High-entropy solid energy storage material, preparation method and application thereof
By using high-entropy vanadium-based Prussian blue analogues, the problems of insufficient active sites and poor structural stability in vanadium redox flow batteries have been solved, achieving efficient vanadium electrolyte reaction and long-life battery performance, supporting the commercialization of vanadium redox flow batteries.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- DALIAN RONGKE ENERGY STORAGE EQUIP CO LTD
- Filing Date
- 2026-01-29
- Publication Date
- 2026-06-09
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Abstract
Description
Technical Field
[0001] This invention relates to the field of solid capacity enhancement technology for flow battery electrolytes, and particularly to a high-entropy solid energy storage material, its preparation method, and its application. Background Technology
[0002] Vanadium redox flow batteries, due to their inherent safety characteristics, excellent cycle life, and the unique advantage of independently designable power and capacity, have shown broad application prospects in large-scale renewable energy storage and smart grid construction. However, their commercialization process is still constrained by two key factors: high electrolyte cost and limited energy density. Vanadium electrolyte, as the active material, accounts for a significant portion of the total system cost, while the solubility limit of vanadium ions in solution directly restricts the electrolyte's volumetric capacity, thus affecting the battery's energy density and economic efficiency.
[0003] To overcome the solubility limitations of vanadium ions in solution, the industry has explored methods to directly increase the concentration of vanadium ions. However, this method faces insurmountable physicochemical obstacles: high concentrations not only cause a sharp increase in electrolyte viscosity, leading to a significant increase in pumping losses, but more seriously, high-valence vanadium ions at the cathode, such as VO2, are also affected. + Chemical instability at high concentrations can lead to precipitation, directly threatening the long-term reliable operation of the battery. Therefore, while maintaining good physicochemical stability of the electrolyte, an innovative solution that can fundamentally improve the energy storage system is urgently needed.
[0004] The "redox-targeted reaction" technology offers a promising solution to the aforementioned problems. This technology constructs a "solid-liquid" two-phase energy storage system by adding potential-matched solid energy storage materials to the electrolyte storage tank. The principle is based on the reversible electron exchange reaction between redox mediators dissolved in the electrolyte, such as vanadium ions, and active sites on the surface of the solid material, thereby storing some energy in the solid material with a higher theoretical capacity. This mechanism can significantly increase the overall vanadium electrolyte volumetric capacity of the system without significantly altering the bulk properties of the electrolyte.
[0005] In the selection of solid materials, Prussian blue analogues (PBA) are considered potential candidates due to their open framework structure and tunable redox potential. However, existing PBA-based solid compatibilizers still have significant drawbacks in practical applications, specifically in the following three aspects:
[0006] 1. Insufficient active sites limit capacity enhancement and reaction kinetics: Existing technologies are mostly limited to single vanadium-based or bimetallic PBA systems, which offer a limited variety and number of redox active sites. This directly leads to low efficiency of the "targeted reaction" between the material and the vanadium electrolyte, and the capacity enhancement effect per unit mass of material quickly reaches a bottleneck. More importantly, the single metal composition results in slow electron conduction and ion diffusion kinetics. At high charge-discharge rates, such as >150 mA / cm², charge transfer resistance increases sharply, causing a significant drop in battery voltage efficiency, typically below 75%, which cannot meet the high power output requirements of large-scale energy storage.
[0007] 2. Poor structural stability, short cycle life, and susceptibility to electrolyte environment: The crystal lattice of traditional bimetallic PBAs is prone to distortion due to differences in metal ion radii. During charge-discharge cycles, repeated insertion / extraction of ions continuously accumulates stress, eventually leading to crystal framework collapse and the continuous dissolution of active metal ions. Furthermore, existing research often overlooks the complex ionic atmosphere in the mixed acid electrolyte environment of actual vanadium redox flow batteries, such as the presence of Cl... - SO4 2- The corrosive effect on the structural stability of materials, and the lack of sufficient attention and verification on the issue of ion dissolution, have led to prominent phase transformation or dissolution problems in materials over a wide temperature range, making it difficult for them to meet the requirements of long cycle life of thousands of cycles.
[0008] Due to the aforementioned performance defects, existing technologies still require the use of high-concentration vanadium electrolytes, typically 1.5-2.0 M, in order to achieve the expected capacity increase. This means that the cost of expensive vanadium resources still accounts for more than 30% of the total cost, failing to fundamentally reduce dependence on vanadium resources through solid-state capacity enhancement technology, which is not conducive to commercialization.
[0009] Therefore, there is an urgent need to develop a new type of high-efficiency solid compatibilizer material that can overcome the above-mentioned multiple defects at the same time. Summary of the Invention
[0010] (a) Technical problems to be solved
[0011] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a high-entropy solid energy storage material, its preparation method and application, aiming to solve the technical problems of insufficient active sites, poor structural stability and slow reaction kinetics in existing solid energy storage materials for vanadium redox flow batteries.
[0012] (II) Technical Solution
[0013] To achieve the above objectives, the main technical solutions adopted by the present invention include:
[0014] In a first aspect, the present invention provides a high-entropy solid energy storage material, wherein the material is a high-entropy vanadium-based Prussian blue analogue, and its general chemical formula is V. x M y [Fe(CN)6] z Furthermore, the general chemical formula satisfies the relationship 3≤x+y+2z≤4; where M is a combination of ions corresponding to at least four transition metal elements, and the molar ratio of each transition metal ion to vanadium ion in M is 1:1 to 2:1; x is the number of moles of vanadium ions; y is the total number of moles of all metal ions in M; and z is [Fe(CN)6]. 4- The number of moles.
[0015] Optionally, M is a combination of ions selected from at least four transition metal elements chosen from Fe, Mn, Co, Ni, Cu, and Zn.
[0016] Optionally, the ion corresponding to Fe is Fe2+. 2+ or Fe 3+ The ion corresponding to the Mn element is Mn 2+ or Mn 3+ The ion corresponding to Co is Co. 2+ or Co 3+ The ion corresponding to Ni is Ni 2+ The ion corresponding to Cu is Cu. 2+ The ion corresponding to the element Zn is Zn 2+ .
[0017] Optionally, the high-entropy vanadium-based Prussian blue analogue contains anionic vacancies. The abundance of anionic vacancies enables the high-entropy solid-state energy storage material to operate at wavenumbers of 2040-2080 cm⁻¹. -1 The characteristic peaks of the infrared spectrum within the range are broadened or redshifted.
[0018] Secondly, the present invention provides a method for preparing a high-entropy solid energy storage material, comprising the following steps:
[0019] S1. According to the molar ratio of each transition metal ion to vanadium ion in M of the high-entropy solid energy storage material, obtain the transition metal salt or transition metal salt solution used as the source of transition metal ions in the high-entropy solid energy storage material, and mix them to obtain a mixed salt or mixed salt solution; dissolve the mixed salt or mixed salt solution in a mixed acid solution of sulfuric acid and hydrochloric acid, and then add a metal ion stabilizer to obtain the first solution;
[0020] S2. Add the second solution to the first solution, mix well, and then add the third solution to obtain a mixed solution. Let the mixed solution stand and age, separate the precipitate, and then perform centrifugation washing and drying treatment on the precipitate in sequence to obtain a high-entropy solid energy storage material.
[0021] The second solution is an aqueous solution of ferrocyanide, and the third solution is V. 5+ acid solution.
[0022] Optionally, in a mixed acid solution of sulfuric acid and hydrochloric acid, SO4 2- Cl - The total concentration is 0.8-1.4 M; the concentration of metal ion stabilizer in the first solution is 0.02-0.05 M; the total concentration of transition metal ions in the first solution is 0.09-0.5 M; the concentration of ferrocyanide in the second solution is 0.03-0.25 M; and the concentration of V in the third solution is... 5+ The concentration is 0.03-0.08M.
[0023] Optionally, the second solution is added dropwise to the first solution at a volume ratio of 1:0.8 to 1:1.2, and after stirring and mixing evenly, the third solution is added at a volume ratio of 1:3 to 1:5, and after stirring evenly, a mixed solution is obtained.
[0024] Optionally, the transition metal salt from which each transition metal ion in M is sourced is a nitrate, sulfate, or chloride; the transition metal salt solution from which each transition metal ion in M is sourced is a nitrate solution, sulfate solution, or chloride solution; the transition metal salt from which the corresponding ion of element V is sourced in the high-entropy solid-state energy storage material is vanadium oxysulfate or vanadium oxychloride; the transition metal salt solution from which the corresponding ion of element V is sourced in the high-entropy solid-state energy storage material is a vanadium oxysulfate solution, a metal salt solution of divalent, trivalent, and pentavalent vanadium ions obtained by oxidation-reduction of vanadium oxysulfate solution, a vanadium oxychloride solution, a metal salt solution of divalent, trivalent, and pentavalent vanadium ions obtained by oxidation-reduction of vanadium oxychloride solution, a metal salt solution of divalent, trivalent, and tetravalent vanadium ions obtained by reduction of vanadium pentoxide, or a metal salt solution of divalent, trivalent, and tetravalent vanadium ions obtained by reduction of ammonium metavanadate; the metal ion stabilizer is a chelating agent capable of forming a complex with the transition metal ion.
[0025] Optionally, the ferrocyanide is potassium ferrocyanide, sodium ferrocyanide, ammonium ferrocyanide, potassium ferrocyanide, sodium ferrocyanide, or ammonium ferrocyanide; V 5+ The acid solution is prepared by electrolysis of VOSO4 solution or VCl3 solution. 5+ acid solution.
[0026] Thirdly, the present invention provides an application of the high-entropy solid energy storage material as described above or the high-entropy solid energy storage material prepared by the preparation method described above in a vanadium redox flow battery.
[0027] (III) Beneficial Effects
[0028] The beneficial effects of this invention are:
[0029] In the high-entropy solid-state energy storage material and its preparation and application provided by this invention, the constructed vanadium-based Prussian blue analogue contains at least five transition metal elements and controls their molar ratio between 1:1 and 2:1. Simultaneously, the chemical formula satisfies the charge balance relationship of 3≤x+y+2z≤4, successfully constructing a stable crystal structure with high configurational entropy. This high-entropy structure, through the synergistic effect of multiple metal elements, not only provides a rich variety of redox active sites, significantly improving the targeted reaction efficiency and capacity enhancement per unit mass of the material with the vanadium electrolyte, but also effectively suppresses lattice distortion during ion insertion / extraction, significantly enhancing the structural stability and cycle life of the material in a mixed acid electrolyte environment. Furthermore, the optimized crystal framework provides an efficient pathway for charge transport, improving reaction kinetics performance, enabling the battery to maintain high voltage efficiency even at high rates. Thus, while overcoming the technical bottlenecks of limited active sites, poor structural stability, and slow reaction kinetics in traditional PBA materials, it significantly reduces dependence on high-priced vanadium resources, providing key material support for the commercialization of vanadium redox flow batteries. Detailed Implementation
[0030] To better explain and facilitate understanding of the present invention, a detailed description of the invention will be provided through specific embodiments.
[0031] In a first aspect, the present invention provides a high-entropy solid energy storage material, which is a high-entropy vanadium-based Prussian blue analogue with the general chemical formula V. x M y [Fe(CN)6] z Furthermore, the general chemical formula satisfies the relationship 3 ≤ x + y + 2z ≤ 4. Where M is a combination of at least four transition metal ions corresponding to their corresponding ions, and the molar ratio of each transition metal ion to vanadium ion in M is 1:1 to 2:1; x is the number of moles of vanadium ions; y is the total number of moles of all metal ions in M; and z is [Fe(CN)6]. 4- The number of moles.
[0032] The vanadium-based Prussian blue analogue constructed in this invention contains at least five transition metal elements with their molar ratio controlled between 1:1 and 2:1. Simultaneously, the chemical formula satisfies the charge balance relationship 3≤x+y+2z≤4, successfully constructing a stable crystal structure with high configurational entropy. This high-entropy structure, through the synergistic effect of multiple metal elements, not only provides a rich variety of redox active sites, significantly improving the targeted reaction efficiency and capacity enhancement per unit mass of the material with the vanadium electrolyte, but also effectively suppresses lattice distortion during ion insertion / extraction, significantly enhancing the structural stability and cycle life of the material in a mixed acid electrolyte environment. Furthermore, the optimized crystal framework provides an efficient pathway for charge transport, improving reaction kinetics and enabling the battery to maintain high voltage efficiency even at high rates. Thus, while overcoming the technical bottlenecks of limited active sites, poor structural stability, and slow reaction kinetics in traditional PBA materials, it significantly reduces dependence on high-priced vanadium resources, providing key material support for the commercialization of vanadium redox flow batteries.
[0033] Preferably, M is a combination of ions corresponding to at least four transition metal elements selected from Fe, Mn, Co, Ni, Cu, and Zn. This specific element selection enables a significant synergistic enhancement effect among the metal ions: multiple metals with different ionic radii and electronic structures form a stable high-entropy solid solution structure in the Prussian blue analog lattice. This not only provides richer redox reaction active centers through valence state complementarity but also effectively mitigates lattice volume changes during charge and discharge by utilizing the mutual restraint between ions. At the same time, the selected elements all exhibit excellent chemical stability in the sulfuric acid-hydrochloric acid mixed acid system, jointly ensuring the long-term structural integrity of the material in a highly acidic electrolyte environment. This provides a key material composition guarantee for achieving high-capacity and long-life flow battery performance.
[0034] Specifically, M is a combination of ions selected from 4-6 transition metal elements among Fe, Mn, Co, Ni, Cu, and Zn.
[0035] Among them, the ion corresponding to the Fe element is Fe. 2+ or Fe 3+ The ion corresponding to the Mn element is Mn 2+ or Mn 3+ The ion corresponding to Co is Co. 2+ or Co 3+ The ion corresponding to Ni is Ni 2+ The ion corresponding to Cu is Cu. 2+ The ion corresponding to the element Zn is Zn 2+ .
[0036] Preferably, the high-entropy vanadium-based Prussian blue analogue contains anionic vacancies, and the abundance of anionic vacancies enables the high-entropy solid-state energy storage material to operate at wavenumbers of 2040-2080 cm⁻¹. -1 The characteristic peaks of the infrared spectrum within the range are broadened or redshifted. Thus, the presence of vacancies provides an efficient diffusion channel for ion migration, significantly improving the reaction kinetics of the material. At the same time, this structural defect, in synergy with the high-entropy framework, effectively suppresses lattice stress concentration and metal ion dissolution during charging and discharging, thereby greatly enhancing the structural stability and cycle life of the material.
[0037] Secondly, the present invention provides a method for preparing the above-mentioned high-entropy solid energy storage material, comprising the following steps:
[0038] S1. According to the molar ratio of each transition metal ion to vanadium ion in M of the high-entropy solid energy storage material, obtain transition metal salts or transition metal salt solutions as the source of transition metal ions in the high-entropy solid energy storage material, and mix them to obtain mixed salts or mixed salt solutions; dissolve the mixed salts or mixed salt solutions in a mixed acid solution of sulfuric acid and hydrochloric acid, and then add a metal ion stabilizer to obtain a first solution; dissolve ferrocyanide in deionized water to obtain a second solution; prepare V by electrolyzing VOSO4 solution or VCl3 solution. 5+ An acidic solution is used as a third solution.
[0039] In the mixed acid solution of sulfuric acid and hydrochloric acid, SO4 2- Cl - The total concentration is 0.8-1.4 M; the concentration of the metal ion stabilizer in the first solution is 0.02-0.05 M; the total concentration of transition metal ions in the first solution is 0.09-0.5 M. The concentration of ferrocyanide in the second solution is 0.03-0.25 M. The concentration of V in the third solution... 5+ The concentration is 0.03-0.08M.
[0040] The transition metal salts used as the source of each transition metal ion in M are nitrates, sulfates, or chlorides. The transition metal salt solutions used as the source of each transition metal ion in M are nitrate solutions, sulfate solutions, or chloride solutions. The transition metal salts used as the source of the corresponding ions of element V in the high-entropy solid-state energy storage material are vanadium oxysulfate or vanadium oxychloride. The transition metal salt solutions used as the source of the corresponding ions of element V in the high-entropy solid-state energy storage material are vanadium oxysulfate solutions, metal salt solutions of divalent, trivalent, and pentavalent vanadium ions obtained by the oxidation-reduction of vanadium oxysulfate solutions, vanadium oxychloride solutions, metal salt solutions of divalent, trivalent, and pentavalent vanadium ions obtained by the oxidation-reduction of vanadium oxychloride solutions, metal salt solutions of divalent, trivalent, and tetravalent vanadium ions obtained by the reduction of vanadium pentoxide, or metal salt solutions of divalent, trivalent, and tetravalent vanadium ions obtained by the reduction of ammonium metavanadate.
[0041] The metal ion stabilizer is a chelating agent capable of forming a complex with transition metal ions. Preferably, the chelating agent is sodium citrate, an organic carboxylate, a phosphonate, or a sugar alcohol compound.
[0042] Among them, ferrocyanide is potassium ferrocyanide, sodium ferrocyanide, ammonium ferrocyanide, potassium ferrocyanide, sodium ferrocyanide or ammonium ferrocyanide.
[0043] S2. Add the second solution to the first solution, mix well, and then add the third solution to obtain a mixed solution. Let the mixed solution stand and age, separate the precipitate, and then perform centrifugal washing and drying treatment on the precipitate in sequence to obtain a high-entropy solid energy storage material.
[0044] In this process, the second solution is added dropwise to the first solution at a volume ratio of 1:0.8 to 1:1.2, and after stirring and mixing evenly, the third solution is added at a volume ratio of 1:3 to 1:5, and after stirring evenly, a mixed solution is obtained.
[0045] Specifically, the mixed solution is allowed to stand and age at 25-35℃ for 10-24 hours.
[0046] Specifically, the centrifugation process is as follows: centrifuge at 8000-12000 rpm for 10-15 min, and wash with deionized water and anhydrous ethanol alternately 4-6 times until the pH of the supernatant is 2.0-2.5.
[0047] Specifically, the drying process is as follows: vacuum drying at 60-75℃ for 10-16 hours.
[0048] The preparation method provided by this invention effectively regulates the co-precipitation kinetics of multiple transition metal ions by introducing a specific concentration of metal ion stabilizer into an acidic solution of a multi-metal salt, slowing down the precipitation rate, avoiding heterogeneous agglomeration, and ensuring the uniform distribution of elements at the atomic scale and the successful construction of high-entropy structures. By employing a stepwise feeding strategy and precisely controlling the concentration and volume ratio of each solution, controllable adjustment of crystal nucleation and growth is achieved, ensuring the accuracy of the material's chemical composition and batch-to-batch consistency. In particular, the use of V... 5+ Acid solutions, acting as structure modifiers, introduce anion vacancies in situ during precipitation, optimizing the ion diffusion channels and electrochemical activity of the material. Ultimately, high-entropy solid energy storage materials with excellent compositional uniformity, structural stability, and electrochemical performance can be prepared.
[0049] Thirdly, the present invention provides an application of the above-mentioned high-entropy solid energy storage material or the high-entropy solid energy storage material prepared by the above-mentioned preparation method in vanadium redox flow batteries.
[0050] Specifically, high-entropy solid energy storage materials are applied to the positive electrode electrolyte system of vanadium redox flow batteries through the following methods:
[0051] A1. Disperse high-entropy solid energy storage material powder in a solvent to obtain an energy storage solution. Mix the energy storage solution with a film-forming agent solution to prepare a slurry.
[0052] The solvent is a mixture of isopropanol and water, and the film-forming agent is a perfluorosulfonic acid resin solution with a mass fraction of 5-20%. Preferably, the volume ratio of isopropanol to water is 1:1.
[0053] Specifically, the mass concentration of the high-entropy solid energy storage material in the slurry is 0.125 g / mL, and the volume ratio of the energy storage solution to the film-forming agent solution is 5.5:1-4.5:1.
[0054] A2. Spray the slurry onto the surface of the ion exchange membrane to obtain the modified ion exchange membrane.
[0055] The loading rate of the slurry on the ion exchange membrane is 0.5-2.0 mg / cm³. 2 .
[0056] A3. The modified ion exchange membrane is assembled into the positive electrode electrolyte circuit of the vanadium redox flow battery.
[0057] The vanadium redox flow battery uses a sulfuric acid-hydrochloric acid mixed acid electrolyte system. The concentration of tetravalent vanadium ions in the positive electrode electrolyte is 0.3-1.65 M, and the concentration of trivalent vanadium ions in the negative electrode electrolyte is 0.3-1.65 M.
[0058] This invention utilizes a high-entropy solid-state energy storage material loaded onto an ion-exchange membrane and placed within a positive electrode electrolyte tank. This enables the application of high-entropy solid-state energy storage materials in vanadium redox flow batteries. By leveraging the diverse redox active sites of the material to conduct reversible targeted reactions with vanadium ions in the electrolyte, the volumetric capacity and energy density of the battery system are significantly improved. Furthermore, the application method effectively solves the problem of channel clogging caused by directly adding powdered solid materials. Simultaneously, it fully utilizes the structural stability and reaction kinetics advantages of high-entropy materials, enabling the battery to maintain high voltage efficiency while significantly improving cycle life. Specifically, the battery voltage efficiency is >80%, and the capacity retention rate still reaches over 86% after 500 cycles, providing a reliable technical solution for the commercial application of vanadium redox flow batteries.
[0059] The present invention will be further illustrated below with reference to specific embodiments. It is important to note that these embodiments are for illustrative purposes only and do not limit the scope of application of the invention. Adjustments made by those skilled in the art based on the teachings of this invention should be limited to the scope defined in the appended claims.
[0060] Example 1:
[0061] S1. Weigh out VOSO4, FeSO4·7H2O, MnSO4·H2O, CoCl2·6H2O, NiSO4·6H2O, CuSO4·5H2O, and ZnSO4·7H2O according to a molar ratio of 1:1:1:1:1:1:1, and mix them to obtain a mixed salt. Dissolve the mixed salt in 500 mL of a mixed acid solution of sulfuric acid and hydrochloric acid, and then add 0.02 M sodium citrate to obtain the first solution. In the mixed acid solution of sulfuric acid and hydrochloric acid, SO42-... 2- Cl - The total concentration is 1M; the total concentration of transition metal ions in the first solution is 0.09M.
[0062] Dissolve 0.015 mol of potassium ferrocyanide in 500 mL of deionized water to obtain a 0.03 M potassium ferrocyanide solution, which is the second solution.
[0063] A 0.03 M VSO4 solution was obtained by electrolytic oxidation of the VOSO4 solution. 5+ 100 mL of acid solution, i.e., the third solution.
[0064] S2. Add the second solution dropwise to the first solution while stirring. After the addition is complete, add the third solution and continue stirring for 1 hour to obtain a mixed solution. Let the mixed solution stand at room temperature for 10 hours, discard the supernatant, and centrifuge and dry the precipitate to obtain the high-entropy solid energy storage material, i.e., high-entropy PBA powder.
[0065] The centrifugation process involved centrifuging at 10,000 rpm for 10 minutes, followed by washing four times with alternating deionized water and anhydrous ethanol until the supernatant pH reached 2.0-2.5. The drying process involved vacuum drying at 70℃ for 10 hours.
[0066] The application of high-entropy PBA powder in the positive electrode electrolyte system of vanadium redox flow batteries is achieved through the following methods:
[0067] A1. High-entropy solid energy storage material powder was dispersed in a mixed solvent of isopropanol and water at a volume ratio of 1:1 to obtain an energy storage solution. The energy storage solution was then mixed with a 17% perfluorosulfonic acid resin solution at a volume ratio of 5.5:1 and ultrasonically mixed for 4 hours to obtain a slurry. The concentration of high-entropy solid energy storage material in the slurry was 0.125 g / mL.
[0068] A2. Spray the slurry onto the surface of the ion exchange membrane to obtain the modified ion exchange membrane.
[0069] A3, using 48cm 2The single cell serves as the power unit for charging and discharging. The electrolyte is a mixed acid system of sulfuric acid and hydrochloric acid. The positive electrode storage tank contains 70 mL of 0.3 M tetravalent vanadium electrolyte and has an ion-exchange membrane loaded with 2.5 g of high-entropy PBA solid energy storage material. The negative electrode storage tank contains 120 mL of 0.3 M trivalent vanadium electrolyte. Charge-discharge cycle tests are conducted using a constant current density of 110.
[0070] Comparative Example 1:
[0071] Use 48cm 2 The single cell is used as the power unit for charging and discharging. The electrolyte is a mixed acid system of sulfuric acid and hydrochloric acid. The positive electrode storage tank is 70 mL of 0.3 M tetravalent vanadium electrolyte, and the negative electrode storage tank is 120 mL of 0.3 M trivalent vanadium electrolyte. The charge and discharge cycle test is carried out using a constant current density of 110.
[0072] Example 2:
[0073] S1. Weigh out VOSO4, FeSO4·7H2O, MnSO4·H2O, CoCl2·6H2O, NiSO4·6H2O, CuSO4·5H2O, and ZnSO4·7H2O according to a molar ratio of 1:2:2:2:2:2:2, and mix them to obtain a mixed salt. Dissolve the mixed salt in 500 mL of a mixed acid solution of sulfuric acid and hydrochloric acid, and then add 0.05 M sodium citrate to obtain the first solution. In the mixed acid solution of sulfuric acid and hydrochloric acid, SO42-... 2- Cl - The total concentration is 1M; the total concentration of transition metal ions in the first solution is 0.15M.
[0074] Dissolve 0.03 mol of potassium ferrocyanide in 500 mL of deionized water to obtain a 0.06 M potassium ferrocyanide solution, which is the second solution.
[0075] A 0.05 M VSO4 solution was obtained by electrolytic oxidation of the VOSO4 solution. 5+ 100 mL of acid solution, i.e., the third solution.
[0076] S2. Add the second solution dropwise to the first solution while stirring. After the addition is complete, add the third solution and continue stirring for 1 hour to obtain a mixed solution. Let the mixed solution stand at room temperature for 10 hours, discard the supernatant, and centrifuge and dry the precipitate to obtain the high-entropy solid energy storage material, i.e., high-entropy PBA powder.
[0077] The centrifugation process involved centrifuging at 10,000 rpm for 10 minutes, followed by washing four times with alternating deionized water and anhydrous ethanol until the supernatant pH reached 2.0-2.5. The drying process involved vacuum drying at 70℃ for 10 hours.
[0078] The application of high-entropy PBA powder in the positive electrode electrolyte system of vanadium redox flow batteries is achieved through the following methods:
[0079] A1. High-entropy solid energy storage material powder was dispersed in a mixed solvent of isopropanol and water at a volume ratio of 1:1 to obtain an energy storage solution. The energy storage solution was then mixed with a 15% perfluorosulfonic acid resin solution at a volume ratio of 5.5:1 and ultrasonically mixed for 4 hours to obtain a slurry. The concentration of high-entropy solid energy storage material in the slurry was 0.125 g / mL.
[0080] A2. Spray the slurry onto the surface of the ion exchange membrane to obtain the modified ion exchange membrane.
[0081] A3, using 48cm 2 The single cell serves as the power unit for charging and discharging. The electrolyte is a mixed acid system of sulfuric acid and hydrochloric acid. The positive electrode storage tank contains 70 mL of 0.3 M tetravalent vanadium electrolyte and has an ion-exchange membrane loaded with 2.5 g of high-entropy PBA solid energy storage material. The negative electrode storage tank contains 120 mL of 0.3 M trivalent vanadium electrolyte. Charge-discharge cycle tests are conducted using a constant current density of 110.
[0082] Example 3:
[0083] S1. Weigh out VOSO4, FeSO4·7H2O, MnSO4·H2O, CoCl2·6H2O, NiSO4·6H2O, CuSO4·5H2O, and ZnSO4·7H2O according to a molar ratio of 1:1.5:1.5:2:2:1.2:1.4, and mix them to obtain a mixed salt. Dissolve the mixed salt in 500 mL of a mixed acid solution of sulfuric acid and hydrochloric acid, and then add 0.05 M sodium citrate to obtain the first solution. In the mixed acid solution of sulfuric acid and hydrochloric acid, SO42-... 2- Cl - The total concentration is 1M; the total concentration of transition metal ions in the first solution is 0.5M.
[0084] Dissolve 0.125 mol of potassium ferrocyanide in 500 mL of deionized water to obtain a 0.25 M potassium ferrocyanide solution, which is the second solution.
[0085] A 0.05 M VCl3 solution was obtained by electrolytic oxidation of VCl3 solution. 5+ 200 mL of acid solution, i.e., the third solution.
[0086] S2. Add the second solution dropwise to the first solution while stirring. After the addition is complete, add the third solution and continue stirring for 1 hour to obtain a mixed solution. Let the mixed solution stand at room temperature for 10 hours, discard the supernatant, and centrifuge and dry the precipitate to obtain the high-entropy solid energy storage material, i.e., high-entropy PBA powder.
[0087] The centrifugation process involved centrifuging at 10,000 rpm for 10 minutes, followed by washing four times with alternating deionized water and anhydrous ethanol until the supernatant pH reached 2.0-2.5. The drying process involved vacuum drying at 70℃ for 10 hours.
[0088] The application of high-entropy PBA powder in the positive electrode electrolyte system of vanadium redox flow batteries is achieved through the following methods:
[0089] A1. High-entropy solid energy storage material powder was dispersed in a mixed solvent of isopropanol and water at a volume ratio of 1:1 to obtain an energy storage solution. The energy storage solution was then mixed with a 13% perfluorosulfonic acid resin solution at a volume ratio of 5.5:1 and ultrasonically mixed for 4 hours to obtain a slurry. The concentration of high-entropy solid energy storage material in the slurry was 0.125 g / mL.
[0090] A2. Spray the slurry onto the surface of the ion exchange membrane to obtain the modified ion exchange membrane.
[0091] A3, using 48cm 2 The single cell serves as the power unit for charging and discharging. The electrolyte is a mixed acid system of sulfuric acid and hydrochloric acid. The positive electrode storage tank contains 70 mL of 0.3 M tetravalent vanadium electrolyte and has an ion-exchange membrane loaded with 2.5 g of high-entropy PBA solid energy storage material. The negative electrode storage tank contains 120 mL of 0.3 M trivalent vanadium electrolyte. Charge-discharge cycle tests are conducted using a constant current density of 110.
[0092] Example 4:
[0093] S1. Weigh out VCl3, FeCl2·4H2O, MnCl2·4H2O, CoSO4·7H2O, NiCl2·6H2O, CuCl2·2H2O, and ZnCl2 according to a molar ratio of 1:2:2:2:2:2:2, and mix them to obtain a mixed salt. Dissolve the mixed salt in 500 mL of a mixed acid solution of sulfuric acid and hydrochloric acid, and then add 0.02 M sodium tartrate to obtain the first solution. In the mixed acid solution of sulfuric acid and hydrochloric acid, SO42-... 2- Cl - The total concentration is 1M; the total concentration of transition metal ions in the first solution is 0.15M.
[0094] Dissolve 0.03 mol of sodium ferrocyanide in 500 mL of deionized water to obtain a 0.06 M sodium ferrocyanide solution, which is the second solution.
[0095] A 0.03 M VSO4 solution was obtained by electrolytic oxidation of the VOSO4 solution. 5+ 100 mL of acid solution, i.e., the third solution.
[0096] S2. Add the second solution dropwise to the first solution while stirring. After the addition is complete, add the third solution and continue stirring for 1 hour to obtain a mixed solution. Let the mixed solution stand at room temperature for 10 hours, discard the supernatant, and centrifuge and dry the precipitate to obtain the high-entropy solid energy storage material, i.e., high-entropy PBA powder.
[0097] The centrifugation process involved centrifuging at 10,000 rpm for 10 minutes, followed by washing four times with alternating deionized water and anhydrous ethanol until the supernatant pH reached 2.0-2.5. The drying process involved vacuum drying at 70℃ for 10 hours.
[0098] The application of high-entropy PBA powder in the positive electrode electrolyte system of vanadium redox flow batteries is achieved through the following methods:
[0099] A1. High-entropy solid energy storage material powder was dispersed in a mixed solvent of isopropanol and water at a volume ratio of 1:1 to obtain an energy storage solution. The energy storage solution was then mixed with a 17% perfluorosulfonic acid resin solution at a volume ratio of 5.5:1 and ultrasonically mixed for 4 hours to obtain a slurry. The concentration of high-entropy solid energy storage material in the slurry was 0.125 g / mL.
[0100] A2. Spray the slurry onto the surface of the ion exchange membrane to obtain the modified ion exchange membrane.
[0101] A3, using 48cm 2 The single cell serves as the power unit for charging and discharging. The electrolyte is a mixed acid system of sulfuric acid and hydrochloric acid. The positive electrode storage tank contains 70 mL of 0.3 M tetravalent vanadium electrolyte and has an ion-exchange membrane loaded with 2.5 g of high-entropy PBA solid energy storage material. The negative electrode storage tank contains 120 mL of 0.3 M trivalent vanadium electrolyte. Charge-discharge cycle tests are conducted using a constant current density of 110.
[0102] Example 5:
[0103] S1. Weigh out VCl3, FeCl2·4H2O, MnCl2·4H2O, CoSO4·7H2O, NiCl2·6H2O, CuNO3·3H2O, and ZnSO4·7H2O according to a molar ratio of 1:2:2:2:2:2:2, and mix them to obtain a mixed salt. Dissolve the mixed salt in 500 mL of a mixed acid solution of sulfuric acid and hydrochloric acid, and then add 0.03 M potassium gluconate to obtain the first solution. In the mixed acid solution of sulfuric acid and hydrochloric acid, SO42-... 2- Cl - The total concentration is 1M; the total concentration of transition metal ions in the first solution is 0.15M.
[0104] Dissolve 0.03 mol of potassium ferrocyanide in 500 mL of deionized water to obtain a 0.06 M potassium ferrocyanide solution, which is the second solution.
[0105] A 0.05 M VSO4 solution was obtained by electrolytic oxidation of the VOSO4 solution. 5+ 100 mL of acid solution, i.e., the third solution.
[0106] The subsequent preparation process of the high-entropy PBA powder is the same as in Example 2. The process of applying the high-entropy PBA powder prepared in Example 5 to the positive electrode electrolyte system of the vanadium redox flow battery for testing is the same as in Example 2, and will not be repeated here.
[0107] Example 6:
[0108] S1. Weigh out VOSO4, MnSO4·H2O, CoCl2·6H2O, NiSO4·6H2O, CuSO4·5H2O, and ZnSO4·7H2O according to a molar ratio of 1:2:2:2:2:2, and mix them to obtain a mixed salt. Dissolve the mixed salt in 500 mL of a mixed acid solution of sulfuric acid and hydrochloric acid, and then add 0.05 M sodium citrate to obtain the first solution. In the mixed acid solution of sulfuric acid and hydrochloric acid, SO42-... 2- Cl - The total concentration is 1M; the total concentration of transition metal ions in the first solution is 0.15M.
[0109] Dissolve 0.03 mol of potassium ferrocyanide in 500 mL of deionized water to obtain a 0.06 M potassium ferrocyanide solution, which is the second solution.
[0110] A 0.05 M VSO4 solution was obtained by electrolytic oxidation of the VOSO4 solution. 5+ 100 mL of acid solution, i.e., the third solution.
[0111] The subsequent preparation process of the high-entropy PBA powder is the same as in Example 2. The process of applying the high-entropy PBA powder prepared in Example 6 to the positive electrode electrolyte system of the vanadium redox flow battery for testing is the same as in Example 2, and will not be repeated here.
[0112] Example 7:
[0113] S1. Weigh out VOSO4, FeSO4·7H2O, CoCl2·6H2O, NiSO4·6H2O, CuSO4·5H2O, and ZnSO4·7H2O according to a molar ratio of 1:2:2:2:2:2, and mix them to obtain a mixed salt. Dissolve the mixed salt in 500 mL of a mixed acid solution of sulfuric acid and hydrochloric acid, and then add 0.05 M sodium citrate to obtain the first solution. In the mixed acid solution of sulfuric acid and hydrochloric acid, SO42-... 2- Cl -The total concentration is 1M; the total concentration of transition metal ions in the first solution is 0.15M.
[0114] Dissolve 0.03 mol of potassium ferrocyanide in 500 mL of deionized water to obtain a 0.06 M potassium ferrocyanide solution, which is the second solution.
[0115] A 0.05 M VSO4 solution was obtained by electrolytic oxidation of the VOSO4 solution. 5+ 100 mL of acid solution, i.e., the third solution.
[0116] The subsequent preparation process of the high-entropy PBA powder is the same as in Example 2. The process of applying the high-entropy PBA powder prepared in Example 7 to the positive electrode electrolyte system of the vanadium redox flow battery for testing is the same as in Example 2, and will not be repeated here.
[0117] Example 8:
[0118] S1. Weigh out VOSO4, FeSO4·7H2O, MnSO4·H2O, NiSO4·6H2O, CuSO4·5H2O, and ZnSO4·7H2O according to a molar ratio of 1:2:2:2:2:2, and mix them to obtain a mixed salt. Dissolve the mixed salt in 500 mL of a mixed acid solution of sulfuric acid and hydrochloric acid, and then add 0.05 M sodium citrate to obtain the first solution. In the mixed acid solution of sulfuric acid and hydrochloric acid, SO42-... 2- Cl - The total concentration is 1M; the total concentration of transition metal ions in the first solution is 0.15M.
[0119] Dissolve 0.03 mol of potassium ferrocyanide in 500 mL of deionized water to obtain a 0.06 M potassium ferrocyanide solution, which is the second solution.
[0120] A 0.05 M VSO4 solution was obtained by electrolytic oxidation of the VOSO4 solution. 5+ 100 mL of acid solution, i.e., the third solution.
[0121] The subsequent preparation process of the high-entropy PBA powder is the same as in Example 2. The process of applying the high-entropy PBA powder prepared in Example 8 to the positive electrode electrolyte system of the vanadium redox flow battery for testing is the same as in Example 2, and will not be repeated here.
[0122] Example 9:
[0123] S1. Weigh out VOSO4, FeSO4·7H2O, MnSO4·H2O, CoCl2·6H2O, CuSO4·5H2O, and ZnSO4·7H2O according to a molar ratio of 1:2:2:2:2:2, and mix them to obtain a mixed salt. Dissolve the mixed salt in 500 mL of a mixed acid solution of sulfuric acid and hydrochloric acid, and then add 0.05 M sodium citrate to obtain the first solution. In the mixed acid solution of sulfuric acid and hydrochloric acid, SO42-... 2- Cl - The total concentration is 1M; the total concentration of transition metal ions in the first solution is 0.15M.
[0124] Dissolve 0.03 mol of potassium ferrocyanide in 500 mL of deionized water to obtain a 0.06 M potassium ferrocyanide solution, which is the second solution.
[0125] A 0.05 M VSO4 solution was obtained by electrolytic oxidation of the VOSO4 solution. 5+ 100 mL of acid solution, i.e., the third solution.
[0126] The subsequent preparation process of the high-entropy PBA powder is the same as in Example 2. The process of applying the high-entropy PBA powder prepared in Example 9 to the positive electrode electrolyte system of the vanadium redox flow battery for testing is the same as in Example 2, and will not be repeated here.
[0127] Example 10:
[0128] S1. Weigh out VOSO4, FeSO4·7H2O, MnSO4·H2O, CoCl2·6H2O, NiSO4·6H2O, and ZnSO4·7H2O according to a molar ratio of 1:2:2:2:2:2, and mix them to obtain a mixed salt. Dissolve the mixed salt in 500 mL of a mixed acid solution of sulfuric acid and hydrochloric acid, and then add 0.05 M sodium citrate to obtain the first solution. In the mixed acid solution of sulfuric acid and hydrochloric acid, SO42-... 2- Cl - The total concentration is 1M; the total concentration of transition metal ions in the first solution is 0.15M.
[0129] Dissolve 0.03 mol of potassium ferrocyanide in 500 mL of deionized water to obtain a 0.06 M potassium ferrocyanide solution, which is the second solution.
[0130] A 0.05 M VSO4 solution was obtained by electrolytic oxidation of the VOSO4 solution. 5+ 100 mL of acid solution, i.e., the third solution.
[0131] The subsequent preparation process of the high-entropy PBA powder is the same as in Example 2. The process of applying the high-entropy PBA powder prepared in Example 10 to the positive electrode electrolyte system of the vanadium redox flow battery for testing is the same as in Example 2, and will not be repeated here.
[0132] Example 11:
[0133] S1. Weigh out VOSO4, FeSO4·7H2O, MnSO4·H2O, CoCl2·6H2O, NiSO4·6H2O, and CuSO4·5H2O according to a molar ratio of 1:2:2:2:2:2, and mix them to obtain a mixed salt. Dissolve the mixed salt in 500 mL of a mixed acid solution of sulfuric acid and hydrochloric acid, and then add 0.05 M sodium citrate to obtain the first solution. In the mixed acid solution of sulfuric acid and hydrochloric acid, SO42-... 2- Cl - The total concentration is 1M; the total concentration of transition metal ions in the first solution is 0.15M.
[0134] Dissolve 0.03 mol of potassium ferrocyanide in 500 mL of deionized water to obtain a 0.06 M potassium ferrocyanide solution, which is the second solution.
[0135] A 0.05 M VSO4 solution was obtained by electrolytic oxidation of the VOSO4 solution. 5+ 100 mL of acid solution, i.e., the third solution.
[0136] The subsequent preparation process of the high-entropy PBA powder is the same as in Example 2. The process of applying the high-entropy PBA powder prepared in Example 11 to the positive electrode electrolyte system of the vanadium redox flow battery for testing is the same as in Example 2, and will not be repeated here.
[0137] Example 12:
[0138] S1. Weigh out VOSO4, FeSO4·7H2O, MnSO4·H2O, CuSO4·5H2O, and ZnSO4·7H2O according to a molar ratio of 1:1:2:2:1.5:1.2, and mix them to obtain a mixed salt. Dissolve the mixed salt in 500 mL of a mixed acid solution of sulfuric acid and hydrochloric acid, and then add 0.05 M sodium citrate to obtain the first solution. In the mixed acid solution of sulfuric acid and hydrochloric acid, SO42-... 2- Cl - The total concentration is 1M; the total concentration of transition metal ions in the first solution is 0.15M.
[0139] Dissolve 0.03 mol of potassium ferrocyanide in 500 mL of deionized water to obtain a 0.06 M potassium ferrocyanide solution, which is the second solution.
[0140] A 0.05 M VSO4 solution was obtained by electrolytic oxidation of the VOSO4 solution. 5+ 100 mL of acid solution, i.e., the third solution.
[0141] The subsequent preparation process of the high-entropy PBA powder is the same as in Example 2. The process of applying the high-entropy PBA powder prepared in Example 12 to the positive electrode electrolyte system of the vanadium redox flow battery for testing is the same as in Example 2, and will not be repeated here.
[0142] Example 13:
[0143] S1. Weigh out VOSO4, FeSO4·7H2O, MnSO4·H2O, CoCl2·6H2O, and NiSO4·6H2O according to a molar ratio of 1:2:2:2:2:2, and mix them to obtain a mixed salt. Dissolve the mixed salt in 500 mL of a mixed acid solution of sulfuric acid and hydrochloric acid, and then add 0.05 M sodium citrate to obtain the first solution. In the mixed acid solution of sulfuric acid and hydrochloric acid, SO42-... 2- Cl - The total concentration is 1M; the total concentration of transition metal ions in the first solution is 0.15M.
[0144] Dissolve 0.03 mol of potassium ferrocyanide in 500 mL of deionized water to obtain a 0.06 M potassium ferrocyanide solution, which is the second solution.
[0145] A 0.05 M VSO4 solution was obtained by electrolytic oxidation of the VOSO4 solution. 5+ 100 mL of acid solution, i.e., the third solution.
[0146] The subsequent preparation process of the high-entropy PBA powder is the same as in Example 2. The process of applying the high-entropy PBA powder prepared in Example 13 to the positive electrode electrolyte system of the vanadium redox flow battery for testing is the same as in Example 2, and will not be repeated here.
[0147] Example 14:
[0148] S1. Weigh out V₂O₅, FeSO₄·7H₂O, MnSO₄·H₂O, CoCl₂·6H₂O, NiSO₄·6H₂O, CuSO₄·5H₂O, and ZnSO₄·7H₂O according to a molar ratio of 1:2:2:2:2:2, and mix them to obtain a mixed salt. Dissolve the mixed salt in 500 mL of a mixed acid solution of sulfuric acid and hydrochloric acid, and then add 0.05 M sodium citrate to obtain the first solution. In the mixed acid solution of sulfuric acid and hydrochloric acid, SO₄²⁻... 2- Cl - The total concentration is 1M; the total concentration of transition metal ions in the first solution is 0.15M.
[0149] Dissolve 0.03 mol of potassium ferrocyanide in 500 mL of deionized water to obtain a 0.06 M potassium ferrocyanide solution, which is the second solution.
[0150] A 0.05 M VSO4 solution was obtained by electrolytic oxidation of the VOSO4 solution. 5+ 100 mL of acid solution, i.e., the third solution.
[0151] S2. Add the second solution dropwise to the first solution while stirring. After the addition is complete, add the third solution and 10 mL of hydrazine hydrate. Continue stirring for 1 hour to obtain a mixed solution. Let the mixed solution stand at room temperature for 10 hours, discard the supernatant, and centrifuge and dry the precipitate to obtain the high-entropy solid energy storage material, namely high-entropy PBA powder.
[0152] The centrifugation process involved centrifuging at 10,000 rpm for 10 minutes, followed by washing four times with alternating deionized water and anhydrous ethanol until the supernatant pH reached 2.0-2.5. The drying process involved vacuum drying at 70℃ for 10 hours.
[0153] The process of testing the high-entropy PBA powder prepared in Example 14 in the positive electrode electrolyte system of vanadium redox flow battery is the same as in Example 2, and will not be repeated here.
[0154] Comparative Example 2:
[0155] S1. Dissolve 0.09 mol VOSO4 in 500 mL of a sulfuric acid-hydrochloric acid mixed acid solution to obtain a 0.18 M VOSO4 acid solution, i.e., the first solution. In this mixed acid solution of sulfuric acid and hydrochloric acid, SO42-... 2- Cl - The total concentration is 1M.
[0156] Dissolve 0.03 mol of potassium ferrocyanide in 500 mL of deionized water to obtain a 0.06 M potassium ferrocyanide solution, which is the second solution.
[0157] S2. Add the second solution dropwise to the first solution while stirring. After the addition is complete, a mixed solution is obtained. Let the mixed solution stand at room temperature for 10 hours, discard the supernatant, and centrifuge and dry the precipitate to obtain monometallic PBA powder.
[0158] The centrifugation process involved centrifuging at 10,000 rpm for 10 minutes, followed by washing four times with alternating deionized water and anhydrous ethanol until the supernatant pH reached 2.0-2.5. The drying process involved vacuum drying at 70℃ for 10 hours.
[0159] The process of applying the monometallic PBA powder prepared in Comparative Example 2 to the positive electrode electrolyte system of a vanadium redox flow battery for testing is the same as in Example 2, and will not be repeated here.
[0160] Comparative Example 3:
[0161] S1. Dissolve VOSO4 and CoCl2·6H2O in 500 mL of a sulfuric acid-hydrochloric acid mixed acid solution at a molar ratio of 1:6 to obtain a first solution with a total transition metal ion concentration of 0.18 M. In this mixed acid solution of sulfuric acid and hydrochloric acid, SO42-... 2- Cl - The total concentration is 1M.
[0162] Dissolve 0.03 mol of potassium ferrocyanide in 500 mL of deionized water to obtain a 0.06 M potassium ferrocyanide solution, which is the second solution.
[0163] S2. Add the second solution dropwise to the first solution while stirring. After the addition is complete, a mixed solution is obtained. Let the mixed solution stand at room temperature for 10 hours, discard the supernatant, and centrifuge and dry the precipitate to obtain bimetallic PBA powder.
[0164] The centrifugation process involved centrifuging at 10,000 rpm for 10 minutes, followed by washing four times with alternating deionized water and anhydrous ethanol until the supernatant pH reached 2.0-2.5. The drying process involved vacuum drying at 70℃ for 10 hours.
[0165] The process of applying the bimetallic PBA powder prepared in Comparative Example 3 to the positive electrode electrolyte system of a vanadium redox flow battery for testing is the same as in Example 2, and will not be repeated here.
[0166] Comparative Example 4:
[0167] S1. Dissolve VOSO4 and MnSO4·H2O in 500 mL of a sulfuric acid-hydrochloric acid mixed acid solution at a molar ratio of 1:6 to obtain a first solution with a total transition metal ion concentration of 0.18 M. In this mixed acid solution of sulfuric acid and hydrochloric acid, SO42-... 2- Cl - The total concentration is 1M.
[0168] Dissolve 0.03 mol of potassium ferrocyanide in 500 mL of deionized water to obtain a 0.06 M potassium ferrocyanide solution, which is the second solution.
[0169] S2. Add the second solution dropwise to the first solution while stirring. After the addition is complete, a mixed solution is obtained. Let the mixed solution stand at room temperature for 10 hours, discard the supernatant, and centrifuge and dry the precipitate to obtain bimetallic PBA powder.
[0170] The centrifugation process involved centrifuging at 10,000 rpm for 10 minutes, followed by washing four times with alternating deionized water and anhydrous ethanol until the supernatant pH reached 2.0-2.5. The drying process involved vacuum drying at 70℃ for 10 hours.
[0171] The process of applying the bimetallic PBA powder prepared in Comparative Example 4 to the positive electrode electrolyte system of a vanadium redox flow battery for testing is the same as in Example 2, and will not be repeated here.
[0172] Comparative Example 5:
[0173] S1. Dissolve VOSO4, MnSO4·H2O, and CoCl2·6H2O in 500 mL of a sulfuric acid-hydrochloric acid mixed acid solution at a molar ratio of 1:3:3 to obtain a first solution with a total transition metal ion concentration of 0.18 M. In the mixed acid solution of sulfuric acid and hydrochloric acid, SO42-... 2- Cl - The total concentration is 1M.
[0174] Dissolve 0.03 mol of potassium ferrocyanide in 500 mL of deionized water to obtain a 0.06 M potassium ferrocyanide solution, which is the second solution.
[0175] S2. Add the second solution dropwise to the first solution while stirring. After the addition is complete, a mixed solution is obtained. Let the mixed solution stand at room temperature for 10 hours, discard the supernatant, and centrifuge and dry the precipitate to obtain trimetallic PBA powder.
[0176] The centrifugation process involved centrifuging at 10,000 rpm for 10 minutes, followed by washing four times with alternating deionized water and anhydrous ethanol until the supernatant pH reached 2.0-2.5. The drying process involved vacuum drying at 70℃ for 10 hours.
[0177] The process of applying the trimetallic PBA powder prepared in Comparative Example 5 to the positive electrode electrolyte system of a vanadium redox flow battery for testing is the same as in Example 2, and will not be repeated here.
[0178] Comparative Example 6:
[0179] S1. Dissolve VOSO4, MnSO4·H2O, CoCl2·6H2O, and NiSO4·6H2O in 500 mL of a sulfuric acid-hydrochloric acid mixed acid solution according to a molar ratio of 1:2:2:2 to obtain a first solution with a total transition metal ion concentration of 0.18 M. In the mixed acid solution of sulfuric acid and hydrochloric acid, SO42-... 2- Cl - The total concentration is 1M.
[0180] Dissolve 0.03 mol of potassium ferrocyanide in 500 mL of deionized water to obtain a 0.06 M potassium ferrocyanide solution, which is the second solution.
[0181] S2. Add the second solution dropwise to the first solution while stirring. After the addition is complete, a mixed solution is obtained. Let the mixed solution stand at room temperature for 10 hours, discard the supernatant, and centrifuge and dry the precipitate to obtain tetrametallic PBA powder.
[0182] The centrifugation process involved centrifuging at 10,000 rpm for 10 minutes, followed by washing four times with alternating deionized water and anhydrous ethanol until the supernatant pH reached 2.0-2.5. The drying process involved vacuum drying at 70℃ for 10 hours.
[0183] The process of applying the tetrametallic PBA powder prepared in Comparative Example 6 to the positive electrode electrolyte system of a vanadium redox flow battery for testing is the same as in Example 2, and will not be repeated here.
[0184] Example 15:
[0185] The difference between this embodiment and Embodiment 2 is that a constant current density of 160 is used for single-cell testing.
[0186] The remaining contents are the same as in Example 2, and will not be repeated here.
[0187] Example 16:
[0188] The difference between this embodiment and embodiment 8 is that a constant current density of 160 is used for single-cell testing.
[0189] The remaining contents are the same as in Example 8, and will not be repeated here.
[0190] Comparative Example 7:
[0191] The difference between this comparative example and Comparative Example 4 is that a constant current density of 160 was used for single-cell testing.
[0192] The remaining content is the same as that in Comparative Example 4, so it will not be repeated here.
[0193] Example 17:
[0194] The difference between this embodiment and Embodiment 2 is that the positive electrode storage tank is 70 mL of 1.65M tetravalent vanadium electrolyte, and the negative electrode storage tank is 100 mL of 1.65M trivalent vanadium electrolyte. After three charge-discharge cycles, an ion membrane loaded with 10g of the solid energy storage material prepared in Embodiment 2 is added to the positive electrode storage tank, and the charge-discharge cycle test is continued.
[0195] The remaining contents are the same as in Example 2, and will not be repeated here.
[0196] The test results of the above embodiments and comparative examples are shown in Tables 1, 2 and 3 below.
[0197] Table 1. Charge-discharge cycle test results of Comparative Example 1 and Examples 1-7
[0198]
[0199] Table 2. Charge-discharge cycle test results of Examples 8-14
[0200]
[0201] Table 3. Charge-discharge cycle test results of Comparative Examples 2-7 and Examples 15-17
[0202]
[0203] The above examples and comparative results show that introducing the high-entropy effect into vanadium-based Prussian blue analogues can effectively improve the unit mass capacity enhancement, voltage efficiency, and material stability of solid energy storage materials in vanadium battery applications.
[0204] Examples 1-5 are all complete high-entropy systems containing seven transition metals: Fe, Mn, Co, Ni, Cu, V, and Zn. The molar ratio of the metals is controlled between 1:1:1:1:1:1:1 and 1:2:2:2:2:2:2, with a total transition metal ion concentration of 0.09-0.5 M. The number and effectiveness of active sites are optimal. Among them, Example 2 shows the best capacity increase, with a capacity increase of 160.41 mAh compared to Comparative Example 1, representing a capacity increase of 64.16 mAh per unit mass. With a capacity of mAh / g, the voltage efficiency reaches 82.51%, and the capacity retention rate is 95.16% after 500 cycles. Under the synergistic effect of chelating agents and vacancies, the transition metal elements are uniformly distributed in the framework entropy, which fully exposes the active sites. The seven-element high-entropy lattice has stronger tolerance to sulfuric acid-hydrochloric acid mixed acids, reduces metal ion hydrolysis, reduces charge transfer resistance, and significantly improves voltage efficiency. It has the highest thermodynamic stability. The lattice stress caused by ion insertion / deintercalation during charging and discharging is dispersed by multi-metal synergy, resulting in the lowest ion dissolution and high active site retention rate. The capacity can still be maintained at a high level after 500 cycles.
[0205] The comparison of the results of Examples 1-3 shows that concentration has a significant impact on the performance of the material. An appropriate concentration is conducive to effective nucleation and uniform crystal growth, while at high concentrations, metal ions tend to aggregate locally, and some sites are encapsulated and cannot participate in the reaction, thus slightly reducing the compatibilization.
[0206] The comparison of the results of Examples 2 with Examples 4 and 5 shows that the compatibilization effect per unit mass of the sample synthesized using sodium ferrocyanide is slightly lower than that of the sample synthesized using potassium ferrocyanide. This is because the radius of sodium ions is smaller than that of potassium ions, resulting in a slightly weaker opening effect on the interstitial spaces and a decrease in the ion diffusion rate, which leads to a decrease in the utilization rate of active sites. The type of metal salt used has little effect on the compatibilization effect per unit mass.
[0207] A comparison of the results of Example 2 and Example 14 shows that when the feed material is potassium ferricyanide and pentavalent vanadium ions, the capacity contribution of the solid-phase energy storage material is relatively low. This is because the solid-phase energy storage material is currently in the highest oxidation state and cannot be further charged.
[0208] A comparison of the results of Examples 2 and Examples 6-13 shows that the reduction in the number of elements reduces the number of reactive sites and decreases the increase in capacity per unit mass. Co is the key metal for improving the targeted reaction efficiency of vanadium electrolyte. After the absence of Ni, the amount of metal ion dissolution increases, the stability decreases, and the active sites are gradually lost.
[0209] Comparative Examples 2-6 are low-entropy systems with far fewer metal types than in the Examples, resulting in a natural bottleneck in the number of active sites, high lattice distortion rate, and easy lattice collapse.
[0210] The results of Example 15 and Comparative Example 7 further demonstrate that, under high electrical density, the framework collapse rate of the low-entropy system is accelerated during cycling, and the capacity retention rate of Example 15 is 35% higher than that of Comparative Example 7.
[0211] In summary, the changes in capacity increase per unit mass, voltage efficiency, and cycle retention are essentially due to differences in the "entropy effect intensity" determined by the type and ratio of metals. The seven-element all-metal high-entropy system (Examples 1-5) achieves "maximization of active sites + optimization of reaction kinetics + enhancement of lattice stability" through high configurational entropy, resulting in optimal overall performance. The reduced-metal high-entropy system (Examples 6-13) exhibits a gradient decline in performance due to the decrease in entropy value. The low-metal system (Comparative Examples 2-6) suffers from a natural performance bottleneck due to the absence of a high-entropy effect. The type and distribution of active sites in the material, as well as their targeted reaction efficiency with the vanadium electrolyte, jointly determine the capacity increase per unit mass, voltage efficiency, and cycle capacity retention of the material in the electrolyte. Therefore, the high-entropy effect can serve as an effective strategy for improving the performance of PBA as a solid-state energy storage material in vanadium redox flow batteries.
[0212] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.
Claims
1. A high-entropy solid-state energy storage material, characterized in that, The material is a high-entropy vanadium-based Prussian blue analogue with the general chemical formula V. x M y [Fe(CN)6] z Furthermore, the general chemical formula satisfies the relation 3≤x+y+2z≤4; Wherein, M is a combination of ions selected from at least four transition metal elements from Fe, Mn, Co, Ni, Cu, and Zn, and the molar ratio of each transition metal ion to vanadium ion in M is 1:1 to 2:1; x is the number of moles of vanadium ions; y is the total number of moles of all metal ions in M; and z is [Fe(CN)6]. 4- The number of moles.
2. The high-entropy solid-state energy storage material according to claim 1, characterized in that, The ion corresponding to the element Fe is Fe. 2+ or Fe 3+ The ion corresponding to the Mn element is Mn 2+ or Mn 3+ The ion corresponding to Co is Co. 2+ or Co 3+ The ion corresponding to the element Ni is Ni. 2+ The ion corresponding to Cu is Cu. 2+ The ion corresponding to the element Zn is Zn 2+ .
3. The high-entropy solid-state energy storage material according to claim 1, characterized in that, The high-entropy vanadium-based Prussian blue analogue contains anionic vacancies, and the abundance of these anionic vacancies enables the high-entropy solid-state energy storage material to operate at wavenumbers of 2040-2080 cm⁻¹. -1 The characteristic peaks of the infrared spectrum within the range are broadened or redshifted.
4. A method for preparing a high-entropy solid-state energy storage material, characterized in that, Includes the following steps: S1. According to the molar ratio of each transition metal ion to vanadium ion in M of the high-entropy solid energy storage material according to any one of claims 1 to 3, obtain a transition metal salt or a transition metal salt solution as the source of transition metal ions in the high-entropy solid energy storage material, and mix them to obtain a mixed salt or a mixed salt solution; dissolve the mixed salt or mixed salt solution in a mixed acid solution of sulfuric acid and hydrochloric acid, and then add a metal ion stabilizer to obtain a first solution; S2. Add the second solution to the first solution, mix well, and then add the third solution to obtain a mixed solution; The mixed solution was allowed to stand and age, and the precipitate was separated. Then the precipitate was centrifuged, washed and dried in sequence to obtain a high-entropy solid energy storage material. The second solution is an aqueous solution of ferrocyanide, and the third solution is V. 5+ acid solution.
5. The method for preparing high-entropy solid energy storage material according to claim 4, characterized in that, In the mixed acid solution of sulfuric acid and hydrochloric acid, SO4 2- Cl - The total concentration is 0.8-1.4 M; the concentration of the metal ion stabilizer in the first solution is 0.02-0.05 M; The total concentration of transition metal ions in the first solution is 0.09-0.5 M; The concentration of ferrocyanide in the second solution is 0.03-0.25 M; V in the third solution 5+ The concentration is 0.03-0.08M.
6. The method for preparing high-entropy solid-state energy storage material according to claim 5, characterized in that, The second solution is added dropwise to the first solution at a volume ratio of 1:0.8 to 1:1.
2. After stirring and mixing evenly, the third solution is added at a volume ratio of 1:3 to 1:
5. After stirring evenly, a mixed solution is obtained.
7. The method for preparing high-entropy solid-state energy storage material according to claim 4, characterized in that, The transition metal salt from which each transition metal ion in M, used as a high-entropy solid energy storage material, originates, is a nitrate, sulfate, or chloride salt; The transition metal salt solution from which each transition metal ion in M, used as a high-entropy solid energy storage material, originates, is a nitrate solution, a sulfate solution, or a chloride solution. The transition metal salts used as the source of V ions in high-entropy solid energy storage materials are vanadium oxysulfate or vanadium trichloride. The transition metal salt solutions used as the source of V element corresponding ions in high-entropy solid energy storage materials are vanadium oxysulfate solution, metal salt solutions of divalent, trivalent and pentavalent vanadium ions obtained by oxidation-reduction of vanadium oxysulfate solution, vanadium oxychloride solution, metal salt solutions of divalent, trivalent and pentavalent vanadium ions obtained by oxidation-reduction of vanadium oxychloride solution, metal salt solutions of divalent, trivalent and tetravalent vanadium ions obtained by reduction of vanadium pentoxide, or metal salt solutions of divalent, trivalent and tetravalent vanadium ions obtained by reduction of ammonium metavanadate. The metal ion stabilizer is a chelating agent capable of forming complexes with transition metal ions.
8. The method for preparing high-entropy solid-state energy storage material according to claim 4, characterized in that, The ferrocyanide is potassium ferrocyanide, sodium ferrocyanide, ammonium ferrocyanide, potassium ferrocyanide, sodium ferrocyanide, or ammonium ferrocyanide. The V 5+ The acid solution is prepared by electrolysis of VOSO4 solution or VCl3 solution. 5+ acid solution.
9. The application of a high-entropy solid-state energy storage material as described in any one of claims 1-3 or a high-entropy solid-state energy storage material prepared by the preparation method described in any one of claims 4-8 in a vanadium redox flow battery.