Porous graphene flakes (PGFs) with controllable pore sizes are selectively prepared through self-assembly of Fe3O4 nanoparticles on organic modified montmorillonite combined with carbonization and subsequent annealing treatment. The resulting PGFs with a thickness of 5 nm have a specific surface area of 337 m(2)/g, pore volume of 0.66 cm(3)/g, and mean pore diameter of 15 nm. Due to their unique porous flake structures, PGFs show an impressive rate performance in lithium-ion batteries, especially at high current densities (238 mA h/g at 10 C) as well as long-term stability in comparison to the commercial graphite (55 mA h/g at 10 C). Therefore, PGFs with their key structural properties serve as ideal candidates as electrode components in lithium-ion batteries and show great potential application in other energy storage fields.