Encapsulating Trogtalite CoSe2 Nanobuds into BCN Nanotubes as High Storage Capacity Sodium Ion Battery Anodes

Trogtalite CoSe2 nanobuds encapsulated into boron and nitrogen codoped graphene (BCN) nanotubes (CoSe2@BCN‐750) are synthesized via a concurrent thermal decomposition and selenization processes. The CoSe2@BCN‐750 nanotubes deliver an excellent storage capacity of 580 mA h g−1 at current density of 100 mA g−1 at 100th cycle, as the anode of a sodium ion battery. The CoSe2@BCN‐750 nanotubes exhibit a significant rate capability (100–2000 mA g−1 current density) and high stability (almost 98% storage retention after 4000 cycles at large current density of 8000 mA g−1). The reasons for these excellent storage properties are illuminated by theoretical calculations of the relevant models, and various possible Na+ ion storage sites are identified through first‐principles calculations. These results demonstrate that the insertion of heteroatoms, B–C, N–C as well as CoSe2, into BCN tubes, enables the observed excellent adsorption energy of Na+ ions in high energy storage devices, which supports the experimental results. Metal organic frameworks derived Trogtalite CoSe2 nanobuds encapsulated into BCN Nanotubes are fabricated through concurrent thermal decomposition and selenization processes. The as developed CoSe2@BCN nanotubes present high storage capacity sodium ion battery anodes.