Preparation method and application of ultrathin hydrophobic zincophilic artificial solid protective layer

Abstract

The application relates to a preparation method and application of an ultrathin hydrophobic zincophilic artificial solid protective layer, and belongs to the field of aqueous zinc ion batteries. 2+ The selective nanofilm eliminates the problem of a water layer between a zinc negative electrode and an electrolyte interface. Method: I. Preparation of the FeHCF nanofilm; II. Transfer of the FeHCF nanofilm.Application, which is used as a protective layer of a zinc negative electrode in an aqueous zinc ion battery.The application is used for the preparation and application of an ultrathin hydrophobic zincophilic artificial solid protective layer.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of aqueous zinc-ion batteries. BACKGROUND

[0002] Aqueous zinc metal batteries (AZMBs) have great prospects as cost-effective, intrinsically safe, and environmentally benign energy storage systems. However, the instability of zinc metal anodes seriously hinders the practical application of AZMBs. In the commonly used weakly acidic aqueous electrolyte, the zinc anode suffers from uncontrolled dendrite growth and side reactions, leading to reduced coulombic efficiency, shortened cycle life, and safety problems, thus hindering the realization of high-performance zinc-based batteries.

[0003] One of the main challenges faced by zinc anodes comes from water-related reactions, such as the hydrogen evolution reaction (HER). Zinc deposition (Zn / Zn 2+ ) occurs at a relatively low potential (-0.76 V vs. SHE), which is much lower than the standard hydrogen evolution potential. However, in weakly acidic electrolytes, the competition between zinc deposition and HER is quite severe. During zinc deposition, protons will enter the anode surface along with Zn 2+ and be reduced to hydrogen (i.e., 2H + + 2e - → H2). In addition, the vertical growth of zinc dendrites will expose more HER active sites. The HER on the anode surface is largely dependent on the water structure at the interface. It has been reported that the solvation structure of the Helmholtz outer layer plays an important role in regulating the HER activity on the electrode surface. Under the guidance of this principle, various strategies such as high-concentration electrolyte, ionic liquid, water-poor hydrogel, and hydrophobic organic matter are adopted to regulate the electric double layer. It has been proven that these strategies are successful in reducing the water activity at the interface. However, in order to exclude the possible HER at the interface, the unwanted water layer at the electrode interface should be completely eliminated. Therefore, it is very necessary to achieve direct solid-solid contact between the electrode and the electrolyte to prevent the formation of a water layer on the anode surface. At the same time, the electrode interface should exhibit ionic selectivity for fast Zn 2+ transport. However, common electrode interface protective layers will gradually absorb and diffuse water in the protective layer, inevitably leading to the formation of an ultra-thin water layer. Therefore, how to construct an ultra-thin, waterproof, Zn 2+ selective nanofilm to eliminate the water layer between the zinc anode and the electrolyte interface is a technical difficulty that needs to be solved in the prior art. SUMMARY

[0004] The present application solves the problem that the prior art cannot construct an ultra-thin, waterproof, Zn 2+ selective nanofilm to eliminate the water layer between the zinc anode and the electrolyte interface, and further provides a preparation method and application of an ultra-thin hydrophobic zincophilic artificial solid protective layer.

[0005] A preparation method of an ultrathin hydrophobic zincophilic artificial solid protective layer, which is carried out according to the following steps:

[0006] I. Preparation of FeHCF nanofilm:

[0007] A potassium ferricyanide aqueous solution is mixed with deionized water, a chloroform solution of didodecyldimethylammonium bromide is dispersed on the liquid surface and left to stand, a surfactant layer is formed at the air-water interface, and then a ferric chloride aqueous solution is added dropwise to the solution under the surfactant layer, reaction is carried out at room temperature, a FeHCF nanofilm is formed at the air-water interface, and a liquid containing the FeHCF nanofilm is obtained;

[0008] II. Transfer of FeHCF nanofilm:

[0009] The substrate is vertically immersed in the liquid containing the FeHCF nanofilm, and then the substrate is slowly lifted, the FeHCF nanofilm formed at the air-water interface is transferred to the substrate, and finally drying is carried out, thereby completing the preparation method of the ultrathin hydrophobic zincophilic artificial solid protective layer.

[0010] Application of the ultrathin hydrophobic zincophilic artificial solid protective layer, which is used as a protective layer for a zinc negative electrode in a water-based zinc ion battery.

[0011] The present application has the following beneficial effects:

[0012] The present application provides a new method for stabilizing a zinc metal negative electrode, which is achieved by constructing an ultrathin (~ 16.9 nm), Zn 2+ selective and water-resistant layer. This interface engineering strategy effectively eliminates the electrode interface water layer, inhibits hydrogen evolution and corrosion, and thus overcomes the long-standing obstacle to the development of water-based zinc batteries. The "Faraday cation pumping" mechanism generated within the FeHCF nanofilm ensures fast and selective Zn 2+ transport, while maintaining negligible water permeation, thereby creating a stable, dendrite-free environment.

[0013] Drawings of the specification

[0014] Figure 1 The drawings show the formation of the FeHCF nanofilm at the air-water interface in step one of Example Two, a is a whole drawing, and b is a local enlarged view of the edge of the FeHCF nanofilm;

[0015] Figure 2 The optical microscope and transmission electron microscope images of the FeHCF nanofilm prepared in step one of Example One, (a) optical microscope image, (b) transmission electron microscope image;

[0016] Figure 3XRD pattern and TEM high resolution image of FeHCF nanofilm prepared in step one of Example One, (a) XRD image, (b) TEM high resolution image, inset is electron diffraction pattern;

[0017] Figure 4 Elemental mapping, AFM image, Raman image, XPS full spectrum of FeHCF nanofilm prepared in step one of Example One, (a) elemental mapping image, (b) AFM image, (c) Raman image, (d) XPS full spectrum;

[0018] Figure 5 Infrared image and contact angle image, (a) infrared image of FeHCF nanofilm prepared in step one of Example One, (b) contact angle comparison image of zinc sheet coated with ultrathin hydrophobic zincophilic artificial solid protective layer prepared in Example One and bare Zn;

[0019] Figure 6 Deposition / stripping coulombic efficiency test comparison chart of Zn||Cu half battery assembled in Example Three and Comparative Experiment One, a is the CE chart of Zn||Cu half battery at 10 mA / cm 2 and 1 mAh / cm 2 , b is the CE chart of Zn||Cu half battery at 5 mA / cm 2 and 1 mAh / cm 2 ;

[0020] Figure 7 Voltage distribution comparison chart of Zn||Cu half battery assembled in Example Three and Comparative Experiment One at 10 mA / cm 2 and 1 mAh / cm 2 , a is Example Three, b is Comparative Experiment One;

[0021] Figure 8 Cycle test comparison chart of Zn||Zn symmetric battery assembled by transferring FeHCF nanofilm to zinc foil in Example Four and Comparative Experiment Two, a is cycle performance at 1 mA / cm 2 and 1 mAh / cm 2 , b is DOD cycle performance at 2 mA / cm 2 and 10 mAh / cm 2 ;

[0022] Figure 9 In-situ optical microscope image of zinc deposition / stripping of FeHCF / Cu and bare Cu after cycling of Zn||Cu half battery assembled in Example Three and Comparative Experiment One, a is bare Cu, b is FeHCF / Cu;

[0023] Figure 10Zinc deposition and stripping thickness of FeHCF / Cu and bare Cu for Zn||Cu half-cell assembled in Example 3 and Comparative Experiment 1 group after cycling;

[0024] Figure 11 Zinc foil morphology and mechanical strength test figure of FeHCF nanofilm prepared in Example 1 attached to titanium foil (experimental group) and pure titanium foil (control group) after deposition, a is the stripping schematic diagram and physical figure of zinc foil deposited on the surface of titanium foil in the experimental group, b is the physical figure of large area (10 cm x 10 cm) zinc foil after stripping of the experimental group titanium foil surface deposition, c is the physical figure of zinc foil deposited on the surface of titanium foil in the experimental group after stripping and folding, d is the physical figure of zinc foil deposited on the surface of titanium foil in the control group after stripping and folding;

[0025] Figure 12 Scanning electron microscope figure of the negative electrode of Zn||Zn symmetric cell assembled in Example 4 and Comparative Experiment 2 after cycling, a and b are Example 4, c and d are Comparative Experiment 2;

[0026] Figure 13 Reversible color change of zinc foil attached with FeHCF powder prepared in Example 1 during zinc deposition and stripping process; a is not cycled; b is 2.5 mAh deposited under the current of 20 mA; c is 5 mAh deposited under the current of 20 mA; d is 5 mAh deposited under the current of 20 mA and then 2.5 mAh stripped; e is 5 mAh deposited under the current of 20 mA and then 5 mAh stripped;

[0027] Figure 14 XPS spectrum of FeHCF prepared in Example 1 during zinc deposition and stripping process and Fe 2p XPS spectrum of FeHCF nanofilm not cycled, a is FeHCF after 15 minutes of deposition, b is FeHCF after 15 minutes of deposition and 15 minutes of stripping, c is Fe 2p XPS spectrum of FeHCF nanofilm prepared in Example 1 step 1 not cycled;

[0028] Figure 15 XRD figure, theoretically calculated electrostatic potential figure and theoretically calculated electric field distribution of the negative electrode of Zn||Zn symmetric cell assembled in Example 4 after charge and discharge cycling; a is XRD spectrum of FeHCF / Zn, 1 is the initial state, 2 is after 5 minutes of discharge, 3 is after 10 minutes of discharge, 4 is after 10 minutes of discharge and 5 minutes of charge, 5 is after 10 minutes of discharge and 10 minutes of charge; b is theoretically calculated electrostatic potential figure of Fe III Fe III (CN)6and [Fe II Fe II (CN)6] 2- ; c is theoretically calculated electric field distribution of bare Zn and FeHCF / Zn;

[0029] Figure 16 In-situ Raman test of the negative electrode of the Zn||Zn symmetrical battery assembled for Example Four and Comparative Experiment Two after deposition and sulfate peak separation diagram, a is the in-situ Raman test of Example Four, b is the in-situ Raman test of Comparative Experiment Two, c is the sulfate peak separation of Example Four, d is the sulfate peak separation of Comparative Experiment Two, 1 is 0 minutes of deposition, 2 is 10 minutes of deposition, 3 is 20 minutes of deposition, 4 is 30 minutes of deposition, 5 is 40 minutes of deposition, 6 is 50 minutes of deposition in c and d;

[0030] Figure 17 In-situ pH change diagram of the negative electrode region of the symmetrical battery of Example Four and Comparative Experiment Two, LSV curve of the electrode, in-situ EIS measurement of the negative electrode of the symmetrical battery, a is the in-situ pH change of the negative electrode region of the symmetrical battery, b is the LSV curve of the electrode, c is the in-situ EIS measurement of Example Four, d is the in-situ EIS measurement of Comparative Experiment Two. DETAILED DESCRIPTION

[0031] Specific implementation method one: the preparation method of the ultrathin hydrophobic zinc-phil artificial solid protective layer is carried out according to the following steps:

[0032] I. Preparation of FeHCF nanofilm:

[0033] Mix the potassium ferricyanide aqueous solution with deionized water, disperse the chloroform solution of didodecyldimethylammonium bromide on the liquid surface and stand still, form a surfactant layer at the air-water interface, then add the aqueous solution of ferric chloride drop by drop to the solution under the surfactant layer, react at room temperature, and form a FeHCF nanofilm at the air-water interface to obtain a liquid containing the FeHCF nanofilm;

[0034] II. Transfer of FeHCF nanofilm:

[0035] Vertically immerse the substrate into the liquid containing the FeHCF nanofilm, then slowly lift the substrate, transfer the FeHCF nanofilm formed at the air-water interface to the substrate, and finally dry, thereby completing the preparation method of the ultrathin hydrophobic zinc-phil artificial solid protective layer.

[0036] The beneficial effects of the present embodiment are:

[0037] The present embodiment provides a new method for stabilizing the zinc metal negative electrode, which constructs an ultrathin (~ 16.9 nm), Zn 2+Selective and water-proof layer. This interfacial engineering strategy effectively eliminates the water layer at the electrode interface, suppressing hydrogen evolution and corrosion, thus overcoming the long-standing obstacles for aqueous zinc batteries development. The "Faradaic cation pumping" mechanism generated within the FeHCF nanofilm ensures fast and selective Zn 2+ transport while maintaining negligible water permeation, thus creating a stable, dendrite-free environment.

[0038] Embodiment two: different from embodiment one, the concentration of the potassium ferricyanide aqueous solution in step one is 0.01mol / L-0.2mol / L; the concentration of the dioctadecyldimethylammonium bromide chloroform solution in step one is 1.0mmol / L-2.0mmol / L; the concentration of the ferric chloride aqueous solution in step one is 0.01mol / L-0.2mol / L. The others are the same as embodiment one.

[0039] Embodiment three: different from either embodiment one or two, the volume ratio of the potassium ferricyanide aqueous solution to deionized water in step one is 1:(10-20). The others are the same as either embodiment one or two.

[0040] Embodiment four: different from any one of embodiments one to three, the volume ratio of the potassium ferricyanide aqueous solution to the dioctadecyldimethylammonium bromide chloroform solution in step one is 1:(0.001-0.01). The others are the same as embodiments one to three.

[0041] Embodiment five: different from any one of embodiments one to four, the volume ratio of the potassium ferricyanide aqueous solution to the ferric chloride aqueous solution in step one is 1:(1-2). The others are the same as embodiments one to four.

[0042] Embodiment six: different from any one of embodiments one to five, the standing time in step one is 5min-60min; the reaction time at room temperature in step one is 20h-48h. The others are the same as embodiments one to five.

[0043] Embodiment seven: different from any one of embodiments one to six, the thickness of the FeHCF nanofilm in step one is 10nm-50nm. The others are the same as embodiments one to six.

[0044] Embodiment eight: different from any one of embodiments one to seven, the substrate in step two is a metal zinc negative electrode. The others are the same as embodiments one to seven.

[0045] Specific embodiment nine: the difference between this embodiment and one of the specific embodiments one to eight is that: in step two, the substrate is slowly lifted at a speed of 0.01 m / s to 1 m / s; the drying in step two is specifically drying for 0.5 h to 24 h under the condition that the temperature is 25℃ to 60℃. The others are the same as specific embodiments one to eight.

[0046] Specific embodiment ten: the application of the ultra-thin hydrophobic and zincophilic artificial solid protective layer, which is used as a protective layer for zinc negative electrode in aqueous zinc ion battery.

[0047] The beneficial effects of the present application are verified by the following examples:

[0048] Example one:

[0049] A preparation method of an ultra-thin hydrophobic and zincophilic artificial solid protective layer, which is carried out according to the following steps:

[0050] I. Preparation of FeHCF nanofilm:

[0051] 2 mL of potassium ferricyanide (K3Fe(CN)6) aqueous solution was added to a culture dish with a diameter of 8.5 cm, then 20 mL of deionized water was added and mixed uniformly, 20 μL of dioctadecyl dimethyl ammonium bromide (DODA) chloroform solution was dispersed on the liquid surface and stood for 5 min, a surfactant layer was formed at the air-water interface, then 2 mL of ferric chloride aqueous solution was added dropwise to the solution under the surfactant layer, and the reaction was carried out at room temperature for 20 h, and FeHCF nanofilm was formed at the air-water interface, and a liquid containing FeHCF nanofilm was obtained;

[0052] The concentration of the potassium ferricyanide aqueous solution is 0.05 mol / L; the concentration of the dioctadecyl dimethyl ammonium bromide chloroform solution is 1.8 mmol / L; the concentration of the ferric chloride aqueous solution is 0.025 mol / L;

[0053] The thickness of the FeHCF nanofilm is 16.9 nm;

[0054] II. Transfer of FeHCF nanofilm:

[0055] The substrate was vertically immersed in the liquid containing FeHCF nanofilm, then the substrate was slowly lifted at a speed of 0.01 m / s, the FeHCF nanofilm formed at the air-water interface was transferred to the substrate, and finally dried for 0.5 h at a temperature of 60℃, to obtain zinc sheet covered with ultra-thin hydrophobic and zincophilic artificial solid protective layer (FeHCF / Zn) and copper sheet covered with ultra-thin hydrophobic and zincophilic artificial solid protective layer;

[0056] The zinc sheet is a zinc sheet polished with sandpaper to a smooth surface; the substrate is a zinc sheet (thickness 200 pm) or a copper sheet (thickness 100 pm).

[0057] Example Two: This example is different from Example One in that in Step One, 200 mL of an aqueous potassium ferricyanide (K3Fe(CN)6) solution is added to a container with a size of 1.2 m x 0.3 m, then 2000 mL of deionized water is added and mixed uniformly, 1000 pL of a dioctadecyldimethylammonium bromide (DODA) chloroform solution is dispersed on the liquid surface and left to stand for 5 min, a surfactant layer is formed at the air-water interface, then 200 mL of an aqueous ferric chloride solution is added dropwise to the solution below the surfactant layer, and the reaction is carried out at room temperature for 20 h, an FeHCF nanofilm is formed at the air-water interface, and a liquid containing the FeHCF nanofilm is obtained. The rest is the same as in Example One.

[0058] Example Three, Preparation of Zn||Cu Half Cell:

[0059] The zinc sheet (diameter 1 cm) coated with an ultrathin hydrophobic zinc-phil artificial solid protective layer prepared in Example One is used as the negative electrode of the battery, the copper sheet (diameter 1 cm) coated with an ultrathin hydrophobic zinc-phil artificial solid protective layer prepared in Example One is used as the positive electrode of the battery, glass fiber is used as the separator, and 80 pL of zinc sulfate electrolyte (2M) is added to prepare a CR2032 button cell.

[0060] Comparative Experiment One: This comparative experiment is different from Example Three in that the zinc sheet (thickness 200 pm, diameter 1 cm) and the copper sheet (thickness 100 pm, diameter 1 cm) are polished with sandpaper to smooth the surface, the polished zinc sheet is used as the negative electrode of the battery, and the polished copper sheet is used as the positive electrode of the battery. The rest is the same as in Example Three.

[0061] Example Four, Preparation of Zn||Zn Symmetric Cell:

[0062] The zinc sheet (diameter 1 cm) coated with an ultrathin hydrophobic zinc-phil artificial solid protective layer prepared in Example One is used as the negative electrode and the positive electrode of the battery, glass fiber is used as the separator, and 80 pL of zinc sulfate electrolyte (2M) is added to prepare a CR2032 button cell.

[0063] Comparative Experiment Two: This comparative experiment is different from Example Four in that the zinc sheet (diameter 1 cm) is polished with sandpaper to smooth the surface, and the polished zinc sheet is used as the negative electrode and the positive electrode of the battery. The rest is the same as in Example Four.

[0064] Figure 1Figure 1 shows the optical microscope and transmission electron microscope images of the FeHCF nanofilm prepared in Example 1, Step 1, (a) optical microscope image, (b) transmission electron microscope image; the optical and transmission electron microscope images confirm the uniformity, continuity and defect-free of the transferred nanofilm in macro and micro.

[0065] For optical microscope test, the FeHCF nanofilm prepared in Example 1, Step 1, was transferred to a silicon substrate; for transmission electron microscope test, the FeHCF nanofilm prepared in Example 1, Step 1, was transferred to a copper mesh substrate. Figure 2 Figure 1 shows the optical microscope and transmission electron microscope images of the FeHCF nanofilm prepared in Example 1, Step 1, (a) optical microscope image, (b) transmission electron microscope image; the optical and transmission electron microscope images confirm the uniformity, continuity and defect-free of the transferred nanofilm in macro and micro.

[0066] Figure 3 Figure 2 shows the XRD and high-resolution TEM images of the FeHCF nanofilm prepared in Example 1, Step 1, (a) XRD image, (b) high-resolution TEM image, inset is the electron diffraction pattern; the X-ray diffraction (XRD) pattern shows the characteristic peaks of face-centered cubic FeHCF phase; the high-resolution TEM image shows the lattice fringes with a spacing of 0.49 nm, corresponding to the (200) plane; the selected area electron diffraction (SAED) verifies the cubic structure.

[0067] For elemental mapping, AFM, Raman and XPS test, the FeHCF nanofilm prepared in Example 1, Step 1, was transferred to a silicon substrate. Figure 4 Figure 3 shows the elemental mapping, AFM, Raman and XPS spectra of the FeHCF nanofilm prepared in Example 1, Step 1, (a) elemental mapping image, (b) AFM image, (c) Raman image, (d) XPS spectrum; the elemental mapping shows the uniform distribution of Fe, N and C throughout the film; the AFM image shows that the thickness of the synthesized nanofilm is about 16.9 nm; the Raman spectrum shows the stretching vibration of cyanide at 2156 cm -1 and 2092 cm -1 ; respectively, CN- is coordinated with Fe(III) and Fe(II). The X-ray photoelectron spectroscopy (XPS) full spectrum again confirms the presence of carbon, nitrogen, iron and oxygen; the X-ray photoelectron spectroscopy (XPS) peak separation of Fe 2p signal (c) further confirms the mixed state of Fe(II) / Fe(III). Figure 14

[0068] The zinc sheet coated with the ultrathin hydrophobic and zincophilic artificial solid protective layer prepared in Example 1 was used for infrared and contact angle tests. Figure 5 ​The infrared image and contact angle image are as follows: (a) infrared image of the FeHCF nanofilm prepared in step 1 of Example 1; (b) contact angle comparison of the zinc sheet covered with the ultra-thin hydrophobic zinc-philic artificial solid protective layer prepared in Example 1 and bare Zn; the FTIR spectrum of the FeHCF nanofilm at 2087 cm -1 A CN stretching band is shown at 2918 cm -1 and 2850cm -1 The observed antisymmetric and symmetric methylene stretching bands match those of crystalline DODABr, confirming the presence of ordered alkyl chains in the FeHCF nanofilm. The incorporation of these alkyl chains imparts pronounced hydrophobicity to the FeHCF nanofilm. Consequently, the FeHCF / Zn nanofilm exhibits a larger contact angle (110°) compared to bare Zn (72°), reflecting an effective water-repellent interface.

[0069] Figure 6 This is a comparison chart of the deposition / stripping coulombic efficiency test of the Zn||Cu half-cell assembled in Example 3 and Comparative Experiment 1. a is the value at 10 mA / cm 2 and 1mAh / cm 2 CE diagram of Zn||Cu half-cell, b is at 5mA / cm 2 and 1mAh / cm 2 CE diagram of Zn||Cu half-cell when ; Figure 7 At 10mA / cm 2 and 1mAh / cm 2 Comparison of the voltage distribution of the Zn||Cu half-cells assembled in Example 3 and Comparative Experiment 1, a is Example 3, b is Comparative Experiment 1; at 10 mA / cm 2 and 1mAh / cm 2 In the Zn||Cu battery, the coulombic efficiency (CE) of the bare zinc electrode suddenly dropped after only 800 cycles. In sharp contrast, the CE of the FeHCF / Zn electrode remained at 99.94% for more than 10,000 cycles. Moreover, the voltage distribution of the FeHCF / Zn electrode remained stable, reducing polarization, confirming that the FeHCF layer effectively stabilized the interface and alleviated the polarization effect. Even at 5 mA / cm 2 and 1mAh / cm 2 Even at a lower current density of 1.5 GHz, FeHCF / Zn can still operate reliably for more than 10,000 cycles with an average CE of 99.91%.

[0070] To conduct DOD testing, the FeHCF nanofilm was transferred onto zinc foil in step 2 of Example 1, and a Zn||Zn symmetrical cell was constructed using Example 4 and Comparative Experiment 2; Figure 8FeHCF nanomembranes were transferred to Zn||Zn symmetric cells assembled with zinc foil for cycling tests. a) Cycling performance at 1 mA / cm 2 and 1 mAh / cm 2 b) DOD cycling performance at 2 mA / cm 2 and 10 mAh / cm 2 ; symmetric Zn||Zn cells 1 mA / cm 2 and 1 mAh / cm 2 , bare zinc failed after only 146 h due to uncontrolled dendrite growth and side reactions, while FeHCF / Zn achieved stable cycling for over 2000 h with a low overpotential (38 mV vs. 60 mV for bare zinc), extending the operation lifetime by about 14 times. At a current density of 2 mA / cm 2 and a large-area capacity of 10 mAh / cm 2 (~60% DOD), the FeHCF / Zn electrode remained stable for 160 h, while the bare zinc anode failed rapidly.

[0071] Meanwhile, the Zn||Zn symmetric cells assembled for Example IV and Comparative Experiment II were tested as follows: at 1 mAh / cm 2 and a higher current density of 5 mA / cm 2 , bare zinc short-circuited after 125 h, while FeHCF / Zn failed after more than 3200 h, further demonstrating the special protective effect of the FeHCF nanomembrane. At 1 mAh / cm 2 and a higher current density of 50 mA / cm 2 , bare zinc ran for less than 60 h, while FeHCF / Zn ran for about 240 h without failure, indicating that the FeHCF nanomembrane has a protective effect at high current densities. At a high capacity density of 10 mAh / cm 2 and a low current density of 1 mA / cm 2 , bare zinc short-circuited after 50 h, while FeHCF / Zn cycled for 400 h, with a lifetime about 8 times that of bare zinc. In summary, the FeHCF nanomembrane improves the stability, reversibility, and cycle life of the metal zinc anode. By suppressing dendrite growth, minimizing side reactions, and ensuring uniform Zn 2+ deposition, the FeHCF / Zn interface greatly improves the prospects for high-performance, durable, and safe zinc-based energy storage systems.

[0072] To observe the morphological evolution of the electrode interface during zinc deposition and stripping, the current density was 40 mA / cm 2 and the capacity density was 6 mAh / cm 2The Zn || Cu half-cells assembled in Example Three and Comparative Experiment One were subjected to cycling tests under the above conditions, and then the FeHCF / Cu and bare Cu electrodes of the positive electrode were subjected to in-situ optical microscope tests and zinc thickness and deposition / detachment time tests, and the test results are as follows Figure 9 and Figure 10 ;

[0073] Figure 9 The in-situ optical microscope images of zinc deposition / detachment of FeHCF / Cu and bare Cu after cycling of the Zn || Cu half-cells assembled in Example Three and Comparative Experiment One, a is bare Cu, b is FeHCF / Cu; the FeHCF / Cu electrode always shows compact and uniform zinc deposition without obvious dendrite formation, confirming the stable Zn 2+ flux and controlled ion transport. In contrast, the bare Cu electrode gradually forms irregular protrusions and accumulated deposits, which still exist even after detachment, reflecting the continuous and uneven deposition and detachment process.

[0074] Figure 10 The zinc deposition thickness and deposition / detachment time of FeHCF / Cu and bare Cu after cycling of the Zn || Cu half-cells assembled in Example Three and Comparative Experiment One; quantitative comparison shows that the zinc growth density is greater and more controllable on the FeHCF / Cu electrode. After 540 seconds of electrodeposition at 40 mA / cm 2 (corresponding to 6 mAh / cm 2 ), the FeHCF / Cu electrode produces a zinc layer only 18.1 μm thick - close to the theoretical value (Theoretical curve in the figure), while the bare Cu electrode produces a thicker (95.5 μm) and more uneven layer. During the subsequent detachment process, the FeHCF-based electrode cleanly and uniformly detaches the deposited zinc, while the bare electrode surface remains rough and incompletely detached with residual dendritic structures. These observations indicate that the FeHCF nanofilm not only facilitates efficient and compact zinc deposition, but also ensures uniform and reversible detachment.

[0075] In step two of Example One, the prepared FeHCF nanofilm was transferred to a titanium foil, and a battery was assembled in an electrolytic cell, with a zinc sheet (area 10 x 10 cm 2 , thickness 200 μm) coated with an ultrathin hydrophobic zincophilic artificial solid protective layer prepared in Example One on one side, and a titanium foil (area 10 x 10 cm 2 , thickness 10 μm) coated with an ultrathin hydrophobic zincophilic artificial solid protective layer on the other side, 1 L of zinc sulfate electrolyte (2 M) was added, and the current density was 20 mA / cm 2The zinc foil deposited on the titanium foil was observed for its morphology, and the zinc foil was peeled off to test its mechanical strength. The above process was the experimental group, and the FeHCF nanofilm was peeled off together and attached to the surface of the zinc foil during the peeling process; the control group was a pure titanium foil. Figure 11 The zinc foil deposited on the titanium foil was observed for its morphology, and the zinc foil was peeled off to test its mechanical strength. The above process was the experimental group, and the FeHCF nanofilm was peeled off together and attached to the surface of the zinc foil during the peeling process; the control group was a pure titanium foil.

[0076] Under the conditions of 10 mA / cm 2 and 1 mAh / cm 2 , the Zn||Zn symmetric batteries assembled in Example Four and Comparative Experiment Two were cycled for 500 cycles, and then the negative electrodes were tested by SEM. Figure 12 The SEM images of the negative electrodes of the Zn||Zn symmetric batteries assembled in Example Four and Comparative Experiment Two after cycling are shown in FIG. 8. As shown in FIG. 8c and FIG. 8d, due to the non-uniform zinc deposition and serious side reactions, the morphology of the bare zinc negative electrode is non-uniform, and there are obvious dendrites and pits. In contrast, the surface of the zinc electrode with a protective layer is still dense and uniform after cycling, and there is no obvious Zn protrusion, as shown in FIG. 8a and FIG. 8b, which indicates that the uniform FeHCF layer can guide the horizontal uniform deposition of Zn, and confirms the effect of the FeHCF nanofilm on inhibiting dendrites.

[0077] Prussian blue material itself has the characteristic of electrochromism, that is, under the action of an electric field, redox reaction occurs, electrons are gained or lost, and the color of the material changes. In order to directly observe its redox ability, the FeHCF nanofilm prepared in Step One of Example One was vacuum filtered to obtain a film powder. The FeHCF powder and the PVDF binder were uniformly mixed in a mass ratio of 9:1, and then coated on a zinc foil (area 1×1 cm 2 , thickness 10 μm) using a doctor blade to obtain a zinc foil attached with FeHCF powder. The zinc foil was assembled into a battery with a zinc sheet (area 1×1 cm 2 ) coated with an ultrathin hydrophobic zincophilic artificial solid protective layer prepared in Example One in an electrolytic cell, 5 mL of zinc sulfate electrolyte (2M) was added, and the current density was 20 mA / cm2 and 3 mAh / cm 2 The FeHCF powder-attached zinc foil was cycled under the above conditions, and the zinc foil was photographed every 5 minutes and tested by XPS every 5 minutes. The results are shown in Figure 13 and Figure 14 .

[0078] Figure 13 The reversible color change of the zinc foil attached with the FeHCF powder prepared in Example One during zinc deposition and stripping; a is not cycled; b is 2.5 mAh of deposition under a current of 20 mA; c is 5 mAh of deposition under a current of 20 mA; d is 5 mAh of deposition and 2.5 mAh of stripping under a current of 20 mA; e is 5 mAh of deposition and 5 mAh of stripping under a current of 20 mA; as can be seen from the figure, the color of FeHCF gradually changes from dark green to bright blue during deposition, and gradually returns to dark green during stripping, indicating that electron gain and loss indeed occurs during deposition and stripping, and has redox properties.

[0079] Figure 14 The XPS spectra of FeHCF during zinc deposition and stripping and the Fe 2p XPS spectrum of the FeHCF nanofilm not cycled, a is FeHCF after 15 minutes of deposition, b is FeHCF after 15 minutes of deposition and 15 minutes of stripping, and c is the Fe 2p XPS spectrum of the FeHCF nanofilm prepared in Example One, step one, not cycled; as can be seen from the figure, the film contains both Fe 3+ and Fe 2+ , during deposition, the content of Fe 2+ in the FeHCF film increases significantly, indicating that part of the Fe 3+ is reduced to Fe 2+ , which can produce a net negative charge distribution on the surface of the zinc negative electrode, spontaneously attract positively charged Zn 2+ , and make the Zn 2+ flux uniform, and inhibit Zn 2+ aggregation. During the process of deposition first and then stripping, the content of Fe 3+ increases significantly, indicating that the FeHCF protective layer is reversible and is expected to become a fast ionic conductive SEI layer on the zinc electrode.

[0080] To verify the structural stability, the Zn||Zn symmetric battery assembled in Example Four was tested by XRD after charge and discharge cycles. During the charge and discharge cycles, the battery was stopped after 5 minutes of discharge, 10 minutes of discharge, 5 minutes of charge after 10 minutes of discharge, and 10 minutes of charge after 10 minutes of discharge under a current of 20 mA / cm 2 , and the negative electrode was tested by XRD; Figure 15XRD patterns of the negative electrode of the Zn||Zn symmetric cell assembled in Example 4 after charge-discharge cycles, the theoretical calculation of the electrostatic potential map and the theoretical calculation of the electric field distribution; a is the XRD spectrum of FeHCF / Zn, 1 is the initial state, 2 is after 5 minutes of discharge, 3 is after 10 minutes of discharge, 4 is after 10 minutes of discharge and then 5 minutes of charge, and 5 is after 10 minutes of discharge and then 10 minutes of charge; b is the theoretical calculation of the electrostatic potential map of Fe III Fe III (CN)6and [Fe II Fe II (CN)6] 2- ; c is the theoretical calculation of the electric field distribution of bare Zn and FeHCF / Zn; as can be seen from the figure, under different charge-discharge states, the crystal structure of FeHCF is still stable. The peak position of the enlarged view first shifts to the right and then shifts to the left, which confirms that this redox-mediated Faraday "cation pumping" is reversible in structure. b and c are theoretical calculations. First, the electrostatic potential containing trivalent iron and divalent iron is calculated, which can be directly observed that the transformation of trivalent iron to divalent iron increases the overall negative charge. Then the adsorption energy of zinc ions on FeHCF with trivalent iron and divalent iron is calculated, both of which show strong attraction to zinc ions, which is conducive to the rapid transfer of Zn 2+ . Finally, in the electric field simulation, it can be seen that the protective layer indeed homogenizes the electric field at the metal zinc electrode-electrolyte interface.

[0081] To explore the changes in the structure of the metal zinc electrode interface during the deposition process, in-situ Raman tests were performed on the negative electrode of the Zn||Zn symmetric cell assembled in Example 4 and Comparative Experiment 2 at 1 mA / cm 2 and 1 mAh / cm 2 . Figure 16 In-situ Raman tests and sulfate peak separation of the negative electrode of the Zn||Zn symmetric cell assembled in Example 4 and Comparative Experiment 2 during the deposition process; a is the in-situ Raman test of Example 4, b is the in-situ Raman test of Comparative Experiment 2, c is the sulfate peak separation of Example 4, and d is the sulfate peak separation of Comparative Experiment 2; in c and d, 1 is 0 minutes of deposition, 2 is 10 minutes of deposition, 3 is 20 minutes of deposition, 4 is 30 minutes of deposition, 5 is 40 minutes of deposition, and 6 is 50 minutes of deposition; the intensity of sulfate at the electrode interface can represent the transport of zinc ions at the electrode-electrolyte interface. During the deposition process, the concentration of hydroxide ions increases due to the hydrogen evolution reaction, which combines with sulfate to form byproducts, resulting in a decrease in the concentration of sulfate. As can be seen from the a and b figures, the peak intensity of sulfate in the experimental group with the protective layer is stable and basically unchanged, and the peak position does not shift, indicating that the transport of zinc ions at the electrode-electrolyte interface is stable, and the occurrence of side reactions is reduced. As can be seen from the c and d figures, the fitting belongs to SO4 2-Raman spectra of the Zn||Zn symmetric cell, the stretching vibration can be integrated into two different peaks, respectively, solvent separated ion pairs (SSIPs) and contact ion pairs (CIPs). By comparison, it can be found that the peak area of the protected Zn negative electrode surface SSIP gradually increases, which proves that it inhibits the occurrence of side reactions.

[0082] The Zn||Zn symmetric cell was monitored in Zn 2+ The in-situ pH change during ion deposition process, at 10 mA / cm 2 and 1 mAh / cm 2 The Zn||Zn symmetric cell assembled in Example 4 and Comparative Experiment 2 was cycled, and the pH of the negative electrode region was recorded once every minute when discharging for one minute each cycle, and the test results are as shown in Figure 17 FIG. a.

[0083] Water erosion can cause hydrogen evolution reaction. In order to evaluate the effect of FeHCF layer on the inhibition of hydrogen evolution HER, a three-electrode system was used, and the FeHCF nanofilm prepared in Example 1 step 2 was transferred to a titanium foil. In a 1M Na2SO4 aqueous solution, the polarization behavior was characterized by linear sweep voltammetry (LSV) at 1mV / s, wherein the titanium foil coated with FeHCF nanofilm or pure titanium foil was used as the working electrode, and Ag / AgCl was used as the reference electrode. The test results are as shown in Figure 17 FIG. b.

[0084] The interface electrochemical stability was investigated, and the Zn||Zn symmetric cell assembled in Example 4 and Comparative Experiment 2 was tested by in-situ EIS at 10 mA / cm 2 and 1 mAh / cm 2 , and the negative electrode was tested by EIS once every 60 cycles, and the test results are as shown in Figure 17 FIG. c and d.

[0085] Figure 17 The in-situ pH change of the negative electrode region of the symmetric cell of Example 4 and Comparative Experiment 2, the LSV curve of the electrode, and the in-situ EIS measurement of the negative electrode of the symmetric cell, a is the in-situ pH change of the negative electrode region of the symmetric cell, b is the LSV curve of the electrode, c is the in-situ EIS measurement of Example 4, and d is the in-situ EIS measurement of Comparative Experiment 2. As can be seen from a, the pH value of the bare Zn electrode rises rapidly from 3.5 to 5.92, which is due to the strong hydrogen evolution reaction and the formation of by-products. On the contrary, the pH value at the FeHCF / Zn interface rises from 3.47 to 5.25, and the rising trend is relatively slow, indicating that the side reaction and hydrogen evolution reaction are effectively inhibited, which shows that the FeHCF protective layer effectively isolates the direct contact between the aqueous electrolyte and the zinc negative electrode. As can be seen from b, in the absence of Zn 2+In the case of deposition, it can be seen that the presence of FeHCF significantly increases the electrochemical window, increasing the HER potential from -123 mV to -139 mV. From c and d, it can be seen that the interfacial charge transfer resistance of FeHCF / Zn is smaller than that of bare Zn throughout, which proves that the FeHCF interfacial layer promotes the electrochemical kinetics of the Zn anode. According to the test data of bare zinc, it can be found that the interfacial charge transfer resistance of bare zinc jumps up and down with the increase of the cycle number, which can be due to the non-uniform deposition of bare zinc during the deposition process, which makes the EIS curve during the deposition process unstable, and the generation and falling of by-products. In contrast, FeHCF / Zn is more stable during the cycle process. It proves that the protective layer can reduce the occurrence of side reactions, and also make the zinc ions uniformly deposited.

[0086] Principle:

[0087] First, during the cycle process, the FeHCF nanofilm actively responds to the change of electrode potential, maintaining dynamic electrochemical regulation. The color change between dark green (reduced state) and blue (oxidized state) during zinc deposition and stripping clearly shows its reversible redox characteristics. Although the ultra-thin (16.9 nm) layer undergoes redox transformation, its total area capacity contribution is still negligible (0.58 μAh / cm 2 ), which ensures that the active anode capacity is not affected. XPS analysis during zinc deposition and stripping shows that Fe 3+ ions in FeHCF are reversibly reduced to Fe 2+ during Zn 2+ deposition, and oxidized back to Fe 2+ during Zn 3+ stripping. This reversible redox transformation provides an adjustable interfacial charge environment: during Zn 2+ deposition, the FeHCF layer generates a net negative charge, electrostatically attracting Zn 2+ and regulating its spatial distribution at the interface. This electrostatic gating promotes uniform Zn 2+ flux, reduces concentration polarization, and reduces uncontrolled lateral ion diffusion, which helps to reduce dendrite formation. In addition, the negatively charged FeHCF surface repels sulfate anions, inhibiting the formation of by-products. During the subsequent stripping process, Fe 3+ is re-oxidized to Fe 2+ , reducing the negative charge and allowing Zn 2+ to be released smoothly, thereby improving the stripping efficiency. XRD measurements confirm that this redox-dominated Faradaic "cation pumping" is structurally reversible, with FeHCF maintaining its crystal framework during the cycle. Theoretical calculations show that both the oxidized and reduced states exhibit higher Zn 2+transport. The electric field simulation further demonstrates that the FeHCF layer homogenizes the interfacial field, reducing sites that can nucleate dendrites. This Faradaic cation pumping mechanism, facilitated by the open three-dimensional FeHCF lattice and its redox-active Fe centers, ensures abundant, uniform, and fast Zn 2+ channeling. As a result, zinc deposition occurs as a compact, uniform layer, rather than forming protrusions, significantly suppressing dendrite growth, ensuring stable, long-term electrode operation.

[0088] Secondly, to further elucidate the stability of the interface with the FeHCF layer, the behavior of sulfate (SO4 2- ) during zinc deposition was monitored using in-situ Raman spectroscopy. On the FeHCF / Zn electrode, the band intensity of v-SO4 2- initially increased slightly and then remained relatively stable throughout the deposition process. In sharp contrast, the v-SO4 2- intensity on the bare Zn electrode decreased rapidly, reflecting the rapid depletion of sulfate and unstable interfacial conditions. Because zinc ions in aqueous zinc sulfate can exist in the form of solvent-separated ion pairs (SSIPs) and contact ion pairs (CIPs), changes in their ratio provide insights into ion transport kinetics. On the FeHCF / Zn, the SSIP ratio increased significantly from 38.0% to 69.3% during deposition, indicating that the negatively charged and hydrophobic FeHCF surface promotes selective Zn 2+ ion pumping and repels sulfate anions, thus maintaining a good SSIP environment. In contrast, the bare Zn electrode did not maintain such a good SSIP / CIP ratio. The activation energy for Zn 2+ desolvation decreased from 63.4 kJ / mol for bare Zn to 55.6 kJ / mol for FeHCF / Zn, further confirming this selective ion transport and confirming enhanced Zn2+ion transport kinetics. At the same time, the hydrophobic alkyl chains repel water molecules, reducing water-induced side reactions and broadening the electrochemical stability window. In-situ pH monitoring showed that the pH increase on the FeHCF / Zn electrode was milder compared to bare Zn, implying effective HER suppression. In-situ electrochemical impedance spectroscopy (EIS) further confirmed that the FeHCF / Zn maintained a lower and more stable interfacial resistance throughout long-term cycling, while the bare Zn faced escalating resistance, likely caused by irregular zinc deposition and byproduct accumulation. More importantly, the fitted EIS showed a stable filmic resistance, with no indication of water layer formation. Overall, these observations indicate that the FeHCF nanofilm ensures a good water-repellent and ion-selective interface, effectively mitigating detrimental side reactions and maintaining superior electrochemical stability.

[0089] FeHCF nanofilm prevents the zinc electrode from contacting water and Zn 2+ selective dual effects. Under the protection of these two effects, the FeHCF nanofilm can inhibit dendrites, byproducts, etc., and improve the cycle stability and cycle life of the battery.

[0090] Therefore, the embodiment can improve the stability of the zinc negative electrode by constructing an ultrathin (~ 16.9 nm), Zn 2+ selective and water-proof layer. This interface engineering strategy effectively eliminates the water layer at the electrode interface, inhibits hydrogen evolution and corrosion, thereby overcoming the long-term obstacle in the development of aqueous zinc metal batteries. The "Faradaic cation pumping" mechanism generated in the FeHCF framework ensures fast and selective Zn 2+ transport, while maintaining negligible water permeation, thereby creating a stable, dendrite-free environment. The benefits of this design are obvious, and significant electrochemical performance can be achieved. The FeHCF / Zn electrode lasted for more than 10,000 deposition / stripping cycles at 5 mA / cm 2 and 1 mAh / cm 2 , with an average CE of 99.91%, far exceeding the stability of traditional zinc negative electrodes.

Claims

1. A method for preparing an ultra-thin hydrophobic zinc-philic artificial solid protective layer, characterized in that It is carried out in the following steps:

1. Preparation of FeHCF nanofilm: An aqueous solution of potassium ferricyanide is mixed with deionized water, a chloroform solution of dioctadecyldimethylammonium bromide is dispersed on the surface of the liquid and allowed to stand to form a surfactant layer at the air-water interface. An aqueous solution of ferric chloride is then added dropwise to the solution below the surfactant layer, and the mixture reacts at room temperature to form an FeHCF nanofilm at the air-water interface, thereby obtaining a liquid containing the FeHCF nanofilm.

2. Transfer of FeHCF nanofilm: The substrate is vertically immersed in a liquid containing FeHCF nanofilm, and then the substrate is slowly lifted, and the FeHCF nanofilm formed at the air-water interface is transferred to the substrate, and finally dried to complete the preparation method of the ultra-thin hydrophobic zinc-philic artificial solid protective layer.

2. The method for preparing an ultra-thin hydrophobic zinc-philic artificial solid protective layer according to claim 1, characterized in that The concentration of the potassium ferricyanide aqueous solution in step 1 is 0.01 mol / L to 0.2 mol / L; the concentration of the dioctadecyldimethylammonium bromide chloroform solution in step 1 is 1.0 mmol / L to 2.0 mmol / L; the concentration of the ferric chloride aqueous solution in step 1 is 0.01 mol / L to 0.2 mol / L.

3. The method for preparing an ultra-thin hydrophobic zinc-philic artificial solid protective layer according to claim 1, characterized in that The volume ratio of the potassium ferricyanide aqueous solution to deionized water in step 1 is 1:(10-20).

4. The method for preparing an ultra-thin hydrophobic zinc-philic artificial solid protective layer according to claim 1, characterized in that The volume ratio of the potassium ferricyanide aqueous solution to the dioctadecyldimethylammonium bromide chloroform solution in step 1 is 1:(0.001-0.01).

5. The method for preparing an ultra-thin hydrophobic zinc-philic artificial solid protective layer according to claim 1, characterized in that The volume ratio of the potassium ferricyanide aqueous solution to the ferric chloride aqueous solution in step 1 is 1:(1-2).

6. The method for preparing an ultra-thin hydrophobic zinc-philic artificial solid protective layer according to claim 1, characterized in that In step 1, the mixture is allowed to stand for 5 to 60 minutes; in step 2, the mixture is allowed to react at room temperature for 20 to 48 hours.

7. The method for preparing an ultra-thin hydrophobic zinc-philic artificial solid protective layer according to claim 1, characterized in that The thickness of the FeHCF nanofilm described in step 1 is 10 nm to 50 nm.

8. The method for preparing an ultra-thin hydrophobic zinc-philic artificial solid protective layer according to claim 1, characterized in that The substrate described in step 2 is a metal zinc negative electrode.

9. The method for preparing an ultra-thin hydrophobic zinc-philic artificial solid protective layer according to claim 1, characterized in that In step 2, the substrate is slowly lifted at a speed of 0.01 m / s to 1 m / s; the drying in step 2 is specifically carried out at a temperature of 25° C. to 60° C. for 0.5 h to 24 h.

10. Use of the ultra-thin hydrophobic zinc-philic artificial solid protective layer prepared as claimed in claim 1, characterized in that It is used as a protective layer for the zinc anode in aqueous zinc-ion batteries.

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