Stable Cycling of Phosphorus Anode for Sodium-Ion Batteries through Chemical Bonding with Sulfurized Polyacrylonitrile

Sodium-ion batteries are attracting increasing interests as a promising alternative to lithium-ion batteries due to the abundant resource and low cost of sodium. Despite phosphorus (P) has extremely high theoretical capacity of 2595 mAh g⁻¹, its wide application for sodium-ion battery is highly hampered by its fast capacity fading and low Coulombic efficiency as a result of large volume change upon cycling. Herein, a robust phosphorus anode with long cycle life for sodium-ion battery via hybridization with functional conductive polymer is presented. To this end, the polyacrylonitrile is first dehydrogenated by sulfur via a facile thermal treatment, forming a conductive main chain embedded with C–S–S moieties. This functional conductive polymer enables the formation of PS bonds between phosphorus and functional conductive matrix, leading to a robust electrode that can accommodate the large volume change upon substantial volume change in cycling. Consequently, this hybrid anode delivers a high capacity of ≈1300 mAh g⁻¹ at a current density of 520 mA g⁻¹ with high Coulombic efficiency (>99%) and good cycling performance (91% capacity retention after 100 cycles).