Aqueous zinc battery electrolyte based on propionamide-caprolactam eutectic solvent and preparation method thereof

Abstract

The invention discloses an aqueous zinc battery electrolyte based on a propanamide-caprolactam deep eutectic solvent (PES) and a preparation method thereof, and belongs to the technical field of deep eutectic solvents (DES). The preparation method of the electrolyte comprises the following steps: mixing 2mol / L of ZnSO4 and synthesized PES according to different volume ratios, and then carrying out ultrasonic treatment to obtain a mixed electrolyte ZPES-X (wherein X represents the volume ratio of ZS to PES); the propanamide-caprolactam eutectic solvent is synthesized from propanamide (PAD) and caprolactam (CPL). The prepared mixed electrolyte solution can broaden the electrochemical hydrogen evolution potential (HER), inhibit the hydrogen evolution side reaction and improve the battery performance, and the mixed electrolyte shows lower impedance (EIS), higher linear polarization resistance (LPR) and lower corrosion current (Icorr), which indicates that the ionic conductivity and the corrosion resistance are remarkably improved, and the battery performance is improved. And the propanamide-caprolactam eutectic solvent also has the advantages of simple synthesis, low price and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of deep eutectic solvents, and in particular to an aqueous zinc battery electrolyte based on a propionamide-caprolactam deep eutectic solvent and a preparation method thereof. Background Art

[0002] The application of deep eutectic solvents (DES) as additives in electrochemistry has shown many remarkable properties and greatly optimized the electrochemical performance.

[0003] The hydrogen evolution potential of traditional electrolytes is relatively narrow, which makes the hydrogen evolution reaction easy to occur in a wide potential range. This will not only aggravate metal corrosion (such as accelerating dissolution and causing hydrogen embrittlement), but also may cause safety hazards due to gas accumulation. At the same time, this will increase unnecessary consumption in the process of water electrolysis; the H + Consumption will change the pH of the electrolyte and induce side reactions. In addition, the high electrochemical impedance and serious corrosion problems of traditional electrolytes further reduce the electrochemical performance: high impedance will significantly reduce the efficiency of ion migration, resulting in increased energy loss during charging and discharging, severe battery heating, and thus shortened service life. Severe corrosion problems not only accelerate the loss of electrode materials and reduce the utilization rate of active substances, but also destroy the surface structure of the electrode, resulting in poor contact between the electrode and the electrolyte interface, further increasing the impedance; the metal ions produced by corrosion enter the electrolyte and may also trigger other side reactions, interfering with the main reaction, and ultimately significantly affecting the stability of the system and energy utilization efficiency. Summary of the Invention

[0004] In order to solve the above-mentioned problems, the present invention provides an aqueous zinc battery electrolyte based on a propionamide-caprolactam deep eutectic solvent and a preparation method thereof. The method is simple to operate and has excellent effects.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] A water-based zinc battery electrolyte based on a propionamide-caprolactam deep eutectic solvent is provided. The preparation method of the water-based zinc battery electrolyte is as follows: first, propionamide PAD and caprolactam CPL are heated and stirred to form a propionamide-caprolactam deep eutectic solvent PES; then, a ZnSO4 electrolyte and PES are mixed according to a volume ratio; and then, the two are ultrasonically mixed to uniformly mix and remove bubbles, thereby finally obtaining the water-based zinc battery electrolyte;

[0007] The structural formulas of the PAD and CPL are shown in (I) and (II), respectively:

[0008]

[0009] Furthermore, in the above-mentioned aqueous zinc battery electrolyte based on propionamide-caprolactam low eutectic solvent, the molar ratio of PAD and CPL is 1:1.

[0010] Furthermore, in the above-mentioned aqueous zinc battery electrolyte based on propionamide-caprolactam low eutectic solvent, the heating temperature is 80°C.

[0011] Furthermore, the above-mentioned aqueous zinc battery electrolyte based on propionamide-caprolactam low eutectic solvent has a stirring time of 2 hours.

[0012] Furthermore, in the above-mentioned aqueous zinc battery electrolyte based on propionamide-caprolactam low eutectic solvent, the concentration of ZnSO4 in the ZnSO4 electrolyte is 2 mol / L.

[0013] Furthermore, in the above-mentioned aqueous zinc battery electrolyte based on propionamide-caprolactam low eutectic solvent, ZnSO4 electrolyte and PES are mixed in a volume ratio of 3:1, 4:1, 5:1, 10:1, 20:1 or 40:1.

[0014] Furthermore, the above-mentioned aqueous zinc battery electrolyte based on propionamide-caprolactam deep eutectic solvent, the preparation method of PES comprises the following steps:

[0015] 1) vacuum drying the PAD and CPL;

[0016] 2) Mixing the dried PAD and CPL, heating and stirring the mixture until a uniform, transparent, light yellow liquid is formed to obtain PES;

[0017] 3) The PES was vacuum dried.

[0018] Furthermore, in the above-mentioned method for preparing PES, in step 1), the vacuum drying condition is: vacuum drying for 24 hours.

[0019] Furthermore, in the above-mentioned method for preparing PES, in step 3), the vacuum drying condition is: vacuum drying at 80° C. for 12 h.

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

[0021] 1. The synthesis of the propionamide-caprolactam deep eutectic solvent (PES) of the present invention is simple to operate and low in price.

[0022] 2. The PES synthesized by the present invention can react with Zn 2+ The formation of solvation effect can significantly broaden the electrochemical hydrogen evolution potential (HER), inhibit the hydrogen evolution side reaction; reduce the charge transfer internal resistance (R ct ), improve linear polarization resistance (LPR) and reduce corrosion current (Icorr ).

[0023] 3. The aqueous zinc battery electrolyte based on the propionamide-caprolactam deep eutectic solvent of the present invention and the preparation method thereof are conducive to the concept of green environmental protection and are more conducive to the life and survival of humans, animals and plants. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is the hydrogen nuclear magnetic resonance spectrum of the propionamide-caprolactam deep eutectic solvent (PES) in Example 1.

[0025] Figure 2 This is the infrared spectrum of the propionamide-caprolactam deep eutectic solvent (PES) in Example 1.

[0026] Figure 3 1 is a linear sweep voltammetry (LSV) diagram of seven electrolyte solutions in Example 2.

[0027] Figure 4 The seven electrolyte solutions in Example 2 were respectively -2 Hydrogen evolution potential (HER) diagram at two current densities.

[0028] Figure 5 2 is the electrochemical impedance spectroscopy (EIS) graph of the seven electrolyte solutions in Example 2.

[0029] Figure 6 is the charge transfer internal resistance (R ct )picture.

[0030] Figure 7 is the Tafel curve diagram of the seven electrolyte solutions in Example 2.

[0031] Figure 8 is the linear polarization resistance (LPR) and corrosion current (I corr )picture. DETAILED DESCRIPTION

[0032] The present invention is further illustrated below by specific examples. The present invention is not limited to the examples, but is also applicable to other deep eutectic solvents, and slight variations are possible without departing from the scope described.

[0033] Example 1 A preparation method based on a propionamide-caprolactam deep eutectic solvent (I) Preparation method:

[0034] 1) Dry propionamide (PAD) and caprolactam (CPL) under vacuum conditions for 24 h;

[0035] 2) Mixing the dried propionamide (PAD) and caprolactam (CPL) in a molar ratio of 1:1, heating and stirring at 80° C. for 2 h until a homogeneous, transparent, light yellow liquid is formed to obtain a propionamide-caprolactam deep eutectic solvent (PES);

[0036] 3) The propionamide-caprolactam deep eutectic solvent (PES) was dried under vacuum at 80° C. for 12 h.

[0037] (2) Characterization methods:

[0038] (1) H NMR spectrum: H NMR spectrum of propionamide-caprolactam deep eutectic solvent 1 H NMR characterization (300 MHz, solvent: DMSO-d6) Figure 1 . The nuclear magnetic resonance hydrogen spectrum analysis found that 1 The chemical shift, number of resonance peaks, and integrated area of ​​H NMR were consistent with those of the target deep eutectic solvent, and no impurity peaks were found.

[0039] (2) Infrared spectrum: Infrared characterization of propionamide-caprolactam deep eutectic solvent (PES) is shown in Figure 2 . Analysis of the infrared spectrum shows that the infrared spectrum of PES contains both characteristic peaks of the hydrogen bond acceptor (CPL) and characteristic absorption peaks of the hydrogen bond donor (PAD), and no new characteristic peaks are generated, indicating that no chemical reaction occurs between CPL and PAD to produce new substances, and they are only combined through hydrogen bond interactions.

[0040] Example 2 A method for preparing an aqueous zinc battery electrolyte based on a propionamide-caprolactam deep eutectic solvent (PES)

[0041] A 2 mol / L ZnSO4 electrolyte was prepared. This was then mixed with a prepared propionamide-caprolactam deep eutectic solvent (PES) at six volume ratios: 3:1, 4:1, 5:1, 10:1, 20:1, and 40:1. These electrolyte solutions, ZPES-3, ZPES-4, ZPES-5, ZPES-10, ZPES-20, and ZPES-40, were then ultrasonicated in an ultrasonic water bath to remove internal bubbles and obtain uniform, stable solutions. A 2 mol / L ZnSO4 electrolyte solution (ZS) was used as a blank control, for a total of seven electrolyte solutions.

[0042] Example 3 Application of an aqueous zinc battery electrolyte based on propionamide-caprolactam deep eutectic solvent (PES)

[0043] First, the linear sweep voltammetry (LSV) curves of seven electrolyte solutions were measured, such as Figure 3As shown, and at 40 and 90 mA·cm -2 The hydrogen evolution potential of different electrolyte solutions was observed at two current densities, such as Figure 4 As shown in the figure, with the increase of PES, the delayed hydrogen evolution potential is larger, among which ZPES-03 electrolyte has a larger delayed hydrogen evolution potential at 40 mA·cm -2 The hydrogen evolution potential of ZS electrolyte is higher than 430mV at the current density of 90mA·cm -2 The delayed hydrogen evolution potential exceeding 830 mV at this current density indicates that the kinetics of the hydrogen evolution reaction are relatively slow. This suggests that under the same conditions, the hydrogen evolution reaction is more difficult to occur in the ZPES-03 system compared to other electrolyte solutions, which helps suppress the hydrogen evolution side reaction.

[0044] Then the electrochemical impedance spectroscopy (EIS) of seven electrolyte solutions was measured, such as Figure 5 As shown, the corresponding circuit diagram and charge transfer resistance (R ct ),like Figure 6 As shown in Figure 2, with the increase of PES, R ct Significantly reduced, among which the R ct The lowest, indicating that the resistance to ion migration in the ZPES-03 electrolyte solution is small, and charge transfer can be carried out quickly at the electrode / electrolyte interface, accelerating the electrochemical reaction rate.

[0045] Finally, the Tafel curves of seven electrolyte solutions were measured, such as Figure 7 As shown, the changes in linear polarization resistance and corrosion current of different electrolyte solutions are fitted, as shown in Figure 8 As shown in the figure, with the increase of PES, the linear polarization resistance increases and the corrosion current becomes smaller. Among them, the ZPES-03 electrolyte solution shows a larger linear polarization resistance and a lower corrosion current, which indicates that the corrosion rate in the electrolyte solution is lower and the anti-corrosion performance of the electrolyte solution is better.

Claims

1. An aqueous zinc battery electrolyte based on a propionamide-caprolactam deep eutectic solvent, characterized in that: The preparation method of the aqueous zinc battery electrolyte is as follows: first, propionamide PAD and caprolactam CPL are heated and stirred to form a propionamide-caprolactam deep eutectic solvent PES, then ZnSO4 electrolyte and PES are mixed according to a volume ratio, and then ultrasonically mixed to uniformly mix the two and remove bubbles, finally obtaining an aqueous zinc battery electrolyte; The structural formulas of the PAD and CPL are shown in (I) and (II), respectively:

2. The aqueous zinc battery electrolyte based on the propionamide-caprolactam deep eutectic solvent according to claim 1, characterized in that: The molar ratio of PAD and CPL was 1:

1.

3. The aqueous zinc battery electrolyte based on the propionamide-caprolactam deep eutectic solvent according to claim 1, characterized in that: The heating temperature is 80°C.

4. The aqueous zinc battery electrolyte based on the propionamide-caprolactam deep eutectic solvent according to claim 1, characterized in that: The stirring time is 2h.

5. The aqueous zinc battery electrolyte based on propionamide-caprolactam deep eutectic solvent according to claim 1, characterized in that: The concentration of ZnSO4 in the ZnSO4 electrolyte is 2 mol / L.

6. The aqueous zinc battery electrolyte based on the propionamide-caprolactam deep eutectic solvent according to claim 1, characterized in that: The ZnSO4 electrolyte and PES were mixed in a volume ratio of 3:1, 4:1, 5:1, 10:1, 20:1 or 40:

1.

7. The aqueous zinc battery electrolyte based on a propionamide-caprolactam deep eutectic solvent according to any one of claims 1 to 4, characterized in that: The preparation method of the PES comprises the following steps: 1) vacuum drying the PAD and CPL; 2) Mixing the dried PAD and CPL, heating and stirring the mixture until a uniform, transparent, light yellow liquid is formed to obtain PES; 3) The PES was vacuum dried.

8. The aqueous zinc battery electrolyte based on the propionamide-caprolactam deep eutectic solvent according to claim 7, characterized in that: In step 1), the vacuum drying condition is: vacuum drying for 24 hours.

9. The aqueous zinc battery electrolyte based on the propionamide-caprolactam deep eutectic solvent according to claim 7, characterized in that: In step 3), the vacuum drying condition is: vacuum drying at 80° C. for 12 h.

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