Sodium superionic conductor (NASICON) -Na4 VMn (PO4) 3 (NVMP) cathode is attractive for sodium-ion battery application due to its reduced cost and toxicity, and high energy density (≈425 Wh kg-1). However, it exhibits significant polarization, limited rate and cycling performances due to its lower electronic conductivity and formation of Jahn-Teller active Mn3+ during cycling . In this report, a chemical approach is presented to partially replace Mn2+ of the NVMP framework by Mg2+ and Al3+ substitutions . The Mg- and Al-substituted NVMP cathodes present smoother voltage profiles, facile sodium (de) intercalation, enhanced rate performances (80 mA h g-1 at 5C rate) and capacity retention (≈96% after 100 cycles) in comparison with the unsubstituted sample . Their enhanced performances are attributed to suppressed Jahn-Teller effect, increased covalent character and sodium ion vacancies of the NASICON framework . These results highlight the significance of fine tuning the chemical compositions to attain high performance NASICON cathodes.