NaMnO2−x thin nanosheets assembled microspheres as electrode for aqueous asymmetric supercapacitor

Abstract

This study proposes MnO _2 thin nanosheets assembled microspheres with oxygen vacancies and pre-insertion of Na ions (NaMnO _2−x ) as highly capable supercapacitor electrodes. The NaMnO _2−x electrode can reach a stable potential window of 1.2 V without oxygen evolution reactions in three-electrode configuration. The voltage window of the assembled aqueous ASC device can be expanded to 2.4 V (1 M Na _2 SO _4 ) by using NaMnO _2−x electrode and activated carbon electrode as positive and negative electrodes, respectively. The NaMnO _2−x electrode delivers a good specific capacitance of 215 F · g ^−1 at current density of 1 A · g ^−1 . It displays high-rate capability and an excellent cycling stability, maintaining 95.5% of its initial specific capacitance at 2 A · g ^−1 after 2500 cycles. The ASC device shows a high energy density and power density of 28.56 W · h · kg ^−1 and 1246 W · kg ^−1 , respectively, at a current density of 1 A · g ^−1 .

Keywords

• supercapacitor
• pre-insertion
• oxygen vacancies
• asymmetric