Understanding the Roles of Anionic Redox and Oxygen Release during Electrochemical Cycling of Lithium-Rich Layered Li4FeSbO6статья
Статья опубликована в высокорейтинговом журнале
Информация о цитировании статьи получена из
Web of Science,
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Статья опубликована в журнале из списка Web of Science и/или Scopus
Дата последнего поиска статьи во внешних источниках: 8 декабря 2015 г.
Аннотация:Li-rich oxides continue to be of immense
interest as potential next generation Li-ion battery positive
electrodes, and yet the role of oxygen during cycling is still
poorly understood. Here, the complex electrochemical
behavior of Li4FeSbO6 materials is studied thoroughly with a
variety of methods. Herein, we show that oxygen release
occurs at a distinct voltage plateau from the peroxo/superoxo
formation making this material ideal for revealing new aspects
of oxygen redox processes in Li-rich oxides. Moreover, we
directly demonstrate the limited reversibility of the oxygenated
species (O2
n−; n = 1, 2, 3) for the first time. We also find that
during charge to 4.2 V iron is oxidized from +3 to an unusual
+4 state with the concomitant formation of oxygenated species. Upon further charge to 5.0 V, an oxygen release process
associated with the reduction of iron +4 to +3 is present, indicative of the reductive coupling mechanism between oxygen and
metals previously reported. Thus, in full state of charge, lithium removal is fully compensated by oxygen only, as the iron and
antimony are both very close to their pristine states. Besides, this charging step results in complex phase transformations that are
ultimately destructive to the crystallinity of the material. Such findings again demonstrate the vital importance of fully
understanding the behavior of oxygen in such systems. The consequences of these new aspects of the electrochemical behavior of
lithium-rich oxides are discussed in detail.