A secondary battery, which can improve safety during a longitudinal compression test by reinforcing strength of a cap plate, is provided. The aircraft considered have existing landing gear such as wheeled landing gear to equip said aircraft to optionally takeoff or land on a solid surface such as a beach or landing strip, the method including the steps of: a) mounting at least one float retraction arm to the aircraft; and b) attaching the floats to the float retraction arm. and pressure of 650 torr that is greater than 400 grams arsine per liter of adsorbent; at least 30% of overall porosity of the adsorbent including slit-shaped pores having a size in a range of from about 0.