Preparation method and system of modified electrode material

Abstract

The invention discloses a preparation method and system of a modified electrode material, and the method comprises the steps: an electrode material moves into a modification tank, the modification tank contains a modification solution with continuously changing concentration, and the electrode material is always soaked in the modification solution when passing through the modification tank; after leaving the modification tank, the electrode material is cleaned, dried and subjected to heat treatment, and the modified electrode material with continuous electrochemical activity change is obtained. According to the invention, by controlling the continuous change of the reaction active sites on the surface of the electrode material, the electrochemical activity of the reaction sites is fully utilized, the electrochemical activity change is concentrated on the same electrode material, and the tedious process caused by splicing of multiple sections of electrodes is also avoided.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electrochemistry, in particular to a preparation method and system of modified electrode material. BACKGROUND

[0002] As an electrochemical energy storage device, the all-vanadium redox flow battery can realize the mutual conversion of electrical energy and chemical energy through the oxidation-reduction reaction of different valence vanadium ions in the electrolyte, thereby completing the storage and release of energy. During the operation of the battery, the electrolyte comes from the storage tank, flows into the electrolyte inlet in the stack, and after the oxidation-reduction reaction of different valence vanadium ions in the electrolyte on the electrode surface, the electrolyte flows out from the outlet and finally returns to the storage tank. Therefore, the electrochemical activity of the electrode plays a key role in the performance of the battery.

[0003] In order to improve the electrochemical activity, the existing technology generally starts from the modification of the electrode material. Since the electrode material used in the current all-vanadium redox flow battery is mostly porous carbon material such as carbon felt, graphite felt, carbon cloth, and carbon paper, CN102136579A proposes a simple and feasible modification method for graphite felt electrode, that is, using hydrogen peroxide solution or Fenton reagent to modify it, thereby greatly increasing the number of functional groups on the surface of carbon fibers and improving the electrochemical activity.

[0004] In addition, since the active ions in the electrolyte are continuously consumed during the process from the inlet to the outlet of the stack, and the concentration is the highest at the inlet, CN112768705A proposes a segmented electrode arrangement, that is, the segmented electrode is arranged from the electrolyte inlet to the outlet by multiple electrode monomers with different electrochemical activities obtained by different modification methods, thereby improving the electrode activity and the utilization rate of the electrolyte.

[0005] However, although this segmented electrode arrangement can improve the utilization rate of the electrode and the electrolyte, this method requires different modification methods for the electrode, the effects achieved by different methods are not easy to compare, and the electrode of a single battery also needs to be arranged and spliced by multiple monomer modified electrodes, which is complicated and not convenient for assembling the battery. SUMMARY

[0006] To solve the above-mentioned defects in the prior art, the present application provides a preparation method and system of modified electrode material, which can realize continuous change of electrochemical activity on a single electrode, and the battery assembly process does not require splicing of the electrode.

[0007] To achieve the above-mentioned application purposes, the first aspect of the present application provides a preparation method of modified electrode material, comprising:

[0008] The electrode material moves into the modification tank, which contains a modification solution with a constantly changing concentration. The electrode material is always immersed in the modification solution as it passes through the modification tank.

[0009] After leaving the modification tank, the electrode material is cleaned, dried, and heat-treated to obtain a modified electrode material with continuous changes in electrochemical activity.

[0010] Furthermore, the modified solution is selected from one or more strong oxidizing agent solutions such as sulfuric acid, nitric acid, ammonium persulfate and hydrogen peroxide, and the concentration is preferably 0.1-18M.

[0011] Furthermore, the electrode material passes through the modification tank for 1-24 hours.

[0012] Furthermore, the drying conditions include drying at 80-110°C for 8-24 hours.

[0013] Furthermore, the heat treatment conditions include: heat treatment at 300-900℃ for 1-6 hours, preferably under an inert atmosphere such as nitrogen or argon.

[0014] Furthermore, the modified solution enters the modification tank at a certain flow rate, while the modified solution in the modification tank is output at the same flow rate; preferably, the flow rate range is 1-10 L / h.

[0015] Furthermore, the variation law of the modified solution concentration in the modification tank is as follows: as the concentration of the modified solution in the storage tank increases, the flow rate of the modified solution increases, and / or the electrode material passes through the modification tank for a longer period of time, the variation range of the modified solution concentration in the modification tank gradually increases to [0-0.1M]~[0-10M], preferably [0-1M]~[0-6M].

[0016] Furthermore, the electrode material is selected from one or more of graphite felt, carbon felt, carbon cloth, and carbon paper.

[0017] A second aspect of the present invention provides a system for preparing a modified electrode material, comprising:

[0018] Storage tank, used to store modified solutions;

[0019] A modification tank, connected to the storage tank, is used to receive the modified solution from the storage tank;

[0020] A collection tank, connected to the modification tank, is used to receive the modified solution discharged from the modification tank;

[0021] A conveying device is used to transport electrode material and move it through the interior of the modification tank.

[0022] The modified solution flows between the storage tank, the modification tank, and the collection tank, changing the concentration of the modified solution, the flow rate of the modified solution, and / or the time it takes for the electrode material to pass through the modification tank, so that the concentration of the modified solution contained in the modification tank changes continuously.

[0023] Furthermore, a pump for conveying the modified solution is provided between the storage tank and the modification tank, and between the modification tank and the collection tank.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] This invention involves continuously feeding electrode material into a modified solution with varying concentrations. As the concentration of the modified solution increases, the effect of the modified solution treatment on the electrode material also changes. After a final heat treatment, the functional groups on the electrode material gradually increase along the electrode feeding direction, enabling the preparation of electrode materials with continuously varying electrochemical activity. In contrast, existing segmented electrode technologies require comparison and combination of multiple modification methods, and the changes in electrochemical activity are not continuous on the same electrode.

[0026] Therefore, this invention fully utilizes the electrochemical activity of reactive sites by controlling the continuous changes in the reactive sites on the electrode surface. This not only concentrates the changes in electrochemical activity on a single electrode material but also avoids the cumbersome process of splicing multiple electrode segments. Furthermore, the trend or range of the continuous changes in electrochemical activity can be altered according to the actual requirements of the fuel cell stack, thereby improving the adaptability of the electrode.

[0027] Other features and advantages of the present invention will be described in detail through the following specific embodiments. Attached Figure Description

[0028] Figure 1 A schematic diagram of a modified electrode material preparation system provided in this embodiment of the invention.

[0029] Among them, 1 is the storage tank, 2 is the modification tank, 3 is the collection tank, 4 is the pump, 5 is the conveying shaft (conveying device), and 6 is the electrode material. Detailed Implementation

[0030] The following will clearly and completely describe the concept and technical effects of this application in conjunction with embodiments, so as to fully understand the purpose, features and effects of this application. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are all within the scope of protection of this application.

[0031] In the description of this invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0032] refer to Figure 1 As shown, the present invention provides a system for preparing modified electrode materials, comprising:

[0033] Storage tank 1 is used to store the modified solution;

[0034] Modification tank 2 is connected to the storage tank and is used to receive the modified solution from the storage tank;

[0035] The collection tank 3 is connected to the modification tank and is used to receive the modified solution discharged from the modification tank.

[0036] Conveying device 5 is used to transport electrode material 6 so that the electrode material moves through the interior of the modification tank;

[0037] The modified solution flows between the storage tank 1, the modification tank 2, and the collection tank 3, changing the concentration of the modified solution, the flow rate of the modified solution, and / or the time it takes for the electrode material to pass through the modification tank, so that the concentration of the modified solution contained in the modification tank 2 changes continuously, and the solution in the modification tank is controlled to be maintained within a certain volume range.

[0038] In some specific embodiments, a pump 4 for conveying the modified solution is provided between the storage tank 1 and the modification tank 2, and between the modification tank 2 and the collection tank 3.

[0039] In some specific embodiments, the conveying device 5 adopts a conventional conveying mechanism, such as a conveyor belt or a conveyor shaft, with the conveyor shaft driving the electrode material forward.

[0040] This invention also provides a method for preparing a modified electrode material, comprising:

[0041] The electrode material moves into the modification tank, which contains a modification solution with a constantly changing concentration. The electrode material is always immersed in the modification solution as it passes through the modification tank.

[0042] After leaving the modification tank, the electrode material is cleaned, dried, and heat-treated to obtain a modified electrode material with continuous changes in electrochemical activity.

[0043] In some specific embodiments, the modified solution is selected from one or more strong oxidizing agent solutions such as sulfuric acid, nitric acid, ammonium persulfate, and hydrogen peroxide.

[0044] In the modification process of this invention, the content of functional group reaction sites on the electrode surface is affected by several factors, including the concentration of the modification solution, the flow rate of the modification solution, and the treatment time of the electrode material in the modification solution. The treatment time of the electrode material can be controlled by the speed of the conveying device. The speed of the conveying device can be estimated using the following formula: Let L be the effective processing length of the modification tank, t be the time the electrode material spends in the modification tank, and V be the travel speed V of the conveying device calculated using the formula V = L / t.

[0045] In some specific embodiments, the concentration of the modified solution is preferably 0.1-18M.

[0046] In some specific embodiments, the modified solution enters the modification tank at a certain flow rate, while the modified solution in the modification tank is output at the same flow rate to control the volume of the solution in the modification tank; preferably, the pump flow rate is 1-10 L / h.

[0047] In some specific embodiments, the electrode material passes through the modification tank for 1-24 hours.

[0048] In some specific embodiments, the variation range of the modified solution concentration in the modification tank is as follows: as the concentration of the modified solution in the storage tank increases, the flow rate of the modified solution increases, and / or the electrode material passes through the modification tank for a longer period of time, the variation range of the modified solution concentration in the modification tank gradually increases to [0-0.1M]~[0-10M], preferably [0-1M]~[0-6M].

[0049] In some specific implementations, a certain volume of solution, preferably deionized water, may be added to the modification tank first.

[0050] In some specific embodiments, the drying conditions include drying at 80-110°C for 8-24 hours.

[0051] In some specific embodiments, the heat treatment conditions include: heat treatment at 300-900°C for 1-6 hours, preferably under an inert atmosphere such as nitrogen or argon.

[0052] In some specific embodiments, the heat treatment is carried out in a muffle furnace or a tube furnace.

[0053] In some specific embodiments, the electrode material is selected from one or more of graphite felt, carbon felt, carbon cloth, and carbon paper.

[0054] The present invention will be further illustrated by the following examples, but the present invention is not limited thereto.

[0055] Example 1

[0056] (1) Prepare a 3M hydrogen peroxide solution and place it in a storage tank;

[0057] (2) Place the carbon felt electrode on the conveyor shaft and immerse it in the modification tank; a certain volume of deionized water is also added to the modification tank so that the liquid level covers the carbon felt electrode.

[0058] (3) Pump the modified solution in the storage tank into the modification tank at a rate of 1L / h, and at the same time pump the solution in the modification tank into the collection tank at the same rate, and at the same time turn on the conveyor shaft to make the electrode in motion.

[0059] (4) By controlling the speed of the conveyor shaft, the carbon felt electrode passes through the modification tank for 4 hours;

[0060] (5) The concentration range of the modified solution in the modified tank is 0-1.67M;

[0061] (6) After modification, the electrode is removed, washed with deionized water, and dried in a drying oven for 8 hours.

[0062] (7) The dried modified electrode material is placed in a muffle furnace and heat-treated at 600°C for 2 hours in a nitrogen atmosphere. After cooling with the furnace, the modified carbon felt electrode material is obtained.

[0063] (8) Cut the modified carbon felt electrode to a suitable size and use it directly in the assembly of the flow battery. Place the side of the modified carbon felt electrode with low activity on the electrolyte inlet side and the side with high activity on the electrolyte outlet side.

[0064] Example 2

[0065] The concentration of hydrogen peroxide solution in step (1) of Example 1 was changed to 6.3M, and the concentration of modified solution in the modification tank in step (5) was changed to 0-3.46M. Other steps remained unchanged.

[0066] Example 3

[0067] The concentration of hydrogen peroxide solution in step (1) of Example 1 was changed to 9.8M, and the concentration of modified solution in the modification tank in step (5) was changed to 0-5.4M. Other steps remained unchanged.

[0068] Example 4

[0069] In step (3) of Example 1, the pump flow rate is changed to 5L / h, and the concentration of the modified solution in the modification tank in step (5) is changed to 0-2.96M. Other steps remain unchanged.

[0070] Example 5

[0071] In step (3) of Example 1, the pump flow rate is changed to 10 L / h, and the concentration of the modified solution in the modification tank in step (5) is changed to 0-3.2 M. Other steps remain unchanged.

[0072] Example 6

[0073] In step (4) of Example 1, the time for the electrode to pass through the modification tank is changed to 1 hour, and in step (5), the concentration of the modification solution in the modification tank varies from 0 to 0.55 M. Other steps remain unchanged.

[0074] Example 7

[0075] In step (4) of Example 1, the time for the electrode to pass through the modification tank is changed to 24 hours, and in step (5), the concentration of the modification solution in the modification tank varies from 0 to 3 M. Other steps remain unchanged.

[0076] Comparative Example 1

[0077] (1) Prepare a 1.5M hydrogen peroxide solution and place it in a storage tank;

[0078] (2) Place the carbon felt electrode on the conveyor shaft and immerse it in the modification tank; a certain volume of deionized water is also added to the modification tank so that the liquid level covers the carbon felt electrode.

[0079] (3) Pump the modified solution in the storage tank into the modified tank at a rate of 0.1 L / h, and at the same time pump the solution in the modified tank into the collection tank at the same rate, and at the same time turn on the conveyor shaft to make the electrode in motion.

[0080] (4) By controlling the speed of the conveyor shaft, the carbon felt electrode passes through the modification tank for 0.5 hours;

[0081] (5) The concentration range of the modified solution in the modified tank is 0-0.015M;

[0082] (6) After modification, the electrode is removed, washed with deionized water, and dried in a drying oven for 8 hours.

[0083] (7) The dried modified electrode material is placed in a muffle furnace and heat-treated at 600°C for 2 hours in a nitrogen atmosphere. After cooling with the furnace, the modified carbon felt electrode material is obtained.

[0084] (8) Cut the modified carbon felt electrode to a suitable size and use it directly in the assembly of the flow battery. Place the side of the modified carbon felt electrode with low activity on the electrolyte inlet side and the side with high activity on the electrolyte outlet side.

[0085] Comparative Example 2

[0086] In step (3) of Example 3, the pump flow rate is changed to 10 L / h, the electrode time in the modification tank in step (4) is changed to 5 h, and the concentration of the modified solution in the modification tank in step (5) is changed to 0-9.8 M. Other steps remain unchanged.

[0087] Table 1. Results of Functional Group Content Test

[0088]

[0089]

[0090] The content of functional groups on the electrode material surface was obtained by X-ray photoelectron spectroscopy using a Thermal Scientific ESCALAB 250Xi diffractometer. Selected regions 1-3 represent samples taken from the modified electrode along the electrode transport direction. As shown in Example 1, the functional group content gradually increases along the electrode transport direction and exhibits a linear change, suggesting that the electrochemical activity can be continuously varied. Examples 2-7 show that increasing the concentration of the modification solution, the flow rate of the modification solution, and the electrode treatment time all increase the range of variation in functional group content. In Comparative Example 1, when the concentration, flow rate, and electrode treatment time of the modification solution are all relatively low, the modification effect is not significant. In Comparative Example 2, when the range of variation in the concentration of the modification solution is sufficiently large, the change in functional group content becomes insignificant.

[0091] Furthermore, in this embodiment of the invention, the change in electrochemical activity is concentrated on a single electrode. There is no electrode splicing during the battery assembly process, which not only makes assembly simpler, but also ensures that the change in electrochemical activity is continuous and mild, with minimal impact on overpotential.

[0092] Although the present invention has been described in detail through the preferred embodiments described above, it should be understood that the above description should not be considered as a limitation of the present invention. Those skilled in the art will understand that modifications or adjustments can be made to the present invention based on the teachings of this specification. These modifications or adjustments should also be within the scope defined by the claims of the present invention.

Claims

1. A method for preparing a modified electrode material, characterized in that, include: The electrode material moves into the modification tank, which contains a modification solution with a constantly changing concentration. The electrode material is always immersed in the modification solution as it passes through the modification tank. After leaving the modification tank, the electrode material is cleaned, dried, and heat-treated to obtain a modified electrode material with continuous changes in electrochemical activity.

2. The method for preparing the modified electrode material according to claim 1, characterized in that, The modified solution is a strong oxidizing agent solution. Preferably, the modified solution is selected from one or more of sulfuric acid, nitric acid, ammonium persulfate and hydrogen peroxide, and the concentration is preferably 0.1-18M.

3. The method for preparing the modified electrode material according to claim 1 or 2, characterized in that, The electrode material passes through the modification tank for 1-24 hours.

4. The method for preparing the modified electrode material according to any one of claims 1-3, characterized in that, The modified solution enters the modification tank at a certain flow rate, and the modified solution in the modification tank is output at the same flow rate; preferably, the flow rate range is 1-10 L / h.

5. The method for preparing the modified electrode material according to any one of claims 1-4, characterized in that, The variation range of the modified solution concentration in the modification tank is as follows: as the concentration of the modified solution in the storage tank increases, the flow rate of the modified solution increases, and / or the electrode material passes through the modification tank for a longer period of time, the variation range of the modified solution concentration in the modification tank gradually increases to [0-0.1M]~[0-10M], preferably [0-1M]~[0-6M].

6. The method for preparing the modified electrode material according to claim 1, characterized in that, The drying conditions include drying at 80-110℃ for 8-24 hours.

7. The method for preparing the modified electrode material according to any one of claims 1-6, characterized in that, The heat treatment conditions include: heat treatment at 300-900℃ for 1-6 hours, preferably under an inert atmosphere of nitrogen or argon.

8. The method for preparing the modified electrode material according to any one of claims 1-7, characterized in that, The electrode material is selected from one or more of graphite felt, carbon felt, carbon cloth, and carbon paper.

9. A system for preparing a modified electrode material, characterized in that, include: Storage tank, used to store modified solutions; A modification tank, connected to the storage tank, is used to receive the modified solution from the storage tank; A collection tank, connected to the modification tank, is used to receive the modified solution discharged from the modification tank; A conveying device is used to transport electrode material and move it through the interior of the modification tank. The modified solution flows between the storage tank, the modification tank, and the collection tank. Changing the concentration of the modified solution, the flow rate of the modified solution, and / or the time it takes for the electrode material to pass through the modification tank causes the concentration of the modified solution contained inside the modification tank to change continuously.

10. The preparation system for the modified electrode material according to claim 9, characterized in that, Pumps for conveying the modified solution are provided between the storage tank and the modification tank, and between the modification tank and the collection tank.

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