Solid polymer electrolyte gel film for electrochromic device and method of making and use thereof

Abstract

This invention discloses a solid polymer electrolyte film for electrochromic devices, its preparation method, and its application. The preparation method includes: premixing an ethylene-vinyl acetate copolymer with a lithium salt additive under heat to obtain a first solid product; and subjecting the first solid product to roll pressing and isothermal-humidity treatment to obtain the solid polymer electrolyte film for electrochromic devices. The solid polymer electrolyte film prepared by this invention exhibits high ionic conductivity, good optical, thermal, and mechanical properties, and meets the processing and application requirements of sandwich-type WO3-NiO electrochromic devices.

Description

Technical Field

[0001] This invention belongs to the field of polymer thin film technology, specifically relating to a solid polymer electrolyte film for electrochromic devices, its preparation method, and its application. Background Technology

[0002] WO3-NiO-based electrochromic devices can actively modulate visible and infrared light under small stimuli from an external electric field (1~3 V), and are attracting more attention due to their huge application potential in a variety of fields, such as smart windows in energy-efficient buildings. Typically, complementary electrochromic devices have two symmetrical conductive layers, two electrochromic layers, and an electrolyte layer from the outside to the inside.

[0003] To date, there are two main configurations for constructing WO3-NiO devices based on the assembly process. One is the so-called "layer-by-layer" configuration, where the five layers mentioned above are successively deposited on a single substrate by magnetron sputtering to form a stacked structure. Unfortunately, this stacked structure configuration is affected by the extremely thin (<100 nm) inorganic electrolyte layer. Therefore, during the sputtering process, unavoidable defects such as pinholes and impurity particle retention will occur in such a thin layer. Through these defects, the two electrodes will come into direct contact, leading to a short circuit and disrupting the stable operation of the device. The other is the so-called "laminated" configuration, in which the individual components of the substrate / ITO / WO3 and substrate / ITO / NiO are first produced by magnetron sputtering, and then a micron-thick transparent polymer electrolyte is used as an interlayer film, and the assembled device is formed by lamination. In this laminated configuration, the application of such a thick electrolyte can fundamentally eliminate the adverse effects of defects caused by the thinner electrolyte on the device, and also makes the device assembly more efficient. In laminated WO3-NiO ECDs, the polymer electrolyte is a crucial factor determining the response speed, transparency, and mechanical strength. Therefore, it should possess comprehensive properties such as high ionic conductivity, wide potential window, thermal stability, chemical and electrochemical stability, high optical transparency, robustness, low cost, and environmental friendliness.

[0004] Currently, existing polymer electrolytes are mainly divided into two categories: gel electrolytes containing some plasticizers or other organic solvents, and solid electrolytes containing no plasticizers or other organic solvents. Regarding gel electrolytes... Electrochimica Acta 2022, 432, 141216 disclosed a method for forming a gel polymer electrolyte by adding ionic liquid [BMIM][TFSI] and lithium salt LiTFSI to PVDF-HFP, PMMA and PEG; J. Mater. Chem. A On November 2023, 8939, a gel polymer electrolyte system composed of PVDF, LiClO4, PC, and a UV curing agent was disclosed. Regarding solid electrolytes... Adv. Funct. Mater. 2023, 33, 2214417 discloses a method for forming a solid polymer electrolyte based on the crosslinking reaction of PVB and KH560 followed by the addition of LiTFSI. However, the preparation of the polymer film relies on a large amount of organic solvent (dimethylacetamide) to assist in film formation. According to publicly available information, although both systems can achieve relatively high ionic conductivity (>1.0 × 10⁻⁶),... -4 S / cm), but there are still the following shortcomings: (1) For gel electrolytes, the presence of a large amount of liquid solvent medium in the system will seriously lead to a decrease in the mechanical properties of the polymer film, making it difficult to achieve a firm bond with the glass, affecting the safety performance of the laminated glass. In addition, it also brings about the flammability problem of the device. These solvents are highly flammable and not only cannot block the spread of flames, but also accelerate the combustion process. (2) For solid electrolyte materials, since a large amount of organic solvent (dimethylacetamide) is required to assist in the film formation during the preparation of polymer film, a large amount of volatile organic compounds are emitted during the preparation process, causing air pollution. Therefore, the production process of this material is not environmentally friendly. On the other hand, ethylene-vinyl acetate copolymer (EVA) for photovoltaic module encapsulation has good optical transparency, low temperature flexibility and other properties. As a laminated polymer material, it has been maturely applied in the photovoltaic field for many years. However, when applied to polymer electrolyte materials, its room temperature ionic conductivity is low (usually less than 10). -8 The S / cm ratio does not meet the requirements for electrochromic devices to operate at room temperature. Summary of the Invention

[0005] The main objective of this invention is to provide a solid polymer electrolyte film for electrochromic devices, its preparation method and application, in order to overcome the shortcomings of the prior art.

[0006] To achieve the aforementioned objectives, the technical solution adopted by this invention includes:

[0007] This invention provides a method for preparing a solid polymer electrolyte film for electrochromic devices, comprising:

[0008] The first solid product was obtained by heating and premixing the ethylene-vinyl acetate copolymer with lithium salt additive.

[0009] Furthermore, the first solid product is subjected to roll pressing and constant temperature and humidity treatment to obtain a solid polymer electrolyte film for electrochromic devices.

[0010] The present invention also provides a solid polymer electrolyte film for electrochromic devices prepared by the aforementioned preparation method. The solid polymer electrolyte film is prepared from at least ethylene-vinyl acetate copolymer, water, and lithium salt additives. The surface of the solid polymer electrolyte film has a mesh-like wrinkled structure.

[0011] This invention also provides an electrochromic device, which includes at least the aforementioned solid polymer electrolyte film.

[0012] This invention also provides an electrochromic smart window, which includes at least the aforementioned solid polymer electrolyte film or electrochromic device.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0014] (1) The solid polymer electrolyte membrane prepared by this invention has excellent ionic conductivity, with a room temperature ionic conductivity as high as 3.43 × 10⁻⁶. -4 S / cm;

[0015] (2) The solid polymer electrolyte film prepared by the present invention has properties such as colorless transparency, excellent optical transmittance (>90%), and no haze, which can meet the visual requirements of application scenarios such as electrochromic smart windows.

[0016] (3) The solid polymer electrolyte membrane prepared by the present invention has a temperature resistance of >200℃, which meets the temperature requirements for device assembly and safe operation;

[0017] (4) The tensile strength of the solid polymer electrolyte membrane prepared by the present invention can reach up to 1.61 MPa, which meets the requirements for safe operation of the device;

[0018] (5) The solid polymer electrolyte membrane prepared by the present invention can be used to assemble high-quality WO3-NiO electrochromic devices using existing lamination processes; at the same time, the prepared devices have fast switching speed; excellent stability in colored and faded states; excellent cycle stability (can still work normally after 10,000 cycles without failure phenomena such as bubbles or shedding); and outstanding visible light and near-infrared light modulation capabilities.

[0019] (5) No organic solvents are introduced in the process of preparing solid polymer electrolyte membranes, making this invention green, environmentally friendly and pollution-free;

[0020] (6) The solid polymer electrolyte membrane preparation process provided by the present invention makes it easy to prepare electrolyte membranes with larger area. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is the XRD pattern of the polymer solid electrolyte membrane prepared in Example 1 of the present invention;

[0023] Figure 2 This is a surface SEM image of the polymer solid electrolyte membrane of Example 1 of the present invention;

[0024] Figure 3 This is a thermogravimetric analysis curve of the polymer solid electrolyte membrane prepared in Example 1 of the present invention;

[0025] Figure 4 This is a comparison chart of the optical transmittance of the polymer solid electrolyte film prepared in Example 1 of the present invention and ultra-white glass.

[0026] Figure 5 This is a photograph of the appearance of the polymer solid electrolyte membrane prepared in Example 1 of the present invention;

[0027] Figure 6 This is the 20×25 cm sample prepared according to Example 1 of the present invention. 2 Photographs showing the appearance of a large-size polymer solid electrolyte membrane;

[0028] Figure 7 This is a bar chart comparing the room temperature ionic conductivity of the polymer solid electrolyte membranes prepared in Example 1 and Comparative Example 1 of this invention.

[0029] Figure 8 These are tensile stress-strain curves of the polymer solid electrolyte films prepared in Example 1 and Comparative Example 1 of this invention.

[0030] Figures 9a-9b It is a 20×20 cm sample prepared using Example 1 of the present invention. 2 Photographs of the colored and faded states of a large-size electrochromic device. Detailed Implementation

[0031] In view of the deficiencies of the prior art, the inventors of this invention, through long-term research and extensive practice, have proposed the technical solution of this invention. The main method is to introduce a small amount of water into the electrolyte of ethylene-vinyl acetate copolymer by constant temperature and humidity treatment, so as to improve the room temperature ionic conductivity without changing the visible light transmittance, mechanical and thermal properties of the film.

[0032] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] Specifically, as one aspect of the technical solution of this invention, a method for preparing a solid polymer electrolyte film for an electrochromic device includes:

[0034] The first solid product was obtained by heating and premixing the ethylene-vinyl acetate copolymer with lithium salt additive.

[0035] Furthermore, the first solid product is subjected to roll pressing and constant temperature and humidity treatment to obtain a solid polymer electrolyte film for electrochromic devices.

[0036] In some preferred embodiments, the preparation method specifically includes: heating and premixing ethylene-vinyl acetate copolymer with lithium salt additive at 100~150°C for 0.2~1h to obtain a first solid product.

[0037] Furthermore, the molecular structural formula of the ethylene-vinyl acetate copolymer is as follows: .

[0038] Furthermore, the ethylene-vinyl acetate copolymer (EVA) is a random copolymer.

[0039] Furthermore, the vinyl acetate (VA) content in the ethylene-vinyl acetate copolymer is 12~44 wt%.

[0040] Furthermore, the melt index of the ethylene-vinyl acetate copolymer is 8~52 g / 10 min.

[0041] Furthermore, the lithium salt additive includes any one or more combinations of lithium bis(trifluoromethanesulfonyl)imide, lithium perchlorate, lithium trifluoromethanesulfonate, lithium hexafluorophosphate, and lithium tetrafluoroborate, and is not limited thereto.

[0042] Furthermore, the mass ratio of the ethylene-vinyl acetate copolymer to the lithium salt additive is 100:(20~200).

[0043] In some preferred embodiments, the preparation method specifically includes: placing the first solid product in a two-roll mill and rolling it at 50~100°C for 0.2~1h, while adding a crosslinking agent and a co-crosslinking agent during the rolling process to obtain a first adhesive film.

[0044] In some preferred embodiments, the preparation method specifically includes: treating the first adhesive film in a constant temperature and humidity environment of 30~80℃ and 10~50% for 0.2~1h to obtain a solid polymer electrolyte adhesive film for electrochromic devices.

[0045] Furthermore, the crosslinking agent includes any one or more combinations of tert-butyl-2-ethylhexanoate peroxide, 3-2-tert-butyl peroxide, tert-dicumyl peroxide, 2,5-disperoxide, tert-butyl benzoate peroxide, tert-butyl-3,3,5-trimethylcyclohexanoate peroxide, tert-butyl laurate peroxide, tert-butyl-2-ethylhexyl carbonate, and 4-methylbenzoyl peroxide, and is not limited thereto.

[0046] Furthermore, the co-crosslinking agent includes any one or more combinations of trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, ethoxylated trimethylolpropane triacrylate, ethoxylated trimethylolpropane trimethacrylate, N,N-m-phenylbismaleimide, 1,2-polybutadiene, diallyl phthalate, triallyl isocyanate, and triallyl cyanate, and is not limited thereto.

[0047] In some more specific embodiments, the method for preparing the solid polymer electrolyte film for the electrochromic device includes the following steps:

[0048] S1. Ethylene-vinyl acetate copolymer and lithium salt additive are premixed on a heating plate at 100℃~150℃ for 0.2~1h to obtain an opaque white gel block;

[0049] S2. The opaque white rubber block prepared in S1 is placed between the two rolls of a two-roll mill and rolled and mixed at 50~100°C for 0.2~1h. During the rolling and mixing process, a crosslinking agent and a co-crosslinking agent are added to obtain a uniform and transparent rubber film.

[0050] S3. The uniform and transparent film obtained in S2 is placed in a constant temperature and humidity chamber at a temperature of 30~80℃ and a relative humidity of 10~50% for 0.2~1h to finally obtain a solid polymer electrolyte film.

[0051] The solid polymer electrolyte membrane provided by the above scheme uses water as an additive, utilizing the reaction between water and Li + Coordination interactions weaken Li + The coordination with the C=O group of the ester carbonyl group in the ethylene-vinyl acetate copolymer simultaneously reduces the crystallinity of the solid polymer electrolyte film, thereby promoting the Li +The rapid conduction of this material, while maintaining excellent optical, thermal, and mechanical properties, also enhances room-temperature ionic conductivity, achieving a high level of 3.43 × 10⁻⁶ room-temperature ionic conductivity. -4 S / cm; to meet the application requirements of electrochromic devices.

[0052] Meanwhile, the solid polymer electrolyte film has good thermal stability and mechanical properties, and can withstand the process temperature of device lamination (130℃) and the highest operating temperature of the device during operation (80℃). Its tensile strength can reach up to 1.61 MPa.

[0053] In summary, the solid polymer electrolyte film obtained using the technical solution of this invention possesses excellent optical, thermal, and mechanical properties, while also exhibiting a maximum strength of 3.43 × 10⁻⁶. -4 With a room-temperature ionic conductivity of S / cm, it meets the requirements for electrochromic devices and also satisfies the visual requirements for applications such as electrochromic smart windows.

[0054] Another aspect of the present invention provides a solid polymer electrolyte film for electrochromic devices prepared by the aforementioned preparation method, wherein the solid polymer electrolyte film is prepared from at least ethylene-vinyl acetate copolymer, water, and lithium salt additives, and the surface of the solid polymer electrolyte film has a mesh-like wrinkled structure.

[0055] In some preferred embodiments, the solid polymer electrolyte membrane is prepared from ethylene-vinyl acetate copolymer, water, crosslinking agent, co-crosslinking agent and lithium salt additive; wherein the mass ratio of ethylene-vinyl acetate copolymer, water, crosslinking agent, co-crosslinking agent and lithium salt additive is 100:(0.2~2):(0~2):(0~4):(20~200).

[0056] In some preferred embodiments, the thickness of the solid polymer electrolyte membrane is 30~300 μm.

[0057] In some preferred embodiments, the solid polymer electrolyte membrane may have a size of 20 × 25 cm. 2 .

[0058] Another aspect of the present invention provides an electrochromic device, which includes at least the aforementioned solid polymer electrolyte film.

[0059] Another aspect of the present invention provides an electrochromic smart window, which includes at least the aforementioned solid polymer electrolyte film or electrochromic device.

[0060] The technical solution of the present invention will be further described in detail below with reference to several preferred embodiments and accompanying drawings. This embodiment is implemented on the premise of the technical solution of the invention, and provides detailed implementation methods and specific operation processes. However, the protection scope of the present invention is not limited to the following embodiments.

[0061] Unless otherwise specified, the experimental materials used in the examples below can be purchased from conventional biochemical reagent companies.

[0062] Example 1

[0063] This embodiment provides a process for preparing a solid polymer electrolyte film capable of conducting Li ions, the specific steps of which are as follows:

[0064] S1. Select 10 parts of ethylene-vinyl acetate copolymer (VA content of 40wt.%) and 12 parts of lithium bis(trifluoromethanesulfonylimide) and premix them on a heating table at 130℃ for 50 min to obtain an opaque white gel block;

[0065] S2. The opaque white rubber block prepared in S1 is placed between the two rolls of a two-roll mill and rolled and mixed at 75°C for 40 minutes to obtain a uniform and transparent rubber film.

[0066] S3. The uniform and transparent film obtained in S2 is placed in a constant temperature and humidity chamber at 50°C and 25% relative humidity for 1 hour to finally obtain the polymer solid electrolyte film.

[0067] Example 2

[0068] The difference between this embodiment and Embodiment 1 is that the relative humidity during the constant temperature and humidity treatment is 15%. Testing showed that the film had an optical transmittance of 90%, a tensile strength of 1.52 MPa, and an ionic conductivity of 1.18 × 10⁻⁶. -4 S / cm.

[0069] Example 3

[0070] The difference between this embodiment and Embodiment 1 is that the relative humidity during the constant temperature and humidity treatment is 35%. Testing showed that the film had an optical transmittance of 90%, a tensile strength of 1.45 MPa, and an ionic conductivity of 4.56 × 10⁻⁶. -4 S / cm.

[0071] Example 4

[0072] The difference between this embodiment and Embodiment 1 is that 0.2 parts of the crosslinking agent dicumyl peroxide were added during the rolling and mixing process on the open mill, and the constant temperature and humidity treatment was not performed. Testing showed that the optical transmittance of the film was 90%, and the ionic conductivity was 2.81 × 10⁻⁶. -5 S / cm.

[0073] Example 5

[0074] The difference between this embodiment and Embodiment 1 is that 0.2 parts of the crosslinking agent dicumyl peroxide and 0.5 parts of the co-crosslinking agent ethoxylated trimethylolpropane triacrylate were added during the rolling mixing process on an open mill, and no constant temperature and humidity treatment was performed. Testing showed that the optical transmittance of the film was 90%, and the ionic conductivity was 1.11 × 10⁻⁶. -6 S / cm.

[0075] Comparative Example 1

[0076] The difference between this comparative example and Example 1 is that the constant temperature and humidity treatment is not performed; otherwise, they are the same.

[0077] Performance characterization:

[0078] 1. Phase structure and surface morphology: The phase structure of the thin film was observed using X-ray diffraction (XRD); the surface morphology of the thin film was observed using scanning electron microscopy (SEM).

[0079] 2. Optical properties: The optical properties (transmittance) of the thin film were measured using a UV-Vis spectrophotometer.

[0080] 3. Thermogravimetric analysis (TGA) was used to characterize the thermal stability of the film.

[0081] 4. Mechanical properties were measured using a 1kN universal testing machine.

[0082] 5. The electrochemical properties of the film were measured using an electrochemical workstation.

[0083] The performance of Example 1 and Comparative Example 1 was compared using the above-described analytical equipment or methods to further illustrate the superiority and advancement of the present invention.

[0084] Figure 1 The XRD patterns of Example 1 and Comparative Example 1 are given. As can be seen from the figure, Example 1 has a wider EVA diffraction peak compared with Comparative Example 1, indicating that Example 1 has lower crystallinity and increased amorphous region, which is beneficial to the segment migration of the main chain and achieves higher room temperature ionic conductivity.

[0085] Figure 2 SEM images from Example 1 are provided, through... Figure 2 It can be seen that the film surface of Example 1 has uniform mesh-like wrinkles. This structure facilitates the expulsion of air during the lamination process, thereby ensuring a tight adhesion between the polymer solid electrolyte and the electrochromic active layer, which in turn helps to form a high-quality laminated electrochromic device.

[0086] Figure 3The thermogravimetric curves of the adhesive film prepared in Example 1 at 30~220℃ are given. It can be seen that the adhesive film has almost no weight loss, which indicates that the adhesive film has high thermal stability. It can not only withstand the process temperature of device lamination (130℃), but also the highest operating temperature of the device during operation (80℃).

[0087] Figure 4 The optical transmittance spectrum of the polymer solid electrolyte film prepared in Example 1 is given. It can be seen from the spectrum that the visible light transmittance of the film exceeds 90%, which is comparable to the optical transmittance of ultra-white glass (the transmittance is generally greater than 91.5%).

[0088] Figure 5 The appearance morphology of the film is shown, which can be seen to be colorless and transparent with clear boundaries and no haze, which can meet the visual requirements of application scenarios such as electrochromic smart windows.

[0089] Figure 6 The 20×25 cm prepared in Example 1 of this invention 2 Photograph of the appearance of a large-size polymer solid electrolyte membrane.

[0090] Figure 7 The room temperature ionic conductivity of the polymer solid electrolyte membranes prepared in Example 1 and Comparative Example 1 is given. Compared with Comparative Example 1, the room temperature ionic conductivity of Example 1 is 0.79 × 10⁻⁶. -4 S / cm increased to 3.43×10 -4 S / cm. Clearly, this embodiment significantly improves the room-temperature ionic conductivity of the EVA-based polymer solid electrolyte.

[0091] Figure 8 The tensile stress-strain curves of the polymer solid electrolyte films prepared in Example 1 and Comparative Example 1 are shown. As can be seen from the figures, the tensile strength of Comparative Example 1 is 1.48 MPa, while the tensile strength of Example 1 is 1.61 MPa. This invention improves the mechanical properties of polymer solid electrolytes.

[0092] Figures 9a-9b It is the 20×20 cm prepared in Example 1 of this invention. 2 Photographs of the colored and faded states of a large-size electrochromic device.

[0093] The properties of the films prepared in Examples 1-5 and Comparative Examples 1-2 are shown in Table 1.

[0094] Table 1. Properties of the films prepared in Examples 1-5 and Comparative Examples 1-2

[0095]

[0096] Note: - indicates not detected.

[0097] In summary, Example 1 represents the optimal implementation of the present invention. The EVA polymer solid electrolyte obtained by constant temperature and humidity treatment at 50°C and 25% relative humidity exhibits a room temperature ionic conductivity as high as 3.43 × 10⁻⁶. -4 It has a strength of S / cm and can also have superior tensile strength.

[0098] Specifically, the light transmittance of Examples 1 and 2 is 90%, indicating that the technical solution of the present invention can obtain materials with stable optical performance.

[0099] The results from Example 1 and Comparative Example 1 show that, under the same conditions, the polymer solid electrolyte prepared in Example 1 after constant temperature and humidity treatment at 50°C and 25% relative humidity significantly improves the room temperature ionic conductivity, compared to 0.79 × 10⁻⁶ in Comparative Example 1. -4 S / cm increased to 3.43×10 -4 The tensile strength also increased from 1.48 MPa to 1.61 MPa. Clearly, this invention, through constant temperature and humidity treatment, can improve the room temperature ionic conductivity and mechanical properties of the polymer solid electrolyte.

[0100] In addition, the inventors of this case also conducted experiments with other raw materials, process operations, and process conditions described in this specification, referring to the aforementioned embodiments, and obtained relatively ideal results in all cases.

[0101] It should be understood that the technical solutions of the present invention are not limited to the specific embodiments described above. Any technical modifications made to the technical solutions of the present invention without departing from the spirit and scope of the claims are within the scope of protection of the present invention.

Claims

1. A method for preparing a solid-state polymer electrolyte gel film for an electrochromic device, characterized by, include: The first solid product was obtained by heating and premixing the ethylene-vinyl acetate copolymer with lithium salt additive. The mass ratio of the ethylene-vinyl acetate copolymer to the lithium salt additive is 100:(20~200); the content of vinyl acetate in the ethylene-vinyl acetate copolymer is 12~44 wt%; Furthermore, the first solid product is rolled and mixed at 50~100℃ for 0.2~1h to obtain a first adhesive film, and the first adhesive film is placed in a constant temperature and humidity environment at 30~80℃ and 10~50% for 0.2~1h to obtain a solid polymer electrolyte adhesive film for electrochromic devices.

2. The production method according to claim 1, characterized by, Specifically, it includes: The first solid product was obtained by heating and premixing the ethylene-vinyl acetate copolymer with lithium salt additive at 100-150℃ for 0.2-1h.

3. The method of claim 2, wherein: The melt index of the ethylene-vinyl acetate copolymer is 8~52 g / 10 min.

4. The method of claim 2, wherein: The lithium salt additive includes any one or a combination of lithium bis(trifluoromethanesulfonyl)imide, lithium perchlorate, lithium trifluoromethanesulfonate, lithium hexafluorophosphate, and lithium tetrafluoroborate.

5. A solid polymer electrolyte film for electrochromic devices prepared by the method according to any one of claims 1-4, characterized in that: The solid polymer electrolyte membrane is made from at least ethylene-vinyl acetate copolymer, water, and lithium salt additives, and the surface of the solid polymer electrolyte membrane has a mesh-like wrinkled structure.

6. The solid-state polymer electrolyte gum film according to claim 5, characterized in that: The thickness of the solid polymer electrolyte membrane is 30~300 μm.

7. An electrochromic device, characterized by: It includes at least the solid polymer electrolyte membrane as described in claim 5 or 6.

8. An electrochromic smart window, characterized in that: It includes at least the solid polymer electrolyte membrane of any one of claims 5-6 or the electrochromic device of claim 7.

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