Fluorinated Polymer Liquid Composition for Fuel Cell Catalyst Layers
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Solution Overview
Problem
The existing processes for producing polymer electrolyte fuel cells face challenges in suppressing the formation of fluorinated polymers with large particle sizes, leading to filter clogging and potential inclusion of foreign matters in the catalyst layer and membrane, which can affect the performance and durability of the fuel cell.
Innovation Solution
A process involving heat-treating a fluorinated polymer with -SO2F groups at 140 to 160°C for at least 45 minutes, followed by rapid cooling to less than 110°C at a rate of at least 50°C/min, to convert the -SO2F groups into ion exchange groups, and mixing with a liquid medium to form a liquid composition that suppresses the formation of large particle sizes and facilitates filtration, thereby reducing foreign matter inclusion in the catalyst layer and membrane.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the liquid composition is filtered to remove foreign matters, then the purity of the catalyst layer and membrane is improved, but the filter is likely to be clogged due to large particle size fluorinated polymers
Solution Approach 1:
The patent applies parameter changes by controlling the temperature profile during polymer formation. Specifically, the polymerization is conducted at 140-160°C followed by rapid cooling at 50°C/min or faster. This temperature parameter control changes the physical state and particle size distribution of the fluorinated polymer, preventing aggregation into large particles that would clog filters, while still achieving complete conversion of -SO2F groups to ion exchange groups.
2Productivity
If the polymer electrolyte membrane is made thin to improve performance, then the power density is improved, but foreign matter inclusion becomes more problematic
Solution Approach 1:
The patent applies preliminary action by controlling the particle size distribution of the fluorinated polymer before the membrane formation process. By conducting polymerization at 140-160°C followed by rapid cooling, the method prevents the formation of large particles and aggregates in advance. This preliminary control of particle morphology ensures that even when the membrane is made thin, there are no large foreign particles to cause inclusion problems during the subsequent membrane fabrication and assembly processes.
3Shape
If rapid cooling is applied to suppress large particle formation, then the particle size is reduced, but the conversion of -SO2F groups may be incomplete
Solution Approach 1:
The patent applies periodic action through a two-stage temperature process. First, the polymerization is conducted at a sustained temperature of 140-160°C for sufficient time to ensure complete conversion of -SO2F groups to ion exchange groups. Second, rapid cooling at 50°C/min or faster is applied to suppress particle aggregation. This periodic temperature control sequence ensures both complete chemical conversion and desirable particle size characteristics are achieved.
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
This approach effectively prevents filter clogging and minimizes the inclusion of foreign matters, resulting in a catalyst layer and polymer electrolyte membrane with improved performance and durability for polymer electrolyte fuel cells.
Implementation Method 1
holding a fluorinated polymer having -SO 2 F groups at from 140 to 160°C for at least 45 minutes, cooling it to less than 110°C at a rate of at least 50°C/min, converting the -SO 2 F groups in the fluorinated polymer to ion exchange groups
Implementation Method 2
cooling it to less than 110°C at a rate of at least 50°C/min
Data Source
Figure 1~2
AI summary
To provide a process for producing a liquid composition in which formation of a fluorinated polymer having ion exchange groups with a relatively large particle size is suppressed; a process for producing a catalyst layer-forming coating liquid capable of forming a catalyst layer in which inclusion of foreign matters is suppressed; and a method for producing a membrane/electrode assembly by which a catalyst layer or a polymer electrolyte membrane in which inclusion of foreign matters is suppressed, can be formed. A process for producing a liquid composition, which comprises holding a fluorinated polymer having -SO2F groups at from 140 to 160°C for at least 45 minutes; cooling the fluorinated polymer having -SO2F groups held at from 140 to 160°C to less than 110°C at a rate of at least 50°C/min; converting the -SO2F groups in the fluorinated polymer having -SO2F groups cooled to less than 110°C to ion exchange groups to obtain a fluorinated polymer having ion exchange groups; and mixing the fluorinated polymer having ion exchange groups and a liquid medium.