Anchoring atomic antimony in an intercalative Mo–S framework via soft covalent bonding for fast-charging and long-lived sodium ion batteries

Abstract

Large volume change and grain pulverization are two major challenges of alloy-type anode materials for sodium ion batteries. Herein, we propose a soft covalent bonding confinement strategy for dispersing high capacity Sb into a robust and conductive Mo–S framework. The high capacity and high rate sodium storage are integrated into a single-phase Mo₂SbS₂ anode, in which atomic Sb is confined in a zig-zag Mo–S layer via soft Mo–Sb bonds. The robust and conductive Mo–S framework can effectively buffer the volume expansion of Sb during sodiation and provide an enhanced surface pseudocapacitive reaction for ultrafast sodium storage. This novel Mo₂SbS₂ anode can provide a high capacity of 373 mA h g⁻¹ at 0.6C and show an excellent rate performance and a long cycling life (289 mA h g⁻¹ at 30C and ∼90% capacity retention at 60C after 11 000 cycles). Interestingly, an intercalative-like sodiation process is observed from the in situ XRD patterns, in situ Raman spectra, ex situ TEM and XPS characterization. The integrity of the robust Mo–S framework can be confirmed after discharge. This soft covalent bonding confinement strategy can broaden the horizons of the design of anode materials for high energy density and power density of SIBs.