Battery Separator Coating for Heat Resistance and Fast Shutdown

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Solution Overview

Problem

Existing separators for rechargeable lithium batteries lack adequate heat resistance and shutdown functionality during high-temperature conditions, leading to potential safety risks and performance deterioration.

Innovation Solution

A separator for rechargeable lithium batteries comprising a porous substrate with a coating layer containing a (meth)acryl copolymer, polyethylene particles, and first inorganic particles, where the polyethylene particles have a smaller average size than the inorganic particles, ensuring the coating maintains air permeability and provides a fast shutdown function upon high temperature exposure.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If a coating layer is applied to enhance heat resistance, then thermal stability improves, but ion conductivity may deteriorate

Engineering Contradiction:

Improveheat resistanceVSAvoidion conductivity

Core Design Contradiction:

TemperatureVSReliability

Solution Approach 1:

The coating layer incorporates inorganic particles (alumina, silica) and polyethylene particles within a porous matrix structure. This porous architecture allows ion transport pathways to be maintained while the inorganic particles provide thermal stability and prevent membrane rupture at elevated temperatures, thus resolving the contradiction between heat resistance and ion conductivity.

Inventive Principle:

Principle #31Porous materials

Solution Approach 2:

The coating layer is formulated as a composite material containing multiple components: inorganic particles for heat resistance, polyethylene particles for shutdown functionality, and a binder matrix for structural integrity. This composite structure enables simultaneous achievement of thermal stability, ion conductivity, and safety functions that individual materials cannot provide alone.

Inventive Principle:

Principle #40Composite materials

2Reliability

If polyethylene particles are used for shutdown function, then safety improves, but mechanical strength may worsen

Engineering Contradiction:

Improveshutdown functionVSAvoidmechanical strength

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The polyethylene particles are distributed locally within the coating layer at specific concentrations (1-10 wt%) to provide shutdown functionality only where needed. The binder matrix and inorganic particles provide the bulk mechanical strength, while the polyethylene particles localized throughout the coating ensure shutdown function is activated at appropriate temperatures without compromising overall structural integrity.

Inventive Principle:

Principle #3Local quality

3Temperature

If inorganic particles are added to improve heat resistance, then thermal stability improves, but manufacturing complexity increases

Engineering Contradiction:

Improvethermal stabilityVSAvoidmanufacturing complexity

Core Design Contradiction:

TemperatureVSDevice complexity

Solution Approach 1:

The inorganic particles (alumina, silica) are pre-dispersed in the binder solution before coating application. This preliminary dispersion ensures uniform distribution of heat-resistant particles throughout the coating layer, eliminating the need for complex post-coating thermal processing or sintering steps, thus maintaining manufacturing simplicity while achieving thermal stability.

Inventive Principle:

Principle #10Preliminary action

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 enhances heat resistance and safety by maintaining air permeability while effectively shutting down battery operations during high temperatures, preventing performance deterioration and ensuring safety.

Implementation Method 1

polyethylene particles... ensures the coating maintains air permeability and provides a fast shutdown function upon high temperature exposure

Methodology Applied

Scientific EffectMelting: Melting

Implementation Method 2

continuously maintains ion conductivity to facilitate charge and discharge of a battery

Methodology Applied

Scientific EffectIon conduction: Conduction (electrical)

Data Source

PatentUS12444808B2Separator for rechargeable lithium battery and rechargeable lithium battery including the same

Publication Date: 2025.10.14 SAMSUNG SDI CO LTD

AI summary

A separator for a rechargeable lithium battery and a rechargeable lithium battery including the separator, the separator including a porous substrate, and a coating layer on at least one surface of the porous substrate, wherein the coating layer includes a heat resistant binder including a (meth)acryl copolymer including a first structural unit and a second structural unit, the first structural unit being a structural unit of a (meth)acrylamide and the second structural unit being a structural unit of a (meth)acrylic acid, a (meth)acrylate, a (meth)acrylonitrile, a (meth)acrylamido sulfonic acid, a (meth)acrylamido sulfonate salt, or a combination thereof; polyethylene particles; and first inorganic particles, and an average particle size (D50) of the first inorganic particles is larger than an average particle size (D50) of the polyethylene particles.