Effect of Electrode Thickness on Cell Energy Density

In Li-ion batteries, the cathode thickness will heavily influence the energy density of the cell. A thicker cathode means there will be more cathode active material in the electrode. This increases the capacity of the electrode and hence increase the energy density of the cell.

However, this relationship is not linear. Using the CAMS model, the cell energy density for a Li-ion NMC622||Graphite cell at different cathode thicknesses was modelled. As the cathode thickness is increased, the cell energy (in Wh) increases linearly, while the cell energy density (in Wh/kg) shows an asymptotic relationship, converging at around 300 Wh/kg.

Although increasing electrode thicknesses in Li-ion cells is desirable precisely because of the increase in energy density it provides, the graph below demonstrates this increase has diminishing returns. In addition, thicker electrodes are not always advantageous, with thicker electrodes generally restricting power performance.

The following data was produced using the following inputs in the model. Default values were used for all inputs apart from cathode loading which was altered to model different thicknesses:

  1. Battery chemistry: Li-ion
  2. Cell type: Energy
  3. Cell Format: Pouch cell
  4. Cell Dimensions: A5 (Size of cathode)
  5. Cathode: NMC 622
  6. Anode: Graphite anode (Li-ion)
  7. Separator: Model 2320 – Cellgard – PP/PE/PP
  8. Electrolyte: Li-ion electrolyte

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