A trans-perovskite composite graphite felt electrode and a preparation method and application thereof

Abstract

The application relates to the technical field of electrodes of all-vanadium redox flow batteries, and discloses a trans-perovskite composite graphite felt electrode and a preparation method and application thereof, which comprises the following steps: trans-perovskite preparation; trans-perovskite composite graphite felt electrode preparation; the application uses the trans-perovskite rich in cations and introduces metal Sr, improves the conductivity of the composite graphite felt electrode, and has obvious effects of improving the voltage efficiency and energy efficiency of the battery, reducing the increased activation polarization and ohmic polarization of V2O5 deposition electrodes at high temperatures, and through the introduction of non-metal P and Cl, the P and Cl ions carrying lone pair electrons can be coordinated with water and vanadium ions in an electrolyte to form V-O-P and V-O-Cl intermediates which are lower in reaction energy barrier and more stable, the formation of V-O-V is reduced, the generation selectivity of V2O5 deposition is reduced, and the battery efficiency is further improved.

Description

Technical Field

[0001] This invention relates to the field of graphite felt electrode technology for all-vanadium redox flow batteries, and particularly to an inverse perovskite composite graphite felt electrode, its preparation method, and its application. Background Technology

[0002] Among various flow batteries, the vanadium redox flow battery (vanadium battery for short) is considered one of the most promising large-scale energy storage batteries due to its reduced cross-contamination between positive and negative electrode materials, high electrochemical reversibility, and greatly extended electrolyte lifespan.

[0003] However, due to the limited solubility of V(Ⅴ) in sulfuric acid, the hydrated pentavalent ion [VO₂(H₂O)₃] is exposed to temperatures above 40°C. + The condensation reaction of proton exchange to form VOV bonds is easily precipitated, and the generated V2O5 is deposited on the electrode, resulting in increased electrode polarization resistance and rapid performance degradation, which affects the long-term service life of the battery. This greatly limits the normal operation of vanadium redox flow batteries in extreme regions and hinders their widespread application. Therefore, it is necessary to develop a graphite felt electrode for high-temperature use, which is of great significance to the development of vanadium battery technology. Summary of the Invention

[0004] This invention provides a trans-perovskite composite graphite felt electrode, its preparation method, and its application, overcoming the above-mentioned problems.

[0005] In the first aspect, a method for preparing an inverse perovskite composite graphite felt electrode is disclosed, comprising the following steps:

[0006] Step S1: Strontium oxide, strontium phosphate and strontium chloride are mixed in proportion and ground evenly in a mortar in a glove box. Then, they are transferred to a ball mill jar lined with zirconium oxide for ball milling and mixing. After vacuum calcination and cooling to room temperature, trans-perovskite powder is obtained.

[0007] Step S2: Disperse the trans-perovskite powder in a perfluorosulfonic acid resin solution to obtain an impregnation solution;

[0008] Step S3: Immerse the pretreated graphite felt in the impregnation solution for physical impregnation, and then dry it to obtain the trans-perovskite composite graphite felt electrode.

[0009] In one implementation, in step S1:

[0010] The molar ratio of strontium oxide, strontium phosphate and strontium chloride is x:(1-x):1; where 0.1≤x≤0.9.

[0011] The introduction of strontium is beneficial to improving the conductivity of the composite graphite felt electrode and reducing the increase in activation polarization and ohmic polarization caused by V2O5 deposition on the electrode at high temperatures. P and Cl ions carrying lone pair electrons can coordinate with water and vanadium ions in the electrolyte to form VOP and VO-Cl intermediates with lower reaction barriers and greater stability, reducing the formation of VOV and decreasing the selectivity of V2O5 precipitation.

[0012] In one implementation, in step S1:

[0013] The grinding time in the mortar is 10-30 minutes;

[0014] The ball milling process is as follows: rotation speed 300~500 rpm, ball milling time 4~12 h, and zirconium oxide diameter 4~10 mm.

[0015] In one implementation, in step S1:

[0016] The vacuum calcination process is as follows: under vacuum conditions, calcination is carried out at 700~900℃ for 2~4 hours, with a heating rate of 2~6℃ / min and a cooling rate of 2~4℃ / min, until the temperature is reduced to 25℃.

[0017] In one implementation, in step S2:

[0018] The concentration of the perfluorosulfonic acid resin solution is 5 wt%;

[0019] The concentration of trans-perovskite in the impregnation solution is 1 g / L.

[0020] Trans-perovskite is a metal oxide with unique cation-rich properties. With higher metal doping levels, it has better conductivity and can effectively improve the voltage efficiency and energy efficiency of batteries.

[0021] In one implementation, in step S3:

[0022] The physical impregnation time is 12~24h, and the temperature is 20~60℃;

[0023] The drying temperature is 50°C.

[0024] Physical impregnation and low-temperature drying can effectively prevent the loss of non-metallic atoms P and Cl.

[0025] In one embodiment, the pretreated graphite felt in step S3 is obtained by heat-treating the graphite felt, then washing it with dilute hydrochloric acid and ultrapure water, and finally drying it.

[0026] Pretreatment can improve the defects and oxygen-containing groups on the surface of graphite felt fibers, which is beneficial for the subsequent loading of trans-perovskite onto the fibers.

[0027] In one embodiment, the heat treatment process is as follows: under a nitrogen atmosphere, the temperature is held at 400~500℃ for 3~5 hours, and the heating rate is 3~6℃ / min;

[0028] The concentration of the dilute hydrochloric acid is 2 mol / L;

[0029] The drying process is carried out at a temperature of 50°C.

[0030] Secondly, a trans-perovskite composite graphite felt electrode is disclosed, which is prepared by the above-described method for preparing trans-perovskite composite graphite felt electrodes.

[0031] Thirdly, an application of an inverted perovskite composite graphite felt electrode is disclosed, wherein the inverted perovskite composite graphite felt electrode prepared by the above-described preparation method or the inverted perovskite composite graphite felt electrode described above is applied to an all-vanadium redox flow battery.

[0032] Beneficial effects of the present invention

[0033] 1. This invention improves the conductivity of the composite graphite felt electrode by introducing metallic Sr, reduces the increased activation polarization and ohmic polarization during V2O5 deposition at high temperatures, and improves the voltage efficiency and energy efficiency of the battery.

[0034] 2. By introducing non-metallic P and Cl, the P and Cl ions carrying lone pairs of electrons can coordinate with water and vanadium ions in the electrolyte to form VOP and VO-Cl intermediates with lower reaction energy barriers and greater stability, thereby reducing the formation of VOV, reducing the selectivity of V2O5 precipitation, and further improving battery efficiency.

[0035] 3. The trans-perovskite used in this invention has unique cation-rich characteristics compared to conventional formal metal oxides, with higher metal doping content, better conductivity, and more significant improvement in battery voltage efficiency and energy efficiency. Attached Figure Description

[0036] Figure 1 This is a mapping diagram of the trans-perovskite composite graphite felt electrode of Embodiment 1 of the present invention. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. However, it should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0038] A method for preparing an inverse perovskite composite graphite felt electrode includes the following steps:

[0039] Step S1: Place the graphite felt in a nitrogen atmosphere in an atmosphere furnace and heat it at 400~500℃ for 3~5h with a heating rate of 3~6℃ / min. After heat treatment, the graphite felt is washed with 2mol / L hydrochloric acid and ultrapure water and dried in an oven at 50℃ to obtain pretreated graphite felt.

[0040] Step S2: In a glove box, strontium oxide, strontium phosphate, and strontium chloride are mixed in a certain proportion and ground evenly using a mortar. The mixed powder is then transferred to a ball mill jar lined with zirconia for ball milling. The ball-milled powder is then calcined under vacuum and cooled to room temperature to obtain trans-perovskite powder. The molar concentration ratio of strontium oxide, strontium phosphate, and strontium chloride is x:(1-x):1, 0.1≤x≤0.9; the mortar grinding time is 10~30min. The ball milling process is as follows: rotation speed 300~500rpm, ball milling time 4~12h, zirconia diameter 4~10mm. The calcination process is as follows: vacuum calcination at 700~900℃ for 2~4h, heating rate 2~6℃ / min, cooling rate 2~4℃ / min, reducing to 25℃.

[0041] Step S3: Disperse trans-perovskite powder in a 5wt% perfluorosulfonic acid resin solution to obtain an impregnation solution containing 1g / L trans-perovskite; immerse the pretreated graphite felt in the impregnation solution for physical impregnation, and then dry it in a 50℃ oven to obtain a trans-perovskite composite graphite felt electrode. The physical impregnation time is 12~24h, and the temperature is 20~60℃.

[0042] Example 1: This example is obtained through the following operations.

[0043] Step S1: Place the graphite felt in an atmosphere furnace and heat treat it at 400℃ for 5 hours. The heating rate is 3℃ / min. After treatment, the graphite felt is washed with 2mol / L hydrochloric acid and ultrapure water and dried in an oven at 50℃ to obtain pretreated graphite felt.

[0044] Step S2: In a glove box, 0.001 mol of strontium oxide, 0.009 mol of strontium phosphate, and 0.01 mol of strontium chloride powder were mixed and ground in a mortar for 10 min. The mixture was then transferred to a ball mill jar with a 4 mm zirconium oxide liner and ball-milled at 300 rpm for 4 h. The resulting precursor powder was then sintered at 700 °C for 4 h under vacuum, with a heating rate of 2 °C / min and a cooling rate of 2 °C / min, to obtain trans-perovskite Sr3O. 0.1 P 0.9 Cl.

[0045] Step S3: The trans-perovskite Sr3O obtained in the above steps0.1 P 0.9 Cl powder was dispersed in a 5 wt% perfluorosulfonic acid resin solution to obtain an impregnation solution containing 1 g / L trans-perovskite. Pretreated graphite felt was placed in the impregnation solution and immersed at 60°C for 12 h. After impregnation, it was dried in a 50°C oven to obtain Sr3O. 0.1 P 0.9 Cl composite graphite felt.

[0046] Example 2: This example is obtained through the following operations.

[0047] Step S1: Place the graphite felt in an atmosphere furnace and heat treat it at 425℃ for 4.5h with a heating rate of 3℃ / min. After treatment, the graphite felt is washed with 2mol / L hydrochloric acid and ultrapure water and dried in an oven at 50℃ to obtain pretreated graphite felt.

[0048] Step S2: In a glove box, 0.01 mol of strontium oxide, 0.03 mol of strontium phosphate, and 0.04 mol of strontium chloride powder were mixed and ground in a mortar for 15 min. The mixture was then transferred to a 5 mm zirconium oxide-lined ball mill jar and ball-milled at 350 rpm for 6 h. The resulting precursor powder was sintered at 750 °C for 3.5 h under vacuum, with a heating rate of 3 °C / min and a cooling rate of 2 °C / min, to obtain trans-perovskite Sr3O. 0.25 P 0.75 Cl.

[0049] Step S3: The trans-perovskite Sr3O obtained in the above steps 0.25 P 0.75 Cl powder was dispersed in a 5 wt% perfluorosulfonic acid resin solution to obtain an impregnation solution containing 1 g / L trans-perovskite. Pretreated graphite felt was placed in the impregnation solution and immersed at 40°C for 15 h. After impregnation, it was dried in a 50°C oven to obtain Sr3O. 0.25 P 0.75 Cl composite graphite felt.

[0050] Example 3: This example is obtained through the following operations.

[0051] Step S1: Place the graphite felt in an atmosphere furnace and heat treat it at 450℃ for 4 hours. The heating rate is 4℃ / min. After treatment, the graphite felt is washed with 2mol / L hydrochloric acid and ultrapure water and dried in an oven at 50℃ to obtain pretreated graphite felt.

[0052] Step S2: In a glove box, 0.03 mol of strontium oxide, 0.03 mol of strontium phosphate, and 0.06 mol of strontium chloride powder were mixed and ground in a mortar for 20 min. The mixture was then transferred to a 6 mm zirconium oxide-lined ball mill jar and ball-milled at 400 rpm for 8 h. The resulting precursor powder was then sintered at 800 °C for 3 h under vacuum, with a heating rate of 4 °C / min and a cooling rate of 3 °C / min, to obtain trans-perovskite Sr3O. 0.5 P 0.5 Cl.

[0053] Step S3: The trans-perovskite Sr3O obtained in the above steps 0.5 P 0.5 Cl powder was dispersed in a 5 wt% perfluorosulfonic acid resin solution to obtain an impregnation solution containing 1 g / L trans-perovskite. Pretreated graphite felt was placed in the impregnation solution and immersed at 30°C for 18 h. After impregnation, it was dried in a 50°C oven to obtain Sr3O. 0.5 P 0.5 Cl composite graphite felt.

[0054] Example 4: This example is obtained through the following operations.

[0055] Step S1: Place the graphite felt in an atmosphere furnace and heat treat it at 475℃ for 3.5h with a heating rate of 5℃ / min. After treatment, the graphite felt is washed with 2mol / L hydrochloric acid and ultrapure water and dried in an oven at 50℃ to obtain pretreated graphite felt.

[0056] Step S2: In a glove box, 0.06 mol of strontium oxide, 0.02 mol of strontium phosphate, and 0.08 mol of strontium chloride powder were mixed and ground in a mortar for 25 min. The mixture was then transferred to an 8 mm zirconium oxide-lined ball mill jar and ball-milled at 450 rpm for 10 h. The resulting precursor powder was sintered at 850 °C for 2.5 h under vacuum, with a heating rate of 5 °C / min and a cooling rate of 4 °C / min, to obtain trans-perovskite Sr3O. 0.75 P 0.25 Cl.

[0057] Step S3: The trans-perovskite Sr3O obtained in the above steps 0.75 P 0.25 Cl powder was dispersed in a 5 wt% perfluorosulfonic acid resin solution to obtain an impregnation solution containing 1 g / L trans-perovskite. Pretreated graphite felt was placed in the impregnation solution and immersed at 25°C for 21 h. After impregnation, it was dried in a 50°C oven to obtain Sr3O. 0.75 P 0.25 Cl composite graphite felt.

[0058] Example 5: This example is obtained through the following operations.

[0059] Step S1: Pretreatment of graphite felt: The graphite felt is placed in an atmosphere furnace and heat-treated at 50°C for 3 hours with a heating rate of 6°C / min. The treated graphite felt is then washed with 2mol / L hydrochloric acid and ultrapure water and dried in a 50°C oven to obtain pretreated graphite felt.

[0060] Step S2, Preparation of trans-perovskite: 0.09 mol of strontium oxide, 0.01 mol of strontium phosphate, and 0.1 mol of strontium chloride powder were mixed in a glove box and ground in a mortar for 30 min. The mixture was then transferred to a 10 mm zirconium oxide-lined ball mill jar and ball-milled at 500 rpm for 12 h. The resulting precursor powder was sintered at 900 °C for 2 h under vacuum, with a heating rate of 6 °C / min and a cooling rate of 4 °C / min, to obtain trans-perovskite Sr3O. 0.9 P 0.1 Cl.

[0061] Step S3, Preparation of trans-perovskite composite graphite felt electrode: The trans-perovskite Sr3O prepared in the above steps 0.9 P 0.1 Cl powder was dispersed in a 5 wt% perfluorosulfonic acid resin solution to obtain an impregnation solution containing 1 g / L trans-perovskite. The pretreated graphite felt was placed in the impregnation solution and soaked at 20°C for 24 h. After impregnation, it was dried in a 50°C oven to obtain Sr3O. 0.9 P 0.1 Cl composite graphite felt.

[0062] Comparative Example 1: The following technical solution is adopted.

[0063] This comparative example serves as a blank control group, using untreated graphite felt as the electrode.

[0064] Comparative Example 2: The following technical solution is adopted.

[0065] The only difference between the preparation process of the comparative graphite felt electrode and that of Example 1 is that the pretreated graphite felt obtained in step S1 was soaked in a 0.01M phosphoric acid / hydrochloric acid mixture for 24 hours.

[0066] Comparative Example 3: The following technical solution is adopted.

[0067] The only difference between the preparation process of the graphite felt electrode in this comparative example and that in Example 1 is that strontium chloride is not added in step S2.

[0068] Comparative Example 4: The following technical solution is adopted.

[0069] The only difference between the preparation process of the graphite felt electrode in this comparative example and that in Example 1 is that strontium phosphate is not added in step S2.

[0070] Comparative Example 5: The following technical solution is adopted.

[0071] The only difference between the preparation process of the graphite felt electrode in this comparative example and that in Example 1 is the addition of 0.05 mol strontium oxide, 0.08 mol strontium phosphate, and 0.01 mol strontium chloride in step S2.

[0072] Comparative Example 6: The following technical solution was adopted.

[0073] The only difference between the preparation process of the graphite felt electrode in this comparative example and that in Example 1 is that strontium chloride and strontium phosphate are not added in step S2.

[0074] Battery testing: The graphite felts prepared in Examples 1-5 and Comparative Examples 1-5 were assembled into fuel cells and subjected to charge-discharge tests under the same test conditions. The coulombic efficiency, voltage efficiency, energy efficiency, and whether there was deposit adhesion on the electrodes at 50°C were recorded. The test results are shown in Table 1.

[0075] Table 1. Electrode performance and high-temperature stability test results for the examples and comparative examples.

[0076]

[0077] As can be seen from Table 1, Examples 1-5 are combined Figure 1 Compared to Comparative Example 1, it exhibits higher energy, voltage efficiency, and discharge capacity, indicating that the present invention effectively improves the reactivity of the electrode, demonstrating the superior performance of the three-dimensional material Sr3O. 0.1 P 0.9 Cl optimizes the adsorption of vanadium ions in the flow battery, catalyzes the redox ability of vanadium, lowers the reaction energy barrier, and improves the battery's energy efficiency. Comparing Example 1 and Comparative Example 2, Example 1 exhibits higher energy, voltage efficiency, and discharge capacity, indicating that the introduction of metallic Sr improves the conductivity of the composite graphite felt electrode, reduces the increased activation polarization and ohmic polarization during V2O5 deposition at high temperatures, and improves the battery's voltage and energy efficiency. Comparing Example 1 and Comparative Examples 3-4, Example 1 shows more stable electrode operation at 50°C with no V2O5 precipitate adhesion, indicating that the introduction of non-metallic P and Cl allows P and Cl ions carrying lone pairs of electrons to coordinate with water and vanadium ions in the electrolyte, forming VOP and VO-Cl intermediates with lower and more stable reaction energy barriers, reducing VOV formation, lowering the selectivity of V2O5 precipitation, and further improving battery efficiency. Comparing Example 1 and Comparative Examples 5-6, Example 1 exhibits higher energy efficiency, voltage efficiency, and high-temperature stability. Since Comparative Example 6 did not form an effective trans-perovskite structure, this indicates that the trans-perovskite Sr3O used in this invention... 0.1 P 0.9 Compared to conventional formal metal oxides (strontium oxide), Cl has unique cation-rich characteristics, higher metal doping content, better conductivity, and more significant effects on improving battery voltage efficiency and energy efficiency.

[0078] 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 or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing an inverse perovskite composite graphite felt electrode, characterized in that, Includes the following steps: Step S1: Strontium oxide, strontium phosphate, and strontium chloride are mixed in a certain proportion and ground evenly in a mortar and pestle in a glove box. Then, the mixture is transferred to a ball mill jar lined with zirconium oxide for ball milling and mixing. Afterward, it is calcined under vacuum and cooled to room temperature to obtain trans-perovskite powder. The molar ratio of strontium oxide, strontium phosphate, and strontium chloride is x:(1-x):1, where 0.1≤x≤0.

9. Step S2: Disperse the trans-perovskite powder in a perfluorosulfonic acid resin solution to obtain an impregnation solution; the concentration of the perfluorosulfonic acid resin solution is 5 wt%; the concentration of trans-perovskite in the impregnation solution is 1 g / L; Step S3: Immerse the pretreated graphite felt in the impregnation solution for physical impregnation, and then dry to obtain an inverse perovskite composite graphite felt electrode; the physical impregnation time is 12~24h, and the temperature is 20~60℃; the drying temperature is 50℃; the pretreated graphite felt is obtained by heat-treating the graphite felt, then washing it with dilute hydrochloric acid and ultrapure water, and then drying it; the heat treatment process is as follows: under a nitrogen atmosphere, hold at 400~500℃ for 3~5h, with a heating rate of 3~6℃ / min; the concentration of the dilute hydrochloric acid is 2mol / L; the drying temperature is 50℃.

2. The preparation method according to claim 1, characterized in that, In step S1: The grinding time in the mortar is 10-30 minutes; The ball milling process is as follows: rotation speed 300~500 rpm, ball milling time 4~12 h, and zirconium oxide diameter 4~10 mm.

3. The preparation method according to claim 1, characterized in that, In step S1: The vacuum calcination process is as follows: under vacuum conditions, calcination is carried out at 700~900℃ for 2~4 hours, with a heating rate of 2~6℃ / min and a cooling rate of 2~4℃ / min, until the temperature is reduced to 25℃.

4. A trans-perovskite composite graphite felt electrode, wherein the trans-perovskite composite graphite felt electrode is prepared by the preparation method of the trans-perovskite composite graphite felt electrode as described in any one of claims 1-3.

5. An application of a trans-perovskite composite graphite felt electrode, characterized in that, The inverted perovskite composite graphite felt electrode prepared by the preparation method according to any one of claims 1-3 or the inverted perovskite composite graphite felt electrode according to claim 4 is applied to an all-vanadium redox flow battery.

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