As a star representative of transition metal sulfides, SnS is viewed as a promising anode-material candidate for sodium ion batteries due to its high theoretical capacity and unique layered structure. However, the extremely poor electrical conductivity and severe volume expansion strongly hinder its practical application while achieving a high reversible capacity with long-cyclic stability still remains a grand challenge. Herein, different from the conventional enhancement method of elemental doping, we report a rational strategy to introduce PO43- into the SnS layers using phytic acid as the special phosphorus source. Intriguingly, the presence of PO43- in the form of Sn-O-P covalent bonds can act as a conductive pillar to buffer the volume expansion of SnS while expanding its interlay spacing to allow more Na+ storage, supported by both experimental and theoretical evidences. Profiting from this effect combined with microstructural metrics by loading on high pyridine N-doped reduced graphene oxide, the as-prepared material presented an unprecedented ultra-long cyclic stability even after 10,000 cycles along with high reversible capacity and excellent full-cell performances. The findings herein open up new opportunities for elevating electrochemical performances of metal sulfides and provide inspirations for the fabrication of advanced electrode materials for broad energy use.
Keywords: Anode; Phytic acid; SnS; Sodium ion batteries; Ultra-long cyclic stability.
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