Solid-state electrolyte material, electrochromic device and preparation method
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-04-22
- Publication Date
- 2026-07-03
Smart Images
Figure CN122331182A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of electrochromic materials and devices, specifically to a solid electrolyte material, an electrochromic device, and a preparation method thereof. Background Technology
[0002] Electrochromic (EC) refers to the phenomenon where a material undergoes a stable and reversible color change under the influence of an applied electric field. Electrochromic glass (EC glass), made from electrochromic materials, can achieve controllable changes in light transmittance through dynamic voltage adjustment, showing broad application prospects in building energy conservation, improving safety and comfort in transportation, and upgrading smart home consumption. It is estimated that traditional glass curtain walls account for more than 40% of building energy consumption, and static shading solutions (such as Low-E glass and blinds) cannot dynamically adjust light transmittance; 12% of nighttime traffic accidents are caused by blindness due to glare from following vehicles' high beams; and aircraft windows have ultraviolet transmittance exceeding 50%, resulting in a three times higher incidence of skin cancer among crew members and passengers near windows compared to the general population. Therefore, developing electrochromic glass that integrates multiple functions such as energy saving, safety, and intelligence is of significant practical importance.
[0003] A typical structure of an electrochromic device comprises five functional layers: a transparent conductive layer, an electrochromic layer, an electrolyte layer, an ion storage layer, and an encapsulation and protective layer. Among these, the electrolyte layer is a core component, serving to: provide migration channels for lithium ions (or hydrogen ions, sodium ions) to drive the electrochromic reaction; block direct electron transfer between electrodes to prevent short circuits; and inhibit electrode corrosion to maintain interface stability. However, traditional electrolyte materials suffer from numerous performance defects, severely limiting the overall performance and widespread application of electrochromic devices.
[0004] Traditional liquid electrolytes (such as LiClO4 / PC solutions) possess high ionic conductivity, but they suffer from problems such as a narrow electrochemical window (decomposition voltage <4.5V, operating voltage typically <3V), encapsulation difficulties, easy leakage, and poor safety. While traditional gel electrolytes (such as PEO-based gels) have improved the encapsulation issues of liquid electrolytes to some extent, their mechanical properties are insufficient (elongation at break <50%), and they are prone to interfacial detachment between the electrolyte and electrode materials during long-term cycling, leading to device failure.
[0005] In recent years, solid polymer electrolytes have attracted widespread attention due to their excellent safety, processability, and mechanical flexibility. Among them, polyvinyl butyral (PVB), as an interlayer material that has been successfully applied in laminated safety glass, is considered a potential matrix material for solid electrolytes due to its advantages such as high transparency (light transmittance > 92%), strong adhesion (high bonding strength with glass), and flexibility (elongation at break > 200%).
[0006] However, the ionic conductivity of pure PVB materials is extremely low (<10). -6 S / cm), which cannot meet the requirements of electrochromic devices for ion transport efficiency. Existing studies have attempted to improve the ionic conductivity of PVB-based electrolytes by doping with lithium salts and additives, but the existing technology still has the following shortcomings: (1) It is difficult to ensure the uniformity of lithium salt dispersion in the PVB matrix, resulting in a limited increase in ionic conductivity. Most schemes can only increase the ionic conductivity to 10. -5 The S / cm level is difficult to reach 10. -4 (2) The improvement of ionic conductivity often comes at the cost of sacrificing mechanical strength and optical transparency, making it difficult to achieve a balanced optimization of comprehensive performance; (3) Traditional electrochromic devices use a five-layer coating process, which is complex, requires a large investment in equipment, and has a low yield, resulting in high production costs and hindering large-scale application.
[0007] Therefore, it is necessary to propose a solid electrolyte material, an electrochromic device, and a preparation method to address the above-mentioned problems. Summary of the Invention
[0008] The technical problem to be solved by the present invention is to provide a solid electrolyte material, an electrochromic device and a preparation method thereof. Specifically, it includes a polyvinyl butyral-based solid electrolyte material for electrochromic devices and a preparation method thereof, a solid electrochromic device comprising the solid electrolyte material, and a preparation method thereof.
[0009] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: In a first aspect, the present invention provides a solid electrolyte material for electrochromic devices, wherein the solid electrolyte material has a sheet-like or film-like structure and is prepared by melt blending and extrusion casting of raw materials in the following mass proportions: 65-70 parts of polyvinyl butyral resin, 10-20 parts of lithium bis(trifluoromethanesulfonyl)imide, and 15-25 parts of an additive composition; The polyvinyl butyral resin has a hydroxyl content of 18% to 22%, and the additive composition includes plasticizers, antioxidants, ultraviolet absorbers, and heat stabilizers. The solid electrolyte material has the following characteristics: ionic conductivity S / cm to S / cm, visible light transmittance >92%, tensile strength >20 MPa, elongation at break >200%; When the solid electrolyte material is used as an electrolyte layer in an electrochromic device, it enables rapid migration of lithium ions in the three-dimensional network transport channels between polymer segments, effectively reducing ion transport resistance, shortening the coloring and fading response time of the electrochromic device to within 60 seconds, and improving cycle stability to more than 50,000 cycles.
[0010] The beneficial effects of this invention are: by constructing a three-dimensional ion transport network through the coordination bond between hydroxyl groups and lithium ions, the migration of lithium ions from the traditional inorganic lattice gaps is transformed into a creeping movement on the flexible polymer segments, which significantly reduces the activation energy of ion migration. Thus, while ensuring good mechanical strength and optical transparency, a significant improvement in ionic conductivity is achieved, providing key material support for the rapid response and long-life cycling of solid-state electrochromic devices.
[0011] Based on the above technical solution, the present invention can be further improved as follows.
[0012] Furthermore, the lithium ion transference number in the bis(trifluoromethanesulfonyl)imide lithium is 0.5, and the thermal decomposition temperature is >300℃; The plasticizer is selected from one or more of dibutyl phthalate, dioctyl phthalate, and tricresyl phosphate, and is used to fill the gaps between polyvinyl butyral molecular chains to improve ionic conductivity. The antioxidant is selected from a composite system of hindered phenolic antioxidants and phosphite antioxidants; The ultraviolet light absorber is selected from benzotriazole compounds; The heat stabilizer is selected from organotin or calcium-zinc composite heat stabilizers.
[0013] The beneficial effects of adopting the above-mentioned further scheme are: Using lithium bis(trifluoromethanesulfonyl)imide, which has high lithium-ion transference number and high thermal stability, as the lithium salt, it can achieve nanoscale uniform dispersion in the polyvinyl butyral matrix. Combined with the interfacial filling effect of the plasticizer, the ionic conductivity is reduced from < that of pure polyvinyl butyral. S / cm increased to ~ The combined use of antioxidants, UV absorbers, and thermal stabilizers ensures the performance stability of the solid electrolyte material under long-term use and extreme environmental conditions.
[0014] Furthermore, the mass ratio of the polyvinyl butyral resin, lithium bis(trifluoromethanesulfonyl)imide, and the additive composition is 70:10:20.
[0015] The beneficial effects of adopting the above-mentioned further scheme are as follows: under the condition that the mass ratio of polyvinyl butyral to lithium bis(trifluoromethanesulfonyl)imide is 7:1 and the additive accounts for 20%, the orthogonal experiment verified that this ratio can obtain the highest ionic conductivity and the widest light modulation range. This ratio achieves the synergistic optimization of the optimal dispersion concentration of lithium salt in polymer matrix and the plasticizing and toughening effect of additive.
[0016] Secondly, the present invention provides a method for preparing a solid electrolyte material for electrochromic devices, comprising the following steps: S1 Raw material pretreatment: Dry polyvinyl butyral resin at 40~60℃ for 2~4 hours to reduce its moisture content to <0.5%; S2 Premix: Weigh the dried polyvinyl butyral resin, lithium bis(trifluoromethanesulfonyl)imide and additive composition according to the formula, put them into a high-speed mixer, and mix for 10 to 20 minutes at a speed of 300 to 500 rpm to obtain the premix. S3 Melt Blending Extrusion: The premix obtained in step S2 is added to a twin-screw extruder and melt blended extrusion is carried out at an extrusion temperature of 150~180℃ and a screw speed of 200~300 rpm to obtain a blended material; S4 Extrusion casting: The blend material obtained in step S3 is extruded through a T-die onto a casting roller. The surface temperature of the casting roller is 80~120℃. After cooling and shaping, a film is formed. S5 Online Thickness Measurement and Rewinding: An online infrared thickness gauge is used to monitor and control the film thickness in real time, so that the film thickness error is controlled within ±5%, and the solid electrolyte membrane product is obtained by rewinding. The twin-screw extruder has a length-to-diameter ratio of 32:1 to 48:1, and a vacuum exhaust port is provided in the middle of the extruder barrel during the extrusion process to remove low-molecular-weight volatiles.
[0017] The beneficial effects of this invention are as follows: By combining twin-screw melt blending with extrusion casting, the high shear force of the twin-screw extruder is used to achieve nanoscale dispersion of lithium bis(trifluoromethanesulfonyl)imide in the polyvinyl butyral matrix (scanning electron microscopy shows particle size <100 nm). At the same time, low-molecular-weight volatiles generated during processing are promptly removed through the vacuum exhaust port, avoiding the generation of bubbles and defects. The extrusion casting molding combined with feedback control from an online infrared thickness gauge ensures high uniformity of film thickness, providing key process assurance for the subsequent assembly of large-area electrochromic devices.
[0018] Based on the above technical solution, the present invention can be further improved as follows.
[0019] Furthermore, in step S4, the surface temperature of the casting roller is 100°C, and the cooling and shaping adopts a cooling method combining air cooling and water cooling. The feedback control frequency of the online infrared thickness gauge in step S5 is 10 times / second. When the detected thickness deviation exceeds the preset threshold, the opening of the die lip of the T-shaped die head is automatically adjusted.
[0020] The beneficial effects of adopting the above-mentioned further solutions are as follows: by optimizing the surface temperature of the casting roller to 100°C and using a stepped cooling method that combines air cooling and water cooling, the uniform cooling of the film from the molten state to the solid state is ensured, avoiding the accumulation of internal stress and film warping deformation caused by a sudden drop in temperature, while also ensuring production efficiency; the high-frequency feedback control of the online infrared thickness gauge combined with the automatic adjustment of the T-die lip opening realizes closed-loop precise control of the film thickness, providing technical support for the large-scale continuous production of high-performance solid electrolyte materials.
[0021] Thirdly, the present invention provides a solid-state electrochromic device, comprising a first transparent conductive substrate, an electrochromic layer, a solid electrolyte material for electrochromic devices in the first aspect, an ion storage layer, and a second transparent conductive substrate, which are sequentially stacked. The electrochromic layer is made of tungsten oxide, and the ion storage layer is made of nickel oxide. The solid electrolyte material forms a tight interface with the electrochromic layer and the ion storage layer, providing a lithium ion transport channel and blocking direct electron transfer during the electrochromic reaction. The solid-state electrochromic device has the following electrochromic properties: the optical modulation range between the colored state and the faded state is 4%~75%, the coloring response time is ≤60 seconds, the fading response time is ≤60 seconds, the cycle life is ≥50,000 times, and the ultraviolet blocking rate is >99%.
[0022] The beneficial effects of this invention are as follows: by directly bonding the solid electrolyte material with the electrochromic layer and the ion storage layer to form a "sandwich" structure, and utilizing the strong bonding properties of the polyvinyl butyral resin in the solid electrolyte material (the interfacial bonding strength with the tungsten oxide electrochromic layer is 8.5 MPa), the additional bonding layer and encapsulation layer in traditional electrochromic devices are eliminated, simplifying the number of device layers from 5 to 3. This reduces the interfacial impedance and accelerates the response speed, while significantly reducing manufacturing costs and encapsulation difficulty, thus achieving integrated electrochromic device.
[0023] Based on the above technical solution, the present invention can be further improved as follows.
[0024] Furthermore, the first transparent conductive substrate and the second transparent conductive substrate are each independently selected from indium tin oxide conductive glass or fluorine-doped tin oxide conductive glass; The tungsten oxide electrochromic layer is doped with molybdenum and titanium, with a total doping amount of 4% to 12%.
[0025] The beneficial effects of adopting the above-mentioned further scheme are as follows: the electrochromic layer of tungsten oxide is synergistically doped with molybdenum and titanium bimetallic elements. Molybdenum doping replaces tungsten ions to form a solid solution to adjust the band structure and enhance conductivity. Titanium modification inhibits abnormal growth of tungsten oxide grains and refines the microstructure. At the same time, the introduction of titanium in the form of titanium dioxide forms a ternary system with tungsten oxide and molybdenum oxide, which improves the mechanical strength and thermal shock resistance of the electrochromic layer. The bimetallic doping further widens the internal pores of the tungsten oxide material and increases the diffusion channels of lithium ions, so that the ion transport efficiency between the electrochromic layer and the solid electrolyte layer is synergistically improved.
[0026] Furthermore, after the solid-state electrochromic device was continuously placed in an environment of 85℃ / 85% relative humidity for 1000 hours, the visible light transmittance fluctuated by <3%; Even at a low temperature of -40℃, the color response time is 12 seconds, and the electrochromic function is still maintained.
[0027] The beneficial effects of adopting the above-mentioned further solution are as follows: Since the solid electrolyte material uses high molecular weight polyvinyl butyral as the matrix and adds ultraviolet light absorbers and antioxidants, combined with the excellent tolerance of the bimetallic doped tungsten oxide electrochromic layer in high temperature, high humidity and low temperature environments, the assembled solid electrochromic device can work stably for a long time in a wide temperature range of -40℃ to 85℃ and in a high humidity environment of 85%, meeting the stringent requirements of extreme environmental adaptability for practical application scenarios such as building curtain walls, automotive glass, and aircraft windows.
[0028] Fourthly, the present invention also provides a method for preparing a solid-state electrochromic device, comprising the following steps: S100 deposits an electrochromic layer and an ion storage layer on a first transparent conductive substrate and a second transparent conductive substrate respectively by magnetron sputtering. The deposition vacuum degree is 0.1~1 Pa, the sputtering power is 1~5 W / cm², and the substrate temperature is 200~300℃. S200 Cut the solid electrolyte material according to any one of claims 1 to 3 or the solid electrolyte material prepared according to the method of claim 4 or 5 into the required size; S300 The second transparent conductive substrate, the ion storage layer, the solid electrolyte material, the electrochromic layer, and the first transparent conductive substrate are stacked in sequence, with the solid electrolyte material sandwiched between the electrochromic layer and the ion storage layer. S400 places the stacked components in a vacuum laminator and performs hot-pressing composite under conditions of vacuum degree <100 Pa, temperature 120~160℃, and pressure 0.3~0.8 MPa for 20~60 minutes. After the S500 is naturally cooled to room temperature, it is removed to obtain a solid-state electrochromic device.
[0029] The beneficial effects of this invention are as follows: A two-step fabrication process combining magnetron sputtering and solid electrolyte hot-pressing composite is employed. First, an electrochromic layer and an ion storage layer are fabricated on a transparent conductive substrate. Then, a pre-prepared solid electrolyte film is sandwiched between the two as an independent functional layer for vacuum hot-pressing composite. This avoids the complex process of depositing the electrolyte layer and ion storage layer layer by layer on the electrochromic layer in traditional processes. During the vacuum hot-pressing process, the solid electrolyte film softens and flows under the influence of temperature and pressure, forming a tight interfacial contact and chemical bond with the electrochromic layer and the ion storage layer. This ensures the low impedance characteristics of the ion transport interface and utilizes the self-adhesive properties of polyvinyl butyral to achieve self-encapsulation of the device, eliminating the need for a separate encapsulation step and significantly reducing manufacturing costs.
[0030] Based on the above technical solution, the present invention can be further improved as follows.
[0031] Furthermore, the conditions for hot-pressing composite in step S400 are: vacuum degree <50 Pa, temperature 140℃, pressure 0.5MPa, and hot-pressing time 30 minutes; Before hot-pressing composite, step S400 includes a step of adjusting the moisture content of the solid electrolyte material: the moisture content of the solid electrolyte material is adjusted to 0.1%~0.5% using a temperature and humidity controller to adjust the active state of the hydroxyl groups in the polyvinyl butyral resin and enhance the interfacial bonding performance between the solid electrolyte material and the electrochromic layer and ion storage layer.
[0032] The beneficial effects of adopting the above-mentioned further scheme are as follows: by optimizing the hot-pressing composite conditions to a vacuum degree <50 Pa, a temperature of 140℃, a pressure of 0.5 MPa, and a time of 30 minutes, the solid electrolyte is ensured to soften and flow sufficiently to fill the microscopic gaps at the interface, while avoiding excessive flow or deformation of the solid electrolyte due to excessive temperature and pressure. The moisture content of the solid electrolyte material is precisely controlled by a temperature and humidity regulator, so that the activity of the hydroxyl groups in the polyvinyl butyral resin is in the optimal state, promoting sufficient ion exchange reaction between the solid electrolyte material and the electrochromic layer (tungsten oxide) and the ion storage layer (nickel oxide), thereby significantly improving the bonding strength between the solid electrolyte and the functional layers on both sides, and ensuring the interface stability and consistency of electrochromic performance of the device during long-term cyclic use. Attached Figure Description
[0033] The present invention will be further described below with reference to the accompanying drawings and embodiments.
[0034] Figure 1 This is a schematic diagram of the preparation process of the PVB / Li solid electrolyte material in this invention; Figure 2 This is a schematic diagram comparing the performance of the solid electrolyte material in this invention with that of traditional electrolyte materials; Figure 3 This is a schematic diagram of the solid-state electrochromic device in this invention; Figure 4 This is a schematic diagram of the structure of a conventional electrochromic device in this invention; Figure 5 This is a comparison diagram between the preparation process in this invention and the traditional preparation process; Figure 6 This is another performance comparison diagram between the solid electrolyte material in this invention and traditional electrolyte materials; Figure 7 This is a schematic diagram illustrating the color-changing principle of the electrochromic glass in this invention. Detailed Implementation
[0035] The following will clearly and completely describe the concept, specific structure, and technical effects of the present invention in conjunction with embodiments and accompanying drawings, so as to fully understand the purpose, features, and effects of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention. Furthermore, all connections / linkages involved in the patent do not simply refer to direct contact between components, but rather to the ability to form a better connection structure by adding or reducing connecting accessories according to specific implementation conditions. The various technical features in this invention can be combined interactively without contradicting each other.
[0036] The first aspect of this invention is a solid electrolyte material for electrochromic devices.
[0037] Through in-depth research and extensive experiments, it was discovered that a solid electrolyte material prepared by melt blending and extrusion casting of a composition of polyvinyl butyral resin, lithium bis(trifluoromethanesulfonyl)imide, and additives in specific mass ratios can simultaneously achieve high ionic conductivity. With its excellent combined properties of high S / cm, high visible light transmittance (>92%), high tensile strength (>20MPa), and high elongation at break (>200%), it is particularly suitable as a solid electrolyte layer for electrochromic devices.
[0038] Reference Figure 1The solid electrolyte material of this invention mainly uses polyvinyl butyral as a flexible polymer matrix, and uses lithium bis(trifluoromethanesulfonyl)imide as a lithium-ion source by doping it, and adds an additive composition consisting of plasticizers, antioxidants, ultraviolet light absorbers and heat stabilizers to form a ternary composite system of "polymer-lithium salt-additive". This system utilizes the coordination bond between the hydroxyl groups on the polyvinyl butyral molecular chain and lithium ions to construct a three-dimensional ion transport network, which transforms the traditional jumping migration of lithium ions from the interstitial inorganic lattice into a creeping movement on the flexible polymer chain segments, significantly reducing the activation energy of ion migration.
[0039] The polyvinyl butyral resin has a hydroxyl content of 18% to 22%. Specifically, PVB resins with a hydroxyl content within this range can provide sufficient coordination sites to bind with lithium ions while maintaining good mechanical strength and optical transparency. Too low a hydroxyl content leads to insufficient coordination with lithium ions and a decrease in ionic conductivity; too high a hydroxyl content enhances hydrogen bonding between PVB molecular chains, hindering molecular chain movement and also impeding ion transport.
[0040] The lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), as a lithium salt, has a large anion volume and a lithium-ion transference number as high as 0.5 (compared to only 0.2 for conventional LiClO4). Its thermal decomposition temperature is >300℃, thus avoiding electrolyte failure under high-temperature operating conditions. LiTFSI exhibits good compatibility with the PVB matrix, achieving nanoscale uniform dispersion (SEM showing particle size <100 nm) during melt blending, forming continuous three-dimensional ion transport channels.
[0041] The additive composition comprises a plasticizer, an antioxidant, a UV absorber, and a heat stabilizer. The functions and synergistic effects of each component are as follows: Plasticizer: Selected from one or more of dibutyl phthalate, dioctyl phthalate, and tricresyl phosphate, used to fill the gaps between PVB molecular chains, increase the free volume between molecular chains, lower the glass transition temperature of the polymer, and enhance the mobility of molecular chains, thereby providing more space and a lower energy barrier for lithium ion migration, and reducing the ionic conductivity from... Upgraded to The plasticizer is on the order of S / cm. At the same time, the addition of plasticizers can also improve the material's flexibility and processing flowability.
[0042] Antioxidants: A composite system selected from hindered phenolic antioxidants (such as antioxidant 1010) and phosphite antioxidants (such as antioxidant 168) is used to inhibit the thermal oxidative degradation of the PVB matrix during high-temperature processing and long-term use, thus extending the material's service life. This results in a composite antioxidant system with superior synergistic antioxidant effects compared to single antioxidants.
[0043] Ultraviolet (UV) absorbers: selected from benzotriazole compounds (such as UV-326 and UV-328), used to absorb ultraviolet light with wavelengths of 280-380 nm, reducing the damage of UV light to the PVB matrix and electrochromic layer. Especially in building and transportation applications, improving UV blocking efficiency is crucial for extending device lifespan and protecting passenger health. This allows the solid electrolyte material of this invention to achieve a UV blocking efficiency of over 99%.
[0044] Heat stabilizers: Selected from organotin or calcium-zinc composite heat stabilizers, used to improve the thermal stability of PVB matrix during high-temperature processing, prevent PVC impurities from decomposing at high temperatures to produce corrosive gases such as hydrogen chloride, and improve the long-term stability of materials in high-temperature and high-humidity environments.
[0045] The above-mentioned additive composition comprises 15-25 parts by weight, wherein the plasticizer accounts for 50%-70% of the total mass of the additive composition, and the antioxidant, ultraviolet absorber, and heat stabilizer each account for approximately 10%-20%. Through the synergistic effect of the additive composition, the tensile strength of the solid electrolyte membrane can be increased by more than 20%.
[0046] The relationship between the ionic conductivity and temperature of the solid electrolyte material of this invention conforms to the Arrhenius equation: , of which activation energy The reduction of [amount] is key to the improvement of ionic conductivity. The ionic conductivity of pure PVB is < [value missing]. S / cm, improved to [value missing] after modification according to this invention. S / cm. See also Figure 2 According to the test results of this invention, compared with traditional electrolytes (ionic conductivity) Compared to the previous solid electrolyte material (S / cm, tensile strength 5~10 MPa, cycle life 10,000~25,000 cycles), the ionic conductivity of the solid electrolyte material of the present invention is increased by an order of magnitude, the tensile strength is increased to more than 20 MPa, and the cycle life is increased to more than 50,000 cycles.
[0047] Regarding the formulation, when the mass ratio of polyvinyl butyral resin, lithium bis(trifluoromethanesulfonyl)imide, and additives was 65-70:10-20:15-25, the resulting electrochromic device exhibited the highest ionic conductivity and the widest optical modulation range. Among these, a ratio of 70:10:20 (i.e., PVB:LiTFSI:additives = 7:1:2) showed the best performance in orthogonal experiments, achieving an ionic conductivity of 9.6 × 10⁻⁶. -5 With an S / cm, an optical modulation range of 4% to 75%, a tensile strength of 22.5 MPa, and an elongation at break of 235%, the overall performance achieves an optimal balance.
[0048] The second aspect of the present invention is a method for preparing a solid electrolyte material according to the first aspect.
[0049] Research has shown that an integrated process combining twin-screw melt blending and extrusion casting can be used to prepare solid electrolyte materials, achieving nanoscale uniform dispersion of lithium salts in a PVB matrix and precise control of film thickness. This provides a feasible technical solution for the large-scale continuous production of solid electrolyte materials.
[0050] Specifically, see Figure 1 The preparation method of the present invention includes the following steps: S1 Raw material pretreatment: Dry polyvinyl butyral resin at 40~60℃ for 2~4 hours to reduce its moisture content to <0.5%; Specifically, polyvinyl butyral resin is dried at 40-60°C for 2-4 hours to reduce its moisture content to <0.5%. Too low a drying temperature or insufficient time will result in excessively high moisture content, causing water to vaporize and form bubbles during subsequent high-temperature processing, affecting film quality. Too high a drying temperature or too long a drying time may lead to thermal oxidative degradation or darkening of the PVB resin. Preferably, the drying conditions are 50°C for 3 hours.
[0051] S2 Premix: Weigh the dried polyvinyl butyral resin, lithium bis(trifluoromethanesulfonyl)imide and additive composition according to the formula, put them into a high-speed mixer, and mix for 10 to 20 minutes at a speed of 300 to 500 rpm to obtain the premix. Specifically, the dried polyvinyl butyral resin, lithium bis(trifluoromethanesulfonyl)imide, and additive composition are weighed according to the specified ratio and added to a high-speed mixer. The mixture is then mixed at 300-500 rpm for 10-20 minutes to obtain a premix. The purpose of premixing is to ensure that the components are initially and uniformly dispersed, laying the foundation for subsequent melt blending. Too low a mixing speed or too short a time will result in uneven mixing, while too high a speed or too long a time may lead to overheating or mechanical degradation of the material.
[0052] S3 Melt Blending Extrusion: The premix obtained in step S2 is added to a twin-screw extruder and melt blended extrusion is carried out at an extrusion temperature of 150~180℃ and a screw speed of 200~300 rpm to obtain a blended material; Specifically, the premix obtained in step S2 is added to a twin-screw extruder for melt blending and extrusion. The length-to-diameter ratio of the twin-screw extruder is 32:1 to 48:1, preferably 40:1, to ensure sufficient material residence time and adequate shear mixing. The extrusion temperature is controlled at 150 to 180°C, and the screw speed is controlled at 200 to 300 rpm. Too low an extrusion temperature will result in insufficient melting of the PVB matrix, making it difficult to uniformly disperse the lithium salt and additives; too high an extrusion temperature may lead to thermal oxidative degradation of the PVB matrix or decomposition of the lithium salt.
[0053] Specifically, a vacuum vent is installed in the middle of the extruder barrel, at 1 / 2 to 2 / 3 of the screw length. A vacuum pump is used to promptly remove low-molecular-weight volatiles generated during extrusion (such as moisture, unreacted residual monomers, and small molecule components in the plasticizer), maintaining a vacuum level of 0.06–0.09 MPa. The placement of the vacuum vent is crucial for obtaining high-quality films free of bubbles and defects.
[0054] S4 Extrusion casting: The blend material obtained in step S3 is extruded through a T-die onto a casting roller. The surface temperature of the casting roller is 80~120℃. After cooling and shaping, a film is formed. Specifically, the blend material obtained in step S3 is extruded onto a casting roller through a T-die for casting. The die lip opening of the T-die is adjustable to accommodate films with different thickness requirements. The surface temperature of the casting roller is 80~120℃, preferably 100℃. Controlling the surface temperature of the casting roller has a significant impact on the cooling and setting rate and crystallization behavior of the film: too low a temperature will cause the film to cool too quickly, generating internal stress and warping deformation; too high a temperature may cause the film to adhere to the casting roller or result in insufficient cooling.
[0055] The cooling and setting process employs a combination of air cooling and water cooling: firstly, air cooling is used at the exit of the casting roll to rapidly cool the film surface to below 80°C, and then water cooling is applied to further cool it to room temperature. This stepped cooling method ensures rapid film setting while avoiding the accumulation of internal stress caused by a sudden drop in temperature.
[0056] S5 Online Thickness Measurement and Rewinding: An online infrared thickness gauge is used to monitor and control the film thickness in real time, so that the film thickness error is controlled within ±5%, and the solid electrolyte membrane product is obtained by rewinding. Specifically, an online infrared thickness gauge is used for real-time monitoring and feedback control of the film thickness. The online infrared thickness gauge works on the principle that films of different thicknesses have different absorption rates of infrared light; the film thickness is calculated by detecting the change in light intensity after infrared light passes through the film. The detection frequency is 10 times / second. When the detected thickness deviation exceeds a preset threshold (e.g., ±5% of the target thickness), the control system automatically adjusts the die lip opening of the T-die (driven by thermal expansion bolts or a servo motor), causing a change in the extrusion amount, thereby controlling the thickness deviation within the allowable range. After thickness measurement and adjustment, the film is drawn to the winding system via a traction roller station to obtain the finished solid electrolyte membrane.
[0057] The above preparation method can be used to prepare solid electrolyte membranes with a thickness of 0.1~1.0 mm (which can be adjusted according to actual needs), a thickness error of <±5%, and a smooth surface without bubbles or defects.
[0058] The third aspect of this invention is a solid-state electrochromic device, referring to... Figure 3 Its structure includes a first transparent conductive substrate, an electrochromic layer, a solid electrolyte material as described in the first aspect of the present invention, an ion storage layer, and a second transparent conductive substrate, which are stacked sequentially.
[0059] Reference Figure 4 Traditional five-layer electrochromic devices consist of a transparent conductive layer, an electrochromic layer, an electrolyte layer, an ion storage layer, and a protective encapsulation layer. The solid-state electrochromic device of this invention differs from this. This invention utilizes the strong bonding properties of PVB resin in the solid electrolyte material (its interfacial bonding strength with the tungsten oxide electrochromic layer reaches 8.5 MPa, higher than PVC's 3.2 MPa), enabling the solid electrolyte material to simultaneously perform multiple functions of ion transport, electronic isolation, and interfacial bonding. This eliminates the need for an additional protective encapsulation layer, simplifying the device structure from five layers to three. (Reference) Figure 5 It can be concluded that the beneficial effects of the present invention through structural simplification include: reducing the number of interface layers, lowering the interface impedance during ion transport, and accelerating the response speed; simplifying the preparation process, changing from traditional layer-by-layer coating to one-step hot-pressing composite of solid electrolyte membrane and functional layer, which greatly reduces manufacturing costs; and improving the structural stability and safety of the device by utilizing the bonding and impact resistance properties of PVB.
[0060] The first and second transparent conductive substrates are each independently selected from indium tin oxide (ITO) conductive glass or fluorine-doped tin oxide (FTO) conductive glass, with a sheet resistance of 5~15 Ω / □ and a transmittance of >85% at a wavelength of 550 nm.
[0061] The electrochromic layer is preferably composed of tungsten oxide (WO3) with a thickness of 200-500 nm. WO3 is the most classic cathode electrochromic material, undergoing a reduction reaction when a voltage is applied: WO3 (colorless) + Li + + e - → LiWO3 (deep blue), achieving a reversible color change from transparent to deep blue. To improve ion transport efficiency, the tungsten oxide electrochromic layer is doped with molybdenum (Mo) and titanium (Ti), with a total doping amount of molybdenum and titanium atoms of 4%~12% (atomic percentage), preferably 10%. Molybdenum doping can replace some of the W. 6+ The formation of a solid solution modulates the band structure, enhances conductivity, and simultaneously suppresses abnormal growth of WO3 grains, refining the microstructure. Titanium doping is introduced in the form of TiO2, forming a WO3-Mo-TiO2 ternary system, which improves the mechanical strength and thermal shock resistance of the target material, widens the internal porosity, and enhances ion transport efficiency. See also... Figure 6 The conductivity of the doped WO3 electrochromic layer increased from S / cm increased to The response time has been reduced from >120 seconds to 60 seconds, the coloring efficiency has been increased from 50~80 cm² / C to 80~120 cm² / C, the optical modulation range has been broadened from 25~60% to 4~75%, and the cycle life has been increased from about 10,000 times to more than 50,000 times.
[0062] The ion storage layer is preferably made of nickel oxide (NiO) with a thickness of 200-500 nm. NiO is a typical anodic electrochromic material, playing a charge balancing role in the electrochromic reaction and storing / releasing Li₂ ions. + This maintains electrical neutrality while preventing the transparent conductive electrode from degrading due to ion intercalation.
[0063] See Figure 7 The working mechanism of the solid-state electrochromic device of the present invention is as follows: When a positive voltage is applied between the first and second transparent conductive substrates, lithium ions (Li) in the solid electrolyte material... + Under the influence of an electric field, electrons migrate to the electrochromic layer (WO3), while simultaneously being injected into the electrochromic layer through an external circuit, resulting in a reduction reaction: WO3 + Li + + e - → LiWO3, the electrochromic layer changes from colorless and transparent to dark blue, and the device exhibits a colored state.
[0064] When the voltage is removed or a reverse voltage is applied, lithium ions are released from LiWO3 and undergo an oxidation reaction: LiWO3 → WO3 + Li + + e -The electrochromic layer returns to colorless and transparent, and the device becomes transparent.
[0065] During the coloring and fading process, the ion storage layer (NiO) undergoes a reversible redox reaction to balance the charge: when Li + Upon entering WO3, the NiO layer releases Li + When Li + When leaving WO3, the NiO layer absorbs Li. + This maintains the electrical neutrality of the entire system.
[0066] Table 1 Main Technical Specifications of the Work
[0067] Table 2 Comparison of Key Performance Parameters with Other Products
[0068] Referring to Tables 1 and 2, it can be seen that the optical modulation range between the colored state and the fading state of the present invention is 4%~75%, the coloring response time is ≤60 seconds, the fading response time is ≤60 seconds, the cycle life is ≥50,000 times, and the ultraviolet blocking rate is >99%.
[0069] Compared with mainstream products on the market (Sage Glass from the United States, View from the United States, Econtrol-Glas from Germany, and AGC from Japan), the device of this invention has superior performance in terms of visible light transmittance (75.6%~4.0%), response time (60 seconds), maximum size (1.2×1.6m²), and power consumption (0.3 W·h / m²).
[0070] Furthermore, the solid-state electrochromic device of this invention also exhibits excellent adaptability to extreme environments. After being continuously placed in a high-temperature and high-humidity environment (85℃ / 85% RH) for 1000 hours, the visible light transmittance fluctuates by <3%, indicating that the device has good resistance to damp heat aging. In a low-temperature environment (-40℃), the color response time is extended to 12 seconds (still far superior to the 60 seconds of traditional WO3), and the device can still maintain normal electrochromic function, meeting the needs of building and transportation applications in cold regions.
[0071] The fourth aspect of this invention is a method for preparing a solid-state electrochromic device according to the third aspect.
[0072] Traditional electrochromic devices are fabricated using a five-layer sequential deposition process, which involves depositing an electrochromic layer, an electrolyte layer, and an ion storage layer on a transparent conductive substrate in sequence, followed by encapsulation and protection. This process is complex, requires long equipment lines, and has a low yield rate. Furthermore, magnetron sputtering and screen printing methods are not suitable for large-area fabrication.
[0073] See Figure 5The preparation method proposed in this invention adopts a two-step process of "stepwise preparation + hot-pressing composite", specifically including the following steps: Step S100 Functional layer deposition: Electrochromic layer and ion storage layer are deposited on the first transparent conductive substrate and the second transparent conductive substrate respectively by magnetron sputtering. The deposition vacuum degree is 0.1~1 Pa, the sputtering power is 1~5 W / cm², and the substrate temperature is 200~300℃. Specifically, an electrochromic layer and an ion storage layer are deposited on a first transparent conductive substrate and a second transparent conductive substrate, respectively, using magnetron sputtering. The deposition vacuum level is 0.1–1 Pa, the sputtering power is 1–5 W / cm², and the substrate temperature is 200–300 °C. The deposition atmosphere is a mixture of argon and oxygen, with an argon to oxygen flow ratio of 10:1–20:1. By controlling the sputtering time and power, the thickness of the functional layer can be precisely controlled. After deposition, annealing is performed at 400–500 °C for 1–2 hours to improve the crystallinity and stability of the functional layer.
[0074] S200 Solid electrolyte material preparation: Cut the solid electrolyte material according to any one of claims 1 to 3 or the solid electrolyte material prepared according to the method of claim 4 or 5 into the required size; Specifically, the solid electrolyte material according to the first aspect of the present invention or the solid electrolyte material prepared by the method according to the second aspect of the present invention is cut to the required size. Before cutting, it is preferable to adjust the moisture content of the solid electrolyte material using a temperature and humidity controller: the solid electrolyte material is placed in an environment with a temperature of 20~30°C and a relative humidity of 40%~60% for 24~48 hours to equilibrate it, so that its moisture content is adjusted to 0.1%~0.5%. Precise control of moisture content can adjust the active state of hydroxyl groups in PVB resin, promote sufficient ion exchange reaction between the solid electrolyte material and the electrochromic layer (WO3) and the ion storage layer (NiO), thereby significantly improving the interfacial bonding strength.
[0075] S300 stacking assembly: The second transparent conductive substrate, the ion storage layer, the solid electrolyte material, the electrochromic layer, and the first transparent conductive substrate are stacked in sequence, with the solid electrolyte material sandwiched between the electrochromic layer and the ion storage layer. Specifically, the components are stacked sequentially in the following order: second transparent conductive substrate, ion storage layer, solid electrolyte material, electrochromic layer, and first transparent conductive substrate, with the solid electrolyte material sandwiched between the electrochromic layer and the ion storage layer. During stacking, attention should be paid to alignment accuracy to avoid device failure due to misalignment.
[0076] S400 Hot Press Lamination: The stacked components are placed in a vacuum laminator and hot-pressed under conditions of vacuum degree <100 Pa, temperature 120~160℃, and pressure 0.3~0.8 MPa for 20~60 minutes. Specifically, the stacked components are placed in a vacuum laminator and hot-pressed under conditions of vacuum <100 Pa (preferably <50 Pa), temperature 120~160℃ (preferably 140℃), and pressure 0.3~0.8 MPa (preferably 0.5 MPa) for 20~60 minutes (preferably 30 minutes). During the hot-pressing process, the solid electrolyte membrane softens and flows under the influence of temperature and pressure, filling the microscopic irregularities and pores on the surface of the electrochromic layer and ion storage layer, forming a tight interfacial contact. Simultaneously, the hydroxyl groups on the PVB molecular chains form hydrogen bonds or even chemical bonds with the oxygen atoms on the surfaces of WO3 and NiO, further enhancing the interfacial bonding strength.
[0077] The purpose of a vacuum environment is to: remove residual air between stacked components to prevent air bubbles from forming during hot pressing; promote the further escape of low-molecular-weight volatiles from the PVB matrix to improve film quality; and prevent oxygen and moisture in the air from causing oxidation or hydrolysis damage to the functional layer under high-temperature conditions.
[0078] S500 Cooling: After naturally cooling to room temperature, the device is removed to obtain a solid-state electrochromic device.
[0079] Specifically, after hot-pressing lamination, the device is naturally cooled to room temperature in a vacuum laminator (or cooled with cooling water to accelerate cooling), and then removed to obtain a solid-state electrochromic device. During the cooling process, a vacuum state should be maintained or the vacuum should be released slowly to avoid warping or deformation of the device due to sudden pressure changes.
[0080] The above preparation method can realize the large-area (1.2 m × 1.6 m and above) preparation of solid electrochromic devices. Compared with the existing technology, the process flow is simplified from layer-by-layer coating to simultaneous coating at both ends + one-step hot pressing composite, which greatly reduces equipment investment and production costs.
[0081] Example 1 This embodiment provides a method for preparing a solid electrolyte material for electrochromic devices, the specific steps of which are as follows: 1. Raw material preparation Weigh each raw material according to the following parts by weight: Polyvinyl butyral resin (hydroxyl content 20%, molecular weight approximately 150,000): 70 parts Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI, purity >99%): 10 parts Plasticizer (dibutyl phthalate): 12 parts Antioxidant (Antioxidant 1010 and Antioxidant 168 mixed in a 1:1 mass ratio): 3 parts UV absorber (UV-326): 3 parts Heat stabilizer (calcium-zinc compound): 2 parts The additive composition consists of plasticizer, antioxidant, ultraviolet absorber and heat stabilizer, totaling 20 parts, i.e. PVB:LiTFSI:additive = 70:10:20.
[0082] 2. Raw material pretreatment The PVB resin was placed in a forced-air drying oven and dried at 50°C for 3 hours to reduce its moisture content to below 0.3%.
[0083] 3. Premix The dried PVB resin, LiTFSI and additive composition were put into a high-speed mixer and mixed at 400 rpm for 15 minutes to obtain a uniform premix.
[0084] 4. Melt blending extrusion The premixed material was added to a twin-screw extruder (L / D ratio 40:1). The extrusion temperatures were set as follows: Zone 1 150℃, Zone 2 160℃, Zone 3 170℃, Zone 4 175℃, Zone 5 180℃, and Die Head 175℃. The screw speed was 250 rpm. A vacuum vent was installed in the 6th section of the extruder barrel (approximately 2 / 3 of the screw length), with the vacuum level controlled at 0.08 MPa to promptly remove low-molecular-weight volatiles.
[0085] 5. Extrusion casting The blended material is extruded onto a casting roller through a T-die (die lip opening 0.5 mm), and the surface temperature of the casting roller is 100℃. Cooling and shaping are achieved by a combination of air cooling (air volume 1000 m³ / h) and water cooling (cooling water temperature 20℃).
[0086] 6. Online thickness measurement and winding An online infrared thickness gauge (detection frequency 10 times / second) is used to monitor the film thickness in real time. When the thickness deviation exceeds ±5%, the opening of the T-die lip is automatically adjusted. The film is pulled to the winding system by the traction roller station to obtain a solid electrolyte membrane with a thickness of 0.38 mm (±0.01 mm) and a width of 1.2 m.
[0087] Performance test results: Ionic conductivity (room temperature, AC impedance method): 9.6 × 10⁻⁶ -5 S / cm; Visible light transmittance (550 nm wavelength): 93.2%; Tensile strength: 22.5 MPa; Elongation at break: 235%; Scanning electron microscope observation: LiTFSI exhibits uniform nanoscale dispersion in a PVB matrix, with a particle size of <80 nm.
[0088] Example 2 This embodiment provides a method for preparing a solid electrochromic device comprising the solid electrolyte material of Example 1. The specific steps are as follows: 1. Preparation of transparent conductive substrate ITO conductive glass with dimensions of 1.2 m × 1.6 m and a thickness of 3.2 mm (sheet resistivity 10 Ω / □, transmittance at 550 nm wavelength 88%) was selected as the first and second transparent conductive substrates. The conductive glass was ultrasonically cleaned sequentially with deionized water, acetone, and anhydrous ethanol for 15 minutes each, and then dried with nitrogen before use.
[0089] 2. Deposition of electrochromic layer A Ti-Mo co-doped WO3 electrochromic layer was deposited on the conductive surface of a first transparent conductive substrate using magnetron sputtering. The sputtering target was a Ti-Mo co-doped WO3 ceramic target (Ti doping concentration 5 at%, Mo doping concentration 5 at%, total doping concentration 10 at%). Sputtering conditions: background vacuum 5 × 10⁻⁶ -4 The working pressure was 0.5 Pa (Ar:O2=15:1), the sputtering power was 3 W / cm², the substrate temperature was 250℃, and the deposition time was 30 minutes. After deposition, the substrate was annealed at 450℃ for 1.5 hours to obtain an electrochromic layer with a thickness of approximately 350 nm.
[0090] 3. Deposition of ion storage layer A NiO ion storage layer was deposited on the conductive surface of a second transparent conductive substrate using magnetron sputtering. The sputtering target was a NiO ceramic target. Sputtering conditions: base vacuum 5 × 10⁻⁶. -4 The working pressure was 0.5 Pa (Ar:O2=10:1), the sputtering power was 2.5 W / cm², the substrate temperature was 250℃, and the deposition time was 25 minutes. After deposition, the substrate was annealed at 450℃ for 1.5 hours to obtain an ion storage layer with a thickness of approximately 300 nm.
[0091] 4. Preparation of solid electrolyte materials The solid electrolyte membrane prepared in Example 1 was cut into pieces measuring 1.2 m × 1.6 m. The cut solid electrolyte membrane was placed in a temperature and humidity controller and equilibrated for 36 hours at a temperature of 25°C and a relative humidity of 50% to adjust its moisture content to 0.25%.
[0092] 5. Stacking and assembling Stack the following layers in the following order: second transparent conductive substrate (ITO side up), NiO ion storage layer, solid electrolyte membrane, Ti-Mo co-doped WO3 electrochromic layer, and first transparent conductive substrate (ITO side down). Ensure that each layer is aligned during stacking, with edge alignment accuracy controlled within ±1 mm.
[0093] 6. Hot-pressing composite The stacked components are placed in a vacuum laminator, and the chamber door is closed before evacuating to a vacuum level of <50 Pa. The temperature is raised to 140°C while a pressure of 0.5 MPa is applied and maintained for 30 minutes. During the hot-pressing process, the solid electrolyte membrane softens and flows under the influence of temperature and pressure, forming a tight interfacial bond with the electrochromic layers and ion storage layers on both sides.
[0094] 7. Cooling and Removal After hot pressing, the solid electrochromic device is naturally cooled to room temperature in a vacuum laminator (cooling time is about 1.5 hours), then the vacuum is released, the chamber door is opened, and the finished solid electrochromic device is taken out.
[0095] Performance test results (based on the standard JC / T 2631-2021 "Electrochromic Glass", using self-inspection and third-party inspection): Visible light transmittance range: 75.6% in transparent state, 4.0% in colored state (modulation range 71.6%). Coloring response time: 52 seconds (from the application of voltage until the transmittance reaches 90% of the modulation range); Fading response time: 48 seconds; Cycle life: After 56,000 cyclic voltammetric scans, the optical modulation range retains 94% of its initial value; UV blocking rate: 99.3%; High temperature and high humidity test (85℃ / 85% RH, 1000 hours): transmittance fluctuation 2.1%; Low temperature test (-40℃): The coloring response time is 11 seconds, and it can still change color normally; Power consumption: 0.28 W·h / m².
[0096] Example 3 This embodiment uses orthogonal experimental design to investigate the effect of the mass ratio of PVB, LiTFSI, and additives on the performance of solid electrolyte materials. L9(3) 4 Orthogonal experimental setup, with factor levels set as follows:
[0097] The orthogonal experimental design and results are shown in the table below:
[0098] Range analysis showed that the order of influence of each factor on ionic conductivity was: B (parts of LiTFSI) > A (parts of PVB) > C (parts of additives). The optimal ratio was A3B1C2, i.e., 70 parts PVB, 10 parts LiTFSI, and 20 parts additives (Experiment No. 7), which yielded the highest ionic conductivity (8.8 × 10⁻⁶). (S / cm), while visible light transmittance and tensile strength are also maintained at optimal levels.
[0099] Example 4 This embodiment investigates the effect of hot-pressing composite conditions on the interfacial bonding strength and electrochromic performance of a solid-state electrochromic device. The solid electrolyte material is fixed as in Example 1, the deposition conditions for the electrochromic layer and ion storage layer are the same as in Example 2, and the hot-pressing composite conditions are as follows: L9(3) 4 Changes in the orthogonal experimental table:
[0100] Range analysis showed that temperature had the most significant impact on interfacial bonding strength and response time, followed by pressure. The optimal hot-pressing composite conditions were: temperature 140℃, pressure 0.5 MPa, time 40 minutes, and vacuum degree <50 Pa (Experiment No. 5). Under these conditions, the interfacial bonding strength was the highest (8.2 MPa), and the response time was the shortest (52 seconds).
[0101] Example 5 This embodiment verifies the feasibility of using the method of the present invention to prepare large-area solid-state electrochromic devices. Following the method of Example 2, a solid-state electrochromic device with dimensions of 1.2 m × 1.6 m (area 1.92 m²) was prepared. Testing showed good performance uniformity across all regions of the device: sampling tests were conducted at the device center and four corners, with the maximum deviation in visible light transmittance being <2% and the maximum deviation in response time being <5 seconds, indicating that the method of the present invention has good process stability and scalability.
[0102] Performance Comparison The performance of the solid-state electrochromic device prepared in Example 2 of the present invention was compared with that of representative products in the prior art, and the results are as follows:
[0103] As can be seen from the table above, the solid-state electrochromic device of the present invention is superior to or on par with international mainstream products in key indicators such as visible light transmittance range, response time, maximum size, power consumption and cycle life, especially in terms of response speed and size scaling capability.
[0104] The above is a detailed description of the preferred embodiments of the present invention. However, the present invention is not limited to the embodiments described. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention. All such equivalent modifications or substitutions are included within the scope defined by the claims of this application.
Claims
1. A solid electrolyte material for electrochromic devices, characterized in that, The solid electrolyte material has a sheet-like or film-like structure and is prepared by melt blending and extrusion casting of raw materials in the following mass ratios: 65-70 parts of polyvinyl butyral resin, 10-20 parts of lithium bis(trifluoromethanesulfonyl)imide, and 15-25 parts of an additive composition; The polyvinyl butyral resin has a hydroxyl content of 18% to 22%, and the additive composition includes plasticizers, antioxidants, ultraviolet absorbers, and heat stabilizers. The solid electrolyte material has the following characteristics: ionic conductivity S / cm to S / cm, visible light transmittance >92%, tensile strength >20 MPa, elongation at break >200%; When the solid electrolyte material is used as an electrolyte layer in an electrochromic device, it enables rapid migration of lithium ions in the three-dimensional network transport channels between polymer segments, effectively reducing ion transport resistance, shortening the coloring and fading response time of the electrochromic device to within 60 seconds, and improving cycle stability to more than 50,000 cycles.
2. The solid electrolyte material for electrochromic devices according to claim 1, characterized in that, The lithium ion transference number in the bis(trifluoromethanesulfonyl)imide lithium is 0.5, and the thermal decomposition temperature is >300℃. The plasticizer is selected from one or more of dibutyl phthalate, dioctyl phthalate, and tricresyl phosphate, and is used to fill the gaps between polyvinyl butyral molecular chains to improve ionic conductivity. The antioxidant is selected from a composite system of hindered phenolic antioxidants and phosphite antioxidants; The ultraviolet light absorber is selected from benzotriazole compounds; The heat stabilizer is selected from organotin or calcium-zinc composite heat stabilizers.
3. The solid electrolyte material for electrochromic devices according to claim 1 or 2, characterized in that, The mass ratio of the polyvinyl butyral resin, lithium bis(trifluoromethanesulfonyl)imide, and additives is 70:10:
20.
4. A method for preparing a solid electrolyte material for an electrochromic device according to any one of claims 1 to 3, characterized in that, Includes the following steps: S1 Raw material pretreatment: Dry polyvinyl butyral resin at 40~60℃ for 2~4 hours to reduce its moisture content to <0.5%; S2 Premix: Weigh the dried polyvinyl butyral resin, lithium bis(trifluoromethanesulfonyl)imide and additive composition according to the formula, put them into a high-speed mixer, and mix for 10 to 20 minutes at a speed of 300 to 500 rpm to obtain the premix. S3 Melt Blending Extrusion: The premix obtained in step S2 is added to a twin-screw extruder and melt blended extrusion is carried out at an extrusion temperature of 150~180℃ and a screw speed of 200~300 rpm to obtain a blended material; S4 Extrusion casting: The blend material obtained in step S3 is extruded through a T-die onto a casting roller. The surface temperature of the casting roller is 80~120℃. After cooling and shaping, a film is formed. S5 Online Thickness Measurement and Rewinding: An online infrared thickness gauge is used to monitor and control the film thickness in real time, so that the film thickness error is controlled within ±5%, and the solid electrolyte membrane product is obtained by rewinding. The twin-screw extruder has a length-to-diameter ratio of 32:1 to 48:1, and a vacuum exhaust port is provided in the middle of the extruder barrel during the extrusion process to remove low-molecular-weight volatiles.
5. The preparation method according to claim 4, characterized in that, In step S4, the surface temperature of the casting roller is 100°C, and the cooling and shaping adopts a cooling method combining air cooling and water cooling. The feedback control frequency of the online infrared thickness gauge in step S5 is 10 times / second. When the detected thickness deviation exceeds the preset threshold, the opening of the die lip of the T-shaped die head is automatically adjusted.
6. A solid-state electrochromic device, characterized in that, It includes a first transparent conductive substrate, an electrochromic layer, a solid electrolyte material according to any one of claims 1 to 3, an ion storage layer, and a second transparent conductive substrate, which are sequentially stacked. The electrochromic layer is made of tungsten oxide, and the ion storage layer is made of nickel oxide. The solid electrolyte material forms a tight interface with the electrochromic layer and the ion storage layer, providing a lithium ion transport channel and blocking direct electron transfer during the electrochromic reaction. The solid-state electrochromic device has the following electrochromic properties: the optical modulation range between the colored state and the faded state is 4%~75%, the coloring response time is ≤60 seconds, the fading response time is ≤60 seconds, the cycle life is ≥50,000 times, and the ultraviolet blocking rate is >99%.
7. The solid-state electrochromic device according to claim 6, characterized in that, The first transparent conductive substrate and the second transparent conductive substrate are each independently selected from indium tin oxide conductive glass or fluorine-doped tin oxide conductive glass; The tungsten oxide electrochromic layer is doped with molybdenum and titanium, with a total doping amount of 4% to 12%.
8. The solid-state electrochromic device according to claim 6 or 7, characterized in that, After being placed continuously at 85℃ / 85% relative humidity for 1000 hours, the visible light transmittance of the solid-state electrochromic device fluctuated by less than 3%. Even at a low temperature of -40℃, the color response time is 12 seconds, and the electrochromic function is still maintained.
9. A method for preparing a solid-state electrochromic device according to any one of claims 6 to 8, characterized in that, Includes the following steps: S100 deposits an electrochromic layer and an ion storage layer on a first transparent conductive substrate and a second transparent conductive substrate respectively by magnetron sputtering. The deposition vacuum degree is 0.1~1 Pa, the sputtering power is 1~5 W / cm², and the substrate temperature is 200~300℃. S200 Cut the solid electrolyte material according to any one of claims 1 to 3 or the solid electrolyte material prepared according to the method of claim 4 or 5 into the required size; S300 The second transparent conductive substrate, the ion storage layer, the solid electrolyte material, the electrochromic layer, and the first transparent conductive substrate are stacked in sequence, with the solid electrolyte material sandwiched between the electrochromic layer and the ion storage layer. S400 places the stacked components in a vacuum laminator and performs hot-pressing composite under conditions of vacuum degree <100 Pa, temperature 120~160℃, and pressure 0.3~0.8 MPa for 20~60 minutes. After the S500 is naturally cooled to room temperature, it is removed to obtain a solid-state electrochromic device.
10. The preparation method according to claim 9, characterized in that, The conditions for hot-pressing composite in step S400 are: vacuum degree <50 Pa, temperature 140℃, pressure 0.5 MPa, and hot-pressing time 30 minutes; Before hot-pressing composite, step S400 includes a step of adjusting the moisture content of the solid electrolyte material: the moisture content of the solid electrolyte material is adjusted to 0.1%~0.5% using a temperature and humidity controller to adjust the active state of the hydroxyl groups in the polyvinyl butyral resin and enhance the interfacial bonding performance between the solid electrolyte material and the electrochromic layer and ion storage layer.