Na3V2(PO4)2F3　(NVPF)　is　a　suitable　cathode　for　sodium-ion　batteries　owing　to　its　stable　structure.　However,　the　large　radius　of　Na+　restricts　diffusion　kinetics　during　charging　and　discharging.　Thus,　in　this　study,　a　phosphomolybdic　acid　(PMA)-assisted　hydrothermal　method　is　proposed.　In　the　hydrothermal　process,　the　NVPF　morphologies　vary　from　bulk　to　cuboid　with　varying　PMA　contents.　The　optimal　channel　for　accelerated　Na+　transmission　is　obtained　by　cuboid　NVPF.　With　nitrogen-doping　of　carbon,　the　conductivity　of　NVPF　is　further　enhanced.　Combined　with　crystal　growth　engineering　and　surface　modification,　the　optimal　nitrogen-doped　carbon-covered　NVPF　cuboid　(c-NVPF@NC)　exhibits　a　high　initial　discharge　capacity　of　121 mAh g−1　at　0.2 C.　Coupled　with　a　commercial　hard　carbon (CHC)　anode,　the　c-NVPF@NC||CHC　full　battery　delivers　118 mAh g−1　at　0.2 C,　thereby　achieving　a　high　energy　density　of　450 Wh kg−1.　Therefore,　this　work　provides　a　novel　strategy　for　boosting　electrochemical　performance　by　crystal　growth　engineering　and　surface　modification.　©　2023　Wiley-VCH　GmbH.