Synthesis and Electrochemical Properties of Spin-Capable Carbon Nanotube Sheet/MnOx Composites for High-Performance Energy Storage Devices

Abstract

Inspired by the high specific capacitances found using ultrathin films or nanoparticles of manganese oxides (MnO_x), we have electrodeposited MnO_x nanoparticles onto sheets of carbon nanotubes (CNT sheets). The resulting composites have high specific capacitances (C_sp ≤ 1250 F/g), high charge/discharge rate capabilities, and excellent cyclic stability. Both the C_sp and rate capabilities are controlled by the average size of the MnO_x nanoparticles on the CNTs. They are independent of the number of layers of CNT sheets used to form an electrode. The high-performance composites result from a synergistic combination of large surface area and good electron-transport capabilities of the MnO_x nanoparticles with the good conductivity of the CNT sheets. Such composites can be used as electrodes for lithium batteries and supercapacitors.