Zinc negative electrode with protective film as well as preparation method and application of zinc negative electrode

Abstract

The invention relates to the technical field of aqueous zinc ion batteries, in particular to a zinc negative electrode with a protective film and a preparation method and application thereof. The preparation method comprises the following steps: dissolving an organic ligand and zinc chloride in water to obtain an organic ligand solution; metal zinc is used as a positive electrode and a negative electrode respectively, an organic ligand solution is used as an electrolyte, electrolytic treatment is carried out in the electrolyte, in the electrolytic treatment process, Zn < 2 + > generated by oxidation of the negative electrode and Zn < 2 + > in the organic ligand solution jointly form a [Zn (organic ligand)] < 2 + > complex with amino and hydroxyl in organic ligand molecules, and the [Zn (organic ligand)] < 2 + > complex is obtained. And carrying out redox deposition on the [Zn (organic ligand)] < 2 + > complex on the surface of the positive electrode to form a zinc-organic ligand protective film, thereby obtaining the zinc negative electrode with the protective film. According to the preparation method disclosed by the invention, the stable zinc-organic ligand protective film is formed on the surface of the zinc negative electrode, so that the film-forming property and the interface stability of the electrolyte are remarkably improved, and the technical defects in the prior art are overcome.

Description

Technical Field

[0001] This invention relates to the field of aqueous zinc-ion battery technology, specifically to a zinc anode with a protective film, its preparation method, and its application. Background Technology

[0002] Aqueous zinc-ion batteries, as an emerging energy storage technology, have received widespread attention in recent years due to their high safety, environmental friendliness, and low cost. However, the problems of dendrite growth, hydrogen evolution through corrosion, and interfacial side reactions encountered by the zinc anode during cycling severely limit its practical application. Dendrite growth not only leads to battery short circuits but also poses safety hazards; hydrogen evolution through corrosion reduces the battery's coulombic efficiency and cycle life; and an unstable solid electrolyte interfacial film affects the transport and deposition of zinc ions, further accelerating the degradation of battery performance.

[0003] Although researchers have tried to solve these problems through electrolyte modification, negative electrode structure design, and membrane optimization, these methods often have limitations such as high cost, complex processes, or limited performance improvement, making it difficult to meet the needs of large-scale applications. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a zinc anode with a protective film, its preparation method, and its applications. This invention involves dissolving an organic ligand and zinc chloride together in water to obtain an organic ligand solution. Subsequently, metallic zinc is used as both the positive and negative electrodes, and the organic ligand solution is used as the electrolyte for electrolysis, resulting in a zinc anode with a protective film. This invention introduces an organic ligand into a traditional zinc chloride-water electrolyte, utilizing the coordination interaction between the organic ligand and zinc ions to form a stable zinc-organic ligand protective film on the zinc anode surface. This significantly improves the film-forming performance and interfacial stability of the electrolyte, overcoming the technical deficiencies of existing technologies.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The first objective of this invention is to provide a method for preparing a zinc anode with a protective film, comprising the following steps: S1. Dissolve the organic ligand in an aqueous solution of zinc chloride to obtain an organic ligand solution; wherein, zinc chloride and water form a eutectic solvent, which inhibits the activity of water, reduces side reactions, and also serves as a solvent for the organic ligand.

[0006] S2. Using metallic zinc as both the positive and negative electrodes, and an organic ligand solution as the electrolyte, electrolysis is performed in the electrolyte. During the electrolysis process, Zn is oxidized at the negative electrode. 2+ Zn in organic ligand solution 2+ Together with the amino and hydroxyl groups in the organic ligand molecule, they form [Zn (organic ligand)]. 2+Complexes, [Zn (organic ligands)] 2+ The complex is redox-deposited on the positive electrode surface to form a zinc-organic ligand protective film, resulting in a zinc negative electrode with a protective film; wherein metallic zinc is used as both the positive and negative electrodes to avoid the introduction of impurity metals.

[0007] Preferably, the organic ligand is selected from chitosan, glucosamine, serine, or ethanolamine; among them, chitosan, glucosamine, serine, and ethanolamine have good biocompatibility and environmental friendliness, are widely available, and have controllable costs; during electrolysis, they can enhance the adsorption and deposition capacity of zinc ions, thereby improving the stability and cycle performance of the zinc anode with a protective film, while also effectively inhibiting the growth of zinc dendrites and extending the battery's lifespan.

[0008] Preferably, the molar ratio of the organic ligand to zinc chloride in the aqueous solution is 1:1 to 3. This ratio range ensures that the organic ligand is fully dissolved in the acidic environment provided by zinc chloride and forms a uniform and stable protective film during electrolysis, while ensuring sufficient ionic conductivity to promote zinc ion migration. When the molar ratio of the organic ligand to zinc chloride is less than 1:1, there is too little organic ligand and too much zinc chloride; when it is greater than 1:3, there is too much organic ligand and too little zinc chloride. In such cases, the zinc anode with the protective film is difficult to form a dense structure and may crack.

[0009] Preferably, the electrolytic treatment conditions are: at 1 mA / cm 2 ~10mA / cm 2 Electrolysis for 1-2 hours; at low current densities, zinc ion migration and deposition rates are slow, and the zinc-organic ligand protective film has uneven thickness, making it difficult to block zinc dendrite growth and side reactions; above 10 mA / cm 2 When the current is too high, the water in the electrolyte undergoes electrolysis, producing a large amount of hydrogen gas, which damages the membrane structure of the zinc-organic ligand protective film.

[0010] Preferably, the thickness of the zinc-organic ligand protective film is 150nm~200nm; wherein, when the thickness of the zinc-organic ligand protective film is less than 150nm, the zinc anode with the protective film is in direct contact with the electrolyte during charging and discharging, leading to dendrite growth and hydrogen evolution side reaction; when the thickness of the zinc-organic ligand protective film is greater than 200nm, the zinc anode with the protective film is too thick, which increases the ion migration resistance, increases the battery internal resistance, and reduces the charging and discharging efficiency.

[0011] A second objective of this invention is to provide a zinc anode with a protective film prepared by the above-described method.

[0012] Preferably, the zinc-organic ligand protective film is in the form of flat nanosheets or granules, and is deposited on the zinc sheet without dendrite protrusions, and the surface roughness is reduced compared to the unprotected negative electrode.

[0013] Preferably, the zinc-organic ligand protective film comprises a network structure in which amino groups are coordinated with zinc ions and a network structure in which hydroxyl groups are coordinated with zinc ions.

[0014] The third objective of this invention is to provide an aqueous zinc-ion battery, which is made of the aforementioned zinc negative electrode with a protective film, positive electrode, electrolyte, and separator.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention provides a method for preparing a zinc anode with a protective film. An organic ligand and zinc chloride are dissolved together in water to obtain an organic ligand solution. Metallic zinc is used as both the positive and negative electrodes, and the organic ligand solution is used as the electrolyte. Electrolysis is performed in the electrolyte. During the electrolysis process, Zn generated at the negative electrode is oxidized... 2+ Zn in organic ligand solution 2+ Together with the amino and hydroxyl groups in the organic ligand molecule, they form [Zn (organic ligand)]. 2+ Complexes, [Zn (organic ligands)] 2+ The complex undergoes redox deposition on the positive electrode surface to form a zinc-organic ligand protective film, resulting in a zinc negative electrode with a protective film. This invention combines organic ligands with zinc chloride, and through a simple electroplating process, generates a zinc-organic ligand protective film in situ on the zinc negative electrode surface, thereby solving a key problem faced by traditional zinc negative electrodes.

[0016] 2. The zinc-organic ligand protective film of this invention not only effectively inhibits the growth of zinc dendrites but also reduces the occurrence of hydrogen evolution reaction during corrosion, while improving the transport and deposition behavior of zinc ions at the negative electrode interface. Furthermore, the zinc chloride-chitosan-water electrolyte system exhibits high ionic conductivity and good electrochemical stability, further enhancing the battery's rate performance and cycle life. Chitosan, as a natural polysaccharide, possesses advantages such as environmental friendliness, low cost, and biocompatibility. Its amino and hydroxyl groups can coordinate with zinc ions to form stable coordination bonds, generating a uniform and dense zinc-organic ligand protective film on the zinc negative electrode surface.

[0017] 3. The preparation method of the present invention is not only simple and inexpensive, but also suitable for large-scale production. Attached Figure Description

[0018] Figure 1 The infrared spectra of the zinc anode with a protective film in Example 1 of the present invention, the organic ligand solution in Example 1, chitosan, and zinc chloride are shown.

[0019] Figure 2The images show SEM images of the zinc anode with a protective film and the zinc foil of Example 1, where a is the SEM image of the zinc foil and b is the SEM image of the zinc anode with a protective film of Example 1.

[0020] Figure 3 This is a comparison chart of the corrosion rates of the zinc negative electrode with a protective film and the zinc foil in Example 1.

[0021] Figure 4 This is a comparison diagram of the hydrogen evolution performance of the zinc negative electrode with protective film and the zinc foil in Example 1. Detailed Implementation

[0022] The technical solution of the present invention will be clearly and completely described below with reference to the data in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0023] It should be noted that the technical terms used in this invention are only for the purpose of describing specific embodiments 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 on the market or prepared by existing methods.

[0024] In existing technologies, although attempts have been made to improve the performance of zinc anodes through electrolyte modification, anode structure design, and membrane optimization, these methods generally suffer from high costs, complex processes, or limited performance improvements, making it difficult to meet the needs of large-scale applications.

[0025] To address the problems existing in the prior art, this invention provides a method for preparing a zinc anode with a protective film, comprising the following steps: dissolving an organic ligand and zinc chloride together in water to obtain an organic ligand solution; using metallic zinc as both the positive and negative electrodes, and the organic ligand solution as the electrolyte, performing electrolysis in the electrolyte; during the electrolysis process, the Zn generated by the oxidation of the negative electrode... 2+ Zn in organic ligand solution 2+ Together with the amino and hydroxyl groups in the organic ligand molecule, they form [Zn (organic ligand)]. 2+ Complexes, [Zn (organic ligands)] 2+ The complex is redox deposited on the positive electrode surface to obtain a zinc negative electrode with a protective film.

[0026] The amino and hydroxyl groups in the organic ligand can coordinate with zinc ions in zinc chloride to form [Zn(organic ligand)]. 2+The complex enhances the stability of the membrane, and the hydroxyl groups in its molecular structure can adsorb water molecules in the electrolyte, reducing the moisture on the zinc anode surface and inhibiting zinc corrosion and side reactions. The amino and hydroxyl groups of serine form a coordination structure with zinc ions, which not only enhances the binding force between the membrane and the zinc anode, but also regulates the migration path of zinc ions, achieving uniform deposition, reducing the hydrogen evolution reaction of zinc, and improving the deposition / dissolution efficiency of zinc. Ethanolamine coordinates with zinc ions through its amino and hydroxyl groups, has good ion conductivity, reduces interfacial impedance, and at the same time prevents water from directly contacting the zinc anode, inhibiting the occurrence of side reactions.

[0027] This invention utilizes the coordination of amino and hydroxyl groups in chitosan molecules with zinc ions to form a three-dimensional network, uniformly guiding zinc deposition and thus inhibiting dendrite formation; the coordination network simultaneously consumes H+ in the electrolyte. + This technology stabilizes the interface pH and inhibits hydrogen evolution due to corrosion; polar groups reconstruct the zinc ion solvation layer, reducing side reactions initiated by water molecules; and the resulting composite interface broadens the electrolyte stability window. The raw materials used in this technology are biodegradable, significantly reducing costs while maintaining excellent electrochemical performance, thus achieving a balance between high performance and environmental friendliness.

[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 negative electrode with a protective film includes the following steps: S1. Dissolve 136.28g of zinc chloride in 36mL of deionized water to obtain an aqueous solution of zinc chloride; weigh 0.161g of chitosan and dissolve it in 10mL of zinc chloride aqueous solution to prepare a 0.1mol / L organic ligand solution, i.e., a 0.1mol / L chitosan solution.

[0029] S2. An electrolytic cell was assembled using a zinc block as the negative electrode, zinc foil as the positive electrode, and a 0.1 mol / L chitosan solution as the electrolyte. A current density of 5 mA / cm² was applied. 2 The current was applied, and the reaction was carried out for 1 hour. After the reaction was completed, the positive electrode zinc foil was removed, cleaned and dried to obtain a zinc-chitosan modified zinc negative electrode, that is, a zinc negative electrode with a protective film with a thickness of 170 nm.

[0030] Example 2 A method for preparing a zinc negative electrode with a protective film includes the following steps: S1. Dissolve 136.28g of zinc chloride in 36mL of deionized water to obtain an aqueous solution of zinc chloride; weigh 0.322g of chitosan and dissolve it in 10mL of the aqueous solution of zinc chloride to prepare a 0.2mol / L organic ligand solution, i.e., a 0.2mol / L chitosan solution.

[0031] S2. An electrolytic cell was assembled using a zinc block as the negative electrode, zinc foil as the positive electrode, and a 0.2 mol / L chitosan solution as the electrolyte. A current density of 5 mA / cm² was applied. 2 The current was applied, and the reaction was carried out for 1 hour. After the reaction was completed, the positive electrode zinc foil was removed, cleaned and dried to obtain a zinc-chitosan modified zinc negative electrode, that is, a zinc negative electrode with a protective film with a thickness of 150 nm.

[0032] Example 3 A method for preparing a zinc negative electrode with a protective film includes the following steps: S1. Dissolve 136.28g of zinc chloride in 36mL of deionized water to obtain an aqueous solution of zinc chloride; weigh 0.483g of chitosan and dissolve it in 10mL of zinc chloride aqueous solution to prepare a 0.3mol / L organic ligand solution, i.e., a 0.3mol / L chitosan solution.

[0033] S2. An electrolytic cell was assembled using a zinc block as the negative electrode, zinc foil as the positive electrode, and a 0.3 mol / L chitosan solution as the electrolyte. A current density of 5 mA / cm² was applied. 2 The current was applied, and the reaction was carried out for 1 hour. After the reaction was completed, the positive electrode zinc foil was removed, cleaned and dried to obtain a zinc-chitosan modified zinc negative electrode, that is, a zinc negative electrode with a protective film with a thickness of 160 nm.

[0034] Example 4 A method for preparing a zinc anode with a protective film is the same as the preparation method in Example 1, except that the chitosan in S1 is replaced with glucosamine, and includes the following steps: S1. Dissolve 136.28g of zinc chloride in 36mL of deionized water to obtain an aqueous solution of zinc chloride; weigh 0.18g of glucosamine and dissolve it in 10mL of zinc chloride aqueous solution to prepare a 0.1mol / L organic ligand solution, i.e., a 0.1mol / L glucosamine solution.

[0035] S2. Assemble an electrolytic cell using a zinc block as the negative electrode, zinc foil as the positive electrode, and a 0.1 mol / L glucosamine solution as the electrolyte, and apply a current density of 5 mA / cm². 2 The current was applied, and the reaction was carried out for 1 hour. After the reaction was completed, the positive electrode zinc foil was removed, cleaned and dried to obtain a zinc anode modified with zinc-glucosamine, that is, a zinc anode with a protective film with a thickness of 169 nm.

[0036] Example 5 A method for preparing a zinc anode with a protective film is the same as the preparation method in Example 1, except that chitosan in S1 is replaced with serine, and includes the following steps: S1. Dissolve 136.28g of zinc chloride in 36mL of deionized water to obtain an aqueous solution of zinc chloride; weigh 0.105g of serine and dissolve it in 10mL of the aqueous solution of zinc chloride to prepare a 0.1mol / L organic ligand solution, i.e., a 0.1mol / L serine solution.

[0037] S2. An electrolytic cell was assembled using a zinc block as the negative electrode, zinc foil as the positive electrode, and a 0.1 mol / L serine solution as the electrolyte. A current density of 5 mA / cm² was applied. 2 The current was applied, and the reaction was carried out for 1 hour. After the reaction was completed, the positive electrode zinc foil was removed, cleaned and dried to obtain a zinc-serine modified zinc negative electrode, that is, a zinc negative electrode with a protective film with a thickness of 182 nm.

[0038] Example 6 A method for preparing a zinc anode with a protective film is the same as the preparation method in Example 1, except that chitosan in S1 is replaced with ethanolamine, and includes the following steps: S1. Dissolve 136.28g of zinc chloride in 36mL of deionized water to obtain an aqueous solution of zinc chloride; weigh 0.061g of ethanolamine and dissolve it in the aqueous solution of zinc chloride to prepare a 0.1mol / L organic ligand solution, i.e., a 0.1mol / L ethanolamine solution.

[0039] S2. Assemble an electrolytic cell using a zinc block as the negative electrode, zinc foil as the positive electrode, and a 0.1 mol / L ethanolamine solution as the electrolyte, and apply a current density of 5 mA / cm². 2 The current was applied, and the reaction was carried out for 1 hour. After the reaction was completed, the positive electrode zinc foil was removed, cleaned and dried to obtain a zinc anode modified with zinc-ethanolamine, that is, a zinc anode with a protective film with a thickness of 195 nm.

[0040] Comparative Example 1 ZnCl and H2O were mixed at a molar ratio of 1:3 and heated in an oil bath at 80°C for 5 hours. After standing, 0.1 g of chitosan was added and the mixture was stirred at room temperature until the solution became clear. When the molar ratio of ZnCl to H2O was 1:3, the water content was too high, and the hydrogen evolution side reaction was violent during electrolysis, making it impossible to form a zinc anode with a protective film.

[0041] Examples 1 to 6 of this invention yielded zinc anodes with protective films, and the results were parallel. The performance of the zinc anode with a protective film obtained in Example 1 is studied below as an example: observe Figure 1The results showed that the infrared spectrum of the zinc anode with a protective film in Example 1 exhibited significant changes within a specific wavenumber range, indicating that chitosan and ZnCl2 interacted in the aqueous solution of zinc chloride, forming new chemical bonds or structures. In particular, the infrared spectral characteristics of the zinc-organic ligand protective film differed significantly from those of chitosan or zinc chloride, confirming that the electrochemical method, at a current density of 5 mA / cm², could achieve the desired effect. 2 Under these conditions, a zinc anode with a protective film was successfully prepared.

[0042] observe Figure 2 It was found that the zinc anode with protective film in Example 1 has a flat nanosheet-like deposited layer with no significant dendrite protrusions. Compared to zinc foil, the surface roughness of the zinc anode with protective film in Example 1 is reduced.

[0043] Test method: The Tafel testing technique was employed: platinum was used as the working electrode, and a zinc anode with a protective film and zinc foil were used as counter electrodes, respectively. The working and counter electrodes were fixed to an electrode holder, ensuring good electrical conductivity with the lead wire. The other end was placed in a 2 mol / L zinc trifluoromethanesulfonate solution for electrochemical testing. The test systems using the zinc anode with a protective film and zinc foil as counter electrodes were designated as protective film-platinum-zinc trifluoromethanesulfonate and zinc-platinum-zinc trifluoromethanesulfonate, respectively. The test conditions were: scan voltage of -1V to 3V and scan rate of 1mV / s. Among them, the protective film-platinum-zinc trifluoromethanesulfonate underwent three Tafel tests, and was designated as protective film-platinum-zinc trifluoromethanesulfonate-1, protective film-platinum-zinc trifluoromethanesulfonate-2, and protective film-platinum-zinc trifluoromethanesulfonate-3, respectively; the zinc-platinum-zinc trifluoromethanesulfonate underwent four Tafel tests, and was designated as zinc-platinum-zinc trifluoromethanesulfonate-1, zinc-platinum-zinc trifluoromethanesulfonate-2, zinc-platinum-zinc trifluoromethanesulfonate-3, and zinc-platinum-zinc trifluoromethanesulfonate-4, respectively.

[0044] observe Figure 3 It was found that as the current density increases (i.e., increases negatively), the voltage change is gradual and without drastic fluctuations. Compared to the zinc anode, the zinc anode with a protective film of the present invention exhibits a higher corrosion potential, indicating that its corrosion rate is significantly reduced. This further demonstrates that the zinc-organic ligand protective film can effectively regulate the zinc deposition and dissolution process, inhibit dendrite growth and side reactions, thereby improving the cycle stability and reversibility of the zinc anode with the protective film.

[0045] Test method: Linear scanning voltammetry: Platinum was used as the working electrode, and zinc negative electrode with protective film and zinc foil from Example 1 were used as counter electrodes. The working electrode and counter electrode were fixed to the electrode holder to ensure good conductive connection with the wire. The other end was placed in a 4 mol / L lithium sulfate solution. The scanning range was 3V to -2V, scanning from positive to negative, and the scanning rate was 1mV / s for electrochemical testing.

[0046] observe Figure 4 The results show that, within the range of -0.876V to -0.852V, compared to the zinc anode, the zinc anode with a protective film of the present invention exhibits a higher and more stable hydrogen evolution overpotential, indicating that its hydrogen evolution side reaction is significantly suppressed. At the same time, the zinc anode with a protective film of the present invention exhibits a more stable voltage plateau, indicating that it can effectively suppress zinc dendrite growth and side reactions, and improve the cycle stability of the zinc anode with a protective film.

[0047] 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.

[0048] 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. A method for producing a zinc negative electrode having a protective film, characterized by, The method comprises the following steps: The organic ligand is dissolved in the aqueous solution of zinc chloride to obtain an organic ligand solution; Zinc metal is used as the positive and negative electrodes, and an organic ligand solution is used as the electrolyte. During electrolysis, Zn 2+ and Zn 2+ in the organic ligand solution are oxidized to form [Zn(organic ligand)] 2+ complexes with the amino and hydroxyl groups in the organic ligand molecules. The [Zn(organic ligand)] 2+ complexes are redox deposited on the surface of the positive electrode to form a zinc-organic ligand protective film, and a zinc negative electrode with the protective film is obtained.

2. The method for producing a zinc negative electrode with a protective film according to claim 1, characterized by, The organic ligand is selected from chitosan, glucosamine, serine or ethanolamine.

3. The method for producing a zinc negative electrode with a protective film according to claim 1, characterized by, The molar ratio of the organic ligand to zinc chloride in the aqueous solution of zinc chloride is 1:1-3.

4. The method for producing a zinc negative electrode with a protective film according to claim 1, characterized by, The conditions for the electrolysis treatment were: at 1 mA / cm 2 ~10 mA / cm 2 The electrolysis was applied for 1 h~2 h.

5. The method of producing a zinc negative electrode with a protective film according to claim 1, characterized by, The thickness of the zinc-organic ligand protective film is 150-200 nm.

6. A zinc negative electrode with a protective film, characterized by, The zinc negative electrode with the protective film is prepared by the preparation method in any one of claims 1-5.

7. The zinc negative electrode with a protective film according to claim 6, characterized in that, In the zinc negative electrode with the protective film, the zinc-organic ligand protective film presents flat nanosheet or granular shape and is stacked on the zinc sheet without dendrite protrusion.

8. The zinc negative electrode with a protective film according to claim 7, characterized in that, The zinc-organic ligand protective film comprises a network structure of amino groups coordinated with zinc ions and a network structure of hydroxyl groups coordinated with zinc ions.

9. An aqueous zinc-ion battery, characterized in that, The aqueous zinc ion battery is prepared from the zinc negative electrode with the protective film, the positive electrode, the electrolyte and the separator according to claim 6.

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