VSC-doping and VSU-doping of Na3V2-xTix(PO4)2F3 compounds for sodium ion battery cathodes: Analysis of electrochemical performance and kinetic properties

Ion doping strategy is employed to improve the rate performance of insulated Na3V2(PO4)2F3 (NVPF) as cathode of sodium ion batteries. The concepts of VSU-doping (the valence state of the doping ion keeps unchanged during the synthesis) and VSC-doping (the valence state changes during the synthesis) have been introduced in this research. Titanium with different valence states (Ti2+, Ti3+, Ti4+) is selected as the doping element to investigate the...