Three-dimensional porous carbon sheets are successfully prepared from a readily available water-soluble biomasses sodium alginate via a simple method without using chemically activated agents. By adjusting the thickness of wet films, we can produce carbon samples and target the surface area and pore volume. The results show that the porous carbon sheets possess superior electrochemical performance when they are used as anode materials for lithium-ion batteries. The porous nanostructure could provide the pathways for easy accessibility of electrolyte and fast transportation of lithium ions and electrons. The existence of micropores can also ensure high reversible capacity. (C) 2016 Elsevier Ltd. All rights reserved.