Copolyester Battery Separator Film With Ceramic Ion Conduction
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Solution Overview
Problem
Current lithium-ion battery separators, particularly those made from polyolefin films and ceramic materials, face safety concerns such as flammability, low mechanical strength, and brittleness, which can lead to short-circuiting and thermal issues due to lithium dendrite growth and rigid ceramic separators that are prone to cracking.
Innovation Solution
Development of a copolyester film comprising repeating units derived from a diol, a dicarboxylic acid, and a poly(alkylene oxide) with conductive ceramic particulate materials, which provides improved mechanical strength, flexibility, and ionic conductivity, allowing for efficient lithium ion migration while maintaining dimensional stability and ease of manufacture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polyolefin films are used as separators, then ionic conductivity is achieved, but mechanical strength and thermal stability deteriorate
Solution Approach 1:
The invention uses a composite structure consisting of a polyolefin base film combined with a heat-resistant porous layer containing inorganic particles (such as alumina, silica, or titania). This composite structure allows the separator to maintain the ionic conductivity of polyolefin while gaining the mechanical strength and thermal stability of inorganic materials, directly resolving the contradiction between conductivity and strength.
2Temperature
If ceramic materials are used as separators, then thermal stability is improved, but brittleness and mechanical flexibility worsen
Solution Approach 1:
The invention applies local quality by creating a layered structure where the heat-resistant porous layer containing inorganic particles is applied only on the surface of the polyolefin base film. The bulk polyolefin maintains flexibility and toughness, while the surface layer provides thermal stability and dendrite resistance, thus achieving thermal stability without sacrificing flexibility.
Solution Approach 2:
The invention uses a thin porous layer (5-50 μm) of inorganic particles embedded in a binder polymer on the surface of the flexible polyolefin base film. This thin film structure provides thermal stability and mechanical reinforcement without making the overall separator brittle, maintaining flexibility while improving heat resistance.
3Weight of stationary object
If separator thickness is reduced, then battery weight and volume are decreased, but mechanical strength and safety deteriorate
Solution Approach 1:
The invention uses a composite structure where a thin heat-resistant porous layer (5-50 μm) is applied on the polyolefin base film. This allows the total separator thickness to be reduced (20-50 μm) while maintaining safety through the synergistic effect of the polyolefin's flexibility and the inorganic layer's thermal stability and mechanical reinforcement.
Solution Approach 2:
The invention employs a thin porous coating layer containing inorganic particles that provides mechanical reinforcement and thermal stability without adding significant thickness or weight. This thin film structure enables reduced separator thickness (20-50 μm) while maintaining or improving safety performance through enhanced mechanical strength and heat resistance.
4Reliability
If glass transition temperature is lowered, then ionic conductivity is improved, but thermal stability deteriorates
Solution Approach 1:
The invention uses a composite structure where the polyolefin base film provides low glass transition temperature for good ionic conductivity, while the heat-resistant porous layer containing inorganic particles (alumina, silica, titania) provides high thermal stability. The two materials work synergistically to achieve both high conductivity and thermal stability simultaneously.
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 conductivity, high mechanical strength, reduced brittleness, and flexibility, enabling reliable battery operation with reduced thickness and weight, and improved manufacturing efficiency, addressing the safety and performance limitations of existing separators.
Implementation Method 1
the separator must enable migration of the lithium ions within its structure
Implementation Method 2
a copolyester which comprises repeating units derived from a diol, a dicarboxylic acid and a poly(alkylene oxide)
Data Source
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.