Application of multi-charge derivative based on naphthalimide in preparation of flowing electrochromic device

Abstract

The invention discloses application of a multi-charge derivative based on naphthalimide in a flowing electrochromic device, and belongs to the technical field of preparation of intelligent electrochromic devices. A plurality of charged functional groups are introduced into the derivative, the redox activity and the electrochromism performance are improved, the derivative serves as an active electrolyte to be combined with a flow battery framework and electrochromism, reversible conversion from a full-transparent state to a full-black state is achieved, and the derivative has the full-wave-band absorption characteristic. Compared with a traditional device, the flowing electrochromic device has the advantages that a molecular self-recovery mechanism is established by electrolyte flowing, and the cycle life is prolonged; large-area devices are uniformly colored; the functions of self-erasing light writing, light-driven energy storage and the like are achieved; the optical contrast of the device reaches 96%, the cycle exceeds 30,000 times, and the coloring efficiency is high. The building energy-saving simulation shows that the indoor temperature rise can be effectively inhibited under strong light, and the global energy-saving potential is remarkable. An innovative scheme is provided for a high-performance and low-cost electrochromic system, and the method has wide prospects in the fields of intelligent buildings, optical management and the like.

Description

Technical Field

[0001] This invention belongs to the field of intelligent color-changing device fabrication technology, specifically relating to the application of a class of multi-charge derivatives based on naphthalimide in the fabrication of flow electrochromic devices. Background Technology

[0002] With the acceleration of global urbanization, the contradiction between energy supply and demand is becoming increasingly prominent. Building energy consumption accounts for a significant portion of global total energy consumption, with approximately 50% lost through heat exchange via doors and windows. This not only exacerbates energy pressure but also results in substantial carbon emissions. Developing smart window materials with dynamic photothermal regulation capabilities has become an effective way to reduce building energy consumption. Among numerous technologies, electrochromic materials can reversibly adjust their optical properties through external stimuli, achieving dynamic management of solar radiation and demonstrating great potential in the field of energy-efficient buildings. Currently, electrochromic materials mainly include two major systems: inorganic and organic. Although inorganic electrochromic materials (such as tungsten trioxide WO3 and NiO) have excellent environmental stability and long cycle life, their preparation relies on complex, energy-intensive, and costly processes such as magnetron sputtering and vacuum evaporation, which restricts their application and promotion in large-area, flexible smart windows. In contrast, organic electrochromic materials (such as viologen derivatives, NDI derivatives, and polyaniline) offer a new technological path for developing low-cost, large-area smart window systems due to their advantages in molecular designability, good flexibility, and solution processability. These materials can be integrated with various substrates through processes such as coating and printing, showcasing unique application prospects.

[0003] Despite extensive research on organic electrochromic materials, several key issues remain to be addressed regarding their material systems and device structures. First, the optical modulation amplitude of existing electrochromic materials is generally limited, and systems capable of continuous modulation from a completely transparent state to a near-black state are still relatively rare. High contrast, especially the ability to switch to a completely black state, is crucial for smart windows in practical applications such as privacy protection and light-blocking adjustment. Second, the cyclic stability of electrochromic devices, particularly organic systems, remains a core challenge hindering their commercialization. Most organic electrochromic materials struggle to achieve tens of thousands of reversible switches while maintaining high performance, a significant gap compared to the long service life typically required for architectural windows. Furthermore, in the fabrication of large-area electrochromic devices, the decreased response speed and uneven coloring caused by uneven electric field distribution and prolonged ion transport paths are becoming increasingly prominent, severely impacting visual uniformity and user experience.

[0004] Among numerous organic electrochromic materials, naphthalimide (NDI) and its derivatives have shown broad application prospects in electrochromic, flow battery, and smart sensing fields due to their excellent redox activity and significant color change characteristics accompanying electron transfer. In recent years, research has focused on developing electrochromic materials with superior performance through strategies such as combining NDI units with metal-organic frameworks (MOFs), designing novel conjugated electrochromic groups, and constructing donor-acceptor-donor (DAD) electronic structures. However, the performance of existing material systems in terms of high optical contrast, long-term cycling stability, and large-area device fabrication has not yet reached ideal levels. This is partly due to the fact that the synthesis and modification of existing NDI materials often tend to construct supramolecular or macromolecular structures, which, while improving electrochromic performance, weaken the material's flexibility and processability. Furthermore, in traditional solid-state or gel devices, only NDI molecules at the electrode interface participate in the color-changing reaction, lacking an effective molecular turnover mechanism. This results in active sites continuously bearing electrochemical stress, making them prone to degradation and limiting the improvement of cycle life. Especially in large-area devices, limitations in electrode interfaces and ion transport kinetics further exacerbate performance degradation. Therefore, developing novel electrochromic systems that combine high contrast, long cycle life, and good process compatibility has become an urgent need. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide an application of a class of multi-charge derivatives based on naphthalimide in the preparation of flow electrochromic devices, so as to solve the technical problems of limited optical modulation amplitude, difficulty in achieving the transition from fully transparent to fully black state, insufficient cycle life of electrochromic devices, and uneven color change of large-area electrochromic devices.

[0006] To achieve the above objectives, the present invention employs the following technical solution: This invention provides the application of a class of multicharged derivatives based on naphthalimide in the preparation of flow electrochromic devices; The structural formula of the multicharged naphthalimide derivative is: ; Where n is the charge of the main molecule, n = 1~4; R is selected from methyl (-Me), 3-carboxypropyl (-PrCOO) - ), 3-hydroxy-2-hydroxypropyltrimethylammonium (-Pr-OH-N(Me)3) + ), 3-sulfonopropyl (-PrSO3) - ) or 3-trimethylammoniumpropyl (-Pr-N(Me)3 + ); X - Selected from Cl - ,Br - I- TFSI - OTf - or PF6 - ; The multi-charged naphthalimide derivative is the electrochromic active material in the electrolyte of the flow electrochromic device.

[0007] Preferably, the multicharged naphthalimide derivative is (NPr)2NDI or (DEx)2NDI.

[0008] Preferably, the preparation method of the above-mentioned multi-charged naphthalimide derivative is as follows: under inert gas protection, the precursor and XR are dissolved in an organic solvent, and the mixture is stirred and reacted at 95~115℃ for 20~40 h to obtain the multi-charged naphthalimide derivative; wherein in XR, R is selected from -Me, -PrCOO - -Pr-OH-N(Me)3 + -PrSO3 - or - Pr-N(Me)3 + ;X - Selected from Cl - ,Br - I - TFSI - OTf - or PF6 - ; The structural formula of the precursor is: ; Preferably, the molar ratio of the precursor to XR is 1:2.5 to 1:5.

[0009] Preferably, the organic solvent is N,N dimethylformamide, 1,4-dioxane, tetrahydrofuran, or acetonitrile.

[0010] Preferably, the reaction products are sequentially filtered, washed, and dried to obtain the target product.

[0011] This invention provides a flow electrochromic device, comprising: A smart window unit includes at least one pair of transparent substrates and a cavity formed by a spacer layer located between the transparent substrates; The fluid circulation system includes a cathode electrolyte storage tank, an anode electrolyte storage tank, connecting pipes, and a pump device; the cathode electrolyte storage tank and the anode electrolyte storage tank are connected to the cavity of the smart window unit through the connecting pipes, and form an electrolyte circulation loop under the drive of the pump device; The cathode electrolyte in the cathode electrolyte storage tank and / or the anolyte in the anolyte storage tank contain the multi-charged naphthalene diimide derivative as an electrochromic active substance.

[0012] The cathode electrolyte and / or anolyte further contain an electron compensation medium, wherein the molar ratio of the multi-charged naphthalimide derivative to the electron compensation medium is 1:1 to 1:10.

[0013] The electron compensation medium is selected from one or more of the following: disodium ethylenediaminetetraacetate, trisodium ethylenediaminetetraacetate, tetrasodium ethylenediaminetetraacetate, lactic acid, triethanolamine, and methanol.

[0014] The cathode electrolyte and / or anolyte also contain inorganic salts to improve the conductivity of the electrolyte. The inorganic salts dissociate in solution to generate additional charge carriers, reducing the overall resistance of the electrolyte and thus optimizing the uniformity of the electric field distribution within the smart window unit. During device operation, the high conductivity electrolyte ensures that ions can respond quickly to changes in external voltage, shortening the initiation and completion time of the electrochromic reaction and avoiding uneven coloring caused by local current density differences.

[0015] Preferably, the inorganic salt is sodium chloride.

[0016] The flow electrochromic device employs a symmetrical battery structure, wherein the cathode electrolyte and the anolyte both contain the same or different multi-charged naphthalimide derivatives.

[0017] This invention provides an application of the above-mentioned flow electrochromic device, which is used in building energy-saving windows to achieve dynamic control of visible light and solar radiation heat transmittance by adjusting the applied voltage.

[0018] This invention provides the application of the above-mentioned flow electrochromic device in the field of information display. The device is configured to realize optical writing and self-erasing functions by utilizing the synergistic effect of light illumination and electrolyte flow.

[0019] The present invention provides the application of the above-mentioned electrochromic device in the field of energy storage and power supply. The device can store electrical energy while undergoing photochromic reaction and can be used to power external electronic devices.

[0020] Preferably, a photovoltaic energy storage process is required before electrochromism, in which the anode electrolyte is exposed to sunlight for 24 hours, further transferring the electron discharge generated by the light to the cathode electrolyte.

[0021] Compared with the prior art, the present invention has the following beneficial effects: This invention provides the application of a multi-charged derivative based on naphthalimide in the fabrication of a flowing electrochromic device. The multi-charge design enables the molecule to possess higher electron delocalization and rapid ion migration capabilities, supporting broad-band absorption to achieve a complete black state transition. The regulation of the molecule's bulk charge n ensures a faster electron transfer rate, resulting in a quicker response time. The R group is selected to contain hydrophilic groups such as quaternary ammonium salts or sulfonates, enhancing the molecule's dispersion stability in the aqueous electrolyte and optimizing the redox potential. The selection of the X-anion regulates the electrolyte conductivity and ion migration rate, improving electrochemical response efficiency. This derivative is directly used as the electrochromic active material in the flowing electrolyte, utilizing liquid circulation to achieve dynamic renewal of the active molecule and electrode interface, avoiding the degradation caused by continuous electrochemical stress on interface molecules in traditional solid-state devices.

[0022] The electrochromic device provided by this invention uses a smart window unit as its core component to display color changes. The cavity in the middle of the substrate holds the electrolyte before and after the color change and also serves as the main reaction site during photochromism, ensuring basic functionality. The cathode electrolyte tank, anode electrolyte tank, connecting pipes, and pump device in the fluid circulation system work together. The pump drives the electrolyte to circulate within the system, allowing the active molecules involved in the reaction to detach from the electrode interface in a timely manner, avoiding continuous electrochemical stress and thus extending the device's cycle life. The anode electrolyte tank is connected to the smart window unit via a connecting pipe. The two ends of the energy window unit cavity are connected to form a closed loop, ensuring uniform flow of the electrolyte over a large area, eliminating uneven distribution caused by the elongation of ion transport paths, and achieving consistent coloring. By applying a voltage between the cathode electrolyte and the anolyte, the color change and fading of the anolyte are controlled to achieve the basic function of electrochromism. The cathode electrolyte and / or anolyte contain multi-charged naphthalene diimide derivatives as electrochromic active materials. These materials participate efficiently in redox reactions in a flowing environment, and their properties support the maintenance of stable color-changing performance during dynamic rotation. The fluid circulation system drives the electrolyte to continuously circulate in the closed loop and provides a site for electrochromic reactions. The intelligent window unit provides a display area and a photochromic reaction area. The active material achieves molecular rotation during flow. The three work together to ensure that active molecules are replaced by fresh molecules after the reaction, which not only relieves the stress at the electrode interface to improve stability but also ensures uniform ion transport over a large area to achieve consistent color changing.

[0023] Furthermore, the presence of the electron compensation medium in the electrolyte can provide or accept electrons in real time according to the electrochromic reaction process, compensating for the charge gap generated by the multi-charged naphthalimide derivative during the redox process, and preventing structural damage to the active molecules due to excessive oxidation or reduction. At the same time, the electron compensation medium can compensate for electrons in a timely manner during photochromism, which on the one hand improves the photochromic response time, and on the other hand avoids the charge imbalance of the entire system caused by the active molecules gaining electrons, as well as the irreversible chemical side reactions and material degradation caused by this. The setting of a molar ratio of 1:1 to 1:10 ensures that the concentration of the electron compensation medium is sufficient to cover the charge transfer requirements of the active material, while avoiding excessive introduction that would increase the ion migration resistance of the electrolyte or trigger new side reactions. Thus, while maintaining a high-efficiency color-changing response, it significantly reduces the accumulation of electrochemical stress at the electrode interface, providing a basic guarantee for the long-term stable operation of the device.

[0024] This invention provides an application that integrates a mobile electrochromic device into building energy-saving windows, utilizing a voltage regulation mechanism to achieve real-time management of light and heat transmittance, effectively alleviating the problem of high building energy consumption. By applying the mobile electrochromic device to the field of information display and utilizing the synergistic effect of light and electric field to achieve self-erasing light writing, it provides an information display method that allows for writing and automatic erasing without manual intervention. It not only possesses excellent electrochromic performance but also has multiple functions such as self-erasing light writing and light-driven energy storage. Among these, the light-driven energy storage function can power small electronic devices such as LEDs, demonstrating its potential application value in self-powered systems. This multi-functional integration greatly expands the application scenarios of electrochromic technology; it excels in building energy conservation, effectively blocking solar radiation heat and significantly reducing indoor temperature fluctuations. Its excellent thermal management characteristics help maintain a comfortable indoor thermal environment and significantly reduce building cooling energy consumption. It exhibits stable energy-saving benefits under different climatic conditions, providing reliable technical support for green buildings.

[0025] The synthetic route using the naphthalimide derivative is simple, the raw materials are readily available, and the cost is low. Furthermore, the combination of the flow battery architecture and the electrochromic device is easy to scale up for production. In this case study, a large-scale device of 50×50 cm² has been successfully fabricated, verifying its feasibility for large-scale production and providing technical support for industrialization. Attached Figure Description

[0026] Figure 1 This is a physical image of the flow color-changing device based on a multi-electron naphthalimide derivative prepared according to the present invention.

[0027] Figure 2The figures show the spectral changes of the molecules in Examples 1 and 2 of this invention before and after electrochromic and photochromic reactions, where a is the spectral change of (NPr)₂NDI before and after electrochromic reactions; b is the spectral change of (DEx)₂NDI before and after electrochromic reactions; c is the spectral change of (NPr)₂NDI before and after photochromic reactions; and d is the spectral change of (DEx)₂NDI before and after photochromic reactions.

[0028] Figure 3 The following are the spectral and data graphs for characterizing the performance of the electrochromic device in Embodiment 3 of the present invention, wherein a is the change in spectral transmittance of the device before and after color change; b is the in-situ spectral change of the device before and after color change; c is the coloring efficiency of the device; d is the memory effect of the device under power-off conditions; and e is the electrochromic cycle diagram of the device.

[0029] Figure 4 The images show the self-erasing light-removing writing device and related performance test results of this invention. Specifically, a and b are schematic diagrams of the self-erasing light-removing writing device; c is a photograph of a large-area device (50 cm × 50 cm) before and after color change; d is a photograph of a photovoltaic energy storage-driven power device (LED); e is the discharge curve of the photovoltaic energy storage-driven power device under different illumination times (minutes); f is a photograph of the sealed heat chamber used in the heat insulation effect test; and g shows the temperature changes of the sample group and the control group during the heat insulation test.

[0030] Figure 5 This is a diagram illustrating energy-saving effects on a global scale. In the diagram, a is a comparison of Singapore's energy consumption over 12 months of the year; b is a diagram illustrating the average annual reduction in carbon emissions and the average annual energy-saving rate of 15 representative cities. Detailed Implementation

[0031] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0032] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0033] The present invention will now be described in further detail with reference to the accompanying drawings: I. Precursors for preparing electrochromic materials It can be prepared by following the steps of the reaction equation:

[0034] Preferably, under inert gas protection, 1,4,5,8-naphthalenetetracarboxylic acid dianhydride and 3-dimethylaminopropylamine are added to the reactor, a solvent is added, the solution is heated to 110°C, and stirred for 24 h.

[0035] Preferably, the organic solvent used is toluene; After the reaction was completed, the product was filtered, washed with water and ethanol, and dried overnight in a vacuum drying oven to obtain yellow crystals, which were the precursor.

[0036] II. Preparation of the multi-charged naphthalimide derivative electrochromic material of the present invention The following reaction equation is used to prepare it:

[0037] In XR, R is selected from -Me, -PrCOO - -Pr-OH-N(Me)3 + -PrSO3 - or - Pr-N(Me)3 + Any of the substituents; X is selected from Cl, Br, I, TFSI, OTf, or PF6.

[0038] As one of the preferred embodiments, XR preferably uses chloromethane.

[0039] Under inert gas protection, the precursor and XR were added to the reaction vessel at an equivalent ratio of 1:2.5, an organic solvent was added, and the mixture was stirred at 110 °C for 24 h.

[0040] Preferably, DMF is used as the organic solvent.

[0041] After the reaction was complete, the mixture was cooled to room temperature. The mixture was filtered, and the solid was washed successively with cold DMF, acetone, and diethyl ether, and then dried under vacuum to obtain the solid.

[0042] The present invention will be further described in detail below with reference to specific embodiments and accompanying drawings: Example 1 This embodiment provides a multicharged naphthalene diimide derivative (NPr)2NDI, and the specific preparation steps are as follows: (1) Preparation of precursor Prepare a clean 100 mL side-mounted flask (dry it in an oven at 110℃ for at least 2 h before use). After drying, remove the flask and connect it to an inert gas protection device, continuously purging with inert gas (nitrogen). Add 1,4,5,8-naphthalenetetracarboxylic acid dianhydride (NTCDA) (1.00 g, 3.73 mmol), 3-aminopropanol (1.40 g, 18.64 mmol), and zinc acetate (2.40 g, 11.19 mmol) to the flask in sequence. Add 25 mL of pyridine as the reaction solvent, heat the solution to 110 ℃, and stir the reaction for 24 h. After the reaction is complete, vacuum distill the mixture to remove pyridine and obtain the crude product. Purify the crude product by silica gel chromatography using CH2Cl2:MeCN = 20:1 (V:V) as the mobile phase to obtain the precursor.

[0043] (2) Preparation of multicharged naphthalene diimide derivative (NPr)2NDI Prepare a clean 100 mL side-mounted flask (dry in an oven at 110℃ for at least 2 h before use). Under inert gas protection, add the precursor (1.00 g, 2.29 mmol) prepared in step (1) and 5 mL of chloromethanetetrahydrofuran solution (concentration 1.0 mol L) to the flask. 1 (NPr)₂NDI was reacted with 10 mL of N,N-dimethylformamide (DMF) and the solution was stirred and heated at 110 °C for 24 hours. After the reaction, the resulting suspension was cooled to room temperature, and the product was collected by vacuum filtration. The collected product was washed successively with DMF, acetone, and diethyl ether. The washed product was then vacuum dried overnight at 60 °C to obtain a grayish-white solid, which was (NPr)₂NDI, with a mass of 1.15 g, and a yield of 93.40%. The product was subjected to 1H NMR spectroscopy. 1 H NMR) and carbon nuclear magnetic resonance (NMR) 13 C NMR analysis: 1H NMR (400 MHz, Deuterium Oxide) δ 8.58(s, 4H), 4.24 (t, J = 7.0 Hz, 4H), 3.57-3.54 (m, 4H), 3.17 (s, 18H), 2.32-2.27(m, 4H). 13 C NMR (101 MHz, Deuterium Oxide) δ 164.01, 131.05, 125.94, 125.72, 64.04, 52.95, 37.69, 21.41. Electrochromic and photochromic reactions were performed on (NPr)₂NDI, respectively, and significant spectral changes were observed after electrolysis or illumination (see [reference]). Figure 2 (a and c).

[0044] Example 2 Based on Example 1, this embodiment provides a multicharged naphthalene diimide derivative (DEx)2NDI, and the specific preparation steps are as follows: Prepare a clean 100 mL side-mouth flask (dry it in an oven at 110℃ for at least 2 h before use). Under inert gas protection, add the precursor (1.00 g, 2.29 mmol) prepared in step (1) of Example 1, 3-chloro-2-hydroxypropyltrimethylammonium chloride (2.15 g, 11.45 mmol) and 30 mL of water to the flask. Stir and heat the solution at 120℃ for 24 hours. After the reaction is complete, add a mixed solvent (acetone and ethanol in a volume ratio of 1:5) to the resulting aqueous solution to precipitate the pure product. Filter the product and wash it three times with acetone. Then dry it under vacuum to obtain a white powder (DEx)2NDI. The product mass is 1.72 g, and the yield is calculated to be 92.38%. Perform nuclear magnetic resonance hydrogen spectroscopy on the obtained product (1H NMR spectrum). 1 H NMR) and carbon nuclear magnetic resonance (NMR) 13 C NMR analysis: 1 H NMR (400 MHz, D2O) δ 8.57 (s, 4H), 4.86-4.83 (t, J=7.3 Hz, 2H), 4.27-4.20 (m, 4H), 3.68-3.36 (m, 12H), 3.23-3.21(d, J=8.2 Hz, 12H), 3.20 (s, 18H), 2.35-2.21 (m, 4H). 13C NMR (101 MHz, D₂O) δ 163.93, 131.03, 125.94, 125.86, 67.50, 65.20, 63.37, 61.76, 54.34, 52.07, 37.55, 21.08. Electrochromic and photochromic reactions were performed on (DEx)₂NDI, respectively, revealing significant spectral changes in the molecule upon electrolysis or illumination (see [link to relevant documentation]). Figure 2 In the middle, b and d).

[0045] Example 3: A class of flow electrochromic devices based on multicharged derivatives of naphthalimide Based on Examples 1 and 2, a flow electrochromic device was prepared using the multi-charged naphthalene diimide derivative (DEx)2NDI obtained in Example 2 as the electrochromic material. The specific steps are as follows: Step 1: Assemble the flow electrochromic device; The flow electrochromic device of this invention mainly consists of four core components: an intelligent window unit, a circulating pump, an electrolyte storage tank, and a flow battery unit. These components are connected via Teflon tubing to form a complete circulation loop, as shown in the specific connection method below. Figure 1 As shown. After the device is assembled, a rigorous leak test is required. The specific steps are as follows: First, inject ultrapure water as the test medium into the system, and drive the liquid to circulate throughout the entire device using a circulation pump. Adjust the flow rate to the working flow rate (recommended range 5-50 mL / min) to ensure that the intelligent window unit is completely filled with liquid. After continuous circulation for 2 hours, carefully inspect all interfaces, seals, and connections to confirm that there are no leaks.

[0046] Step 2: Prepare and inject the electrochromic solution; After passing the sealing test, the ultrapure water in the system is completely drained, and then the prepared electrolyte is injected. The anolyte is a 1 M NaCl aqueous solution containing 0.01 M (DEx)₂NDI and 0.25 M EDTA-4Na, and the catholyte is a 0.1 M (DEx)₂NDI solution. The amount of electrolyte injected is determined according to the size of the smart window and the capacity of the storage tank, and the volume ratio of anolyte to catholyte is 1:2. The circulation pump is restarted and circulated at the working flow rate for 30 minutes to ensure that the electrolyte is fully mixed and to remove any residual air bubbles in the system. After completing the above preparations, the flow electrochromic device is ready for use. The entire assembly and testing process is carried out at room temperature, and all parts in contact with the electrolyte are made of corrosion-resistant materials to ensure the long-term stable operation of the device.

[0047] Step 3: Photochromic Pretreatment Before conducting the electrochromic test, the smart window area needs to undergo photochromic pretreatment: the smart window area is placed under light for 24 hours with the peristaltic pump turned on, so that the (DEx)2NDI molecules undergo photo-reduction and store electrons; then, the electrons are transferred to the cathode electrolyte through constant current discharge, providing sufficient electrons for subsequent electrochromic transfer.

[0048] Step 4: Performance Testing Systematic testing of the device's electrochromic performance confirmed its excellent optical modulation capability and cycling stability. (See Appendix) Figure 3 Spectroscopic tests showed that after applying a voltage of 0.5 V, the device exhibited significant absorption in both the visible light region (340-570 nm) and the near-infrared region (1000-1700 nm), achieving a reversible transition from completely transparent to completely black, with an optical contrast ratio of 96% at 485 nm. Figure 3 (a) Further in-situ spectral testing before and after electrochromism showed that the device still exhibits good reversibility after achieving a completely black state. Figure 3 (b) Cyclic performance testing further validated the effectiveness of the molecular self-recovery mechanism. After 30,000 consecutive color-to-bleach cycles, the device showed no significant degradation ( Figure 3 (c). Furthermore, the measured coloring efficiency of the device reached 737.4 cm²·C. - ¹( Figure 3 (d), and exhibits excellent memory characteristics under open-circuit conditions, with a transmittance decay rate of only 0.019‰ / h over 24 hours ( Figure 3 (e).

[0049] Example 4: Multi-application Expansion and Performance Verification 1. Self-erasing optical writing device See appendix Figure 4 By using the intelligent window unit of the flow-changing color device as a writing platform and a UV laser pen with a center wavelength of 395 nm and an output power of 50 mW as a controllable writing source, high-contrast text drawing and rapid erasure operations were successfully achieved. Figure 4 Figures a and b demonstrate its flexibility in image-based information encoding. This demonstration experiment fully verifies the feasibility of this system as a type of optically driven writing device with self-erasing characteristics, providing experimental evidence and technical support for its application in fields such as rewritable smart interfaces, dynamic display media, and optically controlled information storage.

[0050] 2. Fabrication and Performance Verification of Large-Area Devices To further expand the practical application potential of flow-changing color-changing devices, this invention successfully fabricated a large-scale intelligent color-changing window device with dimensions of 50 cm × 50 cm. This device can achieve reversible color change from a completely transparent state to a black state under both electrical stimulation (electrical application) and light stimulation (light illumination). Figure 4 (c) The color change is uniform and the contrast is high, demonstrating good large-scale preparation capability and practical application prospects.

[0051] 3. Performance Verification of Photovoltaic Energy Storage-Driven Energy Devices The potential of this device for light capture and power output was further explored. Potassium ferricyanide is a high-performance cathode electrolyte material for flow batteries. Therefore, this invention assembled a flow battery by combining the solution from the smart window after 1 hour of light exposure with potassium ferricyanide. A boost converter circuit was introduced to increase the voltage to 3V, successfully achieving stable lighting of the LED. Figure 4 (d) verified its feasibility as a light-driven energy device and demonstrated its potential in light capture and power output.

[0052] 4. Verification of actual thermal insulation performance Two sealed thermal boxes, each encased in foam insulation and covered with aluminum foil, were fitted with the intelligent color-changing window developed in this study and ordinary glass, respectively, as controls. Figure 4 (e). The experiment was conducted outdoors at a geographical location of 108.89°E, 34.23°N, with an ambient temperature of 35°C and an ultraviolet index of 5, to simulate a high-temperature, high-radiation environment in summer. Over time, the internal temperature of both types of windows increased, but the temperature rise was more significant in the ordinary glass group, while the temperature rise inside the device studied was relatively slow. After 30 minutes of irradiation, the internal temperature difference between the two reached 8°C (e). Figure 4 (f and g). This device can effectively slow down the rise in indoor temperature and reduce the heat load of buildings in high-temperature environments in summer, thereby helping to reduce the energy consumption of active cooling equipment such as air conditioners. It has significant potential for energy-saving applications, indicating that the smart color-changing window can effectively slow down the rise in indoor temperature and reduce the heat load of buildings, thus having significant potential for energy-saving applications.

[0053] 5. Global Energy Saving Simulation Using ordinary commercial glass as a reference, annual energy consumption simulations were conducted in 15 cities worldwide (including Singapore, Chittagong, Veracruz, etc.) representing different Köppen-Geiger climate types, based on EnergyPlus software. The simulation results are attached. Figure 5 As shown. Figure 5 Figure 'a' simulates Singapore's energy conservation throughout the year, demonstrating energy savings in all 12 months, indicating significant energy-saving effects. Figure 5The data in Figure b shows the average annual CO2 emission reduction and energy saving rate of 15 representative cities, with cities in various climate zones around the world demonstrating a certain degree of energy saving. Therefore, the applicability and energy-saving potential of this technology in different climate regions provide a theoretical basis and design guidance for the large-scale application of smart window technology in building energy conservation in the future.

[0054] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. The application of a class of multicharged derivatives based on naphthalimide in the preparation of flow electrochromic devices, characterized in that, The structural formula of the multicharged naphthalimide derivative is: ; Where n is the charge of the main molecule, n=1~4; R is selected from methyl, 3-carboxypropyl, 3-hydroxy-2-hydroxypropyltrimethylammonium, 3-sulfonylpropyl, or 3-trimethylammoniumpropyl; X - Selected from Cl - ,Br - I - TFSI - OTf - or PF6 - ; The multi-charged naphthalimide derivative is the electrochromic active material in the electrolyte of the flow electrochromic device.

2. A flow electrochromic device, characterized in that, include: A smart window unit includes at least one pair of transparent substrates and a cavity formed by a spacer layer located between the substrates; The fluid circulation system includes a cathode electrolyte storage tank, an anode electrolyte storage tank, connecting pipes, and a pump device; the cathode electrolyte storage tank and the anode electrolyte storage tank are connected to the cavity of the smart window unit through the connecting pipes, and form an electrolyte circulation loop under the drive of the pump device; The cathode electrolyte in the cathode electrolyte storage tank and / or the anolyte in the anolyte storage tank contain the multi-charged naphthalene diimide derivative as described in claim 1 as an electrochromic active substance.

3. The flow electrochromic device according to claim 2, characterized in that, The anolyte further contains an electron compensation medium; the molar ratio of the multi-charged naphthalimide derivative to the electron compensation medium is 1:1 to 1:

10.

4. The flow electrochromic device according to claim 3, characterized in that, The electron compensation medium is selected from one or more of the following: disodium ethylenediaminetetraacetate, trisodium ethylenediaminetetraacetate, tetrasodium ethylenediaminetetraacetate, lactic acid, triethanolamine, and methanol.

5. A flow electrochromic device according to claim 2, characterized in that, The cathode electrolyte and / or anolyte further contain inorganic salts for improving the conductivity of the electrolyte.

6. The flow electrochromic device according to claim 5, characterized in that, The inorganic salt is sodium chloride.

7. A flow electrochromic device according to any one of claims 2-6, characterized in that, The flow electrochromic device employs a symmetrical battery structure, wherein the cathode electrolyte and the anolyte both contain the same or different multi-charged naphthalimide derivatives as described in claim 1.

8. An application of a flow electrochromic device as described in any one of claims 2-7, characterized in that, The device is used in energy-saving windows for buildings, and dynamically controls the transmittance of visible light and solar radiation by adjusting the applied voltage.

9. The application of a flow electrochromic device as described in any one of claims 2-7 in the field of information display, characterized in that, The device is configured to utilize the synergistic effect of light illumination and electrolyte flow to achieve optical writing and self-erasing functions.

10. An application of a flow electrochromic device as described in any one of claims 2-7 in the field of energy storage and power supply, characterized in that, The device is capable of storing electrical energy while undergoing a photochromic reaction and can be used to power external electronic devices.

Images