3D Foam-Like Composites of Mo2C Nanorods Coated by N-Doped Carbon: A Novel Self-Standing and Binder-Free O2 Electrode for Li–O2 Batteries

The development of self-standing and binder-free O2 electrodes is significant for enhancing the total specific energy density and suppressing parasitic reactions for Li–O2 batteries, which is still a formidable challenge thus far. Here, a three-dimensional foam-like composite composed of Mo2C nanorods decorated by different amounts of N-doped carbon (Mo2C-NR@xNC (x = 5, 11, and 16 wt %)) was directly employed as the O2 electrode without applications of any binders and current collectors. Mo2C-NR@xNC presents a network microstructure with interconnected macropore and mesoporous channels, which is beneficial to achieving fast Li+ migration and O2 diffusion, facilitating the electrolyte impregnation, and providing enough space for Li2O2 storage. Additionally, the coated N-doped carbon layer can largely improve the electrochemical stability and conductivity of Mo2C. The cell with Mo2C-NR@11NC shows a considerable cyclability of 200 cycles with an overpotential of 0.28 V in the first cycle at a constant current density of 100 mA g–1, a superior reversibility associated with the formation and decomposition of Li2O2 as desired, and a high electrochemical stability. On the basis of the experimental results, the electrochemical mechanism for the cell using Mo2C-NR@11NC is proposed. These results represent a promising process in the development of a self-standing and binder-free foam-based electrode for Li–O2 batteries.