Hierarchical mesoporous perovskite nanowires for ultrahigh-capacity Li-air battery

Li-ion batteries have developed rapidly in recent years because of their low cost, long cycle life, good reversibility and no memory effect. However, the highest energy storage of Li-ion batteries is insufficient to satisfy the ever-increasing requirements for batteries with high capacities. Recently, Li-air batteries have attracted great interest because they potentially have much higher energy storage density compared with all other chemical batteries. They could theoretically offer very high specific energies (i.e. 5000 Whkg⁻¹) because of the cathode reaction: 2Li + O₂ → Li₂O₂ and 2Li + 0.5O₂ → Li₂O in nonaqueous electrolyte. However, it also brings many problems including the precipitation of reaction products Li₂O₂/Li₂O or electrolyte decomposition products on the catalyst and electrode eventually blocked the oxygen pathway and limited the capacity of the Li-air batteries. To enhance the performance, constructing a structure with continuous oxygen diffusion channels is very important.

In WUT-Harvard Joint Nano Key Laboratory，Liqiang Mai and colleagues synthesized hierarchical mesoporous perovskite structure La_0.5Sr_0.5CoO_2.91 (LSCO) nanowires constructed by nanorods using a facile multi-step micro-emulsion followed by a slow annealing method. The high-performance catalysts for the oxygen reduction reaction (ORR) of hierarchical mesoporous LSCO nanowires was demonstrated, with low peak-up potential and high limiting diffusion current, via rotating disk electrode (RDE) measurements in both aqueous electrolytes and nonaqueous electrolytes. Furthermore, Li-air battery based on hierarchical mesoporous LSCO nanowires and nonaqueous electrolyte was fabricated, which exhibits ultrahigh capacity, c.a., over 11000 mAh g ^–1, with the improvement of one order of magnitude than LSCO nanoparticles. A large specific surface area with ~10 nm size pores was confirmed by BET. HRTEM demonstrated LSCO nanorods are tightly attached to each other at atomic level when they formed the hierarchical nanowire. This structure can provide continuous oxygen diffusion channels that contribute to its electrocatalytic performance.

“Constructing hierarchical perovskite LSCO mesoporous nanowires in this paper is a simple and efficient route to provide continuous channels for oxygen transmission and ionic diffusion. The hierarchical perovskite mesoporous LSCO will have great potential applications in Li-air battery, fuel cells or other electrochemical devices.” says Mai.

Reference

1.     Y. Zhao, L. Xu, L. Mai^*, C. Han, Q. An, X. Xu, X. Liu, and Q. Zhang, Hierarchical mesoporous perovskite La_0.5Sr_0.5CoO_2.91 nanowires with ultrahigh capacity for Li-air battery. PNAS. (2012).

Author affiliation

State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070, China

*Email: mlq518@whut.edu.cn