SECONDARY BATTERY

A secondary battery in which graphite that is an active material can occlude and release lithium efficiently is provided. Further, a highly reliable secondary battery in which the amount of lithium inserted and extracted into/from graphite that is an active material is prevented from varying is provided. The secondary battery includes a negative electrode including a current collector and graphite provided over the current collector, and a positive electrode. The graphite includes a plurality of graphene layers. Surfaces of the plurality of graphene layers are provided substantially along the direction of an electric field generated between the positive electrode and the negative electrode.