A NASICON-type Na3Al1/3Mn2/3V1/3Ti2/3(PO4)3 cathode for high-performance sodium-ion battery

To develop NASICON-type cathode with high energy density and long cycle life for sodium-ion batteries (SIBs), it is essential to achieve multi-electron redox reactions while suppressing lattice strain evolution during Na + intercalation/deintercalation processes. In this study, a medium-entropy NASICON-type cathode, Na 3 Al 1/3 Mn 2/3 V 1/3 Ti 2/3 (PO 4 ) 3 (NAMVTP), was designed and synthesized via a ball milling combined with solid-state sintering, which displays exceptional Na + storage properties. The NAMVTP delivers a high capacity of 156.9 and 127 mAh g −1 at 0.11C and 11.11C, respectively, retains 95 mAh g −1 after 5000 cycles at 11.11C. In-situ X-ray diffraction and electrochemical impedance spectroscopy characterizations demonstrate that the medium-entropy effect can accelerate the migration of Na + ions and electrons, while effectively suppressing volume variation and structural phase evolution during cycling. This work proposes a facile medium-entropy strategy to modify the polyanion-type cathodes, which efficiently improves the Na + storage capability and offers important guidance for SIB cathode development.