Modified Recovered Carbon from Aluminum Electrolysis by Expansion Treatment as an Anode for Sodium-Ion Batteries

Recovered carbon from aluminum electrolysis is extremely valuable for use, and it has been well used as a low-cost anode material for lithium-ion batteries. However, recovered carbon as a sodium-ion battery anode exhibits very low capacity due to its small interlayer spacing. Herein, we report an expanded recovered carbon as a sodium-ion battery anode. By introducing interlayer oxygen-containing groups to widen the interlayer spacing and regulating the oxygen content by reduction temperature, the expanded recovered carbon has a moderate oxygen content of 22.5 at. % and an expanded interlayer spacing of 0.3475 nm. The expanded recovered carbon can deliver an excellent initial Coulombic efficiency of 83.87% and a high reversible capacity of 252.5 mAh g^–1 after 300 cycles at 200 mA g^–1. In addition, it also maintains a high average capacity of 171.76 mAh g^–1 for 1500 cycles at a high current density of 1000 mA g^–1.