title: Reversibility of Noble Metal-Catalyzed Aprotic Li-O₂ Batteries.
abstract: The aprotic Li-O2 battery has attracted a great deal of interest because, theoretically, it can store far more energy than today's batteries. Toward unlocking the energy capabilities of this neotype energy storage system, noble metal-catalyzed high surface area carbon materials have been widely used as the O2 cathodes, and some of them exhibit excellent electrochemical performances in terms of round-trip efficiency and cycle life. However, whether these outstanding electrochemical performances are backed by the reversible formation/decomposition of Li2O2, i.e., the desired Li-O2 electrochemistry, remains unclear due to a lack of quantitative assays for the Li-O2 cells. Here, noble metal (Ru and Pd)-catalyzed carbon nanotube (CNT) fabrics, prepared by magnetron sputtering, have been used as the O2 cathode in aprotic Li-O2 batteries. The catalyzed Li-O2 cells exhibited considerably high round-trip efficiency and prolonged cycle life, which could match or even surpass some of the best literature results. However, a combined analysis using differential electrochemical mass spectrometry and Fourier transform infrared spectroscopy, revealed that these catalyzed Li-O2 cells (particularly those based on Pd-CNT cathodes) did not work according to the desired Li-O2 electrochemistry. Instead the presence of noble metal catalysts impaired the cells' reversibility, as evidenced by the decreased O2 recovery efficiency (the ratio of the amount of O2 evolved during recharge/that consumed in the preceding discharge) coupled with increased CO2 evolution during charging. The results reported here provide new insights into the O2 electrochemistry in the aprotic Li-O2 batteries containing noble metal catalysts and exemplified the importance of the quantitative assays for the Li-O2 reactions in the course of pursuing truly rechargeable Li-O2 batteries.
authors.affiliation: State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences , Changchun 130022, P. R. China.|University of Chinese Academy of Sciences , Beijing 100039, P. R. China.
authors.forename: Shunchao
authors.initials: S
authors.lastname: Ma
authors.affiliation: Department of Physics and Tsinghua-Foxconn Nanotechnology Research Center, Tsinghua University , Beijing 100084, P. R. China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Wu
authors.affiliation: State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences , Changchun 130022, P. R. China.
authors.forename: Jiawei
authors.initials: J
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences , Changchun 130022, P. R. China.|University of Chinese Academy of Sciences , Beijing 100039, P. R. China.
authors.forename: Yelong
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences , Changchun 130022, P. R. China.|University of Chinese Academy of Sciences , Beijing 100039, P. R. China.
authors.forename: Yantao
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences , Changchun 130022, P. R. China.
authors.forename: Xinxiu
authors.initials: X
authors.lastname: Yan
authors.affiliation: Department of Physics and Tsinghua-Foxconn Nanotechnology Research Center, Tsinghua University , Beijing 100084, P. R. China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Wei
authors.affiliation: Department of Physics and Tsinghua-Foxconn Nanotechnology Research Center, Tsinghua University , Beijing 100084, P. R. China.
authors.forename: Peng
authors.initials: P
authors.lastname: Liu
authors.affiliation: Department of Physics and Tsinghua-Foxconn Nanotechnology Research Center, Tsinghua University , Beijing 100084, P. R. China.
authors.forename: Jiaping
authors.initials: J
authors.lastname: Wang
authors.affiliation: Department of Physics and Tsinghua-Foxconn Nanotechnology Research Center, Tsinghua University , Beijing 100084, P. R. China.
authors.forename: Kaili
authors.initials: K
authors.lastname: Jiang
authors.affiliation: Department of Physics and Tsinghua-Foxconn Nanotechnology Research Center, Tsinghua University , Beijing 100084, P. R. China.
authors.forename: Shoushan
authors.initials: S
authors.lastname: Fan
authors.affiliation: Department of Chemical Engineering, Louisiana State University , Baton Rouge, Louisiana 70803, United States.
authors.forename: Ye
authors.initials: Y
authors.lastname: Xu
authors.affiliation: State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences , Changchun 130022, P. R. China.
authors.forename: Zhangquan
authors.initials: Z
authors.lastname: Peng
keywords: Aprotic Li-O2 battery; O2 reduction/evolution reaction; differential electrochemical mass spectrometry; noble metal catalyst; reversibility