Aqueous composite electrolyte and preparation method and application thereof

Abstract

The invention provides a water-based composite electrolyte and a preparation method and application thereof. The water-based composite electrolyte comprises soluble zinc salt, amino acid hydrochloride additives and deionized water. The aqueous composite electrolyte can be used for a symmetrical button cell, a half cell or an aqueous zinc ion total cell. By adjusting zinc ion deposition on the surface of the zinc electrode, the growth of zinc dendrites is reduced, and the shuttle effect of the iodine positive electrode is inhibited, so that the coulombic efficiency and the cycle performance of the water-based zinc-iodine battery are improved. The additive disclosed by the invention can be adsorbed on the surface of a zinc negative electrode, delays the nucleation process and inhibits the growth of zinc dendrites; the form of hydrochloride can play a role of a buffer solution, stabilize the pH value of the electrolyte, inhibit the corrosion of the zinc negative electrode and reduce the hydrogen evolution reaction; the hydrochloride form can weaken the protonation effect of amino acid groups and enhance the electrostatic interaction between the amino acid groups and the polyiodide, so that the shuttle effect is inhibited, and the coulombic efficiency and the cycle performance of the aqueous zinc-iodine battery are improved.

Description

Technical Field

[0001] This invention relates to the field of electrolyte technology, and in particular to a method for preparing and applying an aqueous composite electrolyte that can simultaneously suppress zinc dendrite growth and shuttle effect. Background Technology

[0002] With the rapid growth in demand for renewable energy power generation and storage, aqueous zinc-based batteries have become a research hotspot due to their advantages such as high safety, environmental friendliness, and low cost. Among them, aqueous zinc-iodine (Zn-I2) batteries, with their high theoretical capacity of iodine cathode (211 mAh / g) and low redox potential of zinc anode (-0.76 V vs. SHE), exhibit high energy density potential and are regarded as a strong candidate for next-generation energy storage systems.

[0003] However, the practical application of zinc-iodine batteries still faces the following key challenges: First, the zinc anode interface problem. Zinc metal anodes are prone to dendrite growth, hydrogen evolution reaction, and surface passivation in traditional aqueous electrolytes. Uncontrolled dendrite growth can lead to battery short circuits, and hydrogen evolution reaction poses a risk of explosion to aqueous batteries, severely impacting cycle life. Side reactions also reduce coulombic efficiency and accelerate electrolyte consumption. Second, the shuttle effect and slow kinetics of the iodine cathode. Iodine cathodes easily form soluble polyiodides (such as...) during charge and discharge. , (etc.), leading to loss of active material and shuttle effect, significantly reducing battery capacity and coulombic efficiency. At the same time, the low conductivity and slow redox kinetics of elemental iodine limit its rate performance.

[0004] Therefore, there is an urgent need to provide a method for preparing a composite electrolyte that can simultaneously suppress zinc dendrite growth and shuttle effect. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides an aqueous composite electrolyte, its preparation method, and its application. By adjusting the zinc ion deposition on the zinc electrode surface, this invention reduces the growth of zinc dendrites and suppresses the shuttle effect of the iodine cathode, thereby improving the coulombic efficiency and cycle performance of the aqueous zinc-iodine battery.

[0006] The technical solution of the present invention is: an aqueous composite electrolyte, comprising soluble zinc salt and amino acid hydrochloride additives, and deionized water; The amino acid hydrochloride additive is selected from one or more of L-arginine hydrochloride, glycine hydrochloride, L-lysine hydrochloride, and L-histidine hydrochloride.

[0007] Preferably, the water-soluble zinc salt is selected from one or more of zinc sulfate, zinc chloride, zinc acetate, zinc nitrate, zinc perchlorate, and zinc trifluoromethanesulfonate.

[0008] Preferably, the concentration of the soluble zinc salt is 0.2-4 mol / L, and the concentration of the amino acid hydrochloride additive is 0.01-1.0 mol / L.

[0009] Preferably, the present invention also provides a method for preparing an aqueous composite electrolyte, comprising the following steps: S1) Take a certain amount of soluble zinc salt and amino acid hydrochloride additives and mix them evenly; S2) Add deionized water, make up to volume, and let stand until the pH value stabilizes to obtain a stable aqueous composite electrolyte with amino acid hydrochloride additives.

[0010] Preferably, in step S1), the amino acid hydrochloride additive is selected from one or more of L-arginine hydrochloride, glycine hydrochloride, L-lysine hydrochloride, and L-histidine hydrochloride.

[0011] Preferably, in step S1), the water-soluble zinc salt is selected from one or more of zinc sulfate, zinc chloride, zinc acetate, zinc nitrate, zinc perchlorate, and zinc trifluoromethanesulfonate.

[0012] Preferably, in step S1), the concentration of the soluble zinc salt is 0.2-4 mol / L, and the concentration of the amino acid hydrochloride additive is 0.01-1.0 mol / L.

[0013] Preferably, in step S2), the standing time is more than 2 hours, and the stable pH value range is 3.4-4.0.

[0014] Preferably, the present invention also provides an application of an aqueous composite electrolyte, wherein the aqueous composite electrolyte is used in a symmetrical button cell, a half cell, or an aqueous zinc-ion full cell.

[0015] Preferably, the symmetrical button cell uses zinc sheets as the positive and negative electrodes.

[0016] Preferably, the half-cell uses a zinc sheet as the negative electrode and a copper foil as the positive electrode.

[0017] Preferably, the aqueous zinc-ion full battery uses zinc sheet as the negative electrode material and I2 / C as the positive electrode material.

[0018] The beneficial effects of this invention are as follows: 1. The electrolyte of the present invention can simultaneously suppress zinc dendrite growth and shuttle effect. By adjusting the zinc ion deposition on the zinc electrode surface, the growth of zinc dendrites is reduced and the shuttle effect of the iodine cathode is suppressed, thereby improving the coulombic efficiency and cycle performance of aqueous zinc-iodine batteries. 2. This invention, by adding amino acid hydrochloride additives to the electrolyte, achieves extremely high stability. Furthermore, the amino acid macromolecules can adsorb onto the surface of the zinc anode, delaying the nucleation process and inhibiting zinc dendrite growth; they can also strongly interact with water molecules and the zinc electrode, thereby altering the hydrated Zn. 2+ The solvation sheath structure of ions regulates the electrochemical reaction process on the zinc electrode surface, reduces the desolvation activation energy, and promotes the uniform deposition of zinc ions. 3. The hydrochloride form of the present invention can act as a buffer solution, stabilize the pH value of the electrolyte, inhibit the corrosion of the zinc anode, reduce the hydrogen evolution reaction, and reduce the generation of corrosive by-products, thereby effectively improving the corrosion resistance and cycle stability of the zinc anode. The symmetrical battery can cycle for more than 3300 hours, and it is suitable for long-term storage and use of commercial aqueous zinc-iodine battery electrolytes. 4. The electrolyte of the present invention exists in the form of hydrochloride, which can weaken the deprotonation effect of positively charged amino acid groups, enhance the electrostatic interaction between amino acid groups and polyiodides, thereby suppressing the shuttle effect and improving the coulombic efficiency and cycle performance of aqueous zinc-iodine batteries. Attached Figure Description

[0019] Figure 1 The symmetrical battery assembled in Example 2 of this invention using ArHCl / ZnSO4 and blank / ZnSO4 as electrolytes operates at 5 mA / cm. 2 5mAh / cm 2 High-magnification scanning electron microscope (SEM) image of the zinc sheet surface after 50 cycles of current density cycling; among which, Figure 1 (a) is a SEM image of the zinc sheet surface of the symmetrical battery using blank / ZnSO4 as the electrolyte in Comparative Example 1. Figure 1 (b) is a SEM image of the zinc sheet surface of the symmetrical battery using ArHCl / ZnSO4 as the electrolyte in Example 1; Figure 2 The figures show the electrokinetic polarization curves of commercial zinc sheets in the electrolytes ArHCl / ZnSO4 and blank / ZnSO4, respectively, in Embodiment 2 of the present invention. Figure 3 This is a comparison curve of the coulombic efficiency of the half-cells assembled with ArHCl / ZnSO4 and blank / ZnSO4 as electrolytes in Example 2 of the present invention. Figure 4 The symmetrical cells assembled in Example 2 of this invention using ArHCl / ZnSO4 and blank / ZnSO4 as electrolytes respectively, at 5 mA / cm 2 5mAh / cm 2 Time-voltage comparison graph of cyclic stability test under current density; Figure 5The symmetrical cells assembled in Example 2 of this invention using ArHCl / ZnSO4 and blank / ZnSO4 as electrolytes respectively, at 1 mA / cm 2 1mAh / cm 2 Time-voltage comparison graph of cyclic stability test under current density; Figure 6 The diagram shows the specific capacity and coulombic efficiency of the aqueous zinc-ion batteries assembled in Example 2 of this invention using ArHCl / ZnSO4 and blank / ZnSO4 as electrolytes, respectively. Detailed Implementation

[0020] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings: Example 1 This embodiment provides a method for preparing an aqueous composite electrolyte, comprising the following steps: S1) Mix 5.7512 g of zinc sulfate heptahydrate and 1.0533 g of L-arginine hydrochloride powder evenly; S2) Add deionized water and bring to a final volume until the powder is completely dissolved. Let stand for 2 hours until the pH of the solution stabilizes at around 3.4 to obtain a stable aqueous composite electrolyte for amino acid hydrochloride additives, namely ArHCl / ZnSO4.

[0021] Comparative Example 1 This embodiment provides a method for preparing zinc sulfate electrolyte, including the following steps: Take 5.7512 g of zinc sulfate heptahydrate, dissolve it in deionized water, make up the volume, and let it stand for 2 hours until the pH of the composite aqueous electrolyte stabilizes at around 4.4. A stable single zinc sulfate aqueous electrolyte is obtained, which is denoted as blank / ZnSO4.

[0022] Example 2 1) In this embodiment, the aqueous composite electrolyte ArHCl / ZnSO4 prepared in Example 1 is assembled into a symmetrical battery with commercial zinc sheet, or a commercial zinc sheet is used as the negative electrode and a commercial copper foil is used as the positive electrode to assemble a half battery with the aqueous composite electrolyte ArHCl / ZnSO4 prepared in Example 1. An aqueous zinc-iodine coin cell was assembled using commercial zinc sheets as the negative electrode material, I2 / C as the positive electrode material, and the electrolyte ArHCl / ZnSO4 prepared in Example 1. Under the same conditions, the blank / ZnSO4 zinc sulfate electrolyte obtained in Comparative Example 1 without any additives was used to assemble symmetrical cells, half-cells, and aqueous zinc-iodine button cells. 100 μL of electrolyte was taken from each cell.

[0023] 2) Performance Testing The symmetrical cells assembled in Example 1 with an aqueous composite electrolyte containing L-arginine hydrochloride and in Comparative Example 1 with a single zinc sulfate electrolyte and commercial zinc sheets were tested at 5 mA / cm². 2 5 mAh / cm 2 Scanning electron microscopy was performed on the surface of a commercial zinc sheet after 50 cycles at a current density, and the results are as follows: Figure 1 As shown in (a) and (b) in the figure, after cycling the symmetrical battery with blank / ZnSO4 as the electrolyte in Comparative Example 1, spiky zinc dendrites appeared on the zinc electrode surface due to uneven deposition. After cycling the symmetrical battery with ArHCl / ZnSO4 as the aqueous composite electrolyte in Example 1, a smooth and regular hexagonal zinc deposit was formed on the zinc electrode surface. It can be seen that the aqueous composite electrolyte with arginine hydrochloride additives promotes the uniform deposition of zinc ions, inhibits the formation of zinc dendrites, improves the utilization rate of zinc metal in the negative electrode, and ensures long-term stable cycling of the negative electrode.

[0024] Figure 2 The results of Tafel curve determination for commercial zinc sheets in the electrolyte ArHCl / ZnSO4 of Example 1 and the electrolyte blank / ZnSO4 of Comparative Example 1 are as follows: Figure 2 It can be seen that, compared with blank / ZnSO4, the aqueous composite electrolyte ArHCl / ZnSO4 containing L-arginine hydrochloride additive obtained in Example 1 has a higher corrosion potential and exhibits a smaller corrosion current density, indicating that the aqueous electrolyte reduces the damage to the zinc anode.

[0025] Figure 3 A half-cell assembled with commercial zinc foil as the negative electrode, commercial copper foil as the positive electrode, and the aqueous composite electrolyte ArHCl / ZnSO4 of Example 1 and the electrolyte blank / ZnSO4 of Comparative Example 1, operates at 10 mA / cm². 2 5 mAh / cm 2 Coulomb efficiency plot at current density. The half-cell of ArHCl / ZnSO4 at 10 mA / cm². 2 It can stably cycle for more than 600 times at a current density, with an average coulombic efficiency of up to 99.83%; while the blank / ZnSO4 half-cell can cycle at 10 mA / cm². 2 It exhibited poor cycling performance at current densities, with a stable cycle count of less than 200, and an average coulombic efficiency of 99.10%, which was significantly lower than that of ArHCl / ZnSO4 electrolyte.

[0026] The aqueous composite electrolyte ArHCl / ZnSO4 of Example 1 and the electrolyte blank / ZnSO4 of Comparative Example 1 were respectively assembled with commercial zinc sheets to form symmetrical cells, which achieved an efficiency of 5 mA / cm². 2 5mAh / cm2 and 1mA / cm 2 1mAh / cm 2 Deposition / stripping stability tests were conducted at current densities, such as... Figure 4 , Figure 5 As shown. A symmetrical cell using ArHCl / ZnSO4 as the electrolyte can achieve a current of 5 mA / cm². 2 5mAh / cm 2 Stable cycling for over 1400 h under certain conditions, at 1 mA / cm 2 1mAh / cm 2 The zinc anode achieved stable cycling for over 3300 hours at the specified current density, while the symmetric battery using blank / ZnSO4 as the electrolyte only achieved stable cycling for approximately 200 hours and 75 hours at the same current density. This indicates that the cycling stability and cycle life of the zinc anode in the aqueous composite electrolyte ArHCl / ZnSO4 of Example 1 were greatly improved.

[0027] Figure 6 To use commercial zinc sheets as the negative electrode material and I2 / C as the positive electrode material, coin cells were assembled with the aqueous composite electrolyte ArHCl / ZnSO4 of Example 1 and the electrolyte blank / ZnSO4 of Comparative Example 1, respectively. Electrochemical performance tests were conducted at a current density of 1C. The specific capacity, coulombic efficiency and cycle stability of ArHCl / ZnSO4 were significantly higher than those of blank / ZnSO4.

[0028] Therefore, it can be seen that aqueous composite electrolytes containing amino acid hydrochloride can promote uniform deposition of zinc anode, reduce interfacial side reactions, and inhibit iodine shuttle, thus significantly improving the cycle performance of zinc-iodine batteries and showing great application prospects in energy storage.

[0029] Examples 3-9 Based on the scheme of Example 1, the cycle stability of the aqueous zinc-iodine battery was affected by adjusting the type and concentration of different amino acid hydrochloride and the pH value of the aqueous composite electrolyte. The results are shown in Table 1. Table 1. Effects of different amino acid hydrochloride types and concentrations on the cycle stability of aqueous zinc-based batteries. Table 1 shows that Examples 1, 3, 4, and 5 demonstrate that the concentration of amino acid hydrochloride additives in the aqueous composite electrolyte has a significant impact on the performance of the aqueous zinc-ion battery. Examples 1, 6, and 7 show that the electrolyte pH value causes severe side reactions at the zinc anode interface. Examples 1, 8, and 9 show that the type of amino acid hydrochloride can affect the performance of the aqueous zinc-iodine battery to some extent. The electrolyte performance in Examples 3-9 is inferior to that in Example 1. These examples demonstrate that the appropriate type and concentration of added electrolyte can regulate the interaction between amino acid hydrochloride molecules, water molecules, and the zinc anode, thereby adjusting the hydrated Zn. 2+ The solvation sheath structure of the ion reduces the number of free water molecules. OH - The reaction of ions with water molecules and zinc ions produces an inert byproduct, basic zinc sulfate, on the zinc anode surface. This disrupts the surface uniformity of the zinc anode, leading to a decrease in Zn... 2+ Disordered deposition sites induce the "point effect" and dendrites, leading to uneven zinc dendrite deposition. Amino acids in hydrochloride form can effectively dissolve byproducts and regulate the Zn content on the zinc surface. 2+ Deposition and suppression of zinc dendrite growth. Protonated groups can bind polyiodide ions in the electrolyte through electrostatic interactions, suppressing the shuttle effect and effectively improving the coulombic efficiency and cycle stability of aqueous zinc-ion batteries.

[0030] The embodiments and descriptions above are merely illustrative of the principles and preferred embodiments of the present invention. Various changes and modifications may be made to the present invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed.

Claims

1. An aqueous composite electrolyte, characterized in that: Includes soluble zinc salts and amino acid hydrochloride additives, and deionized water; The amino acid hydrochloride additive is selected from one or more of L-arginine hydrochloride, glycine hydrochloride, L-lysine hydrochloride, and L-histidine hydrochloride.

2. The aqueous composite electrolyte according to claim 1, characterized in that: The concentration of the soluble zinc salt is 0.2-4 mol / L, and the concentration of the amino acid hydrochloride additive is 0.01-1.0 mol / L.

3. The aqueous composite electrolyte according to claim 2, characterized in that: The water-soluble zinc salt is selected from one or more of zinc sulfate, zinc chloride, zinc acetate, zinc nitrate, zinc perchlorate, and zinc trifluoromethanesulfonate.

4. A method for preparing the aqueous composite electrolyte according to any one of claims 1-3, characterized in that, Includes the following steps: S1) Take a certain amount of soluble zinc salt and amino acid hydrochloride additives and mix them evenly; The concentration of the soluble zinc salt is 0.2-4 mol / L, and the concentration of the amino acid hydrochloride additive is 0.01-1.0 mol / L. Furthermore, the amino acid hydrochloride additives are selected from one or more of L-arginine hydrochloride, glycine hydrochloride, L-lysine hydrochloride, and L-histidine hydrochloride; S2) Add deionized water, make up to volume, and let stand until the pH value stabilizes to obtain a stable aqueous composite electrolyte with amino acid hydrochloride additives.

5. The method for preparing an aqueous composite electrolyte according to claim 4, characterized in that: In step S1), the water-soluble zinc salt is selected from one or more combinations of zinc sulfate, zinc chloride, zinc acetate, zinc nitrate, zinc perchlorate, and zinc trifluoromethanesulfonate.

6. The method for preparing an aqueous composite electrolyte according to claim 4, characterized in that: In step S2), the standing time is more than 2 hours, and the stable pH value range is 3.4-4.

0.

7. An application of an aqueous composite electrolyte, characterized in that, The aqueous composite electrolyte according to any one of claims 1-3 is used as the electrolyte for a symmetrical button cell, a half cell, or an aqueous zinc-ion full cell.

8. The application of the aqueous composite electrolyte according to claim 7, characterized in that, The symmetrical button cell uses zinc sheets as the positive and negative electrodes.

9. The application of the aqueous composite electrolyte according to claim 7, characterized in that, The half-cell uses a zinc sheet as the negative electrode and a copper foil as the positive electrode.

10. The application of the aqueous composite electrolyte according to claim 7, characterized in that, The aforementioned aqueous zinc-ion full battery uses zinc sheet as the negative electrode material and I2 / C as the positive electrode material.

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