Composite Metal Bipolar Plate for Fuel Cell Power Density
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Solution Overview
Problem
Bipolar plates in fuel cell stacks face challenges with graphite being too thick for power density and metal plates corroding, leading to increased electrical contact resistance.
Innovation Solution
A bipolar plate design featuring a first metal layer for mechanical strength and a second metal layer with slower oxide growth for corrosion resistance, maintaining electrical conductivity, allowing for a thinner, more efficient metal plate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If graphite is used for bipolar plates to provide electrical conductivity and corrosion resistance, then the plate achieves desired strength, but the plate must be relatively thick which reduces power density
Solution Approach 1:
The bipolar plate uses a composite structure combining stainless steel substrate with nickel-chromium-oxide surface layer. The stainless steel provides mechanical strength and structural integrity, while the oxide layer provides corrosion resistance and maintains electrical conductivity. This composite approach allows the plate to be thinner than pure graphite plates while achieving both strength and corrosion resistance requirements.
2Productivity
If metal is used to fabricate bipolar plates to reduce thickness and increase power density, then the plate becomes thinner, but the metal corrodes producing electrically insulating layers that increase electrical contact resistance
Solution Approach 1:
The surface composition and oxidation state of the bipolar plate are carefully controlled to optimize performance. The nickel-chromium-oxide layer is formed with specific compositional parameters (nickel, chromium, and oxygen ratios) that create an electrically conductive surface. The oxidation parameters (temperature, atmosphere, time) are controlled to form a stable, conductive oxide layer rather than insulating corrosion products.
Solution Approach 2:
Different regions of the bipolar plate have different properties: the bulk stainless steel substrate provides mechanical strength, while the surface nickel-chromium-oxide layer provides electrical conductivity and corrosion resistance. This local differentiation of material properties allows the plate to meet multiple performance requirements simultaneously without compromising electrical performance.
3Productivity
If metal bipolar plates are used to reduce cost and increase power density, then the overall stack cost and size are reduced, but corrosion resistance is insufficient
Solution Approach 1:
The bipolar plate employs a composite material system where the stainless steel substrate (e.g., 316L or 304) provides mechanical strength and structural integrity, while the nickel-chromium-oxide surface layer provides enhanced corrosion resistance in the fuel cell environment. This composite structure enables thinner plate design with improved power density while maintaining adequate corrosion resistance through the protective oxide layer.
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 enhances power density and reduces costs by maintaining electrical conductivity and mechanical strength in a thinner, corrosion-resistant metal bipolar plate, improving fuel cell stack performance.
Implementation Method 1
at least one first metal layer that will grow an electrically passive layer at a first rate in the presence of a fuel cell reactant gas
Implementation Method 2
the second metal layer has the ability to resist growing a second metal oxide layer in the presence of the fuel cell reactant gas
Implementation Method 3
The second metal layer also provides an electrically conductive path between the electrode and the first metal layer
Data Source
AI summary
A bipolar plate (30) for use in a fuel cell stack (10) includes one or more first metal layers (40a) having a tendency to grow an electrically passive layer in the presence of a fuel cell reactant gas and one or more second metal layers (40b) directly adjacent the one or more first metal layers (40a). The second metal layer has a tendency to resist growing any oxide layer in the presence of the fuel cell reactant gas to maintain a threshold electrical conductivity. The second metal layer also has a section for contacting an electrode (12, 14) and providing an electrically conductive path between the electrode (12, 14) and the first metal layer.