Cylindrical Battery Tab Placement and Welded End Cap Design
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Solution Overview
Problem
Conventional battery cell designs face challenges in maximizing discharge capacity due to constraints in volume, inefficient sealing methods, and unreliable pressure relief mechanisms, leading to reduced energy capacity and potential explosions from clogging of vent mechanisms.
Innovation Solution
A cylindrical electrochemical cell design featuring a spirally wound assembly with multiple conducting tabs and a centrally located fill hole and vent mechanism, utilizing thick aluminum end caps for robustness and efficient welding, and a nickel interface terminal for improved sealing and power transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional crimping techniques are used to seal the end cap to the can after electrolyte fill, then hermetic sealing is achieved, but cell volume efficiency is reduced and total energy capacity is reduced
Solution Approach 1:
The patent replaces the mechanical crimping system with a welding system. The end cap is welded to the can before electrolyte fill, eliminating the need for post-fill mechanical sealing. This substitution of welding (thermal/electrical process) for crimping (mechanical process) achieves hermetic sealing while maintaining cell volume efficiency, as the weld joint is more volumetrically efficient than crimping structures.
Solution Approach 2:
The patent performs the sealing action before electrolyte fill rather than after. The end cap is welded to the can in the preliminary assembly stage, creating a hermetic seal before the electrolyte is introduced. This preliminary sealing action eliminates the volume loss associated with post-fill crimping while ensuring hermetic integrity.
2Ease of operation
If a fill hole is placed off center to give central placement priority to the power terminal, then power terminal placement is optimized, but the wall thickness where the fill hole exists becomes very thin making sealing challenging and unreliable
Solution Approach 1:
The patent performs the sealing action before electrolyte fill rather than after. The end cap is welded to the can in the preliminary assembly stage, creating a hermetic seal before the electrolyte is introduced. This preliminary sealing action eliminates the volume loss associated with post-fill crimping while ensuring hermetic integrity.
Solution Approach 2:
The patent replaces the mechanical crimping system with a welding system. The end cap is welded to the can before electrolyte fill, eliminating the need for post-fill mechanical sealing. This substitution of welding (thermal/electrical process) for crimping (mechanical process) achieves hermetic sealing while maintaining cell volume efficiency, as the weld joint is more volumetrically efficient than crimping structures.
3Reliability
If conventional vent mechanisms are used with clearance between the vent and other cell components, then pressure relief function is achieved, but additional internal volume is consumed that could be used for energy capacity
Solution Approach 1:
The patent merges the vent mechanism with the end cap structure itself. The vent is integrated into the end cap design, eliminating the need for separate vent components and their associated clearances. This merging allows the vent function to be achieved while minimizing internal volume consumption, as the vent is part of the structural end cap rather than a separate mechanism requiring additional space.
Solution Approach 2:
The end cap serves multiple functions: it provides structural closure, houses the power terminal, and incorporates the vent mechanism. By making the end cap a multi-functional component that includes the vent, the patent eliminates the need for dedicated vent space, thereby maximizing the volume available for energy-storing materials.
4Reliability
If multiple conducting tabs are used to reduce impedance and inductance, then electrical performance is improved, but the complexity of managing and sealing the tabs increases
Solution Approach 1:
The patent merges multiple conducting tabs into a single integrated current collector structure. Instead of managing separate tabs that require individual sealing and positioning, the current collector is designed as a unified component that collects current from multiple points and provides a single interface for connection to the external circuit. This merging reduces the complexity of tab management while maintaining low impedance and inductance through the distributed current collection design.
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 significantly increases energy storage capacity, reduces impedance and inductance, and enhances mechanical robustness while minimizing the risk of explosions by using a centrally located fill hole and vent mechanism, and efficiently managing internal pressure.
Implementation Method 1
Attempts to create a robust hermetic seal between the cell's can and the cell's end cap after the cell has been activated are complicated by the presence of electrolyte. This becomes especially true when using a welding process at this seam.
Implementation Method 2
a nickel interface terminal for improved sealing and power transfer
Data Source
AI summary
A compact, robust, multifunctional and highly manufacturable rechargeable cylindrical electrochemical cell is provided. In some embodiments, a cell can include a spirally wound assembly having an anode sheet and a cathode sheet separated by separator membranes, each sheet having a electroactive layer on a current collector. At least one of the current collectors can be in electrical communication with conducting tabs that extend from at least one of the anode sheet and the cathode sheet, the conducting tabs extends from an end face of the spirally wound assembly. The centers of the plurality of conducting tabs can be located within a 90 degree quadrant of an end face of the spirally wound assembly.