An ultralong-life SnS-based anode through phosphate-induced structural regulation for high-performance sodium ion batteries

基于PO_(4)^(3-)诱导结构调节的SnS基超长循环寿命钠离子电池负极研究

As a star representative of transition metal sulfides, Sn S 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 PO_(4)^(3-)into the Sn S layers using phytic acid as the special phosphorus source.Intriguingly, the presence of PO_(4)^(3-)in the form of Sn–O–P covalent bonds can act as a conductive pillar to buffer the volume expansion of Sn S 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.

作为过渡金属硫化物的代表, SnS因其优异的理论容量和独特的层状结构被认为是理想的钠离子电池负极材料.然而较差的导电性以及巨大的体积膨胀严重阻碍了SnS作为钠离子电池负极材料的实际应用,如何实现长循环寿命及高可逆容量是发展其作为高性能负极材料的巨大挑战.基于此,本文提出利用具有螯合作用的植酸作为磷源,并将PO_(4)^(3-)-引入SnS层间的结构修饰思路.研究发现不同于常规掺杂手段,以Sn±O±P共价键形式存在的PO_(4)^(3-)作为多向导电柱能够有效抑制SnS的结构塌陷并扩大层间间距,从而实现高效Na~+存储.密度泛函理论计算结果表明PO_(4)^(3-)的引入导致SnS内部电荷分布发生变化并产生内建电场,有效促进了Na^(+)的吸附.因此,所制备的PO_(4)-SnS/NG复合负极材料呈现出优异的超长循环寿命;在5 A g^(-1)下10,000次循环后,材料仍表现出优异的稳定性,每次容量衰减仅为0.0028%.该工作为制备高性能金属硫化物电极材料提供了新思路.