A modified MOF-doped gel electrolyte film, its preparation method and application

Abstract

This invention discloses a modified MOF-doped gel electrolyte film, its preparation method, and its application in the field of electrochromism. The preparation method includes: ultrasonically dispersing ZIF-8 in a first organic solvent and mixing and stirring with an organic solution containing dissolved TPHD; after the reaction, separating the solid and liquid phases, washing and drying the solid to obtain TPHD@ZIF-8; ultrasonically dispersing TPHD@ZIF-8 in a second organic solvent, mixing it with a gel polymer electrolyte solution, removing the solvent, and forming a film to obtain a TPHD@ZIF-8-doped gel polymer electrolyte film. This invention solves the problem of severe devitrification of the electrolyte film due to uneven distribution of the polymer electrolyte introduced by ZIF-8, making it unsuitable for the electrochromic field. Furthermore, in this invention, the uniform doping of ZIF-8 improves the ionic conductivity and electrochemical window of the film, enabling its excellent application in the electrochromic field.

Description

Technical Field

[0001] This invention relates to the field of electrochromic technology, specifically to a modified MOF-doped gel electrolyte film, its preparation method, and its applications. Background Technology

[0002] Electrochromism refers to the reversible change in the optical properties of a material, such as transmittance, absorptivity, and reflectivity, under the influence of an applied electric field, resulting in a reversible change in its color, i.e., transmittance. An electrochromic device consists of five layers: a transparent conductive layer, an electrochromic layer, an electrolyte layer, an ion storage layer, and another transparent conductive layer. The electrolyte layer serves to transport ions and separate the two electrodes to prevent direct contact and short circuits. Therefore, research on the electrolyte is crucial for the development of electrochromic devices.

[0003] In current research, electrolytes are classified into three states: solid electrolytes, liquid electrolytes, and gel electrolytes. Liquid electrolytes have low ion movement resistance and high mobility. Based on these characteristics, electrochromic devices using liquid electrolytes exhibit fast response speeds and excellent optical transparency. However, liquid electrolytes have several problems. First, long-term use can easily lead to electrolyte leakage. Second, hydrogen ions from acidic liquid electrolytes can corrode the electrochromic layer material. Organic liquid electrolytes pose safety hazards such as flammability, explosiveness, poor heat resistance, and poor chemical stability, all of which can lead to uneven coloring and poor stability in the device. Solid electrolytes are easy to process into films and have high stability after encapsulation, resisting external interference. However, they have low ion conductivity, slow migration rate, small color adjustment range, and poor interfacial bonding, forming ion transport barriers, resulting in slow color change speeds and short cycle lifespans. Gel electrolytes combine the advantages of liquid and solid electrolytes, exhibiting high ion conductivity, good stability, and good mechanical properties. They inherit the efficient ion transport of liquid electrolytes, possess the structure and chemical stability of solid electrolytes, and prevent leakage, making them widely used in electrochromic devices and subject to in-depth research.

[0004] To improve the overall performance of gel electrolytes, inorganic materials such as SiO2, Al2O3, and TiO2 are often added. These materials can effectively promote ion conduction, and the fillers can dissociate lithium salts and reduce the crystallinity of the polymer. However, non-conductive solid fillers can hinder ion migration pathways, potentially limiting the compatibility between the electrolyte interface and the electrode. Metal-organic frameworks (MOFs), as a novel class of porous crystalline materials, have been increasingly used in electrolytes in recent years due to their insulating properties and highly designable network framework structures. Their periodic crystal structure with abundant porosity provides uniformly dispersed sites and pathways for ion diffusion. Simultaneously, their large specific surface area facilitates sufficient contact with other components, optimizing overall electrochemical performance. Furthermore, they can enhance cation diffusion and suppress undesirable side reactions. For example, existing literature (Liu R, Lai X, Xue J, et al. Anionic Anchoring Enhanced QuasiSolid Composite Polymer Electrolytes for High Performance Lithium MetalBattery[J].Polymers,2023,15(24):4716.) reports a modification method incorporating ZIF-8 as a filler into a gel polymer electrolyte composed of PVDF-HFP, lithium salt (lithium bis(trifluoromethanesulfonyl)imide, LiTFSI), and plasticizer (fluorinated ethylene carbonate, FEC), and applying it to lithium-ion batteries. The incorporation of ZIF-8 improves lithium-ion transport through the metal-rich sites of ZIF-8 and TFSI. -The strong interaction between anions, high dielectric constant PVDF-HFP, and a small amount of small molecule plasticizer improves the lithium-ion mobility and interfacial compatibility between the electrode and electrolyte in the composite solid electrolyte, and enhances the thermal stability of the composite solid electrolyte. However, due to the enhanced light scattering caused by nanoparticle aggregation, the optical transmittance of this electrolyte membrane is not ideal, making it unsuitable for electrochromic device applications. Another paper (Bai Z, Li R, Li K, et al. Transparent metal–organic framework-based gel electrolytes for generalized assembly of quasi-solid-state electrochromic devices[J]. ACS Applied) Materials & Interfaces, 2020, 12(38): 42955-42961.) MOF material was used to replace the commonly used polymer matrix. ZIF-8 was used as the matrix and LiClO4 / PC was used as the electrolyte. 2-Methylimidazole was added to fill the micro-gaps between MOF nanocrystals. This effectively suppressed the strong optical scattering of MOF nanocrystals and prepared a gel electrolyte membrane suitable for electrochromic devices. However, the membrane prepared by this method has poor mechanical properties, and the WO3 electrochromic device assembled with this electrolyte membrane has an optical modulation amplitude of only 30.8%, which is poor electrochromic performance.

[0005] In summary, the application of MOF materials in electrolytes still faces many challenges. First, the cumbersome and costly manufacturing process and expensive ligands severely hinder the mass production and feasibility of MOF materials. Second, when MOF materials are added to electrolytes, the nano-effect can cause MOF nanoparticles to aggregate, resulting in less than ideal optical properties of the electrolyte membrane, making it unsuitable for electrochromic applications. Summary of the Invention

[0006] In view of the above-mentioned technical problems and the shortcomings existing in the field, the present invention provides a modified MOF, a gel electrolyte film doped with the modified MOF, and their preparation methods and applications.

[0007] This invention is the first to use terephthalic acid dihydrazide (TPHD) to modify the surface of ZIF-8, which maintains the original size of ZIF-8 and reduces its nanoparticle aggregation effect. This allows ZIF-8 to exhibit ultra-high dispersibility in various solvents, solving the problem of severe electrolyte membrane depermeability caused by uneven distribution of polymer electrolytes introduced by ZIF-8, thus making it unsuitable for electrochromic applications. Furthermore, in this invention, the uniform doping of ZIF-8 improves the ionic conductivity and electrochemical window of the film, making it well-suited for electrochromic applications. The method of this invention is simple, low-cost, and easy to industrialize.

[0008] [1] A method for preparing a modified MOF-doped gel electrolyte film, comprising:

[0009] ZIF-8, which was ultrasonically dispersed in the first organic solvent, was mixed and stirred with an organic solution containing TPHD. After the reaction was completed, the solid was separated, washed, and dried to obtain TPHD@ZIF-8.

[0010] TPHD@ZIF-8 was ultrasonically dispersed in a second organic solvent, mixed with a gel polymer electrolyte solution, the solvent was removed, and a film was formed to obtain a TPHD@ZIF-8 doped gel polymer electrolyte film.

[0011] The first organic solvent and the solvent in the organic solution may each independently include at least one of dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), acetonitrile, and tetrahydrofuran.

[0012] The second organic solvent may include at least one of acetone, N,N-dimethylformamide, acetonitrile, and tetrahydrofuran.

[0013] In the preparation of TPHD@ZIF-8, the molar ratio of ZIF-8 to TPHD can be 1:0.4 to 2.2, preferably 1:1.6 to 2.2. Excessive addition of TPHD can improve the modification effect and dispersibility of the modified ZIF-8.

[0014] In the preparation of TPHD@ZIF-8, the reaction temperature between ZIF-8 and TPHD can be from room temperature to 90℃, such as 25℃, 60℃, etc.

[0015] In some embodiments, the doping ratio of TPHD@ZIF-8 in the TPHD@ZIF-8 doped gel polymer electrolyte film may not exceed 8 wt% of the polymer matrix.

[0016] [2] The TPHD@ZIF-8 doped gel polymer electrolyte film prepared according to the preparation method described in [1].

[0017] [3] Application of TPHD@ZIF-8 doped gel polymer electrolyte film in the field of electrochromism according to [2].

[0018] [4] A method for preparing a modified MOF includes: mixing and stirring ZIF-8, which is ultrasonically dispersed in a first organic solvent, with an organic solution containing TPHD, and after the reaction, separating the solid and liquid, washing and drying the solid to obtain TPHD@ZIF-8.

[0019] The first organic solvent and the solvent in the organic solution may each independently include at least one of dimethyl sulfoxide, N,N-dimethylformamide, acetonitrile, and tetrahydrofuran.

[0020] In the preparation of TPHD@ZIF-8, the molar ratio of ZIF-8 to TPHD can be 1:0.4 to 2.2, preferably 1:1.6 to 2.2. Excessive addition of TPHD can improve the modification effect and dispersibility of the modified ZIF-8.

[0021] In the preparation of TPHD@ZIF-8, the reaction temperature between ZIF-8 and TPHD can be from room temperature to 90℃, such as 25℃, 60℃, etc.

[0022] [5] TPHD@ZIF-8 prepared according to the preparation method described in [4].

[0023] The TPHD@ZIF-8 is a ZIF-8 surface coated with a TPHD molecular layer.

[0024] [6] The application of TPHD@ZIF-8 in the preparation of gel polymer electrolyte films as described in [5].

[0025] When TPHD@ZIF-8 is used to prepare gel polymer electrolyte films, in some embodiments, the doping ratio of TPHD@ZIF-8 in the gel polymer electrolyte film may not exceed 8 wt% of the polymer matrix.

[0026] In some embodiments, the application may specifically include: ultrasonically dispersing the TPHD@ZIF-8 in a second organic solvent, mixing it with a gel polymer electrolyte solution, removing the solvent, and forming a film to obtain a TPHD@ZIF-8 doped gel polymer electrolyte film. The second organic solvent may include at least one of acetone, N,N-dimethylformamide, acetonitrile, and tetrahydrofuran.

[0027] The ZIF-8 used in this invention can be based on existing technology, preferably nanoparticles. Here, an exemplary method for preparing ZIF-8 is provided, comprising: dissolving zinc nitrate and 2-methylimidazole separately in an organic solvent, then mixing the two solutions, allowing the mixture to stand at room temperature for reaction, and after the reaction is complete, separating the solid and liquid phases, washing and drying the solid to obtain ZIF-8 nanoparticles. The organic solvent used to dissolve zinc nitrate and 2-methylimidazole may independently include at least one of methanol and N,N-dimethylformamide.

[0028] The gel polymer electrolyte system of the present invention may include polymethyl methacrylate (PMMA). In addition, the gel polymer electrolyte system of the present invention may further include at least one of polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) and LiClO4 / PC solution (a propylene carbonate solution of LiClO4). Optionally, the mass ratio of PVDF-HFP to PMMA may be 0–0.84:1.96–2.8. Optionally, the concentration of LiClO4 in the LiClO4 / PC solution may be 0.5–1.5 M. Optionally, the volume ratio of LiClO4 / PC solution to PMMA mass may be 0–5.22 mL:1.96–2.8 g.

[0029] The solvent removal film-forming process of the present invention can employ methods commonly used in the art, such as casting, vacuum drying, etc. Furthermore, the vacuum drying temperature can be 50–70°C, and the vacuum drying duration can be 2–4 days.

[0030] This invention effectively improves the dispersion problem of ZIF-8 filler, ensuring its uniform distribution in polymer electrolyte films and significantly enhancing the overall performance of the electrolyte membrane. Furthermore, the preferred use of PVDF-HFP and PMMA as the blended polymer matrix imparts certain mechanical properties to the membrane. The method provided by this invention is low-cost, operates under mild reaction conditions, and is suitable for industrial application.

[0031] The gel polymer electrolyte film doped with TPHD@ZIF-8 of this invention can be matched with different electrochromic materials and applied to electrochromic devices, exhibiting excellent electrochemical performance.

[0032] Compared with the prior art, the beneficial effects of this invention are as follows:

[0033] 1) This invention successfully improves the dispersibility of ZIF-8 filler in polymer electrolyte membranes by attaching the polar molecule TPHD to the surface of ZIF-8 through coordination interactions. The abundant amino and amide groups in TPHD can not only coordinate with the large number of uncoordinated Zn atoms exposed on the outer surface of ZIF-8, but also form hydrogen bonds with the carbonyl groups on PMMA molecules. Therefore, the resulting TPHD-modified ZIF-8 nanoparticles not only exhibit excellent dispersibility in various solvents such as acetone, DMF, and dimethyl sulfoxide, but also enhance the interfacial interaction with the PMMA matrix through strong hydrogen bonds, thereby improving the uniform dispersion of ZIF-8 in the electrolyte film. This results in modified gel polymer electrolyte membranes with very good electrochemical performance, excellent film-forming properties, and high mechanical strength.

[0034] 2) The preparation process of the present invention is simple, highly operable, and suitable for industrial production.

[0035] 3) The introduction of modified filler in this invention can effectively reduce polymer crystallinity, change the local structural movement of polymer chain segments, accelerate the dissociation activity of lithium salt, and enhance ion conduction. The polymer chain segments with modified filler attached have a three-dimensional interconnected structure that provides long-range, continuous conduction channels for ion transport, further improving ion conduction capability. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 The image shows the dynamic light scattering particle size results of the nano ZIF-8 / acetone dispersions prepared in Example 1 and Comparative Example 1 of this invention.

[0038] Figure 2 These are digital photographs of the nano-ZIF-8 / acetone dispersions prepared in Example 1 and Comparative Example 1 of this invention under natural light; wherein, Figure 2 The sample vial on the left contains the ZIF-8 / acetone dispersion prepared in Comparative Example 1. Figure 2 The sample bottle on the right contains the TPHD@ZIF-8 / acetone dispersion prepared in Example 1.

[0039] Figure 3 Transmission electron microscope images of the nano ZIF-8 / acetone dispersions prepared in Comparative Example 1(A) and Example 1(B) of this invention.

[0040] Figure 4Fourier transform infrared spectra of ZIF-8 powder and TPHD powder prepared in Example 1 and Comparative Example 1 of this invention, before and after modification.

[0041] Figure 5 Scanning electron microscope images of the surface morphology of the electrolyte membranes prepared for Comparative Example 1(A) and Example 1(B) of the present invention.

[0042] Figure 6 The ultraviolet-visible transmission spectra of the gel polymer electrolyte membranes prepared in Examples 1, 1, and 2 of this invention are shown.

[0043] Figure 7 The electrochemical impedance spectroscopy of the gel polymer electrolyte membranes prepared in Examples 1, 1, and 2 of this invention is shown.

[0044] Figure 8 The transmission spectra of the “glass / FTO / PB / gel polymer electrolyte membrane / FTO / glass” electrochromic device assembled from the electrolyte membrane prepared in Example 1 of the present invention at different voltages.

[0045] Figure 9 A digital photograph of an electrochromic device assembled from the electrolyte membrane prepared in Example 1 of this invention in a bleached (A) / colored (B) state. Detailed Implementation

[0046] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Operating methods not specifically specified in the following embodiments are generally performed under conventional conditions or as recommended by the manufacturer.

[0047] Example 1:

[0048] (1) Preparation of ZIF-8: 0.735 g of zinc nitrate hexahydrate and 1.623 g of 2-methylimidazole were each dissolved in 35 mL of methanol. The latter clear solution was poured into the former clear solution under magnetic stirring. Stirring was stopped after mixing the component solutions. The mixture was allowed to stand at room temperature for 1 h, and the solid was separated from the emulsion colloidal dispersion by centrifugation. The product was washed with methanol and centrifuged three times. The product was dried under reduced pressure at 25 °C.

[0049] (2) Preparation of TPHD@ZIF-8: 0.4 g ZIF-8 was ultrasonically dispersed in 15 mL DMSO and mixed with a DMSO solution containing 0.535 g TPHD. The mixture was magnetically stirred at 25 °C for 24 h and washed twice with DMSO to remove residual TPHD. The product was vacuum dried to obtain TPHD@ZIF-8.

[0050] (3) Preparation of gel polymer electrolyte membrane: TPHD@ZIF-8 with a polymer mass of 6 wt% (PVDF-HFP+PMMA, the same below) was added to 15 mL of acetone and ultrasonically dispersed for 12 h. 0.8 g of PVDF-HFP and 2.52 g of PMMA were added sequentially to this precursor solution, and the mixture was magnetically stirred at 60 °C for a total of 10 h. Then, 5 mL of 1 M LiClO4 / PC solution was added to the precursor solution and magnetically stirred until homogeneous. The precursor solution was poured onto a polytetrafluoroethylene template and dried in a vacuum oven to form a film. The electrochemical performance measured using an electrochemical workstation is shown in Table 1.

[0051] Comparative Example 1:

[0052] (1) Preparation of ZIF-8: 0.735 g of zinc nitrate hexahydrate and 1.623 g of 2-methylimidazole were each dissolved in 35 mL of methanol. The latter clear solution was poured into the former clear solution under magnetic stirring. Stirring was stopped after mixing the component solutions. The mixture was allowed to stand at room temperature for 1 h, and the solid was separated from the emulsion colloidal dispersion by centrifugation. The product was washed with methanol and centrifuged three times. The product was dried under reduced pressure at 25 °C.

[0053] (2) Preparation of the gel polymer electrolyte membrane: ZIF-8 powder (6 wt% relative to the polymer mass) was added to 15 mL of acetone and ultrasonically dispersed for 12 h. Then, 0.8 g of PVDF-HFP and 2.52 g of PMMA were added sequentially to the precursor solution, and the mixture was magnetically stirred at 60 °C for 10 h. Next, 5 mL of 1 M LiClO4 / PC solution was added to the precursor solution and magnetically stirred until homogeneous. The precursor solution was poured onto a polytetrafluoroethylene template and dried in a vacuum oven to form a membrane. The electrochemical performance measured using an electrochemical workstation is shown in Table 1.

[0054] Comparative Example 2:

[0055] Preparation of the gel polymer electrolyte membrane: 0.8 g of PVDF-HFP and 2.52 g of PMMA were added sequentially to 15 mL of acetone and magnetically stirred at 60 °C for 10 h. Then, 5 mL of 1 M LiClO4 / PC solution was added to the precursor solution and magnetically stirred until homogeneous. The precursor solution was poured onto a polytetrafluoroethylene template and the solvent was dried in a vacuum oven to form a membrane. The electrochemical performance measured using an electrochemical workstation is shown in Table 1.

[0056] Table 1

[0057]

[0058] Example 2:

[0059] (1) Preparation of ZIF-8: 0.735 g of zinc nitrate hexahydrate and 1.623 g of 2-methylimidazole were each dissolved in 35 mL of methanol. The latter clear solution was poured into the former clear solution under magnetic stirring. Stirring was stopped after mixing the component solutions. The mixture was allowed to stand at room temperature for 1 h, and the solid was separated from the emulsion colloidal dispersion by centrifugation. The product was washed with methanol and centrifuged three times. The product was dried under reduced pressure at 25 °C.

[0060] (2) Preparation of TPHD@ZIF-8: 0.4 g ZIF-8 was ultrasonically dispersed in 15 mL DMSO and mixed with a DMSO solution containing 0.136 g TPHD. The mixture was magnetically stirred at 25 °C for 24 h and washed twice with DMSO to remove residual TPHD. The product was vacuum dried to obtain TPHD@ZIF-8.

[0061] Example 3:

[0062] (1) Preparation of ZIF-8: 0.735 g of zinc nitrate hexahydrate and 1.623 g of 2-methylimidazole were each dissolved in 35 mL of methanol. The latter clear solution was poured into the former clear solution under magnetic stirring. Stirring was stopped after mixing the component solutions. The mixture was allowed to stand at room temperature for 1 h, and the solid was separated from the emulsion colloidal dispersion by centrifugation. The product was washed with methanol and centrifuged three times. The product was dried under reduced pressure at 25 °C.

[0063] (2) Preparation of TPHD@ZIF-8: 0.4 g ZIF-8 was ultrasonically dispersed in 15 mL DMSO and mixed with a DMSO solution containing 0.34 g TPHD. The mixture was magnetically stirred at 25 °C for 24 h and washed twice with DMSO to remove residual TPHD. The product was vacuum dried to obtain TPHD@ZIF-8.

[0064] Example 4:

[0065] (1) Preparation of ZIF-8: 0.735 g of zinc nitrate hexahydrate and 1.623 g of 2-methylimidazole were each dissolved in 35 mL of methanol. The latter clear solution was poured into the former clear solution under magnetic stirring. Stirring was stopped after mixing the component solutions. The mixture was allowed to stand at room temperature for 1 h, and the solid was separated from the emulsion colloidal dispersion by centrifugation. The product was washed with methanol and centrifuged three times. The product was dried under reduced pressure at 25 °C.

[0066] (2) Preparation of TPHD@ZIF-8: 0.4 g ZIF-8 was ultrasonically dispersed in 15 mL DMSO and mixed with a DMSO solution containing 0.748 g TPHD. The mixture was magnetically stirred at 25 °C for 24 h and washed twice with DMSO to remove residual TPHD. The product was vacuum dried to obtain TPHD@ZIF-8.

[0067] Example 5:

[0068] (1) Preparation of ZIF-8: 0.735 g of zinc nitrate hexahydrate and 1.623 g of 2-methylimidazole were each dissolved in 35 mL of methanol. The latter clear solution was poured into the former clear solution under magnetic stirring. Stirring was stopped after mixing the component solutions. The mixture was allowed to stand at room temperature for 1 h, and the solid was separated from the emulsion colloidal dispersion by centrifugation. The product was washed with methanol and centrifuged three times. The product was dried under reduced pressure at 25 °C.

[0069] (2) Preparation of TPHD@ZIF-8: 0.4 g ZIF-8 was ultrasonically dispersed in 15 mL DMSO and mixed with a DMSO solution containing 0.535 g TPHD. The mixture was magnetically stirred at 60 °C for 24 h and washed twice with DMSO to remove residual TPHD. The product was vacuum dried to obtain TPHD@ZIF-8.

[0070] Example 6:

[0071] (1) Preparation of ZIF-8: 0.735 g of zinc nitrate hexahydrate and 1.623 g of 2-methylimidazole were each dissolved in 35 mL of methanol. The latter clear solution was poured into the former clear solution under magnetic stirring. Stirring was stopped after mixing the component solutions. The mixture was allowed to stand at room temperature for 1 h, and the solid was separated from the emulsion colloidal dispersion by centrifugation. The product was washed with methanol and centrifuged three times. The product was dried under reduced pressure at 25 °C.

[0072] (2) Preparation of TPHD@ZIF-8: 0.4 g ZIF-8 was ultrasonically dispersed in 15 mL DMSO and mixed with a DMSO solution containing 0.535 g TPHD. The mixture was magnetically stirred at 90 °C for 24 h and washed twice with DMSO to remove residual TPHD. The product was vacuum dried to obtain TPHD@ZIF-8.

[0073] Sample analysis:

[0074] Figure 1The dynamic light scattering particle size results of the nano-ZIF-8 / acetone dispersions prepared in Example 1 and Comparative Example 1 of this invention are presented. It can be seen that the ZIF-8 modified by TPHD surface grafting exhibits better dispersibility in acetone compared to the unmodified ZIF-8.

[0075] Figure 2 These are digital photographs of the nano-ZIF-8 / acetone dispersions prepared in Example 1 and Comparative Example 1 of this invention under natural light; wherein, Figure 2 The sample vial on the left contains the ZIF-8 / acetone dispersion prepared in Comparative Example 1. Figure 2 The sample bottle on the right contains the TPHD@ZIF-8 / acetone dispersion prepared in Example 1. It can be seen that the unmodified ZIF-8 quickly precipitated after ultrasonic dispersion in acetone solution, while the ZIF-8 modified by TPHD grafting did not precipitate even after being left to stand for more than a month after ultrasonic dispersion in acetone solution. This indicates that TPHD grafting modification of ZIF-8 can effectively improve its dispersibility in acetone.

[0076] Figure 3 These are transmission electron microscope images of the nano-ZIF-8 / acetone dispersions prepared in Example 1 and Comparative Example 1 of this invention. Figure 3 A is a transmission electron microscope image of the ZIF-8 / acetone dispersion prepared in Comparative Example 1. Figure 3 B is a transmission electron microscope image of the TPHD@ZIF-8 / acetone dispersion prepared in Example 1. It can be seen that when ZIF-8 is directly dispersed in acetone, it is tightly packed and aggregated due to the characteristics of nanoparticles. At this time, although the size of ZIF-8 is small, the agglomeration cannot be dispersed. The abundant amino and amide groups in TPHD can coordinate with the uncoordinated zinc atoms exposed on the outer surface of ZIF-8. Their presence increases the steric hindrance between ZIF-8 nanoparticles, promoting the dispersion of ZIF-8 nanocrystals.

[0077] Figure 4 The Fourier transform infrared (FTIR) spectra of the modified and unmodified ZIF-8 powder and TPHD powder prepared in Example 1 and Comparative Example 1 of this invention are shown. Example 1: FTIR spectra at 3300–3600 cm⁻¹ -1 The characteristic absorption peaks in the vicinity are due to the NH bond vibrations in TPHD, and at 1600 cm⁻¹. -1 The absorption peaks generated nearby are attributed to carbonyl stretching vibrations. The new bands appearing in TPHD@ZIF-8 confirm the presence of TPHD on ZIF-8.

[0078] Figure 5 Scanning electron microscope images of the surface morphology of the electrolyte membranes prepared in Comparative Example 1(A) and Example 1(B) of this invention, such as... Figure 5As shown in B, the electrolyte membrane surface in Example 1 is smooth and flat, without any aggregated nanoparticles. Figure 5 As can be seen from A, the electrolyte membrane surface of Comparative Example 1 has wrinkles and protrusions, as well as agglomerated MOF particles, which indicates that the electrolyte membrane of Example 1 will have better interfacial contact with the working electrode layer during the operation of the electrochromic device.

[0079] Figure 6 The images show the UV-Vis transmittance spectra of the gel polymer electrolyte membranes prepared in Examples 1, 1, and 2 of this invention. It can be seen that compared to Comparative Example 2, the optical transmittance of Examples 1 and 1 is reduced, indicating that the incorporation of MOF filler impairs the high optical transmittance of the electrolyte membrane. This is because excessively large agglomerated nanoparticles in the membrane increase light scattering, leading to a decrease in the membrane's optical transmittance. However, compared to Comparative Example 1, Example 1 shows a significant increase in optical transmittance in the visible light wavelength range. This is because the surface coating modification of ZIF-8 by TPHD greatly improves the dispersion of ZIF-8 in the gel membrane, allowing ZIF-8 to be better dispersed, thereby reducing the light scattering effect of agglomerated nanoparticles. This makes the modified gel membrane more suitable for use in electrochromic devices.

[0080] Figure 7 The electrochemical impedance spectroscopy spectra of the gel polymer electrolyte membranes prepared in Example 1, Comparative Example 1, and Comparative Example 2 of this invention are shown. Figure 7 The smaller image in the figure is a magnified view of a typical blocking electrode impedance spectrum curve, which is a straight line. The intersection of this line with the X-axis represents the bulk resistance of the gel film, which can be expressed by the formula... Calculate the ionic conductivity σ of the gel membrane, where R b Let A be the bulk resistance, A be the contact area between the stainless steel electrode and the electrolyte membrane, and d be the thickness of the electrolyte membrane. The bulk resistance values ​​of the gel membrane obtained from this figure are statistically shown in Table 1. Since the thickness and contact area of ​​the test membrane are constant, the ionic conductivity of the gel membrane is only related to its bulk resistance. The smaller the bulk resistance, the greater the ionic conductivity. It can be seen from the figure that the bulk resistance of the electrolyte membrane in Example 1 is less than that of the electrolyte membrane in Comparative Example 1, which is less than that of the electrolyte membrane in Comparative Example 2. Correspondingly, it can be concluded that the ionic conductivity of the electrolyte membrane is improved after ZIF-8 doping, and the ionic conductivity of the electrolyte membrane further improved after ZIF-8 surface modification by TPHD is further improved.

[0081] Figure 8The transmission spectra of the “glass / FTO / Prussian blue electrochromic layer / gel polymer electrolyte membrane / FTO / glass” electrochromic device assembled from the electrolyte membrane prepared in Example 1 of the present invention are shown at voltages of -2.7V and 2V, respectively. As can be seen from the figure, the transmittance of the electrochromic device prepared in Example 1 is 6% in the colored state and 70% in the faded state at 633nm, and the adjustment range (transmittance difference) is about 64%.

[0082] Figure 9 The image shows a digital photograph of the electrochromic device assembled from the electrolyte membrane prepared in Example 1 of this invention in a bleached (A) / colored (B) state. As can be seen from the image, the device exhibits uniform color change and a large optical modulation amplitude, indicating that the electrochromic device has good electrochromic performance.

[0083] Furthermore, it should be understood that after reading the above description of the present invention, those skilled in the art can make various alterations or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims.

Claims

1. A method for preparing a modified MOF-doped gel electrolyte film, characterized in that, include: ZIF-8, ultrasonically dispersed in a first organic solvent, was mixed and stirred with an organic solution containing dissolved terephthalic acid dihydrazide. After the reaction, the solid was separated, washed, and dried to obtain terephthalic acid dihydrazide@ZIF-8. The molar ratio of ZIF-8 to terephthalic acid dihydrazide was 1:0.4~2.

2. Dihydrazide terephthalate@ZIF-8 was ultrasonically dispersed in a second organic solvent, mixed with a gel polymer electrolyte solution, the solvent was removed, and a film was formed to obtain a dihydrazide terephthalate@ZIF-8 doped gel polymer electrolyte film; the gel polymer electrolyte included polymethyl methacrylate. In the terephthalic acid dihydrazide@ZIF-8 doped gel polymer electrolyte film, the doping ratio of terephthalic acid dihydrazide@ZIF-8 does not exceed 8 wt% of the polymer matrix.

2. The preparation method according to claim 1, characterized in that, The first organic solvent and the solvent in the organic solution each independently include at least one of dimethyl sulfoxide, N,N-dimethylformamide, acetonitrile, and tetrahydrofuran; The second organic solvent includes at least one of acetone, N,N-dimethylformamide, acetonitrile, and tetrahydrofuran.

3. The preparation method according to claim 1, characterized in that, The molar ratio of ZIF-8 to dihydrazide terephthalate is 1:1.6~2.

2.

4. The preparation method according to claim 1, characterized in that, The reaction temperature of ZIF-8 with dihydrazide terephthalate is from room temperature to 90°C.

5. The terephthalic acid dihydrazide@ZIF-8 doped gel polymer electrolyte film prepared by the preparation method according to any one of claims 1 to 4.

6. The application of the terephthalic acid dihydrazide@ZIF-8 doped gel polymer electrolyte film according to claim 5 in the field of electrochromism.

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