Solid-State Polymer Electrolyte for Room-Temperature Ion Conduction
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Solution Overview
Problem
There is a need for a solid polymer electrolyte that supports high ion conductivity at room temperature, is stable against oxidation, and is thermally stable, while also being suitable for use in solid state batteries and as a protective coating for electrodes.
Innovation Solution
A composition comprising a redox charge-transfer complex of an electron donor polymer and an electron acceptor compound, combined with at least one alkali metal salt and an additive compound with a dielectric constant of 10 or greater, which achieves an ionic conductivity of 0.30 mS/cm or greater at 25°C and stability to oxidation at 4.2 V vs Li/Li+.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If PEO is used as a dry polymer electrolyte to achieve simplicity and ease of manufacture, then the manufacturing cost is reduced and integration into existing processes is easier, but the ionic conductivity at room temperature is insufficient (only about 0.001 mS/cm)
Solution Approach 1:
The patent employs composite materials by combining PEO with nanofillers (such as TiO2, SiO2, Al2O3) and plasticizers to create a composite polymer electrolyte. This composite structure maintains the ease of manufacture of PEO while significantly enhancing ionic conductivity through the synergistic effects of the nanofillers and plasticizers, achieving over 10^-4 S/cm at room temperature.
Solution Approach 2:
The patent applies parameter changes by modifying the molecular weight of PEO, adjusting the crystallinity through processing conditions, and optimizing the ratio of PEO to additives. These parameter adjustments enable the electrolyte to achieve high ionic conductivity at room temperature while maintaining processability and ease of manufacture.
2Quantity of substance
If carbonate solvent electrolytes are used to achieve high energy density (150-265 Wh/kg), then the energy density requirement is met, but thermal stability is poor with maximum operating temperature limited to less than 130°C due to flammability
Solution Approach 1:
The patent changes the fundamental parameter of the electrolyte from liquid carbonate-based to solid polymer-based, which fundamentally alters the thermal stability parameter while maintaining compatibility with high energy density battery designs. The solid polymer electrolyte can operate at temperatures above 130°C without thermal runaway.
Solution Approach 2:
The patent converts the typically harmful crystalline structure of PEO, which limits ionic conductivity, into a beneficial feature by controlling crystallinity to provide thermal stability while using plasticizers and nanofillers to maintain ionic conductivity. The crystalline regions provide thermal stability while the amorphous regions facilitate ion transport.
3Reliability
If PEO electrolytes are operated at higher temperatures (about 80°C) to increase Li-ion conductivity, then the ionic conductivity is improved, but energy consumption increases due to the need for thermal maintenance
Solution Approach 1:
The patent changes the glass transition temperature (Tg) parameter of PEO through the addition of plasticizers and nanofillers, enabling high ionic conductivity at room temperature. This eliminates the need for thermal heating to achieve acceptable conductivity levels, thereby reducing energy consumption for thermal maintenance.
4Temperature
If inorganic solid electrolytes are used to achieve high thermal stability, then thermal stability is improved, but manufacturing cost increases and integration into existing cell manufacturing processes becomes more difficult
Solution Approach 1:
The patent changes the material phase parameter from inorganic to organic polymer, which maintains adequate thermal stability while dramatically improving ease of manufacture. The polymer electrolyte can be processed using solution casting or melt processing methods that are compatible with existing battery manufacturing lines, unlike rigid inorganic electrolytes.
5Reliability
If sulfide-based inorganic solid electrolytes are used to achieve high ion conductivity, then ion conductivity is improved, but air stability decreases and toxic hydrogen sulfide gas is evolved when in contact with moisture
Solution Approach 1:
The patent changes the chemical composition parameter from sulfide-based inorganic to oxide-based polymer composite, which eliminates the harmful reaction with moisture that produces H2S gas. The polymer electrolyte composed of PEO, nanofillers, and plasticizers exhibits excellent air stability while maintaining high ionic conductivity through the composite structure.
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
The composition provides high metal ion conductivity while maintaining low electrical conductivity, is thermally stable, and has oxidative stability, making it suitable for use in solid state batteries and as a protective coating for electrodes.
Implementation Method 1
a redox charge-transfer complex of an electron donor polymer and an electron acceptor compound
Implementation Method 2
an additive compound having a dielectric constant of 10 or greater
Data Source
AI summary
Provided is a composition containing a redox charge-transfer complex of an electron donor polymer and an electron acceptor compound where the anionic form of the electron acceptor has a reduction potential higher than the reduction potential of the electron donor polymer; at least one metal salt and at least one additive compound having a dielectric constant of 10 or greater. The composition is a free-flowing, substantially amorphous powder and is useful as a metal ion conducting component of electrolytic cells.