Superparamagnetic Fe Conversion Induces MoS₂ Fast Ion Transport in Wide‐Temperature‐Range Sodium‐Ion Batteries

Abstract

MoS2 is widely reported as anode material for sodium‐ion batteries (SIBs). However, its ability to operate effectively across a wide temperature range and at high rates continues to pose fundamental challenges, limiting its further development. Herein, a monolayer Fe‐doped MoS2/N,O‐codoped C overlapping structure is designed and employed as an anode for wide‐temperature‐range SIBs. Fe doping imparts MoS2 electrode with zero bandgap characteristics, an increased interlayer spacing, and low sodium‐ion diffusion energy barriers across wide operation temperatures. Impressively, Fe atoms doped into the MoS2 lattice can be reduced to superparamagnetic Fe0 nanocrystals of ≈2 nm during conversion reactions. In situ magnetometry reveals that these Fe0 nanocrystals can be used as electron acceptor in the formation of space charge zones with Na+, thereby triggering strong spin‐polarized surface capacitance that facilitates fast sodium‐ion storage over a wide temperature range. Consequently, the designed MoS2 electrode demonstrates exceptional fast‐charging capability in half/full cells operating at −40–60 °C. This study provides novel perspectives on the utilization of heteroatom doping strategies in conversion‐type electrode material design and proves the effectiveness of spin‐polarized surface capacitance effect on enhancing sodium‐ion storage over a wide temperature range.