Reversible coordination reaction-based electrochromic layer as well as preparation method and application thereof
By using an electrochromic layer based on reversible coordination reaction, the complexation reaction between electrochemically active materials and inorganic coordination-capable materials is utilized to solve the problems of dendrite growth and color-changing performance degradation in traditional electrochromic devices, achieving efficient and rapid color change and improved stability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-13
- Publication Date
- 2026-04-03
AI Technical Summary
Traditional electrochromic devices are prone to dendrite growth due to metal ion deposition during the fabrication process, which can cause short circuits, reduce cycle life, and lead to lattice deformation of the color-changing material, resulting in a decline in color-changing performance.
An electrochromic layer based on reversible coordination reaction is used to form a complex through the reversible reaction of electrochemically active substances and inorganic coordination-capable substances, thereby achieving color change. The dynamic equilibrium of the reaction system is maintained by reducing substances to avoid dendrite growth.
It improves the cycle life and response speed of electrochromic devices, maintains the stability and uniformity of color-changing performance, and uses readily available and low-cost raw materials.
Smart Images
Figure CN121785020A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of electrochromic materials technology, specifically relating to an electrochromic layer based on reversible coordination reaction, its preparation method, and its application. Background Technology
[0002] Electrochromic technology has broad application prospects in fields such as intelligent dimming, energy-saving displays, and anti-glare. Traditional electrochromic devices mainly consist of three components: an electrochromic layer, an electrolyte, and an ion storage layer. The electrochromic layer is often pre-fabricated, and color changes are achieved through electron and ion co-intercalation. Ion implantation typically causes lattice deformation of the color-changing material, disrupting its structure and leading to a decay in color-changing performance, thus reducing the device's cycle stability.
[0003] Metal deposition electrochromic devices utilize the redox reaction of metal ions in an electrolyte to electrochemically deposit an electrochromic coating on the electrode, simultaneously achieving color change. This simplifies the device fabrication process and avoids the structural damage to the color-changing layer caused by repeated insertion and extraction. However, during deposition, metal ions may experience dendrite growth due to tip discharge, leading to short circuits and reduced cycle life. Therefore, there is an urgent need to develop novel electrochromic coating fabrication mechanisms. Summary of the Invention
[0004] This invention provides an electrochromic layer based on reversible coordination reaction, its preparation method, and its application. The color change can be completed during the preparation of the coating, while avoiding the problem of dendrite growth during metal deposition.
[0005] To achieve the following objectives, the present invention adopts the following technical solution: First, an electrochromic layer based on reversible coordination reaction is proposed. The electrochromic layer regulates color change through reversible inorganic coordination reaction between electrochemically active substances with multiple redox states and substances with inorganic coordination ability.
[0006] Optionally, the electrochromic layer comprises electrochemically active substances with multiple redox states, substances with inorganic coordination capabilities, and reducing substances. The electrochemically active substances undergo valence state changes during color change, and the substances with inorganic coordination capabilities form complexes when they react with the electrochemically active substances undergoing valence state changes. The reducing substances promote the reversible restoration of the complexes to the electrochemically active substances and the substances with inorganic coordination capabilities. The oxidation products of the reducing substances are reversibly reduced to the reducing substances in the reaction system, maintaining the dynamic equilibrium of the substances in the reaction system. This constructs a closed-loop electrochemical cycle, where the reducing substances ensure the high reversibility of the electrochromic reaction, thereby significantly improving cycle life and response speed, while maintaining stable concentrations of the components within the system and preventing the accumulation of byproducts.
[0007] Optionally, the electrochemically active material is a variable-valence metal ion salt or a variable-valence metal ion salt complex. Variable-valence metal ions provide abundant redox pairs, serving as the electron source and color development center for color changes. Their salt or complex form ensures good solubility or dispersibility in solution or solid layer, laying the foundation for uniform and stable electrochromic properties.
[0008] Optionally, the electrochemically active material has Fe 2+ or Co 2+ Based on Fe 2+ or Co 2+ The color change reaction is obvious, making it easier to clearly understand the reaction state.
[0009] Optionally, the substance with inorganic coordination ability is selected from those with SCN. - NH4 + One of the complexing agents. SCN - Complexing agents and NH4 + All complexing agents facilitate reaction coordination.
[0010] Optionally, the reducing agent may be one or both of ascorbic acid and citric acid. Ascorbic acid and citric acid are both environmentally friendly mild reducing agents with high reversibility of redox reactions, which facilitates the formation of sustainable redox cycles.
[0011] Secondly, a method for preparing an electrochromic layer based on a reversible coordination reaction is proposed, comprising the following steps: S1: Dissolve electrochemically active substances with multiple redox states and substances with inorganic coordination ability in deionized water to form a clear solution; S2: Add a reducing agent to a clear solution and mix thoroughly to obtain a mixed solution; S3: Immerse the conductive glass in the mixed solution, and then apply a voltage to the conductive glass to allow electrochemically active substances with multiple redox states to change their valence and combine with substances with inorganic coordination ability to form complexes. S4: After the voltage is removed, the reducing substances in the mixed solution undergo a spontaneous redox reaction with the complex. The complex reversibly transforms back into electrochemically active substances with multiple redox states and substances with inorganic coordination ability, while the reducing substances are oxidized. S5: The oxides of reducing substances are reversibly reduced in the reaction system to maintain the dynamic equilibrium of substances in the reaction system.
[0012] Optionally, the concentration of the electrochemically active substance with multiple redox states is 0.1M-0.5M, and the concentration of the substance with inorganic coordination ability is 0.3M-3M; the molar ratio of the electrochemically active substance with multiple redox states to the substance with inorganic coordination ability is 1:3-1:6; and the concentration of the reducing substance is 6-12 times that of the electrochemically active substance with multiple redox states.
[0013] Optionally, the voltage applied in S3 is 0.7-1.7V, and the application time is 1-100s.
[0014] In addition, an application of electrochromic layers based on reversible coordination reactions is proposed, which can be used in electrochromic devices.
[0015] Beneficial effects: This invention provides an electrochromic layer based on a reversible coordination reaction, its preparation method, and its application, which have the following advantages compared with the prior art: The raw materials used are readily available and are all common, low-cost inorganic salts; A novel preparation mechanism is proposed, which can complete the color change during the coating preparation process while avoiding problems such as dendrite formation during metal deposition. The electrochromic process used is based on a reversible coordination reaction, which has a fast response speed and can complete the rapid preparation of the electrochromic coating within 15 seconds, while simultaneously completing the color change during the coating preparation process. The system has a high degree of inorganic composition and is safer than organic electrochromic materials. It is highly adaptable and can be applied to both rigid glass and flexible substrates. Attached Figure Description
[0016] Figure 1 Images of the FTO electrode (left) and the Fe[SCN]3 / FTO electrode (right); Figure 2 This is the spectral modulation curve; Figure 3 This is the response time curve. Detailed Implementation
[0017] The principles and features of the present invention are described below with reference to the accompanying drawings. These examples are for illustrative purposes only and are not intended to limit the scope of the invention. Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods; the materials and reagents used in the following embodiments are commercially available unless otherwise specified.
[0018] like Figure 1 The image shows an FTO electrode (left) and a Fe[SCN]3 / FTO electrode (right), demonstrating the contrast between an electrochromic layer based on a reversible coordination reaction before and after color change. This electrochromic layer regulates color change through a reversible inorganic coordination reaction between electrochemically active substances with multiple redox states and substances with inorganic coordination capabilities.
[0019] The electrochromic layer comprises electrochemically active substances with multiple redox states, substances with inorganic coordination capabilities, and reducing substances. During the color change, the electrochemically active substances undergo a valence state change. The substances with inorganic coordination capabilities form complexes when they react with the electrochemically active substances that have undergone valence state changes; this complex is the electrochromic layer. The reducing substances facilitate the reversible reversion of the complexes back to the electrochemically active substances and the substances with inorganic coordination capabilities. The oxidation products of the reducing substances are reversibly reduced back to the reducing substances in the reaction system, maintaining the dynamic equilibrium of the substances within the system.
[0020] Electrochemically active substances are either salts or complexes of variable-valence metal ions. Variable-valence metal ions provide abundant redox pairs, serving as the electron source and color development center for color changes. Their salt or complex form ensures good solubility or dispersibility in solution or solid layers, laying the foundation for uniform and stable electrochromic properties.
[0021] Electrochemically active materials must contain Fe 2+ or Co 2+ It is also the main component that changes color; after being oxidized, it can coordinate with ligands to complete the color change.
[0022] Furthermore, substances with inorganic coordination ability are selected from those containing SCN. - NH4 + One of the complexing agents. SCN - Complexing agents and NH4 + Complexing agents are all used for reactive coordination, for example, Fe 2+ Fe after oxidation 3+ and SCN - To react, Co 2+Co after oxidation 3+ and NH4 + The reaction will proceed.
[0023] The reducing agents are one or both of ascorbic acid and citric acid. Ascorbic acid and citric acid are both environmentally friendly mild reducing agents with high reversibility of redox reactions, which facilitates the formation of sustainable redox cycles.
[0024] It should be noted that the core mechanism of the electrochromic layer lies in: utilizing electrochemically active substances with multiple redox states (such as Fe). 2+ Under the influence of an electric field, the valence state changes (e.g., oxidation to Fe). 3+ The newly generated valence state and substances with inorganic coordination ability in the system (such as SCN) - A rapid coordination reaction occurs, forming a complex with specific absorption in the visible light region (such as the red [Fe(SCN)n)). 3-n This achieves coloring. When the electric field is removed or reversed, reducing substances in the system (such as ascorbic acid) spontaneously release high-valence metal ions (Fe2+) into the system. 3+ ) Restore to the initial valence state (Fe) 2+ This leads to the breaking of coordination bonds, dissociation of the complex, and restoration of the material to its initial colorless or light-colored state; the oxidized reducing agent can be reduced and regenerated in subsequent electric field cycles, thus forming a dynamic and sustainable closed-loop electrochemical cycle.
[0025] Secondly, this application also proposes a method for preparing an electrochromic layer based on a reversible coordination reaction, comprising the following steps: S1: Dissolve electrochemically active substances with multiple redox states and substances with inorganic coordination ability in deionized water to form a clear solution; S2: Add a reducing agent to a clear solution and mix thoroughly to obtain a mixed solution; S3: Immerse the conductive glass in the mixed solution, and then apply a voltage of 0.7-1.7V to the conductive glass for 1-100s. This is used to combine electrochemically active substances with multiple redox states after valence change with substances with inorganic coordination ability to form complexes (i.e., electrochromic layers). S4: After the voltage is removed, the reducing substances in the mixed solution undergo a spontaneous redox reaction with the complex. The complex reversibly transforms back into electrochemically active substances with multiple redox states and substances with inorganic coordination ability, while the reducing substances are oxidized. S5: The oxides of reducing substances are reversibly reduced in the reaction system to maintain the dynamic equilibrium of substances in the reaction system.
[0026] The concentration of electrochemically active substances with multiple redox states is 0.1M-0.5M, and the concentration of substances with inorganic coordination ability is 0.3M-3M, where M is the molar concentration. The molar ratio of electrochemically active substances with multiple redox states to substances with inorganic coordination ability is 1:3 to 1:6, and the concentration of reducing substances is 6-12 times that of electrochemically active substances with multiple redox states. By controlling the concentration ratio and molar ratio, the coordination reaction can be ensured to proceed fully and rapidly.
[0027] In addition, this application also proposes an application of an electrochromic layer based on a reversible coordination reaction, which can be used in electrochromic devices.
[0028] Based on the above preparation method, here are two specific application examples:
[0029] Specific application example 1
[0030] A method for preparing an electrochromic layer based on a reversible coordination chemical reaction includes the following steps: S1. Dissolve 0.76g of ferrous sulfate (electrochemically active substance A) in 50mL of deionized water, then add 1.45g of potassium thiocyanate (coordinating substance B) and stir until a clear solution is obtained. S2. Add 5.28g of ascorbic acid to the clear solution in S1 and mix thoroughly to obtain a mixed solution; S3. In the electrolytic cell, immerse the FTO conductive glass in the mixed solution, and then apply 1.2 V to the conductive glass. vs. With AgCl / Ag voltage, ferrous sulfate (active substance A) is oxidized to ferric sulfate (active substance A with variable valence), which then combines with potassium thiocyanate (coordinating substance B) to form Fe[SCN]3 (complex C), thus obtaining an electrochromic layer; S4. In the mixed solution, ascorbic acid (reducing substance) undergoes a spontaneous redox reaction with Fe[SCN]3 (complex C), causing Fe[SCN]3 (complex C) to reversibly transform back into ferrous sulfate (active substance A) and potassium thiocyanate (coordinating substance B). At the same time, ascorbic acid (reducing substance) is oxidized to dehydroascorbic acid (oxidation product E of D). S5, dehydroascorbic acid (substance E) is reversibly reduced to ascorbic acid (substance) by H2 generated at the counter electrode in the reaction system, maintaining the dynamic equilibrium of substances in the reaction system.
[0031] The electrochromic properties of the electrochromic coating in this embodiment were tested and characterized, such as... Figure 1 During the coating preparation process shown, with the successful preparation of the Fe[SCN]3 coating on FTO, the electrode color changed from colorless and transparent to blood red; as shown Figure 2 and Figure 3The figures shown are the spectral modulation curve and the response time curve, respectively, where ΔT is the dimming amplitude and t is the response time. coloring Indicates the time taken for the color to change, t bleaching The text indicates the time required for stripping, with Wavelength representing wavelength, transmittance representing transmittance, and Time representing time. Figure 2 and Figure 3 It can be seen that a light modulation amplitude of up to 98.5% was achieved in this process, which is extremely outstanding in the field of electrochromism. In addition, the coating preparation process is relatively fast, achieving 90% light modulation capability in about 15 seconds, while the peeling process can be completed in only 3 seconds.
[0032] Specific Application Example 2
[0033] A method for preparing an electrochromic layer based on a reversible coordination chemical reaction includes the following steps: S1. Dissolve 0.78g of cobalt sulfate (electrochemically active substance A) in 50mL of deionized water, then add 1.61g of ammonium chloride (coordinating substance B) and stir until a clear solution is obtained. S2. Add 7.05g of ascorbic acid to the clear solution in S1 and mix thoroughly to obtain a mixed solution; S3. In the electrolytic cell, immerse the FTO conductive glass in the mixed solution, and then apply 1.7V to the conductive glass. vs. At an AgCl / Ag voltage, cobalt(II) sulfate (active substance A) is oxidized to cobalt(III) sulfate (active substance A with variable valence), which then combines with ammonium chloride (coordinating substance B) to form [Co(NH3)6]Cl3 (complex C), thus obtaining an electrochromic layer; S4. In the mixed solution, ascorbic acid (reducing substance) undergoes a spontaneous redox reaction with [Co(NH3)6]Cl3 (complex C), causing [Co(NH3)6]Cl3 (complex C) to reversibly transform back into cobalt(II) sulfate (active substance A) and ammonium chloride (coordinating substance B). At the same time, ascorbic acid (reducing substance) is oxidized to dehydroascorbic acid (oxidation product E of D). S5, dehydroascorbic acid (substance E) is reversibly reduced to ascorbic acid (reducing substance) by H2 generated at the counter electrode in the reaction system, maintaining the dynamic equilibrium of substances in the reaction system.
[0034] The electrochromic properties of the electrochromic coating in this embodiment were tested and characterized. With the successful preparation of the [Co(NH3)6]Cl3 coating on FTO, the electrode color changed from colorless and transparent to yellow.
[0035] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make corresponding changes and adjustments to the technology of the present invention without departing from the basic principles of the present invention, and such changes and adjustments are all within the protection scope of the present invention.
Claims
1. An electrochromic layer based on a reversible coordination reaction, characterized in that, Electrochromic layers regulate color change through reversible inorganic coordination reactions between electrochemically active substances with multiple redox states and substances with inorganic coordination capabilities.
2. The electrochromic layer based on reversible coordination reaction according to claim 1, characterized in that, The components of the electrochromic layer include electrochemically active substances with multiple redox states, substances with inorganic coordination ability, and substances with reducing properties; Electrochemically active substances undergo a change in valence state when they change color. Substances with inorganic coordination ability form complexes when they undergo an inorganic coordination reaction with the electrochemically active substances that have undergone a change in valence state. Substances with reducing properties are used to promote the reversible restoration of complexes to electrochemically active substances and substances with inorganic coordination capabilities; The oxidation products of reducing substances can be reversibly reduced to reducing substances in the reaction system to maintain the dynamic equilibrium of the substances in the reaction system.
3. The electrochromic layer based on reversible coordination reaction according to claim 1 or 2, characterized in that, The electrochemically active material is one of the variable valence metal ion salts or variable valence metal ion salt complexes.
4. The electrochromic layer based on reversible coordination reaction according to claim 3, characterized in that, Electrochemically active materials have Fe 2+ or Co 2+ .
5. The electrochromic layer based on a reversible coordination reaction according to claim 1 or 2, characterized in that, Substances with inorganic coordination ability are selected from those containing SCN. - NH4 + One of the complexing agents.
6. The electrochromic layer based on a reversible coordination reaction according to claim 1 or 2, characterized in that, The reducing agent is one or both of ascorbic acid and citric acid.
7. A method for preparing an electrochromic layer based on a reversible coordination reaction, characterized in that, Includes the following steps: S1: Dissolve electrochemically active substances with multiple redox states and substances with inorganic coordination ability in deionized water to form a clear solution; S2: Add a reducing agent to a clear solution and mix thoroughly to obtain a mixed solution; S3: Immerse the conductive glass in the mixed solution, and then apply a voltage to the conductive glass to allow electrochemically active substances with multiple redox states to change their valence and combine with substances with inorganic coordination ability to form complexes. S4: After the voltage is removed, the reducing substances in the mixed solution undergo a spontaneous redox reaction with the complex. The complex reversibly transforms back into electrochemically active substances with multiple redox states and substances with inorganic coordination ability, while the reducing substances are oxidized. S5: The oxides of reducing substances are reversibly reduced in the reaction system to maintain the dynamic equilibrium of substances in the reaction system.
8. The method for preparing an electrochromic layer based on a reversible coordination reaction according to claim 7, characterized in that, The concentration of electrochemically active substances with multiple redox states is 0.1M-0.5M, and the concentration of substances with inorganic coordination ability is 0.3M-3M; the molar ratio of electrochemically active substances with multiple redox states to substances with inorganic coordination ability is 1:3 to 1:6; the concentration of reducing substances is 6-12 times that of electrochemically active substances with multiple redox states.
9. The method for preparing an electrochromic layer based on a reversible coordination reaction according to claim 7, characterized in that, The voltage applied in S3 is 0.7-1.7V, and the application time is 1-100s.
10. The application of the electrochromic layer based on reversible coordination reaction as described in any one of claims 1-6, characterized in that, Electrochromic layers can be used in electrochromic devices.