Bimetal particle loaded graphite felt electrode material and preparation method and application thereof

Abstract

The invention relates to a preparation method of a bimetallic particle loaded graphite felt electrode material, which comprises the following steps: (1) carrying out in-situ state recovery on a flow battery system to ensure that the flow battery system is in an initial state; (2) weighing a certain amount of metal modifier, adding the metal modifier into a certain amount of concentrated hydrochloric acid, and magnetically stirring until the metal modifier is completely dissolved to obtain an electroplating solution A; (3) adding a certain amount of electroplating liquid A into the negative electrode electrolyte, starting a liquid path circulation system, and fully rinsing the graphite felt by the electroplating liquid; and (4) performing electrochemical deposition through a pulse type electroplating method, and stopping electroplating when the voltage reaches a specified value. Through in-situ online improvement, the preparation process is simple, the cost is low, the battery structure is not changed, the method is suitable for flow battery stacks of various models and sizes, the loading capacity and uniformity of metal particles can be controlled by adjusting the pulse process and the electroplating liquid concentration, the prepared composite electrode material can effectively improve the performance of the battery, and the application prospect is wide. And the system efficiency is obviously improved.

Description

Technical Field

[0001] This invention relates to the field of electrode materials technology, and more specifically, to a bimetallic particle-supported graphite felt electrode material, its preparation method, and its application. Background Technology

[0002] As the global energy structure transitions towards cleaner and lower-carbon energy, large-scale energy storage technology has become crucial for addressing the intermittency and volatility issues of renewable energy sources such as wind and solar power. Among numerous energy storage technologies, flow batteries are considered one of the most promising large-scale energy storage technologies due to their outstanding advantages, including power-capacity decoupling, high safety, and long cycle life.

[0003] Iron-chromium (FeCr) flow batteries, as the earliest proposed flow battery system, possess unique advantages such as abundant raw material reserves, low cost, and environmental friendliness. Their working principle is based on Cr... 3+ / Cr 2+ The redox couple (negative electrode) and Fe 2+ / Fe 3+ Redox reactions between redox couples (positive electrodes). In the entire battery system, the electrodes are the sites of electrochemical reactions, and their performance directly determines the battery's energy efficiency, power density, and long-term cycle stability.

[0004] However, the reaction kinetics of the negative electrode chromium couple are slow: Cr 3+ / Cr 2+ The reaction rate constant of the redox couple is much lower than that of the Fe at the cathode. 2 + / Fe 3+ The high polarization voltage of the battery, especially at high current densities, leads to a significant reduction in voltage and energy efficiency. This has become a core bottleneck restricting the performance improvement of iron-chromium redox flow batteries.

[0005] Currently, existing technologies employ offline methods for improvement. However, these methods require disassembling and desealing the iron-chromium flow battery, a cumbersome process that also presents challenges in achieving homogenization. Therefore, targeted in-situ modification of the graphite felt electrode to enhance its electrochemical activity (especially its catalytic activity for the chromium reaction) and suppress hydrogen evolution is crucial for the commercial application of iron-chromium flow battery technology. Summary of the Invention

[0006] The purpose of this invention is to solve the problem of Cr 3+ / Cr 2+ The reaction rate constant of the redox couple is much lower than that of the Fe at the cathode. 2+ / Fe 3+The high polarization voltage of the iron-chromium redox flow battery, especially at high current densities, leads to a significant reduction in voltage and energy efficiency. Existing technologies employ offline methods to improve this, but these methods require disassembling and desealing the battery, are cumbersome, and suffer from difficulties in homogenization. This invention provides a bimetallic particle-loaded graphite felt electrode material, its preparation method, and its applications. This invention utilizes a pulse electroplating method to modify the negative electrode material in an iron-chromium redox flow battery, improving the Cr... 3+ / Cr 2+ The reactivity of the redox couple can improve the performance of the battery.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solution: The present invention provides a method for preparing a bimetallic particle-supported graphite felt electrode material, comprising the following steps: (1) Perform in-situ state restoration on the flow battery system to ensure that the flow battery system is in its initial state; (2) Weigh a certain amount of metal modifier, add it to a certain amount of concentrated hydrochloric acid, and stir magnetically until the metal modifier is completely dissolved to obtain electroplating solution A; (3) Add a certain amount of electroplating solution A to the negative electrode electrolyte, start the liquid circulation system, and let the electroplating solution fully wet the graphite felt; (4) Electrochemical deposition is carried out by pulse electroplating. Electroplating is stopped when the voltage reaches the specified value.

[0008] According to claim 1, the method for preparing a bimetallic particle-supported graphite felt electrode material is characterized in that the in-situ recovery method of the flow battery system in step (1) is multiple low-current discharges, specifically as follows: 1) At 80-100 mA / cm 2 Discharge under constant current condition, cutoff voltage 0.2-0.3 V / cell; 2) At 40-60 mA / cm 2 Discharge under constant current condition, cutoff voltage 0.1-0.2 V / cell; 3) At 20-40 mA / cm 2 Discharge under constant current condition, cutoff voltage 0-0.01 V / cell.

[0009] Furthermore, in step (1) of this invention, the criterion for determining the initial state of the flow battery system is that the voltage of a single cell of the stack is ≤0.1 V / cell under the pump operating state.

[0010] Furthermore, the metal modifier in step (2) of this invention is any two of the following four pairs: bismuth oxide or bismuth chloride, tin oxide or stannous chloride, lead chloride or lead oxide, and indium chloride, and the concentration of the metal modifier is 4-15 mmol / L.

[0011] Furthermore, in step (2) of this invention, the mass-volume ratio of the metal modifier to concentrated hydrochloric acid is 1:(8-12).

[0012] Furthermore, in step (3) of this invention, the amount of electroplating solution A added is positively correlated with the surface area of ​​the graphite felt, and the ratio of the total surface area of ​​electroplating solution A to that of the negative electrode graphite felt is 0.08-0.16 mL / cm². 2 .

[0013] Furthermore, in step (4) of this invention, the pulse current of the pulse electroplating method is 5-10 mA / cm. 2 Constant current; pulse duration 4-10 min; turn-off time 2-5 min; pulse count 5-10 times; cut-off voltage 0.9 V / section. The pulse cut-off voltage of 0.9 V in this invention is a slightly larger cut-off potential than the theoretical value, calculated based on the reduction potentials of the four metal ions and the ions in the electrolyte. When the cut-off voltage is below 0.9 V, the number of metal particles loaded is small, and the particle distribution uniformity is poor; while in the 0.9-1.2 V range, there is no significant effect, and the voltage rises rapidly; above 1.2 V, irreversible damage will be caused to the graphite felt.

[0014] The present invention also provides a method for preparing a bimetallic particle-loaded graphite felt electrode material, and the resulting bimetallic particle-loaded graphite felt electrode material is obtained.

[0015] The present invention also provides an application of a bimetallic particle-supported graphite felt electrode material.

[0016] This invention addresses the problems of low activity, poor mass transfer, and insufficient stability of traditional graphite felt by loading bimetallic ions onto graphite felt electrode materials. The deposited metal ions serve as electrocatalytic active centers, reducing the activation energy of the reaction, accelerating ion oxidation-reduction, and lowering the overpotential.

[0017] This invention improves the battery structure in situ online, resulting in a simple and low-cost preparation process that does not alter the battery structure. It is applicable to flow battery stacks of various sizes and models. Furthermore, the loading and uniformity of metal particles can be controlled by adjusting the pulse process and the concentration of the electroplating solution. The prepared composite electrode material can effectively improve battery performance and significantly enhance system efficiency. Attached Figure Description

[0018] Figure 1 This is an electron microscope image of the bimetallic particle-supported graphite felt electrode material prepared in Example 1 of the present invention; Figure 2 This is an electron microscope image of the bimetallic particle-loaded graphite felt electrode material prepared in Example 2 of the present invention; Figure 3The voltage efficiency diagrams for Embodiments 1-2 and Comparative Examples 1-3 of the present invention after 5 cycles are shown. Figure 4 The diagram shows the energy efficiency of Embodiments 1-2 and Comparative Examples 1-3 after 5 cycles. Detailed Implementation

[0019] To facilitate understanding of the technical solution of the present invention, the principles and features of the present invention will be described below in conjunction with specific embodiments. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention. Example 1

[0020] The preparation method of a bimetallic particle-supported graphite felt electrode material according to this embodiment includes the following steps: (1) The 90-cell flow battery system that has been in operation was restored to its original state. The restoration method is as follows: 1) At 80-100 mA / cm 2 Discharge under constant current condition, with a cutoff voltage of 20 V; 2) At 40-60 mA / cm 2 Discharge under constant current condition, with a cutoff voltage of 15 V; 3) At 20-40 mA / cm 2 Discharge under constant current condition, cutoff voltage 1 V; Under pump operating conditions, the voltage of a single fuel cell stack section is determined to be ≤0.1 V / section.

[0021] (2) Weigh 108 g of anhydrous stannous chloride and 86 g of bismuth chloride, add 1 L of concentrated hydrochloric acid, and stir magnetically until completely dissolved. The resulting solution is electroplating solution A. Then add the prepared electroplating solution A to the negative electrode electrolyte of the flow battery system and wait for the liquid circuit to circulate for half an hour.

[0022] (3) Set the pulse constant current to 10 mA / cm 2 The pulse duration is 10 min, the turn-off time is 5 min, the number of pulses is 10, and the cut-off voltage is 81 V.

[0023] (4) Using the above method, tin and bismuth particles were loaded onto the negative electrode graphite felt to obtain a finished electroplating stack of 90 sections. The bimetallic particle-loaded graphite felt electrode material obtained in this embodiment was subjected to electron microscopy scanning (see attached figure). Figure 1 As can be seen from the figure, the modified particles exhibit highly uniform morphology, with a concentrated particle size distribution and no obvious agglomeration, demonstrating excellent dispersion among particles. The modified particles have regular surface morphology and clear outlines, with no impurity particles attached or local defects, fully indicating that the modification process has achieved uniform modification of the particle surface, laying a good structural foundation for improving the electrochemical performance of graphite felt.

[0024] The bimetallic particle-supported graphite felt electrode material prepared in this embodiment was used in a negative electrode flow battery at 140 mA / cm². 2 At current density, the performance of the fuel cell stack was tested, and the results were obtained. Figure 3 and Figure 4 ,from Figure 3 As can be seen, compared with the blank sample, the voltage efficiency of this embodiment is 1.5% higher. From Figure 4 As can be seen, the energy efficiency of this embodiment is 2% higher than that of the blank sample, proving that the method for loading bimetallic particles is effective. Example 2

[0025] The preparation method of a bimetallic particle-supported graphite felt electrode material according to this embodiment includes the following steps: (1) The 90-cell flow battery system that has been in operation was restored to its original state. The restoration method is as follows: 1) At 80-100 mA / cm 2 Discharge under constant current condition, with a cutoff voltage of 20 V; 2) At 40-60 mA / cm 2 Discharge under constant current condition, with a cutoff voltage of 15 V; 3) At 20-40 mA / cm 2 Discharge under constant current condition, cutoff voltage 1 V; Under pump operating conditions, the voltage of a single fuel cell stack section is determined to be ≤0.1 V / section.

[0026] (2) Weigh 108 g of lead chloride and 86 g of bismuth chloride, add 1 L of concentrated hydrochloric acid, and stir magnetically until completely dissolved. The resulting solution is electroplating solution A. Then add the prepared electroplating solution A to the negative electrode electrolyte of the flow battery system and wait for the liquid circuit to circulate for half an hour.

[0027] (3) Set the pulse constant current to 10 mA / cm 2 The pulse duration is 10 min, the turn-off time is 5 min, the number of pulses is 10, and the cut-off voltage is 81 V.

[0028] (4) Using the above method, lead and bismuth particles are loaded onto the negative electrode graphite felt to obtain a finished product of 90 electroplating piles.

[0029] The bimetallic particle-loaded graphite felt electrode material prepared in this embodiment was subjected to electron microscopy scanning (see attached figure). Figure 2 As can be seen from the figure, the modified particles and attached... Figure 1 In contrast, there is uneven distribution of metal particles and local agglomeration.

[0030] The bimetallic particle-supported graphite felt electrode material prepared in this embodiment was used in a negative electrode flow battery at 140 mA / cm². 2 Under current density, the voltage efficiency and energy efficiency of the fuel cell stack were tested, and the results were obtained respectively. Figure 3 and Figure 4 ,from Figure 3 It can be seen that, compared with the blank sample, the voltage efficiency of this embodiment is 1% higher. From Figure 4 It can be seen that after 5 cycles, the energy efficiency does not change much, remaining at 74-75%. Example 3

[0031] The preparation method of a bimetallic particle-supported graphite felt electrode material according to this embodiment includes the following steps: (1) The 90-cell flow battery system that has been in operation was restored to its original state. The restoration method is as follows: 1) At 80-100 mA / cm 2 Discharge under constant current condition, with a cutoff voltage of 20 V; 2) At 40-60 mA / cm 2 Discharge under constant current condition, with a cutoff voltage of 15 V; 3) At 20-40 mA / cm 2 Discharge under constant current condition, cutoff voltage 1 V; Under pump operating conditions, the voltage of a single fuel cell stack section is determined to be ≤0.1 V / section.

[0032] (2) Weigh 60 g of indium chloride and 149 g of tin chloride, add 1 L of concentrated hydrochloric acid, and stir magnetically until completely dissolved. The resulting solution is electroplating solution A. Then add the prepared electroplating solution A to the negative electrode electrolyte of the flow battery system and wait for the liquid circuit to circulate for half an hour.

[0033] (3) Set the pulse constant current to 10 mA / cm 2 The pulse duration is 10 min, the turn-off time is 5 min, the number of pulses is 10, and the cut-off voltage is 81 V.

[0034] (4) Using the above method, lead and bismuth particles are loaded onto the negative electrode graphite felt to obtain a finished product of 90 electroplating piles. Example 4

[0035] The preparation method of a bimetallic particle-supported graphite felt electrode material according to this embodiment includes the following steps: (1) The 90-cell flow battery system that has been in operation was restored to its original state. The restoration method is as follows: 1) At 80-100 mA / cm 2 Discharge under constant current condition, with a cutoff voltage of 20 V; 2) At 40-60 mA / cm 2 Discharge under constant current condition, with a cutoff voltage of 15 V; 3) At 20-40 mA / cm 2 Discharge under constant current condition, cutoff voltage 1 V; Under pump operating conditions, the voltage of a single fuel cell stack section is determined to be ≤0.1 V / section.

[0036] (2) Weigh 127 g of lead oxide and 60 g of indium chloride, add 1 L of concentrated hydrochloric acid, and stir magnetically until completely dissolved. The resulting solution is electroplating solution A. Then add the prepared electroplating solution A to the negative electrode electrolyte of the flow battery system and wait for the liquid circuit to circulate for half an hour.

[0037] (3) Set the pulse constant current to 10 mA / cm 2 The pulse duration is 10 min, the turn-off time is 5 min, the number of pulses is 10, and the cut-off voltage is 81 V.

[0038] (4) Using the above method, lead and bismuth particles are loaded onto the negative electrode graphite felt to obtain a finished product of 90 electroplating piles. Example 5

[0039] The preparation method of a bimetallic particle-supported graphite felt electrode material according to this embodiment includes the following steps: (1) The 90-cell flow battery system that has been in operation was restored to its original state. The restoration method is as follows: 1) At 80-100 mA / cm 2 Discharge under constant current condition, with a cutoff voltage of 20 V; 2) At 40-60 mA / cm 2 Discharge under constant current condition, with a cutoff voltage of 15 V; 3) At 20-40 mA / cm 2 Discharge under constant current condition, cutoff voltage 1 V; Under pump operating conditions, the voltage of a single fuel cell stack section is determined to be ≤0.1 V / section.

[0040] (2) Weigh 61 g of lead oxide and 149 g of tin chloride, add 1 L of concentrated hydrochloric acid, and stir magnetically until completely dissolved. The resulting solution is electroplating solution A. Then add the prepared electroplating solution A to the negative electrode electrolyte of the flow battery system and wait for the liquid circuit to circulate for half an hour.

[0041] (3) Set the pulse constant current to 10 mA / cm 2 The pulse duration is 10 min, the turn-off time is 5 min, the number of pulses is 10, and the cut-off voltage is 81 V.

[0042] (4) Using the above method, lead and bismuth particles are loaded onto the negative electrode graphite felt to obtain a finished product of 90 electroplating piles.

[0043] blank sample To highlight the impact of the pulse electroplating method of this invention on the graphite felt electrode material, a blank experiment was also conducted, directly testing the stack voltage efficiency and energy efficiency of the flow battery system, and obtaining the results... Figure 3 and Figure 4 .

[0044] Comparative Example 1 The difference between this comparative example and Example 1 is that the prepared electroplating solution contains 216 g of anhydrous stannous chloride and 172 g of bismuth chloride, thus increasing the amount of metal modifier. Figure 3 and Figure 4 As can be seen, the performance of the 90-cell reactor decreased after increasing the amounts of stannous chloride and bismuth chloride, and deteriorated outside the range of additions described in the invention. Excessive dosage caused blockage in the negative electrode channel, slowing the electrolyte flow rate and thus reducing reactor performance.

[0045] Comparative Example 2 The difference between this comparative example and Example 1 is that pulse electroplating was not performed; instead, 10 mA / cm² electroplating was used directly. 2 Electroplating is performed using a constant current. From Figure 3 and Figure 4 As can be seen, the voltage efficiency of the fuel cell stack has improved, but the energy efficiency has not improved significantly. During electroplating, uneven additive concentrations in the electrolyte lead to uneven metal particles on the graphite felt. Pulse electroplating can suppress this issue to some extent.

[0046] Comparative Example 3 The difference between this comparative example and Example 1 is that the turn-off time is 1 minute. Figure 3 and Figure 4 As can be seen, the performance improvement of the fuel cell stack is not significant after shortening the turn-off time. This is because if the turn-off time is too short, the additives in the electrolyte will still be unevenly distributed. In this invention, the turn-off time is set under reasonable conditions.

Claims

1. A method for preparing a bimetallic particle-supported graphite felt electrode material, characterized in that, Includes the following steps: (1) Perform in-situ state restoration on the flow battery system to ensure that the flow battery system is in its initial state; (2) Weigh a certain amount of metal modifier, add it to a certain amount of concentrated hydrochloric acid, and stir magnetically until the metal modifier is completely dissolved to obtain electroplating solution A; (3) Add a certain amount of electroplating solution A to the negative electrode electrolyte, start the liquid circulation system, and let the electroplating solution fully wet the graphite felt; (4) Electrochemical deposition is carried out by pulse electroplating. Electroplating is stopped when the voltage reaches the specified value.

2. The method for preparing a bimetallic particle-supported graphite felt electrode material according to claim 1, characterized in that, The in-situ restoration method for the flow battery system in step (1) is multiple low-current discharges, specifically as follows: 1) At 80-100 mA / cm 2 Discharge under constant current condition, cutoff voltage 0.2-0.3 V / cell; 2) At 40-60 mA / cm 2 Discharge under constant current condition, cutoff voltage 0.1-0.2 V / cell; 3) At 20-40 mA / cm 2 Discharge under constant current condition, cutoff voltage 0-0.01 V / cell.

3. The method for preparing a bimetallic particle-supported graphite felt electrode material according to claim 1, characterized in that: The criterion for judging the initial state of the flow battery system in step (1) is that the voltage of a single cell of the stack is ≤0.1 V / cell when the pump is running.

4. The method for preparing a bimetallic particle-supported graphite felt electrode material according to claim 1, characterized in that: The metal modifier in step (2) is any two of the following four pairs: bismuth oxide or bismuth chloride, tin oxide or stannous chloride, lead chloride or lead oxide, and indium chloride. The concentration of the metal modifier is 4-15 mmol / L.

5. The method for preparing a bimetallic particle-supported graphite felt electrode material according to claim 1, characterized in that: The mass-volume ratio of the metal modifier to concentrated hydrochloric acid in step (2) is 1:(8-12).

6. The method for preparing a bimetallic particle-supported graphite felt electrode material according to claim 1, characterized in that: In step (3), the amount of electroplating solution A added is positively correlated with the surface area of ​​the graphite felt, and the ratio of the total surface area of ​​electroplating solution A to that of the negative electrode graphite felt is 0.08-0.16 mL / cm². 2 .

7. The method for preparing a bimetallic particle-supported graphite felt electrode material according to claim 1, characterized in that: In step (4), the pulse current of the pulse electroplating method is 5-10 mA / cm. 2 Constant current; pulse time is 4-10 min; turn-off time is 2-5 min; number of pulses is 5-10; cut-off voltage is 0.9 V / section.

8. The bimetallic particle-loaded graphite felt electrode material prepared by the method for preparing bimetallic particle-loaded graphite felt electrode material as described in claims 1-7.

9. The application of the bimetallic particle-supported graphite felt electrode material as described in claim 8.

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