Mn-doped FeS with larger lattice spacing as advance anode for sodium ion half/full battery

Owing to their high theoretical capacity, transition metal sulfides are appearing as reliable electrode materials for sodium ion batteries (SIBs), but achieving both high capacity and enduring cyclic stability remain a serious challenge. Here, multi-core Mn-doped FeS/NC was synthesized by one-pot solvothermal and annealing process. Larger lattice spacing, inducing by doping Mn-atoms, provides more space to store sodium ions. The doping of Mn-atoms increases the conductivity, enhancing the transport of charge carrier and rate performance. Multi-core structure and attached carbon can improve tolerance of volume expansion, which is beneficial to the long-term cyclic performance. In addition, it is also proved by density functional theory (DFT) that Mn-doping FeS can enhance the conductivity and lattice spacing. As a result, Mn-doped FeS/NC delivers high reversible capacity (563.3 mAh·g−1 at 0.5 A·g−1), excellent rate capability (442.8 mAh·g−1 at 8 A·g−1) and enduring cyclic stability (206.2 mAh·g−1 after 8000 cycles) as an anode for SIBs. Specially, a cathode of Na3V2(PO4)3/C is paired with the anode of Mn-doped FeS/NC to assembled into a full battery, showing a highly energy density (281.4 Wh·kg−1 at a power density 625.3 W·kg−1) and capacity retention rate. The present work provide a promise strategy to improve electrochemical performance of the monometallic sulfide.