An electrochromic energy storage device with anti-self-discharge

Abstract

The present invention discloses an electrochromic energy storage device with anti-self-discharge properties. The device comprises a transparent conductive glass substrate layer and, from bottom to top, an ion storage layer, a first nanofunctional layer, an ionic electrolyte layer, a second nanofunctional layer, an electrochromic layer, and a top transparent conductive layer. The electrochromic energy storage device of the present invention introduces nanofunctional layers on both sides of the ionic electrolyte layer to modify the electrode / electrolyte interface, effectively suppressing ion self-diffusion and achieving low self-discharge in the device. The electrochromic energy storage device of the present invention has broad application prospects in fields such as smart windows, intelligent electronic products, and micro-energy harvesting and storage.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrochromic devices and relates to an electrochromic energy storage device, in particular to an electrochromic energy storage device with the function of inhibiting self-discharge. Background Art

[0002] Electrochromism refers to the phenomenon in which the optical properties of a material or device undergo a stable and reversible color change under the action of an external electric field, which manifests itself as a reversible change in color and transparency.

[0003] The ability of electrochromic devices to change color in response to external stimuli gives them distinct advantages in certain applications. Currently, electrochromic technology is widely used in a wide range of fields, including smart windows, aerospace vehicles, automotive rearview mirrors, smart displays, information storage, and sensors.

[0004] Electrochromic devices share similarities with supercapacitors / batteries in terms of electrode materials, device structure, and reaction kinetics, and are also known as "rocking chair" lithium-ion batteries (Yang et al., Materials Today, 19(2016):394-402.; Wang et al., Materials Science & Engineering R, 140(2020):100524.). Therefore, electrochromic technology can be integrated into supercapacitors / batteries to construct electrochromic energy storage devices, allowing consumers to directly estimate the operating status of these electrochromic energy storage devices through visible color changes, effectively avoiding irreversible damage to device performance caused by external factors. These excellent properties make electrochromic energy storage devices have broad application prospects in smart electronic products.

[0005] Current electrochromic energy storage devices typically consist of a five-layer structure: a bottom transparent electrode / ion storage layer / ion electrolyte layer / electrochromic layer / top transparent electrode. They are a typical optoelectronic multifunctional device. When a certain positive or negative voltage is applied across the device's electrodes, ions and free electrons continuously move within and outside the device, enabling the device to change color and store energy (Lu et al., Phys. Chem. Chem. Phys., 2021, 23, 141-26).

[0006] However, due to the high electronic conductivity of the electrolyte within electrochromic energy storage devices or defects at the electrode / electrolyte interface, they generally exhibit severe self-discharge behavior, a phenomenon in which the open-circuit potential spontaneously decreases after being fully charged and left standing for a long time. The existence of this self-discharge problem not only affects the energy storage efficiency and optical memory effect of the entire device, but also hinders the precise control of its optical properties and cyclic stability, thus severely restricting its practical application in intelligent microelectronic products. Therefore, the development of an anti-self-discharge electrochromic energy storage device that can suppress this self-discharge process is of great significance. Summary of the Invention

[0007] The purpose of the present invention is to provide an anti-self-discharge electrochromic energy storage device to solve the self-discharge problem that is prevalent in electrochromic energy storage devices.

[0008] To achieve the above-mentioned purpose of the invention, the present invention provides an electrochromic energy storage device capable of suppressing the self-discharge process of the device. The device includes a transparent conductive glass substrate layer, and an ion storage layer, an ion electrolyte layer, an electrochromic layer and a top transparent conductive layer located from bottom to top on the transparent conductive glass substrate layer. The device also includes a first nanofunctional layer arranged between the ion storage layer and the ion electrolyte layer, and a second nanofunctional layer arranged between the ion electrolyte layer and the electrochromic layer.

[0009] Specifically, in the electrochromic energy storage device described in the present invention, the ion storage layer material is a MnO2 nanosheet film.

[0010] More specifically, the MnO2 nanosheet film of the present invention is formed by depositing it on a transparent conductive glass substrate layer using an electrochemical deposition method.

[0011] Specifically, in the electrochromic energy storage device of the present invention, the ionic electrolyte layer material is any one of inorganic LiNbO3 or LiTaO3 thin films. The ionic electrolyte layer material is used to provide the lithium ions required for color change / energy storage.

[0012] Specifically, in the electrochromic energy storage device of the present invention, the electrochromic layer material is any one of a WO3 thin film or a MoO3 thin film.

[0013] The color change / energy storage characteristics of the electrochromic energy storage device of the present invention are achieved based on the redox reaction of lithium ions in the ion storage layer and the electrochromic layer.

[0014] Furthermore, the electrochromic energy storage device of the present invention blocks the spontaneous diffusion of lithium ions in a static state of the electrochromic energy storage device by means of the nanofunctional layer composed of the first nanofunctional layer and the second nanofunctional layer.

[0015] The materials used to constitute the first nano-functional layer and the second nano-functional layer are Ta2O5, ZrO2 or Si3N4 thin films respectively.

[0016] Furthermore, the materials constituting the first nano-functional layer and the second nano-functional layer of the electrochromic energy storage device of the present invention may be the same or different.

[0017] However, more preferably, the first nano-functional layer and the second nano-functional layer of the electrochromic energy storage device of the present invention are made of the same material.

[0018] Furthermore, in order to better achieve the function of blocking the spontaneous diffusion of lithium ions, the thickness of the first nano-functional layer and the second nano-functional layer is preferably 40-50 nm.

[0019] More specifically, in the electrochromic energy storage device of the present invention, the conductive material coated on the transparent conductive glass substrate layer is an FTO film or an ITO film.

[0020] More specifically, in the electrochromic energy storage device of the present invention, the top transparent conductive layer material is an ITO film.

[0021] Furthermore, the present invention also provides a method for preparing the anti-self-discharge electrochromic energy storage device, which is to prepare a MnO2 nanosheet film as an ion storage layer on a transparent conductive glass substrate by electrochemical deposition, and then use a magnetron sputtering method to sequentially prepare a first nanofunctional layer, an ion electrolyte layer, a second nanofunctional layer, an electrochromic layer and a top transparent conductive layer to obtain the anti-self-discharge electrochromic energy storage device.

[0022] The specific method of electrochemically depositing the MnO2 nanosheet film on the transparent conductive glass substrate is to place the transparent conductive glass in a MnO2 deposition solution for electrochemical deposition to obtain the MnO2 nanosheet film, and then heat-treat the obtained MnO2 nanosheet film at 180°C.

[0023] The anti-self-discharge electrochromic energy storage device prepared by the present invention can be applied to technical fields such as smart windows, smart electronic products (smart bracelets, smart displays, etc.) and micro energy collection and storage.

[0024] The anti-self-discharge electrochromic energy storage device of the present invention adopts the strategy of introducing nano-functional layers on both sides of the ionic electrolyte layer to modify the electrode / electrolyte interface, effectively suppressing the self-diffusion process of ions, thereby constructing an electrochromic energy storage device with a low self-discharge rate of only 12.6mV h -1 , achieving a low self-discharge process of the device.

[0025] The anti-self-discharge electrochromic energy storage device constructed by the present invention has an ultra-thin all-inorganic structure, which not only has a low self-discharge rate but also has a high volume capacity of 77.3F cm -3 , the optical modulation amplitude is wide (about 41.2% at 550nm).

[0026] The present invention adopts a method combining electrochemical deposition and magnetron sputtering to prepare an electrochromic energy storage device, which has the advantages of being green and energy-saving and having a high degree of controllability of the process flow. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is the electrochromic and energy storage performance test curve of MnO2 thin film electrode.

[0028] Figure 2 Schematic diagram of the transmittance of the electrochromic energy storage device in Example 1 at different voltages in the faded state.

[0029] Figure 3 Schematic diagram of the volume capacity change of the electrochromic energy storage device of Example 1 at different temperatures.

[0030] Figure 4 It is a parameter curve for testing the self-discharge behavior of electro-energy storage devices.

[0031] Figure 5 1 is the open circuit voltage curve of the electrochromic energy storage device in Example 1 at different initial applied voltages.

[0032] Figure 6 1 is the optical memory curve of the electrochromic energy storage device in Example 1 at different temperatures.

[0033] Figure 7 3 is a comparison chart of the open circuit voltage of the electrochromic energy storage device of Example 1 and the control example.

[0034] Figure 8 3 is a comparison chart of the optical memory effects of the electrochromic energy storage device of Example 1 and the control example. DETAILED DESCRIPTION

[0035] The following embodiments are only used to more clearly illustrate the technical solutions of the present invention so that those skilled in the art can better understand and utilize the present invention, but are not intended to limit the scope of protection of the present invention.

[0036] Unless otherwise specified, the production processes, experimental methods or detection methods involved in the embodiments of the present invention are all conventional methods in the prior art, and their names and / or abbreviations are conventional names in the field and are very clear and unambiguous in the relevant fields of use. Those skilled in the art can understand the conventional process steps based on the names and apply the corresponding equipment to implement them according to conventional conditions or the conditions recommended by the manufacturer.

[0037] The various instruments, equipment, raw materials or reagents used in the embodiments of the present invention are not particularly limited in their sources and are all conventional products that can be purchased through regular commercial channels or prepared according to conventional methods well known to those skilled in the art.

[0038] The various electrochromic energy storage devices based on anti-self-discharge provided in the following embodiments of the present invention are specifically prepared according to the following methods.

[0039] The FTO transparent conductive glass substrate to be used was ultrasonically cleaned with alcohol and acetone for 30 minutes respectively, rinsed with deionized water, and finally dried with a hair dryer for later use.

[0040] Weigh 2.84 g of sodium sulfate and 4.90 g of manganese acetate, add them to 200 mL of deionized water, and stir until they are completely dissolved to obtain a MnO2 deposition solution.

[0041] Using Ag / AgCl as the reference electrode, platinum electrode as the counter electrode, and FTO transparent conductive glass as the working electrode, a three-electrode system electrochemical workstation was used to carry out electrochemical deposition on the FTO transparent conductive glass in a MnO2 deposition solution. The deposition was carried out for 300s at a polarization current of 2.5 mA to obtain a MnO2 thin film electrode deposited on the FTO transparent conductive glass.

[0042] The FTO transparent conductive glass deposited with the MnO2 thin film electrode was placed in a heat treatment equipment, and the heating rate and cooling rate of the heat treatment equipment were set to 2°C / min. In an Ar atmosphere, the temperature was first raised to 100°C and kept for 30 minutes, then raised to 140°C and kept for 30 minutes, and finally raised to 180°C and kept constant for 2 hours. Then the temperature began to drop, first to 140°C and kept for 30 minutes, then to 100°C and kept for 30 minutes, and finally naturally cooled to room temperature to complete the heat treatment of the MnO2 thin film electrode.

[0043] The MnO2 thin film electrode obtained by heat treatment has excellent electrochromic and energy storage properties. Figure 1The corresponding test curve is given. It can be seen that during the electrochemical reaction of constant current charge and discharge (the current remains unchanged, and the voltage changes with time), the optical transmittance of the MnO2 thin film electrode changes repeatedly and stably and reversibly in the range of 19.1% (colored state) to 47.5% (faded state), and the optical modulation amplitude can reach 28.4%, indicating that the MnO2 thin film electrode has stable and reversible electrochromic properties during the electrochemical reaction process.

[0044] The above-mentioned heat-treated FTO transparent conductive glass deposited with MnO2 thin film electrodes is placed in the vacuum chamber of a magnetron sputtering coating machine. The magnetron sputtering method is used to sequentially deposit a first nano-functional layer, an ionic electrolyte layer, a second nano-functional layer, an electrochromic layer, and a top transparent conductive layer on the surface of the MnO2 thin film electrode according to the device structure designed in each embodiment.

[0045] The magnetron sputtering process conditions of using Ta2O5, ZrO2 or Si3N4 thin films as the first or second nano-functional layer materials are controlled as follows.

[0046] Ta2O5 nano-functional layer was prepared by DC reactive magnetron sputtering of tantalum target: background vacuum degree 5×10 -4 Pa, the ratio of pure argon / pure oxygen is 2:1, so that the working pressure reaches 0.5Pa, the sputtering power is 150W, the distance between the target and the substrate is 15cm, and the sputtered film thickness is 50nm of Ta2O5 nano-functional layer.

[0047] ZrO2 nano-functional layer was prepared by DC reactive magnetron sputtering of metal zirconium target: background vacuum degree 5×10 -4 Pa, the ratio of pure argon / pure oxygen is 2:1, so that the working pressure reaches 1.0 Pa, the sputtering power is 200 W, the distance between the target and the substrate is 15 cm, and the sputtered film thickness is 40 nm of ZrO2 nano-functional layer.

[0048] Si3N4 nano-functional layer was prepared by DC reactive magnetron sputtering of pure silicon target: background vacuum degree 5×10 -4 Pa, pure nitrogen was introduced to make the working pressure reach 2.0 Pa, the sputtering power was 200 W, the distance between the target and the substrate was 10 cm, and the sputtered film thickness was 40 nm of Si3N4 nano-functional layer.

[0049] The magnetron sputtering process conditions of using LiNbO3 or LiTaO3 thin films as the ionic electrolyte layer material are controlled as follows.

[0050] The LiNbO3 ion electrolyte layer was prepared by radio frequency reactive magnetron sputtering of pure LiNbO3 ceramic target: the background vacuum was 5×10 -4Pa, 100 sccm pure argon and 5 sccm pure oxygen were introduced to make the working pressure reach 0.9 Pa, the sputtering power was 200 W, the distance between the target and the substrate was 7 cm, and the sputtered film thickness was 350 nm of LiNbO3 ion electrolyte layer.

[0051] The LiTaO3 ion electrolyte layer was prepared by radio frequency reactive magnetron sputtering of pure LiTaO3 ceramic target: the background vacuum was 5×10 -4 Pa, 100 sccm pure argon and 5 sccm pure oxygen were introduced to make the working pressure reach 1.5 Pa, the sputtering power was 250 W, the distance between the target and the substrate was 7 cm, and the sputtered film thickness was 450 nm of LiTaO3 ion electrolyte layer.

[0052] The magnetron sputtering process conditions of WO3 thin film as electrochromic layer material are as follows: WO3 electrochromic layer is prepared by reactive magnetron sputtering with metal tungsten target, and the background vacuum is 5×10 -4 Pa, the ratio of pure argon / pure oxygen is 3:1, so that the working pressure reaches 2.0 Pa, the sputtering power is 150 W, the distance between the target and the substrate is 15 cm, and the sputtered film thickness is 550 nm of WO3 electrochromic layer.

[0053] The top transparent conductive layer was prepared by reactive magnetron sputtering of pure indium tin oxide ceramic target: the background vacuum was 5×10 - 4 Pa, 100 sccm pure argon and 1 sccm pure oxygen are introduced to make the working gas pressure reach 0.6 Pa, the sputtering power is 100 W, the distance between the target and the substrate is 15 cm, and the sputtered film thickness is 100 nm of ITO transparent conductive layer.

[0054] After the above preparation process, the ion storage layer, the first nano-functional layer, the ion electrolyte layer, the second nano-functional layer, the electrochromic layer, and the top transparent conductive layer were deposited in sequence on the transparent conductive FTO glass to prepare an anti-self-discharge electrochromic energy storage device.

[0055] The device was removed from the vacuum chamber, and the burrs around it were removed. Copper tape was attached to both ends of the bottom and top transparent conductive layers to lead out the positive and negative test electrodes. The electrodes were attached to a high and low temperature control plate with holes and placed in a UV-visible spectrophotometer. The positive and negative test electrodes led out of the device were connected to the electrochemical workstation for in-situ testing and characterization.

[0056] Example 1.

[0057] The device structure of the anti-self-discharge electrochromic energy storage device prepared in this embodiment includes, from bottom to top: FTO transparent conductive glass; MnO2 thin film layer, 400nm thick; Ta2O5 thin film layer, 50nm thick; LiNbO3 thin film layer, 350nm thick; Ta2O5 thin film layer, 50nm thick; WO3 thin film layer, 550nm thick; ITO transparent conductive layer, 100nm thick.

[0058] The color-changing energy storage and self-discharge properties of the anti-self-discharge electrochromic energy storage device were in situ tested using an electrochemical workstation and UV-visible spectrophotometer.

[0059] from Figure 2 The diagram of the device's full-spectrum transmittance during color fading shows that the spectral transmittance of the electrochromic energy storage device in the visible light range gradually changes under different voltages. As the voltage increases, the device continues to color, accompanied by a gradual decrease in its transmittance in the visible light range. Under different voltages, the device's transmittance in the visible light range exhibits significant modulation amplitude. For example, as the device transitions from the faded state to the 1.8V colored state, its optical modulation amplitude at 550nm reaches approximately 41.2%.

[0060] Figure 3 This figure shows how the volume capacitance of an electrochromic energy storage device changes with scan speed at different temperatures. As the scan speed increases, the volume capacitance of the electrochromic device decreases; as the operating temperature continues to rise, the volume capacitance of the electrochromic device increases. The maximum capacitance of the device at -20°C, 25°C, and 60°C is 49.4 F cm-1, respectively. -3 、61.6F cm -3 and 77.3F cm -3 When the operating temperature is 60℃, as the scanning speed increases from 5mV s -1 Increase to 200mV s -1 , the volume capacitance of the device can still reach 27.4F cm -3 , with better capacity retention effect.

[0061] Figure 4 The parameter curves used to test the self-discharge behavior of electrochemical energy storage devices are presented. Specifically, the prepared device is connected to an electrochemical workstation and fully charged using a constant current method (i.e., to a certain rated voltage). After maintaining this voltage for a period of time, the voltage is removed from the device while recording the device's open-circuit potential.

[0062] Figure 5 To adopt Figure 4The parameters shown in the figure are used to test the open-circuit voltage curves of the electrochromic energy storage device prepared above at different initial applied voltages. It can be seen that after 10 hours of self-discharge at different initial applied voltages, the open-circuit potential of the electrochromic energy storage device can still maintain above 90% of the initial value, indicating that the prepared electrochromic energy storage device has a low self-discharge rate.

[0063] In order to further study the self-discharge behavior of electrochromic energy storage devices, the optical memory effect of the above-prepared devices at open circuit voltage was tested. Figure 2 This indicates that the device voltage can affect its transmittance. Therefore, changes in the open-circuit voltage during the device's self-discharge process will cause corresponding changes in its optical transmittance. The self-discharge performance of the device can be reflected by testing its optical memory effect.

[0064] Figure 6 The optical memory curves of the electrochromic energy storage device at different temperatures are presented. After the device is fully colored at -20°C, 25°C, and 60°C and left to stand for 10 hours, its optical transmittance recovers by only 7.8%, 9.8%, and 11.2%, respectively. The low optical transmittance recovery at different temperatures further demonstrates the device's excellent anti-self-discharge properties.

[0065] Comparison example.

[0066] The device structure of the electrochromic energy storage device prepared in this control example includes, from bottom to top: FTO transparent conductive glass; MnO2 thin film layer, 400nm thick; LiNbO3 thin film layer, 350nm thick; WO3 thin film layer, 550nm thick; ITO transparent conductive layer, 100nm thick.

[0067] The electrochromic energy storage device of this comparative example has the same structure and materials as those of Example 1 except that no Ta2O5 nano-functional layer is added on both sides of the ionic electrolyte layer.

[0068] Figure 7 and Figure 8 A comparison chart of the open circuit voltage and optical memory effect of the electrochromic energy storage device prepared in this control example and Example 1 is provided.

[0069] Figure 7 In the experiment, the two devices were simultaneously charged to 1.8V and then left to stand for 10 hours. The open circuit voltage of the electrochromic energy storage device in Example 1, which introduced Ta2O5 nano-functional layers on both sides of the electrolyte, was still able to maintain above 1.5V, while the open circuit voltage of the device in the control example, which did not introduce Ta2O5 nano-functional layers on both sides of the electrolyte, was reduced to about 0.4V. This fully proves that introducing nano-functional layers on both sides of the electrolyte of the device can greatly improve the self-discharge performance of the device.

[0070] Figure 8The comparison of the optical memory effects of the two devices further proves the above conclusion.

[0071] Example 2.

[0072] The device structure of the anti-self-discharge electrochromic energy storage device prepared in this embodiment includes, from bottom to top: FTO transparent conductive glass; MnO2 thin film layer, thickness 400nm; Si3N4 thin film layer, thickness 40nm; LiNbO3 thin film layer, thickness 350nm; Si3N4 thin film layer, thickness 40nm; WO3 thin film layer, thickness 550nm; ITO transparent conductive layer, thickness 100nm.

[0073] Example 3.

[0074] The device structure of the anti-self-discharge electrochromic energy storage device prepared in this embodiment includes, from bottom to top: FTO transparent conductive glass; MnO2 thin film layer, thickness 400nm; ZrO2 thin film layer, thickness 40nm; LiNbO3 thin film layer, thickness 350nm; ZrO2 thin film layer, thickness 40nm; WO3 thin film layer, thickness 550nm; ITO transparent conductive layer, thickness 100nm.

[0075] Example 4.

[0076] The device structure of the anti-self-discharge electrochromic energy storage device prepared in this embodiment includes, from bottom to top: FTO transparent conductive glass; MnO2 thin film layer, 400nm thick; Ta2O5 thin film layer, 50nm thick; LiTaO3 thin film layer, 450nm thick; Ta2O5 thin film layer, 50nm thick; WO3 thin film layer, 550nm thick; ITO transparent conductive layer, 100nm thick.

[0077] Example 5.

[0078] The device structure of the anti-self-discharge electrochromic energy storage device prepared in this embodiment includes, from bottom to top: FTO transparent conductive glass; MnO2 thin film layer, thickness 400nm; Si3N4 thin film layer, thickness 40nm; LiTaO3 thin film layer, thickness 450nm; Si3N4 thin film layer, thickness 40nm; WO3 thin film layer, thickness 550nm; ITO transparent conductive layer, thickness 100nm.

[0079] Example 6.

[0080] The device structure of the anti-self-discharge electrochromic energy storage device prepared in this embodiment includes, from bottom to top: FTO transparent conductive glass; MnO2 thin film layer, thickness 400nm; ZrO2 thin film layer, thickness 40nm; LiTaO3 thin film layer, thickness 450nm; ZrO2 thin film layer, thickness 40nm; WO3 thin film layer, thickness 550nm; ITO transparent conductive layer, thickness 100nm.

[0081] The above embodiments of the present invention do not describe all details in detail, nor do they limit the present invention to the above embodiments. Various changes, modifications, substitutions, and variations made by those skilled in the art without departing from the principles and purpose of the present invention are intended to be included within the scope of protection of the present invention.

Claims

1. An anti-self-discharge electrochromic energy storage device, comprising a transparent conductive glass substrate layer, and an ion storage layer, an ion electrolyte layer, an electrochromic layer, and a top transparent conductive layer located on the transparent conductive glass substrate layer from bottom to top, characterized in that It also includes a first nanofunctional layer arranged between the ion storage layer and the ion electrolyte layer, and a second nanofunctional layer arranged between the ion electrolyte layer and the electrochromic layer. The ion storage layer material is a MnO2 nanosheet film, and the material used to constitute the first nanofunctional layer and the second nanofunctional layer is one of Ta2O5, ZrO2 or Si3N4 films.

2. The electrochromic energy storage device according to claim 1, characterized in that The MnO2 nanosheet film is formed by depositing on a transparent conductive glass substrate layer using an electrochemical deposition method.

3. The electrochromic energy storage device according to claim 1, characterized in that The materials of the first nano-functional layer and the second nano-functional layer may be the same or different.

4. The electrochromic energy storage device according to claim 3, characterized in that The first nano-functional layer and the second nano-functional layer are made of the same material.

5. The electrochromic energy storage device according to claim 1, characterized in that The thickness of the first nano-functional layer and the second nano-functional layer is 40-50 nm.

6. The electrochromic energy storage device according to claim 1, characterized in that The ionic electrolyte layer material is any one of LiNbO3 or LiTaO3 thin films.

7. The electrochromic energy storage device according to claim 1, characterized in that The electrochromic layer material is any one of WO3 thin film and MoO3 thin film.

8. The electrochromic energy storage device according to claim 1, characterized in that The conductive material coated on the transparent conductive glass substrate layer is an FTO film or an ITO film, and the top transparent conductive layer material is an ITO film.

9. Use of the anti-self-discharge electrochromic energy storage device according to claim 1 in the preparation of smart windows, smart electronic products and micro energy collection and storage devices.

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