Organic salts based on the bicyclic (spiro) ammonium cation were synthesized with a systematic variation in the size of the rings. The salts show high melting points and plastic crystal phases. The SP-56 salt showed the lowest melting point, highest ionic conductivity, and a reduction potential more positive than that of the Li/Li+ couple; therefore, it was mixed with EC before being employed in a Li/LiFePO4 battery. The battery maintained capacities between 100 and 113 mA hg(-1) over 100 cycles.