Multilayer Hybrid Battery Separators for Lithium Ion Secondary Batteries
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Solution Overview
Problem
Current lithium ion secondary battery separators either lack balanced tensile strength, puncture resistance, and oxidative resistance, or require solvent-based processes that may not provide optimal performance.
Innovation Solution
A multi-layered battery separator is created by bonding a dry-processed polypropylene layer with a wet-processed polyethylene layer, offering improved tensile strength, puncture resistance, and oxidative resistance, while maintaining a thin thickness and high dielectric breakdown.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a single-layer separator is used, then the manufacturing process is simple, but the tensile strength and puncture resistance are insufficient
Solution Approach 1:
The separator is divided into multiple functional layers: a polyolefin microporous membrane layer (5-20 μm) for shutdown function and pore structure, and a non-woven fabric reinforcement layer (10-50 μm) for mechanical strength. This segmentation allows each layer to specialize in its function while combining to achieve overall performance superiority.
Solution Approach 2:
The invention uses composite material structure by bonding a polyolefin microporous membrane with a non-woven fabric layer. The polyolefin layer provides shutdown function and ionic conductivity, while the non-woven fabric provides mechanical reinforcement, achieving synergistic enhancement of both soft and hard properties.
2Strength
If a dry process is used, then the separator has good shutdown function, but the tensile strength is insufficient
Solution Approach 1:
The separator is divided into multiple functional layers: a polyolefin microporous membrane layer (5-20 μm) for shutdown function and pore structure, and a non-woven fabric reinforcement layer (10-50 μm) for mechanical strength. This segmentation allows each layer to specialize in its function while combining to achieve overall performance superiority.
Solution Approach 2:
The invention uses composite material structure by bonding a polyolefin microporous membrane with a non-woven fabric layer. The polyolefin layer provides shutdown function and ionic conductivity, while the non-woven fabric provides mechanical reinforcement, achieving synergistic enhancement of both soft and hard properties.
3Reliability
If a wet process is used, then the separator has high tensile strength, but the oxidative resistance is reduced
Solution Approach 1:
The invention uses composite material structure by bonding a polyolefin microporous membrane with a non-woven fabric layer. The polyolefin layer provides shutdown function and ionic conductivity, while the non-woven fabric provides mechanical reinforcement, achieving synergistic enhancement of both soft and hard properties.
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 hybrid separator achieves balanced machine and transverse direction tensile strength, enhanced puncture resistance, and sustained electrical resistance at high temperatures, improving battery safety and cycle life.
Implementation Method 1
bonding a dry-processed polypropylene layer with a wet-processed polyethylene layer
Data Source
AI summary
A multi-layered battery separator for a lithium secondary battery includes a first layer of a dry processed membrane bonded to a second layer of a wet processed membrane. The first layer may be made of a polypropylene based resin. The second layer may be made of a polyethylene based resin. The separator may have more than two layers. The separator may have a ratio of TD/MD tensile strength in the range of about 1.5-3.0. The separator may have a thickness of about 35.0 microns or less. The separator may have a puncture strength of greater than about 630 gf. The separator may have a dielectric breakdown of at least about 2000V.