PXE-PEO Block Copolymer Electrolytes for High-Temperature Battery Stability
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Solution Overview
Problem
The development of solid polymer electrolytes for lithium batteries is hindered by the challenge of achieving high ionic conductivity while maintaining mechanical stability, as high conductivity often requires high polymer chain mobility, which compromises mechanical properties, and existing block copolymers fail to operate at temperatures above 150°C with both high conductivity and mechanical strength.
Innovation Solution
The synthesis of microphase-separated polyester-based block copolymers, specifically diblock and triblock copolymers with ionically conductive and structural polymer domains, where the structural domains have high softening temperatures, enabling operation at elevated temperatures without losing mechanical integrity, using polymers like poly(2,6-dimethyl-1,4-phenylene oxide) (PXE) and polyethylene oxide (PEO), and polyesters, which form ordered nanostructures for enhanced conductivity and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high polymer chain mobility is achieved to increase ionic conductivity, then ionic conductivity is improved, but mechanical properties deteriorate
Solution Approach 1:
The patent divides the polymer electrolyte into distinct microphase-separated domains: conductive domains rich in polyethylene oxide (PEO) segments that provide ionic conductivity, and structural domains rich in poly(2,6-dimethyl-1,4-phenylene oxide) (PXE) segments that provide mechanical strength. This segmentation allows each domain to optimize its function independently, resolving the contradiction between conductivity and mechanical properties.
Solution Approach 2:
Different regions of the block copolymer are designed with locally optimized properties: PEO-rich regions provide high ionic conductivity through their flexible, mobile chains, while PXE-rich regions provide rigid mechanical support. This local quality differentiation enables the material to simultaneously exhibit both high conductivity and mechanical stability.
2Reliability
If operating temperature is increased above 150°C to improve ionic conductivity, then conductivity is improved, but mechanical strength is lost
Solution Approach 1:
The patent changes the thermal parameter of the structural PXE domains, which have a glass transition temperature (Tg) of 210°C. This high Tg allows the structural domains to maintain their rigid, glassy state and mechanical strength at operating temperatures up to 210°C, while the conductive PEO domains remain sufficiently mobile to provide high ionic conductivity throughout this temperature range.
3Strength
If polyethylene oxide (PEO) is used to provide good mechanical properties at room temperature, then mechanical properties are improved, but ionic conductivity is reduced due to crystalline structure
Solution Approach 1:
The patent segments the PEO content into specific blocks within the block copolymer structure, controlling the morphology to form nanoscale conductive domains. This segmentation prevents excessive crystallization while maintaining mechanical integrity through the interconnected PXE structural domains, thereby improving conductivity without sacrificing mechanical properties.
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
These microphase-separated block copolymers exhibit higher ionic conductivity and longer cell cycling lifespan, maintaining mechanical properties at high temperatures, thus addressing the limitations of existing electrolytes by enabling operation up to 210°C with improved thermal stability and mechanical integrity.
Implementation Method 1
The block copolymer chains are arranged in an ordered nanostructure comprising a continuous matrix of first domains defined by an association of the ionically-conductive block(s) and second domains defined by an association of poly(2,6-dimethyl-1,4-phenylene oxide) block(s)
Data Source
AI summary
New polymer compositions based on poly(2,6-dimethyl-1,4-phenylene oxide) and other high-softening-temperature polymers are disclosed. These materials have a microphase domain structure that has an ionically-conductive phase and a phase with good mechanical strength and a high softening temperature. In some arrangements, the structural block has a softening temperature of about 210° C. These materials can be made with either homopolymers or with block copolymers. When these polymers are combined with electrolyte salts, they can be used as electrolytes that have both high ionic conductivity and good mechanical properties.