High-Performance Aqueous Sodium-Ion Battery Based on Graphene-Doped Na2MnFe(CN)6–Zinc with a Highly Stable Discharge Platform and Wide Electrochemical Stability

The development of aqueous sodium-ion batteries (ASIBs) has been greatly restricted as a result of their narrow electrochemical stability window (ESW) (about 1.23 V). Many researchers attempt to expand the ESW using high concentrations of electrolyte solution or choosing titanium or other inert materials as collectors. However, these methods would lead to higher battery costs. In this work, we demonstrated a low-cost ASIB system, in which the cathode, anode, and electrolyte solution were applied by graphene oxide (GO)-modified Na2MnFe(CN)6 (PBM), zinc sheet, and solution of Na2SO4 (1 M) and ZnSO4 (1 M), respectively. When the graphite sheet with high hydrogen and oxygen evolution overpotential was used as the collector, the ESW was expanded to about 3.4 V. The full cell owned a stable discharge platform and high discharge potential (∼1.8 V). Furthermore, the modification of PBM by reduced graphene oxide (rGO) obviously increased the discharge capacity to 110 mAh g–1, extended the cycle life (91% capacity retention after 200 cycles), and greatly improved the rate capacity (76% capacity for 500 mA g–1 rate). It should also be noted that the full cell consisting of a rGO/PBM cathode and zinc anode could achieve an energy density as high as 165 Wh kg–1.