Synergistic effect of 1D bismuth Nanowires/2D graphene composites for high performance flexible anodes in sodium-ion batteries

Abstract

Considering the high gravimetric/volumetric specific capacity, bismuth (Bi) has been widely explored as a prospective anode material for Na-ion batteries (NIBs). However, the huge volumetric variation during the sodiation/desodiation process and resultant pulverization hinder its further development. Herein, a flexible and foldable film was successfully constructed with ultrafine Bi nanowires and reduced graphene oxide (BNW@G). When used as the anode of NIBs, the flexible BNW@G film delivers stable cycling performance (276 mA h g⁻¹ after 1000 cycles at 1 A g⁻¹) and superior rate capability (295 mA h g⁻¹ at 5 A g⁻¹). The full cell paired with a Na₃V₂(PO₄)₃/rGO cathode achieves long-term cycling performance (86% capacity retention after 200 cycles). The remarkable electrochemical performance is owing to the multidimensional hybrid structure. The rGO sheets not only act as a flexible current collector and carbon matrix, facilitating the rapid transfer of electrons and Na⁺ ions, but also buffer the volume change to boost the cycling stability of the BNWs. In situ XRD reveals the alloy phase transition mechanism of the BNW@G electrode. This work provides new insight into the design of alloy-based anode materials and contributes important guidance to energy storage devices.