An electrochromic supercapacitor based on a soluble conjugated polymer and a preparation method thereof

Abstract

The present invention discloses an electrochromic supercapacitor based on a soluble conjugated polymer and a preparation method thereof. The capacitor comprises two pieces of conductive glass as a working electrode and a counter electrode, a silver wire as a reference electrode, and an electrolyte. Different soluble conjugated polymers are sprayed on the conductive glass of the working electrode and the counter electrode, and the soluble conjugated polymers are P1, P2 or P3. The present invention synthesizes three electrochromic conjugated polymer materials for the first time through Stille coupling reaction and arylation reaction, and systematically studies the optical absorption, electrochemical behavior, film micromorphology, electrochromic performance and capacitance of the three polymers. The electrochromic supercapacitors invented based on the three conjugated polymers all have good capacitance performance, and their mass specific capacitance is greater than 100F g ‑1 , and realized the visual monitoring of the supercapacitor energy storage status.

Description

Technical Field

[0001] The present invention belongs to the fields of electrochemistry, conductive polymer synthesis, and intelligent energy storage, and particularly relates to an electrochromic supercapacitor based on a soluble conjugated polymer and a preparation method thereof. Background Art

[0002] Electrochromic materials have shown great application prospects in many fields such as energy-saving smart windows, flexible displays, and color-changing camouflage. On the one hand, integrating electrochromism with other properties, such as energy storage, luminescence, and photoelectric sensors, can effectively improve the integration of devices. Therefore, electrochromic materials are increasingly attracting the attention of enterprises and research institutions. Conjugated polymers can be used as ideal electrochromic materials due to their advantages such as rich color changes, light weight, easy modification of molecular structure, and good solution processability. It should be pointed out that only very few conjugated polymers can meet the performance requirements of electrochromic products. This is because conjugated polymers usually only present one satisfactory electrochromic parameter. Therefore, how to prepare high-performance conjugated polymers is one of the most concerned issues in the field of electrochromism.

[0003] Methods for optimizing the performance of conjugated polymers include constructing new conjugated skeletons, modifying side chain structures, and optimizing post-processing processes. Among them, methods for modifying side chain structures can improve the redox ability and kinetic parameters of conjugated polymers, such as cyclic stability, optical contrast, response time, etc. For example, Zhang's group reported a polytriphenylamine derivative that has a fast conversion time due to the presence of pendant ionic liquid units in the side chains of the derivative. Reynolds' group demonstrated that polythiophene modified with branched side chains has higher oxidation potential and band gap than derivatives modified with linear side chains. In addition, the substitution position of the side chain also plays an important role in optimizing the performance of conjugated polymers. For example, Xu's group systematically studied the effect of side chain position on polyindole derivatives. The results show that the side chain position can regulate the capacitive properties of polyindole derivatives. In short, side chain optimization is an effective method to regulate the performance of conjugated polymers.

[0004] Among the reported conjugated polymers, p-phenylene-based conjugated polymers with para-substituted bis(alkoxy) groups have attracted considerable attention due to their excellent optoelectronic properties and easily tunable molecular structures. Notably, p-phenylene-based conjugated polymers with para-substituted bis(alkoxy) groups possess several advantages: 1) long side chains can improve the solubility of organic polymers in organic solvents, thus meeting the requirements of solution processing; 2) the introduction of alkoxy groups can reduce the torsion angle between conjugated units in the polymer backbone, attributed to intramolecular non-covalent interactions between heteroatoms of adjacent conjugated units and the side chain oxygen atoms; and 3) the electron-donating ability of the side chain oxygen atoms can modulate optical absorption and energy levels. The Reynolds group prepared and characterized a series of p-phenylene-based conjugated polymers. These polymers exhibited unique electrochromic properties, such as high coloring efficiency and a wide range of color variations. However, it should be noted that these polymers exhibit very strong intramolecular copolymerization, which can hinder ion transfer. Our group prepared a series of p-phenylene-based conjugated polymers with different side chain structures. We investigated the relationship between molecular aggregation and electrochromic performance and found that strong molecular aggregation of p-phenylene-based polymers negatively impacts the reduction process. Therefore, there is still much room for improvement in the performance of p-phenylene-based conjugated polymers. Summary of the Invention

[0005] The purpose of the present invention is to provide an electrochromic supercapacitor based on a soluble conjugated polymer and a preparation method thereof.

[0006] In order to achieve the above-mentioned objectives, the present invention adopts the following technical solution: an electrochromic supercapacitor based on a soluble conjugated polymer, wherein the capacitor comprises two pieces of conductive glass as a working electrode and a counter electrode, a silver wire as a reference electrode, and an electrolyte; different soluble conjugated polymers are sprayed on the conductive glass of the working electrode and the counter electrode, and the soluble conjugated polymer is P1, P2 or P3.

[0007] Furthermore, the molecular formula of P1 is The molecular formula of P2 is The molecular formula of P3 is Where R is C6H 13 , methyl or propyl.

[0008] Furthermore, P1 is prepared by the following reaction:

[0009]

[0010] Furthermore, P2 is prepared by the following reaction:

[0011]

[0012] Furthermore, P3 is prepared by the following reaction:

[0013]

[0014] Furthermore, the conductive glass is ITO glass.

[0015] Furthermore, the electrolyte is Me-Bu4NPF6 or Me-TBABF4 solution.

[0016] Furthermore, the soluble conjugated polymer was dissolved in chloroform and then sprayed onto the conductive glass.

[0017] A method for preparing the above-mentioned electrochromic supercapacitor based on a soluble conjugated polymer comprises the following steps:

[0018] (1) The three conjugated polymers P1, P2 or P3 were dissolved in chloroform and then sprayed onto ITO conductive glass; (2) Then, silver wire was used as the reference electrode, the two polymer-modified ITO glasses were used as the working electrode and the counter electrode, and electrolyte was added to assemble them into three electrochromic supercapacitors.

[0019] This application prepares three soluble conjugated polymers by copolymerizing bis(hexyloxy)-ortho-substituted p-phenylene with three thiophene derivatives. Furthermore, we systematically study the optical absorption, electrochemical behavior, film micromorphology, electrochromic properties, and capacitance of these three polymers. Based on these three electrochromic conjugated polymers, we successfully invented and assembled three electrochromic supercapacitors, all with specific capacitances exceeding 100 F g. -1 The focus is on realizing the application of energy storage visualization monitoring by combining the energy storage properties and electrochromic properties of these three polymers.

[0020] The beneficial technical effects of the present invention are:

[0021] 1. Three electrochromic conjugated polymers, P1, P2, and P3, were synthesized for the first time via Stille coupling and arylation reactions. Their optical absorption, electrochemical behavior, film micromorphology, electrochromic properties, and capacitance were systematically investigated. In their neutral state, P1 appears yellow, P2 appears orange, and P3 appears magenta. Upon oxidation, all three polymers become transparent blue. Kinetic studies demonstrate that all three conjugated polymers exhibit high optical contrast.

[0022] 2. The electrochromic supercapacitors invented based on these three conjugated polymers have good capacitance performance, and their mass specific capacitance is greater than 100F g-1 , and realized the visual monitoring of the supercapacitor energy storage status. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 These are the XRD curves of three conjugated polymers: P1, P2, and P3.

[0024] Figure 2 These are the optical absorption spectra of three conjugated polymers P1, P2 and P3 in chloroform (a) and thin film state (b).

[0025] Figure 3 (a) P1, (c) P2, and (e) P3 in 0.1 mol L -1 Cyclic voltammograms of Me-Bu4NPF6 at different scan rates; (b) P1, (d) P2, and (f) P3 redox peak current versus scan rate.

[0026] Figure 4 (a, b, c) are the values ​​of P1, P2, and P3 in 0.1 mol L -1 Light absorption spectra of Me-Bu4NPF6 at different voltages. The inset shows the color change of the polymer film; (d, e, f) are the L*a*b* values ​​of P1, P2 and P3.

[0027] Figure 5 These are the time-transmittance curves of the three polymers at different switching times, (a): P1 at 450 nm, (b): P2 at 476 nm, (c): P3 at 500 nm; (d) Time-transmittance curves of P1, (e) P2 and (f) P3 at different wavelengths, switching time: 5 s.

[0028] Figure 6 (a) The charge-discharge curves of P1, (b) P2 and (c) P3 at different current densities; (d) The mass specific capacitance of the three polymers at different current densities.

[0029] Figure 7 It is the color change corresponding to the three polymers P1, P2 and P3 during the charging and discharging process. DETAILED DESCRIPTION

[0030] In order to enable those skilled in the art to better understand the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of this application.

[0031] It should be noted that the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned drawings are intended to cover non-exclusive inclusions. For example, a process, method, system, product or apparatus that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or are inherent to these processes, methods, products or apparatuses.

[0032] Synthesis of P1, P2 and P3:

[0033]

[0034] Where R is C6H 13 , the specific synthetic route is as follows:

[0035] (1) Conjugated polymer P1 was prepared by Stille coupling reaction of 1,4-dibromo-2,3-bis(hexyloxy)benzene (Th-2Sn) and 2,5-bis(trimethylstannyl)thiophene (BE-2Br);

[0036] (2) The conjugated polymer P2 was prepared by Stille coupling reaction of Bis(1,4-dibromo-2,3-bis(hexyloxy)benzene)(BisTh-2Sn) with BE-2Br;

[0037] (3) P3 was prepared by arylation reaction of EDOT-o-BE and 2,5-dibromo-3,4-bis(hexyloxy)thiophene (Th-2Br).

[0038] Test example: Structural characterization of three conjugated polymers and their electrochromic and electrochemical properties in acetonitrile

[0039] (1) Microstructure characterization

[0040] The molecular stacking patterns of the three polymers on ITO glass were studied by X-ray diffraction (XRD). Figure 1 As shown, for P1, the diffraction peak is located at 26.17°, for P2 at 4.05° and 25.07°, and for P3 at 4.48° and 25.08°. It is worth noting that the three polymers all show relatively broad diffraction peaks around 25°, but only P3 has a relatively sharp diffraction peak at 4.48°, and P2 has a relatively weak diffraction peak at 4.05°. These differences indicate that P3 has stronger molecular aggregation than P1 and P2. According to the position of the diffraction peaks, the π-π stacking distances of the three polymers were calculated to be P1, P2, P3, P4, P5, P6, P7, P8, P9, P10, P11, P12, P13, P14, P15, P16, P17, P18, P19, P20, P21, P22, P23, P24, P25, P26, P27, P28, P29, P21, P2 Both P2 and P3 are The calculated interlayer spacing, P2, is P3 is

[0041] (2) Optical properties of polymers

[0042] like Figure 2 As shown, we measured the absorption spectra of these three polymers in chloroform and thin films. In chloroform, the absorption peak of P1 is located at 432 nm, that of P2 at 461 nm, and that of P3 at 516 nm. P2 exhibits a red-shifted absorption relative to P1, which can be attributed to the presence of more electron-dense thiophene units. The more red-shifted absorption of P3 stems from the electron-donating ability of the alkoxy groups connecting the thiophene units. We also observed that the thin film polymers exhibit red-shifted and broader absorption peaks relative to the corresponding polymers in chloroform, which is attributed to the formation of J-aggregates between the solid polymer chains. Based on the onset absorption positions of these three polymers in the thin film state, the optical band gaps of the three polymers are 2.34 eV for P1, 2.14 eV for P2, and 1.98 eV for P3, respectively.

[0043] (3) Electrochemical behavior of polymers

[0044] In 0.1 mol L -1 We tested the electrochemical behavior of these three polymers by cyclic voltammetry (CV) in Me-Bu4NPF6 electrolyte. Figure 3 As shown in Figure 2, P1 and P2 both have a pair of redox peaks, showing similar electrochemical behavior. The scan rate is 100 mV s -1 When the voltage is 0.5 V, the oxidation peak of P1 is at 1.2 V, and the reduction peak is at 0.61 V. The oxidation peak of P2 is at 1.09 V, and the reduction peak is at 0.68 V. Compared with P1 and P2, P3 shows multiple pairs of redox peaks at more negative voltages, which is mainly attributed to the molecular stacking of P3. In addition, there is a large potential difference between the oxidation peak and the reduction peak of P1 and P2, which is 0.59 V and 0.41 V, respectively, which is attributed to the larger ion transport resistance. For P3, the potential difference is 0.2 V. The smaller potential difference makes it easier for doped ions to be doped and dedoped in the P3 film. When the scan rate is 50 mV s -1 When the onset oxidation potential of P3 is 0.02V, which is lower than that of P1 and P2. The lower oxidation potential of P3 is attributed to the electron-donating ability of the alkoxy group. In addition, the doping and dedoping mechanism of ions in polymers can be characterized by the relationship between scan rate and current density, such as Figure 3 As shown in Fig. bf, the redox peak current density of the three polymers has a linear relationship with the scan rate, which indicates that the ion doping and dedoping mechanisms of the three polymers are non-diffusion controlled processes.

[0045] (4) Spectroelectrochemistry of polymers

[0046] Spectroelectrochemistry is an effective method to study the structural changes of electrochromic materials during redox processes. -1 The spectroelectrochemical properties of the three polymers were tested in MeCN-Bu4NPF6. The voltage ranges for the tests of P1, P2, and P3 were 0-1.6V, 0-1.4V, and 0-1.0V, respectively. Figure 4 As shown in the figure, the light absorption of P3 in the neutral state is located at 500nm. As the applied voltage increases, the light absorption peak intensity at 500nm gradually decreases, and a new absorption peak appears at 770nm, which indicates the formation of polarons. When the applied voltage exceeds 0.8V, the absorption peak intensity at 770nm also begins to decrease. During the oxidation process, the color of P3 changes from magenta to transparent blue. The light absorption curves of P1 and P2 are similar to that of P3. Figure 4 As shown in a and 4b, during the oxidation process, P1 changes from yellow to blue and P2 changes from orange to blue. As we all know, there is a color difference between the picture of the polymer film and the actual object. Figure 4 d-4f, we use the L*a*b model to characterize the colors of these three polymers. During the oxidation process, the L*a*b values ​​change from (L*=82.14, a*=-1.36, b*=10.68) to (L*=81.70, a*=-0.45, b*=0.22) for P1; from (L*=68.85, a*=6.79, b*=8.50) to (L*=69.28, a*=-1.36, b*=-1.96) for P2; and from (L*=59.04, a*=24.88, b*=1.96) to (L*=70.59, a*=-2.26, b*=0.22) for P3. The chromaticity results are consistent with the changes in light absorption. Figure 4 As can be seen in Figure d, the color brightness of P1 and P2 remains unchanged during the oxidation process, but when the applied potential exceeds 0.3 V, the color brightness of P3 increases. Figure 5 As shown in e, the a* values ​​of P2 and P3 changed from the red area to the green area during the oxidation process, while the a* value of P1 changed from the green area to the red area. Figure 4 As shown in f, the b* values ​​of these three polymers all change from the yellow area to the blue area.

[0047] (5) Kinetic studies of polymers

[0048] Through kinetic studies, we can obtain the electrochromic parameters of polymers, such as optical contrast, response time and coloring efficiency. Figure 5(a)-(c) show the time-transmittance curves of the three polymers at different switching times. As the switching time changes from 20 s to 5 s, the optical contrast of P1 and P3 remains unchanged, while the contrast of P2 decreases slightly. These results demonstrate that all three polymers exhibit fast response rates during the redox process.

[0049] like Figure 5 e-5f. Based on the time-transmittance curves with a switching time of 5 s, the optical contrasts of P1 are calculated to be 17% at 450 nm and 6% at 633 nm; 23% at 476 nm and 14% at 683 nm for P2; and 54% and 45% at 500 nm and 770 nm for P3, respectively. The response times for the oxidation and reduction processes of P1 are 0.9 s / 0.4 s at 450 nm and 3.0 s / 0.9 s at 633 nm; 0.7 s / 0.3 s at 476 nm and 0.5 s / 0.2 s at 683 nm for P2; and 0.4 s / 0.4 s at 500 nm and 0.6 s / 0.4 s at 770 nm for P3. We found that all three polymers exhibit fast response times of < 1 s (except for the oxidation process of P1 at 633 nm). Furthermore, the response time of P1 and P2 during oxidation is shorter than that during reduction. However, the response time of P3 during oxidation is similar to that during reduction, indicating that the resistance of dopant ions entering / leaving P3 is low. The coloring efficiency of P1 during the redox process is 38 cm at 450 nm. 2 C -1 / 39cm 2 C -1 , 11 cm at 633 nm 2 C -1 / 12cm 2 C -1 ; P2 is 75cm at 476nm 2 C -1 / 82cm 2 C -1 , 31cm at 683nm 2 C -1 / 34cm 2 C -1 ; P3 is 623cm at 500nm 2 C -1 / 641cm 2 C -1 , 365cm at 770nm 2 C -1 / 375cm 2 C -1We found that P3 has higher color rendering efficiency than P1 and P2, which is attributed to the higher optical contrast and less charge consumption in the redox process of P3.

[0050] (6) Capacitive properties of polymers

[0051] Electrochromic capacitors can achieve self-monitoring of energy storage status through color changes, and therefore have attracted increasing attention. In addition to the obvious color change, good energy storage performance of electrochromic capacitor electrodes is also very important. In this work, we tested the energy storage performance of these three polymers by chronopotentiometry. Figure 6 As shown in a-6c, at a current density of 1.0 A g -1 When the mass specific capacitance of P1, P2 and P3 is 139F g -1 、170F g -1 and 103F g -1 P3 exhibits a lower mass specific capacitance than P1 and P2, which is related to the fact that P3 contains more insulating side chains. The higher mass specific capacitance of P2 relative to P1 can be attributed to the more planar molecular structure that increases the degree of conjugation. Figure 6 As shown in Figure d, the specific capacitance of P1 and P2 decreases with increasing current density, primarily because the polymer cannot fully participate in the redox reaction at short times. This phenomenon is commonly seen in conjugated polymers. Notably, the specific capacitance of P3 remains stable with increasing current density, demonstrating that the doped ions can rapidly participate in the redox reaction.

[0052] Finally, we studied the self-monitoring characteristics of the energy storage state in a three-electrode cell with silver wire as the reference electrode and two polymer-modified ITO glasses as the working electrode and the counter electrode. The preparation process of polymer ITO glass is as follows. The prepared polymer is dissolved in chloroform and sprayed on the ITO glass. Figure 7 As shown in Figure a, for P1, during the charging process, the positive electrode changes from yellow to blue, and the negative electrode changes from blue to yellow. During the discharging process, the positive electrode changes from blue to yellow, and the negative electrode changes from yellow to blue. Based on the changes in electrode color, the energy storage status of the capacitor can be detected. And, as Figure 7 As shown in b-7c, the color changes of P2 and P3 during the charge and discharge processes are also obvious. These results indicate that these three polymers have great application potential as electrodes for electrochromic supercapacitors.

[0053] It should be understood that the present invention is described by way of example only and is susceptible to modification within the scope and spirit of the present invention. The preferred embodiments of the present invention have been described in detail above. It should be understood that numerous modifications and variations based on the concepts of the present invention can be made by one of ordinary skill in the art without requiring creative effort. Therefore, any technical solution that can be derived by one of ordinary skill in the art based on the concepts of the present invention through logical analysis, reasoning, or limited experimentation on the basis of the prior art should be within the scope of protection defined by the claims.

Claims

1. An electrochromic supercapacitor based on a soluble conjugated polymer, characterized in that: The capacitor comprises two pieces of conductive glass as a working electrode and a counter electrode, a silver wire as a reference electrode, and an electrolyte. Different soluble conjugated polymers are sprayed on the conductive glass of the working electrode and the counter electrode, and the soluble conjugated polymer is P1, P2 or P3. The molecular formula of P1 is , the molecular formula of P2 is , the molecular formula of P3 is , where R is C6H 13 .

2. The electrochromic supercapacitor based on a soluble conjugated polymer according to claim 1, characterized in that: The P1 is prepared by the following reaction: 。 3. The electrochromic supercapacitor based on a soluble conjugated polymer according to claim 1, characterized in that: The P2 is prepared by the following reaction: 。 4. The electrochromic supercapacitor based on a soluble conjugated polymer according to claim 1, characterized in that: The P3 is prepared by the following reaction: 。 5. The electrochromic supercapacitor based on a soluble conjugated polymer according to claim 1, characterized in that: The conductive glass is ITO glass.

6. The electrochromic supercapacitor based on a soluble conjugated polymer according to claim 1, characterized in that: The electrolyte is Me-Bu4NPF6 or Me-TBABF4 solution.

7. The electrochromic supercapacitor based on a soluble conjugated polymer according to claim 1, characterized in that: The soluble conjugated polymer is dissolved in chloroform and then sprayed onto the conductive glass.

8. A method for preparing an electrochromic supercapacitor based on a soluble conjugated polymer according to any one of claims 1 to 7, characterized in that The following steps are involved: (1) Dissolve the three conjugated polymers P1, P2 or P3 in chloroform and then spray them onto ITO conductive glass; (2) Then, three electrochromic supercapacitors were assembled using silver wire as the reference electrode, two polymer-modified ITO glasses as the working electrode and counter electrode, and electrolytes were added.

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