Battery Separator Mixed Layer for Heat and Voltage Withstand
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Solution Overview
Problem
Conventional nonaqueous electrolyte secondary battery separators have insufficient heat resistance and voltage withstand characteristics, particularly in regions with low weight per unit area, necessitating improvement in safety and voltage handling.
Innovation Solution
A nonaqueous electrolyte secondary battery separator with a mixed layer containing a heat-resistant resin and a porous base material, where the heat-resistant resin penetrates substantially throughout the porous film, enhancing heat resistance and voltage withstand characteristics, as indicated by a peak intensity ratio of at least 0.02 in attenuated total reflection infrared spectroscopy (ATR-IR) analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the resin constituting the heat-resistant layer is caused to penetrate into the porous film, then the heat resistance is improved, but the shutdown characteristic may deteriorate and resistance may excessively increase
Solution Approach 1:
The patent applies local quality by creating a mixed layer with specific composition and structure at the interface between the heat-resistant layer and porous film, while maintaining the original properties of the bulk porous film. This localized modification allows heat-resistant resin penetration only in the necessary region to improve heat resistance without compromising the overall shutdown characteristic of the separator.
2Temperature
If the resin constituting the heat-resistant layer is caused to penetrate into the porous film, then the heat resistance is improved, but the voltage withstand characteristics may deteriorate
Solution Approach 1:
The patent applies parameter changes by carefully controlling the penetration depth and concentration of heat-resistant resin into the porous film. By optimizing these parameters, the invention achieves sufficient heat resistance improvement while maintaining voltage withstand characteristics within acceptable ranges.
3Temperature
If more resin is added to improve heat resistance, then the heat resistance increases, but the weight per unit area increases and may affect battery energy density
Solution Approach 1:
The patent utilizes the porous structure of the mixed layer to achieve heat resistance improvement with minimal weight increase. The porous configuration allows heat-resistant resin to be distributed throughout the layer while maintaining low material density and weight, thus improving heat resistance without significantly increasing the weight per unit area.
Data Source
AI summary
As a nonaqueous electrolyte secondary battery separator which has excellent heat resistance and excellent voltage withstand characteristics, provided is a separator including a mixed layer which contains a heat-resistant resin and a porous base material that includes a polyolefin porous film. When attenuated total reflection infrared spectroscopy is carried out with respect to an opposite surface of the separator, a ratio between an intensity of a peak indicating the heat-resistant resin and an intensity of a peak indicating the polyolefin-based resin is not less than 0.02.