Block Copolymer Electrolyte for Low-Humidity Fuel Cells

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Solution Overview

Problem

Current polymer electrolyte materials for fuel cells suffer from inadequate proton conductivity under low-humidification conditions, mechanical strength, chemical stability, and physical durability, making them unsuitable for industrial applications.

Innovation Solution

A block copolymer comprising segments with and without ionic groups, connected by a linker moiety, where the ionic segment includes a specific arylene group-based constituent unit, forming a nano- or micro-phase separated structure for enhanced proton conductivity and durability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional polymer electrolyte materials are used, then fuel cell operation is possible, but proton conductivity under low-humidification conditions is insufficient

Engineering Contradiction:

Improveproton conductivity under low-humidification conditionsVSAvoidoperational performance in low-humidity environment

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The polymer electrolyte is segmented into distinct blocks: hydrophobic blocks (polyether ketone or polyether sulfone) and hydrophilic blocks (sulfonated polyether ketone or sulfonated polyether sulfone). This segmentation creates phase-separated structures where ionic groups concentrate in hydrophilic domains, maintaining proton conductivity pathways even under low-humidification conditions while the hydrophobic blocks provide structural integrity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the polymer electrolyte are赋予 different properties: hydrophobic blocks provide mechanical strength and dimensional stability, while hydrophilic blocks with sulfonic acid groups provide high proton conductivity. This local differentiation of properties enables the material to maintain excellent proton conductivity under low-humidification conditions while preserving mechanical integrity.

Inventive Principle:

Principle #3Local quality

2Reliability

If Nafion is used as polymer electrolyte material, then high proton conductivity is achieved, but cost is extremely high and fuel-crossover is large

Engineering Contradiction:

Improveproton conductivityVSAvoidfuel-crossover

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The invention uses composite block copolymer structures combining hydrophobic polyether ketone or polyether sulfone blocks with hydrophilic sulfonated counterparts. This composite structure achieves high proton conductivity through the sulfonated blocks while the non-sulfonated blocks provide dense packing that reduces fuel-crossover, offering an alternative to Nafion with potentially lower cost and reduced fuel permeation.

Inventive Principle:

Principle #40Composite materials

3Reliability

If Nafion is used, then high proton conductivity is achieved, but mechanical strength and physical durability are lost due to swelling-drying

Engineering Contradiction:

Improveproton conductivityVSAvoidmechanical strength and physical durability

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The block copolymer structure segments the material into hydrophobic mechanical-support blocks and hydrophilic ion-conducting blocks. The hydrophobic polyether ketone or polyether sulfone blocks maintain mechanical strength and dimensional stability during swelling-drying cycles, while the sulfonated blocks provide proton conductivity, preventing the mechanical degradation observed in Nafion.

Inventive Principle:

Principle #1Segmentation

4Reliability

If Nafion is used, then high proton conductivity is achieved, but use at high temperatures is not possible due to low softening point

Engineering Contradiction:

Improveproton conductivityVSAvoidsoftening point

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The block copolymer combines polyether ketone or polyether sulfone blocks with inherently high thermal stability and high glass transition temperatures with sulfonated blocks. This composite structure raises the overall softening point of the membrane, enabling high-temperature operation while maintaining proton conductivity through the sulfonated segments.

Inventive Principle:

Principle #40Composite materials

5Ease of manufacture

If hydrocarbon-based electrolyte membranes are used, then cost is reduced, but proton conductivity under low-humidification conditions and physical durability are insufficient

Engineering Contradiction:

ImprovecostVSAvoidproton conductivity and physical durability

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The block copolymer structure segments hydrocarbon-based polymers into hydrophobic and hydrophilic blocks, creating phase-separated morphologies that concentrate ionic groups in continuous pathways. This segmentation enables hydrocarbon-based membranes to achieve high proton conductivity under low-humidification conditions and improved physical durability while maintaining cost advantages over perfluorinated membranes.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different blocks are赋予 specialized functions: hydrophobic blocks provide mechanical strength, chemical stability, and dimensional stability, while hydrophilic sulfonated blocks provide high proton conductivity. This local quality differentiation enables cost-effective hydrocarbon-based membranes to meet performance requirements that previously only perfluorinated membranes could achieve.

Inventive Principle:

Principle #3Local quality

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 block copolymer exhibits excellent proton conductivity, mechanical strength, and chemical stability, enabling high output and physical durability in polymer electrolyte fuel cells, even under low-humidification conditions.

Implementation Method 1

forming a nano- or micro-phase separated structure for enhanced proton conductivity and durability

Methodology Applied

Scientific EffectPhase separation:

Implementation Method 2

segment (A1) containing an ionic group... exhibits excellent proton conductivity

Methodology Applied

Scientific EffectProton conduction: Conduction (electrical)

Data Source

PatentUS9653745B2Block copolymer, manufacturing method therefor, and polymer electrolyte material, molded polymer electrolyte, and solid-polymer fuel cell using said block copolymer

Publication Date: 2017.05.16 TORAY INDUSTRIES INC

AI summary

To provide: a block copolymer that exhibits excellent proton conductivity even under low-humidification conditions, exhibits excellent mechanical strength and chemical stability, and when used in a polymer electrolyte fuel cell, allows high output and excellent physical durability; a polymer electrolyte material; and a polymer electrolyte form article and a polymer electrolyte fuel cell, using the same.The block copolymer of the present invention includes each one or more of: a segment (A1) containing an ionic group; a segment (A2) not containing an ionic group; and a linker moiety connecting the segments. The segment (A1) containing an ionic group comprises a constituent unit represented by a specific structure. The polymer electrolyte material, the polymer electrolyte form article, and the polymer electrolyte fuel cell according to the present invention are manufactured by using the above block copolymer.