Zirconia Electrolyte Binder for SOFC Strength
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Solution Overview
Problem
Existing zirconia electrolytes used in solid oxide fuel cells (SOFCs) often lack sufficient strength, leading to instability and reduced durability due to inadequate binder properties, such as high carbon residue and pore generation when using polyvinyl butyral, and insufficient thermal decomposability with poly(meth)acrylic acid.
Innovation Solution
A zirconia electrolyte with improved strength is achieved by using a slurry containing a binder with a graft copolymer having a polyvinyl butyral main chain and a poly(meth)acrylic graft chain, where the amine value of the poly(meth)acrylic graft chain is between 1 mg KOH/g and 90 mg KOH/g, and the glass transition temperature of the poly(meth)acrylic graft chain is lower than 0°C, resulting in controlled pore distribution and high relative density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If polyvinyl butyral is used as a binder to increase green body strength, then green body strength is improved, but carbon residue increases and pores easily generate
Solution Approach 1:
The invention changes the chemical composition parameters of the binder by using a graft copolymer with specific amine value (1-90 mg KOH/g) and glass transition temperature (below 0°C), which modifies the thermal decomposition behavior to reduce carbon residue while maintaining green body strength
Solution Approach 2:
The invention uses a composite binder structure consisting of polyvinyl butyral main chain with poly(meth)acrylic graft chains, combining the strength-providing capability of polyvinyl butyral with the thermal decomposability of poly(meth)acrylic to achieve both high green body strength and low carbon residue
2Ease of manufacture
If poly(meth)acrylic acid is used as a binder to improve thermal decomposability, then thermal decomposability is improved, but green body strength becomes insufficient
Solution Approach 1:
The graft copolymer structure combines polyvinyl butyral main chain (providing strength) with poly(meth)acrylic graft chains (providing thermal decomposability), achieving a balance between green body strength and ease of manufacturing through sintering
3Reliability
If high strength is required for zirconia electrolyte to ensure SOFC durability, then durability is improved, but manufacturing complexity increases due to strict pore distribution control
Solution Approach 1:
The invention controls pore distribution by precisely controlling binder parameters (amine value and glass transition temperature), which simplifies the manufacturing process while achieving high strength and durability through uniform pore structure with standard deviation of 0.15 μm or less
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 zirconia electrolyte exhibits enhanced strength and durability, suitable for long-term stable operation of SOFCs, with a relative density of 99.0% or more and a standard deviation of pore numbers and diameters that contribute to improved mechanical properties.
Implementation Method 1
polyvinyl butyral binder, the strength of a green body, which is a precursor of the zirconia sinter, may be insufficient in some cases. It has been known that when polyvinyl butyral is used as a binder, a green body having relatively high strength can be obtained. However, when a ceramic sinter is produced with using a polyvinyl butyral binder, the strength of a green body becomes relatively high but an amount of a remaining carbon is large and pores easily generate.
Implementation Method 2
a binder for forming a ceramic green sheet and a binder for producing an inorganic sinter which binders contain a graft copolymer having a polyvinyl butyral unit and a poly(meth)acrylic unit.
Implementation Method 3
a zirconia slurry excellent in dispersion stability can be obtained with using a specific binder
Implementation Method 4
sintering the green body at room temperature to remove an organic component or the like
Data Source
Figure 1
AI summary
The objective of the present invention is to provide a zirconia electrolyte which has high strength and which is suitable for a solid electrolyte layer of a solid oxide fuel cell, and a method for producing a zirconia electrolyte having high strength. The zirconia electrolyte according to the present invention is characterized in essentially consisting of zirconia stabilized by one or a plurality of oxides of rare earth selected from the group of scandium, yttrium, cerium, gadolinium and ytterbium, wherein a standard deviation of pore numbers in 10 or more regions having an area of 50 µm2 and not overlapping with each other on a fracture surface is 2.5 or more.