Li Ion Exchanged α-MnO2 Nanowires as Efficient Catalysts for Li-O2 Batteries

Due to the limited energy densities, which could be achieved by lithium-ion cells, Li-O-2 batteries, which could provide a promising super energy storage medium, attract much attention nowadays. For its high activity, high storage and low cost, Mn-based oxides have shown versatile application in various batteries. To enhance the cyclability of Li-O-2 batteries, here, we synthesized a kind of alpha-MnO2 nanowires as a bifunctional catalyst for Li-O-2 batteries. The particular structure of alpha-MnO2 reduces the mass transfer resistance of the battery, and the MnO2 nanowires were ion exchanged by saturated lithium sulfate solution so as to further improve the performance of the catalyst. The exchanged alpha-MnO2 catalyst showed a high discharge specific capacity(6243 mA center dot h/g at a current density of 200 mA/g) and significantly improved the cyclability up to the 55th cycle(200 mA/g with capacity of 1000 mA center dot h/g). The results show that the Li ion exchange method is a promising strategy for improving the performance of MnO2 catalyst for Li-O-2 batteries.