Development and performance characteristics of bipolar lithium/iron disulfide battery

The purpose of this paper is to review the projected performance and safety characteristics of the bipolar lithium/iron disulfide battery as it relates to a propulsion device for electric vehicles (EVs). Lithium/iron disulfide cells with a molten-salt electrolyte are well suited to the development of a bipolar battery. Long strings of series-connected cells are practical since these cells always fail in a short-circuit condition, and a technique has been developed to equalize the cells whose capacity may have gotten out of balance after many cycles. To maintain the electrolyte molten, the battery is normally operated at 425{degrees}C. The LiFeS{sub 2} cell exhibits the high performance and long life needed for the electric vehicle application. The cell uses a molten-salt electrolyte whose composition is 34 mol% LiCl 32.5 mol% LiBr-33.5. mol% KBr (m.p. 322{degrees}C, and a densely loaded FeS{sub 2} electrode that is only operated on the upper voltage plateau (UP). The Li-Al alloy is used as the negative electrode in the cell. The alloy is normally operated in the {alpha}+{beta} region of the phase diagram and covers a compositional range of 9 to 47 atom % lithium. This two-phase alloy is within 300 mV of the pure lithium metal potential,more » but remains solid at cell operating temperatures (400-450{degrees}C).« less