Composite functional interface layer on surface of metal base material and preparation method and application of composite functional interface layer

Abstract

The invention discloses a composite function interface layer on the surface of a metal base material and a preparation method and application thereof, the composite function interface layer is of a porous structure and comprises C, F and O elements, and the thickness of the composite function interface layer is 3-100 nm. The preparation method comprises the following steps: coating a liquid fluorocarbon polymer on the surface of a metal substrate, and drying to form a precursor film; and placing the obtained product in a protective atmosphere, heating and preserving heat, and then cooling to room temperature to form an ultrathin porous composite functional interface layer on the surface of the metal substrate in situ. The liquid fluorocarbon polymer is pyrolyzed on the metal substrate, the carbon-based interface layer with the thickness of only nanoscale can be constructed on the surface of the substrate in situ, the interface layer has the porous characteristic, abundant channels are provided for ion transmission, the ion diffusion path is greatly shortened, the ion migration energy barrier is effectively reduced, and the performance of the device is improved. The ion transmission rate and the deposition / stripping dynamic performance of the electrode are remarkably improved, and the utilization rate and the cycle life of the metal electrode are improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the interface layer and its preparation and application, and particularly relates to a composite functional interface layer on the surface of a metal substrate and a preparation method and application thereof. BACKGROUND

[0002] Metal secondary batteries (such as lithium metal batteries, sodium metal batteries, zinc metal batteries, etc.) have become the research focus of the next generation of electrochemical energy storage systems due to their high theoretical capacity and high energy density. However, the commercialization process of such batteries is generally limited by the interface instability of the metal anode. The main performance is that during the cycle process, the non-uniform deposition of the metal on the electrode surface will cause dendrite growth, which has the risk of piercing the separator and causing short circuit of the battery; at the same time, the interface side reaction (such as corrosion, hydrogen evolution, etc.) between the metal anode and the electrolyte will cause continuous consumption of active materials and low coulombic efficiency.

[0003] In order to compensate for the irreversible loss of the metal anode during the cycle process, the battery design usually needs to use a metal sheet with a large thickness as the anode, which causes a serious excess of active materials. The excess metal not only cannot contribute to the effective capacity, but also significantly reduces the overall energy density of the battery, which becomes one of the core bottlenecks restricting its industrial application. Therefore, it is crucial to develop a new stable anode architecture that can realize low metal loading and high utilization. In response to this challenge, the research community has attempted to construct an artificial interface layer on the surface of the current collector in order to guide the uniform nucleation and deposition of the metal. Among them, the technical path of calcining polymer, biomass and other coatings has been widely explored. However, the interface layer prepared by such methods is usually micron thick, which can block the corrosion of the electrolyte interface, but also hinders the diffusion of ions, making it difficult to achieve high metal utilization and long cycle life. SUMMARY

[0004] The purpose of the present application is to overcome the deficiencies in the prior art, and the purpose of the present application is to provide a composite functional interface layer on the surface of a metal substrate, and the purpose of the present application is to provide a simple and convenient, easy to scale production method for preparing a composite functional interface layer on the surface of a metal substrate, and the purpose of the present application is to provide a composite functional interface layer on the surface of a metal substrate in the field of metal surface functionalization and electrode protection.

[0005] Technical solution: The composite functional interface layer on the surface of a metal substrate according to the present application is a porous structure, which comprises C, F and O elements, and the thickness is 3-100 nm.

[0006] Further, the atomic percentage of F element is 0.3-21.9 at.%, and the atomic percentage of O element is 8.2-45.2 at.%.

[0007] The preparation method of the composite functional interface layer on the surface of the metal substrate comprises the following steps:

[0008] Step one, coating a liquid fluorocarbon polymer on the surface of the metal substrate, drying to form a precursor film;

[0009] Step two, placing the product obtained in step one in a protective atmosphere, heating and holding, and then cooling to room temperature to form an ultrathin porous composite functional interface layer in situ on the surface of the metal substrate.

[0010] Further, in step one, the liquid fluorocarbon polymer includes one or more of anionic fluorocarbon surfactant, cationic fluorocarbon surfactant, non-ionic fluorocarbon surfactant, fluorine-containing polyether, and fluorinated organic small molecule. Preferably, the liquid fluorocarbon polymer is one or any combination of FS3100, FSO-100, and FS-60.

[0011] Further, in step one, the mass concentration of the solution is 1-100%.

[0012] Further, in step one, the metal substrate is a metal material, an alloy material, or a non-metal material with a metalized layer on the surface. Preferably, the metal material is any one of zinc, aluminum, copper, iron, nickel, and stainless steel. More preferably, the metal material is copper, iron, or nickel.

[0013] Further, in step one, the coating is any one of spin coating, blade coating, drop coating, and pulling.

[0014] Further, in step two, the protective atmosphere is one or more of nitrogen, argon, helium, and hydrogen.

[0015] Further, in step two, the heating temperature is 200-600°C, and the holding time is 0-180 min.

[0016] The composite functional interface layer on the surface of the metal substrate is used in the modification of electrode current collectors of electrochemical devices, metal corrosion protection coatings, and interface modification layers.

[0017] Further, the electrochemical device includes zinc ion batteries, zinc metal batteries, lithium ion batteries, lithium metal batteries, and sodium ion batteries. The composite functional interface layer is used to induce uniform metal deposition, inhibit dendrite growth, improve metal deposition / peeling efficiency, and adjust ion permeation.

[0018] Preparation principle: it is a common scheme to prepare coating by pyrolysis of organic polymers, biomacromolecules and the like as raw materials, but due to poor compatibility of polymers with metal substrates, molecular chain entanglement and phase separation are prone to occur, and the thickness of the prepared pyrolysis product coating is difficult to control below micron level and is uneven. The surface energy of liquid fluorocarbon polymer is extremely low, and the flowability is better, so that a precursor film with small thickness can be obtained, and a product film with lower thickness can be obtained; and the elements of fluorine and oxygen in the precursor can generate gas during pyrolysis, forming a porous structure, and finally a fluorine and oxygen doped porous ultrathin functional interface layer is obtained.

[0019] Beneficial effects: compared with the prior art, the present application has the following remarkable features:

[0020] 1. By pyrolyzing liquid fluorocarbon polymers and the like on a metal substrate, a carbon-based interface layer with a thickness of only nanometer level can be constructed in situ on the surface of the substrate, and the interface layer also has a porous property, providing abundant channels for ion transmission. When the ultrathin interface layer is used for metal electrode modification, the ion diffusion path is greatly shortened, the ion migration energy barrier is effectively reduced, the ion transmission rate and deposition / detachment kinetic performance of the electrode are significantly improved, and the metal utilization rate and cycle life are improved;

[0021] 2. The functional interface layer mainly contains fluorine and oxygen co-doped carbon materials and part of fluorides, oxides and the like. The strong electronegative fluorine species can effectively guide the uniform nucleation and deposition of metal ions and inhibit the growth of dendrites. The introduced oxygen element further improves the gold affinity and ion conductivity of the interface, and the synergistic effect of the two realizes efficient regulation of the metal deposition behavior;

[0022] 3. The preparation steps are simple, time-consuming is short, no complex post-treatment is needed, and the liquid fluorocarbon polymer used has low cost and is easy to obtain. This efficient and low-cost process route has great potential for large-scale industrial production. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a scanning electron microscope image of the product obtained in Examples 1-4 and Comparative Examples 1-2, wherein (a) is a scanning electron microscope image of the product obtained in Example 1 at a magnification of 20000, (b) is a scanning electron microscope image of the product obtained in Example 2 at a magnification of 20000, (c) is a scanning electron microscope image of the product obtained in Example 2 at a magnification of 50000, (d) is a scanning electron microscope image of the product obtained in Example 3 at a magnification of 20000, (e) is a scanning electron microscope image of the product obtained in Example 3 at a magnification of 50000, and (f) is a scanning electron microscope image of the product obtained in Example 4 at a magnification of 20000.

[0024] Figure 2 is an X-ray photoelectron spectroscopy F 1s graph of the present application;

[0025] Figure 3 is the X-ray photoelectron spectroscopy O 1s graph of the present application;

[0026] Figure 4 is the X-ray photoelectron spectroscopy Cu 2p graph of the present application;

[0027] Figure 5 is the Raman spectrogram of the material obtained in Example 1-4 and Comparative Example 1;

[0028] Figure 6 is the specific surface area and pore size test of the material obtained in Example 2, wherein (a) nitrogen adsorption-desorption curve, (b) BJH, (c) HK, (d) DA pore size distribution graph;

[0029] Figure 7 is the time-voltage curve of symmetrical battery of Example 2, Example 3 and Comparative Example 2 at current density 2 mA cm -2 and current 5 mA cm -2 ;

[0030] Figure 8 is the long cycle charge-discharge cycle curve of Example 2, Example 3 and Comparative Example 2 in the voltage window of 0.8-1.8 V at current density 1 A g -1 . DETAILED DESCRIPTION

[0031] In the following examples, the materials, reagents and the like used are commercially available unless otherwise specified. The experimental methods in the examples not specifically noted are usually carried out according to the conventional conditions or according to the conditions suggested by the manufacturer.

[0032] Example 1

[0033] A method for preparing a composite functional interface layer on the surface of a metal substrate, comprising the following steps:

[0034] (1) Precursor coating: take a copper foil with a size of 10 cm x 5 cm and a thickness of 20 μm, and fix it on the substrate of a doctor blade. Measure 0.5 mL of non-ionic liquid fluorocarbon polymer FS3100 liquid, and drop it on one end of the copper foil. Use a doctor blade with a set gap of 25 μm to uniformly coat it on the entire surface of the copper foil. Dry at 100 ℃ to form a precursor film.

[0035] (2) Controllable pyrolysis: transfer the coated copper foil to a ceramic capsule and place it in a tube furnace. After sealing the tube furnace, introduce nitrogen as a protective atmosphere, with a gas flow rate of 50 ml / min, and ventilate for 30 minutes to fully replace the air in the furnace. Then, program the temperature to rise to 200 ℃ at a rate of 1 ℃ / min.

[0036] (3) After pyrolysis is completed, the heating power is turned off, and the sample is naturally cooled to room temperature in the tube furnace to obtain a composite functional interface layer. After the sample is taken out, a puncher is used to cut it into a circular electrode with a diameter of 12 mm. The electrode is marked as sample 1.

[0037] The composite functional interface layer of sample 1 is a porous structure with a thickness of 91 nm. The composite functional interface layer includes C, F and O elements, the atomic percentage of F element is 21.9 at.%, the atomic percentage of O element is 45.2 at.%, and the rest is C.

[0038] Example 2

[0039] A method for preparing a composite functional interface layer on a surface of a metal substrate includes the following steps:

[0040] (1) Precursor coating: take a copper foil with a size of 10 cm x 5 cm and a thickness of 20 μm, and fix it on the substrate of a doctor blade. 0.5 mL of non-ionic fluorocarbon surfactant FS3100 liquid is added to one end of the copper foil, and a doctor blade with a gap of 25 μm is used to uniformly coat the entire surface of the copper foil. Dry at 100°C to form a precursor film.

[0041] (2) Controllable pyrolysis: transfer the coated copper foil to a ceramic capsule and place it in a tube furnace. After sealing the tube furnace, a mixed gas composed of 5vol% hydrogen and 95vol% argon is introduced as a protective atmosphere, and the gas flow rate is 50 ml / min. The gas is flowed for 30 minutes to fully replace the air in the furnace. Then, the temperature is programmed to rise to 300°C at a rate of 5°C / min, and the temperature is maintained for 60 min.

[0042] (3) After pyrolysis is completed, the heating power is turned off, and the sample is naturally cooled to room temperature in the tube furnace to obtain a composite functional interface layer. After the sample is taken out, a puncher is used to cut it into a circular electrode with a diameter of 12 mm. The electrode is marked as sample 2.

[0043] The composite functional interface layer of sample 2 is a porous structure with a thickness of 5.5 nm. The composite functional interface layer includes C, F and O elements, the atomic percentage of F element is 10.7 at.%, the atomic percentage of O element is 33.9 at.%, and the rest is C.

[0044] Example 3

[0045] A method for preparing a composite functional interface layer on a surface of a metal substrate includes the following steps:

[0046] (1) Precursor coating: take a copper foil with a size of 10 cm x 5 cm and a thickness of 20 μm, and fix it on the substrate of a doctor blade. Measure 0.5 mL of non-ionic fluorocarbon surfactant FS3100 liquid, and drop it on one end of the copper foil. Use a doctor blade with a set gap of 25 μm to uniformly coat the entire surface of the copper foil. Dry at 120 °C to form a precursor film.

[0047] (2) Controllable pyrolysis: transfer the coated copper foil to a ceramic capsule and place it in a tube furnace. After sealing the tube furnace, a mixed gas composed of 5 vol% hydrogen and 95 vol% argon is introduced as a protective atmosphere, with a gas flow rate of 50 ml / min. The gas is flowed for 30 minutes to fully displace the air in the furnace. Subsequently, the temperature is programmed to rise to 400 °C at a rate of 5 °C / min, and held for 60 min.

[0048] (3) After pyrolysis is complete, turn off the heating power and allow the sample to cool naturally in the tube furnace to room temperature to obtain a composite functional interface layer. After removing the sample, use a puncher to cut it into a circular electrode with a diameter of 12 mm. Label the electrode as sample 3.

[0049] The composite functional interface layer of sample 3 has a porous structure and a thickness of 4.7 nm. The composite functional interface layer includes C, F, and O elements, with the atomic percentage of F being 2.2 at.%, and the atomic percentage of O being 40.8 at.%, and the rest being C.

[0050] Example 4

[0051] A method for preparing a composite functional interface layer on the surface of a metal substrate, comprising the following steps:

[0052] (1) Precursor coating: take a copper foil with a size of 10 cm x 5 cm and a thickness of 20 μm, and fix it on the substrate of a doctor blade. Measure 0.5 mL of non-ionic fluorocarbon surfactant FS3100 liquid, and drop it on one end of the copper foil. Use a doctor blade with a set gap of 25 μm to uniformly coat the entire surface of the copper foil. Dry at 120 °C to form a precursor film.

[0053] (2) Controllable pyrolysis: transfer the coated copper foil to a ceramic capsule and place it in a tube furnace. After sealing the tube furnace, a mixed gas composed of 5 vol% hydrogen and 95 vol% argon is introduced as a protective atmosphere, with a gas flow rate of 50 ml / min. The gas is flowed for 30 minutes to fully displace the air in the furnace. Subsequently, the temperature is programmed to rise to 400 °C at a rate of 5 °C / min, and held for 60 min.

[0054] (3) After pyrolysis is completed, the heating power is turned off, and the sample is naturally cooled to room temperature in the tube furnace to obtain the composite functional interface layer. After the sample is taken out, a puncher is used to cut it into a circular electrode with a diameter of 12 mm. The electrode is marked as sample 4.

[0055] The composite functional interface layer of sample 4 is a porous structure with a thickness of 3 nm. The composite functional interface layer comprises C, F and O elements, the atomic percentage of F element is 0.3 at.%, the atomic percentage of O element is 38.9 at.%, and the rest is C.

[0056] Example 5

[0057] A method for preparing a composite functional interface layer on a surface of a metal substrate comprises the following steps:

[0058] (1) Precursor coating: take a zinc sheet with a size of 10 cm x 5 cm and a thickness of 20 μm, and fix it on the substrate of a doctor blade. Measure 0.5 mL of non-ionic fluorocarbon surfactant FSO-100 liquid, and drop it on one end of the zinc sheet and spin it on the entire surface of the zinc sheet. Dry at 150°C to form a precursor film.

[0059] (2) Controllable pyrolysis: transfer the coated zinc sheet to a ceramic capsule and place it in a tube furnace. After sealing the tube furnace, helium gas is introduced as a protective atmosphere, and the gas flow rate is 50 ml / min. The gas is flowed for 30 minutes to fully replace the air in the furnace. Then, the temperature is programmed to rise to 600°C at a rate of 10°C / min, and the temperature is maintained for 90 min.

[0060] (3) After pyrolysis is completed, the heating power is turned off, and the sample is naturally cooled to room temperature in the tube furnace to obtain the composite functional interface layer. After the sample is taken out, a puncher is used to cut it into a circular electrode with a diameter of 12 mm. The electrode is marked as sample 5.

[0061] The composite functional interface layer of sample 5 is a porous structure with a thickness of 3 nm. The composite functional interface layer comprises C, F and O elements, the atomic percentage of F element is 3.1 at.%, the atomic percentage of O element is 13.8 at.%, and the rest is C.

[0062] Example 6

[0063] A method for preparing a composite functional interface layer on a surface of a metal substrate comprises the following steps:

[0064] (1) Precursor coating: Take a piece of aluminum sheet with a size of 10 cm x 5 cm and a thickness of 20 μm, and fix it on the substrate of the doctor blade. Measure 0.5 mL of non-ionic fluorocarbon surfactant FS-60 liquid, and drop it on one end of the aluminum sheet to make drop coating on the entire surface of the aluminum sheet. Dry at 150°C to form a precursor film.

[0065] (2) Controllable pyrolysis: Transfer the coated aluminum sheet to the ceramic capsule and place it in the tube furnace. After sealing the tube furnace, introduce nitrogen as the protective atmosphere, with a gas flow rate of 50 ml / min, and ventilate for 30 minutes to fully replace the air in the furnace. Then, program the temperature to rise to 450°C at a rate of 30°C / min, and keep it at this temperature for 120 min.

[0066] (3) After pyrolysis is completed, turn off the heating power, and let the sample cool naturally in the tube furnace to room temperature to obtain a composite functional interface layer. After removing the sample, use a puncher to cut it into a circular electrode with a diameter of 12 mm. Label the electrode as sample 6.

[0067] The composite functional interface layer of sample 6 has a porous structure with a thickness of 100 nm. The composite functional interface layer includes C, F, and O elements, with the atomic percentage of F being 10.0 at.%, and the atomic percentage of O being 8.2 at.%, and the rest being C.

[0068] Example 7

[0069] A method for preparing a composite functional interface layer on the surface of a metal substrate, comprising the following steps:

[0070] (1) Precursor coating: Take a piece of stainless steel sheet with a size of 10 cm x 5 cm and a thickness of 20 μm, and fix it on the substrate of the doctor blade. Measure 0.5 mL of perfluoropolyether PFPE liquid, and drop it on one end of the stainless steel sheet to make spin coating on the entire surface of the stainless steel sheet. Dry at 150°C to form a precursor film.

[0071] (2) Controllable pyrolysis: Transfer the coated stainless steel sheet to the ceramic capsule and place it in the tube furnace. After sealing the tube furnace, introduce argon as the protective atmosphere, with a gas flow rate of 50 ml / min, and ventilate for 30 minutes to fully replace the air in the furnace. Then, program the temperature to rise to 450°C at a rate of 30°C / min, and keep it at this temperature for 120 min.

[0072] (3) After pyrolysis is completed, turn off the heating power, and let the sample cool naturally in the tube furnace to room temperature to obtain a composite functional interface layer. After removing the sample, use a puncher to cut it into a circular electrode with a diameter of 12 mm. Label the electrode as sample 6.

[0073] The composite functional interface layer of sample 6 is a porous structure with a thickness of 94 nm. The composite functional interface layer comprises C, F and O elements, the atomic percentage of F element is 19.7 at.%, the atomic percentage of O element is 25.4 at.%, and the rest is C.

[0074] Comparative Example 1

[0075] The electrode coated with FS-3100 but without pyrolysis treatment is marked as Comparative Sample 1.

[0076] Comparative Example 2

[0077] The electrode cut from the pure copper foil without any treatment is marked as Comparative Sample 2.

[0078] Application Example

[0079] The electrodeposition of zinc metal was carried out by assembling half-cells. In the half-cell, zinc metal was the negative electrode, 2 M ZnSO4 solution was the electrolyte, glass fiber separator (GF / D) was the separator, and the electrode obtained in Examples 1-4 and Comparative Examples 1 and 2 was the positive electrode, and the change of coulombic efficiency with cycle number was tested.

[0080] The symmetric cell used zinc metal as the negative electrode, 2 M ZnSO4 solution as the electrolyte, glass fiber separator (GF / D) as the separator, and the electrode obtained in Example 1 was pre-deposited with 5 mAh cm -2 The composite electrode of zinc metal was the positive electrode, and the change of voltage with cycle time was tested.

[0081] In the full cell, MnO2 powder, Ketjen black and sodium carboxymethyl cellulose were uniformly dispersed in deionized water at a mass ratio of 7:2:1, and the slurry was uniformly coated on carbon paper and placed in a vacuum drying oven at 80 ℃ for 12 hours to obtain a positive electrode. The average loading of the positive electrode active material was about 1.8 mg cm -2 The zinc-manganese dioxide full cell was pre-deposited with 10 mAh cm -2 The composite electrode of zinc metal was the negative electrode, and the mixture solution of 2 M ZnSO4 and 0.1 M MnSO4 was used as the electrolyte, and the glass fiber separator (GF / D) was used as the separator. The full cell charging and discharging voltage range was 0.8-1.8 V.

[0082] Experimental results: Figure 1 The micro-morphology diagrams of different examples and comparative examples are shown, and it can be seen that the surfaces of Examples 2 and 3 exhibit a porous morphology. Figure 2 The high-resolution X-ray photoelectron spectroscopy of F of different examples is shown from Figure 2 It can be seen from the above table that covalent C-F and ionic F exist in Examples 2 and 3, and the intensity of covalent C-F in Example 3 is significantly reduced. Figure 3The high-resolution X-ray photoelectron spectroscopy of CO shows that CO is present in both Examples 2 and 3. Therefore, the carbon material interface layer in the examples can be reasonably represented as C. x F y O z Figure 4 shows the Cu 2p spectra of different embodiments. It can be seen that obvious Cu 2p spectra are present in Examples 2 and 3. 2+ Peak and Cu 0 peak. Figure 5 Raman spectra of different embodiments and Comparative Example 1, such as Figure 5 As shown, Examples 2 and 3 exhibit obvious D-peak and G-peak signals, and Example 2 shows I... D / I G It has a higher strength ratio, exhibiting a lower degree of graphitization and a higher defect rate. Figure 6 The nitrogen adsorption-desorption curves and pore size distribution diagrams for the sample from Example 2 are shown below. Based on the nitrogen adsorption-desorption curves, the specific surface area of ​​Example 2 can be calculated to be 124 m². 2 g -1 It has a microporous mesoporous structure. Figure 7 Examples 2, 3, and Comparative Example 2 were performed at a current density of 2 mA cm⁻¹. -2 The fixed capacity is 1mAh cm -2 and current 5 mA cm -2 The fixed capacity is 2mAh cm -2 The following is a symmetrical battery time-voltage diagram. (See below) Figure 7 As shown, Example 2 exhibits significant performance improvement under different current conditions, at 5 mA cm⁻¹ -2 / 2 mAh cm -2 Achieve a cycle life of up to 1500 hours under conditions of 40% depth of discharge. Figure 8 The graph shows the cycle performance of full cells assembled with manganese dioxide cathodes in Examples 2, 3, and Comparative Example 2 under 1 A g⁻¹ conditions. Figure 8 As can be seen, Example 2 exhibits a higher discharge specific capacity (193.6 mAh g⁻¹), and after 800 cycles, the specific capacity remains at 170.7 mAh g⁻¹ (capacity retention rate of 88.2%). Example 3 has a lower discharge specific capacity and capacity retention rate than Example 2, with Comparative Example 2 showing the worst performance. This indicates that the ultrathin porous fluorine-oxygen-doped carbon interface layer prepared in this invention can significantly improve the electrochemical performance of zinc-ion batteries.

Claims

1. A composite functional interface layer on the surface of a metal substrate, characterized in that: It has a porous structure, containing C, F, and O elements, with a thickness of 3~100nm.

2. The composite functional interface layer on the surface of a metal substrate according to claim 1, characterized in that: The atomic percentage of element F is 0.3 to 21.9 at.%, and the atomic percentage of element O is 8.2 to 45.2 at.%.

3. A method for preparing a composite functional interface layer on the surface of a metal substrate according to claim 1 or 2, characterized in that, Includes the following steps: Step 1: Apply liquid fluorocarbon polymer to the surface of a metal substrate and dry it to form a precursor film; Step 2: Place the material obtained in Step 1 in a protective atmosphere, heat and keep it at a certain temperature, and then cool it to room temperature to form an ultra-thin porous composite functional interface layer in situ on the surface of the metal substrate.

4. The method for preparing the composite functional interface layer on the surface of a metal substrate according to claim 3, characterized in that: In step one, the liquid fluorocarbon polymer includes one or more of the following: anionic fluorocarbon surfactants, cationic fluorocarbon surfactants, nonionic fluorocarbon surfactants, fluorinated polyethers, and fluorinated organic small molecules.

5. The method for preparing the composite functional interface layer on the surface of a metal substrate according to claim 3, characterized in that: In step one, the mass concentration of the solution is 1~100%.

6. The method for preparing the composite functional interface layer on the surface of a metal substrate according to claim 3, characterized in that: In step one, the metal substrate is a metal material, an alloy material, or a non-metallic material with a metallized layer on its surface.

7. The method for preparing the composite functional interface layer on the surface of a metal substrate according to claim 3, characterized in that: In step one, the coating can be any one of spin coating, scraping coating, drip coating, or lift coating.

8. The method for preparing the composite functional interface layer on the surface of a metal substrate according to claim 3, characterized in that: In step two, the protective atmosphere is one or more of nitrogen, argon, helium, and hydrogen.

9. The method for preparing the composite functional interface layer on the surface of a metal substrate according to claim 3, characterized in that: In step two, the heating temperature is 200~600 ℃, and the holding time is 0~180 min.

10. The application of the composite functional interface layer on the surface of the metal substrate according to claim 1 or 2 in the modification of electrode current collectors, metal corrosion protection coatings and interface modification layers of electrochemical devices.

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