A ferrocene-based neutral aqueous electrolyte, a preparation method thereof, and application in aqueous organic liquid flow batteries

Abstract

The present invention proposes a novel preparation method of a ferrocenyl-based neutral aqueous electrolyte and its application in an aqueous organic liquid flow battery, belonging to the field of battery materials and energy storage. The electrolyte is composed of ferrocenylbenzenesulfonate, water and a supporting electrolyte. First, ferrocenylbenzenesulfonic acid is prepared by a diazotization reaction, and then the hydrogen ions are replaced with cations such as ammonium ions, imidazole or choline based on an acid-base neutralization reaction to obtain a series of ferrocenylbenzenesulfonates. The solubility of ferrocenylbenzenesulfonate in a neutral aqueous solution is effectively improved, and due to the introduction of the benzenesulfonic acid electron-withdrawing group, the potential of ferrocenyl in a neutral aqueous solution is increased. With ferrocenylbenzenesulfonate as the cathode reaction active substance, the corresponding halide salt as the supporting electrolyte, and water as the solvent, a series of low-cost, high-performance neutral aqueous organic electrolytes can be obtained. The synthesis method of the present invention is simple, the raw material cost is low, and it is easy to achieve large-scale production.

Description

Technical Field

[0001] The present invention relates to the technical field of battery materials and energy storage, and in particular to a ferrocene-based neutral aqueous electrolyte, a preparation method thereof, and an application thereof in an aqueous organic liquid flow battery. Background Art

[0002] Due to the inherent intermittent nature of solar radiation and wind, they cannot be directly connected to the power grid. Energy storage technology is needed to support the efficient use of these clean energy sources. Rechargeable batteries have been widely developed as an effective electrochemical energy storage technology. Using this technology, the surplus electricity generated by solar and wind energy can be stored in the form of chemical energy, then converted into electrical energy and output stably. Among various rechargeable battery technologies, redox flow battery (RFB) has the advantage of independent power and capacity, which makes it more flexible and scalable in large-scale energy storage.

[0003] Aqueous organic redox flow battery (AORFB) is a new type of flow battery technology. Compared with traditional flow batteries with inorganic metal ions as electroactive components, it has the following advantages: 1) The components of organic electroactive substances are mainly C, N and O, which are naturally abundant on the earth. By structurally designing the electroactive molecules, such as introducing different functional groups, the solubility, stability and redox potential of electroactive organic matter can be comprehensively regulated; 2) Aqueous organic flow batteries use water as solvent and acid, alkali or salt as supporting electrolyte, which has higher safety and lower cost; 3) Aqueous electrolytes have higher conductivity than all-organic flow batteries, and the diaphragms used in the corresponding batteries can adopt mature ion exchange membranes, which makes it easy to achieve high-power operation of the battery.

[0004] The electroactive substances of aqueous organic flow batteries are the most critical materials in the battery and are the core of energy storage and release. At present, there are relatively more studies on anode active substances, such as derivatives of quinone, flavin, alizarin, pyrimidine, phenazine and viologen; while the selection of cathode active substances is relatively limited, and the more commonly used ones are potassium ferrocyanide, ferrocene and 2,2,6,6-tetramethylpiperidine (TEMPO). Among them, ferrocene is a commonly used redox species in organic electrochemistry, with excellent reversibility and low cost. However, the low solubility of ferrocene in water and the low potential as a cathode limit its application in aqueous organic flow batteries. Therefore, exploring ferrocene derivatives with higher water solubility and higher potential is the key to improving its application performance. Summary of the invention

[0005] The present invention is based on mature diazotization and green acid-base neutralization reaction to prepare a series of ferrocenyl benzenesulfonates with different cations to effectively improve the solubility and potential value of ferrocenyl electroactive substances in water. Using it as a new cathode active material for aqueous organic liquid flow batteries can effectively improve the energy density and power density of ferrocenyl-based aqueous organic liquid flow batteries.

[0006] To achieve the above object, the technical solution adopted by the present invention is: a ferrocene-based neutral aqueous electrolyte, the preparation method of which comprises the following steps:

[0007] 1) Synthesis of sodium ferrocene benzenesulfonate: 3-aminobenzenesulfonic acid was dissolved in NaOH solution, placed in an ice bath, and NaNO2 aqueous solution was added, mixed evenly, and a slightly excess amount of concentrated hydrochloric acid was slowly added, stirred, and reacted at low temperature until the solution turned reddish brown, and allowed to stand to obtain solution A; glacial acetic acid was used to completely dissolve the ferrocene derivative, and then solution A was slowly added dropwise thereto, and after the addition was complete, the solution was reacted at room temperature for 16 hours to obtain solution B, and NaOH was added to solution B, and the obtained precipitate was recrystallized with NaOH, and purified by column with a mixed solvent to obtain pure sodium ferrocene benzenesulfonate;

[0008] 2) Synthesis of ferrocenylbenzenesulfonic acid: Sodium ferrocenylbenzenesulfonate is reacted with concentrated hydrochloric acid to obtain ferrocenylbenzenesulfonic acid;

[0009] 3) Cation replacement reaction: ferrocenylbenzenesulfonic acid is reacted with ammonia, choline hydroxide or imidazole hydroxide to obtain ferrocenylbenzenesulfonate with ammonium radical, choline or imidazole cation;

[0010] 4) Preparation of electrolyte: The above-mentioned ferrocene benzenesulfonate is used as the electroactive substance, water is used as the solvent, and ammonium chloride or the corresponding choline or imidazole chloride salt is used as the supporting electrolyte to prepare the electrolyte.

[0011] Preferably, in the above-mentioned ferrocene-based neutral aqueous electrolyte, in step 1), the temperature of the low-temperature reaction is -5°C to 10°C.

[0012] Preferably, in the above-mentioned ferrocene-based neutral aqueous electrolyte, in step 1), the mixed solvent is chloroform and methanol in a volume ratio of 5:1.

[0013] Preferably, in the above-mentioned ferrocene-based neutral aqueous electrolyte, in step 2), the molar ratio of sodium ferrocene benzenesulfonate to concentrated hydrochloric acid is 1:1.

[0014] Preferably, in the above-mentioned ferrocene-based neutral aqueous electrolyte, in step 2), the reaction is carried out at 25° C. for 3 to 5 hours.

[0015] Preferably, in the above-mentioned ferrocene-based neutral aqueous electrolyte, in step 3), the preparation method of the choline or hydroxyimidazolium salt comprises the following steps: soaking the strongly basic anion exchange resin in a NaOH solution for 3 days in advance, adding the soaked resin to the chromatography column, adding the NaOH solution, and stirring until the dripped solution does not contain Cl - , wash the resin to neutrality, then add choline or imidazole chloride or bromide to carry out ion exchange reaction, and after drying, obtain choline hydroxide or imidazole hydroxide.

[0016] Preferably, in the above-mentioned ferrocene-based neutral aqueous electrolyte, in step 3), the imidazole chloride or bromide salt includes imidazole chloride or bromide salts with different alkyl chains, hydroxyl groups, and amino groups.

[0017] Preferably, in the above-mentioned ferrocene-based neutral aqueous electrolyte, in step 4), the concentration of the electrolyte is 0.05-0.5M.

[0018] Application of the above-mentioned ferrocene-based neutral aqueous electrolyte in neutral aqueous organic liquid flow batteries.

[0019] In the above application, a ferrocene-based neutral aqueous electrolyte is used as the cathode electrolyte of the organic liquid flow battery, an anode electrolyte uses a sulfonate of anthraquinone or viologen derivative with the same cation as the active substance, and an ion exchange membrane or a porous membrane is used as the diaphragm.

[0020] The beneficial effects of the present invention are:

[0021] 1. The present invention uses cheap ferrocene as a basic raw material and utilizes mature diazotization and green acid-base neutralization reactions to prepare the target electroactive substance. The method is simple, easy to purify, and low in cost.

[0022] 2. The ferrocenylbenzenesulfonate synthesized in the present invention has a high solubility and a relatively positive potential in a neutral aqueous solution, which is beneficial to improving the energy density and power density of the corresponding organic liquid flow battery.

[0023] 3. The ferrocene benzenesulfonate derivative synthesized by the present invention can effectively increase the distance between ferrocene molecules and increase the steric hindrance effect, thereby effectively alleviating the cross-contamination problem of liquid flow batteries.

[0024] 4. The present invention uses novel ferrocene benzenesulfonate as an active component, ammonium chloride or imidazole chloride as a supporting electrolyte, and water as a solvent to construct a neutral aqueous organic flow battery. An anion exchange membrane or a porous membrane can be selected as a diaphragm to further reduce the energy storage cost.

[0025] 5. The neutral aqueous organic liquid flow battery proposed in the present invention has better stability than acidic or alkaline liquid flow batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is the cyclic voltammetry curve of pure ferrocene in aqueous sodium sulfate solution.

[0027] Figure 2 The cyclic voltammetry curve of sodium ferrocenylbenzenesulfonate prepared in Example 1 in a sodium sulfate aqueous solution. DETAILED DESCRIPTION

[0028] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0029] Example 1

[0030] Dissolve 3-aminobenzenesulfonic acid (1.73g, 0.01mol) in 10mL of 5% NaOH solution, then add 5mL of aqueous solution containing NaNO2 (0.759g, 0.01mol), mix well, and cool in an ice bath to below 5°C. Prepare a solution with 3mL of concentrated hydrochloric acid and 10mL of water, add it dropwise to the above mixed solution under stirring, and let it stand for 15min after the addition is complete. Slowly drip this solution into 40mL of acetic acid solution of ferrocene (1.86g, 0.1mmol). Continue to react at room temperature for 24h after the addition. Add an appropriate amount of 40% NaOH solution to adjust the pH to 5-9, and obtain a crude product after vacuum filtration. Recrystallize with 5% NaOH solution, add to a chromatography column, mix chloroform: methanol at a molar ratio of 5:1 to obtain pure sodium ferrocene benzenesulfonate. The structure of the obtained sodium ferrocene benzenesulfonate is:

[0031]

[0032] Example 2

[0033] Dissolve 3-aminobenzenesulfonic acid (1.73g, 0.01mol) in 10mL of 5% NaOH solution, add 5mL of aqueous solution containing NaNO2 (0.759g, 0.01mol), mix well, and cool to below 5°C in an ice bath. Prepare a solution with 3mL of concentrated hydrochloric acid and 10mL of water, add it dropwise to the above mixed solution under stirring, and let it stand for 15min after the addition is complete. Slowly drip this solution into 40mL of acetic acid solution of ferrocene (1.86g, 0.1mmol). Continue to react at room temperature for 24h after the addition. Add an appropriate amount of 40% NaOH solution to adjust the pH to 5-9, and obtain a crude product after vacuum filtration. Recrystallize with 5% NaOH solution, add to the chromatography column, mix chloroform and methanol at a molar ratio of 5:1 to obtain pure sodium ferrocene benzenesulfonate. Add 36% concentrated hydrochloric acid to sodium ferrocenylbenzenesulfonate at a molar ratio of 1:1, react at room temperature for 5 hours, extract the organic phase with ethyl acetate, and then evaporate the ethyl acetate at 60°C to obtain ferrocenylbenzenesulfonic acid. Add ammonia water to the ferrocenylbenzenesulfonic acid solution at a molar ratio of 1:1, stir at room temperature for 2 hours, and obtain ammonium ferrocenylbenzenesulfonate, the structure of which is:

[0034]

[0035] Example 3

[0036] Dissolve 3-aminobenzenesulfonic acid (1.73g, 0.01mol) in 10mL of 5% NaOH solution, add 5mL of aqueous solution containing NaNO2 (0.759g, 0.01mol), mix well, and cool to below 5°C in an ice bath. Prepare a solution with 3mL of concentrated hydrochloric acid and 10mL of water, add it dropwise to the above mixed solution under stirring, and let it stand for 15 minutes after the addition is complete. Slowly drip this solution into 40mL of acetic acid solution of ferrocene (1.86g, 0.1mmol). Continue to react at room temperature for 24h after the addition. Add an appropriate amount of 40% NaOH solution to adjust the pH to 5-9, and obtain a crude product after vacuum filtration. Recrystallize with 5% NaOH solution, add to the chromatography column, mix chloroform and methanol at a molar ratio of 5:1 to obtain pure sodium ferrocene benzenesulfonate. Add 36% concentrated hydrochloric acid to sodium ferrocenylbenzenesulfonate at a molar ratio of 1:1, react at room temperature for 6 hours, extract the organic phase with ethyl acetate, and evaporate the ethyl acetate at 60°C to obtain pure ferrocenylbenzenesulfonic acid.

[0037] Soak the resin in 1 mol / L NaOH solution for 3 days in advance, add the soaked resin to the chromatography column to 1 / 3 to 2 / 3, and add 1 mol / L NaOH solution until the dripping solution does not contain Cl - , can be detected with silver nitrate / nitric acid solution. Wash the resin with deionized water until it is neutral, then add [C6mim] + Br- , react for 0.5 to 2 hours, and dry to obtain hydroxyimidazole salt. Add hydroxyimidazole to the ferrocenylbenzenesulfonic acid solution at a molar ratio of 1:1, and react for 5 hours to obtain ferrocenylbenzenesulfonic acid-alkylimidazole salt, the structure of which is:

[0038]

[0039] Example 4

[0040] A three-electrode system was used, with ferrocene as the electroactive substance, sodium chloride as the supporting electrolyte, a 3 mm glassy carbon electrode as the working electrode, a saturated calomel electrode as the reference electrode, and a platinum sheet as the counter electrode. Cyclic voltammetry was performed at a scan rate of 5 mV / s. Figure 1 The cyclic voltammetry curves are shown.

[0041] Cyclic voltammetry was performed using a three-electrode system, with ferrocene benzenesulfonic acid prepared in Example 1 as the electroactive substance, choline chloride as the supporting electrolyte, a 3 mm glassy carbon electrode as the working electrode, a saturated calomel electrode as the reference electrode, and a platinum sheet as the counter electrode. Figure 2 The cyclic voltammetry curves are shown.

[0042] like Figure 1 and Figure 2 As shown in the figure, both groups of CV curves show a pair of redox peaks in the range of 0.1 to 0.3 V, corresponding to the Fe 3+ / Fe 2+ Electrochemical redox reaction of redox couple. However, the redox potential of ferrocene is about 0.17V, while the redox potential of sodium ferrocene benzenesulfonate is shifting to about 0.23V, which helps to increase the battery voltage. In addition, Figure 2 The symmetry of the CV curve shown in is better, indicating that the synthesized ferrocenylbenzenesulfonate derivative has better electrochemical redox reversibility in neutral aqueous solution, which helps to further improve the power density and operation efficiency of the battery.

Claims

1. A ferrocene-based neutral aqueous electrolyte, characterized in that: The preparation method comprises the following steps: 1) Synthesis of sodium ferrocene benzenesulfonate: Dissolve 3-aminobenzenesulfonic acid in NaOH solution, place in an ice bath, add NaNO2 aqueous solution, mix well, slowly add slightly excess concentrated hydrochloric acid, stir, react at low temperature until the solution turns reddish brown, let stand, and obtain solution A; use glacial acetic acid to completely dissolve the ferrocene derivative, then slowly add solution A dropwise, react at room temperature for 16 h after complete addition, and obtain solution B; add NaOH to solution B, recrystallize the obtained precipitate with NaOH, and purify with a mixed solvent column to obtain pure sodium ferrocene benzenesulfonate; 2) Synthesis of ferrocenylbenzenesulfonic acid: Sodium ferrocenylbenzenesulfonate is reacted with concentrated hydrochloric acid to obtain ferrocenylbenzenesulfonic acid; 3) Cation replacement reaction: ferrocenylbenzenesulfonic acid is reacted with ammonia, choline hydroxide or imidazole hydroxide to obtain ferrocenylbenzenesulfonate with ammonium radical, choline or imidazole cation; 4) Preparation of electrolyte: using the above-mentioned ferrocene benzenesulfonate as the electroactive substance, water as the solvent, and ammonium chloride or the corresponding choline or imidazole chloride as the supporting electrolyte to prepare an electrolyte; In step 3), the preparation method of choline hydroxide or imidazole hydroxide comprises the following steps: soaking a strongly basic anion exchange resin in a NaOH solution for 3 days, adding the soaked resin to a chromatography column, and adding a NaOH solution until the dripped solution does not contain Cl - , washing the resin to neutrality, then adding choline or imidazole chloride or bromide to carry out ion exchange reaction, and drying to obtain choline hydroxide or imidazole hydroxide; In step 3), the chloride or bromide salt of imidazole includes chloride or bromide salts of imidazole with different alkyl chains, hydroxyl groups, and amino groups.

2. A ferrocene-based neutral aqueous electrolyte according to claim 1, characterized in that: In step 1), the temperature of the low temperature reaction is -5°C to 10°C.

3. A ferrocene-based neutral aqueous electrolyte according to claim 1, characterized in that: In step 1), the mixed solvent is chloroform and methanol in a volume ratio of 5:

1.

4. A ferrocene-based neutral aqueous electrolyte according to claim 1, characterized in that: In step 2), the molar ratio of sodium ferrocenylbenzenesulfonate to concentrated hydrochloric acid is 1:

1.

5. The ferrocene-based neutral aqueous electrolyte according to claim 1, characterized in that: In step 2), the reaction is carried out at 25°C for 3 to 5 hours.

6. A ferrocene-based neutral aqueous electrolyte according to claim 1, characterized in that: In step 4), the concentration of the electrolyte is 0.05~0.5M.

7. Use of the ferrocene-based neutral aqueous electrolyte described in claim 1 in a neutral aqueous organic flow battery.

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