Asymmetric Anode Cathode Substrate Thickness in Phosphoric Acid Fuel Cells
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional phosphoric acid fuel cells face issues with acid distribution imbalance and expulsion due to the thickness mismatch between anode and cathode substrates, leading to reduced performance and life, especially when diluted for shipping to prevent freezing.
Innovation Solution
The anode substrate layer is made significantly thicker than the cathode substrate layer, typically between 1.75 and 3 times thicker, to accommodate the higher acid fill level and prevent acid expulsion, while maintaining power density and thermal characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the anode substrate layer is made thicker to accommodate higher acid fill level, then acid management and fuel cell life are improved, but the overall cell thickness and manufacturing cost increase
Solution Approach 1:
The patent applies asymmetry by making the anode substrate layer significantly thicker than the cathode substrate layer. Specifically, the anode substrate has a thickness of 0.5-2.0 mm while the cathode substrate has a thickness of 0.1-0.5 mm. This asymmetric design allows the anode side to accommodate the higher acid fill level (70-90% of void volume) required for improved fuel cell life and acid management, while the thinner cathode substrate maintains acceptable performance on the cathode side.
Solution Approach 2:
The patent applies local quality by giving different thickness specifications to different parts of the cell structure. The anode substrate is made locally thicker (0.5-2.0 mm) to handle acid storage and prevent expulsion, while the cathode substrate remains thinner (0.1-0.5 mm). This localized variation in substrate thickness optimizes acid management where needed without unnecessarily increasing the thickness of the entire cell assembly.
2Reliability
If the anode substrate layer is made thicker to prevent acid expulsion, then acid management is improved, but the power density decreases
Solution Approach 1:
The asymmetric substrate thickness design allows the anode side to have sufficient thickness (0.5-2.0 mm) to prevent acid expulsion and maintain reliable acid management, while the cathode side maintains thinner substrate (0.1-0.5 mm) to preserve power density. This asymmetric configuration balances the conflicting requirements of acid management reliability and power output.
Solution Approach 2:
The patent changes the thickness parameter of the anode substrate to a specific range (0.5-2.0 mm) that is sufficient to prevent acid expulsion while maintaining acceptable power density. The cathode substrate thickness is also optimized (0.1-0.5 mm) to maintain high power output. These parameter optimizations resolve the contradiction between acid management reliability and power density.
3Ease of manufacture
If conventional symmetric substrate thickness is used, then manufacturing is simpler, but acid distribution imbalance occurs leading to acid expulsion
Solution Approach 1:
The patent deliberately introduces asymmetry in substrate thickness to resolve the acid distribution imbalance problem. The anode substrate (0.5-2.0 mm) is made thicker than the cathode substrate (0.1-0.5 mm) to accommodate the higher acid fill level required for proper acid distribution. This asymmetric design prevents acid expulsion while the thickness specifications remain within standard manufacturing capabilities.
Solution Approach 2:
The patent applies local quality by making the anode substrate locally thicker to handle acid storage requirements, while keeping the cathode substrate thinner. This localized thickness variation addresses the acid distribution imbalance without requiring complete redesign of the entire cell structure, maintaining reasonable manufacturing simplicity while improving acid management reliability.
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 improves acid management and performance of the fuel cells by ensuring the acid fill level does not exceed the void volume, thereby extending the life and maintaining power density without increasing overall thickness or cost.
Implementation Method 1
Porosity need not be a factor, since the flow fields are both non-porous. The '232 cell has poorer electrolyte management characteristics which are the subject hereof.
Implementation Method 2
Graphite flow fields are not acceptable because they absorb a significant quantity of acid and thus reduce the life of the fuel cell.
Implementation Method 3
Porous anode substrate 16 and porous cathode substrate 17 are hydrophilic as is known in the art. The acid that is required for operation of the fuel cell, which must sustain the fuel cell for the life thereof, is ideally sealed within the fuel cell at the time of manufacture.
Implementation Method 4
The fuel cells (except at the ends or adjacent to cooler plates) share non-porous, hydrophobic separator plate assemblies 19 which include fuel channels 20 adjacent the anode substrate 16 and air (or other oxidant) channels 21 adjacent the cathode substrate 17.
Implementation Method 5
a fuel cell comprising a proton-conducting liquid electrolyte, such as phosphoric acid, or a mixture of phosphoric acid with either a fluorinated compound or siloxanes, or a liquid in which the anion is a fluoroborate or a fluoroheteroborate
Data Source
AI summary
A fuel cell (8a) having a matrix (11) for containing phosphoric acid (or other liquid) electrolyte with an anode catalyst (12) on one side and a cathode catalyst (13) on the other side includes an anode substrate (16a) in contact with the anode catalyst and a cathode substrate (17a) in contact with the cathode catalyst, the anode substrate being thicker than the cathode substrate by a ratio of between 1.75 to 1.0 and 3.0 to 1.0. Non-porous, hydrophobic separator plate assemblies (19) provide fuel flow channels (20) and oxidant flow channels (21) as well as demarcating the fuel cells.