The electronic and geometric structure modifications of LiFePO4 with vanadium doping to achieve ultrafast discharging capability: The experimental and theoretical investigations

Abstract

The electrochemical performance of vanadium doped LiFePO4 has been significantly enhanced as a result of improved electron conductivity and lithium ion diffusion capability. These findings enable the utilization of LiFePO4 to power electric vehicles with faster acceleration and reliable long-term cycling stability. Herein, optimization of the band structure of LiFePO4 with effective reduction of forbidden bandwidth after vanadium doping were demonstrated via theoretical calculation. Meanwhile, the decreased energy barrier of lithium ion diffusion enabled a fast transfer. The vanadium doped LiFePO4/C composites were synthesized via a solid state method with iron powder as direct precursor and realized 100% atomic efficiency as well as a higher tap density. The specific capacity and high rate performance were apparently ameliorated, 2% V-doped LiFe0.98V0.02PO4/C measured 141.4 mAh g−1 at 1 C and 93.9 mAh g−1 at 20 C, while the pristine counterpart only performed 130.1 mAh g−1 and 80.5 mAh g−1, respectively. Furthermore, the capacity retention rate after 500 cycles at 1 C was 98.3% for LiFe0.98V0.02PO4/C. Based on these DFT calculation and experimental results, the dramatic improvement of vanadium doped LiFePO4/C materials may provide novel opportunities for the evolution of olivine cathode materials and satisfy the demand in electric vehicles.