode is good for the positive electrode reaction (Fe ³⁺ /Fe ²⁺ ). Both the negative electrode reaction (Fe ²⁺ /Fe) and the negative electrode reaction (Fe 2+ /Fe) have good electrochemical activity.

Example 5

In order to simplify the description, the preparation process of Example 5 is the same as that of Example 1, and the electrochemical performance of the prepared high-performance carbon felt electrode is characterized in an iron-chromium flow battery electrolytic cell. The only difference between the operation steps and the electrochemical characterization in the mixed all-iron liquid flow system is that the electrolyte composition is: 0.1mol/L Fe ²⁺ +3mol/L HCl (positive electrode) and 0.1mol/LCr ³⁺ +3mol/ L HCl (negative electrode). The results of the cyclic voltammetry curve are shown in Figure 6. The high-performance carbon felt electrode prepared by this method has the smallest redox peak position difference and the largest peak current. Compared with the original carbon felt, it shows superior electrochemical activity. This further demonstrates the universal applicability and generalizability of the electrode prepared by this method for improving the electrochemical reaction activity of iron-based redox flow batteries.

Example 6

In order to simplify the description, the preparation process of Example 6 is the same as that of Example 1. In this embodiment, the prepared high-performance carbon felt electrodes or original carbon felt electrodes are used as positive and negative electrodes to assemble a hybrid all-iron flow battery. The battery follows the instructions of end plate-bipolar plate-electrode-perfluorosulfonic acid membrane. -The structure of electrode-bipolar plate-end plate is assembled in sequence. The battery was subjected to a constant current charge and discharge test at 20mA/ ^cm2 , and the results are shown in Figure 7. The results show that compared with the original carbon felt, the prepared high-performance carbon felt electrode has higher Coulombic efficiency and longer cycle life.

Example 7

In order to simplify the description, the preparation process of Example 7 is the same as that of Example 1. In this embodiment, the prepared high-performance carbon felt electrode is applied to an iron-chromium flow battery. The battery is assembled in the same manner as in Example 5. The battery is charged and discharged at a constant current within an electrical density range of 60 to 120 mA/cm ² rate performance test. The results show that the battery has high Coulombic efficiency and energy under various electrically tight operating conditions, which fully demonstrates that the prepared electrode has excellent electrochemical activity, can significantly reduce battery polarization, and improve the reversibility of electrochemical reactions. , improve battery performance.

Although the above-described embodiments only describe several implementations of the present invention, they are not to be construed as limiting the scope of the present invention. It is obvious to those skilled in the art that if other changes and modifications are made to the present invention without departing from the spirit and scope of the present invention, they should be covered by the claims of the present invention.

Claims (8)

1. The preparation method of the high-performance carbon felt electrode for the iron-based flow battery is characterized by comprising the following steps of:

step 1) putting enough metal oxide powder and a raw carbon felt into a fluidized bed dryer, drying and fully mixing to fully load the metal oxide powder on the surface of carbon felt fibers;

step 2) taking out the carbon felt, placing the carbon felt in a quartz tube furnace, heating to 1000-1500 ℃ at a constant rate under a protective atmosphere, preserving heat for 1-2 hours at the temperature, performing carbothermic reduction treatment, and naturally cooling to room temperature;

and 3) soaking the treated carbon felt in sulfuric acid solution, performing ultrasonic vibration treatment, then flushing with deionized water, and drying to obtain the iron-based flow battery high-performance carbon felt electrode.

2. The method for producing a high-performance carbon felt electrode for an iron-based flow battery according to claim 1, wherein in step 1), the metal oxide powder is FeO or Fe ₃ O ₄ 、Cr ₂ O ₃ One or more of CuO, and the particle size of the metal oxide powder is 10-105 μm.

3. The method for producing a high-performance carbon felt electrode for an iron-based flow battery according to claim 1, wherein in step 1), the average pore diameter of the raw carbon felt is 3 to 6nm, the average fiber diameter is 8 to 12 μm, and the average BET specific surface area is 5 to 20 square meters/g.

4. The method for producing a high-performance carbon felt electrode for an iron-based flow battery according to claim 1, wherein in step 1), the fluidized bed drying and mixing time is 20 to 40 minutes.

5. The method for preparing the high-performance carbon felt electrode for the iron-based flow battery according to claim 1, wherein in the step 2), the protective atmosphere is one or two mixed gases of nitrogen and argon, and the heating rate is 5-10 ℃/min.

6. The method for preparing the high-performance carbon felt electrode for the iron-based flow battery according to claim 1, wherein in the step 3), the concentration of sulfuric acid solution is 4.0-7.0 mol/L, and the ultrasonic vibration treatment time is 20-40 min.

7. The method for preparing the high-performance carbon felt electrode for the iron-based flow battery, which is disclosed in claim 1, is characterized in that the BET specific surface area of the carbon felt is increased by etching an irregular hole structure rich in edge carbon defects on the surface of the carbon felt fiber, the contact angle of the carbon felt electrode is 0 DEG, the polarization of the positive electrode and the negative electrode of the battery is effectively improved, the negative iron has uniform and compact deposition morphology, and the energy efficiency and the cycle life of the battery are improved.

8. Use of a high performance carbon felt electrode prepared according to the method of any one of claims 1 to 7 in an iron-based flow battery.