Electrolyte of wide-temperature-range flow battery as well as preparation method and application of electrolyte

Abstract

The invention discloses an electrolyte of a wide-temperature-range flow battery as well as a preparation method and application of the electrolyte, and belongs to the field of flow batteries. The method comprises the following steps: adding VOCl3 into an aqueous solution of sulfuric acid, then adding V2O5 into the aqueous solution of sulfuric acid, then adding oxalic acid into the aqueous solution of sulfuric acid, and carrying out electrolysis to obtain the electrolyte of the wide-temperature-range flow battery. By regulating and controlling the reaction proportion of each ion, high-temperature positive electrode precipitation and low-temperature negative electrode precipitation can be effectively prevented, and all tetravalence states are ensured to be stable. The stable state of the electrolyte can be kept for more than 15 days in the range of-5 to 50 DEG C, and meanwhile, the electrolyte has excellent energy efficiency and energy density, and the economic value and practical value of the battery are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of flow battery technology, specifically to an electrolyte for a wide-temperature-range flow battery, its preparation method, and its application. Background Technology

[0002] Vanadium redox flow batteries (VRFBs) are widely used in large-scale energy storage due to their excellent reversibility and safety. They can help solve the instability problem of renewable energy generation such as wind and solar power, and ensure the stable operation of the power grid. Currently, the mainstream electrolyte system for VRFBs is sulfuric acid or a sulfuric acid-hydrochloric acid mixed acid system. These systems can meet the basic operating requirements of the battery well within a certain concentration range. However, when the vanadium ion concentration increases to above 3.0M, a series of technical bottlenecks gradually emerge, seriously restricting the efficient and stable operation of the battery.

[0003] Specifically, under high concentration conditions, the V in the positive electrode electrolyte 5+ At high temperatures, precipitation reactions readily occur, forming V₂O₅ solid precipitates. This not only reduces the concentration of active materials in the electrolyte, decreasing battery capacity, but can also cause problems such as blockage of internal battery circuits and electrode surface coating, significantly shortening battery life. Simultaneously, V₂O₅ in the negative electrode electrolyte... 3+ At low temperatures, precipitates such as VOCl and V2(SO4)3 are easily formed, which can also lead to the deterioration of electrolyte performance and affect the charging and discharging efficiency and stability of the battery.

[0004] Furthermore, the temperature adaptability range of the aforementioned mixed acid system is relatively narrow, typically operating stably only within the range of 5–45°C. Therefore, how to address the issue of V in high-concentration sulfuric acid or sulfuric acid-hydrochloric acid mixed acid systems remains a challenge. 5+ High temperature precipitation, V 3+ Addressing the issue of low-temperature precipitation, while simultaneously expanding the temperature adaptability range of the electrolyte and reducing the system's reliance on thermal management, has become a key technical problem that urgently needs to be solved in the current development of vanadium redox flow battery technology. Summary of the Invention

[0005] To address the issues of narrow temperature adaptability and instability of existing flow batteries under high or low temperature conditions, this invention provides an electrolyte for a wide-temperature-range flow battery, its preparation method, and its application.

[0006] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a method for preparing an electrolyte for a wide-temperature-range flow battery, comprising: VOCl3 is added to an aqueous solution of sulfuric acid to obtain the first solution, and then V2O5 is added to the first solution to obtain the second solution; Oxalic acid is added to the second solution to obtain a third solution, and the third solution is electrolyzed to obtain the electrolyte for a wide-temperature-range flow battery.

[0007] Furthermore, the mass ratio of VOCl3, sulfuric acid, and V2O5 is 1:(0.87~1.06):(0.4~0.42).

[0008] Furthermore, the molar ratio of vanadium ions to chloride ions in the electrolyte is (0.9~1.1):(1.8~2.0).

[0009] Furthermore, the molar ratio of oxalic acid to vanadium ions in the second solution is (0.5~0.6):1.

[0010] Furthermore, the electrolysis specifically involves: first, using a current density of 180 mA / cm². 2 Charge to 1.7V, then apply a current density of 100mA / cm². 2 Charge to 1.7V, then charge at a constant voltage of 1.7V until the current is less than 180mA.

[0011] The present invention also provides a method for preparing the electrolyte of the above-mentioned wide-temperature-range flow battery.

[0012] Furthermore, the electrolyte comprises vanadium ions, chloride ions, and sulfate ions, with a vanadium ion concentration of 2.8~3.1 mol / L, a chloride ion concentration of 5.4~6.1 mol / L, and a sulfate ion concentration of 2.5~3.1 mol / L.

[0013] Furthermore, the vanadium ions include divalent vanadium ions, trivalent vanadium ions, tetravalent vanadium ions, and pentavalent vanadium ions.

[0014] Furthermore, the electrolyte of the wide-temperature-range flow battery has a temperature range of -5 to 50°C.

[0015] The present invention also provides a flow battery, wherein the flow battery includes the above-mentioned electrolyte.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: The preparation method provided by this invention uses VOCl3 as both a chlorine and vanadium source, avoiding the problem of excessively high acidity caused by directly adding HCl. This reduces the acidity of the system and inhibits V... 3+ Hydrolysis, V 3+ It can form VCl(H2O)4SO4 type complex complex ions in the system, enhancing V 3+Low-temperature stability is achieved. An aqueous solution of sulfuric acid is used as both solvent and acid source. High-valence vanadium ions are replenished with V₂O₅, which gradually dissolves in an acidic environment, replenishing the high-valence vanadium ions and forming a mixed-valence system with the low-valence vanadium ions produced by hydrolysis, thus constructing a wide-temperature-range electrolyte. The carboxylic acid groups of oxalic acid coordinate with vanadium ions to form stable water-soluble complexes, reducing the concentration of free vanadium ions. During electrolysis, low-valence vanadium ion oxidation occurs at the anode, while high-valence vanadium ion reduction occurs at the cathode, ultimately forming a dynamic equilibrium system of divalent to pentavalent vanadium ions. Furthermore, this preparation process allows for rapid dissolution without heating, improving preparation efficiency and making it suitable for industrial application.

[0017] Furthermore, by adjusting the concentrations and ratios of vanadium ions, chloride ions, and sulfate ions, the problem of ion precipitation was avoided, significantly improving the battery's stability and electrochemical performance over a wide temperature range.

[0018] Furthermore, ensuring that the molar ratio of vanadium to chlorine is controlled at (0.9~1.1):(1.8~2.0) can effectively prevent precipitation at high-temperature positive electrode and low-temperature negative electrode, ensuring that all four valence states are stable.

[0019] Within the temperature range of -5 to 50°C, this electrolyte can maintain a stable state for more than 15 days, reducing reliance on temperature control equipment and saving 10% to 20% in energy, while maintaining the electrochemical activity of the high-concentration vanadium ion system. At a high vanadium concentration of 3.0 mol / L, the energy efficiency of the electrolyte can reach over 80%, and the energy density can reach over 40 Wh / L. The excellent electrical properties enable this electrolyte to store more electrical energy in the same volume, significantly reducing the size of the flow battery and lowering production costs. Detailed Implementation

[0020] To make the technical problem to be solved, the technical solution, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0021] In this invention, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0022] In this invention, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0023] It should be understood that in various embodiments of the present invention, the order of the above-mentioned processes does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0024] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a,” “the,” and “the” as used in the embodiments of this invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0025] The weights of the relevant components mentioned in the embodiments of this invention can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this invention is within the scope disclosed in the embodiments of this invention. Specifically, the mass described in the embodiments of this invention can be a mass unit known in the chemical industry, such as μg, mg, g, or kg.

[0026] To address the aforementioned issues, existing high-concentration electrolyte systems exhibit a contradiction between high-temperature vanadium ion deposition and low-temperature precipitation, necessitating a simultaneous solution to stability problems at different temperatures. Analysis of vanadium ion valence state transformation patterns reveals that the coexistence of multiple valence states can improve electrolyte stability, while the synergistic effect of chloride ions and complexing agents can inhibit precipitation formation. Based on this, a stepwise preparation method involving the introduction of a chloride source, a high-valence vanadium source, and a complexing agent is proposed. By controlling the solution acidity and ion coordination state, a stable system with a wide temperature range is constructed.

[0027] This invention provides a method for preparing an electrolyte for a wide-temperature-range flow battery, comprising: adding VOCl3 to an aqueous solution of sulfuric acid to obtain a first solution, and then adding V2O5 to the first solution to obtain a second solution; Oxalic acid is added to the second solution to obtain a third solution, and the third solution is electrolyzed to obtain the electrolyte for a wide-temperature-range flow battery.

[0028] Compared with existing technologies, traditional methods use a single sulfuric acid or mixed acid system to directly dissolve vanadium compounds, which cannot effectively control the distribution and stability of vanadium ions with different valence states.

[0029] In some embodiments of this application, the mass ratio of VOCl3, sulfuric acid, and V2O5 is 1:(0.87~1.06):(0.4~0.42), and the molar ratio of vanadium ions to chloride ions in the electrolyte is (0.9-1.1):(1.8-2.0). By controlling the molar ratio of vanadium ions to chloride ions, V2O5 is suppressed. 3+ Hydrolysis and precipitation form a stable VCl(H2O)4SO4 complex ion, which can significantly improve the stability of the electrolyte at low temperatures and prevent V 3+ The formation of VOCl or V2(SO4)3 precipitates ensures the normal operation of the battery in low-temperature environments.

[0030] In some embodiments of this application, oxalic acid is added to promote V. 4+ The formation of vanadium ions, and subsequently the preparation of solutions with vanadium ions in other valence states through electrolysis. The appropriate addition of oxalic acid not only accelerates the formation of vanadium ions... 4+ Furthermore, through subsequent electrolysis, the required electrolyte can be prepared efficiently, thus improving the preparation efficiency.

[0031] In some embodiments of this application, electrolysis specifically involves: first applying a current density of 180 mA / cm². 2 Charge to 1.7V, then apply a current density of 100mA / cm². 2 Charge to 1.7V, then charge at a constant voltage of 1.7V until the current is less than 180mA. By setting a reasonable electrolysis voltage, the required electrolyte can be prepared quickly, while ensuring the purity and stability of the electrolyte.

[0032] This application also provides an electrolyte prepared according to the above-described method for preparing electrolytes for wide-temperature-range flow batteries. This electrolyte maintains excellent stability even at a high concentration of 3.0 mol / L. In low-temperature environments, traditional high-concentration electrolytes are prone to solid precipitation due to decreased solubility, leading to electrolyte turbidity and a sharp drop in conductivity. However, this electrolyte can form VCl(H₂O)₄SO₄ type complex ions, enabling V... 3+ It does not easily crystallize and precipitate; under high-temperature conditions, a reasonable vanadium / chlorine ratio inhibits V... 5+ The supersaturation precipitation in the positive electrode region prevents the formation of deposits that block ion transport channels. The electrolyte provided by this invention can remain stable for more than 15 days in a temperature range of -5 to 50°C, significantly improving the energy density of the battery. At the same time, it achieves an energy efficiency of more than 80% in the -5 to 50°C range and maintains stable long-cycle performance.

[0033] In some embodiments of this application, the electrolyte includes vanadium ions, chloride ions, and sulfate ions, with a vanadium ion concentration of 2.8–3.1 mol / L, a chloride ion concentration of 5.4–6.1 mol / L, and a sulfate ion concentration of 2.5–3.1 mol / L. Regulating the concentration of each ion in the electrolyte, especially a high concentration of vanadium ions, helps to improve the energy density of the battery. A high-concentration electrolyte not only improves the battery's energy efficiency but also extends its operating temperature range, enabling the battery to maintain stable performance even in more extreme environments.

[0034] One aspect of this application provides a flow battery comprising the aforementioned electrolyte. The electrolyte is stable within a temperature range of -5 to 50°C, enabling the flow battery to operate normally in various climatic environments. The electrolyte has an energy density greater than 40 Wh / L, increasing the energy storage capacity of the flow battery; reducing the size of the battery system; reducing the burden on the thermal management system and saving 10-20% energy; simultaneously, the energy efficiency is >80%, resulting in low energy loss during charge-discharge cycles. This high energy efficiency significantly enhances the economic and practical value of the battery while reducing production costs.

[0035] To make the technical problem to be solved, the technical solution, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0036] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under standard conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications in the art, unless otherwise stated.

[0037] Example 1 100g of VOCl3 was slowly added to 200mL of aqueous solution containing 87g of sulfuric acid and stirred for 30min until it was completely dissolved to obtain the first solution; 40g of V2O5 was added to the first solution and stirred for 1h until it was completely dissolved to obtain the second solution.

[0038] 67.8 g of oxalic acid was slowly added to the second solution, and the mixture was stirred at room temperature for 2 hours to obtain the third solution.

[0039] The third solution was transferred to the electrolytic cell (electrode area 10 cm²). 2 ), first at 180mA / cm 2 Charge to 1.7V; then charge at 100mA / cm 2Continue charging to 1.7V; finally, charge at a constant voltage of 1.7V to a current of 180mA to obtain the electrolyte for the wide-temperature-range flow battery. The concentration of vanadium ions in the electrolyte is 2.85mol / L; the concentration of chloride ions is 5.42mol / L; and the concentration of sulfate ions is 2.51mol / L.

[0040] The electrolyte prepared in this embodiment was used in a flow battery, and the energy density reached 42.9 Wh / L. The electrolyte remained stable at 10°C for 30 days, and the energy efficiency reached 82.5% across the entire temperature range when tested at different temperatures.

[0041] Example 2 100g VOCl3 was slowly added to 200mL of aqueous solution containing 90g sulfuric acid and stirred for 30min until it was completely dissolved to obtain the first solution; 40.5g V2O5 was added to the first solution and stirred for 1h until it was completely dissolved to obtain the second solution.

[0042] 68.2 g of oxalic acid was slowly added to the second solution, and the mixture was stirred at room temperature for 2 hours to obtain the third solution.

[0043] The third solution was transferred to the electrolytic cell (electrode area 10 cm²). 2 ), first at 180mA / cm 2 Charge to 1.7V; then charge at 100mA / cm 2 Continue charging to 1.7V; finally, charge at a constant voltage of 1.7V to a current of 180mA to obtain the electrolyte for the wide-temperature-range flow battery. The concentration of vanadium ions in the electrolyte is 2.9mol / L; the concentration of chloride ions is 5.5mol / L; and the concentration of sulfate ions is 2.6mol / L.

[0044] The electrolyte prepared in this embodiment was used in a flow battery, and the energy density reached 42.5 Wh / L. The electrolyte remained stable at 20°C for 35 days, and the energy efficiency reached 83.1% across the entire temperature range when tested at different temperatures.

[0045] Example 3 100g of VOCl3 was slowly added to 200mL of aqueous solution containing 93g of sulfuric acid and stirred for 30min until it was completely dissolved to obtain the first solution; 41g of V2O5 was added to the first solution and stirred for 1h until it was completely dissolved to obtain the second solution.

[0046] 68.5 g of oxalic acid was slowly added to the second solution, and the mixture was stirred at room temperature for 2 hours to obtain the third solution.

[0047] The third solution was transferred to the electrolytic cell (electrode area 10 cm²). 2 ), first at 180mA / cm 2 Charge to 1.7V; then charge at 100mA / cm2 Continue charging to 1.7V; finally, charge at a constant voltage of 1.7V to a current of 180mA to obtain the electrolyte for the wide-temperature-range flow battery. The concentration of vanadium ions in the electrolyte is 2.95mol / L; the concentration of chloride ions is 5.6mol / L; and the concentration of sulfate ions is 2.7mol / L.

[0048] The electrolyte prepared in this embodiment was used in a flow battery, and the energy density reached 42.8 Wh / L. The electrolyte remained stable at -5°C for 16 days, and the energy efficiency reached 82.6% across the entire temperature range when tested at different temperatures.

[0049] Example 4 100g of VOCl3 was slowly added to 200mL of aqueous solution containing 96g of sulfuric acid and stirred for 30min until it was completely dissolved to obtain the first solution; 41.5g of V2O5 was added to the first solution and stirred for 1h until it was completely dissolved to obtain the second solution.

[0050] 68.9 g of oxalic acid was slowly added to the second solution, and the mixture was stirred at room temperature for 2 hours to obtain the third solution.

[0051] The third solution was transferred to the electrolytic cell (electrode area 10 cm²). 2 ), first at 180mA / cm 2 Charge to 1.7V; then charge at 100mA / cm 2 Continue charging to 1.7V; finally, charge at a constant voltage of 1.7V to a current of 180mA to obtain the electrolyte for the wide-temperature-range flow battery. The concentration of vanadium ions in the electrolyte is 3mol / L; the concentration of chloride ions is 5.7mol / L; and the concentration of sulfate ions is 2.8mol / L.

[0052] The electrolyte prepared in this embodiment was used in a flow battery, and the energy density reached 43.1 Wh / L. The electrolyte remained stable at 0°C for 18 days, and the energy efficiency reached 82% across the entire temperature range when tested at different temperatures.

[0053] Example 5 100 g of VOCl3 was slowly added to 200 mL of aqueous solution containing 99 g of sulfuric acid and stirred for 30 min until it was completely dissolved to obtain the first solution; 42 g of V2O5 was added to the first solution and stirred for 1 h until it was completely dissolved to obtain the second solution.

[0054] 69.3 g of oxalic acid was slowly added to the second solution and stirred at room temperature for 2 hours to obtain the third solution.

[0055] The third solution was transferred to the electrolytic cell (electrode area 10 cm²). 2 ), first at 180mA / cm 2 Charge to 1.7V; then charge at 100mA / cm2 Continue charging to 1.7V; finally, charge at a constant voltage of 1.7V to a current of 180mA to obtain the electrolyte for the wide-temperature-range flow battery. The concentration of vanadium ions in the electrolyte is 3.05mol / L; the concentration of chloride ions is 5.8mol / L; and the concentration of sulfate ions is 2.9mol / L.

[0056] The electrolyte prepared in this embodiment was used in a flow battery, and the energy density reached 42.6 Wh / L. The electrolyte remained stable at 40°C for 17 days, and the energy efficiency reached 82.6% across the entire temperature range when tested at different temperatures.

[0057] Example 6 100g of VOCl3 was slowly added to 200mL of aqueous solution containing 102g of sulfuric acid and stirred for 30min until it was completely dissolved to obtain the first solution; 40.2g of V2O5 was added to the first solution and stirred for 1h until it was completely dissolved to obtain the second solution.

[0058] 67.9 g of oxalic acid was slowly added to the second solution, and the mixture was stirred at room temperature for 2 hours to obtain the third solution.

[0059] The third solution was transferred to the electrolytic cell (electrode area 10 cm²). 2 ), first at 180mA / cm 2 Charge to 1.7V; then charge at 100mA / cm 2 Continue charging to 1.7V; finally, charge at a constant voltage of 1.7V to a current of 180mA to obtain the electrolyte for the wide-temperature-range flow battery. The concentration of vanadium ions in the electrolyte is 2.88mol / L; the concentration of chloride ions is 5.9mol / L; and the concentration of sulfate ions is 3mol / L.

[0060] The electrolyte prepared in this embodiment was used in a flow battery, and the energy density reached 44.7 Wh / L. The electrolyte remained stable at 50°C for 15 days, and the energy efficiency reached 82.3% across the entire temperature range when tested at different temperatures.

[0061] Example 7 100.0g VOCl3 was slowly added to 200mL of aqueous solution containing 105g sulfuric acid and stirred for 30min until it was completely dissolved to obtain the first solution; 41.8g V2O5 was added to the first solution and stirred for 1h until it was completely dissolved to obtain the second solution.

[0062] 69.1 g of oxalic acid was slowly added to the second solution, and the mixture was stirred at room temperature for 2 hours to obtain the third solution.

[0063] The third solution was transferred to the electrolytic cell (electrode area 10 cm²). 2 ), first at 180mA / cm 2Charge to 1.7V; then charge at 100mA / cm 2 Continue charging to 1.7V; finally, charge at a constant voltage of 1.7V to a current of 180mA to obtain the electrolyte for the wide-temperature-range flow battery. The concentration of vanadium ions in the electrolyte is 3.08mol / L; the concentration of chloride ions is 6mol / L; and the concentration of sulfate ions is 3.05mol / L.

[0064] The electrolyte prepared in this embodiment was used in a flow battery, and the energy density reached 44.2 Wh / L. The electrolyte remained stable at 10°C for 28 days, and the energy efficiency reached 83.5% across the entire temperature range when tested at different temperatures.

[0065] Example 8 100.0g VOCl3 was slowly added to 200mL of aqueous solution containing 88g sulfuric acid and stirred for 30min until it was completely dissolved to obtain the first solution; 40.8g V2O5 was added to the first solution and stirred for 1h until it was completely dissolved to obtain the second solution.

[0066] 68.3 g of oxalic acid was slowly added to the second solution, and the mixture was stirred at room temperature for 2 hours to obtain the third solution.

[0067] The third solution was transferred to the electrolytic cell (electrode area 10 cm²). 2 ), first at 180mA / cm 2 Charge to 1.7V; then charge at 100mA / cm 2 Continue charging to 1.7V; finally, charge at a constant voltage of 1.7V to a current of 180mA to obtain the electrolyte for the wide-temperature-range flow battery. The concentration of vanadium ions in the electrolyte is 2.92mol / L; the concentration of chloride ions is 5.45mol / L; and the concentration of sulfate ions is 2.55mol / L.

[0068] The electrolyte prepared in this embodiment was used in a flow battery, and the energy density reached 43.8 Wh / L. The electrolyte remained stable at 20°C for 32 days, and the energy efficiency reached 83.3% across the entire temperature range when tested at different temperatures.

[0069] Example 9 100.0g VOCl3 was slowly added to 200mL of aqueous solution containing 95g sulfuric acid and stirred for 30min until it was completely dissolved to obtain the first solution; 41.2g V2O5 was added to the first solution and stirred for 1h until it was completely dissolved to obtain the second solution.

[0070] 68.6 g of oxalic acid was slowly added to the second solution, and the mixture was stirred at room temperature for 2 hours to obtain the third solution.

[0071] The third solution was transferred to the electrolytic cell (electrode area 10 cm²). 2 ), first at 180mA / cm2 Charge to 1.7V; then charge at 100mA / cm 2 Continue charging to 1.7V; finally, charge at a constant voltage of 1.7V to a current of 180mA to obtain the electrolyte for the wide-temperature-range flow battery. The concentration of vanadium ions in the electrolyte is 2.98mol / L; the concentration of chloride ions is 5.665mol / L; and the concentration of sulfate ions is 2.75mol / L.

[0072] The electrolyte prepared in this embodiment was used in a flow battery, and the energy density reached 43.6 Wh / L. The electrolyte remained stable at 30°C for 26 days, and the energy efficiency reached 82.6% across the entire temperature range when tested at different temperatures.

[0073] Example 10 100.0g VOCl3 was slowly added to 200mL of aqueous solution containing 100g sulfuric acid and stirred for 30min until it was completely dissolved to obtain the first solution; 41.6g V2O5 was added to the first solution and stirred for 1h until it was completely dissolved to obtain the second solution.

[0074] 69g of oxalic acid was slowly added to the second solution, and the mixture was stirred at room temperature for 2 hours to obtain the third solution.

[0075] The third solution was transferred to the electrolytic cell (electrode area 10 cm²). 2 ), first at 180mA / cm 2 Charge to 1.7V; then charge at 100mA / cm 2 Continue charging to 1.7V; finally, charge at a constant voltage of 1.7V to a current of 180mA to obtain the electrolyte for the wide-temperature-range flow battery. The concentration of vanadium ions in the electrolyte is 3.02mol / L; the concentration of chloride ions is 5.95mol / L; and the concentration of sulfate ions is 2.95mol / L.

[0076] The electrolyte prepared in this embodiment was used in a flow battery, and the energy density reached 45.3 Wh / L. The electrolyte remained stable at 10°C for 25 days, and the energy efficiency reached 82.2% across the entire temperature range when tested at different temperatures.

[0077] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values; these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. In the following, various technical solutions can, in principle, be combined with each other to obtain new technical solutions, which should also be considered as specifically disclosed herein.

[0078] The above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art can still make modifications or equivalent substitutions to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention are within the protection scope of the claims of the present invention pending approval.

Claims

1. A method for preparing an electrolyte for a wide-temperature-range flow battery, characterized in that, The application relates to a preparation method of an electrolyte of a wide-temperature-range flow battery. VOCl3 is added into an aqueous solution of sulfuric acid to obtain a first solution, and V2O5 is added into the first solution to obtain a second solution; oxalic acid is added into the second solution to obtain a third solution, and the third solution is electrolyzed to obtain the electrolyte of the wide-temperature-range flow battery.

2. The method of claim 1, wherein the electrolyte is prepared by mixing the redox active material, the supporting electrolyte, and the solvent. The mass ratio of the VOCl3, the sulfuric acid and the V2O5 is 1: (0.87-1.06): (0.4-0.42).

3. The method of claim 1, wherein the electrolyte is prepared by mixing the redox active material, the supporting electrolyte, and the solvent. The molar ratio of vanadium ions to chlorine ions in the electrolyte is (0.9-1.1):(1.8-2.0).

4. The method of claim 1, wherein the electrolyte is prepared by mixing the redox active material, the supporting electrolyte, and the solvent. The molar ratio of the oxalic acid to vanadium ions in the second solution is (0.5-0.6):

1.

5. The method of claim 1, wherein the electrolyte is prepared by mixing the redox active material, the supporting electrolyte, and the solvent. The electrolysis is specifically: first charging to 1.7V, then charging to 1.7V at a current density of 100 mA / cm 2 charging to 1.7V, then charging to 1.7V at a current density of 100 mA / cm 2 charging to 1.7V, then charging to 1.7V at a current density of 100 mA / cm 6. An electrolyte of a wide-temperature-range flow battery prepared by the preparation method in any one of claims 1-5.

7. The electrolyte of the wide-temperature-range flow battery according to claim 6, wherein, The electrolyte comprises vanadium ions, chlorine ions and sulfate ions, the concentration of the vanadium ions is 2.8-3.1 mol / L, the concentration of the chlorine ions is 5.4-6.1 mol / L, and the concentration of the sulfate ions is 2.5-3.1 mol / L.

8. The electrolyte of the wide-temperature-range flow battery according to claim 7, wherein, The vanadium ions comprise divalent vanadium ions, trivalent vanadium ions, tetravalent vanadium ions and pentavalent vanadium ions.

9. The electrolyte of the wide-temperature-range flow battery according to claim 6, wherein, The temperature adaptation range of the electrolyte of the wide-temperature-range flow battery is -5-50 DEG C.

10. A flow battery, characterized in that, The flow battery comprises the electrolyte in any one of claims 6-9.