An electrolyte with imidazole ionic liquid as an additive for use in zinc sulfate electrolytes and its preparation method.

Abstract

This invention discloses an electrolyte with imidazole ionic liquid as an additive for use in zinc sulfate electrolytes and its preparation method, belonging to the field of ionic liquid technology. The electrolyte preparation method is as follows: using a 2 M ZnSO4 aqueous solution as the base electrolyte solution, different volume fractions of the ionic liquid [EP-IM]Br are added to prepare a series of modified electrolyte solutions, which are then ultrasonically treated for 1 hour to ensure thorough dispersion. The additive [EP-IM]Br is synthesized from 1-methylimidazole and ethyl 3-bromopropionate. The ionic liquid additive prepared by this invention effectively inhibits the hydrogen evolution side reaction and negative electrode corrosion behavior, and the mixed electrolyte exhibits a lower corrosion current (Ig). corr ) and corrected corrosion voltage (E corr This indicates that the ionic conductivity and corrosion resistance are significantly improved. At the same time, the ionic liquid has the advantages of simple synthesis route and readily available raw materials.

Description

Technical Field

[0001] This invention relates to the field of ionic liquids, and more specifically to an electrolyte for use in zinc sulfate electrolytes, using imidazole ionic liquids as additives, and a method for preparing the same. Background Technology

[0002] With the global energy structure transformation and the advancement of "dual-carbon" goals, safe, efficient, and low-cost large-scale energy storage technologies have become crucial for the stable utilization of renewable energy. Zinc sulfate electrolytes, with their inherent safety, fast ion transport rates, readily available and inexpensive raw materials, have shown great application potential in the field of electrochemical energy storage. However, significant interfacial electrochemical stability issues still exist in zinc sulfate electrolyte systems. Side reactions such as dendrite growth, hydrogen evolution reaction, and electrode corrosion easily occur at the electrode interface, not only disrupting the interfacial charge transfer balance but also generating insoluble byproducts, significantly increasing interfacial impedance, resulting in low energy utilization efficiency and poor cycle stability of the electrochemical system, severely hindering its industrialization. Therefore, developing efficient functional additives that can simultaneously regulate interfacial reactions and improve the overall performance of zinc sulfate electrolytes is crucial for improving the comprehensive electrochemical performance of zinc sulfate-based electrochemical energy storage systems.

[0003] Ionic liquids, as a class of room-temperature molten salts composed of organic cations and inorganic anions, are typical representatives of "designable green solvents." Besides possessing core characteristics such as low volatility, excellent thermal stability, high ionic conductivity, and non-flammability, they also offer advantages such as precisely tunable molecular structure, good compatibility with electrolytes, effective widening of the electrochemical window, and suppression of side reactions in electrolyte systems. This has led to the development of simple, cost-effective, and high-performance electrolyte additives, achieving a dual improvement in the electrochemical performance and economic benefits of electrochemical energy storage systems, and demonstrating broad application prospects in the field of electrochemical energy storage. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides an electrolyte with imidazole ionic liquid as an additive for use in zinc sulfate electrolytes, and a method for preparing the same. This method is simple to operate and has excellent results.

[0005] To achieve the above objectives, the technical solution adopted by this invention is: an electrolyte based on imidazole ionic liquid as an additive, prepared by the following method: mixing the ionic liquid [EP-IM]Br with an aqueous ZnSO4 solution and sonicating to obtain a homogeneous and stable electrolyte. The structural formulas of 1-methylimidazolium and ethyl 3-bromopropionate used in the synthesis of the ionic liquid [EP-IM]Br are shown in formulas (I) and (II), respectively:

[0006] (I) (II)

[0007] Furthermore, the electrolyte based on imidazole ionic liquid as an additive is characterized in that ZnSO4 electrolyte and [EP-IM]-Br are mixed in a volume ratio of 400:1 to 400:4.

[0008] Furthermore, in the aforementioned electrolyte based on imidazole ionic liquid as an additive, the concentration of zinc sulfate is 2 mol / L.

[0009] Furthermore, in the aforementioned electrolyte based on imidazole ionic liquid as an additive, the ultrasonication time is 1 hour.

[0010] Furthermore, the above-mentioned electrolyte based on imidazole ionic liquid as an additive, the preparation method of the imidazole ionic liquid [EP-IM]Br includes the following steps:

[0011] (1) Dissolve ethyl 3-bromopropionate and 1-methylimidazole in acetonitrile.

[0012] (2) Heat and reflux overnight under nitrogen atmosphere and magnetic stirring.

[0013] (3) After the reaction is complete, the mixture is cooled to room temperature and the residual organic solvent is removed by rotary evaporator.

[0014] (4) After the reaction is complete, cool to room temperature, add ethyl acetate, evaporate by rotary evaporation, and dry to obtain the final product.

[0015] Furthermore, in the above-mentioned method for preparing the imidazole ionic liquid [EP-IM]Br, the molar ratio of ethyl 3-bromopropionate and 1-methylimidazole in step (1) is 1:1.

[0016] Furthermore, in the above-mentioned method for preparing the imidazole ionic liquid [EP-IM]Br, the heating temperature in step (2) is 80 ℃.

[0017] The application of any of the above-mentioned electrolytes based on imidazole ionic liquids as additives in zinc sulfate electrolytes.

[0018] The beneficial effects of this invention are:

[0019] (1) The electrolyte with imidazole ionic liquid as an additive and its preparation method are simple to synthesize, highly practical and easy to promote.

[0020] (2) The mixed electrolyte synthesized in this invention exhibits a more positive corrosion potential and a lower corrosion current density, effectively suppressing the occurrence of hydrogen evolution side reactions.

[0021] (3) The present invention utilizes an electrolyte based on imidazole ionic liquid as an additive in zinc sulfate electrolyte. The content of this invention is conducive to the concept of green environmental protection and is more beneficial to the life and survival of humans, animals and plants. Attached Figure Description

[0022] Figure 1 This is the 1H NMR spectrum of the [EP-IM]Br ionic liquid from Example 1.

[0023] Figure 2 The infrared spectra of H2O, ZnSO4, ionic liquid [EP-IM]Br and mixed electrolyte 400:1 in Example 2 are shown.

[0024] Figure 3 This is the thermogravimetric analysis diagram of ZnSO4 and the ionic liquid [EP-IM]Br in Example 2.

[0025] Figure 4 This is the Tafel curve of the five electrolyte solutions in Example 3.

[0026] Figure 5 The corrosion current (I) fitted by five electrolyte solutions in Example 3 is... corr ) and corrosion voltage (E corr )picture.

[0027] Figure 6 This is the electrochemical impedance spectroscopy (EIS) diagram of the five electrolyte solutions in Example 3.

[0028] Figure 7 The charge transfer internal resistance (R) of the five electrolyte solutions in Example 3 is... ct )picture.

[0029] Figure 8 This is a linear sweep voltammetry (LSV) curve of the five electrolyte solutions in Example 3. Detailed Implementation

[0030] The invention will be further illustrated below with specific examples. The invention is not limited to the embodiments described, but is equally applicable to other ionic liquids, with minor variations possible without departing from the scope described.

[0031] Example 1: An imidazole ionic liquid for use as an electrolyte additive

[0032] (a) Preparation method:

[0033] Ethyl 3-bromopropionate and 1-methylimidazolium were dissolved in acetonitrile at a molar ratio of 1:1 to achieve a concentration of 3.33 mol / L. The mixture was refluxed at 80 °C for 12–14 h under a nitrogen atmosphere and with magnetic stirring. After the reaction was complete, the mixture was cooled to room temperature, and 30–50 mL of ethyl acetate was added. The solution was then rotary evaporated, washed, and dried to obtain [EP-IM]Br.

[0034] (ii) Characterization methods:

[0035] 1H NMR spectrum: 1H NMR spectrum of ionic liquid [EP-IM]Br 1 ¹H NMR characterization (300 MHz, DMSO-d6 solvent) is shown in [reference needed]. Figure 1 Analysis of the proton nuclear magnetic resonance spectrum revealed that... 1 The chemical shifts, number of resonance peaks, and integrated area of ​​the H NMR were consistent with those of the target ionic liquid, and no impurity peaks were found.

[0036] Example 2: Preparation of an electrolyte based on imidazole ionic liquid as an additive

[0037] (a) Preparation method:

[0038] A 2 mol / L ZnSO4 electrolyte was prepared, and then the ZnSO4 electrolyte was mixed with the prepared [EP-IM]Br at four volume ratios of 400:1, 400:2, 400:3, and 400:4 to obtain electrolyte solutions containing ionic liquids. The four electrolyte solutions were then sonicated in an ultrasonic water bath to remove internal air bubbles, resulting in homogeneous and stable solutions. A 2 mol / L ZnSO4 electrolyte solution (ZS) was used as a blank control, for a total of five electrolyte solutions.

[0039] (ii) Characterization methods:

[0040] Infrared characterization of pure water, ZnSO4 solution, ionic liquid [EP-IM]Br, and mixed electrolyte 400:1 is shown in [reference needed]. Figure 2 Infrared spectral analysis revealed that the 400:1 mixed electrolyte spectrum simultaneously contained characteristic absorption peaks of water, ZnSO4, and [EP-IM]Br ionic liquid, without the formation of new characteristic absorption peaks. This indicates that no chemical reaction occurred between the ionic liquid and water or ZnSO4 to generate new substances. The wavenumber shift and peak shape change of the OH stretching vibration characteristic peak of water molecules prove that the three components are combined through hydrogen bonds, electrostatic interactions, and ion-dipole interactions to form a composite electrolyte system.

[0041] Thermogravimetric analysis of ZnSO4 and the ionic liquid [EP-IM]Br is shown in [see...]. Figure 3Test results show that the ionic liquid prepared by this invention begins to decompose at about 350 °C. Compared with ZnSO4, it has excellent thermal stability, strong structural stability at high temperatures, and better thermal safety performance, which can effectively improve the thermal stability and operating temperature range of the electrolyte system.

[0042] Example 3: Application of an electrolyte based on imidazole ionic liquid as an additive in zinc sulfate electrolyte.

[0043] First, the Tafel curves of the five electrolyte solutions were measured, such as... Figure 4 As shown, the changes in corrosion current and corrosion voltage for different electrolyte solutions are fitted, as follows: Figure 5 As shown, compared with the blank system, the corrosion potential shifts negatively with increasing ionic liquid concentration. The electrolyte solution with a ratio of 400:1 exhibits the most positive corrosion voltage and the lowest corrosion current. This indicates that the addition of low-concentration ionic liquid results in a lower corrosion kinetic rate, better corrosion resistance, and enhanced thermodynamic stability of the electrolyte solution. This effectively inhibits the erosion of the electrode by the electrolyte and reduces the occurrence of side reactions.

[0044] Then the electrochemical impedance spectroscopy (EIS) of the five electrolyte solutions was measured, such as... Figure 6 As shown, the charge transfer resistance (R) is fitted. ct ),like Figure 7 As shown, with the increase of ionic liquid concentration, R ct The overall trend is upward; among them, the system with a ratio of 400:2 has the lowest R. ct This result indicates that the electrolyte solution exhibits minimal resistance to ion migration, which facilitates rapid charge transfer at the electrode / electrolyte interface, thereby effectively increasing the rate of electrochemical reactions.

[0045] Finally, the linear sweep voltammetry (LSV) curves of the five electrolyte solutions were measured, such as... Figure 8 As shown, with increasing ionic liquid concentration, the hydrogen evolution potential gradually shifts positively (i.e., the ability to delay hydrogen evolution is enhanced), and the kinetics of the hydrogen evolution reaction are significantly suppressed. Among them, the electrolyte with a 400:2 ratio exhibits the largest delayed hydrogen evolution potential, meaning that the overpotential required for the hydrogen evolution reaction in this system is higher, and the reaction kinetics are the most sluggish. Compared with other electrolytes, the 400:2 system is less likely to undergo hydrogen evolution under the same potential conditions, thus more effectively suppressing hydrogen evolution side reactions.

Claims

1. An electrolyte based on imidazole ionic liquid as an additive, characterized in that, The method is as follows: the ionic liquid [EP-IM]Br is mixed with an aqueous solution of ZnSO4 and sonicated to obtain a homogeneous and stable electrolyte; the structural formulas of 1-methylimidazolium and ethyl 3-bromopropionate used in the synthesis of the ionic liquid [EP-IM]Br are shown in formulas (I) and (II) respectively: (Ⅰ) (Ⅱ)。 2. The electrolyte based on imidazole ionic liquid as an additive according to claim 1, characterized in that, ZnSO4 electrolyte is mixed with [EP-IM]Br at a volume ratio of 400:1 to 400:

4.

3. The electrolyte based on imidazole ionic liquid as an additive according to claim 1, characterized in that, The concentration of zinc sulfate is 2 mol / L.

4. An electrolyte based on imidazole ionic liquid as an additive according to claim 1, characterized in that, The ultrasound duration is 1 hour.

5. An electrolyte based on imidazole ionic liquid as an additive according to claim 1, characterized in that, The preparation method of the imidazole ionic liquid [EP-IM]Br is as follows: (1) Dissolve ethyl 3-bromopropionate and 1-methylimidazole in acetonitrile. (2) Heat and reflux overnight under nitrogen atmosphere and magnetic stirring. (3) After the reaction is complete, the mixture is cooled to room temperature and the residual organic solvent is removed by rotary evaporator. (4) After the reaction is complete, cool to room temperature, add ethyl acetate, evaporate by rotary evaporation, and dry to obtain the final product.

6. An electrolyte based on imidazole ionic liquid as an additive according to claim 5, characterized in that, In step (1), the molar ratio of ethyl 3-bromopropionate and 1-methylimidazole is 1:

1.

7. An electrolyte based on imidazole ionic liquid as an additive according to claim 5, characterized in that, The heating temperature in step (2) is 80 ℃.

8. The application of an electrolyte based on imidazole ionic liquid as an additive, as described in any one of claims 1-7, in zinc sulfate electrolyte.

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