Mechanism of Capacity Fade in Sodium Storage and the Strategies of Improvement for FeS Anode.

Pyrite FeS has attracted extensive interest as anode material for sodium-ion batteries due to its high capacity, low cost, and abundant resource. However, the micron-sized FeS usually suffers from poor cyclability, which stems from structure collapse, exfoliation of active materials, and sulfur dissolution. Here, we use a synergistic approach to enhance the sodium storage performance of the micron-sized FeS through voltage control (0.5-3 V), binder choice, and graphene coating. The FeS electrode with the synergistic approach exhibits high specific capacity (524 mA h g), long cycle life (87.8% capacity retention after 800 cycles), and excellent rate capability (323 mA h g at 5 A g). The results prove that a synergistic approach can be applied in the micron-sized sulfides to achieve high electrochemical performance.