Composite metal sodium negative electrode material, preparation method thereof and sodium metal battery

Abstract

The application provides a composite metal sodium negative electrode material, a preparation method thereof and a sodium metal battery. The composite metal sodium negative electrode material comprises a porous organic film skeleton, an alloy type conductive sodium-philic layer and sodium metal filled in the pores inside the porous organic film skeleton. The application takes the porous organic film skeleton as a base material, constructs a three-dimensional flexible skeleton, and deposits the alloy type conductive sodium-philic layer on the porous organic film skeleton, so that the active sites for sodium ion deposition are increased and the rapid transmission of sodium ions is promoted.

Description

Technical Field

[0001] This invention belongs to the field of anode material technology, specifically relating to a composite sodium metal anode material, its preparation method, and a sodium metal battery. Background Technology

[0002] With the development of battery technology, lithium-ion batteries dominate the portable electronics market and are gradually expanding into large-scale energy storage applications. However, existing lithium resources are insufficient to meet the urgent need for establishing large-scale and high-energy-density energy storage systems. Therefore, sodium metal batteries, which have abundant sodium reserves, low cost, and similar electrochemical properties to lithium-ion batteries, have emerged.

[0003] However, sodium metal batteries suffer from problems such as low coulombic efficiency during cycling, which can easily lead to thermal runaway, poor cycle performance, and easy failure, greatly limiting their further application.

[0004] Currently, sodium metal anodes face challenges such as unlimited volume expansion, poor interfacial contact, high chemical reactivity, and sodium dendrite growth. Researchers are using three-dimensional materials as substrates for sodium deposition and stripping to address these issues. Three-dimensional materials can provide space for sodium ion deposition, mitigate unlimited volume expansion, reduce current density to suppress dendrite growth, and increase the number of sodium ion deposition sites, further promoting uniform nucleation. However, commonly used three-dimensional substrate materials, such as carbon materials and copper current collectors, suffer from poor continuous production capabilities, poor processability when used as anode materials in battery cell assembly, and complex manufacturing processes. Furthermore, they also exhibit significant energy density reduction, poor structural stability, and susceptibility to detachment, hindering the further application of sodium metal anodes.

[0005] Therefore, there is an urgent need in this field to develop a composite sodium metal anode material that not only has good structural stability and conductivity, but also has the advantages of easy processing and mass production. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a composite sodium metal anode material, its preparation method, and a sodium metal battery. The present invention uses a porous organic membrane framework as the substrate material to construct a three-dimensional flexible framework, and deposits an alloy-type conductive sodium-loving layer on the porous organic membrane framework, thereby increasing the active sites for sodium ion deposition and promoting rapid sodium ion transport.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a composite sodium metal anode material, the composite sodium metal anode material comprising a porous organic membrane framework, an alloy-type conductive sodium-loving layer, and sodium metal filling the pores of the porous organic membrane framework.

[0009] This invention utilizes a porous organic membrane as a three-dimensional flexible framework, providing a three-dimensional space for sodium metal deposition and suppressing volume expansion. Simultaneously, the porous organic membrane offers advantages such as low density, high processability, low cost, and suitability for mass production. The alloy-type conductive sodium-loving layer exhibits excellent ionic conductivity, sodium affinity, and corrosion resistance, increasing the active sites for sodium ion deposition. Furthermore, its strong adhesion to the porous organic membrane prevents detachment during cycling, thus avoiding sodium metal battery failure.

[0010] Preferably, the material of the porous organic membrane skeleton includes any one or a combination of at least two of the following: porous thermoplastic resin, porous thermosetting resin, porous thermoplastic resin doped with metal, porous thermosetting resin doped with metal, porous thermoplastic resin doped with carbon material, porous thermosetting resin doped with carbon material, conductive polymer, porous thermoplastic resin with surface coated with conductive polymer, or porous thermosetting resin with surface coated with conductive polymer.

[0011] In this invention, the doped carbon materials include, but are not limited to, carbon nanotubes, carbon fibers, graphene nanoparticles, or graphene oxide nanoparticles; the doped metals include, but are not limited to, Cu, Ag, Ni, or Au.

[0012] In this invention, the porous organic membrane framework has interconnected pores that extend throughout the entire porous organic membrane framework, which serves as a host for sodium deposition and dissolution, thereby reducing current density.

[0013] As a further preferred technical solution of the present invention, the material of the porous organic membrane framework includes any one or a combination of at least two of the following: porous thermoplastic resin doped with carbon materials, porous thermosetting resin doped with carbon materials, conductive polymer, porous thermoplastic resin with a surface coated with a conductive polymer, or porous thermosetting resin with a surface coated with a conductive polymer. It has good electrical conductivity, which is beneficial for improving electronic conductivity.

[0014] Preferably, the porous thermoplastic resin includes at least one of polyethylene, polypropylene, polytetrafluoroethylene, polyamide, polyethylene terephthalate, polycarbonate, polystyrene, styrene-acrylonitrile copolymer resin, polyoxymethylene resin, polyethersulfone resin, polyvinyl chloride, polyphenylene ether, cis-polyisoprene, styrene-butadiene rubber, polymethyl methacrylate, and glass fiber reinforced porous thermoplastic resins with the above porous thermoplastic resins as the base material.

[0015] As a further preferred embodiment of the present invention, the porous thermoplastic resin includes at least one of polyethylene, polypropylene, polytetrafluoroethylene, polyamide, and glass fiber reinforced porous thermoplastic resins with the above porous thermoplastic resins as the base material. It has the advantages of good flexibility and strong processability.

[0016] Preferably, the porous thermosetting resin includes at least one of phenolic resin, urea-formaldehyde resin, epoxy resin, polyurethane, thermosetting polyimide, polybutadiene resin, silicone resin or bismaleimide resin.

[0017] As a further preferred embodiment of the present invention, the porous thermosetting resin includes at least one of phenolic resin, polyurethane, thermosetting polyimide, or bismaleimide resin. It possesses advantages such as good strength and high-temperature stability.

[0018] Preferably, the material of the alloy-type conductive sodium-loving layer is at least one of crystalline nickel-phosphorus alloy, crystalline copper-phosphorus alloy, crystalline nickel-copper-phosphorus alloy, amorphous nickel-phosphorus alloy, amorphous copper-phosphorus alloy, or amorphous nickel-copper-phosphorus alloy.

[0019] In this invention, the alloy-type conductive sodium-loving layer serves to conduct electricity within the three-dimensional porous organic membrane framework network and enables uniform deposition of sodium ions. Compared to traditional sodium-loving layers, it not only has the advantage of strong lithiophilicity but also good electrical and ion-conducting properties, and is easy to process.

[0020] Preferably, the thickness of the alloy-type conductive sodium-loving layer is 1 nm to 20 μm, for example, it can be 1 nm, 5 nm, 8 nm, 10 nm, 15 nm, 30 nm, 50 nm, 100 nm, 200 nm, 500 nm, 1 μm, 2 μm, 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm, or 20 μm; the atomic mass ratio of phosphorus in the alloy-type conductive sodium-loving layer is 1% to 40%, for example, it can be 1%, 2%, 5%, 8%, 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, 32%, 35%, 38%, or 40%. For the sake of brevity, the values ​​within the above range will not be listed one by one.

[0021] As a further preferred technical solution of the present invention, the thickness of the alloy-type conductive sodium-loving layer is 10nm to 200nm, for example, it can be 10nm, 15nm, 18nm, 20nm, 22nm, 25nm, 30nm, 35nm, 45nm, 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, 120nm, 150nm, or 200nm; the atomic mass ratio of phosphorus in the alloy-type conductive sodium-loving layer is 3% to 15%, for example, it can be 3%, 4%, 5%, 8%, 10%, 12%, or 15%. For the sake of brevity, the values ​​within the above range will not be listed one by one.

[0022] In this invention, by adjusting the thickness of the alloy-type conductive sodium-affinity layer, the composite sodium metal anode exhibits both sodium affinity and conductivity. Too small a thickness results in weak sodium affinity and conductivity, while a larger thickness negatively impacts the battery's energy density. Similarly, by adjusting the atomic mass ratio of phosphorus in the alloy-type conductive sodium-affinity layer, a lower atomic mass ratio weakens the material's sodium affinity, while a higher ratio weakens its conductivity.

[0023] Preferably, the sodium metal filling the pores of the porous organic membrane skeleton accounts for 5% to 100% of the volume fraction of the pores in the porous organic membrane skeleton. For example, it can be 5%, 8%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or 100%. For the sake of brevity, the values ​​within the above range will not be listed one by one.

[0024] As a further preferred technical solution of the present invention, the sodium metal filling the pores in the porous organic membrane skeleton accounts for 10% to 30% of the volume fraction of the pores in the porous organic membrane skeleton, for example, 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, 30%. For the sake of brevity, the values ​​in the above range will not be listed one by one.

[0025] In this invention, by adjusting the volume fraction of sodium metal in the pores of the porous organic membrane framework, an appropriate amount of sodium metal can be incorporated as an active material. If the volume fraction is too small, it will affect the capacity performance; conversely, if it is too large, it will lead to excessive deposition of sodium metal, reducing the actual energy density.

[0026] Preferably, the thickness of the composite sodium metal anode material is 5μm-150μm, for example, it can be 5μm, 10μm, 20μm, 30μm, 40μm, 50μm, 60μm, 80μm, 100μm, 120μm, or 150μm; the average pore size is 10nm-100μm, for example, it can be 10nm, 15nm, 30nm, 50nm, 100nm, 200nm, or 500nm. nm, 1μm, 5μm, 10μm, 20μm, 50μm, 80μm, 100μm; porosity 20% to 99%, for example, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 99%. For the sake of brevity, the values ​​within the above range will not be listed one by one.

[0027] As a further preferred technical solution of the present invention, the thickness of the composite sodium metal anode material is 40μm to 100μm, for example, it can be 40μm, 45μm, 50μm, 55μm, 60μm, 65μm, 70μm, 75μm, 80μm, 85μm, 90μm, 95μm, or 100μm; the average pore size is 100nm to 5μm, for example, it can be 100nm, 200nm, 500nm, 1μm, 2μm, or 5μm; the porosity is 60% to 85%, for example, it can be 60%, 65%, 70%, 75%, 80%, or 85%. For the sake of brevity, the values ​​within the above range will not be listed one by one.

[0028] In this invention, the thickness of the composite sodium metal anode material is adjusted to meet the capacity requirements of the battery. Too small a thickness results in insufficient battery capacity, while too large a thickness leads to capacity exceeding the requirements. The average pore size of the composite sodium metal anode material is adjusted to ensure suitable rate performance and dendrite suppression. Too low an average pore size affects sodium ion transport and reduces kinetic performance, while too high an average pore size reduces current density and dendrite suppression. Finally, the porosity of the composite sodium metal anode material is adjusted to ensure suitable sodium storage capacity. Too low a porosity reduces sodium storage capacity and affects energy density, while too high a porosity reduces the strength of the organic membrane framework.

[0029] In a second aspect, the present invention provides a method for preparing the composite sodium metal anode material according to the first aspect, the method comprising the following steps:

[0030] A porous organic membrane framework is prepared, and then electrodeposition or chemical deposition is performed on the surface of the porous organic membrane framework to obtain a porous organic membrane framework with an alloy-type conductive sodium-loving layer. Finally, metallic sodium is combined with the porous organic membrane framework with the alloy-type conductive sodium-loving layer to obtain the composite metallic sodium anode material.

[0031] Preferably, the porous organic membrane framework is prepared by sintering, stretching, or template methods.

[0032] In this invention, the sintering method includes, but is not limited to, pressing polymer powder (preferably uniform spherical particles) with relatively uniform particle size after sieving, such as high-density polyethylene, polypropylene or polytetrafluoroethylene, into plates or pipes of different thicknesses under high pressure, and performing heat treatment at a temperature slightly below the melting point, which causes the surface of the powder to soften, the contact area between particles to increase, and after cooling, it becomes a solid porous material.

[0033] Stretching methods include, but are not limited to, stretching semi-crystalline films or hollow fibers obtained by melt extrusion to produce stretched microporous membranes.

[0034] Template methods include, but are not limited to, using silica microspheres or polyethylene microspheres as template agents and polyimide as a precursor, through blending, film formation, carbonization and detemplating processes to prepare ordered porous carbon film materials.

[0035] Preferably, the specific process of the composite is as follows: metallic sodium is composited with a porous organic membrane framework having an alloy-type conductive sodium-loving layer by means of roller pressing, heating and melting or electrochemical deposition.

[0036] Preferably, the temperature of the roller pressing is 30℃ to 70℃, for example, 30℃, 35℃, 40℃, 45℃, 50℃, 55℃, 60℃, 65℃, or 70℃; and the pressure is 1MPa to 20MPa, for example, 1MPa, 5MPa, 8MPa, 10MPa, 12MPa, 15MPa, 18MPa, or 20MPa.

[0037] Preferably, the heating and melting temperature is 40℃~60℃, for example, 40℃, 45℃, 50℃, 55℃, or 60℃; the pressure is 4MPa~10MPa, for example, 4MPa, 6MPa, 8MPa, or 10MPa.

[0038] Preferably, the current density of the electrochemical deposition is 0.5 mAh / cm². 2 ~2mAh / cm 2 For example, it can be 0.5mAh / cm 2 0.8mAh / cm 2 1mAh / cm 2 1.2mAh / cm2 1.5mAh / cm 2 1.8mAh / cm 2 2mAh / cm 2 .

[0039] Thirdly, the present invention provides a sodium metal battery, the sodium metal battery comprising a positive electrode, a negative electrode, an electrolyte and a separator, wherein the negative electrode comprises a composite sodium metal negative electrode material according to the first aspect.

[0040] In this invention, the sodium metal battery prepared by assembling the composite sodium metal anode material provided by this invention can avoid the advantages of volume expansion and reduce current density to promote uniform nucleation, thereby improving interface performance and avoiding sodium dendrite growth.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] This invention provides a composite sodium metal anode material, employing a porous organic membrane as a three-dimensional flexible framework. This provides a three-dimensional space for sodium metal deposition and suppresses volume expansion. The porous organic membrane also offers advantages such as low density, high processability, low cost, and suitability for mass production. The alloy-type conductive sodium-loving layer exhibits excellent ionic conductivity, sodium affinity, and corrosion resistance, increasing the active sites for sodium ion deposition. Furthermore, its strong adhesion to the porous organic membrane prevents detachment during cycling, thus avoiding sodium metal battery failure. Detailed Implementation

[0043] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0044] Example 1

[0045] This embodiment provides a composite sodium metal anode material, comprising a porous polyimide membrane framework, a crystalline nickel-phosphorus alloy conductive sodium-affinity layer, and sodium metal filling the pores of the porous polyimide membrane framework. Specifically, the crystalline nickel-phosphorus alloy conductive sodium-affinity layer has a thickness of 1 nm and a phosphorus atomic mass ratio of 1%; the sodium metal filling the pores of the porous polyimide membrane framework accounts for 5% of the volume fraction of the pores in the porous polyimide membrane framework; the composite sodium metal anode material has a thickness of 5 μm, an average pore size of 10 nm, and a porosity of 99%.

[0046] The preparation method of the composite sodium metal anode material is as follows:

[0047] (1) Preparation of porous polyimide membrane framework:

[0048] A three-dimensional colloidal crystal template was prepared by gravity sedimentation using silica nanospheres with a diameter of 10 nm. The precursor of porous polyimide was immersed in the colloidal crystal template, and after vacuum drying at a certain temperature, the silica was removed by hydrofluoric acid to obtain a porous polyimide membrane skeleton.

[0049] (2) Electroless nickel-phosphorus alloy conductive sodium-loving layer:

[0050] After the porous polyimide is subjected to degreasing, roughening, activation and desizing processes, the plating solution is formulated with nickel sulfate hexahydrate 27g / L, sodium hypophosphite 32g / L, sodium acetate 20g / L and acetic acid 16g / L. The pH of the plating solution is adjusted to 4.8-5.8 using 10% ammonia water, and nickel is electrolessly plated to obtain a crystalline nickel-phosphorus alloy conductive sodium-loving layer deposited on the surface of the pores.

[0051] (3) The composite sodium metal anode material is obtained by heating and pressing sodium metal with a porous polyimide membrane skeleton at 50°C.

[0052] Example 2

[0053] This embodiment provides a composite sodium metal anode material, comprising a porous phenolic resin membrane framework, an amorphous nickel-phosphorus alloy conductive sodium-loving layer, and sodium metal filling the pores within the porous phenolic resin membrane framework. Specifically, the amorphous nickel-phosphorus alloy conductive sodium-loving layer has a thickness of 1 nm and a phosphorus atomic mass ratio of 40%; the sodium metal filling the pores of the porous phenolic resin membrane framework occupies 100% of the pore volume fraction; and the composite sodium metal anode material has a thickness of 50 μm, an average pore size of 100 μm, and a porosity of 20%.

[0054] The preparation method of the composite sodium metal anode material is as follows:

[0055] (1) Preparation of porous phenolic resin membrane skeleton:

[0056] The sintering method is as follows: 1) Preparation of starch-gelatinized sodium bicarbonate granules: Weigh a mixture of sodium bicarbonate and starch according to the proportion, dissolve it in distilled water, stir and mix, and then dry under reduced pressure to obtain starch-gelatinized sodium bicarbonate granules; 2) Molding of phenolic resin: The steps are as follows: a. Preparation of mixture: Add starch-gelatinized sodium bicarbonate, starch and sodium carbonate mixture and curing agent to phenolic resin and mix evenly; b) Hot pressing molding: Preheat the mold temperature to 90℃, add the mixture prepared in the previous step to the mold, maintain for 10 min, then rapidly heat to 190℃ and press for 20 min; c) Hot drying and unloading: Place the pressed blank in an oven, maintain the temperature at 200℃, hot dry for 2 h, and unload to obtain porous phenolic resin film;

[0057] (2) Electrodeposition method for plating nickel-phosphorus alloy conductive sodium-loving layer:

[0058] In an electroplating bath containing 260 g / L nickel sulfate (main salt), 30 g / L boric acid (buffer), 40 g / L nickel chloride (conductive salt), and 60 g / L sodium hypophosphite (phosphating agent), a nickel plate was used as the anode, and an activated porous phenolic resin membrane skeleton was used as the cathode, at a current density of 1 A / dm³. 2 With a pH value of 2-4, after treatment at 60℃ for 10 min, an amorphous nickel-phosphorus alloy conductive sodium-loving layer is obtained deposited on the pore surface.

[0059] (3) The composite sodium metal anode material is obtained by heating and melting the sodium metal with a porous phenolic resin membrane skeleton at 50°C.

[0060] Example 3

[0061] This embodiment provides a composite sodium metal anode material, comprising a porous polyimide film framework doped with graphene particles, a crystalline nickel-copper-phosphorus alloy conductive sodium-loving layer, and sodium metal filling the pores of the porous polyimide film framework doped with graphene particles. Specifically, the crystalline nickel-copper-phosphorus alloy conductive sodium-loving layer has a thickness of 1 nm and a phosphorus atomic mass ratio of 40%; the sodium metal filling the pores of the porous polyimide film framework doped with graphene particles accounts for 100% of the volume fraction of the pores in the porous polyimide film framework; the composite sodium metal anode material has a thickness of 50 μm, an average pore size of 100 μm, and a porosity of 20%.

[0062] The preparation method of the composite sodium metal anode material is as follows:

[0063] (1) Preparation of porous polyimide membrane framework doped with graphene particles:

[0064] The sintering method was adopted: graphene, polyimide powder, and self-lubricating filler were dried in a 120℃ forced-air drying oven for 4 hours; a coupling agent dilution solution was prepared according to the mass fraction, and the dried graphene was added to the coupling agent dilution solution. The mixture was stirred in a high-speed mixer under a closed environment to form a homogeneous graphene dispersion; a certain amount of polyimide powder was weighed according to the mass fraction and added to the prepared homogeneous graphene dispersion. The solvent was removed to obtain a graphene / polyimide mixture; the composite powder was then loaded into a mold and pressed under a pressure of 20 MPa. The molded product and the mold were placed in a sintering furnace, and the temperature in the sintering furnace was raised to 360℃ at a heating rate of 4℃ / min. After holding at this temperature for 30 minutes, the product was removed, allowed to cool naturally to room temperature, and then demolded to obtain a porous polyimide membrane skeleton doped with graphene particles.

[0065] (2) Electrodeposition of a crystalline nickel-copper-phosphorus alloy conductive sodium-loving layer:

[0066] In an electroplating bath containing 260 g / L nickel sulfate (main salt), 30 g / L boric acid (buffer), 40 g / L nickel chloride (conductive salt), and 60 g / L sodium hypophosphite (phosphating agent), a nickel plate was used as the anode, and an activated porous phenolic resin membrane skeleton was used as the cathode, at a current density of 1 A / dm³. 2 With a pH value of 2-4, after treatment at 60℃ for 10 minutes, a crystalline nickel-copper-phosphorus alloy conductive sodium-loving layer is obtained deposited on the pore surface.

[0067] (3) The porous polyimide membrane framework containing metallic sodium and doped graphene particles is passed through a 2A / dm 2 After electrodeposition at a certain current density for 30 minutes, the composite material was obtained by recombination.

[0068] Example 4

[0069] This embodiment provides a composite sodium metal anode material, comprising a porous polyimide membrane framework doped with copper metal particles, a crystalline nickel-phosphorus alloy conductive sodium-loving layer, and sodium metal filling the pores of the porous polyimide membrane framework doped with copper metal particles. Specifically, the crystalline nickel-phosphorus alloy conductive sodium-loving layer has a thickness of 10 nm and a phosphorus atomic mass ratio of 3%; the sodium metal filling the pores of the porous polyimide membrane framework doped with copper metal particles accounts for 10% of the volume fraction of the pores in the porous polyimide membrane framework doped with copper metal particles; the composite sodium metal anode material has a thickness of 40 μm, an average pore size of 100 nm, and a porosity of 60%.

[0070] The preparation method of the composite sodium metal anode material is as follows:

[0071] (1) Preparation of porous polyimide membrane framework doped with copper metal particles:

[0072] A certain amount of nano-copper powder was weighed and added to anhydrous ethanol for ultrasonic dispersion. Silane coupling agent was added to the suspension and stirred for 3 hours. After the anhydrous ethanol evaporated, the mixture was dried. The dried block-shaped modified nano-copper was pulverized to obtain powdered modified nano-copper particles. The modified nano-copper particles were mixed evenly with polyimide, antioxidant, and coupling agent in a mixer. The composite powder was then loaded into a mold and pressed under a pressure of 20 MPa. The molded product and mold were placed in a sintering furnace. The temperature inside the sintering furnace was controlled to rise to 360°C at a rate of 4°C / min. After holding at this temperature for 30 minutes, the product was removed and allowed to cool naturally to room temperature. The product was then demolded to obtain a porous polyimide membrane skeleton doped with copper particles.

[0073] (2) Electroless nickel-phosphorus alloy conductive sodium-loving layer:

[0074] After the porous polyimide is subjected to degreasing, roughening, activation and desizing processes, the plating solution is formulated with nickel sulfate hexahydrate 27g / L, sodium hypophosphite 32g / L, sodium acetate 20g / L and acetic acid 16g / L. The pH of the plating solution is adjusted to 4.8-5.8 using 10% ammonia water, and nickel is electrolessly plated to obtain a crystalline nickel-phosphorus alloy conductive sodium-loving layer deposited on the surface of the pores.

[0075] (3) The composite sodium metal anode material is obtained by heating and pressing a porous polyimide membrane skeleton doped with copper metal particles at 50°C to combine the sodium metal with the membrane skeleton.

[0076] Example 5

[0077] This embodiment provides a composite sodium metal anode material, comprising a porous polyimide membrane framework doped with copper metal particles, a crystalline nickel-phosphorus alloy conductive sodium-loving layer, and sodium metal filling the pores of the porous polyimide membrane framework doped with copper metal particles. Specifically, the crystalline nickel-phosphorus alloy conductive sodium-loving layer has a thickness of 200 nm and a phosphorus atomic mass ratio of 15%; the sodium metal filling the pores of the porous polyimide membrane framework doped with copper metal particles accounts for 30% of the pore volume fraction of the porous polyimide membrane framework doped with copper metal particles; the composite sodium metal anode material has a thickness of 100 μm, an average pore size of 5 μm, and a porosity of 85%.

[0078] The preparation method of the composite sodium metal anode material is as follows:

[0079] (1) Preparation of porous polyimide membrane framework doped with copper metal particles:

[0080] A certain amount of nano-copper powder was weighed and added to anhydrous ethanol for ultrasonic dispersion. Silane coupling agent was added to the suspension and stirred for 3 hours. After the anhydrous ethanol evaporated, the mixture was dried. The dried block-shaped modified nano-copper was pulverized to obtain powdered modified nano-copper particles. The modified nano-copper particles were mixed evenly with polyimide, antioxidant, and coupling agent in a mixer. The composite powder was then loaded into a mold and pressed under a pressure of 20 MPa. The molded product and mold were placed in a sintering furnace. The temperature inside the sintering furnace was controlled to rise to 360°C at a rate of 4°C / min. After holding at this temperature for 30 minutes, the product was removed and allowed to cool naturally to room temperature. The product was then demolded to obtain a porous polyimide membrane skeleton doped with copper particles.

[0081] (2) Electroless nickel-phosphorus alloy conductive sodium-loving layer:

[0082] After the porous polyimide is subjected to degreasing, roughening, activation and desizing processes, the plating solution is formulated with nickel sulfate hexahydrate 27g / L, sodium hypophosphite 32g / L, sodium acetate 20g / L and acetic acid 16g / L. The pH of the plating solution is adjusted to 4.8-5.8 using 10% ammonia water, and nickel is electrolessly plated to obtain a crystalline nickel-phosphorus alloy conductive sodium-loving layer deposited on the surface of the pores.

[0083] (3) The composite sodium metal anode material is obtained by heating and pressing a porous polyimide membrane skeleton doped with copper metal particles at 50°C to combine the sodium metal with the membrane skeleton.

[0084] Example 6

[0085] This embodiment provides a composite sodium metal anode material, comprising a porous polyimide membrane framework, a crystalline nickel-phosphorus alloy conductive sodium-affinity layer, and sodium metal filling the pores of the porous polyimide membrane framework. Specifically, the crystalline nickel-phosphorus alloy conductive sodium-affinity layer has a thickness of 20 μm and a phosphorus atomic mass ratio of 15%; the sodium metal filling the pores of the porous polyimide membrane framework accounts for 30% of the volume fraction of the pores in the porous polyimide membrane framework; the composite sodium metal anode material has a thickness of 150 μm, an average pore size of 100 μm, and a porosity of 85%.

[0086] The preparation method of the composite sodium metal anode material is as follows:

[0087] (1) Preparation of porous polyimide membrane framework:

[0088] A three-dimensional colloidal crystal template was prepared by gravity sedimentation using silica nanospheres with a diameter of 100 μm. The precursor of porous polyimide was immersed in the colloidal crystal template, and after vacuum drying at a certain temperature, the silica was removed by hydrofluoric acid to obtain a porous polyimide membrane skeleton.

[0089] (2) Electroless nickel-phosphorus alloy conductive sodium-loving layer:

[0090] After the porous polyimide is subjected to degreasing, roughening, activation and desizing processes, the plating solution is formulated with nickel sulfate hexahydrate 27g / L, sodium hypophosphite 32g / L, sodium acetate 20g / L and acetic acid 16g / L. The pH of the plating solution is adjusted to 4.8-5.8 using 10% ammonia water, and nickel is electrolessly plated to obtain a crystalline nickel-phosphorus alloy conductive sodium-loving layer deposited on the surface of the pores.

[0091] (3) The composite sodium metal anode material is obtained by heating and pressing sodium metal with a porous polyimide membrane skeleton at 50°C.

[0092] Example 7

[0093] The difference between this embodiment and Embodiment 1 is that the thickness of the crystalline nickel-phosphorus alloy conductive sodium-loving layer is 0.5 nm, while the rest is the same as in Embodiment 1.

[0094] Example 8

[0095] The difference between this embodiment and Embodiment 1 is that the thickness of the crystalline nickel-phosphorus alloy conductive sodium-loving layer is 25 μm, while the rest is the same as in Embodiment 1.

[0096] Example 9

[0097] The difference between this embodiment and Embodiment 1 is that the atomic mass ratio of the crystalline nickel-phosphorus alloy conductive sodium-loving phosphorus layer is 0.5%, while the rest are the same as in Embodiment 1.

[0098] Example 10

[0099] The difference between this embodiment and Embodiment 1 is that the atomic mass ratio of the crystalline nickel-phosphorus alloy conductive sodium-loving phosphorus layer is 45%, while the rest are the same as in Embodiment 1.

[0100] Example 11

[0101] The difference between this embodiment and Embodiment 1 is that the average pore size of the composite sodium metal anode material is 5 nm, while the rest is the same as in Embodiment 1.

[0102] Example 12

[0103] The difference between this embodiment and Embodiment 1 is that the average pore size of the composite sodium metal anode material is 110 μm, while the rest are the same as in Embodiment 1.

[0104] Example 13

[0105] The difference between this embodiment and Embodiment 1 is that the crystalline nickel-phosphorus alloy conductive sodium-loving layer is prepared by other methods, the specific process of which is as follows:

[0106] 510 mg of nickel nitrate hexahydrate, 3 mL of phytic acid and 135 mg of melamine were ground into a slurry in an agate mortar. The sample was heated to 700 °C at a rate of 10 °C / min and calcined for 3 h in a nitrogen atmosphere. Then, 300 mg of the calcined sample and the porous polyimide membrane were immersed in ethanol solution for 3 h, then dried at 50 °C and kept at 300 °C for 3 h.

[0107] Comparative Example 1

[0108] The difference between this comparative example and Example 1 is that the crystalline nickel-phosphorus alloy conductive sodium-loving layer is replaced with a metallic tin conductive sodium-loving layer; otherwise, they are the same as in Example 1.

[0109] Comparative Example 2

[0110] The difference between this comparative example and Example 1 is that the porous polyimide membrane skeleton is replaced with a porous carbon fiber skeleton, while the rest is the same as in Example 1.

[0111] Application Examples 1 to 13 and Comparative Application Examples 1 to 2

[0112] Sodium metal batteries were prepared using the composite sodium metal anode materials provided in Examples 1 to 13 and Comparative Examples 1 to 2. The preparation methods are as follows:

[0113] Preparation of the positive electrode: Prussian blue, acetylene black, and polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 97%:1.5%:1.5% with N-methylpyrrolidone as the solvent. After stirring evenly, the slurry is coated onto an aluminum foil current collector and baked dry to prepare the positive electrode.

[0114] Preparation of negative electrode sheet: The composite sodium metal negative electrode and copper foil are combined with 12μm copper foil at 40℃ and 5MPa pressure to prepare the negative electrode sheet;

[0115] Preparation of sodium metal batteries: The batteries are assembled in the order of positive electrode, electrolyte and negative electrode, and then their electrochemical performance is tested.

[0116] Test conditions

[0117] The sodium metal batteries provided in Application Examples 1 to 13 and Comparative Application Examples 1 to 2 were subjected to performance tests, and the test methods are as follows:

[0118] (1) Cyclic performance: Cyclic performance was tested at 25℃ with a charge / discharge rate of 1C / 1C;

[0119] (2) Rate performance: Rate performance was tested at 25℃ with a charge / discharge rate of 3C / 1C.

[0120] The test results are shown in Table 1:

[0121] Table 1

[0122]

[0123]

[0124] As can be seen from the data in Table 1, and as demonstrated by the examples and comparative examples, the composite sodium metal anode, composed of a porous organic membrane framework, an alloy-type conductive sodium-loving layer, and sodium metal filling the pores of the porous organic membrane framework, exhibits good structural stability and kinetic performance, and improves the cycle and rate performance of the battery.

[0125] (1) As can be seen from Examples 1 and 7 to 8, if the alloy-type conductive sodium-loving layer is too thin, the sodium metal deposition effect and conductivity are poor, which is not conducive to capacity utilization and dynamic performance. If it is too thick, it will affect the energy density of the battery.

[0126] (2) As can be seen from Examples 1 and 9 to 10, if the atomic weight of phosphorus in the alloy-type conductive sodium-loving nickel-phosphorus alloy is too small, the ionic conductivity will be poor, which will affect the kinetic performance; if the atomic weight of phosphorus is too high, the conductivity will be poor, which will also affect the capacity utilization and kinetic performance of the material to a certain extent.

[0127] (3) As can be seen from Examples 1 and 11 to 12, if the pore size of the porous organic membrane skeleton is too large, the effect of dispersing current density will be poor, the effect of inhibiting dendrite growth will be poor, and thus the cycle performance of the battery will be affected; if the pore size of the organic membrane skeleton is too small, the sodium metal deposition and dissolution rate will be affected, and the kinetic performance will be poor.

[0128] (4) As can be seen from Examples 1 and 13, the sodium-loving alloy layers obtained by other methods are prone to fall off during cycling due to poor coating density, uniformity and bonding with the substrate, which affects the cycling performance.

[0129] (5) As can be seen from Example 1 and Comparative Example 1, the type of sodium-loving layer replacement cannot have the advantages of ion conduction, conductivity and sodium affinity at the same time, so the cycle performance of the sodium metal battery provided is poor; As can be seen from the comparison between Example 1 and Comparative Example 2, the porous polyimide membrane skeleton has the advantage of high energy density as a skeleton due to its low density.

[0130] The applicant declares that the present invention is illustrated by the above embodiments, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials used in the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A composite sodium metal anode material, characterized in that, The composite sodium metal anode material includes a porous organic membrane framework, an alloy-type conductive sodium-loving layer, and sodium metal filling the pores of the porous organic membrane framework. The alloy-type conductive sodium-loving layer is made of at least one of crystalline nickel-phosphorus alloy, crystalline copper-phosphorus alloy, crystalline nickel-copper-phosphorus alloy, amorphous nickel-phosphorus alloy, amorphous copper-phosphorus alloy, or amorphous nickel-copper-phosphorus alloy; the thickness of the alloy-type conductive sodium-loving layer is 1 nm to 20 μm, and the atomic mass ratio of phosphorus in the alloy-type conductive sodium-loving layer is 1% to 15%.

2. The composite sodium metal anode material according to claim 1, characterized in that, The material of the porous organic membrane skeleton includes any one or a combination of at least two of the following: porous thermoplastic resin, porous thermosetting resin, porous thermoplastic resin doped with metal, porous thermosetting resin doped with metal, porous thermoplastic resin doped with carbon material, porous thermosetting resin doped with carbon material, conductive polymer, porous thermoplastic resin with conductive polymer coated on the surface, or porous thermosetting resin with conductive polymer coated on the surface.

3. The composite sodium metal anode material according to claim 2, characterized in that, The material of the porous organic membrane framework includes any one or a combination of at least two of the following: a porous thermoplastic resin doped with carbon material, a porous thermosetting resin doped with carbon material, a conductive polymer, a porous thermoplastic resin with a surface coated with a conductive polymer, or a porous thermosetting resin with a surface coated with a conductive polymer.

4. The composite sodium metal anode material according to claim 2, characterized in that, The porous thermoplastic resin includes at least one of polyethylene, polypropylene, polytetrafluoroethylene, polyamide, polyethylene terephthalate, polycarbonate, polystyrene, styrene-acrylonitrile copolymer resin, polyoxymethylene resin, polyethersulfone resin, polyvinyl chloride, polyphenylene ether, cis-polyisoprene, styrene-butadiene rubber, polymethyl methacrylate, and glass fiber reinforced porous thermoplastic resins with the above porous thermoplastic resins as the base material.

5. The composite sodium metal anode material according to claim 4, characterized in that, The porous thermoplastic resin includes at least one of polyethylene, polypropylene, polytetrafluoroethylene, polyamide, and glass fiber reinforced porous thermoplastic resin with the above porous thermoplastic resin as the base material.

6. The composite sodium metal anode material according to claim 2, characterized in that, The porous thermosetting resin includes at least one of phenolic resin, urea-formaldehyde resin, epoxy resin, polyurethane, thermosetting polyimide, polybutadiene resin, silicone resin or bismaleimide resin.

7. The composite sodium metal anode material according to claim 6, characterized in that, The porous thermosetting resin includes at least one of phenolic resin, polyurethane, thermosetting polyimide, or bismaleimide resin.

8. The composite sodium metal anode material according to claim 1, characterized in that, The thickness of the alloy-type conductive sodium-loving layer is 10 nm to 200 nm, and the atomic mass ratio of phosphorus in the alloy-type conductive sodium-loving layer is 3% to 15%.

9. The composite sodium metal anode material according to claim 1, characterized in that, The sodium metal filling the pores of the porous organic membrane framework accounts for 5% to 100% of the volume fraction of the pores in the porous organic membrane framework.

10. The composite sodium metal anode material according to claim 9, characterized in that, The sodium metal filling the pores of the porous organic membrane framework accounts for 10% to 30% of the volume fraction of the pores in the porous organic membrane framework.

11. The composite sodium metal anode material according to claim 1, characterized in that, The composite sodium metal anode material has a thickness of 5 μm to 150 μm, an average pore size of 10 nm to 100 μm, and a porosity of 20% to 99%.

12. The composite sodium metal anode material according to claim 11, characterized in that, The composite sodium metal anode material has a thickness of 40 μm to 100 μm, an average pore size of 100 nm to 5 μm, and a porosity of 60% to 85%.

13. A method for preparing a composite sodium metal anode material according to any one of claims 1-12, characterized in that, The method includes the following steps: A porous organic membrane framework is prepared, and then electrodeposition or chemical deposition is performed on the surface of the porous organic membrane framework to obtain a porous organic membrane framework with an alloy-type conductive sodium-loving layer. Finally, metallic sodium is combined with the porous organic membrane framework with the alloy-type conductive sodium-loving layer to obtain the composite metallic sodium anode material.

14. The method according to claim 13, characterized in that, The porous organic membrane framework is prepared by sintering, stretching or template method.

15. The method according to claim 13, characterized in that, The specific process of the composite is as follows: metallic sodium is composited with a porous organic membrane framework having an alloy-type conductive sodium-loving layer by means of roller pressing, heating and melting or electrochemical deposition.

16. The method according to claim 15, characterized in that, The temperature of the roller press is 30℃~70℃, and the pressure is 1MPa~20MPa.

17. The method according to claim 15, characterized in that, The heating and melting temperature is 40℃~60℃, and the pressure is 4MPa~10MPa.

18. The method according to claim 15, characterized in that, The current density of the electrochemical deposition is 0.5 mAh / cm³. 2 ~2mAh / cm 2 .

19. A sodium metal battery, characterized in that, The sodium metal battery includes a positive electrode, a negative electrode, an electrolyte, and a separator, wherein the negative electrode comprises a composite sodium metal negative electrode material according to any one of claims 1-12.

Images