CN117361495A - Porous carbon composite material, flexible electrode, preparation method and application thereof - Google Patents
Porous carbon composite material, flexible electrode, preparation method and application thereof Download PDFInfo
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- CN117361495A CN117361495A CN202311381919.5A CN202311381919A CN117361495A CN 117361495 A CN117361495 A CN 117361495A CN 202311381919 A CN202311381919 A CN 202311381919A CN 117361495 A CN117361495 A CN 117361495A
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- porous carbon
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- sulfur
- carbon composite
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- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 103
- 239000002131 composite material Substances 0.000 title claims abstract description 102
- 229910052799 carbon Inorganic materials 0.000 title claims abstract description 87
- 238000002360 preparation method Methods 0.000 title claims abstract description 25
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 claims abstract description 32
- 229910052717 sulfur Inorganic materials 0.000 claims abstract description 24
- 239000011593 sulfur Substances 0.000 claims abstract description 24
- 239000000463 material Substances 0.000 claims abstract description 17
- AFCIMSXHQSIHQW-UHFFFAOYSA-N [O].[P] Chemical compound [O].[P] AFCIMSXHQSIHQW-UHFFFAOYSA-N 0.000 claims abstract description 16
- 239000003575 carbonaceous material Substances 0.000 claims abstract description 16
- 238000002156 mixing Methods 0.000 claims abstract description 16
- UMGDCJDMYOKAJW-UHFFFAOYSA-N thiourea Chemical compound NC(N)=S UMGDCJDMYOKAJW-UHFFFAOYSA-N 0.000 claims abstract description 16
- 229920002239 polyacrylonitrile Polymers 0.000 claims abstract description 15
- 239000002041 carbon nanotube Substances 0.000 claims abstract description 14
- 229910021393 carbon nanotube Inorganic materials 0.000 claims abstract description 14
- 238000001354 calcination Methods 0.000 claims abstract description 12
- 239000002121 nanofiber Substances 0.000 claims abstract description 12
- 238000003763 carbonization Methods 0.000 claims abstract description 11
- 239000000126 substance Substances 0.000 claims abstract description 11
- 239000011148 porous material Substances 0.000 claims abstract description 10
- 229910019142 PO4 Inorganic materials 0.000 claims abstract description 9
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 claims abstract description 9
- 239000010452 phosphate Substances 0.000 claims abstract description 9
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Natural products NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 claims abstract description 8
- 238000010000 carbonizing Methods 0.000 claims abstract description 5
- 238000013329 compounding Methods 0.000 claims abstract description 3
- 238000000034 method Methods 0.000 claims description 21
- GJEAMHAFPYZYDE-UHFFFAOYSA-N [C].[S] Chemical compound [C].[S] GJEAMHAFPYZYDE-UHFFFAOYSA-N 0.000 claims description 20
- 239000002388 carbon-based active material Substances 0.000 claims description 19
- 239000006258 conductive agent Substances 0.000 claims description 9
- KOUDKOMXLMXFKX-UHFFFAOYSA-N sodium oxido(oxo)phosphanium hydrate Chemical compound O.[Na+].[O-][PH+]=O KOUDKOMXLMXFKX-UHFFFAOYSA-N 0.000 claims description 5
- 239000003990 capacitor Substances 0.000 claims description 3
- MOMKYJPSVWEWPM-UHFFFAOYSA-N 4-(chloromethyl)-2-(4-methylphenyl)-1,3-thiazole Chemical compound C1=CC(C)=CC=C1C1=NC(CCl)=CS1 MOMKYJPSVWEWPM-UHFFFAOYSA-N 0.000 claims description 2
- 239000011230 binding agent Substances 0.000 claims description 2
- 235000019799 monosodium phosphate Nutrition 0.000 claims description 2
- 229910000403 monosodium phosphate Inorganic materials 0.000 claims description 2
- AJPJDKMHJJGVTQ-UHFFFAOYSA-M sodium dihydrogen phosphate Chemical compound [Na+].OP(O)([O-])=O AJPJDKMHJJGVTQ-UHFFFAOYSA-M 0.000 claims description 2
- FQENQNTWSFEDLI-UHFFFAOYSA-J sodium diphosphate Chemical compound [Na+].[Na+].[Na+].[Na+].[O-]P([O-])(=O)OP([O-])([O-])=O FQENQNTWSFEDLI-UHFFFAOYSA-J 0.000 claims description 2
- 235000019983 sodium metaphosphate Nutrition 0.000 claims description 2
- 229940048086 sodium pyrophosphate Drugs 0.000 claims description 2
- 235000019818 tetrasodium diphosphate Nutrition 0.000 claims description 2
- 239000001577 tetrasodium phosphonato phosphate Substances 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 claims 1
- JDZCKJOXGCMJGS-UHFFFAOYSA-N [Li].[S] Chemical compound [Li].[S] JDZCKJOXGCMJGS-UHFFFAOYSA-N 0.000 abstract description 22
- 239000003792 electrolyte Substances 0.000 abstract description 8
- 239000000835 fiber Substances 0.000 abstract description 5
- 230000005540 biological transmission Effects 0.000 abstract description 4
- 230000007547 defect Effects 0.000 abstract description 4
- 230000008595 infiltration Effects 0.000 abstract description 4
- 238000001764 infiltration Methods 0.000 abstract description 4
- 150000002500 ions Chemical class 0.000 abstract description 4
- PFRUBEOIWWEFOL-UHFFFAOYSA-N [N].[S] Chemical compound [N].[S] PFRUBEOIWWEFOL-UHFFFAOYSA-N 0.000 abstract description 3
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 abstract description 3
- 239000001301 oxygen Substances 0.000 abstract description 3
- 229910052760 oxygen Inorganic materials 0.000 abstract description 3
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 27
- 229910052759 nickel Inorganic materials 0.000 description 13
- 238000012360 testing method Methods 0.000 description 10
- 230000000052 comparative effect Effects 0.000 description 8
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 8
- 239000004810 polytetrafluoroethylene Substances 0.000 description 8
- 239000000853 adhesive Substances 0.000 description 7
- 230000001070 adhesive effect Effects 0.000 description 7
- 239000012300 argon atmosphere Substances 0.000 description 6
- 238000006243 chemical reaction Methods 0.000 description 6
- 230000000694 effects Effects 0.000 description 6
- 238000011068 loading method Methods 0.000 description 6
- 239000000203 mixture Substances 0.000 description 6
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 4
- 229910052744 lithium Inorganic materials 0.000 description 4
- 238000002844 melting Methods 0.000 description 4
- 230000008018 melting Effects 0.000 description 4
- 239000002184 metal Substances 0.000 description 4
- 229910052751 metal Inorganic materials 0.000 description 4
- 238000001027 hydrothermal synthesis Methods 0.000 description 3
- 229920001021 polysulfide Polymers 0.000 description 3
- 239000005077 polysulfide Substances 0.000 description 3
- 150000008117 polysulfides Polymers 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 230000003197 catalytic effect Effects 0.000 description 2
- 239000003153 chemical reaction reagent Substances 0.000 description 2
- 230000001351 cycling effect Effects 0.000 description 2
- 238000007599 discharging Methods 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 238000001000 micrograph Methods 0.000 description 2
- 238000007789 sealing Methods 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 1
- PIICEJLVQHRZGT-UHFFFAOYSA-N Ethylenediamine Chemical compound NCCN PIICEJLVQHRZGT-UHFFFAOYSA-N 0.000 description 1
- 102000004310 Ion Channels Human genes 0.000 description 1
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 1
- 229910000990 Ni alloy Inorganic materials 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 239000012298 atmosphere Substances 0.000 description 1
- 230000002238 attenuated effect Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 239000008151 electrolyte solution Substances 0.000 description 1
- 238000010041 electrostatic spinning Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 239000002657 fibrous material Substances 0.000 description 1
- 239000006260 foam Substances 0.000 description 1
- 238000009472 formulation Methods 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 229910001416 lithium ion Inorganic materials 0.000 description 1
- GLNWILHOFOBOFD-UHFFFAOYSA-N lithium sulfide Chemical compound [Li+].[Li+].[S-2] GLNWILHOFOBOFD-UHFFFAOYSA-N 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000002086 nanomaterial Substances 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- -1 polytetrafluoroethylene Polymers 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/05—Preparation or purification of carbon not covered by groups C01B32/15, C01B32/20, C01B32/25, C01B32/30
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- 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
- H01—ELECTRIC ELEMENTS
- 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
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- 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
- H01M4/139—Processes of manufacture
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- 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
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/362—Composites
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- 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
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- 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
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
- H01M4/581—Chalcogenides or intercalation compounds thereof
- H01M4/5815—Sulfides
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- 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
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
- H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- 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
- H01M2004/021—Physical characteristics, e.g. porosity, surface area
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Inorganic Chemistry (AREA)
- Organic Chemistry (AREA)
- Materials Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Composite Materials (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
The invention relates to a porous carbon composite material, a flexible electrode, a preparation method and application thereof. The preparation method of the porous carbon composite material comprises the following steps: the preparation method comprises the steps of firstly compounding polyacrylonitrile nano fibers and carbon nano tubes to form a composite material, carbonizing to obtain a composite carbon material, mixing the composite carbon material with phosphate, calcining for the first time to obtain a phosphorus-oxygen doped material, mixing the phosphorus-oxygen doped material with thiourea, and calcining for the second time to obtain the porous carbon composite material. According to the invention, polyacrylonitrile fibers and carbon nanotubes are combined to form a composite material, and pore structures with different sizes are formed through high-temperature carbonization treatment, so that the specific surface area of the composite material can be increased to load more sulfur simple substances, and electrolyte infiltration and ion transmission can be promoted; and the phosphorus-oxygen double doping and sulfur-nitrogen co-doping can lead the porous carbon composite material to have rich active sites and oxygen-enriched defects. When the porous carbon composite material is applied to a lithium sulfur battery, the capacity and the cycle stability of the lithium sulfur battery can be improved.
Description
Technical Field
The invention relates to the technical field of electrodes, in particular to a porous carbon composite material, a flexible electrode, a preparation method and application thereof.
Background
Compared with the traditional lithium ion battery, the lithium sulfur battery has higher energy density, and the theoretical specific capacity and the theoretical specific energy of the lithium sulfur battery can reach 1675mAh/g and 2600Wh/kg respectively. However, lithium polysulfide is easy to dissolve in electrolyte, and the volume effect generated by elemental sulfur and lithium sulfide in the charge and discharge process is also problematic, so that the theoretical energy density of the lithium sulfur battery is difficult to reach.
At present, increasing the thickness of the electrode is one of the simplest and effective methods for improving the actual energy density of the lithium-sulfur battery, and has obvious improvement effect on the actual energy density of the lithium-sulfur battery. However, in the practical application process, it is found that, along with the increase of the thickness of the electrode, the gap inside the electrode is reduced, so that the wettability of the electrolyte is worse, and the tortuosity is increased, so that the ion transmission path inside the electrode is increased, and the rate capability and the cycle stability of the lithium-sulfur battery are poorer.
Compared with other carbon materials, the carbon nano tube is a one-dimensional nano material, has a relatively large aspect ratio, has stable chemical property, high conductivity and a rough surface of a microstructure, can form a network structure in a 3D space, and is favorable for improving the sulfur loading capacity after being combined with a sulfur simple substance, so that the influence of a thick electrode on the performance of a lithium-sulfur battery is reduced.
For example, the prior art discloses a lithium sulfur battery with ultra-high sulfur-carrying capacity and a preparation method thereof, and the carbon nano tube fiber material with a cross-linked structure is heated after fully mixing sublimed sulfur to obtain a sulfur-carbon composite material, but the sulfur-carrying capacity of the composite material is still low (1.0-8 mg/cm) 2 ) Resulting in a lithium-sulfur battery having a low capacity and poor cycle performance.
Disclosure of Invention
The invention aims to overcome the defects or shortages of low capacity and poor cycle stability of the existing lithium-sulfur battery and provides a preparation method of a porous carbon composite material.
It is another object of the present invention to provide a porous carbon composite.
It is a further object of the present invention to provide the use of a porous carbon composite for the preparation of a flexible electrode, capacitor or battery.
It is another object of the present invention to provide a sulfur-modified porous carbon composite.
It is a further object of the present invention to provide a flexible electrode.
The above object of the present invention is achieved by the following technical scheme:
the invention provides a preparation method of a porous carbon composite material, which comprises the following steps:
s1, compounding polyacrylonitrile nano fibers and carbon nano tubes to form a composite material, and carbonizing the composite material at 800-1200 ℃ for 1-4 hours to obtain a composite carbon material;
s2, mixing the composite carbon material in the S1 with phosphate, performing first calcination treatment to obtain a phosphorus-oxygen doped material, mixing the phosphorus-oxygen doped material with thiourea, and performing second calcination treatment to obtain the porous carbon composite material.
According to the invention, polyacrylonitrile fibers and carbon nanotubes are combined to form a composite material, and pore structures with different sizes are formed through high-temperature carbonization treatment, so that the specific surface area of the composite material can be increased to load more sulfur simple substances, the pores between adjacent fibers can be increased to facilitate electrolyte infiltration and promote ion transmission and transport, and meanwhile, the composite material has a certain binding effect on polysulfide; and the porous carbon material is subjected to phosphorus-oxygen double doping and sulfur-nitrogen co-doping treatment, so that abundant active sites and oxygen-enriched defects can be formed on a carbon skeleton, thermodynamic and kinetic performances of the sulfur electrode in a catalytic process are enhanced, the electrode has high activity and high stability, and the capacity and the cycling stability of the lithium-sulfur battery are further improved.
In the above preparation method, the carbonization treatment, the first calcination treatment, and the second calcination treatment are all performed in an inert gas atmosphere, such as nitrogen or argon.
Optionally, the mass ratio of the composite carbon material to the phosphate in S2 is 1 (1-10), and specifically may be 1:1, 1:2, 13, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9 or 1:10. Optionally, the mass ratio of the thiourea to the phosphorus-oxygen doped material is 1 (1-10), and specifically may be 1:1, 1:2, 13, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9 or 1:10.
Optionally, the mass ratio of the polyacrylonitrile nanofiber to the carbon nanotube in the S1 is (0.1-1): 1, and specifically may be 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1 or 1:1.
Specifically, the average diameter of the polyacrylonitrile nanofiber in S1 is 1 to 200nm, preferably 80 to 120nm, and more preferably 100nm. The polyacrylonitrile nanofiber can be obtained by purchase, and can also be prepared by electrostatic spinning.
Preferably, the temperature of the carbonization treatment in S1 is 1000-1200 ℃, and the time of the carbonization treatment is 2-4 hours. The carbonization treatment may be carried out at a temperature of 1000 ℃, 1100 ℃ or 1200 ℃.
Optionally, the phosphate in S2 is at least one of sodium hypophosphite monohydrate, sodium metaphosphate, sodium dihydrogen phosphate or sodium pyrophosphate.
The invention also provides the porous carbon composite material prepared by the preparation method.
The application of the porous carbon composite material in preparing a flexible electrode, a battery or a capacitor is also within the protection scope of the invention.
The invention protects a sulfur-modified porous carbon composite material, which comprises a porous carbon carrier and sulfur simple substances loaded on the surface and in holes of the porous carbon carrier; the porous carbon carrier is the porous carbon composite material.
The sulfur-modified porous carbon composite material can be prepared by the following preparation method:
and (3) melting sulfur in the mass ratio of (2-4) to (6-8) of the porous carbon composite material and the sublimated sulfur powder to obtain the sulfur-carbon active material.
The invention also provides a flexible electrode, which comprises a sulfur-carbon active material, an adhesive, a conductive agent and a flexible current collector, wherein the sulfur-carbon active material is the sulfur-modified porous carbon composite material.
Specifically, the thickness of the flexible electrode is 1-2 mm, and the flexible electrode can be prepared by the following preparation method:
uniformly mixing a sulfur-carbon active material with a conductive agent KB and a binder PTFE in a mass ratio of 85:5:10 to form a mixture; finally, the mixture and a flexible (nickel screen) current collector are hot rolled at 150 ℃ to obtain the flexible electrode. The method is a dry electrode method without solvent, which not only can reduce the internal resistance of the battery and improve the energy density of the battery, but also can reduce the drying and recovery of the organic solvent and reduce the cost.
Wherein, the flexible current collector can be flexible metal nickel loaded with sulfur simple substance (specifically can be foam nickel, nickel screen, nickel plate, nickel foil or nickel alloy), and can be prepared by the following preparation method:
dissolving sulfur powder in ethylenediamine, adding absolute ethyl alcohol, and mixing to obtain a reaction solution; then adding the reaction solution and a metal flexible nickel screen (which can be cut into the required size according to the requirement and cleaned and dried) into a reaction kettle (polytetrafluoroethylene reaction kettle) for hydrothermal reaction to obtain a vulcanized metal flexible nickel screen, namely a flexible current collector; the temperature and time of the hydrothermal reaction are not particularly limited, and may be conventionally selected. Optionally, the temperature of the hydrothermal reaction is 80-120 ℃ and the time is 6-10 h; specifically, the temperature can be 100 ℃ for 8 hours.
Compared with the prior art, the invention has the beneficial effects that:
according to the invention, polyacrylonitrile fibers and carbon nanotubes are combined to form a composite material, and pore structures with different sizes are formed through high-temperature carbonization treatment, so that the specific surface area of the composite material can be increased to load more sulfur simple substances, the pores between adjacent fibers can be increased to facilitate electrolyte infiltration and promote ion transmission and transport, and meanwhile, the composite material has a certain binding effect on polysulfide; and the porous carbon material is subjected to phosphorus-oxygen double doping and sulfur-nitrogen co-doping treatment, so that abundant active sites and oxygen-enriched defects can be formed on a carbon skeleton of the porous carbon material. When the porous carbon composite material is applied to an electrode, the thermodynamic and kinetic performances of a sulfur electrode in a catalytic process can be enhanced, so that the electrode has high activity and high stability, and the capacity and the cycling stability of a lithium-sulfur battery are further improved.
Drawings
FIG. 1 is a schematic diagram of the flexible electrode in example 1.
Fig. 2 is a scanning electron microscope image of the flexible electrode in example 1.
Fig. 3 is a graph showing cycle performance of lithium sulfur batteries assembled using the flexible electrodes of examples 1 to 6 and comparative examples 1 to 2.
Detailed Description
The invention is further illustrated in the following drawings and specific examples, which are not intended to limit the invention in any way. Unless specifically stated otherwise, the reagents, methods and apparatus employed in the present invention are those conventional in the art.
Reagents and materials used in the following examples are commercially available unless otherwise specified.
Example 1
A method for preparing a porous carbon composite material, comprising the steps of:
s1, uniformly mixing polyacrylonitrile nanofiber (average diameter is 100 nm) and a carbon nano tube according to a mass ratio of 1:1 to form a composite material, and carbonizing the composite material at 1000 ℃ in an argon atmosphere for 2 hours (the heating rate from room temperature to the required temperature is 5 ℃/min) to obtain the composite carbon material;
s2, mixing the composite carbon material in the S1 with phosphate (sodium hypophosphite monohydrate) according to a mass ratio of 1:10, and performing first calcination treatment for 4 hours at 650 ℃ in an argon atmosphere to obtain a phosphorus-oxygen doped material; and then mixing the phosphorus-oxygen doped material with thiourea, and performing a second calcination treatment for 4 hours at 650 ℃ in an argon atmosphere to obtain the porous carbon composite material.
A sulfur-modified porous carbon composite material comprises a porous carbon carrier and sulfur simple substances loaded on the surface and in the pores of the porous carbon carrier; the porous carbon carrier is the porous carbon composite material; can be prepared by the following preparation method: and (3) preserving the heat of the porous carbon composite material and sublimated sulfur powder for 12 hours at 155 ℃ according to the mass ratio of 3:7, and melting sulfur to obtain the composite material.
A flexible electrode (thickness is 1.8mm as shown in figure 1) comprising a sulfur-carbon active material (i.e. the sulfur-modified porous carbon composite material), an adhesive PTFE, a conductive agent KB and a flexible nickel mesh current collector; can be prepared by the following preparation method:
the sulfur-carbon active material, the conductive agent KB and the adhesive PTFE are uniformly mixed according to the mass ratio of 85:5:10, and then the mixture is hot rolled with a flexible nickel screen current collector at 150 ℃ to obtain the flexible electrode with the thickness of 1.8 mm.
Example 2
A method of preparing a porous carbon composite comprising substantially the same steps as in example 1, except that: in the step S1, the mass ratio of the polyacrylonitrile nanofiber to the carbon nanotube is 0.5:1.
A sulfur-modified porous carbon composite substantially the same as in example 1, except that: the porous carbon carrier is the porous carbon composite material.
A flexible electrode substantially the same as in example 1 except that: the sulfur-carbon active material is the sulfur-modified porous carbon composite material.
Example 3
A method of preparing a porous carbon composite comprising substantially the same steps as in example 1, except that: the temperature of the carbonization treatment in step S1 was 1200 ℃.
A sulfur-modified porous carbon composite substantially the same as in example 1, except that: the porous carbon carrier is the porous carbon composite material.
A flexible electrode substantially the same as in example 1 except that: the sulfur-carbon active material is the sulfur-modified porous carbon composite material.
Example 4
A method of preparing a porous carbon composite comprising substantially the same steps as in example 1, except that: the carbonization treatment time in step S1 is 4 hours.
A sulfur-modified porous carbon composite substantially the same as in example 1, except that: the porous carbon carrier is the porous carbon composite material.
A flexible electrode substantially the same as in example 1 except that: the sulfur-carbon active material is the sulfur-modified porous carbon composite material.
Example 5
A method of preparing a porous carbon composite comprising substantially the same steps as in example 1, except that: the mass ratio of the composite carbon material to the sodium hypophosphite monohydrate in the step S2 is 1:5.
A sulfur-modified porous carbon composite substantially the same as in example 1, except that: the porous carbon carrier is the porous carbon composite material.
A flexible electrode substantially the same as in example 1 except that: the sulfur-carbon active material is the sulfur-modified porous carbon composite material.
Example 6
A method of preparing a porous carbon composite comprising substantially the same steps as in example 1, except that: in the step S2, the mass ratio of the phosphorus-oxygen doped material to the thiourea is 1:5.
A sulfur-modified porous carbon composite substantially the same as in example 1, except that: the porous carbon carrier is the porous carbon composite material.
A flexible electrode substantially the same as in example 1 except that: the sulfur-carbon active material is the sulfur-modified porous carbon composite material.
Comparative example 1
A method for preparing a porous carbon composite material, comprising the steps of:
uniformly mixing polyacrylonitrile nanofiber (average diameter is 100 nm) and carbon nano tubes according to a mass ratio of 1:1 to form a composite material, and carbonizing the composite material at 1000 ℃ in an argon atmosphere for 2 hours (the heating rate from room temperature to the required temperature is 5 ℃/min), so as to obtain the porous carbon composite carbon material.
A sulfur-modified porous carbon composite material comprises a porous carbon carrier and sulfur simple substances loaded on the surface and in the pores of the porous carbon carrier; the porous carbon carrier is the porous carbon composite material; can be prepared by the following preparation method: and (3) preserving the heat of the porous carbon composite material and sublimated sulfur powder for 12 hours at 155 ℃ according to the mass ratio of 3:7, and melting sulfur to obtain the composite material.
A flexible electrode, which comprises a sulfur-carbon active material (namely the sulfur-modified porous carbon composite material), an adhesive PTFE, a conductive agent KB and a flexible nickel screen current collector; can be prepared by the following preparation method:
the sulfur-carbon active material, the conductive agent KB and the adhesive PTFE are uniformly mixed according to the mass ratio of 85:5:10, and then the mixture is hot rolled with a flexible nickel screen current collector at 150 ℃ to obtain the flexible electrode with the thickness of 1.8 mm.
Comparative example 2
A method for preparing a porous carbon composite material, comprising the steps of:
s1, uniformly mixing polyacrylonitrile nanofiber (average diameter is 100 nm) and a carbon nano tube according to a mass ratio of 1:1 to form a composite material;
s2, mixing the composite material in the S1 with phosphate (sodium hypophosphite monohydrate) according to a mass ratio of 1:10, and performing first calcination treatment for 4 hours at 650 ℃ in an argon atmosphere to obtain a phosphorus-oxygen doped material; and then mixing the phosphorus-oxygen doped material with thiourea, and performing a second calcination treatment for 4 hours at 650 ℃ in an argon atmosphere to obtain the porous carbon composite material.
A sulfur-modified porous carbon composite material comprises a porous carbon carrier and sulfur simple substances loaded on the surface and in the pores of the porous carbon carrier; the porous carbon carrier is the porous carbon composite material; can be prepared by the following preparation method: and (3) preserving the heat of the porous carbon composite material and sublimated sulfur powder for 12 hours at 155 ℃ according to the mass ratio of 3:7, and melting sulfur to obtain the composite material.
A flexible electrode, which comprises a sulfur-carbon active material (namely the sulfur-modified porous carbon composite material), an adhesive PTFE, a conductive agent KB and a flexible nickel screen current collector; can be prepared by the following preparation method:
the sulfur-carbon active material, the conductive agent KB and the adhesive PTFE are uniformly mixed according to the mass ratio of 85:5:10, and then the mixture is hot rolled with a flexible nickel screen current collector at 150 ℃ to obtain the flexible electrode with the thickness of 1.8 mm.
Performance testing
(1) Morphology testing: the flexible electrode of example 1 was subjected to SEM testing, and a scanning electron microscope image thereof is shown in fig. 2. It can be seen from fig. 2 that the flexible electrode of example 1 has a plurality of mesopores and micropores on the surface thereof, and the pore structure is advantageous for constructing ion channels and storing electrolytes. The morphology and structure of the flexible electrodes in examples 2-6 are similar to example 1.
(2) Sulfur loading test: the sulfur loading of the flexible electrode is calculated by the ratio of the added sulfur content to the electrode formulation, specifically: the electrodes in examples 1 to 6 and comparative examples 1 to 2 were cut into discs of diameter r (19 mm) and weighed to give m, and then the sulfur loading of the flexible electrode was obtained by the following formula:
sulfur loading of the flexible electrode = m 0.85 x 0.7/(pi (0.5 r)) 2 )；
Wherein, 0.85 in the formula refers to 85 percent of the sulfur-carbon active material in the flexible electrode by mass; 0.7 is the mass percent of sulfur powder in the sulfur-carbon active material is 70%.
(3) Testing the performance of the battery; the flexible electrodes in examples 1 to 6 and comparative examples 1 to 2 were assembled into lithium sulfur batteries by the following specific methods: assembling a button cell in a vacuum glove box, firstly placing a metal lithium sheet on a negative electrode shell, and then dripping an electrolyte solution on the positive electrode shell respectively adhered with the flexible electrodes in the embodiment and the comparative example until no bubbles are generated on the surface of the flexible electrode; then the diaphragm is padded on the lithium sheet, redundant electrolyte of the positive electrode shell electrode is sucked by a rubber head dropper and is dripped on the surface of the diaphragm until no bubble exists between the diaphragm and the lithium sheet; and finally, buckling the positive electrode and the negative electrode shell together, sealing the battery by using a sealing machine, taking the battery out of a glove box, standing for 24 hours, and testing on a new battery testing instrument. In the new Wei test cabinet, the battery is connected with the anode and the cathode, new Wei test software on a computer connected with the battery cabinet is opened, a test channel of the connected battery cabinet is opened, and a battery process step is set.
Test conditions:
standing for 3min, discharging at 0.02C rate until the voltage is less than or equal to 0.5V, standing for 3min, charging at 0.02C rate until the voltage is more than or equal to 3V, and pre-circulating for 3 times.
Standing for 3min, discharging at 0.1C rate until the voltage is less than or equal to 0.5V, standing for 3min, charging at 0.1C rate until the voltage is more than or equal to 3V, and circulating for 97 times.
Table 1 sulfur loadings of flexible electrodes prepared in examples 1 to 6 and comparative examples 1 to 2 and specific capacities of batteries after the flexible electrodes were assembled into lithium sulfur batteries
Since the first 3 cycles of the lithium-sulfur battery are the pre-cycles and the 4 th cycle is the main cycle, the discharge specific capacity of the 4 th cycle is taken as the initial discharge specific capacity of the lithium-sulfur battery. As can be seen from the data in table 1 and fig. 3, the lithium sulfur batteries assembled with the flexible electrodes prepared in examples 1 to 6 have initial discharge specific capacities of 1208.4 to 1443.61mAh/g at 0.1C rate, and the decrease in discharge specific capacities after 100 charge and discharge cycles is small, which indicates that the lithium sulfur batteries assembled with the flexible electrodes prepared in examples have stable cycle performance and high discharge specific capacities. The main reason why the discharge specific capacity of the 100 th cycle in examples 1 and 2 is increased compared with the initial discharge specific capacity is that the flexible electrode is thicker (1.8 mm) per se, so that the electrolyte is different in infiltration, and the material is not fully infiltrated; and as the circulation is carried out, the wettability of the material is improved, so that part of the material which does not participate in the reaction also gradually participates in the reaction, and the discharge specific capacity is increased. The initial specific discharge capacities of the lithium sulfur batteries assembled by the flexible electrodes prepared in comparative examples 1 and 2 are 1132.8mAh/g and 1005.6mAh/g respectively at a rate of 0.1C, which are obviously lower than those of the examples, and after 100 charge-discharge cycles, the specific discharge capacities are respectively attenuated to 596.4mAh/g and 499.2mAh/g, which indicates that the battery cycle performance is poor.
The above examples are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above examples, and any other changes, modifications, substitutions, combinations, and simplifications that do not depart from the spirit and principle of the present invention should be made in the equivalent manner, and the embodiments are included in the protection scope of the present invention.
Claims (10)
1. The preparation method of the porous carbon composite material is characterized by comprising the following steps of:
s1, compounding polyacrylonitrile nano fibers and carbon nano tubes to form a composite material, and carbonizing the composite material at 800-1300 ℃ for 1-4 hours to obtain a composite carbon material;
s2, mixing the composite carbon material in the S1 with phosphate, performing first calcination treatment to obtain a phosphorus-oxygen doped material, mixing the phosphorus-oxygen doped material with thiourea, and performing second calcination treatment to obtain the porous carbon composite material.
2. The preparation method according to claim 1, wherein the mass ratio of the composite carbon material to the phosphate in S2 is 1 (1-10); the mass ratio of the thiourea to the phosphorus-oxygen doped material is 1 (1-10).
3. The preparation method according to claim 1, wherein the mass ratio of the polyacrylonitrile nanofiber to the carbon nanotube in S1 is (0.1-1): 1.
4. The method according to claim 1, wherein the average diameter of the polyacrylonitrile nanofiber in S1 is 1 to 200nm.
5. The method according to claim 1, wherein the temperature of the carbonization treatment in S1 is 1000 to 1200 ℃, and the time of the carbonization treatment is 2 to 4 hours.
6. The method according to claim 1, wherein the phosphate in S2 is at least one of sodium hypophosphite monohydrate, sodium metaphosphate, sodium dihydrogen phosphate, and sodium pyrophosphate.
7. A porous carbon composite material produced by the production method of any one of claims 1 to 6.
8. Use of the porous carbon composite of claim 7 in the preparation of a flexible electrode, capacitor or battery.
9. The sulfur modified porous carbon composite material is characterized by comprising a porous carbon carrier and sulfur simple substances loaded on the surface and in the pores of the porous carbon carrier; the porous carbon support is the porous carbon composite of claim 7.
10. A flexible electrode comprising a sulfur-carbon active material, a binder, a conductive agent, and a flexible current collector, wherein the sulfur-carbon active material is the sulfur-modified porous carbon composite of claim 9.
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