A zinc composite electrode and a preparation method and application thereof

Abstract

The application provides a zinc composite electrode and a preparation method and application thereof. The zinc composite electrode comprises a substrate and a coating attached to the surface of the substrate. The substrate comprises metallic zinc, and the coating comprises open-cage functionalized fullerenes. The open-cage functionalized fullerenes have the following structure: The open-cage functionalized fullerenes with the specific structure are used as a protective coating. The open-cage functionalized fullerenes can not only effectively avoid the contact between an electrolyte and a metallic zinc electrode, but also effectively adsorb Zn 2+ , regulate the structure of an interface double electric layer, guide the uniform nucleation of Zn 2+ , and inhibit the growth of zinc dendrites. When the zinc composite electrode is applied to a water-based zinc ion battery, the cycle life of the water-based zinc ion battery can be significantly improved.

Description

Technical Field

[0001] This invention relates to the field of electrode materials technology, and more specifically, to a zinc composite electrode, its preparation method, and its application. Background Technology

[0002] Aqueous zinc-ion batteries, due to their advantages such as abundant zinc resources, low redox potential, high ionic conductivity, and environmental friendliness, are expected to become a highly promising candidate system for next-generation energy storage applications. However, their development and utilization are hampered by issues such as zinc dendrite growth and side reactions between the zinc electrode and the aqueous electrolyte, which can affect the battery's safety, capacity, and lifespan. Therefore, taking measures to address these issues will help in the development of more advanced and efficient aqueous zinc-ion batteries.

[0003] To address the aforementioned issues, constructing a functionalized coating on the zinc electrode is an effective solution. The coating prevents direct contact between the zinc electrode and the aqueous electrolyte, thus avoiding side reactions. Simultaneously, the functionalized coating can effectively adsorb Zn. 2+ Adjusting the interface double-layer structure can guide uniform nucleation and suppress the growth of zinc dendrites. For example, patent ZL201810307937.1 discloses a method and its application for improving the cycle life of zinc batteries. By setting a porous coating between the zinc anode and the battery separator, new dendrites can be effectively suppressed, thus improving the cycle life of zinc-ion batteries. However, its modification is limited and cannot meet the needs of practical application scenarios. Summary of the Invention

[0004] To address the aforementioned technical problems in the existing technology, this application provides a zinc composite electrode comprising a substrate and a coating. The substrate comprises metallic zinc, and the coating comprises an open-cage functionalized fullerene. This invention uses an open-cage functionalized fullerene with a specific structure as a protective coating, which not only effectively prevents contact between the electrolyte and the metallic zinc electrode but also effectively adsorbs Zn. 2+ Adjusting the interface double-layer structure to guide Zn 2+ Uniform nucleation inhibits the growth of zinc dendrites.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] A zinc composite electrode includes a substrate and a coating attached to the surface of the substrate. The substrate comprises metallic zinc, and the coating comprises an open-cage functionalized fullerene having the following structure:

[0007] .

[0008] In some embodiments, the preparation of the open-cage functionalized fullerene includes the following steps:

[0009] S1. Fullerene and 3,4-diphenyl-6-(2-pyridyl)pyridazine are dissolved in a first organic solvent and mixed evenly to obtain a first mixed solution; the first mixed solution is heated to carry out the reaction; after the reaction is completed, it is cooled to room temperature, and then carbon disulfide is added to the system. The reaction is carried out under an oxygen atmosphere by irradiation with an Xe lamp to obtain an intermediate.

[0010] S2. Dissolve the intermediate, 3,6-bis(thiophen-2-yl)-1,2-phenylenediamine, in a second organic solvent, mix thoroughly, then add excess pyridine, and heat to react to obtain open-cage functionalized fullerene.

[0011] In some embodiments, in step S1, the molar ratio of the fullerene to the 3,4-diphenyl-6-(2-pyridyl)pyridazine is 1:(0.5-1.5).

[0012] In some embodiments, in step S1, the concentration of the fullerene in the first mixed solution is 0.02-0.04 mol / L.

[0013] In some embodiments, the reaction temperature in step S1 is 230-300°C.

[0014] In some implementations, the reaction time in step S1 is 22-30 hours.

[0015] In some embodiments, in step S2, the molar ratio of the intermediate to 3,6-bis(thiophen-2-yl)-1,2-phenylenediamine is 1:(4-6); and the amount of pyridine used is 40-60 eq.

[0016] In some embodiments, the reaction temperature in step S2 is 50-80°C.

[0017] In some implementations, the reaction time in step S2 is 12-24 hours.

[0018] In some embodiments, the first organic solvent includes 1-chloronaphthalene.

[0019] In some embodiments, the second organic solvent includes toluene.

[0020] In some embodiments, the coating thickness is 16-22µm.

[0021] The present invention also provides a method for preparing a zinc composite electrode according to any of the above embodiments, the method comprising the following steps:

[0022] The open-cage functionalized fullerene and binder are dissolved in water to prepare a slurry; then the slurry is coated on the surface of the zinc substrate and dried to obtain the zinc composite electrode.

[0023] In some embodiments, the binder includes carboxymethyl cellulose (CMC).

[0024] The present invention also provides an aqueous zinc-ion battery, wherein the aqueous zinc-ion battery includes the zinc composite electrode of any of the above embodiments.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] This invention uses specific open-cage functionalized fullerenes as a zinc electrode coating, which not only effectively avoids contact between the electrolyte and the metallic zinc electrode and suppresses side reactions between the zinc substrate and the electrolyte, but also effectively adsorbs Zn. 2+ Adjusting the interface double-layer structure to guide Zn 2+ Uniform nucleation inhibits the growth of zinc dendrites. Furthermore, compared to unopened fullerenes, open-cage functionalized fullerenes with specific functional groups can significantly improve adhesion to the zinc matrix, further enhancing the cycle life of aqueous zinc-ion batteries. Attached Figure Description

[0027] Figure 1 The proton NMR spectrum of open-cage functionalized fullerenes;

[0028] Figure 2 The zinc composite electrode (Zn@OC) prepared in Example 6 and Comparative Example 1 60 Contact angle test diagrams of pure metallic zinc electrodes (Bare Zn) without functional protective coatings;

[0029] Figure 3 The Zn@OC electrode of the zinc symmetric battery assembled in Example 6 and Comparative Example 1 after 200 hours of cycling. 60 XRD patterns of BareZn;

[0030] Figure 4 The Zn@OC electrode of the zinc symmetric battery assembled in Example 6 and Comparative Example 1 after 200 hours of cycling. 60 Scanning electron microscope images of BareZn;

[0031] Figure 5 These are cycle test diagrams of the zinc symmetric batteries assembled in Example 6 and Comparative Example 1 of this invention;

[0032] Figure 6 The figures show the electrochemical performance of the zinc-copper half-cells assembled in Example 9 and Comparative Example 1 of this invention, wherein (a) is a figure showing the Zn@OC 60 (a) Linear sweep voltammetry curves of zinc-copper half-cells assembled with Bare Zn; (b) Figure shows Zn@OC 60 Coulombic efficiency test graph of zinc-copper half-cell assembled with BareZn;

[0033] Figure 7 The figures show the electrochemical performance of the full cells assembled in Example 10 and Comparative Example 1 of this invention; wherein, (a) is a Zn@OC 60 Electrochemical impedance spectroscopy of a full cell assembled with Bare Zn; (b) Figure shows Zn@OC 60 Cyclic test diagram of a full battery assembled with Bare Zn. Detailed Implementation

[0034] Numerous specific details are set forth in the following description to provide a full understanding of the invention. However, the invention can be practiced in many other ways different from those described herein, and similar modifications can be made by those skilled in the art without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0036] Example 1

[0037] The preparation of open-cage functionalized fullerenes includes the following steps:

[0038] a. Weigh out fullerene (C) with a molar ratio of 1:1. 60 ) and 3,4-diphenyl-6-(2-pyridyl)pyridazine were dissolved in 1-chloronaphthalene, with a fullerene concentration of 0.03 mol / L. The mixture was refluxed at 255 °C for 48 h. After the reaction was completed and cooled to room temperature, carbon disulfide was added to the system, and the mixture was irradiated with a Xe lamp for 24 h in an oxygen atmosphere to obtain an open-cage functionalized fullerene intermediate (yield 28%).

[0039] b. The synthesized open-cage fullerene intermediate and 3,6-bis(thiophen-2-yl)-1,2-phenylenediamine were dissolved in toluene at a molar ratio of 1:5, and excess pyridine (50 eq) was added to the reaction system. The reaction was carried out at 60 °C for 18 h to obtain open-cage functionalized fullerene (yield 57%).

[0040] 20 mg of the open-cage functionalized fullerene was dissolved in deuterated chloroform and characterized by 1H NMR spectroscopy. The NMR spectrum is shown below. Figure 1 As shown.

[0041] Example 2

[0042] The preparation method of the open-cage functionalized fullerene in this embodiment is the same as that in Example 1, except that the preparation of the intermediate is different. The specific preparation method of the intermediate in this embodiment is as follows:

[0043] Fullerene and 3,4-diphenyl-6-(2-pyridyl)pyridazine were weighed in a molar ratio of 1:0.5 and dissolved in 1-chloronaphthalene, with a fullerene concentration of 0.03 mol / L. The mixture was refluxed at 255 °C for 48 h. After the reaction was completed and cooled to room temperature, carbon disulfide was added to the system, and the mixture was irradiated with a Xe lamp for 24 h under an oxygen atmosphere to obtain an open-cage functionalized fullerene intermediate (yield 24%).

[0044] Example 3

[0045] The preparation method of the open-cage functionalized fullerene in this embodiment is the same as that in Example 1, except that the preparation of the intermediate is different. The specific preparation method of the intermediate in this embodiment is as follows:

[0046] Fullerene and 3,4-diphenyl-6-(2-pyridyl)pyridazine were weighed in a molar ratio of 1:1.5 and dissolved in 1-chloronaphthalene at a concentration of 0.03 mol / L. The mixture was refluxed at 255 °C for 48 h. After the reaction was completed and cooled to room temperature, carbon disulfide was added to the system, and the mixture was irradiated with a Xe lamp for 24 h under an oxygen atmosphere to obtain an open-cage functionalized fullerene intermediate (yield 26%).

[0047] Example 4

[0048] The preparation method of the intermediate in this embodiment is the same as that in Example 1, except that the preparation of the open-cage functionalized fullerene is different. The specific preparation method of the open-cage functionalized fullerene in this embodiment is as follows:

[0049] The synthesized open-cage fullerene intermediate and 3,6-bis(thiophen-2-yl)-1,2-phenylenediamine were dissolved in toluene at a molar ratio of 1:4, and excess pyridine (50 eq) was added to the reaction system. The reaction was carried out at 60 °C for 18 h to obtain the open-cage functionalized fullerene (yield 52%).

[0050] Example 5

[0051] The preparation method of the intermediate in this embodiment is the same as that in Example 1, except that the preparation of the open-cage functionalized fullerene is different. The specific preparation method of the open-cage functionalized fullerene in this embodiment is as follows:

[0052] The synthesized open-cage fullerene intermediate and 3,6-bis(thiophen-2-yl)-1,2-phenylenediamine were dissolved in toluene at a molar ratio of 1:6, and excess pyridine (50 eq) was added to the reaction system. The reaction was carried out at 60 °C for 18 h to obtain the open-cage functionalized fullerene (yield 54%).

[0053] Example 6

[0054] Using the open-cage functionalized fullerene obtained in Example 1 as the coating material, an aqueous zinc-ion battery composite electrode was prepared. The specific method is as follows:

[0055] a. Weigh out open-cage functionalized fullerene and carboxymethyl cellulose (CMC) at a mass ratio of 4:1. Add the weighed CMC to a single crystal bottle, add deionized water and stir to disperse. After complete dispersion, add open-cage functionalized fullerene and continue stirring to mix evenly to obtain the coating slurry.

[0056] b. After polishing the commercial zinc foil with fine sandpaper, clean it with ethanol and dry it. Then, evenly coat the coating slurry obtained in step a onto the flat zinc foil surface and dry it in a vacuum oven at 60°C for 12 hours to obtain a zinc foil with an open-cage functionalized fullerene coating. Cut it to obtain a zinc composite electrode. The final thickness of the coating is about 20µm.

[0057] Preparation of symmetrical cells: The obtained composite electrode is used as the positive and negative electrode, a 2M ZnSO4 aqueous solution is prepared as the electrolyte, and a glass fiber membrane is used as the battery separator. The zinc-ion battery symmetrical cells are assembled in the following order: positive electrode shell, positive electrode, separator, electrolyte, negative electrode, gasket, and 2016 negative electrode shell.

[0058] Example 7

[0059] The preparation method of the zinc composite electrode in this embodiment is the same as that in Example 6, and the preparation of the symmetric cell is the same as that in Example 6. The difference is that the mass ratio of open-cage functionalized fullerene to carboxymethyl cellulose (CMC) is 7:3, and the final thickness of the coating is about 18 μm.

[0060] Example 8

[0061] The preparation method of the zinc composite electrode in this embodiment is the same as that in Example 6, and the preparation of the symmetric cell is the same as that in Example 6. The difference is that the mass ratio of open-cage functionalized fullerene to carboxymethyl cellulose (CMC) is 9:1, and the final thickness of the coating is about 19 μm.

[0062] Example 9

[0063] The preparation method of the zinc composite electrode in this embodiment is the same as that in Example 6, and the preparation method of the symmetrical cell is the same as that in Example 6. The difference is that copper foil is used as the positive electrode and the prepared zinc composite electrode is used as the negative electrode to assemble a zinc-copper half cell.

[0064] Example 10

[0065] The preparation method of the zinc composite electrode in this embodiment is the same as that in Example 6, except that the assembled battery is a full battery, as detailed below:

[0066] Preparation of the positive electrode: NVO, acetylene black and polyvinylidene fluoride (PVDF) were weighed in a mass ratio of 7:2:1 and dissolved in an appropriate amount of N-methylpyrrolidone (NMP). The mixture was stirred evenly to obtain a slurry. The slurry was coated onto a stainless steel mesh electrode sheet (the diameter of the cut electrode sheet was the same as the diameter of the composite electrode sheet). The electrode sheet was dried overnight at 80°C in a vacuum drying oven. The dried electrode sheet was used as the positive electrode of the aqueous zinc-ion full cell.

[0067] Electrolyte preparation: Prepare a 2M ZnSO4 aqueous solution as the electrolyte for the aqueous zinc-ion battery;

[0068] Separator: Glass fiber membrane is used as the separator for aqueous zinc-ion batteries;

[0069] Battery assembly: The 2016 battery positive electrode shell, NVO positive electrode, glass fiber separator, ZnSO4 electrolyte, zinc composite electrode, gasket, and 2016 battery negative electrode shell are placed in sequence to assemble the full battery.

[0070] Comparative Example 1

[0071] Preparation of zinc negative electrode sheet: Commercial zinc foil is polished with fine sandpaper, cleaned with ethanol and dried, and then cut to obtain zinc negative electrode sheet without functional protective coating.

[0072] Preparation of copper positive electrode sheet: copper foil is directly cut to obtain a copper positive electrode sheet with the same diameter as the zinc-coated negative electrode;

[0073] Preparation of copper-zinc half-cell: Same as in Example 9, except that the negative electrode is the zinc negative electrode prepared in this comparative example.

[0074] Preparation of the full cell: The preparation of the positive electrode and the cell is the same as in Example 10, except that the negative electrode is the zinc negative electrode prepared in this comparative example.

[0075] Performance testing and results analysis

[0076] 1. Regarding the zinc composite electrode (Zn@OC) with functionalized coating in Examples 6-10 60The performance of the zinc electrode (Bare Zn) with and without functional coating in Comparative Example 1 were tested as follows:

[0077] (1) Material characteristic testing

[0078] The zinc composite electrode prepared in Example 6 and the zinc negative electrode prepared in Comparative Example 1 were subjected to contact angle tests to test the hydrophilicity and hydrophobicity of the two electrodes. The test results are as follows: Figure 2 As shown.

[0079] like Figure 2 The functionalized coating exhibits good hydrophobicity, which can effectively prevent the zinc metal substrate from directly contacting the aqueous electrolyte and reduce the occurrence of side reactions.

[0080] The full cells assembled in Example 10 and Comparative Example 1 were subjected to cycle tests, and the Zn@OC cells were cycled for 200 hours. 60 Bare Zn was disassembled from the battery, and after cleaning the electrolyte from its surface, X-ray diffraction (XRD) analysis was performed to detect the side reactions occurring during the cycling process of the two electrodes. The test results are as follows: Figure 3 As shown.

[0081] like Figure 3 As shown, characteristic diffraction peaks of Zn4SO4(OH)6·5H2O appeared in the Bare Zn spectrum, while those of Zn@OC... 60 The absence of characteristic diffraction peaks of other substances in the spectral lines indicates that the coating effectively isolates the electrolyte from the zinc substrate and guides the uniform nucleation of zinc ions, thereby inhibiting corrosion and side reactions of the zinc substrate from the source.

[0082] (2) Surface morphology characterization

[0083] The symmetric cells assembled in Example 6 and Comparative Example 1 were cycle-tested for 200 hours. The dendrite growth on the zinc electrode surface before and after cycling was examined using scanning electron microscopy (SEM). The test results are as follows: Figure 4 As shown.

[0084] like Figure 4 After cycling the symmetric cells prepared in Example 6 and Comparative Example 1 for 200 hours, obvious zinc dendrites were formed on the surface of Bare Zn, while Zn@OC 60 The zinc deposition on the surface is relatively uniform, with no obvious dendrite growth.

[0085] (3) Electrochemical testing

[0086] The symmetrical cells assembled in Example 6 and Comparative Example 1 were subjected to long-term constant current cycling tests, and the test results are as follows: Figure 5 As shown.

[0087] like Figure 5At 1mA cm -2 1mAh cm -2 Under the condition of Zn@OC 60 The assembled battery exhibits a cycle life of up to 1000 hours and shows less polarization compared to batteries assembled with Bare Zn. Combined with the characteristics of the coating, it can be demonstrated that the functionalized coating significantly improves the zinc deposition process, suppresses zinc dendrite growth, and enhances the battery's cycle life.

[0088] The zinc-copper half-cells assembled in Example 9 and Comparative Example 1 were used to test the effect of the coating on the Zn peeling / electroplating behavior using linear sweep voltammetry and coulombic efficiency. The results are as follows: Figure 6 As shown;

[0089] like Figure 6 Figure (a) shows that, under the same current density conditions, Zn@OC 60 The assembled battery exhibited a larger hydrogen evolution overpotential than Bare Zn, indicating that the coating significantly suppressed the occurrence of hydrogen evolution side reactions; Figure 6 Figure (b) shows the results at 0.5 mA cm. -2 0.5mAh cm -2 Under the condition of Zn@OC 60 It has a longer cycle life and higher coulombic efficiency (98.7%) than Bare Zn, which indicates that Zn@OC has a longer cycle life and higher coulombic efficiency. 60 Assembling zinc-copper half-cells exhibits good electrochemical reversibility and can effectively improve the lifespan of aqueous zinc-ion batteries.

[0090] Finally, the full cells assembled in Example 10 and Comparative Example 1 were tested using electrochemical impedance spectroscopy and long-cycle constant current charge-discharge performance tests to verify the protective effect of the functionalized coating on the zinc anode. The results are as follows: Figure 7 As shown.

[0091] like Figure 7 Figure (a), Zn@OC 60 It has a smaller R than Bare Zn ct The value indicates that Zn@OC 60 It exhibits a faster charge transfer rate, thanks to the π-conjugated structure of the open-cage functionalized fullerene, which promotes electron delocalization; such as Figure 7 Figure (b) is in 1A g -1 Under the current density test conditions, the specific capacities of the two types of batteries were similar before 300 cycles. However, as the number of cycles continued to increase, a significant capacity decay was observed in the battery assembled with Bare Zn, while the battery assembled with Zn@OC showed a different capacity decay. 60The assembled battery exhibited a relatively small decrease in specific capacity. This is attributed to the protective effect of the functionalized coating, which physically prevents the zinc electrode from directly contacting water, reduces side reactions between the zinc electrode and the electrolyte, and mitigates corrosion and passivation of the zinc electrode; electrochemically, it induces Zn... 2+ Uniform deposition inhibits the growth of zinc dendrites and reduces irreversible zinc metal deposition, thereby maintaining a relatively stable battery capacity.

[0092] Based on the above analysis, this invention, while retaining the original characteristics of fullerenes (intrinsic electron dominance), employs an open-cage functionalization method to functionalize fullerenes with perfectly closed-cage structures. This expands the role of fullerenes as coatings in aqueous zinc-ion batteries. The presence of openings can lower the activation barrier for ion crossing the interface, and the zinc-loving groups (carbonyl, pyridine nitrogen, thiophene ring sulfur) introduced at the opening edges can induce Zn... 2+ Uniform deposition inhibits the growth of zinc dendrites and improves adhesion to the zinc substrate. Using open-cage functionalized fullerenes as a zinc anode coating for aqueous zinc-ion batteries can significantly improve the battery's lifespan, specific capacity, and other electrochemical performance parameters.

[0093] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0094] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A zinc composite electrode, characterized in that, The system includes a substrate and a coating adhered to the surface of the substrate. The substrate comprises metallic zinc, and the coating comprises an open-cage functionalized fullerene having the following structure: 。 2. The zinc composite electrode according to claim 1, characterized in that, The preparation of the open-cage functionalized fullerene includes the following steps: S1. Fullerene and 3,4-diphenyl-6-(2-pyridyl)pyridazine are dissolved in a first organic solvent and mixed evenly to obtain a first mixed solution; the first mixed solution is heated to carry out the reaction; after the reaction is completed, it is cooled to room temperature, and then carbon disulfide is added to the system. The reaction is carried out under an oxygen atmosphere by irradiation with an Xe lamp to obtain an intermediate. S2. Dissolve the intermediate, 3,6-bis(thiophen-2-yl)-1,2-phenylenediamine, in a second organic solvent, mix thoroughly, then add excess pyridine, and heat to react to obtain open-cage functionalized fullerene.

3. The zinc composite electrode according to claim 2, characterized in that, In step S1, the molar ratio of the fullerene to the 3,4-diphenyl-6-(2-pyridyl)pyridazine is 1:(0.5-1.5).

4. The zinc composite electrode according to claim 2, characterized in that, In step S1, the concentration of fullerene in the first mixed solution is 0.02-0.04 mol / L.

5. The zinc composite electrode according to claim 2, characterized in that, In step S1, the reaction temperature is 230-300℃; and / or the reaction time is 22-30h.

6. The zinc composite electrode according to claim 2, characterized in that, In step S2, the molar ratio of the intermediate to 3,6-bis(thiophen-2-yl)-1,2-phenylenediamine is 1:(4-6); the amount of pyridine used is 40-60 eq.

7. The zinc composite electrode according to claim 2, characterized in that, In step S2, the reaction temperature is 50-80℃; and / or the reaction time is 12-24h.

8. The zinc composite electrode according to any one of claims 2-7, characterized in that, The first organic solvent includes 1-chloronaphthalene; and / or, the second organic solvent includes toluene.

9. The method for preparing the zinc composite electrode according to any one of claims 1-8, characterized in that, Includes the following steps: The open-cage functionalized fullerene and binder are dissolved in water to prepare a slurry; then the slurry is coated on the surface of the zinc substrate and dried to obtain the zinc composite electrode.

10. An aqueous zinc-ion battery, characterized in that, Includes the zinc composite electrode according to any one of claims 1-9.

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