Metal zinc surface modification method and application of metal zinc surface modification method in aqueous battery

Abstract

The invention discloses a metal zinc surface modification method and application of the metal zinc surface modification method in an aqueous battery, a metal zinc negative electrode comprises a zinc foil substrate and a modification layer located on the surface of one side of the zinc foil substrate, and the modification layer contains carbon and nitrogen elements and comes from a nitrogen-containing aromatic heterocyclic compound (such as 2, 2 '-bipyridine). The preparation method comprises the following steps: dissolving a nitrogen-containing heteroaromatic compound in a mixed solution of hydrogen peroxide and absolute methanol, and stirring to obtain a uniform and stable solution; and protecting the back surface of a zinc foil substrate with an adhesive tape, soaking the zinc foil substrate in the stable solution, washing after the reaction is completed, and drying to obtain the metal zinc negative electrode with the modification layer. The metal zinc negative electrode is a zinc metal battery negative electrode material with great potential, and the three-dimensional porous modification layer of the metal zinc negative electrode has the characteristics of depassivation, provision of rich zinc-loving sites and induction of preferred deposition of zinc along a (101) crystal face. Due to the characteristic, the zinc dendrite growth and side reaction can be inhibited at the same time, so that the cycle life and the stability of the zinc metal battery are remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of aqueous zinc metal battery technology, specifically relating to a zinc metal anode, its preparation method, and its application. Background Technology

[0002] As the global energy structure accelerates its transition to renewable energy sources such as solar and wind power, the intermittency and instability of renewable energy have created an urgent need for efficient energy storage systems to balance power supply and demand and ensure stable grid operation. Against this backdrop, aqueous zinc metal batteries, due to their inherent safety, environmental friendliness, and low cost, have become a key candidate technology for large-scale electrochemical energy storage and portable electronic power supplies, attracting widespread attention in energy storage research. As a core component of zinc metal batteries, the zinc anode possesses high theoretical capacity (820 mA·h·g⁻¹), low redox potential (-0.76 V vs. SHE), abundant resources, and a crystal structure that eliminates the need for ion insertion / deintercalation, making it considered an ideal anode material for achieving high-performance zinc metal batteries.

[0003] However, in aqueous electrolytes, the zinc anode is prone to water-induced side reactions, including hydrogen evolution reaction, surface corrosion, and passivation layer formation. Furthermore, the "sharp point effect" and concentration polarization lead to uncontrolled zinc dendrite growth, which can puncture the separator and cause short circuits. Commercially available zinc foil itself has surface bumps and scratches, and is covered with a passivation layer with low conductivity. These defects further exacerbate uneven charge distribution and hindered ion transport, ultimately resulting in short battery cycle life and poor reversibility. These factors limit the large-scale application of aqueous zinc metal batteries. Therefore, solving these problems is of great significance for the future practical application of zinc metal batteries.

[0004] To improve the performance of zinc metal anodes, various surface modification strategies have been reported, including passivation removal, electrolyte regulation, and artificial SEI design, which have enhanced the electrochemical performance and extended the lifespan of zinc anodes. However, due to the lack of physical confinement in two-dimensional zinc anodes, the zinc ion deposition process is disordered and the local effective current density is high, which still easily leads to dendrite formation. Furthermore, the complexity and limited effectiveness of single-method modification also hinder the practical application of zinc metal anodes. Summary of the Invention

[0005] Therefore, the main objective of this invention is to achieve multiple modification effects (passivation layer removal, 3D porous structure, control of preferred crystal orientation, and introduction of nitrogen-zinc affinity sites) through a simple one-step reaction, and to improve defects such as zinc dendrites caused by uneven deposition during the zinc ion deposition / dissolution process of zinc metal anodes.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] According to a first aspect of the present invention, a zinc metal anode is provided, characterized in that it comprises a zinc foil substrate and a modification layer grown in situ on one side surface of the zinc foil substrate, wherein the modification layer contains carbon and nitrogen elements derived from nitrogen-containing aromatic heterocyclic compounds, including but not limited to 2,2'-bipyridine and 1,10-phenanthroline.

[0008] Furthermore, in some alternative embodiments, the thickness of the protective layer is H, where 0 μm < H ≤ 2 μm.

[0009] According to a second aspect of the present invention, a method for preparing the above-mentioned zinc metal anode is provided, comprising the following steps:

[0010] S1, dissolve a nitrogen-containing aromatic heterocyclic compound in a mixture of hydrogen peroxide and anhydrous methanol, and stir to obtain a homogeneous and stable solution;

[0011] S2, protect the back of the zinc foil substrate with tape, add it to the stable solution obtained in S1 for immersion reaction, during which the reaction system should be placed on a shaker, after the reaction is completed, wash and air dry to obtain the metallic zinc negative electrode with the modified layer.

[0012] In the above scheme, the volume ratio of hydrogen peroxide to anhydrous methanol is 0~3:13. When the volume ratio of hydrogen peroxide to anhydrous methanol is 3:7, the modified layer morphology of the prepared zinc metal anode is a typical three-dimensional porous structure.

[0013] In the above scheme, the concentration of nitrogen-containing aromatic heterocyclic compounds in the S1 stable solution is from 0 mol / L to saturation concentration (mol / L), and can be arbitrarily selected within this concentration range.

[0014] In the above scheme, the soaking reaction time in S2 is 0.5~24 h, and the ambient temperature is 20~25℃.

[0015] According to a third aspect of the present invention, a zinc metal battery is provided, characterized in that it includes the above-described zinc metal negative electrode, and a modification layer is provided on the side adjacent to the separator.

[0016] The preparation method of this zinc metal battery includes the following steps: stacking a positive electrode sheet, a separator, and a zinc metal negative electrode in sequence to form a battery casing; injecting electrolyte into the battery casing, wherein electrolyte is added to both the positive and negative electrode sides; and encapsulation. The negative electrode used in the zinc metal full battery is surface-modified zinc metal as claimed in this invention, and both the positive and negative electrodes used in the zinc metal full battery are surface-modified zinc metal as claimed in this invention.

[0017] Furthermore, the zinc metal symmetrical battery or metal full battery, wherein the charge / discharge test voltage range of the zinc metal full battery is 0.2-1.6 V.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] 1. Significantly improved performance of zinc anode

[0020] The zinc anode provided by this invention achieves multiple controls over zinc deposition behavior by growing a carbon- and nitrogen-rich modification layer in situ on the surface of a zinc foil substrate. Specifically, this is manifested in the following ways:

[0021] (1) Inducing uniform zinc deposition and inhibiting dendrites: Nitrogen in the modified layer can serve as abundant zinc-loving sites, effectively regulating the initial nucleation process of zinc ions, inducing uniform zinc deposition, and thus inhibiting the growth of zinc dendrites.

[0022] (2) Reduce deposition energy barrier and improve kinetics: This modified layer can remove the original passivation layer on the zinc foil surface, significantly reduce the energy barrier of zinc deposition / dissolution process, achieve uniform charge transfer and electric field distribution, and improve reaction kinetics.

[0023] (3) Buffering volume change and improving stability: The three-dimensional porous structure modification layer formed under the preferred conditions can reduce the local current density on the electrode surface and provide a larger specific surface area to accommodate the volume change during zinc deposition / dissolution, effectively alleviating the "tip effect" that leads to dendrite growth and improving cycle stability.

[0024] (4) Achieving preferred orientation growth: The modified layer can induce zinc to grow along the (101) crystal plane in a preferred orientation. Compared with the (002) crystal plane, the (101) crystal plane has better reactivity and lattice matching in an aqueous environment, which is conducive to achieving dense and continuous epitaxial deposition, which is crucial for long-cycle stability under high-capacity deposition.

[0025] 2. The preparation method is simple and efficient, and suitable for large-scale production.

[0026] The preparation method provided by this invention only requires immersing zinc foil in a methanol solution containing 2,2'-bipyridine and hydrogen peroxide to form a functional modification layer in situ. This method is simple, operates under mild conditions, requires no complex equipment, facilitates precise control and large-scale production, and has significant potential for industrial application.

[0027] 3. Excellent overall battery performance

[0028] The zinc metal battery assembled using the zinc metal anode of this invention inherits all the advantages of the aforementioned anodes, and can simultaneously achieve dendrite suppression and side reaction mitigation, thereby showing significant improvements in cycle life, coulombic efficiency and rate performance, and possessing excellent comprehensive electrochemical performance. Attached Figure Description

[0029] Figure 1These are scanning electron microscope images of Embodiment 3 and Comparative Example 2 of the present invention, from left to right: surface image of Comparative Example 2, surface image of Embodiment 3, and cross-sectional image of Embodiment 3.

[0030] Figure 2 This is a comparison chart of the constant current charge-discharge cycle performance of zinc-zinc symmetrical batteries assembled in all embodiments of the present invention and in comparative examples;

[0031] Figure 3 This is a comparison chart of the X-ray diffraction test results of Embodiment 3, Comparative Example 1, and Comparative Example 2 of the present invention;

[0032] Figure 4 The Fourier transform infrared spectra of Embodiment 3, Comparative Example 1, and Comparative Example 2 of the present invention are shown below.

[0033] Figure 5 The XPS test C1s and N1s energy spectrum images of Embodiment 3, Comparative Example 1, and Comparative Example 2 of the present invention;

[0034] Figure 6 As shown in Embodiment 3 and Comparative Example 2 of the present invention, at 2 mA cm -2 Deposited at a current density of 2 mAh cm -2 Scanning electron microscope (SEM) images of the surface of the zinc anode with areal capacity, and in-situ optical microscope images of the surface deposited at a current of 1 mA for 40 min, from left to right: SEM images of the surface after deposition in Comparative Example 2, SEM images of the surface after deposition in Example 3, in-situ optical microscope images of Comparative Example 2 and in-situ optical microscope images of Example 3.

[0035] Figure 7 This is a comparison chart of the performance of zinc-zinc symmetric cells assembled in Example 3 and Comparative Example 2 of the present invention under constant current deposition test conditions of 1 mA cm⁻².

[0036] Figure 8 The activation energy E of Example 3 and Comparative Example 2 of this invention a Data chart;

[0037] Figure 9 This is a performance comparison chart obtained from Tafel testing of zinc-zinc symmetric batteries assembled in Embodiment 3 and Comparative Example 2 of the present invention;

[0038] Figure 10 This is a comparison chart of the rate performance obtained from rate testing of the assembled full cells in Embodiment 3 and Comparative Example 2 of the present invention;

[0039] Figure 11 This is a performance comparison chart obtained from cyclic voltammetry tests of the assembled full cells in Embodiment 3 and Comparative Example 2 of the present invention.

[0040] Figure 12 This is a comparison diagram of the electrochemical impedance of the full cells assembled in Example 3 and Comparative Example 2 of the present invention;

[0041] Figure 13 This is a comparison diagram of the self-discharge behavior of the full batteries assembled in Embodiment 3 and Comparative Example 2 of the present invention;

[0042] Figure 14 The full cells assembled in Example 3 and Comparative Example 2 of this invention were tested under the condition of 5 A g. -1 Comparison of constant current charge-discharge cycle performance.

[0043] Figure 15 The graphs show a comparison of the constant current charge-discharge cycle performance of zinc-zinc symmetric batteries assembled in Examples 5-7 and Comparative Example 1 of this invention.

[0044] Figure 16 This is a comparison chart of the constant current charge-discharge cycle performance of the zinc-zinc symmetric batteries assembled in Example 8 and Comparative Example 2 of the present invention. Detailed Implementation

[0045] The present invention will be further described in detail below through specific implementation examples. These implementation examples are based on the technology of the present invention, and detailed implementation methods and specific operating procedures are given. However, the scope of protection of the present invention is not limited to the implementation examples given below.

[0046] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0047] Example 1

[0048] This embodiment provides a zinc metal anode, the preparation method of which includes the following steps:

[0049] (1) Dissolve a certain amount of 2,2'-bipyridine in a mixed solution of hydrogen peroxide and anhydrous methanol (volume ratio of hydrogen peroxide to anhydrous methanol 3:7) to prepare a 0.25 mol / L bipyridine solution A;

[0050] (2) The zinc foil (100 μm thick) was then protected with tape on the back and immersed in solution A for 2 h.

[0051] (3) Wash the zinc foil after the reaction is complete with methanol and ethanol three times and air dry to obtain a zinc metal anode with a porous modified layer.

[0052] Example 2

[0053] This embodiment provides a zinc metal anode, the preparation method of which includes the following steps:

[0054] (1) Dissolve a certain amount of 2,2'-bipyridine in a mixed solution of hydrogen peroxide and anhydrous methanol (volume ratio of hydrogen peroxide to anhydrous methanol 3:7) to prepare a 0.25 mol / L bipyridine solution A;

[0055] (2) The zinc foil (100 μm thick) was then protected with tape on the back and immersed in solution A for 4 hours.

[0056] (3) Wash the zinc foil after the reaction is complete with methanol and ethanol three times and air dry to obtain a zinc metal anode with a porous modified layer.

[0057] Example 3

[0058] This embodiment provides a zinc metal anode, the preparation method of which includes the following steps:

[0059] (1) Dissolve a certain amount of 2,2'-bipyridine in a mixed solution of hydrogen peroxide and anhydrous methanol (volume ratio of hydrogen peroxide to anhydrous methanol 3:7) to prepare a 0.25 mol / L bipyridine solution A;

[0060] (2) The zinc foil (100 μm thick) was then protected with tape on the back and immersed in solution A for 8 hours.

[0061] (3) Wash the zinc foil after the reaction is complete with methanol and ethanol three times and air dry to obtain a zinc metal anode with a porous modified layer.

[0062] The scanning electron microscope image of the zinc anode obtained in this embodiment is as follows: Figure 1 As shown, the surface and cross-sectional morphology of the zinc anode were characterized, revealing that a porous modification layer was densely grown on the zinc foil substrate.

[0063] Example 4

[0064] This embodiment provides a zinc metal anode, the preparation method of which includes the following steps:

[0065] (1) Dissolve a certain amount of 2,2'-bipyridine in a mixed solution of hydrogen peroxide and anhydrous methanol (volume ratio of hydrogen peroxide to anhydrous methanol 3:7) to prepare a 0.25 mol / L bipyridine solution A;

[0066] (2) The zinc foil (100 μm thick) was then protected with tape on the back and immersed in solution A for 12 h.

[0067] (3) Wash the zinc foil after the reaction is complete with methanol and ethanol three times and air dry to obtain a zinc metal anode with a porous modified layer.

[0068] Example 5

[0069] This embodiment provides a zinc metal anode, the preparation method of which includes the following steps:

[0070] (1) Dissolve a certain amount of 2,2'-bipyridine in anhydrous methanol to prepare a 0.5 mol / L bipyridine solution A;

[0071] (2) The zinc foil (100 μm thick) was then protected with tape on the back and immersed in solution A for 8 h.

[0072] (3) Wash the zinc foil after the reaction is complete with methanol and ethanol three times and air dry to obtain the modified zinc metal anode.

[0073] Example 6

[0074] This embodiment provides a zinc metal anode, the preparation method of which includes the following steps:

[0075] (1) Dissolve a certain amount of 2,2'-bipyridine in anhydrous methanol to prepare a 1 mol / L bipyridine solution A;

[0076] (2) The zinc foil (100 μm thick) was then protected with tape on the back and immersed in solution A for 8 h.

[0077] (3) Wash the zinc foil after the reaction is complete with methanol and ethanol three times and air dry to obtain the modified zinc metal anode.

[0078] Example 7

[0079] This embodiment provides a zinc metal anode, the preparation method of which includes the following steps:

[0080] (1) Dissolve a certain amount of 2,2'-bipyridine in anhydrous methanol to prepare a 2 mol / L bipyridine solution A;

[0081] (2) The zinc foil (100 μm thick) was then protected with tape on the back and immersed in solution A for 8 h.

[0082] (3) Wash the zinc foil after the reaction is complete with methanol and ethanol three times and air dry to obtain the modified zinc metal anode.

[0083] Example 8

[0084] This embodiment provides a zinc metal anode, the preparation method of which includes the following steps:

[0085] (1) Dissolve a certain amount of 1,10-phenanthroline in anhydrous methanol to prepare a 2 mol / L o-phenanthroline solution A;

[0086] (2) The zinc foil (100 μm thick) was then protected with tape on the back and immersed in solution A for 24 h.

[0087] (3) Wash the zinc foil after the reaction is complete with methanol and ethanol three times and air dry to obtain the modified zinc metal anode.

[0088] Comparative Example 1

[0089] A zinc metal anode is prepared in a manner similar to that in Example 3, except that solution A does not contain hydrogen peroxide.

[0090] Comparative Example 2

[0091] A zinc anode is a zinc foil (100 μm thick) that has only undergone alcohol washing treatment.

[0092] Test case

[0093] The zinc-zinc symmetrical battery described below includes a zinc metal negative electrode, a separator, and a 2M ZnSO4 electrolyte. The separator is a Whatman GF / D glass fiber separator, and the electrolyte is a 2 mol / L ZnSO4 aqueous solution.

[0094] The preparation steps of the zinc-zinc symmetric battery include: injecting electrolyte into the battery casing, with 60 μL of electrolyte added to both the positive and negative electrode sides; stacking the zinc negative electrode, separator, and zinc negative electrode in sequence and then encapsulating them. Battery assembly is completed at room temperature and in air. The working electrode and counter electrode of the symmetric battery both use the zinc negative electrodes provided in the various embodiments and comparative examples.

[0095] The following full cell includes a positive electrode, a negative electrode, a separator, and a 2M ZnSO4 electrolyte. The positive electrode uses nano-V2O5 as the active material, Super P as the conductive carbon, PVDF as the binder, and carbon felt as the current collector. These materials were purchased from the Future Materials Science Mall and the electrode sheets were stamped into 10 mm diameter discs for later use. The separator is a Whatman GF / D glass fiber separator; the electrolyte is a 2 mol / L ZnSO4 aqueous solution.

[0096] The preparation steps of the full cell include: injecting electrolyte into the battery casing, with 60 μL of electrolyte added to both the positive and negative electrode sides; stacking the positive electrode, separator, and negative electrode in sequence and then encapsulating them. Battery assembly is completed at room temperature and in air.

[0097] The zinc anodes provided in the various embodiments and comparative examples were assembled into zinc-zinc symmetric cells using coin cell cases for electrochemical performance testing at a current density of 2 mA cm⁻¹. -2 The cutoff capacity is 2 mAh cm⁻¹ -2A constant current charge-discharge test was conducted under the specified test conditions. The test ended when the battery experienced a short circuit. The test results are as follows: Figure 2 As shown, the introduction of the modification layer effectively improves the constant current charge-discharge lifetime of the zinc-zinc symmetric battery, especially the sample with the porous modification layer.

[0098] X-ray diffraction tests were performed on the zinc anodes from Example 3, Comparative Example 1, and Comparative Example 2. The test results are as follows: Figure 3 As shown in the XRD pattern, the modification layer can increase the proportion of Zn(101) crystal planes.

[0099] The zinc anodes from Examples 3, 1, and 2 were subjected to Fourier transform infrared spectroscopy (FTIR) tests. The test results are as follows: Figure 4 As shown in the spectrum, Example 3 shows no ZnO peak, indicating that the passivation layer on the zinc foil surface was consumed during the preparation process. Furthermore, the presence of stretching vibration peaks for C=C / C=N and CH bonds in Example 3 may be due to the presence of a 2,2'-bipyridine zinc complex in its porous modification layer.

[0100] XPS tests were performed on the zinc anodes from Example 3, Comparative Example 1, and Comparative Example 2. The test results are as follows: Figure 5 As shown, the high-resolution C1s spectrum shows three peaks at 284.8 eV, 286.5 eV, and 288.6 eV, corresponding to C–C / C=C, C–O, and C=O, respectively. For Example 3, the peaks at 287.7 eV and 286.11 eV in the high-resolution C1s spectrum are attributed to C–N and C=N bonds, respectively. For Example 3 and Comparative Example 1, the peak at 400 eV in the high-resolution N1s spectrum is attributed to an N-Zn bond, while the peak at 398.4 eV indicates the presence of pyridine nitrogen. This further confirms that the modified layers on the surfaces of Example 3 and Comparative Example 1 contain zinc-loving nitrogen sites, with the nitrogen element originating from the 2,2'-bipyridine zinc complex.

[0101] For the zinc anodes obtained in Example 3 and Comparative Example 2, the morphology of the assembled zinc-zinc symmetric cells during the first zinc ion deposition process was characterized. Scanning electron microscopy was used to characterize the morphology at 2 mA cm⁻¹. -2 Deposited at a current density of 2 mAh cm -2 The surface morphology of the zinc anode with a surface capacity was measured, and the changes in the deposition morphology of the zinc anode under a current of 1 mA were recorded using in-situ optical microscopy. The results are as follows: Figure 6 As shown, the porous modification layer of this zinc anode effectively inhibits the growth of zinc dendrites, and the surface of the zinc anode exhibits a smoother electrode surface throughout the deposition process.

[0102] For the zinc anodes obtained in Example 3 and Comparative Example 2, zinc-zinc symmetric cells were assembled and subjected to constant current deposition at 1 mA cm⁻² to measure the nucleation overpotential and study the effect of the modification layer on the deposition kinetics. The results are as follows: Figure 7 As shown, the nucleation overpotential decreased significantly from 98.6 mV to 58.1 mV, indicating that the modified layer lowered the nucleation energy barrier and enhanced the affinity for zinc, thereby facilitating the dense deposition of zinc ions and inhibiting dendrite growth.

[0103] For the zinc anodes obtained in Example 3 and Comparative Example 2, zinc-zinc symmetric cells were assembled and their activation energy Ea was tested to study the effect of the modification layer on the desolvation behavior of hydrated zinc ions. The results are as follows: Figure 8 As shown. Example 3, E a The value was 30.62 kJ mol⁻¹, compared to 32.86 kJ mol⁻¹ in Comparative Example 2. This reduction indicates that the modified layer promotes the desolvation of zinc ions, significantly reduces the contact between solvated water and the zinc anode surface, thereby helping to mitigate corrosion caused by moisture in the electrolyte and enhancing deposition kinetics.

[0104] For the zinc anodes obtained in Example 3 and Comparative Example 2, zinc-zinc symmetric cells were assembled and subjected to Tafel testing to obtain their corrosion currents. The results are as follows: Figure 9 As shown, compared to Comparative Example 2, the corrosion current density of Example 3 was significantly lower (0.682 mA cm⁻² vs. 2.317 mA cm⁻²). This indicates that the porous modification layer can effectively slow down the corrosion kinetics of zinc metal and suppress the occurrence of side reactions.

[0105] For the zinc anodes obtained in Example 3 and Comparative Example 2, the zinc anodes provided in the examples and comparative examples, along with a glass fiber separator, 2M ZnSO4 electrolyte, and a positive electrode (active material V2O5), were assembled into a full cell using a coin cell casing. All cell assembly was completed at room temperature and in air. To study the practical application of the full cell, its rate performance was tested, and the results are as follows: Figure 10 As shown. When the current density is 0.1 / 0.5 / 1 / 2 / 3 / 0.1 A g -1 The full cell assembled in Example 3 consistently exhibited higher capacity when the process was varied.

[0106] Cyclic voltammetry tests were conducted on full cells assembled using the zinc anodes obtained in Example 3 and Comparative Example 2. The test results are as follows: Figure 11 As shown. The tests were conducted at a scan rate of 0.1 mV / s, with a voltage window of 0.2–1.6 V relative to Zn / Zn²⁺. Compared to the full cell assembled in Comparative Example 2, the full cell assembled in Example 3 exhibits a larger current density and integral area, indicating superior specific capacity.

[0107] Electrochemical impedance spectroscopy was performed on full cells assembled using the zinc anodes obtained in Example 3 and Comparative Example 2. The test results are as follows: Figure 12 As shown. Because the modification layer can guide the uniform deposition of zinc ions, the electrochemical impedance of the full cell assembled in Example 3 is effectively reduced, resulting in faster reaction kinetics and improved rate performance of the full cell.

[0108] For the zinc anodes obtained in Example 3 and Comparative Example 2, full cells were assembled and their self-discharge behavior was tested to evaluate their electrochemical stability. The test results are as follows: Figure 13 As shown. First, the full battery was charged to 1.6 V, left to stand for 24 hours, and then discharged to 0.2 V. The coulombic efficiency of the full battery in Example 3 was 88.63%, while that of the full battery in Comparative Example 2 was only 85.23%.

[0109] For the zinc anodes obtained in Example 3 and Comparative Example 2, full cells were assembled and their constant current charge-discharge cycle performance was tested under the condition of 5 A g. -1 The test results are as follows Figure 14 As shown, Example 3 improves the rate charge / discharge performance of the full battery and enhances capacity retention. After 2000 cycles, the final discharge capacity is 46.81 mAh g⁻¹, with an excellent capacity retention of 94.9%. Under the same test conditions, the capacity retention of the full battery in Comparative Example 2 is only 90.7%.

[0110] Electrochemical performance tests were conducted on the zinc anodes provided in Examples 5-7 and Comparative Example 1, assembled into zinc-zinc symmetric cells using coin cell casings, at a current density of 1 mA cm⁻¹. -2 The cutoff capacity is 1 mAh cm⁻¹ -2 A constant current charge-discharge test was conducted under the specified test conditions. The test ended when the battery experienced a short circuit. The test results are as follows: Figure 15 As shown, the concentration of solution A during the preparation process affects the performance of the zinc anode.

[0111] Electrochemical performance tests were conducted on the zinc anodes provided in Example 8 and Comparative Example 2, assembled into zinc-zinc symmetric cells using coin cell casings, at a current density of 1 mA cm⁻¹. -2 The cutoff capacity is 1 mAh cm- 2 Constant current charge-discharge tests were performed under the specified test conditions, and the test results are as follows: Figure 16 As shown, when 1,10-phenanthroline was selected as the nitrogen-containing aromatic heterocyclic compound, the performance of the prepared zinc anode was also improved.

[0112] This invention is not limited to the embodiments described above. Those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications are also considered within the scope of protection of this invention. Contents not described in detail in this specification are prior art known to those skilled in the art.

Claims

1. A surface-modified zinc metal, comprising a zinc foil substrate and an in-situ grown modification layer located on at least one side surface of the zinc foil substrate, characterized in that, The modified layer is an organic-inorganic composite layer rich in carbon and nitrogen elements, the carbon and nitrogen elements of which are derived from nitrogen-containing aromatic heterocyclic compounds, including but not limited to 2,2'-bipyridine and 1,10-phenanthroline.

2. The zinc metal according to claim 1, characterized in that, The thickness of the modified layer is greater than 100 nm and less than or equal to 2 μm.

3. The zinc metal according to claim 1 or 2, characterized in that, The modified layer has a three-dimensional porous structure.

4. A method for preparing metallic zinc according to any one of claims 1-3, characterized in that, Includes the following steps: (1) The zinc foil substrate is immersed in a methanol solution containing nitrogen-containing aromatic heterocyclic compounds and hydrogen peroxide to carry out the reaction; (2) After the reaction is complete, the zinc foil substrate is removed, washed and dried to obtain a metallic zinc anode with the modified layer formed on its surface.

5. The preparation method according to claim 4, characterized in that, In the methanol solution, the volume ratio of hydrogen peroxide to anhydrous methanol is 0~3:

13.

6. The preparation method according to claim 4, characterized in that, In the methanol solution, the concentration of nitrogen-containing aromatic heterocyclic compounds ranges from 0 mol / L to a saturation concentration (mol / L), and can be any value within this concentration range.

7. The preparation method according to claim 4, characterized in that, The reaction time is 0.5 to 24 hours.

8. The preparation method according to claim 6, characterized in that, When the volume ratio of hydrogen peroxide to anhydrous methanol is 3:7, the resulting modified layer has a three-dimensional porous structure.

9. A zinc metal battery, comprising a positive electrode, a negative electrode, a separator, and an electrolyte, characterized in that, The negative electrode of the full cell is zinc metal as described in any one of claims 1-3, and the modifying layer is disposed facing the separator. The positive and negative electrodes of the symmetrical cell are both zinc metal as described in any one of claims 1-3, and the modifying layer is disposed facing the separator.

10. The assembly method of the zinc metal battery according to claim 9, characterized in that, include: The positive electrode, the separator, and the zinc metal according to any one of claims 1-3 are stacked in sequence, with the modification layer of the zinc metal negative electrode facing the separator, and then the electrolyte is injected and encapsulated.

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