Potassium doping towards enhanced Na-ion diffusivity in a fluorophosphate cathode for sodium-ion full cells

K + doping into the Na-site of a Na 3 V 2 (PO 4 ) 2 O 2 F cathode creates Na vacancies and increases disordering in the crystal structure, which dramatically accelerates Na ion diffusivity with outstanding rate and cycle performances in sodium-ion full batteries.