Mechanism of Capacity Fade in Sodium Storage and the Strategies of Improvement for FeS2 Anode.

Pyrite FeS2 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 FeS2 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 FeS2 through voltage control (0.5-3 V), binder choice, and graphene coating. The FeS2 electrode with the synergistic approach exhibits high specific capacity (524 mA h g-1), long cycle life (87.8% capacity retention after 800 cycles), and excellent rate capability (323 mA h g-1 at 5 A g-1). The results prove that a synergistic approach can be applied in the micron-sized sulfides to achieve high electrochemical performance.