Laminated Separator Cracks Enhance Battery Heat Resistance
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Solution Overview
Problem
Nonaqueous electrolyte secondary batteries face challenges with heat resistance and initial battery characteristics, as existing technologies do not adequately address these issues.
Innovation Solution
A nonaqueous electrolyte secondary battery laminated separator is developed with a polyolefin porous film and a porous layer containing heat-resistant fillers, where the crack area ratio on the surface is controlled between 0.15% to 10%, incorporating organic or inorganic fillers and specific binder resins to enhance heat resistance and initial performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a porous insulating layer is used in the nonaqueous electrolyte secondary battery, then electrolyte impregnation is improved, but heat resistance deteriorates
Solution Approach 1:
The patent changes the physical parameters of the porous layer by controlling crack area ratios and thickness to optimize both electrolyte impregnation and heat resistance. Specifically, the crack area ratio is controlled at 0.03% to 5%, and the porous layer thickness is set at 1-10 μm, which allows sufficient electrolyte penetration while maintaining structural integrity for heat resistance.
Solution Approach 2:
The patent uses a composite structure consisting of a polyolefin porous film base layer and a porous insulating layer with controlled cracks. This composite design allows the base layer to provide mechanical strength and heat resistance, while the porous top layer with controlled cracks facilitates electrolyte impregnation without compromising overall thermal stability.
2Reliability
If the crack area ratio in the porous layer is increased to improve electrolyte impregnation, then initial battery characteristic is improved, but mechanical strength deteriorates
Solution Approach 1:
The patent precisely controls the crack area ratio parameter within 0.03% to 5% and the porous layer thickness within 1-10 μm. This parameter optimization ensures that cracks are sufficient to allow electrolyte penetration for good initial battery characteristics, while remaining small enough to preserve the mechanical strength of the separator.
3Temperature
If the porous layer thickness is increased to improve heat resistance, then thermal stability is improved, but ion permeability deteriorates
Solution Approach 1:
The patent optimizes the porous layer thickness parameter to be between 1-10 μm, which is thin enough to allow efficient ion permeability but sufficient to provide thermal stability and heat resistance. This precise thickness control resolves the contradiction between thermal protection and ion transport efficiency.
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 solution provides excellent heat resistance and initial battery characteristics, maintaining mechanical strength and safety while improving electrolyte and ion permeability, as demonstrated by the controlled crack area ratio and specific material combinations.
Implementation Method 1
a porous layer which (i) is disposed on at least one surface of the polyolefin porous film and (ii) includes a heat resistant filler, the porous layer having a surface which has cracks
Data Source
AI summary
An aspect of the present invention achieves a nonaqueous electrolyte secondary battery laminated separator which has excellent heat resistance and exhibits an excellent initial battery characteristic when used in a nonaqueous electrolyte secondary battery. A nonaqueous electrolyte secondary battery laminated separator in accordance with an aspect of the present invention includes: a polyolefin porous film; and a porous layer which (i) is disposed on at least one surface of the polyolefin porous film and (ii) includes a heat resistant filler, the porous layer having a surface which has cracks, a ratio of a total area of the cracks to a surface area of the porous layer being 0.15% to 10%.