cm6b03195_si_001.pdf (1.89 MB)
Tuning Surface Chemistry of TiC Electrodes for Lithium–Air Batteries
journal contribution
posted on 2016-10-11, 00:00 authored by Anna Ya. Kozmenkova, Elmar
Yu. Kataev, Alina
I. Belova, Matteo Amati, Luca Gregoratti, Juan Velasco-Vélez, Axel Knop-Gericke, Boris Senkovsky, Denis V. Vyalikh, Daniil M. Itkis, Yang Shao-Horn, Lada
V. YashinaOne
of the key problems hindering practical implementation of lithium–air
batteries is caused by carbon cathode chemical instability leading
to low energy efficiency and short cycle life. Titanium carbide (TiC)
nanopowders are considered as an alternative cathode material; however, they are intrinsically
reactive toward oxygen, and its stability is controlled totally by
a surface overlayers. Using photoemission spectroscopy, we show that
lithium–air battery discharge product, lithium peroxide (Li2O2), easily oxidizes clean TiC surface. At the
same time, TiC surface, which was treated by molecular oxygen under
ambient conditions, shows much better stability in contact with Li2O2 that can be explained by the presence of a surface
layer containing a significant amount of elemental carbon in addition
to oxides and oxycarbides. Nevertheless, such protective coatings
produced by room temperature oxidation are not practically useful
as one of its components, elemental carbon, is oxidized in the presence
of lithium–air battery discharge intermediates. These results
are of critical importance in understanding of TiC surface chemistry
and in design of stable lithium–air battery electrodes. We
postulate that dense, uniform, carbon-free titanium dioxide surface
layers of 2–3 nm thickness on TiC will be a promising solution,
and thus further efforts should be taken for developing synthetic
protocols enabling preparation of TiO2/TiC core–shell
structures.