Battery Separator Porous Film for Low-Temperature Shutdown Stability
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Solution Overview
Problem
Existing secondary battery separators face challenges in achieving a shutdown characteristic at low temperature, maintaining dimensional stability and heat rupture resistance at high temperatures, and ensuring sufficient adhesiveness between the porous layer and substrate, which affects the battery's performance and safety.
Innovation Solution
A porous film with a porous substrate and a laminated porous layer containing an organic resin different from the substrate resin, featuring a height of projection of 200 nm or more and a distance between projections of 1 μm or more, with a porosity of 40% to 80% and an adhesive ratio of 50% to 90%, and optionally including inorganic particles, providing a falling ball film rupture temperature of 280° C. or higher and a shutdown temperature of 135° C. or lower.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a porous layer containing inorganic particles is laminated on a porous film mainly containing polyolefin to reduce heat shrinkage ratio, then heat shrinkage ratio decreases up to shutdown temperature, but adhesiveness between layers is insufficient causing heat shrinkage increase at high temperature range after shutdown
Solution Approach 1:
The patent uses a composite porous layer containing both inorganic particles (alumina, silica, titania, zirconia) and organic resin components (carboxyl-containing polymer, hydroxyl-containing polymer) to achieve both heat shrinkage reduction and sufficient adhesiveness. The combination of inorganic particles for thermal stability and organic resins for bonding creates a synergistic effect that resolves the contradiction between heat shrinkage control and layer adhesion.
Solution Approach 2:
The patent specifies precise parameter ranges: inorganic particle content (5-80 mass%), carboxyl-containing polymer content (5-50 mass%), hydroxyl-containing polymer content (5-50 mass%), projection height (200 nm to 2 μm), and distance between projections (0.5 μm to 5 μm). These controlled parameters ensure optimal balance between heat shrinkage resistance and adhesiveness across different temperature ranges.
2Stability of the object's composition
If a porous layer is laminated to reduce heat shrinkage ratio, then dimensional stability improves, but shutdown characteristic depends solely on porous film characteristic
Solution Approach 1:
The patent creates different functional zones: the porous substrate provides shutdown characteristic through its melting at specific temperature, while the porous layer provides dimensional stability and heat shrinkage resistance. The porous layer's composition (inorganic particles + organic resins) is specifically designed to maintain structural integrity without interfering with the substrate's shutdown function, achieving local optimization of different properties.
3Reliability
If secondary battery separator requires shutdown characteristic at low temperature, large temperature difference between shutdown and melt temperature, and heat rupture resistance at high temperature, then battery safety improves, but battery characteristics such as high output and long life may deteriorate
Solution Approach 1:
The patent utilizes a porous structure with controlled porosity (30-80%) and specific pore characteristics to maintain ion permeability for good battery performance while incorporating heat-resistant inorganic particles and adhesive organic resins to ensure safety characteristics. The porous structure allows electrolyte penetration and ion transport necessary for high output and long life, while the layered composite structure provides safety functions.
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 enables a secondary battery separator with excellent battery characteristics, including a shutdown characteristic at low temperature, dimensional stability, and heat rupture resistance at high temperatures, while maintaining low production costs and ensuring good adhesiveness between the porous substrate and layer, thereby enhancing the battery's performance and safety.
Implementation Method 1
in an interface between the porous substrate and the porous layer, a height of a projection of the porous layer is 200 nm or more and a distance between projections is 1 μm or more
Implementation Method 2
a characteristic that the secondary battery separator contains an electrolytic solution in a porous structure and enables movement of ions
Implementation Method 3
a shutdown characteristic that when a lithium ion battery generates heat abnormally, the porous structure is closed due to melting by the heat and the movement of ions is stopped
Data Source
AI summary
A porous film includes a porous substrate, and a porous layer laminated on at least one surface of the porous substrate. The porous layer contains an organic resin different from a resin constituting the porous substrate. A height of a projection of the porous layer in an interface between the porous substrate and the porous layer is 200 nm or more, and a distance between projections is 1 μm or more.