Flexible all-solid-state electrolyte adhesive film and preparation method thereof

Abstract

The invention discloses a flexible all-solid-state electrolyte adhesive film which is prepared from the following components: EVA (Ethylene Vinyl Acetate) particles, a tetrahydrofuran solvent, lithium salt and propylene carbonate. The invention also discloses a preparation method of the flexible all-solid-state electrolyte adhesive film, which comprises the following steps: slowly adding 10g of EVA particles into 90g of tetrahydrofuran solvent under continuous mechanical stirring, and stirring until the EVA particles are completely dissolved under water bath heating to form an EVA adhesive solution; sequentially adding lithium salt and propylene carbonate into the EVA glue solution, and continuously stirring for 2 hours to form electrolyte slurry; coating the prepared electrolyte slurry on a polyethylene glycol terephthalate isolating membrane by using a slit coating machine; transferring the coated wet film into an air dry oven at 60 DEG C to form a solid adhesive film with a non-sticky surface; peeling off the preliminarily dried adhesive film from the polyethylene glycol terephthalate isolating film, and continuing vacuum drying; and finally obtaining the all-solid-state electrolyte adhesive film. According to the invention, the problems of high leakage current, no adhesion between electrodes, overflow, sealant corrosion and the like can be solved.

Description

Technical Field

[0001] This invention relates to a flexible all-solid electrolyte membrane and its preparation method. Background Technology

[0002] Electrochromic technology is mainly divided into two categories based on the raw materials used: organic electrochromic technology and inorganic electrochromic technology. Organic electrochromic technology can be further subdivided into two main categories: organic polymers and organic small molecules.

[0003] Electrochromic devices manufactured using organic polymer electrochromic technology mainly have a three-layer structure, such as... Figure 2 As shown, from top to bottom are the working electrode, electrolyte, and counter electrode.

[0004] In existing technologies and products, organic polymer technology is mainly used to produce flexible electrochromic films, which are then laminated between two pieces of glass to become the application-end product. The production process of flexible electrochromic films involves first uniformly coating a PEDOT / PSS solution onto a flexible conductive film (typically a PET / ITO film) using slit coating, and obtaining the working electrode after drying. A nickel oxide (or titanium dioxide-doped vanadium pentoxide) film is then fabricated on the flexible conductive film (typically a PET / ITO film) using magnetron sputtering to obtain the counter electrode. A gel electrolyte is then coated onto the counter electrode, and barrier microbeads of a specific diameter are incorporated. Finally, the working electrode is placed on top of the electrolyte to obtain the polymer flexible electrochromic film.

[0005] The polymer flexible electrochromic film is cut into the required shape and electrodes are reserved. It is then laminated between two pieces of specific glass using a low-temperature bonding film. The edges are then sealed with hot melt adhesive and one-component acrylic resin to obtain the final electrochromic glass product.

[0006] The gel electrolyte used in the aforementioned flexible polymer electrochromic film can effectively provide ion migration channels and has a high ion migration rate, which can accelerate the response time of the polymer electrochromic device. However, it also has some obvious drawbacks, including: 1. The high leakage current of gel electrolyte reduces the uniformity of color change in large-size polymer electrochromic devices. 2. There is no adhesion between the working electrode and the counter electrode, which can easily lead to misalignment and blistering of the upper and lower electrodes during the roll-to-roll production of large-size thin film products. 3. During the lamination process, the gel electrolyte lacks support and is prone to overflow. 4. The liquid in the gel will diffuse into the edge sealant, corroding the adhesive and affecting the product's lifespan; 5. During the switching between high and low temperatures, the thermal expansion and contraction effect of the gel is significant, which can easily cause the sealant around the edges to swell and affect the product's service life.

[0007] To address the shortcomings of gel electrolytes mentioned above, a flexible all-solid-state electrolyte membrane and its preparation method are proposed while maintaining the advantages of gel electrolytes. Summary of the Invention

[0008] To address the aforementioned problems in the prior art, this invention provides a flexible all-solid electrolyte membrane and its preparation method, which can solve problems such as high leakage current, lack of adhesion between electrodes, overflow, and corrosion of sealant.

[0009] The technical solution to achieve the above objectives is: One of the present inventions is a flexible all-solid electrolyte membrane composed of the following components: EVA particles, tetrahydrofuran solvent, lithium salt and propylene carbonate.

[0010] Preferably, the lithium salt is lithium perchlorate or lithium hexafluorophosphate.

[0011] Preferably, the vinyl acetate content in the EVA (ethylene-vinyl acetate copolymer) particles is 28%-33%, and the melt index is 25-30 g / 10min.

[0012] Preferably, if the electrolyte membrane is a general-purpose, highly compatible electrolyte membrane, the ratio of EVA particles, tetrahydrofuran solvent, lithium salt, and propylene carbonate is 1:9:0.3:0.5.

[0013] Preferably, if the electrolyte membrane is a high-stability, heat-resistant electrolyte membrane, the ratio of EVA particles, tetrahydrofuran solvent, lithium salt and propylene carbonate is 1:9:0.35:0.45.

[0014] Preferably, if the electrolyte membrane is a high ionic conductivity type electrolyte membrane, the ratio of EVA particles, tetrahydrofuran solvent, lithium salt and propylene carbonate is 1:9:0.25:0.6.

[0015] A method for preparing a flexible all-solid-state electrolyte membrane according to a second aspect of the present invention includes: Step S1: Weigh 10g of EVA particles and measure 90g of tetrahydrofuran solvent, and place them in a sealed container. Step S2: Under continuous mechanical stirring, EVA particles are slowly added to tetrahydrofuran solvent and stirred for 3 hours under a 40°C water bath until the EVA particles are completely dissolved to form a uniform and transparent EVA solution. Step S3: Add lithium salt and propylene carbonate to the above EVA solution in sequence, and continue stirring for 2 hours to form a uniform and viscous electrolyte slurry. Step S4: Using a slot coater, the prepared electrolyte slurry is evenly coated onto the polyethylene terephthalate separator. Step S5: Immediately transfer the coated wet film to a 60°C forced-air drying oven and pre-dry for 15 minutes to allow most of the tetrahydrofuran solvent to evaporate, forming a non-sticky solid film. Step S6: Remove the pre-dried adhesive film from the polyethylene terephthalate release film and transfer it to a vacuum drying oven at 50°C for 12 hours. Step S7 yields a transparent and flexible all-solid electrolyte membrane with a thickness of 50±5μm.

[0016] Preferably, in step S2, the mechanical stirring speed is 300 rpm.

[0017] Preferably, in step S5, the thickness of the wet film after coating is set to 500 μm.

[0018] Compared with the prior art, the beneficial effects of the present invention are: The EVA-based electrolyte prepared by this invention is a uniform, transparent solid film with a dense structure, while traditional gel electrolytes are typically gel-like with a certain degree of fluidity, which is inconvenient in subsequent encapsulation and processing. At 25°C, the ionic conductivity of the electrolyte membrane of this invention was measured to be 1.2 × 10⁻⁶. -4 S / cm, although slightly lower than the approximately 5.0 × 10⁻⁶ of conventional gel electrolytes. -4 The conductivity level is S / cm, but this conductivity level fully meets the requirements for efficient operation of flexible electrochromic devices, successfully achieving the leap from "gel" to "all solid state" while maintaining excellent ion transport capability. The product of this invention exhibits excellent mechanical strength and flexibility, and can withstand repeated bending, folding and other deformations without breaking. In contrast, the mechanical properties of traditional gel electrolytes are generally poor, they are prone to plastic deformation under stress, and the interface stability between them and the functional layer is poor. The EVA-based solid electrolyte membrane of the present invention does not exhibit any dissolution or swelling of common polymer electrochromic layers, showing excellent compatibility. In contrast, the liquid components in traditional gel electrolytes can cause severe dissolution and damage to polymer electrochromic layers. Solving this problem greatly improves the reliability and lifespan of the device. After undergoing a rigorous thermal aging test at 100°C for 1 hour, the electrolyte membrane of the present invention showed no observable changes in morphology and conductivity, demonstrating excellent thermal stability. In contrast, traditional gel electrolytes exhibited significant shrinkage and devitrification, and their electrical properties decreased significantly, making it difficult to operate stably at higher temperatures. Attached Figure Description

[0019] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 This is a flowchart of a method for preparing a flexible all-solid electrolyte membrane according to the present invention; Figure 2 This is a schematic diagram of the structure of an electrochromic device manufactured using organic polymer electrochromic technology in a traditional approach. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and 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.

[0021] A flexible all-solid electrolyte membrane is composed of the following components: EVA particles, tetrahydrofuran solvent, lithium salt and propylene carbonate.

[0022] In the examples, the lithium salt is lithium perchlorate or lithium hexafluorophosphate.

[0023] In the examples, the vinyl acetate content in the EVA particles is 28%-33%, and the melt index is 25-30 g / 10min. As a matrix for the all-solid electrolyte, the EVA polymer material can provide film-forming properties and support for the electrolyte of the invention, as well as adhesion to the two electrodes.

[0024] In this embodiment, tetrahydrofuran is used as a solvent. During the evaporation process, a porous structure is formed, and the non-volatile propylene carbonate / lithium salt solution fills the pores, forming ion channels and improving ion diffusion efficiency.

[0025] In the embodiments, if the electrolyte membrane is a general-purpose, highly compatible electrolyte membrane, the ratio of EVA particles, tetrahydrofuran solvent, lithium salt, and propylene carbonate is 1:9:0.3:0.5.

[0026] In the embodiments, if the electrolyte membrane is a high-stability, heat-resistant electrolyte membrane, the ratio of EVA particles, tetrahydrofuran solvent, lithium salt and propylene carbonate is 1:9:0.35:0.45.

[0027] In the embodiments, if the electrolyte membrane is a high ionic conductivity type electrolyte membrane, the ratio of EVA particles, tetrahydrofuran solvent, lithium salt and propylene carbonate is 1:9:0.25:0.6.

[0028] like Figure 1 As shown, a method for preparing a flexible all-solid-state electrolyte membrane includes: Step S1: Weigh 10g of EVA granules (vinyl acetate content of 28%-33%, melt index of 25-30 g / 10min) and measure 90g of tetrahydrofuran solvent, and place them in a sealed container.

[0029] Step S2: Under continuous mechanical stirring, EVA particles are slowly added to tetrahydrofuran solvent and stirred for 3 hours under a 40°C water bath until the EVA particles are completely dissolved, forming a uniform and transparent EVA solution.

[0030] In this embodiment, the mechanical stirring speed is 300 rpm.

[0031] Step S3: Add lithium salt (generally lithium perchlorate or lithium hexafluorophosphate) and propylene carbonate (PC) sequentially to the above EVA adhesive solution, and continue stirring for 2 hours to form a uniform and viscous electrolyte slurry.

[0032] Step S4: Using a slot coater, the prepared electrolyte slurry is evenly coated onto the polyethylene terephthalate (PET) separator.

[0033] Step S5: Immediately transfer the coated wet film to a 60°C forced-air drying oven and pre-dry for 15 minutes to allow most of the tetrahydrofuran solvent to evaporate, forming a solid film with a non-sticky surface.

[0034] In this embodiment, the thickness of the wet film after coating is set to 500 μm.

[0035] Step S6: Remove the preliminarily dried film from the polyethylene terephthalate release liner and transfer it to a vacuum drying oven at 50°C for 12 hours to completely remove residual solvent.

[0036] Step S7 yields a transparent and flexible all-solid electrolyte membrane with a thickness of 50±5μm.

[0037] Example 1: Universal High-Compatibility Electrolyte Membrane This embodiment aims to provide a general-purpose product that achieves the best balance between ionic conductivity, mechanical strength, and compatibility with polymer color-changing layers.

[0038] Raw material ratio: EVA granules: 100 parts by weight Tetrahydrofuran (THF) solvent: 900 parts by weight Lithium perchlorate (LiClO4): 30 parts by weight Propylene carbonate (PC): 50 parts by weight Key process parameters: Coating wet film thickness: 500μm Drying procedure: Dry at 60°C with forced air for 15 minutes, followed by vacuum drying at 50°C for 12 hours.

[0039] Final product: Dry film thickness: approximately 50 μm Features: The film prepared by this formula is uniform and transparent, with excellent flexibility and extremely high ionic conductivity (1.2×10⁻⁶). -4 (S / cm), while ensuring no dissolution or swelling when in contact with various polymer electrochromic materials, thus solving the core compatibility problem.

[0040] Example 2: High-stability, heat-resistant electrolyte membrane This embodiment improves the thermal and electrochemical stability of the electrolyte membrane by replacing the type of lithium salt, making it suitable for devices with more stringent operating environment requirements.

[0041] Raw material ratio: EVA granules: 100 parts by weight Tetrahydrofuran (THF) solvent: 900 parts by weight Lithium hexafluorophosphate (LiPF6): 35 parts by weight Propylene carbonate (PC): 45 parts by weight Key process parameters: Coating wet film thickness: 800μm Drying procedure: Dry at 60°C with forced air for 20 minutes, followed by vacuum drying at 50°C for 12 hours.

[0042] Final product: Dry film thickness: approximately 80 μm Features: The use of LiPF6 gives this film superior thermal stability and electrochemical window. Its slightly thicker design also increases its mechanical strength, making it suitable for flexible electrochromic devices that need to withstand higher temperatures or more complex stress environments.

[0043] Example 3: High Ionic Conductivity Electrolyte Membrane This embodiment aims to achieve extremely high ionic conductivity by increasing the proportion of plasticizer, in order to meet the requirements of high-performance devices that require rapid color change response.

[0044] Raw material ratio: EVA granules: 100 parts by weight Tetrahydrofuran (THF) solvent: 900 parts by weight Lithium perchlorate (LiClO4): 25 parts by weight Propylene carbonate (PC): 60 parts by weight (higher PC content) Key process parameters: Coating wet film thickness: 1000μm Drying procedure: Dry at 60°C with forced air for 25 minutes, followed by vacuum drying at 50°C for 12 hours.

[0045] Final product: Dry film thickness: approximately 100 μm Features: The proportion of propylene carbonate is significantly increased, creating more efficient ion transport channels within the solid polymer network. Although mechanical strength is slightly sacrificed, its ionic conductivity is expected to exceed 2.0 × 10⁻⁶. -4 S / cm can greatly improve the coloring / fading response speed of electrochromic devices.

[0046] Finally, it should be noted that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A flexible all-solid-state electrolyte gel film, characterized by, The electrolyte gel film is prepared from the following components: EVA particles, tetrahydrofuran solvent, lithium salt and propylene carbonate.

2. The flexible all-solid-state electrolyte gel film according to claim 1, characterized by, The lithium salt is lithium perchlorate or lithium hexafluorophosphate.

3. The flexible all-solid-state electrolyte gel film according to claim 1, wherein The EVA particles have a vinyl acetate content of 28%-33% and a melt index of 25-30 g / 10min.

4. The flexible all-solid-state electrolyte gel film according to claim 1, wherein If the electrolyte gel film is a general-purpose high-compatibility electrolyte gel film, the proportions of the EVA particles, tetrahydrofuran solvent, lithium salt and propylene carbonate are 1:9:0.3:0.

5.

5. The flexible all-solid-state electrolyte gel film according to claim 1, wherein If the electrolyte gel film is a high-stability, heat-resistant electrolyte gel film, the proportions of the EVA particles, tetrahydrofuran solvent, lithium salt and propylene carbonate are 1:9:0.35:0.

45.

6. The flexible all-solid-state electrolyte gel film according to claim 1, wherein If the electrolyte gel film is a high-ionic-conductivity electrolyte gel film, the proportions of the EVA particles, tetrahydrofuran solvent, lithium salt and propylene carbonate are 1:9:0.25:0.

6.

7. A method for preparing a flexible all-solid-state electrolyte gel film, characterized by, The method comprises the following steps: S1, weighing 10 g of EVA particles and 90 g of tetrahydrofuran solvent, and placing them in a sealed container; S2, under continuous mechanical stirring, slowly adding the EVA particles into the tetrahydrofuran solvent, and stirring for 3 hours under heating at 40°C in a water bath until the EVA particles are completely dissolved to form a uniform and transparent EVA glue solution; S3, adding the lithium salt and propylene carbonate into the EVA glue solution in sequence, and continuing to stir for 2 hours to form a uniform and viscous electrolyte slurry; S4, using a slot coater to uniformly coat the prepared electrolyte slurry on a polyethylene terephthalate separator film; S5, immediately transferring the coated wet film to a 60°C air-drying oven for pre-drying for 15 minutes to volatilize most of the tetrahydrofuran solvent and form a solid gel film with a non-sticky surface; S6, peeling the preliminarily dried gel film from the polyethylene terephthalate separator film, and transferring it to a 50°C vacuum drying oven for further vacuum drying for 12 hours; S7, finally obtaining a transparent and flexible all-solid-state electrolyte gel film with a thickness of 50±5 μm.

8. The method for preparing a flexible all-solid-state electrolyte membrane according to claim 7, characterized in that, In the step S2, the rotating speed of the mechanical stirring is 300 rpm.

9. The method of claim 7, wherein the flexible all-solid-state electrolyte gel film is prepared by the steps of: (a) preparing a solution of a polymer and a lithium salt; (b) coating the solution on a substrate; (c) drying the coated solution; and (d) removing the substrate. In the step S5, the thickness of the coated wet film is set to 500 μm.

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