A secondary battery includes a negative electrode; a positive electrode including a plurality of positive electrode plates spaced apart from each other in a width direction, wherein a positive electrode plate of the plurality of positive electrode plates has a planar shape, and a channel between the plurality of positive electrode plates; an electrolyte material disposed in the channel between the plurality of positive electrode plates; a separation membrane between the negative electrode and the positive electrode; and a first metal layer disposed on a surface of the separation membrane facing the positive electrode.