Lithium-sulfur cells: The Gap between the state-of-the-art and the requirements for high energy battery cells

Li-S cells are considered a highly attractive electrochemical storage system, especially due to their high potential gravimetric energy density. The long-term target of all Li-S research activities must be to outperform state-of-the-art Li-ion cells. A current benchmark is the Panasonic NCR18650B, which has a gravimetric energy density of 240 Wh kg-1 and several hundred relatively stable cycles. The possible 18650 Li-S cell energies and cell costs are calculated for various sulfur loads, sulfur utilizations, and electrolyte/sulfur ratios with the aim of determining the cell and electrode property values required to outperform the NCR18650B. These values are compared with statistical information obtained from an extensive literature review of 274 Li-S publications over the last 12 years to show the gap between state-of-the-art Li-S research and requirements for high energy density cells. Finally, a carbon nanotubes-based electrode is introduced, which meets important criteria for obtaining high gravimetric cell energy densities.