Cationic Graphene Oxide Coating for Lithium Polysulfide Retention

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Solution Overview

Problem

The leaching and shuttle phenomenon of lithium polysulfide (LiPS) in lithium-sulfur batteries leads to a sharp decrease in capacity and reduced battery lifetime due to its high solubility in ether-based liquid electrolytes, causing side reactions and irreversible loss of positive electrode active material.

Innovation Solution

A positive electrode coating material is developed by grafting a polymer with cationic functional groups onto the surface of graphene oxide, which is then applied to the positive electrode to prevent lithium polysulfide leaching, enhancing the battery's performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If sulfur is used as a positive electrode active material in a lithium-sulfur battery, then the battery achieves high theoretical capacity and energy density, but lithium polysulfide leaching occurs during charging and discharging causing capacity decrease

Engineering Contradiction:

Improveenergy densityVSAvoidcapacity retention

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent introduces a coating layer as an intermediary substance between the sulfur positive electrode and the electrolyte. This coating layer selectively prevents lithium polysulfide from leaching into the electrolyte while allowing lithium ions to pass through, thus resolving the contradiction between maintaining high energy density and preventing capacity loss.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent applies a thin film coating on the sulfur positive electrode to prevent lithium polysulfide leaching. This thin film acts as a protective barrier that maintains the electrochemical performance while preventing the harmful shuttle effect, thereby preserving both energy density and capacity retention.

Inventive Principle:

Principle #30Flexible shells and thin films

2Productivity

If lithium polysulfide is generated during discharging, then the battery operates normally, but the lithium polysulfide is highly soluble in ether-based liquid electrolytes and passes through the separator causing side reactions

Engineering Contradiction:

Improvebattery operationVSAvoidside reactions

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The coating layer serves as an intermediary that selectively blocks lithium polysulfide from contacting the electrolyte and separator, preventing side reactions while allowing the battery to operate normally. The coating is designed to be ion-conductive but polysulfide-impermeable.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent converts the harmful solubility of lithium polysulfide in ether-based electrolytes into a benefit by designing a coating that specifically addresses this solubility issue. The coating exploits the interaction between polysulfides and the coating material to trap polysulfides, turning the solubility problem into a retention mechanism.

Inventive Principle:

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

3Reliability

If a coating material is applied to prevent lithium polysulfide leaching, then capacity loss is reduced, but the coating material structure and composition must be precisely controlled

Engineering Contradiction:

Improvecapacity retentionVSAvoidcoating structure control

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent optimizes specific parameters of the coating material including thickness (1-10 nm), composition ratios, and functional group concentrations to achieve the desired balance between polysulfide blocking and ion conductivity. By controlling these parameters within specific ranges, the coating achieves high capacity retention without requiring excessive manufacturing precision.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs composite coating materials that combine multiple components with complementary functions. This composite structure provides both polysulfide blocking capability and ion conductivity, reducing the need for extreme precision in manufacturing any single component while achieving the desired performance.

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 coating material effectively suppresses lithium polysulfide leaching, reducing capacity loss and improving battery performance, particularly at high current densities.

Implementation Method 1

graphene oxide surface-modified with cationic functional groups

Methodology Applied

Scientific EffectElectrostatic interaction: Ion Repulsion/Attraction

Data Source

PatentUS12592389B2Positive electrode coating material for lithium secondary battery, preparation method thereof, and positive electrode and lithium secondary battery comprising the coating material

Publication Date: 2026.03.31 LG ENERGY SOLUTION LTD

AI summary

Disclosed are a positive electrode coating material for a lithium secondary battery including graphene oxide surface-modified with cationic functional groups, a preparation method thereof, and a positive electrode and a lithium secondary battery comprising the coating material. The positive electrode coating material prevents the leaching of lithium polysulfide, thereby improving battery performance.