▎ 摘　　要

Spinel LiMn2O4 has been prepared by a facile hydrothermal procedure and the prepared LiMn2O4 exhibits superior electrochemical performance, such as high specific capacitance (409 F g(-1) at 2 mV s(-1)) and excellent rate capability (85% retention at 100 mV s(-1)). In order to achieve high energy and power densities, a high-voltage asymmetric supercapacitor (ASC) is successfully assembled using the as-prepared LiMn2O4 as the positive electrode and nitrogen-doped graphene/porous carbon composite as the negative electrode in a Li2SO4 aqueous electrolyte. The optimized ASC delivers a high specific energy of up to 44.3 Wh kg(-1) at a specific power of 595 W kg(-1) with an output voltage of 1.8 V based on the total weight of the active electrode materials. This novel strategy provides a promising route to design high-performance supercapacitors with high energy density for next-generation storage systems. (C) 2015 Elsevier Ltd. All rights reserved.