Bi₂ O₃ @Reduced Graphene Oxide Nanocomposite: An Anode Material for Sodium-Ion Storage

The high capacity, excellent cyclability, and good rate capability of reduced graphene oxide (rGO) anchored with Bi₂ O₃ nanocomposite for sodium-ion batteries is reported. A simple reduction method is adapted to deposit spherical Bi₂ O₃ nanoparticles on the surface of rGO sheets. The surfactant cetyltrimethylammonium bromide (CTAB) plays a major role in controlling the morphology of the Bi₂ O₃ nanoparticles. This Bi₂ O₃ @rGO nanocomposite has the advantages of high reversible capacity with a capacity retention (at high rate) of 70.2 % after 200 cycles at a current density of 350 mA g^-1 . This superior performance can be attributed to the fact that rGO sheets hamper the volume expansion of Bi₂ O₃ nanoparticles and result in faster diffusion of Na⁺ ions (diffusion coefficient: 5.12×10^-8  cm²  s^-1 ) and smaller internal resistance (84.17 Ω) compared with pristine Bi₂ O₃ nanoparticles. The results suggest that anchoring rGO sheets with metal oxides is one of the simplest ways to enhance the electrochemical performance of sodium-ion batteries.