Layered Sulfur Cathode Material to Prevent Li-S Elution

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Solution Overview

Problem

Lithium-sulfur batteries face challenges in improving reliability, capacity, minimizing sulfur elution, and enhancing life characteristics, with existing lithium-ion batteries having safety concerns and limited impact resistance.

Innovation Solution

A positive active material for lithium-sulfur batteries is developed, comprising alternately stacked carbon and metal compound layers, where the metal compound layers include molybdenum and sulfur, with a carbon layer inherently provided between them, and a carbon shell layer optionally surrounding the structure, to prevent sulfur elution and enhance performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If sulfur is used as positive electrode material to achieve high energy density, then capacity is improved, but sulfur elution occurs causing reliability deterioration

Engineering Contradiction:

ImprovecapacityVSAvoidreliability

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent employs a nested structure where sulfur is enclosed within metal compound layers (MoS2, WS2, or WSe2), which are in turn surrounded by carbon layers. This multi-layer nesting prevents sulfur elution while maintaining high capacity, as the sulfur remains trapped within the protective metallic and carbonous shells during battery operation.

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

The positive electrode material is constructed as a composite structure combining sulfur, metal compounds (MoS2, WS2, WSe2), and carbon materials. This composite approach leverages the high capacity of sulfur, the protective properties of metal compounds, and the structural stability of carbon to simultaneously achieve high capacity and reliability by preventing sulfur dissolution into the electrolyte.

Inventive Principle:

Principle #40Composite materials

2Reliability

If conventional lithium-ion batteries are used, then safety issues and low impact resistance occur, but alternative batteries lack sufficient energy density

Engineering Contradiction:

ImprovesafetyVSAvoidenergy density

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent creates a composite positive electrode material where sulfur is protected by metal compound layers and carbon shells. This composite structure provides both high energy density (from sulfur) and improved safety/reliability (from the protective layers preventing sulfur elution and stabilizing the electrode structure during charge-discharge cycles).

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The carbon layers forming a shell around the metal compound layers containing sulfur act as a protective flexible shell structure. This shell confines the sulfur, prevents its elution into the electrolyte, and maintains structural integrity during battery operation, thereby improving safety and reliability while preserving high energy density.

Inventive Principle:

Principle #30Flexible shells and thin films

3Quantity of substance

If sulfur is used as positive electrode material, then energy density increases, but fabrication cost reduction is needed

Engineering Contradiction:

Improveenergy densityVSAvoidfabrication cost

Core Design Contradiction:

Quantity of substanceVSEase of manufacture

Solution Approach 1:

The metal compounds (MoS2, WS2, WSe2) serve multiple functions: they act as protective barriers against sulfur elution, provide structural support, and potentially enhance electrical conductivity. This multi-functionality reduces the need for additional separate components, simplifying the overall structure and potentially reducing fabrication costs while maintaining high energy density.

Inventive Principle:

Principle #6Universality (Multi-functionality)

4Quantity of substance

If sulfur is used as positive electrode material, then capacity is improved, but life characteristics deteriorate due to sulfur elution

Engineering Contradiction:

ImprovecapacityVSAvoidlife characteristics

Core Design Contradiction:

Quantity of substanceVSDuration of action of stationary object

Solution Approach 1:

The nested multi-layer structure with sulfur enclosed in metal compound layers and further surrounded by carbon layers provides long-term stability by preventing sulfur elution during repeated charge-discharge cycles. This confinement mechanism preserves the electrode structure and maintains high capacity over extended battery life, directly improving life characteristics.

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

The composite structure combining sulfur, metal compounds, and carbon materials creates a stable electrode that resists degradation during cycling. The metal compounds and carbon layers protect the sulfur from reacting with the electrolyte and from mechanical degradation, thereby extending battery life while maintaining high capacity.

Inventive Principle:

Principle #40Composite materials

Data Source

PatentUS11742486B2Positive active material for lithium-sulfur battery and method of fabricating the same

Publication Date: 2023.08.29 INDUSTRY UNIVERSITY COOPERATION FOUNDATION HANYANG UNIVERSITY

AI summary

A positive active material for a lithium-sulfur battery is provided. The positive active material for a lithium-sulfur battery includes carbon layers and metal compound layers alternately and repeatedly stacked. Each of the metal compound layers includes molybdenum and sulfur. Sulfur of the positive active material for a lithium-sulfur battery is provided from the metal compound layer through a preliminary charge/discharge process.