阅读说明：本技术 硫氮共掺三维多孔碳纳米片的制备方法及应用 (Preparation method and application of sulfur-nitrogen co-doped three-dimensional porous carbon nanosheet ) 是由 胡翔 温珍海 于 2019-04-15 设计创作，主要内容包括：本申请公开了一种硫氮共掺三维多孔碳纳米片的制备方法,将含有碳源、硫源、氮源和无机盐模板剂的混合物经煅烧、洗涤,即得到所述硫氮共掺三维多孔碳纳米片。由该方法制得的硫氮共掺三维多孔碳纳米片具有比表面积大、导电性好和活性位点多等优点,将其应用于钾离子混合超级电容器负极中,获得高比能量密度和功率密度的优异性能。(The application discloses a preparation method of a sulfur-nitrogen co-doped three-dimensional porous carbon nanosheet, which comprises the steps of calcining and washing a mixture containing a carbon source, a sulfur source, a nitrogen source and an inorganic salt template agent to obtain the sulfur-nitrogen co-doped three-dimensional porous carbon nanosheet. The sulfur-nitrogen co-doped three-dimensional porous carbon nanosheet prepared by the method has the advantages of large specific surface area, good conductivity, more active sites and the like, and is applied to the negative electrode of a potassium ion hybrid supercapacitor to obtain excellent performances of high specific energy density and power density.)

1. The preparation method of the sulfur-nitrogen co-doped three-dimensional porous carbon nanosheet is characterized in that a mixture containing a carbon source, a sulfur source, a nitrogen source and an inorganic salt template agent is calcined and washed to obtain the sulfur-nitrogen co-doped three-dimensional porous carbon nanosheet.

2. The method according to claim 1, wherein the sulfur source and the nitrogen source in the mixture comprise a substance containing both sulfur and nitrogen;

preferably, the sulfur and nitrogen sources comprise at least one of trithiocyanuric acid, thiourea.

3. The method according to claim 1, wherein the carbon source comprises at least one of organic substances that are readily soluble in water;

preferably, the water-soluble organic substance includes at least one of citric acid, glucose and sucrose.

4. The method of claim 1, wherein the inorganic salt template comprises at least one of sodium chloride and potassium chloride.

5. The method according to claim 1, characterized by comprising at least the following steps:

(a) obtaining a mixture containing a carbon source, a sulfur source, a nitrogen source and an inorganic salt template;

(b) calcining the mixture in an inert atmosphere to obtain an intermediate product;

(c) removing the inorganic salt template agent in the intermediate product to obtain the sulfur-nitrogen co-doped three-dimensional porous carbon nanosheet;

preferably, the step (a) is: dissolving an organic matter which is easy to dissolve in water, a substance containing sulfur and nitrogen and an inorganic salt template agent in water, and drying to obtain a mixture containing a carbon source, a sulfur source, a nitrogen source and the inorganic salt template agent;

preferably, the mass ratio of the water-soluble organic matter, the substance containing sulfur and nitrogen and the inorganic salt template agent is 0.5-1.5: 0.2-0.8: 4 to 6.

6. The production method according to any one of claims 1 to 5, wherein the calcination conditions are: the calcining heating rate is 1-3 ℃/min; the calcining temperature is 700-800 ℃; the calcination time is 1-3 h.

7. A sulfur-nitrogen co-doped three-dimensional porous carbon nanosheet obtained according to the preparation method of any one of claims 1 to 6;

preferably, the sulfur-nitrogen co-doped three-dimensional porous carbon nanosheet comprises macropores, mesopores and micropores;

preferably, the distance between carbon layers in the sulfur-nitrogen co-doped three-dimensional porous carbon nanosheet is 0.38-0.42 nm;

preferably, the specific surface area of the sulfur-nitrogen co-doped three-dimensional porous carbon nanosheet is 450-600 cm²(ii)/g; the pore diameters are distributed in micropores, mesopores and macropores.

8. A negative electrode plate is characterized in that mixed slurry containing the sulfur-nitrogen co-doped three-dimensional porous carbon nanosheet, a conductive agent and a binder, which is obtained by the preparation method of any one of claims 1 to 6, is coated on a copper foil, and is subjected to high-temperature treatment and slicing to obtain the negative electrode plate.

9. The negative electrode sheet according to claim 8, wherein the mass ratio of the sulfur-nitrogen co-doped three-dimensional porous carbon nanosheet, the conductive agent and the binder in the mixed slurry is 7-9: 0.5-1.5: 0.5 to 1.5.

10. A potassium-ion hybrid supercapacitor comprising the negative electrode tab of claim 8 or 9.

Technical Field

The application relates to a preparation method and application of a sulfur-nitrogen co-doped three-dimensional porous carbon nanosheet, and belongs to the technical field of supercapacitors.

Background

Lithium ion batteries, which are currently widely used as energy storage devices, also cause a problem of lithium resource shortage, thereby limiting the use thereof in large-scale energy storage fields. Therefore, scientists turn the research focus to the potassium which is located in the same main group with lithium and has abundant storage and low cost, and the potassium has similar physicochemical properties with lithium, and the working principle of potassium ion batteries and lithium ion batteries is also similar, so that the potassium ion batteries are considered to be one of the most promising energy storage technologies for replacing lithium ion batteries in the future. In recent years, considerable electrode materials have been used for potassium ion storage, among which carbonaceous materials have been widely studied, but the radius of potassium ions is large compared to that of lithium ions, so that diffusion kinetics are seriously affected during electrochemical reaction, and severe volume expansion is caused, thereby resulting in poor cycle stability and low specific capacity. The doped impurity elements can change the energy band structure of the carbonaceous material, improve the conductivity of the material, enlarge the interlayer spacing of the carbonaceous material, facilitate the embedding and the separation of potassium ions with larger radius, provide more reactive active sites and ensure the improvement of specific capacity. Although this approach can improve the specific capacity of the potassium ion battery and thus achieve higher energy density, the power density is still very limited.

The super capacitor has higher power density, can be charged and discharged quickly, has long cycle life, and is widely applied compared with a potassium ion battery, however, compared with the potassium ion battery, the working principle of the super capacitor is that electrolyte ions are absorbed between a positive electrode and a negative electrode to store electric energy, and therefore, the super capacitor has lower energy density. The potassium ion hybrid super capacitor integrates the advantages of a potassium ion battery and the super capacitor, the positive electrode of the potassium ion hybrid super capacitor is made of an activated carbon material with a double electric layer capacitor, and the negative electrode of the potassium ion hybrid super capacitor is made of a negative electrode material in the potassium ion battery with excellent potassium storage capacity, so that high energy density and high power density are simultaneously met. Therefore, the carbon material doped with the hetero element is developed and assembled into the potassium ion capacitor, and the potassium ion capacitor has wide application prospect.

Disclosure of Invention

According to one aspect of the application, the sulfur-nitrogen co-doped three-dimensional porous carbon nanosheet prepared by the method has the advantages of large specific surface area, good conductivity, multiple active sites and the like, and the excellent performances of high specific energy density and power density are obtained by applying the sulfur-nitrogen co-doped three-dimensional porous carbon nanosheet to a negative electrode of a potassium ion hybrid supercapacitor.

A preparation method of a sulfur-nitrogen co-doped three-dimensional porous carbon nanosheet comprises the steps of calcining and washing a mixture containing a carbon source, a sulfur source, a nitrogen source and an inorganic salt template agent to obtain the sulfur-nitrogen co-doped three-dimensional porous carbon nanosheet.

Optionally, the sulfur source and the nitrogen source in the mixture comprise a material containing both sulfur and nitrogen.

Specifically, a substance containing both sulfur and nitrogen, i.e., a substance containing both elemental sulfur and elemental nitrogen.

The preparation method of the sulfur-nitrogen co-doped three-dimensional porous carbon nanosheet at least comprises the following steps: and calcining and washing a mixture containing a carbon source, a substance containing sulfur and nitrogen and an inorganic salt template agent to obtain the sulfur-nitrogen co-doped three-dimensional porous carbon nanosheet.

Optionally, the sulfur and nitrogen sources comprise at least one of trithiocyanuric acid, thiourea.

Optionally, the carbon source comprises at least one of an organic substance that is readily soluble in water.

Optionally, the water-soluble organic substance comprises at least one of citric acid, glucose and sucrose.

Optionally, the inorganic salt templating agent includes at least one of sodium chloride, potassium chloride.

Optionally, at least the following steps are included:

(a) obtaining a mixture containing a carbon source, a sulfur source, a nitrogen source and an inorganic salt template;

(b) calcining the mixture in an inert atmosphere to obtain an intermediate product;

(c) and removing the inorganic salt template agent in the intermediate product to obtain the sulfur-nitrogen co-doped three-dimensional porous carbon nanosheet.

Optionally, the step (a) is: dissolving organic matters which are easy to dissolve in water, substances which simultaneously contain sulfur and nitrogen and inorganic salt template agents in water, and drying to obtain the mixture containing the carbon source, the sulfur source, the nitrogen source and the inorganic salt template agents.

Specifically, the step (a) is as follows: dissolving an organic matter, a sulfur and nitrogen-containing substance and an inorganic salt template agent in water, stirring in a water bath at 50-70 ℃ for 0.5-2 h, and drying in an oven to obtain a mixture (namely the obtained precursor powder) containing a carbon source, a sulfur source, a nitrogen source and the inorganic salt template agent.

The step (b) comprises: the mixture is calcined in an inert atmosphere to obtain an S-N-C/inorganic salt intermediate, for example to obtain an S-N-C/NaCl intermediate. The inert atmosphere comprises at least one of helium, neon, krypton, xenon and radon.

The step (c) comprises: dissolving the obtained S-N-C/inorganic salt intermediate product (such as S-N-C/NaCl intermediate product) in deionized water to obtain an inorganic salt template agent, stirring, and centrifugally drying to obtain the sulfur-nitrogen co-doped three-dimensional porous carbon nanosheet.

Optionally, the mass ratio of the water-soluble organic matter, the substance containing sulfur and nitrogen, and the inorganic salt template agent is 0.5-1.5: 0.2-0.8: 4 to 6.

Alternatively, the calcination conditions in step b) are: the calcining heating rate is 1-3 ℃/min; the calcining temperature is 700-800 ℃; the calcination time is 1-3 h.

According to another aspect of the application, the sulfur-nitrogen co-doped three-dimensional porous carbon nanosheet obtained by the preparation method is also provided.

Optionally, the sulfur-nitrogen co-doped three-dimensional porous carbon nanosheets include macropores, mesopores, and micropores.

Optionally, the distance between carbon layers in the sulfur-nitrogen co-doped three-dimensional porous carbon nanosheet is 0.38-0.42 nm.

In the application, the carbon layer spacing of the sulfur-nitrogen co-doped three-dimensional porous carbon nanosheet is about 0.40 nm.

Optionally, the specific surface area of the sulfur-nitrogen co-doped three-dimensional porous carbon nanosheet is 450-600 cm²(ii)/g; the pore diameters are distributed in micropores, mesopores and macropores.

According to another aspect of the application, a negative electrode sheet is obtained by coating a mixed slurry containing the sulfur-nitrogen co-doped three-dimensional porous carbon nanosheet, the conductive agent and the binder, which is obtained by any one of the preparation methods, on a copper foil, performing high-temperature treatment and slicing.

Optionally, in the mixed slurry, the mass ratio of the sulfur-nitrogen co-doped three-dimensional porous carbon nanosheet to the conductive agent to the binder is 7-9: 0.5-1.5: 0.5 to 1.5.

Specifically, the sulfur and nitrogen co-doped three-dimensional porous carbon nanosheet, the conductive agent and the binder are mixed according to the weight ratio of 7-9: 0.5-1.5: mixing the materials according to a mass ratio of 0.5-1.5, adding deionized water, mixing to obtain mixed slurry, coating the mixed slurry on a copper foil, keeping the temperature of the copper foil in a vacuum drying oven at 90-100 ℃ for 20-30 hours, rolling and slicing to obtain the negative electrode slice.

According to another aspect of the application, a potassium ion hybrid supercapacitor comprises the negative electrode plate.

In the application, a person skilled in the art can select a suitable positive electrode plate in the potassium ion hybrid supercapacitor according to needs, and the application is not strictly limited.

Optionally, the electrolyte in the potassium ion hybrid supercapacitor comprises potassium hexafluorophosphate.

Specific examples are presented below:

in a specific example, a preparation method of a sulfur and nitrogen co-doped three-dimensional porous carbon nanosheet negative electrode material for a potassium ion mixed supercapacitor mainly comprises the following process steps:

(1) dissolving citric acid, trithiocyanuric acid and sodium chloride in water, stirring in a water bath at 60 ℃ for 1h, and evaporating to dryness in an oven at 100 ℃ for 24h to obtain precursor powder;

(2) calcining the obtained precursor powder in argon to obtain an S-N-C/NaCl intermediate product;

(3) dissolving the obtained S-N-C/NaCl intermediate product in deionized water, stirring, and then centrifugally drying to obtain a sulfur-nitrogen co-doped three-dimensional porous carbon nanosheet;

(4) the prepared composite material is used as a negative electrode material and is assembled with an active carbon positive electrode material to form a potassium ion mixed super capacitor, and the electrochemical performance of the super capacitor is tested.

In another specific example, a preparation method of a sulfur and nitrogen co-doped three-dimensional porous carbon nanosheet negative electrode material for a potassium ion mixed supercapacitor mainly comprises the following steps:

(1) sequentially dissolving citric acid, trithiocyanuric acid and sodium chloride in 50ml of water, stirring in a water bath at 60 ℃ for 1h, and evaporating to dryness in an oven at 100 ℃ for 24h to obtain precursor powder;

(2) heating the obtained precursor powder to 750 ℃ in argon at the heating rate of 2 ℃/min, and calcining for 2h to obtain an S-N-C/NaCl intermediate product;

(3) dissolving the obtained S-N-C/NaCl intermediate product in deionized water, stirring, and then centrifugally drying to obtain a sulfur-nitrogen co-doped three-dimensional porous carbon nanosheet;

(4) the prepared composite material is assembled into a potassium ion hybrid supercapacitor, and the electrochemical performance of the supercapacitor is tested in an electrochemical workstation and a blue battery testing system.

In the application, citric acid can be used as a carbon source, trithiocyanuric acid is used as a sulfur source and a nitrogen source, sodium chloride is used as a template agent, the materials are uniformly mixed, and then heat treatment and washing are carried out to obtain the diatom (sulfur and nitrogen) co-doped three-dimensional porous nanosheet carbon material.

The application aims to provide a preparation method of a sulfur and nitrogen co-doped three-dimensional porous carbon nanosheet negative electrode material for a potassium ion mixed super capacitor, the method is simple to operate, and double-hetero-element sulfur and nitrogen can be obtained to be doped simultaneously. The obtained carbon material has unique structural characteristics: double hetero elements (sulfur and nitrogen) are doped in the carbon nano-sheets with three-dimensional porous structures, so that the intrinsic 0.34nm of the carbon layer spacing is enlarged to about 0.40nm, and the active sites of the carbon material are enriched. Thus, there are multiple advantages to potassium ion storage: on one hand, the method is beneficial to the defaulting action of potassium ions, obtains higher potassium storage specific capacity, increases the conductivity of the whole electrode material, is beneficial to the diffusion dynamics of the potassium ions, and obtains excellent rate capability; on the other hand, the three-dimensional porous structure is beneficial to the permeation of electrolyte, reduces the diffusion path of potassium ions and further improves the potassium storage capacity of the electrode material. Finally, high energy density and power density are obtained in the assembled potassium ion hybrid capacitor.

In the present application, the term "substance containing both sulfur and nitrogen" refers to a substance containing both elemental sulfur and elemental nitrogen.

The beneficial effects that this application can produce include:

according to the method, citric acid is used as a carbon source, trithiocyanuric acid is used as a sulfur source and a nitrogen source, sodium chloride is used as a template agent, and the sulfur-nitrogen co-doped nanosheet carbon material with a three-dimensional porous structure can be obtained through a simple dissolving and evaporating process and then high-temperature heat treatment. The sulfur and nitrogen co-doping not only enlarges the interlayer spacing of the carbon material and is beneficial to the embedding and the removing of potassium ions with larger radius, thereby improving the circulating stability of the electrode material, but also enriches the active sites of the carbon material by the sulfur and nitrogen co-doping, so that more potassium ions participate in the reaction, thereby obtaining higher specific capacity; the sulfur and nitrogen codoping also improves the conductivity of the whole electrode material, and is beneficial to the rapid transmission of electrons and ions, so that the diffusion dynamics of the electrode material is improved, and excellent energy density and power density are finally obtained. In addition, the method has the advantages of simple production steps, environmental friendliness, high product yield, easy industrial amplification and realization of commercialization.

Drawings

FIG. 1 is an X-ray diffraction pattern of sample # 1;

FIG. 2 is a field emission scanning electron micrograph of sample # 1;

FIG. 3 is a first TEM image of sample # 1;

FIG. 4 is a second TEM image of sample # 1;

FIG. 5 is a high resolution TEM image of sample # 1;

FIG. 6 shows a nitrogen adsorption/desorption curve (a) and a pore size distribution diagram (b) of sample # 1;

FIG. 7 is a constant current charging and discharging curve diagram of a 1# potassium ion hybrid supercapacitor at different current densities;

FIG. 8 is a graph of energy density of a # 1 potassium ion hybrid supercapacitor at different power densities;

FIG. 9 is a test chart of the long cycle stability performance of the 1# potassium ion hybrid supercapacitor.

Detailed Description

The present application will be described in detail with reference to examples, but the present application is not limited to these examples.

The raw materials in the examples of the present application were all purchased commercially, unless otherwise specified.

In the application, a Miniflex 600 powder X-ray diffractometer is adopted for X-ray diffraction analysis;

the analysis of the field emission scanning electron microscope adopts a Hitachi SU-8020 type field emission scanning electron microscope instrument;

the transmission electron microscope and the high-resolution transmission electron microscope are analyzed by a Tecnai F20 type field emission transmission electron microscope instrument;

the specific surface area and the pore size distribution adopt an ASAP2020 full-automatic specific surface area micropore analyzer;

the electrochemical performance test was performed using CHI760E electrochemical workstation from Shanghai Chenghua, Inc. and Wuhan LANDCT2001 battery test system.