Charge reconfiguration for breaking the V4+/V5+ redox barrier in sodium-based NASICON cathode with higher energy density

Abstract

Na₄FeV(PO₄)₃ (NFV) is a Na-super-ionic conductor (NASICON)-structured cathode material for sodium-ion batteries (SIBs). Nonetheless, how to stabilize the V⁴⁺/V⁵⁺ redox reaction in the high-voltage region and enhance the carrier transport rate are the biggest challenges at present. In this paper, an innovative charge reconfiguration engineering is pro-posed to optimize the charge transfer of the V-O bonds and enhance the carrier transport rate by introducing electron-rich Ti at the Fe site. In this way, the barrier of V⁴⁺/V⁵⁺ redox is broken, which enables the activation and stability of V⁴⁺/V⁵⁺ redox in the high-voltage region to be achieved simultaneously. Furthermore, the significantly lengthened V⁴⁺/V⁵⁺ redox plateau in the high-voltage region contributes superior capacity, leading to a remarkably increased energy density (up to 1.6 times that of the NFV). The proposed charge reconfiguration engineering will create a new avenue for fabricating high-performance cathode materials for SIBs.