Lithium Battery Separator Composite Layer Design
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Solution Overview
Problem
Lithium secondary batteries face challenges in achieving high capacity and output while ensuring safety due to limitations in the thermal and mechanical stability of existing separators, which can lead to risks of overheating, ignition, or explosion, especially as battery capacity increases.
Innovation Solution
A novel separator for lithium secondary batteries is developed, comprising a polyolefin-based porous base layer with a heat-resistant layer made of inorganic particles and a polymer binder, where the entire thickness of the separator ranges from 10 μm to 40 μm and the heat-resistant layer's thickness is at least 0.9 times that of the base layer, enhancing both heat resistance and mechanical strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the thickness of the separator is increased to improve mechanical strength and safety, then the mechanical strength and thermal safety are improved, but the capacity and output of the battery are deteriorated
Solution Approach 1:
The separator is constructed as a composite structure with a polyolefin base layer providing mechanical strength and a heat-resistant layer containing inorganic particles (such as alumina, silica, or boehmite) and polymer binder. This composite structure achieves both high mechanical strength and thermal stability without requiring excessive thickness, thereby maintaining battery capacity while improving safety.
Solution Approach 2:
Different regions of the separator have different functions: the base layer provides mechanical strength and porosity for ion transport, while the heat-resistant layer specifically addresses thermal stability. This localized functional distribution allows each layer to be optimized for its specific purpose without compromising overall battery performance.
2Productivity
If a polyolefin based microporous thin film is used as separator, then the battery can achieve high capacity with thin separator, but the thermal safety is not high and the microporous film may be easily damaged or deformed by temperature increase
Solution Approach 1:
The separator combines polyolefin base material with inorganic heat-resistant particles and polymer binder to create a composite structure. The inorganic particles maintain structural integrity at high temperatures while the polyolefin base provides porosity for ion transport, achieving both high capacity and thermal safety.
Solution Approach 2:
The heat-resistant layer contains inorganic particles with high thermal stability that prevent the separator from deforming or melting at elevated temperatures. This changes the thermal parameters of the separator, raising the temperature threshold for structural failure while maintaining the thin-film characteristics needed for high battery capacity.
3Reliability
If non-woven fabric is used to improve thermal safety by forming coating layer, then the thermal safety is improved, but the separator may be damaged during assembly or by weak impact due to low strength
Solution Approach 1:
The separator uses a composite structure where the polyolefin base layer provides mechanical strength and structural integrity, while the heat-resistant layer with inorganic particles provides thermal stability. This division of functions allows the separator to resist both thermal degradation and mechanical damage during assembly and operation.
Solution Approach 2:
The separator is segmented into distinct functional layers: the base layer handles mechanical strength requirements and the heat-resistant layer handles thermal safety requirements. This segmentation allows each layer to be optimized independently, with the base layer providing the structural foundation that prevents damage during assembly while the heat-resistant layer provides thermal protection.
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
This configuration allows for the manufacture of batteries with improved capacity, output, and safety, maintaining stability under external forces and high temperatures, reducing the risk of internal short-circuits and ensuring the battery's mechanical integrity.
Implementation Method 1
a heat-resistant layer formed on one surface or both surfaces of the polyolefin based porous base layer, wherein the heat-resistant layer is made of a mixture containing inorganic particles and a polymer binder
Implementation Method 2
a polyolefin based porous base layer
Data Source
AI summary
Provided are a separator for a lithium secondary battery in which an entire thickness of the separator and a ratio of a heat-resistant layer included in the separator satisfy specific ranges, respectively, and a battery including the same. The separator has significantly excellent heat resistance and mechanical strength, and it is possible to manufacture a high capacity and high output battery using the separator, thereby making it possible to significantly improve safety even in the high capacity and the high output battery.