• Fe–Mn dual-doping modulates the electronic structure of Na3V2(PO4)2F3, inducing a direct-to-indirect bandgap transition that enhances carrier concentration and lifetime.
• The FM-NVPF cathode achieves a high capacity of 126.6 mAh g⁻1 at 0.1 C and exceptional rate capability of 67.6 mAh g⁻1 at 50 C, with a charge time of only 1.2 minutes.
• Full cells with FM-NVPF cathode and hard carbon anode deliver a high energy density of ~175 Wh kg⁻1 (cathode+anode mass) and excellent cycling stability.
• This work provides a cost-effective strategy using affordable Fe and Mn dopants to improve phase purity and electrochemical performance of NVPF cathodes for advanced sodium-ion batteries.