Reinforced supercapacitive behavior of O-3-type layer-structured Na(3)Ni(2)BiO(6)in 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF4) electrolyte

Abstract

Sodium-ion-based energy storage devices in which the electrochemical properties are influenced by excess Na ions are very important as an alternative energy storage system. In this study, O-3-type multi-metal-oxide layers of Na(3)Ni(2)BiO(6)were synthesized via a simple solid-state method. Their electrochemical properties were examined while employing them as a supercapacitor electrode material with four different electrolytes: H2SO4, Na2SO4, KOH, and 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF4). Among these, BMIMBF(4)ionic liquid electrolyte in a symmetric Na(3)Ni(2)BiO(6)supercapacitor demonstrated the highest specific capacitance performance of 780.49 F g(-1)at 0.5 A g(-1)with 95.2% capacitance retention after 10,000 cycles. Moreover, a maximum energy density of 67.16 Wh center dot kg(-1)was recorded at 349.87 W center dot kg(-1). The enhanced electrochemical performance is a result of the reinforced fast intercalation/deintercalation of Na(+)ions in the Na(3)Ni(2)BiO(6)crystal structure due to high solvation and association mechanism of Na(3)Ni(2)BiO(6)in BMIMBF(4)ionic liquid media. These results indicate that the developed Na3Ni2BiO6-based supercapacitor with BMIMBF(4)ionic liquid electrolyte could be used in the high-performance energy storage devices for smart electrical and electronic units.