Multi-Enhanced High-Entropy NASICON Cathodes for High Voltage and Stability in Sodium-Ion Batteries.

High-voltage cathodes (HVCs) have emerged as a critical focus of research for the next generation of high-energy-density sodium-ion batteries (SIBs). Overcoming the irreversible phase transition and capacity degradation of high-performance sodium superionic conductors (NASICON) under high voltage (≈4.0 V) remains a significant challenge. Accordingly, this work employs a multielement doping approach to engineer the Multi-Enhanced NASICON cathode (Na4Cr0.7Mn0.65Fe0.1Ni0.1V0.2Al0.2(PO4)3, ME-NASICON), achieving high voltage, high entropy, and exceptional cycling stability. The ME-NASICON cathode delivers a remarkable specific capacity of 166.98 mAh/g at 0.1 C. Benefiting from a high-entropy configuration, it exhibits minimal lattice volume variation of just 1.52%, effectively suppressing detrimental structural evolution and demonstrating outstanding lattice stability. Even after 2000 cycles at a high current rate of 10 C (1.2 A g-1), it retains 69.07% of its initial capacity. Furthermore, the voltage hysteresis associated with Mn2+ redox activity is markedly mitigated, resulting in an elevated average operating voltage. Finally, the ME-NASICON//HC fully cell achieves a specific capacity of 146 mAh/g (12 mA/g) and an energy density of 347.5 Wh/kg. This research paves the way for the development of high-energy-density and long-lifetime cathode materials for SIBs, with promising potential applications in the field of energy storage.