Solid Electrolyte Surface Modification for All-Solid-State Battery
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Solution Overview
Problem
Solid electrolytes like LaLiTiO, when in a powder state, exhibit high intergranular resistance and low ionic conductivity, leading to high internal resistance and inadequate output characteristics in all-solid-state secondary batteries, which worsens with high-temperature sintering that can cause electrode decomposition.
Innovation Solution
A solid electrolyte with a surface-modified structure, achieved through hydrogen heat treatment, sulfurization, and surface oxidation, reduces intergranular resistance and enhances ionic conductivity without high-temperature sintering, using a composition like La0.55Li0.33TiO3 with sulfur coupled to an oxygen-deficient portion, allowing compaction molding at room temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-temperature sintering is performed to reduce intergranular resistance, then ionic conductivity between particles is improved, but electrode material suffers from decomposition and solid solution
Solution Approach 1:
The solid electrolyte surface is preliminarily modified through hydrogen heat treatment to create an oxygen-deficient portion, followed by sulfurization to form a sulfur-containing layer. This preliminary surface treatment reduces intergranular resistance before battery assembly, eliminating the need for high-temperature sintering that would decompose electrode materials.
Solution Approach 2:
The invention changes the chemical composition parameters of the solid electrolyte surface by introducing sulfur through controlled sulfurization. This parameter change (adding sulfur to create oxygen-deficient regions) fundamentally alters the intergranular resistance characteristics, enabling low resistance without high-temperature processing.
2Ease of manufacture
If solid electrolyte is used in powder state, then all-solid-state battery fabrication is simplified, but intergranular resistance becomes very high and ionic conductivity is low
Solution Approach 1:
The solid electrolyte particles undergo preliminary surface modification (hydrogen heat treatment and sulfurization) while in powder state before battery assembly. This preliminary action creates oxygen-deficient portions and sulfur-containing regions on particle surfaces, enabling good ionic conductivity to be achieved even without high-temperature sintering, thus maintaining ease of manufacture while improving reliability.
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
This approach decreases intergranular resistance and increases ionic conductivity from 10^-8 S/cm to 10^-5 S/cm, enabling the fabrication of all-solid-state secondary batteries with reduced internal resistance and improved output characteristics without high-temperature sintering, preventing electrode degradation.
Implementation Method 1
a solid electrolyte material La0.55Li0.33TiO3 is reduced by heat treatment with hydrogen gas
Implementation Method 2
sulfurization is then performed on the solid electrolyte material having the oxygen-deficient portion, thereby to couple sulfur (S) to the oxygen-deficient portion
Implementation Method 3
surface oxidation is performed on the solid electrolyte material in which at least a surface portion of the sulfur-containing region is formed
Data Source
Figure 1
Figure 2
Figure 3A~3D
AI summary
A solid electrolyte (3) includes a particle (3X) having a first portion (3A) that includes, as constituent elements, lanthanum (La), lithium (Li), titanium (Ti) and oxygen (O), and a second portion (3B) that covers a surface of the first portion and includes, as constituent elements, lanthanum (La), lithium (Li), titanium (Ti) and oxygen (O) and in which sulfur (S) is coupled to an oxygen deficient portion and at least a surface (3C) is oxidized.