We describe below the electrochemical performance characteristics of cylindrical (18650) and prismatic (48.26 x 25.4 x 7.62) lithium-ion cells at ambient and sub-ambient temperatures. Ragone plots of power and energy data for these cells are compared, and indicate that at room temperature, the similar to 500 mAh prismatic lithium-ion cells exhibit higher specific power and power density than the similar to 1100 mAh cylindrical cells. Over the temperature range from 35 to - 20 degrees C, the cell impedance is almost constant for both cell types. These cells at 100% state-of-charge (s.o.c.) show very little voltage drop for current pulses up to 1 A.