Preparation method and application of deep eutectic electrolyte based on DL-alanine
By using DL-alanine-based hydrated deep eutectic electrolyte in aqueous zinc ion capacitors, the problem of degradation of capacitor performance at extreme temperatures is solved, and the effect of stable operation in wide temperature domain and high cycle life is achieved.
Patent Information
- Application Number
- CN202510218066.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-26
- Publication Date
- 2025-05-27
AI Technical Summary
Under extreme temperature conditions, aqueous zinc ion capacitors face problems such as electrolyte crystallization, decreased ion conductivity and accelerated interface reaction at high temperatures, resulting in reduced performance and shortened cycle life.
A hydrated deep eutectic electrolyte based on DL-alanine was prepared by mixing zinc perchlorate hexahydrate, DL-alanine and water in a specific molar ratio and reacting under heating conditions to prepare a hydrated deep eutectic electrolyte that can operate stably in a wide temperature range.
The zinc ion capacitor is achieved stable operation within a wide temperature range of -40℃ to 60℃, which significantly improves the cycle life of the capacitor, and cycles more than 60,000 times at 25℃, with a Coulomb efficiency of ≥99.7%.
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Abstract
Description
Technical Field
[0001] The present invention relates to a preparation method and application of a hydrated deep eutectic electrolyte based on DL-alanine. Background Art
[0002] With the rapid development of fields such as electric vehicles and energy storage systems, the global energy industry is facing profound technological changes. The application requirements in extreme low-temperature and high-temperature environments (such as high-latitude, high-altitude, and tropical regions) have put forward higher requirements for the wide temperature operating range of electrochemical energy storage devices. Battery performance is very sensitive to temperature changes. The change in operating temperature will significantly affect the rate of chemical reactions and the ion diffusion process in the electrolyte, thereby affecting the overall battery performance. As the medium for ion conduction between electrodes in a battery, the electrolyte plays a core role in this process. Therefore, the design and improvement of electrolytes are crucial for enhancing battery performance in a wide temperature range. To address the problem of battery performance degradation in low-temperature and high-temperature environments, scientific and effective design methods, especially technologies that can inhibit the freezing of electrolytes at low temperatures and avoid the volatilization or decomposition of electrolytes at high temperatures, are urgently needed to be developed.
[0003] Aqueous zinc-ion energy storage devices have become a potential energy storage system due to their low cost, high theoretical specific capacity, excellent safety, and environmental friendliness, and are particularly suitable for fields such as renewable energy storage and power grid dispatching. However, they still face severe challenges under extreme temperature conditions. At low temperatures, the electrolyte is prone to crystallization, resulting in a significant decrease in ionic conductivity and hindered ion migration. At high temperatures, although the ion transport rate and chemical reaction rate are increased, when the temperature exceeds 45 °C, the interfacial reaction between the electrolyte and the electrode accelerates, thereby promoting the hydrogen evolution reaction (HER) and exacerbating the corrosion and oxidation processes of the electrode material, seriously threatening the cycle life of the battery.
[0004] Therefore, it is particularly important to develop a hydrated electrolyte with a wide temperature operating range and good environmental compatibility to cope with the challenges of drastic environmental changes. Summary of the Invention
[0005] The object of the present invention is to solve the problem that the operating temperature range of aqueous zinc-ion capacitors is limited, which has become a major challenge in their practical applications. For this purpose, the present invention proposes a preparation method of a novel wide-temperature hydrated deep eutectic electrolyte based on DL-alanine and its application in zinc-ion capacitors.
[0006] The present invention adopts the following technical solutions:
[0007] A hydrated deep eutectic electrolyte, wherein the hydrated deep eutectic electrolyte is composed of zinc perchlorate hexahydrate, DL-alanine, and H 2 O, and the zinc perchlorate hexahydrate, DL-alanine, and H2 The molar ratio of O is 1:1.5:2 to 8. In a preferred embodiment of the present invention, the zinc perchlorate hexahydrate, DL-alanine and H 2 The molar ratio of O is 1:1.5:4.
[0008] Another object of the present invention is to provide a method for preparing a hydrated deep eutectic electrolyte, which is specifically completed according to the following steps: Mix Zn(ClO 4 ) 2 ·6H 2 O and DL-alanine in a molar ratio of 1:1.5, and then place them in an oven at 70 °C for heating for 2 h. After sufficient reaction, a deep eutectic electrolyte is obtained. Subsequently, add H 2 O with a molar ratio of 2 to 8 to obtain a hydrated deep eutectic electrolyte.
[0009] The third object of the present invention is to provide an application of the above-mentioned hydrated deep eutectic electrolyte in a wide-temperature-range zinc-ion capacitor. In a preferred embodiment of the present invention, the application method of the zinc-ion capacitor is: using activated carbon as the positive electrode material, zinc foil as the negative electrode, and the hydrated deep eutectic electrolyte as the electrolyte to assemble a CR2032 type capacitor device.
[0010] Preparation process of the positive electrode material:
[0011] Mix the AC electrode material, polyvinylidene fluoride and conductive carbon black, grind them, and then drop an appropriate amount of 1-methyl-2-pyrrolidone to obtain a positive electrode slurry; uniformly coat the positive electrode slurry on the titanium foil and place it in an oven to dry to obtain a positive electrode sheet.
[0012] Assembly process:
[0013] The assembly process of the device includes using a CR2032 stainless steel button battery case, a funnel spring sheet, a gasket, and a glass fiber separator. The specific steps are as follows: First, place the positive electrode sheet and the glass fiber separator into the positive electrode case in sequence; then drop 100 μL of the prepared electrolyte into the center of the glass fiber separator; next, place the zinc negative electrode sheet on the glass fiber separator to ensure that the positive and negative electrode sheets are completely aligned; subsequently, cover the gasket, spring sheet and negative electrode case in sequence to complete the preliminary assembly of the device. Finally, place the assembled battery into a sealing machine and seal it under a pressure of 100 MPa to obtain a complete button battery.
[0014] Preferably, the operating temperature range of the capacitor is from -40 °C to 60 °C, and the cycle life at 25 °C exceeds 60,000 times.
[0015] Preferably, the Coulomb efficiency of the capacitor is ≥99.7%, and the zinc negative electrode can stably cycle for more than 1900 hours at a current density of 0.5 mA cm -2
[0016] Advantages of the present invention compared with the prior art:
[0017] 1) The present invention prepares a novel hydrated deep eutectic electrolyte composed of DL-alanine, zinc perchlorate hexahydrate and H 2 O. The introduction of DL-alanine breaks the hydrogen bond network between water molecules in the traditional electrolyte, greatly inhibits the activity of free water and reduces the freezing point. At the same time, DL-alanine enters the primary solvation shell of Zn 2+ , reducing the activity of free water, especially significantly reducing a series of interfacial side reactions caused by H 2 O at high temperatures, realizing the characteristic of being usable in a wide temperature range.
[0018] 2) The hydrated deep eutectic electrolyte prepared by the present invention is simple to prepare, low in cost, green and environmentally friendly, and suitable for large-scale industrial production.
[0019] 3) Compared with the traditional electrolyte, the hydrated deep eutectic electrolyte of the present invention can achieve long-term stable cycling of the zinc negative electrode without dendrites. The assembled zinc ion capacitor can operate stably in a wide temperature range of -40 to 60 °C and exceed 60,000 cycles. BRIEF DESCRIPTION OF THE DRAWINGS
[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.
[0021] Figure 1 (a) Deep eutectic electrolyte with a molar ratio of zinc perchlorate hexahydrate to DL-alanine of 1:1 to 3.5 prepared by the present invention; (b) Hydrated deep eutectic electrolyte with a molar ratio of zinc perchlorate hexahydrate, DL-alanine to H 2 O of 1:1.5:2 to 8.
[0022] Figure 2 Viscosity and conductivity of electrolytes with different ratios prepared by the present invention: (a) Deep eutectic electrolytes with different ratios, (b) Hydrated deep eutectic electrolytes with different water contents.
[0023] Figure 3 DSC spectrum of the prepared sample. It can be intuitively seen from the figure that the freezing point of Example 1 is the lowest, which is -79.8 °C.
[0024] Figure 4 For Example 1 and 2M Zn(ClO 4 ) 2The Zn||Zn symmetric battery assembled with the electrolyte under the test conditions of 0.5 mA cm –2 , 0.5 mAh cm –2 time / voltage curve.
[0025] Figure 5 For the Zn||Cu battery system assembled with the electrolyte of Example 1 and 2 M Zn(ClO 4 ) 2 under the conditions of 2 mA cm –2 , 0.5 mAh cm –2 Coulombic efficiency test results.
[0026] Figure 6 For the performance test results of the CR2032 type zinc ion capacitor assembled with the electrolyte of Example 1 at different temperatures.
[0027] Figure 7 For the long cycle performance graph of the zinc ion capacitor assembled with the electrolyte of Example 1 at 25 °C. Detailed implementation mode
[0028] In order to better understand the technical solution of the present application, the embodiments of the present application will be described in detail below with reference to the accompanying drawings. It should be clear that the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative work belong to the scope of protection of the present application. Unless otherwise stated, the raw materials, reagents, instruments and equipment involved in each embodiment of the present invention can be obtained on the market or prepared according to the existing technical methods.
[0029] Example 1:
[0030] A preparation method of a hydrated deep eutectic electrolyte, comprising the following steps: at room temperature, zinc perchlorate hexahydrate (Zn(ClO 4 ) 2 ·6H 2 O) and DL-alanine are mixed at a molar ratio of 1:1.5, heated to 70 °C in an oven and kept warm for 2 h to obtain a deep eutectic electrolyte, and H 2 O is added to the deep eutectic electrolyte to adjust the molar ratio of zinc salt, DL-alanine and water to 1:1.5:4 to obtain a hydrated deep eutectic electrolyte, denoted as HEE-4.
[0031] Example 2
[0032] A preparation method of a hydrated deep eutectic electrolyte, comprising the following steps: at room temperature, zinc perchlorate hexahydrate (Zn(ClO 4 ) 2 ·6H2 (O) was mixed with DL - Alanine in a molar ratio of 1:1.5, heated to 70 °C in an oven and kept warm for 2 h to obtain a deep eutectic electrolyte. H 2 O was added to the deep eutectic electrolyte to adjust the molar ratio of zinc salt, DL - Alanine and water to 1:1.5:2, obtaining a hydrated deep eutectic electrolyte, denoted as HEE - 2.
[0033] Example 3
[0034] A preparation method of a hydrated deep eutectic electrolyte, comprising the following steps: At room temperature, zinc perchlorate hexahydrate (Zn(ClO 4 )) 2 ·6H 2 O) was mixed with DL - Alanine in a molar ratio of 1:1.5, heated to 70 °C in an oven and kept warm for 2 h to obtain a deep eutectic electrolyte. H 2 O was added to the deep eutectic electrolyte to adjust the molar ratio of zinc salt, DL - Alanine and water to 1:1.5:6, obtaining a hydrated deep eutectic electrolyte, denoted as HEE - 6.
[0035] Example 4
[0036] A preparation method of a hydrated deep eutectic electrolyte, comprising the following steps: At room temperature, zinc perchlorate hexahydrate (Zn(ClO 4 )) 2 ·6H 2 O) was mixed with DL - Alanine in a molar ratio of 1:1.5, heated to 70 °C in an oven and kept warm for 2 h to obtain a deep eutectic electrolyte. H 2 O was added to the deep eutectic electrolyte to adjust the molar ratio of zinc salt, DL - Alanine and water to 1:1.5:8, obtaining a hydrated deep eutectic electrolyte, denoted as HEE - 8.
[0037] Comparative Example 1
[0038] Preparation of a single zinc salt electrolyte without eutectic small molecules: Using distilled water as a solvent, 2 M Zn(ClO 4 )) 2 was prepared as the electrolyte.
[0039] Result Analysis
[0040] Zinc perchlorate hexahydrate (Zn(ClO 4 )) 2 ·6H 2 O) and DL - Alanine with molar ratios of 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5 deep eutectic electrolytes were prepared at 70 °C, such as Figure 1(a) As shown, experiments found that when Zn(ClO 4 ) 2 ·6H 2 O and Dl-alanine were mixed at a ratio of 1:1, some undissolved Zn(ClO 4 ) 2 appeared. After cooling to room temperature, the electrolyte solidified. As the proportion of DL-alanine further increased, DL-alanine and Zn(ClO 4 ) 2 further interacted with each other, and the solution completely dissolved after a ratio of 1:1.5. When the ratio increased to 1:3.5, an excess of undissolved DL-alanine appeared. Zinc perchlorate hexahydrate (Zn(ClO 4 ) 2 ·6H 2 O), DL-alanine (DL-Alanine), and H 2 O had a molar ratio of 1:1.5:2, 1:1.5:4, 1:1.5:6, 1:1.5:8 for the hydrated deep eutectic electrolyte, as shown in Figure 1 (b). The electrolytes of all ratios were colorless transparent liquids at room temperature.
[0041] Figure 2 (a) shows the viscosity and conductivity diagrams of the prepared deep eutectic electrolyte at different ratios. As the proportion of DL-alanine continuously increased, the viscosity gradually increased and the conductivity continuously decreased. Considering the characteristics of the electrolyte itself and the percentage of Zn 2+ content, 1:1.5 was selected as the research object. At the same time, Figure 2 (b) shows that when the molar ratio of H 2 O was 4, there were significant changes in viscosity and conductivity, and HEE-4 had relatively appropriate viscosity and conductivity. This electrolyte was used as the preferred hydrated deep eutectic electrolyte.
[0042] Figure 3 shows the differential scanning calorimetry (DSC) curves of the hydrated deep eutectic electrolyte with different H 2 O contents and 2M Zn(ClO 4 ) 2 , indicating that the most preferred Example 1 of the present invention had the lowest freezing point.
[0043] As shown in Figure 4 , at a current density of 0.5 mA cm –2 and 0.5 mAh cm –2 conditions, a Zn||Zn symmetric battery was assembled, and its cycle life and stability were studied through the time / voltage curve. The study found that the battery assembled with the HEE-4 electrolyte could be stably cycled for more than 1900 hours. For 2M Zn(ClO 4 )2 , The electrolyte suddenly short-circuited after only 120 hours of circulation. At a current density of 2 mA cm –2 , 0.5 mAh cm –2 , the Coulombic efficiency (CE) of the Zn||Cu half-cell was further tested in this invention. As Figure 5 shown, in the 2M Zn(ClO 4 ) 2 electrolyte, after 140 cycles, the CE showed obvious up and down fluctuations. In contrast, the Zn||Cu half-cell assembled with HEE-4 electrolyte showed significantly improved and stable CE, with an average Coulombic efficiency greater than 99.7% after 900 stable cycles.
[0044] Using AC as the positive electrode material, zinc foil as the negative electrode, and HEE-4 as the electrolyte, a CR2032 coin cell was prepared to verify the effectiveness of adding HEE-4. As Figure 6 shown, the performance at different temperatures was measured, and good performance was shown at -40 to 60 °C, achieving a wide temperature range of operation. At the same time, as Figure 7 shown, at 25 °C and a current density of 5 A g –1 , it could be stably cycled more than 60,000 times, indicating that HEE-4 could be well adapted to zinc-ion capacitors.
[0045] As described above, it is only the specific implementation manner of this application. Any person skilled in the art within the technical scope disclosed in this application can easily think of changes or substitutions, which should all be covered within the protection scope of this application. The protection scope of this application shall be subject to the protection scope of the claims.
Claims
1. A hydrated deep eutectic electrolyte, characterized in that: It consists of zinc perchlorate hexahydrate, DL-alanine and H2O, and the molar ratio of the three is 1:1.5:2-8.
2. A hydrated deep eutectic electrolyte according to claim 1, characterized in that: The molar ratio of zinc perchlorate hexahydrate, DL-alanine and H2O is 1:1.5:
4.
3. A method for preparing a hydrated deep eutectic electrolyte, characterized in that: The method comprises the following steps: mixing zinc perchlorate hexahydrate and DL-alanine at a molar ratio of 1:1.5, heating and reacting the mixture to obtain a deep eutectic electrolyte, and then adding H2O at a molar ratio of 2 to 8 to obtain a hydrated deep eutectic electrolyte.
4. The preparation method according to claim 3, characterized in that: The heating reaction was carried out at 70° C. for 2 h.
5. The preparation method according to claim 3, characterized in that: H2O was added to the deep eutectic electrolyte at a molar ratio of 4.
6. A wide temperature range zinc ion capacitor, characterized in that: A positive electrode slurry prepared by mixing activated carbon, polyvinylidene fluoride and conductive carbon black is used as the positive electrode material, zinc foil is used as the negative electrode, and the hydrated deep eutectic electrolyte described in claim 1 or 2 is used as the electrolyte.
7. A wide temperature range zinc ion capacitor according to claim 6, characterized in that: The preparation process of the positive electrode material comprises: mixing and grinding activated carbon, polyvinylidene fluoride and conductive carbon black in a mass ratio of 8:1:1, adding 1-methyl-2-pyrrolidone to form a slurry, coating it on titanium foil and then drying it.
8. A wide temperature range zinc ion capacitor according to claim 6, characterized in that: The assembly process includes: first, placing the positive electrode sheet and the glass fiber separator in the positive electrode shell in turn; then dripping 100μL of the prepared electrolyte into the center of the glass fiber separator; then, placing the zinc foil negative electrode sheet on the glass fiber separator, ensuring that the positive and negative electrode sheets are completely aligned; then covering with gaskets, springs and negative electrode shells in turn to complete the initial assembly of the device; finally, placing the assembled battery into a sealing machine and sealing it at a pressure of 100MPa to obtain a complete button battery.
9. The wide temperature range zinc ion capacitor according to claim 6, characterized in that: The operating temperature range of the capacitor is -40°C to 60°C, and the cycle life is more than 60,000 times at 25°C.
10. A wide temperature range zinc ion capacitor according to claim 6, characterized in that: The coulombic efficiency of the capacitor is ≥99.7%, and the zinc negative electrode is 0.5 mA cm -2 It can stably cycle for more than 1900 hours at the current density.