Copolyester Battery Separator Film With Ceramic Ions and Flexibility

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Lithium-ion batteries face safety concerns due to the flammability and mechanical weakness of polyolefin films used as separators, which can lead to short-circuiting and thermal runaway, while ceramic separators are rigid and brittle, limiting their cycling capability and manufacturing efficiency.

Innovation Solution

A copolyester film comprising repeating units derived from a diol, a dicarboxylic acid, and a poly(alkylene oxide) with conductive ceramic particulate materials and additional metal ions, providing improved conductivity, mechanical strength, and flexibility, allowing for efficient and reliable manufacturing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If polyolefin films are used as separators, then the separator enables lithium ion movement and prevents direct electric contact, but the flammability and mechanical weakness lead to safety concerns and short-circuiting

Engineering Contradiction:

ImprovesafetyVSAvoidflammability

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent uses a composite structure consisting of a polyolefin film base layer combined with a heat-resistant coating layer containing inorganic particles (such as alumina, silica, or boehmite) dispersed in a binder resin. This composite structure combines the mechanical properties and ion conductivity of polyolefin with the thermal stability of inorganic materials, preventing membrane rupture at elevated temperatures while maintaining safety and eliminating flammability issues.

Inventive Principle:

Principle #40Composite materials

2Reliability

If ceramic separators are used, then the rigid structure prevents dendrite growth and provides thermal stability, but the brittleness limits cycling capability and manufacturing efficiency

Engineering Contradiction:

Improvethermal stabilityVSAvoidmanufacturing efficiency

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent employs a flexible polyolefin film as the base separator structure instead of rigid ceramic materials. This flexible film can accommodate electrode volume changes during charging and discharging cycles without cracking or breaking, thereby maintaining cycling capability while providing adequate thermal stability through the added heat-resistant coating layer.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The separator is divided into two functional layers: a polyolefin film base layer that provides mechanical strength, flexibility, and ion conductivity, and a heat-resistant coating layer that provides thermal stability. This segmentation allows each layer to optimize its specific function without the compromises required by monolithic ceramic structures, improving both manufacturing efficiency and cycling performance.

Inventive Principle:

Principle #1Segmentation

3Weight of moving object

If the separator thickness is reduced, then the battery volume and weight are reduced, but the mechanical strength and conductivity may be compromised

Engineering Contradiction:

Improveseparator weightVSAvoidmechanical strength

Core Design Contradiction:

Weight of moving objectVSStrength

Solution Approach 1:

The heat-resistant coating layer containing inorganic particles provides reinforcement to the thin polyolefin film, compensating for the reduced mechanical strength that would normally result from thickness reduction. The composite structure maintains adequate tensile strength and puncture resistance even at reduced thickness, allowing battery weight and volume reduction while preserving mechanical integrity.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The polyolefin film is designed with an optimized porous structure that provides high porosity for excellent lithium ion conductivity. This porous architecture allows the film to maintain adequate ion transport capability and mechanical strength at reduced thickness, as the three-dimensional network of pores provides structural support while facilitating ion movement.

Inventive Principle:

Principle #31Porous 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 copolyester film exhibits excellent ionic conductivity, high mechanical strength, and flexibility, maintaining performance at reduced thickness and weight, accommodating electrode volume changes, and ensuring dimensional stability at elevated temperatures.

Implementation Method 1

The separator enables the movement of the liquid or gel electrolyte through its pores, thereby enabling movement of the lithium ions

Methodology Applied

Scientific EffectIonic conduction: Conduction (electrical)

Implementation Method 2

The separator enables the movement of the liquid or gel electrolyte through its pores

Methodology Applied

Scientific EffectCapillary action: Capillary Action

Data Source

PatentUS20240291105A1Copolyester films for use as separators in metal-ion batteries

Publication Date: 2024.08.29 MYLAR SPECIALTY FILMS U S LLP

AI summary

A copolyester film comprising a copolyester which comprises repeating units derived from a diol, a dicarboxylic acid and a poly(alkylene oxide), wherein the copolyester film further comprises a first metal ion-containing component selected from conductive ceramic particulate materials, and wherein the film may further comprise additional metal ions from one or more sources other than said conductive ceramic particulate material.