Multilayered Proton-Conducting Electrolyte for Fuel Cells
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Solution Overview
Problem
Proton-conducting ceramic electrolytes for fuel cells face challenges with high sintering temperatures that degrade conductivity and chemical instability, particularly for Yttrium-doped barium cerate (BCY) when exposed to CO2 and water.
Innovation Solution
A multilayered composite electrolyte film comprising dense Yttrium-doped barium zirconate (BZY) and BCY layers with an interfacial solid solution (BZCY) is used, where BZY acts as a barrier to protect BCY from detrimental contact, enhancing conductivity and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high sintering temperature (≥1600°C) is used to obtain high density BZY, then grain boundary resistivity decreases and total conductivity increases, but chemical reactions with electrodes are promoted and barium oxide evaporation accelerates
Solution Approach 1:
A BZY interfacial layer is introduced between the BCY electrolyte layer and the electrode to act as a protective barrier. This intermediary layer prevents direct contact between the electrode and BCY, thereby preventing harmful chemical reactions while allowing the BCY layer to be sintered at lower temperatures (≤1400°C) to maintain its high proton conductivity.
Solution Approach 2:
The invention uses a composite electrolyte structure consisting of multiple layers: a BZY layer in contact with the electrode, a BCY layer providing high conductivity, and an interfacial BZY layer between them. This composite structure combines the chemical stability of BZY with the high conductivity of BCY, resolving the contradiction between conductivity and chemical stability.
2Reliability
If high sintering temperature (≥1600°C) is used to obtain high density BZY, then grain growth increases and grain boundary conductivity improves, but barium oxide evaporation accelerates degrading electrolyte conductivity
Solution Approach 1:
The BZY interfacial layer serves as a protective barrier that prevents barium oxide evaporation from the BCY layer during sintering. By placing BZY (which has lower barium oxide volatility) between the BCY and the environment, the harmful evaporation is prevented while the BCY layer can still achieve adequate densification at lower temperatures.
Solution Approach 2:
The invention changes the sintering temperature parameter from high (≥1600°C) to lower (≤1400°C) by using the composite structure. This parameter change is made possible because the BZY interfacial layer provides the necessary protection against barium oxide loss, allowing the BCY layer to be processed at temperatures where barium oxide evaporation is minimized.
3Reliability
If Yttrium-doped barium cerate (BCY) is used to achieve high total conductivity, then transport properties improve, but chemical stability toward CO2 and water deteriorates
Solution Approach 1:
A BZY layer is positioned between the BCY electrolyte and the fuel cell environment (where CO2 and water are present). This BZY layer acts as a protective barrier that is chemically stable toward CO2 and water, preventing their contact with the BCY layer while allowing protons to conduct through the BCY layer, thus maintaining high conductivity while improving chemical stability.
Solution Approach 2:
The electrolyte is designed as a composite structure with BCY providing high proton conductivity and BZY providing chemical stability. The multi-layer composite combines the advantageous properties of both materials: BCY's high conductivity and BZY's stability toward CO2 and water, thereby resolving the contradiction between these two properties.
4Stability of the object's composition
If Yttrium-doped barium zirconate (BZY) is used to achieve high density, then chemical stability improves, but sintering temperature requirement increases to ≥1600°C
Solution Approach 1:
The BZY interfacial layer serves as a protective barrier that enables the BCY layer to be sintered at lower temperatures (≤1400°C). The BZY layer's chemical stability and resistance to barium oxide evaporation allow the BCY layer to achieve adequate densification at lower temperatures without direct exposure to the harsh sintering environment, thus reducing the required sintering temperature while maintaining chemical stability.
Solution Approach 2:
The composite structure allows the BCY layer to benefit from BZY's protective properties during sintering. The BZY interfacial layer creates a protected environment that enables lower temperature processing of the BCY layer, thereby reducing the overall sintering temperature requirement while maintaining the chemical stability provided by the BZY component.
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 multilayer design maintains high proton conductivity and chemical stability, enabling stable operation in intermediate temperature fuel cells while avoiding the chemical instability of BCY when exposed to CO2 and water.
Implementation Method 1
The BZY layer acts as a barrier to protect the BCY layer from detrimental contact with CO2 and H2O
Implementation Method 2
The interfacial layer is a solid solution of the BZY and BCY electrolytes, also referred to herein as 'BZCY'. The solid solution is formed from the reaction of the BZY and BCY layers during sintering
Implementation Method 3
The electrolyte film is supported on a porous anode substrate forming a layered assembly
Data Source
AI summary
The present invention provides a multilayer anode/electrolyte assembly comprising a porous anode substrate and a layered solid electrolyte in contact therewith. The layered solid electrolyte includes a first dense layer of yttrium-doped barium zirconate (BZY), optionally including another metal besides Y, Ba, and Zr (e.g., a lanthanide metal such as Pr) on one surface thereof, a second dense layer of yttrium-doped barium cerate (BCY), and an interfacial layer between and contacting the BZY and BCY layers. The interfacial layer comprises a solid solution of the BZY and BCY electrolytes. The porous anode substrate comprises at least one porous ceramic material that is stable to carbon dioxide and water (e.g., porous BZY), as well as an electrically conductive metal and/or metal oxide (e.g., Ni, NiO, and the like).