Design and testing of lithium/iron sulfide batteries for electric vehicle propulsion. [Li--Al/KCl--LiCl--FeS/sub 2/]

A program to develop high-performance batteries for use in electric automobiles and for storing off-peak energy for load leveling in electric utility systems is described. The batteries for vehicle propulsion consist of cells with a central positive plate containing FeS/sub 2/ and two facing negative plates containing Li--Al alloy. The electrolyte is the LiCl--KCl eutectic which has a melting point of 352/sup 0/C and requires the cells to be operated at temperatures between 350 and 450/sup 0/C. Prismatic cells 13 cm on a side and 2 to 4 cm thick were fabricated. Laboratory cells demonstrated a capacity at the 10-hour rate of about 120 Ah at 1.5 V, which corresponds to a specific energy of about 150 W-hr/kg. A battery testing laboratory was established which contains equipment for charging and discharging the cells in a mode that simulates the operation of the cells in an electric vehicle battery. Equipment was developed for equalizing the charge in an array of cells; it was tested successfully with lead--acid batteries as well as Li--Al/FeS/sub 2/ batteries. A cell charge equalization system suitable for incorporation in a vehicle propulsion battery was also developed. Calculations and experimental measurements were made to determine resistances of themore » various internal and external cell and battery components. Designs were developed for a 30 kWh vehicle battery suitable for driving a small four-passenger vehicle. The battery design is based upon the use of 160 prismatic sub-cells, 13 x 20 cm, which are arranged in two parallel rows. Adjacent sub-cells are connected in series. The battery is contained in an enclosure which is designed to minimize heat loss during idle periods and remove excess heat generated during operating periods. 10 figures, 4 tables.« less