Silane coupling agent modified sodium metal foil, preparation method and application thereof

Abstract

The application discloses a silane coupling agent modified metal sodium foil, a preparation method and application, and relates to the technical field of sodium batteries. The silane coupling agent modified metal sodium foil comprises a base body and an interface modification layer, the base body is a material containing zero-valent sodium on the surface, and the interface modification layer comprises a silane coupling agent. The silane coupling agent is combined with metal hydrocarbon groups on the base body to form an oxygen alkyl bond (Na-O-Si). Meanwhile, the silane molecules are mutually reacted to form a silane modification layer with a firm crosslinking network structure, so that the mechanical properties of the sodium metal interface are enhanced. The silane modification layer can reduce dendrite growth on the surface of the sodium metal, improve the stability of the sodium metal negative electrode, and thus the energy density of the battery is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sodium battery technology, more particularly to a silane coupling agent modified metal sodium foil, a preparation method and applications. BACKGROUND

[0002] With the rapid development of renewable energy and the expansion of the electric vehicle market, there is an increasing demand for batteries with high energy density, low cost and long cycle life. As one of the most commonly used rechargeable batteries, the energy density of lithium-ion batteries has gradually approached the limit, and the lithium resource is limited, so it is necessary to find a new battery system. Sodium batteries have attracted widespread attention from academia and industry due to their abundant raw material sources and low cost. However, the current sodium-ion battery system still has a large gap in energy density compared to the traditional lithium-ion battery system. Metal sodium is considered to be the most promising anode material in sodium-based batteries due to its high theoretical capacity (1166mAh g -1 ) and low redox potential (-2.71V vs. standard hydrogen electrode).

[0003] Generally, the metal negative electrode studied for sodium metal is 300μm to 1mm thick. Under test conditions, the actual discharge depth is less than 5%, i.e. only 5% of the negative electrode material participates in the metal deposition / dissolution reaction. In the actual application process, the excess metal negative electrode will reduce the energy density of the battery and pose a safety hazard. Therefore, the development of thin sodium metal negative electrode can greatly improve the energy density of sodium battery. However, the flexibility and stickiness of metal sodium make it difficult to produce thin sodium foil, and its high reactivity also poses new challenges for production and storage. In addition, during the charging and discharging process of the battery, the sodium metal anode has problems such as dendrite growth and unstable electrode / electrolyte interface, which will increase the internal resistance of the battery, reduce the coulombic efficiency, consume the electrolyte and eventually fail.

[0004] Searches have found that there have been related reports on the modification of metal interfaces by silane coupling agents, such as patent CN 117038868A, which discloses a modified metal electrode for inducing directional advantage crystal orientation growth of electro-deposited metal, a metal battery and a preparation method: spreading trifluoromethyltrimethylsilane on the surface of metal (lithium, sodium, zinc, aluminum, magnesium) to generate a solid-state electrolyte interface film in situ, which can effectively induce directional advantage crystal orientation growth of electro-deposited metal and inhibit dendrite growth, obtaining uniform, dendrite-free, flat and blocky metal deposition. However, there is no record of the technical effects of silane coupling agents on the modification of sodium metal interface, the enhancement of its surface mechanical properties, the reduction of sodium metal surface viscosity, the reduction of metal sodium material thickness, the preparation of metal sodium foil and the improvement of battery energy density. SUMMARY

[0005] Therefore, one of the purposes of the present application is to provide a silane coupling agent modified sodium foil, which comprises a substrate and a silane modified layer on the surface of the substrate. The silane coupling agent provided by the present application is hydrolyzed into silanol, which is coordinated with the metal hydroxyl on the surface of the sodium metal to form an oxygen-alkyl bond. At the same time, the silane molecules form a stable cross-linked network structure of the silane modified layer on the surface of the sodium metal through cross-linking reaction, which improves the interface stability of the substrate, reduces the consumption of electrolyte, and inhibits the generation of sodium dendrites.

[0006] In order to achieve the above-mentioned purposes, the present application adopts the following technical solutions:

[0007] A silane coupling agent modified sodium foil, comprising a substrate and a silane coupling agent modified layer: the substrate is a metal material containing zero-valent sodium on the surface.

[0008] Preferably, the molecular structure of the silane coupling agent is

[0009]

[0010] In the formula, R is alkoxy, acyloxy, halogen, amine, etc.; X is alkyl, alkenyl, epoxy, aryl, fluoroalkyl, chloroalkyl, bromoalkyl, iodoalkyl, amino, diazo, azido, cyano, isocyan, mercapto, etc.; n and i are positive integers, n = 1-3, i = 1-1000000.

[0011] Further, the silane coupling agent modified layer is grafted on the surface of the metal material through Na-O-Si chemical bond:

[0012]

[0013] Preferably, the substrate is at least one of sodium element and sodium alloy.

[0014] Preferably, the chemical formula of the sodium alloy is Na x M y M includes but is not limited to at least one of lithium, potassium, calcium, magnesium, titanium, zirconium, nickel, tin, phosphorus, iron, copper, manganese, silicon, bismuth, germanium, cobalt, antimony, lead, molybdenum, indium, zinc, niobium, scandium, vanadium, technetium, ruthenium, rhodium, palladium, cadmium, tungsten; x = 0.65-0.95, y = 0.05-0.35.

[0015] Further preferably, the substrate includes but is not limited to a composite material formed by at least one of sodium element and sodium alloy combined with a porous framework or a supporting framework through physical and / or chemical methods.

[0016] The porous framework includes, but is not limited to, foamed copper, foamed nickel, copper mesh, nickel mesh, carbon cloth, carbon paper, powder metallurgy porous copper, powder metallurgy porous nickel, porous stainless steel, porous polymer fiber, porous polymer conductive material such as aramid mesh, polyester mesh, acrylic mesh, nylon mesh, polyimide mesh, polypropylene mesh, polytetrafluoroethylene mesh, polyvinylidene fluoride mesh, etc.

[0017] The support framework includes, but is not limited to, aluminum, copper, carbon cloth, conductive polymer, etc. The physical or chemical method includes, but is not limited to, rolling, stamping, extrusion, vapor deposition, etc.

[0018] Further preferably, the thickness of the substrate is 10-100 mu m, and the thickness of the silane modification layer is 20-300 nm.

[0019] The second object of the present application is to provide a preparation method of a silane coupling agent modified metal sodium foil, comprising the following steps: dissolving a silane coupling agent in a Class I base oil or an ester oil or a mineral oil at a volume of 1-5 mL / cm 2 Coating the contact surface of the substrate and the processing equipment, and obtaining the silane coupling agent modified metal sodium foil through mechanical processing.

[0020] The beneficial effects of the above technical solution are: the specific surface area of the substrate increases continuously during mechanical processing, and the surface of the substrate needs to be in contact with the silane coupling agent solution to form a complete modification layer covering the surface of the substrate.

[0021] Preferably, the water content in the substrate processing environment is less than 0.5 ppm, and the oxygen content is less than 30 ppm.

[0022] The beneficial effects of the above technical solution are: in order to ensure the stability and safety of the metal sodium substrate, it is usually necessary to operate in an inert atmosphere to prevent the metal sodium substrate from reacting seriously with oxygen and moisture.

[0023] Preferably, the mass fraction of the silane coupling agent in the Class I base oil, ester oil or mineral oil is 5%-30%, preferably 10%-20%.

[0024] Further preferably, the mineral oil is CAS:8020-83-5.

[0025] The beneficial effects of the above technical solution are: by controlling the mass fraction of the silane coupling agent, the thickness and uniformity of the modification layer on the surface of the substrate are adjusted.

[0026] Preferably, the mechanical processing is at least one selected from rolling, stamping, and extrusion processes, wherein the single deformation amount of the thickness of the substrate during mechanical processing is greater than or equal to 5% and less than 100%, preferably 50%.

[0027] The beneficial effects of the above technical solution are that: when the metal sodium substrate is rolled, stamped and extruded, the single deformation amount should not be too large, so as to avoid causing internal stress concentration of the metal, uneven deformation and crack generation. Meanwhile, the temperature of the metal sodium substrate can be controlled, the plasticity of the material can be improved and the equipment overload can be avoided.

[0028] The third object of the present application is to provide the application of the silane coupling agent modified metal sodium foil, in particular, the silane coupling agent modified metal sodium foil is used as a negative electrode in an electrochemical energy storage device.

[0029] Further, the electrochemical energy storage device includes but is not limited to a sodium metal battery, a sodium-sulfur battery, a sodium-air battery and the like.

[0030] Through the above technical solution, the beneficial effects of the present application are as follows:

[0031] (1) The silane coupling agent can form a silane modified layer with a strong cross-linked network structure on the surface of the sodium metal, improve the substrate interface stability, reduce the consumption of electrolyte and inhibit the generation of sodium dendrites.

[0032] (2) The sodium metal electrode material can be directly thinned in the in-situ reaction process by applying a load, so that the thickness of the prepared sodium metal electrode material can reach 10-100 μm, and the modification and processing integration can be realized.

[0033] (3) Compared with the traditional commercially available thick sodium sheet (450 μm), the silane coupling agent modified metal sodium foil of the present application can realize the preparation of 10-100 μm thickness, so as to improve the energy density of the battery. BRIEF DESCRIPTION OF DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are only embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of the provided drawings.

[0035] Figure 1 The SEM images of the composite electrode surfaces prepared by the comparative example, example 1 and example 2 of the present application are as follows: (a) is the surface of the sodium metal of the comparative example; (b) is the surface of the composite electrode prepared by example 1; and (c) is the surface of the composite electrode prepared by example 2. Figure 1

[0036] Figure 2 ​Cross-sectional SEM images of the composite electrodes made for the inventive comparative example, Example 2, Example 3, Example 4, Example 5, and Example 6: (a) is a cross-section of sodium metal of 76 μιη thickness for the comparative example; (b) is a cross-section of silane coupling agent modified sodium metal composite electrode of 76 μιη thickness made for Example 2; (c) is a cross-section of silane coupling agent modified sodium metal composite electrode of 60 μιη thickness made for Example 3; (d) is a cross-section of silane coupling agent modified sodium metal composite electrode of 25 μιη thickness made for Example 4; (e) is a cross-section of silane coupling agent modified sodium metal composite electrode of 20 μιη thickness made for Example 5; (f) is a cross-section of silane coupling agent modified sodium metal composite electrode of 14 μιη thickness made for Example 6.

[0037] Figure 3 Elemental distribution maps of the surface SEM-EDS mapping of the composite electrode made for Example 2 of the present invention: (a) is a surface SEM image of the silane coupling agent modified sodium metal composite electrode; (b) is a Na elemental distribution map; (c) is a C elemental distribution map; (d) is an O elemental distribution map; (e) is a Si elemental distribution map.

[0038] Figure 4 Elemental distribution maps of the cross-sectional SEM-EDS mapping of the composite electrode made for Example 3 of the present invention: (a) is a cross-sectional SEM image of the silane coupling agent modified sodium metal composite electrode; (b) is a Na elemental distribution map; (c) is a C elemental distribution map; (d) is an O elemental distribution map; (e) is a Si elemental distribution map.

[0039] Figure 5 XPS plots of the composite electrode material prepared in Example 2; (a) C 1s; (b) O 1s; (c) Si 2p.

[0040] Figure 6 Nanoindentation test results plots of the composite electrode materials prepared for the inventive comparative example and Example 2 (a) is the surface Young's modulus of the composite electrode materials prepared for the inventive comparative example and Example 2; (b) is the surface hardness of the composite electrode materials prepared for the inventive comparative example and Example 2.

[0041] Figure 7 Symmetric cycling performance plots of the composite electrode materials prepared for the inventive comparative example and Example 2 tested at 1 mA / cm 2 , 1 mAh / cm 2 .

[0042] Figure 8 Symmetric rate capability plots of the composite electrode materials prepared for the inventive comparative example and Example 2 tested at 0.25, 0.5, 1, 1.5, 2, 2.5, 3 mA / cm 2 & 0.5 mAh / cm 2 .

[0043] Figure 9 Symmetrical batteries assembled with the composite electrode material of the present application and comparative example 2 were tested at 1 mA / cm 2 & 1 mAh / cm 2 Surface morphology after 50 cycles under test conditions: (a) is the SEM image of sodium ion deposition surface morphology on the electrode material of the comparative example, (b) is the SEM image of sodium ion deposition surface morphology on the surface of the composite electrode material of example 2;

[0044] Figure 10 Electrochemical performance chart of the battery assembled with the composite electrode material prepared by the present application and comparative example 2 and sodium vanadium phosphate at 1C rate condition: (a) cycle performance chart; (b) coulombic efficiency chart.

[0045] Figure 11 Cycle performance chart of the full battery assembled with the composite electrode material prepared by example 4 of the present application and sodium vanadium phosphate tested at 1C rate condition, the positive active material surface density is 7.2 mg / cm 2 .

[0046] Figure 12 Cycle performance chart of the full battery assembled with the composite electrode material prepared by example 4 of the present application and sodium vanadium phosphate tested at 2C rate condition, the positive active material surface density is 6.0 mg / cm 2 .

[0047] Figure 13 Element distribution chart of the composite electrode surface prepared by example 7 of the present application: (a) SEM image of the surface of the silane coupling agent modified sodium metal composite electrode with 500 times magnification; (b) SEM image of the surface of the silane coupling agent modified sodium metal composite electrode with 2000 times magnification; (c) Na element distribution chart; (d) N element distribution chart; (e) Si element distribution chart.

[0048] Figure 14 Symmetrical cycle performance chart of the composite electrode material prepared by example 7 of the present application tested at 1 mA / cm 2 , 1 mAh / cm 2 .

[0049] Figure 15 Symmetrical cycle performance chart of the composite electrode material prepared by example 8 of the present application tested at 1 mA / cm 2 , 1 mAh / cm 2 . DETAILED DESCRIPTION

[0050] With reference to the drawings of the embodiments of the present application, the technical solutions in the embodiments of the present application will be described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0051] Example 1

[0052] (1) Preparation of the composite electrode material

[0053] Methyl triethoxysilane and mineral oil (CAS: 8020-83-5) were mixed in a mass ratio of 0.5:9.5, stirred at 45°C in air for 30 min to obtain a uniform solution. In an argon-filled glove box, the metal sodium block was peeled off the oxide skin and rolled into a metal sodium sheet of 300-400 μm. The prepared mixed solution was uniformly coated on the surface of the roller and the substrate of the rolling machine at a rate of 1-5 mL / cm 2 The metal sodium sheet was rolled by adjusting the roller gap to 300 μm at room temperature. Then, the roller gap was gradually reduced to 250, 200, 150 μm, and finally to 100 μm. After rolling, the silane coupling agent modified metal sodium foil composite sheet (Na@MTES) was obtained. After air blowing, the composite sheet was cut into a circular electrode sheet with a diameter of 16 mm.

[0054] The SEM image of the surface thereof is shown in Figure 1 (b), and the silane modification layer formed on the surface of the metal sodium is unevenly distributed.

[0055] Example 2

[0056] (1) Preparation of the composite electrode material

[0057] This example was a parallel test similar to Example 1, except that methyl triethoxysilane and mineral oil (CAS: 8020-83-5) were mixed in a mass ratio of 1:9, stirred at 45°C in air for 30 min to obtain a uniform solution. Then, the sodium sheet was gradually rolled in an argon-filled glove box to obtain a silane coupling agent modified metal sodium foil (Na@MTES). After air blowing, the actual thickness of the silane coupling agent modified metal sodium foil composite electrode sheet was about 76 μm. The surface film formation state is shown in Figure 3 (a), and the surface composition is shown in Figure 3 (b-e) and Figure 5 The mechanical property test of the obtained silane coupling agent modified metal sodium foil composite electrode sheet was performed, and the test results are shown in Figure 6 Compared with the comparative example, the surface Young's modulus and surface hardness of the silane coupling agent modified metal sodium foil composite electrode were improved.

[0058] (2) Battery assembly

[0059] In an argon-filled glove box, the silane coupling agent modified sodium foil composite electrode was assembled into symmetric button cells (Na@MTES||Na@MTES) with Celgard 2500 as the separator and 1.0 M NaPF6 / DIGLYME as the electrolyte. The composite electrode was subjected to constant current charge-discharge test. 1 mA / cm 2 & 1 mAh / cm 2 Symmetric cell cycle test was carried out under the test conditions, and the test results are shown in Figure 7 , which can achieve stable cycle for more than 700 h. In addition, 0.25, 0.5, 1, 1.5, 2, 2.5, 3 mA / cm 2 & 0.5 mAh / cm 2 Symmetric cell rate performance test was carried out under the test conditions, and the test results are shown in Figure 8 , compared with the symmetric cell of the comparative example, the symmetric cell assembled by the silane coupling agent modified sodium foil composite electrode has higher overpotential. Figure 9 , 1 mA / cm 2 & 1 mAh / cm 2 The SEM image of the electrode surface after 50 cycles under the test conditions shows that the silane modification layer can effectively inhibit the dendrite growth of sodium.

[0060] The composite electrode with a diameter of 16 mm was assembled into a half cell with a sodium vanadium phosphate positive electrode, Celgard 2500 was used as the separator, and 1.0 M NaPF6 / DIGLYME was used as the electrolyte. The battery cycle test was carried out under the test conditions of 1C, Figure 10 , compared with the comparative example, the silane coupling agent modified sodium foil composite electrode showed more excellent cycle stability and coulombic efficiency.

[0061] Example 3

[0062] (1) Preparation of composite electrode material

[0063] This example is a parallel test similar to Example 2, the difference is that the roll gap is gradually reduced to 250, 200, 150, 100 μm for rolling, and the roll gap is reduced to 80 μm after rolling. The silane coupling agent modified sodium foil composite sheet (Na@MTES) is obtained, and the composite sheet is cut into a circular electrode with a diameter of 16 mm after air blowing.

[0064] The SEM image of its cross section is shown in Figure 2 (c), the actual thickness of the silane coupling agent modified sodium foil composite electrode is about 60 μm. The film state of its cross section and the surface composition are as followsFigure 4 as shown.

[0065] Example 4

[0066] (1) Preparation of composite electrode material

[0067] This example is a parallel test similar to Example 2, except that the rolling gap is gradually reduced to 250, 200, 150, 100, 80, and 40 μm, and the silane coupling agent modified metal sodium foil composite sheet (Na@MTES) is obtained after rolling. After air blowing, the composite sheet is cut into a circular electrode with a diameter of 16 mm.

[0068] The SEM image of the cross section is shown in Figure 2 (d), and the actual thickness of the silane coupling agent modified metal sodium foil composite electrode after rolling is about 25 μm.

[0069] (2) Battery assembly

[0070] In an argon-filled glove box, the composite electrode with a diameter of 16 mm is assembled with a vanadium sodium phosphate positive electrode to form a half-cell, glass fiber is used as a separator, and 1.0 M NaClO4 / DEC:EC (volume ratio = 1:1) + 5% FEC is used as an electrolyte. Full cell cycle test is carried out under 1C and 2C test conditions. As shown in Figure 11 , under the test conditions of N / P = 3.6 and 1C rate, the silane coupling agent modified metal sodium foil composite electrode can be stably cycled for more than 80 times. As shown in Figure 12 , under the test conditions of N / P = 4.28 and 2C rate, the silane coupling agent modified metal sodium foil composite electrode can be stably cycled for more than 120 times.

[0071] Example 5

[0072] (1) Preparation of composite electrode material

[0073] This example is a parallel test similar to Example 2, except that the rolling gap is gradually reduced to 250, 200, 150, 100, 80, and 40 μm, and the silane coupling agent modified metal sodium foil composite sheet (Na@MTES) is obtained after rolling. After air blowing, the composite sheet is cut into a circular electrode with a diameter of 16 mm.

[0074] The SEM image of the cross section is shown in Figure 2 (e), and the actual thickness of the silane coupling agent modified metal sodium foil composite electrode after rolling is about 20 μm.

[0075] Example 6

[0076] (1) Preparation of composite electrode material

[0077] The present example and example 2 were tested in parallel, the difference being that the inter-roller gap was gradually reduced to 250, 200, 150, 100, 80, 40, until the gap was reduced to 30 pm, and the silane coupling agent modified metal sodium foil composite sheet (Na@MTES) was obtained after rolling. After air blowing, the composite sheet was cut into a circular pole piece with a diameter of 16 mm.

[0078] The SEM image of the cross section thereof is shown in Figure 2 (f), and the actual thickness of the silane coupling agent modified metal sodium foil composite pole piece obtained after rolling was about 14 pm.

[0079] Example 7

[0080] (1) Preparation of composite electrode material

[0081] The present example and example 2 were tested in parallel, the difference being that 3-aminopropyltriethoxysilane and mineral oil (CAS: 8020-83-5) were prepared into a mixed solution at a mass ratio of 1:9, and then the silane coupling agent modified metal sodium foil composite electrode (Na@APTES) was prepared.

[0082] The surface SEM and EDS spectrum thereof are shown in Figure 13 .

[0083] (2) Battery assembly

[0084] In an argon-filled glove box, the silane coupling agent modified metal sodium foil composite pole piece was assembled into a button cell, Celgard 2500 was used as the separator, 1.0 M NaPF6 / DIGLYME was used as the electrolyte, and the composite pole piece was subjected to constant current charge and discharge test, 1 mA / cm 2 & 1 mAh / cm 2 Symmetric battery cycle test was carried out under the test conditions, and the test results are shown in Figure 14 , which can realize stable cycle for more than 900 h.

[0085] Example 8

[0086] (1) Preparation of composite electrode material

[0087] The present example and example 2 were tested in parallel, the difference being that 3-aminopropyltriethoxysilane and mineral oil (CAS: 8020-83-5) were prepared into a mixed solution at a mass ratio of 1:9, and then the silane coupling agent modified metal sodium foil composite electrode (Na@APTES) was prepared.

[0088] (2) Battery assembly

[0089] In an argon-filled glove box, silane coupling agent-modified sodium foil composite electrodes were assembled into coin cells. Celgard 2500 was used as the separator, and 1.0 M NaPF6 / DIGLYME was used as the electrolyte. Constant current charge-discharge tests were performed on the composite electrodes at 1 mA / cm². 2 &1mAh / cm 2 Symmetrical battery cycle tests were conducted under the test conditions, and the test results are as follows: Figure 15 As shown, it can achieve a stable cycle of more than 600 hours.

[0090] Comparative Example

[0091] (1) Preparation of electrode materials

[0092] Parallel experiments similar to those in Example 2 were conducted in the comparative example, except that an untreated single mineral oil (CAS: 8020-83-5) was used as the solvent to obtain a sodium metal electrode (Bare Na).

[0093] The SEM image of its surface is as follows. Figure 1 As shown in (a), its cross-section SEM image is as follows: Figure 2 (a) The actual thickness of the sodium foil electrode obtained after rolling is approximately 76 μm.

[0094] (2) Battery assembly

[0095] In an argon-filled glove box, sodium metal electrodes were assembled into coin cells, using Celgard 2500 as the separator and 1.0 M NaPF6 / DIGLYME as the electrolyte. Symmetrical cell cycle testing and rate performance testing were conducted under the same test conditions as in Example 2. The test results are as follows: Figure 7 and 8 At 1mA / cm 2 &1mAh / cm 2 Under these conditions, it can only cycle stably for 180 hours, after which a short circuit occurs. For example... Figure 9 As shown, 1mA / cm 2 &1mAh / cm 2 SEM images of the electrode surface after 50 cycles under test conditions show obvious sodium dendrite growth on the untreated sodium metal surface.

[0096] A half-cell was assembled using a 16mm diameter sodium metal electrode and a sodium vanadium phosphate positive electrode, with Celgard 2500 as the separator and 1M NaPF6 / DIGLYME as the electrolyte. Battery cycle tests were conducted under 1C conditions. Figure 10 As shown, the comparative example can only cycle stably for 60 times, and the Coulomb efficiency fluctuates greatly.

[0097] The foregoing description of the disclosed embodiments enables a person skilled in the art to make or use the application. Modifications of these embodiments will occur to persons of skill in the art, and that the appended claims are intended to cover all such modifications that do not depart from the true spirit and scope of the application. Therefore, the application is not limited to the embodiments shown but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A silane coupling agent modified sodium metal foil, characterized in that, Includes the matrix and the silane coupling agent modification layer; The substrate includes a metallic material with zero-valent sodium on its surface; The silane coupling agent modification layer is grafted onto the surface of the metal material via Na-O-Si chemical bonds; The metallic material includes at least one of elemental sodium and sodium alloys; The structural formula of the silane coupling agent molecule is as follows: ； Wherein, R is alkoxy, acyloxy, halogen or amine; X is alkyl, alkenyl, epoxy, aryl, fluoroalkyl, chloroalkyl, bromoalkyl, iodoalkyl, amino, diazo, azide, cyano, isocyano or mercapto; n and i are positive integers, n=1-3, i=1-1000000.

2. The silane coupling agent modified sodium metal foil according to claim 1, characterized in that, The matrix further includes: a porous skeleton or a support skeleton; The porous skeleton or support skeleton is combined with the metallic material by physical and / or chemical methods to form the matrix.

3. The silane coupling agent modified sodium metal foil according to claim 1, characterized in that, The thickness of the substrate is 10 μm-100 μm; The thickness of the silane coupling agent modified layer is 20-300 nm.

4. A method for preparing silane coupling agent modified sodium metal foil, characterized in that, include: The silane coupling agent is dissolved in ester oil or mineral oil and then coated onto the contact surface between the substrate and the processing equipment as described in claim 1. The silane coupling agent modified sodium foil as described in claim 1 is obtained by mechanical processing.

5. The method for preparing silane coupling agent modified sodium metal foil according to claim 4, characterized in that, The silane coupling agent has a mass fraction of 5%-30% in the ester oil or mineral oil.

6. The method for preparing silane coupling agent modified sodium metal foil according to claim 4, characterized in that, The mineral oil is a Group I base oil.

7. The method for preparing silane coupling agent modified sodium metal foil according to claim 4, characterized in that, The machining process is selected from at least one of rolling, stamping, and extrusion processes.

8. The method for preparing silane coupling agent modified sodium metal foil according to claim 7, characterized in that, The thickness of the substrate during machining is subject to a single deformation of 5% ≤ single deformation < 100%.

9. An application of a silane coupling agent modified sodium metal foil, characterized in that, The silane coupling agent modified sodium metal foil obtained by the preparation method of the silane coupling agent modified sodium metal foil according to any one of claims 1-3 or any one of claims 4-8 is used as the negative electrode in an electrochemical energy storage device.

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