Gradient Sr/Ba Proton Electrolyte for Low-Resistance Fuel Cells
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Solution Overview
Problem
Proton-conductive metal oxides like Yttrium-doped barium zirconate (BZY) and Yttrium-doped strontium zirconate (SZY) face issues with hole conduction, leading to decreased electromotive force and high resistance, which are detrimental for medium-temperature fuel cells and steam electrolysis cells.
Innovation Solution
A proton-conductive cell structure with a solid electrolyte layer made of a metal oxide with a perovskite structure, represented by Ba x1 Sr x2 A 1-y M y O 3-δ, where Element A is Zr, Ce, or Hf, and Element M is Y, Yb, Er, Ho, Tm, Gd, In, or Sc, with a specific gradient of Sr/Ba ratio across the layer to enhance ion transport number while maintaining low resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If proton-conductive metal oxides like BZY or SZY are used as solid electrolytes, then proton conductivity is achieved, but hole conduction occurs leading to decreased electromotive force and high resistance
Solution Approach 1:
The patent applies local quality by creating a composition gradient within the solid electrolyte layer, where the Sr/Ba ratio varies from the air electrode side to the hydrogen electrode side. This gradient structure allows different regions of the electrolyte to have optimized properties: the air electrode side has lower Sr content to suppress hole conduction, while the hydrogen electrode side has higher Sr content to enhance proton conductivity, thus resolving the contradiction between achieving high proton conductivity and suppressing harmful hole conduction.
Solution Approach 2:
The patent uses composite materials by combining barium zirconate and strontium zirconate in a gradient composition within the same electrolyte layer. This composite approach allows the electrolyte to simultaneously exhibit regions with different properties - suppressing hole conduction in Sr-poor regions while maintaining high proton conductivity in Sr-rich regions, thereby resolving the technical contradiction.
2Reliability
If Sr content is increased in the solid electrolyte to improve ion transport number, then proton conductivity increases, but resistance increases
Solution Approach 1:
The patent resolves this contradiction by implementing local quality through a spatial gradient of Sr content. The hydrogen electrode side has high Sr content (x2 ≥ 0.4) to maximize ion transport number, while the air electrode side has lower Sr content to minimize resistance. This localized optimization allows the electrolyte to achieve high ion transport number near the hydrogen electrode while maintaining acceptable resistance through the lower-Sr region near the air electrode.
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 solution achieves a high ion transport number and low resistance, suitable for fuel cells and steam electrolysis cells, by optimizing the Sr/Ba ratio in the solid electrolyte layer, thereby improving both efficiency and output.
Implementation Method 1
a solid electrolyte layer disposed between the air electrode and the hydrogen electrode. The solid electrolyte layer at least includes a first solid electrolyte layer formed of a compact material, the first solid electrolyte layer includes a metal oxide having a perovskite structure and represented by Formula (1)... achieves a high ion transport number and low resistance
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A proton-conductive cell structure includes an air electrode, a hydrogen electrode, and a solid electrolyte layer disposed between the air electrode and the hydrogen electrode, wherein the solid electrolyte layer includes at least a first solid electrolyte layer formed of a compact material. The first solid electrolyte layer includes a metal oxide having a perovskite structure and represented by Formula 1 below, a ratio of Sr to a total amount of Ba and Sr in an air-electrode-side near-surface region of the first solid electrolyte layer is 0.4 or more, and a ratio of Sr to a total amount of Ba and Sr in a hydrogen-electrode-side near-surface region of the first solid electrolyte layer is 0.003 to 0.3. Bax1Srx2A1-yMyO3 - δ (1)