Sodium Ion Insertion in Hollow Carbon Nanowires for Battery Applications

Hollow carbon nanowires (HCNWs) were prepared through pyrolyzation of a hollow polyaniline nanowire precursor. The HCNWs used as anode material for Na-ion batteries deliver a high reversible capacity of 251 mAh g(-1) and 82.2% capacity retention over 400 charge-discharge cycles between 1.2 and 0.01 V (vs Na'/Na) at a constant current of 50 mA g(-1) (0.2 C). Excellent cycling stability is also observed at an even higher charge-discharge rate. A high reversible capacity of 149 rnAh g(-1) also can be obtained at a current rate of 500 rnA g(-1) (2C). The good Na-ion insertion property is attributed to the short diffusion distance in the HCNWIs and the large interlayer distance (0.37 nm) between the graphitic sheets, which agrees with the interlayered distance predicted by theoretical calculations to enable Na-ion insertion in carbon materials.