Facile Synthesis of Hierarchical Porous Three-Dimensional Free-Standing MnCo₂O₄ Cathodes for Long-Life Li - O₂ Batteries

Hierarchical porous three-dimensional MnCo₂O₄ nanowire bundles were obtained by a universal and low-cost hydrothermal method, which subsequently act as a carbon-free and binder-free cathode for Li - O₂ cell applications. This system showed a high discharge capacity of up to 12 919 mAh g^-1 at 0.1 mA cm^-2 and excellent rate capability. Under constrained specific capacities of 500 and 1000 mAh g^-1, Li - O₂ batteries could be successfully operated for over 300 and 144 cycles, respectively. Moreover, their charge voltage was markedly decreased to about 3.5 V. Their excellent electrochemical performance is proposed to be related to the conductivity enhancements resulting from the hierarchical interconnected mesoporous/macroporous weblike structure of the hybrid MnCo₂O₄ cathode, which facilitated the electron and mass transport. More importantly, after 2 months of cycling, the microstructure of the cathode was maintained and a recyclability of over 200 cycles of the reassembled Li - O₂ cells was achieved. The effects of the level of electrolyte and corrosion of the lithium anode during long-term cycling on the electrochemical property of Li - O₂ cells have been explored. Furthermore, the nucleation process of the discharge product morphology has been investigated.