PolyPlus Battery Company is developing advanced secondary batteries based on lithium polysulfide chemistry. The Navy has an immediate need for secondary batteries having energy densities superior to Ag/Zn cells. Given the high energy density of Ag/Zn chemistry, the Navy seeks alternative cathodes having theoretical energy densities in excess of 1500 Wh/kg. PolyPlus Battery Company is developing a battery based on the chemistry of lithium polysulfides. The reversible cell reaction is 2 Li + S = Li2S. The lithium polysulfide cathode has a gravimetric capacity of 1165 mAh/g and a nominal cell potential of 2.0 volts, giving a theoretical energy density of 2330 Wh/kg. The extremely high energy density of the Li/S system is 33 to 55% higher than that requested by the Navy. Furthermore, fully sealed, packaged 2 Ah cells tested at PolyPlus Battery Company's facility have demonstrated exceptionally high specific energies of 150 to 400 Wh/kg at moderate to low rate (C/3 to C/25). These cells have also demonstrated high power densities of over 800 W/kg at room temperature and over 1,000 W/kg (80 Wh/kg) at moderately elevated temperatures (60 ¡C). The superior characteristics of this battery chemistry seem particularly well suited to the Navy's requirements.
