Heteroatom preintercalated Cl-terminated Ti3C2Tx MXene wrapped with mesoporous Fe2O3 nanospheres for improved sodium ion storage

Abstract

Developing multicomponent hybrid materials is an effective method to achieve structurally stable anode materials for high-performance sodium-ion batteries (SIBs). In this work, mesoporous Fe₂O₃ nanospheres wrapped by heteroatom pre-intercalated Cl-terminated Ti₃C₂T_x MXene as SIB anode materials are designed. The Cl-terminated Ti₃C₂T_x MXene is obtained via a Lewis acidic etching route, which offers a green and practicable route to etching MAX precursors without HF. The MXene framework is pretreated with borohydride and thus turns into a 3D structure to better support Fe₂O₃ nanospheres. In order to obtain the Fe₂O₃@Ti₃C₂T_x anode, Fe₂O₃ nanospheres are distributed on the Ti₃C₂T_x MXene framework by virtue of the surfactant CTAB. Benefiting from the synergic effect of Fe₂O₃ nanospheres and a heteroatom-doped MXene framework, which can decrease the Na ion diffusion barrier, this unique structure provides abundant ionic transfer paths and active sites to accelerate the electrochemical process. Furthermore, the volume change of Fe₂O₃ nanospheres can be effectively alleviated during the sodiation/desodiation process. Herein, the resultant Fe₂O₃@Ti₃C₂T_x anode shows excellent sodium storage performance, high reversible capacity (350 mA h g⁻¹ at 1.0 A g⁻¹ after 200 cycles), considerable long-cycle stability (262.8 mA h g⁻¹ at 2.0 A g⁻¹ after 800 cycles) and calculated b values of the cathodic and anodic peaks are 0.89 and 0.94, respectively. All these analyses boost the commercial process of Fe₂O₃@MXene hybrids in SIBs.