Aqueous zinc ion battery electrolyte additive, electrolyte and aqueous zinc ion battery

Abstract

The invention relates to the technical field of aqueous zinc ion batteries, and relates to an aqueous zinc ion battery electrolyte additive, an electrolyte and an aqueous zinc ion battery, a low dosage of ammonium perfluorooctanoate is taken as the electrolyte additive to be directly added into a prepared ZnSO4 electrolyte, and the efficient and long-life aqueous zinc ion battery can be prepared. A trace amount of ammonium perfluorooctanoate surfactant electrolyte additive is introduced into the aqueous zinc ion battery electrolyte, so that the separation behavior of a zinc negative electrode is dynamically regulated and controlled, and the interface stability is optimized. By introducing the additive, the deposition morphology of the zinc negative electrode can be effectively optimized, the cycling stability is improved, the service life of the battery is prolonged, and new support is provided for a high-safety and high-performance water system energy storage system.

Description

Technical Field

[0001] This invention relates to the field of aqueous zinc-ion battery technology, specifically to an aqueous zinc-ion battery electrolyte additive, electrolyte, and aqueous zinc-ion battery. Background Technology

[0002] With the global energy structure shifting towards clean energy, electrochemical energy storage technology has received widespread attention as a key technology for addressing the intermittency and volatility of renewable energy. Aqueous zinc-ion batteries, due to their advantages such as low cost, high safety, environmental friendliness, and abundant resources, are considered one of the most promising large-scale energy storage technologies. However, aqueous zinc-ion batteries still face many challenges in practical applications, with the performance of the zinc anode being the core bottleneck restricting their development.

[0003] In traditional aqueous electrolytes, zinc dendrite growth is prone to occur on the zinc anode during charge and discharge. Irregular growth of zinc dendrites not only reduces the electrode surface area and lowers battery capacity, but can also puncture the separator, causing internal short circuits and severely impacting battery safety and cycle life. Furthermore, hydrogen ions in aqueous electrolytes readily undergo hydrogen evolution reaction on the zinc anode surface. This not only consumes active materials in the electrolyte and reduces the battery's coulombic efficiency, but also leads to bubble formation on the anode surface, damaging the electrode structure and exacerbating corrosion. Simultaneously, zinc readily corrodes in aqueous environments, generating zinc oxides or hydroxides, further deteriorating anode performance.

[0004] To alleviate the aforementioned problems, electrolyte additives have become a research hotspot due to their advantages such as simple operation, low cost, and significant effects. Currently reported electrolyte additives mainly include metal ion additives (such as Pb). 2+ In 3+ Inorganic anionic additives (such as SO4, etc.) 2- Cl - Inorganic anionic additives (such as gelatin and polyvinyl alcohol) and organic additives (such as gelatin and polyvinyl alcohol) have limited regulatory effects. The electrochemical stability and interface modification ability of traditional organic additives need to be improved. Metal ion additives can significantly improve the cycle performance of batteries, but may cause heavy metal pollution problems. Chinese patent CN117673505A discloses an aqueous zinc-ion battery electrolyte based on fluorine modification. The electrolyte contains soluble zinc salt, sodium perfluoroalkoxybenzenesulfonate, bismuth potassium citrate, sodium citrate dihydrate, and alkyl glycosides. Its composition is complex, and the cost and control are high. Some commonly used additives also have common limitations such as single function, high cost, and poor compatibility with aqueous environments. For example, metal ion additives In 3+To initially suppress dendrite formation, an indium (In) concentration of 5 mmol / L or higher is required, and the raw material is expensive, costing over 100,000 yuan per ton. Traditional organic additives like gelatin require a concentration exceeding 1 wt% to achieve interfacial adsorption capacity and are prone to aggregation in the electrolyte, leading to decreased compatibility. These issues directly increase battery manufacturing costs and limit large-scale application.

[0005] Therefore, developing surfactant-based electrolyte additives has become a key direction for overcoming the aforementioned bottlenecks. These additives, with their unique hydrophilic-hydrophobic molecular structure, achieve excellent compatibility with aqueous electrolytes and solve the problem of large dosages required by traditional additives through trace addition (typically only 0.01-0.1 wt%). Furthermore, they leverage the advantages of "widely available raw materials and mature preparation processes" to reduce costs, perfectly meeting the needs of large-scale production of aqueous zinc-ion batteries. Their research and application are of great significance for efficiently solving the zinc anode problem and promoting the transition of aqueous zinc-ion batteries from the laboratory to practical applications. Summary of the Invention

[0006] To overcome the shortcomings of the prior art, this invention provides an aqueous zinc-ion battery electrolyte additive, an electrolyte, and a zinc-ion battery. Ammonium perfluorooctanoate is used as the electrolyte additive. The zinc-ion battery electrolyte is prepared by dissolving ammonium perfluorooctanoate and soluble zinc salt together in water, which can improve the cycle stability and coulombic efficiency of the zinc-ion battery.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The first aspect of this invention provides an additive for an aqueous zinc-ion battery electrolyte, wherein the additive is ammonium perfluorooctanoate, and its chemical structural formula is [insert chemical structural formula here]. .

[0008] A second aspect of the present invention provides an aqueous zinc-ion battery electrolyte, comprising 1 mol / L to 2 mol / L of soluble zinc salt, 0.01 mmol / L to 0.3 mmol / L of the aforementioned additive ammonium perfluorooctanoate, and water.

[0009] Preferably, in the aqueous zinc-ion battery electrolyte, excessively high or low concentrations of ammonium perfluorooctanoate (PFOA) can affect the solvation structure of zinc ions, leading to a decrease in their performance. More preferably, the concentration of PFOA is 0.05 mmol / L.

[0010] Preferably, the soluble zinc salt is zinc sulfate (ZnSO4), zinc chloride, zinc trifluoromethanesulfonate, zinc perchlorate, or zinc acetate, with a concentration of 2 mol / L.

[0011] Preferably, the method for preparing the zinc-ion battery electrolyte includes the following steps: (1) Add zinc sulfate solid slowly to deionized water or ultrapure water according to the preset concentration, and stir at 20-30℃ for 1-3 hours until zinc sulfate is completely dissolved to obtain zinc sulfate basic electrolyte; (2) Add the solid perfluorooctanoate to the zinc sulfate basic electrolyte obtained in step (1) according to the preset addition amount, and continue stirring at 20-30℃ for 2-4 hours to make the ammonium perfluorooctanoate uniformly dispersed in the basic electrolyte to obtain an aqueous zinc ion battery electrolyte.

[0012] A third aspect of the present invention provides an aqueous zinc-ion battery, comprising a negative electrode, a separator, a positive electrode, and the aqueous zinc-ion battery electrolyte.

[0013] Preferably, the negative electrode active material is zinc foil, the separator is a glass fiber membrane, and the positive electrode active material is titanium foil and vanadium-based oxide or manganese-based oxide. More preferably, the vanadium-based oxide is zinc vanadate, sodium vanadate, or vanadium pentoxide.

[0014] Preferably, the aqueous zinc-ion battery is a zinc-zinc symmetrical battery, a zinc-copper half-cell, or a Zn-ZVO full-cell.

[0015] The fourth aspect of this invention provides the application of the aqueous zinc-ion battery electrolyte additive in zinc-ion batteries.

[0016] This invention introduces a low dose of ammonium perfluorooctanoate (APFO) as an additive in the electrolyte of an aqueous zinc-ion battery. Leveraging its surface activity, APFO provides an innovative solution for controlling the zinc anode interface. APFO is a common anionic surfactant with excellent surface activity, chemical stability, and thermal stability. Its molecular structure contains both a hydrophobic perfluoroalkyl chain and a hydrophilic ammonium group, enabling it to form a stable adsorption film at the electrode / electrolyte interface. Introducing APFO as a surfactant additive into the aqueous zinc sulfate electrolyte allows its molecules to preferentially adsorb onto the highly active sites of the zinc anode. The hydrophobic perfluorocarbon chain forms a dynamic shielding layer, homogenizing the interfacial electric field and zinc ion flow. Its surface activity improves the deposition behavior of zinc ions on the anode surface, inducing uniform zinc deposition and inhibiting dendrite growth. Simultaneously, the adsorption film acts as a barrier, preventing water molecules from contacting the anode, reducing hydrogen evolution, water decomposition, and harmful byproduct reactions, thus reducing corrosion and improving the overall performance of the aqueous zinc-ion battery.

[0017] The advantages and beneficial effects of this invention are: (1) The electrolyte additive of the present invention has good chemical stability, strong compatibility with aqueous system, little impact on electrolyte properties and battery energy density, high cost-effectiveness and applicability, and solves multiple challenges of zinc anode at the same time, providing a key technical approach for the development of high-performance, long-life and high-safety aqueous zinc-ion batteries.

[0018] (2) The electrolyte of the aqueous zinc-ion battery of the present invention does not contain heavy metals. Only a low dose of ammonium perfluorooctanoate is introduced and mixed with soluble zinc salt, which is adsorbed on the high active point of the zinc negative electrode. This can block water molecules from contacting the negative electrode, reduce hydrogen evolution, water decomposition and harmful by-product reactions, and inhibit the growth of zinc negative electrode dendrites. The formula is simple and environmentally friendly.

[0019] (3) The zinc-ion battery prepared with the electrolyte of this invention exhibits excellent cycle stability and coulombic efficiency, with high zinc utilization. The prepared zinc-zinc symmetric battery achieves high efficiency at 5 mA cm⁻¹. -2 During constant current charge-discharge testing at current density, the cycle life was no less than 2000 h, and the overpotential remained below 60 mV. The prepared zinc-copper half-cell exhibited a cycle life of no less than 2000 h at 5 mA cm⁻¹. -2 During coulombic efficiency testing at current density, the number of cycles was no less than 1000, and the average coulombic efficiency was 99.7%. The prepared zinc-zinc vanadate full cell achieved a coulombic efficiency of 99.7% at 2 Ag. -1 Capacity retention ≥ 90% after 260 cycles at current density. Attached Figure Description

[0020] Figure 1 SEM images of the Zn surface after zinc foil was immersed in pure ZnSO4 electrolyte and APFO / ZnSO4 electrolyte for 7 days.

[0021] Figure 2 SEM images of the electrolytes after cycling in pure ZnSO4 and APFO / ZnSO4 electrolyte for 100 h.

[0022] Figure 3 The XRD patterns are shown after cycling in pure ZnSO4 electrolyte and APFO / ZnSO4 electrolyte for 100 h.

[0023] Figure 4 The graph shows the long-cycle stability of Zn||Zn symmetric cells in different electrolytes.

[0024] Figure 5 The coulombic efficiency diagrams for Zn||Cu half-cells in ZnSO4 electrolyte and APFO / ZnSO4 electrolyte are shown.

[0025] Figure 6 The graph shows the discharge capacity performance of Zn||ZVO full cells in ZnSO4 electrolyte and APFO / ZnSO4 electrolyte. Detailed Implementation

[0026] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. It should be noted that the described embodiments are merely preferred solutions of the present invention and should not be construed as limiting the scope of protection of the present invention. Based on the technical concept of the present invention, equivalent substitutions and improvements made by those skilled in the art without creative effort should all fall within the scope of protection of the present invention.

[0027] It should be noted that the technical terms used in this invention are for the purpose of describing specific embodiments only and are not intended to limit the scope of protection of this invention. Unless otherwise specified, all raw materials, reagents, instruments, and equipment used in the following embodiments of this invention can be purchased through conventional commercial channels or prepared by existing methods. Among them, ammonium perfluorooctanoate, abbreviated as APFO, has the chemical formula […]. Zinc foil, abbreviated as Zn.

[0028] To enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments: Example 1 A method for preparing a zinc-ion battery electrolyte includes the following steps: 5.75 g of zinc sulfate was added to 10 mL of deionized water and stirred at 25°C for 1 hour until the zinc sulfate was completely dissolved, yielding a basic zinc sulfate electrolyte. 0.216 mg of APFO was added to the basic zinc sulfate electrolyte and stirred at 25°C for 1 hour to obtain a zinc-ion battery electrolyte, denoted as APFO / ZnSO4 electrolyte, or ZS / APFO for short. The concentration of zinc sulfate was 2 mol / L, and the concentration of APFO was 0.05 mmol / L.

[0029] Example 2 A method for preparing a zinc-ion battery electrolyte is the same as that in Example 1, except that the concentration of APFO is 0.01 mmol / L, i.e., 0.043 mg of APFO is added to the zinc sulfate base electrolyte, denoted as APFO / ZnSO4 electrolyte. The concentration of zinc sulfate is 2 mol / L, and the concentration of APFO is 0.01 mmol / L.

[0030] Example 3 A method for preparing a zinc-ion battery electrolyte is the same as that in Example 1, except that the concentration of APFO is 0.1 mmol / L, i.e., 0.431 mg of APFO is added to the zinc sulfate base electrolyte, denoted as APFO / ZnSO4 electrolyte. The concentration of zinc sulfate is 2 mol / L, and the concentration of APFO is 0.1 mmol / L.

[0031] Example 4 A method for preparing a zinc-ion battery electrolyte is the same as that in Example 1, except that the concentration of APFO is 0.3 mmol / L, i.e., 1.29 mg of APFO is added to the zinc sulfate base electrolyte, denoted as APFO / ZnSO4 electrolyte. The concentration of zinc sulfate is 2 mol / L, and the concentration of APFO is 0.3 mmol / L.

[0032] Comparative Example 1 A method for preparing an aqueous zinc-ion battery electrolyte includes the following steps: 5.75 g of zinc sulfate was dissolved in 10 mL of deionized water to obtain an aqueous zinc-ion battery electrolyte, denoted as ZnSO4 electrolyte, or ZS for short. The concentration of zinc sulfate was 2 mol / L.

[0033] Comparative Example 2 A method for preparing a zinc-ion battery electrolyte is the same as that in Example 1, except that the concentration of APFO is 0.5 mmol / L, i.e., 2.16 mg of APFO is dissolved in a zinc sulfate base electrolyte, denoted as APFO / ZnSO4 electrolyte. The concentration of zinc sulfate is 2 mol / L, and the concentration of APFO is 0.5 mmol / L.

[0034] Comparative Example 3 A method for preparing an aqueous zinc-ion battery electrolyte includes the following steps: 5.75 g of zinc sulfate was dissolved in 10 mL of deionized water, and then 0.207 mg of PFOA (perfluorooctanoic acid) was added to obtain a zinc-ion battery electrolyte, denoted as PFOA / ZnSO4 electrolyte. The concentration of zinc sulfate was 2 mol / L, and the concentration of PFOA was 0.05 mmol / L.

[0035] Comparative Example 4 A method for preparing an aqueous zinc-ion battery electrolyte includes the following steps: Dissolve 5.75 g of zinc sulfate in 10 mL of deionized water, then add 0.219 mg of perfluorooctane (C8F). 18The zinc-ion battery electrolyte, denoted as C8F, was obtained. 18 / ZnSO4 electrolyte. The concentration of zinc sulfate is 2 mol / L, C8F 18 The concentration was 0.05 mmol / L.

[0036] Comparative Example 5 A method for preparing an aqueous zinc-ion battery electrolyte includes the following steps: 5.75 g of zinc sulfate was dissolved in 10 mL of deionized water, and then 0.144 mg of sodium dodecyl sulfate (SDS) was added to obtain the zinc-ion battery electrolyte, denoted as SDS / ZnSO4 electrolyte. The concentration of zinc sulfate was 2 mol / L, and the concentration of SDS was 0.05 mmol / L.

[0037] Comparative Example 6 A method for preparing an aqueous zinc-ion battery electrolyte includes the following steps: 2.726 g of zinc chloride (ZnCl2) and 0.216 mg of APFO were dissolved in 10 mL of deionized water to obtain a zinc-ion battery electrolyte, denoted as APFO / ZnCl2 electrolyte. The concentration of ZnCl2 was 2 mol / L, and the concentration of APFO was 0.05 mmol / L.

[0038] Performance testing and analysis Commercially purchased zinc foil was immersed in the ZnSO4 electrolyte of Comparative Example 1 and the APFO / ZnSO4 electrolyte of Example 1 for 7 days, respectively. The zinc foil was then characterized, and its SEM morphology is shown below. Figure 1 As shown, the left side corresponds to Comparative Example 1, and the right side corresponds to Example 1. The results show that the zinc foil surface after immersion in the ZnSO4 electrolyte of Comparative Example 1 is uneven and severely corroded. In contrast, the zinc foil surface immersed in the APFO / ZnSO4 electrolyte of Example 1 remains smooth and flat.

[0039] The APFO / ZnSO4 electrolyte of Example 1 and the ZnSO4 electrolyte of Comparative Example 1 were applied to a zinc-zinc symmetric battery at 5 mA cm⁻¹. -2 Current density and 1 mA cm -2 The zinc foil was cycled for 100 h under the condition of areal capacity, and the post-cycle zinc foil was characterized and detected by SEM. The SEM morphology is as follows: Figure 2 As shown, the left side corresponds to Comparative Example 1, and the right side corresponds to Example 1. The results show that the zinc foil surface after cycling in the ZnSO4 electrolyte of Comparative Example 1 was uneven, with severe dendrite formation and corrosion. In contrast, the zinc foil surface after cycling in the APFO / ZnSO4 electrolyte of Example 1 remained smooth and flat.

[0040] Figure 3 The XRD pattern after 100 h of cycling shows that the zinc foil circulated in the ZnSO4 electrolyte of Comparative Example 1 exhibits the characteristic peak of the byproduct ZnSO4(OH)6·xH2O, while no obvious byproduct was detected in the zinc foil circulated in the APFO / ZnSO4 electrolyte of Example 1.

[0041] The APFO / ZnSO4 electrolyte of Example 1 and the electrolytes of Comparative Examples 1, 2, 3, 4, 5, and 6 were applied to zinc-zinc symmetric cells, i.e., Zn||Zn symmetric cells, using 5 mA·cm⁻¹. -2 Current density and 1 mA·cm -2 Constant current charge-discharge tests were performed under the condition of areal capacity, and the time-voltage curves were observed. The results of long-cycle stability tests are as follows: Figure 4 As shown, at 5 mA·cm -2 At the specified current densities, Zn||Zn symmetric cells assembled using electrolytes from Comparative Examples 1, 2, 3, 4, 5, and 6 could only cycle stably for 120 h, 763 h, 833 h, 445 h, 482 h, and 177 h, respectively. In contrast, the Zn||Zn symmetric cell using the APFO / ZnSO4 electrolyte from Example 1 could cycle stably for 2000 h.

[0042] The APFO / ZnSO4 electrolyte of Example 1 and the ZnSO4 electrolyte of Comparative Example 1 were applied to a zinc-copper half-cell, i.e., a Zn||Cu half-cell, using 5 mA·cm⁻¹. -2 Current density and 1 mA·cm -2 Coulomb efficiency tests were performed under the condition of areal capacity, and the results are as follows: Figure 5 As shown, it can be seen that at 5 mA·cm -2 At the specified current density, the Zn||Zn symmetric cell assembled using the 2 mol / L ZnSO4 electrolyte of Comparative Example 1 could only cycle stably for 300 cycles. In contrast, the Zn||Zn symmetric cell using the APFO / ZnSO4 electrolyte of Example 1 could cycle stably for over 1000 cycles with an average coulombic efficiency of 99.7%.

[0043] The APFO / ZnSO4 electrolyte from Example 1 and the ZnSO4 electrolyte from Comparative Example 1 were used in zinc-ion batteries. Zinc vanadate was used as the positive electrode, and Zn was used as the negative electrode. The positive electrode was prepared by uniformly mixing active material, conductive carbon black, and PVDF at a mass ratio of 7:2:1, coating it onto a 0.1 mm thick titanium foil, drying it, and then assembling it with the negative electrode to obtain an aqueous zinc-ion button cell, i.e., a zinc-zinc vanadate full cell, denoted as Zn||ZVO full cell. The aqueous zinc-ion button cell was charged and discharged within a voltage range of 1.6 V to 0.2 V, with a current density of 2 A·g. -1 The test results are as follows Figure 6 As shown, the Zn||ZVO full cell using the APFO / ZnSO4 electrolyte of Example 1 exhibits superior long-term cycling stability, with its capacity consistently exceeding that of the full cell using the ZnSO4 electrolyte of Comparative Example 1 throughout the entire cycle. Furthermore, the Zn||ZVO full cell using the ZnSO4 electrolyte of Comparative Example 1 experiences faster capacity decay. In contrast, the Zn||ZVO full cell using the APFO / ZnSO4 electrolyte of Example 1 exhibits slower capacity decay, indicating that the APFO additive significantly improves the cycling stability of the Zn||ZVO full cell.

[0044] It should be noted that when numerical ranges are involved in this invention, it should be understood that both endpoints of each numerical range, as well as any value between the two endpoints, can be selected. Since the steps and methods used are the same as in the embodiments, preferred embodiments are described here to avoid redundancy. Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this invention.

[0045] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. An additive for an aqueous zinc-ion battery electrolyte, characterized in that, The additive is ammonium perfluorooctanoate, with the chemical structural formula […]. 。 2. An aqueous zinc-ion battery electrolyte, characterized in that, It is composed of soluble zinc salt, ammonium perfluorooctanoate as an additive according to claim 1, and water; in the electrolyte, the concentration of ammonium perfluorooctanoate is 0.01 mmol / L to 0.3 mmol / L, and the concentration of soluble zinc salt is 1 mol / L to 2 mol / L.

3. The aqueous zinc-ion battery electrolyte according to claim 2, characterized in that, The soluble zinc salt is zinc sulfate, zinc chloride, zinc trifluoromethanesulfonate, zinc perchlorate, or zinc acetate.

4. The aqueous zinc-ion battery electrolyte according to claim 2, characterized in that, The concentration of the soluble zinc salt is 2 mol / L.

5. The aqueous zinc-ion battery electrolyte according to claim 2, characterized in that, The concentration of the perfluorooctanoic acid ammonium is 0.05 mmol / L.

6. The aqueous zinc-ion battery electrolyte according to claim 2, characterized in that, The preparation method includes the following steps: (1) Add zinc sulfate solid slowly to deionized water or ultrapure water according to the preset concentration, and stir at 20-30℃ for 1-3 hours to obtain zinc sulfate basic electrolyte; (2) Add the solid perfluorooctanoate to the zinc sulfate basic electrolyte obtained in step (1) according to the preset addition amount, and continue stirring at 20-30℃ for 2-4 hours to make the ammonium perfluorooctanoate uniformly dispersed in the basic electrolyte to obtain an aqueous zinc ion battery electrolyte.

7. An aqueous zinc-ion battery, characterized in that, It includes a negative electrode, a separator, a positive electrode, and the aqueous zinc-ion battery electrolyte as described in any one of claims 2-6.

8. The aqueous zinc-ion battery according to claim 7, characterized in that, The negative electrode active material is zinc foil, the separator is glass fiber membrane, and the positive electrode active material is titanium foil and vanadium-based oxide or manganese-based oxide.

9. The aqueous zinc-ion battery according to claim 8, characterized in that, The aqueous zinc-ion battery is a zinc-zinc symmetric battery, a zinc-copper half-cell, or a Zn-ZVO full cell.

10. The application of the aqueous zinc-ion battery electrolyte additive of claim 1 in zinc-ion batteries.

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