CN115148977A - Preparation method of carbon material containing single atom and application of carbon material in lithium-sulfur battery - Google Patents

Preparation method of carbon material containing single atom and application of carbon material in lithium-sulfur battery Download PDF

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CN115148977A
CN115148977A CN202210937884.8A CN202210937884A CN115148977A CN 115148977 A CN115148977 A CN 115148977A CN 202210937884 A CN202210937884 A CN 202210937884A CN 115148977 A CN115148977 A CN 115148977A
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carbon material
zinc
lithium
sulfur
metal
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赵冲冲
刘艳侠
张亚涛
刘目浩
高文超
张涛
杨幸遇
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Zhengzhou University
Zhengzhou Institute of Emerging Industrial Technology
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Zhengzhou Institute of Emerging Industrial Technology
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Abstract

The invention discloses a preparation method of a carbon material containing single atoms and application of the carbon material in a lithium-sulfur battery, wherein a zinc-based metal organic framework material of zinc oxide nano particles with metal elements doped on the surface is directly carbonized at high temperature to prepare a uniform carbon material containing single atoms with catalytic activity, and the method comprises the following steps: preparing a zinc-based metal organic framework material; preparing zinc oxide nano-particles (X-ZnO) doped with metal elements; adsorbing X-ZnO nano particles on the surface of a zinc-based metal organic framework material through electrostatic interaction; the load carbon material with uniformly dispersed monoatomic atoms is obtained by high-temperature carbonization in an inert atmosphere, and the preparation method is simple and efficient, and has mild and easily-controlled conditions. The invention also discloses application of the carbon material containing the single atom as a carrier material of active substance sulfur in the positive pole piece of the lithium sulfur battery, and the high catalytic activity of the single atom can improve the reaction kinetics, excellent capacity exertion, rate capability, cycling stability and the like of the lithium sulfur battery.

Description

Preparation method of carbon material containing single atom and application of carbon material in lithium-sulfur battery
Technical Field
The invention relates to the technical field of energy materials, in particular to a preparation method of a carbon material containing single atoms and application of the carbon material in a lithium-sulfur battery.
Background
With the progress and development of human society, the problems of traditional petrochemical energy exhaustion, environmental pollution and the like are faced, and the development of a clean and recyclable energy storage system is a key point for promoting the development of the fields of electric automobiles, smart power grids and the like. In the electrochemical energy storage system, lithium ion secondary batteries are widely researched and applied by virtue of the advantages of high working voltage, long service life, high power density and the like. However, the maximum energy density of the current commercial lithium ion battery system can only reach 300Wh/kg, which is close to the limit of the energy density of the existing lithium ion battery system, and the requirement of people for improving the performance of the lithium ion battery system can not be met.
The lithium-sulfur battery is composed of a sulfur composite material positive electrode, a metallic lithium negative electrode, a diaphragm and electricityThe electrolyte composition is a multi-electron reversible reaction based on 'solid → liquid → solid' between sulfur and lithium, and the general reaction equation is as follows: 2Li + S8596and Li 2 S has high theoretical energy density (2600 Wh/kg), which is far higher than that of a commercial lithium ion battery, and simultaneously, sulfur has the advantages of rich resource reserves, low price, environmental friendliness and the like, has a good application prospect, and is considered to be a new generation high specific energy secondary battery system with the most development potential. However, lithium sulfur batteries still have many technical problems: on one hand, the sulfur elementary substance of the positive active substance is non-conductive, a large amount of carbon material with good conductivity is required to be added as a carrier, and the positive sulfur has large volume change in the charging and discharging processes to cause pulverization of a battery pole piece, so that the problems of low utilization rate of the active substance, poor cycle stability, poor rate performance and the like are brought; on the other hand, during the reaction of the lithium-sulfur battery, a discharge product polysulfide (Li) which is easily dissolved in an organic solvent of the electrolyte is inevitably generated 2 S n N is more than or equal to 4 and less than or equal to 8), and the n diffuses and migrates between the positive electrode and the negative electrode under the action of concentration gradient and electric field, so that the active substances of the positive electrode are reduced, the capacity is rapidly attenuated, the coulomb efficiency is reduced, and the shuttle effect is called.
In order to solve the problems of poor conductivity, volume expansion, polysulfide shuttling and the like in the lithium-sulfur battery, the main method is to load anode sulfur in a porous carbon matrix material matrix which has good electronic conductivity and ionic conductivity and limits polysulfide diffusion, such as porous carbon, carbon nano tubes and other materials. Or by introducing polar electrode materials which have chemical interaction with polysulfide, the shuttling of the polysulfide is reduced by surface adsorption and other actions, such as heteroatom-doped carbon, oxide and other materials. However, the strategy of "physical confinement" or "chemical adsorption" by polar groups using porous materials can only improve the electrochemical performance of lithium-sulfur batteries to a certain extent, and cannot improve the conversion efficiency of lithium-sulfur battery reactions fundamentally. Recent researchers have proposed the concept of "catalytic conversion", and synthesized a series of catalysts, which have improved the reaction kinetics of lithium-sulfur batteries through catalytic action, can accelerate the interconversion between sulfur-containing substances, and reduce the concentration and conversion time of polysulfide in electrolyte, thereby reducing the diffusion time and diffusion power of polysulfide, and achieving the purpose of inhibiting "shuttle effect", such as noble metals, metal nitrides, metal sulfides, etc., but these catalysts have the problems of complex synthesis, high cost, poor conductivity, etc.
Disclosure of Invention
In order to solve the problems in the lithium-sulfur battery, the invention provides the preparation method of the carbon material containing the monoatomic atom, which is simple in synthesis process and low in cost, the material is applied to the lithium-sulfur battery as an anode sulfur-carrying material, has a catalytic effect, the catalyst improves the conversion reaction kinetics of the lithium-sulfur battery, and the specific capacity, the cycle performance and the rate capability of the lithium-sulfur battery can be obviously improved.
The technical problem to be solved by the invention is realized by adopting the following technical scheme:
a preparation method of a carbon material containing single atoms and application of the carbon material in a lithium-sulfur battery mainly comprise the following steps:
1. preparing a zinc-based metal organic framework material (Zn-MOF);
2. preparing zinc oxide nano-particles doped with metal elements (X-ZnO, X refers to transition metal elements such as Ni, co, fe and the like);
3. adsorbing X-ZnO nanoparticles on the surface of a Zn-MOF material through electrostatic action;
4. carbonizing the composite material at high temperature in an inert gas environment to obtain a load carbon material with uniformly dispersed single atoms;
5. carbon materials containing single atoms are used in lithium sulfur batteries.
In the first step, the zinc-based metal organic framework material is a zinc-based metal organic framework material formed by combining metal ions only containing zinc metal and organic ligands, such as ZIF-7, ZIF-8, ZIF-62, ZIF-90, MOF-5, MOF-74 (Zn), MOF-177 and the like, and the preparation method of the zinc-based metal organic framework material can be a conventional preparation method in the field, such as a hydrothermal/solvothermal synthesis method, an ultrasonic method, a microwave heating method, an electrochemical method, a mechanochemical synthesis method and the like.
Preferably, the prepared zinc-based metal organic framework material has the particle size of 50 to 500nm, a micropore and mesoporous structure and a specific surface area of more than 200m 2 /g。
Preferably, the prepared organic ligand of the zinc-based metal organic framework material contains nitrogen element.
In the second step, zinc oxide nanoparticles doped with metal elements are prepared, the metal elements refer to one or more of transition metal elements, preferably, the transition metal elements are nickel, cobalt, iron, manganese, chromium and the like, and the preparation steps are as follows:
(a) Dissolving zinc salt and doped metal salt in a dimethyl sulfoxide solvent according to a certain proportion, wherein the zinc salt and the doped metal salt can be one or a mixed salt of more than two of acetate, nitrate, chlorate, chloride and the like, and the molar ratio of zinc in the zinc salt to metal in the doped metal salt or the mixed salt is 1000.
Preferably, the molar ratio of zinc in the zinc salt to metal in the doped metal salt or mixed salt is 200 to 10.
(b) Slowly adding an excessive ethanol solution of tetramethylammonium hydroxide with the concentration of 0.1g/ml while stirring, wherein the molar usage of the tetramethylammonium hydroxide is 1 to 3 times of the molar usage of all the salts in the step (a).
(c) And (b) adding an ethyl acetate solution with volume more than twice of that of the dimethyl sulfoxide solvent in the step (a), collecting precipitates through centrifugation or suction filtration, washing, and drying in a vacuum oven at 60 ℃ for 4-12 hours to obtain the zinc oxide nanoparticles doped with the metal element.
And in the third step, the X-ZnO nanoparticles are adsorbed on the surface of the Zn-MOF material through electrostatic interaction, specifically, one or more of the X-ZnO nanoparticles and the Zn-MOF material are dispersed in a solution of deionized water, ethanol or methanol and the like according to a certain proportion, the mixture is magnetically stirred for 6 to 24 hours, then the precipitate is collected by centrifugation or suction filtration and washed, and the precipitate is placed in a vacuum oven to be dried for 4 to 12 hours at 60 ℃.
The molar ratio of the zinc oxide nanoparticles X-ZnO to the zinc-based metal organic framework material Zn-MOF is 1 to 1000 to 1.
In the fourth step, the inert gas is nitrogen or argon, the carbonization temperature is 800-1100 ℃, the carbonization time is 1-4 hours, in the carbonization process, the zinc oxide nanoparticles are reduced into zinc by carbon in a high-temperature environment, and the zinc in the Zn-MOF is evaporated along with airflow at high temperature, so that only the loaded monoatomic metal and carbon are left.
Preferably, the carbonization temperature is 900 to 1000 ℃ and the carbonization time is 2 hours.
According to the preparation method of the carbon material containing the single atom, the prepared metal elements are partially or completely dispersed on the carbon carrier in a single atom form, and the metal elements can be one or more, and the mass percentage of the single atom is 0.01-10%.
Preferably, the prepared carbon carrier material has the grain diameter of 50 to 200nm, a micropore and mesopore structure and a specific surface area of more than 200m 2 Per g, pore volume is more than 0.5cm 3 The mass percent of the loaded single atom is 0.1-5%.
The application of the carbon material containing the single atom catalyst in the lithium sulfur battery adopts the carbon material containing the single atom catalyst as a positive electrode sulfur-carrying material of the lithium sulfur battery, and comprises the following specific steps:
(a) Uniformly mixing sublimed sulfur and a carbon material containing a single atom according to a certain proportion, mixing sulfur powder and the carbon material containing the single atom in a melting sulfur filling mode under the vacuum or inert gas protection atmosphere to obtain a carbon/sulfur composite positive electrode material, and keeping the temperature for 12-24h at the heating temperature of 155 ℃, wherein the mass ratio of the carbon material containing the single atom in the composite positive electrode material is 5-50%.
Preferably, the sulfur carrying mode adopts vacuum sulfur carrying, and the mass ratio of the carbon material containing single atoms in the obtained composite anode material is 10-40%.
(b) And (b) mixing the sulfur-carbon composite positive electrode material obtained in the step (a), a conductive agent and a binder according to a certain proportion, taking N-methyl pyrrolidone (NMP) as a solvent, uniformly mixing to prepare slurry, coating the slurry on a current collector, and drying in vacuum to prepare the positive electrode plate of the lithium-sulfur battery.
Preferably, the proportion of the sulfur-carbon composite positive electrode material is 80-90%, the proportion of the conductive agent is 5-10% of a positive electrode active material, and the proportion of the binder is 5-10%.
The conductive agent is one or more of conductive carbon black, conductive graphite, carbon nanotubes and graphene, and the binder is polyvinylidene fluoride.
Preferably, a ball milling method is adopted in a homogenizing and mixing mode, the ball milling time is 2 to 3 hours, and the loading capacity of the active material sulfur of the positive pole piece is 0.8 to 4mg/cm 2 。
(c) And (c) assembling the positive pole piece obtained in the step (b), the lithium negative pole, the diaphragm, the electrolyte and the shell to obtain the lithium-sulfur battery.
The diaphragm is a microporous polyolefin diaphragm, a ceramic diaphragm or a non-woven fabric diaphragm, and the like, and preferably, the polyolefin diaphragm is composed of one or more layers of Polyethylene (PE) and polypropylene (PP).
The electrolyte is composed of a lithium-containing electrolyte and a nonaqueous organic solvent, the electrolyte is lithium bistrifluoromethanesulfonimide (LiTFSI), and the nonaqueous organic solvent is one or two of Dioxolane (DOL) and ethylene glycol dimethyl ether (DME).
The invention also provides a lithium-sulfur battery, and the carbon material containing single atoms is used as a sulfur-carrying material in the positive electrode of the lithium-sulfur battery.
The invention has the beneficial effects that: the invention provides a preparation method of a carbon material containing one or more metal element monoatomic atoms, which comprises the steps of preparing zinc oxide nanoparticles (X-ZnO) doped with transition metal elements, adsorbing the zinc oxide nanoparticles on the surface of a zinc-based organic framework material (Zn-MOF), and carbonizing the zinc oxide nanoparticles in an inert atmosphere to finally prepare the carbon material with uniformly dispersed metal monoatomic atoms, high electrical conductivity and better catalytic activity. The method has the advantages of low cost, simple process and environmental friendliness, and can realize large-scale production.
The carbon material containing single atoms prepared by the invention has larger pore volume and larger specific surface area, and can play a role in physical confinement and chemical adsorption of polysulfide as a carrier of a lithium-sulfur battery cathode material, thereby reducing shuttle effect. In addition, the embedding of the metal monatomic active sites increases the electron transmission capability and the number of the active sites of the carbon material, so that the electrical conductivity of the carbon material is improved, the monatomic metal has catalytic performance, the reaction kinetics of the lithium-sulfur battery can be well improved, the electron transmission in the electrochemical reaction process is accelerated, the shuttle of polysulfide is reduced, and the polarization of the battery is reduced. The experimental result shows that due to the introduction of the monoatomic group, the lithium-sulfur battery can show higher gram capacity, good cycle performance, excellent rate performance, faster reaction kinetics and the like, the electrochemical performance of the lithium-sulfur battery is obviously improved, and the method has important significance for further commercialization of the lithium-sulfur battery.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the embodiments or the prior art descriptions will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
FIG. 1 is an X-ray diffraction (XRD) pattern of a precursor ZIF-8 of examples of the present invention and comparative examples;
FIG. 2 is a Scanning Electron Microscope (SEM) image of a precursor ZIF-8 of examples and comparative examples of the present invention;
FIG. 3 is an X-ray diffraction (XRD) pattern of a Ni-Co-N-C (curve 1) and a N-doped C (curve 2) material, which are prepared according to examples and comparative examples of the present invention, and which are loaded with nitrogen by single atoms of Ni and Co;
FIG. 4 is a Scanning Electron Microscope (SEM) image of a single-atom carbon material (Ni-Co-N-C) loaded with nickel and cobalt prepared by an embodiment of the invention;
FIG. 5 is a transmission electron microscope (STEM) image of the spherical aberration of the carbon material (Ni-Co-N-C) loaded with single atoms of Ni and Co prepared by the embodiment of the invention;
FIG. 6 is an X-ray photoelectron spectroscopy (XPS) survey of a carbon material supported on a single atom of Ni and Co (Ni-Co-N-C) prepared according to an embodiment of the present invention;
FIG. 7 is a graph showing the cycle performance at a current density of 0.5C in a lithium sulfur battery after sulfur loading of carbon materials prepared in examples of the present invention and comparative examples;
FIG. 8 is a graph of performance at different rates in a lithium sulfur battery after sulfur loading of carbon materials prepared according to examples of the present invention and comparative examples;
FIG. 9 is a graph showing the first charge and discharge curves of the carbon material prepared in the examples of the present invention and comparative examples after sulfur loading in a lithium sulfur battery according to the rate performance test of FIG. 8;
FIG. 10 is a graph showing cyclic voltammetry curves in a lithium sulfur battery after sulfur loading of carbon materials prepared according to examples of the present invention and comparative examples;
wherein, the abscissa of the obtained XRD diagram is diffraction angle (2 theta), and the ordinate is diffraction peak Intensity (Intensity); the abscissa of the obtained XPS graph is electron Binding energy (Binding energy), and the ordinate is electron Intensity (Intensity); the abscissa of the obtained Cycle performance graph and the ordinate of the obtained rate performance graph is Cycle number (Cycle number), and the ordinate of the obtained Cycle performance graph and rate performance graph is Specific capacity (Specific capacity); in the obtained charge-discharge curve, the abscissa represents a Specific capacity (Specific capacity) and the ordinate represents a Voltage (Voltage); the resulting cyclic voltammogram has a voltage (Pontetial) on the abscissa and a Current (Current) on the ordinate.
Detailed Description
The technical solutions of the present invention will be described clearly and completely below with reference to embodiments of the present invention, and it should be apparent that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without inventive effort based on the embodiments of the present invention, are within the scope of the present invention.
Example 1
The preparation of the carbon material containing nickel and cobalt double monoatomic atoms and the performance test of the carbon material applied in the lithium-sulfur battery.
The preparation method of the carbon material containing nickel and cobalt double monoatomic atoms in this example is as follows:
1. preparation of zinc-based metal organic framework material ZIF-8
First, 0.28mol (23 g) of 2-methylimidazoleAzole (C) 4 H 6 N 2 ) Added to 500ml of methanol (CH) 4 O) solution, 0.035mol (10.41 g) of zinc nitrate hexahydrate 12 N 2 O 12 Zn) was added to another 500ml of methanol (CH) 4 O) solution, and then adding the zinc nitrate solution to the 2-methylimidazole solution. And magnetically stirring for 24 hours in a room temperature environment, centrifugally collecting precipitates, washing for more than three times by using a methanol solution at a centrifugal rotation speed of 9000r/min for 5 minutes, and drying for 6 hours at the temperature of 60 ℃ in a vacuum oven to obtain the ZIF-8 nanoparticles. The XRD is shown in figure 1, and the material can be determined to be ZIF-8; as shown in FIG. 2, the scanning electron microscope showed that the approximate size of the ZIF-8 nanoparticles was 50 to 60nm.
2. Preparation of Nickel and cobalt Metal element doped Zinc oxide nanoparticles (Ni-ZnO, co-ZnO)
Preparation of Ni-ZnO: 0.5mmol (124.4 mg) of nickel acetate tetrahydrate (C) 4 H 14 NiO 8 ) And 10mmol (2195.1 mg) of zinc acetate dihydrate (C) 4 H 10 O 6 Zn) was added to 100ml of dimethyl sulfoxide (C) 2 H 6 OS) solution, magnetically stirred. Then 30.8ml of the prepared tetramethylammonium hydroxide pentahydrate (C) with the concentration of 0.1g/ml is added 4 H 13 NO 5 (H 2 O)) was slowly added to the above-mentioned dimethyl sulfoxide solution in a stirred state. 240ml of ethyl acetate (C) 4 H 8 O 2 ) Adding into the mixed solution, finally collecting the precipitate by centrifugation at 6000r/min for 3min, and then washing with ethyl acetate solution for more than three times to obtain nickel-doped zinc oxide particles (Ni-ZnO).
Preparation of Co-ZnO: 0.5mmol (124.5 mg) of cobalt acetate tetrahydrate (C) 4 H 14 CoO 8 ) And 10mmol (2195.1 mg) of zinc acetate dihydrate (C) 4 H 10 O 6 Zn) was added to 100ml of dimethyl sulfoxide (C) 2 H 6 OS) solution, magnetically stirred well. Then 30.8ml of prepared tetramethyl ammonium hydroxide pentahydrate with the concentration of 0.1g/ml（C 4 H 13 NO 5 (H 2 O)) was slowly added to the above-mentioned dimethyl sulfoxide solution in a stirred state. 240ml of ethyl acetate (C) are then added 4 H 8 O 2 ) Adding the mixed solution into the mixed solution, finally collecting the precipitate by centrifugation, wherein the centrifugation rotation speed is 6000r/min, the centrifugation time is 3min, and then washing the precipitate for more than three times by using ethyl acetate solution to obtain cobalt-doped zinc oxide particles (Co-ZnO).
3. Ni-ZnO and Co-ZnO nanoparticles are adsorbed on the surface of a ZIF-8 material through electrostatic interaction
Respectively dispersing the Ni-ZnO and Co-ZnO nano-particles obtained in the step two into 25ml of ethanol solution; weighing the ZIF-8 material powder (15.68 mmol) obtained in the step one, dispersing in 360ml of ethanol solution, performing ultrasonic treatment for 10min, and magnetically stirring for 1 hour until the material is uniformly dispersed. Then, the ethanol solution of the Ni-ZnO (containing 0.5mmol of Ni) and the Co-ZnO (containing 0.5mmol of Co) nano particles is poured into the ZIF-8 ethanol solution, and is stirred for 24 hours under the magnetic force, so that the Ni-ZnO and the Co-ZnO are adsorbed on the surface of Zn-O under the electrostatic action. And finally, collecting the precipitate through centrifugation, wherein the centrifugal rotation speed is 9000r/min, the centrifugation time is 5min, then washing the precipitate for more than three times by using ethanol, and placing the precipitate in a vacuum oven for drying for 6 hours at the temperature of 60 ℃ to obtain the ZIF-8 material adsorbed with the Ni-ZnO and Co-ZnO nanoparticles.
4. Carbonizing ZIF-8 composite material to obtain monatomic uniformly dispersed loaded carbon material
Grinding the ZIF-8 material adsorbed with the Ni-ZnO and Co-ZnO nano particles into powder, placing the powder in a tubular furnace, heating to 900 ℃ at the speed of 5 ℃/min in the nitrogen atmosphere, preserving the heat for 2 hours at 900 ℃, cooling to room temperature along with the furnace, reducing the zinc oxide nano particles into zinc by carbon in the high-temperature environment and evaporating the zinc in the ZIF-8 along with airflow at high temperature in the high-temperature carbonization process to only leave a carbon material doped with nickel, cobalt metal and nitrogen, and collecting the obtained black powder material, namely the loaded carbon material (Ni-Co-N-C) with uniformly dispersed nickel/cobalt diatoms.
The XRD pattern of the nickel/cobalt double-monatomic carbon-loaded material (Ni-Co-N-C) prepared in the example is shown as curve 1 in FIG. 3, the scanning electron microscope pattern is shown as FIG. 4, the spherical aberration transmission electron microscope pattern is shown as FIG. 5, and the XPS full spectrum pattern is shown as FIG. 6. From the XRD, the diffraction peaks of carbon are about 23 degrees and 43 degrees, and no other characteristic diffraction peaks appear; the scanning electron microscope image shows that the carbon material maintains the ZIF-8 structure and does not collapse; the spherical aberration transmission electron microscope image shows that Ni and Co are dispersed on the carrier in a monoatomic form, and the existence of the monoatomic material is proved; from the XPS survey, it can be seen that nickel and cobalt are dispersed in the carbon material.
The application and test of the carbon material containing nickel/cobalt double monoatomic atoms as the anode sulfur-carrying material
Weighing a carbon material containing nickel/cobalt double monoatomic atoms and sublimed sulfur according to a mass ratio of 3.
Mixing the obtained sulfur-carbon composite positive electrode material, a conductive agent (conductive carbon black, super P) and a binder (polyvinylidene fluoride, PVDF) according to a mass ratio of 8. Coating the slurry on an aluminum foil current collector by using a scraper, wherein the height of the edge of the scraper is 150 mu m, placing the pole piece in a vacuum oven to bake for 6 hours at 60 ℃, and preparing the lithium-sulfur battery positive pole piece after baking, wherein the sulfur carrying capacity of the coating surface is about 1mg/cm 2 。
A positive pole piece of the lithium-sulfur battery is cut into a wafer with the diameter of 14mm to be used as a working electrode (positive electrode), a metal lithium piece is used as a counter electrode (negative electrode), a polyethylene/polypropylene composite diaphragm (celgard 2400), 1mol/L lithium bistrifluoromethylsulfonyl imide (LTFSI) salt, 1, 3-Dioxolane (DOL) and ethylene glycol dimethyl ether (DME) (volume ratio is 1. And (3) carrying out cycle performance test on the battery, wherein the current for charging and discharging in the first three circles is 0.1C, and then carrying out test according to 0.5C, wherein 1C =1675mAh/g, and the test voltage range is 1.7-2.8V. The cycling performance of the nickel/cobalt-containing double-monoatomic carbon material serving as the sulfur-carrying material of the positive electrode of the lithium-sulfur battery at a current of 0.5 ℃ is shown in fig. 7, the performance with different multiplying factors is shown in fig. 8, the first charge-discharge curve (0.1C) of the multiplying factor performance is shown in fig. 9, and the cyclic voltammetry curve is shown in fig. 10.
Comparative example
Preparation of carbon material without any monoatomic atom and performance test of its application in lithium sulfur battery.
Unlike the examples, the carbon material in the comparative example was prepared by directly carbonizing ZIF-8 at a high temperature to obtain a nitrogen-doped carbon material (N-C), whose XRD pattern is shown as curve 2 in fig. 3, and other preparation steps and lithium sulfur test aspects were completely consistent with the examples. From the XRD pattern, diffraction peaks of carbon at about 23 degrees and 43 degrees can be seen, and no other characteristic diffraction peaks appear. The cycling performance of the carbon material without any single atom as the sulfur-carrying material of the lithium sulfur battery anode under the current of 0.5C is shown in FIG. 7, the different rate performance is shown in FIG. 8, the first charge-discharge curve (0.1C) of the rate performance is shown in FIG. 9, and the cyclic voltammetry curve is shown in FIG. 10.
As shown in FIG. 7, the first discharge gram capacity of the example is 1348.5mAh/g, the comparative example is 1172.2mAh/g, the discharge gram capacity of the example after 250 weeks of cycling is 726.3mAh/g, the comparative example is only 469.6mAh/g, and the capacity and the cycling stability of the example are higher than those of the comparative example. As shown in FIG. 8, the examples have a discharge gram capacity of 1098.8mAh/g, 833.6mAh/g, 707.8mAh/g and 573.6mAh/g after 5 weeks of each cycle at 0.1C, 0.5C, 1C and 2C rate, respectively, and the corresponding comparative example has a discharge gram capacity of 966mAh/g, 701.4mAh/g, 583.4mAh/g and 464.2mAh/g, respectively, and the rate performance of the examples is significantly better than the comparative examples. Fig. 9 is a first charge-discharge curve corresponding to the rate performance test of fig. 8, and it can be seen from the graph that the material shows a charge-discharge platform curve specific to a typical lithium-sulfur battery, the discharge capacities are 1332.5mAh/g and 1198.3mAh/g, respectively, and the overvoltage Δ E of the example is much smaller than that of the comparative example, indicating that the conversion rate of polysulfide ions is improved, and the example has a certain catalytic effect. FIG. 10 is a cyclic voltammogram of the examples and comparative examples, and it can be seen that the reduction peak-to-peak positions of the examples are 2.288V and 2.07V, respectively, the reduction peak positions of the comparative examples are 2.281V and 2.065V, respectively, and the reduction peaks of the examples are larger than those of the comparative examples; the peak positions of the oxidation peaks of the examples and the comparative examples are respectively 2.327V and 2.42V, the oxidation peaks of the examples are smaller than those of the comparative examples, the oxidation or reduction reactions of the examples are earlier than those of the redox reactions of the comparative examples, and the monatomic materials obtained in the examples are further shown to improve the reaction kinetics and have a catalytic effect. Therefore, experimental data show that the performance of the embodiment is obviously superior to that of the comparative example and shows better electrochemical performance as the sulfur-carrying material in the aspects of gram discharge capacity, cycle performance, rate performance, reaction kinetics and the like of a lithium-sulfur battery. Therefore, the carbon material containing the single atom provided by the invention is feasible to be applied to the lithium-sulfur battery and has a better performance improvement effect.
The invention provides a preparation method of a monatomic carbon material containing metal elements, wherein the metal monatomic in the carbon material is uniformly dispersed, has high conductivity and better catalytic activity, and the preparation method has the advantages of low cost, simple process and environmental friendliness, can realize large-scale production, and provides a new method and a new thought for solving the problems of low gram capacity exertion, poor cycle performance, shuttle effect and the like of a lithium-sulfur battery.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims (9)

1. A method for producing a carbon material containing a single atom, comprising the steps of:
(1) Preparing a zinc-based metal organic framework material Zn-MOF;
(2) Preparing zinc oxide nano-particles X-ZnO doped with metal elements;
(3) Adsorbing zinc oxide nano particles X-ZnO on the surface of a zinc-based metal organic framework material Zn-MOF through electrostatic interaction to obtain a composite material;
(4) And (4) carbonizing the composite material obtained in the step (3) at high temperature in an inert gas environment to obtain a load carbon material with uniformly dispersed single atoms, namely a single atom-containing carbon material.
2. The method for producing a monoatomic-containing carbon material according to claim 1, wherein the zinc-based metal organic framework material in the step (1) is a zinc-based metal organic framework material Zn-MOF having a combination of only zinc metal ions and organic ligands.
3. The method for producing a monoatomic-containing carbon material according to claim 1, wherein in the step (2), the metal element X in the metal-element-doped zinc oxide nanoparticles X — ZnO is one or more of transition metal elements, and the metal-element-doped zinc oxide nanoparticles X — ZnO are produced by:
dissolving zinc salt and doped metal salt in dimethyl sulfoxide, wherein the molar ratio of zinc in the zinc salt to metal in the doped metal salt is 1000; the zinc salt is one or more of zinc acetate, zinc nitrate or zinc chloride; the doped metal salt is one or more of acetate, nitrate, chlorate and chloride containing metal element X;
slowly adding an excessive ethanol solution of tetramethylammonium hydroxide with the concentration of 0.1g/ml under the stirring condition, wherein the molar usage of the tetramethylammonium hydroxide is 1 to 3 times of that of all the salts in the step (a);
and (b) adding an ethyl acetate solution with the volume of 2-3 times that of the dimethyl sulfoxide solvent in the step (a), collecting a precipitate through centrifugation or suction filtration, and drying the precipitate in a vacuum oven at 60 ℃ for 4-12 hours to obtain the zinc oxide nano-particles X-ZnO doped with the metal element.
4. The method for producing a monoatomic-containing carbon material according to claim 1, wherein the method for producing the composite material in the step (3) is: dispersing zinc oxide nano particles X-ZnO doped with metal elements and zinc-based metal organic framework material Zn-MOF in deionized water, ethanol or methanol, magnetically stirring for 6-24 hours, centrifuging or suction filtering, collecting precipitate, washing, and drying in a vacuum oven at 60 ℃ for 4-12 hours.
5. The method for producing a monoatomic-containing carbon material according to claim 4, wherein the molar ratio of the metal-element-doped zinc oxide nanoparticles X-ZnO to the zinc-based metal-organic framework material Zn-MOF is 1 to 1000 to 1.
6. The method for producing the monoatomic-containing carbon material according to claim 1, wherein the inert gas in the step (4) is nitrogen or argon, and the high-temperature carbonization temperature is 800 to 1100 ℃ for 1 to 4 hours.
7. The monoatomic carbon material produced by the production method according to any one of claims 1 to 6, wherein the carbon material has a particle size of 50 to 500nm, a microporous or mesoporous structure, and a specific surface area of more than 200m 2 Per g, pore volume is more than 0.5cm 3 The metal element is partially or completely dispersed on the carbon carrier in a monoatomic form, and the mass percent of the monoatomic metal element on the carbon carrier is 0.01-10%.
8. The use of the monoatomic-containing carbon material according to claim 7 in a lithium sulfur battery, comprising the steps of:
1) Uniformly mixing sublimed sulfur and a carbon material containing a single atom, mixing sulfur powder and the carbon material containing the single atom in a melting sulfur filling mode under the vacuum or inert gas protection atmosphere to obtain a carbon/sulfur composite positive electrode material, and keeping the temperature for 12-24h under the condition that the heating temperature is 155 ℃, wherein the mass ratio of the carbon material containing the single atom in the carbon/sulfur composite positive electrode material is 5-50%;
2) Mixing the carbon/sulfur composite positive electrode material obtained in the step 1), a conductive agent and a binder, uniformly mixing the materials by taking N-methyl pyrrolidone as a solvent to prepare slurry, coating the slurry on a current collector, and drying the slurry in vacuum to prepare a positive electrode plate of the lithium-sulfur battery;
3) Assembling the positive pole piece, the lithium negative pole, the diaphragm, the electrolyte and the shell of the lithium-sulfur battery obtained in the step 2) to obtain the lithium-sulfur battery.
9. A lithium sulfur battery characterized by: the positive electrode of the lithium-sulfur battery contains the carbon material containing a single atom according to claim 7 as a sulfur-carrying material.
CN202210937884.8A 2022-08-05 2022-08-05 Preparation method of carbon material containing single atom and application of carbon material in lithium-sulfur battery Pending CN115148977A (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116328771A (en) * 2023-03-23 2023-06-27 中国科学技术大学 Preparation method for preparing carbon-loaded monoatomic material by microwave-assisted heating
CN118016909A (en) * 2024-01-29 2024-05-10 中国石油大学(北京) N-doped and anchored Sn porous carbonaceous electrode for iron-chromium flow battery and preparation method thereof

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116328771A (en) * 2023-03-23 2023-06-27 中国科学技术大学 Preparation method for preparing carbon-loaded monoatomic material by microwave-assisted heating
CN118016909A (en) * 2024-01-29 2024-05-10 中国石油大学(北京) N-doped and anchored Sn porous carbonaceous electrode for iron-chromium flow battery and preparation method thereof

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