Na<sub>2.5</sub>VTi<sub>0.5</sub>Al<sub>0.5</sub>(PO<sub>4</sub>)<sub>3</sub> as Long Lifespan Cathode for Fast Charging Sodium‐Ion Batteries
Zechen Li, Chen Sun, Meng Li, Xiaoyang Wang, Yang Li, Xuanyi Yuan, Haibo Jin, Yongjie Zhao
Abstract
Abstract Vanadium 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 V 4+ /V 5+ couple is proposed to improve the electrochemical performance together with energy density of V‐based cathodes. Making full use of V 2+ /V 3+ /V 4+ /V 5+ and Ti 3+ /Ti 4+ redox couples, Na 2.5 VTi 0.5 Al 0.5 (PO 4 ) 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 Na 2.5 VTi 0.5 Al 0.5 (PO 4 ) 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.