Aqueous rechargeable sodium-ion batteries (ARSIBs) are highly desirable for the large-scale energy storage due to their inherent high safety and low-cost. Na-Mn-O electrode material has been considered as a promising cathode, yet the redox potential window is still not fully explored and utilized in aqueous rechargeable sodium-ion batteries. Herein, a chemical bonded Na0.44MnO2 (NMO) plates are successfully synthesized via a poly-vinylpyrrolidone-assisted sol-gel route followed by annealing process. The possibility of utilizing a wider potential window ranging between - 0.3 V and 1.0 V vs. Ag/AgCl in mild aqueous electrolyte has been thus demonstrated by using NMO plates as cathodes for the first time. As a result, the as-synthesized NMO plates can deliver a highest initial discharge capacity of 77.2 mA h g(-1) at a current density of 100 mA g(-1), compared with previous Na-Mn-O reports in mild aqueous electrolyte in ARSIBs. Even at a high rate of 500 mA g(-1), it still maintains a large capacity of 35 mA h g(-1) after 1000 cycles, demonstrating its superior cycling stability. In addition, ex situ SEM and TEM-EDX results reveal that there is a newly formed sheet-like layer Na-birnessite Na0.55Mn2O4-1.5H(2)O on the surface of NMO cathodes, which can provide extra ion channel for sodium ions and stabilize the electrode from pulverization, resulting in improved cycling stability. This study provides a broad implication for developing low-cost, high performance cathode materials to broaden the applied potential window towards high performance ARSIBs.