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

Abstract Na-doped lithium vanadium fluorophosphates, Li 1− x Na x VPO 4 F ( 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 LiVPO 4 F became larger, the content of Li 3 V 2 (PO 4 ) 3 impurity decreased, and the particles tended to agglomeration. The Na-doped LiVPO 4 F samples showed better cycle ability than the pristine one in the voltage range of 3.0–4.5 V. Moreover, the Li 0.99 Na 0.01 VPO 4 F 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.