Achieving highly reversible and fast sodium storage of Na4VMn(PO4)3/C-rGO composite with low-fraction rGO via spray-drying technique

Abstract

NASICON-type (Na super ionic conductor) Na4VMn(PO4)3 (NVMP) cathode material has attracted increasing attention due to its higher sodium de-/intercalation voltage, lower cost and greener resources compared with Na3V2(PO4)3. However, the poor electronic conductivity limits the exploitation of its electrochemical performance. In this work, we achieved an ultrahigh rate capable and long cycle life NVMP/C-rGO composite using the simple and scalable spray-drying technique, in which low-fraction rGO nanosheets (2.14 wt%) highly dispersed and bridged the carbon shelled NVMP nanoparticles to form an effective electron conductive network. Benefiting from this favorable nano-architecture, the elaborately designed NVMP/C-rGO composite exhibited excellent performance as cathode in sodium ion batteries, delivering reversible capacities of 105.5 mA h g−1 at 1 C (1 C = 110 mA h g−1) and 102.6 mA h g−1 at 50 C with capacity retention of 90.6% (1 C) and 80.4% (50 C) over 500 cycles, respectively. This is the highest rate performance for Na4VMn(PO4)3 materials reported so far. This work provides a practicable tactic for fabricating advanced polyanion-type cathode materials which can be commercially scale up for sodium energy storage.