Asymmetric Separator Design for Lithium Battery Thermal Stability
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Solution Overview
Problem
Conventional lithium secondary batteries face issues with electrical short-circuits due to thermal deformation of the polymer separator during heat fusion, which can lead to increased volume when trying to prevent short-circuits, and corrosion risks from exposed metal foil layers.
Innovation Solution
The battery unit design features a separator with varying widths of protruding portions, where the wider portion corresponds to the electrode lead extraction side to prevent short-circuits and deformation, and a narrower portion on the non-heat-fused side to maintain structural integrity and prevent corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the separator width is increased to prevent short-circuits caused by thermal deformation, then the reliability is improved, but the volume of the battery unit increases
Solution Approach 1:
The separator is designed with different widths at different locations: a first width at the first shorter side (from which electrode leads are drawn) and a second width at the second shorter side. This local differentiation allows the separator to provide enhanced protection against thermal deformation at the critical side while maintaining compact dimensions at the non-critical side, thus preventing short-circuits without unnecessarily increasing overall battery volume.
Solution Approach 2:
The separator intentionally breaks symmetry by having unequal widths at opposite shorter sides. The first width is greater than the second width, creating an asymmetric configuration that addresses the specific thermal deformation risk at the side with electrode leads while optimizing space utilization, thereby resolving the contradiction between reliability and volume.
2Stability of the object's composition
If the separator width is increased to account for thermal deformation, then the stability is improved, but the manufacturing precision requirements increase
Solution Approach 1:
Rather than uniformly increasing the separator width throughout, the invention applies width enhancement only at the specific location (first shorter side) where thermal deformation poses the greatest risk. This localized approach maintains structural stability where needed while avoiding the need for high-precision control across the entire separator, thus reducing overall manufacturing precision requirements.
Solution Approach 2:
The separator width is segmented into different regions with different dimensions. By dividing the separator into zones of different widths (first width at one shorter side, second width at the other), the invention simplifies the manufacturing control problem, as each segment can be optimized independently rather than requiring uniform precision across the whole separator.
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
This design enhances stability by preventing electrical contact between electrode plates and reduces the likelihood of corrosion, allowing for a high-capacity battery without increasing volume or compromising performance.
Implementation Method 1
a separator interposed between the opposing electrode plates, having a width greater than that of each electrode plate, and having different widths of protruding portions which stick out on either side of the electrode plate
Data Source
AI summary
A battery unit and a lithium secondary battery employing the same are provided. The battery unit includes a positive electrode plate having a positive current collector and a positive active material layer formed on at least one plane of the positive current collector, a positive electrode lead electrically connected with the positive current collector, a negative electrode plate having a negative current collector and a negative active material layer formed on at least one plane of the negative current collector, a negative electrode lead electrically connected with the negative current collector, and a separator interposed between the positive electrode plate and the negative electrode plate, having a width greater than that of each electrode plate, and having different widths of protruding portions which stick out on either side of the electrode plate. Since the design margins of protruding portions of a separator which stick out on either side of each electrode plate are made different from each other, deformation of the separator due to heat applied during heat fusion can be prevented. Accordingly, electrical contact between electrode plates having different polarities can be prevented, thereby improving the stability of a battery.