Hierarchical mesoporous perovskite La _{0 .5} Sr _0.5 CoO _2.91 nanowires with ultrahigh capacity for Li-air batteries

Abstract

Lithium-air batteries have captured worldwide attention due to their highest energy density among the chemical batteries. To provide continuous oxygen channels, here, we synthesized hierarchical mesoporous perovskite La 0.5 Sr 0.5 CoO 2.91 (LSCO) nanowires. We tested the intrinsic oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) activity in both aqueous electrolytes and nonaqueous electrolytes via rotating disk electrode (RDE) measurements and demonstrated that the hierarchical mesoporous LSCO nanowires are high-performance catalysts for the ORR with low peak-up potential and high limiting diffusion current. Furthermore, we fabricated Li-air batteries on the basis of hierarchical mesoporous LSCO nanowires and nonaqueous electrolytes, which exhibited ultrahigh capacity, ca. over 11,000 mAh·g -1 , one order of magnitude higher than that of LSCO nanoparticles. Besides, the possible reaction mechanism is proposed to explain the catalytic activity of the LSCO mesoporous nanowire. electrocatalysis | energy storage W ith the growth of energy demand, searching for new clean energy sources to replace conventional fuel energy has been a challenge today (1-6). Li-ion batteries have developed rapidly in recent years because of their low cost, long cycle life, good reversibility, and no memory effect. However, even when it was fully developed, the highest energy storage of Li-ion batteries is insufficient to satisfy the ever-increasing requirements for batteries with high capacities (7,8). Recently, Li-air batteries have attracted great interest because they potentially have much higher gravimetric energy storage density compared with all other chemical batteries (9-18). They could theoretically offer very high specific energies (i.e., 5,000 Wh·kg −1 ) because oxygen, the cathode active material, is not stored in the battery, but can be accessed from the environment. Thus, Li-air batteries are eco-friendly electrochemical power sources.However, there are some challenges in Li-air battery research. In an aprotic electrolyte, the fundamental cathode discharge reactions are thought to be 2Li + O 2 → Li 2 O 2 and 2Li + 0.5O 2 → Li 2 O. Recent studies demonstrated the degradation of the electrolyte (19,20), and the precipitation of reaction products Li 2 O 2 / Li 2 O 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, it has been suggested that one method for enhancing the mobility of oxygen ions is to provide disorder-free channels of oxygen vacancies, using compounds with the perovskite structure that exhibits cation ordering (21,22). It is well known that perovskite materials have wide applications in catalysis for fuel cells and metal-air batteries due to their defective structures and excellent oxygen mobility. Shao-Horn and coworkers have deeply studied perovskite oxides for oxygen evolution reaction (OER) catalysis and found that Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-x and La 0.5 C...

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Perovskite Electrocatalysts for the Oxygen Reduction Reaction in Alkaline Media

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