Na2.5VTi0.5Al0.5(PO4)3 as Long Lifespan Cathode for Fast Charging Sodium‐Ion Batteries

Abstract

AbstractVanadium based NASICON‐type cathodes are faced with the exorbitant cost and underdeveloped multi‐electrons reaction of V species. In this work, a strategy of increased covalency of the NASICON framework combined with the reversible activation of V4+/V5+ couple is proposed to improve the electrochemical performance together with energy density of V‐based cathodes. Making full use of V2+/V3+/V4+/V5+ and Ti3+/Ti4+ redox couples, Na2.5VTi0.5Al0.5(PO4)3 exhibits admirable electrochemical performance, including a high specific capacity of 160.9 mAh g−1 at 0.1 C and favorable cycling stability (a capacity retention of 88.3% at 20 C after 1000 cycles). Moreover, this cathode displays outstanding low temperature performance at 0 °C with a capacity retention of 89% after 1200 cycles at 5 C. In situ XRD and EIS analysis are conducted to reveal the Na+ storage mechanism. The cathode reveals a lattice volume variation of 2.16% upon cycling, which is responsible for the high structural stability during the extraction and intercalation process of Na+. Applying Na2.5VTi0.5Al0.5(PO4)3 as both cathode and anode electrode, the symmetric cell is assembled and displays exceptional capacity of 59.8 mAh g−1 at 20 C. The research provides an effective routine to stimulate the electrochemical potential of V‐based electrode materials.