Microlayer Battery Separators for Thin, High-Strength Membranes
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Solution Overview
Problem
Existing methods for manufacturing microporous bi-layered or tri-layered battery separator membranes do not fully optimize the balance of strength and performance properties, particularly in lithium ion rechargeable batteries, as they fail to meet the increasing demands for thinner and stronger separators.
Innovation Solution
The development of multilayer microporous battery separators is achieved through a co-extrusion process using multiple extruders to create layers with different or distinct polymers, additives, and fillers, which are then laminated together, resulting in improved properties such as increased dielectric breakdown strength, puncture resistance, and reduced splitting propensity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional laminating or coextrusion methods are used to manufacture microporous bi-layered or tri-layered battery separator membranes, then the basic separator structure is formed, but the balance of strength and performance properties is not fully optimized
Solution Approach 1:
The separator membrane is divided into multiple distinct layers (first layer, second layer, third layer, etc.) with different polymer compositions and microporous structures. Each layer serves specific functions: outer layers provide mechanical strength while inner layers provide shutdown function. This segmentation allows optimization of strength and performance properties independently in different regions of the separator.
Solution Approach 2:
The invention uses composite multi-layer structures combining different polyolefin materials (polyethylene, polypropylene) with distinct properties. Each layer has tailored composition, porosity, and micropore characteristics to achieve optimal balance between mechanical strength, thermal shutdown function, and electrolyte wettability without requiring overly complex single-layer structures.
2Length of moving object
If the separator membrane is made thinner to meet battery design requirements, then battery energy density improves, but the separator strength and durability decrease
Solution Approach 1:
The thin separator is segmented into multiple layers, each contributing to overall strength. The multi-layer construction distributes mechanical stress across several interfaces, preventing catastrophic failure that would occur in a single thin layer. This enables achieving both thinness for high energy density and sufficient strength for safety.
Solution Approach 2:
Different polymer layers with complementary properties are combined to create a thin yet strong composite structure. The outer layers use polymers optimized for mechanical strength while inner layers use polymers optimized for shutdown function, achieving both thinness and durability through material composition rather than increasing thickness.
3Reliability
If multiple layers with different polymers are combined to improve performance, then dielectric breakdown strength and puncture resistance increase, but the manufacturing process becomes more complex
Solution Approach 1:
Multiple layers with different polymer compositions and functions are merged into a single integrated multi-layer membrane structure through coextrusion or lamination. This combining approach achieves superior dielectric breakdown strength and puncture resistance by distributing electrical and mechanical stresses across multiple material interfaces, while the integrated structure simplifies handling compared to separate components.
Solution Approach 2:
Each layer in the multi-layer structure is designed to perform multiple functions simultaneously: mechanical support, thermal shutdown, electrolyte absorption, and electrical insulation. This multi-functionality reduces the need for additional specialized components, simplifying the overall manufacturing process despite the increased material complexity.
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 multilayer microporous battery separators exhibit enhanced safety, strength, and durability, with increased dielectric breakdown, shutdown speed, and puncture resistance, leading to improved performance in lithium ion batteries.
Implementation Method 1
The development of multilayer microporous battery separators is achieved through a co-extrusion process using multiple extruders to create layers with different or distinct polymers, additives, and fillers, which are then laminated together
Implementation Method 2
layers with different or distinct polymers, additives, and fillers, which are then laminated together, resulting in improved properties
Data Source
AI summary
Described herein is a multilayer microporous film or membrane that may exhibit improved properties, including improved dielectric break down and strength, compared to prior monolayer or tri-layer microporous membranes of the same thickness. The preferred multilayer microporous membrane comprises microlayers and one or more lamination barriers. Also disclosed is a battery separator or battery comprising one or more of the multilayer microporous films or membranes. The inventive battery and battery separator is preferably safer and more robust than batteries and battery separators using prior monolayer and tri-layer microporous membranes. Also, described herein is a method for making the multilayer microporous separators, membranes or films described herein.