Current Collector Tail Structure to Prevent Battery Short Circuits
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Solution Overview
Problem
Lithium-ion batteries are prone to failure and safety accidents, particularly due to dropping, which can cause short circuits when the bare aluminum foil tears, leading to weak friction and displacement between layers.
Innovation Solution
The design includes a first current collector with a tail end that exceeds the second current collector by at least half a circle, ensuring that even if the tail end is torn, the outermost and secondary outer circles of the cell are of the same polarity, preventing short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the bare cell is strengthened fixation by double-sided tape or hot melt adhesive, then the movement and collision of the bare cell is reduced, but the bare aluminum foil is easily torn due to weak friction between layers
Solution Approach 1:
The current collector is divided into multiple layers with different materials (aluminum foil and copper foil) arranged in a specific sequence. This segmentation allows each layer to perform its specific function: the aluminum foil provides fixation strength while the copper foil provides flexibility and electrical conductivity, preventing the single-layer structure from having to compromise between conflicting requirements.
Solution Approach 2:
The patent uses a composite structure consisting of multiple current collector layers with different material properties. The aluminum foil layer provides high strength and fixation capability, while the copper foil layer provides flexibility and electrical conductivity. This composite material approach allows the system to simultaneously achieve strong fixation and resistance to tearing.
2Reliability
If the length of the first current collector is increased so that its tail end exceeds the second current collector by at least half a circle, then short circuits are prevented when the outermost and secondary outer circles contact, but the device complexity increases
Solution Approach 1:
The first current collector is designed to extend beyond the second current collector by at least half a circle in advance, creating an overlapping region before any potential short circuit could occur. This preliminary positioning ensures that when the battery undergoes deformation or displacement, the extended portion of the first current collector maintains electrical isolation between the outermost and secondary outer circles, preventing short circuits before they can happen.
3Stability of the object's composition
If double-sided tape or hot melt adhesive is used to fix the bare cell, then the cell stability is improved, but the friction between layers is insufficient causing displacement and tears
Solution Approach 1:
The patent merges the fixation function and the structural integrity function into a single multi-layer current collector structure. Instead of relying on external adhesives that provide only fixation, the layered structure itself provides both fixation stability and sufficient inter-layer friction through the combination of aluminum foil (high friction) and copper foil (flexibility) layers, eliminating the need for additional adhesive materials.
Data Source
AI summary
A cell includes a first current collector and a second current collector. A tail end of the first current collector exceeds a tail end of the second current collector by at least half a circle in a winding direction. The tail end of the first current collector does not include an active material and is bonded on an outer peripheral surface of an outermost circle of the first current collector by a first adhesive, the first adhesive is a double-sided tape or a hot melt adhesive. The cell is bonded with another double-sided tape or another hot melt adhesive on a side opposite from the tail end of the first current collector.