Composite Current Collector Structure for Cylindrical Cell Swelling
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Solution Overview
Problem
Cylindrical battery cells with high energy density face reliability issues due to electrode plate breakage under large swelling forces, leading to potential short circuits and thermal runaway, as the current collector cannot withstand the increased volume during charging.
Innovation Solution
A battery cell design featuring a current collector with a support layer having greater elongation and thickness than the conductive layer, allowing for improved extensibility and strength, along with a protrusion on the conductive layer to enhance connection stability, and using insulating materials like polypropylene or polyethylene terephthalate for the support layer to reduce weight and enhance insulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thickness of the conductive layer is increased to improve current flow capability, then the current flow capability is improved, but the elongation and swelling resistance of the current collector deteriorates
Solution Approach 1:
The current collector is segmented into two distinct layers: a support layer and a conductive layer. The support layer (made of aluminum or aluminum alloy) provides mechanical strength and swelling resistance, while the conductive layer (made of copper or copper alloy) provides electrical conductivity. This segmentation allows each layer to optimize its function without compromising the other, resolving the contradiction between swelling resistance and current flow capability.
Solution Approach 2:
The current collector uses a composite structure combining aluminum (or aluminum alloy) and copper (or copper alloy) layers. The aluminum support layer offers high strength-to-weight ratio and excellent swelling resistance, while the copper conductive layer provides superior electrical conductivity. This composite material approach enables the current collector to simultaneously achieve both swelling resistance and current flow capability.
2Strength
If the thickness of the support layer is increased to improve strength and elongation, then the strength and elongation are improved, but the current flow capability deteriorates
Solution Approach 1:
The current collector is divided into functional segments: the support layer handles mechanical requirements (strength and elongation), while the conductive layer handles electrical requirements (current flow). This functional segmentation allows the support layer to be optimized for mechanical properties without negatively impacting current flow, as the conductive layer compensates for any thickness limitations.
Solution Approach 2:
The invention optimizes the thickness parameters of both layers within specific ranges: the support layer thickness is controlled at 1-20 μm to provide sufficient mechanical strength, while the conductive layer thickness is optimized at 0.1-10 μm to ensure adequate electrical conductivity. These parameter changes enable both strength and current flow capability to be satisfied simultaneously.
3Quantity of substance
If higher energy density is achieved by reducing current collector thickness, then energy density is improved, but the swelling resistance and reliability deteriorate
Solution Approach 1:
The composite aluminum-copper current collector structure achieves high strength-to-weight ratio and excellent swelling resistance in a thin profile. The aluminum support layer provides mechanical integrity while the copper conductive layer ensures electrical performance, allowing the overall current collector thickness to be minimized (1-20 μm for support layer) without compromising swelling resistance, thereby enabling higher energy density.
Solution Approach 2:
By optimizing the thickness parameters within specific ranges (support layer: 1-20 μm, conductive layer: 0.1-10 μm) and controlling the thickness ratio (H1/H2 between 2-20), the invention achieves a balance where the current collector is thin enough to allow high energy density but maintains sufficient swelling resistance through the optimized composite structure.
Data Source
AI summary
A battery cell of a cylindrical structure includes a wound electrode assembly. An electrode plate of the electrode assembly includes a current collector, and the current collector includes a support layer and a conductive layer. In a thickness direction of the current collector, the conductive layer is disposed on at least one side of the support layer, and elongation of the support layer is greater than elongation of the conductive layer. In the thickness direction of the current collector, the support layer has a thickness greater than a total thickness of the conductive layer of the current collector.