Encapsulating N-Doped Carbon Nanorod Bundles/MoO2 Nanoparticles via Surface Growth of Ultrathin MoS2 Nanosheets for Ultrafast and Ultralong Cycling Sodium Storage.

Conversion-type anode materials possess high theoretical capacity for sodium-ion batteries (SIBs), owing to multi-electron transmission (2-6 electrons). Mo-based chalcogenides are a class of great promise, high-capacity host materials, but their development still undergoes serious volume changes and low transport kinetics during the cycling process. Here, MoO2 nanoparticles anchored on N-doped carbon nanorod bundles (N-CNRBs/MoO2) are synthesized by a facile self-polymerized route and a following annealing. After hydrothermal sulfuration, N-CNRBs/MoO2 composites are encapsulated by surface growth of ultrathin MoS2 nanosheets, acquiring hierarchical N-CNRBs/MoO2@MoS2 composites. Serving as the SIB anode, the N-CNRBs/MoO2@MoS2 electrode exhibits significantly improved sodium-ion storage properties. The reversible capacity is up to 554.4 mA h g-1 at 0.05 A g-1 and maintains 249.3 mA h g-1 even at 10.0 A g-1. During 5000 cycles, no obvious capacity decay is observed and the reversible capacities retain 334.8 mA h g-1 at 3.0 A g-1 and 301.4 mA h g-1 at 5.0 A g-1. These properties could be ascribed to the vertical encapsulation of MoS2 nanosheets on high-crystalline N-CNRBs/MoO2 substrates. The hierarchical architecture and unique heterostructure between MoO2 and MoS2 synergistically facilitate sodium-ion diffusion, relieve volume changes, and boost pseudocapacitive charge storage of N-CNRBs/MoO2@MoS2 electrode. Therefore, the rational growth of nanosheets on complex substrates shows promising potential to construct anode materials for high-performance batteries.