High capacitance LiMn2O4 microspheres with different microstructures as cathode material for aqueous asymmetric supercapacitors

Abstract

Asymmetric supercapacitors (ASCS) with a battery-type electrode and a capacitor-type electrode have been regarded as the most promising energy-storage devices with high-energy and high-power densities. In this paper, the porous and hollow LiMn2O4 microspheres were prepared using MnCO3 microspheres as template and subsequently an ASCS with the as-prepared LiMn2O4 as cathode and activated carbon (AC) as anode in Li2SO4 aqueous electrolyte (designated by AC//LiMn2O4 ASCS) was assembled and investigated electrochemically. The results indicate that the porous LiMn2O4 exhibits a higher reversible capacity and rate capability compared to hollow LiMn2O4 microspheres, and delivers a specific capacitance of 536 F g−1 at 1 mV s−1. The assembled AC//porous LiMn2O4 ASCS presents a high energy density of 33.12 Wh kg−1 at the power density of 90 W kg−1. All these might be attributed to the unique microstructure of the as-prepared porous LiMn2O4 microspheres.