Dry-Process Microporous Battery Separators With Low Splittiness
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for producing microporous battery separators do not fully optimize strength and performance properties, particularly for thin separators, and often involve environmentally challenging wet processes that require solvent handling and disposal issues, failing to combine high strength with low environmental impact and excellent cycle performance in lithium batteries.
Innovation Solution
A dry process method using high molecular weight, low melt flow index polymer resins to produce microporous battery separators with a high crystalline lamellae orientation, resulting in reduced splittiness, increased strength, and improved porosity, without the need for solvents, thus achieving enhanced cycle life and safety in lithium ion batteries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If wet process methods are used to produce microporous battery separators, then porosity and permeability are improved, but environmental impact increases due to solvent handling and disposal requirements
Solution Approach 1:
The patent changes the fundamental parameter of the manufacturing process from wet to dry process, eliminating solvent usage while maintaining porosity through alternative pore formation mechanisms in the extruded membrane structure
Solution Approach 2:
The invention extracts and eliminates the harmful solvent component from the manufacturing process, achieving porosity without requiring plasticizer extraction and solvent disposal systems
2Quantity of substance
If separator thickness is reduced to increase energy density, then energy density improves, but strength and splitting resistance deteriorate
Solution Approach 1:
The patent applies local quality by creating regions of high crystalline orientation and extended chain structures at critical stress points within the thin membrane, providing localized strength enhancement without increasing overall thickness
Solution Approach 2:
The invention uses composite material structures combining highly oriented crystalline regions with controlled amorphous phases, creating a multi-phase architecture that provides both thinness and mechanical strength
3Strength
If high molecular weight polymer resins are used to increase strength, then processing difficulty increases due to higher viscosity
Solution Approach 1:
The patent changes processing parameters including extrusion temperature, shear rate, and cooling conditions to enable effective processing of high molecular weight polymers that would otherwise be too viscous for conventional extrusion
Solution Approach 2:
The invention performs preliminary actions by pre-drying the extruded membrane to remove moisture before heat treatment, preventing defects and ensuring proper crystalline structure formation during subsequent processing steps
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 dry process method produces thin microporous battery separators with reduced splittiness and improved strength, matching or exceeding the performance of wet process separators while avoiding environmental issues, thus enhancing energy density and cycle life in lithium ion batteries.
Implementation Method 1
produces a precursor membrane with an internal microstructure having a high level of crystalline lamellae orientation
Implementation Method 2
extruding a film precursor by a blown film method
Implementation Method 3
biaxial stretching technique involving both MD and TD stretching of a dry process precursor membrane
Data Source
AI summary
The present invention relates in at least selected embodiments to novel or improved microporous battery separators for lithium rechargeable batteries and/or related methods of making and/or using such separators. A particular inventive dry process battery separator or membrane separator exhibits a thickness that is less than about 14 μm and has increased strength performance as defined by reduced splittiness. The mode of splitting failure has been investigated, and the improvement in splittiness quantified by a novel test method known as the Composite Splittiness Index (CSI).