Development of prototype sealed bipolar lithium/sulfide cells

Development of a prototype bipolar battery containing 13-cm dia cells for electric-vehicle propulsion is underway at Argonne National Laboratory (ANL). Both Li/FeS and Li/FeS2 cells have been tested with LiCl-LiBr-KBr electrolyte and MgO powder separators for electrolyte-starved cell operation at 400 to 425 C. These cells achieved the high performance and stability needed for the intended application. An innovative feature of this bipolar battery is a metal/ceramic bonded peripheral seal for each cell. The development of corrosion-resistant sealant materials at ANL has let to metal/ceramic bonds about 100 times stronger that obtainable with commercially available sealants for service at over 300 C. This peripheral seal promotes long battery life by eliminating electrolyte loss and prohibiting transport of electrolyte from one cell to the next in a bipolar stack. Fabrication facilities have been recently constructed that enable development of 13-cm I.D. peripheral seals. The initial tests of prototype bipolar Li/FeS and Li/FeS2 cells indicate improved performance as a result of scale-up. The 7-mm thick, 13-cm dia cells have total weight of 0.25 kg (cell density 2.8 g/cu cm). These cells are operated at 425 C. The Li/FeS2 cell exhibits 180 Wh/kg at a 30 W/kg discharge rate and the Li/FeS cell delivered 130 Wh/kg at a 25 W/kg rate. The low internal impedance of these cells enables high peak specific power capability; 400 W/kg for Li/FeS2 and 24 W/kg for Li/FeS at 80 percent DOD.