Laminated Battery Current Collector for Internal Short Blocking
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Solution Overview
Problem
Secondary batteries, such as lithium ion batteries, face issues with inside short circuits caused by contamination, leading to temperature rises. There is a need for a current collector that can promptly block current and maintain capacity retention and low electric resistance.
Innovation Solution
A current collector with a laminate structure comprising a resin layer and metal layers on both surfaces of the resin layer, where the metal layer has a rough surface with protruding and recessed parts, and a resin coat layer is formed on the rough surface. This design allows the resin to melt and increase pressure on the metal layer during a short circuit, drastically increasing electric resistance to block current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a smooth metal foil is used as current collector, then the manufacturing process is simple, but the composite material layer peels off easily due to volume change of active substance
Solution Approach 1:
The metal foil surface is made non-uniform with protruding parts having different heights, creating local variations in surface topology. This local quality change enhances adhesion by providing mechanical interlocking features while maintaining the overall simplicity of the metal foil structure.
Solution Approach 2:
The surface of the metal foil is modified to include curved protruding parts instead of flat surfaces. These curved features increase the contact area and mechanical interlocking with the composite material layer, preventing peeling during volume changes of the active substance.
2Reliability
If the metal layer is made thicker to prevent peeling, then adhesion improves, but the electric resistance increases
Solution Approach 1:
Instead of uniformly thickening the metal layer, protruding parts of varying heights are created on the surface. This local modification provides enhanced adhesion through mechanical interlocking while maintaining the overall thin profile and low electric resistance of the current collector.
Solution Approach 2:
The solution moves from modifying the thickness dimension to modifying the surface topology dimension. By creating protruding parts with varying heights on the surface, adhesion is enhanced without increasing the average thickness of the metal layer, thus maintaining low electric resistance.
3Reliability
If a laminate structure with resin layer and metal layer is used, then current blocking during short circuit is improved, but the device complexity increases
Solution Approach 1:
The resin layer and metal layer are merged into a single integrated current collector component. The metal foil serves dual functions as both the conductive current collector and the structural backbone, while the resin coating provides both adhesion enhancement and current blocking functionality, reducing the need for separate components.
Solution Approach 2:
The metal foil with protruding parts serves multiple functions: it acts as the current collector, provides mechanical support, enhances adhesion through surface topology, and contributes to current blocking when combined with the resin layer. This multi-functionality reduces overall device complexity.
4Reliability
If the resin coat layer is made thicker to improve adhesion, then capacity retention improves, but the electric resistance increases
Solution Approach 1:
The resin coat layer is applied selectively on the protruding parts rather than as a uniform thick coating. This local application provides sufficient adhesion enhancement at the critical contact points while minimizing the overall resin thickness and associated electric resistance.
Solution Approach 2:
Instead of increasing adhesion by thickening the resin layer in the thickness dimension, the solution uses the surface topology dimension with protruding parts. The resin coat layer covers these protrusions, creating mechanical interlocking without requiring excessive resin thickness, thus maintaining low electric resistance.
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 proposed current collector effectively blocks current during inside short circuits, suppresses temperature rises, and improves capacity retention and low temperature resistance by preventing the composite material layer from peeling off and reducing electric resistance.
Implementation Method 1
the heat generated by the short circuit current melts the resin layer and the resin coat layer so as to increase the volume of the resin layer and the volume of the resin coat layer
Implementation Method 2
melts the resin layer and the resin coat layer so as to increase the volume of the resin layer and the volume of the resin coat layer
Implementation Method 3
particularly under the low temperature condition, the resin coat layer is shrunk so as to be capable of drawing the composite material layer near the current collector
Data Source
AI summary
The present disclosure provides a current collector of a secondary battery in which the current inside the battery is easily blocked at the time of inside short circuit, and in which the capacity retention rate and the decreasing rate of the electric resistance are outstanding. The current collector herein disclosed includes a laminate structure in which a resin layer and a metal layers formed on the both surfaces of the resin layer are laminated. The surface of the metal layer includes a rough surface part provided with a plurality of protruding parts and a plurality of recessed parts. On the rough surface part, a resin coat layer is formed, and at least one part of the protruding part among the plurality of protruding parts includes an exposed part that is exposed from the resin coat layer.