Fuel Cell Backing Layer with Random Carbon Fibers
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Solution Overview
Problem
The high manufacturing costs and inefficiencies of carbon or graphite layers in fuel cells, which impede hydrogen and oxygen diffusion and hinder the outflow of product water, necessitate a cost-effective alternative for substrate materials.
Innovation Solution
A fuel cell design incorporating a backing layer made of randomly-dispersed carbon fibers with a hydrophobic polymer, which replaces the traditional substrate and diffusion layers, providing enhanced electrical conductivity and compressive strength while minimizing manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional carbon or graphite layers are used as substrate material, then structural strength is provided, but manufacturing costs increase and diffusion of hydrogen and oxygen is impeded
Solution Approach 1:
The patent applies composite materials by combining carbon fibers with a hydrophobic polymer matrix to create a backing layer that integrates multiple functions. This composite structure provides the necessary mechanical strength while maintaining porosity for gas diffusion and reducing manufacturing costs compared to traditional graphite layers.
Solution Approach 2:
The patent utilizes porous materials by creating a backing layer with controlled porosity through the carbon fiber-polymer composite structure. The porous network allows efficient diffusion of hydrogen and oxygen gases while maintaining structural integrity, eliminating the need for dense graphite layers that impede gas transport.
2Strength
If traditional substrate layers are used, then mechanical support is provided, but outflow of product water is hindered
Solution Approach 1:
The porous structure of the carbon fiber composite backing layer facilitates efficient water removal through capillary action and pressure-driven flow. The interconnected pores provide pathways for product water to exit the catalyst layer without compromising the mechanical support function.
Solution Approach 2:
The hydrophobic polymer matrix acts as an intermediary that repels liquid water while allowing gas transport. This creates a selective interface that promotes water removal from the catalyst layer while maintaining the structural framework of the backing layer.
3Strength
If thick substrate layers are used to provide adequate compressive strength, then structural integrity is maintained, but manufacturing costs and material usage increase
Solution Approach 1:
The carbon fiber-polymer composite provides high specific strength, allowing the backing layer to achieve adequate compressive strength with reduced thickness and material quantity. The carbon fibers bear the mechanical load while the polymer matrix binds them together, creating an efficient load-bearing structure.
Solution Approach 2:
The patent optimizes the thickness and composition parameters of the backing layer to achieve the minimum required compressive strength. By controlling the carbon fiber content, fiber orientation, and polymer matrix properties, the layer provides sufficient structural integrity with minimized material usage.
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 use of a backing layer with randomly-dispersed carbon fibers reduces substrate costs, enhances electrical conductivity, and efficiently removes product water, thereby improving fuel cell performance and reducing manufacturing burdens.
Implementation Method 1
The backing layer is made from between 5 weight percent ("wt %") and 25 wt % carbon black, between 50 wt % and 90 wt % carbon fibers, and between 5 wt % and 25 wt % of a hydrophobic polymer
Implementation Method 2
The substrate conducts electrons both through the plane of the substrate and in the plane of the substrate from a centerline of an adjacent flow channel to ribs of the flow field
Implementation Method 3
The substrate also facilitates the diffusion and flow of reactant streams and product water both through the plane of the substrate and in the plane of the substrate
Data Source
AI summary
A fuel cell (40) includes first and second catalysts (12′), (14′) secured to opposed surfaces of an electrolyte (16′); a first flow field (26′) secured in fluid communication with the first catalyst (12′) defining a plurality of flow channels (30A′, 30B′, 30C′, 30D′) between a plurality of ribs (32A′, 32B′, 32C′, 32D′, 32E′) of the first flow field (26′); and a backing layer (42) secured between the first flow field (26′) and the first catalyst (12′). The backing layer (42) includes a carbon black, a hydrophobic polymer, and randomly-dispersed carbon fibers (44). The carbon fibers (44) are at least twice as long as a width (46) of the flow channels (30A′, 30B′, 30C′, 30D′) defined in the adjacent first flow field (26′). The backing layer (42) replaces a known substrate (22) and diffusion layer (18).