Role of Tabs in Current Flow
During discharge, the current generated by electrochemical reactions flows through the sequence:
Active Material → Conductive Additive → Current Collector → Tab
The tab serves as the final current-carrying element in this path. Its current-carrying capacity is therefore a critical factor that affects both electrical efficiency and thermal stability. Any limitation in tab conductance can result in increased ohmic losses, localized heating, and potential degradation of cell lifetime and safety.
Conductance and Electrical Behavior
Tab conductance (𝐺) is defined as:
where:
- G: Conductance (S)
- σ: Electrical conductivity (S/m)
- A: Cross-sectional area (m²)
- L: Conductor length (m)
Higher conductivity or larger cross-sectional area increases current-carrying ability, while longer paths reduce it. Conductance is the reciprocal of resistance and represents how easily current flows through the tab.
Influence of Tab Cross-Sectional Area
The cross-sectional area of a tab directly affects its ability to carry electrical current. A larger cross-sectional area provides a wider pathway for electrons, reducing electrical resistance and enabling the tab to conduct higher currents more efficiently. Lower resistance minimizes ohmic losses, which in turn reduces localized heating and helps maintain the cell’s thermal stability.
Material Conductivity Comparison: Nickel vs. Aluminum
In cylindrical Li-ion cells:
- Anode tabs are typically nickel
- Cathode tabs are typically aluminum
Their conductivities differ significantly:
| Material | Conductivity σ [MS/m] | Relative Ratio |
|---|---|---|
| Aluminum (Al) | ~36 | 1.0 |
| Nickel (Ni) | ~14 | ~0.39 |
For the same current, the required tab area is inversely proportional to conductivity:
This means nickel tabs need roughly 2.5–3 times larger cross-sectional area than aluminum tabs to carry equivalent current while maintaining similar temperature rise.
Peak Current vs Tab Cross-Sectional Area Relation Graph
Clad Tab Structures
While not shown in the figure, clad tab materials are increasingly used in modern cells. Because nickel has relatively low conductivity, higher-conductivity solutions are needed in limited space to enable high-power and energy-dense cells. As a result, sandwich-like or two-layer combinations of nickel and copper are commonly employed in high-performance cells. These clad designs increase the anode tab’s effective conductivity, making it nearly comparable to that of the aluminum cathode tab, while maintaining mechanical robustness and weldability.
By leveraging advanced design strategies, such as optimized tab materials and layered structures, high-performance cells achieve both maximum current-carrying capacity and thermal stability. At AION, such detailed engineering insights are applied to tailor cell designs that balance material properties, geometry, and performance requirements, ensuring that each battery solution meets the demands of power-dense and energy-efficient applications.
Kerem Buğra Batuş, Cell Design & Process Development
At AION Engineering, we accelerate lithium-ion cell development using AI-driven design and advanced technologies, delivering innovative, sustainable energy solutions for a better future
See also: Cell Tab Design