Integrated electrochromic material and application thereof in electrochromic device

Abstract

The invention belongs to the technical field of functional materials, and particularly relates to an integrated electrochromic material and application thereof in an electrochromic device. The integrated electrochromic material comprises an active substance A with an electrochromic function, an electrochemical active substance B with a charge supplementing function, an adsorbate C and an ion exchange substance D with an ion selective exchange function. The integrated electrochromic material disclosed by the invention is safe and non-toxic, can maintain a charge separation state of an electrochromic device for a long time and stabilize a high-energy color state, has excellent bistable characteristics and an energy-saving effect, has color memorability superior to that of a viologen type organic small molecule electrochromic material, and has a good application prospect. The cycling stability is far better than that of crystal and polymer electrochromic materials, and the preparation difficulty and cost of the device can be remarkably reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of functional materials, and in particular relates to an integrated electrochromic material and its application in an electrochromic device. Background Art

[0002] Electrochromic technology has broad application prospects in the fields of intelligent dimming, energy-saving display and anti-glare. However, traditional electrochromic devices are usually composed of multiple independent functional units, such as electrolyte layers, ion storage layers and color-changing layers. This layered design is conducive to maintaining the charge separation state of the electrochromic device and giving the device good color memory. However, this design not only increases the structural complexity and manufacturing cost of the device, but is also prone to poor interface contact, affecting the device's response speed, color change uniformity and service life. In addition, the crystal or polymer electrochromic materials used in traditional electrochromic devices are prone to volume changes and structural damage during the color change process, resulting in attenuation of the color change performance, thereby reducing the cyclic stability of the device.

[0003] Viologen-based small-molecule electrochromic materials are dispersed in the electrolyte as molecules or ions. The color change process does not involve volume change or stress strain, resulting in cyclic stability far superior to crystalline and polymer-based electrochromic materials. However, after changing color, small-molecule electrochromic materials form oxidized and reduced species at the two electrodes, respectively. These species can freely migrate in the electrolyte and continuously recombine and quench. This causes the high-energy color state of small-molecule electrochromic devices to quickly fade under open-circuit conditions, resulting in poor color memory. Therefore, in actual use, small-molecule electrochromic devices require continuous energy consumption to resist the recombination quenching of oxidized and reduced species and maintain a stable charge-separated state. In other words, small-molecule electrochromic devices generally lack color bistability and require continuous energy consumption to maintain their high-energy color state. This characteristic significantly increases the device's operating energy consumption, significantly limiting its energy-saving potential and application scenarios. Furthermore, viologens are highly biotoxic, further restricting the application scope of these devices. Therefore, there is an urgent need to develop low-cost electrochromic materials with excellent cycling stability and bistability. Summary of the Invention

[0004] In response to the problems in the prior art, the present invention provides an integrated electrochromic material and its application in an electrochromic device.

[0005] In order to achieve the above objectives, the specific technical solutions are as follows: The present invention provides an integrated electrochromic material, comprising an active substance A having an electrochromic function, an electrochemically active substance B having a charge supplementing function, an adsorbent C, and an ion exchange substance D having an ion selective exchange function.

[0006] The active material A and electrochemically active material B undergo different valence changes when changing color, i.e., one material increases in valence to an oxidized state, while the other decreases in valence to a reduced state. Optionally, the active material A and electrochemically active material B are selected from one or more soluble salts, iodine compounds, or bromine compounds containing tungsten, molybdenum, manganese, niobium, vanadium, copper, bismuth, silver, nickel, iron, or zinc. The electrochemically active material B can provide the charge required for the color-changing reaction of the color-changing active material A through an electrochemical reaction.

[0007] The adsorbent C is capable of adsorbing active substance A and electrochemically active substance B, and inhibiting the migration of active substance A / B in the integrated electrochromic material. Optionally, the adsorbent C is selected from one or more of soluble or dispersible polymers with polar functional groups and metal-organic framework materials. Preferably, the polymer is selected from one or more of alginic acid, chitosan, polyquaternary ammonium salts, polyacrylic acid, cellulose and its derivatives, and amide-containing polymers. Preferably, the alginic acid polymer is sodium alginate, the chitosan polymer is chitosan, the polyquaternary ammonium salt polymer is polyquaternary ammonium salt, the polyacrylic acid polymer is polyacrylic acid, the cellulose and its derivative polymer is hydroxyethyl cellulose, and the amide-containing polymer is polyvinyl pyrrolidone.

[0008] Optionally, the ion exchange material D is selected from one or more of ion exchange resins, inorganic ion exchangers, polyanionic polymers, polycationic polymers, bentonite, montmorillonite, zeolite, and MOF.

[0009] Optionally, the integrated electrochromic material further contains an ion conductive substance E to ensure that the material has excellent ion conductivity; preferably, the ion conductive substance E is one or more of LiClO4, LiCF3SO3, ZnSO4, NaClO4, Na2SO4, KCl, and (NH4)2SO4.

[0010] The present invention also provides a method for preparing the integrated electrochromic material, comprising the following steps: S1: dissolving the electrochemically active substance B and the adsorbent C in deionized water to form a transparent viscous solution; S2: uniformly mixing the ion exchange material D with the transparent viscous solution in step S1 to obtain a mixed solution; S3 injects the mixed solution into a mold and forms a film through polymerization; S4: Soak the film obtained in step S3 in a solution of color-changing active substance A for 3 to 5 hours to obtain an integrated electrochromic material.

[0011] Preferably, the integrated electrochromic material has a thickness of 50-200 μm.

[0012] In the present invention, active material A, electrochemically active material B, adsorbent C and ion exchange material D are blended into a film through a sol-gel method, replacing the traditional multi-layer stacking structure to form a single-layer multifunctional composite material.

[0013] Preferably, in step S1 , the concentration of the electrochemically active substance B is 0.01-1 M, and the concentration of the adsorbate C is 2-3 wt.%.

[0014] Preferably, the mass ratio of the ion exchange material D in step S2 to the adsorbent C in step S1 is 1-5:2-6.

[0015] Preferably, an ion conductive material E may be added in step S1, and the amount added is 10-25% of the mass of the adsorbent C in step S1; the ion conductive material E serves as an ion migration medium and can further improve the ion conductivity.

[0016] Preferably, in step S3, the polymerization temperature is 50-80° C., and the polymerization time is 10-15 h.

[0017] Furthermore, in step S4, the concentration of the color-changing active substance A solution is 0.5-2 M.

[0018] The present invention also provides an application of the integrated electrochromic material in an electrochromic device. The electrochromic device can be used in architecture, aviation, anti-glare, information display, flexible wearable electronic devices, electric vehicles, medical monitoring equipment, etc.

[0019] Compared with the prior art, the present invention has the following beneficial effects: 1) The integrated electrochromic material of the present invention is composed of non-toxic or low-toxic materials, and has an overwhelming advantage in biosafety over violet-type materials; 2) Compared with violet-type materials, the integrated electrochromic material of the present invention can effectively maintain a charge separation state during the color change process, has excellent color bistability, and the device energy consumption is significantly improved compared with small molecule materials; 3) The integrated electrochromic material of the present invention does not suffer from stress strain and structural damage, and its cyclic stability is far superior to that of crystal and polymer electrochromic materials; 4) The integrated electrochromic material of the present invention has a simple structure and inexpensive materials, which can significantly reduce device costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 4 is a cross-sectional view of the structure of the electrochromic device of Example 1; Figure 2 This is a test chart of the light transmittance of the electrochromic material of Example 1; Figure 3This is a color memory test chart of the electrochromic material of Example 1; Figure 4 This is a test chart of the cycle life of the electrochromic material of Example 1; Figure 5 This is a light transmittance test chart of the electrochromic material of Example 2; Figure 6 This is a light transmittance test chart of the electrochromic material of Example 3; Figure 7 This is a color memory test chart of the electrochromic material of Comparative Example 1; Figure 8 This is a cycle life test diagram of the electrochromic material of Comparative Example 1; Figure 9 This is a cycle life test chart of the electrochromic material of comparative example 2. DETAILED DESCRIPTION

[0021] The principles and features of the present invention are described below with reference to the accompanying drawings and examples. The examples are intended only to illustrate the present invention and are not intended to limit the scope of the present invention. The experimental methods used in the following examples are conventional methods unless otherwise specified; the materials and reagents used in the following examples are all commercially available unless otherwise specified. Example 1

[0022] The preparation method of the integrated electrochromic material is as follows: S1: Dissolve 0.36 g of potassium ferrocyanide (electrochemically active substance B) in 20 mL of deionized water, add 0.6 g of sodium alginate (adsorbent C) and 0.12 g of lithium perchlorate (ion conductive substance E), and stir for 2 h to obtain a transparent viscous solution. S2: crushing 0.3 g of zeolite (ion exchange material D) to a particle size of 500 nm, adding the zeolite to the transparent viscous solution obtained in step S1, and stirring to obtain a mixed solution; S3: The mixed solution was injected into a glass mold (mold thickness 500 μm) and placed in an oven at 60 °C for polymerization for 12 h to form a thin film; S4: 6.0 g of zinc sulfate (active substance A) was dissolved in 20 mL of deionized water. The film obtained in step S3 was immersed in the prepared zinc sulfate solution for 4 h. Due to the cross-linking effect of zinc sulfate and sodium alginate, the integrated electrochromic material was obtained. The thickness of the integrated electrochromic material was 200 μm.

[0023] The electrochromic material was cut into 1.5×1.5 cm thin films, sandwiched between two pieces of fluorine-doped tin oxide (FTO) glass, and fixed with a clamp to obtain a minimalist electrochromic device. The structural cross-sectional view of the electrochromic device is shown in the figure. Figure 1As shown, 1 and 5 represent substrates, 2 and 4 represent conductive layers, and 3 represents the integrated electrochromic material.

[0024] The electrochromic performance of the electrochromic device of this example was tested and characterized, such as Figure 2 As shown in Figure 2, the transmittance of the electrochromic device at a wavelength of 550 nm changes from 73.6% to 21.8%, showing good optical modulation capabilities. The device also has excellent color memory. After the voltage is stopped, the device color can be maintained for more than 60 minutes (e.g. Figure 3 ), and after 2700 cycles, the optical modulation capability still maintains more than 95% (such as Figure 4 ). Example 2

[0025] Refer to Example 1, except that the added amount of zeolite (ion exchange material D) is 0.1 g, and other materials and preparation processes remain unchanged.

[0026] The electrochromic performance of the electrochromic device in this example is characterized, such as Figure 5 As shown in the figure, the transmittance of the electrochromic device changes from 90.4% to 61.9% at a wavelength of 550 nm. The device has excellent color memory, and the color of the device can be maintained for more than 40 minutes after the voltage is removed. After 1500 cycles, the optical modulation ability still maintains more than 85%. Example 3

[0027] Refer to Example 1, except that the added amount of zeolite (ion exchange material D) is 1.0 g, and other materials and preparation processes remain unchanged.

[0028] The electrochromic performance of the electrochromic device in this example is characterized, such as Figure 6 As shown, the transmittance of the electrochromic device changes from 50.9% to 13.3% at a wavelength of 550 nm; after the voltage is stopped, the color of the device can be maintained for more than 120 minutes, with excellent color memory, and after 500 cycles, the optical modulation ability remains above 73%. Comparative Example 1

[0029] Refer to Example 1, except that no zeolite is present in the preparation process, and other materials and preparation processes remain unchanged.

[0030] By comparing the color memory and cycle stability of electrochromic devices, we explored the advantages of ion exchange materials (zeolites) in suppressing device self-discharge. The experimental results are as follows: The color retention time of the electrochromic device of Example 1 is more than 60 minutes, while the color retention time of the device of Comparative Example 1 is only 10 minutes due to the lack of zeolite (e.g. Figure 7The device of Example 1 has undergone 2700 cycles with a color contrast change of less than 25%, while the device of Comparative Example 1 can only undergo 600 cycles with a significant decrease in optical contrast (e.g. Figure 8 ), which cannot meet the requirements of practical applications. Comparative Example 2

[0031] Refer to Example 1, except that sodium alginate is not present in the preparation process, and other materials and preparation processes remain unchanged.

[0032] By comparing the color memory and cycle stability of electrochromic devices, we explored the advantages of the adsorbent (sodium alginate) in suppressing device self-discharge. The experimental results are as follows: The color retention time of the electrochromic device of Example 1 exceeds 60 minutes. The device of Comparative Example 2 has no color memory due to the removal of the adsorbed material. The material after color change immediately dissolves into the electrolyte, and the electrode fades. The color contrast of the device of Example 1 changes by less than 25% after 2700 cycles. The device of Comparative Example 2 can only be cycled for 200 times, and the optical contrast decreases significantly (such as Figure 9 ), which cannot meet the requirements of practical applications.

[0033] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An integrated electrochromic material, characterized in that: The integrated electrochromic material includes an active substance A having an electrochromic function, an electrochemically active substance B having a charge supplementing function, an adsorbent C, and an ion exchange substance D having an ion selective exchange function.

2. The integrated electrochromic material according to claim 1, characterized in that: The color-changing active substance A is selected from one or more of soluble salts, iodine compounds or bromine compounds containing tungsten, molybdenum, manganese, niobium, vanadium, copper, bismuth, silver, nickel, iron or zinc.

3. The integrated electrochromic material according to claim 1, characterized in that: The electrochemically active material B is selected from one or more of soluble salts, iodine compounds or bromine compounds containing tungsten, molybdenum, manganese, niobium, vanadium, copper, bismuth, silver, nickel, iron or zinc.

4. The integrated electrochromic material according to claim 1, characterized in that: The adsorbent C is selected from one or more of soluble or dispersible polymers with polar functional groups and metal-organic framework materials; the polymer is selected from one or more of alginates, chitosans, polyquaternary ammonium salts, polyacrylic acids, cellulose and its derivatives, and amide-containing polymers.

5. The integrated electrochromic material according to claim 1, characterized in that: The ion exchange material D is selected from one or more of ion exchange resins, inorganic ion exchangers, polyanionic polymers, polycationic polymers, bentonite, montmorillonite, zeolite, and MOF.

6. The integrated electrochromic material according to claim 1, characterized in that: The integrated electrochromic material further contains an ion conductive substance E, and the ion conductive substance E is one or more of LiClO4, LiCF3SO3, ZnSO4, NaClO4, Na2SO4, KCl, and (NH4)2SO4.

7. The method for preparing the integrated electrochromic material according to any one of claims 1 to 6, characterized in that: The method comprises the following steps: S1: dissolving the electrochemically active substance B and the adsorbent C in deionized water to form a transparent viscous solution; S2: uniformly mixing the ion exchange material D with the transparent viscous solution in step S1 to obtain a mixed solution; S3 injects the mixed solution into a mold and forms a film through polymerization; S4: Soak the film obtained in step S3 in a solution of color-changing active substance A for 3 to 5 hours to obtain an integrated electrochromic material.

8. The preparation method according to claim 7, characterized in that In step S1, the concentration of the electrochemically active substance B is 0.01~1 M, and the concentration of the adsorbate C is 2~3 wt.%; in step S2, the mass ratio of the ion exchange material D to the adsorbate C in step S1 is 1~5:2~6; in step S4, the concentration of the color-changing active substance A solution is 0.5~2 M.

9. The preparation method according to claim 7, characterized in that An ion conductive material E may also be added in step S1, with the added amount being 10-25% of the mass of the adsorbate C in step S1.

10. Use of the integrated electrochromic material according to any one of claims 1 to 6 in an electrochromic device.

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