Superior performance of Na 7 V 4 (P 2 O 7 ) 4 PO 4 in sodium ion batteries.

A novel synthetic method has been investigated to fabricate a 1D nanostructure Na 7 V 4 (P 2 O 7 ) 4 PO 4 . Mixed polyanion materials with a well-defined 3D framework channel can improve the electrochemical performance of sodium reversible insertion/extraction reactions, and can be especially beneficial for high rate performance and cycling capability. It approaches an initial reversible electrochemical capacity of 92.0 mA h g -1 with a high discharge potential over 3.85 V ( vs. Na/Na + ) and good cycling properties with a capacity retention of 81.4% after 300 cycles at a 0.5C rate in sodium systems. Taking into consideration the superior electrochemical characteristics, the phase-pure composite is considered to have a promising high rate capability as well as being a high capacity electrode material for advanced energy storage applications.