Biaxially Oriented Separator Membranes With Doubled Production Output
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Solution Overview
Problem
Existing lithium-ion battery separators face challenges in ensuring reliable shutdown at high temperatures to prevent thermal runaway, and there is a need to reduce production costs while maintaining performance and safety, particularly in electric vehicle applications.
Innovation Solution
A process involving the biaxial orientation of stacked, oil-filled polyethylene films followed by solvent extraction and heat stabilization to produce freestanding microporous membranes, utilizing ultrahigh molecular weight polyethylene (UHMWPE) and compatible plasticizers, which allows for increased production efficiency and reduced material costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional single-layer separator manufacturing is used, then production cost is controlled, but production output is limited
Solution Approach 1:
The manufacturing process is segmented into two independent parallel lines, each producing single-layer oil-filled sheets that are subsequently stacked and bonded. This segmentation allows each line to operate independently at full capacity, effectively doubling overall production output without requiring a complete redesign of the manufacturing system.
Solution Approach 2:
Two separate oil-filled sheets produced by independent manufacturing lines are stacked and bonded together to form a multi-layer separator. This merging of independently produced layers achieves doubled production capacity while maintaining the simplicity of single-layer manufacturing processes.
2Reliability
If polyethylene separator is used for shutdown function, then safety at low temperature is improved, but high temperature dimensional stability deteriorates
Solution Approach 1:
The separator employs a multi-layer composite structure where polyethylene layers provide shutdown function at low temperatures and ceramic-coated layers provide high temperature dimensional stability. The ceramic coating prevents shrinkage and deformation at elevated temperatures while the polyethylene base layers maintain their shutdown capability, achieving both safety functions simultaneously.
3Reliability
If ceramic coating is applied to improve high temperature stability, then safety is improved, but manufacturing complexity increases
Solution Approach 1:
The manufacturing process is segmented into base layer production and ceramic coating as separate operational stages. The oil-filled sheet formation, biaxial stretching, and ceramic coating are performed in distinct process steps, allowing each to be optimized independently and simplifying the overall manufacturing complexity.
Solution Approach 2:
The polyethylene base layers with oil-filled structure are fully formed and stabilized before ceramic coating is applied. This preliminary preparation of the substrate ensures optimal adhesion and uniform coating distribution, reducing manufacturing complexity compared to simultaneous or post-coating processes.
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 process effectively doubles the output of separator production lines, reduces material costs, and maintains high-temperature dimensional stability, enhancing the safety and manufacturability of energy storage devices like lithium-ion batteries.
Implementation Method 1
subjected to biaxial orientation, followed by solvent extraction of the process oil
Implementation Method 2
solvent extraction of the process oil (i.e., plasticizer), evaporation of the solvent
Implementation Method 3
evaporation of the solvent
Implementation Method 4
heat stabilization prior to separation into individual microporous membranes
Data Source
AI summary
The present disclosure relates to a process for the formation of freestanding, biaxially-oriented, microporous polyolefin films. In this approach, at least two separate oil-filled, cast or calendered films are stacked on top of each other and then subjected to biaxial orientation, followed by solvent extraction of the process oil (i.e., plasticizer), evaporation of the solvent, and heat stabilization prior to separation into individual microporous membranes that are wound into rolls.