A flower-like polyaniline conductive hydrogel, a preparation method thereof and application of the flower-like polyaniline conductive hydrogel in an integrated supercapacitor

Abstract

The application belongs to the technical field of supercapacitors, and specifically discloses a flower-like polyaniline conductive hydrogel, a preparation method thereof and application of the flower-like polyaniline conductive hydrogel in an integrated supercapacitor. A novel microcrystalline cellulose / β-cyclodextrin / polyacrylamide hydrogel is prepared, and then aniline is in-situ polymerized on both sides of the prepared microcrystalline cellulose / β-cyclodextrin / polyacrylamide hydrogel electrolyte, so as to form an integrated structure. The flexible supercapacitor has not only good tensile property and excellent adhesion property, but also large area capacitance, high energy density and excellent cycle performance.

Description

Technical Field

[0001] This invention belongs to the field of supercapacitor technology, and relates to a flower-shaped polyaniline conductive hydrogel, its preparation method, and its application in an integrated supercapacitor. Background Technology

[0002] With the rapid development of portable and wearable electronic devices, flexible displays, bendable smartphones, foldable capacitive touchscreens, electronic skin, and implantable medical devices have been applied in various fields such as smart devices, microrobots, medical monitoring, rehabilitation, and motion detection. Considering the need for flexible power supply to these electronic devices, it is necessary to design energy storage devices that are small in size, lightweight, highly safe, mechanically durable, and possess excellent electrochemical performance. This would allow them to maintain excellent electrochemical performance even when bent or folded. Energy storage devices include capacitors, chemical batteries, and supercapacitors. Traditional capacitors have high power density and low energy density, while chemical batteries have high energy density and low power density. Supercapacitors are an energy storage device that falls between traditional capacitors and chemical batteries. Compared to chemical batteries, they have higher energy density, faster charge / discharge rates, and longer lifespan. Therefore, the fabrication of flexible supercapacitors has become a key research focus for energy storage devices in portable and wearable electronic devices.

[0003] Based on their structure, flexible supercapacitors can be divided into integrated flexible supercapacitors and non-integrated flexible supercapacitors. Non-integrated flexible supercapacitors consist of flexible electrodes, a flexible electrolyte, and a separator. They are assembled in an electrode-electrolyte-electrode sequence, with the electrodes and electrolyte separated by a separator. However, this traditional sandwich structure leads to significant contact resistance and interfacial diffusion resistance, ultimately affecting the overall electrochemical performance of the flexible supercapacitor. Therefore, there is an urgent need for an integrated flexible supercapacitor to improve its electrochemical performance. Summary of the Invention

[0004] The purpose of this invention is to address the problems existing in the prior art by providing a flower-shaped polyaniline conductive hydrogel, its preparation method, and its application in an integrated supercapacitor. The flower-shaped polyaniline integrated supercapacitor provided by this invention integrates electrodes, electrolyte, and separator on a flexible substrate. This not only reduces interfacial diffusion resistance but also avoids the use of inactive materials (such as polyvinylidene fluoride), effectively improving device performance. Based on these advantages, the integrated flexible supercapacitor is more suitable as an energy storage device for flexible electronic devices.

[0005] A flower-shaped polyaniline conductive hydrogel includes a microcrystalline cellulose / β-cyclodextrin / polyacrylamide hydrogel, wherein aniline is polymerized in situ on both sides of the microcrystalline cellulose / β-cyclodextrin / polyacrylamide hydrogel.

[0006] A method for preparing a flower-shaped polyaniline conductive hydrogel includes the following steps:

[0007] Microcrystalline cellulose / β-cyclodextrin / polyacrylamide hydrogels were prepared by a one-pot method; aniline was then polymerized in situ onto both sides of the prepared microcrystalline cellulose / β-cyclodextrin / polyacrylamide hydrogels to form an integrated polyaniline conductive hydrogel.

[0008] The method for preparing the integrated supercapacitor containing flower-shaped polyaniline specifically includes the following steps:

[0009] (1) After mixing the microcrystalline cellulose solution and the β-cyclodextrin solution evenly, a microcrystalline cellulose / β-cyclodextrin solution is prepared;

[0010] (2) Add epichlorohydrin to the microcrystalline cellulose / β-cyclodextrin solution obtained in step (1), and add acrylamide, N,N′-methylenebisacrylamide and potassium persulfate during mechanical stirring to obtain a transparent solution;

[0011] (3) Pour the transparent solution obtained in step (2) into a mold and keep it at 40~80℃ for 5~8h to crosslink and obtain the matrix hydrogel, namely microcrystalline cellulose / β-cyclodextrin / acrylamide hydrogel.

[0012] (4) Immerse the matrix hydrogel prepared in step (3) in a solution of aniline / hydrochloric acid, add ammonium persulfate / hydrochloric acid solution, stir for 5-7 hours, rinse with deionized water to remove polyaniline particles deposited on the surface of the hydrogel, and immerse it in a phosphoric acid solution to remove ammonium persulfate, and then immerse it in a solution of aniline / hydrochloric acid to obtain a polyaniline conductive hydrogel.

[0013] In step (1), the concentrations of both microcrystalline cellulose and β-cyclodextrin are 1.5~4 wt%. The β-cyclodextrin can not only form a cross-linked network structure with microcrystalline cellulose, but also act as an adhesive to make aniline more easily polymerized in the hydrogel.

[0014] In step (2), the molar ratio of epichlorohydrin / microcrystalline cellulose is less than 9.

[0015] Preferably, the epichlorohydrin is added at a temperature of 0°C.

[0016] In step (2), the molar ratio of β-cyclodextrin:microcrystalline cellulose:acrylamide is (10~12):(75~80):(115~120); the amount of N,N′-methylenebisacrylamide added is 0.17~0.18wt% of the total mass of the matrix hydrogel; the amount of potassium persulfate added is 1.7~1.8wt% of the total mass of the matrix hydrogel.

[0017] Preferably, in step (3), the crosslinking temperature is 60°C.

[0018] In step (4), the concentration of aniline in the aniline / hydrochloric acid solution is 0.5~2 mol / L.

[0019] In step (4), the concentration of ammonium persulfate in the ammonium persulfate / hydrochloric acid solution is 0.125~1.25 mol / L.

[0020] In step (4), the molar concentration of the phosphoric acid solution is 0.5~2M.

[0021] The aniline has a purity of ≥99.9% and a hydrochloric acid concentration of 35~38%; the aniline needs to be purified by vacuum distillation before use.

[0022] This invention prepares a microcrystalline cellulose / β-cyclodextrin solution, and then uses epichlorohydrin and N,N′-methylenebisacrylamide as chemical crosslinking agents to induce crosslinking reactions in microcrystalline cellulose and β-cyclodextrin, respectively, to form a first crosslinking network. Polyacrylamide then crosslinks to form a second crosslinking network. The epoxy and chlorine atoms of epichlorohydrin undergo ring-opening reactions with the hydroxyl groups on microcrystalline cellulose and β-cyclodextrin, respectively, to form ether bonds, thus forming the first crosslinking network of β-cyclodextrin / microcrystalline cellulose. By controlling the molar ratio of epichlorohydrin / microcrystalline cellulose to less than 9, crosslinking between adjacent cellulose molecules is prevented (epichlorohydrin reaction mechanism with cellulose), thereby forming the first crosslinking network (hydrogel cannot be formed without the addition of acrylamide). Acrylamide reacts with N,N′-methylenebisacrylamide to form the second crosslinking network, thus forming a synchronous interpenetrating poly(IPN) hydrogel. Subsequently, the microcrystalline cellulose / β-cyclodextrin / acrylamide hydrogel is transferred to a dilute hydrochloride solution to terminate the chemical crosslinking reaction.

[0023] The present invention also provides the application of the above-mentioned polyaniline conductive hydrogel in an integrated supercapacitor. The polyaniline conductive hydrogel is cut and placed in a phosphoric acid solution to fill the electrolyte solution, thereby obtaining an integrated supercapacitor containing flower-shaped polyaniline.

[0024] In the phosphoric acid solution, the volume ratio of phosphoric acid to water is (0.5~1.5):(0.5~1.5).

[0025] The integrated supercapacitor containing flower-shaped polyaniline has strong stability: the amino and imine groups of polyaniline can form hydrogen bonds with the hydroxyl groups in cellulose and β-CD in the matrix hydrogel; the microcrystalline hydrates of cellulose II crystal form in microcrystalline cellulose induce physical cross-linking between the matrix hydrogel and polyaniline; and the molecular chains are intertwined.

[0026] The technical advantages of this invention are as follows:

[0027] (1) The present invention uses β-cyclodextrin to rapidly polymerize aniline to form a sheet structure, which is then stacked to form a flower structure. The resulting integrated supercapacitor containing flower-shaped polyaniline significantly improves the electrochemical performance of the monolithic supercapacitor.

[0028] (2) The present invention integrates electrodes, electrolytes and separators on a flexible substrate, which not only reduces the interfacial diffusion resistance, but also avoids the use of inactive materials (such as polyvinylidene fluoride), effectively improving the performance of the device.

[0029] (3) The present invention avoids the problem of electrode and electrolyte detachment and slippage during cyclic bending and stretching. In addition, the integrated flexible supercapacitor can be prepared in various shapes and sizes according to requirements. Attached Figure Description

[0030] Figure 1 This is a scanning electron microscope image of the integrated supercapacitor containing flower-shaped polyaniline prepared in Example 1 of the present invention.

[0031] Figure 2 The infrared spectrum shows the functional group composition of the integrated supercapacitor containing flower-shaped polyaniline prepared in Example 1 of this invention.

[0032] Figure 3 Thermogravimetric analysis diagram of the polyaniline content in the integrated supercapacitor containing flower-shaped polyaniline prepared in Example 1 of the present invention;

[0033] Figure 4 The constant current charge-discharge diagram is shown for the integrated supercapacitor containing flower-shaped polyaniline prepared in Example 1 of this invention.

[0034] Figure 5 The cyclic voltammetry diagram is shown for the integrated supercapacitor containing flower-shaped polyaniline prepared in Example 1 of this invention.

[0035] Figure 6 This is a scanning electron microscope image of the supercapacitor prepared in Comparative Example 1 of the present invention.

[0036] Figure 7 This is a scanning electron microscope image of the integrated supercapacitor containing flower-shaped polyaniline prepared in Example 1 of the present invention.

[0037] Figure 8This is a constant current charge-discharge diagram of the supercapacitor prepared in Comparative Example 1 of this invention. Detailed Implementation

[0038] The present invention will be further described below with reference to specific embodiments and accompanying drawings, but is not limited thereto.

[0039] In addition, the experimental methods described in the following embodiments are conventional methods unless otherwise specified; the reagents and materials described are commercially available unless otherwise specified.

[0040] Example 1:

[0041] Solutions of 2wt% microcrystalline cellulose and β-cyclodextrin were prepared separately. Equal masses (2.5g) of both solutions were mixed thoroughly to obtain a microcrystalline cellulose / β-cyclodextrin solution. Simultaneously, epichlorohydrin (72µL) was added to the microcrystalline cellulose / β-cyclodextrin solution at 0℃ and stirred for 2 hours to obtain good dispersibility. Then, under mechanical stirring, 1.76g acrylamide, 0.0035g N,N′-methylenebisacrylamide, and 0.035g potassium persulfate were added to the above solution. After thorough mixing, the mixture was poured into a pre-made mold (40mm×10mm×2mm) and maintained at 60℃ to promote the cross-linking reaction. After 6 hours of cross-linking, the matrix hydrogel, namely the microcrystalline cellulose / β-cyclodextrin / acrylamide hydrogel, was obtained.

[0042] 1M aniline monomer was dissolved in 1M hydrochloric acid solution to obtain an aniline / hydrochloric acid solution. The prepared matrix hydrogel was immersed in the aniline / hydrochloric acid solution for 6 hours. Then, a 1M ammonium persulfate hydrochloric acid solution was added dropwise, and the mixture was gently stirred continuously at 0°C for 6 hours. After the reaction was complete, the hydrogel was removed from the solution and rinsed four times with deionized water to remove polyaniline particles deposited on the surface of the hydrogel. It was then immersed in a 1M phosphoric acid solution to remove unreacted aniline and ammonium persulfate, and subsequently immersed in the aniline / hydrochloric acid solution (1M) to obtain a polyaniline conductive hydrogel. The concentration of the hydrochloric acid solution was 37 wt%.

[0043] To prevent short circuits, the edges of the prepared polyaniline conductive hydrogel were trimmed, and then cut into 20mm × 5mm × 2mm pieces. These pieces were then immersed in a phosphoric acid solution (phosphoric acid to water volume ratio of 1:1) for 14 hours to ensure the hydrogel was filled with the electrolyte solution. The immersed hydrogel was then placed between two pieces of carbon cloth and gently pressed to obtain a monolithic supercapacitor containing flower-shaped polyaniline.

[0044] The scanning electron microscope image of the integrated supercapacitor containing flower-shaped polyaniline prepared in this embodiment is shown below. Figure 1As shown in the figure, at 300 nm, due to the presence of β-cyclodextrin on the surface of the matrix hydrogel, β-cyclodextrin can adsorb aniline, forming a high-concentration aniline region. When N,N′-methylenebisacrylamide is added, aniline is present in the cavity of β-cyclodextrin, causing aniline to polymerize rapidly, forming a plate-like structure, which is then stacked to form a flower-like structure.

[0045] The infrared spectrum of the integrated supercapacitor containing flower-shaped polyaniline (polyaniline / microcrystalline cellulose / β-cyclodextrin / polyacrylamide composite hydrogel) prepared in this embodiment is as follows: Figure 2 As shown in the figure, it can be seen that at 3400cm -1 and 1640cm -1 The peaks on the left and right represent the stretching vibration of OH and the bending vibration of -OH, respectively, at 1020 cm⁻¹. -1 ~1160cm -1 The peaks on the left and right represent the tensile vibrations of CO and COC, while the typical characteristic peak of polyacrylamide is at 3400 cm⁻¹. -1 The peak is due to the bending vibration of NH, at 1660 cm⁻¹. -1 The absorption bands on the left and right sides represent the tensile vibration of C=O, 1401 cm⁻¹. -1 The absorption bands on the left and right sides are due to the tensile vibration of -OCH3.

[0046] Thermogravimetric analysis (TGA) curve of the integrated supercapacitor containing flower-shaped polyaniline (polyaniline / microcrystalline cellulose / β-cyclodextrin / polyacrylamide composite hydrogel) prepared in this embodiment is shown in the figure below. Figure 3 As shown in the figure, all three hydrogel samples exhibit slight weight loss (4%–7%) below 100°C. The mass loss of the polyaniline / microcrystalline cellulose / β-cyclodextrin / polyacrylamide composite material is much smaller than that of the microcrystalline cellulose / β-cyclodextrin / polyacrylamide and microcrystalline cellulose / β-cyclodextrin materials, indicating that the polyaniline / microcrystalline cellulose / β-cyclodextrin / polyacrylamide composite material has more stable thermal properties.

[0047] The cyclic voltammogram of the integrated supercapacitor containing flower-shaped polyaniline (polyaniline / microcrystalline cellulose / β-cyclodextrin / polyacrylamide composite hydrogel) prepared in this embodiment is shown in the figure below. Figure 5 As shown in the figure, the CV curve is rectangular. The more rectangular the CV curve is, the more stable its cyclic characteristics are.

[0048] The constant current charge-discharge diagram of the integrated supercapacitor (polyaniline / microcrystalline cellulose / β-cyclodextrin / polyacrylamide composite hydrogel) containing flower-shaped polyaniline prepared in this embodiment is shown in the figure below. Figure 4 As shown, according to the formula: C t =(2×I× t) / (Z× V) From the graph, we can see that 1.0 mA / cm 2 The measured area capacitance was 1830 F / cm². 2 1.5mA / cm 2 The measured area capacitance was 1728 F / cm². 2 The areal capacitance measured at 2.0 A / g was 1570 F / cm². 2 The specific capacitance was measured to be 1102 F / cm at 8.0 A / g. 2 It exhibits good stability.

[0049] Comparative Example 1:

[0050] This comparative example did not contain β-cyclodextrin, and the remaining components and preparation process were the same as in Example 1.

[0051] like Figure 6 , 7 The images shown are scanning electron microscope (SEM) images of the supercapacitors prepared in Comparative Example 1 and Example 1, respectively. It can be seen from the images that the supercapacitor without the addition of β-cyclodextrin cannot form a flower-like structure.

[0052] like Figure 4 , 8 As shown, at 1mA / cm 2 Under constant current, the areal capacitance of the integrated polyaniline / microcrystalline cellulose / β-cyclodextrin / polyacrylamide supercapacitor is 1814 mF / cm². 2 The areal capacitance of the polyaniline / microcrystalline cellulose / acrylamide integrated supercapacitor is only 892.5 mF / cm². 2 The areal specific capacitance is less than half that of the integrated supercapacitor of polyaniline / microcrystalline cellulose / β-cyclodextrin / polyacrylamide, indicating that the addition of β-cyclodextrin can effectively improve the areal specific capacitance of the integrated supercapacitor.

Claims

1. A flower-shaped polyaniline conductive hydrogel, characterized in that, Includes synchronous interpenetrating IPN hydrogels formed from microcrystalline cellulose / β-cyclodextrin / polyacrylamide, wherein aniline is polymerized in situ on both sides of the microcrystalline cellulose / β-cyclodextrin / polyacrylamide hydrogel; The preparation method of the flower-shaped polyaniline conductive hydrogel specifically includes the following steps: (1) After mixing microcrystalline cellulose and β-cyclodextrin evenly, a microcrystalline cellulose / β-cyclodextrin solution is prepared; (2) Add epichlorohydrin to the microcrystalline cellulose / β-cyclodextrin solution obtained in step (1), and add acrylamide, N,N′-methylenebisacrylamide and potassium persulfate during mechanical stirring to obtain a transparent solution; (3) Pour the transparent solution obtained in step (2) into a mold and keep it at 40~80℃ for 5~8h to crosslink and obtain the matrix hydrogel, namely microcrystalline cellulose / β-cyclodextrin / acrylamide hydrogel. (4) Immerse the matrix hydrogel prepared in step (3) in a solution of aniline / hydrochloric acid, add ammonium persulfate / hydrochloric acid solution, stir for 5-7 hours, rinse with deionized water to remove polyaniline particles deposited on the surface of the hydrogel, and immerse it in a phosphoric acid solution to remove ammonium persulfate, and then immerse it in a solution of aniline / hydrochloric acid to obtain a polyaniline conductive hydrogel. In step (4), the concentration of aniline in the aniline / hydrochloric acid solution is 0.5~2 mol / L.

2. The method for preparing the flower-shaped polyaniline conductive hydrogel according to claim 1, characterized in that, Specifically, the steps include the following: (1) After mixing microcrystalline cellulose and β-cyclodextrin evenly, a microcrystalline cellulose / β-cyclodextrin solution is prepared; (2) Add epichlorohydrin to the microcrystalline cellulose / β-cyclodextrin solution obtained in step (1), and add acrylamide, N,N′-methylenebisacrylamide and potassium persulfate during mechanical stirring to obtain a transparent solution; (3) Pour the transparent solution obtained in step (2) into a mold and keep it at 40~80℃ for 5~8h to crosslink and obtain the matrix hydrogel, namely microcrystalline cellulose / β-cyclodextrin / acrylamide hydrogel. (4) Immerse the matrix hydrogel prepared in step (3) in a solution of aniline / hydrochloric acid, add ammonium persulfate / hydrochloric acid solution, stir for 5-7 hours, rinse with deionized water to remove polyaniline particles deposited on the surface of the hydrogel, and immerse it in a phosphoric acid solution to remove ammonium persulfate, and then immerse it in a solution of aniline / hydrochloric acid to obtain a polyaniline conductive hydrogel.

3. The method for preparing the flower-shaped polyaniline conductive hydrogel according to claim 2, characterized in that, In step (1), the concentrations of microcrystalline cellulose and β-cyclodextrin are both 1.5~4wt%.

4. The method for preparing the flower-shaped polyaniline conductive hydrogel according to claim 2, characterized in that, In step (2), the molar ratio of epichlorohydrin / microcrystalline cellulose is less than 9.

5. The method for preparing the flower-shaped polyaniline conductive hydrogel according to claim 2, characterized in that, In step (2), the molar ratio of β-cyclodextrin:microcrystalline cellulose:acrylamide is (10~12):(75~80):(115~120); the amount of N,N′-methylenebisacrylamide added is 0.17~0.18wt% of the total mass of the matrix hydrogel; the amount of potassium persulfate added is 1.7~1.8wt% of the total mass of the matrix hydrogel.

6. The method for preparing the flower-shaped polyaniline conductive hydrogel according to claim 2, characterized in that, In step (3), the crosslinking temperature is 60°C.

7. The method for preparing the flower-shaped polyaniline conductive hydrogel according to claim 2, characterized in that, In step (4), the concentration of aniline in the aniline / hydrochloric acid solution is 0.5~2 mol / L; In step (4), the concentration of ammonium persulfate in the ammonium persulfate / hydrochloric acid solution is 0.125~1.25 mol / L; The aniline has a purity of ≥99.9% and a hydrochloric acid concentration of 35~38%.

8. The application of the flower-shaped polyaniline conductive hydrogel as described in claim 1 in an integrated supercapacitor.

9. The application of the flower-shaped polyaniline conductive hydrogel according to claim 8 in an integrated supercapacitor, characterized in that, After cutting the polyaniline conductive hydrogel, it was placed in a phosphoric acid solution to fill the hydrogel with an electrolyte solution, thus obtaining an integrated supercapacitor containing flower-shaped polyaniline.

10. The application of the flower-shaped polyaniline conductive hydrogel according to claim 9 in an integrated supercapacitor, characterized in that, In the phosphoric acid solution, the volume ratio of phosphoric acid to water is (0.5~1.5):(0.5~1.5).

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