An organic-inorganic composite multi-interface layer modified zinc metal negative electrode and a preparation method and application thereof

Abstract

The application belongs to the technical field of aqueous zinc ion batteries, and discloses an organic-inorganic composite multi-element interface layer modified zinc metal negative electrode and a preparation method and application thereof, so as to solve the technical problems that zinc deposition is prone to occur on the electrode surface, the zinc deposition process is uncontrollable, and the cycle stability of the zinc negative electrode is extremely poor under a large surface capacity. The application constructs an organic-inorganic composite multi-element interface layer with multiple parameter regulation functions on the surface of the zinc metal electrode. After a carbon fiber coating layer is constructed on the zinc electrode, a static spinning polymer fiber membrane layer containing a cerium-based MOF is further constructed. The carbon fiber layer can realize uniform zinc deposition and block the electrochemical side reaction between the electrolyte and zinc. The polymer fiber membrane layer containing Ce-based MOF particles can realize Zn 2+ selective permeation, provide zincophilic adsorption sites, and due to the unique Ce 3+ / Ce 4+ redox characteristics optimize the interface electrochemical environment. The composite multi-element interface layer composed of the carbon fiber layer and the static spinning membrane can effectively buffer the volume change of the electrode during the zinc electrode plating and stripping process, and improve the cycle stability of the zinc metal electrode.

Description

Technical Field

[0001] This invention belongs to the field of aqueous zinc-ion battery technology, and particularly relates to a zinc metal anode and its preparation method. Background Technology

[0002] Aqueous zinc-ion batteries possess advantages such as good intrinsic safety, abundant resources, and environmental friendliness, making them a focus of attention in the field of large-scale energy storage. However, their practical application is limited by the poor cycle life of the zinc electrode. This stems from the tendency for zinc deposition to occur on the zinc electrode surface during charging and discharging, leading to problems such as zinc dendrite growth, hydrogen evolution reaction, corrosion, and byproduct accumulation, which severely restrict the battery's cycle life and coulombic efficiency.

[0003] To address the aforementioned issues, constructing an artificial interface protective layer on the surface of the zinc anode is an effective strategy. Recently, our research group proposed a zinc anode modified with a carbon-based / carboxymethyl chitosan (CMCS) dual interface layer in our previous application (CN120978003A). This structure achieves physical shielding and ion flow homogenization through the uniform electric field of the lower carbon-based electron conduction layer and the upper CMCS ion regulation layer, achieving better results than a single coating. However, this interface optimization design strategy still needs improvement: (1) Although CMCS, as an electronic insulator, can block dendrites, its density increases the ion transport barrier, which is not conducive to ion transport and the improvement of the battery's rate performance; (2) The CMCS layer has a single function, mainly acting as a passive physical barrier, lacking regulation of the electrochemical environment of the zinc electrode interface, such as actively suppressing the occurrence of side reactions.

[0004] On the other hand, metal-organic framework (MOF) materials have attracted attention due to their regular pore structure and abundant active sites. For example, CN117038836A discloses a zinc anode modified by electrospun monolayer MOF-808 / PAN, which utilizes the pores of MOF to promote zinc ion transport. However, it uses a zirconium-based MOF and is a monolayer structure, lacking synergistic effects on multidimensional parameters of the zinc electrode interface and failing to guarantee the uniformity of the interfacial electric field distribution. CN114613933A discloses using porous CeO2 derived from Ce-MOF by high-temperature calcination as a coating material, but the high-temperature treatment destroys the organic ligands and intact pore structure of the MOF, losing the advantages of MOF as a crystalline porous material for ion sieving and functional group modification. Ce-MOF electrospun fibers also exist in the prior art, but they are applied in the field of photocatalysis and do not involve zinc anode interface modification. In addition, long-term zinc electroplating and stripping processes, especially under large surface stripping capacities, place higher demands on the volume adaptability of the zinc interface layer.

[0005] In summary, how to effectively integrate the structural and chemical advantages of rare earth MOFs (especially cerium-based MOFs) with the zinc anode interface protective layer to construct a composite interface that combines uniform interfacial electric field distribution, limited bottom zinc deposition, good zinc ion transport performance, and active side reaction suppression capability, while also possessing good volume adaptability, thereby further improving the cycle life, rate performance, and reversibility of zinc electroplating and stripping reactions under high area stripping capacity, is a technical challenge that urgently needs to be solved in this field. Summary of the Invention

[0006] To address the technical problems in existing technologies, such as the single-function upper ion regulation layer of double-layer interface modification layers (e.g., carbon / CMCS structure) leading to increased interface impedance due to electronic insulation, and the lack of electronic conduction synergy in existing MOF modification layers (either being single-layer structures or losing the original MOF structure after high-temperature treatment), resulting in poor cycle life of batteries at high area stripping capacity, this invention proposes an organic-inorganic composite multi-element interface layer modified zinc metal anode, its preparation method, and its application.

[0007] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0008] An organic-inorganic composite multi-element interface layer modified zinc metal anode includes a zinc substrate, a carbon fiber coating on the zinc substrate, and an electrospun fiber membrane doped with cerium-based MOF (Ce-MOF) on the carbon fiber coating; wherein the thickness of the carbon fiber coating is 30-60 μm, and the thickness of the electrospun fiber membrane doped with cerium-based MOF is 10-30 μm.

[0009] The aforementioned lower carbon layer (carbon fiber coating) provides a fast electron transport channel and a uniform electric field; the Ce-MOF particles in the upper electrospun fiber membrane realize Zn through regular channels. 2+ Selective permeability, Ce-O clusters provide zinc-loving adsorption sites, Ce 3+ / Ce 4+ Redox reactions suppress hydrogen evolution side reactions; bilayer synergy achieves "electron-ion dual pathways" and "active-passive dual protection".

[0010] The above-mentioned cerium-based MOF is prepared as follows: it is obtained by hydrothermal reaction of terephthalic acid and cerium ammonium nitrate at 90-110℃ for 2-4 h.

[0011] Specifically, the preparation method of cerium-based MOF is as follows: terephthalic acid is dissolved in N,N-dimethylformamide (DMF), and cerium ammonium nitrate is dissolved in deionized water. The two solutions are then mixed, sealed, and heated and stirred at 90-110℃ for 2-4 h. After cooling, the mixture is centrifuged, washed, and dried to obtain cerium-based MOF powder, denoted as Ce-MOF. The molar ratio of terephthalic acid to cerium ammonium nitrate is 0.8-1.5:1. 6-10 mL of DMF is required for every 1 mmol of terephthalic acid, and 1.5-2.5 mL of deionized water is required for every 1 mmol of cerium ammonium nitrate. The washing solvents are DMF and ethanol, each used for 2-3 washes. The drying temperature is 80-100℃, and the drying time is 12-24 h.

[0012] The preparation method of the above-mentioned organic-inorganic composite multi-element interface layer modified zinc metal anode includes the following steps:

[0013] (1) Mix carbon fiber powder with binder, add solvent I to make a slurry, coat it on the surface of zinc substrate, and dry it to obtain carbon fiber coating, thus obtaining a zinc anode modified with carbon substrate (denoted as Zn@C).

[0014] (2) Cerium-based MOF powder, polyacrylonitrile, and polyvinylidene fluoride were added to solvent II to obtain electrospinning solution I; then, electrospinning was performed on the carbon fiber coating surface of the carbon-based zinc anode modified in step (1) to form a three-dimensional porous electrospinned fiber membrane doped with cerium-based MOF (Ce-MOF). After drying at 60-80℃ for 2-4 h, an organic-inorganic composite multi-element interface layer modified zinc metal anode (denoted as Zn@C / Ce-MOF@NFM) was obtained.

[0015] In step (1) above, the mass ratio of carbon fiber powder to binder is (7-9):(1-3), solvent I is N-methylpyrrolidone (NMP), dimethyl sulfoxide, or dihydrol-L-glucanone, and the binder is at least one of polyvinylidene fluoride, polytetrafluoroethylene, polyacrylic acid, carboxymethyl cellulose, sodium alginate, polyvinyl alcohol, hydroxypropyl methylcellulose, and styrene-butadiene rubber. The viscosity of the homogenate is 2000-3000 cP.

[0016] Furthermore, the preparation method of the above-mentioned carbon fiber powder is as follows: polyacrylonitrile (PAN) and polyvinylidene fluoride (PVDF) are dissolved in solvent II to obtain electrospinning solution II; then, carbon fiber powder is obtained by electrospinning, pre-oxidation, carbonization, and grinding. The pre-oxidation atmosphere is air, the temperature is 240-280 ℃, and the time is 1-3 h. The carbonization temperature is 600-800 ℃, the time is 1-5 h, and the atmosphere is an inert gas (Ar or N2); the grinding time is ≥30 min.

[0017] In the above electrospinning solution I and electrospinning solution II, the mass ratio of polyacrylonitrile to polyvinylidene fluoride is 0.1-10:1; the total concentration of polyacrylonitrile and polyvinylidene fluoride is 8-12 wt%; and in electrospinning solution I, the mass of cerium-based MOF powder is 5-15% of the total mass of polyacrylonitrile and polyvinylidene fluoride. Solvent II is at least one of N,N-dimethylformamide, dimethyl sulfoxide, and sulfolane.

[0018] Furthermore, the process parameters for the electrospinning are as follows: spinning voltage of 15-20 kV, spinning distance of 15-20 cm, and flow rate of 0.3-2 mL / h. Specifically, when preparing electrospun fiber membranes containing cerium-based MOF (Ce-MOF), the spinning time is 30-90 min.

[0019] The above-mentioned organic-inorganic composite multi-element interface layer modified zinc metal anode is used in aqueous zinc-ion batteries or aqueous zinc-ion capacitors.

[0020] The beneficial effects of this invention are:

[0021] (1) The organic-inorganic composite multi-element interface layer of the present invention modifies the zinc metal anode to achieve synergistic "electron-ion" dual pathways. The lower carbonized PAN / PVDF fiber membrane has excellent electronic conductivity, which can uniformly distribute the electric field on the surface of the zinc anode, reduce the local current density, and provide an "electron highway" for zinc deposition. The upper Ce-MOF-containing fiber membrane retains the three-dimensional porous structure of electrospinning, and the regular channels (~0.8 nm) of Ce-MOF are Zn 2+ It provides selective transport channels, while its insulating properties prevent electrons from directly penetrating the upper layer and causing surface side reactions. The two layers work together to achieve a perfect functional partitioning where the lower layer conducts electrons and the upper layer conducts ions.

[0022] (2) The organic-inorganic composite multi-element interface layer modified zinc metal anode of the present invention has an "active-passive" dual protection mechanism. Passive protection: The upper hydrophobic fiber membrane (contact angle up to 150°) forms a physical barrier, effectively repelling water molecules and SO4 in the electrolyte. 2- This inhibits hydrogen evolution and corrosion side reactions at the source. Active protection: The abundant Ce-O clusters in Ce-MOFs can act as zinc-loving sites, inducing Zn... 2+ Uniform nucleation; more importantly, Ce 3+ / Ce 4+ Redox pairs exhibit excellent redox activity, enabling them to actively scavenge reactive free radicals (such as ·OH and ·H) generated during electrochemical reactions, thereby effectively inhibiting the hydrogen evolution reaction.

[0023] (3) This invention achieves a balance between structural stability and ion transport. The upper fiber membrane uses uncarbonized PAN / PVDF as a skeleton, which has good flexibility and can adapt to the volume changes of the zinc anode during charging and discharging, thus avoiding coating cracking. At the same time, the uniformly dispersed Ce-MOF particles avoid agglomeration and ensure unobstructed ion transport pathways.

[0024] (4) By introducing Ce-MOF with redox activity, this invention endows the upper interface with a new function of actively suppressing side reactions while maintaining the physical barrier function; at the same time, the porous fiber structure has a lower ion transport impedance. In addition, the introduction of conductive carbon substrate realizes the functional decoupling of electron transport and ion sieving, avoiding the problem of increased interface impedance caused by a single organic layer. More importantly, the upper fiber membrane of this invention is not carbonized, thus fully retaining the crystalline pore structure and organic ligand function of MOF, realizing selective transport at the molecular / ion level.

[0025] (5) This invention achieves integrated interface control of “rapid electron conduction - selective ion sieving - active suppression of side reactions” through a dual-layer synergistic design of “lower layer conduction and upper layer functionalization”, which significantly improves the cycle stability of zinc anode and the cycle stability under high area capacity. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 The images show the SEM morphology and XRD pattern of the Ce-MOF prepared in Example 1 of this invention.

[0028] Figure 2 SEM images (a) of the samples prepared in Example 1 and Comparative Examples 1-3 of the present invention, and EDS elemental distribution diagram (b) of the Zn@C / Ce-MOF@NFM electrode prepared in Example 1.

[0029] Figure 3 The image shows a cross-sectional scanning electron microscope (SEM) image of the zinc metal anode modified with an organic-inorganic composite multi-element interface layer prepared in Example 1.

[0030] Figure 4 This is a comparison diagram of the contact angles of the zinc negative electrodes prepared in Example 1 and Comparative Examples 1-3 of the present invention.

[0031] Figure 5The Tafel polarization curves and LSV curves of the zinc anodes prepared in Example 1 and Comparative Examples 1-3 of this invention are shown.

[0032] Figure 6 EIS diagrams of symmetrical cells assembled with zinc anodes prepared according to Example 1 and Comparative Examples 1-3 of the present invention.

[0033] Figure 7 For symmetrical cells at 1 mA cm -2 / 15 mAh cm -2 Performance graph under long-cycle conditions.

[0034] Figure 8 For symmetrical cells at 1 mA cm -2 / 1mAh cm -2 Performance graph under long-cycle conditions.

[0035] Figure 9 The diagram shows the coulombic efficiency of a half-cell. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] Example 1

[0038] The preparation method of the organic-inorganic composite multi-element interface layer modified zinc metal anode in this embodiment includes the following steps:

[0039] (1) Terephthalic acid (0.7968 g, 1.2 mmol) was dissolved in 32 mL of DMF and stirred until completely dissolved to obtain a terephthalic acid DMF solution. Cerium ammonium nitrate (3.0688 g, 1.4 mmol) was dissolved in 10.8 mL of deionized water and stirred until dissolved to obtain a cerium ammonium nitrate aqueous solution. The cerium ammonium nitrate aqueous solution was slowly added to a reaction flask containing the terephthalic acid DMF solution, and stirring was continued at room temperature for 30 min. Then, the reaction flask was sealed and placed in a magnetically stirred oil bath, heated to 100 °C, and stirred for 3 h. After the reaction was completed, it was naturally cooled to room temperature. The white precipitate was collected by centrifugation, washed twice each with DMF and ethanol, and finally dried in a 90 °C oven for 24 h to obtain Ce-MOF powder. Figure 1 Ce-MOF is shown to be a crystal with a size of approximately 100 nm.

[0040] (2) Weigh 8 g of PAN (molecular weight 150,000) and 2 g of PVDF (molecular weight 534,000) and add them to 90 g of DMF. Stir at 60°C for 12 h to form a spinning solution. Electrospinning parameters: voltage 18 kV, receiving distance 15 cm, flow rate 0.5 mL / h, spinning for 2 h, and after standing for 1.5 h, peel off the composite fiber membrane from the aluminum foil. Place the fiber membrane in a muffle furnace and pre-oxidize it at 280°C for 2 h (air atmosphere) at a temperature of 5 °C / min. After cooling, transfer it to a tube furnace and carbonize it at 800°C for 2 h at a temperature of 5 °C / min under Ar atmosphere. The product is then manually ground in an agate mortar for 30 min to obtain carbon fiber powder. Carbon fiber powder and PVDF were mixed at a mass ratio of 8:2, and NMP was added dropwise to form a slurry with a viscosity of 2000 cP. The slurry was then coated onto the surface of zinc foil (thickness 0.1 mm, purity 99.99%) and onto a zinc substrate. The slurry was dried at 80 °C for 12 h to obtain a zinc anode modified with a carbon substrate, denoted as Zn@C electrode.

[0041] (3) Take 0.5 g of Ce-MOF powder obtained in step (1), dissolve it together with 8 g of PAN and 2 g of PVDF in 90 g of DMF, stir at 60 ℃ for 12 h, and ultrasonically disperse for 30 min to obtain a spinning solution containing Ce-MOF (based on solid content). Using an electrospinning device, the above spinning solution is directly spun onto the carbon layer surface of the Zn@C electrode obtained in step (2). The spinning parameters are: voltage 18 kV, receiving distance 15 cm, flow rate 1 mL / h, and spinning time 30 min. After spinning, the electrode is placed in a vacuum drying oven at 60 ℃ and dried for 2 h to obtain an organic-inorganic composite multi-element interface layer modified zinc metal anode, denoted as the target electrode Zn@C / Ce-MOF@NFM. In the organic-inorganic composite multi-element interface layer modified zinc metal anode, the thickness of the lower carbon fiber coating (carbon base layer) is 30 μm, and the thickness of the upper electrospun fiber film containing Ce-MOF doping is 10 μm.

[0042] Example 2

[0043] The preparation method of the organic-inorganic composite multi-element interface layer modified zinc metal anode in this embodiment includes the following steps:

[0044] (1) Terephthalic acid (4.8 mmol) was dissolved in 28.8 mL of DMF and stirred until completely dissolved to obtain a terephthalic acid DMF solution. Cerium ammonium nitrate (4.8 mmol) was dissolved in 7.2 mL of deionized water and stirred until dissolved to obtain a cerium ammonium nitrate aqueous solution. The cerium ammonium nitrate aqueous solution was slowly added to a reaction flask containing the terephthalic acid DMF solution, and stirring was continued at room temperature for 30 min. Then, the reaction flask was sealed and placed in a magnetically stirred oil bath, heated to 90 °C, and stirred for 4 h. After the reaction was completed, it was naturally cooled to room temperature. The white precipitate was collected by centrifugation, washed twice each with DMF and ethanol, and finally dried in an oven at 100 °C for 12 h to obtain Ce-MOF powder.

[0045] (2) Weigh 10 g of PAN (molecular weight 150,000) and 2 g of PVDF (molecular weight 534,000) and add them to 88 g of DMF. Stir at 60 °C for 12 h to form a spinning solution. Electrospinning parameters: voltage 18 kV, receiving distance 15 cm, spinning time 2 h, flow rate 1 mL / h. After standing for 1.5 h, peel off the composite fiber membrane from the aluminum foil. Place the fiber membrane in a muffle furnace and pre-oxidize it at 240 °C for 3 h (air atmosphere) by heating at 5 °C / min. After cooling, transfer it to a tube furnace and carbonize it at 600 °C for 5 h under Ar atmosphere by heating at 5 °C / min. The product is then manually ground in an agate mortar for 30 min to obtain carbon fiber powder. Carbon fiber powder and PVDF were mixed at a mass ratio of 7:2, and NMP was added dropwise to form a slurry with a viscosity of 3000 cP. The slurry was then coated onto the surface of zinc foil (thickness 0.1 mm, purity 99.99%) and onto a zinc substrate. The slurry was dried at 50 °C for 14 h to obtain a zinc anode modified with a carbon substrate, denoted as Zn@C electrode.

[0046] (3) Take 1 g of Ce-MOF powder obtained in step (1), dissolve it together with 8 g of PAN and 2 g of PVDF in 90 g of DMF, stir at 60℃ for 12 h, and ultrasonically disperse for 30 min to obtain a spinning solution containing Ce-MOF (based on solid content). Using an electrospinning device, the above spinning solution is directly spun onto the carbon layer surface of the Zn@C electrode obtained in step (2). The spinning parameters are: voltage 18 kV, receiving distance 15 cm, flow rate 1 mL / h, and spinning time 40 min. After spinning, the electrode is placed in a vacuum drying oven at 70 ℃ and dried for 4 h to obtain an organic-inorganic composite multi-element interface layer modified zinc metal anode, denoted as the target electrode Zn@C / Ce-MOF@NFM. In the organic-inorganic composite multi-element interface layer modified zinc metal anode, the thickness of the lower carbon fiber coating (carbon base layer) is 40 μm, and the thickness of the upper electrospun fiber film containing Ce-MOF doping is 20 μm.

[0047] Example 3

[0048] The preparation method of the organic-inorganic composite multi-element interface layer modified zinc metal anode in this embodiment includes the following steps:

[0049] (1) Dissolve 5 mmol of terephthalic acid in 50 mL of DMF and stir until completely dissolved to obtain a terephthalic acid DMF solution. Dissolve 5 mmol of cerium ammonium nitrate in 12.5 mL of deionized water and stir until dissolved to obtain an aqueous solution of cerium ammonium nitrate. Slowly add the aqueous solution of cerium ammonium nitrate to a reaction flask containing the terephthalic acid DMF solution and continue stirring at room temperature for 30 min. Then, seal the reaction flask and place it in a magnetically stirred oil bath, heat to 110 °C, and stir for 2 h. After the reaction is complete, allow it to cool naturally to room temperature. Centrifuge to collect the white precipitate, wash it twice each with DMF and ethanol, and finally dry it in a 90 °C oven for 24 h to obtain Ce-MOF powder.

[0050] (2) Weigh 4 g of PAN (molecular weight 150,000) and 4 g of PVDF (molecular weight 534,000) and add them to 92 g of DMF. Stir at 60°C for 12 h to form a spinning solution. Electrospinning parameters: voltage 18 kV, receiving distance 15 cm, flow rate 1.5 mL / h, spinning for 2 h, and after standing for 1.5 h, peel off the composite fiber membrane from the aluminum foil. Place the fiber membrane in a muffle furnace and pre-oxidize it at 260°C for 1 h (air atmosphere) by heating at 5 °C / min. After cooling, transfer it to a tube furnace and carbonize it at 750°C for 1 h under Ar atmosphere by heating at 5 °C / min. The product is then manually ground in an agate mortar for 30 min to obtain carbon fiber powder. Carbon fiber powder and PVDF were mixed at a mass ratio of 9:3, and NMP was added dropwise to form a slurry with a viscosity of 2500 cP. The slurry was then coated onto the surface of zinc foil (thickness 0.1 mm, purity 99.99%) and onto a zinc substrate. The slurry was dried at 70 ℃ for 10 h to obtain a zinc anode modified with a carbon substrate, denoted as Zn@C electrode.

[0051] (3) Take 1.5 g of Ce-MOF powder obtained in step (1), dissolve it together with 8 g of PAN and 2 g of PVDF in 90 g of DMF, stir at 60 ℃ for 12 h, and ultrasonically disperse for 30 min to obtain a spinning solution containing 5 wt% Ce-MOF (based on solid content). Using an electrospinning device, the above spinning solution is directly spun onto the carbon layer surface of the Zn@C electrode obtained in step (2). The spinning parameters are: voltage 18 kV, receiving distance 15 cm, flow rate 1.5 mL / h, and spinning time 1 h. After spinning, the electrode is placed in an 80 ℃ vacuum drying oven for 3 h to obtain an organic-inorganic composite multi-element interface layer modified zinc metal anode, denoted as the target electrode Zn@C / Ce-MOF@NFM. In the organic-inorganic composite multi-element interface layer modified zinc metal anode, the thickness of the lower carbon fiber coating (carbon base layer) is 50 μm, and the thickness of the upper electrospun fiber film containing Ce-MOF dopant is 30 μm.

[0052] Example 4

[0053] The preparation method of the organic-inorganic composite multi-element interface layer modified zinc metal anode in this embodiment includes the following steps:

[0054] (1) Dissolve 3 mmol of terephthalic acid in 24 mL of DMF and stir until completely dissolved to obtain a terephthalic acid DMF solution. Dissolve 2 mmol of cerium ammonium nitrate in 5 mL of deionized water and stir until dissolved to obtain an aqueous solution of cerium ammonium nitrate. Slowly add the aqueous solution of cerium ammonium nitrate to a reaction flask containing the terephthalic acid DMF solution and continue stirring at room temperature for 30 min. Then, seal the reaction flask and place it in a magnetically stirred oil bath, heat to 100 °C, and stir for 3 h. After the reaction is complete, allow it to cool naturally to room temperature. Centrifuge to collect the white precipitate, wash it three times each with DMF and ethanol, and finally dry it in a 90 °C oven for 24 h to obtain Ce-MOF powder.

[0055] (2) Weigh 10 g of PAN (molecular weight 150,000) and 1 g of PVDF (molecular weight 534,000) and add them to 89 g of DMF. Stir at 60 °C for 12 h to form a spinning solution. Electrospinning parameters: voltage 20 kV, receiving distance 20 cm, flow rate 2 mL / min, spinning for 2 h, and after standing for 1.5 h, peel off the composite fiber membrane from the aluminum foil. Place the fiber membrane in a muffle furnace and pre-oxidize it at 280 °C for 2 h (air atmosphere) by heating at 5 °C / min. After cooling, transfer it to a tube furnace and carbonize it at 800 °C for 2 h under Ar atmosphere by heating at 5 °C / min. The product is then manually ground in an agate mortar for 30 min to obtain carbon fiber powder. Carbon fiber powder and PVDF were mixed at a mass ratio of 8:2, and NMP was added dropwise to form a slurry with a viscosity of 2000 cP. The slurry was then coated onto the surface of zinc foil (thickness 0.1 mm, purity 99.99%) and onto a zinc substrate. The slurry was dried at 80 °C for 12 h to obtain a zinc anode modified with a carbon substrate, denoted as Zn@C electrode.

[0056] (3) Take 0.4 g of Ce-MOF powder obtained in step (1), dissolve it together with 4 g of PAN and 4 g of PVDF in 92 g of DMF, stir at 60 ℃ for 12 h, and ultrasonically disperse for 30 min to obtain a Ce-MOF-containing spinning solution (based on solid content). Using an electrospinning device, the above spinning solution is directly spun onto the carbon layer surface of the Zn@C electrode obtained in step (2). The spinning parameters are: voltage 18 kV, receiving distance 20 cm, flow rate 1.5 mL / h, and spinning time 1 h. After spinning, the electrode is placed in a vacuum drying oven at 60 ℃ and dried for 2 h to obtain an organic-inorganic composite multi-element interface layer modified zinc metal anode, denoted as the target electrode Zn@C / Ce-MOF@NFM. In the organic-inorganic composite multi-element interface layer modified zinc metal anode, the thickness of the lower carbon fiber coating (carbon base layer) is 60 μm, and the thickness of the upper electrospun fiber film containing Ce-MOF doping is 30 μm.

[0057] Example 5

[0058] The preparation method of the organic-inorganic composite multi-element interface layer modified zinc metal anode in this embodiment includes the following steps:

[0059] (1) Dissolve 3 mmol of terephthalic acid in 24 mL of DMF and stir until completely dissolved to obtain a terephthalic acid DMF solution. Dissolve 2 mmol of cerium ammonium nitrate in 5 mL of deionized water and stir until dissolved to obtain an aqueous solution of cerium ammonium nitrate. Slowly add the aqueous solution of cerium ammonium nitrate to a reaction flask containing the terephthalic acid DMF solution and continue stirring at room temperature for 30 min. Then, seal the reaction flask and place it in a magnetically stirred oil bath, heat to 100 °C, and stir for 3 h. After the reaction is complete, allow it to cool naturally to room temperature. Centrifuge to collect the white precipitate, wash it twice each with DMF and ethanol, and finally dry it in a 90 °C oven for 24 h to obtain Ce-MOF powder.

[0060] (2) Weigh 1 g of PAN (molecular weight 150,000) and 10 g of PVDF (molecular weight 534,000) and add them to 89 g of DMF. Stir at 60 °C for 12 h to form a spinning solution. Electrospinning parameters: voltage 15 kV, receiving distance 18 cm, flow rate 2 mL / h, spinning for 70 min, and after standing for 1.5 h, peel off the composite fiber membrane from the aluminum foil. Place the fiber membrane in a muffle furnace and pre-oxidize it at 280 °C for 2 h (air atmosphere) by heating at 5 °C / min. After cooling, transfer it to a tube furnace and carbonize it at 800 °C for 2 h under Ar atmosphere by heating at 5 °C / min. The product is then manually ground in an agate mortar for 30 min to obtain carbon fiber powder. Carbon fiber powder and PVDF were mixed at a mass ratio of 8:2, and NMP was added dropwise to form a slurry with a viscosity of 2000 cP. The slurry was then coated onto the surface of zinc foil (thickness 0.1 mm, purity 99.99%) and onto a zinc substrate. The slurry was dried at 80 °C for 12 h to obtain a zinc anode modified with a carbon substrate, denoted as Zn@C electrode.

[0061] (3) Take 0.55 g of Ce-MOF powder obtained in step (1), dissolve it together with 10 g of PAN and 1 g of PVDF in 89 g of DMF, stir at 60 ℃ for 12 h, and ultrasonically disperse for 30 min to obtain a Ce-MOF-containing spinning solution (based on solid content). Using an electrospinning device, the above spinning solution is directly spun onto the carbon layer surface of the Zn@C electrode obtained in step (2). The spinning parameters are: voltage 16 kV, receiving distance 15 cm, flow rate 3 mL / h, and spinning time 1 h. After spinning, the electrode is placed in a vacuum drying oven at 60 ℃ and dried for 2 h to obtain an organic-inorganic composite multi-element interface layer modified zinc metal anode, denoted as the target electrode Zn@C / Ce-MOF@NFM. In the organic-inorganic composite multi-element interface layer modified zinc metal anode, the thickness of the lower carbon fiber coating (carbon base layer) is 50 μm, and the thickness of the upper electrospun fiber film containing Ce-MOF doping is 30 μm.

[0062] Comparative Example 1

[0063] The zinc anode used in this comparative example is pure zinc foil (0.1 mm thick, 99.99% pure).

[0064] Comparative Example 2

[0065] The zinc anode preparation method used in this comparative example differs from that in Example 1 in that it is only a zinc anode modified with a carbon substrate. The steps are as follows:

[0066] 8 g of PAN (molecular weight 150,000) and 2 g of PVDF (molecular weight 534,000) were added to 90 g of DMF and stirred at 60 °C for 12 h to form a spinning solution. Electrospinning parameters: voltage 18 kV, receiving distance 15 cm, spinning time 2 h, and after standing for 1.5 h, the composite fiber membrane was peeled off from the aluminum foil. The fiber membrane was placed in a muffle furnace and pre-oxidized at 280 °C for 2 h (air atmosphere) at a heating rate of 5 °C / min. After cooling, it was transferred to a tube furnace and carbonized at 800 °C for 2 h (Ar atmosphere) at a heating rate of 5 °C / min. The carbon fiber powder was then obtained by grinding for 30 min. Carbon fiber powder and PVDF were mixed at a mass ratio of 8:2, and NMP was added dropwise to form a slurry with a viscosity of 2000 cP. This slurry was then coated onto the surface of zinc foil (0.1 mm thick, 99.99% pure) to a thickness of 50 μm. The coating was dried at 80 ℃ for 12 h to obtain a carbon-modified zinc anode, denoted as Zn@C electrode. The thickness of the carbon layer in the carbon-modified zinc anode was 50 μm.

[0067] Comparative Example 3

[0068] The zinc anode preparation method used in this comparative example differs from that in Example 1 in that it uses a single Ce-MOF coating layer, and the steps are as follows:

[0069] Ce-MOF powder and PVDF were mixed at a mass ratio of 8:2, and NMP was added dropwise to form a slurry with a viscosity of 2000 cP. This slurry was then coated onto the surface of zinc foil (0.1 mm thick, 99.99% pure) to a thickness of 50 μm. After drying at 80 ℃ for 12 h, a zinc anode modified with a Ce-MOF coating was obtained, denoted as Zn@Ce-MOF. The thickness of the Ce-MOF coating was 50 μm.

[0070] Implementation Results Example

[0071] The surface morphology, contact angle, and electrochemical performance of the assembled zinc anode were tested, and the specific results are as follows.

[0072] 1. SEM morphology and elemental distribution testing

[0073] Figure 1The images show the XRD pattern and SEM morphology of the Ce-MOF prepared in Example 1 of this invention. Figure 1 The XRD pattern showed characteristic diffraction peaks of Ce-MOF, confirming its crystal structure. SEM images showed that the prepared Ce-MOF consisted of nanoparticles with a size of approximately 100 nm, exhibiting regular morphology and good dispersion, providing a foundation for subsequent uniform doping in fiber membranes.

[0074] Figure 2 SEM images (a) of the samples prepared in Example 1 and Comparative Examples 1-3, and EDS elemental distribution map (b) of the Zn@C / Ce-MOF@NFM electrode prepared in Example 1. Figure 2 The EDS elemental distribution diagram of b shows that C is uniformly distributed throughout the coating area, while Ce is uniformly dispersed in the upper fiber film without obvious agglomeration, confirming the successful and uniform doping of Ce-MOF particles in electrospun fibers. In contrast, Comparative Example 2 (Zn@C) only has a carbon layer without an upper fiber structure, and Comparative Example 3 (Zn@Ce-MOF) has a dense Ce-MOF coating layer on the surface, lacking a porous fiber structure. Figure 2 a). From Figure 3 As can be seen from the cross-sectional SEM, the organic-inorganic composite multi-element interface layer modified zinc metal anode prepared in Example 1 has a clear three-layer structure: the bottom layer is a zinc substrate, the middle layer is a carbon fiber coating, and the top layer is an electrospun fiber membrane containing Ce-MOF doping.

[0075] 2. Electrolyte contact angle test

[0076] Using a contact angle testing instrument, the electrode sheet is fixed horizontally, and 2 µL of ZnSO4 electrolyte (2M ZnSo4) is dropped into it using a contact angle meter. After the droplet is balanced, the outline is photographed, and the left and right contact angles are obtained by software fitting. Figure 4 This is a comparison diagram of the contact angles of the zinc negative electrodes prepared in Example 1 and Comparative Examples 1-3 of the present invention.

[0077] As shown in the figure, the Zn@C / Ce-MOF@NFM electrode prepared in Example 1 of this invention exhibits a contact angle as high as 150.0°, demonstrating superhydrophobic properties. In contrast, the contact angle of the pure zinc anode (Comparative Example 1) is only 70.2°, the Zn@C electrode (Comparative Example 2) is 119.4°, and the Zn@Ce-MOF electrode (Comparative Example 3) is 100.7°. In the bilayer structure of this invention, the upper layer, an electrospun fiber membrane containing Ce-MOF, possesses abundant micro-nano rough structures and a low surface energy hydrophobic fiber skeleton, which synergistically endow the interface with excellent electrolyte repulsion. This superhydrophobic property can effectively repel free water and SO4 in the electrolyte. 2- This physically inhibits hydrogen evolution and corrosion side reactions at the source.

[0078] 3. Three-electrode test

[0079] (a) Linear Voltmeter-Voltage (LSV) Test

[0080] The zinc metal anode modified with a double interface layer prepared in Example 1 of this invention and the zinc anodes prepared in Comparative Examples 1-3 were cut into 2 cm × 2 cm square pieces. A platinum sheet was used as the counter electrode, a saturated calomel electrode (SCE) as the reference electrode, and 1 M NaSO4 solution as the electrolyte. An electrochemical workstation was used with a voltage of 1 mV / s. -1 The scan rate was used to test the LSV curve, characterizing its ability to suppress the hydrogen evolution reaction (HER). The results are as follows: Figure 5 As shown in the right-hand figure, the hydrogen evolution initiation potential of the zinc anode in this embodiment of the invention is -1.90 V (vs. SCE), which is significantly negative than that of the blank Zn anode (Comparative Example 1, approximately -1.68 V), the Zn@C anode (Comparative Example 2, approximately -1.78 V), and the Zn@Ce-MOF anode (Comparative Example 3, approximately -1.75 V). At a potential of -1.8 V (vs. SCE), the hydrogen evolution current density of this embodiment of the invention is only 0.05 mA cm⁻¹. -2 The values ​​are significantly lower than those in the respective proportions. This fully demonstrates that the present invention achieves its effect through the electric field homogenization of the lower carbon fiber and the Ce content in the upper Ce-MOF. 3+ / Ce 4+ The synergistic effect of redox reactions on the active scavenging of reactive free radicals can most effectively broaden the electrochemical stability window and suppress hydrogen evolution side reactions.

[0081] (b) Tafel curve test

[0082] The zinc metal anode modified with a double interface layer prepared in Example 1 of this invention and the zinc anodes prepared in Comparative Examples 1-3 were cut into 2 cm × 2 cm square pieces. A platinum sheet was used as the counter electrode, a saturated calomel electrode (SCE) as the reference electrode, and a 2 M ZnSO4 solution as the electrolyte. An electrochemical workstation with a voltage of 1 mV / s was used. -1 The scan rate was used to perform a Tafel test to evaluate its corrosion resistance, and the results are as follows: Figure 5 As shown in the left-middle figure, it can be seen that the corrosion potential of the zinc anode in this embodiment of the invention is -0.9 V (vs. SCE), which is 0.06 V positively shifted compared to -0.96 V (vs. SCE) of the blank Zn anode (Comparative Example 1), and also shows a significant positive shift compared to Comparative Example 2 (-0.92 V) and Comparative Example 3 (-0.93 V). Meanwhile, the corrosion current density of this embodiment of the invention (approximately 0.08 mA cm⁻¹) is... -2 It was also significantly lower than that of control 1 (approximately 0.35 mA cm⁻¹). -2Comparative Example 2 (approximately 0.20 mA cm⁻¹) -2 ) and Comparative Example 3 (approximately 0.15 mA cm) -2 The significant positive shift in corrosion potential and the reduction in corrosion current density together indicate that the bilayer interface modification of the present invention greatly enhances the corrosion resistance of the zinc anode, which is attributed to the synergistic effect of the physical barrier of the upper hydrophobic fiber membrane and the chemical passivation of Ce-MOF.

[0083] 4. Electrochemical Impedance Spectroscopy (EIS) Testing

[0084] The zinc anode prepared in Example 1 of this invention and the zinc anodes prepared in Comparative Examples 1-3 were punched into 8 mm diameter discs and assembled into CR2032 symmetrical cells (glass fiber membrane, 2M ZnSO4 electrolyte). AC impedance testing was performed using a CHI660e electrochemical workstation with a frequency range of 100 kHz to 0.01 Hz and an amplitude of 5 mV. The results are as follows: Figure 6 As shown, the Zn@C / Ce-MOF@NFM electrode of Example 1 of this invention has the smallest R_ct, approximately 270 Ω. In contrast, Comparative Example 1 (pure Zn) has the largest R_ct, approximately 673 Ω; Comparative Example 2 (Zn@C) has an R_ct of approximately 316 Ω; and Comparative Example 3 (Zn@Ce-MOF) has an R_ct of approximately 367 Ω. The results indicate that the lower conductive carbon layer of this invention provides a fast electron transport channel, while the upper porous fiber membrane containing Ce-MOF ensures the Zn... 2+ The low impedance transmission of the two, together with the low impedance transmission of the two, significantly reduces the interface charge transfer impedance, which is beneficial to the improvement of rate performance.

[0085] 5. Electrochemical performance of symmetrical cells and full cells

[0086] (1) Symmetrical cell

[0087] Assembly of Zinc Symmetric Cells: The zinc metal anodes prepared in Example 1 and Comparative Examples 1-3 were punched into 8mm diameter discs. Using glass fiber as a separator and 2M ZnSO4 solution as the electrolyte, CR2032 coin-type symmetric cells were assembled, corresponding to Application Examples 1-4. Deposition / stripping performance was tested using a blue electrode testing instrument to characterize cycle stability and polarization potential, as shown below. Figure 6 , Figure 7 As shown.

[0088] Figure 7 The symmetrical cells assembled for application examples 1-4 at 1 mA cm⁻¹ -2 / 15 mAh cm -2 Long-cycle performance diagram under large capacity conditions. From Figure 7As can be seen, the symmetrical battery assembled with the zinc anode prepared in Example 1 of this invention (Application Example 1) can cycle stably for more than 500 hours, and the polarization voltage remains stable without significant fluctuations throughout the cycle. In contrast, the symmetrical battery assembled with Comparative Example 1 (pure Zn) (Application Example 2) experienced short-circuit failure after about 45 hours; the symmetrical battery assembled with Comparative Example 2 (Zn@C) (Application Example 3) had a cycle life of about 180 hours; and the symmetrical battery assembled with Comparative Example 3 (Zn@Ce-MOF) (Application Example 4) had a cycle life of about 300 hours.

[0089] Figure 8 The symmetrical cells assembled for application examples 1-4 at 1 mA cm⁻¹ -2 / 1 mAh cm -2 Long-cycle performance under certain conditions. From Figure 8 As can be seen, the symmetrical battery assembled in Example 1 of the present invention (Application Example 1) has a stable cycle time of over 1000 hours, and its polarization voltage (approximately 50 mV) is much lower than that of Comparative Example 2 (approximately 80 mV) and Comparative Example 3 (approximately 65 mV). This indicates that the bilayer structure of the present invention can effectively suppress dendrite growth and maintain interface stability under both large area capacity and long cycle conditions.

[0090] (2) Zinc-copper half-cell

[0091] Assembly of Zinc-Copper Half-Cells: The zinc metal anodes prepared in Example 1 and Comparative Examples 1-3 were punched into discs with a diameter of 8 mm. An 8 mm diameter copper sheet was used as the counter electrode, glass fiber as the separator, 2M ZnSO4 solution as the electrolyte, and metal gaskets and spring sheets as filler materials. CR-2032 coin cells were assembled and packaged using a packaging machine, corresponding to Application Examples 5-8 respectively. After standing for 8 hours, electrochemical performance was tested. The deposition / stripping performance of the cells was tested using a constant current method on a Blue Electric charge-discharge tester to characterize their cycle performance and coulombic efficiency.

[0092] Figure 9 The coulombic efficiency diagram for the zinc-copper half-cell assembled in Application Example 5-8 is shown. Figure 9 It can be seen that at a current density of 2 mA cm⁻¹ -2 The deposition capacity is 1 mAh cm⁻¹ -2 Under the specified conditions, Example 1 exhibits an average coulombic efficiency of up to 99.6%, which remains stable even after more than 1200 cycles. In contrast, the coulombic efficiencies of Application Example 6 (pure Zn), Application Example 7 (Zn@C), and Application Example 8 (Zn@Ce-MOF) show dramatic fluctuations and decreases after 150, 400, and 560 cycles, respectively, indicating that the bilayer structure of this invention significantly improves the reversibility of zinc deposition / stripping.

[0093] (3) Zinc ion capacitor (Zn / / AC)

[0094] Assembly of zinc-ion capacitors: The zinc metal negative electrodes prepared in Examples 1-5 and Comparative Examples 1-3 were punched into circular pieces with a diameter of 8 mm. A slurry of activated carbon (AC), acetylene black, and binder (PVDF) in a mass ratio of 7:2:1 was coated onto titanium foil. After vacuum drying at 80 °C, the slurry was cut into electrode sheets with a diameter of 8 mm, and the active loading was controlled at 1 mg / cm³. -2 The capacitor was used as the positive electrode. A CR-2032 coin cell capacitor was assembled using glass fiber as the separator, 2M ZnSO4 solution as the electrolyte, and metal gaskets and springs as filler materials. It was then packaged using a packaging machine, corresponding to Application Examples 9-12. After standing for 12 hours, its electrochemical performance was tested. The cycle stability of the capacitor was tested using a constant current method on a Blue Electric charge-discharge tester, and the results are shown in Table 1.

[0095] Table 1. Long-cycle performance of full-cell (Zn / / AC capacitor)

[0096]

[0097] As shown in Table 1, in 1 A g -1 At the specified current density, the capacitor assembled in Example 1 of this invention (Application Example 9) maintained a capacitance retention of >92% after 20,000 cycles. In contrast, the capacitor assembled in Comparative Example 1 (pure Zn) (Application Example 10) rapidly degraded in capacitance after approximately 2,500 cycles, with a capacitance retention of only 62%; the capacitor assembled in Comparative Example 2 (Zn@C) (Application Example 11) saw its capacitance retention drop to 70% after approximately 4,500 cycles; and the capacitor assembled in Comparative Example 3 (Zn@Ce-MOF) (Application Example 12) saw its capacitance retention drop to 75% after approximately 6,500 cycles. These results clearly demonstrate that this invention, through integrated interface control, significantly improves the structural stability and electrochemical reversibility of the zinc anode under high current and long-cycle conditions.

[0098] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An organic-inorganic composite multi-element interface layer modified zinc metal anode, characterized in that, It includes a zinc substrate, a carbon fiber coating on the zinc substrate, and an electrospun fiber membrane doped with cerium-based MOF on the carbon fiber coating.

2. The organic-inorganic composite multi-element interface layer modified zinc metal anode according to claim 1, characterized in that, The cerium-based MOF is prepared as follows: it is obtained by reacting terephthalic acid and cerium ammonium nitrate as raw materials.

3. The method for preparing an organic-inorganic composite multi-element interface layer modified zinc metal anode according to claim 2, characterized in that, The molar ratio of terephthalic acid to cerium ammonium nitrate is 0.8-1.5:1, the reaction temperature is 90-110℃, and the reaction time is 2-4 h.

4. The preparation method of the organic-inorganic composite multi-element interface layer modified zinc metal anode according to claim 3, characterized in that, The steps are as follows: (1) Mix carbon fiber powder with binder, add solvent I to make a slurry, coat it on the surface of zinc substrate, and dry it to obtain carbon fiber coating, thus obtaining a zinc anode modified with carbon substrate; (2) Add cerium-based MOF powder, polyacrylonitrile and polyvinylidene fluoride to solvent II to obtain electrospinning solution I; then electrospin the carbon fiber coating surface of the carbon-based zinc anode prepared in step (1), and after drying, obtain an organic-inorganic composite multi-element interface layer modified zinc metal anode.

5. The method for preparing an organic-inorganic composite multi-element interface layer modified zinc metal anode according to claim 4, characterized in that, The mass ratio of carbon fiber powder to binder is (7-9):(1-3), solvent I is N-methylpyrrolidone, dimethyl sulfoxide or dihydrol-glucanone, and the viscosity of the homogenate is 2000-3000 cP.

6. The method for preparing an organic-inorganic composite multi-element interface layer modified zinc metal anode according to claim 5, characterized in that, The carbon fiber powder is prepared by dissolving polyacrylonitrile and polyvinylidene fluoride in solvent II to obtain electrospinning solution II; then, carbon fiber powder is obtained by electrospinning, pre-oxidation, carbonization and grinding.

7. The method for preparing an organic-inorganic composite multi-element interface layer modified zinc metal anode according to claim 6, characterized in that, In the electrospinning solution I and electrospinning solution II, the mass ratio of polyacrylonitrile to polyvinylidene fluoride is 0.1-10:1; the total concentration of polyacrylonitrile and polyvinylidene fluoride is 8-12 wt%; and in electrospinning solution I, the mass of cerium-based MOF powder is 5-15% of the total mass of polyacrylonitrile and polyvinylidene fluoride.

8. The method for preparing an organic-inorganic composite multi-element interface layer modified zinc metal anode according to claim 4, characterized in that, The adhesive is at least one of polyvinylidene fluoride, polytetrafluoroethylene, polyacrylic acid, carboxymethyl cellulose, sodium alginate, polyvinyl alcohol, hydroxypropyl methylcellulose and styrene-butadiene rubber; solvent II is at least one of N,N-dimethylformamide, dimethyl sulfoxide and sulfolane.

9. The method for preparing an organic-inorganic composite multi-element interface layer modified zinc metal anode according to claim 8, characterized in that, The electrospinning process parameters are as follows: spinning voltage is 15-20 kV, spinning distance is 15-20 cm, and flow rate is 0.3-2.0 mL / h; pre-oxidation temperature is 240-280 ℃, and time is 1-3 h; carbonization temperature is 600-800 ℃, and time is 1-5 h.

10. The application of the organic-inorganic composite multi-element interface layer modified zinc metal anode as described in claim 1 in aqueous zinc-ion batteries or aqueous zinc-ion capacitors.

Images