Modified negative electrode material for all-vanadium redox flow battery and preparation method and application thereof

Abstract

The application relates to the technical field of electrode materials for liquid flow batteries, and provides a modified negative electrode material for a vanadium redox flow battery as well as a preparation method and application thereof. The method comprises the following steps: placing the negative electrode material in an assembled liquid flow battery to perform segmented electrodeposition, and obtaining a modified electrode; wherein the negative electrode electrolyte of the liquid flow battery is a solution containing at least one active substance selected from Bi, Sb, In, Ag and Sn; in the segmented electrodeposition process, the segmented electrodeposition is 3-8 segments, the current density of single-stage electrodeposition is not greater than 10 mA / cm 2 , the process parameters of the segmented electrodeposition are controlled, so that the total deposition amount of the segmented electrodeposition process is 0.01-0.9 mg / cm 2 . The method provided by the application adopts segmented electrodeposition and small current density, directly performs catalytic loading on the negative electrode material in the liquid flow battery, can form a deposit with uniform particle size on the surface of the negative electrode material, and improves the operation energy efficiency and current density of the liquid flow battery system.

Description

Technical Field

[0001] This invention relates to the field of electrode materials for flow batteries, and in particular to a modified all-vanadium redox flow battery anode material, its preparation method, and its application. Background Technology

[0002] In flow batteries, the electrodes are the core carriers of electrochemical reactions, and must simultaneously meet requirements such as high conductivity, excellent catalytic activity, resistance to electrolyte corrosion, and long-term stability. The electrocatalytic activity of the electrodes directly determines the intrinsic reaction rate of the electrochemical reaction, and greatly affects the battery's operating current density and energy efficiency.

[0003] Loading Bi, Sb, In, Ag, Sn, etc. onto the electrodes can reduce the activation energy of redox reactions of vanadium ions / iron-chromium ions, enhance the catalytic activity of the electrode materials, and thus improve the energy efficiency and current density of the flow battery system.

[0004] CN104518221A discloses a bifunctional anode for vanadium redox flow batteries. The bifunctional anode uses a carbon material as a matrix, with its surface modified with a Bi-containing electrocatalyst. The Bi-containing electrocatalyst is one or more of elemental Bi, Bi₂O₃, Bi halides, or Bi metal salts; wherein the Bi halide is bismuth fluoride, bismuth chloride, bismuth bromide, or bismuth iodide; and the Bi metal salt is bismuth sulfate, bismuth nitrate, bismuth phosphate, bismuth formate, or bismuth acetate. This electrode is suitable for use as the anode in vanadium redox flow batteries and can significantly improve the electrode material's performance against V₂O₃. 2+ / V 3+ It exhibits electrocatalytic activity and electrochemical reversibility in redox reactions, reducing charge transfer resistance; it also possesses a high hydrogen evolution overpotential, which can inhibit the occurrence of hydrogen evolution reaction and extend the battery's working life.

[0005] However, the aforementioned method has an excessively high deposition density, which leads to uneven deposition and the formation of large particles of catalytic active material that adhere to the electrode, clogging the electrode and increasing the contact resistance between the electrode and the current collector, thereby increasing the internal resistance of the battery and reducing voltage efficiency. Summary of the Invention

[0006] The main objective of this invention is to provide a modified vanadium redox flow battery anode material, its preparation method, and its application, in order to solve the problems of excessive deposition density, uneven deposition, catalytic active material clogging the electrode, and increased battery internal resistance in the preparation of vanadium battery anode materials in the prior art.

[0007] To achieve the above objectives, a first aspect of the present invention provides a method for preparing a modified vanadium redox flow battery anode material, comprising: The negative electrode material is placed in the assembled flow battery and subjected to segmented electrodeposition to obtain the modified electrode; The negative electrode electrolyte of the flow battery is a solution containing at least one active substance selected from Bi, Sb, In, Ag, and Sn. In the segmented electrodeposition process, the electrodeposition is performed in 3-8 segments, and the current density of a single segment electrodeposition is no greater than 10 mA / cm². 2 The process parameters of the segmented electrodeposition are controlled so that the total deposition amount of the segmented electrodeposition process is 0.01-0.9 mg / cm³. 2 .

[0008] The preparation method provided by this invention adopts a segmented electrodeposition process to directly catalytically load the negative electrode material in the flow battery. The electrochemical deposition process is optimized and controlled by using a small amount of material multiple times and a low current density for deposition. This can form deposits with uniform particle size on the surface of the negative electrode material, improve the reactivity of the negative electrode material, and thus improve the operating energy efficiency and current density of the flow battery system.

[0009] In some embodiments, the process parameters of the segmented electrodeposition are controlled such that the total deposition amount of the segmented electrodeposition process is 0.05-0.4 mg / cm³. 2 .

[0010] In some embodiments, the deposition amount of a single-segment electrodeposition is 0.01-0.2 mg / cm³. 2 .

[0011] In some embodiments, the amount of electrodeposited material varies in a gradient as electrodeposition proceeds, with the amount of electrodeposited material in a later stage being 0-0.05 mg / cm³ higher than that in the earlier stage. 2 Furthermore, the electrodeposition amount described in the last paragraph is 0-0.08 mg / cm³ lower than that described in the previous paragraph. 2 .

[0012] In some embodiments, the positive electrode electrolyte of the flow battery is a vanadium-containing solution; Optionally, the vanadium-containing solution is a trivalent vanadium-containing solution and / or a divalent vanadium-containing solution.

[0013] In some embodiments, the concentration of vanadium ions in the vanadium-containing solution is 0.01-0.5 mol / L.

[0014] In some embodiments, the segmented electrodeposition satisfies at least one of the following conditions: A. The time for single-segment electrodeposition is 10-30 minutes; B. The voltage of a single cell in the flow battery is 0.8-1.5V.

[0015] A second aspect of the present invention provides a modified vanadium redox flow battery anode material, said modified vanadium redox flow battery anode material being prepared by the method described in the first aspect.

[0016] In some embodiments, the modified vanadium redox flow battery anode material includes a substrate and a loading layer deposited on the substrate, wherein the loading layer contains at least one of Bi, Sb, In, Ag, and Sn; Optionally, the matrix is ​​selected from carbon felt or graphite felt.

[0017] A third aspect of the present invention provides a vanadium redox flow battery, the vanadium redox flow battery comprising the modified all-vanadium redox flow battery negative electrode material as described in the second aspect; or The vanadium redox flow battery includes a modified vanadium redox flow battery anode material, which is prepared by the method described in the first aspect.

[0018] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the present application. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0020] Figure 1 The figures show the cyclic voltammetry curves of the modified electrodes in Examples 1-4 and the electrodes in the control group of this invention.

[0021] The realization of the objective, functional characteristics and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Furthermore, in this invention, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature.

[0024] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0025] As described above, the first aspect of the present invention provides a method for preparing a modified vanadium redox flow battery anode material, comprising: The negative electrode material is placed in the assembled flow battery and subjected to segmented electrodeposition to obtain the modified electrode; The negative electrode electrolyte of the flow battery is a solution containing at least one active substance selected from Bi, Sb, In, Ag, and Sn. In the segmented electrodeposition process, the electrodeposition is performed in 3-8 segments, and the current density of a single segment electrodeposition is no greater than 10 mA / cm². 2 The process parameters of the segmented electrodeposition are controlled so that the total deposition amount of the segmented electrodeposition process is 0.01-0.9 mg / cm³. 2 .

[0026] The preparation method provided by this invention adopts a segmented electrodeposition process to directly catalytically load the negative electrode material in the flow battery. The electrochemical deposition process is optimized and controlled by using a small amount of material multiple times and a low current density for deposition. This can form deposits with uniform particle size on the surface of the negative electrode material, improve the reactivity of the negative electrode material, and thus improve the operating energy efficiency and current density of the flow battery system.

[0027] The preparation method provided by this invention also has the advantages of simple process, low energy consumption, fast processing speed and uniform and stable catalytic effect.

[0028] In the segmented electrodeposition process, the segmented electrodeposition can be, for example, 3, 4, 5, 6, 7, 8 segments or any value between 3 and 8 segments, and the current density of a single segment electrodeposition can be, for example, 1 mA / cm². 2 2mA / cm 2 3mA / cm 2 4mA / cm 2 5mA / cm 2 6mA / cm 2 7mA / cm 2 8mA / cm2 9mA / cm 2 10mA / cm 2 Or not greater than 10 mA / cm 2 Any value. Preferably, the segmented electrodeposition consists of 3-5 segments. During their research, the inventors discovered that excessively high current density in a single-segment electrodeposition leads to uneven deposition, easily forming large particles of catalytic active material that adhere to the electrode, clogging it and causing increased internal pressure and decreased flow rate. Conversely, excessively low current density makes it difficult to load onto the electrode, failing to improve the reactivity of the negative electrode material. However, this invention divides the electrodeposition into 3-5 segments, with a current density not exceeding 10 mA / cm². 2 The high current density allows for direct catalytic loading of the negative electrode material in the flow battery, which can deposit small particles of catalytic active material, avoid electrode blockage, and significantly improve the reactivity of the negative electrode, thereby improving the energy efficiency of the flow battery.

[0029] In some embodiments, the negative electrode electrolyte of the flow battery is a Bi-containing solution. The inventors have discovered that by using the segmented electrodeposition process provided in this application, and using a Bi-containing solution as the deposition liquid to directly deposit on the surface of the negative electrode in a flow battery, it is easier to load elemental Bi onto the negative electrode.

[0030] In some embodiments, the process parameters of the segmented electrodeposition are controlled such that the total deposition amount of the segmented electrodeposition process is 0.05-0.4 mg / cm³. 2 The total deposition amount in the segmented electrodeposition process can be, for example, 0.05 mg / cm³. 2 0.06 mg / cm 2 0.07 mg / cm 2 0.08 mg / cm 2 0.09 mg / cm 2 0.1 mg / cm 2 0.2 mg / cm 2 0.3 mg / cm 2 0.4 mg / cm 2 Or 0.05-0.4 mg / cm 2 Any value between; preferably, the present invention controls the process parameters of the segmented electrodeposition so that the total deposition amount of the segmented electrodeposition process is 0.05-0.4 mg / cm³. 2 This is because the inventors of this application discovered during their research that excessive total deposition can easily clog the negative electrode material matrix, while insufficient deposition will not achieve the desired catalytic activation effect. By controlling the total deposition amount to 0.05-0.4 mg / cm³, this problem can be mitigated. 2This allows for the production of anode materials with higher reactivity while reducing clogging, thereby improving the energy efficiency of flow batteries.

[0031] In some embodiments, the deposition amount of a single-segment electrodeposition is 0.01-0.2 mg / cm³. 2 The deposition amount of the single-segment electrodeposition can be, for example, 0.01 mg / cm³. 2 0.02 mg / cm 2 0.03 mg / cm 2 0.04 mg / cm 2 0.05 mg / cm 2 0.06 mg / cm 2 0.07 mg / cm 2 0.08 mg / cm 2 0.09 mg / cm 2 0.1 mg / cm 2 0.11 mg / cm 2 0.12 mg / cm 2 0.13 mg / cm 2 0.14 mg / cm 2 0.15 mg / cm 2 0.16 mg / cm 2 0.17 mg / cm 2 0.18 mg / cm 2 0.19 mg / cm 2 0.2 mg / cm 2 Or 0.01-0.2 mg / cm 2 Any value between.

[0032] In some embodiments, the amount of electrodeposited material varies in a gradient as electrodeposition proceeds, with the amount of electrodeposited material in a later stage being 0-0.05 mg / cm³ higher than that in the earlier stage. 2 Furthermore, the electrodeposition amount described in the last paragraph is 0-0.08 mg / cm³ lower than that described in the previous paragraph. 2 For example, the deposition amount of electrodeposition described in the latter paragraph can be 0 mg / cm³ higher than that described in the former paragraph. 2 0.01 mg / cm 2 0.02 mg / cm 2 0.03 mg / cm 2 0.04 mg / cm 2 0.05 mg / cm 2 Or 0-0.05 mg / cm 2Any value between these ranges. For example, the electrodeposition amount described in the last paragraph is 0 mg / cm³ lower than the electrodeposition amount described in the previous paragraph. 2 0.005 mg / cm 2 0.01 mg / cm 2 0.04 mg / cm 2 0.06 mg / cm 2 0.07 mg / cm 2 0.015 mg / cm 2 0.017 mg / cm 2 0.02 mg / cm 2 Or 0-0.02 mg / cm 2 Any value between.

[0033] It should be noted that the segmented electrodeposition method used in this invention is beneficial for the removal of bubbles and impurities. Combined with the gradient change of the deposition amount, a smaller deposition amount is used first, and the deposition amount is gradually increased as the deposition process progresses. This can optimize the nucleation conditions during each deposition and obtain a smoother and denser surface.

[0034] In some embodiments, after each electrodeposition stage, fresh negative electrode electrolyte is added to the flow battery, and the amount of negative electrode electrolyte added each time is controlled so that the concentration of active material in the negative electrode electrolyte is maintained at 20-300 ppm.

[0035] It is worth noting that this invention decomposes the continuous electrodeposition process into multiple independent short-duration deposition cycles. After each deposition cycle, fresh negative electrode electrolyte is added before the next deposition cycle. This avoids adding an electrolyte with a high concentration of active material at once. Excessive concentration of active material during deposition, coupled with a sufficient supply of active material near the electrode surface, promotes continuous nucleation, leading to abnormally large particle sizes and uneven deposits that are prone to falling off the negative electrode material, causing blockage. By periodically replenishing the negative electrode electrolyte to control the concentration of active material, and combining this with segmented deposition, each segment deposits an appropriate concentration of active material, ensuring that each deposition cycle takes place in an optimal and consistent chemical environment. This significantly improves the uniformity, density, purity, and overall performance of the deposited layer.

[0036] In some embodiments, the positive electrode electrolyte of the flow battery is a vanadium-containing solution.

[0037] In some embodiments, the vanadium-containing solution is a trivalent vanadium-containing solution and / or a divalent vanadium-containing solution. Preferably, the vanadium-containing solution is a trivalent vanadium-containing solution. The vanadium-containing solution may be, for example, at least one of vanadium sulfate, vanadium chloride, and vanadium oxalate.

[0038] In some embodiments, the concentration of vanadium ions in the vanadium-containing solution is 0.01-0.5 mol / L. The concentration of vanadium ions in the vanadium-containing solution can be, for example, any value between 0.01 mol / L, 0.02 mol / L, 0.03 mol / L, 0.04 mol / L, 0.05 mol / L, 0.06 mol / L, 0.07 mol / L, 0.08 mol / L, 0.09 mol / L, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, or 0.01-0.5 mol / L.

[0039] In some embodiments, the segmented electrodeposition satisfies at least one of the following conditions: A. The single-segment electrodeposition time is 10-30 min; the single-segment electrodeposition time can be, for example, any value between 10 min, 15 min, 20 min, 25 min, 30 min, or 10-30 min. B. The individual cell voltage of the flow battery is 0.8-1.5V. The individual cell voltage of the flow battery can be, for example, 0.8V, 0.9V, 1.0V, 1.1V, 1.2V, 1.3V, 1.4V, 1.5V, or any value between 0.8-1.5V. If the voltage is too low, the deposition effect will not be achieved; if it is too high, sulfuric acid may undergo a side reaction at the negative electrode to produce hydrogen sulfide, resulting in poor deposition. By using the segmented electrodeposition process provided by this invention, and simultaneously controlling the individual cell voltage within 0.8-1.5V, excellent deposition effects can be obtained, improving the energy efficiency of the flow battery.

[0040] It is worth noting that the flow battery described in this application can be a single cell or a flow battery stack. It should be noted that this invention does not impose any special requirements on the structure of the flow battery; conventional flow battery structures in the prior art can be used, and will not be elaborated upon here. The aforementioned positive and negative electrolytes are added to the positive and negative electrode tanks respectively. The pipes and tanks are connected according to conventional methods in the art. The current density and single-cell voltage are set, and the active material is converted into catalytic active sites under electrochemical action, uniformly loaded onto the negative electrode material.

[0041] As previously described, a second aspect of the present invention provides a modified vanadium redox flow battery anode material, which is prepared by the method described in the first aspect.

[0042] In some embodiments, the modified vanadium redox flow battery anode material includes a substrate and a loading layer deposited on the substrate, wherein the loading layer contains at least one of Bi, Sb, In, Ag, and Sn. Preferably, the loading layer contains elemental Bi.

[0043] The inventors of this invention do not have any particular requirements for the materials used in the flow battery or stack; materials well known in the art can be used, and will not be described in detail here. In some embodiments, the substrate is selected from carbon felt or graphite felt.

[0044] As previously described, a third aspect of the present invention provides a vanadium redox flow battery, the vanadium redox flow battery comprising the modified all-vanadium redox flow battery negative electrode material as described in the second aspect; or The vanadium redox flow battery includes a modified vanadium redox flow battery anode material, which is prepared by the method described in the first aspect.

[0045] The present invention will be described in detail below through examples. In the following examples, unless otherwise specified, all raw materials and instruments used are commercially available products.

[0046] In the following examples, unless otherwise stated, the separator, current collector, and electrode materials used in the single cell or stack are all commercially available products, with specific specifications as follows: The diaphragm is a 50μm full sulfonated fluoride diaphragm, the current collector is a graphite plate with a thickness of 0.8mm, and both the positive and negative electrodes are carbon felt with a thickness of 4.5mm. Example 1

[0047] This embodiment provides a method for preparing a modified vanadium redox flow battery anode material, the preparation method of which is as follows: Place the positive and negative electrodes at the assembled 24cm. 2 In a single cell, pipes and storage tanks are connected to the positive and negative electrodes respectively. 70 mL of 4.2 mol / L H₂SO₄ is added to the positive electrode storage tank, followed by 1.7 mol / L V₂SO₄. 3+ Add 3 mL of 4.2 mol / L H₂SO₄ to the negative electrode storage tank; then add 70 mL of 4.2 mol / L H₂SO₄, followed by 4 mL of 0.6 mg / mL BiCl₃ solution. At a current density of 10 mA / cm²... 2 The modified electrode was obtained by electrodeposition in three stages under a single-element voltage of 1.5V. The total deposition amount of elemental Bi on the modified electrode was 0.05 mg / cm³. 2 .

[0048] The specific process parameters for each electrodeposition stage in this embodiment are shown in Table 1.

[0049] Table 1 Example 2

[0050] This embodiment provides a method for preparing a modified vanadium redox flow battery anode material, the preparation method of which is as follows: Place the positive and negative electrodes at the assembled 24cm. 2 In a single cell, pipes and storage tanks are connected to the positive and negative electrodes respectively. 70 mL of 4.2 mol / L H₂SO₄ is added to the positive electrode storage tank, followed by 1.7 mol / L V₂SO₄. 3+ Add 8 mL of 4.2 mol / L H₂SO₄ to the negative electrode storage tank; then add 70 mL of 4.2 mol / L H₂SO₄, followed by 4 mL of 0.6 mg / mL BiCl₃ solution, at a current density of 10 mA / cm². 2 The modified electrode was obtained by electrodeposition in four stages under a single-element voltage of 1.5V. The total deposition amount of elemental Bi on the modified electrode was 0.192 mg / cm³. 2 .

[0051] The specific process parameters for each electrodeposition stage in this embodiment are shown in Table 2.

[0052] Table 2 Example 3

[0053] This embodiment provides a method for preparing a modified vanadium redox flow battery anode material, the preparation method of which is as follows: Place the positive and negative electrodes at the assembled 24cm. 2 In a single cell, connect pipes and storage tanks to the positive and negative electrodes respectively. Add 70 mL of 4.2 mol / L H₂SO₄ to the positive electrode storage tank, and then add 1.7 mol / L V₂SO₄. 3+ Add 3 mL of 4.2 mol / L H₂SO₄ to the negative electrode storage tank; then add 70 mL of 4.2 mol / L H₂SO₄, followed by 16 mL of 0.6 mg / mL BiCl₃ solution, at a current density of 10 mA / cm². 2 The modified electrode was obtained by electrodeposition in four stages under a single-element voltage of 1.5V. The total deposition amount of elemental Bi on the modified electrode was 0.4 mg / cm³. 2 .

[0054] The specific process parameters for each electrodeposition stage in this embodiment are shown in Table 3.

[0055] Table 3 Example 4

[0056] This embodiment was prepared according to the method of Example 1, except that the total deposition amount of elemental Bi on the modified electrode was 0.49 mg / cm³. 2 .

[0057] Place the positive and negative electrodes at the assembled 24cm. 2In a single cell, connect pipes and storage tanks to the positive and negative electrodes respectively. Add 70 mL of 4.2 mol / L H₂SO₄ to the positive electrode storage tank, and then add 1.7 mol / L V₂SO₄. 3+ Add 3 mL of 4.2 mol / L H₂SO₄ to the negative electrode storage tank; then add 70 mL of 4.2 mol / L H₂SO₄, followed by 18 mL of 0.6 mg / mL BiCl₃ solution, at a current density of 10 mA / cm². 2 Electrodeposition was performed in four segments under a single-cell voltage of 1.5V.

[0058] The specific process parameters for each electrodeposition stage in this embodiment are shown in Table 4.

[0059] Table 4 Example 5

[0060] This embodiment is prepared according to the method of Example 2, the difference being that the current density is 1 mA / cm². 2 . Example 6

[0061] This embodiment is prepared according to the method of Example 2, the difference being that the current density is 5 mA / cm². 2 . Example 7

[0062] This embodiment provides a method for preparing a modified vanadium redox flow battery anode material, the preparation method of which is as follows: The positive and negative electrodes were placed in the assembled fuel cell stack, which contained 1600 cm⁻¹ of fuel cell. 2 The battery consists of 88 individual cells. Pipes and storage tanks are connected to the positive and negative terminals respectively. 500L of 4.2mol / L H₂SO₄ solution is added to the positive terminal storage tank. 4， Add another 7L of 1.7mol / L V 3+ Add 3 mL of 4.2 mol / L H₂SO₄ to the negative electrode storage tank; then add 40 mL of 0.6 mg / mL BiCl₃ solution. The current density is 10 mA / cm². 2 The modified electrode was obtained by electrodeposition in four stages under a single-element voltage of 1.5V. The total deposition amount of elemental Bi on the modified electrode was 0.115 mg / cm³. 2 .

[0063] The specific process parameters for each electrodeposition stage in this embodiment are shown in Table 5.

[0064] Table 5 Example 8

[0065] This embodiment was prepared according to the method of Example 7, except that the total deposition amount of elemental Bi on the modified electrode was 0.16 mg / cm³. 2 .

[0066] The positive and negative electrodes were placed in the assembled fuel cell stack, which contained 1600 cm⁻¹ of fuel cell. 2 The battery consists of 88 individual cells. Pipes and storage tanks are connected to the positive and negative terminals respectively. 500L of 4.2mol / L H₂SO₄ solution is added to the positive terminal storage tank. 4， Add another 7L of 1.7mol / L V 3+ Add 3 mL of 4.2 mol / L H₂SO₄; add 500 L of 4.2 mol / L H₂SO₄ to the negative electrode storage tank, followed by 50 L of 0.6 mg / mL BiCl₃ solution. At a current density of 10 mA / cm²... 2 The modified electrode was obtained by electrodeposition in four stages under a single-cell voltage of 1.5V.

[0067] The specific process parameters for each electrodeposition stage in this embodiment are shown in Table 6.

[0068] Table 6 Example 9

[0069] This embodiment was prepared according to the method of Example 7, except that the total deposition amount of elemental Bi on the modified electrode was 0.2 mg / cm³. 2 .

[0070] The positive and negative electrodes were placed in the assembled fuel cell stack, which contained 1600 cm⁻¹ of fuel cell. 2 The battery consists of 88 individual cells. Pipes and storage tanks are connected to the positive and negative terminals respectively. 500L of 4.2mol / L H₂SO₄ solution is added to the positive terminal storage tank. 4， Add another 7L of 1.7mol / L V 3+ Add 3 mL of 4.2 mol / L H₂SO₄ to the negative electrode storage tank; then add 500 L of 4.2 mol / L H₂SO₄ and 60 L of 0.6 mg / mL BiCl₃ solution. At a current density of 10 mA / cm²... 2 The modified electrode was obtained by electrodeposition in four stages under a single-cell voltage of 1.5V.

[0071] The specific process parameters for each electrodeposition stage in this embodiment are shown in Table 7.

[0072] Table 7 Example 10

[0073] This embodiment was prepared according to the method of Example 7, except that the total deposition amount of elemental Bi on the modified electrode was 0.42 mg / cm³. 2 .

[0074] The positive and negative electrodes were placed in the assembled fuel cell stack, which contained 1600 cm⁻¹ of fuel cell. 2 The battery consists of 88 individual cells. Pipes and storage tanks are connected to the positive and negative terminals respectively. 500L of 4.2mol / L H₂SO₄ solution is added to the positive terminal storage tank. 4， Add another 7L of 1.7mol / L V 3+ Add 3 mL of 4.2 mol / L H₂SO₄ to the negative electrode storage tank; then add 95 mL of 0.6 mg / mL BiCl₃ solution. The current density is 10 mA / cm². 2 The modified electrode was obtained by electrodeposition in four stages under a single-cell voltage of 1.5V.

[0075] The specific process parameters for each electrodeposition stage in this embodiment are shown in Table 8.

[0076] Table 8

[0077] Comparative Example 1 This comparative example was prepared according to the method of Example 2, except that a single deposition was used instead of segmentation.

[0078] The specific method includes the following steps: Place the positive and negative electrodes at the assembled 24cm. 2 In a single cell, pipes and storage tanks are connected to the positive and negative electrodes respectively. 70 mL of 4.2 mol / L H₂SO₄ is added to the positive electrode storage tank, followed by 1.7 mol / L V₂SO₄. 3+ Add 3 mL of 4.2 mol / L H₂SO₄ to the negative electrode storage tank; then add 70 mL of 4.2 mol / L H₂SO₄, followed by 27 mL of 0.6 mg / mL BiCl₃ solution, at a current density of 10 mA / cm². 2 A modified electrode was obtained through a single deposition process, with a total Bi deposition amount of 0.2 mg / cm³. 2 .

[0079] Comparative Example 2 This comparative example was prepared according to the method in Example 2, except that the current density was 20 mA / cm². 2 .

[0080] The specific method includes the following steps: Place the positive and negative electrodes at the assembled 24cm. 2In a single cell, pipes and storage tanks are connected to the positive and negative electrodes respectively. 70 mL of 4.2 mol / L H₂SO₄ is added to the positive electrode storage tank, followed by 1.7 mol / L V₂SO₄. 3+ Add 3 mL of 4.2 mol / L H₂SO₄ to the negative electrode storage tank; then add 70 mL of 4.2 mol / L H₂SO₄, followed by 4 mL of 0.6 mg / mL BiCl₃ solution, at a current density of 20 mA / cm². 2 The modified electrode was obtained by electrodeposition in three stages under a single-element voltage of 1.5V. The total deposition amount of elemental Bi on the modified electrode was 0.2 mg / cm³. 2 .

[0081] The specific process parameters for each electrodeposition stage in this comparative example are shown in Table 1.

[0082] Test Example 1 The modified electrodes obtained in Examples 1-4 were removed, washed with deionized water, and subjected to cyclic voltammetry tests. An electrode without Bi loading was used as a control group. Specific results are shown in [link to results]. Figure 1 .

[0083] Cyclic voltammetry test method: The working electrode is a modified electrode, the counter electrode is a platinum electrode, the reference electrode is a calomel electrode, the scan rate is 5 mV / s, and the solution is a mixed solution of 0.1 mol / L V with a valence of 3.5 and 2.0 mol / L H2SO4.

[0084] from Figure 1 As can be seen from the positions and sizes of the reduction and oxidation peaks, the modified electrode exhibits significantly improved electrocatalytic activity and electrochemical reversibility compared to the Bi-loaded electrode in the control group; especially when the deposition amount is 0.2 mg / cm³. 2 When the potential difference is around 100°C, the modified electrode exhibits the best activity, with the highest oxidation peaks from divalent to trivalent oxidation and the smallest potential difference. At this point, the activity and reversibility of the carbon felt are superior to other electrodes.

[0085] Test Example 2 The modified electrodes obtained in Examples 1-6 and Comparative Examples 1-2 were used as negative electrodes, and the electrode without Bi loading was used as control group 1. Single cells were assembled using carbon felt as the positive electrode, and charge-discharge performance tests were conducted. Both the positive and negative electrode electrolytes were 1.7 mol / L V3.5 valence electrolytes. 3+ / V 4+ The test results are shown in Table 9.

[0086] Table 9

[0087] As can be seen from the table above, this invention performs electrodeposition in stages, with a current not exceeding 10 mA / cm. 2By directly loading the negative electrode material with a high current density in the flow battery, the reactivity of the negative electrode can be significantly improved, thereby improving the current efficiency, voltage efficiency and energy efficiency of the flow battery.

[0088] Test Example 3 The fuel cell stacks deposited in Examples 7-10 were subjected to charge-discharge performance tests in an all-vanadium redox flow battery system. Both the positive and negative electrode electrolytes were: V: 1.66 mol / L, SO42-. 2- The concentration was 4.26 mol / L. An electrode without Bi loading was used as control group 2. The test results are shown in Table 10.

[0089] Table 10

[0090] As can be seen from the table above, this invention achieves its goal by strictly controlling the deposition amount of Bi on the surface of the negative electrode material to be between 0.05-0.4 mg / cm³. 2 This can avoid the formation of large deposited particles, significantly reduce pressure changes caused by electrode material blockage, and improve the reactivity of the negative electrode, thereby improving the current efficiency, voltage efficiency and energy efficiency of the flow battery.

[0091] It should be noted that, in this document, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0092] The above technical solutions of the present invention are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made under the technical concept of the present invention using the contents of the present invention specification and drawings, or direct / indirect applications in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A method for preparing a modified vanadium redox flow battery anode material, characterized in that, include: The negative electrode material is placed in the assembled flow battery and subjected to segmented electrodeposition to obtain the modified electrode; The negative electrode electrolyte of the flow battery is a solution containing at least one active substance selected from Bi, Sb, In, Ag, and Sn. In the segmented electrodeposition process, the electrodeposition is performed in 3-8 segments, and the current density of a single segment electrodeposition is no greater than 10 mA / cm². 2 The process parameters of the segmented electrodeposition are controlled so that the total deposition amount of the segmented electrodeposition process is 0.01-0.9 mg / cm³. 2 .

2. The preparation method according to claim 1, characterized in that, The process parameters for the segmented electrodeposition are controlled so that the total deposition amount in the segmented electrodeposition process is 0.05-0.4 mg / cm³. 2 .

3. The preparation method according to claim 2, characterized in that, The deposition rate of a single-stage electrodeposition is 0.01-0.2 mg / cm³. 2 .

4. The preparation method according to claim 3, characterized in that, The deposition amount varies gradually as the electrodeposition process proceeds, with the deposition amount in later stages being 0-0.05 mg / cm³ higher than that in earlier stages. 2 Furthermore, the electrodeposition amount described in the last paragraph is 0-0.08 mg / cm³ lower than that described in the previous paragraph. 2 .

5. The preparation method according to claim 1, characterized in that, The positive electrode electrolyte of the flow battery is a vanadium-containing solution; Optionally, the vanadium-containing solution is a trivalent vanadium-containing solution and / or a divalent vanadium-containing solution.

6. The preparation method according to claim 5, characterized in that, The concentration of vanadium ions in the vanadium-containing solution is 0.01-0.5 mol / L.

7. The preparation method according to claim 1, characterized in that, The segmented electrodeposition satisfies at least one of the following conditions: A. The time for single-segment electrodeposition is 10-30 minutes; B. The voltage of a single cell in the flow battery is 0.8-1.5V.

8. A modified vanadium redox flow battery anode material, characterized in that, The modified vanadium redox flow battery anode material is prepared by the method described in any one of claims 1-7.

9. The modified vanadium redox flow battery anode material according to claim 8, characterized in that, The modified vanadium redox flow battery anode material includes a substrate and a loading layer deposited on the substrate, wherein the loading layer contains at least one of Bi, Sb, In, Ag, and Sn; Optionally, the matrix is ​​selected from carbon felt or graphite felt.

10. A vanadium redox flow battery, characterized in that, The vanadium redox flow battery comprises the modified all-vanadium redox flow battery anode material as described in claim 8 or 9; or The vanadium redox flow battery includes a modified vanadium redox flow battery anode material, which is prepared by the method described in any one of claims 1-7.

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