Lithium-sulfur cells

Nitash Balsara, LBNL

Lithium-sulfur cells are attractive targets for energy storage applications as their theoretical specific energy of 2600 Wh/kg is much greater than the theoretical specific energy of current lithium-ion batteries.  Unfortunately, the cycle-life of lithium-sulfur cells is limited due to migration of species generated at the sulfur cathode. These species, collectively known as polysulfides, can transform spontaneously, depending on the environment, and it has thus proven difficult to determine the nature of redox reactions that occur at the sulfur electrode.

X-ray spectroscopy was used to fingerprint the polysulfides present in a solid polymer electrolyte film. Molecular simulations were used to determine the molecular underpinnings of the polysulfide spectra. The first simulated spectra of polysulfides are presented in the adjoining figure.

This works lays the foundation for rational design of sulfur cathodes with improved cycle life.