This paper relates to development of a new generation of Li/S rechargeable batteries with energy density exceeding 180 Wh/kg and rate capability comparable with aqueous systems. The cells demonstrate 5 C discharge rate at -40degreesC. Retained energy and capacity at -40degreesC exceeded 60 and 80%, respectively. At room temperature cells generate specific power up to 750 W/kg. Cells are inherently protected from overcharge at low and room temperatures by internal chemistry and can sustain 30 times overcharge. It was shown that at 240degreesC sulfur cathode discharge includes at least five steps, in contrast to the known two steps at room temperature. Thermal effects related to different charge-discharge steps were analyzed. Cell thermal model including Ohm and Arrhenius parts of polarization allowed simulation Ragone plots and capacity over a wide range of currents and temperatures. (C) 2003 The Electrochemical Society.