Search

US-20260126693-A1 - OPTICALLY TRANSPARENT POLYMER ELECTROLYTE FILMS

US20260126693A1US 20260126693 A1US20260126693 A1US 20260126693A1US-20260126693-A1

Abstract

Provided are electrolyte films or cells for use in variety of applications, such as electrochromic windows. An electrolytic film comprises a polymer layer, such as thermoplastic polyurethane or polymethyl methacrylate, and an electrolyte within the polymer layer. The electrolyte comprises a salt, a plasticizer and a tinting agent. The plasticizer and tinting agent comprise one or more materials that are selected to provide sufficient conductivity and optical transparency for operation of the electrolyte film in an application requiring substantial optical clarity and switching speed, such as a smart window.

Inventors

  • Nandan Ukidwe

Assignees

  • DELSTAR TECHNOLOGIES, INC.

Dates

Publication Date
20260507
Application Date
20251104

Claims (20)

  1. 1 . An electrolyte film comprising: a polymer layer; an electrolyte within the polymer layer, wherein the electrolyte comprises a salt and a plasticizer; and a tinting agent within the polymer layer.
  2. 2 . The film of claim 1 , wherein the tinting agent comprises an inorganic pigment.
  3. 3 . The film of claim 2 , wherein the inorganic pigment is selected from the group consisting of anthraquinone, diazo benzimidazolone, isoindolinone, quinacridone and phthalocyanine and combinations thereof.
  4. 4 . The film of claim 2 , wherein the inorganic pigment comprises carbon black.
  5. 5 . The film of claim 4 , wherein the carbon black has a particle size of about 50 nm to about 150 nm.
  6. 6 . The film of claim 1 , wherein the tinting agent is present in an amount of about 0.1% to about 10% wt %, based on the total weight of the polymer layer.
  7. 7 . The film of claim 1 , wherein the polymer layer comprises a polymer present in an amount of about 40 wt % to about 60% wt %, based on the total weight of the polymer layer.
  8. 8 . The film of claim 1 , wherein the plasticizer is present in an amount of about 40 wt % to about 60% wt %, based on the total weight of the polymer layer.
  9. 9 . The film of claim 1 , wherein the plasticizer comprises an organic carbonate, wherein the organic carbonate is selected from the group consisting of diethyl carbonate, propylene carbonate, ethylene carbonate, gamma-butyrolactone, dimethyl carbonate, methyl ethyl carbonate, glycerin carbonate, butylene carbonate, alkylene carbonate and combinations thereof.
  10. 10 . The film of claim 1 , wherein the plasticizer comprises an organic carbonate and a second material selected from the group consisting of a benzoate, a monobenzoate, a dibenzoate, an acrylate monomer, a phthalate, an aliphatic ester, a non-aliphatic ester, an ethylene glycol bis, a trimellitate, a sebacate, an adipate, a terephthalate, a gluterate, a glyceride, an azelate, a maleate, an epoxidized soybean oil, glycols and/or polyether, triethylene glycol dihexanoate (3G6), tetraethylene glycol diheptanoate (4G7), triethylene glycol bis(2-ethyl hexanoate) (TEG-EH), tetra ethylene glycol bis(2-ethyl hexanoate) (4GEH), polyethylene glycol bis(2-ethylhexanoate) (PEG-EH), an organophosphate tricresyl phosphate (TCP), tributyl phosphate (TBP), alkyl citrates, glycerol, acetylated monoglycerides and combinations thereof.
  11. 11 . The film of claim 1 , wherein the plasticizer comprises an organic carbonate and triethylene glycol bis(2-ethyl hexanoate) (TEG-EH).
  12. 12 . The film of claim 11 , wherein the organic carbonate comprises propylene carbonate.
  13. 13 . The film of claim 10 , wherein the second material has a volume percentage of about 20% to about 80% of the plasticizer and the organic carbonate has a volume percentage of about 20% to about 80% of the plasticizer.
  14. 14 . The film of claim 1 , wherein an Ra between the plasticizer and the polymer layer is less than about 5.
  15. 15 . An electrochromic cell comprising: first and second layers of an optically transparent material; and an electrolyte film between the first and second layers, the electrolyte film comprising a polymer, a plasticizer and a tinting agent.
  16. 16 . The electrochromic cell of claim 15 , wherein the cell has a switching speed from a first state to a second state of less than about 6 minutes, wherein the first state has a greater light transmittance than the second state.
  17. 17 . The electrochromic cell of claim 15 , wherein the cell has a light transmittance in the first state of less than about 60%.
  18. 18 . The electrochromic cell of claim 15 , wherein the cell has a light transmittance in the second state of less than about 10%.
  19. 19 . The electrochromic cell of claim 15 , wherein the tinting agent is present in an amount of about 0.1% to about 10% wt %, based on the total weight of the electrolyte film.
  20. 20 . The electrochromic cell of claim 15 , wherein the tinting agent comprises an inorganic pigment selected from the group consisting of anthraquinone, diazo benzimidazolone, isoindolinone, quinacridone and phthalocyanine and combinations thereof.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Application Ser. No. 63/717,380, filed Nov. 7, 2024, the complete disclosure of which is incorporated herein by reference. TECHNICAL FIELD This description generally relates to electrolyte films and more particularly to electrolyte films for use in electrochromic cells, such as those used in electrochromic windows. BACKGROUND Electrochromic windows, also known as smart windows, are a new technology for energy efficiency in buildings that controls the amount of sunlight passing through. They can also produce less glare than fritted glass. Their efficiency depends on their placement, size, and weather, which affect the amount of sunlight exposure. Smart windows with switchable light transmittance and reflectance are fast gaining popularity. They are very much tied into the emerging trend of sustainable, energy efficient dwellings. Among the different possible technologies for smart windows, electrochromism is one of the most promising. Electrochromism is a phenomenon where the color or opacity of a material changes depending on the application of voltage. Changing the light transmission properties in response to voltage allows for control over the amount of light and heat passing through. Once the change has been effected, no electricity is needed for maintaining the particular shade which has been reached. By doing so, an electrochromic window can block certain wavelengths of UV, IR or visible light on demand. The basic structure of an electrochromic device or ECD typically embodies five superimposed layers on one substrate or positioned between two substrates in a laminated configuration. In this structure, there are three principally different kinds of layered materials in the ECD: electrochromic (EC) layers, transparent conductive layers and an electrolyte. The EC layers conduct ions and electrons and belong to the class of mixed conductors. The electrolyte layer is a pure ion conductor and separates the two EC layers. The transparent conductors are pure electron conductors. Optical absorption occurs when electrons move into the EC layers from the transparent conductors along with charge balancing ions entering from the electrolyte. The ion conductive layer can be a liquid as is found in wet cell batteries. An example of such liquid ion conductive layer is propylene carbonate containing lithium perchlorate. One drawback with liquid electrolyte is that while it demonstrates acceptable ionic conductivity, it can leak out of the ECD, posing significant risk to end users. To solve this problem, the ion conductive layer can be a polymeric interlayer that is in solid state under ambient conditions. Examples of such solid-state ionic conductive layers are described in Ionic Conductivity of Polyether-Polyurethane Networks Containing Alkali Metal Salts. An Analysis of the Concentration Effect, Macromolecules, Vol. 17, No. 1, 1984, pgs. 63-66, to Killis, et al; and Poly(dimethylsiloxane)-Poly(ethylene oxide) Based Polyurethane Networks Used As Electrolytes in Lithium Electrochemical Solid State Batteries, Solid State Ionics, 15 (1985) 233-240, to Bouridah, et al., the complete disclosures of which are incorporated herein by reference in their entirely for all purposes. While the solid polymeric interlayer electrolyte eliminates the possibility of electrolyte leakage, it suffers from poor ionic conductivity. One solution to this problem is to imbibe or plasticize the polymer with a liquid electrolyte to combine the mechanical benefits of a solid-state electrolyte with the high ionic conductivities of liquid electrolytes. For example, a thermoplastic urethane polymer can be plasticized with propylene carbonate containing a lithium salt. This film can be in solid state and with good mechanical strength under ambient conditions. Furthermore, it can also show a significant improvement in ionic conductivity compared to a film comprising the neat polymer containing the lithium salt additive. An example of this type of electrolyte is described in U.S. Pat. No. 8,673,503, the complete disclosure of which is incorporated herein by reference in its entirety for all purposes. While films such as the one described above may work well in batteries or other applications, they are not optimized for smart windows because they are not sufficiently transparent. This is because the polymer and the plasticizer are not compatible with each other, i.e., they do not completely dissolve into each other in solution. For example, it has surprisingly been discovered that an optical grade polyether-based thermoplastic polyurethane polymer (i.e., Estane AG8451 from Lubrizol) plasticized with 43 phr propylene carbonate containing either 8.3 or 12.5% w lithium perchlorate (LiClO4) develops significant haze under ambient conditions, although the resulting film shows good mechanical properties. Loss of optical clarity on account of incompatibility betwee