Dry-Process Polyolefin Separator Membranes for Thin High-Puncture Batteries
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Solution Overview
Problem
Existing microporous membranes used as battery separators often fail to meet the requirements of being thin, puncture-resistant, and having uniform thickness while maintaining high tensile strength and electrochemical stability, leading to issues in modern battery equipment and performance.
Innovation Solution
Development of a dry-process polyolefin microporous membrane with specific thickness ranges and properties, including high tensile strength, increased surface roughness, and a polypropylene blend with long chain branching, which enhances puncture resistance and reduces ply-to-ply adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the separator thickness is reduced to increase energy density, then the energy density is improved, but the puncture strength and thickness uniformity deteriorate
Solution Approach 1:
The patent uses a composite material system consisting of polypropylene blend (including linear polypropylene and long chain branched polypropylene) combined with a specific microporous membrane structure. This composite approach allows the thin separator (12 microns or less) to achieve both high energy density and sufficient puncture strength (230 gf or more) through the synergistic effect of the polymer blend and controlled pore structure.
Solution Approach 2:
The patent changes key material parameters including the polypropylene blend composition (specific ratio of linear to long chain branched polypropylene), micropore size distribution (0.03 to 0.08 microns), and crystallinity (40 to 60%). These parameter optimizations enable the thin separator to maintain mechanical integrity while achieving reduced thickness for higher energy density.
2Quantity of substance
If the separator thickness is reduced, then the energy density is improved, but the thickness uniformity deteriorates
Solution Approach 1:
The patent optimizes processing parameters including extrusion temperature, stretching ratio, and annealing conditions to achieve uniform thickness distribution. The specific combination of polypropylene blend composition and controlled micropore formation parameters enables consistent thickness control at 12 microns or less, preventing defects while maintaining high energy density.
3Reliability
If the pore size is increased to improve ion conductivity, then the ionic conductivity is improved, but the puncture strength deteriorates
Solution Approach 1:
The patent creates a hierarchical pore structure with different size distributions: micropores (0.03 to 0.08 microns) for ion transport and macrovoids (0.3 to 0.8 microns) for mechanical reinforcement. This local quality differentiation allows regions optimized for ionic conductivity while other regions provide structural support for puncture resistance, achieving both wettability and mechanical strength in the thin separator.
Data Source
AI summary
An improved microporous membrane is described herein. The microporous membrane may be useful as a battery separator, separator membrane, base film, or membrane with a variety of uses thereof. The improved microporous membranes described herein may be dry process polyolefin membranes and may be used as battery separators or as a component of a composite or battery separator. The battery separators or composites may be used in energy storage devices including primary batteries, secondary batteries, fuel cells, capacitors, or super capacitors.