A secondary particle and a lithium battery including the same are provided wherein the secondary particle includes a plurality of primary particles and each primary particle contains n polycyclic nano-sheets disposed upon one another. The polycyclic nano-sheets include hexagonal rings of six carbon atoms linked to each other, wherein a first carbon and a second carbon have a distance therebetween of L1. L2 is a distance between a third carbon and a fourth carbon, and the arrangement of the polycyclic nano-sheets is such that L1≧L2. The secondary particle is used as a negative active material in the lithium battery, and the secondary particle contains pores, thereby allowing for effective intercalating and deintercalating of the lithium ions into the secondary particle to impart improved capacity and cycle lifespan.