Porous electrode material, preparation method thereof and capacitor

Abstract

The invention discloses a porous electrode material, a preparation method thereof and a capacitor, and relates to the technical field of electrode materials. When the porous electrode material is prepared, firstly, terephthalaldehyde reacts with nickel tetra (4-aminophenyl) porphyrin and cobalt tetra (4-aminophenyl) porphyrin to prepare a metal complex covalent organic framework; mixing the metal complexing covalent organic framework with polyacrylonitrile, and performing electrostatic spinning to obtain a metal-loaded porous polyacrylonitrile membrane; carbonizing the metal-loaded porous polyacrylonitrile membrane and then phosphorizing to obtain a phosphorized porous coated metal material; and mixing the phosphatized porous coated metal material with a binder and a conductive agent to prepare conductive slurry, coating the surface of a substrate with the conductive slurry, and performing flash freezing and freeze drying to prepare the porous electrode material. The porous electrode material prepared by the invention has the advantages of high specific capacity, good rate capability and good cycle performance.

Description

Technical Field

[0001] This invention relates to the field of electrode materials technology, specifically to a porous electrode material, its preparation method, and a capacitor. Background Technology

[0002] As the global energy structure accelerates its transition to renewable energy, efficient energy storage technology has become a core support for achieving carbon neutrality. In electrochemical energy storage systems such as batteries and supercapacitors, electrode materials, as carriers of energy storage and conversion, directly determine the electrochemical characteristics of the devices. Currently, the theoretical capacity of commercially available graphite anodes is only 372 mAh / g, which is insufficient to meet the demands of high-energy-density energy storage; while silicon-based materials, although possessing an ultra-high theoretical capacity of approximately 4200 mAh / g, suffer from a sharp decline in cycle stability due to drastic volume expansion. This contradiction between capacity and stability has prompted researchers to turn their attention to novel composite electrode material systems.

[0003] Meanwhile, in the microstructure of electrode materials, porous structures similar to porous carbon mostly imply better electrochemical performance. Their intrinsic high specific surface area and multi-level conductive pathways formed by micropores significantly reduce ion diffusion resistance and accelerate charge transport speed. Furthermore, multi-level porous composite structures have better performance improvement effects, which is crucial for enhancing the energy storage performance of supercapacitors. Summary of the Invention

[0004] The purpose of this invention is to provide a porous electrode material, its preparation method, and a capacitor, in order to solve the problems existing in the prior art.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: A porous electrode material is prepared by mixing a phosphated porous coated metal material with a binder and a conductive agent to form a conductive slurry, coating it on the surface of a substrate, flash-freezing, and then freeze-drying. The phosphated porous coated metal material is prepared by pre-oxidizing and carbonizing a metal-loaded porous polyacrylonitrile film, followed by phosphate treatment. The metal-supported porous polyacrylonitrile membrane is prepared by electrospinning a mixture of a metal complex covalent organic framework and polyacrylonitrile. The metal complex covalent organic framework is prepared by reacting terephthalaldehyde with tetrakis(4-aminophenyl)porphyrin nickel and tetrakis(4-aminophenyl)porphyrin cobalt. The tetra(4-aminophenyl)porphyrin nickel and tetra(4-aminophenyl)porphyrin cobalt are prepared by coordinating tetra(4-aminophenyl)porphyrin with nickel source and cobalt source, respectively.

[0006] As an optimization, the binder is one or more of polyvinylidene fluoride, polyvinyl alcohol, polymethyl methacrylate, and sodium carboxymethyl cellulose.

[0007] As an optimization, the conductive agent is one or more of acetylene black and carbon black.

[0008] As an optimization, the matrix includes nickel foam and carbon paper.

[0009] As an optimization, the nickel source is one or more of nickel chloride, nickel chloride hydrate, nickel sulfate, nickel sulfate hydrate, nickel nitrate, nickel nitrate hydrate, nickel acetate, and nickel acetate hydrate.

[0010] As an optimization, the cobalt source is one or more of cobalt chloride, cobalt chloride hydrate, cobalt sulfate, cobalt sulfate hydrate, cobalt nitrate, cobalt nitrate hydrate, cobalt acetate, and cobalt acetate hydrate.

[0011] A method for preparing a porous electrode material includes the following preparation steps: (1) Terephthalaldehyde, tetra(4-aminophenyl)porphyrin nickel and tetra(4-aminophenyl)porphyrin cobalt are mixed evenly, 1,2-dichlorobenzene and butanol are added, ultrasonication is performed, acetic acid aqueous solution is added, after freeze-thaw degassing, vacuum sealing is performed, the reaction is heated at 120~130℃, cooled to room temperature, filtered, washed, dried, ground and sieved to obtain metal complex covalent organic framework; (2) Polyacrylonitrile was dissolved in dimethyl sulfoxide to obtain a polyacrylonitrile solution. The metal complex covalent organic framework was dispersed in dimethyl sulfoxide, ultrasonically dispersed, added to the polyacrylonitrile solution and mixed evenly. Ultrasonication was continued, and the mixture was allowed to stand to remove bubbles to obtain a polyacrylonitrile spinning solution. The polyacrylonitrile spinning solution was added to a syringe, electrospun, and dried to obtain a metal-loaded porous polyacrylonitrile membrane. (3) The metal-loaded porous polyacrylonitrile membrane is pre-oxidized in an air atmosphere and then carbonized in an argon atmosphere to obtain a porous coated metal material; sodium hypophosphite monohydrate is placed upstream of a tube furnace and the porous coated metal material is placed downstream of the tube furnace. Phosphating is carried out in a nitrogen atmosphere, and the material is naturally cooled to room temperature. The material is then ground and sieved to obtain a phosphated porous coated metal material. (4) Mix the phosphating porous coated metal material, conductive agent and binder evenly, add N-methylpyrrolidone, grind to obtain conductive slurry, coat the conductive slurry on the substrate surface, place it on the copper plate surface pre-cooled by liquid nitrogen for flash freezing, and then freeze dry to obtain porous electrode material.

[0012] As an optimization, the molar ratio of terephthalaldehyde, tetra(4-aminophenyl)porphyrin nickel, and tetra(4-aminophenyl)porphyrin cobalt in step (1) is 1:(0.16~0.24):(0.16~0.24).

[0013] As an optimization, the volume ratio of 1,2-dichlorobenzene to butanol in step (1) is 1:(1~1.2).

[0014] As an optimization, the mass ratio of terephthalaldehyde to butanol in step (1) is 1:(40~50).

[0015] As an optimization, the concentration of the acetic acid aqueous solution in step (1) is 6 mol / L.

[0016] As an optimization, the volume ratio of the acetic acid aqueous solution to butanol in step (1) is 1:(1.8~2.4).

[0017] As an optimization, the heating reaction time in step (1) is 70~72h.

[0018] As an optimization, the reaction process of the metal complex covalent organic framework in step (1) is as follows: .

[0019] As an optimization, the tetra(4-aminophenyl)porphyrin nickel in step (1) is prepared by mixing 0.2-0.3 parts of tetra(4-aminophenyl)porphyrin and 0.28-0.42 parts of nickel chloride hexahydrate under a nitrogen atmosphere, adding 15-18 parts of methanol, 50-60 parts of chloroform, and 20-25 parts of dimethylformamide, sonicating for 10-15 min, stirring and refluxing at 80-90℃ and 200-300 r / min for 22-24 h, naturally cooling to room temperature, washing with pure water, collecting the organic layer and removing water with anhydrous sodium sulfate, and purifying by rotary evaporation to remove the solvent.

[0020] As an optimization, the tetra(4-aminophenyl)porphyrin cobalt in step (1) is prepared by mixing 0.2-0.3 parts of tetra(4-aminophenyl)porphyrin and 0.28-0.42 parts of cobalt chloride hexahydrate by mass under a nitrogen atmosphere, adding 15-18 parts of methanol, 50-60 parts of chloroform, and 20-25 parts of dimethylformamide, sonicating for 10-15 min, stirring and refluxing at 80-90℃ and 200-300 r / min for 24-28 h, naturally cooling to room temperature, washing with pure water, collecting the organic layer and removing water with anhydrous sodium sulfate, and purifying by rotary evaporation to remove the solvent.

[0021] As an optimization, the polyacrylonitrile spinning solution in step (2) contains 14wt%~16wt% polyacrylonitrile.

[0022] As an optimization, the polyacrylonitrile spinning solution in step (2) also contains 3wt%~4wt% of metal complex covalent organic framework.

[0023] As an optimization, the electrospinning process conditions in step (2) are: 22~28℃, 46%~54%RH, voltage 16~18kV, feed speed 0.8~0.9ml / h, roller speed 400~500r / min, and distance between needle tip and collecting roller 18cm.

[0024] As an optimization, the electrospinning time in step (2) is 6~7h.

[0025] As an optimization, the pre-oxidation process conditions in step (3) are to heat to 240-250℃ at a heating rate of 1.5-2℃ / min and hold for 80-100min.

[0026] As an optimization, the carbonization process conditions in step (3) are to heat to 600-700℃ at a heating rate of 4-6℃ / min and hold for 100-120min.

[0027] As an optimization, the mass ratio of the porous coated metal material to sodium hypophosphite monohydrate in step (3) is 1:(9~11).

[0028] As an optimization, the phosphating process conditions in step (3) are to heat to 340-360℃ at a heating rate of 2-3℃ / min and hold for 2-2.5h.

[0029] As an optimization, the mass ratio of the phosphating porous coated metal material, conductive agent, and binder in step (4) is (7~8):(1~2):1.

[0030] As an optimization, the solid content of the conductive paste in step (4) is 25wt%~30wt%.

[0031] As an optimization, the flash freezing time in step (4) is 30~40 min.

[0032] As an optimization, the loading of the phosphated porous coated metal material on the porous electrode material in step (4) is 0.1~30 mg / cm³. 2 .

[0033] A capacitor, wherein the electrode material of the capacitor is a porous electrode material prepared according to a method for preparing porous electrode materials.

[0034] Compared with the prior art, the beneficial effects achieved by the present invention are: In preparing porous electrode materials, this invention first involves coordinating tetra(4-aminophenyl)porphyrin with nickel and cobalt sources to prepare tetra(4-aminophenyl)porphyrin nickel and tetra(4-aminophenyl)porphyrin cobalt, respectively; then reacting terephthalaldehyde with tetra(4-aminophenyl)porphyrin nickel and tetra(4-aminophenyl)porphyrin cobalt to obtain a metal-complexed covalent organic framework; mixing the metal-complexed covalent organic framework with polyacrylonitrile and electrospinning to obtain a metal-supported porous polyacrylonitrile membrane; carbonizing and then phosphating the metal-supported porous polyacrylonitrile membrane to obtain a phosphated porous coated metal material; mixing the phosphated porous coated metal material with a binder and a conductive agent to form a conductive slurry, coating it on the substrate surface, flash-freezing, and then freeze-drying to obtain the porous electrode material.

[0035] First, tetra(4-aminophenyl)porphyrin is coordinated with nickel and cobalt sources to prepare tetra(4-aminophenyl)porphyrin nickel and tetra(4-aminophenyl)porphyrin cobalt, respectively. Nickel and cobalt ions enter the porphyrin ring by forming coordinate bonds with nitrogen atoms inside the porphyrin ring, resulting in tetra(4-aminophenyl)porphyrin nickel and tetra(4-aminophenyl)porphyrin cobalt containing nickel and cobalt ions. Then, terephthalaldehyde is reacted with tetra(4-aminophenyl)porphyrin nickel and tetra(4-aminophenyl)porphyrin cobalt to prepare a metal complex covalent organic framework. Terephthalaldehyde undergoes a Schiff base reaction with the amino groups on tetra(4-aminophenyl)porphyrin nickel and tetra(4-aminophenyl)porphyrin cobalt to form a covalent organic framework structure. Due to its ordered growth, the covalent organic framework structure has a fixed-size two-dimensional channel structure, and the metal ions are fixed by coordinate bonds and uniformly fixed within it as the covalent organic framework grows.

[0036] Secondly, a metal-supported porous polyacrylonitrile membrane was prepared by electrospinning a mixture of a metal-complexed covalent organic framework and polyacrylonitrile. Through electrospinning, the metal-complexed covalent organic framework and polyacrylonitrile were mixed to obtain an electrospun film. Due to the porosity characteristics of electrospinning, the resulting polyacrylonitrile membrane contained a large number of macropores with diameters ranging from 10 to 1000 nm, while the metal-complexed covalent organic framework was uniformly dispersed within the film. Subsequently, the fibrous structure of the polyacrylonitrile was pre-oxidized and fixed in an air atmosphere, followed by high-temperature carbonization under an inert argon atmosphere. During the carbonization process, the organic framework within the metal-complexed covalent organic framework retained the canonical pore structure of the covalent organic framework and coated the membrane. On the metal surface, a porous nitrogen-doped carbon-coated metal structure is formed. Within this structure, a cobalt-nickel composite metal is introduced. The nickel-cobalt composite structure has more redox sites, and the different oxidation potentials of the two metals broaden the operating voltage window. Furthermore, the lattice distortion caused by the bimetallic structure facilitates rapid ion insertion and extraction, resulting in a synergistic effect between the cobalt and nickel composite metals. This composite metal exhibits significantly stronger electrochemical performance than the single metal. Simultaneously, the polyacrylonitrile framework also forms a porous carbon fiber structure during carbonization, further coating the outer layer of the nitrogen-doped carbon-coated metal structure, forming a double-layer carbon-coated structure. The two carbon layers retain different structures due to inheritance. Its internal pore structure and the content of internal doped atoms are also different. The outer carbon layer forms a macroporous polyacrylonitrile fiber skeleton, while the inner carbon layer forms a microporous structure of a covalent organic framework. This results in micropores with a pore size of 2-5 nm and a regular pore structure. The different pore sizes create a hierarchical channel structure. This structure effectively improves charge transport efficiency, and the regular channels of the covalent organic framework further enhance the improvement effect, reducing ion transport resistance. This improves its specific capacity and energy density as an electrode material. Furthermore, the two carbon coating layers with different pore sizes effectively reduce the expansion and activity loss of the internal metal during repeated cycles. The rate performance and cycle life were improved. Then, the nickel and cobalt metal inside the porous coated metal material were phosphated using a gas-phase phosphating method. Since phosphorus has a lower electronegativity than oxygen and sulfur, the phosphated nickel and cobalt transition metals can accelerate electron transport and improve redox reactions, thereby improving conductivity. At the same time, since the radii of nickel and cobalt ions are similar, a NiCoP solid solution structure is formed during the carbonization and phosphating process. After phosphating, the phosphated crystal has two types of chemical bonds: covalent bonds and metallic bonds. The covalent bonds participate in redox reactions, while the metallic bonds can improve conductivity, thereby effectively improving electrochemical performance and resulting in higher specific capacity, rate performance and cycle life.

[0037] Finally, the phosphated porous coated metal material was mixed with binder and conductive agent to form a conductive slurry, which was then coated onto the substrate surface. After flash freezing, the slurry was freeze-dried to produce a porous electrode material. The directional flash freezing technology can effectively fix the prepared porous structure and double-layer carbon coating structure, avoiding performance loss caused by structural damage during the electrode material preparation process. Furthermore, since the freeze-drying was carried out at low temperature, the solvent was removed while the framework was fixed, leaving a richer porous framework structure. This further improved the hierarchical structure of the pores, provided a higher specific surface area, effectively increased the ion contact area, reduced ion transport resistance, and promoted charge transport efficiency, thereby improving the specific capacity. Detailed Implementation

[0038] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0039] The raw material information used in all the following examples and comparative examples is as follows: Polyacrylonitrile: weight average molecular weight 150,000, purchased from Hubei Kemaidi Chemical Co., Ltd. Conductive agent: Acetylene black, model N550, purchased from Tianjin Yiborui Chemical Co., Ltd.; Adhesive: Polyvinylidene fluoride, model Solef 5130 / 0001, purchased from Shenzhen Boen New Materials Co., Ltd.; Substrate: Nickel foam, 1 mm thick, with a porosity greater than 95%, purchased from Wuzhou Sanhe New Material Technology Co., Ltd. Nickel tetra(4-aminophenyl)porphyrin: By mass, under a nitrogen atmosphere, 0.25 parts of tetra(4-aminophenyl)porphyrin and 0.35 parts of nickel chloride hexahydrate were mixed, and 16 parts of methanol, 55 parts of chloroform and 22 parts of dimethylformamide were added. The mixture was sonicated for 12 min, and then stirred and refluxed at 85 °C and 250 r / min for 23 h. After naturally cooling to room temperature, the mixture was washed with pure water, the organic layer was collected and dehydrated with anhydrous sodium sulfate, and the solvent was removed by rotary evaporation to obtain nickel tetra(4-aminophenyl)porphyrin. Tetra(4-aminophenyl)porphyrin cobalt: By mass, under a nitrogen atmosphere, 0.25 parts of tetra(4-aminophenyl)porphyrin and 0.35 parts of cobalt chloride hexahydrate were mixed, and 17 parts of methanol, 55 parts of chloroform and 23 parts of dimethylformamide were added. The mixture was sonicated for 13 min, stirred and refluxed at 85 °C and 250 r / min for 26 h, and allowed to cool naturally to room temperature. The mixture was washed with pure water, the organic layer was collected and dehydrated with anhydrous sodium sulfate, and the solvent was removed by rotary evaporation before purification to obtain tetra(4-aminophenyl)porphyrin cobalt.

[0040] Example 1: A method for preparing a porous electrode material, the method comprising the following preparation steps: (1) Terephthalaldehyde, tetra(4-aminophenyl)porphyrin nickel, and tetra(4-aminophenyl)porphyrin cobalt were added to a thick-walled pressure tube in a molar ratio of 1:0.16:0.24. 1,2-dichlorobenzene and butanol were added in a volume ratio of 1:1. The mass ratio of terephthalaldehyde to butanol was 1:40. The mixture was sonicated for 10 min. A 6 mol / L aqueous acetic acid solution was added. The volume ratio of the aqueous acetic acid solution to butanol was 1:1.8. After freeze-thaw degassing, the mixture was sealed under vacuum and heated at 120 °C for 72 h. After cooling to room temperature, the mixture was filtered and washed three times alternately with acetone and tetrahydrofuran. The mixture was dried under vacuum at 60 °C for 12 h and ground through a 400-mesh sieve to obtain a metal complex covalent organic framework. (2) Polyacrylonitrile was dissolved in dimethyl sulfoxide to obtain a polyacrylonitrile solution. The metal complex covalent organic framework was dispersed in dimethyl sulfoxide and ultrasonically dispersed for 15 min. It was then added to the polyacrylonitrile solution and mixed evenly. Ultrasonication was continued for 20 min, and then the mixture was allowed to stand to remove bubbles to obtain a polyacrylonitrile spinning solution containing 14 wt% polyacrylonitrile and 3 wt% metal complex covalent organic framework. The polyacrylonitrile spinning solution was added to a syringe and electrospun for 7 h at 22℃, 46%RH, with a voltage of 16 kV, a feed rate of 0.8 ml / h, a roller speed of 400 r / min, and a distance of 18 cm between the needle tip and the collecting roller. The mixture was then vacuum dried at 60℃ for 20 h to obtain a metal-loaded porous polyacrylonitrile membrane. (3) The metal-loaded porous polyacrylonitrile membrane was heated to 240℃ and held for 80 min at a heating rate of 1.5℃ / min in an air atmosphere, and then transferred to an argon atmosphere and heated to 600℃ for 100 min at a heating rate of 4℃ / min to obtain a porous coated metal material; the porous coated metal material and sodium hypophosphite monohydrate were placed in two crucibles at a mass ratio of 1:9, the sodium hypophosphite monohydrate was placed upstream of the tube furnace, and the porous coated metal material was placed downstream of the tube furnace. Under a nitrogen atmosphere, the temperature was raised to 340℃ at a heating rate of 2℃ / min and held for 2 h. After naturally cooling to room temperature, it was ground through a 325-mesh sieve to obtain a phosphated porous coated metal material. (4) The phosphating porous coated metal material, conductive agent and binder are mixed evenly in a mass ratio of 7:2:1. N-methylpyrrolidone is added and ground in a mortar for 30 min to obtain a conductive slurry with a solid content of 25 wt%. The conductive slurry is coated on the substrate surface and placed on a copper plate pre-cooled by liquid nitrogen for flash freezing for 30 min. Then it is freeze-dried for 48 h to obtain a porous electrode material.

[0041] Example 2: A method for preparing a porous electrode material, the method comprising the following preparation steps: (1) Terephthalaldehyde, tetra(4-aminophenyl)porphyrin nickel, and tetra(4-aminophenyl)porphyrin cobalt were added to a thick-walled pressure tube in a molar ratio of 1:0.2:0.2. 1,2-dichlorobenzene and butanol were added in a volume ratio of 1:1.1. The mass ratio of terephthalaldehyde to butanol was 1:45. The mixture was sonicated for 12 min. A 6 mol / L aqueous acetic acid solution was added. The volume ratio of the aqueous acetic acid solution to butanol was 1:2.1. After freeze-thaw degassing, the mixture was sealed under vacuum and heated at 125 °C for 71 h. After cooling to room temperature, the mixture was filtered and washed three times alternately with acetone and tetrahydrofuran. The mixture was dried under vacuum at 65 °C for 11 h and ground through a 400-mesh sieve to obtain a metal complex covalent organic framework. (2) Polyacrylonitrile was dissolved in dimethyl sulfoxide to obtain a polyacrylonitrile solution. The metal complex covalent organic framework was dispersed in dimethyl sulfoxide and ultrasonically dispersed for 18 min. It was then added to the polyacrylonitrile solution and mixed evenly. Ultrasonication was continued for 25 min, and then the solution was allowed to stand to remove bubbles to obtain a polyacrylonitrile spinning solution containing 15 wt% polyacrylonitrile and 3.5 wt% metal complex covalent organic framework. The polyacrylonitrile spinning solution was added to a syringe and electrospun for 6.5 h at 25 °C, 50% RH, with a voltage of 17 kV, a feed rate of 0.85 ml / h, a roller speed of 450 r / min, and a distance of 18 cm between the needle tip and the collecting roller. The solution was then vacuum dried at 65 °C for 19 h to obtain a metal-loaded porous polyacrylonitrile membrane. (3) The metal-loaded porous polyacrylonitrile membrane was heated to 245℃ and held for 90 min at a heating rate of 1.8℃ / min in an air atmosphere, and then transferred to an argon atmosphere and heated to 650℃ for 110 min at a heating rate of 5℃ / min to obtain a porous coated metal material; the porous coated metal material and sodium hypophosphite monohydrate were placed in two crucibles at a mass ratio of 1:10, the sodium hypophosphite monohydrate was placed upstream of the tube furnace, and the porous coated metal material was placed downstream of the tube furnace. Under a nitrogen atmosphere, the temperature was raised to 350℃ at a heating rate of 2.5℃ / min and held for 2 h. After naturally cooling to room temperature, it was ground through a 325-mesh sieve to obtain a phosphated porous coated metal material. (4) The phosphated porous coated metal material, conductive agent and binder are mixed evenly in a mass ratio of 7.5:1.5:1, N-methylpyrrolidone is added, and the mixture is ground in a mortar for 35 min to obtain a conductive slurry with a solid content of 27.5 wt%. The conductive slurry is coated on the substrate surface and placed on a copper plate pre-cooled by liquid nitrogen for flash freezing for 35 min. Then it is freeze-dried for 50 h to obtain a porous electrode material.

[0042] Example 3: A method for preparing a porous electrode material, the method comprising the following preparation steps: (1) Terephthalaldehyde, tetra(4-aminophenyl)porphyrin nickel, and tetra(4-aminophenyl)porphyrin cobalt were added to a thick-walled pressure tube in a molar ratio of 1:0.24:0.16. 1,2-dichlorobenzene and butanol were added in a volume ratio of 1:1.2. The mass ratio of terephthalaldehyde to butanol was 1:50. The mixture was sonicated for 15 min. A 6 mol / L aqueous acetic acid solution was added. The volume ratio of the aqueous acetic acid solution to butanol was 1:2.4. After freeze-thaw degassing, the mixture was sealed under vacuum and heated at 130 °C for 70 h. After cooling to room temperature, the mixture was filtered and washed 4 times alternately with acetone and tetrahydrofuran. The mixture was dried under vacuum at 70 °C for 10 h and ground through a 400-mesh sieve to obtain a metal complex covalent organic framework. (2) Polyacrylonitrile was dissolved in dimethyl sulfoxide to obtain a polyacrylonitrile solution. The metal complex covalent organic framework was dispersed in dimethyl sulfoxide and ultrasonically dispersed for 20 min. It was then added to the polyacrylonitrile solution and mixed evenly. Ultrasonication was continued for 30 min, and then the mixture was allowed to stand to remove bubbles to obtain a polyacrylonitrile spinning solution containing 16 wt% polyacrylonitrile and 4 wt% metal complex covalent organic framework. The polyacrylonitrile spinning solution was added to a syringe and electrospun for 6 h at 28 °C, 54% RH, with a voltage of 18 kV, a feed rate of 0.9 ml / h, a roller speed of 500 r / min, and a distance of 18 cm between the needle tip and the collecting roller. The mixture was then vacuum dried at 70 °C for 18 h to obtain a metal-loaded porous polyacrylonitrile membrane. (3) The metal-loaded porous polyacrylonitrile membrane was heated to 250℃ and held for 100 min at a heating rate of 2℃ / min in an air atmosphere, and then transferred to an argon atmosphere and heated to 700℃ at a heating rate of 6℃ / min for 120 min to obtain a porous coated metal material; the porous coated metal material and sodium hypophosphite monohydrate were placed in two crucibles at a mass ratio of 1:11, the sodium hypophosphite monohydrate was placed upstream of the tube furnace, and the porous coated metal material was placed downstream of the tube furnace. Under a nitrogen atmosphere, the temperature was raised to 360℃ at a heating rate of 3℃ / min and held for 2.5 h. After natural cooling to room temperature, it was ground through a 325-mesh sieve to obtain a phosphated porous coated metal material. (4) The phosphated porous coated metal material, conductive agent and binder are mixed evenly in a mass ratio of 8:1:1. N-methylpyrrolidone is added and ground in a mortar for 40 min to obtain a conductive slurry with a solid content of 30 wt%. The conductive slurry is coated on the substrate surface and placed on the copper plate surface pre-cooled by liquid nitrogen for flash freezing for 40 min. Then it is freeze-dried for 52 h to obtain a porous electrode material.

[0043] Comparative Example 1: The difference between the preparation method of the porous electrode material in Comparative Example 1 and Example 2 lies in step (1). Step (1) is modified as follows: terephthalaldehyde, tetra(4-aminophenyl)porphyrin, and tetra(4-aminophenyl)porphyrin cobalt are added to a thick-walled pressure tube in a molar ratio of 1:0.2:0.2. 1,2-dichlorobenzene and butanol are added in a volume ratio of 1:1.1, with a mass ratio of terephthalaldehyde to butanol of 1:45. The mixture is sonicated for 12 min, and a 6 mol / L aqueous acetic acid solution is added, with a volume ratio of the aqueous acetic acid solution to butanol of 1:2.1. After freeze-thaw degassing, the mixture is sealed under vacuum and heated at 125°C for 71 h. After cooling to room temperature, the mixture is filtered, washed three times alternately with acetone and tetrahydrofuran, dried under vacuum at 65°C for 11 h, and ground through a 400-mesh sieve to obtain a metal-complexed covalent organic framework. The remaining steps are the same as in Example 2.

[0044] Comparative Example 2: The difference between the preparation method of the porous electrode material in Comparative Example 2 and Example 2 lies in step (1). Step (1) is modified as follows: terephthalaldehyde, nickel tetra(4-aminophenyl)porphyrin, and tetra(4-aminophenyl)porphyrin are added to a thick-walled pressure tube in a molar ratio of 1:0.2:0.2. 1,2-dichlorobenzene and butanol are added in a volume ratio of 1:1.1, with a mass ratio of terephthalaldehyde to butanol of 1:45. The mixture is sonicated for 12 min, and a 6 mol / L aqueous acetic acid solution is added, with a volume ratio of the aqueous acetic acid solution to butanol of 1:2.1. After freeze-thaw degassing, the mixture is sealed under vacuum and heated at 125°C for 71 h. After cooling to room temperature, the mixture is filtered, washed three times alternately with acetone and tetrahydrofuran, dried under vacuum at 65°C for 11 h, and ground through a 400-mesh sieve to obtain a metal-complexed covalent organic framework. The remaining steps are the same as in Example 2.

[0045] Comparative Example 3: The difference between the preparation method of the porous electrode material in Comparative Example 3 and Example 2 lies in step (1). Step (1) is modified as follows: terephthalaldehyde and tetrakis(4-aminophenyl)porphyrin are added to a thick-walled pressure tube at a molar ratio of 1:0.4, followed by 1,2-dichlorobenzene and butanol at a volume ratio of 1:1.1 (the mass ratio of terephthalaldehyde to butanol is 1:45). The mixture is sonicated for 12 min, and then a 6 mol / L aqueous acetic acid solution is added (the volume ratio of the aqueous acetic acid solution to butanol is 1:2.1). After freeze-thaw degassing, the mixture is sealed under vacuum and heated at 125°C for 71 h. After cooling to room temperature, the mixture is filtered, washed three times alternately with acetone and tetrahydrofuran, dried under vacuum at 65°C for 11 h, and ground through a 400-mesh sieve to obtain a metal-complexed covalent organic framework. The remaining steps are the same as in Example 2.

[0046] Comparative Example 4: The difference between the preparation method of the porous electrode material in Comparative Example 4 and Example 2 is that step (1) is omitted, and step (2) is modified as follows: Polyacrylonitrile is dissolved in dimethyl sulfoxide to obtain a polyacrylonitrile solution. Tetra(4-aminophenyl)porphyrin nickel and tetra(4-aminophenyl)porphyrin cobalt are dispersed in dimethyl sulfoxide, ultrasonically dispersed for 15 min, added to the polyacrylonitrile solution and mixed evenly. Ultrasonication is continued for 20 min, and then allowed to stand to remove bubbles to obtain a polyacrylonitrile spinning solution. The polyacrylonitrile spinning solution contains 14 wt% polyacrylonitrile, 1 wt% tetra(4-aminophenyl)porphyrin nickel, and 1 wt% tetra(4-aminophenyl)porphyrin cobalt. The polyacrylonitrile spinning solution is added to a syringe and electrospun for 7 h at 22°C, 46%RH, with a voltage of 16 kV, a feed rate of 0.8 ml / h, a roller speed of 400 r / min, and a distance of 18 cm between the needle tip and the collecting roller. The solution is then vacuum dried at 60°C for 20 h to obtain a metal-loaded porous polyacrylonitrile membrane. The remaining steps are the same as in Example 2.

[0047] Comparative Example 5: The difference between the preparation method of the porous electrode material in Comparative Example 5 and Example 2 is that step (2) is omitted, and step (3) is modified as follows: the metal complex covalent organic framework is heated to 650°C for 110 min at a heating rate of 5°C / min under an argon atmosphere to obtain a porous coated metal material; the porous coated metal material and sodium hypophosphite monohydrate are placed in two crucibles at a mass ratio of 1:10, the sodium hypophosphite monohydrate is placed upstream of the tube furnace, and the porous coated metal material is placed downstream of the tube furnace. Under a nitrogen atmosphere, the temperature is raised to 350°C at a heating rate of 2.5°C / min and held for 2 h. After natural cooling to room temperature, the material is ground through a 325-mesh sieve to obtain a phosphated porous coated metal material. The remaining steps are the same as in Example 2.

[0048] Comparative Example 6: The difference between the preparation method of the porous electrode material in Comparative Example 6 and Example 2 lies in step (3). Step (3) is modified as follows: the metal-loaded porous polyacrylonitrile film is heated to 245°C for 90 min at a heating rate of 1.8°C / min in an air atmosphere, and then transferred to an argon atmosphere and heated to 650°C for 110 min at a heating rate of 5°C / min to obtain a porous coated metal material. Step (4) is modified as follows: the porous coated metal material, conductive agent, and binder are mixed evenly at a mass ratio of 7.5:1.5:1, N-methylpyrrolidone is added, and the mixture is ground in a mortar for 35 min to obtain a conductive slurry with a solid content of 27.5 wt%. The conductive slurry is coated on the substrate surface, placed on a copper plate pre-cooled by liquid nitrogen for flash freezing for 35 min, and then freeze-dried for 50 h to obtain a porous electrode material. The remaining steps are the same as in Example 2.

[0049] Comparative Example 7: The difference between the preparation method of the porous electrode material in Comparative Example 7 and Example 2 lies in step (4). Step (4) is modified as follows: Phosphated porous coated metal material, conductive agent, and binder are mixed evenly in a mass ratio of 7.5:1.5:1, N-methylpyrrolidone is added, and the mixture is ground in a mortar for 35 min to obtain a conductive slurry with a solid content of 27.5 wt%. The conductive slurry is coated on the substrate surface and vacuum dried at 70°C for 20 h to obtain the porous electrode material. The remaining steps are the same as in Example 2.

[0050] In all the following test examples, the loading of the phosphated porous metal-coated material on the porous electrode materials prepared in the various embodiments and comparative examples was 2.5 mg / cm³. 2 The loading of porous coated metal material on the porous electrode material prepared in Comparative Example 6 was 2.5 mg / cm³. 2 .

[0051] Test Example 1: Electrochemical performance testing: The specific capacity, specific capacity at different rate currents, and specific capacity retention after cycling of the prepared porous electrode material were tested to evaluate its electrochemical performance. The tests were conducted on a Chenhua CHI660E electrochemical workstation, using the prepared porous electrode material as the working electrode, a platinum sheet as the counter electrode, saturated calomel as the reference electrode, and a 3 mol / L potassium hydroxide solution as the electrolyte. The specific testing methods are as follows: Specific capacity and rate performance: The galvanostatic charge-discharge analysis method was used. The galvanostatic charge-discharge curves of the prepared porous electrode material were tested with a voltage window of 0–1 V and current densities of 1 A / g and 10 A / g. The results are expressed by the formula: C = I × ∆t ÷ m; Calculate the specific capacity, where C is the specific capacity in F / g, I is the current density, ∆t is the discharge time, and m is the mass of the phosphated porous coated metal material or porous coated metal material loaded on the porous electrode material; 5 samples are tested in parallel for each group, and the average value is recorded; Cyclic performance: Cyclic charge-discharge tests were conducted with a voltage window of 0~1V and a current density of 1A / g. One charge and one discharge constituted one cycle. After 10,000 cycles, the specific capacity was calculated according to the above formula and compared with the initial value to calculate the specific capacity retention rate. Five samples were tested in parallel in each group, and the average value was recorded.

[0052] The results are shown in Table 1.

[0053] A comparison of the experimental data of Examples 1-3 and Comparative Examples 1-7 in Table 1 reveals that the porous electrode material prepared by the present invention has high specific capacity as well as good rate performance and cycle performance.

[0054] By comparing the data, the data from Comparative Examples 1 and 2 show that the simultaneous introduction of cobalt and nickel composite metals results in more redox sites in the nickel-cobalt composite structure. Furthermore, the different oxidation potentials of the two metals broaden the operating voltage window. The lattice distortion caused by the bimetallic structure facilitates the rapid insertion and extraction of ions, thus giving the cobalt-nickel composite metal structure a synergistic effect. The composite metal exhibits significantly stronger electrochemical performance than the single metal, effectively improving the specific capacity, rate performance, and cycle life of porous electrode materials.

[0055] By comparing the data, the data in Comparative Example 3 shows that although the porous carbon structure formed purely by the organic framework has high cycling performance and good capacity retention, it lacks the complexation of phosphating transition metals. It loses the charge storage mechanism of redox reaction and has almost only the double-layer capacity remaining, resulting in a serious decrease in mass specific capacity.

[0056] By comparing the data, the data from Comparative Examples 4 and 5 show that the covalent organic framework forms the first microporous carbon coating layer on the surface of the composite metal material, while the macroporous framework of polyacrylonitrile-based carbon fiber forms the second carbon coating layer on the outside. The presence of macropores improves the wettability of the electrolyte, while the presence of micropores reduces the resistance to ion transport. The hierarchical porous structure formed by the two synergistically improves the electrochemical performance of the porous electrode material. At the same time, the presence of the double carbon coating layer effectively suppresses the volume expansion during cycling, thereby improving the cycling performance.

[0057] By comparing the data, the data in Comparative Example 6 shows that phosphating of metallic materials effectively improves the electrochemical performance of porous electrode materials. Since phosphorus has a lower electronegativity than oxygen, phosphated nickel and cobalt transition metals can accelerate electron transport and improve redox reactions, thereby increasing conductivity. At the same time, since nickel and cobalt ions have similar radii, a NiCoP solid solution structure is formed during carbonization and phosphating. After phosphating, the phosphated crystals have two types of chemical bonds: covalent bonds and metallic bonds. The covalent bonds participate in redox reactions, while the metallic bonds can improve conductivity, thereby effectively improving electrochemical performance and resulting in higher specific capacity, rate performance, and cycle life.

[0058] By comparing the data, the data in Comparative Example 7 shows that the application of flash freezing and freeze drying technology helps to fix the multi-level porous microstructure of the electrode material during the preparation of porous electrode materials, avoiding the collapse of micropore channels caused by high-temperature vacuum drying, thereby avoiding performance loss.

[0059] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A porous electrode material, characterized in that, The porous electrode material is prepared by mixing phosphated porous coated metal material with binder and conductive agent to form a conductive slurry, coating it on the substrate surface, flash-freezing and then freeze-drying. The phosphated porous coated metal material is prepared by pre-oxidizing and carbonizing a metal-loaded porous polyacrylonitrile film, followed by phosphate treatment. The metal-supported porous polyacrylonitrile membrane is prepared by electrospinning a mixture of a metal complex covalent organic framework and polyacrylonitrile. The metal complex covalent organic framework is prepared by reacting terephthalaldehyde with tetrakis(4-aminophenyl)porphyrin nickel and tetrakis(4-aminophenyl)porphyrin cobalt. The tetra(4-aminophenyl)porphyrin nickel and tetra(4-aminophenyl)porphyrin cobalt are prepared by coordinating tetra(4-aminophenyl)porphyrin with nickel source and cobalt source, respectively.

2. The porous electrode material according to claim 1, characterized in that, The adhesive is one or more of polyvinylidene fluoride, polyvinyl alcohol, polymethyl methacrylate, and sodium carboxymethyl cellulose; The conductive agent is one or more of acetylene black and carbon black; The matrix includes nickel foam and carbon paper.

3. The porous electrode material according to claim 1, characterized in that, The nickel source is one or more of nickel chloride, nickel chloride hydrate, nickel sulfate, nickel sulfate hydrate, nickel nitrate, nickel nitrate hydrate, nickel acetate, and nickel acetate hydrate; The cobalt source is one or more of cobalt chloride, cobalt chloride hydrate, cobalt sulfate, cobalt sulfate hydrate, cobalt nitrate, cobalt nitrate hydrate, cobalt acetate, and cobalt acetate hydrate.

4. A method for preparing a porous electrode material, characterized in that, The preparation steps include the following: (1) Terephthalaldehyde, tetra(4-aminophenyl)porphyrin nickel and tetra(4-aminophenyl)porphyrin cobalt are mixed evenly, 1,2-dichlorobenzene and butanol are added, ultrasonication is performed, acetic acid aqueous solution is added, after freeze-thaw degassing, vacuum sealing is performed, the reaction is heated at 120~130℃, cooled to room temperature, filtered, washed, dried, ground and sieved to obtain metal complex covalent organic framework; (2) Polyacrylonitrile was dissolved in dimethyl sulfoxide to obtain a polyacrylonitrile solution. The metal complex covalent organic framework was dispersed in dimethyl sulfoxide, ultrasonically dispersed, added to the polyacrylonitrile solution and mixed evenly. Ultrasonication was continued, and the mixture was allowed to stand to remove bubbles to obtain a polyacrylonitrile spinning solution. The polyacrylonitrile spinning solution was added to a syringe, electrospun, and dried to obtain a metal-loaded porous polyacrylonitrile membrane. (3) The metal-loaded porous polyacrylonitrile membrane is pre-oxidized in an air atmosphere and then carbonized in an argon atmosphere to obtain a porous coated metal material; sodium hypophosphite monohydrate is placed upstream of a tube furnace and the porous coated metal material is placed downstream of the tube furnace. Phosphating is carried out in a nitrogen atmosphere, and the material is naturally cooled to room temperature. The material is then ground and sieved to obtain a phosphated porous coated metal material. (4) Mix the phosphating porous coated metal material, conductive agent and binder evenly, add N-methylpyrrolidone, grind to obtain conductive slurry, coat the conductive slurry on the substrate surface, place it on the copper plate surface pre-cooled by liquid nitrogen for flash freezing, and then freeze dry to obtain porous electrode material.

5. The method for preparing a porous electrode material according to claim 4, characterized in that, The molar ratio of terephthalaldehyde, tetra(4-aminophenyl)porphyrin nickel, and tetra(4-aminophenyl)porphyrin cobalt in step (1) is 1:(0.16~0.24):(0.16~0.24); The volume ratio of 1,2-dichlorobenzene to butanol is 1:(1~1.2); The mass ratio of terephthalaldehyde to butanol is 1:(40~50); The concentration of the acetic acid aqueous solution is 6 mol / L; The volume ratio of the acetic acid aqueous solution to butanol is 1:(1.8~2.4); The heating reaction takes 70-72 hours.

6. The method for preparing a porous electrode material according to claim 4, characterized in that, The polyacrylonitrile spinning solution in step (2) contains 14wt%~16wt% polyacrylonitrile; The polyacrylonitrile spinning solution also contains 3wt%~4wt% of a metal complex covalent organic framework; The electrospinning process conditions are: 22~28℃, 46%~54%RH, voltage 16~18kV, feed speed 0.8~0.9ml / h, drum speed 400~500r / min, and distance between needle tip and collecting drum 18cm. The electrospinning time is 6-7 hours.

7. The method for preparing a porous electrode material according to claim 4, characterized in that, The pre-oxidation process conditions in step (3) are to heat to 240-250℃ at a heating rate of 1.5-2℃ / min and hold for 80-100min; The carbonization process conditions are as follows: heating to 600-700℃ at a heating rate of 4-6℃ / min and holding for 100-120min; The mass ratio of the porous coated metal material to sodium hypophosphite monohydrate is 1:(9~11); The phosphating process conditions are as follows: heating to 340-360℃ at a heating rate of 2-3℃ / min and holding at that temperature for 2-2.5 hours.

8. The method for preparing a porous electrode material according to claim 4, characterized in that, In step (4), the mass ratio of the phosphated porous coated metal material, the conductive agent, and the binder is (7~8):(1~2):1; The solid content of the conductive paste is 25wt%~30wt%; The flash freezing time is 30-40 minutes.

9. The method for preparing a porous electrode material according to claim 4, characterized in that, In step (4), the loading of the phosphating porous coated metal material on the porous electrode material is 0.1~30 mg / cm³. 2 .

10. A capacitor, characterized in that, The electrode material of the capacitor is a porous electrode material prepared using the method for preparing porous electrode materials according to any one of claims 4 to 9.

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