Porosity-Graded Battery Separator for Ionic Conductivity Balance
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Solution Overview
Problem
The difference in ionic conductivity between positive and negative electrodes in secondary batteries leads to performance deterioration, including reduced lifespan and capacity, which existing technologies have not effectively addressed.
Innovation Solution
A separator with a porous structure having varying porosity along its thickness direction, featuring different coating layers on either surface, with one layer having high hardness and the other low, to balance ionic conductivity by positioning electrodes with high and low conductivity accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the ionic conductivity of positive and negative electrodes is made equal by adjusting electrode area or thickness, then battery performance is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The separator is designed with non-uniform porosity distribution, where different regions of the separator have different porosity values. Specifically, the porosity varies along the thickness direction, creating zones with different ionic conductivity characteristics. This allows the separator to locally compensate for electrode ionic conductivity differences without requiring complex electrode area or thickness adjustments.
Solution Approach 2:
The invention changes the porosity parameter of the separator to resolve the ionic conductivity imbalance. By controlling the porosity distribution within the separator (making it non-uniform), the effective ionic conductivity pathway is adjusted to match the different ionic conductivity characteristics of positive and negative electrodes, thereby balancing mass transfer rates without modifying electrode geometry.
2Ease of manufacture
If uniform porosity is maintained throughout the separator, then manufacturing is simpler, but ionic conductivity balance between electrodes with different properties cannot be achieved
Solution Approach 1:
The separator incorporates spatially varying porosity characteristics, where different regions serve different functions. The porosity is designed to be higher in regions adjacent to electrodes with lower ionic conductivity and lower in regions adjacent to electrodes with higher ionic conductivity, creating a tailored ionic transport pathway that balances overall cell performance.
Solution Approach 2:
The invention addresses the ionic conductivity balance by introducing variation in the thickness direction of the separator. Instead of modifying electrode dimensions (area or thickness), the solution moves to another dimension - the internal porosity distribution through the separator thickness - to achieve the desired ionic conductivity matching.
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 configuration reduces initial resistance and enhances capacity retention by aligning electrodes with high and low ionic conductivity to the appropriate porosity levels, thereby improving battery performance and energy density.
Implementation Method 1
improving lithium ionic conductivity and an electrolyte impregnation rate of the SRS separator
Implementation Method 2
A volume in which a liquid electrolyte solution is placed is increased by virtue of the porous structure, thereby improving lithium ionic conductivity and an electrolyte impregnation rate
Data Source
AI summary
Disclosed is a separator for a secondary battery comprising a polyolefin and a separator body having a porous structure, wherein the separator body is configured to be in a form having a difference in porosity along a thickness direction, and it is possible to improve the problem of imbalance in ionic conductivity caused by differences in thickness and electrical conductivity between a positive electrode and a negative electrode.