<p>Sodium-ion batteries (SIBs) have recently emerged as one of the most appealing candidates to substitute the lithium-ion technologies. Particularly, owing to high energy density, high operating voltage, and good structural stability, Na₃V₂(PO₄)₂F₃ (NVPF), as a polyanion with a NASICON-type structured compound, has been extensively investigated as a cathode material for SIBs. However, the polarization and structural changes of NVPF can induce significant voltage hysteresis in NVPF, resulting in notable energy loss, compromised reversibility, and shortened cycle life. Therefore, elemental doping of Co in NVPF crystals was proposed to insight the doping effect on the electrochemical performance of NVPF, which is due to the fact that Co²⁺ can enhance the structural stability of the material and, meanwhile, the intrinsic electronic conductivity of the NVPF, thereby improving the rate performance of sodium-ion batteries. The samples of NV_1-xCo_xPF/C (<i>x</i> = 0, 0.03, 0.05, and 0.10) with different doping contents were prepared by the sol–gel method. Eventually, by evaluating the performances of these Co-doped NV_1-xCo_xPF/C (<i>x</i> = 0, 0.03, 0.05, 0.10) samples, it was gotten that NV_0.95Co_0.05PF/C can offer a stable storage capacity of 71.8 mAh g⁻¹ after 300 cycles with a capacity retention rate of 63%. Even as-assembled NV_0.95Co_0.05PF/C//hard carbon full batteries can give rise to a maintained capacity of 87.3 mAh g⁻¹ at a current density of 2C after 150 cycles.</p>