Pouch Cell Sealing Layer for Pressure-Triggered Thermal Venting

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Solution Overview

Problem

Lithium ion secondary batteries face issues with thermal runaway and propagation due to increased cell pressure from electrolyte vaporization and chemical reactions, posing safety concerns as temperature rises.

Innovation Solution

A secondary battery design incorporating a polymer compound layer on the sealing portion of the pouch that expands or contracts with temperature changes, creating a vent to release gas and electrolyte, thereby preventing thermal runaway and ensuring safety by dissipating heat.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the sealing portion is made strong and airtight to prevent leakage, then sealing performance is improved, but gas and electrolyte cannot be released during thermal runaway, worsening safety

Engineering Contradiction:

Improvesealing performanceVSAvoidthermal runaway risk

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The sealing portion transitions from a static sealed state to a dynamic venting state when temperature increases. The polymer compound layer expands thermally at elevated temperatures, creating gaps that allow gas and electrolyte to escape, thus adapting the sealing function based on temperature conditions

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The physical state and dimensions of the polymer compound layer change with temperature. At normal temperatures, the layer maintains sealing integrity. At elevated temperatures, thermal expansion causes the layer to expand and create venting pathways, changing the sealing parameter dynamically

Inventive Principle:

Principle #35Parameter changes

2Stability of the object's composition

If the pouch is made rigid to maintain structure, then structural stability is improved, but the pouch cannot expand to accommodate gas generation, worsening pressure buildup

Engineering Contradiction:

Improvestructural stabilityVSAvoidinternal pressure

Core Design Contradiction:

Stability of the object's compositionVSStress or pressure

Solution Approach 1:

The pouch incorporates a flexible polymer compound layer in the sealing portion that can deform and expand when internal pressure increases due to gas generation. This flexibility allows the pouch to accommodate volume expansion while maintaining overall structural integrity

Inventive Principle:

Principle #30Flexible shells and thin films

3Object-affected harmful factors

If early venting is induced to prevent thermal runaway, then safety is improved, but battery performance and energy retention deteriorate

Engineering Contradiction:

Improvethermal runaway preventionVSAvoidbattery performance

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The polymer compound layer is pre-positioned in the sealing portion to provide preliminary protection against thermal runaway. When temperature increases, it proactively expands to create venting pathways before catastrophic failure occurs, preventing the harmful thermal runaway effect

Inventive Principle:

Principle #9Preliminary anti-action

Solution Approach 2:

The polymer compound undergoes a phase transition or significant physical change at elevated temperatures, transforming from a compact sealing state to an expanded venting state. This phase change enables early intervention to prevent thermal runaway while maintaining battery performance at normal operating temperatures

Inventive Principle:

Principle #36Phase transitions

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 polymer compound layer effectively stabilizes the battery by allowing controlled gas and electrolyte discharge, preventing thermal propagation and maintaining performance and safety by releasing pressure before it leads to explosions.

Implementation Method 1

The polymer compound is a thermally expandable polymer compound of a composite of a hydroxy group-containing polymer and silica; or at least one heat-shrinkable polymer compound selected from the group comprising polyphenylene ether (PPE), polycarbonate (PC), polyoxymethylene (POM) and polyamide (PA)

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS20230361400A1Secondary battery

Publication Date: 2023.11.09 SK ON CO LTD

AI summary

A secondary battery includes an electrode assembly, and a pouch including an upper sheet and a lower sheet and accommodating the electrode assembly. The pouch is formed with a sealing portion sealing the upper sheet and the lower sheet on an outer portion. The sealing portion includes a polymer compound layer between the top sheet and the bottom sheet in at least a portion. The polymer compound layer includes a polymer compound, and the polymer compound is a thermally expandable polymer compound of a composite of a hydroxy group-containing polymer-silica hybrid, or at least one heat-shrinkable polymer compound selected from the group comprising polyphenylene ether (PPE), polycarbonate (PC), polyoxymethylene (POM) and polyamide (PA).