A Medium‐Entropy NASICON Cathode for Sodium‐Ion Batteries Achieving High Energy Density Through Dual Enhancement of Voltage and Capacity

This is the authors' abstract. We don't add key points for this paper.

Na 3 V 2 (PO 4 ) 3 (NVP) is recognized for its promising commercialization potential as a sodium‐ion battery (SIB) cathode, due to its thermodynamic stability and open structure. However, the limited energy density remains a major obstacle to further advancement of NVP. Herein, a medium‐entropy NASICON Na 3.3 V 1.4 Al 0.3 (MgCoNiCuZn) 0.06 (PO 4 ) 3 (NVAMP‐0.3) is designed by introducing Al 3+ , Mg 2+ , Co 2+ , Ni 2+ , Cu 2+ , and Zn 2+ to regulate configurational entropy. These NVAMP‐0.3 achieve an elevated average operating voltage (3.33 V) and high capacity (138.1 mAh g −1 , based on 2.3 Na + ) through V 3+ /V 4+ /V 5+ multi‐electron reactions. By simultaneously enhancing capacity and voltage, NVAMP‐0.3 exhibits an impressive energy density of 460 Wh kg −1 . Furthermore, NVAMP‐0.3 demonstrates excellent low‐temperature tolerance with a capacity retention rate of 94.6% after 300 cycles at −40 °C. In situ XRD unveils the underlying cause of the unique phenomenon where the solid‐solution reaction accounts for the faster electrochemical reaction kinetics of the V 4+ /V 5+ compared to the V 3+ /V 4+ redox. DFT calculations indicate that NVAMP‐0.3 possesses superior electronic conductivity and reduced Na + migration energy barriers. A pouch cell assembled with the NVAMP‐0.3 cathode and hard carbon anode exhibits highly stable cycling (89.3% after 200 cycles at 1 C). This study provides valuable insights into developing NASICON‐type cathodes with high energy densities for SIBs.