Transition-metal-doped zinc oxide has gathered significant interest in the scientific community because of its potential for application in spintronics devices. This same material has been recently reported as a very promising alternative anode material for Li-ion batteries . The introduction of Fe or Co into the wurtzite structure results into an enhanced reversible capacity exceeding 900 mAh/g (almost three times higher than in pure ZnO), and improved cycling stability even at high rate. The further optimization of such class of materials requires the understanding of the electrochemical (de-)lithiation reaction mechanism at the atomic scale.
Within this contribution we report a complete structural study of carbon coated Zn0.9Fe0.1O nanoparticles prepared through sucrose assisted wet chemical synthesis. X-ray absorption spectroscopy (XAS) has been used to probe oxidation state and local structural environment of the transition metals on the pristine material as well as on anodes measured both ex-situ and in operando during galvanostatic cycling.
The reported study provides a full characterization of the different crystalline but also amorphous and nanocrystalline phases that commonly form upon Li-uptake/release and fundamental insight into the mechanism of the conversion/alloying reaction in these materials. During discharge, the reduction of Zn and alloying with Li has been observed, concurrently with the formation of very small Fe metal clusters. A significant fraction of Zn reversibly oxidizes during charge (up to ~ 75%). Such enhanced reversibility, almost five-fold, compared with pure ZnO could be related to the advantageous influence of the dopant on the highly reversible conversion-alloying lithium storage of such class of materials.
 D. Bresser, F. Mueller, M. Fiedler, S., Krueger, R. Kloepsch, D. Baiter, M. Winter, E. Paillard, S. Passerini Chemistry of Materials 2013, 25, 4977.
 G. Giuli, A. Trapananti, F. Mueller, D. Bresser, F. d’Acapito, S. Passerini Inorganic Chemistry 2015, 54, 9393.
 A. Trapananti, G. Giuli, F. Mueller, D. Bresser, S. Passerini, in preparation