Bi/3DPG composite structure optimization realizes high specific capacity and rapid sodium-ion storage

As an anode material for sodium-ion batteries (SIBs), bismuth (Bi) has attracted widespread attention due to its suitable voltage platform and high volumetric energy density. However, the severe volume expansion of Bi during charging and discharging leads to a rapid decline in battery capacity. Loading Bi on the graphene can relieve volume expansion and improve electrochemical performance. However, excessive loading of Bi on graphene will cause the porosity of the composite material to decrease, which leads to a decrease of the Na⁺ transmission rate. Herein, the Bi/three-dimensional porous graphene (Bi/3DPG) composite material was prepared and the pore structure was optimized to obtain the medium-load Bi/3DPG (Bi/3DPG-M) with better electrochemical performance. Bi/3DPG-M exhibited a fast kinetic process while maintaining a high specific capacity. The specific capacity still remained at 270 mA·h·g⁻¹ (93.3%) after 500 cycles at a current density of 0.1 A·g⁻¹. Even at 5 A·g⁻¹, the specific capacity of Bi/3DPG-M could still reach 266.1 mA·h·g⁻¹. This work can provide a reference for research on the use of alloy—graphene composite in the anode of SIBs.