A NaV3(PO4)3@C hierarchical nanofiber in high alignment: exploring a novel high-performance anode for aqueous rechargeable sodium batteries

Abstract

The development of aqueous rechargeable sodium batteries (ARSBs) demands high-performance electrode materials, especially anode materials with low operating potential and competent electrochemical properties. The lithium/sodium vanadium phosphate family with good structural stability and abundant vanadium chemistry versatility is a promising series for energy storage applications. Herein, a new member in the sodium vanadium phosphate family, i.e. NaV₃(PO₄)₃, is introduced as a novel anode candidate for ARSBs. For the first time, its sodium intercalation mechanism in an aqueous electrolyte is explored, and moreover, the well-aligned NaV₃(PO₄)₃@porous carbon nanofiber is constructed to fulfil its full potential. Based on the reversible phase transformation and 3D open framework, the NaV₃(PO₄)₃ is demonstrated to be reliable in the aqueous electrolyte. Favored by the well-aligned, highly porous and hierarchical 1D nanoarchitecture, the freestanding aligned NaV₃(PO₄)₃@porous carbon hybrid film achieves fast electron/ion transport capability and good mechanical flexibility, resulting in its superior high-rate properties and excellent cycling durability. Moreover, a full cell is fabricated using the aligned NaV₃(PO₄)₃@C nanofiber as the anode and Na_0.44MnO₂ as the cathode. The cell is capable of high-rate long-term cycling, which retains 84% of the capacity after five hundred cycles at alternate 20 and 5C. Therefore, this work not only demonstrates a novel high-performance anode material for ARSBs, but also introduces a general applicable and highly efficient architecture of aligned 1D nanofibers for energy storage applications.