Rational Architecture Design Enables Superior Na Storage in Greener NASICON‐Na 4 MnV(PO 4 ) 3 Cathode

Na 3 V 2 (PO 4 ) 3 has attracted great attention due to its high energy density and stable structure. However, in order to boost its application, the discharge potential of 3.3–3.4 V (vs Na + /Na) still needs to be improved and substitution of vanadium with other lower cost and earth‐abundant active redox elements is imperative. Therefore, the Na superionic conductor (NASICON)‐structured Na 4 MnV(PO 4 ) 3 seems to be more attractive due to its lower toxicity and higher voltage platform resulting from the partial substitution of V with Mn. However, Na 4 MnV(PO 4 ) 3 still suffers from poor electronic conductivity, leading to unsatisfactory capacity delivering and poor high‐rate capability. In this work, a graphene aerogel–supported in situ carbon–coated Na 4 MnV(PO 4 ) 3 material is synthesized through a feasible solution‐route method. The elaborately designed Na 4 MnV(PO 4 ) 3 can reach ≈380 Wh kg −1 at 0.5 C (1 C = 110 mAh g −1 ) and realize superior high‐rate capability evenat 50 C (60.1 mAh g −1 ) with a long cycle‐life of 4000 cycles at 20 C. This impressive progress should be ascribed to the multifunctional 3D carbon framework and the distinctive structure of trigonal Na 4 MnV(PO 4 ) 3 , which are deeply investigated by both experiments and calculations.