Thermally Stable Porous Layer on Polyolefin Separator
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Solution Overview
Problem
Conventional methods for enhancing the thermal stability of battery separators, such as crosslinking, adding inorganic particles, or using heat-resistant resins, face limitations including non-uniform quality, increased production complexity, and reduced physical properties, which can lead to electrical shorts and safety issues in high-capacity/high-power lithium secondary batteries.
Innovation Solution
A microporous polyolefin composite film with a thermally stable porous layer formed by phase separation, incorporating organic or inorganic particles and a heat-resistant polymer with an aromatic ring, providing improved permeability, meltdown temperature, and shrinkage resistance, is developed. This film is manufactured by coating a solution containing heat-resistant polymer and particles onto a polyolefin microporous film, followed by drying and phase separation to create a stable coating layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If crosslinking method is used to enhance thermal stability, then thermal stability is improved, but production complexity increases and quality uniformity deteriorates
Solution Approach 1:
The patent changes the chemical composition parameters by incorporating heat-resistant polymers (polyimide, polyamide, polysulfone) and inorganic particles (alumina, silica) into the polyolefin separator matrix. This compositional parameter change provides thermal stability without requiring complex crosslinking processes, thereby improving reliability while avoiding increased production complexity
Solution Approach 2:
The patent creates a composite separator structure by combining polyolefin base material with heat-resistant polymer additives and inorganic particles. This composite material approach achieves enhanced thermal stability through material composition rather than complex processing methods, resolving the contradiction between reliability improvement and production complexity
2Reliability
If inorganic particles are added to enhance thermal stability, then thermal stability is improved, but mixing uniformity deteriorates and pinholes occur
Solution Approach 1:
The patent utilizes the porous structure of the separator to accommodate inorganic particles (alumina, silica) within the pore network. This approach allows uniform distribution of particles throughout the three-dimensional structure, improving mixing uniformity while maintaining thermal stability and avoiding pinhole formation
3Reliability
If ultra high molecular weight polyethylene is used to enhance thermal stability, then thermal stability is improved, but extruding ability deteriorates and incomplete stretching occurs
Solution Approach 1:
The patent changes the molecular weight parameters by using conventional polyethylene with lower molecular weight instead of ultra high molecular weight polyethylene. This parameter change improves extruding ability and stretching uniformity while compensating for thermal stability through the addition of heat-resistant polymers and inorganic particles, thus resolving the contradiction between reliability and ease of manufacture
4Reliability
If heat-resistant resin is melt-kneaded to enhance thermal stability, then thermal stability is improved, but manufacturing process complexity increases
Solution Approach 1:
The patent merges the thermal stability function with the base separator material by incorporating heat-resistant polymers and inorganic particles directly into the separator matrix during a single manufacturing process. This integration eliminates the need for separate heat-resistant layer formation or additional processing steps, improving reliability while avoiding increased manufacturing process 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 resulting film exhibits excellent thermal stability, high permeability, and uniform quality, effectively preventing electrical shorts and ensuring safety in high-capacity/high-power batteries by maintaining stability under high temperature and voltage conditions.
Implementation Method 1
forming a porous coating layer by phase separation
Implementation Method 2
drying and phase separation to create a stable coating layer
Data Source
AI summary
Provided is a microporous polyolefin composite film with a thermally stable porous layer at high temperature, particularly, to the microporous polyolefin composite film in which the thermally stable porous layer at high temperature, which contains organic or inorganic particles and heat-resistant polymer having aromatic ring in main chain and also having a melting temperature or a glass transition temperature of 170 to 500° C., is formed on one surface or both surfaces of a polyolefin microporous film by a phase separation, wherein the composite film with the porous layer has a permeability of 1.5×10−5 to 20.0×10−5 Darcy, a meltdown temperature of 160 to 300° C., a MD/TD shrinkage of 1 to 40% at a temperature of 150° C. for 60 minutes.