A modified electrode for in-situ growth of copper sulfide, a preparation method thereof, and a flow battery

Abstract

The present invention belongs to the field of electrochemical energy storage and electrocatalysis technology, and provides a modified electrode for in-situ grown copper sulfide, a preparation method thereof, and a liquid flow battery. The preparation method comprises the following steps: (1) doping sulfur atoms and fluorine atoms on a substrate material using a plasma cleaning method to obtain a doped substrate; (2) spraying a copper ion solution on the doped substrate to fully wet it, and then spraying a sulfur ion solution on the wetted surface of the doped substrate to react; (3) cleaning and drying the doped substrate to obtain a modified electrode for in-situ grown copper sulfide. The low-cost, high-performance in-situ grown copper sulfide modified electrode of the present application has the advantages of high electrical conductivity, specific surface area, electrochemical activity, catalytic performance and stability, as well as improved polysulfide redox reversibility, and can be applied to sulfur-based liquid flow battery systems using polysulfide as the active material.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrochemical energy storage and electrocatalysis, and in particular relates to a modified electrode for in-situ growth of copper sulfide, a preparation method thereof, and a liquid flow battery. Background Art

[0002] Polysulfide electrolytes are primarily used in lithium-sulfur batteries and flow batteries. Their slow reaction kinetics, large reaction energy barriers, and overpotentials limit the operating current density and energy efficiency of sulfide-iron flow batteries. Furthermore, mature, commercially available electrode materials for flow batteries are still lacking. The most widely used carbon felt material suffers from poor conductivity and low catalytic activity. Direct application in sulfide-iron flow batteries results in low stack power density and excessively high power module costs. Optimizing flow battery electrode activity is a bottleneck that urgently needs to be overcome.

[0003] Some researchers have proposed using catalysts to accelerate the conversion of polysulfides, reduce the battery's charging voltage, and thus improve energy efficiency. However, the various catalysts reported so far require complex synthesis processes and are expensive, making them unsuitable for large-scale production. Summary of the Invention

[0004] The technical problem to be solved by the present invention is that the operating current density and energy efficiency of liquid flow batteries are low, and the catalyst cost is high. In order to overcome the shortcomings and defects mentioned in the above background technology, a modified electrode for in-situ growth of copper sulfide, a preparation method thereof, and a liquid flow battery are provided.

[0005] In order to solve the above technical problems, the technical solution proposed by the present invention is:

[0006] A modified electrode for in-situ growth of copper sulfide comprises a substrate and a copper sulfide catalyst coated on the substrate. The substrate is doped with sulfur atoms and fluorine atoms, and the copper sulfide catalyst is uniformly coated on the surface of the substrate in a granular form.

[0007] Preferably, the doping amount of the sulfur atoms and fluorine atoms is 0.1-10% of the surface area of ​​the substrate, the coating thickness of the copper sulfide catalyst is 100-10000 nm, the loading amount of the copper sulfide catalyst is 5-30% wt of the substrate material, and the particle size is 0.1-1.5 μm.

[0008] This application utilizes substrate doping to modify the morphology of the supported catalyst and enhance the binding force between the substrate and the catalyst. Sulfur doping can enhance the substrate's adsorption of copper ions and copper sulfide. Sulfur ions, fluoride ions, and their free radicals in the plasma react with the surface of the substrate carbon material to form groups containing sulfur and fluorine atoms, altering the surface energy and hydrophilicity of the substrate.

[0009] Metal sulfides have a suitable adsorption capacity for polysulfides and have a certain degree of conductivity, which can significantly reduce the activation energy of the reaction and improve the energy conversion efficiency of the battery. Compared with other metal sulfides, copper sulfide has low cost, simple preparation process and high catalytic activity. The granular morphology of the copper sulfide catalyst can effectively expose the catalytic sites and increase the reaction area. The appropriate thickness will not significantly increase the resistance and reduce the electron conduction efficiency. Copper sulfide is evenly attached to the fiber surface in the form of particles, as shown in the SEM image, with a thickness of about hundreds to thousands of nanometers. Since the base material is a fibrous porous material, copper sulfide can be evenly attached to the fiber surface in the form of particles, thereby improving the adhesion rate of its catalyst.

[0010] Under the same technical concept, the present application also provides a method for preparing a modified electrode for in-situ growth of copper sulfide, comprising the following steps:

[0011] (1) Doping sulfur atoms and fluorine atoms on a substrate material using a plasma cleaning method to obtain a doped substrate;

[0012] (2) spraying a copper ion solution on the doped substrate to wet it, and then spraying a sulfur ion solution on the wetted surface of the doped substrate to react;

[0013] (3) Cleaning and drying the doped substrate after the reaction in step (2) to obtain a modified electrode with in-situ growth of copper sulfide.

[0014] This application uses plasma to dope sulfur atoms and fluorine atoms. Compared with other methods such as hydrothermal and high-temperature calcination, plasma can achieve ion doping under milder conditions without significantly changing the material morphology. The processing time is short, which facilitates the subsequent loading of copper sulfide. At the same time, it can reduce the contact resistance between the electrode and the electrolyte and improve the electrode performance.

[0015] Fluorine atoms have the strongest electronegativity, and the fluorine-carbon bonds formed with the base carbon material have extremely low polarity and strong hydrophobicity. It is difficult for catalysts to attach and grow on their surface. Fluorine atoms can act as surfactants to induce catalysts to produce structural vacancies.

[0016] The doped sulfur atoms have a strong interaction with copper atoms, can better adsorb copper atoms, and can play the role of anchoring the catalyst.

[0017] After spraying a copper ion solution onto the doped substrate, some copper ions are adsorbed onto the substrate surface. These ions then react with the sulfur ions in the sprayed sulfur ion solution to form granular copper sulfide, which adheres to the substrate surface. Compared to using adhesives to support catalysts, in-situ growth allows direct contact between the catalyst and the substrate, forming a direct electron transport channel, reducing interfacial resistance and lowering electrochemical reaction resistance.

[0018] Preferably, the base material in step (1) comprises one or more of graphite felt, carbon felt, carbon paper, carbon cloth or nickel foam.

[0019] Preferably, the plasma cleaning method in step (1) uses sulfur tetrafluoride or sulfur hexafluoride gas as the cleaning raw material, more preferably sulfur hexafluoride gas, and the volume flow rate of the gas is 5 to 15 sccm; the plasma cleaning power is 1200 to 1800 W, the cleaning time per square meter unit area is 10 to 30 seconds, and the number of cleaning times is 1 to 2 times.

[0020] Preferably, the copper ion solution in step (2) comprises one or more of an aqueous solution of copper sulfate, copper nitrate, copper chloride, copper acetate or copper bromide, and the copper ion solution contains Cu 2+ The concentration is 0.05-0.5M; when spraying the copper ion solution, dilute hydrochloric acid and / or dilute sulfuric acid are added to adjust the pH of the solution to 1-2.

[0021] Preferably, the sulfide ion solution in step (2) contains potassium sulfide and / or sodium sulfide, and the sulfide ion solution contains potassium sulfide and / or sodium sulfide. 2- The concentration is 0.075-0.75M, and the volume of the sulfide ion solution is 150-200% of the copper ion solution; when spraying the sulfide ion solution, an aqueous solution of potassium hydroxide and / or sodium hydroxide is added to adjust the pH of the solution to 12-13.

[0022] The pH value affects the coordination state of the copper ions, which in turn influences their reaction with the sulfur ions. By controlling the solution pH, the structure and morphology of the reaction products can be controlled.

[0023] Preferably, the reaction time of the reaction in step (3) is 60-180s, the cleaning time is 60-180s, and the number of cleanings is 2 to 5 times; and the drying environment is at normal pressure and 80 to 120°C.

[0024] Under the same technical concept, the present application also provides a liquid flow battery, which comprises the modified electrode of in-situ grown copper sulfide or the modified electrode of in-situ grown copper sulfide prepared by the above-mentioned preparation method, and the liquid flow battery adopts a polysulfide electrolyte.

[0025] Preferably, the electrolyte system used in the liquid flow battery includes a sulfide / polysulfide electrolyte system, and the diaphragm used in the liquid flow battery includes a perfluorosulfonic acid membrane or a non-fluorinated ion exchange membrane.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) The modified electrode of in-situ grown copper sulfide of the present application has the advantages of high conductivity, specific surface area, electrochemical activity, catalytic performance and stability, as well as improved polysulfide redox reversibility. It has low preparation cost and high product performance, and can be applied to sulfur-based liquid flow battery systems using polysulfide as active material.

[0028] (2) Fluorine atoms are doped on the surface of the substrate material as a surfactant to induce the catalyst to generate structural vacancies, sulfur atoms are doped to anchor the catalyst to uniform growth sites, plasma treatment is performed to enhance the hydrophilicity of the substrate, and finally, a copper sulfide catalyst is in situ grown on the surface of the substrate material in combination with a continuous adsorption ion layer reaction. The catalyst grows uniformly on the surface of the substrate material, has a large specific surface area, and a highly ordered crystal structure, which greatly accelerates the conversion of polysulfides.

[0029] (3) The preparation method of the present application has low raw material and equipment process costs, simple procedures, easy operation, and can achieve fully automated mass production. It solves the problems existing in the prior art of high electrode material preparation costs, complex production processes, and insufficient physical and chemical properties, which hinder the large-scale development of sulfur-based liquid flow batteries in the field of energy storage. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0031] Figure 1 This is a process flow chart for in-situ growth of a modified electrode of copper sulfide according to an embodiment of the present invention;

[0032] Figure 2 This is an electron microscope image of the surface of the modified electrode with in-situ growth of copper sulfide according to Example 1 of the present invention;

[0033] Figure 3 This is the X-ray diffraction pattern of the copper sulfide modified electrode prepared in Example 1 of the present invention;

[0034] Figure 4 Cyclic voltammetry curves of copper sulfide modified electrodes prepared in examples and comparative examples of the present invention in polysulfide electrolytes;

[0035] Figure 5 This is a cycle efficiency diagram of an alkaline iron-sulfur redox flow battery assembled using an embodiment of the present invention, with the original carbon felt as the positive electrode and Example 1 as the negative electrode;

[0036] Figure 6This is a cycle efficiency diagram of an alkaline sulfur-iron redox flow battery assembled using Example 6 of the present invention, with the original carbon felt as the positive electrode and Example 6 as the negative electrode;

[0037] Figure 7 This is a cycle efficiency diagram of an alkaline iron-sulfur redox flow battery assembled using Example 7 of the present invention, with the original carbon felt as the positive electrode and Example 7 as the negative electrode;

[0038] Figure 8 This is a cycle efficiency diagram of an alkaline iron-sulfur redox flow battery assembled using Example 8 of the present invention, with the original carbon felt as the positive electrode and Example 8 as the negative electrode;

[0039] Figure 9 This is a cycle efficiency diagram of an alkaline iron-sulfur redox flow battery assembled using Comparative Example 1 of the present invention, with the original carbon felt as the positive electrode and Comparative Example 1 as the negative electrode;

[0040] Figure 10 This is a cycle efficiency diagram of an alkaline sulfur-iron redox flow battery assembled using Example 9 of the present invention, with the original carbon felt as the positive electrode and Example 9 as the negative electrode;

[0041] Figure 11 This is a cycle efficiency diagram of an alkaline iron-sulfur redox flow battery assembled using Example 10 of the present invention, with the original carbon felt as the positive electrode and Example 10 as the negative electrode;

[0042] Figure 12 This is a cycle efficiency diagram of the alkaline sulfur-iron redox flow battery assembled using Example 11 of the present invention, where the original carbon felt is the positive electrode and Example 11 is the negative electrode. DETAILED DESCRIPTION

[0043] To facilitate understanding of the present invention, the present invention will be described in more comprehensive and detailed form below in conjunction with the accompanying drawings and preferred embodiments. However, the protection scope of the present invention is not limited to the following specific embodiments.

[0044] Unless otherwise defined, all technical terms used hereinafter have the same meanings as those generally understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0045] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0046] Example 1

[0047] This embodiment relates to a method for preparing a modified electrode for in-situ growth of copper sulfide. Figure 1 The specific steps are as follows:

[0048] Step 1: Cut a piece of carbon felt with an area of ​​15cm*25cm as the base material;

[0049] Step 2: Place the cut carbon felt in the chamber of a plasma cleaning device, introduce sulfur hexafluoride gas, adjust the volume flow rate to 10 sccm, control the plasma cleaning power to 1500 W, the cleaning time per square meter to 20 seconds, and the number of cleanings to 1, thereby obtaining carbon felt doped with sulfur atoms and fluorine atoms;

[0050] Step 3: Place the carbon felt doped with sulfur atoms and fluorine atoms in the cavity of the spraying equipment, add 0.3M copper sulfate solution into the liquid spray gun, and add an appropriate amount of dilute sulfuric acid to adjust the pH to 2;

[0051] Step 4: Use the equipment program to control the liquid spray gun to spray 80 mL of copper sulfate solution on the surface of the carbon felt, and observe that the carbon felt has been fully and evenly wetted;

[0052] Step 5: Place the wetted carbon felt in the cavity of another spraying equipment, add 0.45M sodium sulfide solution into the spray gun, and add appropriate amount of sodium hydroxide to adjust the pH to 12;

[0053] Step 6: Use the equipment program to control the liquid spray gun to spray 120mL of sodium sulfide solution on the surface of the carbon felt treated in step (4). It is observed that the Cu adsorbed on the carbon felt 2+ With S 2- Reacts quickly to form a black substance;

[0054] Step 7: The sprayed carbon felt is left to stand for 60 seconds until the surface color of the carbon felt becomes evenly darker. The carbon felt is then immersed in deionized water for 60 seconds, and then the deionized water is replaced and the immersion is repeated once.

[0055] Step 8: Place the carbon felt after soaking and cleaning in a normal pressure forced air drying oven, adjust the temperature to 80° C., and dry for 4 hours to ensure that the carbon felt is completely dried to obtain an in-situ grown copper sulfide modified electrode material.

[0056] The copper sulfide modified electrode obtained in Example 1 was tested by electron microscope. The test results are as follows: Figure 2 As shown, the electrode surface is uniformly loaded with granular catalysts, with particle sizes ranging from 0.2 to 0.5 μm; the doping amount of sulfur atoms and fluorine atoms in the substrate material is approximately 2% of the substrate surface area, the loading amount of the granular copper sulfide catalyst is approximately 15%wt of the substrate material, and the thickness is approximately 1000 nm.

[0057] The electrode was used to conduct X-ray diffraction test, and the test results were as follows: Figure 3As shown, compared with the copper sulfide standard card PDF#00-002-0820, the characteristic peak in the 25-65° region is obvious, indicating that the crystal phase structure of the catalyst has a high degree of order. At the same time, the characteristic peak in the 65-85° region disappears, indicating that the doping of fluorine atoms causes copper sulfide to produce more lattice vacancies. This structural change is actually caused by the melting of the copper ion sublattice, which can increase the conductivity of copper sulfide to a certain extent.

[0058] The electrode was used to conduct cyclic voltammetry test in polysulfide electrolyte, and the test results are as follows: Figure 4 As shown, the results show that the electrode has an extra pair of redox peaks compared with the original carbon felt, and the peak current is significantly greater than that of the original carbon felt, and the peak potential difference is significantly smaller than that of the original carbon felt, indicating that the electrode has better electrochemical activity.

[0059] The electrode was used as the negative electrode and the original carbon felt as the positive electrode to assemble the sulfide iron flow battery. The negative electrode electrolyte of the sulfide iron flow battery contains polysulfide, and the positive electrode electrolyte contains potassium ferrocyanide and potassium ferrocyanide. Due to the inherent characteristics of the sulfide iron flow battery, the battery must be operated at 20mA / cm 2 Start at a low current density and gradually increase the current density after a certain period of circulation. The specific test results are as follows Figure 5 As shown, at 80mA / cm 2 At a current density of 1.5 GHz, the average energy efficiency can reach 74.26%.

[0060] Example 2

[0061] This embodiment relates to a method for preparing a modified electrode for in-situ growth of copper sulfide, and the specific steps are as follows:

[0062] Except that the volume flow rate of sulfur hexafluoride gas in step 2 is 5 sccm, the remaining steps are the same as those in Example 1.

[0063] The copper sulfide modified electrode obtained in Example 2 was used as the negative electrode and the original carbon felt was used as the positive electrode to assemble the sulfur iron flow battery. The test results showed that at 80 mA / cm 2 At a current density of 1.5 GHz, the average energy efficiency can reach 73.61%.

[0064] Example 3

[0065] This embodiment relates to a method for preparing a modified electrode for in-situ growth of copper sulfide, and the specific steps are as follows:

[0066] Except that the volume flow rate of sulfur hexafluoride gas in step 2 is 15 sccm, the remaining steps are the same as those in Example 1.

[0067] The copper sulfide modified electrode obtained in Example 3 was used as the negative electrode and the original carbon felt was used as the positive electrode to assemble the sulfur iron flow battery. The test results showed that at 80 mA / cm2 At a current density of 1.5 GHz, the average energy efficiency can reach 73.28%.

[0068] Example 4

[0069] This embodiment relates to a method for preparing a modified electrode for in-situ growth of copper sulfide, and the specific steps are as follows:

[0070] Except that the plasma cleaning power in step 2 is 1200 W and the cleaning time per unit area is 10 s, the remaining steps are the same as those in Example 1.

[0071] The copper sulfide modified electrode obtained in Example 4 was used as the negative electrode and the original carbon felt was used as the positive electrode to assemble the sulfur iron flow battery. The test results showed that at 80 mA / cm 2 At a current density of 1.5 GHz, the average energy efficiency can reach 73.96%.

[0072] Example 5

[0073] This embodiment relates to a method for preparing a modified electrode for in-situ growth of copper sulfide, and the specific steps are as follows:

[0074] Except that the plasma cleaning power in step 2 is 1800 W and the cleaning time per unit area is 30 s, the remaining steps are the same as those in Example 1.

[0075] The copper sulfide modified electrode obtained in Example 5 was used as the negative electrode and the original carbon felt was used as the positive electrode to assemble the sulfur iron flow battery. The test results showed that at 80 mA / cm 2 At a current density of 1.5 GHz, the average energy efficiency can reach 73.45%.

[0076] Example 6

[0077] This embodiment relates to a method for preparing a modified electrode for in-situ growth of copper sulfide, and the specific steps are as follows:

[0078] Except that the concentration of the copper sulfate solution in step 3 is 0.05 M and the concentration of the sodium sulfide solution in step 5 is 0.075 M, the remaining steps are the same as those in Example 1.

[0079] The copper sulfide modified electrode obtained in Example 6 was used as the negative electrode and the original carbon felt was used as the positive electrode to assemble the sulfur iron flow battery. The test results are as follows: Figure 6 As shown, it shows that at 80mA / cm 2 At a current density of 1.5 GHz, the average energy efficiency can reach 72.94%.

[0080] Example 7

[0081] This embodiment relates to a method for preparing a modified electrode for in-situ growth of copper sulfide, and the specific steps are as follows:

[0082] Except that the concentration of the copper sulfate solution in step 3 is 0.5 M and the concentration of the sodium sulfide solution in step 5 is 0.75 M, the remaining steps are the same as those in Example 1.

[0083] The copper sulfide modified electrode obtained in Example 7 was used as the negative electrode and the original carbon felt was used as the positive electrode to assemble the sulfur iron flow battery. The test results are as follows: Figure 7 As shown, it shows that at 80mA / cm 2 At a current density of 1.5 GHz, the average energy efficiency can reach 69.15%.

[0084] Example 8

[0085] This embodiment relates to a method for preparing a modified electrode for in-situ growth of copper sulfide, and the specific steps are as follows:

[0086] Except that the standing time in step 7 is 120 s, the remaining steps are the same as those in Example 1.

[0087] The copper sulfide modified electrode obtained in Example 8 was used to perform cyclic voltammetry in a polysulfide electrolyte. The test results are as follows: Figure 4 As shown, the results show that the electrode has an additional pair of redox peaks compared to the original carbon felt, and the peak current is significantly greater than that of the original carbon felt, and the peak potential difference is significantly smaller than that of the original carbon felt, indicating that the electrode has better electrochemical activity; the copper sulfide modified electrode obtained in Example 8 is used as the negative electrode and the original carbon felt is used as the positive electrode to assemble the sulfur-iron liquid flow battery. The test results are shown in FIG. Figure 8 As shown, it shows that at 80mA / cm 2 At a current density of 1.5 GHz, the average energy efficiency can reach 74.18%.

[0088] Example 9

[0089] This embodiment relates to a method for preparing a modified electrode for in-situ growth of copper sulfide, and the specific steps are as follows:

[0090] Except that dilute sulfuric acid is not added dropwise in step 3 to adjust the pH of the pure copper sulfate solution and maintain its pH at about 4, and sodium hydroxide is not added dropwise in step 5 to adjust the pH of the pure sodium sulfide solution and maintain its pH at about 10, the remaining steps are the same as in Example 1.

[0091] The copper sulfide modified electrode obtained in Example 9 was used as the negative electrode and the original carbon felt was used as the positive electrode to assemble the sulfur iron flow battery. The test results are as follows: Figure 10 As shown, it shows that at 80mA / cm 2 At a current density of 1.5 GHz, the average energy efficiency is 68.12%.

[0092] Example 10

[0093] This embodiment relates to a method for preparing a modified electrode for in-situ growth of copper sulfide, and the specific steps are as follows:

[0094] Except that the concentration of sodium sulfide in step 5 is 0.3 M and the volume of sodium sulfide in step 6 is 80 mL, the remaining steps are the same as those in Example 1.

[0095] The copper sulfide modified electrode obtained in Example 10 was used as the negative electrode and the original carbon felt was used as the positive electrode to assemble the sulfur iron flow battery. The test results are as follows: Figure 11 As shown, it shows that at 80mA / cm 2 At a current density of 1.5 GHz, the average energy efficiency is 67.88%.

[0096] Example 11

[0097] This embodiment relates to a method for preparing a modified electrode for in-situ growth of copper sulfide, and the specific steps are as follows:

[0098] Except that the cleaning time in step 7 was changed to 1800s and the number of cleanings was changed to 10 times, the remaining steps were the same as in Example 1.

[0099] The copper sulfide modified electrode obtained in Example 11 was used as the negative electrode and the original carbon felt was used as the positive electrode to assemble the sulfur iron flow battery. The test results are as follows: Figure 12 As shown, it shows that at 80mA / cm 2 At a current density of 1.5 GHz, the average energy efficiency can reach 74.28%.

[0100] Example 12

[0101] This embodiment relates to a method for preparing a modified electrode for in-situ growth of copper sulfide, and the specific steps are as follows:

[0102] Except that the cleaning method in step 7 is changed to repeatedly rinsing the carbon felt under water for 10 minutes, the remaining steps are the same as those in Example 1.

[0103] The copper sulfide modified electrode obtained in Example 12 was used as the negative electrode and the original carbon felt was used as the positive electrode to assemble the sulfur iron flow battery. The test results showed that at 80 mA / cm 2 At a current density of 1.5 GHz, the average energy efficiency can reach 74.19%.

[0104] Compared with Example 1 of the present invention, Examples 11 and 12 only adjusted the cleaning step after the catalyst loading, by extending the immersion cleaning time and frequency or adjusting the cleaning method to use water flushing. Battery test results show that after adjusting the cleaning step, the battery performance remains consistent with Example 1, indicating that the cleaning step does not affect the performance of the catalyst. It also proves that the in-situ grown catalyst is stably bonded to the carbon fiber and is unlikely to fall off under the flushing of water or electrolyte, thereby causing electrode failure. Therefore, to improve production efficiency and reduce costs, a simple immersion cleaning of 60s-180s, 2-5 times, and the excess sulfide salt solution is sufficient to clean the carbon fiber.

[0105] Comparative Example 1

[0106] This comparative example relates to a method for preparing a copper sulfide modified electrode, and the specific steps are as follows:

[0107] Except that step 2 is omitted, the remaining steps are the same as those in Example 1;

[0108] The copper sulfide modified electrode obtained in Comparative Example 1 was used to perform cyclic voltammetry in a polysulfide electrolyte. The test results are as follows: Figure 4 As shown, the results show that the electrode has no significant improvement compared with the original carbon felt.

[0109] The copper sulfide modified electrode obtained in Comparative Example 1 was used as the negative electrode and the original carbon felt was used as the positive electrode to assemble the sulfur iron flow battery. The test results are as follows: Figure 9 As shown, it shows that at 80mA / cm 2 At a current density of 1.5 GHz, the average energy efficiency is only 64.28%.

[0110] Comparative Example 2

[0111] This comparative example relates to a method for preparing a copper sulfide modified electrode, and the specific steps are as follows:

[0112] Except that sulfur hexafluoride gas is not introduced in step 2, and the surface of the carbon felt is directly cleaned by plasma, the remaining steps are the same as those in Example 1.

[0113] The copper sulfide modified electrode obtained in Comparative Example 2 was used as the negative electrode and the original carbon felt was used as the positive electrode to assemble the sulfur iron flow battery. The test results showed that the present invention has a high current density of 80 mA / cm 2 At a current density of 1.5 GHz, the average energy efficiency is 66.82%.

[0114] Comparative Example 3

[0115] This comparative example relates to a method for preparing a copper sulfide modified electrode, and the specific steps are as follows:

[0116] Except that the sprayed carbon felt was directly washed in step 7 and the reaction was not performed for 60 seconds, the remaining steps were the same as those in Example 1.

[0117] The copper sulfide modified electrode obtained in Comparative Example 3 was used to perform cyclic voltammetry in a polysulfide electrolyte. The test results are as follows: Figure 4 As shown, the results show that the electrode has an additional pair of redox peaks compared to the original carbon felt, the peak potential difference is significantly smaller than that of the original carbon felt, and the peak current is close to that of the original carbon felt, indicating that the electrochemical activity of the electrode has been improved to a certain extent; the copper sulfide modified electrode obtained in Comparative Example 3 is used as the negative electrode and the original carbon felt is used as the positive electrode to assemble the sulfur-iron flow battery. The test results show that the present invention has a good performance at 80 mA / cm 2At a current density of 1.5 GHz, the average energy efficiency is 69.46%.

[0118] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various variations or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A modified electrode for in-situ growth of copper sulfide, characterized in that: The modified electrode includes a substrate and a copper sulfide catalyst coated on the substrate, wherein the substrate is doped with sulfur atoms and fluorine atoms, and the copper sulfide catalyst is in a granular form and uniformly coated on the surface of the substrate. The modified electrode with in-situ copper sulfide growth is prepared by the following preparation method, which includes the following steps: (1) Doping sulfur atoms and fluorine atoms on a substrate material using a plasma cleaning method to obtain a doped substrate; wherein the plasma cleaning method uses sulfur tetrafluoride or sulfur hexafluoride gas as a cleaning raw material; (2) spraying a copper ion solution on the doped substrate to wet it, and then spraying a sulfur ion solution on the wetted surface of the doped substrate to react; (3) Cleaning and drying the doped substrate after the reaction in step (2) to obtain a modified electrode with in-situ growth of copper sulfide.

2. The modified electrode according to claim 1, wherein The doping amount of the sulfur atoms and fluorine atoms is 0.1-10% of the surface area of ​​the substrate, the coating thickness of the copper sulfide catalyst is 100-10000 nm, the loading amount of the copper sulfide catalyst is 5-30 wt% of the substrate material, and the particle size is 0.1-1.5 μm.

3. A method for preparing a modified electrode for in-situ growth of copper sulfide according to claim 1 or 2, characterized in that: The following steps are involved: (1) Doping sulfur atoms and fluorine atoms on a substrate material using a plasma cleaning method to obtain a doped substrate; (2) spraying a copper ion solution on the doped substrate to wet it, and then spraying a sulfur ion solution on the wetted surface of the doped substrate to react; (3) Cleaning and drying the doped substrate after the reaction in step (2) to obtain a modified electrode with in-situ growth of copper sulfide.

4. The preparation method according to claim 3, wherein The substrate material in step (1) comprises one or more of graphite felt, carbon felt, carbon paper, carbon cloth or nickel foam.

5. The preparation method according to claim 3, wherein The plasma cleaning method in step (1) uses sulfur tetrafluoride or sulfur hexafluoride gas as a cleaning raw material, and the volume flow rate of the gas is 5 to 15 sccm; the plasma cleaning power is 1200 to 1800 W, the cleaning time per square meter is 10 to 30 seconds, and the number of cleaning times is 1 to 2 times.

6. The preparation method according to claim 3, wherein The copper ion solution in step (2) comprises one or more of copper sulfate, copper nitrate, copper chloride, copper acetate or copper bromide aqueous solution, wherein the copper ion solution contains copper 2+ The concentration is 0.05-0.5M; when spraying the copper ion solution, dilute hydrochloric acid and / or dilute sulfuric acid are added to adjust the pH of the solution to 1-2.

7. The preparation method according to claim 3, wherein The sulfide ion solution in step (2) contains potassium sulfide and / or sodium sulfide, and the sulfide ion solution contains potassium sulfide and / or sodium sulfide. 2- The concentration is 0.075-0.75M, and the volume of the sulfide ion solution is 150-200% of the copper ion solution; when spraying the sulfide ion solution, an aqueous solution of potassium hydroxide and / or sodium hydroxide is added to adjust the pH of the solution to 12-13.

8. The preparation method according to claim 3, wherein The reaction time of the reaction in step (3) is 60-180s, the cleaning time is 60-180s, and the number of cleanings is 2 to 5 times; the drying environment is normal pressure and the temperature is 80 to 120°C.

9. A flow battery, characterized in that: The liquid flow battery comprises the modified electrode of in-situ grown copper sulfide according to claim 1 or 2, or the modified electrode of in-situ grown copper sulfide prepared by the preparation method according to any one of claims 3 to 8.

10. The flow battery according to claim 9, wherein The liquid flow battery adopts a polysulfide electrolyte, and the polysulfide electrolyte includes a sulfide / polysulfide electrolyte; the diaphragm adopted by the liquid flow battery includes a perfluorosulfonic acid membrane or a non-fluorine ion exchange membrane.

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