Wound Electrode Assembly Layout for Shorter Battery Current Paths
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Solution Overview
Problem
Conventional cylindrical secondary batteries face high resistance and heat generation issues due to lengthy current paths, particularly in large form factors, which can lead to ignition risks when used in electric vehicles.
Innovation Solution
The electrode assembly design minimizes the lengthwise direction current path by using uncoated portions of the electrodes as electrode tabs and optimizing the current path ratio, with a current path ratio L2/L1 of 11 or less, and incorporates a segment piece structure to enhance welding strength and prevent deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the cell size is increased to increase capacity, then the energy density is improved, but the current path length increases causing higher resistance and heat generation
Solution Approach 1:
The electrode assembly is divided into multiple electrode tabs instead of using a single tab, segmenting the current collection points. This segmentation reduces the maximum current path length from the electrode center to any tab, thereby reducing overall resistance and heat generation while maintaining high capacity in large form factor batteries
Solution Approach 2:
The patent transitions from a conventional single-tab configuration to a multi-tab configuration that utilizes both the width and length dimensions of the electrode. By strategically positioning multiple tabs across the electrode surface, the current path is shortened in the lengthwise direction while effectively utilizing the width dimension for current collection
2Object-generated harmful factors
If the current path is minimized to reduce resistance, then heat generation is reduced, but the electrode structure becomes more complex
Solution Approach 1:
Multiple electrode tabs are merged into a single integrated electrode assembly structure, where all tabs are formed as part of the same electrode body during the winding process. This merging approach reduces the need for separate tab attachments and simplifies the overall manufacturing process while achieving reduced current path length
Solution Approach 2:
The electrode structure itself provides the current collection function through its own tabs, eliminating the need for separate external tab components. The electrode serves dual functions: active material containment and current collection, thereby simplifying the overall cell structure while achieving low resistance
Data Source
AI summary
Discussed is an electrode assembly having a positive electrode, a negative electrode, and a separator wound around a winding axis, wherein the positive electrode or the negative electrode includes a current collector that has sheet-shape and having a long side and a short side and has an uncoated portion at an end of the long side, wherein the uncoated portion includes an electrode tab defined section used as an electrode tab by itself and at least one electrode tab undefined section not used as an electrode tab, wherein a maximum current path includes a widthwise direction current path along the short side of the current collector and a lengthwise direction current path along the long side of the current collector, and a current path ratio L2/L1 is approximately 11 or less when lengths of the lengthwise direction current path and the widthwise direction current path are L1 and L2, respectively.