A self-bleaching electrochromic device based on titanium dioxide and lithium iodide

Abstract

The application relates to a self-bleaching electrochromic device based on titanium dioxide and lithium iodide, and belongs to the technical field of electrochromic devices. The application discloses a self-bleaching electrochromic device based on titanium dioxide and lithium iodide, which comprises a non-polar self-bleaching electrochromic device or a polar self-bleaching electrochromic device. The application has the following advantages: (1) the cycle life of the electrochromic device is improved, and the color change contrast of the electrode in the 300nm-800nm visible light band is less than 5% after at least 4000 coloring-bleaching on-off cycle operations; (2) the electrode is self-bleached, that is, the electrode can be completely restored to the state before color change within 60s under the condition of no additional voltage; and (3) the device is non-polar, that is, both electrodes can be used as cathodes or anodes, and can normally work under the condition of an additional positive or negative voltage, and the same color change performance index is achieved.

Description

Technical Field

[0001] This invention belongs to the field of color-changing device technology, and relates to a self-bleaching electrochromic device based on titanium dioxide and lithium iodide. Background Technology

[0002] Electrochromic materials alter their optical properties or light transmittance by applying an external voltage, and are widely used in smart windows in buildings, aircraft, and automobiles to meet needs such as energy management, architectural aesthetics, information display, and adjustable reflectivity / transmittance. Electrochromic materials can be broadly classified into two categories: inorganic and organic. Organic electrochromic materials achieve color change directly through reversible redox reactions; inorganic electrochromic materials are generally based on Li... + Electrochromic materials achieve color change by inducing electron injection and release through embedding and extraction. In contrast, inorganic electrochromic materials have become the preferred choice for smart windows due to their better environmental compatibility, chemical stability, and operability. Currently, the main candidate materials for commercially available electrochromic smart windows are transition metal oxides, such as tungsten oxide. Titanium oxide Nickel oxide etc. Among them, titanium dioxide, due to its affinity for Li... + Due to its high carrier capacity, it exhibits high optical modulation properties, is inexpensive and environmentally friendly, and has stable chemical and optical properties. In recent years, it has also been discovered to have color-changing responses in both visible and infrared bands, making it a commercially viable electrochromic material with broad development prospects.

[0003] The structure of inorganic electrochromic devices generally includes three parts: an electrochromic layer, an ion transport layer, and an ion storage layer. Under an applied voltage, Li... + An electrochromic layer is embedded, simultaneously triggering a large number of electron injections, causing the electrochromic material to change color due to a localized polarization effect. The ion transport layer is typically a lithium-containing electrolyte, such as Li. + The medium transported between the two electrodes. During bleaching, a reverse voltage is typically required to make the Li... + Electrons are extracted from the lattice of the electrochromic material, migrate through the electrolyte, and embed into the ion storage layer on the counter electrode; at the same time, electrons accumulated in the electrochromic material are released into the external circuit.

[0004] Existing electrochromic device structures have the following shortcomings: 1) Li + Frequent insertion and extraction within the lattice of electrochromic materials can cause irreversible mechanical damage, leading to electrode blistering, delamination, and peeling over time, severely impacting device lifespan and long-term performance stability; 2) The coloring-bleaching switching speed of the device is limited by Li + The embedding, extraction, and diffusion dynamics, especially Li +The extraction of the electrode usually requires an additional reverse voltage, so restoring the electrode to transparency (i.e., bleaching) consumes extra energy, which is not conducive to energy saving requirements in large-scale use; 3) Of the two electrodes of the device, one needs to have Li + And the characteristic of electron dual injection (thus achieving color change), another requirement is to have Li + It retains its storage properties but won't change color (otherwise, if both colors changed, the bleached state wouldn't be possible), Li + The migration of these particles also exhibits a specific directionality, thus displaying distinct cathode and anode characteristics. If the polarity is reversed when an external voltage is applied, the device will malfunction or be damaged. This reduces the operational flexibility of the color-changing device and is detrimental to the requirements of intelligent control.

[0005] To address the shortcomings of existing technologies, the following technical issues need to be addressed: 1) Avoid irreversible mechanical damage to electrode materials caused by device color-changing cycles, thereby greatly extending device lifespan and improving long-term performance stability; 2) Electrode bleaching does not require an external voltage and can be spontaneously bleached; 3) The device can operate normally when both positive and reverse voltages are applied, achieving non-polarity control. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a self-bleaching electrochromic device based on titanium dioxide and lithium iodide.

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

[0008] 1. A self-bleaching electrochromic device based on titanium dioxide and lithium iodide, wherein the self-bleaching electrochromic device is a non-polar self-bleaching electrochromic device or a polar self-bleaching electrochromic device.

[0009] The nonpolar self-bleaching electrochromic device comprises, from bottom to top, a conductive glass substrate, a transparent titanium dioxide (TiO2) nanocrystalline mesoporous film, an organic electrolyte containing lithium iodide (LiI), a transparent titanium dioxide nanocrystalline mesoporous film, and a conductive glass substrate.

[0010] The polar self-bleaching electrochromic device comprises, from bottom to top, a conductive glass substrate, a transparent titanium dioxide (TiO2) nanocrystalline mesoporous film, an organic electrolyte containing lithium iodide (LiI), and a conductive glass substrate.

[0011] Preferably, in the nonpolar self-bleaching electrochromic device, the transparent titanium dioxide (TiO2) nanocrystalline mesoporous film, the organic electrolyte containing lithium iodide (LiI), and the four sides of the transparent titanium dioxide nanocrystalline mesoporous film are sealed with insulating sealant, wherein the upper and lower ends of the insulating sealant are connected to the conductive glass substrate.

[0012] Preferably, in a polar self-bleaching electrochromic device, the transparent titanium dioxide (TiO2) nanocrystalline mesoporous film and the organic electrolyte containing lithium iodide (LiI) are sealed on all four sides by an insulating sealant, wherein the upper and lower ends of the insulating sealant are connected to a conductive glass substrate.

[0013] Preferably, the conductive glass substrate is FTO or ITO glass, and the light transmittance of the conductive glass substrate is ≥85% and the sheet resistance is ≤30Ω.

[0014] Preferably, the transparent titanium dioxide (TiO2) nanocrystalline mesoporous film uses titanium dioxide (TiO2) nanocrystals with anatase or anatase / rutile mixed crystal structure and grain size ≤50nm;

[0015] The titanium dioxide (TiO2) nanocrystalline mesoporous film has a pore size < 50 nm and a specific surface area (BET) ≥ 100 m². 2 g -1 Thin film thickness ≤ 5μm.

[0016] Preferably, the concentration of lithium iodide (LiI) in the organic electrolyte is 0.007 mol / L. -1 ~0.2 mol L -1 The solvent in the organic electrolyte containing lithium iodide (LiI) is any one of acetonitrile, propylene carbonate (PC), or ethylene carbonate (EC).

[0017] More preferably, the organic electrolyte containing lithium iodide (LiI) further includes a concentration of 0.1 mol / L. -1 ~1mol L -1 Tetrabutylammonium hexafluorophosphate (TBAPF6).

[0018] The beneficial effects of this invention are as follows: This invention discloses a self-bleaching electrochromic device based on titanium dioxide and lithium iodide, comprising a non-polar self-bleaching electrochromic device (comprising, from top to bottom, a conductive glass substrate, a transparent titanium dioxide (TiO2) nanocrystalline mesoporous film, an organic electrolyte containing lithium iodide (LiI), a transparent titanium dioxide nanocrystalline mesoporous film, and a conductive glass substrate) or a polar self-bleaching electrochromic device (comprising, from top to bottom, a conductive glass substrate, a transparent titanium dioxide (TiO2) nanocrystalline mesoporous film, an organic electrolyte containing lithium iodide (LiI), and a conductive glass substrate). In the non-polar self-bleaching electrochromic device, two transparent titanium dioxide (TiO2) nanocrystalline mesoporous films serve as the cathode and anode, respectively, while in the polar self-bleaching electrochromic device, the transparent titanium dioxide (TiO2) nanocrystalline mesoporous film serves as the cathode and the conductive glass substrate serves as the anode. The self-bleaching electrochromic device of the present invention has the following advantages: (1) It improves the cycle life of the electrochromic device, and after at least 4000 color-bleaching switch cycles, the color contrast attenuation of the electrode in the visible light band of 300nm to 800nm ​​is less than 5%; (2) It realizes the self-bleaching of the electrode, that is, it can be completely restored to the state before color change within 60s without external voltage; (3) It realizes the non-polarity operation of the device, that is, both electrodes can be used as cathodes or anodes, and can work normally under external positive or reverse voltage to achieve the same color change performance index.

[0019] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0020] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein:

[0021] Figure 1 The diagram shows the structure of the polar self-bleaching electrochromic device (a) in Example 1 and the non-polar self-bleaching electrochromic device (b) in Example 2.

[0022] Figure 2 Cyclic voltammetry curves of the devices prepared in Example 1(a) and Comparative Example 1(b) in different voltage ranges;

[0023] Figure 3 The images show the changes in the color-changing current spectrum and the electrodes after 300 rapid color-changing cycles of the devices prepared in Comparative Examples 1(a) and 1(b).

[0024] Figure 4 This is a schematic diagram of the electrode reaction mechanism of the device in Example 1 during the electron injection (coloring) (a) and electron release (bleaching) (b) processes;

[0025] Figure 5 The images and transmission spectra of the device in Example 1 under different applied voltages are shown, where a represents a positive voltage and b represents a negative voltage.

[0026] Figure 6 The image shows the changes in the bleached and colored states of the electrochromic device designed in Example 1 after long-term cycling, where a is the transmission spectrum under forward bias, b is the transmission spectrum under reverse bias, and c is a photograph of the corresponding colored and bleached device.

[0027] Figure 7 The cyclic voltammetric characteristic curves of the polar self-bleaching electrochromic device prepared in Example 2 are shown.

[0028] Figure 8 The transmission spectrum of the polar self-bleaching electrochromic device prepared in Example 2 under positive voltage;

[0029] Figure 9 The image shows the color change of the polar self-bleaching electrochromic device prepared in Example 2 under a positive voltage.

[0030] Figure 10 The image shows the changes in the transmission spectrum of the polar self-bleaching electrochromic device prepared in Example 2 under positive voltage before and after long-term cycling. Detailed Implementation

[0031] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0032] The relevant components in the following embodiments are prepared according to the following method:

[0033] A polar / non-polar self-bleaching electrochromic device based on titanium dioxide and lithium iodide, the preparation method of which includes the following steps:

[0034] (1) Transparent titanium dioxide (TiO2) nanocrystalline mesoporous film: Tetrabutyl titanate and ethanol were mixed at a volume ratio of 1:1 to obtain a homogeneous reaction solution. The reaction solution was then added dropwise to a concentration of 3.2 × 10⁻⁶. -2 Hydrolysis was carried out in a mol / L dilute nitric acid aqueous solution to obtain a white precipitate hydrolysis product. The hydrolysis product was dissolved in 0℃~4℃ to obtain a transparent sol, which served as a precursor for hydrothermal reaction. The precursor was transferred into a hydrothermal reactor and hydrothermally treated at 100℃~180℃ for 3~12 hours to obtain anatase-type or anatase / rutile mixed-type TiO2 nanocrystalline sol with a grain size ≤50nm. The obtained TiO2 nanocrystalline sol was centrifuged and the excess water was filtered off to obtain a concentrated sol. The concentrated sol was mixed with water, acetylacetone, polyethylene glycol 2000, and OP emulsifier in a mass ratio of 1:5:0.5:1:1 and stirred to obtain a uniform TiO2 nanocrystalline slurry. The slurry was coated on an FTO or ITO conductive glass substrate, dried at 80℃ for 5 minutes, and then calcined at 450℃ for 30 minutes to obtain a transparent titanium dioxide (TiO2) nanocrystalline mesoporous film with a thickness ≤5μm.

[0035] (2) Preparation of organic electrolyte containing lithium iodide (LiI): Anhydrous lithium iodide (LiI) is uniformly mixed with an organic solvent (acetonitrile, propylene carbonate (PC) or ethylene carbonate (EC)) to prepare an electrolyte solution with a LiI concentration of 0.007 mol / L to 0.2 mol / L; Tetrabutyl hexafluorophosphate (TBAPF6) is added to the electrolyte solution as a buffer solution (the concentration of tetrabutyl hexafluorophosphate in the electrolyte is 0.1 mol / L to 1 mol / L).

[0036] Example 1

[0037] A nonpolar self-bleaching electrochromic device based on titanium dioxide and lithium iodide is shown in the schematic diagram below. Figure 1 As shown in Figure a, from bottom to top, the structure includes a conductive glass substrate (the conductive glass substrate is FTO glass, with a light transmittance ≥85% and a sheet resistance ≤30Ω), a transparent titanium dioxide (TiO2) nanocrystalline mesoporous film (the titanium dioxide (TiO2) nanocrystals used in this film have anatase or anatase / rutile mixed crystal structure, with a grain size ≤50nm, and the pore size of the titanium dioxide (TiO2) nanocrystalline mesoporous film is <50nm, and the specific surface area (BET) is ≥100m²). 2 g -1 (1) Thin film thickness ≤ 5 μm; (2) Organic electrolyte containing lithium iodide (LiI) (the concentration of lithium iodide in the organic electrolyte containing lithium iodide (LiI) is 0.1 mol L / L) -1The solvent in the organic electrolyte containing lithium iodide (LiI) is acetonitrile, a titanium dioxide film (as above), and a conductive glass substrate (as above). In this non-polar self-bleaching electrochromic device, the transparent titanium dioxide (TiO2) nanocrystalline mesoporous film, the organic electrolyte containing lithium iodide (LiI), and the two ends of the titanium dioxide film are sealed with insulating sealant, wherein the upper and lower ends of the insulating sealant are connected to the conductive glass substrate.

[0038] When assembling a nonpolar device, two identical transparent titanium dioxide (TiO2) nanocrystalline mesoporous films are used as the cathode and anode, respectively, and sealed relative to each other with a 0.1 mm gap. Electrolyte is injected into the gap between the two electrodes to form a sandwich-structured electrochromic device.

[0039] Example 2

[0040] A polar self-bleaching electrochromic device based on titanium dioxide and lithium iodide is shown in the schematic diagram below. Figure 1 As shown in Figure b, from bottom to top, the structure includes a conductive glass substrate (the conductive glass substrate is TO glass, with a light transmittance ≥85% and a sheet resistance ≤30Ω), a transparent titanium dioxide (TiO2) nanocrystalline mesoporous film (the titanium dioxide (TiO2) nanocrystals used in this film have anatase or anatase / rutile mixed crystal structure, with a grain size ≤50nm, and the pore size of the titanium dioxide (TiO2) nanocrystalline mesoporous film is <50nm, and the specific surface area (BET) is ≥100m²). 2 g -1 (1) Thin film thickness ≤ 5 μm; (2) Organic electrolyte containing lithium iodide (LiI) (the concentration of lithium iodide in the organic electrolyte containing lithium iodide (LiI) is 0.1 mol L / L) -1 The solvent in the organic electrolyte containing lithium iodide (LiI) is propylene carbonate (PC) and the conductive glass substrate (as above). In this polar self-bleaching electrochromic device, the transparent titanium dioxide (TiO2) nanocrystalline mesoporous film and the two ends of the organic electrolyte containing lithium iodide (LiI) are sealed with insulating sealant, wherein the upper and lower ends of the insulating sealant are connected to the conductive glass substrate.

[0041] When assembling polarized devices, a transparent titanium dioxide (TiO2) nanocrystalline mesoporous film is used as the cathode and a conductive glass substrate is used as the anode. The electrodes are sealed with a 0.1 mm gap, and the electrolyte is injected into the gap between the two electrodes to form a sandwich-structured electrochromic device.

[0042] Comparative Example 1

[0043] The lithium iodide (LiI) in the organic electrolyte containing lithium iodide (LiI) in Example 1 was replaced with lithium tetrafluoroborate (LiBF4), and the rest was the same as in Example 1.

[0044] Comparative Example 2

[0045] The lithium iodide (LiI) in the organic electrolyte containing lithium iodide (LiI) in Example 2 was replaced with lithium tetrafluoroborate (LiBF4), and the rest was the same as in Example 2.

[0046] Performance testing

[0047] 1. This invention uses lithium iodide, an iodine salt with redox properties, in the electrolyte. Lithium iodide (LiI) provides the Li required for the electrode reaction. + and redox couple I3 - / I - Li + It is used to embed into the TiO2 lattice under an applied positive voltage to induce electron injection, causing TiO2 to change color. However, when releasing electrons to bleach the TiO2 electrode, the electrons accumulated in TiO2 react with I3... - The charge recombination effect between them replaces Li + The electrons released from the LiO2 bleach the TiO2. This avoids the LiO2 from being bleached. + Frequent insertion and extraction within the TiO2 lattice greatly reduces the probability of irreversible mechanical damage to the TiO2 lattice, thereby enabling non-destructive color-changing cycling of the electrode.

[0048] Figure 2 Cyclic volt-ampere curves of the devices prepared in Example 1(a) and Comparative Example 1(b) in different voltage ranges are shown below. Figure 2 As can be seen, when the electrochromic device in Comparative Example 1 uses a non-redox lithium salt (such as LiBF4) as the electrolyte, its cyclic voltammetry curve shows mirror-symmetric positive and negative current peaks between -1.5V and +1.5V. This is because Li + This is caused by the insertion and extraction of lithium into TiO2. However, the electrochromic device designed in Example 1, which uses a redox lithium salt electrolyte (LiI), did not show this symmetrical current peak on its cyclic voltammetry curve, indicating that Li2O3 did not continuously undergo Li2O3 deposition. + The process of embedding and unembedding.

[0049] Figure 3 The images show the changes in the color-changing current spectrum and the electrodes after 300 rapid color-changing cycles for the devices prepared in Comparative Examples 1(a) and 1(b). Figure 3It can be seen that the color-changing cycling current spectrum of the electrochromic device designed in Comparative Example 1 continuously decreases with the increase of the number of cycles, and after 300 cycles, the electrode shows blistering and cracking; while the color-changing cycling current spectrum of the electrochromic device designed in Example 1 remains stable with the increase of the number of cycles, and the electrode is undamaged after 350 cycles. Therefore, it is evident that the electrode of the device design in Example 1 remains undamaged after rapid color-changing cycling, while the electrode of the device design used in Comparative Example 1 shows obvious blistering and damage after rapid color-changing cycling.

[0050] 2. The device design scheme adopted in this invention causes I3 to occur in the TiO2 electrode during bleaching. - The reduction reaction is a spontaneous process, so no external voltage is required, and self-bleaching can be carried out in an open circuit state.

[0051] Figure 4 This is a schematic diagram of the electrode reaction mechanism of the device in Example 1 during the electron injection (coloring) (a) and electron release (bleaching) (b) processes. From... Figure 4 It can be seen that when a forward bias is applied to the device in Example 1, the Li in the electrolyte... + Under the influence of an electric field, electrons are injected into the lattice of the cathode TiO2, causing the TiO2 to change color. Simultaneously, I... - Under the influence of an electric field, it migrates towards the anode, where it undergoes an oxidation reaction to generate I3. - And release electrons into the external circuit. The generated I3 - Due to its negative charge, it is also attracted near the anode. When the applied voltage is turned off (open circuit), I3 accumulated on the anode side... - Driven by the concentration gradient, the material diffuses towards the cathode through a reduction reaction. Electrons accumulated on the TiO2 surface during coloring recombine, thereby restoring the TiO2 electrode to a transparent state (bleaching). This demonstrates that the electrochromic device designed in Example 1 of this invention can exhibit gradient color changes with increasing applied voltage, and all of them can spontaneously bleach.

[0052] Figure 5 The images show photographs and transmission spectra of the device in Example 1 operating under different applied voltages, where a represents a positive voltage and b represents a negative voltage. Figure 5 It can be seen that the electrochromic device designed in Embodiment 1 of the present invention can achieve gradient color change under different applied voltages and can spontaneously bleach in the open circuit state. The coloring time tc of the device in Embodiment 1 is 5s to 15s, which increases with the degree of coloring; its corresponding spontaneous bleaching time tb is 12±0.5s, which is independent of the degree of coloring.

[0053] 3. The device design scheme adopted in this invention can achieve polarized or non-polarized operation as needed. If the device uses two identical TiO2 electrodes, the two electrodes alternately serve as cathode and anode depending on the applied forward or reverse bias voltage, resulting in non-polar color change. If a TiO2 electrode is used as the cathode and conductive glass as the anode, the device changes color under a forward bias voltage. The electrolyte used in both schemes is the same. Under both design schemes, the color-changing performance indicators of the device are the same: during coloring, the minimum transmittance in the 300nm~800nm ​​wavelength band (visible light region) is 1±0.5%; during bleaching, the maximum transmittance in the 300nm~800nm ​​wavelength band (visible light region) is 90±2%; the maximum optical contrast ratio in the visible light region is 90±2%; the cycle life when the maximum optical contrast ratio attenuation is less than 5% is not less than 4000 cycles; the color-changing voltage is adjustable within the range of ±2V~±4V; and bleaching is possible under open circuit conditions.

[0054] Figure 6 This image shows the changes in the bleached and colored states of the electrochromic device designed in Example 1 after long-term cycling, where a is the transmission spectrum under forward bias, b is the transmission spectrum under reverse bias, and c is a photograph of the corresponding colored and bleached devices. Copper Figure 6 It can be seen that after 4600 cycles of forward bias or reverse bias, the maximum color-changing optical contrast of the device in Embodiment 1 of the present invention decreased by 1.7% at a wavelength of 700nm and by 4.7% at a wavelength of 516nm.

[0055] Figure 7 The cyclic voltammetric characteristic curves of the polar self-bleaching electrochromic device prepared in Example 2 are shown. Figure 8 The transmission spectrum of the polar self-bleaching electrochromic device prepared in Example 2 under positive voltage; Figure 9 The image shows the color change of the polar self-bleaching electrochromic device prepared in Example 2 under a positive voltage. Figure 10 This shows the changes in the transmission spectrum of the polar self-bleaching electrochromic device prepared in Example 2 under positive voltage before and after long-term cycling, reflecting the bleaching and coloring states. Figure 7 It can be seen that the polar self-bleaching electrochromic device prepared in Example 2 exhibits asymmetrical curve shapes in the positive and negative potential ranges (it cannot change color normally in the negative potential range); from Figure 8 As can be seen, under different applied positive voltages, the transmission spectrum of the electrochromic device exhibits a gradient change from... Figure 9 As can be seen, the device exhibits gradient coloring under different applied positive voltages, and spontaneously bleachs when no voltage is applied. No color change occurs under negative voltage, therefore no performance data or images are available. From... Figure 10As can be seen from the data, the polar self-bleaching electrochromic device prepared in Example 2, because it operates with a single electrode, has a transmittance after 2300 cycles that is almost the same as that of the non-polar electrochromic device prepared in Example 1.

[0056] Therefore, the difference between the polarized self-bleaching electrochromic device and the non-polarized self-bleaching electrochromic device disclosed in this invention is that the polarized self-bleaching electrochromic device can only work under positive voltage, while the non-polarized self-bleaching electrochromic device can work under both positive and negative voltage, and the two electrodes can work alternately, thus achieving double the cycle performance.

[0057] In summary, this invention discloses a self-bleaching electrochromic device based on titanium dioxide and lithium iodide, comprising a non-polar self-bleaching electrochromic device (comprising, from top to bottom, a conductive glass substrate, a transparent titanium dioxide (TiO2) nanocrystalline mesoporous film, an organic electrolyte containing lithium iodide (LiI), a titanium dioxide film, and a conductive glass substrate) or a polar self-bleaching electrochromic device (comprising, from top to bottom, a conductive glass substrate, a transparent titanium dioxide (TiO2) nanocrystalline mesoporous film, an organic electrolyte containing lithium iodide (LiI), and a conductive glass substrate). In the non-polar self-bleaching electrochromic device, the two transparent titanium dioxide (TiO2) nanocrystalline mesoporous films serve as the cathode and anode, respectively, while in the polar self-bleaching electrochromic device, the transparent titanium dioxide (TiO2) nanocrystalline mesoporous film serves as the cathode and the conductive glass substrate serves as the anode. The self-bleaching electrochromic device of the present invention has the following advantages: (1) It improves the cycle life of the electrochromic device, and after at least 4000 color-bleaching switching cycles, the color contrast attenuation of the electrode in the 300nm~800nm ​​visible light band is less than 5%; (2) It realizes the self-bleaching of the electrode, that is, it can be completely restored to the state before color change within 60s without external voltage; (3) It realizes the non-polarity operation of the device, that is, both electrodes can be used as cathodes or anodes, and can work normally under external positive or reverse voltage to achieve the same color change performance index.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A self-bleaching electrochromic device based on titanium dioxide and lithium iodide, wherein the self-bleaching electrochromic device is a non-polar self-bleaching electrochromic device or a polar self-bleaching electrochromic device. The nonpolar self-bleaching electrochromic device comprises, from bottom to top, a conductive glass substrate, a transparent titanium dioxide nanocrystalline mesoporous film, an organic electrolyte containing lithium iodide, another transparent titanium dioxide nanocrystalline mesoporous film, and a conductive glass substrate; the four sides of the transparent titanium dioxide nanocrystalline mesoporous film, the organic electrolyte containing lithium iodide, and the transparent titanium dioxide nanocrystalline mesoporous film are sealed with insulating sealant, wherein the upper and lower ends of the insulating sealant are connected to the conductive glass substrate; The polar self-bleaching electrochromic device comprises, from bottom to top, a conductive glass substrate, a transparent titanium dioxide nanocrystalline mesoporous film, an organic electrolyte containing lithium iodide, and a conductive glass substrate; the four sides of the transparent titanium dioxide nanocrystalline mesoporous film and the organic electrolyte containing lithium iodide are sealed with insulating sealant, wherein the upper and lower ends of the insulating sealant are connected to the conductive glass substrate. The concentration of lithium iodide in the organic electrolyte containing lithium iodide is 0.007 mol / L. -1 ~ 0.2 mol L -1 The solvent in the organic electrolyte containing lithium iodide is any one of acetonitrile, propylene carbonate, or ethylene carbonate; Its features are, The titanium dioxide nanocrystalline mesoporous film has a pore size of <50 nm and a specific surface area of ​​≥100 m². 2 g -1 The film thickness is ≤5 μm; the organic electrolyte containing lithium iodide comprises 0.1 mol L⁻¹ -1 ~ 1 mol L -1 Tetrabutylammonium hexafluorophosphate.

2. The self-bleaching electrochromic device according to claim 1, characterized in that, The conductive glass substrate is FTO or ITO glass, and the light transmittance of the conductive glass substrate is ≥85% and the sheet resistance is ≤30Ω.

3. The self-bleaching electrochromic device according to claim 1, characterized in that, The transparent titanium dioxide nanocrystalline mesoporous film uses titanium dioxide nanocrystals with anatase or anatase / rutile mixed crystal structure and a grain size ≤50nm.

Images