Multilayer Battery Separator Structure for Ionic Conductivity and Insulation
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Solution Overview
Problem
Lithium-ion secondary batteries face challenges with direct contact between electrodes leading to safety hazards, self-discharge, and mechanical failure due to whisker-like structures, while achieving desired ionic conductivity and mechanical strength in separators is difficult, especially in flexible batteries that require stress relief.
Innovation Solution
A multilayer separator structure with different pore sizes and thicknesses is used between the positive and negative electrodes, allowing for tailored ionic conductivity and mechanical strength, preventing electrode contact and enhancing flexibility and stress relief in the battery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single separator is used between electrodes, then the structure is simple, but it cannot simultaneously achieve desired ionic conductivity and mechanical strength
Solution Approach 1:
The separator is divided into multiple layers (first separator layer and second separator layer) with different pore sizes. The first layer has larger pores for high ionic conductivity, while the second layer has smaller pores for mechanical strength and whisker prevention. This segmentation allows each layer to specialize in one function, resolving the contradiction between simplicity and performance.
Solution Approach 2:
Different regions of the separator structure are assigned different properties: the first separator layer has larger pore diameter for ionic conductivity, while the second separator layer has smaller pore diameter for mechanical strength. This local differentiation of properties allows the separator as a whole to achieve both ionic conductivity and mechanical strength simultaneously.
2Reliability
If larger pores are used in separator to improve ionic conductivity, then ionic conductivity increases, but electrode insulation performance deteriorates
Solution Approach 1:
The separator is segmented into two layers with different pore sizes. The first layer has larger pores optimized for ionic conductivity, while the second layer has smaller pores optimized for electrode insulation. This segmentation allows the system to achieve both high ionic conductivity and effective electrode insulation simultaneously.
Solution Approach 2:
The separator structure implements local quality differentiation where the first separator layer has larger pore diameter for ionic conductivity and the second separator layer has smaller pore diameter for electrode insulation. This local property assignment resolves the contradiction between ionic conductivity and safety.
3Object-affected harmful factors
If smaller pores are used in separator to improve electrode insulation, then safety improves, but ionic conductivity decreases
Solution Approach 1:
The separator is divided into two functional layers: the first layer with larger pores for ionic conductivity and the second layer with smaller pores for electrode insulation. This segmentation allows each layer to optimize for its specific function without compromising the other.
Solution Approach 2:
Different pore sizes are assigned to different layers of the separator structure. The first separator layer has larger pore diameter for ionic conductivity while the second separator layer has smaller pore diameter for electrode insulation, resolving the contradiction between safety and ionic conductivity.
4Object-affected harmful factors
If thicker separator is used to improve mechanical strength and prevent whisker penetration, then electrode insulation improves, but ionic conductivity and flexibility deteriorate
Solution Approach 1:
The separator is segmented into multiple layers with different thicknesses and pore sizes. The first layer has larger pores and optimized thickness for ionic conductivity, while the second layer has smaller pores and optimized thickness for mechanical strength and whisker prevention. This segmentation allows the separator to achieve both protection and conductivity without requiring excessive thickness.
Solution Approach 2:
Different layers of the separator have different thicknesses and pore sizes optimized for specific functions. The first separator layer has larger pore diameter for ionic conductivity while the second separator layer has smaller pore diameter for whisker prevention. This local differentiation allows the separator to provide both protection and maintain flexibility without compromising ionic conductivity.
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 multilayer separator structure effectively prevents electrode contact, maintains ionic conductivity, and enhances the mechanical strength and flexibility of lithium-ion secondary batteries, ensuring long-term reliability and safety by managing stress and whisker growth.
Implementation Method 1
The first separator is provided with a first pore, the second separator is provided with a second pore, and the size of the first pore is different from the size of the second pore
Data Source
AI summary
To provide a novel structure of a separator in a secondary battery. A nonaquesous secondary battery includes a positive electrode, a negative electrode, an electrolyte solution, a first separator, and a second separator. The first separator and the second separator are provided between the positive electrode and the negative electrode. The first separator is provided with a first pore, the second separator is provided with a second pore, and the size of the first pore is different from the size of the second pore. Furthermore, the proportion of the volume of the first pores in the first separator is different from the proportion of the volume of the second pores in the second separator.