Polyolefin Separator with Porous Functional Layer
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Solution Overview
Problem
Conventional polyolefin microporous membranes used in lithium ion secondary batteries face challenges in achieving sufficient impregnating performance and ion conductivity, leading to deteriorated battery characteristics due to narrow internal structures despite having large open holes on the surface.
Innovation Solution
A separator comprising a base material layer of polyolefin resin and a functional resin layer with a porous interconnected structure, where the diameter of the narrowest portion of the through-holes in the functional resin layer is larger than that of the base material layer, enhancing impregnating performance and battery characteristics without obstructing ion conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a polyolefin microporous membrane is used as a separator, then it provides basic insulation between cathode and anode, but the narrow internal structure deteriorates ion conductivity and impregnating performance
Solution Approach 1:
The patent applies composite materials by combining a polyolefin microporous membrane base layer with a functional resin coating layer containing porous particles. This composite structure maintains the insulation properties of the polyolefin base while the porous particles on the surface provide enhanced ion conductivity and electrolyte impregnation, resolving the contradiction between reliability and harmful effects.
Solution Approach 2:
The patent utilizes porous materials by incorporating porous particles (such as porous polymer beads or inorganic porous materials) into the functional resin coating layer. These porous particles create channels that facilitate ion transport and improve electrolyte penetration, directly addressing the ion conductivity obstruction problem while maintaining the insulating function of the base membrane.
2Manufacturing precision
If the internal structure is made narrow to improve separation precision, then insulation is enhanced, but impregnating performance and ion conductivity deteriorate
Solution Approach 1:
The patent applies local quality by creating different structural characteristics in different regions of the separator. The base layer maintains a fine microporous structure for precise separation and insulation, while the surface coating layer incorporates larger porous particles that provide open channels for ion transport. This localized differentiation allows the separator to simultaneously achieve high separation precision and good ion conductivity.
3Reliability
If a coating layer is applied to the polyolefin microporous membrane to enhance performance, then functional properties are improved, but the narrow internal structure may obstruct ion passage
Solution Approach 1:
The patent specifically addresses this contradiction by using porous particles within the functional resin coating layer. These particles create a three-dimensional porous network that allows electrolyte penetration and ion passage while the resin matrix provides the desired functional properties. The porous structure ensures that the coating enhances separator performance without obstructing ion transport.
4Productivity
If the pore size is increased to improve ion conductivity, then ion passage is enhanced, but the separation precision and insulation performance may deteriorate
Solution Approach 1:
The patent applies segmentation by dividing the separator into two functional zones: a base layer with fine micropores for precise separation and insulation, and a surface coating layer with larger porous particles for enhanced ion conductivity. This segmentation allows each layer to optimize its specific function without compromising the other, enabling both high separation precision and good ion conductivity to coexist.
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 proposed separator design improves impregnating performance and battery characteristics by ensuring sufficient ion conductivity, maintaining cycle stability and preventing lithium precipitation, thus extending battery life and performance.
Implementation Method 1
a functional resin layer which is made of a resin different from the polyolefin resin and has a porous interconnected structure in which many holes are mutually interconnected
Implementation Method 2
diameter of a narrowest portion of through-holes of the functional resin layer is larger than a diameter of a narrowest portion of through-holes of the base material layer
Data Source
AI summary
A separator having at least: a base material layer made of a microporous membrane of a polyolefin resin; and a functional resin layer which is made of a resin different from the polyolefin resin and has a porous interconnected structure in which many holes are mutually interconnected. A diameter of a narrowest portion of through-holes of said functional resin layer is larger than a diameter of a narrowest portion of through-holes of said base material layer.