Cylindrical Li-Ion Cell Contact Structure for Lower Resistance
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Solution Overview
Problem
Lithium-ion cells face challenges in achieving high energy density, low internal resistance, and efficient thermal management, particularly in cylindrical round cells with ribbon-shaped electrode-separator assemblies, which can lead to thermomechanical stresses and deformation during fast charging.
Innovation Solution
The design incorporates a metallic tubular housing with a contact element that includes a metal disk, contact sheet metal member, and insulator, where the electrode-separator assembly is axially aligned within the housing, allowing for direct contact and reduced internal resistance, and features a contact element that serves both as an electrical connector and housing part, enhancing heat dissipation and manufacturability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the electrode-separator assembly is wound in a cylindrical configuration with protruding current collector edges, then the cell structure is simplified and manufacturing is easier, but thermomechanical stresses during fast charging cause deformation and damage to the cell structure
Solution Approach 1:
The patent combines the current collector edges with the housing structure by integrating the contact elements directly into the housing. The first current collector edge is in direct contact with the housing, and the second current collector edge is connected to a contact element that is integrated into the housing structure. This merging eliminates the need for separate external connectors and reduces the number of components, thereby simplifying manufacturing while distributing mechanical stresses more evenly throughout the integrated structure to prevent deformation during fast charging.
2Ease of operation
If separate electrical conductor tabs are used to connect current collectors, then electrical connection is achieved, but local heating occurs at the conductor tabs during high current operation
Solution Approach 1:
The patent merges the electrical connection function with the housing structure by integrating contact elements directly into the housing. The first current collector edge makes direct contact with the housing, and the second current collector edge connects to a contact element that is part of the housing. This integration creates larger contact areas and distributes current flow more evenly, reducing current density and minimizing Joule heating at connection points during high current operation.
Solution Approach 2:
The patent transitions from point-contact or small-area connectors to extended surface contact by having the current collector edges make contact along their lengths with the housing and integrated contact elements. This dimensional expansion of the contact area reduces current density and associated thermal effects, effectively managing heat generation during high current operation.
3Temperature
If the contact element is integrated into the housing structure, then heat dissipation is improved and device complexity is reduced, but the manufacturing process becomes more complex
Solution Approach 1:
The patent implements multi-functionality by designing the housing structure to simultaneously serve as mechanical containment, thermal management pathway, and electrical connection interface. The integrated contact elements perform multiple functions: providing structural support, conducting heat away from current collectors, and establishing electrical connections. This consolidation reduces the number of separate components needed while improving thermal management through the housing's inherent heat dissipation capabilities.
4Loss of energy
If the current collector edges are in direct contact with the housing, then internal resistance is reduced and energy density is improved, but the housing material must withstand both mechanical and electrical demands
Solution Approach 1:
The patent employs composite construction by combining metallic current collectors with housing materials that possess both mechanical strength and electrical conductivity. The housing structure is designed to accommodate and integrate with the current collector edges, requiring materials that can withstand mechanical stresses while providing efficient electrical contact. This composite approach allows the system to achieve low internal resistance through direct metal-to-metal contact while maintaining structural integrity through appropriately selected housing materials.
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
This configuration improves energy density, reduces internal resistance, and enhances thermal management, leading to improved safety and manufacturability of lithium-ion cells by ensuring homogeneous current distribution and efficient heat dissipation.
Implementation Method 1
The edge of the metal disk is arranged to abut an inside of the tubular housing part along a circumferential contact zone
Implementation Method 2
The edge of the metal disk is connected to the tubular housing part by a circumferential weld seam
Implementation Method 3
Electrochemical cells can convert stored chemical energy into electrical energy by virtue of a redox-reaction
Implementation Method 4
This ion current crosses the separator and is ensured by an ion-conducting electrolyte
Data Source
AI summary
A lithium-ion cell includes a housing comprising a metallic tubular housing part made of aluminum or an aluminum alloy with a terminal circular opening. The cell further includes a contact element that closes the terminal circular opening of the tubular housing part, the contact element comprising a metal disk, a contact sheet metal member, a metal pole pin and an insulator. In addition, the cell includes an electrode-separator assembly having an anode, a cathode, and a separator with the sequence anode/separator/cathode. The electrode-separator assembly is in the form of a cylindrical winding with two terminal end faces and a winding shell located therebetween. The electrode-separator assembly is disposed in the winding and is axially aligned so that the winding shell abuts an inside of the tubular housing part.