Na_<i>x</i>MV(PO₄)₃ (M = Mn, Fe, Ni) Structure and Properties for Sodium Extraction

Abstract

NASICON (Na⁺ super ionic conductor) structures of Na_xMV(PO₄)₃ (M = Mn, Fe, Ni) were prepared, characterized by aberration-corrected STEM and synchrotron radiation, and demonstrated to be durable cathode materials for rechargeable sodium-ion batteries. In Na₄MnV(PO₄)₃, two redox couples of Mn³⁺/Mn²⁺ and V⁴⁺/V³⁺ are accessed with two voltage plateaus located at 3.6 and 3.3 V and a capacity of 101 mAh g^-1 at 1 C. Furthermore, the Na₄MnV(PO₄)₃ cathode delivers a high initial efficiency of 97%, long durability over 1000 cycles, and good rate performance to 10 C. The robust framework structure and stable electrochemical performance makes it a reliable cathode materials for sodium-ion batteries.