Inorganic-Coated Battery Separator for Thermal Runaway Resistance

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Solution Overview

Problem

Lithium secondary batteries face challenges in stability and safety due to thermal runaway, which can occur from heat-generated decomposition reactions, leading to excessive current and potential short-circuits within the battery.

Innovation Solution

A separator for secondary batteries is developed, comprising a porous substrate with an inorganic coating layer containing specific inorganic materials. The separator has improved pore state and thermal resistance, with an average particle diameter of the inorganic material ranging from 3 to 20% of the coating layer thickness, and a TMA fracture temperature of 150°C or higher.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If a separator is used in lithium secondary batteries, then electrical connection and capacity increase are enabled, but thermal runaway risk increases due to separator damage and short-circuit

Engineering Contradiction:

Improvecapacity and outputVSAvoidthermal stability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The separator is constructed as a composite material consisting of a porous substrate combined with an inorganic coating layer containing specific inorganic materials (such as metal oxides or hydroxides). This composite structure enables the separator to maintain its mechanical integrity and electrical insulation properties even at elevated temperatures, thereby preventing thermal runaway while allowing the battery to operate at higher capacities and outputs.

Inventive Principle:

Principle #40Composite materials

2Temperature

If the inorganic coating layer thickness is increased to improve thermal resistance, then thermal stability improves, but voltage resistance decreases

Engineering Contradiction:

Improvethermal resistanceVSAvoidvoltage resistance

Core Design Contradiction:

TemperatureVSStrength

Solution Approach 1:

The patent optimizes the thickness of the inorganic coating layer to a specific range (0.1 to 5 μm) to achieve the desired balance between thermal resistance and voltage resistance. By precisely controlling this parameter, the separator gains sufficient thermal stability to prevent shrinkage at elevated temperatures while maintaining adequate electrical insulation properties to withstand operating voltages without breakdown.

Inventive Principle:

Principle #35Parameter changes

3Temperature

If the average particle diameter of inorganic material is increased to improve thermal resistance, then thermal stability improves, but manufacturing precision decreases

Engineering Contradiction:

Improvethermal resistanceVSAvoidcoating uniformity

Core Design Contradiction:

TemperatureVSManufacturing precision

Solution Approach 1:

The patent specifies an optimal range for the average particle diameter of the inorganic material (0.1 to 3 μm) to achieve a balance between thermal resistance and coating uniformity. Particles within this size range provide sufficient thermal stability while being small enough to distribute uniformly throughout the coating layer during the manufacturing process, ensuring consistent performance across the entire separator surface.

Inventive Principle:

Principle #35Parameter changes

4Productivity

If a porous substrate is used to enable ion transport, then battery performance improves, but mechanical strength decreases leading to breakdown

Engineering Contradiction:

Improveion transport efficiencyVSAvoidmechanical strength

Core Design Contradiction:

ProductivityVSStrength

Solution Approach 1:

The separator employs a porous substrate with controlled porosity to facilitate efficient ion transport between electrodes, maintaining high battery performance. The porous structure allows adequate electrolyte penetration and ion flow while the specific pore size distribution and substrate material selection ensure sufficient mechanical strength to prevent breakdown during battery assembly and operation.

Inventive Principle:

Principle #31Porous materials

Solution Approach 2:

The porous substrate is combined with an inorganic coating layer to create a composite structure that enhances the mechanical strength of the inherently weak porous material. The inorganic coating provides a protective framework that prevents the porous substrate from breaking down under mechanical stress while preserving the pore structure necessary for ion transport.

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 improved separator enhances voltage resistance and thermal stability, reducing the frequency of breakdown and improving the safety of lithium secondary batteries, especially during overcharge conditions.

Implementation Method 1

the inorganic coating layer... including an inorganic material... a TMA fracture temperature of the separator is 150° C. or higher

Methodology Applied

Scientific EffectEndothermic reaction: Endothermic Reaction

Implementation Method 2

a porous substrate

Methodology Applied

Scientific EffectPorosity: Porosity

Data Source

PatentUS20250062492A1Separator for secondary battery and lithium secondary battery comprising the same

Publication Date: 2025.02.20 SK ON CO LTD

AI summary

A separator for a secondary battery includes a porous substrate and an inorganic coating layer formed on one or both surfaces of the porous substrate and including an inorganic material, wherein an average particle diameter D50 of the inorganic material is 3 to 20% of a thickness of the inorganic coating layer, wherein a TMA fracture temperature of the separator is 150° C. or higher.