Composite Separator With Multi-Phase Polymer Coating for Thermal Stability
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Solution Overview
Problem
Conventional polyethylene separators used in secondary batteries lack sufficient electrolyte wettability and thermal stability, posing safety concerns for high-capacity applications such as electric vehicles and power storage systems.
Innovation Solution
A composite separator is developed, comprising a heat-resistant nonwoven fabric with a porous coating film containing a multi-phase polymer with a stationary phase segment and a reversible phase segment, where the stationary phase segment is predominant, providing improved thermal and mechanical stability and a shutdown function to prevent ion migration and internal short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a polyethylene separator is used, then good electrochemical stability and mechanical strength are achieved, but insufficient electrolyte wettability and unsatisfactory thermal stability occur
Solution Approach 1:
The patent uses a composite structure consisting of a heat-resistant base layer (polyester nonwoven fabric) and a porous coating layer containing a multi-phase polymer. This composite design combines the high-temperature resistance of polyester with the functional properties of the polymer coating, achieving both thermal stability and electrochemical performance without relying on low-melting-point polyethylene.
Solution Approach 2:
The patent modifies the thermal properties of the separator by selecting a base material (polyester) with a melting point of 200°C or higher, fundamentally changing the temperature threshold at which structural collapse occurs compared to conventional polyethylene separators. This parameter change enables the separator to maintain integrity at elevated temperatures while preserving electrochemical functionality.
2Strength
If a polyethylene separator is used, then good electrochemical stability and mechanical strength are achieved, but insufficient electrolyte wettability occurs
Solution Approach 1:
The patent applies a porous coating layer with specific properties (porosity of 30-70%, specific surface area of 0.5-5.0 m²/g) onto the surface of the heat-resistant base layer. This local modification enhances electrolyte wettability and ion transport at the critical interface where electrolyte contact occurs, while the bulk base layer maintains mechanical strength and thermal resistance.
3Object-affected harmful factors
If ceramic particles or binder polymer are coated on polyethylene separator, then thermal stability is improved, but the low melting point of polyethylene itself remains a drawback
Solution Approach 1:
The patent divides the separator into two functional segments: a heat-resistant base layer (polyester nonwoven fabric) that provides structural integrity at high temperatures, and a porous coating layer that provides electrochemical functionality. This segmentation allows each layer to optimize its specific function without being constrained by the limitations of a single material system.
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 composite separator enhances safety and performance by maintaining structural integrity at high temperatures, ensuring rapid shutdown and preventing battery ignition or explosion, while maintaining ion conductivity and stability across a wide temperature range.
Implementation Method 1
contacting, with a non-solvent, the heat-resistant nonwoven fabric coated with the composition for forming the porous coating film, to thereby induce phase transition
Data Source
AI summary
A composite separator, a method of preparing the composite separator, and a secondary battery including the composite separator are provided. The composite separator includes a heat-resistant nonwoven fabric, and a porous coating film on at least one surface of the heat-resistant nonwoven fabric and including a multi-phase polymer including a stationary phase segment and a reversible phase segment, wherein an amount of the stationary phase segment is larger than an amount of the reversible phase segment.