Nanoporous LiMn₂O₄ spinel prepared at low temperature as cathode material for aqueous supercapacitors

LiMn₂O₄ spinel was prepared by a hydrothermal method using α-MnO₂ nanotubes as precursor at 180 C, a temperature much lower than that in previously reported methods. It is nanoporous with a pore size of about 40-50 nm and a BET surface area of 9.76 m² g ^-1. It exhibits a high specific capacitance of 189 F g^-1 at 0.3 A g^-1 as a cathode for an aqueous supercapacitor. Even at 12 A g^-1, it still has a capacitance of 166 F g^-1. After 1500 cycles, there is no evident capacity fading. The LiMn₂O₄ cathode can deliver an energy density of 31.9 Wh kg^-1 at 3480 W kg^-1 and even maintain 19.4 Wh kg^-1 at about 5100 W kg^-1 based on the mass of LiMn₂O₄.