CN113921778B - Reduced graphene oxide-based hollow Co-MOF composite flexible electrode material and preparation method thereof - Google Patents

Reduced graphene oxide-based hollow Co-MOF composite flexible electrode material and preparation method thereof Download PDF

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CN113921778B
CN113921778B CN202111024317.5A CN202111024317A CN113921778B CN 113921778 B CN113921778 B CN 113921778B CN 202111024317 A CN202111024317 A CN 202111024317A CN 113921778 B CN113921778 B CN 113921778B
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graphene oxide
mof
reduced graphene
hollow
ammonium sulfide
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CN113921778A (en
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刘治明
何燕
魏晴
由杰
孙洪冉
李海昌
王晓君
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Qingdao University of Science and Technology
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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
    • H01M4/362—Composites
    • 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
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/60—Selection of substances as active materials, active masses, active liquids of organic compounds
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    • 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
    • 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
    • Y02E60/13—Energy storage using capacitors

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Abstract

The invention belongs to the technical field of electrode material preparation, and particularly relates to a reduced graphene oxide-based hollow Co-MOF composite flexible electrode material and a preparation method thereof, wherein the reduced graphene oxide-based hollow Co-MOF composite flexible electrode material is obtained by freeze drying, then the oxidized graphene oxide-based Co-MOF composite material is rapidly reduced and etched into a hollow part by using a hot ammonium sulfide solution, and the reduced graphene oxide-based hollow Co-MOF composite flexible material is obtained by freeze drying again; the characteristics of high specific capacity of the Co-MOF derivative, excellent mechanical property of the reduced graphene oxide and high conductivity are fully exerted, the prepared composite material can effectively buffer the volume expansion in the circulation process, meanwhile, the hollow structure formed by the Co-MOF further shortens the ion transmission path, the electrochemical reaction kinetics is improved, and the composite material has obvious advantages.

Description

Reduced graphene oxide-based hollow Co-MOF composite flexible electrode material and preparation method thereof
The technical field is as follows:
the invention belongs to the technical field of electrode material preparation, and particularly relates to a reduced graphene oxide-based hollow Co-MOF composite flexible electrode material and a preparation method thereof.
Background art:
the information disclosed in this background section is only for enhancement of some understanding of the general background of the disclosure and is not necessarily to be taken as an acknowledgement or any form of suggestion that this information forms the prior art that is already known to a person skilled in the art.
In recent years, carbon-based composite materials have been widely studied and applied in electrode materials of energy storage devices due to advantages such as large specific surface area and good buffer characteristics. The graphene is used as an excellent self-buffering framework material, the three-dimensional self-buffering network constructed by the graphene can enable the material to have more active sites, high conductivity and high mechanical strength, and the graphene-based hybrid structure often shows the characteristics of capacity increase, speed improvement, stability improvement and the like in a lithium ion battery.
In the prior art, the method for preparing the rGO-based (graphene-based) composite material usually needs complex high-temperature heating (generally 120-180 ℃,1-12 h) and other processes for preparation, such as a hydrothermal method; thus requiring a greater time and energy consumption. The graphene-based composite membrane material obtained by the suction filtration method usually consumes long time, and graphene sheets are stacked seriously, so that the graphene-based composite membrane material has a poor three-dimensional network structure, and the rate capability in a battery test is greatly reduced. Moreover, the conventional slurry coating method requires the addition of a conductive agent and a binder when preparing an electrode, which undoubtedly lowers the energy density of the battery.
MOFs and their derivatives are of interest as metal compounds, with their porous framework structural properties and high theoretical capacity, but their application is limited by their large volume expansion during cycling.
Therefore, compounding the MOF material and the graphene has the advantages of becoming a trend in the material field, however, the conventional method for preparing the graphene-based composite material usually requires complicated steps such as high-temperature heating, consumes a large amount of energy and requires a long time. Meanwhile, the obtained graphene-based composite material often has the problems of serious stacking of graphene sheets and the like, so that a poor three-dimensional network structure is caused.
Furthermore, most of the applications of Co-MOF only stay in the stage of their derivative porous framework, and thus a new electrode form is required to solve the above problems.
The invention content is as follows:
the invention provides a reduced graphene oxide based hollow Co-MOF composite flexible electrode material, and aims to provide an MOF material and a graphene oxide composite electrode material with new structures, which are synergistic with each other and jointly improve the electrochemical reaction kinetics in the application process.
The invention also aims to provide a preparation method of the reduced graphene oxide-based hollow Co-MOF composite flexible electrode material, aiming at solving the problems that in the composite preparation process of the graphene oxide and Co-MOF composite material, the traditional reduction treatment of the graphene oxide causes the graphene oxide to have a poor three-dimensional network structure, and further the rate performance in the battery test is greatly reduced; in addition, the traditional slurry coating method needs to add a conductive agent and a binder when preparing an electrode, which undoubtedly reduces the energy density of the battery, and therefore, the practical application of the graphene oxide and Co-MOF composite material is limited.
In order to achieve the purpose, the invention is realized by the following technical scheme that the preparation method of the reduced graphene oxide-based hollow Co-MOF composite flexible electrode material comprises the following steps:
s1, uniformly mixing Co-MOF with a porous framework structure with a reduced graphene oxide dispersion liquid, and freeze-drying the mixed liquid to obtain a graphene oxide-based Co-MOF composite material;
s2, treating the graphene oxide Co-MOF composite material by using a hot ammonium sulfide solution at the temperature of 50-90 ℃ in a room temperature environment; performing rapid crosslinking reduction reaction on ammonium sulfide and graphene oxide, etching Co-MOF into a hollow structure, and washing off residual ammonium sulfide by using deionized water after 1-5 min;
and S3, freezing and drying again to obtain the reduced graphene oxide based hollow Co-MOF composite flexible membrane material.
Preferably, the Co-MOF is etched into a hollow structure by utilizing ammonium sulfide, and simultaneously, the graphene oxide Co-MOF is rapidly crosslinked and reduced.
Preferably, the temperature of the hot ammonium sulfide solution in step S2 is 50 ℃ to 90 ℃; the reaction time is 1-5min.
A reduction-oxidation graphene-based hollow Co-MOF composite flexible electrode material is characterized in that Co-MOF with a porous skeleton structure and reduction-oxidation graphene are compounded together, the reduction-oxidation graphene is a cross-linking structure, and the Co-MOF etched into the hollow structure is wrapped in the cross-linking structure to form a stable structure.
The invention has the beneficial effects that: the composite electrode prepared by the invention takes the reduced graphene oxide as a conductive substrate, and combines the characteristics of high specific capacity of the hollow Co-MOF derivative, excellent mechanical buffer performance and high conductivity of the reduced graphene oxide, so that the prepared electrode material has the structural characteristics of looseness and porosity, has good flexibility, can effectively relieve the problem of volume expansion in the circulation process, enhances the circulation stability, further shortens the ion transmission path, and improves the electrochemical reaction kinetics
The biggest innovation of the invention is that the flexible self-supporting film electrode can be rapidly prepared at room temperature by freeze-drying film forming, ammonium sulfide cross-linking reduction of graphene oxide and a method for etching Co-MOF, and the flexible self-supporting film electrode is easy to prepare in large scale.
(1) According to the invention, at room temperature, ammonium sulfide is used for etching Co-MOF into a hollow structure, graphene oxide is rapidly crosslinked and reduced, and freeze drying is adopted, so that the method is used for directly forming a film, the preparation process is rapid and simple, the cost is low, a complex heating process is not needed, the use of a conductive agent and a binder in a slurry method is avoided, and the energy density of the material can be improved.
(2) Compared with other traditional methods, the reduced graphene oxide-based membrane electrode material synthesized by the method is easy to regulate and control in structure, components, morphology, thickness, loading capacity and other parameters, and is easy for large-scale preparation.
(3) According to the invention, the Co-MOF is etched into the hollow structure by utilizing the etching effect of the ammonium sulfide on the Co-MOF, and compared with the traditional structure only combining the Co-MOF and the ammonium sulfide, the hollow structure can effectively improve the specific surface area of the material, shorten the ion transmission path and further improve the electrochemical reaction kinetics, thereby improving the electrochemical performance of the derivative.
(4) The composite material disclosed by the invention combines the characteristics of high specific capacity of the hollow Co-MOF derivative, excellent mechanical buffering performance of the reduced graphene oxide and high conductivity, and can effectively relieve the problem of volume expansion in the circulation process, so that the circulation stability is enhanced.
Drawings
FIG. 1 is an SEM picture of a reduced graphene oxide-based hollow Co-MOF composite flexible material;
fig. 2 is an SEM picture of the reduced graphene oxide-based hollow Co-MOF composite flexible material at another magnification.
The specific implementation mode is as follows:
in order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are clearly and completely described below, and it is obvious that the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, belong to the protection scope of the present invention.
Example 1
The preparation method of the reduced graphene oxide based hollow Co-MOF composite flexible material comprises the following steps:
s1: adding a certain amount of pre-prepared Co-MOF into a dispersion liquid containing a certain amount of GO, mixing in a ratio of 3.
S2: and transferring the uniformly stirred mixed solution to a culture dish with a certain size, and freeze-drying to obtain the graphene oxide Co-MOF composite material.
S3: and (2) pouring a preheated ammonium sulfide solution (wt 20%,50-90 ℃) into the graphene oxide based Co-MOF composite membrane obtained after freeze drying for rapid reduction crosslinking treatment, simultaneously etching the Co-MOF into a hollow structure, immediately washing off residual ammonium sulfide by using DIW after 1-5min, and freeze drying again to obtain the flexible self-supporting membrane composite electrode material of the reduced graphene oxide and the hollow Co-MOF.
S4: and then the flexible self-supporting film composite electrode compounded by the corresponding oxides, sulfides and the like and the reduced graphene oxide can be obtained through heat treatment.
S5: by changing the amount of the mixed liquid in the step S1, flexible self-supporting thin film electrodes with different surface loading amounts can be obtained.
Comparative example 1
Fe 2 O 3 A rapid preparation method of a @ rGO flexible self-supporting membrane composite electrode comprises the following steps:
s1: mixing a predetermined amount of pre-prepared Fe 2 O 3 Adding the mixture into a dispersion liquid containing a certain amount of GO, stirring the mixture for 5-10min by using a defoaming stirrer after mixing the mixture with a ratio of 3 2 O 3 A mixed solution with GO;
s2: transferring the uniformly stirred mixed solution into a culture dish with a certain size, and freeze-drying to obtain a graphene oxide-based membrane material;
s3: pouring a preheated ammonium sulfide solution (wt 20%,50-90 ℃) into the graphene oxide base membrane obtained after freeze drying for rapid reduction crosslinking treatment, then washing off residual ammonium sulfide by using DIW, and freeze drying again to obtain the reduced graphene oxide-based flexible self-supporting membrane electrode material;
s4: by changing the amount of the mixed liquid in the step S1, flexible self-supporting membrane electrodes with different surface loading amounts can be obtained;
from FIGS. 1-2, it can be seen that the Co-MOF is well encapsulated, and in addition, the Co-MOF exhibits a contrast characteristic of hollow interior.
In conclusion, the flexible self-supporting film electrode can be rapidly prepared at room temperature by freeze drying film forming, ammonium sulfide crosslinking reduction of graphene oxide and Co-MOF etching, and is easy for large-scale preparation.
The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments, and it should be understood by those skilled in the art that various modifications or changes can be made by those skilled in the art without inventive efforts based on the technical solutions of the present invention.

Claims (4)

1. A preparation method of a reduced graphene oxide-based hollow Co-MOF composite flexible electrode material is characterized by comprising the following steps: the method comprises the following steps:
s1, uniformly mixing Co-MOF with a porous framework structure with graphene oxide dispersion liquid, and freeze-drying the mixed liquid to obtain a graphene oxide-based Co-MOF composite material;
s2, treating the graphene oxide Co-MOF composite material by using a hot ammonium sulfide solution in a room temperature environment, performing a rapid cross-linking reduction reaction on ammonium sulfide and graphene oxide, etching the Co-MOF into a hollow structure, and washing off residual ammonium sulfide by using deionized water after 1-5 min;
s3, freeze-drying again to obtain a reduced graphene oxide based hollow Co-MOF composite flexible membrane material;
the prepared reduced graphene oxide-based hollow Co-MOF composite flexible electrode material is prepared by compounding Co-MOF with a porous framework structure and reduced graphene oxide, wherein the reduced graphene oxide is a cross-linked structure, and the Co-MOF etched into the hollow structure is wrapped in the cross-linked structure to form a stable structure.
2. The method of claim 1, wherein: and (3) etching the Co-MOF into a hollow structure by utilizing ammonium sulfide, and simultaneously, rapidly crosslinking and reducing the graphene oxide.
3. The method of claim 1, wherein: the temperature of the ammonium sulfide solution in the step S2 is 50-90 ℃, the concentration of the ammonium sulfide solution is 10-30 wt%, and the reaction time is 1-5min.
4. The method of claim 1, wherein: adding pre-prepared Co-MOF into a dispersion liquid containing a certain amount of GO, wherein the molar ratio of the Co-MOF to the graphene oxide is 0.2-5.
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Citations (1)

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Publication number Priority date Publication date Assignee Title
CN108336310A (en) * 2017-01-20 2018-07-27 中国科学院物理研究所 A kind of composite material and preparation method based on self-supporting redox graphene volume

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CN105130380A (en) * 2015-08-21 2015-12-09 哈尔滨工业大学 Preparation method of graphene-zirconia fiber composite aerogel
CN106430166B (en) * 2016-10-28 2018-11-23 武汉理工大学 A kind of preparation method of MOFs- graphene composite material
CN111072402A (en) * 2019-12-31 2020-04-28 青岛科技大学 Preparation method of graphene-coated carbon nanotube and MOF three-dimensional composite electrode material

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CN108336310A (en) * 2017-01-20 2018-07-27 中国科学院物理研究所 A kind of composite material and preparation method based on self-supporting redox graphene volume

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