New sodium-sulfur battery delivers extreme energy density at a fraction of the price

The shift to green energy has increased demand for batteries, but lithium-ion technology is reaching its limits. In addition to the risk of spontaneous combustion (thermal runaway), the high price of lithium is inhibiting wider use. Researchers at Shanghai Jiao Tong University have therefore developed a sodium-sulfur-based alternative that uses abundant and cheap raw materials.

Previous attempts with this chemistry have failed due to low voltage and the need for huge amounts of sodium. The team solved the problem by switching to so-called redox chemistry, which allowed the development of a battery without an anode. The design includes an aluminum foil current collector, a sulfur cathode, and a special non-flammable chloroaluminate electrolyte with the addition of sodium dicyanamide (NaDCA). This compound allows stable operation at room temperature and improves the efficiency of the processes at the electrodes.

The results are impressive: the battery achieves an energy density of up to 1,198 Wh/kg and a specific power of 23,773 W/kg. Using the Bi-COF catalyst, the energy density has risen to 2,021 Wh/kg. The cost aspect is even more impressive. The estimated price is only around 4.65 euros per kWh, which is an order of magnitude cheaper than lithium batteries.

Despite the excitement, challenges remain. The electrolyte is highly corrosive and requires special handling, and long-term stability in air has not yet been fully confirmed. The researchers are confident that these hurdles will be overcome, opening the way for applications ranging from smartwatches to large-scale grid-connected storage systems.