Department of Materials Science and Engineering, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
Sci Rep. 2012;2:715. doi: 10.1038/srep00715. Epub 2012 Oct 8.
The lack of fundamental understanding of the oxygen reduction and oxygen evolution in nonaqueous electrolytes significantly hinders the development of rechargeable lithium-air batteries. Here we employ a solid-state Li(4+x)Ti(5)O(12)/LiPON/Li(x)V(2)O(5) cell and examine in situ the chemistry of Li-O(2) reaction products on Li(x)V(2)O(5) as a function of applied voltage under ultra high vacuum (UHV) and at 500 mtorr of oxygen pressure using ambient pressure X-ray photoelectron spectroscopy (APXPS). Under UHV, lithium intercalated into Li(x)V(2)O(5) while molecular oxygen was reduced to form lithium peroxide on Li(x)V(2)O(5) in the presence of oxygen upon discharge. Interestingly, the oxidation of Li(2)O(2) began at much lower overpotentials (240 mV) than the charge overpotentials of conventional Li-O(2) cells with aprotic electrolytes (1000 mV). Our study provides the first evidence of reversible lithium peroxide formation and decomposition in situ on an oxide surface using a solid-state cell, and new insights into the reaction mechanism of Li-O(2) chemistry.
在非水电解液中，对氧还原和氧析出反应缺乏基本认识，这极大地阻碍了可充电锂空气电池的发展。在这里，我们采用固态 Li(4+x)Ti(5)O(12)/LiPON/Li(x)V(2)O(5) 电池，并在超高真空（UHV）和 500 毫托氧气压力下，使用常压 X 射线光电子能谱（APXPS）原位研究了 Li-O(2)反应产物在 Li(x)V(2)O(5)上的化学性质，这取决于施加的电压。在 UHV 下，当放电时，氧气存在于 Li(x)V(2)O(5)中，锂离子嵌入 Li(x)V(2)O(5)中，而氧气被还原为过氧化锂。有趣的是，Li(2)O(2)的氧化起始过电位（240 mV）远低于具有非质子电解质的传统 Li-O(2)电池的充电过电位（1000 mV）。我们的研究首次提供了在固态电池中使用原位方法在氧化物表面上形成和分解可逆过氧化锂的证据，并为 Li-O(2)化学的反应机制提供了新的见解。
