MnMoO4 Electrocatalysts for Superior Long-Life and High-Rate Lithium-Oxygen Batteries

Abstract

Lithium-oxygen batteries represent a significant scientific challenge for high-rate and long-term cycling using oxygen electrodes that contain efficient electrocatalysts. The mixed transition metal oxide catalysts provide the most efficient catalytic activity for partial heterogeneous surface cations with oxygen vacancies as the active phase. They include multiple oxidation states and oxygen vacancies. Here, using a combination of transmission electron microscopy, differential electrochemical mass spectrometry, X-ray photoelectron spectroscopy, and electrochemical properties to probe the surface of the MnMoO4 nanowires, it is shown that the intrinsic MnMoO4 oxygen vacancies on the oxygen electrode are an effective strategy to achieve a high reversibility and high efficiency for lithium-oxygen (Li-O-2) batteries. The modified MnMoO4 nanowires exhibit a highly stable capacity at a fixed capacity of 5000 mA h g(sp)(-1) (calculated weight of Super P carbon black) during 50 cycles, a high-rate capability at a current rate of 3000 mA g(sp)(-1) during 70 cycles, and a long-term reversible capacity during 188 cycles at a fixed capacity of 1000 mA h g(sp)(-1). It is demonstrated that this strategy for creating mixed transition metal oxides (e. g., MnMoO4) may pave the way for the new structural design of electrocatalysts for Li-O-2 batteries.