MOF derivative modified sodium-philic current collector and preparation method and application thereof

Abstract

The invention provides a preparation method of an MOF derivative modified sodium-philic current collector, which comprises the following steps: respectively stirring a metal salt or a metal oxide and an organic ligand in deionized water or an organic solvent to obtain two mixed solutions, mixing the two mixed solutions to obtain a new mixed solution, heating the new mixed solution, cooling the new mixed solution to room temperature, washing, centrifuging and drying to obtain a precursor material; heating the precursor material in inert gas, keeping constant temperature, and carbonizing to obtain M (at) C; mixing the M (at) C, a conductive agent, a binder and a dispersing agent in proportion, and then mixing with a solvent to form slurry; coating the slurry on a current collector base material, and drying to obtain M (at) C containing a sodium-philic metal central atom; the invention also provides the MOF-derived modified sodium-philic current collector prepared by the method and a negative-electrode-free sodium metal battery comprising the MOF-derived modified sodium-philic current collector. The M and C can reduce sodium deposition nucleation overpotential, inhibit sodium dendrites and volume expansion caused by sodium deposition, and promote formation of a uniform and compact sodium deposition layer.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium metal batteries without a negative electrode, and particularly to a MOF-derived modified sodiumophilic current collector and a preparation method and application thereof. Background Art

[0002] Due to numerous advantages such as abundant sodium reserves, wide temperature range, low cost, and high safety, sodium-ion batteries have become one of the potential alternatives to lithium-ion batteries in the post-lithium era.

[0003] However, the development of sodium-ion batteries still faces great challenges. Currently, the most ideal negative electrode material in sodium storage materials, hard carbon, has a low carbon production rate, high cost, and low degree of large-scale production. Moreover, due to the influence of the positive electrode material of sodium-ion batteries, the current energy density of sodium-ion batteries (100 - 130 Wh / kg) is lower than that of lithium-ion batteries (150 - 200 Wh / kg). The design of a new type of sodium metal battery without a negative electrode not only improves the energy density of the sodium metal battery but also avoids the problems of difficult manufacturing and transportation of the sodium metal negative electrode. There are mainly two problems with existing sodium metal batteries without a negative electrode: one is that traditional flat current collectors such as copper foils have a low binding energy with sodium metal. Coupled with the high chemical reactivity and nucleation overpotential of sodium metal, uneven deposition inevitably occurs on the negative electrode current collector after battery charging, resulting in a "tip effect" and the formation of sodium dendrites and inactive sodium; the other is that due to the limited amount of active sodium in the battery, the continuous reconstruction of the SEI film is caused by the volume change of the deposited sodium metal, consuming a large amount of active sodium and exacerbating the battery capacity decay.

[0004] To solve the above problems, the present invention proposes a MOF-derived modified sodiumophilic current collector and a preparation method and application thereof. Summary of the Invention

[0005] One of the purposes of the present application is to provide a MOF-derived modified sodiumophilic current collector and a preparation method and application thereof to solve the problems that due to traditional flat current collectors such as copper foils having a low binding energy with sodium metal, and the high chemical reactivity and nucleation overpotential of sodium metal, uneven deposition inevitably occurs on the negative electrode current collector after battery charging, resulting in a "tip effect" and the formation of sodium dendrites and inactive sodium; and due to the limited amount of active sodium in the battery, the continuous reconstruction of the SEI film is caused by the volume change of the deposited sodium metal, consuming a large amount of active sodium and exacerbating the battery capacity decay.

[0006] To achieve the above purpose, the present application adopts the following technical solutions:

[0007] A preparation method of a MOF-derived modified sodiumophilic current collector, which comprises the following steps:

[0008] Step S1, at room temperature, dissolve one or more of sodiumophilic metal salts or sodiumophilic metal oxides and one or more of the regulators in deionized water or an organic solvent and stir ultrasonically to obtain solution A;

[0009] Step S2, mix one or more of the organic ligands and dissolve them in deionized water or an organic solvent and stir ultrasonically to obtain solution B;

[0010] Step S3, slowly add solution B to solution A and continuously stir ultrasonically to form a uniform mixed solution C;

[0011] Step S4, heat the mixed solution C, wash, centrifuge and dry it after cooling to room temperature to obtain the MOF precursor material;

[0012] Step S5, heat the collected MOF precursor material from room temperature to 200 - 1500 °C at a rate of 2 - 5 °C / min under an inert gas atmosphere, and then keep it at a constant temperature for 1 - 5 h for carbonization to obtain the MOF-derived three-dimensional porous carbon;

[0013] Step S6, mix 70 - 98 wt% of the MOF-derived three-dimensional porous carbon, 0 - 20 wt% of the conductive agent, 0 - 20 wt% of the binder, and 0 - 20 wt% of the dispersant in proportion, and then mix with a solvent to form a slurry;

[0014] Step S7, by means of the coating method, uniformly coat the slurry on both sides of the current collector substrate to form a modified sodiumophilic coating, and obtain the MOF-derived modified sodiumophilic current collector after drying.

[0015] Further, the regulator used in step S1 is polyvinylpyrrolidone.

[0016] Further, the sodiumophilic metal salts used in step S1 include one or more arbitrary combinations of sodiumophilic metal salts of copper, bismuth, zinc, aluminum, tin, antimony, indium, gold, silver, platinum, nickel, chromium, and manganese, and the sodiumophilic metal oxides include one or more arbitrary combinations of sodiumophilic metal oxides of copper, bismuth, zinc, aluminum, tin, antimony, indium, gold, silver, platinum, nickel, chromium, and manganese.

[0017] Further, the organic solvents used in step S1 and step S2 include one or more arbitrary combinations of ethanol, methanol, isopropanol, dimethylformamide, dichloromethane, and dimethyl sulfoxide.

[0018] Further, the organic ligands used in the step S2 include one or more arbitrary combinations of 1,3,5-benzenetricarboxylic acid, 3,5-pyridinedicarboxylic acid, phthalic acid (H2BDC), 3,3,5,5-biphenyltetracarboxylic acid, 2-methylimidazole, 2,5-dihydroxyterephthalic acid, pyrrole, 2-aminoterephthalic acid, 2,5-dicarboxyl, 1,3,5-tris(4-carboxyphenyl)benzene.

[0019] Further, in the step S4, the mixed solution C is heated to 0-400 °C at a rate of 1-5 °C / min, kept at a constant temperature for 6-72 h, and then cooled at a rate of 1-5 °C / min. The drying temperature is 20-95 °C.

[0020] Further, the heating temperature for the MOF precursor material collected in the step S5 is 300-1000 °C.

[0021] Further, the solvents used in the step S5 include one or more arbitrary combinations of N-methylpyrrolidone, ethanol, acetone, N,N-dimethylformamide, water, and ethylene glycol.

[0022] A MOF-derived modified sodiumophilic current collector is prepared by using the preparation method of the MOF-derived modified sodiumophilic current collector described in any one of the above.

[0023] A sodium metal battery without a negative electrode includes the above-mentioned MOF-derived modified sodiumophilic current collector, a separator, an electrolyte, and a positive electrode sheet.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] First, by constructing a modified sodiumophilic coating with sodiumophilic characteristics on the surface of the negative electrode current collector to promote sodium ion nucleation, allowing more and more uniform sodium deposition. The preparation method is simple in operation, rich in optional raw materials, and easy to achieve the preparation conditions, suitable for popularization.

[0026] Second, using a three-dimensional porous carbon modified current collector derived from a MOF metal-organic framework containing a sodiumophilic metal center atom. Due to its large specific surface area, three-dimensional porous framework structure, and sodiumophilic metal center atom, it can reduce the sodium deposition nucleation overpotential, provide abundant nucleation sites, and inhibit sodium dendrites, promoting the formation of a uniform and dense sodium deposition layer; at the same time, it can also inhibit the volume expansion caused during sodium deposition, thus preventing the continuous reconstruction of the SEI film, avoiding the consumption of a large amount of active sodium, and maintaining the service life of the battery. Description of the Drawings

[0027] To more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the accompanying drawings required for the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can also be obtained based on these drawings.

[0028] Figure 1 It is a schematic flow chart of the preparation method of the MOF-derived modified sodiumophilic current collector provided by the present invention;

[0029] Figure 2 It is a schematic structural diagram of the MOF-derived modified sodiumophilic current collector provided by the present invention;

[0030] Figure 3 It is a schematic structural diagram of the non-aqueous sodium metal battery provided by the present invention;

[0031] Figure 4 It is a charge-discharge curve diagram of the 18650 model non-aqueous sodium metal battery provided by the present invention at 0.5C / 0.5C.

[0032] Description of the drawings: 10. MOF-derived modified sodiumophilic current collector; 101. Current collector substrate; 102. Modified sodiumophilic coating; 20. Separator; 30. Electrolyte; 40. Positive electrode sheet. Detailed embodiments

[0033] In the following, only some exemplary embodiments are briefly described. As those skilled in the art can recognize, the described embodiments can be modified in various different ways without departing from the spirit or scope of the present invention. Therefore, the drawings and the description are considered to be exemplary in nature rather than restrictive.

[0034] The terms "including" and "having" and any variations thereof in the present application are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the listed steps or units, but optionally further includes steps or units not listed, or optionally further includes other steps or units inherent to these processes, methods, products, or devices.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs. The terms used in the description of the present application are only for describing specific embodiments and are not intended to limit this application. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0036] Reference to "embodiment" in this application means that the specific features, structures, or characteristics described in connection with the embodiment can be included in at least one embodiment of this application. The phrase appears in various places in the specification and does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0037] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that the following embodiments are only exemplary explanations and descriptions of the above technical solutions, and only a part of the embodiments, not all embodiments, and should not be regarded as limiting the scope of the present invention.

[0038] Figure 1 It is a schematic flow chart of a preparation method of a MOF-derived modified sodiumophilic current collector provided by the present invention. This preparation method promotes sodium ion nucleation by constructing a modified sodiumophilic coating 102 with sodiumophilic characteristics on the surface of the negative electrode current collector substrate 101, thereby allowing more and more uniform sodium deposition. Among them, the MOF-derived three-dimensional porous carbon (M@C, where M is a sodiumophilic metal center atom) generated in step S5 is a three-dimensional porous carbon coating material with a topological structure derived from a MOF metal-organic framework containing a sodiumophilic metal center atom as a precursor. This M@C has excellent surface area, significant porosity, and electrochemical performance, can provide space for metal sodium deposition, slow down the large volume change brought to the battery cell during the repeated deposition / dissolution process of metal sodium, thereby preventing the continuous reconstruction of the SEI film, avoiding the consumption of a large amount of active sodium, and maintaining the service life of the battery; and uses the sodiumophilic metal center atom of M@C to reduce the sodium deposition nucleation overpotential, provide abundant nucleation sites, inhibit sodium dendrites, and promote the formation of a uniform and dense sodium deposition layer.

[0039] Specifically, the current collector substrate 101 used in this MOF-derived modified sodiumophilic current collector preparation method includes one or more of stainless steel foil, aluminum foil, carbon-coated aluminum foil, porous aluminum foil, copper foil, carbon-coated copper foil, porous copper foil, copper foam, carbon cloth, carbon paper, nickel foil, porous nickel, nickel foam, titanium mesh, titanium foil in any combination.

[0040] The conductive agent includes, but is not limited to, one or more of acetylene black, Ketjen black, graphite KS-6, conductive carbon black, carbon fiber, carbon nanotube, artificial graphite, natural graphite, etc. in any combination.

[0041] The binder includes, but is not limited to, one or any combination of polyvinyl fluoride, polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR) emulsion, carboxymethyl cellulose (CMC), polyacrylic acid (PAA), polyacrylonitrile (PAN), polyacrylate, polyvinyl alcohol (PVA), polyvinyl butyral, polyurethane, fluorinated rubber, polyamide (PAI), and polyethyleneimine (PEI).

[0042] The sodiumophilic metal salts include, but are not limited to, one or any combination of copper nitrate (Cu(NO3)2·3H2O), bismuth nitrate (Bi(NO3)3·5H2O), bismuth triiodide (BiI3), bismuth chlorate (Bi(ClO3)3), zinc nitrate (Zn(NO3)2·6H2O), zinc sulfate (ZnSO4·7H2O), zinc chloride (ZnCl2), zinc carbonate (ZnCO3), aluminum chloride (AlCl3), aluminum sulfate (Al2(SO4)3), aluminum nitrate (Al(NO3)3), aluminum silicate (Al2(SiO3)3), aluminum sulfide (Al2S3), stannous sulfate (SnSO4), anhydrous stannous chloride (SnCl2), stannous acetate (C4H6O4Sn), antimony trichloride (SbCl3), indium nitrate (In(NO3)3·6H2O), and one or more other metal salts of indium (In), gold (Au), silver (Ag), platinum (Pt), nickel (Ni), chromium (Cr), and manganese (Mn) that have an affinity for sodium ions.

[0043] The sodiumophilic metal oxides include, but are not limited to, one or any combination of copper oxide (CuO), bismuth oxide (Bi2O3), zinc oxide (ZnO), aluminum oxide (Al2O3), antimony oxide (Sb2O3, Sb2O5), tin oxide (SnO), and one or more other metal oxides of indium (In), gold (Au), silver (Ag), platinum (Pt), nickel (Ni), chromium (Cr), and manganese (Mn) that have an affinity for sodium ions.

[0044] The organic ligands include, but are not limited to, one or any combination of 1,3,5-benzenetricarboxylic acid, 3,5-pyridinedicarboxylic acid, phthalic acid (H2BDC), 3,3,5,5-biphenyltetracarboxylic acid, 2-methylimidazole, 2,5-dihydroxyterephthalic acid, pyrrole, 2-aminoterephthalic acid, 2,5-dicarboxyl, and 1,3,5-tris(4-carboxyphenyl)benzene.

[0045] The solvents include one or any combination of N-methylpyrrolidone, ethanol, acetone, N,N-dimethylformamide (DMF), and ethylene glycol.

[0046] The preparation method of the MOF-derived modified sodiumophilic current collector is further described below in conjunction with specific embodiments, but the present invention is not limited to the following embodiments.

[0047] Example 1: A copper metal salt is used to prepare the MOF precursor material. Specifically:

[0048] Step S1: At room temperature, 5 - 10 mmol of copper nitrate (Cu(NO3)2·3H2O) is added to 10 - 50 mL of deionized water and stirred ultrasonically to obtain solution A.

[0049] Step S2: 2 - 5 mmol of 1,3,5-benzenetricarboxylic acid is dissolved in 10 - 50 mL of absolute ethanol and stirred ultrasonically to obtain solution B.

[0050] Step S3: Solution B is slowly added to solution A, and then 0.3 - 1 g of polyvinylpyrrolidone (PVP) is added and continuously stirred ultrasonically for 30 - 60 min until it is completely dissolved to form solution C.

[0051] Step S4: Solution C is transferred to a polytetrafluoroethylene stainless steel autoclave, heated to 100 - 200 °C at a rate of 2 - 5 °C / min, kept at a constant temperature for 8 - 24 h, washed with absolute ethanol after cooling to room temperature, centrifuged at a speed of 5000 - 8000 r / min, and then dried in an oven at 65 °C to obtain the Cu-MOF precursor material.

[0052] Step S5: The Cu-MOF precursor material collected in the previous step is heated to 200 - 600 °C at a rate of 2 - 5 °C / min in an inert gas (Ar gas) atmosphere, kept at a constant temperature for 2 - 4 h, and then carbonized to obtain the carbon-coated material Cu@C with a three-dimensional porous structure.

[0053] Step S6: 70 - 98 wt% of Cu@C, 0 - 20 wt% of conductive agent, 0 - 20 wt% of binder, and 0 - 20 wt% of dispersant are mixed in proportion, and then mixed with a solvent (one or more of water, N-methylpyrrolidone, and ethanol) to form a slurry.

[0054] Step S7: By the coating method, the slurry is evenly coated on both sides of the current collector substrate 101 and dried at 50 - 80 °C to form the Cu@C modified sodiumophilic current collector.

[0055] Example 2: Based on step S4 of Example 1, a bimetallic MOF precursor material is prepared:

[0056] Step S1: Weigh silver nitrate (AgNO3) and the Cu-MOF precursor material in a mass ratio of 1:1. First, dissolve silver nitrate in a mixed solution of 10 - 50 mL of deionized water and 10 - 50 mL of absolute ethanol and ultrasonically dissolve it to obtain solution A.

[0057] Step S2: The Cu-MOF precursor material is added to solution A and stirred ultrasonically to obtain solution B.

[0058] Step S3: Transfer solution B into a polytetrafluoroethylene stainless steel reactor, heat it up to 100 - 200 °C at a rate of 2 - 5 °C / min, keep it at a constant temperature for 8 - 24 h, wash it with absolute ethanol after cooling to room temperature, centrifuge it at a speed of 5000 - 8000 r / min, and then dry it in an oven at 65 °C to obtain a bimetallic Ag / Cu-MOF precursor material;

[0059] Step S4: Heat the Ag / Cu-MOF precursor powder collected in the previous step to 200 - 600 °C at a rate of 2 - 5 °C / min in an inert gas (Ar gas) atmosphere, keep it at a constant temperature for 2 - 4 h and then carry out carbonization to obtain a carbon-coated material Ag / Cu@C with a three-dimensional porous structure;

[0060] Step S5: Mix 70 - 98 wt% of Ag / Cu@C, 0 - 20 wt% of conductive agent, 0 - 20 wt% of binder, and 0 - 20 wt% of dispersant in proportion, and then mix it with a solvent (one or more of water, N-methylpyrrolidone, ethanol) to form a slurry;

[0061] Step S6: By means of the coating method, uniformly coat the slurry on both sides of the current collector substrate 101, and form an Ag / Cu@C modified sodiumophilic current collector after drying at 50 - 80 °C.

[0062] Example 3 is different from Example 1 in that the metal salt for making the MOF precursor material is replaced with a bismuth metal salt, thereby obtaining a MOF-derived modified sodiumophilic current collector 10 with different sodiumophilic metal center atoms. Specifically:

[0063] Step S1: At room temperature, add 3 - 6 mmol of bismuth nitrate (Bi(NO3)3·5H2O) and 1.5 - 3 mmol of 3,5-pyridinedicarboxylic acid into 30 - 100 mL of deionized water and stir it ultrasonically to obtain solution A;

[0064] Step S2: Continuously stir solution A ultrasonically for 5 - 30 min, then transfer it into a polytetrafluoroethylene stainless steel reactor, heat it up to 100 - 300 °C at a rate of 2 - 5 °C / min, keep it at a constant temperature for 8 - 24 h, wash it with absolute ethanol after cooling to room temperature, centrifuge it at a speed of 5000 - 8000 r / min, and then dry it in an oven at 65 °C to obtain a Bi-MOF precursor material;

[0065] Step S3: Heat the Bi-MOF precursor material collected in the previous step to 600 - 900 °C at a rate of 2 - 5 °C / min in an inert gas (Ar gas) atmosphere, keep it at a constant temperature for 2 h and then carry out carbonization to obtain a three-dimensional porous carbon-coated material Bi@C with a tubular structure;

[0066] Step S4: Mix Bi@C with a mass percentage of 70 - 98 wt%, 0 - 20 wt% of conductive agent, 0 - 20 wt% of binder, and 0 - 20 wt% of dispersant in proportion, and then mix with a solvent (one or more of water, N-methylpyrrolidone, and ethanol) to form a slurry;

[0067] Step S5: By the coating method, uniformly coat the slurry on both sides of the current collector substrate 101, and dry it at 50 - 80 °C to form a Bi@C modified sodiumophilic current collector.

[0068] Example 4 is different from Example 3 in that the metal salt for making the Bi-MOF precursor material is replaced with another bismuth metal salt, thereby obtaining a MOF-derived modified sodiumophilic current collector 10 with a different structure. Specifically:

[0069] Step S1: Add 0.1 - 2 g of bismuth triiodide (BiI3) to 5 - 150 mL of N,N-dimethylformamide (DMF) at room temperature and stir ultrasonically to obtain solution A;

[0070] Step S2: Dissolve 0.2 - 4 g of 1,3,5-benzenetricarboxylic acid in 5 - 150 mL of absolute ethanol and stir ultrasonically to obtain solution B;

[0071] Step S3: Slowly add solution B to solution A and continuously stir ultrasonically for 5 - 30 min until it is completely dissolved to form solution C;

[0072] Step S4: Heat solution C to 100 - 200 °C at a rate of 2 - 5 °C / min, keep it at a constant temperature for 8 - 24 h, wash it with absolute ethanol after cooling to room temperature, centrifuge it at a speed of 5000 - 8000 r / min, and then dry it in an oven at 65 °C to obtain the Bi-MOF precursor material;

[0073] Step S5: Heat the Bi-MOF precursor material collected in the previous step to 400 - 600 °C at a rate of 2 - 5 °C / min in an inert gas (Ar gas) atmosphere, keep it at a constant temperature for 2 h, and then carry out carbonization to obtain a three-dimensional porous carbon-coated material Bi@C with a three-dimensional porous structure;

[0074] Step S6: Mix Bi@C with a mass percentage of 70 - 98 wt%, 0 - 20 wt% of conductive agent, 0 - 20 wt% of binder, and 0 - 20 wt% of dispersant in proportion, and then mix with a solvent (one or more of water, N-methylpyrrolidone, and ethanol) to form a slurry;

[0075] Step S7: By means of the coating method, the slurry is uniformly coated on both sides of the current collector substrate 101, and after drying at 50-80 °C, a Bi@C modified sodium-philic current collector is formed.

[0076] Example 5 is different from Example 3 in that the metal salt for making the MOF precursor material is replaced with a zinc metal salt, thereby obtaining a MOF-derived modified sodium-philic current collector with different sodium-philic metal center atoms. Specifically:

[0077] Step S1: At room temperature, 5-10 g of zinc nitrate (Zn(NO3)2·6H2O) is added to 100-300 mL of methanol and stirred ultrasonically to obtain solution A.

[0078] Step S2: 10-20 g of 2-methylimidazole is dissolved in 100-300 mL of methanol and stirred ultrasonically to obtain solution B.

[0079] Step S3: Solution A is slowly added to solution B, aged at room temperature for 12-48 h, washed with absolute ethanol, centrifuged at a speed of 5000-8000 r / min, and then dried in an oven at 65 °C to obtain the Zn-MOF precursor material.

[0080] Step S4: The Zn-MOF precursor material collected in the previous step is heated to 600-1200 °C at a rate of 2-5 °C / min in an inert gas (Ar gas) atmosphere, and then carbonized after holding at a constant temperature for 2-8 h to obtain a carbon-coated material Zn@C with a three-dimensional porous structure.

[0081] Step S5: 70-98 wt% of Zn@C, 0-20 wt% of conductive agent, 0-20 wt% of binder, and 0-20 wt% of dispersant are mixed in proportion, and then mixed with a solvent (one or more of water, N-methylpyrrolidone, and ethanol) to form a slurry.

[0082] Step S6: By means of the coating method, the slurry is uniformly coated on both sides of the current collector substrate 101, and after drying at 50-80 °C, a Zn@C modified sodium-philic current collector is formed.

[0083] Example 6 is different from Example 5 in that the metal salt for making the MOF precursor material is replaced with a mixture of iron metal salt and manganese metal salt, thereby obtaining a bimetallic MOF-derived modified sodium-philic current collector 10 with different sodium-philic metal center atoms. Specifically:

[0084] Step S1: At room temperature, ferric chloride (FeCl3·6H2O) and manganese chloride (MnCl2·4H2O) are added to 100-500 mL of N,N-dimethylformamide in a certain molar ratio and stirred ultrasonically to obtain solution A.

[0085] Step S2: Dissolve an appropriate amount of terephthalic acid in 100 - 500 mL of N,N - dimethylformamide and stir ultrasonically to obtain solution B.

[0086] Step S3: Slowly add solution B to solution A and continuously stir ultrasonically for 30 - 60 min until it is completely dissolved to form solution C.

[0087] Step S4: Transfer solution C to a polytetrafluoroethylene digestion tube, perform microwave extraction in a microwave workstation for 30 min, then wash with absolute ethanol, centrifuge at a speed of 5000 - 8000 r / min, and then dry in an oven at 65 °C to obtain the Fe / Mn - MOF precursor material.

[0088] Step S5: Heat the Fe / Mn - MOF precursor material collected in the previous step from room temperature to 200 - 600 °C at a rate of 2 - 5 °C / min in an inert gas (Ar gas) atmosphere, keep it at a constant temperature for 2 - 4 h, and then perform carbonization to obtain the carbon - coated material Fe / Mn@C with a three - dimensional porous structure.

[0089] Step S6: Mix 70 - 98 wt% of Fe / Mn@C, 0 - 20 wt% of conductive agent, 0 - 20 wt% of binder, and 0 - 20 wt% of dispersant in proportion, and then mix with a solvent (one or more of water, N - methylpyrrolidone, and ethanol) to form a slurry.

[0090] Step S7: By the coating method, uniformly coat the slurry on both sides of the current collector substrate 101, and dry it at 50 - 80 °C to form the Fe / Mn@C - modified sodium - philic current collector.

[0091] Example 7: Different from Example 6 in that the metal salt for making the MOF precursor material is replaced with another manganese metal salt, thereby obtaining a single - metal MOF - derived modified sodium - philic current collector 10 containing the same sodium - philic metal center atom. Specifically:

[0092] Step S1: At room temperature, add 1 - 5 g of manganese acetate (Mn(CH3COO)·4H2O) and 0.1 - 1 g of polyvinylpyrrolidone (PVP) to a mixed solution of ethanol and water with a mass ratio of 1:1 and stir ultrasonically to obtain solution A.

[0093] Step S2: Dissolve 2 - 10 g of 1,3,5 - benzenetricarboxylic acid in a mixed solution of ethanol and water with a mass ratio of 1:1 and stir ultrasonically to obtain solution B.

[0094] Step S3: Slowly add Solution B to Solution A, continuously stir with ultrasonic waves for 30 min, then age for 10 - 24 h, wash with absolute ethanol, centrifuge at a rotation speed of 5000 - 8000 r / min, and then dry in an oven at 65 °C to obtain the Mn-MOF precursor material;

[0095] Step S4: Heat the Mn-MOF precursor material collected in the previous step to 400 - 900 °C at a rate of 2 - 5 °C / min under an inert gas (Ar gas), then keep it at a constant temperature for 2 - 4 h and perform carbonization to obtain the carbon-coated material Mn@C with a three-dimensional porous structure;

[0096] Step S5: Mix 70 - 98 wt% of Mn@C, 0 - 20 wt% of conductive agent, 0 - 20 wt% of binder, and 0 - 20 wt% of dispersant in proportion, and then mix with a solvent (one or more of water, N-methylpyrrolidone, and ethanol) to form a slurry;

[0097] Step S6: By the coating method, uniformly coat the slurry on both sides of the current collector substrate 101, and dry at 50 - 80 °C to form the Mn@C-modified sodiumophilic current collector.

[0098] As can be seen from the above embodiments, three-dimensional porous carbon-coated materials with a variety of different sodiumophilic metal center atoms can all be used as MOF-derived three-dimensional porous carbon (M@C), and one kind of M@C can have not only a single sodiumophilic metal center atom but also multiple different sodiumophilic metal center atoms; it should be noted that when preparing M@C, according to the different metal salts or metal oxides selected, the selection and dosage of organic ligands, solvents, regulators, etc. are different, and there are also corresponding differences in subsequent time and temperature treatments; when the sodiumophilic metal center atom, organic ligand change, or the stirring method, heating temperature and time exceed the scope of this application, the corresponding material morphology will also change, which will also affect the final cycle life of the sodium metal battery without a negative electrode; the above method for preparing the MOF-derived modified sodiumophilic current collector is simple in operation, has rich optional raw materials, and easy-to-reach preparation conditions, and is suitable for popularization.

[0099] It should be noted that M@C can be divided into multiple types according to different sodiumophilic metal center atoms. When making the MOF-derived modified sodiumophilic current collector 10, within the optional range, the reagents and materials with relatively lower costs can be considered from the perspective of low cost, so as to achieve the purpose of reducing the preparation cost.

[0100] In addition, since the stirring speed of ultrasonic waves determines the generation and rupture rate of bubbles in the liquid, if the stirring speed is too low, sufficient bubbles may not be generated, resulting in poor stirring effect; conversely, if the stirring speed is too high, it may cause overheating of the equipment or other mechanical problems. Therefore, in all the above embodiments, the optimal stirring speed of ultrasonic stirring is 1000 - 5000 r / min.

[0101] Figure 2 FIG. is a schematic structural diagram of the MOF-derived modified sodiumophilic current collector provided by the present invention. The MOF-derived modified sodiumophilic current collector 10 is prepared by using any one of the above-mentioned MOF-derived modified sodiumophilic current collector preparation methods.

[0102] Since it is necessary to control the occupied space of the modified sodiumophilic coating 102 during application and at the same time ensure the functionality of the modified sodiumophilic coating 102, the thickness of the modified sodiumophilic coating 102 is 1 - 25 μm. Preferably, the thickness of the modified sodiumophilic coating 102 is optimally between 5 - 15 μm.

[0103] Figure 3 FIG. is a schematic structural diagram of the sodium metal battery without a negative electrode provided by the present invention. The sodium metal battery without a negative electrode includes the above-mentioned MOF-derived modified sodiumophilic current collector 10, a separator 20, an electrolyte 30, and a positive electrode sheet 40.

[0104] Preferably, the models of the sodium metal battery without a negative electrode include but are not limited to 14500, 18500, 18650, 21700, 26650, 32140, 4680, 4695, 46120.

[0105] Figure 4 FIG. is the charge-discharge curve of the 18650 model sodium metal battery without a negative electrode at 0.5C / 0.5C. It can be seen from the figure that compared with the traditional 18650 model sodium ion battery, the sodium metal battery without a negative electrode provided with the MOF-derived modified sodiumophilic current collector has a higher discharge capacity.

[0106] The above-mentioned specific embodiments have further elaborated on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above-mentioned are only specific embodiments of the present invention and are not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of a MOF-derived modified sodiumophilic current collector, characterized in that, It includes the following steps: Step S1, at room temperature, dissolve one or more of sodiumophilic metal salts or sodiumophilic metal oxides and one or more of the regulators in deionized water or an organic solvent and stir ultrasonically to obtain solution A; Step S2, dissolve one or more of the organic ligands after mixing in deionized water or an organic solvent and stir ultrasonically to obtain solution B; Step S3, slowly add solution B to solution A and continuously stir ultrasonically to form a uniform mixed solution C; Step S4, heat the mixed solution C, wash, centrifuge and dry after cooling to room temperature to obtain the MOF precursor material; Step S5, heat the collected MOF precursor material to 200 - 1500 °C at a rate of 2 - 5 °C / min in an inert gas atmosphere, and then keep it at a constant temperature for 1 - 5 h for carbonization to obtain the MOF-derived three-dimensional porous carbon; Step S6, mix 70 - 98 wt% of the MOF-derived three-dimensional porous carbon, 0 - 20 wt% of the conductive agent, 0 - 20 wt% of the binder, and 0 - 20 wt% of the dispersant in proportion, and then mix with a solvent to form a slurry; Step S7, by the coating method, uniformly coat the slurry on both sides of the current collector substrate to form a modified sodiumophilic coating, and obtain the MOF-derived modified sodiumophilic current collector after drying treatment.

2. The preparation method of the MOF-derived modified sodiumophilic current collector according to claim 1, wherein: The regulator used in step S1 is polyvinylpyrrolidone.

3. The preparation method of the MOF-derived modified sodiumophilic current collector according to claim 1, characterized in that: The sodiumophilic metal salts used in step S1 include one or more arbitrary combinations of sodiumophilic metal salts of copper, bismuth, zinc, aluminum, tin, antimony, indium, gold, silver, platinum, nickel, chromium, manganese, and the sodiumophilic metal oxides include one or more arbitrary combinations of sodiumophilic metal oxides of copper, bismuth, zinc, aluminum, tin, antimony, indium, gold, silver, platinum, nickel, chromium, manganese.

4. The preparation method of the MOF-derived modified sodiumophilic current collector according to claim 1, characterized in that: The organic solvents used in steps S1 and S2 include one or more arbitrary combinations of ethanol, methanol, isopropanol, dimethylformamide, dichloromethane, dimethyl sulfoxide.

5. The preparation method of the MOF-derived modified sodiumophilic current collector according to claim 1, wherein: The organic ligands used in step S2 include one or more arbitrary combinations of 1,3,5-benzenetricarboxylic acid, 3,5-pyridinedicarboxylic acid, phthalic acid (H2BDC), 3,3,5,5-biphenyltetracarboxylic acid, 2-methylimidazole, 2,5-dihydroxyterephthalic acid, pyrrole, 2-aminoterephthalic acid, 2,5-dicarboxy, 1,3,5-tris(4-carboxyphenyl)benzene.

6. The method for preparing the MOF-derived modified sodiumophilic current collector according to claim 1, wherein: In step S4, the mixed solution C is heated to 0 - 400 °C at a rate of 1 - 5 °C / min, kept at a constant temperature for 6 - 72 h, and then cooled at a rate of 1 - 5 °C / min, and the drying temperature is 20 - 95 °C.

7. The preparation method of the MOF-derived modified sodiumophilic current collector according to claim 1, characterized in that: The heating temperature of the collected MOF precursor material in step S5 is 300 - 1000 °C.

8. The preparation method of the MOF-derived modified sodiumophilic current collector according to claim 1, characterized in that: The solvents used in step S5 include one or more arbitrary combinations of N-methylpyrrolidone, ethanol, acetone, N,N-dimethylformamide, water, and ethylene glycol.

9. A MOF-derived modified sodiumophilic current collector, characterized in that, Prepared by the method for preparing the MOF-derived modified sodiumophilic current collector according to any one of claims 1 - 8.

10. A sodium metal battery without a negative electrode, characterized in that, Includes the MOF-derived modified sodiumophilic current collector according to claim 9, a separator, an electrolyte, and a positive electrode sheet.

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