CN110931789A - Preparation method of carbon nanosheet, positive electrode material and preparation method thereof - Google Patents

Preparation method of carbon nanosheet, positive electrode material and preparation method thereof Download PDF

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CN110931789A
CN110931789A CN201911182136.8A CN201911182136A CN110931789A CN 110931789 A CN110931789 A CN 110931789A CN 201911182136 A CN201911182136 A CN 201911182136A CN 110931789 A CN110931789 A CN 110931789A
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positive electrode
electrode material
carbon
aluminum
preparation
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曾燮榕
金文武
邹继兆
S·因古瓦
曾绍忠
徐国忠
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Shenzhen University
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Shenzhen University
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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
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • 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
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

The invention belongs to the technical field of nano materials, and particularly relates to a preparation method of a carbon nano sheet, a positive electrode material and a preparation method of the positive electrode material. The preparation method of the carbon nano sheet comprises the following steps: providing an aluminum source and 4,4' -biphenyldicarboxylic acid; dissolving the aluminum source and the 4,4' -biphenyldicarboxylic acid in an organic solvent for heating treatment, and then carrying out solid-liquid separation to obtain a self-assembled aluminum-based metal organic framework; and sequentially carrying out carbonization treatment and acid treatment on the aluminum-based metal organic framework, and then drying to obtain the carbon nanosheet. The preparation method is simple in process and low in cost, the finally obtained carbon nanosheet has a scaly surface structure, a hierarchical porous structure and an ultra-large specific surface area, extra carbon activation and a template stripping process are not needed, the carbon nanosheet can be compounded with selenium to be used as a positive electrode material of a lithium selenium ion battery, and the preparation method has a good application prospect.

Description

Preparation method of carbon nanosheet, positive electrode material and preparation method thereof
Technical Field
The invention belongs to the technical field of nano materials, and particularly relates to a preparation method of a carbon nano sheet, a positive electrode material and a preparation method of the positive electrode material.
Background
The lithium ion battery has the characteristics of high specific energy, long cycle life, environmental friendliness and the like, and is widely applied to the fields of portable electronic equipment and electric automobiles. However, as the demand of lithium ion batteries increases, the problems of scarcity of lithium resources and unevenness of local distribution are becoming more and more prominent, and lithium ion batteries based on graphite and intercalation compounds have not been able to satisfy the social development demand, so in recent years, research and development work on replaceable lithium battery systems has been receiving wide attention from researchers, in which selenium (Se), an element of the same family as sulfur, has a molecular structure similar to that of sulfur (S) although the gravimetric specific capacity (675mAh g) of Se-1) Much lower than S (1675mAh g-1) However, the density of Se is 2.5 times of that of S, so that the Li-Se battery has great advantages in volume specific capacity, and is expected to solve the problem of insufficient power supply preparation space of electric equipment, so that the Li-Se battery has great application prospects in the fields of mobile consumer electronics, hybrid/pure electric vehicles, national defense and military industry and the like.
Conductivity of elemental Se (1X 10)-3S/m) is much higher than S (5X 10)-28S/m), which indicates that Se as an electrode material will have higher active material utilization rate, better electrochemical activity and faster electrochemical reaction speed, so that Li-Se batteries have attracted great attention in the past years, but all current research works are in a very early stage, and there still exist many problems to be solved, like a sulfur-containing cathode material, a cathode material containing Se will dissolve in an electrolyte during the reaction process, and the formed highly ordered polyselenide will generate a "shuttle effect" to cause volume expansion and irreversible damage of the electrode material itself, thereby causing the batteries to show lower coulombic efficiency and rapid capacity fading.
Se (with a lower melting point of 221 ℃) is melted and then compounded with a porous carbon material, so that the composite material can be effectively usedThe dissolution of the polyselenide is reduced, and the conductivity of the positive electrode material can be improved, so that the rate capability of the battery is improved. The voids in the pores are Se converted to lithium selenide (Li)2Se) reserve space, thereby relieving electrode pulverization and fragmentation caused by volume expansion, further improving the cycle life and specific capacity of the battery, among numerous reports, graphene has high mechanical properties, large specific surface area, excellent chemical stability and electrical conductivity, therefore, the graphene-like two-dimensional material is widely applied to the field of energy storage and conversion in recent years, however, the graphene-like two-dimensional material prepared by the chemical vapor deposition method at present adopts a metal sheet (nickel or copper) as a substrate, and the morphology of the graphene-like two-dimensional material mostly presents a planar two-dimensional layered structure, because of the strong pi-pi bonding effect between the graphene-like carbon materials, irreversible aggregation and superposition phenomena often occur between lamellar structures, this increases the interlayer contact resistance between the materials and reduces the conductivity of the graphene, thereby greatly limiting the electrochemical performance of the graphene. In order to effectively inhibit the phenomenon and improve the electrochemical performance of the two-dimensional carbon material, a promising strategy is to make the two-dimensional carbon material into a non-planar two-dimensional structure, but the current preparation methods of the two-dimensional carbon material with special morphology mainly comprise a template method and a chemical vapor deposition method, but from the practical application perspective, unnecessary investment is increased, the preparation process is more complicated, the preparation cost is increased in the template removing process, the environmental pollution is caused, and the like, so that the search of the preparation method with simple process, low cost and excellent performance is the key for promoting the benign development of the two-dimensional carbon material.
In recent years, reports of preparing carbon nanosheets by using Metal Organic Frameworks (MOFs) as precursors appear, for example, CN106025239A reports that 2D nitrogen-doped carbon nanosheets are prepared by using flaky ZIF-8, but the carbon nanosheets prepared by the method have single morphology and are difficult to realize controllable preparation of the morphology, and in addition, in order to realize a large specific surface area, KOH is adopted for activation treatment, which undoubtedly increases the preparation cost and causes certain chemical pollution to the environment and equipment.
Therefore, the prior art is in need of improvement.
Disclosure of Invention
The invention aims to provide a preparation method of a carbon nanosheet, a positive electrode material and a preparation method thereof, and aims to solve the technical problems of single and uncontrollable appearance and high cost of the existing preparation method of the carbon nanosheet.
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention provides a preparation method of a carbon nano sheet, which comprises the following steps:
providing an aluminum source and 4,4' -biphenyldicarboxylic acid;
dissolving the aluminum source and the 4,4' -biphenyldicarboxylic acid in an organic solvent for heating treatment, and then carrying out solid-liquid separation to obtain a self-assembled aluminum-based metal organic framework;
and sequentially carrying out carbonization treatment and acid treatment on the aluminum-based metal organic framework, and then drying to obtain the carbon nanosheet.
The preparation method of the carbon nanosheet provided by the invention has the advantages that an aluminum source and 4,4' -biphenyldicarboxylic acid are taken as raw materials, the raw materials are dissolved in an organic solvent, a self-assembled aluminum-based metal organic framework (Al-MOF) is formed by heating, the aluminum-based metal organic framework superstructure is taken as a precursor raw material, and carbonization and acid treatment are carried out to finally obtain a carbon nanosheet material which is controllable in shape and can be cut out; the preparation method has great significance for deepening the MOF self-assembly nucleation mechanism, researching the problem of the thermal stability of the plate of the MOF-derived carbon super-structure and realizing the industrial production of the carbon nanosheet, can be compounded with a selenium material to be used as a positive electrode material of the lithium selenium ion battery, and has good application prospect.
The invention also provides a positive electrode material which comprises the carbon nano sheet obtained by the preparation method of the carbon nano sheet and selenium loaded in the carbon nano sheet.
The positive electrode material provided by the invention is a composite positive electrode material of carbon nano sheet loaded selenium, and the carbon nano sheet in the positive electrode material is obtained by the special preparation method, so that the positive electrode material has controllable specific surface area and pore size distribution and a unique flaky surface structure, the positive electrode material with the special structure can effectively inhibit the volume expansion of an electrode in the charging and discharging processes, an alternative scheme is provided for adapting to different electrochemical energy storage systems, and the positive electrode material has a good application prospect in a lithium selenium ion battery.
Finally, the invention also provides a preparation method of the cathode material, which comprises the following steps: and mixing the carbon nano sheet with selenium, then heating at the temperature of 250-270 ℃, and cooling to obtain the cathode material.
According to the preparation method of the cathode material, the carbon nano-sheets obtained by the special preparation method are fully mixed with selenium (Se), the mixed sample is heated at the temperature of 250-270 ℃, so that the selenium is melted and fully infiltrated into the carbon nano-sheets, and the finally obtained cathode material effectively inhibits the volume expansion of an electrode in the charging and discharging processes, and has a good application prospect in a lithium selenium ion battery.
Drawings
FIG. 1 is an SEM image of an aluminum-based metal organic framework in an embodiment of the present invention; wherein a is Al-MOF-1, b is Al-MOF-2, c is Al-MOF-3, and d is Al-MOF-4;
fig. 2 is a graph of BET test results for carbon nanoplatelets CNS1, CNS2, CNS3, CNS4 obtained in an example of the invention;
FIG. 3 is a graph showing the results of Al-MOF-1 tests in examples of the present invention; wherein a, b, d and e are scanning electron microscope images of Al-MOF-1; c is the calculated X-ray diffraction pattern of Al-MOF-1 and Al-MOF-1 prepared; f is the TGA curve of the prepared Al-MOF-1;
FIG. 4 is a graph of the results of a CNS1 test in accordance with an embodiment of the present invention; wherein a, b, c, d, e and f are CNS1 transmission electron microscope images obtained by carbonizing Al-MOF-1 for 1 hour at 700 ℃ in a nitrogen atmosphere; g is XPS measured spectrum of CNS 1; n2 adsorption-desorption isotherms at h 77K and pore size distribution of CNS1 using DFT analysis; i is a CNS1 selenium-compounded anode material;
FIG. 5 is a graph showing the results of testing the positive electrode material (CNS1-Se) according to an embodiment of the present invention; wherein a is a TGA result of the cathode material; b is the XRD pattern of pure selenium, CNS1-Se and CNS 1; c is a Raman spectrum; d is XPS measurement spectrum of CNS 1-Se; e is Se 3d and (f) Se 3p-XPS spectra of CNS 1-Se.
FIG. 6 is a graph showing the results of testing the positive electrode material (CNS1-Se) according to an embodiment of the present invention; wherein a is the rate capability of CNS 1-Se; b is the cyclic performance of CNS1-Se (0.25c, 2 c); c is the AC impedance diagram of the battery and its equivalent circuit; the cycling performance of CNS1-Se when d is 8C; e is the CV curve of CNS 1-Se; f is the discharge/charge curve of1, 2, 50, 100, 200 and 300 cycles of CNS1-Se at 0.25C;
FIG. 7 is a graph of the results of a CNS2 test in accordance with an embodiment of the present invention; wherein, a and b are SEM images of CNS 2; c is N at 77K2Adsorption-desorption isotherms and pore size distribution of CNS2 analyzed using DFT; d, e, f are low and high TEM images of CNS 2.
FIG. 8 is a graph showing the results of testing the positive electrode material (CNS2-Se) according to an embodiment of the present invention; wherein a is the total element: b is SEM picture of CNS 2-Se; c is an O element distribution diagram; d is Se element distribution diagram; e is a C element distribution diagram; f is a CNS2-Se thermogravimetric curve with a scale bar of1 μm;
FIG. 9 is a graph showing the results of testing the positive electrode material (CNS2-Se) according to the example of the present invention; wherein a is the Raman spectrum of Se, CNS2 and CNS 2-Se; b is an XRD pattern; c is XPS plot of CNS 2-Se; d is Se 3d XPS spectrum of CNS 2-Se.
FIG. 10 is a graph showing the results of testing the positive electrode material (CNS2-Se) according to the example of the present invention; wherein, a is the rate performance of CNS 2-Se; b is the cyclic performance of CNS2-Se at 0.5 c; c is the CV curve of CNS 2-Se; d is the discharge/charge curve of1 st, 2 nd, 50 th, 100 th, 200 th and 300 th cycles of CNS2-Se at 0.25C;
FIG. 11 is a graph of the cycling performance of the positive electrode material (CNS2-Se) in an example of the invention;
FIG. 12 is an SEM image of a positive electrode material (CNS3-Se) in an example of the present invention;
FIG. 13 is a TGA curve and an XRD pattern of the positive electrode material (CNS3-Se) in an example of the invention;
FIG. 14 is a graph of the cycling performance of the positive electrode material (CNS3-Se) in an example of the invention: wherein, a is the rate performance of CNS 3-Se; b is the cyclic performance of CNS3-Se at 0.25 c;
FIG. 15 is an SEM image of positive electrode material (CNS4-Se) in an example of the invention;
FIG. 16 is a thermogravimetric plot of the positive electrode material (CNS4-Se) in an example of the invention;
FIG. 17 is a graph of the cycling performance of the positive electrode material (CNS4-Se) in an example of the invention: wherein, a is the rate performance of CNS 4-Se; b is the cyclic performance of CNS4-Se at 0.25 c;
fig. 18 is a performance test chart of the positive electrode material (CNS1(800) -Se) in the example of the invention: wherein a is a CNS1(800) -Se thermogravimetric curve; b is the XRD pattern of CNS1(800) -Se and Se; c is a Raman diagram;
fig. 19 is a graph of the cycling performance of the positive electrode material (CNS1(800) -Se) in an example of the invention: wherein, a is the rate capability of CNS1(800) -Se; b is the cyclic performance of CNS1(800) -Se at 2C;
FIG. 20 is an SEM image of positive electrode material (CNS2(900) -Se) in accordance with an embodiment of the present invention;
fig. 21 is a graph of the cycling performance of the positive electrode material (CNS2(900) -Se) in an example of the invention: i.e. the cycling performance of the CNS2(900) -Se composite positive electrode material at 0.25C.
Detailed Description
In order to make the technical problems, technical solutions and advantageous effects to be solved by the present invention more clearly apparent, the present invention is further described in detail below with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
In one aspect, an embodiment of the present invention provides a method for preparing a carbon nanosheet, including the following steps:
s01: providing an aluminum source and 4,4' -biphenyldicarboxylic acid;
s02: dissolving the aluminum source and the 4,4' -biphenyldicarboxylic acid in an organic solvent for heating treatment, and then carrying out solid-liquid separation to obtain a self-assembled aluminum-based metal organic framework;
s03: and sequentially carrying out carbonization treatment and acid treatment on the aluminum-based metal organic framework, and then drying to obtain the carbon nanosheet.
According to the preparation method of the carbon nanosheet, an aluminum source and 4,4' -biphenyldicarboxylic acid are used as raw materials and are dissolved in an organic solvent to be heated to form a self-assembled aluminum-based metal organic framework (Al-MOF), the aluminum-based metal organic framework superstructure is used as a precursor raw material, and carbonization and acid treatment are performed to finally obtain a carbon nanosheet material with controllable morphology and capable of being cut out, the preparation method is simple in process and low in cost, and the finally obtained carbon nanosheet has a scaly surface structure and a hierarchical porous structure and an ultra-large specific surface area, and extra carbon activation and template stripping processes are not needed; the preparation method has great significance for deepening the MOF self-assembly nucleation mechanism, researching the problem of the thermal stability of the plate of the MOF-derived carbon super-structure and realizing the industrial production of the carbon nanosheet, can be compounded with a selenium material to be used as a positive electrode material of the lithium selenium ion battery, and has good application prospect.
In step S01, the aluminum source is provided as a soluble inorganic aluminum salt, such as at least one of aluminum nitrate, aluminum sulfate and aluminum chloride, and in the specific embodiment, Al (NO) is selected3)39H2And O. Forming an aluminum-based metal organic framework through self-assembly reaction of an aluminum source and 4,4 '-biphenyl dicarboxylic Acid (4,4' -Bibenzoic Acid) in an organic solvent; in the embodiment of the invention, the precursor used for preparing the nanosheet is a compound with an aluminum-based metal organic framework, the compound has the characteristics of crystallography, and characteristic peaks of the compound can be characterized by XRD (X-ray diffraction), while if other metal salts or other ligands are used for preparing the metal organic compound, the characteristics of the crystallography cannot be guaranteed to be unchanged.
In the step S02, the temperature of the heating treatment is 110-; under the above heating conditions, the resulting particles agglomerate, the free energy is minimized, and then self-assemble into nanostructures of aluminum-based metal-organic frameworks, which are spherical in morphology if the temperature is too high, e.g., above 180 ℃. The self-assembly process is carried out in organic solvent, specifically, the organic solvent can be N, N-Dimethylformamide (DMF), and the heating environment can be maintained in a polytetrafluoroethylene-lined autoclave at 120 ℃ for 24 hours. In one embodiment, the molar ratio of the aluminum element and the 4,4' -biphenyldicarboxylic acid in the aluminum source is 1: (3-4); within the proportion range, the reaction can be fully carried out, and a precursor used for preparing the nanosheet, namely the aluminum-based metal organic framework, can be better prepared. Further, the solid-liquid separation after the heat treatment includes: firstly, centrifugal separation is carried out, and then the precipitate obtained by the centrifugal separation is dried at 70-200 ℃. After removing the organic solvent by centrifugation, a white precipitate is obtained, after which the remaining organic solvent may be washed with ethanol, e.g. 3 times with ethanol, and then dried to obtain a white powder of the self-assembled aluminum-based metal organic framework.
In step S03, carbonization and acid treatment are performed using the aluminum-based metal organic framework as a precursor. Wherein the temperature of the carbonization treatment is 600-1000 ℃; the carbonization time is 1-1.5 h; further, the temperature increase rate of the carbonization treatment is 5 ℃/min. Further, the carbonization treatment is performed in an inert atmosphere, such as an inert gas, under which the carbon nanosheets can be stably formed. Wherein the acid treatment is to remove aluminum element, in one embodiment, the acid treatment comprises: and (3) placing the carbonized product in an acid solution for ultrasonic treatment. Specifically, the acid solution is a hydrochloric acid solution, such as a 10 wt% hydrochloric acid solution; the ultrasonic treatment time is 20-40 min. After the acid treatment is carried out to remove aluminum, the aluminum can be cleaned and then dried; specifically, it can be left at 80 ℃ for two days, finally washed by centrifugation, ethanol and deionized water, and dried in an 80 ℃ oven.
The embodiment of the invention provides a carbon nanosheet prepared by the preparation method of the carbon nanosheet, and in the embodiment of the invention, the electrochemical performance of the nanosheet as a positive electrode material of a lithium-selenium (Li-Se) battery is characterized. The embodiment of the invention can effectively control the self-assembly growth of Al-MOF, prepare the carbon nanosheet material with a cuttable shape through the carbonization and acid treatment processes, and realize the controllable preparation of the carbon nanosheet through one-step carbonization; the morphology of the Al-MOF is controlled through effectively regulating and controlling the conditions (such asAl-MOF-1, Al-MOF-2, Al-MOF-3, Al-MOF-4 in the examples) to derive Carbon Nanosheets (CNS) of different hierarchical porous structure, such as CNS1, CNS2, CNS3, CNS4 in the examples. Finally, the prepared carbon nano-sheet has controllable specific surface area (2251.9 m)2/g～1096.42m2The distribution of the pore diameter and the unique scaly surface structure, and the structure can effectively inhibit the volume expansion of the electrode in the charging and discharging process. This provides an alternative solution for adapting to different electrochemical energy storage systems, and based on the above consideration, the series of carbon nano sheets will have a great application space in the field of energy storage.
On the other hand, the embodiment of the invention also provides a cathode material, which includes the carbon nanosheet obtained by the preparation method of the carbon nanosheet of the embodiment of the invention and selenium loaded in the carbon nanosheet. The positive electrode material is a composite positive electrode material of carbon nanosheet loaded selenium, and the carbon nanosheets in the positive electrode material are obtained by the special preparation method, so the positive electrode material has controllable specific surface area and pore size distribution and a unique flaky surface structure, the positive electrode material with the special structure can effectively inhibit the volume expansion of an electrode in the charging and discharging process, provides an alternative scheme for adapting to different electrochemical energy storage systems, and has a good application prospect in a lithium selenium ion battery.
In one embodiment, the selenium content of the composite material is 50-65% by mass. The selenium powder with the content can be uniformly mixed with the carbon nanosheets, and the obtained anode material is optimal in performance.
Finally, an embodiment of the present invention further provides a preparation method of the above-mentioned cathode material of the present invention, including the following steps: and mixing the carbon nano sheet with selenium, then heating at the temperature of 250-270 ℃, and cooling to obtain the cathode material. According to the preparation method of the cathode material, the carbon nano-sheets obtained by the preparation method special in the embodiment of the invention are fully mixed with selenium (Se), the mixed sample is heated at the temperature of 250-270 ℃, so that the selenium is melted and fully infiltrated into the carbon nano-sheets, and the finally obtained cathode material effectively inhibits the volume expansion of the electrode in the charging and discharging processes, and has a good application prospect in a lithium selenium ion battery. In the embodiment of the invention, the method for determining the selenium loading amount is to perform a thermal weight loss test by a thermogravimetric analyzer. Because the carbon nano sheet after carbonization can not lose weight before 700 ℃, the weight loss phenomenon of the carbon and selenium anode material before 700 ℃ is caused by the weight change of selenium.
The invention is described in further detail with reference to a part of the test results, which are described in detail below with reference to specific examples.
Example 1
(1) Preparing an Al-MOF-1 precursor:
weighing 0.130842g Al (NO)3)3·9H2Placing O and 0.2828g of4, 4' -biphenyldicarboxylic acid in a beaker, adding 50ml of DMF solution, placing the beaker on a magnetic stirrer, stirring for 30min, transferring the fully stirred solution into a 20ml of polytetrafluoroethylene bottle, heating for 24h at 120 ℃, naturally cooling to room temperature, performing centrifugal separation to obtain white precipitate, drying at 70-200 ℃, and grinding to obtain white powder, namely the self-assembled aluminum-based metal organic framework.
(2) Preparing carbon nano sheets:
putting the Al-MOF1 precursor into a tube furnace, carbonizing under the protection of Ar gas at 700 ℃, heating at a rate of 5 ℃/min, keeping the temperature constant for 1h, naturally cooling to room temperature after the constant temperature is finished, putting the obtained black powder sample into a hydrochloric acid solution (10 wt%), carrying out ultrasonic treatment for 30min, sealing the mixture in an autoclave with a polytetrafluoroethylene lining, keeping the temperature constant for 80 ℃ for two days, finally, carrying out centrifugation, washing with ethanol and deionized water, and drying in an oven at 80 ℃ to obtain carbon nanosheets: CNS 1.
(3) Preparing a positive electrode material:
and fully mixing the obtained CNS1 with selenium according to the mass ratio of 2:3, keeping the temperature at 260 ℃ for 20 hours, and naturally cooling to room temperature to obtain a positive electrode material CNS 1-Se.
Example 2
(1) Preparing an Al-MOF-2 precursor:
weighing 0.0651g Al(NO3)3·9H2Placing O and 0.1401g of4, 4' -biphenyldicarboxylic acid in a beaker, adding 50ml of DMF solution, placing the beaker on a magnetic stirrer, stirring for 30min, transferring the fully stirred solution into a 10ml polytetrafluoroethylene bottle, heating for 24h at 120 ℃, naturally cooling to room temperature, performing centrifugal separation to obtain white precipitate, drying at 70-200 ℃, and grinding to obtain white powder.
(2) Preparing carbon nano sheets:
putting Al-MOF2 into a tube furnace, carbonizing under the protection of Ar gas at 700 ℃, heating at a rate of 5 ℃/min, keeping the temperature constant for 1h, naturally cooling to room temperature after the temperature is kept constant, putting the obtained black powder sample into a hydrochloric acid solution (10 wt%), carrying out ultrasonic treatment for 30min, sealing the mixture in a high-pressure kettle with a polytetrafluoroethylene lining, keeping the temperature constant at 80 ℃, placing for two days, finally, centrifuging, washing with ethanol and deionized water, and drying in an oven at 80 ℃ to obtain carbon nano-sheets: CNS 2.
(3) Preparing a positive electrode material:
fully mixing the obtained CNS2 with selenium according to the mass ratio of 9:16, keeping the temperature at 260 ℃ for 20 hours, and naturally cooling to room temperature to obtain a positive electrode material CNS 2-Se.
Example 3
(1) Preparing an Al-MOF-3 precursor:
weighing 0.2634g Al (NO)3)3·9H2Placing O and 0.5308g of4, 4' -biphenyldicarboxylic acid in a beaker, adding 40ml of DMF solution, placing the beaker on a magnetic stirrer, stirring for 30min, transferring the fully stirred solution into a 50ml polytetrafluoroethylene bottle, heating for 24h at 120 ℃, cooling to room temperature along with a furnace, performing centrifugal separation to obtain white precipitate, drying at 70-200 ℃, and grinding to obtain white powder.
(2) Preparing carbon nano sheets:
putting Al-MOF3 into a tube furnace, carbonizing under the protection of Ar gas at 700 ℃, heating at a rate of 5 ℃/min, keeping the temperature constant for 1h, naturally cooling to room temperature after the temperature is kept constant, putting the obtained black powder sample into a hydrochloric acid solution (10 wt%), carrying out ultrasonic treatment for 30min, sealing the mixture in a high-pressure kettle with a polytetrafluoroethylene lining, keeping the temperature constant at 80 ℃, placing for two days, finally, centrifuging, washing with ethanol and deionized water, and drying in an oven at 80 ℃ to obtain carbon nano-sheets: CNS 3.
(3) Preparing a positive electrode material:
fully mixing the obtained CNS3 with selenium according to the mass ratio of 7:13, keeping the temperature at 260 ℃ for 20 hours, and naturally cooling to room temperature to obtain a positive electrode material CNS 3-Se.
Example 4
(1) Preparing an Al-MOF-4 precursor:
weighing 0.5230g Al (NO)3)3·9H2Placing O and 1.0529g of4, 4' -biphenyldicarboxylic acid in a beaker, adding 60ml of DMF solution, placing the beaker on a magnetic stirrer, stirring for 30min, transferring the fully stirred solution into a 200ml polytetrafluoroethylene bottle, heating for 24h at 120 ℃, cooling to room temperature along with a furnace, performing centrifugal separation to obtain white precipitate, drying at 70-200 ℃, and grinding to obtain white powder.
(2) Preparing carbon nano sheets:
putting Al-MOF4 into a tube furnace, carbonizing under the protection of Ar gas at 700 ℃, heating at a rate of 5 ℃/min, keeping the temperature constant for 1h, naturally cooling to room temperature after the temperature is kept constant, putting the obtained black powder sample into a hydrochloric acid solution (10 wt%), carrying out ultrasonic treatment for 30min, sealing the mixture in a high-pressure kettle with a polytetrafluoroethylene lining, keeping the temperature constant at 80 ℃, placing for two days, finally, centrifuging, washing with ethanol and deionized water, and drying in an oven at 80 ℃ to obtain carbon nano-sheets: CNS 4.
(3) Preparing a positive electrode material:
and fully mixing the obtained CNS4 with selenium according to the mass ratio of 2:3, keeping the temperature at 260 ℃ for 20 hours, and naturally cooling to room temperature to obtain a positive electrode material CNS 4-Se.
Example 5
(1) Preparing an Al-MOF-1 precursor: the same as in example 1.
(2) Preparing carbon nano sheets:
putting Al-MOF1 into a tube furnace, carbonizing under the protection of Ar gas at 800 ℃, heating at a rate of 5 ℃/min, keeping the temperature constant for 1h, naturally cooling to room temperature after the temperature is kept constant, putting the obtained black powder sample into a hydrochloric acid solution (10 wt%), carrying out ultrasonic treatment for 30min, sealing the mixture in a high-pressure kettle with a polytetrafluoroethylene lining, keeping the high-pressure kettle at a constant temperature of 80 ℃ for two days, finally, centrifuging, washing with ethanol and deionized water, and drying in an oven at 80 ℃ to obtain carbon nano-sheets: CNS1 (800).
(3) Preparing a positive electrode material:
fully mixing the CNS1(800) obtained in the above step with selenium according to the mass ratio of 2:3, keeping the temperature at 260 ℃ for 20 hours, and naturally cooling to room temperature to obtain a positive electrode material CNS1(800) -Se.
Example 6
(1) Preparing an Al-MOF-2 precursor: the same as in example 2.
(2) Preparing carbon nano sheets:
putting Al-MOF2 into a tube furnace, carbonizing at 900 ℃ under the protection of Ar gas, heating at a rate of 5 ℃/min, keeping the temperature constant for 1h, naturally cooling to room temperature after the temperature is kept constant, putting the obtained black powder sample into a hydrochloric acid solution (10 wt%), carrying out ultrasonic treatment for 30min, sealing the mixture in a high-pressure kettle with a polytetrafluoroethylene lining, keeping the temperature constant at 80 ℃ for two days, finally centrifuging, washing with ethanol and deionized water, and drying in an oven at 80 ℃ to obtain CNS2 (900).
(3) Preparing a positive electrode material:
fully mixing the CNS2(900) obtained in the above step with selenium according to the mass ratio of 2:3, keeping the temperature at 260 ℃ for 20 hours, and naturally cooling to room temperature to obtain a positive electrode material CNS2(900) -Se.
And (3) electrochemical performance testing:
uniformly mixing the positive electrode material obtained in the embodiment, a binder (sodium alginate) and a conductive agent (acetylene black) according to a mass ratio of 80:10:10, adding a solvent, grinding into uniform slurry, coating the slurry on an aluminum foil in a scraping manner, drying, punching into a circular sheet with the diameter of 14mm, tabletting, drying and assembling into a button cell, wherein a counter electrode is a metal lithium sheet, an electrolyte is 1.0M LiTFSI, and is dissolved in a mixed solution of DOL/DME (volume ratio of 1:1), and 1 wt% of LiNO is added3。
ResultsDisplaying: in example 1, the multiplying factor of the charge and discharge test was 0.25C (1C: 675mA/g), and the specific capacity after 200 cycles was 328.9mAh g-1When the multiplying power is 2C (1C 675mA/g), the specific capacity after 200 cycles is 311.8mAh g-1Even if the circulation is carried out for 1000 times under 8C high magnification, 71.45mAh g can be kept-1Specific capacity and coulombic efficiency of 99.9%. In example 2: when the loading of the active substance is 1.13mg cm-2When the specific capacity is 289.5mAh g after the circulation for 350 times under the multiplying power of 0.5C (1C 675mA/g)-1. And when the loading of the active substance is 1.13mg cm-2Then, the specific capacity after 240 cycles under 2C (1C 675mA/g) multiplying power is 347.3mAh g-1. In example 3: the multiplying power of the charge and discharge test is 0.25C (1C is 675mA/g), and the specific capacity after 300 times of circulation is 121.6mAh g-1. In example 4: the multiplying power of the charge and discharge test is 0.25C (1C 675mA/g), and the specific capacity after 180 times of circulation is 125.9mAh g-1. In example 5: the multiplying power of the charge and discharge test is 2C (1C 675mA/g), and 130.6mAh g can be kept after 1009 cycles-1Specific capacity and coulombic efficiency of 99.5%. In example 6: when the loading of the active substance is 0.8mg cm-2When the test piece is circulated for 130 times under the condition of 0.25C (1C 675mA/g), 435.69mAh g can be kept-1Specific capacity and coulombic efficiency of 99.8%.
FIG. 1 is an SEM image of an aluminum-based metal organic framework in an example; fig. 2 is a graph of BET test results of carbon nanoplates obtained in examples 1-4, and elemental analyses are shown in tables 1 and 2:
TABLE 1
Figure BDA0002291548660000131
TABLE 2
Figure BDA0002291548660000132
The Al-MOF-1 test pattern for example 1 is shown in FIG. 3: (a, b, d, e) are scanning electron microscope images of the self-assembled Al-MOF-1; (e) the dotted circle in (a) represents the morphology of a single MOF. c) The calculated X-ray diffraction patterns of the Al-MOF-1 and the self-assembly Al-MOF-1; f) TGA profile of self-assembled Al-MOF-1.
Carbon nanoplate CNS1 testing in example 1 see fig. 4: (a, b, c, d, e, f) are transmission electron microscopy images of CNS1 obtained by carbonizing self-assembled Al-MOF-1 at 700 ℃ for 1 hour in a nitrogen atmosphere; (g) XPS measurement spectrum of CNS 1; (h) n2 adsorption-desorption isotherm at 77K and pore size distribution of CNS1 analyzed using DFT; (i) is a positive electrode material of CNS1 composite selenium.
The positive electrode material (CNS1-Se) in example 1 was tested as shown in FIG. 5: (a) TGA results for the positive electrode material; (b) XRD patterns of pure selenium, CNS1-Se composite and CNS 1; (c) (ii) a Raman spectrum; (d) XPS measurement spectra of CNS1-Se composites; (e) se 3d and (f) Se 3p-XPS spectra of CNS 1-Se. Positive electrode material (CNS1-Se) was tested as shown in fig. 6: (a) rate capability of CNS 1-Se; (b) cyclic performance of CNS1-Se (0.25c, 2 c); (c) an AC impedance diagram of the battery and an equivalent circuit thereof; (d) cycle performance of CNS1-Se composite anode at 8C; (e) CV curve of CNS1-Se composite positive electrode; (f) discharge/charge curves of CNS1-Se composite positive electrode were cycled 1, 2, 50, 100, 200, and 300 times at 0.25C.
The CNS2 test in example 2 is shown in fig. 7: (a, b) SEM picture of CNS 2; (c) n at 77K2Adsorption-desorption isotherms and pore size distribution of CNS2 analyzed using DFT; (d, e, f) low and high power TEM images of CNS 2. The positive electrode material (CNS2-Se) was tested as shown in FIG. 8: (b) SEM picture of CNS2-Se, and distribution of corresponding EDS-O (c), Se (d), C (e) and total elements (a), (f) is CNS2-Se thermogravimetric curve with scale bar of1 μm. The positive electrode material (CNS2-Se) was tested as shown in FIG. 9: (a) raman spectra and (b) XRD patterns of Se, CNS2 and CNS2-Se composites; (c) XPS plots of CNS2-Se composites; (d) se 3d XPS spectrum of CNS 2-Se. The positive electrode material (CNS2-Se) was tested as shown in FIG. 10: (a) rate performance of CNS 2-Se; (b) the cycle performance of the CNS2-Se composite anode material under 0.5 c; (c) CV curves for CNS2-Se complexation; (d) discharge/charge curves for CNS2-Se composite positive electrode materials at 0.25C at 1 st, 2 nd, 50 th, 100 th, 200 th and 300 th cycles. The cycle performance diagram of the positive electrode material (CNS2-Se) is shown in FIG. 11.
The SEM image of the cathode material (CNS3-Se) in example 3 is shown in FIG. 12; the TGA curve and XRD pattern of CNS3-Se composite are shown in figure 13; the cycle performance is shown in FIG. 14: (a) rate performance of CNS 3-Se; (b) cycling performance of the CNS3-Se composite positive electrode material at 0.25 c.
The SEM picture of the cathode material (CNS4-Se) in example 4 is shown in FIG. 15, the thermogravimetric curve of CNS4-Se is shown in FIG. 16, and the cycle performance is shown in FIG. 17: (a) rate performance of CNS 4-Se; (b) cycling performance of the CNS4-Se composite positive electrode material at 0.25 c.
The performance of the positive electrode material in example 5 is tested in fig. 18: CNS1(800) -Se thermogravimetric curve (a); XRD pattern (b) and Raman pattern (c) of CNS1(800) -Se composite material and Se. The cycle performance is shown in FIG. 19: (a) rate capability of CNS 1-Se; (b) cycling performance of CNS1(800) -Se composite positive electrode material at 2C.
The performance of the positive electrode material in example 6 is tested in fig. 20: SEM picture cycling performance of CNS2(900) -Se fig. 21: cycling performance of the CNS2(900) -Se composite positive electrode material at 0.25C.
In example 1, in order to investigate the influence of the carbonization temperature on the carbon nanosheet structure, the alumina-based metal organic framework was kept at a constant temperature for 1 hour in an argon atmosphere at 600 ℃, 700, 800 and 1000 ℃ and the temperature increase rate was 5 ℃ for min-1. The resulting carbon nanoplates were named CNS1(n) ( n 600, 700, 800 and 1000) respectively, depending on the calcination temperature. The corresponding elemental analysis and structural parameters are shown in tables 3 and 4.
TABLE 3
Figure BDA0002291548660000151
TABLE 4
Figure BDA0002291548660000152
As can be seen from the above: the carbon structure can also be regulated by adjusting the carbonization temperature.
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 and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.

Claims (10)

1. A preparation method of carbon nano-sheets is characterized by comprising the following steps:
providing an aluminum source and 4,4' -biphenyldicarboxylic acid;
dissolving the aluminum source and the 4,4' -biphenyldicarboxylic acid in an organic solvent for heating treatment, and then carrying out solid-liquid separation to obtain a self-assembled aluminum-based metal organic framework;
and sequentially carrying out carbonization treatment and acid treatment on the aluminum-based metal organic framework, and then drying to obtain the carbon nanosheet.
2. A method of making carbon nanoplatelets as in claim 1 wherein the temperature of the heat treatment is 110-130 ℃; and/or the presence of a gas in the gas,
the time of the heating treatment is 22-26 h; and/or the presence of a gas in the gas,
the temperature of the carbonization treatment is 600-1000 ℃; and/or the presence of a gas in the gas,
the carbonization time is 1-1.5 h; and/or the presence of a gas in the gas,
the temperature rise rate of the carbonization treatment is 5 ℃/min.
3. A method of making carbon nanoplatelets according to claim 1 wherein the solid-liquid separation comprises: firstly, centrifugal separation is carried out, and then the precipitate obtained by the centrifugal separation is dried at 70-200 ℃.
4. A method of making carbon nanoplatelets according to claim 1 wherein the acid treatment comprises: and (3) placing the carbonized product in an acid solution for ultrasonic treatment.
5. A method of making a carbon nanoplatelet according to claim 4 wherein the acid solution is a hydrochloric acid solution; and/or the presence of a gas in the gas,
the ultrasonic treatment time is 20-40 min.
6. A method of making carbon nanoplatelets as in claim 1 wherein the molar ratio of aluminum element in the aluminum source to the 4,4' -biphenyldicarboxylic acid is 1: (3-4).
7. A method of making carbon nanoplatelets as in any of claims 1-6 wherein the aluminum source is selected from at least one of aluminum nitrate, aluminum sulfate and aluminum chloride; and/or the presence of a gas in the gas,
the organic solvent is N, N-dimethylformamide.
8. A positive electrode material, characterized in that the positive electrode material comprises the carbon nanosheet obtained by the production method according to any one of claims 1 to 7, and selenium supported in the carbon nanosheet.
9. The positive electrode material according to claim 8, wherein the composite material contains selenium in an amount of 50 to 65% by mass.
10. A method for producing a positive electrode material according to claim 8 or 9, comprising the steps of: and mixing the carbon nano sheet with selenium, then heating at the temperature of 250-270 ℃, and cooling to obtain the cathode material.
CN201911182136.8A 2019-11-27 2019-11-27 Preparation method of carbon nanosheet, positive electrode material and preparation method thereof Pending CN110931789A (en)

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