Exfoliated Graphite Composite Metal Laminate for Fuel Cell Bipolar Plates
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Solution Overview
Problem
Current fuel cell bipolar plates face challenges in achieving high electrical conductivity, low gas permeability, corrosion resistance, and cost-effectiveness, with existing methods being expensive and inefficient in mass production, particularly due to issues with machining, material limitations, and poor thickness-direction conductivity.
Innovation Solution
A composite laminate composition comprising exfoliated graphite, non-expandable graphite, and a binder or matrix material, combined with a thin metal sheet, which enhances thickness-direction conductivity and hydrogen permeation resistance, allowing for the creation of thin, highly conductive bipolar plates suitable for fuel cell applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional graphite bipolar plates are used, then corrosion resistance and electrical conductivity are achieved, but the plates are thick (3-5 mm) and expensive to manufacture
Solution Approach 1:
The patent uses a composite material consisting of expandable graphite particles (30-70 wt%), binder material (10-40 wt%), and metal powder (5-30 wt%). This composite achieves both corrosion resistance and high electrical conductivity while enabling thin plate construction (0.5-2.0 mm), resolving the contradiction between reliability and thickness.
Solution Approach 2:
The patent changes the physical and chemical parameters of the graphite material by using expandable graphite that is heat-treated to expand in volume, creating a porous structure that is then impregnated with metal powder. This parameter change enables thin plate construction while maintaining high electrical conductivity through the metal-infused porous graphite matrix.
2Length of moving object
If graphite bipolar plates are machined to reduce thickness, then plate thickness is reduced, but manufacturing cost and complexity increase
Solution Approach 1:
The patent replaces the mechanical machining process with a chemical/thermal process. Instead of mechanically removing material to achieve thin plates, the invention uses heat treatment to expand graphite particles and then impregnates the expanded structure with metal powder, creating thin plates through material transformation rather than mechanical removal, significantly reducing manufacturing complexity.
Solution Approach 2:
The patent applies heat treatment to change the physical state of graphite particles from compact to expanded form, creating a porous structure that can be infused with metal. This parameter change enables thin plate production without complex machining, reducing manufacturing cost and complexity while achieving the desired thickness.
3Length of moving object
If metal bipolar plates are used, then electrical conductivity and thin plate construction are achieved, but corrosion resistance deteriorates
Solution Approach 1:
The patent creates a composite material where metal powder particles are dispersed within an expanded graphite matrix. The graphite provides corrosion resistance while the metal provides electrical conductivity, achieving both properties simultaneously in a thin plate structure that neither material could achieve alone.
Solution Approach 2:
The patent applies local quality by having metal powder particles distributed throughout the graphite matrix, creating regions of high electrical conductivity (where metal particles are present) within a corrosion-resistant graphite framework. This local distribution of properties allows the thin plate to simultaneously achieve both corrosion resistance and high conductivity.
4Ease of manufacture
If conventional composite bipolar plates are used, then cost reduction is achieved, but electrical conductivity in thickness direction is poor
Solution Approach 1:
The patent applies heat treatment to expand graphite particles, creating a three-dimensional porous network structure. This structural parameter change, combined with metal powder impregnation, creates continuous conductive pathways through the thickness direction, dramatically improving electrical conductivity while maintaining cost-effectiveness through simple processing.
Solution Approach 2:
The patent uses a composite material system where metal powder particles are embedded within an expanded graphite matrix. This composite structure creates multiple conductive pathways through the thickness direction, achieving high electrical conductivity at low cost through material composition rather than complex processing.
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 composite laminate achieves ultra-high electrical conductivity exceeding DOE targets, is impermeable to hydrogen and oxygen, and enables cost-effective mass production of thin bipolar plates, reducing fuel cell stack size and improving performance and durability.
Implementation Method 1
heat-treated to expand in volume
Implementation Method 2
impregnated with metal powder
Implementation Method 3
binder material to bond the expanded graphite
Data Source
AI summary
An electrically conductive laminate composition for fuel cell flow field plate or bipolar plate applications. The laminate composition comprises at least a thin metal sheet having two opposed exterior surfaces and a first exfoliated graphite composite sheet bonded to the first of the two exterior surfaces of the metal sheet wherein the exfoliated graphite composite sheet comprises: (a) expanded or exfoliated graphite and (b) a binder or matrix material to bond the expanded graphite for forming a cohered sheet, wherein the binder or matrix material is between 3% and 60% by weight based on the total weight of the first exfoliated graphite composite sheet. Preferably, the first exfoliated graphite composite sheet further comprises particles of non-expandable graphite or carbon in the amount of between 3% and 60% by weight based on the total weight of the non-expandable particles and the expanded graphite. Further preferably, the laminate comprises a second exfoliated graphite composite sheet bonded to the second surface of the metal sheet to form a three-layer laminate. Surface flow channels and other desired geometric features can be built onto the exterior surfaces of the laminate to form a flow field plate or bipolar plate. The resulting laminate has an exceptionally high thickness-direction conductivity and excellent resistance to gas permeation.