Resilient Battery Separator for Electrode Expansion Control
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Solution Overview
Problem
Secondary batteries, particularly lithium-ion and sodium-ion batteries, face challenges in maintaining cycling performance due to volume expansion and contraction of the negative electrode during charging and discharging, leading to internal stress, housing deformation, and deterioration of the cycling performance.
Innovation Solution
A separator with a resilience coefficient ranging from 10% to 90% is used, which absorbs and rebounds with the negative electrode's volume expansion, mitigating stress and maintaining contact with the electrode plate, thereby improving cycling performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the separator has high resilience to absorb volume expansion, then cycling performance is improved, but the separator thickness increases
Solution Approach 1:
The separator employs a porous structure with controlled porosity (30-80%) that provides elastic deformation space within the thickness direction. This porous architecture allows the separator to absorb volume expansion of the negative electrode during charging while maintaining an optimized thickness, resolving the contradiction between resilience and thickness.
Solution Approach 2:
The patent optimizes the resilience coefficient k within a specific range (10%-90%) and controls porosity (30-80%) to achieve the desired elastic deformation capability. By adjusting these parameters, the separator can provide sufficient resilience to absorb volume expansion without requiring excessive thickness, thus improving cycling performance while maintaining compact dimensions.
2Stress or pressure
If the separator compresses to absorb volume expansion, then stress on electrode plate is reduced, but contact between separator and electrode plate deteriorates
Solution Approach 1:
The separator is designed with dynamic elastic properties, allowing it to compress during charging to absorb volume expansion and reduce stress on the electrode plate. During discharging, the separator rebounds to restore contact with the electrode plate. This dynamic behavior resolves the contradiction between stress reduction and contact maintenance.
Solution Approach 2:
The separator undergoes periodic compression and rebound cycles corresponding to the charging and discharging cycles of the battery. During charging, it compresses to absorb expansion; during discharging, it rebounds to maintain contact. This periodic action ensures both stress reduction and sustained contact throughout the battery's operational cycles.
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
The separator effectively reduces stress and deformation, enhancing the cycling performance and stability of the secondary battery by absorbing and rebounding with the negative electrode's volume changes, thus maintaining good contact with the electrode plate.
Implementation Method 1
The compressed separator can absorb the volume expansion of the negative electrode material through its elastic deformation
Implementation Method 2
When the secondary battery containing the separator discharges to reduce the volume expansion of the negative electrode active material, the separator can rebound, thereby maintaining good contact with the electrode plate
Data Source
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AI summary
This application provides a separator, an electrode assembly, a secondary battery, and an electric apparatus, where a resilience coefficient k of the separator ranges from 10% to 90%, where k = (H0 - H1)/H0 × 100%, H0 represents an initial thickness of the separator at 25°C, and H1 represents a thickness of the separator having the initial thickness H0 after compressed at 25°C with a load of 0.8 MPa for 60 seconds and then relaxed for 60s after the load is removed. The separator of this application has excellent resilience performance.