Battery and portable electronic device with replaceable shell

The present invention discloses a cell and a portable electronic device which is applied with the cell and is provided with a changeable machine case. The cell is used for detaching the changeable machine case of the portable electronic device, and secondly a fastening block extends equally outwards relative to the side part. The portable electronic device comprising the changeable machine case comprises a cell, a cell cap covering on the cell, a machine body and a machine case fastening on the machine body, the machine body is arranged with a plurality of fastening parts at the two side walls, the machine case is arranged with a plurality of fastening pieces corresponding with the fastening parts to be fastened on the fastening parts, the cell comprises a plurality of fastening blocks which are used for extruding the fastening pieces of the machine body to facilitate the disengaging of the fasting piece from the fastening part.