Rational Architecture Design Enables Superior Na Storage in Greener NASICON-Na₄MnV(PO₄)₃ Cathode

Na₃V₂(PO₄)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 Na₄MnV(PO₄)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, Na₄MnV(PO₄)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 Na₄MnV(PO₄)₃ material is synthesized through a feasible solution-route method. The elaborately designed Na₄MnV(PO₄)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 Na₄MnV(PO₄)₃, which are deeply investigated by both experiments and calculations.