CN112993231A - Carbon-sulfur composite electrode and preparation and application thereof - Google Patents

Carbon-sulfur composite electrode and preparation and application thereof Download PDF

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CN112993231A
CN112993231A CN201911276739.4A CN201911276739A CN112993231A CN 112993231 A CN112993231 A CN 112993231A CN 201911276739 A CN201911276739 A CN 201911276739A CN 112993231 A CN112993231 A CN 112993231A
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carbon
sulfur
carbon nitride
nitride
composite
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张洪章
贾子阳
李先锋
张华民
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Dalian Institute of Chemical Physics of CAS
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H01M4/02—Electrodes composed of, or comprising, active material
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    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H01M4/06—Electrodes for primary cells
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
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    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
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    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
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    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
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    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
    • H—ELECTRICITY
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Abstract

The invention discloses a sulfur/carbon nitride-carbon composite electrode taking a composite material of carbon nitride and carbon as a main material and application thereof in a lithium-sulfur battery. The electrode is prepared by compounding carbon nitride and a carbon material as a main body material, and charging sulfur to obtain the sulfur/carbon nitride-carbon composite electrode, so that the sulfur/carbon nitride-carbon composite electrode has a strong chemical adsorption effect on polysulfide generated in the cycle process of the lithium-sulfur battery, inhibits the shuttle flying of the polysulfide, and improves the cycle stability and cycle life of the battery. The carbon material can obviously improve the conductivity of the carbon nitride material, is beneficial to the dispersion of a precursor, reduces the size of carbon nitride particles, improves the ionic electron conductivity, reduces the polarization and improves the multiplying power performance. The preparation process is simple, the material cost is low, the performance is stable, and the method has good application prospect.

Description

Carbon-sulfur composite electrode and preparation and application thereof
Technical Field
The invention relates to preparation and application of a sulfur/carbon nitride-carbon composite electrode for a lithium-sulfur battery.
Background
The lithium-sulfur battery becomes one of the new generation secondary batteries with good potential due to the characteristics of high theoretical specific capacity, low cost, environmental protection and the like, and has wide application prospect. The lithium-sulfur battery mainly comprises four parts, namely a positive electrode, a negative electrode, electrolyte and a diaphragm, and the total reaction equation of the battery is as follows: 16Li + S8→8Li2S, during battery cycling due primarily to (1) the positive discharge process accompanied by 80% volume expansion; (2) the positive electrode active material sulfur has poor conductivity; (3) the shuttle effect (polysulfide dissolves in the electrolyte and diffuses between the positive electrode and the negative electrode under the influence of concentration) and the like lead to the reduction of the battery performance, and influence the industrialization development of the lithium-sulfur battery. At present, the defects are improved mainly by adopting a carbon-sulfur composite positive electrode, in order to further enhance the sulfur fixation performance of the electrode, heteroatom doping such as nitrogen and oxygen is introduced into a carbon material, and the shuttle effect is inhibited through the polar interaction of a heteroatom polar group and polysulfide. Researches show that the polar interaction between pyridine type nitrogen atoms and polysulfide is strongest, but through the traditional nitrogen atom doping means, such as high-temperature treatment under the condition of ammonia gas or mixed calcination with melamine and the like, the content of the nitrogen atoms is difficult to exceed 15at percent, the doping amount is usually less than 10at percent and the regulation is difficult, the sulfur fixing performance of the material is limited due to the low density of active sites of the nitrogen atoms, and the doped nitrogen atoms comprise pyrrole type nitrogen, graphite type nitrogen and the like besides the pyridine type nitrogen, the interaction between the doped nitrogen atoms and the polysulfide is weak, and the sulfur fixing capacity is further influenced. The carbon nitride material is taken as a positive electrode main body material by researchers, has 57 percent of theoretical nitrogen atom content and has the nitrogen atom active site density which is obviously higher than that of conventional materialsThe nitrogen in the carbon nitride material is mainly pyridine type nitrogen, so that the sulfur fixing capacity is strong. However, carbon nitride itself has poor conductivity, and carbon nitride synthesized by the conventional method is mostly a large particle product with low specific surface area, and the practical effect is limited.
Disclosure of Invention
The invention aims to provide a sulfur/carbon nitride-carbon composite electrode for a lithium-sulfur battery. In the invention, a carbon material and a carbon material composite mode are adopted, a continuous conductive network is constructed by the carbon material, the carbon nitride material is loaded on the surface and in a pore structure of the carbon material, and then sulfur is loaded on the carbon nitride material, so that the defect of poor conductivity of the carbon nitride material is overcome, the dispersity of the carbon nitride material is enhanced, the particle size is reduced, the specific surface is improved, the sulfur of an active substance is distributed more uniformly and is contacted with a main material more fully, the polarization of a battery is reduced, and the cycle performance and the rate capability are improved.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
a sulfur/carbon nitride-carbon composite electrode for a lithium sulfur battery.
One or more than two organic polymer resins, a conductive agent and a sulfur/carbon nitride-carbon compound are mixed in an organic solvent, blade-coated on a current collector, and dried to obtain the sulfur/carbon nitride-carbon composite electrode.
The organic polymer resin is one or more of Polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), carboxymethyl cellulose (CMC), Styrene Butadiene Rubber (SBR), polyvinylpyrrolidone (PVP), Polystyrene (PS), polyvinyl alcohol (PVA), polyethylene glycol (PEG), polyvinylidene fluoride (PVDF), polyether sulfone (PES) and polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP).
The conductive agent is one or more than two of commercialized carbon nano-tube, graphene, carbon nano-fiber, BP2000, KB600, KB300, XC-72, Super-P, acetylene black and active carbon.
The sulfur/carbon nitride-carbon composite is one or more of a carbon nano tube, graphene, carbon nano fiber, BP2000, KB600, KB300, XC-72, Super-P, acetylene black, activated carbon or a carbon material modified or activated by the carbon nano tube, is mixed with one or more of a precursor trithiocyanuric acid, cyanamide, aminoguanidine, melamine, melam, melem or a related derivative thereof of the carbon nitride material, is ground and uniformly mixed to enable the precursor of the carbon nitride material to be adsorbed on the surface and in a pore structure of the carbon material, and is then subjected to heat treatment at 400-600 ℃ in a nitrogen or/and argon atmosphere for 1-6 hours to obtain the carbon nitride-carbon composite; and filling sulfur by a melting method to obtain a sulfur/carbon nitride-carbon composite, wherein the sulfur is distributed on the surface and in pores of the composite material, the sulfur content of the sulfur/carbon nitride-carbon composite is 50-80 wt%, and the mass ratio of the carbon nitride to the carbon is 3:1-99:1, preferably 5:1-10: 1.
The sulfur/carbon nitride-carbon composite is characterized in that: the carbon material is coated by the carbon nitride particles, the carbon material forms a continuous conductive network, a precursor of the carbon nitride material is adsorbed on the surface and in the pore structure of the carbon material, the carbon nitride material is distributed around the carbon material and in the pore structure after heat treatment, and the sulfur is distributed on the surface and in the pore structure of the carbon nitride particles.
The sulfur/carbon nitride-carbon composite electrode has the advantages that the mass of the organic polymer resin accounts for 2-20 wt% of the total mass of the electrode; the conductive agent accounts for 0-20 wt% of the total mass of the electrode; the balance being a sulfur/carbon nitride-carbon composite;
the sulfur content of the sulfur/carbon nitride-carbon composite is 50 wt% -80 wt%, and the mass ratio of the carbon nitride to the carbon is 3:1-99: 1.
The sulfur/carbon nitride-carbon composite electrode preferably comprises 5-10 wt% of organic polymer resin; the conductive agent accounts for 5-10 wt% of the total mass of the electrode; the balance being a sulfur/carbon nitride-carbon composite;
the sulfur content in the sulfur/carbon nitride-carbon composite is 60 to 70 weight percent.
The sulfur/carbon nitride-carbon composite electrode can be used in lithium-sulfur secondary batteries and lithium-sulfur primary batteries.
The beneficial results of the invention are:
the carbon nitride material is used as the main body material of the lithium-sulfur positive electrode, and has strong interaction with polysulfide due to high nitrogen atom active site density, so that the effect of inhibiting polysulfide shuttle flying is achieved. However, carbon nitride itself has poor conductivity, and carbon nitride synthesized by the conventional method is mostly a large particle product with low specific surface area, and the practical effect is limited. At present, the defect of poor conductivity of carbon nitride is improved by compounding carbon nitride and a carbon material, but no specific composite structure of carbon nitride and carbon is provided, the carbon material is simply introduced into a carbon nitride system, the performance improvement is limited, and the adopted method is complex, for example, a high molecular template is used as a carbon source or a carbon component is introduced by adopting methods such as vapor deposition and the like, the process is complex, the cost is high, and the large-scale production and application are difficult to realize.
The invention provides a composite structure of a carbon nitride-coated carbon material, which utilizes the characteristics of high specific surface and high porosity of the carbon material, adsorbs a carbon nitride precursor material on the surface and in pores of the carbon material in the process of grinding and uniformly mixing, and leads the precursor to be polymerized in situ to grow carbon nitride on the surface and in the pore structure of the carbon material, thereby improving the dispersibility of the carbon nitride and overcoming the defect of low utilization rate of the traditional large-particle carbon nitride material. The carbon material is in the carbon nitride coating structure, interaction between carbon nitride and polysulfide on the outer layer is not influenced, a continuous carbon material conductive network can be formed, the electron conductivity of the electrode is improved, and excellent effects on the aspects of restraining polysulfide shuttles, improving battery capacity exertion and rate capability are shown. The method has the advantages of few selection limits on carbon nitride precursors and carbon materials, easy regulation and control of material proportion, simple process, low cost, capability of flexibly meeting different production requirements and wide application prospect.
Drawings
FIG. 1: the sulfur/carbon nitride-carbon composite electrode and the sulfur/carbon composite electrode prepared by the method are compared in cycle performance at 0.5C multiplying power. In FIG. 1, the abscissa represents the number of cycles and the ordinate represents the specific discharge capacity mAh g-1。
FIG. 2: the sulfur/carbon nitride-carbon composite electrode and the sulfur/carbon composite electrode prepared by the method have a comparison graph of the cycle performance under the multiplying power of 1C. In FIG. 2, the abscissa represents the number of cycles, and the ordinate represents the lengthLabeled as specific discharge capacity mAh g-1。
FIG. 3: the sulfur/carbon nitride-carbon composite electrode and the sulfur/carbon composite electrode prepared by the method are shown in a ratio performance comparison graph under the ratio of 0.2-5C. In FIG. 3, the abscissa represents the number of cycles and the ordinate represents the specific discharge capacity mAh g-1。
FIG. 4: the sulfur/carbon nitride-carbon composite electrode and the sulfur/nitrogen-doped carbon material composite electrode prepared by the method have a comparison graph of the cycle performance at the multiplying power of 0.5C. In FIG. 4, the abscissa represents the number of cycles and the ordinate represents the specific discharge capacity mAh g-1。
FIG. 5: the sulfur/carbon nitride-carbon composite electrode and the sulfur/carbon nitride electrode prepared by the method are compared in cycle performance at 0.5C multiplying power. In FIG. 5, the abscissa represents the number of cycles and the ordinate represents the specific discharge capacity mAh g-1。
FIG. 6: the sulfur/carbon nitride-carbon composite electrode and the sulfur/carbon based composite material electrode prepared by the method have a comparison graph of the cycle performance under the multiplying power of 1C. In FIG. 6, the abscissa represents the number of cycles and the ordinate represents the specific discharge capacity mAh g-1。
Detailed Description
The following examples are further illustrative of the present invention and are not intended to limit the scope of the present invention.
Comparative example 1
10g of commercial carbon material Keqin black was placed in a tube furnace under Ar protection at 5 ℃ for min-1Heating to 900 deg.C, introducing steam for activation for 1.5h, wherein the flow rate of steam is 600mL min-1The activated carbon material was designated A-KB. Mixing 3.0g A-KB with 7.3g S, placing in a tube furnace, heating to 155 deg.C under argon atmosphere, and heating at 1 deg.C for min-1And keeping the temperature for 20 hours, and recording the obtained product sulfur/carbon composite as S/KB, wherein the sulfur content in the S/KB is 70 wt%.
Dissolving PVDF in N-methylpyrrolidone (NMP), stirring until the PVDF is completely dissolved to obtain a PVDF solution with the mass fraction of 5 wt%, adding S/KB, Super P, the PVDF solution and NMP into a weighing bottle according to the proportion, adjusting the solid content of the slurry to be 12.5%, wherein the mass of the S/KB is 0.24g, the mass of the Super P is 0.03g, the mass of the 5 wt% PVDF solution is 0.6g, and the mass of the NMP is 1.5g, stirring for 5 hours to obtain uniform slurry, scraping and coating an electrode with the diameter of 200 mu m on an aluminum foil, drying for 12 hours at the temperature of 60 ℃, and cutting into a wafer with the diameter of 14mm to be a sulfur/carbon composite electrode.
The method comprises the steps of using a sulfur/carbon composite electrode as a positive electrode, a lithium sheet as a negative electrode, a clegard 2325 as a diaphragm, using a mixed solution (volume ratio v/v is 1:1) containing 2 mass percent of lithium nitrate and 1M lithium bis (trifluoromethylsulfonyl) imide (LiTFSI) electrolyte and a solvent of 1, 3-Dioxolane (DOL) and ethylene glycol dimethyl ether (DME) as an electrolyte, assembling a battery, and testing the cycle performance of the battery at the multiplying power of 0.5C.
Example 1
Grinding 4g of trithiocyanuric acid and 0.15g of A-KB, uniformly mixing, placing in a tube furnace, heating to 550 ℃ under the argon atmosphere, and heating at the rate of 5 ℃ for min-1Keeping the temperature for 4 hours to obtain a product which is a carbon nitride-carbon compound and is marked as C3N4KB, C in the product3N4The mass ratio to KB is 7: 1. Take 3.0g C3N4Uniformly mixing-KB and 7.3g S, placing in a tube furnace, heating to 155 ℃ in argon atmosphere, and heating at a rate of 1 ℃ for min-1Keeping the temperature for 20 hours, and marking the obtained product sulfur/carbon nitride-carbon composite as S/C3N4-KB。S/C3N4Sulfur content in-KB was 70%.
Electrodes were prepared in the same manner as in comparative example 1, replacing S/KB with S/C of equal mass3N4KB, i.e. adding S/C3N4-KB mass of 0.24g, Super P mass of 0.03g, 5% PVDF solution mass of 0.6g, NMP mass of 1.5g, electrode preparation and cell assembly according to the same method and cell cycling performance test at 0.5C rate. The sulfur content was 70% by mass of the composite, and the carbon nitride content was 26% by mass of the composite.
Comparative example 2
An electrode was prepared and a battery was assembled in the same manner as in comparative example 1, and a battery cycle performance test was performed at a rate of 1C.
Example 2
An electrode was prepared and a battery was assembled using the same method as in example 1, and a battery cycle performance test was performed at a 1C rate.
Comparative example 3
Electrodes were prepared and cells were assembled in the same manner as in comparative example 1, and different cell rate performance tests were performed.
Example 3
Grinding and uniformly mixing 4g of trithiocyanuric acid (TTCA) and 0.15g of graphene, placing the mixture in a tubular furnace, heating to 550 ℃ under the argon atmosphere, and heating at the rate of 5 ℃ for min-1Keeping the temperature for 4 hours, and obtaining a product which is a carbon nitride-graphene compound and marked as C3N4G, C in the product3N4The mass ratio of the graphene to the graphene is 7: 1. Take 3.0g C3N4Uniformly mixing the-G and 7.3G S, placing in a tube furnace, heating to 155 ℃ in argon atmosphere at a heating rate of 1 ℃ for min-1Keeping the temperature for 20 hours, and marking the obtained product sulfur/carbon nitride-carbon composite as S/C3N4-G。S/C3N4Sulfur content in-KB was 70%.
An electrode was prepared in the same manner as in example 1, and S/C was added3N4-KB replacement by equal mass S/C3N4G, i.e. addition of S/C3N4The mass of G was 0.24G, the mass of Super P was 0.03G, the mass of 5% PVDF solution was 0.6G, and the mass of NMP was 1.5G, and electrodes were prepared and batteries were assembled according to the same method for battery rate performance test. The sulfur content was 70% by mass of the composite, and the carbon nitride content was 26% by mass of the composite.
Comparative example 4
Placing 4gA-KB into a tube furnace, heating to 700 ℃ under argon atmosphere, and heating at a rate of 5 ℃ for min-1Conversion of the atmosphere in NH3Keeping the temperature in the atmosphere for 2h, and marking the obtained nitrogen-doped carbon material as NKB. Mixing 3.0g NKB and 7.3g S, heating to 155 deg.C in a tube furnace at a heating rate of 1 deg.C for min-1And keeping the temperature for 20h, and marking the obtained product sulfur/nitrogen-doped carbon composite as S/NKB. The sulfur content in S/NKB was 70%.
An electrode was fabricated in the same manner as in comparative example 1, S/KB was replaced with S/NKB of equal mass, i.e., S/NKB mass was added in an amount of 0.24g, Super P mass was added in an amount of 0.03g, 5% PVDF solution mass was added in an amount of 0.6g, and NMP mass was added in an amount of 1.5g, and the electrode was fabricated in the same manner and assembled to perform a battery cycle performance test at a rate of 0.5C. The sulfur content accounts for 70% of the mass ratio of the composite, and the nitrogen-doped carbon material accounts for 30% of the mass ratio of the composite. Wherein the nitrogen content accounts for 8 percent of the mass ratio of the carbon material.
Comparative example 5
Putting 4g of trithiocyanuric acid into a tube furnace, heating to 550 ℃ under the argon atmosphere, wherein the heating rate is 5 ℃ for min-1Keeping the temperature for 4 hours to obtain a product of carbon nitride which is marked as C3N4. Take 3.0g C3N4Mixing with 7.3g S, placing in a tube furnace, heating to 155 deg.C under argon atmosphere at a heating rate of 1 deg.C for min-1Keeping the temperature for 20 hours, and marking the obtained product sulfur/carbon nitride compound as S/C3N4。S/C3N4The sulphur content was 70%.
Electrodes were prepared in the same manner as in comparative example 1, replacing S/KB with S/C of equal mass3N4I.e. addition of S/C3N4The mass was 0.24g, the Super P mass was 0.03g, the 5% PVDF solution mass was 0.6g, and the NMP mass was 1.5g, and the electrode was prepared and the cell was assembled according to the same method to perform the cell cycle performance test at 0.5C rate. The sulfur content was 70% by mass of the composite, and the carbon nitride content was 30% by mass of the composite.
Comparative example 6
Weighing 20g of urea, placing into a crucible with a cover, placing into a muffle furnace, heating to 650 deg.C at 2.5 deg.C/min, performing thermal polymerization for 4 hr, and naturally cooling to obtain yellowish block g-C3N4. Mixing the blocks g-C3N4And grinding, dispersing in absolute ethyl alcohol by ultrasonic waves, stirring, setting the temperature to be room temperature, setting the ultrasonic time to be 60min, centrifuging or filtering, cleaning, and drying in vacuum for 12h to obtain the two-dimensional layered graphite carbon nitride.
Weighing 10g of two-dimensional layered graphite carbon nitride and 2.5g of ferric oxide, mixing, grinding for 60min, ball-milling for 90min at the speed of 600rpm, taking out, placing in a quartz boat, placing in a tube furnace, introducing ethylene at the flow rate of 3.5L/min, heating to 750 ℃ at the heating rate of 10 ℃/min, carrying out chemical vapor deposition for 2h, taking out after natural cooling, placing in a beaker, adding 60ml of 30 wt% hydrochloric acid, carrying out ultrasonic treatment for 1h, centrifuging, cleaning to neutrality by using absolute ethyl alcohol and deionized water, and carrying out vacuum drying at the temperature of 60 ℃ to obtain the black carbon-based composite material.
Mixing 3.0g of carbon-based composite material with 7.3g S, placing in a tube furnace, heating to 155 ℃ in argon atmosphere at a heating rate of 1 ℃ for min-1And keeping the temperature for 20h, and recording the obtained product sulfur/carbon-based composite material as S/NC. The sulfur content accounted for 70% by mass of S/NC.
An electrode was fabricated in the same manner as in comparative example 1, replacing S/KB with S/NC of the same mass, i.e., adding 0.24g of S/NC mass, 0.03g of Super P mass, 0.6g of 5% PVDF solution mass, and 1.5g of NMP mass, and fabricating an electrode and assembling a battery to perform a battery cycle performance test at a 1C rate according to the same manner. The sulfur content accounts for 70% of the mass ratio of the composite.
Evaluation of the results of examples:
as can be seen from the comparison of the data in fig. 1, the sample of example 1 has higher capacity exertion and capacity retention than the sample of comparative example 1 at 0.5C rate over 500 cycles of testing. Example 1 the first round specific discharge capacity was 1220mAh g-1The discharge specific capacity of the fifth hundred circles is 617mAh g-1Significantly higher than the sample of comparative example 1. This is also confirmed by the cycling results at 1C rate in FIG. 2, where the first cycle specific discharge capacity of example 2 in FIG. 2 is 1049mAh g-1The discharge specific capacity of the second hundred circles is 758mAh g-1Also higher than the sample of comparative example 2. As can be seen from the comparison of the data in FIG. 3, in the rate capability, the example 3 has higher capacity exertion and rate capability compared with the comparative example 3, and the specific capacity reaches 772mAh g at high rates of 2C, 3C and 5C respectively-1、759mAh g-1、741mAh g-1. As can be seen from the comparison of the data in fig. 4, the sample of example 1 still had higher capacity exertion and capacity retention relative to the sample prepared with the nitrogen-doped carbon material in comparative example 4. From the comparison of the data in FIG. 5, it can be seen thatAs a result, the sample of example 1 exhibited higher capacity exertion and better capacity retention relative to the carbon nitride material not composited with the carbon material in comparative example 5. In comparison with the data in fig. 6, it can be seen from the comparison of the data in fig. 6 that the carbon nitride-carbon material prepared by the method of comparative example 6 shows better electrochemical performance when applied to the positive electrode of the lithium sulfur battery, compared with the carbon-based composite material obtained by coating and depositing a layer of carbon outside the carbon nitride, mainly because the carbon material deposited outside the carbon nitride affects the interaction between the carbon nitride and the polysulfide, the sulfur fixing effect is limited, and the carbon component on the outer layer does not significantly improve the structure of the carbon nitride. As can be seen from the comparison of the performance of the examples, the sulfur/carbon nitride-carbon composite electrode has superior cycle performance and rate capability to the carbon-sulfur composite electrode prepared from the commercial carbon material and the nitrogen-doped carbon material. The main reason is that the carbon nitride material is used as the anode main body material, the density of nitrogen atom active sites is high, and nitrogen atoms in the carbon nitride material are mainly pyridine type nitrogen, so that the sulfur fixing capacity is strong, and good cycle performance is obtained. The carbon nitride material and the carbon material are compounded, a continuous carbon conductive network is introduced, the defect of poor conductivity of the carbon nitride material is overcome, meanwhile, the dispersity of the carbon nitride material is enhanced, the particle size is reduced, the specific surface is improved, the sulfur distribution is more uniform, and the excellent rate capability is ensured.
The data comparison proves that the sulfur/carbon nitride-carbon composite material can obviously improve the comprehensive performance of the electrode and is convenient to apply.

Claims (8)

1. A sulfur/carbon nitride-carbon composite electrode is composed of organic polymer resin, a conductive agent and a sulfur/carbon nitride-carbon composite, or is composed of organic polymer resin and a sulfur/carbon nitride-carbon composite;
the mass of the organic polymer resin accounts for 2-20 wt% of the total mass of the electrode; the conductive agent accounts for 0-20 wt% of the total mass of the electrode; the balance being a sulfur/carbon nitride-carbon composite;
the sulfur content of the sulfur/carbon nitride-carbon composite is 50 wt% -80 wt%, and the mass ratio of the carbon nitride to the carbon is 3:1-99: 1.
2. The sulfur/carbon nitride-carbon composite electrode according to claim 1, wherein: preferably, the mass of the organic polymer resin accounts for 5-10 wt% of the total mass of the electrode; the conductive agent accounts for 5-10 wt% of the total mass of the electrode; the balance being a sulfur/carbon nitride-carbon composite;
the sulfur content in the sulfur/carbon nitride-carbon composite is 60 to 70 weight percent.
3. The sulfur/carbon nitride-carbon composite electrode according to claim 1 or 2, wherein:
the organic polymer resin is one or more of Polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), carboxymethyl cellulose (CMC), Styrene Butadiene Rubber (SBR), polyvinylpyrrolidone (PVP), Polystyrene (PS), polyvinyl alcohol (PVA), polyethylene glycol (PEG), polyvinylidene fluoride (PVDF), polyether sulfone (PES) and polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP);
the conductive agent is one or more than two of commercialized carbon nano-tube, graphene, carbon nano-fiber, BP2000, KB600, KB300, XC-72, Super-P, acetylene black and active carbon.
4. The sulfur/carbon nitride-carbon composite electrode according to claim 1 or 2, wherein: the sulfur/carbon nitride-carbon composite is one or more of a carbon nano tube, graphene, carbon nano fiber, BP2000, KB600, KB300, XC-72, Super-P, acetylene black, activated carbon or a carbon material modified or activated by the carbon nano tube, is mixed with one or more of a precursor trithiocyanuric acid, cyanamide, aminoguanidine, melamine, melam, melem or a related derivative thereof of the carbon nitride material, is ground and uniformly mixed to enable the precursor of the carbon nitride material to be adsorbed on the surface and in a pore structure of the carbon material, and is then subjected to heat treatment at 400-600 ℃ in a nitrogen or/and argon atmosphere for 1-6 hours to obtain the carbon nitride-carbon composite; and filling sulfur by a melting method to obtain a sulfur/carbon nitride-carbon composite, wherein the sulfur is distributed on the surface and in pores of the composite material, the sulfur content of the sulfur/carbon nitride-carbon composite is 50-80 wt%, and the mass ratio of the carbon nitride to the carbon is 3:1-99:1, preferably 5:1-10: 1.
5. The sulfur/carbon nitride-carbon composite according to claim 1 or 4, wherein: the carbon material is coated by the carbon nitride particles, the carbon material forms a continuous conductive network, the carbon nitride material is distributed on the surface and in the pore structure of the carbon material after heat treatment, and the sulfur is distributed on the surface and in the pore structure of the carbon nitride particles.
6. A method for preparing a sulfur/carbon nitride-carbon composite electrode according to any one of claims 1 to 5, characterized in that:
mixing organic polymer resin, a conductive agent and a sulfur/carbon nitride-carbon compound in an organic solvent, blade-coating on a current collector, and drying to obtain the sulfur/carbon nitride-carbon compound electrode.
7. The method of claim 6, wherein: the carbon-sulfur composite electrode can be prepared by the following process,
(1) stirring organic polymer resin in an organic solvent at the temperature of 20-100 ℃ for 0.5-2 h to form a corresponding polymer solution;
adding a conductive agent and a sulfur/carbon nitride-carbon compound into the solution, and fully stirring for 2-10 hours at the temperature of 20-50 ℃ to finally prepare a blending solution; wherein the solid content is 5-30 wt%;
(2) pouring the blending solution prepared in the step (1) on a current collector, and forming an integral body after blade coating;
(3) drying the electrode prepared in the step (2), wherein the drying time is 2-48 h, and obtaining a finished product of the sulfur/carbon nitride-carbon composite electrode;
the organic solvent is one or more than two of DMSO, DMAC, NMP and DMF.
8. Use of a sulfur/carbon nitride-carbon composite electrode according to any one of claims 1 to 7, wherein: the sulfur/carbon nitride-carbon composite electrode can be used in lithium-sulfur secondary batteries and lithium-sulfur primary batteries.
CN201911276739.4A 2019-12-12 2019-12-12 Carbon-sulfur composite electrode and preparation and application thereof Pending CN112993231A (en)

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