Insights into the electrochemical activity of nanosized α-LiFeO2

In recent work [J. Morales, J. Santos-Peña, Electrochem. Commun. 9 (2007) 2116], we prepared nanosized α-LiFeO2 with increased electrochemical activity in lithium cells relative to various lithium ferrite polymorphs. In this work, we studied the previous electrodes in different charge states in order to obtain a more accurate picture of the phenomena occurring during cycling. Exsitu X-ray photoelectron spectroscopy (XPS) measurements confirmed the oxidation/reduction of iron atoms during the charge/discharge process. The electrochemical impedance spectroscopy results suggested that the electrolyte is not oxidised during the first charge, but rather than a solid electrolyte interface is formed after one cycle. Also, thermal tests revealed that Fe(IV) present in the electrodes reacted with the electrolyte to form oxidised carbon species. Finally, α-LiFeO2 was tested as a positive electrode material in a lithium battery under different regimes. Stabilised capacities up to 150 mAh g−1 were obtained under a C/4 regime. This lithium ferrite is therefore an attractive alternative to LiCoO2.