Preparation method and application of porous graphene-based composite film material
阅读说明：本技术 一种多孔石墨烯基复合薄膜材料的制备方法及其应用 (Preparation method and application of porous graphene-based composite film material ) 是由 江丽丽 侯宝权 盛利志 于 2019-09-17 设计创作，主要内容包括：本发明公开了一种多孔石墨烯基复合薄膜材料的制备方法,包括如下步骤：(1)多孔石墨烯分散液的制备；(2)碳纳米管@赝电容材料分散液的制备；(3)复合薄膜材料的制备：将多孔石墨烯分散液和碳纳米管@赝电容材料分散液混合,超声；真空抽滤,滤饼自然干燥,剥离得到多孔石墨烯/碳纳米管@赝电容材料复合薄膜材料。本发明制备的多孔石墨烯基复合薄膜材料在无导电剂和粘结剂的情况下可直接作为柔性电极材料,其具有优异的倍率特性、高能量/功率密度以及长循环使用寿命,原料成本低廉、工艺简单、环境友好,在柔性超级电容器的电极材料领域具有良好的应用前景。(The invention discloses a preparation method of a porous graphene-based composite film material, which comprises the following steps: (1) preparing a porous graphene dispersion liquid; (2) preparing a carbon nano tube @ pseudocapacitance material dispersion liquid; (3) preparing a composite film material: mixing the porous graphene dispersion liquid and the carbon nanotube @ pseudocapacitance material dispersion liquid, and performing ultrasonic treatment; and (3) carrying out vacuum filtration, naturally drying a filter cake, and stripping to obtain the porous graphene/carbon nanotube @ pseudocapacitance material composite film material. The porous graphene-based composite film material prepared by the invention can be directly used as a flexible electrode material without a conductive agent and a binder, has excellent rate characteristic, high energy/power density and long cycle service life, is low in raw material cost, simple in process and environment-friendly, and has good application prospect in the field of electrode materials of flexible supercapacitors.)
1. A preparation method of a porous graphene-based composite film material is characterized by comprising the following steps:
(1) preparing a porous graphene dispersion liquid: preparing graphite oxide dispersion liquid by a Hummers method, uniformly dispersing by ultrasonic, adding potassium permanganate and carrying out microwave treatment; after cooling, adding hydrazine hydrate and ammonia water in turn under the stirring condition, and heating the obtained mixed system in a water bath; cooling the solution, adding oxalic acid, and stirring; performing suction filtration and washing, and preparing a filter cake into a porous graphene dispersion liquid by using deionized water;
(2) preparing a carbon nano tube @ pseudocapacitance material dispersion liquid: ultrasonically dispersing the carbon nano tube in a solvent, adding metal oxide, metal salt or metal salt plus alkali to obtain a hydrothermal treatment system, and carrying out hydrothermal treatment; after cooling, carrying out suction filtration, washing and drying, and preparing a carbon nanotube @ pseudocapacitance material dispersion liquid by using deionized water;
(3) preparing a composite film material: mixing the porous graphene dispersion liquid and the carbon nanotube @ pseudocapacitance material dispersion liquid, and performing ultrasonic treatment; and (3) carrying out vacuum filtration, naturally drying a filter cake, and stripping to obtain the porous graphene/carbon nanotube @ pseudocapacitor material, namely the composite film material.
2. The method for preparing a porous graphene-based composite thin film material according to claim 1, wherein in the step (1):
the graphite oxide concentration in the graphite oxide dispersion liquid is 0.2-2.0mgmL-1；
The mass ratio of the potassium permanganate to the graphite oxide is 1:1-8: 1;
the dosage of hydrazine hydrate is 0.05-5mL/150mL mixed system;
the dosage of the ammonia water is 0.3-8mL/150mL mixed system.
3. The method for preparing a porous graphene-based composite thin film material according to claim 1 or 2, wherein in the step (1):
the microwave treatment time is 5-30min, and the power is 800-;
heating in water bath for 10-60min at 90-100 deg.C;
the dosage of the oxalic acid is 2g/150mL of the mixed system, and the mixed system is stirred for at least 12h after the oxalic acid is added.
4. The method for preparing a porous graphene-based composite thin film material according to claim 1, wherein in the step (2):
the pseudocapacitance material comprises a metal oxide or metal hydroxide;
the metal oxide comprises manganese dioxide, ferric oxide, tin dioxide or vanadium pentoxide;
the metal hydroxide includes nickel hydroxide.
5. The method for preparing a porous graphene-based composite thin film material according to claim 1 or 4, wherein in the step (2):
the concentration of the carbon nano tube in the hydrothermal treatment system is 0.1-0.35mgmL-1；
The concentration of the metal oxide or the metal salt in the hydrothermal treatment system is 5-50 mu molmL-1；
The hydrothermal treatment temperature is 80-240 ℃ and the time is 1-12 h.
6. The method for preparing a porous graphene-based composite thin film material according to claim 1, wherein in the step (3):
the mass ratio of the porous graphene in the porous graphene dispersion liquid to the carbon nano tube @ pseudocapacitance material in the carbon nano tube @ pseudocapacitance material dispersion liquid is 1:4-3: 1.
7. A porous graphene-based composite thin film material prepared by the preparation method of any one of claims 1-6.
8. The porous graphene-based composite film material according to claim 7, wherein the unit mass of the composite film material is 0.5-2mgcm-2。
9. Use of the porous graphene-based composite thin film material of claim 7 or 8 as an electrode material in a flexible supercapacitor.
Technical Field
The invention relates to structural design and preparation of a flexible composite electrode material, belongs to the technical field of material science and electrochemistry, and particularly relates to a preparation method and application of a porous graphene-based composite film material.
Background
With the rapid development of electronic technology, mobile electronic devices are gradually becoming flexible, light, thin, and wearable. However, the conventional energy storage device (such as a battery) is a rigid product, and when the conventional energy storage device is folded or bent, the electrode material and the current collector are easily separated, the electrochemical performance is reduced, even a short circuit is caused, and a great potential safety hazard exists. Therefore, in order to adapt to the development of a new generation of flexible electronic devices, a novel electrochemical energy storage device which is light, thin and flexible becomes a research hotspot nowadays.
In many energy storage devices, the super capacitor is used as a novel green energy storage device, has the characteristics of high charging and discharging efficiency, long cycle life, high power density and the like, and can make up for the defects of batteries. However, the energy density of the flexible supercapacitor is still low at present, and the electrochemical stability of the device is difficult to guarantee during the bending and folding process, which limits the practical application of the flexible supercapacitor to a certain extent. Therefore, how to improve the energy density of the super capacitor while maintaining the original higher power density and longer cycle life of the super capacitor is a new challenge in the research field of flexible energy storage devices in recent years.
As is well known, the core of flexible supercapacitors is a flexible electrode sheet with high performance. At present, flexible electrode pole pieces mainly comprise two types: a non-conductive flexible matrix adopting high molecular polymers, paper, woven cloth and the like hardly contributes to the capacity of an electrode, and has poor conductivity, so that the energy density and the rapid charge and discharge capacity of a super capacitor are reduced, and the possibility of reaction with an electrolyte exists; and the other one adopts a conductive flexible matrix such as graphene, active substances are attached to the structural units of the flexible matrix skeleton to form an integral flexible electrode, and any conductive agent and binder are not required to be added.
However, the graphene sheet layer is easy to agglomerate, and the application of the graphene sheet layer as a flexible electrode sheet substrate is influenced. The researchers at home and abroad proposeA support is introduced between graphene sheet layers, for example, yamingWang et al self-assemble carbon black particles and graphene nano sheets into a graphene/carbon black composite film flexible electrode material (J.Power Sources,2014,271,269-277), the carbon black particles play a role of spacing the graphene nano sheets and show excellent rate characteristics; however, due to the limitation of the double electric layer energy storage mechanism, the specific capacity of the graphene/carbon black composite film is only 112F g-1. Pooi See Lee et al introduce a pseudocapacitance material between graphene sheets, effectively inhibit the agglomeration of graphene, and improve the specific capacity of a flexible electrode material (adv. Mater.,2013,25(20): 2809-2815); however, for pseudo-capacitive materials, particularly metal oxides, added to graphene-based flexible electrode materials tend to destroy the conductive network of graphene. To solve the problem, Jie Liu et al introduce a third phase of carbon nanotubes into graphene/manganese dioxide powder to improve the conductivity and flexibility of the composite material, and prepare a graphene/manganese dioxide/carbon nanotube composite film (Nano lett, 2012,12(8):4206--1(ii) a However, most electrolyte ions are transmitted and diffused in the direction between graphene layers, and the ion transfer capability in the radial direction is poor, so that the specific capacity of the electrode material is rapidly attenuated under the condition of large-current charging and discharging, the rate characteristic of the electrode material is poor, and the specific capacity retention rate is only 45%.
Therefore, how to improve the specific capacity of the flexible electrode material and ensure the specific capacity retention rate under the condition of large-current charge and discharge becomes a technical problem to be solved in the field.
Disclosure of Invention
In view of the above, the porous graphene prepared by a chemical etching method and the carbon nanotube @ pseudocapacitor material prepared by a hydrothermal method are used as elementary materials, and a thin film material with integrated functions of a three-dimensional ion diffusion channel, an integral conductive network, surface modification, high pseudocapacitor and the like is constructed in a vacuum filtration manner.
In order to achieve the purpose, the invention adopts the following technical scheme:
a preparation method of a porous graphene-based composite film material comprises the following steps:
(1) preparing a porous graphene dispersion liquid: preparing graphite oxide dispersion liquid by a Hummers method, uniformly dispersing by ultrasonic, adding potassium permanganate and carrying out microwave treatment; after cooling, adding hydrazine hydrate and ammonia water in turn under the stirring condition, and heating the obtained mixed system in a water bath; cooling the solution, adding oxalic acid, and stirring; performing suction filtration and washing, and preparing a filter cake into a porous graphene dispersion liquid by using deionized water;
(2) preparing a carbon nano tube @ pseudocapacitance material dispersion liquid: ultrasonically dispersing the carbon nano tube in a solvent, adding metal oxide, metal salt or metal salt plus alkali to obtain a hydrothermal treatment system, and carrying out hydrothermal treatment; after cooling, carrying out suction filtration, washing and drying, and preparing a carbon nanotube @ pseudocapacitance material dispersion liquid by using deionized water;
(3) preparing a composite film material: mixing the porous graphene dispersion liquid and the carbon nanotube @ pseudocapacitance material dispersion liquid, and performing ultrasonic treatment; and (3) carrying out vacuum filtration, naturally drying a filter cake, and stripping to obtain the porous graphene/carbon nanotube @ pseudocapacitor material, namely the composite film material.
Preparing a composite film material by taking porous graphene prepared by a chemical etching method and a carbon nanotube @ pseudocapacitor material prepared by a hydrothermal method as elements, growing the pseudocapacitor material on the carbon nanotube in situ, and constructing the carbon nanotube @ pseudocapacitor material with high internal conductivity and high external pseudocapacitor, wherein the carbon nanotube @ pseudocapacitor material is supported between graphene layers, so that the graphene sheet layer agglomeration can be inhibited, and an interlayer ion diffusion channel can be built in the graphene sheet layer; the porous graphene is a supporting framework and a conductive network of the composite film material, and a pore channel on a graphene sheet layer ensures that electrolyte ions can be rapidly diffused in the radial direction, so that a three-dimensional developed ion diffusion channel is established, and the porous graphene can also buffer the volume expansion of the pseudo-capacitor material in the charging and discharging processes.
Preferably, in the step (1):
the concentration of the graphite oxide in the graphite oxide dispersion liquid is 0.2-2.0mg mL-1；
The mass ratio of the potassium permanganate to the graphite oxide is 1:1-8: 1;
the dosage of hydrazine hydrate is 0.05-5mL/150mL mixed system;
the dosage of the ammonia water is 0.3-8mL/150mL mixed system.
Preferably, in the step (1):
the microwave treatment time is 5-30min, and the power is 800-;
heating in water bath for 10-60min at 90-100 deg.C;
the dosage of the oxalic acid is 2g/150mL of the mixed system, and the mixed system is stirred for at least 12h after the oxalic acid is added.
Preferably, in the step (2):
the pseudocapacitance material comprises a metal oxide or metal hydroxide;
the metal oxide comprises manganese dioxide, ferric oxide, tin dioxide or vanadium pentoxide;
the metal hydroxide includes nickel hydroxide.
Preferably, in the step (2):
the concentration of the carbon nano tube in the hydrothermal treatment system is 0.1-0.35mg mL-1；
The concentration of the metal oxide or the metal salt in the hydrothermal treatment system is 5-50 mu mol mL-1；
The hydrothermal treatment temperature is 80-240 ℃ and the time is 1-12 h.
Preferably, in the step (3):
the mass ratio of the porous graphene in the porous graphene dispersion liquid to the carbon nano tube @ pseudocapacitance material in the carbon nano tube @ pseudocapacitance material dispersion liquid is 1:4-3: 1.
Further preferably, the mass ratio of the porous graphene to the carbon nanotube @ pseudocapacitance material is 1:1, 1:2, 1:3, 1:4, 2:1 or 3: 1.
The porous graphene-based composite film material prepared by the preparation method.
Preferably, the unit mass of the composite film material is 0.5-2mg cm-2。
An application of a porous graphene-based composite film material as an electrode material in a flexible supercapacitor. In 1Ag-1At current densityThe specific capacitance can reach 200-900F g-1The energy density of the asymmetric super capacitor can reach 20-50Whkg-1After circulation for 2000 times and 10000 times, the service life can reach 60-110% of the initial specific capacity.
According to the technical scheme, the porous graphene-based composite film material prepared by the invention can be directly used as a flexible electrode material without a conductive agent and a binder, has excellent rate characteristic, high energy/power density and long cycle service life, is low in raw material cost, simple in process and environment-friendly, and has a good application prospect in the field of electrode materials of flexible super capacitors.
Drawings
FIG. 1 shows the porous graphene/carbon nanotube @ MnO obtained in example 12A composite film material object photo;
FIG. 2 shows the porous graphene/carbon nanotube @ MnO obtained in example 12SEM pictures of the composite film material under different magnifications;
FIG. 3 shows the porous graphene/carbon nanotube @ MnO obtained in example 12Constant current charge-discharge curve of the composite film material under different current densities;
FIG. 4 shows the porous graphene/carbon nanotube @ MnO obtained in example 12The specific capacity attenuation curve of the composite film material under different current densities;
FIG. 5 shows the porous graphene/carbon nanotubes @ MnO obtained in example 12Cycle life curve of the composite film material;
FIG. 6 shows the porous graphene/carbon nanotube @ MnO obtained in example 12CV curves of asymmetric supercapacitors assembled by taking the composite film material as a positive electrode and taking the porous graphene/carbon nanotube composite film material as a negative electrode at different scanning speeds;
FIG. 7 shows the porous graphene/carbon nanotube @ MnO obtained in example 12The composite film material is an asymmetric supercapacitor power-energy density diagram assembled by a positive electrode and a porous graphene/carbon nanotube composite film material as a negative electrode.
Detailed Description
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 only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.