Improved electrochemical performance of sol-gel method prepared Na4Mn9O18 in aqueous hybrid Na-ion supercapacitor

The rod-like Na4Mn9O18 material was prepared by sol-gel method and compared with a similar material produced by solid-state method. Their electrochemical properties were examined in aqueous sodium-ion electrolyte cells. The resulting Na4Mn9O18 materials were characterized by SEM, TGA, and XRD techniques. The analysis shows that the rod-like Na4Mn9O18 has a small particle diameter ranging from 0.2 to 1 mu m. The electrochemical performance was characterized by cyclic voltammetry and galvanostatic charge-discharge test in aqueous Na-ion cells with active carbon (AC) as counter electrode. The Na4Mn9O18 materials prepared at 800 A degrees C show a high specific capacity of about 200 F g(-1) at a current density of 200 mA g(-1). The Na4Mn9O18/Na2SO4/AC Na-ion hybrid supercapacitor exhibits excellent cycle performance through 4,000 cycles with 84 % capacity remaining at 500 mA g(-1) charge-discharge current density (an 18 C rate).