Carbon sheet, method for manufacturing same, gas diffusion electrode, and fuel cell
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional gas diffusion electrodes face issues such as fiber breakage during processing, uneven resin distribution leading to high electrical resistance, and delamination causing performance degradation in fuel cells, due to strong fiber orientation and multiple layer lamination.
Innovation Solution
A carbon sheet with a specific fiber orientation gradient and layer structure, where the first surface side region has a high degree of fiber orientation and the second surface side region has a lower average orientation, preventing deflection into gas flow channels and maintaining low through-plane electrical resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If fibers are strongly orientated throughout the whole carbon sheet, then deflection into gas flow channels is inhibited, but resin carbide distribution becomes uneven, worsening electrical resistance in the thickness direction
Solution Approach 1:
The patent resolves this contradiction by localizing strong fiber orientation to only the first surface side region (40% or less of total thickness) where deflection prevention is most critical near the gas flow channels. The second surface side region maintains weaker fiber orientation, allowing resin carbide to distribute more evenly and maintain low electrical resistance in the thickness direction while still providing sufficient structural support.
2Reliability
If two or more layers of carbon sheets are laminated, then gas diffusion and electrical conductivity are improved, but delamination occurs during power generation, causing contact breakage and flooding
Solution Approach 1:
The patent merges multiple carbon sheets into a single integrated structure where the fiber orientation gradient is established across the entire thickness. This creates a unified carbon sheet with continuous fiber orientation control from the first surface through the second surface, eliminating the interfaces between separate laminated layers and preventing delamination during power generation while maintaining gas diffusion and electrical conductivity pathways.
3Reliability
If multiple carbon sheets are produced and laminated, then gas diffusion electrode performance is improved, but the number of processing processes increases, decreasing productivity
Solution Approach 1:
The patent combines what would have been separate lamination processes into a single carbon sheet manufacturing process. By establishing the fiber orientation gradient during the formation of one integrated carbon sheet rather than through subsequent lamination of multiple sheets, the number of processing steps is reduced, eliminating delamination risks and improving productivity while maintaining the performance benefits of a multi-layer structure.
Data Source
AI summary
An object of the present invention is to provide a carbon sheet to be used suitably for a gas diffusion electrode, in which the carbon sheet does not worsen the electrical resistance in the through-plane direction, and can be prevented from the deflection into the gas flow channels provided in the bipolar plate, although such characteristics. A carbon sheet according to the present invention, provided to achieve the above-described object, is a carbon sheet including a first surface and a second surface located at the opposite side to the first surface; wherein, assuming that a specific section is equally divided into 20 portions in the thickness direction to form 20 layers, the degree of fiber orientation of the first surface side outermost layer of the 20 layers is 1.20 or more and 3.00 or less; and wherein, assuming that a region composed of consecutive layers that are included in the 20 layers, and satisfy specific conditions is a first surface side region, and that a region composed of a layer(s) included in the 20 layers but not included in the first surface side region is a second surface side region, the thickness of the first surface side region is 40% or less of the thickness of the whole carbon sheet, and a difference between the average degree of fiber orientation of the second surface side region and the degree of fiber orientation of the first surface side outermost layer is larger than 0.10.