MnOx bound on oxidized multi-walled carbon nanotubes as anode for lithium-ion batteries

Nanocomposites of manganese oxides and carbonaceous materials with strong interfacial connection hold extraordinary potential as high-performance electrode materials for energy storage devices. However, the interfacial interaction between manganese oxides and carbon has not been sufficient elucidated despite it may affect the chemical composition and morphology of the electrode materials and thus impact on the electrochemical performance. Herein, through regulating the amount of oxygen-containing functional groups on the surface of multi-walled carbon nanotubes (MWCNTs), a series of MnOx/MWCNTs nanocomposites with different compositions and morphologies are successfully synthesized. The Mn-O-C bonds, which can act as an ultrafast electron transfer path, are formed in the MnOx/MWCNTs nanocomposites. The influence of the amount and type of oxygen-containing functional groups in MWCNTs on the formation of Mn-O-C bonds, the composition and morphology of the nanocomposites is revealed clearly. The nanocomposite with the highest number of Mn-O-C bonds in the prepared MnOx/MWCNTs, which feature a structure with the binary manganese oxides (38% MnO2 and 62% Mn3O4) nanosheets growing vertically and uniformly on the oxidized MWCNTs, give the best electrochemical properties with high capacity (1353.2 mAh g-1 at 0.1 A g-1), outstanding rate capability (384.9 mAh g-1 at 20 A g-1), and durable long-term cyclability (1000 cycles with 70% retention at 2 A g-1). The quantitative kinetic analysis indicates that over 60% of the charge storage is pseudocapacitive. The distinct interfacial design strategy presents a new route to synthesis transition metal oxides/carbon hybrids with efficient energy storage and conversion.