Crystalline-Coated Cell Stack Separator for Corrosion Resistance
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Solution Overview
Problem
Conventional separators in electrochemical cell stacks, especially those made of metal, face challenges with corrosion due to defects in the corrosion-resistant films, leading to a short operating life.
Innovation Solution
A separator design featuring a metal substrate with a corrosion-resistant film formed of crystals, where the arithmetic average roughness (Ra) and maximum height roughness (Rz) at the film surfaces are smaller than the crystal particle size, reducing defects and enhancing corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If a metal material is used for the separator to reduce weight, then the weight is reduced, but the corrosion resistance deteriorates due to low resistance to acid
Solution Approach 1:
The separator employs a composite structure combining a metal substrate (aluminum, aluminum alloy, or stainless steel) with a corrosion-resistant film layer (Ti, Ta, TiN, TaN, TiC, or TaC). This composite material approach allows the separator to achieve both lightweight properties from the metal substrate and corrosion resistance from the protective film, resolving the contradiction between weight reduction and corrosion resistance.
2Reliability
If a corrosion-resistant film is provided on the metal substrate to improve corrosion resistance, then the corrosion resistance is improved, but defects such as pinholes and cracks are generated in the film
Solution Approach 1:
The patent specifies precise parameter ranges for the corrosion-resistant film: thickness of 1 nm to 100 nm, arithmetic average roughness Ra of 0.01 μm or less, and maximum height roughness Rz of 0.1 μm or less. By controlling these parameters, the film achieves sufficient corrosion protection while minimizing defects. The roughness control ensures the film remains free of pinholes and cracks that would compromise integrity.
3Reliability
If the separator is made of carbon material with high acid resistance, then the corrosion resistance is improved, but the weight cannot be reduced due to the fragile nature of carbon material
Solution Approach 1:
The invention replaces pure carbon materials with a composite of metal substrate and corrosion-resistant film. The metal substrate (aluminum or stainless steel) provides mechanical strength and flexibility enabling thin-section construction, while the corrosion-resistant film layer (Ti, Ta, or their compounds) provides acid resistance comparable to or exceeding carbon materials. This composite approach achieves both weight reduction and acid resistance.
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 proposed separator configuration effectively suppresses the generation of defects in the corrosion-resistant film, thereby improving corrosion resistance and extending the operating life of the electrochemical cell stack while reducing its weight.
Implementation Method 1
a corrosion-resistant film which is formed of crystals of a corrosion-resistant material
Data Source
AI summary
A separator of an embodiment is a separator of an electrochemical cell stack obtained by stacking a cell including a polymer electrolyte membrane, an anode electrode, and a cathode electrode, and the separator. The separator includes a substrate formed of a metal material, and a corrosion-resistant film formed on a surface on the anode electrode side of the substrate and a surface on the cathode electrode side of the substrate, and formed of crystals of a corrosion-resistant material. An arithmetic average roughness Ra and a maximum height roughness Rz at the surface of the substrate are smaller than a particle size of the crystals.