Ration Design of Mn/Si-Codoped Na 3 V 2 (PO 4 ) 3 as Cathode Na-Ion Batteries

NASICON-typed Na 3 V 2 (PO 4 ) 3 is considered the most promising cathode material for sodium-ion batteries. However, it still exhibits a limitation in terms of energy density. Herein, Mn/Si-codoped Na 3.5+ x V 1.5 Mn 0.5 (PO 4 ) 3– x (SiO 4 ) x was synthesized to increase reversible capacity and operating voltage. The effects of co-substitution on structural stability and electrochemical performance are investigated. Among various doping concentrations, the optimized Na 3.55 Mn 0.5 V 1.5 (PO 4 ) 2.95 (SiO 4 ) 0.05 shows remarkably improved cyclability and reversibility. It delivers a reversible capacity of 116 mAh g –1 at 0.2C, good cycling stability (capacity retention of 80.2% after 200 cycles), and an outstanding rate capacity of 92 mAh g –1 at 10C.