posted on 2015-04-28, 00:00authored byHossein Yadegari, Mohammad
Norouzi Banis, Biwei Xiao, Qian Sun, Xia Li, Andrew Lushington, Biqiong Wang, Ruying Li, Tsun-Kong Sham, Xiaoyu Cui, Xueliang Sun
A binder-free three-dimensional (3D)
nanostructured air electrode
composed of vertically grown nitrogen doped carbon nanotubes on carbon
paper (NCNT-CP) is developed and applied to Na–O2 cells. The 3D architecture of the air electrode results in increased
discharge capacity by optimizing the utilized area of the electrode
material. The chemical and electrochemical reaction mechanisms of
the cell are also explored with the use of synchrotron-based X-ray
absorption spectroscopy (XAS). Investigation of the discharge product
of Na–O2 cells during discharge and charge cycles
using X-ray absorption near-edge structure (XANES) indicates that
both sodium superoxide and peroxide are produced under various physicochemical
conditions and can be subsequently decomposed with different overpotentials.
Furthermore, formation of carbonate-based parasitic products is also
shown to restrict the cyclability of the cell.