SOEC Glass Sealant Composition for Thermal Stress Reduction
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Solution Overview
Problem
Solid oxide electrolysis cell (SOEC) stacks face issues with cracking due to thermal expansion coefficient discrepancies between sealants and other components, leading to malfunction and degradation during thermal cycling, and existing sealants often result in gas leakage and reactivity with cell materials.
Innovation Solution
A glass sealant with a composition of 50 to 70 wt % SiO2, 0 to 20 wt % Al2O3, 10 to 50 wt % CaO, 0 to 10 wt % MgO, 0 to 2 wt % (Na2O+K2O), 0 to 10 wt % B2O3, and 0 to 5 wt % of functional elements, applied as a thin sheet of glass fibers, is used to create a gas-tight sealant with a lower thermal expansion coefficient, reducing tensile stress and maintaining stability over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a glass sealant with high thermal expansion coefficient (11 to 13·10−6K−1) is used to match the TEC of interconnect plates and electrolyser cells, then thermal expansion compatibility is improved, but the sealant becomes reactive with cell materials and causes gas leakage
Solution Approach 1:
The patent changes the thermal expansion coefficient parameter of the glass sealant by modifying its chemical composition (reducing Al2O3 to 0-20 wt%, CaO to 10-50 wt%, SiO2 to 50-70 wt%) to achieve a lower TEC (5 to 10·10−6K−1) that prevents both cracking and chemical reactivity with cell materials
Solution Approach 2:
The patent uses a composite glass sealant formulation combining multiple oxides (SiO2, Al2O3, CaO, MgO, B2O3) in specific proportions to achieve the desired balance between thermal expansion properties and chemical stability, creating a material that is neither too reactive nor too expansive
2Strength
If the sealant thickness is reduced to minimize tensile stress from TEC discrepancies, then cracking resistance is improved, but manufacturing precision and thickness control become more difficult
Solution Approach 1:
The patent optimizes the thickness parameter of the glass sealant layer to a specific range (5 to 100 μm) that is thin enough to minimize tensile stress and prevent cracking, yet thick enough to maintain gas tightness and allow for practical manufacturing tolerances
3Reliability
If a conventional glass sealant composition is used to ensure gas tightness, then sealing effectiveness is improved, but the sealant reacts with cell materials causing Si-poisoning and degradation
Solution Approach 1:
The patent changes the chemical composition parameters of the glass sealant by limiting Al2O3 to 0-20 wt% and CaO to 10-50 wt%, which reduces the sealant's chemical reactivity with cell materials while maintaining its gas sealing effectiveness through the optimized oxide composition
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 solution effectively prevents cracking and gas leakage, maintains low reactivity with cell components, and allows for faster production with improved thickness tolerance, while maintaining electrical isolation and reducing manufacturing costs.
Implementation Method 1
The high operating temperature and thermal cycling of an SOEC stack require that the interconnect plates are made of materials which have a TEC similar to that of the fuel cell units. Another source of tensile stress which is difficult to avoid results from the discrepancy in TEC of the sealant
Implementation Method 2
If the tensile stress exceeds the tensile strength of the fuel cell, it cracks, and the whole SOEC stack suffers from a malfunction. The sealant must be inert to corrosion in order to avoid Si-poisoning on the reducing side of the cells
Data Source
AI summary
Solid oxide electrolysis cell (SOEC) stack obtainable by a process comprising the use of a glass sealant with composition 50 to 70 wt % SiO2, 0 to 20 wt % Al2O3, 10 to 50 wt % CaO, 0 to 10 wt % MgO, 0 to 2 wt % (Na2o 1K2O), 0 to 10 wt % b2O3, and 0 to 5 wt % of functional elements selected from TiO2, ZrO2, ZrO2, F, P2O5, Mo03, FeO3, MnO 2, La—Sr—Mn—O perovskite (LSM) and combinations thereof. Preferably, the sealant is a sheet of E-glass fibers with a composition in wt % of 52-56 SiO2, 12-16AL2O3, 16-25 CaO, 0-6MgO, 0-2 Na2+K2O, 0-10 B2O3, 0-1.5 TiO2, O-1F.