Fuel Cell Stack Separators with Differential Corrosion Resistance
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Solution Overview
Problem
Conventional fuel cell stacks face performance degradation and corrosion due to uniform material properties in separators, which fail to accommodate the different operating environments and thermal expansion coefficients between the anode and cathode sides, leading to pressure imbalances and component damage.
Innovation Solution
The use of anode-side and cathode-side separators made from materials with different corrosion resistances and thermal expansion coefficients, such as austenitic stainless steel and ferritic stainless steel, or aluminum and titanium alloys, respectively, to alternate in the stack, ensuring appropriate pressure and enhanced corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If the anode-side separator and cathode-side separator are made of a single material having a high thermal expansion coefficient, then the pressure of the contact face is high, but physical and chemical damage of the MEA and GDLs is accelerated
Solution Approach 1:
The patent applies different material properties to different parts of the separator system: the anode-side separator uses a material with high thermal expansion coefficient to generate high contact pressure, while the cathode-side separator uses a material with low thermal expansion coefficient to prevent damage to MEA and GDLs. This local differentiation of material properties resolves the contradiction between maintaining pressure and preventing damage.
Solution Approach 2:
The separator system is divided into two distinct segments: an anode-side separator and a cathode-side separator, each with different material compositions tailored to their specific functional requirements. This segmentation allows each part to optimize its performance without compromising the other, addressing the contradiction through functional decomposition.
2Reliability
If the anode-side separator and cathode-side separator are made of a single material having a low thermal expansion coefficient, then the damage to components is reduced, but the performance of the stack is degraded due to low pressure of the contact face
Solution Approach 1:
Different material properties are assigned to different separator regions: the cathode-side separator uses low thermal expansion coefficient material to protect components, while the anode-side separator uses high thermal expansion coefficient material to ensure adequate contact pressure for stack performance. This localized quality differentiation resolves the contradiction between component protection and performance maintenance.
3Strength
If a metal separator is used, then the structural integrity is maintained, but the separator is corroded by product water
Solution Approach 1:
The patent employs composite material structures for the separators, combining metal components with corrosion-resistant coatings or alternative materials. The anode-side separator may use metal with protective coatings, while the cathode-side separator uses inherently corrosion-resistant materials, thus maintaining structural integrity while preventing corrosion from product water.
Solution Approach 2:
Different corrosion resistance strategies are applied to different separator regions based on their exposure to product water. The cathode-side separator, which is more exposed to product water, uses materials with higher corrosion resistance, while the anode-side separator can use metal materials with adequate corrosion protection, optimizing both strength and corrosion resistance locally.
4Ease of manufacture
If the cathode-side separator has the same material properties as the anode-side separator, then the manufacturing is simplified, but the corrosion resistance is insufficient due to the acidic atmosphere on the cathode side
Solution Approach 1:
The patent recognizes that the cathode-side environment is more corrosive due to product water accumulation and acidic atmosphere, and accordingly applies materials with higher corrosion resistance specifically to the cathode-side separator. This localized material selection maintains manufacturing feasibility while addressing the specific corrosion challenges of the cathode region.
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
This configuration maintains optimal pressure and prevents performance degradation and corrosion, improving the durability and efficiency of the fuel cell stack by addressing the distinct operating conditions of the anode and cathode sides.
Implementation Method 1
when the anode-side separator 30a and 30 and the cathode-side separator 30b and 40 are made of a single material having a high thermal expansion coefficient, physical and chemical damage of the MEA 10 and the GDLs 20 is accelerated due to the high pressure of the contact face in the stack caused by temperature rise during operation of the fuel cell
Implementation Method 2
the cathode-side separator is required to have a relatively high corrosion resistance compared with the anode-side separator
Data Source
AI summary
The present disclosure relates to a fuel cell stack having a cathode-side separator and an anode-side separator which are made of different materials to prevent performance degradation of stacks and corrosion and damage of components. A fuel cell stack according to exemplary embodiments of the present disclosure may have multiple unit cells stacked therein, in which each unit cell of the multiple unit cells may include: a membrane electrode assembly (MEA); a pair of gas diffusion layers (GDLs) disposed on opposite surfaces of the MEA; and an anode-side separator and a cathode-side separator disposed to face each other, the MEA and the pair of GDLs being disposed therebetween, in which the cathode-side separator has a corrosion resistance higher than a corrosion resistance of the anode-side separator.