Preparation method of low-temperature aqueous electrolyte added with bionic cryoprotectant

Abstract

The invention discloses a preparation method of a low-temperature aqueous electrolyte added with a bionic cryoprotectant, and belongs to the technical field of battery electrolyte materials. The preparation method comprises the following steps: adding a bionic cryoprotectant and an electrolyte salt into a solvent, and uniformly mixing to obtain a low-temperature aqueous electrolyte; wherein the content of the bionic cryoprotectant is 0.5 g mL <-1 >. When the electrolyte is used for the zinc ion battery, the running temperature interval of the zinc ion battery can be effectively widened, so that the zinc ion battery can normally run in a low-temperature area environment. The preparation method of the electrolyte is simple in technological process, and the prepared electrolyte can also be used for other battery systems and is beneficial to promoting large-scale production and application of low-temperature batteries.

Description

Technical Field

[0001] The invention belongs to the technical field of battery electrolyte materials, and in particular relates to a method for preparing a low-temperature aqueous electrolyte added with a bionic cryoprotectant. Background Art

[0002] The increasingly serious energy shortage and climate change problems require the development of safe and efficient energy storage technologies to achieve the transformation of energy infrastructure. In order to maximize the sustainability of the environment and resources, aqueous zinc metal batteries have become an attractive option due to their inherent high safety, environmental friendliness and low manufacturing cost. Aqueous zinc-ion batteries have high theoretical capacity, abundant reserves and low potential, and have good development prospects and competitiveness (Energy Storage Materials 2024, 72, 103761; 10.1016 / j.ensm.2024.103761).

[0003] Although aqueous zinc-ion batteries have many advantages, their application in low-temperature environments still faces severe challenges. Traditional aqueous electrolytes are prone to freezing at sub-zero temperatures, which reduces their adaptability under low-temperature conditions and cannot meet the needs of efficient and sustainable power supply of aqueous energy storage devices in extreme environments. In low-temperature environments, conventional aqueous electrolytes tend to solidify below 0°C due to a large number of hydrogen bonds between water molecules, and the ionic conductivity and interface wettability deteriorate (ACS Nano 2023, 17, 21614-21625; 10.1021 / acsnano.3c06687), the desolvation kinetics decrease, and the battery rate performance seriously deteriorates (Angewandte Chemie International Edition 2024, 63, e202318496; 10.1002 / anie.202318496), and even fail at sub-zero temperatures. In order to improve the performance of zinc-ion batteries at low temperatures, it is thought that in nature, many organisms have amazing "superpowers" to adapt to extreme low temperatures. In the cold Arctic region, Alaskan tree frogs can survive the winter healthily even when the temperature drops to -14°C; coniferous trees distributed in the northern hemisphere have excellent antifreeze properties and can adapt to extreme low temperature environments (-40°C); Arctic ducks can survive in extremely cold places at -110°C because cryoprotectants are released in the organisms. The antifreeze mechanism of cryoprotectants is that these substances can destroy the orderly arrangement of water molecules through hydrogen bond interactions or electrostatic interactions, thereby inhibiting the formation of ice nuclei and the growth of ice crystals in the cell fluid. Inspired by antifreeze organisms, the composition of cell fluid and the transport of nutrients are highly similar to the electrolyte and zinc ion transport in batteries. Therefore, cold-resistant plants and animals can be used as reference models to introduce cryoprotectants to prepare bionic low-temperature electrolytes. Summary of the invention

[0004] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a method for preparing a low-temperature aqueous electrolyte with the addition of a bionic cryoprotectant. The prepared low-temperature aqueous electrolyte with the addition of a bionic cryoprotectant is used for a zinc ion battery, so that the battery can operate normally in an environment with a low temperature range and has good cycle stability at low temperatures.

[0005] To achieve the above objectives, the present invention adopts the following technical scheme: a method for preparing a low-temperature aqueous electrolyte with added bionic cryoprotectant, the preparation method comprising adding the bionic cryoprotectant and electrolyte salt into a solvent and mixing them evenly to obtain the low-temperature aqueous electrolyte.

[0006] Furthermore, the solvent is water.

[0007] Furthermore, the bionic cryoprotectant is L-proline.

[0008] Furthermore, the content of the bionic cryoprotectant is 0.5 g mL -1 .

[0009] Furthermore, the electrolyte salt is one or more of zinc sulfate, zinc chloride, zinc perchlorate, zinc nitrate, zinc acetate, zinc formate, zinc sulfonate, zinc sulfinate, zinc sulfonimide, zinc trifluoromethanesulfonate, and zinc bistrifluoromethanesulfonyl imide.

[0010] Furthermore, the concentration of the electrolyte salt is 0.5 to 3 mol L -1 .

[0011] The low-temperature aqueous electrolyte with added biomimetic cryoprotectant obtained by the above preparation method.

[0012] Application of the above-mentioned low-temperature aqueous electrolyte with added bionic cryoprotectant in zinc ion batteries.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] (1) The low-temperature aqueous electrolyte with added bionic cryoprotectant of the present invention is used for zinc ion batteries, which can make the zinc ion batteries adapt to low-temperature environments. The addition of bionic cryoprotectant can destroy the orderly arrangement of water molecules through hydrogen bond interaction or electrostatic interaction, thereby inhibiting the formation of ice nuclei and the growth of ice crystals in the cell fluid, and improving the stability of the zinc ion battery at low temperatures. At the same time, the structure-activity relationship between the components of the low-temperature aqueous electrolyte with added bionic cryoprotectant and the low-temperature electrochemical performance is established, effectively homogenizing the zinc ion flow, hindering the generation and growth of zinc dendrites, and greatly improving its cycle performance and stability at low temperatures, thereby achieving high capacity, long life and stable cycle of ultra-low temperature zinc batteries;

[0015] (2) The bionic cryoprotectant of the present invention is L-proline. The hydrophilic end of L-proline is adsorbed on the surface of ice crystals, while the other end opposite to the hydrophilic end is a hydrophobic end, which can prevent water from contacting the ice crystals and further inhibit the growth of ice crystals. In addition, the methylene group of the side chain of L-proline gives it a stable conformation in the liquid, increases its solubility in the electrolyte, and forms a stable molecular structure. The stable molecular structure stabilizes the hydrogen bonding between it and the water molecules, thereby effectively inhibiting the freezing of the electrolyte and allowing the battery to operate stably. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The state diagram of the electrolytes of Example 1 and Comparative Examples 1 to 4 at room temperature;

[0017] Figure 2 It is a state diagram of the electrolyte of Example 1 and Comparative Examples 1 to 4 at -20°C;

[0018] Figure 3 The Zn / Zn symmetric battery of Example 1 at 1 mA cm -2 Current density cycle diagram at -20°C;

[0019] Figure 4 The Zn / Zn symmetric battery of Comparative Example 1 is 1 mA cm -2 Current density cycle diagram at -20°C;

[0020] Figure 5 The Zn / Zn symmetric battery of Comparative Example 2 is 1 mA cm -2 Current density cycle diagram at -20°C;

[0021] Figure 6 The Zn / Zn symmetric battery of Comparative Example 3 is 1 mA cm -2 Current density cycle diagram at -20°C;

[0022] Figure 7 The Zn / Zn symmetric battery of Comparative Example 4 is 1 mA cm -2 Current density cycle diagram at -20°C;

[0023] Figure 8 The Zn / Zn symmetric battery of Example 1 at 0.5 mA cm -2 Current density cycle diagram at -20°C;

[0024] Fig. 9 The Zn / Zn symmetric battery of Example 1 at 0.2 mA cm -2 Current density cycle diagram at -20°C;

[0025] Fig.10 The Zn / Cu battery of Example 1 at 0.5 mA cm-2 Coulomb efficiency diagram at current density -20℃;

[0026] Fig.11 The Zn / Cu battery of Example 1 at 0.2 mA cm -2 Coulomb efficiency diagram at current density -20℃;

[0027] Fig.12 1 is a cycle diagram of the Zn / NVO battery of Example 1 and Comparative Example 1 at -20°C. DETAILED DESCRIPTION

[0028] The present invention will be further described below with reference to the embodiments.

[0029] Example 1

[0030] The low-temperature aqueous electrolyte solution with added biomimetic cryoprotectant in this embodiment is prepared by the following method: 1 g of biomimetic cryoprotectant L-proline and 1.15 g of electrolyte salt zinc sulfate heptahydrate are added to 2 mL of water (density 1 g mL -1 ) and mixed evenly to obtain a low-temperature aqueous electrolyte; wherein the mass concentration of L-proline is 0.5 g mL -1 , the molar concentration of the electrolyte salt is 2 molL -1 .

[0031] The Zn / Zn symmetrical battery of this embodiment is assembled by the following method: a CR2032 button battery shell is used, a zinc sheet with a diameter of 12 mm is used as the positive electrode sheet of the symmetrical battery, a zinc sheet with a diameter of 16 mm is used as the negative electrode sheet of the symmetrical battery, glass fiber GF / A is used as a separator, 100 μL of the above-prepared electrolyte is added to the battery to assemble a Zn / Zn symmetrical battery.

[0032] The Zn / Cu battery of this embodiment is assembled by the following method: a CR2032 button battery shell is used, a copper foil with a diameter of 12 mm is used as the positive electrode plate of the zinc ion battery, a zinc sheet with a diameter of 16 mm is used as the negative electrode plate of the symmetrical battery, and glass fiber GF / A is used as a separator. 100 μL of the above-prepared electrolyte is added to the battery to assemble the Zn / Cu battery.

[0033] The Zn / NVO battery of this embodiment is assembled by the following method: using a CR2032 button battery shell, NVO: acetylene black: PVDF (polyvinylidene fluoride) is dispersed in NMP (N-methylpyrrolidone) at a ratio of 7:2:1, and each substance is evenly dispersed to form a slurry, which is then dripped onto a stainless steel mesh disc with a diameter of 12 mm and dried to serve as the positive electrode of the zinc ion battery (the average NVO content of a single electrode is about 2 mg cm -2); a zinc sheet with a diameter of 16 mm was used as the negative electrode of the symmetrical battery, a glass fiber GF / A was used as the separator, 100 μL of the above-prepared electrolyte was added to the battery to assemble a Zn / NVO battery.

[0034] Comparative Example 1

[0035] The zinc ion battery electrolyte of this comparative example was prepared by the following method: 1.15 g zinc sulfate heptahydrate was uniformly dispersed in 2 mL water (density 1 g mL -1 ) to form a uniform solution with a molar concentration of 2 mol L -1 of an aqueous solution of zinc sulfate heptahydrate.

[0036] The assembly method of the Zn / Zn symmetrical battery in this comparative example is the same as that in Example 1.

[0037] The assembly method of the Zn / Cu battery of this comparative example is the same as that of Example 1.

[0038] The assembly method of the Zn / NVO battery in this comparative example is the same as that in Example 1.

[0039] Comparative Example 2

[0040] The preparation method of the low-temperature aqueous electrolyte with added biomimetic cryoprotectant in this comparative example is the same as that in Example 1, except that the mass of added L-proline is 2 g, and the mass concentration of L-proline is 1 g mL -1 .

[0041] The assembly method of the Zn / Zn symmetrical battery in this comparative example is the same as that in Example 1.

[0042] The assembly method of the Zn / Cu battery of this comparative example is the same as that of Example 1.

[0043] Comparative Example 3

[0044] The preparation method of the low-temperature aqueous electrolyte with added biomimetic cryoprotectant in this comparative example is the same as that in Example 1, except that the mass of added L-proline is 0.5 g, and the mass concentration of L-proline is 0.25 g mL -1 .

[0045] The assembly method of the Zn / Zn symmetrical battery in this comparative example is the same as that in Example 1.

[0046] The assembly method of the Zn / Cu battery of this comparative example is the same as that of Example 1.

[0047] Comparative Example 4

[0048] The preparation method of the low-temperature aqueous electrolyte with added biomimetic cryoprotectant in this comparative example is the same as that in Example 1, except that the biomimetic cryoprotectant is L-lysine.

[0049] The assembly method of the Zn / Zn symmetrical battery in this comparative example is the same as that in Example 1.

[0050] The assembly method of the Zn / Cu battery of this comparative example is the same as that of Example 1.

[0051] Figure 1 The state diagram of the electrolyte prepared in Example 1 and Comparative Examples 1 to 4 at room temperature, Figure 2 The state diagram of the electrolyte prepared in Example 1 and Comparative Examples 1 to 4 at -20°C shows that after adding the bionic cryoprotectant, Example 1, Comparative Example 2 and Comparative Example 4 did not solidify, while Comparative Example 3 and Comparative Example 1 both solidified. Since the content of the bionic cryoprotectant added in Comparative Example 3 is relatively small, it is insufficient to inhibit the growth of ice crystals. Figure 3 The cycle diagram of the electrolyte prepared in Example 1 assembled into a Zn / Zn symmetrical battery at -20°C shows that the electrolyte prepared in Example 1 has an overpotential of about 0.3V at -20°C and can maintain stable cycling; Figure 4 The cycle diagram of the Zn / Zn symmetrical battery assembled with the electrolyte prepared in Comparative Example 1 at -20°C shows that the electrolyte prepared in Comparative Example 1 freezes at low temperatures, causing the battery to be unable to cycle; Figure 5 The cycle diagram of the Zn / Zn symmetrical battery assembled with the electrolyte prepared in Comparative Example 2 at -20°C. Although the electrolyte prepared in Comparative Example 2 does not freeze at -20°C, the electrolyte viscosity is too high due to the excessive content of the bionic cryoprotectant, which increases the internal resistance of the battery and ultimately leads to poor battery cycle performance; Figure 6 The cycle diagram of the Zn / Zn symmetrical battery assembled with the electrolyte prepared in Comparative Example 3 at -20°C shows that the electrolyte prepared in Comparative Example 3 freezes at low temperatures, resulting in a large overpotential of the battery and poor cycle stability; Figure 7 The diagram shows the cycle of a Zn / Zn symmetrical battery assembled with the electrolyte prepared in Comparative Example 4 at -20°C. Although the electrolyte prepared in Comparative Example 4 does not freeze at -20°C, it cannot circulate normally. The possible reason is that the solubility of L-lysine in the electrolyte is insufficient, resulting in an unstable molecular structure, which in turn makes the hydrogen bonding between L-lysine and water molecules unstable. Figure 8 , 9 The figure is a cycle diagram of a Zn / Zn battery assembled with the electrolyte prepared in Example 1 at different current densities at -20°C. It can be seen that the Zn / Zn battery assembled with the electrolyte prepared in Example 1 can maintain stable cycling at low temperatures at different current densities; Fig.10 , 11The coulombic efficiency of the Zn / Cu battery of Example 1 at different current densities at -20°C. It can be seen that the Zn / Cu battery prepared in Example 1 has a high coulombic efficiency at different current densities and can remain stable; Fig.12 The cycle comparison diagram of the Zn / NVO battery assembled with the electrolytes prepared in Example 1 and Comparative Example 1 at -20°C shows that the electrolyte prepared in Example 1 greatly improves the stable zinc deposition / dissolution behavior at low temperatures, can be stably cycled at low temperatures, and improves the coulombic efficiency; thus, it can be seen that the low-temperature aqueous electrolyte with added bionic cryoprotectant of the present invention can significantly improve the cycle stability of zinc ion batteries in low temperature environments.

[0052] The low-temperature aqueous electrolyte with added biomimetic cryoprotectant prepared in Example 1 and the electrolytes prepared in Comparative Examples 1 to 4 were assembled into Zn / Zn batteries and Zn / Cu batteries, and the battery performance tests were carried out at -20°C. The results are shown in Table 1.

[0053] Table 1 Zn / Zn battery and Zn / Cu battery of Example 1 and Comparative Examples 1 to 4 at 1 mA cm -2 Current density - Battery performance results at 20°C

[0054]

[0055] It can be seen from Table 1 that the concentration of the bionic cryoprotectant has a great influence on the battery cycle performance. The battery assembled with the low-temperature aqueous electrolyte prepared in Example 1 and adding L-proline as a bionic cryoprotectant has good cycle stability at -20°C. It may be that the methylene group of the side chain of L-proline gives it a stable conformation in the liquid, increases its solubility in the electrolyte, and forms a stable molecular structure. The stable molecular structure stabilizes the hydrogen bonding between it and the water molecules, thereby achieving the purpose of inhibiting the freezing of the electrolyte and enabling the battery to operate stably. Although the electrolyte prepared in Comparative Example 2 did not freeze at -20°C, due to the addition of too much bionic cryoprotectant, the viscosity of the electrolyte was too high, the internal resistance of the battery increased, the zinc ion transmission efficiency was affected, and the charge and discharge performance of the battery was affected, resulting in poor cycle stability of the assembled battery. The electrolyte prepared in Comparative Example 3 has a low concentration of bionic cryoprotectant, and the effect of lowering the freezing point is small, resulting in a low coulombic efficiency. The electrolyte prepared in Comparative Example 1 is pure water, and the operating temperature range is narrow, resulting in the assembled battery being unable to circulate normally at -20°C. The biomimetic cryoprotectant added in Comparative Example 4 is L-lysine, with a mass concentration of 0.5 g mL -1 The prepared electrolyte does not freeze at -20°C, but cannot circulate stably. The possible reason is that the solubility of L-lysine in the electrolyte is insufficient, resulting in an unstable molecular structure, which in turn makes the hydrogen bonding between it and the water molecules unstable.

[0056] Table 2 Battery performance results of Zn / NVO batteries of Example 1 and Comparative Example 1 at -20°C

[0057]

[0058]

[0059] It can be seen from Table 2 that the Zn / NVO battery assembled with the low-temperature aqueous electrolyte with biomimetic cryoprotectant prepared in Example 1 still maintains a high capacity after 60 cycles at -20°C, and has good cycle performance and safety performance. The electrolyte prepared in Comparative Example 1 is pure water and has a narrow operating temperature range, resulting in the assembled Zn / NVO battery having a low initial capacity at -20°C and being unable to cycle normally.

[0060] In summary: the low-temperature aqueous electrolyte with biomimetic cryoprotectant added in the present invention can significantly improve the cycle life and stability of zinc ion batteries. By inhibiting the growth of ice crystals, the freezing point is lowered, and its stability at low temperatures is improved, so that the battery can operate normally in a low-temperature environment. In addition, this method is simple to prepare, the raw materials are cheap and easy to obtain, and it is suitable for large-scale production. It has a good application prospect. The prepared electrolyte can be applied to other battery systems, which is conducive to large-scale production and application.

[0061] The test method used in the embodiments and comparative examples of the present invention is: the assembled battery is tested for constant current charge and discharge using the Xinwei battery test system, and the battery connected to the battery test system is placed in an ultra-low temperature refrigerator to achieve test temperature control. After the battery test is completed, the discharge capacity and charge capacity of the full battery at different cycles can be directly obtained by the battery test system. The capacity retention rate is calculated as the ratio of the discharge capacity of the corresponding cycle number to the discharge capacity of the first cycle, and the coulomb efficiency is calculated as the ratio of the discharge capacity to the charge capacity at the same cycle number.

[0062] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a low-temperature aqueous electrolyte solution with an added biomimetic cryoprotectant, characterized in that: The preparation method comprises adding a bionic cryoprotectant and an electrolyte salt into a solvent and mixing them evenly to obtain a low-temperature aqueous electrolyte.

2. The preparation method according to claim 1, characterized in that: The solvent is water.

3. The preparation method according to claim 1, characterized in that: The bionic cryoprotectant is L-proline.

4. The preparation method according to claim 1, characterized in that: The concentration of the biomimetic cryoprotectant is 0.5 g mL -1 .

5. The preparation method according to claim 1, characterized in that: The electrolyte salt is one or more of zinc sulfate, zinc chloride, zinc perchlorate, zinc nitrate, zinc acetate, zinc formate, zinc sulfonate, zinc sulfinate, zinc sulfonimide, zinc trifluoromethanesulfonate, and zinc bistrifluoromethanesulfonyl imide.

6. The preparation method according to claim 1, characterized in that: The concentration of the electrolyte salt is 0.5 to 3 mol L -1 .

7. A low-temperature aqueous electrolyte solution containing a biomimetic cryoprotectant obtained by the preparation method according to any one of claims 1 to 6.

8. Use of the low-temperature aqueous electrolyte added with a biomimetic cryoprotectant as claimed in claim 7 in a low-temperature zinc ion battery.

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