Multilayer Battery Separator Structure for Thermal Stability and Li+ Transport
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Solution Overview
Problem
Multilayer composite separators in lithium-ion batteries fail to meet the diverse performance requirements of different batteries due to lack of customizable component contents and functions.
Innovation Solution
A separator design comprising at least two base films with controllable component contents and a functional layer interposed between them, utilizing materials like polyethylene and polypropylene for film layers and inorganic/organic functional materials for enhanced performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multilayer composite separators are used, then thermal stability and chemical stability are improved, but the ability to meet diverse performance requirements of different batteries deteriorates due to fixed component contents
Solution Approach 1:
The separator structure is designed to be dynamically adjustable by changing component contents and layer configurations. The base film can incorporate different proportions of polyethylene and polypropylene, and the functional layer can be customized with various inorganic materials (alumina, silica, titania) and organic materials (cellulose derivatives, polyamides) to adapt to different battery performance requirements while maintaining thermal and chemical stability.
Solution Approach 2:
The separator uses composite material structures combining organic polymers (polyethylene, polypropylene, cellulose) with inorganic materials (alumina, silica, titania). This composite approach enables simultaneous achievement of thermal stability from polypropylene, wettability from polyethylene, and enhanced chemical stability from inorganic functional layers, while allowing customization for different battery applications.
2Reliability
If base film thickness is increased to improve thermal stability, then thermal shrinkage resistance is improved, but internal resistance increases affecting Li+ mass transfer
Solution Approach 1:
The separator combines polypropylene base film (providing thermal shrinkage resistance) with functional layers containing inorganic materials and pore-forming agents. This composite structure achieves both thermal stability and controlled porosity, allowing Li+ mass transfer while maintaining dimensional stability at elevated temperatures.
Solution Approach 2:
The base film is designed with controlled porosity (30-80%) through incorporation of pore-forming agents and specific processing methods. This porous structure reduces internal resistance and facilitates Li+ mass transfer while the polypropylene matrix maintains thermal shrinkage resistance. The pore size and distribution are optimized to balance ion transport and mechanical stability.
3Ease of operation
If polyethylene content is increased to improve wettability, then electrolyte wettability is improved, but melting point decreases affecting thermal stability
Solution Approach 1:
The separator uses a composite structure where polyethylene provides wettability enhancement through its polar groups and surface properties, while polypropylene contributes high melting point and thermal stability. The synergistic combination allows the separator to achieve good electrolyte wetting without sacrificing thermal stability, as the polypropylene matrix maintains structural integrity at elevated temperatures.
Solution Approach 2:
The separator structure is designed with local quality differentiation where the surface regions enriched with polyethylene provide enhanced wettability for electrolyte contact, while the bulk structure maintains polypropylene dominance for thermal stability. This spatial distribution of material properties allows simultaneous optimization of wettability and melting point characteristics.
Data Source
AI summary
A separator and a preparation method of separator, a battery cell including the separator, a battery including the battery cell, and an electric device including the battery, where the separator includes at least two base films and a functional layer interposed between two adjacent base films, and the base film includes at least two components.