Lithium-Sulfur Separator Coating for Polysulfide Adsorption

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Solution Overview

Problem

Lithium-sulfur batteries face a decrease in charge capacity and energy due to the solubility of lithium polysulfides in the electrolyte solution, leading to their loss from the positive electrode, which prevents effective charge/discharge reactions.

Innovation Solution

A separator for lithium-sulfur batteries is developed with a polydopamine coating layer and a lithium-substituted water-soluble polymer layer, enhancing interaction with the electrolyte solution to prevent polysulfide diffusion and maintain charge capacity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a hydrophobic separator material (PE or PP) is used, then the separator maintains good structural stability and electrochemical performance, but the separator cannot effectively interact with the water-soluble electrolyte, leading to polysulfide diffusion and capacity loss

Engineering Contradiction:

Improveseparator structural stabilityVSAvoidpolysulfide diffusion

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The separator is constructed as a composite structure combining a hydrophobic base layer (PE or PP) with a hydrophilic coating layer containing water-soluble polymer. This composite structure integrates the structural stability of hydrophobic materials with the polysulfide-trapping capability of hydrophilic materials, resolving the contradiction between structural integrity and polysulfide interaction.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The separator exhibits different local properties: the base layer maintains hydrophobicity for structural stability, while the surface coating layer provides hydrophilicity for electrolyte interaction and polysulfide trapping. This local differentiation allows each layer to perform its specific function optimally.

Inventive Principle:

Principle #3Local quality

2Object-affected harmful factors

If a water-soluble coating layer is applied to improve electrolyte interaction, then polysulfide diffusion is reduced, but the coating layer may detach or fail to form uniform coverage on the hydrophobic separator surface

Engineering Contradiction:

Improvepolysulfide diffusionVSAvoidcoating layer uniformity

Core Design Contradiction:

Object-affected harmful factorsVSManufacturing precision

Solution Approach 1:

The hydrophobic base layer acts as an intermediary between the hydrophobic separator material and the hydrophilic water-soluble coating layer, enabling stable adhesion of the coating to the separator surface and ensuring uniform coverage.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The surface energy and wettability parameters of the separator are modified by applying the hydrophilic coating layer, transforming the surface from hydrophobic to hydrophilic to enable better electrolyte interaction and uniform coating formation.

Inventive Principle:

Principle #35Parameter changes

3Productivity

If the separator surface is made hydrophilic to enhance electrolyte interaction, then charge capacity is maintained, but the separator loses its inherent electrochemical stability and performance

Engineering Contradiction:

Improvecharge capacityVSAvoidelectrochemical performance

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The separator functionality is segmented into two distinct layers: the base layer provides electrochemical stability and structural integrity, while the coating layer enhances electrolyte interaction and maintains charge capacity. This segmentation allows both requirements to be satisfied simultaneously.

Inventive Principle:

Principle #1Segmentation

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 separator improves the interaction between the electrolyte and the battery components, preventing polysulfide loss and maintaining energy capacity during repeated charge/discharge cycles.

Implementation Method 1

a separator for lithium-sulfur batteries, which includes a coating layer including a lithium-substituted water-soluble polymer

Methodology Applied

Scientific EffectAdsorption: Adsorption

Implementation Method 2

a separator for lithium-sulfur batteries, which includes a coating layer including a lithium-substituted water-soluble polymer

Methodology Applied

Scientific EffectSolvation: Solvation

Data Source

PatentUS11742513B2Separator for lithium-sulfur batteries and lithium-sulfur battery comprising the same

Publication Date: 2023.08.29 LG ENERGY SOLUTION LTD

AI summary

A separator for lithium-sulfur batteries and a lithium-sulfur battery including the same. The separator for lithium-sulfur batteries includes a separator substrate, a first coating layer formed on at least one surface of the separator substrate, and a second coating layer formed on the first coating layer. The first coating layer includes a polydopamine, and the second coating layer includes a lithium-substituted water-soluble polymer. Also a method for preparing the separator.