Scalable Room-Temperature Synthesis of Multi-shelled Na-3(VOPO4)(2)F Microsphere Cathodes

The large-scale application of rechargeable batteries in electric vehicles and energy-storage systems is still hindered by their high cost, particularly from the active materials. Here we proposed a concept of integration of extraction-separation and materials-preparation to further reduce the materials' cost. The power of this concept was demonstrated by the large-scale room-temperature synthesis (150 g per batch) of multi-shelled Na-3(VOPO4)(2)F microspheres based on in situ generated bubbles as soft templates. The as-prepared Na-3(VOPO4)(2)F shows superior rate capability with discharge capacity of 81 mAh g(-1) at 15 C current rate and capacity retention of 70% after 3,000 cycles. Ex situ UV-vis was first employed to characterize the variation of oxidation state for vanadium during the charging and discharging process. This is the first report of a rapid and facile large-scale room-temperature controllable synthesis of Na-3(VOPO4)(2)F microspheres, and this approach could be extended to synthesize other similar compounds.