Garnet Solid Electrolyte Composition for Low Grain Boundary Resistance
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Solution Overview
Problem
Current solid electrolytes for all-solid-state lithium batteries face challenges in achieving low grain boundary resistance and high lithium ion conductivity at low firing temperatures, particularly when used with active materials like lithium cobalt oxide, due to interdiffusion issues.
Innovation Solution
A solid electrolyte represented by the formula Li7−x+y(La3−yBay)(Zr2−xMx)O12, where 0.20≤x<1.50 and 0.00<y<0.30, with M being Nb, Ta, or Sb, is produced using a method involving mixing, first heating, and second heating steps to form a crystalline structure, which reduces grain boundary resistance and maintains lithium ion conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solid electrolyte particles are subjected to compression molding and sintering at high temperature (1000°C or higher) to fuse particles together, then grain boundary resistance is reduced, but composition changes due to high heat making it difficult to produce molded body with desired physical property
Solution Approach 1:
The patent changes the chemical composition parameters of the solid electrolyte by substituting specific elements (M = Nb, Ta, or Sb) at controlled ratios (0.20 ≤ x < 1.50, 0.00 < y ≤ 0.30) into the lithium lanthanum zirconate structure. This compositional modification lowers the sintering temperature requirement while maintaining composition stability during the sintering process, resolving the contradiction between reducing grain boundary resistance and preventing composition change.
Solution Approach 2:
The patent creates a composite solid electrolyte material by combining lithium lanthanum zirconate with substituted elements (Nb, Ta, or Sb) in specific ratios. This composite structure achieves both low grain boundary resistance and composition stability during sintering, as the substituted elements work synergistically to enable low-temperature processing while maintaining structural integrity.
2Shape
If solid electrolyte particles are molded by compression molding, then desired shape is achieved, but contact between particles is insufficient leading to high grain boundary resistance
Solution Approach 1:
The patent modifies the physical and chemical parameters of the solid electrolyte particles through elemental substitution, which enhances particle sinterability and contact formation during low-temperature sintering. This allows the molded shape to be maintained while achieving sufficient particle contact and low grain boundary resistance simultaneously.
3Temperature
If substitution is made to develop material suitable for low temperature sintering, then sintering temperature is reduced, but solid electrolyte with sufficiently low grain boundary resistance at sufficiently low firing temperature has not been obtained
Solution Approach 1:
The patent systematically adjusts the compositional parameters by controlling the substitution ratios of M (Nb, Ta, Sb) and La (0.20 ≤ x < 1.50, 0.00 < y ≤ 0.30), which enables sintering at lower temperatures while achieving sufficiently low grain boundary resistance. The specific compositional range identified in the patent provides the optimal balance between sintering temperature and grain boundary resistance.
Solution Approach 2:
The patent develops a composite solid electrolyte material with specific compositional ratios that enable low-temperature sintering while maintaining low grain boundary resistance. The synergistic effect of the substituted elements creates a material structure that achieves both low processing temperature and low grain boundary resistance, resolving the contradiction between these two parameters.
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 proposed solid electrolyte achieves excellent bulk lithium ion conductivity and low grain boundary resistance at a sufficiently low firing temperature, effectively suppressing interdiffusion with active materials, thereby enhancing the performance and reliability of lithium batteries.
Implementation Method 1
a solid electrolyte for lithium ion conduction between the cathode and the anode
Implementation Method 2
a first heating step for subjecting the mixture to a first heat treatment to form a calcined body, and a second heating step for subjecting the calcined body to a second heat treatment to form a crystalline solid electrolyte
Data Source
AI summary
A solid electrolyte represented by the following formula (1): Li7−x+y(La3−yBay)(Zr2−xMx)O12(1), wherein 0.20≤x<1.50, 0.00<y<0.30, and M is two or more elements selected from the group consisting of Nb, Ta, and Sb.