NiSe2 nanoparticles encapsulated in CNTs covered and N-doped TiN/carbon nanofibers as a binder-free anode for advanced sodium-ion batteries

Abstract

Metal selenides are promising anodes for sodium-ion batteries (SIBs) due to the high theoretical capacity through conversion reaction mechanism. However, developing metal selenides with superior electrochemical sodium-ion storage performance is still a great challenge. In this work, a novel composite material of free-standing NiSe2 nanoparticles encapsulated in N-doped TiN/carbon composite nanofibers with carbon nanotubes (CNTs) in-situ grown on the surface (NiSe2@N-TCF/CNTs) is prepared by electrospinning and pyrolysis technique. In this composite materials, NiSe2 nanoparticles on the surface of carbon nanofibers were encapsulated into CNTs, thus avoiding aggregation. The in-situ grown CNTs not only improve the conductivity but also act as a buffer to accommodate the volume expansion. TiN inside the nanofibers further enhances the conductivity and structural stability of carbon-based nanofibers. When directly used as anode for SIBs, the NiSe2@N-TCF/CNT electrode delivered a reversible capacity of 392.1 mAh/g after 1000 cycles and still maintained 334.4 mAh/g even at a high rate of 2 A/g. The excellent sodium-ion storage performance can be attributed to the fast Na+ diffusion and transfer rate and the pseudocapacitance dominated charge storage mechanism, as is evidenced by kinetic analysis. The work provides a novel approach to the fabrication of high-performance anode materials for other batteries.