Nanostructured LiMn2O4 composite as high-rate cathode for high performance aqueous Li-ion hybrid supercapacitors

Abstract Nanostructured spinel LiMn 2 O 4 and super P composite with much enhanced electrochemical performance especially ultrahigh rate capability as the cathode for aqueous hybrid supercapacitors is synthesized by ball milling commercial LiMn 2 O 4 particles together with super P. The as-prepared composite delivers a high capacitance of 306 F g −1 at the current density of 1 A g −1 and superb rate ability of 228.6 F g −1 at 40 A g −1 in 1 M Li 2 SO 4 aqueous electrolyte. The capacitance of the nanostructured composite is 3.5 times higher than that of pristine LiMn 2 O 4 even being charged and discharged 80 times faster. The excellent performances are ascribed to the nanosized LiMn 2 O 4 well dispersed into the conductive carbon matrix. LiMn 2 O 4 and super P composite//active carbon hybrid supercapacitor is assembled and the energy density can reach up to 21.58 Wh kg −1 at 293.16 W kg −1 and 13 Wh kg −1 at 5200 W kg −1 . The hybrid device also shows an excellent cycling performance, which retains 85% of the initial capacitance after 4500 cycles. This work provides an effectively facile way to produce high performance LiMn 2 O 4 -based cathodes for hybrid suercapacitors in practical applications.