Zinc electrode treatment method and zinc symmetric button cell preparation method

Abstract

The invention relates to the technical field of battery materials, in particular to a zinc electrode treatment method and a zinc symmetric button battery preparation method. 1-ethyl-3-methylimidazolium tetrafluoroborate ionic liquid is uniformly smeared on the surface of the zinc foil and is subjected to heat treatment, so that a fluorine functionalized three-dimensional bracket protection layer constructed on the surface of the zinc foil is realized, zinc ions can be guided to be uniformly deposited, and the problems that a traditional zinc metal protection layer is tedious in preparation process, high in cost and hindered in ion diffusion are solved.

Description

Technical Field

[0001] This invention relates to the field of battery materials technology, specifically to a zinc electrode processing method and a method for preparing zinc symmetrical button batteries. Background Technology

[0002] In recent years, rechargeable aqueous zinc ion batteries (AZIBs) have experienced rapid development, leading to increasingly fierce competition in the stationary energy storage field. This is mainly attributed to their superior characteristics, including a high theoretical capacity (820 mAh). −1 Excellent volumetric capacity (5851 mA h cm⁻¹) −3 Zinc ion storage systems (AZIBs) offer several advantages, including high aqueous electrolyte ionic conductivity, low electrochemical potential (-0.76 V vs. SHE), and excellent safety performance. In AZIBs systems, zinc metal serves as the anode and is matched with various cathode materials. However, the commercial application of zinc ion storage systems faces significant challenges, primarily due to defects on the zinc metal anode surface leading to uneven deposition and ultimately dendrite growth. During battery cycling, the stripping / deposition process of zinc causes continuous accumulation of zinc dendrites, forming "dead zinc," increasing internal resistance, and potentially puncturing the separator, leading to a short circuit. Furthermore, because zinc metal is in direct contact with the aqueous electrolyte, its electrode potential is close to the hydrogen evolution potential, inevitably resulting in varying degrees of hydrogen evolution reaction (HER). The irreversible byproduct Zn4SO4(OH)6·xH2O further exacerbates HER, thereby reducing battery stability.

[0003] Recently, various protective strategies have been validated and reported to improve the electrochemical performance of AZIBs, including surface modification, zinc metal electrode structure optimization, electrolyte design, and membrane innovation. Numerous studies have shown that surface protective layer modification is a convenient and effective strategy. This strategy mainly has two functions:

[0004] (1) Protective function: As a spatial physical shielding layer, the protective layer can isolate the zinc metal electrode from the electrolyte, suppress HER and improve corrosion resistance. When dendrites penetrate the separator, the protective layer has certain mechanical properties to prevent the battery from short-circuiting.

[0005] (2) Guiding effect: By regulating the current distribution, the nucleation barrier of zinc is lowered, providing a uniform ion flux for zinc deposition to reduce dendrite formation. Furthermore, zinc has a tightly packed hexagonal structure with predominantly (002), (100), and (101) crystal planes. Numerous studies have shown that the (002) crystal plane of zinc possesses low surface energy and high thermodynamic stability, resulting in strong corrosion resistance. Therefore, guiding zinc ion deposition along the (002) crystal plane is more beneficial to the electrochemical stability of AZIBs.

[0006] Unfortunately, the expensive and cumbersome process of constructing the protective layer poses a significant obstacle to practical applications. Current research on zinc anode protective layers is not only costly and complex in its preparation, but also carries the potential risk of increasing surface ion transfer impedance. Furthermore, the separate research strategies for zinc anode protective layers and crystal plane orientation are detrimental to the electrochemical stability of aqueous zinc-ion batteries.

[0007] Based on the aforementioned technical background, this invention proposes a low-cost, mild, and convenient three-dimensional zinc metal scaffold protective layer, simultaneously achieving an in-situ construction strategy with high (002) crystal face exposure. This technical solution systematically solves the problems of high cost, complex preparation process, and the inability to simultaneously achieve both protective layer and crystal face exposure in existing technologies by optimizing crystal face exposure, improving the preparation process, and innovating construction methods. It offers breakthrough advantages in improving the corrosion resistance of zinc metal, inhibiting HER, and guiding uniform zinc ion deposition, providing an innovative solution for improving AZIBs. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the present invention aims to provide a zinc electrode processing method. Through a mild and convenient one-step in-situ construction strategy, the synergistic effect of zinc metal protective layer and (002) crystal plane exposure can be achieved. Since no binder is involved, it has a positive effect on zinc ion transfer and diffusion.

[0009] This invention first discloses a zinc electrode processing method, comprising the following steps:

[0010] High-purity zinc foil is used as the electrode material, and its surface impurities are removed to make it smooth;

[0011] The ionic liquid of 1-ethyl-3-methylimidazolium tetrafluoroborate was uniformly coated onto the surface of the zinc foil.

[0012] Surface heat treatment is performed to form a fluorine-functionalized three-dimensional scaffold zinc anode protective layer on the surface of the zinc foil by the 1-ethyl-3-methylimidazolium tetrafluoroborate ions.

[0013] After cleaning and drying the zinc foil surface, it is cut into electrode sheets.

[0014] As a preferred embodiment of the present invention, the high-purity zinc foil refers to zinc foil with a purity of ≥99.99%.

[0015] As a preferred technical solution of the present invention, the zinc foil surface is polished smooth by sequentially using sandpaper of 1000 mesh, 2000 mesh, 4000 mesh and 6000 mesh.

[0016] As a preferred embodiment of the present invention, after uniformly coating the zinc foil with 1-ethyl-3-methylimidazolium tetrafluoroborate ionic liquid, the surface of the liquid is covered with waxed paper to remove air bubbles.

[0017] As a preferred embodiment of the present invention, the surface heat treatment involves heating the zinc foil and the waxed paper together to 60–100°C and holding at that temperature for 6–24 hours.

[0018] As a preferred embodiment of the present invention, the drying step uses lint-free paper to completely dry the residual 1-ethyl-3-methylimidazolium tetrafluoroborate ionic liquid on the surface of the zinc foil.

[0019] As a preferred embodiment of the present invention, the cut electrode sheet is a circular sheet with a diameter of 12-14 mm.

[0020] Based on the zinc electrode processed by the above method, the present invention also discloses a method for preparing a zinc symmetric button cell, wherein two zinc electrode sheets are respectively used as positive and negative electrodes and are placed on both sides of a separator, electrolyte is dripped in, and gaskets and spring sheets are used to press the zinc sheets and the separator together to form a zinc symmetric button cell.

[0021] As a preferred embodiment of the present invention, the electrolyte includes one or more of zinc sulfate solution, zinc trifluoromethanesulfonate solution and zinc chloride solution.

[0022] As a preferred embodiment of the present invention, the diaphragm is a glass fiber diaphragm with a diameter of 16 mm and a thickness of 0.26 mm.

[0023] The zinc electrode processing method of the present invention can also be used to process the negative electrode of zinc negative electrode batteries such as alkaline zinc-based batteries and zinc-air batteries.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) The present invention uses a one-step in-situ method to construct a zinc metal surface protective layer without using any binder, which solves the problems of cumbersome preparation process, high cost and ion diffusion obstruction of traditional zinc metal protective layer;

[0026] (2) The fluorinated three-dimensional scaffold protective layer constructed on the zinc foil surface in this invention can guide the uniform deposition of zinc ions, form a fluorinated three-dimensional scaffold protective layer on the surface, and expose the Zn(002) crystal plane. Fluorination enhances the adsorption of zinc ions, the three-dimensional scaffold protective layer guides the uniform deposition of zinc, and the Zn(002) crystal plane reduces the zinc deposition potential energy, inhibits hydrogen evolution activity, and improves corrosion resistance.

[0027] (3) The one-step in-situ construction method used in this invention is gentle and flexible, and can achieve large-scale preparation. Attached Figure Description

[0028] Figure 1 The images show scanning electron microscope (SEM) images of the fluorine-functionalized three-dimensional scaffold protective layer constructed in Embodiment 1 of the present invention and the comparative example (original untreated zinc foil surface);

[0029] Figure 2 The figures show the water contact angle test results of the zinc metal surface in the comparative example and Example 1 of this invention;

[0030] Figure 3 Fourier transform curves of zinc metal surfaces in comparative examples and Example 1 of this invention;

[0031] Figure 4 The X-ray diffraction patterns of zinc metal surfaces in comparative examples and Example 1 of this invention are shown below.

[0032] Figure 5 Electrochemical impedance spectroscopy diagrams for comparative examples and Example 1 of this invention;

[0033] Figure 6 For the comparative examples and Example 1 of the present invention, at 1 mA cm -2 1mAh cm -2 Nucleation overpotential diagram;

[0034] Figure 7 As a comparative example and Example 1 of the present invention, the assembled zinc symmetric battery was tested at a current density of 1 mA cm⁻¹. -2 The surface area capacity is 0.5mAh cm⁻¹ -2 Scanning electron microscope image of zinc metal surface after 100 cycles;

[0035] Figure 8 As a comparative example and Example 1 of the present invention, the assembled zinc symmetric battery was first tested for rate performance, and then at a current density of 1 mA cm⁻¹. -2 The surface area capacity is 0.5mAh cm⁻¹ -2 The following is a long-cycle performance graph. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0037] Example 1

[0038] This embodiment provides a method for preparing a zinc symmetric button cell, including the following steps:

[0039] S1. Select high-purity zinc foil with a purity of ≥99.99%. Polish its surface impurities to make it smooth by successively using sandpaper of 1000 mesh, 2000 mesh, 4000 mesh and 6000 mesh. Then wipe its surface with lint-free paper to remove surface impurities.

[0040] S2. Take an appropriate amount of 1-ethyl-3-methylimidazolium tetrafluoroborate ionic liquid and coat it evenly on the surface of zinc foil. Then cover the surface of the liquid with wax paper and remove any air bubbles.

[0041] S3. Place the zinc foil covered with waxed paper in an oven and heat-treat it at 70°C for 12 hours.

[0042] S4. After heat treatment, the zinc foil is cooled to room temperature and removed. The 1-ethyl-3-methylimidazolium tetrafluoroborate ionic liquid on the surface is wiped off again with lint-free paper. At this time, zinc foil (F-Zn) containing a fluorine-functionalized three-dimensional scaffold zinc anode protective layer is obtained.

[0043] S5. Cut the zinc foil into 12 mm round pieces to obtain F-Zn electrode sheets;

[0044] S6. Two F-Zn electrode plates are used as the positive and negative electrodes respectively and are placed on both sides of a glass fiber membrane with a diameter of 16 mm and a thickness of 0.26 mm. 100 μL of 2 mol / L zinc sulfate electrolyte is dropped in. Gaskets and springs are used to press the zinc plates and membrane together to form a zinc symmetrical button cell, and electrochemical tests are performed on it.

[0045] Example 2

[0046] This embodiment provides a method for preparing a zinc symmetric button cell, including the following steps:

[0047] S1. Select high-purity zinc foil with a purity of ≥99.99%. Polish its surface impurities to make it smooth by successively using sandpaper of 1000 mesh, 2000 mesh, 4000 mesh and 6000 mesh. Then wipe its surface with lint-free paper to remove surface impurities.

[0048] S2. Take an appropriate amount of 1-ethyl-3-methylimidazolium tetrafluoroborate ionic liquid and coat it evenly on the surface of zinc foil. Then cover the surface of the liquid with wax paper and remove any air bubbles.

[0049] S3. Place the zinc foil covered with waxed paper in an oven and heat-treat it at 70°C for 24 hours.

[0050] S4. After heat treatment, the zinc foil is removed at room temperature and the 1-ethyl-3-methylimidazolium tetrafluoroborate ionic liquid on the surface is wiped off again with lint-free paper. At this time, a zinc foil containing a fluorinated three-dimensional scaffold zinc anode protective layer is obtained.

[0051] S5. Cut the zinc foil into 12 mm round pieces to obtain F-Zn electrode sheets;

[0052] S6. Two F-Zn electrode plates are used as the positive and negative electrodes respectively and are placed on both sides of a glass fiber membrane with a diameter of 16 mm and a thickness of 0.26 mm. 100 μL of 2 mol / L zinc trifluoromethanesulfonate electrolyte is dropped in. Gaskets and springs are used to press the zinc plates and membrane together to form a zinc symmetrical button cell, and electrochemical tests are performed on it.

[0053] Example 3

[0054] This embodiment provides a method for preparing a zinc symmetric button cell, including the following steps:

[0055] S1. Select high-purity zinc foil with a purity of ≥99.99%. Polish its surface impurities to make it smooth by successively using sandpaper of 1000 mesh, 2000 mesh, 4000 mesh and 6000 mesh. Then wipe its surface with lint-free paper to remove surface impurities.

[0056] S2. Take an appropriate amount of 1-ethyl-3-methylimidazolium tetrafluoroborate ionic liquid and coat it evenly on the surface of zinc foil. Then cover the surface of the liquid with wax paper and remove any air bubbles.

[0057] S3. Place the zinc foil covered with waxed paper in an oven and heat-treat it at 90°C for 12 hours.

[0058] S4. After heat treatment, the zinc foil is removed at room temperature and the 1-ethyl-3-methylimidazolium tetrafluoroborate ionic liquid on the surface is wiped off again with lint-free paper. At this time, a zinc foil containing a fluorinated three-dimensional scaffold zinc anode protective layer is obtained.

[0059] S5. Cut the zinc foil into 12 mm round pieces to obtain F-Zn electrode sheets;

[0060] S6. Two F-Zn electrode plates were used as the positive and negative electrodes, respectively, and placed on both sides of a glass fiber membrane with a diameter of 16 mm and a thickness of 0.26 mm. 100 μL of 2 mol / L zinc chloride solution was dropped in. Gaskets and springs were used to press the zinc plates and membrane together to form a zinc symmetric button cell, and electrochemical tests were performed on it.

[0061] Comparative Example

[0062] This comparative example is provided as a reference. It uses the same raw materials as the above examples, but without any treatment. Specifically, it uses high-purity zinc foil with a purity of ≥99.99%. The surface impurities are polished by sequentially using 1000-mesh, 2000-mesh, 4000-mesh, and 6000-mesh sandpaper to make it smooth. The foil is then directly cut into electrode sheets for battery assembly. Electrochemical tests are performed and compared with the above examples.

[0063] The following series of tests were conducted to verify the superior performance of the present invention. The test results are as follows:

[0064] First, the above embodiments and comparative examples were scanned by electron microscopy, such as... Figure 1 As shown, it can be clearly observed that the surface of the comparative example is rough and rich in defects; while the protective layer constructed by Example 1 presents a three-dimensional support structure.

[0065] Water contact angle test, such as Figure 2 As shown, the comparative example has a contact angle greater than 100°, exhibiting hydrophobic properties; while the contact angle of Example 1 is less than 90°, exhibiting hydrophilic properties, which is more conducive to the adsorption and transfer of zinc ions.

[0066] Fourier infrared transform curve: such as Figure 3 As shown, the fluorinated functionalized three-dimensional scaffold protective layer constructed in situ in Example 1 is rich in F-Zn and BF bonds.

[0067] X-ray diffraction: such as Figure 4 As shown, the Zn(002) crystal plane strength of Example 1 is much higher than that of the comparative example, proving that the in-situ constructed protective layer used in this invention is beneficial to the exposure of the Zn(002) crystal plane.

[0068] Electrochemical impedance spectroscopy: The test frequency is 100,000~0.01Hz, such as... Figure 5 As shown, the impedance of Example 1 is much smaller than that of the comparative example.

[0069] Nucleation overpotential: such as Figure 6 As shown, the nucleation overpotential of Example 1 is 74 mV, which is less than that of the comparative example (122 mV).

[0070] Electrical testing: such as Figure 7 and 8 As shown, in the comparative example of untreated zinc sheet, the zinc metal surface is severely uneven, producing a large number of dendrites that penetrate into the glass fiber diaphragm; while in Example 1 with fluorinated functionalized three-dimensional scaffold protective layer, the zinc metal surface is very smooth, and no obvious dendrite formation is observed.

[0071] The zinc metal negative electrode of the three-dimensional fluorinated functionalized protective layer constructed in situ in Example 1 has a stable cycle life of over 3000 hours, while the comparative example only has a stable operation of no more than 200 hours.

[0072] In summary, the zinc battery treated by the method of this invention can guide the uniform deposition of zinc ions through the formed fluorine-functionalized three-dimensional scaffold protective layer, which is more conducive to the electrochemical stability of aqueous zinc-ion batteries.

Claims

1. A method for treating a zinc electrode, characterized in that, Includes the following steps: High-purity zinc foil is used as the electrode material, and its surface impurities are removed to make it smooth; The ionic liquid of 1-ethyl-3-methylimidazolium tetrafluoroborate was uniformly coated onto the surface of the zinc foil. Surface heat treatment is performed to form a fluorine-functionalized three-dimensional scaffold zinc anode protective layer on the surface of the zinc foil by the 1-ethyl-3-methylimidazolium tetrafluoroborate ions. After cleaning and drying the zinc foil surface, it is cut into electrode sheets.

2. The electrode processing method according to claim 1, characterized in that, The high-purity zinc foil refers to zinc foil with a purity of ≥99.99%.

3. The electrode processing method according to claim 1, characterized in that, The zinc foil surface is smoothed by sequentially polishing it with sandpaper of 1000 grit, 2000 grit, 4000 grit, and 6000 grit.

4. The electrode processing method according to claim 1, characterized in that, After uniformly coating the zinc foil with 1-ethyl-3-methylimidazolium tetrafluoroborate ionic liquid, the surface of the liquid is covered with waxed paper to remove air bubbles.

5. The electrode processing method according to claim 4, characterized in that, The surface heat treatment involves heating the zinc foil and the waxed paper together to 60–100°C and holding them at that temperature for 6–24 hours.

6. The electrode processing method according to claim 1, characterized in that, The drying step uses lint-free paper to completely dry the residual 1-ethyl-3-methylimidazolium tetrafluoroborate ionic liquid on the surface of the zinc foil.

7. The electrode processing method according to claim 1, characterized in that, The cut electrode sheet is a circular sheet with a diameter of 12-14 mm.

8. A method for preparing a zinc symmetrical button cell using a zinc electrode treated according to claims 1-7, characterized in that, Two zinc electrode plates are used as the positive and negative electrodes respectively and are placed on both sides of the separator. Electrolyte is dripped in, and gaskets and springs are used to press the zinc plates and the separator together to form a zinc symmetrical button cell.

9. The method for preparing a zinc symmetric button cell according to claim 8, characterized in that, The electrolyte includes one or more of zinc sulfate solution, zinc trifluoromethanesulfonate solution, and zinc chloride solution.

10. The method for preparing a zinc symmetric button cell according to claim 8, characterized in that, The diaphragm is a glass fiber diaphragm with a diameter of 16 mm and a thickness of 0.26 mm.

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