Ration Design of Mn/Si-Codoped Na3V2(PO4)3 as Cathode Na-Ion Batteries

NASICON-typed Na3V2(PO4)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 Na3.5+xV1.5Mn0.5(PO4)3–x(SiO4)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 Na3.55Mn0.5V1.5(PO4)2.95(SiO4)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.