Electrolyte system for reducing operating voltage and use in the production of electrochromic devices

Abstract

The application discloses an electrolyte system for reducing working voltage and application in preparation of electrochromic devices, and relates to the technical field of electrochromic devices. The liquid electrolyte system comprises an electrolyte, a solvent and a dopant. The solid electrolyte system comprises a polymer matrix, a plasticizer, an electrolyte and a dopant. The application adds a dopant into the liquid electrolyte system or the full solid gel electrolyte system for the proDOT electrochromic device. The synergistic effect of the oxidation assistance of the dopant and electrochemical oxidation can greatly reduce the working voltage of the electrochromic device and improve the stability of the device. The proDOT electrochromic device with the full solid gel electrolyte system added with the Magic Blue dopant has excellent electrochromic properties, which proves the potential of the novel electrolyte system containing the dopant in improving various performances of the electrochromic device.

Description

(I) Technical Field

[0001] This invention relates to an electrolyte system for reducing operating voltage and its application in the fabrication of electrochromic devices. (II) Background Technology

[0002] In the digital economy era, my country's new display industry is rapidly emerging. Compared to currently used display devices (such as liquid crystal and electroluminescent displays), display devices based on polymer electrochromic materials have advantages such as no blind spots, no need for backlighting, and low driving voltage. However, their low voltage characteristic is still not prominent enough. Therefore, it is necessary to adopt appropriate methods to further reduce the operating voltage of electrochromic devices, which will be more in line with the "dual-carbon" concept. Currently, the liquid electrolyte system used in electrochromic devices mainly includes an electrolyte and a solvent; the solid electrolyte system mainly includes an electrolyte, a polymer matrix, and a plasticizer, which mainly plays the role of ion transfer.

[0003] Based on the above considerations, this invention selects some inorganic / organic dopants, prepares a series of novel electrolyte systems, and assembles electrochromic devices based on proDOT, with the aim of further expanding their applications. (III) Summary of the Invention

[0004] The purpose of this invention is to provide an electrolyte system that can reduce the operating voltage and its application in the preparation of electrochromic devices, thereby significantly reducing the operating voltage of electrochromic devices.

[0005] The technical solution adopted in this invention is:

[0006] This invention provides an electrolyte system for reducing operating voltage, the electrolyte system comprising a liquid electrolyte system and an all-solid gel electrolyte system; the liquid electrolyte system comprises an electrolyte, a solvent, and a dopant; the all-solid gel electrolyte system comprises a polymer matrix, a plasticizer, an electrolyte, and a dopant;

[0007] All dopants are P-type dopants, whose standard electrode potential is higher than that of the electrochromic layer material used in the electrochromic device, and they do not react chemically with other components in the electrolyte system.

[0008] Preferably, the concentration of the electrolyte in the liquid electrolyte system is 0.05–0.1 mol / L (preferably 0.05 mol / L); theoretically, the higher the concentration of the dopant, the better, but considering its application in electrochromic devices, it is advisable to control its addition amount so as not to affect the color change of the electrolyte and the electrochromic performance of the device, and the preferred concentration is 0.05–0.1 mol / L (preferably 0.05 mol / L).

[0009] Preferably, in the all-solid-state gel electrolyte system, the ratio of electrolyte to dopant is 1:1-5, preferably 1:1; the polymer matrix mass is 2-20 g / mmol, preferably 5 g / mmol, based on the amount of electrolyte; the plasticizer volume is 10-60 ml / mmol, preferably 16 ml / mmol, based on the amount of electrolyte; and the solvent volume is 10-30 ml / mmol, preferably 20 ml / mmol, based on the amount of electrolyte.

[0010] Preferably, in the liquid electrolyte system or the all-solid gel electrolyte system, the electrolyte is selected in the same way as the liquid electrolyte described above. It needs to not chemically react with inorganic / organic dopants, and there are no special requirements for the electrolyte content; conventional content is sufficient. The electrolyte is one of tetrabutylammonium perchlorate (TBAP), lithium perchlorate (LiClO4), and ammonium hexafluorophosphate, preferably all of them are tetrabutylammonium perchlorate. The solvent of the liquid electrolyte system is one of acetonitrile or dichloromethane, preferably acetonitrile, which has a wide voltage window and does not dissolve the electrochromic film.

[0011] Preferably, the dopant is one of the following: Ag + Fe 3+ (NO) + Ru 3+ Cu 2+ The terms TCNQ, TAH-6CN, Magic Blue, and F4TCNQ are used, where TCNQ represents 7,7,8,8-tetracyano-p-benzodiquinone dimethane, TAH-6CN represents 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazabenzophenanthrene, Magic Blue represents tris(4-bromophenyl)hexachloroantimonate ammonium, and F4TCNQ represents 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanodimethyl-p-benzoquinone. The Ag mentioned... + The Fe is added in the form of AgTFSI. 3+ It is added in the form of Fe(TFSI)3 or Fe(Tos)3, wherein (NO) + The Ru is added in the form of (NO)PF6. 3+ Cu is added in the form of RuCl3. 2+ It is added in the form of CuCl2.

[0012] Preferably, in the all-solid gel electrolyte system, the polymer matrix can be a polymer matrix commonly used in conventional solid electrolyte systems, and the corresponding component content can be as follows, such as polymethyl methacrylate, polyvinylidene fluoride, poly(vinylidene fluoride-hexachloropropylene), etc., more preferably polymethyl methacrylate (PMMA); the plasticizer, such as propylene carbonate, polyethylene glycol, etc., is preferably propylene carbonate (PC).

[0013] Preferably, when the polymer matrix is ​​PMMA and the plasticizer is PC, the preferred feeding ratio of PMMA to PC is 2-4 g: 5-10 ml, and the PMMA and PC are swollen at 60-80°C for 3-5 days after mixing, before adding the liquid electrolyte. More preferably, the feeding ratio of PMMA to PC is 2.1 g: 5 ml. More preferably, the swelling temperature is 60°C and the swelling time is 5 days.

[0014] Preferably, the liquid electrolyte system comprises: Magic Blue dopant, tetrabutylammonium perchlorate, and acetonitrile; the concentration of tetrabutylammonium perchlorate is 0.05 mol / L, and the concentration of Magic Blue dopant is 0.05 mol / L.

[0015] Preferably, the all-solid-state gel electrolyte system comprises: Magic Blue dopant, tetrabutylammonium perchlorate, acetonitrile, PMMA, and PC; the molar ratio of tetrabutylammonium perchlorate to Magic Blue dopant is 1:1; the mass of the polymer matrix PMMA is 5 g / mmol based on the mass of tetrabutylammonium perchlorate; the volumetric amount of plasticizer PC is 16 ml / mmol based on the mass of tetrabutylammonium perchlorate; and the volumetric amount of acetonitrile is 20 ml / mmol based on the mass of tetrabutylammonium perchlorate.

[0016] Preferably, the liquid electrolyte system is prepared by the following method: mixing electrolyte and dopant, adding solvent, and ultrasonically mixing to obtain the liquid electrolyte system.

[0017] Preferably, the all-solid-state gel electrolyte system is prepared as follows: Electrolyte and dopant are added to a solvent, and the mixture is ultrasonically mixed or allowed to stand until no solid precipitation occurs, resulting in a liquid electrolyte; the polymer matrix and plasticizer are mixed and swollen at 60–80°C for 3–5 days, then added to the liquid electrolyte, ultrasonically homogenized, and the solvent is removed using a rotary evaporator to obtain the all-solid-state gel electrolyte system. Preferably, the swelling temperature is 60°C and the swelling time is 5 days.

[0018] This invention also provides an application of the electrolyte system in the preparation of electrochromic devices. The application can be carried out through conventional operations to prepare electrochromic devices, specifically by the following steps: using ITO glass coated with a conductive polymer film as the working electrode, blank ITO glass as the counter electrode, and the electrolyte system as the electrolyte, placing the film surface of the working electrode opposite to the counter electrode, encapsulating the perimeter with 3M adhesive, adding electrolyte in the middle, and assembling the electrochromic device to obtain the electrochromic device.

[0019] Preferably, the ITO glass coated with the conductive polymer film is prepared by the following method: a conductive polymer solution of 1-10 mg / ml is coated onto the surface of the ITO glass by spin coating to form a conductive polymer film.

[0020] Preferably, in the conductive polymer solution, the conductive polymer is ProDOT (poly3,3-bis(((2-ethylhexyl)oxy)methyl)-3,4-dihydro-2H-thiopheno[3,4-B][1,4]dioxane-heptene), and the solvent is dichloromethane or chloroform, more preferably chloroform; more preferably, the concentration of the conductive polymer solution is 5 mg / ml.

[0021]

[0022] 3,3-bis(((2-ethylhexyl)oxy)methyl)-3,4-dihydro-2H-thiopheno[3,4-B][1,4]dioxane-heptene

[0023] Preferably, the spin coating method is operated according to the following steps: first, ITO glass is placed on a spin coater, then the conductive polymer solution is evenly dripped onto the surface of the ITO glass using a dropper, the spin coater is started at a speed of 500-2000 r / min for 30-90 s, and after stopping, the conductive polymer film is prepared.

[0024] Compared with the prior art, the beneficial effects of the present invention are mainly reflected in:

[0025] The liquid electrolyte system or all-solid-state gel electrolyte system for the proDOT electrochromic device described in this invention incorporates a dopant. The dopant's pro-oxidation effect synergistically with electrochemical oxidation, significantly reducing the operating voltage of the electrochromic device and improving its stability. The proDOT electrochromic device using the all-solid-state gel electrolyte system with added Magic Blue dopant exhibits excellent electrochromic properties, demonstrating the potential of novel dopant-containing electrolyte systems to improve the performance of electrochromic devices. (See attached...) Figure 4As shown, after adding dopants, the final color-changing voltage of the corresponding electrochromic devices decreased by 0.2–1.1V, and the addition of most dopants did not affect the color display of the devices themselves. Among them, the proDOT electrochromic device with an all-solid-state gel electrolyte system containing Magic Blue dopant exhibited excellent electrochromic properties, with the color-changing voltage decreasing from the original 0–1.2V to -1.2–0.8V. Additionally, as shown in the attached figure… Figure 5 As shown, the optical contrast at 525 nm of the device did not decrease significantly after cycling for 1200 s at step voltages of -0.8 and 1 V, demonstrating the potential of novel electrolyte systems containing dopants to improve the performance of electrochromic devices. (iv) Description of the attached drawings

[0026] Figure 1 The synthetic route of the conductive polymer proDOT described in this invention.

[0027] Figure 2 The molecular formula and structural diagram of the dopant described in this invention.

[0028] Figure 3 A schematic diagram of the electrochromic device structure described in this invention.

[0029] Figure 4 The UV-Vis absorption spectra of the proDOT electrochromic device using an all-solid-state gel electrolyte system with / without different dopants as described in this invention in the neutral and oxidized states.

[0030] Figure 5 The stability test of the proDOT electrochromic device using an all-solid-state gel electrolyte system with added Magic Blue dopant in the 525nm wavelength range, as described in this invention. (V) Detailed Implementation

[0031] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto:

[0032] The synthetic route of the conductive polymer ProDOT used in the embodiments of the present invention is as follows: Figure 1 As shown, the synthesis steps are referenced in: ACS Appl. Mater. Interfaces 2019, 11, 47131-47142.

[0033] Example 1: Preparation of Liquid Electrolyte System

[0034] Add 0.0005 mol of Magic Blue dopant and 0.0005 mol of tetrabutylammonium perchlorate to a 10 mL volumetric flask, and then add acetonitrile to make up to the final volume. Sonicate the mixture for 10 min to obtain the liquid electrolyte system.

[0035] Example 2: Preparation of Liquid Electrolyte System

[0036] Add 0.0036 mol of TCNQ dopant and 0.005 mol of tetrabutylammonium perchlorate to a 10 mL volumetric flask, and then add dichloromethane to bring the volume to a final volume. Shake until the solution is homogeneous to obtain the liquid electrolyte system.

[0037] Example 3: Preparation of an all-solid-state gel electrolyte system

[0038] 0.0005 mol of Magic Blue dopant and 0.0005 mol of tetrabutylammonium perchlorate were added to a 10 mL volumetric flask, and acetonitrile was added to bring the volume to a final volume. The mixture was ultrasonically mixed for 10 min, and the resulting liquid electrolyte was set aside. 2.5 g of PMMA and 8 mL of PC were mixed thoroughly and swelled in a vacuum oven at 60 °C for 5 days. The prepared liquid electrolyte was then added to the mixture, ultrasonicated thoroughly, and the acetonitrile was removed using a rotary evaporator to obtain a fully solid gel electrolyte system.

[0039] Under the same conditions, Magic Blue was replaced with (NO)PF6, Fe(TFSI)3, Fe(Tos)3, and CuCl2, while other operations remained the same, resulting in different all-solid-state gel electrolyte systems.

[0040] Example 4: Preparation of an all-solid-state gel electrolyte system

[0041] 0.0005 mol of Fe(TFSI)3 dopant and 0.0005 mol of lithium perchlorate were added to a 10 mL volumetric flask, and dichloromethane was added to bring the volume to a final volume. The mixture was placed in a vibration-free environment for 10 min to ensure no solid precipitation, and then left to stand for 1 day; this is the liquid electrolyte. 10 g of PMMA and 30 mL of PC were mixed thoroughly and swelled in a vacuum oven at 60 °C for 4 days. The prepared liquid electrolyte was then added to the mixture, stirred thoroughly, and the dichloromethane was evaporated to obtain an all-solid-state gel electrolyte system.

[0042] Example 5: Fabrication of electrochromic devices using an all-solid-state gel electrolyte system

[0043] Add 50 mg of ProDOT polymer to a 10 ml volumetric flask, add chloroform to make up the volume, mix thoroughly by ultrasonication, and then drop it onto ITO glass. Spin coat it on a spin coater at 1000 r / min for 60 s to obtain ITO glass with a conductive polymer film spin-coated.

[0044] Reference Figure 3 Using the all-solid-state gel electrolyte system prepared in Example 3 as the electrolyte, ITO glass with a conductive polymer film spin-coated as the working electrode and blank ITO glass as the counter electrode, the electrolyte was added to the space formed between the working electrode film surface and the counter electrode, and the electrochromic device was assembled using 3M adhesive as an encapsulation method.

[0045] Under the same conditions, the electrolyte of the electrochromic device was removed as a control.

[0046] The electrochromic properties of the device were obtained by testing with a Chenhua 660 electrochemical workstation-UV-Vis spectrophotometer. Specifically, different voltages were applied for 30 seconds using the electrochemical workstation, and then the UV-Vis spectrophotometer was used to scan the wavelength range of 300–1100 nm to test the absorption value of the thin film under different voltages.

[0047] Electrochromic properties were detected at different voltages, and the results are shown in [Figure 1]. Figure 4 As shown, the results indicate that after adding dopants, the final color-changing voltage of the corresponding electrochromic devices decreased by 0.2–1.1 V, and the addition of most dopants did not affect the color display of the devices themselves. Among them, the proDOT electrochromic device with Magic Blue dopant in the all-solid-state gel electrolyte system has excellent electrochromic properties, and the color-changing voltage decreased from the original 0–1.2 V to -1.2–0.8 V.

[0048] The stability of the proDOT electrochromic device with an all-solid-state gel electrolyte system containing Magic Blue dopant was tested in the 525 nm wavelength range. The results are shown in [link to data]. Figure 5 As shown, the results indicate that the optical contrast at 525 nm did not decrease significantly after cycling for 1200 s at a step voltage of -0.8 and 1 V, demonstrating the potential of the novel electrolyte system containing dopants in improving the performance of electrochromic devices.

Claims

1. An electrolyte system for reducing operating voltage, characterized in that, The electrolyte system includes an all-solid-state gel electrolyte system; the all-solid-state gel electrolyte system includes a polymer matrix, plasticizer, electrolyte, solvent, and dopant; All dopants are P-type dopants, whose standard electrode potential is higher than that of the electrochromic layer material used in the electrochromic device, and they do not react chemically with other components in the electrolyte system. The dopant is one of the following: Magic Blue, (NO)PF6, Fe(TFSI)3, Fe(Tos)3, CuCl2, wherein Magic Blue represents ammonium tris(4-bromophenyl)hexachloroantimonate.

2. The electrolyte system as described in claim 1, characterized in that, In the all-solid-state gel electrolyte system, the ratio of electrolyte to dopant is 1:1, the polymer matrix mass is 2-20 g / mmol based on the amount of electrolyte, the plasticizer volume is 10-60 ml / mmol based on the amount of electrolyte, and the solvent volume is 10-30 ml / mmol based on the amount of electrolyte.

3. The electrolyte system as described in claim 1, characterized in that, The electrolyte is one of tetrabutylammonium perchlorate, lithium perchlorate, or ammonium hexafluorophosphate; the solvent is one of ethanol or acetonitrile.

4. The electrolyte system as described in claim 1, characterized in that, In the all-solid gel electrolyte system, the polymer matrix is ​​polymethyl methacrylate, polyvinylidene fluoride, and poly(vinylidene fluoride-hexachloropropylene); the plasticizer is propylene carbonate and polyethylene glycol.

5. The electrolyte system as described in claim 4, characterized in that, The all-solid-state gel electrolyte system consists of: Magic Blue dopant, tetrabutylammonium perchlorate, acetonitrile, polymethyl methacrylate, and propylene carbonate; the molar ratio of tetrabutylammonium perchlorate to Magic Blue dopant is 1:1; the mass of polymethyl methacrylate is 5 g / mmol based on the mass of tetrabutylammonium perchlorate; the volume of propylene carbonate is 16 ml / mmol based on the mass of tetrabutylammonium perchlorate; and the volume of acetonitrile is 20 ml / mmol based on the mass of tetrabutylammonium perchlorate.

6. The application of the electrolyte system of claim 1 in the preparation of an electrochromic device with reduced operating voltage.

7. The application as described in claim 6, characterized in that, The application is carried out in the following steps: using ITO glass coated with a conductive polymer film as the working electrode, blank ITO glass as the counter electrode, and an electrolyte system as the electrolyte, the film surface of the working electrode is placed opposite the counter electrode, the perimeter is encapsulated with 3M adhesive, and electrolyte is added in the middle to assemble the electrochromic device and obtain the electrochromic device.

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