Microporous Polypropylene Separator for Dendrite Suppression
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Solution Overview
Problem
Existing separators for power storage devices face challenges in suppressing dendrite short circuiting, maintaining low resistance, and ensuring high puncture strength.
Innovation Solution
A separator for power storage devices comprising multiple microporous layers with specific properties, including polypropylene as a main component, tailored melt tensions, and controlled pore diameters, is designed to enhance dendrite suppression, reduce resistance, and increase puncture strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a thin separator membrane is used to reduce resistance and improve energy density, then low resistance and high energy density are achieved, but puncture strength and safety deteriorate
Solution Approach 1:
The separator uses a composite structure combining a polyolefin microporous membrane (providing shutdown function and basic strength) with a heat-resistant porous coating layer containing inorganic particles (providing high-temperature stability and enhanced puncture resistance). This composite design allows the separator to maintain thin dimensions for low resistance while the inorganic-containing coating layer provides the necessary puncture strength and thermal stability.
2Reliability
If the separator membrane is made thinner to suppress dendrite short circuiting, then dendrite suppression is improved, but puncture strength deteriorates
Solution Approach 1:
The separator applies local quality enhancement by concentrating the heat-resistant inorganic particles specifically in the porous coating layer on the surface of the microporous membrane. This localized reinforcement provides high puncture strength and dendrite suppression capability at the critical interface where dendrites contact the separator, while the bulk membrane remains thin to maintain low resistance and high ion conductivity.
3Strength
If a multilayer barrier structure is added to improve dielectric breakdown and strength, then puncture strength is improved, but device complexity increases
Solution Approach 1:
The separator divides the reinforcement function into two distinct segments: the polyolefin microporous membrane provides the shutdown function and base structural support, while the separate heat-resistant porous coating layer with inorganic particles provides high-temperature stability and puncture enhancement. This segmentation allows each layer to specialize in specific functions, achieving high puncture strength without requiring a complex multilayer barrier structure.
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 proposed separator effectively suppresses dendrite short circuiting, maintains low resistance, and enhances puncture strength, thereby improving the performance and safety of power storage devices.
Implementation Method 1
a separator for a power storage device, the separator excelling in at least one of dendrite short circuiting suppression, low resistance, and high puncture strength
Implementation Method 2
one or a plurality of microporous layers (A) having polypropylene as a main component and one or a plurality of microporous layers (B) having polypropylene as a main component and being stacked on at least one of the microporous layers (A)
Data Source
Figure 1
AI summary
The present disclosure provides a separator for a power storage device, which is excellent in terms of at least one of suppression of dendrite short-circuiting, low resistance and high piercing strength. This separator for a power storage device comprises a separator substrate having: one or more microporous layers (A) comprising mainly polypropylene; and one or more microporous layers (B) which comprise mainly polypropylene and which are layered on at least one of the microporous layers (A). The melt tension MtA of the microporous layer (A) at 240°C is 10-40 mN. The ratio of the melt tension MtA of the microporous layer (A) at 240°C and the melt tension MtB of the microporous layer (B) at 240°C (MtA/MtB) is 1.05-4.0. The area-average long pore diameter of the microporous layer (A) is 50-500 nm.