Nano-confined CoSe₂/Mo₂C nanoparticles encapsulated into porous carbon nanofibers for superior lithium and sodium storage

Heterostructures have been extensively developed with remarkable improvement on the electrochemical properties due to their intriguing synergetic effects. Herein, novel heterostructure of CoSe₂ and Mo₂C nanoparticles confined into porous carbon nanofibers (CoSe₂/Mo₂C/C NFs) is rationally designed and controllably synthesized through a facile hydrothermal approach, followed by the annealing treatment and selenization process. The resultant CoSe₂/Mo₂C/C NFs show around 10 μm in length and 250 nm in diameter. And the CoSe₂ and Mo₂C nanoparticles derived from Co-Mo compound as precursor provide high possibility of constructing their sufficient heterointerfaces, which could facilitate the electron transfer during electrochemical process and boost the surface reaction kinetics because of the heterointerface effect. Furthermore, the CoSe₂ and Mo₂C nanoparticles are conformally confined into the porous carbon nanofibers, which could alleviate the volume change effectively durng charging and discharging process in LIBs. As a result, the CoSe₂/Mo₂C/C NFs electrode possesses high reversible capacities (929.6 mAh g⁻¹ during 100^th cycle at a current density of 0.1 A g⁻¹) and superior rate capability (376.2 mAh g⁻¹ at 10 A g⁻¹) as anodes for LIBs. Furthermore, the CoSe₂/Mo₂C/C NFs also show good sodium storage properties. A high specific capacity of 530.7 mAh g⁻¹ after 100 cycles at 0.1 A g⁻¹, and good rate performance (193.8 mAh g⁻¹ at 8 A g⁻¹) can be achieved in Na ion batteries. The unique hetero-architectures and synergistic effect are significantly responsible for the fascinating electrochemical performance.