Ultrafast Preparation of High‐Entropy NASICON Cathode Enables Stabilized Multielectron Redox and Wide‐Temperature (−50–60 °C) Workability in Sodium‐Ion Batteries

Abstract Avoiding severe structural distortion, irreversible phase transition, and realizing the stabilized multielectron redox are vital for promoting the development of high‐performance NASICON‐type cathode materials for sodium‐ion batteries (SIBs). Herein, a high‐entropy Na 3.45 V 0.4 Fe 0.4 Ti 0.4 Mn 0.45 Cr 0.35 (PO 4 ) 3 (HE‐Na 3.45 TMP) cathode material is prepared by ultrafast high‐temperature shock, which inhibits the possibility of phase separation and achieves reversible and stable multielectron transfer of 2.4/2.8 e − at voltage range of 2.0–4.45/1.5–4.45 V versus Na + /Na (the capacity of 137.2/162.0 mAh g −1 ). The galvanostatic charge/discharge and in‐situ X‐ray diffraction tests indicate the sequential redox reactions and approximate solid solution phase transition behavior of HE‐Na 3.45 TMP. Density functional theory calculations analyze the migration pathways and energy barriers, further confirming the superior reaction kinetics of HE‐Na 3.45 TMP. Accordingly, the HE‐Na 3.45 TMP exhibits outstanding wide temperature applicability and can operate stably in the temperature range of −50–60 °C, accompanied by a capacity retention of 92.8% after 400 cycles at −40 °C and a capacity of 73.7 mAh g −1 even at −50 °C. The assembled hard carbon//HE‐Na 3.45 TMP full‐cell offers an energy density of ≈301 Wh kg −1 based on total cathode and anode active mass, verifying the application feasibility of HE‐Na 3.45 TMP. This work provides an innovative and ultrafast pathway to rationally fabricate high‐performance cathodes for SIBs.