A zinc electrode modified by an in-situ grown passivation film coating, a preparation method thereof, and an application thereof

Abstract

The present invention provides a zinc electrode modified with an in-situ grown passivation film coating, a preparation method thereof and an application thereof, belonging to the technical field of zinc electrode materials. The preparation method provided by the present invention is to immerse zinc in an ammonia aqueous solution, and then wash and dry it to obtain the zinc electrode modified with the in-situ grown passivation film coating. The method provided by the present invention is simple and convenient. The zinc electrode modified with the in-situ grown passivation film coating can be used to assemble a zinc ion battery and a zinc ion capacitor. By comparing other alkaline solutions, as well as the concentration and time of treatment, it can be seen that the symmetrical battery assembled with the zinc electrode obtained from the ammonia water concentration and treatment time provided by the present invention has higher stability and better cycle stability in the application of zinc ion capacitors.

Description

Technical Field

[0001] The present invention relates to the technical field of zinc electrode materials, and particularly to a zinc electrode modified with an in-situ grown passivation film coating, a preparation method thereof, and an application thereof. Background Art

[0002] Supercapacitors are considered to be one of the attractive devices due to their high power density, fast charge and discharge rates, long life, and high safety. However, the energy density of traditional aqueous supercapacitors, especially electric double layer capacitors, is difficult to meet the requirements of electronics. To break and solve this bottleneck, hybrid supercapacitors have been constructed due to the combination of high-energy batteries and high-power supercapacitors. In the past few decades, lithium-ion hybrid supercapacitors have been one of the promising candidates for energy storage. However, the low abundance and uneven distribution of lithium resources on the earth have greatly hindered the further practical application of lithium-ion hybrid supercapacitors. [Zhiwei Li, Yufeng An, Shengyang Dong, Chaojie Chen, Langyuan Wu, Yao Sun, Xiaogang Zhang, Energy Storage Materials 31(2020)252-266.]

[0003] The ionic radius of zinc ions and the mechanism of the ion insertion process are similar to those of lithium ions. More importantly, Zn metal as an anode has a high theoretical capacity of 820 mA h g -1 , a low redox potential of -0.76 V (relative to the standard hydrogen electrode, SHE), a high natural abundance, and an easy operating environment, which greatly reduces the cost. However, the zinc negative electrode still faces three bottleneck problems: dendrite growth, hydrogen evolution reaction, and surface passivation. In the initial stage of capacitor cycling, zinc ions are usually reduced at the energetically favorable charge transfer sites on the negative electrode surface to form small zinc bumps. Due to the lower surface energy, zinc ions tend to aggregate on these bumps to form initial dendrites. The "tip effect" of dendrites enhances the local electric field, further promoting the growth of surface dendrites. When the dendrites grow to a large volume, they will pierce the separator, resulting in a decline in battery performance. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a zinc electrode modified with an in-situ grown passivation film coating, a preparation method thereof, and an application thereof. The present invention realizes the construction of a passivation film through simple immersion of a solution, and further realizes the preparation of a zinc electrode with long cycle life and high life.

[0005] To achieve the above object, the present invention provides the following technical solutions: A preparation method of a zinc electrode modified with an in-situ grown passivation film coating, wherein zinc is immersed in an ammonia aqueous solution, and then washed and dried to obtain the zinc electrode modified with the in-situ grown passivation film coating.

[0006] In some embodiments, before immersing zinc in the ammonia aqueous solution, it further includes a step of pre-treating zinc; the pre-treatment is: grinding and cleaning zinc.

[0007] In some embodiments, the mass concentration of the ammonia aqueous solution is 25-40%, preferably 28-30%; the immersion time is 1-4 h.

[0008] In some embodiments, the solution used for washing is anhydrous ethanol.

[0009] In some embodiments, the drying temperature is 60-70 °C; the drying is carried out in an atmosphere containing oxygen.

[0010] In the present invention, the reaction process of in-situ growing a passivation film coating on the zinc surface is as follows:

[0011] Zn + 4NH₃·H₂O → Zn[(NH₃)₄] 2+ + 4H₂O

[0012] Zn[(NH₃)₄] 2+ + O₂ → ZnO + 4NH₃

[0013] In the present invention, first, the surface of the zinc foil is corroded by the NH₃·H₂O solution to expose more active sites, then the surface residual liquid is removed by rinsing with anhydrous ethanol. After that, it is easy to contact with oxygen during the drying process, and a thin and uniform passivation film modification coating is easily formed on the surface after the corrosion effect.

[0014] The present invention also provides a zinc electrode modified with an in-situ grown passivation film coating prepared by the above preparation method.

[0015] The present invention also provides the application of the zinc electrode modified with the in-situ grown passivation film coating in a zinc ion battery or a zinc ion capacitor.

[0016] The present invention also provides a zinc ion battery, the negative electrode material of which is the zinc electrode modified with the in-situ grown passivation film coating.

[0017] In some embodiments, the zinc ion battery is a symmetric battery or an asymmetric battery. When assembling a symmetric battery, the zinc electrode modified with the in-situ grown passivation film coating serves as both the positive and negative electrodes of the battery, using glass fiber as the separator, and adding 2M ZnSO₄ electrolyte when assembling the symmetric battery;

[0018] When assembling asymmetric batteries (such as Zn-I2 batteries, Zn-Br2 batteries, Zn-MnO2 batteries, Zn-V2O5 batteries, Zn-PBA batteries, etc.), the carbon paper electrode coated with I2, Br2, MnO2, V2O5, PBA, etc. serves as the positive electrode of the battery, and the zinc electrode modified with the in-situ grown passivation film coating serves as the negative electrode of the battery. Glass fiber is used as the separator, and 2M ZnSO4 electrolyte is added dropwise when assembling the battery.

[0019] The present invention also provides a zinc ion capacitor, and the negative electrode material is the zinc electrode modified with the in-situ grown passivation film coating.

[0020] In some embodiments, in the zinc ion capacitor, the carbon paper electrode coated with activated carbon serves as the positive electrode, the zinc electrode modified with the in-situ grown passivation film coating serves as the negative electrode, glass fiber is used as the separator, and 2M ZnSO4 electrolyte is added dropwise when assembling the zinc ion capacitor.

[0021] The present invention discloses the following technical effects:

[0022] The present invention provides a preparation method of a zinc electrode modified with an in-situ grown passivation film coating. The formation of the passivation film layer can be achieved only by soaking and rinsing in an ammonia water solution. The present invention avoids the complex methods for surface modification of common zinc electrodes, and does not require complex coating processes and a series of complex hydrothermal methods to in-situ grow other substances on the surface. The method for modifying the zinc electrode in the present invention is simple and convenient, greatly reducing the production cost and the high requirements for equipment.

[0023] The passivation film formed in the present invention is more uniform, and the passivation film formed within the concentration range provided by the present invention is thinner. While playing a role, it is not easy to affect the zinc ion migration and stripping processes. It can effectively avoid the direct contact between zinc and the electrolyte, thereby preventing hydrogen evolution and corrosion reactions, and effectively improving the cycle life of the zinc ion capacitor.

[0024] By comparing other alkaline solutions, as well as the treatment concentration and time, it can be seen that the symmetric battery assembled with the zinc electrode having the ammonia water concentration and treatment time provided by the present invention has higher stability at a high current density, and has better cycle stability in the application of zinc ion capacitors.

[0025] The electrode material provided by the present invention exhibits excellent electrochemical performance. The zinc foil treated with NH3·H2O as the electrode material to assemble a symmetric battery can stably charge and discharge for more than 2300 h at a current density of 60 mA cm -2 and a capacity of 10 mAh cm -2 while maintaining a low charge-discharge voltage. The zinc ion capacitor assembled by matching this electrode with AC can reach 8 A g -1At a high current density, maintaining a discharge specific capacity of 32 mAh g -1 or more, and the capacity does not decay during 10,000 stable charge-discharge cycles. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0027] Figure 1 SEM images of the zinc electrode modified with the passivation film coating prepared in Example 1 of the present invention at different scales, where a is at a scale of 5 μm and b is at a scale of 1 μm;

[0028] Figure 2 X-ray diffraction (XRD) pattern of the zinc electrode modified with the passivation film coating prepared in Example 1 of the present invention;

[0029] Figure 3 HRTEM image (a) and SEAD image (b) of the zinc electrode modified with the passivation film coating prepared in Example 1 of the present invention;

[0030] Figure 4 SEM images of the zinc-ion capacitors assembled with the zinc electrode modified with the passivation film coating prepared in Example 1 of the present invention and the pure zinc foil electrode of Comparative Example 4 and the AC positive electrode after cycling 50 times at a current density of 2 A g -1 where a is the zinc-ion capacitor assembled with the zinc electrode modified with the passivation film coating prepared in Example 1 at a scale of 50 μm, b is the zinc-ion capacitor assembled with the zinc electrode modified with the passivation film coating prepared in Example 1 at a scale of 10 μm, c is the zinc-ion capacitor assembled with the pure zinc foil electrode of Comparative Example 4 and the AC positive electrode at a scale of 50 μm, and d is the zinc-ion capacitor assembled with the pure zinc foil electrode of Comparative Example 4 and the AC positive electrode at a scale of 10 μm;

[0031] Figure 5 Charge-discharge comparison diagrams of the symmetric cells assembled with the zinc electrode modified with the passivation film coating prepared by treating with ammonia water in Example 1 of the present invention and the zinc electrode treated with sodium hydroxide alkaline solution in Comparative Example 1 at a current density of 60 mA cm –2 and a capacity of 10 mAh cm –2 where a is the symmetric cell assembled with the zinc electrode modified with the passivation film coating prepared by treating with ammonia water in Example 1, and b is the symmetric cell assembled with the zinc electrode treated with sodium hydroxide alkaline solution in Comparative Example 1;

[0032] Figure 6 Charge-discharge comparison diagrams of symmetrical cells assembled with the passivation film-coated zinc electrode prepared by treating with ammonia water in Example 1 of the present invention, the zinc electrode treated with sodium hydroxide alkaline solution in Comparative Example 1, and the pure zinc foil electrode prepared in Comparative Example 4 at a current density of 20 mA cm –2 and a capacity of 0.5 mAh cm –2 ; among them, a is the symmetrical cell assembled with the zinc electrode prepared by treating with ammonia water in Example 1 and the zinc electrode treated with sodium hydroxide alkaline solution in Comparative Example 1, and b is the symmetrical cell assembled with the zinc electrode prepared by treating with ammonia water in Example 1 and the pure zinc foil electrode in Comparative Example 4;

[0033] Figure 7 Charge-discharge diagrams of symmetrical cells assembled with the zinc electrode prepared by treating with 28 wt% ammonia water for 1 h in Example 1 of the present invention, the zinc electrode prepared by treating with 5 wt% ammonia water for 1 h in Comparative Example 2, and the zinc electrode prepared by treating with 28 wt% ammonia water for 5 h in Comparative Example 3 at a current density of 20 mA cm –2 and a capacity of 0.5 mAh cm –2 ; among them, a is the zinc electrode treated with different ammonia water concentrations, and b is the zinc electrode treated with the same concentration of ammonia water for different times;

[0034] Figure 8 Rate performance comparison diagram of symmetrical cells assembled with the passivation film-coated zinc electrode prepared in Example 1 of the present invention and the pure zinc foil electrode in Comparative Example 4;

[0035] Figure 9 Comparison diagram of Tafel tests of the passivation film-coated zinc electrode prepared in Example 1 of the present invention and the pure zinc foil electrode in Comparative Example 4 using a three-electrode system in 1 M Na2SO4 solution;

[0036] Figure 10 Rate diagram of zinc ion capacitors assembled by matching the passivation film-coated zinc electrode prepared in Example 1 of the present invention and the pure zinc foil electrode in Comparative Example 4 with AC; among them, a is the passivation film-coated zinc electrode prepared in Example 1, and b is the pure zinc foil electrode in Comparative Example 4;

[0037] Figure 11 Charge-discharge cycle diagram of zinc ion capacitors assembled by matching the passivation film-coated zinc electrode prepared in Example 1 of the present invention and the pure zinc foil electrode in Comparative Example 4 with AC at a current density of 2 A g –1 ; among them, a is the zinc ion capacitor assembled by matching the passivation film-coated zinc electrode prepared in Example 1 with AC, and b is the zinc ion capacitor assembled by matching the pure zinc foil electrode in Comparative Example 4 with AC;

[0038] Figure 12The zinc electrode modified with the passivation film coating prepared in Example 1 of the present invention and the pure zinc foil electrode of Comparative Example 4 were respectively assembled with AC to form zinc ion capacitors at a current density of 8 A g –1 Charge-discharge cycling diagrams at a current density, where a is the zinc ion capacitor assembled by matching the zinc electrode modified with the passivation film coating prepared in Example 1 with AC, and b is the zinc ion capacitor assembled by matching the pure zinc foil electrode of Comparative Example 4 with AC. Detailed implementation manners

[0039] The various exemplary implementation manners of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention.

[0040] It should be understood that the terms used in the present invention are only for describing specific implementation manners and are not used to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0041] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0042] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific implementation manners of the present invention specification, which are obvious to those skilled in the art. Other implementation manners obtained from the present invention specification are obvious to those skilled in the art. The present invention specification and examples are only exemplary.

[0043] Regarding the terms "comprising", "including", "having", "containing", etc. used herein, they are all open-ended terms, meaning including but not limited to.

[0044] To better understand the present invention, the content of the present invention will be further clarified below in conjunction with examples, but the content of the present invention is not limited to the following examples only.

[0045] Unless otherwise specified, the reagents used in the examples can all be obtained through commercial channels.

[0046] Example 1

[0047] The preparation method of the zinc electrode modified with the in-situ grown passivation film coating in this example is as follows:

[0048] Use sandpapers with 600 meshes and 3000 meshes to polish a zinc foil with a size of 100 cm×20 cm and a thickness of 0.1 nm respectively. Then use a cutting machine to cut it into small round pieces with a diameter of 0.1 cm as the samples for large-scale treatment in Example 1. Subsequently, take a certain amount of 28wt% NH₃·H₂O solution in a watch glass (the amount of ammonia water is sufficient to completely immerse the zinc foil), immerse the treated zinc foil in the solution, take it out after 1 h, then wash it 3 times with absolute ethanol, and finally put it in a blast drying oven at 60 °C for drying to obtain the zinc electrode modified with the in-situ grown passivation film coating.

[0049] Comparative Example 1

[0050] The preparation method of the zinc electrode in this comparative example is as follows:

[0051] Use sandpapers with 600 meshes and 3000 meshes to polish a zinc foil with a size of 100 cm×20 cm and a thickness of 0.1 nm respectively. Then use a cutting machine to cut it into small round pieces with a diameter of 0.1 cm as the samples for large-scale treatment in Example 1. Subsequently, take a certain amount of 8M NaOH solution in a watch glass (the amount of NaOH solution is sufficient to completely immerse the zinc foil), immerse the treated zinc foil in the solution, take it out after 1.5 min, then continuously rinse it with deionized water for 2 min, and finally put it in a vacuum oven at 60 °C for drying to obtain the zinc electrode.

[0052] Comparative Example 2

[0053] The preparation method of the zinc electrode in this comparative example is the same as that in Example 1, except that the 28wt% NH₃·H₂O solution is replaced with a 5wt% NH₃·H₂O solution.

[0054] Comparative Example 3

[0055] The preparation method of the zinc electrode in this comparative example is the same as that in Example 1, except that the soaking time of the zinc foil in the solution is replaced from 1 h to 5 h.

[0056] Comparative Example 4

[0057] The preparation method of the zinc electrode in this comparative example is the same as that in Example 1, except that the step of soaking the zinc foil in the NH₃·H₂O solution is omitted.

[0058] Effect Test Example

[0059] The zinc electrodes obtained in Example 1 and Comparative Examples 1-4 were respectively assembled into zinc-ion batteries and capacitors, and their electrochemical performance was tested.

[0060] Preparation of activated carbon AC positive electrode sheet: Specifically, activated carbon, conductive acetylene black, and PVDF were mixed evenly in a ratio of 8:1:1, and NMP was used as the solvent to form a uniform slurry, which was coated on the surface of carbon paper. The electrode was placed in a vacuum oven at 60 °C and dried for 12 h to obtain the positive electrode material (AC). The carbon paper before and after coating was weighed respectively, and the mass difference between the two was the loading of the coated substance. It can be calculated that the activated carbon loading on each electrode sheet was about 2 mg.

[0061] When assembling a symmetric battery, the activated carbon AC electrode sheet was used as the positive electrode, and the zinc electrode modified with the in-situ grown passivation film coating prepared in Example 1 was used as the negative electrode. An appropriate amount of 2M ZnSO4 electrolyte was added dropwise, and glass fiber was used as the separator. The electrochemical performance of the assembled symmetric battery was tested.

[0062] When assembling a zinc-ion capacitor, the activated carbon AC electrode sheet was used as the positive electrode of the capacitor, and the zinc electrode modified with the in-situ grown passivation film coating prepared in Example 1 was used as the negative electrode. An appropriate amount of 2M ZnSO4 electrolyte was added dropwise, and glass fiber was used as the separator. The electrochemical performance of the assembled zinc-ion capacitor was tested.

[0063] The SEM images of the surface of the zinc electrode obtained in Example 1 are as Figure 1 shown. Figure 1 In a and b, they are the SEM images of the surface of the passivation film-coated zinc electrode under the scales of 5 μm and 1 μm respectively. It can be seen that the passivation film coating was successfully prepared, and a thin separator was formed on the surface of the zinc foil to prevent direct contact between the electrolyte and the zinc foil.

[0064] Figure 2 It is the X-ray diffraction (XRD) pattern of the zinc electrode prepared in Example 1. Figure 2 The three curves in it are respectively the XRD patterns of ZnO@Zn (i.e., ZnO-Zn in the figure), the standard PDF card of zinc, and the standard PDF card of zinc oxide. It can be concluded from the XRD pattern that the passivation film coating was successfully prepared, and the main component of the passivation film was zinc oxide.

[0065] Figure 3 It is the high-resolution transmission electron microscopy (HRTEM) image (a) and selected area electron diffraction (SEAD) image (b) of the passivation film scraped from the surface of the zinc electrode prepared in Example 1. Obvious lattice fringes can be seen in the electron microscopy image, and the selected area electron diffraction shows symmetric spots, indicating that the main component of the prepared passivation film coating was zinc oxide.

[0066] Figure 4The SEM images of the zinc-ion capacitors assembled with the zinc electrodes prepared in Example 1 and the pure zinc foil electrodes in Comparative Example 4 and the AC positive electrode after cycling 50 times at a current density of 2 Ag -1 are shown in Figure 4 . In -1 , a and b are the SEM images of the ZnO@Zn-AC capacitor after cycling 50 times at a current density of 2 Ag -1 ; c and d are the SEM images of the Zn-AC capacitor after cycling 50 times at a current density of 2 Ag -1 . It can be seen that only a small amount of zinc dendrites on the surface of the zinc electrode modified with the passivation film coating grow vertically, while almost all the dendrites on the surface of the zinc foil grow perpendicular to the surface of the zinc foil. This shows that the zinc electrode modified with the passivation film coating can inhibit the vertical growth of zinc dendrites along the electrode surface, thereby reducing the possibility of zinc dendrites piercing the separator and improving the cycling stability of the electrode.

[0067] Figure 5 The charge-discharge curves of the symmetrical cells assembled with the zinc electrodes prepared by treating with ammonia water in Example 1 and the zinc electrodes prepared by treating with sodium hydroxide solution in Comparative Example 1 at a current density of 60 mA cm -2 and a capacity of 10 mAh cm -2 are shown in Figure 5 . In , a is the charge-discharge curve of the symmetrical cell assembled with the zinc electrode in Example 1 at a current density of 60 mA cm -2 and a capacity of 10 mAh cm -2 , and b is the charge-discharge curve of the symmetrical cell assembled with the zinc electrode in Comparative Example 1 at a current density of 60 mA cm -2 and a capacity of 10 mAh cm -2 . It can be seen from Figure 5 that at a large current density of 60 mA cm -2 and a capacity of 10 mAh cm -2 , the symmetrical cell assembled with the zinc electrode treated with ammonia water has better stability than that treated with sodium hydroxide, and can cycle for 2300 h at a large current density with a lower overpotential. While the symmetrical cell assembled with the zinc electrode treated with sodium hydroxide can only cycle for 150 h and is prone to short circuit.

[0068] Figure 6 The charge-discharge comparison curves of the symmetrical cells assembled with the zinc electrodes prepared by treating with ammonia water in Example 1, the zinc electrodes prepared by treating with sodium hydroxide solution in Comparative Example 1, and the pure zinc foil electrodes in Comparative Example 4 at a current density of 20 mA cm -2 and a capacity of 0.5 mAh cm -2 are shown in Figure 6Among them, a is the charge-discharge comparison diagram of symmetric batteries assembled with zinc electrodes prepared by ammonia water treatment in Example 1 and zinc electrodes treated with sodium hydroxide alkaline solution in Comparative Example 1 at a current density of 20 mA cm -2 and a capacity of 0.5 mAh cm -2 . b is the charge-discharge comparison diagram of symmetric batteries assembled with zinc electrodes prepared by ammonia water treatment in Example 1 and pure zinc foil electrodes in Comparative Example 4 at a current density of 20 mA cm -2 and a capacity of 0.5 mAh cm -2 . It can be seen from Figure 6 that the symmetric battery assembled with the zinc electrode treated with ammonia water has a more stable voltage at a relatively small current density compared with the zinc electrode treated with sodium hydroxide and the untreated zinc electrode, and can maintain a lower overpotential after 5000 cycles.

[0069] Figure 7 are the charge-discharge diagrams of symmetric batteries assembled with zinc electrodes prepared by treating with 28 wt% NH₃·H₂O for 1 h in Example 1, zinc electrodes prepared by treating with 5 wt% NH₃·H₂O for 1 h in Comparative Example 2, and zinc electrodes prepared by treating with 28 wt% NH₃·H₂O for 5 h in Comparative Example 3 at a current density of 20 mA cm -2 and a capacity of 0.5 mAh cm -2 . Figure 7 Among them, a is the charge-discharge comparison diagram of symmetric batteries with zinc electrodes treated with different ammonia water concentrations at a current density of 20 mA cm -2 and a capacity of 0.5 mAh cm -2 . b is the charge-discharge comparison diagram of symmetric batteries with zinc electrodes treated with the same concentration of ammonia water for different times at a current density of 20 mA cm -2 and a capacity of 0.5 mAh cm -2 . It can be found from the comparison diagrams a and b in Figure 7 that the symmetric battery assembled with the zinc electrode prepared with the specific ammonia water concentration and time selected in Example 1 of the present invention has better cycle stability and a lower overpotential. Therefore, the ammonia water concentration and time in the present invention are the optimal selection ranges for improving the performance of zinc electrodes.

[0070] Figure 8 is the comparison diagram of the rate performance of symmetric batteries assembled with the zinc electrode prepared in Example 1 and the pure zinc foil electrode in Comparative Example 4 (ZnO@Zn in the figure represents Example 1, and Zn represents Comparative Example 4). It can be seen from Figure 8It can be seen that the passivation film-coated zinc electrode has a smaller nucleation overpotential and a lower polarization potential compared with the unmodified zinc electrode. This means that the passivation film-coated electrode can reduce the energy barrier for metal nucleation, thus promoting uniform zinc metal deposition. It can be seen that the presence of the in-situ grown passivation film coating reduces the charge transfer resistance on the surface of the zinc electrode, showing excellent plating and stripping energy and better rate performance.

[0071] Figure 9 Comparison chart of Tafel tests of the zinc electrode prepared in Example 1 and the pure zinc foil electrode in Comparative Example 4 in 1M Na2SO4 solution using a three-electrode system (ZnO@Zn in the figure represents Example 1, and Bare-Zn represents Comparative Example 4). Figure 9 It can be seen that compared with the unmodified zinc foil electrode in Comparative Example 4, the passivation film-coated zinc electrode prepared in Example 1 has a higher corrosion potential (the corrosion potential of the ZnO@Zn electrode is -1.036V, and the corrosion potential of the zinc foil electrode is -1.122V).

[0072] Figure 10 Rate charts of zinc ion capacitors assembled by matching the zinc electrode prepared in Example 1 and the pure zinc foil electrode in Comparative Example 4 with AC respectively. Figure 10 Among them, a is the rate chart of the zinc ion capacitor assembled by matching the passivation film-coated zinc electrode prepared in Example 1 with AC, and b is the rate chart of the zinc ion capacitor assembled by matching the pure zinc foil electrode in Comparative Example 4 with AC. Figure 10 It can be seen that when the current density gradually increases from 0.2A g -1 、0.5A g -1 、1A g -1 、2A g -1 、3A g -1 The ZnO@Zn-AC capacitors have discharge specific capacities of 54.4mAh g -1 、46.8mAh g -1 、41.5mAh g -1 、38.9mAh g -1 、36.1mAh g -1 respectively, while the Zn-AC capacitors have discharge specific capacities of only 46.3mAh g -1 、38.2mAh g -1 、32.7mAh g -1 、28.3mAh g -1 、26.1mAh g -1 respectively under the same current density. Therefore, the ZnO@Zn-AC capacitor has a higher specific capacity than the Zn-AC capacitor at low currents, from 0.2A g -1 to 3A g-1 At each current density, the ZnO@Zn-AC capacitor has a higher specific capacitance, indicating better rate performance. The reason why the zinc electrode modified with the passivation film coating prepared in the present invention has better rate performance is that this electrode avoids direct contact with the electrolyte, reduces the occurrence of corrosion and hydrogen evolution reactions, and its electrochemical performance is superior to that of the zinc foil electrode.

[0073] Figure 11 For the zinc ion capacitors assembled by matching the passivation film coating-modified zinc electrode prepared in Example 1 and the pure zinc foil electrode of Comparative Example 4 with AC at 2 A g -1 The charge-discharge cycle diagrams at the current density. Diagram a is the charge-discharge cycle diagram of the zinc ion capacitor assembled by matching the passivation film coating-modified zinc electrode prepared in Example 1 with AC at 2 A g -1 The charge-discharge cycle diagrams at the current density. Diagram b is the charge-discharge cycle diagram of the zinc ion capacitor assembled by matching the pure zinc foil electrode in Comparative Example 4 with AC at 2 A g -1 The charge-discharge cycle diagrams at the current density. It can be seen from Figure 11 that after 4000 charge-discharge cycles, the capacity of the Zn-AC capacitor decreased sharply, indicating that the cycle stability of the Zn-AC capacitor is poor. While after 10000 stable charge-discharge cycles, the capacity of the ZnO@Zn-AC capacitor did not decay, indicating that this ZnO@Zn-AC capacitor has good cycle stability and cycle life.

[0074] Figure 12 For the zinc ion capacitors assembled by matching the passivation film coating-modified zinc electrode prepared in Example 1 and the pure zinc foil electrode of Comparative Example 4 with AC at 8 A g -1 The charge-discharge cycle diagrams at the current density. Diagram a is the charge-discharge cycle diagram of the zinc ion capacitor assembled by matching the passivation film coating-modified zinc electrode prepared in Example 1 with AC at 8 A g -1 The charge-discharge cycle diagrams at the current density. Diagram b is the charge-discharge cycle diagram of the zinc ion capacitor assembled by matching the pure zinc foil electrode in Comparative Example 4 with AC at 8 A g -1 The charge-discharge cycle diagrams at the current density. It can be seen from Figure 12 that during the charge-discharge cycle of the Zn-AC capacitor, the overall capacity is relatively low and the cycle stability is poor. While after 10000 stable charge-discharge cycles, the capacity of the ZnO@Zn-AC capacitor still remains at 32 mAh g -1 , indicating that this ZnO@Zn-AC capacitor has good cycle stability and cycle life.

[0075] The present invention also tested the electrochemical performance of a zinc-ion battery assembled with the in-situ grown passivation film-coated zinc electrode prepared in Example 1 as the negative electrode and carbon paper coated with MnO2, V2O5 powder, or PBA powder as the positive electrode. The results showed that when the in-situ grown passivation film-coated zinc electrode provided by the present invention was selected as the negative electrode material, the assembled different zinc-ion batteries all had excellent electrochemical performance.

[0076] Example 2

[0077] In this example, the preparation method of the in-situ grown passivation film-coated zinc electrode was the same as that in Example 1, except that the soaking time of the zinc foil in the solution was replaced from 1 h to 4 h.

[0078] The present invention also carried out electrochemical tests on the zinc electrode obtained in this Example 2, and the test method was similar to that of the zinc electrode obtained in Example 1. The results showed that the in-situ grown passivation film-coated zinc electrode prepared in this example had excellent electrochemical performance.

[0079] Example 3

[0080] In this example, the preparation method of the in-situ grown passivation film-coated zinc electrode was the same as that in Example 1, except that the 28 wt% NH3·H2O solution was replaced by a 30 wt% NH3·H2O solution.

[0081] The present invention also carried out electrochemical tests on the zinc electrode obtained in this Example 3, and the test method was similar to that of the zinc electrode obtained in Example 1. The results showed that the in-situ grown passivation film-coated zinc electrode prepared in this example had excellent electrochemical performance.

[0082] Example 4

[0083] In this example, the preparation method of the in-situ grown passivation film-coated zinc electrode was the same as that in Example 1, except that the 28 wt% NH3·H2O solution was replaced by a 25 wt% NH3·H2O solution.

[0084] The present invention also carried out electrochemical tests on the zinc electrode obtained in this Example 4, and the test method was similar to that of the zinc electrode obtained in Example 1. The results showed that the in-situ grown passivation film-coated zinc electrode prepared in this example had excellent electrochemical performance.

[0085] Example 5

[0086] In this example, the preparation method of the in-situ grown passivation film-coated zinc electrode was the same as that in Example 1, except that the 28 wt% NH3·H2O solution was replaced by a 40 wt% NH3·H2O solution.

[0087] The present invention also carried out electrochemical tests on the zinc electrode obtained in Example 5, and the test method was similar to that of the zinc electrode obtained in Example 1. The results showed that the zinc electrode modified with the in-situ grown passivation film coating prepared in this example had excellent electrochemical performance.

[0088] In summary, the zinc electrode modified with the passivation film coating provided by the present invention can be used as an electrode and applied to zinc-ion batteries or zinc-ion capacitors, and has excellent electrochemical performance.

[0089] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a zinc electrode modified with an in-situ grown passivation film coating, characterized in that: The zinc electrode modified with the in-situ grown passivation film coating can be obtained by immersing the zinc in an ammonia solution, washing it, and drying it; The mass concentration of the ammonia solution is 25-40%; the soaking time is 1-4h; The drying temperature is 60-70° C.; the drying is carried out in an atmosphere containing oxygen.

2. The method for preparing a zinc electrode modified with an in-situ grown passivation film coating according to claim 1, characterized in that: Before immersing the zinc in the ammonia solution, the method also includes a step of pre-treating the zinc; the pre-treatment includes grinding and cleaning the zinc.

3. The method for preparing a zinc electrode modified with an in-situ grown passivation film coating according to claim 1, characterized in that: The solution used for the washing is anhydrous ethanol.

4. A zinc electrode modified with an in-situ grown passivation film coating prepared by the preparation method according to any one of claims 1 to 3.

5. Use of a zinc electrode modified with an in-situ grown passivation film coating as claimed in claim 4 in a zinc ion battery or a zinc ion capacitor.

6. A zinc ion battery, characterized in that: The negative electrode material is the zinc electrode modified with the in-situ grown passivation film coating as described in claim 4.

7. A zinc ion capacitor, characterized in that: The negative electrode material is the zinc electrode modified with the in-situ grown passivation film coating as described in claim 4.

Images