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

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_3.45V_0.4Fe_0.4Ti_0.4Mn_0.45Cr_0.35(PO₄)₃ (HE-Na_3.45TMP) 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_3.45TMP. Density functional theory calculations analyze the migration pathways and energy barriers, further confirming the superior reaction kinetics of HE-Na_3.45TMP. Accordingly, the HE-Na_3.45TMP 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_3.45TMP 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_3.45TMP. This work provides an innovative and ultrafast pathway to rationally fabricate high-performance cathodes for SIBs.