Electrolyte for zinc-based electrochromic deviceTechnical Field
The invention belongs to the technical field of functional materials and devices, and particularly relates to electrolyte for a zinc-based electrochromic device.
Background
Electrochromic is a phenomenon in which certain materials undergo a stable and reversible color change due to a redox reaction that occurs under the influence of an applied electric field. In recent years, electrochromic devices have become increasingly popular for use in displays, sensors, and smart windows.
The conventional electrochromic device can change the type and the depth of the color by applying different voltages so as to realize the adjustment of the light transmittance. However, with the rapid development of intelligent and interactive electronics, conventional electrochromic devices tend to be difficult to adapt to the requirements of practical applications. The main trend in the future will be to design and manufacture electrochromic devices with more states and reversibility to meet consumer needs and expand the range of applications.
The zinc-based electrochromic device realizes the regulation and control of the color and the light transmittance of the device by reversible deposition of zinc ions in electrolyte on a conductive film. The three states of transparency, translucency and complete opacity can be realized by changing the deposition time of zinc, and the method has a wide application prospect in the field of intelligent color-changing windows. However, the electrolyte adopted by the current device in the working mode is usually zinc sulfate aqueous solution, and the reversibility of the device is very low due to uneven electric field of a zinc plating interface and side reaction caused by solvent water, so that the zinc is unevenly deposited on a conductive film, the reversibility is poor and the like.
Disclosure of Invention
The invention aims to solve the problems in the background art and provides an electrolyte for a zinc-based electrochromic device.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:
The electrolyte for the zinc-based electrochromic device comprises a mixed solvent, a zinc salt solute and an additive, wherein the mixed solvent is a mixed solution formed by water, one of alcohols and nitrile organic solvents, and the additive is a hole ether additive.
Further, the alcohol organic solvent is methanol, ethanol, glycol, glycerol, isopropanol or their alcohol isomers or derivatives, and the nitrile organic solvent is acetonitrile, malononitrile, pyruvonitrile, succinonitrile, adiponitrile or their nitrile isomers or derivatives.
Further, the volume ratio of water to the alcohol or nitrile organic solvent is 1 (1-10).
Further, the zinc salt solute is one or more of zinc sulfate, zinc trifluoromethane sulfonate, zinc chloride, zinc bromide, zinc iodide, zinc bis (trifluoromethane sulfonyl) imide, zinc perchlorate, zinc tetrafluoroborate, zinc nitrate and zinc acetate.
Further, in the electrolyte, the concentration of zinc salt is 0.1-4 mol/L.
Further, the additive is one or more of hole ethers such as hole ether 222, hole ether 221, hole ether 211 and the like.
Further, the additive is added in an amount of 0.1-1 wt% of the electrolyte.
The electrolyte for the zinc-based electrochromic device is applied to a reflective electrochromic device or a transmission electrochromic device.
Further, when the above electrolyte is applied to a reflective electrochromic device, the color-changing layer selects a conductive film capable of allowing reversible electroplating and peeling of zinc, such as copper mesh, aluminum mesh, silver mesh, zinc mesh, stainless steel mesh or gold-plated nylon 66, etc., and the electrode material selects zinc or an alloy of zinc and copper, aluminum, silver, magnesium, manganese, etc.
Further, when the above electrolyte is applied to a transmission type electrochromic device, a conductive film, such as FTO, ITO, or conductive PET, which can allow reversible plating and peeling of zinc, is selected as a color-changing layer, and zinc or an alloy of zinc and copper, aluminum, silver, magnesium, manganese, or the like is selected as an electrode material.
Compared with the prior art, the invention has the beneficial effects that:
The electrolyte for the zinc-based electrochromic device adopts the mixed solution formed by water and one of the alcohol and nitrile organic solvents as the mixed solvent, has high ionic conductivity, low viscosity and high dielectric constant, can ensure a rapid reversible deposition process of zinc ions, can effectively dissolve zinc salts by hydroxyl or cyano polar groups, and can reduce the occurrence of interface side reactions and improve reversibility by introducing the alcohol and nitrile organic solvents. The hole ether is used as the additive, the oxygen atoms of the hole ether additive and zinc ions form multielement coordination, and the content of interfacial water is reduced, so that the reversibility is improved, and the uniformity of zinc film deposition is further improved. In summary, the electrolyte provided by the invention has the advantages of low melting point, low viscosity, high dielectric constant, good oxidation-reduction stability and low price, and is very suitable for being applied as the electrolyte of a zinc-based electrochromic device with high reversibility.
Drawings
FIG. 1 is a schematic structural diagram of a zinc-based electrochromic device based on the electrolyte of the present invention;
FIG. 2 is a schematic representation of the interaction of the hole ether 222 molecule with zinc ions in the electrolyte prepared in example 1;
FIG. 3 is a graph showing the color change effect achieved by the electrolyte prepared in example 1 and a conventional electrolyte;
FIG. 4 is a schematic diagram showing the discoloration effect achieved by the electrolyte prepared in example 1 and the conventional electrolyte;
FIG. 5 is an SEM image of a plating layer formed on ITO of the electrolyte prepared in example 2;
FIG. 6 is a graph showing constant current coloring and discoloration of the electrolyte prepared in example 3;
FIG. 7 is a photograph of the plating of the electrolyte prepared in example 4 at various coloring times.
Detailed Description
The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.
Example 1
The mixed solution of water and succinonitrile with the volume ratio of 1:4 is taken as a mixed solvent, zinc tetrafluoroborate is dissolved in the mixed solution according to the molar concentration of 4mol/L, and the cryptate 222 with the mass fraction of 0.5 percent is taken as an additive. ITO is used as a color-changing electrode, a zinc ring is used as a counter electrode, and a zinc-based electrochromic device is assembled, and the structure schematic diagram of the device is shown in figure 1. The mixed solvent can reduce the interfacial side reactions such as corrosion and gas production caused by water, and meanwhile, the hole ether molecules can replace water molecules to form coordination with zinc ions to induce uniform deposition of the zinc ions in the electroplating process. A schematic of the interaction of zinc ions with the hole ether 222 is shown in fig. 2. After applying a potential of-1.3V to the device for 1 minute, zinc ions were deposited on the ITO to form uniform gray regions, thereby changing the color and transmittance of the ITO glass (fig. 3). If the traditional 2M ZnSO4 pure water solution is used for coloring for 1 minute under the same condition, the zinc electroplating is uneven due to the uneven electric field at the interface, and the ITO surface is unevenly colored. The principle diagram of the discoloration effect achieved by the two electrolytes is shown in fig. 4.
Example 2
The mixed solution of water and glycol with the volume ratio of 1:1 is taken as a mixed solvent, zinc triflate is dissolved in the mixed solution according to the molar concentration of 2mol/L, and the cryptate 222 with the mass fraction of 0.1 percent is taken as an additive. ITO is used as a color-changing electrode, a copper zinc alloy ring is used as a counter electrode, and a zinc-based electrochromic device is assembled. The glycol molecules in the mixed solvent can reduce interfacial side reactions such as water-induced corrosion and gas production, and meanwhile, the hole ether molecules can replace water molecules to form coordination with zinc ions so as to further reduce adverse reactions of the zinc ions in the electroplating process. After applying a potential of-1.3V to the device for 3 minutes, scanning electron microscopy tests on gray areas formed on ITO show that zinc ions are uniformly deposited on the ITO due to the existence of hole ether molecules, no obvious dendrite zinc is generated, and the electrolyte provided by the invention is beneficial to the application of zinc-based electrochromic devices (figure 5).
Example 3
The mixed solution of water and acetonitrile with the volume ratio of 1:1 is taken as a mixed solvent, zinc chloride is dissolved in the mixed solvent according to the molar concentration of 1mol/L, and 0.1 percent of cryptate 211 is taken as an additive. ITO is used as a color-changing electrode, a zinc ring is used as a counter electrode, and a zinc-based electrochromic device is assembled. The acetonitrile molecules in the mixed solvent can reduce interfacial side reactions such as water-induced corrosion and gas production, and meanwhile, the hole ether molecules can replace water molecules to form coordination with zinc ions so as to further reduce adverse reactions of the zinc ions in the electroplating process. After applying a current density of 1mA cm-2 to the device for 30 seconds, the zinc plating on the ITO was peeled off with a current density of 1mA cm-2, and the plating and peeling curves are shown in FIG. 6. It can be seen that the interfacial water decomposition reaction is inhibited due to the use of the mixed solvent of acetonitrile and water, and the coulomb efficiency of zinc electroplating and stripping is higher than that of the conventional electrolyte, which indicates that most of zinc can be reversibly electroplated and stripped, thus indicating that the electrolyte provided by the invention has higher reversibility in application in zinc-based electrochromic devices.
Example 4
The mixed solution of water and glycerol with the volume ratio of 1:1 is taken as a mixed solvent, zinc triflate is dissolved in the mixed solution according to the molar concentration of 2mol/L, and 0.1 percent of cryptate 221 is taken as an additive. ITO is used as a color-changing electrode, a zinc ring is used as a counter electrode, and a zinc-based electrochromic device is assembled. The glycerol molecules in the mixed solvent can reduce interfacial side reactions such as water-induced corrosion and gas production, and meanwhile, the hole ether 221 molecules can replace water molecules to form coordination with zinc ions so as to further reduce the water molecule content of the zinc ions introduced into the interface in the electroplating process. After applying a potential of-1.3V to the device for 10 minutes, the gray area gradually formed on the ITO was further energized for 30 minutes, zinc formed a mirror surface on the ITO to be completely opaque, and the voltage was reversed, i.e., after applying a potential of 1.1V to the device for 10 minutes, the zinc coating on the ITO surface completely disappeared and changed back to a transparent state (fig. 7). The use of the conventional electrolyte not only can lead to uneven plating, but also can lead to a large amount of zinc particles remaining after reverse electrification, which indicates that the electrolyte can realize a highly reversible zinc-based electrochromic device.