Electrolyte applied to zinc sulfate electrolyte and using formamido deep-eutectic solvent as additive and preparation method of electrolyte

Abstract

The invention discloses an electrolyte which is applied to a zinc sulfate electrolyte and takes a formamido deep eutectic solvent (FDES) as an additive and a preparation method of the electrolyte, and belongs to the technical field of deep eutectic solvents. The preparation method of the electrolyte comprises the following steps: mixing 2mol / L ZnSO4 electrolyte and FDES according to different volume ratios, and carrying out ultrasonic treatment to obtain a final electrolyte solution. The additive FDES is synthesized from formamide (FAD) and caprolactam (CPL). The formamido deep-eutectic solvent prepared by the invention can widen an electrochemical window of a zinc sulfate electrolyte, enhance the stability of an electrochemical system, reduce double-layer capacitance (Cdl) and reduce charge consumption in a non-Faraday process, thereby reducing excessive internal energy consumption in voltage lag and cycle processes. And meanwhile, the ZnSO4 electrolyte has good electrochemical stability, is lower in cost compared with ZnCl2 and Zn (OTf) 2, and has excellent performance in various electrochemical systems. And the formamido 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 electrolyte using a formamide-based deep eutectic solvent (FDES) as an additive for use in zinc sulfate electrolyte and a preparation method thereof. Background Art

[0002] As additives in electrolytes, deep eutectic solvents (DESs) exhibit many remarkable properties and greatly optimize the performance of electrolytes.

[0003] DESs excel in broadening the electrochemical window. The electrochemical window of traditional electrolytes is often limited, which restricts the potential range of electrode reactions. After the addition of DESs, the properties of the electrode / electrolyte interface can be changed through unique intermolecular interactions, inhibiting unnecessary redox side reactions. This allows only the target electrochemical reaction to occur on the electrode surface within a wider potential range, creating conditions for reactions that were originally difficult to achieve. The broadened electrochemical window allows the battery to operate stably at a higher voltage, increasing the battery's energy density and output power, and effectively improving battery performance.

[0004] Deep eutectic solvents (DESs) perform well in reducing double-layer capacitance. Smaller double-layer capacitance can effectively reduce charge consumption in non-Faradaic processes. This is because DESs can form a special adsorption layer on the electrode surface, which reduces the effective reaction area of ​​the electrode surface, thereby reducing the probability of non-Faradaic processes such as double-layer charging. Given the significant advantages of DESs in reducing double-layer capacitance, exploring a DESs with the lowest cost, easiest operation and best effect has become a key way to maximize economic benefits, and is expected to bring more substantial benefits to related industries. Summary of the invention

[0005] In order to solve the above problems, the present invention provides an electrolyte with a formamide-based deep eutectic solvent (FDES) as an additive for zinc sulfate electrolyte and a preparation method thereof. The method is simple to operate and has excellent effect.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] An electrolyte with a formamide-based low eutectic solvent FDES as an additive, the preparation method of which is as follows: ZnSO 4 The electrolyte is mixed with FDES, and then ultrasound is used to mix the two evenly and remove bubbles, finally obtaining an electrolyte solution;

[0008] The FDES is synthesized from formamide FAD and caprolactam CPL, whose structural formulas are shown in (I) and (II), respectively.

[0009]

[0010] Furthermore, in the above-mentioned electrolyte with formamide-based low eutectic solvent FDES as an additive, the ZnSO 4 ZnSO in electrolyte 4 The concentration is 2mol / L.

[0011] Furthermore, the electrolyte with the formamide-based low eutectic solvent FDES as an additive, ZnSO 4 The electrolyte and FDES were mixed at a volume ratio of 5:1, 10:1, 20:1 or 40:1.

[0012] Preferably, ZnSO 4 The electrolyte and FDES were mixed in a volume ratio of 5:1.

[0013] Furthermore, in the electrolyte containing the formamide-based low eutectic solvent FDES as an additive, the ultrasonic time is 1 h.

[0014] Furthermore, the above-mentioned electrolyte using formamide-based low eutectic solvent FDES as an additive, the preparation method of FDES comprises the following steps:

[0015] 1) vacuum drying the CPL;

[0016] 2) Mix the dried CPL and FAD and stir to react until a uniform transparent liquid is formed to obtain FDES;

[0017] 3) The FDES was dried under vacuum.

[0018] Furthermore, in the above-mentioned method for preparing FDES, in step 1), the vacuum drying condition is: vacuum drying at 60° C. for 24 hours.

[0019] Furthermore, in the above-mentioned method for preparing FDES, in step 2), the molar ratio of FAD to CPL is 2:1.

[0020] Furthermore, in the above-mentioned method for preparing FDES, in step 2), the stirring reaction time is 2 hours.

[0021] Furthermore, in the above-mentioned method for preparing FDES, in step 3), the vacuum drying condition is: vacuum drying at 60° C. for 12 h.

[0022] The use of an electrolyte containing a formamide-based low eutectic solvent FDES as an additive in a zinc sulfate electrolyte as described in any one of the above items.

[0023] The beneficial effects of the present invention are:

[0024] 1. The synthesis of the formamide-based deep eutectic solvent (FDES) of the present invention is simple and inexpensive.

[0025] 2. The FDES synthesized by the present invention can react with Zn 2+ The formation of a solvation effect can broaden the electrochemical window and reduce the double-layer capacitance.

[0026] 3. The present invention uses FDES as an electrolyte additive in zinc sulfate electrolyte, which is conducive to the concept of green environmental protection and is more conducive to the life and survival of humans, animals and plants. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is the infrared spectrum of the formamide-based deep eutectic solvent (FDES) in Example 1.

[0028] Figure 2 3 is the linear sweep voltammetry curve of the five electrolyte solutions in Example 3.

[0029] Figure 3 These are the cyclic voltammograms of the two electrolytes, FDES-ZS-5 and 2M ZS, at different scan rates in a Zn||Zn symmetric battery in Example 3.

[0030] Figure 4 It is the linear fitting diagram of the double-layer capacitance of the two electrolytes FDES-ZS-5 and 2M ZS in the Zn||Zn symmetric battery in Example 3. DETAILED DESCRIPTION

[0031] The present invention is further described below by means of specific examples. The present invention is not limited to the examples, and is also applicable to other deep eutectic solvents, and may be slightly modified without departing from the described scope.

[0032] Example 1 Preparation of a formamide-based deep eutectic solvent for electrolyte additives

[0033] Formamide-based deep eutectic solvent (FDES) is synthesized from formamide (FAD) and caprolactam (CPL) with structural formulas shown in (Ⅰ) and (Ⅱ), respectively.

[0034]

[0035] (I) Preparation method:

[0036] 1) drying caprolactam (CPL) under vacuum at 60°C for 24h;

[0037] 2) Mixing the dried formamide (FAD) and caprolactam (CPL) in a molar ratio of 2:1 and stirring for 2 hours until a uniform transparent liquid is formed to obtain a formamide caprolactam deep eutectic solvent (FDES);

[0038] 3) Dry the formamide-caprolactam deep eutectic solvent (FDES) at 60° C. in vacuum for 12 h.

[0039] (II) Characterization methods:

[0040] Infrared spectrum: infrared characterization of formamide-based deep eutectic solvent (FDES) Figure 1 The infrared spectrum analysis shows that the infrared spectrum of FDES contains both the characteristic peaks of the hydrogen bond acceptor (CPL) and the characteristic absorption peaks of the hydrogen bond donor (FAD), and no new characteristic peaks are generated, indicating that there is no chemical reaction between CPL and FAD to produce new substances, but they are only combined through hydrogen bond interactions.

[0041] Example 2 Preparation of an electrolyte using a formamide-based deep eutectic solvent (FDES) as an additive

[0042] Prepare 2 mol / L ZnSO 4 electrolyte, then ZnSO 4 The electrolyte was mixed with the prepared formamide-based low eutectic solvent (FDES) at four volume ratios of 5:1, 10:1, 20:1, and 40:1 to obtain electrolyte solutions containing low eutectic solvents: FDES-ZS-5, FDES-ZS-10, FDES-ZS-20, and FDES-ZS-40. The four electrolytes were then placed in an ultrasonic water bath for 1 h to remove internal bubbles and obtain a uniform and stable solution. At the same time, a 2 mol / L ZnSO 4 The electrolyte solutions were used as blank controls, for a total of five electrolyte solutions.

[0043] Example 3 Application of an electrolyte with a formamide-based deep eutectic solvent (FDES) as an additive in a zinc sulfate electrolyte

[0044] First, the linear sweep voltammetry (LSV) curves of five electrolyte solutions were measured at a sweep voltage between -1 and 2 V. Figure 2 As shown in the figure, it can be clearly seen that in terms of oxidation potential: From the enlarged figure on the right, it can be seen that during the oxidation process, the initial oxidation potential of the FDES-ZS-5 electrolyte is about 1.78V, while ZnSO 4 The electrolyte is about 1.75V, and generally, the higher the initial oxidation potential, the less likely the system is to be oxidized, and the system can withstand higher oxidation potentials without side reactions, which also broadens the oxidation end of the electrochemical window. In terms of reduction potential: From the enlarged image on the left, we can see that during the reduction process, the curve corresponding to the FDES-ZS-5 electrolyte begins to change significantly at around -0.51V, which is significantly different from other volume ratios and ZnSO 4The electrolyte shows a significant change in current density only at a more negative potential, which indicates that in the reduction direction, the FDES-ZS-5 electrolyte system can remain stable in a more negative potential range, is less likely to undergo reduction reactions, and is also beneficial to broadening the reduction end of the electrochemical window.

[0045] Next, the cyclic voltammetry (CV) curves of FDES-ZS-5 and ZS electrolytes were measured and the double layer capacitance (C dl ), applied to Zn||Zn symmetric cells, in the non-Faraday region, cyclic voltammetry (CV) at different scan rates (v) of 2, 4, 6, 8, and 10 mv / s, such as Figure 3 The double layer capacitance (C dl ),like Figure 4 As shown:

[0046] i c =C dl ×v (1-1)

[0047] i c = (i 0v+ -i 0v- ) / 2 (1-2)

[0048] where i c is the double layer current, i 0v+ and i 0v- They represent the average values ​​of positive scan and negative scan at 0V, respectively. From the actual data comparison, in the 2M ZS electrolyte system, the double layer capacitance is about 759μF / cm 2 In the FDES-ZS-5 electrolyte, the double layer capacitance dropped sharply to about 22.1 μF / cm 2 Such a significant numerical difference intuitively reflects that the addition of low eutectic solvents has a significant effect on reducing the double-layer capacitance. A smaller double-layer capacitance means that the charge consumption of non-Faraday processes in the electrochemical process is greatly reduced, which not only improves the energy utilization efficiency of the electrochemical system, but also enhances the stability and cycle life of the system.

Claims

1. An electrolyte with a formamide-based deep eutectic solvent FDES as an additive, characterized in that: The preparation method is as follows: ZnSO4 electrolyte is mixed with FDES, and then ultrasonically mixed to make the two uniform and remove bubbles, and finally obtain an electrolyte solution; The FDES is synthesized from formamide FAD and caprolactam CPL, whose structural formulas are shown in (I) and (II), respectively.

2. The electrolyte with formamide-based deep eutectic solvent FDES as an additive according to claim 1, characterized in that: The concentration of ZnSO4 in the ZnSO4 electrolyte is 2 mol / L.

3. The electrolyte with formamide-based deep eutectic solvent FDES as an additive according to claim 1, characterized in that: ZnSO4 electrolyte and FDES were mixed in a volume ratio of 5:1, 10:1, 20:1 or 40:

1.

4. The electrolyte with formamide-based deep eutectic solvent FDES as an additive according to claim 1, characterized in that: The ultrasonic time is 1 h.

5. The electrolyte with formamide-based deep eutectic solvent FDES as an additive according to claim 1, characterized in that: The preparation method of the FDES comprises the following steps: 1) vacuum drying the CPL; 2) Mix the dried CPL and FAD and stir to react until a uniform transparent liquid is formed to obtain FDES; 3) The FDES was dried under vacuum.

6. The electrolyte with formamide-based deep eutectic solvent FDES as an additive according to claim 5, characterized in that: In step 1), the vacuum drying condition is: vacuum drying at 60° C. for 24 h.

7. The electrolyte with formamide-based deep eutectic solvent FDES as an additive according to claim 5, characterized in that: In step 2), the molar ratio of FAD to CPL is 2:

1.

8. The electrolyte with formamide-based deep eutectic solvent FDES as an additive according to claim 5, characterized in that: In step 2), the stirring reaction time is 2 h.

9. The electrolyte with formamide-based deep eutectic solvent FDES as an additive according to claim 5, characterized in that: In step 3), the vacuum drying condition is: vacuum drying at 60° C. for 12 h.

10. Use of an electrolyte comprising a formamide-based deep eutectic solvent FDES as an additive as claimed in any one of claims 1 to 9 in a zinc sulfate electrolyte.

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