Garnet Solid Electrolyte Composition for Low-Temperature Co-Firing
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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 Li7-2x-zLa3(Zr2-x-zWxMz)O12, where 0.10≤x≤0.60 and 0.00<z≤0.25, and M is at least one of Nb, Ta, or Sb, is produced using a method involving mixing raw materials, followed by calcination and crystallization at lower temperatures, which enhances bulk 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 the formulation is likely to change and it becomes difficult to produce a solid electrolyte molded body having desired physical properties
Solution Approach 1:
The patent changes the chemical composition parameters of the solid electrolyte by substituting Zr4+ ions with W6+ ions and M5+ ions (Nb, Ta, or Sb) in specific proportions. This compositional modification enables the material to achieve low grain boundary resistance at lower firing temperatures (900-1000°C) while maintaining formulation stability, as the specific substitution ratios prevent excessive formulation changes during the heating process.
Solution Approach 2:
The patent creates a composite solid electrolyte material by combining multiple elements (Li, La, Zr, W, and M where M is Nb, Ta, or Sb) in a specific compositional formula. This multi-element composite structure synergistically reduces grain boundary resistance and stabilizes the formulation during heating, allowing simultaneous achievement of high lithium ion conductivity and compositional stability at practical firing temperatures.
2Manufacturing precision
If solid electrolyte particles are compression molded and sintered at high temperature to reduce grain boundary resistance, then contact between particles is improved, but the firing temperature must be very high (1000°C or higher) which causes formulation change
Solution Approach 1:
The patent modifies the chemical composition by introducing W6+ and M5+ ion substitutions, which fundamentally changes the sintering behavior of the material. This compositional parameter change enables achieving satisfactory grain boundary resistance at lower firing temperatures (900-1000°C) compared to conventional materials that require 1000°C or higher, thus reducing the thermal stress and formulation changes during processing.
Solution Approach 2:
The patent applies local quality improvement by specifically targeting the grain boundary regions through compositional modification. The substitution of Zr4+ with W6+ and M5+ ions creates localized chemical environments that reduce grain boundary resistance, allowing effective sintering at lower temperatures without requiring uniform high-temperature treatment throughout the entire material structure.
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 reduced firing temperatures, 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
a second heating step of subjecting the calcined body to a second heating treatment thereby forming a crystalline solid electrolyte
Data Source
AI summary
A solid electrolyte according to the present disclosure is represented by the following compositional formula (1).Li7-2x-zLa3(Zr2-x-zWxMz)O12 (1)In the formula (1), x and z satisfy 0.10≤x≤0.60 and 0.00<z≤0.25, and M is at least one type of element selected from the group consisting of Nb, Ta, and Sb.