A High‐Energy NASICON‐Type Na3.2MnTi0.8V0.2(PO4)3 Cathode Material with Reversible 3.2‐Electron Redox Reaction for Sodium‐Ion Batteries

Abstract Na superionic conductor (NASICON) structured cathode materials with robust structural stability and large Na + diffusion channels have aroused great interest in sodium‐ion batteries (SIBs). However, most of NASICON‐type cathode materials exhibit redox reaction of no more than three electrons per formula, which strictly limits capacity and energy density. Herein, a series of NASICON‐type Na 3+ x MnTi 1− x V x (PO 4 ) 3 cathode materials are designed, which demonstrate not only a multi‐electron reaction but also high voltage platform. With five redox couples from V 5+/4+ (≈4.1 V), Mn 4+/3+ (≈4.0 V), Mn 3+/2+ (≈3.6 V), V 4+/3+ (≈3.4 V), and Ti 4+/3+ (≈2.1 V), the optimized material, Na 3.2 MnTi 0.8 V 0.2 (PO 4 ) 3 , realizes a reversible 3.2‐electron redox reaction, enabling a high discharge capacity (172.5 mAh g −1 ) and an ultrahigh energy density (527.2 Wh kg −1 ). This work sheds light on the rational construction of NASICON‐type cathode materials with multi‐electron redox reaction for high‐energy SIBs.