Block Copolymer Separator Membrane With Low Swelling and Ion Conductivity
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Solution Overview
Problem
Existing separator materials for fuel cells, such as Nafion, face challenges with high cost, methanol crossover, and increased membrane resistance when enhancing mechanical properties, while hydrocarbon-based alternatives suffer from decreased stability under humidity conditions.
Innovation Solution
A polymer comprising a hydrophilic block with perfluorosulfonic acid and a hydrophobic block with fluorine functional groups is developed, forming a block copolymer that maintains ion conductivity and mechanical stability, with a low swelling ratio and suppressed side reactions during polymerization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If silane-modified polyethylene crosslinking reaction is promoted in the extruder using a crosslinking catalyst master batch, then crosslinking reaction efficiency is improved, but resin aggregates are generated and homogeneity of physical properties deteriorates
Solution Approach 1:
The crosslinking process is divided into two separate stages: first, silane grafting occurs during extrusion to modify the polyethylene; second, the actual crosslinking reaction occurs after membrane formation through moisture exposure or heat treatment. This segmentation prevents resin aggregation during extrusion while achieving the desired crosslinked structure in the final product, thereby maintaining both production efficiency and membrane homogeneity.
Solution Approach 2:
The silane modification is performed as a preliminary action during the extrusion process, preparing the polyethylene for subsequent crosslinking without completing the full crosslinking reaction at that stage. This preliminary grafting allows the resin to remain processable during membrane formation, while the crosslinking structure develops later to provide the required mechanical and chemical properties without causing aggregation issues.
2Productivity
If membrane thickness is reduced to achieve smaller fuel cell stacks, then cell voltage and power density are improved, but membrane rupture risk increases
Solution Approach 1:
The patent employs a composite structure where polyethylene forms the base matrix and silane-crosslinked sections create a reinforced network within the membrane. This composite approach allows the membrane to maintain extremely thin dimensions (5 μm or less) while the crosslinked polyethylene sections provide enhanced mechanical strength and rupture resistance, enabling high power density without sacrificing reliability.
Solution Approach 2:
The membrane exhibits non-uniform crosslinking density, with crosslinked polyethylene sections distributed throughout the polyethylene matrix. These localized crosslinked regions provide targeted reinforcement at critical stress points while maintaining overall membrane thinness. The local quality enhancement allows the membrane to resist rupture even at thicknesses of 5 μm or less, achieving both high power density and reliability.
3Stability of the object's composition
If polyethylene resin is used to reduce cost and improve chemical inertness, then chemical stability is improved, but cold temperature flexibility and hot temperature strength deteriorate
Solution Approach 1:
The patent modifies the polyethylene structure by introducing silane groups that undergo crosslinking reactions, fundamentally changing the physical and mechanical parameters of the material. The crosslinked network structure transforms polyethylene from a thermoplastic with poor temperature resistance to a thermoset-like material that maintains flexibility at cold temperatures and strength at hot temperatures, while preserving the inherent chemical stability of the polyethylene backbone.
Solution Approach 2:
The patent creates a composite material system where crosslinked polyethylene sections are embedded within the polyethylene matrix. This composite structure combines the chemical stability of polyethylene with the enhanced mechanical properties of crosslinked networks, achieving simultaneous improvement in chemical inertness and temperature-dependent strength while maintaining cold temperature flexibility.
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 polymer separator achieves high ion conductivity, mechanical stability, and low swelling ratio, preventing gas crossover and vanadium ion crossover, enhancing durability and efficiency in fuel cells and redox flow batteries.
Implementation Method 1
it has gradually come to light by experimentation that high-strength flat-pressed membranes can be obtained by forming a silane crosslinked structure in a polyolefin, in particular, in polyethylene
Implementation Method 2
a proton exchange membrane for a fuel cell
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
The present specification relates to a polymer comprising a hydrophilic block and a hydrophobic block, wherein the hydrophilic block includes a unit derived from a compound represented by Chemical Formula 1, and the hydrophobic block includes a unit derived from a fluorine-containing compound, a polymer separator comprising the same, and a membrane electrode assembly, a fuel cell and a redox flow battery comprising the same.