Electrochemical and Chemical Na<sup>+</sup>/Li<sup>+</sup>Ion Exchange in Na-Based Cathode Materials: Na<sub>1.56</sub>Fe<sub>1.22</sub>P<sub>2</sub>O<sub>7</sub>and Na<sub>3</sub>V<sub>2</sub>(PO<sub>4</sub>)<sub>2</sub>F<sub>3</sub>
作者:Nina V. Kosova、Daria O. Rezepova、Sergey A. Petrov、Arseny B. Slobodyuk
DOI:10.1149/2.0301701jes
日期:——
In this work, XRD, EDX, Mossbauer and NMR spectroscopy were used to study chemical and electrochemical Na+/Li+ ion exchange in the sodium iron pyrophosphate Na1.56Fe1.22P2O7 with a triclinic symmetry, S. G. P-1, and sodium vanadium fluorophosphate Na3V2(PO4)(2)F-3 with a tetragonal symmetry, S. G. P4(2)/mnm, cathode materials. Electrochemical Na+/Li+ ion exchange was performed in hybrid-ion cells with Li metal anode and LiPF6-based electrolyte, while chemical ion exchange was realized in the solution of LiBr in acetonitrile. A facile electrochemical and chemical Na+/Li+ ion exchange was observed for both cathode materials, resulting in the formation of the mixed Na-Li compositions: similar to Na1.2Li0.36Fe1.22P2O7 and similar to Na2.47Li0.53V2(PO4)(2)F-3, respectively. Partial Na+/Li+ ion exchange did not cause noticeable structural changes to the pristine sodium-based materials. Both materials showed an excellent electrochemical performance in hybrid-ion cells. It was suggested that during cycling, a mixed Na+/Li+ cathode reactions occurred. (C) The Author(s) 2016. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited. All rights reserved.