Battery Cell Separator Layout for Puncture Resistance
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Solution Overview
Problem
Secondary batteries face issues with safety and reliability due to thin separators that are prone to puncture, leading to short circuits and reduced pass rates in high-voltage and impact tests, increasing defect rates and reducing energy density.
Innovation Solution
The battery cell design includes a first separator with a greater thickness than a second separator, positioned at the ends of the electrode assembly, to enhance strength and reduce puncture risk, while maintaining energy density by adjusting the thickness difference within specific ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the separator thickness is increased to reduce puncture risk and improve safety, then the strength and reliability improve, but the energy density decreases
Solution Approach 1:
The patent applies different separator thicknesses at different locations: the first separator at the ends of the electrode assembly has a greater thickness (first thickness) to provide enhanced puncture resistance, while the second separator in the middle region has a smaller thickness (second thickness) to maintain energy density. This local differentiation resolves the contradiction by providing strength where needed while minimizing overall volume loss.
2Reliability
If the separator thickness is uniformly increased throughout the electrode assembly, then the safety and puncture resistance improve, but the energy density significantly decreases
Solution Approach 1:
Instead of uniform thickness increase, the patent implements localized thickness increase only at the end regions where the first separators are positioned. The middle region retains thinner second separators. This resolves the contradiction by providing enhanced safety at critical locations without the penalty of uniformly reduced energy density.
Solution Approach 2:
The separator system is segmented into two distinct types: first separators with greater thickness at the ends and second separators with smaller thickness in the middle. This segmentation allows each region to be optimized for its specific function - safety at the ends and energy density in the middle - resolving the overall contradiction.
3Strength
If the thickness difference between first and second separators is increased, then the puncture resistance at ends improves, but the energy density decreases more significantly
Solution Approach 1:
The patent optimizes the thickness parameter by establishing a specific difference range (2-5 μm) between the first and second separators. This parameter change resolves the contradiction by providing sufficient strength improvement at the ends while limiting the energy density penalty to an acceptable range.
Data Source
AI summary
A battery cell includes an electrode assembly, where the electrode assembly includes a first separator, a second separator, and multiple electrode plates stacked. The multiple electrode plates include two outer electrode plates located at two ends and multiple inner electrode plates located between the two outer electrode plates. The first separator is disposed between the outer electrode plate and the inner electrode plate adjacent to the outer electrode plate; and the second separator is disposed between adjacent two of the inner electrode plates; where thickness of the first separator is greater than thickness of the second separator.