Argyrodite Sulfide Solid Electrolyte With Polyanions for Heat Stability
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Solution Overview
Problem
Sulfide solid electrolytes containing argyrodite crystals face limitations in achieving high lithium ion conductivity due to grain boundary resistance, which decreases with high-temperature heat treatment leading to thermal decomposition.
Innovation Solution
Incorporating a polyanionic structure with an oxide anion having a P—O bond, separate from the anion constituting the argyrodite crystal, to enhance heat resistance and reduce grain boundary resistance without thermal decomposition, achieved by specific composition and production methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-temperature heat treatment is performed to reduce grain boundary resistance, then lithium ion conductivity is improved, but thermal decomposition occurs
Solution Approach 1:
The invention changes the chemical composition parameters by introducing oxide anions with P—O bonds at grain boundaries. This compositional modification allows the material to maintain structural integrity at temperatures where conventional argyrodite crystals would decompose, thereby enabling heat treatment without thermal decomposition while reducing grain boundary resistance and improving lithium ion conductivity.
Solution Approach 2:
The invention creates a composite structure by combining argyrodite crystals with oxide anions containing P—O bonds at the grain boundaries. This composite approach integrates the high lithium ion conductivity of argyrodite with the thermal stability of oxide-containing phases, resolving the contradiction between achieving high conductivity through heat treatment and preventing thermal decomposition.
2Reliability
If heat treatment is performed to reduce grain boundary resistance, then lithium ion conductivity increases, but the argyrodite crystal decomposes
Solution Approach 1:
The invention modifies the chemical composition by incorporating oxide anions with P—O bonds into the grain boundary regions. This compositional change raises the thermal stability threshold, allowing heat treatment processes to proceed at temperatures that effectively reduce grain boundary resistance without reaching the decomposition point of the argyrodite crystal structure.
Solution Approach 2:
The oxide anions with P—O bonds act as intermediary species at the grain boundaries, mediating between the heat treatment process and the argyrodite crystal structure. These intermediary oxide-containing phases protect the argyrodite crystals from direct thermal decomposition while still allowing the heat treatment to reduce grain boundary resistance and improve lithium ion conductivity.
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 approach results in a sulfide solid electrolyte with improved heat resistance and high lithium ion conductivity, suitable for lithium-ion secondary batteries, maintaining performance even after heat treatment.
Implementation Method 1
the anion includes an oxide anion having a P—O bond in which P and O are bonded
Implementation Method 2
when the heat treatment is performed at a high temperature of about 600° C., the argyrodite crystal thermally decomposes into Li2S, LiCl, and Li3PS4
Implementation Method 3
reduction of the grain boundary resistance due to the sintering
Data Source
AI summary
A sulfide solid electrolyte includes: a crystal phase and an anion, in which the phase includes an argyrodite crystal including Li, P, S, and Ha, the Ha is at least one element selected from F, Cl, Br, and I, the anion includes an oxide anion having a P—O bond, at least a part of the oxide anion is different from an anion constituting the argyrodite crystal and constitutes a polyanionic structure, when an entire composition of the electrolyte is LiaMSbHacOx, certain relationships are satisfied, the M is at least one element selected from a metal element and a metalloid element in groups 2 to 15 of a periodic table, the at least one element including P, and 60% or more of a total content of O is bonded to the M.