Porous Composite Separator Coating for Thermal Stability and Air Permeability
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Solution Overview
Problem
Current secondary battery separators lack simultaneous high thermal resistance and air permeability, leading to safety issues such as overheating and capacity degradation, especially in high-capacity and high-power applications like hybrid vehicles.
Innovation Solution
A porous composite separator with a coating layer formed by inorganic particles connected by a composite binder comprising a particle type polymer binder and an interpenetrating polymer network (IPN) type binder, which has a thermal decomposition temperature of 300°C or higher, ensuring improved thermal stability and air permeability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a separator uses an IPN polymer binder to improve thermal resistance, then thermal stability is improved, but air permeability is lowered
Solution Approach 1:
The patent uses a composite binder system combining IPN polymer binder with silane-modified polyethylene binder, creating a multi-component material that balances thermal stability and porosity. The IPN structure provides thermal resistance while the silane-modified polyethylene component maintains pore structure for ion transport.
Solution Approach 2:
The separator employs a porous coating layer with controlled pore structure formed by the binder system. The porous structure allows lithium ion permeation while the IPN polymer matrix provides thermal stability. The pore size and distribution are optimized to maintain air permeability despite the presence of thermally stable binder.
2Stability of the object's composition
If a separator coating layer is formed with inorganic particles and IPN polymer binder to improve thermal resistance, then shrinkage is reduced, but air permeability and battery capacity are degraded
Solution Approach 1:
The separator features a coating layer with locally optimized properties on the porous substrate surface. The coating layer contains inorganic particles dispersed in the composite binder, creating a structure with enhanced thermal resistance at the surface while maintaining bulk porosity for ion transport. This local modification approach preserves overall air permeability.
Solution Approach 2:
The patent modifies the binder composition parameters by combining IPN polymer with silane-modified polyethylene in specific ratios. This parameter change in the binder system allows the coating layer to achieve adequate thermal resistance while maintaining sufficient porosity for lithium ion permeation, preventing capacity degradation.
3Strength
If a separator uses IPN polymer binder from copolymerization to improve thermal stability, then binding strength is increased, but air permeability and battery capacity retention are insufficient
Solution Approach 1:
The patent creates a composite binder system where IPN polymer binder is combined with silane-modified polyethylene binder. This composite approach leverages the strong adhesive properties of IPN polymer while the silane-modified component contributes to pore structure maintenance, achieving both strong binding and adequate air permeability.
Solution Approach 2:
The binder system forms a porous network structure that provides both mechanical strength for particle binding and pathways for ion transport. The porous morphology of the binder assembly ensures that adhesive strength is sufficient while air permeability and battery capacity retention are maintained.
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 enhances thermal stability, preventing ignition and rupture due to rapid temperature rises while maintaining excellent air permeability, thereby improving electrical properties and capacity retention of secondary batteries.
Implementation Method 1
an interpenetrating polymer network (IPN) type binder having no melting point and having a thermal decomposition temperature of 300° C. or higher
Implementation Method 2
excellent air permeability so that lithium ions move well
Data Source
AI summary
The present invention relates to: a porous composite separator for a secondary battery including a porous substrate, and a coating layer formed on the porous substrate, wherein the coating layer has a plurality of inorganic particles, which are connected and fixed by a composite binder including a particulate polymer binder and an interpenetrating polymer network (IPN)-type binder having no melting point and having a thermal decomposition temperature of 300° C. or higher; and a lithium secondary battery including the same.