Niobium-doped tungsten oxide difunctional electrochromic energy storage material as well as preparation method and application thereof

Abstract

The invention discloses a niobium-doped tungsten oxide difunctional electrochromic energy storage material as well as a preparation method and application thereof, and belongs to the field of electrochromism and energy storage. The preparation method comprises the following steps: by adopting a magnetron sputtering method, respectively taking niobium and tungsten oxide as target materials and taking mixed gas of inert gas and oxygen as working gas, depositing on the surface of the conductive glass substrate to form an amorphous niobium-doped tungsten oxide film, thereby obtaining the niobium-doped tungsten oxide difunctional electrochromic energy storage material. The electrochromic material effectively improves the electrochromic response speed of a film, has high fading state transmittance, optical modulation amplitude, charge capacity, film coloring efficiency and electrochemical cycle stability, also has low color change driving voltage and good energy storage capability, and has good application prospects when applied to zinc-induced electrochromic energy storage devices. And the electrochromic function and the energy storage function are integrated, the working state can be visually indicated through real-time color change, and the electrochromic energy storage device has important application prospects.

Description

Technical Field

[0001] The present invention relates to the fields of electrochromism and energy storage, and particularly relates to a niobium-doped tungsten oxide bifunctional electrochromic energy storage material, a preparation method thereof, and an application thereof. Background Art

[0002] Electrochromic materials have attracted much attention because they can undergo stable and reversible color changes under the action of an external electric field. As a new type of functional material, they have good physical and chemical properties and reversible optical properties, and can be used to make devices such as displays, dimming glass, and information storage, and have broad application prospects in many fields such as information, electronics, energy, architecture, and national defense, and are of great significance for energy conservation and environmental protection. At present, researchers have proposed an electrochromic energy storage device that combines electrochromism and energy storage functions to meet the growing demand for multifunctional integrated devices and has broad prospects in becoming the next-generation energy-saving electrochromic smart window.

[0003] In recent years, Zn 2+ Electrochromic devices have attracted the research interest of many scholars because they can transport more charges relative to traditional Li + electrolytes, making them have more excellent optical modulation and response time. Tungsten oxide (WO3), as a typical electrochromic material, has been widely studied because of its high optical modulation rate and good cycle stability. However, pure tungsten oxide thin films have deficiencies such as slow response speed and low coloring efficiency in electrochromic performance. Especially, Zn 2+ has a larger ionic radius, making the stability of tungsten oxide in Zn 2+ electrolytes often only have one hundred cycles, seriously hindering its practical application. In order to improve the electrochromic performance of tungsten oxide thin films, researchers have tried to improve their performance by doping other elements.

[0004] At present, metals such as Ti, Mo, and Ni have been widely studied for doping tungsten oxide to improve its optical modulation amplitude and response time. The main preparation method is the chemical sol-gel method. However, it is difficult to effectively control the doping metal elements by chemical doping, and a uniformly doped structure cannot be obtained. In addition, the improvement of the stability of tungsten oxide doped with the above doping elements is still limited.

[0005] Therefore, it is of great research significance to improve the electrochromic performance of metal-doped tungsten oxide thin films and combine them with Zn 2+ batteries. Summary of the Invention

[0006] The object of the present invention is to provide a niobium-doped tungsten oxide bifunctional electrochromic energy storage material, a preparation method thereof and an application thereof. The electrochromic material has both good electrochromic and energy storage functions. When applied to a zinc-based electrochromic energy storage device, it can achieve reversible conversion between transparency and dark blue at a relatively low voltage and has long-term cycling stability.

[0007] To achieve the above object, the present invention provides the following technical solutions: A preparation method of a niobium-doped tungsten oxide bifunctional electrochromic energy storage material, comprising the following steps: By using magnetron sputtering method, niobium and tungsten oxide are used as targets respectively, and a mixed gas of inert gas and oxygen is used as the working gas to deposit an amorphous niobium-doped tungsten oxide thin film on the surface of a conductive glass substrate to obtain a niobium-doped tungsten oxide bifunctional electrochromic energy storage material; wherein: In the mixed gas of inert gas and oxygen, the volume ratio of inert gas to oxygen is 15-30:1.

[0008] The sputtering time is 60-120 min.

[0009] According to the above scheme, the volume ratio of inert gas to oxygen is 15-25:1, and more preferably 19-21:1.

[0010] According to the above scheme, the sputtering time is 80-110 min; preferably 85-95 min.

[0011] According to the above scheme, in the magnetron sputtering method, the sputtering mode is DC sputtering and RF sputtering; wherein, the target for DC sputtering is niobium, and the target for RF sputtering is tungsten trioxide.

[0012] Preferably, the DC sputtering power is 10-80 W, and more preferably 45-55 W; the RF sputtering power is 50-200 W, and more preferably 75-85 W.

[0013] According to the above scheme, the atomic ratio of niobium to tungsten in the niobium-doped tungsten oxide thin film is 0.15-0.9:1, preferably 0.15-0.4:1.

[0014] According to the above scheme, the inert gas is argon.

[0015] According to the above scheme, the introduction rates of oxygen and inert gas are 2-8 sccm and 50-80 sccm respectively.

[0016] According to the above scheme, the sputtering pressure is 0.5-2.0 Pa.

[0017] According to the above scheme, the temperature of the conductive glass substrate is 25-200 °C, and the vacuum degree of the reaction chamber is 1×10 -4 Pa - 1×10-3 Pa.

[0018] According to the above solution, the conductive glass substrate is ultrasonically cleaned in acetone, absolute ethanol, and deionized water in sequence for 10 - 20 min before magnetron sputtering, and dried with high-pressure N2 gas before use.

[0019] According to the above solution, the conductive glass substrate is any one of ITO, FTO, AZO, and GZO transparent conductive glasses.

[0020] Provide a niobium-doped tungsten oxide bifunctional electrochromic energy storage material prepared by the above preparation method.

[0021] According to the above solution, the thickness of the niobium-doped tungsten oxide bifunctional electrochromic energy storage material is 300 - 500 nm, the film is flat and uniform, composed of loose nanoparticles, there are many cracks dozens of nanometers wide on the surface, and the cross-sectional morphology is a columnar structure.

[0022] According to the above solution, the amorphous-structured niobium-doped tungsten oxide bifunctional electrochromic energy storage material is transparent in the initial state, and realizes the color transition between the colored state of dark blue and the faded state of transparent in the ZnSO4 liquid electrolyte, has excellent visible light modulation performance, the light modulation range at 633 nm is 70 - 95%, the coloring response time is 5 - 10 s, and the fading response time is 2 - 6 s.

[0023] The niobium-doped tungsten oxide electrochromic film has a relatively high coloring voltage and a relatively low fading voltage, and realizes complete coloring and fading at 0 V and 1.2 V respectively.

[0024] The niobium-doped tungsten oxide electrochromic film has relatively high cycle stability. After 2000 cycles, the light modulation of the niobium-doped tungsten oxide film of the present invention at 633 nm is still 74%, about 80% of the initial state.

[0025] The niobium-doped tungsten oxide electrochromic film has good energy storage ability. In the current density range of 0.1 to 0.5 mA cm -2 in the potential window of 0 to 1.2 V, with 1 M Zn 2+ aqueous solution as the electrolyte and the film as the cathode, it shows a constant current charge-discharge characteristic and has a relatively high charge capacity, and its discharge capacity is as high as 100 mAh m -2 above.

[0026] The present invention also provides the application of the above niobium-doped tungsten oxide bifunctional electrochromic energy storage material in a zinc electrochromic device.

[0027] The present invention also provides a zinc electrochromic device, which includes a Zn sheet, a ZnSO4 electrolyte, and an electrochromic material layer; wherein, the electrochromic material layer is the above-mentioned niobium-doped tungsten oxide bifunctional electrochromic energy storage material.

[0028] According to the above solution, the concentration of the ZnSO4 electrolyte is 0.8 - 1.2 mol / L.

[0029] The beneficial effects of the present invention are as follows: 1. The present invention provides a preparation method of a niobium-doped tungsten oxide bifunctional electrochromic energy storage material. By using the magnetron sputtering method, with niobium and tungsten oxide as target materials respectively, a flat and uniform amorphous niobium-doped tungsten oxide electrochromic thin film is obtained by controlling the appropriate ratio of argon-oxygen mixed gas and sputtering time. The thin film is composed of loose nanoparticles and has many cracks dozens of nanometers wide on the surface. Its cross-sectional morphology presents a columnar structure, effectively improving the electrochromic response speed of the niobium-doped tungsten oxide thin film. At the same time, it has a high transmittance in the bleached state, an optical modulation amplitude, a charge capacity, a thin film coloring efficiency, and an electrochemical cycle stability, and also has a low color change driving voltage and good energy storage capacity, showing great application potential in the field of energy storage.

[0030] 2. The niobium-doped tungsten oxide bifunctional electrochromic energy storage material of the present invention is applied to a zinc electrochromic energy storage device (ZEESD), integrating electrochromic and energy storage functions. It can intuitively indicate the working state through real-time color changes, and can realize reversible conversion between transparency and dark blue at a lower voltage, showing good application prospects in the fields of energy-saving buildings and intelligent electronics, such as electrochromic smart windows, anti-glare rearview mirrors, skylights of new energy vehicles, etc. Description of the Drawings

[0031] Figure 1 Visible light transmittance of the electrochromic energy storage materials prepared in Examples 2 - 3 and Comparative Example 1 of the present invention ( Figure 1 a) and response time ( Figure 1 b).

[0032] Figure 2 Visible light transmittance of the electrochromic energy storage materials prepared in Examples 1, 2 and 4 of the present invention ( Figure 2 a) and response time ( Figure 2 b).

[0033] Figure 3 Surface of the niobium-doped tungsten oxide electrochromic thin film prepared in Example 1 of the present invention ( Figure 3 a) and cross-sectional SEM image ( Figure 3 b).

[0034] Figure 4XRD pattern of the niobium-doped tungsten oxide electrochromic film prepared in Example 1 of the present invention.

[0035] Figure 5 Energy storage performance spectrum of the niobium-doped tungsten oxide electrochromic film prepared in Example 1 of the present invention.

[0036] Figure 6 For the Zn assembled in the embodiments of the present invention 2+ Electrochromic energy storage device spectrum; where Figure 6 a is the visible light transmittance of the device in the colored and faded states; Figure 6 b is the real-time transmittance response of the device at 633 nm visible light under 0 V (colored state) and 1.2 V (faded state) and its corresponding i-t curve.

[0037] Figure 7 For the application of the niobium-doped tungsten oxide prepared in Example 1 of the present invention to an electrochromic device, Zn 2+ Performance spectrum of the electrochromic energy storage device (ZEESD). Detailed implementation manners

[0038] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention. The test methods without specific conditions noted in the following embodiments are generally in accordance with conventional conditions.

[0039] Example 1 The preparation method of the niobium-doped tungsten oxide electrochromic film in this example specifically includes the following steps: S1. The conductive transparent ITO substrate is ultrasonically cleaned with acetone, ethanol and deionized water for 15 min in sequence, dried with N2 gas and then placed on the sputtering workpiece; S2. The ITO substrate in S1 is placed on the substrate tray in the vacuum chamber of the PD-400 high-vacuum magnetron sputtering coating machine, and the vacuum is pumped to 8×10 -4 Pa; S3. Place the niobium target and tungsten trioxide target on the DC sputtering target position and RF sputtering target position in the vacuum chamber of the magnetron sputtering equipment respectively. Adjust the substrate rotation speed to 10 r / min and the substrate temperature to 25 °C. Introduce oxygen and argon at rates of 3 sccm and 60 sccm respectively, control the working pressure at 1.5 Pa, adjust the DC sputtering power and RF sputtering power to 50 W and 80 W respectively, and sputter for 90 min to deposit a niobium-doped tungsten oxide film with a thickness of 425 nm on the transparent conductive glass substrate, obtaining a niobium-doped tungsten oxide bifunctional electrochromic energy storage material. The purity of the niobium target is 99.99%, the thickness is 5 mm, the purity of the tungsten trioxide target is 99.99%, the thickness is 3 mm, and the area of both is 76.2 mm 2 . The atomic ratio of niobium to tungsten in the niobium-doped tungsten oxide film is about 2:7.

[0040] Example 2 This example is basically the same as that of Example 1, except that the sputtering time is 60 min.

[0041] Example 3 This example is basically the same as that of Example 1, except that the rate of argon is 60 sccm; the rate of oxygen is 2 sccm, argon:oxygen = 30:1, and the sputtering time is 60 min.

[0042] Example 4 This example is basically the same as that of Example 1, except that the sputtering time is 120 min.

[0043] Comparative Example 1 This comparative example is basically the same as that of Example 1, except that the rate of argon is 60 sccm; the rate of oxygen is 6 sccm, argon:oxygen = 10:1 (rate ratio), and the sputtering time is 60 min.

[0044] Perform spectral scanning and in-situ electrochemistry-optics tests on the films of the above Examples 1-4 and Comparative Example 1 respectively to obtain visible light transmittance spectra and in-situ optical response spectra, refer to Figure 1 and Figure 2 . Among them: Figure 1 are the electrochromic visible light transmittance (a) and response time (b) at different gas ratios (argon:oxygen) during the magnetron sputtering reaction in Examples 2-3 and Comparative Example 1. The figure shows that the optical modulation ranges of the films in Comparative Example 1 and Examples 2-3 are 38.91% (10:1), 83.99% (20:1), and 74.89% (30:1) respectively; the response times are 3 s / 9 s, 2 s / 8 s, and 3 s / 10 s respectively, where the former is the fading time and the latter is the coloring time. Figure 2Electrochromic visible light transmittance (a) and response time (b) of the thin films obtained at different sputtering times in Examples 2, 1, and 4; as shown in the figure: the optical modulation ranges of the thin films in Examples 2, 1, and 4 are 83.99% (60 min), 93.1% (90 min), and 91.36% (120 min), respectively; the response times are 2 s / 8 s, 4 s / 5 s, and 6 s / 10 s, respectively. It can be seen that Examples 1-4 all exhibit good optical modulation performance and fast coloring and fading response times, and also have a high coloring efficiency. Among them, the coloring efficiency of the thin film obtained in Example 1 at 633 nm is 75.02 cm 2 / C.

[0045] Figure 3 Surface and cross-sectional SEM images of the niobium-doped tungsten oxide electrochromic thin film prepared in Example 1. As Figure 3 seen from a, the niobium-doped tungsten oxide thin film shows a uniform and smooth morphology, consisting of loose nanoparticles, and there are many cracks dozens of nanometers wide on the surface. This structure provides a large number of channels and reaction sites for the rapid movement of Zn 2+ and helps the insertion and extraction of Zn 2+ , enhancing the cycling ability. The cross-sectional SEM image of the niobium-doped tungsten oxide thin film is shown in Figure 3 b, presenting a columnar structure with a thickness of about 425 nm, uniformly deposited on the ITO surface and tightly attached.

[0046] Figure 4 XRD pattern of the niobium-doped tungsten oxide electrochromic thin film prepared in Example 1. It can be seen that the prepared electrochromic thin film is in an amorphous structure, which is beneficial to the rapid response of electrochromism.

[0047] The amorphous niobium-doped tungsten oxide electrochromic thin film prepared in Example 1 of the present invention has a low color change driving voltage: at 0 V, the transmittance at 633 nm is 3.11%; at 1.2 V, the transmittance at 633 nm is 96.21%, achieving full coloring and fading at 0 V and 1.2 V, respectively.

[0048] The cycling performance of the niobium-doped tungsten oxide electrochromic thin film prepared in Example 1 of the present invention was tested by in-situ chronoamperometry, and the applied voltage was switched between 0 and 1.2 V, with each cycle time being 20 s. The results show that the thin film has good cycling performance. After 2000 cycles, the optical modulation of the thin film at 633 nm is still 74%, about 80% of the initial state.

[0049] The niobium-doped tungsten oxide electrochromic thin film prepared in Example 1 of the present invention has high energy storage performance (please refer to Figure 5 ). At 0.1 to 0.5 mAcm -2Within the current density range, within the potential window of 0 to 1.2 V, the thin film cathode exhibits a constant current charge-discharge characteristic. In 1 M Zn 2+ electrolyte, the discharge capacity of the thin film is as high as 100 mAhm -2 . The thin film shows strong reversibility under the constant current charge-discharge conditions of 0 - 1.2 V, indicating its application potential in the energy storage field.

[0050] The niobium-doped tungsten oxide prepared in Example 1 of the present invention is applied to an electrochromic device to assemble a Zn 2+ electrochromic energy storage device (ZEESD), which consists of a Zn metal anode, 1 M ZnSO4 liquid electrolyte, and an electrochromic thin film. The optical modulation range of this device at 633 nm is 76.42% (please refer to Figure 6 a), and the coloring and bleaching switching times are 8 s and 9 s respectively under the conditions of 0 V and 1.2 V (please refer to Figure 6 b), and the color display efficiency CE is 80.02 cm 2 / C. Please refer to Figure 7 .

[0051] The above are only the preferred embodiments of the present invention, and it does not thereby limit the protection scope of the present invention. For those skilled in the art, the present invention can have various changes and modifications. All changes, modifications, substitutions, integrations, and parameter changes made to these embodiments by conventional substitutions or capable of achieving the same functions without departing from the principle and spirit of the present invention fall within the protection scope of the present invention.

Claims

1. A method for preparing a niobium-doped tungsten oxide bifunctional electrochromic energy storage material, characterized in that: The following steps are involved: By adopting magnetron sputtering method, niobium and tungsten oxide are used as target materials respectively, and a mixed gas of inert gas and oxygen is used as working gas, an amorphous niobium-doped tungsten oxide film is deposited on the surface of a conductive glass substrate to obtain a niobium-doped tungsten oxide bifunctional electrochromic energy storage material; wherein: In the mixed gas of inert gas and oxygen, the volume ratio of inert gas to oxygen is 15-30:1; The sputtering time is 60-120min.

2. The preparation method according to claim 1, characterized in that: In the magnetron sputtering method, the sputtering modes are direct current sputtering and radio frequency sputtering; wherein the target material of direct current sputtering is niobium, and the target material of radio frequency sputtering is tungsten trioxide.

3. The preparation method according to claim 2, characterized in that: The DC sputtering power is 10-80W, and the RF sputtering power is 50-200W.

4. The preparation method according to claim 1, characterized in that: The atomic ratio of niobium to tungsten in the niobium-doped tungsten oxide film is 0.15-0.9:

1.

5. The preparation method according to claim 1, characterized in that: The feeding rates of oxygen and inert gas are 2-8 sccm and 50-80 sccm, respectively.

6. The preparation method according to claim 1, characterized in that: The temperature of the conductive glass substrate is 25-200°C, and the vacuum degree of the reaction chamber is 1×10 -4 Pa-1×10 -3 Pa; The sputtering gas pressure is 0.5-2.0Pa.

7. A niobium-doped tungsten oxide bifunctional electrochromic energy storage material prepared by the preparation method according to any one of claims 1 to 6.

8. The niobium-doped tungsten oxide bifunctional electrochromic energy storage material according to claim 7, characterized in that: The niobium-doped tungsten oxide bifunctional electrochromic energy storage material has a thickness of 300-500nm, a flat and uniform film, and is composed of loose nanoparticles. There are a large number of cracks with a width of tens of nanometers on the surface, and the cross-sectional morphology is a columnar structure.

9. Use of the niobium-doped tungsten oxide bifunctional electrochromic energy storage material according to claim 7 in a zinc electrochromic device.

10. A zinc electrochromic device, comprising a Zn sheet, a ZnSO4 electrolyte and an electrochromic material layer; characterized in that: The electrochromic material layer is the niobium-doped tungsten oxide bifunctional electrochromic energy storage material as claimed in claim 7.

Images