Sulfur-Carbon Composite Coating for Polysulfide Shuttle Suppression

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Solution Overview

Problem

Lithium-sulfur batteries face challenges in commercialization due to the leaching and shuttle phenomenon of lithium polysulfide, which leads to reduced capacity and shortened battery lifetime.

Innovation Solution

A sulfur-carbon composite is developed, where a porous carbon material is coated with a copolymer containing a redox functional group and a lithium ion conducting functional group, enhancing the reduction of lithium polysulfide and facilitating lithium ion delivery.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a physical membrane or protective film is used to prevent polysulfide leaching, then polysulfide migration is reduced, but the battery capacity and lifetime are still insufficient due to incomplete prevention of shuttle phenomenon

Engineering Contradiction:

Improvepolysulfide leaching preventionVSAvoidbattery capacity and lifetime

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

A copolymer coating layer comprising a redox functional group and a lithium ion conducting functional group is applied to the surface of the porous carbon material. This intermediary layer actively mediates the polysulfide shuttle phenomenon by catalyzing the reduction reaction of lithium polysulfide to lithium sulfide, while simultaneously conducting lithium ions. This goes beyond passive physical membrane protection by providing active chemical transformation of polysulfides, thereby improving both polysulfide leaching prevention and battery capacity/lifetime performance.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Use of energy by moving object

If sulfur is directly used as positive electrode material, then high energy density is achieved, but polysulfide leaching and shuttle phenomenon cause capacity reduction and shortened battery lifetime

Engineering Contradiction:

Improveenergy densityVSAvoidbattery lifetime and capacity stability

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The invention uses a composite structure where sulfur is combined with porous carbon material, and the surface of the carbon material is coated with a copolymer comprising a redox functional group and a lithium ion conducting functional group. This composite material structure maintains the high energy density of sulfur while the porous carbon material and copolymer coating work together to prevent polysulfide leaching and catalyze reduction reactions, thereby improving battery lifetime and capacity stability.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The copolymer coating is applied locally on the surface of the porous carbon material where sulfur is loaded. This localized coating provides the redox functional groups and lithium ion conducting pathways exactly where they are needed - at the interface between sulfur and electrolyte - without requiring modification of the entire battery structure, thus maintaining high energy density while improving reliability.

Inventive Principle:

Principle #3Local quality

3Reliability

If conventional coating materials are used on carbon material surface, then polysulfide leaching is partially prevented, but overvoltage occurs and reactivity is not improved

Engineering Contradiction:

Improvepolysulfide leaching preventionVSAvoidovervoltage and reactivity

Core Design Contradiction:

ReliabilityVSPower

Solution Approach 1:

The invention changes the chemical parameters of the coating material by incorporating a redox functional group that can undergo reversible redox reactions. This parameter change enables the coating to catalyze the reduction reaction of lithium polysulfide to lithium sulfide, thereby reducing overvoltage and improving reactivity. Simultaneously, the lithium ion conducting functional group maintains fast lithium ion transport, ensuring high power performance while preventing polysulfide leaching.

Inventive Principle:

Principle #35Parameter changes

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 sulfur-carbon composite reduces overvoltage, improves reactivity, and extends the lifetime of lithium secondary batteries by promoting the reduction of lithium polysulfide and preventing its leaching.

Implementation Method 1

a copolymer containing a redox functional group and a lithium ion conducting functional group... capable of performing a catalytic function that promotes the reduction reaction of the lithium polysulfide

Methodology Applied

Scientific EffectRedox reaction: Redox Reactions

Implementation Method 2

a copolymer containing a redox functional group and a lithium ion conducting functional group... capable of improving the delivery of lithium ions

Methodology Applied

Scientific EffectIon conduction: Fast Ion Conductor

Data Source

PatentUS12327870B2Sulfur-carbon composite, positive electrode for lithium secondary battery including same, and lithium secondary battery

Publication Date: 2025.06.10 LG ENERGY SOLUTION LTD

AI summary

Disclosed is a sulfur-carbon composite, a method for manufacturing the same, and a positive electrode for a lithium secondary battery and a lithium secondary battery including the same, which has excellent reactivity and lifetime characteristics and has an effect of reducing overvoltage.