A porous carbon / vanadium nitride composite electrode material, its preparation method and application

Abstract

The present invention discloses a porous carbon / vanadium nitride composite electrode material, a preparation method thereof and an application thereof, belonging to the technical field of electrode materials. The preparation method of the porous carbon / vanadium nitride composite electrode material comprises the following steps: using an amino-containing interpenetrating network polymer as a precursor, after removing moisture, impregnating and complexing with a vanadium oxide sol, and after the impregnation is completed, obtaining an impregnated complex; pyrolyzing the impregnated complex once at 280°C to 350°C under a protective atmosphere, and then pyrolyzing it a second time at 700°C to 900°C to prepare the porous carbon / vanadium nitride composite electrode material. When the present invention is prepared, there is no need to introduce a reducing atmosphere, the preparation environment is safe, and the prepared porous carbon / vanadium nitride composite electrode material has excellent cycle life.

Description

Technical Field

[0001] The present invention relates to the technical field of electrode materials, and more particularly to a porous carbon / vanadium nitride composite electrode material, a preparation method thereof, and an application thereof. Background Art

[0002] Electrochemical energy storage devices include rechargeable batteries and capacitors. Rechargeable batteries usually have a high energy density, but their charge and discharge times are long and their cycling performance is poor, which limits their wide application. Traditional capacitors have an extremely high specific power, but their storage capacity is not ideal. The new energy storage device, the electrochemical capacitor, also called the supercapacitor, has a higher specific power than lithium-ion batteries, a better energy density than traditional capacitors, and has outstanding advantages such as short charging time, wide operating temperature range, long cycle life, and safe and environmentally friendly. It has been widely studied in the fields of new energy vehicles, aerospace, sensors, etc.

[0003] At present, the low energy density of supercapacitors limits their development. The methods to improve their energy density mainly include increasing the specific capacitance of the electrode material and expanding its potential window. The supercapacitor electrode materials studied by researchers are mainly transition metal oxides such as RuO2, MnO2, V2O5, etc. They have a high theoretical specific capacitance. However, RuO2 is expensive, and the conductivity of other transition metal oxides is poor. Conductive polymers have a high specific capacitance and electronic conductivity, but their stability is poor.

[0004] Vanadium nitride is an ideal supercapacitor electrode material due to its wide potential window (-1.2V to 0V) and high specific capacitance. However, its cycling life is poor. Composite carbon materials are an effective method to improve its stability. The common ways of composite carbon materials are mainly to composite carbon materials with vanadium oxide precursors, such as carbon nanotubes and graphene. When sintering at a high temperature of 900 °C, a reducing atmosphere such as hydrogen and ammonia needs to be used, which has certain safety hazards. Summary of the Invention

[0005] In view of the above problems, the present invention provides a porous carbon / vanadium nitride composite electrode material, a preparation method thereof, and an application thereof. When the present invention is prepared, it is not necessary to introduce a reducing atmosphere, the preparation environment is safe, and the prepared porous carbon / vanadium nitride composite electrode material has excellent cycling life.

[0006] To achieve the object of the present invention, the present invention adopts the following technical solutions:

[0007] In the first aspect, the present invention provides a preparation method of a porous carbon / vanadium nitride composite electrode material, including the following steps:

[0008] Using an amino-containing interpenetrating network polymer as a precursor, after removing moisture, a vanadium oxide sol is impregnated and complexed. After the impregnation is completed, an impregnated complex is obtained.

[0009] The impregnated complex is pyrolyzed once at 280 °C to 350 °C under a protective atmosphere. During the first pyrolysis process, the amino-containing interpenetrating network polymer undergoes a cyclization reaction. Then, it is pyrolyzed a second time at 700 °C to 900 °C. During the second pyrolysis process, the easily decomposable polymers in the amino-containing interpenetrating network polymer decompose to generate a pore structure, and the hardly decomposable polymers pyrolyze and crosslink to form a carbon network structure. The C-N-H bonds and V-O bonds break and reconstruct to generate vanadium nitride, and carbon thermally reduces vanadium oxide to generate vanadium nitride, thereby preparing a porous carbon / vanadium nitride composite electrode material.

[0010] For example, the temperature of the first pyrolysis can be 280 °C, 290 °C, 300 °C, 310 °C, 320 °C, 330 °C, 340 °C, 350 °C, etc.

[0011] The temperature of the second pyrolysis can be 700 °C, 720 °C, 740 °C, 760 °C, 780 °C, 800 °C, 820 °C, 840 °C, 860 °C, 880 °C, 900 °C, etc., but is not limited to the listed values. Other unlisted values within the above numerical range are equally applicable and will not be elaborated here one by one.

[0012] The following are the preferred technical solutions of the present invention, but not the limitations of the technical solutions provided by the present invention. Through the following technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

[0013] As a preferred technical solution of the present invention, the ratio of the interpenetrating network polymer to the vanadium oxide is 1.5 g to 2 g: 2 mmol to 3 mmol. For example, the ratio of the interpenetrating network polymer to the vanadium oxide can be 1.5 g: 2 mmol, 1.5 g: 2.2 mmol, 1.5 g: 2.4 mmol, 1.5 g: 2.6 mmol, 1.5 g: 2.8 mmol, 1.5 g: 3 mmol, 1.7 g: 2 mmol, 1.7 g: 2.2 mmol, 1.7 g: 2.4 mmol, 1.7 g: 2.6 mmol, 1.7 g: 2.8 mmol, 1.7 g: 3 mmol, 1 g: 1 mmol, 1 g: 1.1 mmol, 1 g: 1.2 mmol, 1 g: 1.3 mmol, 1 g: 1.4 mmol, 1 g: 1.5 mmol, etc., but is not limited to the listed values. Other unlisted values within the above numerical range are equally applicable and will not be elaborated here one by one.

[0014] As a preferred technical solution of the present invention, the time for secondary pyrolysis is 2h to 4h. For example, the time for secondary pyrolysis can be 2h, 2.4h, 2.8h, 3.2h, 3.6h, 4h, etc., but is not limited to the listed values. Other unlisted values within the above numerical range are equally applicable and will not be elaborated one by one here.

[0015] As a preferred technical solution of the present invention, the time for primary pyrolysis is 2h to 4h. For example, the time for primary pyrolysis can be 2h, 2.4h, 2.8h, 3.2h, 3.6h, 4h, etc., but is not limited to the listed values. Other unlisted values within the above numerical range are equally applicable and will not be elaborated one by one here.

[0016] As a preferred technical solution of the present invention, the impregnation time is 6h to 12h. It can be understood that as the impregnation time extends, more vanadium oxide sol solution is absorbed. For example, the impregnation time can be 6h, 6.5h, 7h, 7.5h, 8h, 8.5h, 9h, 9.5h, 10h, 10.5h, 11h, 11.5h, 12h, etc., but is not limited to the listed values. Other unlisted values within the above numerical range are equally applicable and will not be elaborated one by one here.

[0017] As a preferred technical solution of the present invention, the preparation steps of the vanadium oxide sol are as follows: disperse vanadium oxide in water, add H2O2 and NaCl and stir to obtain the vanadium oxide sol.

[0018] As a preferred technical solution of the present invention, the ratio of vanadium oxide to water is 1mmol to 1.5mmol: 30mL; for example, the ratio of vanadium oxide to water is 1mmol: 30mL, 1.1mmol: 30mL, 1.2mmol: 30mL; 1.3mmol: 30mL, 1.4mmol: 30mL, 1.5mmol: 30mL, etc.

[0019] The volume ratio of water to H2O2 is 12:1 to 1.2; for example, the volume ratio of water to H2O2 is 12:1, 12:1.1, 12:1.2, etc.

[0020] The ratio of vanadium oxide to NaCl is 2mmol to 3mmol: 1.2g to 1.4g. For example, the ratio of vanadium oxide to NaCl is 2mmol: 1.2g, 2mmol: 1.3g, 2mmol: 1.4g, 2.5mmol: 1.2g, 2.5mmol: 1.3g, 2.5mmol: 1.4g, 3mmol: 1.2g, 3mmol: 1.3g, 3mmol: 1.4g, etc., but is not limited to the listed values. Other unlisted values within the above numerical range are equally applicable and will not be elaborated one by one here.

[0021] As a preferred technical solution of the present invention, the interpenetrating network polymer is a polyvinyl alcohol / polyacrylamide interpenetrating network polymer, a polyvinylpyrrolidone / polyacrylamide interpenetrating network polymer, a polyvinyl alcohol / chitosan interpenetrating network polymer or a polyvinylpyrrolidone / chitosan interpenetrating network polymer.

[0022] In a second aspect, the present invention provides a porous carbon / vanadium nitride composite electrode material prepared by the above preparation method.

[0023] In a third aspect, the present invention provides the application of the above porous carbon / vanadium nitride composite electrode material in the preparation of a supercapacitor.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] Under a protective atmosphere, the present invention uses an amino-containing interpenetrating network polymer for pyrolysis to prepare a porous carbon material. At the same time, the presence of amino groups can decompose to spontaneously generate an ammonia atmosphere for reducing vanadium oxide to form vanadium nitride or the N-H bond breaks and combines with V-O to prepare a porous carbon / vanadium nitride composite material. According to the method of the present invention, reducing atmospheres such as ammonia and hydrogen are avoided, and a new method for safely preparing a porous carbon / vanadium nitride composite material in a protective gas environment is provided.

[0026] Compared with traditional VN materials, when preparing the porous carbon / vanadium nitride composite material of the present invention, during the pyrolysis process, the presence of V increases the order of the local carbon material and improves the graphitization degree, resulting in an increase in I G and a decrease in I D / I G , which improves the conductivity of the composite material, thereby enhancing electron transfer; the presence of pores helps the full infiltration and mass transfer of the electrolyte; the vanadium nitride nanoparticles and pore structure increase the contact area between the electrode material and the electrolyte; ultimately, the electrochemical activity of the porous carbon / vanadium nitride composite material is improved. Description of the Drawings

[0027] Figure 1 are the scanning electron microscope images, transmission electron microscope images and element distribution maps of different samples. Among them, a is the scanning electron microscope image of NPC prepared in Comparative Example 2, b is the scanning electron microscope image of VN / NPC prepared in Example 1, c is the transmission electron microscope image of VN / NPC prepared in Example 1 at a scale of 100 nm, d is the transmission electron microscope image of VN / NPC prepared in Example 1 at a scale of 20 nm, the inset in d is the pore size distribution map of VN / NPC prepared in Example 1, e is the transmission electron microscope image of VN / NPC prepared in Example 1 at a scale of 20 nm, and the inset in e is the particle size distribution map and crystal plane spacing map of VN / NPC prepared in Example 1, and f is the element distribution map of different elements.

[0028] Figure 2 XRD patterns (a) of VN / NPC prepared in Example 1 and Raman spectra (b) of different composite materials.

[0029] Figure 3 Electrochemical properties of different composite materials, where a is the cyclic voltammetry curve, b is the charge-discharge curve, and c is the specific capacitance.

[0030] Figure 4 Scanning electron microscope images, XRD patterns, and electrochemical properties of different samples. Among them, a is the scanning electron microscope image of NPC-CS prepared in Comparative Example 4, b is the scanning electron microscope image of VN / NPC-PVACS prepared in Example 6, c is the XRD pattern of VN / NPC-PVACS prepared in Example 6, d is the cyclic voltammetry curves of the materials prepared in Example 6 and Comparative Example 4, e is the charge-discharge curves of the materials prepared in Example 6 and Comparative Example 4, and f is the specific capacitance of the materials prepared in Example 6 and Comparative Example 4. Detailed implementation manners

[0031] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0032] As shown in the background art, the current methods for preparing vanadium nitride powder mainly involve high-temperature preparation of metal oxide precursors in a reducing atmosphere (such as hydrogen, ammonia, etc.). Ammonia, hydrogen, etc. have potential safety hazards. The present invention proposes a method for preparing a porous carbon / vanadium nitride composite electrode material, which avoids the use of dangerous gases during the preparation process. The specific technical solutions are as follows.

[0033] A method for preparing a porous carbon / vanadium nitride composite electrode material, comprising the following steps:

[0034] Using an amino-containing interpenetrating network polymer gel as a precursor, after freeze-drying to remove moisture, impregnating and absorbing a vanadium oxide sol solution. After impregnation is completed, an impregnated composite is obtained, and then freeze-drying is carried out.

[0035] The frozen impregnated composite is pyrolyzed once at 280°C to 350°C under the protection of a protective atmosphere, and then the temperature is continuously raised to 700°C to 900°C for secondary pyrolysis to obtain a porous carbon / vanadium nitride composite electrode material.

[0036] The present invention constructs an interpenetrating network polymer hydrogel containing amino groups and freeze-dries it. This freeze-drying step can keep the framework structure in the hydrogel undamaged. It is soaked in a vanadium oxide sol. The amino groups in the dry gel serve as active sites and, due to hydrogen bonding, fully absorb vanadium oxide ions. The solutes in its aqueous solution can be evenly dispersed in the gel, and NaCl can be used as a salt template and can be washed away later to obtain an interpenetrating network polymer / vanadium oxide / NaCl hydrogel. After freeze-drying again, solid particles will precipitate and be fixed on the surface of the dry gel. Thereafter, a pyrolysis treatment is carried out at 280°C to 350°C. Within this temperature range, the polymer will undergo a cyclization reaction to form a more stable structure through the cyclization reaction. These stable structures can be better retained at subsequent high temperatures, thereby increasing the residual carbon content to a certain extent. In addition, some small molecules are decomposed in advance, and then a secondary pyrolysis treatment is carried out at 700°C to 900°C. The easily decomposable polymers in the interpenetrating network polymer decompose to generate pore structures, and the hardly decomposable polymers pyrolyze and crosslink into a carbon network structure. The C-N-H in the amino group breaks, and undergoes high-temperature reconstruction with the broken V-O to generate vanadium nitride. In addition, the carbon network structure also thermally reduces VO compounds at high temperatures to prepare vanadium nitride, and finally a d-porous carbon / vanadium nitride composite material is obtained.

[0037] Furthermore, the interpenetrating network polymer is a polyvinyl alcohol / polyacrylamide interpenetrating network polymer, a polyvinylpyrrolidone / polyacrylamide interpenetrating network polymer, a polyvinyl alcohol / chitosan interpenetrating network polymer, or a polyvinylpyrrolidone / chitosan interpenetrating network polymer. The present invention does not particularly limit the source of the interpenetrating network polymer, and those skilled in the art can select and adjust it according to the actual application situation, product quality, and product performance.

[0038] The preparation method of the polyvinyl alcohol / polyacrylamide interpenetrating network polymer is as follows:

[0039] 2 g of polyvinyl alcohol (PVA) is placed in 20 mL of deionized water and stirred evenly at 90°C until transparent. Then, 2 g of acrylamide monomer is added. After stirring evenly, 10 mg of oxidant ammonium persulfate and 2 mg of crosslinking agent N,N'-methylenebisacrylamide are added. The above mixed solution is sealed and degassed, and the free radical polymerization of the acrylamide monomer is completed by reacting at 60°C for 3 h. After repeated freezing and thawing three times, a polyvinyl alcohol / polyacrylamide interpenetrating network polymer hydrogel can be obtained, denoted as PVA / PAM IPNs hydrogel.

[0040] The preparation method of the polyvinylpyrrolidone / polyacrylamide interpenetrating network polymer is as follows:

[0041] 2 g of polyvinylpyrrolidone (PVP) was placed in 20 mL of deionized water and stirred evenly at 90 °C until transparent. Then, 2 g of acrylamide monomer was added. After stirring evenly, 10 mg of ammonium persulfate as the oxidant and 2 mg of N,N'-methylenebisacrylamide as the crosslinking agent were added. The above mixed solution was sealed and degassed, and the free radical polymerization of acrylamide monomer was completed by reacting at 60 °C for 3 h. After repeated freezing and thawing three times, a polyvinylpyrrolidone / polyacrylamide interpenetrating network polymer hydrogel was obtained, denoted as PVP / PAM IPNs hydrogel.

[0042] The preparation method of polyvinyl alcohol / chitosan interpenetrating network polymer is as follows:

[0043] 2 g of PVA was placed in 20 mL of deionized water and stirred evenly at 90 °C until transparent. Then, 2 g of chitosan was added. After stirring evenly, 10 mg of ammonium persulfate as the oxidant and 2 mg of N,N'-methylenebisacrylamide as the crosslinking agent were added. The above mixed solution was sealed and degassed, and the free radical polymerization of acrylamide monomer was completed by reacting at 60 °C for 3 h. After repeated freezing and thawing three times, a polyvinyl alcohol / chitosan interpenetrating network polymer hydrogel was obtained, denoted as PVA / CS IPNs hydrogel.

[0044] The preparation method of polyvinylpyrrolidone / chitosan interpenetrating network polymer is as follows:

[0045] 2 g of PVP was placed in 20 mL of deionized water and stirred evenly at 90 °C until transparent. Then, 2 g of chitosan was added. After stirring evenly, 10 mg of ammonium persulfate as the oxidant and 2 mg of N,N'-methylenebisacrylamide as the crosslinking agent were added. The above mixed solution was sealed and degassed, and the free radical polymerization of acrylamide monomer was completed by reacting at 60 °C for 3 h. After repeated freezing and thawing three times, a polyvinylpyrrolidone / chitosan interpenetrating network polymer hydrogel was obtained, denoted as PVP / CS IPNs hydrogel.

[0046] It should be noted that the molecular weight of PVA used in the present invention is 80,000, and the degree of polymerization is 1799. The molecular weight of chitosan is 700,000 - 800,000, and the molecular weight of PVP is 58,000. The vanadium oxide used in the present invention is vanadium pentoxide, denoted as V2O5.

[0047] Example 1

[0048] Step 1: 2 g of PVA is placed in 20 mL of deionized water, stirred evenly at 90 °C until transparent, then 2 g of acrylamide monomer is added. After stirring evenly, 10 mg of oxidant ammonium persulfate and 2 mg of crosslinker N,N'-methylenebisacrylamide are added. The above mixed solution is sealed and degassed, and the free radical polymerization of acrylamide monomer is completed by reacting at 60 °C for 3 h. After repeated freezing and thawing three times, a polyvinyl alcohol / polyacrylamide interpenetrating network polymer, denoted as PVA / PAM IPNs hydrogel, can be obtained.

[0049] Step 2: 0.364 g of V2O5 is dispersed in 60 mL of water, and 5 mL of H2O2 is added dropwise and stirred for 30 min until the solution turns orange-red. Then 1.2 g of NaCl is added and stirred for 10 min until clear, obtaining a vanadium oxide sol solution.

[0050] Step 3: Take 1.5 g of PVA / PAM IPNs hydrogel, immerse it in the 60 mL of vanadium oxide sol solution prepared in Step 2, soak for 12 h and then perform freeze-drying. Then, under a nitrogen atmosphere, it is carbonized at a low temperature of 280 °C for 2 h, and the temperature is continuously raised to 700 °C for high-temperature carbonization for 2 h. After washing and drying, a porous carbon / vanadium nitride composite electrode material, denoted as VN / NPC, can be obtained.

[0051] Example 2

[0052] Step 1: 2 g of PVA is placed in 20 mL of deionized water, stirred evenly at 90 °C until transparent, then 2 g of acrylamide monomer is added. After stirring evenly, 10 mg of oxidant ammonium persulfate and 2 mg of crosslinker N,N'-methylenebisacrylamide are added. The above mixed solution is sealed and degassed, and the free radical polymerization of acrylamide monomer is completed by reacting at 60 °C for 3 h. After repeated freezing and thawing three times, a PVA / PAM IPNs hydrogel can be obtained.

[0053] Step 2: 0.364 g of V2O5 is dispersed in 60 mL of water, and 5 mL of H2O2 is added dropwise and stirred for 30 min until the solution turns orange-red. Then 1.2 g of NaCl is added and stirred for 10 min until clear, obtaining a vanadium oxide sol solution.

[0054] Step 3: Take 1.5 g of PVA / PAM IPNs hydrogel, immerse it in the 60 mL of vanadium oxide sol solution prepared in Step 2, soak for 12 h and then perform freeze-drying. Then, under a nitrogen atmosphere, it is carbonized at a low temperature of 280 °C for 2 h, and the temperature is continuously raised to 800 °C for high-temperature carbonization for 2 h. After washing and drying, a porous carbon / vanadium nitride composite electrode material can be obtained.

[0055] Example 3

[0056] Step 1: 2 g of PVA is placed in 20 mL of deionized water, stirred evenly at 90 °C until transparent, then 2 g of acrylamide monomer is added. After stirring evenly, 10 mg of oxidant ammonium persulfate and 2 mg of crosslinker N,N'-methylenebisacrylamide are added. The above mixed solution is sealed and degassed, and the free radical polymerization of acrylamide monomer is completed by reacting at 60 °C for 3 h. After freeze-thawing three times, PVA / PAM IPNs hydrogel can be obtained.

[0057] Step 2: 0.364 g of V2O5 is dispersed in 60 mL of water, and 5 mL of H2O2 is added dropwise and stirred for 30 min until the solution turns orange-red. Then 1.2 g of NaCl is added and stirred for 10 min until clear to obtain a vanadium oxide sol solution.

[0058] Step 3: Take 1.5 g of PVA / PAM IPNs hydrogel, immerse it in the 60 mL of vanadium oxide sol solution prepared in Step 2, soak for 12 h and then perform freeze-drying. Then, under a nitrogen atmosphere, it is carbonized at a low temperature of 280 °C for 2 h, and the temperature is continuously raised to 900 °C for high-temperature carbonization for 2 h. After washing and drying, a porous carbon / vanadium nitride composite electrode material can be obtained.

[0059] Example 4

[0060] Step 1: 2 g of PVA is placed in 20 mL of deionized water, stirred evenly at 90 °C until transparent, then 2 g of acrylamide monomer is added. After stirring evenly, 10 mg of oxidant ammonium persulfate and 2 mg of crosslinker N,N'-methylenebisacrylamide are added. The above mixed solution is sealed and degassed, and the free radical polymerization of acrylamide monomer is completed by reacting at 60 °C for 3 h. After freeze-thawing three times, PVA / PAM IPNs hydrogel can be obtained.

[0061] Step 2: 0.564 g of V2O5 is dispersed in 60 mL of water, and 6 mL of H2O2 is added dropwise and stirred for 30 min until the solution turns orange-red. Then 1.3 g of NaCl is added and stirred for 10 min until clear to obtain a vanadium oxide sol solution.

[0062] Step 3: Take 2 g of PVA / PAM IPNs hydrogel, immerse it in the 60 mL of vanadium oxide sol solution prepared in Step 2, soak for 6 h and then perform freeze-drying. Then, under a nitrogen atmosphere, it is carbonized at a low temperature of 350 °C for 3 h, and the temperature is continuously raised to 700 °C for high-temperature carbonization for 4 h. After washing and drying, a porous carbon / vanadium nitride composite electrode material can be obtained.

[0063] Example 5

[0064] Step 1: 2 g of PVA is placed in 20 mL of deionized water, stirred evenly at 90 °C until transparent, then 2 g of acrylamide monomer is added. After stirring evenly, 10 mg of oxidant ammonium persulfate and 2 mg of crosslinker N,N'-methylenebisacrylamide are added. The above mixed solution is sealed and degassed, and the free radical polymerization of acrylamide monomer is completed by reacting at 60 °C for 3 h. After freeze-thawing three times, PVA / PAM IPNs hydrogel can be obtained.

[0065] Step 2: 0.455 g of V2O5 is dispersed in 60 mL of water, and 5.5 mL of H2O2 is added dropwise and stirred for 30 min until the solution turns orange-red, then 1.4 g of NaCl is added and stirred for 10 min until clarified to obtain a vanadium oxide sol solution.

[0066] Step 3: Take 1.8 g of PVA / PAM IPNs hydrogel, immerse it in 60 mL of the vanadium oxide sol solution prepared in Step 2, soak for 6 h and then perform freeze-drying. Then, under a nitrogen atmosphere, it is carbonized at a low temperature of 300 °C for 4 h, and the temperature is continuously raised to 700 °C for high-temperature carbonization for 3 h. After washing and drying, a porous carbon / vanadium nitride composite electrode material can be obtained.

[0067] Example 6

[0068] Step 1: 2 g of PVA is placed in 20 mL of deionized water, stirred evenly at 90 °C until transparent, then 2 g of chitosan is added. After stirring evenly, 10 mg of oxidant ammonium persulfate and 2 mg of crosslinker N,N'-methylenebisacrylamide are added. The above mixed solution is sealed and degassed, and polymerization is carried out by reacting at 60 °C for 3 h. After freeze-thawing three times, a polyvinyl alcohol / chitosan interpenetrating network polymer, denoted as PVA / CS IPNs hydrogel, can be obtained.

[0069] Step 2: 0.364 g of V2O5 is dispersed in 60 mL of water, and 5 mL of H2O2 is added dropwise and stirred for 30 min until the solution turns orange-red, then 1.2 g of NaCl is added and stirred for 10 min until clarified to obtain a vanadium oxide sol solution.

[0070] Step 3: Take 1.5 g of PVA / CS IPNs hydrogel, immerse it in 60 mL of the vanadium oxide sol solution prepared in Step 2, soak for 12 h and then perform freeze-drying. Then, under a nitrogen atmosphere, it is carbonized at a low temperature of 280 °C for 2 h, and the temperature is continuously raised to 700 °C for high-temperature carbonization for 2 h. After washing and drying, a porous carbon / vanadium nitride composite electrode material, marked as VN / NPC-PVACS, can be obtained.

[0071] Example 7

[0072] Step 1: 2 g of polyvinylpyrrolidone (PVP) is placed in 20 mL of deionized water, stirred evenly until transparent at 90 °C, then 2 g of acrylamide monomer is added. After stirring evenly, 10 mg of oxidant ammonium persulfate and 2 mg of crosslinking agent N,N'-methylenebisacrylamide are added. The above mixed solution is sealed and degassed, and the free radical polymerization of acrylamide monomer is completed by reacting at 60 °C for 3 h. After repeated freezing and thawing three times, PVP / PAM IPN hydrogel can be obtained.

[0073] Step 2: 0.564 g of V2O5 is dispersed in 60 mL of water, and 6 mL of H2O2 is added dropwise and stirred for 30 min until the solution turns orange-red. Then 1.2 g of NaCl is added and stirred for 10 min until clarified to obtain a vanadium oxide sol solution.

[0074] Step 3: Take 2 g of PVP / PAM IPN hydrogel, immerse it in 60 mL of the vanadium oxide sol solution prepared in Step 2, soak for 10 h and then perform freeze-drying. Then, under a nitrogen atmosphere, it is carbonized at a low temperature of 350 °C for 3 h, and the temperature is continuously raised to 700 °C for high-temperature carbonization for 2 h. After washing and drying, a porous carbon / vanadium nitride composite electrode material can be obtained.

[0075] Example 8

[0076] Step 1: 2 g of PVP is placed in 20 mL of deionized water, stirred evenly until transparent at 90 °C, then 2 g of chitosan is added. After stirring evenly, 10 mg of oxidant ammonium persulfate and 2 mg of crosslinking agent N,N'-methylenebisacrylamide are added. The above mixed solution is sealed and degassed, and the free radical polymerization of acrylamide monomer is completed by reacting at 60 °C for 3 h. After repeated freezing and thawing three times, PVP / CS IPN hydrogel can be obtained.

[0077] Step 2: 0.564 g of V2O5 is dispersed in 60 mL of water, and 5 mL of H2O2 is added dropwise and stirred for 30 min until the solution turns orange-red. Then 1.4 g of NaCl is added and stirred for 10 min until clarified to obtain a vanadium oxide sol solution.

[0078] Step 3: Take 2 g of PVP / PAM IPN hydrogel, immerse it in 60 mL of the vanadium oxide sol solution prepared in Step 2, soak for 8 h and then perform freeze-drying. Then, under a nitrogen atmosphere, it is carbonized at a low temperature of 350 °C for 2 h, and the temperature is continuously raised to 700 °C for high-temperature carbonization for 4 h. After washing and drying, a porous carbon / vanadium nitride composite electrode material can be obtained.

[0079] Comparative Example 1

[0080] Step 1: 2 g of PVA was placed in 20 mL of deionized water, stirred evenly at 90 °C until transparent, then 2 g of acrylamide monomer was added. After stirring evenly, 10 mg of oxidant ammonium persulfate and 2 mg of crosslinker N,N'-methylenebisacrylamide were added. The above mixed solution was sealed and degassed, and the free radical polymerization of acrylamide monomer was completed by reacting at 60 °C for 3 h. After freeze-thawing three times, the PVA / PAM IPNs hydrogel could be obtained.

[0081] Step 2: 5 mL of H2O2 was added dropwise to 60 mL of water and stirred for 30 min to obtain a solution.

[0082] Step 3: Take 1.5 g of PVA / PAM IPNs hydrogel, immerse it in the 60 mL solution prepared in Step 2, soak for 12 h, then perform freeze-drying. Then, under a nitrogen atmosphere, low-temperature carbonization was carried out at 280 °C for 2 h, and the temperature was continuously raised to 700 °C for high-temperature carbonization for 2 h. After washing and drying, the carbon electrode material could be obtained, marked as NC.

[0083] Comparative Example 2

[0084] Step 1: 2 g of PVA was placed in 20 mL of deionized water, stirred evenly at 90 °C until transparent, then 2 g of acrylamide monomer was added. After stirring evenly, 10 mg of oxidant ammonium persulfate and 2 mg of crosslinker N,N'-methylenebisacrylamide were added. The above mixed solution was sealed and degassed, and the free radical polymerization of acrylamide monomer was completed by reacting at 60 °C for 3 h. After freeze-thawing three times, the PVA / PAM IPNs hydrogel could be obtained.

[0085] Step 2: 5 mL of H2O2 was added dropwise to 60 mL of water and stirred for 30 min, then 1.2 g of NaCl was added and stirred for 10 min until clear to obtain a solution.

[0086] Step 3: Take 1.5 g of PVA / PAM IPNs hydrogel, immerse it in the 60 mL solution prepared in Step 2, soak for 12 h, then perform freeze-drying. Then, under a nitrogen atmosphere, low-temperature carbonization was carried out at 280 °C for 2 h, and the temperature was continuously raised to 700 °C for high-temperature carbonization for 2 h. After washing and drying, the porous carbon electrode material could be obtained, marked as NPC.

[0087] Comparative Example 3

[0088] Step 1: 2 g of PVA was placed in 20 mL of deionized water, stirred evenly at 90 °C until transparent, then 2 g of acrylamide monomer was added. After stirring evenly, 10 mg of oxidant ammonium persulfate and 2 mg of crosslinker N,N'-methylenebisacrylamide were added. The above mixed solution was sealed and degassed, and the free radical polymerization of acrylamide monomer was completed by reacting at 60 °C for 3 h. After freeze-thawing three times, the PVA / PAM IPNs hydrogel could be obtained.

[0089] Step 2: 0.364 g of V2O5 is dispersed in 60 mL of water, and 5 mL of H2O2 is added dropwise with stirring for 30 min to obtain a vanadium oxide sol solution.

[0090] Step 3: Take 1.5 g of PVA / PAM IPNs hydrogel, immerse it in the 60 mL of vanadium oxide sol solution prepared in Step 2, freeze-dry it after soaking for 12 h, and then carry out low-temperature carbonization at 280 °C for 2 h under a nitrogen atmosphere, continue to heat up to 900 °C for high-temperature carbonization for 2 h, and after washing and drying, a porous carbon / vanadium nitride composite electrode material can be obtained, marked as VN / NC.

[0091] Comparative Example 4

[0092] Step 1: 2 g of PVA is placed in 20 mL of deionized water, stirred evenly until transparent at 90 °C, then 2 g of chitosan is added, and after stirring evenly, 10 mg of oxidant ammonium persulfate and 2 mg of cross-linking agent N,N'-methylenebisacrylamide are added. The above mixed solution is sealed and degassed, and polymerized at 60 °C for 3 h. After repeated freezing and thawing three times, a PVA / CS IPNs hydrogel can be obtained.

[0093] Step 2: 5 mL of H2O2 is added dropwise to 60 mL of water with stirring for 30 min, and then 1.2 g of NaCl is added and stirred for 10 min until clear to obtain a solution.

[0094] Step 3: Take 1.5 g of PVA / CS IPNs hydrogel, immerse it in the 60 mL of solution prepared in Step 2, freeze-dry it after soaking for 12 h, and then carry out low-temperature carbonization at 280 °C for 2 h under a nitrogen atmosphere, continue to heat up to 700 °C for high-temperature carbonization for 2 h, and after washing and drying, a porous carbon electrode material can be obtained, marked as NPC-CS.

[0095] Commercially available vanadium nitride is additionally purchased as a control group, marked as VN.

[0096] Figure 1 In a, it is the scanning electron microscope image of NPC, and it can be seen that it presents a flaky morphology. Figure 1 In b, it is the scanning electron microscope image of the prepared VN / NPC, and it can be seen that it is also flaky and the surface becomes smooth. Figure 1 In c, it is the transmission electron microscope image of the prepared VN / NPC, and it can be seen that it is flaky. In addition, Figure 1 In d, it is the transmission electron microscope image of the prepared VN / NPC, and white dots can also be seen, representing pore diameters, and the small pore diameters are concentrated at 2.5 nm. Figure 1 In e, the interplanar spacing of the VN(111) crystal plane can also be clearly identified. Figure 1In it, f is the elemental distribution map, and it can be seen that the distributions of C, N, and V elements in the material are uniform.

[0097] Figure 2 In it, a is the XRD pattern of VN / NPC. After comparison, it is the VN phase (JCPDF 35 - 0768), and the score around 24° is attributed to the carbon material, which proves the successful preparation of the VN / NPC material. Figure 2 In it, b is the Raman spectrum. It can be clearly seen that the I D / I G of NPC is close to 1.20, and that of the composite material VN / NPC is 0.91. This is mainly because during the pyrolysis process, the presence of the metal element V increases the orderliness of the local carbon material and improves the graphitization degree, resulting in an increase in I G and a decrease in I D / I G , and further increases the conductivity of the composite material.

[0098] Figure 3 show the electrochemical performances of VN, NC, NPC, VN / NC, and VN / NPC. Figure 3 In it, a is the cyclic voltammetry curve. It can be seen that the shape of the curve is different from the regular rectangular structure, and the energy storage of VN is the pseudocapacitive energy storage mechanism. The synthesized VN / NPC has a larger enclosed area compared with commercial VN, as well as NC, NPC, and VN / PC prepared during the process, which proves that the prepared VN / NPC has a higher specific capacitance. In addition, Figure 3 the charge - discharge curve of b in it also shows that VN / NPC has a longer discharge time. After calculation, as shown in Figure 3 c in it, the specific capacitance of the composite material is 248.3 F / g at a current density of 0.5 A / g, which is greater than the specific capacitances of other materials. The specific capacitance of VN at a current density of 0.5 A / g is 5.4 F / g, that of NC at a current density of 0.5 A / g is 22.3 F / g, that of NPC at a current density of 0.5 A / g is 43.4 F / g, and that of VN / NC at a current density of 0.5 A / g is 213.7 F / g. The reasons for the increase in the specific capacitance of VN / NPC are mainly as follows: (1) The improvement of conductivity helps to improve electron transfer; (2) The emergence of the pore structure helps the full infiltration and mass transfer of the electrolyte; (3) The vanadium nitride nanoparticles and pore structure help to increase the contact area between the electrode material and the electrolyte; (4) NaCl as an inorganic salt template can improve the specific surface area to a certain extent and, in addition, ensure the stability of the gel in the salt solution. Due to the above four reasons, the porous carbon / vanadium nitride composite material prepared in the present invention has a relatively high specific capacitance.

[0099] Figure 4Figure a in [reference] is the SEM image of the carbon material prepared from the PVA / CS IPNs hydrogel as the precursor in Comparative Example 4, and it can be seen that a porous structure is presented. After heat treatment in combination with the VO sol solution, that is, in Example 6, as Figure 4 shown in Figure b in [reference], its morphology is consistent with that of the carbon material, and its surface becomes relatively smooth. By testing the XRD of VN / NPC-PVACS prepared in Example 6, the presence of vanadium nitride and carbon material is found, which proves that the VN / carbon composite material of the present invention is successfully prepared. Figure 4 Figure d in [reference] is the cyclic voltammetry curve. The results show that the carbon material presents a relatively regular rectangular structure, while a peak appears near -0.6 for the VN / NPC-PVACS composite material, which is also an embodiment of the pseudocapacitance of VN. Figure 4 It can be clearly seen from Figure e in [reference] that the composite material has a longer discharge time. After calculation, as Figure 4 shown in Figure f in [reference], the specific capacitance of VN / NPC-PVACS is 120 F / g at 0.5 A / g, which is higher than the corresponding prepared carbon material.

[0100] For VN / NPC prepared in Example 1, under the condition of a current density of 4 A·g -1 , after 10,000 cycles, the capacitance retention rate is 96.2%, indicating that the composite material has a good cycle life.

[0101] Although the preferred embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications to these embodiments once they know the basic creative concept. Therefore, the appended claims are intended to be construed to include the preferred embodiments as well as all changes and modifications falling within the scope of the present invention.

[0102] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these modifications and variations.

Claims

1. A preparation method of a porous carbon / vanadium nitride composite electrode material, characterized in that It includes the following steps: Using an amino-group-containing interpenetrating network polymer as a precursor, after removing moisture, impregnating and complexing it with a vanadium oxide sol, and after the impregnation is completed, an impregnated complex is obtained; Performing primary pyrolysis on the impregnated complex at 280°C to 350°C under a protective atmosphere. During the primary pyrolysis process, the amino-group-containing interpenetrating network polymer undergoes a cyclization reaction, and then performing secondary pyrolysis at 700°C to 900°C. During the secondary pyrolysis process, the easily decomposed macromolecules in the amino-group-containing interpenetrating network polymer decompose to generate pore structures, and the hardly decomposed macromolecules pyrolyze and crosslink into a carbon network structure. The N-H bond and V-O bond break and reconstruct to generate vanadium nitride, and carbon thermally reduces vanadium oxide to generate vanadium nitride, thereby preparing a porous carbon / vanadium nitride composite electrode material.

2. The preparation method of a porous carbon / vanadium nitride composite electrode material according to claim 1, characterized in that, The ratio of the interpenetrating network polymer to the vanadium oxide is 1.5 g to 2 g: 2 mmol to 3 mmol.

3. The preparation method of a porous carbon / vanadium nitride composite electrode material according to claim 1, characterized in that, The time for secondary pyrolysis is 2 h to 4 h.

4. The preparation method of a porous carbon / vanadium nitride composite electrode material according to claim 1, characterized in that, The time for primary pyrolysis is 2 h to 4 h.

5. The preparation method of a porous carbon / vanadium nitride composite electrode material according to claim 1, wherein The impregnation time is 6 h to 12 h.

6. The preparation method of a porous carbon / vanadium nitride composite electrode material according to claim 1, wherein, The preparation steps of the vanadium oxide sol are: dispersing vanadium oxide in water, adding H2O2 and NaCl and stirring to obtain the vanadium oxide sol.

7. The preparation method of a porous carbon / vanadium nitride composite electrode material according to claim 6, characterized in that, The ratio of vanadium oxide to water is 1 mmol to 1.5 mmol: 30 mL; The volume ratio of water to H2O2 is 12:1 to 1.2; The ratio of vanadium oxide to NaCl is 2 mmol to 3 mmol: 1.2 g to 1.4 g.

8. The preparation method of a porous carbon / vanadium nitride composite electrode material according to claim 1, characterized in that, The interpenetrating network polymer is a polyvinyl alcohol / polyacrylamide interpenetrating network polymer, a polyvinylpyrrolidone / polyacrylamide interpenetrating network polymer, a polyvinyl alcohol / chitosan interpenetrating network polymer, or a polyvinylpyrrolidone / chitosan interpenetrating network polymer.

9. A porous carbon / vanadium nitride composite electrode material prepared by the preparation method according to any one of claims 1-8.

10. An application of the porous carbon / vanadium nitride composite electrode material according to claim 9 in the preparation of a supercapacitor.

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