Rapid kinetics of Na-ion storage in bimetallic sulfide composite

Abstract

Bimetallic sulfides display good electroconductibility and more redox active sites for sodium ion storage, which are expected to realize fast charging/discharging of sodium ion hybrid capacitors (SIHCs) integration. Herein, Sb was introduced into SnS2 on graphene (ATS/GNS) to enhance the kinetics of Na+ storage. The introduction of Sb at Sn site in SnS2 leads to a residual delocalized s electron and forms a half-filled and delocalized intermediate band, which can effectively improve electroconductivity. ATS possesses a high adsorption energy (-3.13 eV) and low diffusion energy barrier (0.26 eV) of Na+ by density functional theory calculations. ATS/GNS with remarkable stability possesses a reversible capacity of 507 mAh g−1 at 1 A g−1 after 3000 cycles. The ATS/GNS//N, S doped porous carbon SIHC delivers high energy/power densities (115 Wh kg−1/351 W kg−1 and 41 Wh kg−1/18750 W kg−1), and an excellent capacity retention of 70% after 10000 cycles at 5 A g−1. This work may present a feasible approach to design high-rate and long-term stability of sodium-based devices.