Gradient-Porosity Sodium Battery Separator for Swelling Resistance
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Solution Overview
Problem
Sodium batteries experience rapid degradation in cycle life due to volume swelling during intercalation and deintercalation processes, leading to irreversible swelling and compression of the separator, which affects electrolyte infiltration and cycle performance.
Innovation Solution
A separator for sodium batteries with a porosity gradient along its thickness direction, where the porosity decreases from one surface to the other, providing rigidity to resist swelling and deformation while ensuring effective electrolyte infiltration and release.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the separator has high porosity to ensure electrolyte infiltration, then the electrolyte infiltration is sufficient, but the separator lacks rigidity and cannot resist electrode swelling
Solution Approach 1:
The separator employs a porosity gradient structure where the porosity varies along the thickness direction. The first surface has higher porosity (50-70%) to ensure sufficient electrolyte infiltration, while the second surface has lower porosity (30-50%) to provide rigidity and resist electrode swelling. This local differentiation of porosity resolves the contradiction between electrolyte infiltration and structural strength.
2Ease of manufacture
If the separator has uniform porosity to simplify manufacturing, then the manufacturing process is easier, but the separator cannot simultaneously achieve both electrolyte infiltration and swelling resistance
Solution Approach 1:
The separator changes the porosity parameter along the thickness direction, creating a gradient structure. The porosity decreases from the first surface to the second surface, allowing different regions to perform different functions. This parameter variation enables the separator to maintain both good electrolyte infiltration and effective swelling resistance, thereby improving cycle performance while remaining manufacturable through established gradient structure techniques.
3Force
If the separator is compressed to resist electrode swelling, then the swelling resistance is improved, but the electrolyte infiltration becomes insufficient
Solution Approach 1:
The porosity gradient structure allows the separator to locally adapt to compression forces. When the separator is compressed by electrode swelling, the lower porosity region (second surface) provides structural support and resistance, while the higher porosity region (first surface) maintains sufficient space for electrolyte infiltration. This local differentiation prevents the trade-off between swelling resistance and electrolyte access.
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 mitigates rapid degradation by resisting electrode swelling, maintaining electrolyte infiltration, and prolonging the cycle life of sodium batteries.
Implementation Method 1
a porosity of the separator decreases gradually from the first surface to the second surface
Implementation Method 2
The separator with this structure has a certain rigidity, facilitating its ability to resist swelling and deformation
Implementation Method 3
The separator also has a certain compressibility, enabling sufficient and effective infiltration of an electrolyte before compression and effectively and promptly release of the electrolyte after compression
Data Source
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AI summary
The present application relates to the field of battery technologies, and specifically, to a separator for a sodium battery, a secondary battery, and an electric apparatus. The separator for the sodium battery has a first surface and a second surface along its thickness direction, and a porosity of the separator decreases gradually from the first surface to the second surface. The separator with this structure has a certain rigidity, facilitating its ability to resist swelling and deformation of a positive electrode plate and a negative electrode plate to a certain extent, while also having a certain compressibility, effectively ensuring sufficient infiltration of an electrolyte, thereby mitigating the rapid degradation of the cycle life of a battery caused by volume swelling during the use of the sodium battery.