Dual-Layer Battery Separator Balancing Porosity and Puncture Strength
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Solution Overview
Problem
Secondary batteries face limitations in ion transport, leading to poor cycling performance.
Innovation Solution
A separator comprising two base films with different porosities and melting points, where the porosity ratio of the first base film to the second base film is 1.02≤P1/P2≤3, balanced to enhance air permeability and strength, thereby improving the reliability and cycling performance of the secondary battery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the porosity of the base film is increased to improve ion transport, then the air permeability is improved, but the strength decreases and the film becomes easily punctured
Solution Approach 1:
The separator is divided into two distinct base films with different porosity characteristics. The first base film has higher porosity (P1) to facilitate ion transport, while the second base film has lower porosity (P2) to provide mechanical strength. The porosity ratio P1/P2 is controlled within 1.02-3 to balance these opposing requirements, allowing the composite separator to achieve both good ion permeability and resistance to dendrite puncture.
2Productivity
If the porosity of the base film is increased to improve air permeability, then the air permeability is improved, but the strength decreases
Solution Approach 1:
The separator structure is segmented into two functional layers: the first base film with higher porosity (P1) that provides excellent air permeability for electrolyte penetration, and the second base film with lower porosity (P2) that provides robust mechanical strength. By controlling the porosity ratio P1/P2 within 1.02-3, the invention achieves optimal balance between air permeability and strength, preventing both insufficient ion transport and structural failure.
3Device complexity
If a single base film structure is used, then the device complexity is low, but the cycling performance is poor due to limited ion transport
Solution Approach 1:
The separator employs a composite structure consisting of two different base films bonded together. Each base film can be made from suitable polyolefin materials, and their combination creates a separator with superior properties: the higher porosity first film enhances ion transport pathways, while the lower porosity second film provides structural integrity. This composite approach significantly improves cycling performance compared to single-film separators, while maintaining reasonable manufacturing complexity.
Data Source
AI summary
The present application provides a separator, which includes a first base film and a second base film, where the melting point of the second base film is lower than the melting point of the first base film; the porosity of the first base film is denoted as P1, the porosity of the second base film is denoted as P2, and 1.02≤P1/P2≤3. The base film with high porosity has good air permeability, so the first base film with high porosity exhibits excellent air permeability. The base film with low porosity has good strength, so the second base film with low porosity exhibits good strength and is not easily punctured by lithium dendrites. Therefore, through the cooperation of the first base film and the second base film in the present application, the separator has good air permeability and strength, thus improving the reliability and cycling performance of the secondary battery.