CN114497499A - Lithium sulfide/carbon composite material with multilevel structure and preparation method and application thereof - Google Patents
Lithium sulfide/carbon composite material with multilevel structure and preparation method and application thereof Download PDFInfo
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- 229910052799 carbon Inorganic materials 0.000 title claims abstract description 114
- GLNWILHOFOBOFD-UHFFFAOYSA-N lithium sulfide Chemical compound [Li+].[Li+].[S-2] GLNWILHOFOBOFD-UHFFFAOYSA-N 0.000 title claims abstract description 110
- 239000002131 composite material Substances 0.000 title claims abstract description 92
- 238000002360 preparation method Methods 0.000 title claims abstract description 40
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- 239000000463 material Substances 0.000 claims abstract description 69
- 238000000137 annealing Methods 0.000 claims abstract description 65
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- 238000000034 method Methods 0.000 claims abstract description 38
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- 229910052744 lithium Inorganic materials 0.000 claims abstract description 27
- 239000000843 powder Substances 0.000 claims abstract description 25
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims abstract description 24
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- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 30
- 238000010438 heat treatment Methods 0.000 claims description 27
- INHCSSUBVCNVSK-UHFFFAOYSA-L lithium sulfate Inorganic materials [Li+].[Li+].[O-]S([O-])(=O)=O INHCSSUBVCNVSK-UHFFFAOYSA-L 0.000 claims description 24
- RBTVSNLYYIMMKS-UHFFFAOYSA-N tert-butyl 3-aminoazetidine-1-carboxylate;hydrochloride Chemical compound Cl.CC(C)(C)OC(=O)N1CC(N)C1 RBTVSNLYYIMMKS-UHFFFAOYSA-N 0.000 claims description 24
- 229910052573 porcelain Inorganic materials 0.000 claims description 21
- 238000003756 stirring Methods 0.000 claims description 20
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- 229910052757 nitrogen Inorganic materials 0.000 claims description 15
- 238000011065 in-situ storage Methods 0.000 claims description 14
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- 238000009777 vacuum freeze-drying Methods 0.000 claims description 13
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- JDZCKJOXGCMJGS-UHFFFAOYSA-N [Li].[S] Chemical compound [Li].[S] JDZCKJOXGCMJGS-UHFFFAOYSA-N 0.000 claims description 8
- 239000012298 atmosphere Substances 0.000 claims description 6
- 230000001681 protective effect Effects 0.000 claims description 6
- UMGDCJDMYOKAJW-UHFFFAOYSA-N thiourea Chemical compound NC(N)=S UMGDCJDMYOKAJW-UHFFFAOYSA-N 0.000 claims description 6
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- 230000014759 maintenance of location Effects 0.000 abstract description 11
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- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 2
- 239000002033 PVDF binder Substances 0.000 description 2
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- 238000011068 loading method Methods 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
- 239000002073 nanorod Substances 0.000 description 2
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
- 150000002815 nickel Chemical class 0.000 description 2
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 2
- 239000007774 positive electrode material Substances 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 239000002344 surface layer Substances 0.000 description 2
- -1 triethylborohydride Chemical compound 0.000 description 2
- 238000007740 vapor deposition Methods 0.000 description 2
- WNXJIVFYUVYPPR-UHFFFAOYSA-N 1,3-dioxolane Chemical compound C1COCO1 WNXJIVFYUVYPPR-UHFFFAOYSA-N 0.000 description 1
- 239000013543 active substance Substances 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
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- 150000003949 imides Chemical class 0.000 description 1
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- 238000002791 soaking Methods 0.000 description 1
- 238000013112 stability test Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
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- 230000002194 synthesizing effect Effects 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- YLQBMQCUIZJEEH-UHFFFAOYSA-N tetrahydrofuran Natural products C=1C=COC=1 YLQBMQCUIZJEEH-UHFFFAOYSA-N 0.000 description 1
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- 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
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y40/00—Manufacture or treatment of nanostructures
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- 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
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- 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
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- 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
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- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
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- H01M4/625—Carbon or graphite
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- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/028—Positive electrodes
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Abstract
The invention provides a lithium sulfide/carbon composite material with a multilevel structure and a preparation method and application thereof, wherein the preparation method comprises the following steps: mixing a lithium source, a metal salt solution and a graphene oxide solution, drying to obtain a precursor material, carrying out annealing treatment on the precursor material and organic compound powder together, and carrying out autocatalytic reaction and thermal reduction reaction under the annealing treatment condition to obtain the multi-level structure lithium sulfide/carbon composite material. The lithium sulfide/carbon composite material with the multilevel structure, which is obtained by the preparation method, can stabilize the structure through the composite action of lithium sulfide, reductive graphene oxide and the carbon hybrid nanotube, improves the conductivity, can effectively relieve the volume change of the lithium sulfide/carbon composite nanomaterial in the charging and discharging processes, and has excellent specific cyclic capacity and capacity retention rate.
Description
Technical Field
The invention belongs to the technical field of material science, and relates to a lithium sulfide/carbon composite material with a multilevel structure, and a preparation method and application thereof.
Background
Lithium-sulfur batteries have high theoretical specific energy and abundant raw material resources, and have attracted extensive attention as a new generation of energy devices with development prospects. The existing lithium-sulfur battery anode material can be divided into a carbon/elemental sulfur composite material and a carbon/lithium sulfide composite material, wherein the carbon/elemental sulfur composite material can generate larger volume expansion in the first cycle of charge and discharge, the structure of the material is damaged, and the utilization rate of active sulfur is reduced, so that the electrochemical performance of the battery is influenced; the carbon/lithium sulfide composite material has a certain shrinkage structure in the primary charging process, provides space for lithium-embedded discharge reaction, protects an electrode structure from being damaged, and can be assembled with a non-lithium metal negative electrode material to effectively avoid potential safety hazards caused by lithium dendrites. Therefore, the carbon/lithium sulfide composite material has wider application as a cathode material of the lithium-sulfur battery.
At present, most of the carbon/lithium sulfide composite materials are prepared by a method of firstly synthesizing and then compounding, namely, a carbon material is prepared firstly, and then lithium sulfide is loaded in the carbon material through various ways. In addition, the lithium sulfide material is sensitive to moisture, so that the preparation process of the carbon/lithium sulfide composite material is complex and expensive.
CN106784754A discloses a method for preparing a carbon nanotube-lithium sulfide-carbon composite material, which comprises mixing a tetrahydrofuran solution of carbon nanotube/lithium triethylborohydride and an anhydrous toluene solution of sublimed sulfur powder, heating and evaporating to dryness, and then performing vapor deposition to obtain the carbon nanotube-lithium sulfide-carbon composite material. The method has a complex operation process, is difficult to uniformly compound the carbon material and the lithium sulfide, has high requirements on production equipment and environment for the preparation of the lithium sulfide material, and invisibly improves the preparation cost of the material.
CN106229487A discloses a method for preparing a carbon/lithium sulfide composite cathode material of a lithium-sulfur battery by carbothermic reduction of lithium sulfate, which takes a composite material containing lithium sulfate as a precursor, and directly prepares the carbon/lithium sulfide composite material by carbothermic reduction. The method directly uses lithium sulfate and carbon or carbon-containing organic matter to prepare the carbon/lithium sulfide composite material by high-temperature carbothermic reduction. The composite material synthesized by the method has poor shape controllability and unstable material quality, and finally the electrochemical performance of the synthesized composite material is seriously influenced.
CN105406034A discloses a three-dimensional porous graphene loaded carbon-coated lithium sulfide cathode material and a preparation method and application thereof, wherein the method comprises the steps of dispersing graphene oxide in water, adding a reducing agent, stirring and dissolving, and then placing at 120-200 ℃ for hydrothermal reaction for 4-12 h to obtain a solution of columnar three-dimensional porous graphene; adding lithium sulfate and a carbon source into the solution of the columnar three-dimensional porous graphene to form a soaking solution of the columnar three-dimensional porous graphene; freeze-drying the soak solution to obtain a precursor; and calcining the precursor for 2-12 h at 800-1000 ℃ in a protective atmosphere to obtain the three-dimensional porous graphene loaded carbon-coated lithium sulfide material. The three-dimensional porous graphene loaded carbon-coated lithium sulfide material prepared by the method can be directly sliced to prepare the battery anode, and the steps of slurry preparation, coating and drying are omitted.
None of the above documents effectively solves the problems of poor dispersion of the lithium sulfide active material in the composite material and general structural stability of the carbon/lithium sulfide composite material. Therefore, it is urgently needed to develop a novel carbon/lithium sulfide composite material to further improve the electrochemical performance of the battery.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a multi-level structure lithium sulfide/carbon composite material and a preparation method and application thereof.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the present invention provides a method for preparing a lithium sulfide/carbon composite material with a multilevel structure, the method comprising:
mixing a lithium source, a metal salt solution and a graphene oxide solution, drying to obtain a precursor material, carrying out annealing treatment on the precursor material and organic compound powder together, and carrying out autocatalytic reaction and thermal reduction reaction under the annealing treatment condition to obtain the multi-level structure lithium sulfide/carbon composite material.
The precursor material comprises a graphene oxide layer, and a lithium source and metal salt which are uniformly dispersed on the two side surfaces of the graphene oxide layer, and it is noted that in the annealing treatment process, the precursor material and the organic compound powder are not mixed, but are respectively placed at the two ends of the porcelain boat for annealing treatment together. Wherein, in the annealing process, the lithium source on the surface of the graphene oxide layer reacts under the condition of thermal reduction to generate lithium sulfide; carrying out thermal reduction reaction on the graphene oxide layer to generate reductive graphene oxide with better conductivity; in the annealing process, the organic compound powder generates the carbon hybrid nanotube in situ under the autocatalysis of the active metal nanoparticles through chemical molecular vapor deposition. Therefore, thermal reduction reaction and autocatalytic reaction are carried out under the condition of annealing treatment, and the lithium sulfide/carbon composite material with the multi-level structure is constructed, wherein lithium sulfide particles are dispersed on the surfaces of two sides of the reductive graphene oxide layer, and meanwhile, carbon hybrid nanotubes grow on the reduction sites on the surfaces of two sides of the reductive graphene oxide layer.
The multi-level structure lithium sulfide/carbon composite material obtained by the preparation method provided by the invention simultaneously has lithium sulfide, reductive graphene oxide and a carbon hybrid nanotube, the composite effect of the lithium sulfide, the reductive graphene oxide and the carbon hybrid nanotube can stabilize the structure of the material, the conductivity of the material is improved, the layered structure of the reductive graphene oxide and the carbon hybrid nanotube generated in situ have unique space confinement effect on the lithium sulfide material, the volume expansion and contraction of the lithium sulfide/carbon composite nanomaterial in the charging and discharging process are relieved, and the lithium sulfide/carbon composite material has excellent specific cycle capacity and capacity retention rate.
As a preferred technical solution of the present invention, the preparation process of the precursor material comprises:
dissolving the lithium source in the metal salt solution, adding the graphene oxide solution to obtain a mixed solution, separating the mixed solution to obtain a precipitate, and drying the precipitate to obtain the precursor material.
The lithium source and the metal salt solution in the precursor material obtained by the invention can be uniformly dispersed on the surface of the graphene oxide layer, thereby ensuring that the subsequent lithium sulfide active substance has better dispersibility in the composite material. In addition, the concentration of the selected graphene oxide solution is preferably 10mg/mL, and the added volume is 30-100 mL.
In a preferred embodiment of the present invention, the lithium source includes lithium sulfate.
The lithium source in the present invention is preferably lithium sulfate because lithium sulfate is inexpensive and forms a lithium sulfide material by the annealing treatment provided by the present invention. Further, the amount of the lithium source added in the present invention is preferably 0.1 g.
Preferably, the solute in the metal salt solution comprises Co (NO)3)2·6H2O、Fe(NO3)2·9H2O or Ni (NO)3)2·6H2Any of O, more preferably Co (NO)3)2·6H2O。
Preferably, the metal salt solution has a concentration of 1 to 10 wt%, for example 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt% or 10 wt%, but is not limited to the recited values, and other values not recited within the range of values are also applicable; further preferably 4 to 6 wt%.
According to the invention, a certain mass of metal salt solid is weighed according to the concentration of a metal salt solution, and then the metal salt solid is dissolved in 50mL of deionized water to obtain the metal salt solution.
Preferably, the mass ratio of the lithium source to the graphene oxide in the graphene oxide solution is 1 (3-10), and may be, for example, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9 or 1:10, but is not limited to the enumerated values, and other unrecited values within the numerical range are also applicable; further preferably 1 (3-5).
The mass ratio of the lithium source to the graphene oxide in the graphene oxide solution is limited to 1 (3-10), and when the mass ratio is lower than 1:3, the shape controllability of the synthesized lithium sulfide/carbon composite anode material is poor and the material quality is unstable, because the addition amount of the graphene oxide is small, the lithium sulfate carbon thermal reduction reaction and the in-situ autocatalysis reaction of active metal nanoparticles are incomplete; when the mass ratio is higher than 1:10, the first-turn capacity and cycle capacity of the positive electrode of the lithium sulfur battery are greatly reduced, because the excessive carbon material reduces the loading amount of lithium sulfide as a positive active material.
As a preferable technical scheme of the invention, the mixed solution is sequentially subjected to stirring, ultrasonic dispersion and separation treatment to obtain a precipitate.
Preferably, the stirring speed is 450-550 rpm/min, such as 450rpm/min, 470rpm/min, 490rpm/min, 510rpm/min, 530rpm/min or 550rpm/min, but not limited to the recited values, and other values not recited in the range of the values are also applicable.
Preferably, the stirring time is 10-14 h, for example, 10h, 10.5h, 11h, 11.5h, 12h, 12.5h, 13h, 13.5h or 14h, but is not limited to the values listed, and other values not listed in the range of the values are also applicable.
Preferably, the ultrasonic dispersion time is 20-40 min, such as 20min, 22min, 24min, 26min, 28min, 30min, 32min, 34min, 36min, 38min or 40min, but not limited to the enumerated values, and other non-enumerated values in the range of the enumerated values are also applicable.
The invention adopts a high-power ultrasonic machine to perform basic Ningultrasonic dispersion.
Preferably, the separation process comprises centrifugation.
The rotational speed of the centrifugal separation in the present invention is preferably 8000rpm/min, and the time is preferably 5 min.
Preferably, the precipitate is pretreated in liquid nitrogen for 8-12 min, such as 8min, 8.5min, 9min, 9.5min, 10min, 10.5min, 11min, 11.5min or 12min before drying, but not limited to the recited values, and other values not recited in the range of the values are also applicable.
Preferably, the drying time is 10-14 h, for example, 10h, 10.5h, 11h, 11.5h, 12h, 12.5h, 13h, 13.5h or 14h, but is not limited to the recited values, and other values not recited in the range of the values are also applicable.
Preferably, the drying comprises vacuum freeze drying.
As a preferable technical scheme of the invention, the precursor material and the organic compound powder are respectively placed at two ends in the porcelain boat, and annealing treatment is carried out after covering.
The annealing treatment according to the invention is preferably carried out in a tube furnace.
Preferably, the mass ratio of the organic compound powder to the precursor material is (1-20): 1, and may be, for example, 1:1, 2:1, 4:1, 6:1, 8:1, 10:1, 12:1, 14:1, 16:1, 18:1 or 20:1, but is not limited to the recited values, and other values not recited within the numerical range are equally applicable; more preferably (8-12): 1.
The mass ratio of the organic compound powder to the precursor material is limited to (1-20): 1, and when the mass ratio is lower than 1:1, the active metal nanoparticles cannot be subjected to autocatalysis to generate the carbon hybrid nanotubes in situ, because a small amount of organic compound powder is completely vaporized at high temperature and is not enough to support chemical vapor deposition reaction; when the quality is higher than 20:1, the shape controllability of the generated carbon hybrid nanotube is poor, so that the material has poor electrochemical performance, and the large amount of organic compound powder generates the carbon hybrid nanotube with the uncontrollable shape in the annealing process, thereby influencing the capacity exertion of the lithium sulfide active material.
Preferably, the organic compound powder includes any one of melamine, urea, or thiourea, and is further preferably melamine.
In a preferred embodiment of the present invention, the annealing temperature is 600 to 900 ℃, for example, 600 ℃, 630 ℃, 650 ℃, 680 ℃, 700 ℃, 720 ℃, 750 ℃, 780 ℃, 800 ℃, 830 ℃, 850 ℃, 880 ℃, or 900 ℃, but not limited to the recited values, and other values not recited within the range of the values are also applicable; further preferably 650 to 750 ℃.
The annealing temperature is limited to 600-900 ℃, and when the temperature is lower than 600 ℃, the raw material lithium sulfate cannot be completely carbothermally reduced to generate lithium sulfide, because the lower temperature does not meet the condition of high-temperature thermal reduction; when the temperature is higher than 900 ℃, the in-situ chemical vapor deposition can be caused to generate thicker and shorter carbon hybrid nanorods, because the excessive temperature limits the self-catalytic thermal reduction reaction kinetics of the active metal nanoparticles.
Preferably, the annealing time is 0.5-2 h, such as 0.5h, 0.8h, 1h, 1.2h, 1.5h, 1.8h or 2h, but not limited to the recited values, and other values not recited in the range of the values are also applicable; more preferably 0.5 to 1 hour.
The annealing treatment time is limited to 0.5-2 h, and when the annealing treatment time is less than 0.5h, the carbothermic reduction reaction is incomplete, because the shorter annealing time does not meet the condition of high-temperature thermal reduction; when the time is longer than 2h, the carbon hybrid nanotubes with uncontrollable morphology can be generated in situ, which is caused by the long annealing time, and the carbon hybrid nanotubes can grow on the surface layer of the reduced graphene oxide uncontrollably and continuously.
Preferably, the temperature increase rate of the annealing treatment is 1 to 20 ℃/min, for example, 1 ℃/min, 2 ℃/min, 4 ℃/min, 6 ℃/min, 8 ℃/min, 10 ℃/min, 12 ℃/min, 14 ℃/min, 16 ℃/min, 18 ℃/min or 20 ℃/min, but is not limited to the enumerated values, and other non-enumerated values within the numerical range are also applicable; further preferably 5 to 10 ℃/min.
Preferably, the annealing treatment is performed under a protective atmosphere.
As a preferable technical solution of the present invention, the preparation method comprises:
(1) dissolving a lithium source in a metal salt solution with the concentration of 1-10 wt%, and adding a graphene oxide solution with the concentration of 8-12 mg/mL to obtain a mixed solution, wherein the mass ratio of the lithium source to the graphene oxide in the graphene oxide solution is 1 (3-10);
(2) stirring the mixed solution obtained in the step (1) at the rotating speed of 450-550 rpm/min for 10-14 h, then performing ultrasonic dispersion for 20-40 min, separating to obtain a precipitate, then placing the precipitate in liquid nitrogen for pretreatment for 8-12 min, and drying for 10-14 h to obtain a precursor material;
(3) and (3) respectively placing the organic compound powder and the precursor material obtained in the step (2) at two ends in a porcelain boat according to the mass ratio of (1-20) to 1, covering the porcelain boat, heating to 600-900 ℃ at the heating rate of 1-20 ℃/min in a protective atmosphere, carrying out annealing treatment for 0.5-2 h, and carrying out autocatalytic reaction and thermal reduction reaction under the annealing treatment condition to obtain the multi-stage structure lithium sulfide/carbon composite material.
In the invention, after the multi-level structure lithium sulfide/carbon composite material is obtained by annealing treatment and is cooled to room temperature, the multi-level structure lithium sulfide/carbon composite material is taken out under protective atmosphere.
In a second aspect, the invention provides a lithium sulfide/carbon composite material with a multilevel structure, which is prepared by the preparation method of the first aspect.
As a preferable technical scheme, the lithium sulfide/carbon composite material with the multilevel structure comprises a reductive graphene oxide layer, lithium sulfide particles are dispersed on the two side surfaces of the reductive graphene oxide layer, and carbon hybrid nanotubes grow in situ on the two side surfaces of the reductive graphene oxide layer.
In a third aspect, the present invention provides a lithium-sulfur battery comprising the multi-stage structure lithium sulfide/carbon composite of the second aspect.
Compared with the prior art, the invention has the beneficial effects that:
the multi-level structure lithium sulfide/carbon composite material prepared by the preparation method provided by the invention simultaneously has lithium sulfide, reductive graphene oxide and a carbon hybrid nanotube, the composite effect of the lithium sulfide, the reductive graphene oxide and the carbon hybrid nanotube can stabilize the structure of the material, the conductivity of the material is improved, the layered structure of the reductive graphene oxide and the carbon hybrid nanotube generated in situ have unique space confinement effect on the lithium sulfide material, the volume expansion and contraction of the lithium sulfide/carbon composite nanomaterial in the charging and discharging process are relieved, and the lithium sulfide/carbon composite material has excellent specific circulation capacity and capacity retention rate.
Drawings
Fig. 1 is a flow chart illustrating the preparation of a multi-stage structure lithium sulfide/carbon composite material provided in examples 1 to 9 of the present invention.
Detailed Description
The technical solution of the present invention is further explained by the following embodiments. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.
Example 1
The embodiment provides a preparation method of a lithium sulfide/carbon composite material with a multilevel structure, as shown in fig. 1, the preparation method comprises the following steps:
(1) 2.5g of Co (NO)3)2·6H2Dissolving O in 50mL of deionized water to obtain a cobalt salt solution with the concentration of 5 wt%, adding 0.1g of lithium sulfate to dissolve in the cobalt salt solution, and then adding 50mL of graphene oxide solution with the concentration of 10mg/mL to obtain a mixed solution;
(2) stirring the mixed solution obtained in the step (1) at the rotating speed of 500rpm/min for 12h, then performing ultrasonic dispersion for 30min, then performing centrifugal separation at the rotating speed of 8000rpm/min for 5min to obtain a precipitate, then placing the precipitate in liquid nitrogen for pretreatment for 10min, and performing vacuum freeze drying for 12h to obtain a precursor material;
(3) and (3) respectively placing melamine powder and the precursor material obtained in the step (2) at two ends in a porcelain boat according to a mass ratio of 10:1, covering, heating to 700 ℃ at a heating rate of 5 ℃/min in a nitrogen atmosphere, carrying out annealing treatment for 0.5h, and carrying out autocatalytic reaction and thermal reduction reaction under the annealing treatment condition to obtain the multi-stage structure lithium sulfide/carbon composite material.
Example 2
The embodiment provides a preparation method of a lithium sulfide/carbon composite material with a multilevel structure, as shown in fig. 1, the preparation method comprises the following steps:
(1) 2.5g of Fe (NO)3)2·9H2Dissolving O in 50mL of deionized water to obtain an iron salt solution with the concentration of 5 wt%, adding 0.1g of lithium sulfate to dissolve in the iron salt solution, and then adding 50mL of graphene oxide solution with the concentration of 10mg/mL to obtain a mixed solution;
(2) stirring the mixed solution obtained in the step (1) at the rotating speed of 500rpm/min for 12h, then performing ultrasonic dispersion for 30min, then performing centrifugal separation at the rotating speed of 8000rpm/min for 5min to obtain a precipitate, then placing the precipitate in liquid nitrogen for pretreatment for 10min, and performing vacuum freeze drying for 12h to obtain a precursor material;
(3) and (3) respectively placing the urea powder and the precursor material obtained in the step (2) at two ends in a porcelain boat according to the mass ratio of 10:1, covering the porcelain boat, heating to 750 ℃ at the heating rate of 5 ℃/min in the nitrogen atmosphere, carrying out annealing treatment for 0.5h, and carrying out autocatalytic reaction and thermal reduction reaction under the annealing treatment condition to obtain the multi-stage structure lithium sulfide/carbon composite material.
Example 3
The embodiment provides a preparation method of a lithium sulfide/carbon composite material with a multilevel structure, as shown in fig. 1, the preparation method comprises the following steps:
(1) 2.5g of Ni (NO)3)2·6H2Dissolving O in 50mL of deionized water to obtain a nickel salt solution with the concentration of 5 wt%, adding 0.1g of lithium sulfate to dissolve in the nickel salt solution, and then adding 50mL of graphene oxide solution with the concentration of 10mg/mL to obtain a mixed solution;
(2) stirring the mixed solution obtained in the step (1) at the rotating speed of 500rpm/min for 12h, then performing ultrasonic dispersion for 30min, then performing centrifugal separation at the rotating speed of 8000rpm/min for 5min to obtain a precipitate, then placing the precipitate in liquid nitrogen for pretreatment for 10min, and performing vacuum freeze drying for 12h to obtain a precursor material;
(3) and (3) respectively placing melamine powder and the precursor material obtained in the step (2) at two ends in a porcelain boat according to a mass ratio of 20:1, covering, heating to 800 ℃ at a heating rate of 10 ℃/min in a nitrogen atmosphere, carrying out annealing treatment for 1h, and carrying out autocatalytic reaction and thermal reduction reaction under the annealing treatment condition to obtain the multi-stage structure lithium sulfide/carbon composite material.
Example 4
The embodiment provides a preparation method of a lithium sulfide/carbon composite material with a multilevel structure, as shown in fig. 1, the preparation method comprises the following steps:
(1) 5g of Co (NO)3)2·6H2Dissolving O in 50mL of deionized water to obtain a cobalt salt solution with the concentration of 10 wt%, adding 0.1g of lithium sulfate to dissolve in the cobalt salt solution, and then adding 100mL of graphene oxide solution with the concentration of 10mg/mL to obtain a mixed solution;
(2) stirring the mixed solution obtained in the step (1) at the rotating speed of 500rpm/min for 12h, then performing ultrasonic dispersion for 30min, then performing centrifugal separation at the rotating speed of 8000rpm/min for 5min to obtain a precipitate, then placing the precipitate in liquid nitrogen for pretreatment for 10min, and performing vacuum freeze drying for 12h to obtain a precursor material;
(3) and (3) respectively placing thiourea powder and the precursor material obtained in the step (2) at two ends in a porcelain boat according to a mass ratio of 10:1, covering, heating to 700 ℃ at a heating rate of 2 ℃/min in a nitrogen atmosphere, carrying out annealing treatment for 2h, and carrying out autocatalytic reaction and thermal reduction reaction under the annealing treatment condition to obtain the multi-stage structure lithium sulfide/carbon composite material.
Example 5
The embodiment provides a preparation method of a lithium sulfide/carbon composite material with a multilevel structure, as shown in fig. 1, the preparation method comprises the following steps:
(1) 2.5g of Co (NO)3)2·6H2Dissolving O in 50mL of deionized water to obtain a cobalt salt solution with the concentration of 5 wt%, adding 0.1g of lithium sulfate to dissolve in the cobalt salt solution, and then adding 50mL of graphene oxide solution with the concentration of 10mg/mL to obtain a mixed solution;
(2) stirring the mixed solution obtained in the step (1) at the rotating speed of 500rpm/min for 12h, then performing ultrasonic dispersion for 30min, then performing centrifugal separation at the rotating speed of 8000rpm/min for 5min to obtain a precipitate, then placing the precipitate in liquid nitrogen for pretreatment for 10min, and performing vacuum freeze drying for 12h to obtain a precursor material;
(3) and (3) respectively placing melamine powder and the precursor material obtained in the step (2) at two ends in a porcelain boat according to a mass ratio of 5:1, covering, heating to 850 ℃ at a heating rate of 20 ℃/min in a nitrogen atmosphere, carrying out annealing treatment for 1h, and carrying out autocatalytic reaction and thermal reduction reaction under the annealing treatment condition to obtain the multi-stage structure lithium sulfide/carbon composite material.
Example 6
The embodiment provides a preparation method of a lithium sulfide/carbon composite material with a multilevel structure, as shown in fig. 1, the preparation method comprises the following steps:
(1) 2.5g of Co (NO)3)2·6H2Dissolving O in 50mL of deionized water to obtain a cobalt salt solution with the concentration of 5 wt%, adding 0.1g of lithium sulfate to dissolve in the cobalt salt solution, and then adding 100mL of graphene oxide solution with the concentration of 10mg/mL to obtain a mixed solution;
(2) stirring the mixed solution obtained in the step (1) at the rotating speed of 500rpm/min for 12h, then performing ultrasonic dispersion for 30min, then performing centrifugal separation at the rotating speed of 8000rpm/min for 5min to obtain a precipitate, then placing the precipitate in liquid nitrogen for pretreatment for 10min, and performing vacuum freeze drying for 12h to obtain a precursor material;
(3) and (3) respectively placing melamine powder and the precursor material obtained in the step (2) at two ends in a porcelain boat according to a mass ratio of 20:1, covering, heating to 900 ℃ at a heating rate of 2 ℃/min in a nitrogen atmosphere, carrying out annealing treatment for 1h, and carrying out autocatalytic reaction and thermal reduction reaction under the annealing treatment condition to obtain the multi-stage structure lithium sulfide/carbon composite material.
Example 7
The embodiment provides a preparation method of a lithium sulfide/carbon composite material with a multilevel structure, as shown in fig. 1, the preparation method comprises the following steps:
(1) 3.2g of Co (NO)3)2·6H2Dissolving O in 50mL of deionized water to obtain a cobalt salt solution with the concentration of 6 wt%, adding 0.1g of lithium sulfate to dissolve in the cobalt salt solution, and then adding 40mL of graphene oxide solution with the concentration of 10mg/mL to obtain a mixed solution;
(2) stirring the mixed solution obtained in the step (1) at the rotating speed of 550rpm/min for 10 hours, then performing ultrasonic dispersion for 20 minutes, then performing centrifugal separation at the rotating speed of 8000rpm/min for 5 minutes to obtain a precipitate, then placing the precipitate in liquid nitrogen for pretreatment for 12 minutes, and performing vacuum freeze drying for 10 hours to obtain a precursor material;
(3) and (3) respectively placing melamine powder and the precursor material obtained in the step (2) at two ends in a porcelain boat according to the mass ratio of 12:1, covering, heating to 650 ℃ at the heating rate of 8 ℃/min in the nitrogen atmosphere, carrying out annealing treatment for 0.5h, and carrying out autocatalytic reaction and thermal reduction reaction under the annealing treatment condition to obtain the multi-stage structure lithium sulfide/carbon composite material.
Example 8
The embodiment provides a preparation method of a lithium sulfide/carbon composite material with a multilevel structure, as shown in fig. 1, the preparation method comprises the following steps:
(1) 2g of Co (NO)3)2·6H2Dissolving O in 50mL of deionized water to obtain a cobalt salt solution with a concentration of 4 wt%, adding 0.1g of lithium sulfate dissolved in cobaltAdding 30mL of graphene oxide solution with the concentration of 10mg/mL into the salt solution to obtain a mixed solution;
(2) stirring the mixed solution obtained in the step (1) at the rotating speed of 450rpm/min for 14h, then performing ultrasonic dispersion for 40min, then performing centrifugal separation at the rotating speed of 8000rpm/min for 5min to obtain a precipitate, then placing the precipitate in liquid nitrogen for pretreatment for 8min, and performing vacuum freeze drying for 14h to obtain a precursor material;
(3) and (3) respectively placing melamine powder and the precursor material obtained in the step (2) at two ends in a porcelain boat according to a mass ratio of 8:1, covering, heating to 600 ℃ at a heating rate of 1 ℃/min in a nitrogen atmosphere, carrying out annealing treatment for 2h, and carrying out autocatalytic reaction and thermal reduction reaction under the annealing treatment condition to obtain the multi-stage structure lithium sulfide/carbon composite material.
Example 9
The embodiment provides a preparation method of a lithium sulfide/carbon composite material with a multilevel structure, as shown in fig. 1, the preparation method comprises the following steps:
(1) 0.5g of Co (NO)3)2·6H2Dissolving O in 50mL of deionized water to obtain a cobalt salt solution with the concentration of 1 wt%, adding 0.1g of lithium sulfate to dissolve in the cobalt salt solution, and then adding 50mL of graphene oxide solution with the concentration of 10mg/mL to obtain a mixed solution;
(2) stirring the mixed solution obtained in the step (1) at the rotating speed of 500rpm/min for 12h, then performing ultrasonic dispersion for 30min, then performing centrifugal separation at the rotating speed of 8000rpm/min for 5min to obtain a precipitate, then placing the precipitate in liquid nitrogen for pretreatment for 10min, and performing vacuum freeze drying for 12h to obtain a precursor material;
(3) and (3) respectively placing melamine powder and the precursor material obtained in the step (2) at two ends in a porcelain boat according to the mass ratio of 1:1, covering, heating to 700 ℃ at the heating rate of 5 ℃/min in the nitrogen atmosphere, carrying out annealing treatment for 0.5h, and carrying out autocatalytic reaction and thermal reduction reaction under the annealing treatment condition to obtain the multi-stage structure lithium sulfide/carbon composite material.
Example 10
The present example is different from example 1 in that 20mL of graphene oxide solution is added in step (1), and the rest of the process parameters and operation steps are the same as example 1.
Example 11
The present example is different from example 1 in that 120mL of graphene oxide solution is added in step (1), and the rest of the process parameters and the operation steps are the same as example 1.
Example 12
The present example differs from example 1 in that the mass ratio of melamine powder in step (3) to the precursor material obtained in step (2) is 0.5:1, and the remaining process parameters and operating steps are the same as in example 1.
Example 13
The present example differs from example 1 in that the mass ratio of melamine powder in step (3) to the precursor material obtained in step (2) is 22:1, and the remaining process parameters and operating steps are the same as in example 1.
Example 14
This example is different from example 1 in that the annealing temperature in step (3) is 550 ℃, and the rest of the process parameters and the operation steps are the same as example 1.
Example 15
This example is different from example 1 in that the annealing temperature in step (3) is 950 ℃, and the rest of the process parameters and the operation steps are the same as example 1.
Example 16
The difference between this example and example 1 is that the annealing time in step (3) is 0.3h, and the rest of the process parameters and operation steps are the same as example 1.
Example 17
The difference between this example and example 1 is that the annealing time in step (3) is 2.5h, and the rest of the process parameters and operation steps are the same as example 1.
Comparative example 1
The present comparative example provides a method of preparing a lithium sulfide/carbon composite, the method comprising:
(1) dissolving 0.1g of lithium sulfate in 50mL of deionized water, adding 0.15g of porous carbon (C), and uniformly mixing to obtain a mixed solution;
(2) stirring the mixed solution obtained in the step (1) at the rotating speed of 500rpm/min for 12h, then performing ultrasonic dispersion for 30min, then performing centrifugal separation at the rotating speed of 8000rpm/min for 5min to obtain a precipitate, then placing the precipitate in liquid nitrogen for pretreatment for 10min, and performing vacuum freeze drying for 12h to obtain a precursor material;
(3) and (4) placing the precursor material obtained in the step (3) into a porcelain boat, covering the porcelain boat, heating to 700 ℃ at a heating rate of 5 ℃/min under a nitrogen atmosphere, and carrying out annealing treatment for 0.5h to obtain the lithium sulfide/carbon composite material.
Comparative example 2
The present comparative example provides a method of preparing a lithium sulfide/carbon composite, the method comprising:
(1) dissolving 0.1g of lithium sulfate in 50mL of deionized water, adding 50mL of graphene oxide solution with the concentration of 10mg/mL, and uniformly mixing to obtain a mixed solution;
(2) stirring the mixed solution obtained in the step (1) at the rotating speed of 500rpm/min for 12h, then performing ultrasonic dispersion for 30min, then performing centrifugal separation at the rotating speed of 8000rpm/min for 5min to obtain a precipitate, then placing the precipitate in liquid nitrogen for pretreatment for 10min, and performing vacuum freeze drying for 12h to obtain a precursor material;
(3) and (4) placing the precursor material obtained in the step (3) into a porcelain boat, covering the porcelain boat, heating to 700 ℃ at a heating rate of 5 ℃/min under a nitrogen atmosphere, and carrying out annealing treatment for 0.5h to obtain the lithium sulfide/carbon composite material.
Electrochemical tests were performed on the lithium sulfide/carbon composites prepared in examples 1 to 17 and comparative examples 1 to 2:
(1) preparing a positive pole piece: dispersing a lithium sulfide/carbon composite material, conductive carbon black (SP) and polyvinylidene fluoride (PVDF) in N-methylpyrrolidone (NMP) according to a mass ratio of 8:1:1, uniformly mixing to form slurry, coating the slurry on the surface of an aluminum foil, drying and stamping to form a positive pole piece with the diameter of 14 mm.
(2) Assembling the battery: a metal lithium sheet is taken as a negative electrode, 1mol/L lithium bistrifluoromethylenesulfonate imide (LiTFSI)/ethylene glycol dimethyl ether (DME):1, 3-Dioxolane (DOL), wherein the DME: DOL is 1:1, and the metal lithium sheet is assembled into a CR2032 button cell in a glove box filled with argon.
(3) And (3) performance testing: firstly, charging to 3.6V at a multiplying power of 0.05C, and then discharging to 1.8V; then, in a voltage range of 1.7 to 2.8V, a charge/discharge and cycle stability test was performed at a rate of 0.2C (1C 1166 mA/g).
The results of electrochemical tests performed on the lithium sulfide/carbon composites prepared in examples 1 to 17 and comparative examples 1 to 2 are shown in Table 1.
TABLE 1
From the data of table 1, one can see:
(1) the multi-stage structure lithium sulfide/carbon composite materials in embodiments 1 to 9 all have excellent specific cyclic capacity and capacity retention rate, which illustrates that the multi-stage structure lithium sulfide/carbon composite material prepared by the preparation method provided by the present invention can stabilize the structure of the material and improve the conductivity of the material through the composite action among lithium sulfide, reductive graphene oxide and carbon hybrid nanotubes, and the layered structure of the reductive graphene oxide and the in-situ generated carbon hybrid nanotubes have a unique spatial confinement effect on the lithium sulfide material, and simultaneously alleviate the volume expansion and contraction of the lithium sulfide/carbon composite nanomaterial in the charging and discharging processes, so as to have excellent specific cyclic capacity and capacity retention rate.
(2) The cycle specific capacity and the capacity retention rate of the multi-stage structure lithium sulfide/carbon composite materials in the embodiments 10 and 11 are lower than those in the embodiment 1, because the addition amount of the graphene oxide solution in the embodiment 10 is too low, and the addition amount of the graphene oxide in the embodiment 11 is too high. When the addition amount of the graphene oxide is too low, the lithium sulfate carbothermic reduction reaction and the in-situ autocatalytic reaction of the active metal nanoparticles are incomplete, so that the synthesized lithium sulfide/carbon composite anode material has poor shape controllability and unstable material quality; when the addition amount of the graphene oxide is too high, the loading amount of the lithium sulfide serving as the positive active material is reduced by excessive carbon materials, so that the first-turn capacity and the cycle capacity of the positive electrode of the lithium-sulfur battery are greatly reduced.
(3) The cyclic specific capacity and the capacity retention rate of the multi-level structure lithium sulfide/carbon composite materials in the embodiments 12 and 13 are lower than those in the embodiment 1, because the addition amount of the organic compound powder in the embodiment 12 is too low, a small amount of the organic compound powder is completely vaporized at high temperature and is not enough to support the chemical vapor deposition reaction, and thus the active metal nanoparticles cannot be used for in-situ generation of the carbon hybrid nanotubes through autocatalysis; in example 13, the addition amount of the organic compound powder is too high, and a large amount of the organic compound powder generates carbon hybrid nanotubes with uncontrollable morphology during annealing, which affects the capacity exertion of the lithium sulfide active material.
(4) The cycle specific capacity and the capacity retention rate of the multi-level structure lithium sulfide/carbon composite materials in the embodiments 14 and 15 are lower than those in the embodiment 1, which is because the annealing temperature in the embodiment 14 is too low to meet the condition of high-temperature thermal reduction, so that the lithium sulfate serving as a raw material cannot be completely carbothermally reduced to generate lithium sulfide; in example 15, the annealing temperature is too high, which limits the kinetics of the autocatalytic thermal reduction reaction of the active metal nanoparticles, resulting in the formation of coarser and shorter carbon-hybridized nanorods by in-situ chemical vapor deposition.
(5) The cycle specific capacity and the capacity retention rate of the multi-level structure lithium sulfide/carbon composite materials in the embodiments 16 and 17 are lower than those in the embodiment 1, because the annealing time in the embodiment 16 is too short, the high-temperature thermal reduction condition cannot be met, and the carbothermic reduction reaction is incomplete; in example 17, the annealing time is too long, which causes the uncontrollable continuous growth of the carbon-hybridized nanotubes on the surface layer of the reduced graphene oxide, resulting in the in-situ generation of the carbon-hybridized nanotubes with uncontrollable morphology.
(6) The cyclic specific capacity and the capacity retention rate of the multi-stage structure lithium sulfide/carbon composite material in the comparative examples 1 and 2 are far lower than those of the embodiment 1, because the lithium sulfate is added into deionized water in the comparative example 1, porous carbon is adopted to replace graphene oxide solution, and organic compound powder is also omitted in the annealing process; in comparative example 2, lithium sulfate was added to deionized water while omitting the organic compound powder during annealing. The composite materials obtained in comparative examples 1 and 2 do not form a multi-level structure lithium sulfide/carbon composite material simultaneously containing lithium sulfide, reductive graphene oxide and a carbon hybrid nanotube, so that the multi-level structure lithium sulfide/carbon composite material obtained by the preparation method provided by the invention can stabilize the structure of the material through the composite action among the lithium sulfide, the reductive graphene oxide and the carbon hybrid nanotube, improve the conductivity of the material, effectively relieve the volume expansion and contraction of the lithium sulfide/carbon composite nanomaterial in the charging and discharging process, and have excellent specific cyclic capacity and capacity retention rate.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention, and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A preparation method of a lithium sulfide/carbon composite material with a multilevel structure is characterized by comprising the following steps:
mixing a lithium source, a metal salt solution and a graphene oxide solution, drying to obtain a precursor material, carrying out annealing treatment on the precursor material and organic compound powder together, and carrying out autocatalytic reaction and thermal reduction reaction under the annealing treatment condition to obtain the multi-level structure lithium sulfide/carbon composite material.
2. The method according to claim 1, wherein the precursor material is prepared by a process comprising:
dissolving the lithium source in the metal salt solution, adding the graphene oxide solution to obtain a mixed solution, separating the mixed solution to obtain a precipitate, and drying the precipitate to obtain the precursor material.
3. The production method according to claim 1 or 2, characterized in that the lithium source includes lithium sulfate;
preferably, the solute in the metal salt solution comprises Co (NO)3)2·6H2O、Fe(NO3)2·9H2O or Ni (NO)3)2·6H2Any of O, more preferably Co (NO)3)2·6H2O；
Preferably, the concentration of the metal salt solution is 1-10 wt%, and further preferably 4-6 wt%;
preferably, the mass ratio of the lithium source to the graphene oxide in the graphene oxide solution is 1 (3-10), and more preferably 1 (3-5).
4. The preparation method according to claim 2 or 3, wherein the mixed solution is subjected to stirring, ultrasonic dispersion and separation treatment in sequence to obtain a precipitate;
preferably, the rotating speed of the stirring is 450-550 rpm/min;
preferably, the stirring time is 10-14 h;
preferably, the time of ultrasonic dispersion is 20-40 min;
preferably, the separation process comprises centrifugation;
preferably, the precipitate is placed in liquid nitrogen for pretreatment for 8-12 min before being dried;
preferably, the drying time is 10-14 h;
preferably, the drying comprises vacuum freeze drying.
5. The method according to any one of claims 1 to 4, wherein the precursor material and the organic compound powder are placed at both ends of a porcelain boat, respectively, and are subjected to annealing treatment after being covered;
preferably, the mass ratio of the organic compound powder to the precursor material is (1-20): 1, and more preferably (8-12): 1;
preferably, the organic compound powder includes any one of melamine, urea, or thiourea, and is further preferably melamine.
6. The method according to any one of claims 1 to 5, wherein the annealing treatment is performed at a temperature of 600 to 900 ℃, more preferably 650 to 750 ℃;
preferably, the time of the annealing treatment is 0.5-2 hours, and further preferably 0.5-1 hour;
preferably, the temperature rise rate of the annealing treatment is 1-20 ℃/min, and further preferably 5-10 ℃/min;
preferably, the annealing treatment is performed under a protective atmosphere.
7. The production method according to any one of claims 1 to 6, characterized by comprising:
(1) dissolving a lithium source in a metal salt solution with the concentration of 1-10 wt%, and adding a graphene oxide solution to obtain a mixed solution, wherein the mass ratio of the lithium source to the graphene oxide in the graphene oxide solution is 1 (3-10);
(2) stirring the mixed solution obtained in the step (1) at the rotating speed of 450-550 rpm/min for 10-14 h, then performing ultrasonic dispersion for 20-40 min, separating to obtain a precipitate, then placing the precipitate in liquid nitrogen for pretreatment for 8-12 min, and drying for 10-14 h to obtain a precursor material;
(3) and (3) respectively placing the organic compound powder and the precursor material obtained in the step (2) at two ends in a porcelain boat according to the mass ratio of (1-20) to 1, covering the porcelain boat, heating to 600-900 ℃ at the heating rate of 1-20 ℃/min in a protective atmosphere, carrying out annealing treatment for 0.5-2 h, and carrying out autocatalytic reaction and thermal reduction reaction under the annealing treatment condition to obtain the multi-stage structure lithium sulfide/carbon composite material.
8. A lithium sulfide/carbon composite material having a multilevel structure, which is produced by the production method according to any one of claims 1 to 7.
9. The multi-stage structure lithium sulfide/carbon composite material according to claim 8, wherein the multi-stage structure lithium sulfide/carbon composite material comprises a reductive graphene oxide layer, lithium sulfide particles are dispersed on both side surfaces of the reductive graphene oxide layer, and carbon hybrid nanotubes are grown in situ on both side surfaces of the reductive graphene oxide layer.
10. A lithium sulfur battery comprising the multi-stage structure lithium sulfide/carbon composite material according to claim 8 or 9.
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