BATTERY

A battery includes a first casing. The first casing includes a first metal piece and a second metal piece disposed inside the first metal piece, such that the first metal piece forms an outer surface of the first casing and the second metal piece forms an inner surface of the first casing. A material of the first metal piece is inconsistent with a material of the second metal piece. A corrosion potential of the second metal piece is higher than a corrosion potential of the first metal piece, and the corrosion potential of the second metal piece is higher than a negative electrode potential of the battery.