Garnet Solid Electrolyte Single Crystals for Low Grain Boundary Resistance
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Solution Overview
Problem
Existing polycrystalline materials with a cubic garnet structure face challenges in achieving high ionic conductivity due to grain boundary resistance and interface resistance, making it difficult to produce high-density molded bodies for all-solid-state lithium-ion secondary batteries.
Innovation Solution
The production of Li7-3x-w-vGaxLa3Zr2-w-vTaWNbvO12 single crystals through a melting method, followed by mechanical thinning, results in a lithium composite oxide with improved ionic conductivity, achieving a relative density of 90% or more and belonging to a cubic system with a garnet structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polycrystalline materials with cubic garnet structure are used, then high ionic conductivity is achieved, but grain boundary resistance and interface resistance increase making it difficult to produce high-density molded bodies
Solution Approach 1:
The patent changes the manufacturing method from sintering to melting method, and uses excessive raw materials (excess Li, Ga, La, Zr, Ta, Nb) to ensure complete reaction and eliminate unreacted particles, achieving both high density and high ionic conductivity
Solution Approach 2:
The patent utilizes the melting phase transition of raw materials to form a liquid state during processing, then controls solidification to produce dense single crystals or polycrystals without grain boundary issues, thereby achieving high ionic conductivity
2Ease of manufacture
If sintering method is used to produce polycrystalline materials, then production is easier, but grain boundary resistance increases reducing ionic conductivity
Solution Approach 1:
The patent fundamentally changes the processing parameter from sintering temperature to melting temperature, and uses excessive raw materials to ensure complete reaction, producing dense structures without grain boundaries that would reduce ionic conductivity
Solution Approach 2:
The patent employs melting and solidification phase transitions to create a dense microstructure without grain boundaries, thereby maintaining high ionic conductivity while still using relatively simple processing steps
3Reliability
If high-density molded body is produced, then short circuits between electrodes are prevented, but manufacturing difficulty increases due to sintering challenges
Solution Approach 1:
The patent changes from sintering to melting method and uses excessive raw materials to ensure complete reaction and eliminate porosity, achieving high density that prevents short circuits while simplifying the manufacturing process
Solution Approach 2:
The patent uses melting and controlled solidification to produce fully dense structures without porosity, preventing electrode short circuits while avoiding the difficulties of achieving high density through sintering
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 produces lithium composite oxides with enhanced lithium ionic conductivity, reducing grain boundary resistance and enabling the production of high-density, thin pieces suitable for all-solid-state lithium-ion secondary batteries.
Implementation Method 1
a case of growing, by a melting method, a Li7-xLa3Zr2-xTaxO12 single crystal or a Li7-xLa3Zr2-xNbxO12 single crystal having a garnet structure has been reported
Data Source
AI summary
The lithium composite oxide single crystal has a chemical composition represented by Li7-3x-w-vGaxLa3Zr2-w-vTaWNbvO12 (0.02≤x<0.5, 0≤W≤1.0, 0≤V≤1.0, and 0.05≤W+V≤1.0), which belongs to a space group I-43d in a cubic system and has a garnet structure.