Sulfur-enriched, hierarchically nanoporous carbonaceous materials for sodium-ion storage

• SH-NCMs were fabricated from an inclusion complex based on cellulose and urea.
• SH-NCMs had a 3D-interconnected mesostructure and numerous heteroatoms.
• Sulfur atoms doped on SH-NCMs highly affected their electrochemical performances.
• SH-NCMs showed high capacities and rate capabilities for sodium-ion storage.

Na-ion batteries (NIBs) have had much attention as post Li-ion batteries (LIBs) due to abundant Na resources and a similar chemistry to LIBs; however NIBs have suffered from a lack of proper anode materials. In this study, sulfur-enriched, hierarchically nanoporous carbonaceous materials (SH-NCMs) were fabricated by an inclusion complex of cellulose hosted by urea hydrate through simple pyrolysis and heating with elemental sulfur. SH-NCMs had unique materials characteristics, such as a large amount of heteroatoms, containing 21.7 at.% sulfur, 12.6 at.% oxygen and 5.7 at.% nitrogen, and a 3D-interconnected mesostructure with a high surface area of 201 m2 g−1. Interestingly, SH-NCMs showed a high specific capacity of 456 mAh g−1 at a current density of 1 A g−1, and even after 50 cycles at 10 A g−1, a specific capacity of 170 mAh g−1 was achieved. In addition, stability over more than 500 repetitive cycles with nearly 100% Coulombic efficiency was maintained.