Porous Heat-Resistant Separator for Thermal Stability
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Solution Overview
Problem
Electrochemical batteries face safety concerns due to thermal runaway and potential explosions when short-circuited, as existing separators made from thermally fusible resins may melt and cause electrode contact, leading to re-short circuits and further heating.
Innovation Solution
A porous heat-resistant separator is developed using a composition with a cross-linking binder, first inorganic particles of 300-700 nm diameter, and second inorganic particles of 50-200 nm diameter, in a 7:3 to 8.5:1.5 weight ratio, which forms a layer with low thermal shrinkage, high elastic modulus, and improved heat resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a separator is made from thermally fusible resin to enable shutdown function, then safety shutdown capability is improved, but heat resistance and structural stability at high temperature deteriorate
Solution Approach 1:
The separator is constructed as a composite structure combining a thermally fusible resin base layer (providing shutdown function) with a heat-resistant porous layer containing inorganic particles (alumina, silica) and cross-linkable binder (providing high-temperature stability). This composite structure allows both the shutdown capability and heat resistance to coexist without compromising either function.
2Temperature
If a porous heat-resistant layer is formed on the separator, then heat resistance and thermal shrinkage resistance are improved, but manufacturing complexity increases
Solution Approach 1:
The patent specifies precise parameter ranges for the porous heat-resistant layer composition, including inorganic particle size distribution (300-700 nm and 50-200 nm with specific weight ratios), binder content (5-20 parts by weight per 100 parts inorganic particles), and porosity (30-70%). By controlling these parameters within defined ranges, the patent achieves optimal heat resistance and thermal shrinkage resistance while maintaining manageable manufacturing complexity through standardized formulation guidelines.
3Stability of the object's composition
If inorganic particles with specific size distribution are used in the porous layer, then thermal shrinkage ratio and heat resistance are improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent employs a bimodal particle size distribution strategy where different sized inorganic particles (300-700 nm and 50-200 nm) serve different functional roles within the porous layer. The larger particles provide structural framework for thermal stability, while smaller particles fill interstices to enhance heat resistance. This local differentiation of particle functions within the composite structure achieves optimal thermal shrinkage resistance (≤10% at 150°C) while allowing flexibility in manufacturing through the use of commercially available particle size ranges.
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 separator maintains its shape and prevents short circuits at high temperatures, ensuring thermal stability and safety by maintaining a thermal shrinkage ratio below 10% and resisting rupture at 230°C, while maintaining adequate air permeability and charge/discharge characteristics.
Implementation Method 1
a monomer including at least one cross-linkable functional group, an oligomer including at least one cross-linkable functional group, a polymer including at least one cross-linkable functional group, or a mixture thereof
Implementation Method 2
first inorganic particles having an average particle diameter (D50) X of about 300 nm to about 700 nm; and second inorganic particles having an average particle diameter (D50) of 0.1X to 0.4X
Data Source
AI summary
A composition for forming a porous heat-resistant layer of a separator, a separator, and an electrochemical battery, the composition including a monomer including a cross-linkable functional group, an oligomer including a cross-linkable functional group, a polymer including a cross-linkable functional group, or a mixture thereof; a solvent; an initiator; first inorganic particles having an average particle diameter (D50) X of about 300 nm to about 700 nm; and second inorganics particle having an average particle diameter (D50) of 0.1X to 0.4X, wherein a weight ratio of the first inorganic particles to the second inorganic particles in the composition is about 7:3 to about 8.5:1.5.