Polygonal Spiral Wound Electrode Assembly for Battery Volumetric Efficiency
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Solution Overview
Problem
Conventional spiral wound electrode assemblies in polygonal cell housings suffer from low volumetric efficiency due to rounded corners that do not effectively fill the interior space, leading to inefficient use of internal volume.
Innovation Solution
A spiral wound electrode assembly with a constant radius of corner portions and varying lengths of linear portions, allowing for a polygonal shape that optimizes the use of space within the cell housing, achieved through a specific winding method and device using a segmented mandrel and roller assemblies to maintain consistent corner radii and adjust linear lengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional circular mandrel is used to wind the electrode pair, then the winding process is simple and straightforward, but the resulting electrode assembly has rounded corners that reduce volumetric efficiency in polygonal cell housings
Solution Approach 1:
The mandrel is divided into multiple segments that can be independently positioned and adjusted. Each segment can be moved to form straight edges and corners, allowing the mandrel to create a polygonal cross-section shape that matches the cell housing geometry, thereby improving volumetric efficiency while maintaining manufacturability
Solution Approach 2:
The mandrel segments are made movable and adjustable during the winding process. The segments can be dynamically repositioned to form the desired polygonal shape, and the mandrel can be rotated to wind the electrode pair while maintaining the polygonal cross-section, resolving the contradiction between manufacturing simplicity and volumetric efficiency
2Volume of moving object
If spindles with rectangular or flat shape are used to form a winding with rectangular cross-section, then the shape matches polygonal cell housings better, but the outer layers develop rounded corners where the radius increases with the number of turns
Solution Approach 1:
The mandrel is segmented into multiple movable sections that can be independently positioned to maintain sharp corners throughout the winding process. Each segment can be adjusted to compensate for the natural rounding that occurs during winding, ensuring consistent corner radii across all layers and maintaining manufacturing precision while achieving good volumetric efficiency
Solution Approach 2:
The mandrel segment positions and orientations are dynamically adjusted during the winding process to maintain constant corner radius parameters. By changing the geometric parameters of the mandrel segments in real-time, the system compensates for the tendency of corners to round out, thereby maintaining manufacturing precision while achieving the desired volumetric efficiency
Data Source
AI summary
An electrochemical cell includes a cell housing and an electrode assembly disposed in the cell housing. The electrode assembly includes an electrode pair that is arranged to form a winding having a polygonal spiral wound shape in which a radius of the corner portions of each turn of the winding is constant, regardless of the number of turns. In addition, a length of the linear portions of one turn of the winding is different than a length of the linear portions of another turn of the winding. Since each turn of the winding includes the corner portions having a desired radius, the volumetric efficiency of the electrode assembly including the winding within a cell housing is improved relative to some cells that use conventional windings. An apparatus and method of forming a polygonal spiral wound winding are disclosed.