A reflective flexible electrochromic device based on hydrogel electrolyte, preparation method and application

Abstract

This invention relates to the field of electrochromic device technology, specifically a reflective flexible electrochromic device based on a hydrogel electrolyte, its fabrication method, and its application. The electrochromic device includes a first conductive substrate and a second conductive substrate, which are disposed opposite to each other. A hydrogel electrolyte layer is bonded to one side of the first conductive substrate, and an electrochromic layer is bonded to one side of the second conductive substrate. The hydrogel electrolyte layer and the electrochromic layer are bonded together. Both the bonded surfaces of the hydrogel electrolyte layer and the electrochromic layer have protruding structures formed using a porous polystyrene template. The electrochromic device prepared by this invention exhibits strong interfacial compatibility and minimal color difference on its surface.

Description

Technical Field

[0001] This invention relates to the field of electrochromic device technology, specifically a reflective flexible electrochromic device based on hydrogel electrolyte, its preparation method, and its application. Background Technology

[0002] Electrochromism refers to the phenomenon where the optical properties of a material or device undergo stable and reversible color changes under the influence of an applied electric field, manifesting as reversible changes in color and transparency. The ability of electrochromic devices to change color in response to external stimuli gives them significant advantages in certain applications. Electrochromic devices primarily consist of a five-layer structure: a bottom conductive electrode, an ion storage layer, an ion electrolyte layer, an electrochromic layer, and a top conductive electrode, making them a typical multifunctional optoelectronic device. When a certain positive or negative voltage is applied across the device's electrodes, ions and free electrons continuously move within and outside the device, thus enabling spectral modulation. Currently, electrochromic technology is widely used in numerous fields, including smart windows, aerospace vehicles, automotive rearview mirrors, smart displays, information storage devices, and sensors.

[0003] Current research on electrochromic devices mainly focuses on transmission-type devices, while research on reflective flexible electrochromic devices is relatively limited. At present, the fabrication process for reflective electrochromic devices is complex, costly, and lacks flexibility. Flexible electrochromic devices place high demands on the reflective layer material, which limits their widespread application. To improve the overall performance of reflective flexible electrochromic devices, most research focuses on the design and fabrication of high-performance electrochromic layer materials, with less emphasis on exploring and designing high-performance electrolyte layers that meet specific requirements. The electrolyte layer, located between the upper and lower electrodes of the device, plays a crucial role in ion transport, charge balancing, and electron blocking, significantly impacting the safety and overall performance of reflective flexible electrochromic devices. Therefore, improving the material properties of the electrolyte layer is of great significance for optimizing the performance of reflective flexible electrochromic devices and promoting the development of electrochromic spectral modulation technology.

[0004] Generally, an ideal electrolyte for reflective flexible electrochromic devices should possess excellent mechanical, chemical, and thermal stability, be easy to prepare, low in cost, and bend resistance. Traditional liquid electrolytes suffer from limitations such as easy leakage and difficulty in encapsulation during device fabrication. Inorganic solid electrolytes have problems such as unstable contact interfaces with electrodes, low ionic conductivity, brittleness, and high preparation costs. Therefore, developing an electrolyte that is environmentally friendly, easy to prepare, and combines the advantages of both liquid and solid electrolytes is key to solving these problems. Hydrogel electrolytes are quasi-solid electrolytes formed by filling a porous structure with salt ion solution through a 3D network structure formed by cross-linking hydrophilic polymers. They have advantages such as high ionic conductivity, good interfacial compatibility, environmental friendliness, and good flexibility.

[0005] However, existing electrochromic devices using hydrogels as electrolytes typically involve cross-linking and curing the hydrogel within the device's cavity. During the curing process, the gel effect can easily lead to uneven contact between the hydrogel and the electrochromic layer, resulting in decreased compatibility and color differences in the electrochromic device. Therefore, to address the problems mentioned in the background, those skilled in the art propose a reflective flexible electrochromic device based on a hydrogel electrolyte, its fabrication method, and its applications. Summary of the Invention

[0006] The purpose of this invention is to provide a reflective flexible electrochromic device based on hydrogel electrolyte, its preparation method, and its application, so as to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A reflective flexible electrochromic device based on hydrogel electrolyte includes a first conductive substrate and a second conductive substrate, which are disposed opposite to each other.

[0009] A hydrogel electrolyte layer is attached to one side of the first conductive substrate, and an electrochromic layer is attached to one side of the second conductive substrate. The hydrogel electrolyte layer and the electrochromic layer are attached to each other.

[0010] Both the hydrogel electrolyte layer and the electrochromic layer have protruding structures formed on the surfaces where they are bonded together, and both the hydrogel electrolyte layer and the electrochromic layer are formed with a porous polystyrene template to form the protruding structures.

[0011] Furthermore, both the first conductive substrate and the second conductive substrate are zinc foil metal conductive substrates, and the first conductive substrate and the second conductive substrate need to undergo pretreatment.

[0012] Furthermore, the pretreatment steps for the first and second conductive substrates are as follows:

[0013] The first and second conductive substrates were first ultrasonically cleaned for 30 minutes with a 1:1 volume ratio of alcohol and acetone, then rinsed with sufficient deionized water, and finally dried with a hair dryer.

[0014] Furthermore, the method for preparing the porous polystyrene template includes the following steps:

[0015] Polystyrene is dissolved in toluene containing sodium dodecyl sulfate to form a mixed solution. The mixed solution is cast on a glass substrate. After the toluene evaporates naturally at a relative humidity of 20-40% and a temperature of 25-35°C, a porous polystyrene template is obtained. The mass ratio of sodium dodecyl sulfate, polystyrene and toluene is 1:(10-25):(400-600).

[0016] Furthermore, the method for preparing the hydrogel electrolyte layer with the protruding structure on its surface includes the following steps:

[0017] S101. Add zinc chloride and acrylamide to deionized water and stir to dissolve to obtain a mixed solution;

[0018] S102. Add N,N'-methylenebisacrylamide and ammonium persulfate to the mixed solution obtained in step S101, stir continuously for 60 min, and introduce argon gas during the stirring process to obtain a hydrogel solution.

[0019] S103. The hydrogel solution obtained in step S102 is coated on the surface of the porous polystyrene template, and the hydrogel with the porous polystyrene template is obtained by irradiating with ultraviolet light with a wavelength of 350nm for 1-5 hours.

[0020] S104. The template of the hydrogel with porous polystyrene template obtained in step S103 is removed by dissolving in toluene to obtain a hydrogel electrolyte layer with a raised structure on the surface.

[0021] Furthermore, in step S101, the mass ratio of zinc chloride, acrylamide, and deionized water is 1:(4-8):(12-20), and in step S102, the mass ratio of N,N'-methylenebisacrylamide and ammonium persulfate to acrylamide in step S101 is 1:(8-14):(300-500).

[0022] Furthermore, the method for preparing the electrochromic layer with the raised structure on the surface includes the following steps:

[0023] S201. Dissolve tungstic acid in 30% hydrogen peroxide and stir to mix evenly to obtain a mixed solution;

[0024] S202. Add propanol and deionized water to the mixed solution obtained in step S201, and then add hydrochloric acid with a concentration of 2 mol / L to adjust the pH to 1-2 to obtain tungsten oxide precursor solution.

[0025] S203. The tungsten oxide precursor solution obtained in step S202 is coated onto a porous polystyrene template and reacted at 75-95°C for 18-36 hours to obtain a porous polyethylene template with a tungsten oxide film. The polystyrene template is dissolved by toluene to obtain an electrochromic layer with a raised structure on the surface.

[0026] Furthermore, in step S201, the mass ratio between tungstic acid and hydrogen peroxide is 1:(15-30), and in step S202, the mass ratio between propanol and deionized water and the mass ratio between tungstic acid in step S201 are (10-20):(20-35):1.

[0027] A method for fabricating a reflective flexible electrochromic device based on a hydrogel electrolyte, the method comprising the following steps:

[0028] S1. Coat the side of the electrochromic layer and the hydrogel electrolyte layer that are in contact with each other with a polyethylene glycol solution. After the electrochromic layer and the hydrogel electrolyte layer are bonded together, vacuum the surface and let it stand for 3-8 hours.

[0029] S2. The first conductive substrate, the hydrogel electrolyte layer, the electrochromic layer and the second conductive substrate are assembled together in sequence and sealed with sealing glue to obtain a reflective flexible electrochromic device based on hydrogel electrolyte.

[0030] In step S1, the polyethylene glycol solution also contains ultrasonically dispersed graphene, and the mass ratio of polyethylene glycol, deionized water and graphene in the polyethylene glycol solution is 1:20:0.2.

[0031] The above-mentioned reflective flexible electrochromic devices based on hydrogel electrolytes are used in smart windows, aerospace vehicles, automotive rearview mirrors, smart displays, information storage, and sensors.

[0032] Compared with the prior art, the beneficial effects of the present invention are:

[0033] 1. In this invention, one side of both the hydrogel electrolyte layer and the electrochromic layer is formed with a protruding structure through a polystyrene template. The size of the protruding structure is at the micrometer level. The small protruding structure greatly enhances the compatibility between the hydrogel electrolyte layer and the electrochromic layer, prevents uneven contact caused by the gel effect, and reduces the color difference of the electrochromic device.

[0034] 2. In this invention, the hydrogel electrolyte layer and the electrochromic layer are treated with polyethylene glycol solution, which effectively wets both layers and improves the compatibility of the protruding structures on their surfaces. The graphene contained in the polyethylene glycol solution improves the conductivity between the layers and facilitates ion migration. Attached Figure Description

[0035] Figure 1 A process flow diagram for preparing the reflective flexible electrochromic device based on hydrogel electrolyte according to the present invention;

[0036] Figure 2 This is a process flow diagram for preparing a hydrogel electrolyte layer with a raised structure on its surface in this invention.

[0037] Figure 3 This is a flowchart illustrating the process for preparing an electrochromic layer with a raised surface structure in this invention.

[0038] Figure 4 The images show the spectra of the electrochromic layer with a raised structure on its surface in different states of the visible light band in Embodiment 1 of the present invention.

[0039] Figure 5 The images show the spectra of the reflective flexible electrochromic device based on hydrogel electrolyte prepared in Example 1 of this invention at different voltages.

[0040] Figure 6 The image shows the emission power of the reflective flexible electrochromic device based on hydrogel electrolyte prepared in Example 1 of this invention at different voltages in the infrared band.

[0041] Figure 7 This is a comparison of the emissivity of the hydrogel electrolyte-based reflective flexible electrochromic device prepared in Example 1 of the present invention at different voltages and in different infrared bands. Detailed Implementation

[0042] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] Please see Figures 1 to 7 The present invention provides:

[0044] Example 1

[0045] A method for fabricating a reflective flexible electrochromic device based on a hydrogel electrolyte includes the following steps:

[0046] S1. Coat the side of the electrochromic layer and the hydrogel electrolyte layer that are in contact with each other with a polyethylene glycol solution. After the electrochromic layer and the hydrogel electrolyte layer are bonded together, vacuum the surface and let it stand for 6 hours.

[0047] S2. The first conductive substrate, the hydrogel electrolyte layer, the electrochromic layer and the second conductive substrate are assembled together in sequence and sealed with sealing glue to obtain a reflective flexible electrochromic device based on hydrogel electrolyte.

[0048] A raised structure is formed on the side where the hydrogel electrolyte layer and the electrochromic layer are bonded together. Both the hydrogel electrolyte layer and the electrochromic layer are formed with a porous polystyrene template to form the raised structure.

[0049] The preparation method of the above-mentioned porous polystyrene template includes the following steps:

[0050] 10.2g of polystyrene was dissolved in toluene containing sodium dodecyl sulfate to form a mixed solution. The amount of sodium dodecyl sulfate was 0.51g and the amount of toluene was 250g. The mixed solution was cast on a glass substrate. After the toluene evaporated naturally at a relative humidity of 30% and a temperature of 30°C, a porous polystyrene template was obtained.

[0051] The method for preparing the hydrogel electrolyte layer with the above-mentioned surface having a raised structure includes the following steps:

[0052] S101. Add 0.7g zinc chloride and 4.2g acrylamide to 11.2g deionized water and stir to dissolve to obtain a mixed solution;

[0053] S102. Add 0.011g N,N'-methylenebisacrylamide and 0.12g ammonium persulfate to the mixed solution obtained in step S101, stir continuously for 60min, and introduce argon gas during the stirring process to obtain a hydrogel solution.

[0054] S103. The hydrogel solution obtained in step S102 is coated on the surface of the porous polystyrene template, and the hydrogel with the porous polystyrene template is obtained by irradiating with ultraviolet light with a wavelength of 350nm for 4h.

[0055] S104. The template of the hydrogel with porous polystyrene template obtained in step S103 is removed by dissolving in toluene to obtain a hydrogel electrolyte layer with a raised structure on the surface.

[0056] The method for preparing the electrochromic layer with the above-mentioned protruding structure includes the following steps:

[0057] S201. Dissolve 2.4g of tungstic acid in 58g of 30% hydrogen peroxide and stir until homogeneous to obtain a mixed solution;

[0058] S202. Add 36g of propanol and 72g of deionized solution to the mixed solution obtained in step S201, and then add 2mol / L hydrochloric acid to adjust the pH to 1 to obtain tungsten oxide precursor solution.

[0059] S203. The tungsten oxide precursor solution obtained in step S202 is coated onto a porous polystyrene template. After reacting at 90°C for 25 hours, a porous polyethylene template with a tungsten oxide film is obtained. The polystyrene template is dissolved by toluene to obtain an electrochromic layer with a raised structure on the surface.

[0060] Example 2

[0061] A method for fabricating a reflective flexible electrochromic device based on a hydrogel electrolyte includes the following steps:

[0062] S1. Coat the side of the electrochromic layer and the hydrogel electrolyte layer that are in contact with each other with a polyethylene glycol solution. After the electrochromic layer and the hydrogel electrolyte layer are bonded together, vacuum the surface and let it stand for 3 hours.

[0063] S2. The first conductive substrate, the hydrogel electrolyte layer, the electrochromic layer and the second conductive substrate are assembled together in sequence and sealed with sealing glue to obtain a reflective flexible electrochromic device based on hydrogel electrolyte.

[0064] On the side where the hydrogel electrolyte layer and the electrochromic layer are bonded together, a raised structure is formed. Both the hydrogel electrolyte layer and the electrochromic layer are formed with a porous polystyrene template to form the raised structure.

[0065] The preparation method of the above-mentioned porous polystyrene template includes the following steps:

[0066] 10.2g of polystyrene was dissolved in toluene containing sodium dodecyl sulfate to form a mixed solution. The amount of sodium dodecyl sulfate was 1.02g and the amount of toluene was 408g. The mixed solution was cast on a glass substrate. After the toluene evaporated naturally at a relative humidity of 20% and a temperature of 25°C, a porous polystyrene template was obtained.

[0067] The method for preparing the hydrogel electrolyte layer with the above-mentioned surface having a raised structure includes the following steps:

[0068] S101. Add 1.05g of zinc chloride and 4.2g of acrylamide to 12.6g of deionized water and stir to dissolve to obtain a mixed solution;

[0069] S102. Add 0.014g N,N'-methylenebisacrylamide and 0.112g ammonium persulfate to the mixed solution obtained in step S101, stir continuously for 60min, and introduce argon gas during the stirring process to obtain a hydrogel solution.

[0070] S103. The hydrogel solution obtained in step S102 is coated on the surface of the porous polystyrene template, and the hydrogel with the porous polystyrene template is obtained by irradiating it with ultraviolet light with a wavelength of 350nm for 1h.

[0071] S104. The template of the hydrogel with porous polystyrene template obtained in step S103 is removed by dissolving in toluene to obtain a hydrogel electrolyte layer with a raised structure on the surface.

[0072] The method for preparing the electrochromic layer with the above-mentioned protruding structure includes the following steps:

[0073] S201. Dissolve 2.4g of tungstic acid in 36g of 30% hydrogen peroxide and stir until homogeneous to obtain a mixed solution.

[0074] S202. Add 24g of propanol and 48g of deionized solution to the mixed solution obtained in step S201, and then add hydrochloric acid with a concentration of 2mol / L to adjust the pH to 1 to obtain tungsten oxide precursor solution.

[0075] S203. The tungsten oxide precursor solution obtained in step S202 is coated onto a porous polystyrene template. After reacting at 75°C for 18 hours, a porous polyethylene template with a tungsten oxide film is obtained. The polystyrene template is dissolved by toluene to obtain an electrochromic layer with a raised structure on the surface.

[0076] Example 3

[0077] A method for fabricating a reflective flexible electrochromic device based on a hydrogel electrolyte includes the following steps:

[0078] S1. Coat the side of the electrochromic layer and the hydrogel electrolyte layer that are in contact with each other with a polyethylene glycol solution. After the electrochromic layer and the hydrogel electrolyte layer are bonded together, vacuum the surface and let it stand for 8 hours.

[0079] S2. The first conductive substrate, the hydrogel electrolyte layer, the electrochromic layer and the second conductive substrate are assembled together in sequence and sealed with sealing glue to obtain a reflective flexible electrochromic device based on hydrogel electrolyte.

[0080] On the side where the hydrogel electrolyte layer and the electrochromic layer are bonded together, a raised structure is formed. Both the hydrogel electrolyte layer and the electrochromic layer are formed with a porous polystyrene template to form the raised structure.

[0081] The preparation method of the above-mentioned porous polystyrene template includes the following steps:

[0082] 10.2g of polystyrene was dissolved in toluene containing sodium dodecyl sulfate to form a mixed solution. The amount of sodium dodecyl sulfate was 0.408g and the amount of toluene was 244.8g. The mixed solution was cast on a glass substrate. After the toluene evaporated naturally at a relative humidity of 40% and a temperature of 35°C, a porous polystyrene template was obtained.

[0083] The method for preparing the hydrogel electrolyte layer with the above-mentioned surface having a raised structure includes the following steps:

[0084] S101. Add 0.525g of zinc chloride and 4.2g of acrylamide to 10.5g of deionized water and stir to dissolve to obtain a mixed solution;

[0085] S102. Add 0.0084g N,N'-methylenebisacrylamide and 0.117g ammonium persulfate to the mixed solution obtained in step S101, stir continuously for 60min, and introduce argon gas during the stirring process to obtain a hydrogel solution.

[0086] S103. The hydrogel solution obtained in step S102 is coated on the surface of the porous polystyrene template, and the hydrogel with the porous polystyrene template is obtained by irradiating it with ultraviolet light with a wavelength of 350nm for 5h.

[0087] S104. The template of the hydrogel with porous polystyrene template obtained in step S103 is removed by dissolving in toluene to obtain a hydrogel electrolyte layer with a raised structure on the surface.

[0088] The method for preparing the electrochromic layer with the above-mentioned protruding structure includes the following steps:

[0089] S201. Dissolve 2.4g of tungstic acid in 72g of 30% hydrogen peroxide and stir until homogeneous to obtain a mixed solution;

[0090] S202. Add 48g of propanol and 84g of deionized solution to the mixed solution obtained in step S201, and then add 2mol / L hydrochloric acid to adjust the pH to 2 to obtain tungsten oxide precursor solution.

[0091] S203. The tungsten oxide precursor solution obtained in step S202 is coated onto a porous polystyrene template. After reacting at 95°C for 36 hours, a porous polyethylene template with a tungsten oxide film is obtained. The polystyrene template is dissolved by toluene to obtain an electrochromic layer with a raised structure on the surface.

[0092] Example 4

[0093] A method for fabricating a reflective flexible electrochromic device based on a hydrogel electrolyte includes the following steps:

[0094] S1. Coat the side of the electrochromic layer and the hydrogel electrolyte layer that are in contact with each other with a polyethylene glycol solution. After the electrochromic layer and the hydrogel electrolyte layer are bonded together, vacuum the surface and let it stand for 7 hours.

[0095] S2. The first conductive substrate, the hydrogel electrolyte layer, the electrochromic layer and the second conductive substrate are assembled together in sequence and sealed with sealing glue to obtain a reflective flexible electrochromic device based on hydrogel electrolyte.

[0096] On the side where the hydrogel electrolyte layer and the electrochromic layer are bonded together, a raised structure is formed. Both the hydrogel electrolyte layer and the electrochromic layer are formed with a porous polystyrene template to form the raised structure.

[0097] The preparation method of the above-mentioned porous polystyrene template includes the following steps:

[0098] 10.2g of polystyrene was dissolved in toluene containing sodium dodecyl sulfate to form a mixed solution. The amount of sodium dodecyl sulfate was 0.56g and the amount of toluene was 250g. The mixed solution was cast on a glass substrate. After the toluene evaporated naturally at a relative humidity of 35% and a temperature of 25°C, a porous polystyrene template was obtained.

[0099] The method for preparing the hydrogel electrolyte layer with the above-mentioned surface having a raised structure includes the following steps:

[0100] S101. Add 0.65g of zinc chloride and 4.2g of acrylamide to 11.7g of deionized water and stir to dissolve to obtain a mixed solution;

[0101] S102. Add 0.013g N,N'-methylenebisacrylamide and 0.14g ammonium persulfate to the mixed solution obtained in step S101, stir continuously for 60min, and introduce argon gas during the stirring process to obtain a hydrogel solution.

[0102] S103. The hydrogel solution obtained in step S102 is coated on the surface of the porous polystyrene template, and the hydrogel with the porous polystyrene template is obtained by irradiating with ultraviolet light with a wavelength of 350nm for 1-5 hours.

[0103] S104. The template of the hydrogel with porous polystyrene template obtained in step S103 is removed by dissolving in toluene to obtain a hydrogel electrolyte layer with a raised structure on the surface.

[0104] The method for preparing the electrochromic layer with the above-mentioned protruding structure includes the following steps:

[0105] S201. Dissolve 2.4g of tungstic acid in 52g of 30% hydrogen peroxide and stir until homogeneous to obtain a mixed solution; the mass ratio of tungstic acid to hydrogen peroxide in step S201 is 1:(15-30).

[0106] S202. Add 28g of propanol and 65g of deionized water to the mixed solution obtained in step S201, and then add 2mol / L hydrochloric acid to adjust the pH to 1.5 to obtain tungsten oxide precursor solution.

[0107] S203. The tungsten oxide precursor solution obtained in step S202 is coated onto a porous polystyrene template. After reacting at 85°C for 30 hours, a porous polyethylene template with a tungsten oxide film is obtained. The polystyrene template is dissolved by toluene to obtain an electrochromic layer with a raised structure on the surface.

[0108] In step S1 of Examples 1-4 above, the polyethylene glycol solution also contains ultrasonically dispersed graphene, and the mass ratio of polyethylene glycol, deionized water and graphene in the polyethylene glycol solution is 1:20:0.2.

[0109] The degree of polymerization of the polystyrene selected in the above embodiments is 50-100.

[0110] Comparative Example 1

[0111] The difference between Comparative Example 1 and Example 1 is that steps S103 and S104 are omitted, and the hydrogel electrolyte layer is cured directly on a smooth glass substrate. The surface of the resulting hydrogel electrolyte layer is smooth. The remaining steps are exactly the same as in Example 1.

[0112] Comparative Example 2

[0113] The difference between Comparative Example 2 and Example 1 is that step S203 is omitted and replaced by forming an electrochromic layer directly on a smooth glass substrate. The surface of the formed electrochromic layer is smooth. The remaining steps are exactly the same as in Example 1.

[0114] Comparative Example 3

[0115] The difference between Comparative Example 3 and Example 1 is that step S1 was partially omitted, thus eliminating the addition of polyethylene glycol solution; the remaining steps are exactly the same as in Example 1.

[0116] Comparative Example 4

[0117] The difference between Comparative Example 4 and Comparative Example 1 is that step S203 is omitted and replaced by forming an electrochromic layer directly on a smooth glass substrate. The surfaces of the electrochromic layer and the hydrogel electrolyte layer are both smooth. The remaining steps are exactly the same as those in Comparative Example 1.

[0118] Comparative Example 5

[0119] The difference between Comparative Example 5 and Example 1 is that the first conductive substrate, the electrochromic layer and the second conductive substrate are assembled together first, and a cavity is formed between the first conductive substrate and the electrochromic layer. The electrochromic layer is prepared in the same way as the electrochromic layer in Comparative Example 2. Then, the hydrogel solution prepared in Example 1 is poured into the cavity, and the hydrogel solution is cured by ultraviolet light in the cavity.

[0120] Nine sets of reflective flexible electrochromic devices based on hydrogel electrolytes were prepared using Examples 1-4 and Comparative Examples 1-5. A point was selected at the center of eight sets of reflective flexible electrochromic devices based on hydrogel electrolytes and denoted as E. a Four points are selected on the edge and labeled E1, E2, E3 and E4 respectively. The four points on the edge are equidistant from the center point. The ring formed by the four points on the edge bisects the ring.

[0121] Nine sets of reflective flexible electrochromic devices based on hydrogel electrolytes were connected to a power source. When the edge positions E1, E2, E3, and E4 changed from a faded state to a colored state, the power was immediately turned off. A colorimeter was used to measure the values ​​at the edge positions E1, E2, E3, and E4, and the center position E1. a The color difference ΔE, the color difference between the four edge positions and the center point is denoted as ΔE respectively. a1 ΔE a2 ΔE a3 ΔE a4 The test results are shown in Table 1:

[0122] Table 1: Color difference display of 9 groups of hydrogel electrolyte-based reflective flexible electrochromic devices prepared in Examples 1-4 and Comparative Examples 1-5

[0123]

[0124]

[0125] As can be seen from the data in Table 1 above for Example 1 and Comparative Examples 4-5, the present invention can effectively reduce the surface color difference of the electrochromic device by forming a raised structure on the surface of the hydrogel electrolyte layer and the electrochromic layer. The color difference of the electrochromic devices in Comparative Examples 1-2 is greater than that in Comparative Examples 4-5. Since only one side of the hydrogel electrolyte layer and the electrochromic layer has a raised structure, it may lead to more uneven contact, which in turn increases the color difference. The data comparison between Comparative Example 3 and Example 1 shows that by coating the contact surface of the hydrogel electrolyte layer and the electrochromic layer with polyethylene glycol solution, the compatibility between the two is further improved, the uniformity of ion conduction is improved, and the color difference is reduced.

[0126] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A reflective flexible electrochromic device based on a hydrogel electrolyte, characterized in that, It includes a first conductive substrate and a second conductive substrate, which are disposed opposite to each other; A hydrogel electrolyte layer is attached to one side of the first conductive substrate, and an electrochromic layer is attached to one side of the second conductive substrate. The hydrogel electrolyte layer and the electrochromic layer are attached to each other. Both the hydrogel electrolyte layer and the electrochromic layer have protruding structures formed on the surfaces where they are bonded together, and both the hydrogel electrolyte layer and the electrochromic layer are formed with a porous polystyrene template to form the protruding structures.

2. The reflective flexible electrochromic device based on hydrogel electrolyte according to claim 1, characterized in that, Both the first conductive substrate and the second conductive substrate are zinc foil metal conductive substrates, and the first conductive substrate and the second conductive substrate need to undergo pretreatment.

3. The reflective flexible electrochromic device based on hydrogel electrolyte according to claim 2, characterized in that, The pretreatment steps for the first and second conductive substrates are as follows: The first and second conductive substrates were first ultrasonically cleaned for 30 minutes with a 1:1 volume ratio of alcohol and acetone, then rinsed with sufficient deionized water, and finally dried with a hair dryer.

4. The reflective flexible electrochromic device based on hydrogel electrolyte according to claim 1, characterized in that, The method for preparing the porous polystyrene template includes the following steps: Polystyrene is dissolved in toluene containing sodium dodecyl sulfate to form a mixed solution. The mixed solution is cast on a glass substrate. After the toluene evaporates naturally at a relative humidity of 20-40% and a temperature of 25-35°C, a porous polystyrene template is obtained. The mass ratio of sodium dodecyl sulfate, polystyrene and toluene is 1:(10-25):(400-600).

5. The reflective flexible electrochromic device based on hydrogel electrolyte according to claim 4, characterized in that, The method for preparing the hydrogel electrolyte layer with a raised structure on its surface includes the following steps: S101. Add zinc chloride and acrylamide to deionized water and stir to dissolve to obtain a mixed solution; S102. Add N,N'-methylenebisacrylamide and ammonium persulfate to the mixed solution obtained in step S101, stir continuously for 60 min, and introduce argon gas during the stirring process to obtain a hydrogel solution. S103. The hydrogel solution obtained in step S102 is coated on the surface of the porous polystyrene template, and the hydrogel with the porous polystyrene template is obtained by irradiating with ultraviolet light with a wavelength of 350nm for 1-5 hours. S104. The template of the hydrogel with porous polystyrene template obtained in step S103 is removed by dissolving in toluene to obtain a hydrogel electrolyte layer with a raised structure on the surface.

6. The reflective flexible electrochromic device based on hydrogel electrolyte according to claim 5, characterized in that, In step S101, the mass ratio of zinc chloride, acrylamide, and deionized water is 1:(4-8):(12-20), and in step S102, the mass ratio of N,N'-methylenebisacrylamide and ammonium persulfate to acrylamide in step S101 is 1:(8-14):(300-500).

7. The reflective flexible electrochromic device based on hydrogel electrolyte according to claim 4, characterized in that, The method for preparing the electrochromic layer with the protruding structure on the surface includes the following steps: S201. Dissolve tungstic acid in 30% hydrogen peroxide and stir until homogeneous to obtain a mixed solution; S202. Add a mixture of propanol and deionized water to the mixed solution obtained in step S201, and then add 2 mol / L hydrochloric acid to adjust the pH to 1-2 to obtain a tungsten oxide precursor solution. S203. The tungsten oxide precursor solution obtained in step S202 is coated onto a porous polystyrene template and reacted at 75-95°C for 18-36 hours to obtain a porous polyethylene template with a tungsten oxide film. The polystyrene template is dissolved by toluene to obtain an electrochromic layer with a raised structure on the surface.

8. The reflective flexible electrochromic device based on hydrogel electrolyte according to claim 7, characterized in that, In step S201, the mass ratio of tungstic acid to hydrogen peroxide is 1:(15-30), and in step S202, the mass ratio of propanol to deionized water and the mass ratio of tungstic acid to propanol in step S201 are (10-20):(20-35):

1.

9. A method for fabricating a reflective flexible electrochromic device based on a hydrogel electrolyte as described in any one of claims 1-8, characterized in that, The preparation method includes the following steps: S1. Coat the side of the electrochromic layer and the hydrogel electrolyte layer that are in contact with each other with a polyethylene glycol solution. After the electrochromic layer and the hydrogel electrolyte layer are bonded together, vacuum the surface and let it stand for 3-8 hours. S2. The first conductive substrate, the hydrogel electrolyte layer, the electrochromic layer and the second conductive substrate are assembled together in sequence and sealed with sealing glue to obtain a reflective flexible electrochromic device based on hydrogel electrolyte. In step S1, the polyethylene glycol solution also contains ultrasonically dispersed graphene, and the mass ratio of polyethylene glycol, deionized water and graphene in the polyethylene glycol solution is 1:20:0.

2.

10. An application of a hydrogel electrolyte-based reflective flexible electrochromic device as described in any one of claims 1-8 in the fields of smart windows, aerospace vehicles, automotive rearview mirrors, smart displays, information storage, and sensors.

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