Investigating the structure, electronic properties, and ion migration of Na3V2(PO4)3 cathodes via mono/multi-element doping of Cr, Fe, and Si

Na3V2(PO4)3 (NVP) has received extensive attention as a cathode material for Na-ion batteries (SIBs), but the low electronic conductivity limits its practical electrochemical performance. Elemental doping is an effective way to optimize the conductivity of NVP electrodes. Meanwhile, purifying vanadium requires removing Si, Cr, and Fe impurities that can be directly utilized as effective dopants at low cost. Herein, steered via first-principles calculation, we comprehensively investigate the structure, electronic properties, and Na ion diffusion behavior of Si, Cr, and Fe mono/multi-doped NVPs. The results show that Si doping effectively promotes the electrochemical reaction of V for higher electronic conductivity. Fe doping generates new electronic energy levels in the band gap of NVP, improving the electrode reaction and reducing the migration barrier of Na ions. Notably, Cr doping can greatly reduce the migration barrier of Na ions. Moreover, multi-element doping of Si, Cr, and Fe exhibits a synergistic effect of the individual doping elements. Our work can inspire searching for cost-effective multi-component cathode materials for NIBs.