Microlayer Battery Separators for Strength and Shutdown Balance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing battery separator membranes lack optimal balance of strength and performance properties, particularly in lithium ion rechargeable batteries, with issues related to splitting, tensile strength, and dielectric breakdown.
Innovation Solution
Development of multi-layered microporous membranes created through co-extrusion and lamination of polymer layers, such as polyethylene and polypropylene, with each layer being micrometer or nanometer thick, to enhance mechanical strength, porosity, and reduced splitting propensity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If single-layer membranes are used, then manufacturing is simpler, but mechanical strength and resistance to splitting are insufficient
Solution Approach 1:
The membrane is divided into multiple layers (typically 3-5 layers) with each layer serving specific functions. The segmentation allows optimization of each layer's properties while collectively achieving superior mechanical strength and split resistance compared to single-layer membranes.
Solution Approach 2:
The invention uses composite membrane structures combining different polymer materials in multiple layers. Each layer may contain different polymers or polymer blends optimized for specific properties, creating a composite structure that achieves both high strength and manufacturing feasibility.
2Strength
If membrane thickness is increased, then mechanical strength improves, but porosity and ion transport performance deteriorate
Solution Approach 1:
By dividing the total membrane thickness into multiple thinner layers, each layer can maintain high porosity for good ion transport while the stacked multi-layer structure collectively provides the required mechanical strength. This resolves the trade-off between thickness and porosity.
Solution Approach 2:
The multi-layer composite structure allows different layers to have optimized porosity and thickness ratios, achieving overall high porosity while maintaining structural integrity and mechanical strength through the layered architecture.
3Reliability
If polymer material composition is simplified, then manufacturing is easier, but shutdown function and dielectric breakdown strength are insufficient
Solution Approach 1:
Different polymer layers are assigned specific functions: some layers provide shutdown function (closing pores at elevated temperatures), while others provide dielectric breakdown strength. This functional segmentation allows optimization of each layer's polymer composition for its specific role.
Solution Approach 2:
The multi-layer composite structure combines different polymer materials (e.g., polyethylene, polypropylene, PVDF) in specific configurations, where each polymer contributes specific properties such as shutdown temperature, dielectric strength, or mechanical support, achieving superior overall performance.
4Manufacturing precision
If co-extrusion and lamination processes are used, then membrane performance is optimized, but manufacturing complexity increases
Solution Approach 1:
The manufacturing process is segmented into distinct stages: co-extrusion of multiple layers followed by lamination. This segmentation allows optimization of each process step independently, achieving precise layer control while managing overall manufacturing complexity.
Solution Approach 2:
The co-extrusion and lamination processes are specifically designed to create the multi-layer composite structure, where process parameters are optimized for each stage to achieve the desired layer precision and bonding quality.
Data Source
AI summary
In accordance with at least selected embodiments, a battery separator or separator membrane comprises one or more co-extruded multi-microlayer membranes optionally laminated or adhered to another polymer membrane. The separators described herein may provide improved strength, for example, improved puncture strength, particularly at a certain thickness, and may exhibit improved shutdown and/or a reduced propensity to split.