Hyper-branched Polymer Fuel Cell Electrolyte Membrane
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Solution Overview
Problem
Fuel cells with polymer electrolyte membranes face challenges in high-temperature operation due to moisture evaporation, gas diffusion issues with liquid phosphoric acid, and inadequate mechanical and chemical stability, leading to reduced performance and activation time.
Innovation Solution
A hyper-branched polymer with a dendritic, linear, and terminal unit structure is used in the electrode and electrolyte membrane, enhancing oxygen permeability, heat resistance, and phosphoric acid retention, allowing for high-temperature, non-humidified operation and improved fuel cell performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If polymer electrolyte membranes are operated at high temperatures (at least 100°C) to enhance cell system efficiencies, then the operating temperature is improved, but the moisture in the membrane evaporates which reduces the effectiveness of proton conduction
Solution Approach 1:
The patent changes the chemical composition and structural parameters of the polymer electrolyte membrane by incorporating hyper-branched polymers with specific dendritic units, linear units, and terminal units. This structural modification allows the membrane to maintain proton conduction effectiveness at high temperatures (at least 100°C) without requiring humidification, thus resolving the contradiction between operating temperature and proton conduction effectiveness
Solution Approach 2:
The patent uses composite materials by combining hyper-branched polymer structures with phosphoric acid doping. This composite approach creates a non-humidified electrolyte membrane that can operate at high temperatures while maintaining effective proton conduction, overcoming the limitation of moisture evaporation in conventional polymer electrolyte membranes
2Temperature
If liquid phosphoric acid electrolyte is used in fuel cells operating at temperatures of from 150 to 200°C, then the operating temperature is improved, but the liquid phosphoric acid interferes with gas diffusion in the electrodes
Solution Approach 1:
The patent employs porous electrode structures with optimized pore sizes and distributions that prevent clogging by phosphoric acid while maintaining gas diffusion pathways. The porous structure allows gas to diffuse effectively even at high temperatures (150-200°C) with liquid phosphoric acid present, resolving the contradiction between operating temperature and gas diffusion productivity
Solution Approach 2:
The patent applies local quality by creating regions within the electrode with different properties - areas with phosphoric acid retention and areas with open pore structures for gas diffusion. This spatial differentiation allows the electrode to simultaneously handle high-temperature operation and maintain gas diffusion productivity
3Productivity
If polytetrafluoroethylene (PTFE) waterproofing agent is added to electrodes to prevent gas diffusion issues, then gas diffusion is improved, but the electrode structure becomes more complex and may affect oxygen permeability
Solution Approach 1:
The patent extracts or removes the need for PTFE waterproofing agents by using alternative approaches - specifically, by optimizing the porous structure and using hyper-branched polymer modifications that provide water management without requiring additional waterproofing materials. This simplifies the electrode structure while maintaining gas diffusion prevention capabilities
4Ease of operation
If the polymer electrolyte membrane is formed of PBI with phosphoric acid doping, then non-humidified operation is achieved, but the membrane does not have satisfactory mechanical properties, chemical stability, or capability of containing phosphoric acid
Solution Approach 1:
The patent changes the structural parameters of the polymer by introducing hyper-branched architectures with specific dendritic units, linear units, and terminal units. This structural modification enhances the mechanical properties and chemical stability of PBI-based membranes while improving their phosphoric acid containment capability, thus enabling reliable non-humidified operation
Solution Approach 2:
The patent creates composite material structures by combining PBI with hyper-branched polymer modifications and phosphoric acid doping. This composite approach simultaneously achieves non-humidified operation while improving mechanical properties, chemical stability, and phosphoric acid containment capability
5Loss of time
If air is supplied to the cathode with optimized electrode composition, then activation time is reduced to about 1 week, but replacing air with oxygen is undesirable for commercial use
Solution Approach 1:
The patent applies preliminary action by pre-modifying the electrode composition and structure with hyper-branched polymers before operation. This pre-preparation enables the electrode to achieve rapid activation (about 1 week) when air is supplied to the cathode, eliminating the need for subsequent oxygen replacement while maintaining commercial usability
Data Source
AI summary
A hyper-branched polymer that has a dendritic unit, a linear unit, a terminal unit, and a degree of branching of about 0.05 to about 1. The hyper-branched polymer can be included in an electrode and/or an electrolyte membrane of a fuel cell.