Solid Electrolyte Grain Boundary Resistance Reduction
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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 using lithium lanthanum zirconate-based materials, due to insufficient contact between particles and composition changes during high-temperature sintering.
Innovation Solution
A solid electrolyte represented by the formula Li7-x-yLa3(Zr2-x-yInxMy)O12, where 0.00<x<0.20 and 0.20≤y<1.50, with M being Nb, Ta, or Sb, is produced through a method involving mixing, first heating to form a calcined body, and a second heating step to achieve a crystalline structure, effectively reducing grain boundary resistance and maintaining desired physical properties at lower temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solid electrolyte particles are sintered 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 Zr4+ ions with In3+ ions and M3+ ions (where M is Al, Ga, or Sc) in specific ratios. This compositional modification lowers the sintering temperature from 1000°C or higher to 900°C or lower, enabling particle fusion at reduced temperatures that preserve composition stability while achieving low grain boundary resistance
Solution Approach 2:
The patent creates a composite solid electrolyte material by combining multiple elements (Li, La, Zr, In, and M where M is Al, Ga, or Sc) in a specific formula Li7-x-yLa3(Zr2-x-yInxMy)O12. This multi-element composite structure enables simultaneous achievement of low sintering temperature and low grain boundary resistance, resolving the contradiction between reducing grain boundary resistance and maintaining composition stability
2Shape
If solid electrolyte particles are compression molded to desired shape, then molded body is obtained, but contact between particles is insufficient leading to high grain boundary resistance and low lithium ion conductivity
Solution Approach 1:
The patent modifies the physical and chemical parameters of the solid electrolyte particles through compositional substitution, which enhances particle sinterability. This enables effective particle contact and fusion during compression molding at lower temperatures, significantly reducing grain boundary resistance and improving lithium ion conductivity while maintaining the desired molded body shape
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 exhibits excellent bulk lithium ion conductivity and low grain boundary resistance, even when co-fired with active materials like lithium cobalt oxide, preventing interdiffusion and maintaining conductivity, thus enhancing battery performance and safety.
Implementation Method 1
A solid electrolyte can conduct lithium ions without the use of an organic electrolyte solution
Implementation Method 2
a second heating step for subjecting the calcined body to a second heat treatment to form a crystalline solid electrolyte represented by the following formula (1)
Data Source
AI summary
The solid electrolyte according to an embodiment of the present disclosure is represented by the following formula (1):Li7-x-yLa3(Zr2-x-yInxMy)O12 (1)wherein 0.00<x<0.20, 0.20≤y<1.50, M is two or more elements selected from the group consisting of Nb, Ta, and Sb.