Battery Separator Pore Structure for Winding-Induced Deformation
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Solution Overview
Problem
The deformation of pores in battery separators during the winding process of jelly roll formation leads to non-uniform electrolyte distribution, causing battery degradation, reduced power capability, and shortened longevity.
Innovation Solution
The battery separator is designed with varying pore characteristics across its thickness, including differences in cross-sectional area, size, shape, and orientation between different segments. These variations leverage the deformation caused by winding, resulting in more uniform pore sizes and shapes in the wound state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the separator is wound to form a jelly roll, then the battery structure is formed, but the pores deform and electrolyte distribution becomes non-uniform
Solution Approach 1:
The separator is pre-formed with specific pore characteristics (different cross-sectional areas) in the unwound state before winding. This preliminary configuration of non-uniform pores compensates for the deformation that will occur during winding, ensuring uniform pore shapes and electrolyte distribution in the final wound state.
Solution Approach 2:
Different regions of the separator thickness are designed with different pore cross-sectional areas. The first pores in the first segment have different characteristics than the second pores in the second segment, allowing each region to deform differently during winding to achieve overall uniformity.
2Productivity
If the separator has high porosity to maintain active material access to electrolyte, then ionic movement is supported, but pore deformation during winding causes battery degradation
Solution Approach 1:
The separator employs spatially varying pore characteristics where different segments of the thickness have different pore cross-sectional areas. This local differentiation allows the high porosity needed for ionic movement while controlling deformation behavior during winding to prevent battery degradation.
Data Source
AI summary
A separator of a battery cell includes first pores disposed through a first segment of a thickness of the separator, and second pores disposed through a second segment of the thickness. In an unwound state of the separator, a first cross-sectional area of the first pores differs in size from a second cross-sectional area of the second pores by a first amount. In a wound state of the separator, the first cross-sectional area is substantially equal in size to the second cross-sectional area, or the first cross-sectional area differs in size from the second cross-sectional area by a second amount that is less than the first amount.