Solid energy storage material, preparation method and application thereof

Abstract

The application belongs to the technical field of solid capacity of liquid flow battery electrolyte, and particularly relates to a solid energy storage material and a preparation method and application thereof. x [Fe(CN)6] y , and the chemical general formula satisfies a relationship formula 3<=x+2y<=4; wherein M is an ion corresponding to one element in Co, Ni, Mn and Cu, or M is a V ion, and there is an anion vacancy in the Prussian blue analogue, or M is a combination of ions corresponding to two elements in V, Co, Ni, Mn and Cu; x is the total number of moles of various metal ions in M; and y is the number of moles of [Fe(CN)6] 4‑ . The utilization of vanadium resources by the liquid flow battery system is reduced.

Description

Technical Field

[0001] This invention relates to the field of solid capacity enhancement technology for flow battery electrolytes, and particularly to a solid energy storage material, its preparation method, and its application. Background Technology

[0002] Vanadium redox flow batteries have shown great promise in large-scale energy storage due to their advantages such as power-capacity decoupling, long cycle life, and high safety. However, the cost of vanadium electrolyte, the active material, accounts for a relatively high proportion of the total system cost, affecting the battery's economic efficiency.

[0003] Currently, the industry has proposed a two-phase energy storage system of "solid energy storage material + vanadium electrolyte," which involves adding a potential-matched solid energy storage material to the electrolyte tank. The principle is to utilize redox mediators dissolved in the electrolyte, such as vanadium ions, to undergo a reversible electron exchange reaction with active sites on the surface of the solid material, thereby storing some energy within the solid material. However, existing solid energy storage materials still use vanadium as the primary metallic active center, failing to fundamentally reduce the overall battery system's dependence on expensive vanadium resources, resulting in limited overall cost reduction.

[0004] Therefore, there is an urgent need to provide an improved solid energy storage material. Summary of the Invention

[0005] (a) Technical problems to be solved

[0006] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a solid energy storage material, its preparation method and application, thereby reducing the utilization of vanadium resources by flow battery systems.

[0007] (II) Technical Solution

[0008] To achieve the above objectives, the main technical solutions adopted by the present invention include:

[0009] In a first aspect, the present invention provides a solid energy storage material, which is a Prussian blue analogue with the general chemical formula M. x [Fe(CN)6] y Furthermore, the general chemical formula satisfies the relationship 3≤x+2y≤4; where M is the ion corresponding to one of the elements Co, Ni, Mn, and Cu, or M is a V ion, and an anion vacancy exists in the Prussian blue analogue, or M is a combination of the ions corresponding to two of the elements V, Co, Ni, Mn, and Cu; x is the total number of moles of various metal ions in M; y is [Fe(CN)6] 4- The number of moles.

[0010] Optionally, when M is a combination of corresponding ions of two elements, if the combination includes V ions, the molar ratio of V ions to the other element ions is 1:1 to 1:9; if the combination does not include V ions, the molar ratio of the two element ions is 1:1 to 1:9.

[0011] Alternatively, the general chemical formula of Prussian blue analogues is V x1 W x2 [Fe(CN)6] y Furthermore, the general chemical formula satisfies the relationship 3≤x1+x2+2y≤4; where W is the ion corresponding to one of the elements Co, Ni, Mn, and Cu; x1 is the number of moles of V ions; x2 is the number of moles of the ion corresponding to W; the molar ratio of V ions to the ion corresponding to W is 1:1 to 1:9, and anion vacancies exist in Prussian blue analogues.

[0012] Optionally, the Prussian blue analogue is prepared by a method comprising the following steps:

[0013] Provide solution A containing ferrocyanide;

[0014] Provide an acidic solution B containing low-valent vanadium ions and the corresponding W ion; wherein the low-valent vanadium ion is V 2+ V 3+ One or two of them;

[0015] Provides V 5+ Acidic solution C;

[0016] Solution A and solution B were mixed and reacted, and then solution C was added to the reaction system to obtain a Prussian blue analogue.

[0017] Optionally, the ion corresponding to element V is V 4+ 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 the Mn element is Mn 2+ or Mn 3+ The ion corresponding to Cu is Cu. 2+ .

[0018] Secondly, the present invention provides a method for preparing the solid energy storage material as described above, comprising the following steps:

[0019] Provide solution A containing ferrocyanide;

[0020] Provide an acidic solution B containing the ion corresponding to M;

[0021] When solution A is mixed with solution B, a Prussian blue analogue is obtained.

[0022] Optionally, the concentration of ferrocyanide in solution A is 0.02-0.1 M;

[0023] In solution B, the total concentration of ions corresponding to M is 0.06-0.3M, and the acidity of solution B is adjusted by adding an inorganic strong acid with a concentration of 0.5-4M; wherein the inorganic strong acid is selected from at least one of sulfuric acid, hydrochloric acid, and nitric acid;

[0024] Add solution A dropwise to solution B according to a volume ratio of 1:1 to 1:3 between solution A and solution B to mix and react.

[0025] Optionally, when preparing a solid energy storage material where M is a V ion and anion vacancies exist in the Prussian blue analogue:

[0026] Provide an acidic solution B containing low-valent vanadium ions; wherein the low-valent vanadium ions are V. 2+ V 3+ One or two of them;

[0027] Provides V 5+ Acidic solution C;

[0028] Solution A and solution B were mixed and reacted, and then solution C was added to the reaction system to obtain a Prussian blue analogue.

[0029] Optionally, when preparing the above-mentioned chemical formula V x1 W x2 [Fe(CN)6] y When using solid energy storage materials with Prussian blue analogues:

[0030] Provide an acidic solution B containing low-valent vanadium ions and the corresponding W ion; wherein the low-valent vanadium ion is V 2+ V 3+ One or two of them;

[0031] Provides V 5+ Acidic solution C;

[0032] Solution A and solution B were mixed and reacted, and then solution C was added to the reaction system to obtain a Prussian blue analogue.

[0033] Optionally, V in solution C 5+ The concentration is 0.06~0.3M; solution C is prepared by electrolysis of VOSO4 solution or VCl3 solution. 5+ acid solution;

[0034] Solution C was added to the reaction system at a volume ratio of 1:1 to that of solution B. After stirring until homogeneous, a mixed solution was obtained. The mixed solution was then subjected to aging, centrifugation, washing, and drying to obtain a Prussian blue analogue.

[0035] Optionally, the ion sources corresponding to the elements Co, Ni, Mn, and Cu in M ​​are nitrates, sulfates, or chlorides; the ion sources corresponding to the element V in M ​​are vanadium oxysulfate, vanadium oxychloride, metal salt solutions of divalent, trivalent, and pentavalent vanadium ions obtained by the oxidation and reduction of vanadium oxysulfate solution, metal salt solutions of divalent, trivalent, and pentavalent vanadium ions obtained by the oxidation and reduction of vanadium oxychloride solution, 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.

[0036] Ferrocyanides are potassium ferrocyanide, sodium ferrocyanide, ammonium ferrocyanide, potassium ferrocyanide, sodium ferrocyanide, or ammonium ferrocyanide.

[0037] Thirdly, the present invention provides an application of the solid energy storage material as described above or the solid energy storage material prepared by the preparation method as described above in a vanadium redox flow battery.

[0038] (III) Beneficial Effects

[0039] The beneficial effects of this invention are:

[0040] In the solid energy storage material and its preparation and application provided by this invention, a chemical formula M is provided. x [Fe(CN)6] y This invention provides a solid-state energy storage material that offers an effective path to reduce the dependence of vanadium redox flow battery systems on expensive vanadium resources. Specifically, when M is one of the elements Co, Ni, Mn, and Cu, a completely vanadium-free solid-state energy storage material is achieved, minimizing the amount of vanadium used. When M is V ions and anionic vacancies exist in the Prussian blue analogue, the introduction of anionic vacancies significantly optimizes the electronic structure and ion transport kinetics of the single vanadium-based Prussian blue analogue, enabling the material to achieve higher energy storage capacity and efficiency per unit mass or unit volume than traditional vanadium-based materials. This means that the total amount of vanadium resources required to achieve the same battery capacity is effectively reduced, thus reducing dependence on vanadium resources from the perspective of material utilization efficiency. When M is a combination of V and another element from Co, Ni, Mn, and Cu, the proportion of vanadium in the material is significantly reduced. This invention reduces dependence on vanadium resources through multiple technical paths, including "significantly improving vanadium utilization efficiency," "partial substitution," and "complete vanadium-free." Furthermore, the solid-state energy storage material provided by this invention possesses electrochemical performance suitable for application in vanadium redox flow batteries. Detailed Implementation

[0041] To better explain and facilitate understanding of the present invention, a detailed description of the invention will be provided through specific embodiments.

[0042] In a first aspect, the present invention provides a solid energy storage material, which is a Prussian blue analogue with the general chemical formula M. x [Fe(CN)6] y Furthermore, the general chemical formula satisfies the relationship 3≤x+2y≤4; where M is the ion corresponding to one of the elements Co, Ni, Mn, and Cu, or M is a V ion, and an anion vacancy exists in the Prussian blue analogue, or M is a combination of the ions corresponding to two of the elements V, Co, Ni, Mn, and Cu; x is the total number of moles of various metal ions in M; y is [Fe(CN)6] 4- The number of moles.

[0043] This invention provides an effective path to reduce the dependence of vanadium redox flow battery systems on expensive vanadium resources. Specifically, when M is one of Co, Ni, Mn, or Cu, a completely vanadium-free solid energy storage material is achieved, minimizing vanadium consumption. When M is V ions and anionic vacancies exist in the Prussian blue analogue, the introduction of anionic vacancies significantly optimizes the electronic structure and ion transport kinetics of the single vanadium-based Prussian blue analogue, enabling the material to achieve higher energy storage capacity and efficiency per unit mass or unit volume than traditional vanadium-based materials. This means that the total amount of vanadium resources required to achieve the same battery capacity is effectively reduced, decreasing dependence on vanadium resources from the perspective of material utilization efficiency. When M is a combination of V and another element from Co, Ni, Mn, or Cu, the vanadium content in the material is significantly reduced. This invention reduces dependence on vanadium resources through multiple technical paths, including "significantly improving vanadium utilization efficiency," "partial substitution," and "complete vanadium-free." Furthermore, the solid energy storage material provided by this invention possesses electrochemical performance suitable for application in vanadium redox flow batteries.

[0044] Preferably, when M is a combination of corresponding ions of two elements, if the combination includes V ions, the molar ratio of V ions to the other element ion is 1:1 to 1:9; if the combination does not include V ions, the molar ratio of the two element ions is 1:1 to 1:9. This specific ratio range is key to achieving efficient synergy between element ions and optimizing the electrochemical performance of the material; this preferred molar ratio range enables solid energy storage materials to achieve low vanadium content while possessing excellent electrochemical performance, ensuring the feasibility and effectiveness of their application in vanadium redox flow batteries.

[0045] Preferably, the general chemical formula of the Prussian blue analogue is V x1 W x2 [Fe(CN)6] yFurthermore, the general chemical formula satisfies the relationship 3≤x1+x2+2y≤4; where W is the ion corresponding to one of the elements Co, Ni, Mn, and Cu; x1 is the molar number of V ions; and x2 is the molar number of W-corresponding ions. The molar ratio of V ions to W-corresponding ions is 1:1 to 1:9, and anion vacancies exist in the Prussian blue analogue.

[0046] Thus, a synergistic effect is achieved by introducing anion vacancies and doping them with a specific ratio of bimetallic materials. Specifically, the presence of anion vacancies effectively modulates the electronic structure of the material, providing more channels and active sites for ion transport, thereby greatly improving the material's reaction kinetics and reversibility. Furthermore, the preferred molar ratio of V ions to their corresponding W ions of 1:1 to 1:9 can synergize with the anion vacancies. The combined effect of these two factors, compared to vacancy-free VW materials and single-metal materials, demonstrates a significant improvement in capacity enhancement and voltage efficiency per unit mass in vanadium redox flow batteries. The "vacancy-doping synergy" strategy employed in this invention not only successfully achieves the goal of reducing the vanadium content but also overcomes the technical bottlenecks of slow reaction kinetics and limited capacity enhancement effects in existing solid-state energy storage materials, providing support for the realization of high-performance, low-cost vanadium redox flow batteries.

[0047] More preferably, W is an ion corresponding to one of the elements Co, Ni, and Mn. Within the material framework of "vacancy-doping synergy," the V-Co, V-Ni, and V-Mn systems exhibit more significant improvements in capacity enhancement and voltage efficiency per unit mass.

[0048] Preferably, the Prussian blue analogue is prepared by a method comprising the following steps: providing a solution A containing ferrocyanide; providing an acidic solution B containing low-valent vanadium ions and W corresponding ions, wherein the low-valent vanadium ions are V 2+ V 3+ One or two of them; providing V 5+ Acidic solution C; solutions A and B are mixed and reacted, then solution C is added to the reaction system to obtain a Prussian blue analogue. Thus, the initial Prussian blue framework is first formed by mixing solutions A and B, followed by the subsequent addition of solution C, V 5+ The subsequent addition of [a specific substance] allows for the targeted oxidation of low-valent vanadium in the previously formed lattice, thereby introducing anionic vacancies within the crystal. This preparation process ensures that the material possesses excellent ionic conductivity and abundant active sites, providing the technological basis for achieving the "vacancy-doping synergy" effect and significantly improving the material's capacity and voltage efficiency per unit mass in vanadium redox flow batteries.

[0049] Among them, the ion corresponding to element V is V 4+ 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 the Mn element is Mn 2+ or Mn 3+ The ion corresponding to Cu is Cu. 2+ .

[0050] Secondly, the present invention provides a method for preparing the above-mentioned solid energy storage material, comprising the following steps:

[0051] S1. Provide solution A containing ferrocyanide; provide acidic solution B containing the ion corresponding to M in the solid energy storage material.

[0052] In solution A, the concentration of ferrocyanide is 0.02-0.1 M. In solution B, the total concentration of ions corresponding to M is 0.06-0.3 M, and the acidity of solution B is adjusted by adding an inorganic strong acid with a concentration of 0.5-4 M; wherein the inorganic strong acid is selected from at least one of sulfuric acid, hydrochloric acid, and nitric acid.

[0053] Preferably, the inorganic strong acid is selected from sulfuric acid.

[0054] Among them, the ions corresponding to Co, Ni, Mn, and Cu in M ​​are nitrates, sulfates, or chlorides; the ions corresponding to V in M ​​are vanadium oxysulfate, vanadium oxychloride, metal salt solutions of divalent, trivalent, and pentavalent vanadium ions obtained by oxidation-reduction of vanadium oxysulfate 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 ferrocyanide is potassium ferrocyanide, sodium ferrocyanide, ammonium ferrocyanide, potassium ferrocyanide, sodium ferrocyanide, or ammonium ferrocyanide.

[0055] S2. Mix solution A and solution B to react and obtain a Prussian blue analogue.

[0056] In this process, solution A is added dropwise to solution B to mix and react, with the volume ratio of solution A to solution B being 1:1 to 1:3.

[0057] Thus, the method for preparing solid energy storage materials provided by the present invention ensures the high efficiency of the synthesis reaction and the uniformity of product quality by limiting the specific concentration range of reactants in solution A and solution B, the suitable acidity of solution B, and the optimized volume ratio of solution A and solution B.

[0058] When the above preparation method is used to prepare a solid energy storage material in which M is a V ion and anion vacancies exist in the Prussian blue analogue:

[0059] S1 also includes: providing V 5+An acidic solution C is provided in S1. An acidic solution B containing low-valent vanadium ions is also provided in S1. The low-valent vanadium ions are V... 2+ V 3+ One or two of them.

[0060] S2 also includes: mixing solution A with solution B and reacting them, then adding solution C to the reaction system to obtain a Prussian blue analogue.

[0061] When the above preparation method prepares a chemical formula with an anion vacancy of V x1 W x2 [Fe(CN)6] y When it comes to solid energy storage materials:

[0062] S1 also includes: providing V 5+ S1 provides an acidic solution C. S1 also provides an acidic solution B containing low-valent vanadium ions and the corresponding W ions. The low-valent vanadium ions are V... 2+ V 3+ One or two of them.

[0063] S2 also includes: after mixing and reacting solutions A and B, adding solution C to the reaction system to obtain a Prussian blue analogue.

[0064] Among them, V in solution C 5+ The concentration is 0.06~0.3M. Solution C is prepared by electrolysis of VOSO4 solution or VCl3 solution. 5+ acid solution.

[0065] In this process, solution C is added to the reaction system at a volume ratio of 1:1 to solution B, and after stirring until homogeneous, a mixed solution is obtained. The mixed solution is then subjected to aging, centrifugation, washing, and drying to obtain a Prussian blue analogue.

[0066] Thus, using V 5+ Acid solution acts as a structure regulator, introducing anion vacancies in situ into the product framework formed after the reaction of solution A and solution B. This optimizes the ion diffusion channels and electrochemical activity of the material, thereby improving the specific capacitance and voltage efficiency of the prepared solid energy storage material.

[0067] Specifically, the mixed solution is allowed to stand and age at 25-35℃ for 10-24 hours.

[0068] Specifically, the drying process is as follows: vacuum drying at 60-75℃ for 10-16 hours.

[0069] Thirdly, the present invention provides an application of the above-mentioned solid energy storage material or the solid energy storage material prepared by the above-mentioned preparation method in a vanadium redox flow battery.

[0070] Specifically, solid energy storage materials are applied to the positive electrode electrolyte system of vanadium redox flow batteries through the following methods:

[0071] A1. Solid energy storage material, conductive carbon material, and PVDF are uniformly dispersed in N-methylpyrrolidone at a mass ratio of 7:2:1, so that the total mass concentration of solid energy storage material, conductive carbon material, and PVDF is 5%-40%. Then, vacuum drying is carried out at 60°C to obtain Prussian blue analog particles.

[0072] A2, using 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 a 0.3-1.65M tetravalent vanadium electrolyte with Prussian blue analog particles added. The negative electrode storage tank is a 0.3-1.65M trivalent vanadium electrolyte. The charge-discharge cycle test is carried out using a constant current density of 110.

[0073] 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.

[0074] Example 1:

[0075] S1. Dissolve potassium ferrocyanide in deionized water to provide a 0.02M potassium ferrocyanide solution, denoted as solution A; dissolve vanadium oxysulfate in 2M sulfuric acid to prepare a 0.06M vanadium oxysulfate solution. Reduce a portion of the vanadium oxysulfate solution by electrolysis to obtain V with a 0.06M vanadium oxysulfate solution. 3+ An acidic solution, denoted as solution B, is used to oxidize another portion of a sulfuric acid-vanadium acid solution via electrolysis to obtain V with a molar concentration of 0.06 M. 5+ An acidic solution is denoted as solution C.

[0076] S2. Take 300 mL of solution A and add it dropwise to 300 mL of solution B while stirring. After the addition is complete, add 300 mL of solution C and continue stirring for 1 hour. After standing at room temperature for 10 hours, centrifuge and wash the precipitate 4 times and vacuum dry it at 60°C for 12 hours to obtain a Prussian blue analog containing vacancies, i.e., a solid energy storage material.

[0077] The application of solid energy storage materials in the positive electrode electrolyte system of vanadium redox flow batteries is achieved through the following methods:

[0078] A1. Solid energy storage material, conductive carbon material, and PVDF are uniformly dispersed in N-methylpyrrolidone at a mass ratio of 7:2:1, so that the total mass concentration of solid energy storage material, conductive carbon material, and PVDF is 20%. Then, vacuum drying is carried out at 60°C to obtain Prussian blue analog particles.

[0079] A2, using 48cm 2 The single cell was used as the power unit for charging and discharging. The electrolyte was a mixed acid system of sulfuric acid and hydrochloric acid. The positive electrode storage tank contained 70 mL of 1.6 M tetravalent vanadium electrolyte and 25 g of Prussian blue analog particles were added. The negative electrode storage tank contained 100 mL of 1.6 M trivalent vanadium electrolyte. The charge-discharge cycle test was conducted using a constant current density of 110.

[0080] Example 2:

[0081] S1. Dissolve potassium ferrocyanide in deionized water to provide a 0.04 M potassium ferrocyanide solution, denoted as solution A; dissolve vanadium oxysulfate in 2 M sulfuric acid to prepare a 0.12 M vanadium oxysulfate solution. Reduce a portion of the vanadium oxysulfate solution by electrolysis to obtain V with a 0.12 M vanadium oxysulfate solution. 3+ An acidic solution, denoted as solution B, is used to oxidize another portion of a sulfuric acid-vanadium acid solution via electrolysis to obtain V with a molar concentration of 0.12 M. 5+ An acidic solution is denoted as solution C.

[0082] S2. Take 300 mL of solution A and add it dropwise to 300 mL of solution B while stirring. After the addition is complete, add 300 mL of solution C and continue stirring for 1 hour. After standing at room temperature for 10 hours, centrifuge and wash the precipitate 4 times and vacuum dry it at 60°C for 12 hours to obtain a Prussian blue analog containing vacancies, i.e., a solid energy storage material.

[0083] The method for testing the performance of solid energy storage materials applied to the positive electrode electrolyte system of vanadium redox flow batteries is the same as in Example 1, and will not be repeated here.

[0084] Example 3:

[0085] S1. Dissolve potassium ferrocyanide in deionized water to provide a 0.06 M potassium ferrocyanide solution, denoted as solution A; dissolve vanadium oxysulfate in 2 M sulfuric acid to prepare a 0.18 M vanadium oxysulfate solution. Reduce a portion of the vanadium oxysulfate solution by electrolysis to obtain V with a 0.18 M vanadium oxysulfate solution. 3+ An acidic solution, denoted as solution B, is used to oxidize another portion of a sulfuric acid-vanadium acid solution via electrolysis to obtain V with a molar concentration of 0.18 M. 5+ An acidic solution is denoted as solution C.

[0086] S2. Take 300 mL of solution A and add it dropwise to 300 mL of solution B while stirring. After the addition is complete, add 300 mL of solution C and continue stirring for 1 hour. After standing at room temperature for 10 hours, centrifuge and wash the precipitate 4 times and vacuum dry it at 60°C for 12 hours to obtain a Prussian blue analog containing vacancies, i.e., a solid energy storage material.

[0087] The method for testing the performance of solid energy storage materials applied to the positive electrode electrolyte system of vanadium redox flow batteries is the same as in Example 1, and will not be repeated here.

[0088] Example 4:

[0089] S1. Dissolve potassium ferrocyanide in deionized water to provide a 0.1M potassium ferrocyanide solution, denoted as solution A; dissolve vanadium oxysulfate in 2M sulfuric acid to prepare a 0.3M vanadium oxysulfate solution. Reduce a portion of the vanadium oxysulfate solution by electrolysis to obtain V with a 0.3M vanadium oxysulfate solution. 3+ An acidic solution, denoted as solution B, is used to oxidize another portion of a sulfuric acid-vanadium acid solution via electrolysis to obtain V with a molar concentration of 0.3 M. 5+ An acidic solution is denoted as solution C.

[0090] S2. Take 300 mL of solution A and add it dropwise to 300 mL of solution B while stirring. After the addition is complete, add 300 mL of solution C and continue stirring for 1 hour. After standing at room temperature for 10 hours, centrifuge and wash the precipitate 4 times and vacuum dry it at 60°C for 12 hours to obtain a Prussian blue analog containing vacancies, i.e., a solid energy storage material.

[0091] The method for testing the performance of solid energy storage materials applied to the positive electrode electrolyte system of vanadium redox flow batteries is the same as in Example 1, and will not be repeated here.

[0092] Comparative Example 1:

[0093] S1. Dissolve potassium ferrocyanide in deionized water to provide a potassium ferrocyanide solution with a molar concentration of 0.06M, denoted as solution A; dissolve vanadium oxysulfate in 2M sulfuric acid to prepare a vanadium oxysulfate solution with a molar concentration of 0.18M, ​​denoted as solution B.

[0094] S2. Take 300 mL of solution A and add it dropwise to 300 mL of solution B while stirring. After the addition is complete, let it stand at room temperature for 10 h. Then, centrifuge and wash the precipitate 4 times and vacuum dry it at 60 °C for 12 h to obtain a Prussian blue analog without vacancies, i.e., a solid energy storage material.

[0095] The method for testing the performance of solid energy storage materials applied to the positive electrode electrolyte system of vanadium redox flow batteries is the same as in Example 1, and will not be repeated here.

[0096] Example 5:

[0097] S1. Dissolve potassium ferrocyanide in deionized water to provide a potassium ferrocyanide solution with a molar concentration of 0.06M, denoted as solution A; dissolve manganese sulfate in 2M sulfuric acid to prepare a manganese sulfate solution with a molar concentration of 0.18M, ​​denoted as solution B.

[0098] S2. Take 300 mL of solution A and add it dropwise to 300 mL of solution B while stirring. After the addition is complete, let it stand at room temperature for 10 h. Then, centrifuge and wash the precipitate 4 times and vacuum dry it at 60 °C for 12 h to obtain a Prussian blue analog without vacancies, i.e., a solid energy storage material.

[0099] The method for testing the performance of solid energy storage materials applied to the positive electrode electrolyte system of vanadium redox flow batteries is the same as in Example 1, and will not be repeated here.

[0100] Example 6:

[0101] S1. Dissolve potassium ferrocyanide in deionized water to provide a 0.06 M potassium ferrocyanide solution, denoted as solution A; dissolve vanadium oxysulfate in 2 M sulfuric acid to prepare a 0.09 M vanadium oxysulfate solution. Reduce a portion of the vanadium oxysulfate solution by electrolysis to obtain V with a 0.09 M vanadium oxysulfate solution. 3+ A certain amount of manganese sulfate was added to an acid solution to prepare a mixed metal salt acid solution with a total concentration of 0.18 M, wherein the molar ratio of V to Mn was 1:1, denoted as solution B. Another portion of the vanadate-sulfuric acid solution was oxidized by electrolysis to obtain a V solution with a molar concentration of 0.09 M. 5+ An acidic solution is denoted as solution C.

[0102] S2. Take 300 mL of solution A and add it dropwise to 300 mL of solution B while stirring. After the addition is complete, add 300 mL of solution C and continue stirring for 1 hour. After standing at room temperature for 10 hours, centrifuge and wash the precipitate 4 times and vacuum dry it at 60°C for 12 hours to obtain a Prussian blue analog containing vacancies, i.e., a solid energy storage material.

[0103] The method for testing the performance of solid energy storage materials applied to the positive electrode electrolyte system of vanadium redox flow batteries is the same as in Example 1, and will not be repeated here.

[0104] Example 7:

[0105] S1. Dissolve potassium ferrocyanide in deionized water to provide a 0.06 M potassium ferrocyanide solution, denoted as solution A; dissolve vanadium oxysulfate in 2 M sulfuric acid to prepare a 0.05 M vanadium oxysulfate solution. Reduce a portion of the vanadium oxysulfate solution by electrolysis to obtain V with a 0.05 M vanadium oxysulfate solution. 3+ A certain amount of manganese sulfate was added to an acid solution to prepare a mixed metal salt acid solution with a total concentration of 0.20 M, wherein the molar ratio of V to Mn was 1:3, denoted as solution B. Another portion of the vanadate-sulfuric acid solution was oxidized by electrolysis to obtain a V solution with a molar concentration of 0.05 M. 5+ An acidic solution is denoted as solution C.

[0106] S2. Take 300 mL of solution A and add it dropwise to 300 mL of solution B while stirring. After the addition is complete, add 300 mL of solution C and continue stirring for 1 hour. After standing at room temperature for 10 hours, centrifuge and wash the precipitate 4 times and vacuum dry it at 60°C for 12 hours to obtain a Prussian blue analog containing vacancies, i.e., a solid energy storage material.

[0107] The method for testing the performance of solid energy storage materials applied to the positive electrode electrolyte system of vanadium redox flow batteries is the same as in Example 1, and will not be repeated here.

[0108] Example 8:

[0109] S1. Dissolve potassium ferrocyanide in deionized water to provide a 0.06 M potassium ferrocyanide solution, denoted as solution A; dissolve vanadium oxysulfate in 2 M sulfuric acid to prepare a 0.03 M vanadium oxysulfate solution. Reduce a portion of the vanadium oxysulfate solution by electrolysis to obtain V with a 0.03 M vanadium oxysulfate solution. 3+ A certain amount of manganese sulfate was added to an acid solution to prepare a mixed metal salt acid solution with a total concentration of 0.21 M, wherein the molar ratio of V to Mn was 1:6, denoted as solution B. Another portion of the vanadate-sulfuric acid solution was oxidized by electrolysis to obtain a V solution with a molar concentration of 0.03 M. 5+ An acidic solution is denoted as solution C.

[0110] S2. Take 300 mL of solution A and add it dropwise to 300 mL of solution B while stirring. After the addition is complete, add 300 mL of solution C and continue stirring for 1 hour. After standing at room temperature for 10 hours, centrifuge and wash the precipitate 4 times and vacuum dry it at 60°C for 12 hours to obtain a Prussian blue analog containing vacancies, i.e., a solid energy storage material.

[0111] The method for testing the performance of solid energy storage materials applied to the positive electrode electrolyte system of vanadium redox flow batteries is the same as in Example 1, and will not be repeated here.

[0112] Example 9:

[0113] S1. Dissolve potassium ferrocyanide in deionized water to provide a 0.06 M potassium ferrocyanide solution, denoted as solution A; dissolve vanadium oxysulfate in 2 M sulfuric acid to prepare a 0.018 M vanadium oxysulfate solution. Reduce a portion of the vanadium oxysulfate solution by electrolysis to obtain V with a 0.018 M vanadium oxysulfate solution. 3+ A certain amount of manganese sulfate was added to an acid solution to prepare a mixed metal salt acid solution with a total concentration of 0.18 M, wherein the molar ratio of V to Mn was 1:9, denoted as solution B. Another portion of the vanadate-sulfuric acid solution was oxidized by electrolysis to obtain a V solution with a molar concentration of 0.018 M. 5+ An acidic solution is denoted as solution C.

[0114] S2. Take 300 mL of solution A and add it dropwise to 300 mL of solution B while stirring. After the addition is complete, add 300 mL of solution C and continue stirring for 1 hour. After standing at room temperature for 10 hours, centrifuge and wash the precipitate 4 times and vacuum dry it at 60°C for 12 hours to obtain a Prussian blue analog containing vacancies, i.e., a solid energy storage material.

[0115] The method for testing the performance of solid energy storage materials applied to the positive electrode electrolyte system of vanadium redox flow batteries is the same as in Example 1, and will not be repeated here.

[0116] Example 10:

[0117] S1. Dissolve potassium ferrocyanide in deionized water to provide a potassium ferrocyanide solution with a molar concentration of 0.06M, denoted as solution A; dissolve cobalt sulfate in 2M sulfuric acid to prepare a cobalt sulfate solution with a molar concentration of 0.18M, ​​denoted as solution B.

[0118] S2. Take 300 mL of solution A and add it dropwise to 300 mL of solution B while stirring. After the addition is complete, let it stand at room temperature for 10 h. Then, centrifuge and wash the precipitate 4 times and vacuum dry it at 60 °C for 12 h to obtain a Prussian blue analog without vacancies, i.e., a solid energy storage material.

[0119] The method for testing the performance of solid energy storage materials applied to the positive electrode electrolyte system of vanadium redox flow batteries is the same as in Example 1, and will not be repeated here.

[0120] Example 11:

[0121] S1. Dissolve potassium ferrocyanide in deionized water to provide a 0.06 M potassium ferrocyanide solution, denoted as solution A; dissolve vanadium oxysulfate in 2 M sulfuric acid to prepare a 0.09 M vanadium oxysulfate solution. Reduce a portion of the vanadium oxysulfate solution by electrolysis to obtain V with a 0.09 M vanadium oxysulfate solution. 3+ A certain amount of cobalt sulfate was added to an acid solution to prepare a mixed metal salt acid solution with a total concentration of 0.18 M, wherein the molar ratio of V to Co was 1:1, denoted as solution B. Another portion of the vanadate sulfate solution was oxidized by electrolysis to obtain a V solution with a molar concentration of 0.09 M. 5+ An acidic solution is denoted as solution C.

[0122] S2. Take 300 mL of solution A and add it dropwise to 300 mL of solution B while stirring. After the addition is complete, add 300 mL of solution C and continue stirring for 1 hour. After standing at room temperature for 10 hours, centrifuge and wash the precipitate 4 times and vacuum dry it at 60°C for 12 hours to obtain a Prussian blue analog containing vacancies, i.e., a solid energy storage material.

[0123] The method for testing the performance of solid energy storage materials applied to the positive electrode electrolyte system of vanadium redox flow batteries is the same as in Example 1, and will not be repeated here.

[0124] Example 12:

[0125] S1. Dissolve potassium ferrocyanide in deionized water to provide a 0.06 M potassium ferrocyanide solution, denoted as solution A; dissolve vanadium oxysulfate in 2 M sulfuric acid to prepare a 0.05 M vanadium oxysulfate solution. Reduce a portion of the vanadium oxysulfate solution by electrolysis to obtain V with a 0.05 M vanadium oxysulfate solution. 3+ A certain amount of cobalt sulfate was added to an acid solution to prepare a mixed metal salt acid solution with a total concentration of 0.20 M, wherein the molar ratio of V to Co was 1:3, denoted as solution B. Another portion of the vanadate sulfate solution was oxidized by electrolysis to obtain a V solution with a molar concentration of 0.05 M. 5+ An acidic solution is denoted as solution C.

[0126] S2. Take 300 mL of solution A and add it dropwise to 300 mL of solution B while stirring. After the addition is complete, add 300 mL of solution C and continue stirring for 1 hour. After standing at room temperature for 10 hours, centrifuge and wash the precipitate 4 times and vacuum dry it at 60°C for 12 hours to obtain a Prussian blue analog containing vacancies, i.e., a solid energy storage material.

[0127] The method for testing the performance of solid energy storage materials applied to the positive electrode electrolyte system of vanadium redox flow batteries is the same as in Example 1, and will not be repeated here.

[0128] Example 13:

[0129] S1. Dissolve potassium ferrocyanide in deionized water to provide a 0.06 M potassium ferrocyanide solution, denoted as solution A; dissolve vanadium oxysulfate in 2 M sulfuric acid to prepare a 0.03 M vanadium oxysulfate solution. Reduce a portion of the vanadium oxysulfate solution by electrolysis to obtain V with a 0.03 M vanadium oxysulfate solution. 3+ A certain amount of cobalt sulfate was added to an acid solution to prepare a mixed metal salt acid solution with a total concentration of 0.21 M, wherein the molar ratio of V to Co was 1:6, denoted as solution B. Another portion of the vanadate sulfate solution was oxidized by electrolysis to obtain a V solution with a molar concentration of 0.03 M. 5+ An acidic solution is denoted as solution C.

[0130] S2. Take 300 mL of solution A and add it dropwise to 300 mL of solution B while stirring. After the addition is complete, add 300 mL of solution C and continue stirring for 1 hour. After standing at room temperature for 10 hours, centrifuge and wash the precipitate 4 times and vacuum dry it at 60°C for 12 hours to obtain a Prussian blue analog containing vacancies, i.e., a solid energy storage material.

[0131] The method for testing the performance of solid energy storage materials applied to the positive electrode electrolyte system of vanadium redox flow batteries is the same as in Example 1, and will not be repeated here.

[0132] Example 14:

[0133] S1. Dissolve potassium ferrocyanide in deionized water to provide a 0.06 M potassium ferrocyanide solution, denoted as solution A; dissolve vanadium oxysulfate in 2 M sulfuric acid to prepare a 0.018 M vanadium oxysulfate solution. Reduce a portion of the vanadium oxysulfate solution by electrolysis to obtain V with a 0.018 M vanadium oxysulfate solution. 3+ A certain amount of cobalt sulfate was added to an acid solution to prepare a mixed metal salt acid solution with a total concentration of 0.18 M, wherein the molar ratio of V to Co was 1:9, denoted as solution B. Another portion of the vanadate sulfate solution was oxidized by electrolysis to obtain a V solution with a molar concentration of 0.018 M. 5+ An acidic solution is denoted as solution C.

[0134] S2. Take 300 mL of solution A and add it dropwise to 300 mL of solution B while stirring. After the addition is complete, add 300 mL of solution C and continue stirring for 1 hour. After standing at room temperature for 10 hours, centrifuge and wash the precipitate 4 times and vacuum dry it at 60°C for 12 hours to obtain a Prussian blue analog containing vacancies, i.e., a solid energy storage material.

[0135] The method for testing the performance of solid energy storage materials applied to the positive electrode electrolyte system of vanadium redox flow batteries is the same as in Example 1, and will not be repeated here.

[0136] Example 15:

[0137] S1. Dissolve potassium ferrocyanide in deionized water to provide a potassium ferrocyanide solution with a molar concentration of 0.06M, denoted as solution A; dissolve nickel sulfate in 2M sulfuric acid to prepare a nickel sulfate solution with a molar concentration of 0.18M, ​​denoted as solution B.

[0138] S2. Take 300 mL of solution A and add it dropwise to 300 mL of solution B while stirring. After the addition is complete, let it stand at room temperature for 10 h. Then, centrifuge and wash the precipitate 4 times and vacuum dry it at 60 °C for 12 h to obtain a Prussian blue analog without vacancies, i.e., a solid energy storage material.

[0139] The method for testing the performance of solid energy storage materials applied to the positive electrode electrolyte system of vanadium redox flow batteries is the same as in Example 1, and will not be repeated here.

[0140] Example 16:

[0141] S1. Dissolve potassium ferrocyanide in deionized water to provide a 0.06 M potassium ferrocyanide solution, denoted as solution A; dissolve vanadium oxysulfate in 2 M sulfuric acid to prepare a 0.09 M vanadium oxysulfate solution. Reduce a portion of the vanadium oxysulfate solution by electrolysis to obtain V with a 0.09 M vanadium oxysulfate solution. 3+ A certain amount of nickel sulfate was added to an acid solution to prepare a mixed metal salt acid solution with a total concentration of 0.18 M, wherein the molar ratio of V to Ni was 1:1, denoted as solution B. Another portion of the vanadate-sulfuric acid solution was oxidized by electrolysis to obtain a V solution with a molar concentration of 0.09 M. 5+ An acidic solution is denoted as solution C.

[0142] S2. Take 300 mL of solution A and add it dropwise to 300 mL of solution B while stirring. After the addition is complete, add 300 mL of solution C and continue stirring for 1 hour. After standing at room temperature for 10 hours, centrifuge and wash the precipitate 4 times and vacuum dry it at 60°C for 12 hours to obtain a Prussian blue analog containing vacancies, i.e., a solid energy storage material.

[0143] The method for testing the performance of solid energy storage materials applied to the positive electrode electrolyte system of vanadium redox flow batteries is the same as in Example 1, and will not be repeated here.

[0144] Example 17:

[0145] S1. Dissolve potassium ferrocyanide in deionized water to provide a 0.06 M potassium ferrocyanide solution, denoted as solution A; dissolve vanadium oxysulfate in 2 M sulfuric acid to prepare a 0.05 M vanadium oxysulfate solution. Reduce a portion of the vanadium oxysulfate solution by electrolysis to obtain V with a 0.05 M vanadium oxysulfate solution. 3+ A certain amount of nickel sulfate was added to an acid solution to prepare a mixed metal salt acid solution with a total concentration of 0.20 M, wherein the molar ratio of V to Ni was 1:3, denoted as solution B. Another portion of the vanadate-sulfuric acid solution was oxidized by electrolysis to obtain a V solution with a molar concentration of 0.05 M. 5+ An acidic solution is denoted as solution C.

[0146] S2. Take 300 mL of solution A and add it dropwise to 300 mL of solution B while stirring. After the addition is complete, add 300 mL of solution C and continue stirring for 1 hour. After standing at room temperature for 10 hours, centrifuge and wash the precipitate 4 times and vacuum dry it at 60°C for 12 hours to obtain a Prussian blue analog containing vacancies, i.e., a solid energy storage material.

[0147] The method for testing the performance of solid energy storage materials applied to the positive electrode electrolyte system of vanadium redox flow batteries is the same as in Example 1, and will not be repeated here.

[0148] Example 18:

[0149] S1. Dissolve potassium ferrocyanide in deionized water to provide a 0.06 M potassium ferrocyanide solution, denoted as solution A; dissolve vanadium oxysulfate in 2 M sulfuric acid to prepare a 0.03 M vanadium oxysulfate solution. Reduce a portion of the vanadium oxysulfate solution by electrolysis to obtain V with a 0.03 M vanadium oxysulfate solution. 3+ A certain amount of nickel sulfate was added to an acid solution to prepare a mixed metal salt acid solution with a total concentration of 0.21 M, wherein the molar ratio of V to Ni was 1:6, denoted as solution B. Another portion of the vanadate-sulfuric acid solution was oxidized by electrolysis to obtain a V solution with a molar concentration of 0.03 M. 5+ An acidic solution is denoted as solution C.

[0150] S2. Take 300 mL of solution A and add it dropwise to 300 mL of solution B while stirring. After the addition is complete, add 300 mL of solution C and continue stirring for 1 hour. After standing at room temperature for 10 hours, centrifuge and wash the precipitate 4 times and vacuum dry it at 60°C for 12 hours to obtain a Prussian blue analog containing vacancies, i.e., a solid energy storage material.

[0151] The method for testing the performance of solid energy storage materials applied to the positive electrode electrolyte system of vanadium redox flow batteries is the same as in Example 1, and will not be repeated here.

[0152] Example 19:

[0153] S1. Dissolve potassium ferrocyanide in deionized water to provide a 0.06 M potassium ferrocyanide solution, denoted as solution A; dissolve vanadium oxysulfate in 2 M sulfuric acid to prepare a 0.018 M vanadium oxysulfate solution. Reduce a portion of the vanadium oxysulfate solution by electrolysis to obtain V with a 0.018 M vanadium oxysulfate solution. 3+ A certain amount of nickel sulfate was added to an acid solution to prepare a mixed metal salt acid solution with a total concentration of 0.18 M, wherein the molar ratio of V to Ni was 1:9, denoted as solution B. Another portion of the vanadate-sulfuric acid solution was oxidized by electrolysis to obtain a V solution with a molar concentration of 0.018 M. 5+ An acidic solution is denoted as solution C.

[0154] S2. Take 300 mL of solution A and add it dropwise to 300 mL of solution B while stirring. After the addition is complete, add 300 mL of solution C and continue stirring for 1 hour. After standing at room temperature for 10 hours, centrifuge and wash the precipitate 4 times and vacuum dry it at 60°C for 12 hours to obtain a Prussian blue analog containing vacancies, i.e., a solid energy storage material.

[0155] The method for testing the performance of solid energy storage materials applied to the positive electrode electrolyte system of vanadium redox flow batteries is the same as in Example 1, and will not be repeated here.

[0156] Example 20:

[0157] S1. Dissolve potassium ferrocyanide in deionized water to provide a potassium ferrocyanide solution with a molar concentration of 0.06M, denoted as solution A; dissolve copper sulfate in 2M sulfuric acid to prepare a copper sulfate acid solution with a molar concentration of 0.18M, ​​denoted as solution B.

[0158] S2. Take 300 mL of solution A and add it dropwise to 300 mL of solution B while stirring. After the addition is complete, let it stand at room temperature for 10 h. Then, centrifuge and wash the precipitate 4 times and vacuum dry it at 60 °C for 12 h to obtain a Prussian blue analog without vacancies, i.e., a solid energy storage material.

[0159] The method for testing the performance of solid energy storage materials applied to the positive electrode electrolyte system of vanadium redox flow batteries is the same as in Example 1, and will not be repeated here.

[0160] Example 21:

[0161] S1. Dissolve potassium ferrocyanide in deionized water to provide a 0.06 M potassium ferrocyanide solution, denoted as solution A; dissolve vanadium oxysulfate in 2 M sulfuric acid to prepare a 0.09 M vanadium oxysulfate solution. Reduce a portion of the vanadium oxysulfate solution by electrolysis to obtain V with a 0.09 M vanadium oxysulfate solution. 3+ A certain amount of copper sulfate was added to an acid solution to prepare a mixed metal salt acid solution with a total concentration of 0.18 M, wherein the molar ratio of V to Cu was 1:1, denoted as solution B. Another portion of the vanadate-sulfuric acid solution was oxidized by electrolysis to obtain a solution with a molar concentration of 0.09 M. 5+ An acidic solution is denoted as solution C.

[0162] S2. Take 300 mL of solution A and add it dropwise to 300 mL of solution B while stirring. After the addition is complete, add 300 mL of solution C and continue stirring for 1 hour. After standing at room temperature for 10 hours, centrifuge and wash the precipitate 4 times and vacuum dry it at 60°C for 12 hours to obtain a Prussian blue analog containing vacancies, i.e., a solid energy storage material.

[0163] The method for testing the performance of solid energy storage materials applied to the positive electrode electrolyte system of vanadium redox flow batteries is the same as in Example 1, and will not be repeated here.

[0164] Example 22:

[0165] S1. Dissolve potassium ferrocyanide in deionized water to provide a 0.06 M potassium ferrocyanide solution, denoted as solution A; dissolve vanadium oxysulfate in 2 M sulfuric acid to prepare a 0.05 M vanadium oxysulfate solution. Reduce a portion of the vanadium oxysulfate solution by electrolysis to obtain V with a 0.05 M vanadium oxysulfate solution. 3+ A certain amount of copper sulfate was added to an acid solution to prepare a mixed metal salt acid solution with a total concentration of 0.20 M, wherein the molar ratio of V to Cu was 1:3, denoted as solution B. Another portion of the vanadate-sulfuric acid solution was oxidized by electrolysis to obtain a V solution with a molar concentration of 0.05 M. 5+ An acidic solution is denoted as solution C.

[0166] S2. Take 300 mL of solution A and add it dropwise to 300 mL of solution B while stirring. After the addition is complete, add 300 mL of solution C and continue stirring for 1 hour. After standing at room temperature for 10 hours, centrifuge and wash the precipitate 4 times and vacuum dry it at 60°C for 12 hours to obtain a Prussian blue analog containing vacancies, i.e., a solid energy storage material.

[0167] The method for testing the performance of solid energy storage materials applied to the positive electrode electrolyte system of vanadium redox flow batteries is the same as in Example 1, and will not be repeated here.

[0168] Example 23:

[0169] S1. Dissolve potassium ferrocyanide in deionized water to provide a 0.06 M potassium ferrocyanide solution, denoted as solution A; dissolve vanadium oxysulfate in 2 M sulfuric acid to prepare a 0.03 M vanadium oxysulfate solution. Reduce a portion of the vanadium oxysulfate solution by electrolysis to obtain V with a 0.03 M vanadium oxysulfate solution. 3+ A certain amount of copper sulfate was added to an acid solution to prepare a mixed metal salt acid solution with a total concentration of 0.21 M, wherein the molar ratio of V to Cu was 1:6, denoted as solution B. Another portion of the vanadate-sulfuric acid solution was oxidized by electrolysis to obtain a V solution with a molar concentration of 0.03 M. 5+ An acidic solution is denoted as solution C.

[0170] S2. Take 300 mL of solution A and add it dropwise to 300 mL of solution B while stirring. After the addition is complete, add 300 mL of solution C and continue stirring for 1 hour. After standing at room temperature for 10 hours, centrifuge and wash the precipitate 4 times and vacuum dry it at 60°C for 12 hours to obtain a Prussian blue analog containing vacancies, i.e., a solid energy storage material.

[0171] The method for testing the performance of solid energy storage materials applied to the positive electrode electrolyte system of vanadium redox flow batteries is the same as in Example 1, and will not be repeated here.

[0172] Example 24:

[0173] S1. Dissolve potassium ferrocyanide in deionized water to provide a 0.06 M potassium ferrocyanide solution, denoted as solution A; dissolve vanadium oxysulfate in 2 M sulfuric acid to prepare a 0.018 M vanadium oxysulfate solution. Reduce a portion of the vanadium oxysulfate solution by electrolysis to obtain V with a 0.018 M vanadium oxysulfate solution. 3+ A certain amount of copper sulfate was added to an acid solution to prepare a mixed metal salt acid solution with a total concentration of 0.18 M, wherein the molar ratio of V to Cu was 1:9, denoted as solution B. Another portion of the vanadate-sulfuric acid solution was oxidized by electrolysis to obtain a V solution with a molar concentration of 0.018 M. 5+ An acidic solution is denoted as solution C.

[0174] S2. Take 300 mL of solution A and add it dropwise to 300 mL of solution B while stirring. After the addition is complete, add 300 mL of solution C and continue stirring for 1 hour. After standing at room temperature for 10 hours, centrifuge and wash the precipitate 4 times and vacuum dry it at 60°C for 12 hours to obtain a Prussian blue analog containing vacancies, i.e., a solid energy storage material.

[0175] The method for testing the performance of solid energy storage materials applied to the positive electrode electrolyte system of vanadium redox flow batteries is the same as in Example 1, and will not be repeated here.

[0176] Example 25:

[0177] S1. Dissolve potassium ferrocyanide in deionized water to provide a potassium ferrocyanide solution with a molar concentration of 0.06M, denoted as solution A; dissolve cobalt chloride in 2M sulfuric acid to prepare a cobalt chloride acid solution with a molar concentration of 0.18M, ​​denoted as solution B.

[0178] S2. Take 300 mL of solution A and add it dropwise to 300 mL of solution B while stirring. After the addition is complete, let it stand at room temperature for 10 h. Then, centrifuge and wash the precipitate 4 times and vacuum dry it at 60 °C for 12 h to obtain a Prussian blue analog without vacancies, i.e., a solid energy storage material.

[0179] The method for testing the performance of solid energy storage materials applied to the positive electrode electrolyte system of vanadium redox flow batteries is the same as in Example 1, and will not be repeated here.

[0180] Example 26:

[0181] S1. Dissolve potassium ferrocyanide in deionized water to provide a 0.06 M potassium ferrocyanide solution, denoted as solution A; dissolve vanadium oxysulfate in 2 M sulfuric acid to prepare a 0.03 M vanadium oxysulfate solution. Reduce a portion of the vanadium oxysulfate solution by electrolysis to obtain V with a 0.03 M vanadium oxysulfate solution. 3+ A certain amount of cobalt chloride was added to an acid solution to prepare a mixed metal salt acid solution with a total concentration of 0.21 M, wherein the molar ratio of V to Co was 1:6, denoted as solution B. Another portion of the sulfuric acid-vanadate solution was oxidized by electrolysis to obtain a V solution with a molar concentration of 0.03 M. 5+ An acidic solution is denoted as solution C.

[0182] S2. Take 300 mL of solution A and add it dropwise to 300 mL of solution B while stirring. After the addition is complete, add 300 mL of solution C and continue stirring for 1 hour. After standing at room temperature for 10 hours, centrifuge and wash the precipitate 4 times and vacuum dry it at 60°C for 12 hours to obtain a Prussian blue analog containing vacancies, i.e., a solid energy storage material.

[0183] The method for testing the performance of solid energy storage materials applied to the positive electrode electrolyte system of vanadium redox flow batteries is the same as in Example 1, and will not be repeated here.

[0184] Example 27:

[0185] S1. Dissolve potassium ferrocyanide in deionized water to provide a 0.06 M potassium ferrocyanide solution, denoted as solution A; dissolve vanadium oxysulfate in 0.02 M sulfuric acid to prepare a 0.03 M vanadium oxysulfate solution. Reduce a portion of the vanadium oxysulfate solution by electrolysis to obtain V with a 0.03 M vanadium oxysulfate solution. 3+ A certain amount of cobalt sulfate was added to an acid solution to prepare a mixed metal salt acid solution with a total concentration of 0.21 M, wherein the molar ratio of V to Co was 1:6, denoted as solution B. Another portion of the vanadate sulfate solution was oxidized by electrolysis to obtain a V solution with a molar concentration of 0.03 M. 5+ An acidic solution is denoted as solution C.

[0186] S2. Take 300 mL of solution A and add it dropwise to 300 mL of solution B while stirring. After the addition is complete, add 300 mL of solution C and continue stirring for 1 hour. After standing at room temperature for 10 hours, centrifuge and wash the precipitate 4 times and vacuum dry it at 60°C for 12 hours to obtain a Prussian blue analog containing vacancies, i.e., a solid energy storage material.

[0187] The method for testing the performance of solid energy storage materials applied to the positive electrode electrolyte system of vanadium redox flow batteries is the same as in Example 1, and will not be repeated here.

[0188] Example 28:

[0189] S1. Dissolve potassium ferrocyanide in deionized water to provide a 0.06 M potassium ferrocyanide solution, denoted as solution A; dissolve vanadium oxysulfate in 0.5 M sulfuric acid to prepare a 0.03 M vanadium oxysulfate solution. Reduce a portion of the vanadium oxysulfate solution by electrolysis to obtain V with a 0.03 M vanadium oxysulfate solution. 3+ A certain amount of cobalt sulfate was added to an acid solution to prepare a mixed metal salt acid solution with a total concentration of 0.21 M, wherein the molar ratio of V to Co was 1:6, denoted as solution B. Another portion of the vanadate sulfate solution was oxidized by electrolysis to obtain a V solution with a molar concentration of 0.03 M. 5+ An acidic solution is denoted as solution C.

[0190] S2. Take 300 mL of solution A and add it dropwise to 300 mL of solution B while stirring. After the addition is complete, add 300 mL of solution C and continue stirring for 1 hour. After standing at room temperature for 10 hours, centrifuge and wash the precipitate 4 times and vacuum dry it at 60°C for 12 hours to obtain a Prussian blue analog containing vacancies, i.e., a solid energy storage material.

[0191] The method for testing the performance of solid energy storage materials applied to the positive electrode electrolyte system of vanadium redox flow batteries is the same as in Example 1, and will not be repeated here.

[0192] Example 29:

[0193] S1. Dissolve potassium ferrocyanide in deionized water to provide a 0.06 M potassium ferrocyanide solution, denoted as solution A; dissolve vanadium oxysulfate in 1 M sulfuric acid to prepare a 0.03 M vanadium oxysulfate solution. Reduce a portion of the vanadium oxysulfate solution by electrolysis to obtain V with a 0.03 M vanadium oxysulfate solution. 3+ A certain amount of cobalt sulfate was added to an acid solution to prepare a mixed metal salt acid solution with a total concentration of 0.21 M, wherein the molar ratio of V to Co was 1:6, denoted as solution B. Another portion of the vanadate sulfate solution was oxidized by electrolysis to obtain a V solution with a molar concentration of 0.03 M. 5+ An acidic solution is denoted as solution C.

[0194] S2. Take 300 mL of solution A and add it dropwise to 300 mL of solution B while stirring. After the addition is complete, add 300 mL of solution C and continue stirring for 1 hour. After standing at room temperature for 10 hours, centrifuge and wash the precipitate 4 times and vacuum dry it at 60°C for 12 hours to obtain a Prussian blue analog containing vacancies, i.e., a solid energy storage material.

[0195] The method for testing the performance of solid energy storage materials applied to the positive electrode electrolyte system of vanadium redox flow batteries is the same as in Example 1, and will not be repeated here.

[0196] Example 30:

[0197] S1. Dissolve potassium ferrocyanide in deionized water to provide a 0.06 M potassium ferrocyanide solution, denoted as solution A; dissolve vanadium oxysulfate in 4 M sulfuric acid to prepare a 0.03 M vanadium oxysulfate solution. Reduce a portion of the vanadium oxysulfate solution by electrolysis to obtain V with a 0.03 M vanadium oxysulfate solution. 3+ A certain amount of cobalt sulfate was added to an acid solution to prepare a mixed metal salt acid solution with a total concentration of 0.21 M, wherein the molar ratio of V to Co was 1:6, denoted as solution B. Another portion of the vanadate sulfate solution was oxidized by electrolysis to obtain a V solution with a molar concentration of 0.03 M. 5+ An acidic solution is denoted as solution C.

[0198] S2. Take 300 mL of solution A and add it dropwise to 300 mL of solution B while stirring. After the addition is complete, add 300 mL of solution C and continue stirring for 1 hour. After standing at room temperature for 10 hours, centrifuge and wash the precipitate 4 times and vacuum dry it at 60°C for 12 hours to obtain a Prussian blue analog containing vacancies, i.e., a solid energy storage material.

[0199] The method for testing the performance of solid energy storage materials applied to the positive electrode electrolyte system of vanadium redox flow batteries is the same as in Example 1, and will not be repeated here.

[0200] The test results of the above embodiments and comparative examples are shown in Tables 1 and 2 below.

[0201] Table 1. Charge-discharge cycle test results of Examples 1-15 and Comparative Example 1

[0202]

[0203] Table 2. Charge-discharge cycle test results of Examples 16-30

[0204]

[0205] The comparative results of Examples 1-30 show that the voltage efficiency during the test process is positively correlated with the increase in capacity per unit mass. These results demonstrate that improving the reaction kinetics of solid-state energy storage materials can simultaneously improve both voltage efficiency and capacity per unit mass.

[0206] The test results of Examples 1-4 show that the concentration of reactants during the synthesis process affects the increase in sample capacity. The best effect is achieved when the concentration of potassium ferrocyanide is 0.06 M, with a capacity increase of 20.58 mAh / g per unit mass. When the reactant concentration is too low, the probability of ion collisions in the reaction system decreases significantly, and metal ions and cyanide ions cannot fully coordinate to form a complete cubic framework, easily generating amorphous cyanometallic compounds (such as amorphous Fe4[Fe(CN)6)). 3 Incomplete reactions and low yields can occur due to local ion concentration imbalances, such as the formation of impurities like metal hydroxides (e.g., M(OH)2, M(OH)3) and carbonates. When reactant concentrations are too high, the ion activity in the system increases sharply, leading to local supersaturation. Metal ions rapidly combine with cyanide ions to form unstable intermediates. Simultaneously, the salting-out effect causes high-concentration electrolytes to precipitate and adsorb onto the surface of PBA particles, contaminating the product and hindering crystal growth. A suitable reactant concentration can satisfy the collision frequency required for coordination between metal ions and cyanide ions, resulting in moderate crystal growth, while maintaining the stoichiometric ratio of metal ions to cyanide ions in the system and balancing the effective yield.

[0207] The comparison of the experimental results of Example 3 and Comparative Example 1 shows that, under the condition of constant concentration, the presence of anion vacancies increased the capacity by 68.75 mAh, and the capacity increase per unit mass increased by 2.75 mAh / g. This indicates that the sample containing anion vacancies has high ionic conductivity and can effectively improve the efficiency of capacity increase per unit mass of solid energy storage materials in flow batteries.

[0208] A comparison of the experimental results of Examples 3, 5, 10, and 15 with Examples 6-9, 11-14, and 16-19 shows that doping with manganese, cobalt, and nickel has a significant effect on improving the efficiency of capacity increase per unit mass of the samples. Among them, cobalt doping has the best effect, with a capacity increase of 1271 mAh, a maximum capacity increase per unit mass of 50.84 mAh / g, and a voltage efficiency of 82.00%. Compared with Example 3, the capacity increase is 756.50 mAh, and the capacity increase per unit mass is 30.26 mAh / g. Examples 20-24 show that due to the low potential of copper ions, copper doping slows down the reaction kinetics of the solid energy storage material, and its performance is not as good as that of the all-vanadium solid energy storage material. The above results indicate that by selecting metal ions with appropriate potentials for doping, the performance of solid energy storage materials synthesized by binary metals is significantly better than that of solid energy storage materials synthesized by single elements.

[0209] A comparison of the results of Examples 6-9, 11-14, 16-19 and 21-24 shows that the performance of the solid energy storage material synthesized by bimetallic elements is significantly correlated with the feed ratio, and the capacity increase per unit mass of the sample exhibits a volcano-shaped distribution as the vanadium input decreases.

[0210] The comparison of the results of Examples 10 and 25, and Examples 13 and 26 shows that different types of metal salts have little effect on the final performance of the samples during synthesis.

[0211] A comparison of the results of Examples 13 and 27-30 shows that the acid concentration during sample synthesis has a certain impact on the sample performance. When the acid concentration is too low, metal ions are prone to hydrolysis, such as Ni. 2+ +2OH - →Ni(OH)2↓, the generated hydroxide competes with the cyanide ion for binding with metal ions, preventing the formation of a complete "M-CN-M'" framework. The "M-CN-M'" framework is the core skeletal structure of Prussian blue materials, where M and M' represent two different metal ions, and CN represents the cyanide ion; when the acid concentration is too high, CN... - Under strongly acidic conditions, it will rapidly protonate to form HCN, and further hydrolyze to NH4. + and CO3 2- This leads to a sharp drop in the effective cyanide concentration in the system, preventing the formation of a complete framework with metal ions; simultaneously, the already formed PBAs framework is unstable under strongly acidic conditions, and the MN bonds in the cubic structure are easily broken by H+. + Damage may occur, potentially leading to the dissolution and formation of mononuclear cyanide complexes, such as [Fe(CN)6]. 4- [Ni(CN)4] 2- Alternatively, it may be converted into metal salts, such as FeCl3 or NiCl2, ultimately failing to yield the target product; a suitable acid concentration can effectively inhibit the hydrolysis of metal ions, H...+ Consume OH - To avoid M(OH) n It generates cyanide without destroying its coordination activity.

[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 solid energy storage material, characterized in that, The material is a Prussian blue analogue with the general chemical formula M. x [Fe(CN)6] y Furthermore, the general chemical formula satisfies the relation 3≤x+2y≤4; Where M is a V ion and an anionic vacancy exists in the Prussian blue analogue, or M is a combination of two elemental ions, one of which is a V ion and the other is an ion corresponding to any one of Co, Ni, or Mn; x is the total number of moles of various metal ions in M; y is [Fe(CN)6]. 4- The number of moles; The Prussian blue analogue was prepared by a method comprising the following steps: A solution A containing ferrocyanide is provided; an acidic solution B containing the corresponding ion of M is provided; the solution A and the solution B are mixed and reacted to obtain a Prussian blue analogue; The concentration of ferrocyanide in solution A is 0.02-0.1 M.

2. The solid energy storage material according to claim 1, characterized in that, When M is a combination of ions corresponding to two elements, the molar ratio of V ion to the ion of the other element is 1:1 to 1:

9.

3. The solid energy storage material according to claim 1, characterized in that, The general chemical formula of the Prussian blue analogue is V. x1 W x2 [Fe(CN)6] y Furthermore, the general chemical formula satisfies the relation 3≤x1+x2+2y≤4; Where W is the ion corresponding to one of the elements Co, Ni, Mn, and Cu; x1 is the number of moles of V ions; and x2 is the number of moles of the ion corresponding to W. The molar ratio of V ions to corresponding W ions is 1:1 to 1:9, and anionic vacancies exist in the Prussian blue analogue.

4. The solid energy storage material according to claim 3, characterized in that, The Prussian blue analogue was prepared by a method comprising the following steps: Provide solution A containing ferrocyanide; Provide an acidic solution B containing low-valent vanadium ions and the corresponding W ion; wherein the low-valent vanadium ion is V 2+ V 3+ One or two of them; Provides V 5+ Acidic solution C; Solution A and solution B are mixed and reacted, and then solution C is added to the reaction system to obtain a Prussian blue analogue.

5. The solid energy storage material according to claim 1, characterized in that, The ion corresponding to element V is V. 4+ The ion corresponding to Co is Co. 2+ or Co 3+ The ion corresponding to Ni is Ni 2+ The ion corresponding to the Mn element is Mn 2+ or Mn 3+ .

6. A method for preparing a solid energy storage material as described in any one of claims 1-5, characterized in that, Includes the following steps: Provide solution A containing ferrocyanide; Provide an acidic solution B containing the ion corresponding to M; The solution A and the solution B are mixed and reacted to obtain a Prussian blue analogue.

7. The method for preparing solid energy storage materials according to claim 6, characterized in that, The concentration of ferrocyanide in solution A is 0.02-0.1 M; In solution B, the total concentration of ions corresponding to M is 0.06-0.3M, and the acidity of solution B is adjusted by adding an inorganic strong acid with a concentration of 0.5-4M; wherein the inorganic strong acid is selected from at least one of sulfuric acid, hydrochloric acid, and nitric acid; Solution A is added dropwise to solution B and the mixture reacts according to a volume ratio of solution A to solution B of 1:1 to 1:

3.

8. The method for preparing solid energy storage materials according to claim 6 or 7, characterized in that, When preparing solid energy storage materials where M is a V ion and anionic vacancies exist in Prussian blue analogues: Provide an acidic solution B containing low-valent vanadium ions; wherein the low-valent vanadium ions are V. 2+ V 3+ One or two of them; Provides V 5+ Acidic solution C; Solution A and solution B are mixed and reacted, and then solution C is added to the reaction system to obtain a Prussian blue analogue.

9. The method for preparing solid energy storage materials according to claim 6 or 7, characterized in that, When the chemical formula of the Prussian blue analogue of the prepared solid energy storage material is V x1 W x2 [Fe(CN)6] y hour: Provide an acidic solution B containing low-valent vanadium ions and the corresponding W ion; wherein the low-valent vanadium ion is V 2+ V 3+ One or two of them; Provides V 5+ Acidic solution C; Solution A and solution B are mixed and reacted, and then solution C is added to the reaction system to obtain a Prussian blue analogue.

10. The method for preparing solid energy storage material according to claim 9, characterized in that, V in solution C 5+ The concentration is 0.06~0.3M; The solution C is prepared by electrolysis of VOSO4 solution or VCl3 solution. 5+ acid solution; Solution C was added to the reaction system at a volume ratio of 1:1 to solution B. After stirring until homogeneous, a mixed solution was obtained. The mixed solution was then subjected to aging, centrifugation, washing, and drying to obtain a Prussian blue analogue.

11. The method for preparing solid energy storage material according to claim 6, characterized in that, The ions corresponding to Co, Ni, and Mn elements in M ​​are derived from nitrates, sulfates, or chlorides; the ions corresponding to V elements in M ​​are derived from vanadium oxysulfate, vanadium oxychloride, metal salt solutions of divalent, trivalent, and pentavalent vanadium ions obtained by the oxidation and reduction of vanadium oxysulfate solution, metal salt solutions of divalent, trivalent, and pentavalent vanadium ions obtained by the oxidation and reduction of vanadium oxychloride solution, 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. The ferrocyanide is potassium ferrocyanide, sodium ferrocyanide, or ammonium ferrocyanide.

12. The application of a solid energy storage material as described in any one of claims 1-5 or a solid energy storage material prepared by the preparation method as described in any one of claims 6-11 in a vanadium redox flow battery.

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