Consecutive hybrid mechanism boosting Na+ storage performance of dual-confined SnSe2 in N, Se-doping double-walled hollow carbon spheres

Abstract

Rationally designed hierarchical structures and heteroatomic doping of carbon are effective strategies to enhance the stability and electrical conductivity of materials. Herein, SnSe2 flakes were generated in the double-walled hollow carbon spheres (DWHCSs), in which N and Se atoms were doped in the carbon walls, to construct SnSe2@N, Se-DWHCSs by confined growth and in-situ derivatization. The N and Se-doped DWHCSs can effectively limit the size increase of SnSe2, promote ion diffusion kinetics, and buffer volume expansion, which can be proved by electron microscope observation and density functional theory calculation. Consequently, the SnSe2@N, Se-DWHCSs as an anode material for sodium ion batteries (SIBs) demonstrated a distinguished reversible capacity of 322.8 mAh g−1 at 5 A g−1 after 1000 cycles and a superior rate ability of 235.3 mAh g−1 at an ultrahigh rate of 15 A g−1. Furthermore, the structure evolution and electrochemical reaction processes of SnSe2@N, Se-DWHCSs in SIBs were analyzed by ex-situ methods, which confirmed the consecutive hybrid mechanism and the phase transition process.