Heterogeneous NASICON-Type Composite as Low-Cost, High-Performance Cathode for Sodium-Ion Batteries

As promising cathode for sodium-ion batteries, Na+ Superionic Conductor (NASICON)-type materials have attracted attention owing to their excellent structural stability, superior ionic conductivity, and small volume expansion. However, the vanadium-based NASICON-type cathode with the biotoxicity and exorbitant price of V element and the iron-based cathode with low mean working voltage as well as the intrinsic poor electronic conductivity of polyanionic compounds hinder their practical applications. Herein, a double-carbon-layer decorated heterogeneous composite, Na3V2(PO4)(3)-Na3Fe2(PO4)(P2O7) (NVFPP/C/G), is successfully prepared for addressing these limitations. Due to their synergistic effect, NVFPP/C/G exhibits excellent electrochemical performance in half-cell system and superior full-cell performance when matched with hard carbon anode. Furthermore, the phase composition, electrode kinetics, and phase transition are confirmed by combined analyses of slow scanning power X-ray diffraction, high-resolution transmission electron microscopy, cyclic voltammetry with various scan rates, galvanostatic intermittent titration technique, ex situ X-ray photoelectron spectra, and in situ X-ray diffraction. This study portends a promising strategy to utilize composite structure engineering for developing advanced polyanionic cathodes.

Automated summary

A double-carbon-layer decorated heterogeneous composite, Na3V2(PO4)(3)-Na3Fe2(PO4)(P2O7) (NVFPP/C/G), is successfully prepared to address the limitations of sodium-ion battery cathodes. The composite exhibits excellent electrochemical performance in both half-cell and full-cell systems.