Negative-Outermost Electrode Assembly for Bend-Resistant Li-Ion Cells
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Solution Overview
Problem
Conventional lithium secondary batteries face safety issues and reduced capacity due to mechanical damage when bent, caused by stress on the electrode assembly and misalignment of components, leading to potential short circuits and terminal breakage.
Innovation Solution
The electrode assembly is designed with a negative electrode as the outermost electrode, featuring electrode parallel and lead connection tabs, and a reinforcing tab to enhance structural integrity and energy density, with the tab-lead joint portion placed inside the separator to minimize exposure and mechanical stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional electrode assembly with positive electrode as outermost electrode is used, then the battery structure is simple, but the terminal portion is easily cut by external impact or force causing capacity reduction and functional failure
Solution Approach 1:
The patent inverts the conventional electrode assembly structure by placing the negative electrode as the outermost electrode instead of the positive electrode. This inversion positions the electrode lead connection tab inside the separator, protecting it from external impacts and bending forces that would otherwise cause terminal breakage and capacity loss.
2Reliability
If the tab-lead joint portion is placed outside the separator, then the connection is accessible, but the joint structure decreases in coherence during welding and is prone to breakage when bent
Solution Approach 1:
The patent nests the electrode lead connection tab inside the separator structure, similar to a nested doll configuration. This nesting protects the joint portion from mechanical damage while maintaining electrical connectivity, as the separator envelops and protects the connection point from external bending forces.
3Reliability
If multiple electrodes are stacked in vertical direction with conventional configuration, then the battery achieves required capacity, but compressive and tensile stress during bending causes mechanical damage and short circuits
Solution Approach 1:
The patent introduces asymmetry in the electrode assembly by making the negative electrode wider than the positive electrode, creating an overlapping configuration where the negative electrode extends beyond the positive electrode on both sides. This asymmetric design distributes bending stresses more evenly and prevents misalignment during flexing.
Data Source
AI summary
An electrode assembly according to the present disclosure includes one or more unit cells each equipped with a pair of electrodes having different polarities with a separator interposed therebetween, an electrode mixture coated on one or both surfaces of the pair of electrodes, and electrode tabs located on the edges of the respective electrodes and not coated with the electrode mixture, and the electrode tabs include an electrode parallel connection tab and an electrode lead connection tab, and any one or more of the electrode parallel connection tab and the electrode lead connection tab are formed on the electrodes, and an outermost electrode is a negative electrode.