Abstract:

MOF-derived metal selenides are promising candidates as effective anode materials in sodium-ion batteries (SIBs) owing to their ordered carbon skeleton structure and the high conductivity of selenides. They can be imparted with rapid electron/ion transport channels for the insertion/de-insertion of Na⁺. In this study, MOF-derived In₂Se₃ was prepared as an anode material for SIBs. However, the large volume expansion during cycling leads to structural collapse, which affects the charging and discharging circulation life of the battery. To address this, a two-dimensional rGO network was introduced on the MOF-derived In₂Se₃ surface by surface modification. Field-emission scanning electron microscopy (FE-SEM) and X-ray photoelectron spectroscopy (XPS) results confirmed the successful synthesis of the In₂Se₃@C/rGO composite. The structures with two types of carbon enhanced the charge transfer kinetics and provided two stress-buffering layers. Thus, the volume change could be accommodated and simultaneously, electron transfer was accelerated. This technique was effective, as proved by the enhanced capacity retention of 95.2% at 1 A·g⁻¹ after 500 cycles. In contrast, the capacity retention of the MOF-derived material without rGO was only 74.2%. Additionally, due to the synergistic effect of the rGO network and the MOF-derived In₂Se₃, the anode showed a superior capacity of 468 mAh·g⁻¹ at 0.1 A·g⁻¹. Conversely, at the same current density, the uncoated material delivered only a capacity of 393 mAh·g⁻¹. To study the electrochemical process of the electrode, the In₂Se₃@C/rGO electrode was subjected to cyclic voltammetry (CV) measurements; the results showed that the In₂Se₃@C/rGO electrode had notable electrochemical reactivity. In addition, in situ X-ray diffraction (XRD) was performed to explore the sodium storage mechanism of In₂Se₃, demonstrating that In₂Se₃ had a dual Na⁺ storage mechanism involving conversion and alloying reactions, and revealing the origin of its high theoretical specific capacity. This study is expected to serve as a reference for preparing optimized rGO-based materials for use as SIB anodes.

Key words: Reduced graphene oxide, Synergistic effect, Electron transfer, Volume expansion