Transparent supramolecular ionic gel, method of preparation and use as electrolyte for electrochromic devices

Abstract

This invention relates to the field of ionogel electrolyte technology, specifically to a transparent supramolecular ionogel, its preparation method, and its application as an electrolyte in electrochromic devices. The transparent supramolecular ionogel contains a gelling agent and an ionic liquid; the gelling agent is at least one selected from sugars, stearic acids, surfactants, and cholesterol-based gelling agents, with a molecular weight not exceeding 1000; the ionic liquid is at least one selected from imidazole ionic liquids, quaternary ammonium salt ionic liquids, pyrrole ionic liquids, and quaternary phosphonium salt ionic liquids; the proportion of the gelling agent in the transparent supramolecular ionogel is 0.1-10 wt%. This invention uses a transparent supramolecular ionogel as the electrolyte for electrochromic devices, which, compared to traditional ionogel-polymer gel electrolytes, exhibits higher purity and transparency, thereby improving the performance of electrochromic devices.

Description

Technical Field

[0001] This invention relates to the field of ion gel electrolyte technology, specifically to a transparent supramolecular ion gel, its preparation method, and its application as an electrolyte for electrochromic devices. Background Technology

[0002] Electrochromic devices are electronic devices that utilize electrochromic materials to achieve stable optical changes under the drive of an external voltage. They have been widely used in civilian and military fields such as anti-glare rearview mirrors, smart windows, electronic information displays, and military equipment camouflage. Currently, most research on electrochromic devices is based on liquid electrolytes. Liquid electrolytes are mostly composed of salts (such as lithium perchlorate, lithium bromide, lithium hexafluorophosphate, etc.) and organic solvents (acetonitrile, propylene glycol carbonate, ethylene carbonate, etc.). Although these electrolytes have good transparency and high ion mobility, making them easy to fill into devices and assembling them into devices with good electrochromic effects, they also have problems such as high toxicity, difficulty in encapsulation, easy leakage, and flammability.

[0003] Ionic liquids, as room-temperature molten salts, have attracted widespread attention due to their non-flammability, low volatility, high ionic conductivity, thermal stability, and wide electrochemical window. Current research includes the use of ionic gels prepared by combining ionic liquids with polymers such as polyvinylidene fluoride-hexafluoropropylene, polyethylene oxide, and polymethyl methacrylate as electrolytes in electrochromic devices. While this avoids the problems of high toxicity, difficult encapsulation, easy leakage, and flammability associated with traditional liquid electrolytes, their relatively low ionic conductivity and transparency can lead to reduced performance of electrochromic devices, limiting their practical applications. Summary of the Invention

[0004] (a) Technical problems to be solved

[0005] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a transparent supramolecular ionic gel, a preparation method thereof, and its application as an electrolyte for electrochromic devices. It solves the problems of low ionic conductivity and poor transparency of ionic liquid-polymer gel electrolytes, thereby improving the performance of electrochromic devices and expanding their applications.

[0006] (II) Technical Solution

[0007] In a first aspect, the present invention provides a transparent supramolecular ionic gel comprising a gelling agent and an ionic liquid; the gelling agent is at least one selected from sugars, stearic acids, surfactants and cholesterol-based gelling agents, and the molecular weight of the gelling agent does not exceed 1000; the proportion of the gelling agent in the transparent supramolecular ionic gel is 0.1-10 wt%.

[0008] Among them, gelling agents with a molecular weight not exceeding 1000 help enhance the ionic conductivity and improve the transparency of the gel. At the same time, relatively low molecular weight gelling agents are more soluble in ionic liquids and may provide better processing properties, such as easier formation of uniform films or coatings.

[0009] According to a preferred embodiment of the present invention, the transparent supramolecular ionic gel is composed of a gelling agent and an ionic liquid, wherein the gelling agent accounts for 0.1-10 wt% of the total mass of the gelling agent and the ionic liquid.

[0010] According to a preferred embodiment of the present invention, the transparent supramolecular ionogel further comprises a redox medium and an electrochromic material.

[0011] According to a preferred embodiment of the present invention, the redox medium is ferrocene, and the electrochromic material is a viologen small molecule compound, preferably diheptyl-substituted viologen. The electrochromic material may also be other small molecule compounds or polymeric color-changing materials.

[0012] According to a preferred embodiment of the present invention, the ionic liquid is selected from at least one of imidazole ionic liquids, quaternary ammonium salt ionic liquids, pyrrole ionic liquids, and quaternary phosphonium salt ionic liquids.

[0013] According to a preferred embodiment of the present invention, the content of the redox medium in the transparent supramolecular ionogel is 0.5-1.0 wt%; and the content of the electrochromic material in the transparent supramolecular ionogel is 2-4 wt%.

[0014] The explanations for the gelling factors, including carbohydrates, stearic acid, surfactants, and cholesterol, are as follows:

[0015] Glycosyl gelling agents: These agents typically contain one or more glycosyl units linked together by glycosidic bonds or combined with other types of molecules to form complex structures. For example, cyclodextrins (α-cyclodextrin, β-cyclodextrin, and γ-cyclodextrin) are common glycosyl gelling agents, consisting of cyclic structures composed of glucose units. In addition, there are gelling agents based on natural polysaccharide derivatives such as cellulose and chitosan.

[0016] Stearic acid gelling agents: Stearic acid and its derivatives are typical examples. These compounds contain long-chain alkyl moieties and polar head groups. Sodium stearate is a commonly used gelling agent. Its long chains can intertwine and stack, and its carboxylate ions can enhance this stacking through hydrogen bonds or other weak interactions, thereby forming a stable gel network.

[0017] Surfactant-based gelling agents: This class includes various cationic, anionic, and nonionic surfactants. They generally have a hydrophilic head and a hydrophobic tail, and can self-assemble into micelles, lamellar phases, or other more complex structures under appropriate conditions. Some specific surfactants, such as hexadecyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS), can form gels at suitable concentrations, especially when used in conjunction with appropriate additives.

[0018] Cholesterol-based gelling agents: Cholesterol itself is an important gelling agent. Due to its unique rigid steroidal backbone, it can effectively participate in the formation and stabilization of membrane structures. Cholesterol-based gelling agents also include some cholesterol derivatives, such as cholesterol esters or cholesterol-grafted polymers. These substances can regulate the properties of gels by modulating intermolecular interactions.

[0019] Secondly, the present invention provides a method for preparing a transparent supramolecular ionic gel, comprising: S1, mixing a gelling agent with an ionic liquid and homogenizing the mixture to obtain a mixture;

[0020] S2. Heat the mixture until it becomes a homogeneous and transparent solution;

[0021] S3. Cool the homogeneous and transparent solution to obtain the transparent supramolecular ionic gel.

[0022] According to a preferred embodiment of the present invention, in S1, during the mixing of the gelling agent and the ionic liquid, a redox medium and an electrochromic material are also added; preferably, the redox medium is ferrocene, and the electrochromic material is a viologen small molecule compound, preferably diheptyl-substituted viologen. Further, the content of ferrocene in the transparent supramolecular ionic gel is 0.5-1.0 wt%; the content of diheptyl-substituted viologen in the transparent supramolecular ionic gel is 2-4 wt%.

[0023] According to a preferred embodiment of the present invention, in S1, the homogenization process includes any one of the following operations: stirring, oscillation, suction, and ultrasonic treatment.

[0024] According to a preferred embodiment of the present invention, in S2, the heating temperature is 110-120°C and the heating time is 10-30 min.

[0025] Thirdly, the present invention provides the application of the above-mentioned transparent supramolecular ionogel in the preparation of electrochromic devices.

[0026] Fourthly, the present invention provides an electrochromic device comprising a first transparent electrode layer, a transparent supramolecular ion gel electrolyte membrane layer, and a second transparent electrode layer stacked sequentially.

[0027] The transparent supramolecular ionogel electrolytic film layer is formed from the transparent supramolecular ionogel of any of the above embodiments.

[0028] According to a preferred embodiment of the present invention, the first transparent electrode layer is composed of a first transparent electrode and a first electrochromic film covering its surface, and the second transparent electrode layer is composed of a second transparent electrode and a second electrochromic film covering its surface.

[0029] Preferably, the electrochromic device is a flexible electrochromic device or a rigid electrochromic device; specifically, when the first transparent electrode layer and the second transparent electrode layer are flexible, a flexible electrochromic device can be obtained; conversely, when the first transparent electrode layer and the second transparent electrode layer are rigid, a rigid electrochromic device can be obtained.

[0030] According to a preferred embodiment of the present invention, the first transparent electrode and the second transparent electrode are ITO electrodes.

[0031] According to a preferred embodiment of the present invention, the first electrochromic film is a PRODT polymer, and the second electrochromic film is a PEDOT:PSS polymer.

[0032] Fifthly, the present invention provides a method for preparing an electrochromic device, comprising:

[0033] S1. Mix the gelling agent with the ionic liquid and homogenize the mixture to obtain a mixture;

[0034] S2. Heat the mixture until it becomes a homogeneous and transparent solution;

[0035] S3. The homogeneous transparent solution is injected between two electrochromic electrode layers and cooled to form a transparent supramolecular ionic gel electrolyte; or, the homogeneous transparent solution is cooled to form a transparent supramolecular ionic gel, and then the transparent supramolecular ionic gel is injected between two electrochromic electrode layers using an injection method.

[0036] Preferably, the first transparent electrode layer is composed of a first transparent electrode and a first electrochromic film covering its surface, and the second transparent electrode layer is composed of a second transparent electrode and a second electrochromic film covering its surface; the first electrochromic film is a PRODT polymer, and the second electrochromic film is a PEDOT:PSS polymer.

[0037] In electrochromic devices, ferrocene acts as a redox medium, serving as an electron transfer hub, while bis-heptyl replaces viologen as the primary color-changing material to achieve optical response. The performance of both is synergistically optimized through molecular design. Ferrocene can reduce the driving voltage of electrochromic devices, improve cycle stability, and shorten response time. Ferrocene itself is pale yellow, which can also affect the color display of the device. Therefore, when selecting a redox medium, colorless or light-colored materials are preferred.

[0038] (III) Beneficial Effects

[0039] This invention uses gelling agents and ionic liquids to prepare a non-polymer-based gel. The gel is dissolved by direct heating to form a homogeneous and transparent solution. During the cooling process, the solution forms a supramolecular ionic gel based on the self-assembly of the gelling agents. The entire preparation process is simple and convenient. Compared with traditional polymer ionic gels, the preparation method of this invention is simpler.

[0040] Because the amount of gelling agent used in supramolecular ionic gels is extremely low, typically less than 5 wt%, this results in supramolecular ionic gels exhibiting high ionic conductivity and high optical transmittance, approaching that of pure ionic liquids. This solves the problems of low ionic conductivity and poor transparency in ionic liquid-polymer gel electrolytes, thereby improving the performance of electrochromic devices and expanding their applications. Furthermore, the non-covalent self-assembly based on the gelling agent also endows the gel with self-healing properties.

[0041] This invention uses a supramolecular ionogel that is easy to prepare, has high ionic conductivity and optical transmittance, and is self-healing as an electrolyte for electrochromic devices. This not only avoids the problems of high toxicity, difficult encapsulation, easy leakage and flammability caused by traditional liquid electrolytes, but also improves the performance of the electrochromic device, such as response rate, coloring efficiency and optical contrast. Attached Figure Description

[0042] Figure 1 This is a photograph of the supramolecular ionogel from Example 1.

[0043] Figure 2 The results show the ionic conductivity of the supramolecular ionic gel in Example 1.

[0044] Figure 3 This is a SEM image of the supramolecular ionic gel from Example 1.

[0045] Figure 4 The voltage-UV absorption spectrum test results are for the electrochromic device of Example 9.

[0046] Figure 5 This is a comparison image of the electrochromic device of Example 9 before and after color change when voltage is applied.

[0047] Figure 6 This is the ultraviolet kinetic spectrum of the electrochromic device in Example 9.

[0048] Figure 7 This is a test diagram of the color-changing cycle stability of the electrochromic device in Example 9.

[0049] Figure 8 This is a bending cycle test diagram of the flexible electrochromic device in Example 17.

[0050] Figure 9 The image shows the voltage-UV absorption spectrum of the composite electrochromic device in Example 18.

[0051] Figure 10 The image shows the ultraviolet kinetic spectrum of the composite electrochromic device in Example 18.

[0052] Figure 11 This is a test diagram of the color-changing cycle stability of the composite electrochromic device in Example 18. Detailed Implementation

[0053] According to the inventors' research, besides polymers, certain special small molecules can also cause ionic liquids to form gels; these special small molecules are also called gel factors. First, upon cooling, the gel factor self-assembles into a slender fibrous structure through non-covalent weak interactions such as hydrogen bonding, van der Waals interactions, π-π stacking, hydrophobic effects, and electrostatic interactions. Then, these slender fibers entangle with each other to form a three-dimensional network structure that can constrain and fix the solvent, thus trapping the ionic liquid within it to obtain a macroscopically visible supramolecular ionic gel. This type of supramolecular ionic gel is characterized by its simple preparation, high ionic conductivity, and self-healing properties. If used as an electrolyte in electrochromic ionic gels, it can not only avoid the problems of high toxicity, difficulty in encapsulation, easy leakage, and flammability associated with liquid electrolytes, like polymeric ionic gels, but also, compared to traditional ionic liquid-polymer gel electrolytes, the supramolecular ionic gel based on gel factors provided in this invention has higher ionic conductivity and transparency, thus significantly improving the performance of electrochromic devices.

[0054] To better explain and facilitate understanding of the present invention, a detailed description of the invention is provided below with reference to the accompanying drawings and specific embodiments. The specific testing methods and instruments used in the following embodiments include:

[0055] Ionic conductivity testing: Leici DZS-706-A multi-parameter analyzer;

[0056] Scanning electron microscopy (SEM) test: TESCAN MIRA3 field emission scanning electron microscope;

[0057] Voltage-UV absorption spectroscopy test: Shimadzu UV-2600 UV-Vis spectrophotometer was used in conjunction with Chenhua CHI760EA17427 electrochemical workstation, and the test mode was spectral scanning.

[0058] Ultraviolet kinetic spectroscopy test: Shimadzu UV-2600 UV-Vis spectrophotometer was used in conjunction with Chenhua CHI760E A17427 electrochemical workstation, and the test mode was kinetic scan;

[0059] Bending cycle test: Jiangsu Moxin MX-0580 electronic universal testing machine.

[0060] Example 1

[0061] This embodiment provides a supramolecular ionic gel, the preparation method of which is as follows:

[0062] Accurately weigh 0.95 g of the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (BMIM[TFSI]) and 0.05 g of the saccharide gelling agent (β-cyclodextrin) using an electronic balance, add them to a sample vial, and sonicate for 10 min to mix thoroughly, obtaining a mixture. Place the mixture in a 120°C forced-air drying oven and heat for 20 min until it becomes a homogeneous and transparent solution. Allow the homogeneous and transparent solution to cool from the heat to room temperature; the homogeneous and transparent solution gradually transforms into a gel, which is the supramolecular ionic gel of this embodiment (e.g., Figure 1 (As shown), the gelling factor content is 5 wt%.

[0063] The supramolecular ionic gel prepared in this embodiment was tested, and the test results are as follows.

[0064] (1) Ionic conductivity test

[0065] Test results are as follows Figure 2 As shown in the figure, the ionic conductivity of the supramolecular ionic gel in this embodiment is 3.13 mS / cm, which is close to the 4.10 mS / cm of pure ionic liquid. This is because the content of the gelling factor used is extremely low, only 5 wt%, which makes the binding force of the gelling factor low, and the ionic liquid can be freely transported inside the gel.

[0066] (2) Observation by scanning electron microscopy (SEM)

[0067] The results are as follows Figure 3 As shown in the figure, in the microstructure of supramolecular ionic gels, gelling factors self-assemble into slender fibrous structures through weak non-covalent interactions such as hydrogen bonds, van der Waals forces, and π-π stacking. These slender fibers further form a three-dimensional network structure through mutual entanglement, binding the ionic liquid within it, thus forming the gel observed macroscopically.

[0068] Example 2

[0069] This embodiment provides a supramolecular ionic gel, the preparation method and ionic conductivity testing method of which are the same as those in Example 1. The difference is that the ionic liquid used is 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt ([EMIM][TFSI]).

[0070] Example 3

[0071] This embodiment provides a supramolecular ionic gel, the preparation method and ionic conductivity testing method of which are the same as those in Example 1. The difference is that the ionic liquid used is a pyridine-based ionic liquid, 1-butylpyridine hexafluorophosphate ([BPy][PF6]).

[0072] Example 4

[0073] This embodiment provides a supramolecular ionic gel, the preparation method and ionic conductivity testing method of which are the same as those in Example 1. The difference is that the ionic liquid used is a quaternary ammonium salt ionic liquid, tetrabutylammonium bis(trifluoromethanesulfonyl)imide salt ([N4441][TFSI]).

[0074] Example 5

[0075] This embodiment provides a supramolecular ionic gel, the preparation method and ionic conductivity testing method of which are the same as those in Example 1. The difference is that the ionic liquid used is a quaternary phosphonium salt-based ionic liquid, trihexyltetradecylphosphonium bis(trifluoromethanesulfonyl)imide salt ([P66614][TFSI]).

[0076] Example 6

[0077] This embodiment provides a supramolecular ionic gel, the preparation method and ionic conductivity testing method of which are the same as in Example 1. The difference is that sodium stearate is used as the gelling agent.

[0078] Example 7

[0079] This embodiment provides a supramolecular ionic gel, the preparation method and ionic conductivity testing method of which are the same as in Example 1. The difference is that the gelling agent used is hexadecyltrimethylammonium bromide (CTAB).

[0080] Example 8

[0081] This embodiment provides a supramolecular ionic gel, the preparation method and ionic conductivity testing method of which are the same as in Example 1. The difference is that the gelling agent used is cholesterol benzoate.

[0082] Example 9

[0083] This embodiment provides an electrochromic device, the preparation method of which is as follows:

[0084] Accurately weigh 2.88 g of ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (BMIM[TFSI]), 0.15 g of glycosyl gelling agent (γ-cyclodextrin), 0.0186 g of ferrocene, and 0.092 g of diheptyl-substituted viologen (electrochromic material) using an electronic balance. Add these substances to a sample vial and sonicate for 10 min to mix thoroughly, obtaining a homogeneous solution. Place the solution in a 120°C forced-air drying oven and heat for 25 min until it becomes a homogeneous solution (gelling agent content 4.776 wt%). Attach two 5*5 cm ITO glass pieces together with double-sided tape, with the ITO side as the bonding surface and the two sides separated by the tape with a gap of approximately 0.1 mm. Inject the heated homogeneous solution into the gap formed by the two ITO glass pieces using a syringe, and wait for the solution to cool and form an electrochromic gel. The electrochromic device is now complete.

[0085] The electrochromic device prepared in this embodiment was tested as follows:

[0086] (1) Voltage-UV absorption spectroscopy test

[0087] The electrochromic devices under different applied voltages were tested using an ultraviolet spectrometer. The test results are as follows: Figure 4 As shown, the electrochromic device exhibits a maximum absorption peak at 607 nm. As the voltage increases, its absorbance also increases until it reaches -1.2V. Further increasing the voltage value has a limited effect on increasing the absorbance. At the same time, since excessively high voltage will reduce the stability of the device, its optimal operating voltage is -1.2V. The following tests will be conducted with the applied voltage between -1.2V and 0V.

[0088] like Figure 5 The image shows a comparison of the electrochromic device before and after the color change. As can be seen from the image, when no voltage is applied, the device is a light yellow color, which is due to the addition of ferrocene, which is yellow in color. When a voltage of -1.2V is applied, the device turns blue.

[0089] (2) Ultraviolet dynamic spectroscopy test

[0090] The ultraviolet kinetic spectrum of this electrochromic device between -1.2V and 0V was measured at 607nm. The test results are as follows: Figure 6 As shown in the figure, the optical contrast of the electrochromic device is 91%, the coloring time is 21s, and the color fading time is 48s.

[0091] (3) Electrochromic Cyclic Stability Test

[0092] The voltage was repeatedly applied between -1.2V and 0V, and the cycle stability of the electrochromic device was tested at 607nm. The test results are as follows: Figure 7 As shown in the figure, after 1000 cycles, the optical contrast of the electrochromic device remains at 85.8% of its original value, indicating that the electrochromic device has good color-changing cycle stability. In practical applications, it is generally desirable for the optical contrast to reach at least 30% to 50%, while an optical contrast of 60% or higher is considered to have very high contrast and can produce a very clear visual effect.

[0093] Example 10

[0094] This embodiment provides an electrochromic device, the preparation and testing methods of which are the same as those in Example 9. The difference is that the ionic liquid used is 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt ([EMIM][TFSI]).

[0095] Example 11

[0096] This embodiment provides an electrochromic device, the preparation and testing methods of which are the same as those in Example 9. The difference is that the ionic liquid used is a pyridine-based ionic liquid, 1-butylpyridine hexafluorophosphate ([BPy][PF6]).

[0097] Example 12

[0098] This embodiment provides an electrochromic device, the preparation and testing methods of which are the same as those in Example 9. The difference is that the ionic liquid used is a quaternary ammonium salt ionic liquid, tetrabutylammonium bis(trifluoromethanesulfonyl)imide salt ([N4441][TFSI]).

[0099] Example 13

[0100] This embodiment provides an electrochromic device, the preparation and testing methods of which are the same as those in Example 9. The difference is that the ionic liquid used is a quaternary phosphonium salt-based ionic liquid, trihexyltetradecylphosphonium bis(trifluoromethanesulfonyl)imide salt ([P66614][TFSI]).

[0101] Example 14

[0102] This embodiment provides an electrochromic device, the preparation and testing methods of which are the same as in Example 9. The difference is that the gelling agent used is sodium stearate.

[0103] Example 15

[0104] This embodiment provides an electrochromic device, the preparation and testing methods of which are the same as in Example 9. The difference is that the gelling agent used is hexadecyltrimethylammonium bromide (CTAB).

[0105] Example 16

[0106] This embodiment provides an electrochromic device, the preparation and testing methods of which are the same as in Example 9. The difference is that the gelling agent used is cholesterol benzoate.

[0107] Example 17

[0108] This embodiment provides a flexible electrochromic device, the preparation method of which is as follows:

[0109] Accurately weigh 2.88 g of the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (BMIM[TFSI]), 0.15 g of the saccharide gelling agent (β-cyclodextrin), 0.0186 g of ferrocene, and 0.092 g of diheptyl-substituted viologen (electrochromic material) using an electronic balance. Add these substances to a sample vial and sonicate for 10 min to mix thoroughly, obtaining a mixture (gelling agent content 4.776 wt%). Place the mixture in a 120℃ forced-air drying oven and heat for 25 min until it becomes a homogeneous solution. Adhere two 4*4 cm ITO-PET films (approximately 200 μm thick) together using double-sided tape, with the ITO side as the bonding surface and the two sides separated by the double-sided tape with a gap of approximately 0.1 mm. The heated homogeneous solution is injected into the gap between two ITO-PET films using a syringe. The solution is then allowed to cool and form an electrochromic gel. At this point, the flexible electrochromic device that can be bent is complete.

[0110] The flexible electrochromic device prepared in this embodiment was subjected to a bending cycle test, and the results are as follows:

[0111] The flexible electrochromic device of this embodiment was placed in a universal testing machine and subjected to 50 and 1000 bending cycle tests with a compression range of 10 mm. The test results are as follows. Figure 8 As shown, after 50 bending cycles, the ultraviolet kinetic spectrum of the electrochromic device almost coincides with the initial ultraviolet kinetic spectrum. Furthermore, after 1000 bending cycles, the optical contrast of the flexible electrochromic device remains above 88% of its initial value. This demonstrates that the flexible electrochromic device exhibits excellent flexibility.

[0112] Example 18

[0113] This embodiment relates to a composite electrochromic device composed of a first transparent electrode layer, a transparent supramolecular ion gel electrolyte membrane layer, and a second transparent electrode layer. The preparation method is as follows:

[0114] Solution A was prepared by dissolving 20 mg of the electrochromic polymer PRODT in 10 mL of xylene, and solution B was prepared by dissolving 4 mL of PEDOT:PSS in 16 mL of ethanol. Solutions A and B were sprayed onto the ITO surface of 5*5 cm ITO glass using a spraying method, and then placed in an 80℃ forced-air drying oven to allow film formation. The two coated ITO glass pieces were then bonded together with double-sided tape, with the ITO side facing each other and a gap of approximately 0.1 mm between the two sides.

[0115] Accurately weigh 0.95 g of the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (BMIM[TFSI]) and 0.05 g of the saccharide gelling agent (α-cyclodextrin) using an electronic balance, add them to a sample vial, and sonicate for 10 min to mix thoroughly, obtaining a mixture. Place the mixture in a 120°C forced-air drying oven and heat until it becomes a homogeneous and transparent solution. Inject the heated homogeneous solution into the gap formed by two pre-coated ITO glass pieces using a syringe, and wait for the solution to cool and form an electrochromic gel. The electrochromic device is now complete.

[0116] The electrochromic device prepared in this embodiment was tested, and the results are as follows:

[0117] (1) Voltage-UV absorption spectroscopy test

[0118] Electrochromic devices under different applied voltages were tested using an ultraviolet spectrometer. The test results are as follows: Figure 9 As shown, the electrochromic device exhibits a maximum absorption peak at 548 nm. As the voltage increases, its absorbance also increases until it reaches 0.8 V. Further increasing the voltage value has a limited effect on increasing the absorbance. At the same time, since excessively high voltage will reduce the stability of the device, its optimal operating voltage is 0.8 V. The following tests will be conducted with the applied voltage between -0.8 V and 0.8 V.

[0119] (2) Ultraviolet dynamic spectroscopy test

[0120] The ultraviolet kinetic spectrum of this electrochromic device between 0.8V and -0.8V was measured at 548nm. The test results are as follows: Figure 10 As shown, the electrochromic device has an optical contrast ratio of 52%, a coloring time of 0.6s, and a color fading time of 0.4s, exhibiting a very fast response speed that surpasses most known electrochromic devices.

[0121] (3) Cyclic stability test

[0122] A voltage was applied between 0.8V and -0.8V, and the cycling stability of the electrochromic device was tested at 548nm. The test results are as follows: Figure 11As shown, the electrochromic device retains 94.7% of its original optical contrast after 10,000 cycles. This demonstrates the excellent stability of the electrochromic device and reflects the stable electrochemical performance of the supramolecular ionogel used.

[0123] Comparative Example 1

[0124] The glycogel factor (β-cyclodextrin) in Example 1 was removed, and the ionic conductivity of the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt ([BMIM][TFSI]) was directly tested.

[0125] Comparative Example 2

[0126] This embodiment provides a conventional polymer ionogel. Its preparation method is as follows: 1.18 g of the polymer polymethyl methacrylate (PMMA, molecular weight approximately 200,000) and 2.75 g of the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([BMIM][TFSI]) are added to 20 mL of tetrahydrofuran, stirred uniformly for 30 min, and then treated with an ultrasonicator for 10 min. The treated mixture is poured into a polytetrafluoroethylene mold and dried at 40°C for 24 h to remove the tetrahydrofuran, obtaining the polymer ionogel.

[0127] Comparative Example 3

[0128] This embodiment provides an electrochromic device, the preparation and testing methods of which are the same as in Example 9. The difference is that the gelling agent γ-cyclodextrin is not used in the preparation process.

[0129] Comparative Example 4

[0130] This embodiment provides an electrochromic device, the preparation method of which is as follows: 1.18g of the polymer polymethyl methacrylate (PMMA, molecular weight approximately 200,000), 2.75g of the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([BMIM][TFSI]), 0.0186g of ferrocene, and 0.092g of diheptyl-substituted viologen (DHV[TFSI]2, electrochromic material) were added to 20mL of tetrahydrofuran and stirred uniformly for 30min, followed by ultrasonic treatment for 10min. The treated mixture was poured into a polytetrafluoroethylene mold and baked at 40°C for 24h to remove the tetrahydrofuran, obtaining a polymer gel. The obtained polymer was placed between two pieces of ITO glass and adhered tightly using double-sided adhesive to obtain the electrochromic device.

[0131] Table 1 shows the ion gel preparation parameters and ion conductivity test results for Examples 1-8 and Comparative Examples 1-2.

[0132]

[0133]

[0134] Table 2 shows the fabrication parameters and performance test results of the electrochromic devices in Examples 9-16 and Comparative Examples 3-4.

[0135]

[0136] By comparing Example 1 and Comparative Examples 1-2 with Table 1-2, it can be seen that when a gelling agent is added to an ionic liquid to form a gel, its ionic conductivity does not decrease much compared to that of a pure ionic liquid. However, when a polymer gel is prepared using a conventional polymer, its ionic conductivity decreases by orders of magnitude.

[0137] As can be seen from Examples 1-8, supramolecular ionic gels can still be formed using other gelling agents or ionic liquids. The magnitude of its ionic conductivity depends on the ionic conductivity of the ionic liquid itself, which is related to the size of its structure and the ease of dissociation, and is less affected by the gelling agent.

[0138] As can be seen from Examples 9, 3, and 4, when supramolecular ionogel is used as the electrolyte for electrochromic devices, the response time and cycling performance of the electrochromic devices are not much different from those when pure ionic liquid is used as the electrolyte, but the performance is better than that of electrochromic devices using traditional polymer ionogel as the electrolyte.

[0139] Examples 18 and 19 show that supramolecular ionogels can be used in electrochromic devices assembled from electrochromic polymers, and can also be used as electrolytes for flexible electrochromic devices.

[0140] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features. These modifications or substitutions, or combinations of technical features in the above embodiments that do not conflict with each other, can be made in accordance with the manner described in the embodiments. These modifications, substitutions or combinations do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A transparent supramolecular ionic gel for electrochromic devices, characterized in that, It is composed of a gelling agent, an ionic liquid, a redox medium, and an electrochromic material; the gelling agent is selected from at least one of sugars, stearic acids, surfactants, and cholesterol-based gelling agents, and the molecular weight of the gelling agent does not exceed 1000; the ionic liquid is selected from at least one of imidazole ionic liquids, quaternary ammonium salt ionic liquids, pyrrole ionic liquids, and quaternary phosphonium salt ionic liquids; the proportion of the gelling agent in the transparent supramolecular ionic gel is 0.1-5 wt%; the electrochromic material is diheptyl-substituted viologen; the redox medium in the transparent supramolecular ionic gel is 0.5-1.0 wt%, and the redox medium is ferrocene; the content of the electrochromic material in the transparent supramolecular ionic gel is 2-4 wt%.

2. A process for the preparation of a transparent supramolecular ionic gel for electrochromic devices according to claim 1, characterized in that, It includes: S1. Mix the gelling agent with the ionic liquid, add the redox medium and the electrochromic material, and homogenize to obtain the mixture. S2. Heat the mixture until it becomes a homogeneous and transparent solution; S3. Cool the homogeneous and transparent solution to obtain the transparent supramolecular ionic gel.

3. The production method according to claim 2, characterized by, In S1, the homogenization process includes any one of the following operations: stirring, oscillation, suction, and ultrasonic treatment; in S2, the heating temperature is 110-120℃ and the heating time is 10-30 min.

4. The application of the transparent supramolecular ionogel according to claim 1 in the preparation of electrochromic devices.

5. An electrochromic device, characterized in that, It includes a first transparent electrode layer, a transparent supramolecular ion gel electrolyte membrane layer, and a second transparent electrode layer stacked sequentially; The transparent supramolecular ionogel electrolytic membrane layer is formed from the transparent supramolecular ionogel as described in claim 1.

6. The electrochromic device according to claim 5, characterized in that, The first transparent electrode layer consists of a first transparent electrode and a first electrochromic film covering its surface, and the second transparent electrode layer consists of a second transparent electrode and a second electrochromic film covering its surface.

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