Battery Separator Resin Fiber Structure for Ion Permeability
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Solution Overview
Problem
Lithium ion secondary batteries used in vehicle battery packs experience deterioration in input and output characteristics and an increased risk of micro-short-circuiting due to continuous restraining pressure and electrode expansion, which causes the separator to collapse and inhibit ion permeability.
Innovation Solution
A separator with a specific resin fiber configuration, including a linearity index of 80% or higher and a thickness-diameter ratio between 300 and 1500, is designed to maintain ion permeability and prevent collapse, ensuring superior input and output characteristics and safety, even under continuous pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a separator with uniform pore size and uniform internal space is used, then ion permeability is improved, but the separator collapses under continuous restraining pressure, causing pore paths to become zigzag and ion permeability to deteriorate
Solution Approach 1:
The separator is constructed with multiple types of fibers (ultrafine fibers, modified cross-section fibers, and resin fibers) with different functions. The ultrafine fibers provide uniform pore structure for ion permeability, while the resin fibers with specific linearity index (80% or higher) maintain structural stability under pressure, preventing collapse and maintaining linear pore paths.
Solution Approach 2:
The invention specifies precise parameter ranges: fiber diameter (3μm or less), linearity index (80% or higher), and thickness (300-1500 μm). These parameter controls ensure the separator maintains both ion permeability and structural stability under continuous restraining pressure during battery operation.
2Stability of the object's composition
If the separator is pressed by continuous restraining pressure during battery pack operation, then the battery pack structure is stabilized, but the separator collapses and the distance between electrodes is narrowed
Solution Approach 1:
The separator is pre-designed with resin fibers having a linearity index of 80% or higher, which provides preliminary structural reinforcement. This pre-configured structure resists the continuous restraining pressure from the battery pack, preventing collapse and maintaining electrode distance before pressure is applied.
3Reliability
If the separator has a linear pore path configuration, then ion permeability is maximized, but the risk of micro-short-circuiting increases when the separator collapses
Solution Approach 1:
The separator uses a composite structure combining ultrafine fibers (for linear pore paths and ion permeability) with resin fibers having high linearity index (for structural stability). This composite approach maintains linear pore configurations while preventing collapse, thereby eliminating micro-short-circuiting risks.
Data Source
AI summary
Provided is a separator for a battery in which, when a ratio of a total length of line segments (Sa), in which an arbitrary straight line (La) intersects with resin fibers (4), to a total length of the straight line (La) on a cross-section of the separator in a thickness direction (TD) is represented by s (%) and when a thickness of the separator is represented by d (μm), 0<s≤100, 3≤d≤50, and 300≤d×s≤1500 are satisfied, the straight line (La) being parallel to a first main surface (40a) and crossing the cross-section.