Mn‐Doped‐Iron Sulfide as Long‐Term Stability Anode for High‐Performance Sodium‐Ion Batteries at Wide Temperature and High‐Rate Conditions

Abstract Iron‐based sulfides are promising anode materials for sodium‐ion batteries (SIBs) due to high theoretical capacities, but their short cycle life—caused by volume expansion and polysulfide shuttle effect—limits wide‐temperature applications. To solve this, a novel three‐dimensional MFS@rGO composite anode was prepared via one‐step solvothermal method followed by annealing sulfurization, composed of Mn‐doped Fe ₇ S ₈ (MFS) embedded in nitrogen‐doped reduced graphene oxide (N‐doped rGO). Mn doping enlarges Fe ₇ S ₈ lattice spacing, reducing Na⁺ diffusion resistance to boost ionic conductivity and Na storage. DFT calculations confirm Mn increases Fermi‐level electronic density, lowers Na⁺ migration energy barrier, and accelerates ion transport. N‐doped rGO builds a stable conductive network and synergizes with Mn to suppress shuttle effect and alleviate volume expansion, enhancing structural stability. Benefiting from this synergy, MFS@rGO performs well at −40–60 °C: 282.71 mAh g ⁻¹ after cycling at −40 °C, 310 mAh g ⁻¹ over 500 cycles at −20 °C, 450 mAh g ⁻¹ over 1000 cycles (60 °C, 2 A g ⁻¹ ). At room temperature, it retains 407.09 mAh g ⁻¹ ; over 100 cycles (1 A g ⁻¹ ); even at 50 A g ⁻¹ , it maintains 206.14 mAh g ⁻¹ over 100,000 cycles with negligible degradation. It also works well in full cells, offering a strategy for high‐performance SIBs under extreme conditions.