Prussian blue ion storage layer material and preparation method thereof

Abstract

The invention discloses a Prussian blue ion storage layer material for an electrochromic device and a preparation method of the Prussian blue ion storage layer material. The invention relates to an ion storage layer material, in particular to a water-phase coating liquid composition which is prepared from Prussian blue nano powder, a nano conductive additive, an adhesion promoter, a wetting dispersant and a film-forming binder as functional materials according to a certain proportion. The coating liquid is spread on a transparent conductive substrate in a wet coating manner to form a film, and the film is baked to obtain the transparent conductive film. The ion storage material provided by the invention has the advantages of uniform dispersion, low haze, good adhesion to a base material, environmental friendliness and the like; and compared with an ion storage material prepared by a conventional technology, an electrochromic device prepared from the ion storage material has the characteristics of high color change contrast ratio, high color change speed, good high-temperature cycling stability and the like.

Description

Technical Field

[0001] The invention relates to a Prussian blue ion storage layer material for an electrochromic device and a preparation method thereof, belonging to the technical field of electrochromic devices. Background Art

[0002] As a special metal organic framework compound (MOFs), Prussian blue and its derivatives are hot cathode materials in the research of sodium ion batteries and potassium ion batteries due to their special structure and physicochemical properties. The chemical structure of Prussian blue material is Fe4[Fe(CN)6]3. Since it contains 4 positive trivalent Fe atoms and 3 positive divalent iron atoms, it has a variety of color-changing properties during oxidation or reduction reactions. It is a commonly used electrochromic material. By applying Prussian blue to the electrode, the electrode potential is used to control the valence state of the iron ions in the complex, thereby causing color changes. In addition to being used as an electrochromic material, Prussian blue has also been reported to be used as the counter electrode of the electrochromic layer - the ion storage layer material, and it has a greater bright state transmittance and color change contrast than vanadium pentoxide materials. However, Prussian blue nanoparticles still have the following problems as ion storage layer materials: first, the surface is relatively inert, and the dispersibility is poor in various solvents, especially in the aqueous system, which cannot meet the requirements of the coating solution; second, the film-forming property of the Prussian blue coating and the adhesion to the transparent conductive substrate are both poor; third, the Prussian blue nanoparticles are cubic in morphology, and the film structure is loose, which limits the current transmission between the conductive layer, the charge storage capacity is small, the color change speed is slow, and the charge and discharge cycle stability is also poor. Therefore, the existing technology needs to be improved and developed. Summary of the invention

[0003] In order to overcome the defects and shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a Prussian blue ion storage layer material for an electrochromic device and a preparation method thereof; the Prussian blue composition formula provided by the present invention can significantly improve the uniform dispersion of nano Prussian blue particles in the aqueous phase, the adhesion to the conductive substrate and the electron conduction ability, and the electrochromic device made using the ion storage layer material has a fast color change speed and excellent charge and discharge cycle stability.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0005] In a first aspect, the present invention provides a Prussian blue ion storage layer material for an electrochromic device, wherein the ion storage layer material is prepared by a Prussian blue coating composition through a roll-to-roll wet coating method, and the composition comprises 2-15% by mass of Prussian blue nanopowder, 0.2-2.0% of a film-forming binder, 0.1-2.0% of an adhesion promoter, 0.1-2.0% of a wetting dispersant, 0.02-0.5% of a nano conductive additive and 78.5-97.5% of deionized water.

[0006] Furthermore, the particle size of the Prussian blue nanopowder in the coating composition is 10-100 nm.

[0007] Furthermore, the film-forming binder in the coating composition is selected from one or a combination of two of polyvinyl alcohol, polyvinyl pyrrolidone, polytetrafluoroethylene emulsion, polyethylene oxide, polyethylene glycol, and water-soluble cellulose nanofibers. Considering the lithium ion transmission capacity, a combination of one or two of polytetrafluoroethylene emulsion, polyethylene oxide, and water-soluble cellulose nanofibers is more preferred.

[0008] Furthermore, the adhesion promoter in the coating composition is selected from at least one of polyethyleneimine, polyacrylic acid, sodium alginate, chitosan, and hydroxypropyl cellulose.

[0009] Further, the wetting and dispersing agent in the coating composition is selected from a combination of any two of the commercially available BYK-2001, BYK-181, BYK-ET3033, Hychemsol-2844, TEGO-760W, TEGO-228E, TEGO-752W, and TEGO-755W. Considering the dispersibility of Prussian blue / conductive nanomaterials and the wetting and spreading properties of the coating on the substrate, a combination of any two of BYK-181, TEGO-228E, BYK-2001 and Hychemsol-2844 is more preferred, and more preferably, a combination of BYK-2001 and TEGO-228E is obtained.

[0010] Furthermore, the nano conductive additive in the coating composition is selected from one of carbon nanotubes, conductive carbon black, transition metal carbide (commonly known as Mxene), graphene, conductive graphite powder, fullerene, and indium tin oxide nanoparticles. Preferably, the material has good dispersibility, conductivity, and inertness to lithium ion electrochemical reaction.

[0011] In a second aspect, the present invention provides a method for preparing the ion storage layer material described in the first aspect, comprising: providing a Prussian blue coating composition for preparing the ion storage layer material; after uniformly mixing the composition, spreading it on a transparent conductive substrate by wet coating, and after high-temperature drying, obtaining a Prussian blue thin film material.

[0012] Furthermore, the mixing order of the above coating composition is not limited, and it is preferred to first dissolve the film-forming binder, wetting dispersant and adhesion promoter in water, and then add other components. The coating composition is subjected to ultrasonic vibration to uniformly disperse the components.

[0013] Furthermore, the thickness of the Prussian blue coating layer is 10-1000 nm.

[0014] Furthermore, the conductive substrate includes PET-ITO film, ITO conductive glass, PET-metal grid or PET-nanosilver wire film.

[0015] Furthermore, the coating and film formation includes coating and film formation by spin coating, screen printing, micro gravure coating or slit coating.

[0016] In a third aspect, the present invention provides an electrochromic device, comprising the ion storage layer material described in the first aspect.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The Prussian blue coating composition of the present invention can achieve uniform dispersion of Prussian blue nanoparticles and nano-conductive additives in the aqueous phase system and have a good spreading effect on the conductive substrate by using a suitable wetting dispersant; a good connection between Prussian blue and the conductive substrate is achieved by adding a multifunctional adhesion promoter, so that the Prussian blue coating layer has good adhesion, ensuring that the coating layer does not scratch or fall off during the roll-to-roll production process; the addition of a film-forming binder with good lithium ion transmission characteristics can not only fill the gaps between the Prussian blue nanoparticles, but also make the coating structure more compact and complete, while not affecting the transmission of lithium ions in the ion storage layer; the addition of nano-conductive additives can enhance the electron transmission capacity between the conductive substrate and the Prussian blue nanoparticles, and the electrochromic device made as the ion storage layer can significantly improve its color change speed and charge and discharge cycle stability. In addition, the preparation method of the present invention is simple, the baking temperature is low, it can adapt to the large-scale production of precision coating roll-to-roll, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The photographs are of the coating wettability and uniformity of the coating composition described in the examples;

[0020] Figure 2 The wettability of the coating composition of Comparative Example 3 without adding a wetting aid;

[0021] Figure 3 This is the coating distribution uniformity of the coating composition described in Comparative Example 4 without adding a dispersant. DETAILED DESCRIPTION

[0022] For ease of understanding, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that these embodiments are only used to explain the present invention and are not used to limit the scope of the present invention.

[0023] The present disclosure also relates to an electrochromic device comprising a charge storage material as described herein as a main functional layer. Other components of the electrochromic device are generally known in the art, such as the electrochromic device involved in the following embodiments further comprising an electrochromic polymer as described in U.S. Patent No. 9975989, which is incorporated herein by reference in its entirety; and an electrolyte layer as described in U.S. Patent No. 20170299932, which is incorporated herein by reference in its entirety.

[0024] Example 1

[0025] Weigh 0.8g of commercially available 60% polytetrafluoroethylene aqueous emulsion (solid content 60%), 0.4g of polyethyleneimine with a weight average molecular weight of 1800, 0.2g of TEGO-228E, and 0.2g of BYK-2001, add them to 75.35g of deionized water, stir to fully dissolve them, then add 4g of commercially available Prussian blue powder (diameter 50-70nm, Xianfeng Nano) and 0.05g of carboxylated multi-walled carbon nanotubes (diameter 10-20nm, length <30μm, Xianfeng Nano), and after sufficient infiltration, perform ultrasonic oscillation to obtain a uniformly dispersed Prussian blue coating composition.

[0026] The above coating composition was coated on a PET film with indium tin oxide sputtered on the surface (surface resistance 20Ω / □) by slit coating at a speed of 400mm / min, and the wet film thickness was controlled to be 18um. It was first baked on a substrate at 40℃ for 3min to remove most of the water, and then transferred to a high-temperature oven for further baking to obtain the final Prussian blue ion storage layer film. The coating effect is as follows Figure 1 As shown, the coating liquid is evenly spread without shrinkage cavities or shrinkage edges, and the coating surface is smooth and uniform after baking.

[0027] Example 2

[0028] Compared with Example 1, the addition amount of the 60% polytetrafluoroethylene aqueous solution was adjusted, and the amount of deionized water was adaptively fine-tuned.

[0029] Weigh 1.2g of commercially available 60% polytetrafluoroethylene aqueous emulsion (solid content 60%), 0.4g of polyethyleneimine with a weight average molecular weight of 1800, 0.2g of TEGO-228E, and 0.2g of BYK-2001, add them to 74.95g of deionized water, stir to fully dissolve them, then add 4g of commercially available Prussian blue powder (diameter 50-70nm, Xianfeng Nano) and 0.05g of carboxylated multi-walled carbon nanotubes (diameter 10-20nm, length <30μm, Xianfeng Nano), and after sufficient infiltration, perform ultrasonic oscillation to obtain a uniformly dispersed Prussian blue coating composition.

[0030] The coating effect is not significantly different from that of Example 1, the coating liquid is evenly spread, there is no shrinkage cavity or edge shrinkage phenomenon, and the coating surface is smooth and uniform after baking.

[0031] The coating composition was coated on a PET film with indium tin oxide sputtered on the surface (surface resistance 20Ω / □) by slit coating at a speed of 400 mm / min, and the wet film thickness was controlled to be 18 um. It was first baked on a substrate at 40°C for 3 min to remove most of the water, and then transferred to a high-temperature oven for further baking to obtain the final Prussian blue ion storage layer film.

[0032] Example 3

[0033] Compared with Example 1, the amount of polyethyleneimine added was adjusted, and the amount of deionized water was adaptively fine-tuned.

[0034] Weigh 0.8g of commercially available 60% polytetrafluoroethylene aqueous emulsion (solid content 60%), 0.6g of polyethyleneimine with a weight average molecular weight of 1800, 0.2g of TEGO-228E, and 0.2g of BYK-2001, add them to 75.15g of deionized water, stir to fully dissolve them, then add 4g of commercially available Prussian blue powder (diameter 50-70nm, Xianfeng Nano) and 0.05g of carboxylated multi-walled carbon nanotubes (diameter 10-20nm, length <30μm, Xianfeng Nano), and after sufficient infiltration, perform ultrasonic oscillation to obtain a uniformly dispersed Prussian blue coating composition.

[0035] The coating composition was coated on a PET film with indium tin oxide sputtered on the surface (surface resistance 20Ω / □) by slit coating at a speed of 400 mm / min, and the wet film thickness was controlled to be 18 um. It was first baked on a substrate at 40°C for 3 min to remove most of the water, and then transferred to a high-temperature oven for further baking to obtain the final Prussian blue ion storage layer film.

[0036] The coating effect is not significantly different from that of Example 1, the coating liquid is evenly spread, there is no shrinkage cavity or edge shrinkage phenomenon, and the coating surface is smooth and uniform after baking.

[0037] Example 4

[0038] Compared with Example 1, the added amount of carboxylated multi-walled carbon nanotubes was adjusted.

[0039] Weigh 0.8g of commercially available 60% polytetrafluoroethylene aqueous emulsion (solid content 60%), 0.4g of polyethyleneimine with a weight average molecular weight of 1800, 0.2g of TEGO-228E, and 0.2g of BYK-2001, add them to 75.35g of deionized water, stir to fully dissolve them, then add 4g of commercially available Prussian blue powder (diameter 50-70nm, Xianfeng Nano) and 0.08g of carboxylated multi-walled carbon nanotubes (diameter 10-20nm, length <30μm, Xianfeng Nano), and after sufficient infiltration, perform ultrasonic oscillation to obtain a uniformly dispersed Prussian blue coating composition.

[0040] The coating composition was coated on a PET film with indium tin oxide sputtered on the surface (surface resistance 20Ω / □) by slit coating at a speed of 400 mm / min, and the wet film thickness was controlled to be 18 um. It was first baked on a substrate at 40°C for 3 min to remove most of the water, and then transferred to a high-temperature oven for further baking to obtain the final Prussian blue ion storage layer film.

[0041] The coating effect is not significantly different from that of Example 1, the coating liquid is evenly spread, there is no shrinkage cavity or edge shrinkage phenomenon, and the coating surface is smooth and uniform after baking.

[0042] Comparative Example 1

[0043] Compared with Example 1, polytetrafluoroethylene aqueous emulsion is not added to the formula, and an equal amount of deionized water is used instead.

[0044] Weigh 0.4 g of polyethyleneimine with a weight average molecular weight of 1800, 0.2 g of TEGO-228E, and 0.2 g of BYK-2001, add them into 76.15 g of deionized water, stir to fully dissolve them, then add 4 g of commercially available Prussian blue powder (diameter 50-70 nm, Xianfeng Nano) and 0.05 g of carboxylated multi-walled carbon nanotubes (diameter 10-20 nm, length <30 μm, Xianfeng Nano), and after sufficient infiltration, perform ultrasonic oscillation to obtain a uniformly dispersed Prussian blue coating composition.

[0045] The coating composition was coated on a PET film (surface resistance 20Ω / □) with indium tin oxide sputtered on the surface by slit coating at a speed of 400 mm / min, and the wet film thickness was controlled to be 18 um. It was first baked on a substrate at 40°C for 3 minutes to remove most of the water, and then transferred to a high-temperature oven for further baking to obtain the final Prussian blue ion storage layer film. The surface gloss of the prepared Prussian blue coating layer was low, the haze was high, and there was a phenomenon of powdering and falling.

[0046] Comparative Example 2

[0047] Compared with Example 1, polyethyleneimine is not added to the coating liquid formulation, and an equal amount of deionized water is used instead.

[0048] Weigh 0.8 g of commercially available 60% polytetrafluoroethylene aqueous emulsion (solid content 60%), 0.2 g of TEGO-228E, and 0.2 g of BYK-2001, add them into 75.75 g of deionized water, stir to fully dissolve them, then add 4 g of commercially available Prussian blue powder (diameter 50-70 nm, Xianfeng Nano) and 0.05 g of carboxylated multi-walled carbon nanotubes (diameter 10-20 nm, length <30 μm, Xianfeng Nano), perform ultrasonic oscillation after sufficient infiltration, and obtain a uniformly dispersed Prussian blue coating composition.

[0049] The coating composition was coated on a PET film (surface resistance 20Ω / □) with indium tin oxide sputtered on the surface by slit coating at a speed of 400 mm / min, and the wet film thickness was controlled to be 18 um. It was first baked on a substrate at 40°C for 3 minutes to remove most of the water, and then transferred to a high-temperature oven for further baking to obtain the final Prussian blue ion storage layer film. The coating effect was normal, but the coating adhesion was poor.

[0050] Comparative Example 3

[0051] Compared with Example 1, the wetting agent TEGO-228E is not added to the coating liquid formula, and the amount of deionized water is adaptively adjusted.

[0052] Weigh 0.8g of commercially available 60% polytetrafluoroethylene aqueous emulsion (solid content 60%), 0.4g of polyethyleneimine with a weight average molecular weight of 1800, and 0.2g of BYK-2001, add them to 75.15g of deionized water, stir to fully dissolve them, then add 4g of commercially available Prussian blue powder (diameter 50-70nm, Xianfeng Nano) and 0.05g of carboxylated multi-walled carbon nanotubes (diameter 10-20nm, length <30μm, Xianfeng Nano), and after sufficient infiltration, perform ultrasonic oscillation to obtain a uniformly dispersed Prussian blue coating composition.

[0053] The above coating composition was coated on a PET film (surface resistance 20 ohms) with indium tin oxide sputtered on the surface by slit coating at a speed of 400 mm / min, and the wet film thickness was controlled to be 18 um. It was first baked on a substrate at 40°C for 3 minutes to remove most of the water, and then transferred to a high-temperature oven for further baking to obtain the final Prussian blue ion storage layer film. The coating effect is as follows Figure 2 As shown, the coating liquid cannot wet the substrate and there is a significant edge shrinkage phenomenon.

[0054] Comparative Example 4

[0055] Compared with Example 1, the dispersant BYK-2001 is not added to the coating liquid formulation, and the amount of deionized water is adaptively fine-tuned.

[0056] Weigh 0.8g of commercially available 60% polytetrafluoroethylene aqueous emulsion (solid content 60%), 0.4g of polyethyleneimine with a weight average molecular weight of 1800, and 0.2g of TEGO-228E, add them to 75.15g of deionized water, stir to fully dissolve them, then add 4g of commercially available Prussian blue powder (diameter 50-70nm, Xianfeng Nano) and 0.05g of carboxylated multi-walled carbon nanotubes (diameter 10-20nm, length <30μm, Xianfeng Nano), and after sufficient infiltration, perform ultrasonic oscillation to obtain a uniformly dispersed Prussian blue coating composition.

[0057] The above coating composition was coated on a PET film (surface resistance 20 ohms) with indium tin oxide sputtered on the surface by slit coating at a speed of 400 mm / min, and the wet film thickness was controlled to be 18 um. It was first baked on a substrate at 40°C for 3 minutes to remove most of the water, and then transferred to a high-temperature oven for further baking to obtain the final Prussian blue ion storage layer film. The coating effect is as follows Figure 3 As shown, the particle dispersion effect is poor and the coating has serious uneven dispersion.

[0058] Comparative Example 5

[0059] Compared with Example 1, no carboxylated multi-walled carbon nanotubes are added to the coating composition, and the amount of deionized water is adaptively adjusted.

[0060] Weigh 0.8g of commercially available 60% polytetrafluoroethylene aqueous emulsion (solid content 60%), 0.4g of polyethyleneimine with a weight average molecular weight of 1800, 0.2g of TEGO-228E, and 0.2g of BYK-2001, add them to 75.3g of deionized water, stir to fully dissolve them, then add 4g of commercially available Prussian blue powder (diameter 50-70nm, Xianfeng Nano), perform ultrasonic oscillation after sufficient infiltration, and obtain a uniformly dispersed Prussian blue coating composition.

[0061] The coating composition was coated on a PET film with indium tin oxide sputtered on the surface (surface resistance 20Ω / □) by slit coating at a speed of 400 mm / min, and the wet film thickness was controlled to be 18 um. It was first baked on a substrate at 40°C for 3 min to remove most of the water, and then transferred to a high-temperature oven for further baking to obtain the final Prussian blue ion storage layer film.

[0062] The ion storage membrane prepared in the above embodiments and comparative examples is combined with an electrochromic polymer (for example, the electrochromic polymer described in U.S. Patent No. 9975989) and an electrolyte (the electrolyte layer described in U.S. Patent No. 0299932) to prepare an electrochromic device. The electrochromic parameters of the prepared electrochromic device (100*100mm) before and after 10,000 cycles calculated under the control logic of 80°C high temperature, 1.0V charge and discharge voltage, and 40s charge and discharge time are shown in Table 1.

[0063] Table 1 Changes of electrochromic devices prepared from ion storage layer materials in Examples and Comparative Examples before and after aging

[0064]

[0065] From the response speed and transmittance changes of the electrochromic devices before and after aging of Examples 1-4 and Comparative Examples 1-5 shown in Table 1, it can be seen that the addition of fluorine-containing film-forming binders, adhesion promoters and nano-conductive additives makes the electrochromic devices show faster response speed and better high-temperature charge and discharge cycle stability. In addition, it is expected that the ion storage material described in the present invention can be mass-produced by conventional precision coating methods.

[0066] The above description is only a preferred embodiment of the present invention and is not any formal or substantial limitation of the present invention. It should be pointed out that a person skilled in the art can make several improvements and supplements without departing from the present invention, and these improvements and supplements should also be regarded as the protection scope of the present invention.

Claims

1. A Prussian blue ion storage layer material, characterized in that: The ion storage layer material is prepared by a Prussian blue coating composition through a roll-to-roll wet coating method, wherein the coating composition comprises 2-15% by mass of Prussian blue nano powder, 0.2-2.0% of a film-forming binder, 0.1-2.0% of an adhesion promoter, 0.1-2.0% of a wetting dispersant, 0.02-0.5% of a nano conductive additive and 78.5-97.5% of deionized water.

2. The Prussian blue ion storage layer material according to claim 1, characterized in that: The particle size of the Prussian blue nano powder in the coating composition is 10-100 nm.

3. The Prussian blue ion storage layer material according to claim 1, characterized in that: The film-forming binder in the coating composition is selected from one or a combination of two of polyvinyl alcohol, polyvinyl pyrrolidone, polytetrafluoroethylene emulsion, polyethylene glycol, and water-soluble cellulose nanofibers.

4. The Prussian blue ion storage layer material according to claim 1, characterized in that: The adhesion promoter in the coating composition is selected from polyethylene imine, polyacrylic acid, sodium alginate, hydroxypropyl cellulose in chitosan, or a combination of two thereof.

5. The Prussian blue ion storage layer material according to claim 1, characterized in that: The wetting and dispersing agent in the coating composition is selected from a combination of any two of commercially available BYK-2001, BYK-181, BYK-ET3033, Hychemsol-2844, TEGO-760W, TEGO-228E, TEGO-752W, and TEGO-755W.

6. The Prussian blue ion storage layer material according to claim 1, characterized in that: The nano conductive additive in the coating composition is selected from one or a combination of two of carbon nanotubes, conductive carbon black, transition metal carbides (commonly known as Mxene), graphene, conductive graphite powder, fullerene, and indium tin oxide nanoparticles.

7. The method for preparing the Prussian blue ion storage layer material according to any one of claims 1 to 6, characterized in that: The coating liquid composition is dispersed by ultrasonic and then spread on a transparent conductive substrate by wet coating, and then dried to remove the solvent to obtain a Prussian blue ion storage layer material.

8. The preparation method according to claim 7, characterized in that: The thickness of the Prussian blue coating layer on the transparent conductive substrate is 50-1000nm.

9. The preparation method according to claim 7, characterized in that: The conductive substrate includes PET-ITO film, ITO conductive glass, PET-metal grid or PET-nanosilver wire film; and / or, The wet coating method includes coating to form a film by spin coating, screen printing, inkjet coating, micro gravure coating or slit coating.

10. An electrochromic device, characterized in that: The invention comprises the Prussian blue ion storage layer material according to any one of claims 1 to 6.

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