Stacked vs Wound Cells

When we talk about Stacked vs Wound cells we are considering the Anode-Separator-Cathode stack and how that is assembled within a battery cell. Kong et al [1] show a simple schematic of the two arrangements.

Pouch and Prismatic cells can be stacked or wound, but what is the advantage and disadvantage of each approach?

Cell Stack

Within this what we see is a repeating element. This is the cell stack, the fundamental building block of the cell.

At a fundamental level we can consider this building block as the working unit.

At this point we should note that both of these electrode assembly processes are used in both Pouch and Prismatic format cells.

What we are really interested in is the advantage and disadvantages of Stacked vs Wound Cells.

This post has been built based on the support and sponsorship from: Thermo Fisher Scientific, Eatron Technologies, About:Energy, Quarto Technical Services and Alvatek.

Pressure Distribution

Stacked cells experience more even pressure distribution across the electrode surface, while wound cells can have stress concentration at the bends, leading to potential degradation over time. 

Volume Utilization

Stacked cells can utilize more space within the battery casing due to their flat design, leading to higher energy density. 

Manufacturing Complexity

Stacking can be a more complex process than winding, requiring precise alignment and cutting of electrode sheets. Thus making the stacking process slower with a lower yield.

The stacking process also requires more slitting of the electrodes and hence more likelihood of burrs or metallic particles.

Electrical and Thermal Comparison

Each of the layers in the stacked cell are welded together to a tab and hence the resistance of the stacked cell is lower than a wound cell that will have less tabs per unit area. Although, tabless wound cell designs are addressing this resistance difference.

Thermal Conductivity of the Active Layers

If we look at the active layers of a cell the thermal conductivity in the plane of the layers is approximately 10x to 100x of that through the planes.

This should not be unexpected as the electrodes are made from sheets of aluminium and copper. Two of the best materials for thermal conductivity.

Hence the orientation of the would cell with the cooling plate has an impact on the temperature gradient through the cell and the heat management.

This is also a limitation with the stacked cell. However, the orientation of the would cell must be considered as cooling against the wound end will increase the temperature gradient and limit the cooling performance.

References

1. Lingxi Kong, Ryan Aalund, Mohammad Alipour, Stanislav I. Stoliarov and Michael Pecht, Evaluating the Manufacturing Quality of Lithium Ion Pouch Batteries, Journal of The Electrochemical Society, Volume 169, Number 4, 2022
2. Stacking battery vs winding – detail comparison analysis, Tycorun
3. Winding Vs Stacking, Which Technology Works Best For Lithium-Ion Batteries?, Bonnen Battery