Highly Nitrogen-Doped Three-Dimensional Carbon Fibers Network with Superior Sodium Storage Capacity

Inspired by the excellent absorption capability of spongelike bacterial cellulose (BC), three-dimensional hierarchical porous carbon fibers doped with an ultrahigh content of N (21.2 atom %) (i.e., nitrogen -doped carbon fibers, NDCFs) 800 were synthesized by an adsorption swelling strategy using BC as the carbonaceous 0) material. When used as anode materials for sodium-ion batteries, the NDCFs deliver a 600 high reversible capacity of 86.2 mAh g(-1). even after 2000 cycles at a high current density of 10.0 A g(-1). It is proposed that the excellent Na+ storage performance is mainly due to the defective surface of the NDCFs created by the high content of N dopant. Density functional theory (DFT) calculations show that the defect sites created by N doping can strongly host Na+ and therefore contribute to the enhanced storage capacity.