Core-Shell Separator Coating to Suppress Moisture-Driven Gas Generation

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Solution Overview

Problem

Lithium secondary batteries face performance degradation and gas generation due to moisture absorption by inorganic materials with high hygroscopicity in the separator coating layer, leading to increased resistance and capacity loss.

Innovation Solution

A separator with a core-shell structure is developed, where a polymer is bonded to the surface of an inorganic particle using a coupling agent, reducing moisture absorption and adsorption, and incorporating a surface-modified inorganic material with a moisture content of 1,500 ppm or less, thereby inhibiting gas generation and performance degradation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If an inorganic material with high hygroscopicity is used in the separator coating layer, then the moisture absorption capability is improved, but gas generation and performance degradation occur due to moisture

Engineering Contradiction:

Improvemoisture absorption capabilityVSAvoidgas generation

Core Design Contradiction:

Object-affected harmful factorsVSObject-generated harmful factors

Solution Approach 1:

The patent converts the harmful hygroscopicity of inorganic materials into a beneficial feature by using the moisture absorbed by the inorganic material to drive in-situ decomposition reactions. The moisture that would normally cause gas generation is instead utilized to decompose the inorganic material and form a protective coating, transforming the harmful moisture into a useful reactant that enhances safety without causing performance degradation

Inventive Principle:

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

Solution Approach 2:

The patent creates a composite structure where an inorganic material with high hygroscopicity is combined with an organic coating layer formed through in-situ decomposition. This composite material integrates the moisture absorption capability of the inorganic material with the protective and gas-generation-preventing properties of the organic coating, achieving both moisture management and safety improvement simultaneously

Inventive Principle:

Principle #40Composite materials

2Temperature

If a coating layer including an inorganic material is added to improve heat resistance, then thermal stability is improved, but moisture content increases leading to electrolyte decomposition

Engineering Contradiction:

Improveheat resistanceVSAvoidmoisture content

Core Design Contradiction:

TemperatureVSQuantity of substance

Solution Approach 1:

The patent applies preliminary action by forming an organic coating layer on the inorganic material particles before they are incorporated into the separator. This pre-formed coating prevents moisture from being retained in the final separator structure, eliminating the source of moisture that would cause electrolyte decomposition while maintaining the heat resistance benefits of the inorganic material

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent extracts the harmful moisture from the system by using thermal treatment to remove adsorbed water from the inorganic material surface before forming the final separator structure. This extraction process eliminates the moisture that would otherwise cause electrolyte decomposition, while the inorganic material's heat resistance properties are preserved

Inventive Principle:

Principle #2Taking out (Extraction)

3Reliability

If the separator thickness is increased to prevent short circuit, then safety is improved, but thickness increase problem due to swelling occurs

Engineering Contradiction:

Improveshort circuit preventionVSAvoidseparator thickness

Core Design Contradiction:

ReliabilityVSLength of stationary object

Solution Approach 1:

The patent uses a thin organic coating film formed on the inorganic material particles that provides protective functions without adding significant thickness. This thin film structure maintains the separator's overall thin profile while providing the necessary protective barrier, preventing both short circuits and moisture-related issues without causing swelling problems

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 core-shell structure effectively prevents moisture absorption and gas generation, enhancing the battery's capacity retention and preventing electrolyte decomposition, thus improving the battery's performance and lifespan.

Implementation Method 1

a polymer is bonded to a surface of an inorganic particle

Methodology Applied

Scientific EffectChemical bonding: Chemical Bonding

Implementation Method 2

a polymer is bonded to a surface of an inorganic particle having hygroscopicity such that the surface of the inorganic particle is modified

Methodology Applied

Scientific EffectCoupling agent reaction: Chemical Bonding

Data Source

PatentUS20230387547A1Separator including inorganic material having core-shell structure and method of manufacturing the same

Publication Date: 2023.11.30 LG ENERGY SOLUTION LTD

AI summary

A separator including a separator substrate having a porous structure and a coating layer on at least one surface of the separator substrate. The coating layer includes a surface-modified inorganic material, wherein the surface-modified inorganic material includes particles having a core-shell structure wherein a polymer is bonded to a surface of an inorganic particle.