High-energy-density 0.5Li(2)MnO(3)-0.5Li(Mn0.375Ni0.375Co0.25)O-2 composite cathodes for lithium rechargeable batteries are synthesized using an auto-combustion method. The electrode charge-discharge properties are studied at 25 and 50 degrees C in Lit-containing N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (BMP-TFSI) and N-propyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PMP-TFSI) ionic liquid (IL) electrolytes. The IL electrolytes have a high decomposition temperature (similar to 400 C) and thus are ideal for high-safety applications. Compared to Li+/BMP-TFSI IL, Li+/PMP-TFSI IL exhibits higher ionic conductivity and lower viscosity. As a result, the composite cathode shows superior electrochemical performance in Li+/PMP-TFSI IL electrolyte. With the increase in cell temperature from 25 to 50 degrees C, the maximum capacities and rate capabilities of both IL cells improve significantly. Thus at 50 degrees C, discharge capacities of 304 mAh g(-1) (@10 mA g(-1)) and 223 mAh g(-1) (@100 mA g(-1)) are obtained for the Li+/PMP-TFSI cell. These capacities are superior to those for a control cell made with the same composite cathode and a conventional organic electrolyte. At elevated temperature, the cyclability of the composite cathode in the IL electrolytes is markedly higher than that obtained in a conventional organic electrolyte. (C) 2015 Elsevier B.V. All rights reserved.