Application of cathode material in reduction of oxidation-reduction potential and electrochromic device

Abstract

The invention discloses application of a cathode material in reduction of oxidation-reduction potential and an electrochromic device, and belongs to the technical field of electrochromic materials. The general formula of the cathode material is # imgabs0 #, wherein R1 and R1'are independently selected from an alkyl group, an aryl group or an alkoxy group; r2, R6, R2'and R6 'are independently selected from H, F, Cl, Br, I, CN, NO2, alkyl, alkoxy or aryl; x <-> is selected from BF4 <-> or PF6 <->. Compared with a conventional cathode material, the cathode material has the advantages that the electron obtaining capacity is weakened, the electron losing capacity is enhanced, the potential difference absolute value of an electrochromic solution prepared from the cathode material and dimethyl phenazine is increased, and the potential energy required by a positive reaction of the cathode material in the oxidation-reduction process is increased; correspondingly, the electric potential energy required by the reverse reaction is reduced, so that the transmittance of the device in the initial state is improved, and the time required for color fading is shortened.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochromic materials, and in particular to an application of a cathode material in reducing redox potential and an electrochromic device. Background Art

[0002] The potential of the existing cathode bipyridine material used in electrochromic mirror devices is around -0.4V, and the potential of the anode dimethylphenazine material is around 0.3V. The absolute value of (Φanode-Φcathode) is too small. Applying a voltage less than 0.7V to the electrochromic device prepared by the existing anode and cathode materials can cause the device to be colored. The high redox potential brings about the problems of low maximum transmittance of the device, dark initial color of the appearance, high yellowness index, and long fading response time. The application scenarios are limited, and it is difficult to meet the requirements for appearance color and application performance after the electrochromic device is bonded to the waveguide lens module.

[0003] In view of this, the present invention is proposed. Summary of the invention

[0004] The object of the present invention is to provide an application of a cathode material in reducing redox potential and an electrochromic device to solve or improve the above technical problems.

[0005] The present invention can be implemented like this:

[0006] In a first aspect, the present invention provides an application of a cathode material in reducing redox potential, wherein the cathode material has a general formula of:

[0007] wherein R1 and R1′ are independently selected from an alkyl group, an aryl group or an alkoxy group; R2, R6, R2′ and R6′ are independently selected from H, F, Cl, Br, I, CN, NO2, an alkyl group, an alkoxy group or an aryl group; X - Selected from BF4 - or PF6 - .

[0008] In an alternative embodiment, R1 and R1' are independently aryl groups with alkyl groups.

[0009] In an alternative embodiment, R1 and R1' are independently aryl groups having a methyl group.

[0010] In an alternative embodiment, at least one of R1 and R1' is a methylphenyl group.

[0011] In an alternative embodiment, either one of R1 and R1' is methylphenyl and the other is methyl.

[0012] In an optional embodiment, R and R1' are both methylphenyl, R2, R6, R2' and R6' are all H, X- For BF4 - .

[0013] In an optional embodiment, the cathode material has the structural formula:

[0014]

[0015] In an optional embodiment, the structural formula is The preparation method of the cathode material comprises: adding 2,6-dimethylaniline to a mixed solution of dimethylformamide and water, heating and refluxing the solution under a protective atmosphere to obtain a first reaction solution; adding 1,1"-bis(2,4-dinitrophenyl)-4,4"-bipyridine (Cl - salt) is dissolved in water and then added to the first reaction solution, and refluxed to obtain a reaction mixture; the reaction mixture is cooled to produce a yellow-brown oily precipitate; the precipitate is removed, water in the reaction mixture is evaporated and removed, and acetone is added after concentration to obtain a brown precipitate; the brown precipitate is dissolved in a mixture of methanol and water, an excess amount of sodium tetrafluoroborate aqueous solution is added, the mixture is allowed to stand, and separated to obtain a light brown needle-shaped substance;

[0016] Or, the structural formula is The preparation method of the cathode material comprises: adding 2,4,6-trimethylaniline to a mixed solution of dimethylformamide and water, heating and refluxing the solution under a protective atmosphere to obtain a first reaction solution; adding 1,1"-bis(2,4-dinitrophenyl)-4,4"-bipyridine (Cl - The first reaction solution is added with a salt (salt) dissolved in water, and refluxed to obtain a reaction mixture; the reaction mixture is cooled to produce a yellow-brown precipitate; the precipitate is removed, water in the reaction mixture is evaporated to remove the water, and acetone is added after concentration to obtain a yellow-brown solid; the yellow-brown solid is dissolved in a mixture of methanol and water, an excess amount of sodium tetrafluoroborate aqueous solution is added, and the mixture is separated to obtain a bright yellow solid.

[0017] In an optional embodiment, any one of R and R1' is methyl, the other is methylphenyl, R2, R6, R2' and R6' are all H, X - PF6 - .

[0018] In an optional embodiment, the cathode material has the structural formula:

[0019]

[0020] In an optional embodiment, the structural formula is The preparation method of the cathode material comprises: adding 3,5-dimethoxyaniline to a mixed solution of dimethylformamide and water, heating and refluxing the solution under a protective atmosphere to obtain a first reaction solution; adding 1-(2,4-dinitrophenyl)-4,4"-bipyridinium (Cl - The method comprises the following steps: dissolving the light yellow solid in acetonitrile, adding an excess of methyl iodide, and reacting under a protective atmosphere, followed by cooling to room temperature, and separating to obtain a bright orange precipitate; dissolving the bright orange precipitate in water, adding an aqueous sodium tetrafluoroborate solution, refrigerating, and separating to obtain a yellow-orange solid; dissolving the yellow-orange solid in acetonitrile, and then adding an acetone solution of tetraethylammonium chloride to precipitate it as a chloride salt; separating the chloride salt and dissolving it in water, performing solid-liquid separation, mixing the separated liquid with an aqueous ammonium hexafluorophosphate solution, and vacuum filtering to obtain a white-gray solid.

[0021] In an alternative embodiment, R1 and R1' are independently an aryl group with an alkoxy group.

[0022] In an alternative embodiment, R1 and R1' are independently aryl groups with a methoxy group.

[0023] In an alternative embodiment, at least one of R1 and R1' is methoxyphenyl.

[0024] In an alternative embodiment, either one of R1 and R1' is methoxyphenyl and the other is methyl.

[0025] In an optional embodiment, any one of R and R1' is methyl, the other is methoxyphenyl, R2, R6, R2' and R6' are all H, X - PF6 - .

[0026] In an optional embodiment, the cathode material has the structural formula:

[0027]

[0028] In an optional embodiment, the structural formula is The preparation method of the cathode material comprises: adding o-toluidine to a mixed solution of dimethylformamide and water, heating and refluxing the solution under a protective atmosphere to obtain a first reaction solution; adding 1-(2,4-dinitrophenyl)-4,4"-bipyridinium (Cl -The salt) is dissolved in water and added to the first reaction solution, and refluxed to react to obtain a reaction mixture; the reaction mixture is cooled until a precipitate is generated; the precipitate is removed, the remaining liquid is concentrated, and an acetone solution is added to obtain a light yellow solid; the solid is dissolved in water and washed with an ammonium hexafluorophosphate aqueous solution, and separated by vacuum filtration to obtain a white precipitate.

[0029] In a second aspect, the present invention provides an electrochromic device, which includes a cathode electrochromic material and an anode electrochromic material, wherein the cathode electrochromic material includes the cathode material in the application of any of the aforementioned embodiments, and the anode electrochromic material includes dimethylphenazine.

[0030] In an optional embodiment, the molar ratio of the cathode material to dimethylphenazine is 20:(24-26).

[0031] The beneficial effects of the present invention include:

[0032] The present invention introduces electron-donating groups on the N atom or pyridine ring of the 4,4'-bipyridine cathode material to perform structural modification, so that its electron-acquiring ability is weakened and its electron-losing ability is enhanced. In this way, when voltage is applied, the difficulty of the coloring process of the modified bipyridine material from +2 valence to +1 valence increases, and when power is off, the difficulty of changing from +1 valence to +2 valence decreases, thereby reducing its redox potential. The redox potential after modification has a larger absolute value than before modification, and the absolute value of the potential difference (Φ anode - Φ cathode) of the electrochromic solution prepared by the cathode material and the anode material (such as dimethylphenazine) with reduced redox potential increases, and the potential energy required for the cathode material to undergo a forward reaction in the redox process increases, and the corresponding potential energy required for the reverse reaction decreases, thereby improving the transmittance of the device in the initial state and shortening the fading time. The electrochromic device prepared by the modified cathode material can meet the requirements for appearance and application performance after being bonded to the waveguide lens module. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0034] Figure 1 This is the CV diagram of the cathode material prepared in Example 1;

[0035] Figure 2 This is the CV diagram of the cathode material prepared in Example 2;

[0036] Figure 3 This is the CV diagram of the cathode material prepared in Example 3;

[0037] Figure 4 This is the CV diagram of the cathode material prepared in Example 4. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0039] The application of the cathode material provided by the present invention in reducing the redox potential and the electrochromic device are described in detail below.

[0040] The present invention provides an application of a cathode material in reducing redox potential. The general formula of the cathode material is:

[0041] wherein R1 and R1′ are independently selected from an alkyl group, an aryl group or an alkoxy group; R2, R6, R2′ and R6′ are independently selected from H, F, Cl, Br, I, CN, NO2, an alkyl group, an alkoxy group or an aryl group; X - Selected from BF4 - or PF6 - .

[0042] In some optional embodiments, R1 and R1' are independently aryl groups with alkyl groups. In some typical embodiments, R1 and R1' are independently aryl groups with methyl groups, wherein the number of methyl groups can be 2 or 3, etc. In some typical embodiments, at least one of R1 and R1' is methylphenyl.

[0043] For example, R and R1' are both methylphenyl, R2, R6, R2' and R6' are all H, X - For BF4 - For example, the structural formula of the cathode material can be:

[0044] The former is denoted as compound A, and the latter is denoted as compound B. Compound A is 1,1'-bis(2,6-dimethylphenyl)-4,4'-bipyridinium bis(tetrafluoroboric acid), and compound B is 1,1'-bis(2,4,6-trimethylphenyl)-4,4'-bipyridinium bis(tetrafluoroboric acid).

[0045] In some optional embodiments, the preparation method of chemical A may include: adding 2,6-dimethylaniline to a mixed solution of dimethylformamide and water, heating and refluxing under a protective atmosphere to obtain a first reaction solution; adding 1,1"-bis(2,4-dinitrophenyl)-4,4"-bipyridine (Cl - salt) is dissolved in water and added to the first reaction solution, and refluxed to react to obtain a reaction mixture; the reaction mixture is cooled to produce a yellow-brown oily precipitate; the precipitate is removed, water in the reaction mixture is evaporated and removed, and acetone is added after concentration to obtain a brown precipitate; the brown precipitate is dissolved in a mixture of methanol and water, an excess amount of sodium tetrafluoroborate aqueous solution is added, the mixture is allowed to stand, and separated to obtain a light brown needle-shaped substance.

[0046] In some optional embodiments, the preparation method of chemical B may include: adding 2,4,6-trimethylaniline to a mixed solution of dimethylformamide and water, heating and refluxing under a protective atmosphere to obtain a first reaction solution; adding 1,1"-bis(2,4-dinitrophenyl)-4,4"-bipyridine (Cl - The first reaction solution is added with a salt (salt) dissolved in water, and refluxed to obtain a reaction mixture; the reaction mixture is cooled to produce a yellow-brown precipitate; the precipitate is removed, water in the reaction mixture is evaporated to remove the water, and acetone is added after concentration to obtain a yellow-brown solid; the yellow-brown solid is dissolved in a mixture of methanol and water, an excess amount of sodium tetrafluoroborate aqueous solution is added, and the mixture is separated to obtain a bright yellow solid.

[0047] For example, any one of R1 and R1' is methylphenyl, the other is methyl, R2, R6, R2' and R6' are all H, X - PF6 - For example, the structural formula of the cathode material can be:

[0048] This compound is referred to as Compound C, and specifically is 1-(3,5-dimethoxyphenyl)-1'-methyl-4,4'-bipyridinium bis(hexafluorophosphate).

[0049] In some optional embodiments, the preparation method of chemical C may include: adding 3,5-dimethoxyaniline to a mixed solution of dimethylformamide and water, heating and refluxing under a protective atmosphere to obtain a first reaction solution; adding 1-(2,4-dinitrophenyl)-4,4"-bipyridinium (Cl -The method comprises the following steps: dissolving the light yellow solid in acetonitrile, adding an excess of methyl iodide, and reacting under a protective atmosphere, followed by cooling to room temperature, and separating to obtain a bright orange precipitate; dissolving the bright orange precipitate in water, adding an aqueous sodium tetrafluoroborate solution, refrigerating, and separating to obtain a yellow-orange solid; dissolving the yellow-orange solid in acetonitrile, and then adding an acetone solution of tetraethylammonium chloride to precipitate it as a chloride salt; separating the chloride salt and dissolving it in water, performing solid-liquid separation, mixing the separated liquid with an aqueous ammonium hexafluorophosphate solution, and vacuum filtering to obtain a white-gray solid.

[0050] In some other optional embodiments, R1 and R1' are independently aryl groups with alkoxy groups. In some more typical embodiments, R1 and R1' are independently aryl groups with methoxy groups, wherein the number of methoxy groups can be 2 or 3, etc. In some more typical embodiments, at least one of R1 and R1' is methoxyphenyl.

[0051] For example, any one of R1 and R1' is methoxyphenyl, the other is methyl, R2, R6, R2' and R6' are all H, X - PF6 - For example, the structural formula of the cathode material can be: This compound is referred to as compound D, and specifically is 1-methyl-1′-(2-methylphenyl)-4,4′-bipyridinium bis(hexafluorophosphate).

[0052] In some optional embodiments, the preparation method of chemical D may include: adding o-toluidine to a mixed solution of dimethylformamide and water, heating and refluxing under a protective atmosphere to obtain a first reaction solution; adding 1-(2,4-dinitrophenyl)-4,4"-bipyridinium (Cl - The salt) is dissolved in water and added to the first reaction solution, and refluxed to react to obtain a reaction mixture; the reaction mixture is cooled until a precipitate is generated; the precipitate is removed, the remaining liquid is concentrated, and an acetone solution is added to obtain a light yellow solid; the solid is dissolved in water and washed with an ammonium hexafluorophosphate aqueous solution, and separated by vacuum filtration to obtain a white precipitate.

[0053] As mentioned above, the present invention introduces electron-donating groups on the N atom or pyridine ring of the 4,4'-bipyridine cathode material to perform structural modification, so that its electron-acquiring ability is weakened and its electron-losing ability is enhanced. In this way, when voltage is applied, the difficulty of the coloring process of the modified bipyridine material from +2 valence to +1 valence increases, and when the power is off, the difficulty of changing from +1 valence to +2 valence decreases, thereby reducing its redox potential. The redox potential after modification has a larger absolute value than before modification, and the absolute value of the potential difference (Φ anode - Φ cathode) of the electrochromic solution prepared by the cathode material and the anode material (such as dimethylphenazine) with reduced redox potential increases, and the potential energy required for the cathode material to undergo a forward reaction in the redox process increases, and the corresponding potential energy required for the reverse reaction decreases, thereby improving the transmittance of the device in the initial state and shortening the fading time. The electrochromic device prepared with the modified cathode material can meet the requirements for appearance and application performance after being bonded to the waveguide lens module.

[0054] Correspondingly, the present invention also provides an electrochromic device, which includes a cathode electrochromic material and an anode electrochromic material, wherein the cathode electrochromic material includes the above-mentioned cathode material provided by the present invention, and the anode electrochromic material includes dimethylphenazine.

[0055] In some optional embodiments, the molar ratio of the cathode material to dimethylphenazine can be 20:(24-26), such as 20:24, 20:25 or 20:26.

[0056] In some optional embodiments, the initial maximum transmittance of the electrochromic device is ≥90%, and the fading time is ≤10s.

[0057] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0058] Example 1

[0059] This embodiment provides a 1,1'-bis(2,6-dimethylphenyl)-4,4'-bipyridinium bis(tetrafluoroboric acid), the preparation method of which is as follows: 7.0 mL of 2,6-dimethylaniline is added to 30 mL of a mixed solution of dimethylformamide and water (volume ratio is 3:2), and the mixture is heated under reflux reaction (80°C, 10 h) in a nitrogen atmosphere to obtain a first reaction solution. 5.0 g of 1,1'-bis(2,4-dinitrophenyl)-4,4'-bipyridinium (Cl -Salt) was dissolved in 50 mL of water and then slowly added to the first reaction solution through a constant pressure funnel, followed by reflux reaction at 80 ° C for 2.5 hours to obtain a reaction mixture. The reaction mixture was cooled to produce a yellow-brown oily precipitate. The precipitate was filtered to remove the water in the filtrate by rotary evaporation, the solution was concentrated to 10 mL, and then a large amount of acetone was added to the concentrate to obtain a brown precipitate. The brown precipitate was dissolved in a mixture of methanol and water (volume ratio of 10:1) and purified, and then an excess of sodium tetrafluoroborate aqueous solution was added thereto, and then allowed to stand at room temperature overnight. A light brown needle-shaped substance was separated by suction filtration, which was the target product 1,1'-(2,6-dimethylphenyl)-4,4'-bipyridinium bis(tetrafluoroboric acid), also known as compound A.

[0060] The yield of compound A obtained by the method is about 59%, which is about 3% higher than the yield of the compound synthesized by the prior art.

[0061] The target product obtained above was characterized by nuclear magnetic hydrogen spectrum data, and the data results are as follows: 1 HNMR (400 MHz, DMSO-d6), δ2.35 (s1, 2H), δ7.09 (d, J = 6.4 Hz, 4H), δ7.49 (t, J = 6.9 Hz, 2H), δ8.87 (d, J = 6.7 Hz, H), δ9.24 (d, J = 7.1 Hz, 4H). The data indicated that the product was indeed 1,1'-(2,6-dimethylphenyl)-4,4'-bipyridinium bis(tetrafluoroborate).

[0062] Example 2

[0063] The present embodiment provides a 1,1'-bis(2,4,6-trimethylphenyl)-4,4'-bipyridinium bis(tetrafluoroboric acid), the preparation method of which is as follows: 7.5 mL of 2,4,6-trimethylaniline is added to 40 mL of a mixed solution of dimethylformamide and water (volume ratio is 3:2), and the mixture is heated under reflux reaction (80°C, 10 h) in a nitrogen atmosphere to obtain a first reaction solution; 5.0 g of 1,1'-bis(2,4-dinitrophenyl)-4,4'-bipyridyl(Cl -The salt was dissolved in 50 mL of water and then slowly added to the first reaction solution through a constant pressure funnel, and refluxed at 80 ° C for 6 hours to obtain a reaction mixture. The reaction mixture was cooled until a yellow-brown precipitate was produced. The precipitate was filtered out, and the water in the filtrate was removed by rotary evaporation. The filtrate was concentrated to 10 mL, and then a large amount of acetone was added to the concentrate to obtain a yellow-brown solid. The yellow-brown solid was dissolved in a mixture of methanol and water (volume ratio of 10:1) for purification, and an excess of sodium tetrafluoroborate aqueous solution was added thereto. The crude product was separated by suction filtration, and the product was washed with appropriate amounts of cold methanol and water. After adding water and removing methanol by rotary evaporation, a bright yellow solid was separated by suction filtration, which was the target product 1,1′-bis(2,4,6-trimethylphenyl)-4,4′-bipyridinium bis(tetrafluoroboric acid), also known as compound B.

[0064] The yield of compound B obtained by the method is about 71%, which is about 5% higher than the yield of the compound synthesized by the prior art.

[0065] The target product obtained above was characterized by nuclear magnetic hydrogen spectrum data, and the data results are as follows: 1 HNMR (400Hz, DMSO-d6), δ3.81 (s, 6H), δ4.39 (s, 3H), δ6.39 (s, 1H), δ6.63 (s, 2H), δ8.90-8.96 (m, 4H), δ9.10 (d, J = 4.8Hz, 2H), δ9.28 (d, J = 6.2Hz, 2H). The data showed that the product was indeed 1,1′-bis(2,4,6-trimethylphenyl)-4,4′-bipyridinium bis(tetrafluoroborate).

[0066] Example 3

[0067] This embodiment provides 1-(3,5-dimethoxyphenyl)-1'-methyl-4,4'-bipyridinium bis(hexafluorophosphate), the preparation method of which is as follows: 3.0 mL of 3,5-dimethoxyaniline is added to 25 mL of a mixed solution of dimethylformamide and water (volume ratio is 3:2), and heated under reflux reaction (80°C, 12h) in a nitrogen atmosphere to obtain a first reaction solution. 5.0 g of 1-(2,4-dinitrophenyl)-4,4'-bipyridinium (Cl -After the salt is dissolved in 50mL of water, it is slowly added to the first reaction solution through a constant pressure funnel, refluxed at 80°C for 3h, cooled, and a colorless precipitate is produced. The colorless precipitate is filtered to remove the colorless precipitate, and the filtrate volume is concentrated to 10mL by rotary evaporation. A large amount of acetone is then added to the filtrate to produce a light yellow solid. 3.0g of the light yellow solid is dissolved in 80mL of acetonitrile, followed by an excess of iodomethane, refluxed at 80°C for 4h under a nitrogen atmosphere, then cooled to room temperature, and vacuum filtered to separate a bright orange precipitate. The bright orange precipitate is dissolved in water, an aqueous solution of sodium tetrafluoroborate is added, refrigerated overnight, and a yellow-orange solid is obtained by vacuum filtration. The above-mentioned yellow-orange solid is first dissolved in acetonitrile, and then an acetone solution of tetraethylammonium chloride is added thereto, and it is precipitated as a chloride salt for purification. The chloride salt is separated by filtration and air-dried briefly, then dissolved in water, filtered again, an aqueous solution of ammonium hexafluorophosphate is added to the filtrate, and vacuum filtered to precipitate a white-gray solid. That is the target product 1-(3,5-dimethoxyphenyl)-1'-methyl-4,4'-bipyridinium bis(hexafluorophosphate), also known as compound C.

[0068] The yield of compound C obtained by the method is about 68%, which is about 2% higher than the yield of the compound synthesized by the prior art.

[0069] The target product obtained above was characterized by nuclear magnetic hydrogen spectrum data, and the data results are as follows: 1 HNMR (400Hz, DMSO-d6), δ2.33 (s, 3H), δ4.39 (s, 3H), δ7.16-7.25 (m, 3H), δ7.99 (m, 1H), δ8.9-8.96 (m, 4H), δ9.0 (d, J=6.3Hz, 2H), δ9.26 (d, J=7.2Hz, 2H). The data showed that the product was indeed 1-(3,5-dimethoxyphenyl)-1'-methyl-4,4'-bipyridinium bis(hexafluorophosphate).

[0070] Example 4

[0071] This embodiment provides 1-methyl-1'-(2-methylphenyl)-4,4'-bipyridinium bis(hexafluorophosphate), the preparation method of which is as follows: 3.0 mL of o-toluidine is added to a mixed solution of 25 mL of dimethylformamide and water (volume ratio is 3:2), and the mixture is heated under reflux reaction (80°C, 12h) in a nitrogen atmosphere to obtain a first reaction solution. 3.0 g of 1-(2,4-dinitrophenyl)-4,4'-bipyridinium (Cl -The salt was dissolved in 50 mL of water and then slowly added to the first reaction solution through a constant pressure funnel, refluxed at 80°C for 3.5 hours, and cooled until a precipitate was produced. The precipitate was removed by filtration, and the volume of the filtrate was concentrated to 10 mL by rotary evaporation. A large amount of acetone solution was added to the concentrate to obtain a light yellow solid. The light yellow solid was dissolved in water, and then washed with an appropriate amount of ammonium hexafluorophosphate aqueous solution, and separated by vacuum filtration to obtain a white precipitate. This is the target product 1-methyl-1'-(2-methylphenyl)-4,4'-bipyridinium bis(hexafluorophosphate), also known as compound D.

[0072] The yield of compound D obtained by the method is about 71%, which is about 7% higher than the yield of the compound synthesized by the prior art.

[0073] The target product obtained above was characterized by nuclear magnetic hydrogen spectrum data, and the data results are as follows: 1 H NMR (400 Hz, DMSO-d6), δ2.18 (s, 6H), δ2.33 (s, 12H), δ6.97 (s, 4H), δ8.90 (d, J = 5.6 Hz, 4H), δ9.24 (d, J = 5.2 Hz, 4H). The data showed that the product was indeed 1-methyl-1'-(2-methylphenyl)-4,4'-bipyridinium bis(hexafluorophosphate).

[0074] Test Example 1

[0075] The four cathode materials prepared in Examples 1 to 4 were respectively used in an electrochemical workstation, with AgCl / Ag as the reference electrode, to measure their redox potentials by cyclic voltammetry, and the CV diagrams of the four cathode materials were obtained as shown in FIG. Figures 1 to 4 shown.

[0076] Combination Figures 1 to 4 It can be proved that the reduction potentials of the four cathode materials after the introduction of electron-donating groups are -0.55V, -0.69V, -0.62V and -0.64V, respectively, which are lower than the reduction potential of the existing bipyridine material (-0.4V). This shows that the introduction of specific electron-donating groups on the N atom of bipyridine for structural modification can reduce its redox potential.

[0077] Test Example 2

[0078] The four cathode materials prepared in Examples 1 to 4 are taken as examples, and 4,4'-bipyridine is taken as a comparative example.

[0079] The performance of each cathode material was tested according to the following method: 20mmol of cathode material and anode electrochromic material dimethylphenazine (25mmol) and ferrocene tetrafluoroborate buffer (5mmol) were dissolved in propylene carbonate solution to obtain an electrochromic solution. Two pieces of 30mm×30mm×0.21mm soda-lime ITO glass were used, with the ITO side facing up, and the frame glue was applied at the left and right edges of the glass at a 2mm offset using thermosetting frame glue, leaving a 2mm filling port. After bonding, it was baked at 120℃ for 1h to prepare a glass box. The glue width of the prepared device was 2mm, and the box thickness was controlled to be 125μm. The above electrochromic solution was filled into the ITO glass box by vacuum filling, and sealed and cured with UV glue. A total of 3 devices were prepared for testing. The maximum transmittance and chromaticity values ​​(L*, a*, b*) of the center points of the 3 devices were tested using a color haze meter. Metal clips connected to the power wires were fixed at both ends of the device to test the response time of the 3 devices when powered on at 1.2V. The results are shown in Tables 1 to 5.

[0080] Table 1 Test results

[0081] serial number Initial transmittance L* a* b* Coloring time Fading time 1 84％ 92.46 -2.83 11.92 9s 11s 2 85％ 91.89 -2.76 12.13 9s 10s 3 85％ 92.62 -2.91 11.19 8s 12s

[0082] From the distribution of L*, a*, and b* values ​​in Table 1, it can be seen that the electrochromic device prepared by the comparative example has an initial yellowish color, an initial maximum transmittance ≤85%, and a fading time ≥10s, which is very unfavorable for actual application in products.

[0083] Table 2 Test results

[0084]

[0085]

[0086] From the distribution of L*, a*, and b* values ​​in Table 2, it can be seen that, compared with the comparative example, the initial yellow color of the electrochromic device prepared in Example 1 is improved, the initial maximum transmittance is ≥90%, and the fading time is ≤9s, indicating that the introduction of electron-donating groups reduces the redox potential of the cathode material, increases the initial maximum transmittance, and shortens the fading time.

[0087] Table 3 Test results

[0088] serial number Initial transmittance L* a* b* Coloring time Fading time 1 92％ 95.18 -2.14 9.17 8s 7s 2 91％ 96.04 -2.23 9.08 9s 8s 3 91％ 96.49 -2.16 8.94 8s 7s

[0089] From the distribution of L*, a*, and b* values ​​in Table 3, it can be seen that, compared with the comparative example, the initial yellow color of the electrochromic device prepared in Example 2 is also improved, the initial maximum transmittance is ≥91%, and the fading time is ≤8s, which also indicates that the introduction of electron-donating groups reduces the redox potential of the cathode material, increases the initial maximum transmittance, and shortens the fading time.

[0090] Table 4 Test results

[0091] serial number Initial transmittance L* a* b* Coloring time Fading time 1 92％ 96.97 -1.46 7.48 8s 7s 2 92％ 96.74 -1.57 7.89 8s 6s 3 91％ 95.83 -1.41 7.81 7s 6s

[0092] From the distribution of L*, a*, and b* values ​​in Table 4, it can be seen that, compared with the comparative example, the initial yellow color of the electrochromic device prepared in Example 3 is improved, the initial maximum transmittance is ≥91%, and the fading time is ≤7s, which also indicates that the introduction of electron-donating groups reduces the redox potential of the cathode material, increases the initial maximum transmittance, and shortens the fading time.

[0093] Table 5 Test results

[0094]

[0095]

[0096] From the distribution of L*, a*, and b* values ​​in Table 5, it can be seen that, compared with the comparative example, the initial yellow color of the electrochromic device prepared by Example 4 is improved to the greatest extent, the initial maximum transmittance is ≥92%, and the fading time is about 6s. Similarly, the introduction of electron-donating groups reduces the redox potential of the cathode material, increases the initial maximum transmittance, and shortens the fading time.

[0097] In summary, the present invention introduces electron-donating groups onto the N atoms of the 4,4'-bipyridine cathode electrochromic material to reduce its redox potential, thereby increasing the initial maximum transmittance of the electrochromic device prepared using the material, reducing the initial appearance color of the device, and increasing the fading response time of the electrochromic device, thereby meeting the requirements for appearance color and application performance of the electrochromic device prepared by the material after being bonded to a waveguide lens module.

[0098] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. Use of a cathode material in reducing redox potential, characterized in that: The general formula of the cathode material is: wherein R1 and R1′ are independently selected from an alkyl group, an aryl group or an alkoxy group; R2, R6, R2′ and R6′ are independently selected from H, F, Cl, Br, I, CN, NO2, an alkyl group, an alkoxy group or an aryl group; X - Selected from BF4 - or PF6 - .

2. The use according to claim 1, characterized in that: R1 and R1' are independently aryl groups with alkyl groups; Preferably, R1 and R1' are independently aryl groups with a methyl group; Preferably, at least one of R1 and R1' is a methylphenyl group; Preferably, either one of R1 and R1' is a methylphenyl group, and the other is a methyl group.

3. The use according to claim 2, characterized in that: R and R1' are both methylphenyl, R2, R6, R2' and R6' are all H, X - For BF4 - ; Preferably, the cathode material has the structural formula:

4. The use according to claim 3, characterized in that: The structural formula is The preparation method of the cathode material comprises: adding 2,6-dimethylaniline to a mixed solution of dimethylformamide and water, heating and refluxing the solution under a protective atmosphere to obtain a first reaction solution; adding 1,1'-bis(2,4-dinitrophenyl)-4,4'-bipyridine (Cl - salt) is dissolved in water and then added to the first reaction solution, and refluxed to obtain a reaction mixture; the reaction mixture is cooled to produce a yellow-brown oily precipitate; the precipitate is removed, water in the reaction mixture is evaporated and removed, and acetone is added after concentration to obtain a brown precipitate; the brown precipitate is dissolved in a mixture of methanol and water, an excess amount of sodium tetrafluoroborate aqueous solution is added, the mixture is allowed to stand, and separation is performed to obtain a light brown needle-shaped substance; Or, the structural formula is The preparation method of the cathode material comprises: adding 2,4,6-trimethylaniline to a mixed solution of dimethylformamide and water, heating and refluxing the solution under a protective atmosphere to obtain a first reaction solution; adding 1,1'-bis(2,4-dinitrophenyl)-4,4'-bipyridine (Cl - salt) is dissolved in water and added to the first reaction solution, refluxed to react, and a reaction mixture is obtained; the reaction mixture is cooled to produce a yellow-brown precipitate; the precipitate is removed, water in the reaction mixture is evaporated to remove the water, and acetone is added after concentration to obtain a yellow-brown solid; the yellow-brown solid is dissolved in a mixture of methanol and water, an excess amount of sodium tetrafluoroborate aqueous solution is added, and the mixture is separated to obtain a bright yellow solid.

5. The use according to claim 2, characterized in that: Any one of R and R1' is methyl, the other is methylphenyl, R2, R6, R2' and R6' are all H, X - PF6 - ; Preferably, the cathode material has the structural formula:

6. The use according to claim 5, characterized in that: The structural formula is The preparation method of the cathode material comprises: adding 3,5-dimethoxyaniline to a mixed solution of dimethylformamide and water, heating and refluxing the solution under a protective atmosphere to obtain a first reaction solution; adding 1-(2,4-dinitrophenyl)-4,4'-bipyridinium (Cl - The method comprises the following steps: dissolving the light yellow solid in acetonitrile, adding an excess of methyl iodide, and reacting under a protective atmosphere, followed by cooling to room temperature, and separating to obtain a bright orange precipitate; dissolving the bright orange precipitate in water, adding an aqueous sodium tetrafluoroborate solution, refrigerating, and separating to obtain a yellow-orange solid; dissolving the yellow-orange solid in acetonitrile, and then adding an acetone solution of tetraethylammonium chloride to precipitate it as a chloride salt; separating the chloride salt and dissolving it in water, performing solid-liquid separation, mixing the separated liquid with an aqueous ammonium hexafluorophosphate solution, and vacuum filtering to obtain a white-gray solid.

7. The use according to claim 1, characterized in that: R1 and R1' are independently an aryl group with an alkoxy group; Preferably, R1 and R1' are independently aryl groups with methoxy groups; Preferably, at least one of R1 and R1' is methoxyphenyl; Preferably, either one of R1 and R1' is methoxyphenyl, and the other is methyl.

8. The use according to claim 7, characterized in that: Any one of R and R1' is methyl, the other is methoxyphenyl, R2, R6, R2' and R6' are all H, X - PF6 - ; Preferably, the cathode material has the structural formula:

9. The use according to claim 8, characterized in that: The structural formula is The preparation method of the cathode material comprises: adding o-toluidine to a mixed solution of dimethylformamide and water, heating and refluxing the solution under a protective atmosphere to obtain a first reaction solution; adding 1-(2,4-dinitrophenyl)-4,4'-bipyridinium (Cl - The salt) is dissolved in water and then added to the first reaction solution, and refluxed to react to obtain a reaction mixture; the reaction mixture is cooled until a precipitate is generated; the precipitate is removed, the remaining liquid is concentrated, and an acetone solution is added to obtain a light yellow solid; the solid is dissolved in water and then washed with an aqueous solution of ammonium hexafluorophosphate, and separated by vacuum filtration to obtain a white precipitate.

10. An electrochromic device, characterized in that: The electrochromic device comprises a cathode electrochromic material and an anode electrochromic material, wherein the cathode electrochromic material comprises the cathode material in the application according to any one of claims 1 to 9, and the anode electrochromic material comprises dimethylphenazine; Preferably, the molar ratio of the cathode material to the dimethylphenazine is 20:(24-26).

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