Exfoliated Graphene Oxide @ Sb2O3 Octahedrons as Alloy-Conversion Anode for High-Performance Na-Ion Batteries with P2-Type Na2/3Ni1/3Mn2/3O2 Cathode

Abstract

Conversion–alloying–based anodes for sodium–ion batteries (SIBs) have attracted wide interest due to their high energy density and specific capacity. However, it suffers from volume expansion during operation, leading to poor cycling stability. This study introduces a novel carbon matrix, exfoliated graphene oxide (EGO), to alleviate the issues due to volume expansion in the antimony (III) oxide anode for SIBs. Four combinations of Sb2O3 with EGO were explored, and electrochemical performance was compared. An optimized combination (Sb–E1) showed a capacity of ∼100 mAh g–1 at a high current density of 1 A g–1 with good cycling stability. The results show that EGO can effectively buffer the volume expansion and promote fast kinetics. An in–situ electrochemical impedance spectroscopy study revealed that the exceptional charge-transfer resistance varies during the alloying reaction but not during the conversion reaction. The full-cell is fabricated with P2-type layered Na2/3Ni1/3Mn2/3O2 (NNMO) cathode. The Sb–E1/NNMO cell displayed an average operating potential of ∼2.95 V, a high capacity of ∼100 mAh g–1 at a current density of 1 A g–1, and a maximum energy density of ∼100 Wh kg–1.