Fuel Cell Separator Composite for Conductivity and Strength
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Solution Overview
Problem
Existing separator members for fuel cells using expanded graphite sheets suffer from low strength and toughness due to their thickness, which affects conductivity.
Innovation Solution
A separator member for fuel cells is designed with a first resin layer and a graphite layer, where the graphite layer has a layering amount of 50 g/m² or less and a volume resistivity of 3 mΩ·cm or less, optionally with a conductive fiber base material and a second resin layer, to enhance conductivity and strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an expanded graphite sheet is used to improve conductivity, then conductivity is improved, but the strength and toughness decrease due to the thickness of the graphite sheet
Solution Approach 1:
The invention changes the critical parameter of graphite layer thickness/weight to resolve the contradiction. By specifying that the graphite layer has a layering amount of 50 g/m² or less, the patent achieves optimal conductivity while preventing the strength deterioration that occurs with thicker graphite sheets. This parameter optimization allows the graphite layer to provide sufficient electrical conductivity without compromising the mechanical strength and toughness of the separator member.
Solution Approach 2:
The invention creates a composite structure combining a resin layer with a graphite layer. The resin layer provides mechanical strength and structural integrity, while the graphite layer contributes electrical conductivity. This composite material approach allows both requirements—strength and conductivity—to be satisfied simultaneously by leveraging the complementary properties of different materials in a layered configuration.
2Reliability
If a thick expanded graphite sheet is used, then conductivity is improved, but the toughness decreases
Solution Approach 1:
The invention optimizes the graphite layer thickness parameter to resolve the contradiction between conductivity and toughness. By limiting the layering amount to 50 g/m² or less, the patent ensures that the graphite layer is thin enough to maintain the toughness and flexibility of the separator member while still providing adequate electrical conductivity for fuel cell operation.
3Strength
If a thin graphite layer is used to improve strength, then strength is improved, but conductivity decreases
Solution Approach 1:
The invention identifies and optimizes the critical parameter of graphite layer thickness to simultaneously satisfy both strength and conductivity requirements. The specified layering amount of 50 g/m² or less represents an optimized value that provides sufficient electrical conductivity for fuel cell operation while maintaining the mechanical strength needed for structural integrity, eliminating the need to trade off between these two properties.
4Reliability
If a thick graphite layer is used, then conductivity is improved, but the separator member swells or deforms
Solution Approach 1:
The invention controls the graphite layer thickness parameter to prevent swelling and deformation while maintaining conductivity. By limiting the layering amount to 50 g/m² or less, the patent ensures that the graphite layer is thin enough to avoid excessive swelling or deformation during fuel cell operation, yet still provides adequate electrical conductivity. This parameter control maintains the dimensional stability and shape of the separator member.
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 solution provides a separator member with improved conductivity and strength, facilitating easy integration into fuel cells without swelling or deformation, while reducing the need for mold release agents.
Implementation Method 1
a graphite layer that is layered on the first resin layer and substantially made of graphite... a volume resistivity of 3 mΩ·cm or less
Data Source
Figure 1
Figure 2A~2D
Figure 3
AI summary
A separator member (10) for a fuel cell includes: a first resin layer (13) including a resin; and a graphite layer (11) that is layered on the first resin layer (13) and substantially made of graphite. The layering amount of the graphite layer (11) is 50 g/m2 or less, and the volume resistivity of the graphite is 3 mΩ·cm or less.