Negative Enthalpy Doping Enables High‐Performance NASICON‐Type Cathode for Sodium‐Ion Batteries

ABSTRACT Sodium Superionic Conductor (NASICON) cathodes possess a favorable Na + diffusion pathway and structural stability, making them promising cathode materials for sodium‐ion batteries. However, upon electrochemical cycling V‐based and Mn‐based NASICON‐type cathodes still hold apparent drawbacks of lattice distortion and structural instability. In this work, a strategy of negative enthalpy doping has been developed to address these issues. Na 3.25 VMn 0.5 Ti 0.25 Al 0.25 (PO 4 ) 3 (NVMTAP) is proposed and prepared through multi‐element doping, which fully utilizes the reversible activation of the high‐voltage platforms of V 4+ /V 5+ and Mn 3+ /Mn 4+ . Moreover, excellent lattice structure stability with a cell volume variation of only 1.74% is achieved. The as‐designed NVMTAP can deliver a specific capacity of 136.3 mAh g −1 at 0.1 C with an energy density of 430 Wh kg −1 and a high‐capacity retention of 74.8% over 4000 cycles under an ultra‐high rate of 30 C (4.2 A g −1 ). Furthermore, the cathode also demonstrates excellent low‐temperature performance, with a capacity retention of 93.5% after 1000 cycles at 15 C and ‐20°C. This research provides a beneficial reference for enhancing the energy density of NASICON‐type electrode materials and simultaneously realizing robust structural stability.