Zhou, Dong, Permien, Stefan, Rana, Jatinkumar, Krengel, Markus, Sun, Fu, Schumacher, Gerhard, Bensch, Wolfgang and Banhart, John (2017) Investigation of electronic and local structural changes during lithium uptake and release of nano-crystalline NiFe2O4 by X-ray absorption spectroscopy. Journal of Power Sources, 342 . pp. 56-63. DOI 10.1016/j.jpowsour.2016.12.038.

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Abstract

Nano-crystalline NiFe2O4 particles were synthesized and used as active electrode material for a lithium ion battery that showed a high discharge capacity of 1534 mAh g−1 and charge capacity of 1170 mAh g−1 during the 1st cycle. X-ray absorption spectroscopy including XANES and EXAFS were used to investigate electronic and local structural changes of NiFe2O4 during the 1st lithiation and de-lithiation process. As lithium is inserted into the structure, tetrahedral site Fe3+ ions are reduced to Fe2+ and moved from tetrahedral sites to empty octahedral sites, while Ni2+ ions are unaffected. As a consequence, the matrix spinel structure collapses and transforms to an intermediate rock-salt monoxide phase. Meanwhile, the inserted Li is partially consumed by the formation of SEI and other side reactions during the conversion reaction. With further lithiation, the monoxide phase is reduced to highly disordered metallic Fe/Ni nanoparticles with a number of nearest neighbors of 6.0(8) and 8.1(4) for Fe and Ni, respectively. During subsequent de-lithiation, the metal particles are individually re-oxidized to Fe2O3 and NiO phases instead to the original NiFe2O4 spinel phase.

Document Type:	Article
Research affiliation:	Kiel University > Kiel Marine Science OceanRep > The Future Ocean - Cluster of Excellence Kiel University
Refereed:	Yes
Open Access Journal?:	Yes
Publisher:	Elsevier
Date Deposited:	16 Jan 2018 15:19
Last Modified:	16 May 2019 08:55
URI:	https://oceanrep.geomar.de/id/eprint/41514

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