Sulfide Solid Electrolyte Stability via LiCl Composite

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Solution Overview

Problem

Sulfide-based solid electrolyte compounds with a cubic argyrodite-type crystal structure are prone to high reactivity with moisture and oxygen, leading to hydrogen sulfide generation and conductivity degradation when exposed to air.

Innovation Solution

A sulfide-based solid electrolyte compound with a composition formula Li7-x+yPS6-xClx+y, where 0.05 ≤ y ≤ 0.9 and -3.0x + 1.8 ≤ y ≤ -3.0x + 5.7, maintaining high conductivity and suppressing hydrogen sulfide generation by incorporating a crystal phase of cubic argyrodite-type structure and LiCl, with specific peak intensity ratios and composition ranges.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a sulfide-based solid electrolyte compound with cubic argyrodite-type crystal structure is used, then high ionic conductivity is achieved, but reactivity with moisture and oxygen increases leading to hydrogen sulfide generation and conductivity degradation

Engineering Contradiction:

Improveionic conductivityVSAvoidreactivity with moisture and oxygen

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

LiCl is introduced as an intermediary substance that forms a protective layer or intermediate phase between the sulfide-based solid electrolyte and the external environment (moisture and oxygen). This intermediary component reduces the direct contact and chemical reaction between the reactive sulfide electrolyte and harmful environmental factors, thereby suppressing hydrogen sulfide generation while maintaining ionic conductivity pathways.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention creates a composite material system combining the sulfide-based solid electrolyte (Li7-xPS6-x) with LiCl to form a new composite solid electrolyte (Li7-x+yPS6-xClx+y). This composite structure leverages the high ionic conductivity of the sulfide phase while the LiCl component provides chemical stability and resistance to moisture and oxygen, achieving a balance between conductivity and stability.

Inventive Principle:

Principle #40Composite materials

2Ease of operation

If the solid electrolyte is exposed to air for ease of handling, then operational convenience is improved, but hydrogen sulfide generation and conductivity degradation occur

Engineering Contradiction:

Improvehandling convenienceVSAvoidhydrogen sulfide generation

Core Design Contradiction:

Ease of operationVSObject-generated harmful factors

Solution Approach 1:

LiCl serves as a protective intermediary that enables the solid electrolyte to be handled in air without immediate degradation. The LiCl component acts as a barrier that prevents direct reaction between atmospheric moisture/oxygen and the sulfide electrolyte, allowing convenient handling while suppressing hydrogen sulfide generation and conductivity loss.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention converts the potentially harmful reaction between sulfide electrolyte and air into a beneficial outcome by controlling the composition (specific x and y ranges). The controlled presence of LiCl and optimized stoichiometry transform the reactive sulfide material into a composite that can withstand air exposure, turning what would be a harmful degradation process into a manageable operational condition.

Inventive Principle:

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

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 sulfide-based solid electrolyte exhibits excellent oxidation and water resistance, maintaining high conductivity and reducing hydrogen sulfide generation, even when exposed to dry air, thus enhancing the safety and durability of lithium ion batteries.

Implementation Method 1

a sulfide-based solid electrolyte compound which comprises a crystal phase of a cubic argyrodite-type crystal structure, and has a composition formula (1): Li7-x+yPS6-xClx+y... having excellent oxidation resistance as compared with a sulfide-based solid electrolyte compound... high conductivity can be maintained

Methodology Applied

Scientific EffectIonic conduction: Conduction (electrical)

Implementation Method 2

comprises a crystal phase of a cubic argyrodite-type crystal structure... excellent oxidation and water resistance, maintaining high conductivity... even when exposed to dry air

Methodology Applied

Scientific EffectCrystalline structure stability: Crystallisation

Data Source

PatentEP3240089B1Sulfide-based solid electrolyte for lithium ion cell, and solid electrolyte compound

Publication Date: 2019.04.24 MITSUI MINING & SMELTING CO LTD

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AI summary

Relating to a sulfide-based solid electrolyte compound for lithium ion batteries which has a cubic argyrodite-type crystal structure, the purpose of the present invention is to propose a novel compound which can suppress a generation amount of hydrogen sulfide when being left to stand in the air and which can maintain high conductivity even when being left to stand in dry air. Proposed is a sulfide-based solid electrolyte compound for lithium ion batteries contains a crystal phase of the cubic argyrodite-type crystal structure and is represented by a composition formula (1): Li7-x+yPS6-xClx+y, wherein x and y in the composition formula (1) satisfy 0.05 ≤ y ≤ 0.9 and -3.0x + 1.8 ≤ y ≤ -3.0x + 5.7.