Segmented Tab-Less Electrode Assembly for Cylindrical Cell Current Paths
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Solution Overview
Problem
Conventional cylindrical battery cells face issues with high resistance, heat generation, and internal short circuits due to concentrated current flow at electrode tabs, leading to potential ignition during rapid charging, especially when scaled for electric vehicles.
Innovation Solution
A tab-less cylindrical battery cell design with uncoated portions positioned at the top and bottom of the jelly-roll electrode assembly, where current collecting plates are welded to these uncoated portions, improving current collection efficiency and reducing resistance by increasing the cross-sectional area of the current path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a strip-shaped electrode tab is used to connect the positive and negative electrodes, then the battery cell structure is simple and easy to manufacture, but the current collection efficiency is poor due to large resistance and large heat generation
Solution Approach 1:
The uncoated portion of the electrode plate is divided into multiple segments along the winding direction, with each segment having a different height. This segmentation allows the current collecting plate to contact multiple segments, effectively increasing the current collection area and reducing resistance while maintaining manufacturing simplicity
Solution Approach 2:
Different segments of the uncoated portion are designed with different heights to create local variations in current collection. The varying heights allow for optimized current distribution at different locations, improving overall current collection efficiency without complicating the overall structure
2Reliability
If the uncoated portion is bent to improve current collection, then the current collection efficiency improves, but the separator may be damaged causing internal short circuits
Solution Approach 1:
The separator is positioned in advance to cover the uncoated portion before any bending occurs. This preliminary positioning ensures that the separator is already in place to protect the electrode structure during the bending process, preventing damage and short circuits
Solution Approach 2:
The separator acts as an intermediary protective layer between the uncoated portion and the external environment. By positioning the separator to cover the uncoated portion, it mediates the potential damage from bending operations while still allowing the current collection function to operate
3Reliability
If the uncoated portion is bent toward the core, then the current collection efficiency improves, but the cavity in the core is blocked preventing electrolyte injection
Solution Approach 1:
The uncoated portion is divided into segments with different heights, creating local variations that allow the core cavity to remain accessible. The varying segment heights ensure that not all uncoated portions block the cavity, maintaining electrolyte injection capability while improving current collection at critical locations
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 design reduces internal resistance, prevents short circuits, and enhances energy density by ensuring uniform electrolyte impregnation and stable solid electrolyte interface formation, thereby improving the safety and performance of the battery cell.
Implementation Method 1
the current collection efficiency is not good due to large resistance and large heat generation
Implementation Method 2
ensuring uniform electrolyte impregnation
Implementation Method 3
enhances energy density by ensuring uniform electrolyte impregnation and stable solid electrolyte interface formation
Data Source
AI summary
An electrode assembly having a first electrode, a second electrode, and a separator positioned between the first electrode and the second electrode. The first electrode, the second electrode, and the separator are together wound about an axis in a winding direction resulting in a plurality of winding turns. Each of the first electrode and the second electrode has a first side and a second side opposite the first side in the direction of the axis, as well as a first, electrode active material portion, coated with an electrode active material, extending from the second side in the direction of the first side, and a second, uncoated portion extending from the first side in the direction of the second side to the active material of the first portion. Additionally, the first side of the first electrode and the first side of the second electrode are divided into a plurality of segments by a cut groove, and each of the segments has a first end corresponding to the first side of either the first or the second electrode. One or more of the segments are bent in a radial direction relative to the axis, at a point below the first end of each bent segment, and the separator has a side that is positioned between the bending point of each bent segment and a boundary between the first and the second portions.