A method for stabilizing a znohf protective layer in zinc sulfate and its application in aqueous zinc ion battery

Abstract

The application discloses a method for stabilizing a ZnOHF protective layer in zinc sulfate and application of the method to a water-based zinc ion battery, only introduces an external ion, that is, the existence of ZnOHF is stabilized in 2M ZnSO4 through electrolyte regulation, so that the ZnOHF can synergize, a uniform electric field is achieved, and the purpose of uniform zinc deposition is achieved, meanwhile, the protective layer in the solution is continuously repaired, so that the method for stabilizing a zinc negative electrode is realized. The electrolyte solvent is water, and the solute is zinc fluoride (ZnF2) and zinc sulfate (ZnSO4). The protective layer is zinc hydroxide fluoride (ZnOHF). The zinc negative electrode comprises zinc sheets, zinc foils, zinc powders, zinc meshes, porous zinc or zinc alloys. Under the synergistic effect of the electrolyte and the protective layer, the zinc negative electrode exhibits excellent deposition-dissolution reversibility, the dendrite growth is inhibited, the hydrogen evolution reaction is inhibited, and the generation of by-products is slowed down. The method is simple and low in cost, and can significantly improve the cycle stability of the zinc negative electrode in the water-based zinc ion battery.

Description

Technical Field

[0001] The present invention relates to a method for stabilizing a ZnOHF protective layer in zinc sulfate and application thereof in an aqueous zinc ion battery, namely a negative electrode protection method for improving the reversibility of zinc deposition and dissolution in a zinc ion battery, and belongs to the field of electrochemistry. Background Art

[0002] Zinc metal reserves are abundant in my country (ranking first in the world) and offer advantages such as low cost, non-toxicity, and a high theoretical capacity (5851 mAh / mL; 820 mAh / g). Its relatively low redox potential (-0.76 V vs SHE) allows the direct use of aqueous electrolytes in zinc-ion batteries. The ionic conductivity of aqueous electrolytes is approximately two orders of magnitude higher than that of organic electrolytes (~1000 mS cm -1 vs ~1-10 mS cm -1 ), allowing aqueous zinc-ion batteries to charge and discharge rapidly. Furthermore, thanks to the relatively stable chemical and physical properties of zinc metal, aqueous zinc-based batteries pose no risk of explosion or fire. Their high safety profile holds great potential for applications in portable devices, electric vehicles, and large-scale energy storage.

[0003] However, current aqueous zinc-ion battery anodes face critical challenges such as dendrites and side reactions, which can lead to battery short-circuit failure and reduced cycle life. Zinc dendrites can easily pierce the separator, causing a short circuit. Furthermore, side reactions not only reduce zinc utilization and the battery's overall coulombic efficiency, but also hydrogen evolution reactions, which can affect the battery's safety and electrochemical performance. Therefore, effectively suppressing the occurrence of zinc dendrites and side reactions is a crucial challenge that must be addressed in the development of zinc-ion batteries. Summary of the Invention

[0004] The purpose of the present invention is to avoid zinc dendrites and side reactions, thereby improving the cycle stability of the negative electrode of a zinc ion battery. The present invention provides a method for stabilizing a ZnOHF protective layer in zinc sulfate, that is, a zinc negative electrode protection method that improves the reversibility of zinc negative electrode deposition and dissolution in a zinc ion battery through the synergistic effect of the ZnOHF protective layer and the regulation of electrolyte components. That is, by adjusting the components and concentrations of the electrolyte in the battery system, the ZnOHF protective layer, which is originally unstable in the zinc sulfate electrolyte, is stabilized, and the zinc deposition behavior is guided at the electrode-electrolyte interface on the zinc negative electrode side of the zinc ion battery. At the same time, side reactions such as hydrogen evolution and water corrosion can be effectively suppressed, thereby showing excellent zinc deposition and dissolution reversibility. Battery cycle performance results show that: this synergistic strategy suppresses the occurrence of zinc dendrites and side reactions, has efficient and reversible deposition and dissolution performance; the method is simple and low-cost.

[0005] A method for protecting the zinc negative electrode in a zinc-ion battery is achieved by synergistically controlling the electrolyte and using a ZnOHF protective layer. The method is characterized in that ZnOHF, which would otherwise be converted into a byproduct in ZnSO4, can be stabilized, and only one foreign ion is introduced. First, a protective layer with adjustable morphology and thickness is prepared on the surface of a zinc substrate. The method is characterized in that a ZnOHF protective layer (abbreviated as ZnOHF@Zn) with adjustable morphology and thickness can be prepared on the zinc substrate by electrolyzing conventional two electrodes at a constant voltage for a certain period of time. The solvent of the zinc-ion battery electrolyte is water, and the solutes are zinc fluoride (ZnF2) and zinc sulfate (ZnSO4).

[0006] This invention provides a neutral zinc-ion battery protection method, characterized by: a zinc substrate with a ZnOHF protective layer on its surface; and an electrolyte solution containing water as the solvent and zinc fluoride (ZnF2) and zinc sulfate (ZnSO4) as the solutes. Optimizing the ZnOHF protective layer and electrolyte composition can synergistically improve the reversibility of zinc anode deposition and dissolution.

[0007] Furthermore, in the above technical solution, a traditional two-electrode device is used to prepare the ZnOHF protective layer, wherein the working electrode is a zinc substrate, the counter electrode is an inert electrode, the electrolyte solvent is water, and the solute is NH4F. The device is electrolyzed at a constant voltage for a certain period of time; that is, a ZnOHF protective layer is formed on the surface of the zinc substrate.

[0008] Furthermore, in the above technical solution, when preparing the protective layer, the electrolyte concentration is 1~2M.

[0009] Furthermore, in the above technical solution, when preparing the protective layer, the constant voltage is 6~15V.

[0010] Furthermore, in the above technical solution, in preparing the protective layer, the electrolysis time is 2 to 120 seconds.

[0011] Furthermore, in the above technical solution, in the preparation of the protective layer, the optimal electrolyte concentration is 2M, the optimal constant voltage is 15V, and the optimal electrolysis time is 2s.

[0012] Furthermore, in the above technical solution, the electrolyte is prepared by first preparing a 1-2M ZnSO4 solution, wherein the solvent is water and the solute is ZnSO4, then weighing a certain amount of zinc fluoride powder, adding a certain volume of ZnSO4 solution of a certain concentration, and magnetically stirring for 1 day. The optimal electrolyte preparation method is to first prepare a 2M ZnSO4 solution, wherein the solvent is water and the solute is ZnSO4, then weighing 0.0827g of zinc fluoride powder, adding 10mL of 2M ZnSO4, and magnetically stirring for 1 day.

[0013] Furthermore, in the above technical solution, the zinc substrate is zinc sheet, zinc foil, zinc powder, zinc mesh, porous zinc or zinc alloy.

[0014] Furthermore, in the above technical solution, the counter electrode in the preparation of the ZnOHF protective layer is a carbon paper or a platinum electrode.

[0015] Furthermore, in the above technical solution, the solvent in the zinc-ion battery electrolyte is water, and the solutes are zinc fluoride (ZnF2) and zinc sulfate (ZnSO4); the concentrations are 0.07-0.09 M and 1-2 M, respectively. The optimal zinc fluoride concentration is 0.08 M, and the optimal zinc sulfate (ZnSO4) concentration is 2 M.

[0016] The ZnOHF protective layer and fluorine-containing electrolyte prepared by the above method are used in zinc-ion batteries, and when used as negative electrode protection for zinc-ion batteries, they exhibit excellent reversibility of zinc deposition and dissolution. The process is as follows:

[0017] Place the zinc sheet coated with ZnOHF protective layer in the center of the negative electrode shell, then place the GF separator on it and wet the separator with the regulated electrolyte. Then, place the zinc sheet coated with ZnOHF protective layer, the gasket, the spring, and finally put the positive electrode shell on it. Then, use the button cell packaging machine to complete the packaging of the zinc negative electrode symmetrical battery. The packaged battery is connected to the electrochemical charge and discharge instrument and the current density (0.1~20 mA / cm 2 ) were tested for cyclic stability.

[0018] Beneficial results:

[0019] The present invention uses a ZnOHF protective layer and a regulated electrolyte to synergistically increase the cycling stability of the zinc negative electrode during zinc cyclic deposition. The comparison of battery thickness after cycling shows that this strategy effectively inhibits the hydrogen evolution reaction ( Figure 6 ), XRD test results show that the recycled zinc sheet inhibits the formation of by-products ( Figure 7 The zinc symmetric battery exhibits excellent zinc deposition and dissolution reversibility at 0.5 mA / cm 2 At a current density of 1.5 GHz, the cycle life can reach 3100 h ( Figure 5 ).

[0020] The method provided by the invention is time-saving, simple in steps, low in cost and good in repeatability. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is the XRD pattern of the ZnOHF protective layer in Example 1-3.

[0022] Figure 2 This is the SEM image of the ZnOHF protective layer in Example 1-3.

[0023] Figure 3XRD and SEM images of the ZnOHF protective layer after immersion in 2M ZnSO4 for 2 h.

[0024] Figure 4 XRD and SEM images of the ZnOHF protective layer after immersion in the regulated electrolyte for 1 day.

[0025] Figure 5 The voltage-time curves of the battery cycle stability tests in Examples 1-3 and Comparative Examples 1-3 are shown.

[0026] Figure 6 The thickness of the batteries after cycling in Example 1 and Comparative Example 1 was measured.

[0027] Figure 7 2 are XRD patterns of the batteries after cycling in Examples 1-2 and Comparative Example 1. DETAILED DESCRIPTION

[0028] The following examples will further illustrate the present invention, but are not intended to limit the invention.

[0029] Example 1

[0030] Preparation of ZnOHF protective layer: The preparation method uses a traditional two-electrode device, in which the working electrode is a zinc sheet, the counter electrode is a platinum electrode, the electrolyte solvent is water, and the solute is NH4F. That is, a 2M NH4F aqueous solution is prepared and the device is electrolyzed at a constant voltage of 15V for 2s. The X-ray diffraction (XRD) spectrum of the material is shown in Figure 1 , the SEM image of the microscopic surface morphology is shown in Figure 2 ;

[0031] Preparation of zinc ion battery electrolyte: weigh 0.0827 g zinc fluoride powder and dissolve it in 10 mL 2 M ZnSO4. Stir magnetically for 1 day to prepare 0.08 M ZnF2-ZnSO4 mixed electrolyte.

[0032] The prepared ZnOHF protective layer zinc sheet and the electrolyte were used to assemble a zinc ion symmetrical battery, that is, the zinc sheet coated with the ZnOHF protective layer was placed in the center of the negative electrode shell, the GF separator was placed on it and the separator was wetted with the regulated electrolyte, and then the zinc sheet coated with the ZnOHF protective layer, the gasket, and the spring were placed in sequence, and finally the positive electrode shell was buckled and the zinc negative electrode symmetrical battery was packaged using a button battery packaging machine. At 0.5 mA / cm 2 At a current density of , the voltage-time curve of the symmetrical battery cycle stability test is shown in Figure 5 ; Battery thickness measurement after cycling see Figure 6 ; X-ray diffraction (XRD) spectrum results after battery cycling are shown in Figure 7 .

[0033] Example 2

[0034] Preparation of ZnOHF protective layer: The preparation method is to use a traditional two-electrode device, in which the working electrode is a zinc sheet, the counter electrode is a platinum electrode, the electrolyte solvent is water, and the solute is NH4F. That is, a 2M NH4F aqueous solution is prepared and the device is electrolyzed at a constant voltage of 10 V for 10 s. The X-ray diffraction (XRD) spectrum of the material is shown in Figure 1 , the SEM image of the microscopic surface morphology is shown in Figure 2 ;

[0035] Preparation of zinc ion battery electrolyte: weigh 0.0827 g zinc fluoride powder and dissolve it in 10 mL 2 M ZnSO4. Stir magnetically for 1 day to prepare 0.08 M ZnF2-ZnSO4 mixed electrolyte.

[0036] The prepared ZnOHF protective layer zinc sheet and the electrolyte were used to assemble a zinc ion symmetrical battery, that is, the zinc sheet coated with the ZnOHF protective layer was placed in the center of the negative electrode shell, the GF separator was placed on it and the separator was wetted with the regulated electrolyte, and then the zinc sheet coated with the ZnOHF protective layer, the gasket, and the spring were placed in sequence, and finally the positive electrode shell was buckled and the zinc negative electrode symmetrical battery was packaged using a button battery packaging machine. At 1 mA / cm 2 At a current density of , the voltage-time curve of the symmetrical battery cycle stability test is shown in Figure 5 ; X-ray diffraction (XRD) spectrum results after battery cycling are shown in Figure 7 .

[0037] Example 3

[0038] Preparation of ZnOHF protective layer: The preparation method uses a traditional two-electrode device, in which the working electrode is a zinc sheet, the counter electrode is a platinum electrode, the electrolyte solvent is water, and the solute is NH4F. That is, a 2M NH4F aqueous solution is prepared and the device is electrolyzed at a constant voltage of 6 V for 10 s. The X-ray diffraction (XRD) spectrum of the material is shown in Figure 1 , the SEM image of the microscopic surface morphology is shown in Figure 2 ;

[0039] Preparation of zinc ion battery electrolyte: weigh 0.0827 g zinc fluoride powder and dissolve it in 10 mL 2 M ZnSO4. Stir magnetically for 1 day to prepare 0.08 M ZnF2-ZnSO4 mixed electrolyte.

[0040] The prepared ZnOHF protective layer zinc sheet and the electrolyte were used to assemble a zinc ion symmetrical battery, that is, the zinc sheet coated with the ZnOHF protective layer was placed in the center of the negative electrode shell, the GF separator was placed on it and the separator was wetted with the regulated electrolyte, and then the zinc sheet coated with the ZnOHF protective layer, the gasket, and the spring were placed in sequence, and finally the positive electrode shell was buckled and the zinc negative electrode symmetrical battery was packaged using a button battery packaging machine. At 10 mA / cm2 At a current density of , the voltage-time curve of the symmetrical battery cycle stability test is shown in Figure 5 .

[0041] Example 4

[0042] Preparation of ZnOHF protective layer: The preparation method uses a traditional two-electrode device, in which the working electrode is a zinc sheet, the counter electrode is carbon paper, the electrolyte solvent is water, and the solute is NH4F. That is, a 1 M NH4F aqueous solution is prepared and the device is electrolyzed at a constant voltage of 15 V for 2 s;

[0043] Preparation of zinc ion battery electrolyte: weigh 0.0827 g zinc fluoride powder and dissolve it in 10 mL 2 M ZnSO4. Stir magnetically for 1 day to prepare 0.08 M ZnF2-ZnSO4 mixed electrolyte.

[0044] The prepared ZnOHF protective layer zinc sheet and the electrolyte are used to assemble a zinc ion symmetrical battery, that is, the zinc sheet coated with the ZnOHF protective layer is placed in the center of the negative electrode shell, the GF separator is placed on it, and the separator is moistened with the regulated electrolyte, and then the zinc sheet coated with the ZnOHF protective layer, the gasket, and the spring are placed in sequence, and finally the positive electrode shell is buckled and the zinc negative electrode symmetrical battery is packaged using a button battery packaging machine.

[0045] Example 5

[0046] Preparation of the ZnOHF protective layer: The preparation method uses a traditional two-electrode device, in which the working electrode is a zinc sheet, the counter electrode is a platinum electrode, the electrolyte solvent is water, and the solute is NH4F. That is, a 1 M NH4F aqueous solution is prepared and the device is electrolyzed at a constant voltage of 10 V for 2 s;

[0047] Preparation of zinc ion battery electrolyte: weigh 0.0827 g zinc fluoride powder and dissolve it in 10 mL 2 M ZnSO4. Stir magnetically for 1 d to prepare 0.08 M ZnF2-ZnSO4 mixed electrolyte.

[0048] The prepared ZnOHF protective layer zinc sheet and the electrolyte are used to assemble a zinc ion symmetrical battery, that is, the zinc sheet coated with the ZnOHF protective layer is placed in the center of the negative electrode shell, the GF separator is placed on it, and the separator is moistened with the regulated electrolyte, and then the zinc sheet coated with the ZnOHF protective layer, the gasket, and the spring are placed in sequence, and finally the positive electrode shell is buckled and the zinc negative electrode symmetrical battery is packaged using a button battery packaging machine.

[0049] Comparative Example 1

[0050] A zinc ion symmetrical battery was assembled using a commercial zinc sheet and a 2 M ZnSO4 electrolyte. The solvent of the electrolyte was water and the solute was ZnSO4. The commercial zinc sheet was placed in the center of the negative electrode shell, a GF separator was placed on it, and the separator was moistened with 2 M ZnSO4 electrolyte. The commercial zinc sheet, gasket, and spring were then placed in sequence. Finally, the positive electrode shell was buckled on and the zinc negative electrode symmetrical battery was packaged using a button cell packaging machine. At 0.5 mA / cm 2 At a current density of , the voltage-time curve of the symmetrical battery cycle stability test is shown in Figure 5 ; Battery thickness measurement after cycling see Figure 6 ; X-ray diffraction (XRD) spectrum results after battery cycling are shown in Figure 7 .

[0051] Comparative Example 2

[0052] Preparation of ZnOHF protective layer: The preparation method uses a traditional two-electrode device, in which the working electrode is a zinc sheet, the counter electrode is a platinum electrode, the electrolyte solvent is water, and the solute is NH4F. That is, a 2M NH4F aqueous solution is prepared and the device is electrolyzed at a constant voltage of 15V for 2s. The X-ray diffraction (XRD) spectrum of the material is shown in Figure 1 (Same as Example 1), SEM images of microscopic surface morphology are shown in Figure 2 (Same as Example 1);

[0053] The zinc ion symmetrical battery was assembled using the prepared ZnOHF protective layer zinc sheet and 2 M ZnSO4 electrolyte, wherein the solvent of the electrolyte was water and the solute was ZnSO4. The zinc sheet coated with the ZnOHF protective layer was placed in the center of the negative electrode shell, the GF separator was placed on it and the separator was wetted with 2 M ZnSO4 electrolyte, and then the zinc sheet coated with the ZnOHF protective layer, the gasket, the spring, and finally the positive electrode shell were buckled and the zinc negative electrode symmetrical battery was packaged using a button cell packaging machine. At 0.5 mA / cm 2 At a current density of , the voltage-time curve of the symmetrical battery cycle stability test is shown in Figure 5 .

[0054] Comparative Example 3

[0055] Preparation of zinc ion battery electrolyte: weigh 0.0827 g zinc fluoride powder and dissolve it in 10 mL 2 M ZnSO4. Stir magnetically for 1 day to prepare 0.08 M ZnF2-ZnSO4 mixed electrolyte.

[0056] A zinc ion symmetrical battery was assembled using a commercial zinc sheet and the electrolyte. The commercial zinc sheet was placed in the center of the negative electrode shell, a GF separator was placed on it, and the separator was moistened with the regulated electrolyte. Then, the commercial zinc sheet, gasket, and spring were placed in sequence. Finally, the positive electrode shell was buckled and the zinc negative electrode symmetrical battery was packaged using a button cell packaging machine. 2 At a current density of , the voltage-time curve of the symmetrical battery cycle stability test is shown in Figure 5 .

Claims

1. A neutral zinc ion battery, characterized in that: The negative electrode is a zinc substrate with a ZnOHF protective layer on the surface; the solvent of the electrolyte is water, and the solutes are zinc fluoride ZnF2 and zinc sulfate ZnSO4; the concentrations of zinc fluoride ZnF2 and zinc sulfate ZnSO4 are 0.07~0.09 M and 1~2 M, respectively.

2. A neutral zinc ion battery according to claim 1, characterized in that: Preparation of a zinc substrate coated with a ZnOHF protective layer: Use a two-electrode device, in which the working electrode is the zinc substrate, the counter electrode is an inert electrode, the electrolyte solvent is water, and the solute is NH4F, and electrolyze the device at a constant voltage for a certain time.

3. The neutral zinc ion battery according to claim 2, wherein: During the preparation of the protective layer, the electrolyte concentration is 1-2 M.

4. The neutral zinc ion battery according to claim 2, wherein: During the preparation of the protective layer, the constant voltage is 6~15V.

5. The neutral zinc ion battery according to claim 2, wherein: During the preparation of the protective layer, the electrolysis time is 2 to 120 seconds.

6. The neutral zinc ion battery according to claim 2, wherein: During the preparation of the protective layer, the electrolyte concentration was 2 M, the constant voltage was 15 V, and the electrolysis time was 2 s.

7. The neutral zinc ion battery according to claim 1, characterized in that: The electrolyte is prepared by first preparing a 1-2M ZnSO4 solution, wherein the solvent is water and the solute is ZnSO4; then a certain amount of zinc fluoride powder is weighed and added to a certain volume and concentration of ZnSO4 solution, and magnetic stirring is carried out for 1 day.

8. The neutral zinc ion battery according to claim 4, characterized in that: The zinc substrate is zinc sheet, zinc foil, zinc powder, zinc mesh, porous zinc or zinc alloy.

9. The neutral zinc ion battery according to any one of claims 2 to 6, characterized in that: In the preparation of the ZnOHF protective layer, the counter electrode is a carbon paper or a platinum electrode.

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