Cylindrical Battery Tab Structure to Reduce Electrode Cracking
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Solution Overview
Problem
Cylindrical secondary batteries face issues with cracking and deformation of electrode plates due to stress caused by the composition and thickness of metal tabs, affecting safety and reliability.
Innovation Solution
The battery design incorporates partially cut and folded substrate tabs that protrude from the electrode uncoated portions, with insulating tape applied to prevent short circuits, and a lead tab that is wider than the substrate tabs for welding, minimizing the step difference and stress concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metal tab is welded onto an uncoated portion of an electrode plate, then electrical connection is achieved, but stress concentration causes cracking and deformation of the electrode plate
Solution Approach 1:
The invention changes the thickness parameter of the tab from a conventional thick metal tab to a thin substrate tab with thickness less than or equal to the active material layer thickness. This parameter change reduces stress concentration on the electrode plate while maintaining electrical connection functionality through a wider lead tab that is welded to the substrate tab.
Solution Approach 2:
The invention uses a composite structure consisting of a substrate tab made from the electrode plate material itself and a separate lead tab for welding. This composite approach allows the substrate tab to maintain structural integrity with the electrode plate while the lead tab provides the welding interface, distributing stress more effectively.
2Reliability
If a thick metal tab is used for electrical connection, then electrical conductivity is improved, but stress inside the electrode assembly increases causing cracking
Solution Approach 1:
The invention changes the thickness parameter of the tab from thick to thin (thickness ≤ active material layer thickness), which directly reduces the stress inside the electrode assembly. The electrical conductivity requirement is met through a wider lead tab that compensates for the reduced thickness.
Solution Approach 2:
The invention transitions from a thick tab structure to a thin tab with increased width (the lead tab is wider than the substrate tab). This dimensional change redistributes the stress across a larger area while maintaining electrical conductivity through the wider cross-section of the lead tab.
3Strength
If a thin substrate tab is used, then stress on the electrode plate is reduced, but electrical connection capability may be compromised
Solution Approach 1:
The invention compensates for the reduced thickness of the substrate tab by increasing the width of the lead tab. This dimensional change in the width direction maintains the electrical connection capability while the thin substrate tab reduces stress on the electrode plate.
Solution Approach 2:
The substrate tab acts as an intermediary between the electrode plate and the lead tab. It transfers the electrical connection function from the thick lead tab to the thin structure, allowing the lead tab to provide both mechanical strength for welding and electrical conductivity while the substrate tab minimizes stress on the electrode plate.
Data Source
AI summary
Embodiments relate to a cylindrical secondary battery including a can having a cylindrical shape and an open one end portion, an electrode assembly which is wound in a cylindrical shape by stacking a first electrode plate including a first electrode uncoated portion, a separator, and a second electrode plate including a second electrode uncoated portion disposed in a direction opposite to the first electrode uncoated portion and accommodated in the can, and a cap assembly to close the open one end portion of the can in a state in which the electrode assembly is accommodated in the can, wherein the first electrode uncoated portion includes a first substrate tab which is partially cut and folded to protrude outward from the first electrode uncoated portion, and the second electrode uncoated portion includes a second substrate tab which is partially cut and folded to protrude outward from the second electrode uncoated portion.