Low-temperature metal-catalyzed synthesis of encapsulated metal oxide nanoparticles in nitrogen-doped carbon nanotubes from carbon nitride as anodic materials of high-performance lithium-ion batteries

Metal oxides have been considered as a promising anode material for lithium ion batteries (LIBs) due to their high theoretical capacities, low cost, natural abundance and environmental friendliness. However, the severe volume expansion upon cycling and poor conductivity limit their cycling stability and rate capability. To address this issue, Co3O4 and NiO nanoparticles encapsulated at the endpoints of nitrogen-doped carbon nanotube (NCNT) hybrids are designed and prepared by a metal catalyzed graphitization-nitridization driven tip-growth process and the subsequent oxidation in air, using (carbon nitride) C3N4 as a new solid-state carbon and nitrogen source. When used as an anode material for LIBs, the representative Co3O4@NCNT hybrid exhibits a high capacity of 1002 mA h g(-1) at 100 mA g(-1), an excellent rate capability of 673 mA h g(-1) at 5.0 A g(-1) and remarkable cycling stability of 837 mA h g(-1) after 800 cycles at 1 A g(-1), which are much superior to those of the Co3O4/CB control sample. The outstanding electrochemical performances of MxOy@NCNTs are due to their unique nanoarchitecture, which offers a porous conductive matrix for effective electron-ion transport and forms carbon nanocap confined MxOy nanoparticles as well as stress buffer nanocavities for robust structural stability during lithiation/delithiation processes. The results may pave a way for the rational structural design of high-performance metal oxide-based anode materials for next-generation LIBs.