Modulating the kinetics of CoSe2 yolk-shell spheres via nitrogen doping with high pseudocapacitance toward ultra-high-rate and high-energy density sodium-ion half/full batteries

Abstract

Developing advanced anode materials with high capacity, and good rate and cycling performance for sodium-ion batteries still remains a major challenge at the moment. Herein, it is demonstrated that the introduction of nitrogen elements into CoSe2 yolk–shell spheres (N-CoSe2 yss) with rapid electrochemical kinetics contributes to excellent sodium storage performance. Specifically, the N-CoSe2 yss deliver a high capacity of 431 mA h g−1 at a high current density of 50 A g−1 and a high reversible capacity of 500 mA h g−1 after 1000 cycles at 10 A g−1 with nearly 100% coulombic efficiency. Experimental and density functional theory calculation results indicate that the superior electrochemical performance can be attributed to the synergistic effect of nitrogen doping and structure engineering, which can not only enhance the electronic/ion transport kinetics, but also improve the structural stability during cycling. When coupled with a high-voltage cathode, the full cell shows a high energy density of 129.38 W h kg−1 at a power density of 187.5 W kg−1, confirming the potential applications of N-CoSe2 yss in high-performance sodium-ion batteries.