CN117784487B - Electrolyte, preparation method thereof and electrochromic device - Google Patents

Abstract

The application belongs to the technical field of electrochromic, and particularly relates to electrolyte, a preparation method thereof and an electrochromic device. The electrolyte comprises: an organic solvent and a metal salt and an acid reagent dissolved in the organic solvent; wherein the metal salt is a salt corresponding to a multivalent metal ion, the multivalent metal ion comprises at least one of a divalent metal ion and a trivalent metal ion, the concentration of the multivalent metal ion is 1-2 mol/L, and the concentration of the hydrogen ion corresponding to the acid reagent is 0.1-0.3 mol/L. The application makes the electrochromic film layer have low driving potential required by the electrolyte of the application through the combined action of the polyvalent metal ion in the metal salt and the hydrogen ion of the acid reagent, has wider electrochromic modulation amplitude and faster optical conversion speed, and has excellent cycling stability, thus being well applied to electrochromic devices.

Description

Electrolyte and preparation method thereof, and electrochromic device

Technical Field

The present application belongs to the field of electrochromic technology, and in particular relates to an electrolyte and a preparation method thereof, and an electrochromic device.

Background Art

The construction industry consumes a lot of energy, among which the heat loss of building glass curtain walls is the main cause of building energy loss. Therefore, electrochromic smart glass technology is favored because of its unique energy-saving methods such as low-voltage drive, open-circuit ion storage memory, and independent and continuous adjustment of visible-near infrared dual-bands. As a building energy-saving glass technology, electrochromic smart glass meets the requirements of green and sustainable buildings and is the main trend of future construction industry development. Under the action of an external electric field, electrochromic smart glass can change its own optical properties through the reversible extraction and injection of color-causing ions in its internal functional materials, thereby realizing the dynamic management of indoor sunlight and radiant heat energy, which can effectively reduce building energy consumption, reduce building light pollution, and improve living comfort and privacy. Electrochromic smart glass has a similar structure and working principle to lithium-ion batteries, so it also has a certain electrochemical energy storage function.

At present, there are many routes that can be realized by electrochromic glass technology, presenting a brilliant trend, but its mainstream route is still based on inorganic transition metal oxides as the core functional materials. Tungsten trioxide (WO ₃ ) is the most widely used electrochromic material. The tungsten trioxide film in the colored state is dark blue and becomes colorless after fading. Electrochromic tungsten trioxide film can be divided into amorphous and crystalline states according to the crystal type. The crystalline a-WO ₃ has a relatively slow response characteristic due to its relatively compact crystal structure, but can achieve stable electrochemical cycles; the amorphous c-WO ₃ crystal structure is relatively loose, which can achieve a faster color change rate, but the cycle stability is poor. The electrochromic phenomenon originates from the light absorption transition behavior caused by the interaction between the coloring ions and the lattice atoms. Therefore, the selection of coloring ions with different polarization capabilities can achieve different degrees of electrochromic effects.

Currently, alkali metal lithium ions have become the most commonly used conductive ions in the field of electrochromic and other electrochemical energy storage devices. However, lithium ions are highly toxic and easily react with air/water vapor in the environment. The environmental requirements for their preparation and application are also relatively high. These have brought safety issues to the use of lithium-ion-containing electrolytes. At the same time, the electrochromic performance of electrochromic materials in such electrolytes is unstable.

Summary of the invention

The purpose of this application is to provide an electrolyte and a preparation method thereof, and an electrochromic device, aiming to solve the technical problem of how to improve the electrochromic performance of electrochromic materials in electrolytes at low cost.

In order to achieve the above application purpose, the technical solution adopted in this application is as follows:

In a first aspect, the present application provides an electrolyte comprising: an organic solvent and a metal salt and an acid reagent dissolved in the organic solvent; wherein the metal salt is a salt corresponding to a multivalent metal ion, the multivalent metal ion comprises at least one of a divalent metal ion and a trivalent metal ion, and the concentration of the multivalent metal ion is 1~2 mol/L, and the hydrogen ion concentration corresponding to the acid reagent is 0.1~0.3 mol/L.

In some embodiments, the acid reagent comprises an organic acid or an inorganic acid.

In some embodiments, the inorganic acid includes at least one of hydrochloric acid, sulfuric acid, and nitric acid; or the organic acid includes acetic acid.

In some embodiments, the organic solvent includes at least one of an ester solvent, an ether solvent, and an alcohol solvent.

In some embodiments, the multivalent metal ions include at least one of aluminum ions and zinc ions.

In some embodiments, the multivalent metal ions include aluminum ions, and the corresponding metal salts include at least one of aluminum chloride, aluminum nitrate, and aluminum sulfate; or,

The multivalent metal ions include zinc ions, and the corresponding metal salts include at least one of zinc chloride, zinc nitrate and zinc sulfate.

In some embodiments, the metal salt comprises zinc chloride, the acid reagent comprises hydrochloric acid, and the organic solvent comprises propylene carbonate.

In a second aspect, the present application provides a method for preparing an electrolyte, comprising the following steps:

Weighing each raw material component in the electrolyte provided in the first aspect of the present application;

The organic solvent, the metal salt and the acid reagent are mixed to obtain the electrolyte.

In some embodiments, the mixing process includes: first adding the metal salt into the organic solvent, and then adding the acid reagent during stirring.

In a third aspect, the present application provides an electrochromic device, comprising: an electrolytic cell and the electrolyte provided in the first aspect of the present application and/or the electrolyte prepared by the preparation method provided in the second aspect of the present application contained in the electrolytic cell, wherein the electrolytic cell is provided with an electrochromic film layer and a counter electrode placed in the electrolyte and separated from each other.

The electrolyte provided in the first aspect of the present application contains a certain concentration of metal salt and acid reagent, specifically including an organic solvent and a metal salt dissolved in the organic solvent (wherein the concentration corresponding to the multivalent metal ion is 1-2 mol/L) and an acid reagent (wherein the concentration corresponding to the hydrogen ion is 0.1-0.3 mol/L). Through the combined action of the multivalent metal ions in the metal salt and the hydrogen ions of the acid reagent, the electrochromic film layer used in the electrolyte of the present application has a low driving potential, a wide electrochromic modulation range and a fast optical conversion speed, and excellent cycle stability, so it can be well applied to electrochromic devices.

The second aspect of the present application provides a method for preparing an electrolyte, wherein the electrolyte is obtained by mixing an organic solvent, a metal salt and an acid reagent required for the electrolyte formula. Such a preparation method is not only simple in process, but also enables the obtained electrolyte to enable the electrochromic film to have a wider electrochromic modulation range and a fast optical conversion speed at a lower driving potential, and also has excellent cycle stability.

The electrochromic device provided in the third aspect of the present application uses the electrolyte unique to the present application. Therefore, the electrochromic device of the present application has a wider electrochromic modulation range and a fast optical conversion speed at a lower driving potential, and also has excellent cycle stability.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

FIG1 is a schematic diagram of a solid electrolyte interface (SEI) formed at the solid-liquid interface of an electrolyte and an electrochromic film layer provided in an embodiment of the present application;

FIG2 is a transparent comparison diagram of the appearance of the electrolyte provided in the embodiment of the present application; wherein a does not contain an acid reagent, and b contains an acid reagent;

FIG3 is a cyclic voltammetry curve (CV curve) of an amorphous tungsten trioxide film in an electrolyte in an electrochromic device provided in an embodiment of the present application;

FIG4 is an optical transmission curve at a wavelength of 633 nm synchronized with the CV curve of FIG3 ;

FIG5 is an optical response diagram of an amorphous tungsten trioxide film in an electrolyte in an electrochromic device provided in an embodiment of the present application;

FIG6 is a cyclic stability diagram of an amorphous tungsten trioxide film in an electrolyte in an electrochromic device provided in an embodiment of the present application;

FIG7 is a cycle stability diagram corresponding to an electrolyte in which the cations are hydrogen ions;

FIG8 is a cyclic stability diagram corresponding to an electrolyte in which the cation is zinc ion.

DETAILED DESCRIPTION

In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

In this application, the term "and/or" describes the association relationship of associated objects, indicating that there may be three relationships. For example, A and/or B can mean: A exists alone, A and B exist at the same time, and B exists alone. A and B can be singular or plural. The character "/" generally indicates that the associated objects are in an "or" relationship.

In this application, "at least one" means one or more, "more than one" means two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single or plural items.

It should be understood that in the various embodiments of the present application, the size of the serial numbers of the above-mentioned processes does not mean the order of execution, some or all of the steps can be executed in parallel or sequentially, and the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "said" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

The weight of the relevant components mentioned in the embodiment description of the present application can not only refer to the specific content of each component, but also indicate the proportional relationship between the weights of the components. Therefore, as long as the content of the relevant components is proportionally enlarged or reduced according to the embodiment description of the present application, it is within the scope disclosed in the embodiment description of the present application. Specifically, the mass described in the embodiment description of the present application can be a mass unit known in the chemical industry such as µg, mg, g, kg, etc.

The terms "first" and "second" are used only for descriptive purposes to distinguish objects such as substances from each other, and should not be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. For example, without departing from the scope of the embodiments of the present application, the first XX may also be referred to as the second XX, and similarly, the second XX may also be referred to as the first XX. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features.

The electrochromic phenomenon originates from the light absorption transition behavior caused by the interaction between the color-causing ions and the lattice atoms. Therefore, the selection of color-causing ions with different polarization capabilities can achieve different degrees of electrochromic effects. Currently, alkali metal lithium ions have become the most commonly used conductive ions in the field of electrochromic and other electrochemical energy storage devices.

Compared with the particle size of alkali metal ions such as Li ⁺ (0.059 nm), Na ⁺ (0.095 nm) and K ⁺ (0.138 nm), the smaller proton H ⁺ (0.038 nm) can achieve faster optical conversion speed. However, due to the corrosion of metal oxides in acidic environment, electrochromic films can only maintain stable color change cycles of hundreds or dozens of times in proton electrolytes. Although small-sized high-valent metal ions (such as Al ³⁺ , Zn ²⁺ , etc.) also have high polarization ability, due to the strong Coulomb repulsion between them and the host lattice, electrochromic films often require high driving potentials in electrolytes containing such high-valent metal ions to achieve the required electrochromic modulation amplitude and have a slower optical conversion speed.

Based on the above considerations, in order to overcome the defects of current color-causing ions, the present application embodiment designs an electrolyte for the field of electrochromicity. The present application uses metal salts and acid reagents corresponding to multivalent metal ions as electrolytes, comprehensively utilizing the advantages of multivalent metal ions and protons H ⁺ , and forming a safe, low-cost, and environmentally friendly non-aqueous mixed cation electrolyte solution. The following technical solution is proposed.

Electrolyte

The first aspect of the embodiment of the present application provides an electrolyte, comprising: an organic solvent and a metal salt and an acid reagent dissolved in the organic solvent. The metal salt and the acid reagent are electrolytes, the metal salt is a salt corresponding to a multivalent metal ion, the multivalent metal ion includes at least one of a divalent metal ion and a trivalent metal ion, and the concentration of the multivalent metal ion is 1-2 mol/L, and the concentration of hydrogen ions corresponding to the acid reagent is 0.1-0.3 mol/L.

Multivalent metal ions include divalent or trivalent metal ions, and multivalent metal ions have high polarizability and ensure high conductivity in the electrolyte. Acid reagents provide hydrogen ions, which can achieve faster optical conversion speeds. When each is used alone in the electrolyte, there are certain defects. In the electrolyte provided in the embodiment of the present application, both are used comprehensively and formulated into a certain concentration, that is, the concentration of multivalent metal ions is 1~2 mol/L, and the hydrogen ion concentration corresponding to the acid reagent is 0.1~0.3 mol/L. The electrolyte under this concentration condition can give play to their respective advantages, so that the driving potential required for the electrochromic film to be used in such an electrolyte is low, and it has a wider electrochromic modulation amplitude and a faster optical conversion speed, and at the same time has excellent cycle stability, so it can be well applied to electrochromic devices.

Specifically, the embodiments of the present application can achieve better performance of the electrochromic film in this electrolyte by adjusting the type of multivalent metal ions, the type of acid reagent, the type of organic solvent, and the corresponding ion concentration, such as: (1) a wider electrochromic modulation range: ≥70%; (2) a fast optical conversion speed: ≤10s; (3) excellent cycle stability: ≥2000 times; (4) a lower driving potential: can be as low as about 0.3 V vs. Ag/AgCl, which is lower than the driving potential of traditional lithium-ion electrolytes.

In some embodiments, the acid reagent in the electrolyte includes an organic acid or an inorganic acid. Specifically, the organic acid may include at least one of hydrochloric acid, sulfuric acid and nitric acid. The inorganic acid may include acetic acid. The above acid reagent can provide hydrogen ions well to achieve a faster optical conversion speed. Since the hydrogen ion concentration of the acid reagent in the electrolyte is very low, it is less corrosive to metal oxides.

In some embodiments, the organic solvent includes at least one of an ester solvent, an ether solvent, and an alcohol solvent. For example, the alcohol solvent may include a polyol such as propylene glycol (PG), etc., the ester solvent may include at least one of propylene carbonate (PC) and ethylene carbonate (EC), etc., and the ether solvent may include ether, etc. The above organic solvents can dissolve metal salts and acid reagents well, and also have certain antioxidant properties and good stability, and the acid reagent is not easy to destroy its molecular structure.

In some embodiments, the multivalent metal ions in the electrolyte include at least one of aluminum ions and zinc ions. Aluminum ions and zinc ions have high polarizability and high conductivity in the electrolyte. Further, the multivalent metal ions include aluminum ions, and the corresponding metal salts include at least one of aluminum chloride, aluminum nitrate and aluminum sulfate. The multivalent metal ions include zinc ions, and the corresponding metal salts include at least one of zinc chloride, zinc nitrate and zinc sulfate.

Furthermore, the electrolyte may be added with some conventional additives, such as indicators, regulators, etc., as required, and these additives do not affect the normal use of the electrolyte.

In some embodiments, the metal salt in the electrolyte includes zinc chloride, the acid reagent includes hydrochloric acid, and the organic solvent includes propylene carbonate. In the electrolyte, there are acidic monovalent H ⁺ and multivalent metal ions Zn ^2+, the H ⁺ concentration range is 0.1~0.3 mol/L, and the Zn ²⁺ concentration range is 1~2 mol/L. The higher Zn ²⁺ concentration can improve the conductivity of the electrolyte, and the small-sized H ⁺ can be quickly inserted/extracted in the electrochromic film layer under low-potential driving conditions, achieving a fast optical conversion speed; the lower H ⁺ concentration reduces the acid etching rate of the electrochromic film layer. In addition, the insertion/extraction of Zn ²⁺ under low-potential driving conditions is limited to the superficial layer of the electrochromic film layer, which will promote the formation of a SEI film containing ZnO and Zn(OH) ₂ compounds between the electrochromic film layer and the electrolyte interface. As shown in Figure 1, due to the presence of the SEI protective film, the damage of H ⁺ to the electrochromic film layer is reduced, which can greatly improve the cycle stability of the electrochromic film layer.

Preparation method of electrolyte

A second aspect of the present application provides a method for preparing an electrolyte, comprising the following steps:

S01: Weighing each raw material component in the electrolyte provided in the first aspect of the embodiment of the present application;

S02: An organic solvent, a metal salt and an acid reagent are mixed to obtain an electrolyte.

In order to improve the cycle life of electrochromic products, achieve rapid optical conversion at a lower driving potential, and a higher electrochromic modulation range, the present application embodiment proposes a method for preparing a non-aqueous electrolyte, which is obtained by mixing the organic solvent, metal salt and acid reagent required for the electrolyte formula. Such a preparation method is not only simple in process, but also the obtained electrolyte enables the electrochromic film to have a wider electrochromic modulation range and a faster optical conversion speed, and at the same time has excellent cycle stability.

Step S01 is a step for preparing the raw material components in the electrolyte, that is, preparing the required metal salts, acid reagents and organic solvents, which can all be purchased from the market. The specific types and concentration parameters required to be prepared are mentioned above.

Step S02 is a step of mixing the raw materials in the electrolyte.

In some embodiments, the mixing process includes: first adding the metal salt into the organic solvent, and then adding the acid reagent during stirring.

The metal salt of the required multivalent metal ion and the organic solvent are weighed, and a certain amount of acid reagent solution is added thereto during the mixing and stirring process. When the solid particles and precipitates in the solution completely disappear, the prepared electrolyte is obtained. In this process, the introduction of the acid reagent will increase the solubility and dissolution rate of the metal salt of the multivalent metal ion in the organic solvent. For example, the metal salt is zinc chloride, the acid reagent is hydrochloric acid, and the organic solvent is propylene carbonate. After adding hydrochloric acid to the turbid solution of zinc chloride propylene carbonate, the solution can be clarified. As shown in Figure 2, a is a turbid solution without adding hydrochloric acid, and b is a clear solution after adding hydrochloric acid. Therefore, the embodiment of the present application can obtain an electrolyte whose optical transparency meets the use requirements.

In some embodiments, the acid reagent is generally added in the form of a high-concentration acid reagent solution or a pure acid reagent solution, so that the introduction of water molecules can be reduced during the preparation process.

Electrochromic device

A third aspect of an embodiment of the present application provides an electrochromic device, comprising: an electrolytic cell and an electrolyte provided in the first aspect of the embodiment of the present application and/or an electrolyte prepared by the preparation method provided in the second aspect of the embodiment of the present application contained in the electrolytic cell, wherein the electrolytic cell is provided with an electrochromic film layer and a counter electrode placed in the electrolyte and separated from each other.

The electrochromic device of the embodiment of the present application uses the electrolyte unique to the present application. Therefore, the electrochromic device of the embodiment of the present application has a wider electrochromic modulation range and a fast optical conversion speed at a lower driving potential, and also has excellent cycle stability.

Specifically, the electrochromic device can be electrochromic smart glass, in which the electrolytic cell is the glass material, which can be well used in building glass curtain walls.

Specifically, the electrochromic film layer can be a tungsten oxide film layer, a titanium oxide film layer, a molybdenum oxide film layer, etc., and the counter electrode can be an electrochemically inert metal sheet, a carbon material sheet, a transparent conductive film material, etc.

The following describes it in conjunction with specific embodiments.

Example 1

An electrolyte for electrochromic smart glass includes: propylene carbonate solvent, zinc chloride and hydrochloric acid, wherein the concentration of zinc chloride is 2 mol/L and the concentration of hydrochloric acid is 0.3 mol/L.

The electrolyte is prepared by dissolving corresponding zinc chloride and hydrochloric acid in propylene carbonate solvent.

Example 2

An electrolyte for electrochromic smart glass includes: propylene carbonate solvent, zinc chloride and hydrochloric acid, wherein the concentration of zinc chloride is 1.5 mol/L and the concentration of hydrochloric acid is 0.2 mol/L.

The method for preparing the electrolyte is the same as that in Example 1.

Example 3

An electrolyte for electrochromic smart glass includes: propylene carbonate solvent, zinc chloride and hydrochloric acid, wherein the concentration of zinc chloride is 1 mol/L and the concentration of hydrochloric acid is 0.1 mol/L.

The method for preparing the electrolyte is the same as that in Example 1.

Example 4

An electrolyte for electrochromic smart glass includes: propylene carbonate solvent, aluminum chloride and hydrochloric acid, wherein the concentration of aluminum chloride is 1 mol/L and the concentration of hydrochloric acid is 0.1 mol/L.

The electrolyte preparation method is similar to that in Example 1.

Example 5

An electrolyte for electrochromic smart glass includes: propylene glycol solvent, zinc chloride and hydrochloric acid, wherein the concentration of zinc chloride is 1 mol/L and the concentration of hydrochloric acid is 0.1 mol/L.

The electrolyte preparation method is similar to that in Example 1.

Example 6

An electrolyte for electrochromic smart glass includes: propylene glycol solvent, zinc sulfate and sulfuric acid, wherein the concentration of zinc sulfate is 1 mol/L and the concentration of sulfuric acid is 0.1 mol/L.

The electrolyte preparation method is similar to that in Example 1.

Performance Testing

Assembly of electrochromic device: The amorphous tungsten trioxide film, Pt electrode, and Ag/AgCl electrode were placed in the electrolyte of the above-mentioned Example 1 to assemble an electrochromic device for performance testing, and a comparative analysis was performed with an electrolyte containing only zinc chloride (the difference from Example 1 is that hydrochloric acid is not added) and an electrolyte containing only hydrochloric acid (the difference from Example 1 is that zinc chloride is not added). The results are as follows:

Figure 3 shows the cyclic voltammetry curves of the amorphous tungsten trioxide film in an electrolyte whose cations are H ⁺ & Zn ²⁺ (i.e., the electrolyte of Example 1, corresponding to the H ⁺ & Zn ²⁺ curve in the figure), an electrolyte whose cation is H ⁺ (the difference from Example 1 is that zinc chloride is not added, corresponding to the H ⁺ curve in the figure), and an electrolyte whose cation is Zn ²⁺ (the difference from Example 1 is that hydrochloric acid is not added, corresponding to the Zn ²⁺ curve in the figure). In the electrolyte where the cation is H ⁺ , the number of H ⁺ ions is small and the corresponding electrolyte conductivity is low, thus limiting the injection/extraction reaction speed and degree of H ⁺ ions in the amorphous tungsten trioxide film; in the electrolyte where the cation is Zn2 ⁺ , the number of Zn2 ⁺ at a higher concentration is relatively large, and the corresponding electrolyte conductivity is relatively high, but Zn2 ⁺ is not easy to be deeply injected into the amorphous tungsten trioxide film; while the electrolyte of Example 1 of the present application contains both H ⁺ and Zn2 ⁺ , Zn2 ⁺ provides conductive ions, improves the electrolyte conductivity, and further promotes the injection/extraction reaction speed and degree of H ⁺ ions in the amorphous tungsten trioxide film; therefore, the CV envelope surfaces corresponding to the H ⁺ curve and the Zn2 ⁺ curve in Figure 3 are relatively small, while the envelope area of the H ⁺ & Zn2 ⁺ curves is large.

FIG4 shows the optical transmission curve at a wavelength of 633 nm, which is synchronized with the cyclic voltammetry test in FIG3. The achievable electrochromic modulation amplitude is obtained by calculating the difference between the transmittance before and after different ion injections. The optical modulation amplitude of the amorphous tungsten trioxide film in the electrolyte provided in Example 1 of the present application can reach about 80%, which is much higher than the electrochromic modulation range that can be achieved in general lithium ion electrolytes.

FIG5 shows the change curve of coloration/fading optical transmittance of the amorphous tungsten trioxide film in the electrolyte of Example 1 at a wavelength of 633 nm under the condition of low potential -0.3/0.8 V, and the reference electrode used is Ag/AgCl electrode. It can be seen that even if the coloration potential used is much lower than the fading potential, the coloration rate is significantly faster than its fading rate. The coloration/fading time is usually defined as the time required for the spectral transmittance to reach 90% of its maximum change. It can be seen that the coloration and fading time to achieve 72% of the electrochromic modulation amplitude are both less than 10s.

Figures 6-8 are the cycle stability test results. Among them, Figure 6 is the cycle stability corresponding to the electrolyte of Example 1, Figure 7 is the cycle stability corresponding to the electrolyte containing only hydrochloric acid (the difference from Example 1 is that zinc chloride is not added), and Figure 8 is the cycle stability corresponding to the electrolyte containing only zinc chloride (the difference from Example 1 is that hydrochloric acid is not added). By comparison, it can be seen that in the corresponding H ⁺ & Zn ²⁺ region in Figure 6, the amorphous tungsten trioxide film driven by a -0.3 V cathode potential can still maintain the initial optical modulation amplitude after 2000 cycles, which is far beyond the case of general proton system electrolytes.

In the above-mentioned cycle stability test, the test conditions corresponding to the three electrolytes include: the electrolyte containing only hydrochloric acid and the electrolyte containing only zinc chloride are both tested under -0.8 V cathode potential drive, while the electrolyte of Example 1 containing both hydrochloric acid and zinc chloride is tested under -0.3 V cathode potential drive; the results show that the electrolyte of Example 1 requires a low driving voltage, has a high optical modulation amplitude, and has good cycle stability.

Through analysis, there are three reasons to explain this excellent stability: (1) The lower driving potential reduces the destructive effect of ion injection/extraction on the amorphous tungsten trioxide film layer; (2) The lower proton concentration reduces the acid etching rate of the electrolyte on the amorphous tungsten trioxide film layer; (3) During the continuous cycle process, the Zn2 ⁺ ions and the compounds formed by them accumulated on the surface of the amorphous tungsten trioxide film layer will form a partially reversible SEI protective film with the participation of organic solvent molecules.

The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims (2)

1. A method for preparing an electrolyte, characterized in that it comprises the following steps: Weighing each raw material component in the electrolyte; the raw material components include: a metal salt, an acid reagent and an organic solvent; the metal salt is a salt corresponding to a multivalent metal ion, the multivalent metal ion includes at least one of a divalent metal ion and a trivalent metal ion, the metal salt includes zinc chloride, the acid reagent includes hydrochloric acid, and the organic solvent includes propylene carbonate; Mixing the organic solvent, the metal salt and the acid reagent to obtain the electrolyte; Wherein, the mixing treatment includes: first adding the metal salt into the organic solvent, and then adding the acid reagent during stirring; the concentration of the zinc chloride in the electrolyte is 1-2 mol/L, and the concentration of the hydrochloric acid is 0.1-0.3 mol/L. 2. An electrochromic device, characterized in that it comprises: an electrolytic cell and an electrolyte prepared by the preparation method according to claim 1 contained in the electrolytic cell, wherein the electrolytic cell is provided with an electrochromic film layer and a counter electrode placed in the electrolyte and separated from each other.