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A study of transition metal oxide cathodes to replace the iron disulfide used in thermal batteries was conducted at Saft ABSD in Cockeysville, MD. The goal was to identify cathode materials yielding higher voltage and improvements in energy density. Selected materials were evaluated versus lithium immobilized by iron powder (LAN) anodes in molten nitrate electrolytes. Single cells were tested between heated platens inside an argon atmosphere glove box over the temperature range of 240°C to 425°C. The best cathode material tested was lithiated manganese dioxide, LiMn2O4. After extensive experimentation, we were able to achieve a peak voltage of 2.8 V under a load of 200 ma/cm2 and a two-plateau voltage discharge yielding 221 Wh/kg at 260°C. This exceeds the specific energy of state-of-the-art cells with iron disulfide.

Rechargeable lithium ion batteries provide significant advantages over lead acid and nickel cadmium batteries for manned and unmanned aerial vehicles. Lithium ion has excellent cycle life and calendar life and exceptionally low self-discharge. The high energy density of lithium ion provides weight and volume savings, which allows for additional aircraft payload. Cell configurations containing high surface area electrodes and low temperature electrolyte can provide required power over military temperature extremes of −40°C to +71°C. Such batteries provide engine starting, load leveling, switching, and emergency aircraft power. Prototype batteries have been tested to fighter aircraft loads and floated on a 28-volt bus. Hermetically sealed cell construction and electronic cell balancing and charge control provide maintenance free operation. Our solutions are cylindrical cells in high energy and high power configurations.