A method for preparing a zinc anode protective coating based on a dual-gradient zinc-affinity-conductivity structure

Abstract

This invention provides a method for preparing a zinc anode protective coating based on a dual-gradient zinc-affinity-conductivity structure. First, polymer-derived carbon fibers and silver-coated carbon fibers are prepared, and silver-coated carbon fiber slurries and polymer-derived carbon fiber slurries are formed respectively. These are then sequentially coated onto a zinc sheet using a stepwise slurry coating method to obtain a CF / Ag-CF@Zn electrode. This CF / Ag-CF@Zn electrode forms a dual-gradient protective coating with a top layer of polymer-derived carbon fibers and a bottom layer of silver-coated carbon fibers. By relying on the inherent zinc affinity-conductivity difference of the materials, it can directionally guide the internal ion-electron flow to achieve a safe bottom zinc deposition mode, thereby avoiding unfavorable top zinc dendrite growth. This achieves a highly reversible and stable zinc anode, providing a more competitive approach for rationally designing zinc anode coatings to construct ultra-stable aqueous zinc batteries.

Description

Technical Field

[0001] This invention belongs to the field of zinc metal battery technology, specifically relating to a method for preparing a zinc anode protective coating based on a dual-gradient zinc-affinity-conductivity structure. Background Technology

[0002] The growing demand for renewable energy has driven the development of highly stable, eco-friendly, and economically viable energy storage technologies. Among these, aqueous zinc batteries have attracted widespread attention as an emerging large-scale energy storage system. Zinc metal anodes possess a theoretically high capacity (820 mAh g / g). -1 The zinc-based battery offers several advantages, including low redox potential (-0.76V vs. standard hydrogen electrode (SHE)) and low cost. Furthermore, the non-flammable aqueous electrolyte simplifies assembly requirements, reduces the risk of battery device explosion, and lowers manufacturing costs. However, the practical application of aqueous zinc batteries still faces numerous challenges due to the short cycle life and low utilization rate of the zinc anode. During zinc deposition / stripping, uncontrolled 2D diffusion and uneven electric field distribution can lead to continuous zinc dendrite growth, causing volume changes, parasitic reactions, and even membrane puncture, resulting in capacity decay and ultimately battery failure. Therefore, effectively protecting the zinc anode to suppress dendrite growth and side reactions, and achieving stable and safe zinc deposition, is crucial.

[0003] To address the aforementioned issues, researchers have proposed various strategies to improve the stability of the zinc anode / electrolyte interface, primarily including the construction of artificial protective coatings, electrolyte optimization, and structural design. Among these, constructing functional protective layers is considered a simple and efficient strategy for improving the interfacial environment and stability, as it avoids the continuous consumption of functional additives, expensive concentrated electrolytes, and complex manufacturing techniques. Alloy anodes and metal-based coating materials possess high zinc affinity and conductivity, which can increase nucleation sites and uniform electric field distribution. However, corrosion, competitive reactions among metal species, and harsh manufacturing conditions hinder their widespread application. Furthermore, while inorganic or organic functional coatings exhibit high ion transport capabilities, their lower electronic conductivity can disrupt interfacial charge transfer and increase polarization voltage. Additionally, during repeated cycling, zinc deposits between the zinc surface and the coating can cause the functional layer to detach from the zinc surface. Therefore, the rational design of functional protective coatings for the safe and targeted regulation of zinc ion deposition patterns is a key strategy for achieving high-performance and dendrite-free zinc anodes. Summary of the Invention

[0004] This invention is made to solve the above-mentioned problems, and aims to provide a method for preparing a zinc negative electrode protective coating based on a dual-gradient zinc-affinity-conductivity structure.

[0005] This invention provides a method for preparing a zinc anode protective coating based on a dual-gradient zinc-affinity-conductive structure, characterized by the following steps: Step S1, trithiocyanate and perylene-3,4,9,10-tetracarboxylic acid dianhydride are added to dimethylformamide, stirred and mixed at room temperature, and then transferred to a high-pressure reactor for polymerization to obtain a reactant. The reactant is filtered, washed and dried to obtain a black-green porous polymer, which is then annealed in a nitrogen atmosphere to obtain polymer-derived carbon fibers.

[0006] Step S2: SnCl2·2H2O is dissolved in H2O, and polymer-derived carbon fibers are added. After ultrasonic treatment, Sn is obtained. 2+ Sensitized carbon fibers;

[0007] Step S3, Sn 2+ Sensitized carbon fibers were added to a fresh silver ammonia solution, and glucose and NaOH were added dropwise. After stirring at room temperature, the product was obtained. The product was washed and dried to obtain silver-coated carbon fibers.

[0008] Step S4: Polyvinylidene fluoride is mixed with polymer-derived carbon fiber and silver-coated carbon fiber respectively, and stirred in N-methylpyrrolidone to obtain polymer-derived carbon fiber slurry and silver-coated carbon fiber slurry respectively. The silver-coated carbon fiber slurry and polymer-derived carbon fiber slurry are coated onto zinc sheet by a stepwise slurry coating method. After vacuum drying, CF / Ag-CF@Zn electrode is obtained. The CF / Ag-CF@Zn electrode has a dual-gradient protective coating consisting of a top layer of polymer-derived carbon fiber and a bottom layer of silver-coated carbon fiber.

[0009] The method for preparing a zinc anode protective coating based on a dual-gradient zinc-conductive structure provided by the present invention may also have the following feature: wherein the ratio of trithiocyanate to perylene-3,4,9,10-tetracarboxylic acid dianhydride and dimethylformamide is 1 mmol:1 mmol:10 mL.

[0010] The method for preparing a zinc negative electrode protective coating based on dual gradient zinc affinity and conductivity provided by the present invention may also have the following feature: in step S1, during polymerization, polymerization is carried out at 160℃-200℃ for 22h-26h.

[0011] The method for preparing a zinc anode protective coating based on a dual-gradient zinc-conductive coating provided by the present invention may also have the following feature: in step S1, the stirring time is 10h-14h.

[0012] The method for preparing a zinc anode protective coating based on a dual-gradient zinc-conductive coating provided by the present invention may also have the following feature: in step S1, when drying, the coating is vacuum dried at 70℃-90℃ for 22h-26h.

[0013] The method for preparing a zinc negative electrode protective coating based on dual gradient zinc affinity and conductivity provided by the present invention may also have the following feature: in step S1, during the annealing process, the coating is annealed in a nitrogen atmosphere at a temperature of 550℃-650℃ for 1h-3h.

[0014] The method for preparing a zinc anode protective coating based on a dual-gradient zincophilic-conductive structure provided by this invention may also have the following characteristics: In step S2, the mass ratio of SnCl2·2H2O to polymer-derived carbon fibers is 4:1, the ultrasonic treatment time is 20-40 minutes, and Sn is washed multiple times with deionized water and ethanol after the ultrasonic treatment. 2+ Sensitized carbon fiber.

[0015] The method for preparing a zinc anode protective coating based on a dual-gradient zinc-conductive coating provided by the present invention may also have the following feature: in step S3, a fresh silver ammonia solution is prepared by adding silver nitrate to deionized water and then adding ammonia dropwise.

[0016] The method for preparing a zinc anode protective coating based on a dual-gradient zinc-conductive structure provided by this invention may also have the following features: in step S3, the stirring time is 20 min to 40 min, the product is washed multiple times with deionized water and ethanol, and then vacuum dried at 70℃ to 90℃ for 22 h to 26 h to obtain silver-coated carbon fibers.

[0017] The method for preparing a zinc anode protective coating based on a dual-gradient zinc-conductive structure provided by the present invention may also have the following characteristics: in step S4, the mass ratio of polyvinylidene fluoride to polymer-derived carbon fiber and silver-coated carbon fiber is 1:4, and the stirring time is 10h-14h.

[0018] The role and effect of invention

[0019] According to the preparation method of the zinc anode protective coating based on dual-gradient zinc affinity and conductivity of the present invention, polymer-derived carbon fibers and silver-coated carbon fibers are first prepared, and corresponding slurries are formed respectively. These are then coated onto a zinc sheet using a stepwise slurry coating method, forming a carbon-silver dual-gradient protective coating with a polymer-derived carbon fiber top layer and a silver-coated carbon fiber bottom layer. This dual-gradient protective coating can rely on the inherent zinc affinity and conductivity difference of the materials to directionally guide the internal ion-electron flow to achieve a safe bottom zinc deposition mode, avoiding unfavorable top zinc dendrite growth and short circuits caused by penetration of the separator. This constructs a highly reversible and highly stable zinc anode, providing a more competitive approach for rationally designing zinc anode coatings to construct ultra-stable aqueous zinc batteries. Furthermore, compared to existing methods such as electrolyte optimization and structural design, the method of constructing a dual-gradient protective coating in this invention avoids the continuous consumption of functional additives, expensive concentrated electrolytes, and complex manufacturing techniques. Attached Figure Description

[0020] Figure 1 This is a schematic diagram illustrating the working mechanism of the dual-gradient protective coating in an embodiment of the present invention;

[0021] Figure 2 These are scanning electron microscope images of the initial cross-section, the cross-section after cycling, and the top of the zinc electrode modified with the dual-gradient protective coating and the pure zinc electrode prepared in the embodiments of the present invention.

[0022] Figure 3 This describes the rate performance of symmetrical cells prepared in the embodiments of the present invention, specifically the zinc electrode modified with a dual-gradient protective coating and the pure zinc electrode.

[0023] Figure 4 The symmetrical battery cycle stability of the zinc electrode modified with the dual gradient protective coating and the pure zinc electrode prepared in the embodiments of the present invention;

[0024] Figure 5 The coulombic efficiency of zinc deposition / stripping in half-cells of copper electrodes modified with dual-gradient protective coatings and pure copper electrodes prepared in the embodiments of the present invention.

[0025] Figure 6 These are the cyclic voltammetry curves and constant current charge-discharge curves of KVOH full cells constructed from zinc electrodes modified with dual gradient protective coatings and pure zinc electrodes prepared in the embodiments of the present invention.

[0026] Figure 7 The cycling performance of the KVOH full cell constructed from the zinc electrode modified with a dual-gradient protective coating and the pure zinc electrode prepared in the embodiments of the present invention is shown. Detailed Implementation

[0027] To make the technical means, creative features, objectives and effects of this invention easier to understand, the following embodiments, in conjunction with the accompanying drawings, specifically illustrate a method for preparing a zinc negative electrode protective coating based on a dual-gradient zinc-affinity-conductive coating.

[0028] <Example>

[0029] This embodiment describes a method for preparing a zinc anode protective coating based on a dual-gradient zinc-affinity-conductivity structure, comprising the following steps:

[0030] Step S1: 5 mmol of trithiocyanate and 5 mmol of perylene-3,4,9,10-tetracarboxylic acid dianhydride were added to 50 mL of dimethylformamide. The mixture was stirred and mixed at room temperature for 12 h and then transferred to a high-pressure reactor. After polymerization at 180 °C for 24 h, the reactant was obtained. The reactant was filtered and washed with ethanol, and then vacuum dried at 80 °C for 24 h to obtain a black-green porous polymer. The product was then annealed at 600 °C in a nitrogen atmosphere for 2 h to obtain polymer-derived carbon fiber (CF).

[0031] Step S2: Dissolve 0.12g SnCl2·2H2O in 10mL H2O, add 0.03g polymer-derived carbon fiber, and sonicate for 30min to obtain Sn. 2+ Sensitized carbon fibers were washed multiple times with deionized water and ethanol.

[0032] Step S3: First, prepare a fresh silver ammonia solution: Add 0.6g of silver nitrate to 2ml of deionized water, then add an appropriate amount of ammonia water (6.6wt%) to form a fresh silver ammonia solution. Then, Sn... 2+ Sensitized carbon fibers were added to a fresh silver ammonia solution, and an appropriate amount of glucose and NaOH were added dropwise. After stirring at room temperature for 30 minutes, the product was obtained. The product was washed multiple times with deionized water and ethanol, and then dried under vacuum at 80°C for 24 hours to obtain silver-coated carbon fibers (Ag-CF).

[0033] In step S4, polyvinylidene fluoride (PVDF) was mixed with polymer-derived carbon fiber (CF) and silver-coated carbon fiber (Ag-CF) at a mass ratio of 1:4, and stirred in N-methylpyrrolidone for 12 hours to obtain polymer-derived carbon fiber slurry and silver-coated carbon fiber slurry, respectively. Then, using a stepwise slurry coating method, the silver-coated carbon fiber slurry and polymer-derived carbon fiber slurry were sequentially coated onto a zinc sheet with a thickness of 30 μm using blade coaters with heights of 20 μm and 40 μm, respectively. After vacuum drying at 80 °C for 24 hours, the CF / Ag-CF@Zn electrode was obtained.

[0034] The aforementioned CF / Ag-CF@Zn electrode has a dual-gradient protective coating consisting of a top layer of polymer-derived carbon fibers and a bottom layer of silver-coated carbon fibers.

[0035] Figure 1 This is a schematic diagram illustrating the working mechanism of the dual-gradient protective coating in an embodiment of the present invention. Figure 2 These are scanning electron microscope images of the initial cross-section, the cross-section after cycling, and the top of the zinc electrode modified with a dual-gradient protective coating and the pure zinc electrode prepared in the embodiments of the present invention. Figure 2 (a) Zinc electrode modified with a dual-gradient protective coating, and (b) pure zinc electrode.

[0036] like Figure 1 and Figure 2 As shown, during the zinc deposition / stripping process, uncontrollable 2D diffusion and uneven electric field distribution in the zinc anode will cause continuous growth of top zinc dendrites. However, the dual-gradient protective coating in this embodiment can safely regulate the zinc ion deposition mode by forming a dual-gradient zinc-loving-conductive structure on the zinc anode surface, and guide the ion-electron flow to achieve a safe bottom zinc deposition mode, avoiding the unfavorable top zinc dendrite growth, thus realizing a high-performance and dendrite-free zinc anode.

[0037] Furthermore, electrochemical tests were also performed in this embodiment, as detailed below:

[0038] The battery device uses a GE-Whatman glass fiber separator, 2.0M ZnSO4 as electrolyte, and a CR2032 type battery.

[0039] Symmetrical cells employ two identical zinc electrodes modified with a dual-gradient protective coating or pure zinc electrodes.

[0040] Asymmetric cells use copper foil or pure copper foil with a dual-gradient protective coating as the working electrode and pure zinc as the counter electrode.

[0041] The full cell uses a zinc electrode modified with a dual-gradient protective coating or a pure zinc electrode as the negative electrode, and KVOH as the positive electrode. The preparation method of the KVOH positive electrode is as follows:

[0042] First, KVOH was synthesized using a modified hydrothermal method: 0.182 mg V₂O₅ was dissolved in 25 mL of deionized water, and then 1 mL of 30% H₂O₂ was added dropwise. 0.0435 mg K₂SO₄ was dissolved in 15 mL of deionized water. The resulting precipitate was washed three times with deionized water and ethanol, and then dried under vacuum at 80 °C for 24 hours to obtain green KVOH. 12 O 30-y ·nH2O(KVOH).

[0043] KVOH, graphite, and polyvinylidene fluoride were then mixed in a mass ratio of 7:2:1, and an appropriate amount of N-methylpyrrolidone was added and thoroughly ground to prepare a slurry. This slurry was then uniformly coated onto titanium foil and vacuum dried at 80°C for 24 hours to obtain the KVOH cathode, with a KVOH loading of approximately 3-5 mg / cm³. -2 The energy storage performance of the device was tested using a CHI660E electrochemical workstation.

[0044] Figure 3 This describes the rate performance of symmetrical cells prepared in the embodiments of the present invention, using zinc electrodes modified with a dual-gradient protective coating and pure zinc electrodes.

[0045] like Figure 3 As shown, compared with the symmetric cell assembled from pure zinc electrodes, the symmetric cell assembled from zinc electrodes modified with dual-gradient protective coatings has a smaller overpotential, indicating that the modified electrode has more efficient zinc deposition kinetics.

[0046] Figure 4 This refers to the symmetrical battery cycle stability of the zinc electrode modified with a dual-gradient protective coating and the pure zinc electrode prepared in the embodiments of the present invention.

[0047] like Figure 4 As shown, the symmetrical zinc battery assembled in this embodiment operates at 5 mA cm⁻¹. -2 At current density, a remarkable cycle life of over 6700 hours was achieved.

[0048] In this embodiment, based on the above method, the pure zinc electrode is replaced with a pure copper electrode, and a copper electrode modified with a dual-gradient protective coating is prepared. At the same time, a comparative test is conducted on the pure copper electrode and the copper electrode modified with the dual-gradient protective coating. Figure 5 This refers to the coulombic efficiency of zinc deposition / stripping in half-cells of copper electrodes modified with dual-gradient protective coatings and pure copper electrodes prepared in the embodiments of the present invention.

[0049] like Figure 5 As shown, compared with the half-cell assembled with pure copper electrodes, the half-cell assembled with copper electrodes modified with a dual-gradient protective coating has a more stable coulombic efficiency.

[0050] Figure 6 These are the cyclic voltammetry and galvanostatic charge-discharge curves of KVOH full cells constructed from zinc electrodes modified with a dual-gradient protective coating and pure zinc electrodes prepared in the embodiments of the present invention. Figure 6 In the figure, (a) is the cyclic voltammetry curve, and (b) is the constant current charge-discharge curve.

[0051] like Figure 6As shown, the full cell assembled with zinc electrodes modified with a dual-gradient protective coating in this embodiment exhibits higher current density and discharge capacity in both the cyclic voltammetry curve and the constant current charge-discharge curve compared to the pure zinc electrode KVOH full cell, indicating that the zinc-loving-conductive protective coating can improve the reaction kinetics of the battery. Figure 7 The cycling performance of the KVOH full cell constructed from the zinc electrode modified with a dual-gradient protective coating and the pure zinc electrode prepared in the embodiments of the present invention is shown.

[0052] like Figure 7 As shown, the zinc-vanadium oxide hydrate (KVOH) full cell assembled in this embodiment operates at 5A g. -1 The capacity retention rate is over 73% after 2000 charge-discharge cycles at the current density.

[0053] The role and effect of the embodiments

[0054] According to the preparation method of the zinc anode protective coating based on dual-gradient zinc affinity and conductivity involved in this embodiment, polymer-derived carbon fibers and silver-coated carbon fibers are first prepared, and corresponding slurries are formed respectively. These are then coated onto a zinc sheet using a stepwise slurry coating method, forming a carbon-silver dual-gradient protective coating with a polymer-derived carbon fiber top layer and a silver-coated carbon fiber bottom layer. This dual-gradient protective coating can rely on the inherent zinc affinity and conductivity difference of the materials to directionally guide the internal ion-electron flow to achieve a safe bottom zinc deposition mode, avoiding unfavorable top zinc dendrite growth and short circuits caused by penetration of the separator. This constructs a highly reversible and highly stable zinc anode, providing a more competitive approach for rationally designing zinc anode coatings to construct ultra-stable aqueous zinc batteries. Furthermore, compared to existing methods such as electrolyte optimization and structural design, the dual-gradient protective coating method in this embodiment avoids the continuous consumption of functional additives, expensive concentrated electrolytes, and complex manufacturing techniques.

[0055] Furthermore, electrochemical tests in this embodiment show that, thanks to the safe bottom deposition mode induced by the dual-gradient protective coating, the symmetric zinc battery assembled in this embodiment achieves a performance of 5 mA cm⁻¹. -2 At current density, a remarkable cycle life of over 6700 hours and a high 16.75 Ah cm⁻¹ were achieved. -2 The cumulative capacity. Meanwhile, the assembled zinc||vanadium oxide hydrate (KVOH) full cell at 5A g. -1 The capacity retention rate is over 68% after 2000 charge-discharge cycles at the current density.

[0056] Those skilled in the art should understand that this invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to this invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a zinc anode protective coating based on a dual-gradient zinc-affinity-conductivity structure, characterized in that, Includes the following steps: Step S1: Trithiocyanate and perylene-3,4,9,10-tetracarboxylic acid dianhydride are added to dimethylformamide, stirred and mixed at room temperature, and then transferred to a high-pressure reactor for polymerization to obtain a reactant. The reactant is filtered, washed and dried to obtain a black-green porous polymer, which is then annealed in a nitrogen atmosphere to obtain polymer-derived carbon fibers. Step S2: Dissolve SnCl2·2H2O in H2O, add the polymer-derived carbon fibers, and then ultrasonically treat to obtain Sn. 2+ Sensitized carbon fibers; Step S3, the Sn 2+ Sensitized carbon fibers were added to a fresh silver ammonia solution, and glucose and NaOH were added dropwise. After stirring at room temperature, a product was obtained. The product was washed and dried to obtain silver-coated carbon fibers. Step S4: Polyvinylidene fluoride is mixed with the polymer-derived carbon fiber and the silver-coated carbon fiber, respectively, and stirred in N-methylpyrrolidone to obtain polymer-derived carbon fiber slurry and silver-coated carbon fiber slurry, respectively. The silver-coated carbon fiber slurry and the polymer-derived carbon fiber slurry are then coated onto a zinc sheet sequentially using a stepwise slurry coating method. After vacuum drying, a CF / Ag-CF@Zn electrode is obtained. The CF / Ag-CF@Zn electrode has a dual-gradient protective coating consisting of a top layer of polymer-derived carbon fiber and a bottom layer of silver-coated carbon fiber.

2. The method for preparing a zinc anode protective coating based on a dual-gradient zincophilic-conductive coating according to claim 1, characterized in that: in, In step S1, the ratio of trithiocyanate to perylene-3,4,9,10-tetracarboxylic acid dianhydride and dimethylformamide is 1 mmol:1 mmol:10 mL.

3. The method for preparing a zinc anode protective coating based on a dual-gradient zincophilic-conductive coating according to claim 1, characterized in that: in, In step S1, polymerization is carried out at 160℃-200℃ for 22h-26h.

4. The method for preparing a zinc anode protective coating based on a dual-gradient zincophilic-conductive coating according to claim 1, characterized in that: in, In step S1, the stirring time is 10h-14h.

5. The method for preparing a zinc anode protective coating based on a dual-gradient zincophilic-conductive coating according to claim 1, characterized in that: in, In step S1, during drying, vacuum drying is performed at 70℃-90℃ for 22h-26h.

6. The method for preparing a zinc anode protective coating based on a dual-gradient zincophilic-conductive coating according to claim 1, characterized in that: in, In step S1, during the annealing process, the annealing is carried out at a temperature of 550℃-650℃ in a nitrogen atmosphere for 1-3 hours.

7. The method for preparing a zinc anode protective coating based on a dual-gradient zincophilic-conductive coating according to claim 1, characterized in that: in, In step S2, the mass ratio of SnCl2·2H2O to polymer-derived carbon fibers is 4:1, the ultrasonic treatment time is 20-40 minutes, and after the ultrasonic treatment, the Sn is washed multiple times with deionized water and ethanol. 2+ Sensitized carbon fiber.

8. The method for preparing a zinc anode protective coating based on a dual-gradient zincophilic-conductive coating according to claim 1, characterized in that: in, In step S3, the fresh silver ammonia solution is prepared by adding silver nitrate to deionized water and then adding ammonia dropwise.

9. The method for preparing a zinc anode protective coating based on a dual-gradient zincophilic-conductive coating according to claim 1, characterized in that: in, In step S3, the stirring time is 20-40 minutes, the product is washed multiple times with deionized water and ethanol, and then vacuum dried at 70℃-90℃ for 22-26 hours to obtain the silver-coated carbon fiber.

10. The method for preparing a zinc anode protective coating based on a dual-gradient zincophilic-conductive coating according to claim 1, characterized in that: in, In step S4, the mass ratio of the polyvinylidene fluoride to the polymer-derived carbon fiber and the silver-coated carbon fiber is 1:4, and the stirring time is 10h-14h.

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