Anchored SnS nanorods based on a carbon-enhanced Nb2CTx three-dimensional nanoflower framework achieve stable, high capacity Na-ion storage

Abstract

Tin (Sn) and its derivatives have outstanding theoretical capacities; however, the phase transformation and alloying processes of SnSx in sodium-ion batteries (SIBs) greatly hinder their application. Compared with hexagonal SnS2, orthorhombic SnS exhibits a better structural stability and a smaller volume expansion, while undergoing a less severe conversion reaction. Thus, it can achieve better sodium-ion storage performance. Herein, we designed a strategy to grow SnS nanorods in situ on a Nb2CTx framework and three-dimensional (3D) carbon-reinforced Nb2CTx/SnS nanorods (C@SnS@Nb2CTx/Nb2O5). With the reducibility of Nb2CTx, hexagonal SnS2 can be transformed into a more stable orthorhombic SnS phase, thereby affording a more stable performance for SIBs. The resulting C@SnS@Nb2CTx/Nb2O5 electrodes exhibited excellent cycle capacities after 100 cycles at 0.1 A·g−1 (∼384 mAh·g−1) and after 1,000 cycles at 1 A·g−1 (∼220 mAh·g−1); they also exhibited excellent stability (73% capacity retention after 1,000 cycles, relative to the tenth cycle at a current density of 1 A·g−1). In addition, to analyze the underlying mechanism of the observed capacity decay in the cycle process, we conducted ex situ X-ray photoelectron spectroscopy, X-ray diffraction, and density-functional theory analyses. Thus, we compared and revealed the factors influencing the capacity decline observed during the SnS cycle process.