Lithium-Tin-Metal-Sulfide Solid Electrolyte Moisture Stability

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Solution Overview

Problem

Sulfide-based solid electrolytes containing phosphorus react with moisture, leading to rapid deterioration, safety concerns, and the generation of toxic gases, limiting their stability and handling.

Innovation Solution

A lithium-tin-metal-sulfide (LTMS) based compound is developed, represented by the formula LiaSnbMcSd, where M is a metal from specific groups of the periodic table, replacing phosphorus to enhance safety and stability while maintaining high ion conductivity, prepared by mixing lithium sulfide, tin sulfide, and sulfide containing M and heat-treating the mixture.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If phosphorus element is used in sulfide-based solid electrolyte, then high ion conductivity is achieved, but reactivity with moisture increases and toxic gas is generated

Engineering Contradiction:

Improveion conductivityVSAvoidreactivity with moisture

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent changes the chemical composition parameters by replacing phosphorus element (P) with metal elements from Groups 13-15 (such as Ga, In, Sb, Bi) in the sulfide-based solid electrolyte. This substitution maintains the desired ion conductivity while fundamentally altering the chemical properties to reduce moisture reactivity and eliminate toxic gas generation.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces local quality changes by selectively substituting specific metal elements at particular sites in the crystal structure. The general formula LiaSnbMcSd allows different metal elements (M) to occupy specific positions, creating localized regions with optimized properties that balance ion conductivity and moisture stability.

Inventive Principle:

Principle #3Local quality

2Reliability

If phosphorus element is used in sulfide-based solid electrolyte, then high ion conductivity is achieved, but safety deteriorates due to toxic gas generation

Engineering Contradiction:

Improveion conductivityVSAvoidtoxic gas generation

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent converts the harmful property of phosphorus-containing sulfides that react with moisture to generate toxic H2S gas by replacing P with metal elements from Groups 13-15. This substitution eliminates the toxic gas generation mechanism while preserving the beneficial high ion conductivity, effectively turning a harmful material system into a safe one.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent changes the chemical composition parameters by substituting phosphorus with specific metal elements (Ga, In, Sb, Bi) in the sulfide-based solid electrolyte. This compositional parameter change fundamentally alters the chemical reactivity, eliminating toxic gas generation while maintaining ion conductivity.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If phosphorus element is used in sulfide-based solid electrolyte, then high ion conductivity is achieved, but storage stability decreases

Engineering Contradiction:

Improveion conductivityVSAvoidstorage stability

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The patent changes the chemical composition parameters by replacing phosphorus element with metal elements from Groups 13-15 in the sulfide-based solid electrolyte. This substitution maintains the crystal structure and ion conductivity while improving chemical stability and storage performance by eliminating the phosphorus-moisture reaction pathway.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite material system with the general formula LiaSnbMcSd, where multiple elements (Li, Sn, M, S) are combined in specific ratios. This composite approach allows optimization of both ion conductivity and storage stability by selecting appropriate metal elements M and controlling the stoichiometric parameters.

Inventive Principle:

Principle #40Composite materials

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 LTMS solid electrolyte improves reactivity to moisture, prevents toxic gas generation, maintains high ion conductivity, and enhances shelf stability, making it safer and easier to handle, with improved safety and stability compared to traditional sulfide-based electrolytes.

Implementation Method 1

the ion conductivity of such solid electrolytes has been developed to materials which have an ion conductivity close to that of the organic electrolyte solution

Methodology Applied

Scientific EffectIonic conduction: Conduction (electrical)

Data Source

PatentUS10854912B2Sulfide-based solid electrolyte and all-solid-state battery applied therewith

Publication Date: 2020.12.01 LG ENERGY SOLUTION LTD

AI summary

The present invention relates to a solid electrolyte comprising a sulfide-based compound and an all-solid-state battery applied therewith and, more particularly, to a solid electrolyte comprising a sulfide-based compound that is free of phosphorus (P) element but exhibits high ionic conductivity, and an all-solid-state battery applied therewith. The sulfide-based solid electrolyte and the all-solid-state battery applied therewith according to the present invention exhibit improved reactivity to moisture to prevent the generation of toxic gas, resulting in an improvement in safety and stability and do not reduce in ion conductivity even after being left in air, and the solid electrolyte is easy to handle and store thanks to the improved shelf stability thereof.