Composite Separator for PEMFC with Graphite Foil Conductive Path
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Solution Overview
Problem
Conventional separators for polymer electrolyte membrane fuel cells face challenges in achieving low electrical contact resistance, mechanical durability, and efficient water discharge, as they are either vulnerable to impact or difficult to process, and lack optimal surface energy for water circulation.
Innovation Solution
A composite separator is created by stacking graphite foil layers on both sides of a carbon fiber reinforced composite material with holes, allowing direct contact through deformation under high temperature and pressure, which reduces electrical contact resistance and increases hydrophilicity, facilitating water discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If graphite is used as separator material, then electrical contact resistance is reduced, but mechanical strength and impact resistance deteriorate
Solution Approach 1:
The invention uses a composite structure combining carbon fiber reinforced plastic (CFRP) for mechanical strength and graphite foil for electrical conductivity. The CFRP base layer provides high strength and rigidity, while the graphite foil layers bonded to both sides provide low electrical contact resistance. This composite approach resolves the contradiction by integrating two materials with complementary properties rather than using a single material that must compromise between strength and conductivity.
2Productivity
If separator material has high surface energy for hydrophilicity, then water discharge is improved, but electrical contact resistance increases
Solution Approach 1:
The invention applies different surface properties to different parts of the separator structure. The graphite foil layers provide hydrophilic surfaces with high surface energy for efficient water discharge, while the CFRP base layer provides the structural framework. By localizing the hydrophilic property to the graphite foil surfaces that contact the electrolyte membrane, the invention achieves improved water discharge without compromising the overall electrical conductivity of the separator structure.
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 effectively reduces electrical contact resistance and enhances hydrophilicity, improving the efficiency of water circulation and energy output in fuel cell stacks by creating a conductive path between graphite foils and reinforcing mechanical properties.
Implementation Method 1
graphite foils are brought into direct contact with each other through a plurality of holes formed in a composite material layer interposed between graphite foils prepared by compressing expanded graphite
Implementation Method 2
compressing expanded graphite
Implementation Method 3
a connecting portion formed in each hole of the carbon fiber reinforced composite material as a portion of the graphite foils becomes filled into the holes, thereby conductively connecting the graphite foils stacked on both sides of the carbon fiber reinforced composite material to each other
Implementation Method 4
increases the hydrophilicity by the graphite foils, and improves the electrical conductivity in the thickness direction of the separator
Data Source
AI summary
The present invention provides a composite separator for a polymer electrolyte membrane fuel cell (PEMFC) and a method for manufacturing the same. The inventive method involves allowing graphite foil layers to be brought into direct contact with each other when graphite foils are stacked on both sides of a carbon fiber reinforced composite material prepreg, thereby improving electrical conductivity in the thickness direction of the separator.