Composite Battery Separator for Heat Resistance and Dendrite Blocking
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Solution Overview
Problem
Commercial secondary batteries face issues with poor heat resistance and thermal shrinkage, leading to increased safety risks and reduced reliability due to direct contact between electrodes, and lithium dendrite growth causing short circuits.
Innovation Solution
A separator design comprising a first base film with higher tortuosity and lower melting point, and a second base film with lower tortuosity and higher melting point, along with an adhesive layer, to enhance heat resistance, ion conduction, and block lithium dendrites, thereby improving reliability and cycle life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single base film is used in the separator, then the structure is simple, but the heat resistance and thermal shrinkage resistance are insufficient
Solution Approach 1:
The separator is divided into a first base film and a second base film with different properties. The first base film has higher tortuosity to block lithium dendrites, while the second base film has lower tortuosity to maintain ion conduction. This segmentation allows each layer to specialize in one function, resolving the contradiction between structural simplicity and heat resistance.
Solution Approach 2:
The separator uses a composite structure combining two different base films with distinct characteristics. The first base film (higher tortuosity) and second base film (lower tortuosity) work together to provide both dendrite blocking and ion conduction capabilities, achieving superior heat resistance without excessive structural complexity.
2Reliability
If the base film has higher tortuosity to block lithium dendrites, then dendrite growth is delayed, but thermal shrinkage increases under heated conditions
Solution Approach 1:
The separator divides the tortuosity function between two layers: the first base film has higher tortuosity specifically for blocking lithium dendrites, while the second base film has lower tortuosity to minimize thermal shrinkage. This segmentation allows each layer to optimize for its specific function without compromising the other.
Solution Approach 2:
Different regions of the separator have different tortuosity values tailored to their specific functions. The first base film located near the negative electrode has higher tortuosity for dendrite blocking, while the second base film has lower tortuosity for thermal stability, creating local quality variations that resolve the contradiction.
3Object-affected harmful factors
If the base film has lower tortuosity to reduce thermal shrinkage, then heat resistance improves, but ion conduction performance decreases
Solution Approach 1:
The separator assigns different tortuosity characteristics to different layers: the second base film has lower tortuosity to reduce thermal shrinkage and improve heat resistance, while the first base film has higher tortuosity to maintain ion conduction pathways. This segmentation ensures both thermal and ionic performance requirements are met.
Solution Approach 2:
The composite separator structure combines a low-tortuosity second base film for thermal stability with a high-tortuosity first base film for ion conduction. This composite approach allows the separator to simultaneously achieve low thermal shrinkage and good ion conduction performance that neither single material could provide alone.
4Ease of manufacture
If a single-layer separator is used, then manufacturing is simple, but lithium dendrites can pierce through causing short circuits
Solution Approach 1:
The separator is segmented into multiple functional layers: a first base film for dendrite blocking and a second base film for structural support. This multi-layer segmentation provides enhanced dendrite resistance while maintaining manufacturing feasibility through standardized lamination processes.
Solution Approach 2:
The composite separator combines multiple base films with different properties to create a multi-barrier structure that effectively blocks lithium dendrites. The adhesive layer bonds the first and second base films together, creating a unified composite structure that prevents short circuits while remaining manufacturable.
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 separator design reduces thermal shrinkage, delays lithium dendrite growth, and maintains good ion conduction, enhancing the reliability and extending the cycle life of secondary batteries.
Implementation Method 1
the first base film with a lower melting point has a greater tortuosity, which, on one hand, reduces the probability of shrinkage of the first base film under heated conditions, thereby decreasing a thermal shrinkage rate of the separator
Implementation Method 2
a first base film, a second base film, and an adhesive layer, where the adhesive layer is disposed between the first base film and the second base film
Data Source
AI summary
This application provides a separator, a secondary battery, and an electric apparatus, where the separator includes a first base film, a second base film, and an adhesive layer. The adhesive layer is disposed between the first base film and the second base film. A melting point of the second base film is higher than a melting point of the first base film. A tortuosity of the first base film is greater than a tortuosity of the second base film.