Mechanical activation assisted soft chemical synthesis of Na-doped lithium vanadium fluorophosphates with improved lithium storage properties

摘要

Na-doped lithium vanadium fluorophosphates, Li1-xNaxVPO4F (x=0, 0.01, 0.02), were prepared through a soft chemical route with mechanical activation assist followed by low-temperature calcination. The structure and morphology of the prepared samples were analyzed by XRD and SEM, respectively. After Na doping, the cell volume of LiVPO4F became larger, the content of Li3V2(PO4)(3) impurity decreased, and the particles tended to agglomeration. The Na-doped LiVPO4F samples showed better cycle ability than the pristine one in the voltage range of 3.0-4.5 V. Moreover, the Li0.99Na0.01VPO4F exhibited the best performance, delivering an initial reversible capacity of 136 mA h g(-1) at 0.5 C and maintaining 95.5% capacity retention after 50 cycles. CV tests indicated that the Na-doped samples possessed lower polarization and higher discharge potential plateaus than the pristine one. (C) 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.