Lithium Ion Capacitor Laminated Separator Thermal Safety
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Solution Overview
Problem
Lithium ion capacitors face challenges in achieving high output density, safety, and cycle characteristics, particularly in preventing temperature rise and internal short circuiting issues such as gasification and ignition.
Innovation Solution
A laminated separator structure is used, combining a polyolefin porous membrane with an insulating porous membrane, where the insulating membrane is in contact with the negative electrode body, to enhance safety and output characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a polyolefin microporous membrane is used as a separator to achieve high output characteristic through low membrane resistance, then output density is improved, but temperature rise during internal short circuiting increases causing gasification and ignition
Solution Approach 1:
The separator is divided into multiple functional layers: a polyolefin microporous membrane layer for providing low resistance and high output, and an additional heat-resistant porous layer for suppressing temperature rise and preventing gasification. This segmentation allows each layer to specialize in one function, resolving the contradiction between output density and thermal safety.
Solution Approach 2:
The separator uses a composite structure combining polyolefin material (for electrical performance) with heat-resistant porous material (for thermal management). This composite approach integrates the advantages of both materials: the polyolefin provides low resistance while the heat-resistant component suppresses temperature rise during internal short circuits, eliminating gasification and ignition risks.
2Device complexity
If the separator structure is simplified to maintain high output characteristic, then device complexity is reduced, but safety during internal short circuit deteriorates
Solution Approach 1:
The separator is segmented into distinct functional layers with clear division of labor: the polyolefin microporous membrane handles electrical conduction and ion transport, while the heat-resistant porous layer handles thermal management. This functional segmentation achieves high safety without excessive complexity, as each layer performs its specific function efficiently.
Solution Approach 2:
The heat-resistant porous layer serves multiple functions simultaneously: it acts as a physical barrier to prevent direct contact between electrodes during internal short circuits, provides thermal management by suppressing temperature rise, and maintains structural integrity at elevated temperatures. This multi-functionality enhances safety without proportionally increasing device complexity.
3Productivity
If membrane resistance is reduced to improve output characteristic, then productivity is improved, but harmful effects during internal short circuit increase
Solution Approach 1:
The separator structure segments the functions of electrical conduction and thermal management into separate layers. The polyolefin microporous membrane layer provides low resistance for high productivity, while the heat-resistant porous layer specifically addresses harmful effects by suppressing temperature rise and preventing gasification during internal short circuits.
Solution Approach 2:
The heat-resistant porous layer converts the potential harmful effect of temperature rise during internal short circuits into a beneficial outcome by actively suppressing temperature increase and preventing gasification and ignition. This layer transforms what would be a dangerous situation into a controlled, safe condition while maintaining the low-resistance characteristics needed for high productivity.
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 effectively suppresses temperature rise and prevents gasification and ignition during internal short circuits, while maintaining high output density and cycle characteristics.
Implementation Method 1
a positive electrode body, a separator, a negative electrode body, an electrolytic solution
Implementation Method 2
the insulating porous membrane is in contact with the negative electrode body, to enhance safety and output characteristics. This configuration effectively suppresses temperature rise and prevents gasification and ignition during internal short circuits
Data Source
Figure 1~2
Figure 3
AI summary
Provided is a lithium ion capacitor that is capable, during internal short circuiting, of suppressing an increase in capacitor temperature and controlling the onset of gasification, smoking and ignition, and of having preferably both low resistance (i.e., high output density) and high cycle characteristics. The lithium ion capacitor comprises an electrode laminated body stored in a casing together with a non-aqueous electrolytic solution containing a lithium ion-containing electrolyte; wherein the electrode laminated body is laminated so that a negative electrode collector having a negative electrode active material comprised of a carbon material, and a positive electrode body having a positive electrode active material face each other through a laminated separator where a polyolefin porous membrane and an insulating porous membrane are laminated; and characterized in that the insulating porous membrane is in contact with the negative electrode body.