Lithium Ion Capacitor Porous Layer Thermal Management
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Solution Overview
Problem
Lithium ion capacitors face challenges with internal short circuits leading to high surface temperatures and reduced performance due to low capacitance and high resistance, compromising safety and high output characteristics required for applications like power devices and vehicle mounting.
Innovation Solution
A porous layer is formed on the outer surface of the lithium ion capacitor element, with its thickness optimized to balance capacitance and resistance, allowing the electrolyte solution to absorb thermal energy during internal short circuits, thereby suppressing surface temperature increases and maintaining high performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a polyethylene-made plate is disposed between the outer container and the lithium ion capacitor element to suppress deformation, then safety is improved, but capacitance decreases and resistance increases
Solution Approach 1:
The patent applies porous materials (porous sheets) as the protective layer between the outer container and lithium ion capacitor element. These porous sheets allow electrolyte solution to penetrate through them, maintaining electrical contact and ion transport while providing mechanical protection. This resolves the contradiction by preventing the capacitance loss and resistance increase that would occur with solid polyethylene plates, as the porous structure permits electrolyte infiltration to compensate for any separation between electrodes.
Solution Approach 2:
The patent uses composite material structures where porous sheets are combined with electrolyte solution to create a protective layer that兼具 mechanical strength and electrical conductivity. The composite system allows the porous sheets to provide deformation resistance while the electrolyte-filled pores maintain electrical contact, thus improving safety without sacrificing capacitance or increasing resistance.
2Reliability
If the thickness of the porous layer is increased to improve safety, then heat absorption capacity improves, but capacitance decreases
Solution Approach 1:
The patent optimizes the thickness parameter of the porous layer to achieve a balance between safety and capacitance. By carefully controlling the thickness within specific ranges, the design ensures sufficient heat absorption capacity for safety while minimizing the impact on capacitance. This parameter optimization resolves the contradiction by finding the optimal point where the protective function is adequate without excessive thickness that would reduce electrical performance.
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 solution achieves high capacity, high output characteristics, and enhanced safety by preventing excessive surface temperature rises during internal short circuits, ensuring reliable operation in demanding applications.
Implementation Method 1
the thermal energy of abrupt heat generation caused by a large flow of electric current is absorbed by the electrolyte solution with which the porous layer is impregnated
Data Source
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AI summary
The present invention has as its object the provision of a lithium ion capacitor having high capacity and high output characteristics and also having high safety that allows suppression of an increase in surface temperature even when an internal short circuit accidentally occurs. The lithium ion capacitor of the present invention comprises: a lithium ion capacitor element formed by overlaying a positive electrode sheet and a negative electrode sheet on top of one another with a separator interposed therebetween; an electrolyte solution; and an outer container that contains the lithium ion capacitor element and the electrolyte solution, a porous layer is formed on an outer surface of the lithium ion capacitor element, and the lithium ion capacitor satisfies following relational expressions (1) and (2): relational expression (1): 35 ≤ T x R/C relational expression (2): 0.01 ≤ R/C ≤ 5 where C is a capacitance [kF] of the lithium ion capacitor, R is a direct current resistance value [mΩ] of the lithium ion capacitor, and T is a thickness [µm] of the porous layer.