Electrochromic Device Based on Poly(N,N'-dimethylacrylamide) Gel Polymer Electrolyte and Its Fabrication Method

Abstract

This invention relates to the field of electrochromic materials technology, specifically a low-cost, high-performance electrochromic device. The invention provides an electrochromic device based on a poly(N,N'-dimethylacrylamide) gel polymer electrolyte, electrodeposited Prussian blue, and electrodeposited tungsten oxide, along with its preparation method. This results in a simple, inexpensive, and highly transparent gel electrolyte. When this gel electrolyte is assembled with electrodeposited Prussian blue and electrodeposited tungsten oxide to form an electrochromic device, a device with a large light modulation amplitude and fast response time can be obtained. By adjusting experimental parameters, the controllable preparation of a poly(N,N'-dimethylacrylamide) gel polymer electrolyte with high ionic conductivity and high transmittance can be achieved.

Description

Technical Field

[0001] This invention relates to the field of electrochromic materials technology, and to a low-cost, high-performance electrochromic device, particularly to an electrochromic device based on poly(N,N'-dimethylacrylamide) gel polymer electrolyte and its preparation method. Background Technology

[0002] Since the beginning of the 21st century, the strategic goal of energy conservation and emission reduction has gradually entered the public eye, seeking a balance between social and environmental benefits. Building heating, ventilation, and air conditioning account for 30-40% of global primary energy consumption and approximately 15% of carbon dioxide emissions; therefore, energy-efficient buildings are crucial for achieving carbon neutrality. Changing the optical and thermal properties of windows can reduce building energy consumption by up to 40%. Therefore, it is essential to develop technologies to dynamically adjust window transmittance to reduce building energy consumption. Smart windows are energy-efficient windows that regulate solar radiation by combining dimming materials with substrates such as glass. Electrochromic smart windows are a promising solution to this challenge because they undergo optical changes in response to applied external voltage. Dynamically controlling the ability of windows to transmit sunlight can reduce energy consumption and lighting costs in commercial buildings by 20%. Electrochromic technology is used to manufacture smart windows that can dynamically control the building's solar heat and lighting input, responding positively to changes in indoor temperature and light.

[0003] Electrochromism refers to the phenomenon where the optical properties of a material change reversibly when an electric field is applied. The electrolyte, as a crucial component of electrochromic devices, facilitates ion transport between the two electrodes while preventing direct contact. The main structure of an electrochromic device consists of a transparent conductive layer, an electrochromic layer, an electrolyte layer, and a complementary counter electrode layer or ion storage layer. In 2022, Gao Yanfeng's research group constructed a novel electrochromic energy storage dual-function device using tungsten oxide as the positive electrode and zinc metal as the negative electrode. This device not only exhibits high-efficiency electrochromic performance but also possesses energy storage capabilities (Cell Rep Phys Sci, 2022, 3 (11): 101148). However, the poor matching degree between the electrochromic film and the electrolyte layer results in low cycle stability of the electrochromic device, maintaining only 80% of its initial value after 9200 cycles. Furthermore, the slow response time limits the practical application of the device. In 2023, Liu Jian's research group developed a novel hydrogel electrolyte based on hydroxypropyl methylcellulose-modified polyacrylamide. Electrochromic devices based on this electrolyte exhibited high performance (Eur Polym J, 2023, 186, 111856). They fabricated an electrochromic device using Prussian blue and tungsten oxide as complementary electrodes, which maintained 85.8% of its initial light modulation amplitude after 1000 cycles. Simultaneously, as an energy storage device, the device's surface capacitance retained 76.3% of its original value after 1000 charge-discharge cycles. However, due to the incompatibility between the electrolyte layer and the device, the cyclic stability of the electrochromic device was not high, limiting its application in fields such as electrochromic smart windows and display devices.

[0004] Currently, gel electrolytes used in the field of electrochromic devices are typically prepared by adding plasticizers (such as polymethyl methacrylate) to traditional liquid electrolytes (propylene acrylate and lithium perchlorate). The prepared electrolytes have low ionic conductivity, and the devices exhibit poor cycle stability, making it difficult to meet practical application requirements. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, this invention provides a low-cost, high-performance electrochromic device, its preparation method, and its applications. A poly(N,N'-dimethylacrylamide) gel polymer electrolyte is used, and an electrochromic device is prepared based on this electrolyte. The electrochromic device prepared by this invention not only significantly improves cycle life but also features fast response time and large light modulation amplitude.

[0006] The first aspect of this invention discloses an electrochromic device, comprising the preparation of a poly(N,N'-dimethylacrylamide) gel polymer electrolyte and an electrochromic material by in-situ polymerization.

[0007] The electrochromic material is electrodeposited Prussian blue and / or electrodeposited tungsten oxide.

[0008] The second aspect of this invention discloses a method for preparing the electrochromic device, characterized by comprising the following steps:

[0009] S1: Mix and dissolve N,N-methylenebisacrylamide, potassium persulfate, N,N'-dimethylacrylamide, potassium chloride and deionized water to obtain a reaction precursor solution;

[0010] S2: Electrodeposition preparation of Prussian blue thin film: In a three-electrode system, potassium ferricyanide, ferric chloride and potassium chloride of a set concentration are used as electrolytes, FTO transparent conductive glass is used as working electrode, platinum sheet is used as counter electrode, and Ag / AgCl electrode is used as reference electrode. Prussian blue thin film is prepared by constant current electrodeposition method to obtain FTO glass with Prussian blue thin film.

[0011] S3: Electrodeposition preparation of tungsten oxide thin film: In a three-electrode system, sodium tungstate dihydrate, nitric acid, and hydrogen peroxide of a set concentration were used as electrolytes, transparent conductive substrate FTO glass was used as working electrode, platinum sheet was used as counter electrode, and Ag / AgCl electrode was used as reference electrode. FTO glass with tungsten oxide thin film was prepared by constant voltage electrodeposition method.

[0012] S4: The FTO glass of the Prussian blue thin film prepared in S2 is bonded together with the FTO glass of the tungsten oxide thin film prepared in S3 to obtain the Prussian blue / tungsten oxide electrochromic device.

[0013] S5: The reaction precursor solution obtained in S1 is injected into the gap of the Prussian blue / tungsten oxide electrochromic device described in S4, and a polymerization reaction is carried out at a set temperature. After the reaction is completed, it is naturally cooled to room temperature to obtain a Prussian blue / tungsten oxide electrochromic device containing in-situ polymerized poly(N,N'-dimethylacrylamide) gel polymer electrolyte.

[0014] Preferably, the concentration of the monomer N,N'-dimethylacrylamide in the S1 reaction precursor solution is 16.7-44.5%.

[0015] Preferably, in the S1 reaction precursor solution, the crosslinking agent N,N'-methylenebisacrylamide and the initiator potassium persulfate content are 0.1% and 0.5% of the mass of N,N'-methylenebisacrylamide, respectively.

[0016] In S2, the concentration ratio of potassium ferricyanide, ferric chloride, and potassium chloride is 1:1:5; the constant current electrodeposition method described in S2 specifically involves an electrodeposition process at -40 to -60 μA / cm². -2 Electrodeposition was performed at a constant current density for 150-250 s.

[0017] The concentration of sodium tungstate dihydrate in S3 is 50 mmol·L⁻¹. -1The hydrogen peroxide solution is 0.6 mL, and the pH of the solution is adjusted to 1.2 with nitric acid. The constant current electrodeposition method described in S3 is specifically electrodeposition at a constant voltage of -0.6 to -0.8 V for 350-450 s.

[0018] The polymerization reaction described in S5 is carried out at a temperature of 60–80 °C for 1–4 h.

[0019] The above-mentioned poly(N,N'-dimethylacrylamide) gel polymer electrolyte is used in electrochromic devices.

[0020] A third aspect of this invention discloses the application of the aforementioned salt-free polyacrylic acid gel electrolyte in electrochromic devices. These electrochromic devices include those used in smart glass, displays, and other fields.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] (1) This invention provides an electrochromic device based on poly(N,N'-dimethylacrylamide) gel polymer electrolyte, electrodeposited Prussian blue, and electrodeposited tungsten oxide, and a method for preparing the same, forming a simple, inexpensive, and highly transparent gel electrolyte. When this gel electrolyte is assembled with electrodeposited Prussian blue and electrodeposited tungsten oxide to form an electrochromic device, an electrochromic device with a large light modulation amplitude and fast response time can be obtained. By adjusting experimental parameters, the controllable preparation of poly(N,N'-dimethylacrylamide) gel polymer electrolyte with high ionic conductivity and high transmittance can be achieved.

[0023] (2) The preparation method of the present invention controls the monomer concentration, and the prepared poly(N,N'-dimethylacrylamide) gel has good ionic conductivity and high transmittance; the prepared poly(N,N'-dimethylacrylamide) gel polymer electrolyte has good stability, and the in-situ polymerization method has high compatibility with the Prussian blue / tungsten oxide electrochromic device; the prepared Prussian blue / tungsten oxide electrochromic device containing poly(N,N'-dimethylacrylamide) gel polymer electrolyte has a fast response speed; at the same time, the gel preparation process is simple, the raw materials are inexpensive and easy to obtain, the cost is low, the requirements for the experimental environment are low, and it is harmless to the human body. Attached Figure Description

[0024] Figure 1 The images shown are scanning electron microscope images and energy dispersive spectra of the poly(N,N'-dimethylacrylamide) gel polymer electrolyte in Example 1 of this invention.

[0025] Figure 2 The image shows the permeability curve of the poly(N,N'-dimethylacrylamide) gel polymer electrolyte in Example 1 of this invention.

[0026] Figure 3The Fourier transform infrared spectrum of the poly(N,N'-dimethylacrylamide) gel polymer electrolyte in Example 1 of this invention is shown.

[0027] Figure 4 The cyclic voltammetry curves are for the Prussian blue / tungsten oxide electrochromic device of the poly(N,N'-dimethylacrylamide) gel polymer electrolyte in Example 1 of this invention.

[0028] Figure 5 The images show the effects of the Prussian blue / tungsten oxide electrochromic device of the poly(N,N'-dimethylacrylamide) gel polymer electrolyte in Example 1 of this invention in the faded state (a) and colored state (b).

[0029] Figure 6 The transmittance curve of the Prussian blue / tungsten oxide electrochromic device of the poly(N,N'-dimethylacrylamide) gel polymer electrolyte in Example 1 of the present invention is shown.

[0030] Figure 7 The image shows the response time curve of the Prussian blue / tungsten oxide electrochromic device using poly(N,N'-dimethylacrylamide) gel polymer electrolyte in Example 1 of this invention.

[0031] Figure 8 The transmittance curves of the Prussian blue / tungsten oxide electrochromic device of the poly(N,N'-dimethylacrylamide) gel polymer electrolyte in Example 1 of this invention are the transmittance curves of the device after 1-30,000 cycles of cycle stability testing. Detailed Implementation

[0032] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.

[0033] Example 1

[0034] (1) In a three-electrode system, at 10 mmol·L -1 Potassium ferricyanide, 10 mmol·L -1 Ferric chloride, 50 mmol·L -1 Potassium chloride was used as the electrolyte; FTO glass was used as the working electrode, a platinum sheet as the counter electrode, and an Ag / AgCl electrode as the reference electrode; a constant current electrodeposition method was used at -50 μA / cm². -2 FTO glass with a Prussian blue film was obtained by electrodeposition at a constant current density for 200 s.

[0035] (2) In the three-electrode system, at 50 mmol·L -1Sodium tungstate dihydrate, 0.6 mL hydrogen peroxide, and nitric acid were used to adjust the pH of the solution to 1.2 to obtain the electrolyte for tungsten oxide electrodeposition. Using a transparent conductive substrate FTO glass as the working electrode, a platinum sheet as the counter electrode, and an Ag / AgCl electrode as the reference electrode, a constant voltage electrodeposition method was employed to electrodeposit FTO glass with a tungsten oxide film at a constant voltage of -0.7 V for 400 s. This was then double-sided bonded with the FTO glass with a Prussian blue film obtained in (1) to obtain a Prussian blue / tungsten oxide electrochromic device.

[0036] (3) 1 mol·L -1 Potassium chloride was dissolved in 10 mL of deionized water. After complete dissolution, 3 g of N,N'-dimethylacrylamide monomer, 3 mg of crosslinking agent N,N'-methylenebisacrylamide (0.1 wt% of N,N'-dimethylacrylamide monomer), and 15 mg of initiator potassium persulfate (0.5 wt% of N,N'-dimethylacrylamide monomer) were added sequentially. The volume was adjusted to 20 mL, and the solution was magnetically stirred for 0.5 h until it was completely dissolved into a transparent solution. Then, the solution was sonicated for 10 min to remove dissolved oxygen.

[0037] (4) The precursor solution of (3) is injected into the cavity of the double-sided adhesive Prussian blue / tungsten oxide electrochromic device obtained in (2), and then placed in an oven at 60 °C for 2 h to polymerize. After natural cooling to room temperature, the Prussian blue / tungsten oxide electrochromic device containing poly(N,N'-dimethylacrylamide) gel polymer electrolyte with the performance to be tested is obtained.

[0038] Scanning electron microscope images of the poly(N,N'-dimethylacrylamide) gel polymer electrolyte prepared in this embodiment are shown below. Figure 1 As shown, N,N'-dimethylacrylamide has good water solubility and gelation ability, and can form a three-dimensional network structure in water. The freeze-dried hydrogel has a micron-pore structure; the free movement of ions is relatively easy, making it suitable for fields such as electrochromic electrolytes. Figure 2 The transmittance curve of the poly(N,N'-dimethylacrylamide) gel polymer electrolyte prepared in this embodiment is shown. The scanning cyclic voltammetry (CV) curve of the Prussian blue / tungsten oxide electrochromic device containing the poly(N,N'-dimethylacrylamide) gel polymer electrolyte obtained in this embodiment is shown below. Figure 4 As shown, 1.1 V was selected as the coloring voltage and -2.4 V as the fading voltage. The electrochemical workstation was coupled with a UV-Vis spectrophotometer to conduct tests in the wavelength range of 300~1100 nm. The transmittance reached the maximum light modulation amplitude at a wavelength of 658 nm. The response time curve of the electrochromic device transitioning once every 30 s between 1.1 V and -2.4 V was obtained. All data were measured at 658 nm. Figure 5The images show the color changes (a) and fading (b) of the Prussian blue / tungsten oxide electrochromic device containing poly(N,N'-dimethylacrylamide) gel polymer electrolyte prepared in this embodiment. Figure 6 The transmittance curves are for a Prussian blue / tungsten oxide electrochromic device containing a poly(N,N'-dimethylacrylamide) gel polymer electrolyte. The light modulation amplitude at 658 nm in the colored and faded states is approximately 74.0%. Figure 7 The response time curve shows that the device rapidly turns blue at 1.1 V and changes colorless when a positive voltage of -2.4 V is applied. Calculations show that the coloring time of the Prussian blue / tungsten oxide electrochromic device containing poly(N,N'-dimethylacrylamide) gel polymer electrolyte is approximately 2.2 s, and the fading time is approximately 3.0 s when the light modulation amplitude change reaches 90%. Figure 8 The transmittance curve of the Prussian blue / tungsten oxide electrochromic device containing poly(N,N'-dimethylacrylamide) gel polymer electrolyte after 30,000 cycles is shown, with the light modulation amplitude retention rate remaining at 97.4% of the initial value.

[0039] Comparative Example 1

[0040] In contrast, a comparative example is set up here, in which a polyaniline-Prussian blue / tungsten oxide electrochromic device is constructed with a composite film of polyaniline and Prussian blue as the electrochromic layer, tungsten oxide as the complementary counter electrode layer, and in-situ polymerized polyacrylamide gel as the electrolyte layer.

[0041] (1) In a three-electrode system, 0.5 mol·L -1 Aniline monomer, 0.5 mol·L -1 Sulfuric acid was used as the electrolyte; FTO glass was used as the working electrode, a platinum sheet as the counter electrode, and an Ag / AgCl electrode as the reference electrode; a constant current electrodeposition method was used at 100 μA·cm⁻¹. -2 FTO glass with a polyaniline film was obtained by electrodeposition at a constant current density for 300 s; at 10 mmol·L⁻¹ -1 Potassium ferricyanide, 10 mmol·L -1 Ferric chloride, 50 mmol·L -1 Potassium chloride was used as the electrolyte; FTO glass with polyaniline was used as the working electrode, a platinum sheet as the counter electrode, and an Ag / AgCl electrode as the reference electrode; a constant current electrodeposition method was used at -50 μAcm. -2 FTO glass with a polyaniline / Prussian blue composite film was obtained by electrodeposition at a constant current density for 80 s.

[0042] (2) In the three-electrode system, at 50 mmol·L -1Sodium tungstate dihydrate, 0.6 mL hydrogen peroxide, and 1.65 mL concentrated nitric acid were used to obtain the electrolyte for tungsten oxide electrodeposition. Using a transparent conductive FTO glass substrate as the working electrode, a platinum sheet as the counter electrode, and an Ag / AgCl electrode as the reference electrode, a constant voltage electrodeposition method was employed to electrodeposit FTO glass with a tungsten oxide film at a constant voltage of -0.7 V for 400 s. This was then double-sided bonded with the FTO glass with a polyaniline-Prussian blue composite film obtained in (1) to obtain a polyaniline / Prussian blue / tungsten oxide electrochromic device.

[0043] (3) 1 mol·L -1 Potassium chloride was dissolved in 20 mL of deionized water. After complete dissolution, 2 g of acrylamide monomer, 2 mg of crosslinking agent N,N'-methylenebisacrylamide (0.1 wt% of acrylamide monomer mass), and 10 mg of initiator potassium persulfate (0.5 wt% of acrylamide monomer mass) were added sequentially. The mixture was magnetically stirred for 0.5 h until it was completely dissolved into a transparent solution. Then, the solution was sonicated for 10 min to remove dissolved oxygen.

[0044] (4) Inject the precursor solution of (3) into the cavity of the polyaniline-Prussian blue / tungsten oxide electrochromic device with double-sided adhesive obtained in (2), place it in an oven at 60 °C for 2 h to polymerize, and then cool it naturally to room temperature to obtain the polyaniline / Prussian blue / tungsten oxide electrochromic device containing polyacrylamide gel polymer electrolyte with the performance to be tested.

[0045] The polyaniline / Prussian blue / tungsten oxide electrochromic device prepared in this comparative example achieved a maximum optical modulation amplitude of 69.4% at 677 nm under applied voltages of -2.5 V and 1 V, with a coloring time of 1.6 s and a fading time of 1.5 s. Meanwhile, the optical modulation amplitude remained at 88.9% of its initial value after 700 cycles.

[0046] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing an electrochromic device based on a poly(N,N'-dimethylacrylamide) gel polymer electrolyte, characterized in that, This includes the in-situ polymerization method for preparing poly(N,N'-dimethylacrylamide) gel polymer electrolytes and electrochromic materials; The electrochromic material is electrodeposited Prussian blue and / or electrodeposited tungsten oxide; The preparation method includes the following steps: S1: Mix and dissolve N,N-methylenebisacrylamide, potassium persulfate, N,N'-dimethylacrylamide, potassium chloride and deionized water to obtain a reaction precursor solution; S2: Electrodeposition preparation of Prussian blue thin film: In a three-electrode system, potassium ferricyanide, ferric chloride and potassium chloride of a set concentration were used as electrolytes, fluorine-doped tin oxide (FTO) transparent conductive glass was used as working electrode, platinum sheet was used as counter electrode, and Ag / AgCl electrode was used as reference electrode. Prussian blue thin film was prepared by constant current electrodeposition method to obtain FTO glass with Prussian blue thin film; S3: Electrodeposition preparation of tungsten oxide thin film: In a three-electrode system, sodium tungstate dihydrate, nitric acid, and hydrogen peroxide of a set concentration were used as electrolytes, transparent conductive substrate FTO glass was used as working electrode, platinum sheet was used as counter electrode, and Ag / AgCl electrode was used as reference electrode. FTO glass with tungsten oxide thin film was prepared by constant voltage electrodeposition method. S4: The FTO glass of the Prussian blue thin film prepared in S2 is bonded together with the FTO glass of the tungsten oxide thin film prepared in S3 to obtain the Prussian blue / tungsten oxide electrochromic device. S5: The reaction precursor solution obtained in S1 is injected into the gap of the Prussian blue / tungsten oxide electrochromic device described in S4, and a polymerization reaction is carried out at a set temperature. After the reaction is completed, it is naturally cooled to room temperature to obtain a Prussian blue / tungsten oxide electrochromic device containing in-situ polymerized poly(N,N'-dimethylacrylamide) gel polymer electrolyte. In the S1 reaction precursor solution, the concentration of the monomer N,N'-dimethylacrylamide is 16.7-44.5%.

2. The preparation method according to claim 1, characterized in that, In the S1 reaction precursor solution, the crosslinking agent N,N'-methylenebisacrylamide and the initiator potassium persulfate contain 0.1% and 0.5% of the mass of N,N'-methylenebisacrylamide, respectively.

3. The preparation method according to claim 1, characterized in that, The concentration ratio of potassium ferricyanide, ferric chloride and potassium chloride in S2 is 1:1:5; the constant current electrodeposition method in S2 is specifically -40 to -60 μAcm -2 Electrodeposition for 150-250 s under constant current density.

4. The preparation method according to claim 1, characterized in that, S3 sodium tungstate dihydrate concentration was 50 mmol·L -1 , hydrogen peroxide was 0.6 mL, the solution pH was adjusted to 1.2 with nitric acid, and the constant current electrodeposition method in S3 was specifically electrodeposition at a constant voltage of-0.6 to-0.8 V for 350-450 s.

5. The preparation method according to claim 1, characterized in that, The polymerization reaction described in S5 is carried out at a temperature of 60–80 °C for 1–4 h.

6. An electrochromic device, characterized in that, It is prepared by the preparation method according to any one of claims 1-5.

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