NASICON-structured Na3Mn0.5V0.5Ti(PO4)3 cathode with high capacity for sodium-ion batteries

Sodium super-ionic conductor (NASICON) materials are believed as competitive cathodes for sodium-ion batteries, however, their practical application is still prohibited by the limited reversible capacity. In this study, the tri-metal NASICON structured Na3Mn0.5V0.5Ti(PO4)3 is designed to combine with reduced graphene oxide (NMVTP/rGO) as cathode material. Benefited from the multi-step redox couples of Mn, V, and Ti, NMVTP/rGO realizes high reversible capacity and wide operating voltage. The small sizes of Na3Mn0.5V0.5Ti(PO4)3 and rGO ensure the fast charge migration. The rGO inhibits the dissolution of electrode material. As a result, NMVTP/rGO exhibits large specific capacity of 284.6 mAh g−1 at 0.1C, high rate performance (170.2 mAh g−1 at 1C and 108.5 mAh g−1 at 5C), and good cyclic stability. This work demonstrates a new insight for designing tri-metal NASICON structured materials with high capacity for sodium-ion batteries.