Porous Battery Separator Coating for Heat Resistance and Low Resistance
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Solution Overview
Problem
Conventional lithium secondary battery separators face issues with heat resistance, electrical resistance, and peel strength due to the use of inorganic particles and binder polymers, which either increase resistance or degrade adhesion when adjusted for safety and energy density.
Innovation Solution
A separator design incorporating small- and large-particle diameter inorganic particles with adhesive polymer particles, maintaining a porosity of 40-50% and a peel strength of 50 gf/15 mm or more, addresses these issues by enhancing heat resistance and reducing electrical resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the content of inorganic particles is increased to increase heat resistance, then heat resistance is improved, but the content of binder polymer must also be increased causing resistance to increase
Solution Approach 1:
The patent changes the particle size parameter of inorganic particles, using a bimodal distribution with small particles (0.1-10 μm) and large particles (10-100 μm). This parameter change allows achieving adequate heat resistance with reduced total inorganic particle content, thereby reducing the required binder polymer content and electrical resistance
Solution Approach 2:
The patent creates a composite coating layer combining two different particle sizes of inorganic particles. The small particles fill voids between large particles, creating a denser structure that achieves heat resistance with lower overall particle content, reducing binder polymer requirements and electrical resistance
2Reliability
If the content of binder polymer is reduced to reduce resistance, then electrical resistance is reduced, but peel strength to porous substrate is degraded
Solution Approach 1:
The patent optimizes the particle size parameter of inorganic particles to achieve better packing efficiency. This allows reducing binder polymer content while maintaining coating layer integrity and adhesion to the porous substrate through improved particle-particle and particle-substrate interactions
3Temperature
If a porous coating layer is formed with inorganic particles and binder polymer to ensure heat resistance, then heat resistance is improved, but electrical resistance and peel strength issues arise
Solution Approach 1:
The patent simplifies the coating layer composition by using only inorganic particles with a bimodal size distribution, eliminating the need for binder polymer. The small particles (0.1-10 μm) and large particles (10-100 μm) work together to provide heat resistance while maintaining low electrical resistance and adequate adhesion through optimized packing 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 separator achieves improved heat resistance, reduced electrical resistance, and increased peel strength, ensuring enhanced safety and performance in lithium secondary batteries.
Implementation Method 1
a porous coating layer which includes a plurality of inorganic particles and adhesive polymer particles positioned on the whole or a part of the surface of the inorganic particles to connect and fix the inorganic particles with one another
Implementation Method 2
adhesive polymer particles positioned on the whole or a part of the surface of the inorganic particles to connect and fix the inorganic particles with one another
Implementation Method 3
the porous coating layer has a porosity of 40-50%
Data Source
AI summary
A separator for a lithium secondary battery. The separator for a lithium secondary battery is provided with a porous coating layer including small-particle diameter inorganic particles, large-particle diameter inorganic particles and adhesive polymer particles. The porous coating layer has a predetermined level of porosity. The separator has reinforced heat resistance, reduced resistance and improved peel strength to a porous polymer substrate.