Garnet Solid Electrolyte Porosity and Conductivity
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Solution Overview
Problem
Conventional solid electrolytes with a Li—La—Zr garnet phase and Li2+xC1−xBxO3 phase have low ionic conductivity and struggle to maintain porosity during the sintering process, leading to high relative density and decreased conductivity.
Innovation Solution
A method involving the use of fine particles made of garnet-type oxide and lithium hydroxide as a sintering aid, sintered at a low temperature to produce a sintered body with porosity and high ionic conductivity, where lithium hydroxide decomposes to Li2O and Li2CO3, promoting neck growth and retaining fine crystal grains.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional sintering process is used to manufacture solid electrolyte, then sintered body is obtained, but porosity is lost and relative density becomes high leading to decreased conductivity
Solution Approach 1:
The patent applies parameter changes by conducting sintering at a low temperature (900°C or less) compared to conventional high-temperature sintering. This temperature parameter change prevents excessive densification while still achieving sufficient bonding, thereby maintaining porosity (8% by volume or more) and preserving ionic conductivity (1.0×10−5 S/cm or more at 25°C).
Solution Approach 2:
The patent intentionally maintains a porous structure in the sintered body by using fine particles (0.1 μm or more and 5 μm or less) and low-temperature sintering. The resulting sintered body has 8% by volume or more porosity, which provides pathways for ion transport and maintains high ionic conductivity while avoiding the density increase that would occur with conventional sintering.
2Reliability
If fine particles are used to maintain porosity, then ionic conductivity is improved, but sintering becomes more difficult due to particle aggregation
Solution Approach 1:
The patent applies preliminary action by pre-synthesizing fine garnet-type oxide particles (0.1 μm or more and 5 μm or less) with controlled morphology and composition before sintering. This preliminary preparation ensures that the fine particles have appropriate surface characteristics and packing behavior, enabling successful low-temperature sintering without excessive aggregation while maintaining the desired porous structure and high ionic conductivity.
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 method achieves a sintered body with 8% or more void volume and ionic conductivity of 1.0×10−5 S/cm at 25° C., effectively suppressing the decrease in conductivity while maintaining a dense skeletal structure.
Implementation Method 1
lithium hydroxide decomposes to Li2O and Li2CO3, promoting neck growth and retaining fine crystal grains
Implementation Method 2
a molded body formed of the particles is sintered at 1130° C. for 18 minutes
Implementation Method 3
heat-treated at 900° C. for 2 hours to obtain a sintered body having a density of 95% by volume
Data Source
AI summary
The sintered body has an average particle size in the range of 0.1 μm or more and 5 μm or less, includes gamet-type oxide base material particles having at least Li, La, and Zr, has 8% by volume or more of voids, and has an ionic conductivity of 1.0×10−5 S/cm or more at temperature of 25° C.