Selenium copper compound, preparation method and application thereof

Abstract

The application discloses a selenocopper compound and a preparation method and application thereof. The preparation process of the selenocopper compound is as follows: selenium powder is dissolved in an alkaline solution under heating, then a reducing agent is added, and then a mixed solution containing a copper salt and a surfactant is added to perform a co-precipitation reaction, and the reaction product is filtered, washed and dried to obtain the selenocopper compound; or raw materials including a copper salt are dissolved in an alkaline solution, then a reducing agent is added to perform a precipitation reaction, and then the reaction product is filtered, washed and dried to obtain an orange-red powder, and the powder is co-calcined with selenium powder to obtain the selenocopper compound. Compared with general chalcogen compounds, the selenocopper compound has higher conductivity, various crystal structures, higher electrocatalytic activity and stability. Tests show that the energy efficiency of a flow battery with a negative electrode modified by the selenocopper compound can reach about 80% under an electric current density of 80 mA / cm 2 , and the energy storage performance of the flow battery is greatly improved.

Description

Technical Field

[0001] This invention relates to a copper selenide, specifically to a copper selenide, its preparation method, and its application, belonging to the field of flow battery technology. Background Technology

[0002] Redox flow batteries are a promising energy storage technology due to their high safety, long cycle life, and independent power and energy characteristics. They can address the instability and uncontrollability issues associated with discontinuous renewable energy sources such as wind and solar power. Among various flow batteries, those using polysulfides as redox couples are gradually gaining popularity due to their low cost and readily available raw materials. However, the low redox activity and slow reaction kinetics of polysulfides themselves result in poor efficiency in flow batteries based on polysulfide couples, hindering their commercial development.

[0003] Currently, most electrodes used in flow batteries are carbon electrodes, which have advantages such as good conductivity and high specific surface area. However, unmodified carbon electrodes have limited activity, thus necessitating the search for electrodes with higher activity to meet the requirements. While foamed metal electrodes, such as nickel foam, possess higher catalytic activity, the metal reacts with polysulfide ions in the electrolyte to form metal sulfides. Since metal sulfides lack a dense structure, they cannot prevent further reactions with polysulfides, thus failing to effectively improve battery performance. Therefore, the market urgently needs a material with high catalytic activity to enhance the redox activity of polysulfides and improve the overall performance of flow batteries. Summary of the Invention

[0004] To address the problems existing in the prior art, the first objective of this invention is to provide a copper selenide. The copper selenide provided by this invention has a direct band gap between 2.1 and 2.39 eV and an indirect band gap between 1.2 and 1.7 eV, exhibiting higher conductivity compared to general chalcogenides. Furthermore, this copper selenide also possesses various crystal structures, endowing the material with higher electrocatalytic activity and stability.

[0005] The second objective of this invention is to provide a method for preparing copper selenide. This method uses a liquid-phase coprecipitation method or a temperature-programmed solid-state sintering method to directly react copper salt and selenium powder to obtain polycrystalline copper selenide. In particular, the liquid-phase coprecipitation method can directly synthesize nanoscale copper selenide under low-temperature conditions. Furthermore, the morphology of the obtained copper selenide can be directly controlled by adjusting the type and amount of reducing agent and surfactant.

[0006] A third objective of this invention is to provide an application of copper selenide for modifying the negative electrode of a polysulfide flow battery. Based on the unique properties and structure of the aforementioned copper selenide, its use as a modified polysulfide flow battery negative electrode exhibits excellent technical effects. Testing has shown that the flow battery using the aforementioned copper selenide-modified negative electrode achieves a performance of 80 mA / cm². 2 At current densities of up to 80%, its energy efficiency can reach about 80%, which greatly improves the energy storage performance of flow batteries.

[0007] To achieve the above-mentioned technical objectives, the present invention provides a method for preparing copper selenide, comprising: dissolving selenium powder in an alkaline solution under heating conditions to obtain a clear solution A; adding a reducing agent to the clear solution A to obtain a solution B; dissolving a copper salt and a surfactant in deionized water to obtain a solution C; adding solution B to solution C to carry out a co-precipitation reaction; and filtering, washing and drying the reaction product to obtain the final product.

[0008] Alternatively, raw materials, including copper salts, are dissolved in an alkaline solution, and a reducing agent is added to carry out a precipitation reaction. The reaction product is filtered, washed, and dried to obtain an orange-red powder, which is then co-calcined with selenium powder to obtain the final product.

[0009] The mass ratio of the selenium powder, reducing agent and copper salt is 1:(1~2):(1~2).

[0010] The method provided by this invention, by strictly controlling the addition amounts of the main raw materials, achieves efficient synthesis of copper selenide compounds while effectively controlling the crystal morphology and improving their dispersibility, significantly reducing product agglomeration. It should be noted that if the amount of reducing agent added is too high, excessive SeO3 will exist in the solution. 2- If the amount of reducing agent added is too low, it will not be enough to reduce the selenium powder to Se. 2- All of these will affect the purity and yield of the final product.

[0011] As a preferred embodiment, when the selenium powder and copper salt are mixed at a molar ratio of selenium to copper of 1:0.8~1, the main component of the resulting copper selenide is CuSe.

[0012] As a preferred embodiment, when the selenium powder and copper salt are in a molar ratio of selenium to copper of 1:1.8~2, the main component of the resulting copper selenium compound is Cu3Se2.

[0013] As a preferred embodiment, the alkaline solution is at least one of sodium hydroxide, potassium hydroxide, and sodium sulfite solution.

[0014] As a preferred embodiment, the reducing agent is at least one selected from cystine, cysteine, glutathione, and ascorbic acid. The organic reducing agents listed in this invention have similar reducing abilities, require mild reaction conditions, and can act as both reducing agents and surface modifiers during the reaction, thereby further controlling the crystal morphology.

[0015] As a preferred embodiment, the copper salt is a soluble divalent copper salt. More preferably, the copper salt is copper sulfate.

[0016] As a preferred embodiment, the surfactant is any one of polyvinyl alcohol, polyvinylpyrrolidone, polyacrylic acid, and polyethylene glycol. The surfactant can selectively interact with different crystal faces, altering their surface energy. By adding an appropriate amount of surfactant, the size and crystal structure of the product can be controlled.

[0017] As a preferred embodiment, the amount of surfactant added does not exceed 10 wt% of the copper salt mass.

[0018] As a preferred embodiment, the mass ratio of the orange-red powder to the selenium powder is 1:(1~2).

[0019] As a preferred embodiment, the co-calcination conditions are as follows: under a protective atmosphere, the temperature is increased from room temperature to 300-400°C at a rate of 8-12°C / min, held for 2-5 hours, and then cooled to room temperature in the furnace. Excessive temperature will lead to excessively rapid grain growth, excessively large crystal size, and easy agglomeration; excessively low temperature will not reach the transformation temperature from CuSe to CuSe2.

[0020] The present invention also provides a copper selenide, obtained by any of the preparation methods described above; the copper selenide is Cu. x Se y ; where x:y takes values ​​in the range of (1~3):2.

[0021] The present invention also provides an application of copper selenide for modifying the negative electrode of a polysulfide flow battery. The process is as follows: the above-mentioned copper selenide and Nafion resin are dissolved in ethanol and thoroughly mixed to obtain a modified slurry, which is then uniformly coated on the surface of the negative electrode of the flow battery and dried.

[0022] The present invention uses copper selenide as a surface modifier for the negative electrode of a flow battery, which not only significantly improves the conductivity and electrocatalytic activity of the electrode, but also avoids the reaction with polysulfide ions in the electrolyte of the flow battery due to its excellent stability. This completely solves the problem of low battery efficiency caused by the easy reaction of metal modified electrodes with polysulfide ions to form metal sulfides in the prior art, and greatly improves the overall performance of flow batteries, especially polysulfide flow batteries.

[0023] As a preferred embodiment, the mass ratio of copper selenide to Nafion resin is (1.5~15):1. Nafion resin acts as a binder, adhering the copper selenide to the carbon felt, preventing it from falling off during cycling and ensuring electrode stability. Furthermore, Nafion resin is also an ion exchange resin, which can play a certain role in ion / electron conduction, helping to reduce the negative impact of the binder on electrode conductivity. The amount of Nafion resin added must strictly adhere to the above requirements; too little resin will result in weak adhesion and easy falling off, while too much will affect the contact between the catalyst and the active material, leading to increased internal resistance and affecting electrode performance.

[0024] As a preferred embodiment, the drying process is as follows: drying the material in an oven at 50~80℃ until constant weight.

[0025] As a preferred embodiment, the polysulfide flow battery includes: a positive electrode, a negative electrode coated with copper selenide, a positive electrode electrolyte, a negative electrode electrolyte, and an ion exchange membrane.

[0026] As a preferred embodiment, the positive electrode is a carbon felt, and the negative electrode is a carbon felt coated with copper selenide.

[0027] As a preferred embodiment, the positive electrode electrolyte is a potassium ferricyanide alkaline solution.

[0028] As a preferred embodiment, the negative electrode electrolyte is a sodium disulfide alkaline solution.

[0029] As a preferred embodiment, the ion exchange membrane is a Nafion membrane. More preferably, the ion exchange membrane is a Nafion 212 membrane.

[0030] Compared with the prior art, the beneficial technical effects of the technical solution of the present invention are as follows:

[0031] 1) The direct band gap of the copper selenide provided by the present invention is between 2.1 and 2.39 eV, and the indirect band gap is between 1.2 and 1.7 eV. Compared with general chalcogenides, it has higher conductivity. In addition, the copper selenide has a variety of crystal structures, which endows the material with higher electrocatalytic activity and stability.

[0032] 2) The preparation method provided by the present invention uses liquid-phase coprecipitation or temperature-programmed solid-state sintering to directly react copper salt with selenium powder to obtain polycrystalline copper selenide. In particular, the liquid-phase coprecipitation method can directly synthesize nanoscale copper selenide under low temperature conditions. Moreover, the morphology of the obtained copper selenide can be directly controlled by adjusting the type and amount of reducing agent and surfactant. In addition, the method has the advantages of low synthesis difficulty, simple operation, easy control and suitability for large-scale production.

[0033] 3) In the technical solution provided by this invention, based on the unique properties and structure of the aforementioned copper selenide, its use in modifying the negative electrode of polysulfide flow batteries exhibits excellent technical effects. Tests have shown that flow batteries using the aforementioned copper selenide-modified negative electrode achieve a performance of 80 mA / cm². 2 At current densities of up to 80%, its energy efficiency can reach about 80%, which greatly improves the energy storage performance of flow batteries. Attached Figure Description

[0034] Figure 1 The XRD image of CuSe provided in Embodiment 1 of the present invention;

[0035] Figure 2 This is the cyclic voltammetry curve of CuSe in polysulfide ion solution provided in Example 1 of the present invention;

[0036] Figure 3 The rate capability diagram of a sulfur-iron battery using a CuSe-modified negative electrode;

[0037] Figure 4 The image shown is an XRD image of Cu3Se2 provided in Embodiment 2 of the present invention.

[0038] Figure 5 This is the cyclic voltammetry curve of Cu3Se2 in polysulfide ion solution provided in Example 2 of the present invention; Figure 6 The rate capability diagram of a sulfur-iron battery using a Cu3Se2 modified negative electrode;

[0039] Figure 7 The XRD image of CuSe2 provided in Embodiment 3 of the present invention;

[0040] Figure 8 This is the cyclic voltammetry curve of CuSe2 in polysulfide ion solution provided in Example 3 of the present invention;

[0041] Figure 9 The rate capability diagram of a sulfur-iron battery using a CuSe2 modified negative electrode;

[0042] Figure 10 Rate profile of a sulfur-iodine battery using the CuSe modified negative electrode provided in Example 1 of this invention;

[0043] Figure 11 This is a rate curve of the sulfur-iron battery provided in Comparative Example 1 of the present invention. Detailed Implementation

[0044] The technical solution of the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings. To facilitate understanding of the present invention, a more comprehensive and detailed description of the present invention will be provided below with reference to the accompanying drawings and preferred embodiments. It should be noted that the described embodiments are merely some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0045] Unless otherwise specified in the embodiments of this invention, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained through conventional technical means or purchased from the market.

[0046] Example 1

[0047] This embodiment provides a copper selenide, the specific preparation process of which is as follows:

[0048] Add 0.05 mol selenium powder and 0.3 mol sodium hydroxide to 80 ml of deionized water and stir for 0.5 h to form a homogeneous solution. Add cysteine ​​(cysteine ​​to selenium powder ratio of 4:3) to the solution, heat to 80 °C, and continue stirring for 0.5 h to obtain a homogeneous solution. Add 0.045 mol copper sulfate and 1 g polyvinylpyrrolidone to 100 ml of deionized water and stir for 0.5 h to form a homogeneous transparent solution. Mix the two solutions and stir for 1.5 h. After the reaction is complete, filter the resulting mixed solution, wash three times each with deionized water and ethanol, and then dry the resulting solid at 60 °C for 12 h to obtain the final product.

[0049] The XRD pattern of the copper selenide obtained in this embodiment is as follows: Figure 1 As shown, its crystal form is hexagonal, and its main component is CuSe.

[0050] To more intuitively demonstrate the advantages of the technical solution of this invention, the electrochemical performance of the aforementioned copper selenide was also tested. Specifically, the prepared copper selenide powder catalyst was added to ethanol, and 50 μL of Nafion resin was added as a binder. The mixture was ultrasonicated for 1 hour to obtain a uniform slurry ink, wherein the content of copper selenide was 18 mg / mL. In this embodiment, a three-electrode system was used for the electrochemical performance test. The working electrode was a glassy carbon electrode with a catalyst loading of 0.9 mg / mL. 2 The counter electrode is 1×1.5cm. 2 The test used a platinum mesh, with a Hg / HgO electrode as the reference electrode, and the electrolyte was 0.1 mol / L Na2S2 + 1 mol / L NaOH. The scan rate was 10 mV / s, and argon gas was continuously introduced during the test to prevent the electrolyte from being oxidized.

[0051] like Figure 2 As shown, the blank glassy carbon electrode has no oxidation or reduction peaks, indicating that pure glassy carbon has no redox activity. However, the glassy carbon electrode loaded with the aforementioned copper selenide has three distinct reduction peaks, corresponding to S4 from right to left. 2- S2 2- S 2- The peak currents of the reduction, oxidation, and reduction peaks also increased further, indicating that copper selenide has significant catalytic activity for the redox reaction of polysulfide ions.

[0052] Furthermore, this invention also uses the aforementioned copper selenide as a modified negative electrode for a sulfur-iron battery. Specifically, the copper selenide and Nafion resin are added to ethanol and mixed evenly to obtain a uniform slurry, which is then uniformly loaded onto a carbon felt and dried at 60°C for use. The battery uses an unloaded carbon felt as the positive electrode and a copper selenide-modified electrode as the negative electrode; the positive electrode electrolyte is 0.3M K3Fe(CN)6 + 1M NaOH, and the negative electrode electrolyte is 0.5M Na2S2 + 1M NaOH; the volume of both positive and negative electrolytes is 70ml; the ion exchange membrane is Nafion212; a polysulfide-based sulfur-iron flow battery is assembled, and the rate test range is 20-140mA / cm. 2 The current density interval is 20 mA / cm². 2 .

[0053] like Figure 3 As shown, the electrode modified with copper selenide prepared in this embodiment exhibits excellent performance, reaching 20 mA / cm². 2 Under low current density, its energy efficiency reaches 91%, and the current density increases to 120 mA / cm². 2 Even at that time, the energy efficiency can still reach 69%. It can be seen that the electrode modified with copper selenide catalyst has higher performance than the commercial original carbon felt electrode and can be widely used in polysulfide system flow batteries.

[0054] Example 2

[0055] This embodiment provides a copper selenide, the specific preparation process of which is as follows:

[0056] Add 4 mmol of selenium powder and 10 mmol of sodium sulfite to 50 ml of deionized water, heat to 80 °C and stir for 2 h; cool the reaction solution to room temperature and filter to obtain the supernatant; add 8 mmol of copper sulfate to the supernatant and stir for 2 h; after the reaction is complete, filter the resulting mixed solution, wash three times with deionized water and ethanol, and dry the obtained solid at 60 °C for 12 h to obtain the final product.

[0057] The XRD pattern of the copper selenide obtained in this embodiment is as follows: Figure 4As shown, its crystal form is tetragonal, and its main component is Cu3Se2.

[0058] To more intuitively demonstrate the advantages of the technical solution of this invention, the electrochemical performance of the above-mentioned copper selenide was also tested. Specifically, the prepared copper selenide powder was added to ethanol, and 50 μL of Nafion resin was added as a binder. The mixture was ultrasonicated for 1 hour to obtain a uniform slurry ink, wherein the content of copper selenide was 6 mg / mL. In this embodiment, a three-electrode system was used for the electrochemical performance test, with the working electrode being a glassy carbon electrode with a catalyst loading of 0.3 mg / mL. 2 The counter electrode is 1×1.5cm. 2 The test used a platinum mesh, with a Hg / HgO electrode as the reference electrode, and the electrolyte was 0.1 mol / L Na2S2 + 1 mol / L NaOH. The scan rate was 10 mV / s, and argon gas was continuously introduced during the test to prevent the electrolyte from being oxidized.

[0059] like Figure 5 As shown, the blank glassy carbon electrode has no oxidation or reduction peaks, indicating that pure glassy carbon has no redox activity. However, the glassy carbon electrode loaded with the aforementioned copper selenide has three distinct reduction peaks, corresponding to S4 from right to left. 2- S2 2- S 2- The peak currents of the reduction, oxidation, and reduction peaks also increased further, indicating that the copper selenide has significant catalytic activity for the redox reaction of polysulfide ions.

[0060] Furthermore, this invention also uses the aforementioned copper selenide as a modified negative electrode for a sulfur-iron battery. Specifically, the prepared copper selenide is mixed evenly with Nafion resin in ethanol to obtain a uniform slurry, which is then uniformly loaded onto a carbon felt and dried at 60°C for use. The battery uses an unloaded carbon felt as the positive electrode and a copper selenide-loaded electrode as the negative electrode; the positive electrode electrolyte is 0.3M K3Fe(CN)6 + 1M NaOH, and the negative electrode electrolyte is 0.5M Na2S2 + 1M NaOH; the volume of both the positive and negative electrolytes is 70ml; the ion exchange membrane is Nafion212; a polysulfide-based sulfur-iron flow battery is assembled, and the rate test range is 20-140mA / cm. 2 The current density interval is 20 mA / cm². 2 .

[0061] from Figure 6 As shown, the electrode modified with copper selenide prepared in this embodiment exhibits excellent performance, reaching 20 mA / cm². 2 Under high current density, its energy efficiency reaches 93%, and the current density increases to 120 mA / cm². 2Even at this time, the energy efficiency can still reach 64%. It can be seen that the Cu3Se2 catalyst has excellent catalytic activity for polysulfide systems and is also very suitable for redox flow batteries of polysulfide systems.

[0062] Example 3

[0063] This embodiment provides a copper selenide, the specific preparation process of which is as follows: 7.5 mmol of copper sulfate and 2.5 mmol of sodium citrate are added to 500 ml of sodium hydroxide solution and stirred for 0.5 h to obtain a mixed solution; 7.5 mmol of ascorbic acid is added to the above mixed solution and the reaction is continued for 0.5 h; after the reaction is completed, the mixed solution is filtered, washed three times with deionized water and ethanol respectively, and dried at 60 °C for 12 h to obtain Cu2O powder; Cu2O and selenium powder are placed in a tube furnace at a mass ratio of 1:2 and reacted at 300 °C for 3 h in an Ar atmosphere to obtain the final product.

[0064] The XRD pattern of the copper selenide obtained in this embodiment is as follows: Figure 7 As shown, its crystal form is tetragonal, and its main component is CuSe2.

[0065] To more intuitively demonstrate the advantages of the technical solution of this invention, the electrochemical performance of the above-mentioned copper selenide was also tested. Specifically, the prepared CuSe2 powder catalyst was added to ethanol, and 50 μL of Nafion resin was added as a binder. The mixture was ultrasonicated for 1 hour to obtain a uniform slurry ink, wherein the catalyst content was 6 mg / mL. In this embodiment, a three-electrode system was used for electrochemical performance testing, with the working electrode being a glassy carbon electrode loaded with the catalyst at a loading of 0.3 mg / mL. 2 The counter electrode is 1×1.5cm. 2 The test used a platinum mesh, with a Hg / HgO electrode as the reference electrode, and the electrolyte was 0.1 mol / L Na2S2 + 1 mol / L NaOH. The scan rate was 10 mV / s, and argon gas was continuously introduced during the test to prevent the electrolyte from being oxidized.

[0066] like Figure 8 As shown, the glassy carbon electrode loaded with the above-mentioned copper selenide has three distinct reduction peaks, corresponding to S4 from right to left. 2- S2 2- S 2- The peak currents of the reduction, oxidation, and reduction peaks also increased further, indicating that the copper selenide has significant catalytic activity for the redox reaction of polysulfide ions.

[0067] Furthermore, this invention also uses the aforementioned copper selenide as a modified negative electrode for a sulfur-iron battery. Specifically, the prepared copper selenide is mixed evenly with Nafion resin in ethanol to obtain a uniform slurry, which is then uniformly loaded onto a carbon felt and dried at 60°C for use. The battery uses an unloaded carbon felt as the positive electrode and a copper selenide-loaded electrode as the negative electrode; the positive electrode electrolyte is 0.3M K3Fe(CN)6 + 1M NaOH, and the negative electrode electrolyte is 0.5M Na2S2 + 1M NaOH; the volume of both the positive and negative electrolytes is 70ml; the ion exchange membrane is Nafion212; a polysulfide-based sulfur-iron flow battery is assembled, and the rate test range is 20-140mA / cm. 2 The current density interval is 20 mA / cm². 2 .

[0068] from Figure 9 As shown, the electrode modified with copper selenide prepared in this embodiment exhibits excellent performance, reaching 20 mA / cm². 2 Under low current density, its energy efficiency reaches 91%, and the current density increases to 100 mA / cm². 2 At the same time, the energy efficiency can still reach 64%. It can be seen that the CuSe2 catalyst also has excellent catalytic activity for polysulfide systems and is also suitable for redox flow batteries of polysulfide systems.

[0069] Example 4

[0070] In this embodiment, the CuSe-loaded electrode prepared in Example 1 above is applied to a sulfur-iodine flow battery. The specific process is as follows:

[0071] The battery uses unloaded carbon felt as the positive electrode and CuSe-loaded electrode as the negative electrode; the positive electrode electrolyte is 0.75 M NaI + 1 M NaOH, and the negative electrode electrolyte is 0.5 M Na2S2 + 1 M NaOH; the volume of both positive and negative electrolytes is 70 ml; the ion exchange membrane is Nafion 212; a polysulfide-based sulfur-iodine flow battery was assembled, and the rate testing range was 20-140 mA / cm. 2 The current density interval is 20 mA / cm². 2 Its rate performance is as follows Figure 10 As shown.

[0072] from Figure 10 It can be seen that the electrode battery performance is significantly improved after modification with the CuSe catalyst prepared in this example. At the same 20 mA / cm²... 2 Under low current density, its energy efficiency reaches 83%, and the current density increases to 100 mA / cm². 2Even at that time, the energy efficiency can still reach 59%. It can be seen that the electrode modified with copper selenide catalyst can not only be used in sulfur-iron batteries, but also in other polysulfide flow batteries.

[0073] Comparative Example 1

[0074] Both the positive and negative electrodes of the battery use unloaded carbon felt as electrodes; the positive electrode electrolyte is 0.3M K3Fe(CN)6 + 1M NaOH, and the negative electrode electrolyte is 0.5M Na2S2 + 1M NaOH; the volume of both positive and negative electrolytes is 70ml; the ion exchange membrane is Nafion 212; a polysulfide-based sulfur-iron flow battery was assembled, and the rate testing range was 20-140mA / cm. 2 The current density interval is 20 mA / cm². 2 Its rate performance is as follows Figure 11 As shown.

[0075] from Figure 11 It can be seen that the battery performance of the unmodified carbon felt electrode is very poor, and it can only operate at low charge density, exceeding 40 mA / cm². 2 The electrical seal cannot continue to operate.

Claims

1. A method for producing a selenocupride, characterized by, The application relates to a method for preparing a selenium copper compound, which comprises the following steps: dissolving selenium powder in an alkaline solution under heating to obtain a clear solution A; adding a reducing agent to the clear solution A to obtain a solution B; dissolving a copper salt and a surfactant in deionized water to obtain a solution C; adding the solution B to the solution C to carry out a coprecipitation reaction; and filtering, washing and drying the reaction product to obtain the selenium copper compound. The application also relates to a method for modifying a polysulfide flow battery negative electrode, which comprises the following steps: dissolving the selenium copper compound and a Nafion resin in ethanol to obtain a modified slurry; uniformly coating the modified slurry on the surface of the flow battery negative electrode; and drying to obtain the modified flow battery negative electrode. The application further relates to a polysulfide flow battery, which comprises a positive electrode, a selenium copper compound-coated negative electrode, a positive electrode electrolyte, a negative electrode electrolyte and an ion exchange membrane. The selenium copper compound and the Nafion resin have a mass ratio of (1.5-15):1; and the drying process is carried out in an oven at 50-80 DEG C until the weight of the material is constant. The positive electrode is carbon felt, the negative electrode is the selenium copper compound-coated carbon felt, the positive electrode electrolyte is any one of an iron cyanide alkali solution and a polyiodine ion alkali solution, the negative electrode electrolyte is a sodium disulfide alkali solution, and the ion exchange membrane is a Nafion resin membrane. ​ ​ ​ 2. A method of preparing a selenocupride according to claim 1, characterized in that: ​ 3. The method for preparing a copper selenide according to claim 1, characterized in that: ​ 4. The method for preparing a copper selenide according to claim 1, characterized in that: ​ 5. A selenocupride characterized by: obtained by the production method according to any one of claims 1 to 4; the selenocupride is Cu x Se y ; wherein the value range of x:y is (1~3):

2.

6. Use of selenocopper compounds according to claim 5, characterized in that: ​ 7. Use of selenocopper compounds according to claim 6, characterized in that: ​ 8. Use of selenocopper according to claim 7, characterized in that: ​ 9. Use of selenocopper compounds according to claim 8, characterized in that: ​

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