Fuel Cell Stack Selective Separator Treatment
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Solution Overview
Problem
Solid polymer fuel cell stacks face corrosion issues with metal separators and terminal plates due to exposure to corrosive environments, leading to decreased ion conductivity and increased production costs when all metal components are surface-treated with noble metals.
Innovation Solution
A fuel cell stack design where the metal separator on the plus side, which experiences higher oxidation current, is subjected to more extensive anticorrosive surface treatment than the minus side, and the terminal plates are protected from moisture and coolant contact, reducing corrosion and production costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If all metal separators are surface treated with noble metals, then corrosion resistance is improved, but production cost increases
Solution Approach 1:
The patent applies surface treatment with noble metals selectively only to the plus side metal separators where oxidation current flows and corrosion occurs, rather than treating all metal separators uniformly. This local quality approach maintains necessary corrosion resistance at the critical locations while avoiding unnecessary treatment elsewhere, thereby reducing production cost.
2Reliability
If terminal plates are protected from corrosion by resin insertion, then corrosion resistance is improved, but device complexity increases
Solution Approach 1:
The patent segments the terminal plate structure by inserting resin materials into specific coolant channels where corrosion occurs. This segmentation approach protects only the critical areas exposed to corrosive environments while maintaining the overall terminal plate structure, avoiding the need for complete structural redesign.
3Reliability
If uniform corrosion protection is applied to all metal components, then reliability is improved, but manufacturing cost increases
Solution Approach 1:
The patent implements differentiated corrosion protection strategies: the plus side metal separators receive noble metal surface treatment due to oxidation current exposure, while the minus side metal separators use alternative protection methods or no treatment since they are exposed to reduction current. This local quality approach optimizes manufacturing cost by applying expensive treatments only where necessary.
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 enhances corrosion resistance on the plus side while maintaining overall stack performance at a lower cost compared to uniform corrosion protection across all metal components.
Implementation Method 1
the plus side of the cell stack has corrosion resistance higher than that of the minus side... the plus side where the oxidation current flows and corrosion advances easier
Implementation Method 2
Japanese Patent Laid-open Publication No 2000-21418 suggested a method for surface treating (plating) the conductive separator with a metal layer, for example, a layer of gold or silver, that is inactive in an oxidizing atmosphere
Implementation Method 3
Japanese Patent Laid-open Publication No. 2003-163026 suggested a stack structure in which the terminal plate is prevented from coming into direct contact with humid gases or coolant by using a configuration in which a resin serving as an end plate material is fitted and inserted into a coolant channel of the terminal plate
Data Source
AI summary
The object of the present invention is to provide a fuel cell stack with improved corrosion resistance of metal separators and reduced cost. To attain this object, the fuel cell stack according to the present invention has a cell stack constituted by stacking a prescribed number of unit cells obtained by sandwiching both surfaces of an electrolyte membrane between an anode and a cathode and sandwiching the outer sides thereof with a pair of metal separators, wherein the metal separator positioned on the plus side of the cell stack is subjected to surface treatment providing for relatively higher corrosion resistance than the metal separator positioned on the minus side of the cell stack. Cost reduction can be realized, while maintaining corrosion resistance comparable with that obtained in the case when all the separators are subjected to the anticorrosive surface treatment to the same degree.