Solid-State Lithium-Sulfur Battery Based on Composite Electrode and Bi-layer Solid Electrolyte Operable at Room Temperature

We report a unique solid-state lithium-sulfur cell based on a bilayer electrolyte and composite solid-state cathode. The bilayer electrolyte that contains a layer of mixed conduction membrane and a layer of polymer electrolyte eliminates the use of organic flammable liquid electrolytes and separators. The sulfur electrode is also a unique composite of sulfur with ionically-conducting intercalating nano-particulate material. Unlike many other solid-state batteries, this cell can be cycled at room temperature to utilize 85% of the active material at the sulfur electrode. The low internal resistance of the cell is comparable to that of a liquid electrolyte based lithium-sulfur cell. Impedance studies indicate that the low internal resistance results from the high ionic conductivity of the intercalating nano-particulate materials and the thin layer of polymeric electrolyte. While the volume changes at the cathode result in loss of inter-particle contact with repeated cycling, the addition of alumina to the polymer layer improved the capacity retention. This unique solid-state cell configuration opens a new pathway towards a safer high-energy lithium battery.