A potassium ion-doped V2O5 electrochromic thin film, its preparation method and application

Abstract

The present invention discloses a potassium-ion doped V2O5 electrochromic thin film, its preparation method and application, which include the following steps: Dissolve V2O5 powder in water and mix evenly, then add potassium chloride solution thereto to obtain a mixed solution, the concentration of potassium chloride is 1-3 mol / L, stir to obtain a colloid; Wash the colloid with water and centrifuge to remove excess potassium chloride; Ultrasonically dilute the washed colloid with distilled water; Add cellulose to the diluted colloid; Heat and stir to obtain a KVO paste; Apply the KVO paste on a conductive substrate with a clean glass rod, after tearing off the tape, remove the cellulose by thermal curing to obtain a KVO electrochromic thin film. Doping potassium element in V2O5 by a simple solution method broadens the color regulation range of V2O5, and a one-step film formation is achieved by the rod coating method. Moreover, using metallic zinc as the anode can realize the self-coloring process of the electrochromic V2O5 thin film.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrochromic thin films, and particularly relates to a potassium ion-doped V2O5 electrochromic thin film, a preparation method thereof, and an application thereof. Background Art

[0002] The statements herein only provide background art related to the present invention and do not necessarily constitute prior art.

[0003] Vanadium element has multiple oxidation states (V 2+ 、V 3+ 、V 4+ and V 5+ ), which enables the existence of various vanadium oxides. Among them, V2O5 is the most thermodynamically stable and exhibits excellent optical and electrochemical properties. Under the action of an external electric field, V2O5 can generate electron transitions and changes in the valence state of vanadium element, which are manifested as reversible changes in color and transparency in appearance. The electrochromic phenomenon of V2O5 makes it have good application prospects in many fields. Currently, the main application directions include electrochromic smart windows, electrochromic supercapacitors, passive light-emitting flat panel displays, and intelligent anti-glare rearview mirrors, etc.

[0004] However, the problems of the original V2O5 are single color change, complex film-forming method with high cost, and the structure will collapse due to repeated ion deintercalation and intercalation during the electrochromic process, shortening the device life. Therefore, the research of researchers focuses on increasing the color regulation range and extending the life by adjusting the synthesis environment, element doping, composite materials, etc.

[0005] However, the current film-forming methods of V2O5, such as hydrothermal method, magnetron sputtering method, and chemical vapor deposition method, often require expensive equipment and have strict requirements for preparation conditions. Particularly importantly, these methods are not suitable for large-area and low-cost applications. Summary of the Invention

[0006] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a potassium ion-doped V2O5 electrochromic thin film, a preparation method thereof, and an application thereof. Doping potassium element into V2O5 by a simple solution method broadens the color regulation range of V2O5, and one-step film formation is achieved by the bar coating method. Moreover, using metallic zinc as the anode can realize the self-coloring process of the electrochromic V2O5 thin film, greatly reducing energy consumption. The preparation method of the thin film is simple, with low cost, and is green and environmentally friendly.

[0007] To achieve the above purpose, the present invention is realized by the following technical solutions:

[0008] In the first aspect, the present invention provides a preparation method of a potassium ion-doped V2O5 electrochromic thin film, including the following steps:

[0009] Dissolve V2O5 powder in water and mix evenly. Then add potassium chloride solution thereto to obtain a mixed solution. In the mixed solution, the concentration of V2O5 is 50 - 80 g / L, and the concentration of potassium chloride is 1 - 3 mol / L. Stir to obtain a colloid.

[0010] Wash the colloid with water and centrifuge to remove excess potassium chloride.

[0011] Ultrasonically dilute the washed colloid with distilled water, and the diluted concentration is 6 - 10 mg / mL.

[0012] Add cellulose to the diluted colloid, and the concentration of cellulose is 20 - 30 mg / mL.

[0013] Heat and stir at 55 - 65 °C for 5 - 7 h to obtain a KVO paste.

[0014] Apply the KVO paste onto a conductive substrate with a clean glass rod. After tearing off the tape, remove the cellulose by thermal curing to obtain a KVO electrochromic film.

[0015] In a second aspect, the present invention provides a potassium ion-doped V2O5 electrochromic film prepared by the above preparation method.

[0016] In a third aspect, the present invention provides the application of the potassium ion-doped V2O5 electrochromic film in the preparation of a non-active light-emitting flat panel.

[0017] The beneficial effects obtained by one or more of the above embodiments of the present invention are as follows:

[0018] 1. The electrochromic KVO film prepared by the present invention has a simplified doping and film-forming process. By adding a salt solution containing K + to the purchased commercial V2O5 suspension, metal ions are doped into the layered structure of V2O5, expanding the layer spacing of V2O5 and improving the ion migration kinetics during electrochromism. And it is manifested that V2O5 changes from a yellow suspension to an orange-yellow colloid. By utilizing the thickening property of hydroxyethyl cellulose and its easy removal at low temperature, the prepared KVO cellulose paste can be formed into a film in one step by the rod coating method. Therefore, the KVO film of the present invention is more capable of realizing large-scale production and meeting the industrialization requirements.

[0019] 2. The electrochromic KVO film prepared by the present invention has a high color contrast and excellent color switching performance (or the characteristic of fast response speed). At the same time, without an external power supply and connected to zinc, it can change from orange-yellow to green in only 7.8 s. In the case of a two-electrode system power supply, the response time of KVO is the fading time t b = 16.9 s, and the coloring time t c= 12.9 s. It has advantages such as simple synthesis process, high reversible color change efficiency, and long cycle life.

[0020] 3. The electrochromic KVO thin film prepared by the present invention exhibits excellent cycling performance after using a mixed solvent of deionized water and tetramethyldiethylether as the electrolyte, and the number of cycles can reach more than 1000 times.

[0021] 4. The preparation process of the electrochromic KVO thin film of the present invention is simple, the raw materials used are inexpensive and easily available, and it is non-toxic and harmless to the environment. In addition, due to its excellent performance in fast response and reversibility, combined with the simple manufacturing and operation process, the electrochromic KVO thin film has broad prospects in non-emissive flat panel displays, complex information coding, electrochromic smart windows, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The specification drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention.

[0023] Figure 1 It is a schematic diagram of the process for preparing the electrochromic KVO thin film by the bar coating method of the present invention.

[0024] Figure 2 It is the XRD pattern (a) of the KVO electrochromic material prepared in Example 1; the morphology photograph (b) of the KVO electrochromic material.

[0025] Figure 3 It is a macroscopic photograph of the reversible color switching process of the KVO electrochromic thin film prepared in Example 1.

[0026] Figure 4 It is the transmittance curve of the KVO electrochromic thin film prepared in Example 1 at different voltages.

[0027] Figure 5 It is the transmittance vs. time curve (a) of the self-coloring process of KVO at a wavelength of 520 nm, and the transmittance vs. time curve of the coloring / fading process of the KVO thin film at a wavelength of 520 nm.

[0028] Figure 6 It is the test chart (a) of 1000 CV cycles of the KVO electrochromic thin film prepared in Example 1, and the transmittance spectrum chart (b) after 1000 cycles at a wavelength of 520 nm.

[0029] Figure 7 (a) is the transmittance curve of the KVO electrochromic thin film prepared in Example 2 at different voltages; (b) is the transmittance curve of the KVO electrochromic thin film prepared in Example 3 at different voltages

[0030] Figure 8 Test graph (a) of 1000 CV cycles of the KVO electrochromic film prepared as Comparative Example 2 in an aqueous electrolyte, and transmittance spectrogram (b) after 1000 cycles in the aqueous electrolyte at a wavelength of 520 nm.

[0031] Figure 9 Photo of the electrochromic process of a color display based on the KVO electrochromic film. Detailed implementation mode

[0032] It should be noted that the following detailed description is illustrative and aims to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0033] In a first aspect, the present invention provides a method for preparing a potassium ion-doped V2O5 electrochromic film, comprising the following steps:

[0034] Dissolve V2O5 powder in water and mix evenly, then add potassium chloride solution thereto to obtain a mixed solution. In the mixed solution, the concentration of V2O5 is 50 - 80 g / L, and the concentration of potassium chloride is 1 - 3 mol / L. Stir to obtain a colloid;

[0035] Wash the colloid with water and centrifuge to remove excess potassium chloride;

[0036] Ultrasonically dilute the washed colloid with distilled water, and the diluted concentration is 6 - 15 mg / mL;

[0037] Add cellulose to the diluted colloid, and the concentration of cellulose is 20 - 30 mg / mL;

[0038] Heat and stir at 55 - 65 °C for 5 - 7 h to obtain a KVO paste;

[0039] Apply the KVO paste on the conductive substrate with a clean glass rod. After tearing off the tape, remove the cellulose by heat curing. After removing the cellulose, a KVO electrochromic film is obtained.

[0040] The cellulose is removed by heating because cellulose itself does not have conductivity, and the presence of cellulose will reduce the electrochemical performance of the electrochromic film.

[0041] In some embodiments, the cellulose is cellulose nanocrystal or hydroxyethyl cellulose. After adding cellulose to the KVO colloid, it can improve the viscosity of the colloid and then form a KVO paste, and can form a uniform and consistent film during the bar coating process. Moreover, by utilizing the advantage that cellulose is easily removed at low temperature, it can make up for the disadvantage that the ITO conductive glass substrate is not resistant to high temperature, and at the same time reduce the energy consumption during the film preparation process.

[0042] Preferably, the cellulose is hydroxyethyl cellulose.

[0043] In some embodiments, in the mixed solution, the concentration of V2O5 is 60 - 70 g / L.

[0044] Preferably, the mixing time of the mixed solution is 80 - 100 h, preferably 90 - 100 h.

[0045] In some embodiments, the number of times of washing the colloid and centrifuging to remove potassium chloride is 4 - 8 times, preferably 6 times.

[0046] Preferably, the rotation speed of the centrifugation is 8000 - 12000 r / min and the time is 5 - 15 min.

[0047] In some embodiments, the conductive substrate is ITO glass, and its pre - washing steps are: ultrasonically washing with deionized water, acetone, ethanol, and deionized water for 10 - 20 min respectively, and drying with nitrogen.

[0048] Preferably, both sides of the conductive substrate are adhered with tapes. When bar - coating, both sides of the glass rod are placed on the tapes on both sides.

[0049] More preferably, the tape is 3M Scotch tear - off tape, and the number of layers is 1 layer or 2 layers.

[0050] The thickness of the coated film is adjusted by the thickness of the tape.

[0051] In some embodiments, the heating gradient for thermally curing to remove cellulose is: 80 °C, 10 min → 120 °C, 1 h → 160 °C, 1 h → 180 °C, 12 h.

[0052] In a second aspect, the present invention provides a potassium - ion - doped V2O5 electrochromic film prepared by the preparation method.

[0053] In a third aspect, the self - coloring method of the potassium - ion - doped V2O5 electrochromic film provided by the present invention is: using the potassium - ion - doped V2O5 electrochromic film as the working electrode, zinc foil as the counter electrode, and using an aqueous solution of Zn(OTf)2 (zinc trifluoromethanesulfonate) or a mixed aqueous solution of Zn(OTf)2 and tetramethylethylenediethyl ether as the electrolyte to achieve self - coloring of the film;

[0054] Or, using the potassium - ion - doped V2O5 electrochromic film as the working electrode, zinc foil as the counter electrode and reference electrode, and using an aqueous solution of Zn(OTf)2 (zinc trifluoromethanesulfonate) or a mixed aqueous solution of Zn(OTf)2 and tetramethylethylenediethyl ether as the electrolyte to achieve electrochromic switching of the film.

[0055] In some embodiments, the concentration of Zn(OTf)2 is 0.3 - 0.8 mol / L.

[0056] In some embodiments, the solvent of the electrolyte is a mixed solvent of deionized water and tetramethylethylenediamine, and the volume ratio of deionized water to tetramethylethylenediamine is 3 - 5:1. The organic solvent in the mixed solvent can form a uniform and firm electrolyte interface film on the film surface during the color change process, thereby effectively inhibiting the dissolution of KVO, and the water solvent plays a lubricating role to facilitate the rapid diffusion of Zn 2+ ions.

[0057] Thirdly, the present invention provides an application of the potassium ion-doped V2O5 electrochromic film in the preparation of a non-active light-emitting flat panel.

[0058] Meanwhile, in the following examples, the experimental methods are all conventional methods unless otherwise specified; the reagents and materials can be obtained from commercial sources unless otherwise specified.

[0059] Example 1

[0060] A preparation method of an electrochromic KVO film includes the following steps:

[0061] (1) Preparation of KVO material

[0062] The ITO glass (10*40mm 2 ) was successively ultrasonically washed with deionized water, acetone, ethanol and deionized water for 15 minutes, and dried with nitrogen for standby; 100 g of V2O5 powder was dissolved in 1.5 L of deionized water, magnetically stirred, and a prepared 2 mol / L potassium chloride solution was added, and the stirring was continued at room temperature for 96 h to obtain an orange-red colloid.

[0063] The stirred colloid was washed with deionized water and centrifuged at 10000 r / min for 10 min to remove the excess potassium chloride. This process was repeated six times. The washed colloid was diluted with distilled water to 8 mg / mL to form a precursor solution. Hydroxyethyl cellulose was added to the diluted colloid at a ratio of 23 mg / mL, and magnetically stirred at 60 °C for 6 h.

[0064] (2) Preparation of electrochromic KVO film

[0065] The KVO paste was applied on the ITO with a layer of 3M Scotch tape attached to both sides using a glass rod, the tape was torn off and heated for curing, and the heating gradient was set as 80 °C, 10 min → 120 °C, 1 h → 160 °C, 1 h → 200 °C, 12 h. An electrochromic KVO film was obtained.

[0066] (3) Preparation of organic-water mixed electrolyte

[0067] Dissolve 0.5 M of Zn(OTf)₂ (zinc trifluoromethanesulfonate) in a mixed solvent of deionized water and tetramethylethylenediamine with a mixing volume ratio of 4:1 as the electrolyte.

[0068] Use the obtained electrochromic KVO film to characterize its electrochromic performance:

[0069] (4) Take the film prepared in step (2) as the working electrode, a zinc foil as the counter electrode and reference electrode, and place them in the electrolyte prepared in step (3). Connect an electrochemical workstation to conduct electrochemical performance characterization under a two-electrode system. At the same time, connect the electrochemical workstation with a UV-Vis spectrometer to conduct electrochromic performance characterization.

[0070] For the K-doped V₂O₅ material of the present invention, its structure is determined by an X-ray diffractometer, as Figure 2 shown in a. It can be seen from the XRD pattern that the obtained material composition is K 1.11 V₃O₈. Observe the morphology of the material using a transmission electron microscope, as Figure 2 shown in b. The morphology of KVO is rod-shaped, different from the initial flaky V₂O₅, indicating that the doping of K causes a morphological change in V₂O₅. When different voltages between 0.2 - 2.0 V are applied through an electrochemical workstation, the film exhibits different colors, as Figure 3 shown. When the applied voltage is 0.2 V, the film is green; when the applied voltage is 1.2 V, the film is yellow; when the applied voltage is 2.0 V, the film is red.

[0071] When in-situ monitoring the color switching through a UV-Vis spectrometer, the transmittance curves of different colors are as Figure 4 shown. As the applied voltage decreases, the peak of the transmittance will undergo a blue shift. It indicates that the process of Zn 2+ insertion (coloring) and extraction (bleaching) realizes the reversible color switching of the KVO film ( ). At a wavelength of 520 nm, the transmittance modulation range of the KVO film prepared in this example is 25.8%, and the maximum transmittance is 68%. The pattern under the film can be clearly distinguished. And using zinc as the electrochromic anode, utilizing the redox potential between zinc and KVO, the spontaneous coloring process of the KVO film can be realized ( Figure 5 a), and the coloring time is 8.8 s. The color switching times t b and t c during the bleaching (orange) and coloring (green) processes are respectively defined as the time required to achieve 90% of the final modulation, which are 16.9 s and 12.9 s respectively ( Figure 5 b).

[0072] The cycle life of the thin film was measured by cyclic voltammetry. The KVO thin film retained 55% of its initial capacity ( Figure 6 a), and had an optical contrast of 19% after 1000 CV cycles ( Figure 6 b), showing excellent reversibility and repeatability.

[0073] Example 2

[0074] A method for preparing an electrochromic KVO thin film, comprising the following steps:

[0075] (1) Preparation of KVO material

[0076] The ITO glass (10*40mm 2 ) was ultrasonically washed with deionized water, acetone, ethanol and deionized water for 15 minutes in sequence, and dried with nitrogen for standby; 100 g of V2O5 powder was dissolved in 1.5 L of deionized water, magnetically stirred, and the prepared 1 mol / L potassium chloride solution was added, and stirring was continued at room temperature for 5 days to obtain an orange-red colloid.

[0077] The stirred colloid was washed with deionized water and centrifuged at 10000 r / min for 10 min to remove the excess potassium chloride. This process was repeated eight times. The washed colloid was diluted with distilled water to 15 mg / mL to form a precursor solution. Hydroxyethyl cellulose was added to the diluted colloid at a ratio of 23 mg / mL, and magnetic stirring was carried out at 60 °C for 6 h.

[0078] (2) The preparation of the electrochromic KVO thin film was the same as that in Example 1;

[0079] (3) The preparation of the organic-water mixed electrolyte was the same as that in Example 1;

[0080] Using the obtained electrochromic KVO thin film, its electrochromic performance was characterized: the electrochromic performance characterization method was the same as that in Example 1. When different voltages between 0.2 - 2.0 V were applied through an electrochemical workstation, the thin film still showed reversible color switching (orange yellow green). Because the colloid concentration in the thin film increased to 15 mg / ml, the transmittance modulation range of the KVO thin film prepared in this example was 18.5% at a wavelength of 520 nm, and the maximum transmittance was 38% ( Figure 7 a).

[0081] Example 3

[0082] A method for preparing an electrochromic KVO thin film, comprising the following steps:

[0083] (1) Preparation of KVO material

[0084] The ITO glass (10*40 mm 2 ) was successively ultrasonically washed with deionized water, acetone, ethanol and deionized water for 15 minutes and dried with nitrogen for standby; 100 g of V2O5 powder was dissolved in 1.5 L of deionized water, magnetically stirred, and the prepared 2.5 mol / L potassium chloride solution was added, and stirring was continued at room temperature for 5 days to obtain an orange-red colloid.

[0085] The stirred colloid was washed with deionized water and centrifuged at 10000 r / min for 10 min to remove the excess potassium chloride. This process was repeated eight times. The washed colloid was diluted to 5 mg / mL with distilled water to form a precursor solution. Hydroxyethyl cellulose was added to the diluted colloid at a ratio of 23 mg / mL, and magnetic stirring was carried out at 60 °C for 6 h.

[0086] (2) The preparation of the electrochromic KVO film was the same as that in Example 1.

[0087] (3) Preparation of the organic-water mixed electrolyte

[0088] 0.3 M of Zn(OTf)2 (zinc trifluoromethanesulfonate) was dissolved in a mixed solvent of deionized water and tetramethylethylenediamine with a mixing volume ratio of 4:1 as the electrolyte. The preparation of the organic-water mixed electrolyte was the same as that in Example 1.

[0089] Using the obtained electrochromic KVO film, its electrochromic performance was characterized:

[0090] The electrochromic performance characterization method was the same as that in Example 1. When different voltages between 0.2 - 2.0 V were applied through an electrochemical workstation, the film still showed reversible color switching (orange yellow green). Because the colloid concentration in the film decreased to 5 mg / ml, at a wavelength of 520 nm, the transmittance modulation range of the KVO film prepared in this example was 18.2%, and the maximum transmittance was 75% ( Figure 7 b).

[0091] Comparative Example 1

[0092] The difference from Example 1 was that the type of cellulose in step (1) was changed to cellulose nanofibers, and the other steps remained unchanged. After the corresponding KVO paste was prepared on the ITO glass by the bar coating method, carbonization occurred during the high-temperature treatment, the film turned black and the carbon could not be completely removed at 180 °C, destroying the electrochromic performance of the film.

[0093] Comparative Example 2

[0094] The difference from Example 1 was that the electrolyte solvent in step (3) was changed to water.

[0095] The film prepared in this comparative example has poor cycle stability in aqueous electrolyte; after 1000 CV cycles, the KVO material completely falls off and dissolves in water.

[0096] 1000 CV cycles of KVO in aqueous electrolyte are as Figure 8 (a) shown. After 1000 cycles, the CV curve tends to a straight line, indicating that the charge capacity is almost zero at this time. Moreover, the optical contrast after 1000 CV is also zero ( Figure 8 b).

[0097] Application Example 1

[0098] KVO electrochromic display based on color superposition effect

[0099] The preparation steps are as follows:

[0100] (1) Device assembly

[0101] Cleaning: Take two pieces of 5×5 cm 2 ITO glass and ultrasonically wash them with deionized water, acetone, ethanol and deionized water for 15 minutes in sequence, and dry them with nitrogen for standby;

[0102] Film formation: As described in step (2) of Example 1, coat 2×2 cm 2 KVO electrochromic film in the center of each piece of glass;

[0103] Assembly: Stick a 1-cm-wide conductive copper tape around the periphery of each of the two prepared ITO glasses and press it firmly. Then stick two layers of 3M transparent double-sided tape on the conductive copper tape. The width of the double-sided tape should just completely cover the copper tape without allowing the tape to contact the electrolyte. Then cut out a zinc foil frame such that when the zinc frame is attached to the double-sided tape on the glass, a distance of 3-5 mm can be exposed inward around the periphery and the KVO film is not blocked. Finally, cover the other piece of ITO glass without the zinc frame on it and press the two pieces of glass tightly to form an electrochromic device;

[0104] Compaction: Place the device under a heavy object and compact it for 4-6 days;

[0105] Prepare the gel electrolyte: As described in step (3) of Example 1, and add 9% by mass fraction of polyvinyl alcohol (PVA Mw~195,000), and stir until it is clear and transparent;

[0106] Inject the electrolyte: Take out the compacted electrochromic device and inject the gel electrolyte into the cavity of the device using a syringe;

[0107] (2) Electro-deposit a patterned flexible PB / ITO / PET film

[0108] As described in step (1) of Example 1, a flexible PB / ITO / PET film with a pattern is obtained.

[0109] (3) Color expression of the KVO electrochromic display

[0110] Taking advantage of the fact that the upper and lower KVO electrochromic thin films in the device can independently adjust colors, that is, each electrode can achieve three-color expression (orange yellow green). Therefore, when the upper and lower colors are superimposed, six-color expression of the device can be achieved through the color accumulation effect (such as orange, amber, yellow, brown, yellowish green, and green). Photos of its electrochromic process are as Figure 9 shown. When both electrochromic thin films are green, the display shows a deeper green ( Figure 9 a), when one layer is green and the other is yellow, the display shows yellowish green ( Figure 9 b), when one layer is green and the other is orange, the display color shows brown ( Figure 9 c), when both layers are yellow, it shows a deeper yellow ( Figure 9 d), when one layer is orange and the other is yellow, the display shows amber ( Figure 9 e), and finally when both are orange, the display shows a deeper orange ( Figure 9 f).

[0111] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of potassium ion-doped V2O5 electrochromic thin film, characterized in that: It includes the following steps: Dissolve V2O5 powder in water and mix evenly, then add potassium chloride solution thereto to obtain a mixed solution. In the mixed solution, the concentration of V2O5 is 50 - 80 g / L, and the concentration of potassium chloride is 1 - 3 mol / L. Stir to obtain a colloid; Wash the colloid with water and centrifuge to remove excess potassium chloride; Ultrasonically dilute the washed colloid with distilled water, and the concentration after dilution is 6 - 10 mg / mL; Add cellulose to the diluted colloid, and the concentration of cellulose is 20 - 30 mg / mL; Heat and stir at 55 - 65 °C for 5 - 7 h to obtain KVO paste; Apply the KVO paste on the conductive substrate with a clean glass rod. After tearing off the tape, remove the cellulose by thermal curing to obtain a KVO electrochromic film.

2. The preparation method of potassium ion-doped V2O5 electrochromic thin film according to claim 1, characterized in that: The cellulose is cellulose nanocrystal or hydroxyethyl cellulose.

3. The preparation method of potassium ion-doped V2O5 electrochromic thin film according to claim 1, characterized in that: In the mixed solution, the concentration of V2O5 is 60 - 70 g / L.

4. The preparation method of potassium ion-doped V2O5 electrochromic thin film according to claim 3, characterized in that: The stirring time of the mixed solution is 80 - 100 h.

5. The preparation method of potassium ion-doped V2O5 electrochromic thin film according to claim 4, characterized in that: The stirring time of the mixed solution is 90 - 100 h.

6. The preparation method of potassium ion-doped V2O5 electrochromic thin film according to claim 1, characterized in that: The number of times of washing the colloid and centrifuging to remove potassium chloride is 4 - 8 times.

7. The preparation method of potassium ion-doped V2O5 electrochromic thin film according to claim 6, characterized in that: The rotation speed of the centrifugation is 8000 - 12000 r / min, and the time is 5 - 15 min.

8. The preparation method of potassium ion-doped V2O5 electrochromic thin film according to claim 1, characterized in that: The conductive substrate is ITO glass, and its pre-washing steps are: ultrasonically wash with deionized water, acetone, ethanol and deionized water for 10 - 20 min respectively, and dry with nitrogen.

9. The preparation method of potassium ion-doped V2O5 electrochromic thin film according to claim 8, characterized in that: Tapes are adhered to both sides of the conductive substrate. During bar coating, place both sides of the glass rod on the tapes on both sides.

10. The preparation method of potassium ion-doped V2O5 electrochromic thin film according to claim 1, characterized in that: The heating gradient for removing cellulose by thermal curing is: 80 °C, 10 min → 120 °C, 1 h → 160 °C, 1 h → 180 °C, 12 h.

11. A potassium ion-doped V2O5 electrochromic thin film, characterized in that: Prepared by the preparation method according to any one of claims 1 - 10.

12. The self-coloring method of the potassium ion-doped V2O5 electrochromic thin film according to claim 11, characterized in that: It includes the following steps: Use the potassium ion-doped V2O5 electrochromic film as the working electrode, zinc foil as the counter electrode, and use an aqueous solution of Zn(OTf)2 or a mixed aqueous solution of Zn(OTf)2 and tetramethylethylenediamine as the electrolyte to achieve self-coloring of the film; Or, use the potassium ion-doped V2O5 electrochromic film as the working electrode, zinc foil as the counter electrode and reference electrode, and use an aqueous solution of Zn(OTf)2 or a mixed aqueous solution of Zn(OTf)2 and tetramethylethylenediamine as the electrolyte to achieve electrochromic switching of the film.

13. The self-coloring method of the potassium ion-doped V2O5 electrochromic thin film according to claim 12, characterized in that: The concentration of Zn(OTf)2 is 0.3 - 0.8 mol / L.

14. The self-coloring method of the potassium-ion doped V2O5 electrochromic thin film according to claim 12, characterized in that: The solvent of the electrolyte is a mixed solvent of deionized water and tetramethylethylenediamine, and the volume ratio of deionized water to tetramethylethylenediamine is 3 - 5:

1.

15. Application of the potassium-ion doped V2O5 electrochromic thin film according to claim 11 in the preparation of a non-active light-emitting flat panel.

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