CN107331526B

CN107331526B - Preparation method and application of compressible graphene aerogel and supercapacitor thereof

Info

Publication number: CN107331526B
Application number: CN201710596826.2A
Authority: CN
Inventors: 刘利彬; 向宇; 杜永旭
Original assignee: Qilu University of Technology
Current assignee: Qilu University of Technology
Priority date: 2017-07-20
Filing date: 2017-07-20
Publication date: 2021-05-11
Anticipated expiration: 2037-07-20
Also published as: CN107331526A

Abstract

The invention provides a compressible graphene aerogel and a preparation method and application of a supercapacitor of the compressible graphene aerogel. Pyrrole (Py) and silver nitrate are used as oxidation-reduction agents, and the RGO-PPy-Ag hydrogel is prepared with graphite oxide through a one-step hydrothermal method and is subjected to freeze drying to obtain the RGO-PPy-Ag aerogel. Successful GO reduction is confirmed by a series of testing methods such as infrared spectroscopy, XPS, Raman, XRD and the like by using common characterization methods, a large number of oxygen-containing functional groups on GO lamellar structures are removed, and Py and AgNO are combined₃And the oxidation and reduction are PPy-Ag and are fixed on the three-dimensional framework of the graphene. When the Strain is 40%, the composite aerogel can be compressed more than 20 times, and the recovery rate can reach more than 75%. The electrochemical performance of the assembled compressible graphene super capacitor is explored, and after the compressible graphene super capacitor is compressed for 20 times, the electrochemical performance of the compressible graphene super capacitor is not obviously changed, and the compressible graphene super capacitor has certain stability.

Description

Preparation method and application of compressible graphene aerogel and supercapacitor thereof

Technical Field

The invention belongs to the field of electrochemical energy, and particularly relates to a compressible graphene aerogel and a preparation method and application of a supercapacitor of the compressible graphene aerogel.

Background

In recent years, deformable electronic devices have received great attention because they can be flexibly applied to non-conventional forms of high-tech electronic products while maintaining their characteristics, playing an important role in the field of high-tech electronics. Stretchable electronics, an indispensable component of advanced electronics, have been able to accommodate high frequency strain without significant loss of functionality. Among various power devices, supercapacitors have attracted extensive interest from researchers due to the advantages of high power density, long cycle life, short charging time, and the like of their energy storage devices. The advantages of the composite material make the composite material very promising for electric vehicles and other high-power energy sources. The super capacitor has achieved the achievement of plastic manufacturing, has high electrochemical capacitance performance even in a mechanical stretching process, and has strategic significance for developing portable and flexible wearable electronic equipment.

Researchers are constantly striving to increase the energy/power density of supercapacitors beyond what has been invented for electronic devices, but few attempts have been made to compress the development of supercapacitors, which, while being an inverse mechanical stress, is one of the most influential factors in developing the electrochemical performance of flexible supercapacitors, as the compression and tension processes are reversed. The spongy structure has high porosity and excellent flexibility, can keep the stability of the structure and the performance of the spongy structure under mechanical strain/stress almost without any change, has important significance in the aspects of application to brakes, catalytic carriers, adsorption, separation and the like, and simultaneously has the potential of application to the manufacture of compressible high-voltage-resistance electrode materials. However, it is a great challenge to produce supercapacitors with highly elastic, highly conductive, highly robust porous foam-like structures.

Recently, the nanocarbon material has the characteristics of a spongy mechanism structure, high porosity, flexible structure, restorable deformation and the like. Graphene, as a two-dimensional single-layer carbon material, attracts a wide attention due to its characteristics of large specific surface area, high electron mobility, excellent thermal conductivity, high elasticity, high toughness, and the like, and is considered to be an optimal component for manufacturing a 3D porous large module with low density and high conductivity. However, the original three-dimensional graphene mechanism has relatively poor compression performance and elastic performance, and is easy to generate irreversible deformation during the compression process and even cause structural collapse. Therefore, even though graphene is currently used in large quantities in the manufacture of supercapacitors and electrodes, there is essentially no report on the preparation of graphene compressible supercapacitors.

Disclosure of Invention

In order to overcome the defects, the invention prepares the compressible RGO-PPy-Ag aerogel by a one-step synthesis hydrothermal method and applies the aspect of the compressible super capacitor. When the Strain is 40%, the composite aerogel can be compressed more than 20 times, and the recovery rate can reach more than 75%. The electrochemical performance of the assembled compressible graphene super capacitor is explored, and after the compressible graphene super capacitor is compressed for 20 times, the electrochemical performance of the compressible graphene super capacitor is not obviously changed, and the compressible graphene super capacitor has certain stability.

In order to achieve the purpose, the invention adopts the following technical scheme:

a compressible graphene RGO-PPy-Ag aerogel comprising:

a graphene three-dimensional network skeleton;

PPy-Ag nanoparticles dispersed on the graphene sheets;

the PPy-Ag nano particles are formed by aggregation of PPy and Ag.

In order to form RGO-PPy-Ag foam through in-situ polymerization, silver nitrate is used as an oxidation-reduction agent, Py monomers are subjected to oxidation polymerization to form an aggregate of PPy and Ag, part of oxygen-containing functional groups on a GO lamellar structure are removed, and the introduced silver nanoparticles effectively improve the conductivity, chemical durability and mechanical stability of the aerogel. The results show that: the obtained RGO-PPy-Ag aerogel presents a better three-dimensional network connected pore structure, the PPy-Ag nano particles on the single-layer graphene have better dispersibility, and the PPy-Ag is blended, so that the compressibility, electrochemical performance and thermal stability of the graphene aerogel are effectively improved.

Preferably, the particle size of the PPy-Ag nano particle is 50-100 nm.

Preferably, in the aerogel, the mass ratio of RGO, PPy and Ag is 2-12: 1: 0.5-1.

Most preferably, the mass ratio of RGO, PPy and Ag in the aerogel is 8:1: 0.5.

The invention also provides a preparation method of the compressible graphene RGO-PPy-Ag aerogel, which comprises the following steps:

mixing graphene oxide dispersion liquid, Py organic solution and AgNO₃Uniformly mixing the aqueous solution to obtain a mixed solution;

carrying out hydrothermal reaction on the mixed solution at 160-180 ℃ for 12-36h, and drying to obtain RGO-PPy-Ag hydrogel;

and standing the RGO-PPy-Ag hydrogel in water for 12-14 h, and freeze-drying to obtain the RGO-PPy-Ag aerogel.

Preferably, RGO, PPy, Ag in the mixed solution⁺The mass ratio of (A) to (B) is 2-12: 1: 0.5-1.

Most preferably, the mass ratio of RGO, PPy and Ag in the mixed solution is 8:1: 0.5.

The invention also provides aerogels prepared by any of the above methods.

The invention also provides a preparation method of the compressible graphene RGO-PPy-Ag hydrogel, which comprises the following steps:

and carrying out hydrothermal reaction on the mixed solution at 160-180 ℃ for 12-36h, and drying to obtain the RGO-PPy-Ag hydrogel.

The invention also provides RGO-PPy-Ag hydrogel prepared by any one of the methods.

The invention also provides an assembled compressible graphene supercapacitor, and an electrode material of the supercapacitor is the hydrogel or any one of the aerogels.

The invention also provides the use of any of the above aerogels, or the above hydrogels, in the preparation of a deformable electronic device.

The invention has the advantages of

(1) When the strength of the compressed graphene RGO-PPy-Ag aerogel prepared by the invention is 40%, the composite aerogel can be compressed for more than 20 times, and the recovery rate of the composite aerogel can reach more than 75%. The electrochemical performance of the assembled compressible graphene super capacitor is explored, and after the compressible graphene super capacitor is compressed for 20 times, the electrochemical performance of the compressible graphene super capacitor is not obviously changed, and the compressible graphene super capacitor has certain stability.

(2) Compared with the original graphene material, the compressible graphene RGO-PPy-Ag aerogel prepared by the invention has excellent electrochemical performance, and the specific capacitance of the compressible graphene RGO-PPy-Ag aerogel can reach the highestTo 447.5F g^-1。

(3) The graphene oxide dispersion GO is synthesized and prepared by the method. Pyrrole (Py) and silver nitrate are used as oxidation-reduction agents, and the RGO-PPy-Ag hydrogel is prepared with graphite oxide through a one-step hydrothermal method and is subjected to freeze drying to obtain the RGO-PPy-Ag aerogel. Successful GO reduction is confirmed by a series of testing methods such as infrared spectroscopy, XPS, Raman, XRD and the like by using common characterization methods, a large number of oxygen-containing functional groups on GO lamellar structures are removed, and Py and AgNO are combined₃And the oxidation and reduction are PPy-Ag and are fixed on the three-dimensional framework of the graphene.

(4) The preparation method is simple, high in efficiency, strong in practicability and easy to popularize.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the application and, together with the description, serve to explain the application and are not intended to limit the application.

FIG. 1 is a schematic diagram of the (a) synthesis of RGO-PPy-Ag aerogel; (b) SEM images at different magnifications; (c) a TEM image;

FIG. 2 is an XRD spectrum of RGO and RGO-PPy-Ag aerogels;

FIG. 3 is an infrared spectrum of an RGO-PPy-Ag aerogel;

FIG. 4 is a spectrum of RGO-PPy-Ag aerogel (a) N1 s; (b) spectrum C1 s;

FIG. 5 is a Raman spectrum of GO and RGO-PPy-Ag aerogels;

figure 6 is an electrochemical characterization of RGO and RGO-PPy-Ag 2:1:0.5, 4:1:0.5, 8:1:0.5, 12:1: 0.5: (a) a CV curve at a scan rate of 200 mV/s; (b) GCD at a current density of 1A/g; (c) an impedance curve; (d) bode plot of phase versus frequency;

FIG. 7 is a CV curve of RGO versus RGO-PPy-Ag ═ (a)2:1: 0.5; (b) CV curve 4:1: 0.5; (c) CV curve of 8:1: 0.5; (d) CV curve of 12:1: 0.5;

FIG. 8 is a CV curve for (a) different scan rates of RGO-PPy-Ag-8: 1: 1; (b) RGO-PPy-Ag 8:1:0.5 and 8:1:1 at a current density of 1 A.g^-1A GCD curve of (1); (c) an impedance plot; (d) a graph of frequency versus phase Bode;

fig. 9 is an electrochemical characterization of RGO-PPy-Ag at 8:1:0.5 reaction times of 12h, 24h, 36 h: (a) the scanning rate is 100mV s^-1(ii) a (b) The current density is 1 A.g^-1GCD; (c) an impedance plot; (d) a graph of frequency versus phase Bode; (e) specific capacitance; (f) graph of energy density versus power density;

FIG. 10 is a graph of (a) stress-strain curves for RGO-PPy-Ag at different stresses; (b) stress-Strain plot of 20 cycles of compression at 50% Strain; (c) compression of different percentages of R/R₀(ii) a (d) Piezoresistive properties compressed to 50%;

FIG. 11 is (a) a schematic view of an electrochemical compression test apparatus; (b) original CV curves in four states of 20% compression, 50% compression and complete release; (c) the current density is 1 A.g^-1(ii) GCD; (d) an impedance plot; (e) the scanning rate is 5 mV.s^-1Original and CV after 50% compression 20 times; (f) the current density is 1 A.g^-1(ii) GCD;

FIG. 12 is (a) a CV curve of original RGO-PPy-Ag; (b) CV curve after 20 cycles of 50% compression when Strain equals.

Detailed Description

It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

Example 1

1 experimental part

1.1 starting materials and reagents

TABLE 1 Main raw materials and reagents

1.2 Experimental instrumentation

TABLE 2 Main Experimental Equipment

1.3 preparation method

1.3.1 purification of pyrrole

10mL of pyrrole (yellow liquid) is distilled under reduced pressure by using an oil bath (attention is paid to the tightness and the light shielding property of the experimental operation), the temperature is firstly set to be 40 ℃, when steam is generated in the thorn distillation head, the temperature is slowly increased to 65 ℃, and colorless liquid in the ox horn tube slowly flows out at the moment, so that the purified pyrrole (Py) monomer is obtained.

1.3.2 preparation of RGO-PPy-Ag aerogels by one-step hydrothermal method

The specific preparation process of the graphene oxide is as follows: adding ultrasonically dispersed GO water solution 25mg, Py ethanol solution 2.1-12.5mg and AgNO into a small beaker with the volume of 25mL₃1-6.3mg of the aqueous solution, sealing the beaker by using a preservative film and tin foil paper, placing the beaker on a magnetic stirrer, stirring the beaker at room temperature for 2-4h, transferring the mixed solution into a high-pressure reaction kettle, and reacting the mixed solution in a forced air drying oven for 12-36h to form the RGO-PPy-Ag hydrogel. Placing the obtained hydrogel in deionized water for 12h, and freeze-drying to obtain RGO-PPy-Ag aerogel.

1.3.3 Assembly of compressible graphene supercapacitors

(1) Assembling an aqueous electrolyte capacitor: 2 pieces of RGO-PPy-Ag were cut out on a cylindrical hydrogel, each piece having a thickness dimension of about 1 mm. Two pieces of RGO-PPy-Ag hydrogel were immersed in 1M H₂SO₄In an aqueous electrolyte for 12H to obtain H⁺The ions fully penetrate the hydrogel. Two pieces of RGO-PPy-Ag were then pressed onto each foil and soaked in electrolyte (1M H)₂SO₄) The filter paper in (1) is separated as a separation layer. All parts were assembled in a sandwich laminate and sandwiched between two glass slides, soaked in 1M H₂SO₄Electrochemical tests were performed in solution.

(2) Assembling the compressible graphene supercapacitor: cutting 2 pieces of RGO-PPy-Ag per cylinder of hydrogelOne sheet has a thickness dimension of about 2-4 mm. Two pieces of RGO-PPy-Ag hydrogel were immersed in 1M H₂SO₄In an aqueous electrolyte for 12H to obtain H⁺The ions fully penetrate the hydrogel. Two pieces of RGO-PPy-Ag were carefully placed on each foil (the device was placed vertically) to avoid deformation of the hydrogel pieces due to external forces, and a soaked electrolyte (1 MH) was used₂SO₄) The filter paper in (1) is separated as a separation layer. All parts were assembled in a sandwich laminate and sandwiched between two glass slides, lightly pressed to make them just touching, and the whole part was placed in a specially made compression unit and soaked in 1M H₂SO₄Electrochemical tests were performed in solution.

1.4 test characterization

1.4.1FT-IR characterization

The sample was mixed with a certain amount of KBr using an infrared spectrometer from shimadzu corporation, japan, and was ground using an agate mortar and then subjected to a tabletting treatment.

1.4.2XRD characterization

XRD analysis of the samples GO and RGO-PPy-Ag was performed using a D-8ADVANCE X-ray diffractometer (Bruker-AXS, Germany) using a graphite monochromator at a voltage of 40kV and a current of 40mA and with a scanning angle in the range of 5-80 deg..

1.4.3TGA test

TGA was measured using an SDT Q600 thermogravimetric analyzer from TA, USA, at a flow rate of 150 mL-min under nitrogen^-1The heating rate is 10 ℃ min^-1The mass of the graphene oxide and graphene measured from room temperature to 800 ℃ was about 2 mg.

1.4.4XPS characterization

Al-K α was monochromatized using an X-ray photoelectron spectrometer (Thermo Fisher Scientific, Semmer, USA) model ESCALB 250.

1.4.5 scanning Electron microscope

The SEM image of the RGO-PPy-Ag sample is obtained by clamping a small piece of graphene aerogel sample with tweezers by using a Mutimode 8 type electron microscope of Bruker, Germany, fixing the sample on an aluminum support table by using double-sided adhesive tape, and spraying a thin layer of gold on the surface of the sample.

1.4.6Raman spectra characterization

The Raman spectrum test adopts a micro laser confocal Raman spectrometer with the United states HORIBA JY model number Lab RAM H6OO, the excitation wavelength is 514.5nm, the diameter of a focused laser beam spot is 1 mu m, and the exposure time is 20 s. And respectively selecting three different positions for the graphene oxide sample and the aerogel sample to be tested repeatedly.

1.4.7 Transmission Electron microscope

TEM image of RGO-PPy-Ag sample is obtained by taking a small sample of RGO-PPy-Ag aerogel, ultrasonically dispersing with ethanol solution, taking out with copper mesh, and air drying with QUANTA 200 type electron microscope of Hitachi, Japan.

1.4.8DMA characterization

The compression test was performed using a Q800 instrument of a TA instrument (waters technologies, ltd), placing the composite aerogel in the middle of a round table, setting the value of Strain and the cycle parameters, and testing at room temperature.

1.4.9 electrochemical test

Cyclic Voltammetry (CV) and electrochemical damping spectroscopy (EIS) tests were performed using an electrochemical workstation, a frequency response analyzer model Solartron 1255 and an electrochemical interface of Solartron 1287. The impedance spectrum was recorded using a sine wave with an amplitude of 5mV at a voltage in the range of 100kHz to 0.01 Hz. The specific capacitance is obtained by deducing and calculating a constant current discharge curve according to the following formula: c ═ 2(I Δ t)/(m Δ V), I is the discharge current, Δ t is the time of the entire discharge, m is the mass of the entire device, and Δ V is the change in voltage throughout the discharge.

2 discussion of results

2.1 microscopic analysis of RGO-PPy-Ag aerogels

PPy is one of important active materials of a super capacitor due to high conductivity, simple synthesis, low cost, high stability and excellent performance of high redox capacitance charging storage. For in situ polymerization to form RGO-PPy-Ag foams, we prepared a one-step hydrothermal method (as shown in FIG. 1a) by reacting Py monomer with AgNO₃Is formed by redox. And three-dimensional RGO-PPy-Ag foam formationBonded by Py monomer and AgNO₃And the graphene enters a GO aqueous solution to form a homogeneous phase solution, so that the framework of the three-dimensional graphene is maximized in the hydrothermal reduction process, and the graphene has a large specific surface area and excellent mechanical properties. FIG. 1b is an SEM image of an RGO-PPy-Ag aerogel, which macroscopically presents a relatively good three-dimensional network-connected pore structure, providing a strong support for application in a supercapacitor. Microscopically we can see that there are small sphere-like white particles present in the graphene sheets of the monolithic layer, possibly aggregates of PPy and Ag. We then performed TEM testing to prove our guesswork. In FIG. 1c it can be observed that the PPy-Ag nanoparticles have been synthesized in large quantities on monolithic graphene, with diameters between about 50-100 nm. Some particles have better dispersibility, and a small amount of particles are aggregated and adhered together to form a large sheet-shaped structure.

2.2 structural characterization of RGO-PPy-Ag aerogels

XRD spectrum of 2.2.1RGO-PPy-Ag aerogel

FIG. 2 is an XRD spectrum of RGO and RGO-PPy-Ag aerogel, the diffraction peak of GO is about 11.2 degrees, and the corresponding lamella spacing is

After the hydrothermal reduction is used, RGO-PPy-Ag presents a weaker wide diffraction peak, and a characteristic peak corresponding to graphite oxide does not appear, so that the successful reduction of GO is proved. And all diffraction peaks in fig. 2 indicate that it is silver crystal, and the diffraction peaks correspond to four faces of 38.1 ° (111), 44.3 ° (200), 64.5 ° (220), 77.4 ° (311) of face centered cubic Ag, respectively. The diffraction peak at 25.3 ° appeared to be the PPy (110) face center.

2.2.2 Fourier transform Infrared Spectroscopy of RGO-PPy-Ag aerogels

FIG. 3 is an IR spectrum of RGO-PPy-Ag aerogel. Is shown at 1522cm in FIG. 3^-1A characteristic peak absorption peak of the pyrrole ring appears and is at 1208cm^-1The absorption peak indicates that the polypyrrole is in a doped state. At 1372cm^-1The peak is from AgNO₃In NO₃ ^-N of (A)^-Stretching peak, which indicates that pyrrole monomer is indeed AgNO₃Oxidative polymerization to give polypyrrole. Indicating that PPy and Ag are successfully doped into the three-dimensional graphene framework.

XPS spectra of 2.2.3RGO-PPy-Ag aerogels

The RGO-PPy-Ag aerogel surface chemistry was further characterized by XPS. Compared with GO, RGO-PPy-Ag has two more new elements, N, Ag, as shown in FIG. 4 b. The C/O of GO is 2.1, while the C/O of RGO-PPy-Ag is increased to 4.2 and the N/C is as high as 0.90. The reduction of the oxygen-containing functional group is further confirmed by the C1s spectrum. For GO, four different peaks at 284.5, 286.5, 287.1, 288.6eV correspond to C-C of the unoxidized graphene carbon backbone, C-OH of the hydroxyl group, C-O-C of the epoxy group, O-C ═ O of the carboxyl group, respectively. After the reaction of hydrothermal reduction and doping with PPy, Ag, the oxygen-containing functional group in RGO-PPy-Ag is obviously weakened. In addition, a new characteristic peak appears: the C-N group is located at 285.4 eV. We analyzed the N1s spectrum (fig. 4b), and three characteristic peaks appeared: N-H at 399.2eV, -N at 400.5eV, -N + at 402eV, indicating successful incorporation of PPy into the GO sheet structure.

Raman spectrum of 2.2.2.4RGO-PPy-Ag aerogel

FIG. 5 is Raman spectrum of GO and RGO-PPy-Ag aerogel

Raman spectroscopy is an effective tool for characterizing test carbon materials and can confirm the degree of reduction of graphite oxide. For GO, the ratio of the intensity of the D band to the G band was 0.83, and the D band and the G band increased to 1.24 due to hydrothermal reduction to obtain RGO-PPy-Ag aerogel, indicating that graphene oxide lamellar structure was reduced and conjugated structure was gradually restored, and more oxygen-containing functional groups were removed. It can be seen that the D band and G band of RGO-PPy-Ag aerogel are slightly shifted, and the shift of the peak in graphene is related to the charge transfer. Peaks are typically shifted when a covalent structure is formed between RGO and other components. Therefore, the shift of the graphene G peak in the complex may reflect the formation of a covalent bond between graphene and PPy. The PPy is formed by polymerization of a Py monomer in a hydrothermal process and is uniformly distributed on a three-dimensional framework of the graphene, and if the Py monomer is remained, the residual amount of the Py monomer can be ignored. The results thereof were consistent with the above XPS, FTIR and other test results.

2.3 analysis of influencing factors and electrochemical properties of RGO-PPy-Ag aerogel as supercapacitor

2.3.1 Effect of different RGO to PPy mass ratios

To explore the influencing factors of RGO-PPy-Ag supercapacitors, we first explored the influence of the mass ratio between GO and Py. Four hydrogels with different mass ratios, namely RGO-PPy-Ag (2: 1:0.5, 4:1:0.5, 8:1:0.5 and 12:1:0.5, are prepared by a one-step hydrothermal method, and assembled into a two-electrode capacitor, and the electrochemical properties of the two-electrode capacitor are evaluated by adopting tests such as impedance, Cyclic Voltammetry (CV), constant current charge/discharge and the like. The assembly method comprises the following steps: RGO-PPy-Ag hydrogels of different mass ratios were cut into two sheets of about 1mm in thickness, then fixed on two foils, and applied directly as electrodes in supercapacitors at 1M H₂SO₄In solution electrolyte. As a result of the test, it was found that the scanning rate was 200mV · s as shown in FIG. 6a^-1Four different mass ratios Cyclic Voltammograms (CVs), RGO-PPy-Ag 2:1:0.5, 4:1:0.5, 8:1:0.5, 12:1:0.5, were able to maintain a relatively complete rectangle with a potential window within 0.8V. Among them, the CV curve of RGO-PPy-Ag 8:1:0.5 has the best rectangular shape compared to the CV curve of the original RGO. In the constant current charge and discharge test (GCD), they all presented a standard inverted triangle with very good linearity and symmetry curves, indicating that the RGO-PPy-Ag supercapacitor had very good capacitor performance, as shown in FIG. 6 b. To more clearly compare the electrochemical properties of graphene hydrogels with different mass ratios, we combined the CV curves and the GCD curves of the RGO-PPy-Ag hydrogels with four different mass ratios and the pristine graphene gel. The GCD curve for RGO-PPy-Ag shows a gradual increase in charge and discharge time with increasing GO amount, suggesting a very large improvement in capacitor performance for RGO-PPy-Ag devices with increasing GO, but the GCD for RGO-PPy-Ag (12:1:0.5) begins to decrease when the amount of GO increases to a certain mass. To further understand the structure of RGO-PPy-Ag, as shown in FIG. 6c, in the frequency range of 0.01Hz to 100Hz, KWe tested the impedance spectra of the original RGO and RGO-PPy-Ag at 5mV amplitude frequency 2:1:0.5, 4:1:0.5, 8:1:0.5, 12:1: 0.5. For all RGO-PPy-Ag devices, the straight line is nearly parallel to the Y-axis, indicating that RGO-PPy-Ag has very good capacitor performance. Analysis of the information in the graph shows that at higher frequencies the RGO-PPy-Ag 8:1:0.5 electrode still maintains a minimum semi-circle shape, consistent with minimum charge transfer resistance, and a linear transition at low frequencies, all of which show very desirable capacitor performance. In addition, RGO-PPy-Ag exhibits a very small Warburg region compared to RGO-PPy-Ag 2:1:0.5, 4:1:0.5, 8:1:0.5, 12:1:0.5, suggesting a better ion diffusion effect, mainly due to very small contact resistance in the material and ion action. We determined the optimal mass ratio of RGO to PPy to be 8: 1. FIG. 7 is a plot of frequency versus phase and scan rate from 10-500mV · s for RGO and RGO-PPy-Ag ═ 2:1:0.5, 4:1:0.5, 8:1:0.5, 12:1:0.5^-1Graph of CV of (a).

2.3.2 Effect of different PPy to Ag Mass ratios

To explore the effect of Ag content on capacitor electrical signals, we prepared two hydrogels with different Ag content. FIG. 8a is a graph of RGO-PPy-Ag ═ 8:1:1 scan rates 10-500 mV. s^-1Graph of CV of (a). As can be seen by comparing the RGO-PPy-Ag 8:1:0.5CV diagram in fig. 7c, the RGO-PPy-Ag 8:1:0.5 maintains a regular rectangular shape and has a better rectangular shape than the RGO-PPy-Ag 8:1:1, and its current density can reach 35A · g at a scan rate of 500mV/s^-117A g much higher than RGO-PPy-Ag 8:1:1^-1. FIG. 8b shows the current density at 1 A.g^-1Their GCD, RGO-PPy-Ag 8:1:0.5 in the figure, presents a standard inverted triangle with very good linearity and symmetry curves, with charge and discharge times that can reach 180s much higher than 74s for RGO-PPy-Ag 8:1: 1. FIG. 8c and FIG. 8d are EIS curves of the two, at higher frequencies, the RGO-PPy-Ag 8:1:0.5 electrode still maintains a minimum semi-circle shape, consistent with minimum charge transfer resistance, and at low frequencies there is a linear transition, both of which results show that RGO-PPy-Ag 8:1:0.5 is very goodIdeal capacitor performance. Combining the above results, we selected RGO-PPy-Ag as 8:1:0.5 as the optimal ratio for assembling the supercapacitor.

2.3.3 Effect of different reaction times of RGO-PPy-Ag

In order to further optimize reaction conditions and prepare a graphene supercapacitor with more excellent performance, the influence of reaction time on the electrochemical signal of the RGO-PPy-Ag supercapacitor is explored. We prepared RGO-PPy-Ag hydrogels with reaction times of 12h, 24h, and 36h, respectively, according to the difference in reaction time, and studied the CV curves (FIG. 9a), GCD (FIG. 9b), impedance (FIG. 9c), frequency and phase (FIG. 9d), and specific capacitance (FIG. 9e) and energy density (FIG. 9f) thereof. From the EIS plot it can be observed that the line is nearly parallel to the Y-axis at a reaction time of 24h, and still maintains a minimum semi-circle shape at higher frequencies, indicating very desirable capacitor performance. In the CV graph, the reaction time was 24h with the most perfect rectangular shape and the maximum current density. Its GCD curve presents a perfect inverted triangle and the charging and discharging time is longest. Finally, by comparing the specific capacitance of devices with different reaction time, the specific capacitance with the reaction time of 24h is up to 447.5F g^-1. Therefore, the optimum reaction time is 24 h. So far we have found the optimal condition to be RGO-PPy-Ag 8:1: 0.5.

2.3.4 compressible RGO-PPy-Ag supercapacitor

2.4.1 compressibility of RGO-PPy-Ag

Notably, other material viscoelastic properties of hydrogels were reported decades ago. However, one unique strategy that is currently being worked on is to form an RGO-PPy-Ag hydrogel and enable its application as a compressible supercapacitor. When RGO-PPy-Ag aerogel is prepared by hydrothermal method, the reduced graphene oxide layer self-assembles due to strong interfacial interaction between its lamellae. And in hydrothermal treatment, a Py monomer is a typical conjugated structure with electron-rich nitrogen atoms, and the monomer is easily attached to the surface of a GO sheet layer through pi-pi interaction or hydrogen bond interaction. Thus, the presence of Py will effectively prevent the self-stacking behavior of GO sheets during hydrothermal processes, forming a three-dimensional graphene network structure with thin connecting walls. The graphene is different from the original graphene, when the original graphene is subjected to compressive strain, the structure is collapsed and loses elasticity, and the stable structure of the graphene enables the graphene to have good mechanical properties and be compressible.

FIG. 10a is a stress-strain plot of RGO-PPy-Ag at different strains. From FIG. 10a, it can be observed that RGO-PPy-Ag aerogel has excellent elasticity when compressed by external force, forming a complete closed curve. Fig. 10b is a stress-Strain plot of 50 cycles of compression at 50% Strain. And its stress drop value at the initial stage after it is subjected to repeated compression is reduced very insignificantly. These results fully demonstrate that the blending of PPy-Ag has a great improvement effect on the compressibility of the graphene aerogel, which also makes the composite structure have more excellent practical application value. When the aerogel was compressed 20%, its resistance dropped to 73.3% of the initial state, compressed 40% to 65.3% of the initial state, and compressed to 58.8% of the initial state of the 50% resistance drop band (fig. 10 c). This may be due to the compression creating a large number of new temporary contacts between graphene sheets, and the contact between the edges of the graphene sheets may also establish a conductive path through the aerogel, thereby reducing the electrical resistance of the aerogel. FIG. 10d is the change in resistivity (Δ R/R) for RGO-PPy-Ag aerogel over 100 compression cycles when the Strain is 50%₀＝(r₀-r)/R₀Wherein R is₀Representing the initial resistance). The curve of compression/release of its resistivity change is symmetrical, producing a sharp resistance change (Δ R/R) when compressed by an external force₀92%) and this state is kept almost unchanged during each compression cycle. When compressed by an external force, the stress-strain curve of the aerogel almost completely coincided with the uncompressed foam curve, indicating complete recovery of conductivity. This feature also further demonstrates the excellent compressibility characteristics of RGO-PPy-Ag graphene aerogels. The resistance of RGO-PPy-Ag aerogels decreases linearly with deformation during compression, while the resistance increases linearly during release.

Application of 2.4.2RGO-PPy-Ag as compressible super capacitor

In order to verify that the RGO-PPy-Ag aerogel has compressible performance and can be applied to a compressible supercapacitor, the compressible graphene supercapacitor is assembled in the method, and the specific process is as follows: 2 pieces of RGO-PPy-Ag were cut out on a cylindrical hydrogel, each piece having a thickness dimension of about 2-4 mm. Two pieces of RGO-PPy-Ag hydrogel were immersed in 1M H₂SO₄In an aqueous electrolyte for 12H to obtain H⁺The ions fully penetrate the hydrogel. Two pieces of RGO-PPy-Ag were carefully placed on two foils (the device was placed vertically) to avoid deformation of the hydrogel sheet due to external force, and a soaked electrolyte (1M H) was used₂SO₄) The cotton cloth is separated as an isolating layer. All parts were assembled in a sandwich laminate and sandwiched between two glass slides, lightly pressed to make them just touching, and the whole part was placed in a specially made compression unit and soaked in 1M H₂SO₄Electrochemical tests were performed in solution (fig. 11 a). FIG. 12 is a graph showing a scan rate of 5-200 mV. s^-1When the original RGO-PPy-Ag CV curve (a) and the original RGO-PPy-Ag CV curve (b) are subjected to 50% cyclic compression 20 times, the RGO-PPy-Ag super capacitor has no obvious change before and after compression and has certain stability. To more clearly compare the CV of the RGO-PPy-Ag supercapacitor before and after compression, we chose the two to scan at 5 mV. s^-1To observe the change in the four states initially, compressed 20%, compressed 50%, and fully recovered (fig. 11 b). It is observed from fig. 12 that there is no significant change between the initial and fully released states, but the rectangular area compressed to 50% is significantly higher than compressed to 20%, as also illustrated by the charge and discharge times in fig. 11c, and the results obtained are consistent with the findings of fig. 10. Fig. 11d is an impedance diagram in these four states, and the analysis result is consistent with the above. To more clearly compare the CV of the RGO-PPy-Ag supercapacitor before and after compression, we chose the two to scan at 5 mV. s^-1To observe their changes (fig. 11 e). It is observed that there is no significant change between the two before and after compression, but the RGO-PPy-Ag super after 20 times of compressionThe rectangular area of the capacitor is slightly higher than before compression. The conducting path is established by the contact between the graphene sheets in the compression process of the hydrogel and conducts in the whole hydrogel, so that a larger stacking interface is formed in the aerogel, the number of microcosmic connecting nodes is effectively controlled, more stable and efficient channels are provided for electron transmission, the resistance of the hydrogel is reduced, and the electrochemical performance of the hydrogel is improved. This work will facilitate the development of a new generation of advanced supercapacitors that can withstand external mechanical shock and compression.

3. Small knot

(1) The graphene oxide dispersion GO is obtained through synthesis and preparation. Pyrrole (Py) and silver nitrate are used as oxidation-reduction agents, and the RGO-PPy-Ag hydrogel is prepared with graphite oxide through a one-step hydrothermal method and is subjected to freeze drying to obtain the RGO-PPy-Ag aerogel. Successful GO reduction is confirmed by a series of testing methods such as infrared spectroscopy, XPS, Raman, XRD and the like by using common characterization methods, a large number of oxygen-containing functional groups on GO lamellar structures are removed, and Py and AgNO are combined₃And the oxidation and reduction are PPy-Ag and are fixed on the three-dimensional framework of the graphene.

(2) The influence of different proportions on the electrochemical performance of the assembled graphene supercapacitor is researched, the proportion for preparing the graphene supercapacitor is obtained, and the electrochemical performance of the graphene supercapacitor is explored. Compared with the original graphene material, the RGO-PPy-Ag has excellent electrochemical performance, and the specific capacitance of the RGO-PPy-Ag can reach 447.5F g at most^-1。

(3) The compressibility of the graphene aerogel is researched, when the Strain is 40%, the composite aerogel can be compressed more than 20 times, and the recovery rate of the composite aerogel can reach more than 75%. The electrochemical performance of the assembled compressible graphene super capacitor is explored, and after the compressible graphene super capacitor is compressed for 20 times, the electrochemical performance of the compressible graphene super capacitor is not obviously changed, and the compressible graphene super capacitor has certain stability.

The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A compressible graphene RGO-PPy-Ag aerogel, comprising:

a graphene three-dimensional network skeleton;

PPy-Ag nanoparticles dispersed on the graphene sheets;

the PPy-Ag nano particles are formed by aggregation of PPy and Ag;

the preparation method of the compressible graphene RGO-PPy-Ag aerogel comprises the following steps:

2. The aerogel of claim 1, wherein said PPy-Ag nanoparticles have a particle size of 50-100 nm.

3. The aerogel of claim 1, wherein the mass ratio of RGO, PPy, and Ag in the aerogel is 2-12: 1: 0.5-1.

4. A preparation method of a compressible graphene RGO-PPy-Ag hydrogel is characterized by comprising the following steps:

5. An RGO-PPy-Ag hydrogel prepared by the method of claim 4.

6. An assembled compressible graphene supercapacitor, wherein the electrode material of the supercapacitor is the hydrogel according to claim 5, or the aerogel according to any one of claims 1 to 3.

7. Use of an aerogel according to any of claims 1 to 3, or a hydrogel according to claim 5, for the manufacture of a deformable electronic device.