GBL Electrolyte for Stable Electrochromic Devices
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Solution Overview
Problem
Existing electrochromic devices face issues with solvents that have high vapor pressures, flammability, and toxicity, leading to instability and degradation of the electrolyte composition, which affects the functionality of the device.
Innovation Solution
The use of γ-butyrolactone (GBL) as an electrolyte in electrochromic devices, which includes a salt such as lithium perchlorate and propylene carbonate, providing high ionic conductivity, low electric conductivity, and stability over time and temperature, while minimizing vapor pressure and toxicity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional solvents like acetonitrile or ethylene carbonate are used in electrolytes, then high ionic conductivity is achieved, but vapor pressure increases and stability decreases
Solution Approach 1:
The patent changes the chemical parameters of the electrolyte solvent from traditional high-vapor-pressure solvents (acetonitrile, ethylene carbonate) to γ-butyrolactone, which has lower vapor pressure and higher thermal stability. This parameter change resolves the contradiction by maintaining ionic conductivity while reducing evaporation and improving stability.
Solution Approach 2:
The patent creates a composite electrolyte system by combining γ-butyrolactone with specific salts (lithium perchlorate, lithium trifluoromethanesulfonate) and optionally with gel-forming polymers. This composite approach maintains high ionic conductivity through the salt-solvent interaction while the γ-butyrolactone provides low vapor pressure and enhanced stability.
2Reliability
If volatile solvents are used to ensure ion mobility, then ionic conductivity improves, but flammability and toxicity increase
Solution Approach 1:
The patent changes the chemical composition parameter from volatile solvents to γ-butyrolactone, which has higher boiling point (204°C) and lower flammability. This maintains sufficient ionic conductivity for device operation while dramatically reducing flammability and toxicity hazards.
Solution Approach 2:
The patent converts the potential harm of solvent volatility into a benefit by selecting γ-butyrolactone, whose moderate viscosity actually enhances ion solvation and conductivity while its higher molecular weight provides inherent fire resistance and reduced vapor pressure, turning safety concerns into advantages.
3Stability of the object's composition
If gel electrolytes are used to prevent leakage, then dimensional stability improves, but ion transport may be restricted
Solution Approach 1:
The patent creates a composite gel electrolyte by combining γ-butyrolactone with gel-forming polymers (such as polyacrylonitrile, polyvinylidene fluoride, or carboxymethyl cellulose). The polymer network provides dimensional stability and leak prevention, while the γ-butyrolactone maintains high ionic conductivity by solvating the salt ions effectively within the gel matrix.
Solution Approach 2:
The patent applies local quality by having the gel polymer network provide structural stability in certain regions while maintaining open channels or pores that allow efficient ion transport. The γ-butyrolactone distributes ions locally throughout the gel matrix, ensuring both dimensional stability and ion transport efficiency in different spatial zones of the electrolyte.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
GBL-based electrolytes enhance the stability and longevity of electrochromic devices by maintaining high ionic conductivity and transmittance, reducing the risk of degradation and improving safety in applications like aircraft windows.
Implementation Method 1
The salt is typically dissociated in a solvent in the electrolyte, freeing the ions for use in activating the electrochromic layer
Implementation Method 2
When the voltage is applied across the outer conductors, ions in an electrolyte typically move to the electrochromic layer causing the electrochromic material to change color states
Implementation Method 3
at least one electrochromic layer is sandwiched between the electrodes. This layer is able to change color or opacity in response to changes in the applied electric field or current
Data Source
AI summary
The present invention provides an electrolyte for electrochromic devices, the substance comprising γ-butyrolactone (gamma-butyrolactone or GBL). The electrolyte may include polymethylmethacrylate. The electrolyte may further include a salt, such as a salt that includes lithium perchlorate or trifluorosulfonimide. In accordance with further aspects to the invention, the electrolyte may include propylene carbonate.