Garnet Solid Electrolyte 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 at low firing temperatures, leading to reduced lithium ion conductivity and stability issues when co-fired with active materials.
Innovation Solution
A solid electrolyte with the compositional formula Li7−x+y(La3−ySry)(Zr2−xMx)O12, where x satisfies 0.20≤x<1.50 and 0.00<y<0.30, and M is selected from Nb, Ta, and Sb, is produced using a method involving mixing raw materials, followed by calcination and crystallization at lower temperatures to form a garnet-type crystal structure, which enhances lithium ion conductivity and suppresses mutual diffusion with active materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solid electrolyte particles are compression molded at high temperature (1000°C or higher) to reduce grain boundary resistance, then lithium ion conductivity is improved, but formulation changes occur and production of solid electrolyte molded body with desired physical properties becomes difficult
Solution Approach 1:
The patent changes the compositional parameters by substituting Zr with Nb, Ta, or Sb elements and adjusting the Li content according to the specific formula Li7-x+y(La3-ySry)(Zr2-xMx)O12. This compositional parameter change enables sintering at lower temperatures (900-1000°C) while maintaining formulation stability and achieving sufficient lithium ion conductivity without the formulation changes that occur at higher temperatures.
Solution Approach 2:
The patent creates a composite solid electrolyte material by combining multiple elements (Li, La, Sr, Zr, and dopants Nb/Ta/Sb) in a garnet-type crystal structure. This composite material approach allows the solid electrolyte to achieve both low grain boundary resistance and formulation stability at lower sintering temperatures, resolving the contradiction between conductivity improvement and formulation stability.
2Stability of the object's composition
If solid electrolyte particles are compression molded without high temperature sintering, then formulation stability is maintained, but grain boundary resistance becomes high and lithium ion conductivity decreases
Solution Approach 1:
The patent modifies the compositional parameters by introducing specific dopants (Nb, Ta, or Sb) at controlled concentrations and adjusting Li content. These parameter changes reduce the sintering temperature requirement while maintaining formulation stability, enabling the solid electrolyte to achieve low grain boundary resistance without high-temperature processing that would cause formulation changes.
Solution Approach 2:
The patent applies local quality by creating a garnet-type crystal structure with specific elemental distribution and substitution patterns. This local structural optimization at the grain boundary regions reduces grain boundary resistance while maintaining overall formulation stability, allowing good lithium ion conductivity without high-temperature sintering.
3Reliability
If conventional solid electrolyte materials are used, then high lithium ion conductivity is achieved, but mutual diffusion with active materials occurs during co-firing causing degradation of conductivity
Solution Approach 1:
The patent develops a composite solid electrolyte material with a garnet-type crystal structure containing Li, La, Sr, Zr, and dopant elements (Nb, Ta, or Sb). This composite material design provides both high lithium ion conductivity and compositional stability during co-firing with active materials, preventing mutual diffusion and degradation that occur with conventional solid electrolyte materials.
Solution Approach 2:
The patent changes the compositional parameters by optimizing the ratios of Li, La, Sr, Zr, and dopant elements according to the formula Li7-x+y(La3-ySry)(Zr2-xMx)O12. This parameter optimization enhances the material's resistance to mutual diffusion during co-firing while maintaining high lithium ion conductivity, resolving the contradiction between conductivity and compositional stability.
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 provides a solid electrolyte with excellent bulk lithium ion conductivity and low grain boundary resistance at a low firing temperature, effectively preventing the degradation of lithium ion conductivity when co-fired with active materials like lithium cobalt oxide.
Implementation Method 1
a solid electrolyte for lithium conduction between positive and negative electrodes
Implementation Method 2
a first heating step of subjecting the mixture to a first heating treatment thereby forming a calcined body; and a second heating step of subjecting the calcined body to a second heating treatment thereby forming a crystalline solid electrolyte
Implementation Method 3
forming a crystalline solid electrolyte represented by the following compositional formula (1)
Data Source
AI summary
A solid electrolyte according to the present disclosure is represented by the following compositional formula (1).Li7−x+y(La3−ySry)(Zr2−xMx)O12 (1)In the formula (1), x and y satisfy 0.20≤x<1.50 and 0.00<y<0.30, and M is two or more types of elements selected from the group consisting of Nb, Ta, and Sb.