Metal Cation-Assisted Synthesis of Amorphous B, N Co-Doped Carbon Nanotubes for Superior Sodium Storage.

Nearly inexhaustible sodium sources on earth make sodium ion batteries (SIBs) the best candidate for large-scale energy storage. However, the main obstacles faced by SIBs are the low rate performance and poor cycle stability caused by the large size of Na ions. Herein, a universal strategy for synthesizing amorphous metals encapsulated into amorphous B, N co-doped carbon (a-M@a-BCN; M = Co, Ni, Mn) nanotubes by metal cation-assisted carbonization is explored. The methodology allows tailoring the structures (e.g., length, wall thickness, and metals doping) of a-M@a-BCN nannotubes at the molecular level. Furthermore, the amorphous metal sulfide encapsulated into a-BCN (a-MS @a-BCN; MS : CoS, Ni S , MnS) nanotubes are obtained by one-step sulfidation process. The a-M@a-BCN and a-MS @a-BCN possess the larger interlayer spacing (0.40 nm) amorphous carbon nanotube rich in heteroatoms active sites, making them exhibit excellent Na ions diffusion kinetics and capacitive storage behavior. As SIBs anodes, they show high capacity, excellent rate performance, and long cycle stability.