Construction of a hollow Sb2S3@NC core-shell nanorod as an anode via a microstructure regulation strategy for high-performance Na+/K+ storage

Abstract

Antimony trisulfide (Sb₂S₃) is a highly promising anode material for alkali-metal batteries due to its high theoretical capacity and abundant resources. However, severe volume expansion during charge–discharge and low electrical conductivity restrict its electrochemical performance. In this study, a hollow Sb₂S₃@NC core–shell nanorod (H-Sb₂S₃@NC) is successfully prepared via the high-temperature carbonization and secondary sulfidation of the inorganic–organic Sb₂S₃@PDA composite precursor. It induces the volatilization of partial Sb₂S₃ by controlling the temperature during carbonization, concurrently forming the inorganic and hollow core–shell nanorod structure. Compared with Sb₂S₃@NC without the internal void, H-Sb₂S₃@NC exhibits superior cycling and rate performance when used as an anode for sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs). Specifically, as an anode for SIBs, H-Sb₂S₃@NC delivers a specific capacity of 517.0 mA h g⁻¹ after 100 cycles at 100 mA g⁻¹ and delivers 535.5 mA h g⁻¹ at 1000 mA g⁻¹ (Sb₂S₃@NC: 60.6 mA h g⁻¹ after 100 cycles at 100 mA g⁻¹ and 39.7 mA h g⁻¹ at 1000 mA g⁻¹). For PIBs, H-Sb₂S₃@NC delivers a specific capacity of 431.1 mA h g⁻¹ after 50 cycles at 100 mA g⁻¹ (Sb₂S₃@NC: 208.3 mA h g⁻¹ under the same conditions). Ex situ characterizations confirm that Sb₂S₃ undergoes a reversible conversion-alloying reaction during Na⁺/K⁺ storage. The internal voids of H-Sb₂S₃@NC could effectively buffer the volume expansion stress, while N-doping in the NC (nitrogen-doped carbon) layer enhances ion/electron transport. These two factors synergistically ensure the electrode's structural stability and excellent kinetics. The temperature-controlled microstructure regulation strategy proposed in this study provides an effective approach for addressing the volume expansion problem of Sb₂S₃-based anodes and optimizing the electrode performance of alkali-metal ion batteries.