Fuel Cell Bipolar Plate Graphite Coating Delamination
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Solution Overview
Problem
Conventional bipolar plates for fuel cells face issues with poor conductivity and air tightness due to the formation of small air bubbles in the conductive protective film and delamination caused by the use of tin-containing materials, leading to increased production costs and potential corrosion.
Innovation Solution
A method involving a metal substrate with a conducting adhesion layer and expanded graphite powder, where the graphite layer is press-fitted to match the flow field structure, embedding the graphite powder into the adhesion layer to enhance bonding strength and prevent infiltration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple layers of polymeric materials are coated and multiple pyrolytic processes are conducted to improve film density, then air bubble infiltration is reduced, but processing complexity and production cost increase
Solution Approach 1:
The patent separates the protective function from the conductive function by using a metal substrate with inherent corrosion resistance combined with a pressed expanded graphite layer for conductivity. This segmentation eliminates the need for multiple polymeric coating layers and pyrolytic processes, simplifying the manufacturing procedure while maintaining film density.
Solution Approach 2:
The patent changes the graphite material to expanded graphite powder and applies direct contact pressing instead of spray-coating followed by pyrolysis. This parameter change achieves dense film formation in a single step, dramatically reducing processing complexity and production cost.
2Strength
If tin paste is used to bond a graphite layer to a stainless steel base, then bonding is achieved, but delamination occurs due to hetero-junction and poor strength, and acid solution permeation causes corrosion
Solution Approach 1:
The patent removes the tin paste bonding layer from the structure. Instead of using a separate bonding agent that creates hetero-junctions, the expanded graphite powder is directly pressed onto the stainless steel substrate, eliminating the source of delamination and acid solution permeation while maintaining strong adhesion.
Solution Approach 2:
The patent creates a composite structure where expanded graphite powder is directly bonded to the stainless steel substrate through pressing. This composite approach eliminates the need for intermediate bonding layers, ensuring strong adhesion and preventing acid solution permeation that would cause corrosion.
3Power
If the bipolar plate structure uses a complex flow field structure on the metal substrate surface, then fuel cell performance is improved, but coating effectiveness is reduced at specific angles
Solution Approach 1:
The patent uses expanded graphite powder that is pressed to copy the complex flow field structure of the bipolar plate surface. This copying method ensures complete coverage of the complex geometry without the angle-dependent limitations of spray-coating, achieving uniform coverage while maintaining the high-performance flow field 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
This approach results in a dense, conductive graphite layer that effectively protects the metal substrate, reduces voltage decay, and improves the durability of the bipolar plate, while simplifying the production process and reducing costs.
Implementation Method 1
press-fitting the metal substrate and the expanded graphite powder with a mold structurally corresponding to the flow field structure, so as to form a graphite layer covering the surface of the metal substrate from the expanded graphite powder
Implementation Method 2
providing a metal substrate having a conducting adhesion layer on the surface thereof
Data Source
AI summary
A bipolar plate for a fuel cell is provided, which includes: a metal substrate having a flow field structure; a conducting adhesion layer formed on the metal substrate and having a polymeric adhesive and a plurality of conductive particles; and a pure graphite layer formed on the conducting adhesion layer and structurally corresponding to the flow field structure of the metal substrate. The graphite layer including expanded graphite powder is adhered to the metal substrate via the conducting adhesion layer, and a portion of the expanded graphite powder is embedded into the conducting adhesion layer.