Three-color-state electrochromic device and preparation method thereof

Abstract

The invention discloses a three-color-state electrochromic device and a preparation method thereof, the three-color-state electrochromic device comprises a working electrode, an electrolyte and a counter electrode, the electrolyte is filled between the working electrode and the counter electrode, the working electrode is transparent conductive glass of which the surface is modified with a catalyst, the catalyst comprises a carbon material, and the carbon material is a carbon material. The counter electrode is glass attached with a copper foil frame or a copper grid, the electrolyte is a water-based electrolyte, and the electrolyte contains HCl, BiCl3, CuCl2, LiBr and MPIBr. Reversible switching of the three color states (yellow, transparent and black) is successfully achieved, three different color developing mechanisms can be triggered by simply regulating and controlling the working voltage, the color expression of the electrochromic device is enriched, the electrochromic device has larger application potential in the field of intelligent windows, and the application potential in other fields is greatly expanded.

Description

Technical Field

[0001] The present invention relates to a three-color electrochromic device and a preparation method thereof, in particular to a method based on Bi-Cu reversible electrodeposition and Br - / Br3 - The invention discloses a three-color electrochromic device capable of redox conversion and a preparation method thereof, belonging to the technical field of electrochromism. Background Art

[0002] Electrochromism refers to the reversible and stable change in the optical properties (such as reflectivity, transmittance, and absorptivity) of a material under an applied electric field, enabling dynamic control of color and transparency. This property holds great promise for electrochromic technology in a variety of applications, including smart displays, wearable devices, automotive rearview mirrors, thermal management systems, and military camouflage. Traditional electrochromic materials primarily include transition metal oxides, conductive polymers, and organic small molecules. Their color-changing mechanisms typically rely on ion insertion / extraction or redox processes, resulting in the material exhibiting different colors in different oxidation states. For example, tungsten oxide (WO3) can achieve a transparent-to-blue color transition, while polyaniline (PANI) can be tuned between transparent, green, and blue. Although these materials exhibit high optical modulation rates within specific wavelength ranges, their optical response is limited by the electronic structure and redox behavior of the materials themselves, making it difficult to cover the entire visible light band. Consequently, achieving black (color neutrality) with traditional electrochromic materials is often difficult, limiting their ability to meet the privacy and visual comfort requirements in applications such as smart windows.

[0003] In recent years, electrochromic devices based on reversible metal electrodeposition (RME) have gained increasing attention. These devices, which control the reversible deposition and dissolution of metal ions in an electrolyte via an applied voltage, can achieve high-contrast optical modulation from transparent to black. Due to the high absorption properties of metals, RME devices offer superior color-neutral control. However, while these devices can dynamically switch between transparent and black, they struggle to expand to multi-color control, failing to meet user demands for diverse colors. To achieve three-state electrochromic control (transparent-black-color), a straightforward approach is to combine metal deposition-based electrochromic materials with traditional color electrochromic materials to create "hybrid dynamic windows." However, in these complementary devices, the coloring process occurs simultaneously with the coloring of the counter electrode, resulting in color overlays and the inability to independently achieve color control beyond black. An ideal strategy would be to make the optical modulation of metal deposition independent of the optical modulation of another electrochromic material, thereby achieving multi-color dynamic switching within a single device. Given that the metal deposition process is usually cathodic coloring, if an electrochromic material based on anodic electrodeposition or electrochemical redox reaction can be found and combined with the metal deposition mechanism, it is expected to achieve reversible control of the three color states of transparent-black-color in a single device.

[0004] The paper "Shingo Araki et al. Electrochemical Optical-Modulation Device with Reversible Transformation Between Transparent, Mirror, and Black" (Adv. Mater. 2012, 24, OP122–OP126) reports a three-state electrochromic device based on silver electrodeposition, capable of reversibly switching between transparent, mirror-reflective, and light-absorbing black. The core structure consists of a pair of transparent electrodes (a flat ITO electrode and a roughened electrode modified with ITO particles), intercalated with a DMSO gel electrolyte containing silver nitrate, copper chloride, and tetrabutylammonium bromide (TBABr). Applying voltages of varying polarity (-2.5 V or +2.5 V) causes silver ions to uniformly deposit on the flat electrode, forming a mirror-reflective layer, or to form large silver particle aggregates on the roughened electrode, resulting in light scattering and absorption, resulting in a black appearance. Removing the voltage causes the silver to dissolve, restoring the transparent state. Copper ions and bromide ions act as redox mediators and complexing agents, respectively, enhancing the reversibility and stability of the silver deposition / dissolution process. Although this technology achieves multi-color electrochromism, the copper-assisted reaction may introduce potential challenges such as by-product accumulation and silver particle agglomeration during long-term circulation, leading to performance degradation. More importantly, the organic electrolyte used in this system limits its further application in terms of health and environmental protection.

[0005] The paper "Dai et al Fast constructing polarity-switchable zinc-bromine microbatteries with high areal energy density Sci. Adv. 8, eabo6688 (2022)" discloses a zinc-bromine microbattery (Zn-Br2MBs) prepared by a double-plating strategy with high areal energy density (3.6 mWh cm -2 ) and polarity switchable properties. Its core is a bromine ion (Br-) and a zinc ion (Zn 2+ ) electrolyte, Br- is oxidized to liquid Br2 cathode during charging, Zn 2+ The ion liquid MPIBr is used as a bromine source to inhibit Br3- diffusion and improve reaction kinetics. This technology, combined with laser-engraved flexible carbon nanotube interdigitated electrodes, enables rapid fabrication. This technology, through a liquid cathode and dual-plating strategy, addresses the complex manufacturing of traditional microbatteries and the difficulty of balancing energy density and power density with solid cathodes. However, the strong corrosiveness of bromine, zinc dendrite growth during long-term cycling, and the stability of bromine byproducts still require further optimization. Summary of the Invention

[0006] The present invention innovatively proposes a metal (Bi-Cu co-deposition composite material) and non-metal (Br - / Br3 - A transparent-black-yellow three-state reversible electrochromic device was successfully constructed by using a coordinated deposition strategy of redox system. Specifically, the black-transparent conversion is caused by the Bi 3+ / Cu 2+ Co-deposition is achieved, while the yellow-transparent transition is achieved by MPI + Complexation-assisted Br - / Br3 - Reversible transition control. Through precise voltage regulation, metal deposition and non-metal redox reactions are independently implemented in the same device, enabling free switching between three color states: transparent, black, and yellow. This multi-color modulation capability provides smart windows with both color-neutral and multi-color modulation modes, significantly enhancing their potential for privacy protection and aesthetic design, and providing new insights for the development of next-generation multifunctional smart optical devices.

[0007] The present invention provides a three-color electrochromic device, comprising: a working electrode, an electrolyte and a counter electrode, wherein the electrolyte is filled between the working electrode and the counter electrode, the working electrode is a transparent conductive glass with a catalyst modified on the surface, the catalyst comprising a carbon material, the counter electrode is a glass with a copper foil frame or a copper grid, and the electrolyte is a water-based electrolyte comprising HCl, BiCl3, CuCl2, LiBr and MPIBr.

[0008] Furthermore, the transparent conductive oxide glass may be FTO conductive glass, ITO conductive glass, etc.

[0009] Furthermore, the present invention modifies transparent conductive glass by catalyst, and regulates the interfacial catalytic activity at the atomic scale. The catalyst modified on the surface of transparent conductive oxide glass is a carbon material, and the carbon material is carbon nanotubes or graphene, preferably carbon nanotubes. First, the abundant edge defects and oxygen-containing functional groups on the surface of the carbon material significantly reduce the Br - The oxidation reaction energy barrier effectively avoids the water decomposition potential window. Secondly, the three-dimensional conductive network of carbon materials promotes rapid charge transfer and improves Br - / Br3 - Conversion efficiency. Finally, the high specific surface area of ​​carbon materials enhances the adsorption of reactants and inhibits the conversion of Br3 - Ion shuttling effect.

[0010] Furthermore, the thickness of the catalyst layer modified on the surface of the transparent conductive oxide glass is 0.1 nm-20 nm, for example, 0.1 nm, 0.5 nm, 1 nm, 5 nm, 10 nm, 15 nm, and 20 nm.

[0011] Furthermore, the catalyst is uniformly attached to the surface of the transparent conductive oxide glass in a layered manner, and the attachment method can be spin coating, blade coating, spray coating, etc.

[0012] Furthermore, the outer diameter of the carbon nanotube is 15-30 nm and the length is less than 50 μm.

[0013] Furthermore, in the electrolyte, the concentration of BiCl3 is 1-5 mmol / L, for example, 1 mmol / L, 2 mmol / L, 3mmol / L, 4 mmol / L, 5 mmol / L, the concentration of CuCl2 is 3-15 mmol / L, for example, 3 mmol / L, 4 mmol / L, 5mmol / L, 6 mmol / L, 7 mmol / L, 8 mmol / L, 9 mmol / L, 10 mmol / L, 11 mmol / L, 12 mmol / L, 13mmol / L, 14 mmol / L, 15 mmol / L, the concentration of LiBr is 0.5-1.5 mol / L, for example, 0.5 mol / L, 1 mol / L, 1.5 mol / L, MPIBr (1-methyl-3-propylimidazolium bromide, cas number 85100-76-1, molecular formula C7H 13 The concentration of BrN2 is 0.5-1 mol / L, for example, 0.5 mol / L and 1 mol / L. The concentration of HCl in the electrolyte is 70-144 mmol / L, for example, 70 mmol / L, 80 mmol / L, 90 mmol / L, 100 mmol / L, 110 mmol / L, 120 mmol / L, 130 mmol / L, and 140 mmol / L. The solvent of the electrolyte is water.

[0014] Furthermore, in the electrolyte, the molar ratio of BiCl3 to CuCl2 is 1:2.5-3.5.

[0015] Furthermore, the electrolyte can also contain PVA (polyvinyl alcohol) to promote uniform metal deposition. The alcoholysis degree of PVA is 87.0-89.0% (mol / mol). The concentration of PVA in the electrolyte is 8-12 wt%.

[0016] Furthermore, when preparing the electrolyte, hydrochloric acid and water are first mixed, and then BiCl 3、CuCl2 and LiBr are stirred until they are completely dissolved, then MPIBr is added and continued stirring to obtain a transparent electrolyte.

[0017] Furthermore, the MPI in the electrolyte + Can be used with Br - Oxidation to generate Br3 - Complexation forms yellow liquid complex MPIBr3, achieving yellow Transparent color switching.

[0018] The present invention also provides a method for preparing the above-mentioned three-color electrochromic device, which comprises the following steps: (1) dispersing the catalyst in a solvent to obtain a dispersion; (2) coating the catalyst-containing dispersion onto the surface of the transparent conductive glass and drying the dispersion to obtain a transparent conductive glass with the catalyst modified on the surface; (3) attaching a copper foil frame or a copper grid to the glass to obtain glass with a copper foil frame or a copper grid frame; (4) A transparent conductive glass with a catalyst modified on its surface is used as the working electrode, and a glass with a copper foil frame or a copper grid frame is used as the counter electrode. The working electrode and the counter electrode are sealed with tape, and then the electrolyte is filled in the middle to obtain a three-color electrochromic device.

[0019] Furthermore, in step (1), the solvent is ethanol. In order to better disperse the catalyst into the solvent, the dispersion can be assisted by ultrasound, stirring, etc.

[0020] Furthermore, in step (1), the concentration of the catalyst in the dispersion is 0.3-0.5 mg / mL.

[0021] Furthermore, in step (2), the catalyst-containing dispersion is applied to the surface of the transparent conductive glass by spin coating, blade coating, spray coating, etc. In order to achieve the required catalyst thickness, the coating can be applied multiple times.

[0022] The present invention has the following beneficial effects: 1. This invention innovatively combines the neutral color state of Bi-Cu metal deposition with the bright yellow color of MPIBr3 through material design and electrolyte optimization strategy, and constructs a metal-nonmetal synergistic electrodeposition system for the first time, successfully achieving a three-color state (yellow transparent The device can reversibly switch between black and white, triggering three distinct color-display mechanisms by simply adjusting the operating voltage. This invention not only demonstrates the feasibility of non-metallic redox systems in electrochromism but also provides a new paradigm for developing high-performance multicolor electrochromic devices through a multi-mechanism synergistic strategy. The ingenious combination of metal and non-metal deposition not only enriches the color performance of electrochromic devices, enhancing their potential for application in smart windows, but also significantly expands their potential in other fields.

[0023] 2. The present invention constructs a carbon material catalyst modification layer on transparent conductive glass, and utilizes the high conductivity and catalytic activity of carbon materials to significantly reduce the reaction activation energy of the Br- / Br3- redox couple. At the same time, voltage regulation is used to achieve the coordinated regulation of the controllable electrodeposition of silver and the redox reaction of non-metallic bromine. Secondly, 1-methyl-3-propylimidazolium cation (MPI) is introduced into the electrolyte. + ), which forms a stable complex [MPIBr3] with Br3-, effectively suppressing the shuttling effect of polybromine ions. This dual-control mechanism enables efficient switching between transparent, black, and yellow states, exhibiting high optical modulation rates of 57.3% and 60.8% respectively, as well as good resting stability. This successfully overcomes the core issues of traditional bromine-based systems, such as uneven deposition and byproduct accumulation caused by sluggish reaction kinetics, and provides a more stable and scalable solution for electrochromic smart windows and displays.

[0024] 3. The present invention adopts environmentally friendly aqueous electrolyte, avoiding the environmental risks of traditional organic systems.

[0025] 4. The working electrode modified with the carbon material catalyst of the present invention converts Br - The oxidation potential was significantly reduced to 2.2 V, breaking through the kinetic bottleneck of the bromine-based system in aqueous electrolytes, and MPI + Complexation strategy effectively inhibits Br3 - diffusion, ensuring the cycling stability of the device.

[0026] 5. In the absence of voltage drive, the modulation rate of the electrochromic device after depositing metal Bi-Cu is almost attenuated after being placed for about 24 hours. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a diagram of the structure and working mechanism of the three-color electrochromic device of the present invention.

[0028] Figure 2 Catalyzing MPI for CNTs + With Br3 - Schematic diagram of the complexation mechanism for generating MPIBr3 on FTO glass.

[0029] Figure 3 For the three color states of the present invention (yellow transparent (Black) Electrochromic device demonstration diagram.

[0030] Figure 4 Transmittance curves of the Bi-Cu reversible metal electrodeposition electrochromic device in the colored (-0.7 V) and faded (0.8 V) states, as well as an illustration of the device display.

[0031] Figure 5 Based on Br − / Br3 − Transmittance curves of the converted non-metal electrodeposited electrochromic device in the colored (2.2 V) and faded (0 V) states, along with an inset diagram of the device.

[0032] Figure 6 Transmittance curve of the non-metal deposition of the three-color electrochromic device of Example 3.

[0033] Figure 7 The transmittance curves of the colored metal deposits with and without PVA in the electrolyte in the cuvette.

[0034] Figure 8 The transmittance curves of the colored state of the electrochromic device with non-metal deposition at various voltages when the working electrode is bare FTO.

[0035] Figure 9 This is the transmittance curve of non-metal deposition of electrochromic device when ZnBr2 is used instead of MPIBr as bromine source.

[0036] Figure 10 The coloring / fading response time of the metal deposition (Bi-Cu) in Example 1.

[0037] Figure 11 The non-metallic deposition of Example 1 (Br - / Br3 - Redox conversion) coloration / fading response time.

[0038] Figure 12 The non-metallic deposition of Example 2 (Br - / Br3 - Redox conversion) coloration / fading response time (MPIBr concentration is 0.5 mol / L).

[0039] Figure 13 The coloring / fading response time of the metal deposition (Bi-Cu) in Example 2 (MPIBr concentration is 0.5 mol / L).

[0040] Figure 14This is a transmittance change curve of the electrochromic device based on metal deposition in Example 1 at 500 nm during 500 coloring / fading cycles.

[0041] Figure 15 This is a transmittance change curve of the electrochromic device based on non-metal deposition in Example 1 at 600 nm during 500 coloring / fading cycles.

[0042] Figure 16 Figure 2 shows the cycling stability of metal deposition at 500 nm in a cuvette (the working electrode is FTO / RuO2 conductive glass).

[0043] Figure 17 Figure 3 shows the cycling stability of non-metal deposition at 600 nm in a cuvette (the working electrode is FTO / RuO2 conductive glass).

[0044] Figure 18 Figure 2 shows the cycling stability of metalloid deposition at 600 nm in a cuvette (MPIBr replaced by MPII in the electrolyte).

[0045] Figure 19 1 is a curve of optical transmittance at 500 nm varying with time of the electrochromic device based on metal deposition in Example 1 in a colored state at rest for 24 h. DETAILED DESCRIPTION

[0046] The following description of exemplary embodiments of the present invention includes various details to facilitate understanding, which should be considered merely exemplary. Therefore, those skilled in the art will recognize that various changes and modifications may be made to the embodiments described herein without departing from the scope and spirit of the present invention. Similarly, for the sake of clarity and conciseness, descriptions of well-known functions, operations, and structures are omitted from the following description.

[0047] Unless otherwise defined, technical and scientific terms used in this specification have the same meanings as commonly understood by those skilled in the art. Although methods and materials similar or equivalent to those described herein can be used in experiments or applications, the present invention describes the materials and methods below. In the event of conflict, the present specification, including definitions, will control.

[0048] In the following examples and comparative examples, the carbon nanotubes used were from Aladdin Company, with an outer diameter of 30-80 nm and a length of less than 10 μm.

[0049] Example 1 The present invention is based on Bi-Cu reversible electrodeposition and Br - / Br3 -The redox conversion three-color electrochromic device consists of a working electrode, an electrolyte and a counter electrode. The electrolyte is filled between the working electrode and the counter electrode. The working electrode is FTO / CNTs, the counter electrode is glass with a copper foil frame, and the electrolyte is a hydrochloric acid solution containing BiCl3, CuCl2, LiBr and MPIBr.

[0050] The method for manufacturing the three-color electrochromic device is as follows: 1. Preparation of FTO / CNTs: The purchased carbon nanotube slurry (0.2 g, alcohol-soluble carbon nanotubes: 10% carbon nanotubes, 2% pvp dispersant, the rest is ethanol, Changzhou Tanbo New Material Technology Co., Ltd.) was dispersed in ethanol (50 mL) and then ultrasonicated for one hour. After that, the dispersion was spin-coated onto a 3 × 3 cm 2 The FTO glass was deposited on the substrate and then dried in a 60 °C oven overnight to obtain a FTO / CNTs composite electrode. The thickness of the CNTs layer was about 10 nm.

[0051] 2. Preparation of electrolyte: Dilute 12 mol / L hydrochloric acid to 70 mmol / L. Then, take 20 mL of 70 mmol / L hydrochloric acid. Add 0.0063 g BiCl₃, 0.008 g CuCl₂, and 1.737 g LiBr to the 20 mL hydrochloric acid solution. Stir thoroughly, then add 4.102 g MPIBr. Continue stirring to obtain a transparent electrolyte.

[0052] 3. Preparation of counter electrode: Take 3×3 cm 2 The bare glass was then placed on a commercially available copper foil frame, which was a hollow square with a size of 3 × 3 cm. 2 The copper foil frame has a width of 2 cm and a thickness of 0.01 cm. The copper foil frame is adhered to the bare glass surface using 3 mm thick transparent double-sided tape to form a counter electrode.

[0053] 4. Assembly of devices: The electrochromic device is assembled as a sandwich structure consisting of a working electrode, electrolyte, and counter electrode, and encapsulated with UV-curable adhesive. The working electrode is FTO / CNTs, and the counter electrode is glass with a copper foil frame. The FTO / CNTs serve as the electrochromic layer, the copper foil serves as the ion storage layer, and the bare glass serves as the encapsulation layer. The working and counter electrodes are bonded together with a non-deformable 3M adhesive layer, and the remaining space is filled with electrolyte using a syringe.

[0054] Example 2 The electrolyte was prepared in the same manner as in Example 1, except that when preparing the electrolyte, “4.102 g MPIBr” was replaced with “2.05 g MPIBr”.

[0055] Example 3 A three-color electrochromic device was assembled according to the method of Example 1, with the following exceptions: To prepare the electrolyte, 12 mol / L hydrochloric acid was diluted to 140 mmol / L. Then, 20 mL of 140 mmol / L hydrochloric acid was added. 0.0063 g of BiCl₃, 0.008 g of CuCl₂, and 1.737 g of LiBr were added to the 20 mL hydrochloric acid solution, stirred until uniform, and then 4.102 g of MPIBr was added. Stirring continued until uniform, resulting in a transparent electrolyte.

[0056] Example 4 A three-color electrochromic device was prepared and assembled according to the method of Example 1, with the following exceptions: To prepare the electrolyte, 12 mol / L hydrochloric acid was diluted to 70 mmol / L. Then, 20 mL of 70 mmol / L hydrochloric acid was added. 0.0063 g of BiCl₃, 0.008 g of CuCl₂, and 1.737 g of LiBr were added to the 20 mL hydrochloric acid solution, stirred evenly, and then 4.102 g of MPIBr was added. After stirring evenly, 2 g of PVA was added and stirred again to obtain a transparent electrolyte.

[0057] Comparative Example 1 A three-color electrochromic device was assembled in the same manner as in Example 1, except that the working electrode was bare FTO conductive glass.

[0058] Comparative Example 2 The three-color electrochromic device was assembled in the same manner as in Example 1, except that the working electrode was FTO / RuO2 conductive glass. RuO2 thin film was deposited on fluorine-doped tin oxide (FTO) glass using DC reactive magnetron sputtering technology. A 3×3 cm 2 The FTO glass was ultrasonically cleaned in acetone, anhydrous ethanol, and deionized water for 15 minutes each. The FTO glass was then placed in a treatment chamber, and UV light and ozone were simultaneously introduced for 10 minutes to reduce interfacial defects. The treated FTO glass was mounted on a support in the sputtering chamber. The distance between the ruthenium target and the support was adjusted to 100 mm. The sputtering atmosphere flow rates were: 10 sccm Ar, 8 sccm O, 3.0 Pa sputtering pressure, 45 W sputtering power, and a sputtering time of 10 minutes, resulting in a RuO2 layer approximately 185 nm thick.

[0059] Comparative Example 3 A three-color electrochromic device was assembled in the manner of Example 1, except that when preparing the electrolyte, MPIBr was replaced with an equal molar amount of MPII (1-methyl-3-propyl imidazolium iodide).

[0060] Comparative Example 4 A three-color electrochromic device was assembled in the same manner as in Example 1, except that MPIBr was replaced with an equimolar amount of ZnBr2 during the preparation of the electrolyte.

[0061] Performance Verification 1. Optical contrast test 1.1 Experimental samples: three-color electrochromic devices prepared in Example 1, Example 3, Example 4, Comparative Example 1, and Comparative Example 4.

[0062] 1.2 Experimental steps: The samples of Example 1, Example 3, and Comparative Example 4 were tested according to the following procedures: Testing was performed using a UV-Vis spectrophotometer (Hitachi UH5700) with a wavelength range of 400-850 nm. For metal deposition, a voltage of -0.7 V was applied to the device for 30 seconds. After the device was completely colored, its transmittance at 400-850 nm was measured. For non-metal deposition, a voltage of 0.8 V was applied to the device for 30 seconds. After the device was completely discolored, its transmittance at 400-850 nm was measured. For non-metal deposition, a voltage of 2.2 V was applied to the device for 30 seconds. After the device was completely colored, its transmittance at 400-850 nm was measured. For non-metal deposition, a voltage of 0 V was applied to the device for 20 seconds. After the device was completely discolored, its transmittance at 400-850 nm was measured.

[0063] The sample from Example 4 was tested according to the following steps: The electrolyte from Example 4 was added to a cuvette. FTO / CNTs and copper foil were then added to the cuvette as the working and counter electrodes, respectively. Testing was performed using a UV-visible spectrophotometer (Hitachi UH5700) set to a wavelength range of 400-850 nm. A voltage of -0.7 V was applied to the electrodes for 30 seconds. After complete coloration, the transmittance at 400-850 nm was measured. An electrolyte without PVA was also used as a control.

[0064] The samples from Comparative Example 1 were tested using a UV-Vis spectrophotometer (Hitachi UH5700) with a wavelength range of 400-850 nm. For non-metal deposition, voltages of 2.4 V, 2.7 V, and 3 V were applied to the device for 30 seconds each. After the device was fully colored, its transmittance was measured in the 400-850 nm range.

[0065] 1.3 Experimental results: The transmittance curve of the three-color electrochromic device prepared in Example 1 is Figure 4 and Figure 5 ,in Figure 4 is the transmittance curve of metal deposition, Figure 5 is the transmittance curve of non-metal deposition. Figure 4 It can be seen that the optical modulation rate of the device is the largest at 500 nm, the transmittance of the faded state at 500 nm is 77.3%, the transmittance of the colored state is 20.0%, and the modulation rate at 500 nm is 57.3%. Figure 5 As can be seen in the figure, the device has the highest optical modulation rate at 600 nm, with a bleached state transmittance of 81.2% and a tinted state transmittance of 20.4% at 600 nm, resulting in a modulation rate of 60.8% at 600 nm. This multi-color modulation capability provides smart windows with both color-neutral and multi-color modulation modes, significantly enhancing their potential for privacy protection and aesthetic design, and providing new ideas for the development of next-generation multifunctional smart optical devices.

[0066] The concentration of hydrochloric acid was increased in the electrolyte of the electrochromic device of Example 3. The transmittance of the non-metallic deposit of the device in the colored and faded states was as follows: Figure 6 As shown in Figure 3, the modulation rate at 600 nm wavelength is as high as 33.4%.

[0067] 2 g PVA was added to the electrolyte of the electrochromic device of Example 4 to promote uniform metal deposition. The transmittance of metal deposited in the colored state with and without PVA in the electrolyte is shown in the figure. Figure 7 As shown, it can be seen that after adding PVA, the transmittance of metal deposition decreases slightly.

[0068] The electrochromic device of Comparative Example 1 uses bare FTO glass (not modified with CNTs) as the working electrode. The transmittance of the electrochromic device with non-metal deposition in the colored state is as follows: Figure 8 As shown in the figure, it can be seen that due to the lack of active sites, Br - The oxidation potential is very high. When coloring voltages of 2.4 V and 2.7 V are applied to the device, the transmittance changes very little. Specifically, when a coloring voltage of 2.4 V is applied, the transmittance at a wavelength of 400 nm decreases by only 3.1%. When the voltage is increased to 2.7 V, the transmittance at 400 nm decreases by only 13.4%. It is not until the voltage is applied to 3 V that a significant change in transmittance and color is observed, with the transmittance at 400 nm decreasing by 51.0%. However, this voltage exceeds the voltage required for water decomposition, causing the device to generate a large number of bubbles, which in turn affects its performance.

[0069] The electrochromic device of Comparative Example 4 replaces the MPIBr in the electrolyte with ZnBr2. The transmittance of the electrochromic device with non-metal deposits in the colored and faded states is as follows: Figure 9 As shown in the figure, it can be seen that the device has obvious transmittance changes at a wavelength of 400 nm. In the rest of the wavelength range, the transmittance changes very little, which indicates that compared with ZnBr2, MPIBr has a wider wavelength modulation range.

[0070] 2. Optical contrast and response time test 2.1 Experimental sample: the three-color electrochromic device prepared in Example 1 and Example 2.

[0071] 2.2 Experimental steps: Using a UV-visible spectrophotometer (Hitachi UH5700), the response time of the device in the faded state (0 V, 0.8 V) and the colored state (2.2 V, -0.7 V) was measured at a wavelength of 600 nm. The response time is the time required for the device transmittance to reach the maximum modulation rate of 90%.

[0072] The sample from Example 1 was tested according to the following steps: The three-color electrochromic device from Example 1 was directly tested using a UV-visible spectrophotometer. Metal deposition: coloring voltage -0.7 V (15 s) → fading voltage 0.8 V (20 s), wavelength 500 nm. Non-metal deposition: coloring voltage 2.2 V (12 s) → fading voltage 0 V (15 s), wavelength 600 nm.

[0073] The sample from Example 2 was tested according to the following steps: The electrolyte from Example 2 was added to a cuvette, followed by the FTO / CNTs and copper foil as the working and counter electrodes, respectively. Testing was performed using a UV-Vis spectrophotometer (Hitachi UH5700) with the following parameters: Metal deposition: coloring voltage -0.7 V (15 s) → fading voltage 0.8 V (20 s), wavelength 500 nm. Non-metal deposition: coloring voltage 2.2 V (12 s) → fading voltage 0 V (15 s), wavelength 600 nm.

[0074] 2.3 Experimental results: The response time curves of the device coloring and fading in Example 1 are as follows: Figure 10 、 11 As shown, Figure 10 is the coloring and fading time of the metal deposition device, the coloring time is 7.5 s, the fading time is 4.5 s, Figure 11 The coloring and fading time of the non-metal deposition device is 7 s and the fading time is 3.7 s. Both have a fast response time.

[0075] In the electrolyte of Example 2, the concentration of MPIBr was reduced from 1 mol / L to 0.5 mol / L. The response time curves of coloration and fading were as follows: Figure 12 、 13 shown. Figure 12 is the coloring and fading time of non-metallic deposition, the coloring time is 10 s, the fading time is 11 s, Figure 13 is the coloring and fading time of metal deposition, the coloring time is 16 s and the fading time is 5 s.

[0076] 3. Cyclic stability test 3.1 Experimental samples: three-color electrochromic devices prepared in Example 1, Comparative Example 2, and Comparative Example 3.

[0077] 3.2 Experimental steps: The sample of Example 1 was tested according to the following steps: The three-color electrochromic device of Example 1 was directly tested using a UV-visible spectrophotometer with the following parameters: Metal deposition: coloring voltage -0.7 V (15 s) → fading voltage 0.8 V (20 s), wavelength 500 nm. Non-metal deposition: coloring voltage 2.2 V (12 s) → fading voltage 0 V (15 s), wavelength 600 nm.

[0078] The sample from Comparative Example 2 was tested according to the following steps: The electrolyte from Example 1 was added to a cuvette, followed by the FTO / RuO2 conductive glass and copper foil prepared in Comparative Example 2 as the working and counter electrodes, respectively. Testing was performed using a UV-Vis spectrophotometer (Hitachi UH5700) with the following parameters: Metal deposition: coloring voltage -0.7 V (15 s) → fading voltage 0.8 V (20 s), wavelength 500 nm. Non-metal deposition: coloring voltage 2.2 V (12 s) → fading voltage 0 V (15 s), wavelength 600 nm.

[0079] The sample from Comparative Example 3 was tested according to the following steps: The electrolyte from Comparative Example 3 (MPII replaced with MPIBr) was added to a cuvette. FTO and copper foil were then added as the working and counter electrodes, respectively. Testing was performed using a UV-Vis spectrophotometer (Hitachi UH5700) using the following parameters: coloring voltage 1.5 V (5 s) → fading voltage -0.4 V (25 s), wavelength 600 nm.

[0080] 3.2.2 The transmittance of each device after each cycle was automatically recorded using an electrochemical workstation (Chenhua Chi660E).

[0081] 3.3 Data processing: Optical modulation retention rate after device cycling = optical modulation rate after cycling n times / initial optical modulation rate * 100%.

[0082] 3.4 Experimental results: The transmittance change of the electrochromic device prepared in Example 1 during 500 coloring / fading cycles is as follows: Figure 14 、 15 As shown, Figure 14 For metal deposition, Figure 15 As can be seen from the figure, after 500 cycles of coloring / fading, the retention rate of the metal deposition device is 85.0%, and the retention rate of the non-metal deposition device is 100%.

[0083] The working electrode in Comparative Example 2 is FTO / RuO2 conductive glass. Figure 16 、 17 These are the cyclic stability diagrams of metal deposition and non-metal deposition, respectively. It can be seen from the figure that the cyclic stability of metal deposition and non-metal deposition is not very ideal, which may be related to the strong catalytic effect of RuO2. The strong catalytic effect will cause bubbles to form in the working electrode during the cycle, thus affecting the stability.

[0084] In the electrolyte of Comparative Example 3, MPII was used to replace MPIBr. Figure 18 The transmittance variation of a non-metallic deposition at 600 nm after a 6000-second coloring / fading cycle. As can be seen from the figure, the transmittance of the colored state increases over time, indicating poor cyclic stability.

[0085] 4. Resting stability test 4.1 Experimental sample: the electrochromic device prepared in Example 1.

[0086] 4.2 Experimental steps: 4.2.1 Setting conditions: After coloring voltage -0.7 V (120 s), monitor at a wavelength of 500 nm for 24 h.

[0087] 4.2.2 The electrochemical workstation (Chenhua Chi660E) was used for staining at -0.7 V for 120 s, and then a UV-visible spectrophotometer (Hitachi UH5700) was used for 24 h monitoring.

[0088] 4.3 Data Processing: Electrochromic resting stability refers to the ability of an electrochromic device to maintain its color and optical properties unchanged when it is not in operation (resting state).

[0089] 4.4 Experimental results: Figure 19As shown, after standing for 24 hours, the transmittance of the electrochromic device prepared in Example 1 only increased from the original 0.25% to 1.53%, indicating that it has excellent color memory ability and privacy protection application prospects.

Claims

1. A three-color electrochromic device, characterized by: The invention comprises a working electrode, an electrolyte and a counter electrode, wherein the electrolyte is filled between the working electrode and the counter electrode. The working electrode is a transparent conductive glass with a surface modified with a catalyst, wherein the catalyst comprises a carbon material. The counter electrode is a glass with a copper foil frame or a copper grid. The electrolyte is a water-based electrolyte containing HCl, BiCl3, CuCl2, LiBr and MPIBr.

2. The three-color electrochromic device according to claim 1, wherein: The carbon material includes carbon nanotubes or graphene.

3. The three-color electrochromic device according to claim 1 or 2, characterized in that: The thickness of the catalyst layer is 0.1 nm-20 nm.

4. The three-color electrochromic device according to claim 1, wherein the concentration of BiCl3 in the electrolyte is 1-5 mmol / L, the concentration of CuCl2 is 3-15 mmol / L, the concentration of LiBr is 0.5-1.5 mol / L, the concentration of MPIBr is 0.5-1 mol / L, and the concentration of HCl is 70-144 mmol / L.

5. The three-color electrochromic device according to claim 1 or 4, characterized in that the molar ratio of BiCl3 to CuCl2 in the electrolyte is 1:2.5-3.

5.

6. The three-color electrochromic device according to claim 1 or 4, characterized in that: The electrolyte further contains PVA; preferably, the alcoholysis degree of the PVA is 87.0-89.0 mol%; preferably, the concentration of the PVA in the electrolyte is 8-12 wt%.

7. The three-color electrochromic device according to claim 1, wherein: The transparent conductive oxide glass is FTO conductive glass or ITO conductive glass.

8. A method for preparing a three-color electrochromic device according to any one of claims 1 to 7, characterized in that The following steps are involved: (1) dispersing the catalyst in a solvent to obtain a dispersion; (2) coating the catalyst-containing dispersion onto the surface of the transparent conductive glass and drying the dispersion to obtain a transparent conductive glass with the catalyst modified on the surface; (3) attaching a copper foil frame or a copper grid to the glass to obtain glass with a copper foil frame or a copper grid frame; (4) A transparent conductive glass with a catalyst modified on its surface is used as the working electrode, and a glass with a copper foil frame or a copper grid frame is used as the counter electrode. The working electrode and the counter electrode are sealed with tape, and then the electrolyte is filled in the middle to obtain a three-color electrochromic device.

9. The preparation method according to claim 8, characterized in that: The solvent is ethanol.

10. The preparation method according to claim 8, characterized in that: The concentration of the catalyst in the dispersion was 0.3-0.5 mg / mL.

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