Battery Separator Pore Structure for Anti-Clogging Thermal Stability
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Solution Overview
Problem
Lithium-ion battery separators face issues with clogging due to cycle deterioration and require improved thermal stability and air permeability, especially as battery sizes increase.
Innovation Solution
A separator for electric storage devices is designed with a substrate comprising microporous layers containing 70 wt% or more of polypropylene, where the area average major pore diameter in one layer is controlled relative to another, and the substrate exhibits minimal change in air permeability after high-temperature treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If separator thickness is reduced to increase energy density, then battery energy density is improved, but separator strength and reliability deteriorate
Solution Approach 1:
The separator uses a composite structure combining a polyolefin microporous membrane with a heat-resistant non-woven fabric layer. This composite design allows the separator to maintain reduced thickness for high energy density while the heat-resistant layer provides enhanced mechanical strength and thermal stability, preventing membrane rupture at elevated temperatures.
Solution Approach 2:
The separator applies different material properties to different regions/layers: the polyolefin microporous membrane provides ion permeability and shutdown function, while the heat-resistant non-woven fabric layer provides mechanical strength and thermal stability. This local differentiation allows each layer to optimize its function without compromising overall performance.
2Use of energy by moving object
If separator thickness is reduced, then battery energy density is improved, but thermal stability deteriorates
Solution Approach 1:
The heat-resistant non-woven fabric layer with melting point of 200°C or higher is integrated with the polyolefin microporous membrane to create a composite separator that maintains structural integrity at high temperatures despite reduced overall thickness, preventing thermal runaway and membrane rupture.
Solution Approach 2:
The heat-resistant layer is strategically positioned to provide thermal stability where needed, while the polyolefin layer maintains ion permeability and shutdown characteristics. This functional differentiation allows the thin separator to achieve both high energy density and thermal stability.
3Duration of action of stationary object
If cycle life is extended, then battery durability is improved, but pore clogging increases
Solution Approach 1:
The separator maintains a controlled microporous structure in the polyolefin layer that allows efficient ion transport while the heat-resistant non-woven fabric layer prevents pore clogging by providing a robust framework that resists deformation and blockage during extended cycling, thereby extending battery cycle life.
4Quantity of substance
If air permeability is improved for larger batteries, then heat dissipation is enhanced, but dimensional stability deteriorates
Solution Approach 1:
The combination of polyolefin microporous membrane and heat-resistant non-woven fabric creates a composite structure that balances air permeability for heat dissipation with dimensional stability. The heat-resistant layer acts as a stable framework that maintains separator dimensions while allowing sufficient air flow through the microporous structure.
Data Source
AI summary
The present disclosure provides a separator for an electric storage device, which separator is capable of reducing clogging and has an excellent thermal stability, and an electric storage device using the same. The above-described separator for an electric storage device includes a microporous layer (A) and a microporous layer (B) that contain 70 wt % or more of polypropylene, and the area average major pore diameter in an ND-MD cross section of the microporous layer (B) is not more than 0.95 times the area average major pore diameter in an ND-MD cross section of the microporous layer (A). Alternatively, the separator for an electric storage device contains 70% by weight or more of a polyolefin, and the area average major pore diameter of a first porous surface (X) of the separator is not less than 1.05 times and not more than 10 times the area average major pore diameter of a second porous surface (Y) on the side opposite thereto.