No abstract

In this paper, the polarization of an oxygen electrode in rechargeable lithium oxygen batteries was investigated and found to be closely related to the fading of discharge capacity and ceasing of cycling. Electrochemical tests showed that with an α-MnO2 catalyzed air electrode, the cell could deliver a high initial discharge capacity of 2300mAhnormalg−1 of carbon with rapid fading to 150mAhnormalg−1 at the fourth cycle. When the cell was cycled at a restricted depth of discharge, the cycle life could be prolonged. Electrochemical impedance spectra responses and scanning electron microscopy observations indicated that the discharged product could block the air pathway, increase electrochemical resistance, and lose electrical contact. To improve the electrochemical performance of lithium oxygen batteries, the oxygen reduction catalyst and the structure of the normalO2 electrode deserve further investigation.

Nano-sized La 0.8 Sr 0.2 MnO 3 prepared by the polyethylene glycol assisting sol-gel method was applied as oxygen reduction catalyst in nonaqueous Li/O 2 batteries. The as-synthesized La 0.8 Sr 0.2 MnO 3 was characterized by X-ray diffraction (XRD), scanning electron microscopy, and Brunauer-Emmet-Teller measurements. The XRD results indicate that the sample possesses a pure perovskite-type crystal structure, even sintered at a temperature as low as 600°C, whereas for solid-state reaction method it can only be synthesized above 1,200°C. The as-prepared nano-sized La 0.8 Sr 0.2 MnO 3 has a specific surface area of 32 m 2 g −1 , which is much larger than the solid-state one (1 m 2 g −1 ), and smaller particle size of about 100 nm. Electrochemical results show that the nano-sized La 0.8 Sr 0.2 MnO 3 has better catalytic activity for oxygen reduction, higher discharge plateau and specific capacity.

No abstract