Lithium-Sulfur Coated Cathode for Sulfide Solid-State Batteries

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Solution Overview

Problem

Sulfide-based solid electrolytes in all-solid-state batteries exhibit lower lithium ion diffusivity and increased interfacial resistance due to physical contact with cathode electrode active materials, leading to degraded rate properties and safety concerns from side reactions.

Innovation Solution

A cathode active material with a secondary particle structure incorporating a lithium-sulfur-containing portion between primary particles, formed through a method involving a sulfur compound aqueous solution and heat treatment, is used to enhance lithium ion conductivity and electrochemical properties, reducing interfacial resistance and improving battery performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If sulfide-based solid electrolyte is used to improve ionic conductivity and battery cell performance, then high ionic conductivity is achieved, but lithium ion diffusivity becomes lower and interfacial resistance increases due to physical contact with cathode electrode active material

Engineering Contradiction:

Improveionic conductivityVSAvoidlithium ion diffusivity

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent introduces a sulfur compound coating layer as an intermediary substance between the sulfide-based solid electrolyte and the cathode electrode active material. This coating layer prevents direct physical contact that causes harmful side reactions and lithium ion diffusion barriers, while maintaining good ionic conductivity. The sulfur compound acts as a mediator that resolves the contradiction by allowing ionic transport without direct contact-induced degradation.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent creates a composite structure where the cathode electrode active material is coated with a sulfur compound layer. This composite material combines the high ionic conductivity benefits of sulfide-based electrolytes with the protective properties of the sulfur compound coating, preventing direct contact issues while maintaining performance.

Inventive Principle:

Principle #40Composite materials

2Use of energy by moving object

If sulfide-based solid electrolyte is used to achieve high ionic conductivity, then battery cell performance is improved, but side reactions occur due to mutual diffusion of sulfur component and transition metal component

Engineering Contradiction:

Improvebattery cell performanceVSAvoidside reactions

Core Design Contradiction:

Use of energy by moving objectVSObject-generated harmful factors

Solution Approach 1:

The sulfur compound coating layer serves as an intermediary barrier that prevents direct mutual diffusion between the sulfur component of the solid electrolyte and the transition metal component of the cathode active material. This intermediary layer eliminates the harmful side reactions while preserving the high ionic conductivity and battery cell performance.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent applies preliminary anti-action by pre-coating the cathode electrode active material with a sulfur compound layer before assembling the battery. This preliminary protective layer prevents the harmful side reactions from occurring in the first place, rather than attempting to address them after they occur.

Inventive Principle:

Principle #9Preliminary anti-action

3Device complexity

If direct contact between solid electrolyte and cathode active material is maintained, then simple structure is achieved, but interfacial resistance increases and rate properties are degraded

Engineering Contradiction:

Improvestructure simplicityVSAvoidrate properties

Core Design Contradiction:

Device complexityVSProductivity

Solution Approach 1:

The patent applies a thin film coating of sulfur compound on the cathode electrode active material particles. This thin film layer does not significantly increase structural complexity but effectively reduces interfacial resistance and improves rate properties by facilitating lithium ion transport while preventing harmful direct contact.

Inventive Principle:

Principle #30Flexible shells and thin films

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 cathode active material design improves lithium ion diffusion and battery rate properties, while maintaining stability and safety by reducing interfacial resistance and preventing sulfur diffusion, thus enhancing the overall performance and lifespan of sulfide-based all-solid-state batteries.

Implementation Method 1

The first lithium-transition metal composite oxide particle includes a lithium-sulfur-containing portion formed between the primary particles... having improved lithium ion conductivity

Methodology Applied

Scientific EffectIonic conduction: Conduction (electrical)

Implementation Method 2

a method of preparing the same... involving a sulfur compound aqueous solution and heat treatment

Methodology Applied

Scientific EffectHeat treatment: Heat Treatment

Data Source

PatentUS20230155129A1CATHODE ACTIVE MATERIAL FOR SULFIDE-BASED ALL-SOLID-STATE BATTERY, METHOD OF PREPARING THE SAME, CATHODE COMPLEX INCLUDING THE SAME AND METHOD OF FABRICATING the CATHODE COMPLEX

Publication Date: 2023.05.18 SK ON CO LTD

AI summary

A cathode active material for a sulfide-based all-solid-state battery according to embodiments of the present invention includes a first lithium-transition metal composite oxide particle having a secondary particle structure that includes a plurality of primary particles therein. The first lithium-transition metal composite oxide particle includes a lithium-sulfur-containing portion formed between the primary particles.